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d0a5eb32 | 1 | @c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, |
c41b7b13 | 2 | @c 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 |
5b3e6663 | 3 | @c Free Software Foundation, Inc. |
74291a4b MM |
4 | @c This is part of the GCC manual. |
5 | @c For copying conditions, see the file gcc.texi. | |
6 | ||
9d86bffc | 7 | @ignore |
9d530538 MM |
8 | @c man begin INCLUDE |
9 | @include gcc-vers.texi | |
10 | @c man end | |
11 | ||
9d86bffc | 12 | @c man begin COPYRIGHT |
2b6dd222 | 13 | Copyright @copyright{} 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, |
c41b7b13 | 14 | 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 |
28a08168 | 15 | Free Software Foundation, Inc. |
9d86bffc | 16 | |
77bd67cb | 17 | Permission is granted to copy, distribute and/or modify this document |
07a67d6a | 18 | under the terms of the GNU Free Documentation License, Version 1.3 or |
77bd67cb JM |
19 | any later version published by the Free Software Foundation; with the |
20 | Invariant Sections being ``GNU General Public License'' and ``Funding | |
21 | Free Software'', the Front-Cover texts being (a) (see below), and with | |
22 | the Back-Cover Texts being (b) (see below). A copy of the license is | |
23 | included in the gfdl(7) man page. | |
9d86bffc | 24 | |
77bd67cb | 25 | (a) The FSF's Front-Cover Text is: |
9d86bffc | 26 | |
77bd67cb JM |
27 | A GNU Manual |
28 | ||
29 | (b) The FSF's Back-Cover Text is: | |
30 | ||
31 | You have freedom to copy and modify this GNU Manual, like GNU | |
32 | software. Copies published by the Free Software Foundation raise | |
33 | funds for GNU development. | |
9d86bffc JM |
34 | @c man end |
35 | @c Set file name and title for the man page. | |
36 | @setfilename gcc | |
37 | @settitle GNU project C and C++ compiler | |
38 | @c man begin SYNOPSIS | |
630d3d5a JM |
39 | gcc [@option{-c}|@option{-S}|@option{-E}] [@option{-std=}@var{standard}] |
40 | [@option{-g}] [@option{-pg}] [@option{-O}@var{level}] | |
41 | [@option{-W}@var{warn}@dots{}] [@option{-pedantic}] | |
42 | [@option{-I}@var{dir}@dots{}] [@option{-L}@var{dir}@dots{}] | |
43 | [@option{-D}@var{macro}[=@var{defn}]@dots{}] [@option{-U}@var{macro}] | |
44 | [@option{-f}@var{option}@dots{}] [@option{-m}@var{machine-option}@dots{}] | |
9d530538 | 45 | [@option{-o} @var{outfile}] [@@@var{file}] @var{infile}@dots{} |
9d86bffc JM |
46 | |
47 | Only the most useful options are listed here; see below for the | |
48 | remainder. @samp{g++} accepts mostly the same options as @samp{gcc}. | |
49 | @c man end | |
50 | @c man begin SEEALSO | |
77bd67cb | 51 | gpl(7), gfdl(7), fsf-funding(7), |
b4117c30 ZW |
52 | cpp(1), gcov(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1) |
53 | and the Info entries for @file{gcc}, @file{cpp}, @file{as}, | |
9d86bffc JM |
54 | @file{ld}, @file{binutils} and @file{gdb}. |
55 | @c man end | |
2642624b JM |
56 | @c man begin BUGS |
57 | For instructions on reporting bugs, see | |
2f41c1d6 | 58 | @w{@value{BUGURL}}. |
2642624b JM |
59 | @c man end |
60 | @c man begin AUTHOR | |
24dbb440 GP |
61 | See the Info entry for @command{gcc}, or |
62 | @w{@uref{http://gcc.gnu.org/onlinedocs/gcc/Contributors.html}}, | |
63 | for contributors to GCC@. | |
2642624b | 64 | @c man end |
9d86bffc JM |
65 | @end ignore |
66 | ||
74291a4b | 67 | @node Invoking GCC |
0c2d1a2a JB |
68 | @chapter GCC Command Options |
69 | @cindex GCC command options | |
74291a4b | 70 | @cindex command options |
0c2d1a2a | 71 | @cindex options, GCC command |
74291a4b | 72 | |
9d86bffc | 73 | @c man begin DESCRIPTION |
0c2d1a2a | 74 | When you invoke GCC, it normally does preprocessing, compilation, |
74291a4b | 75 | assembly and linking. The ``overall options'' allow you to stop this |
630d3d5a | 76 | process at an intermediate stage. For example, the @option{-c} option |
74291a4b MM |
77 | says not to run the linker. Then the output consists of object files |
78 | output by the assembler. | |
79 | ||
80 | Other options are passed on to one stage of processing. Some options | |
81 | control the preprocessor and others the compiler itself. Yet other | |
82 | options control the assembler and linker; most of these are not | |
83 | documented here, since you rarely need to use any of them. | |
84 | ||
85 | @cindex C compilation options | |
0c2d1a2a | 86 | Most of the command line options that you can use with GCC are useful |
74291a4b MM |
87 | for C programs; when an option is only useful with another language |
88 | (usually C++), the explanation says so explicitly. If the description | |
89 | for a particular option does not mention a source language, you can use | |
90 | that option with all supported languages. | |
91 | ||
92 | @cindex C++ compilation options | |
93 | @xref{Invoking G++,,Compiling C++ Programs}, for a summary of special | |
94 | options for compiling C++ programs. | |
95 | ||
96 | @cindex grouping options | |
97 | @cindex options, grouping | |
bedc7537 | 98 | The @command{gcc} program accepts options and file names as operands. Many |
b192711e | 99 | options have multi-letter names; therefore multiple single-letter options |
cb7c15f8 JH |
100 | may @emph{not} be grouped: @option{-dv} is very different from @w{@samp{-d |
101 | -v}}. | |
74291a4b MM |
102 | |
103 | @cindex order of options | |
104 | @cindex options, order | |
105 | You can mix options and other arguments. For the most part, the order | |
70f57af1 ILT |
106 | you use doesn't matter. Order does matter when you use several |
107 | options of the same kind; for example, if you specify @option{-L} more | |
108 | than once, the directories are searched in the order specified. Also, | |
109 | the placement of the @option{-l} option is significant. | |
74291a4b MM |
110 | |
111 | Many options have long names starting with @samp{-f} or with | |
cb7ad97b | 112 | @samp{-W}---for example, |
efa1cdf0 | 113 | @option{-fmove-loop-invariants}, @option{-Wformat} and so on. Most of |
74291a4b | 114 | these have both positive and negative forms; the negative form of |
630d3d5a | 115 | @option{-ffoo} would be @option{-fno-foo}. This manual documents |
74291a4b MM |
116 | only one of these two forms, whichever one is not the default. |
117 | ||
9d86bffc JM |
118 | @c man end |
119 | ||
cd3bb277 JM |
120 | @xref{Option Index}, for an index to GCC's options. |
121 | ||
74291a4b | 122 | @menu |
6ccde948 | 123 | * Option Summary:: Brief list of all options, without explanations. |
74291a4b MM |
124 | * Overall Options:: Controlling the kind of output: |
125 | an executable, object files, assembler files, | |
126 | or preprocessed source. | |
6ccde948 | 127 | * Invoking G++:: Compiling C++ programs. |
74291a4b MM |
128 | * C Dialect Options:: Controlling the variant of C language compiled. |
129 | * C++ Dialect Options:: Variations on C++. | |
46e34f96 ZL |
130 | * Objective-C and Objective-C++ Dialect Options:: Variations on Objective-C |
131 | and Objective-C++. | |
764dbbf2 | 132 | * Language Independent Options:: Controlling how diagnostics should be |
02f52e19 | 133 | formatted. |
74291a4b MM |
134 | * Warning Options:: How picky should the compiler be? |
135 | * Debugging Options:: Symbol tables, measurements, and debugging dumps. | |
136 | * Optimize Options:: How much optimization? | |
137 | * Preprocessor Options:: Controlling header files and macro definitions. | |
138 | Also, getting dependency information for Make. | |
139 | * Assembler Options:: Passing options to the assembler. | |
140 | * Link Options:: Specifying libraries and so on. | |
141 | * Directory Options:: Where to find header files and libraries. | |
142 | Where to find the compiler executable files. | |
a743d340 | 143 | * Spec Files:: How to pass switches to sub-processes. |
0c2d1a2a | 144 | * Target Options:: Running a cross-compiler, or an old version of GCC. |
74291a4b MM |
145 | * Submodel Options:: Specifying minor hardware or convention variations, |
146 | such as 68010 vs 68020. | |
147 | * Code Gen Options:: Specifying conventions for function calls, data layout | |
148 | and register usage. | |
0c2d1a2a | 149 | * Environment Variables:: Env vars that affect GCC. |
17211ab5 | 150 | * Precompiled Headers:: Compiling a header once, and using it many times. |
74291a4b MM |
151 | @end menu |
152 | ||
4bc1997b JM |
153 | @c man begin OPTIONS |
154 | ||
74291a4b MM |
155 | @node Option Summary |
156 | @section Option Summary | |
157 | ||
158 | Here is a summary of all the options, grouped by type. Explanations are | |
159 | in the following sections. | |
160 | ||
161 | @table @emph | |
162 | @item Overall Options | |
163 | @xref{Overall Options,,Options Controlling the Kind of Output}. | |
c3224d6f | 164 | @gccoptlist{-c -S -E -o @var{file} -no-canonical-prefixes @gol |
ba0c638e | 165 | -pipe -pass-exit-codes @gol |
0631b69f | 166 | -x @var{language} -v -### --help@r{[}=@var{class}@r{[},@dots{}@r{]]} --target-help @gol |
ab940b73 | 167 | --version -wrapper @@@var{file} -fplugin=@var{file} -fplugin-arg-@var{name}=@var{arg} @gol |
c6a13190 | 168 | -fdump-ada-spec@r{[}-slim@r{]}} -fdump-go-spec=@var{file} |
74291a4b MM |
169 | |
170 | @item C Language Options | |
171 | @xref{C Dialect Options,,Options Controlling C Dialect}. | |
da1c7394 ILT |
172 | @gccoptlist{-ansi -std=@var{standard} -fgnu89-inline @gol |
173 | -aux-info @var{filename} @gol | |
9a94f7f3 | 174 | -fno-asm -fno-builtin -fno-builtin-@var{function} @gol |
478a1c5b | 175 | -fhosted -ffreestanding -fopenmp -fms-extensions -fplan9-extensions @gol |
8a035a6b | 176 | -trigraphs -no-integrated-cpp -traditional -traditional-cpp @gol |
00c8e9f6 | 177 | -fallow-single-precision -fcond-mismatch -flax-vector-conversions @gol |
4bc1997b | 178 | -fsigned-bitfields -fsigned-char @gol |
3521b33c | 179 | -funsigned-bitfields -funsigned-char} |
74291a4b MM |
180 | |
181 | @item C++ Language Options | |
182 | @xref{C++ Dialect Options,,Options Controlling C++ Dialect}. | |
9a94f7f3 | 183 | @gccoptlist{-fabi-version=@var{n} -fno-access-control -fcheck-new @gol |
cfb10bd3 | 184 | -fconserve-space -ffriend-injection @gol |
aa0cc562 | 185 | -fno-elide-constructors @gol |
7813d14c | 186 | -fno-enforce-eh-specs @gol |
1dbb6023 | 187 | -ffor-scope -fno-for-scope -fno-gnu-keywords @gol |
90ecce3e | 188 | -fno-implicit-templates @gol |
4bc1997b JM |
189 | -fno-implicit-inline-templates @gol |
190 | -fno-implement-inlines -fms-extensions @gol | |
d3f28910 | 191 | -fno-nonansi-builtins -fnothrow-opt -fno-operator-names @gol |
4bc1997b | 192 | -fno-optional-diags -fpermissive @gol |
6ea2bd47 | 193 | -fno-pretty-templates @gol |
124e0d27 | 194 | -frepo -fno-rtti -fstats -ftemplate-depth=@var{n} @gol |
40aac948 | 195 | -fno-threadsafe-statics -fuse-cxa-atexit -fno-weak -nostdinc++ @gol |
d7afec4b | 196 | -fno-default-inline -fvisibility-inlines-hidden @gol |
ddbfd28d | 197 | -fvisibility-ms-compat @gol |
17251338 | 198 | -Wabi -Wconversion-null -Wctor-dtor-privacy @gol |
59f9c2ed | 199 | -Wnoexcept -Wnon-virtual-dtor -Wreorder @gol |
899015a0 | 200 | -Weffc++ -Wstrict-null-sentinel @gol |
4bc1997b JM |
201 | -Wno-non-template-friend -Wold-style-cast @gol |
202 | -Woverloaded-virtual -Wno-pmf-conversions @gol | |
4e2db7a8 | 203 | -Wsign-promo} |
74291a4b | 204 | |
46e34f96 ZL |
205 | @item Objective-C and Objective-C++ Language Options |
206 | @xref{Objective-C and Objective-C++ Dialect Options,,Options Controlling | |
207 | Objective-C and Objective-C++ Dialects}. | |
dd508457 | 208 | @gccoptlist{-fconstant-string-class=@var{class-name} @gol |
264fa2db ZL |
209 | -fgnu-runtime -fnext-runtime @gol |
210 | -fno-nil-receivers @gol | |
6e955430 ZL |
211 | -fobjc-call-cxx-cdtors @gol |
212 | -fobjc-direct-dispatch @gol | |
264fa2db | 213 | -fobjc-exceptions @gol |
6e955430 | 214 | -fobjc-gc @gol |
22d8d616 | 215 | -fobjc-std=objc1 @gol |
264fa2db ZL |
216 | -freplace-objc-classes @gol |
217 | -fzero-link @gol | |
218 | -gen-decls @gol | |
6e955430 ZL |
219 | -Wassign-intercept @gol |
220 | -Wno-protocol -Wselector @gol | |
221 | -Wstrict-selector-match @gol | |
222 | -Wundeclared-selector} | |
60de6385 | 223 | |
764dbbf2 GDR |
224 | @item Language Independent Options |
225 | @xref{Language Independent Options,,Options to Control Diagnostic Messages Formatting}. | |
9a94f7f3 | 226 | @gccoptlist{-fmessage-length=@var{n} @gol |
dd508457 BM |
227 | -fdiagnostics-show-location=@r{[}once@r{|}every-line@r{]} @gol |
228 | -fdiagnostics-show-option} | |
764dbbf2 | 229 | |
74291a4b MM |
230 | @item Warning Options |
231 | @xref{Warning Options,,Options to Request or Suppress Warnings}. | |
3a789837 NF |
232 | @gccoptlist{-fsyntax-only fmax-errors=@var{n} -pedantic @gol |
233 | -pedantic-errors @gol | |
f6aa72dd | 234 | -w -Wextra -Wall -Waddress -Waggregate-return -Warray-bounds @gol |
c047ce93 SB |
235 | -Wno-attributes -Wno-builtin-macro-redefined @gol |
236 | -Wc++-compat -Wc++0x-compat -Wcast-align -Wcast-qual @gol | |
e1f1ee86 | 237 | -Wchar-subscripts -Wclobbered -Wcomment @gol |
87cf0651 | 238 | -Wconversion -Wcoverage-mismatch -Wcpp -Wno-deprecated @gol |
1ebc7e68 | 239 | -Wno-deprecated-declarations -Wdisabled-optimization @gol |
0a0b3574 MM |
240 | -Wno-div-by-zero -Wdouble-promotion -Wempty-body -Wenum-compare @gol |
241 | -Wno-endif-labels -Werror -Werror=* @gol | |
c65a01af | 242 | -Wfatal-errors -Wfloat-equal -Wformat -Wformat=2 @gol |
802e3f8c | 243 | -Wno-format-contains-nul -Wno-format-extra-args -Wformat-nonliteral @gol |
a214518f | 244 | -Wformat-security -Wformat-y2k @gol |
e1b7793c | 245 | -Wframe-larger-than=@var{len} -Wjump-misses-init -Wignored-qualifiers @gol |
fb0317c6 | 246 | -Wimplicit -Wimplicit-function-declaration -Wimplicit-int @gol |
c24d4112 | 247 | -Winit-self -Winline @gol |
63a08740 | 248 | -Wno-int-to-pointer-cast -Wno-invalid-offsetof @gol |
e8fc888d | 249 | -Winvalid-pch -Wlarger-than=@var{len} -Wunsafe-loop-optimizations @gol |
63a08740 | 250 | -Wlogical-op -Wlong-long @gol |
eaac4679 | 251 | -Wmain -Wmissing-braces -Wmissing-field-initializers @gol |
b02398bd | 252 | -Wmissing-format-attribute -Wmissing-include-dirs @gol |
7ea6b6cf | 253 | -Wno-mudflap @gol |
71834ad3 | 254 | -Wno-multichar -Wnonnull -Wno-overflow @gol |
2cd36c22 | 255 | -Woverlength-strings -Wpacked -Wpacked-bitfield-compat -Wpadded @gol |
94564826 KT |
256 | -Wparentheses -Wpedantic-ms-format -Wno-pedantic-ms-format @gol |
257 | -Wpointer-arith -Wno-pointer-to-int-cast @gol | |
53a2494e | 258 | -Wredundant-decls @gol |
4bc1997b | 259 | -Wreturn-type -Wsequence-point -Wshadow @gol |
7060db96 | 260 | -Wsign-compare -Wsign-conversion -Wstack-protector @gol |
79bedddc | 261 | -Wstrict-aliasing -Wstrict-aliasing=n @gol |
6ac01510 | 262 | -Wstrict-overflow -Wstrict-overflow=@var{n} @gol |
212580ff | 263 | -Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{]} @gol |
23462d4d | 264 | -Wswitch -Wswitch-default -Wswitch-enum -Wsync-nand @gol |
8ffadef9 MG |
265 | -Wsystem-headers -Wtrampolines -Wtrigraphs -Wtype-limits -Wundef @gol |
266 | -Wuninitialized -Wunknown-pragmas -Wno-pragmas @gol | |
6ec637a4 | 267 | -Wunsuffixed-float-constants -Wunused -Wunused-function @gol |
ab940b73 RW |
268 | -Wunused-label -Wunused-parameter -Wno-unused-result -Wunused-value @gol |
269 | -Wunused-variable -Wunused-but-set-parameter -Wunused-but-set-variable @gol | |
270 | -Wvariadic-macros -Wvla -Wvolatile-register-var -Wwrite-strings} | |
74291a4b | 271 | |
670b0231 | 272 | @item C and Objective-C-only Warning Options |
9a94f7f3 | 273 | @gccoptlist{-Wbad-function-cast -Wmissing-declarations @gol |
b1ed4cb4 MLI |
274 | -Wmissing-parameter-type -Wmissing-prototypes -Wnested-externs @gol |
275 | -Wold-style-declaration -Wold-style-definition @gol | |
05170031 | 276 | -Wstrict-prototypes -Wtraditional -Wtraditional-conversion @gol |
f4e9414e | 277 | -Wdeclaration-after-statement -Wpointer-sign} |
fe50c0eb | 278 | |
74291a4b MM |
279 | @item Debugging Options |
280 | @xref{Debugging Options,,Options for Debugging Your Program or GCC}. | |
9a94f7f3 | 281 | @gccoptlist{-d@var{letters} -dumpspecs -dumpmachine -dumpversion @gol |
0a090f42 | 282 | -fdbg-cnt-list -fdbg-cnt=@var{counter-value-list} @gol |
2aa7c49b | 283 | -fdump-noaddr -fdump-unnumbered -fdump-unnumbered-links @gol |
058e97ec | 284 | -fdump-translation-unit@r{[}-@var{n}@r{]} @gol |
aee96fe9 | 285 | -fdump-class-hierarchy@r{[}-@var{n}@r{]} @gol |
fed39e22 | 286 | -fdump-ipa-all -fdump-ipa-cgraph -fdump-ipa-inline @gol |
9fe0cb7d | 287 | -fdump-statistics @gol |
6de9cd9a | 288 | -fdump-tree-all @gol |
9a94f7f3 JM |
289 | -fdump-tree-original@r{[}-@var{n}@r{]} @gol |
290 | -fdump-tree-optimized@r{[}-@var{n}@r{]} @gol | |
6de9cd9a DN |
291 | -fdump-tree-cfg -fdump-tree-vcg -fdump-tree-alias @gol |
292 | -fdump-tree-ch @gol | |
293 | -fdump-tree-ssa@r{[}-@var{n}@r{]} -fdump-tree-pre@r{[}-@var{n}@r{]} @gol | |
294 | -fdump-tree-ccp@r{[}-@var{n}@r{]} -fdump-tree-dce@r{[}-@var{n}@r{]} @gol | |
295 | -fdump-tree-gimple@r{[}-raw@r{]} -fdump-tree-mudflap@r{[}-@var{n}@r{]} @gol | |
296 | -fdump-tree-dom@r{[}-@var{n}@r{]} @gol | |
297 | -fdump-tree-dse@r{[}-@var{n}@r{]} @gol | |
248fc9f3 | 298 | -fdump-tree-phiprop@r{[}-@var{n}@r{]} @gol |
6de9cd9a DN |
299 | -fdump-tree-phiopt@r{[}-@var{n}@r{]} @gol |
300 | -fdump-tree-forwprop@r{[}-@var{n}@r{]} @gol | |
301 | -fdump-tree-copyrename@r{[}-@var{n}@r{]} @gol | |
79fe1b3b | 302 | -fdump-tree-nrv -fdump-tree-vect @gol |
fa555252 | 303 | -fdump-tree-sink @gol |
6de9cd9a | 304 | -fdump-tree-sra@r{[}-@var{n}@r{]} @gol |
248fc9f3 | 305 | -fdump-tree-forwprop@r{[}-@var{n}@r{]} @gol |
ff2ad0f7 | 306 | -fdump-tree-fre@r{[}-@var{n}@r{]} @gol |
08873e96 | 307 | -fdump-tree-vrp@r{[}-@var{n}@r{]} @gol |
c866976a | 308 | -ftree-vectorizer-verbose=@var{n} @gol |
0bca51f0 | 309 | -fdump-tree-storeccp@r{[}-@var{n}@r{]} @gol |
2153915d AO |
310 | -fdump-final-insns=@var{file} @gol |
311 | -fcompare-debug@r{[}=@var{opts}@r{]} -fcompare-debug-second @gol | |
a37db56b | 312 | -feliminate-dwarf2-dups -feliminate-unused-debug-types @gol |
e713adf6 | 313 | -feliminate-unused-debug-symbols -femit-class-debug-always @gol |
77831620 | 314 | -fenable-icf-debug @gol |
a5573239 | 315 | -fmem-report -fpre-ipa-mem-report -fpost-ipa-mem-report -fprofile-arcs @gol |
a37db56b | 316 | -frandom-seed=@var{string} -fsched-verbose=@var{n} @gol |
e855c69d | 317 | -fsel-sched-verbose -fsel-sched-dump-cfg -fsel-sched-pipelining-verbose @gol |
d3c12306 | 318 | -fstack-usage -ftest-coverage -ftime-report -fvar-tracking @gol |
b55b184a | 319 | -fvar-tracking-assignments -fvar-tracking-assignments-toggle @gol |
53b2323e | 320 | -g -g@var{level} -gtoggle -gcoff -gdwarf-@var{version} @gol |
dc67413d JJ |
321 | -ggdb -gstabs -gstabs+ -gstrict-dwarf -gno-strict-dwarf @gol |
322 | -gvms -gxcoff -gxcoff+ @gol | |
8f57ac5a JJ |
323 | -fno-merge-debug-strings -fno-dwarf2-cfi-asm @gol |
324 | -fdebug-prefix-map=@var{old}=@var{new} @gol | |
39ef6592 LC |
325 | -femit-struct-debug-baseonly -femit-struct-debug-reduced @gol |
326 | -femit-struct-debug-detailed@r{[}=@var{spec-list}@r{]} @gol | |
4bc1997b | 327 | -p -pg -print-file-name=@var{library} -print-libgcc-file-name @gol |
de55f03a | 328 | -print-multi-directory -print-multi-lib -print-multi-os-directory @gol |
4bc1997b | 329 | -print-prog-name=@var{program} -print-search-dirs -Q @gol |
3def1397 | 330 | -print-sysroot -print-sysroot-headers-suffix @gol |
bdde878c | 331 | -save-temps -save-temps=cwd -save-temps=obj -time@r{[}=@var{file}@r{]}} |
74291a4b MM |
332 | |
333 | @item Optimization Options | |
334 | @xref{Optimize Options,,Options that Control Optimization}. | |
ab940b73 | 335 | @gccoptlist{-falign-functions[=@var{n}] -falign-jumps[=@var{n}] @gol |
71733172 KZ |
336 | -falign-labels[=@var{n}] -falign-loops[=@var{n}] -fassociative-math @gol |
337 | -fauto-inc-dec -fbranch-probabilities -fbranch-target-load-optimize @gol | |
338 | -fbranch-target-load-optimize2 -fbtr-bb-exclusive -fcaller-saves @gol | |
ccaeeafe NC |
339 | -fcheck-data-deps -fcombine-stack-adjustments -fconserve-stack @gol |
340 | -fcprop-registers -fcrossjumping @gol | |
ab940b73 RW |
341 | -fcse-follow-jumps -fcse-skip-blocks -fcx-fortran-rules @gol |
342 | -fcx-limited-range @gol | |
8cc6d3e0 | 343 | -fdata-sections -fdce -fdce @gol |
71733172 | 344 | -fdelayed-branch -fdelete-null-pointer-checks -fdse -fdse @gol |
07ffa034 | 345 | -fearly-inlining -fipa-sra -fexpensive-optimizations -ffast-math @gol |
8ce94e44 | 346 | -ffinite-math-only -ffloat-store -fexcess-precision=@var{style} @gol |
16949072 | 347 | -fforward-propagate -ffp-contract=@var{style} -ffunction-sections @gol |
384a5197 | 348 | -fgcse -fgcse-after-reload -fgcse-las -fgcse-lm -fgraphite-identity @gol |
3e293154 MJ |
349 | -fgcse-sm -fif-conversion -fif-conversion2 -findirect-inlining @gol |
350 | -finline-functions -finline-functions-called-once -finline-limit=@var{n} @gol | |
ab940b73 RW |
351 | -finline-small-functions -fipa-cp -fipa-cp-clone -fipa-matrix-reorg @gol |
352 | -fipa-pta -fipa-profile -fipa-pure-const -fipa-reference @gol | |
353 | -fipa-struct-reorg -fira-algorithm=@var{algorithm} @gol | |
22b0982c | 354 | -fira-region=@var{region} @gol |
1833192f | 355 | -fira-loop-pressure -fno-ira-share-save-slots @gol |
058e97ec VM |
356 | -fno-ira-share-spill-slots -fira-verbose=@var{n} @gol |
357 | -fivopts -fkeep-inline-functions -fkeep-static-consts @gol | |
98af4c9f | 358 | -floop-block -floop-flatten -floop-interchange -floop-strip-mine @gol |
3abe8cab JH |
359 | -floop-parallelize-all -flto -flto-compression-level |
360 | -flto-partition=@var{alg} -flto-report -fmerge-all-constants @gol | |
852e4bd2 JH |
361 | -fmerge-constants -fmodulo-sched -fmodulo-sched-allow-regmoves @gol |
362 | -fmove-loop-invariants fmudflap -fmudflapir -fmudflapth -fno-branch-count-reg @gol | |
ab940b73 | 363 | -fno-default-inline @gol |
71733172 KZ |
364 | -fno-defer-pop -fno-function-cse -fno-guess-branch-probability @gol |
365 | -fno-inline -fno-math-errno -fno-peephole -fno-peephole2 @gol | |
366 | -fno-sched-interblock -fno-sched-spec -fno-signed-zeros @gol | |
367 | -fno-toplevel-reorder -fno-trapping-math -fno-zero-initialized-in-bss @gol | |
368 | -fomit-frame-pointer -foptimize-register-move -foptimize-sibling-calls @gol | |
ab940b73 RW |
369 | -fpartial-inlining -fpeel-loops -fpredictive-commoning @gol |
370 | -fprefetch-loop-arrays @gol | |
52c76998 PY |
371 | -fprofile-correction -fprofile-dir=@var{path} -fprofile-generate @gol |
372 | -fprofile-generate=@var{path} @gol | |
2f908293 SP |
373 | -fprofile-use -fprofile-use=@var{path} -fprofile-values @gol |
374 | -freciprocal-math -fregmove -frename-registers -freorder-blocks @gol | |
71733172 KZ |
375 | -freorder-blocks-and-partition -freorder-functions @gol |
376 | -frerun-cse-after-loop -freschedule-modulo-scheduled-loops @gol | |
57257f0d | 377 | -frounding-math -fsched2-use-superblocks -fsched-pressure @gol |
ce18efcb | 378 | -fsched-spec-load -fsched-spec-load-dangerous @gol |
71733172 | 379 | -fsched-stalled-insns-dep[=@var{n}] -fsched-stalled-insns[=@var{n}] @gol |
ee4764a8 | 380 | -fsched-group-heuristic -fsched-critical-path-heuristic @gol |
ce18efcb VM |
381 | -fsched-spec-insn-heuristic -fsched-rank-heuristic @gol |
382 | -fsched-last-insn-heuristic -fsched-dep-count-heuristic @gol | |
8393a9c8 | 383 | -fschedule-insns -fschedule-insns2 -fsection-anchors @gol |
e855c69d AB |
384 | -fselective-scheduling -fselective-scheduling2 @gol |
385 | -fsel-sched-pipelining -fsel-sched-pipelining-outer-loops @gol | |
71733172 KZ |
386 | -fsignaling-nans -fsingle-precision-constant -fsplit-ivs-in-unroller @gol |
387 | -fsplit-wide-types -fstack-protector -fstack-protector-all @gol | |
ab940b73 RW |
388 | -fstrict-aliasing -fstrict-overflow -fthread-jumps -ftracer @gol |
389 | -ftree-bit-ccp @gol | |
c2699190 | 390 | -ftree-builtin-call-dce -ftree-ccp -ftree-ch -ftree-copy-prop @gol |
384a5197 | 391 | -ftree-copyrename -ftree-dce -ftree-dominator-opts -ftree-dse @gol |
bd544141 SP |
392 | -ftree-forwprop -ftree-fre -ftree-loop-if-convert @gol |
393 | -ftree-loop-if-convert-memory-writes -ftree-loop-im @gol | |
20769d5e | 394 | -ftree-phiprop -ftree-loop-distribution -ftree-loop-distribute-patterns @gol |
71733172 | 395 | -ftree-loop-ivcanon -ftree-loop-linear -ftree-loop-optimize @gol |
248fc9f3 | 396 | -ftree-parallelize-loops=@var{n} -ftree-pre -ftree-pta -ftree-reassoc @gol |
dce2b2f6 | 397 | -ftree-sink -ftree-sra -ftree-switch-conversion @gol |
b6e99746 MJ |
398 | -ftree-ter -ftree-vect-loop-version -ftree-vectorize -ftree-vrp @gol |
399 | -funit-at-a-time -funroll-all-loops -funroll-loops @gol | |
400 | -funsafe-loop-optimizations -funsafe-math-optimizations -funswitch-loops @gol | |
71733172 | 401 | -fvariable-expansion-in-unroller -fvect-cost-model -fvpt -fweb @gol |
3abe8cab | 402 | -fwhole-program -fwpa -fuse-linker-plugin @gol |
3af64fd6 | 403 | --param @var{name}=@var{value} |
be6d3f0e | 404 | -O -O0 -O1 -O2 -O3 -Os -Ofast} |
74291a4b MM |
405 | |
406 | @item Preprocessor Options | |
407 | @xref{Preprocessor Options,,Options Controlling the Preprocessor}. | |
c2d635bc | 408 | @gccoptlist{-A@var{question}=@var{answer} @gol |
9a94f7f3 | 409 | -A-@var{question}@r{[}=@var{answer}@r{]} @gol |
4bc1997b JM |
410 | -C -dD -dI -dM -dN @gol |
411 | -D@var{macro}@r{[}=@var{defn}@r{]} -E -H @gol | |
412 | -idirafter @var{dir} @gol | |
413 | -include @var{file} -imacros @var{file} @gol | |
414 | -iprefix @var{file} -iwithprefix @var{dir} @gol | |
bdd42dd9 | 415 | -iwithprefixbefore @var{dir} -isystem @var{dir} @gol |
2b6dd222 | 416 | -imultilib @var{dir} -isysroot @var{dir} @gol |
b20d9f0c AO |
417 | -M -MM -MF -MG -MP -MQ -MT -nostdinc @gol |
418 | -P -fworking-directory -remap @gol | |
9a94f7f3 JM |
419 | -trigraphs -undef -U@var{macro} -Wp,@var{option} @gol |
420 | -Xpreprocessor @var{option}} | |
74291a4b MM |
421 | |
422 | @item Assembler Option | |
423 | @xref{Assembler Options,,Passing Options to the Assembler}. | |
9a94f7f3 | 424 | @gccoptlist{-Wa,@var{option} -Xassembler @var{option}} |
74291a4b MM |
425 | |
426 | @item Linker Options | |
427 | @xref{Link Options,,Options for Linking}. | |
9a94f7f3 | 428 | @gccoptlist{@var{object-file-name} -l@var{library} @gol |
0cbc4d77 | 429 | -nostartfiles -nodefaultlibs -nostdlib -pie -rdynamic @gol |
96be7a11 ILT |
430 | -s -static -static-libgcc -static-libstdc++ -shared @gol |
431 | -shared-libgcc -symbolic @gol | |
3027350e | 432 | -T @var{script} -Wl,@var{option} -Xlinker @var{option} @gol |
4bc1997b | 433 | -u @var{symbol}} |
74291a4b MM |
434 | |
435 | @item Directory Options | |
436 | @xref{Directory Options,,Options for Directory Search}. | |
4adbd5dd MK |
437 | @gccoptlist{-B@var{prefix} -I@var{dir} -iplugindir=@var{dir}} |
438 | -iquote@var{dir} -L@var{dir} -specs=@var{file} -I- | |
439 | --sysroot=@var{dir} | |
74291a4b | 440 | |
74291a4b MM |
441 | @item Machine Dependent Options |
442 | @xref{Submodel Options,,Hardware Models and Configurations}. | |
39bc1876 NS |
443 | @c This list is ordered alphanumerically by subsection name. |
444 | @c Try and put the significant identifier (CPU or system) first, | |
445 | @c so users have a clue at guessing where the ones they want will be. | |
5d22c1a5 | 446 | |
39bc1876 NS |
447 | @emph{ARC Options} |
448 | @gccoptlist{-EB -EL @gol | |
449 | -mmangle-cpu -mcpu=@var{cpu} -mtext=@var{text-section} @gol | |
450 | -mdata=@var{data-section} -mrodata=@var{readonly-data-section}} | |
74291a4b | 451 | |
74291a4b | 452 | @emph{ARM Options} |
9a94f7f3 | 453 | @gccoptlist{-mapcs-frame -mno-apcs-frame @gol |
5848830f | 454 | -mabi=@var{name} @gol |
310668e8 JM |
455 | -mapcs-stack-check -mno-apcs-stack-check @gol |
456 | -mapcs-float -mno-apcs-float @gol | |
457 | -mapcs-reentrant -mno-apcs-reentrant @gol | |
458 | -msched-prolog -mno-sched-prolog @gol | |
459 | -mlittle-endian -mbig-endian -mwords-little-endian @gol | |
34a86306 | 460 | -mfloat-abi=@var{name} -msoft-float -mhard-float -mfpe @gol |
0fd8c3ad | 461 | -mfp16-format=@var{name} |
310668e8 | 462 | -mthumb-interwork -mno-thumb-interwork @gol |
9b66ebb1 | 463 | -mcpu=@var{name} -march=@var{name} -mfpu=@var{name} @gol |
247f8561 | 464 | -mstructure-size-boundary=@var{n} @gol |
4bc1997b | 465 | -mabort-on-noreturn @gol |
310668e8 JM |
466 | -mlong-calls -mno-long-calls @gol |
467 | -msingle-pic-base -mno-single-pic-base @gol | |
247f8561 PB |
468 | -mpic-register=@var{reg} @gol |
469 | -mnop-fun-dllimport @gol | |
9b6b54e2 | 470 | -mcirrus-fix-invalid-insns -mno-cirrus-fix-invalid-insns @gol |
247f8561 | 471 | -mpoke-function-name @gol |
310668e8 JM |
472 | -mthumb -marm @gol |
473 | -mtpcs-frame -mtpcs-leaf-frame @gol | |
d3585b76 | 474 | -mcaller-super-interworking -mcallee-super-interworking @gol |
5fd42423 PB |
475 | -mtp=@var{name} @gol |
476 | -mword-relocations @gol | |
477 | -mfix-cortex-m3-ldrd} | |
74291a4b | 478 | |
39bc1876 | 479 | @emph{AVR Options} |
007a178c | 480 | @gccoptlist{-mmcu=@var{mcu} -mno-interrupts @gol |
4223ff5f | 481 | -mcall-prologues -mtiny-stack -mint8} |
861bb6c1 | 482 | |
0d4a78eb | 483 | @emph{Blackfin Options} |
ea2382be JZ |
484 | @gccoptlist{-mcpu=@var{cpu}@r{[}-@var{sirevision}@r{]} @gol |
485 | -msim -momit-leaf-frame-pointer -mno-omit-leaf-frame-pointer @gol | |
486 | -mspecld-anomaly -mno-specld-anomaly -mcsync-anomaly -mno-csync-anomaly @gol | |
487 | -mlow-64k -mno-low64k -mstack-check-l1 -mid-shared-library @gol | |
488 | -mno-id-shared-library -mshared-library-id=@var{n} @gol | |
489 | -mleaf-id-shared-library -mno-leaf-id-shared-library @gol | |
490 | -msep-data -mno-sep-data -mlong-calls -mno-long-calls @gol | |
bf85bc3d BS |
491 | -mfast-fp -minline-plt -mmulticore -mcorea -mcoreb -msdram @gol |
492 | -micplb} | |
0d4a78eb | 493 | |
39bc1876 NS |
494 | @emph{CRIS Options} |
495 | @gccoptlist{-mcpu=@var{cpu} -march=@var{cpu} -mtune=@var{cpu} @gol | |
496 | -mmax-stack-frame=@var{n} -melinux-stacksize=@var{n} @gol | |
497 | -metrax4 -metrax100 -mpdebug -mcc-init -mno-side-effects @gol | |
498 | -mstack-align -mdata-align -mconst-align @gol | |
499 | -m32-bit -m16-bit -m8-bit -mno-prologue-epilogue -mno-gotplt @gol | |
500 | -melf -maout -melinux -mlinux -sim -sim2 @gol | |
501 | -mmul-bug-workaround -mno-mul-bug-workaround} | |
74291a4b | 502 | |
53054e77 PW |
503 | @emph{CRX Options} |
504 | @gccoptlist{-mmac -mpush-args} | |
505 | ||
48aec0bc | 506 | @emph{Darwin Options} |
6d2f9dd3 JM |
507 | @gccoptlist{-all_load -allowable_client -arch -arch_errors_fatal @gol |
508 | -arch_only -bind_at_load -bundle -bundle_loader @gol | |
509 | -client_name -compatibility_version -current_version @gol | |
5079843a | 510 | -dead_strip @gol |
6d2f9dd3 JM |
511 | -dependency-file -dylib_file -dylinker_install_name @gol |
512 | -dynamic -dynamiclib -exported_symbols_list @gol | |
513 | -filelist -flat_namespace -force_cpusubtype_ALL @gol | |
514 | -force_flat_namespace -headerpad_max_install_names @gol | |
1f1d5130 | 515 | -iframework @gol |
6d2f9dd3 JM |
516 | -image_base -init -install_name -keep_private_externs @gol |
517 | -multi_module -multiply_defined -multiply_defined_unused @gol | |
5079843a DP |
518 | -noall_load -no_dead_strip_inits_and_terms @gol |
519 | -nofixprebinding -nomultidefs -noprebind -noseglinkedit @gol | |
6d2f9dd3 JM |
520 | -pagezero_size -prebind -prebind_all_twolevel_modules @gol |
521 | -private_bundle -read_only_relocs -sectalign @gol | |
522 | -sectobjectsymbols -whyload -seg1addr @gol | |
523 | -sectcreate -sectobjectsymbols -sectorder @gol | |
5826770c | 524 | -segaddr -segs_read_only_addr -segs_read_write_addr @gol |
6d2f9dd3 JM |
525 | -seg_addr_table -seg_addr_table_filename -seglinkedit @gol |
526 | -segprot -segs_read_only_addr -segs_read_write_addr @gol | |
527 | -single_module -static -sub_library -sub_umbrella @gol | |
528 | -twolevel_namespace -umbrella -undefined @gol | |
529 | -unexported_symbols_list -weak_reference_mismatches @gol | |
337f2a22 | 530 | -whatsloaded -F -gused -gfull -mmacosx-version-min=@var{version} @gol |
57164024 | 531 | -mkernel -mone-byte-bool} |
48aec0bc | 532 | |
74291a4b | 533 | @emph{DEC Alpha Options} |
9a94f7f3 | 534 | @gccoptlist{-mno-fp-regs -msoft-float -malpha-as -mgas @gol |
4bc1997b JM |
535 | -mieee -mieee-with-inexact -mieee-conformant @gol |
536 | -mfp-trap-mode=@var{mode} -mfp-rounding-mode=@var{mode} @gol | |
537 | -mtrap-precision=@var{mode} -mbuild-constants @gol | |
58605ba0 RH |
538 | -mcpu=@var{cpu-type} -mtune=@var{cpu-type} @gol |
539 | -mbwx -mmax -mfix -mcix @gol | |
540 | -mfloat-vax -mfloat-ieee @gol | |
9a94f7f3 JM |
541 | -mexplicit-relocs -msmall-data -mlarge-data @gol |
542 | -msmall-text -mlarge-text @gol | |
4bc1997b | 543 | -mmemory-latency=@var{time}} |
74291a4b | 544 | |
d7c23cdc | 545 | @emph{DEC Alpha/VMS Options} |
5e3fef6c | 546 | @gccoptlist{-mvms-return-codes -mdebug-main=@var{prefix} -mmalloc64} |
d7c23cdc | 547 | |
18a3bdcb NC |
548 | @emph{FR30 Options} |
549 | @gccoptlist{-msmall-model -mno-lsim} | |
550 | ||
39bc1876 NS |
551 | @emph{FRV Options} |
552 | @gccoptlist{-mgpr-32 -mgpr-64 -mfpr-32 -mfpr-64 @gol | |
553 | -mhard-float -msoft-float @gol | |
554 | -malloc-cc -mfixed-cc -mdword -mno-dword @gol | |
555 | -mdouble -mno-double @gol | |
556 | -mmedia -mno-media -mmuladd -mno-muladd @gol | |
c557edf4 RS |
557 | -mfdpic -minline-plt -mgprel-ro -multilib-library-pic @gol |
558 | -mlinked-fp -mlong-calls -malign-labels @gol | |
559 | -mlibrary-pic -macc-4 -macc-8 @gol | |
39bc1876 | 560 | -mpack -mno-pack -mno-eflags -mcond-move -mno-cond-move @gol |
38c28a25 | 561 | -moptimize-membar -mno-optimize-membar @gol |
39bc1876 NS |
562 | -mscc -mno-scc -mcond-exec -mno-cond-exec @gol |
563 | -mvliw-branch -mno-vliw-branch @gol | |
564 | -mmulti-cond-exec -mno-multi-cond-exec -mnested-cond-exec @gol | |
565 | -mno-nested-cond-exec -mtomcat-stats @gol | |
e4dd71de | 566 | -mTLS -mtls @gol |
39bc1876 NS |
567 | -mcpu=@var{cpu}} |
568 | ||
464aea98 | 569 | @emph{GNU/Linux Options} |
51b9db92 MK |
570 | @gccoptlist{-mglibc -muclibc -mbionic -mandroid @gol |
571 | -tno-android-cc -tno-android-ld} | |
464aea98 | 572 | |
74291a4b | 573 | @emph{H8/300 Options} |
9a94f7f3 | 574 | @gccoptlist{-mrelax -mh -ms -mn -mint32 -malign-300} |
74291a4b | 575 | |
39bc1876 NS |
576 | @emph{HPPA Options} |
577 | @gccoptlist{-march=@var{architecture-type} @gol | |
578 | -mbig-switch -mdisable-fpregs -mdisable-indexing @gol | |
579 | -mfast-indirect-calls -mgas -mgnu-ld -mhp-ld @gol | |
a2017852 | 580 | -mfixed-range=@var{register-range} @gol |
39bc1876 NS |
581 | -mjump-in-delay -mlinker-opt -mlong-calls @gol |
582 | -mlong-load-store -mno-big-switch -mno-disable-fpregs @gol | |
583 | -mno-disable-indexing -mno-fast-indirect-calls -mno-gas @gol | |
584 | -mno-jump-in-delay -mno-long-load-store @gol | |
585 | -mno-portable-runtime -mno-soft-float @gol | |
586 | -mno-space-regs -msoft-float -mpa-risc-1-0 @gol | |
587 | -mpa-risc-1-1 -mpa-risc-2-0 -mportable-runtime @gol | |
588 | -mschedule=@var{cpu-type} -mspace-regs -msio -mwsio @gol | |
d711cf67 | 589 | -munix=@var{unix-std} -nolibdld -static -threads} |
74291a4b | 590 | |
39bc1876 NS |
591 | @emph{i386 and x86-64 Options} |
592 | @gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol | |
593 | -mfpmath=@var{unit} @gol | |
594 | -masm=@var{dialect} -mno-fancy-math-387 @gol | |
c33104d6 | 595 | -mno-fp-ret-in-387 -msoft-float @gol |
39bc1876 | 596 | -mno-wide-multiply -mrtd -malign-double @gol |
2e3f842f | 597 | -mpreferred-stack-boundary=@var{num} |
ab940b73 | 598 | -mincoming-stack-boundary=@var{num} @gol |
2767a7f2 | 599 | -mcld -mcx16 -msahf -mmovbe -mcrc32 -mrecip -mvzeroupper @gol |
31cb596a | 600 | -mmmx -msse -msse2 -msse3 -mssse3 -msse4.1 -msse4.2 -msse4 -mavx @gol |
4ee89d5f | 601 | -maes -mpclmul -mfsgsbase -mrdrnd -mf16c -mfused-madd @gol |
94d13ad1 | 602 | -msse4a -m3dnow -mpopcnt -mabm -mbmi -mtbm -mfma4 -mxop -mlwp @gol |
39bc1876 | 603 | -mthreads -mno-align-stringops -minline-all-stringops @gol |
9946ca2d | 604 | -minline-stringops-dynamically -mstringop-strategy=@var{alg} @gol |
39bc1876 | 605 | -mpush-args -maccumulate-outgoing-args -m128bit-long-double @gol |
fa283935 | 606 | -m96bit-long-double -mregparm=@var{num} -msseregparm @gol |
2770264a RO |
607 | -mveclibabi=@var{type} -mvect8-ret-in-mem @gol |
608 | -mpc32 -mpc64 -mpc80 -mstackrealign @gol | |
1f97667f | 609 | -momit-leaf-frame-pointer -mno-red-zone -mno-tls-direct-seg-refs @gol |
51212b32 | 610 | -mcmodel=@var{code-model} -mabi=@var{name} @gol |
04e1d06b | 611 | -m32 -m64 -mlarge-data-threshold=@var{num} @gol |
26ec9308 | 612 | -msse2avx -mfentry -m8bit-idiv} |
56b2d7a7 | 613 | |
39bc1876 NS |
614 | @emph{IA-64 Options} |
615 | @gccoptlist{-mbig-endian -mlittle-endian -mgnu-as -mgnu-ld -mno-pic @gol | |
bf3c6caf SE |
616 | -mvolatile-asm-stop -mregister-names -msdata -mno-sdata @gol |
617 | -mconstant-gp -mauto-pic -mfused-madd @gol | |
618 | -minline-float-divide-min-latency @gol | |
39bc1876 | 619 | -minline-float-divide-max-throughput @gol |
bf3c6caf | 620 | -mno-inline-float-divide @gol |
39bc1876 | 621 | -minline-int-divide-min-latency @gol |
28b43def | 622 | -minline-int-divide-max-throughput @gol |
bf3c6caf | 623 | -mno-inline-int-divide @gol |
28b43def | 624 | -minline-sqrt-min-latency -minline-sqrt-max-throughput @gol |
bf3c6caf SE |
625 | -mno-inline-sqrt @gol |
626 | -mdwarf2-asm -mearly-stop-bits @gol | |
28b43def | 627 | -mfixed-range=@var{register-range} -mtls-size=@var{tls-size} @gol |
bf3c6caf SE |
628 | -mtune=@var{cpu-type} -milp32 -mlp64 @gol |
629 | -msched-br-data-spec -msched-ar-data-spec -msched-control-spec @gol | |
048d0d36 | 630 | -msched-br-in-data-spec -msched-ar-in-data-spec -msched-in-control-spec @gol |
bf3c6caf SE |
631 | -msched-spec-ldc -msched-spec-control-ldc @gol |
632 | -msched-prefer-non-data-spec-insns -msched-prefer-non-control-spec-insns @gol | |
633 | -msched-stop-bits-after-every-cycle -msched-count-spec-in-critical-path @gol | |
634 | -msel-sched-dont-check-control-spec -msched-fp-mem-deps-zero-cost @gol | |
635 | -msched-max-memory-insns-hard-limit -msched-max-memory-insns=@var{max-insns}} | |
282a61e6 | 636 | |
dcad28fd DR |
637 | @emph{IA-64/VMS Options} |
638 | @gccoptlist{-mvms-return-codes -mdebug-main=@var{prefix} -mmalloc64} | |
639 | ||
aa4945c1 JB |
640 | @emph{LM32 Options} |
641 | @gccoptlist{-mbarrel-shift-enabled -mdivide-enabled -mmultiply-enabled @gol | |
642 | -msign-extend-enabled -muser-enabled} | |
643 | ||
39bc1876 NS |
644 | @emph{M32R/D Options} |
645 | @gccoptlist{-m32r2 -m32rx -m32r @gol | |
646 | -mdebug @gol | |
647 | -malign-loops -mno-align-loops @gol | |
648 | -missue-rate=@var{number} @gol | |
649 | -mbranch-cost=@var{number} @gol | |
650 | -mmodel=@var{code-size-model-type} @gol | |
651 | -msdata=@var{sdata-type} @gol | |
652 | -mno-flush-func -mflush-func=@var{name} @gol | |
653 | -mno-flush-trap -mflush-trap=@var{number} @gol | |
654 | -G @var{num}} | |
83575957 | 655 | |
38b2d076 DD |
656 | @emph{M32C Options} |
657 | @gccoptlist{-mcpu=@var{cpu} -msim -memregs=@var{number}} | |
658 | ||
39bc1876 | 659 | @emph{M680x0 Options} |
900ec02d JB |
660 | @gccoptlist{-march=@var{arch} -mcpu=@var{cpu} -mtune=@var{tune} |
661 | -m68000 -m68020 -m68020-40 -m68020-60 -m68030 -m68040 @gol | |
662 | -m68060 -mcpu32 -m5200 -m5206e -m528x -m5307 -m5407 @gol | |
64826589 NS |
663 | -mcfv4e -mbitfield -mno-bitfield -mc68000 -mc68020 @gol |
664 | -mnobitfield -mrtd -mno-rtd -mdiv -mno-div -mshort @gol | |
665 | -mno-short -mhard-float -m68881 -msoft-float -mpcrel @gol | |
39bc1876 | 666 | -malign-int -mstrict-align -msep-data -mno-sep-data @gol |
884316ff JM |
667 | -mshared-library-id=n -mid-shared-library -mno-id-shared-library @gol |
668 | -mxgot -mno-xgot} | |
789a3090 | 669 | |
39bc1876 NS |
670 | @emph{M68hc1x Options} |
671 | @gccoptlist{-m6811 -m6812 -m68hc11 -m68hc12 -m68hcs12 @gol | |
672 | -mauto-incdec -minmax -mlong-calls -mshort @gol | |
673 | -msoft-reg-count=@var{count}} | |
052a4b28 | 674 | |
789a3090 | 675 | @emph{MCore Options} |
9a94f7f3 | 676 | @gccoptlist{-mhardlit -mno-hardlit -mdiv -mno-div -mrelax-immediates @gol |
310668e8 JM |
677 | -mno-relax-immediates -mwide-bitfields -mno-wide-bitfields @gol |
678 | -m4byte-functions -mno-4byte-functions -mcallgraph-data @gol | |
679 | -mno-callgraph-data -mslow-bytes -mno-slow-bytes -mno-lsim @gol | |
680 | -mlittle-endian -mbig-endian -m210 -m340 -mstack-increment} | |
f84271d9 | 681 | |
e2491744 DD |
682 | @emph{MeP Options} |
683 | @gccoptlist{-mabsdiff -mall-opts -maverage -mbased=@var{n} -mbitops @gol | |
684 | -mc=@var{n} -mclip -mconfig=@var{name} -mcop -mcop32 -mcop64 -mivc2 @gol | |
685 | -mdc -mdiv -meb -mel -mio-volatile -ml -mleadz -mm -mminmax @gol | |
686 | -mmult -mno-opts -mrepeat -ms -msatur -msdram -msim -msimnovec -mtf @gol | |
687 | -mtiny=@var{n}} | |
688 | ||
80920132 ME |
689 | @emph{MicroBlaze Options} |
690 | @gccoptlist{-msoft-float -mhard-float -msmall-divides -mcpu=@var{cpu} @gol | |
691 | -mmemcpy -mxl-soft-mul -mxl-soft-div -mxl-barrel-shift @gol | |
692 | -mxl-pattern-compare -mxl-stack-check -mxl-gp-opt -mno-clearbss @gol | |
693 | -mxl-multiply-high -mxl-float-convert -mxl-float-sqrt @gol | |
694 | -mxl-mode-@var{app-model}} | |
695 | ||
39bc1876 NS |
696 | @emph{MIPS Options} |
697 | @gccoptlist{-EL -EB -march=@var{arch} -mtune=@var{arch} @gol | |
f2d6ca50 AN |
698 | -mips1 -mips2 -mips3 -mips4 -mips32 -mips32r2 @gol |
699 | -mips64 -mips64r2 @gol | |
f9e4a411 | 700 | -mips16 -mno-mips16 -mflip-mips16 @gol |
1ec3b87b | 701 | -minterlink-mips16 -mno-interlink-mips16 @gol |
f9e4a411 | 702 | -mabi=@var{abi} -mabicalls -mno-abicalls @gol |
e21d5757 DJ |
703 | -mshared -mno-shared -mplt -mno-plt -mxgot -mno-xgot @gol |
704 | -mgp32 -mgp64 -mfp32 -mfp64 -mhard-float -msoft-float @gol | |
500fc425 | 705 | -msingle-float -mdouble-float -mdsp -mno-dsp -mdspr2 -mno-dspr2 @gol |
0bb7b92e | 706 | -mfpu=@var{fpu-type} @gol |
0aa222d1 | 707 | -msmartmips -mno-smartmips @gol |
500fc425 | 708 | -mpaired-single -mno-paired-single -mdmx -mno-mdmx @gol |
66471b47 | 709 | -mips3d -mno-mips3d -mmt -mno-mt -mllsc -mno-llsc @gol |
fb8136b2 | 710 | -mlong64 -mlong32 -msym32 -mno-sym32 @gol |
a318179e RS |
711 | -G@var{num} -mlocal-sdata -mno-local-sdata @gol |
712 | -mextern-sdata -mno-extern-sdata -mgpopt -mno-gopt @gol | |
713 | -membedded-data -mno-embedded-data @gol | |
39bc1876 | 714 | -muninit-const-in-rodata -mno-uninit-const-in-rodata @gol |
c93c5160 | 715 | -mcode-readable=@var{setting} @gol |
500fc425 TS |
716 | -msplit-addresses -mno-split-addresses @gol |
717 | -mexplicit-relocs -mno-explicit-relocs @gol | |
39bc1876 | 718 | -mcheck-zero-division -mno-check-zero-division @gol |
9f0df97a | 719 | -mdivide-traps -mdivide-breaks @gol |
39bc1876 NS |
720 | -mmemcpy -mno-memcpy -mlong-calls -mno-long-calls @gol |
721 | -mmad -mno-mad -mfused-madd -mno-fused-madd -nocpp @gol | |
722 | -mfix-r4000 -mno-fix-r4000 -mfix-r4400 -mno-fix-r4400 @gol | |
ee9a72e5 JK |
723 | -mfix-r10000 -mno-fix-r10000 -mfix-vr4120 -mno-fix-vr4120 @gol |
724 | -mfix-vr4130 -mno-fix-vr4130 -mfix-sb1 -mno-fix-sb1 @gol | |
39bc1876 | 725 | -mflush-func=@var{func} -mno-flush-func @gol |
a05bea76 | 726 | -mbranch-cost=@var{num} -mbranch-likely -mno-branch-likely @gol |
39bc1876 | 727 | -mfp-exceptions -mno-fp-exceptions @gol |
b53da244 | 728 | -mvr4130-align -mno-vr4130-align -msynci -mno-synci @gol |
c376dbfb | 729 | -mrelax-pic-calls -mno-relax-pic-calls -mmcount-ra-address} |
bcf684c7 | 730 | |
39bc1876 NS |
731 | @emph{MMIX Options} |
732 | @gccoptlist{-mlibfuncs -mno-libfuncs -mepsilon -mno-epsilon -mabi=gnu @gol | |
733 | -mabi=mmixware -mzero-extend -mknuthdiv -mtoplevel-symbols @gol | |
734 | -melf -mbranch-predict -mno-branch-predict -mbase-addresses @gol | |
735 | -mno-base-addresses -msingle-exit -mno-single-exit} | |
df6194d4 | 736 | |
39bc1876 NS |
737 | @emph{MN10300 Options} |
738 | @gccoptlist{-mmult-bug -mno-mult-bug @gol | |
f3f63737 NC |
739 | -mno-am33 -mam33 -mam33-2 -mam34 @gol |
740 | -mtune=@var{cpu-type} @gol | |
b1eb8119 | 741 | -mreturn-pointer-on-d0 @gol |
39bc1876 | 742 | -mno-crt0 -mrelax} |
91abf72d | 743 | |
9f85bca7 | 744 | @emph{PDP-11 Options} |
9a94f7f3 | 745 | @gccoptlist{-mfpu -msoft-float -mac0 -mno-ac0 -m40 -m45 -m10 @gol |
9f85bca7 JM |
746 | -mbcopy -mbcopy-builtin -mint32 -mno-int16 @gol |
747 | -mint16 -mno-int32 -mfloat32 -mno-float64 @gol | |
748 | -mfloat64 -mno-float32 -mabshi -mno-abshi @gol | |
749 | -mbranch-expensive -mbranch-cheap @gol | |
dde9c901 | 750 | -munix-asm -mdec-asm} |
9f85bca7 | 751 | |
358da97e | 752 | @emph{picoChip Options} |
ab940b73 | 753 | @gccoptlist{-mae=@var{ae_type} -mvliw-lookahead=@var{N} @gol |
358da97e HS |
754 | -msymbol-as-address -mno-inefficient-warnings} |
755 | ||
39bc1876 NS |
756 | @emph{PowerPC Options} |
757 | See RS/6000 and PowerPC Options. | |
758 | ||
759 | @emph{RS/6000 and PowerPC Options} | |
760 | @gccoptlist{-mcpu=@var{cpu-type} @gol | |
761 | -mtune=@var{cpu-type} @gol | |
070b27da | 762 | -mcmodel=@var{code-model} @gol |
39bc1876 NS |
763 | -mpower -mno-power -mpower2 -mno-power2 @gol |
764 | -mpowerpc -mpowerpc64 -mno-powerpc @gol | |
765 | -maltivec -mno-altivec @gol | |
766 | -mpowerpc-gpopt -mno-powerpc-gpopt @gol | |
767 | -mpowerpc-gfxopt -mno-powerpc-gfxopt @gol | |
29e6733c MM |
768 | -mmfcrf -mno-mfcrf -mpopcntb -mno-popcntb -mpopcntd -mno-popcntd @gol |
769 | -mfprnd -mno-fprnd @gol | |
4daf6471 | 770 | -mcmpb -mno-cmpb -mmfpgpr -mno-mfpgpr -mhard-dfp -mno-hard-dfp @gol |
39bc1876 NS |
771 | -mnew-mnemonics -mold-mnemonics @gol |
772 | -mfull-toc -mminimal-toc -mno-fp-in-toc -mno-sum-in-toc @gol | |
de17c25f | 773 | -m64 -m32 -mxl-compat -mno-xl-compat -mpe @gol |
39bc1876 NS |
774 | -malign-power -malign-natural @gol |
775 | -msoft-float -mhard-float -mmultiple -mno-multiple @gol | |
696e45ba | 776 | -msingle-float -mdouble-float -msimple-fpu @gol |
39bc1876 | 777 | -mstring -mno-string -mupdate -mno-update @gol |
001b9eb6 | 778 | -mavoid-indexed-addresses -mno-avoid-indexed-addresses @gol |
39bc1876 NS |
779 | -mfused-madd -mno-fused-madd -mbit-align -mno-bit-align @gol |
780 | -mstrict-align -mno-strict-align -mrelocatable @gol | |
781 | -mno-relocatable -mrelocatable-lib -mno-relocatable-lib @gol | |
782 | -mtoc -mno-toc -mlittle -mlittle-endian -mbig -mbig-endian @gol | |
042abba2 | 783 | -mdynamic-no-pic -maltivec -mswdiv -msingle-pic-base @gol |
39bc1876 NS |
784 | -mprioritize-restricted-insns=@var{priority} @gol |
785 | -msched-costly-dep=@var{dependence_type} @gol | |
786 | -minsert-sched-nops=@var{scheme} @gol | |
787 | -mcall-sysv -mcall-netbsd @gol | |
788 | -maix-struct-return -msvr4-struct-return @gol | |
7f970b70 | 789 | -mabi=@var{abi-type} -msecure-plt -mbss-plt @gol |
d95016e0 | 790 | -mblock-move-inline-limit=@var{num} @gol |
78f5898b | 791 | -misel -mno-isel @gol |
39bc1876 | 792 | -misel=yes -misel=no @gol |
78f5898b | 793 | -mspe -mno-spe @gol |
39bc1876 | 794 | -mspe=yes -mspe=no @gol |
96038623 | 795 | -mpaired @gol |
c921bad8 | 796 | -mgen-cell-microcode -mwarn-cell-microcode @gol |
78f5898b | 797 | -mvrsave -mno-vrsave @gol |
131aeb82 | 798 | -mmulhw -mno-mulhw @gol |
716019c0 | 799 | -mdlmzb -mno-dlmzb @gol |
4d4cbc0e | 800 | -mfloat-gprs=yes -mfloat-gprs=no -mfloat-gprs=single -mfloat-gprs=double @gol |
39bc1876 NS |
801 | -mprototype -mno-prototype @gol |
802 | -msim -mmvme -mads -myellowknife -memb -msdata @gol | |
92902797 | 803 | -msdata=@var{opt} -mvxworks -G @var{num} -pthread @gol |
8bcc0304 MM |
804 | -mrecip -mrecip=@var{opt} -mno-recip -mrecip-precision |
805 | -mno-recip-precision @gol | |
688e4919 | 806 | -mveclibabi=@var{type} -mfriz -mno-friz} |
39bc1876 | 807 | |
65a324b4 | 808 | @emph{RX Options} |
9595a419 | 809 | @gccoptlist{-m64bit-doubles -m32bit-doubles -fpu -nofpu@gol |
1890bccc | 810 | -mcpu=@gol |
65a324b4 NC |
811 | -mbig-endian-data -mlittle-endian-data @gol |
812 | -msmall-data @gol | |
813 | -msim -mno-sim@gol | |
814 | -mas100-syntax -mno-as100-syntax@gol | |
815 | -mrelax@gol | |
816 | -mmax-constant-size=@gol | |
9595a419 NC |
817 | -mint-register=@gol |
818 | -msave-acc-in-interrupts} | |
65a324b4 | 819 | |
39bc1876 NS |
820 | @emph{S/390 and zSeries Options} |
821 | @gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol | |
59a1bff3 AK |
822 | -mhard-float -msoft-float -mhard-dfp -mno-hard-dfp @gol |
823 | -mlong-double-64 -mlong-double-128 @gol | |
f61a2c7d | 824 | -mbackchain -mno-backchain -mpacked-stack -mno-packed-stack @gol |
39bc1876 NS |
825 | -msmall-exec -mno-small-exec -mmvcle -mno-mvcle @gol |
826 | -m64 -m31 -mdebug -mno-debug -mesa -mzarch @gol | |
d75f90f1 AK |
827 | -mtpf-trace -mno-tpf-trace -mfused-madd -mno-fused-madd @gol |
828 | -mwarn-framesize -mwarn-dynamicstack -mstack-size -mstack-guard} | |
39bc1876 | 829 | |
93ef7c1f | 830 | @emph{Score Options} |
c6681463 CL |
831 | @gccoptlist{-meb -mel @gol |
832 | -mnhwloop @gol | |
833 | -muls @gol | |
93ef7c1f | 834 | -mmac @gol |
c6681463 | 835 | -mscore5 -mscore5u -mscore7 -mscore7d} |
cb7ad97b | 836 | |
39bc1876 | 837 | @emph{SH Options} |
b4589acc TY |
838 | @gccoptlist{-m1 -m2 -m2e @gol |
839 | -m2a-nofpu -m2a-single-only -m2a-single -m2a @gol | |
840 | -m3 -m3e @gol | |
39bc1876 | 841 | -m4-nofpu -m4-single-only -m4-single -m4 @gol |
312209c6 | 842 | -m4a-nofpu -m4a-single-only -m4a-single -m4a -m4al @gol |
39bc1876 NS |
843 | -m5-64media -m5-64media-nofpu @gol |
844 | -m5-32media -m5-32media-nofpu @gol | |
845 | -m5-compact -m5-compact-nofpu @gol | |
846 | -mb -ml -mdalign -mrelax @gol | |
6a799f6e | 847 | -mbigtable -mfmovd -mhitachi -mrenesas -mno-renesas -mnomacsave @gol |
9eb3a0dd | 848 | -mieee -mbitops -misize -minline-ic_invalidate -mpadstruct -mspace @gol |
73a4d10b | 849 | -mprefergot -musermode -multcost=@var{number} -mdiv=@var{strategy} @gol |
3217af3e | 850 | -mdivsi3_libfunc=@var{name} -mfixed-range=@var{register-range} @gol |
73a4d10b | 851 | -madjust-unroll -mindexed-addressing -mgettrcost=@var{number} -mpt-fixed @gol |
7a296495 | 852 | -maccumulate-outgoing-args -minvalid-symbols} |
39bc1876 | 853 | |
c28aa982 RO |
854 | @emph{Solaris 2 Options} |
855 | @gccoptlist{-mimpure-text -mno-impure-text @gol | |
856 | -threads -pthreads -pthread} | |
857 | ||
39bc1876 NS |
858 | @emph{SPARC Options} |
859 | @gccoptlist{-mcpu=@var{cpu-type} @gol | |
860 | -mtune=@var{cpu-type} @gol | |
861 | -mcmodel=@var{code-model} @gol | |
862 | -m32 -m64 -mapp-regs -mno-app-regs @gol | |
863 | -mfaster-structs -mno-faster-structs @gol | |
864 | -mfpu -mno-fpu -mhard-float -msoft-float @gol | |
865 | -mhard-quad-float -msoft-quad-float @gol | |
c28aa982 | 866 | -mlittle-endian @gol |
39bc1876 NS |
867 | -mstack-bias -mno-stack-bias @gol |
868 | -munaligned-doubles -mno-unaligned-doubles @gol | |
c28aa982 | 869 | -mv8plus -mno-v8plus -mvis -mno-vis} |
39bc1876 | 870 | |
85d9c13c TS |
871 | @emph{SPU Options} |
872 | @gccoptlist{-mwarn-reloc -merror-reloc @gol | |
873 | -msafe-dma -munsafe-dma @gol | |
874 | -mbranch-hints @gol | |
32fb22af | 875 | -msmall-mem -mlarge-mem -mstdmain @gol |
299456f3 BE |
876 | -mfixed-range=@var{register-range} @gol |
877 | -mea32 -mea64 @gol | |
878 | -maddress-space-conversion -mno-address-space-conversion @gol | |
879 | -mcache-size=@var{cache-size} @gol | |
880 | -matomic-updates -mno-atomic-updates} | |
85d9c13c | 881 | |
39bc1876 NS |
882 | @emph{System V Options} |
883 | @gccoptlist{-Qy -Qn -YP,@var{paths} -Ym,@var{dir}} | |
884 | ||
39bc1876 NS |
885 | @emph{V850 Options} |
886 | @gccoptlist{-mlong-calls -mno-long-calls -mep -mno-ep @gol | |
887 | -mprolog-function -mno-prolog-function -mspace @gol | |
888 | -mtda=@var{n} -msda=@var{n} -mzda=@var{n} @gol | |
889 | -mapp-regs -mno-app-regs @gol | |
890 | -mdisable-callt -mno-disable-callt @gol | |
223a9d64 N |
891 | -mv850e2v3 @gol |
892 | -mv850e2 @gol | |
39bc1876 NS |
893 | -mv850e1 @gol |
894 | -mv850e @gol | |
895 | -mv850 -mbig-switch} | |
896 | ||
897 | @emph{VAX Options} | |
898 | @gccoptlist{-mg -mgnu -munix} | |
899 | ||
cd773ac4 RS |
900 | @emph{VxWorks Options} |
901 | @gccoptlist{-mrtp -non-static -Bstatic -Bdynamic @gol | |
902 | -Xbind-lazy -Xbind-now} | |
903 | ||
39bc1876 NS |
904 | @emph{x86-64 Options} |
905 | See i386 and x86-64 Options. | |
906 | ||
46994828 KT |
907 | @emph{i386 and x86-64 Windows Options} |
908 | @gccoptlist{-mconsole -mcygwin -mno-cygwin -mdll | |
ab940b73 RW |
909 | -mnop-fun-dllimport -mthread @gol |
910 | -municode -mwin32 -mwindows -fno-set-stack-executable} | |
46994828 | 911 | |
69a0611f | 912 | @emph{Xstormy16 Options} |
9a94f7f3 | 913 | @gccoptlist{-msim} |
69a0611f | 914 | |
03984308 | 915 | @emph{Xtensa Options} |
6cedbe44 | 916 | @gccoptlist{-mconst16 -mno-const16 @gol |
9a94f7f3 | 917 | -mfused-madd -mno-fused-madd @gol |
1b408ba1 | 918 | -mforce-no-pic @gol |
66e58b33 | 919 | -mserialize-volatile -mno-serialize-volatile @gol |
9a94f7f3 JM |
920 | -mtext-section-literals -mno-text-section-literals @gol |
921 | -mtarget-align -mno-target-align @gol | |
922 | -mlongcalls -mno-longcalls} | |
03984308 | 923 | |
39bc1876 NS |
924 | @emph{zSeries Options} |
925 | See S/390 and zSeries Options. | |
70899148 | 926 | |
74291a4b MM |
927 | @item Code Generation Options |
928 | @xref{Code Gen Options,,Options for Code Generation Conventions}. | |
9a94f7f3 JM |
929 | @gccoptlist{-fcall-saved-@var{reg} -fcall-used-@var{reg} @gol |
930 | -ffixed-@var{reg} -fexceptions @gol | |
5d22c1a5 | 931 | -fnon-call-exceptions -funwind-tables @gol |
a944ceb9 | 932 | -fasynchronous-unwind-tables @gol |
4bc1997b | 933 | -finhibit-size-directive -finstrument-functions @gol |
8d5a7d1f ILT |
934 | -finstrument-functions-exclude-function-list=@var{sym},@var{sym},@dots{} @gol |
935 | -finstrument-functions-exclude-file-list=@var{file},@var{file},@dots{} @gol | |
dc170a87 | 936 | -fno-common -fno-ident @gol |
24a4dd31 | 937 | -fpcc-struct-return -fpic -fPIC -fpie -fPIE @gol |
82c0180d | 938 | -fno-jump-tables @gol |
e0d9d0dd | 939 | -frecord-gcc-switches @gol |
f5e605e5 | 940 | -freg-struct-return -fshort-enums @gol |
271bd540 | 941 | -fshort-double -fshort-wchar @gol |
467cecf3 | 942 | -fverbose-asm -fpack-struct[=@var{n}] -fstack-check @gol |
4bc1997b | 943 | -fstack-limit-register=@var{reg} -fstack-limit-symbol=@var{sym} @gol |
7458026b | 944 | -fno-stack-limit -fsplit-stack @gol |
0698a1d2 | 945 | -fleading-underscore -ftls-model=@var{model} @gol |
d7afec4b | 946 | -ftrapv -fwrapv -fbounds-check @gol |
c1721efb | 947 | -fvisibility -fstrict-volatile-bitfields} |
74291a4b MM |
948 | @end table |
949 | ||
950 | @menu | |
951 | * Overall Options:: Controlling the kind of output: | |
952 | an executable, object files, assembler files, | |
953 | or preprocessed source. | |
954 | * C Dialect Options:: Controlling the variant of C language compiled. | |
955 | * C++ Dialect Options:: Variations on C++. | |
46e34f96 ZL |
956 | * Objective-C and Objective-C++ Dialect Options:: Variations on Objective-C |
957 | and Objective-C++. | |
764dbbf2 | 958 | * Language Independent Options:: Controlling how diagnostics should be |
02f52e19 | 959 | formatted. |
74291a4b MM |
960 | * Warning Options:: How picky should the compiler be? |
961 | * Debugging Options:: Symbol tables, measurements, and debugging dumps. | |
962 | * Optimize Options:: How much optimization? | |
963 | * Preprocessor Options:: Controlling header files and macro definitions. | |
964 | Also, getting dependency information for Make. | |
965 | * Assembler Options:: Passing options to the assembler. | |
966 | * Link Options:: Specifying libraries and so on. | |
967 | * Directory Options:: Where to find header files and libraries. | |
968 | Where to find the compiler executable files. | |
a743d340 | 969 | * Spec Files:: How to pass switches to sub-processes. |
0c2d1a2a | 970 | * Target Options:: Running a cross-compiler, or an old version of GCC. |
74291a4b MM |
971 | @end menu |
972 | ||
973 | @node Overall Options | |
974 | @section Options Controlling the Kind of Output | |
975 | ||
976 | Compilation can involve up to four stages: preprocessing, compilation | |
d1bd0ded GK |
977 | proper, assembly and linking, always in that order. GCC is capable of |
978 | preprocessing and compiling several files either into several | |
979 | assembler input files, or into one assembler input file; then each | |
980 | assembler input file produces an object file, and linking combines all | |
981 | the object files (those newly compiled, and those specified as input) | |
982 | into an executable file. | |
74291a4b MM |
983 | |
984 | @cindex file name suffix | |
985 | For any given input file, the file name suffix determines what kind of | |
986 | compilation is done: | |
987 | ||
2642624b | 988 | @table @gcctabopt |
74291a4b MM |
989 | @item @var{file}.c |
990 | C source code which must be preprocessed. | |
991 | ||
992 | @item @var{file}.i | |
993 | C source code which should not be preprocessed. | |
994 | ||
995 | @item @var{file}.ii | |
996 | C++ source code which should not be preprocessed. | |
997 | ||
998 | @item @var{file}.m | |
46e34f96 ZL |
999 | Objective-C source code. Note that you must link with the @file{libobjc} |
1000 | library to make an Objective-C program work. | |
74291a4b | 1001 | |
b9265ec1 JM |
1002 | @item @var{file}.mi |
1003 | Objective-C source code which should not be preprocessed. | |
1004 | ||
46e34f96 ZL |
1005 | @item @var{file}.mm |
1006 | @itemx @var{file}.M | |
1007 | Objective-C++ source code. Note that you must link with the @file{libobjc} | |
1008 | library to make an Objective-C++ program work. Note that @samp{.M} refers | |
1009 | to a literal capital M@. | |
1010 | ||
1011 | @item @var{file}.mii | |
1012 | Objective-C++ source code which should not be preprocessed. | |
1013 | ||
74291a4b | 1014 | @item @var{file}.h |
46e34f96 | 1015 | C, C++, Objective-C or Objective-C++ header file to be turned into a |
9cc54940 AC |
1016 | precompiled header (default), or C, C++ header file to be turned into an |
1017 | Ada spec (via the @option{-fdump-ada-spec} switch). | |
74291a4b MM |
1018 | |
1019 | @item @var{file}.cc | |
b9265ec1 | 1020 | @itemx @var{file}.cp |
74291a4b MM |
1021 | @itemx @var{file}.cxx |
1022 | @itemx @var{file}.cpp | |
ee8acf89 | 1023 | @itemx @var{file}.CPP |
b9265ec1 | 1024 | @itemx @var{file}.c++ |
74291a4b MM |
1025 | @itemx @var{file}.C |
1026 | C++ source code which must be preprocessed. Note that in @samp{.cxx}, | |
1027 | the last two letters must both be literally @samp{x}. Likewise, | |
161d7b59 | 1028 | @samp{.C} refers to a literal capital C@. |
74291a4b | 1029 | |
6e955430 ZL |
1030 | @item @var{file}.mm |
1031 | @itemx @var{file}.M | |
1032 | Objective-C++ source code which must be preprocessed. | |
1033 | ||
1034 | @item @var{file}.mii | |
1035 | Objective-C++ source code which should not be preprocessed. | |
1036 | ||
17211ab5 GK |
1037 | @item @var{file}.hh |
1038 | @itemx @var{file}.H | |
5958f5cb AM |
1039 | @itemx @var{file}.hp |
1040 | @itemx @var{file}.hxx | |
1041 | @itemx @var{file}.hpp | |
1042 | @itemx @var{file}.HPP | |
1043 | @itemx @var{file}.h++ | |
1044 | @itemx @var{file}.tcc | |
9cc54940 | 1045 | C++ header file to be turned into a precompiled header or Ada spec. |
17211ab5 | 1046 | |
b9265ec1 JM |
1047 | @item @var{file}.f |
1048 | @itemx @var{file}.for | |
3135ce84 | 1049 | @itemx @var{file}.ftn |
80a0c50a | 1050 | Fixed form Fortran source code which should not be preprocessed. |
b9265ec1 JM |
1051 | |
1052 | @item @var{file}.F | |
3135ce84 | 1053 | @itemx @var{file}.FOR |
b9265ec1 JM |
1054 | @itemx @var{file}.fpp |
1055 | @itemx @var{file}.FPP | |
3135ce84 | 1056 | @itemx @var{file}.FTN |
80a0c50a | 1057 | Fixed form Fortran source code which must be preprocessed (with the traditional |
b9265ec1 JM |
1058 | preprocessor). |
1059 | ||
6de9cd9a DN |
1060 | @item @var{file}.f90 |
1061 | @itemx @var{file}.f95 | |
3135ce84 FXC |
1062 | @itemx @var{file}.f03 |
1063 | @itemx @var{file}.f08 | |
80a0c50a | 1064 | Free form Fortran source code which should not be preprocessed. |
6de9cd9a | 1065 | |
5a006700 MR |
1066 | @item @var{file}.F90 |
1067 | @itemx @var{file}.F95 | |
3135ce84 FXC |
1068 | @itemx @var{file}.F03 |
1069 | @itemx @var{file}.F08 | |
80a0c50a | 1070 | Free form Fortran source code which must be preprocessed (with the |
5a006700 MR |
1071 | traditional preprocessor). |
1072 | ||
7a938933 ILT |
1073 | @item @var{file}.go |
1074 | Go source code. | |
1075 | ||
b9265ec1 JM |
1076 | @c FIXME: Descriptions of Java file types. |
1077 | @c @var{file}.java | |
1078 | @c @var{file}.class | |
1079 | @c @var{file}.zip | |
1080 | @c @var{file}.jar | |
1081 | ||
e23381df GB |
1082 | @item @var{file}.ads |
1083 | Ada source code file which contains a library unit declaration (a | |
1084 | declaration of a package, subprogram, or generic, or a generic | |
1085 | instantiation), or a library unit renaming declaration (a package, | |
1086 | generic, or subprogram renaming declaration). Such files are also | |
1087 | called @dfn{specs}. | |
1088 | ||
33558d94 | 1089 | @item @var{file}.adb |
e23381df GB |
1090 | Ada source code file containing a library unit body (a subprogram or |
1091 | package body). Such files are also called @dfn{bodies}. | |
1092 | ||
b9265ec1 | 1093 | @c GCC also knows about some suffixes for languages not yet included: |
b9265ec1 JM |
1094 | @c Pascal: |
1095 | @c @var{file}.p | |
1096 | @c @var{file}.pas | |
80a0c50a TS |
1097 | @c Ratfor: |
1098 | @c @var{file}.r | |
b9265ec1 | 1099 | |
74291a4b MM |
1100 | @item @var{file}.s |
1101 | Assembler code. | |
1102 | ||
1103 | @item @var{file}.S | |
55b8093e | 1104 | @itemx @var{file}.sx |
74291a4b MM |
1105 | Assembler code which must be preprocessed. |
1106 | ||
1107 | @item @var{other} | |
1108 | An object file to be fed straight into linking. | |
1109 | Any file name with no recognized suffix is treated this way. | |
1110 | @end table | |
1111 | ||
cd3bb277 | 1112 | @opindex x |
630d3d5a | 1113 | You can specify the input language explicitly with the @option{-x} option: |
74291a4b | 1114 | |
2642624b | 1115 | @table @gcctabopt |
74291a4b MM |
1116 | @item -x @var{language} |
1117 | Specify explicitly the @var{language} for the following input files | |
1118 | (rather than letting the compiler choose a default based on the file | |
1119 | name suffix). This option applies to all following input files until | |
630d3d5a | 1120 | the next @option{-x} option. Possible values for @var{language} are: |
3ab51846 | 1121 | @smallexample |
2962b1bb | 1122 | c c-header cpp-output |
17211ab5 | 1123 | c++ c++-header c++-cpp-output |
46e34f96 ZL |
1124 | objective-c objective-c-header objective-c-cpp-output |
1125 | objective-c++ objective-c++-header objective-c++-cpp-output | |
74291a4b | 1126 | assembler assembler-with-cpp |
e23381df | 1127 | ada |
b885a4c1 | 1128 | f77 f77-cpp-input f95 f95-cpp-input |
7a938933 | 1129 | go |
e23381df | 1130 | java |
3ab51846 | 1131 | @end smallexample |
74291a4b MM |
1132 | |
1133 | @item -x none | |
1134 | Turn off any specification of a language, so that subsequent files are | |
630d3d5a | 1135 | handled according to their file name suffixes (as they are if @option{-x} |
74291a4b | 1136 | has not been used at all). |
14a774a9 RK |
1137 | |
1138 | @item -pass-exit-codes | |
cd3bb277 | 1139 | @opindex pass-exit-codes |
bedc7537 | 1140 | Normally the @command{gcc} program will exit with the code of 1 if any |
14a774a9 | 1141 | phase of the compiler returns a non-success return code. If you specify |
630d3d5a | 1142 | @option{-pass-exit-codes}, the @command{gcc} program will instead return with |
14a774a9 | 1143 | numerically highest error produced by any phase that returned an error |
ddaf3b86 VR |
1144 | indication. The C, C++, and Fortran frontends return 4, if an internal |
1145 | compiler error is encountered. | |
74291a4b MM |
1146 | @end table |
1147 | ||
1148 | If you only want some of the stages of compilation, you can use | |
630d3d5a JM |
1149 | @option{-x} (or filename suffixes) to tell @command{gcc} where to start, and |
1150 | one of the options @option{-c}, @option{-S}, or @option{-E} to say where | |
bedc7537 NC |
1151 | @command{gcc} is to stop. Note that some combinations (for example, |
1152 | @samp{-x cpp-output -E}) instruct @command{gcc} to do nothing at all. | |
74291a4b | 1153 | |
2642624b | 1154 | @table @gcctabopt |
74291a4b | 1155 | @item -c |
cd3bb277 | 1156 | @opindex c |
74291a4b MM |
1157 | Compile or assemble the source files, but do not link. The linking |
1158 | stage simply is not done. The ultimate output is in the form of an | |
1159 | object file for each source file. | |
1160 | ||
1161 | By default, the object file name for a source file is made by replacing | |
1162 | the suffix @samp{.c}, @samp{.i}, @samp{.s}, etc., with @samp{.o}. | |
1163 | ||
1164 | Unrecognized input files, not requiring compilation or assembly, are | |
1165 | ignored. | |
1166 | ||
1167 | @item -S | |
cd3bb277 | 1168 | @opindex S |
74291a4b MM |
1169 | Stop after the stage of compilation proper; do not assemble. The output |
1170 | is in the form of an assembler code file for each non-assembler input | |
1171 | file specified. | |
1172 | ||
1173 | By default, the assembler file name for a source file is made by | |
1174 | replacing the suffix @samp{.c}, @samp{.i}, etc., with @samp{.s}. | |
1175 | ||
1176 | Input files that don't require compilation are ignored. | |
1177 | ||
1178 | @item -E | |
cd3bb277 | 1179 | @opindex E |
74291a4b MM |
1180 | Stop after the preprocessing stage; do not run the compiler proper. The |
1181 | output is in the form of preprocessed source code, which is sent to the | |
1182 | standard output. | |
1183 | ||
1184 | Input files which don't require preprocessing are ignored. | |
1185 | ||
1186 | @cindex output file option | |
1187 | @item -o @var{file} | |
cd3bb277 | 1188 | @opindex o |
74291a4b MM |
1189 | Place output in file @var{file}. This applies regardless to whatever |
1190 | sort of output is being produced, whether it be an executable file, | |
1191 | an object file, an assembler file or preprocessed C code. | |
1192 | ||
488061c8 GK |
1193 | If @option{-o} is not specified, the default is to put an executable |
1194 | file in @file{a.out}, the object file for | |
1195 | @file{@var{source}.@var{suffix}} in @file{@var{source}.o}, its | |
1196 | assembler file in @file{@var{source}.s}, a precompiled header file in | |
1197 | @file{@var{source}.@var{suffix}.gch}, and all preprocessed C source on | |
1198 | standard output. | |
74291a4b MM |
1199 | |
1200 | @item -v | |
cd3bb277 | 1201 | @opindex v |
74291a4b MM |
1202 | Print (on standard error output) the commands executed to run the stages |
1203 | of compilation. Also print the version number of the compiler driver | |
1204 | program and of the preprocessor and the compiler proper. | |
1205 | ||
e8b3c8ac IR |
1206 | @item -### |
1207 | @opindex ### | |
09b201fc JJ |
1208 | Like @option{-v} except the commands are not executed and arguments |
1209 | are quoted unless they contain only alphanumeric characters or @code{./-_}. | |
1210 | This is useful for shell scripts to capture the driver-generated command lines. | |
e8b3c8ac | 1211 | |
74291a4b | 1212 | @item -pipe |
cd3bb277 | 1213 | @opindex pipe |
74291a4b MM |
1214 | Use pipes rather than temporary files for communication between the |
1215 | various stages of compilation. This fails to work on some systems where | |
1216 | the assembler is unable to read from a pipe; but the GNU assembler has | |
1217 | no trouble. | |
844642e6 NC |
1218 | |
1219 | @item --help | |
cd3bb277 | 1220 | @opindex help |
844642e6 | 1221 | Print (on the standard output) a description of the command line options |
bedc7537 NC |
1222 | understood by @command{gcc}. If the @option{-v} option is also specified |
1223 | then @option{--help} will also be passed on to the various processes | |
1224 | invoked by @command{gcc}, so that they can display the command line options | |
c662432e NC |
1225 | they accept. If the @option{-Wextra} option has also been specified |
1226 | (prior to the @option{--help} option), then command line options which | |
1227 | have no documentation associated with them will also be displayed. | |
10501d8f CC |
1228 | |
1229 | @item --target-help | |
cd3bb277 | 1230 | @opindex target-help |
c662432e | 1231 | Print (on the standard output) a description of target-specific command |
67e6ba46 NC |
1232 | line options for each tool. For some targets extra target-specific |
1233 | information may also be printed. | |
e03b7153 | 1234 | |
0631b69f | 1235 | @item --help=@{@var{class}@r{|[}^@r{]}@var{qualifier}@}@r{[},@dots{}@r{]} |
c662432e | 1236 | Print (on the standard output) a description of the command line |
0631b69f RW |
1237 | options understood by the compiler that fit into all specified classes |
1238 | and qualifiers. These are the supported classes: | |
c662432e | 1239 | |
5bb43e6d BM |
1240 | @table @asis |
1241 | @item @samp{optimizers} | |
c662432e NC |
1242 | This will display all of the optimization options supported by the |
1243 | compiler. | |
1244 | ||
5bb43e6d | 1245 | @item @samp{warnings} |
c662432e NC |
1246 | This will display all of the options controlling warning messages |
1247 | produced by the compiler. | |
1248 | ||
5bb43e6d | 1249 | @item @samp{target} |
c662432e NC |
1250 | This will display target-specific options. Unlike the |
1251 | @option{--target-help} option however, target-specific options of the | |
1252 | linker and assembler will not be displayed. This is because those | |
1253 | tools do not currently support the extended @option{--help=} syntax. | |
1254 | ||
5bb43e6d | 1255 | @item @samp{params} |
c662432e NC |
1256 | This will display the values recognized by the @option{--param} |
1257 | option. | |
5bb43e6d BM |
1258 | |
1259 | @item @var{language} | |
7a61cf6f NC |
1260 | This will display the options supported for @var{language}, where |
1261 | @var{language} is the name of one of the languages supported in this | |
5bb43e6d | 1262 | version of GCC. |
06a97569 BM |
1263 | |
1264 | @item @samp{common} | |
1265 | This will display the options that are common to all languages. | |
c662432e NC |
1266 | @end table |
1267 | ||
0631b69f | 1268 | These are the supported qualifiers: |
c662432e | 1269 | |
5bb43e6d BM |
1270 | @table @asis |
1271 | @item @samp{undocumented} | |
c662432e NC |
1272 | Display only those options which are undocumented. |
1273 | ||
5bb43e6d | 1274 | @item @samp{joined} |
c662432e NC |
1275 | Display options which take an argument that appears after an equal |
1276 | sign in the same continuous piece of text, such as: | |
1277 | @samp{--help=target}. | |
1278 | ||
5bb43e6d | 1279 | @item @samp{separate} |
c662432e NC |
1280 | Display options which take an argument that appears as a separate word |
1281 | following the original option, such as: @samp{-o output-file}. | |
1282 | @end table | |
1283 | ||
1284 | Thus for example to display all the undocumented target-specific | |
1285 | switches supported by the compiler the following can be used: | |
1286 | ||
1287 | @smallexample | |
1288 | --help=target,undocumented | |
1289 | @end smallexample | |
1290 | ||
1291 | The sense of a qualifier can be inverted by prefixing it with the | |
0631b69f | 1292 | @samp{^} character, so for example to display all binary warning |
021efafc | 1293 | options (i.e., ones that are either on or off and that do not take an |
c662432e NC |
1294 | argument), which have a description the following can be used: |
1295 | ||
1296 | @smallexample | |
1297 | --help=warnings,^joined,^undocumented | |
1298 | @end smallexample | |
1299 | ||
0631b69f RW |
1300 | The argument to @option{--help=} should not consist solely of inverted |
1301 | qualifiers. | |
1302 | ||
1303 | Combining several classes is possible, although this usually | |
c662432e NC |
1304 | restricts the output by so much that there is nothing to display. One |
1305 | case where it does work however is when one of the classes is | |
1306 | @var{target}. So for example to display all the target-specific | |
1307 | optimization options the following can be used: | |
1308 | ||
1309 | @smallexample | |
1310 | --help=target,optimizers | |
1311 | @end smallexample | |
1312 | ||
1313 | The @option{--help=} option can be repeated on the command line. Each | |
1314 | successive use will display its requested class of options, skipping | |
1315 | those that have already been displayed. | |
1316 | ||
1317 | If the @option{-Q} option appears on the command line before the | |
1318 | @option{--help=} option, then the descriptive text displayed by | |
1319 | @option{--help=} is changed. Instead of describing the displayed | |
1320 | options, an indication is given as to whether the option is enabled, | |
1321 | disabled or set to a specific value (assuming that the compiler | |
1322 | knows this at the point where the @option{--help=} option is used). | |
1323 | ||
1324 | Here is a truncated example from the ARM port of @command{gcc}: | |
1325 | ||
1326 | @smallexample | |
1327 | % gcc -Q -mabi=2 --help=target -c | |
1328 | The following options are target specific: | |
1329 | -mabi= 2 | |
1330 | -mabort-on-noreturn [disabled] | |
1331 | -mapcs [disabled] | |
1332 | @end smallexample | |
1333 | ||
1334 | The output is sensitive to the effects of previous command line | |
1335 | options, so for example it is possible to find out which optimizations | |
1336 | are enabled at @option{-O2} by using: | |
1337 | ||
1338 | @smallexample | |
0631b69f | 1339 | -Q -O2 --help=optimizers |
c662432e NC |
1340 | @end smallexample |
1341 | ||
1342 | Alternatively you can discover which binary optimizations are enabled | |
1343 | by @option{-O3} by using: | |
1344 | ||
1345 | @smallexample | |
1346 | gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts | |
1347 | gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts | |
1348 | diff /tmp/O2-opts /tmp/O3-opts | grep enabled | |
1349 | @end smallexample | |
1350 | ||
ba0c638e SB |
1351 | @item -no-canonical-prefixes |
1352 | @opindex no-canonical-prefixes | |
1353 | Do not expand any symbolic links, resolve references to @samp{/../} | |
1354 | or @samp{/./}, or make the path absolute when generating a relative | |
1355 | prefix. | |
1356 | ||
e03b7153 RS |
1357 | @item --version |
1358 | @opindex version | |
8a36672b | 1359 | Display the version number and copyrights of the invoked GCC@. |
9d530538 | 1360 | |
fe7df9c4 SP |
1361 | @item -wrapper |
1362 | @opindex wrapper | |
1363 | Invoke all subcommands under a wrapper program. It takes a single | |
1364 | comma separated list as an argument, which will be used to invoke | |
1365 | the wrapper: | |
1366 | ||
1367 | @smallexample | |
1368 | gcc -c t.c -wrapper gdb,--args | |
1369 | @end smallexample | |
1370 | ||
1371 | This will invoke all subprograms of gcc under "gdb --args", | |
1372 | thus cc1 invocation will be "gdb --args cc1 ...". | |
1373 | ||
68a607d8 DN |
1374 | @item -fplugin=@var{name}.so |
1375 | Load the plugin code in file @var{name}.so, assumed to be a | |
1376 | shared object to be dlopen'd by the compiler. The base name of | |
1377 | the shared object file is used to identify the plugin for the | |
1378 | purposes of argument parsing (See | |
1379 | @option{-fplugin-arg-@var{name}-@var{key}=@var{value}} below). | |
1380 | Each plugin should define the callback functions specified in the | |
1381 | Plugins API. | |
1382 | ||
1383 | @item -fplugin-arg-@var{name}-@var{key}=@var{value} | |
1384 | Define an argument called @var{key} with a value of @var{value} | |
1385 | for the plugin called @var{name}. | |
1386 | ||
9cc54940 AC |
1387 | @item -fdump-ada-spec@r{[}-slim@r{]} |
1388 | For C and C++ source and include files, generate corresponding Ada | |
1389 | specs. @xref{Generating Ada Bindings for C and C++ headers,,, gnat_ugn, | |
1390 | GNAT User's Guide}, which provides detailed documentation on this feature. | |
1391 | ||
c6a13190 ILT |
1392 | @item -fdump-go-spec=@var{file} |
1393 | For input files in any language, generate corresponding Go | |
1394 | declarations in @var{file}. This generates Go @code{const}, | |
1395 | @code{type}, @code{var}, and @code{func} declarations which may be a | |
1396 | useful way to start writing a Go interface to code written in some | |
1397 | other language. | |
1398 | ||
9d530538 | 1399 | @include @value{srcdir}/../libiberty/at-file.texi |
74291a4b MM |
1400 | @end table |
1401 | ||
1402 | @node Invoking G++ | |
1403 | @section Compiling C++ Programs | |
1404 | ||
1405 | @cindex suffixes for C++ source | |
1406 | @cindex C++ source file suffixes | |
1407 | C++ source files conventionally use one of the suffixes @samp{.C}, | |
17211ab5 | 1408 | @samp{.cc}, @samp{.cpp}, @samp{.CPP}, @samp{.c++}, @samp{.cp}, or |
5958f5cb AM |
1409 | @samp{.cxx}; C++ header files often use @samp{.hh}, @samp{.hpp}, |
1410 | @samp{.H}, or (for shared template code) @samp{.tcc}; and | |
0c2d1a2a | 1411 | preprocessed C++ files use the suffix @samp{.ii}. GCC recognizes |
bba975d4 | 1412 | files with these names and compiles them as C++ programs even if you |
17211ab5 GK |
1413 | call the compiler the same way as for compiling C programs (usually |
1414 | with the name @command{gcc}). | |
74291a4b MM |
1415 | |
1416 | @findex g++ | |
1417 | @findex c++ | |
63b08b60 MS |
1418 | However, the use of @command{gcc} does not add the C++ library. |
1419 | @command{g++} is a program that calls GCC and treats @samp{.c}, | |
1420 | @samp{.h} and @samp{.i} files as C++ source files instead of C source | |
1421 | files unless @option{-x} is used, and automatically specifies linking | |
5548b688 MS |
1422 | against the C++ library. This program is also useful when |
1423 | precompiling a C header file with a @samp{.h} extension for use in C++ | |
1424 | compilations. On many systems, @command{g++} is also installed with | |
1425 | the name @command{c++}. | |
74291a4b | 1426 | |
bedc7537 | 1427 | @cindex invoking @command{g++} |
74291a4b MM |
1428 | When you compile C++ programs, you may specify many of the same |
1429 | command-line options that you use for compiling programs in any | |
1430 | language; or command-line options meaningful for C and related | |
1431 | languages; or options that are meaningful only for C++ programs. | |
1432 | @xref{C Dialect Options,,Options Controlling C Dialect}, for | |
161d7b59 | 1433 | explanations of options for languages related to C@. |
74291a4b MM |
1434 | @xref{C++ Dialect Options,,Options Controlling C++ Dialect}, for |
1435 | explanations of options that are meaningful only for C++ programs. | |
1436 | ||
1437 | @node C Dialect Options | |
1438 | @section Options Controlling C Dialect | |
1439 | @cindex dialect options | |
1440 | @cindex language dialect options | |
1441 | @cindex options, dialect | |
1442 | ||
1443 | The following options control the dialect of C (or languages derived | |
46e34f96 ZL |
1444 | from C, such as C++, Objective-C and Objective-C++) that the compiler |
1445 | accepts: | |
74291a4b | 1446 | |
2642624b | 1447 | @table @gcctabopt |
74291a4b | 1448 | @cindex ANSI support |
c1030c7c | 1449 | @cindex ISO support |
74291a4b | 1450 | @item -ansi |
cd3bb277 | 1451 | @opindex ansi |
7e1542b9 | 1452 | In C mode, this is equivalent to @samp{-std=c90}. In C++ mode, it is |
89fe7f1b | 1453 | equivalent to @samp{-std=c++98}. |
74291a4b | 1454 | |
c1030c7c | 1455 | This turns off certain features of GCC that are incompatible with ISO |
3764f879 | 1456 | C90 (when compiling C code), or of standard C++ (when compiling C++ code), |
0c2d1a2a | 1457 | such as the @code{asm} and @code{typeof} keywords, and |
74291a4b MM |
1458 | predefined macros such as @code{unix} and @code{vax} that identify the |
1459 | type of system you are using. It also enables the undesirable and | |
02f52e19 | 1460 | rarely used ISO trigraph feature. For the C compiler, |
0c2d1a2a | 1461 | it disables recognition of C++ style @samp{//} comments as well as |
775afb25 | 1462 | the @code{inline} keyword. |
74291a4b MM |
1463 | |
1464 | The alternate keywords @code{__asm__}, @code{__extension__}, | |
1465 | @code{__inline__} and @code{__typeof__} continue to work despite | |
630d3d5a | 1466 | @option{-ansi}. You would not want to use them in an ISO C program, of |
74291a4b | 1467 | course, but it is useful to put them in header files that might be included |
630d3d5a | 1468 | in compilations done with @option{-ansi}. Alternate predefined macros |
74291a4b | 1469 | such as @code{__unix__} and @code{__vax__} are also available, with or |
630d3d5a | 1470 | without @option{-ansi}. |
74291a4b | 1471 | |
630d3d5a JM |
1472 | The @option{-ansi} option does not cause non-ISO programs to be |
1473 | rejected gratuitously. For that, @option{-pedantic} is required in | |
1474 | addition to @option{-ansi}. @xref{Warning Options}. | |
74291a4b | 1475 | |
630d3d5a | 1476 | The macro @code{__STRICT_ANSI__} is predefined when the @option{-ansi} |
74291a4b MM |
1477 | option is used. Some header files may notice this macro and refrain |
1478 | from declaring certain functions or defining certain macros that the | |
c1030c7c | 1479 | ISO standard doesn't call for; this is to avoid interfering with any |
74291a4b MM |
1480 | programs that might use these names for other things. |
1481 | ||
89fe7f1b | 1482 | Functions that would normally be built in but do not have semantics |
c771326b | 1483 | defined by ISO C (such as @code{alloca} and @code{ffs}) are not built-in |
89fe7f1b | 1484 | functions when @option{-ansi} is used. @xref{Other Builtins,,Other |
f0523f02 | 1485 | built-in functions provided by GCC}, for details of the functions |
01702459 | 1486 | affected. |
74291a4b | 1487 | |
49419c8f | 1488 | @item -std= |
cd3bb277 | 1489 | @opindex std |
89fe7f1b MLI |
1490 | Determine the language standard. @xref{Standards,,Language Standards |
1491 | Supported by GCC}, for details of these standard versions. This option | |
7a61cf6f | 1492 | is currently only supported when compiling C or C++. |
89fe7f1b | 1493 | |
7e1542b9 | 1494 | The compiler can accept several base standards, such as @samp{c90} or |
93e052a8 | 1495 | @samp{c++98}, and GNU dialects of those standards, such as |
7e1542b9 | 1496 | @samp{gnu90} or @samp{gnu++98}. By specifying a base standard, the |
93e052a8 MLI |
1497 | compiler will accept all programs following that standard and those |
1498 | using GNU extensions that do not contradict it. For example, | |
7e1542b9 | 1499 | @samp{-std=c90} turns off certain features of GCC that are |
93e052a8 MLI |
1500 | incompatible with ISO C90, such as the @code{asm} and @code{typeof} |
1501 | keywords, but not other GNU extensions that do not have a meaning in | |
1502 | ISO C90, such as omitting the middle term of a @code{?:} | |
a640c13b | 1503 | expression. On the other hand, by specifying a GNU dialect of a |
93e052a8 MLI |
1504 | standard, all features the compiler support are enabled, even when |
1505 | those features change the meaning of the base standard and some | |
1506 | strict-conforming programs may be rejected. The particular standard | |
1507 | is used by @option{-pedantic} to identify which features are GNU | |
1508 | extensions given that version of the standard. For example | |
7e1542b9 | 1509 | @samp{-std=gnu90 -pedantic} would warn about C++ style @samp{//} |
93e052a8 MLI |
1510 | comments, while @samp{-std=gnu99 -pedantic} would not. |
1511 | ||
89fe7f1b | 1512 | A value for this option must be provided; possible values are |
3932261a | 1513 | |
ee457005 | 1514 | @table @samp |
7e1542b9 MLI |
1515 | @item c90 |
1516 | @itemx c89 | |
aee96fe9 | 1517 | @itemx iso9899:1990 |
93e052a8 MLI |
1518 | Support all ISO C90 programs (certain GNU extensions that conflict |
1519 | with ISO C90 are disabled). Same as @option{-ansi} for C code. | |
3043b30e ML |
1520 | |
1521 | @item iso9899:199409 | |
3764f879 | 1522 | ISO C90 as modified in amendment 1. |
3043b30e | 1523 | |
49419c8f | 1524 | @item c99 |
aee96fe9 JM |
1525 | @itemx c9x |
1526 | @itemx iso9899:1999 | |
1527 | @itemx iso9899:199x | |
1528 | ISO C99. Note that this standard is not yet fully supported; see | |
1529 | @w{@uref{http://gcc.gnu.org/c99status.html}} for more information. The | |
1530 | names @samp{c9x} and @samp{iso9899:199x} are deprecated. | |
3043b30e | 1531 | |
2778d766 JM |
1532 | @item c1x |
1533 | ISO C1X, the draft of the next revision of the ISO C standard. | |
1534 | Support is limited and experimental and features enabled by this | |
1535 | option may be changed or removed if changed in or removed from the | |
1536 | standard draft. | |
1537 | ||
7e1542b9 MLI |
1538 | @item gnu90 |
1539 | @itemx gnu89 | |
93e052a8 MLI |
1540 | GNU dialect of ISO C90 (including some C99 features). This |
1541 | is the default for C code. | |
3043b30e | 1542 | |
49419c8f | 1543 | @item gnu99 |
31775d31 | 1544 | @itemx gnu9x |
93e052a8 | 1545 | GNU dialect of ISO C99. When ISO C99 is fully implemented in GCC, |
d15a05b3 | 1546 | this will become the default. The name @samp{gnu9x} is deprecated. |
49419c8f | 1547 | |
2778d766 JM |
1548 | @item gnu1x |
1549 | GNU dialect of ISO C1X. Support is limited and experimental and | |
1550 | features enabled by this option may be changed or removed if changed | |
1551 | in or removed from the standard draft. | |
1552 | ||
f749a36b | 1553 | @item c++98 |
93e052a8 MLI |
1554 | The 1998 ISO C++ standard plus amendments. Same as @option{-ansi} for |
1555 | C++ code. | |
f749a36b NB |
1556 | |
1557 | @item gnu++98 | |
93e052a8 MLI |
1558 | GNU dialect of @option{-std=c++98}. This is the default for |
1559 | C++ code. | |
966541e3 DG |
1560 | |
1561 | @item c++0x | |
1562 | The working draft of the upcoming ISO C++0x standard. This option | |
1563 | enables experimental features that are likely to be included in | |
1564 | C++0x. The working draft is constantly changing, and any feature that is | |
1565 | enabled by this flag may be removed from future versions of GCC if it is | |
1566 | not part of the C++0x standard. | |
1567 | ||
1568 | @item gnu++0x | |
93e052a8 MLI |
1569 | GNU dialect of @option{-std=c++0x}. This option enables |
1570 | experimental features that may be removed in future versions of GCC. | |
ee457005 | 1571 | @end table |
3043b30e | 1572 | |
da1c7394 ILT |
1573 | @item -fgnu89-inline |
1574 | @opindex fgnu89-inline | |
1575 | The option @option{-fgnu89-inline} tells GCC to use the traditional | |
1576 | GNU semantics for @code{inline} functions when in C99 mode. | |
1577 | @xref{Inline,,An Inline Function is As Fast As a Macro}. This option | |
1578 | is accepted and ignored by GCC versions 4.1.3 up to but not including | |
1579 | 4.3. In GCC versions 4.3 and later it changes the behavior of GCC in | |
1580 | C99 mode. Using this option is roughly equivalent to adding the | |
1581 | @code{gnu_inline} function attribute to all inline functions | |
1582 | (@pxref{Function Attributes}). | |
1583 | ||
1584 | The option @option{-fno-gnu89-inline} explicitly tells GCC to use the | |
1585 | C99 semantics for @code{inline} when in C99 or gnu99 mode (i.e., it | |
1586 | specifies the default behavior). This option was first supported in | |
7e1542b9 MLI |
1587 | GCC 4.3. This option is not supported in @option{-std=c90} or |
1588 | @option{-std=gnu90} mode. | |
da1c7394 | 1589 | |
44c7bd63 | 1590 | The preprocessor macros @code{__GNUC_GNU_INLINE__} and |
da1c7394 ILT |
1591 | @code{__GNUC_STDC_INLINE__} may be used to check which semantics are |
1592 | in effect for @code{inline} functions. @xref{Common Predefined | |
7d07e4ea | 1593 | Macros,,,cpp,The C Preprocessor}. |
da1c7394 | 1594 | |
b1018de6 AO |
1595 | @item -aux-info @var{filename} |
1596 | @opindex aux-info | |
1597 | Output to the given filename prototyped declarations for all functions | |
1598 | declared and/or defined in a translation unit, including those in header | |
161d7b59 | 1599 | files. This option is silently ignored in any language other than C@. |
b1018de6 AO |
1600 | |
1601 | Besides declarations, the file indicates, in comments, the origin of | |
1602 | each declaration (source file and line), whether the declaration was | |
1603 | implicit, prototyped or unprototyped (@samp{I}, @samp{N} for new or | |
1604 | @samp{O} for old, respectively, in the first character after the line | |
1605 | number and the colon), and whether it came from a declaration or a | |
1606 | definition (@samp{C} or @samp{F}, respectively, in the following | |
1607 | character). In the case of function definitions, a K&R-style list of | |
1608 | arguments followed by their declarations is also provided, inside | |
1609 | comments, after the declaration. | |
1610 | ||
74291a4b | 1611 | @item -fno-asm |
cd3bb277 | 1612 | @opindex fno-asm |
74291a4b MM |
1613 | Do not recognize @code{asm}, @code{inline} or @code{typeof} as a |
1614 | keyword, so that code can use these words as identifiers. You can use | |
1615 | the keywords @code{__asm__}, @code{__inline__} and @code{__typeof__} | |
630d3d5a | 1616 | instead. @option{-ansi} implies @option{-fno-asm}. |
74291a4b MM |
1617 | |
1618 | In C++, this switch only affects the @code{typeof} keyword, since | |
1619 | @code{asm} and @code{inline} are standard keywords. You may want to | |
630d3d5a | 1620 | use the @option{-fno-gnu-keywords} flag instead, which has the same |
5490d604 JM |
1621 | effect. In C99 mode (@option{-std=c99} or @option{-std=gnu99}), this |
1622 | switch only affects the @code{asm} and @code{typeof} keywords, since | |
1623 | @code{inline} is a standard keyword in ISO C99. | |
74291a4b MM |
1624 | |
1625 | @item -fno-builtin | |
a3926fe1 | 1626 | @itemx -fno-builtin-@var{function} |
cd3bb277 | 1627 | @opindex fno-builtin |
c771326b JM |
1628 | @cindex built-in functions |
1629 | Don't recognize built-in functions that do not begin with | |
01702459 | 1630 | @samp{__builtin_} as prefix. @xref{Other Builtins,,Other built-in |
f0523f02 | 1631 | functions provided by GCC}, for details of the functions affected, |
c771326b | 1632 | including those which are not built-in functions when @option{-ansi} or |
5490d604 JM |
1633 | @option{-std} options for strict ISO C conformance are used because they |
1634 | do not have an ISO standard meaning. | |
74291a4b | 1635 | |
c771326b | 1636 | GCC normally generates special code to handle certain built-in functions |
74291a4b MM |
1637 | more efficiently; for instance, calls to @code{alloca} may become single |
1638 | instructions that adjust the stack directly, and calls to @code{memcpy} | |
1639 | may become inline copy loops. The resulting code is often both smaller | |
1640 | and faster, but since the function calls no longer appear as such, you | |
1641 | cannot set a breakpoint on those calls, nor can you change the behavior | |
e6e931b7 JM |
1642 | of the functions by linking with a different library. In addition, |
1643 | when a function is recognized as a built-in function, GCC may use | |
1644 | information about that function to warn about problems with calls to | |
1645 | that function, or to generate more efficient code, even if the | |
1646 | resulting code still contains calls to that function. For example, | |
1647 | warnings are given with @option{-Wformat} for bad calls to | |
1648 | @code{printf}, when @code{printf} is built in, and @code{strlen} is | |
1649 | known not to modify global memory. | |
74291a4b | 1650 | |
a3926fe1 RS |
1651 | With the @option{-fno-builtin-@var{function}} option |
1652 | only the built-in function @var{function} is | |
7d14c755 | 1653 | disabled. @var{function} must not begin with @samp{__builtin_}. If a |
d1facce0 | 1654 | function is named that is not built-in in this version of GCC, this |
7d14c755 JM |
1655 | option is ignored. There is no corresponding |
1656 | @option{-fbuiltin-@var{function}} option; if you wish to enable | |
1657 | built-in functions selectively when using @option{-fno-builtin} or | |
1658 | @option{-ffreestanding}, you may define macros such as: | |
1659 | ||
1660 | @smallexample | |
1661 | #define abs(n) __builtin_abs ((n)) | |
1662 | #define strcpy(d, s) __builtin_strcpy ((d), (s)) | |
1663 | @end smallexample | |
1664 | ||
861bb6c1 | 1665 | @item -fhosted |
cd3bb277 | 1666 | @opindex fhosted |
861bb6c1 JL |
1667 | @cindex hosted environment |
1668 | ||
1669 | Assert that compilation takes place in a hosted environment. This implies | |
630d3d5a | 1670 | @option{-fbuiltin}. A hosted environment is one in which the |
861bb6c1 JL |
1671 | entire standard library is available, and in which @code{main} has a return |
1672 | type of @code{int}. Examples are nearly everything except a kernel. | |
630d3d5a | 1673 | This is equivalent to @option{-fno-freestanding}. |
861bb6c1 JL |
1674 | |
1675 | @item -ffreestanding | |
cd3bb277 | 1676 | @opindex ffreestanding |
861bb6c1 JL |
1677 | @cindex hosted environment |
1678 | ||
1679 | Assert that compilation takes place in a freestanding environment. This | |
630d3d5a | 1680 | implies @option{-fno-builtin}. A freestanding environment |
861bb6c1 JL |
1681 | is one in which the standard library may not exist, and program startup may |
1682 | not necessarily be at @code{main}. The most obvious example is an OS kernel. | |
630d3d5a | 1683 | This is equivalent to @option{-fno-hosted}. |
861bb6c1 | 1684 | |
c1030c7c JM |
1685 | @xref{Standards,,Language Standards Supported by GCC}, for details of |
1686 | freestanding and hosted environments. | |
1687 | ||
17d6caa1 AP |
1688 | @item -fopenmp |
1689 | @opindex fopenmp | |
ab940b73 | 1690 | @cindex OpenMP parallel |
17d6caa1 AP |
1691 | Enable handling of OpenMP directives @code{#pragma omp} in C/C++ and |
1692 | @code{!$omp} in Fortran. When @option{-fopenmp} is specified, the | |
1693 | compiler generates parallel code according to the OpenMP Application | |
848bc769 | 1694 | Program Interface v3.0 @w{@uref{http://www.openmp.org/}}. This option |
01a550c2 SP |
1695 | implies @option{-pthread}, and thus is only supported on targets that |
1696 | have support for @option{-pthread}. | |
17d6caa1 | 1697 | |
750491fc RH |
1698 | @item -fms-extensions |
1699 | @opindex fms-extensions | |
1700 | Accept some non-standard constructs used in Microsoft header files. | |
1701 | ||
b17b584f KT |
1702 | It allows for c++ that member-names in structures can be similiar |
1703 | to previous types declarations. | |
1704 | ||
1705 | @smallexample | |
1706 | typedef int UOW; | |
1707 | struct ABC @{ | |
1708 | UOW UOW; | |
1709 | @}; | |
1710 | @end smallexample | |
1711 | ||
2fbebc71 JM |
1712 | Some cases of unnamed fields in structures and unions are only |
1713 | accepted with this option. @xref{Unnamed Fields,,Unnamed struct/union | |
1714 | fields within structs/unions}, for details. | |
1715 | ||
478a1c5b ILT |
1716 | @item -fplan9-extensions |
1717 | Accept some non-standard constructs used in Plan 9 code. | |
1718 | ||
1719 | This enables @option{-fms-extensions}, permits passing pointers to | |
1720 | structures with anonymous fields to functions which expect pointers to | |
1721 | elements of the type of the field, and permits referring to anonymous | |
1722 | fields declared using a typedef. @xref{Unnamed Fields,,Unnamed | |
1723 | struct/union fields within structs/unions}, for details. This is only | |
1724 | supported for C, not C++. | |
1725 | ||
74291a4b | 1726 | @item -trigraphs |
cd3bb277 | 1727 | @opindex trigraphs |
3bce8a01 NB |
1728 | Support ISO C trigraphs. The @option{-ansi} option (and @option{-std} |
1729 | options for strict ISO C conformance) implies @option{-trigraphs}. | |
74291a4b | 1730 | |
8a035a6b AH |
1731 | @item -no-integrated-cpp |
1732 | @opindex no-integrated-cpp | |
1733 | Performs a compilation in two passes: preprocessing and compiling. This | |
1734 | option allows a user supplied "cc1", "cc1plus", or "cc1obj" via the | |
8a36672b | 1735 | @option{-B} option. The user supplied compilation step can then add in |
8a035a6b | 1736 | an additional preprocessing step after normal preprocessing but before |
8a36672b | 1737 | compiling. The default is to use the integrated cpp (internal cpp) |
8a035a6b AH |
1738 | |
1739 | The semantics of this option will change if "cc1", "cc1plus", and | |
1740 | "cc1obj" are merged. | |
1741 | ||
74291a4b MM |
1742 | @cindex traditional C language |
1743 | @cindex C language, traditional | |
1744 | @item -traditional | |
f458d1d5 | 1745 | @itemx -traditional-cpp |
cd3bb277 | 1746 | @opindex traditional-cpp |
f458d1d5 ZW |
1747 | @opindex traditional |
1748 | Formerly, these options caused GCC to attempt to emulate a pre-standard | |
1749 | C compiler. They are now only supported with the @option{-E} switch. | |
1750 | The preprocessor continues to support a pre-standard mode. See the GNU | |
1751 | CPP manual for details. | |
74291a4b MM |
1752 | |
1753 | @item -fcond-mismatch | |
cd3bb277 | 1754 | @opindex fcond-mismatch |
74291a4b | 1755 | Allow conditional expressions with mismatched types in the second and |
a7537031 JM |
1756 | third arguments. The value of such an expression is void. This option |
1757 | is not supported for C++. | |
74291a4b | 1758 | |
00c8e9f6 MS |
1759 | @item -flax-vector-conversions |
1760 | @opindex flax-vector-conversions | |
1761 | Allow implicit conversions between vectors with differing numbers of | |
1762 | elements and/or incompatible element types. This option should not be | |
1763 | used for new code. | |
1764 | ||
74291a4b | 1765 | @item -funsigned-char |
cd3bb277 | 1766 | @opindex funsigned-char |
74291a4b MM |
1767 | Let the type @code{char} be unsigned, like @code{unsigned char}. |
1768 | ||
1769 | Each kind of machine has a default for what @code{char} should | |
1770 | be. It is either like @code{unsigned char} by default or like | |
1771 | @code{signed char} by default. | |
1772 | ||
1773 | Ideally, a portable program should always use @code{signed char} or | |
1774 | @code{unsigned char} when it depends on the signedness of an object. | |
1775 | But many programs have been written to use plain @code{char} and | |
1776 | expect it to be signed, or expect it to be unsigned, depending on the | |
1777 | machines they were written for. This option, and its inverse, let you | |
1778 | make such a program work with the opposite default. | |
1779 | ||
1780 | The type @code{char} is always a distinct type from each of | |
1781 | @code{signed char} or @code{unsigned char}, even though its behavior | |
1782 | is always just like one of those two. | |
1783 | ||
1784 | @item -fsigned-char | |
cd3bb277 | 1785 | @opindex fsigned-char |
74291a4b MM |
1786 | Let the type @code{char} be signed, like @code{signed char}. |
1787 | ||
630d3d5a JM |
1788 | Note that this is equivalent to @option{-fno-unsigned-char}, which is |
1789 | the negative form of @option{-funsigned-char}. Likewise, the option | |
1790 | @option{-fno-signed-char} is equivalent to @option{-funsigned-char}. | |
74291a4b | 1791 | |
74291a4b MM |
1792 | @item -fsigned-bitfields |
1793 | @itemx -funsigned-bitfields | |
1794 | @itemx -fno-signed-bitfields | |
1795 | @itemx -fno-unsigned-bitfields | |
cd3bb277 JM |
1796 | @opindex fsigned-bitfields |
1797 | @opindex funsigned-bitfields | |
1798 | @opindex fno-signed-bitfields | |
1799 | @opindex fno-unsigned-bitfields | |
c771326b | 1800 | These options control whether a bit-field is signed or unsigned, when the |
74291a4b | 1801 | declaration does not use either @code{signed} or @code{unsigned}. By |
c771326b | 1802 | default, such a bit-field is signed, because this is consistent: the |
74291a4b | 1803 | basic integer types such as @code{int} are signed types. |
74291a4b MM |
1804 | @end table |
1805 | ||
1806 | @node C++ Dialect Options | |
1807 | @section Options Controlling C++ Dialect | |
1808 | ||
1809 | @cindex compiler options, C++ | |
1810 | @cindex C++ options, command line | |
1811 | @cindex options, C++ | |
1812 | This section describes the command-line options that are only meaningful | |
1813 | for C++ programs; but you can also use most of the GNU compiler options | |
1814 | regardless of what language your program is in. For example, you | |
1815 | might compile a file @code{firstClass.C} like this: | |
1816 | ||
3ab51846 | 1817 | @smallexample |
1dc5fc4b | 1818 | g++ -g -frepo -O -c firstClass.C |
3ab51846 | 1819 | @end smallexample |
74291a4b MM |
1820 | |
1821 | @noindent | |
630d3d5a | 1822 | In this example, only @option{-frepo} is an option meant |
74291a4b | 1823 | only for C++ programs; you can use the other options with any |
161d7b59 | 1824 | language supported by GCC@. |
74291a4b MM |
1825 | |
1826 | Here is a list of options that are @emph{only} for compiling C++ programs: | |
1827 | ||
2642624b | 1828 | @table @gcctabopt |
2d3e278d MM |
1829 | |
1830 | @item -fabi-version=@var{n} | |
1831 | @opindex fabi-version | |
8a36672b | 1832 | Use version @var{n} of the C++ ABI@. Version 2 is the version of the |
57702a80 MM |
1833 | C++ ABI that first appeared in G++ 3.4. Version 1 is the version of |
1834 | the C++ ABI that first appeared in G++ 3.2. Version 0 will always be | |
1835 | the version that conforms most closely to the C++ ABI specification. | |
1836 | Therefore, the ABI obtained using version 0 will change as ABI bugs | |
1837 | are fixed. | |
2d3e278d | 1838 | |
d150ccef | 1839 | The default is version 2. |
46c83bce | 1840 | |
0e7750a0 JM |
1841 | Version 3 corrects an error in mangling a constant address as a |
1842 | template argument. | |
1843 | ||
1844 | Version 4 implements a standard mangling for vector types. | |
1845 | ||
1846 | See also @option{-Wabi}. | |
1847 | ||
74291a4b | 1848 | @item -fno-access-control |
cd3bb277 | 1849 | @opindex fno-access-control |
74291a4b MM |
1850 | Turn off all access checking. This switch is mainly useful for working |
1851 | around bugs in the access control code. | |
1852 | ||
74291a4b | 1853 | @item -fcheck-new |
cd3bb277 | 1854 | @opindex fcheck-new |
74291a4b | 1855 | Check that the pointer returned by @code{operator new} is non-null |
6d9c4c83 JW |
1856 | before attempting to modify the storage allocated. This check is |
1857 | normally unnecessary because the C++ standard specifies that | |
1858 | @code{operator new} will only return @code{0} if it is declared | |
1859 | @samp{throw()}, in which case the compiler will always check the | |
1860 | return value even without this option. In all other cases, when | |
1861 | @code{operator new} has a non-empty exception specification, memory | |
1862 | exhaustion is signalled by throwing @code{std::bad_alloc}. See also | |
1863 | @samp{new (nothrow)}. | |
1dc5fc4b | 1864 | |
74291a4b | 1865 | @item -fconserve-space |
cd3bb277 | 1866 | @opindex fconserve-space |
74291a4b MM |
1867 | Put uninitialized or runtime-initialized global variables into the |
1868 | common segment, as C does. This saves space in the executable at the | |
1869 | cost of not diagnosing duplicate definitions. If you compile with this | |
1870 | flag and your program mysteriously crashes after @code{main()} has | |
1871 | completed, you may have an object that is being destroyed twice because | |
1872 | two definitions were merged. | |
1873 | ||
1dc5fc4b JM |
1874 | This option is no longer useful on most targets, now that support has |
1875 | been added for putting variables into BSS without making them common. | |
1876 | ||
5f5babf1 JM |
1877 | @item -fno-deduce-init-list |
1878 | @opindex fno-deduce-init-list | |
1879 | Disable deduction of a template type parameter as | |
1880 | std::initializer_list from a brace-enclosed initializer list, i.e. | |
1881 | ||
1882 | @smallexample | |
1883 | template <class T> auto forward(T t) -> decltype (realfn (t)) | |
1884 | @{ | |
1885 | return realfn (t); | |
1886 | @} | |
1887 | ||
1888 | void f() | |
1889 | @{ | |
1890 | forward(@{1,2@}); // call forward<std::initializer_list<int>> | |
1891 | @} | |
1892 | @end smallexample | |
1893 | ||
1894 | This option is present because this deduction is an extension to the | |
1895 | current specification in the C++0x working draft, and there was | |
1896 | some concern about potential overload resolution problems. | |
1897 | ||
d63d5d0c ILT |
1898 | @item -ffriend-injection |
1899 | @opindex ffriend-injection | |
1900 | Inject friend functions into the enclosing namespace, so that they are | |
1901 | visible outside the scope of the class in which they are declared. | |
1902 | Friend functions were documented to work this way in the old Annotated | |
1903 | C++ Reference Manual, and versions of G++ before 4.1 always worked | |
1904 | that way. However, in ISO C++ a friend function which is not declared | |
1905 | in an enclosing scope can only be found using argument dependent | |
1906 | lookup. This option causes friends to be injected as they were in | |
1907 | earlier releases. | |
1908 | ||
1909 | This option is for compatibility, and may be removed in a future | |
1910 | release of G++. | |
1911 | ||
1dc5fc4b | 1912 | @item -fno-elide-constructors |
cd3bb277 | 1913 | @opindex fno-elide-constructors |
1dc5fc4b JM |
1914 | The C++ standard allows an implementation to omit creating a temporary |
1915 | which is only used to initialize another object of the same type. | |
aee96fe9 | 1916 | Specifying this option disables that optimization, and forces G++ to |
1dc5fc4b | 1917 | call the copy constructor in all cases. |
74291a4b | 1918 | |
dd1ba632 | 1919 | @item -fno-enforce-eh-specs |
cd3bb277 | 1920 | @opindex fno-enforce-eh-specs |
4381020e JM |
1921 | Don't generate code to check for violation of exception specifications |
1922 | at runtime. This option violates the C++ standard, but may be useful | |
1923 | for reducing code size in production builds, much like defining | |
1924 | @samp{NDEBUG}. This does not give user code permission to throw | |
1925 | exceptions in violation of the exception specifications; the compiler | |
1926 | will still optimize based on the specifications, so throwing an | |
1927 | unexpected exception will result in undefined behavior. | |
dd1ba632 | 1928 | |
74291a4b | 1929 | @item -ffor-scope |
8c81598d | 1930 | @itemx -fno-for-scope |
cd3bb277 JM |
1931 | @opindex ffor-scope |
1932 | @opindex fno-for-scope | |
695ac33f | 1933 | If @option{-ffor-scope} is specified, the scope of variables declared in |
74291a4b | 1934 | a @i{for-init-statement} is limited to the @samp{for} loop itself, |
34527c47 | 1935 | as specified by the C++ standard. |
695ac33f | 1936 | If @option{-fno-for-scope} is specified, the scope of variables declared in |
74291a4b | 1937 | a @i{for-init-statement} extends to the end of the enclosing scope, |
aee96fe9 | 1938 | as was the case in old versions of G++, and other (traditional) |
74291a4b MM |
1939 | implementations of C++. |
1940 | ||
1941 | The default if neither flag is given to follow the standard, | |
1942 | but to allow and give a warning for old-style code that would | |
1943 | otherwise be invalid, or have different behavior. | |
1944 | ||
1945 | @item -fno-gnu-keywords | |
cd3bb277 | 1946 | @opindex fno-gnu-keywords |
9762e8a4 | 1947 | Do not recognize @code{typeof} as a keyword, so that code can use this |
767094dd | 1948 | word as an identifier. You can use the keyword @code{__typeof__} instead. |
630d3d5a | 1949 | @option{-ansi} implies @option{-fno-gnu-keywords}. |
74291a4b | 1950 | |
1dc5fc4b | 1951 | @item -fno-implicit-templates |
cd3bb277 | 1952 | @opindex fno-implicit-templates |
bba975d4 | 1953 | Never emit code for non-inline templates which are instantiated |
e979f9e8 | 1954 | implicitly (i.e.@: by use); only emit code for explicit instantiations. |
bba975d4 JM |
1955 | @xref{Template Instantiation}, for more information. |
1956 | ||
1957 | @item -fno-implicit-inline-templates | |
cd3bb277 | 1958 | @opindex fno-implicit-inline-templates |
bba975d4 JM |
1959 | Don't emit code for implicit instantiations of inline templates, either. |
1960 | The default is to handle inlines differently so that compiles with and | |
1961 | without optimization will need the same set of explicit instantiations. | |
1dc5fc4b | 1962 | |
74291a4b | 1963 | @item -fno-implement-inlines |
cd3bb277 | 1964 | @opindex fno-implement-inlines |
74291a4b MM |
1965 | To save space, do not emit out-of-line copies of inline functions |
1966 | controlled by @samp{#pragma implementation}. This will cause linker | |
1967 | errors if these functions are not inlined everywhere they are called. | |
1968 | ||
631cf95d | 1969 | @item -fms-extensions |
cd3bb277 | 1970 | @opindex fms-extensions |
32fb1fb2 PE |
1971 | Disable pedantic warnings about constructs used in MFC, such as implicit |
1972 | int and getting a pointer to member function via non-standard syntax. | |
631cf95d | 1973 | |
fcca588c | 1974 | @item -fno-nonansi-builtins |
cd3bb277 | 1975 | @opindex fno-nonansi-builtins |
c771326b | 1976 | Disable built-in declarations of functions that are not mandated by |
161d7b59 | 1977 | ANSI/ISO C@. These include @code{ffs}, @code{alloca}, @code{_exit}, |
fcca588c MM |
1978 | @code{index}, @code{bzero}, @code{conjf}, and other related functions. |
1979 | ||
9feb3d6a JM |
1980 | @item -fnothrow-opt |
1981 | @opindex fnothrow-opt | |
1982 | Treat a @code{throw()} exception specification as though it were a | |
1983 | @code{noexcept} specification to reduce or eliminate the text size | |
d3f28910 JM |
1984 | overhead relative to a function with no exception specification. If |
1985 | the function has local variables of types with non-trivial | |
1986 | destructors, the exception specification will actually make the | |
1987 | function smaller because the EH cleanups for those variables can be | |
1988 | optimized away. The semantic effect is that an exception thrown out of | |
1989 | a function with such an exception specification will result in a call | |
1990 | to @code{terminate} rather than @code{unexpected}. | |
9feb3d6a | 1991 | |
775afb25 | 1992 | @item -fno-operator-names |
cd3bb277 | 1993 | @opindex fno-operator-names |
775afb25 | 1994 | Do not treat the operator name keywords @code{and}, @code{bitand}, |
74291a4b | 1995 | @code{bitor}, @code{compl}, @code{not}, @code{or} and @code{xor} as |
775afb25 | 1996 | synonyms as keywords. |
74291a4b | 1997 | |
4f8b4fd9 | 1998 | @item -fno-optional-diags |
cd3bb277 | 1999 | @opindex fno-optional-diags |
4f8b4fd9 | 2000 | Disable diagnostics that the standard says a compiler does not need to |
aee96fe9 | 2001 | issue. Currently, the only such diagnostic issued by G++ is the one for |
bba975d4 | 2002 | a name having multiple meanings within a class. |
4f8b4fd9 | 2003 | |
8c7707b0 | 2004 | @item -fpermissive |
cd3bb277 | 2005 | @opindex fpermissive |
4a386498 MM |
2006 | Downgrade some diagnostics about nonconformant code from errors to |
2007 | warnings. Thus, using @option{-fpermissive} will allow some | |
2008 | nonconforming code to compile. | |
8c7707b0 | 2009 | |
6ea2bd47 JM |
2010 | @item -fno-pretty-templates |
2011 | @opindex fno-pretty-templates | |
2012 | When an error message refers to a specialization of a function | |
2013 | template, the compiler will normally print the signature of the | |
2014 | template followed by the template arguments and any typedefs or | |
2015 | typenames in the signature (e.g. @code{void f(T) [with T = int]} | |
2016 | rather than @code{void f(int)}) so that it's clear which template is | |
2017 | involved. When an error message refers to a specialization of a class | |
2018 | template, the compiler will omit any template arguments which match | |
2019 | the default template arguments for that template. If either of these | |
2020 | behaviors make it harder to understand the error message rather than | |
2021 | easier, using @option{-fno-pretty-templates} will disable them. | |
2022 | ||
8c81598d | 2023 | @item -frepo |
cd3bb277 | 2024 | @opindex frepo |
9c34dbbf ZW |
2025 | Enable automatic template instantiation at link time. This option also |
2026 | implies @option{-fno-implicit-templates}. @xref{Template | |
2027 | Instantiation}, for more information. | |
8c81598d | 2028 | |
8c7707b0 | 2029 | @item -fno-rtti |
cd3bb277 | 2030 | @opindex fno-rtti |
a7fbfcf9 JM |
2031 | Disable generation of information about every class with virtual |
2032 | functions for use by the C++ runtime type identification features | |
2033 | (@samp{dynamic_cast} and @samp{typeid}). If you don't use those parts | |
2034 | of the language, you can save some space by using this flag. Note that | |
2035 | exception handling uses the same information, but it will generate it as | |
6c9384c3 | 2036 | needed. The @samp{dynamic_cast} operator can still be used for casts that |
a31cfd58 | 2037 | do not require runtime type information, i.e.@: casts to @code{void *} or to |
6c9384c3 | 2038 | unambiguous base classes. |
8c7707b0 | 2039 | |
fcca588c | 2040 | @item -fstats |
cd3bb277 | 2041 | @opindex fstats |
fcca588c MM |
2042 | Emit statistics about front-end processing at the end of the compilation. |
2043 | This information is generally only useful to the G++ development team. | |
2044 | ||
cbb4feb3 JM |
2045 | @item -fstrict-enums |
2046 | @opindex fstrict-enums | |
2047 | Allow the compiler to optimize using the assumption that a value of | |
2048 | enumeration type can only be one of the values of the enumeration (as | |
2049 | defined in the C++ standard; basically, a value which can be | |
2050 | represented in the minimum number of bits needed to represent all the | |
2051 | enumerators). This assumption may not be valid if the program uses a | |
2052 | cast to convert an arbitrary integer value to the enumeration type. | |
2053 | ||
124e0d27 | 2054 | @item -ftemplate-depth=@var{n} |
cd3bb277 | 2055 | @opindex ftemplate-depth |
1dc5fc4b JM |
2056 | Set the maximum instantiation depth for template classes to @var{n}. |
2057 | A limit on the template instantiation depth is needed to detect | |
767094dd | 2058 | endless recursions during template class instantiation. ANSI/ISO C++ |
6c879482 JM |
2059 | conforming programs must not rely on a maximum depth greater than 17 |
2060 | (changed to 1024 in C++0x). | |
1dc5fc4b | 2061 | |
40aac948 JM |
2062 | @item -fno-threadsafe-statics |
2063 | @opindex fno-threadsafe-statics | |
2064 | Do not emit the extra code to use the routines specified in the C++ | |
2065 | ABI for thread-safe initialization of local statics. You can use this | |
2066 | option to reduce code size slightly in code that doesn't need to be | |
2067 | thread-safe. | |
2068 | ||
fc693822 | 2069 | @item -fuse-cxa-atexit |
cd3bb277 | 2070 | @opindex fuse-cxa-atexit |
fc693822 MM |
2071 | Register destructors for objects with static storage duration with the |
2072 | @code{__cxa_atexit} function rather than the @code{atexit} function. | |
2073 | This option is required for fully standards-compliant handling of static | |
2074 | destructors, but will only work if your C library supports | |
2075 | @code{__cxa_atexit}. | |
2076 | ||
c7b5e395 GK |
2077 | @item -fno-use-cxa-get-exception-ptr |
2078 | @opindex fno-use-cxa-get-exception-ptr | |
2079 | Don't use the @code{__cxa_get_exception_ptr} runtime routine. This | |
2080 | will cause @code{std::uncaught_exception} to be incorrect, but is necessary | |
2081 | if the runtime routine is not available. | |
2082 | ||
d7afec4b ND |
2083 | @item -fvisibility-inlines-hidden |
2084 | @opindex fvisibility-inlines-hidden | |
46bdbc00 GK |
2085 | This switch declares that the user does not attempt to compare |
2086 | pointers to inline methods where the addresses of the two functions | |
2087 | were taken in different shared objects. | |
2088 | ||
2089 | The effect of this is that GCC may, effectively, mark inline methods with | |
d7afec4b ND |
2090 | @code{__attribute__ ((visibility ("hidden")))} so that they do not |
2091 | appear in the export table of a DSO and do not require a PLT indirection | |
8a36672b | 2092 | when used within the DSO@. Enabling this option can have a dramatic effect |
d7afec4b | 2093 | on load and link times of a DSO as it massively reduces the size of the |
46bdbc00 GK |
2094 | dynamic export table when the library makes heavy use of templates. |
2095 | ||
9f5ed61a | 2096 | The behavior of this switch is not quite the same as marking the |
7c0de6a5 GK |
2097 | methods as hidden directly, because it does not affect static variables |
2098 | local to the function or cause the compiler to deduce that | |
2099 | the function is defined in only one shared object. | |
2100 | ||
46bdbc00 GK |
2101 | You may mark a method as having a visibility explicitly to negate the |
2102 | effect of the switch for that method. For example, if you do want to | |
7c0de6a5 | 2103 | compare pointers to a particular inline method, you might mark it as |
bd741f34 JM |
2104 | having default visibility. Marking the enclosing class with explicit |
2105 | visibility will have no effect. | |
d7afec4b | 2106 | |
dfb84d62 MS |
2107 | Explicitly instantiated inline methods are unaffected by this option |
2108 | as their linkage might otherwise cross a shared library boundary. | |
2109 | @xref{Template Instantiation}. | |
2110 | ||
ddbfd28d GK |
2111 | @item -fvisibility-ms-compat |
2112 | @opindex fvisibility-ms-compat | |
2113 | This flag attempts to use visibility settings to make GCC's C++ | |
2114 | linkage model compatible with that of Microsoft Visual Studio. | |
2115 | ||
2116 | The flag makes these changes to GCC's linkage model: | |
2117 | ||
2118 | @enumerate | |
2119 | @item | |
2120 | It sets the default visibility to @code{hidden}, like | |
2121 | @option{-fvisibility=hidden}. | |
2122 | ||
2123 | @item | |
2124 | Types, but not their members, are not hidden by default. | |
2125 | ||
2126 | @item | |
2127 | The One Definition Rule is relaxed for types without explicit | |
2128 | visibility specifications which are defined in more than one different | |
2129 | shared object: those declarations are permitted if they would have | |
2130 | been permitted when this option was not used. | |
2131 | @end enumerate | |
2132 | ||
2133 | In new code it is better to use @option{-fvisibility=hidden} and | |
2134 | export those classes which are intended to be externally visible. | |
2135 | Unfortunately it is possible for code to rely, perhaps accidentally, | |
cea618ac | 2136 | on the Visual Studio behavior. |
ddbfd28d GK |
2137 | |
2138 | Among the consequences of these changes are that static data members | |
2139 | of the same type with the same name but defined in different shared | |
2140 | objects will be different, so changing one will not change the other; | |
2141 | and that pointers to function members defined in different shared | |
2142 | objects may not compare equal. When this flag is given, it is a | |
2143 | violation of the ODR to define types with the same name differently. | |
2144 | ||
02f52e19 | 2145 | @item -fno-weak |
cd3bb277 | 2146 | @opindex fno-weak |
90ecce3e | 2147 | Do not use weak symbol support, even if it is provided by the linker. |
fcca588c MM |
2148 | By default, G++ will use weak symbols if they are available. This |
2149 | option exists only for testing, and should not be used by end-users; | |
2150 | it will result in inferior code and has no benefits. This option may | |
2151 | be removed in a future release of G++. | |
2152 | ||
74291a4b | 2153 | @item -nostdinc++ |
cd3bb277 | 2154 | @opindex nostdinc++ |
74291a4b MM |
2155 | Do not search for header files in the standard directories specific to |
2156 | C++, but do still search the other standard directories. (This option | |
e5e809f4 | 2157 | is used when building the C++ library.) |
74291a4b MM |
2158 | @end table |
2159 | ||
2160 | In addition, these optimization, warning, and code generation options | |
2161 | have meanings only for C++ programs: | |
2162 | ||
2642624b | 2163 | @table @gcctabopt |
74291a4b | 2164 | @item -fno-default-inline |
cd3bb277 | 2165 | @opindex fno-default-inline |
74291a4b | 2166 | Do not assume @samp{inline} for functions defined inside a class scope. |
1dc5fc4b JM |
2167 | @xref{Optimize Options,,Options That Control Optimization}. Note that these |
2168 | functions will have linkage like inline functions; they just won't be | |
2169 | inlined by default. | |
74291a4b | 2170 | |
bce08d50 | 2171 | @item -Wabi @r{(C, Objective-C, C++ and Objective-C++ only)} |
eca7f13c | 2172 | @opindex Wabi |
ccd4e386 | 2173 | @opindex Wno-abi |
eca7f13c | 2174 | Warn when G++ generates code that is probably not compatible with the |
8a36672b | 2175 | vendor-neutral C++ ABI@. Although an effort has been made to warn about |
daf2f129 | 2176 | all such cases, there are probably some cases that are not warned about, |
eca7f13c MM |
2177 | even though G++ is generating incompatible code. There may also be |
2178 | cases where warnings are emitted even though the code that is generated | |
2179 | will be compatible. | |
2180 | ||
2181 | You should rewrite your code to avoid these warnings if you are | |
2182 | concerned about the fact that code generated by G++ may not be binary | |
2183 | compatible with code generated by other compilers. | |
2184 | ||
0e7750a0 JM |
2185 | The known incompatibilities in @option{-fabi-version=2} (the default) include: |
2186 | ||
2187 | @itemize @bullet | |
2188 | ||
2189 | @item | |
2190 | A template with a non-type template parameter of reference type is | |
2191 | mangled incorrectly: | |
2192 | @smallexample | |
2193 | extern int N; | |
2194 | template <int &> struct S @{@}; | |
2195 | void n (S<N>) @{2@} | |
2196 | @end smallexample | |
2197 | ||
2198 | This is fixed in @option{-fabi-version=3}. | |
2199 | ||
2200 | @item | |
2201 | SIMD vector types declared using @code{__attribute ((vector_size))} are | |
2202 | mangled in a non-standard way that does not allow for overloading of | |
2203 | functions taking vectors of different sizes. | |
2204 | ||
2205 | The mangling is changed in @option{-fabi-version=4}. | |
2206 | @end itemize | |
2207 | ||
2208 | The known incompatibilities in @option{-fabi-version=1} include: | |
eca7f13c MM |
2209 | |
2210 | @itemize @bullet | |
2211 | ||
2212 | @item | |
2213 | Incorrect handling of tail-padding for bit-fields. G++ may attempt to | |
2214 | pack data into the same byte as a base class. For example: | |
2215 | ||
2216 | @smallexample | |
2217 | struct A @{ virtual void f(); int f1 : 1; @}; | |
2218 | struct B : public A @{ int f2 : 1; @}; | |
2219 | @end smallexample | |
2220 | ||
2221 | @noindent | |
2222 | In this case, G++ will place @code{B::f2} into the same byte | |
daf2f129 | 2223 | as@code{A::f1}; other compilers will not. You can avoid this problem |
eca7f13c MM |
2224 | by explicitly padding @code{A} so that its size is a multiple of the |
2225 | byte size on your platform; that will cause G++ and other compilers to | |
2226 | layout @code{B} identically. | |
2227 | ||
2228 | @item | |
2229 | Incorrect handling of tail-padding for virtual bases. G++ does not use | |
2230 | tail padding when laying out virtual bases. For example: | |
2231 | ||
2232 | @smallexample | |
2233 | struct A @{ virtual void f(); char c1; @}; | |
2234 | struct B @{ B(); char c2; @}; | |
2235 | struct C : public A, public virtual B @{@}; | |
2236 | @end smallexample | |
2237 | ||
2238 | @noindent | |
2239 | In this case, G++ will not place @code{B} into the tail-padding for | |
2240 | @code{A}; other compilers will. You can avoid this problem by | |
2241 | explicitly padding @code{A} so that its size is a multiple of its | |
2242 | alignment (ignoring virtual base classes); that will cause G++ and other | |
2243 | compilers to layout @code{C} identically. | |
2244 | ||
2d3e278d MM |
2245 | @item |
2246 | Incorrect handling of bit-fields with declared widths greater than that | |
2247 | of their underlying types, when the bit-fields appear in a union. For | |
2248 | example: | |
2249 | ||
2250 | @smallexample | |
2251 | union U @{ int i : 4096; @}; | |
2252 | @end smallexample | |
2253 | ||
2254 | @noindent | |
2255 | Assuming that an @code{int} does not have 4096 bits, G++ will make the | |
2256 | union too small by the number of bits in an @code{int}. | |
2257 | ||
956d9305 MM |
2258 | @item |
2259 | Empty classes can be placed at incorrect offsets. For example: | |
daf2f129 | 2260 | |
956d9305 MM |
2261 | @smallexample |
2262 | struct A @{@}; | |
2263 | ||
2264 | struct B @{ | |
2265 | A a; | |
2266 | virtual void f (); | |
2267 | @}; | |
2268 | ||
2269 | struct C : public B, public A @{@}; | |
2270 | @end smallexample | |
2271 | ||
2272 | @noindent | |
c0478a66 | 2273 | G++ will place the @code{A} base class of @code{C} at a nonzero offset; |
956d9305 MM |
2274 | it should be placed at offset zero. G++ mistakenly believes that the |
2275 | @code{A} data member of @code{B} is already at offset zero. | |
2276 | ||
6397d80b MM |
2277 | @item |
2278 | Names of template functions whose types involve @code{typename} or | |
2279 | template template parameters can be mangled incorrectly. | |
2280 | ||
2281 | @smallexample | |
2282 | template <typename Q> | |
2283 | void f(typename Q::X) @{@} | |
2284 | ||
2285 | template <template <typename> class Q> | |
2286 | void f(typename Q<int>::X) @{@} | |
2287 | @end smallexample | |
2288 | ||
2289 | @noindent | |
3364c33b | 2290 | Instantiations of these templates may be mangled incorrectly. |
6397d80b | 2291 | |
eca7f13c MM |
2292 | @end itemize |
2293 | ||
bce08d50 L |
2294 | It also warns psABI related changes. The known psABI changes at this |
2295 | point include: | |
2296 | ||
2297 | @itemize @bullet | |
2298 | ||
2299 | @item | |
2300 | For SYSV/x86-64, when passing union with long double, it is changed to | |
2301 | pass in memory as specified in psABI. For example: | |
2302 | ||
2303 | @smallexample | |
2304 | union U @{ | |
2305 | long double ld; | |
2306 | int i; | |
2307 | @}; | |
2308 | @end smallexample | |
2309 | ||
2310 | @noindent | |
2311 | @code{union U} will always be passed in memory. | |
2312 | ||
2313 | @end itemize | |
2314 | ||
670b0231 | 2315 | @item -Wctor-dtor-privacy @r{(C++ and Objective-C++ only)} |
cd3bb277 | 2316 | @opindex Wctor-dtor-privacy |
ccd4e386 | 2317 | @opindex Wno-ctor-dtor-privacy |
9eff22bc LG |
2318 | Warn when a class seems unusable because all the constructors or |
2319 | destructors in that class are private, and it has neither friends nor | |
78d0a54d | 2320 | public static member functions. |
bba975d4 | 2321 | |
59f9c2ed JM |
2322 | @item -Wnoexcept @r{(C++ and Objective-C++ only)} |
2323 | @opindex Wnoexcept | |
2324 | @opindex Wno-noexcept | |
2325 | Warn when a noexcept-expression evaluates to false because of a call | |
2326 | to a function that does not have a non-throwing exception | |
2327 | specification (i.e. @samp{throw()} or @samp{noexcept}) but is known by | |
2328 | the compiler to never throw an exception. | |
2329 | ||
670b0231 | 2330 | @item -Wnon-virtual-dtor @r{(C++ and Objective-C++ only)} |
cd3bb277 | 2331 | @opindex Wnon-virtual-dtor |
ccd4e386 | 2332 | @opindex Wno-non-virtual-dtor |
43f14744 PS |
2333 | Warn when a class has virtual functions and accessible non-virtual |
2334 | destructor, in which case it would be possible but unsafe to delete | |
2335 | an instance of a derived class through a pointer to the base class. | |
2336 | This warning is also enabled if -Weffc++ is specified. | |
bba975d4 | 2337 | |
670b0231 | 2338 | @item -Wreorder @r{(C++ and Objective-C++ only)} |
cd3bb277 | 2339 | @opindex Wreorder |
ccd4e386 | 2340 | @opindex Wno-reorder |
bba975d4 JM |
2341 | @cindex reordering, warning |
2342 | @cindex warning for reordering of member initializers | |
2343 | Warn when the order of member initializers given in the code does not | |
2344 | match the order in which they must be executed. For instance: | |
2345 | ||
2346 | @smallexample | |
2347 | struct A @{ | |
2348 | int i; | |
2349 | int j; | |
2350 | A(): j (0), i (1) @{ @} | |
2351 | @}; | |
2352 | @end smallexample | |
2353 | ||
9eff22bc LG |
2354 | The compiler will rearrange the member initializers for @samp{i} |
2355 | and @samp{j} to match the declaration order of the members, emitting | |
2356 | a warning to that effect. This warning is enabled by @option{-Wall}. | |
bba975d4 JM |
2357 | @end table |
2358 | ||
630d3d5a | 2359 | The following @option{-W@dots{}} options are not affected by @option{-Wall}. |
bba975d4 | 2360 | |
2642624b | 2361 | @table @gcctabopt |
670b0231 | 2362 | @item -Weffc++ @r{(C++ and Objective-C++ only)} |
cd3bb277 | 2363 | @opindex Weffc++ |
ccd4e386 | 2364 | @opindex Wno-effc++ |
77f6c1eb RS |
2365 | Warn about violations of the following style guidelines from Scott Meyers' |
2366 | @cite{Effective C++} book: | |
2367 | ||
2368 | @itemize @bullet | |
2369 | @item | |
2370 | Item 11: Define a copy constructor and an assignment operator for classes | |
2371 | with dynamically allocated memory. | |
2372 | ||
2373 | @item | |
2374 | Item 12: Prefer initialization to assignment in constructors. | |
2375 | ||
2376 | @item | |
2377 | Item 14: Make destructors virtual in base classes. | |
2378 | ||
2379 | @item | |
2380 | Item 15: Have @code{operator=} return a reference to @code{*this}. | |
2381 | ||
2382 | @item | |
2383 | Item 23: Don't try to return a reference when you must return an object. | |
2384 | ||
2385 | @end itemize | |
2386 | ||
daf2f129 | 2387 | Also warn about violations of the following style guidelines from |
9eff22bc | 2388 | Scott Meyers' @cite{More Effective C++} book: |
77f6c1eb RS |
2389 | |
2390 | @itemize @bullet | |
2391 | @item | |
2392 | Item 6: Distinguish between prefix and postfix forms of increment and | |
2393 | decrement operators. | |
2394 | ||
2395 | @item | |
2396 | Item 7: Never overload @code{&&}, @code{||}, or @code{,}. | |
2397 | ||
2398 | @end itemize | |
2399 | ||
9eff22bc LG |
2400 | When selecting this option, be aware that the standard library |
2401 | headers do not obey all of these guidelines; use @samp{grep -v} | |
77f6c1eb | 2402 | to filter out those warnings. |
bba975d4 | 2403 | |
670b0231 | 2404 | @item -Wstrict-null-sentinel @r{(C++ and Objective-C++ only)} |
b2f97e4a | 2405 | @opindex Wstrict-null-sentinel |
ccd4e386 | 2406 | @opindex Wno-strict-null-sentinel |
b2f97e4a MM |
2407 | Warn also about the use of an uncasted @code{NULL} as sentinel. When |
2408 | compiling only with GCC this is a valid sentinel, as @code{NULL} is defined | |
2409 | to @code{__null}. Although it is a null pointer constant not a null pointer, | |
1df48f5c | 2410 | it is guaranteed to be of the same size as a pointer. But this use is |
b2f97e4a MM |
2411 | not portable across different compilers. |
2412 | ||
670b0231 | 2413 | @item -Wno-non-template-friend @r{(C++ and Objective-C++ only)} |
cd3bb277 | 2414 | @opindex Wno-non-template-friend |
ccd4e386 | 2415 | @opindex Wnon-template-friend |
bba975d4 | 2416 | Disable warnings when non-templatized friend functions are declared |
9eff22bc | 2417 | within a template. Since the advent of explicit template specification |
aee96fe9 | 2418 | support in G++, if the name of the friend is an unqualified-id (i.e., |
bba975d4 | 2419 | @samp{friend foo(int)}), the C++ language specification demands that the |
767094dd | 2420 | friend declare or define an ordinary, nontemplate function. (Section |
aee96fe9 | 2421 | 14.5.3). Before G++ implemented explicit specification, unqualified-ids |
bba975d4 | 2422 | could be interpreted as a particular specialization of a templatized |
767094dd | 2423 | function. Because this non-conforming behavior is no longer the default |
aee96fe9 | 2424 | behavior for G++, @option{-Wnon-template-friend} allows the compiler to |
9eff22bc | 2425 | check existing code for potential trouble spots and is on by default. |
2228d450 | 2426 | This new compiler behavior can be turned off with |
630d3d5a | 2427 | @option{-Wno-non-template-friend} which keeps the conformant compiler code |
2228d450 | 2428 | but disables the helpful warning. |
bba975d4 | 2429 | |
670b0231 | 2430 | @item -Wold-style-cast @r{(C++ and Objective-C++ only)} |
cd3bb277 | 2431 | @opindex Wold-style-cast |
ccd4e386 | 2432 | @opindex Wno-old-style-cast |
323728aa | 2433 | Warn if an old-style (C-style) cast to a non-void type is used within |
7cd5c075 GP |
2434 | a C++ program. The new-style casts (@samp{dynamic_cast}, |
2435 | @samp{static_cast}, @samp{reinterpret_cast}, and @samp{const_cast}) are | |
2436 | less vulnerable to unintended effects and much easier to search for. | |
bba975d4 | 2437 | |
670b0231 | 2438 | @item -Woverloaded-virtual @r{(C++ and Objective-C++ only)} |
cd3bb277 | 2439 | @opindex Woverloaded-virtual |
ccd4e386 | 2440 | @opindex Wno-overloaded-virtual |
ab940b73 RW |
2441 | @cindex overloaded virtual function, warning |
2442 | @cindex warning for overloaded virtual function | |
3747f3dc MM |
2443 | Warn when a function declaration hides virtual functions from a |
2444 | base class. For example, in: | |
2445 | ||
2446 | @smallexample | |
2447 | struct A @{ | |
2448 | virtual void f(); | |
2449 | @}; | |
2450 | ||
2451 | struct B: public A @{ | |
2452 | void f(int); | |
2453 | @}; | |
2454 | @end smallexample | |
2455 | ||
2456 | the @code{A} class version of @code{f} is hidden in @code{B}, and code | |
9eff22bc | 2457 | like: |
3747f3dc MM |
2458 | |
2459 | @smallexample | |
2460 | B* b; | |
2461 | b->f(); | |
2462 | @end smallexample | |
2463 | ||
2464 | will fail to compile. | |
bba975d4 | 2465 | |
670b0231 | 2466 | @item -Wno-pmf-conversions @r{(C++ and Objective-C++ only)} |
cd3bb277 | 2467 | @opindex Wno-pmf-conversions |
ccd4e386 | 2468 | @opindex Wpmf-conversions |
bba975d4 JM |
2469 | Disable the diagnostic for converting a bound pointer to member function |
2470 | to a plain pointer. | |
2471 | ||
670b0231 | 2472 | @item -Wsign-promo @r{(C++ and Objective-C++ only)} |
cd3bb277 | 2473 | @opindex Wsign-promo |
ccd4e386 | 2474 | @opindex Wno-sign-promo |
bba975d4 | 2475 | Warn when overload resolution chooses a promotion from unsigned or |
2eac577f | 2476 | enumerated type to a signed type, over a conversion to an unsigned type of |
aee96fe9 | 2477 | the same size. Previous versions of G++ would try to preserve |
bba975d4 JM |
2478 | unsignedness, but the standard mandates the current behavior. |
2479 | ||
bba975d4 JM |
2480 | @smallexample |
2481 | struct A @{ | |
2482 | operator int (); | |
2483 | A& operator = (int); | |
2484 | @}; | |
2485 | ||
2486 | main () | |
2487 | @{ | |
2488 | A a,b; | |
2489 | a = b; | |
2490 | @} | |
2491 | @end smallexample | |
74291a4b | 2492 | |
aee96fe9 | 2493 | In this example, G++ will synthesize a default @samp{A& operator = |
bba975d4 | 2494 | (const A&);}, while cfront will use the user-defined @samp{operator =}. |
74291a4b MM |
2495 | @end table |
2496 | ||
46e34f96 ZL |
2497 | @node Objective-C and Objective-C++ Dialect Options |
2498 | @section Options Controlling Objective-C and Objective-C++ Dialects | |
60de6385 | 2499 | |
46e34f96 ZL |
2500 | @cindex compiler options, Objective-C and Objective-C++ |
2501 | @cindex Objective-C and Objective-C++ options, command line | |
2502 | @cindex options, Objective-C and Objective-C++ | |
2503 | (NOTE: This manual does not describe the Objective-C and Objective-C++ | |
2504 | languages themselves. See @xref{Standards,,Language Standards | |
2505 | Supported by GCC}, for references.) | |
264fa2db | 2506 | |
60de6385 | 2507 | This section describes the command-line options that are only meaningful |
46e34f96 ZL |
2508 | for Objective-C and Objective-C++ programs, but you can also use most of |
2509 | the language-independent GNU compiler options. | |
2510 | For example, you might compile a file @code{some_class.m} like this: | |
60de6385 | 2511 | |
3ab51846 | 2512 | @smallexample |
60de6385 | 2513 | gcc -g -fgnu-runtime -O -c some_class.m |
3ab51846 | 2514 | @end smallexample |
60de6385 SS |
2515 | |
2516 | @noindent | |
9eff22bc | 2517 | In this example, @option{-fgnu-runtime} is an option meant only for |
46e34f96 ZL |
2518 | Objective-C and Objective-C++ programs; you can use the other options with |
2519 | any language supported by GCC@. | |
2520 | ||
2521 | Note that since Objective-C is an extension of the C language, Objective-C | |
f0eb93a8 | 2522 | compilations may also use options specific to the C front-end (e.g., |
46e34f96 ZL |
2523 | @option{-Wtraditional}). Similarly, Objective-C++ compilations may use |
2524 | C++-specific options (e.g., @option{-Wabi}). | |
60de6385 SS |
2525 | |
2526 | Here is a list of options that are @emph{only} for compiling Objective-C | |
46e34f96 | 2527 | and Objective-C++ programs: |
60de6385 SS |
2528 | |
2529 | @table @gcctabopt | |
630d3d5a | 2530 | @item -fconstant-string-class=@var{class-name} |
cd3bb277 | 2531 | @opindex fconstant-string-class |
630d3d5a | 2532 | Use @var{class-name} as the name of the class to instantiate for each |
695ac33f | 2533 | literal string specified with the syntax @code{@@"@dots{}"}. The default |
264fa2db ZL |
2534 | class name is @code{NXConstantString} if the GNU runtime is being used, and |
2535 | @code{NSConstantString} if the NeXT runtime is being used (see below). The | |
2536 | @option{-fconstant-cfstrings} option, if also present, will override the | |
2537 | @option{-fconstant-string-class} setting and cause @code{@@"@dots{}"} literals | |
2538 | to be laid out as constant CoreFoundation strings. | |
60de6385 SS |
2539 | |
2540 | @item -fgnu-runtime | |
cd3bb277 | 2541 | @opindex fgnu-runtime |
60de6385 SS |
2542 | Generate object code compatible with the standard GNU Objective-C |
2543 | runtime. This is the default for most types of systems. | |
2544 | ||
2545 | @item -fnext-runtime | |
cd3bb277 | 2546 | @opindex fnext-runtime |
60de6385 | 2547 | Generate output compatible with the NeXT runtime. This is the default |
1f676100 NP |
2548 | for NeXT-based systems, including Darwin and Mac OS X@. The macro |
2549 | @code{__NEXT_RUNTIME__} is predefined if (and only if) this option is | |
2550 | used. | |
60de6385 | 2551 | |
264fa2db | 2552 | @item -fno-nil-receivers |
5ad7ae7f | 2553 | @opindex fno-nil-receivers |
35e711d3 NP |
2554 | Assume that all Objective-C message dispatches (@code{[receiver |
2555 | message:arg]}) in this translation unit ensure that the receiver is | |
2556 | not @code{nil}. This allows for more efficient entry points in the | |
2557 | runtime to be used. Currently, this option is only available in | |
2558 | conjunction with the NeXT runtime on Mac OS X 10.3 and later. | |
264fa2db | 2559 | |
6e955430 ZL |
2560 | @item -fobjc-call-cxx-cdtors |
2561 | @opindex fobjc-call-cxx-cdtors | |
2562 | For each Objective-C class, check if any of its instance variables is a | |
2563 | C++ object with a non-trivial default constructor. If so, synthesize a | |
2564 | special @code{- (id) .cxx_construct} instance method that will run | |
2565 | non-trivial default constructors on any such instance variables, in order, | |
2566 | and then return @code{self}. Similarly, check if any instance variable | |
2567 | is a C++ object with a non-trivial destructor, and if so, synthesize a | |
2568 | special @code{- (void) .cxx_destruct} method that will run | |
2569 | all such default destructors, in reverse order. | |
2570 | ||
35e711d3 NP |
2571 | The @code{- (id) .cxx_construct} and @code{- (void) .cxx_destruct} |
2572 | methods thusly generated will only operate on instance variables | |
2573 | declared in the current Objective-C class, and not those inherited | |
2574 | from superclasses. It is the responsibility of the Objective-C | |
2575 | runtime to invoke all such methods in an object's inheritance | |
2576 | hierarchy. The @code{- (id) .cxx_construct} methods will be invoked | |
2577 | by the runtime immediately after a new object instance is allocated; | |
2578 | the @code{- (void) .cxx_destruct} methods will be invoked immediately | |
2579 | before the runtime deallocates an object instance. | |
6e955430 ZL |
2580 | |
2581 | As of this writing, only the NeXT runtime on Mac OS X 10.4 and later has | |
2582 | support for invoking the @code{- (id) .cxx_construct} and | |
2583 | @code{- (void) .cxx_destruct} methods. | |
2584 | ||
2585 | @item -fobjc-direct-dispatch | |
2586 | @opindex fobjc-direct-dispatch | |
2587 | Allow fast jumps to the message dispatcher. On Darwin this is | |
128a79fb | 2588 | accomplished via the comm page. |
6e955430 | 2589 | |
264fa2db | 2590 | @item -fobjc-exceptions |
5ad7ae7f | 2591 | @opindex fobjc-exceptions |
35e711d3 NP |
2592 | Enable syntactic support for structured exception handling in |
2593 | Objective-C, similar to what is offered by C++ and Java. This option | |
2594 | is required to use the Objective-C keywords @code{@@try}, | |
2595 | @code{@@throw}, @code{@@catch}, @code{@@finally} and | |
2596 | @code{@@synchronized}. This option is available with both the GNU | |
2597 | runtime and the NeXT runtime (but not available in conjunction with | |
2598 | the NeXT runtime on Mac OS X 10.2 and earlier). | |
264fa2db | 2599 | |
6e955430 ZL |
2600 | @item -fobjc-gc |
2601 | @opindex fobjc-gc | |
35e711d3 NP |
2602 | Enable garbage collection (GC) in Objective-C and Objective-C++ |
2603 | programs. This option is only available with the NeXT runtime; the | |
2604 | GNU runtime has a different garbage collection implementation that | |
2605 | does not require special compiler flags. | |
6e955430 | 2606 | |
22d8d616 NP |
2607 | @item -fobjc-std=objc1 |
2608 | @opindex fobjc-std | |
2609 | Conform to the language syntax of Objective-C 1.0, the language | |
2610 | recognized by GCC 4.0. This only affects the Objective-C additions to | |
2611 | the C/C++ language; it does not affect conformance to C/C++ standards, | |
2612 | which is controlled by the separate C/C++ dialect option flags. When | |
2613 | this option is used with the Objective-C or Objective-C++ compiler, | |
2614 | any Objective-C syntax that is not recognized by GCC 4.0 is rejected. | |
2615 | This is useful if you need to make sure that your Objective-C code can | |
2616 | be compiled with older versions of GCC. | |
2617 | ||
264fa2db | 2618 | @item -freplace-objc-classes |
5ad7ae7f | 2619 | @opindex freplace-objc-classes |
264fa2db ZL |
2620 | Emit a special marker instructing @command{ld(1)} not to statically link in |
2621 | the resulting object file, and allow @command{dyld(1)} to load it in at | |
2622 | run time instead. This is used in conjunction with the Fix-and-Continue | |
daf2f129 | 2623 | debugging mode, where the object file in question may be recompiled and |
264fa2db ZL |
2624 | dynamically reloaded in the course of program execution, without the need |
2625 | to restart the program itself. Currently, Fix-and-Continue functionality | |
daf2f129 | 2626 | is only available in conjunction with the NeXT runtime on Mac OS X 10.3 |
264fa2db ZL |
2627 | and later. |
2628 | ||
2629 | @item -fzero-link | |
5ad7ae7f | 2630 | @opindex fzero-link |
264fa2db ZL |
2631 | When compiling for the NeXT runtime, the compiler ordinarily replaces calls |
2632 | to @code{objc_getClass("@dots{}")} (when the name of the class is known at | |
2633 | compile time) with static class references that get initialized at load time, | |
2634 | which improves run-time performance. Specifying the @option{-fzero-link} flag | |
2635 | suppresses this behavior and causes calls to @code{objc_getClass("@dots{}")} | |
daf2f129 | 2636 | to be retained. This is useful in Zero-Link debugging mode, since it allows |
264fa2db | 2637 | for individual class implementations to be modified during program execution. |
35e711d3 NP |
2638 | The GNU runtime currently always retains calls to @code{objc_get_class("@dots{}")} |
2639 | regardless of command line options. | |
264fa2db | 2640 | |
60de6385 | 2641 | @item -gen-decls |
cd3bb277 | 2642 | @opindex gen-decls |
60de6385 SS |
2643 | Dump interface declarations for all classes seen in the source file to a |
2644 | file named @file{@var{sourcename}.decl}. | |
2645 | ||
670b0231 | 2646 | @item -Wassign-intercept @r{(Objective-C and Objective-C++ only)} |
6e955430 | 2647 | @opindex Wassign-intercept |
ccd4e386 | 2648 | @opindex Wno-assign-intercept |
6e955430 ZL |
2649 | Warn whenever an Objective-C assignment is being intercepted by the |
2650 | garbage collector. | |
2651 | ||
670b0231 | 2652 | @item -Wno-protocol @r{(Objective-C and Objective-C++ only)} |
cd3bb277 | 2653 | @opindex Wno-protocol |
ccd4e386 | 2654 | @opindex Wprotocol |
1f676100 NP |
2655 | If a class is declared to implement a protocol, a warning is issued for |
2656 | every method in the protocol that is not implemented by the class. The | |
6335b0aa | 2657 | default behavior is to issue a warning for every method not explicitly |
1f676100 | 2658 | implemented in the class, even if a method implementation is inherited |
4ec7afd7 | 2659 | from the superclass. If you use the @option{-Wno-protocol} option, then |
1f676100 NP |
2660 | methods inherited from the superclass are considered to be implemented, |
2661 | and no warning is issued for them. | |
60de6385 | 2662 | |
670b0231 | 2663 | @item -Wselector @r{(Objective-C and Objective-C++ only)} |
cd3bb277 | 2664 | @opindex Wselector |
ccd4e386 | 2665 | @opindex Wno-selector |
1f676100 NP |
2666 | Warn if multiple methods of different types for the same selector are |
2667 | found during compilation. The check is performed on the list of methods | |
2668 | in the final stage of compilation. Additionally, a check is performed | |
9eff22bc LG |
2669 | for each selector appearing in a @code{@@selector(@dots{})} |
2670 | expression, and a corresponding method for that selector has been found | |
1f676100 NP |
2671 | during compilation. Because these checks scan the method table only at |
2672 | the end of compilation, these warnings are not produced if the final | |
2673 | stage of compilation is not reached, for example because an error is | |
4ec7afd7 | 2674 | found during compilation, or because the @option{-fsyntax-only} option is |
1f676100 NP |
2675 | being used. |
2676 | ||
670b0231 | 2677 | @item -Wstrict-selector-match @r{(Objective-C and Objective-C++ only)} |
6e955430 | 2678 | @opindex Wstrict-selector-match |
ccd4e386 | 2679 | @opindex Wno-strict-selector-match |
6e955430 ZL |
2680 | Warn if multiple methods with differing argument and/or return types are |
2681 | found for a given selector when attempting to send a message using this | |
2682 | selector to a receiver of type @code{id} or @code{Class}. When this flag | |
2683 | is off (which is the default behavior), the compiler will omit such warnings | |
2684 | if any differences found are confined to types which share the same size | |
2685 | and alignment. | |
2686 | ||
670b0231 | 2687 | @item -Wundeclared-selector @r{(Objective-C and Objective-C++ only)} |
1f676100 | 2688 | @opindex Wundeclared-selector |
ccd4e386 | 2689 | @opindex Wno-undeclared-selector |
1f676100 NP |
2690 | Warn if a @code{@@selector(@dots{})} expression referring to an |
2691 | undeclared selector is found. A selector is considered undeclared if no | |
daf2f129 | 2692 | method with that name has been declared before the |
9eff22bc LG |
2693 | @code{@@selector(@dots{})} expression, either explicitly in an |
2694 | @code{@@interface} or @code{@@protocol} declaration, or implicitly in | |
2695 | an @code{@@implementation} section. This option always performs its | |
2696 | checks as soon as a @code{@@selector(@dots{})} expression is found, | |
4ec7afd7 | 2697 | while @option{-Wselector} only performs its checks in the final stage of |
9eff22bc | 2698 | compilation. This also enforces the coding style convention |
1f676100 | 2699 | that methods and selectors must be declared before being used. |
60de6385 | 2700 | |
7989e4dc | 2701 | @item -print-objc-runtime-info |
5ad7ae7f | 2702 | @opindex print-objc-runtime-info |
7989e4dc RO |
2703 | Generate C header describing the largest structure that is passed by |
2704 | value, if any. | |
60de6385 SS |
2705 | |
2706 | @end table | |
2707 | ||
764dbbf2 GDR |
2708 | @node Language Independent Options |
2709 | @section Options to Control Diagnostic Messages Formatting | |
2710 | @cindex options to control diagnostics formatting | |
2711 | @cindex diagnostic messages | |
2712 | @cindex message formatting | |
2713 | ||
b192711e | 2714 | Traditionally, diagnostic messages have been formatted irrespective of |
e979f9e8 | 2715 | the output device's aspect (e.g.@: its width, @dots{}). The options described |
764dbbf2 | 2716 | below can be used to control the diagnostic messages formatting |
e979f9e8 | 2717 | algorithm, e.g.@: how many characters per line, how often source location |
6c0a4eab | 2718 | information should be reported. Right now, only the C++ front end can |
764dbbf2 | 2719 | honor these options. However it is expected, in the near future, that |
6c0a4eab | 2720 | the remaining front ends would be able to digest them correctly. |
764dbbf2 | 2721 | |
2642624b | 2722 | @table @gcctabopt |
764dbbf2 | 2723 | @item -fmessage-length=@var{n} |
cd3bb277 | 2724 | @opindex fmessage-length |
764dbbf2 | 2725 | Try to format error messages so that they fit on lines of about @var{n} |
aee96fe9 | 2726 | characters. The default is 72 characters for @command{g++} and 0 for the rest of |
161d7b59 | 2727 | the front ends supported by GCC@. If @var{n} is zero, then no |
02f52e19 | 2728 | line-wrapping will be done; each error message will appear on a single |
764dbbf2 GDR |
2729 | line. |
2730 | ||
cd3bb277 | 2731 | @opindex fdiagnostics-show-location |
764dbbf2 | 2732 | @item -fdiagnostics-show-location=once |
b192711e | 2733 | Only meaningful in line-wrapping mode. Instructs the diagnostic messages |
764dbbf2 GDR |
2734 | reporter to emit @emph{once} source location information; that is, in |
2735 | case the message is too long to fit on a single physical line and has to | |
2736 | be wrapped, the source location won't be emitted (as prefix) again, | |
2737 | over and over, in subsequent continuation lines. This is the default | |
c21cd8b1 | 2738 | behavior. |
764dbbf2 GDR |
2739 | |
2740 | @item -fdiagnostics-show-location=every-line | |
2741 | Only meaningful in line-wrapping mode. Instructs the diagnostic | |
2742 | messages reporter to emit the same source location information (as | |
4fe9b91c | 2743 | prefix) for physical lines that result from the process of breaking |
b192711e | 2744 | a message which is too long to fit on a single line. |
764dbbf2 | 2745 | |
1576e2be RM |
2746 | @item -fdiagnostics-show-option |
2747 | @opindex fdiagnostics-show-option | |
ccf08a6e DD |
2748 | This option instructs the diagnostic machinery to add text to each |
2749 | diagnostic emitted, which indicates which command line option directly | |
2750 | controls that diagnostic, when such an option is known to the | |
2751 | diagnostic machinery. | |
2752 | ||
16c1c158 RG |
2753 | @item -Wcoverage-mismatch |
2754 | @opindex Wcoverage-mismatch | |
2755 | Warn if feedback profiles do not match when using the | |
2756 | @option{-fprofile-use} option. | |
2757 | If a source file was changed between @option{-fprofile-gen} and | |
2758 | @option{-fprofile-use}, the files with the profile feedback can fail | |
2759 | to match the source file and GCC can not use the profile feedback | |
650cfcab NV |
2760 | information. By default, this warning is enabled and is treated as an |
2761 | error. @option{-Wno-coverage-mismatch} can be used to disable the | |
2762 | warning or @option{-Wno-error=coverage-mismatch} can be used to | |
2763 | disable the error. Disable the error for this warning can result in | |
2764 | poorly optimized code, so disabling the error is useful only in the | |
2765 | case of very minor changes such as bug fixes to an existing code-base. | |
2766 | Completely disabling the warning is not recommended. | |
16c1c158 | 2767 | |
764dbbf2 GDR |
2768 | @end table |
2769 | ||
74291a4b MM |
2770 | @node Warning Options |
2771 | @section Options to Request or Suppress Warnings | |
2772 | @cindex options to control warnings | |
2773 | @cindex warning messages | |
2774 | @cindex messages, warning | |
2775 | @cindex suppressing warnings | |
2776 | ||
2777 | Warnings are diagnostic messages that report constructions which | |
2778 | are not inherently erroneous but which are risky or suggest there | |
2779 | may have been an error. | |
2780 | ||
2b60abb7 MLI |
2781 | The following language-independent options do not enable specific |
2782 | warnings but control the kinds of diagnostics produced by GCC. | |
74291a4b | 2783 | |
2642624b | 2784 | @table @gcctabopt |
74291a4b MM |
2785 | @cindex syntax checking |
2786 | @item -fsyntax-only | |
cd3bb277 | 2787 | @opindex fsyntax-only |
74291a4b MM |
2788 | Check the code for syntax errors, but don't do anything beyond that. |
2789 | ||
3a789837 NF |
2790 | @item -fmax-errors=@var{n} |
2791 | @opindex fmax-errors | |
2792 | Limits the maximum number of error messages to @var{n}, at which point | |
2793 | GCC bails out rather than attempting to continue processing the source | |
2794 | code. If @var{n} is 0 (the default), there is no limit on the number | |
2795 | of error messages produced. If @option{-Wfatal-errors} is also | |
2796 | specified, then @option{-Wfatal-errors} takes precedence over this | |
2797 | option. | |
2798 | ||
2b60abb7 MLI |
2799 | @item -w |
2800 | @opindex w | |
2801 | Inhibit all warning messages. | |
2802 | ||
2803 | @item -Werror | |
2804 | @opindex Werror | |
ccd4e386 | 2805 | @opindex Wno-error |
2b60abb7 MLI |
2806 | Make all warnings into errors. |
2807 | ||
2808 | @item -Werror= | |
2809 | @opindex Werror= | |
ccd4e386 | 2810 | @opindex Wno-error= |
2b60abb7 MLI |
2811 | Make the specified warning into an error. The specifier for a warning |
2812 | is appended, for example @option{-Werror=switch} turns the warnings | |
2813 | controlled by @option{-Wswitch} into errors. This switch takes a | |
2814 | negative form, to be used to negate @option{-Werror} for specific | |
2815 | warnings, for example @option{-Wno-error=switch} makes | |
2816 | @option{-Wswitch} warnings not be errors, even when @option{-Werror} | |
2817 | is in effect. You can use the @option{-fdiagnostics-show-option} | |
2818 | option to have each controllable warning amended with the option which | |
2819 | controls it, to determine what to use with this option. | |
2820 | ||
2821 | Note that specifying @option{-Werror=}@var{foo} automatically implies | |
2822 | @option{-W}@var{foo}. However, @option{-Wno-error=}@var{foo} does not | |
2823 | imply anything. | |
2824 | ||
2825 | @item -Wfatal-errors | |
2826 | @opindex Wfatal-errors | |
ccd4e386 | 2827 | @opindex Wno-fatal-errors |
2b60abb7 MLI |
2828 | This option causes the compiler to abort compilation on the first error |
2829 | occurred rather than trying to keep going and printing further error | |
2830 | messages. | |
2831 | ||
2832 | @end table | |
2833 | ||
2834 | You can request many specific warnings with options beginning | |
2835 | @samp{-W}, for example @option{-Wimplicit} to request warnings on | |
2836 | implicit declarations. Each of these specific warning options also | |
2837 | has a negative form beginning @samp{-Wno-} to turn off warnings; for | |
2838 | example, @option{-Wno-implicit}. This manual lists only one of the | |
2839 | two forms, whichever is not the default. For further, | |
2840 | language-specific options also refer to @ref{C++ Dialect Options} and | |
2841 | @ref{Objective-C and Objective-C++ Dialect Options}. | |
2842 | ||
09ccff9f | 2843 | When an unrecognized warning option is requested (e.g., |
b8360603 | 2844 | @option{-Wunknown-warning}), GCC will emit a diagnostic stating |
09ccff9f | 2845 | that the option is not recognized. However, if the @option{-Wno-} form |
e54655a2 DN |
2846 | is used, the behavior is slightly different: No diagnostic will be |
2847 | produced for @option{-Wno-unknown-warning} unless other diagnostics | |
2848 | are being produced. This allows the use of new @option{-Wno-} options | |
2849 | with old compilers, but if something goes wrong, the compiler will | |
2850 | warn that an unrecognized option was used. | |
2851 | ||
2b60abb7 | 2852 | @table @gcctabopt |
74291a4b | 2853 | @item -pedantic |
cd3bb277 | 2854 | @opindex pedantic |
074e95e3 JM |
2855 | Issue all the warnings demanded by strict ISO C and ISO C++; |
2856 | reject all programs that use forbidden extensions, and some other | |
2857 | programs that do not follow ISO C and ISO C++. For ISO C, follows the | |
630d3d5a | 2858 | version of the ISO C standard specified by any @option{-std} option used. |
74291a4b | 2859 | |
074e95e3 | 2860 | Valid ISO C and ISO C++ programs should compile properly with or without |
5490d604 | 2861 | this option (though a rare few will require @option{-ansi} or a |
161d7b59 | 2862 | @option{-std} option specifying the required version of ISO C)@. However, |
b1d16193 JL |
2863 | without this option, certain GNU extensions and traditional C and C++ |
2864 | features are supported as well. With this option, they are rejected. | |
74291a4b | 2865 | |
630d3d5a | 2866 | @option{-pedantic} does not cause warning messages for use of the |
74291a4b MM |
2867 | alternate keywords whose names begin and end with @samp{__}. Pedantic |
2868 | warnings are also disabled in the expression that follows | |
2869 | @code{__extension__}. However, only system header files should use | |
2870 | these escape routes; application programs should avoid them. | |
2871 | @xref{Alternate Keywords}. | |
2872 | ||
630d3d5a | 2873 | Some users try to use @option{-pedantic} to check programs for strict ISO |
74291a4b | 2874 | C conformance. They soon find that it does not do quite what they want: |
c1030c7c | 2875 | it finds some non-ISO practices, but not all---only those for which |
074e95e3 JM |
2876 | ISO C @emph{requires} a diagnostic, and some others for which |
2877 | diagnostics have been added. | |
74291a4b | 2878 | |
074e95e3 | 2879 | A feature to report any failure to conform to ISO C might be useful in |
74291a4b | 2880 | some instances, but would require considerable additional work and would |
630d3d5a | 2881 | be quite different from @option{-pedantic}. We don't have plans to |
892d0a6d | 2882 | support such a feature in the near future. |
74291a4b | 2883 | |
91ea548a | 2884 | Where the standard specified with @option{-std} represents a GNU |
7e1542b9 | 2885 | extended dialect of C, such as @samp{gnu90} or @samp{gnu99}, there is a |
91ea548a JM |
2886 | corresponding @dfn{base standard}, the version of ISO C on which the GNU |
2887 | extended dialect is based. Warnings from @option{-pedantic} are given | |
2888 | where they are required by the base standard. (It would not make sense | |
2889 | for such warnings to be given only for features not in the specified GNU | |
2890 | C dialect, since by definition the GNU dialects of C include all | |
2891 | features the compiler supports with the given option, and there would be | |
2892 | nothing to warn about.) | |
2893 | ||
74291a4b | 2894 | @item -pedantic-errors |
cd3bb277 | 2895 | @opindex pedantic-errors |
630d3d5a | 2896 | Like @option{-pedantic}, except that errors are produced rather than |
74291a4b MM |
2897 | warnings. |
2898 | ||
60df726b MLI |
2899 | @item -Wall |
2900 | @opindex Wall | |
ccd4e386 | 2901 | @opindex Wno-all |
60df726b MLI |
2902 | This enables all the warnings about constructions that some users |
2903 | consider questionable, and that are easy to avoid (or modify to | |
2904 | prevent the warning), even in conjunction with macros. This also | |
2905 | enables some language-specific warnings described in @ref{C++ Dialect | |
2906 | Options} and @ref{Objective-C and Objective-C++ Dialect Options}. | |
2907 | ||
2908 | @option{-Wall} turns on the following warning flags: | |
7b6cb843 MLI |
2909 | |
2910 | @gccoptlist{-Waddress @gol | |
e4d35515 | 2911 | -Warray-bounds @r{(only with} @option{-O2}@r{)} @gol |
7b6cb843 MLI |
2912 | -Wc++0x-compat @gol |
2913 | -Wchar-subscripts @gol | |
6866c6e8 | 2914 | -Wenum-compare @r{(in C/Objc; this is on by default in C++)} @gol |
3734d960 MLI |
2915 | -Wimplicit-int @r{(C and Objective-C only)} @gol |
2916 | -Wimplicit-function-declaration @r{(C and Objective-C only)} @gol | |
7b6cb843 MLI |
2917 | -Wcomment @gol |
2918 | -Wformat @gol | |
2919 | -Wmain @r{(only for C/ObjC and unless} @option{-ffreestanding}@r{)} @gol | |
2920 | -Wmissing-braces @gol | |
2921 | -Wnonnull @gol | |
2922 | -Wparentheses @gol | |
2923 | -Wpointer-sign @gol | |
2924 | -Wreorder @gol | |
2925 | -Wreturn-type @gol | |
2926 | -Wsequence-point @gol | |
2927 | -Wsign-compare @r{(only in C++)} @gol | |
2928 | -Wstrict-aliasing @gol | |
027b740e | 2929 | -Wstrict-overflow=1 @gol |
7b6cb843 MLI |
2930 | -Wswitch @gol |
2931 | -Wtrigraphs @gol | |
2dc74010 | 2932 | -Wuninitialized @gol |
7b6cb843 MLI |
2933 | -Wunknown-pragmas @gol |
2934 | -Wunused-function @gol | |
2935 | -Wunused-label @gol | |
2936 | -Wunused-value @gol | |
2937 | -Wunused-variable @gol | |
16302daf | 2938 | -Wvolatile-register-var @gol |
60df726b MLI |
2939 | } |
2940 | ||
e847d3bf MLI |
2941 | Note that some warning flags are not implied by @option{-Wall}. Some of |
2942 | them warn about constructions that users generally do not consider | |
2943 | questionable, but which occasionally you might wish to check for; | |
2944 | others warn about constructions that are necessary or hard to avoid in | |
2945 | some cases, and there is no simple way to modify the code to suppress | |
2946 | the warning. Some of them are enabled by @option{-Wextra} but many of | |
2947 | them must be enabled individually. | |
2948 | ||
2949 | @item -Wextra | |
2950 | @opindex W | |
2951 | @opindex Wextra | |
ccd4e386 | 2952 | @opindex Wno-extra |
e847d3bf MLI |
2953 | This enables some extra warning flags that are not enabled by |
2954 | @option{-Wall}. (This option used to be called @option{-W}. The older | |
2955 | name is still supported, but the newer name is more descriptive.) | |
2956 | ||
2957 | @gccoptlist{-Wclobbered @gol | |
2958 | -Wempty-body @gol | |
5db2e9ca | 2959 | -Wignored-qualifiers @gol |
e847d3bf MLI |
2960 | -Wmissing-field-initializers @gol |
2961 | -Wmissing-parameter-type @r{(C only)} @gol | |
2962 | -Wold-style-declaration @r{(C only)} @gol | |
2963 | -Woverride-init @gol | |
2964 | -Wsign-compare @gol | |
2965 | -Wtype-limits @gol | |
2dc74010 | 2966 | -Wuninitialized @gol |
ebfbbdc5 JJ |
2967 | -Wunused-parameter @r{(only with} @option{-Wunused} @r{or} @option{-Wall}@r{)} @gol |
2968 | -Wunused-but-set-parameter @r{(only with} @option{-Wunused} @r{or} @option{-Wall}@r{)} @gol | |
e847d3bf MLI |
2969 | } |
2970 | ||
2971 | The option @option{-Wextra} also prints warning messages for the | |
2972 | following cases: | |
2973 | ||
2974 | @itemize @bullet | |
2975 | ||
2976 | @item | |
2977 | A pointer is compared against integer zero with @samp{<}, @samp{<=}, | |
2978 | @samp{>}, or @samp{>=}. | |
2979 | ||
7a61cf6f | 2980 | @item |
e847d3bf MLI |
2981 | (C++ only) An enumerator and a non-enumerator both appear in a |
2982 | conditional expression. | |
2983 | ||
7a61cf6f | 2984 | @item |
e847d3bf MLI |
2985 | (C++ only) Ambiguous virtual bases. |
2986 | ||
7a61cf6f | 2987 | @item |
e847d3bf MLI |
2988 | (C++ only) Subscripting an array which has been declared @samp{register}. |
2989 | ||
7a61cf6f | 2990 | @item |
e847d3bf MLI |
2991 | (C++ only) Taking the address of a variable which has been declared |
2992 | @samp{register}. | |
2993 | ||
7a61cf6f | 2994 | @item |
e847d3bf MLI |
2995 | (C++ only) A base class is not initialized in a derived class' copy |
2996 | constructor. | |
2997 | ||
2998 | @end itemize | |
2999 | ||
74291a4b | 3000 | @item -Wchar-subscripts |
cd3bb277 | 3001 | @opindex Wchar-subscripts |
ccd4e386 | 3002 | @opindex Wno-char-subscripts |
74291a4b MM |
3003 | Warn if an array subscript has type @code{char}. This is a common cause |
3004 | of error, as programmers often forget that this type is signed on some | |
3005 | machines. | |
69cdf050 | 3006 | This warning is enabled by @option{-Wall}. |
74291a4b MM |
3007 | |
3008 | @item -Wcomment | |
cd3bb277 | 3009 | @opindex Wcomment |
ccd4e386 | 3010 | @opindex Wno-comment |
74291a4b MM |
3011 | Warn whenever a comment-start sequence @samp{/*} appears in a @samp{/*} |
3012 | comment, or whenever a Backslash-Newline appears in a @samp{//} comment. | |
69cdf050 | 3013 | This warning is enabled by @option{-Wall}. |
74291a4b | 3014 | |
87cf0651 SB |
3015 | @item -Wno-cpp \ |
3016 | @r{(C, Objective-C, C++, Objective-C++ and Fortran only)} | |
3017 | ||
3018 | Suppress warning messages emitted by @code{#warning} directives. | |
3019 | ||
c5ee1358 | 3020 | @item -Wdouble-promotion @r{(C, C++, Objective-C and Objective-C++ only)} |
0a0b3574 MM |
3021 | @opindex Wdouble-promotion |
3022 | @opindex Wno-double-promotion | |
3023 | Give a warning when a value of type @code{float} is implicitly | |
3024 | promoted to @code{double}. CPUs with a 32-bit ``single-precision'' | |
3025 | floating-point unit implement @code{float} in hardware, but emulate | |
3026 | @code{double} in software. On such a machine, doing computations | |
3027 | using @code{double} values is much more expensive because of the | |
3028 | overhead required for software emulation. | |
3029 | ||
3030 | It is easy to accidentally do computations with @code{double} because | |
3031 | floating-point literals are implicitly of type @code{double}. For | |
3032 | example, in: | |
3033 | @smallexample | |
3034 | @group | |
3035 | float area(float radius) | |
3036 | @{ | |
3037 | return 3.14159 * radius * radius; | |
3038 | @} | |
3039 | @end group | |
3040 | @end smallexample | |
3041 | the compiler will perform the entire computation with @code{double} | |
3042 | because the floating-point literal is a @code{double}. | |
3043 | ||
74291a4b | 3044 | @item -Wformat |
cd3bb277 | 3045 | @opindex Wformat |
ccd4e386 | 3046 | @opindex Wno-format |
e6e931b7 JM |
3047 | @opindex ffreestanding |
3048 | @opindex fno-builtin | |
74291a4b MM |
3049 | Check calls to @code{printf} and @code{scanf}, etc., to make sure that |
3050 | the arguments supplied have types appropriate to the format string | |
26f6672d JM |
3051 | specified, and that the conversions specified in the format string make |
3052 | sense. This includes standard functions, and others specified by format | |
3053 | attributes (@pxref{Function Attributes}), in the @code{printf}, | |
3054 | @code{scanf}, @code{strftime} and @code{strfmon} (an X/Open extension, | |
a2bec818 | 3055 | not in the C standard) families (or other target-specific families). |
e6e931b7 JM |
3056 | Which functions are checked without format attributes having been |
3057 | specified depends on the standard version selected, and such checks of | |
3058 | functions without the attribute specified are disabled by | |
3059 | @option{-ffreestanding} or @option{-fno-builtin}. | |
74291a4b | 3060 | |
8308e0b7 | 3061 | The formats are checked against the format features supported by GNU |
3764f879 | 3062 | libc version 2.2. These include all ISO C90 and C99 features, as well |
8308e0b7 JM |
3063 | as features from the Single Unix Specification and some BSD and GNU |
3064 | extensions. Other library implementations may not support all these | |
3065 | features; GCC does not support warning about features that go beyond a | |
630d3d5a JM |
3066 | particular library's limitations. However, if @option{-pedantic} is used |
3067 | with @option{-Wformat}, warnings will be given about format features not | |
26f6672d JM |
3068 | in the selected standard version (but not for @code{strfmon} formats, |
3069 | since those are not in any version of the C standard). @xref{C Dialect | |
3070 | Options,,Options Controlling C Dialect}. | |
8308e0b7 | 3071 | |
b34c7881 JT |
3072 | Since @option{-Wformat} also checks for null format arguments for |
3073 | several functions, @option{-Wformat} also implies @option{-Wnonnull}. | |
3074 | ||
630d3d5a | 3075 | @option{-Wformat} is included in @option{-Wall}. For more control over some |
c76f4e8e | 3076 | aspects of format checking, the options @option{-Wformat-y2k}, |
e964a556 JT |
3077 | @option{-Wno-format-extra-args}, @option{-Wno-format-zero-length}, |
3078 | @option{-Wformat-nonliteral}, @option{-Wformat-security}, and | |
3079 | @option{-Wformat=2} are available, but are not included in @option{-Wall}. | |
4d808927 | 3080 | |
c76f4e8e JM |
3081 | @item -Wformat-y2k |
3082 | @opindex Wformat-y2k | |
ccd4e386 | 3083 | @opindex Wno-format-y2k |
c76f4e8e | 3084 | If @option{-Wformat} is specified, also warn about @code{strftime} |
4d808927 JM |
3085 | formats which may yield only a two-digit year. |
3086 | ||
802e3f8c RW |
3087 | @item -Wno-format-contains-nul |
3088 | @opindex Wno-format-contains-nul | |
3089 | @opindex Wformat-contains-nul | |
3090 | If @option{-Wformat} is specified, do not warn about format strings that | |
3091 | contain NUL bytes. | |
3092 | ||
4d808927 | 3093 | @item -Wno-format-extra-args |
cd3bb277 | 3094 | @opindex Wno-format-extra-args |
ccd4e386 | 3095 | @opindex Wformat-extra-args |
630d3d5a | 3096 | If @option{-Wformat} is specified, do not warn about excess arguments to a |
4d808927 JM |
3097 | @code{printf} or @code{scanf} format function. The C standard specifies |
3098 | that such arguments are ignored. | |
3099 | ||
7e5fb12f JM |
3100 | Where the unused arguments lie between used arguments that are |
3101 | specified with @samp{$} operand number specifications, normally | |
3102 | warnings are still given, since the implementation could not know what | |
3103 | type to pass to @code{va_arg} to skip the unused arguments. However, | |
3104 | in the case of @code{scanf} formats, this option will suppress the | |
3105 | warning if the unused arguments are all pointers, since the Single | |
3106 | Unix Specification says that such unused arguments are allowed. | |
3107 | ||
670b0231 | 3108 | @item -Wno-format-zero-length @r{(C and Objective-C only)} |
e964a556 | 3109 | @opindex Wno-format-zero-length |
ccd4e386 | 3110 | @opindex Wformat-zero-length |
e964a556 JT |
3111 | If @option{-Wformat} is specified, do not warn about zero-length formats. |
3112 | The C standard specifies that zero-length formats are allowed. | |
3113 | ||
4d808927 | 3114 | @item -Wformat-nonliteral |
cd3bb277 | 3115 | @opindex Wformat-nonliteral |
ccd4e386 | 3116 | @opindex Wno-format-nonliteral |
630d3d5a | 3117 | If @option{-Wformat} is specified, also warn if the format string is not a |
4d808927 JM |
3118 | string literal and so cannot be checked, unless the format function |
3119 | takes its format arguments as a @code{va_list}. | |
3120 | ||
c907e684 | 3121 | @item -Wformat-security |
cd3bb277 | 3122 | @opindex Wformat-security |
ccd4e386 | 3123 | @opindex Wno-format-security |
630d3d5a | 3124 | If @option{-Wformat} is specified, also warn about uses of format |
c907e684 JM |
3125 | functions that represent possible security problems. At present, this |
3126 | warns about calls to @code{printf} and @code{scanf} functions where the | |
3127 | format string is not a string literal and there are no format arguments, | |
3128 | as in @code{printf (foo);}. This may be a security hole if the format | |
3129 | string came from untrusted input and contains @samp{%n}. (This is | |
630d3d5a JM |
3130 | currently a subset of what @option{-Wformat-nonliteral} warns about, but |
3131 | in future warnings may be added to @option{-Wformat-security} that are not | |
3132 | included in @option{-Wformat-nonliteral}.) | |
c907e684 | 3133 | |
4d808927 | 3134 | @item -Wformat=2 |
cd3bb277 | 3135 | @opindex Wformat=2 |
ccd4e386 | 3136 | @opindex Wno-format=2 |
630d3d5a JM |
3137 | Enable @option{-Wformat} plus format checks not included in |
3138 | @option{-Wformat}. Currently equivalent to @samp{-Wformat | |
c76f4e8e | 3139 | -Wformat-nonliteral -Wformat-security -Wformat-y2k}. |
4d808927 | 3140 | |
670b0231 | 3141 | @item -Wnonnull @r{(C and Objective-C only)} |
b34c7881 | 3142 | @opindex Wnonnull |
ccd4e386 | 3143 | @opindex Wno-nonnull |
f6d9224f | 3144 | Warn about passing a null pointer for arguments marked as |
b34c7881 JT |
3145 | requiring a non-null value by the @code{nonnull} function attribute. |
3146 | ||
3147 | @option{-Wnonnull} is included in @option{-Wall} and @option{-Wformat}. It | |
3148 | can be disabled with the @option{-Wno-nonnull} option. | |
3149 | ||
46e34f96 | 3150 | @item -Winit-self @r{(C, C++, Objective-C and Objective-C++ only)} |
3390f9c9 | 3151 | @opindex Winit-self |
ccd4e386 | 3152 | @opindex Wno-init-self |
f6d9224f | 3153 | Warn about uninitialized variables which are initialized with themselves. |
2dc74010 | 3154 | Note this option can only be used with the @option{-Wuninitialized} option. |
3390f9c9 | 3155 | |
f6d9224f GP |
3156 | For example, GCC will warn about @code{i} being uninitialized in the |
3157 | following snippet only when @option{-Winit-self} has been specified: | |
3390f9c9 AP |
3158 | @smallexample |
3159 | @group | |
3160 | int f() | |
3161 | @{ | |
3162 | int i = i; | |
3163 | return i; | |
3164 | @} | |
3165 | @end group | |
3166 | @end smallexample | |
3167 | ||
670b0231 | 3168 | @item -Wimplicit-int @r{(C and Objective-C only)} |
cd3bb277 | 3169 | @opindex Wimplicit-int |
ccd4e386 | 3170 | @opindex Wno-implicit-int |
e9a25f70 | 3171 | Warn when a declaration does not specify a type. |
69cdf050 | 3172 | This warning is enabled by @option{-Wall}. |
e9a25f70 | 3173 | |
670b0231 | 3174 | @item -Wimplicit-function-declaration @r{(C and Objective-C only)} |
cd3bb277 | 3175 | @opindex Wimplicit-function-declaration |
dc90f45b MLI |
3176 | @opindex Wno-implicit-function-declaration |
3177 | Give a warning whenever a function is used before being declared. In | |
3178 | C99 mode (@option{-std=c99} or @option{-std=gnu99}), this warning is | |
3179 | enabled by default and it is made into an error by | |
3180 | @option{-pedantic-errors}. This warning is also enabled by | |
3181 | @option{-Wall}. | |
e9a25f70 | 3182 | |
3734d960 | 3183 | @item -Wimplicit @r{(C and Objective-C only)} |
cd3bb277 | 3184 | @opindex Wimplicit |
ccd4e386 | 3185 | @opindex Wno-implicit |
630d3d5a | 3186 | Same as @option{-Wimplicit-int} and @option{-Wimplicit-function-declaration}. |
69cdf050 | 3187 | This warning is enabled by @option{-Wall}. |
861bb6c1 | 3188 | |
670b0231 | 3189 | @item -Wignored-qualifiers @r{(C and C++ only)} |
5db2e9ca DK |
3190 | @opindex Wignored-qualifiers |
3191 | @opindex Wno-ignored-qualifiers | |
3192 | Warn if the return type of a function has a type qualifier | |
3193 | such as @code{const}. For ISO C such a type qualifier has no effect, | |
3194 | since the value returned by a function is not an lvalue. | |
3195 | For C++, the warning is only emitted for scalar types or @code{void}. | |
3196 | ISO C prohibits qualified @code{void} return types on function | |
3197 | definitions, so such return types always receive a warning | |
3198 | even without this option. | |
3199 | ||
3200 | This warning is also enabled by @option{-Wextra}. | |
3201 | ||
861bb6c1 | 3202 | @item -Wmain |
cd3bb277 | 3203 | @opindex Wmain |
ccd4e386 | 3204 | @opindex Wno-main |
4003301d MLI |
3205 | Warn if the type of @samp{main} is suspicious. @samp{main} should be |
3206 | a function with external linkage, returning int, taking either zero | |
3207 | arguments, two, or three arguments of appropriate types. This warning | |
3208 | is enabled by default in C++ and is enabled by either @option{-Wall} | |
3209 | or @option{-pedantic}. | |
4a870dba | 3210 | |
1f0c3120 | 3211 | @item -Wmissing-braces |
cd3bb277 | 3212 | @opindex Wmissing-braces |
ccd4e386 | 3213 | @opindex Wno-missing-braces |
1f0c3120 JM |
3214 | Warn if an aggregate or union initializer is not fully bracketed. In |
3215 | the following example, the initializer for @samp{a} is not fully | |
3216 | bracketed, but that for @samp{b} is fully bracketed. | |
3217 | ||
3218 | @smallexample | |
3219 | int a[2][2] = @{ 0, 1, 2, 3 @}; | |
3220 | int b[2][2] = @{ @{ 0, 1 @}, @{ 2, 3 @} @}; | |
3221 | @end smallexample | |
3222 | ||
69cdf050 JM |
3223 | This warning is enabled by @option{-Wall}. |
3224 | ||
46e34f96 | 3225 | @item -Wmissing-include-dirs @r{(C, C++, Objective-C and Objective-C++ only)} |
b02398bd | 3226 | @opindex Wmissing-include-dirs |
ccd4e386 | 3227 | @opindex Wno-missing-include-dirs |
b02398bd BE |
3228 | Warn if a user-supplied include directory does not exist. |
3229 | ||
74291a4b | 3230 | @item -Wparentheses |
cd3bb277 | 3231 | @opindex Wparentheses |
ccd4e386 | 3232 | @opindex Wno-parentheses |
74291a4b MM |
3233 | Warn if parentheses are omitted in certain contexts, such |
3234 | as when there is an assignment in a context where a truth value | |
3235 | is expected, or when operators are nested whose precedence people | |
2a67bec2 | 3236 | often get confused about. |
3e3970a2 JM |
3237 | |
3238 | Also warn if a comparison like @samp{x<=y<=z} appears; this is | |
3239 | equivalent to @samp{(x<=y ? 1 : 0) <= z}, which is a different | |
3240 | interpretation from that of ordinary mathematical notation. | |
74291a4b | 3241 | |
e9a25f70 JL |
3242 | Also warn about constructions where there may be confusion to which |
3243 | @code{if} statement an @code{else} branch belongs. Here is an example of | |
3244 | such a case: | |
3245 | ||
3246 | @smallexample | |
aee96fe9 | 3247 | @group |
e9a25f70 JL |
3248 | @{ |
3249 | if (a) | |
3250 | if (b) | |
3251 | foo (); | |
3252 | else | |
3253 | bar (); | |
3254 | @} | |
aee96fe9 | 3255 | @end group |
e9a25f70 JL |
3256 | @end smallexample |
3257 | ||
2a67bec2 ILT |
3258 | In C/C++, every @code{else} branch belongs to the innermost possible |
3259 | @code{if} statement, which in this example is @code{if (b)}. This is | |
3260 | often not what the programmer expected, as illustrated in the above | |
3261 | example by indentation the programmer chose. When there is the | |
3262 | potential for this confusion, GCC will issue a warning when this flag | |
3263 | is specified. To eliminate the warning, add explicit braces around | |
3264 | the innermost @code{if} statement so there is no way the @code{else} | |
3265 | could belong to the enclosing @code{if}. The resulting code would | |
3266 | look like this: | |
e9a25f70 JL |
3267 | |
3268 | @smallexample | |
aee96fe9 | 3269 | @group |
e9a25f70 JL |
3270 | @{ |
3271 | if (a) | |
3272 | @{ | |
3273 | if (b) | |
3274 | foo (); | |
3275 | else | |
3276 | bar (); | |
3277 | @} | |
3278 | @} | |
aee96fe9 | 3279 | @end group |
e9a25f70 JL |
3280 | @end smallexample |
3281 | ||
d166d4c3 AK |
3282 | Also warn for dangerous uses of the |
3283 | ?: with omitted middle operand GNU extension. When the condition | |
3284 | in the ?: operator is a boolean expression the omitted value will | |
3285 | be always 1. Often the user expects it to be a value computed | |
3286 | inside the conditional expression instead. | |
3287 | ||
69cdf050 JM |
3288 | This warning is enabled by @option{-Wall}. |
3289 | ||
bb58bec5 | 3290 | @item -Wsequence-point |
cd3bb277 | 3291 | @opindex Wsequence-point |
ccd4e386 | 3292 | @opindex Wno-sequence-point |
bb58bec5 | 3293 | Warn about code that may have undefined semantics because of violations |
7127d9c7 DM |
3294 | of sequence point rules in the C and C++ standards. |
3295 | ||
3296 | The C and C++ standards defines the order in which expressions in a C/C++ | |
3297 | program are evaluated in terms of @dfn{sequence points}, which represent | |
3298 | a partial ordering between the execution of parts of the program: those | |
3299 | executed before the sequence point, and those executed after it. These | |
3300 | occur after the evaluation of a full expression (one which is not part | |
3301 | of a larger expression), after the evaluation of the first operand of a | |
bb58bec5 JM |
3302 | @code{&&}, @code{||}, @code{? :} or @code{,} (comma) operator, before a |
3303 | function is called (but after the evaluation of its arguments and the | |
3304 | expression denoting the called function), and in certain other places. | |
3305 | Other than as expressed by the sequence point rules, the order of | |
3306 | evaluation of subexpressions of an expression is not specified. All | |
3307 | these rules describe only a partial order rather than a total order, | |
3308 | since, for example, if two functions are called within one expression | |
3309 | with no sequence point between them, the order in which the functions | |
3310 | are called is not specified. However, the standards committee have | |
3311 | ruled that function calls do not overlap. | |
3312 | ||
3313 | It is not specified when between sequence points modifications to the | |
3314 | values of objects take effect. Programs whose behavior depends on this | |
7127d9c7 DM |
3315 | have undefined behavior; the C and C++ standards specify that ``Between |
3316 | the previous and next sequence point an object shall have its stored | |
cb7ad97b | 3317 | value modified at most once by the evaluation of an expression. |
7127d9c7 DM |
3318 | Furthermore, the prior value shall be read only to determine the value |
3319 | to be stored.''. If a program breaks these rules, the results on any | |
bb58bec5 JM |
3320 | particular implementation are entirely unpredictable. |
3321 | ||
3322 | Examples of code with undefined behavior are @code{a = a++;}, @code{a[n] | |
3323 | = b[n++]} and @code{a[i++] = i;}. Some more complicated cases are not | |
3324 | diagnosed by this option, and it may give an occasional false positive | |
3325 | result, but in general it has been found fairly effective at detecting | |
3326 | this sort of problem in programs. | |
3327 | ||
7127d9c7 | 3328 | The standard is worded confusingly, therefore there is some debate |
9c34dbbf ZW |
3329 | over the precise meaning of the sequence point rules in subtle cases. |
3330 | Links to discussions of the problem, including proposed formal | |
962e6e00 | 3331 | definitions, may be found on the GCC readings page, at |
ab940b73 | 3332 | @uref{http://gcc.gnu.org/@/readings.html}. |
bb58bec5 | 3333 | |
7127d9c7 | 3334 | This warning is enabled by @option{-Wall} for C and C++. |
69cdf050 | 3335 | |
74291a4b | 3336 | @item -Wreturn-type |
cd3bb277 | 3337 | @opindex Wreturn-type |
ffd5f276 MLI |
3338 | @opindex Wno-return-type |
3339 | Warn whenever a function is defined with a return-type that defaults | |
3340 | to @code{int}. Also warn about any @code{return} statement with no | |
3341 | return-value in a function whose return-type is not @code{void} | |
3342 | (falling off the end of the function body is considered returning | |
e4ae5e77 | 3343 | without a value), and about a @code{return} statement with an |
ffd5f276 | 3344 | expression in a function whose return-type is @code{void}. |
32c4c36c ML |
3345 | |
3346 | For C++, a function without return type always produces a diagnostic | |
767094dd | 3347 | message, even when @option{-Wno-return-type} is specified. The only |
32c4c36c | 3348 | exceptions are @samp{main} and functions defined in system headers. |
74291a4b | 3349 | |
69cdf050 JM |
3350 | This warning is enabled by @option{-Wall}. |
3351 | ||
74291a4b | 3352 | @item -Wswitch |
cd3bb277 | 3353 | @opindex Wswitch |
ccd4e386 | 3354 | @opindex Wno-switch |
2eac577f | 3355 | Warn whenever a @code{switch} statement has an index of enumerated type |
74291a4b MM |
3356 | and lacks a @code{case} for one or more of the named codes of that |
3357 | enumeration. (The presence of a @code{default} label prevents this | |
3358 | warning.) @code{case} labels outside the enumeration range also | |
cdb88468 ILT |
3359 | provoke warnings when this option is used (even if there is a |
3360 | @code{default} label). | |
69cdf050 | 3361 | This warning is enabled by @option{-Wall}. |
74291a4b | 3362 | |
d6961341 | 3363 | @item -Wswitch-default |
ccd4e386 RW |
3364 | @opindex Wswitch-default |
3365 | @opindex Wno-switch-default | |
d6961341 AC |
3366 | Warn whenever a @code{switch} statement does not have a @code{default} |
3367 | case. | |
3368 | ||
173028e5 AC |
3369 | @item -Wswitch-enum |
3370 | @opindex Wswitch-enum | |
ccd4e386 | 3371 | @opindex Wno-switch-enum |
2eac577f | 3372 | Warn whenever a @code{switch} statement has an index of enumerated type |
173028e5 AC |
3373 | and lacks a @code{case} for one or more of the named codes of that |
3374 | enumeration. @code{case} labels outside the enumeration range also | |
cdb88468 ILT |
3375 | provoke warnings when this option is used. The only difference |
3376 | between @option{-Wswitch} and this option is that this option gives a | |
3377 | warning about an omitted enumeration code even if there is a | |
3378 | @code{default} label. | |
173028e5 | 3379 | |
a072f1cf | 3380 | @item -Wsync-nand @r{(C and C++ only)} |
23462d4d UB |
3381 | @opindex Wsync-nand |
3382 | @opindex Wno-sync-nand | |
3383 | Warn when @code{__sync_fetch_and_nand} and @code{__sync_nand_and_fetch} | |
3384 | built-in functions are used. These functions changed semantics in GCC 4.4. | |
3385 | ||
74291a4b | 3386 | @item -Wtrigraphs |
cd3bb277 | 3387 | @opindex Wtrigraphs |
ccd4e386 | 3388 | @opindex Wno-trigraphs |
f2ecb02d JM |
3389 | Warn if any trigraphs are encountered that might change the meaning of |
3390 | the program (trigraphs within comments are not warned about). | |
69cdf050 | 3391 | This warning is enabled by @option{-Wall}. |
74291a4b | 3392 | |
ebfbbdc5 JJ |
3393 | @item -Wunused-but-set-parameter |
3394 | @opindex Wunused-but-set-parameter | |
3395 | @opindex Wno-unused-but-set-parameter | |
3396 | Warn whenever a function parameter is assigned to, but otherwise unused | |
3397 | (aside from its declaration). | |
3398 | ||
3399 | To suppress this warning use the @samp{unused} attribute | |
3400 | (@pxref{Variable Attributes}). | |
3401 | ||
3402 | This warning is also enabled by @option{-Wunused} together with | |
3403 | @option{-Wextra}. | |
3404 | ||
3405 | @item -Wunused-but-set-variable | |
3406 | @opindex Wunused-but-set-variable | |
3407 | @opindex Wno-unused-but-set-variable | |
3408 | Warn whenever a local variable is assigned to, but otherwise unused | |
3409 | (aside from its declaration). | |
3410 | This warning is enabled by @option{-Wall}. | |
3411 | ||
3412 | To suppress this warning use the @samp{unused} attribute | |
3413 | (@pxref{Variable Attributes}). | |
3414 | ||
3415 | This warning is also enabled by @option{-Wunused}, which is enabled | |
3416 | by @option{-Wall}. | |
3417 | ||
078721e1 | 3418 | @item -Wunused-function |
cd3bb277 | 3419 | @opindex Wunused-function |
ccd4e386 | 3420 | @opindex Wno-unused-function |
078721e1 | 3421 | Warn whenever a static function is declared but not defined or a |
aa58883c | 3422 | non-inline static function is unused. |
69cdf050 | 3423 | This warning is enabled by @option{-Wall}. |
74291a4b | 3424 | |
078721e1 | 3425 | @item -Wunused-label |
cd3bb277 | 3426 | @opindex Wunused-label |
ccd4e386 | 3427 | @opindex Wno-unused-label |
078721e1 | 3428 | Warn whenever a label is declared but not used. |
69cdf050 | 3429 | This warning is enabled by @option{-Wall}. |
078721e1 AC |
3430 | |
3431 | To suppress this warning use the @samp{unused} attribute | |
3432 | (@pxref{Variable Attributes}). | |
3433 | ||
3434 | @item -Wunused-parameter | |
cd3bb277 | 3435 | @opindex Wunused-parameter |
ccd4e386 | 3436 | @opindex Wno-unused-parameter |
078721e1 AC |
3437 | Warn whenever a function parameter is unused aside from its declaration. |
3438 | ||
3439 | To suppress this warning use the @samp{unused} attribute | |
3440 | (@pxref{Variable Attributes}). | |
956d6950 | 3441 | |
156f545a MLI |
3442 | @item -Wno-unused-result |
3443 | @opindex Wunused-result | |
3444 | @opindex Wno-unused-result | |
3445 | Do not warn if a caller of a function marked with attribute | |
3446 | @code{warn_unused_result} (@pxref{Variable Attributes}) does not use | |
3447 | its return value. The default is @option{-Wunused-result}. | |
3448 | ||
078721e1 | 3449 | @item -Wunused-variable |
cd3bb277 | 3450 | @opindex Wunused-variable |
ccd4e386 | 3451 | @opindex Wno-unused-variable |
078721e1 | 3452 | Warn whenever a local variable or non-constant static variable is unused |
bc49e371 | 3453 | aside from its declaration. |
69cdf050 | 3454 | This warning is enabled by @option{-Wall}. |
078721e1 AC |
3455 | |
3456 | To suppress this warning use the @samp{unused} attribute | |
74291a4b MM |
3457 | (@pxref{Variable Attributes}). |
3458 | ||
078721e1 | 3459 | @item -Wunused-value |
cd3bb277 | 3460 | @opindex Wunused-value |
ccd4e386 | 3461 | @opindex Wno-unused-value |
27f33b15 MLI |
3462 | Warn whenever a statement computes a result that is explicitly not |
3463 | used. To suppress this warning cast the unused expression to | |
3464 | @samp{void}. This includes an expression-statement or the left-hand | |
3465 | side of a comma expression that contains no side effects. For example, | |
3466 | an expression such as @samp{x[i,j]} will cause a warning, while | |
3467 | @samp{x[(void)i,j]} will not. | |
078721e1 | 3468 | |
27f33b15 | 3469 | This warning is enabled by @option{-Wall}. |
078721e1 AC |
3470 | |
3471 | @item -Wunused | |
cd3bb277 | 3472 | @opindex Wunused |
ccd4e386 | 3473 | @opindex Wno-unused |
d3075b6c | 3474 | All the above @option{-Wunused} options combined. |
078721e1 AC |
3475 | |
3476 | In order to get a warning about an unused function parameter, you must | |
65ca2d60 PE |
3477 | either specify @samp{-Wextra -Wunused} (note that @samp{-Wall} implies |
3478 | @samp{-Wunused}), or separately specify @option{-Wunused-parameter}. | |
078721e1 | 3479 | |
74291a4b | 3480 | @item -Wuninitialized |
cd3bb277 | 3481 | @opindex Wuninitialized |
ccd4e386 | 3482 | @opindex Wno-uninitialized |
c73d5dd9 MLI |
3483 | Warn if an automatic variable is used without first being initialized |
3484 | or if a variable may be clobbered by a @code{setjmp} call. In C++, | |
3485 | warn if a non-static reference or non-static @samp{const} member | |
3486 | appears in a class without constructors. | |
74291a4b | 3487 | |
3390f9c9 AP |
3488 | If you want to warn about code which uses the uninitialized value of the |
3489 | variable in its own initializer, use the @option{-Winit-self} option. | |
3490 | ||
8ceac9f8 JM |
3491 | These warnings occur for individual uninitialized or clobbered |
3492 | elements of structure, union or array variables as well as for | |
3493 | variables which are uninitialized or clobbered as a whole. They do | |
3494 | not occur for variables or elements declared @code{volatile}. Because | |
3495 | these warnings depend on optimization, the exact variables or elements | |
3496 | for which there are warnings will depend on the precise optimization | |
3497 | options and version of GCC used. | |
74291a4b MM |
3498 | |
3499 | Note that there may be no warning about a variable that is used only | |
3500 | to compute a value that itself is never used, because such | |
3501 | computations may be deleted by data flow analysis before the warnings | |
3502 | are printed. | |
3503 | ||
0c2d1a2a | 3504 | These warnings are made optional because GCC is not smart |
74291a4b MM |
3505 | enough to see all the reasons why the code might be correct |
3506 | despite appearing to have an error. Here is one example of how | |
3507 | this can happen: | |
3508 | ||
3509 | @smallexample | |
aee96fe9 | 3510 | @group |
74291a4b MM |
3511 | @{ |
3512 | int x; | |
3513 | switch (y) | |
3514 | @{ | |
3515 | case 1: x = 1; | |
3516 | break; | |
3517 | case 2: x = 4; | |
3518 | break; | |
3519 | case 3: x = 5; | |
3520 | @} | |
3521 | foo (x); | |
3522 | @} | |
aee96fe9 | 3523 | @end group |
74291a4b MM |
3524 | @end smallexample |
3525 | ||
3526 | @noindent | |
3527 | If the value of @code{y} is always 1, 2 or 3, then @code{x} is | |
0c2d1a2a | 3528 | always initialized, but GCC doesn't know this. Here is |
74291a4b MM |
3529 | another common case: |
3530 | ||
3531 | @smallexample | |
3532 | @{ | |
3533 | int save_y; | |
3534 | if (change_y) save_y = y, y = new_y; | |
3535 | @dots{} | |
3536 | if (change_y) y = save_y; | |
3537 | @} | |
3538 | @end smallexample | |
3539 | ||
3540 | @noindent | |
3541 | This has no bug because @code{save_y} is used only if it is set. | |
3542 | ||
20300b05 | 3543 | @cindex @code{longjmp} warnings |
b192711e | 3544 | This option also warns when a non-volatile automatic variable might be |
c5c76735 JL |
3545 | changed by a call to @code{longjmp}. These warnings as well are possible |
3546 | only in optimizing compilation. | |
20300b05 GK |
3547 | |
3548 | The compiler sees only the calls to @code{setjmp}. It cannot know | |
3549 | where @code{longjmp} will be called; in fact, a signal handler could | |
3550 | call it at any point in the code. As a result, you may get a warning | |
3551 | even when there is in fact no problem because @code{longjmp} cannot | |
3552 | in fact be called at the place which would cause a problem. | |
3553 | ||
74291a4b MM |
3554 | Some spurious warnings can be avoided if you declare all the functions |
3555 | you use that never return as @code{noreturn}. @xref{Function | |
3556 | Attributes}. | |
3557 | ||
2dc74010 | 3558 | This warning is enabled by @option{-Wall} or @option{-Wextra}. |
69cdf050 | 3559 | |
d300e551 | 3560 | @item -Wunknown-pragmas |
cd3bb277 | 3561 | @opindex Wunknown-pragmas |
ccd4e386 | 3562 | @opindex Wno-unknown-pragmas |
d300e551 NC |
3563 | @cindex warning for unknown pragmas |
3564 | @cindex unknown pragmas, warning | |
3565 | @cindex pragmas, warning of unknown | |
3566 | Warn when a #pragma directive is encountered which is not understood by | |
161d7b59 | 3567 | GCC@. If this command line option is used, warnings will even be issued |
d300e551 | 3568 | for unknown pragmas in system header files. This is not the case if |
630d3d5a | 3569 | the warnings were only enabled by the @option{-Wall} command line option. |
d300e551 | 3570 | |
b9b8dde3 DD |
3571 | @item -Wno-pragmas |
3572 | @opindex Wno-pragmas | |
3573 | @opindex Wpragmas | |
3574 | Do not warn about misuses of pragmas, such as incorrect parameters, | |
3575 | invalid syntax, or conflicts between pragmas. See also | |
3576 | @samp{-Wunknown-pragmas}. | |
3577 | ||
bf52f899 NS |
3578 | @item -Wstrict-aliasing |
3579 | @opindex Wstrict-aliasing | |
ccd4e386 | 3580 | @opindex Wno-strict-aliasing |
bf52f899 NS |
3581 | This option is only active when @option{-fstrict-aliasing} is active. |
3582 | It warns about code which might break the strict aliasing rules that the | |
8a36672b JM |
3583 | compiler is using for optimization. The warning does not catch all |
3584 | cases, but does attempt to catch the more common pitfalls. It is | |
bf52f899 | 3585 | included in @option{-Wall}. |
60df726b | 3586 | It is equivalent to @option{-Wstrict-aliasing=3} |
bf52f899 | 3587 | |
79bedddc SR |
3588 | @item -Wstrict-aliasing=n |
3589 | @opindex Wstrict-aliasing=n | |
ccd4e386 | 3590 | @opindex Wno-strict-aliasing=n |
5399d643 | 3591 | This option is only active when @option{-fstrict-aliasing} is active. |
66f33c03 | 3592 | It warns about code which might break the strict aliasing rules that the |
79bedddc SR |
3593 | compiler is using for optimization. |
3594 | Higher levels correspond to higher accuracy (fewer false positives). | |
3595 | Higher levels also correspond to more effort, similar to the way -O works. | |
3596 | @option{-Wstrict-aliasing} is equivalent to @option{-Wstrict-aliasing=n}, | |
3597 | with n=3. | |
3598 | ||
3599 | Level 1: Most aggressive, quick, least accurate. | |
3600 | Possibly useful when higher levels | |
7a61cf6f | 3601 | do not warn but -fstrict-aliasing still breaks the code, as it has very few |
79bedddc | 3602 | false negatives. However, it has many false positives. |
7a61cf6f | 3603 | Warns for all pointer conversions between possibly incompatible types, |
79bedddc SR |
3604 | even if never dereferenced. Runs in the frontend only. |
3605 | ||
3606 | Level 2: Aggressive, quick, not too precise. | |
3607 | May still have many false positives (not as many as level 1 though), | |
3608 | and few false negatives (but possibly more than level 1). | |
3609 | Unlike level 1, it only warns when an address is taken. Warns about | |
3610 | incomplete types. Runs in the frontend only. | |
3611 | ||
7a61cf6f NC |
3612 | Level 3 (default for @option{-Wstrict-aliasing}): |
3613 | Should have very few false positives and few false | |
79bedddc | 3614 | negatives. Slightly slower than levels 1 or 2 when optimization is enabled. |
02a9370c | 3615 | Takes care of the common pun+dereference pattern in the frontend: |
79bedddc | 3616 | @code{*(int*)&some_float}. |
7a61cf6f | 3617 | If optimization is enabled, it also runs in the backend, where it deals |
79bedddc SR |
3618 | with multiple statement cases using flow-sensitive points-to information. |
3619 | Only warns when the converted pointer is dereferenced. | |
3620 | Does not warn about incomplete types. | |
5399d643 | 3621 | |
6ac01510 | 3622 | @item -Wstrict-overflow |
b29bb640 | 3623 | @itemx -Wstrict-overflow=@var{n} |
edc5f63b | 3624 | @opindex Wstrict-overflow |
ccd4e386 | 3625 | @opindex Wno-strict-overflow |
6ac01510 ILT |
3626 | This option is only active when @option{-fstrict-overflow} is active. |
3627 | It warns about cases where the compiler optimizes based on the | |
3628 | assumption that signed overflow does not occur. Note that it does not | |
3629 | warn about all cases where the code might overflow: it only warns | |
3630 | about cases where the compiler implements some optimization. Thus | |
3631 | this warning depends on the optimization level. | |
3632 | ||
3633 | An optimization which assumes that signed overflow does not occur is | |
3634 | perfectly safe if the values of the variables involved are such that | |
3635 | overflow never does, in fact, occur. Therefore this warning can | |
3636 | easily give a false positive: a warning about code which is not | |
3637 | actually a problem. To help focus on important issues, several | |
4df28528 ILT |
3638 | warning levels are defined. No warnings are issued for the use of |
3639 | undefined signed overflow when estimating how many iterations a loop | |
3640 | will require, in particular when determining whether a loop will be | |
3641 | executed at all. | |
6ac01510 | 3642 | |
f85138bc | 3643 | @table @gcctabopt |
6ac01510 ILT |
3644 | @item -Wstrict-overflow=1 |
3645 | Warn about cases which are both questionable and easy to avoid. For | |
3646 | example: @code{x + 1 > x}; with @option{-fstrict-overflow}, the | |
4d4362c8 ILT |
3647 | compiler will simplify this to @code{1}. This level of |
3648 | @option{-Wstrict-overflow} is enabled by @option{-Wall}; higher levels | |
3649 | are not, and must be explicitly requested. | |
6ac01510 ILT |
3650 | |
3651 | @item -Wstrict-overflow=2 | |
3652 | Also warn about other cases where a comparison is simplified to a | |
3653 | constant. For example: @code{abs (x) >= 0}. This can only be | |
3654 | simplified when @option{-fstrict-overflow} is in effect, because | |
3655 | @code{abs (INT_MIN)} overflows to @code{INT_MIN}, which is less than | |
4d4362c8 ILT |
3656 | zero. @option{-Wstrict-overflow} (with no level) is the same as |
3657 | @option{-Wstrict-overflow=2}. | |
6ac01510 ILT |
3658 | |
3659 | @item -Wstrict-overflow=3 | |
3660 | Also warn about other cases where a comparison is simplified. For | |
3661 | example: @code{x + 1 > 1} will be simplified to @code{x > 0}. | |
3662 | ||
3663 | @item -Wstrict-overflow=4 | |
3664 | Also warn about other simplifications not covered by the above cases. | |
3665 | For example: @code{(x * 10) / 5} will be simplified to @code{x * 2}. | |
3666 | ||
3667 | @item -Wstrict-overflow=5 | |
3668 | Also warn about cases where the compiler reduces the magnitude of a | |
3669 | constant involved in a comparison. For example: @code{x + 2 > y} will | |
3670 | be simplified to @code{x + 1 >= y}. This is reported only at the | |
3671 | highest warning level because this simplification applies to many | |
3672 | comparisons, so this warning level will give a very large number of | |
3673 | false positives. | |
3674 | @end table | |
3675 | ||
212580ff | 3676 | @item -Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{]} |
5dc16b19 MLI |
3677 | @opindex Wsuggest-attribute= |
3678 | @opindex Wno-suggest-attribute= | |
3679 | Warn for cases where adding an attribute may be beneficial. The | |
3680 | attributes currently supported are listed below. | |
3681 | ||
3682 | @table @gcctabopt | |
3683 | @item -Wsuggest-attribute=pure | |
3684 | @itemx -Wsuggest-attribute=const | |
212580ff | 3685 | @itemx -Wsuggest-attribute=noreturn |
5dc16b19 MLI |
3686 | @opindex Wsuggest-attribute=pure |
3687 | @opindex Wno-suggest-attribute=pure | |
3688 | @opindex Wsuggest-attribute=const | |
3689 | @opindex Wno-suggest-attribute=const | |
7ea6b6cf JH |
3690 | @opindex Wsuggest-attribute=noreturn |
3691 | @opindex Wno-suggest-attribute=noreturn | |
5dc16b19 MLI |
3692 | |
3693 | Warn about functions which might be candidates for attributes | |
7ea6b6cf JH |
3694 | @code{pure}, @code{const} or @code{noreturn}. The compiler only warns for |
3695 | functions visible in other compilation units or (in the case of @code{pure} and | |
3696 | @code{const}) if it cannot prove that the function returns normally. A function | |
3697 | returns normally if it doesn't contain an infinite loop nor returns abnormally | |
3698 | by throwing, calling @code{abort()} or trapping. This analysis requires option | |
3699 | @option{-fipa-pure-const}, which is enabled by default at @option{-O} and | |
3700 | higher. Higher optimization levels improve the accuracy of the analysis. | |
5dc16b19 MLI |
3701 | @end table |
3702 | ||
590b1f2d DM |
3703 | @item -Warray-bounds |
3704 | @opindex Wno-array-bounds | |
3705 | @opindex Warray-bounds | |
e4d35515 | 3706 | This option is only active when @option{-ftree-vrp} is active |
5dc16b19 | 3707 | (default for @option{-O2} and above). It warns about subscripts to arrays |
e4d35515 | 3708 | that are always out of bounds. This warning is enabled by @option{-Wall}. |
590b1f2d | 3709 | |
75227a33 GK |
3710 | @item -Wno-div-by-zero |
3711 | @opindex Wno-div-by-zero | |
3712 | @opindex Wdiv-by-zero | |
3713 | Do not warn about compile-time integer division by zero. Floating point | |
3714 | division by zero is not warned about, as it can be a legitimate way of | |
3715 | obtaining infinities and NaNs. | |
3716 | ||
3717 | @item -Wsystem-headers | |
3718 | @opindex Wsystem-headers | |
ccd4e386 | 3719 | @opindex Wno-system-headers |
75227a33 GK |
3720 | @cindex warnings from system headers |
3721 | @cindex system headers, warnings from | |
3722 | Print warning messages for constructs found in system header files. | |
3723 | Warnings from system headers are normally suppressed, on the assumption | |
3724 | that they usually do not indicate real problems and would only make the | |
3725 | compiler output harder to read. Using this command line option tells | |
3726 | GCC to emit warnings from system headers as if they occurred in user | |
3727 | code. However, note that using @option{-Wall} in conjunction with this | |
3728 | option will @emph{not} warn about unknown pragmas in system | |
3729 | headers---for that, @option{-Wunknown-pragmas} must also be used. | |
3730 | ||
8ffadef9 MG |
3731 | @item -Wtrampolines |
3732 | @opindex Wtrampolines | |
3733 | @opindex Wno-trampolines | |
3734 | Warn about trampolines generated for pointers to nested functions. | |
3735 | ||
3736 | A trampoline is a small piece of data or code that is created at run | |
3737 | time on the stack when the address of a nested function is taken, and | |
3738 | is used to call the nested function indirectly. For some targets, it | |
3739 | is made up of data only and thus requires no special treatment. But, | |
3740 | for most targets, it is made up of code and thus requires the stack | |
3741 | to be made executable in order for the program to work properly. | |
3742 | ||
f793a95e | 3743 | @item -Wfloat-equal |
cd3bb277 | 3744 | @opindex Wfloat-equal |
ccd4e386 | 3745 | @opindex Wno-float-equal |
f793a95e JL |
3746 | Warn if floating point values are used in equality comparisons. |
3747 | ||
488d3985 GK |
3748 | The idea behind this is that sometimes it is convenient (for the |
3749 | programmer) to consider floating-point values as approximations to | |
3750 | infinitely precise real numbers. If you are doing this, then you need | |
c0478a66 | 3751 | to compute (by analyzing the code, or in some other way) the maximum or |
488d3985 GK |
3752 | likely maximum error that the computation introduces, and allow for it |
3753 | when performing comparisons (and when producing output, but that's a | |
3754 | different problem). In particular, instead of testing for equality, you | |
3755 | would check to see whether the two values have ranges that overlap; and | |
3756 | this is done with the relational operators, so equality comparisons are | |
3757 | probably mistaken. | |
3758 | ||
670b0231 | 3759 | @item -Wtraditional @r{(C and Objective-C only)} |
cd3bb277 | 3760 | @opindex Wtraditional |
ccd4e386 | 3761 | @opindex Wno-traditional |
74291a4b | 3762 | Warn about certain constructs that behave differently in traditional and |
161d7b59 | 3763 | ISO C@. Also warn about ISO C constructs that have no traditional C |
c8abc684 | 3764 | equivalent, and/or problematic constructs which should be avoided. |
74291a4b MM |
3765 | |
3766 | @itemize @bullet | |
3767 | @item | |
da312b55 NB |
3768 | Macro parameters that appear within string literals in the macro body. |
3769 | In traditional C macro replacement takes place within string literals, | |
161d7b59 | 3770 | but does not in ISO C@. |
da312b55 NB |
3771 | |
3772 | @item | |
3773 | In traditional C, some preprocessor directives did not exist. | |
3774 | Traditional preprocessors would only consider a line to be a directive | |
3775 | if the @samp{#} appeared in column 1 on the line. Therefore | |
630d3d5a | 3776 | @option{-Wtraditional} warns about directives that traditional C |
da312b55 NB |
3777 | understands but would ignore because the @samp{#} does not appear as the |
3778 | first character on the line. It also suggests you hide directives like | |
3779 | @samp{#pragma} not understood by traditional C by indenting them. Some | |
c21cd8b1 | 3780 | traditional implementations would not recognize @samp{#elif}, so it |
da312b55 NB |
3781 | suggests avoiding it altogether. |
3782 | ||
3783 | @item | |
3784 | A function-like macro that appears without arguments. | |
3785 | ||
3786 | @item | |
3787 | The unary plus operator. | |
3788 | ||
3789 | @item | |
c771326b JM |
3790 | The @samp{U} integer constant suffix, or the @samp{F} or @samp{L} floating point |
3791 | constant suffixes. (Traditional C does support the @samp{L} suffix on integer | |
da312b55 | 3792 | constants.) Note, these suffixes appear in macros defined in the system |
e979f9e8 | 3793 | headers of most modern systems, e.g.@: the @samp{_MIN}/@samp{_MAX} macros in @code{<limits.h>}. |
c8abc684 | 3794 | Use of these macros in user code might normally lead to spurious |
2dd76960 | 3795 | warnings, however GCC's integrated preprocessor has enough context to |
c8abc684 | 3796 | avoid warning in these cases. |
74291a4b MM |
3797 | |
3798 | @item | |
3799 | A function declared external in one block and then used after the end of | |
3800 | the block. | |
3801 | ||
3802 | @item | |
3803 | A @code{switch} statement has an operand of type @code{long}. | |
db838bb8 KG |
3804 | |
3805 | @item | |
3806 | A non-@code{static} function declaration follows a @code{static} one. | |
3807 | This construct is not accepted by some traditional C compilers. | |
48776cde KG |
3808 | |
3809 | @item | |
c1030c7c | 3810 | The ISO type of an integer constant has a different width or |
48776cde | 3811 | signedness from its traditional type. This warning is only issued if |
e979f9e8 | 3812 | the base of the constant is ten. I.e.@: hexadecimal or octal values, which |
48776cde | 3813 | typically represent bit patterns, are not warned about. |
bb66adca KG |
3814 | |
3815 | @item | |
c1030c7c | 3816 | Usage of ISO string concatenation is detected. |
7f094a94 | 3817 | |
895ea614 KG |
3818 | @item |
3819 | Initialization of automatic aggregates. | |
3820 | ||
3821 | @item | |
3822 | Identifier conflicts with labels. Traditional C lacks a separate | |
3823 | namespace for labels. | |
253b6b82 KG |
3824 | |
3825 | @item | |
3826 | Initialization of unions. If the initializer is zero, the warning is | |
3827 | omitted. This is done under the assumption that the zero initializer in | |
e979f9e8 | 3828 | user code appears conditioned on e.g.@: @code{__STDC__} to avoid missing |
253b6b82 KG |
3829 | initializer warnings and relies on default initialization to zero in the |
3830 | traditional C case. | |
03829ad2 KG |
3831 | |
3832 | @item | |
3ed56f8a KG |
3833 | Conversions by prototypes between fixed/floating point values and vice |
3834 | versa. The absence of these prototypes when compiling with traditional | |
3835 | C would cause serious problems. This is a subset of the possible | |
05170031 | 3836 | conversion warnings, for the full set use @option{-Wtraditional-conversion}. |
622d3731 KG |
3837 | |
3838 | @item | |
3839 | Use of ISO C style function definitions. This warning intentionally is | |
3840 | @emph{not} issued for prototype declarations or variadic functions | |
3841 | because these ISO C features will appear in your code when using | |
3842 | libiberty's traditional C compatibility macros, @code{PARAMS} and | |
3843 | @code{VPARAMS}. This warning is also bypassed for nested functions | |
2dd76960 | 3844 | because that feature is already a GCC extension and thus not relevant to |
622d3731 | 3845 | traditional C compatibility. |
74291a4b MM |
3846 | @end itemize |
3847 | ||
670b0231 | 3848 | @item -Wtraditional-conversion @r{(C and Objective-C only)} |
05170031 | 3849 | @opindex Wtraditional-conversion |
ccd4e386 | 3850 | @opindex Wno-traditional-conversion |
05170031 MLI |
3851 | Warn if a prototype causes a type conversion that is different from what |
3852 | would happen to the same argument in the absence of a prototype. This | |
3853 | includes conversions of fixed point to floating and vice versa, and | |
3854 | conversions changing the width or signedness of a fixed point argument | |
3855 | except when the same as the default promotion. | |
3856 | ||
670b0231 | 3857 | @item -Wdeclaration-after-statement @r{(C and Objective-C only)} |
85617eba | 3858 | @opindex Wdeclaration-after-statement |
ccd4e386 | 3859 | @opindex Wno-declaration-after-statement |
85617eba HPN |
3860 | Warn when a declaration is found after a statement in a block. This |
3861 | construct, known from C++, was introduced with ISO C99 and is by default | |
3862 | allowed in GCC@. It is not supported by ISO C90 and was not supported by | |
3863 | GCC versions before GCC 3.0. @xref{Mixed Declarations}. | |
3864 | ||
861bb6c1 | 3865 | @item -Wundef |
cd3bb277 | 3866 | @opindex Wundef |
ccd4e386 | 3867 | @opindex Wno-undef |
861bb6c1 JL |
3868 | Warn if an undefined identifier is evaluated in an @samp{#if} directive. |
3869 | ||
90689ae1 JM |
3870 | @item -Wno-endif-labels |
3871 | @opindex Wno-endif-labels | |
909de5da | 3872 | @opindex Wendif-labels |
90689ae1 | 3873 | Do not warn whenever an @samp{#else} or an @samp{#endif} are followed by text. |
909de5da | 3874 | |
74291a4b | 3875 | @item -Wshadow |
cd3bb277 | 3876 | @opindex Wshadow |
ccd4e386 | 3877 | @opindex Wno-shadow |
3f59fa1c LCW |
3878 | Warn whenever a local variable or type declaration shadows another variable, |
3879 | parameter, type, or class member (in C++), or whenever a built-in function | |
3880 | is shadowed. Note that in C++, the compiler will not warn if a local variable | |
3881 | shadows a struct/class/enum, but will warn if it shadows an explicit typedef. | |
74291a4b | 3882 | |
e8fc888d MLI |
3883 | @item -Wlarger-than=@var{len} |
3884 | @opindex Wlarger-than=@var{len} | |
ccd4e386 | 3885 | @opindex Wlarger-than-@var{len} |
74291a4b MM |
3886 | Warn whenever an object of larger than @var{len} bytes is defined. |
3887 | ||
a214518f SP |
3888 | @item -Wframe-larger-than=@var{len} |
3889 | @opindex Wframe-larger-than | |
c1a3620a SP |
3890 | Warn if the size of a function frame is larger than @var{len} bytes. |
3891 | The computation done to determine the stack frame size is approximate | |
3892 | and not conservative. | |
3893 | The actual requirements may be somewhat greater than @var{len} | |
3894 | even if you do not get a warning. In addition, any space allocated | |
3895 | via @code{alloca}, variable-length arrays, or related constructs | |
3896 | is not included by the compiler when determining | |
3897 | whether or not to issue a warning. | |
a214518f | 3898 | |
f9cc1a70 PB |
3899 | @item -Wunsafe-loop-optimizations |
3900 | @opindex Wunsafe-loop-optimizations | |
ccd4e386 | 3901 | @opindex Wno-unsafe-loop-optimizations |
f9cc1a70 PB |
3902 | Warn if the loop cannot be optimized because the compiler could not |
3903 | assume anything on the bounds of the loop indices. With | |
3904 | @option{-funsafe-loop-optimizations} warn if the compiler made | |
3905 | such assumptions. | |
3906 | ||
a072f1cf | 3907 | @item -Wno-pedantic-ms-format @r{(MinGW targets only)} |
94564826 KT |
3908 | @opindex Wno-pedantic-ms-format |
3909 | @opindex Wpedantic-ms-format | |
3910 | Disables the warnings about non-ISO @code{printf} / @code{scanf} format | |
3911 | width specifiers @code{I32}, @code{I64}, and @code{I} used on Windows targets | |
3912 | depending on the MS runtime, when you are using the options @option{-Wformat} | |
3913 | and @option{-pedantic} without gnu-extensions. | |
3914 | ||
74291a4b | 3915 | @item -Wpointer-arith |
cd3bb277 | 3916 | @opindex Wpointer-arith |
ccd4e386 | 3917 | @opindex Wno-pointer-arith |
74291a4b MM |
3918 | Warn about anything that depends on the ``size of'' a function type or |
3919 | of @code{void}. GNU C assigns these types a size of 1, for | |
3920 | convenience in calculations with @code{void *} pointers and pointers | |
b9edb4b1 MLI |
3921 | to functions. In C++, warn also when an arithmetic operation involves |
3922 | @code{NULL}. This warning is also enabled by @option{-pedantic}. | |
74291a4b | 3923 | |
f6aa72dd MLI |
3924 | @item -Wtype-limits |
3925 | @opindex Wtype-limits | |
3926 | @opindex Wno-type-limits | |
3927 | Warn if a comparison is always true or always false due to the limited | |
3928 | range of the data type, but do not warn for constant expressions. For | |
3929 | example, warn if an unsigned variable is compared against zero with | |
3930 | @samp{<} or @samp{>=}. This warning is also enabled by | |
3931 | @option{-Wextra}. | |
3932 | ||
670b0231 | 3933 | @item -Wbad-function-cast @r{(C and Objective-C only)} |
cd3bb277 | 3934 | @opindex Wbad-function-cast |
ccd4e386 | 3935 | @opindex Wno-bad-function-cast |
74291a4b MM |
3936 | Warn whenever a function call is cast to a non-matching type. |
3937 | For example, warn if @code{int malloc()} is cast to @code{anything *}. | |
3938 | ||
670b0231 | 3939 | @item -Wc++-compat @r{(C and Objective-C only)} |
b7e20b53 GDR |
3940 | Warn about ISO C constructs that are outside of the common subset of |
3941 | ISO C and ISO C++, e.g.@: request for implicit conversion from | |
3942 | @code{void *} to a pointer to non-@code{void} type. | |
3943 | ||
e1f1ee86 DG |
3944 | @item -Wc++0x-compat @r{(C++ and Objective-C++ only)} |
3945 | Warn about C++ constructs whose meaning differs between ISO C++ 1998 and | |
cb7ad97b | 3946 | ISO C++ 200x, e.g., identifiers in ISO C++ 1998 that will become keywords |
e1f1ee86 DG |
3947 | in ISO C++ 200x. This warning is enabled by @option{-Wall}. |
3948 | ||
74291a4b | 3949 | @item -Wcast-qual |
cd3bb277 | 3950 | @opindex Wcast-qual |
ccd4e386 | 3951 | @opindex Wno-cast-qual |
74291a4b MM |
3952 | Warn whenever a pointer is cast so as to remove a type qualifier from |
3953 | the target type. For example, warn if a @code{const char *} is cast | |
3954 | to an ordinary @code{char *}. | |
3955 | ||
67165eb3 ILT |
3956 | Also warn when making a cast which introduces a type qualifier in an |
3957 | unsafe way. For example, casting @code{char **} to @code{const char **} | |
3958 | is unsafe, as in this example: | |
3959 | ||
3960 | @smallexample | |
3961 | /* p is char ** value. */ | |
3962 | const char **q = (const char **) p; | |
3963 | /* Assignment of readonly string to const char * is OK. */ | |
3964 | *q = "string"; | |
3965 | /* Now char** pointer points to read-only memory. */ | |
3966 | **p = 'b'; | |
3967 | @end smallexample | |
3968 | ||
74291a4b | 3969 | @item -Wcast-align |
cd3bb277 | 3970 | @opindex Wcast-align |
ccd4e386 | 3971 | @opindex Wno-cast-align |
74291a4b MM |
3972 | Warn whenever a pointer is cast such that the required alignment of the |
3973 | target is increased. For example, warn if a @code{char *} is cast to | |
3974 | an @code{int *} on machines where integers can only be accessed at | |
3975 | two- or four-byte boundaries. | |
3976 | ||
3977 | @item -Wwrite-strings | |
cd3bb277 | 3978 | @opindex Wwrite-strings |
ccd4e386 | 3979 | @opindex Wno-write-strings |
aee96fe9 | 3980 | When compiling C, give string constants the type @code{const |
f4185118 MLI |
3981 | char[@var{length}]} so that copying the address of one into a |
3982 | non-@code{const} @code{char *} pointer will get a warning. These | |
3983 | warnings will help you find at compile time code that can try to write | |
3984 | into a string constant, but only if you have been very careful about | |
3985 | using @code{const} in declarations and prototypes. Otherwise, it will | |
3986 | just be a nuisance. This is why we did not make @option{-Wall} request | |
3987 | these warnings. | |
3988 | ||
3989 | When compiling C++, warn about the deprecated conversion from string | |
3990 | literals to @code{char *}. This warning is enabled by default for C++ | |
3991 | programs. | |
74291a4b | 3992 | |
2b001724 MLI |
3993 | @item -Wclobbered |
3994 | @opindex Wclobbered | |
ccd4e386 | 3995 | @opindex Wno-clobbered |
2b001724 MLI |
3996 | Warn for variables that might be changed by @samp{longjmp} or |
3997 | @samp{vfork}. This warning is also enabled by @option{-Wextra}. | |
3998 | ||
74291a4b | 3999 | @item -Wconversion |
cd3bb277 | 4000 | @opindex Wconversion |
7060db96 | 4001 | @opindex Wno-conversion |
422c3a54 MLI |
4002 | Warn for implicit conversions that may alter a value. This includes |
4003 | conversions between real and integer, like @code{abs (x)} when | |
4004 | @code{x} is @code{double}; conversions between signed and unsigned, | |
4005 | like @code{unsigned ui = -1}; and conversions to smaller types, like | |
4006 | @code{sqrtf (M_PI)}. Do not warn for explicit casts like @code{abs | |
4007 | ((int) x)} and @code{ui = (unsigned) -1}, or if the value is not | |
7060db96 MLI |
4008 | changed by the conversion like in @code{abs (2.0)}. Warnings about |
4009 | conversions between signed and unsigned integers can be disabled by | |
4010 | using @option{-Wno-sign-conversion}. | |
74291a4b | 4011 | |
17251338 MLI |
4012 | For C++, also warn for confusing overload resolution for user-defined |
4013 | conversions; and conversions that will never use a type conversion | |
4014 | operator: conversions to @code{void}, the same type, a base class or a | |
4015 | reference to them. Warnings about conversions between signed and | |
4016 | unsigned integers are disabled by default in C++ unless | |
7060db96 | 4017 | @option{-Wsign-conversion} is explicitly enabled. |
07231d4f | 4018 | |
02a9370c | 4019 | @item -Wno-conversion-null @r{(C++ and Objective-C++ only)} |
17251338 MLI |
4020 | @opindex Wconversion-null |
4021 | @opindex Wno-conversion-null | |
4022 | Do not warn for conversions between @code{NULL} and non-pointer | |
4023 | types. @option{-Wconversion-null} is enabled by default. | |
4024 | ||
b3b433c5 MLI |
4025 | @item -Wempty-body |
4026 | @opindex Wempty-body | |
ccd4e386 | 4027 | @opindex Wno-empty-body |
841cc7da | 4028 | Warn if an empty body occurs in an @samp{if}, @samp{else} or @samp{do |
084eb830 | 4029 | while} statement. This warning is also enabled by @option{-Wextra}. |
b3b433c5 | 4030 | |
6866c6e8 | 4031 | @item -Wenum-compare |
a3299096 MM |
4032 | @opindex Wenum-compare |
4033 | @opindex Wno-enum-compare | |
6866c6e8 ILT |
4034 | Warn about a comparison between values of different enum types. In C++ |
4035 | this warning is enabled by default. In C this warning is enabled by | |
4036 | @option{-Wall}. | |
a3299096 | 4037 | |
13ebf17b ILT |
4038 | @item -Wjump-misses-init @r{(C, Objective-C only)} |
4039 | @opindex Wjump-misses-init | |
4040 | @opindex Wno-jump-misses-init | |
4041 | Warn if a @code{goto} statement or a @code{switch} statement jumps | |
4042 | forward across the initialization of a variable, or jumps backward to a | |
4043 | label after the variable has been initialized. This only warns about | |
4044 | variables which are initialized when they are declared. This warning is | |
4045 | only supported for C and Objective C; in C++ this sort of branch is an | |
4046 | error in any case. | |
4047 | ||
4048 | @option{-Wjump-misses-init} is included in @option{-Wc++-compat}. It | |
4049 | can be disabled with the @option{-Wno-jump-misses-init} option. | |
4050 | ||
e9a25f70 | 4051 | @item -Wsign-compare |
cd3bb277 | 4052 | @opindex Wsign-compare |
ccd4e386 | 4053 | @opindex Wno-sign-compare |
e9a25f70 JL |
4054 | @cindex warning for comparison of signed and unsigned values |
4055 | @cindex comparison of signed and unsigned values, warning | |
4056 | @cindex signed and unsigned values, comparison warning | |
4057 | Warn when a comparison between signed and unsigned values could produce | |
4058 | an incorrect result when the signed value is converted to unsigned. | |
65ca2d60 PE |
4059 | This warning is also enabled by @option{-Wextra}; to get the other warnings |
4060 | of @option{-Wextra} without this warning, use @samp{-Wextra -Wno-sign-compare}. | |
e9a25f70 | 4061 | |
7060db96 MLI |
4062 | @item -Wsign-conversion |
4063 | @opindex Wsign-conversion | |
4064 | @opindex Wno-sign-conversion | |
4065 | Warn for implicit conversions that may change the sign of an integer | |
4066 | value, like assigning a signed integer expression to an unsigned | |
4067 | integer variable. An explicit cast silences the warning. In C, this | |
4068 | option is enabled also by @option{-Wconversion}. | |
4069 | ||
c116cd05 MLI |
4070 | @item -Waddress |
4071 | @opindex Waddress | |
4072 | @opindex Wno-address | |
4073 | Warn about suspicious uses of memory addresses. These include using | |
4074 | the address of a function in a conditional expression, such as | |
4075 | @code{void func(void); if (func)}, and comparisons against the memory | |
4076 | address of a string literal, such as @code{if (x == "abc")}. Such | |
4077 | uses typically indicate a programmer error: the address of a function | |
4078 | always evaluates to true, so their use in a conditional usually | |
4079 | indicate that the programmer forgot the parentheses in a function | |
4080 | call; and comparisons against string literals result in unspecified | |
4081 | behavior and are not portable in C, so they usually indicate that the | |
4082 | programmer intended to use @code{strcmp}. This warning is enabled by | |
4083 | @option{-Wall}. | |
4084 | ||
63a08740 DM |
4085 | @item -Wlogical-op |
4086 | @opindex Wlogical-op | |
4087 | @opindex Wno-logical-op | |
4088 | Warn about suspicious uses of logical operators in expressions. | |
4089 | This includes using logical operators in contexts where a | |
7bb27074 | 4090 | bit-wise operator is likely to be expected. |
63a08740 | 4091 | |
74291a4b | 4092 | @item -Waggregate-return |
cd3bb277 | 4093 | @opindex Waggregate-return |
ccd4e386 | 4094 | @opindex Wno-aggregate-return |
74291a4b MM |
4095 | Warn if any functions that return structures or unions are defined or |
4096 | called. (In languages where you can return an array, this also elicits | |
4097 | a warning.) | |
4098 | ||
5c498b10 DD |
4099 | @item -Wno-attributes |
4100 | @opindex Wno-attributes | |
4101 | @opindex Wattributes | |
4102 | Do not warn if an unexpected @code{__attribute__} is used, such as | |
4103 | unrecognized attributes, function attributes applied to variables, | |
4104 | etc. This will not stop errors for incorrect use of supported | |
4105 | attributes. | |
4106 | ||
c047ce93 SB |
4107 | @item -Wno-builtin-macro-redefined |
4108 | @opindex Wno-builtin-macro-redefined | |
4109 | @opindex Wbuiltin-macro-redefined | |
4110 | Do not warn if certain built-in macros are redefined. This suppresses | |
4111 | warnings for redefinition of @code{__TIMESTAMP__}, @code{__TIME__}, | |
4112 | @code{__DATE__}, @code{__FILE__}, and @code{__BASE_FILE__}. | |
4113 | ||
670b0231 | 4114 | @item -Wstrict-prototypes @r{(C and Objective-C only)} |
cd3bb277 | 4115 | @opindex Wstrict-prototypes |
ccd4e386 | 4116 | @opindex Wno-strict-prototypes |
74291a4b MM |
4117 | Warn if a function is declared or defined without specifying the |
4118 | argument types. (An old-style function definition is permitted without | |
4119 | a warning if preceded by a declaration which specifies the argument | |
4120 | types.) | |
4121 | ||
670b0231 | 4122 | @item -Wold-style-declaration @r{(C and Objective-C only)} |
b1ed4cb4 | 4123 | @opindex Wold-style-declaration |
ccd4e386 | 4124 | @opindex Wno-old-style-declaration |
b1ed4cb4 MLI |
4125 | Warn for obsolescent usages, according to the C Standard, in a |
4126 | declaration. For example, warn if storage-class specifiers like | |
4127 | @code{static} are not the first things in a declaration. This warning | |
4128 | is also enabled by @option{-Wextra}. | |
4129 | ||
670b0231 | 4130 | @item -Wold-style-definition @r{(C and Objective-C only)} |
c034f121 | 4131 | @opindex Wold-style-definition |
ccd4e386 | 4132 | @opindex Wno-old-style-definition |
c034f121 AJ |
4133 | Warn if an old-style function definition is used. A warning is given |
4134 | even if there is a previous prototype. | |
4135 | ||
670b0231 | 4136 | @item -Wmissing-parameter-type @r{(C and Objective-C only)} |
cb4af25a | 4137 | @opindex Wmissing-parameter-type |
ccd4e386 | 4138 | @opindex Wno-missing-parameter-type |
cb4af25a MLI |
4139 | A function parameter is declared without a type specifier in K&R-style |
4140 | functions: | |
4141 | ||
4142 | @smallexample | |
4143 | void foo(bar) @{ @} | |
4144 | @end smallexample | |
4145 | ||
4146 | This warning is also enabled by @option{-Wextra}. | |
4147 | ||
670b0231 | 4148 | @item -Wmissing-prototypes @r{(C and Objective-C only)} |
cd3bb277 | 4149 | @opindex Wmissing-prototypes |
ccd4e386 | 4150 | @opindex Wno-missing-prototypes |
74291a4b MM |
4151 | Warn if a global function is defined without a previous prototype |
4152 | declaration. This warning is issued even if the definition itself | |
4153 | provides a prototype. The aim is to detect global functions that fail | |
4154 | to be declared in header files. | |
4155 | ||
670b0231 | 4156 | @item -Wmissing-declarations |
cd3bb277 | 4157 | @opindex Wmissing-declarations |
ccd4e386 | 4158 | @opindex Wno-missing-declarations |
74291a4b MM |
4159 | Warn if a global function is defined without a previous declaration. |
4160 | Do so even if the definition itself provides a prototype. | |
4161 | Use this option to detect global functions that are not declared in | |
dfdec7a7 ILT |
4162 | header files. In C++, no warnings are issued for function templates, |
4163 | or for inline functions, or for functions in anonymous namespaces. | |
74291a4b | 4164 | |
eaac4679 RS |
4165 | @item -Wmissing-field-initializers |
4166 | @opindex Wmissing-field-initializers | |
ccd4e386 | 4167 | @opindex Wno-missing-field-initializers |
eaac4679 RS |
4168 | @opindex W |
4169 | @opindex Wextra | |
ccd4e386 | 4170 | @opindex Wno-extra |
eaac4679 RS |
4171 | Warn if a structure's initializer has some fields missing. For |
4172 | example, the following code would cause such a warning, because | |
4173 | @code{x.h} is implicitly zero: | |
4174 | ||
4175 | @smallexample | |
4176 | struct s @{ int f, g, h; @}; | |
4177 | struct s x = @{ 3, 4 @}; | |
4178 | @end smallexample | |
4179 | ||
4180 | This option does not warn about designated initializers, so the following | |
4181 | modification would not trigger a warning: | |
4182 | ||
4183 | @smallexample | |
4184 | struct s @{ int f, g, h; @}; | |
4185 | struct s x = @{ .f = 3, .g = 4 @}; | |
4186 | @end smallexample | |
4187 | ||
4188 | This warning is included in @option{-Wextra}. To get other @option{-Wextra} | |
4189 | warnings without this one, use @samp{-Wextra -Wno-missing-field-initializers}. | |
4190 | ||
74ff4629 | 4191 | @item -Wmissing-format-attribute |
cd3bb277 | 4192 | @opindex Wmissing-format-attribute |
ccd4e386 | 4193 | @opindex Wno-missing-format-attribute |
cd3bb277 | 4194 | @opindex Wformat |
ccd4e386 | 4195 | @opindex Wno-format |
7876a414 KG |
4196 | Warn about function pointers which might be candidates for @code{format} |
4197 | attributes. Note these are only possible candidates, not absolute ones. | |
4198 | GCC will guess that function pointers with @code{format} attributes that | |
4199 | are used in assignment, initialization, parameter passing or return | |
4200 | statements should have a corresponding @code{format} attribute in the | |
4201 | resulting type. I.e.@: the left-hand side of the assignment or | |
4202 | initialization, the type of the parameter variable, or the return type | |
4203 | of the containing function respectively should also have a @code{format} | |
4204 | attribute to avoid the warning. | |
4205 | ||
4206 | GCC will also warn about function definitions which might be | |
4207 | candidates for @code{format} attributes. Again, these are only | |
4208 | possible candidates. GCC will guess that @code{format} attributes | |
4209 | might be appropriate for any function that calls a function like | |
4210 | @code{vprintf} or @code{vscanf}, but this might not always be the | |
74ff4629 | 4211 | case, and some functions for which @code{format} attributes are |
7876a414 | 4212 | appropriate may not be detected. |
74ff4629 | 4213 | |
75227a33 GK |
4214 | @item -Wno-multichar |
4215 | @opindex Wno-multichar | |
4216 | @opindex Wmultichar | |
4217 | Do not warn if a multicharacter constant (@samp{'FOOF'}) is used. | |
4218 | Usually they indicate a typo in the user's code, as they have | |
4219 | implementation-defined values, and should not be used in portable code. | |
4220 | ||
50668cf6 | 4221 | @item -Wnormalized=<none|id|nfc|nfkc> |
ccd4e386 | 4222 | @opindex Wnormalized= |
50668cf6 GK |
4223 | @cindex NFC |
4224 | @cindex NFKC | |
4225 | @cindex character set, input normalization | |
4226 | In ISO C and ISO C++, two identifiers are different if they are | |
4227 | different sequences of characters. However, sometimes when characters | |
4228 | outside the basic ASCII character set are used, you can have two | |
4229 | different character sequences that look the same. To avoid confusion, | |
4230 | the ISO 10646 standard sets out some @dfn{normalization rules} which | |
4231 | when applied ensure that two sequences that look the same are turned into | |
4232 | the same sequence. GCC can warn you if you are using identifiers which | |
4233 | have not been normalized; this option controls that warning. | |
4234 | ||
4235 | There are four levels of warning that GCC supports. The default is | |
4236 | @option{-Wnormalized=nfc}, which warns about any identifier which is | |
4237 | not in the ISO 10646 ``C'' normalized form, @dfn{NFC}. NFC is the | |
4238 | recommended form for most uses. | |
4239 | ||
4240 | Unfortunately, there are some characters which ISO C and ISO C++ allow | |
4241 | in identifiers that when turned into NFC aren't allowable as | |
4242 | identifiers. That is, there's no way to use these symbols in portable | |
0ee2ea09 | 4243 | ISO C or C++ and have all your identifiers in NFC@. |
50668cf6 GK |
4244 | @option{-Wnormalized=id} suppresses the warning for these characters. |
4245 | It is hoped that future versions of the standards involved will correct | |
4246 | this, which is why this option is not the default. | |
4247 | ||
4248 | You can switch the warning off for all characters by writing | |
4249 | @option{-Wnormalized=none}. You would only want to do this if you | |
4250 | were using some other normalization scheme (like ``D''), because | |
4251 | otherwise you can easily create bugs that are literally impossible to see. | |
4252 | ||
4253 | Some characters in ISO 10646 have distinct meanings but look identical | |
4254 | in some fonts or display methodologies, especially once formatting has | |
4255 | been applied. For instance @code{\u207F}, ``SUPERSCRIPT LATIN SMALL | |
4256 | LETTER N'', will display just like a regular @code{n} which has been | |
4257 | placed in a superscript. ISO 10646 defines the @dfn{NFKC} | |
6fc0bb99 | 4258 | normalization scheme to convert all these into a standard form as |
50668cf6 GK |
4259 | well, and GCC will warn if your code is not in NFKC if you use |
4260 | @option{-Wnormalized=nfkc}. This warning is comparable to warning | |
4261 | about every identifier that contains the letter O because it might be | |
4262 | confused with the digit 0, and so is not the default, but may be | |
4263 | useful as a local coding convention if the programming environment is | |
4264 | unable to be fixed to display these characters distinctly. | |
4265 | ||
899015a0 TT |
4266 | @item -Wno-deprecated |
4267 | @opindex Wno-deprecated | |
4268 | @opindex Wdeprecated | |
4269 | Do not warn about usage of deprecated features. @xref{Deprecated Features}. | |
4270 | ||
e23bd218 IR |
4271 | @item -Wno-deprecated-declarations |
4272 | @opindex Wno-deprecated-declarations | |
ccd4e386 | 4273 | @opindex Wdeprecated-declarations |
e8c96d09 MS |
4274 | Do not warn about uses of functions (@pxref{Function Attributes}), |
4275 | variables (@pxref{Variable Attributes}), and types (@pxref{Type | |
4276 | Attributes}) marked as deprecated by using the @code{deprecated} | |
4277 | attribute. | |
e23bd218 | 4278 | |
71834ad3 RS |
4279 | @item -Wno-overflow |
4280 | @opindex Wno-overflow | |
ccd4e386 | 4281 | @opindex Woverflow |
71834ad3 RS |
4282 | Do not warn about compile-time overflow in constant expressions. |
4283 | ||
670b0231 | 4284 | @item -Woverride-init @r{(C and Objective-C only)} |
7ed322d7 | 4285 | @opindex Woverride-init |
ccd4e386 | 4286 | @opindex Wno-override-init |
7ed322d7 JM |
4287 | @opindex W |
4288 | @opindex Wextra | |
ccd4e386 | 4289 | @opindex Wno-extra |
7ed322d7 JM |
4290 | Warn if an initialized field without side effects is overridden when |
4291 | using designated initializers (@pxref{Designated Inits, , Designated | |
4292 | Initializers}). | |
4293 | ||
4294 | This warning is included in @option{-Wextra}. To get other | |
4295 | @option{-Wextra} warnings without this one, use @samp{-Wextra | |
4296 | -Wno-override-init}. | |
4297 | ||
3c12fcc2 | 4298 | @item -Wpacked |
cd3bb277 | 4299 | @opindex Wpacked |
ccd4e386 | 4300 | @opindex Wno-packed |
3c12fcc2 | 4301 | Warn if a structure is given the packed attribute, but the packed |
02f52e19 | 4302 | attribute has no effect on the layout or size of the structure. |
3c12fcc2 GM |
4303 | Such structures may be mis-aligned for little benefit. For |
4304 | instance, in this code, the variable @code{f.x} in @code{struct bar} | |
4305 | will be misaligned even though @code{struct bar} does not itself | |
4306 | have the packed attribute: | |
4307 | ||
4308 | @smallexample | |
4309 | @group | |
4310 | struct foo @{ | |
4311 | int x; | |
4312 | char a, b, c, d; | |
4313 | @} __attribute__((packed)); | |
4314 | struct bar @{ | |
4315 | char z; | |
4316 | struct foo f; | |
4317 | @}; | |
4318 | @end group | |
4319 | @end smallexample | |
4320 | ||
2cd36c22 AN |
4321 | @item -Wpacked-bitfield-compat |
4322 | @opindex Wpacked-bitfield-compat | |
4323 | @opindex Wno-packed-bitfield-compat | |
4324 | The 4.1, 4.2 and 4.3 series of GCC ignore the @code{packed} attribute | |
4325 | on bit-fields of type @code{char}. This has been fixed in GCC 4.4 but | |
4326 | the change can lead to differences in the structure layout. GCC | |
4327 | informs you when the offset of such a field has changed in GCC 4.4. | |
4328 | For example there is no longer a 4-bit padding between field @code{a} | |
4329 | and @code{b} in this structure: | |
4330 | ||
4331 | @smallexample | |
4332 | struct foo | |
4333 | @{ | |
4334 | char a:4; | |
4335 | char b:8; | |
4336 | @} __attribute__ ((packed)); | |
4337 | @end smallexample | |
4338 | ||
4339 | This warning is enabled by default. Use | |
4340 | @option{-Wno-packed-bitfield-compat} to disable this warning. | |
4341 | ||
3c12fcc2 | 4342 | @item -Wpadded |
cd3bb277 | 4343 | @opindex Wpadded |
ccd4e386 | 4344 | @opindex Wno-padded |
3c12fcc2 GM |
4345 | Warn if padding is included in a structure, either to align an element |
4346 | of the structure or to align the whole structure. Sometimes when this | |
4347 | happens it is possible to rearrange the fields of the structure to | |
4348 | reduce the padding and so make the structure smaller. | |
4349 | ||
74291a4b | 4350 | @item -Wredundant-decls |
cd3bb277 | 4351 | @opindex Wredundant-decls |
ccd4e386 | 4352 | @opindex Wno-redundant-decls |
74291a4b MM |
4353 | Warn if anything is declared more than once in the same scope, even in |
4354 | cases where multiple declaration is valid and changes nothing. | |
4355 | ||
670b0231 | 4356 | @item -Wnested-externs @r{(C and Objective-C only)} |
cd3bb277 | 4357 | @opindex Wnested-externs |
ccd4e386 | 4358 | @opindex Wno-nested-externs |
252215a7 | 4359 | Warn if an @code{extern} declaration is encountered within a function. |
74291a4b MM |
4360 | |
4361 | @item -Winline | |
cd3bb277 | 4362 | @opindex Winline |
ccd4e386 | 4363 | @opindex Wno-inline |
c5c76735 | 4364 | Warn if a function can not be inlined and it was declared as inline. |
ae4a7155 | 4365 | Even with this option, the compiler will not warn about failures to |
daf2f129 | 4366 | inline functions declared in system headers. |
ae4a7155 MM |
4367 | |
4368 | The compiler uses a variety of heuristics to determine whether or not | |
4369 | to inline a function. For example, the compiler takes into account | |
0bdcd332 | 4370 | the size of the function being inlined and the amount of inlining |
ae4a7155 MM |
4371 | that has already been done in the current function. Therefore, |
4372 | seemingly insignificant changes in the source program can cause the | |
4373 | warnings produced by @option{-Winline} to appear or disappear. | |
74291a4b | 4374 | |
670b0231 | 4375 | @item -Wno-invalid-offsetof @r{(C++ and Objective-C++ only)} |
a01fff59 | 4376 | @opindex Wno-invalid-offsetof |
ccd4e386 | 4377 | @opindex Winvalid-offsetof |
a01fff59 MA |
4378 | Suppress warnings from applying the @samp{offsetof} macro to a non-POD |
4379 | type. According to the 1998 ISO C++ standard, applying @samp{offsetof} | |
4380 | to a non-POD type is undefined. In existing C++ implementations, | |
4381 | however, @samp{offsetof} typically gives meaningful results even when | |
4382 | applied to certain kinds of non-POD types. (Such as a simple | |
4383 | @samp{struct} that fails to be a POD type only by virtue of having a | |
4384 | constructor.) This flag is for users who are aware that they are | |
4385 | writing nonportable code and who have deliberately chosen to ignore the | |
4386 | warning about it. | |
4387 | ||
4388 | The restrictions on @samp{offsetof} may be relaxed in a future version | |
4389 | of the C++ standard. | |
4390 | ||
dc8d2739 | 4391 | @item -Wno-int-to-pointer-cast |
53a2494e | 4392 | @opindex Wno-int-to-pointer-cast |
ccd4e386 | 4393 | @opindex Wint-to-pointer-cast |
53a2494e | 4394 | Suppress warnings from casts to pointer type of an integer of a |
dc8d2739 MLI |
4395 | different size. In C++, casting to a pointer type of smaller size is |
4396 | an error. @option{Wint-to-pointer-cast} is enabled by default. | |
4397 | ||
53a2494e | 4398 | |
670b0231 | 4399 | @item -Wno-pointer-to-int-cast @r{(C and Objective-C only)} |
53a2494e | 4400 | @opindex Wno-pointer-to-int-cast |
ccd4e386 | 4401 | @opindex Wpointer-to-int-cast |
53a2494e JM |
4402 | Suppress warnings from casts from a pointer to an integer type of a |
4403 | different size. | |
4404 | ||
17211ab5 GK |
4405 | @item -Winvalid-pch |
4406 | @opindex Winvalid-pch | |
ccd4e386 | 4407 | @opindex Wno-invalid-pch |
17211ab5 GK |
4408 | Warn if a precompiled header (@pxref{Precompiled Headers}) is found in |
4409 | the search path but can't be used. | |
4410 | ||
795add94 | 4411 | @item -Wlong-long |
cd3bb277 JM |
4412 | @opindex Wlong-long |
4413 | @opindex Wno-long-long | |
9c650d90 MLI |
4414 | Warn if @samp{long long} type is used. This is enabled by either |
4415 | @option{-pedantic} or @option{-Wtraditional} in ISO C90 and C++98 | |
4416 | modes. To inhibit the warning messages, use @option{-Wno-long-long}. | |
795add94 | 4417 | |
7c4d376d RH |
4418 | @item -Wvariadic-macros |
4419 | @opindex Wvariadic-macros | |
4420 | @opindex Wno-variadic-macros | |
4421 | Warn if variadic macros are used in pedantic ISO C90 mode, or the GNU | |
4422 | alternate syntax when in pedantic ISO C99 mode. This is default. | |
4423 | To inhibit the warning messages, use @option{-Wno-variadic-macros}. | |
4424 | ||
50d50fc7 SP |
4425 | @item -Wvla |
4426 | @opindex Wvla | |
4427 | @opindex Wno-vla | |
4428 | Warn if variable length array is used in the code. | |
4429 | @option{-Wno-vla} will prevent the @option{-pedantic} warning of | |
4430 | the variable length array. | |
4431 | ||
d35a40fc DE |
4432 | @item -Wvolatile-register-var |
4433 | @opindex Wvolatile-register-var | |
4434 | @opindex Wno-volatile-register-var | |
4435 | Warn if a register variable is declared volatile. The volatile | |
4436 | modifier does not inhibit all optimizations that may eliminate reads | |
16302daf MLI |
4437 | and/or writes to register variables. This warning is enabled by |
4438 | @option{-Wall}. | |
d35a40fc | 4439 | |
18424ae1 | 4440 | @item -Wdisabled-optimization |
cd3bb277 | 4441 | @opindex Wdisabled-optimization |
ccd4e386 | 4442 | @opindex Wno-disabled-optimization |
18424ae1 BL |
4443 | Warn if a requested optimization pass is disabled. This warning does |
4444 | not generally indicate that there is anything wrong with your code; it | |
4445 | merely indicates that GCC's optimizers were unable to handle the code | |
4446 | effectively. Often, the problem is that your code is too big or too | |
4447 | complex; GCC will refuse to optimize programs when the optimization | |
4448 | itself is likely to take inordinate amounts of time. | |
4449 | ||
670b0231 | 4450 | @item -Wpointer-sign @r{(C and Objective-C only)} |
f4e9414e | 4451 | @opindex Wpointer-sign |
f2fd3821 | 4452 | @opindex Wno-pointer-sign |
f4e9414e AO |
4453 | Warn for pointer argument passing or assignment with different signedness. |
4454 | This option is only supported for C and Objective-C@. It is implied by | |
4455 | @option{-Wall} and by @option{-pedantic}, which can be disabled with | |
4456 | @option{-Wno-pointer-sign}. | |
f2fd3821 | 4457 | |
0aca9021 | 4458 | @item -Wstack-protector |
d77314ec | 4459 | @opindex Wstack-protector |
ccd4e386 | 4460 | @opindex Wno-stack-protector |
0aca9021 JW |
4461 | This option is only active when @option{-fstack-protector} is active. It |
4462 | warns about functions that will not be protected against stack smashing. | |
4463 | ||
7621f5d5 VR |
4464 | @item -Wno-mudflap |
4465 | @opindex Wno-mudflap | |
4466 | Suppress warnings about constructs that cannot be instrumented by | |
4467 | @option{-fmudflap}. | |
4468 | ||
89a42ac8 ZW |
4469 | @item -Woverlength-strings |
4470 | @opindex Woverlength-strings | |
ccd4e386 | 4471 | @opindex Wno-overlength-strings |
89a42ac8 ZW |
4472 | Warn about string constants which are longer than the ``minimum |
4473 | maximum'' length specified in the C standard. Modern compilers | |
4474 | generally allow string constants which are much longer than the | |
4475 | standard's minimum limit, but very portable programs should avoid | |
4476 | using longer strings. | |
4477 | ||
4478 | The limit applies @emph{after} string constant concatenation, and does | |
7e1542b9 | 4479 | not count the trailing NUL@. In C90, the limit was 509 characters; in |
89a42ac8 ZW |
4480 | C99, it was raised to 4095. C++98 does not specify a normative |
4481 | minimum maximum, so we do not diagnose overlength strings in C++@. | |
4482 | ||
4483 | This option is implied by @option{-pedantic}, and can be disabled with | |
4484 | @option{-Wno-overlength-strings}. | |
6ec637a4 | 4485 | |
da667743 | 4486 | @item -Wunsuffixed-float-constants @r{(C and Objective-C only)} |
6ec637a4 JJ |
4487 | @opindex Wunsuffixed-float-constants |
4488 | ||
4489 | GCC will issue a warning for any floating constant that does not have | |
4490 | a suffix. When used together with @option{-Wsystem-headers} it will | |
4491 | warn about such constants in system header files. This can be useful | |
4492 | when preparing code to use with the @code{FLOAT_CONST_DECIMAL64} pragma | |
4493 | from the decimal floating-point extension to C99. | |
74291a4b MM |
4494 | @end table |
4495 | ||
4496 | @node Debugging Options | |
0c2d1a2a | 4497 | @section Options for Debugging Your Program or GCC |
74291a4b MM |
4498 | @cindex options, debugging |
4499 | @cindex debugging information options | |
4500 | ||
0c2d1a2a | 4501 | GCC has various special options that are used for debugging |
74291a4b MM |
4502 | either your program or GCC: |
4503 | ||
2642624b | 4504 | @table @gcctabopt |
74291a4b | 4505 | @item -g |
cd3bb277 | 4506 | @opindex g |
74291a4b | 4507 | Produce debugging information in the operating system's native format |
f8ca7e49 | 4508 | (stabs, COFF, XCOFF, or DWARF 2)@. GDB can work with this debugging |
74291a4b MM |
4509 | information. |
4510 | ||
630d3d5a | 4511 | On most systems that use stabs format, @option{-g} enables use of extra |
74291a4b MM |
4512 | debugging information that only GDB can use; this extra information |
4513 | makes debugging work better in GDB but will probably make other debuggers | |
4514 | crash or | |
4515 | refuse to read the program. If you want to control for certain whether | |
630d3d5a | 4516 | to generate the extra information, use @option{-gstabs+}, @option{-gstabs}, |
def66b10 | 4517 | @option{-gxcoff+}, @option{-gxcoff}, or @option{-gvms} (see below). |
74291a4b | 4518 | |
f8ca7e49 | 4519 | GCC allows you to use @option{-g} with |
630d3d5a | 4520 | @option{-O}. The shortcuts taken by optimized code may occasionally |
74291a4b MM |
4521 | produce surprising results: some variables you declared may not exist |
4522 | at all; flow of control may briefly move where you did not expect it; | |
4523 | some statements may not be executed because they compute constant | |
4524 | results or their values were already at hand; some statements may | |
4525 | execute in different places because they were moved out of loops. | |
4526 | ||
4527 | Nevertheless it proves possible to debug optimized output. This makes | |
4528 | it reasonable to use the optimizer for programs that might have bugs. | |
4529 | ||
0c2d1a2a | 4530 | The following options are useful when GCC is generated with the |
74291a4b MM |
4531 | capability for more than one debugging format. |
4532 | ||
4533 | @item -ggdb | |
cd3bb277 | 4534 | @opindex ggdb |
161d7b59 | 4535 | Produce debugging information for use by GDB@. This means to use the |
861bb6c1 JL |
4536 | most expressive format available (DWARF 2, stabs, or the native format |
4537 | if neither of those are supported), including GDB extensions if at all | |
4538 | possible. | |
74291a4b MM |
4539 | |
4540 | @item -gstabs | |
cd3bb277 | 4541 | @opindex gstabs |
74291a4b MM |
4542 | Produce debugging information in stabs format (if that is supported), |
4543 | without GDB extensions. This is the format used by DBX on most BSD | |
4544 | systems. On MIPS, Alpha and System V Release 4 systems this option | |
161d7b59 | 4545 | produces stabs debugging output which is not understood by DBX or SDB@. |
74291a4b MM |
4546 | On System V Release 4 systems this option requires the GNU assembler. |
4547 | ||
6a08f7b3 DP |
4548 | @item -feliminate-unused-debug-symbols |
4549 | @opindex feliminate-unused-debug-symbols | |
4550 | Produce debugging information in stabs format (if that is supported), | |
c0cbdbd9 | 4551 | for only symbols that are actually used. |
6a08f7b3 | 4552 | |
e713adf6 CD |
4553 | @item -femit-class-debug-always |
4554 | Instead of emitting debugging information for a C++ class in only one | |
4555 | object file, emit it in all object files using the class. This option | |
4556 | should be used only with debuggers that are unable to handle the way GCC | |
4557 | normally emits debugging information for classes because using this | |
4558 | option will increase the size of debugging information by as much as a | |
4559 | factor of two. | |
4560 | ||
74291a4b | 4561 | @item -gstabs+ |
cd3bb277 | 4562 | @opindex gstabs+ |
74291a4b | 4563 | Produce debugging information in stabs format (if that is supported), |
161d7b59 | 4564 | using GNU extensions understood only by the GNU debugger (GDB)@. The |
74291a4b MM |
4565 | use of these extensions is likely to make other debuggers crash or |
4566 | refuse to read the program. | |
4567 | ||
4568 | @item -gcoff | |
cd3bb277 | 4569 | @opindex gcoff |
74291a4b MM |
4570 | Produce debugging information in COFF format (if that is supported). |
4571 | This is the format used by SDB on most System V systems prior to | |
4572 | System V Release 4. | |
4573 | ||
4574 | @item -gxcoff | |
cd3bb277 | 4575 | @opindex gxcoff |
74291a4b MM |
4576 | Produce debugging information in XCOFF format (if that is supported). |
4577 | This is the format used by the DBX debugger on IBM RS/6000 systems. | |
4578 | ||
4579 | @item -gxcoff+ | |
cd3bb277 | 4580 | @opindex gxcoff+ |
74291a4b | 4581 | Produce debugging information in XCOFF format (if that is supported), |
161d7b59 | 4582 | using GNU extensions understood only by the GNU debugger (GDB)@. The |
74291a4b MM |
4583 | use of these extensions is likely to make other debuggers crash or |
4584 | refuse to read the program, and may cause assemblers other than the GNU | |
4585 | assembler (GAS) to fail with an error. | |
4586 | ||
53b2323e RH |
4587 | @item -gdwarf-@var{version} |
4588 | @opindex gdwarf-@var{version} | |
4589 | Produce debugging information in DWARF format (if that is | |
4590 | supported). This is the format used by DBX on IRIX 6. The value | |
b5b8b0ac | 4591 | of @var{version} may be either 2, 3 or 4; the default version is 2. |
53b2323e RH |
4592 | |
4593 | Note that with DWARF version 2 some ports require, and will always | |
4594 | use, some non-conflicting DWARF 3 extensions in the unwind tables. | |
74291a4b | 4595 | |
b5b8b0ac AO |
4596 | Version 4 may require GDB 7.0 and @option{-fvar-tracking-assignments} |
4597 | for maximum benefit. | |
4598 | ||
dc67413d JJ |
4599 | @item -gstrict-dwarf |
4600 | @opindex gstrict-dwarf | |
4601 | Disallow using extensions of later DWARF standard version than selected | |
4602 | with @option{-gdwarf-@var{version}}. On most targets using non-conflicting | |
4603 | DWARF extensions from later standard versions is allowed. | |
4604 | ||
4605 | @item -gno-strict-dwarf | |
4606 | @opindex gno-strict-dwarf | |
4607 | Allow using extensions of later DWARF standard version than selected with | |
4608 | @option{-gdwarf-@var{version}}. | |
4609 | ||
5f98259a RK |
4610 | @item -gvms |
4611 | @opindex gvms | |
4612 | Produce debugging information in VMS debug format (if that is | |
4613 | supported). This is the format used by DEBUG on VMS systems. | |
4614 | ||
74291a4b MM |
4615 | @item -g@var{level} |
4616 | @itemx -ggdb@var{level} | |
4617 | @itemx -gstabs@var{level} | |
4618 | @itemx -gcoff@var{level} | |
4619 | @itemx -gxcoff@var{level} | |
5f98259a | 4620 | @itemx -gvms@var{level} |
74291a4b MM |
4621 | Request debugging information and also use @var{level} to specify how |
4622 | much information. The default level is 2. | |
4623 | ||
ec75a430 GK |
4624 | Level 0 produces no debug information at all. Thus, @option{-g0} negates |
4625 | @option{-g}. | |
4626 | ||
74291a4b MM |
4627 | Level 1 produces minimal information, enough for making backtraces in |
4628 | parts of the program that you don't plan to debug. This includes | |
4629 | descriptions of functions and external variables, but no information | |
4630 | about local variables and no line numbers. | |
4631 | ||
4632 | Level 3 includes extra information, such as all the macro definitions | |
4633 | present in the program. Some debuggers support macro expansion when | |
630d3d5a | 4634 | you use @option{-g3}. |
74291a4b | 4635 | |
f8ca7e49 ZW |
4636 | @option{-gdwarf-2} does not accept a concatenated debug level, because |
4637 | GCC used to support an option @option{-gdwarf} that meant to generate | |
4638 | debug information in version 1 of the DWARF format (which is very | |
4639 | different from version 2), and it would have been too confusing. That | |
4640 | debug format is long obsolete, but the option cannot be changed now. | |
4641 | Instead use an additional @option{-g@var{level}} option to change the | |
53b2323e | 4642 | debug level for DWARF. |
eb7715a4 | 4643 | |
2153915d AO |
4644 | @item -gtoggle |
4645 | @opindex gtoggle | |
4646 | Turn off generation of debug info, if leaving out this option would have | |
4647 | generated it, or turn it on at level 2 otherwise. The position of this | |
4648 | argument in the command line does not matter, it takes effect after all | |
4649 | other options are processed, and it does so only once, no matter how | |
4650 | many times it is given. This is mainly intended to be used with | |
4651 | @option{-fcompare-debug}. | |
4652 | ||
b5b8b0ac AO |
4653 | @item -fdump-final-insns@r{[}=@var{file}@r{]} |
4654 | @opindex fdump-final-insns | |
4655 | Dump the final internal representation (RTL) to @var{file}. If the | |
4656 | optional argument is omitted (or if @var{file} is @code{.}), the name | |
4657 | of the dump file will be determined by appending @code{.gkd} to the | |
4658 | compilation output file name. | |
2153915d AO |
4659 | |
4660 | @item -fcompare-debug@r{[}=@var{opts}@r{]} | |
4661 | @opindex fcompare-debug | |
4662 | @opindex fno-compare-debug | |
4663 | If no error occurs during compilation, run the compiler a second time, | |
4664 | adding @var{opts} and @option{-fcompare-debug-second} to the arguments | |
4665 | passed to the second compilation. Dump the final internal | |
4666 | representation in both compilations, and print an error if they differ. | |
4667 | ||
4668 | If the equal sign is omitted, the default @option{-gtoggle} is used. | |
4669 | ||
4670 | The environment variable @env{GCC_COMPARE_DEBUG}, if defined, non-empty | |
4671 | and nonzero, implicitly enables @option{-fcompare-debug}. If | |
4672 | @env{GCC_COMPARE_DEBUG} is defined to a string starting with a dash, | |
4673 | then it is used for @var{opts}, otherwise the default @option{-gtoggle} | |
4674 | is used. | |
4675 | ||
4676 | @option{-fcompare-debug=}, with the equal sign but without @var{opts}, | |
4677 | is equivalent to @option{-fno-compare-debug}, which disables the dumping | |
4678 | of the final representation and the second compilation, preventing even | |
4679 | @env{GCC_COMPARE_DEBUG} from taking effect. | |
4680 | ||
4681 | To verify full coverage during @option{-fcompare-debug} testing, set | |
4682 | @env{GCC_COMPARE_DEBUG} to say @samp{-fcompare-debug-not-overridden}, | |
4683 | which GCC will reject as an invalid option in any actual compilation | |
4684 | (rather than preprocessing, assembly or linking). To get just a | |
4685 | warning, setting @env{GCC_COMPARE_DEBUG} to @samp{-w%n-fcompare-debug | |
4686 | not overridden} will do. | |
4687 | ||
4688 | @item -fcompare-debug-second | |
4689 | @opindex fcompare-debug-second | |
4690 | This option is implicitly passed to the compiler for the second | |
4691 | compilation requested by @option{-fcompare-debug}, along with options to | |
4692 | silence warnings, and omitting other options that would cause | |
4693 | side-effect compiler outputs to files or to the standard output. Dump | |
4694 | files and preserved temporary files are renamed so as to contain the | |
4695 | @code{.gk} additional extension during the second compilation, to avoid | |
4696 | overwriting those generated by the first. | |
4697 | ||
4698 | When this option is passed to the compiler driver, it causes the | |
4699 | @emph{first} compilation to be skipped, which makes it useful for little | |
4700 | other than debugging the compiler proper. | |
4701 | ||
e03b7153 RS |
4702 | @item -feliminate-dwarf2-dups |
4703 | @opindex feliminate-dwarf2-dups | |
4704 | Compress DWARF2 debugging information by eliminating duplicated | |
4705 | information about each symbol. This option only makes sense when | |
4706 | generating DWARF2 debugging information with @option{-gdwarf-2}. | |
4707 | ||
39ef6592 LC |
4708 | @item -femit-struct-debug-baseonly |
4709 | Emit debug information for struct-like types | |
4710 | only when the base name of the compilation source file | |
4711 | matches the base name of file in which the struct was defined. | |
4712 | ||
4713 | This option substantially reduces the size of debugging information, | |
4714 | but at significant potential loss in type information to the debugger. | |
4715 | See @option{-femit-struct-debug-reduced} for a less aggressive option. | |
4716 | See @option{-femit-struct-debug-detailed} for more detailed control. | |
4717 | ||
4718 | This option works only with DWARF 2. | |
4719 | ||
4720 | @item -femit-struct-debug-reduced | |
4721 | Emit debug information for struct-like types | |
4722 | only when the base name of the compilation source file | |
4723 | matches the base name of file in which the type was defined, | |
4724 | unless the struct is a template or defined in a system header. | |
4725 | ||
4726 | This option significantly reduces the size of debugging information, | |
4727 | with some potential loss in type information to the debugger. | |
4728 | See @option{-femit-struct-debug-baseonly} for a more aggressive option. | |
4729 | See @option{-femit-struct-debug-detailed} for more detailed control. | |
4730 | ||
4731 | This option works only with DWARF 2. | |
4732 | ||
4733 | @item -femit-struct-debug-detailed@r{[}=@var{spec-list}@r{]} | |
4734 | Specify the struct-like types | |
4735 | for which the compiler will generate debug information. | |
4736 | The intent is to reduce duplicate struct debug information | |
4737 | between different object files within the same program. | |
4738 | ||
4739 | This option is a detailed version of | |
4740 | @option{-femit-struct-debug-reduced} and @option{-femit-struct-debug-baseonly}, | |
4741 | which will serve for most needs. | |
4742 | ||
ab940b73 | 4743 | A specification has the syntax@* |
39ef6592 LC |
4744 | [@samp{dir:}|@samp{ind:}][@samp{ord:}|@samp{gen:}](@samp{any}|@samp{sys}|@samp{base}|@samp{none}) |
4745 | ||
4746 | The optional first word limits the specification to | |
4747 | structs that are used directly (@samp{dir:}) or used indirectly (@samp{ind:}). | |
4748 | A struct type is used directly when it is the type of a variable, member. | |
4749 | Indirect uses arise through pointers to structs. | |
4750 | That is, when use of an incomplete struct would be legal, the use is indirect. | |
4751 | An example is | |
4752 | @samp{struct one direct; struct two * indirect;}. | |
4753 | ||
4754 | The optional second word limits the specification to | |
4755 | ordinary structs (@samp{ord:}) or generic structs (@samp{gen:}). | |
4756 | Generic structs are a bit complicated to explain. | |
4757 | For C++, these are non-explicit specializations of template classes, | |
4758 | or non-template classes within the above. | |
4759 | Other programming languages have generics, | |
4760 | but @samp{-femit-struct-debug-detailed} does not yet implement them. | |
4761 | ||
4762 | The third word specifies the source files for those | |
4763 | structs for which the compiler will emit debug information. | |
4764 | The values @samp{none} and @samp{any} have the normal meaning. | |
4765 | The value @samp{base} means that | |
4766 | the base of name of the file in which the type declaration appears | |
4767 | must match the base of the name of the main compilation file. | |
4768 | In practice, this means that | |
4769 | types declared in @file{foo.c} and @file{foo.h} will have debug information, | |
4770 | but types declared in other header will not. | |
4771 | The value @samp{sys} means those types satisfying @samp{base} | |
4772 | or declared in system or compiler headers. | |
4773 | ||
4774 | You may need to experiment to determine the best settings for your application. | |
4775 | ||
4776 | The default is @samp{-femit-struct-debug-detailed=all}. | |
4777 | ||
4778 | This option works only with DWARF 2. | |
4779 | ||
77831620 CC |
4780 | @item -fenable-icf-debug |
4781 | @opindex fenable-icf-debug | |
4782 | Generate additional debug information to support identical code folding (ICF). | |
4783 | This option only works with DWARF version 2 or higher. | |
4784 | ||
987b399a | 4785 | @item -fno-merge-debug-strings |
28a08168 | 4786 | @opindex fmerge-debug-strings |
987b399a | 4787 | @opindex fno-merge-debug-strings |
44ab0f0e RW |
4788 | Direct the linker to not merge together strings in the debugging |
4789 | information which are identical in different object files. Merging is | |
4790 | not supported by all assemblers or linkers. Merging decreases the size | |
4791 | of the debug information in the output file at the cost of increasing | |
4792 | link processing time. Merging is enabled by default. | |
28a08168 | 4793 | |
c8aea42c PB |
4794 | @item -fdebug-prefix-map=@var{old}=@var{new} |
4795 | @opindex fdebug-prefix-map | |
4796 | When compiling files in directory @file{@var{old}}, record debugging | |
4797 | information describing them as in @file{@var{new}} instead. | |
4798 | ||
8f57ac5a JJ |
4799 | @item -fno-dwarf2-cfi-asm |
4800 | @opindex fdwarf2-cfi-asm | |
4801 | @opindex fno-dwarf2-cfi-asm | |
4802 | Emit DWARF 2 unwind info as compiler generated @code{.eh_frame} section | |
4803 | instead of using GAS @code{.cfi_*} directives. | |
4804 | ||
05739753 | 4805 | @cindex @command{prof} |
74291a4b | 4806 | @item -p |
cd3bb277 | 4807 | @opindex p |
74291a4b | 4808 | Generate extra code to write profile information suitable for the |
05739753 | 4809 | analysis program @command{prof}. You must use this option when compiling |
74291a4b MM |
4810 | the source files you want data about, and you must also use it when |
4811 | linking. | |
4812 | ||
05739753 | 4813 | @cindex @command{gprof} |
74291a4b | 4814 | @item -pg |
cd3bb277 | 4815 | @opindex pg |
74291a4b | 4816 | Generate extra code to write profile information suitable for the |
05739753 | 4817 | analysis program @command{gprof}. You must use this option when compiling |
74291a4b MM |
4818 | the source files you want data about, and you must also use it when |
4819 | linking. | |
4820 | ||
898f531b | 4821 | @item -Q |
cd3bb277 | 4822 | @opindex Q |
898f531b JL |
4823 | Makes the compiler print out each function name as it is compiled, and |
4824 | print some statistics about each pass when it finishes. | |
4825 | ||
1f0c3120 | 4826 | @item -ftime-report |
cd3bb277 | 4827 | @opindex ftime-report |
1f0c3120 JM |
4828 | Makes the compiler print some statistics about the time consumed by each |
4829 | pass when it finishes. | |
4830 | ||
4831 | @item -fmem-report | |
cd3bb277 | 4832 | @opindex fmem-report |
1f0c3120 JM |
4833 | Makes the compiler print some statistics about permanent memory |
4834 | allocation when it finishes. | |
4835 | ||
a5573239 JH |
4836 | @item -fpre-ipa-mem-report |
4837 | @opindex fpre-ipa-mem-report | |
4838 | @item -fpost-ipa-mem-report | |
4839 | @opindex fpost-ipa-mem-report | |
4840 | Makes the compiler print some statistics about permanent memory | |
4841 | allocation before or after interprocedural optimization. | |
4842 | ||
d3c12306 EB |
4843 | @item -fstack-usage |
4844 | @opindex fstack-usage | |
4845 | Makes the compiler output stack usage information for the program, on a | |
4846 | per-function basis. The filename for the dump is made by appending | |
4847 | @file{.su} to the AUXNAME. AUXNAME is generated from the name of | |
4848 | the output file, if explicitly specified and it is not an executable, | |
4849 | otherwise it is the basename of the source file. An entry is made up | |
4850 | of three fields: | |
4851 | ||
4852 | @itemize | |
4853 | @item | |
4854 | The name of the function. | |
4855 | @item | |
4856 | A number of bytes. | |
4857 | @item | |
4858 | One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}. | |
4859 | @end itemize | |
4860 | ||
4861 | The qualifier @code{static} means that the function manipulates the stack | |
4862 | statically: a fixed number of bytes are allocated for the frame on function | |
4863 | entry and released on function exit; no stack adjustments are otherwise made | |
4864 | in the function. The second field is this fixed number of bytes. | |
4865 | ||
4866 | The qualifier @code{dynamic} means that the function manipulates the stack | |
4867 | dynamically: in addition to the static allocation described above, stack | |
4868 | adjustments are made in the body of the function, for example to push/pop | |
4869 | arguments around function calls. If the qualifier @code{bounded} is also | |
4870 | present, the amount of these adjustments is bounded at compile-time and | |
4871 | the second field is an upper bound of the total amount of stack used by | |
4872 | the function. If it is not present, the amount of these adjustments is | |
4873 | not bounded at compile-time and the second field only represents the | |
4874 | bounded part. | |
4875 | ||
861bb6c1 | 4876 | @item -fprofile-arcs |
cd3bb277 | 4877 | @opindex fprofile-arcs |
23af32e6 NS |
4878 | Add code so that program flow @dfn{arcs} are instrumented. During |
4879 | execution the program records how many times each branch and call is | |
4880 | executed and how many times it is taken or returns. When the compiled | |
4881 | program exits it saves this data to a file called | |
8a36672b | 4882 | @file{@var{auxname}.gcda} for each source file. The data may be used for |
23af32e6 | 4883 | profile-directed optimizations (@option{-fbranch-probabilities}), or for |
8a36672b | 4884 | test coverage analysis (@option{-ftest-coverage}). Each object file's |
23af32e6 NS |
4885 | @var{auxname} is generated from the name of the output file, if |
4886 | explicitly specified and it is not the final executable, otherwise it is | |
8a36672b | 4887 | the basename of the source file. In both cases any suffix is removed |
431ae0bf | 4888 | (e.g.@: @file{foo.gcda} for input file @file{dir/foo.c}, or |
a4878735 | 4889 | @file{dir/foo.gcda} for output file specified as @option{-o dir/foo.o}). |
992f396f | 4890 | @xref{Cross-profiling}. |
23af32e6 | 4891 | |
ee4c708e BE |
4892 | @cindex @command{gcov} |
4893 | @item --coverage | |
4894 | @opindex coverage | |
4895 | ||
4896 | This option is used to compile and link code instrumented for coverage | |
4897 | analysis. The option is a synonym for @option{-fprofile-arcs} | |
4898 | @option{-ftest-coverage} (when compiling) and @option{-lgcov} (when | |
4899 | linking). See the documentation for those options for more details. | |
4900 | ||
23af32e6 NS |
4901 | @itemize |
4902 | ||
4903 | @item | |
4904 | Compile the source files with @option{-fprofile-arcs} plus optimization | |
8a36672b JM |
4905 | and code generation options. For test coverage analysis, use the |
4906 | additional @option{-ftest-coverage} option. You do not need to profile | |
23af32e6 NS |
4907 | every source file in a program. |
4908 | ||
4909 | @item | |
8555daff NS |
4910 | Link your object files with @option{-lgcov} or @option{-fprofile-arcs} |
4911 | (the latter implies the former). | |
23af32e6 NS |
4912 | |
4913 | @item | |
4914 | Run the program on a representative workload to generate the arc profile | |
8a36672b | 4915 | information. This may be repeated any number of times. You can run |
8555daff | 4916 | concurrent instances of your program, and provided that the file system |
8a36672b | 4917 | supports locking, the data files will be correctly updated. Also |
8555daff NS |
4918 | @code{fork} calls are detected and correctly handled (double counting |
4919 | will not happen). | |
23af32e6 NS |
4920 | |
4921 | @item | |
4922 | For profile-directed optimizations, compile the source files again with | |
4923 | the same optimization and code generation options plus | |
630d3d5a | 4924 | @option{-fbranch-probabilities} (@pxref{Optimize Options,,Options that |
3de87bf2 JJ |
4925 | Control Optimization}). |
4926 | ||
23af32e6 NS |
4927 | @item |
4928 | For test coverage analysis, use @command{gcov} to produce human readable | |
8a36672b | 4929 | information from the @file{.gcno} and @file{.gcda} files. Refer to the |
23af32e6 NS |
4930 | @command{gcov} documentation for further information. |
4931 | ||
4932 | @end itemize | |
3de87bf2 JJ |
4933 | |
4934 | With @option{-fprofile-arcs}, for each function of your program GCC | |
4935 | creates a program flow graph, then finds a spanning tree for the graph. | |
4936 | Only arcs that are not on the spanning tree have to be instrumented: the | |
4937 | compiler adds code to count the number of times that these arcs are | |
4938 | executed. When an arc is the only exit or only entrance to a block, the | |
4939 | instrumentation code can be added to the block; otherwise, a new basic | |
4940 | block must be created to hold the instrumentation code. | |
4941 | ||
861bb6c1 JL |
4942 | @need 2000 |
4943 | @item -ftest-coverage | |
cd3bb277 | 4944 | @opindex ftest-coverage |
a4878735 | 4945 | Produce a notes file that the @command{gcov} code-coverage utility |
23af32e6 | 4946 | (@pxref{Gcov,, @command{gcov}---a Test Coverage Program}) can use to |
8a36672b JM |
4947 | show program coverage. Each source file's note file is called |
4948 | @file{@var{auxname}.gcno}. Refer to the @option{-fprofile-arcs} option | |
23af32e6 | 4949 | above for a description of @var{auxname} and instructions on how to |
8a36672b | 4950 | generate test coverage data. Coverage data will match the source files |
23af32e6 | 4951 | more closely, if you do not optimize. |
3de87bf2 | 4952 | |
0a090f42 SP |
4953 | @item -fdbg-cnt-list |
4954 | @opindex fdbg-cnt-list | |
4955 | Print the name and the counter upperbound for all debug counters. | |
4956 | ||
4957 | @item -fdbg-cnt=@var{counter-value-list} | |
4958 | @opindex fdbg-cnt | |
7a61cf6f | 4959 | Set the internal debug counter upperbound. @var{counter-value-list} |
0a090f42 SP |
4960 | is a comma-separated list of @var{name}:@var{value} pairs |
4961 | which sets the upperbound of each debug counter @var{name} to @var{value}. | |
4962 | All debug counters have the initial upperbound of @var{UINT_MAX}, | |
4963 | thus dbg_cnt() returns true always unless the upperbound is set by this option. | |
4964 | e.g. With -fdbg-cnt=dce:10,tail_call:0 | |
4965 | dbg_cnt(dce) will return true only for first 10 invocations | |
4966 | and dbg_cnt(tail_call) will return false always. | |
4967 | ||
74291a4b | 4968 | @item -d@var{letters} |
33558d94 | 4969 | @itemx -fdump-rtl-@var{pass} |
cd3bb277 | 4970 | @opindex d |
74291a4b | 4971 | Says to make debugging dumps during compilation at times specified by |
e71da632 MH |
4972 | @var{letters}. This is used for debugging the RTL-based passes of the |
4973 | compiler. The file names for most of the dumps are made by appending | |
4974 | a pass number and a word to the @var{dumpname}, and the files are | |
ae758cb2 BS |
4975 | created in the directory of the output file. Note that the pass |
4976 | number is computed statically as passes get registered into the pass | |
4977 | manager. Thus the numbering is not related to the dynamic order of | |
4978 | execution of passes. In particular, a pass installed by a plugin | |
4979 | could have a number over 200 even if it executed quite early. | |
4980 | @var{dumpname} is generated from the name of the output file, if | |
4981 | explicitly specified and it is not an executable, otherwise it is the | |
4982 | basename of the source file. These switches may have different effects | |
4983 | when @option{-E} is used for preprocessing. | |
74291a4b | 4984 | |
cb7c15f8 JH |
4985 | Debug dumps can be enabled with a @option{-fdump-rtl} switch or some |
4986 | @option{-d} option @var{letters}. Here are the possible | |
00b251a0 | 4987 | letters for use in @var{pass} and @var{letters}, and their meanings: |
9f8628ba PB |
4988 | |
4989 | @table @gcctabopt | |
00b251a0 KZ |
4990 | |
4991 | @item -fdump-rtl-alignments | |
4992 | @opindex fdump-rtl-alignments | |
4993 | Dump after branch alignments have been computed. | |
4994 | ||
4995 | @item -fdump-rtl-asmcons | |
4996 | @opindex fdump-rtl-asmcons | |
4997 | Dump after fixing rtl statements that have unsatisfied in/out constraints. | |
4998 | ||
4999 | @item -fdump-rtl-auto_inc_dec | |
5000 | @opindex fdump-rtl-auto_inc_dec | |
5001 | Dump after auto-inc-dec discovery. This pass is only run on | |
5002 | architectures that have auto inc or auto dec instructions. | |
5003 | ||
5004 | @item -fdump-rtl-barriers | |
5005 | @opindex fdump-rtl-barriers | |
5006 | Dump after cleaning up the barrier instructions. | |
5007 | ||
5008 | @item -fdump-rtl-bbpart | |
5009 | @opindex fdump-rtl-bbpart | |
5010 | Dump after partitioning hot and cold basic blocks. | |
9f8628ba | 5011 | |
33558d94 | 5012 | @item -fdump-rtl-bbro |
9f8628ba | 5013 | @opindex fdump-rtl-bbro |
00b251a0 KZ |
5014 | Dump after block reordering. |
5015 | ||
5016 | @item -fdump-rtl-btl1 | |
5017 | @itemx -fdump-rtl-btl2 | |
5018 | @opindex fdump-rtl-btl2 | |
5019 | @opindex fdump-rtl-btl2 | |
5020 | @option{-fdump-rtl-btl1} and @option{-fdump-rtl-btl2} enable dumping | |
5021 | after the two branch | |
5022 | target load optimization passes. | |
5023 | ||
5024 | @item -fdump-rtl-bypass | |
5025 | @opindex fdump-rtl-bypass | |
5026 | Dump after jump bypassing and control flow optimizations. | |
9f8628ba | 5027 | |
33558d94 | 5028 | @item -fdump-rtl-combine |
9f8628ba | 5029 | @opindex fdump-rtl-combine |
00b251a0 KZ |
5030 | Dump after the RTL instruction combination pass. |
5031 | ||
5032 | @item -fdump-rtl-compgotos | |
5033 | @opindex fdump-rtl-compgotos | |
048fd785 | 5034 | Dump after duplicating the computed gotos. |
9f8628ba | 5035 | |
33558d94 | 5036 | @item -fdump-rtl-ce1 |
9f8628ba | 5037 | @itemx -fdump-rtl-ce2 |
00b251a0 | 5038 | @itemx -fdump-rtl-ce3 |
9f8628ba PB |
5039 | @opindex fdump-rtl-ce1 |
5040 | @opindex fdump-rtl-ce2 | |
00b251a0 KZ |
5041 | @opindex fdump-rtl-ce3 |
5042 | @option{-fdump-rtl-ce1}, @option{-fdump-rtl-ce2}, and | |
5043 | @option{-fdump-rtl-ce3} enable dumping after the three | |
7a61cf6f | 5044 | if conversion passes. |
00b251a0 KZ |
5045 | |
5046 | @itemx -fdump-rtl-cprop_hardreg | |
5047 | @opindex fdump-rtl-cprop_hardreg | |
5048 | Dump after hard register copy propagation. | |
5049 | ||
5050 | @itemx -fdump-rtl-csa | |
5051 | @opindex fdump-rtl-csa | |
5052 | Dump after combining stack adjustments. | |
5053 | ||
5054 | @item -fdump-rtl-cse1 | |
5055 | @itemx -fdump-rtl-cse2 | |
5056 | @opindex fdump-rtl-cse1 | |
5057 | @opindex fdump-rtl-cse2 | |
5058 | @option{-fdump-rtl-cse1} and @option{-fdump-rtl-cse2} enable dumping after | |
5059 | the two common sub-expression elimination passes. | |
5060 | ||
5061 | @itemx -fdump-rtl-dce | |
5062 | @opindex fdump-rtl-dce | |
5063 | Dump after the standalone dead code elimination passes. | |
9f8628ba | 5064 | |
9f8628ba | 5065 | @itemx -fdump-rtl-dbr |
9f8628ba | 5066 | @opindex fdump-rtl-dbr |
00b251a0 | 5067 | Dump after delayed branch scheduling. |
9f8628ba | 5068 | |
00b251a0 KZ |
5069 | @item -fdump-rtl-dce1 |
5070 | @itemx -fdump-rtl-dce2 | |
5071 | @opindex fdump-rtl-dce1 | |
5072 | @opindex fdump-rtl-dce2 | |
5073 | @option{-fdump-rtl-dce1} and @option{-fdump-rtl-dce2} enable dumping after | |
5074 | the two dead store elimination passes. | |
9f8628ba | 5075 | |
33558d94 | 5076 | @item -fdump-rtl-eh |
9f8628ba | 5077 | @opindex fdump-rtl-eh |
00b251a0 | 5078 | Dump after finalization of EH handling code. |
9f8628ba | 5079 | |
00b251a0 KZ |
5080 | @item -fdump-rtl-eh_ranges |
5081 | @opindex fdump-rtl-eh_ranges | |
5082 | Dump after conversion of EH handling range regions. | |
5083 | ||
5084 | @item -fdump-rtl-expand | |
5085 | @opindex fdump-rtl-expand | |
5086 | Dump after RTL generation. | |
5087 | ||
5088 | @item -fdump-rtl-fwprop1 | |
5089 | @itemx -fdump-rtl-fwprop2 | |
5090 | @opindex fdump-rtl-fwprop1 | |
5091 | @opindex fdump-rtl-fwprop2 | |
5092 | @option{-fdump-rtl-fwprop1} and @option{-fdump-rtl-fwprop2} enable | |
5093 | dumping after the two forward propagation passes. | |
5094 | ||
5095 | @item -fdump-rtl-gcse1 | |
5096 | @itemx -fdump-rtl-gcse2 | |
5097 | @opindex fdump-rtl-gcse1 | |
5098 | @opindex fdump-rtl-gcse2 | |
5099 | @option{-fdump-rtl-gcse1} and @option{-fdump-rtl-gcse2} enable dumping | |
5100 | after global common subexpression elimination. | |
5101 | ||
5102 | @item -fdump-rtl-init-regs | |
5103 | @opindex fdump-rtl-init-regs | |
5104 | Dump after the initialization of the registers. | |
5105 | ||
5106 | @item -fdump-rtl-initvals | |
5107 | @opindex fdump-rtl-initvals | |
5108 | Dump after the computation of the initial value sets. | |
5109 | ||
5110 | @itemx -fdump-rtl-into_cfglayout | |
5111 | @opindex fdump-rtl-into_cfglayout | |
5112 | Dump after converting to cfglayout mode. | |
5113 | ||
5114 | @item -fdump-rtl-ira | |
5115 | @opindex fdump-rtl-ira | |
5116 | Dump after iterated register allocation. | |
9f8628ba | 5117 | |
33558d94 | 5118 | @item -fdump-rtl-jump |
9f8628ba | 5119 | @opindex fdump-rtl-jump |
00b251a0 | 5120 | Dump after the second jump optimization. |
9f8628ba | 5121 | |
33558d94 | 5122 | @item -fdump-rtl-loop2 |
9f8628ba | 5123 | @opindex fdump-rtl-loop2 |
00b251a0 KZ |
5124 | @option{-fdump-rtl-loop2} enables dumping after the rtl |
5125 | loop optimization passes. | |
9f8628ba | 5126 | |
33558d94 | 5127 | @item -fdump-rtl-mach |
9f8628ba | 5128 | @opindex fdump-rtl-mach |
00b251a0 KZ |
5129 | Dump after performing the machine dependent reorganization pass, if that |
5130 | pass exists. | |
5131 | ||
5132 | @item -fdump-rtl-mode_sw | |
5133 | @opindex fdump-rtl-mode_sw | |
5134 | Dump after removing redundant mode switches. | |
9f8628ba | 5135 | |
33558d94 | 5136 | @item -fdump-rtl-rnreg |
9f8628ba | 5137 | @opindex fdump-rtl-rnreg |
00b251a0 | 5138 | Dump after register renumbering. |
9f8628ba | 5139 | |
00b251a0 KZ |
5140 | @itemx -fdump-rtl-outof_cfglayout |
5141 | @opindex fdump-rtl-outof_cfglayout | |
5142 | Dump after converting from cfglayout mode. | |
5143 | ||
5144 | @item -fdump-rtl-peephole2 | |
5145 | @opindex fdump-rtl-peephole2 | |
5146 | Dump after the peephole pass. | |
9f8628ba | 5147 | |
33558d94 | 5148 | @item -fdump-rtl-postreload |
9f8628ba | 5149 | @opindex fdump-rtl-postreload |
00b251a0 | 5150 | Dump after post-reload optimizations. |
9f8628ba | 5151 | |
00b251a0 KZ |
5152 | @itemx -fdump-rtl-pro_and_epilogue |
5153 | @opindex fdump-rtl-pro_and_epilogue | |
5154 | Dump after generating the function pro and epilogues. | |
9f8628ba | 5155 | |
00b251a0 KZ |
5156 | @item -fdump-rtl-regmove |
5157 | @opindex fdump-rtl-regmove | |
5158 | Dump after the register move pass. | |
9f8628ba | 5159 | |
33558d94 | 5160 | @item -fdump-rtl-sched1 |
00b251a0 | 5161 | @itemx -fdump-rtl-sched2 |
5c9ab0a6 | 5162 | @opindex fdump-rtl-sched1 |
00b251a0 KZ |
5163 | @opindex fdump-rtl-sched2 |
5164 | @option{-fdump-rtl-sched1} and @option{-fdump-rtl-sched2} enable dumping | |
5165 | after the basic block scheduling passes. | |
9f8628ba | 5166 | |
00b251a0 KZ |
5167 | @item -fdump-rtl-see |
5168 | @opindex fdump-rtl-see | |
5169 | Dump after sign extension elimination. | |
9f8628ba | 5170 | |
00b251a0 KZ |
5171 | @item -fdump-rtl-seqabstr |
5172 | @opindex fdump-rtl-seqabstr | |
7a61cf6f | 5173 | Dump after common sequence discovery. |
9f8628ba | 5174 | |
00b251a0 KZ |
5175 | @item -fdump-rtl-shorten |
5176 | @opindex fdump-rtl-shorten | |
5177 | Dump after shortening branches. | |
9f8628ba | 5178 | |
00b251a0 KZ |
5179 | @item -fdump-rtl-sibling |
5180 | @opindex fdump-rtl-sibling | |
5181 | Dump after sibling call optimizations. | |
5182 | ||
5183 | @item -fdump-rtl-split1 | |
5184 | @itemx -fdump-rtl-split2 | |
5185 | @itemx -fdump-rtl-split3 | |
5186 | @itemx -fdump-rtl-split4 | |
5187 | @itemx -fdump-rtl-split5 | |
5188 | @opindex fdump-rtl-split1 | |
5189 | @opindex fdump-rtl-split2 | |
5190 | @opindex fdump-rtl-split3 | |
5191 | @opindex fdump-rtl-split4 | |
5192 | @opindex fdump-rtl-split5 | |
5193 | @option{-fdump-rtl-split1}, @option{-fdump-rtl-split2}, | |
5194 | @option{-fdump-rtl-split3}, @option{-fdump-rtl-split4} and | |
5195 | @option{-fdump-rtl-split5} enable dumping after five rounds of | |
5196 | instruction splitting. | |
9f8628ba | 5197 | |
00b251a0 KZ |
5198 | @item -fdump-rtl-sms |
5199 | @opindex fdump-rtl-sms | |
5200 | Dump after modulo scheduling. This pass is only run on some | |
5201 | architectures. | |
5202 | ||
5203 | @item -fdump-rtl-stack | |
5204 | @opindex fdump-rtl-stack | |
5205 | Dump after conversion from GCC's "flat register file" registers to the | |
5206 | x87's stack-like registers. This pass is only run on x86 variants. | |
5207 | ||
5208 | @item -fdump-rtl-subreg1 | |
5209 | @itemx -fdump-rtl-subreg2 | |
5210 | @opindex fdump-rtl-subreg1 | |
5211 | @opindex fdump-rtl-subreg2 | |
5212 | @option{-fdump-rtl-subreg1} and @option{-fdump-rtl-subreg2} enable dumping after | |
5213 | the two subreg expansion passes. | |
5214 | ||
5215 | @item -fdump-rtl-unshare | |
5216 | @opindex fdump-rtl-unshare | |
5217 | Dump after all rtl has been unshared. | |
5218 | ||
5219 | @item -fdump-rtl-vartrack | |
5220 | @opindex fdump-rtl-vartrack | |
5221 | Dump after variable tracking. | |
5222 | ||
5223 | @item -fdump-rtl-vregs | |
5224 | @opindex fdump-rtl-vregs | |
5225 | Dump after converting virtual registers to hard registers. | |
9f8628ba | 5226 | |
33558d94 | 5227 | @item -fdump-rtl-web |
9f8628ba | 5228 | @opindex fdump-rtl-web |
00b251a0 KZ |
5229 | Dump after live range splitting. |
5230 | ||
5231 | @item -fdump-rtl-regclass | |
5232 | @itemx -fdump-rtl-subregs_of_mode_init | |
5233 | @itemx -fdump-rtl-subregs_of_mode_finish | |
5234 | @itemx -fdump-rtl-dfinit | |
5235 | @itemx -fdump-rtl-dfinish | |
5236 | @opindex fdump-rtl-regclass | |
5237 | @opindex fdump-rtl-subregs_of_mode_init | |
5238 | @opindex fdump-rtl-subregs_of_mode_finish | |
5239 | @opindex fdump-rtl-dfinit | |
5240 | @opindex fdump-rtl-dfinish | |
5241 | These dumps are defined but always produce empty files. | |
9f8628ba | 5242 | |
33558d94 | 5243 | @item -fdump-rtl-all |
9f8628ba | 5244 | @opindex fdump-rtl-all |
74291a4b | 5245 | Produce all the dumps listed above. |
9f8628ba | 5246 | |
00b251a0 KZ |
5247 | @item -dA |
5248 | @opindex dA | |
5249 | Annotate the assembler output with miscellaneous debugging information. | |
5250 | ||
5251 | @item -dD | |
5252 | @opindex dD | |
5253 | Dump all macro definitions, at the end of preprocessing, in addition to | |
5254 | normal output. | |
5255 | ||
9f8628ba | 5256 | @item -dH |
886e0865 GK |
5257 | @opindex dH |
5258 | Produce a core dump whenever an error occurs. | |
9f8628ba PB |
5259 | |
5260 | @item -dm | |
cd3bb277 | 5261 | @opindex dm |
74291a4b MM |
5262 | Print statistics on memory usage, at the end of the run, to |
5263 | standard error. | |
9f8628ba PB |
5264 | |
5265 | @item -dp | |
cd3bb277 | 5266 | @opindex dp |
74291a4b | 5267 | Annotate the assembler output with a comment indicating which |
f20b5577 MM |
5268 | pattern and alternative was used. The length of each instruction is |
5269 | also printed. | |
9f8628ba PB |
5270 | |
5271 | @item -dP | |
cd3bb277 | 5272 | @opindex dP |
2856c3e3 | 5273 | Dump the RTL in the assembler output as a comment before each instruction. |
630d3d5a | 5274 | Also turns on @option{-dp} annotation. |
9f8628ba PB |
5275 | |
5276 | @item -dv | |
cd3bb277 | 5277 | @opindex dv |
cb7c15f8 JH |
5278 | For each of the other indicated dump files (@option{-fdump-rtl-@var{pass}}), |
5279 | dump a representation of the control flow graph suitable for viewing with VCG | |
5280 | to @file{@var{file}.@var{pass}.vcg}. | |
9f8628ba PB |
5281 | |
5282 | @item -dx | |
cd3bb277 | 5283 | @opindex dx |
62a1403d | 5284 | Just generate RTL for a function instead of compiling it. Usually used |
cb7c15f8 | 5285 | with @option{-fdump-rtl-expand}. |
74291a4b MM |
5286 | @end table |
5287 | ||
24a7799e R |
5288 | @item -fdump-noaddr |
5289 | @opindex fdump-noaddr | |
cb7c15f8 JH |
5290 | When doing debugging dumps, suppress address output. This makes it more |
5291 | feasible to use diff on debugging dumps for compiler invocations with | |
5292 | different compiler binaries and/or different | |
5293 | text / bss / data / heap / stack / dso start locations. | |
24a7799e | 5294 | |
b707b450 | 5295 | @item -fdump-unnumbered |
cd3bb277 | 5296 | @opindex fdump-unnumbered |
cb7c15f8 JH |
5297 | When doing debugging dumps, suppress instruction numbers and address output. |
5298 | This makes it more feasible to use diff on debugging dumps for compiler | |
5299 | invocations with different options, in particular with and without | |
5300 | @option{-g}. | |
b707b450 | 5301 | |
2aa7c49b AO |
5302 | @item -fdump-unnumbered-links |
5303 | @opindex fdump-unnumbered-links | |
5304 | When doing debugging dumps (see @option{-d} option above), suppress | |
5305 | instruction numbers for the links to the previous and next instructions | |
5306 | in a sequence. | |
5307 | ||
223dcf1c AN |
5308 | @item -fdump-translation-unit @r{(C++ only)} |
5309 | @itemx -fdump-translation-unit-@var{options} @r{(C++ only)} | |
f70a54cb CR |
5310 | @opindex fdump-translation-unit |
5311 | Dump a representation of the tree structure for the entire translation | |
5312 | unit to a file. The file name is made by appending @file{.tu} to the | |
e71da632 MH |
5313 | source file name, and the file is created in the same directory as the |
5314 | output file. If the @samp{-@var{options}} form is used, @var{options} | |
f70a54cb CR |
5315 | controls the details of the dump as described for the |
5316 | @option{-fdump-tree} options. | |
5317 | ||
aee96fe9 | 5318 | @item -fdump-class-hierarchy @r{(C++ only)} |
22367161 | 5319 | @itemx -fdump-class-hierarchy-@var{options} @r{(C++ only)} |
cd3bb277 | 5320 | @opindex fdump-class-hierarchy |
e76b4820 | 5321 | Dump a representation of each class's hierarchy and virtual function |
e71da632 MH |
5322 | table layout to a file. The file name is made by appending |
5323 | @file{.class} to the source file name, and the file is created in the | |
5324 | same directory as the output file. If the @samp{-@var{options}} form | |
5325 | is used, @var{options} controls the details of the dump as described | |
5326 | for the @option{-fdump-tree} options. | |
22367161 | 5327 | |
9b3e897d PB |
5328 | @item -fdump-ipa-@var{switch} |
5329 | @opindex fdump-ipa | |
83c99486 | 5330 | Control the dumping at various stages of inter-procedural analysis |
e71da632 MH |
5331 | language tree to a file. The file name is generated by appending a |
5332 | switch specific suffix to the source file name, and the file is created | |
5333 | in the same directory as the output file. The following dumps are | |
5334 | possible: | |
9b3e897d PB |
5335 | |
5336 | @table @samp | |
5337 | @item all | |
fed39e22 | 5338 | Enables all inter-procedural analysis dumps. |
9b3e897d PB |
5339 | |
5340 | @item cgraph | |
5341 | Dumps information about call-graph optimization, unused function removal, | |
5342 | and inlining decisions. | |
fed39e22 MLI |
5343 | |
5344 | @item inline | |
5345 | Dump after function inlining. | |
5346 | ||
9b3e897d PB |
5347 | @end table |
5348 | ||
9fe0cb7d | 5349 | @item -fdump-statistics-@var{option} |
d376d545 | 5350 | @opindex fdump-statistics |
9fe0cb7d | 5351 | Enable and control dumping of pass statistics in a separate file. The |
e71da632 MH |
5352 | file name is generated by appending a suffix ending in |
5353 | @samp{.statistics} to the source file name, and the file is created in | |
5354 | the same directory as the output file. If the @samp{-@var{option}} | |
5355 | form is used, @samp{-stats} will cause counters to be summed over the | |
5356 | whole compilation unit while @samp{-details} will dump every event as | |
5357 | the passes generate them. The default with no option is to sum | |
5358 | counters for each function compiled. | |
9fe0cb7d | 5359 | |
0c8c236b JJ |
5360 | @item -fdump-tree-@var{switch} |
5361 | @itemx -fdump-tree-@var{switch}-@var{options} | |
22367161 NS |
5362 | @opindex fdump-tree |
5363 | Control the dumping at various stages of processing the intermediate | |
e71da632 MH |
5364 | language tree to a file. The file name is generated by appending a |
5365 | switch specific suffix to the source file name, and the file is | |
5366 | created in the same directory as the output file. If the | |
5367 | @samp{-@var{options}} form is used, @var{options} is a list of | |
5368 | @samp{-} separated options that control the details of the dump. Not | |
5369 | all options are applicable to all dumps, those which are not | |
5370 | meaningful will be ignored. The following options are available | |
f71f87f9 | 5371 | |
e76b4820 | 5372 | @table @samp |
22367161 | 5373 | @item address |
767094dd | 5374 | Print the address of each node. Usually this is not meaningful as it |
8a36672b | 5375 | changes according to the environment and source file. Its primary use |
22367161 | 5376 | is for tying up a dump file with a debug environment. |
394bd84d RH |
5377 | @item asmname |
5378 | If @code{DECL_ASSEMBLER_NAME} has been set for a given decl, use that | |
5379 | in the dump instead of @code{DECL_NAME}. Its primary use is ease of | |
5380 | use working backward from mangled names in the assembly file. | |
22367161 NS |
5381 | @item slim |
5382 | Inhibit dumping of members of a scope or body of a function merely | |
6de9cd9a DN |
5383 | because that scope has been reached. Only dump such items when they |
5384 | are directly reachable by some other path. When dumping pretty-printed | |
5385 | trees, this option inhibits dumping the bodies of control structures. | |
5386 | @item raw | |
5387 | Print a raw representation of the tree. By default, trees are | |
5388 | pretty-printed into a C-like representation. | |
5389 | @item details | |
5390 | Enable more detailed dumps (not honored by every dump option). | |
5391 | @item stats | |
5392 | Enable dumping various statistics about the pass (not honored by every dump | |
5393 | option). | |
5394 | @item blocks | |
5395 | Enable showing basic block boundaries (disabled in raw dumps). | |
5396 | @item vops | |
5397 | Enable showing virtual operands for every statement. | |
5398 | @item lineno | |
5399 | Enable showing line numbers for statements. | |
5400 | @item uid | |
5401 | Enable showing the unique ID (@code{DECL_UID}) for each variable. | |
3e894af1 KZ |
5402 | @item verbose |
5403 | Enable showing the tree dump for each statement. | |
cae63f88 DN |
5404 | @item eh |
5405 | Enable showing the EH region number holding each statement. | |
22367161 | 5406 | @item all |
3e894af1 KZ |
5407 | Turn on all options, except @option{raw}, @option{slim}, @option{verbose} |
5408 | and @option{lineno}. | |
e76b4820 NS |
5409 | @end table |
5410 | ||
5411 | The following tree dumps are possible: | |
5412 | @table @samp | |
6de9cd9a | 5413 | |
e76b4820 | 5414 | @item original |
d376d545 | 5415 | @opindex fdump-tree-original |
e76b4820 | 5416 | Dump before any tree based optimization, to @file{@var{file}.original}. |
6de9cd9a | 5417 | |
e76b4820 | 5418 | @item optimized |
d376d545 | 5419 | @opindex fdump-tree-optimized |
e76b4820 | 5420 | Dump after all tree based optimization, to @file{@var{file}.optimized}. |
6de9cd9a | 5421 | |
6de9cd9a DN |
5422 | @item gimple |
5423 | @opindex fdump-tree-gimple | |
5424 | Dump each function before and after the gimplification pass to a file. The | |
5425 | file name is made by appending @file{.gimple} to the source file name. | |
5426 | ||
5427 | @item cfg | |
5428 | @opindex fdump-tree-cfg | |
5429 | Dump the control flow graph of each function to a file. The file name is | |
5430 | made by appending @file{.cfg} to the source file name. | |
5431 | ||
5432 | @item vcg | |
5433 | @opindex fdump-tree-vcg | |
5434 | Dump the control flow graph of each function to a file in VCG format. The | |
5435 | file name is made by appending @file{.vcg} to the source file name. Note | |
5436 | that if the file contains more than one function, the generated file cannot | |
8a36672b | 5437 | be used directly by VCG@. You will need to cut and paste each function's |
6de9cd9a DN |
5438 | graph into its own separate file first. |
5439 | ||
5440 | @item ch | |
5441 | @opindex fdump-tree-ch | |
5442 | Dump each function after copying loop headers. The file name is made by | |
5443 | appending @file{.ch} to the source file name. | |
5444 | ||
5445 | @item ssa | |
5446 | @opindex fdump-tree-ssa | |
5447 | Dump SSA related information to a file. The file name is made by appending | |
5448 | @file{.ssa} to the source file name. | |
5449 | ||
5450 | @item alias | |
5451 | @opindex fdump-tree-alias | |
5452 | Dump aliasing information for each function. The file name is made by | |
5453 | appending @file{.alias} to the source file name. | |
5454 | ||
5455 | @item ccp | |
5456 | @opindex fdump-tree-ccp | |
8a36672b | 5457 | Dump each function after CCP@. The file name is made by appending |
6de9cd9a DN |
5458 | @file{.ccp} to the source file name. |
5459 | ||
0bca51f0 DN |
5460 | @item storeccp |
5461 | @opindex fdump-tree-storeccp | |
0ee2ea09 | 5462 | Dump each function after STORE-CCP@. The file name is made by appending |
0bca51f0 DN |
5463 | @file{.storeccp} to the source file name. |
5464 | ||
6de9cd9a DN |
5465 | @item pre |
5466 | @opindex fdump-tree-pre | |
5467 | Dump trees after partial redundancy elimination. The file name is made | |
5468 | by appending @file{.pre} to the source file name. | |
5469 | ||
ff2ad0f7 DN |
5470 | @item fre |
5471 | @opindex fdump-tree-fre | |
5472 | Dump trees after full redundancy elimination. The file name is made | |
5473 | by appending @file{.fre} to the source file name. | |
5474 | ||
0bca51f0 DN |
5475 | @item copyprop |
5476 | @opindex fdump-tree-copyprop | |
5477 | Dump trees after copy propagation. The file name is made | |
5478 | by appending @file{.copyprop} to the source file name. | |
5479 | ||
5480 | @item store_copyprop | |
5481 | @opindex fdump-tree-store_copyprop | |
5482 | Dump trees after store copy-propagation. The file name is made | |
5483 | by appending @file{.store_copyprop} to the source file name. | |
5484 | ||
6de9cd9a DN |
5485 | @item dce |
5486 | @opindex fdump-tree-dce | |
5487 | Dump each function after dead code elimination. The file name is made by | |
5488 | appending @file{.dce} to the source file name. | |
5489 | ||
5490 | @item mudflap | |
5491 | @opindex fdump-tree-mudflap | |
5492 | Dump each function after adding mudflap instrumentation. The file name is | |
5493 | made by appending @file{.mudflap} to the source file name. | |
5494 | ||
5495 | @item sra | |
5496 | @opindex fdump-tree-sra | |
5497 | Dump each function after performing scalar replacement of aggregates. The | |
5498 | file name is made by appending @file{.sra} to the source file name. | |
5499 | ||
fa555252 DB |
5500 | @item sink |
5501 | @opindex fdump-tree-sink | |
5502 | Dump each function after performing code sinking. The file name is made | |
cb7ad97b | 5503 | by appending @file{.sink} to the source file name. |
fa555252 | 5504 | |
6de9cd9a DN |
5505 | @item dom |
5506 | @opindex fdump-tree-dom | |
5507 | Dump each function after applying dominator tree optimizations. The file | |
5508 | name is made by appending @file{.dom} to the source file name. | |
5509 | ||
5510 | @item dse | |
5511 | @opindex fdump-tree-dse | |
5512 | Dump each function after applying dead store elimination. The file | |
5513 | name is made by appending @file{.dse} to the source file name. | |
5514 | ||
5515 | @item phiopt | |
5516 | @opindex fdump-tree-phiopt | |
5517 | Dump each function after optimizing PHI nodes into straightline code. The file | |
5518 | name is made by appending @file{.phiopt} to the source file name. | |
5519 | ||
5520 | @item forwprop | |
5521 | @opindex fdump-tree-forwprop | |
5522 | Dump each function after forward propagating single use variables. The file | |
5523 | name is made by appending @file{.forwprop} to the source file name. | |
5524 | ||
5525 | @item copyrename | |
5526 | @opindex fdump-tree-copyrename | |
5527 | Dump each function after applying the copy rename optimization. The file | |
5528 | name is made by appending @file{.copyrename} to the source file name. | |
5529 | ||
5530 | @item nrv | |
5531 | @opindex fdump-tree-nrv | |
5532 | Dump each function after applying the named return value optimization on | |
5533 | generic trees. The file name is made by appending @file{.nrv} to the source | |
5534 | file name. | |
5535 | ||
79fe1b3b DN |
5536 | @item vect |
5537 | @opindex fdump-tree-vect | |
f0eb93a8 | 5538 | Dump each function after applying vectorization of loops. The file name is |
79fe1b3b DN |
5539 | made by appending @file{.vect} to the source file name. |
5540 | ||
ca0b0bf8 IR |
5541 | @item slp |
5542 | @opindex fdump-tree-slp | |
5543 | Dump each function after applying vectorization of basic blocks. The file name | |
5544 | is made by appending @file{.slp} to the source file name. | |
5545 | ||
08873e96 DN |
5546 | @item vrp |
5547 | @opindex fdump-tree-vrp | |
5548 | Dump each function after Value Range Propagation (VRP). The file name | |
5549 | is made by appending @file{.vrp} to the source file name. | |
5550 | ||
6de9cd9a DN |
5551 | @item all |
5552 | @opindex fdump-tree-all | |
5553 | Enable all the available tree dumps with the flags provided in this option. | |
e76b4820 | 5554 | @end table |
9965d119 | 5555 | |
c866976a LB |
5556 | @item -ftree-vectorizer-verbose=@var{n} |
5557 | @opindex ftree-vectorizer-verbose | |
5558 | This option controls the amount of debugging output the vectorizer prints. | |
cb7ad97b EC |
5559 | This information is written to standard error, unless |
5560 | @option{-fdump-tree-all} or @option{-fdump-tree-vect} is specified, | |
7ffe0f0d DN |
5561 | in which case it is output to the usual dump listing file, @file{.vect}. |
5562 | For @var{n}=0 no diagnostic information is reported. | |
cb7ad97b | 5563 | If @var{n}=1 the vectorizer reports each loop that got vectorized, |
7ffe0f0d | 5564 | and the total number of loops that got vectorized. |
cb7ad97b | 5565 | If @var{n}=2 the vectorizer also reports non-vectorized loops that passed |
021efafc | 5566 | the first analysis phase (vect_analyze_loop_form) - i.e.@: countable, |
cb7ad97b | 5567 | inner-most, single-bb, single-entry/exit loops. This is the same verbosity |
7ffe0f0d | 5568 | level that @option{-fdump-tree-vect-stats} uses. |
cb7ad97b | 5569 | Higher verbosity levels mean either more information dumped for each |
7ffe0f0d | 5570 | reported loop, or same amount of information reported for more loops: |
ca0b0bf8 IR |
5571 | if @var{n}=3, vectorizer cost model information is reported. |
5572 | If @var{n}=4, alignment related information is added to the reports. | |
5573 | If @var{n}=5, data-references related information (e.g.@: memory dependences, | |
7ffe0f0d | 5574 | memory access-patterns) is added to the reports. |
ca0b0bf8 | 5575 | If @var{n}=6, the vectorizer reports also non-vectorized inner-most loops |
021efafc | 5576 | that did not pass the first analysis phase (i.e., may not be countable, or |
7ffe0f0d | 5577 | may have complicated control-flow). |
ca0b0bf8 IR |
5578 | If @var{n}=7, the vectorizer reports also non-vectorized nested loops. |
5579 | If @var{n}=8, SLP related information is added to the reports. | |
5580 | For @var{n}=9, all the information the vectorizer generates during its | |
7ffe0f0d DN |
5581 | analysis and transformation is reported. This is the same verbosity level |
5582 | that @option{-fdump-tree-vect-details} uses. | |
c866976a | 5583 | |
a37db56b | 5584 | @item -frandom-seed=@var{string} |
d376d545 | 5585 | @opindex frandom-seed |
a37db56b | 5586 | This option provides a seed that GCC uses when it would otherwise use |
e61a2eb7 | 5587 | random numbers. It is used to generate certain symbol names |
8a36672b | 5588 | that have to be different in every compiled file. It is also used to |
e61a2eb7 | 5589 | place unique stamps in coverage data files and the object files that |
8a36672b | 5590 | produce them. You can use the @option{-frandom-seed} option to produce |
e61a2eb7 | 5591 | reproducibly identical object files. |
a37db56b GK |
5592 | |
5593 | The @var{string} should be different for every file you compile. | |
5594 | ||
e03b7153 RS |
5595 | @item -fsched-verbose=@var{n} |
5596 | @opindex fsched-verbose | |
5597 | On targets that use instruction scheduling, this option controls the | |
5598 | amount of debugging output the scheduler prints. This information is | |
cb7c15f8 JH |
5599 | written to standard error, unless @option{-fdump-rtl-sched1} or |
5600 | @option{-fdump-rtl-sched2} is specified, in which case it is output | |
4cad6dba | 5601 | to the usual dump listing file, @file{.sched1} or @file{.sched2} |
cb7c15f8 JH |
5602 | respectively. However for @var{n} greater than nine, the output is |
5603 | always printed to standard error. | |
e03b7153 RS |
5604 | |
5605 | For @var{n} greater than zero, @option{-fsched-verbose} outputs the | |
cb7c15f8 JH |
5606 | same information as @option{-fdump-rtl-sched1} and @option{-fdump-rtl-sched2}. |
5607 | For @var{n} greater than one, it also output basic block probabilities, | |
5608 | detailed ready list information and unit/insn info. For @var{n} greater | |
5609 | than two, it includes RTL at abort point, control-flow and regions info. | |
5610 | And for @var{n} over four, @option{-fsched-verbose} also includes | |
5611 | dependence info. | |
e03b7153 | 5612 | |
74291a4b | 5613 | @item -save-temps |
14fdc613 | 5614 | @itemx -save-temps=cwd |
cd3bb277 | 5615 | @opindex save-temps |
74291a4b MM |
5616 | Store the usual ``temporary'' intermediate files permanently; place them |
5617 | in the current directory and name them based on the source file. Thus, | |
5618 | compiling @file{foo.c} with @samp{-c -save-temps} would produce files | |
f2ecb02d JM |
5619 | @file{foo.i} and @file{foo.s}, as well as @file{foo.o}. This creates a |
5620 | preprocessed @file{foo.i} output file even though the compiler now | |
5621 | normally uses an integrated preprocessor. | |
74291a4b | 5622 | |
1f7edb8b RS |
5623 | When used in combination with the @option{-x} command line option, |
5624 | @option{-save-temps} is sensible enough to avoid over writing an | |
5625 | input source file with the same extension as an intermediate file. | |
5626 | The corresponding intermediate file may be obtained by renaming the | |
5627 | source file before using @option{-save-temps}. | |
5628 | ||
14fdc613 MM |
5629 | If you invoke GCC in parallel, compiling several different source |
5630 | files that share a common base name in different subdirectories or the | |
5631 | same source file compiled for multiple output destinations, it is | |
5632 | likely that the different parallel compilers will interfere with each | |
5633 | other, and overwrite the temporary files. For instance: | |
5634 | ||
5635 | @smallexample | |
5636 | gcc -save-temps -o outdir1/foo.o indir1/foo.c& | |
5637 | gcc -save-temps -o outdir2/foo.o indir2/foo.c& | |
5638 | @end smallexample | |
5639 | ||
5640 | may result in @file{foo.i} and @file{foo.o} being written to | |
5641 | simultaneously by both compilers. | |
5642 | ||
5643 | @item -save-temps=obj | |
5644 | @opindex save-temps=obj | |
5645 | Store the usual ``temporary'' intermediate files permanently. If the | |
5646 | @option{-o} option is used, the temporary files are based on the | |
5647 | object file. If the @option{-o} option is not used, the | |
5648 | @option{-save-temps=obj} switch behaves like @option{-save-temps}. | |
5649 | ||
5650 | For example: | |
5651 | ||
5652 | @smallexample | |
5653 | gcc -save-temps=obj -c foo.c | |
5654 | gcc -save-temps=obj -c bar.c -o dir/xbar.o | |
5655 | gcc -save-temps=obj foobar.c -o dir2/yfoobar | |
5656 | @end smallexample | |
5657 | ||
5658 | would create @file{foo.i}, @file{foo.s}, @file{dir/xbar.i}, | |
5659 | @file{dir/xbar.s}, @file{dir2/yfoobar.i}, @file{dir2/yfoobar.s}, and | |
5660 | @file{dir2/yfoobar.o}. | |
5661 | ||
bdde878c | 5662 | @item -time@r{[}=@var{file}@r{]} |
cd3bb277 | 5663 | @opindex time |
03c41c05 | 5664 | Report the CPU time taken by each subprocess in the compilation |
f2ecb02d | 5665 | sequence. For C source files, this is the compiler proper and assembler |
bdde878c AO |
5666 | (plus the linker if linking is done). |
5667 | ||
5668 | Without the specification of an output file, the output looks like this: | |
03c41c05 ZW |
5669 | |
5670 | @smallexample | |
03c41c05 ZW |
5671 | # cc1 0.12 0.01 |
5672 | # as 0.00 0.01 | |
5673 | @end smallexample | |
5674 | ||
d78aa55c JM |
5675 | The first number on each line is the ``user time'', that is time spent |
5676 | executing the program itself. The second number is ``system time'', | |
03c41c05 ZW |
5677 | time spent executing operating system routines on behalf of the program. |
5678 | Both numbers are in seconds. | |
5679 | ||
bdde878c AO |
5680 | With the specification of an output file, the output is appended to the |
5681 | named file, and it looks like this: | |
5682 | ||
5683 | @smallexample | |
5684 | 0.12 0.01 cc1 @var{options} | |
5685 | 0.00 0.01 as @var{options} | |
5686 | @end smallexample | |
5687 | ||
5688 | The ``user time'' and the ``system time'' are moved before the program | |
5689 | name, and the options passed to the program are displayed, so that one | |
5690 | can later tell what file was being compiled, and with which options. | |
5691 | ||
014a1138 JZ |
5692 | @item -fvar-tracking |
5693 | @opindex fvar-tracking | |
8a36672b JM |
5694 | Run variable tracking pass. It computes where variables are stored at each |
5695 | position in code. Better debugging information is then generated | |
014a1138 JZ |
5696 | (if the debugging information format supports this information). |
5697 | ||
5698 | It is enabled by default when compiling with optimization (@option{-Os}, | |
923158be | 5699 | @option{-O}, @option{-O2}, @dots{}), debugging information (@option{-g}) and |
014a1138 JZ |
5700 | the debug info format supports it. |
5701 | ||
b5b8b0ac AO |
5702 | @item -fvar-tracking-assignments |
5703 | @opindex fvar-tracking-assignments | |
5704 | @opindex fno-var-tracking-assignments | |
5705 | Annotate assignments to user variables early in the compilation and | |
5706 | attempt to carry the annotations over throughout the compilation all the | |
5707 | way to the end, in an attempt to improve debug information while | |
5708 | optimizing. Use of @option{-gdwarf-4} is recommended along with it. | |
5709 | ||
5710 | It can be enabled even if var-tracking is disabled, in which case | |
5711 | annotations will be created and maintained, but discarded at the end. | |
5712 | ||
5713 | @item -fvar-tracking-assignments-toggle | |
5714 | @opindex fvar-tracking-assignments-toggle | |
5715 | @opindex fno-var-tracking-assignments-toggle | |
5716 | Toggle @option{-fvar-tracking-assignments}, in the same way that | |
5717 | @option{-gtoggle} toggles @option{-g}. | |
5718 | ||
74291a4b | 5719 | @item -print-file-name=@var{library} |
cd3bb277 | 5720 | @opindex print-file-name |
74291a4b MM |
5721 | Print the full absolute name of the library file @var{library} that |
5722 | would be used when linking---and don't do anything else. With this | |
0c2d1a2a | 5723 | option, GCC does not compile or link anything; it just prints the |
74291a4b MM |
5724 | file name. |
5725 | ||
b1018de6 AO |
5726 | @item -print-multi-directory |
5727 | @opindex print-multi-directory | |
5728 | Print the directory name corresponding to the multilib selected by any | |
5729 | other switches present in the command line. This directory is supposed | |
5730 | to exist in @env{GCC_EXEC_PREFIX}. | |
5731 | ||
5732 | @item -print-multi-lib | |
5733 | @opindex print-multi-lib | |
5734 | Print the mapping from multilib directory names to compiler switches | |
5735 | that enable them. The directory name is separated from the switches by | |
5736 | @samp{;}, and each switch starts with an @samp{@@} instead of the | |
5737 | @samp{-}, without spaces between multiple switches. This is supposed to | |
5738 | ease shell-processing. | |
5739 | ||
de55f03a JJ |
5740 | @item -print-multi-os-directory |
5741 | @opindex print-multi-os-directory | |
5742 | Print the path to OS libraries for the selected | |
5743 | multilib, relative to some @file{lib} subdirectory. If OS libraries are | |
5744 | present in the @file{lib} subdirectory and no multilibs are used, this is | |
5745 | usually just @file{.}, if OS libraries are present in @file{lib@var{suffix}} | |
5746 | sibling directories this prints e.g.@: @file{../lib64}, @file{../lib} or | |
5747 | @file{../lib32}, or if OS libraries are present in @file{lib/@var{subdir}} | |
5748 | subdirectories it prints e.g.@: @file{amd64}, @file{sparcv9} or @file{ev6}. | |
5749 | ||
74291a4b | 5750 | @item -print-prog-name=@var{program} |
cd3bb277 | 5751 | @opindex print-prog-name |
630d3d5a | 5752 | Like @option{-print-file-name}, but searches for a program such as @samp{cpp}. |
74291a4b MM |
5753 | |
5754 | @item -print-libgcc-file-name | |
cd3bb277 | 5755 | @opindex print-libgcc-file-name |
630d3d5a | 5756 | Same as @option{-print-file-name=libgcc.a}. |
74291a4b | 5757 | |
630d3d5a | 5758 | This is useful when you use @option{-nostdlib} or @option{-nodefaultlibs} |
74291a4b MM |
5759 | but you do want to link with @file{libgcc.a}. You can do |
5760 | ||
3ab51846 | 5761 | @smallexample |
74291a4b | 5762 | gcc -nostdlib @var{files}@dots{} `gcc -print-libgcc-file-name` |
3ab51846 | 5763 | @end smallexample |
74291a4b MM |
5764 | |
5765 | @item -print-search-dirs | |
cd3bb277 | 5766 | @opindex print-search-dirs |
74291a4b | 5767 | Print the name of the configured installation directory and a list of |
2dd76960 | 5768 | program and library directories @command{gcc} will search---and don't do anything else. |
74291a4b | 5769 | |
2dd76960 | 5770 | This is useful when @command{gcc} prints the error message |
3c0b7970 JM |
5771 | @samp{installation problem, cannot exec cpp0: No such file or directory}. |
5772 | To resolve this you either need to put @file{cpp0} and the other compiler | |
2dd76960 | 5773 | components where @command{gcc} expects to find them, or you can set the environment |
bedc7537 | 5774 | variable @env{GCC_EXEC_PREFIX} to the directory where you installed them. |
78466c0e | 5775 | Don't forget the trailing @samp{/}. |
74291a4b | 5776 | @xref{Environment Variables}. |
1f0c3120 | 5777 | |
3def1397 VP |
5778 | @item -print-sysroot |
5779 | @opindex print-sysroot | |
5780 | Print the target sysroot directory that will be used during | |
5781 | compilation. This is the target sysroot specified either at configure | |
d1facce0 | 5782 | time or using the @option{--sysroot} option, possibly with an extra |
3def1397 VP |
5783 | suffix that depends on compilation options. If no target sysroot is |
5784 | specified, the option prints nothing. | |
5785 | ||
14da6073 JM |
5786 | @item -print-sysroot-headers-suffix |
5787 | @opindex print-sysroot-headers-suffix | |
5788 | Print the suffix added to the target sysroot when searching for | |
5789 | headers, or give an error if the compiler is not configured with such | |
5790 | a suffix---and don't do anything else. | |
5791 | ||
1f0c3120 | 5792 | @item -dumpmachine |
cd3bb277 | 5793 | @opindex dumpmachine |
1f0c3120 JM |
5794 | Print the compiler's target machine (for example, |
5795 | @samp{i686-pc-linux-gnu})---and don't do anything else. | |
5796 | ||
5797 | @item -dumpversion | |
cd3bb277 | 5798 | @opindex dumpversion |
1f0c3120 JM |
5799 | Print the compiler version (for example, @samp{3.0})---and don't do |
5800 | anything else. | |
5801 | ||
5802 | @item -dumpspecs | |
cd3bb277 | 5803 | @opindex dumpspecs |
1f0c3120 JM |
5804 | Print the compiler's built-in specs---and don't do anything else. (This |
5805 | is used when GCC itself is being built.) @xref{Spec Files}. | |
73c68f61 SS |
5806 | |
5807 | @item -feliminate-unused-debug-types | |
5808 | @opindex feliminate-unused-debug-types | |
5809 | Normally, when producing DWARF2 output, GCC will emit debugging | |
5810 | information for all types declared in a compilation | |
5811 | unit, regardless of whether or not they are actually used | |
5812 | in that compilation unit. Sometimes this is useful, such as | |
5813 | if, in the debugger, you want to cast a value to a type that is | |
5814 | not actually used in your program (but is declared). More often, | |
5815 | however, this results in a significant amount of wasted space. | |
5816 | With this option, GCC will avoid producing debug symbol output | |
5817 | for types that are nowhere used in the source file being compiled. | |
74291a4b MM |
5818 | @end table |
5819 | ||
5820 | @node Optimize Options | |
5821 | @section Options That Control Optimization | |
5822 | @cindex optimize options | |
5823 | @cindex options, optimization | |
5824 | ||
147d1cd3 JQ |
5825 | These options control various sorts of optimizations. |
5826 | ||
5827 | Without any optimization option, the compiler's goal is to reduce the | |
5828 | cost of compilation and to make debugging produce the expected | |
5829 | results. Statements are independent: if you stop the program with a | |
5830 | breakpoint between statements, you can then assign a new value to any | |
5831 | variable or change the program counter to any other statement in the | |
5832 | function and get exactly the results you would expect from the source | |
5833 | code. | |
5834 | ||
5835 | Turning on optimization flags makes the compiler attempt to improve | |
5836 | the performance and/or code size at the expense of compilation time | |
5837 | and possibly the ability to debug the program. | |
5838 | ||
d6cc6ec9 JH |
5839 | The compiler performs optimization based on the knowledge it has of the |
5840 | program. Compiling multiple files at once to a single output file mode allows | |
5841 | the compiler to use information gained from all of the files when compiling | |
5842 | each of them. | |
d1bd0ded | 5843 | |
147d1cd3 | 5844 | Not all optimizations are controlled directly by a flag. Only |
8c70d28b SL |
5845 | optimizations that have a flag are listed in this section. |
5846 | ||
711a778c GP |
5847 | Most optimizations are only enabled if an @option{-O} level is set on |
5848 | the command line. Otherwise they are disabled, even if individual | |
5849 | optimization flags are specified. | |
83bb5ce3 | 5850 | |
7a61cf6f NC |
5851 | Depending on the target and how GCC was configured, a slightly different |
5852 | set of optimizations may be enabled at each @option{-O} level than | |
5853 | those listed here. You can invoke GCC with @samp{-Q --help=optimizers} | |
8c70d28b SL |
5854 | to find out the exact set of optimizations that are enabled at each level. |
5855 | @xref{Overall Options}, for examples. | |
74291a4b | 5856 | |
2642624b | 5857 | @table @gcctabopt |
74291a4b MM |
5858 | @item -O |
5859 | @itemx -O1 | |
cd3bb277 JM |
5860 | @opindex O |
5861 | @opindex O1 | |
74291a4b MM |
5862 | Optimize. Optimizing compilation takes somewhat more time, and a lot |
5863 | more memory for a large function. | |
5864 | ||
630d3d5a | 5865 | With @option{-O}, the compiler tries to reduce code size and execution |
9c34dbbf ZW |
5866 | time, without performing any optimizations that take a great deal of |
5867 | compilation time. | |
74291a4b | 5868 | |
daf2f129 | 5869 | @option{-O} turns on the following optimization flags: |
71733172 KZ |
5870 | @gccoptlist{ |
5871 | -fauto-inc-dec @gol | |
08711fdf | 5872 | -fcprop-registers @gol |
0c166d0f | 5873 | -fdce @gol |
71733172 KZ |
5874 | -fdefer-pop @gol |
5875 | -fdelayed-branch @gol | |
0c166d0f | 5876 | -fdse @gol |
71733172 | 5877 | -fguess-branch-probability @gol |
9a94f7f3 | 5878 | -fif-conversion2 @gol |
71733172 | 5879 | -fif-conversion @gol |
71733172 | 5880 | -fipa-pure-const @gol |
e65bb9be | 5881 | -fipa-profile @gol |
71733172 KZ |
5882 | -fipa-reference @gol |
5883 | -fmerge-constants | |
e53a16e7 | 5884 | -fsplit-wide-types @gol |
0b4b14ac | 5885 | -ftree-bit-ccp @gol |
c2699190 | 5886 | -ftree-builtin-call-dce @gol |
08711fdf | 5887 | -ftree-ccp @gol |
71733172 KZ |
5888 | -ftree-ch @gol |
5889 | -ftree-copyrename @gol | |
08711fdf | 5890 | -ftree-dce @gol |
ec7dea0a | 5891 | -ftree-dominator-opts @gol |
08711fdf | 5892 | -ftree-dse @gol |
248fc9f3 | 5893 | -ftree-forwprop @gol |
08711fdf | 5894 | -ftree-fre @gol |
248fc9f3 | 5895 | -ftree-phiprop @gol |
71733172 | 5896 | -ftree-sra @gol |
248fc9f3 | 5897 | -ftree-pta @gol |
71733172 KZ |
5898 | -ftree-ter @gol |
5899 | -funit-at-a-time} | |
fad893da JQ |
5900 | |
5901 | @option{-O} also turns on @option{-fomit-frame-pointer} on machines | |
5902 | where doing so does not interfere with debugging. | |
5903 | ||
74291a4b | 5904 | @item -O2 |
cd3bb277 | 5905 | @opindex O2 |
0c2d1a2a | 5906 | Optimize even more. GCC performs nearly all supported optimizations |
28c11eb3 | 5907 | that do not involve a space-speed tradeoff. |
630d3d5a | 5908 | As compared to @option{-O}, this option increases both compilation time |
74291a4b MM |
5909 | and the performance of the generated code. |
5910 | ||
fad893da JQ |
5911 | @option{-O2} turns on all optimization flags specified by @option{-O}. It |
5912 | also turns on the following optimization flags: | |
08711fdf | 5913 | @gccoptlist{-fthread-jumps @gol |
71733172 KZ |
5914 | -falign-functions -falign-jumps @gol |
5915 | -falign-loops -falign-labels @gol | |
5916 | -fcaller-saves @gol | |
08711fdf | 5917 | -fcrossjumping @gol |
9a94f7f3 | 5918 | -fcse-follow-jumps -fcse-skip-blocks @gol |
71733172 | 5919 | -fdelete-null-pointer-checks @gol |
9a94f7f3 | 5920 | -fexpensive-optimizations @gol |
71733172 | 5921 | -fgcse -fgcse-lm @gol |
95da10ea | 5922 | -finline-small-functions @gol |
3e293154 | 5923 | -findirect-inlining @gol |
07ffa034 | 5924 | -fipa-sra @gol |
71733172 | 5925 | -foptimize-sibling-calls @gol |
3e485f62 | 5926 | -fpartial-inlining @gol |
9a94f7f3 | 5927 | -fpeephole2 @gol |
08711fdf | 5928 | -fregmove @gol |
08711fdf | 5929 | -freorder-blocks -freorder-functions @gol |
71733172 KZ |
5930 | -frerun-cse-after-loop @gol |
5931 | -fsched-interblock -fsched-spec @gol | |
5932 | -fschedule-insns -fschedule-insns2 @gol | |
5933 | -fstrict-aliasing -fstrict-overflow @gol | |
b6e99746 | 5934 | -ftree-switch-conversion @gol |
71733172 KZ |
5935 | -ftree-pre @gol |
5936 | -ftree-vrp} | |
74291a4b | 5937 | |
081ca317 BL |
5938 | Please note the warning under @option{-fgcse} about |
5939 | invoking @option{-O2} on programs that use computed gotos. | |
5940 | ||
74291a4b | 5941 | @item -O3 |
cd3bb277 | 5942 | @opindex O3 |
3e293154 MJ |
5943 | Optimize yet more. @option{-O3} turns on all optimizations specified |
5944 | by @option{-O2} and also turns on the @option{-finline-functions}, | |
4e359692 | 5945 | @option{-funswitch-loops}, @option{-fpredictive-commoning}, |
da1cc2e4 MJ |
5946 | @option{-fgcse-after-reload}, @option{-ftree-vectorize} and |
5947 | @option{-fipa-cp-clone} options. | |
74291a4b MM |
5948 | |
5949 | @item -O0 | |
cd3bb277 | 5950 | @opindex O0 |
e0f7e748 GK |
5951 | Reduce compilation time and make debugging produce the expected |
5952 | results. This is the default. | |
74291a4b | 5953 | |
c6aded7c | 5954 | @item -Os |
cd3bb277 | 5955 | @opindex Os |
630d3d5a | 5956 | Optimize for size. @option{-Os} enables all @option{-O2} optimizations that |
c6aded7c AG |
5957 | do not typically increase code size. It also performs further |
5958 | optimizations designed to reduce code size. | |
5959 | ||
fad893da | 5960 | @option{-Os} disables the following optimization flags: |
9a94f7f3 | 5961 | @gccoptlist{-falign-functions -falign-jumps -falign-loops @gol |
c12cc930 KB |
5962 | -falign-labels -freorder-blocks -freorder-blocks-and-partition @gol |
5963 | -fprefetch-loop-arrays -ftree-vect-loop-version} | |
fad893da | 5964 | |
be6d3f0e RG |
5965 | @item -Ofast |
5966 | @opindex Ofast | |
5967 | Disregard strict standards compliance. @option{-Ofast} enables all | |
5968 | @option{-O3} optimizations. It also enables optimizations that are not | |
5969 | valid for all standard compliant programs. | |
5970 | It turns on @option{-ffast-math}. | |
5971 | ||
630d3d5a | 5972 | If you use multiple @option{-O} options, with or without level numbers, |
74291a4b MM |
5973 | the last such option is the one that is effective. |
5974 | @end table | |
5975 | ||
630d3d5a | 5976 | Options of the form @option{-f@var{flag}} specify machine-independent |
74291a4b | 5977 | flags. Most flags have both positive and negative forms; the negative |
147d1cd3 JQ |
5978 | form of @option{-ffoo} would be @option{-fno-foo}. In the table |
5979 | below, only one of the forms is listed---the one you typically will | |
5980 | use. You can figure out the other form by either removing @samp{no-} | |
5981 | or adding it. | |
5982 | ||
5983 | The following options control specific optimizations. They are either | |
5984 | activated by @option{-O} options or are related to ones that are. You | |
5985 | can use the following flags in the rare cases when ``fine-tuning'' of | |
5986 | optimizations to be performed is desired. | |
74291a4b | 5987 | |
2642624b | 5988 | @table @gcctabopt |
74291a4b | 5989 | @item -fno-default-inline |
cd3bb277 | 5990 | @opindex fno-default-inline |
74291a4b MM |
5991 | Do not make member functions inline by default merely because they are |
5992 | defined inside the class scope (C++ only). Otherwise, when you specify | |
630d3d5a | 5993 | @w{@option{-O}}, member functions defined inside class scope are compiled |
74291a4b MM |
5994 | inline by default; i.e., you don't need to add @samp{inline} in front of |
5995 | the member function name. | |
5996 | ||
5997 | @item -fno-defer-pop | |
cd3bb277 | 5998 | @opindex fno-defer-pop |
74291a4b MM |
5999 | Always pop the arguments to each function call as soon as that function |
6000 | returns. For machines which must pop arguments after a function call, | |
6001 | the compiler normally lets arguments accumulate on the stack for several | |
6002 | function calls and pops them all at once. | |
6003 | ||
38df970e JQ |
6004 | Disabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
6005 | ||
a52b023a PB |
6006 | @item -fforward-propagate |
6007 | @opindex fforward-propagate | |
0ee2ea09 | 6008 | Perform a forward propagation pass on RTL@. The pass tries to combine two |
a52b023a PB |
6009 | instructions and checks if the result can be simplified. If loop unrolling |
6010 | is active, two passes are performed and the second is scheduled after | |
6011 | loop unrolling. | |
6012 | ||
00952e97 PB |
6013 | This option is enabled by default at optimization levels @option{-O}, |
6014 | @option{-O2}, @option{-O3}, @option{-Os}. | |
a52b023a | 6015 | |
16949072 RG |
6016 | @item -ffp-contract=@var{style} |
6017 | @opindex ffp-contract | |
6018 | @option{-ffp-contract=off} disables floating-point expression contraction. | |
6019 | @option{-ffp-contract=fast} enables floating-point expression contraction | |
6020 | such as forming of fused multiply-add operations if the target has | |
6021 | native support for them. | |
6022 | @option{-ffp-contract=on} enables floating-point expression contraction | |
6023 | if allowed by the language standard. This is currently not implemented | |
6024 | and treated equal to @option{-ffp-contract=off}. | |
6025 | ||
6026 | The default is @option{-ffp-contract=fast}. | |
6027 | ||
74291a4b | 6028 | @item -fomit-frame-pointer |
cd3bb277 | 6029 | @opindex fomit-frame-pointer |
74291a4b MM |
6030 | Don't keep the frame pointer in a register for functions that |
6031 | don't need one. This avoids the instructions to save, set up and | |
6032 | restore frame pointers; it also makes an extra register available | |
6033 | in many functions. @strong{It also makes debugging impossible on | |
6034 | some machines.} | |
6035 | ||
8aeea6e6 | 6036 | On some machines, such as the VAX, this flag has no effect, because |
74291a4b MM |
6037 | the standard calling sequence automatically handles the frame pointer |
6038 | and nothing is saved by pretending it doesn't exist. The | |
6039 | machine-description macro @code{FRAME_POINTER_REQUIRED} controls | |
6040 | whether a target machine supports this flag. @xref{Registers,,Register | |
b11cc610 | 6041 | Usage, gccint, GNU Compiler Collection (GCC) Internals}. |
74291a4b | 6042 | |
ef7e0035 UB |
6043 | Starting with GCC version 4.6, the default setting (when not optimizing for |
6044 | size) for 32-bit Linux x86 and 32-bit Darwin x86 targets has been changed to | |
6045 | @option{-fomit-frame-pointer}. The default can be reverted to | |
6046 | @option{-fno-omit-frame-pointer} by configuring GCC with the | |
6047 | @option{--enable-frame-pointer} configure option. | |
6048 | ||
38df970e JQ |
6049 | Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
6050 | ||
1aaef9c1 | 6051 | @item -foptimize-sibling-calls |
cd3bb277 | 6052 | @opindex foptimize-sibling-calls |
1aaef9c1 JH |
6053 | Optimize sibling and tail recursive calls. |
6054 | ||
38df970e JQ |
6055 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
6056 | ||
74291a4b | 6057 | @item -fno-inline |
cd3bb277 | 6058 | @opindex fno-inline |
74291a4b MM |
6059 | Don't pay attention to the @code{inline} keyword. Normally this option |
6060 | is used to keep the compiler from expanding any functions inline. | |
6061 | Note that if you are not optimizing, no functions can be expanded inline. | |
6062 | ||
4d4b8cb9 JH |
6063 | @item -finline-small-functions |
6064 | @opindex finline-small-functions | |
6065 | Integrate functions into their callers when their body is smaller than expected | |
6066 | function call code (so overall size of program gets smaller). The compiler | |
6067 | heuristically decides which functions are simple enough to be worth integrating | |
6068 | in this way. | |
6069 | ||
6070 | Enabled at level @option{-O2}. | |
6071 | ||
3e293154 MJ |
6072 | @item -findirect-inlining |
6073 | @opindex findirect-inlining | |
6074 | Inline also indirect calls that are discovered to be known at compile | |
6075 | time thanks to previous inlining. This option has any effect only | |
6076 | when inlining itself is turned on by the @option{-finline-functions} | |
6077 | or @option{-finline-small-functions} options. | |
6078 | ||
6079 | Enabled at level @option{-O2}. | |
6080 | ||
74291a4b | 6081 | @item -finline-functions |
cd3bb277 | 6082 | @opindex finline-functions |
74291a4b MM |
6083 | Integrate all simple functions into their callers. The compiler |
6084 | heuristically decides which functions are simple enough to be worth | |
6085 | integrating in this way. | |
6086 | ||
6087 | If all calls to a given function are integrated, and the function is | |
6088 | declared @code{static}, then the function is normally not output as | |
6089 | assembler code in its own right. | |
6090 | ||
38df970e | 6091 | Enabled at level @option{-O3}. |
355866de RG |
6092 | |
6093 | @item -finline-functions-called-once | |
6094 | @opindex finline-functions-called-once | |
6095 | Consider all @code{static} functions called once for inlining into their | |
6096 | caller even if they are not marked @code{inline}. If a call to a given | |
6097 | function is integrated, then the function is not output as assembler code | |
6098 | in its own right. | |
6099 | ||
d6cc6ec9 | 6100 | Enabled at levels @option{-O1}, @option{-O2}, @option{-O3} and @option{-Os}. |
38df970e | 6101 | |
d63db217 JH |
6102 | @item -fearly-inlining |
6103 | @opindex fearly-inlining | |
6104 | Inline functions marked by @code{always_inline} and functions whose body seems | |
6105 | smaller than the function call overhead early before doing | |
6106 | @option{-fprofile-generate} instrumentation and real inlining pass. Doing so | |
6107 | makes profiling significantly cheaper and usually inlining faster on programs | |
6108 | having large chains of nested wrapper functions. | |
6109 | ||
6110 | Enabled by default. | |
6111 | ||
07ffa034 MJ |
6112 | @item -fipa-sra |
6113 | @opindex fipa-sra | |
6114 | Perform interprocedural scalar replacement of aggregates, removal of | |
6115 | unused parameters and replacement of parameters passed by reference | |
6116 | by parameters passed by value. | |
6117 | ||
6118 | Enabled at levels @option{-O2}, @option{-O3} and @option{-Os}. | |
6119 | ||
efa3896a | 6120 | @item -finline-limit=@var{n} |
cd3bb277 | 6121 | @opindex finline-limit |
2dd76960 | 6122 | By default, GCC limits the size of functions that can be inlined. This flag |
7c9c2f2a RG |
6123 | allows coarse control of this limit. @var{n} is the size of functions that |
6124 | can be inlined in number of pseudo instructions. | |
f9e814f1 | 6125 | |
bc522472 KG |
6126 | Inlining is actually controlled by a number of parameters, which may be |
6127 | specified individually by using @option{--param @var{name}=@var{value}}. | |
daf2f129 | 6128 | The @option{-finline-limit=@var{n}} option sets some of these parameters |
bc522472 KG |
6129 | as follows: |
6130 | ||
6131 | @table @gcctabopt | |
dc5abe77 | 6132 | @item max-inline-insns-single |
6ccde948 | 6133 | is set to @var{n}/2. |
dc5abe77 | 6134 | @item max-inline-insns-auto |
6ccde948 | 6135 | is set to @var{n}/2. |
bc522472 KG |
6136 | @end table |
6137 | ||
f7a01847 | 6138 | See below for a documentation of the individual |
7c9c2f2a RG |
6139 | parameters controlling inlining and for the defaults of these parameters. |
6140 | ||
6141 | @emph{Note:} there may be no value to @option{-finline-limit} that results | |
6142 | in default behavior. | |
bc522472 | 6143 | |
f9e814f1 | 6144 | @emph{Note:} pseudo instruction represents, in this particular context, an |
0fa2e4df | 6145 | abstract measurement of function's size. In no way does it represent a count |
f9e814f1 TP |
6146 | of assembly instructions and as such its exact meaning might change from one |
6147 | release to an another. | |
6148 | ||
74291a4b | 6149 | @item -fkeep-inline-functions |
cd3bb277 | 6150 | @opindex fkeep-inline-functions |
1a10290c MM |
6151 | In C, emit @code{static} functions that are declared @code{inline} |
6152 | into the object file, even if the function has been inlined into all | |
6153 | of its callers. This switch does not affect functions using the | |
7e1542b9 | 6154 | @code{extern inline} extension in GNU C90@. In C++, emit any and all |
1a10290c | 6155 | inline functions into the object file. |
74291a4b MM |
6156 | |
6157 | @item -fkeep-static-consts | |
cd3bb277 | 6158 | @opindex fkeep-static-consts |
74291a4b MM |
6159 | Emit variables declared @code{static const} when optimization isn't turned |
6160 | on, even if the variables aren't referenced. | |
6161 | ||
0c2d1a2a | 6162 | GCC enables this option by default. If you want to force the compiler to |
74291a4b | 6163 | check if the variable was referenced, regardless of whether or not |
630d3d5a | 6164 | optimization is turned on, use the @option{-fno-keep-static-consts} option. |
74291a4b | 6165 | |
201556f0 | 6166 | @item -fmerge-constants |
7d95b692 | 6167 | @opindex fmerge-constants |
201556f0 | 6168 | Attempt to merge identical constants (string constants and floating point |
3364c33b | 6169 | constants) across compilation units. |
201556f0 | 6170 | |
3364c33b JQ |
6171 | This option is the default for optimized compilation if the assembler and |
6172 | linker support it. Use @option{-fno-merge-constants} to inhibit this | |
6173 | behavior. | |
201556f0 | 6174 | |
38df970e JQ |
6175 | Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
6176 | ||
201556f0 | 6177 | @item -fmerge-all-constants |
7d95b692 | 6178 | @opindex fmerge-all-constants |
201556f0 JJ |
6179 | Attempt to merge identical constants and identical variables. |
6180 | ||
6181 | This option implies @option{-fmerge-constants}. In addition to | |
431ae0bf | 6182 | @option{-fmerge-constants} this considers e.g.@: even constant initialized |
201556f0 | 6183 | arrays or initialized constant variables with integral or floating point |
403066cf SE |
6184 | types. Languages like C or C++ require each variable, including multiple |
6185 | instances of the same variable in recursive calls, to have distinct locations, | |
6186 | so using this option will result in non-conforming | |
c21cd8b1 | 6187 | behavior. |
201556f0 | 6188 | |
e5626198 AZ |
6189 | @item -fmodulo-sched |
6190 | @opindex fmodulo-sched | |
6191 | Perform swing modulo scheduling immediately before the first scheduling | |
6192 | pass. This pass looks at innermost loops and reorders their | |
6193 | instructions by overlapping different iterations. | |
6194 | ||
517d76fa VY |
6195 | @item -fmodulo-sched-allow-regmoves |
6196 | @opindex fmodulo-sched-allow-regmoves | |
6197 | Perform more aggressive SMS based modulo scheduling with register moves | |
6198 | allowed. By setting this flag certain anti-dependences edges will be | |
6199 | deleted which will trigger the generation of reg-moves based on the | |
12749440 RE |
6200 | life-range analysis. This option is effective only with |
6201 | @option{-fmodulo-sched} enabled. | |
517d76fa | 6202 | |
e03b7153 RS |
6203 | @item -fno-branch-count-reg |
6204 | @opindex fno-branch-count-reg | |
6205 | Do not use ``decrement and branch'' instructions on a count register, | |
6206 | but instead generate a sequence of instructions that decrement a | |
6207 | register, compare it against zero, then branch based upon the result. | |
6208 | This option is only meaningful on architectures that support such | |
6209 | instructions, which include x86, PowerPC, IA-64 and S/390. | |
6210 | ||
efa1cdf0 | 6211 | The default is @option{-fbranch-count-reg}. |
38df970e | 6212 | |
74291a4b | 6213 | @item -fno-function-cse |
cd3bb277 | 6214 | @opindex fno-function-cse |
74291a4b MM |
6215 | Do not put function addresses in registers; make each instruction that |
6216 | calls a constant function contain the function's address explicitly. | |
6217 | ||
6218 | This option results in less efficient code, but some strange hacks | |
6219 | that alter the assembler output may be confused by the optimizations | |
6220 | performed when this option is not used. | |
6221 | ||
38df970e JQ |
6222 | The default is @option{-ffunction-cse} |
6223 | ||
27b41650 KG |
6224 | @item -fno-zero-initialized-in-bss |
6225 | @opindex fno-zero-initialized-in-bss | |
6226 | If the target supports a BSS section, GCC by default puts variables that | |
6227 | are initialized to zero into BSS@. This can save space in the resulting | |
6228 | code. | |
6229 | ||
6230 | This option turns off this behavior because some programs explicitly | |
6231 | rely on variables going to the data section. E.g., so that the | |
6232 | resulting executable can find the beginning of that section and/or make | |
6233 | assumptions based on that. | |
6234 | ||
6235 | The default is @option{-fzero-initialized-in-bss}. | |
e03b7153 | 6236 | |
6de9cd9a DN |
6237 | @item -fmudflap -fmudflapth -fmudflapir |
6238 | @opindex fmudflap | |
6239 | @opindex fmudflapth | |
6240 | @opindex fmudflapir | |
6241 | @cindex bounds checking | |
6242 | @cindex mudflap | |
6243 | For front-ends that support it (C and C++), instrument all risky | |
6244 | pointer/array dereferencing operations, some standard library | |
6245 | string/heap functions, and some other associated constructs with | |
6246 | range/validity tests. Modules so instrumented should be immune to | |
6247 | buffer overflows, invalid heap use, and some other classes of C/C++ | |
6248 | programming errors. The instrumentation relies on a separate runtime | |
6249 | library (@file{libmudflap}), which will be linked into a program if | |
6250 | @option{-fmudflap} is given at link time. Run-time behavior of the | |
6251 | instrumented program is controlled by the @env{MUDFLAP_OPTIONS} | |
6252 | environment variable. See @code{env MUDFLAP_OPTIONS=-help a.out} | |
6253 | for its options. | |
6254 | ||
6255 | Use @option{-fmudflapth} instead of @option{-fmudflap} to compile and to | |
6256 | link if your program is multi-threaded. Use @option{-fmudflapir}, in | |
6257 | addition to @option{-fmudflap} or @option{-fmudflapth}, if | |
6258 | instrumentation should ignore pointer reads. This produces less | |
6259 | instrumentation (and therefore faster execution) and still provides | |
6260 | some protection against outright memory corrupting writes, but allows | |
6261 | erroneously read data to propagate within a program. | |
6262 | ||
74291a4b | 6263 | @item -fthread-jumps |
cd3bb277 | 6264 | @opindex fthread-jumps |
74291a4b MM |
6265 | Perform optimizations where we check to see if a jump branches to a |
6266 | location where another comparison subsumed by the first is found. If | |
6267 | so, the first branch is redirected to either the destination of the | |
6268 | second branch or a point immediately following it, depending on whether | |
6269 | the condition is known to be true or false. | |
6270 | ||
08711fdf | 6271 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
38df970e | 6272 | |
e53a16e7 | 6273 | @item -fsplit-wide-types |
edc5f63b | 6274 | @opindex fsplit-wide-types |
e53a16e7 ILT |
6275 | When using a type that occupies multiple registers, such as @code{long |
6276 | long} on a 32-bit system, split the registers apart and allocate them | |
6277 | independently. This normally generates better code for those types, | |
6278 | but may make debugging more difficult. | |
6279 | ||
6280 | Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, | |
6281 | @option{-Os}. | |
6282 | ||
74291a4b | 6283 | @item -fcse-follow-jumps |
cd3bb277 | 6284 | @opindex fcse-follow-jumps |
d6a64b9d | 6285 | In common subexpression elimination (CSE), scan through jump instructions |
74291a4b MM |
6286 | when the target of the jump is not reached by any other path. For |
6287 | example, when CSE encounters an @code{if} statement with an | |
6288 | @code{else} clause, CSE will follow the jump when the condition | |
6289 | tested is false. | |
6290 | ||
38df970e JQ |
6291 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
6292 | ||
74291a4b | 6293 | @item -fcse-skip-blocks |
cd3bb277 | 6294 | @opindex fcse-skip-blocks |
630d3d5a | 6295 | This is similar to @option{-fcse-follow-jumps}, but causes CSE to |
74291a4b MM |
6296 | follow jumps which conditionally skip over blocks. When CSE |
6297 | encounters a simple @code{if} statement with no else clause, | |
630d3d5a | 6298 | @option{-fcse-skip-blocks} causes CSE to follow the jump around the |
74291a4b MM |
6299 | body of the @code{if}. |
6300 | ||
38df970e JQ |
6301 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
6302 | ||
74291a4b | 6303 | @item -frerun-cse-after-loop |
cd3bb277 | 6304 | @opindex frerun-cse-after-loop |
74291a4b MM |
6305 | Re-run common subexpression elimination after loop optimizations has been |
6306 | performed. | |
6307 | ||
38df970e JQ |
6308 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
6309 | ||
7506f491 | 6310 | @item -fgcse |
cd3bb277 | 6311 | @opindex fgcse |
7506f491 DE |
6312 | Perform a global common subexpression elimination pass. |
6313 | This pass also performs global constant and copy propagation. | |
6314 | ||
081ca317 BL |
6315 | @emph{Note:} When compiling a program using computed gotos, a GCC |
6316 | extension, you may get better runtime performance if you disable | |
3364c33b | 6317 | the global common subexpression elimination pass by adding |
081ca317 BL |
6318 | @option{-fno-gcse} to the command line. |
6319 | ||
38df970e JQ |
6320 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
6321 | ||
a13d4ebf | 6322 | @item -fgcse-lm |
cd3bb277 | 6323 | @opindex fgcse-lm |
695ac33f | 6324 | When @option{-fgcse-lm} is enabled, global common subexpression elimination will |
767094dd | 6325 | attempt to move loads which are only killed by stores into themselves. This |
a13d4ebf | 6326 | allows a loop containing a load/store sequence to be changed to a load outside |
02f52e19 | 6327 | the loop, and a copy/store within the loop. |
a13d4ebf | 6328 | |
38df970e JQ |
6329 | Enabled by default when gcse is enabled. |
6330 | ||
a13d4ebf | 6331 | @item -fgcse-sm |
cd3bb277 | 6332 | @opindex fgcse-sm |
f5f2e3cd MH |
6333 | When @option{-fgcse-sm} is enabled, a store motion pass is run after |
6334 | global common subexpression elimination. This pass will attempt to move | |
6335 | stores out of loops. When used in conjunction with @option{-fgcse-lm}, | |
6336 | loops containing a load/store sequence can be changed to a load before | |
6337 | the loop and a store after the loop. | |
6338 | ||
08711fdf | 6339 | Not enabled at any optimization level. |
f5f2e3cd MH |
6340 | |
6341 | @item -fgcse-las | |
6342 | @opindex fgcse-las | |
6343 | When @option{-fgcse-las} is enabled, the global common subexpression | |
6344 | elimination pass eliminates redundant loads that come after stores to the | |
2206e783 | 6345 | same memory location (both partial and full redundancies). |
a13d4ebf | 6346 | |
08711fdf | 6347 | Not enabled at any optimization level. |
38df970e | 6348 | |
db643b91 SH |
6349 | @item -fgcse-after-reload |
6350 | @opindex fgcse-after-reload | |
6351 | When @option{-fgcse-after-reload} is enabled, a redundant load elimination | |
8a36672b | 6352 | pass is performed after reload. The purpose of this pass is to cleanup |
db643b91 SH |
6353 | redundant spilling. |
6354 | ||
f9cc1a70 PB |
6355 | @item -funsafe-loop-optimizations |
6356 | @opindex funsafe-loop-optimizations | |
6357 | If given, the loop optimizer will assume that loop indices do not | |
6358 | overflow, and that the loops with nontrivial exit condition are not | |
6359 | infinite. This enables a wider range of loop optimizations even if | |
6360 | the loop optimizer itself cannot prove that these assumptions are valid. | |
6361 | Using @option{-Wunsafe-loop-optimizations}, the compiler will warn you | |
6362 | if it finds this kind of loop. | |
6363 | ||
96327cdc | 6364 | @item -fcrossjumping |
7d95b692 | 6365 | @opindex fcrossjumping |
8a36672b | 6366 | Perform cross-jumping transformation. This transformation unifies equivalent code and save code size. The |
96327cdc JH |
6367 | resulting code may or may not perform better than without cross-jumping. |
6368 | ||
53071270 | 6369 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
38df970e | 6370 | |
71733172 KZ |
6371 | @item -fauto-inc-dec |
6372 | @opindex fauto-inc-dec | |
6373 | Combine increments or decrements of addresses with memory accesses. | |
6374 | This pass is always skipped on architectures that do not have | |
6375 | instructions to support this. Enabled by default at @option{-O} and | |
6376 | higher on architectures that support this. | |
6377 | ||
0c166d0f JJ |
6378 | @item -fdce |
6379 | @opindex fdce | |
0ee2ea09 | 6380 | Perform dead code elimination (DCE) on RTL@. |
0c166d0f JJ |
6381 | Enabled by default at @option{-O} and higher. |
6382 | ||
6383 | @item -fdse | |
6384 | @opindex fdse | |
0ee2ea09 | 6385 | Perform dead store elimination (DSE) on RTL@. |
0c166d0f JJ |
6386 | Enabled by default at @option{-O} and higher. |
6387 | ||
2c4b77f3 | 6388 | @item -fif-conversion |
7d95b692 | 6389 | @opindex fif-conversion |
2c4b77f3 JH |
6390 | Attempt to transform conditional jumps into branch-less equivalents. This |
6391 | include use of conditional moves, min, max, set flags and abs instructions, and | |
6392 | some tricks doable by standard arithmetics. The use of conditional execution | |
6393 | on chips where it is available is controlled by @code{if-conversion2}. | |
6394 | ||
38df970e JQ |
6395 | Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
6396 | ||
2c4b77f3 | 6397 | @item -fif-conversion2 |
7d95b692 | 6398 | @opindex fif-conversion2 |
2c4b77f3 JH |
6399 | Use conditional execution (where available) to transform conditional jumps into |
6400 | branch-less equivalents. | |
6401 | ||
38df970e JQ |
6402 | Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
6403 | ||
b6d24183 | 6404 | @item -fdelete-null-pointer-checks |
cd3bb277 | 6405 | @opindex fdelete-null-pointer-checks |
567a90f5 PB |
6406 | Assume that programs cannot safely dereference null pointers, and that |
6407 | no code or data element resides there. This enables simple constant | |
6408 | folding optimizations at all optimization levels. In addition, other | |
6409 | optimization passes in GCC use this flag to control global dataflow | |
6410 | analyses that eliminate useless checks for null pointers; these assume | |
6411 | that if a pointer is checked after it has already been dereferenced, | |
6412 | it cannot be null. | |
6413 | ||
6414 | Note however that in some environments this assumption is not true. | |
6415 | Use @option{-fno-delete-null-pointer-checks} to disable this optimization | |
9c34dbbf | 6416 | for programs which depend on that behavior. |
b6d24183 | 6417 | |
567a90f5 PB |
6418 | Some targets, especially embedded ones, disable this option at all levels. |
6419 | Otherwise it is enabled at all levels: @option{-O0}, @option{-O1}, | |
6420 | @option{-O2}, @option{-O3}, @option{-Os}. Passes that use the information | |
6421 | are enabled independently at different optimization levels. | |
38df970e | 6422 | |
74291a4b | 6423 | @item -fexpensive-optimizations |
cd3bb277 | 6424 | @opindex fexpensive-optimizations |
74291a4b MM |
6425 | Perform a number of minor optimizations that are relatively expensive. |
6426 | ||
38df970e JQ |
6427 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
6428 | ||
639726ba | 6429 | @item -foptimize-register-move |
59d40964 | 6430 | @itemx -fregmove |
cd3bb277 JM |
6431 | @opindex foptimize-register-move |
6432 | @opindex fregmove | |
9ec36da5 JL |
6433 | Attempt to reassign register numbers in move instructions and as |
6434 | operands of other simple instructions in order to maximize the amount of | |
56159047 | 6435 | register tying. This is especially helpful on machines with two-operand |
38df970e | 6436 | instructions. |
9ec36da5 | 6437 | |
bedc7537 | 6438 | Note @option{-fregmove} and @option{-foptimize-register-move} are the same |
9ec36da5 JL |
6439 | optimization. |
6440 | ||
38df970e JQ |
6441 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
6442 | ||
058e97ec | 6443 | @item -fira-algorithm=@var{algorithm} |
7db7ed3c VM |
6444 | Use specified coloring algorithm for the integrated register |
6445 | allocator. The @var{algorithm} argument should be @code{priority} or | |
6446 | @code{CB}. The first algorithm specifies Chow's priority coloring, | |
6447 | the second one specifies Chaitin-Briggs coloring. The second | |
6448 | algorithm can be unimplemented for some architectures. If it is | |
6449 | implemented, it is the default because Chaitin-Briggs coloring as a | |
6450 | rule generates a better code. | |
6451 | ||
6452 | @item -fira-region=@var{region} | |
6453 | Use specified regions for the integrated register allocator. The | |
6454 | @var{region} argument should be one of @code{all}, @code{mixed}, or | |
6455 | @code{one}. The first value means using all loops as register | |
6456 | allocation regions, the second value which is the default means using | |
6457 | all loops except for loops with small register pressure as the | |
6458 | regions, and third one means using all function as a single region. | |
6459 | The first value can give best result for machines with small size and | |
6460 | irregular register set, the third one results in faster and generates | |
6461 | decent code and the smallest size code, and the default value usually | |
6462 | give the best results in most cases and for most architectures. | |
058e97ec | 6463 | |
1833192f VM |
6464 | @item -fira-loop-pressure |
6465 | @opindex fira-loop-pressure | |
6466 | Use IRA to evaluate register pressure in loops for decision to move | |
6467 | loop invariants. Usage of this option usually results in generation | |
7e1e7d4c VM |
6468 | of faster and smaller code on machines with big register files (>= 32 |
6469 | registers) but it can slow compiler down. | |
1833192f | 6470 | |
7e1e7d4c | 6471 | This option is enabled at level @option{-O3} for some targets. |
1833192f | 6472 | |
058e97ec VM |
6473 | @item -fno-ira-share-save-slots |
6474 | @opindex fno-ira-share-save-slots | |
6475 | Switch off sharing stack slots used for saving call used hard | |
6476 | registers living through a call. Each hard register will get a | |
6477 | separate stack slot and as a result function stack frame will be | |
6478 | bigger. | |
6479 | ||
6480 | @item -fno-ira-share-spill-slots | |
6481 | @opindex fno-ira-share-spill-slots | |
6482 | Switch off sharing stack slots allocated for pseudo-registers. Each | |
6483 | pseudo-register which did not get a hard register will get a separate | |
6484 | stack slot and as a result function stack frame will be bigger. | |
6485 | ||
6486 | @item -fira-verbose=@var{n} | |
6487 | @opindex fira-verbose | |
6488 | Set up how verbose dump file for the integrated register allocator | |
6489 | will be. Default value is 5. If the value is greater or equal to 10, | |
6490 | the dump file will be stderr as if the value were @var{n} minus 10. | |
6491 | ||
74291a4b | 6492 | @item -fdelayed-branch |
cd3bb277 | 6493 | @opindex fdelayed-branch |
74291a4b MM |
6494 | If supported for the target machine, attempt to reorder instructions |
6495 | to exploit instruction slots available after delayed branch | |
6496 | instructions. | |
6497 | ||
38df970e JQ |
6498 | Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
6499 | ||
74291a4b | 6500 | @item -fschedule-insns |
cd3bb277 | 6501 | @opindex fschedule-insns |
74291a4b MM |
6502 | If supported for the target machine, attempt to reorder instructions to |
6503 | eliminate execution stalls due to required data being unavailable. This | |
6504 | helps machines that have slow floating point or memory load instructions | |
6505 | by allowing other instructions to be issued until the result of the load | |
6506 | or floating point instruction is required. | |
6507 | ||
4de29d8f | 6508 | Enabled at levels @option{-O2}, @option{-O3}. |
38df970e | 6509 | |
74291a4b | 6510 | @item -fschedule-insns2 |
cd3bb277 | 6511 | @opindex fschedule-insns2 |
630d3d5a | 6512 | Similar to @option{-fschedule-insns}, but requests an additional pass of |
74291a4b MM |
6513 | instruction scheduling after register allocation has been done. This is |
6514 | especially useful on machines with a relatively small number of | |
6515 | registers and where memory load instructions take more than one cycle. | |
6516 | ||
38df970e JQ |
6517 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
6518 | ||
e03b7153 RS |
6519 | @item -fno-sched-interblock |
6520 | @opindex fno-sched-interblock | |
6521 | Don't schedule instructions across basic blocks. This is normally | |
6522 | enabled by default when scheduling before register allocation, i.e.@: | |
6523 | with @option{-fschedule-insns} or at @option{-O2} or higher. | |
6524 | ||
6525 | @item -fno-sched-spec | |
6526 | @opindex fno-sched-spec | |
6527 | Don't allow speculative motion of non-load instructions. This is normally | |
6528 | enabled by default when scheduling before register allocation, i.e.@: | |
6529 | with @option{-fschedule-insns} or at @option{-O2} or higher. | |
6530 | ||
ce18efcb VM |
6531 | @item -fsched-pressure |
6532 | @opindex fsched-pressure | |
6533 | Enable register pressure sensitive insn scheduling before the register | |
6534 | allocation. This only makes sense when scheduling before register | |
6535 | allocation is enabled, i.e.@: with @option{-fschedule-insns} or at | |
6536 | @option{-O2} or higher. Usage of this option can improve the | |
6537 | generated code and decrease its size by preventing register pressure | |
6538 | increase above the number of available hard registers and as a | |
6539 | consequence register spills in the register allocation. | |
6540 | ||
e03b7153 RS |
6541 | @item -fsched-spec-load |
6542 | @opindex fsched-spec-load | |
6543 | Allow speculative motion of some load instructions. This only makes | |
6544 | sense when scheduling before register allocation, i.e.@: with | |
6545 | @option{-fschedule-insns} or at @option{-O2} or higher. | |
6546 | ||
6547 | @item -fsched-spec-load-dangerous | |
6548 | @opindex fsched-spec-load-dangerous | |
6549 | Allow speculative motion of more load instructions. This only makes | |
6550 | sense when scheduling before register allocation, i.e.@: with | |
6551 | @option{-fschedule-insns} or at @option{-O2} or higher. | |
6552 | ||
7d95b692 JJ |
6553 | @item -fsched-stalled-insns |
6554 | @itemx -fsched-stalled-insns=@var{n} | |
569fa502 DN |
6555 | @opindex fsched-stalled-insns |
6556 | Define how many insns (if any) can be moved prematurely from the queue | |
6557 | of stalled insns into the ready list, during the second scheduling pass. | |
b423089e JJ |
6558 | @option{-fno-sched-stalled-insns} means that no insns will be moved |
6559 | prematurely, @option{-fsched-stalled-insns=0} means there is no limit | |
6560 | on how many queued insns can be moved prematurely. | |
6561 | @option{-fsched-stalled-insns} without a value is equivalent to | |
6562 | @option{-fsched-stalled-insns=1}. | |
569fa502 | 6563 | |
7d95b692 JJ |
6564 | @item -fsched-stalled-insns-dep |
6565 | @itemx -fsched-stalled-insns-dep=@var{n} | |
569fa502 | 6566 | @opindex fsched-stalled-insns-dep |
daf2f129 JM |
6567 | Define how many insn groups (cycles) will be examined for a dependency |
6568 | on a stalled insn that is candidate for premature removal from the queue | |
7d95b692 | 6569 | of stalled insns. This has an effect only during the second scheduling pass, |
b423089e | 6570 | and only if @option{-fsched-stalled-insns} is used. |
7d95b692 JJ |
6571 | @option{-fno-sched-stalled-insns-dep} is equivalent to |
6572 | @option{-fsched-stalled-insns-dep=0}. | |
6573 | @option{-fsched-stalled-insns-dep} without a value is equivalent to | |
6574 | @option{-fsched-stalled-insns-dep=1}. | |
569fa502 | 6575 | |
b9422b69 JH |
6576 | @item -fsched2-use-superblocks |
6577 | @opindex fsched2-use-superblocks | |
61aeb06f | 6578 | When scheduling after register allocation, do use superblock scheduling |
62b9c42c | 6579 | algorithm. Superblock scheduling allows motion across basic block boundaries |
b9422b69 | 6580 | resulting on faster schedules. This option is experimental, as not all machine |
62b9c42c | 6581 | descriptions used by GCC model the CPU closely enough to avoid unreliable |
daf2f129 | 6582 | results from the algorithm. |
b9422b69 JH |
6583 | |
6584 | This only makes sense when scheduling after register allocation, i.e.@: with | |
6585 | @option{-fschedule-insns2} or at @option{-O2} or higher. | |
6586 | ||
ee4764a8 GS |
6587 | @item -fsched-group-heuristic |
6588 | @opindex fsched-group-heuristic | |
96809b41 GS |
6589 | Enable the group heuristic in the scheduler. This heuristic favors |
6590 | the instruction that belongs to a schedule group. This is enabled | |
6591 | by default when scheduling is enabled, i.e.@: with @option{-fschedule-insns} | |
ee4764a8 GS |
6592 | or @option{-fschedule-insns2} or at @option{-O2} or higher. |
6593 | ||
6594 | @item -fsched-critical-path-heuristic | |
6595 | @opindex fsched-critical-path-heuristic | |
96809b41 GS |
6596 | Enable the critical-path heuristic in the scheduler. This heuristic favors |
6597 | instructions on the critical path. This is enabled by default when | |
6598 | scheduling is enabled, i.e.@: with @option{-fschedule-insns} | |
ee4764a8 GS |
6599 | or @option{-fschedule-insns2} or at @option{-O2} or higher. |
6600 | ||
6601 | @item -fsched-spec-insn-heuristic | |
6602 | @opindex fsched-spec-insn-heuristic | |
96809b41 GS |
6603 | Enable the speculative instruction heuristic in the scheduler. This |
6604 | heuristic favors speculative instructions with greater dependency weakness. | |
6605 | This is enabled by default when scheduling is enabled, i.e.@: | |
6606 | with @option{-fschedule-insns} or @option{-fschedule-insns2} | |
6607 | or at @option{-O2} or higher. | |
ee4764a8 | 6608 | |
ee4764a8 GS |
6609 | @item -fsched-rank-heuristic |
6610 | @opindex fsched-rank-heuristic | |
96809b41 GS |
6611 | Enable the rank heuristic in the scheduler. This heuristic favors |
6612 | the instruction belonging to a basic block with greater size or frequency. | |
6613 | This is enabled by default when scheduling is enabled, i.e.@: | |
6614 | with @option{-fschedule-insns} or @option{-fschedule-insns2} or | |
6615 | at @option{-O2} or higher. | |
ee4764a8 GS |
6616 | |
6617 | @item -fsched-last-insn-heuristic | |
6618 | @opindex fsched-last-insn-heuristic | |
96809b41 GS |
6619 | Enable the last-instruction heuristic in the scheduler. This heuristic |
6620 | favors the instruction that is less dependent on the last instruction | |
6621 | scheduled. This is enabled by default when scheduling is enabled, | |
6622 | i.e.@: with @option{-fschedule-insns} or @option{-fschedule-insns2} or | |
6623 | at @option{-O2} or higher. | |
ee4764a8 GS |
6624 | |
6625 | @item -fsched-dep-count-heuristic | |
6626 | @opindex fsched-dep-count-heuristic | |
96809b41 GS |
6627 | Enable the dependent-count heuristic in the scheduler. This heuristic |
6628 | favors the instruction that has more instructions depending on it. | |
6629 | This is enabled by default when scheduling is enabled, i.e.@: | |
6630 | with @option{-fschedule-insns} or @option{-fschedule-insns2} or | |
6631 | at @option{-O2} or higher. | |
ee4764a8 | 6632 | |
d72372e4 | 6633 | @item -freschedule-modulo-scheduled-loops |
7d95b692 | 6634 | @opindex freschedule-modulo-scheduled-loops |
13c59415 UB |
6635 | The modulo scheduling comes before the traditional scheduling, if a loop |
6636 | was modulo scheduled we may want to prevent the later scheduling passes | |
6637 | from changing its schedule, we use this option to control that. | |
d72372e4 | 6638 | |
e855c69d AB |
6639 | @item -fselective-scheduling |
6640 | @opindex fselective-scheduling | |
6641 | Schedule instructions using selective scheduling algorithm. Selective | |
6642 | scheduling runs instead of the first scheduler pass. | |
6643 | ||
6644 | @item -fselective-scheduling2 | |
6645 | @opindex fselective-scheduling2 | |
6646 | Schedule instructions using selective scheduling algorithm. Selective | |
6647 | scheduling runs instead of the second scheduler pass. | |
6648 | ||
6649 | @item -fsel-sched-pipelining | |
6650 | @opindex fsel-sched-pipelining | |
7a61cf6f NC |
6651 | Enable software pipelining of innermost loops during selective scheduling. |
6652 | This option has no effect until one of @option{-fselective-scheduling} or | |
e855c69d AB |
6653 | @option{-fselective-scheduling2} is turned on. |
6654 | ||
6655 | @item -fsel-sched-pipelining-outer-loops | |
6656 | @opindex fsel-sched-pipelining-outer-loops | |
6657 | When pipelining loops during selective scheduling, also pipeline outer loops. | |
6658 | This option has no effect until @option{-fsel-sched-pipelining} is turned on. | |
6659 | ||
74291a4b | 6660 | @item -fcaller-saves |
cd3bb277 | 6661 | @opindex fcaller-saves |
74291a4b MM |
6662 | Enable values to be allocated in registers that will be clobbered by |
6663 | function calls, by emitting extra instructions to save and restore the | |
6664 | registers around such calls. Such allocation is done only when it | |
6665 | seems to result in better code than would otherwise be produced. | |
6666 | ||
81610a0d HPN |
6667 | This option is always enabled by default on certain machines, usually |
6668 | those which have no call-preserved registers to use instead. | |
6669 | ||
38df970e | 6670 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
74291a4b | 6671 | |
ccaeeafe NC |
6672 | @item -fcombine-stack-adjustments |
6673 | @opindex fcombine-stack-adjustments | |
6674 | Tracks stack adjustments (pushes and pops) and stack memory references | |
6675 | and then tries to find ways to combine them. | |
6676 | ||
6677 | Enabled by default at @option{-O1} and higher. | |
6678 | ||
6a78eaa3 JH |
6679 | @item -fconserve-stack |
6680 | @opindex fconserve-stack | |
6681 | Attempt to minimize stack usage. The compiler will attempt to use less | |
6682 | stack space, even if that makes the program slower. This option | |
6683 | implies setting the @option{large-stack-frame} parameter to 100 | |
6684 | and the @option{large-stack-frame-growth} parameter to 400. | |
6685 | ||
13c59415 | 6686 | @item -ftree-reassoc |
7d95b692 | 6687 | @opindex ftree-reassoc |
d6a64b9d | 6688 | Perform reassociation on trees. This flag is enabled by default |
13c59415 UB |
6689 | at @option{-O} and higher. |
6690 | ||
6de9cd9a | 6691 | @item -ftree-pre |
7d95b692 | 6692 | @opindex ftree-pre |
d6a64b9d | 6693 | Perform partial redundancy elimination (PRE) on trees. This flag is |
08711fdf | 6694 | enabled by default at @option{-O2} and @option{-O3}. |
ff2ad0f7 | 6695 | |
248fc9f3 RG |
6696 | @item -ftree-forwprop |
6697 | @opindex ftree-forwprop | |
6698 | Perform forward propagation on trees. This flag is enabled by default | |
6699 | at @option{-O} and higher. | |
6700 | ||
ff2ad0f7 | 6701 | @item -ftree-fre |
7d95b692 | 6702 | @opindex ftree-fre |
d6a64b9d | 6703 | Perform full redundancy elimination (FRE) on trees. The difference |
ff2ad0f7 DN |
6704 | between FRE and PRE is that FRE only considers expressions |
6705 | that are computed on all paths leading to the redundant computation. | |
06e2b6a0 | 6706 | This analysis is faster than PRE, though it exposes fewer redundancies. |
4ec7afd7 | 6707 | This flag is enabled by default at @option{-O} and higher. |
6de9cd9a | 6708 | |
248fc9f3 RG |
6709 | @item -ftree-phiprop |
6710 | @opindex ftree-phiprop | |
6711 | Perform hoisting of loads from conditional pointers on trees. This | |
6712 | pass is enabled by default at @option{-O} and higher. | |
6713 | ||
0bca51f0 | 6714 | @item -ftree-copy-prop |
7d95b692 | 6715 | @opindex ftree-copy-prop |
0bca51f0 DN |
6716 | Perform copy propagation on trees. This pass eliminates unnecessary |
6717 | copy operations. This flag is enabled by default at @option{-O} and | |
6718 | higher. | |
6719 | ||
71733172 KZ |
6720 | @item -fipa-pure-const |
6721 | @opindex fipa-pure-const | |
6722 | Discover which functions are pure or constant. | |
6723 | Enabled by default at @option{-O} and higher. | |
6724 | ||
6725 | @item -fipa-reference | |
6726 | @opindex fipa-reference | |
6727 | Discover which static variables do not escape cannot escape the | |
6728 | compilation unit. | |
6729 | Enabled by default at @option{-O} and higher. | |
6730 | ||
5bb06e18 GO |
6731 | @item -fipa-struct-reorg |
6732 | @opindex fipa-struct-reorg | |
7a61cf6f NC |
6733 | Perform structure reorganization optimization, that change C-like structures |
6734 | layout in order to better utilize spatial locality. This transformation is | |
6735 | affective for programs containing arrays of structures. Available in two | |
5bb06e18 | 6736 | compilation modes: profile-based (enabled with @option{-fprofile-generate}) |
6b87d1b4 | 6737 | or static (which uses built-in heuristics). It works only in whole program |
c3224d6f | 6738 | mode, so it requires @option{-fwhole-program} to be |
5bb06e18 GO |
6739 | enabled. Structures considered @samp{cold} by this transformation are not |
6740 | affected (see @option{--param struct-reorg-cold-struct-ratio=@var{value}}). | |
6741 | ||
6742 | With this flag, the program debug info reflects a new structure layout. | |
6743 | ||
4cf4d6a3 | 6744 | @item -fipa-pta |
7d95b692 | 6745 | @opindex fipa-pta |
25a6a873 RG |
6746 | Perform interprocedural pointer analysis and interprocedural modification |
6747 | and reference analysis. This option can cause excessive memory and | |
6748 | compile-time usage on large compilation units. It is not enabled by | |
6749 | default at any optimization level. | |
4cf4d6a3 | 6750 | |
e65bb9be JH |
6751 | @item -fipa-profile |
6752 | @opindex fipa-profile | |
6753 | Perform interprocedural profile propagation. The functions called only from | |
6754 | cold functions are marked as cold. Also functions executed once (such as | |
6755 | @code{cold}, @code{noreturn}, static constructors or destructors) are identified. Cold | |
6756 | functions and loop less parts of functions executed once are then optimized for | |
6757 | size. | |
6758 | Enabled by default at @option{-O} and higher. | |
6759 | ||
aa1a4968 RL |
6760 | @item -fipa-cp |
6761 | @opindex fipa-cp | |
6762 | Perform interprocedural constant propagation. | |
6763 | This optimization analyzes the program to determine when values passed | |
7a61cf6f | 6764 | to functions are constants and then optimizes accordingly. |
aa1a4968 | 6765 | This optimization can substantially increase performance |
5e45130d | 6766 | if the application has constants passed to functions. |
fcbe056b | 6767 | This flag is enabled by default at @option{-O2}, @option{-Os} and @option{-O3}. |
5e45130d JH |
6768 | |
6769 | @item -fipa-cp-clone | |
6770 | @opindex fipa-cp-clone | |
6771 | Perform function cloning to make interprocedural constant propagation stronger. | |
6772 | When enabled, interprocedural constant propagation will perform function cloning | |
6773 | when externally visible function can be called with constant arguments. | |
6774 | Because this optimization can create multiple copies of functions, | |
6775 | it may significantly increase code size | |
6776 | (see @option{--param ipcp-unit-growth=@var{value}}). | |
fcbe056b | 6777 | This flag is enabled by default at @option{-O3}. |
aa1a4968 RL |
6778 | |
6779 | @item -fipa-matrix-reorg | |
6780 | @opindex fipa-matrix-reorg | |
6781 | Perform matrix flattening and transposing. | |
e4ae5e77 RW |
6782 | Matrix flattening tries to replace an @math{m}-dimensional matrix |
6783 | with its equivalent @math{n}-dimensional matrix, where @math{n < m}. | |
aa1a4968 RL |
6784 | This reduces the level of indirection needed for accessing the elements |
6785 | of the matrix. The second optimization is matrix transposing that | |
048fd785 | 6786 | attempts to change the order of the matrix's dimensions in order to |
aa1a4968 | 6787 | improve cache locality. |
7a61cf6f | 6788 | Both optimizations need the @option{-fwhole-program} flag. |
1df48f5c | 6789 | Transposing is enabled only if profiling information is available. |
aa1a4968 | 6790 | |
fa555252 | 6791 | @item -ftree-sink |
7d95b692 | 6792 | @opindex ftree-sink |
fa555252 DB |
6793 | Perform forward store motion on trees. This flag is |
6794 | enabled by default at @option{-O} and higher. | |
6795 | ||
0b4b14ac RG |
6796 | @item -ftree-bit-ccp |
6797 | @opindex ftree-bit-ccp | |
6798 | Perform sparse conditional bit constant propagation on trees and propagate | |
6799 | pointer alignment information. | |
6800 | This pass only operates on local scalar variables and is enabled by default | |
6801 | at @option{-O} and higher. It requires that @option{-ftree-ccp} is enabled. | |
6802 | ||
6de9cd9a | 6803 | @item -ftree-ccp |
7d95b692 | 6804 | @opindex ftree-ccp |
0bca51f0 DN |
6805 | Perform sparse conditional constant propagation (CCP) on trees. This |
6806 | pass only operates on local scalar variables and is enabled by default | |
6807 | at @option{-O} and higher. | |
6808 | ||
b6e99746 MJ |
6809 | @item -ftree-switch-conversion |
6810 | Perform conversion of simple initializations in a switch to | |
6811 | initializations from a scalar array. This flag is enabled by default | |
6812 | at @option{-O2} and higher. | |
6813 | ||
6de9cd9a | 6814 | @item -ftree-dce |
7d95b692 | 6815 | @opindex ftree-dce |
6de9cd9a | 6816 | Perform dead code elimination (DCE) on trees. This flag is enabled by |
4ec7afd7 | 6817 | default at @option{-O} and higher. |
6de9cd9a | 6818 | |
c2699190 XDL |
6819 | @item -ftree-builtin-call-dce |
6820 | @opindex ftree-builtin-call-dce | |
7a61cf6f NC |
6821 | Perform conditional dead code elimination (DCE) for calls to builtin functions |
6822 | that may set @code{errno} but are otherwise side-effect free. This flag is | |
6823 | enabled by default at @option{-O2} and higher if @option{-Os} is not also | |
c2699190 XDL |
6824 | specified. |
6825 | ||
6de9cd9a | 6826 | @item -ftree-dominator-opts |
7d95b692 | 6827 | @opindex ftree-dominator-opts |
5c1c631e DN |
6828 | Perform a variety of simple scalar cleanups (constant/copy |
6829 | propagation, redundancy elimination, range propagation and expression | |
6830 | simplification) based on a dominator tree traversal. This also | |
6831 | performs jump threading (to reduce jumps to jumps). This flag is | |
6832 | enabled by default at @option{-O} and higher. | |
6de9cd9a | 6833 | |
e3d66ec3 RIL |
6834 | @item -ftree-dse |
6835 | @opindex ftree-dse | |
6836 | Perform dead store elimination (DSE) on trees. A dead store is a store into | |
6837 | a memory location which will later be overwritten by another store without | |
6838 | any intervening loads. In this case the earlier store can be deleted. This | |
6839 | flag is enabled by default at @option{-O} and higher. | |
6840 | ||
6de9cd9a | 6841 | @item -ftree-ch |
7d95b692 | 6842 | @opindex ftree-ch |
6de9cd9a | 6843 | Perform loop header copying on trees. This is beneficial since it increases |
83c99486 | 6844 | effectiveness of code motion optimizations. It also saves one jump. This flag |
4ec7afd7 KH |
6845 | is enabled by default at @option{-O} and higher. It is not enabled |
6846 | for @option{-Os}, since it usually increases code size. | |
6de9cd9a | 6847 | |
c66b6c66 | 6848 | @item -ftree-loop-optimize |
7d95b692 | 6849 | @opindex ftree-loop-optimize |
4ec7afd7 KH |
6850 | Perform loop optimizations on trees. This flag is enabled by default |
6851 | at @option{-O} and higher. | |
c66b6c66 | 6852 | |
599eabdb | 6853 | @item -ftree-loop-linear |
7d95b692 | 6854 | @opindex ftree-loop-linear |
8a36672b | 6855 | Perform linear loop transformations on tree. This flag can improve cache |
599eabdb DB |
6856 | performance and allow further loop optimizations to take place. |
6857 | ||
f8bf9252 | 6858 | @item -floop-interchange |
98af4c9f | 6859 | @opindex floop-interchange |
f8bf9252 SP |
6860 | Perform loop interchange transformations on loops. Interchanging two |
6861 | nested loops switches the inner and outer loops. For example, given a | |
6862 | loop like: | |
6863 | @smallexample | |
6864 | DO J = 1, M | |
6865 | DO I = 1, N | |
6866 | A(J, I) = A(J, I) * C | |
6867 | ENDDO | |
6868 | ENDDO | |
6869 | @end smallexample | |
6870 | loop interchange will transform the loop as if the user had written: | |
6871 | @smallexample | |
6872 | DO I = 1, N | |
6873 | DO J = 1, M | |
6874 | A(J, I) = A(J, I) * C | |
6875 | ENDDO | |
6876 | ENDDO | |
6877 | @end smallexample | |
6878 | which can be beneficial when @code{N} is larger than the caches, | |
6879 | because in Fortran, the elements of an array are stored in memory | |
6880 | contiguously by column, and the original loop iterates over rows, | |
6881 | potentially creating at each access a cache miss. This optimization | |
6882 | applies to all the languages supported by GCC and is not limited to | |
a9a7a9a2 SP |
6883 | Fortran. To use this code transformation, GCC has to be configured |
6884 | with @option{--with-ppl} and @option{--with-cloog} to enable the | |
6885 | Graphite loop transformation infrastructure. | |
f8bf9252 SP |
6886 | |
6887 | @item -floop-strip-mine | |
98af4c9f | 6888 | @opindex floop-strip-mine |
f8bf9252 | 6889 | Perform loop strip mining transformations on loops. Strip mining |
7a61cf6f NC |
6890 | splits a loop into two nested loops. The outer loop has strides |
6891 | equal to the strip size and the inner loop has strides of the | |
9d198913 SP |
6892 | original loop within a strip. The strip length can be changed |
6893 | using the @option{loop-block-tile-size} parameter. For example, | |
6894 | given a loop like: | |
f8bf9252 SP |
6895 | @smallexample |
6896 | DO I = 1, N | |
6897 | A(I) = A(I) + C | |
6898 | ENDDO | |
6899 | @end smallexample | |
6900 | loop strip mining will transform the loop as if the user had written: | |
6901 | @smallexample | |
9d198913 SP |
6902 | DO II = 1, N, 51 |
6903 | DO I = II, min (II + 50, N) | |
f8bf9252 SP |
6904 | A(I) = A(I) + C |
6905 | ENDDO | |
6906 | ENDDO | |
6907 | @end smallexample | |
6908 | This optimization applies to all the languages supported by GCC and is | |
a9a7a9a2 SP |
6909 | not limited to Fortran. To use this code transformation, GCC has to |
6910 | be configured with @option{--with-ppl} and @option{--with-cloog} to | |
6911 | enable the Graphite loop transformation infrastructure. | |
f8bf9252 SP |
6912 | |
6913 | @item -floop-block | |
98af4c9f | 6914 | @opindex floop-block |
f8bf9252 SP |
6915 | Perform loop blocking transformations on loops. Blocking strip mines |
6916 | each loop in the loop nest such that the memory accesses of the | |
9d198913 SP |
6917 | element loops fit inside caches. The strip length can be changed |
6918 | using the @option{loop-block-tile-size} parameter. For example, given | |
6919 | a loop like: | |
f8bf9252 SP |
6920 | @smallexample |
6921 | DO I = 1, N | |
6922 | DO J = 1, M | |
6923 | A(J, I) = B(I) + C(J) | |
6924 | ENDDO | |
6925 | ENDDO | |
6926 | @end smallexample | |
6927 | loop blocking will transform the loop as if the user had written: | |
6928 | @smallexample | |
9d198913 SP |
6929 | DO II = 1, N, 51 |
6930 | DO JJ = 1, M, 51 | |
6931 | DO I = II, min (II + 50, N) | |
6932 | DO J = JJ, min (JJ + 50, M) | |
f8bf9252 SP |
6933 | A(J, I) = B(I) + C(J) |
6934 | ENDDO | |
6935 | ENDDO | |
6936 | ENDDO | |
6937 | ENDDO | |
6938 | @end smallexample | |
6939 | which can be beneficial when @code{M} is larger than the caches, | |
6940 | because the innermost loop will iterate over a smaller amount of data | |
6941 | that can be kept in the caches. This optimization applies to all the | |
a9a7a9a2 SP |
6942 | languages supported by GCC and is not limited to Fortran. To use this |
6943 | code transformation, GCC has to be configured with @option{--with-ppl} | |
6944 | and @option{--with-cloog} to enable the Graphite loop transformation | |
6945 | infrastructure. | |
f8bf9252 | 6946 | |
66a7961b SP |
6947 | @item -fgraphite-identity |
6948 | @opindex fgraphite-identity | |
6949 | Enable the identity transformation for graphite. For every SCoP we generate | |
6950 | the polyhedral representation and transform it back to gimple. Using | |
6951 | @option{-fgraphite-identity} we can check the costs or benefits of the | |
6952 | GIMPLE -> GRAPHITE -> GIMPLE transformation. Some minimal optimizations | |
6953 | are also performed by the code generator CLooG, like index splitting and | |
6954 | dead code elimination in loops. | |
6955 | ||
98af4c9f SP |
6956 | @item -floop-flatten |
6957 | @opindex floop-flatten | |
6958 | Removes the loop nesting structure: transforms the loop nest into a | |
6959 | single loop. This transformation can be useful to vectorize all the | |
6960 | levels of the loop nest. | |
6961 | ||
3cf0e270 | 6962 | @item -floop-parallelize-all |
98af4c9f | 6963 | @opindex floop-parallelize-all |
109e0d57 SP |
6964 | Use the Graphite data dependence analysis to identify loops that can |
6965 | be parallelized. Parallelize all the loops that can be analyzed to | |
6966 | not contain loop carried dependences without checking that it is | |
6967 | profitable to parallelize the loops. | |
6968 | ||
3d8864c0 | 6969 | @item -fcheck-data-deps |
7d95b692 | 6970 | @opindex fcheck-data-deps |
3d8864c0 SP |
6971 | Compare the results of several data dependence analyzers. This option |
6972 | is used for debugging the data dependence analyzers. | |
6973 | ||
384a5197 SP |
6974 | @item -ftree-loop-if-convert |
6975 | Attempt to transform conditional jumps in the innermost loops to | |
6976 | branch-less equivalents. The intent is to remove control-flow from | |
6977 | the innermost loops in order to improve the ability of the | |
6978 | vectorization pass to handle these loops. This is enabled by default | |
6979 | if vectorization is enabled. | |
6980 | ||
bd544141 SP |
6981 | @item -ftree-loop-if-convert-stores |
6982 | Attempt to also if-convert conditional jumps containing memory writes. | |
6983 | This transformation can be unsafe for multi-threaded programs as it | |
6984 | transforms conditional memory writes into unconditional memory writes. | |
6985 | For example, | |
6986 | @smallexample | |
6987 | for (i = 0; i < N; i++) | |
6988 | if (cond) | |
6989 | A[i] = expr; | |
6990 | @end smallexample | |
6991 | would be transformed to | |
6992 | @smallexample | |
6993 | for (i = 0; i < N; i++) | |
6994 | A[i] = cond ? expr : A[i]; | |
6995 | @end smallexample | |
6996 | potentially producing data races. | |
6997 | ||
dea61d92 SP |
6998 | @item -ftree-loop-distribution |
6999 | Perform loop distribution. This flag can improve cache performance on | |
7000 | big loop bodies and allow further loop optimizations, like | |
9886a872 SP |
7001 | parallelization or vectorization, to take place. For example, the loop |
7002 | @smallexample | |
7003 | DO I = 1, N | |
7004 | A(I) = B(I) + C | |
7005 | D(I) = E(I) * F | |
7006 | ENDDO | |
7007 | @end smallexample | |
7008 | is transformed to | |
7009 | @smallexample | |
7010 | DO I = 1, N | |
7011 | A(I) = B(I) + C | |
7012 | ENDDO | |
7013 | DO I = 1, N | |
7014 | D(I) = E(I) * F | |
7015 | ENDDO | |
7016 | @end smallexample | |
dea61d92 | 7017 | |
20769d5e SP |
7018 | @item -ftree-loop-distribute-patterns |
7019 | Perform loop distribution of patterns that can be code generated with | |
7020 | calls to a library. This flag is enabled by default at @option{-O3}. | |
7021 | ||
7022 | This pass distributes the initialization loops and generates a call to | |
7023 | memset zero. For example, the loop | |
7024 | @smallexample | |
7025 | DO I = 1, N | |
7026 | A(I) = 0 | |
7027 | B(I) = A(I) + I | |
7028 | ENDDO | |
7029 | @end smallexample | |
7030 | is transformed to | |
7031 | @smallexample | |
7032 | DO I = 1, N | |
7033 | A(I) = 0 | |
7034 | ENDDO | |
7035 | DO I = 1, N | |
7036 | B(I) = A(I) + I | |
7037 | ENDDO | |
7038 | @end smallexample | |
7039 | and the initialization loop is transformed into a call to memset zero. | |
7040 | ||
3450cbc4 | 7041 | @item -ftree-loop-im |
7d95b692 | 7042 | @opindex ftree-loop-im |
3450cbc4 | 7043 | Perform loop invariant motion on trees. This pass moves only invariants that |
ec7dea0a | 7044 | would be hard to handle at RTL level (function calls, operations that expand to |
a7e5372d ZD |
7045 | nontrivial sequences of insns). With @option{-funswitch-loops} it also moves |
7046 | operands of conditions that are invariant out of the loop, so that we can use | |
7047 | just trivial invariantness analysis in loop unswitching. The pass also includes | |
7048 | store motion. | |
7049 | ||
3450cbc4 | 7050 | @item -ftree-loop-ivcanon |
7d95b692 | 7051 | @opindex ftree-loop-ivcanon |
82b85a85 ZD |
7052 | Create a canonical counter for number of iterations in the loop for that |
7053 | determining number of iterations requires complicated analysis. Later | |
7054 | optimizations then may determine the number easily. Useful especially | |
7055 | in connection with unrolling. | |
7056 | ||
8b11a64c | 7057 | @item -fivopts |
7d95b692 | 7058 | @opindex fivopts |
8b11a64c ZD |
7059 | Perform induction variable optimizations (strength reduction, induction |
7060 | variable merging and induction variable elimination) on trees. | |
7061 | ||
5f40b3cb | 7062 | @item -ftree-parallelize-loops=n |
d228aace | 7063 | @opindex ftree-parallelize-loops |
5f40b3cb ZD |
7064 | Parallelize loops, i.e., split their iteration space to run in n threads. |
7065 | This is only possible for loops whose iterations are independent | |
7066 | and can be arbitrarily reordered. The optimization is only | |
7067 | profitable on multiprocessor machines, for loops that are CPU-intensive, | |
021efafc | 7068 | rather than constrained e.g.@: by memory bandwidth. This option |
01a550c2 SP |
7069 | implies @option{-pthread}, and thus is only supported on targets |
7070 | that have support for @option{-pthread}. | |
5f40b3cb | 7071 | |
248fc9f3 RG |
7072 | @item -ftree-pta |
7073 | @opindex ftree-pta | |
7074 | Perform function-local points-to analysis on trees. This flag is | |
7075 | enabled by default at @option{-O} and higher. | |
7076 | ||
6de9cd9a | 7077 | @item -ftree-sra |
7d95b692 | 7078 | @opindex ftree-sra |
6de9cd9a DN |
7079 | Perform scalar replacement of aggregates. This pass replaces structure |
7080 | references with scalars to prevent committing structures to memory too | |
4ec7afd7 | 7081 | early. This flag is enabled by default at @option{-O} and higher. |
6de9cd9a DN |
7082 | |
7083 | @item -ftree-copyrename | |
7d95b692 | 7084 | @opindex ftree-copyrename |
f26c1794 EC |
7085 | Perform copy renaming on trees. This pass attempts to rename compiler |
7086 | temporaries to other variables at copy locations, usually resulting in | |
7087 | variable names which more closely resemble the original variables. This flag | |
4ec7afd7 | 7088 | is enabled by default at @option{-O} and higher. |
6de9cd9a DN |
7089 | |
7090 | @item -ftree-ter | |
7d95b692 | 7091 | @opindex ftree-ter |
6de9cd9a | 7092 | Perform temporary expression replacement during the SSA->normal phase. Single |
f26c1794 EC |
7093 | use/single def temporaries are replaced at their use location with their |
7094 | defining expression. This results in non-GIMPLE code, but gives the expanders | |
6de9cd9a | 7095 | much more complex trees to work on resulting in better RTL generation. This is |
4ec7afd7 | 7096 | enabled by default at @option{-O} and higher. |
6de9cd9a | 7097 | |
79fe1b3b | 7098 | @item -ftree-vectorize |
7d95b692 | 7099 | @opindex ftree-vectorize |
4e359692 IR |
7100 | Perform loop vectorization on trees. This flag is enabled by default at |
7101 | @option{-O3}. | |
79fe1b3b | 7102 | |
ca0b0bf8 IR |
7103 | @item -ftree-slp-vectorize |
7104 | @opindex ftree-slp-vectorize | |
7105 | Perform basic block vectorization on trees. This flag is enabled by default at | |
7106 | @option{-O3} and when @option{-ftree-vectorize} is enabled. | |
7107 | ||
c12cc930 KB |
7108 | @item -ftree-vect-loop-version |
7109 | @opindex ftree-vect-loop-version | |
7110 | Perform loop versioning when doing loop vectorization on trees. When a loop | |
7111 | appears to be vectorizable except that data alignment or data dependence cannot | |
7112 | be determined at compile time then vectorized and non-vectorized versions of | |
7113 | the loop are generated along with runtime checks for alignment or dependence | |
7114 | to control which version is executed. This option is enabled by default | |
7115 | except at level @option{-Os} where it is disabled. | |
7116 | ||
792ed98b | 7117 | @item -fvect-cost-model |
7d95b692 | 7118 | @opindex fvect-cost-model |
792ed98b HJ |
7119 | Enable cost model for vectorization. |
7120 | ||
08873e96 | 7121 | @item -ftree-vrp |
7d95b692 | 7122 | @opindex ftree-vrp |
08873e96 DN |
7123 | Perform Value Range Propagation on trees. This is similar to the |
7124 | constant propagation pass, but instead of values, ranges of values are | |
7125 | propagated. This allows the optimizers to remove unnecessary range | |
7126 | checks like array bound checks and null pointer checks. This is | |
7127 | enabled by default at @option{-O2} and higher. Null pointer check | |
7128 | elimination is only done if @option{-fdelete-null-pointer-checks} is | |
7129 | enabled. | |
7130 | ||
6de9cd9a DN |
7131 | @item -ftracer |
7132 | @opindex ftracer | |
8a36672b | 7133 | Perform tail duplication to enlarge superblock size. This transformation |
6de9cd9a DN |
7134 | simplifies the control flow of the function allowing other optimizations to do |
7135 | better job. | |
7136 | ||
7137 | @item -funroll-loops | |
7138 | @opindex funroll-loops | |
7139 | Unroll loops whose number of iterations can be determined at compile | |
efa1cdf0 ZD |
7140 | time or upon entry to the loop. @option{-funroll-loops} implies |
7141 | @option{-frerun-cse-after-loop}. This option makes code larger, | |
7142 | and may or may not make it run faster. | |
6de9cd9a DN |
7143 | |
7144 | @item -funroll-all-loops | |
7145 | @opindex funroll-all-loops | |
7146 | Unroll all loops, even if their number of iterations is uncertain when | |
7147 | the loop is entered. This usually makes programs run more slowly. | |
7148 | @option{-funroll-all-loops} implies the same options as | |
7149 | @option{-funroll-loops}, | |
7150 | ||
113d659a | 7151 | @item -fsplit-ivs-in-unroller |
edc5f63b | 7152 | @opindex fsplit-ivs-in-unroller |
113d659a ZD |
7153 | Enables expressing of values of induction variables in later iterations |
7154 | of the unrolled loop using the value in the first iteration. This breaks | |
7869fe47 | 7155 | long dependency chains, thus improving efficiency of the scheduling passes. |
113d659a ZD |
7156 | |
7157 | Combination of @option{-fweb} and CSE is often sufficient to obtain the | |
8a36672b | 7158 | same effect. However in cases the loop body is more complicated than |
113d659a ZD |
7159 | a single basic block, this is not reliable. It also does not work at all |
7160 | on some of the architectures due to restrictions in the CSE pass. | |
7161 | ||
7162 | This optimization is enabled by default. | |
7163 | ||
f37a4f14 | 7164 | @item -fvariable-expansion-in-unroller |
edc5f63b | 7165 | @opindex fvariable-expansion-in-unroller |
f0eb93a8 | 7166 | With this option, the compiler will create multiple copies of some |
f37a4f14 RE |
7167 | local variables when unrolling a loop which can result in superior code. |
7168 | ||
3e485f62 JH |
7169 | @item -fpartial-inlining |
7170 | @opindex fpartial-inlining | |
7171 | Inline parts of functions. This option has any effect only | |
7172 | when inlining itself is turned on by the @option{-finline-functions} | |
7173 | or @option{-finline-small-functions} options. | |
7174 | ||
7175 | Enabled at level @option{-O2}. | |
7176 | ||
bbc8a8dc ZD |
7177 | @item -fpredictive-commoning |
7178 | @opindex fpredictive-commoning | |
7179 | Perform predictive commoning optimization, i.e., reusing computations | |
7180 | (especially memory loads and stores) performed in previous | |
7181 | iterations of loops. | |
7182 | ||
7183 | This option is enabled at level @option{-O3}. | |
7184 | ||
6de9cd9a DN |
7185 | @item -fprefetch-loop-arrays |
7186 | @opindex fprefetch-loop-arrays | |
7187 | If supported by the target machine, generate instructions to prefetch | |
7188 | memory to improve the performance of loops that access large arrays. | |
7189 | ||
efa1cdf0 | 7190 | This option may generate better or worse code; results are highly |
e5eb27e5 JL |
7191 | dependent on the structure of loops within the source code. |
7192 | ||
efa1cdf0 ZD |
7193 | Disabled at level @option{-Os}. |
7194 | ||
74291a4b | 7195 | @item -fno-peephole |
6cfc0341 | 7196 | @itemx -fno-peephole2 |
cd3bb277 | 7197 | @opindex fno-peephole |
6cfc0341 RH |
7198 | @opindex fno-peephole2 |
7199 | Disable any machine-specific peephole optimizations. The difference | |
630d3d5a | 7200 | between @option{-fno-peephole} and @option{-fno-peephole2} is in how they |
6cfc0341 RH |
7201 | are implemented in the compiler; some targets use one, some use the |
7202 | other, a few use both. | |
861bb6c1 | 7203 | |
38df970e JQ |
7204 | @option{-fpeephole} is enabled by default. |
7205 | @option{-fpeephole2} enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. | |
7206 | ||
454d0cc7 | 7207 | @item -fno-guess-branch-probability |
cd3bb277 | 7208 | @opindex fno-guess-branch-probability |
ddd8e3ca JW |
7209 | Do not guess branch probabilities using heuristics. |
7210 | ||
7211 | GCC will use heuristics to guess branch probabilities if they are | |
7212 | not provided by profiling feedback (@option{-fprofile-arcs}). These | |
7213 | heuristics are based on the control flow graph. If some branch probabilities | |
7214 | are specified by @samp{__builtin_expect}, then the heuristics will be | |
7215 | used to guess branch probabilities for the rest of the control flow graph, | |
7216 | taking the @samp{__builtin_expect} info into account. The interactions | |
7217 | between the heuristics and @samp{__builtin_expect} can be complex, and in | |
7218 | some cases, it may be useful to disable the heuristics so that the effects | |
7219 | of @samp{__builtin_expect} are easier to understand. | |
454d0cc7 | 7220 | |
38df970e JQ |
7221 | The default is @option{-fguess-branch-probability} at levels |
7222 | @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. | |
7223 | ||
194734e9 JH |
7224 | @item -freorder-blocks |
7225 | @opindex freorder-blocks | |
7226 | Reorder basic blocks in the compiled function in order to reduce number of | |
7227 | taken branches and improve code locality. | |
7228 | ||
3f8b659d | 7229 | Enabled at levels @option{-O2}, @option{-O3}. |
38df970e | 7230 | |
750054a2 CT |
7231 | @item -freorder-blocks-and-partition |
7232 | @opindex freorder-blocks-and-partition | |
7233 | In addition to reordering basic blocks in the compiled function, in order | |
7234 | to reduce number of taken branches, partitions hot and cold basic blocks | |
7235 | into separate sections of the assembly and .o files, to improve | |
7236 | paging and cache locality performance. | |
7237 | ||
8e8d5162 CT |
7238 | This optimization is automatically turned off in the presence of |
7239 | exception handling, for linkonce sections, for functions with a user-defined | |
7240 | section attribute and on any architecture that does not support named | |
7241 | sections. | |
7242 | ||
194734e9 JH |
7243 | @item -freorder-functions |
7244 | @opindex freorder-functions | |
3e8cb558 JM |
7245 | Reorder functions in the object file in order to |
7246 | improve code locality. This is implemented by using special | |
3a4bdd05 RH |
7247 | subsections @code{.text.hot} for most frequently executed functions and |
7248 | @code{.text.unlikely} for unlikely executed functions. Reordering is done by | |
194734e9 | 7249 | the linker so object file format must support named sections and linker must |
3364c33b | 7250 | place them in a reasonable way. |
194734e9 JH |
7251 | |
7252 | Also profile feedback must be available in to make this option effective. See | |
7253 | @option{-fprofile-arcs} for details. | |
7254 | ||
38df970e JQ |
7255 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
7256 | ||
41472af8 | 7257 | @item -fstrict-aliasing |
cd3bb277 | 7258 | @opindex fstrict-aliasing |
460ba396 | 7259 | Allow the compiler to assume the strictest aliasing rules applicable to |
41472af8 MM |
7260 | the language being compiled. For C (and C++), this activates |
7261 | optimizations based on the type of expressions. In particular, an | |
7262 | object of one type is assumed never to reside at the same address as an | |
7263 | object of a different type, unless the types are almost the same. For | |
7264 | example, an @code{unsigned int} can alias an @code{int}, but not a | |
7265 | @code{void*} or a @code{double}. A character type may alias any other | |
02f52e19 | 7266 | type. |
41472af8 | 7267 | |
917db97b | 7268 | @anchor{Type-punning}Pay special attention to code like this: |
3ab51846 | 7269 | @smallexample |
02f52e19 | 7270 | union a_union @{ |
41472af8 MM |
7271 | int i; |
7272 | double d; | |
7273 | @}; | |
7274 | ||
7275 | int f() @{ | |
460ba396 | 7276 | union a_union t; |
41472af8 MM |
7277 | t.d = 3.0; |
7278 | return t.i; | |
7279 | @} | |
3ab51846 | 7280 | @end smallexample |
41472af8 MM |
7281 | The practice of reading from a different union member than the one most |
7282 | recently written to (called ``type-punning'') is common. Even with | |
630d3d5a | 7283 | @option{-fstrict-aliasing}, type-punning is allowed, provided the memory |
41472af8 | 7284 | is accessed through the union type. So, the code above will work as |
917db97b HPN |
7285 | expected. @xref{Structures unions enumerations and bit-fields |
7286 | implementation}. However, this code might not: | |
3ab51846 | 7287 | @smallexample |
02f52e19 | 7288 | int f() @{ |
460ba396 | 7289 | union a_union t; |
41472af8 MM |
7290 | int* ip; |
7291 | t.d = 3.0; | |
7292 | ip = &t.i; | |
7293 | return *ip; | |
7294 | @} | |
3ab51846 | 7295 | @end smallexample |
41472af8 | 7296 | |
917db97b HPN |
7297 | Similarly, access by taking the address, casting the resulting pointer |
7298 | and dereferencing the result has undefined behavior, even if the cast | |
7299 | uses a union type, e.g.: | |
7300 | @smallexample | |
7301 | int f() @{ | |
7302 | double d = 3.0; | |
7303 | return ((union a_union *) &d)->i; | |
7304 | @} | |
7305 | @end smallexample | |
7306 | ||
7307 | The @option{-fstrict-aliasing} option is enabled at levels | |
7308 | @option{-O2}, @option{-O3}, @option{-Os}. | |
852b81bb | 7309 | |
eeef0e45 ILT |
7310 | @item -fstrict-overflow |
7311 | @opindex fstrict-overflow | |
7312 | Allow the compiler to assume strict signed overflow rules, depending | |
7313 | on the language being compiled. For C (and C++) this means that | |
7314 | overflow when doing arithmetic with signed numbers is undefined, which | |
7315 | means that the compiler may assume that it will not happen. This | |
7316 | permits various optimizations. For example, the compiler will assume | |
7317 | that an expression like @code{i + 10 > i} will always be true for | |
7318 | signed @code{i}. This assumption is only valid if signed overflow is | |
7319 | undefined, as the expression is false if @code{i + 10} overflows when | |
7320 | using twos complement arithmetic. When this option is in effect any | |
7321 | attempt to determine whether an operation on signed numbers will | |
7322 | overflow must be written carefully to not actually involve overflow. | |
7323 | ||
4c9db6e0 ILT |
7324 | This option also allows the compiler to assume strict pointer |
7325 | semantics: given a pointer to an object, if adding an offset to that | |
7326 | pointer does not produce a pointer to the same object, the addition is | |
7327 | undefined. This permits the compiler to conclude that @code{p + u > | |
7328 | p} is always true for a pointer @code{p} and unsigned integer | |
7329 | @code{u}. This assumption is only valid because pointer wraparound is | |
7330 | undefined, as the expression is false if @code{p + u} overflows using | |
7331 | twos complement arithmetic. | |
7332 | ||
eeef0e45 | 7333 | See also the @option{-fwrapv} option. Using @option{-fwrapv} means |
4c9db6e0 | 7334 | that integer signed overflow is fully defined: it wraps. When |
eeef0e45 | 7335 | @option{-fwrapv} is used, there is no difference between |
4c9db6e0 ILT |
7336 | @option{-fstrict-overflow} and @option{-fno-strict-overflow} for |
7337 | integers. With @option{-fwrapv} certain types of overflow are | |
7338 | permitted. For example, if the compiler gets an overflow when doing | |
7339 | arithmetic on constants, the overflowed value can still be used with | |
eeef0e45 ILT |
7340 | @option{-fwrapv}, but not otherwise. |
7341 | ||
7342 | The @option{-fstrict-overflow} option is enabled at levels | |
7343 | @option{-O2}, @option{-O3}, @option{-Os}. | |
7344 | ||
efa3896a GK |
7345 | @item -falign-functions |
7346 | @itemx -falign-functions=@var{n} | |
cd3bb277 | 7347 | @opindex falign-functions |
efa3896a GK |
7348 | Align the start of functions to the next power-of-two greater than |
7349 | @var{n}, skipping up to @var{n} bytes. For instance, | |
630d3d5a JM |
7350 | @option{-falign-functions=32} aligns functions to the next 32-byte |
7351 | boundary, but @option{-falign-functions=24} would align to the next | |
efa3896a GK |
7352 | 32-byte boundary only if this can be done by skipping 23 bytes or less. |
7353 | ||
630d3d5a | 7354 | @option{-fno-align-functions} and @option{-falign-functions=1} are |
efa3896a GK |
7355 | equivalent and mean that functions will not be aligned. |
7356 | ||
7357 | Some assemblers only support this flag when @var{n} is a power of two; | |
7358 | in that case, it is rounded up. | |
7359 | ||
561913cb | 7360 | If @var{n} is not specified or is zero, use a machine-dependent default. |
efa3896a | 7361 | |
38df970e JQ |
7362 | Enabled at levels @option{-O2}, @option{-O3}. |
7363 | ||
efa3896a GK |
7364 | @item -falign-labels |
7365 | @itemx -falign-labels=@var{n} | |
cd3bb277 | 7366 | @opindex falign-labels |
efa3896a | 7367 | Align all branch targets to a power-of-two boundary, skipping up to |
630d3d5a | 7368 | @var{n} bytes like @option{-falign-functions}. This option can easily |
efa3896a GK |
7369 | make code slower, because it must insert dummy operations for when the |
7370 | branch target is reached in the usual flow of the code. | |
7371 | ||
561913cb AP |
7372 | @option{-fno-align-labels} and @option{-falign-labels=1} are |
7373 | equivalent and mean that labels will not be aligned. | |
7374 | ||
630d3d5a | 7375 | If @option{-falign-loops} or @option{-falign-jumps} are applicable and |
efa3896a GK |
7376 | are greater than this value, then their values are used instead. |
7377 | ||
561913cb AP |
7378 | If @var{n} is not specified or is zero, use a machine-dependent default |
7379 | which is very likely to be @samp{1}, meaning no alignment. | |
efa3896a | 7380 | |
38df970e JQ |
7381 | Enabled at levels @option{-O2}, @option{-O3}. |
7382 | ||
efa3896a GK |
7383 | @item -falign-loops |
7384 | @itemx -falign-loops=@var{n} | |
cd3bb277 | 7385 | @opindex falign-loops |
efa3896a | 7386 | Align loops to a power-of-two boundary, skipping up to @var{n} bytes |
630d3d5a | 7387 | like @option{-falign-functions}. The hope is that the loop will be |
efa3896a GK |
7388 | executed many times, which will make up for any execution of the dummy |
7389 | operations. | |
7390 | ||
561913cb AP |
7391 | @option{-fno-align-loops} and @option{-falign-loops=1} are |
7392 | equivalent and mean that loops will not be aligned. | |
7393 | ||
7394 | If @var{n} is not specified or is zero, use a machine-dependent default. | |
efa3896a | 7395 | |
38df970e JQ |
7396 | Enabled at levels @option{-O2}, @option{-O3}. |
7397 | ||
efa3896a GK |
7398 | @item -falign-jumps |
7399 | @itemx -falign-jumps=@var{n} | |
cd3bb277 | 7400 | @opindex falign-jumps |
efa3896a GK |
7401 | Align branch targets to a power-of-two boundary, for branch targets |
7402 | where the targets can only be reached by jumping, skipping up to @var{n} | |
630d3d5a | 7403 | bytes like @option{-falign-functions}. In this case, no dummy operations |
efa3896a GK |
7404 | need be executed. |
7405 | ||
561913cb AP |
7406 | @option{-fno-align-jumps} and @option{-falign-jumps=1} are |
7407 | equivalent and mean that loops will not be aligned. | |
7408 | ||
7409 | If @var{n} is not specified or is zero, use a machine-dependent default. | |
efa3896a | 7410 | |
38df970e JQ |
7411 | Enabled at levels @option{-O2}, @option{-O3}. |
7412 | ||
7797ff53 PB |
7413 | @item -funit-at-a-time |
7414 | @opindex funit-at-a-time | |
d6cc6ec9 JH |
7415 | This option is left for compatibility reasons. @option{-funit-at-a-time} |
7416 | has no effect, while @option{-fno-unit-at-a-time} implies | |
7417 | @option{-fno-toplevel-reorder} and @option{-fno-section-anchors}. | |
7797ff53 | 7418 | |
d6cc6ec9 | 7419 | Enabled by default. |
7797ff53 | 7420 | |
474eccc6 | 7421 | @item -fno-toplevel-reorder |
e0d91975 | 7422 | @opindex fno-toplevel-reorder |
474eccc6 ILT |
7423 | Do not reorder top-level functions, variables, and @code{asm} |
7424 | statements. Output them in the same order that they appear in the | |
7425 | input file. When this option is used, unreferenced static variables | |
7426 | will not be removed. This option is intended to support existing code | |
7427 | which relies on a particular ordering. For new code, it is better to | |
7428 | use attributes. | |
7429 | ||
d6cc6ec9 JH |
7430 | Enabled at level @option{-O0}. When disabled explicitly, it also imply |
7431 | @option{-fno-section-anchors} that is otherwise enabled at @option{-O0} on some | |
7432 | targets. | |
7433 | ||
7260e9a0 JH |
7434 | @item -fweb |
7435 | @opindex fweb | |
7436 | Constructs webs as commonly used for register allocation purposes and assign | |
962e6e00 | 7437 | each web individual pseudo register. This allows the register allocation pass |
7260e9a0 JH |
7438 | to operate on pseudos directly, but also strengthens several other optimization |
7439 | passes, such as CSE, loop optimizer and trivial dead code remover. It can, | |
7440 | however, make debugging impossible, since variables will no longer stay in a | |
7441 | ``home register''. | |
7442 | ||
7869fe47 | 7443 | Enabled by default with @option{-funroll-loops}. |
d4463dfc | 7444 | |
ce91e74c JH |
7445 | @item -fwhole-program |
7446 | @opindex fwhole-program | |
e4ae5e77 | 7447 | Assume that the current compilation unit represents the whole program being |
ce91e74c | 7448 | compiled. All public functions and variables with the exception of @code{main} |
f341de7b | 7449 | and those merged by attribute @code{externally_visible} become static functions |
6d41cd02 | 7450 | and in effect are optimized more aggressively by interprocedural optimizers. If @command{gold} is used as the linker plugin, @code{externally_visible} attributes are automatically added to functions (not variable yet due to a current @command{gold} issue) that are accessed outside of LTO objects according to resolution file produced by @command{gold}. For other linkers that cannot generate resolution file, explicit @code{externally_visible} attributes are still necessary. |
e4ae5e77 RW |
7451 | While this option is equivalent to proper use of the @code{static} keyword for |
7452 | programs consisting of a single file, in combination with option | |
014d92e1 | 7453 | @option{-flto} this flag can be used to |
05927e0d TB |
7454 | compile many smaller scale programs since the functions and variables become |
7455 | local for the whole combined compilation unit, not for the single source file | |
7456 | itself. | |
ce91e74c | 7457 | |
ebaa6ea7 | 7458 | This option implies @option{-fwhole-file} for Fortran programs. |
ce91e74c | 7459 | |
014d92e1 | 7460 | @item -flto[=@var{n}] |
d7f09764 DN |
7461 | @opindex flto |
7462 | This option runs the standard link-time optimizer. When invoked | |
7463 | with source code, it generates GIMPLE (one of GCC's internal | |
7464 | representations) and writes it to special ELF sections in the object | |
7465 | file. When the object files are linked together, all the function | |
7466 | bodies are read from these ELF sections and instantiated as if they | |
7467 | had been part of the same translation unit. | |
7468 | ||
7469 | To use the link-timer optimizer, @option{-flto} needs to be specified at | |
7470 | compile time and during the final link. For example, | |
7471 | ||
7472 | @smallexample | |
7473 | gcc -c -O2 -flto foo.c | |
7474 | gcc -c -O2 -flto bar.c | |
7475 | gcc -o myprog -flto -O2 foo.o bar.o | |
7476 | @end smallexample | |
7477 | ||
7478 | The first two invocations to GCC will save a bytecode representation | |
7479 | of GIMPLE into special ELF sections inside @file{foo.o} and | |
7480 | @file{bar.o}. The final invocation will read the GIMPLE bytecode from | |
7481 | @file{foo.o} and @file{bar.o}, merge the two files into a single | |
7482 | internal image, and compile the result as usual. Since both | |
7483 | @file{foo.o} and @file{bar.o} are merged into a single image, this | |
7484 | causes all the inter-procedural analyses and optimizations in GCC to | |
7485 | work across the two files as if they were a single one. This means, | |
7486 | for example, that the inliner will be able to inline functions in | |
7487 | @file{bar.o} into functions in @file{foo.o} and vice-versa. | |
7488 | ||
7489 | Another (simpler) way to enable link-time optimization is, | |
7490 | ||
7491 | @smallexample | |
7492 | gcc -o myprog -flto -O2 foo.c bar.c | |
7493 | @end smallexample | |
7494 | ||
7495 | The above will generate bytecode for @file{foo.c} and @file{bar.c}, | |
7496 | merge them together into a single GIMPLE representation and optimize | |
7497 | them as usual to produce @file{myprog}. | |
7498 | ||
7499 | The only important thing to keep in mind is that to enable link-time | |
7500 | optimizations the @option{-flto} flag needs to be passed to both the | |
7501 | compile and the link commands. | |
7502 | ||
3abe8cab JH |
7503 | To make whole program optimization effective, it is necesary to make |
7504 | certain whole program assumptions. The compiler needs to know | |
7505 | what functions and variables can be accessed by libraries and runtime | |
7506 | outside of the link time optimized unit. When supported by the linker, | |
7507 | the linker plugin (see @option{-fuse-linker-plugin}) passes to the | |
7508 | compiler information about used and externally visible symbols. When | |
7509 | the linker plugin is not available, @option{-fwhole-program} should be | |
7510 | used to allow the compiler to make these assumptions, which will lead | |
7511 | to more aggressive optimization decisions. | |
7512 | ||
d7f09764 DN |
7513 | Note that when a file is compiled with @option{-flto}, the generated |
7514 | object file will be larger than a regular object file because it will | |
7515 | contain GIMPLE bytecodes and the usual final code. This means that | |
7516 | object files with LTO information can be linked as a normal object | |
7517 | file. So, in the previous example, if the final link is done with | |
7518 | ||
7519 | @smallexample | |
7520 | gcc -o myprog foo.o bar.o | |
7521 | @end smallexample | |
7522 | ||
7523 | The only difference will be that no inter-procedural optimizations | |
7524 | will be applied to produce @file{myprog}. The two object files | |
7525 | @file{foo.o} and @file{bar.o} will be simply sent to the regular | |
7526 | linker. | |
7527 | ||
7528 | Additionally, the optimization flags used to compile individual files | |
7529 | are not necessarily related to those used at link-time. For instance, | |
7530 | ||
7531 | @smallexample | |
7532 | gcc -c -O0 -flto foo.c | |
7533 | gcc -c -O0 -flto bar.c | |
7534 | gcc -o myprog -flto -O3 foo.o bar.o | |
7535 | @end smallexample | |
7536 | ||
7537 | This will produce individual object files with unoptimized assembler | |
7538 | code, but the resulting binary @file{myprog} will be optimized at | |
7539 | @option{-O3}. Now, if the final binary is generated without | |
7540 | @option{-flto}, then @file{myprog} will not be optimized. | |
7541 | ||
7542 | When producing the final binary with @option{-flto}, GCC will only | |
7543 | apply link-time optimizations to those files that contain bytecode. | |
7544 | Therefore, you can mix and match object files and libraries with | |
7545 | GIMPLE bytecodes and final object code. GCC will automatically select | |
7546 | which files to optimize in LTO mode and which files to link without | |
7547 | further processing. | |
7548 | ||
7549 | There are some code generation flags that GCC will preserve when | |
7550 | generating bytecodes, as they need to be used during the final link | |
7551 | stage. Currently, the following options are saved into the GIMPLE | |
7552 | bytecode files: @option{-fPIC}, @option{-fcommon} and all the | |
7553 | @option{-m} target flags. | |
7554 | ||
7555 | At link time, these options are read-in and reapplied. Note that the | |
7556 | current implementation makes no attempt at recognizing conflicting | |
7557 | values for these options. If two or more files have a conflicting | |
7558 | value (e.g., one file is compiled with @option{-fPIC} and another | |
7559 | isn't), the compiler will simply use the last value read from the | |
7560 | bytecode files. It is recommended, then, that all the files | |
7561 | participating in the same link be compiled with the same options. | |
7562 | ||
7563 | Another feature of LTO is that it is possible to apply interprocedural | |
7564 | optimizations on files written in different languages. This requires | |
7565 | some support in the language front end. Currently, the C, C++ and | |
7566 | Fortran front ends are capable of emitting GIMPLE bytecodes, so | |
7567 | something like this should work | |
7568 | ||
7569 | @smallexample | |
7570 | gcc -c -flto foo.c | |
7571 | g++ -c -flto bar.cc | |
7572 | gfortran -c -flto baz.f90 | |
7573 | g++ -o myprog -flto -O3 foo.o bar.o baz.o -lgfortran | |
7574 | @end smallexample | |
7575 | ||
7576 | Notice that the final link is done with @command{g++} to get the C++ | |
7577 | runtime libraries and @option{-lgfortran} is added to get the Fortran | |
7578 | runtime libraries. In general, when mixing languages in LTO mode, you | |
7579 | should use the same link command used when mixing languages in a | |
7580 | regular (non-LTO) compilation. This means that if your build process | |
7581 | was mixing languages before, all you need to add is @option{-flto} to | |
7582 | all the compile and link commands. | |
7583 | ||
53b79425 RW |
7584 | If LTO encounters objects with C linkage declared with incompatible |
7585 | types in separate translation units to be linked together (undefined | |
7586 | behavior according to ISO C99 6.2.7), a non-fatal diagnostic may be | |
7587 | issued. The behavior is still undefined at runtime. | |
7588 | ||
d7f09764 DN |
7589 | If object files containing GIMPLE bytecode are stored in a library |
7590 | archive, say @file{libfoo.a}, it is possible to extract and use them | |
7591 | in an LTO link if you are using @command{gold} as the linker (which, | |
7592 | in turn requires GCC to be configured with @option{--enable-gold}). | |
180a2539 | 7593 | To enable this feature, use the flag @option{-fuse-linker-plugin} at |
d7f09764 DN |
7594 | link-time: |
7595 | ||
7596 | @smallexample | |
180a2539 | 7597 | gcc -o myprog -O2 -flto -fuse-linker-plugin a.o b.o -lfoo |
d7f09764 DN |
7598 | @end smallexample |
7599 | ||
7600 | With the linker plugin enabled, @command{gold} will extract the needed | |
7601 | GIMPLE files from @file{libfoo.a} and pass them on to the running GCC | |
7602 | to make them part of the aggregated GIMPLE image to be optimized. | |
7603 | ||
7604 | If you are not using @command{gold} and/or do not specify | |
180a2539 | 7605 | @option{-fuse-linker-plugin} then the objects inside @file{libfoo.a} |
d7f09764 DN |
7606 | will be extracted and linked as usual, but they will not participate |
7607 | in the LTO optimization process. | |
7608 | ||
014d92e1 JH |
7609 | Link time optimizations do not require the presence of the whole program to |
7610 | operate. If the program does not require any symbols to be exported, it is | |
7611 | possible to combine @option{-flto} and with @option{-fwhole-program} to allow | |
7612 | the interprocedural optimizers to use more aggressive assumptions which may | |
7613 | lead to improved optimization opportunities. | |
7614 | Use of @option{-fwhole-program} is not needed when linker plugin is | |
7615 | active (see @option{-fuse-linker-plugin}). | |
05927e0d | 7616 | |
d7f09764 DN |
7617 | Regarding portability: the current implementation of LTO makes no |
7618 | attempt at generating bytecode that can be ported between different | |
7619 | types of hosts. The bytecode files are versioned and there is a | |
7620 | strict version check, so bytecode files generated in one version of | |
7621 | GCC will not work with an older/newer version of GCC. | |
7622 | ||
2a71eb48 | 7623 | Link time optimization does not play well with generating debugging |
014d92e1 | 7624 | information. Combining @option{-flto} with |
3abe8cab JH |
7625 | @option{-g} is currently experimental and expected to produce wrong |
7626 | results. | |
2a71eb48 | 7627 | |
3abe8cab JH |
7628 | If you specify the optional @var{n}, the optimization and code |
7629 | generation done at link time is executed in parallel using @var{n} | |
7630 | parallel jobs by utilizing an installed @command{make} program. The | |
7631 | environment variable @env{MAKE} may be used to override the program | |
7632 | used. The default value for @var{n} is 1. | |
c04b6b38 | 7633 | |
3abe8cab | 7634 | You can also specify @option{-flto=jobserver} to use GNU make's |
a478ffff | 7635 | job server mode to determine the number of parallel jobs. This |
3abe8cab | 7636 | is useful when the Makefile calling GCC is already executing in parallel. |
a478ffff AK |
7637 | The parent Makefile will need a @samp{+} prepended to the command recipe |
7638 | for this to work. This will likely only work if @env{MAKE} is | |
7639 | GNU make. | |
7640 | ||
014d92e1 | 7641 | This option is disabled by default. |
d7f09764 | 7642 | |
852e4bd2 JH |
7643 | @item -flto-partition=@var{alg} |
7644 | @opindex flto-partition | |
3abe8cab JH |
7645 | Specify the partitioning algorithm used by the link time optimizer. |
7646 | The value is either @code{1to1} to specify a partitioning mirroring | |
7647 | the original source files or @code{balanced} to specify partitioning | |
7648 | into equally sized chunks (whenever possible). Specifying @code{none} | |
7649 | as an algorithm disables partitioning and streaming completely. The | |
7650 | default value is @code{balanced}. | |
d7f09764 DN |
7651 | |
7652 | @item -flto-compression-level=@var{n} | |
7653 | This option specifies the level of compression used for intermediate | |
7654 | language written to LTO object files, and is only meaningful in | |
3abe8cab | 7655 | conjunction with LTO mode (@option{-flto}). Valid |
d7f09764 DN |
7656 | values are 0 (no compression) to 9 (maximum compression). Values |
7657 | outside this range are clamped to either 0 or 9. If the option is not | |
7658 | given, a default balanced compression setting is used. | |
7659 | ||
7660 | @item -flto-report | |
7661 | Prints a report with internal details on the workings of the link-time | |
7662 | optimizer. The contents of this report vary from version to version, | |
7663 | it is meant to be useful to GCC developers when processing object | |
3abe8cab | 7664 | files in LTO mode (via @option{-flto}). |
d7f09764 DN |
7665 | |
7666 | Disabled by default. | |
7667 | ||
180a2539 | 7668 | @item -fuse-linker-plugin |
d7f09764 DN |
7669 | Enables the extraction of objects with GIMPLE bytecode information |
7670 | from library archives. This option relies on features available only | |
7671 | in @command{gold}, so to use this you must configure GCC with | |
7672 | @option{--enable-gold}. See @option{-flto} for a description on the | |
7673 | effect of this flag and how to use it. | |
7674 | ||
7675 | Disabled by default. | |
7676 | ||
d228aace JJ |
7677 | @item -fcprop-registers |
7678 | @opindex fcprop-registers | |
d4463dfc JQ |
7679 | After register allocation and post-register allocation instruction splitting, |
7680 | we perform a copy-propagation pass to try to reduce scheduling dependencies | |
7681 | and occasionally eliminate the copy. | |
7682 | ||
d228aace | 7683 | Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
d4463dfc | 7684 | |
52c76998 PY |
7685 | @item -fprofile-correction |
7686 | @opindex fprofile-correction | |
7687 | Profiles collected using an instrumented binary for multi-threaded programs may | |
7688 | be inconsistent due to missed counter updates. When this option is specified, | |
7689 | GCC will use heuristics to correct or smooth out such inconsistencies. By | |
7690 | default, GCC will emit an error message when an inconsistent profile is detected. | |
7691 | ||
2f908293 SP |
7692 | @item -fprofile-dir=@var{path} |
7693 | @opindex fprofile-dir | |
7694 | ||
7695 | Set the directory to search the profile data files in to @var{path}. | |
7696 | This option affects only the profile data generated by | |
7697 | @option{-fprofile-generate}, @option{-ftest-coverage}, @option{-fprofile-arcs} | |
7a61cf6f | 7698 | and used by @option{-fprofile-use} and @option{-fbranch-probabilities} |
2f908293 SP |
7699 | and its related options. |
7700 | By default, GCC will use the current directory as @var{path} | |
7701 | thus the profile data file will appear in the same directory as the object file. | |
7702 | ||
a8a5f53a | 7703 | @item -fprofile-generate |
2f908293 | 7704 | @itemx -fprofile-generate=@var{path} |
a8a5f53a | 7705 | @opindex fprofile-generate |
a8a5f53a | 7706 | |
33adcb6c MM |
7707 | Enable options usually used for instrumenting application to produce |
7708 | profile useful for later recompilation with profile feedback based | |
4ec7afd7 | 7709 | optimization. You must use @option{-fprofile-generate} both when |
33adcb6c MM |
7710 | compiling and when linking your program. |
7711 | ||
7712 | The following options are enabled: @code{-fprofile-arcs}, @code{-fprofile-values}, @code{-fvpt}. | |
a8a5f53a | 7713 | |
2f908293 | 7714 | If @var{path} is specified, GCC will look at the @var{path} to find |
a640c13b | 7715 | the profile feedback data files. See @option{-fprofile-dir}. |
2f908293 | 7716 | |
a8a5f53a | 7717 | @item -fprofile-use |
2f908293 | 7718 | @itemx -fprofile-use=@var{path} |
a8a5f53a JH |
7719 | @opindex fprofile-use |
7720 | Enable profile feedback directed optimizations, and optimizations | |
7721 | generally profitable only with profile feedback available. | |
7722 | ||
8a76829c | 7723 | The following options are enabled: @code{-fbranch-probabilities}, @code{-fvpt}, |
37818e7c | 7724 | @code{-funroll-loops}, @code{-fpeel-loops}, @code{-ftracer} |
a8a5f53a | 7725 | |
16c1c158 RG |
7726 | By default, GCC emits an error message if the feedback profiles do not |
7727 | match the source code. This error can be turned into a warning by using | |
7728 | @option{-Wcoverage-mismatch}. Note this may result in poorly optimized | |
7729 | code. | |
2f908293 SP |
7730 | |
7731 | If @var{path} is specified, GCC will look at the @var{path} to find | |
7732 | the profile feedback data files. See @option{-fprofile-dir}. | |
d4463dfc JQ |
7733 | @end table |
7734 | ||
7735 | The following options control compiler behavior regarding floating | |
7736 | point arithmetic. These options trade off between speed and | |
7737 | correctness. All must be specifically enabled. | |
7738 | ||
7739 | @table @gcctabopt | |
7740 | @item -ffloat-store | |
7741 | @opindex ffloat-store | |
7742 | Do not store floating point variables in registers, and inhibit other | |
7743 | options that might change whether a floating point value is taken from a | |
7744 | register or memory. | |
7745 | ||
7746 | @cindex floating point precision | |
7747 | This option prevents undesirable excess precision on machines such as | |
7748 | the 68000 where the floating registers (of the 68881) keep more | |
7749 | precision than a @code{double} is supposed to have. Similarly for the | |
7750 | x86 architecture. For most programs, the excess precision does only | |
7751 | good, but a few programs rely on the precise definition of IEEE floating | |
7752 | point. Use @option{-ffloat-store} for such programs, after modifying | |
7753 | them to store all pertinent intermediate computations into variables. | |
7754 | ||
8ce94e44 JM |
7755 | @item -fexcess-precision=@var{style} |
7756 | @opindex fexcess-precision | |
7757 | This option allows further control over excess precision on machines | |
7758 | where floating-point registers have more precision than the IEEE | |
7759 | @code{float} and @code{double} types and the processor does not | |
7760 | support operations rounding to those types. By default, | |
7761 | @option{-fexcess-precision=fast} is in effect; this means that | |
7762 | operations are carried out in the precision of the registers and that | |
7763 | it is unpredictable when rounding to the types specified in the source | |
7764 | code takes place. When compiling C, if | |
7765 | @option{-fexcess-precision=standard} is specified then excess | |
7766 | precision will follow the rules specified in ISO C99; in particular, | |
7767 | both casts and assignments cause values to be rounded to their | |
7768 | semantic types (whereas @option{-ffloat-store} only affects | |
7769 | assignments). This option is enabled by default for C if a strict | |
7770 | conformance option such as @option{-std=c99} is used. | |
7771 | ||
7772 | @opindex mfpmath | |
7773 | @option{-fexcess-precision=standard} is not implemented for languages | |
7774 | other than C, and has no effect if | |
7775 | @option{-funsafe-math-optimizations} or @option{-ffast-math} is | |
7776 | specified. On the x86, it also has no effect if @option{-mfpmath=sse} | |
7777 | or @option{-mfpmath=sse+387} is specified; in the former case, IEEE | |
7778 | semantics apply without excess precision, and in the latter, rounding | |
7779 | is unpredictable. | |
7780 | ||
d4463dfc JQ |
7781 | @item -ffast-math |
7782 | @opindex ffast-math | |
4aba7b11 EB |
7783 | Sets @option{-fno-math-errno}, @option{-funsafe-math-optimizations}, |
7784 | @option{-ffinite-math-only}, @option{-fno-rounding-math}, | |
7785 | @option{-fno-signaling-nans} and @option{-fcx-limited-range}. | |
d4463dfc JQ |
7786 | |
7787 | This option causes the preprocessor macro @code{__FAST_MATH__} to be defined. | |
7788 | ||
c9516c38 | 7789 | This option is not turned on by any @option{-O} option since |
d4463dfc JQ |
7790 | it can result in incorrect output for programs which depend on |
7791 | an exact implementation of IEEE or ISO rules/specifications for | |
c9516c38 WB |
7792 | math functions. It may, however, yield faster code for programs |
7793 | that do not require the guarantees of these specifications. | |
d4463dfc JQ |
7794 | |
7795 | @item -fno-math-errno | |
7796 | @opindex fno-math-errno | |
7797 | Do not set ERRNO after calling math functions that are executed | |
7798 | with a single instruction, e.g., sqrt. A program that relies on | |
7799 | IEEE exceptions for math error handling may want to use this flag | |
7800 | for speed while maintaining IEEE arithmetic compatibility. | |
7801 | ||
c9516c38 | 7802 | This option is not turned on by any @option{-O} option since |
d4463dfc JQ |
7803 | it can result in incorrect output for programs which depend on |
7804 | an exact implementation of IEEE or ISO rules/specifications for | |
c9516c38 WB |
7805 | math functions. It may, however, yield faster code for programs |
7806 | that do not require the guarantees of these specifications. | |
d4463dfc JQ |
7807 | |
7808 | The default is @option{-fmath-errno}. | |
7809 | ||
db02da79 RS |
7810 | On Darwin systems, the math library never sets @code{errno}. There is |
7811 | therefore no reason for the compiler to consider the possibility that | |
7812 | it might, and @option{-fno-math-errno} is the default. | |
2e3f0db6 | 7813 | |
d4463dfc JQ |
7814 | @item -funsafe-math-optimizations |
7815 | @opindex funsafe-math-optimizations | |
a1a82611 | 7816 | |
d4463dfc JQ |
7817 | Allow optimizations for floating-point arithmetic that (a) assume |
7818 | that arguments and results are valid and (b) may violate IEEE or | |
7819 | ANSI standards. When used at link-time, it may include libraries | |
7820 | or startup files that change the default FPU control word or other | |
7821 | similar optimizations. | |
7822 | ||
c9516c38 | 7823 | This option is not turned on by any @option{-O} option since |
d4463dfc JQ |
7824 | it can result in incorrect output for programs which depend on |
7825 | an exact implementation of IEEE or ISO rules/specifications for | |
c9516c38 WB |
7826 | math functions. It may, however, yield faster code for programs |
7827 | that do not require the guarantees of these specifications. | |
c5edab65 EB |
7828 | Enables @option{-fno-signed-zeros}, @option{-fno-trapping-math}, |
7829 | @option{-fassociative-math} and @option{-freciprocal-math}. | |
d4463dfc JQ |
7830 | |
7831 | The default is @option{-fno-unsafe-math-optimizations}. | |
7832 | ||
a1a82611 | 7833 | @item -fassociative-math |
7d95b692 | 7834 | @opindex fassociative-math |
a1a82611 RE |
7835 | |
7836 | Allow re-association of operands in series of floating-point operations. | |
7837 | This violates the ISO C and C++ language standard by possibly changing | |
7838 | computation result. NOTE: re-ordering may change the sign of zero as | |
7839 | well as ignore NaNs and inhibit or create underflow or overflow (and | |
7840 | thus cannot be used on a code which relies on rounding behavior like | |
7841 | @code{(x + 2**52) - 2**52)}. May also reorder floating-point comparisons | |
7842 | and thus may not be used when ordered comparisons are required. | |
c5edab65 EB |
7843 | This option requires that both @option{-fno-signed-zeros} and |
7844 | @option{-fno-trapping-math} be in effect. Moreover, it doesn't make | |
72bd130e TB |
7845 | much sense with @option{-frounding-math}. For Fortran the option |
7846 | is automatically enabled when both @option{-fno-signed-zeros} and | |
7847 | @option{-fno-trapping-math} are in effect. | |
a1a82611 RE |
7848 | |
7849 | The default is @option{-fno-associative-math}. | |
7850 | ||
7851 | @item -freciprocal-math | |
7d95b692 | 7852 | @opindex freciprocal-math |
a1a82611 RE |
7853 | |
7854 | Allow the reciprocal of a value to be used instead of dividing by | |
7855 | the value if this enables optimizations. For example @code{x / y} | |
7856 | can be replaced with @code{x * (1/y)} which is useful if @code{(1/y)} | |
7857 | is subject to common subexpression elimination. Note that this loses | |
7858 | precision and increases the number of flops operating on the value. | |
7859 | ||
7860 | The default is @option{-fno-reciprocal-math}. | |
7861 | ||
d4463dfc JQ |
7862 | @item -ffinite-math-only |
7863 | @opindex ffinite-math-only | |
7864 | Allow optimizations for floating-point arithmetic that assume | |
7865 | that arguments and results are not NaNs or +-Infs. | |
7866 | ||
c9516c38 | 7867 | This option is not turned on by any @option{-O} option since |
d4463dfc | 7868 | it can result in incorrect output for programs which depend on |
c9516c38 WB |
7869 | an exact implementation of IEEE or ISO rules/specifications for |
7870 | math functions. It may, however, yield faster code for programs | |
7871 | that do not require the guarantees of these specifications. | |
d4463dfc JQ |
7872 | |
7873 | The default is @option{-fno-finite-math-only}. | |
7874 | ||
db02da79 RS |
7875 | @item -fno-signed-zeros |
7876 | @opindex fno-signed-zeros | |
7877 | Allow optimizations for floating point arithmetic that ignore the | |
7878 | signedness of zero. IEEE arithmetic specifies the behavior of | |
78681dbd RS |
7879 | distinct +0.0 and @minus{}0.0 values, which then prohibits simplification |
7880 | of expressions such as x+0.0 or 0.0*x (even with @option{-ffinite-math-only}). | |
db02da79 RS |
7881 | This option implies that the sign of a zero result isn't significant. |
7882 | ||
7883 | The default is @option{-fsigned-zeros}. | |
7884 | ||
d4463dfc JQ |
7885 | @item -fno-trapping-math |
7886 | @opindex fno-trapping-math | |
7887 | Compile code assuming that floating-point operations cannot generate | |
7888 | user-visible traps. These traps include division by zero, overflow, | |
c5edab65 EB |
7889 | underflow, inexact result and invalid operation. This option requires |
7890 | that @option{-fno-signaling-nans} be in effect. Setting this option may | |
7891 | allow faster code if one relies on ``non-stop'' IEEE arithmetic, for example. | |
d4463dfc JQ |
7892 | |
7893 | This option should never be turned on by any @option{-O} option since | |
7894 | it can result in incorrect output for programs which depend on | |
7895 | an exact implementation of IEEE or ISO rules/specifications for | |
7896 | math functions. | |
7897 | ||
7898 | The default is @option{-ftrapping-math}. | |
7899 | ||
039c3d42 RS |
7900 | @item -frounding-math |
7901 | @opindex frounding-math | |
7902 | Disable transformations and optimizations that assume default floating | |
7903 | point rounding behavior. This is round-to-zero for all floating point | |
7904 | to integer conversions, and round-to-nearest for all other arithmetic | |
7905 | truncations. This option should be specified for programs that change | |
7906 | the FP rounding mode dynamically, or that may be executed with a | |
7907 | non-default rounding mode. This option disables constant folding of | |
7908 | floating point expressions at compile-time (which may be affected by | |
7909 | rounding mode) and arithmetic transformations that are unsafe in the | |
7910 | presence of sign-dependent rounding modes. | |
7911 | ||
7912 | The default is @option{-fno-rounding-math}. | |
7913 | ||
7914 | This option is experimental and does not currently guarantee to | |
7915 | disable all GCC optimizations that are affected by rounding mode. | |
2dd76960 | 7916 | Future versions of GCC may provide finer control of this setting |
039c3d42 RS |
7917 | using C99's @code{FENV_ACCESS} pragma. This command line option |
7918 | will be used to specify the default state for @code{FENV_ACCESS}. | |
7919 | ||
d4463dfc JQ |
7920 | @item -fsignaling-nans |
7921 | @opindex fsignaling-nans | |
7922 | Compile code assuming that IEEE signaling NaNs may generate user-visible | |
7923 | traps during floating-point operations. Setting this option disables | |
7924 | optimizations that may change the number of exceptions visible with | |
7925 | signaling NaNs. This option implies @option{-ftrapping-math}. | |
7926 | ||
7927 | This option causes the preprocessor macro @code{__SUPPORT_SNAN__} to | |
7928 | be defined. | |
7929 | ||
7930 | The default is @option{-fno-signaling-nans}. | |
7931 | ||
7932 | This option is experimental and does not currently guarantee to | |
7933 | disable all GCC optimizations that affect signaling NaN behavior. | |
7934 | ||
7935 | @item -fsingle-precision-constant | |
7936 | @opindex fsingle-precision-constant | |
7937 | Treat floating point constant as single precision constant instead of | |
7938 | implicitly converting it to double precision constant. | |
7939 | ||
c7463669 | 7940 | @item -fcx-limited-range |
c7463669 | 7941 | @opindex fcx-limited-range |
c7463669 | 7942 | When enabled, this option states that a range reduction step is not |
8cc6d3e0 JB |
7943 | needed when performing complex division. Also, there is no checking |
7944 | whether the result of a complex multiplication or division is @code{NaN | |
7945 | + I*NaN}, with an attempt to rescue the situation in that case. The | |
7946 | default is @option{-fno-cx-limited-range}, but is enabled by | |
7947 | @option{-ffast-math}. | |
c7463669 | 7948 | |
cb7ad97b | 7949 | This option controls the default setting of the ISO C99 |
c7463669 RH |
7950 | @code{CX_LIMITED_RANGE} pragma. Nevertheless, the option applies to |
7951 | all languages. | |
d4463dfc | 7952 | |
35085f76 JB |
7953 | @item -fcx-fortran-rules |
7954 | @opindex fcx-fortran-rules | |
7955 | Complex multiplication and division follow Fortran rules. Range | |
7956 | reduction is done as part of complex division, but there is no checking | |
7957 | whether the result of a complex multiplication or division is @code{NaN | |
7958 | + I*NaN}, with an attempt to rescue the situation in that case. | |
7959 | ||
7960 | The default is @option{-fno-cx-fortran-rules}. | |
7961 | ||
d4463dfc JQ |
7962 | @end table |
7963 | ||
7964 | The following options control optimizations that may improve | |
7965 | performance, but are not enabled by any @option{-O} options. This | |
7966 | section includes experimental options that may produce broken code. | |
7967 | ||
7968 | @table @gcctabopt | |
7969 | @item -fbranch-probabilities | |
7970 | @opindex fbranch-probabilities | |
7971 | After running a program compiled with @option{-fprofile-arcs} | |
7972 | (@pxref{Debugging Options,, Options for Debugging Your Program or | |
7973 | @command{gcc}}), you can compile it a second time using | |
7974 | @option{-fbranch-probabilities}, to improve optimizations based on | |
7975 | the number of times each branch was taken. When the program | |
7976 | compiled with @option{-fprofile-arcs} exits it saves arc execution | |
a4878735 | 7977 | counts to a file called @file{@var{sourcename}.gcda} for each source |
bbd29fdc | 7978 | file. The information in this data file is very dependent on the |
d4463dfc JQ |
7979 | structure of the generated code, so you must use the same source code |
7980 | and the same optimization options for both compilations. | |
7981 | ||
daf2f129 | 7982 | With @option{-fbranch-probabilities}, GCC puts a |
d4463dfc JQ |
7983 | @samp{REG_BR_PROB} note on each @samp{JUMP_INSN} and @samp{CALL_INSN}. |
7984 | These can be used to improve optimization. Currently, they are only | |
7985 | used in one place: in @file{reorg.c}, instead of guessing which path a | |
7986 | branch is mostly to take, the @samp{REG_BR_PROB} values are used to | |
7987 | exactly determine which path is taken more often. | |
7988 | ||
fc5eb4a1 ZD |
7989 | @item -fprofile-values |
7990 | @opindex fprofile-values | |
7991 | If combined with @option{-fprofile-arcs}, it adds code so that some | |
7992 | data about values of expressions in the program is gathered. | |
7993 | ||
6e885ee3 ZD |
7994 | With @option{-fbranch-probabilities}, it reads back the data gathered |
7995 | from profiling values of expressions and adds @samp{REG_VALUE_PROFILE} | |
7996 | notes to instructions for their later usage in optimizations. | |
7997 | ||
7797ff53 | 7998 | Enabled with @option{-fprofile-generate} and @option{-fprofile-use}. |
8d3b3fb7 | 7999 | |
fca9dc00 ZD |
8000 | @item -fvpt |
8001 | @opindex fvpt | |
8002 | If combined with @option{-fprofile-arcs}, it instructs the compiler to add | |
8003 | a code to gather information about values of expressions. | |
8004 | ||
8005 | With @option{-fbranch-probabilities}, it reads back the data gathered | |
8006 | and actually performs the optimizations based on them. | |
8007 | Currently the optimizations include specialization of division operation | |
8008 | using the knowledge about the value of the denominator. | |
8009 | ||
a7b1dc36 PB |
8010 | @item -frename-registers |
8011 | @opindex frename-registers | |
8012 | Attempt to avoid false dependencies in scheduled code by making use | |
8013 | of registers left over after register allocation. This optimization | |
8014 | will most benefit processors with lots of registers. Depending on the | |
8015 | debug information format adopted by the target, however, it can | |
8016 | make debugging impossible, since variables will no longer stay in | |
8017 | a ``home register''. | |
8018 | ||
37740cd3 | 8019 | Enabled by default with @option{-funroll-loops} and @option{-fpeel-loops}. |
a7b1dc36 | 8020 | |
d4463dfc JQ |
8021 | @item -ftracer |
8022 | @opindex ftracer | |
8a36672b | 8023 | Perform tail duplication to enlarge superblock size. This transformation |
d4463dfc JQ |
8024 | simplifies the control flow of the function allowing other optimizations to do |
8025 | better job. | |
8026 | ||
7797ff53 | 8027 | Enabled with @option{-fprofile-use}. |
8d3b3fb7 | 8028 | |
d4463dfc JQ |
8029 | @item -funroll-loops |
8030 | @opindex funroll-loops | |
b17d5d7c ZD |
8031 | Unroll loops whose number of iterations can be determined at compile time or |
8032 | upon entry to the loop. @option{-funroll-loops} implies | |
cb7ad97b | 8033 | @option{-frerun-cse-after-loop}, @option{-fweb} and @option{-frename-registers}. |
7869fe47 ZD |
8034 | It also turns on complete loop peeling (i.e.@: complete removal of loops with |
8035 | small constant number of iterations). This option makes code larger, and may | |
8036 | or may not make it run faster. | |
d4463dfc | 8037 | |
7797ff53 | 8038 | Enabled with @option{-fprofile-use}. |
8d3b3fb7 | 8039 | |
d4463dfc JQ |
8040 | @item -funroll-all-loops |
8041 | @opindex funroll-all-loops | |
8042 | Unroll all loops, even if their number of iterations is uncertain when | |
8043 | the loop is entered. This usually makes programs run more slowly. | |
8044 | @option{-funroll-all-loops} implies the same options as | |
b17d5d7c ZD |
8045 | @option{-funroll-loops}. |
8046 | ||
8047 | @item -fpeel-loops | |
8048 | @opindex fpeel-loops | |
8049 | Peels the loops for that there is enough information that they do not | |
8050 | roll much (from profile feedback). It also turns on complete loop peeling | |
431ae0bf | 8051 | (i.e.@: complete removal of loops with small constant number of iterations). |
b17d5d7c | 8052 | |
7797ff53 | 8053 | Enabled with @option{-fprofile-use}. |
8d3b3fb7 | 8054 | |
5e962776 ZD |
8055 | @item -fmove-loop-invariants |
8056 | @opindex fmove-loop-invariants | |
37818e7c | 8057 | Enables the loop invariant motion pass in the RTL loop optimizer. Enabled |
5e962776 ZD |
8058 | at level @option{-O1} |
8059 | ||
b17d5d7c ZD |
8060 | @item -funswitch-loops |
8061 | @opindex funswitch-loops | |
8062 | Move branches with loop invariant conditions out of the loop, with duplicates | |
8063 | of the loop on both branches (modified according to result of the condition). | |
8064 | ||
d4463dfc JQ |
8065 | @item -ffunction-sections |
8066 | @itemx -fdata-sections | |
8067 | @opindex ffunction-sections | |
8068 | @opindex fdata-sections | |
8069 | Place each function or data item into its own section in the output | |
8070 | file if the target supports arbitrary sections. The name of the | |
8071 | function or the name of the data item determines the section's name | |
8072 | in the output file. | |
8073 | ||
8074 | Use these options on systems where the linker can perform optimizations | |
f401d0f5 JDA |
8075 | to improve locality of reference in the instruction space. Most systems |
8076 | using the ELF object format and SPARC processors running Solaris 2 have | |
8077 | linkers with such optimizations. AIX may have these optimizations in | |
8078 | the future. | |
d4463dfc JQ |
8079 | |
8080 | Only use these options when there are significant benefits from doing | |
8081 | so. When you specify these options, the assembler and linker will | |
8082 | create larger object and executable files and will also be slower. | |
8083 | You will not be able to use @code{gprof} on all systems if you | |
8084 | specify this option and you may have problems with debugging if | |
8085 | you specify both this option and @option{-g}. | |
8086 | ||
fe3ad572 SC |
8087 | @item -fbranch-target-load-optimize |
8088 | @opindex fbranch-target-load-optimize | |
8089 | Perform branch target register load optimization before prologue / epilogue | |
8090 | threading. | |
8091 | The use of target registers can typically be exposed only during reload, | |
8092 | thus hoisting loads out of loops and doing inter-block scheduling needs | |
8093 | a separate optimization pass. | |
8094 | ||
8095 | @item -fbranch-target-load-optimize2 | |
8096 | @opindex fbranch-target-load-optimize2 | |
8097 | Perform branch target register load optimization after prologue / epilogue | |
8098 | threading. | |
8099 | ||
1194fc79 R |
8100 | @item -fbtr-bb-exclusive |
8101 | @opindex fbtr-bb-exclusive | |
8d3b3fb7 | 8102 | When performing branch target register load optimization, don't reuse |
1194fc79 R |
8103 | branch target registers in within any basic block. |
8104 | ||
0aca9021 | 8105 | @item -fstack-protector |
d228aace | 8106 | @opindex fstack-protector |
0aca9021 JW |
8107 | Emit extra code to check for buffer overflows, such as stack smashing |
8108 | attacks. This is done by adding a guard variable to functions with | |
8109 | vulnerable objects. This includes functions that call alloca, and | |
8110 | functions with buffers larger than 8 bytes. The guards are initialized | |
8111 | when a function is entered and then checked when the function exits. | |
8112 | If a guard check fails, an error message is printed and the program exits. | |
8113 | ||
8114 | @item -fstack-protector-all | |
d228aace | 8115 | @opindex fstack-protector-all |
0aca9021 JW |
8116 | Like @option{-fstack-protector} except that all functions are protected. |
8117 | ||
aacd3885 RS |
8118 | @item -fsection-anchors |
8119 | @opindex fsection-anchors | |
8120 | Try to reduce the number of symbolic address calculations by using | |
8121 | shared ``anchor'' symbols to address nearby objects. This transformation | |
8122 | can help to reduce the number of GOT entries and GOT accesses on some | |
8123 | targets. | |
8124 | ||
8125 | For example, the implementation of the following function @code{foo}: | |
8126 | ||
8127 | @smallexample | |
8128 | static int a, b, c; | |
8129 | int foo (void) @{ return a + b + c; @} | |
8130 | @end smallexample | |
8131 | ||
8132 | would usually calculate the addresses of all three variables, but if you | |
8133 | compile it with @option{-fsection-anchors}, it will access the variables | |
8134 | from a common anchor point instead. The effect is similar to the | |
8135 | following pseudocode (which isn't valid C): | |
8136 | ||
8137 | @smallexample | |
8138 | int foo (void) | |
8139 | @{ | |
8140 | register int *xr = &x; | |
8141 | return xr[&a - &x] + xr[&b - &x] + xr[&c - &x]; | |
8142 | @} | |
8143 | @end smallexample | |
8144 | ||
8145 | Not all targets support this option. | |
8146 | ||
3af64fd6 | 8147 | @item --param @var{name}=@var{value} |
cd3bb277 | 8148 | @opindex param |
3af64fd6 MM |
8149 | In some places, GCC uses various constants to control the amount of |
8150 | optimization that is done. For example, GCC will not inline functions | |
8151 | that contain more that a certain number of instructions. You can | |
8152 | control some of these constants on the command-line using the | |
630d3d5a | 8153 | @option{--param} option. |
3af64fd6 | 8154 | |
b00567b0 ILT |
8155 | The names of specific parameters, and the meaning of the values, are |
8156 | tied to the internals of the compiler, and are subject to change | |
8157 | without notice in future releases. | |
8158 | ||
4fe9b91c | 8159 | In each case, the @var{value} is an integer. The allowable choices for |
3af64fd6 MM |
8160 | @var{name} are given in the following table: |
8161 | ||
8162 | @table @gcctabopt | |
5bb06e18 GO |
8163 | @item struct-reorg-cold-struct-ratio |
8164 | The threshold ratio (as a percentage) between a structure frequency | |
8165 | and the frequency of the hottest structure in the program. This parameter | |
8166 | is used by struct-reorg optimization enabled by @option{-fipa-struct-reorg}. | |
7a61cf6f NC |
8167 | We say that if the ratio of a structure frequency, calculated by profiling, |
8168 | to the hottest structure frequency in the program is less than this | |
5bb06e18 GO |
8169 | parameter, then structure reorganization is not applied to this structure. |
8170 | The default is 10. | |
8171 | ||
67018619 | 8172 | @item predictable-branch-outcome |
3a4fd356 JH |
8173 | When branch is predicted to be taken with probability lower than this threshold |
8174 | (in percent), then it is considered well predictable. The default is 10. | |
8175 | ||
5f24e0dc RH |
8176 | @item max-crossjump-edges |
8177 | The maximum number of incoming edges to consider for crossjumping. | |
d203738b | 8178 | The algorithm used by @option{-fcrossjumping} is @math{O(N^2)} in |
5f24e0dc RH |
8179 | the number of edges incoming to each block. Increasing values mean |
8180 | more aggressive optimization, making the compile time increase with | |
8181 | probably small improvement in executable size. | |
8182 | ||
12183e0f PH |
8183 | @item min-crossjump-insns |
8184 | The minimum number of instructions which must be matched at the end | |
8185 | of two blocks before crossjumping will be performed on them. This | |
8186 | value is ignored in the case where all instructions in the block being | |
8187 | crossjumped from are matched. The default value is 5. | |
8188 | ||
f935b9e0 DE |
8189 | @item max-grow-copy-bb-insns |
8190 | The maximum code size expansion factor when copying basic blocks | |
8191 | instead of jumping. The expansion is relative to a jump instruction. | |
8192 | The default value is 8. | |
8193 | ||
bbcb0c05 SB |
8194 | @item max-goto-duplication-insns |
8195 | The maximum number of instructions to duplicate to a block that jumps | |
8196 | to a computed goto. To avoid @math{O(N^2)} behavior in a number of | |
8197 | passes, GCC factors computed gotos early in the compilation process, | |
8198 | and unfactors them as late as possible. Only computed jumps at the | |
8199 | end of a basic blocks with no more than max-goto-duplication-insns are | |
8200 | unfactored. The default value is 8. | |
8201 | ||
1c4c47db JO |
8202 | @item max-delay-slot-insn-search |
8203 | The maximum number of instructions to consider when looking for an | |
8204 | instruction to fill a delay slot. If more than this arbitrary number of | |
8205 | instructions is searched, the time savings from filling the delay slot | |
8206 | will be minimal so stop searching. Increasing values mean more | |
8207 | aggressive optimization, making the compile time increase with probably | |
8208 | small improvement in executable run time. | |
8209 | ||
8210 | @item max-delay-slot-live-search | |
8211 | When trying to fill delay slots, the maximum number of instructions to | |
8212 | consider when searching for a block with valid live register | |
8213 | information. Increasing this arbitrarily chosen value means more | |
8214 | aggressive optimization, increasing the compile time. This parameter | |
8215 | should be removed when the delay slot code is rewritten to maintain the | |
8216 | control-flow graph. | |
33d3b05b MM |
8217 | |
8218 | @item max-gcse-memory | |
8219 | The approximate maximum amount of memory that will be allocated in | |
8220 | order to perform the global common subexpression elimination | |
8221 | optimization. If more memory than specified is required, the | |
8222 | optimization will not be done. | |
3af64fd6 | 8223 | |
4a121cc3 | 8224 | @item max-pending-list-length |
0c688a7d | 8225 | The maximum number of pending dependencies scheduling will allow |
4a121cc3 AM |
8226 | before flushing the current state and starting over. Large functions |
8227 | with few branches or calls can create excessively large lists which | |
8228 | needlessly consume memory and resources. | |
8229 | ||
bc522472 KG |
8230 | @item max-inline-insns-single |
8231 | Several parameters control the tree inliner used in gcc. | |
2dd76960 | 8232 | This number sets the maximum number of instructions (counted in GCC's |
daf2f129 | 8233 | internal representation) in a single function that the tree inliner |
bc522472 KG |
8234 | will consider for inlining. This only affects functions declared |
8235 | inline and methods implemented in a class declaration (C++). | |
125cae84 | 8236 | The default value is 300. |
bc522472 KG |
8237 | |
8238 | @item max-inline-insns-auto | |
8239 | When you use @option{-finline-functions} (included in @option{-O3}), | |
8240 | a lot of functions that would otherwise not be considered for inlining | |
8241 | by the compiler will be investigated. To those functions, a different | |
8242 | (more restrictive) limit compared to functions declared inline can | |
8243 | be applied. | |
7802ca7c | 8244 | The default value is 40. |
bc522472 | 8245 | |
b58b1157 | 8246 | @item large-function-insns |
74515a0a | 8247 | The limit specifying really large functions. For functions larger than this |
d1facce0 | 8248 | limit after inlining, inlining is constrained by |
74515a0a RG |
8249 | @option{--param large-function-growth}. This parameter is useful primarily |
8250 | to avoid extreme compilation time caused by non-linear algorithms used by the | |
8251 | backend. | |
e5c4f28a | 8252 | The default value is 2700. |
b58b1157 JH |
8253 | |
8254 | @item large-function-growth | |
e53e0c56 | 8255 | Specifies maximal growth of large function caused by inlining in percents. |
74515a0a RG |
8256 | The default value is 100 which limits large function growth to 2.0 times |
8257 | the original size. | |
b58b1157 | 8258 | |
b4f32d07 JH |
8259 | @item large-unit-insns |
8260 | The limit specifying large translation unit. Growth caused by inlining of | |
8261 | units larger than this limit is limited by @option{--param inline-unit-growth}. | |
8262 | For small units this might be too tight (consider unit consisting of function A | |
8263 | that is inline and B that just calls A three time. If B is small relative to | |
8264 | A, the growth of unit is 300\% and yet such inlining is very sane. For very | |
a31cfd58 | 8265 | large units consisting of small inlineable functions however the overall unit |
b4f32d07 JH |
8266 | growth limit is needed to avoid exponential explosion of code size. Thus for |
8267 | smaller units, the size is increased to @option{--param large-unit-insns} | |
6416ae7f | 8268 | before applying @option{--param inline-unit-growth}. The default is 10000 |
b4f32d07 | 8269 | |
b58b1157 JH |
8270 | @item inline-unit-growth |
8271 | Specifies maximal overall growth of the compilation unit caused by inlining. | |
d562c668 | 8272 | The default value is 30 which limits unit growth to 1.3 times the original |
74515a0a | 8273 | size. |
b58b1157 | 8274 | |
5e45130d JH |
8275 | @item ipcp-unit-growth |
8276 | Specifies maximal overall growth of the compilation unit caused by | |
8277 | interprocedural constant propagation. The default value is 10 which limits | |
8278 | unit growth to 1.1 times the original size. | |
8279 | ||
ff28a94d JH |
8280 | @item large-stack-frame |
8281 | The limit specifying large stack frames. While inlining the algorithm is trying | |
8282 | to not grow past this limit too much. Default value is 256 bytes. | |
8283 | ||
8284 | @item large-stack-frame-growth | |
8285 | Specifies maximal growth of large stack frames caused by inlining in percents. | |
8286 | The default value is 1000 which limits large stack frame growth to 11 times | |
8287 | the original size. | |
8288 | ||
6de9cd9a DN |
8289 | @item max-inline-insns-recursive |
8290 | @itemx max-inline-insns-recursive-auto | |
8291 | Specifies maximum number of instructions out-of-line copy of self recursive inline | |
8292 | function can grow into by performing recursive inlining. | |
8293 | ||
8294 | For functions declared inline @option{--param max-inline-insns-recursive} is | |
37470119 | 8295 | taken into account. For function not declared inline, recursive inlining |
6de9cd9a DN |
8296 | happens only when @option{-finline-functions} (included in @option{-O3}) is |
8297 | enabled and @option{--param max-inline-insns-recursive-auto} is used. The | |
e5c4f28a | 8298 | default value is 450. |
6de9cd9a DN |
8299 | |
8300 | @item max-inline-recursive-depth | |
8301 | @itemx max-inline-recursive-depth-auto | |
8302 | Specifies maximum recursion depth used by the recursive inlining. | |
8303 | ||
8304 | For functions declared inline @option{--param max-inline-recursive-depth} is | |
37470119 | 8305 | taken into account. For function not declared inline, recursive inlining |
6de9cd9a DN |
8306 | happens only when @option{-finline-functions} (included in @option{-O3}) is |
8307 | enabled and @option{--param max-inline-recursive-depth-auto} is used. The | |
a60b56a4 | 8308 | default value is 8. |
e5c4f28a | 8309 | |
c5a4444c JH |
8310 | @item min-inline-recursive-probability |
8311 | Recursive inlining is profitable only for function having deep recursion | |
8312 | in average and can hurt for function having little recursion depth by | |
8313 | increasing the prologue size or complexity of function body to other | |
8314 | optimizers. | |
8315 | ||
8316 | When profile feedback is available (see @option{-fprofile-generate}) the actual | |
8317 | recursion depth can be guessed from probability that function will recurse via | |
8318 | given call expression. This parameter limits inlining only to call expression | |
8319 | whose probability exceeds given threshold (in percents). The default value is | |
8320 | 10. | |
8321 | ||
125cae84 JH |
8322 | @item early-inlining-insns |
8323 | Specify growth that early inliner can make. In effect it increases amount of | |
211ceaca | 8324 | inlining for code having large abstraction penalty. The default value is 10. |
6de9cd9a | 8325 | |
796bda22 JH |
8326 | @item max-early-inliner-iterations |
8327 | @itemx max-early-inliner-iterations | |
8328 | Limit of iterations of early inliner. This basically bounds number of nested | |
8329 | indirect calls early inliner can resolve. Deeper chains are still handled by | |
8330 | late inlining. | |
8331 | ||
c5d0600d JH |
8332 | @item comdat-sharing-probability |
8333 | @itemx comdat-sharing-probability | |
8334 | Probability (in percent) that C++ inline function with comdat visibility | |
8335 | will be shared acroess multiple compilation units. The default value is 20. | |
8336 | ||
acdc40df | 8337 | @item min-vect-loop-bound |
cb7ad97b EC |
8338 | The minimum number of iterations under which a loop will not get vectorized |
8339 | when @option{-ftree-vectorize} is used. The number of iterations after | |
acdc40df DN |
8340 | vectorization needs to be greater than the value specified by this option |
8341 | to allow vectorization. The default value is 0. | |
8342 | ||
20160347 MK |
8343 | @item gcse-cost-distance-ratio |
8344 | Scaling factor in calculation of maximum distance an expression | |
8345 | can be moved by GCSE optimizations. This is currently supported only in | |
8346 | code hoisting pass. The bigger the ratio, the more agressive code hoisting | |
8347 | will be with simple expressions, i.e., the expressions which have cost | |
8348 | less than @option{gcse-unrestricted-cost}. Specifying 0 will disable | |
8349 | hoisting of simple expressions. The default value is 10. | |
8350 | ||
8351 | @item gcse-unrestricted-cost | |
8352 | Cost, roughly measured as the cost of a single typical machine | |
8353 | instruction, at which GCSE optimizations will not constrain | |
8354 | the distance an expression can travel. This is currently | |
8355 | supported only in code hoisting pass. The lesser the cost, | |
8356 | the more aggressive code hoisting will be. Specifying 0 will | |
8357 | allow all expressions to travel unrestricted distances. | |
8358 | The default value is 3. | |
8359 | ||
cad9aa15 MK |
8360 | @item max-hoist-depth |
8361 | The depth of search in the dominator tree for expressions to hoist. | |
8362 | This is used to avoid quadratic behavior in hoisting algorithm. | |
8363 | The value of 0 will avoid limiting the search, but may slow down compilation | |
8364 | of huge functions. The default value is 30. | |
8365 | ||
03e9dbc9 MM |
8366 | @item max-unrolled-insns |
8367 | The maximum number of instructions that a loop should have if that loop | |
8368 | is unrolled, and if the loop is unrolled, it determines how many times | |
8369 | the loop code is unrolled. | |
8370 | ||
b17d5d7c ZD |
8371 | @item max-average-unrolled-insns |
8372 | The maximum number of instructions biased by probabilities of their execution | |
8373 | that a loop should have if that loop is unrolled, and if the loop is unrolled, | |
8374 | it determines how many times the loop code is unrolled. | |
8375 | ||
8376 | @item max-unroll-times | |
8377 | The maximum number of unrollings of a single loop. | |
8378 | ||
8379 | @item max-peeled-insns | |
8380 | The maximum number of instructions that a loop should have if that loop | |
8381 | is peeled, and if the loop is peeled, it determines how many times | |
8382 | the loop code is peeled. | |
8383 | ||
8384 | @item max-peel-times | |
8385 | The maximum number of peelings of a single loop. | |
8386 | ||
8387 | @item max-completely-peeled-insns | |
8388 | The maximum number of insns of a completely peeled loop. | |
8389 | ||
8390 | @item max-completely-peel-times | |
8391 | The maximum number of iterations of a loop to be suitable for complete peeling. | |
8392 | ||
30bc1dca RG |
8393 | @item max-completely-peel-loop-nest-depth |
8394 | The maximum depth of a loop nest suitable for complete peeling. | |
8395 | ||
01a132bb ZD |
8396 | @item max-unswitch-insns |
8397 | The maximum number of insns of an unswitched loop. | |
8398 | ||
8399 | @item max-unswitch-level | |
8400 | The maximum number of branches unswitched in a single loop. | |
8401 | ||
a7e5372d ZD |
8402 | @item lim-expensive |
8403 | The minimum cost of an expensive expression in the loop invariant motion. | |
8404 | ||
8b11a64c ZD |
8405 | @item iv-consider-all-candidates-bound |
8406 | Bound on number of candidates for induction variables below that | |
8407 | all candidates are considered for each use in induction variable | |
8408 | optimizations. Only the most relevant candidates are considered | |
8409 | if there are more candidates, to avoid quadratic time complexity. | |
8410 | ||
8411 | @item iv-max-considered-uses | |
8412 | The induction variable optimizations give up on loops that contain more | |
8413 | induction variable uses. | |
8414 | ||
36f5ada1 ZD |
8415 | @item iv-always-prune-cand-set-bound |
8416 | If number of candidates in the set is smaller than this value, | |
8417 | we always try to remove unnecessary ivs from the set during its | |
8418 | optimization when a new iv is added to the set. | |
8419 | ||
2412d35c SP |
8420 | @item scev-max-expr-size |
8421 | Bound on size of expressions used in the scalar evolutions analyzer. | |
8422 | Large expressions slow the analyzer. | |
8423 | ||
3d8864c0 SP |
8424 | @item omega-max-vars |
8425 | The maximum number of variables in an Omega constraint system. | |
8426 | The default value is 128. | |
8427 | ||
8428 | @item omega-max-geqs | |
8429 | The maximum number of inequalities in an Omega constraint system. | |
8430 | The default value is 256. | |
8431 | ||
8432 | @item omega-max-eqs | |
8433 | The maximum number of equalities in an Omega constraint system. | |
8434 | The default value is 128. | |
8435 | ||
8436 | @item omega-max-wild-cards | |
8437 | The maximum number of wildcard variables that the Omega solver will | |
8438 | be able to insert. The default value is 18. | |
8439 | ||
8440 | @item omega-hash-table-size | |
8441 | The size of the hash table in the Omega solver. The default value is | |
8442 | 550. | |
8443 | ||
8444 | @item omega-max-keys | |
8445 | The maximal number of keys used by the Omega solver. The default | |
8446 | value is 500. | |
8447 | ||
8448 | @item omega-eliminate-redundant-constraints | |
8449 | When set to 1, use expensive methods to eliminate all redundant | |
8450 | constraints. The default value is 0. | |
8451 | ||
bc1edb77 VK |
8452 | @item vect-max-version-for-alignment-checks |
8453 | The maximum number of runtime checks that can be performed when | |
8454 | doing loop versioning for alignment in the vectorizer. See option | |
8455 | ftree-vect-loop-version for more information. | |
8456 | ||
8457 | @item vect-max-version-for-alias-checks | |
8458 | The maximum number of runtime checks that can be performed when | |
8459 | doing loop versioning for alias in the vectorizer. See option | |
8460 | ftree-vect-loop-version for more information. | |
c12cc930 | 8461 | |
e9eb809d ZD |
8462 | @item max-iterations-to-track |
8463 | ||
8464 | The maximum number of iterations of a loop the brute force algorithm | |
8465 | for analysis of # of iterations of the loop tries to evaluate. | |
8466 | ||
194734e9 JH |
8467 | @item hot-bb-count-fraction |
8468 | Select fraction of the maximal count of repetitions of basic block in program | |
8469 | given basic block needs to have to be considered hot. | |
8470 | ||
8471 | @item hot-bb-frequency-fraction | |
8472 | Select fraction of the maximal frequency of executions of basic block in | |
8473 | function given basic block needs to have to be considered hot | |
5c856b23 | 8474 | |
95b9a3a5 JH |
8475 | @item max-predicted-iterations |
8476 | The maximum number of loop iterations we predict statically. This is useful | |
8477 | in cases where function contain single loop with known bound and other loop | |
8478 | with unknown. We predict the known number of iterations correctly, while | |
c83eecad KH |
8479 | the unknown number of iterations average to roughly 10. This means that the |
8480 | loop without bounds would appear artificially cold relative to the other one. | |
95b9a3a5 | 8481 | |
edbed3d3 JH |
8482 | @item align-threshold |
8483 | ||
8484 | Select fraction of the maximal frequency of executions of basic block in | |
8485 | function given basic block will get aligned. | |
8486 | ||
8487 | @item align-loop-iterations | |
8488 | ||
8489 | A loop expected to iterate at lest the selected number of iterations will get | |
8490 | aligned. | |
8491 | ||
5c856b23 JH |
8492 | @item tracer-dynamic-coverage |
8493 | @itemx tracer-dynamic-coverage-feedback | |
8494 | ||
3364c33b JQ |
8495 | This value is used to limit superblock formation once the given percentage of |
8496 | executed instructions is covered. This limits unnecessary code size | |
8497 | expansion. | |
5c856b23 JH |
8498 | |
8499 | The @option{tracer-dynamic-coverage-feedback} is used only when profile | |
8500 | feedback is available. The real profiles (as opposed to statically estimated | |
8501 | ones) are much less balanced allowing the threshold to be larger value. | |
8502 | ||
8503 | @item tracer-max-code-growth | |
8504 | Stop tail duplication once code growth has reached given percentage. This is | |
3364c33b | 8505 | rather hokey argument, as most of the duplicates will be eliminated later in |
5c856b23 JH |
8506 | cross jumping, so it may be set to much higher values than is the desired code |
8507 | growth. | |
8508 | ||
8509 | @item tracer-min-branch-ratio | |
8510 | ||
8511 | Stop reverse growth when the reverse probability of best edge is less than this | |
8512 | threshold (in percent). | |
8513 | ||
8514 | @item tracer-min-branch-ratio | |
8515 | @itemx tracer-min-branch-ratio-feedback | |
8516 | ||
8517 | Stop forward growth if the best edge do have probability lower than this | |
8518 | threshold. | |
8519 | ||
3364c33b | 8520 | Similarly to @option{tracer-dynamic-coverage} two values are present, one for |
5c856b23 JH |
8521 | compilation for profile feedback and one for compilation without. The value |
8522 | for compilation with profile feedback needs to be more conservative (higher) in | |
8523 | order to make tracer effective. | |
8524 | ||
c48ec590 ZD |
8525 | @item max-cse-path-length |
8526 | ||
8d3b3fb7 | 8527 | Maximum number of basic blocks on path that cse considers. The default is 10. |
c48ec590 | 8528 | |
95b9a3a5 JH |
8529 | @item max-cse-insns |
8530 | The maximum instructions CSE process before flushing. The default is 1000. | |
8531 | ||
3788cc17 ZW |
8532 | @item ggc-min-expand |
8533 | ||
8534 | GCC uses a garbage collector to manage its own memory allocation. This | |
8535 | parameter specifies the minimum percentage by which the garbage | |
8536 | collector's heap should be allowed to expand between collections. | |
8537 | Tuning this may improve compilation speed; it has no effect on code | |
8538 | generation. | |
8539 | ||
9ac121af | 8540 | The default is 30% + 70% * (RAM/1GB) with an upper bound of 100% when |
8a36672b JM |
8541 | RAM >= 1GB@. If @code{getrlimit} is available, the notion of "RAM" is |
8542 | the smallest of actual RAM and @code{RLIMIT_DATA} or @code{RLIMIT_AS}. If | |
16226f1e KG |
8543 | GCC is not able to calculate RAM on a particular platform, the lower |
8544 | bound of 30% is used. Setting this parameter and | |
737c38d1 GK |
8545 | @option{ggc-min-heapsize} to zero causes a full collection to occur at |
8546 | every opportunity. This is extremely slow, but can be useful for | |
8547 | debugging. | |
3788cc17 ZW |
8548 | |
8549 | @item ggc-min-heapsize | |
8550 | ||
8551 | Minimum size of the garbage collector's heap before it begins bothering | |
8552 | to collect garbage. The first collection occurs after the heap expands | |
8553 | by @option{ggc-min-expand}% beyond @option{ggc-min-heapsize}. Again, | |
8554 | tuning this may improve compilation speed, and has no effect on code | |
8555 | generation. | |
8556 | ||
d37e6b50 GK |
8557 | The default is the smaller of RAM/8, RLIMIT_RSS, or a limit which |
8558 | tries to ensure that RLIMIT_DATA or RLIMIT_AS are not exceeded, but | |
8559 | with a lower bound of 4096 (four megabytes) and an upper bound of | |
8560 | 131072 (128 megabytes). If GCC is not able to calculate RAM on a | |
8561 | particular platform, the lower bound is used. Setting this parameter | |
8562 | very large effectively disables garbage collection. Setting this | |
8563 | parameter and @option{ggc-min-expand} to zero causes a full collection | |
8564 | to occur at every opportunity. | |
3788cc17 | 8565 | |
0bcf8261 JH |
8566 | @item max-reload-search-insns |
8567 | The maximum number of instruction reload should look backward for equivalent | |
8568 | register. Increasing values mean more aggressive optimization, making the | |
8569 | compile time increase with probably slightly better performance. The default | |
8570 | value is 100. | |
8571 | ||
60ee1fe3 | 8572 | @item max-cselib-memory-locations |
37470119 | 8573 | The maximum number of memory locations cselib should take into account. |
c65ecebc JH |
8574 | Increasing values mean more aggressive optimization, making the compile time |
8575 | increase with probably slightly better performance. The default value is 500. | |
8576 | ||
26f74aa3 JH |
8577 | @item reorder-blocks-duplicate |
8578 | @itemx reorder-blocks-duplicate-feedback | |
8579 | ||
65d2d764 | 8580 | Used by basic block reordering pass to decide whether to use unconditional |
b222f49a | 8581 | branch or duplicate the code on its destination. Code is duplicated when its |
26f74aa3 | 8582 | estimated size is smaller than this value multiplied by the estimated size of |
65d2d764 | 8583 | unconditional jump in the hot spots of the program. |
26f74aa3 JH |
8584 | |
8585 | The @option{reorder-block-duplicate-feedback} is used only when profile | |
8586 | feedback is available and may be set to higher values than | |
8587 | @option{reorder-block-duplicate} since information about the hot spots is more | |
8588 | accurate. | |
f72c6b56 | 8589 | |
6f8dd94b EB |
8590 | @item max-sched-ready-insns |
8591 | The maximum number of instructions ready to be issued the scheduler should | |
8592 | consider at any given time during the first scheduling pass. Increasing | |
8593 | values mean more thorough searches, making the compilation time increase | |
8594 | with probably little benefit. The default value is 100. | |
8595 | ||
f72c6b56 DE |
8596 | @item max-sched-region-blocks |
8597 | The maximum number of blocks in a region to be considered for | |
8598 | interblock scheduling. The default value is 10. | |
8599 | ||
e855c69d AB |
8600 | @item max-pipeline-region-blocks |
8601 | The maximum number of blocks in a region to be considered for | |
8602 | pipelining in the selective scheduler. The default value is 15. | |
8603 | ||
fbce7685 | 8604 | @item max-sched-region-insns |
f72c6b56 DE |
8605 | The maximum number of insns in a region to be considered for |
8606 | interblock scheduling. The default value is 100. | |
31ebd7c8 | 8607 | |
e855c69d AB |
8608 | @item max-pipeline-region-insns |
8609 | The maximum number of insns in a region to be considered for | |
8610 | pipelining in the selective scheduler. The default value is 200. | |
8611 | ||
36968131 PS |
8612 | @item min-spec-prob |
8613 | The minimum probability (in percents) of reaching a source block | |
8614 | for interblock speculative scheduling. The default value is 40. | |
6f48c21a | 8615 | |
d08eefb9 MK |
8616 | @item max-sched-extend-regions-iters |
8617 | The maximum number of iterations through CFG to extend regions. | |
8618 | 0 - disable region extension, | |
8619 | N - do at most N iterations. | |
bb83aa4b | 8620 | The default value is 0. |
d08eefb9 | 8621 | |
496d7bb0 MK |
8622 | @item max-sched-insn-conflict-delay |
8623 | The maximum conflict delay for an insn to be considered for speculative motion. | |
8624 | The default value is 3. | |
8625 | ||
8626 | @item sched-spec-prob-cutoff | |
8627 | The minimal probability of speculation success (in percents), so that | |
8628 | speculative insn will be scheduled. | |
8629 | The default value is 40. | |
8630 | ||
e855c69d AB |
8631 | @item sched-mem-true-dep-cost |
8632 | Minimal distance (in CPU cycles) between store and load targeting same | |
8633 | memory locations. The default value is 1. | |
8634 | ||
8635 | @item selsched-max-lookahead | |
8636 | The maximum size of the lookahead window of selective scheduling. It is a | |
8637 | depth of search for available instructions. | |
8638 | The default value is 50. | |
49c3b9a8 | 8639 | |
e855c69d | 8640 | @item selsched-max-sched-times |
7a61cf6f NC |
8641 | The maximum number of times that an instruction will be scheduled during |
8642 | selective scheduling. This is the limit on the number of iterations | |
e855c69d AB |
8643 | through which the instruction may be pipelined. The default value is 2. |
8644 | ||
8645 | @item selsched-max-insns-to-rename | |
8646 | The maximum number of best instructions in the ready list that are considered | |
8647 | for renaming in the selective scheduler. The default value is 2. | |
8648 | ||
8649 | @item max-last-value-rtl | |
49c3b9a8 JJ |
8650 | The maximum size measured as number of RTLs that can be recorded in an expression |
8651 | in combiner for a pseudo register as last known value of that register. The default | |
8652 | is 10000. | |
8653 | ||
31ebd7c8 NS |
8654 | @item integer-share-limit |
8655 | Small integer constants can use a shared data structure, reducing the | |
8656 | compiler's memory usage and increasing its speed. This sets the maximum | |
a31cfd58 | 8657 | value of a shared integer constant. The default value is 256. |
31ebd7c8 | 8658 | |
84d65814 DN |
8659 | @item min-virtual-mappings |
8660 | Specifies the minimum number of virtual mappings in the incremental | |
8661 | SSA updater that should be registered to trigger the virtual mappings | |
8662 | heuristic defined by virtual-mappings-ratio. The default value is | |
8663 | 100. | |
8664 | ||
8665 | @item virtual-mappings-ratio | |
8666 | If the number of virtual mappings is virtual-mappings-ratio bigger | |
8667 | than the number of virtual symbols to be updated, then the incremental | |
8668 | SSA updater switches to a full update for those symbols. The default | |
8669 | ratio is 3. | |
8670 | ||
0aca9021 | 8671 | @item ssp-buffer-size |
a31cfd58 | 8672 | The minimum size of buffers (i.e.@: arrays) that will receive stack smashing |
0aca9021 JW |
8673 | protection when @option{-fstack-protection} is used. |
8674 | ||
43f31be5 JL |
8675 | @item max-jump-thread-duplication-stmts |
8676 | Maximum number of statements allowed in a block that needs to be | |
8677 | duplicated when threading jumps. | |
98035a75 DB |
8678 | |
8679 | @item max-fields-for-field-sensitive | |
8680 | Maximum number of fields in a structure we will treat in | |
0e1f4c6b RG |
8681 | a field sensitive manner during pointer analysis. The default is zero |
8682 | for -O0, and -O1 and 100 for -Os, -O2, and -O3. | |
98035a75 | 8683 | |
47eb5b32 ZD |
8684 | @item prefetch-latency |
8685 | Estimate on average number of instructions that are executed before | |
8686 | prefetch finishes. The distance we prefetch ahead is proportional | |
8687 | to this constant. Increasing this number may also lead to less | |
8688 | streams being prefetched (see @option{simultaneous-prefetches}). | |
8689 | ||
8690 | @item simultaneous-prefetches | |
8691 | Maximum number of prefetches that can run at the same time. | |
8692 | ||
8693 | @item l1-cache-line-size | |
8694 | The size of cache line in L1 cache, in bytes. | |
8695 | ||
8696 | @item l1-cache-size | |
46cb0441 ZD |
8697 | The size of L1 cache, in kilobytes. |
8698 | ||
8699 | @item l2-cache-size | |
8700 | The size of L2 cache, in kilobytes. | |
47eb5b32 | 8701 | |
db34470d | 8702 | @item min-insn-to-prefetch-ratio |
7a61cf6f | 8703 | The minimum ratio between the number of instructions and the |
d3a9b459 | 8704 | number of prefetches to enable prefetching in a loop. |
db34470d GS |
8705 | |
8706 | @item prefetch-min-insn-to-mem-ratio | |
7a61cf6f | 8707 | The minimum ratio between the number of instructions and the |
db34470d GS |
8708 | number of memory references to enable prefetching in a loop. |
8709 | ||
7313518b DG |
8710 | @item use-canonical-types |
8711 | Whether the compiler should use the ``canonical'' type system. By | |
8712 | default, this should always be 1, which uses a more efficient internal | |
8713 | mechanism for comparing types in C++ and Objective-C++. However, if | |
8714 | bugs in the canonical type system are causing compilation failures, | |
8715 | set this value to 0 to disable canonical types. | |
06d40de8 | 8716 | |
b6e99746 MJ |
8717 | @item switch-conversion-max-branch-ratio |
8718 | Switch initialization conversion will refuse to create arrays that are | |
b1ae1681 | 8719 | bigger than @option{switch-conversion-max-branch-ratio} times the number of |
b6e99746 MJ |
8720 | branches in the switch. |
8721 | ||
f0ed4cfb NC |
8722 | @item max-partial-antic-length |
8723 | Maximum length of the partial antic set computed during the tree | |
8724 | partial redundancy elimination optimization (@option{-ftree-pre}) when | |
8725 | optimizing at @option{-O3} and above. For some sorts of source code | |
8726 | the enhanced partial redundancy elimination optimization can run away, | |
8727 | consuming all of the memory available on the host machine. This | |
8728 | parameter sets a limit on the length of the sets that are computed, | |
a640c13b KH |
8729 | which prevents the runaway behavior. Setting a value of 0 for |
8730 | this parameter will allow an unlimited set length. | |
f0ed4cfb | 8731 | |
863d2a57 RG |
8732 | @item sccvn-max-scc-size |
8733 | Maximum size of a strongly connected component (SCC) during SCCVN | |
8734 | processing. If this limit is hit, SCCVN processing for the whole | |
8735 | function will not be done and optimizations depending on it will | |
8736 | be disabled. The default maximum SCC size is 10000. | |
8737 | ||
058e97ec VM |
8738 | @item ira-max-loops-num |
8739 | IRA uses a regional register allocation by default. If a function | |
30ea859e VM |
8740 | contains loops more than number given by the parameter, only at most |
8741 | given number of the most frequently executed loops will form regions | |
8742 | for the regional register allocation. The default value of the | |
8743 | parameter is 100. | |
058e97ec | 8744 | |
311aab06 VM |
8745 | @item ira-max-conflict-table-size |
8746 | Although IRA uses a sophisticated algorithm of compression conflict | |
8747 | table, the table can be still big for huge functions. If the conflict | |
8748 | table for a function could be more than size in MB given by the | |
8749 | parameter, the conflict table is not built and faster, simpler, and | |
8750 | lower quality register allocation algorithm will be used. The | |
8751 | algorithm do not use pseudo-register conflicts. The default value of | |
8752 | the parameter is 2000. | |
8753 | ||
1833192f VM |
8754 | @item ira-loop-reserved-regs |
8755 | IRA can be used to evaluate more accurate register pressure in loops | |
8756 | for decision to move loop invariants (see @option{-O3}). The number | |
8757 | of available registers reserved for some other purposes is described | |
8758 | by this parameter. The default value of the parameter is 2 which is | |
8759 | minimal number of registers needed for execution of typical | |
8760 | instruction. This value is the best found from numerous experiments. | |
8761 | ||
b1fb9f56 JJ |
8762 | @item loop-invariant-max-bbs-in-loop |
8763 | Loop invariant motion can be very expensive, both in compile time and | |
8764 | in amount of needed compile time memory, with very large loops. Loops | |
8765 | with more basic blocks than this parameter won't have loop invariant | |
8766 | motion optimization performed on them. The default value of the | |
8767 | parameter is 1000 for -O1 and 10000 for -O2 and above. | |
8768 | ||
ec8c3978 JJ |
8769 | @item max-vartrack-size |
8770 | Sets a maximum number of hash table slots to use during variable | |
8771 | tracking dataflow analysis of any function. If this limit is exceeded | |
8772 | with variable tracking at assignments enabled, analysis for that | |
8773 | function is retried without it, after removing all debug insns from | |
8774 | the function. If the limit is exceeded even without debug insns, var | |
8775 | tracking analysis is completely disabled for the function. Setting | |
8776 | the parameter to zero makes it unlimited. | |
8777 | ||
b5b8b0ac AO |
8778 | @item min-nondebug-insn-uid |
8779 | Use uids starting at this parameter for nondebug insns. The range below | |
8780 | the parameter is reserved exclusively for debug insns created by | |
8781 | @option{-fvar-tracking-assignments}, but debug insns may get | |
8782 | (non-overlapping) uids above it if the reserved range is exhausted. | |
8783 | ||
07ffa034 MJ |
8784 | @item ipa-sra-ptr-growth-factor |
8785 | IPA-SRA will replace a pointer to an aggregate with one or more new | |
8786 | parameters only when their cumulative size is less or equal to | |
8787 | @option{ipa-sra-ptr-growth-factor} times the size of the original | |
8788 | pointer parameter. | |
8789 | ||
4e7dd376 SP |
8790 | @item graphite-max-nb-scop-params |
8791 | To avoid exponential effects in the Graphite loop transforms, the | |
d97c90ae SP |
8792 | number of parameters in a Static Control Part (SCoP) is bounded. The |
8793 | default value is 10 parameters. A variable whose value is unknown at | |
8794 | compile time and defined outside a SCoP is a parameter of the SCoP. | |
4e7dd376 | 8795 | |
b6bb0094 | 8796 | @item graphite-max-bbs-per-function |
d97c90ae SP |
8797 | To avoid exponential effects in the detection of SCoPs, the size of |
8798 | the functions analyzed by Graphite is bounded. The default value is | |
8799 | 100 basic blocks. | |
b6bb0094 | 8800 | |
9d198913 | 8801 | @item loop-block-tile-size |
d97c90ae SP |
8802 | Loop blocking or strip mining transforms, enabled with |
8803 | @option{-floop-block} or @option{-floop-strip-mine}, strip mine each | |
8804 | loop in the loop nest by a given number of iterations. The strip | |
8805 | length can be changed using the @option{loop-block-tile-size} | |
8806 | parameter. The default value is 51 iterations. | |
9d198913 | 8807 | |
3949c4a7 MJ |
8808 | @item devirt-type-list-size |
8809 | IPA-CP attempts to track all possible types passed to a function's | |
8810 | parameter in order to perform devirtualization. | |
8811 | @option{devirt-type-list-size} is the maximum number of types it | |
8812 | stores per a single formal parameter of a function. | |
8813 | ||
852e4bd2 JH |
8814 | @item lto-partitions |
8815 | Specify desired nuber of partitions produced during WHOPR copmilation. | |
8816 | Number of partitions should exceed number of CPUs used for compilatoin. | |
8817 | Default value is 32. | |
8818 | ||
8819 | @item lto-minpartition | |
8820 | Size of minimal paritition for WHOPR (in estimated instructions). | |
8821 | This prevents expenses of splitting very small programs into too many | |
8822 | partitions. | |
8823 | ||
1c4c47db | 8824 | @end table |
74291a4b MM |
8825 | @end table |
8826 | ||
8827 | @node Preprocessor Options | |
8828 | @section Options Controlling the Preprocessor | |
8829 | @cindex preprocessor options | |
8830 | @cindex options, preprocessor | |
8831 | ||
8832 | These options control the C preprocessor, which is run on each C source | |
8833 | file before actual compilation. | |
8834 | ||
630d3d5a JM |
8835 | If you use the @option{-E} option, nothing is done except preprocessing. |
8836 | Some of these options make sense only together with @option{-E} because | |
74291a4b MM |
8837 | they cause the preprocessor output to be unsuitable for actual |
8838 | compilation. | |
8839 | ||
4977bab6 | 8840 | @table @gcctabopt |
98f6c600 | 8841 | @item -Wp,@var{option} |
cd3bb277 | 8842 | @opindex Wp |
40adaa27 NB |
8843 | You can use @option{-Wp,@var{option}} to bypass the compiler driver |
8844 | and pass @var{option} directly through to the preprocessor. If | |
8845 | @var{option} contains commas, it is split into multiple options at the | |
8846 | commas. However, many options are modified, translated or interpreted | |
8847 | by the compiler driver before being passed to the preprocessor, and | |
8848 | @option{-Wp} forcibly bypasses this phase. The preprocessor's direct | |
8849 | interface is undocumented and subject to change, so whenever possible | |
8850 | you should avoid using @option{-Wp} and let the driver handle the | |
8851 | options instead. | |
8852 | ||
4977bab6 | 8853 | @item -Xpreprocessor @var{option} |
98f6c600 | 8854 | @opindex Xpreprocessor |
4977bab6 ZW |
8855 | Pass @var{option} as an option to the preprocessor. You can use this to |
8856 | supply system-specific preprocessor options which GCC does not know how to | |
8857 | recognize. | |
8858 | ||
8859 | If you want to pass an option that takes an argument, you must use | |
8860 | @option{-Xpreprocessor} twice, once for the option and once for the argument. | |
8861 | @end table | |
8862 | ||
40adaa27 | 8863 | @include cppopts.texi |
74291a4b MM |
8864 | |
8865 | @node Assembler Options | |
8866 | @section Passing Options to the Assembler | |
8867 | ||
8868 | @c prevent bad page break with this line | |
8869 | You can pass options to the assembler. | |
8870 | ||
2642624b | 8871 | @table @gcctabopt |
aee96fe9 | 8872 | @item -Wa,@var{option} |
cd3bb277 | 8873 | @opindex Wa |
74291a4b MM |
8874 | Pass @var{option} as an option to the assembler. If @var{option} |
8875 | contains commas, it is split into multiple options at the commas. | |
4977bab6 ZW |
8876 | |
8877 | @item -Xassembler @var{option} | |
8878 | @opindex Xassembler | |
8879 | Pass @var{option} as an option to the assembler. You can use this to | |
8880 | supply system-specific assembler options which GCC does not know how to | |
8881 | recognize. | |
8882 | ||
8883 | If you want to pass an option that takes an argument, you must use | |
8884 | @option{-Xassembler} twice, once for the option and once for the argument. | |
8885 | ||
74291a4b MM |
8886 | @end table |
8887 | ||
8888 | @node Link Options | |
8889 | @section Options for Linking | |
8890 | @cindex link options | |
8891 | @cindex options, linking | |
8892 | ||
8893 | These options come into play when the compiler links object files into | |
8894 | an executable output file. They are meaningless if the compiler is | |
8895 | not doing a link step. | |
8896 | ||
2642624b | 8897 | @table @gcctabopt |
74291a4b MM |
8898 | @cindex file names |
8899 | @item @var{object-file-name} | |
8900 | A file name that does not end in a special recognized suffix is | |
8901 | considered to name an object file or library. (Object files are | |
8902 | distinguished from libraries by the linker according to the file | |
8903 | contents.) If linking is done, these object files are used as input | |
8904 | to the linker. | |
8905 | ||
8906 | @item -c | |
8907 | @itemx -S | |
8908 | @itemx -E | |
cd3bb277 JM |
8909 | @opindex c |
8910 | @opindex S | |
8911 | @opindex E | |
74291a4b MM |
8912 | If any of these options is used, then the linker is not run, and |
8913 | object file names should not be used as arguments. @xref{Overall | |
8914 | Options}. | |
8915 | ||
8916 | @cindex Libraries | |
8917 | @item -l@var{library} | |
4275c4c4 | 8918 | @itemx -l @var{library} |
cd3bb277 | 8919 | @opindex l |
4275c4c4 JS |
8920 | Search the library named @var{library} when linking. (The second |
8921 | alternative with the library as a separate argument is only for | |
8922 | POSIX compliance and is not recommended.) | |
74291a4b MM |
8923 | |
8924 | It makes a difference where in the command you write this option; the | |
4275c4c4 | 8925 | linker searches and processes libraries and object files in the order they |
74291a4b MM |
8926 | are specified. Thus, @samp{foo.o -lz bar.o} searches library @samp{z} |
8927 | after file @file{foo.o} but before @file{bar.o}. If @file{bar.o} refers | |
8928 | to functions in @samp{z}, those functions may not be loaded. | |
8929 | ||
8930 | The linker searches a standard list of directories for the library, | |
8931 | which is actually a file named @file{lib@var{library}.a}. The linker | |
8932 | then uses this file as if it had been specified precisely by name. | |
8933 | ||
8934 | The directories searched include several standard system directories | |
630d3d5a | 8935 | plus any that you specify with @option{-L}. |
74291a4b MM |
8936 | |
8937 | Normally the files found this way are library files---archive files | |
8938 | whose members are object files. The linker handles an archive file by | |
8939 | scanning through it for members which define symbols that have so far | |
8940 | been referenced but not defined. But if the file that is found is an | |
8941 | ordinary object file, it is linked in the usual fashion. The only | |
630d3d5a JM |
8942 | difference between using an @option{-l} option and specifying a file name |
8943 | is that @option{-l} surrounds @var{library} with @samp{lib} and @samp{.a} | |
74291a4b MM |
8944 | and searches several directories. |
8945 | ||
8946 | @item -lobjc | |
cd3bb277 | 8947 | @opindex lobjc |
630d3d5a | 8948 | You need this special case of the @option{-l} option in order to |
46e34f96 | 8949 | link an Objective-C or Objective-C++ program. |
74291a4b MM |
8950 | |
8951 | @item -nostartfiles | |
cd3bb277 | 8952 | @opindex nostartfiles |
74291a4b | 8953 | Do not use the standard system startup files when linking. |
bedc7537 NC |
8954 | The standard system libraries are used normally, unless @option{-nostdlib} |
8955 | or @option{-nodefaultlibs} is used. | |
74291a4b MM |
8956 | |
8957 | @item -nodefaultlibs | |
cd3bb277 | 8958 | @opindex nodefaultlibs |
74291a4b | 8959 | Do not use the standard system libraries when linking. |
5c6927bd RW |
8960 | Only the libraries you specify will be passed to the linker, options |
8961 | specifying linkage of the system libraries, such as @code{-static-libgcc} | |
8962 | or @code{-shared-libgcc}, will be ignored. | |
bedc7537 | 8963 | The standard startup files are used normally, unless @option{-nostartfiles} |
8f99553f JM |
8964 | is used. The compiler may generate calls to @code{memcmp}, |
8965 | @code{memset}, @code{memcpy} and @code{memmove}. | |
8966 | These entries are usually resolved by entries in | |
4754172c CM |
8967 | libc. These entry points should be supplied through some other |
8968 | mechanism when this option is specified. | |
74291a4b MM |
8969 | |
8970 | @item -nostdlib | |
cd3bb277 | 8971 | @opindex nostdlib |
74291a4b MM |
8972 | Do not use the standard system startup files or libraries when linking. |
8973 | No startup files and only the libraries you specify will be passed to | |
5c6927bd RW |
8974 | the linker, options specifying linkage of the system libraries, such as |
8975 | @code{-static-libgcc} or @code{-shared-libgcc}, will be ignored. | |
8976 | The compiler may generate calls to @code{memcmp}, @code{memset}, | |
8f99553f JM |
8977 | @code{memcpy} and @code{memmove}. |
8978 | These entries are usually resolved by entries in | |
4754172c CM |
8979 | libc. These entry points should be supplied through some other |
8980 | mechanism when this option is specified. | |
74291a4b | 8981 | |
630d3d5a JM |
8982 | @cindex @option{-lgcc}, use with @option{-nostdlib} |
8983 | @cindex @option{-nostdlib} and unresolved references | |
8984 | @cindex unresolved references and @option{-nostdlib} | |
8985 | @cindex @option{-lgcc}, use with @option{-nodefaultlibs} | |
8986 | @cindex @option{-nodefaultlibs} and unresolved references | |
8987 | @cindex unresolved references and @option{-nodefaultlibs} | |
8988 | One of the standard libraries bypassed by @option{-nostdlib} and | |
8989 | @option{-nodefaultlibs} is @file{libgcc.a}, a library of internal subroutines | |
0c2d1a2a | 8990 | that GCC uses to overcome shortcomings of particular machines, or special |
74291a4b | 8991 | needs for some languages. |
b11cc610 JM |
8992 | (@xref{Interface,,Interfacing to GCC Output,gccint,GNU Compiler |
8993 | Collection (GCC) Internals}, | |
74291a4b | 8994 | for more discussion of @file{libgcc.a}.) |
74291a4b | 8995 | In most cases, you need @file{libgcc.a} even when you want to avoid |
630d3d5a JM |
8996 | other standard libraries. In other words, when you specify @option{-nostdlib} |
8997 | or @option{-nodefaultlibs} you should usually specify @option{-lgcc} as well. | |
0c2d1a2a | 8998 | This ensures that you have no unresolved references to internal GCC |
74291a4b | 8999 | library subroutines. (For example, @samp{__main}, used to ensure C++ |
b11cc610 JM |
9000 | constructors will be called; @pxref{Collect2,,@code{collect2}, gccint, |
9001 | GNU Compiler Collection (GCC) Internals}.) | |
74291a4b | 9002 | |
24a4dd31 JJ |
9003 | @item -pie |
9004 | @opindex pie | |
9005 | Produce a position independent executable on targets which support it. | |
9006 | For predictable results, you must also specify the same set of options | |
9007 | that were used to generate code (@option{-fpie}, @option{-fPIE}, | |
9008 | or model suboptions) when you specify this option. | |
9009 | ||
0cbc4d77 WB |
9010 | @item -rdynamic |
9011 | @opindex rdynamic | |
9012 | Pass the flag @option{-export-dynamic} to the ELF linker, on targets | |
9013 | that support it. This instructs the linker to add all symbols, not | |
9014 | only used ones, to the dynamic symbol table. This option is needed | |
9015 | for some uses of @code{dlopen} or to allow obtaining backtraces | |
9016 | from within a program. | |
9017 | ||
74291a4b | 9018 | @item -s |
cd3bb277 | 9019 | @opindex s |
74291a4b MM |
9020 | Remove all symbol table and relocation information from the executable. |
9021 | ||
9022 | @item -static | |
cd3bb277 | 9023 | @opindex static |
74291a4b MM |
9024 | On systems that support dynamic linking, this prevents linking with the shared |
9025 | libraries. On other systems, this option has no effect. | |
9026 | ||
9027 | @item -shared | |
cd3bb277 | 9028 | @opindex shared |
74291a4b | 9029 | Produce a shared object which can then be linked with other objects to |
1d3b0e2c | 9030 | form an executable. Not all systems support this option. For predictable |
02f52e19 | 9031 | results, you must also specify the same set of options that were used to |
630d3d5a | 9032 | generate code (@option{-fpic}, @option{-fPIC}, or model suboptions) |
2642624b | 9033 | when you specify this option.@footnote{On some systems, @samp{gcc -shared} |
767094dd | 9034 | needs to build supplementary stub code for constructors to work. On |
2642624b | 9035 | multi-libbed systems, @samp{gcc -shared} must select the correct support |
1d3b0e2c | 9036 | libraries to link against. Failing to supply the correct flags may lead |
767094dd | 9037 | to subtle defects. Supplying them in cases where they are not necessary |
1d3b0e2c | 9038 | is innocuous.} |
74291a4b | 9039 | |
9db0819e RH |
9040 | @item -shared-libgcc |
9041 | @itemx -static-libgcc | |
cd3bb277 JM |
9042 | @opindex shared-libgcc |
9043 | @opindex static-libgcc | |
9db0819e RH |
9044 | On systems that provide @file{libgcc} as a shared library, these options |
9045 | force the use of either the shared or static version respectively. | |
9046 | If no shared version of @file{libgcc} was built when the compiler was | |
9047 | configured, these options have no effect. | |
9048 | ||
9049 | There are several situations in which an application should use the | |
9050 | shared @file{libgcc} instead of the static version. The most common | |
9051 | of these is when the application wishes to throw and catch exceptions | |
9052 | across different shared libraries. In that case, each of the libraries | |
9053 | as well as the application itself should use the shared @file{libgcc}. | |
9054 | ||
5c181756 AO |
9055 | Therefore, the G++ and GCJ drivers automatically add |
9056 | @option{-shared-libgcc} whenever you build a shared library or a main | |
9057 | executable, because C++ and Java programs typically use exceptions, so | |
9058 | this is the right thing to do. | |
9059 | ||
9060 | If, instead, you use the GCC driver to create shared libraries, you may | |
9061 | find that they will not always be linked with the shared @file{libgcc}. | |
d3144423 EB |
9062 | If GCC finds, at its configuration time, that you have a non-GNU linker |
9063 | or a GNU linker that does not support option @option{--eh-frame-hdr}, | |
9064 | it will link the shared version of @file{libgcc} into shared libraries | |
9065 | by default. Otherwise, it will take advantage of the linker and optimize | |
9066 | away the linking with the shared version of @file{libgcc}, linking with | |
9067 | the static version of libgcc by default. This allows exceptions to | |
9068 | propagate through such shared libraries, without incurring relocation | |
9069 | costs at library load time. | |
5c181756 AO |
9070 | |
9071 | However, if a library or main executable is supposed to throw or catch | |
9072 | exceptions, you must link it using the G++ or GCJ driver, as appropriate | |
9073 | for the languages used in the program, or using the option | |
9074 | @option{-shared-libgcc}, such that it is linked with the shared | |
049f6ec9 | 9075 | @file{libgcc}. |
9db0819e | 9076 | |
96be7a11 ILT |
9077 | @item -static-libstdc++ |
9078 | When the @command{g++} program is used to link a C++ program, it will | |
9079 | normally automatically link against @option{libstdc++}. If | |
9080 | @file{libstdc++} is available as a shared library, and the | |
9081 | @option{-static} option is not used, then this will link against the | |
9082 | shared version of @file{libstdc++}. That is normally fine. However, it | |
9083 | is sometimes useful to freeze the version of @file{libstdc++} used by | |
9084 | the program without going all the way to a fully static link. The | |
9085 | @option{-static-libstdc++} option directs the @command{g++} driver to | |
9086 | link @file{libstdc++} statically, without necessarily linking other | |
9087 | libraries statically. | |
9088 | ||
74291a4b | 9089 | @item -symbolic |
cd3bb277 | 9090 | @opindex symbolic |
74291a4b MM |
9091 | Bind references to global symbols when building a shared object. Warn |
9092 | about any unresolved references (unless overridden by the link editor | |
9093 | option @samp{-Xlinker -z -Xlinker defs}). Only a few systems support | |
9094 | this option. | |
9095 | ||
3027350e SL |
9096 | @item -T @var{script} |
9097 | @opindex T | |
9098 | @cindex linker script | |
9099 | Use @var{script} as the linker script. This option is supported by most | |
9100 | systems using the GNU linker. On some targets, such as bare-board | |
7a61cf6f | 9101 | targets without an operating system, the @option{-T} option may be required |
3027350e SL |
9102 | when linking to avoid references to undefined symbols. |
9103 | ||
74291a4b | 9104 | @item -Xlinker @var{option} |
cd3bb277 | 9105 | @opindex Xlinker |
74291a4b | 9106 | Pass @var{option} as an option to the linker. You can use this to |
0c2d1a2a | 9107 | supply system-specific linker options which GCC does not know how to |
74291a4b MM |
9108 | recognize. |
9109 | ||
a2fa6772 | 9110 | If you want to pass an option that takes a separate argument, you must use |
630d3d5a JM |
9111 | @option{-Xlinker} twice, once for the option and once for the argument. |
9112 | For example, to pass @option{-assert definitions}, you must write | |
74291a4b | 9113 | @samp{-Xlinker -assert -Xlinker definitions}. It does not work to write |
630d3d5a | 9114 | @option{-Xlinker "-assert definitions"}, because this passes the entire |
74291a4b MM |
9115 | string as a single argument, which is not what the linker expects. |
9116 | ||
7a61cf6f | 9117 | When using the GNU linker, it is usually more convenient to pass |
a2fa6772 SL |
9118 | arguments to linker options using the @option{@var{option}=@var{value}} |
9119 | syntax than as separate arguments. For example, you can specify | |
9120 | @samp{-Xlinker -Map=output.map} rather than | |
9121 | @samp{-Xlinker -Map -Xlinker output.map}. Other linkers may not support | |
9122 | this syntax for command-line options. | |
9123 | ||
aee96fe9 | 9124 | @item -Wl,@var{option} |
cd3bb277 | 9125 | @opindex Wl |
74291a4b | 9126 | Pass @var{option} as an option to the linker. If @var{option} contains |
a2fa6772 | 9127 | commas, it is split into multiple options at the commas. You can use this |
7a61cf6f | 9128 | syntax to pass an argument to the option. |
a2fa6772 SL |
9129 | For example, @samp{-Wl,-Map,output.map} passes @samp{-Map output.map} to the |
9130 | linker. When using the GNU linker, you can also get the same effect with | |
9131 | @samp{-Wl,-Map=output.map}. | |
74291a4b MM |
9132 | |
9133 | @item -u @var{symbol} | |
cd3bb277 | 9134 | @opindex u |
74291a4b | 9135 | Pretend the symbol @var{symbol} is undefined, to force linking of |
630d3d5a | 9136 | library modules to define it. You can use @option{-u} multiple times with |
74291a4b MM |
9137 | different symbols to force loading of additional library modules. |
9138 | @end table | |
9139 | ||
9140 | @node Directory Options | |
9141 | @section Options for Directory Search | |
9142 | @cindex directory options | |
9143 | @cindex options, directory search | |
9144 | @cindex search path | |
9145 | ||
9146 | These options specify directories to search for header files, for | |
9147 | libraries and for parts of the compiler: | |
9148 | ||
2642624b | 9149 | @table @gcctabopt |
74291a4b | 9150 | @item -I@var{dir} |
cd3bb277 | 9151 | @opindex I |
861bb6c1 JL |
9152 | Add the directory @var{dir} to the head of the list of directories to be |
9153 | searched for header files. This can be used to override a system header | |
9154 | file, substituting your own version, since these directories are | |
d0a5eb32 RK |
9155 | searched before the system header file directories. However, you should |
9156 | not use this option to add directories that contain vendor-supplied | |
767094dd | 9157 | system header files (use @option{-isystem} for that). If you use more than |
630d3d5a | 9158 | one @option{-I} option, the directories are scanned in left-to-right |
74291a4b MM |
9159 | order; the standard system directories come after. |
9160 | ||
dbead49c | 9161 | If a standard system include directory, or a directory specified with |
48209ce5 JDA |
9162 | @option{-isystem}, is also specified with @option{-I}, the @option{-I} |
9163 | option will be ignored. The directory will still be searched but as a | |
9164 | system directory at its normal position in the system include chain. | |
9165 | This is to ensure that GCC's procedure to fix buggy system headers and | |
3364c33b | 9166 | the ordering for the include_next directive are not inadvertently changed. |
48209ce5 JDA |
9167 | If you really need to change the search order for system directories, |
9168 | use the @option{-nostdinc} and/or @option{-isystem} options. | |
dbead49c | 9169 | |
4adbd5dd MK |
9170 | @item -iplugindir=@var{dir} |
9171 | Set the directory to search for plugins which are passed | |
9172 | by @option{-fplugin=@var{name}} instead of | |
9173 | @option{-fplugin=@var{path}/@var{name}.so}. This option is not meant | |
9174 | to be used by the user, but only passed by the driver. | |
9175 | ||
4bed3787 MS |
9176 | @item -iquote@var{dir} |
9177 | @opindex iquote | |
9178 | Add the directory @var{dir} to the head of the list of directories to | |
9179 | be searched for header files only for the case of @samp{#include | |
9180 | "@var{file}"}; they are not searched for @samp{#include <@var{file}>}, | |
9181 | otherwise just like @option{-I}. | |
74291a4b MM |
9182 | |
9183 | @item -L@var{dir} | |
cd3bb277 | 9184 | @opindex L |
74291a4b | 9185 | Add directory @var{dir} to the list of directories to be searched |
630d3d5a | 9186 | for @option{-l}. |
74291a4b MM |
9187 | |
9188 | @item -B@var{prefix} | |
cd3bb277 | 9189 | @opindex B |
74291a4b MM |
9190 | This option specifies where to find the executables, libraries, |
9191 | include files, and data files of the compiler itself. | |
9192 | ||
9193 | The compiler driver program runs one or more of the subprograms | |
9194 | @file{cpp}, @file{cc1}, @file{as} and @file{ld}. It tries | |
9195 | @var{prefix} as a prefix for each program it tries to run, both with and | |
9196 | without @samp{@var{machine}/@var{version}/} (@pxref{Target Options}). | |
9197 | ||
9198 | For each subprogram to be run, the compiler driver first tries the | |
630d3d5a | 9199 | @option{-B} prefix, if any. If that name is not found, or if @option{-B} |
74291a4b | 9200 | was not specified, the driver tries two standard prefixes, which are |
8e5f33ff | 9201 | @file{/usr/lib/gcc/} and @file{/usr/local/lib/gcc/}. If neither of |
74291a4b MM |
9202 | those results in a file name that is found, the unmodified program |
9203 | name is searched for using the directories specified in your | |
bedc7537 | 9204 | @env{PATH} environment variable. |
74291a4b | 9205 | |
07804c3b NC |
9206 | The compiler will check to see if the path provided by the @option{-B} |
9207 | refers to a directory, and if necessary it will add a directory | |
9208 | separator character at the end of the path. | |
9209 | ||
630d3d5a | 9210 | @option{-B} prefixes that effectively specify directory names also apply |
74291a4b | 9211 | to libraries in the linker, because the compiler translates these |
630d3d5a | 9212 | options into @option{-L} options for the linker. They also apply to |
74291a4b | 9213 | includes files in the preprocessor, because the compiler translates these |
630d3d5a | 9214 | options into @option{-isystem} options for the preprocessor. In this case, |
74291a4b MM |
9215 | the compiler appends @samp{include} to the prefix. |
9216 | ||
9217 | The run-time support file @file{libgcc.a} can also be searched for using | |
630d3d5a | 9218 | the @option{-B} prefix, if needed. If it is not found there, the two |
74291a4b MM |
9219 | standard prefixes above are tried, and that is all. The file is left |
9220 | out of the link if it is not found by those means. | |
9221 | ||
630d3d5a | 9222 | Another way to specify a prefix much like the @option{-B} prefix is to use |
bedc7537 | 9223 | the environment variable @env{GCC_EXEC_PREFIX}. @xref{Environment |
74291a4b | 9224 | Variables}. |
861bb6c1 | 9225 | |
07804c3b | 9226 | As a special kludge, if the path provided by @option{-B} is |
bf4eebe0 NC |
9227 | @file{[dir/]stage@var{N}/}, where @var{N} is a number in the range 0 to |
9228 | 9, then it will be replaced by @file{[dir/]include}. This is to help | |
7dac2f89 | 9229 | with boot-strapping the compiler. |
07804c3b | 9230 | |
861bb6c1 | 9231 | @item -specs=@var{file} |
cd3bb277 | 9232 | @opindex specs |
861bb6c1 JL |
9233 | Process @var{file} after the compiler reads in the standard @file{specs} |
9234 | file, in order to override the defaults that the @file{gcc} driver | |
9235 | program uses when determining what switches to pass to @file{cc1}, | |
9236 | @file{cc1plus}, @file{as}, @file{ld}, etc. More than one | |
630d3d5a | 9237 | @option{-specs=@var{file}} can be specified on the command line, and they |
861bb6c1 | 9238 | are processed in order, from left to right. |
4bed3787 | 9239 | |
160633c6 MM |
9240 | @item --sysroot=@var{dir} |
9241 | @opindex sysroot | |
9242 | Use @var{dir} as the logical root directory for headers and libraries. | |
9243 | For example, if the compiler would normally search for headers in | |
9244 | @file{/usr/include} and libraries in @file{/usr/lib}, it will instead | |
cb7ad97b | 9245 | search @file{@var{dir}/usr/include} and @file{@var{dir}/usr/lib}. |
160633c6 MM |
9246 | |
9247 | If you use both this option and the @option{-isysroot} option, then | |
9248 | the @option{--sysroot} option will apply to libraries, but the | |
9249 | @option{-isysroot} option will apply to header files. | |
9250 | ||
9251 | The GNU linker (beginning with version 2.16) has the necessary support | |
9252 | for this option. If your linker does not support this option, the | |
9253 | header file aspect of @option{--sysroot} will still work, but the | |
9254 | library aspect will not. | |
9255 | ||
4bed3787 MS |
9256 | @item -I- |
9257 | @opindex I- | |
9258 | This option has been deprecated. Please use @option{-iquote} instead for | |
9259 | @option{-I} directories before the @option{-I-} and remove the @option{-I-}. | |
9260 | Any directories you specify with @option{-I} options before the @option{-I-} | |
9261 | option are searched only for the case of @samp{#include "@var{file}"}; | |
9262 | they are not searched for @samp{#include <@var{file}>}. | |
9263 | ||
9264 | If additional directories are specified with @option{-I} options after | |
9265 | the @option{-I-}, these directories are searched for all @samp{#include} | |
9266 | directives. (Ordinarily @emph{all} @option{-I} directories are used | |
9267 | this way.) | |
9268 | ||
9269 | In addition, the @option{-I-} option inhibits the use of the current | |
9270 | directory (where the current input file came from) as the first search | |
9271 | directory for @samp{#include "@var{file}"}. There is no way to | |
9272 | override this effect of @option{-I-}. With @option{-I.} you can specify | |
9273 | searching the directory which was current when the compiler was | |
9274 | invoked. That is not exactly the same as what the preprocessor does | |
9275 | by default, but it is often satisfactory. | |
9276 | ||
9277 | @option{-I-} does not inhibit the use of the standard system directories | |
9278 | for header files. Thus, @option{-I-} and @option{-nostdinc} are | |
9279 | independent. | |
74291a4b MM |
9280 | @end table |
9281 | ||
ee457005 JM |
9282 | @c man end |
9283 | ||
a743d340 NC |
9284 | @node Spec Files |
9285 | @section Specifying subprocesses and the switches to pass to them | |
9286 | @cindex Spec Files | |
d2d42a91 | 9287 | |
bedc7537 | 9288 | @command{gcc} is a driver program. It performs its job by invoking a |
a743d340 NC |
9289 | sequence of other programs to do the work of compiling, assembling and |
9290 | linking. GCC interprets its command-line parameters and uses these to | |
9291 | deduce which programs it should invoke, and which command-line options | |
c21cd8b1 | 9292 | it ought to place on their command lines. This behavior is controlled |
a743d340 NC |
9293 | by @dfn{spec strings}. In most cases there is one spec string for each |
9294 | program that GCC can invoke, but a few programs have multiple spec | |
c21cd8b1 | 9295 | strings to control their behavior. The spec strings built into GCC can |
630d3d5a | 9296 | be overridden by using the @option{-specs=} command-line switch to specify |
a743d340 NC |
9297 | a spec file. |
9298 | ||
9299 | @dfn{Spec files} are plaintext files that are used to construct spec | |
9300 | strings. They consist of a sequence of directives separated by blank | |
9301 | lines. The type of directive is determined by the first non-whitespace | |
9302 | character on the line and it can be one of the following: | |
9303 | ||
9304 | @table @code | |
9305 | @item %@var{command} | |
9306 | Issues a @var{command} to the spec file processor. The commands that can | |
02f52e19 | 9307 | appear here are: |
a743d340 NC |
9308 | |
9309 | @table @code | |
9310 | @item %include <@var{file}> | |
ab940b73 | 9311 | @cindex @code{%include} |
a743d340 NC |
9312 | Search for @var{file} and insert its text at the current point in the |
9313 | specs file. | |
9314 | ||
9315 | @item %include_noerr <@var{file}> | |
ab940b73 | 9316 | @cindex @code{%include_noerr} |
a743d340 NC |
9317 | Just like @samp{%include}, but do not generate an error message if the include |
9318 | file cannot be found. | |
9319 | ||
9320 | @item %rename @var{old_name} @var{new_name} | |
ab940b73 | 9321 | @cindex @code{%rename} |
a743d340 NC |
9322 | Rename the spec string @var{old_name} to @var{new_name}. |
9323 | ||
9324 | @end table | |
9325 | ||
9326 | @item *[@var{spec_name}]: | |
9327 | This tells the compiler to create, override or delete the named spec | |
9328 | string. All lines after this directive up to the next directive or | |
9329 | blank line are considered to be the text for the spec string. If this | |
9330 | results in an empty string then the spec will be deleted. (Or, if the | |
9331 | spec did not exist, then nothing will happened.) Otherwise, if the spec | |
9332 | does not currently exist a new spec will be created. If the spec does | |
9333 | exist then its contents will be overridden by the text of this | |
9334 | directive, unless the first character of that text is the @samp{+} | |
9335 | character, in which case the text will be appended to the spec. | |
9336 | ||
9337 | @item [@var{suffix}]: | |
9338 | Creates a new @samp{[@var{suffix}] spec} pair. All lines after this directive | |
9339 | and up to the next directive or blank line are considered to make up the | |
02f52e19 | 9340 | spec string for the indicated suffix. When the compiler encounters an |
a743d340 NC |
9341 | input file with the named suffix, it will processes the spec string in |
9342 | order to work out how to compile that file. For example: | |
9343 | ||
9344 | @smallexample | |
9345 | .ZZ: | |
9346 | z-compile -input %i | |
9347 | @end smallexample | |
9348 | ||
9349 | This says that any input file whose name ends in @samp{.ZZ} should be | |
9350 | passed to the program @samp{z-compile}, which should be invoked with the | |
630d3d5a | 9351 | command-line switch @option{-input} and with the result of performing the |
a743d340 NC |
9352 | @samp{%i} substitution. (See below.) |
9353 | ||
9354 | As an alternative to providing a spec string, the text that follows a | |
9355 | suffix directive can be one of the following: | |
9356 | ||
9357 | @table @code | |
9358 | @item @@@var{language} | |
9359 | This says that the suffix is an alias for a known @var{language}. This is | |
bedc7537 | 9360 | similar to using the @option{-x} command-line switch to GCC to specify a |
a743d340 NC |
9361 | language explicitly. For example: |
9362 | ||
9363 | @smallexample | |
9364 | .ZZ: | |
9365 | @@c++ | |
9366 | @end smallexample | |
9367 | ||
9368 | Says that .ZZ files are, in fact, C++ source files. | |
9369 | ||
9370 | @item #@var{name} | |
9371 | This causes an error messages saying: | |
9372 | ||
9373 | @smallexample | |
9374 | @var{name} compiler not installed on this system. | |
9375 | @end smallexample | |
9376 | @end table | |
9377 | ||
9378 | GCC already has an extensive list of suffixes built into it. | |
9379 | This directive will add an entry to the end of the list of suffixes, but | |
9380 | since the list is searched from the end backwards, it is effectively | |
9381 | possible to override earlier entries using this technique. | |
9382 | ||
9383 | @end table | |
9384 | ||
9385 | GCC has the following spec strings built into it. Spec files can | |
9386 | override these strings or create their own. Note that individual | |
02f52e19 | 9387 | targets can also add their own spec strings to this list. |
a743d340 NC |
9388 | |
9389 | @smallexample | |
9390 | asm Options to pass to the assembler | |
9391 | asm_final Options to pass to the assembler post-processor | |
9392 | cpp Options to pass to the C preprocessor | |
9393 | cc1 Options to pass to the C compiler | |
9394 | cc1plus Options to pass to the C++ compiler | |
9395 | endfile Object files to include at the end of the link | |
9396 | link Options to pass to the linker | |
9397 | lib Libraries to include on the command line to the linker | |
9398 | libgcc Decides which GCC support library to pass to the linker | |
9399 | linker Sets the name of the linker | |
9400 | predefines Defines to be passed to the C preprocessor | |
310668e8 JM |
9401 | signed_char Defines to pass to CPP to say whether @code{char} is signed |
9402 | by default | |
a743d340 NC |
9403 | startfile Object files to include at the start of the link |
9404 | @end smallexample | |
9405 | ||
9406 | Here is a small example of a spec file: | |
9407 | ||
9408 | @smallexample | |
9409 | %rename lib old_lib | |
9410 | ||
9411 | *lib: | |
9412 | --start-group -lgcc -lc -leval1 --end-group %(old_lib) | |
9413 | @end smallexample | |
9414 | ||
9415 | This example renames the spec called @samp{lib} to @samp{old_lib} and | |
9416 | then overrides the previous definition of @samp{lib} with a new one. | |
9417 | The new definition adds in some extra command-line options before | |
9418 | including the text of the old definition. | |
9419 | ||
9420 | @dfn{Spec strings} are a list of command-line options to be passed to their | |
9421 | corresponding program. In addition, the spec strings can contain | |
9422 | @samp{%}-prefixed sequences to substitute variable text or to | |
9423 | conditionally insert text into the command line. Using these constructs | |
9424 | it is possible to generate quite complex command lines. | |
9425 | ||
9426 | Here is a table of all defined @samp{%}-sequences for spec | |
9427 | strings. Note that spaces are not generated automatically around the | |
9428 | results of expanding these sequences. Therefore you can concatenate them | |
02f52e19 | 9429 | together or combine them with constant text in a single argument. |
a743d340 NC |
9430 | |
9431 | @table @code | |
9432 | @item %% | |
9433 | Substitute one @samp{%} into the program name or argument. | |
9434 | ||
9435 | @item %i | |
9436 | Substitute the name of the input file being processed. | |
9437 | ||
9438 | @item %b | |
9439 | Substitute the basename of the input file being processed. | |
9440 | This is the substring up to (and not including) the last period | |
9441 | and not including the directory. | |
9442 | ||
371e300b NC |
9443 | @item %B |
9444 | This is the same as @samp{%b}, but include the file suffix (text after | |
9445 | the last period). | |
9446 | ||
a743d340 NC |
9447 | @item %d |
9448 | Marks the argument containing or following the @samp{%d} as a | |
9449 | temporary file name, so that that file will be deleted if GCC exits | |
9450 | successfully. Unlike @samp{%g}, this contributes no text to the | |
02f52e19 | 9451 | argument. |
a743d340 NC |
9452 | |
9453 | @item %g@var{suffix} | |
9454 | Substitute a file name that has suffix @var{suffix} and is chosen | |
9455 | once per compilation, and mark the argument in the same way as | |
9456 | @samp{%d}. To reduce exposure to denial-of-service attacks, the file | |
02f52e19 | 9457 | name is now chosen in a way that is hard to predict even when previously |
695ac33f | 9458 | chosen file names are known. For example, @samp{%g.s @dots{} %g.o @dots{} %g.s} |
a743d340 NC |
9459 | might turn into @samp{ccUVUUAU.s ccXYAXZ12.o ccUVUUAU.s}. @var{suffix} matches |
9460 | the regexp @samp{[.A-Za-z]*} or the special string @samp{%O}, which is | |
9461 | treated exactly as if @samp{%O} had been preprocessed. Previously, @samp{%g} | |
9462 | was simply substituted with a file name chosen once per compilation, | |
9463 | without regard to any appended suffix (which was therefore treated | |
9464 | just like ordinary text), making such attacks more likely to succeed. | |
9465 | ||
9466 | @item %u@var{suffix} | |
9467 | Like @samp{%g}, but generates a new temporary file name even if | |
9468 | @samp{%u@var{suffix}} was already seen. | |
9469 | ||
9470 | @item %U@var{suffix} | |
9471 | Substitutes the last file name generated with @samp{%u@var{suffix}}, generating a | |
9472 | new one if there is no such last file name. In the absence of any | |
9473 | @samp{%u@var{suffix}}, this is just like @samp{%g@var{suffix}}, except they don't share | |
695ac33f | 9474 | the same suffix @emph{space}, so @samp{%g.s @dots{} %U.s @dots{} %g.s @dots{} %U.s} |
a743d340 NC |
9475 | would involve the generation of two distinct file names, one |
9476 | for each @samp{%g.s} and another for each @samp{%U.s}. Previously, @samp{%U} was | |
9477 | simply substituted with a file name chosen for the previous @samp{%u}, | |
9478 | without regard to any appended suffix. | |
9479 | ||
4977bab6 | 9480 | @item %j@var{suffix} |
aee96fe9 | 9481 | Substitutes the name of the @code{HOST_BIT_BUCKET}, if any, and if it is |
371e300b NC |
9482 | writable, and if save-temps is off; otherwise, substitute the name |
9483 | of a temporary file, just like @samp{%u}. This temporary file is not | |
9484 | meant for communication between processes, but rather as a junk | |
9485 | disposal mechanism. | |
9486 | ||
4977bab6 ZW |
9487 | @item %|@var{suffix} |
9488 | @itemx %m@var{suffix} | |
9489 | Like @samp{%g}, except if @option{-pipe} is in effect. In that case | |
9490 | @samp{%|} substitutes a single dash and @samp{%m} substitutes nothing at | |
9491 | all. These are the two most common ways to instruct a program that it | |
9492 | should read from standard input or write to standard output. If you | |
9493 | need something more elaborate you can use an @samp{%@{pipe:@code{X}@}} | |
9494 | construct: see for example @file{f/lang-specs.h}. | |
9495 | ||
371e300b NC |
9496 | @item %.@var{SUFFIX} |
9497 | Substitutes @var{.SUFFIX} for the suffixes of a matched switch's args | |
767094dd | 9498 | when it is subsequently output with @samp{%*}. @var{SUFFIX} is |
371e300b NC |
9499 | terminated by the next space or %. |
9500 | ||
a743d340 NC |
9501 | @item %w |
9502 | Marks the argument containing or following the @samp{%w} as the | |
9503 | designated output file of this compilation. This puts the argument | |
9504 | into the sequence of arguments that @samp{%o} will substitute later. | |
9505 | ||
9506 | @item %o | |
9507 | Substitutes the names of all the output files, with spaces | |
9508 | automatically placed around them. You should write spaces | |
9509 | around the @samp{%o} as well or the results are undefined. | |
9510 | @samp{%o} is for use in the specs for running the linker. | |
9511 | Input files whose names have no recognized suffix are not compiled | |
9512 | at all, but they are included among the output files, so they will | |
9513 | be linked. | |
9514 | ||
9515 | @item %O | |
9516 | Substitutes the suffix for object files. Note that this is | |
9517 | handled specially when it immediately follows @samp{%g, %u, or %U}, | |
9518 | because of the need for those to form complete file names. The | |
9519 | handling is such that @samp{%O} is treated exactly as if it had already | |
9520 | been substituted, except that @samp{%g, %u, and %U} do not currently | |
9521 | support additional @var{suffix} characters following @samp{%O} as they would | |
9522 | following, for example, @samp{.o}. | |
9523 | ||
9524 | @item %p | |
9525 | Substitutes the standard macro predefinitions for the | |
9526 | current target machine. Use this when running @code{cpp}. | |
9527 | ||
9528 | @item %P | |
9529 | Like @samp{%p}, but puts @samp{__} before and after the name of each | |
9530 | predefined macro, except for macros that start with @samp{__} or with | |
c1030c7c | 9531 | @samp{_@var{L}}, where @var{L} is an uppercase letter. This is for ISO |
161d7b59 | 9532 | C@. |
a743d340 NC |
9533 | |
9534 | @item %I | |
047d636f | 9535 | Substitute any of @option{-iprefix} (made from @env{GCC_EXEC_PREFIX}), |
2b6dd222 | 9536 | @option{-isysroot} (made from @env{TARGET_SYSTEM_ROOT}), |
047d636f | 9537 | @option{-isystem} (made from @env{COMPILER_PATH} and @option{-B} options) |
2b6dd222 | 9538 | and @option{-imultilib} as necessary. |
a743d340 NC |
9539 | |
9540 | @item %s | |
9541 | Current argument is the name of a library or startup file of some sort. | |
9542 | Search for that file in a standard list of directories and substitute | |
3beb864c NC |
9543 | the full name found. The current working directory is included in the |
9544 | list of directories scanned. | |
9545 | ||
9546 | @item %T | |
9547 | Current argument is the name of a linker script. Search for that file | |
9548 | in the current list of directories to scan for libraries. If the file | |
9549 | is located insert a @option{--script} option into the command line | |
9550 | followed by the full path name found. If the file is not found then | |
9551 | generate an error message. Note: the current working directory is not | |
9552 | searched. | |
a743d340 NC |
9553 | |
9554 | @item %e@var{str} | |
9555 | Print @var{str} as an error message. @var{str} is terminated by a newline. | |
9556 | Use this when inconsistent options are detected. | |
9557 | ||
a743d340 NC |
9558 | @item %(@var{name}) |
9559 | Substitute the contents of spec string @var{name} at this point. | |
9560 | ||
9561 | @item %[@var{name}] | |
630d3d5a | 9562 | Like @samp{%(@dots{})} but put @samp{__} around @option{-D} arguments. |
a743d340 NC |
9563 | |
9564 | @item %x@{@var{option}@} | |
9565 | Accumulate an option for @samp{%X}. | |
9566 | ||
9567 | @item %X | |
630d3d5a | 9568 | Output the accumulated linker options specified by @option{-Wl} or a @samp{%x} |
a743d340 NC |
9569 | spec string. |
9570 | ||
9571 | @item %Y | |
630d3d5a | 9572 | Output the accumulated assembler options specified by @option{-Wa}. |
a743d340 NC |
9573 | |
9574 | @item %Z | |
630d3d5a | 9575 | Output the accumulated preprocessor options specified by @option{-Wp}. |
a743d340 | 9576 | |
a743d340 NC |
9577 | @item %a |
9578 | Process the @code{asm} spec. This is used to compute the | |
9579 | switches to be passed to the assembler. | |
9580 | ||
9581 | @item %A | |
9582 | Process the @code{asm_final} spec. This is a spec string for | |
9583 | passing switches to an assembler post-processor, if such a program is | |
9584 | needed. | |
9585 | ||
9586 | @item %l | |
9587 | Process the @code{link} spec. This is the spec for computing the | |
9588 | command line passed to the linker. Typically it will make use of the | |
9589 | @samp{%L %G %S %D and %E} sequences. | |
9590 | ||
9591 | @item %D | |
630d3d5a | 9592 | Dump out a @option{-L} option for each directory that GCC believes might |
a743d340 | 9593 | contain startup files. If the target supports multilibs then the |
02f52e19 | 9594 | current multilib directory will be prepended to each of these paths. |
a743d340 NC |
9595 | |
9596 | @item %L | |
9597 | Process the @code{lib} spec. This is a spec string for deciding which | |
02f52e19 | 9598 | libraries should be included on the command line to the linker. |
a743d340 NC |
9599 | |
9600 | @item %G | |
9601 | Process the @code{libgcc} spec. This is a spec string for deciding | |
02f52e19 | 9602 | which GCC support library should be included on the command line to the linker. |
a743d340 NC |
9603 | |
9604 | @item %S | |
9605 | Process the @code{startfile} spec. This is a spec for deciding which | |
9606 | object files should be the first ones passed to the linker. Typically | |
02f52e19 | 9607 | this might be a file named @file{crt0.o}. |
a743d340 NC |
9608 | |
9609 | @item %E | |
9610 | Process the @code{endfile} spec. This is a spec string that specifies | |
02f52e19 | 9611 | the last object files that will be passed to the linker. |
a743d340 NC |
9612 | |
9613 | @item %C | |
9614 | Process the @code{cpp} spec. This is used to construct the arguments | |
9615 | to be passed to the C preprocessor. | |
9616 | ||
a743d340 NC |
9617 | @item %1 |
9618 | Process the @code{cc1} spec. This is used to construct the options to be | |
9619 | passed to the actual C compiler (@samp{cc1}). | |
9620 | ||
9621 | @item %2 | |
9622 | Process the @code{cc1plus} spec. This is used to construct the options to be | |
9623 | passed to the actual C++ compiler (@samp{cc1plus}). | |
9624 | ||
9625 | @item %* | |
9626 | Substitute the variable part of a matched option. See below. | |
9627 | Note that each comma in the substituted string is replaced by | |
9628 | a single space. | |
9629 | ||
4977bab6 ZW |
9630 | @item %<@code{S} |
9631 | Remove all occurrences of @code{-S} from the command line. Note---this | |
9632 | command is position dependent. @samp{%} commands in the spec string | |
9633 | before this one will see @code{-S}, @samp{%} commands in the spec string | |
9634 | after this one will not. | |
9635 | ||
f3226a90 JT |
9636 | @item %:@var{function}(@var{args}) |
9637 | Call the named function @var{function}, passing it @var{args}. | |
9638 | @var{args} is first processed as a nested spec string, then split | |
9639 | into an argument vector in the usual fashion. The function returns | |
9640 | a string which is processed as if it had appeared literally as part | |
9641 | of the current spec. | |
9642 | ||
9643 | The following built-in spec functions are provided: | |
9644 | ||
9645 | @table @code | |
03d12b64 MM |
9646 | @item @code{getenv} |
9647 | The @code{getenv} spec function takes two arguments: an environment | |
9648 | variable name and a string. If the environment variable is not | |
9649 | defined, a fatal error is issued. Otherwise, the return value is the | |
9650 | value of the environment variable concatenated with the string. For | |
9651 | example, if @env{TOPDIR} is defined as @file{/path/to/top}, then: | |
9652 | ||
9653 | @smallexample | |
9654 | %:getenv(TOPDIR /include) | |
9655 | @end smallexample | |
9656 | ||
9657 | expands to @file{/path/to/top/include}. | |
9658 | ||
f3226a90 JT |
9659 | @item @code{if-exists} |
9660 | The @code{if-exists} spec function takes one argument, an absolute | |
9661 | pathname to a file. If the file exists, @code{if-exists} returns the | |
9662 | pathname. Here is a small example of its usage: | |
9663 | ||
9664 | @smallexample | |
9665 | *startfile: | |
9666 | crt0%O%s %:if-exists(crti%O%s) crtbegin%O%s | |
9667 | @end smallexample | |
152a5a9c JT |
9668 | |
9669 | @item @code{if-exists-else} | |
9670 | The @code{if-exists-else} spec function is similar to the @code{if-exists} | |
9671 | spec function, except that it takes two arguments. The first argument is | |
9672 | an absolute pathname to a file. If the file exists, @code{if-exists-else} | |
9673 | returns the pathname. If it does not exist, it returns the second argument. | |
9674 | This way, @code{if-exists-else} can be used to select one file or another, | |
9675 | based on the existence of the first. Here is a small example of its usage: | |
9676 | ||
daf2f129 | 9677 | @smallexample |
152a5a9c | 9678 | *startfile: |
f5034c5e JM |
9679 | crt0%O%s %:if-exists(crti%O%s) \ |
9680 | %:if-exists-else(crtbeginT%O%s crtbegin%O%s) | |
152a5a9c | 9681 | @end smallexample |
3dd53121 AP |
9682 | |
9683 | @item @code{replace-outfile} | |
9684 | The @code{replace-outfile} spec function takes two arguments. It looks for the | |
9685 | first argument in the outfiles array and replaces it with the second argument. Here | |
9686 | is a small example of its usage: | |
9687 | ||
9688 | @smallexample | |
9689 | %@{fgnu-runtime:%:replace-outfile(-lobjc -lobjc-gnu)@} | |
9690 | @end smallexample | |
9691 | ||
2642f659 JH |
9692 | @item @code{remove-outfile} |
9693 | The @code{remove-outfile} spec function takes one argument. It looks for the | |
9694 | first argument in the outfiles array and removes it. Here is a small example | |
9695 | its usage: | |
9696 | ||
9697 | @smallexample | |
9698 | %:remove-outfile(-lm) | |
9699 | @end smallexample | |
9700 | ||
9a37bc07 DK |
9701 | @item @code{pass-through-libs} |
9702 | The @code{pass-through-libs} spec function takes any number of arguments. It | |
9703 | finds any @option{-l} options and any non-options ending in ".a" (which it | |
9704 | assumes are the names of linker input library archive files) and returns a | |
9705 | result containing all the found arguments each prepended by | |
9706 | @option{-plugin-opt=-pass-through=} and joined by spaces. This list is | |
9707 | intended to be passed to the LTO linker plugin. | |
9708 | ||
9709 | @smallexample | |
9710 | %:pass-through-libs(%G %L %G) | |
9711 | @end smallexample | |
9712 | ||
a0f87454 RS |
9713 | @item @code{print-asm-header} |
9714 | The @code{print-asm-header} function takes no arguments and simply | |
9715 | prints a banner like: | |
9716 | ||
9717 | @smallexample | |
c80b4100 KH |
9718 | Assembler options |
9719 | ================= | |
a0f87454 RS |
9720 | |
9721 | Use "-Wa,OPTION" to pass "OPTION" to the assembler. | |
9722 | @end smallexample | |
9723 | ||
9724 | It is used to separate compiler options from assembler options | |
9725 | in the @option{--target-help} output. | |
daf2f129 | 9726 | @end table |
f3226a90 | 9727 | |
a743d340 | 9728 | @item %@{@code{S}@} |
161d7b59 | 9729 | Substitutes the @code{-S} switch, if that switch was given to GCC@. |
a743d340 NC |
9730 | If that switch was not specified, this substitutes nothing. Note that |
9731 | the leading dash is omitted when specifying this option, and it is | |
9732 | automatically inserted if the substitution is performed. Thus the spec | |
630d3d5a JM |
9733 | string @samp{%@{foo@}} would match the command-line option @option{-foo} |
9734 | and would output the command line option @option{-foo}. | |
a743d340 NC |
9735 | |
9736 | @item %W@{@code{S}@} | |
9737 | Like %@{@code{S}@} but mark last argument supplied within as a file to be | |
02f52e19 | 9738 | deleted on failure. |
a743d340 NC |
9739 | |
9740 | @item %@{@code{S}*@} | |
9741 | Substitutes all the switches specified to GCC whose names start | |
9742 | with @code{-S}, but which also take an argument. This is used for | |
695ac33f | 9743 | switches like @option{-o}, @option{-D}, @option{-I}, etc. |
630d3d5a | 9744 | GCC considers @option{-o foo} as being |
a743d340 | 9745 | one switch whose names starts with @samp{o}. %@{o*@} would substitute this |
02f52e19 | 9746 | text, including the space. Thus two arguments would be generated. |
a743d340 | 9747 | |
371e300b NC |
9748 | @item %@{@code{S}*&@code{T}*@} |
9749 | Like %@{@code{S}*@}, but preserve order of @code{S} and @code{T} options | |
9750 | (the order of @code{S} and @code{T} in the spec is not significant). | |
9751 | There can be any number of ampersand-separated variables; for each the | |
9752 | wild card is optional. Useful for CPP as @samp{%@{D*&U*&A*@}}. | |
9753 | ||
a743d340 | 9754 | @item %@{@code{S}:@code{X}@} |
4977bab6 | 9755 | Substitutes @code{X}, if the @samp{-S} switch was given to GCC@. |
a743d340 NC |
9756 | |
9757 | @item %@{!@code{S}:@code{X}@} | |
4977bab6 | 9758 | Substitutes @code{X}, if the @samp{-S} switch was @emph{not} given to GCC@. |
a743d340 | 9759 | |
4977bab6 ZW |
9760 | @item %@{@code{S}*:@code{X}@} |
9761 | Substitutes @code{X} if one or more switches whose names start with | |
9762 | @code{-S} are specified to GCC@. Normally @code{X} is substituted only | |
9763 | once, no matter how many such switches appeared. However, if @code{%*} | |
9764 | appears somewhere in @code{X}, then @code{X} will be substituted once | |
9765 | for each matching switch, with the @code{%*} replaced by the part of | |
9766 | that switch that matched the @code{*}. | |
a743d340 NC |
9767 | |
9768 | @item %@{.@code{S}:@code{X}@} | |
4977bab6 | 9769 | Substitutes @code{X}, if processing a file with suffix @code{S}. |
a743d340 NC |
9770 | |
9771 | @item %@{!.@code{S}:@code{X}@} | |
4977bab6 | 9772 | Substitutes @code{X}, if @emph{not} processing a file with suffix @code{S}. |
a743d340 | 9773 | |
98312a9b GK |
9774 | @item %@{,@code{S}:@code{X}@} |
9775 | Substitutes @code{X}, if processing a file for language @code{S}. | |
9776 | ||
9777 | @item %@{!,@code{S}:@code{X}@} | |
9778 | Substitutes @code{X}, if not processing a file for language @code{S}. | |
9779 | ||
a743d340 | 9780 | @item %@{@code{S}|@code{P}:@code{X}@} |
98312a9b GK |
9781 | Substitutes @code{X} if either @code{-S} or @code{-P} was given to |
9782 | GCC@. This may be combined with @samp{!}, @samp{.}, @samp{,}, and | |
9783 | @code{*} sequences as well, although they have a stronger binding than | |
9784 | the @samp{|}. If @code{%*} appears in @code{X}, all of the | |
9785 | alternatives must be starred, and only the first matching alternative | |
9786 | is substituted. | |
4977bab6 ZW |
9787 | |
9788 | For example, a spec string like this: | |
a743d340 NC |
9789 | |
9790 | @smallexample | |
9791 | %@{.c:-foo@} %@{!.c:-bar@} %@{.c|d:-baz@} %@{!.c|d:-boggle@} | |
9792 | @end smallexample | |
9793 | ||
9794 | will output the following command-line options from the following input | |
9795 | command-line options: | |
9796 | ||
9797 | @smallexample | |
9798 | fred.c -foo -baz | |
9799 | jim.d -bar -boggle | |
9800 | -d fred.c -foo -baz -boggle | |
9801 | -d jim.d -bar -baz -boggle | |
9802 | @end smallexample | |
9803 | ||
4977bab6 ZW |
9804 | @item %@{S:X; T:Y; :D@} |
9805 | ||
c0cbdbd9 KH |
9806 | If @code{S} was given to GCC, substitutes @code{X}; else if @code{T} was |
9807 | given to GCC, substitutes @code{Y}; else substitutes @code{D}. There can | |
daf2f129 | 9808 | be as many clauses as you need. This may be combined with @code{.}, |
98312a9b | 9809 | @code{,}, @code{!}, @code{|}, and @code{*} as needed. |
4977bab6 ZW |
9810 | |
9811 | ||
a743d340 NC |
9812 | @end table |
9813 | ||
4977bab6 ZW |
9814 | The conditional text @code{X} in a %@{@code{S}:@code{X}@} or similar |
9815 | construct may contain other nested @samp{%} constructs or spaces, or | |
9816 | even newlines. They are processed as usual, as described above. | |
9817 | Trailing white space in @code{X} is ignored. White space may also | |
9818 | appear anywhere on the left side of the colon in these constructs, | |
9819 | except between @code{.} or @code{*} and the corresponding word. | |
a743d340 | 9820 | |
4977bab6 ZW |
9821 | The @option{-O}, @option{-f}, @option{-m}, and @option{-W} switches are |
9822 | handled specifically in these constructs. If another value of | |
9823 | @option{-O} or the negated form of a @option{-f}, @option{-m}, or | |
9824 | @option{-W} switch is found later in the command line, the earlier | |
9825 | switch value is ignored, except with @{@code{S}*@} where @code{S} is | |
9826 | just one letter, which passes all matching options. | |
a743d340 | 9827 | |
4977bab6 ZW |
9828 | The character @samp{|} at the beginning of the predicate text is used to |
9829 | indicate that a command should be piped to the following command, but | |
9830 | only if @option{-pipe} is specified. | |
a743d340 NC |
9831 | |
9832 | It is built into GCC which switches take arguments and which do not. | |
9833 | (You might think it would be useful to generalize this to allow each | |
9834 | compiler's spec to say which switches take arguments. But this cannot | |
9835 | be done in a consistent fashion. GCC cannot even decide which input | |
9836 | files have been specified without knowing which switches take arguments, | |
9837 | and it must know which input files to compile in order to tell which | |
02f52e19 | 9838 | compilers to run). |
a743d340 | 9839 | |
630d3d5a | 9840 | GCC also knows implicitly that arguments starting in @option{-l} are to be |
a743d340 NC |
9841 | treated as compiler output files, and passed to the linker in their |
9842 | proper position among the other output files. | |
9843 | ||
ee457005 JM |
9844 | @c man begin OPTIONS |
9845 | ||
74291a4b MM |
9846 | @node Target Options |
9847 | @section Specifying Target Machine and Compiler Version | |
9848 | @cindex target options | |
9849 | @cindex cross compiling | |
9850 | @cindex specifying machine version | |
9851 | @cindex specifying compiler version and target machine | |
9852 | @cindex compiler version, specifying | |
9853 | @cindex target machine, specifying | |
9854 | ||
37a4aa31 GK |
9855 | The usual way to run GCC is to run the executable called @file{gcc}, or |
9856 | @file{<machine>-gcc} when cross-compiling, or | |
9857 | @file{<machine>-gcc-<version>} to run a version other than the one that | |
1401cf37 | 9858 | was installed last. |
74291a4b MM |
9859 | |
9860 | @node Submodel Options | |
9861 | @section Hardware Models and Configurations | |
9862 | @cindex submodel options | |
9863 | @cindex specifying hardware config | |
9864 | @cindex hardware models and configurations, specifying | |
9865 | @cindex machine dependent options | |
9866 | ||
1401cf37 | 9867 | Each target machine types can have its own |
74291a4b MM |
9868 | special options, starting with @samp{-m}, to choose among various |
9869 | hardware models or configurations---for example, 68010 vs 68020, | |
9870 | floating coprocessor or none. A single installed version of the | |
9871 | compiler can compile for any model or configuration, according to the | |
9872 | options specified. | |
9873 | ||
9874 | Some configurations of the compiler also support additional special | |
9875 | options, usually for compatibility with other compilers on the same | |
9876 | platform. | |
9877 | ||
39bc1876 NS |
9878 | @c This list is ordered alphanumerically by subsection name. |
9879 | @c It should be the same order and spelling as these options are listed | |
9880 | @c in Machine Dependent Options | |
9881 | ||
74291a4b | 9882 | @menu |
39bc1876 | 9883 | * ARC Options:: |
74291a4b | 9884 | * ARM Options:: |
39bc1876 | 9885 | * AVR Options:: |
0d4a78eb | 9886 | * Blackfin Options:: |
39bc1876 | 9887 | * CRIS Options:: |
53054e77 | 9888 | * CRX Options:: |
48aec0bc | 9889 | * Darwin Options:: |
74291a4b | 9890 | * DEC Alpha Options:: |
d7c23cdc | 9891 | * DEC Alpha/VMS Options:: |
18a3bdcb | 9892 | * FR30 Options:: |
39bc1876 | 9893 | * FRV Options:: |
464aea98 | 9894 | * GNU/Linux Options:: |
74291a4b | 9895 | * H8/300 Options:: |
39bc1876 NS |
9896 | * HPPA Options:: |
9897 | * i386 and x86-64 Options:: | |
46994828 | 9898 | * i386 and x86-64 Windows Options:: |
39bc1876 | 9899 | * IA-64 Options:: |
dcad28fd | 9900 | * IA-64/VMS Options:: |
aa4945c1 | 9901 | * LM32 Options:: |
38b2d076 | 9902 | * M32C Options:: |
39bc1876 NS |
9903 | * M32R/D Options:: |
9904 | * M680x0 Options:: | |
9905 | * M68hc1x Options:: | |
9906 | * MCore Options:: | |
e2491744 | 9907 | * MeP Options:: |
80920132 | 9908 | * MicroBlaze Options:: |
39bc1876 NS |
9909 | * MIPS Options:: |
9910 | * MMIX Options:: | |
9911 | * MN10300 Options:: | |
39bc1876 | 9912 | * PDP-11 Options:: |
358da97e | 9913 | * picoChip Options:: |
39bc1876 NS |
9914 | * PowerPC Options:: |
9915 | * RS/6000 and PowerPC Options:: | |
65a324b4 | 9916 | * RX Options:: |
39bc1876 | 9917 | * S/390 and zSeries Options:: |
93ef7c1f | 9918 | * Score Options:: |
74291a4b | 9919 | * SH Options:: |
c28aa982 | 9920 | * Solaris 2 Options:: |
39bc1876 | 9921 | * SPARC Options:: |
85d9c13c | 9922 | * SPU Options:: |
74291a4b | 9923 | * System V Options:: |
f84271d9 | 9924 | * V850 Options:: |
39bc1876 | 9925 | * VAX Options:: |
cd773ac4 | 9926 | * VxWorks Options:: |
39bc1876 | 9927 | * x86-64 Options:: |
69a0611f | 9928 | * Xstormy16 Options:: |
03984308 | 9929 | * Xtensa Options:: |
39bc1876 | 9930 | * zSeries Options:: |
74291a4b MM |
9931 | @end menu |
9932 | ||
39bc1876 NS |
9933 | @node ARC Options |
9934 | @subsection ARC Options | |
9935 | @cindex ARC Options | |
74291a4b | 9936 | |
39bc1876 | 9937 | These options are defined for ARC implementations: |
74291a4b | 9938 | |
2642624b | 9939 | @table @gcctabopt |
39bc1876 NS |
9940 | @item -EL |
9941 | @opindex EL | |
9942 | Compile code for little endian mode. This is the default. | |
74cf1c6d | 9943 | |
39bc1876 NS |
9944 | @item -EB |
9945 | @opindex EB | |
9946 | Compile code for big endian mode. | |
74291a4b | 9947 | |
39bc1876 NS |
9948 | @item -mmangle-cpu |
9949 | @opindex mmangle-cpu | |
9950 | Prepend the name of the cpu to all public symbol names. | |
9951 | In multiple-processor systems, there are many ARC variants with different | |
9952 | instruction and register set characteristics. This flag prevents code | |
9953 | compiled for one cpu to be linked with code compiled for another. | |
9954 | No facility exists for handling variants that are ``almost identical''. | |
9955 | This is an all or nothing option. | |
74291a4b | 9956 | |
39bc1876 NS |
9957 | @item -mcpu=@var{cpu} |
9958 | @opindex mcpu | |
9959 | Compile code for ARC variant @var{cpu}. | |
9960 | Which variants are supported depend on the configuration. | |
9961 | All variants support @option{-mcpu=base}, this is the default. | |
74291a4b | 9962 | |
39bc1876 NS |
9963 | @item -mtext=@var{text-section} |
9964 | @itemx -mdata=@var{data-section} | |
9965 | @itemx -mrodata=@var{readonly-data-section} | |
9966 | @opindex mtext | |
9967 | @opindex mdata | |
9968 | @opindex mrodata | |
9969 | Put functions, data, and readonly data in @var{text-section}, | |
9970 | @var{data-section}, and @var{readonly-data-section} respectively | |
9971 | by default. This can be overridden with the @code{section} attribute. | |
9972 | @xref{Variable Attributes}. | |
74291a4b | 9973 | |
39bc1876 | 9974 | @end table |
74291a4b | 9975 | |
39bc1876 NS |
9976 | @node ARM Options |
9977 | @subsection ARM Options | |
9978 | @cindex ARM options | |
74291a4b | 9979 | |
39bc1876 NS |
9980 | These @samp{-m} options are defined for Advanced RISC Machines (ARM) |
9981 | architectures: | |
74cf1c6d | 9982 | |
39bc1876 NS |
9983 | @table @gcctabopt |
9984 | @item -mabi=@var{name} | |
9985 | @opindex mabi | |
8a36672b | 9986 | Generate code for the specified ABI@. Permissible values are: @samp{apcs-gnu}, |
077fc835 | 9987 | @samp{atpcs}, @samp{aapcs}, @samp{aapcs-linux} and @samp{iwmmxt}. |
74cf1c6d | 9988 | |
39bc1876 NS |
9989 | @item -mapcs-frame |
9990 | @opindex mapcs-frame | |
9991 | Generate a stack frame that is compliant with the ARM Procedure Call | |
9992 | Standard for all functions, even if this is not strictly necessary for | |
9993 | correct execution of the code. Specifying @option{-fomit-frame-pointer} | |
9994 | with this option will cause the stack frames not to be generated for | |
9995 | leaf functions. The default is @option{-mno-apcs-frame}. | |
74291a4b | 9996 | |
39bc1876 NS |
9997 | @item -mapcs |
9998 | @opindex mapcs | |
9999 | This is a synonym for @option{-mapcs-frame}. | |
74291a4b | 10000 | |
39bc1876 NS |
10001 | @ignore |
10002 | @c not currently implemented | |
10003 | @item -mapcs-stack-check | |
10004 | @opindex mapcs-stack-check | |
10005 | Generate code to check the amount of stack space available upon entry to | |
10006 | every function (that actually uses some stack space). If there is | |
10007 | insufficient space available then either the function | |
10008 | @samp{__rt_stkovf_split_small} or @samp{__rt_stkovf_split_big} will be | |
10009 | called, depending upon the amount of stack space required. The run time | |
10010 | system is required to provide these functions. The default is | |
10011 | @option{-mno-apcs-stack-check}, since this produces smaller code. | |
74cf1c6d | 10012 | |
39bc1876 NS |
10013 | @c not currently implemented |
10014 | @item -mapcs-float | |
10015 | @opindex mapcs-float | |
10016 | Pass floating point arguments using the float point registers. This is | |
10017 | one of the variants of the APCS@. This option is recommended if the | |
10018 | target hardware has a floating point unit or if a lot of floating point | |
10019 | arithmetic is going to be performed by the code. The default is | |
10020 | @option{-mno-apcs-float}, since integer only code is slightly increased in | |
10021 | size if @option{-mapcs-float} is used. | |
74291a4b | 10022 | |
39bc1876 NS |
10023 | @c not currently implemented |
10024 | @item -mapcs-reentrant | |
10025 | @opindex mapcs-reentrant | |
10026 | Generate reentrant, position independent code. The default is | |
10027 | @option{-mno-apcs-reentrant}. | |
10028 | @end ignore | |
74291a4b | 10029 | |
39bc1876 NS |
10030 | @item -mthumb-interwork |
10031 | @opindex mthumb-interwork | |
10032 | Generate code which supports calling between the ARM and Thumb | |
10033 | instruction sets. Without this option the two instruction sets cannot | |
10034 | be reliably used inside one program. The default is | |
10035 | @option{-mno-thumb-interwork}, since slightly larger code is generated | |
10036 | when @option{-mthumb-interwork} is specified. | |
10037 | ||
10038 | @item -mno-sched-prolog | |
10039 | @opindex mno-sched-prolog | |
10040 | Prevent the reordering of instructions in the function prolog, or the | |
10041 | merging of those instruction with the instructions in the function's | |
10042 | body. This means that all functions will start with a recognizable set | |
10043 | of instructions (or in fact one of a choice from a small set of | |
10044 | different function prologues), and this information can be used to | |
10045 | locate the start if functions inside an executable piece of code. The | |
10046 | default is @option{-msched-prolog}. | |
10047 | ||
26cd0fcc SL |
10048 | @item -mfloat-abi=@var{name} |
10049 | @opindex mfloat-abi | |
10050 | Specifies which floating-point ABI to use. Permissible values | |
10051 | are: @samp{soft}, @samp{softfp} and @samp{hard}. | |
10052 | ||
7a61cf6f | 10053 | Specifying @samp{soft} causes GCC to generate output containing |
26cd0fcc | 10054 | library calls for floating-point operations. |
7a61cf6f NC |
10055 | @samp{softfp} allows the generation of code using hardware floating-point |
10056 | instructions, but still uses the soft-float calling conventions. | |
10057 | @samp{hard} allows generation of floating-point instructions | |
26cd0fcc SL |
10058 | and uses FPU-specific calling conventions. |
10059 | ||
26cd0fcc SL |
10060 | The default depends on the specific target configuration. Note that |
10061 | the hard-float and soft-float ABIs are not link-compatible; you must | |
10062 | compile your entire program with the same ABI, and link with a | |
10063 | compatible set of libraries. | |
10064 | ||
39bc1876 NS |
10065 | @item -mhard-float |
10066 | @opindex mhard-float | |
26cd0fcc | 10067 | Equivalent to @option{-mfloat-abi=hard}. |
861bb6c1 | 10068 | |
74291a4b | 10069 | @item -msoft-float |
cd3bb277 | 10070 | @opindex msoft-float |
26cd0fcc | 10071 | Equivalent to @option{-mfloat-abi=soft}. |
74291a4b | 10072 | |
39bc1876 NS |
10073 | @item -mlittle-endian |
10074 | @opindex mlittle-endian | |
10075 | Generate code for a processor running in little-endian mode. This is | |
10076 | the default for all standard configurations. | |
74291a4b | 10077 | |
39bc1876 NS |
10078 | @item -mbig-endian |
10079 | @opindex mbig-endian | |
10080 | Generate code for a processor running in big-endian mode; the default is | |
10081 | to compile code for a little-endian processor. | |
74291a4b | 10082 | |
39bc1876 NS |
10083 | @item -mwords-little-endian |
10084 | @opindex mwords-little-endian | |
10085 | This option only applies when generating code for big-endian processors. | |
10086 | Generate code for a little-endian word order but a big-endian byte | |
10087 | order. That is, a byte order of the form @samp{32107654}. Note: this | |
10088 | option should only be used if you require compatibility with code for | |
10089 | big-endian ARM processors generated by versions of the compiler prior to | |
10090 | 2.8. | |
74291a4b | 10091 | |
39bc1876 NS |
10092 | @item -mcpu=@var{name} |
10093 | @opindex mcpu | |
10094 | This specifies the name of the target ARM processor. GCC uses this name | |
10095 | to determine what kind of instructions it can emit when generating | |
10096 | assembly code. Permissible names are: @samp{arm2}, @samp{arm250}, | |
10097 | @samp{arm3}, @samp{arm6}, @samp{arm60}, @samp{arm600}, @samp{arm610}, | |
10098 | @samp{arm620}, @samp{arm7}, @samp{arm7m}, @samp{arm7d}, @samp{arm7dm}, | |
10099 | @samp{arm7di}, @samp{arm7dmi}, @samp{arm70}, @samp{arm700}, | |
10100 | @samp{arm700i}, @samp{arm710}, @samp{arm710c}, @samp{arm7100}, | |
7ab23fd0 | 10101 | @samp{arm720}, |
d98a72fd | 10102 | @samp{arm7500}, @samp{arm7500fe}, @samp{arm7tdmi}, @samp{arm7tdmi-s}, |
7ab23fd0 JM |
10103 | @samp{arm710t}, @samp{arm720t}, @samp{arm740t}, |
10104 | @samp{strongarm}, @samp{strongarm110}, @samp{strongarm1100}, | |
10105 | @samp{strongarm1110}, | |
39bc1876 | 10106 | @samp{arm8}, @samp{arm810}, @samp{arm9}, @samp{arm9e}, @samp{arm920}, |
d98a72fd RE |
10107 | @samp{arm920t}, @samp{arm922t}, @samp{arm946e-s}, @samp{arm966e-s}, |
10108 | @samp{arm968e-s}, @samp{arm926ej-s}, @samp{arm940t}, @samp{arm9tdmi}, | |
10109 | @samp{arm10tdmi}, @samp{arm1020t}, @samp{arm1026ej-s}, | |
f9e8581a | 10110 | @samp{arm10e}, @samp{arm1020e}, @samp{arm1022e}, |
fa91adc6 | 10111 | @samp{arm1136j-s}, @samp{arm1136jf-s}, @samp{mpcore}, @samp{mpcorenovfp}, |
ead204d9 | 10112 | @samp{arm1156t2-s}, @samp{arm1156t2f-s}, @samp{arm1176jz-s}, @samp{arm1176jzf-s}, |
508371fe | 10113 | @samp{cortex-a5}, @samp{cortex-a8}, @samp{cortex-a9}, @samp{cortex-a15}, |
f6e47b26 | 10114 | @samp{cortex-r4}, @samp{cortex-r4f}, @samp{cortex-m4}, @samp{cortex-m3}, |
302c3d8e | 10115 | @samp{cortex-m1}, |
9833720d | 10116 | @samp{cortex-m0}, |
442dc742 | 10117 | @samp{xscale}, @samp{iwmmxt}, @samp{iwmmxt2}, @samp{ep9312}. |
74291a4b | 10118 | |
33558d94 | 10119 | @item -mtune=@var{name} |
39bc1876 NS |
10120 | @opindex mtune |
10121 | This option is very similar to the @option{-mcpu=} option, except that | |
10122 | instead of specifying the actual target processor type, and hence | |
10123 | restricting which instructions can be used, it specifies that GCC should | |
10124 | tune the performance of the code as if the target were of the type | |
10125 | specified in this option, but still choosing the instructions that it | |
10126 | will generate based on the cpu specified by a @option{-mcpu=} option. | |
10127 | For some ARM implementations better performance can be obtained by using | |
10128 | this option. | |
861bb6c1 | 10129 | |
39bc1876 NS |
10130 | @item -march=@var{name} |
10131 | @opindex march | |
10132 | This specifies the name of the target ARM architecture. GCC uses this | |
10133 | name to determine what kind of instructions it can emit when generating | |
10134 | assembly code. This option can be used in conjunction with or instead | |
10135 | of the @option{-mcpu=} option. Permissible names are: @samp{armv2}, | |
10136 | @samp{armv2a}, @samp{armv3}, @samp{armv3m}, @samp{armv4}, @samp{armv4t}, | |
7ab23fd0 JM |
10137 | @samp{armv5}, @samp{armv5t}, @samp{armv5e}, @samp{armv5te}, |
10138 | @samp{armv6}, @samp{armv6j}, | |
bf98ec6c PB |
10139 | @samp{armv6t2}, @samp{armv6z}, @samp{armv6zk}, @samp{armv6-m}, |
10140 | @samp{armv7}, @samp{armv7-a}, @samp{armv7-r}, @samp{armv7-m}, | |
442dc742 | 10141 | @samp{iwmmxt}, @samp{iwmmxt2}, @samp{ep9312}. |
861bb6c1 | 10142 | |
39bc1876 NS |
10143 | @item -mfpu=@var{name} |
10144 | @itemx -mfpe=@var{number} | |
10145 | @itemx -mfp=@var{number} | |
10146 | @opindex mfpu | |
10147 | @opindex mfpe | |
10148 | @opindex mfp | |
10149 | This specifies what floating point hardware (or hardware emulation) is | |
10150 | available on the target. Permissible names are: @samp{fpa}, @samp{fpe2}, | |
e0dc3601 PB |
10151 | @samp{fpe3}, @samp{maverick}, @samp{vfp}, @samp{vfpv3}, @samp{vfpv3-fp16}, |
10152 | @samp{vfpv3-d16}, @samp{vfpv3-d16-fp16}, @samp{vfpv3xd}, @samp{vfpv3xd-fp16}, | |
1abed66b PB |
10153 | @samp{neon}, @samp{neon-fp16}, @samp{vfpv4}, @samp{vfpv4-d16}, |
10154 | @samp{fpv4-sp-d16} and @samp{neon-vfpv4}. | |
e0dc3601 PB |
10155 | @option{-mfp} and @option{-mfpe} are synonyms for |
10156 | @option{-mfpu}=@samp{fpe}@var{number}, for compatibility with older versions | |
10157 | of GCC@. | |
861bb6c1 | 10158 | |
39bc1876 NS |
10159 | If @option{-msoft-float} is specified this specifies the format of |
10160 | floating point values. | |
fb868474 | 10161 | |
400cfcf5 JB |
10162 | If the selected floating-point hardware includes the NEON extension |
10163 | (e.g. @option{-mfpu}=@samp{neon}), note that floating-point | |
10164 | operations will not be used by GCC's auto-vectorization pass unless | |
10165 | @option{-funsafe-math-optimizations} is also specified. This is | |
10166 | because NEON hardware does not fully implement the IEEE 754 standard for | |
10167 | floating-point arithmetic (in particular denormal values are treated as | |
10168 | zero), so the use of NEON instructions may lead to a loss of precision. | |
10169 | ||
0fd8c3ad SL |
10170 | @item -mfp16-format=@var{name} |
10171 | @opindex mfp16-format | |
10172 | Specify the format of the @code{__fp16} half-precision floating-point type. | |
7a61cf6f NC |
10173 | Permissible names are @samp{none}, @samp{ieee}, and @samp{alternative}; |
10174 | the default is @samp{none}, in which case the @code{__fp16} type is not | |
0fd8c3ad SL |
10175 | defined. @xref{Half-Precision}, for more information. |
10176 | ||
39bc1876 NS |
10177 | @item -mstructure-size-boundary=@var{n} |
10178 | @opindex mstructure-size-boundary | |
10179 | The size of all structures and unions will be rounded up to a multiple | |
10180 | of the number of bits set by this option. Permissible values are 8, 32 | |
10181 | and 64. The default value varies for different toolchains. For the COFF | |
10182 | targeted toolchain the default value is 8. A value of 64 is only allowed | |
10183 | if the underlying ABI supports it. | |
b71733d5 | 10184 | |
39bc1876 NS |
10185 | Specifying the larger number can produce faster, more efficient code, but |
10186 | can also increase the size of the program. Different values are potentially | |
10187 | incompatible. Code compiled with one value cannot necessarily expect to | |
10188 | work with code or libraries compiled with another value, if they exchange | |
10189 | information using structures or unions. | |
24f9c4df | 10190 | |
39bc1876 NS |
10191 | @item -mabort-on-noreturn |
10192 | @opindex mabort-on-noreturn | |
10193 | Generate a call to the function @code{abort} at the end of a | |
10194 | @code{noreturn} function. It will be executed if the function tries to | |
10195 | return. | |
24f9c4df | 10196 | |
39bc1876 NS |
10197 | @item -mlong-calls |
10198 | @itemx -mno-long-calls | |
10199 | @opindex mlong-calls | |
10200 | @opindex mno-long-calls | |
10201 | Tells the compiler to perform function calls by first loading the | |
10202 | address of the function into a register and then performing a subroutine | |
10203 | call on this register. This switch is needed if the target function | |
10204 | will lie outside of the 64 megabyte addressing range of the offset based | |
10205 | version of subroutine call instruction. | |
24f9c4df | 10206 | |
39bc1876 NS |
10207 | Even if this switch is enabled, not all function calls will be turned |
10208 | into long calls. The heuristic is that static functions, functions | |
10209 | which have the @samp{short-call} attribute, functions that are inside | |
10210 | the scope of a @samp{#pragma no_long_calls} directive and functions whose | |
10211 | definitions have already been compiled within the current compilation | |
10212 | unit, will not be turned into long calls. The exception to this rule is | |
10213 | that weak function definitions, functions with the @samp{long-call} | |
10214 | attribute or the @samp{section} attribute, and functions that are within | |
10215 | the scope of a @samp{#pragma long_calls} directive, will always be | |
10216 | turned into long calls. | |
24f9c4df | 10217 | |
39bc1876 NS |
10218 | This feature is not enabled by default. Specifying |
10219 | @option{-mno-long-calls} will restore the default behavior, as will | |
10220 | placing the function calls within the scope of a @samp{#pragma | |
10221 | long_calls_off} directive. Note these switches have no effect on how | |
10222 | the compiler generates code to handle function calls via function | |
10223 | pointers. | |
24f9c4df | 10224 | |
39bc1876 NS |
10225 | @item -msingle-pic-base |
10226 | @opindex msingle-pic-base | |
10227 | Treat the register used for PIC addressing as read-only, rather than | |
10228 | loading it in the prologue for each function. The run-time system is | |
10229 | responsible for initializing this register with an appropriate value | |
10230 | before execution begins. | |
2856c3e3 | 10231 | |
39bc1876 NS |
10232 | @item -mpic-register=@var{reg} |
10233 | @opindex mpic-register | |
10234 | Specify the register to be used for PIC addressing. The default is R10 | |
10235 | unless stack-checking is enabled, when R9 is used. | |
2856c3e3 | 10236 | |
39bc1876 NS |
10237 | @item -mcirrus-fix-invalid-insns |
10238 | @opindex mcirrus-fix-invalid-insns | |
10239 | @opindex mno-cirrus-fix-invalid-insns | |
10240 | Insert NOPs into the instruction stream to in order to work around | |
10241 | problems with invalid Maverick instruction combinations. This option | |
10242 | is only valid if the @option{-mcpu=ep9312} option has been used to | |
10243 | enable generation of instructions for the Cirrus Maverick floating | |
10244 | point co-processor. This option is not enabled by default, since the | |
10245 | problem is only present in older Maverick implementations. The default | |
10246 | can be re-enabled by use of the @option{-mno-cirrus-fix-invalid-insns} | |
10247 | switch. | |
2856c3e3 | 10248 | |
39bc1876 NS |
10249 | @item -mpoke-function-name |
10250 | @opindex mpoke-function-name | |
10251 | Write the name of each function into the text section, directly | |
10252 | preceding the function prologue. The generated code is similar to this: | |
2856c3e3 | 10253 | |
39bc1876 NS |
10254 | @smallexample |
10255 | t0 | |
10256 | .ascii "arm_poke_function_name", 0 | |
10257 | .align | |
10258 | t1 | |
10259 | .word 0xff000000 + (t1 - t0) | |
10260 | arm_poke_function_name | |
10261 | mov ip, sp | |
10262 | stmfd sp!, @{fp, ip, lr, pc@} | |
10263 | sub fp, ip, #4 | |
10264 | @end smallexample | |
f077f169 | 10265 | |
39bc1876 NS |
10266 | When performing a stack backtrace, code can inspect the value of |
10267 | @code{pc} stored at @code{fp + 0}. If the trace function then looks at | |
10268 | location @code{pc - 12} and the top 8 bits are set, then we know that | |
10269 | there is a function name embedded immediately preceding this location | |
10270 | and has length @code{((pc[-3]) & 0xff000000)}. | |
2856c3e3 | 10271 | |
39bc1876 NS |
10272 | @item -mthumb |
10273 | @opindex mthumb | |
5b3e6663 | 10274 | Generate code for the Thumb instruction set. The default is to |
39bc1876 | 10275 | use the 32-bit ARM instruction set. |
5b3e6663 PB |
10276 | This option automatically enables either 16-bit Thumb-1 or |
10277 | mixed 16/32-bit Thumb-2 instructions based on the @option{-mcpu=@var{name}} | |
7a61cf6f | 10278 | and @option{-march=@var{name}} options. This option is not passed to the |
bebc6e07 | 10279 | assembler. If you want to force assembler files to be interpreted as Thumb code, |
7a61cf6f | 10280 | either add a @samp{.thumb} directive to the source or pass the @option{-mthumb} |
bebc6e07 | 10281 | option directly to the assembler by prefixing it with @option{-Wa}. |
8a0b86f5 | 10282 | |
39bc1876 NS |
10283 | @item -mtpcs-frame |
10284 | @opindex mtpcs-frame | |
10285 | Generate a stack frame that is compliant with the Thumb Procedure Call | |
10286 | Standard for all non-leaf functions. (A leaf function is one that does | |
10287 | not call any other functions.) The default is @option{-mno-tpcs-frame}. | |
058edcdb | 10288 | |
39bc1876 NS |
10289 | @item -mtpcs-leaf-frame |
10290 | @opindex mtpcs-leaf-frame | |
10291 | Generate a stack frame that is compliant with the Thumb Procedure Call | |
10292 | Standard for all leaf functions. (A leaf function is one that does | |
10293 | not call any other functions.) The default is @option{-mno-apcs-leaf-frame}. | |
2856c3e3 | 10294 | |
39bc1876 NS |
10295 | @item -mcallee-super-interworking |
10296 | @opindex mcallee-super-interworking | |
10297 | Gives all externally visible functions in the file being compiled an ARM | |
10298 | instruction set header which switches to Thumb mode before executing the | |
10299 | rest of the function. This allows these functions to be called from | |
7a61cf6f | 10300 | non-interworking code. This option is not valid in AAPCS configurations |
3ce14752 | 10301 | because interworking is enabled by default. |
39bc1876 NS |
10302 | |
10303 | @item -mcaller-super-interworking | |
10304 | @opindex mcaller-super-interworking | |
10305 | Allows calls via function pointers (including virtual functions) to | |
10306 | execute correctly regardless of whether the target code has been | |
10307 | compiled for interworking or not. There is a small overhead in the cost | |
7a61cf6f | 10308 | of executing a function pointer if this option is enabled. This option |
3ce14752 RR |
10309 | is not valid in AAPCS configurations because interworking is enabled |
10310 | by default. | |
2856c3e3 | 10311 | |
d3585b76 DJ |
10312 | @item -mtp=@var{name} |
10313 | @opindex mtp | |
10314 | Specify the access model for the thread local storage pointer. The valid | |
10315 | models are @option{soft}, which generates calls to @code{__aeabi_read_tp}, | |
10316 | @option{cp15}, which fetches the thread pointer from @code{cp15} directly | |
10317 | (supported in the arm6k architecture), and @option{auto}, which uses the | |
10318 | best available method for the selected processor. The default setting is | |
10319 | @option{auto}. | |
10320 | ||
571191af PB |
10321 | @item -mword-relocations |
10322 | @opindex mword-relocations | |
10323 | Only generate absolute relocations on word sized values (i.e. R_ARM_ABS32). | |
10324 | This is enabled by default on targets (uClinux, SymbianOS) where the runtime | |
10325 | loader imposes this restriction, and when @option{-fpic} or @option{-fPIC} | |
a640c13b | 10326 | is specified. |
571191af | 10327 | |
fa6aeae1 MK |
10328 | @item -mfix-cortex-m3-ldrd |
10329 | @opindex mfix-cortex-m3-ldrd | |
10330 | Some Cortex-M3 cores can cause data corruption when @code{ldrd} instructions | |
10331 | with overlapping destination and base registers are used. This option avoids | |
10332 | generating these instructions. This option is enabled by default when | |
10333 | @option{-mcpu=cortex-m3} is specified. | |
10334 | ||
2856c3e3 SC |
10335 | @end table |
10336 | ||
39bc1876 NS |
10337 | @node AVR Options |
10338 | @subsection AVR Options | |
10339 | @cindex AVR Options | |
74291a4b | 10340 | |
39bc1876 | 10341 | These options are defined for AVR implementations: |
74291a4b | 10342 | |
2642624b | 10343 | @table @gcctabopt |
39bc1876 NS |
10344 | @item -mmcu=@var{mcu} |
10345 | @opindex mmcu | |
10346 | Specify ATMEL AVR instruction set or MCU type. | |
74291a4b | 10347 | |
39bc1876 NS |
10348 | Instruction set avr1 is for the minimal AVR core, not supported by the C |
10349 | compiler, only for assembler programs (MCU types: at90s1200, attiny10, | |
10350 | attiny11, attiny12, attiny15, attiny28). | |
74291a4b | 10351 | |
39bc1876 NS |
10352 | Instruction set avr2 (default) is for the classic AVR core with up to |
10353 | 8K program memory space (MCU types: at90s2313, at90s2323, attiny22, | |
10354 | at90s2333, at90s2343, at90s4414, at90s4433, at90s4434, at90s8515, | |
10355 | at90c8534, at90s8535). | |
74291a4b | 10356 | |
39bc1876 NS |
10357 | Instruction set avr3 is for the classic AVR core with up to 128K program |
10358 | memory space (MCU types: atmega103, atmega603, at43usb320, at76c711). | |
74291a4b | 10359 | |
39bc1876 NS |
10360 | Instruction set avr4 is for the enhanced AVR core with up to 8K program |
10361 | memory space (MCU types: atmega8, atmega83, atmega85). | |
74291a4b | 10362 | |
39bc1876 NS |
10363 | Instruction set avr5 is for the enhanced AVR core with up to 128K program |
10364 | memory space (MCU types: atmega16, atmega161, atmega163, atmega32, atmega323, | |
10365 | atmega64, atmega128, at43usb355, at94k). | |
74291a4b | 10366 | |
39bc1876 NS |
10367 | @item -mno-interrupts |
10368 | @opindex mno-interrupts | |
10369 | Generated code is not compatible with hardware interrupts. | |
10370 | Code size will be smaller. | |
74291a4b | 10371 | |
39bc1876 NS |
10372 | @item -mcall-prologues |
10373 | @opindex mcall-prologues | |
10374 | Functions prologues/epilogues expanded as call to appropriate | |
10375 | subroutines. Code size will be smaller. | |
74291a4b | 10376 | |
39bc1876 NS |
10377 | @item -mtiny-stack |
10378 | @opindex mtiny-stack | |
10379 | Change only the low 8 bits of the stack pointer. | |
74291a4b | 10380 | |
39bc1876 NS |
10381 | @item -mint8 |
10382 | @opindex mint8 | |
8a36672b | 10383 | Assume int to be 8 bit integer. This affects the sizes of all types: A |
e4ae5e77 | 10384 | char will be 1 byte, an int will be 1 byte, a long will be 2 bytes |
8a36672b | 10385 | and long long will be 4 bytes. Please note that this option does not |
39bc1876 NS |
10386 | comply to the C standards, but it will provide you with smaller code |
10387 | size. | |
10388 | @end table | |
74291a4b | 10389 | |
0d4a78eb BS |
10390 | @node Blackfin Options |
10391 | @subsection Blackfin Options | |
10392 | @cindex Blackfin Options | |
10393 | ||
10394 | @table @gcctabopt | |
ea2382be | 10395 | @item -mcpu=@var{cpu}@r{[}-@var{sirevision}@r{]} |
28f601ff | 10396 | @opindex mcpu= |
ea2382be | 10397 | Specifies the name of the target Blackfin processor. Currently, @var{cpu} |
318b3009 BS |
10398 | can be one of @samp{bf512}, @samp{bf514}, @samp{bf516}, @samp{bf518}, |
10399 | @samp{bf522}, @samp{bf523}, @samp{bf524}, @samp{bf525}, @samp{bf526}, | |
10400 | @samp{bf527}, @samp{bf531}, @samp{bf532}, @samp{bf533}, | |
10401 | @samp{bf534}, @samp{bf536}, @samp{bf537}, @samp{bf538}, @samp{bf539}, | |
64882649 | 10402 | @samp{bf542}, @samp{bf544}, @samp{bf547}, @samp{bf548}, @samp{bf549}, |
5254cd50 | 10403 | @samp{bf542m}, @samp{bf544m}, @samp{bf547m}, @samp{bf548m}, @samp{bf549m}, |
ea2382be JZ |
10404 | @samp{bf561}. |
10405 | The optional @var{sirevision} specifies the silicon revision of the target | |
10406 | Blackfin processor. Any workarounds available for the targeted silicon revision | |
10407 | will be enabled. If @var{sirevision} is @samp{none}, no workarounds are enabled. | |
10408 | If @var{sirevision} is @samp{any}, all workarounds for the targeted processor | |
10409 | will be enabled. The @code{__SILICON_REVISION__} macro is defined to two | |
10410 | hexadecimal digits representing the major and minor numbers in the silicon | |
10411 | revision. If @var{sirevision} is @samp{none}, the @code{__SILICON_REVISION__} | |
10412 | is not defined. If @var{sirevision} is @samp{any}, the | |
10413 | @code{__SILICON_REVISION__} is defined to be @code{0xffff}. | |
10414 | If this optional @var{sirevision} is not used, GCC assumes the latest known | |
10415 | silicon revision of the targeted Blackfin processor. | |
10416 | ||
10417 | Support for @samp{bf561} is incomplete. For @samp{bf561}, | |
10418 | Only the processor macro is defined. | |
28f601ff JZ |
10419 | Without this option, @samp{bf532} is used as the processor by default. |
10420 | The corresponding predefined processor macros for @var{cpu} is to | |
ea2382be JZ |
10421 | be defined. And for @samp{bfin-elf} toolchain, this causes the hardware BSP |
10422 | provided by libgloss to be linked in if @option{-msim} is not given. | |
28f601ff JZ |
10423 | |
10424 | @item -msim | |
10425 | @opindex msim | |
10426 | Specifies that the program will be run on the simulator. This causes | |
10427 | the simulator BSP provided by libgloss to be linked in. This option | |
10428 | has effect only for @samp{bfin-elf} toolchain. | |
28bbc967 BS |
10429 | Certain other options, such as @option{-mid-shared-library} and |
10430 | @option{-mfdpic}, imply @option{-msim}. | |
28f601ff | 10431 | |
0d4a78eb BS |
10432 | @item -momit-leaf-frame-pointer |
10433 | @opindex momit-leaf-frame-pointer | |
10434 | Don't keep the frame pointer in a register for leaf functions. This | |
10435 | avoids the instructions to save, set up and restore frame pointers and | |
10436 | makes an extra register available in leaf functions. The option | |
10437 | @option{-fomit-frame-pointer} removes the frame pointer for all functions | |
10438 | which might make debugging harder. | |
10439 | ||
3fb192d2 BS |
10440 | @item -mspecld-anomaly |
10441 | @opindex mspecld-anomaly | |
0d4a78eb | 10442 | When enabled, the compiler will ensure that the generated code does not |
ea2382be JZ |
10443 | contain speculative loads after jump instructions. If this option is used, |
10444 | @code{__WORKAROUND_SPECULATIVE_LOADS} is defined. | |
0d4a78eb | 10445 | |
3fb192d2 BS |
10446 | @item -mno-specld-anomaly |
10447 | @opindex mno-specld-anomaly | |
0d4a78eb BS |
10448 | Don't generate extra code to prevent speculative loads from occurring. |
10449 | ||
3fb192d2 | 10450 | @item -mcsync-anomaly |
161c21b6 | 10451 | @opindex mcsync-anomaly |
3fb192d2 BS |
10452 | When enabled, the compiler will ensure that the generated code does not |
10453 | contain CSYNC or SSYNC instructions too soon after conditional branches. | |
ea2382be | 10454 | If this option is used, @code{__WORKAROUND_SPECULATIVE_SYNCS} is defined. |
3fb192d2 BS |
10455 | |
10456 | @item -mno-csync-anomaly | |
161c21b6 | 10457 | @opindex mno-csync-anomaly |
3fb192d2 BS |
10458 | Don't generate extra code to prevent CSYNC or SSYNC instructions from |
10459 | occurring too soon after a conditional branch. | |
10460 | ||
0d4a78eb | 10461 | @item -mlow-64k |
9821b257 | 10462 | @opindex mlow-64k |
0d4a78eb BS |
10463 | When enabled, the compiler is free to take advantage of the knowledge that |
10464 | the entire program fits into the low 64k of memory. | |
10465 | ||
10466 | @item -mno-low-64k | |
10467 | @opindex mno-low-64k | |
10468 | Assume that the program is arbitrarily large. This is the default. | |
10469 | ||
d6eb07dc BS |
10470 | @item -mstack-check-l1 |
10471 | @opindex mstack-check-l1 | |
10472 | Do stack checking using information placed into L1 scratchpad memory by the | |
10473 | uClinux kernel. | |
10474 | ||
0d4a78eb BS |
10475 | @item -mid-shared-library |
10476 | @opindex mid-shared-library | |
10477 | Generate code that supports shared libraries via the library ID method. | |
10478 | This allows for execute in place and shared libraries in an environment | |
10479 | without virtual memory management. This option implies @option{-fPIC}. | |
28bbc967 | 10480 | With a @samp{bfin-elf} target, this option implies @option{-msim}. |
0d4a78eb BS |
10481 | |
10482 | @item -mno-id-shared-library | |
10483 | @opindex mno-id-shared-library | |
10484 | Generate code that doesn't assume ID based shared libraries are being used. | |
10485 | This is the default. | |
10486 | ||
d6eb07dc BS |
10487 | @item -mleaf-id-shared-library |
10488 | @opindex mleaf-id-shared-library | |
10489 | Generate code that supports shared libraries via the library ID method, | |
10490 | but assumes that this library or executable won't link against any other | |
10491 | ID shared libraries. That allows the compiler to use faster code for jumps | |
10492 | and calls. | |
10493 | ||
10494 | @item -mno-leaf-id-shared-library | |
10495 | @opindex mno-leaf-id-shared-library | |
10496 | Do not assume that the code being compiled won't link against any ID shared | |
10497 | libraries. Slower code will be generated for jump and call insns. | |
10498 | ||
0d4a78eb BS |
10499 | @item -mshared-library-id=n |
10500 | @opindex mshared-library-id | |
10501 | Specified the identification number of the ID based shared library being | |
10502 | compiled. Specifying a value of 0 will generate more compact code, specifying | |
10503 | other values will force the allocation of that number to the current | |
10504 | library but is no more space or time efficient than omitting this option. | |
b6877196 | 10505 | |
d6eb07dc BS |
10506 | @item -msep-data |
10507 | @opindex msep-data | |
10508 | Generate code that allows the data segment to be located in a different | |
10509 | area of memory from the text segment. This allows for execute in place in | |
10510 | an environment without virtual memory management by eliminating relocations | |
10511 | against the text section. | |
10512 | ||
10513 | @item -mno-sep-data | |
10514 | @opindex mno-sep-data | |
10515 | Generate code that assumes that the data segment follows the text segment. | |
10516 | This is the default. | |
10517 | ||
b6877196 BS |
10518 | @item -mlong-calls |
10519 | @itemx -mno-long-calls | |
10520 | @opindex mlong-calls | |
10521 | @opindex mno-long-calls | |
10522 | Tells the compiler to perform function calls by first loading the | |
10523 | address of the function into a register and then performing a subroutine | |
10524 | call on this register. This switch is needed if the target function | |
10525 | will lie outside of the 24 bit addressing range of the offset based | |
10526 | version of subroutine call instruction. | |
10527 | ||
10528 | This feature is not enabled by default. Specifying | |
10529 | @option{-mno-long-calls} will restore the default behavior. Note these | |
10530 | switches have no effect on how the compiler generates code to handle | |
10531 | function calls via function pointers. | |
2c117a21 JZ |
10532 | |
10533 | @item -mfast-fp | |
10534 | @opindex mfast-fp | |
10535 | Link with the fast floating-point library. This library relaxes some of | |
10536 | the IEEE floating-point standard's rules for checking inputs against | |
10537 | Not-a-Number (NAN), in the interest of performance. | |
e874e49f JZ |
10538 | |
10539 | @item -minline-plt | |
10540 | @opindex minline-plt | |
10541 | Enable inlining of PLT entries in function calls to functions that are | |
10542 | not known to bind locally. It has no effect without @option{-mfdpic}. | |
0d4a78eb | 10543 | |
16869606 BS |
10544 | @item -mmulticore |
10545 | @opindex mmulticore | |
10546 | Build standalone application for multicore Blackfin processor. Proper | |
10547 | start files and link scripts will be used to support multicore. | |
10548 | This option defines @code{__BFIN_MULTICORE}. It can only be used with | |
10549 | @option{-mcpu=bf561@r{[}-@var{sirevision}@r{]}}. It can be used with | |
10550 | @option{-mcorea} or @option{-mcoreb}. If it's used without | |
10551 | @option{-mcorea} or @option{-mcoreb}, single application/dual core | |
10552 | programming model is used. In this model, the main function of Core B | |
10553 | should be named as coreb_main. If it's used with @option{-mcorea} or | |
10554 | @option{-mcoreb}, one application per core programming model is used. | |
10555 | If this option is not used, single core application programming | |
10556 | model is used. | |
10557 | ||
10558 | @item -mcorea | |
10559 | @opindex mcorea | |
10560 | Build standalone application for Core A of BF561 when using | |
10561 | one application per core programming model. Proper start files | |
10562 | and link scripts will be used to support Core A. This option | |
10563 | defines @code{__BFIN_COREA}. It must be used with @option{-mmulticore}. | |
10564 | ||
10565 | @item -mcoreb | |
10566 | @opindex mcoreb | |
10567 | Build standalone application for Core B of BF561 when using | |
10568 | one application per core programming model. Proper start files | |
10569 | and link scripts will be used to support Core B. This option | |
10570 | defines @code{__BFIN_COREB}. When this option is used, coreb_main | |
10571 | should be used instead of main. It must be used with | |
7a61cf6f | 10572 | @option{-mmulticore}. |
16869606 BS |
10573 | |
10574 | @item -msdram | |
10575 | @opindex msdram | |
10576 | Build standalone application for SDRAM. Proper start files and | |
10577 | link scripts will be used to put the application into SDRAM. | |
10578 | Loader should initialize SDRAM before loading the application | |
10579 | into SDRAM. This option defines @code{__BFIN_SDRAM}. | |
bf85bc3d BS |
10580 | |
10581 | @item -micplb | |
10582 | @opindex micplb | |
10583 | Assume that ICPLBs are enabled at runtime. This has an effect on certain | |
10584 | anomaly workarounds. For Linux targets, the default is to assume ICPLBs | |
10585 | are enabled; for standalone applications the default is off. | |
16869606 | 10586 | @end table |
6ccde948 | 10587 | |
39bc1876 NS |
10588 | @node CRIS Options |
10589 | @subsection CRIS Options | |
10590 | @cindex CRIS Options | |
74291a4b | 10591 | |
39bc1876 | 10592 | These options are defined specifically for the CRIS ports. |
74291a4b | 10593 | |
39bc1876 NS |
10594 | @table @gcctabopt |
10595 | @item -march=@var{architecture-type} | |
10596 | @itemx -mcpu=@var{architecture-type} | |
10597 | @opindex march | |
10598 | @opindex mcpu | |
10599 | Generate code for the specified architecture. The choices for | |
10600 | @var{architecture-type} are @samp{v3}, @samp{v8} and @samp{v10} for | |
8a36672b | 10601 | respectively ETRAX@w{ }4, ETRAX@w{ }100, and ETRAX@w{ }100@w{ }LX@. |
39bc1876 NS |
10602 | Default is @samp{v0} except for cris-axis-linux-gnu, where the default is |
10603 | @samp{v10}. | |
c219ddf7 | 10604 | |
39bc1876 NS |
10605 | @item -mtune=@var{architecture-type} |
10606 | @opindex mtune | |
10607 | Tune to @var{architecture-type} everything applicable about the generated | |
10608 | code, except for the ABI and the set of available instructions. The | |
10609 | choices for @var{architecture-type} are the same as for | |
10610 | @option{-march=@var{architecture-type}}. | |
54284728 | 10611 | |
39bc1876 NS |
10612 | @item -mmax-stack-frame=@var{n} |
10613 | @opindex mmax-stack-frame | |
10614 | Warn when the stack frame of a function exceeds @var{n} bytes. | |
54284728 | 10615 | |
39bc1876 NS |
10616 | @item -metrax4 |
10617 | @itemx -metrax100 | |
10618 | @opindex metrax4 | |
10619 | @opindex metrax100 | |
10620 | The options @option{-metrax4} and @option{-metrax100} are synonyms for | |
10621 | @option{-march=v3} and @option{-march=v8} respectively. | |
c0498f43 | 10622 | |
39bc1876 NS |
10623 | @item -mmul-bug-workaround |
10624 | @itemx -mno-mul-bug-workaround | |
10625 | @opindex mmul-bug-workaround | |
10626 | @opindex mno-mul-bug-workaround | |
10627 | Work around a bug in the @code{muls} and @code{mulu} instructions for CPU | |
10628 | models where it applies. This option is active by default. | |
c0498f43 | 10629 | |
39bc1876 NS |
10630 | @item -mpdebug |
10631 | @opindex mpdebug | |
10632 | Enable CRIS-specific verbose debug-related information in the assembly | |
10633 | code. This option also has the effect to turn off the @samp{#NO_APP} | |
10634 | formatted-code indicator to the assembler at the beginning of the | |
10635 | assembly file. | |
c0498f43 | 10636 | |
39bc1876 NS |
10637 | @item -mcc-init |
10638 | @opindex mcc-init | |
10639 | Do not use condition-code results from previous instruction; always emit | |
10640 | compare and test instructions before use of condition codes. | |
74291a4b | 10641 | |
39bc1876 NS |
10642 | @item -mno-side-effects |
10643 | @opindex mno-side-effects | |
10644 | Do not emit instructions with side-effects in addressing modes other than | |
10645 | post-increment. | |
238b11b5 | 10646 | |
39bc1876 NS |
10647 | @item -mstack-align |
10648 | @itemx -mno-stack-align | |
10649 | @itemx -mdata-align | |
10650 | @itemx -mno-data-align | |
10651 | @itemx -mconst-align | |
10652 | @itemx -mno-const-align | |
10653 | @opindex mstack-align | |
10654 | @opindex mno-stack-align | |
10655 | @opindex mdata-align | |
10656 | @opindex mno-data-align | |
10657 | @opindex mconst-align | |
10658 | @opindex mno-const-align | |
10659 | These options (no-options) arranges (eliminate arrangements) for the | |
10660 | stack-frame, individual data and constants to be aligned for the maximum | |
10661 | single data access size for the chosen CPU model. The default is to | |
10662 | arrange for 32-bit alignment. ABI details such as structure layout are | |
10663 | not affected by these options. | |
238b11b5 | 10664 | |
39bc1876 NS |
10665 | @item -m32-bit |
10666 | @itemx -m16-bit | |
10667 | @itemx -m8-bit | |
10668 | @opindex m32-bit | |
10669 | @opindex m16-bit | |
10670 | @opindex m8-bit | |
10671 | Similar to the stack- data- and const-align options above, these options | |
10672 | arrange for stack-frame, writable data and constants to all be 32-bit, | |
10673 | 16-bit or 8-bit aligned. The default is 32-bit alignment. | |
238b11b5 | 10674 | |
39bc1876 NS |
10675 | @item -mno-prologue-epilogue |
10676 | @itemx -mprologue-epilogue | |
10677 | @opindex mno-prologue-epilogue | |
10678 | @opindex mprologue-epilogue | |
10679 | With @option{-mno-prologue-epilogue}, the normal function prologue and | |
10680 | epilogue that sets up the stack-frame are omitted and no return | |
10681 | instructions or return sequences are generated in the code. Use this | |
10682 | option only together with visual inspection of the compiled code: no | |
10683 | warnings or errors are generated when call-saved registers must be saved, | |
10684 | or storage for local variable needs to be allocated. | |
238b11b5 | 10685 | |
39bc1876 NS |
10686 | @item -mno-gotplt |
10687 | @itemx -mgotplt | |
10688 | @opindex mno-gotplt | |
10689 | @opindex mgotplt | |
10690 | With @option{-fpic} and @option{-fPIC}, don't generate (do generate) | |
10691 | instruction sequences that load addresses for functions from the PLT part | |
10692 | of the GOT rather than (traditional on other architectures) calls to the | |
8a36672b | 10693 | PLT@. The default is @option{-mgotplt}. |
238b11b5 | 10694 | |
39bc1876 NS |
10695 | @item -melf |
10696 | @opindex melf | |
10697 | Legacy no-op option only recognized with the cris-axis-elf and | |
10698 | cris-axis-linux-gnu targets. | |
74291a4b | 10699 | |
39bc1876 NS |
10700 | @item -mlinux |
10701 | @opindex mlinux | |
10702 | Legacy no-op option only recognized with the cris-axis-linux-gnu target. | |
ded17aad | 10703 | |
39bc1876 NS |
10704 | @item -sim |
10705 | @opindex sim | |
cd985f66 | 10706 | This option, recognized for the cris-axis-elf arranges |
39bc1876 NS |
10707 | to link with input-output functions from a simulator library. Code, |
10708 | initialized data and zero-initialized data are allocated consecutively. | |
74291a4b | 10709 | |
39bc1876 NS |
10710 | @item -sim2 |
10711 | @opindex sim2 | |
10712 | Like @option{-sim}, but pass linker options to locate initialized data at | |
10713 | 0x40000000 and zero-initialized data at 0x80000000. | |
74291a4b MM |
10714 | @end table |
10715 | ||
53054e77 PW |
10716 | @node CRX Options |
10717 | @subsection CRX Options | |
10718 | @cindex CRX Options | |
10719 | ||
10720 | These options are defined specifically for the CRX ports. | |
10721 | ||
10722 | @table @gcctabopt | |
10723 | ||
10724 | @item -mmac | |
10725 | @opindex mmac | |
10726 | Enable the use of multiply-accumulate instructions. Disabled by default. | |
10727 | ||
10728 | @item -mpush-args | |
10729 | @opindex mpush-args | |
10730 | Push instructions will be used to pass outgoing arguments when functions | |
10731 | are called. Enabled by default. | |
10732 | @end table | |
10733 | ||
39bc1876 NS |
10734 | @node Darwin Options |
10735 | @subsection Darwin Options | |
10736 | @cindex Darwin options | |
74291a4b | 10737 | |
39bc1876 | 10738 | These options are defined for all architectures running the Darwin operating |
965a7e90 GK |
10739 | system. |
10740 | ||
10741 | FSF GCC on Darwin does not create ``fat'' object files; it will create | |
10742 | an object file for the single architecture that it was built to | |
10743 | target. Apple's GCC on Darwin does create ``fat'' files if multiple | |
46bfe5e3 GK |
10744 | @option{-arch} options are used; it does so by running the compiler or |
10745 | linker multiple times and joining the results together with | |
10746 | @file{lipo}. | |
965a7e90 | 10747 | |
46bfe5e3 GK |
10748 | The subtype of the file created (like @samp{ppc7400} or @samp{ppc970} or |
10749 | @samp{i686}) is determined by the flags that specify the ISA | |
10750 | that GCC is targetting, like @option{-mcpu} or @option{-march}. The | |
965a7e90 | 10751 | @option{-force_cpusubtype_ALL} option can be used to override this. |
74291a4b | 10752 | |
38b974a6 | 10753 | The Darwin tools vary in their behavior when presented with an ISA |
46bfe5e3 GK |
10754 | mismatch. The assembler, @file{as}, will only permit instructions to |
10755 | be used that are valid for the subtype of the file it is generating, | |
e4ae5e77 | 10756 | so you cannot put 64-bit instructions in a @samp{ppc750} object file. |
46bfe5e3 GK |
10757 | The linker for shared libraries, @file{/usr/bin/libtool}, will fail |
10758 | and print an error if asked to create a shared library with a less | |
10759 | restrictive subtype than its input files (for instance, trying to put | |
10760 | a @samp{ppc970} object file in a @samp{ppc7400} library). The linker | |
10761 | for executables, @file{ld}, will quietly give the executable the most | |
10762 | restrictive subtype of any of its input files. | |
10763 | ||
2642624b | 10764 | @table @gcctabopt |
39bc1876 NS |
10765 | @item -F@var{dir} |
10766 | @opindex F | |
10767 | Add the framework directory @var{dir} to the head of the list of | |
10768 | directories to be searched for header files. These directories are | |
10769 | interleaved with those specified by @option{-I} options and are | |
10770 | scanned in a left-to-right order. | |
5848830f | 10771 | |
39bc1876 NS |
10772 | A framework directory is a directory with frameworks in it. A |
10773 | framework is a directory with a @samp{"Headers"} and/or | |
10774 | @samp{"PrivateHeaders"} directory contained directly in it that ends | |
10775 | in @samp{".framework"}. The name of a framework is the name of this | |
10776 | directory excluding the @samp{".framework"}. Headers associated with | |
10777 | the framework are found in one of those two directories, with | |
10778 | @samp{"Headers"} being searched first. A subframework is a framework | |
10779 | directory that is in a framework's @samp{"Frameworks"} directory. | |
10780 | Includes of subframework headers can only appear in a header of a | |
10781 | framework that contains the subframework, or in a sibling subframework | |
10782 | header. Two subframeworks are siblings if they occur in the same | |
10783 | framework. A subframework should not have the same name as a | |
10784 | framework, a warning will be issued if this is violated. Currently a | |
10785 | subframework cannot have subframeworks, in the future, the mechanism | |
10786 | may be extended to support this. The standard frameworks can be found | |
3e558e80 MS |
10787 | in @samp{"/System/Library/Frameworks"} and |
10788 | @samp{"/Library/Frameworks"}. An example include looks like | |
39bc1876 NS |
10789 | @code{#include <Framework/header.h>}, where @samp{Framework} denotes |
10790 | the name of the framework and header.h is found in the | |
10791 | @samp{"PrivateHeaders"} or @samp{"Headers"} directory. | |
157a620e | 10792 | |
1f1d5130 MS |
10793 | @item -iframework@var{dir} |
10794 | @opindex iframework | |
10795 | Like @option{-F} except the directory is a treated as a system | |
10796 | directory. The main difference between this @option{-iframework} and | |
10797 | @option{-F} is that with @option{-iframework} the compiler does not | |
10798 | warn about constructs contained within header files found via | |
10799 | @var{dir}. This option is valid only for the C family of languages. | |
10800 | ||
7aded944 | 10801 | @item -gused |
edc5f63b | 10802 | @opindex gused |
8a36672b | 10803 | Emit debugging information for symbols that are used. For STABS |
7aded944 | 10804 | debugging format, this enables @option{-feliminate-unused-debug-symbols}. |
8a36672b | 10805 | This is by default ON@. |
7aded944 DP |
10806 | |
10807 | @item -gfull | |
edc5f63b | 10808 | @opindex gfull |
7aded944 DP |
10809 | Emit debugging information for all symbols and types. |
10810 | ||
ed5b9f96 GK |
10811 | @item -mmacosx-version-min=@var{version} |
10812 | The earliest version of MacOS X that this executable will run on | |
10813 | is @var{version}. Typical values of @var{version} include @code{10.1}, | |
10814 | @code{10.2}, and @code{10.3.9}. | |
10815 | ||
e46b55d0 GK |
10816 | If the compiler was built to use the system's headers by default, |
10817 | then the default for this option is the system version on which the | |
10818 | compiler is running, otherwise the default is to make choices which | |
10819 | are compatible with as many systems and code bases as possible. | |
ed5b9f96 | 10820 | |
57164024 MS |
10821 | @item -mkernel |
10822 | @opindex mkernel | |
b5d713b9 | 10823 | Enable kernel development mode. The @option{-mkernel} option sets |
57164024 MS |
10824 | @option{-static}, @option{-fno-common}, @option{-fno-cxa-atexit}, |
10825 | @option{-fno-exceptions}, @option{-fno-non-call-exceptions}, | |
10826 | @option{-fapple-kext}, @option{-fno-weak} and @option{-fno-rtti} where | |
10827 | applicable. This mode also sets @option{-mno-altivec}, | |
10828 | @option{-msoft-float}, @option{-fno-builtin} and | |
10829 | @option{-mlong-branch} for PowerPC targets. | |
10830 | ||
8f4220dc | 10831 | @item -mone-byte-bool |
edc5f63b | 10832 | @opindex mone-byte-bool |
8f4220dc | 10833 | Override the defaults for @samp{bool} so that @samp{sizeof(bool)==1}. |
f0eb93a8 | 10834 | By default @samp{sizeof(bool)} is @samp{4} when compiling for |
8f4220dc MA |
10835 | Darwin/PowerPC and @samp{1} when compiling for Darwin/x86, so this |
10836 | option has no effect on x86. | |
10837 | ||
10838 | @strong{Warning:} The @option{-mone-byte-bool} switch causes GCC | |
10839 | to generate code that is not binary compatible with code generated | |
10840 | without that switch. Using this switch may require recompiling all | |
f0eb93a8 | 10841 | other modules in a program, including system libraries. Use this |
8f4220dc MA |
10842 | switch to conform to a non-default data model. |
10843 | ||
699c914a MS |
10844 | @item -mfix-and-continue |
10845 | @itemx -ffix-and-continue | |
10846 | @itemx -findirect-data | |
10847 | @opindex mfix-and-continue | |
10848 | @opindex ffix-and-continue | |
10849 | @opindex findirect-data | |
10850 | Generate code suitable for fast turn around development. Needed to | |
10851 | enable gdb to dynamically load @code{.o} files into already running | |
10852 | programs. @option{-findirect-data} and @option{-ffix-and-continue} | |
10853 | are provided for backwards compatibility. | |
10854 | ||
39bc1876 NS |
10855 | @item -all_load |
10856 | @opindex all_load | |
10857 | Loads all members of static archive libraries. | |
10858 | See man ld(1) for more information. | |
74291a4b | 10859 | |
39bc1876 NS |
10860 | @item -arch_errors_fatal |
10861 | @opindex arch_errors_fatal | |
10862 | Cause the errors having to do with files that have the wrong architecture | |
10863 | to be fatal. | |
157a620e | 10864 | |
39bc1876 NS |
10865 | @item -bind_at_load |
10866 | @opindex bind_at_load | |
10867 | Causes the output file to be marked such that the dynamic linker will | |
10868 | bind all undefined references when the file is loaded or launched. | |
157a620e | 10869 | |
39bc1876 NS |
10870 | @item -bundle |
10871 | @opindex bundle | |
10872 | Produce a Mach-o bundle format file. | |
10873 | See man ld(1) for more information. | |
157a620e | 10874 | |
39bc1876 NS |
10875 | @item -bundle_loader @var{executable} |
10876 | @opindex bundle_loader | |
965a7e90 | 10877 | This option specifies the @var{executable} that will be loading the build |
8a36672b | 10878 | output file being linked. See man ld(1) for more information. |
157a620e | 10879 | |
965a7e90 | 10880 | @item -dynamiclib |
edc5f63b | 10881 | @opindex dynamiclib |
965a7e90 GK |
10882 | When passed this option, GCC will produce a dynamic library instead of |
10883 | an executable when linking, using the Darwin @file{libtool} command. | |
157a620e | 10884 | |
965a7e90 | 10885 | @item -force_cpusubtype_ALL |
edc5f63b | 10886 | @opindex force_cpusubtype_ALL |
965a7e90 GK |
10887 | This causes GCC's output file to have the @var{ALL} subtype, instead of |
10888 | one controlled by the @option{-mcpu} or @option{-march} option. | |
10889 | ||
10890 | @item -allowable_client @var{client_name} | |
39bc1876 NS |
10891 | @itemx -client_name |
10892 | @itemx -compatibility_version | |
10893 | @itemx -current_version | |
5079843a | 10894 | @itemx -dead_strip |
39bc1876 NS |
10895 | @itemx -dependency-file |
10896 | @itemx -dylib_file | |
10897 | @itemx -dylinker_install_name | |
10898 | @itemx -dynamic | |
39bc1876 NS |
10899 | @itemx -exported_symbols_list |
10900 | @itemx -filelist | |
ab940b73 | 10901 | @need 800 |
39bc1876 | 10902 | @itemx -flat_namespace |
39bc1876 NS |
10903 | @itemx -force_flat_namespace |
10904 | @itemx -headerpad_max_install_names | |
10905 | @itemx -image_base | |
10906 | @itemx -init | |
10907 | @itemx -install_name | |
10908 | @itemx -keep_private_externs | |
10909 | @itemx -multi_module | |
10910 | @itemx -multiply_defined | |
10911 | @itemx -multiply_defined_unused | |
ab940b73 | 10912 | @need 800 |
39bc1876 | 10913 | @itemx -noall_load |
89aa5a20 | 10914 | @itemx -no_dead_strip_inits_and_terms |
39bc1876 NS |
10915 | @itemx -nofixprebinding |
10916 | @itemx -nomultidefs | |
10917 | @itemx -noprebind | |
10918 | @itemx -noseglinkedit | |
10919 | @itemx -pagezero_size | |
10920 | @itemx -prebind | |
10921 | @itemx -prebind_all_twolevel_modules | |
10922 | @itemx -private_bundle | |
ab940b73 | 10923 | @need 800 |
39bc1876 NS |
10924 | @itemx -read_only_relocs |
10925 | @itemx -sectalign | |
10926 | @itemx -sectobjectsymbols | |
10927 | @itemx -whyload | |
10928 | @itemx -seg1addr | |
10929 | @itemx -sectcreate | |
10930 | @itemx -sectobjectsymbols | |
10931 | @itemx -sectorder | |
5826770c DP |
10932 | @itemx -segaddr |
10933 | @itemx -segs_read_only_addr | |
ab940b73 | 10934 | @need 800 |
5826770c | 10935 | @itemx -segs_read_write_addr |
39bc1876 NS |
10936 | @itemx -seg_addr_table |
10937 | @itemx -seg_addr_table_filename | |
10938 | @itemx -seglinkedit | |
10939 | @itemx -segprot | |
10940 | @itemx -segs_read_only_addr | |
10941 | @itemx -segs_read_write_addr | |
10942 | @itemx -single_module | |
10943 | @itemx -static | |
10944 | @itemx -sub_library | |
ab940b73 | 10945 | @need 800 |
39bc1876 NS |
10946 | @itemx -sub_umbrella |
10947 | @itemx -twolevel_namespace | |
10948 | @itemx -umbrella | |
10949 | @itemx -undefined | |
10950 | @itemx -unexported_symbols_list | |
10951 | @itemx -weak_reference_mismatches | |
10952 | @itemx -whatsloaded | |
39bc1876 | 10953 | @opindex allowable_client |
39bc1876 NS |
10954 | @opindex client_name |
10955 | @opindex compatibility_version | |
10956 | @opindex current_version | |
5079843a | 10957 | @opindex dead_strip |
39bc1876 NS |
10958 | @opindex dependency-file |
10959 | @opindex dylib_file | |
10960 | @opindex dylinker_install_name | |
10961 | @opindex dynamic | |
39bc1876 NS |
10962 | @opindex exported_symbols_list |
10963 | @opindex filelist | |
10964 | @opindex flat_namespace | |
39bc1876 NS |
10965 | @opindex force_flat_namespace |
10966 | @opindex headerpad_max_install_names | |
10967 | @opindex image_base | |
10968 | @opindex init | |
10969 | @opindex install_name | |
10970 | @opindex keep_private_externs | |
10971 | @opindex multi_module | |
10972 | @opindex multiply_defined | |
10973 | @opindex multiply_defined_unused | |
10974 | @opindex noall_load | |
5079843a | 10975 | @opindex no_dead_strip_inits_and_terms |
39bc1876 NS |
10976 | @opindex nofixprebinding |
10977 | @opindex nomultidefs | |
10978 | @opindex noprebind | |
10979 | @opindex noseglinkedit | |
10980 | @opindex pagezero_size | |
10981 | @opindex prebind | |
10982 | @opindex prebind_all_twolevel_modules | |
10983 | @opindex private_bundle | |
10984 | @opindex read_only_relocs | |
10985 | @opindex sectalign | |
10986 | @opindex sectobjectsymbols | |
10987 | @opindex whyload | |
10988 | @opindex seg1addr | |
10989 | @opindex sectcreate | |
10990 | @opindex sectobjectsymbols | |
10991 | @opindex sectorder | |
5826770c DP |
10992 | @opindex segaddr |
10993 | @opindex segs_read_only_addr | |
10994 | @opindex segs_read_write_addr | |
39bc1876 NS |
10995 | @opindex seg_addr_table |
10996 | @opindex seg_addr_table_filename | |
10997 | @opindex seglinkedit | |
10998 | @opindex segprot | |
10999 | @opindex segs_read_only_addr | |
11000 | @opindex segs_read_write_addr | |
11001 | @opindex single_module | |
11002 | @opindex static | |
11003 | @opindex sub_library | |
11004 | @opindex sub_umbrella | |
11005 | @opindex twolevel_namespace | |
11006 | @opindex umbrella | |
11007 | @opindex undefined | |
11008 | @opindex unexported_symbols_list | |
11009 | @opindex weak_reference_mismatches | |
11010 | @opindex whatsloaded | |
965a7e90 | 11011 | These options are passed to the Darwin linker. The Darwin linker man page |
39bc1876 NS |
11012 | describes them in detail. |
11013 | @end table | |
11014 | ||
11015 | @node DEC Alpha Options | |
11016 | @subsection DEC Alpha Options | |
11017 | ||
11018 | These @samp{-m} options are defined for the DEC Alpha implementations: | |
11019 | ||
11020 | @table @gcctabopt | |
11021 | @item -mno-soft-float | |
11022 | @itemx -msoft-float | |
11023 | @opindex mno-soft-float | |
cd3bb277 | 11024 | @opindex msoft-float |
39bc1876 NS |
11025 | Use (do not use) the hardware floating-point instructions for |
11026 | floating-point operations. When @option{-msoft-float} is specified, | |
11027 | functions in @file{libgcc.a} will be used to perform floating-point | |
11028 | operations. Unless they are replaced by routines that emulate the | |
11029 | floating-point operations, or compiled in such a way as to call such | |
11030 | emulations routines, these routines will issue floating-point | |
11031 | operations. If you are compiling for an Alpha without floating-point | |
11032 | operations, you must ensure that the library is built so as not to call | |
11033 | them. | |
74291a4b | 11034 | |
39bc1876 NS |
11035 | Note that Alpha implementations without floating-point operations are |
11036 | required to have floating-point registers. | |
74291a4b | 11037 | |
39bc1876 NS |
11038 | @item -mfp-reg |
11039 | @itemx -mno-fp-regs | |
11040 | @opindex mfp-reg | |
11041 | @opindex mno-fp-regs | |
11042 | Generate code that uses (does not use) the floating-point register set. | |
11043 | @option{-mno-fp-regs} implies @option{-msoft-float}. If the floating-point | |
11044 | register set is not used, floating point operands are passed in integer | |
11045 | registers as if they were integers and floating-point results are passed | |
11046 | in @code{$0} instead of @code{$f0}. This is a non-standard calling sequence, | |
11047 | so any function with a floating-point argument or return value called by code | |
11048 | compiled with @option{-mno-fp-regs} must also be compiled with that | |
11049 | option. | |
9b66ebb1 | 11050 | |
39bc1876 NS |
11051 | A typical use of this option is building a kernel that does not use, |
11052 | and hence need not save and restore, any floating-point registers. | |
9b66ebb1 | 11053 | |
39bc1876 NS |
11054 | @item -mieee |
11055 | @opindex mieee | |
11056 | The Alpha architecture implements floating-point hardware optimized for | |
11057 | maximum performance. It is mostly compliant with the IEEE floating | |
11058 | point standard. However, for full compliance, software assistance is | |
11059 | required. This option generates code fully IEEE compliant code | |
11060 | @emph{except} that the @var{inexact-flag} is not maintained (see below). | |
11061 | If this option is turned on, the preprocessor macro @code{_IEEE_FP} is | |
11062 | defined during compilation. The resulting code is less efficient but is | |
11063 | able to correctly support denormalized numbers and exceptional IEEE | |
11064 | values such as not-a-number and plus/minus infinity. Other Alpha | |
11065 | compilers call this option @option{-ieee_with_no_inexact}. | |
74291a4b | 11066 | |
39bc1876 NS |
11067 | @item -mieee-with-inexact |
11068 | @opindex mieee-with-inexact | |
11069 | This is like @option{-mieee} except the generated code also maintains | |
11070 | the IEEE @var{inexact-flag}. Turning on this option causes the | |
11071 | generated code to implement fully-compliant IEEE math. In addition to | |
11072 | @code{_IEEE_FP}, @code{_IEEE_FP_EXACT} is defined as a preprocessor | |
11073 | macro. On some Alpha implementations the resulting code may execute | |
11074 | significantly slower than the code generated by default. Since there is | |
11075 | very little code that depends on the @var{inexact-flag}, you should | |
11076 | normally not specify this option. Other Alpha compilers call this | |
11077 | option @option{-ieee_with_inexact}. | |
74291a4b | 11078 | |
39bc1876 NS |
11079 | @item -mfp-trap-mode=@var{trap-mode} |
11080 | @opindex mfp-trap-mode | |
11081 | This option controls what floating-point related traps are enabled. | |
11082 | Other Alpha compilers call this option @option{-fptm @var{trap-mode}}. | |
11083 | The trap mode can be set to one of four values: | |
74291a4b | 11084 | |
39bc1876 NS |
11085 | @table @samp |
11086 | @item n | |
11087 | This is the default (normal) setting. The only traps that are enabled | |
11088 | are the ones that cannot be disabled in software (e.g., division by zero | |
11089 | trap). | |
62b10bbc | 11090 | |
39bc1876 NS |
11091 | @item u |
11092 | In addition to the traps enabled by @samp{n}, underflow traps are enabled | |
11093 | as well. | |
157a620e | 11094 | |
39bc1876 | 11095 | @item su |
90150441 | 11096 | Like @samp{u}, but the instructions are marked to be safe for software |
39bc1876 | 11097 | completion (see Alpha architecture manual for details). |
157a620e | 11098 | |
39bc1876 NS |
11099 | @item sui |
11100 | Like @samp{su}, but inexact traps are enabled as well. | |
11101 | @end table | |
9b66ebb1 | 11102 | |
39bc1876 NS |
11103 | @item -mfp-rounding-mode=@var{rounding-mode} |
11104 | @opindex mfp-rounding-mode | |
11105 | Selects the IEEE rounding mode. Other Alpha compilers call this option | |
11106 | @option{-fprm @var{rounding-mode}}. The @var{rounding-mode} can be one | |
11107 | of: | |
157a620e | 11108 | |
39bc1876 NS |
11109 | @table @samp |
11110 | @item n | |
11111 | Normal IEEE rounding mode. Floating point numbers are rounded towards | |
11112 | the nearest machine number or towards the even machine number in case | |
11113 | of a tie. | |
5848830f | 11114 | |
39bc1876 NS |
11115 | @item m |
11116 | Round towards minus infinity. | |
157a620e | 11117 | |
39bc1876 NS |
11118 | @item c |
11119 | Chopped rounding mode. Floating point numbers are rounded towards zero. | |
f5a1b0d2 | 11120 | |
39bc1876 NS |
11121 | @item d |
11122 | Dynamic rounding mode. A field in the floating point control register | |
11123 | (@var{fpcr}, see Alpha architecture reference manual) controls the | |
11124 | rounding mode in effect. The C library initializes this register for | |
11125 | rounding towards plus infinity. Thus, unless your program modifies the | |
11126 | @var{fpcr}, @samp{d} corresponds to round towards plus infinity. | |
11127 | @end table | |
c27ba912 | 11128 | |
39bc1876 NS |
11129 | @item -mtrap-precision=@var{trap-precision} |
11130 | @opindex mtrap-precision | |
11131 | In the Alpha architecture, floating point traps are imprecise. This | |
11132 | means without software assistance it is impossible to recover from a | |
11133 | floating trap and program execution normally needs to be terminated. | |
11134 | GCC can generate code that can assist operating system trap handlers | |
11135 | in determining the exact location that caused a floating point trap. | |
11136 | Depending on the requirements of an application, different levels of | |
11137 | precisions can be selected: | |
c27ba912 | 11138 | |
39bc1876 NS |
11139 | @table @samp |
11140 | @item p | |
11141 | Program precision. This option is the default and means a trap handler | |
11142 | can only identify which program caused a floating point exception. | |
c27ba912 | 11143 | |
39bc1876 NS |
11144 | @item f |
11145 | Function precision. The trap handler can determine the function that | |
11146 | caused a floating point exception. | |
62b10bbc | 11147 | |
39bc1876 NS |
11148 | @item i |
11149 | Instruction precision. The trap handler can determine the exact | |
11150 | instruction that caused a floating point exception. | |
11151 | @end table | |
ed0e6530 | 11152 | |
39bc1876 NS |
11153 | Other Alpha compilers provide the equivalent options called |
11154 | @option{-scope_safe} and @option{-resumption_safe}. | |
ed0e6530 | 11155 | |
39bc1876 NS |
11156 | @item -mieee-conformant |
11157 | @opindex mieee-conformant | |
11158 | This option marks the generated code as IEEE conformant. You must not | |
11159 | use this option unless you also specify @option{-mtrap-precision=i} and either | |
11160 | @option{-mfp-trap-mode=su} or @option{-mfp-trap-mode=sui}. Its only effect | |
11161 | is to emit the line @samp{.eflag 48} in the function prologue of the | |
11162 | generated assembly file. Under DEC Unix, this has the effect that | |
11163 | IEEE-conformant math library routines will be linked in. | |
9b6b54e2 | 11164 | |
39bc1876 NS |
11165 | @item -mbuild-constants |
11166 | @opindex mbuild-constants | |
11167 | Normally GCC examines a 32- or 64-bit integer constant to | |
11168 | see if it can construct it from smaller constants in two or three | |
11169 | instructions. If it cannot, it will output the constant as a literal and | |
11170 | generate code to load it from the data segment at runtime. | |
74291a4b | 11171 | |
39bc1876 NS |
11172 | Use this option to require GCC to construct @emph{all} integer constants |
11173 | using code, even if it takes more instructions (the maximum is six). | |
157a620e | 11174 | |
39bc1876 NS |
11175 | You would typically use this option to build a shared library dynamic |
11176 | loader. Itself a shared library, it must relocate itself in memory | |
11177 | before it can find the variables and constants in its own data segment. | |
11178 | ||
11179 | @item -malpha-as | |
11180 | @itemx -mgas | |
11181 | @opindex malpha-as | |
11182 | @opindex mgas | |
11183 | Select whether to generate code to be assembled by the vendor-supplied | |
11184 | assembler (@option{-malpha-as}) or by the GNU assembler @option{-mgas}. | |
11185 | ||
11186 | @item -mbwx | |
11187 | @itemx -mno-bwx | |
11188 | @itemx -mcix | |
11189 | @itemx -mno-cix | |
11190 | @itemx -mfix | |
11191 | @itemx -mno-fix | |
11192 | @itemx -mmax | |
11193 | @itemx -mno-max | |
11194 | @opindex mbwx | |
11195 | @opindex mno-bwx | |
11196 | @opindex mcix | |
11197 | @opindex mno-cix | |
11198 | @opindex mfix | |
11199 | @opindex mno-fix | |
11200 | @opindex mmax | |
11201 | @opindex mno-max | |
11202 | Indicate whether GCC should generate code to use the optional BWX, | |
11203 | CIX, FIX and MAX instruction sets. The default is to use the instruction | |
11204 | sets supported by the CPU type specified via @option{-mcpu=} option or that | |
11205 | of the CPU on which GCC was built if none was specified. | |
157a620e | 11206 | |
39bc1876 NS |
11207 | @item -mfloat-vax |
11208 | @itemx -mfloat-ieee | |
11209 | @opindex mfloat-vax | |
11210 | @opindex mfloat-ieee | |
11211 | Generate code that uses (does not use) VAX F and G floating point | |
11212 | arithmetic instead of IEEE single and double precision. | |
157a620e | 11213 | |
39bc1876 NS |
11214 | @item -mexplicit-relocs |
11215 | @itemx -mno-explicit-relocs | |
11216 | @opindex mexplicit-relocs | |
11217 | @opindex mno-explicit-relocs | |
11218 | Older Alpha assemblers provided no way to generate symbol relocations | |
11219 | except via assembler macros. Use of these macros does not allow | |
11220 | optimal instruction scheduling. GNU binutils as of version 2.12 | |
11221 | supports a new syntax that allows the compiler to explicitly mark | |
11222 | which relocations should apply to which instructions. This option | |
11223 | is mostly useful for debugging, as GCC detects the capabilities of | |
11224 | the assembler when it is built and sets the default accordingly. | |
157a620e | 11225 | |
39bc1876 NS |
11226 | @item -msmall-data |
11227 | @itemx -mlarge-data | |
11228 | @opindex msmall-data | |
11229 | @opindex mlarge-data | |
11230 | When @option{-mexplicit-relocs} is in effect, static data is | |
11231 | accessed via @dfn{gp-relative} relocations. When @option{-msmall-data} | |
11232 | is used, objects 8 bytes long or smaller are placed in a @dfn{small data area} | |
11233 | (the @code{.sdata} and @code{.sbss} sections) and are accessed via | |
11234 | 16-bit relocations off of the @code{$gp} register. This limits the | |
11235 | size of the small data area to 64KB, but allows the variables to be | |
11236 | directly accessed via a single instruction. | |
62b10bbc | 11237 | |
39bc1876 | 11238 | The default is @option{-mlarge-data}. With this option the data area |
8a36672b | 11239 | is limited to just below 2GB@. Programs that require more than 2GB of |
39bc1876 NS |
11240 | data must use @code{malloc} or @code{mmap} to allocate the data in the |
11241 | heap instead of in the program's data segment. | |
62b10bbc | 11242 | |
39bc1876 NS |
11243 | When generating code for shared libraries, @option{-fpic} implies |
11244 | @option{-msmall-data} and @option{-fPIC} implies @option{-mlarge-data}. | |
4bdc1ac7 | 11245 | |
39bc1876 NS |
11246 | @item -msmall-text |
11247 | @itemx -mlarge-text | |
11248 | @opindex msmall-text | |
11249 | @opindex mlarge-text | |
11250 | When @option{-msmall-text} is used, the compiler assumes that the | |
11251 | code of the entire program (or shared library) fits in 4MB, and is | |
11252 | thus reachable with a branch instruction. When @option{-msmall-data} | |
11253 | is used, the compiler can assume that all local symbols share the | |
11254 | same @code{$gp} value, and thus reduce the number of instructions | |
11255 | required for a function call from 4 to 1. | |
157a620e | 11256 | |
39bc1876 | 11257 | The default is @option{-mlarge-text}. |
d2d42a91 | 11258 | |
39bc1876 NS |
11259 | @item -mcpu=@var{cpu_type} |
11260 | @opindex mcpu | |
11261 | Set the instruction set and instruction scheduling parameters for | |
11262 | machine type @var{cpu_type}. You can specify either the @samp{EV} | |
11263 | style name or the corresponding chip number. GCC supports scheduling | |
11264 | parameters for the EV4, EV5 and EV6 family of processors and will | |
11265 | choose the default values for the instruction set from the processor | |
11266 | you specify. If you do not specify a processor type, GCC will default | |
11267 | to the processor on which the compiler was built. | |
6d6d0fa0 | 11268 | |
39bc1876 | 11269 | Supported values for @var{cpu_type} are |
6d6d0fa0 | 11270 | |
39bc1876 NS |
11271 | @table @samp |
11272 | @item ev4 | |
11273 | @itemx ev45 | |
11274 | @itemx 21064 | |
11275 | Schedules as an EV4 and has no instruction set extensions. | |
ecff22ab | 11276 | |
39bc1876 NS |
11277 | @item ev5 |
11278 | @itemx 21164 | |
11279 | Schedules as an EV5 and has no instruction set extensions. | |
705ac34f | 11280 | |
39bc1876 NS |
11281 | @item ev56 |
11282 | @itemx 21164a | |
11283 | Schedules as an EV5 and supports the BWX extension. | |
705ac34f | 11284 | |
39bc1876 NS |
11285 | @item pca56 |
11286 | @itemx 21164pc | |
11287 | @itemx 21164PC | |
11288 | Schedules as an EV5 and supports the BWX and MAX extensions. | |
c474f76b | 11289 | |
39bc1876 NS |
11290 | @item ev6 |
11291 | @itemx 21264 | |
11292 | Schedules as an EV6 and supports the BWX, FIX, and MAX extensions. | |
ecff22ab | 11293 | |
39bc1876 NS |
11294 | @item ev67 |
11295 | @itemx 21264a | |
11296 | Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX extensions. | |
6d6d0fa0 JL |
11297 | @end table |
11298 | ||
d94a427e AL |
11299 | Native Linux/GNU toolchains also support the value @samp{native}, |
11300 | which selects the best architecture option for the host processor. | |
11301 | @option{-mcpu=native} has no effect if GCC does not recognize | |
11302 | the processor. | |
11303 | ||
39bc1876 NS |
11304 | @item -mtune=@var{cpu_type} |
11305 | @opindex mtune | |
11306 | Set only the instruction scheduling parameters for machine type | |
11307 | @var{cpu_type}. The instruction set is not changed. | |
ecff22ab | 11308 | |
d94a427e AL |
11309 | Native Linux/GNU toolchains also support the value @samp{native}, |
11310 | which selects the best architecture option for the host processor. | |
11311 | @option{-mtune=native} has no effect if GCC does not recognize | |
11312 | the processor. | |
11313 | ||
39bc1876 NS |
11314 | @item -mmemory-latency=@var{time} |
11315 | @opindex mmemory-latency | |
11316 | Sets the latency the scheduler should assume for typical memory | |
11317 | references as seen by the application. This number is highly | |
11318 | dependent on the memory access patterns used by the application | |
11319 | and the size of the external cache on the machine. | |
861bb6c1 | 11320 | |
39bc1876 | 11321 | Valid options for @var{time} are |
6975bd2c | 11322 | |
39bc1876 NS |
11323 | @table @samp |
11324 | @item @var{number} | |
11325 | A decimal number representing clock cycles. | |
98180123 | 11326 | |
39bc1876 NS |
11327 | @item L1 |
11328 | @itemx L2 | |
11329 | @itemx L3 | |
11330 | @itemx main | |
11331 | The compiler contains estimates of the number of clock cycles for | |
11332 | ``typical'' EV4 & EV5 hardware for the Level 1, 2 & 3 caches | |
11333 | (also called Dcache, Scache, and Bcache), as well as to main memory. | |
11334 | Note that L3 is only valid for EV5. | |
de41e41c | 11335 | |
39bc1876 NS |
11336 | @end table |
11337 | @end table | |
861bb6c1 | 11338 | |
39bc1876 NS |
11339 | @node DEC Alpha/VMS Options |
11340 | @subsection DEC Alpha/VMS Options | |
861bb6c1 | 11341 | |
39bc1876 | 11342 | These @samp{-m} options are defined for the DEC Alpha/VMS implementations: |
861bb6c1 | 11343 | |
39bc1876 NS |
11344 | @table @gcctabopt |
11345 | @item -mvms-return-codes | |
11346 | @opindex mvms-return-codes | |
65a324b4 | 11347 | Return VMS condition codes from main. The default is to return POSIX |
9f06d330 | 11348 | style condition (e.g.@: error) codes. |
5ea8f977 DR |
11349 | |
11350 | @item -mdebug-main=@var{prefix} | |
11351 | @opindex mdebug-main=@var{prefix} | |
11352 | Flag the first routine whose name starts with @var{prefix} as the main | |
11353 | routine for the debugger. | |
5e3fef6c DR |
11354 | |
11355 | @item -mmalloc64 | |
11356 | @opindex mmalloc64 | |
11357 | Default to 64bit memory allocation routines. | |
39bc1876 | 11358 | @end table |
861bb6c1 | 11359 | |
18a3bdcb NC |
11360 | @node FR30 Options |
11361 | @subsection FR30 Options | |
11362 | @cindex FR30 Options | |
11363 | ||
11364 | These options are defined specifically for the FR30 port. | |
11365 | ||
11366 | @table @gcctabopt | |
11367 | ||
11368 | @item -msmall-model | |
11369 | @opindex msmall-model | |
11370 | Use the small address space model. This can produce smaller code, but | |
11371 | it does assume that all symbolic values and addresses will fit into a | |
11372 | 20-bit range. | |
11373 | ||
11374 | @item -mno-lsim | |
11375 | @opindex mno-lsim | |
11376 | Assume that run-time support has been provided and so there is no need | |
11377 | to include the simulator library (@file{libsim.a}) on the linker | |
11378 | command line. | |
11379 | ||
11380 | @end table | |
11381 | ||
39bc1876 NS |
11382 | @node FRV Options |
11383 | @subsection FRV Options | |
11384 | @cindex FRV Options | |
861bb6c1 | 11385 | |
39bc1876 NS |
11386 | @table @gcctabopt |
11387 | @item -mgpr-32 | |
11388 | @opindex mgpr-32 | |
861bb6c1 | 11389 | |
39bc1876 | 11390 | Only use the first 32 general purpose registers. |
861bb6c1 | 11391 | |
39bc1876 NS |
11392 | @item -mgpr-64 |
11393 | @opindex mgpr-64 | |
861bb6c1 | 11394 | |
39bc1876 | 11395 | Use all 64 general purpose registers. |
861bb6c1 | 11396 | |
39bc1876 NS |
11397 | @item -mfpr-32 |
11398 | @opindex mfpr-32 | |
861bb6c1 | 11399 | |
39bc1876 | 11400 | Use only the first 32 floating point registers. |
ad126521 | 11401 | |
39bc1876 NS |
11402 | @item -mfpr-64 |
11403 | @opindex mfpr-64 | |
ad126521 | 11404 | |
39bc1876 | 11405 | Use all 64 floating point registers |
ad126521 | 11406 | |
39bc1876 NS |
11407 | @item -mhard-float |
11408 | @opindex mhard-float | |
ad126521 | 11409 | |
39bc1876 | 11410 | Use hardware instructions for floating point operations. |
ad126521 | 11411 | |
39bc1876 NS |
11412 | @item -msoft-float |
11413 | @opindex msoft-float | |
ad126521 | 11414 | |
39bc1876 | 11415 | Use library routines for floating point operations. |
ad126521 | 11416 | |
39bc1876 NS |
11417 | @item -malloc-cc |
11418 | @opindex malloc-cc | |
ad126521 | 11419 | |
39bc1876 | 11420 | Dynamically allocate condition code registers. |
ad126521 | 11421 | |
39bc1876 NS |
11422 | @item -mfixed-cc |
11423 | @opindex mfixed-cc | |
861bb6c1 | 11424 | |
39bc1876 NS |
11425 | Do not try to dynamically allocate condition code registers, only |
11426 | use @code{icc0} and @code{fcc0}. | |
74291a4b | 11427 | |
39bc1876 NS |
11428 | @item -mdword |
11429 | @opindex mdword | |
74291a4b | 11430 | |
39bc1876 | 11431 | Change ABI to use double word insns. |
74291a4b | 11432 | |
39bc1876 NS |
11433 | @item -mno-dword |
11434 | @opindex mno-dword | |
74291a4b | 11435 | |
39bc1876 | 11436 | Do not use double word instructions. |
74291a4b | 11437 | |
39bc1876 NS |
11438 | @item -mdouble |
11439 | @opindex mdouble | |
74291a4b | 11440 | |
39bc1876 | 11441 | Use floating point double instructions. |
7fe90e7b | 11442 | |
39bc1876 NS |
11443 | @item -mno-double |
11444 | @opindex mno-double | |
74291a4b | 11445 | |
39bc1876 | 11446 | Do not use floating point double instructions. |
74291a4b | 11447 | |
39bc1876 NS |
11448 | @item -mmedia |
11449 | @opindex mmedia | |
74291a4b | 11450 | |
39bc1876 | 11451 | Use media instructions. |
9c34dbbf | 11452 | |
39bc1876 NS |
11453 | @item -mno-media |
11454 | @opindex mno-media | |
74291a4b | 11455 | |
39bc1876 | 11456 | Do not use media instructions. |
74291a4b | 11457 | |
39bc1876 NS |
11458 | @item -mmuladd |
11459 | @opindex mmuladd | |
9c34dbbf | 11460 | |
39bc1876 | 11461 | Use multiply and add/subtract instructions. |
66188a7e | 11462 | |
39bc1876 NS |
11463 | @item -mno-muladd |
11464 | @opindex mno-muladd | |
74291a4b | 11465 | |
39bc1876 | 11466 | Do not use multiply and add/subtract instructions. |
74291a4b | 11467 | |
d711cf67 JDA |
11468 | @item -mfdpic |
11469 | @opindex mfdpic | |
11470 | ||
11471 | Select the FDPIC ABI, that uses function descriptors to represent | |
11472 | pointers to functions. Without any PIC/PIE-related options, it | |
11473 | implies @option{-fPIE}. With @option{-fpic} or @option{-fpie}, it | |
11474 | assumes GOT entries and small data are within a 12-bit range from the | |
11475 | GOT base address; with @option{-fPIC} or @option{-fPIE}, GOT offsets | |
11476 | are computed with 32 bits. | |
28bbc967 | 11477 | With a @samp{bfin-elf} target, this option implies @option{-msim}. |
d711cf67 JDA |
11478 | |
11479 | @item -minline-plt | |
11480 | @opindex minline-plt | |
11481 | ||
11482 | Enable inlining of PLT entries in function calls to functions that are | |
11483 | not known to bind locally. It has no effect without @option{-mfdpic}. | |
11484 | It's enabled by default if optimizing for speed and compiling for | |
11485 | shared libraries (i.e., @option{-fPIC} or @option{-fpic}), or when an | |
11486 | optimization option such as @option{-O3} or above is present in the | |
11487 | command line. | |
11488 | ||
e4dd71de | 11489 | @item -mTLS |
d376d545 | 11490 | @opindex mTLS |
e4dd71de AH |
11491 | |
11492 | Assume a large TLS segment when generating thread-local code. | |
11493 | ||
11494 | @item -mtls | |
d376d545 | 11495 | @opindex mtls |
e4dd71de AH |
11496 | |
11497 | Do not assume a large TLS segment when generating thread-local code. | |
11498 | ||
d711cf67 JDA |
11499 | @item -mgprel-ro |
11500 | @opindex mgprel-ro | |
11501 | ||
11502 | Enable the use of @code{GPREL} relocations in the FDPIC ABI for data | |
11503 | that is known to be in read-only sections. It's enabled by default, | |
11504 | except for @option{-fpic} or @option{-fpie}: even though it may help | |
11505 | make the global offset table smaller, it trades 1 instruction for 4. | |
11506 | With @option{-fPIC} or @option{-fPIE}, it trades 3 instructions for 4, | |
11507 | one of which may be shared by multiple symbols, and it avoids the need | |
11508 | for a GOT entry for the referenced symbol, so it's more likely to be a | |
11509 | win. If it is not, @option{-mno-gprel-ro} can be used to disable it. | |
11510 | ||
11511 | @item -multilib-library-pic | |
11512 | @opindex multilib-library-pic | |
11513 | ||
11514 | Link with the (library, not FD) pic libraries. It's implied by | |
11515 | @option{-mlibrary-pic}, as well as by @option{-fPIC} and | |
11516 | @option{-fpic} without @option{-mfdpic}. You should never have to use | |
11517 | it explicitly. | |
11518 | ||
11519 | @item -mlinked-fp | |
11520 | @opindex mlinked-fp | |
11521 | ||
11522 | Follow the EABI requirement of always creating a frame pointer whenever | |
11523 | a stack frame is allocated. This option is enabled by default and can | |
11524 | be disabled with @option{-mno-linked-fp}. | |
11525 | ||
c557edf4 RS |
11526 | @item -mlong-calls |
11527 | @opindex mlong-calls | |
11528 | ||
11529 | Use indirect addressing to call functions outside the current | |
11530 | compilation unit. This allows the functions to be placed anywhere | |
11531 | within the 32-bit address space. | |
11532 | ||
11533 | @item -malign-labels | |
11534 | @opindex malign-labels | |
11535 | ||
11536 | Try to align labels to an 8-byte boundary by inserting nops into the | |
11537 | previous packet. This option only has an effect when VLIW packing | |
11538 | is enabled. It doesn't create new packets; it merely adds nops to | |
11539 | existing ones. | |
11540 | ||
39bc1876 NS |
11541 | @item -mlibrary-pic |
11542 | @opindex mlibrary-pic | |
0ac081f6 | 11543 | |
39bc1876 | 11544 | Generate position-independent EABI code. |
6c8875e5 | 11545 | |
39bc1876 NS |
11546 | @item -macc-4 |
11547 | @opindex macc-4 | |
6c8875e5 | 11548 | |
39bc1876 | 11549 | Use only the first four media accumulator registers. |
6c8875e5 | 11550 | |
39bc1876 NS |
11551 | @item -macc-8 |
11552 | @opindex macc-8 | |
993f19a8 | 11553 | |
39bc1876 | 11554 | Use all eight media accumulator registers. |
5da702b1 | 11555 | |
39bc1876 NS |
11556 | @item -mpack |
11557 | @opindex mpack | |
74291a4b | 11558 | |
39bc1876 | 11559 | Pack VLIW instructions. |
74291a4b | 11560 | |
39bc1876 NS |
11561 | @item -mno-pack |
11562 | @opindex mno-pack | |
74291a4b | 11563 | |
39bc1876 | 11564 | Do not pack VLIW instructions. |
7fe90e7b | 11565 | |
39bc1876 NS |
11566 | @item -mno-eflags |
11567 | @opindex mno-eflags | |
74291a4b | 11568 | |
39bc1876 | 11569 | Do not mark ABI switches in e_flags. |
861bb6c1 | 11570 | |
39bc1876 NS |
11571 | @item -mcond-move |
11572 | @opindex mcond-move | |
6184e8a4 | 11573 | |
39bc1876 | 11574 | Enable the use of conditional-move instructions (default). |
74291a4b | 11575 | |
39bc1876 NS |
11576 | This switch is mainly for debugging the compiler and will likely be removed |
11577 | in a future version. | |
74291a4b | 11578 | |
39bc1876 NS |
11579 | @item -mno-cond-move |
11580 | @opindex mno-cond-move | |
74291a4b | 11581 | |
39bc1876 | 11582 | Disable the use of conditional-move instructions. |
861bb6c1 | 11583 | |
39bc1876 NS |
11584 | This switch is mainly for debugging the compiler and will likely be removed |
11585 | in a future version. | |
861bb6c1 | 11586 | |
39bc1876 NS |
11587 | @item -mscc |
11588 | @opindex mscc | |
74291a4b | 11589 | |
39bc1876 | 11590 | Enable the use of conditional set instructions (default). |
74291a4b | 11591 | |
39bc1876 NS |
11592 | This switch is mainly for debugging the compiler and will likely be removed |
11593 | in a future version. | |
74291a4b | 11594 | |
39bc1876 NS |
11595 | @item -mno-scc |
11596 | @opindex mno-scc | |
74291a4b | 11597 | |
39bc1876 | 11598 | Disable the use of conditional set instructions. |
74291a4b | 11599 | |
39bc1876 NS |
11600 | This switch is mainly for debugging the compiler and will likely be removed |
11601 | in a future version. | |
74291a4b | 11602 | |
39bc1876 NS |
11603 | @item -mcond-exec |
11604 | @opindex mcond-exec | |
74291a4b | 11605 | |
39bc1876 | 11606 | Enable the use of conditional execution (default). |
74291a4b | 11607 | |
39bc1876 NS |
11608 | This switch is mainly for debugging the compiler and will likely be removed |
11609 | in a future version. | |
ab82a49f | 11610 | |
39bc1876 NS |
11611 | @item -mno-cond-exec |
11612 | @opindex mno-cond-exec | |
79ae11c4 | 11613 | |
39bc1876 | 11614 | Disable the use of conditional execution. |
daf2f129 | 11615 | |
39bc1876 NS |
11616 | This switch is mainly for debugging the compiler and will likely be removed |
11617 | in a future version. | |
cbe26ab8 | 11618 | |
39bc1876 NS |
11619 | @item -mvliw-branch |
11620 | @opindex mvliw-branch | |
11621 | ||
11622 | Run a pass to pack branches into VLIW instructions (default). | |
11623 | ||
11624 | This switch is mainly for debugging the compiler and will likely be removed | |
11625 | in a future version. | |
11626 | ||
11627 | @item -mno-vliw-branch | |
11628 | @opindex mno-vliw-branch | |
11629 | ||
11630 | Do not run a pass to pack branches into VLIW instructions. | |
11631 | ||
11632 | This switch is mainly for debugging the compiler and will likely be removed | |
11633 | in a future version. | |
74291a4b | 11634 | |
39bc1876 NS |
11635 | @item -mmulti-cond-exec |
11636 | @opindex mmulti-cond-exec | |
74291a4b | 11637 | |
39bc1876 NS |
11638 | Enable optimization of @code{&&} and @code{||} in conditional execution |
11639 | (default). | |
74291a4b | 11640 | |
39bc1876 NS |
11641 | This switch is mainly for debugging the compiler and will likely be removed |
11642 | in a future version. | |
74291a4b | 11643 | |
39bc1876 NS |
11644 | @item -mno-multi-cond-exec |
11645 | @opindex mno-multi-cond-exec | |
74291a4b | 11646 | |
39bc1876 | 11647 | Disable optimization of @code{&&} and @code{||} in conditional execution. |
48180d68 | 11648 | |
39bc1876 NS |
11649 | This switch is mainly for debugging the compiler and will likely be removed |
11650 | in a future version. | |
edf1b3f3 | 11651 | |
39bc1876 NS |
11652 | @item -mnested-cond-exec |
11653 | @opindex mnested-cond-exec | |
9904592e | 11654 | |
39bc1876 | 11655 | Enable nested conditional execution optimizations (default). |
9904592e | 11656 | |
39bc1876 NS |
11657 | This switch is mainly for debugging the compiler and will likely be removed |
11658 | in a future version. | |
0ac081f6 | 11659 | |
39bc1876 NS |
11660 | @item -mno-nested-cond-exec |
11661 | @opindex mno-nested-cond-exec | |
76a773f3 | 11662 | |
39bc1876 | 11663 | Disable nested conditional execution optimizations. |
74291a4b | 11664 | |
39bc1876 NS |
11665 | This switch is mainly for debugging the compiler and will likely be removed |
11666 | in a future version. | |
74291a4b | 11667 | |
38c28a25 AH |
11668 | @item -moptimize-membar |
11669 | @opindex moptimize-membar | |
11670 | ||
11671 | This switch removes redundant @code{membar} instructions from the | |
11672 | compiler generated code. It is enabled by default. | |
11673 | ||
11674 | @item -mno-optimize-membar | |
11675 | @opindex mno-optimize-membar | |
11676 | ||
11677 | This switch disables the automatic removal of redundant @code{membar} | |
11678 | instructions from the generated code. | |
11679 | ||
39bc1876 NS |
11680 | @item -mtomcat-stats |
11681 | @opindex mtomcat-stats | |
e9a25f70 | 11682 | |
39bc1876 | 11683 | Cause gas to print out tomcat statistics. |
e9a25f70 | 11684 | |
39bc1876 NS |
11685 | @item -mcpu=@var{cpu} |
11686 | @opindex mcpu | |
74291a4b | 11687 | |
39bc1876 | 11688 | Select the processor type for which to generate code. Possible values are |
c557edf4 RS |
11689 | @samp{frv}, @samp{fr550}, @samp{tomcat}, @samp{fr500}, @samp{fr450}, |
11690 | @samp{fr405}, @samp{fr400}, @samp{fr300} and @samp{simple}. | |
bff46771 | 11691 | |
39bc1876 | 11692 | @end table |
8d8269fa | 11693 | |
464aea98 JM |
11694 | @node GNU/Linux Options |
11695 | @subsection GNU/Linux Options | |
11696 | ||
11697 | These @samp{-m} options are defined for GNU/Linux targets: | |
11698 | ||
11699 | @table @gcctabopt | |
11700 | @item -mglibc | |
11701 | @opindex mglibc | |
74c70253 MK |
11702 | Use the GNU C library. This is the default except |
11703 | on @samp{*-*-linux-*uclibc*} and @samp{*-*-linux-*android*} targets. | |
464aea98 JM |
11704 | |
11705 | @item -muclibc | |
11706 | @opindex muclibc | |
74c70253 | 11707 | Use uClibc C library. This is the default on |
7bd85ce0 | 11708 | @samp{*-*-linux-*uclibc*} targets. |
74c70253 MK |
11709 | |
11710 | @item -mbionic | |
11711 | @opindex mbionic | |
11712 | Use Bionic C library. This is the default on | |
11713 | @samp{*-*-linux-*android*} targets. | |
51b9db92 MK |
11714 | |
11715 | @item -mandroid | |
11716 | @opindex mandroid | |
11717 | Compile code compatible with Android platform. This is the default on | |
11718 | @samp{*-*-linux-*android*} targets. | |
11719 | ||
11720 | When compiling, this option enables @option{-mbionic}, @option{-fPIC}, | |
11721 | @option{-fno-exceptions} and @option{-fno-rtti} by default. When linking, | |
11722 | this option makes the GCC driver pass Android-specific options to the linker. | |
11723 | Finally, this option causes the preprocessor macro @code{__ANDROID__} | |
11724 | to be defined. | |
11725 | ||
11726 | @item -tno-android-cc | |
11727 | @opindex tno-android-cc | |
11728 | Disable compilation effects of @option{-mandroid}, i.e., do not enable | |
11729 | @option{-mbionic}, @option{-fPIC}, @option{-fno-exceptions} and | |
11730 | @option{-fno-rtti} by default. | |
11731 | ||
11732 | @item -tno-android-ld | |
11733 | @opindex tno-android-ld | |
11734 | Disable linking effects of @option{-mandroid}, i.e., pass standard Linux | |
11735 | linking options to the linker. | |
11736 | ||
464aea98 JM |
11737 | @end table |
11738 | ||
39bc1876 NS |
11739 | @node H8/300 Options |
11740 | @subsection H8/300 Options | |
74291a4b | 11741 | |
39bc1876 | 11742 | These @samp{-m} options are defined for the H8/300 implementations: |
74291a4b | 11743 | |
39bc1876 NS |
11744 | @table @gcctabopt |
11745 | @item -mrelax | |
11746 | @opindex mrelax | |
11747 | Shorten some address references at link time, when possible; uses the | |
11748 | linker option @option{-relax}. @xref{H8/300,, @code{ld} and the H8/300, | |
11749 | ld, Using ld}, for a fuller description. | |
74291a4b | 11750 | |
39bc1876 NS |
11751 | @item -mh |
11752 | @opindex mh | |
11753 | Generate code for the H8/300H@. | |
74291a4b | 11754 | |
39bc1876 NS |
11755 | @item -ms |
11756 | @opindex ms | |
11757 | Generate code for the H8S@. | |
74291a4b | 11758 | |
39bc1876 NS |
11759 | @item -mn |
11760 | @opindex mn | |
11761 | Generate code for the H8S and H8/300H in the normal mode. This switch | |
4ec7afd7 | 11762 | must be used either with @option{-mh} or @option{-ms}. |
74291a4b | 11763 | |
39bc1876 NS |
11764 | @item -ms2600 |
11765 | @opindex ms2600 | |
11766 | Generate code for the H8S/2600. This switch must be used with @option{-ms}. | |
74291a4b | 11767 | |
39bc1876 NS |
11768 | @item -mint32 |
11769 | @opindex mint32 | |
11770 | Make @code{int} data 32 bits by default. | |
74291a4b | 11771 | |
39bc1876 NS |
11772 | @item -malign-300 |
11773 | @opindex malign-300 | |
11774 | On the H8/300H and H8S, use the same alignment rules as for the H8/300. | |
11775 | The default for the H8/300H and H8S is to align longs and floats on 4 | |
11776 | byte boundaries. | |
11777 | @option{-malign-300} causes them to be aligned on 2 byte boundaries. | |
11778 | This option has no effect on the H8/300. | |
11779 | @end table | |
f5a1b0d2 | 11780 | |
39bc1876 NS |
11781 | @node HPPA Options |
11782 | @subsection HPPA Options | |
11783 | @cindex HPPA Options | |
a5c76ee6 | 11784 | |
39bc1876 | 11785 | These @samp{-m} options are defined for the HPPA family of computers: |
a5c76ee6 | 11786 | |
39bc1876 NS |
11787 | @table @gcctabopt |
11788 | @item -march=@var{architecture-type} | |
11789 | @opindex march | |
11790 | Generate code for the specified architecture. The choices for | |
11791 | @var{architecture-type} are @samp{1.0} for PA 1.0, @samp{1.1} for PA | |
11792 | 1.1, and @samp{2.0} for PA 2.0 processors. Refer to | |
11793 | @file{/usr/lib/sched.models} on an HP-UX system to determine the proper | |
11794 | architecture option for your machine. Code compiled for lower numbered | |
11795 | architectures will run on higher numbered architectures, but not the | |
11796 | other way around. | |
11797 | ||
39bc1876 NS |
11798 | @item -mpa-risc-1-0 |
11799 | @itemx -mpa-risc-1-1 | |
11800 | @itemx -mpa-risc-2-0 | |
11801 | @opindex mpa-risc-1-0 | |
11802 | @opindex mpa-risc-1-1 | |
11803 | @opindex mpa-risc-2-0 | |
11804 | Synonyms for @option{-march=1.0}, @option{-march=1.1}, and @option{-march=2.0} respectively. | |
5a26b329 | 11805 | |
39bc1876 NS |
11806 | @item -mbig-switch |
11807 | @opindex mbig-switch | |
11808 | Generate code suitable for big switch tables. Use this option only if | |
11809 | the assembler/linker complain about out of range branches within a switch | |
11810 | table. | |
efdba735 | 11811 | |
39bc1876 NS |
11812 | @item -mjump-in-delay |
11813 | @opindex mjump-in-delay | |
11814 | Fill delay slots of function calls with unconditional jump instructions | |
11815 | by modifying the return pointer for the function call to be the target | |
11816 | of the conditional jump. | |
a5c76ee6 | 11817 | |
39bc1876 NS |
11818 | @item -mdisable-fpregs |
11819 | @opindex mdisable-fpregs | |
11820 | Prevent floating point registers from being used in any manner. This is | |
11821 | necessary for compiling kernels which perform lazy context switching of | |
11822 | floating point registers. If you use this option and attempt to perform | |
11823 | floating point operations, the compiler will abort. | |
0a379b7a | 11824 | |
39bc1876 NS |
11825 | @item -mdisable-indexing |
11826 | @opindex mdisable-indexing | |
11827 | Prevent the compiler from using indexing address modes. This avoids some | |
11828 | rather obscure problems when compiling MIG generated code under MACH@. | |
f5a1b0d2 | 11829 | |
39bc1876 NS |
11830 | @item -mno-space-regs |
11831 | @opindex mno-space-regs | |
11832 | Generate code that assumes the target has no space registers. This allows | |
11833 | GCC to generate faster indirect calls and use unscaled index address modes. | |
d2d42a91 | 11834 | |
39bc1876 | 11835 | Such code is suitable for level 0 PA systems and kernels. |
d2d42a91 | 11836 | |
39bc1876 NS |
11837 | @item -mfast-indirect-calls |
11838 | @opindex mfast-indirect-calls | |
11839 | Generate code that assumes calls never cross space boundaries. This | |
11840 | allows GCC to emit code which performs faster indirect calls. | |
f08a3544 | 11841 | |
39bc1876 NS |
11842 | This option will not work in the presence of shared libraries or nested |
11843 | functions. | |
f08a3544 | 11844 | |
a2017852 JDA |
11845 | @item -mfixed-range=@var{register-range} |
11846 | @opindex mfixed-range | |
11847 | Generate code treating the given register range as fixed registers. | |
11848 | A fixed register is one that the register allocator can not use. This is | |
11849 | useful when compiling kernel code. A register range is specified as | |
11850 | two registers separated by a dash. Multiple register ranges can be | |
11851 | specified separated by a comma. | |
11852 | ||
39bc1876 NS |
11853 | @item -mlong-load-store |
11854 | @opindex mlong-load-store | |
11855 | Generate 3-instruction load and store sequences as sometimes required by | |
11856 | the HP-UX 10 linker. This is equivalent to the @samp{+k} option to | |
11857 | the HP compilers. | |
61c85ff1 | 11858 | |
39bc1876 NS |
11859 | @item -mportable-runtime |
11860 | @opindex mportable-runtime | |
11861 | Use the portable calling conventions proposed by HP for ELF systems. | |
61c85ff1 | 11862 | |
39bc1876 NS |
11863 | @item -mgas |
11864 | @opindex mgas | |
11865 | Enable the use of assembler directives only GAS understands. | |
61c85ff1 | 11866 | |
39bc1876 NS |
11867 | @item -mschedule=@var{cpu-type} |
11868 | @opindex mschedule | |
11869 | Schedule code according to the constraints for the machine type | |
11870 | @var{cpu-type}. The choices for @var{cpu-type} are @samp{700} | |
11871 | @samp{7100}, @samp{7100LC}, @samp{7200}, @samp{7300} and @samp{8000}. Refer | |
11872 | to @file{/usr/lib/sched.models} on an HP-UX system to determine the | |
11873 | proper scheduling option for your machine. The default scheduling is | |
11874 | @samp{8000}. | |
61c85ff1 | 11875 | |
39bc1876 NS |
11876 | @item -mlinker-opt |
11877 | @opindex mlinker-opt | |
11878 | Enable the optimization pass in the HP-UX linker. Note this makes symbolic | |
11879 | debugging impossible. It also triggers a bug in the HP-UX 8 and HP-UX 9 | |
11880 | linkers in which they give bogus error messages when linking some programs. | |
61c85ff1 | 11881 | |
39bc1876 NS |
11882 | @item -msoft-float |
11883 | @opindex msoft-float | |
11884 | Generate output containing library calls for floating point. | |
11885 | @strong{Warning:} the requisite libraries are not available for all HPPA | |
11886 | targets. Normally the facilities of the machine's usual C compiler are | |
11887 | used, but this cannot be done directly in cross-compilation. You must make | |
11888 | your own arrangements to provide suitable library functions for | |
cd985f66 | 11889 | cross-compilation. |
31775d31 | 11890 | |
39bc1876 NS |
11891 | @option{-msoft-float} changes the calling convention in the output file; |
11892 | therefore, it is only useful if you compile @emph{all} of a program with | |
11893 | this option. In particular, you need to compile @file{libgcc.a}, the | |
11894 | library that comes with GCC, with @option{-msoft-float} in order for | |
11895 | this to work. | |
61c85ff1 | 11896 | |
39bc1876 NS |
11897 | @item -msio |
11898 | @opindex msio | |
8a36672b | 11899 | Generate the predefine, @code{_SIO}, for server IO@. The default is |
39bc1876 | 11900 | @option{-mwsio}. This generates the predefines, @code{__hp9000s700}, |
8a36672b JM |
11901 | @code{__hp9000s700__} and @code{_WSIO}, for workstation IO@. These |
11902 | options are available under HP-UX and HI-UX@. | |
39bc1876 NS |
11903 | |
11904 | @item -mgnu-ld | |
d376d545 | 11905 | @opindex mgnu-ld |
39bc1876 NS |
11906 | Use GNU ld specific options. This passes @option{-shared} to ld when |
11907 | building a shared library. It is the default when GCC is configured, | |
11908 | explicitly or implicitly, with the GNU linker. This option does not | |
11909 | have any affect on which ld is called, it only changes what parameters | |
11910 | are passed to that ld. The ld that is called is determined by the | |
11911 | @option{--with-ld} configure option, GCC's program search path, and | |
11912 | finally by the user's @env{PATH}. The linker used by GCC can be printed | |
a73035ae | 11913 | using @samp{which `gcc -print-prog-name=ld`}. This option is only available |
a31cfd58 | 11914 | on the 64 bit HP-UX GCC, i.e.@: configured with @samp{hppa*64*-*-hpux*}. |
48aec0bc | 11915 | |
39bc1876 | 11916 | @item -mhp-ld |
d376d545 | 11917 | @opindex mhp-ld |
39bc1876 NS |
11918 | Use HP ld specific options. This passes @option{-b} to ld when building |
11919 | a shared library and passes @option{+Accept TypeMismatch} to ld on all | |
11920 | links. It is the default when GCC is configured, explicitly or | |
11921 | implicitly, with the HP linker. This option does not have any affect on | |
11922 | which ld is called, it only changes what parameters are passed to that | |
11923 | ld. The ld that is called is determined by the @option{--with-ld} | |
11924 | configure option, GCC's program search path, and finally by the user's | |
11925 | @env{PATH}. The linker used by GCC can be printed using @samp{which | |
a73035ae | 11926 | `gcc -print-prog-name=ld`}. This option is only available on the 64 bit |
a31cfd58 | 11927 | HP-UX GCC, i.e.@: configured with @samp{hppa*64*-*-hpux*}. |
48aec0bc | 11928 | |
39bc1876 NS |
11929 | @item -mlong-calls |
11930 | @opindex mno-long-calls | |
11931 | Generate code that uses long call sequences. This ensures that a call | |
11932 | is always able to reach linker generated stubs. The default is to generate | |
11933 | long calls only when the distance from the call site to the beginning | |
11934 | of the function or translation unit, as the case may be, exceeds a | |
11935 | predefined limit set by the branch type being used. The limits for | |
11936 | normal calls are 7,600,000 and 240,000 bytes, respectively for the | |
11937 | PA 2.0 and PA 1.X architectures. Sibcalls are always limited at | |
11938 | 240,000 bytes. | |
a27fb29b | 11939 | |
39bc1876 NS |
11940 | Distances are measured from the beginning of functions when using the |
11941 | @option{-ffunction-sections} option, or when using the @option{-mgas} | |
11942 | and @option{-mno-portable-runtime} options together under HP-UX with | |
11943 | the SOM linker. | |
7dac2f89 | 11944 | |
39bc1876 NS |
11945 | It is normally not desirable to use this option as it will degrade |
11946 | performance. However, it may be useful in large applications, | |
11947 | particularly when partial linking is used to build the application. | |
74291a4b | 11948 | |
39bc1876 NS |
11949 | The types of long calls used depends on the capabilities of the |
11950 | assembler and linker, and the type of code being generated. The | |
11951 | impact on systems that support long absolute calls, and long pic | |
11952 | symbol-difference or pc-relative calls should be relatively small. | |
11953 | However, an indirect call is used on 32-bit ELF systems in pic code | |
11954 | and it is quite long. | |
74291a4b | 11955 | |
d711cf67 JDA |
11956 | @item -munix=@var{unix-std} |
11957 | @opindex march | |
11958 | Generate compiler predefines and select a startfile for the specified | |
11959 | UNIX standard. The choices for @var{unix-std} are @samp{93}, @samp{95} | |
11960 | and @samp{98}. @samp{93} is supported on all HP-UX versions. @samp{95} | |
11961 | is available on HP-UX 10.10 and later. @samp{98} is available on HP-UX | |
11962 | 11.11 and later. The default values are @samp{93} for HP-UX 10.00, | |
11963 | @samp{95} for HP-UX 10.10 though to 11.00, and @samp{98} for HP-UX 11.11 | |
11964 | and later. | |
11965 | ||
11966 | @option{-munix=93} provides the same predefines as GCC 3.3 and 3.4. | |
11967 | @option{-munix=95} provides additional predefines for @code{XOPEN_UNIX} | |
11968 | and @code{_XOPEN_SOURCE_EXTENDED}, and the startfile @file{unix95.o}. | |
11969 | @option{-munix=98} provides additional predefines for @code{_XOPEN_UNIX}, | |
11970 | @code{_XOPEN_SOURCE_EXTENDED}, @code{_INCLUDE__STDC_A1_SOURCE} and | |
11971 | @code{_INCLUDE_XOPEN_SOURCE_500}, and the startfile @file{unix98.o}. | |
11972 | ||
11973 | It is @emph{important} to note that this option changes the interfaces | |
11974 | for various library routines. It also affects the operational behavior | |
11975 | of the C library. Thus, @emph{extreme} care is needed in using this | |
11976 | option. | |
11977 | ||
11978 | Library code that is intended to operate with more than one UNIX | |
11979 | standard must test, set and restore the variable @var{__xpg4_extended_mask} | |
11980 | as appropriate. Most GNU software doesn't provide this capability. | |
11981 | ||
39bc1876 NS |
11982 | @item -nolibdld |
11983 | @opindex nolibdld | |
11984 | Suppress the generation of link options to search libdld.sl when the | |
11985 | @option{-static} option is specified on HP-UX 10 and later. | |
11986 | ||
11987 | @item -static | |
11988 | @opindex static | |
11989 | The HP-UX implementation of setlocale in libc has a dependency on | |
11990 | libdld.sl. There isn't an archive version of libdld.sl. Thus, | |
11991 | when the @option{-static} option is specified, special link options | |
11992 | are needed to resolve this dependency. | |
11993 | ||
11994 | On HP-UX 10 and later, the GCC driver adds the necessary options to | |
11995 | link with libdld.sl when the @option{-static} option is specified. | |
11996 | This causes the resulting binary to be dynamic. On the 64-bit port, | |
11997 | the linkers generate dynamic binaries by default in any case. The | |
11998 | @option{-nolibdld} option can be used to prevent the GCC driver from | |
11999 | adding these link options. | |
12000 | ||
12001 | @item -threads | |
12002 | @opindex threads | |
12003 | Add support for multithreading with the @dfn{dce thread} library | |
8a36672b | 12004 | under HP-UX@. This option sets flags for both the preprocessor and |
39bc1876 NS |
12005 | linker. |
12006 | @end table | |
12007 | ||
12008 | @node i386 and x86-64 Options | |
12009 | @subsection Intel 386 and AMD x86-64 Options | |
12010 | @cindex i386 Options | |
12011 | @cindex x86-64 Options | |
12012 | @cindex Intel 386 Options | |
12013 | @cindex AMD x86-64 Options | |
12014 | ||
12015 | These @samp{-m} options are defined for the i386 and x86-64 family of | |
12016 | computers: | |
12017 | ||
12018 | @table @gcctabopt | |
12019 | @item -mtune=@var{cpu-type} | |
12020 | @opindex mtune | |
12021 | Tune to @var{cpu-type} everything applicable about the generated code, except | |
12022 | for the ABI and the set of available instructions. The choices for | |
12023 | @var{cpu-type} are: | |
12024 | @table @emph | |
786872fd | 12025 | @item generic |
ab940b73 | 12026 | Produce code optimized for the most common IA32/@/AMD64/@/EM64T processors. |
786872fd JH |
12027 | If you know the CPU on which your code will run, then you should use |
12028 | the corresponding @option{-mtune} option instead of | |
12029 | @option{-mtune=generic}. But, if you do not know exactly what CPU users | |
12030 | of your application will have, then you should use this option. | |
12031 | ||
12032 | As new processors are deployed in the marketplace, the behavior of this | |
12033 | option will change. Therefore, if you upgrade to a newer version of | |
12034 | GCC, the code generated option will change to reflect the processors | |
12035 | that were most common when that version of GCC was released. | |
12036 | ||
12037 | There is no @option{-march=generic} option because @option{-march} | |
12038 | indicates the instruction set the compiler can use, and there is no | |
12039 | generic instruction set applicable to all processors. In contrast, | |
12040 | @option{-mtune} indicates the processor (or, in this case, collection of | |
12041 | processors) for which the code is optimized. | |
fa959ce4 MM |
12042 | @item native |
12043 | This selects the CPU to tune for at compilation time by determining | |
12044 | the processor type of the compiling machine. Using @option{-mtune=native} | |
12045 | will produce code optimized for the local machine under the constraints | |
12046 | of the selected instruction set. Using @option{-march=native} will | |
12047 | enable all instruction subsets supported by the local machine (hence | |
12048 | the result might not run on different machines). | |
39bc1876 | 12049 | @item i386 |
8a36672b | 12050 | Original Intel's i386 CPU@. |
39bc1876 | 12051 | @item i486 |
8a36672b | 12052 | Intel's i486 CPU@. (No scheduling is implemented for this chip.) |
39bc1876 NS |
12053 | @item i586, pentium |
12054 | Intel Pentium CPU with no MMX support. | |
12055 | @item pentium-mmx | |
12056 | Intel PentiumMMX CPU based on Pentium core with MMX instruction set support. | |
786872fd | 12057 | @item pentiumpro |
8a36672b | 12058 | Intel PentiumPro CPU@. |
786872fd JH |
12059 | @item i686 |
12060 | Same as @code{generic}, but when used as @code{march} option, PentiumPro | |
917f1b7e | 12061 | instruction set will be used, so the code will run on all i686 family chips. |
39bc1876 NS |
12062 | @item pentium2 |
12063 | Intel Pentium2 CPU based on PentiumPro core with MMX instruction set support. | |
12064 | @item pentium3, pentium3m | |
12065 | Intel Pentium3 CPU based on PentiumPro core with MMX and SSE instruction set | |
12066 | support. | |
12067 | @item pentium-m | |
12068 | Low power version of Intel Pentium3 CPU with MMX, SSE and SSE2 instruction set | |
12069 | support. Used by Centrino notebooks. | |
12070 | @item pentium4, pentium4m | |
12071 | Intel Pentium4 CPU with MMX, SSE and SSE2 instruction set support. | |
12072 | @item prescott | |
12073 | Improved version of Intel Pentium4 CPU with MMX, SSE, SSE2 and SSE3 instruction | |
12074 | set support. | |
12075 | @item nocona | |
12076 | Improved version of Intel Pentium4 CPU with 64-bit extensions, MMX, SSE, | |
12077 | SSE2 and SSE3 instruction set support. | |
05f85dbb VM |
12078 | @item core2 |
12079 | Intel Core2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and SSSE3 | |
12080 | instruction set support. | |
b2b01543 BS |
12081 | @item corei7 |
12082 | Intel Core i7 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1 | |
12083 | and SSE4.2 instruction set support. | |
f2a758a2 L |
12084 | @item atom |
12085 | Intel Atom CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and SSSE3 | |
12086 | instruction set support. | |
39bc1876 NS |
12087 | @item k6 |
12088 | AMD K6 CPU with MMX instruction set support. | |
12089 | @item k6-2, k6-3 | |
f8723eb6 | 12090 | Improved versions of AMD K6 CPU with MMX and 3DNow!@: instruction set support. |
39bc1876 | 12091 | @item athlon, athlon-tbird |
f8723eb6 | 12092 | AMD Athlon CPU with MMX, 3dNOW!, enhanced 3DNow!@: and SSE prefetch instructions |
39bc1876 NS |
12093 | support. |
12094 | @item athlon-4, athlon-xp, athlon-mp | |
f8723eb6 | 12095 | Improved AMD Athlon CPU with MMX, 3DNow!, enhanced 3DNow!@: and full SSE |
39bc1876 NS |
12096 | instruction set support. |
12097 | @item k8, opteron, athlon64, athlon-fx | |
12098 | AMD K8 core based CPUs with x86-64 instruction set support. (This supersets | |
f8723eb6 | 12099 | MMX, SSE, SSE2, 3DNow!, enhanced 3DNow!@: and 64-bit instruction set extensions.) |
ed99bffc DR |
12100 | @item k8-sse3, opteron-sse3, athlon64-sse3 |
12101 | Improved versions of k8, opteron and athlon64 with SSE3 instruction set support. | |
aafc814c | 12102 | @item amdfam10, barcelona |
d8f52b02 | 12103 | AMD Family 10h core based CPUs with x86-64 instruction set support. (This |
f8723eb6 | 12104 | supersets MMX, SSE, SSE2, SSE3, SSE4A, 3DNow!, enhanced 3DNow!, ABM and 64-bit |
21efb4d4 | 12105 | instruction set extensions.) |
39bc1876 NS |
12106 | @item winchip-c6 |
12107 | IDT Winchip C6 CPU, dealt in same way as i486 with additional MMX instruction | |
12108 | set support. | |
12109 | @item winchip2 | |
f8723eb6 | 12110 | IDT Winchip2 CPU, dealt in same way as i486 with additional MMX and 3DNow!@: |
39bc1876 NS |
12111 | instruction set support. |
12112 | @item c3 | |
f8723eb6 | 12113 | Via C3 CPU with MMX and 3DNow!@: instruction set support. (No scheduling is |
39bc1876 NS |
12114 | implemented for this chip.) |
12115 | @item c3-2 | |
12116 | Via C3-2 CPU with MMX and SSE instruction set support. (No scheduling is | |
12117 | implemented for this chip.) | |
cfe1b18f | 12118 | @item geode |
f8723eb6 | 12119 | Embedded AMD CPU with MMX and 3DNow!@: instruction set support. |
39bc1876 NS |
12120 | @end table |
12121 | ||
12122 | While picking a specific @var{cpu-type} will schedule things appropriately | |
12123 | for that particular chip, the compiler will not generate any code that | |
12124 | does not run on the i386 without the @option{-march=@var{cpu-type}} option | |
12125 | being used. | |
12126 | ||
12127 | @item -march=@var{cpu-type} | |
12128 | @opindex march | |
12129 | Generate instructions for the machine type @var{cpu-type}. The choices | |
12130 | for @var{cpu-type} are the same as for @option{-mtune}. Moreover, | |
12131 | specifying @option{-march=@var{cpu-type}} implies @option{-mtune=@var{cpu-type}}. | |
74291a4b | 12132 | |
39bc1876 NS |
12133 | @item -mcpu=@var{cpu-type} |
12134 | @opindex mcpu | |
12135 | A deprecated synonym for @option{-mtune}. | |
3398f47f | 12136 | |
39bc1876 | 12137 | @item -mfpmath=@var{unit} |
8ce94e44 | 12138 | @opindex mfpmath |
39bc1876 NS |
12139 | Generate floating point arithmetics for selected unit @var{unit}. The choices |
12140 | for @var{unit} are: | |
2d2a50c3 | 12141 | |
39bc1876 NS |
12142 | @table @samp |
12143 | @item 387 | |
12144 | Use the standard 387 floating point coprocessor present majority of chips and | |
12145 | emulated otherwise. Code compiled with this option will run almost everywhere. | |
12146 | The temporary results are computed in 80bit precision instead of precision | |
12147 | specified by the type resulting in slightly different results compared to most | |
8a36672b | 12148 | of other chips. See @option{-ffloat-store} for more detailed description. |
74291a4b | 12149 | |
39bc1876 | 12150 | This is the default choice for i386 compiler. |
74291a4b | 12151 | |
39bc1876 NS |
12152 | @item sse |
12153 | Use scalar floating point instructions present in the SSE instruction set. | |
12154 | This instruction set is supported by Pentium3 and newer chips, in the AMD line | |
12155 | by Athlon-4, Athlon-xp and Athlon-mp chips. The earlier version of SSE | |
12156 | instruction set supports only single precision arithmetics, thus the double and | |
12157 | extended precision arithmetics is still done using 387. Later version, present | |
12158 | only in Pentium4 and the future AMD x86-64 chips supports double precision | |
12159 | arithmetics too. | |
a27fb29b | 12160 | |
c2b43d7a UB |
12161 | For the i386 compiler, you need to use @option{-march=@var{cpu-type}}, @option{-msse} |
12162 | or @option{-msse2} switches to enable SSE extensions and make this option | |
12163 | effective. For the x86-64 compiler, these extensions are enabled by default. | |
3398f47f | 12164 | |
39bc1876 NS |
12165 | The resulting code should be considerably faster in the majority of cases and avoid |
12166 | the numerical instability problems of 387 code, but may break some existing | |
12167 | code that expects temporaries to be 80bit. | |
cd3f11a6 | 12168 | |
39bc1876 | 12169 | This is the default choice for the x86-64 compiler. |
74291a4b | 12170 | |
39bc1876 | 12171 | @item sse,387 |
ab442df7 MM |
12172 | @itemx sse+387 |
12173 | @itemx both | |
39bc1876 NS |
12174 | Attempt to utilize both instruction sets at once. This effectively double the |
12175 | amount of available registers and on chips with separate execution units for | |
12176 | 387 and SSE the execution resources too. Use this option with care, as it is | |
12177 | still experimental, because the GCC register allocator does not model separate | |
12178 | functional units well resulting in instable performance. | |
12179 | @end table | |
ee692410 | 12180 | |
39bc1876 NS |
12181 | @item -masm=@var{dialect} |
12182 | @opindex masm=@var{dialect} | |
1f4c2c57 MS |
12183 | Output asm instructions using selected @var{dialect}. Supported |
12184 | choices are @samp{intel} or @samp{att} (the default one). Darwin does | |
13b3c362 | 12185 | not support @samp{intel}. |
ee692410 | 12186 | |
39bc1876 NS |
12187 | @item -mieee-fp |
12188 | @itemx -mno-ieee-fp | |
12189 | @opindex mieee-fp | |
12190 | @opindex mno-ieee-fp | |
12191 | Control whether or not the compiler uses IEEE floating point | |
12192 | comparisons. These handle correctly the case where the result of a | |
12193 | comparison is unordered. | |
ee692410 | 12194 | |
39bc1876 NS |
12195 | @item -msoft-float |
12196 | @opindex msoft-float | |
12197 | Generate output containing library calls for floating point. | |
12198 | @strong{Warning:} the requisite libraries are not part of GCC@. | |
12199 | Normally the facilities of the machine's usual C compiler are used, but | |
12200 | this can't be done directly in cross-compilation. You must make your | |
12201 | own arrangements to provide suitable library functions for | |
12202 | cross-compilation. | |
ee692410 | 12203 | |
39bc1876 NS |
12204 | On machines where a function returns floating point results in the 80387 |
12205 | register stack, some floating point opcodes may be emitted even if | |
12206 | @option{-msoft-float} is used. | |
ee692410 | 12207 | |
39bc1876 NS |
12208 | @item -mno-fp-ret-in-387 |
12209 | @opindex mno-fp-ret-in-387 | |
12210 | Do not use the FPU registers for return values of functions. | |
ee692410 | 12211 | |
39bc1876 NS |
12212 | The usual calling convention has functions return values of types |
12213 | @code{float} and @code{double} in an FPU register, even if there | |
12214 | is no FPU@. The idea is that the operating system should emulate | |
12215 | an FPU@. | |
5a4b3afd | 12216 | |
39bc1876 NS |
12217 | The option @option{-mno-fp-ret-in-387} causes such values to be returned |
12218 | in ordinary CPU registers instead. | |
5a4b3afd | 12219 | |
39bc1876 NS |
12220 | @item -mno-fancy-math-387 |
12221 | @opindex mno-fancy-math-387 | |
12222 | Some 387 emulators do not support the @code{sin}, @code{cos} and | |
12223 | @code{sqrt} instructions for the 387. Specify this option to avoid | |
12224 | generating those instructions. This option is the default on FreeBSD, | |
12225 | OpenBSD and NetBSD@. This option is overridden when @option{-march} | |
12226 | indicates that the target cpu will always have an FPU and so the | |
12227 | instruction will not need emulation. As of revision 2.6.1, these | |
12228 | instructions are not generated unless you also use the | |
12229 | @option{-funsafe-math-optimizations} switch. | |
5a4b3afd | 12230 | |
39bc1876 NS |
12231 | @item -malign-double |
12232 | @itemx -mno-align-double | |
12233 | @opindex malign-double | |
12234 | @opindex mno-align-double | |
12235 | Control whether GCC aligns @code{double}, @code{long double}, and | |
12236 | @code{long long} variables on a two word boundary or a one word | |
12237 | boundary. Aligning @code{double} variables on a two word boundary will | |
12238 | produce code that runs somewhat faster on a @samp{Pentium} at the | |
12239 | expense of more memory. | |
5a4b3afd | 12240 | |
dc5abe77 TM |
12241 | On x86-64, @option{-malign-double} is enabled by default. |
12242 | ||
39bc1876 NS |
12243 | @strong{Warning:} if you use the @option{-malign-double} switch, |
12244 | structures containing the above types will be aligned differently than | |
12245 | the published application binary interface specifications for the 386 | |
12246 | and will not be binary compatible with structures in code compiled | |
12247 | without that switch. | |
5a4b3afd | 12248 | |
39bc1876 NS |
12249 | @item -m96bit-long-double |
12250 | @itemx -m128bit-long-double | |
12251 | @opindex m96bit-long-double | |
12252 | @opindex m128bit-long-double | |
8a36672b | 12253 | These switches control the size of @code{long double} type. The i386 |
39bc1876 NS |
12254 | application binary interface specifies the size to be 96 bits, |
12255 | so @option{-m96bit-long-double} is the default in 32 bit mode. | |
5a4b3afd | 12256 | |
39bc1876 NS |
12257 | Modern architectures (Pentium and newer) would prefer @code{long double} |
12258 | to be aligned to an 8 or 16 byte boundary. In arrays or structures | |
12259 | conforming to the ABI, this would not be possible. So specifying a | |
12260 | @option{-m128bit-long-double} will align @code{long double} | |
12261 | to a 16 byte boundary by padding the @code{long double} with an additional | |
12262 | 32 bit zero. | |
5a4b3afd | 12263 | |
39bc1876 NS |
12264 | In the x86-64 compiler, @option{-m128bit-long-double} is the default choice as |
12265 | its ABI specifies that @code{long double} is to be aligned on 16 byte boundary. | |
5a4b3afd | 12266 | |
39bc1876 NS |
12267 | Notice that neither of these options enable any extra precision over the x87 |
12268 | standard of 80 bits for a @code{long double}. | |
5a4b3afd | 12269 | |
39bc1876 NS |
12270 | @strong{Warning:} if you override the default value for your target ABI, the |
12271 | structures and arrays containing @code{long double} variables will change | |
12272 | their size as well as function calling convention for function taking | |
12273 | @code{long double} will be modified. Hence they will not be binary | |
12274 | compatible with arrays or structures in code compiled without that switch. | |
5a4b3afd | 12275 | |
e58d5f65 | 12276 | @item -mlarge-data-threshold=@var{number} |
7dcbf659 JH |
12277 | @opindex mlarge-data-threshold=@var{number} |
12278 | When @option{-mcmodel=medium} is specified, the data greater than | |
12279 | @var{threshold} are placed in large data section. This value must be the | |
a4d05547 | 12280 | same across all object linked into the binary and defaults to 65535. |
5a4b3afd | 12281 | |
39bc1876 NS |
12282 | @item -mrtd |
12283 | @opindex mrtd | |
12284 | Use a different function-calling convention, in which functions that | |
12285 | take a fixed number of arguments return with the @code{ret} @var{num} | |
12286 | instruction, which pops their arguments while returning. This saves one | |
12287 | instruction in the caller since there is no need to pop the arguments | |
12288 | there. | |
5a4b3afd | 12289 | |
39bc1876 NS |
12290 | You can specify that an individual function is called with this calling |
12291 | sequence with the function attribute @samp{stdcall}. You can also | |
12292 | override the @option{-mrtd} option by using the function attribute | |
12293 | @samp{cdecl}. @xref{Function Attributes}. | |
74291a4b | 12294 | |
39bc1876 NS |
12295 | @strong{Warning:} this calling convention is incompatible with the one |
12296 | normally used on Unix, so you cannot use it if you need to call | |
12297 | libraries compiled with the Unix compiler. | |
74291a4b | 12298 | |
39bc1876 NS |
12299 | Also, you must provide function prototypes for all functions that |
12300 | take variable numbers of arguments (including @code{printf}); | |
12301 | otherwise incorrect code will be generated for calls to those | |
12302 | functions. | |
02f52e19 | 12303 | |
39bc1876 NS |
12304 | In addition, seriously incorrect code will result if you call a |
12305 | function with too many arguments. (Normally, extra arguments are | |
12306 | harmlessly ignored.) | |
1cf959cb | 12307 | |
39bc1876 NS |
12308 | @item -mregparm=@var{num} |
12309 | @opindex mregparm | |
12310 | Control how many registers are used to pass integer arguments. By | |
12311 | default, no registers are used to pass arguments, and at most 3 | |
12312 | registers can be used. You can control this behavior for a specific | |
12313 | function by using the function attribute @samp{regparm}. | |
12314 | @xref{Function Attributes}. | |
1cf959cb | 12315 | |
39bc1876 NS |
12316 | @strong{Warning:} if you use this switch, and |
12317 | @var{num} is nonzero, then you must build all modules with the same | |
12318 | value, including any libraries. This includes the system libraries and | |
12319 | startup modules. | |
5a4b3afd | 12320 | |
1f97667f RG |
12321 | @item -msseregparm |
12322 | @opindex msseregparm | |
12323 | Use SSE register passing conventions for float and double arguments | |
12324 | and return values. You can control this behavior for a specific | |
12325 | function by using the function attribute @samp{sseregparm}. | |
12326 | @xref{Function Attributes}. | |
12327 | ||
12328 | @strong{Warning:} if you use this switch then you must build all | |
12329 | modules with the same value, including any libraries. This includes | |
12330 | the system libraries and startup modules. | |
12331 | ||
2770264a RO |
12332 | @item -mvect8-ret-in-mem |
12333 | @opindex mvect8-ret-in-mem | |
12334 | Return 8-byte vectors in memory instead of MMX registers. This is the | |
12335 | default on Solaris~8 and 9 and VxWorks to match the ABI of the Sun | |
12336 | Studio compilers until version 12. Later compiler versions (starting | |
12337 | with Studio 12 Update~1) follow the ABI used by other x86 targets, which | |
12338 | is the default on Solaris~10 and later. @emph{Only} use this option if | |
12339 | you need to remain compatible with existing code produced by those | |
12340 | previous compiler versions or older versions of GCC. | |
12341 | ||
577565f9 UB |
12342 | @item -mpc32 |
12343 | @itemx -mpc64 | |
12344 | @itemx -mpc80 | |
12345 | @opindex mpc32 | |
12346 | @opindex mpc64 | |
12347 | @opindex mpc80 | |
12348 | ||
12349 | Set 80387 floating-point precision to 32, 64 or 80 bits. When @option{-mpc32} | |
80b9cbc9 | 12350 | is specified, the significands of results of floating-point operations are |
d1facce0 | 12351 | rounded to 24 bits (single precision); @option{-mpc64} rounds the |
80b9cbc9 BL |
12352 | significands of results of floating-point operations to 53 bits (double |
12353 | precision) and @option{-mpc80} rounds the significands of results of | |
12354 | floating-point operations to 64 bits (extended double precision), which is | |
12355 | the default. When this option is used, floating-point operations in higher | |
12356 | precisions are not available to the programmer without setting the FPU | |
12357 | control word explicitly. | |
12358 | ||
12359 | Setting the rounding of floating-point operations to less than the default | |
12360 | 80 bits can speed some programs by 2% or more. Note that some mathematical | |
12361 | libraries assume that extended precision (80 bit) floating-point operations | |
12362 | are enabled by default; routines in such libraries could suffer significant | |
12363 | loss of accuracy, typically through so-called "catastrophic cancellation", | |
7a61cf6f | 12364 | when this option is used to set the precision to less than extended precision. |
577565f9 | 12365 | |
33932946 SH |
12366 | @item -mstackrealign |
12367 | @opindex mstackrealign | |
2e3f842f L |
12368 | Realign the stack at entry. On the Intel x86, the @option{-mstackrealign} |
12369 | option will generate an alternate prologue and epilogue that realigns the | |
12370 | runtime stack if necessary. This supports mixing legacy codes that keep | |
12371 | a 4-byte aligned stack with modern codes that keep a 16-byte stack for | |
12372 | SSE compatibility. See also the attribute @code{force_align_arg_pointer}, | |
33932946 SH |
12373 | applicable to individual functions. |
12374 | ||
39bc1876 NS |
12375 | @item -mpreferred-stack-boundary=@var{num} |
12376 | @opindex mpreferred-stack-boundary | |
12377 | Attempt to keep the stack boundary aligned to a 2 raised to @var{num} | |
12378 | byte boundary. If @option{-mpreferred-stack-boundary} is not specified, | |
04df96dd | 12379 | the default is 4 (16 bytes or 128 bits). |
5a4b3afd | 12380 | |
2e3f842f L |
12381 | @item -mincoming-stack-boundary=@var{num} |
12382 | @opindex mincoming-stack-boundary | |
12383 | Assume the incoming stack is aligned to a 2 raised to @var{num} byte | |
12384 | boundary. If @option{-mincoming-stack-boundary} is not specified, | |
12385 | the one specified by @option{-mpreferred-stack-boundary} will be used. | |
12386 | ||
39bc1876 NS |
12387 | On Pentium and PentiumPro, @code{double} and @code{long double} values |
12388 | should be aligned to an 8 byte boundary (see @option{-malign-double}) or | |
12389 | suffer significant run time performance penalties. On Pentium III, the | |
04df96dd L |
12390 | Streaming SIMD Extension (SSE) data type @code{__m128} may not work |
12391 | properly if it is not 16 byte aligned. | |
5a4b3afd | 12392 | |
39bc1876 NS |
12393 | To ensure proper alignment of this values on the stack, the stack boundary |
12394 | must be as aligned as that required by any value stored on the stack. | |
12395 | Further, every function must be generated such that it keeps the stack | |
12396 | aligned. Thus calling a function compiled with a higher preferred | |
12397 | stack boundary from a function compiled with a lower preferred stack | |
12398 | boundary will most likely misalign the stack. It is recommended that | |
12399 | libraries that use callbacks always use the default setting. | |
5a4b3afd | 12400 | |
39bc1876 NS |
12401 | This extra alignment does consume extra stack space, and generally |
12402 | increases code size. Code that is sensitive to stack space usage, such | |
12403 | as embedded systems and operating system kernels, may want to reduce the | |
12404 | preferred alignment to @option{-mpreferred-stack-boundary=2}. | |
5a4b3afd | 12405 | |
39bc1876 NS |
12406 | @item -mmmx |
12407 | @itemx -mno-mmx | |
33558d94 | 12408 | @itemx -msse |
39bc1876 | 12409 | @itemx -mno-sse |
33558d94 | 12410 | @itemx -msse2 |
39bc1876 | 12411 | @itemx -mno-sse2 |
33558d94 | 12412 | @itemx -msse3 |
39bc1876 | 12413 | @itemx -mno-sse3 |
33558d94 | 12414 | @itemx -mssse3 |
b1875f52 | 12415 | @itemx -mno-ssse3 |
33558d94 | 12416 | @itemx -msse4.1 |
ab940b73 | 12417 | @need 800 |
9a5cee02 | 12418 | @itemx -mno-sse4.1 |
33558d94 | 12419 | @itemx -msse4.2 |
3b8dd071 | 12420 | @itemx -mno-sse4.2 |
33558d94 | 12421 | @itemx -msse4 |
3b8dd071 | 12422 | @itemx -mno-sse4 |
31cb596a JY |
12423 | @itemx -mavx |
12424 | @itemx -mno-avx | |
8b96a312 L |
12425 | @itemx -maes |
12426 | @itemx -mno-aes | |
12427 | @itemx -mpclmul | |
ab940b73 | 12428 | @need 800 |
8b96a312 | 12429 | @itemx -mno-pclmul |
4ee89d5f L |
12430 | @itemx -mfsgsbase |
12431 | @itemx -mno-fsgsbase | |
12432 | @itemx -mrdrnd | |
12433 | @itemx -mno-rdrnd | |
12434 | @itemx -mf16c | |
12435 | @itemx -mno-f16c | |
33558d94 AS |
12436 | @itemx -msse4a |
12437 | @itemx -mno-sse4a | |
cbf2e4d4 | 12438 | @itemx -mfma4 |
ab940b73 | 12439 | @need 800 |
cbf2e4d4 | 12440 | @itemx -mno-fma4 |
43a8b705 HJ |
12441 | @itemx -mxop |
12442 | @itemx -mno-xop | |
3e901069 HJ |
12443 | @itemx -mlwp |
12444 | @itemx -mno-lwp | |
33558d94 | 12445 | @itemx -m3dnow |
39bc1876 | 12446 | @itemx -mno-3dnow |
33558d94 | 12447 | @itemx -mpopcnt |
21efb4d4 | 12448 | @itemx -mno-popcnt |
33558d94 | 12449 | @itemx -mabm |
21efb4d4 | 12450 | @itemx -mno-abm |
91afcfa3 QN |
12451 | @itemx -mbmi |
12452 | @itemx -mno-bmi | |
94d13ad1 QN |
12453 | @itemx -mtbm |
12454 | @itemx -mno-tbm | |
39bc1876 NS |
12455 | @opindex mmmx |
12456 | @opindex mno-mmx | |
12457 | @opindex msse | |
12458 | @opindex mno-sse | |
12459 | @opindex m3dnow | |
12460 | @opindex mno-3dnow | |
75576871 | 12461 | These switches enable or disable the use of instructions in the MMX, |
4ee89d5f | 12462 | SSE, SSE2, SSE3, SSSE3, SSE4.1, AVX, AES, PCLMUL, FSGSBASE, RDRND, |
91afcfa3 | 12463 | F16C, SSE4A, FMA4, XOP, LWP, ABM, BMI, or 3DNow!@: extended instruction sets. |
b1875f52 L |
12464 | These extensions are also available as built-in functions: see |
12465 | @ref{X86 Built-in Functions}, for details of the functions enabled and | |
12466 | disabled by these switches. | |
74291a4b | 12467 | |
39bc1876 | 12468 | To have SSE/SSE2 instructions generated automatically from floating-point |
75576871 BB |
12469 | code (as opposed to 387 instructions), see @option{-mfpmath=sse}. |
12470 | ||
31cb596a JY |
12471 | GCC depresses SSEx instructions when @option{-mavx} is used. Instead, it |
12472 | generates new AVX instructions or AVX equivalence for all SSEx instructions | |
12473 | when needed. | |
12474 | ||
75576871 BB |
12475 | These options will enable GCC to use these extended instructions in |
12476 | generated code, even without @option{-mfpmath=sse}. Applications which | |
12477 | perform runtime CPU detection must compile separate files for each | |
12478 | supported architecture, using the appropriate flags. In particular, | |
12479 | the file containing the CPU detection code should be compiled without | |
12480 | these options. | |
74291a4b | 12481 | |
6a790a69 SP |
12482 | @item -mfused-madd |
12483 | @itemx -mno-fused-madd | |
12484 | @opindex mfused-madd | |
12485 | @opindex mno-fused-madd | |
12486 | Do (don't) generate code that uses the fused multiply/add or multiply/subtract | |
12487 | instructions. The default is to use these instructions. | |
12488 | ||
922e3e33 UB |
12489 | @item -mcld |
12490 | @opindex mcld | |
12491 | This option instructs GCC to emit a @code{cld} instruction in the prologue | |
12492 | of functions that use string instructions. String instructions depend on | |
12493 | the DF flag to select between autoincrement or autodecrement mode. While the | |
12494 | ABI specifies the DF flag to be cleared on function entry, some operating | |
12495 | systems violate this specification by not clearing the DF flag in their | |
12496 | exception dispatchers. The exception handler can be invoked with the DF flag | |
12497 | set which leads to wrong direction mode, when string instructions are used. | |
12498 | This option can be enabled by default on 32-bit x86 targets by configuring | |
12499 | GCC with the @option{--enable-cld} configure option. Generation of @code{cld} | |
12500 | instructions can be suppressed with the @option{-mno-cld} compiler option | |
12501 | in this case. | |
12502 | ||
2767a7f2 L |
12503 | @item -mvzeroupper |
12504 | @opindex mvzeroupper | |
12505 | This option instructs GCC to emit a @code{vzeroupper} instruction | |
12506 | before a transfer of control flow out of the function to minimize | |
12507 | AVX to SSE transition penalty as well as remove unnecessary zeroupper | |
12508 | intrinsics. | |
12509 | ||
5be6cb59 | 12510 | @item -mcx16 |
edc5f63b | 12511 | @opindex mcx16 |
5be6cb59 UB |
12512 | This option will enable GCC to use CMPXCHG16B instruction in generated code. |
12513 | CMPXCHG16B allows for atomic operations on 128-bit double quadword (or oword) | |
12514 | data types. This is useful for high resolution counters that could be updated | |
12515 | by multiple processors (or cores). This instruction is generated as part of | |
12516 | atomic built-in functions: see @ref{Atomic Builtins} for details. | |
12517 | ||
12518 | @item -msahf | |
edc5f63b | 12519 | @opindex msahf |
8c5fd59f UB |
12520 | This option will enable GCC to use SAHF instruction in generated 64-bit code. |
12521 | Early Intel CPUs with Intel 64 lacked LAHF and SAHF instructions supported | |
12522 | by AMD64 until introduction of Pentium 4 G1 step in December 2005. LAHF and | |
12523 | SAHF are load and store instructions, respectively, for certain status flags. | |
12524 | In 64-bit mode, SAHF instruction is used to optimize @code{fmod}, @code{drem} | |
12525 | or @code{remainder} built-in functions: see @ref{Other Builtins} for details. | |
5be6cb59 | 12526 | |
cabf85c3 L |
12527 | @item -mmovbe |
12528 | @opindex mmovbe | |
12529 | This option will enable GCC to use movbe instruction to implement | |
12530 | @code{__builtin_bswap32} and @code{__builtin_bswap64}. | |
12531 | ||
8ed0ce99 L |
12532 | @item -mcrc32 |
12533 | @opindex mcrc32 | |
12534 | This option will enable built-in functions, @code{__builtin_ia32_crc32qi}, | |
12535 | @code{__builtin_ia32_crc32hi}. @code{__builtin_ia32_crc32si} and | |
12536 | @code{__builtin_ia32_crc32di} to generate the crc32 machine instruction. | |
12537 | ||
6b889d89 UB |
12538 | @item -mrecip |
12539 | @opindex mrecip | |
12540 | This option will enable GCC to use RCPSS and RSQRTSS instructions (and their | |
048fd785 | 12541 | vectorized variants RCPPS and RSQRTPS) with an additional Newton-Raphson step |
8bce96f5 UB |
12542 | to increase precision instead of DIVSS and SQRTSS (and their vectorized |
12543 | variants) for single precision floating point arguments. These instructions | |
12544 | are generated only when @option{-funsafe-math-optimizations} is enabled | |
12545 | together with @option{-finite-math-only} and @option{-fno-trapping-math}. | |
12546 | Note that while the throughput of the sequence is higher than the throughput | |
12547 | of the non-reciprocal instruction, the precision of the sequence can be | |
b73d1527 | 12548 | decreased by up to 2 ulp (i.e. the inverse of 1.0 equals 0.99999994). |
6b889d89 | 12549 | |
79e22ff8 MM |
12550 | Note that GCC implements 1.0f/sqrtf(x) in terms of RSQRTSS (or RSQRTPS) |
12551 | already with @option{-ffast-math} (or the above option combination), and | |
12552 | doesn't need @option{-mrecip}. | |
12553 | ||
a5ea943c RG |
12554 | @item -mveclibabi=@var{type} |
12555 | @opindex mveclibabi | |
12556 | Specifies the ABI type to use for vectorizing intrinsics using an | |
9aba5d22 UB |
12557 | external library. Supported types are @code{svml} for the Intel short |
12558 | vector math library and @code{acml} for the AMD math core library style | |
12559 | of interfacing. GCC will currently emit calls to @code{vmldExp2}, | |
12560 | @code{vmldLn2}, @code{vmldLog102}, @code{vmldLog102}, @code{vmldPow2}, | |
12561 | @code{vmldTanh2}, @code{vmldTan2}, @code{vmldAtan2}, @code{vmldAtanh2}, | |
12562 | @code{vmldCbrt2}, @code{vmldSinh2}, @code{vmldSin2}, @code{vmldAsinh2}, | |
12563 | @code{vmldAsin2}, @code{vmldCosh2}, @code{vmldCos2}, @code{vmldAcosh2}, | |
12564 | @code{vmldAcos2}, @code{vmlsExp4}, @code{vmlsLn4}, @code{vmlsLog104}, | |
12565 | @code{vmlsLog104}, @code{vmlsPow4}, @code{vmlsTanh4}, @code{vmlsTan4}, | |
12566 | @code{vmlsAtan4}, @code{vmlsAtanh4}, @code{vmlsCbrt4}, @code{vmlsSinh4}, | |
12567 | @code{vmlsSin4}, @code{vmlsAsinh4}, @code{vmlsAsin4}, @code{vmlsCosh4}, | |
12568 | @code{vmlsCos4}, @code{vmlsAcosh4} and @code{vmlsAcos4} for corresponding | |
12569 | function type when @option{-mveclibabi=svml} is used and @code{__vrd2_sin}, | |
12570 | @code{__vrd2_cos}, @code{__vrd2_exp}, @code{__vrd2_log}, @code{__vrd2_log2}, | |
12571 | @code{__vrd2_log10}, @code{__vrs4_sinf}, @code{__vrs4_cosf}, | |
12572 | @code{__vrs4_expf}, @code{__vrs4_logf}, @code{__vrs4_log2f}, | |
12573 | @code{__vrs4_log10f} and @code{__vrs4_powf} for corresponding function type | |
12574 | when @option{-mveclibabi=acml} is used. Both @option{-ftree-vectorize} and | |
12575 | @option{-funsafe-math-optimizations} have to be enabled. A SVML or ACML ABI | |
12576 | compatible library will have to be specified at link time. | |
a5ea943c | 12577 | |
51212b32 L |
12578 | @item -mabi=@var{name} |
12579 | @opindex mabi | |
12580 | Generate code for the specified calling convention. Permissible values | |
12581 | are: @samp{sysv} for the ABI used on GNU/Linux and other systems and | |
12582 | @samp{ms} for the Microsoft ABI. The default is to use the Microsoft | |
12583 | ABI when targeting Windows. On all other systems, the default is the | |
12584 | SYSV ABI. You can control this behavior for a specific function by | |
12585 | using the function attribute @samp{ms_abi}/@samp{sysv_abi}. | |
12586 | @xref{Function Attributes}. | |
12587 | ||
39bc1876 NS |
12588 | @item -mpush-args |
12589 | @itemx -mno-push-args | |
12590 | @opindex mpush-args | |
12591 | @opindex mno-push-args | |
12592 | Use PUSH operations to store outgoing parameters. This method is shorter | |
12593 | and usually equally fast as method using SUB/MOV operations and is enabled | |
12594 | by default. In some cases disabling it may improve performance because of | |
12595 | improved scheduling and reduced dependencies. | |
74291a4b | 12596 | |
39bc1876 NS |
12597 | @item -maccumulate-outgoing-args |
12598 | @opindex maccumulate-outgoing-args | |
12599 | If enabled, the maximum amount of space required for outgoing arguments will be | |
12600 | computed in the function prologue. This is faster on most modern CPUs | |
12601 | because of reduced dependencies, improved scheduling and reduced stack usage | |
12602 | when preferred stack boundary is not equal to 2. The drawback is a notable | |
12603 | increase in code size. This switch implies @option{-mno-push-args}. | |
63357d93 | 12604 | |
39bc1876 NS |
12605 | @item -mthreads |
12606 | @opindex mthreads | |
12607 | Support thread-safe exception handling on @samp{Mingw32}. Code that relies | |
12608 | on thread-safe exception handling must compile and link all code with the | |
12609 | @option{-mthreads} option. When compiling, @option{-mthreads} defines | |
12610 | @option{-D_MT}; when linking, it links in a special thread helper library | |
12611 | @option{-lmingwthrd} which cleans up per thread exception handling data. | |
5ef1a99d | 12612 | |
39bc1876 NS |
12613 | @item -mno-align-stringops |
12614 | @opindex mno-align-stringops | |
12615 | Do not align destination of inlined string operations. This switch reduces | |
12616 | code size and improves performance in case the destination is already aligned, | |
12617 | but GCC doesn't know about it. | |
46490403 | 12618 | |
39bc1876 NS |
12619 | @item -minline-all-stringops |
12620 | @opindex minline-all-stringops | |
12621 | By default GCC inlines string operations only when destination is known to be | |
12622 | aligned at least to 4 byte boundary. This enables more inlining, increase code | |
12623 | size, but may improve performance of code that depends on fast memcpy, strlen | |
12624 | and memset for short lengths. | |
c235ddf2 | 12625 | |
8c996513 JH |
12626 | @item -minline-stringops-dynamically |
12627 | @opindex minline-stringops-dynamically | |
12628 | For string operation of unknown size, inline runtime checks so for small | |
5681c208 | 12629 | blocks inline code is used, while for large blocks library call is used. |
8c996513 JH |
12630 | |
12631 | @item -mstringop-strategy=@var{alg} | |
dbdbfff1 | 12632 | @opindex mstringop-strategy=@var{alg} |
8c996513 | 12633 | Overwrite internal decision heuristic about particular algorithm to inline |
5681c208 | 12634 | string operation with. The allowed values are @code{rep_byte}, |
8c996513 | 12635 | @code{rep_4byte}, @code{rep_8byte} for expanding using i386 @code{rep} prefix |
5db74c32 UB |
12636 | of specified size, @code{byte_loop}, @code{loop}, @code{unrolled_loop} for |
12637 | expanding inline loop, @code{libcall} for always expanding library call. | |
8c996513 | 12638 | |
39bc1876 NS |
12639 | @item -momit-leaf-frame-pointer |
12640 | @opindex momit-leaf-frame-pointer | |
12641 | Don't keep the frame pointer in a register for leaf functions. This | |
12642 | avoids the instructions to save, set up and restore frame pointers and | |
12643 | makes an extra register available in leaf functions. The option | |
12644 | @option{-fomit-frame-pointer} removes the frame pointer for all functions | |
12645 | which might make debugging harder. | |
c235ddf2 | 12646 | |
39bc1876 NS |
12647 | @item -mtls-direct-seg-refs |
12648 | @itemx -mno-tls-direct-seg-refs | |
12649 | @opindex mtls-direct-seg-refs | |
12650 | Controls whether TLS variables may be accessed with offsets from the | |
12651 | TLS segment register (@code{%gs} for 32-bit, @code{%fs} for 64-bit), | |
12652 | or whether the thread base pointer must be added. Whether or not this | |
12653 | is legal depends on the operating system, and whether it maps the | |
12654 | segment to cover the entire TLS area. | |
beadc644 | 12655 | |
39bc1876 | 12656 | For systems that use GNU libc, the default is on. |
04e1d06b | 12657 | |
bd459cb6 L |
12658 | @item -msse2avx |
12659 | @itemx -mno-sse2avx | |
12660 | @opindex msse2avx | |
12661 | Specify that the assembler should encode SSE instructions with VEX | |
12662 | prefix. The option @option{-mavx} turns this on by default. | |
3c5273a9 KT |
12663 | |
12664 | @item -mfentry | |
12665 | @itemx -mno-fentry | |
12666 | @opindex mfentry | |
12667 | If profiling is active @option{-pg} put the profiling | |
12668 | counter call before prologue. | |
12669 | Note: On x86 architectures the attribute @code{ms_hook_prologue} | |
12670 | isn't possible at the moment for @option{-mfentry} and @option{-pg}. | |
26ec9308 L |
12671 | |
12672 | @item -m8bit-idiv | |
12673 | @itemx -mno-8bit-idiv | |
12674 | @opindex 8bit-idiv | |
12675 | On some processors, like Intel Atom, 8bit unsigned integer divide is | |
12676 | much faster than 32bit/64bit integer divide. This option will generate a | |
12677 | runt-time check. If both dividend and divisor are within range of 0 | |
12678 | to 255, 8bit unsigned integer divide will be used instead of | |
12679 | 32bit/64bit integer divide. | |
12680 | ||
39bc1876 | 12681 | @end table |
af34e51e | 12682 | |
39bc1876 NS |
12683 | These @samp{-m} switches are supported in addition to the above |
12684 | on AMD x86-64 processors in 64-bit environments. | |
50d32cf6 | 12685 | |
39bc1876 NS |
12686 | @table @gcctabopt |
12687 | @item -m32 | |
12688 | @itemx -m64 | |
12689 | @opindex m32 | |
12690 | @opindex m64 | |
12691 | Generate code for a 32-bit or 64-bit environment. | |
12692 | The 32-bit environment sets int, long and pointer to 32 bits and | |
12693 | generates code that runs on any i386 system. | |
12694 | The 64-bit environment sets int to 32 bits and long and pointer | |
cb7ad97b EC |
12695 | to 64 bits and generates code for AMD's x86-64 architecture. For |
12696 | darwin only the -m64 option turns off the @option{-fno-pic} and | |
12697 | @option{-mdynamic-no-pic} options. | |
50d32cf6 | 12698 | |
39bc1876 | 12699 | @item -mno-red-zone |
d376d545 | 12700 | @opindex mno-red-zone |
39bc1876 NS |
12701 | Do not use a so called red zone for x86-64 code. The red zone is mandated |
12702 | by the x86-64 ABI, it is a 128-byte area beyond the location of the | |
12703 | stack pointer that will not be modified by signal or interrupt handlers | |
12704 | and therefore can be used for temporary data without adjusting the stack | |
12705 | pointer. The flag @option{-mno-red-zone} disables this red zone. | |
dc884a86 | 12706 | |
39bc1876 NS |
12707 | @item -mcmodel=small |
12708 | @opindex mcmodel=small | |
12709 | Generate code for the small code model: the program and its symbols must | |
12710 | be linked in the lower 2 GB of the address space. Pointers are 64 bits. | |
12711 | Programs can be statically or dynamically linked. This is the default | |
12712 | code model. | |
dc884a86 | 12713 | |
39bc1876 NS |
12714 | @item -mcmodel=kernel |
12715 | @opindex mcmodel=kernel | |
12716 | Generate code for the kernel code model. The kernel runs in the | |
12717 | negative 2 GB of the address space. | |
12718 | This model has to be used for Linux kernel code. | |
12719 | ||
12720 | @item -mcmodel=medium | |
12721 | @opindex mcmodel=medium | |
12722 | Generate code for the medium model: The program is linked in the lower 2 | |
3b139014 | 12723 | GB of the address space. Small symbols are also placed there. Symbols |
e58d5f65 JJ |
12724 | with sizes larger than @option{-mlarge-data-threshold} are put into |
12725 | large data or bss sections and can be located above 2GB. Programs can | |
12726 | be statically or dynamically linked. | |
39bc1876 NS |
12727 | |
12728 | @item -mcmodel=large | |
12729 | @opindex mcmodel=large | |
12730 | Generate code for the large model: This model makes no assumptions | |
cb7ad97b | 12731 | about addresses and sizes of sections. |
74291a4b MM |
12732 | @end table |
12733 | ||
39bc1876 NS |
12734 | @node IA-64 Options |
12735 | @subsection IA-64 Options | |
12736 | @cindex IA-64 Options | |
74291a4b | 12737 | |
39bc1876 | 12738 | These are the @samp{-m} options defined for the Intel IA-64 architecture. |
74291a4b | 12739 | |
2642624b | 12740 | @table @gcctabopt |
39bc1876 NS |
12741 | @item -mbig-endian |
12742 | @opindex mbig-endian | |
12743 | Generate code for a big endian target. This is the default for HP-UX@. | |
6f670fde | 12744 | |
39bc1876 NS |
12745 | @item -mlittle-endian |
12746 | @opindex mlittle-endian | |
12747 | Generate code for a little endian target. This is the default for AIX5 | |
12748 | and GNU/Linux. | |
a9f3e1a4 | 12749 | |
39bc1876 NS |
12750 | @item -mgnu-as |
12751 | @itemx -mno-gnu-as | |
12752 | @opindex mgnu-as | |
12753 | @opindex mno-gnu-as | |
12754 | Generate (or don't) code for the GNU assembler. This is the default. | |
12755 | @c Also, this is the default if the configure option @option{--with-gnu-as} | |
12756 | @c is used. | |
9d913bbf | 12757 | |
39bc1876 NS |
12758 | @item -mgnu-ld |
12759 | @itemx -mno-gnu-ld | |
12760 | @opindex mgnu-ld | |
12761 | @opindex mno-gnu-ld | |
12762 | Generate (or don't) code for the GNU linker. This is the default. | |
12763 | @c Also, this is the default if the configure option @option{--with-gnu-ld} | |
12764 | @c is used. | |
a9f3e1a4 | 12765 | |
39bc1876 NS |
12766 | @item -mno-pic |
12767 | @opindex mno-pic | |
12768 | Generate code that does not use a global pointer register. The result | |
12769 | is not position independent code, and violates the IA-64 ABI@. | |
74291a4b | 12770 | |
39bc1876 NS |
12771 | @item -mvolatile-asm-stop |
12772 | @itemx -mno-volatile-asm-stop | |
12773 | @opindex mvolatile-asm-stop | |
12774 | @opindex mno-volatile-asm-stop | |
12775 | Generate (or don't) a stop bit immediately before and after volatile asm | |
12776 | statements. | |
965f5423 | 12777 | |
39bc1876 NS |
12778 | @item -mregister-names |
12779 | @itemx -mno-register-names | |
12780 | @opindex mregister-names | |
12781 | @opindex mno-register-names | |
12782 | Generate (or don't) @samp{in}, @samp{loc}, and @samp{out} register names for | |
12783 | the stacked registers. This may make assembler output more readable. | |
965f5423 | 12784 | |
39bc1876 NS |
12785 | @item -mno-sdata |
12786 | @itemx -msdata | |
12787 | @opindex mno-sdata | |
12788 | @opindex msdata | |
12789 | Disable (or enable) optimizations that use the small data section. This may | |
12790 | be useful for working around optimizer bugs. | |
12791 | ||
12792 | @item -mconstant-gp | |
12793 | @opindex mconstant-gp | |
12794 | Generate code that uses a single constant global pointer value. This is | |
12795 | useful when compiling kernel code. | |
12796 | ||
12797 | @item -mauto-pic | |
12798 | @opindex mauto-pic | |
12799 | Generate code that is self-relocatable. This implies @option{-mconstant-gp}. | |
12800 | This is useful when compiling firmware code. | |
12801 | ||
12802 | @item -minline-float-divide-min-latency | |
12803 | @opindex minline-float-divide-min-latency | |
12804 | Generate code for inline divides of floating point values | |
12805 | using the minimum latency algorithm. | |
965f5423 | 12806 | |
39bc1876 NS |
12807 | @item -minline-float-divide-max-throughput |
12808 | @opindex minline-float-divide-max-throughput | |
12809 | Generate code for inline divides of floating point values | |
12810 | using the maximum throughput algorithm. | |
965f5423 | 12811 | |
bf3c6caf SE |
12812 | @item -mno-inline-float-divide |
12813 | @opindex mno-inline-float-divide | |
12814 | Do not generate inline code for divides of floating point values. | |
12815 | ||
39bc1876 NS |
12816 | @item -minline-int-divide-min-latency |
12817 | @opindex minline-int-divide-min-latency | |
12818 | Generate code for inline divides of integer values | |
12819 | using the minimum latency algorithm. | |
965f5423 | 12820 | |
39bc1876 NS |
12821 | @item -minline-int-divide-max-throughput |
12822 | @opindex minline-int-divide-max-throughput | |
12823 | Generate code for inline divides of integer values | |
12824 | using the maximum throughput algorithm. | |
965f5423 | 12825 | |
29661412 NC |
12826 | @item -mno-inline-int-divide |
12827 | @opindex mno-inline-int-divide | |
bf3c6caf SE |
12828 | Do not generate inline code for divides of integer values. |
12829 | ||
28b43def SE |
12830 | @item -minline-sqrt-min-latency |
12831 | @opindex minline-sqrt-min-latency | |
12832 | Generate code for inline square roots | |
12833 | using the minimum latency algorithm. | |
12834 | ||
12835 | @item -minline-sqrt-max-throughput | |
12836 | @opindex minline-sqrt-max-throughput | |
12837 | Generate code for inline square roots | |
12838 | using the maximum throughput algorithm. | |
12839 | ||
bf3c6caf SE |
12840 | @item -mno-inline-sqrt |
12841 | @opindex mno-inline-sqrt | |
12842 | Do not generate inline code for sqrt. | |
12843 | ||
12844 | @item -mfused-madd | |
12845 | @itemx -mno-fused-madd | |
12846 | @opindex mfused-madd | |
12847 | @opindex mno-fused-madd | |
12848 | Do (don't) generate code that uses the fused multiply/add or multiply/subtract | |
6a790a69 | 12849 | instructions. The default is to use these instructions. |
bf3c6caf | 12850 | |
39bc1876 NS |
12851 | @item -mno-dwarf2-asm |
12852 | @itemx -mdwarf2-asm | |
12853 | @opindex mno-dwarf2-asm | |
12854 | @opindex mdwarf2-asm | |
12855 | Don't (or do) generate assembler code for the DWARF2 line number debugging | |
12856 | info. This may be useful when not using the GNU assembler. | |
965f5423 | 12857 | |
28b43def SE |
12858 | @item -mearly-stop-bits |
12859 | @itemx -mno-early-stop-bits | |
12860 | @opindex mearly-stop-bits | |
12861 | @opindex mno-early-stop-bits | |
12862 | Allow stop bits to be placed earlier than immediately preceding the | |
12863 | instruction that triggered the stop bit. This can improve instruction | |
12864 | scheduling, but does not always do so. | |
12865 | ||
39bc1876 NS |
12866 | @item -mfixed-range=@var{register-range} |
12867 | @opindex mfixed-range | |
12868 | Generate code treating the given register range as fixed registers. | |
12869 | A fixed register is one that the register allocator can not use. This is | |
12870 | useful when compiling kernel code. A register range is specified as | |
12871 | two registers separated by a dash. Multiple register ranges can be | |
12872 | specified separated by a comma. | |
04e149ab | 12873 | |
28b43def SE |
12874 | @item -mtls-size=@var{tls-size} |
12875 | @opindex mtls-size | |
12876 | Specify bit size of immediate TLS offsets. Valid values are 14, 22, and | |
12877 | 64. | |
12878 | ||
7f9dc823 JW |
12879 | @item -mtune=@var{cpu-type} |
12880 | @opindex mtune | |
28b43def SE |
12881 | Tune the instruction scheduling for a particular CPU, Valid values are |
12882 | itanium, itanium1, merced, itanium2, and mckinley. | |
12883 | ||
28b43def SE |
12884 | @item -milp32 |
12885 | @itemx -mlp64 | |
12886 | @opindex milp32 | |
12887 | @opindex mlp64 | |
12888 | Generate code for a 32-bit or 64-bit environment. | |
12889 | The 32-bit environment sets int, long and pointer to 32 bits. | |
12890 | The 64-bit environment sets int to 32 bits and long and pointer | |
12891 | to 64 bits. These are HP-UX specific flags. | |
12892 | ||
048d0d36 MK |
12893 | @item -mno-sched-br-data-spec |
12894 | @itemx -msched-br-data-spec | |
edc5f63b DF |
12895 | @opindex mno-sched-br-data-spec |
12896 | @opindex msched-br-data-spec | |
048d0d36 MK |
12897 | (Dis/En)able data speculative scheduling before reload. |
12898 | This will result in generation of the ld.a instructions and | |
12899 | the corresponding check instructions (ld.c / chk.a). | |
12900 | The default is 'disable'. | |
12901 | ||
12902 | @item -msched-ar-data-spec | |
12903 | @itemx -mno-sched-ar-data-spec | |
edc5f63b DF |
12904 | @opindex msched-ar-data-spec |
12905 | @opindex mno-sched-ar-data-spec | |
048d0d36 MK |
12906 | (En/Dis)able data speculative scheduling after reload. |
12907 | This will result in generation of the ld.a instructions and | |
12908 | the corresponding check instructions (ld.c / chk.a). | |
12909 | The default is 'enable'. | |
12910 | ||
12911 | @item -mno-sched-control-spec | |
12912 | @itemx -msched-control-spec | |
edc5f63b DF |
12913 | @opindex mno-sched-control-spec |
12914 | @opindex msched-control-spec | |
048d0d36 | 12915 | (Dis/En)able control speculative scheduling. This feature is |
a31cfd58 | 12916 | available only during region scheduling (i.e.@: before reload). |
048d0d36 MK |
12917 | This will result in generation of the ld.s instructions and |
12918 | the corresponding check instructions chk.s . | |
12919 | The default is 'disable'. | |
12920 | ||
12921 | @item -msched-br-in-data-spec | |
12922 | @itemx -mno-sched-br-in-data-spec | |
edc5f63b DF |
12923 | @opindex msched-br-in-data-spec |
12924 | @opindex mno-sched-br-in-data-spec | |
048d0d36 MK |
12925 | (En/Dis)able speculative scheduling of the instructions that |
12926 | are dependent on the data speculative loads before reload. | |
12927 | This is effective only with @option{-msched-br-data-spec} enabled. | |
12928 | The default is 'enable'. | |
12929 | ||
12930 | @item -msched-ar-in-data-spec | |
12931 | @itemx -mno-sched-ar-in-data-spec | |
edc5f63b DF |
12932 | @opindex msched-ar-in-data-spec |
12933 | @opindex mno-sched-ar-in-data-spec | |
048d0d36 MK |
12934 | (En/Dis)able speculative scheduling of the instructions that |
12935 | are dependent on the data speculative loads after reload. | |
12936 | This is effective only with @option{-msched-ar-data-spec} enabled. | |
12937 | The default is 'enable'. | |
12938 | ||
12939 | @item -msched-in-control-spec | |
12940 | @itemx -mno-sched-in-control-spec | |
edc5f63b DF |
12941 | @opindex msched-in-control-spec |
12942 | @opindex mno-sched-in-control-spec | |
048d0d36 MK |
12943 | (En/Dis)able speculative scheduling of the instructions that |
12944 | are dependent on the control speculative loads. | |
12945 | This is effective only with @option{-msched-control-spec} enabled. | |
12946 | The default is 'enable'. | |
12947 | ||
048d0d36 MK |
12948 | @item -mno-sched-prefer-non-data-spec-insns |
12949 | @itemx -msched-prefer-non-data-spec-insns | |
edc5f63b DF |
12950 | @opindex mno-sched-prefer-non-data-spec-insns |
12951 | @opindex msched-prefer-non-data-spec-insns | |
917f1b7e | 12952 | If enabled, data speculative instructions will be chosen for schedule |
048d0d36 MK |
12953 | only if there are no other choices at the moment. This will make |
12954 | the use of the data speculation much more conservative. | |
12955 | The default is 'disable'. | |
12956 | ||
12957 | @item -mno-sched-prefer-non-control-spec-insns | |
12958 | @itemx -msched-prefer-non-control-spec-insns | |
edc5f63b DF |
12959 | @opindex mno-sched-prefer-non-control-spec-insns |
12960 | @opindex msched-prefer-non-control-spec-insns | |
917f1b7e | 12961 | If enabled, control speculative instructions will be chosen for schedule |
048d0d36 MK |
12962 | only if there are no other choices at the moment. This will make |
12963 | the use of the control speculation much more conservative. | |
12964 | The default is 'disable'. | |
12965 | ||
12966 | @item -mno-sched-count-spec-in-critical-path | |
12967 | @itemx -msched-count-spec-in-critical-path | |
edc5f63b DF |
12968 | @opindex mno-sched-count-spec-in-critical-path |
12969 | @opindex msched-count-spec-in-critical-path | |
917f1b7e | 12970 | If enabled, speculative dependencies will be considered during |
048d0d36 MK |
12971 | computation of the instructions priorities. This will make the use of the |
12972 | speculation a bit more conservative. | |
12973 | The default is 'disable'. | |
12974 | ||
bf3c6caf SE |
12975 | @item -msched-spec-ldc |
12976 | @opindex msched-spec-ldc | |
12977 | Use a simple data speculation check. This option is on by default. | |
12978 | ||
12979 | @item -msched-control-spec-ldc | |
12980 | @opindex msched-spec-ldc | |
12981 | Use a simple check for control speculation. This option is on by default. | |
12982 | ||
12983 | @item -msched-stop-bits-after-every-cycle | |
12984 | @opindex msched-stop-bits-after-every-cycle | |
12985 | Place a stop bit after every cycle when scheduling. This option is on | |
12986 | by default. | |
12987 | ||
12988 | @item -msched-fp-mem-deps-zero-cost | |
12989 | @opindex msched-fp-mem-deps-zero-cost | |
12990 | Assume that floating-point stores and loads are not likely to cause a conflict | |
12991 | when placed into the same instruction group. This option is disabled by | |
12992 | default. | |
12993 | ||
12994 | @item -msel-sched-dont-check-control-spec | |
12995 | @opindex msel-sched-dont-check-control-spec | |
12996 | Generate checks for control speculation in selective scheduling. | |
12997 | This flag is disabled by default. | |
12998 | ||
12999 | @item -msched-max-memory-insns=@var{max-insns} | |
13000 | @opindex msched-max-memory-insns | |
13001 | Limit on the number of memory insns per instruction group, giving lower | |
13002 | priority to subsequent memory insns attempting to schedule in the same | |
13003 | instruction group. Frequently useful to prevent cache bank conflicts. | |
13004 | The default value is 1. | |
13005 | ||
13006 | @item -msched-max-memory-insns-hard-limit | |
13007 | @opindex msched-max-memory-insns-hard-limit | |
13008 | Disallow more than `msched-max-memory-insns' in instruction group. | |
13009 | Otherwise, limit is `soft' meaning that we would prefer non-memory operations | |
13010 | when limit is reached but may still schedule memory operations. | |
13011 | ||
39bc1876 | 13012 | @end table |
74291a4b | 13013 | |
dcad28fd DR |
13014 | @node IA-64/VMS Options |
13015 | @subsection IA-64/VMS Options | |
13016 | ||
13017 | These @samp{-m} options are defined for the IA-64/VMS implementations: | |
13018 | ||
13019 | @table @gcctabopt | |
13020 | @item -mvms-return-codes | |
13021 | @opindex mvms-return-codes | |
13022 | Return VMS condition codes from main. The default is to return POSIX | |
13023 | style condition (e.g.@ error) codes. | |
13024 | ||
13025 | @item -mdebug-main=@var{prefix} | |
13026 | @opindex mdebug-main=@var{prefix} | |
13027 | Flag the first routine whose name starts with @var{prefix} as the main | |
13028 | routine for the debugger. | |
13029 | ||
13030 | @item -mmalloc64 | |
13031 | @opindex mmalloc64 | |
13032 | Default to 64bit memory allocation routines. | |
13033 | @end table | |
13034 | ||
aa4945c1 JB |
13035 | @node LM32 Options |
13036 | @subsection LM32 Options | |
13037 | @cindex LM32 options | |
13038 | ||
13039 | These @option{-m} options are defined for the Lattice Mico32 architecture: | |
13040 | ||
13041 | @table @gcctabopt | |
13042 | @item -mbarrel-shift-enabled | |
13043 | @opindex mbarrel-shift-enabled | |
13044 | Enable barrel-shift instructions. | |
13045 | ||
13046 | @item -mdivide-enabled | |
13047 | @opindex mdivide-enabled | |
13048 | Enable divide and modulus instructions. | |
13049 | ||
13050 | @item -mmultiply-enabled | |
13051 | @opindex multiply-enabled | |
13052 | Enable multiply instructions. | |
13053 | ||
13054 | @item -msign-extend-enabled | |
13055 | @opindex msign-extend-enabled | |
13056 | Enable sign extend instructions. | |
13057 | ||
13058 | @item -muser-enabled | |
13059 | @opindex muser-enabled | |
13060 | Enable user-defined instructions. | |
13061 | ||
13062 | @end table | |
13063 | ||
38b2d076 DD |
13064 | @node M32C Options |
13065 | @subsection M32C Options | |
13066 | @cindex M32C options | |
13067 | ||
13068 | @table @gcctabopt | |
13069 | @item -mcpu=@var{name} | |
13070 | @opindex mcpu= | |
13071 | Select the CPU for which code is generated. @var{name} may be one of | |
13072 | @samp{r8c} for the R8C/Tiny series, @samp{m16c} for the M16C (up to | |
13073 | /60) series, @samp{m32cm} for the M16C/80 series, or @samp{m32c} for | |
13074 | the M32C/80 series. | |
13075 | ||
13076 | @item -msim | |
13077 | @opindex msim | |
13078 | Specifies that the program will be run on the simulator. This causes | |
13079 | an alternate runtime library to be linked in which supports, for | |
0ee2ea09 | 13080 | example, file I/O@. You must not use this option when generating |
38b2d076 DD |
13081 | programs that will run on real hardware; you must provide your own |
13082 | runtime library for whatever I/O functions are needed. | |
13083 | ||
13084 | @item -memregs=@var{number} | |
13085 | @opindex memregs= | |
13086 | Specifies the number of memory-based pseudo-registers GCC will use | |
13087 | during code generation. These pseudo-registers will be used like real | |
13088 | registers, so there is a tradeoff between GCC's ability to fit the | |
13089 | code into available registers, and the performance penalty of using | |
13090 | memory instead of registers. Note that all modules in a program must | |
13091 | be compiled with the same value for this option. Because of that, you | |
13092 | must not use this option with the default runtime libraries gcc | |
13093 | builds. | |
13094 | ||
13095 | @end table | |
13096 | ||
39bc1876 NS |
13097 | @node M32R/D Options |
13098 | @subsection M32R/D Options | |
13099 | @cindex M32R/D options | |
74291a4b | 13100 | |
39bc1876 | 13101 | These @option{-m} options are defined for Renesas M32R/D architectures: |
74291a4b | 13102 | |
39bc1876 NS |
13103 | @table @gcctabopt |
13104 | @item -m32r2 | |
13105 | @opindex m32r2 | |
13106 | Generate code for the M32R/2@. | |
74291a4b | 13107 | |
39bc1876 NS |
13108 | @item -m32rx |
13109 | @opindex m32rx | |
13110 | Generate code for the M32R/X@. | |
74291a4b | 13111 | |
39bc1876 NS |
13112 | @item -m32r |
13113 | @opindex m32r | |
13114 | Generate code for the M32R@. This is the default. | |
74291a4b | 13115 | |
39bc1876 NS |
13116 | @item -mmodel=small |
13117 | @opindex mmodel=small | |
13118 | Assume all objects live in the lower 16MB of memory (so that their addresses | |
13119 | can be loaded with the @code{ld24} instruction), and assume all subroutines | |
13120 | are reachable with the @code{bl} instruction. | |
13121 | This is the default. | |
74291a4b | 13122 | |
39bc1876 NS |
13123 | The addressability of a particular object can be set with the |
13124 | @code{model} attribute. | |
74291a4b | 13125 | |
39bc1876 NS |
13126 | @item -mmodel=medium |
13127 | @opindex mmodel=medium | |
13128 | Assume objects may be anywhere in the 32-bit address space (the compiler | |
13129 | will generate @code{seth/add3} instructions to load their addresses), and | |
13130 | assume all subroutines are reachable with the @code{bl} instruction. | |
194734e9 | 13131 | |
39bc1876 NS |
13132 | @item -mmodel=large |
13133 | @opindex mmodel=large | |
13134 | Assume objects may be anywhere in the 32-bit address space (the compiler | |
13135 | will generate @code{seth/add3} instructions to load their addresses), and | |
13136 | assume subroutines may not be reachable with the @code{bl} instruction | |
13137 | (the compiler will generate the much slower @code{seth/add3/jl} | |
13138 | instruction sequence). | |
a5f3dd66 | 13139 | |
39bc1876 NS |
13140 | @item -msdata=none |
13141 | @opindex msdata=none | |
13142 | Disable use of the small data area. Variables will be put into | |
13143 | one of @samp{.data}, @samp{bss}, or @samp{.rodata} (unless the | |
13144 | @code{section} attribute has been specified). | |
13145 | This is the default. | |
a5f3dd66 | 13146 | |
39bc1876 NS |
13147 | The small data area consists of sections @samp{.sdata} and @samp{.sbss}. |
13148 | Objects may be explicitly put in the small data area with the | |
13149 | @code{section} attribute using one of these sections. | |
daf2f129 | 13150 | |
39bc1876 NS |
13151 | @item -msdata=sdata |
13152 | @opindex msdata=sdata | |
13153 | Put small global and static data in the small data area, but do not | |
13154 | generate special code to reference them. | |
2b589241 | 13155 | |
39bc1876 NS |
13156 | @item -msdata=use |
13157 | @opindex msdata=use | |
13158 | Put small global and static data in the small data area, and generate | |
13159 | special instructions to reference them. | |
2b589241 | 13160 | |
39bc1876 NS |
13161 | @item -G @var{num} |
13162 | @opindex G | |
13163 | @cindex smaller data references | |
13164 | Put global and static objects less than or equal to @var{num} bytes | |
13165 | into the small data or bss sections instead of the normal data or bss | |
13166 | sections. The default value of @var{num} is 8. | |
13167 | The @option{-msdata} option must be set to one of @samp{sdata} or @samp{use} | |
13168 | for this option to have any effect. | |
74291a4b | 13169 | |
39bc1876 NS |
13170 | All modules should be compiled with the same @option{-G @var{num}} value. |
13171 | Compiling with different values of @var{num} may or may not work; if it | |
13172 | doesn't the linker will give an error message---incorrect code will not be | |
13173 | generated. | |
74291a4b | 13174 | |
39bc1876 NS |
13175 | @item -mdebug |
13176 | @opindex mdebug | |
13177 | Makes the M32R specific code in the compiler display some statistics | |
13178 | that might help in debugging programs. | |
74291a4b | 13179 | |
39bc1876 NS |
13180 | @item -malign-loops |
13181 | @opindex malign-loops | |
13182 | Align all loops to a 32-byte boundary. | |
74291a4b | 13183 | |
39bc1876 NS |
13184 | @item -mno-align-loops |
13185 | @opindex mno-align-loops | |
13186 | Do not enforce a 32-byte alignment for loops. This is the default. | |
74291a4b | 13187 | |
39bc1876 NS |
13188 | @item -missue-rate=@var{number} |
13189 | @opindex missue-rate=@var{number} | |
13190 | Issue @var{number} instructions per cycle. @var{number} can only be 1 | |
13191 | or 2. | |
74291a4b | 13192 | |
39bc1876 NS |
13193 | @item -mbranch-cost=@var{number} |
13194 | @opindex mbranch-cost=@var{number} | |
13195 | @var{number} can only be 1 or 2. If it is 1 then branches will be | |
13196 | preferred over conditional code, if it is 2, then the opposite will | |
13197 | apply. | |
74291a4b | 13198 | |
39bc1876 NS |
13199 | @item -mflush-trap=@var{number} |
13200 | @opindex mflush-trap=@var{number} | |
13201 | Specifies the trap number to use to flush the cache. The default is | |
13202 | 12. Valid numbers are between 0 and 15 inclusive. | |
74291a4b | 13203 | |
39bc1876 NS |
13204 | @item -mno-flush-trap |
13205 | @opindex mno-flush-trap | |
13206 | Specifies that the cache cannot be flushed by using a trap. | |
74291a4b | 13207 | |
39bc1876 NS |
13208 | @item -mflush-func=@var{name} |
13209 | @opindex mflush-func=@var{name} | |
13210 | Specifies the name of the operating system function to call to flush | |
13211 | the cache. The default is @emph{_flush_cache}, but a function call | |
13212 | will only be used if a trap is not available. | |
3af4bd89 | 13213 | |
39bc1876 NS |
13214 | @item -mno-flush-func |
13215 | @opindex mno-flush-func | |
13216 | Indicates that there is no OS function for flushing the cache. | |
3af4bd89 | 13217 | |
39bc1876 | 13218 | @end table |
3af4bd89 | 13219 | |
39bc1876 NS |
13220 | @node M680x0 Options |
13221 | @subsection M680x0 Options | |
13222 | @cindex M680x0 options | |
f22a97d2 | 13223 | |
900ec02d JB |
13224 | These are the @samp{-m} options defined for M680x0 and ColdFire processors. |
13225 | The default settings depend on which architecture was selected when | |
13226 | the compiler was configured; the defaults for the most common choices | |
13227 | are given below. | |
1255c85c | 13228 | |
39bc1876 | 13229 | @table @gcctabopt |
900ec02d JB |
13230 | @item -march=@var{arch} |
13231 | @opindex march | |
13232 | Generate code for a specific M680x0 or ColdFire instruction set | |
13233 | architecture. Permissible values of @var{arch} for M680x0 | |
13234 | architectures are: @samp{68000}, @samp{68010}, @samp{68020}, | |
13235 | @samp{68030}, @samp{68040}, @samp{68060} and @samp{cpu32}. ColdFire | |
13236 | architectures are selected according to Freescale's ISA classification | |
13237 | and the permissible values are: @samp{isaa}, @samp{isaaplus}, | |
13238 | @samp{isab} and @samp{isac}. | |
13239 | ||
13240 | gcc defines a macro @samp{__mcf@var{arch}__} whenever it is generating | |
13241 | code for a ColdFire target. The @var{arch} in this macro is one of the | |
13242 | @option{-march} arguments given above. | |
13243 | ||
13244 | When used together, @option{-march} and @option{-mtune} select code | |
13245 | that runs on a family of similar processors but that is optimized | |
13246 | for a particular microarchitecture. | |
13247 | ||
13248 | @item -mcpu=@var{cpu} | |
13249 | @opindex mcpu | |
13250 | Generate code for a specific M680x0 or ColdFire processor. | |
13251 | The M680x0 @var{cpu}s are: @samp{68000}, @samp{68010}, @samp{68020}, | |
13252 | @samp{68030}, @samp{68040}, @samp{68060}, @samp{68302}, @samp{68332} | |
13253 | and @samp{cpu32}. The ColdFire @var{cpu}s are given by the table | |
13254 | below, which also classifies the CPUs into families: | |
13255 | ||
13256 | @multitable @columnfractions 0.20 0.80 | |
1cbe999f | 13257 | @item @strong{Family} @tab @strong{@samp{-mcpu} arguments} |
c260f01f | 13258 | @item @samp{51} @tab @samp{51} @samp{51ac} @samp{51cn} @samp{51em} @samp{51qe} |
900ec02d JB |
13259 | @item @samp{5206} @tab @samp{5202} @samp{5204} @samp{5206} |
13260 | @item @samp{5206e} @tab @samp{5206e} | |
13261 | @item @samp{5208} @tab @samp{5207} @samp{5208} | |
13262 | @item @samp{5211a} @tab @samp{5210a} @samp{5211a} | |
13263 | @item @samp{5213} @tab @samp{5211} @samp{5212} @samp{5213} | |
13264 | @item @samp{5216} @tab @samp{5214} @samp{5216} | |
13265 | @item @samp{52235} @tab @samp{52230} @samp{52231} @samp{52232} @samp{52233} @samp{52234} @samp{52235} | |
13266 | @item @samp{5225} @tab @samp{5224} @samp{5225} | |
c260f01f | 13267 | @item @samp{52259} @tab @samp{52252} @samp{52254} @samp{52255} @samp{52256} @samp{52258} @samp{52259} |
900ec02d JB |
13268 | @item @samp{5235} @tab @samp{5232} @samp{5233} @samp{5234} @samp{5235} @samp{523x} |
13269 | @item @samp{5249} @tab @samp{5249} | |
13270 | @item @samp{5250} @tab @samp{5250} | |
13271 | @item @samp{5271} @tab @samp{5270} @samp{5271} | |
13272 | @item @samp{5272} @tab @samp{5272} | |
13273 | @item @samp{5275} @tab @samp{5274} @samp{5275} | |
13274 | @item @samp{5282} @tab @samp{5280} @samp{5281} @samp{5282} @samp{528x} | |
c260f01f | 13275 | @item @samp{53017} @tab @samp{53011} @samp{53012} @samp{53013} @samp{53014} @samp{53015} @samp{53016} @samp{53017} |
900ec02d JB |
13276 | @item @samp{5307} @tab @samp{5307} |
13277 | @item @samp{5329} @tab @samp{5327} @samp{5328} @samp{5329} @samp{532x} | |
13278 | @item @samp{5373} @tab @samp{5372} @samp{5373} @samp{537x} | |
13279 | @item @samp{5407} @tab @samp{5407} | |
13280 | @item @samp{5475} @tab @samp{5470} @samp{5471} @samp{5472} @samp{5473} @samp{5474} @samp{5475} @samp{547x} @samp{5480} @samp{5481} @samp{5482} @samp{5483} @samp{5484} @samp{5485} | |
13281 | @end multitable | |
13282 | ||
13283 | @option{-mcpu=@var{cpu}} overrides @option{-march=@var{arch}} if | |
13284 | @var{arch} is compatible with @var{cpu}. Other combinations of | |
13285 | @option{-mcpu} and @option{-march} are rejected. | |
13286 | ||
7eb4f044 NS |
13287 | gcc defines the macro @samp{__mcf_cpu_@var{cpu}} when ColdFire target |
13288 | @var{cpu} is selected. It also defines @samp{__mcf_family_@var{family}}, | |
13289 | where the value of @var{family} is given by the table above. | |
13290 | ||
900ec02d JB |
13291 | @item -mtune=@var{tune} |
13292 | @opindex mtune | |
13293 | Tune the code for a particular microarchitecture, within the | |
13294 | constraints set by @option{-march} and @option{-mcpu}. | |
13295 | The M680x0 microarchitectures are: @samp{68000}, @samp{68010}, | |
13296 | @samp{68020}, @samp{68030}, @samp{68040}, @samp{68060} | |
13297 | and @samp{cpu32}. The ColdFire microarchitectures | |
8c5c99dc | 13298 | are: @samp{cfv1}, @samp{cfv2}, @samp{cfv3}, @samp{cfv4} and @samp{cfv4e}. |
900ec02d JB |
13299 | |
13300 | You can also use @option{-mtune=68020-40} for code that needs | |
13301 | to run relatively well on 68020, 68030 and 68040 targets. | |
13302 | @option{-mtune=68020-60} is similar but includes 68060 targets | |
13303 | as well. These two options select the same tuning decisions as | |
13304 | @option{-m68020-40} and @option{-m68020-60} respectively. | |
13305 | ||
7eb4f044 NS |
13306 | gcc defines the macros @samp{__mc@var{arch}} and @samp{__mc@var{arch}__} |
13307 | when tuning for 680x0 architecture @var{arch}. It also defines | |
13308 | @samp{mc@var{arch}} unless either @option{-ansi} or a non-GNU @option{-std} | |
13309 | option is used. If gcc is tuning for a range of architectures, | |
13310 | as selected by @option{-mtune=68020-40} or @option{-mtune=68020-60}, | |
13311 | it defines the macros for every architecture in the range. | |
13312 | ||
13313 | gcc also defines the macro @samp{__m@var{uarch}__} when tuning for | |
13314 | ColdFire microarchitecture @var{uarch}, where @var{uarch} is one | |
13315 | of the arguments given above. | |
13316 | ||
39bc1876 NS |
13317 | @item -m68000 |
13318 | @itemx -mc68000 | |
13319 | @opindex m68000 | |
13320 | @opindex mc68000 | |
13321 | Generate output for a 68000. This is the default | |
13322 | when the compiler is configured for 68000-based systems. | |
900ec02d | 13323 | It is equivalent to @option{-march=68000}. |
1255c85c | 13324 | |
39bc1876 NS |
13325 | Use this option for microcontrollers with a 68000 or EC000 core, |
13326 | including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356. | |
7eafc329 | 13327 | |
3197c489 RS |
13328 | @item -m68010 |
13329 | @opindex m68010 | |
13330 | Generate output for a 68010. This is the default | |
13331 | when the compiler is configured for 68010-based systems. | |
900ec02d | 13332 | It is equivalent to @option{-march=68010}. |
3197c489 | 13333 | |
39bc1876 NS |
13334 | @item -m68020 |
13335 | @itemx -mc68020 | |
13336 | @opindex m68020 | |
13337 | @opindex mc68020 | |
13338 | Generate output for a 68020. This is the default | |
13339 | when the compiler is configured for 68020-based systems. | |
900ec02d | 13340 | It is equivalent to @option{-march=68020}. |
f73ad30e | 13341 | |
39bc1876 NS |
13342 | @item -m68030 |
13343 | @opindex m68030 | |
13344 | Generate output for a 68030. This is the default when the compiler is | |
900ec02d JB |
13345 | configured for 68030-based systems. It is equivalent to |
13346 | @option{-march=68030}. | |
79f05c19 | 13347 | |
39bc1876 NS |
13348 | @item -m68040 |
13349 | @opindex m68040 | |
13350 | Generate output for a 68040. This is the default when the compiler is | |
900ec02d JB |
13351 | configured for 68040-based systems. It is equivalent to |
13352 | @option{-march=68040}. | |
79f05c19 | 13353 | |
39bc1876 NS |
13354 | This option inhibits the use of 68881/68882 instructions that have to be |
13355 | emulated by software on the 68040. Use this option if your 68040 does not | |
13356 | have code to emulate those instructions. | |
762e166b | 13357 | |
39bc1876 NS |
13358 | @item -m68060 |
13359 | @opindex m68060 | |
13360 | Generate output for a 68060. This is the default when the compiler is | |
900ec02d JB |
13361 | configured for 68060-based systems. It is equivalent to |
13362 | @option{-march=68060}. | |
74dc3e94 | 13363 | |
39bc1876 NS |
13364 | This option inhibits the use of 68020 and 68881/68882 instructions that |
13365 | have to be emulated by software on the 68060. Use this option if your 68060 | |
13366 | does not have code to emulate those instructions. | |
74dc3e94 | 13367 | |
39bc1876 NS |
13368 | @item -mcpu32 |
13369 | @opindex mcpu32 | |
13370 | Generate output for a CPU32. This is the default | |
13371 | when the compiler is configured for CPU32-based systems. | |
900ec02d | 13372 | It is equivalent to @option{-march=cpu32}. |
3af4bd89 | 13373 | |
39bc1876 NS |
13374 | Use this option for microcontrollers with a |
13375 | CPU32 or CPU32+ core, including the 68330, 68331, 68332, 68333, 68334, | |
13376 | 68336, 68340, 68341, 68349 and 68360. | |
14f73b5a | 13377 | |
39bc1876 NS |
13378 | @item -m5200 |
13379 | @opindex m5200 | |
0ee2ea09 | 13380 | Generate output for a 520X ColdFire CPU@. This is the default |
39bc1876 | 13381 | when the compiler is configured for 520X-based systems. |
900ec02d JB |
13382 | It is equivalent to @option{-mcpu=5206}, and is now deprecated |
13383 | in favor of that option. | |
14f73b5a | 13384 | |
39bc1876 | 13385 | Use this option for microcontroller with a 5200 core, including |
900ec02d JB |
13386 | the MCF5202, MCF5203, MCF5204 and MCF5206. |
13387 | ||
13388 | @item -m5206e | |
13389 | @opindex m5206e | |
0ee2ea09 | 13390 | Generate output for a 5206e ColdFire CPU@. The option is now |
900ec02d JB |
13391 | deprecated in favor of the equivalent @option{-mcpu=5206e}. |
13392 | ||
13393 | @item -m528x | |
13394 | @opindex m528x | |
13395 | Generate output for a member of the ColdFire 528X family. | |
13396 | The option is now deprecated in favor of the equivalent | |
13397 | @option{-mcpu=528x}. | |
13398 | ||
13399 | @item -m5307 | |
13400 | @opindex m5307 | |
0ee2ea09 | 13401 | Generate output for a ColdFire 5307 CPU@. The option is now deprecated |
900ec02d JB |
13402 | in favor of the equivalent @option{-mcpu=5307}. |
13403 | ||
13404 | @item -m5407 | |
13405 | @opindex m5407 | |
0ee2ea09 | 13406 | Generate output for a ColdFire 5407 CPU@. The option is now deprecated |
900ec02d | 13407 | in favor of the equivalent @option{-mcpu=5407}. |
a7701995 | 13408 | |
dcc21c4c PB |
13409 | @item -mcfv4e |
13410 | @opindex mcfv4e | |
900ec02d | 13411 | Generate output for a ColdFire V4e family CPU (e.g.@: 547x/548x). |
dcc21c4c | 13412 | This includes use of hardware floating point instructions. |
900ec02d JB |
13413 | The option is equivalent to @option{-mcpu=547x}, and is now |
13414 | deprecated in favor of that option. | |
a7701995 | 13415 | |
39bc1876 NS |
13416 | @item -m68020-40 |
13417 | @opindex m68020-40 | |
13418 | Generate output for a 68040, without using any of the new instructions. | |
13419 | This results in code which can run relatively efficiently on either a | |
13420 | 68020/68881 or a 68030 or a 68040. The generated code does use the | |
13421 | 68881 instructions that are emulated on the 68040. | |
a7701995 | 13422 | |
900ec02d JB |
13423 | The option is equivalent to @option{-march=68020} @option{-mtune=68020-40}. |
13424 | ||
39bc1876 NS |
13425 | @item -m68020-60 |
13426 | @opindex m68020-60 | |
13427 | Generate output for a 68060, without using any of the new instructions. | |
13428 | This results in code which can run relatively efficiently on either a | |
13429 | 68020/68881 or a 68030 or a 68040. The generated code does use the | |
13430 | 68881 instructions that are emulated on the 68060. | |
a7701995 | 13431 | |
900ec02d JB |
13432 | The option is equivalent to @option{-march=68020} @option{-mtune=68020-60}. |
13433 | ||
13434 | @item -mhard-float | |
13435 | @itemx -m68881 | |
13436 | @opindex mhard-float | |
13437 | @opindex m68881 | |
13438 | Generate floating-point instructions. This is the default for 68020 | |
0ee2ea09 | 13439 | and above, and for ColdFire devices that have an FPU@. It defines the |
7eb4f044 NS |
13440 | macro @samp{__HAVE_68881__} on M680x0 targets and @samp{__mcffpu__} |
13441 | on ColdFire targets. | |
900ec02d | 13442 | |
39bc1876 NS |
13443 | @item -msoft-float |
13444 | @opindex msoft-float | |
900ec02d JB |
13445 | Do not generate floating-point instructions; use library calls instead. |
13446 | This is the default for 68000, 68010, and 68832 targets. It is also | |
13447 | the default for ColdFire devices that have no FPU. | |
13448 | ||
13449 | @item -mdiv | |
13450 | @itemx -mno-div | |
13451 | @opindex mdiv | |
13452 | @opindex mno-div | |
13453 | Generate (do not generate) ColdFire hardware divide and remainder | |
13454 | instructions. If @option{-march} is used without @option{-mcpu}, | |
13455 | the default is ``on'' for ColdFire architectures and ``off'' for M680x0 | |
13456 | architectures. Otherwise, the default is taken from the target CPU | |
13457 | (either the default CPU, or the one specified by @option{-mcpu}). For | |
13458 | example, the default is ``off'' for @option{-mcpu=5206} and ``on'' for | |
13459 | @option{-mcpu=5206e}. | |
13460 | ||
13461 | gcc defines the macro @samp{__mcfhwdiv__} when this option is enabled. | |
14f73b5a | 13462 | |
39bc1876 NS |
13463 | @item -mshort |
13464 | @opindex mshort | |
13465 | Consider type @code{int} to be 16 bits wide, like @code{short int}. | |
13466 | Additionally, parameters passed on the stack are also aligned to a | |
13467 | 16-bit boundary even on targets whose API mandates promotion to 32-bit. | |
74291a4b | 13468 | |
64826589 | 13469 | @item -mno-short |
edc5f63b | 13470 | @opindex mno-short |
64826589 NS |
13471 | Do not consider type @code{int} to be 16 bits wide. This is the default. |
13472 | ||
39bc1876 | 13473 | @item -mnobitfield |
64826589 | 13474 | @itemx -mno-bitfield |
39bc1876 | 13475 | @opindex mnobitfield |
64826589 | 13476 | @opindex mno-bitfield |
39bc1876 NS |
13477 | Do not use the bit-field instructions. The @option{-m68000}, @option{-mcpu32} |
13478 | and @option{-m5200} options imply @w{@option{-mnobitfield}}. | |
74291a4b | 13479 | |
39bc1876 NS |
13480 | @item -mbitfield |
13481 | @opindex mbitfield | |
13482 | Do use the bit-field instructions. The @option{-m68020} option implies | |
13483 | @option{-mbitfield}. This is the default if you use a configuration | |
13484 | designed for a 68020. | |
13485 | ||
13486 | @item -mrtd | |
13487 | @opindex mrtd | |
13488 | Use a different function-calling convention, in which functions | |
13489 | that take a fixed number of arguments return with the @code{rtd} | |
13490 | instruction, which pops their arguments while returning. This | |
13491 | saves one instruction in the caller since there is no need to pop | |
13492 | the arguments there. | |
ea3bfbfe | 13493 | |
39bc1876 NS |
13494 | This calling convention is incompatible with the one normally |
13495 | used on Unix, so you cannot use it if you need to call libraries | |
13496 | compiled with the Unix compiler. | |
74291a4b | 13497 | |
39bc1876 NS |
13498 | Also, you must provide function prototypes for all functions that |
13499 | take variable numbers of arguments (including @code{printf}); | |
13500 | otherwise incorrect code will be generated for calls to those | |
13501 | functions. | |
861bb6c1 | 13502 | |
39bc1876 NS |
13503 | In addition, seriously incorrect code will result if you call a |
13504 | function with too many arguments. (Normally, extra arguments are | |
13505 | harmlessly ignored.) | |
74291a4b | 13506 | |
39bc1876 NS |
13507 | The @code{rtd} instruction is supported by the 68010, 68020, 68030, |
13508 | 68040, 68060 and CPU32 processors, but not by the 68000 or 5200. | |
74291a4b | 13509 | |
64826589 NS |
13510 | @item -mno-rtd |
13511 | @opindex mno-rtd | |
13512 | Do not use the calling conventions selected by @option{-mrtd}. | |
13513 | This is the default. | |
13514 | ||
39bc1876 NS |
13515 | @item -malign-int |
13516 | @itemx -mno-align-int | |
13517 | @opindex malign-int | |
13518 | @opindex mno-align-int | |
13519 | Control whether GCC aligns @code{int}, @code{long}, @code{long long}, | |
13520 | @code{float}, @code{double}, and @code{long double} variables on a 32-bit | |
13521 | boundary (@option{-malign-int}) or a 16-bit boundary (@option{-mno-align-int}). | |
13522 | Aligning variables on 32-bit boundaries produces code that runs somewhat | |
13523 | faster on processors with 32-bit busses at the expense of more memory. | |
74291a4b | 13524 | |
39bc1876 NS |
13525 | @strong{Warning:} if you use the @option{-malign-int} switch, GCC will |
13526 | align structures containing the above types differently than | |
13527 | most published application binary interface specifications for the m68k. | |
74291a4b | 13528 | |
39bc1876 NS |
13529 | @item -mpcrel |
13530 | @opindex mpcrel | |
13531 | Use the pc-relative addressing mode of the 68000 directly, instead of | |
13532 | using a global offset table. At present, this option implies @option{-fpic}, | |
13533 | allowing at most a 16-bit offset for pc-relative addressing. @option{-fPIC} is | |
13534 | not presently supported with @option{-mpcrel}, though this could be supported for | |
13535 | 68020 and higher processors. | |
74291a4b | 13536 | |
39bc1876 NS |
13537 | @item -mno-strict-align |
13538 | @itemx -mstrict-align | |
13539 | @opindex mno-strict-align | |
13540 | @opindex mstrict-align | |
13541 | Do not (do) assume that unaligned memory references will be handled by | |
13542 | the system. | |
74291a4b | 13543 | |
39bc1876 NS |
13544 | @item -msep-data |
13545 | Generate code that allows the data segment to be located in a different | |
13546 | area of memory from the text segment. This allows for execute in place in | |
4ec7afd7 KH |
13547 | an environment without virtual memory management. This option implies |
13548 | @option{-fPIC}. | |
74291a4b | 13549 | |
39bc1876 NS |
13550 | @item -mno-sep-data |
13551 | Generate code that assumes that the data segment follows the text segment. | |
13552 | This is the default. | |
74291a4b | 13553 | |
39bc1876 NS |
13554 | @item -mid-shared-library |
13555 | Generate code that supports shared libraries via the library ID method. | |
13556 | This allows for execute in place and shared libraries in an environment | |
4ec7afd7 | 13557 | without virtual memory management. This option implies @option{-fPIC}. |
74291a4b | 13558 | |
39bc1876 NS |
13559 | @item -mno-id-shared-library |
13560 | Generate code that doesn't assume ID based shared libraries are being used. | |
13561 | This is the default. | |
74291a4b | 13562 | |
39bc1876 NS |
13563 | @item -mshared-library-id=n |
13564 | Specified the identification number of the ID based shared library being | |
13565 | compiled. Specifying a value of 0 will generate more compact code, specifying | |
13566 | other values will force the allocation of that number to the current | |
13567 | library but is no more space or time efficient than omitting this option. | |
74291a4b | 13568 | |
884316ff JM |
13569 | @item -mxgot |
13570 | @itemx -mno-xgot | |
13571 | @opindex mxgot | |
13572 | @opindex mno-xgot | |
13573 | When generating position-independent code for ColdFire, generate code | |
13574 | that works if the GOT has more than 8192 entries. This code is | |
13575 | larger and slower than code generated without this option. On M680x0 | |
13576 | processors, this option is not needed; @option{-fPIC} suffices. | |
13577 | ||
13578 | GCC normally uses a single instruction to load values from the GOT@. | |
13579 | While this is relatively efficient, it only works if the GOT | |
13580 | is smaller than about 64k. Anything larger causes the linker | |
13581 | to report an error such as: | |
13582 | ||
13583 | @cindex relocation truncated to fit (ColdFire) | |
13584 | @smallexample | |
13585 | relocation truncated to fit: R_68K_GOT16O foobar | |
13586 | @end smallexample | |
13587 | ||
13588 | If this happens, you should recompile your code with @option{-mxgot}. | |
13589 | It should then work with very large GOTs. However, code generated with | |
13590 | @option{-mxgot} is less efficient, since it takes 4 instructions to fetch | |
13591 | the value of a global symbol. | |
13592 | ||
13593 | Note that some linkers, including newer versions of the GNU linker, | |
13594 | can create multiple GOTs and sort GOT entries. If you have such a linker, | |
13595 | you should only need to use @option{-mxgot} when compiling a single | |
13596 | object file that accesses more than 8192 GOT entries. Very few do. | |
13597 | ||
13598 | These options have no effect unless GCC is generating | |
13599 | position-independent code. | |
13600 | ||
39bc1876 | 13601 | @end table |
74291a4b | 13602 | |
39bc1876 NS |
13603 | @node M68hc1x Options |
13604 | @subsection M68hc1x Options | |
13605 | @cindex M68hc1x options | |
74291a4b | 13606 | |
39bc1876 NS |
13607 | These are the @samp{-m} options defined for the 68hc11 and 68hc12 |
13608 | microcontrollers. The default values for these options depends on | |
13609 | which style of microcontroller was selected when the compiler was configured; | |
13610 | the defaults for the most common choices are given below. | |
c219e1da | 13611 | |
39bc1876 NS |
13612 | @table @gcctabopt |
13613 | @item -m6811 | |
13614 | @itemx -m68hc11 | |
13615 | @opindex m6811 | |
13616 | @opindex m68hc11 | |
13617 | Generate output for a 68HC11. This is the default | |
13618 | when the compiler is configured for 68HC11-based systems. | |
c5d3d49b | 13619 | |
39bc1876 NS |
13620 | @item -m6812 |
13621 | @itemx -m68hc12 | |
13622 | @opindex m6812 | |
13623 | @opindex m68hc12 | |
13624 | Generate output for a 68HC12. This is the default | |
13625 | when the compiler is configured for 68HC12-based systems. | |
c5d3d49b | 13626 | |
39bc1876 NS |
13627 | @item -m68S12 |
13628 | @itemx -m68hcs12 | |
13629 | @opindex m68S12 | |
13630 | @opindex m68hcs12 | |
13631 | Generate output for a 68HCS12. | |
c5d3d49b | 13632 | |
39bc1876 NS |
13633 | @item -mauto-incdec |
13634 | @opindex mauto-incdec | |
13635 | Enable the use of 68HC12 pre and post auto-increment and auto-decrement | |
13636 | addressing modes. | |
34208acf | 13637 | |
39bc1876 | 13638 | @item -minmax |
d376d545 | 13639 | @itemx -mnominmax |
39bc1876 NS |
13640 | @opindex minmax |
13641 | @opindex mnominmax | |
13642 | Enable the use of 68HC12 min and max instructions. | |
34208acf | 13643 | |
39bc1876 NS |
13644 | @item -mlong-calls |
13645 | @itemx -mno-long-calls | |
13646 | @opindex mlong-calls | |
13647 | @opindex mno-long-calls | |
13648 | Treat all calls as being far away (near). If calls are assumed to be | |
13649 | far away, the compiler will use the @code{call} instruction to | |
13650 | call a function and the @code{rtc} instruction for returning. | |
34208acf | 13651 | |
39bc1876 NS |
13652 | @item -mshort |
13653 | @opindex mshort | |
13654 | Consider type @code{int} to be 16 bits wide, like @code{short int}. | |
34208acf | 13655 | |
39bc1876 NS |
13656 | @item -msoft-reg-count=@var{count} |
13657 | @opindex msoft-reg-count | |
13658 | Specify the number of pseudo-soft registers which are used for the | |
13659 | code generation. The maximum number is 32. Using more pseudo-soft | |
13660 | register may or may not result in better code depending on the program. | |
13661 | The default is 4 for 68HC11 and 2 for 68HC12. | |
34208acf | 13662 | |
39bc1876 | 13663 | @end table |
34208acf | 13664 | |
39bc1876 NS |
13665 | @node MCore Options |
13666 | @subsection MCore Options | |
13667 | @cindex MCore options | |
34208acf | 13668 | |
39bc1876 NS |
13669 | These are the @samp{-m} options defined for the Motorola M*Core |
13670 | processors. | |
34208acf | 13671 | |
39bc1876 | 13672 | @table @gcctabopt |
34208acf | 13673 | |
39bc1876 NS |
13674 | @item -mhardlit |
13675 | @itemx -mno-hardlit | |
13676 | @opindex mhardlit | |
13677 | @opindex mno-hardlit | |
13678 | Inline constants into the code stream if it can be done in two | |
13679 | instructions or less. | |
34208acf | 13680 | |
39bc1876 NS |
13681 | @item -mdiv |
13682 | @itemx -mno-div | |
13683 | @opindex mdiv | |
13684 | @opindex mno-div | |
13685 | Use the divide instruction. (Enabled by default). | |
a02aa5b0 | 13686 | |
39bc1876 NS |
13687 | @item -mrelax-immediate |
13688 | @itemx -mno-relax-immediate | |
13689 | @opindex mrelax-immediate | |
13690 | @opindex mno-relax-immediate | |
13691 | Allow arbitrary sized immediates in bit operations. | |
a02aa5b0 | 13692 | |
39bc1876 NS |
13693 | @item -mwide-bitfields |
13694 | @itemx -mno-wide-bitfields | |
13695 | @opindex mwide-bitfields | |
13696 | @opindex mno-wide-bitfields | |
13697 | Always treat bit-fields as int-sized. | |
a02aa5b0 | 13698 | |
39bc1876 NS |
13699 | @item -m4byte-functions |
13700 | @itemx -mno-4byte-functions | |
13701 | @opindex m4byte-functions | |
13702 | @opindex mno-4byte-functions | |
13703 | Force all functions to be aligned to a four byte boundary. | |
a02aa5b0 | 13704 | |
39bc1876 NS |
13705 | @item -mcallgraph-data |
13706 | @itemx -mno-callgraph-data | |
13707 | @opindex mcallgraph-data | |
13708 | @opindex mno-callgraph-data | |
13709 | Emit callgraph information. | |
f401d0f5 | 13710 | |
39bc1876 NS |
13711 | @item -mslow-bytes |
13712 | @itemx -mno-slow-bytes | |
13713 | @opindex mslow-bytes | |
13714 | @opindex mno-slow-bytes | |
13715 | Prefer word access when reading byte quantities. | |
f401d0f5 | 13716 | |
39bc1876 NS |
13717 | @item -mlittle-endian |
13718 | @itemx -mbig-endian | |
13719 | @opindex mlittle-endian | |
13720 | @opindex mbig-endian | |
13721 | Generate code for a little endian target. | |
f401d0f5 | 13722 | |
39bc1876 NS |
13723 | @item -m210 |
13724 | @itemx -m340 | |
13725 | @opindex m210 | |
13726 | @opindex m340 | |
13727 | Generate code for the 210 processor. | |
40190a76 NC |
13728 | |
13729 | @item -mno-lsim | |
d376d545 | 13730 | @opindex mno-lsim |
40190a76 NC |
13731 | Assume that run-time support has been provided and so omit the |
13732 | simulator library (@file{libsim.a)} from the linker command line. | |
13733 | ||
13734 | @item -mstack-increment=@var{size} | |
13735 | @opindex mstack-increment | |
13736 | Set the maximum amount for a single stack increment operation. Large | |
048fd785 | 13737 | values can increase the speed of programs which contain functions |
40190a76 NC |
13738 | that need a large amount of stack space, but they can also trigger a |
13739 | segmentation fault if the stack is extended too much. The default | |
13740 | value is 0x1000. | |
13741 | ||
74291a4b MM |
13742 | @end table |
13743 | ||
e2491744 DD |
13744 | @node MeP Options |
13745 | @subsection MeP Options | |
13746 | @cindex MeP options | |
13747 | ||
13748 | @table @gcctabopt | |
13749 | ||
13750 | @item -mabsdiff | |
13751 | @opindex mabsdiff | |
13752 | Enables the @code{abs} instruction, which is the absolute difference | |
13753 | between two registers. | |
13754 | ||
13755 | @item -mall-opts | |
13756 | @opindex mall-opts | |
13757 | Enables all the optional instructions - average, multiply, divide, bit | |
13758 | operations, leading zero, absolute difference, min/max, clip, and | |
13759 | saturation. | |
13760 | ||
13761 | ||
13762 | @item -maverage | |
13763 | @opindex maverage | |
13764 | Enables the @code{ave} instruction, which computes the average of two | |
13765 | registers. | |
13766 | ||
13767 | @item -mbased=@var{n} | |
13768 | @opindex mbased= | |
13769 | Variables of size @var{n} bytes or smaller will be placed in the | |
13770 | @code{.based} section by default. Based variables use the @code{$tp} | |
13771 | register as a base register, and there is a 128 byte limit to the | |
13772 | @code{.based} section. | |
13773 | ||
13774 | @item -mbitops | |
13775 | @opindex mbitops | |
13776 | Enables the bit operation instructions - bit test (@code{btstm}), set | |
13777 | (@code{bsetm}), clear (@code{bclrm}), invert (@code{bnotm}), and | |
13778 | test-and-set (@code{tas}). | |
13779 | ||
13780 | @item -mc=@var{name} | |
13781 | @opindex mc= | |
13782 | Selects which section constant data will be placed in. @var{name} may | |
13783 | be @code{tiny}, @code{near}, or @code{far}. | |
13784 | ||
13785 | @item -mclip | |
13786 | @opindex mclip | |
13787 | Enables the @code{clip} instruction. Note that @code{-mclip} is not | |
13788 | useful unless you also provide @code{-mminmax}. | |
13789 | ||
13790 | @item -mconfig=@var{name} | |
13791 | @opindex mconfig= | |
13792 | Selects one of the build-in core configurations. Each MeP chip has | |
13793 | one or more modules in it; each module has a core CPU and a variety of | |
13794 | coprocessors, optional instructions, and peripherals. The | |
13795 | @code{MeP-Integrator} tool, not part of GCC, provides these | |
13796 | configurations through this option; using this option is the same as | |
13797 | using all the corresponding command line options. The default | |
13798 | configuration is @code{default}. | |
13799 | ||
13800 | @item -mcop | |
13801 | @opindex mcop | |
13802 | Enables the coprocessor instructions. By default, this is a 32-bit | |
13803 | coprocessor. Note that the coprocessor is normally enabled via the | |
13804 | @code{-mconfig=} option. | |
13805 | ||
13806 | @item -mcop32 | |
13807 | @opindex mcop32 | |
13808 | Enables the 32-bit coprocessor's instructions. | |
13809 | ||
13810 | @item -mcop64 | |
13811 | @opindex mcop64 | |
13812 | Enables the 64-bit coprocessor's instructions. | |
13813 | ||
13814 | @item -mivc2 | |
13815 | @opindex mivc2 | |
13816 | Enables IVC2 scheduling. IVC2 is a 64-bit VLIW coprocessor. | |
13817 | ||
13818 | @item -mdc | |
13819 | @opindex mdc | |
13820 | Causes constant variables to be placed in the @code{.near} section. | |
13821 | ||
13822 | @item -mdiv | |
13823 | @opindex mdiv | |
13824 | Enables the @code{div} and @code{divu} instructions. | |
13825 | ||
13826 | @item -meb | |
13827 | @opindex meb | |
13828 | Generate big-endian code. | |
13829 | ||
13830 | @item -mel | |
13831 | @opindex mel | |
13832 | Generate little-endian code. | |
13833 | ||
13834 | @item -mio-volatile | |
13835 | @opindex mio-volatile | |
13836 | Tells the compiler that any variable marked with the @code{io} | |
13837 | attribute is to be considered volatile. | |
13838 | ||
13839 | @item -ml | |
13840 | @opindex ml | |
13841 | Causes variables to be assigned to the @code{.far} section by default. | |
13842 | ||
13843 | @item -mleadz | |
13844 | @opindex mleadz | |
13845 | Enables the @code{leadz} (leading zero) instruction. | |
13846 | ||
13847 | @item -mm | |
13848 | @opindex mm | |
13849 | Causes variables to be assigned to the @code{.near} section by default. | |
13850 | ||
13851 | @item -mminmax | |
13852 | @opindex mminmax | |
13853 | Enables the @code{min} and @code{max} instructions. | |
13854 | ||
13855 | @item -mmult | |
13856 | @opindex mmult | |
13857 | Enables the multiplication and multiply-accumulate instructions. | |
13858 | ||
13859 | @item -mno-opts | |
13860 | @opindex mno-opts | |
13861 | Disables all the optional instructions enabled by @code{-mall-opts}. | |
13862 | ||
13863 | @item -mrepeat | |
13864 | @opindex mrepeat | |
13865 | Enables the @code{repeat} and @code{erepeat} instructions, used for | |
13866 | low-overhead looping. | |
13867 | ||
13868 | @item -ms | |
13869 | @opindex ms | |
13870 | Causes all variables to default to the @code{.tiny} section. Note | |
13871 | that there is a 65536 byte limit to this section. Accesses to these | |
13872 | variables use the @code{%gp} base register. | |
13873 | ||
13874 | @item -msatur | |
13875 | @opindex msatur | |
13876 | Enables the saturation instructions. Note that the compiler does not | |
13877 | currently generate these itself, but this option is included for | |
13878 | compatibility with other tools, like @code{as}. | |
13879 | ||
13880 | @item -msdram | |
13881 | @opindex msdram | |
13882 | Link the SDRAM-based runtime instead of the default ROM-based runtime. | |
13883 | ||
13884 | @item -msim | |
13885 | @opindex msim | |
13886 | Link the simulator runtime libraries. | |
13887 | ||
13888 | @item -msimnovec | |
13889 | @opindex msimnovec | |
13890 | Link the simulator runtime libraries, excluding built-in support | |
13891 | for reset and exception vectors and tables. | |
13892 | ||
13893 | @item -mtf | |
13894 | @opindex mtf | |
13895 | Causes all functions to default to the @code{.far} section. Without | |
13896 | this option, functions default to the @code{.near} section. | |
13897 | ||
13898 | @item -mtiny=@var{n} | |
13899 | @opindex mtiny= | |
13900 | Variables that are @var{n} bytes or smaller will be allocated to the | |
13901 | @code{.tiny} section. These variables use the @code{$gp} base | |
13902 | register. The default for this option is 4, but note that there's a | |
13903 | 65536 byte limit to the @code{.tiny} section. | |
13904 | ||
13905 | @end table | |
13906 | ||
80920132 ME |
13907 | @node MicroBlaze Options |
13908 | @subsection MicroBlaze Options | |
13909 | @cindex MicroBlaze Options | |
13910 | ||
13911 | @table @gcctabopt | |
13912 | ||
13913 | @item -msoft-float | |
13914 | @opindex msoft-float | |
13915 | Use software emulation for floating point (default). | |
13916 | ||
13917 | @item -mhard-float | |
13918 | @opindex mhard-float | |
13919 | Use hardware floating point instructions. | |
13920 | ||
13921 | @item -mmemcpy | |
13922 | @opindex mmemcpy | |
13923 | Do not optimize block moves, use @code{memcpy}. | |
13924 | ||
13925 | @item -mno-clearbss | |
13926 | @opindex mno-clearbss | |
13927 | This option is deprecated. Use @option{-fno-zero-initialized-in-bss} instead. | |
13928 | ||
13929 | @item -mcpu=@var{cpu-type} | |
13930 | @opindex mcpu= | |
13931 | Use features of and schedule code for given CPU. | |
13932 | Supported values are in the format @samp{v@var{X}.@var{YY}.@var{Z}}, | |
13933 | where @var{X} is a major version, @var{YY} is the minor version, and | |
13934 | @var{Z} is compatiblity code. Example values are @samp{v3.00.a}, | |
13935 | @samp{v4.00.b}, @samp{v5.00.a}, @samp{v5.00.b}, @samp{v5.00.b}, @samp{v6.00.a}. | |
13936 | ||
13937 | @item -mxl-soft-mul | |
13938 | @opindex mxl-soft-mul | |
13939 | Use software multiply emulation (default). | |
13940 | ||
13941 | @item -mxl-soft-div | |
13942 | @opindex mxl-soft-div | |
13943 | Use software emulation for divides (default). | |
13944 | ||
13945 | @item -mxl-barrel-shift | |
13946 | @opindex mxl-barrel-shift | |
13947 | Use the hardware barrel shifter. | |
13948 | ||
13949 | @item -mxl-pattern-compare | |
13950 | @opindex mxl-pattern-compare | |
13951 | Use pattern compare instructions. | |
13952 | ||
13953 | @item -msmall-divides | |
13954 | @opindex msmall-divides | |
13955 | Use table lookup optimization for small signed integer divisions. | |
13956 | ||
13957 | @item -mxl-stack-check | |
13958 | @opindex mxl-stack-check | |
13959 | This option is deprecated. Use -fstack-check instead. | |
13960 | ||
13961 | @item -mxl-gp-opt | |
13962 | @opindex mxl-gp-opt | |
13963 | Use GP relative sdata/sbss sections. | |
13964 | ||
13965 | @item -mxl-multiply-high | |
13966 | @opindex mxl-multiply-high | |
13967 | Use multiply high instructions for high part of 32x32 multiply. | |
13968 | ||
13969 | @item -mxl-float-convert | |
13970 | @opindex mxl-float-convert | |
13971 | Use hardware floating point converstion instructions. | |
13972 | ||
13973 | @item -mxl-float-sqrt | |
13974 | @opindex mxl-float-sqrt | |
13975 | Use hardware floating point square root instruction. | |
13976 | ||
13977 | @item -mxl-mode-@var{app-model} | |
13978 | Select application model @var{app-model}. Valid models are | |
13979 | @table @samp | |
13980 | @item executable | |
13981 | normal executable (default), uses startup code @file{crt0.o}. | |
13982 | ||
13983 | @item xmdstub | |
13984 | for use with Xilinx Microprocessor Debugger (XMD) based | |
13985 | software intrusive debug agent called xmdstub. This uses startup file | |
13986 | @file{crt1.o} and sets the start address of the program to be 0x800. | |
13987 | ||
13988 | @item bootstrap | |
13989 | for applications that are loaded using a bootloader. | |
13990 | This model uses startup file @file{crt2.o} which does not contain a processor | |
13991 | reset vector handler. This is suitable for transferring control on a | |
13992 | processor reset to the bootloader rather than the application. | |
13993 | ||
13994 | @item novectors | |
13995 | for applications that do not require any of the | |
13996 | MicroBlaze vectors. This option may be useful for applications running | |
13997 | within a monitoring application. This model uses @file{crt3.o} as a startup file. | |
13998 | @end table | |
13999 | ||
14000 | Option @option{-xl-mode-@var{app-model}} is a deprecated alias for | |
14001 | @option{-mxl-mode-@var{app-model}}. | |
14002 | ||
14003 | @end table | |
14004 | ||
39bc1876 NS |
14005 | @node MIPS Options |
14006 | @subsection MIPS Options | |
14007 | @cindex MIPS options | |
74291a4b | 14008 | |
2642624b | 14009 | @table @gcctabopt |
74291a4b | 14010 | |
39bc1876 NS |
14011 | @item -EB |
14012 | @opindex EB | |
14013 | Generate big-endian code. | |
74291a4b | 14014 | |
39bc1876 NS |
14015 | @item -EL |
14016 | @opindex EL | |
14017 | Generate little-endian code. This is the default for @samp{mips*el-*-*} | |
14018 | configurations. | |
74291a4b | 14019 | |
39bc1876 NS |
14020 | @item -march=@var{arch} |
14021 | @opindex march | |
14022 | Generate code that will run on @var{arch}, which can be the name of a | |
14023 | generic MIPS ISA, or the name of a particular processor. | |
14024 | The ISA names are: | |
14025 | @samp{mips1}, @samp{mips2}, @samp{mips3}, @samp{mips4}, | |
f2d6ca50 | 14026 | @samp{mips32}, @samp{mips32r2}, @samp{mips64} and @samp{mips64r2}. |
39bc1876 | 14027 | The processor names are: |
52bcd429 SL |
14028 | @samp{4kc}, @samp{4km}, @samp{4kp}, @samp{4ksc}, |
14029 | @samp{4kec}, @samp{4kem}, @samp{4kep}, @samp{4ksd}, | |
79dad081 DU |
14030 | @samp{5kc}, @samp{5kf}, |
14031 | @samp{20kc}, | |
bdd77024 RS |
14032 | @samp{24kc}, @samp{24kf2_1}, @samp{24kf1_1}, |
14033 | @samp{24kec}, @samp{24kef2_1}, @samp{24kef1_1}, | |
14034 | @samp{34kc}, @samp{34kf2_1}, @samp{34kf1_1}, | |
74d4d024 | 14035 | @samp{74kc}, @samp{74kf2_1}, @samp{74kf1_1}, @samp{74kf3_2}, |
5dce6dbd | 14036 | @samp{1004kc}, @samp{1004kf2_1}, @samp{1004kf1_1}, |
98824c6f | 14037 | @samp{loongson2e}, @samp{loongson2f}, @samp{loongson3a}, |
39bc1876 | 14038 | @samp{m4k}, |
d97e6aca | 14039 | @samp{octeon}, |
39bc1876 | 14040 | @samp{orion}, |
79dad081 DU |
14041 | @samp{r2000}, @samp{r3000}, @samp{r3900}, @samp{r4000}, @samp{r4400}, |
14042 | @samp{r4600}, @samp{r4650}, @samp{r6000}, @samp{r8000}, | |
14043 | @samp{rm7000}, @samp{rm9000}, | |
7a3446ec | 14044 | @samp{r10000}, @samp{r12000}, @samp{r14000}, @samp{r16000}, |
39bc1876 | 14045 | @samp{sb1}, |
79dad081 | 14046 | @samp{sr71000}, |
39bc1876 | 14047 | @samp{vr4100}, @samp{vr4111}, @samp{vr4120}, @samp{vr4130}, @samp{vr4300}, |
d0ae31b0 SM |
14048 | @samp{vr5000}, @samp{vr5400}, @samp{vr5500} |
14049 | and @samp{xlr}. | |
39bc1876 NS |
14050 | The special value @samp{from-abi} selects the |
14051 | most compatible architecture for the selected ABI (that is, | |
14052 | @samp{mips1} for 32-bit ABIs and @samp{mips3} for 64-bit ABIs)@. | |
74291a4b | 14053 | |
900e3ae5 DJ |
14054 | Native Linux/GNU toolchains also support the value @samp{native}, |
14055 | which selects the best architecture option for the host processor. | |
14056 | @option{-march=native} has no effect if GCC does not recognize | |
14057 | the processor. | |
14058 | ||
39bc1876 NS |
14059 | In processor names, a final @samp{000} can be abbreviated as @samp{k} |
14060 | (for example, @samp{-march=r2k}). Prefixes are optional, and | |
14061 | @samp{vr} may be written @samp{r}. | |
74291a4b | 14062 | |
bdd77024 | 14063 | Names of the form @samp{@var{n}f2_1} refer to processors with |
74d4d024 | 14064 | FPUs clocked at half the rate of the core, names of the form |
bdd77024 | 14065 | @samp{@var{n}f1_1} refer to processors with FPUs clocked at the same |
74d4d024 DU |
14066 | rate as the core, and names of the form @samp{@var{n}f3_2} refer to |
14067 | processors with FPUs clocked a ratio of 3:2 with respect to the core. | |
14068 | For compatibility reasons, @samp{@var{n}f} is accepted as a synonym | |
14069 | for @samp{@var{n}f2_1} while @samp{@var{n}x} and @samp{@var{b}fx} are | |
14070 | accepted as synonyms for @samp{@var{n}f1_1}. | |
bdd77024 | 14071 | |
39bc1876 NS |
14072 | GCC defines two macros based on the value of this option. The first |
14073 | is @samp{_MIPS_ARCH}, which gives the name of target architecture, as | |
14074 | a string. The second has the form @samp{_MIPS_ARCH_@var{foo}}, | |
14075 | where @var{foo} is the capitalized value of @samp{_MIPS_ARCH}@. | |
14076 | For example, @samp{-march=r2000} will set @samp{_MIPS_ARCH} | |
14077 | to @samp{"r2000"} and define the macro @samp{_MIPS_ARCH_R2000}. | |
74291a4b | 14078 | |
39bc1876 NS |
14079 | Note that the @samp{_MIPS_ARCH} macro uses the processor names given |
14080 | above. In other words, it will have the full prefix and will not | |
14081 | abbreviate @samp{000} as @samp{k}. In the case of @samp{from-abi}, | |
14082 | the macro names the resolved architecture (either @samp{"mips1"} or | |
14083 | @samp{"mips3"}). It names the default architecture when no | |
14084 | @option{-march} option is given. | |
74291a4b | 14085 | |
39bc1876 NS |
14086 | @item -mtune=@var{arch} |
14087 | @opindex mtune | |
14088 | Optimize for @var{arch}. Among other things, this option controls | |
14089 | the way instructions are scheduled, and the perceived cost of arithmetic | |
14090 | operations. The list of @var{arch} values is the same as for | |
14091 | @option{-march}. | |
74291a4b | 14092 | |
39bc1876 NS |
14093 | When this option is not used, GCC will optimize for the processor |
14094 | specified by @option{-march}. By using @option{-march} and | |
14095 | @option{-mtune} together, it is possible to generate code that will | |
14096 | run on a family of processors, but optimize the code for one | |
14097 | particular member of that family. | |
74291a4b | 14098 | |
39bc1876 NS |
14099 | @samp{-mtune} defines the macros @samp{_MIPS_TUNE} and |
14100 | @samp{_MIPS_TUNE_@var{foo}}, which work in the same way as the | |
14101 | @samp{-march} ones described above. | |
74291a4b | 14102 | |
39bc1876 NS |
14103 | @item -mips1 |
14104 | @opindex mips1 | |
14105 | Equivalent to @samp{-march=mips1}. | |
74291a4b | 14106 | |
39bc1876 NS |
14107 | @item -mips2 |
14108 | @opindex mips2 | |
14109 | Equivalent to @samp{-march=mips2}. | |
74291a4b | 14110 | |
39bc1876 NS |
14111 | @item -mips3 |
14112 | @opindex mips3 | |
14113 | Equivalent to @samp{-march=mips3}. | |
74291a4b | 14114 | |
39bc1876 NS |
14115 | @item -mips4 |
14116 | @opindex mips4 | |
14117 | Equivalent to @samp{-march=mips4}. | |
14118 | ||
14119 | @item -mips32 | |
14120 | @opindex mips32 | |
14121 | Equivalent to @samp{-march=mips32}. | |
74291a4b | 14122 | |
39bc1876 NS |
14123 | @item -mips32r2 |
14124 | @opindex mips32r2 | |
14125 | Equivalent to @samp{-march=mips32r2}. | |
74291a4b | 14126 | |
39bc1876 NS |
14127 | @item -mips64 |
14128 | @opindex mips64 | |
14129 | Equivalent to @samp{-march=mips64}. | |
74291a4b | 14130 | |
f2d6ca50 AN |
14131 | @item -mips64r2 |
14132 | @opindex mips64r2 | |
14133 | Equivalent to @samp{-march=mips64r2}. | |
14134 | ||
39bc1876 NS |
14135 | @item -mips16 |
14136 | @itemx -mno-mips16 | |
14137 | @opindex mips16 | |
14138 | @opindex mno-mips16 | |
7cc63a88 | 14139 | Generate (do not generate) MIPS16 code. If GCC is targetting a |
71cb39e6 | 14140 | MIPS32 or MIPS64 architecture, it will make use of the MIPS16e ASE@. |
74291a4b | 14141 | |
f9e4a411 | 14142 | MIPS16 code generation can also be controlled on a per-function basis |
7a61cf6f | 14143 | by means of @code{mips16} and @code{nomips16} attributes. |
f9e4a411 SL |
14144 | @xref{Function Attributes}, for more information. |
14145 | ||
14146 | @item -mflip-mips16 | |
14147 | @opindex mflip-mips16 | |
14148 | Generate MIPS16 code on alternating functions. This option is provided | |
14149 | for regression testing of mixed MIPS16/non-MIPS16 code generation, and is | |
14150 | not intended for ordinary use in compiling user code. | |
14151 | ||
1ec3b87b RS |
14152 | @item -minterlink-mips16 |
14153 | @itemx -mno-interlink-mips16 | |
14154 | @opindex minterlink-mips16 | |
14155 | @opindex mno-interlink-mips16 | |
14156 | Require (do not require) that non-MIPS16 code be link-compatible with | |
14157 | MIPS16 code. | |
14158 | ||
14159 | For example, non-MIPS16 code cannot jump directly to MIPS16 code; | |
14160 | it must either use a call or an indirect jump. @option{-minterlink-mips16} | |
14161 | therefore disables direct jumps unless GCC knows that the target of the | |
14162 | jump is not MIPS16. | |
14163 | ||
39bc1876 NS |
14164 | @item -mabi=32 |
14165 | @itemx -mabi=o64 | |
14166 | @itemx -mabi=n32 | |
14167 | @itemx -mabi=64 | |
14168 | @itemx -mabi=eabi | |
14169 | @opindex mabi=32 | |
14170 | @opindex mabi=o64 | |
14171 | @opindex mabi=n32 | |
14172 | @opindex mabi=64 | |
14173 | @opindex mabi=eabi | |
14174 | Generate code for the given ABI@. | |
74291a4b | 14175 | |
39bc1876 NS |
14176 | Note that the EABI has a 32-bit and a 64-bit variant. GCC normally |
14177 | generates 64-bit code when you select a 64-bit architecture, but you | |
14178 | can use @option{-mgp32} to get 32-bit code instead. | |
74291a4b | 14179 | |
39bc1876 | 14180 | For information about the O64 ABI, see |
ab940b73 | 14181 | @uref{http://gcc.gnu.org/@/projects/@/mipso64-abi.html}. |
74291a4b | 14182 | |
6f428062 DU |
14183 | GCC supports a variant of the o32 ABI in which floating-point registers |
14184 | are 64 rather than 32 bits wide. You can select this combination with | |
14185 | @option{-mabi=32} @option{-mfp64}. This ABI relies on the @samp{mthc1} | |
14186 | and @samp{mfhc1} instructions and is therefore only supported for | |
14187 | MIPS32R2 processors. | |
14188 | ||
14189 | The register assignments for arguments and return values remain the | |
14190 | same, but each scalar value is passed in a single 64-bit register | |
14191 | rather than a pair of 32-bit registers. For example, scalar | |
14192 | floating-point values are returned in @samp{$f0} only, not a | |
14193 | @samp{$f0}/@samp{$f1} pair. The set of call-saved registers also | |
14194 | remains the same, but all 64 bits are saved. | |
14195 | ||
39bc1876 NS |
14196 | @item -mabicalls |
14197 | @itemx -mno-abicalls | |
14198 | @opindex mabicalls | |
14199 | @opindex mno-abicalls | |
567b3b82 RS |
14200 | Generate (do not generate) code that is suitable for SVR4-style |
14201 | dynamic objects. @option{-mabicalls} is the default for SVR4-based | |
14202 | systems. | |
14203 | ||
14204 | @item -mshared | |
14205 | @itemx -mno-shared | |
bc4a3483 RS |
14206 | Generate (do not generate) code that is fully position-independent, |
14207 | and that can therefore be linked into shared libraries. This option | |
14208 | only affects @option{-mabicalls}. | |
567b3b82 RS |
14209 | |
14210 | All @option{-mabicalls} code has traditionally been position-independent, | |
14211 | regardless of options like @option{-fPIC} and @option{-fpic}. However, | |
14212 | as an extension, the GNU toolchain allows executables to use absolute | |
14213 | accesses for locally-binding symbols. It can also use shorter GP | |
14214 | initialization sequences and generate direct calls to locally-defined | |
14215 | functions. This mode is selected by @option{-mno-shared}. | |
14216 | ||
14217 | @option{-mno-shared} depends on binutils 2.16 or higher and generates | |
14218 | objects that can only be linked by the GNU linker. However, the option | |
14219 | does not affect the ABI of the final executable; it only affects the ABI | |
14220 | of relocatable objects. Using @option{-mno-shared} will generally make | |
14221 | executables both smaller and quicker. | |
14222 | ||
14223 | @option{-mshared} is the default. | |
74291a4b | 14224 | |
e21d5757 DJ |
14225 | @item -mplt |
14226 | @itemx -mno-plt | |
14227 | @opindex mplt | |
14228 | @opindex mno-plt | |
14229 | Assume (do not assume) that the static and dynamic linkers | |
14230 | support PLTs and copy relocations. This option only affects | |
14231 | @samp{-mno-shared -mabicalls}. For the n64 ABI, this option | |
14232 | has no effect without @samp{-msym32}. | |
14233 | ||
14234 | You can make @option{-mplt} the default by configuring | |
14235 | GCC with @option{--with-mips-plt}. The default is | |
14236 | @option{-mno-plt} otherwise. | |
14237 | ||
39bc1876 NS |
14238 | @item -mxgot |
14239 | @itemx -mno-xgot | |
14240 | @opindex mxgot | |
14241 | @opindex mno-xgot | |
14242 | Lift (do not lift) the usual restrictions on the size of the global | |
14243 | offset table. | |
74291a4b | 14244 | |
8a36672b | 14245 | GCC normally uses a single instruction to load values from the GOT@. |
39bc1876 NS |
14246 | While this is relatively efficient, it will only work if the GOT |
14247 | is smaller than about 64k. Anything larger will cause the linker | |
14248 | to report an error such as: | |
74291a4b | 14249 | |
39bc1876 NS |
14250 | @cindex relocation truncated to fit (MIPS) |
14251 | @smallexample | |
14252 | relocation truncated to fit: R_MIPS_GOT16 foobar | |
14253 | @end smallexample | |
74291a4b | 14254 | |
39bc1876 NS |
14255 | If this happens, you should recompile your code with @option{-mxgot}. |
14256 | It should then work with very large GOTs, although it will also be | |
14257 | less efficient, since it will take three instructions to fetch the | |
14258 | value of a global symbol. | |
956d6950 | 14259 | |
39bc1876 NS |
14260 | Note that some linkers can create multiple GOTs. If you have such a |
14261 | linker, you should only need to use @option{-mxgot} when a single object | |
14262 | file accesses more than 64k's worth of GOT entries. Very few do. | |
956d6950 | 14263 | |
39bc1876 NS |
14264 | These options have no effect unless GCC is generating position |
14265 | independent code. | |
956d6950 | 14266 | |
39bc1876 NS |
14267 | @item -mgp32 |
14268 | @opindex mgp32 | |
14269 | Assume that general-purpose registers are 32 bits wide. | |
58605ba0 | 14270 | |
39bc1876 NS |
14271 | @item -mgp64 |
14272 | @opindex mgp64 | |
14273 | Assume that general-purpose registers are 64 bits wide. | |
58605ba0 | 14274 | |
39bc1876 NS |
14275 | @item -mfp32 |
14276 | @opindex mfp32 | |
14277 | Assume that floating-point registers are 32 bits wide. | |
58605ba0 | 14278 | |
39bc1876 NS |
14279 | @item -mfp64 |
14280 | @opindex mfp64 | |
14281 | Assume that floating-point registers are 64 bits wide. | |
58605ba0 | 14282 | |
39bc1876 NS |
14283 | @item -mhard-float |
14284 | @opindex mhard-float | |
14285 | Use floating-point coprocessor instructions. | |
58605ba0 | 14286 | |
39bc1876 NS |
14287 | @item -msoft-float |
14288 | @opindex msoft-float | |
14289 | Do not use floating-point coprocessor instructions. Implement | |
14290 | floating-point calculations using library calls instead. | |
3094247f | 14291 | |
39bc1876 NS |
14292 | @item -msingle-float |
14293 | @opindex msingle-float | |
14294 | Assume that the floating-point coprocessor only supports single-precision | |
14295 | operations. | |
3094247f | 14296 | |
500fc425 | 14297 | @item -mdouble-float |
39bc1876 NS |
14298 | @opindex mdouble-float |
14299 | Assume that the floating-point coprocessor supports double-precision | |
14300 | operations. This is the default. | |
956d6950 | 14301 | |
66471b47 DD |
14302 | @item -mllsc |
14303 | @itemx -mno-llsc | |
14304 | @opindex mllsc | |
14305 | @opindex mno-llsc | |
14306 | Use (do not use) @samp{ll}, @samp{sc}, and @samp{sync} instructions to | |
14307 | implement atomic memory built-in functions. When neither option is | |
14308 | specified, GCC will use the instructions if the target architecture | |
14309 | supports them. | |
14310 | ||
14311 | @option{-mllsc} is useful if the runtime environment can emulate the | |
14312 | instructions and @option{-mno-llsc} can be useful when compiling for | |
14313 | nonstandard ISAs. You can make either option the default by | |
14314 | configuring GCC with @option{--with-llsc} and @option{--without-llsc} | |
14315 | respectively. @option{--with-llsc} is the default for some | |
14316 | configurations; see the installation documentation for details. | |
14317 | ||
500fc425 | 14318 | @item -mdsp |
118ea793 CF |
14319 | @itemx -mno-dsp |
14320 | @opindex mdsp | |
14321 | @opindex mno-dsp | |
0ee2ea09 | 14322 | Use (do not use) revision 1 of the MIPS DSP ASE@. |
da7d4908 RS |
14323 | @xref{MIPS DSP Built-in Functions}. This option defines the |
14324 | preprocessor macro @samp{__mips_dsp}. It also defines | |
14325 | @samp{__mips_dsp_rev} to 1. | |
118ea793 | 14326 | |
500fc425 | 14327 | @item -mdspr2 |
32041385 CF |
14328 | @itemx -mno-dspr2 |
14329 | @opindex mdspr2 | |
14330 | @opindex mno-dspr2 | |
0ee2ea09 | 14331 | Use (do not use) revision 2 of the MIPS DSP ASE@. |
da7d4908 RS |
14332 | @xref{MIPS DSP Built-in Functions}. This option defines the |
14333 | preprocessor macros @samp{__mips_dsp} and @samp{__mips_dspr2}. | |
14334 | It also defines @samp{__mips_dsp_rev} to 2. | |
32041385 | 14335 | |
0aa222d1 SL |
14336 | @item -msmartmips |
14337 | @itemx -mno-smartmips | |
14338 | @opindex msmartmips | |
14339 | @opindex mno-smartmips | |
14340 | Use (do not use) the MIPS SmartMIPS ASE. | |
14341 | ||
500fc425 | 14342 | @item -mpaired-single |
06a4ab70 CF |
14343 | @itemx -mno-paired-single |
14344 | @opindex mpaired-single | |
14345 | @opindex mno-paired-single | |
d840bfd3 | 14346 | Use (do not use) paired-single floating-point instructions. |
e5a2b69d RS |
14347 | @xref{MIPS Paired-Single Support}. This option requires |
14348 | hardware floating-point support to be enabled. | |
06a4ab70 | 14349 | |
500fc425 TS |
14350 | @item -mdmx |
14351 | @itemx -mno-mdmx | |
14352 | @opindex mdmx | |
14353 | @opindex mno-mdmx | |
14354 | Use (do not use) MIPS Digital Media Extension instructions. | |
14355 | This option can only be used when generating 64-bit code and requires | |
14356 | hardware floating-point support to be enabled. | |
14357 | ||
14358 | @item -mips3d | |
06a4ab70 CF |
14359 | @itemx -mno-mips3d |
14360 | @opindex mips3d | |
14361 | @opindex mno-mips3d | |
8a36672b | 14362 | Use (do not use) the MIPS-3D ASE@. @xref{MIPS-3D Built-in Functions}. |
d840bfd3 | 14363 | The option @option{-mips3d} implies @option{-mpaired-single}. |
06a4ab70 | 14364 | |
500fc425 TS |
14365 | @item -mmt |
14366 | @itemx -mno-mt | |
14367 | @opindex mmt | |
14368 | @opindex mno-mt | |
14369 | Use (do not use) MT Multithreading instructions. | |
14370 | ||
39bc1876 NS |
14371 | @item -mlong64 |
14372 | @opindex mlong64 | |
14373 | Force @code{long} types to be 64 bits wide. See @option{-mlong32} for | |
14374 | an explanation of the default and the way that the pointer size is | |
14375 | determined. | |
956d6950 | 14376 | |
39bc1876 NS |
14377 | @item -mlong32 |
14378 | @opindex mlong32 | |
14379 | Force @code{long}, @code{int}, and pointer types to be 32 bits wide. | |
956d6950 | 14380 | |
39bc1876 NS |
14381 | The default size of @code{int}s, @code{long}s and pointers depends on |
14382 | the ABI@. All the supported ABIs use 32-bit @code{int}s. The n64 ABI | |
14383 | uses 64-bit @code{long}s, as does the 64-bit EABI; the others use | |
14384 | 32-bit @code{long}s. Pointers are the same size as @code{long}s, | |
14385 | or the same size as integer registers, whichever is smaller. | |
956d6950 | 14386 | |
acda0e26 RS |
14387 | @item -msym32 |
14388 | @itemx -mno-sym32 | |
14389 | @opindex msym32 | |
14390 | @opindex mno-sym32 | |
14391 | Assume (do not assume) that all symbols have 32-bit values, regardless | |
14392 | of the selected ABI@. This option is useful in combination with | |
14393 | @option{-mabi=64} and @option{-mno-abicalls} because it allows GCC | |
14394 | to generate shorter and faster references to symbolic addresses. | |
14395 | ||
39bc1876 NS |
14396 | @item -G @var{num} |
14397 | @opindex G | |
a318179e RS |
14398 | Put definitions of externally-visible data in a small data section |
14399 | if that data is no bigger than @var{num} bytes. GCC can then access | |
14400 | the data more efficiently; see @option{-mgpopt} for details. | |
14401 | ||
14402 | The default @option{-G} option depends on the configuration. | |
14403 | ||
14404 | @item -mlocal-sdata | |
14405 | @itemx -mno-local-sdata | |
14406 | @opindex mlocal-sdata | |
14407 | @opindex mno-local-sdata | |
14408 | Extend (do not extend) the @option{-G} behavior to local data too, | |
0ee2ea09 | 14409 | such as to static variables in C@. @option{-mlocal-sdata} is the |
a318179e RS |
14410 | default for all configurations. |
14411 | ||
14412 | If the linker complains that an application is using too much small data, | |
14413 | you might want to try rebuilding the less performance-critical parts with | |
14414 | @option{-mno-local-sdata}. You might also want to build large | |
14415 | libraries with @option{-mno-local-sdata}, so that the libraries leave | |
14416 | more room for the main program. | |
14417 | ||
14418 | @item -mextern-sdata | |
14419 | @itemx -mno-extern-sdata | |
14420 | @opindex mextern-sdata | |
14421 | @opindex mno-extern-sdata | |
14422 | Assume (do not assume) that externally-defined data will be in | |
14423 | a small data section if that data is within the @option{-G} limit. | |
14424 | @option{-mextern-sdata} is the default for all configurations. | |
14425 | ||
14426 | If you compile a module @var{Mod} with @option{-mextern-sdata} @option{-G | |
14427 | @var{num}} @option{-mgpopt}, and @var{Mod} references a variable @var{Var} | |
14428 | that is no bigger than @var{num} bytes, you must make sure that @var{Var} | |
14429 | is placed in a small data section. If @var{Var} is defined by another | |
14430 | module, you must either compile that module with a high-enough | |
14431 | @option{-G} setting or attach a @code{section} attribute to @var{Var}'s | |
14432 | definition. If @var{Var} is common, you must link the application | |
14433 | with a high-enough @option{-G} setting. | |
14434 | ||
14435 | The easiest way of satisfying these restrictions is to compile | |
14436 | and link every module with the same @option{-G} option. However, | |
14437 | you may wish to build a library that supports several different | |
14438 | small data limits. You can do this by compiling the library with | |
14439 | the highest supported @option{-G} setting and additionally using | |
14440 | @option{-mno-extern-sdata} to stop the library from making assumptions | |
14441 | about externally-defined data. | |
14442 | ||
14443 | @item -mgpopt | |
14444 | @itemx -mno-gpopt | |
14445 | @opindex mgpopt | |
14446 | @opindex mno-gpopt | |
14447 | Use (do not use) GP-relative accesses for symbols that are known to be | |
14448 | in a small data section; see @option{-G}, @option{-mlocal-sdata} and | |
14449 | @option{-mextern-sdata}. @option{-mgpopt} is the default for all | |
14450 | configurations. | |
14451 | ||
14452 | @option{-mno-gpopt} is useful for cases where the @code{$gp} register | |
14453 | might not hold the value of @code{_gp}. For example, if the code is | |
14454 | part of a library that might be used in a boot monitor, programs that | |
14455 | call boot monitor routines will pass an unknown value in @code{$gp}. | |
14456 | (In such situations, the boot monitor itself would usually be compiled | |
14457 | with @option{-G0}.) | |
14458 | ||
14459 | @option{-mno-gpopt} implies @option{-mno-local-sdata} and | |
14460 | @option{-mno-extern-sdata}. | |
956d6950 | 14461 | |
39bc1876 NS |
14462 | @item -membedded-data |
14463 | @itemx -mno-embedded-data | |
14464 | @opindex membedded-data | |
14465 | @opindex mno-embedded-data | |
14466 | Allocate variables to the read-only data section first if possible, then | |
14467 | next in the small data section if possible, otherwise in data. This gives | |
14468 | slightly slower code than the default, but reduces the amount of RAM required | |
14469 | when executing, and thus may be preferred for some embedded systems. | |
58605ba0 | 14470 | |
39bc1876 NS |
14471 | @item -muninit-const-in-rodata |
14472 | @itemx -mno-uninit-const-in-rodata | |
14473 | @opindex muninit-const-in-rodata | |
14474 | @opindex mno-uninit-const-in-rodata | |
14475 | Put uninitialized @code{const} variables in the read-only data section. | |
14476 | This option is only meaningful in conjunction with @option{-membedded-data}. | |
4f69985c | 14477 | |
c93c5160 RS |
14478 | @item -mcode-readable=@var{setting} |
14479 | @opindex mcode-readable | |
14480 | Specify whether GCC may generate code that reads from executable sections. | |
14481 | There are three possible settings: | |
14482 | ||
14483 | @table @gcctabopt | |
14484 | @item -mcode-readable=yes | |
14485 | Instructions may freely access executable sections. This is the | |
14486 | default setting. | |
14487 | ||
14488 | @item -mcode-readable=pcrel | |
14489 | MIPS16 PC-relative load instructions can access executable sections, | |
14490 | but other instructions must not do so. This option is useful on 4KSc | |
14491 | and 4KSd processors when the code TLBs have the Read Inhibit bit set. | |
14492 | It is also useful on processors that can be configured to have a dual | |
14493 | instruction/data SRAM interface and that, like the M4K, automatically | |
14494 | redirect PC-relative loads to the instruction RAM. | |
14495 | ||
14496 | @item -mcode-readable=no | |
14497 | Instructions must not access executable sections. This option can be | |
14498 | useful on targets that are configured to have a dual instruction/data | |
14499 | SRAM interface but that (unlike the M4K) do not automatically redirect | |
14500 | PC-relative loads to the instruction RAM. | |
14501 | @end table | |
14502 | ||
39bc1876 NS |
14503 | @item -msplit-addresses |
14504 | @itemx -mno-split-addresses | |
14505 | @opindex msplit-addresses | |
14506 | @opindex mno-split-addresses | |
14507 | Enable (disable) use of the @code{%hi()} and @code{%lo()} assembler | |
38b974a6 | 14508 | relocation operators. This option has been superseded by |
39bc1876 | 14509 | @option{-mexplicit-relocs} but is retained for backwards compatibility. |
58605ba0 | 14510 | |
39bc1876 NS |
14511 | @item -mexplicit-relocs |
14512 | @itemx -mno-explicit-relocs | |
14513 | @opindex mexplicit-relocs | |
14514 | @opindex mno-explicit-relocs | |
14515 | Use (do not use) assembler relocation operators when dealing with symbolic | |
14516 | addresses. The alternative, selected by @option{-mno-explicit-relocs}, | |
14517 | is to use assembler macros instead. | |
4f69985c | 14518 | |
12e4afe4 RS |
14519 | @option{-mexplicit-relocs} is the default if GCC was configured |
14520 | to use an assembler that supports relocation operators. | |
4f69985c | 14521 | |
39bc1876 NS |
14522 | @item -mcheck-zero-division |
14523 | @itemx -mno-check-zero-division | |
14524 | @opindex mcheck-zero-division | |
14525 | @opindex mno-check-zero-division | |
78681dbd RS |
14526 | Trap (do not trap) on integer division by zero. |
14527 | ||
14528 | The default is @option{-mcheck-zero-division}. | |
4f69985c | 14529 | |
9f0df97a DD |
14530 | @item -mdivide-traps |
14531 | @itemx -mdivide-breaks | |
14532 | @opindex mdivide-traps | |
14533 | @opindex mdivide-breaks | |
14534 | MIPS systems check for division by zero by generating either a | |
14535 | conditional trap or a break instruction. Using traps results in | |
14536 | smaller code, but is only supported on MIPS II and later. Also, some | |
14537 | versions of the Linux kernel have a bug that prevents trap from | |
8a36672b | 14538 | generating the proper signal (@code{SIGFPE}). Use @option{-mdivide-traps} to |
9f0df97a DD |
14539 | allow conditional traps on architectures that support them and |
14540 | @option{-mdivide-breaks} to force the use of breaks. | |
14541 | ||
14542 | The default is usually @option{-mdivide-traps}, but this can be | |
14543 | overridden at configure time using @option{--with-divide=breaks}. | |
14544 | Divide-by-zero checks can be completely disabled using | |
14545 | @option{-mno-check-zero-division}. | |
14546 | ||
39bc1876 NS |
14547 | @item -mmemcpy |
14548 | @itemx -mno-memcpy | |
14549 | @opindex mmemcpy | |
14550 | @opindex mno-memcpy | |
14551 | Force (do not force) the use of @code{memcpy()} for non-trivial block | |
14552 | moves. The default is @option{-mno-memcpy}, which allows GCC to inline | |
14553 | most constant-sized copies. | |
74291a4b | 14554 | |
39bc1876 NS |
14555 | @item -mlong-calls |
14556 | @itemx -mno-long-calls | |
14557 | @opindex mlong-calls | |
14558 | @opindex mno-long-calls | |
14559 | Disable (do not disable) use of the @code{jal} instruction. Calling | |
14560 | functions using @code{jal} is more efficient but requires the caller | |
14561 | and callee to be in the same 256 megabyte segment. | |
d7c23cdc | 14562 | |
39bc1876 NS |
14563 | This option has no effect on abicalls code. The default is |
14564 | @option{-mno-long-calls}. | |
d7c23cdc | 14565 | |
39bc1876 NS |
14566 | @item -mmad |
14567 | @itemx -mno-mad | |
14568 | @opindex mmad | |
14569 | @opindex mno-mad | |
14570 | Enable (disable) use of the @code{mad}, @code{madu} and @code{mul} | |
8a36672b | 14571 | instructions, as provided by the R4650 ISA@. |
d7c23cdc | 14572 | |
39bc1876 NS |
14573 | @item -mfused-madd |
14574 | @itemx -mno-fused-madd | |
14575 | @opindex mfused-madd | |
14576 | @opindex mno-fused-madd | |
14577 | Enable (disable) use of the floating point multiply-accumulate | |
14578 | instructions, when they are available. The default is | |
14579 | @option{-mfused-madd}. | |
74291a4b | 14580 | |
39bc1876 NS |
14581 | When multiply-accumulate instructions are used, the intermediate |
14582 | product is calculated to infinite precision and is not subject to | |
14583 | the FCSR Flush to Zero bit. This may be undesirable in some | |
14584 | circumstances. | |
74291a4b | 14585 | |
39bc1876 NS |
14586 | @item -nocpp |
14587 | @opindex nocpp | |
14588 | Tell the MIPS assembler to not run its preprocessor over user | |
14589 | assembler files (with a @samp{.s} suffix) when assembling them. | |
74291a4b | 14590 | |
39bc1876 NS |
14591 | @item -mfix-r4000 |
14592 | @itemx -mno-fix-r4000 | |
14593 | @opindex mfix-r4000 | |
14594 | @opindex mno-fix-r4000 | |
14595 | Work around certain R4000 CPU errata: | |
14596 | @itemize @minus | |
14597 | @item | |
14598 | A double-word or a variable shift may give an incorrect result if executed | |
14599 | immediately after starting an integer division. | |
14600 | @item | |
14601 | A double-word or a variable shift may give an incorrect result if executed | |
14602 | while an integer multiplication is in progress. | |
14603 | @item | |
14604 | An integer division may give an incorrect result if started in a delay slot | |
14605 | of a taken branch or a jump. | |
14606 | @end itemize | |
74291a4b | 14607 | |
39bc1876 NS |
14608 | @item -mfix-r4400 |
14609 | @itemx -mno-fix-r4400 | |
14610 | @opindex mfix-r4400 | |
14611 | @opindex mno-fix-r4400 | |
14612 | Work around certain R4400 CPU errata: | |
14613 | @itemize @minus | |
14614 | @item | |
14615 | A double-word or a variable shift may give an incorrect result if executed | |
14616 | immediately after starting an integer division. | |
14617 | @end itemize | |
dcb9d1f0 | 14618 | |
ee9a72e5 JK |
14619 | @item -mfix-r10000 |
14620 | @itemx -mno-fix-r10000 | |
14621 | @opindex mfix-r10000 | |
14622 | @opindex mno-fix-r10000 | |
14623 | Work around certain R10000 errata: | |
14624 | @itemize @minus | |
14625 | @item | |
14626 | @code{ll}/@code{sc} sequences may not behave atomically on revisions | |
14627 | prior to 3.0. They may deadlock on revisions 2.6 and earlier. | |
14628 | @end itemize | |
14629 | ||
14630 | This option can only be used if the target architecture supports | |
14631 | branch-likely instructions. @option{-mfix-r10000} is the default when | |
14632 | @option{-march=r10000} is used; @option{-mno-fix-r10000} is the default | |
14633 | otherwise. | |
14634 | ||
39bc1876 NS |
14635 | @item -mfix-vr4120 |
14636 | @itemx -mno-fix-vr4120 | |
14637 | @opindex mfix-vr4120 | |
14638 | Work around certain VR4120 errata: | |
14639 | @itemize @minus | |
14640 | @item | |
14641 | @code{dmultu} does not always produce the correct result. | |
14642 | @item | |
14643 | @code{div} and @code{ddiv} do not always produce the correct result if one | |
14644 | of the operands is negative. | |
14645 | @end itemize | |
14646 | The workarounds for the division errata rely on special functions in | |
14647 | @file{libgcc.a}. At present, these functions are only provided by | |
14648 | the @code{mips64vr*-elf} configurations. | |
39ba95b5 | 14649 | |
39bc1876 NS |
14650 | Other VR4120 errata require a nop to be inserted between certain pairs of |
14651 | instructions. These errata are handled by the assembler, not by GCC itself. | |
17f0f8fa | 14652 | |
0ac40e7a RS |
14653 | @item -mfix-vr4130 |
14654 | @opindex mfix-vr4130 | |
14655 | Work around the VR4130 @code{mflo}/@code{mfhi} errata. The | |
14656 | workarounds are implemented by the assembler rather than by GCC, | |
14657 | although GCC will avoid using @code{mflo} and @code{mfhi} if the | |
14658 | VR4130 @code{macc}, @code{macchi}, @code{dmacc} and @code{dmacchi} | |
14659 | instructions are available instead. | |
14660 | ||
39bc1876 NS |
14661 | @item -mfix-sb1 |
14662 | @itemx -mno-fix-sb1 | |
14663 | @opindex mfix-sb1 | |
14664 | Work around certain SB-1 CPU core errata. | |
14665 | (This flag currently works around the SB-1 revision 2 | |
14666 | ``F1'' and ``F2'' floating point errata.) | |
74291a4b | 14667 | |
4d210b07 RS |
14668 | @item -mr10k-cache-barrier=@var{setting} |
14669 | @opindex mr10k-cache-barrier | |
14670 | Specify whether GCC should insert cache barriers to avoid the | |
14671 | side-effects of speculation on R10K processors. | |
14672 | ||
14673 | In common with many processors, the R10K tries to predict the outcome | |
14674 | of a conditional branch and speculatively executes instructions from | |
14675 | the ``taken'' branch. It later aborts these instructions if the | |
14676 | predicted outcome was wrong. However, on the R10K, even aborted | |
14677 | instructions can have side effects. | |
14678 | ||
14679 | This problem only affects kernel stores and, depending on the system, | |
14680 | kernel loads. As an example, a speculatively-executed store may load | |
14681 | the target memory into cache and mark the cache line as dirty, even if | |
14682 | the store itself is later aborted. If a DMA operation writes to the | |
14683 | same area of memory before the ``dirty'' line is flushed, the cached | |
14684 | data will overwrite the DMA-ed data. See the R10K processor manual | |
14685 | for a full description, including other potential problems. | |
14686 | ||
14687 | One workaround is to insert cache barrier instructions before every memory | |
14688 | access that might be speculatively executed and that might have side | |
14689 | effects even if aborted. @option{-mr10k-cache-barrier=@var{setting}} | |
14690 | controls GCC's implementation of this workaround. It assumes that | |
14691 | aborted accesses to any byte in the following regions will not have | |
14692 | side effects: | |
14693 | ||
14694 | @enumerate | |
14695 | @item | |
14696 | the memory occupied by the current function's stack frame; | |
14697 | ||
14698 | @item | |
14699 | the memory occupied by an incoming stack argument; | |
14700 | ||
14701 | @item | |
14702 | the memory occupied by an object with a link-time-constant address. | |
14703 | @end enumerate | |
14704 | ||
14705 | It is the kernel's responsibility to ensure that speculative | |
14706 | accesses to these regions are indeed safe. | |
14707 | ||
14708 | If the input program contains a function declaration such as: | |
14709 | ||
14710 | @smallexample | |
14711 | void foo (void); | |
14712 | @end smallexample | |
14713 | ||
14714 | then the implementation of @code{foo} must allow @code{j foo} and | |
14715 | @code{jal foo} to be executed speculatively. GCC honors this | |
14716 | restriction for functions it compiles itself. It expects non-GCC | |
14717 | functions (such as hand-written assembly code) to do the same. | |
14718 | ||
14719 | The option has three forms: | |
14720 | ||
14721 | @table @gcctabopt | |
14722 | @item -mr10k-cache-barrier=load-store | |
14723 | Insert a cache barrier before a load or store that might be | |
14724 | speculatively executed and that might have side effects even | |
14725 | if aborted. | |
14726 | ||
14727 | @item -mr10k-cache-barrier=store | |
14728 | Insert a cache barrier before a store that might be speculatively | |
14729 | executed and that might have side effects even if aborted. | |
14730 | ||
14731 | @item -mr10k-cache-barrier=none | |
14732 | Disable the insertion of cache barriers. This is the default setting. | |
14733 | @end table | |
14734 | ||
39bc1876 NS |
14735 | @item -mflush-func=@var{func} |
14736 | @itemx -mno-flush-func | |
14737 | @opindex mflush-func | |
14738 | Specifies the function to call to flush the I and D caches, or to not | |
14739 | call any such function. If called, the function must take the same | |
14740 | arguments as the common @code{_flush_func()}, that is, the address of the | |
14741 | memory range for which the cache is being flushed, the size of the | |
14742 | memory range, and the number 3 (to flush both caches). The default | |
14743 | depends on the target GCC was configured for, but commonly is either | |
14744 | @samp{_flush_func} or @samp{__cpu_flush}. | |
74291a4b | 14745 | |
a05bea76 RS |
14746 | @item mbranch-cost=@var{num} |
14747 | @opindex mbranch-cost | |
14748 | Set the cost of branches to roughly @var{num} ``simple'' instructions. | |
14749 | This cost is only a heuristic and is not guaranteed to produce | |
14750 | consistent results across releases. A zero cost redundantly selects | |
14751 | the default, which is based on the @option{-mtune} setting. | |
14752 | ||
39bc1876 NS |
14753 | @item -mbranch-likely |
14754 | @itemx -mno-branch-likely | |
14755 | @opindex mbranch-likely | |
14756 | @opindex mno-branch-likely | |
14757 | Enable or disable use of Branch Likely instructions, regardless of the | |
14758 | default for the selected architecture. By default, Branch Likely | |
14759 | instructions may be generated if they are supported by the selected | |
14760 | architecture. An exception is for the MIPS32 and MIPS64 architectures | |
14761 | and processors which implement those architectures; for those, Branch | |
14762 | Likely instructions will not be generated by default because the MIPS32 | |
14763 | and MIPS64 architectures specifically deprecate their use. | |
74291a4b | 14764 | |
39bc1876 NS |
14765 | @item -mfp-exceptions |
14766 | @itemx -mno-fp-exceptions | |
14767 | @opindex mfp-exceptions | |
14768 | Specifies whether FP exceptions are enabled. This affects how we schedule | |
14769 | FP instructions for some processors. The default is that FP exceptions are | |
14770 | enabled. | |
74291a4b | 14771 | |
39bc1876 NS |
14772 | For instance, on the SB-1, if FP exceptions are disabled, and we are emitting |
14773 | 64-bit code, then we can use both FP pipes. Otherwise, we can only use one | |
14774 | FP pipe. | |
74291a4b | 14775 | |
39bc1876 NS |
14776 | @item -mvr4130-align |
14777 | @itemx -mno-vr4130-align | |
14778 | @opindex mvr4130-align | |
14779 | The VR4130 pipeline is two-way superscalar, but can only issue two | |
14780 | instructions together if the first one is 8-byte aligned. When this | |
14781 | option is enabled, GCC will align pairs of instructions that it | |
14782 | thinks should execute in parallel. | |
74291a4b | 14783 | |
39bc1876 NS |
14784 | This option only has an effect when optimizing for the VR4130. |
14785 | It normally makes code faster, but at the expense of making it bigger. | |
14786 | It is enabled by default at optimization level @option{-O3}. | |
b96c5923 DD |
14787 | |
14788 | @item -msynci | |
14789 | @itemx -mno-synci | |
14790 | @opindex msynci | |
14791 | Enable (disable) generation of @code{synci} instructions on | |
14792 | architectures that support it. The @code{synci} instructions (if | |
14793 | enabled) will be generated when @code{__builtin___clear_cache()} is | |
14794 | compiled. | |
14795 | ||
14796 | This option defaults to @code{-mno-synci}, but the default can be | |
14797 | overridden by configuring with @code{--with-synci}. | |
14798 | ||
14799 | When compiling code for single processor systems, it is generally safe | |
14800 | to use @code{synci}. However, on many multi-core (SMP) systems, it | |
14801 | will not invalidate the instruction caches on all cores and may lead | |
14802 | to undefined behavior. | |
b53da244 AN |
14803 | |
14804 | @item -mrelax-pic-calls | |
14805 | @itemx -mno-relax-pic-calls | |
14806 | @opindex mrelax-pic-calls | |
14807 | Try to turn PIC calls that are normally dispatched via register | |
14808 | @code{$25} into direct calls. This is only possible if the linker can | |
14809 | resolve the destination at link-time and if the destination is within | |
14810 | range for a direct call. | |
14811 | ||
14812 | @option{-mrelax-pic-calls} is the default if GCC was configured to use | |
14813 | an assembler and a linker that supports the @code{.reloc} assembly | |
14814 | directive and @code{-mexplicit-relocs} is in effect. With | |
14815 | @code{-mno-explicit-relocs}, this optimization can be performed by the | |
14816 | assembler and the linker alone without help from the compiler. | |
c376dbfb DD |
14817 | |
14818 | @item -mmcount-ra-address | |
14819 | @itemx -mno-mcount-ra-address | |
14820 | @opindex mmcount-ra-address | |
14821 | @opindex mno-mcount-ra-address | |
14822 | Emit (do not emit) code that allows @code{_mcount} to modify the | |
8d023933 | 14823 | calling function's return address. When enabled, this option extends |
c376dbfb DD |
14824 | the usual @code{_mcount} interface with a new @var{ra-address} |
14825 | parameter, which has type @code{intptr_t *} and is passed in register | |
14826 | @code{$12}. @code{_mcount} can then modify the return address by | |
14827 | doing both of the following: | |
14828 | @itemize | |
14829 | @item | |
14830 | Returning the new address in register @code{$31}. | |
14831 | @item | |
14832 | Storing the new address in @code{*@var{ra-address}}, | |
14833 | if @var{ra-address} is nonnull. | |
14834 | @end itemize | |
14835 | ||
14836 | The default is @option{-mno-mcount-ra-address}. | |
14837 | ||
39bc1876 | 14838 | @end table |
3a8699c7 | 14839 | |
39bc1876 NS |
14840 | @node MMIX Options |
14841 | @subsection MMIX Options | |
14842 | @cindex MMIX Options | |
74291a4b | 14843 | |
39bc1876 | 14844 | These options are defined for the MMIX: |
74291a4b | 14845 | |
39bc1876 NS |
14846 | @table @gcctabopt |
14847 | @item -mlibfuncs | |
14848 | @itemx -mno-libfuncs | |
14849 | @opindex mlibfuncs | |
14850 | @opindex mno-libfuncs | |
14851 | Specify that intrinsic library functions are being compiled, passing all | |
14852 | values in registers, no matter the size. | |
3cadd778 | 14853 | |
39bc1876 NS |
14854 | @item -mepsilon |
14855 | @itemx -mno-epsilon | |
14856 | @opindex mepsilon | |
14857 | @opindex mno-epsilon | |
14858 | Generate floating-point comparison instructions that compare with respect | |
14859 | to the @code{rE} epsilon register. | |
3cadd778 | 14860 | |
39bc1876 NS |
14861 | @item -mabi=mmixware |
14862 | @itemx -mabi=gnu | |
d376d545 | 14863 | @opindex mabi=mmixware |
39bc1876 NS |
14864 | @opindex mabi=gnu |
14865 | Generate code that passes function parameters and return values that (in | |
14866 | the called function) are seen as registers @code{$0} and up, as opposed to | |
14867 | the GNU ABI which uses global registers @code{$231} and up. | |
3cadd778 | 14868 | |
39bc1876 NS |
14869 | @item -mzero-extend |
14870 | @itemx -mno-zero-extend | |
14871 | @opindex mzero-extend | |
14872 | @opindex mno-zero-extend | |
14873 | When reading data from memory in sizes shorter than 64 bits, use (do not | |
14874 | use) zero-extending load instructions by default, rather than | |
14875 | sign-extending ones. | |
3cadd778 | 14876 | |
39bc1876 NS |
14877 | @item -mknuthdiv |
14878 | @itemx -mno-knuthdiv | |
14879 | @opindex mknuthdiv | |
14880 | @opindex mno-knuthdiv | |
14881 | Make the result of a division yielding a remainder have the same sign as | |
14882 | the divisor. With the default, @option{-mno-knuthdiv}, the sign of the | |
14883 | remainder follows the sign of the dividend. Both methods are | |
14884 | arithmetically valid, the latter being almost exclusively used. | |
74291a4b | 14885 | |
39bc1876 NS |
14886 | @item -mtoplevel-symbols |
14887 | @itemx -mno-toplevel-symbols | |
14888 | @opindex mtoplevel-symbols | |
14889 | @opindex mno-toplevel-symbols | |
14890 | Prepend (do not prepend) a @samp{:} to all global symbols, so the assembly | |
14891 | code can be used with the @code{PREFIX} assembly directive. | |
74291a4b | 14892 | |
39bc1876 NS |
14893 | @item -melf |
14894 | @opindex melf | |
14895 | Generate an executable in the ELF format, rather than the default | |
14896 | @samp{mmo} format used by the @command{mmix} simulator. | |
3d5a0820 | 14897 | |
39bc1876 NS |
14898 | @item -mbranch-predict |
14899 | @itemx -mno-branch-predict | |
14900 | @opindex mbranch-predict | |
14901 | @opindex mno-branch-predict | |
14902 | Use (do not use) the probable-branch instructions, when static branch | |
14903 | prediction indicates a probable branch. | |
3cadd778 | 14904 | |
39bc1876 NS |
14905 | @item -mbase-addresses |
14906 | @itemx -mno-base-addresses | |
14907 | @opindex mbase-addresses | |
14908 | @opindex mno-base-addresses | |
14909 | Generate (do not generate) code that uses @emph{base addresses}. Using a | |
14910 | base address automatically generates a request (handled by the assembler | |
14911 | and the linker) for a constant to be set up in a global register. The | |
14912 | register is used for one or more base address requests within the range 0 | |
14913 | to 255 from the value held in the register. The generally leads to short | |
14914 | and fast code, but the number of different data items that can be | |
14915 | addressed is limited. This means that a program that uses lots of static | |
14916 | data may require @option{-mno-base-addresses}. | |
3cadd778 | 14917 | |
39bc1876 NS |
14918 | @item -msingle-exit |
14919 | @itemx -mno-single-exit | |
14920 | @opindex msingle-exit | |
14921 | @opindex mno-single-exit | |
14922 | Force (do not force) generated code to have a single exit point in each | |
14923 | function. | |
14924 | @end table | |
3cadd778 | 14925 | |
39bc1876 NS |
14926 | @node MN10300 Options |
14927 | @subsection MN10300 Options | |
14928 | @cindex MN10300 options | |
3cadd778 | 14929 | |
39bc1876 | 14930 | These @option{-m} options are defined for Matsushita MN10300 architectures: |
3cadd778 | 14931 | |
39bc1876 NS |
14932 | @table @gcctabopt |
14933 | @item -mmult-bug | |
14934 | @opindex mmult-bug | |
14935 | Generate code to avoid bugs in the multiply instructions for the MN10300 | |
14936 | processors. This is the default. | |
c474f76b | 14937 | |
39bc1876 NS |
14938 | @item -mno-mult-bug |
14939 | @opindex mno-mult-bug | |
14940 | Do not generate code to avoid bugs in the multiply instructions for the | |
14941 | MN10300 processors. | |
3cadd778 | 14942 | |
39bc1876 NS |
14943 | @item -mam33 |
14944 | @opindex mam33 | |
14945 | Generate code which uses features specific to the AM33 processor. | |
3cadd778 | 14946 | |
39bc1876 NS |
14947 | @item -mno-am33 |
14948 | @opindex mno-am33 | |
14949 | Do not generate code which uses features specific to the AM33 processor. This | |
14950 | is the default. | |
1a66cd67 | 14951 | |
f3f63737 NC |
14952 | @item -mam33-2 |
14953 | @opindex mam33-2 | |
14954 | Generate code which uses features specific to the AM33/2.0 processor. | |
14955 | ||
14956 | @item -mam34 | |
14957 | @opindex mam34 | |
14958 | Generate code which uses features specific to the AM34 processor. | |
14959 | ||
14960 | @item -mtune=@var{cpu-type} | |
14961 | @opindex mtune | |
14962 | Use the timing characteristics of the indicated CPU type when | |
14963 | scheduling instructions. This does not change the targeted processor | |
14964 | type. The CPU type must be one of @samp{mn10300}, @samp{am33}, | |
14965 | @samp{am33-2} or @samp{am34}. | |
14966 | ||
b1eb8119 DD |
14967 | @item -mreturn-pointer-on-d0 |
14968 | @opindex mreturn-pointer-on-d0 | |
14969 | When generating a function which returns a pointer, return the pointer | |
14970 | in both @code{a0} and @code{d0}. Otherwise, the pointer is returned | |
14971 | only in a0, and attempts to call such functions without a prototype | |
14972 | would result in errors. Note that this option is on by default; use | |
14973 | @option{-mno-return-pointer-on-d0} to disable it. | |
14974 | ||
39bc1876 NS |
14975 | @item -mno-crt0 |
14976 | @opindex mno-crt0 | |
14977 | Do not link in the C run-time initialization object file. | |
93ca1662 | 14978 | |
39bc1876 NS |
14979 | @item -mrelax |
14980 | @opindex mrelax | |
14981 | Indicate to the linker that it should perform a relaxation optimization pass | |
14982 | to shorten branches, calls and absolute memory addresses. This option only | |
14983 | has an effect when used on the command line for the final link step. | |
14984 | ||
14985 | This option makes symbolic debugging impossible. | |
74291a4b MM |
14986 | @end table |
14987 | ||
39bc1876 NS |
14988 | @node PDP-11 Options |
14989 | @subsection PDP-11 Options | |
14990 | @cindex PDP-11 Options | |
f84271d9 | 14991 | |
39bc1876 | 14992 | These options are defined for the PDP-11: |
f84271d9 | 14993 | |
2642624b | 14994 | @table @gcctabopt |
39bc1876 NS |
14995 | @item -mfpu |
14996 | @opindex mfpu | |
14997 | Use hardware FPP floating point. This is the default. (FIS floating | |
14998 | point on the PDP-11/40 is not supported.) | |
f84271d9 | 14999 | |
39bc1876 NS |
15000 | @item -msoft-float |
15001 | @opindex msoft-float | |
15002 | Do not use hardware floating point. | |
f84271d9 | 15003 | |
39bc1876 NS |
15004 | @item -mac0 |
15005 | @opindex mac0 | |
15006 | Return floating-point results in ac0 (fr0 in Unix assembler syntax). | |
f84271d9 | 15007 | |
39bc1876 NS |
15008 | @item -mno-ac0 |
15009 | @opindex mno-ac0 | |
15010 | Return floating-point results in memory. This is the default. | |
15011 | ||
15012 | @item -m40 | |
15013 | @opindex m40 | |
15014 | Generate code for a PDP-11/40. | |
15015 | ||
15016 | @item -m45 | |
15017 | @opindex m45 | |
15018 | Generate code for a PDP-11/45. This is the default. | |
f84271d9 | 15019 | |
39bc1876 NS |
15020 | @item -m10 |
15021 | @opindex m10 | |
15022 | Generate code for a PDP-11/10. | |
f84271d9 | 15023 | |
39bc1876 | 15024 | @item -mbcopy-builtin |
d376d545 | 15025 | @opindex mbcopy-builtin |
70128ad9 | 15026 | Use inline @code{movmemhi} patterns for copying memory. This is the |
39bc1876 | 15027 | default. |
f84271d9 | 15028 | |
39bc1876 NS |
15029 | @item -mbcopy |
15030 | @opindex mbcopy | |
70128ad9 | 15031 | Do not use inline @code{movmemhi} patterns for copying memory. |
02f52e19 | 15032 | |
39bc1876 NS |
15033 | @item -mint16 |
15034 | @itemx -mno-int32 | |
15035 | @opindex mint16 | |
15036 | @opindex mno-int32 | |
15037 | Use 16-bit @code{int}. This is the default. | |
48f0be1b | 15038 | |
39bc1876 NS |
15039 | @item -mint32 |
15040 | @itemx -mno-int16 | |
15041 | @opindex mint32 | |
15042 | @opindex mno-int16 | |
15043 | Use 32-bit @code{int}. | |
b4378319 | 15044 | |
39bc1876 NS |
15045 | @item -mfloat64 |
15046 | @itemx -mno-float32 | |
15047 | @opindex mfloat64 | |
15048 | @opindex mno-float32 | |
15049 | Use 64-bit @code{float}. This is the default. | |
b4378319 | 15050 | |
39bc1876 NS |
15051 | @item -mfloat32 |
15052 | @itemx -mno-float64 | |
15053 | @opindex mfloat32 | |
15054 | @opindex mno-float64 | |
15055 | Use 32-bit @code{float}. | |
daf2f129 | 15056 | |
39bc1876 NS |
15057 | @item -mabshi |
15058 | @opindex mabshi | |
15059 | Use @code{abshi2} pattern. This is the default. | |
232830b7 | 15060 | |
39bc1876 NS |
15061 | @item -mno-abshi |
15062 | @opindex mno-abshi | |
15063 | Do not use @code{abshi2} pattern. | |
b4378319 | 15064 | |
39bc1876 NS |
15065 | @item -mbranch-expensive |
15066 | @opindex mbranch-expensive | |
15067 | Pretend that branches are expensive. This is for experimenting with | |
15068 | code generation only. | |
b4378319 | 15069 | |
39bc1876 NS |
15070 | @item -mbranch-cheap |
15071 | @opindex mbranch-cheap | |
15072 | Do not pretend that branches are expensive. This is the default. | |
b4378319 | 15073 | |
39bc1876 NS |
15074 | @item -munix-asm |
15075 | @opindex munix-asm | |
15076 | Use Unix assembler syntax. This is the default when configured for | |
15077 | @samp{pdp11-*-bsd}. | |
56b2d7a7 | 15078 | |
39bc1876 NS |
15079 | @item -mdec-asm |
15080 | @opindex mdec-asm | |
15081 | Use DEC assembler syntax. This is the default when configured for any | |
15082 | PDP-11 target other than @samp{pdp11-*-bsd}. | |
15083 | @end table | |
56b2d7a7 | 15084 | |
358da97e HS |
15085 | @node picoChip Options |
15086 | @subsection picoChip Options | |
15087 | @cindex picoChip options | |
15088 | ||
15089 | These @samp{-m} options are defined for picoChip implementations: | |
15090 | ||
15091 | @table @gcctabopt | |
15092 | ||
15093 | @item -mae=@var{ae_type} | |
15094 | @opindex mcpu | |
15095 | Set the instruction set, register set, and instruction scheduling | |
15096 | parameters for array element type @var{ae_type}. Supported values | |
15097 | for @var{ae_type} are @samp{ANY}, @samp{MUL}, and @samp{MAC}. | |
15098 | ||
15099 | @option{-mae=ANY} selects a completely generic AE type. Code | |
15100 | generated with this option will run on any of the other AE types. The | |
15101 | code will not be as efficient as it would be if compiled for a specific | |
15102 | AE type, and some types of operation (e.g., multiplication) will not | |
15103 | work properly on all types of AE. | |
15104 | ||
15105 | @option{-mae=MUL} selects a MUL AE type. This is the most useful AE type | |
15106 | for compiled code, and is the default. | |
15107 | ||
15108 | @option{-mae=MAC} selects a DSP-style MAC AE. Code compiled with this | |
15109 | option may suffer from poor performance of byte (char) manipulation, | |
15110 | since the DSP AE does not provide hardware support for byte load/stores. | |
15111 | ||
15112 | @item -msymbol-as-address | |
15113 | Enable the compiler to directly use a symbol name as an address in a | |
15114 | load/store instruction, without first loading it into a | |
15115 | register. Typically, the use of this option will generate larger | |
15116 | programs, which run faster than when the option isn't used. However, the | |
15117 | results vary from program to program, so it is left as a user option, | |
15118 | rather than being permanently enabled. | |
15119 | ||
15120 | @item -mno-inefficient-warnings | |
15121 | Disables warnings about the generation of inefficient code. These | |
15122 | warnings can be generated, for example, when compiling code which | |
15123 | performs byte-level memory operations on the MAC AE type. The MAC AE has | |
15124 | no hardware support for byte-level memory operations, so all byte | |
a640c13b | 15125 | load/stores must be synthesized from word load/store operations. This is |
358da97e HS |
15126 | inefficient and a warning will be generated indicating to the programmer |
15127 | that they should rewrite the code to avoid byte operations, or to target | |
15128 | an AE type which has the necessary hardware support. This option enables | |
15129 | the warning to be turned off. | |
15130 | ||
15131 | @end table | |
15132 | ||
39bc1876 NS |
15133 | @node PowerPC Options |
15134 | @subsection PowerPC Options | |
15135 | @cindex PowerPC options | |
56b2d7a7 | 15136 | |
39bc1876 | 15137 | These are listed under @xref{RS/6000 and PowerPC Options}. |
56b2d7a7 | 15138 | |
39bc1876 NS |
15139 | @node RS/6000 and PowerPC Options |
15140 | @subsection IBM RS/6000 and PowerPC Options | |
15141 | @cindex RS/6000 and PowerPC Options | |
15142 | @cindex IBM RS/6000 and PowerPC Options | |
56b2d7a7 | 15143 | |
39bc1876 NS |
15144 | These @samp{-m} options are defined for the IBM RS/6000 and PowerPC: |
15145 | @table @gcctabopt | |
15146 | @item -mpower | |
15147 | @itemx -mno-power | |
15148 | @itemx -mpower2 | |
15149 | @itemx -mno-power2 | |
15150 | @itemx -mpowerpc | |
15151 | @itemx -mno-powerpc | |
15152 | @itemx -mpowerpc-gpopt | |
15153 | @itemx -mno-powerpc-gpopt | |
15154 | @itemx -mpowerpc-gfxopt | |
15155 | @itemx -mno-powerpc-gfxopt | |
ab940b73 | 15156 | @need 800 |
39bc1876 NS |
15157 | @itemx -mpowerpc64 |
15158 | @itemx -mno-powerpc64 | |
9719f3b7 DE |
15159 | @itemx -mmfcrf |
15160 | @itemx -mno-mfcrf | |
15161 | @itemx -mpopcntb | |
15162 | @itemx -mno-popcntb | |
29e6733c MM |
15163 | @itemx -mpopcntd |
15164 | @itemx -mno-popcntd | |
9719f3b7 DE |
15165 | @itemx -mfprnd |
15166 | @itemx -mno-fprnd | |
ab940b73 | 15167 | @need 800 |
b639c3c2 JJ |
15168 | @itemx -mcmpb |
15169 | @itemx -mno-cmpb | |
44cd321e PS |
15170 | @itemx -mmfpgpr |
15171 | @itemx -mno-mfpgpr | |
4daf6471 AK |
15172 | @itemx -mhard-dfp |
15173 | @itemx -mno-hard-dfp | |
39bc1876 NS |
15174 | @opindex mpower |
15175 | @opindex mno-power | |
15176 | @opindex mpower2 | |
15177 | @opindex mno-power2 | |
15178 | @opindex mpowerpc | |
15179 | @opindex mno-powerpc | |
15180 | @opindex mpowerpc-gpopt | |
15181 | @opindex mno-powerpc-gpopt | |
15182 | @opindex mpowerpc-gfxopt | |
15183 | @opindex mno-powerpc-gfxopt | |
15184 | @opindex mpowerpc64 | |
15185 | @opindex mno-powerpc64 | |
9719f3b7 DE |
15186 | @opindex mmfcrf |
15187 | @opindex mno-mfcrf | |
15188 | @opindex mpopcntb | |
15189 | @opindex mno-popcntb | |
29e6733c MM |
15190 | @opindex mpopcntd |
15191 | @opindex mno-popcntd | |
9719f3b7 DE |
15192 | @opindex mfprnd |
15193 | @opindex mno-fprnd | |
b639c3c2 JJ |
15194 | @opindex mcmpb |
15195 | @opindex mno-cmpb | |
44cd321e PS |
15196 | @opindex mmfpgpr |
15197 | @opindex mno-mfpgpr | |
4daf6471 AK |
15198 | @opindex mhard-dfp |
15199 | @opindex mno-hard-dfp | |
39bc1876 NS |
15200 | GCC supports two related instruction set architectures for the |
15201 | RS/6000 and PowerPC@. The @dfn{POWER} instruction set are those | |
15202 | instructions supported by the @samp{rios} chip set used in the original | |
15203 | RS/6000 systems and the @dfn{PowerPC} instruction set is the | |
9719f3b7 DE |
15204 | architecture of the Freescale MPC5xx, MPC6xx, MPC8xx microprocessors, and |
15205 | the IBM 4xx, 6xx, and follow-on microprocessors. | |
56b2d7a7 | 15206 | |
39bc1876 NS |
15207 | Neither architecture is a subset of the other. However there is a |
15208 | large common subset of instructions supported by both. An MQ | |
15209 | register is included in processors supporting the POWER architecture. | |
56b2d7a7 | 15210 | |
39bc1876 NS |
15211 | You use these options to specify which instructions are available on the |
15212 | processor you are using. The default value of these options is | |
15213 | determined when configuring GCC@. Specifying the | |
15214 | @option{-mcpu=@var{cpu_type}} overrides the specification of these | |
15215 | options. We recommend you use the @option{-mcpu=@var{cpu_type}} option | |
15216 | rather than the options listed above. | |
56b2d7a7 | 15217 | |
39bc1876 NS |
15218 | The @option{-mpower} option allows GCC to generate instructions that |
15219 | are found only in the POWER architecture and to use the MQ register. | |
15220 | Specifying @option{-mpower2} implies @option{-power} and also allows GCC | |
15221 | to generate instructions that are present in the POWER2 architecture but | |
15222 | not the original POWER architecture. | |
83575957 | 15223 | |
39bc1876 NS |
15224 | The @option{-mpowerpc} option allows GCC to generate instructions that |
15225 | are found only in the 32-bit subset of the PowerPC architecture. | |
15226 | Specifying @option{-mpowerpc-gpopt} implies @option{-mpowerpc} and also allows | |
15227 | GCC to use the optional PowerPC architecture instructions in the | |
15228 | General Purpose group, including floating-point square root. Specifying | |
15229 | @option{-mpowerpc-gfxopt} implies @option{-mpowerpc} and also allows GCC to | |
15230 | use the optional PowerPC architecture instructions in the Graphics | |
15231 | group, including floating-point select. | |
83575957 | 15232 | |
9719f3b7 DE |
15233 | The @option{-mmfcrf} option allows GCC to generate the move from |
15234 | condition register field instruction implemented on the POWER4 | |
15235 | processor and other processors that support the PowerPC V2.01 | |
15236 | architecture. | |
15237 | The @option{-mpopcntb} option allows GCC to generate the popcount and | |
15238 | double precision FP reciprocal estimate instruction implemented on the | |
15239 | POWER5 processor and other processors that support the PowerPC V2.02 | |
15240 | architecture. | |
29e6733c MM |
15241 | The @option{-mpopcntd} option allows GCC to generate the popcount |
15242 | instruction implemented on the POWER7 processor and other processors | |
15243 | that support the PowerPC V2.06 architecture. | |
9719f3b7 DE |
15244 | The @option{-mfprnd} option allows GCC to generate the FP round to |
15245 | integer instructions implemented on the POWER5+ processor and other | |
15246 | processors that support the PowerPC V2.03 architecture. | |
b639c3c2 JJ |
15247 | The @option{-mcmpb} option allows GCC to generate the compare bytes |
15248 | instruction implemented on the POWER6 processor and other processors | |
15249 | that support the PowerPC V2.05 architecture. | |
44cd321e PS |
15250 | The @option{-mmfpgpr} option allows GCC to generate the FP move to/from |
15251 | general purpose register instructions implemented on the POWER6X | |
15252 | processor and other processors that support the extended PowerPC V2.05 | |
15253 | architecture. | |
4daf6471 | 15254 | The @option{-mhard-dfp} option allows GCC to generate the decimal floating |
b639c3c2 | 15255 | point instructions implemented on some POWER processors. |
9719f3b7 | 15256 | |
39bc1876 NS |
15257 | The @option{-mpowerpc64} option allows GCC to generate the additional |
15258 | 64-bit instructions that are found in the full PowerPC64 architecture | |
15259 | and to treat GPRs as 64-bit, doubleword quantities. GCC defaults to | |
15260 | @option{-mno-powerpc64}. | |
83575957 | 15261 | |
39bc1876 NS |
15262 | If you specify both @option{-mno-power} and @option{-mno-powerpc}, GCC |
15263 | will use only the instructions in the common subset of both | |
15264 | architectures plus some special AIX common-mode calls, and will not use | |
15265 | the MQ register. Specifying both @option{-mpower} and @option{-mpowerpc} | |
15266 | permits GCC to use any instruction from either architecture and to | |
15267 | allow use of the MQ register; specify this for the Motorola MPC601. | |
83575957 | 15268 | |
39bc1876 NS |
15269 | @item -mnew-mnemonics |
15270 | @itemx -mold-mnemonics | |
15271 | @opindex mnew-mnemonics | |
15272 | @opindex mold-mnemonics | |
15273 | Select which mnemonics to use in the generated assembler code. With | |
15274 | @option{-mnew-mnemonics}, GCC uses the assembler mnemonics defined for | |
15275 | the PowerPC architecture. With @option{-mold-mnemonics} it uses the | |
15276 | assembler mnemonics defined for the POWER architecture. Instructions | |
15277 | defined in only one architecture have only one mnemonic; GCC uses that | |
15278 | mnemonic irrespective of which of these options is specified. | |
83575957 | 15279 | |
39bc1876 NS |
15280 | GCC defaults to the mnemonics appropriate for the architecture in |
15281 | use. Specifying @option{-mcpu=@var{cpu_type}} sometimes overrides the | |
15282 | value of these option. Unless you are building a cross-compiler, you | |
15283 | should normally not specify either @option{-mnew-mnemonics} or | |
15284 | @option{-mold-mnemonics}, but should instead accept the default. | |
83575957 | 15285 | |
39bc1876 NS |
15286 | @item -mcpu=@var{cpu_type} |
15287 | @opindex mcpu | |
15288 | Set architecture type, register usage, choice of mnemonics, and | |
15289 | instruction scheduling parameters for machine type @var{cpu_type}. | |
15290 | Supported values for @var{cpu_type} are @samp{401}, @samp{403}, | |
4adf8008 | 15291 | @samp{405}, @samp{405fp}, @samp{440}, @samp{440fp}, @samp{464}, @samp{464fp}, |
47f67e51 PB |
15292 | @samp{476}, @samp{476fp}, @samp{505}, @samp{601}, @samp{602}, @samp{603}, |
15293 | @samp{603e}, @samp{604}, @samp{604e}, @samp{620}, @samp{630}, @samp{740}, | |
15294 | @samp{7400}, @samp{7450}, @samp{750}, @samp{801}, @samp{821}, @samp{823}, | |
ebde32fd | 15295 | @samp{860}, @samp{970}, @samp{8540}, @samp{a2}, @samp{e300c2}, |
b17f98b1 | 15296 | @samp{e300c3}, @samp{e500mc}, @samp{e500mc64}, @samp{ec603e}, @samp{G3}, |
3c005e6c | 15297 | @samp{G4}, @samp{G5}, @samp{titan}, @samp{power}, @samp{power2}, @samp{power3}, |
b17f98b1 EW |
15298 | @samp{power4}, @samp{power5}, @samp{power5+}, @samp{power6}, @samp{power6x}, |
15299 | @samp{power7}, @samp{common}, @samp{powerpc}, @samp{powerpc64}, @samp{rios}, | |
edae5fe3 | 15300 | @samp{rios1}, @samp{rios2}, @samp{rsc}, and @samp{rs64}. |
83575957 | 15301 | |
39bc1876 NS |
15302 | @option{-mcpu=common} selects a completely generic processor. Code |
15303 | generated under this option will run on any POWER or PowerPC processor. | |
15304 | GCC will use only the instructions in the common subset of both | |
15305 | architectures, and will not use the MQ register. GCC assumes a generic | |
15306 | processor model for scheduling purposes. | |
83575957 | 15307 | |
39bc1876 NS |
15308 | @option{-mcpu=power}, @option{-mcpu=power2}, @option{-mcpu=powerpc}, and |
15309 | @option{-mcpu=powerpc64} specify generic POWER, POWER2, pure 32-bit | |
15310 | PowerPC (i.e., not MPC601), and 64-bit PowerPC architecture machine | |
15311 | types, with an appropriate, generic processor model assumed for | |
15312 | scheduling purposes. | |
83575957 | 15313 | |
39bc1876 NS |
15314 | The other options specify a specific processor. Code generated under |
15315 | those options will run best on that processor, and may not run at all on | |
15316 | others. | |
83575957 | 15317 | |
39bc1876 | 15318 | The @option{-mcpu} options automatically enable or disable the |
78681dbd RS |
15319 | following options: |
15320 | ||
15321 | @gccoptlist{-maltivec -mfprnd -mhard-float -mmfcrf -mmultiple @gol | |
29e6733c | 15322 | -mnew-mnemonics -mpopcntb -mpopcntd -mpower -mpower2 -mpowerpc64 @gol |
696e45ba | 15323 | -mpowerpc-gpopt -mpowerpc-gfxopt -msingle-float -mdouble-float @gol |
29e6733c | 15324 | -msimple-fpu -mstring -mmulhw -mdlmzb -mmfpgpr -mvsx} |
78681dbd | 15325 | |
44cd321e PS |
15326 | The particular options set for any particular CPU will vary between |
15327 | compiler versions, depending on what setting seems to produce optimal | |
15328 | code for that CPU; it doesn't necessarily reflect the actual hardware's | |
15329 | capabilities. If you wish to set an individual option to a particular | |
15330 | value, you may specify it after the @option{-mcpu} option, like | |
15331 | @samp{-mcpu=970 -mno-altivec}. | |
5d7c2819 | 15332 | |
39bc1876 | 15333 | On AIX, the @option{-maltivec} and @option{-mpowerpc64} options are |
9719f3b7 | 15334 | not enabled or disabled by the @option{-mcpu} option at present because |
39bc1876 NS |
15335 | AIX does not have full support for these options. You may still |
15336 | enable or disable them individually if you're sure it'll work in your | |
15337 | environment. | |
83575957 | 15338 | |
39bc1876 NS |
15339 | @item -mtune=@var{cpu_type} |
15340 | @opindex mtune | |
15341 | Set the instruction scheduling parameters for machine type | |
15342 | @var{cpu_type}, but do not set the architecture type, register usage, or | |
15343 | choice of mnemonics, as @option{-mcpu=@var{cpu_type}} would. The same | |
15344 | values for @var{cpu_type} are used for @option{-mtune} as for | |
15345 | @option{-mcpu}. If both are specified, the code generated will use the | |
15346 | architecture, registers, and mnemonics set by @option{-mcpu}, but the | |
15347 | scheduling parameters set by @option{-mtune}. | |
83575957 | 15348 | |
070b27da AM |
15349 | @item -mcmodel=small |
15350 | @opindex mcmodel=small | |
15351 | Generate PowerPC64 code for the small model: The TOC is limited to | |
15352 | 64k. | |
15353 | ||
5a79bcc4 AM |
15354 | @item -mcmodel=medium |
15355 | @opindex mcmodel=medium | |
15356 | Generate PowerPC64 code for the medium model: The TOC and other static | |
15357 | data may be up to a total of 4G in size. | |
15358 | ||
070b27da AM |
15359 | @item -mcmodel=large |
15360 | @opindex mcmodel=large | |
15361 | Generate PowerPC64 code for the large model: The TOC may be up to 4G | |
15362 | in size. Other data and code is only limited by the 64-bit address | |
15363 | space. | |
15364 | ||
39bc1876 NS |
15365 | @item -maltivec |
15366 | @itemx -mno-altivec | |
15367 | @opindex maltivec | |
15368 | @opindex mno-altivec | |
7088c6e4 GK |
15369 | Generate code that uses (does not use) AltiVec instructions, and also |
15370 | enable the use of built-in functions that allow more direct access to | |
15371 | the AltiVec instruction set. You may also need to set | |
39bc1876 NS |
15372 | @option{-mabi=altivec} to adjust the current ABI with AltiVec ABI |
15373 | enhancements. | |
83575957 | 15374 | |
78f5898b | 15375 | @item -mvrsave |
33558d94 | 15376 | @itemx -mno-vrsave |
78f5898b AH |
15377 | @opindex mvrsave |
15378 | @opindex mno-vrsave | |
15379 | Generate VRSAVE instructions when generating AltiVec code. | |
15380 | ||
c921bad8 AP |
15381 | @item -mgen-cell-microcode |
15382 | @opindex mgen-cell-microcode | |
15383 | Generate Cell microcode instructions | |
15384 | ||
15385 | @item -mwarn-cell-microcode | |
15386 | @opindex mwarn-cell-microcode | |
15387 | Warning when a Cell microcode instruction is going to emitted. An example | |
15388 | of a Cell microcode instruction is a variable shift. | |
15389 | ||
7f970b70 AM |
15390 | @item -msecure-plt |
15391 | @opindex msecure-plt | |
15392 | Generate code that allows ld and ld.so to build executables and shared | |
15393 | libraries with non-exec .plt and .got sections. This is a PowerPC | |
15394 | 32-bit SYSV ABI option. | |
15395 | ||
15396 | @item -mbss-plt | |
15397 | @opindex mbss-plt | |
15398 | Generate code that uses a BSS .plt section that ld.so fills in, and | |
15399 | requires .plt and .got sections that are both writable and executable. | |
15400 | This is a PowerPC 32-bit SYSV ABI option. | |
15401 | ||
78f5898b AH |
15402 | @item -misel |
15403 | @itemx -mno-isel | |
39bc1876 | 15404 | @opindex misel |
78f5898b | 15405 | @opindex mno-isel |
39bc1876 | 15406 | This switch enables or disables the generation of ISEL instructions. |
83575957 | 15407 | |
78f5898b AH |
15408 | @item -misel=@var{yes/no} |
15409 | This switch has been deprecated. Use @option{-misel} and | |
15410 | @option{-mno-isel} instead. | |
15411 | ||
15412 | @item -mspe | |
ea574900 | 15413 | @itemx -mno-spe |
39bc1876 | 15414 | @opindex mspe |
78f5898b | 15415 | @opindex mno-spe |
39bc1876 NS |
15416 | This switch enables or disables the generation of SPE simd |
15417 | instructions. | |
83575957 | 15418 | |
96038623 DE |
15419 | @item -mpaired |
15420 | @itemx -mno-paired | |
15421 | @opindex mpaired | |
15422 | @opindex mno-paired | |
15423 | This switch enables or disables the generation of PAIRED simd | |
15424 | instructions. | |
15425 | ||
78f5898b AH |
15426 | @item -mspe=@var{yes/no} |
15427 | This option has been deprecated. Use @option{-mspe} and | |
15428 | @option{-mno-spe} instead. | |
15429 | ||
29e6733c MM |
15430 | @item -mvsx |
15431 | @itemx -mno-vsx | |
15432 | @opindex mvsx | |
15433 | @opindex mno-vsx | |
15434 | Generate code that uses (does not use) vector/scalar (VSX) | |
15435 | instructions, and also enable the use of built-in functions that allow | |
15436 | more direct access to the VSX instruction set. | |
15437 | ||
4d4cbc0e | 15438 | @item -mfloat-gprs=@var{yes/single/double/no} |
39bc1876 NS |
15439 | @itemx -mfloat-gprs |
15440 | @opindex mfloat-gprs | |
15441 | This switch enables or disables the generation of floating point | |
15442 | operations on the general purpose registers for architectures that | |
4d4cbc0e AH |
15443 | support it. |
15444 | ||
15445 | The argument @var{yes} or @var{single} enables the use of | |
15446 | single-precision floating point operations. | |
15447 | ||
15448 | The argument @var{double} enables the use of single and | |
15449 | double-precision floating point operations. | |
15450 | ||
15451 | The argument @var{no} disables floating point operations on the | |
15452 | general purpose registers. | |
15453 | ||
15454 | This option is currently only available on the MPC854x. | |
83575957 | 15455 | |
49bd1d27 SS |
15456 | @item -m32 |
15457 | @itemx -m64 | |
15458 | @opindex m32 | |
15459 | @opindex m64 | |
15460 | Generate code for 32-bit or 64-bit environments of Darwin and SVR4 | |
15461 | targets (including GNU/Linux). The 32-bit environment sets int, long | |
15462 | and pointer to 32 bits and generates code that runs on any PowerPC | |
15463 | variant. The 64-bit environment sets int to 32 bits and long and | |
15464 | pointer to 64 bits, and generates code for PowerPC64, as for | |
15465 | @option{-mpowerpc64}. | |
15466 | ||
39bc1876 NS |
15467 | @item -mfull-toc |
15468 | @itemx -mno-fp-in-toc | |
15469 | @itemx -mno-sum-in-toc | |
15470 | @itemx -mminimal-toc | |
15471 | @opindex mfull-toc | |
15472 | @opindex mno-fp-in-toc | |
15473 | @opindex mno-sum-in-toc | |
15474 | @opindex mminimal-toc | |
15475 | Modify generation of the TOC (Table Of Contents), which is created for | |
15476 | every executable file. The @option{-mfull-toc} option is selected by | |
15477 | default. In that case, GCC will allocate at least one TOC entry for | |
15478 | each unique non-automatic variable reference in your program. GCC | |
15479 | will also place floating-point constants in the TOC@. However, only | |
15480 | 16,384 entries are available in the TOC@. | |
83575957 | 15481 | |
39bc1876 NS |
15482 | If you receive a linker error message that saying you have overflowed |
15483 | the available TOC space, you can reduce the amount of TOC space used | |
15484 | with the @option{-mno-fp-in-toc} and @option{-mno-sum-in-toc} options. | |
15485 | @option{-mno-fp-in-toc} prevents GCC from putting floating-point | |
15486 | constants in the TOC and @option{-mno-sum-in-toc} forces GCC to | |
15487 | generate code to calculate the sum of an address and a constant at | |
15488 | run-time instead of putting that sum into the TOC@. You may specify one | |
15489 | or both of these options. Each causes GCC to produce very slightly | |
15490 | slower and larger code at the expense of conserving TOC space. | |
83575957 | 15491 | |
39bc1876 NS |
15492 | If you still run out of space in the TOC even when you specify both of |
15493 | these options, specify @option{-mminimal-toc} instead. This option causes | |
15494 | GCC to make only one TOC entry for every file. When you specify this | |
15495 | option, GCC will produce code that is slower and larger but which | |
15496 | uses extremely little TOC space. You may wish to use this option | |
15497 | only on files that contain less frequently executed code. | |
83575957 | 15498 | |
39bc1876 NS |
15499 | @item -maix64 |
15500 | @itemx -maix32 | |
15501 | @opindex maix64 | |
15502 | @opindex maix32 | |
15503 | Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit | |
15504 | @code{long} type, and the infrastructure needed to support them. | |
15505 | Specifying @option{-maix64} implies @option{-mpowerpc64} and | |
15506 | @option{-mpowerpc}, while @option{-maix32} disables the 64-bit ABI and | |
15507 | implies @option{-mno-powerpc64}. GCC defaults to @option{-maix32}. | |
83575957 | 15508 | |
de17c25f DE |
15509 | @item -mxl-compat |
15510 | @itemx -mno-xl-compat | |
15511 | @opindex mxl-compat | |
15512 | @opindex mno-xl-compat | |
8fbe3bb2 | 15513 | Produce code that conforms more closely to IBM XL compiler semantics |
0ee2ea09 | 15514 | when using AIX-compatible ABI@. Pass floating-point arguments to |
8fbe3bb2 DE |
15515 | prototyped functions beyond the register save area (RSA) on the stack |
15516 | in addition to argument FPRs. Do not assume that most significant | |
15517 | double in 128-bit long double value is properly rounded when comparing | |
15518 | values and converting to double. Use XL symbol names for long double | |
15519 | support routines. | |
de17c25f DE |
15520 | |
15521 | The AIX calling convention was extended but not initially documented to | |
39bc1876 | 15522 | handle an obscure K&R C case of calling a function that takes the |
8fbe3bb2 | 15523 | address of its arguments with fewer arguments than declared. IBM XL |
39bc1876 NS |
15524 | compilers access floating point arguments which do not fit in the |
15525 | RSA from the stack when a subroutine is compiled without | |
15526 | optimization. Because always storing floating-point arguments on the | |
15527 | stack is inefficient and rarely needed, this option is not enabled by | |
8fbe3bb2 | 15528 | default and only is necessary when calling subroutines compiled by IBM |
39bc1876 | 15529 | XL compilers without optimization. |
83575957 | 15530 | |
39bc1876 NS |
15531 | @item -mpe |
15532 | @opindex mpe | |
15533 | Support @dfn{IBM RS/6000 SP} @dfn{Parallel Environment} (PE)@. Link an | |
15534 | application written to use message passing with special startup code to | |
15535 | enable the application to run. The system must have PE installed in the | |
15536 | standard location (@file{/usr/lpp/ppe.poe/}), or the @file{specs} file | |
15537 | must be overridden with the @option{-specs=} option to specify the | |
15538 | appropriate directory location. The Parallel Environment does not | |
15539 | support threads, so the @option{-mpe} option and the @option{-pthread} | |
15540 | option are incompatible. | |
83575957 | 15541 | |
39bc1876 NS |
15542 | @item -malign-natural |
15543 | @itemx -malign-power | |
15544 | @opindex malign-natural | |
15545 | @opindex malign-power | |
d9168963 | 15546 | On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the option |
39bc1876 NS |
15547 | @option{-malign-natural} overrides the ABI-defined alignment of larger |
15548 | types, such as floating-point doubles, on their natural size-based boundary. | |
15549 | The option @option{-malign-power} instructs GCC to follow the ABI-specified | |
8a36672b | 15550 | alignment rules. GCC defaults to the standard alignment defined in the ABI@. |
83575957 | 15551 | |
d9168963 SS |
15552 | On 64-bit Darwin, natural alignment is the default, and @option{-malign-power} |
15553 | is not supported. | |
15554 | ||
39bc1876 NS |
15555 | @item -msoft-float |
15556 | @itemx -mhard-float | |
15557 | @opindex msoft-float | |
15558 | @opindex mhard-float | |
15559 | Generate code that does not use (uses) the floating-point register set. | |
15560 | Software floating point emulation is provided if you use the | |
15561 | @option{-msoft-float} option, and pass the option to GCC when linking. | |
83575957 | 15562 | |
696e45ba ME |
15563 | @item -msingle-float |
15564 | @itemx -mdouble-float | |
15565 | @opindex msingle-float | |
15566 | @opindex mdouble-float | |
7a61cf6f NC |
15567 | Generate code for single or double-precision floating point operations. |
15568 | @option{-mdouble-float} implies @option{-msingle-float}. | |
696e45ba ME |
15569 | |
15570 | @item -msimple-fpu | |
15571 | @opindex msimple-fpu | |
15572 | Do not generate sqrt and div instructions for hardware floating point unit. | |
15573 | ||
0bb7b92e ME |
15574 | @item -mfpu |
15575 | @opindex mfpu | |
7a61cf6f | 15576 | Specify type of floating point unit. Valid values are @var{sp_lite} |
0bb7b92e ME |
15577 | (equivalent to -msingle-float -msimple-fpu), @var{dp_lite} (equivalent |
15578 | to -mdouble-float -msimple-fpu), @var{sp_full} (equivalent to -msingle-float), | |
15579 | and @var{dp_full} (equivalent to -mdouble-float). | |
15580 | ||
15581 | @item -mxilinx-fpu | |
15582 | @opindex mxilinx-fpu | |
15583 | Perform optimizations for floating point unit on Xilinx PPC 405/440. | |
15584 | ||
39bc1876 NS |
15585 | @item -mmultiple |
15586 | @itemx -mno-multiple | |
15587 | @opindex mmultiple | |
15588 | @opindex mno-multiple | |
15589 | Generate code that uses (does not use) the load multiple word | |
15590 | instructions and the store multiple word instructions. These | |
15591 | instructions are generated by default on POWER systems, and not | |
15592 | generated on PowerPC systems. Do not use @option{-mmultiple} on little | |
15593 | endian PowerPC systems, since those instructions do not work when the | |
15594 | processor is in little endian mode. The exceptions are PPC740 and | |
15595 | PPC750 which permit the instructions usage in little endian mode. | |
83575957 | 15596 | |
39bc1876 NS |
15597 | @item -mstring |
15598 | @itemx -mno-string | |
15599 | @opindex mstring | |
15600 | @opindex mno-string | |
15601 | Generate code that uses (does not use) the load string instructions | |
15602 | and the store string word instructions to save multiple registers and | |
15603 | do small block moves. These instructions are generated by default on | |
15604 | POWER systems, and not generated on PowerPC systems. Do not use | |
15605 | @option{-mstring} on little endian PowerPC systems, since those | |
15606 | instructions do not work when the processor is in little endian mode. | |
15607 | The exceptions are PPC740 and PPC750 which permit the instructions | |
15608 | usage in little endian mode. | |
052a4b28 | 15609 | |
39bc1876 NS |
15610 | @item -mupdate |
15611 | @itemx -mno-update | |
15612 | @opindex mupdate | |
15613 | @opindex mno-update | |
15614 | Generate code that uses (does not use) the load or store instructions | |
15615 | that update the base register to the address of the calculated memory | |
15616 | location. These instructions are generated by default. If you use | |
15617 | @option{-mno-update}, there is a small window between the time that the | |
15618 | stack pointer is updated and the address of the previous frame is | |
15619 | stored, which means code that walks the stack frame across interrupts or | |
15620 | signals may get corrupted data. | |
052a4b28 | 15621 | |
001b9eb6 | 15622 | @item -mavoid-indexed-addresses |
1588fb31 | 15623 | @itemx -mno-avoid-indexed-addresses |
001b9eb6 PH |
15624 | @opindex mavoid-indexed-addresses |
15625 | @opindex mno-avoid-indexed-addresses | |
15626 | Generate code that tries to avoid (not avoid) the use of indexed load | |
15627 | or store instructions. These instructions can incur a performance | |
15628 | penalty on Power6 processors in certain situations, such as when | |
15629 | stepping through large arrays that cross a 16M boundary. This option | |
15630 | is enabled by default when targetting Power6 and disabled otherwise. | |
15631 | ||
39bc1876 NS |
15632 | @item -mfused-madd |
15633 | @itemx -mno-fused-madd | |
15634 | @opindex mfused-madd | |
15635 | @opindex mno-fused-madd | |
15636 | Generate code that uses (does not use) the floating point multiply and | |
fd438373 MM |
15637 | accumulate instructions. These instructions are generated by default |
15638 | if hardware floating point is used. The machine dependent | |
15639 | @option{-mfused-madd} option is now mapped to the machine independent | |
15640 | @option{-ffp-contract=fast} option, and @option{-mno-fused-madd} is | |
15641 | mapped to @option{-ffp-contract=off}. | |
3a69a7d5 | 15642 | |
131aeb82 JM |
15643 | @item -mmulhw |
15644 | @itemx -mno-mulhw | |
15645 | @opindex mmulhw | |
15646 | @opindex mno-mulhw | |
15647 | Generate code that uses (does not use) the half-word multiply and | |
47f67e51 | 15648 | multiply-accumulate instructions on the IBM 405, 440, 464 and 476 processors. |
131aeb82 JM |
15649 | These instructions are generated by default when targetting those |
15650 | processors. | |
15651 | ||
716019c0 JM |
15652 | @item -mdlmzb |
15653 | @itemx -mno-dlmzb | |
15654 | @opindex mdlmzb | |
15655 | @opindex mno-dlmzb | |
15656 | Generate code that uses (does not use) the string-search @samp{dlmzb} | |
47f67e51 | 15657 | instruction on the IBM 405, 440, 464 and 476 processors. This instruction is |
716019c0 JM |
15658 | generated by default when targetting those processors. |
15659 | ||
39bc1876 NS |
15660 | @item -mno-bit-align |
15661 | @itemx -mbit-align | |
15662 | @opindex mno-bit-align | |
15663 | @opindex mbit-align | |
15664 | On System V.4 and embedded PowerPC systems do not (do) force structures | |
15665 | and unions that contain bit-fields to be aligned to the base type of the | |
15666 | bit-field. | |
3a69a7d5 | 15667 | |
39bc1876 NS |
15668 | For example, by default a structure containing nothing but 8 |
15669 | @code{unsigned} bit-fields of length 1 would be aligned to a 4 byte | |
15670 | boundary and have a size of 4 bytes. By using @option{-mno-bit-align}, | |
15671 | the structure would be aligned to a 1 byte boundary and be one byte in | |
15672 | size. | |
3a69a7d5 | 15673 | |
39bc1876 NS |
15674 | @item -mno-strict-align |
15675 | @itemx -mstrict-align | |
15676 | @opindex mno-strict-align | |
15677 | @opindex mstrict-align | |
15678 | On System V.4 and embedded PowerPC systems do not (do) assume that | |
15679 | unaligned memory references will be handled by the system. | |
3a69a7d5 | 15680 | |
39bc1876 NS |
15681 | @item -mrelocatable |
15682 | @itemx -mno-relocatable | |
15683 | @opindex mrelocatable | |
15684 | @opindex mno-relocatable | |
4942323e AM |
15685 | Generate code that allows (does not allow) a static executable to be |
15686 | relocated to a different address at runtime. A simple embedded | |
15687 | PowerPC system loader should relocate the entire contents of | |
15688 | @code{.got2} and 4-byte locations listed in the @code{.fixup} section, | |
15689 | a table of 32-bit addresses generated by this option. For this to | |
15690 | work, all objects linked together must be compiled with | |
15691 | @option{-mrelocatable} or @option{-mrelocatable-lib}. | |
15692 | @option{-mrelocatable} code aligns the stack to an 8 byte boundary. | |
3a69a7d5 | 15693 | |
39bc1876 NS |
15694 | @item -mrelocatable-lib |
15695 | @itemx -mno-relocatable-lib | |
15696 | @opindex mrelocatable-lib | |
15697 | @opindex mno-relocatable-lib | |
4942323e AM |
15698 | Like @option{-mrelocatable}, @option{-mrelocatable-lib} generates a |
15699 | @code{.fixup} section to allow static executables to be relocated at | |
15700 | runtime, but @option{-mrelocatable-lib} does not use the smaller stack | |
15701 | alignment of @option{-mrelocatable}. Objects compiled with | |
15702 | @option{-mrelocatable-lib} may be linked with objects compiled with | |
15703 | any combination of the @option{-mrelocatable} options. | |
052a4b28 | 15704 | |
39bc1876 NS |
15705 | @item -mno-toc |
15706 | @itemx -mtoc | |
15707 | @opindex mno-toc | |
15708 | @opindex mtoc | |
15709 | On System V.4 and embedded PowerPC systems do not (do) assume that | |
15710 | register 2 contains a pointer to a global area pointing to the addresses | |
15711 | used in the program. | |
052a4b28 | 15712 | |
39bc1876 NS |
15713 | @item -mlittle |
15714 | @itemx -mlittle-endian | |
15715 | @opindex mlittle | |
15716 | @opindex mlittle-endian | |
15717 | On System V.4 and embedded PowerPC systems compile code for the | |
15718 | processor in little endian mode. The @option{-mlittle-endian} option is | |
15719 | the same as @option{-mlittle}. | |
052a4b28 | 15720 | |
39bc1876 NS |
15721 | @item -mbig |
15722 | @itemx -mbig-endian | |
15723 | @opindex mbig | |
15724 | @opindex mbig-endian | |
15725 | On System V.4 and embedded PowerPC systems compile code for the | |
15726 | processor in big endian mode. The @option{-mbig-endian} option is | |
15727 | the same as @option{-mbig}. | |
052a4b28 | 15728 | |
39bc1876 NS |
15729 | @item -mdynamic-no-pic |
15730 | @opindex mdynamic-no-pic | |
15731 | On Darwin and Mac OS X systems, compile code so that it is not | |
15732 | relocatable, but that its external references are relocatable. The | |
15733 | resulting code is suitable for applications, but not shared | |
15734 | libraries. | |
3a69a7d5 | 15735 | |
042abba2 JT |
15736 | @item -msingle-pic-base |
15737 | @opindex msingle-pic-base | |
15738 | Treat the register used for PIC addressing as read-only, rather than | |
15739 | loading it in the prologue for each function. The run-time system is | |
15740 | responsible for initializing this register with an appropriate value | |
15741 | before execution begins. | |
15742 | ||
39bc1876 NS |
15743 | @item -mprioritize-restricted-insns=@var{priority} |
15744 | @opindex mprioritize-restricted-insns | |
15745 | This option controls the priority that is assigned to | |
15746 | dispatch-slot restricted instructions during the second scheduling | |
15747 | pass. The argument @var{priority} takes the value @var{0/1/2} to assign | |
15748 | @var{no/highest/second-highest} priority to dispatch slot restricted | |
15749 | instructions. | |
3a69a7d5 | 15750 | |
39bc1876 NS |
15751 | @item -msched-costly-dep=@var{dependence_type} |
15752 | @opindex msched-costly-dep | |
15753 | This option controls which dependences are considered costly | |
15754 | by the target during instruction scheduling. The argument | |
15755 | @var{dependence_type} takes one of the following values: | |
15756 | @var{no}: no dependence is costly, | |
15757 | @var{all}: all dependences are costly, | |
15758 | @var{true_store_to_load}: a true dependence from store to load is costly, | |
15759 | @var{store_to_load}: any dependence from store to load is costly, | |
15760 | @var{number}: any dependence which latency >= @var{number} is costly. | |
11338cda | 15761 | |
39bc1876 NS |
15762 | @item -minsert-sched-nops=@var{scheme} |
15763 | @opindex minsert-sched-nops | |
15764 | This option controls which nop insertion scheme will be used during | |
8a36672b | 15765 | the second scheduling pass. The argument @var{scheme} takes one of the |
39bc1876 NS |
15766 | following values: |
15767 | @var{no}: Don't insert nops. | |
15768 | @var{pad}: Pad with nops any dispatch group which has vacant issue slots, | |
15769 | according to the scheduler's grouping. | |
15770 | @var{regroup_exact}: Insert nops to force costly dependent insns into | |
15771 | separate groups. Insert exactly as many nops as needed to force an insn | |
15772 | to a new group, according to the estimated processor grouping. | |
15773 | @var{number}: Insert nops to force costly dependent insns into | |
15774 | separate groups. Insert @var{number} nops to force an insn to a new group. | |
052a4b28 | 15775 | |
39bc1876 NS |
15776 | @item -mcall-sysv |
15777 | @opindex mcall-sysv | |
15778 | On System V.4 and embedded PowerPC systems compile code using calling | |
15779 | conventions that adheres to the March 1995 draft of the System V | |
15780 | Application Binary Interface, PowerPC processor supplement. This is the | |
15781 | default unless you configured GCC using @samp{powerpc-*-eabiaix}. | |
789a3090 | 15782 | |
39bc1876 | 15783 | @item -mcall-sysv-eabi |
244609a6 | 15784 | @itemx -mcall-eabi |
39bc1876 | 15785 | @opindex mcall-sysv-eabi |
244609a6 | 15786 | @opindex mcall-eabi |
39bc1876 | 15787 | Specify both @option{-mcall-sysv} and @option{-meabi} options. |
789a3090 | 15788 | |
39bc1876 NS |
15789 | @item -mcall-sysv-noeabi |
15790 | @opindex mcall-sysv-noeabi | |
15791 | Specify both @option{-mcall-sysv} and @option{-mno-eabi} options. | |
789a3090 | 15792 | |
244609a6 BE |
15793 | @item -mcall-aixdesc |
15794 | @opindex m | |
15795 | On System V.4 and embedded PowerPC systems compile code for the AIX | |
39bc1876 | 15796 | operating system. |
789a3090 | 15797 | |
39bc1876 NS |
15798 | @item -mcall-linux |
15799 | @opindex mcall-linux | |
15800 | On System V.4 and embedded PowerPC systems compile code for the | |
15801 | Linux-based GNU system. | |
789a3090 | 15802 | |
39bc1876 NS |
15803 | @item -mcall-gnu |
15804 | @opindex mcall-gnu | |
15805 | On System V.4 and embedded PowerPC systems compile code for the | |
15806 | Hurd-based GNU system. | |
789a3090 | 15807 | |
244609a6 BE |
15808 | @item -mcall-freebsd |
15809 | @opindex mcall-freebsd | |
15810 | On System V.4 and embedded PowerPC systems compile code for the | |
15811 | FreeBSD operating system. | |
15812 | ||
39bc1876 NS |
15813 | @item -mcall-netbsd |
15814 | @opindex mcall-netbsd | |
15815 | On System V.4 and embedded PowerPC systems compile code for the | |
15816 | NetBSD operating system. | |
789a3090 | 15817 | |
244609a6 BE |
15818 | @item -mcall-openbsd |
15819 | @opindex mcall-netbsd | |
15820 | On System V.4 and embedded PowerPC systems compile code for the | |
15821 | OpenBSD operating system. | |
15822 | ||
39bc1876 NS |
15823 | @item -maix-struct-return |
15824 | @opindex maix-struct-return | |
15825 | Return all structures in memory (as specified by the AIX ABI)@. | |
789a3090 | 15826 | |
39bc1876 NS |
15827 | @item -msvr4-struct-return |
15828 | @opindex msvr4-struct-return | |
15829 | Return structures smaller than 8 bytes in registers (as specified by the | |
15830 | SVR4 ABI)@. | |
789a3090 | 15831 | |
78f5898b AH |
15832 | @item -mabi=@var{abi-type} |
15833 | @opindex mabi | |
15834 | Extend the current ABI with a particular extension, or remove such extension. | |
15835 | Valid values are @var{altivec}, @var{no-altivec}, @var{spe}, | |
602ea4d3 JJ |
15836 | @var{no-spe}, @var{ibmlongdouble}, @var{ieeelongdouble}@. |
15837 | ||
15838 | @item -mabi=spe | |
15839 | @opindex mabi=spe | |
15840 | Extend the current ABI with SPE ABI extensions. This does not change | |
15841 | the default ABI, instead it adds the SPE ABI extensions to the current | |
15842 | ABI@. | |
15843 | ||
15844 | @item -mabi=no-spe | |
15845 | @opindex mabi=no-spe | |
15846 | Disable Booke SPE ABI extensions for the current ABI@. | |
15847 | ||
15848 | @item -mabi=ibmlongdouble | |
15849 | @opindex mabi=ibmlongdouble | |
15850 | Change the current ABI to use IBM extended precision long double. | |
15851 | This is a PowerPC 32-bit SYSV ABI option. | |
15852 | ||
15853 | @item -mabi=ieeelongdouble | |
15854 | @opindex mabi=ieeelongdouble | |
15855 | Change the current ABI to use IEEE extended precision long double. | |
15856 | This is a PowerPC 32-bit Linux ABI option. | |
789a3090 | 15857 | |
39bc1876 NS |
15858 | @item -mprototype |
15859 | @itemx -mno-prototype | |
15860 | @opindex mprototype | |
15861 | @opindex mno-prototype | |
15862 | On System V.4 and embedded PowerPC systems assume that all calls to | |
15863 | variable argument functions are properly prototyped. Otherwise, the | |
15864 | compiler must insert an instruction before every non prototyped call to | |
15865 | set or clear bit 6 of the condition code register (@var{CR}) to | |
15866 | indicate whether floating point values were passed in the floating point | |
15867 | registers in case the function takes a variable arguments. With | |
15868 | @option{-mprototype}, only calls to prototyped variable argument functions | |
15869 | will set or clear the bit. | |
83575957 | 15870 | |
39bc1876 NS |
15871 | @item -msim |
15872 | @opindex msim | |
15873 | On embedded PowerPC systems, assume that the startup module is called | |
15874 | @file{sim-crt0.o} and that the standard C libraries are @file{libsim.a} and | |
a31cfd58 | 15875 | @file{libc.a}. This is the default for @samp{powerpc-*-eabisim} |
39bc1876 | 15876 | configurations. |
df6194d4 | 15877 | |
39bc1876 NS |
15878 | @item -mmvme |
15879 | @opindex mmvme | |
15880 | On embedded PowerPC systems, assume that the startup module is called | |
15881 | @file{crt0.o} and the standard C libraries are @file{libmvme.a} and | |
15882 | @file{libc.a}. | |
df6194d4 | 15883 | |
39bc1876 NS |
15884 | @item -mads |
15885 | @opindex mads | |
15886 | On embedded PowerPC systems, assume that the startup module is called | |
15887 | @file{crt0.o} and the standard C libraries are @file{libads.a} and | |
15888 | @file{libc.a}. | |
df6194d4 | 15889 | |
39bc1876 NS |
15890 | @item -myellowknife |
15891 | @opindex myellowknife | |
15892 | On embedded PowerPC systems, assume that the startup module is called | |
15893 | @file{crt0.o} and the standard C libraries are @file{libyk.a} and | |
15894 | @file{libc.a}. | |
df6194d4 | 15895 | |
39bc1876 NS |
15896 | @item -mvxworks |
15897 | @opindex mvxworks | |
15898 | On System V.4 and embedded PowerPC systems, specify that you are | |
15899 | compiling for a VxWorks system. | |
df6194d4 | 15900 | |
39bc1876 NS |
15901 | @item -memb |
15902 | @opindex memb | |
15903 | On embedded PowerPC systems, set the @var{PPC_EMB} bit in the ELF flags | |
15904 | header to indicate that @samp{eabi} extended relocations are used. | |
df6194d4 | 15905 | |
39bc1876 NS |
15906 | @item -meabi |
15907 | @itemx -mno-eabi | |
15908 | @opindex meabi | |
15909 | @opindex mno-eabi | |
15910 | On System V.4 and embedded PowerPC systems do (do not) adhere to the | |
15911 | Embedded Applications Binary Interface (eabi) which is a set of | |
15912 | modifications to the System V.4 specifications. Selecting @option{-meabi} | |
15913 | means that the stack is aligned to an 8 byte boundary, a function | |
15914 | @code{__eabi} is called to from @code{main} to set up the eabi | |
15915 | environment, and the @option{-msdata} option can use both @code{r2} and | |
15916 | @code{r13} to point to two separate small data areas. Selecting | |
15917 | @option{-mno-eabi} means that the stack is aligned to a 16 byte boundary, | |
15918 | do not call an initialization function from @code{main}, and the | |
15919 | @option{-msdata} option will only use @code{r13} to point to a single | |
15920 | small data area. The @option{-meabi} option is on by default if you | |
15921 | configured GCC using one of the @samp{powerpc*-*-eabi*} options. | |
df6194d4 | 15922 | |
39bc1876 NS |
15923 | @item -msdata=eabi |
15924 | @opindex msdata=eabi | |
15925 | On System V.4 and embedded PowerPC systems, put small initialized | |
15926 | @code{const} global and static data in the @samp{.sdata2} section, which | |
15927 | is pointed to by register @code{r2}. Put small initialized | |
15928 | non-@code{const} global and static data in the @samp{.sdata} section, | |
15929 | which is pointed to by register @code{r13}. Put small uninitialized | |
15930 | global and static data in the @samp{.sbss} section, which is adjacent to | |
15931 | the @samp{.sdata} section. The @option{-msdata=eabi} option is | |
15932 | incompatible with the @option{-mrelocatable} option. The | |
15933 | @option{-msdata=eabi} option also sets the @option{-memb} option. | |
df6194d4 | 15934 | |
39bc1876 NS |
15935 | @item -msdata=sysv |
15936 | @opindex msdata=sysv | |
15937 | On System V.4 and embedded PowerPC systems, put small global and static | |
15938 | data in the @samp{.sdata} section, which is pointed to by register | |
15939 | @code{r13}. Put small uninitialized global and static data in the | |
15940 | @samp{.sbss} section, which is adjacent to the @samp{.sdata} section. | |
15941 | The @option{-msdata=sysv} option is incompatible with the | |
15942 | @option{-mrelocatable} option. | |
df6194d4 | 15943 | |
39bc1876 | 15944 | @item -msdata=default |
df6194d4 | 15945 | @itemx -msdata |
39bc1876 | 15946 | @opindex msdata=default |
cd3bb277 | 15947 | @opindex msdata |
39bc1876 NS |
15948 | On System V.4 and embedded PowerPC systems, if @option{-meabi} is used, |
15949 | compile code the same as @option{-msdata=eabi}, otherwise compile code the | |
15950 | same as @option{-msdata=sysv}. | |
df6194d4 | 15951 | |
64e4a1a6 BE |
15952 | @item -msdata=data |
15953 | @opindex msdata=data | |
05f25017 AM |
15954 | On System V.4 and embedded PowerPC systems, put small global |
15955 | data in the @samp{.sdata} section. Put small uninitialized global | |
15956 | data in the @samp{.sbss} section. Do not use register @code{r13} | |
39bc1876 NS |
15957 | to address small data however. This is the default behavior unless |
15958 | other @option{-msdata} options are used. | |
df6194d4 | 15959 | |
39bc1876 NS |
15960 | @item -msdata=none |
15961 | @itemx -mno-sdata | |
15962 | @opindex msdata=none | |
15963 | @opindex mno-sdata | |
15964 | On embedded PowerPC systems, put all initialized global and static data | |
15965 | in the @samp{.data} section, and all uninitialized data in the | |
15966 | @samp{.bss} section. | |
df6194d4 | 15967 | |
d95016e0 NF |
15968 | @item -mblock-move-inline-limit=@var{num} |
15969 | @opindex mblock-move-inline-limit | |
15970 | Inline all block moves (such as calls to @code{memcpy} or structure | |
15971 | copies) less than or equal to @var{num} bytes. The minimum value for | |
15972 | @var{num} is 32 bytes on 32-bit targets and 64 bytes on 64-bit | |
15973 | targets. The default value is target-specific. | |
15974 | ||
39bc1876 NS |
15975 | @item -G @var{num} |
15976 | @opindex G | |
15977 | @cindex smaller data references (PowerPC) | |
15978 | @cindex .sdata/.sdata2 references (PowerPC) | |
15979 | On embedded PowerPC systems, put global and static items less than or | |
15980 | equal to @var{num} bytes into the small data or bss sections instead of | |
15981 | the normal data or bss section. By default, @var{num} is 8. The | |
15982 | @option{-G @var{num}} switch is also passed to the linker. | |
15983 | All modules should be compiled with the same @option{-G @var{num}} value. | |
dcffbade | 15984 | |
39bc1876 NS |
15985 | @item -mregnames |
15986 | @itemx -mno-regnames | |
15987 | @opindex mregnames | |
15988 | @opindex mno-regnames | |
15989 | On System V.4 and embedded PowerPC systems do (do not) emit register | |
15990 | names in the assembly language output using symbolic forms. | |
dcffbade | 15991 | |
39bc1876 NS |
15992 | @item -mlongcall |
15993 | @itemx -mno-longcall | |
15994 | @opindex mlongcall | |
15995 | @opindex mno-longcall | |
87c365a4 NS |
15996 | By default assume that all calls are far away so that a longer more |
15997 | expensive calling sequence is required. This is required for calls | |
15998 | further than 32 megabytes (33,554,432 bytes) from the current location. | |
15999 | A short call will be generated if the compiler knows | |
16000 | the call cannot be that far away. This setting can be overridden by | |
16001 | the @code{shortcall} function attribute, or by @code{#pragma | |
16002 | longcall(0)}. | |
dcffbade | 16003 | |
39bc1876 NS |
16004 | Some linkers are capable of detecting out-of-range calls and generating |
16005 | glue code on the fly. On these systems, long calls are unnecessary and | |
16006 | generate slower code. As of this writing, the AIX linker can do this, | |
16007 | as can the GNU linker for PowerPC/64. It is planned to add this feature | |
16008 | to the GNU linker for 32-bit PowerPC systems as well. | |
df6194d4 | 16009 | |
39bc1876 NS |
16010 | On Darwin/PPC systems, @code{#pragma longcall} will generate ``jbsr |
16011 | callee, L42'', plus a ``branch island'' (glue code). The two target | |
d78aa55c | 16012 | addresses represent the callee and the ``branch island''. The |
39bc1876 NS |
16013 | Darwin/PPC linker will prefer the first address and generate a ``bl |
16014 | callee'' if the PPC ``bl'' instruction will reach the callee directly; | |
16015 | otherwise, the linker will generate ``bl L42'' to call the ``branch | |
d78aa55c | 16016 | island''. The ``branch island'' is appended to the body of the |
39bc1876 NS |
16017 | calling function; it computes the full 32-bit address of the callee |
16018 | and jumps to it. | |
df6194d4 | 16019 | |
39bc1876 NS |
16020 | On Mach-O (Darwin) systems, this option directs the compiler emit to |
16021 | the glue for every direct call, and the Darwin linker decides whether | |
16022 | to use or discard it. | |
16023 | ||
16024 | In the future, we may cause GCC to ignore all longcall specifications | |
16025 | when the linker is known to generate glue. | |
16026 | ||
9752c4ad AM |
16027 | @item -mtls-markers |
16028 | @itemx -mno-tls-markers | |
16029 | @opindex mtls-markers | |
16030 | @opindex mno-tls-markers | |
16031 | Mark (do not mark) calls to @code{__tls_get_addr} with a relocation | |
16032 | specifying the function argument. The relocation allows ld to | |
16033 | reliably associate function call with argument setup instructions for | |
16034 | TLS optimization, which in turn allows gcc to better schedule the | |
16035 | sequence. | |
16036 | ||
39bc1876 NS |
16037 | @item -pthread |
16038 | @opindex pthread | |
16039 | Adds support for multithreading with the @dfn{pthreads} library. | |
16040 | This option sets flags for both the preprocessor and linker. | |
30028c85 | 16041 | |
92902797 MM |
16042 | @item -mrecip |
16043 | @itemx -mno-recip | |
16044 | @opindex mrecip | |
16045 | This option will enable GCC to use the reciprocal estimate and | |
16046 | reciprocal square root estimate instructions with additional | |
16047 | Newton-Raphson steps to increase precision instead of doing a divide or | |
16048 | square root and divide for floating point arguments. You should use | |
16049 | the @option{-ffast-math} option when using @option{-mrecip} (or at | |
16050 | least @option{-funsafe-math-optimizations}, | |
16051 | @option{-finite-math-only}, @option{-freciprocal-math} and | |
16052 | @option{-fno-trapping-math}). Note that while the throughput of the | |
16053 | sequence is generally higher than the throughput of the non-reciprocal | |
16054 | instruction, the precision of the sequence can be decreased by up to 2 | |
16055 | ulp (i.e. the inverse of 1.0 equals 0.99999994) for reciprocal square | |
16056 | roots. | |
16057 | ||
16058 | @item -mrecip=@var{opt} | |
16059 | @opindex mrecip=opt | |
16060 | This option allows to control which reciprocal estimate instructions | |
16061 | may be used. @var{opt} is a comma separated list of options, that may | |
16062 | be preceeded by a @code{!} to invert the option: | |
16063 | @code{all}: enable all estimate instructions, | |
16064 | @code{default}: enable the default instructions, equvalent to @option{-mrecip}, | |
16065 | @code{none}: disable all estimate instructions, equivalent to @option{-mno-recip}; | |
16066 | @code{div}: enable the reciprocal approximation instructions for both single and double precision; | |
16067 | @code{divf}: enable the single precision reciprocal approximation instructions; | |
16068 | @code{divd}: enable the double precision reciprocal approximation instructions; | |
16069 | @code{rsqrt}: enable the reciprocal square root approximation instructions for both single and double precision; | |
16070 | @code{rsqrtf}: enable the single precision reciprocal square root approximation instructions; | |
16071 | @code{rsqrtd}: enable the double precision reciprocal square root approximation instructions; | |
16072 | ||
16073 | So for example, @option{-mrecip=all,!rsqrtd} would enable the | |
16074 | all of the reciprocal estimate instructions, except for the | |
16075 | @code{FRSQRTE}, @code{XSRSQRTEDP}, and @code{XVRSQRTEDP} instructions | |
16076 | which handle the double precision reciprocal square root calculations. | |
16077 | ||
16078 | @item -mrecip-precision | |
16079 | @itemx -mno-recip-precision | |
16080 | @opindex mrecip-precision | |
16081 | Assume (do not assume) that the reciprocal estimate instructions | |
16082 | provide higher precision estimates than is mandated by the powerpc | |
16083 | ABI. Selecting @option{-mcpu=power6} or @option{-mcpu=power7} | |
16084 | automatically selects @option{-mrecip-precision}. The double | |
16085 | precision square root estimate instructions are not generated by | |
16086 | default on low precision machines, since they do not provide an | |
16087 | estimate that converges after three steps. | |
8bcc0304 | 16088 | |
b36cf9d2 MM |
16089 | @item -mveclibabi=@var{type} |
16090 | @opindex mveclibabi | |
16091 | Specifies the ABI type to use for vectorizing intrinsics using an | |
16092 | external library. The only type supported at present is @code{mass}, | |
16093 | which specifies to use IBM's Mathematical Acceleration Subsystem | |
16094 | (MASS) libraries for vectorizing intrinsics using external libraries. | |
16095 | GCC will currently emit calls to @code{acosd2}, @code{acosf4}, | |
8bcc0304 MM |
16096 | @code{acoshd2}, @code{acoshf4}, @code{asind2}, @code{asinf4}, |
16097 | @code{asinhd2}, @code{asinhf4}, @code{atan2d2}, @code{atan2f4}, | |
16098 | @code{atand2}, @code{atanf4}, @code{atanhd2}, @code{atanhf4}, | |
16099 | @code{cbrtd2}, @code{cbrtf4}, @code{cosd2}, @code{cosf4}, | |
16100 | @code{coshd2}, @code{coshf4}, @code{erfcd2}, @code{erfcf4}, | |
16101 | @code{erfd2}, @code{erff4}, @code{exp2d2}, @code{exp2f4}, | |
16102 | @code{expd2}, @code{expf4}, @code{expm1d2}, @code{expm1f4}, | |
16103 | @code{hypotd2}, @code{hypotf4}, @code{lgammad2}, @code{lgammaf4}, | |
16104 | @code{log10d2}, @code{log10f4}, @code{log1pd2}, @code{log1pf4}, | |
16105 | @code{log2d2}, @code{log2f4}, @code{logd2}, @code{logf4}, | |
16106 | @code{powd2}, @code{powf4}, @code{sind2}, @code{sinf4}, @code{sinhd2}, | |
16107 | @code{sinhf4}, @code{sqrtd2}, @code{sqrtf4}, @code{tand2}, | |
16108 | @code{tanf4}, @code{tanhd2}, and @code{tanhf4} when generating code | |
16109 | for power7. Both @option{-ftree-vectorize} and | |
16110 | @option{-funsafe-math-optimizations} have to be enabled. The MASS | |
16111 | libraries will have to be specified at link time. | |
688e4919 MM |
16112 | |
16113 | @item -mfriz | |
16114 | @itemx -mno-friz | |
16115 | @opindex mfriz | |
16116 | Generate (do not generate) the @code{friz} instruction when the | |
16117 | @option{-funsafe-math-optimizations} option is used to optimize | |
16118 | rounding a floating point value to 64-bit integer and back to floating | |
16119 | point. The @code{friz} instruction does not return the same value if | |
16120 | the floating point number is too large to fit in an integer. | |
df6194d4 JW |
16121 | @end table |
16122 | ||
65a324b4 NC |
16123 | @node RX Options |
16124 | @subsection RX Options | |
16125 | @cindex RX Options | |
16126 | ||
5f75e477 | 16127 | These command line options are defined for RX targets: |
65a324b4 NC |
16128 | |
16129 | @table @gcctabopt | |
16130 | @item -m64bit-doubles | |
16131 | @itemx -m32bit-doubles | |
16132 | @opindex m64bit-doubles | |
16133 | @opindex m32bit-doubles | |
16134 | Make the @code{double} data type be 64-bits (@option{-m64bit-doubles}) | |
16135 | or 32-bits (@option{-m32bit-doubles}) in size. The default is | |
5f75e477 NC |
16136 | @option{-m32bit-doubles}. @emph{Note} RX floating point hardware only |
16137 | works on 32-bit values, which is why the default is | |
16138 | @option{-m32bit-doubles}. | |
16139 | ||
16140 | @item -fpu | |
16141 | @itemx -nofpu | |
16142 | @opindex fpu | |
16143 | @opindex nofpu | |
16144 | Enables (@option{-fpu}) or disables (@option{-nofpu}) the use of RX | |
16145 | floating point hardware. The default is enabled for the @var{RX600} | |
16146 | series and disabled for the @var{RX200} series. | |
16147 | ||
16148 | Floating point instructions will only be generated for 32-bit floating | |
16149 | point values however, so if the @option{-m64bit-doubles} option is in | |
16150 | use then the FPU hardware will not be used for doubles. | |
16151 | ||
16152 | @emph{Note} If the @option{-fpu} option is enabled then | |
16153 | @option{-funsafe-math-optimizations} is also enabled automatically. | |
16154 | This is because the RX FPU instructions are themselves unsafe. | |
9595a419 NC |
16155 | |
16156 | @item -mcpu=@var{name} | |
9595a419 | 16157 | @opindex -mcpu |
5f75e477 NC |
16158 | Selects the type of RX CPU to be targeted. Currently three types are |
16159 | supported, the generic @var{RX600} and @var{RX200} series hardware and | |
16160 | the specific @var{RX610} cpu. The default is @var{RX600}. | |
16161 | ||
16162 | The only difference between @var{RX600} and @var{RX610} is that the | |
16163 | @var{RX610} does not support the @code{MVTIPL} instruction. | |
16164 | ||
16165 | The @var{RX200} series does not have a hardware floating point unit | |
16166 | and so @option{-nofpu} is enabled by default when this type is | |
16167 | selected. | |
9595a419 | 16168 | |
65a324b4 NC |
16169 | @item -mbig-endian-data |
16170 | @itemx -mlittle-endian-data | |
16171 | @opindex mbig-endian-data | |
16172 | @opindex mlittle-endian-data | |
16173 | Store data (but not code) in the big-endian format. The default is | |
16174 | @option{-mlittle-endian-data}, ie to store data in the little endian | |
16175 | format. | |
16176 | ||
16177 | @item -msmall-data-limit=@var{N} | |
16178 | @opindex msmall-data-limit | |
16179 | Specifies the maximum size in bytes of global and static variables | |
16180 | which can be placed into the small data area. Using the small data | |
16181 | area can lead to smaller and faster code, but the size of area is | |
16182 | limited and it is up to the programmer to ensure that the area does | |
16183 | not overflow. Also when the small data area is used one of the RX's | |
16184 | registers (@code{r13}) is reserved for use pointing to this area, so | |
16185 | it is no longer available for use by the compiler. This could result | |
16186 | in slower and/or larger code if variables which once could have been | |
16187 | held in @code{r13} are now pushed onto the stack. | |
16188 | ||
16189 | Note, common variables (variables which have not been initialised) and | |
16190 | constants are not placed into the small data area as they are assigned | |
a4ce9883 | 16191 | to other sections in the output executable. |
65a324b4 NC |
16192 | |
16193 | The default value is zero, which disables this feature. Note, this | |
16194 | feature is not enabled by default with higher optimization levels | |
a4ce9883 | 16195 | (@option{-O2} etc) because of the potentially detrimental effects of |
65a324b4 NC |
16196 | reserving register @code{r13}. It is up to the programmer to |
16197 | experiment and discover whether this feature is of benefit to their | |
16198 | program. | |
16199 | ||
16200 | @item -msim | |
1588fb31 | 16201 | @itemx -mno-sim |
65a324b4 NC |
16202 | @opindex msim |
16203 | @opindex mno-sim | |
16204 | Use the simulator runtime. The default is to use the libgloss board | |
16205 | specific runtime. | |
16206 | ||
16207 | @item -mas100-syntax | |
1588fb31 | 16208 | @itemx -mno-as100-syntax |
65a324b4 NC |
16209 | @opindex mas100-syntax |
16210 | @opindex mno-as100-syntax | |
16211 | When generating assembler output use a syntax that is compatible with | |
16212 | Renesas's AS100 assembler. This syntax can also be handled by the GAS | |
16213 | assembler but it has some restrictions so generating it is not the | |
16214 | default option. | |
16215 | ||
16216 | @item -mmax-constant-size=@var{N} | |
16217 | @opindex mmax-constant-size | |
02a9370c | 16218 | Specifies the maximum size, in bytes, of a constant that can be used as |
65a324b4 | 16219 | an operand in a RX instruction. Although the RX instruction set does |
a4ce9883 | 16220 | allow constants of up to 4 bytes in length to be used in instructions, |
65a324b4 NC |
16221 | a longer value equates to a longer instruction. Thus in some |
16222 | circumstances it can be beneficial to restrict the size of constants | |
16223 | that are used in instructions. Constants that are too big are instead | |
16224 | placed into a constant pool and referenced via register indirection. | |
16225 | ||
c9c27b72 NC |
16226 | The value @var{N} can be between 0 and 4. A value of 0 (the default) |
16227 | or 4 means that constants of any size are allowed. | |
65a324b4 NC |
16228 | |
16229 | @item -mrelax | |
16230 | @opindex mrelax | |
16231 | Enable linker relaxation. Linker relaxation is a process whereby the | |
16232 | linker will attempt to reduce the size of a program by finding shorter | |
16233 | versions of various instructions. Disabled by default. | |
16234 | ||
16235 | @item -mint-register=@var{N} | |
16236 | @opindex mint-register | |
16237 | Specify the number of registers to reserve for fast interrupt handler | |
16238 | functions. The value @var{N} can be between 0 and 4. A value of 1 | |
02a9370c | 16239 | means that register @code{r13} will be reserved for the exclusive use |
65a324b4 NC |
16240 | of fast interrupt handlers. A value of 2 reserves @code{r13} and |
16241 | @code{r12}. A value of 3 reserves @code{r13}, @code{r12} and | |
16242 | @code{r11}, and a value of 4 reserves @code{r13} through @code{r10}. | |
16243 | A value of 0, the default, does not reserve any registers. | |
9595a419 NC |
16244 | |
16245 | @item -msave-acc-in-interrupts | |
16246 | @opindex msave-acc-in-interrupts | |
16247 | Specifies that interrupt handler functions should preserve the | |
16248 | accumulator register. This is only necessary if normal code might use | |
16249 | the accumulator register, for example because it performs 64-bit | |
16250 | multiplications. The default is to ignore the accumulator as this | |
16251 | makes the interrupt handlers faster. | |
16252 | ||
65a324b4 NC |
16253 | @end table |
16254 | ||
16255 | @emph{Note:} The generic GCC command line @option{-ffixed-@var{reg}} | |
16256 | has special significance to the RX port when used with the | |
16257 | @code{interrupt} function attribute. This attribute indicates a | |
16258 | function intended to process fast interrupts. GCC will will ensure | |
16259 | that it only uses the registers @code{r10}, @code{r11}, @code{r12} | |
16260 | and/or @code{r13} and only provided that the normal use of the | |
16261 | corresponding registers have been restricted via the | |
16262 | @option{-ffixed-@var{reg}} or @option{-mint-register} command line | |
16263 | options. | |
16264 | ||
91abf72d HP |
16265 | @node S/390 and zSeries Options |
16266 | @subsection S/390 and zSeries Options | |
16267 | @cindex S/390 and zSeries Options | |
16268 | ||
16269 | These are the @samp{-m} options defined for the S/390 and zSeries architecture. | |
16270 | ||
16271 | @table @gcctabopt | |
16272 | @item -mhard-float | |
16273 | @itemx -msoft-float | |
16274 | @opindex mhard-float | |
16275 | @opindex msoft-float | |
16276 | Use (do not use) the hardware floating-point instructions and registers | |
16277 | for floating-point operations. When @option{-msoft-float} is specified, | |
16278 | functions in @file{libgcc.a} will be used to perform floating-point | |
16279 | operations. When @option{-mhard-float} is specified, the compiler | |
16280 | generates IEEE floating-point instructions. This is the default. | |
16281 | ||
59a1bff3 AK |
16282 | @item -mhard-dfp |
16283 | @itemx -mno-hard-dfp | |
16284 | @opindex mhard-dfp | |
16285 | @opindex mno-hard-dfp | |
16286 | Use (do not use) the hardware decimal-floating-point instructions for | |
16287 | decimal-floating-point operations. When @option{-mno-hard-dfp} is | |
16288 | specified, functions in @file{libgcc.a} will be used to perform | |
16289 | decimal-floating-point operations. When @option{-mhard-dfp} is | |
16290 | specified, the compiler generates decimal-floating-point hardware | |
16291 | instructions. This is the default for @option{-march=z9-ec} or higher. | |
16292 | ||
f61a2c7d AK |
16293 | @item -mlong-double-64 |
16294 | @itemx -mlong-double-128 | |
16295 | @opindex mlong-double-64 | |
16296 | @opindex mlong-double-128 | |
16297 | These switches control the size of @code{long double} type. A size | |
16298 | of 64bit makes the @code{long double} type equivalent to the @code{double} | |
16299 | type. This is the default. | |
16300 | ||
91abf72d HP |
16301 | @item -mbackchain |
16302 | @itemx -mno-backchain | |
16303 | @opindex mbackchain | |
16304 | @opindex mno-backchain | |
b3d31392 AK |
16305 | Store (do not store) the address of the caller's frame as backchain pointer |
16306 | into the callee's stack frame. | |
adf39f8f AK |
16307 | A backchain may be needed to allow debugging using tools that do not understand |
16308 | DWARF-2 call frame information. | |
b3d31392 AK |
16309 | When @option{-mno-packed-stack} is in effect, the backchain pointer is stored |
16310 | at the bottom of the stack frame; when @option{-mpacked-stack} is in effect, | |
16311 | the backchain is placed into the topmost word of the 96/160 byte register | |
16312 | save area. | |
16313 | ||
16314 | In general, code compiled with @option{-mbackchain} is call-compatible with | |
16315 | code compiled with @option{-mmo-backchain}; however, use of the backchain | |
16316 | for debugging purposes usually requires that the whole binary is built with | |
6b78f6be AK |
16317 | @option{-mbackchain}. Note that the combination of @option{-mbackchain}, |
16318 | @option{-mpacked-stack} and @option{-mhard-float} is not supported. In order | |
16319 | to build a linux kernel use @option{-msoft-float}. | |
b3d31392 AK |
16320 | |
16321 | The default is to not maintain the backchain. | |
16322 | ||
16323 | @item -mpacked-stack | |
33558d94 | 16324 | @itemx -mno-packed-stack |
b3d31392 AK |
16325 | @opindex mpacked-stack |
16326 | @opindex mno-packed-stack | |
16327 | Use (do not use) the packed stack layout. When @option{-mno-packed-stack} is | |
16328 | specified, the compiler uses the all fields of the 96/160 byte register save | |
16329 | area only for their default purpose; unused fields still take up stack space. | |
16330 | When @option{-mpacked-stack} is specified, register save slots are densely | |
16331 | packed at the top of the register save area; unused space is reused for other | |
16332 | purposes, allowing for more efficient use of the available stack space. | |
16333 | However, when @option{-mbackchain} is also in effect, the topmost word of | |
16334 | the save area is always used to store the backchain, and the return address | |
16335 | register is always saved two words below the backchain. | |
16336 | ||
f2fd3821 | 16337 | As long as the stack frame backchain is not used, code generated with |
b3d31392 AK |
16338 | @option{-mpacked-stack} is call-compatible with code generated with |
16339 | @option{-mno-packed-stack}. Note that some non-FSF releases of GCC 2.95 for | |
16340 | S/390 or zSeries generated code that uses the stack frame backchain at run | |
16341 | time, not just for debugging purposes. Such code is not call-compatible | |
16342 | with code compiled with @option{-mpacked-stack}. Also, note that the | |
6b78f6be AK |
16343 | combination of @option{-mbackchain}, |
16344 | @option{-mpacked-stack} and @option{-mhard-float} is not supported. In order | |
16345 | to build a linux kernel use @option{-msoft-float}. | |
b3d31392 AK |
16346 | |
16347 | The default is to not use the packed stack layout. | |
91abf72d HP |
16348 | |
16349 | @item -msmall-exec | |
16350 | @itemx -mno-small-exec | |
16351 | @opindex msmall-exec | |
16352 | @opindex mno-small-exec | |
f282ffb3 JM |
16353 | Generate (or do not generate) code using the @code{bras} instruction |
16354 | to do subroutine calls. | |
91abf72d HP |
16355 | This only works reliably if the total executable size does not |
16356 | exceed 64k. The default is to use the @code{basr} instruction instead, | |
16357 | which does not have this limitation. | |
16358 | ||
16359 | @item -m64 | |
16360 | @itemx -m31 | |
16361 | @opindex m64 | |
16362 | @opindex m31 | |
16363 | When @option{-m31} is specified, generate code compliant to the | |
95fef11f JM |
16364 | GNU/Linux for S/390 ABI@. When @option{-m64} is specified, generate |
16365 | code compliant to the GNU/Linux for zSeries ABI@. This allows GCC in | |
91abf72d | 16366 | particular to generate 64-bit instructions. For the @samp{s390} |
f282ffb3 | 16367 | targets, the default is @option{-m31}, while the @samp{s390x} |
91abf72d HP |
16368 | targets default to @option{-m64}. |
16369 | ||
1fec52be HP |
16370 | @item -mzarch |
16371 | @itemx -mesa | |
16372 | @opindex mzarch | |
16373 | @opindex mesa | |
daf2f129 JM |
16374 | When @option{-mzarch} is specified, generate code using the |
16375 | instructions available on z/Architecture. | |
16376 | When @option{-mesa} is specified, generate code using the | |
8a36672b | 16377 | instructions available on ESA/390. Note that @option{-mesa} is |
1fec52be | 16378 | not possible with @option{-m64}. |
95fef11f | 16379 | When generating code compliant to the GNU/Linux for S/390 ABI, |
f13e0d4e | 16380 | the default is @option{-mesa}. When generating code compliant |
95fef11f | 16381 | to the GNU/Linux for zSeries ABI, the default is @option{-mzarch}. |
1fec52be | 16382 | |
91abf72d HP |
16383 | @item -mmvcle |
16384 | @itemx -mno-mvcle | |
16385 | @opindex mmvcle | |
16386 | @opindex mno-mvcle | |
f282ffb3 | 16387 | Generate (or do not generate) code using the @code{mvcle} instruction |
3364c33b | 16388 | to perform block moves. When @option{-mno-mvcle} is specified, |
8daf098e AS |
16389 | use a @code{mvc} loop instead. This is the default unless optimizing for |
16390 | size. | |
91abf72d HP |
16391 | |
16392 | @item -mdebug | |
16393 | @itemx -mno-debug | |
16394 | @opindex mdebug | |
16395 | @opindex mno-debug | |
16396 | Print (or do not print) additional debug information when compiling. | |
16397 | The default is to not print debug information. | |
16398 | ||
f13e0d4e | 16399 | @item -march=@var{cpu-type} |
1fec52be | 16400 | @opindex march |
f13e0d4e | 16401 | Generate code that will run on @var{cpu-type}, which is the name of a system |
8a36672b | 16402 | representing a certain processor type. Possible values for |
59a1bff3 AK |
16403 | @var{cpu-type} are @samp{g5}, @samp{g6}, @samp{z900}, @samp{z990}, |
16404 | @samp{z9-109}, @samp{z9-ec} and @samp{z10}. | |
f13e0d4e UW |
16405 | When generating code using the instructions available on z/Architecture, |
16406 | the default is @option{-march=z900}. Otherwise, the default is | |
16407 | @option{-march=g5}. | |
1fec52be | 16408 | |
f13e0d4e | 16409 | @item -mtune=@var{cpu-type} |
35082351 | 16410 | @opindex mtune |
1fec52be | 16411 | Tune to @var{cpu-type} everything applicable about the generated code, |
f13e0d4e UW |
16412 | except for the ABI and the set of available instructions. |
16413 | The list of @var{cpu-type} values is the same as for @option{-march}. | |
16414 | The default is the value used for @option{-march}. | |
1fec52be | 16415 | |
f26c1794 EC |
16416 | @item -mtpf-trace |
16417 | @itemx -mno-tpf-trace | |
16418 | @opindex mtpf-trace | |
16419 | @opindex mno-tpf-trace | |
16420 | Generate code that adds (does not add) in TPF OS specific branches to trace | |
16421 | routines in the operating system. This option is off by default, even | |
8a36672b | 16422 | when compiling for the TPF OS@. |
f26c1794 | 16423 | |
f2d226e1 AK |
16424 | @item -mfused-madd |
16425 | @itemx -mno-fused-madd | |
16426 | @opindex mfused-madd | |
16427 | @opindex mno-fused-madd | |
16428 | Generate code that uses (does not use) the floating point multiply and | |
16429 | accumulate instructions. These instructions are generated by default if | |
16430 | hardware floating point is used. | |
d75f90f1 AK |
16431 | |
16432 | @item -mwarn-framesize=@var{framesize} | |
16433 | @opindex mwarn-framesize | |
16434 | Emit a warning if the current function exceeds the given frame size. Because | |
16435 | this is a compile time check it doesn't need to be a real problem when the program | |
f0eb93a8 JM |
16436 | runs. It is intended to identify functions which most probably cause |
16437 | a stack overflow. It is useful to be used in an environment with limited stack | |
431ae0bf | 16438 | size e.g.@: the linux kernel. |
d75f90f1 AK |
16439 | |
16440 | @item -mwarn-dynamicstack | |
16441 | @opindex mwarn-dynamicstack | |
16442 | Emit a warning if the function calls alloca or uses dynamically | |
16443 | sized arrays. This is generally a bad idea with a limited stack size. | |
16444 | ||
16445 | @item -mstack-guard=@var{stack-guard} | |
33558d94 | 16446 | @itemx -mstack-size=@var{stack-size} |
d75f90f1 AK |
16447 | @opindex mstack-guard |
16448 | @opindex mstack-size | |
690e7b63 AK |
16449 | If these options are provided the s390 back end emits additional instructions in |
16450 | the function prologue which trigger a trap if the stack size is @var{stack-guard} | |
16451 | bytes above the @var{stack-size} (remember that the stack on s390 grows downward). | |
16452 | If the @var{stack-guard} option is omitted the smallest power of 2 larger than | |
16453 | the frame size of the compiled function is chosen. | |
16454 | These options are intended to be used to help debugging stack overflow problems. | |
16455 | The additionally emitted code causes only little overhead and hence can also be | |
16456 | used in production like systems without greater performance degradation. The given | |
16457 | values have to be exact powers of 2 and @var{stack-size} has to be greater than | |
16458 | @var{stack-guard} without exceeding 64k. | |
d75f90f1 AK |
16459 | In order to be efficient the extra code makes the assumption that the stack starts |
16460 | at an address aligned to the value given by @var{stack-size}. | |
690e7b63 | 16461 | The @var{stack-guard} option can only be used in conjunction with @var{stack-size}. |
91abf72d HP |
16462 | @end table |
16463 | ||
93ef7c1f CL |
16464 | @node Score Options |
16465 | @subsection Score Options | |
16466 | @cindex Score Options | |
16467 | ||
16468 | These options are defined for Score implementations: | |
16469 | ||
16470 | @table @gcctabopt | |
93ef7c1f CL |
16471 | @item -meb |
16472 | @opindex meb | |
16473 | Compile code for big endian mode. This is the default. | |
16474 | ||
c6681463 | 16475 | @item -mel |
edc5f63b | 16476 | @opindex mel |
7a61cf6f | 16477 | Compile code for little endian mode. |
c6681463 CL |
16478 | |
16479 | @item -mnhwloop | |
edc5f63b | 16480 | @opindex mnhwloop |
c6681463 CL |
16481 | Disable generate bcnz instruction. |
16482 | ||
16483 | @item -muls | |
edc5f63b | 16484 | @opindex muls |
c6681463 CL |
16485 | Enable generate unaligned load and store instruction. |
16486 | ||
93ef7c1f CL |
16487 | @item -mmac |
16488 | @opindex mmac | |
7a61cf6f | 16489 | Enable the use of multiply-accumulate instructions. Disabled by default. |
c6681463 CL |
16490 | |
16491 | @item -mscore5 | |
16492 | @opindex mscore5 | |
16493 | Specify the SCORE5 as the target architecture. | |
93ef7c1f CL |
16494 | |
16495 | @item -mscore5u | |
16496 | @opindex mscore5u | |
16497 | Specify the SCORE5U of the target architecture. | |
16498 | ||
16499 | @item -mscore7 | |
16500 | @opindex mscore7 | |
c6681463 CL |
16501 | Specify the SCORE7 as the target architecture. This is the default. |
16502 | ||
16503 | @item -mscore7d | |
16504 | @opindex mscore7d | |
16505 | Specify the SCORE7D as the target architecture. | |
93ef7c1f CL |
16506 | @end table |
16507 | ||
39bc1876 NS |
16508 | @node SH Options |
16509 | @subsection SH Options | |
bcf684c7 | 16510 | |
39bc1876 | 16511 | These @samp{-m} options are defined for the SH implementations: |
bcf684c7 | 16512 | |
5d22c1a5 | 16513 | @table @gcctabopt |
39bc1876 NS |
16514 | @item -m1 |
16515 | @opindex m1 | |
16516 | Generate code for the SH1. | |
9f85bca7 | 16517 | |
39bc1876 NS |
16518 | @item -m2 |
16519 | @opindex m2 | |
16520 | Generate code for the SH2. | |
9f85bca7 | 16521 | |
39bc1876 NS |
16522 | @item -m2e |
16523 | Generate code for the SH2e. | |
9f85bca7 | 16524 | |
b4589acc TY |
16525 | @item -m2a-nofpu |
16526 | @opindex m2a-nofpu | |
16527 | Generate code for the SH2a without FPU, or for a SH2a-FPU in such a way | |
16528 | that the floating-point unit is not used. | |
16529 | ||
16530 | @item -m2a-single-only | |
16531 | @opindex m2a-single-only | |
16532 | Generate code for the SH2a-FPU, in such a way that no double-precision | |
16533 | floating point operations are used. | |
16534 | ||
16535 | @item -m2a-single | |
16536 | @opindex m2a-single | |
16537 | Generate code for the SH2a-FPU assuming the floating-point unit is in | |
16538 | single-precision mode by default. | |
16539 | ||
16540 | @item -m2a | |
16541 | @opindex m2a | |
16542 | Generate code for the SH2a-FPU assuming the floating-point unit is in | |
16543 | double-precision mode by default. | |
16544 | ||
39bc1876 NS |
16545 | @item -m3 |
16546 | @opindex m3 | |
16547 | Generate code for the SH3. | |
9f85bca7 | 16548 | |
39bc1876 NS |
16549 | @item -m3e |
16550 | @opindex m3e | |
16551 | Generate code for the SH3e. | |
9f85bca7 | 16552 | |
39bc1876 NS |
16553 | @item -m4-nofpu |
16554 | @opindex m4-nofpu | |
16555 | Generate code for the SH4 without a floating-point unit. | |
9f85bca7 | 16556 | |
39bc1876 NS |
16557 | @item -m4-single-only |
16558 | @opindex m4-single-only | |
16559 | Generate code for the SH4 with a floating-point unit that only | |
16560 | supports single-precision arithmetic. | |
9f85bca7 | 16561 | |
39bc1876 NS |
16562 | @item -m4-single |
16563 | @opindex m4-single | |
16564 | Generate code for the SH4 assuming the floating-point unit is in | |
16565 | single-precision mode by default. | |
9f85bca7 | 16566 | |
39bc1876 NS |
16567 | @item -m4 |
16568 | @opindex m4 | |
16569 | Generate code for the SH4. | |
9f85bca7 | 16570 | |
312209c6 AO |
16571 | @item -m4a-nofpu |
16572 | @opindex m4a-nofpu | |
16573 | Generate code for the SH4al-dsp, or for a SH4a in such a way that the | |
16574 | floating-point unit is not used. | |
16575 | ||
16576 | @item -m4a-single-only | |
16577 | @opindex m4a-single-only | |
16578 | Generate code for the SH4a, in such a way that no double-precision | |
16579 | floating point operations are used. | |
16580 | ||
16581 | @item -m4a-single | |
16582 | @opindex m4a-single | |
16583 | Generate code for the SH4a assuming the floating-point unit is in | |
16584 | single-precision mode by default. | |
16585 | ||
16586 | @item -m4a | |
16587 | @opindex m4a | |
16588 | Generate code for the SH4a. | |
16589 | ||
16590 | @item -m4al | |
16591 | @opindex m4al | |
16592 | Same as @option{-m4a-nofpu}, except that it implicitly passes | |
16593 | @option{-dsp} to the assembler. GCC doesn't generate any DSP | |
16594 | instructions at the moment. | |
16595 | ||
39bc1876 NS |
16596 | @item -mb |
16597 | @opindex mb | |
16598 | Compile code for the processor in big endian mode. | |
9f85bca7 | 16599 | |
39bc1876 NS |
16600 | @item -ml |
16601 | @opindex ml | |
16602 | Compile code for the processor in little endian mode. | |
9f85bca7 | 16603 | |
39bc1876 NS |
16604 | @item -mdalign |
16605 | @opindex mdalign | |
16606 | Align doubles at 64-bit boundaries. Note that this changes the calling | |
16607 | conventions, and thus some functions from the standard C library will | |
16608 | not work unless you recompile it first with @option{-mdalign}. | |
9f85bca7 | 16609 | |
39bc1876 NS |
16610 | @item -mrelax |
16611 | @opindex mrelax | |
16612 | Shorten some address references at link time, when possible; uses the | |
16613 | linker option @option{-relax}. | |
9f85bca7 | 16614 | |
39bc1876 NS |
16615 | @item -mbigtable |
16616 | @opindex mbigtable | |
16617 | Use 32-bit offsets in @code{switch} tables. The default is to use | |
16618 | 16-bit offsets. | |
9f85bca7 | 16619 | |
9eb3a0dd N |
16620 | @item -mbitops |
16621 | @opindex mbitops | |
16622 | Enable the use of bit manipulation instructions on SH2A. | |
16623 | ||
6a799f6e CB |
16624 | @item -mfmovd |
16625 | @opindex mfmovd | |
16626 | Enable the use of the instruction @code{fmovd}. Check @option{-mdalign} for | |
16627 | alignment constraints. | |
16628 | ||
39bc1876 NS |
16629 | @item -mhitachi |
16630 | @opindex mhitachi | |
16631 | Comply with the calling conventions defined by Renesas. | |
9f85bca7 | 16632 | |
2acc29bd NC |
16633 | @item -mrenesas |
16634 | @opindex mhitachi | |
16635 | Comply with the calling conventions defined by Renesas. | |
16636 | ||
16637 | @item -mno-renesas | |
16638 | @opindex mhitachi | |
16639 | Comply with the calling conventions defined for GCC before the Renesas | |
16640 | conventions were available. This option is the default for all | |
16641 | targets of the SH toolchain except for @samp{sh-symbianelf}. | |
16642 | ||
39bc1876 NS |
16643 | @item -mnomacsave |
16644 | @opindex mnomacsave | |
16645 | Mark the @code{MAC} register as call-clobbered, even if | |
16646 | @option{-mhitachi} is given. | |
9f85bca7 | 16647 | |
39bc1876 NS |
16648 | @item -mieee |
16649 | @opindex mieee | |
16650 | Increase IEEE-compliance of floating-point code. | |
73a4d10b R |
16651 | At the moment, this is equivalent to @option{-fno-finite-math-only}. |
16652 | When generating 16 bit SH opcodes, getting IEEE-conforming results for | |
16653 | comparisons of NANs / infinities incurs extra overhead in every | |
16654 | floating point comparison, therefore the default is set to | |
16655 | @option{-ffinite-math-only}. | |
9f85bca7 | 16656 | |
dc557046 R |
16657 | @item -minline-ic_invalidate |
16658 | @opindex minline-ic_invalidate | |
16659 | Inline code to invalidate instruction cache entries after setting up | |
16660 | nested function trampolines. | |
16661 | This option has no effect if -musermode is in effect and the selected | |
16662 | code generation option (e.g. -m4) does not allow the use of the icbi | |
16663 | instruction. | |
16664 | If the selected code generation option does not allow the use of the icbi | |
16665 | instruction, and -musermode is not in effect, the inlined code will | |
16666 | manipulate the instruction cache address array directly with an associative | |
16667 | write. This not only requires privileged mode, but it will also | |
16668 | fail if the cache line had been mapped via the TLB and has become unmapped. | |
16669 | ||
39bc1876 NS |
16670 | @item -misize |
16671 | @opindex misize | |
16672 | Dump instruction size and location in the assembly code. | |
9f85bca7 | 16673 | |
39bc1876 NS |
16674 | @item -mpadstruct |
16675 | @opindex mpadstruct | |
16676 | This option is deprecated. It pads structures to multiple of 4 bytes, | |
16677 | which is incompatible with the SH ABI@. | |
9f85bca7 | 16678 | |
39bc1876 NS |
16679 | @item -mspace |
16680 | @opindex mspace | |
16681 | Optimize for space instead of speed. Implied by @option{-Os}. | |
9f85bca7 | 16682 | |
39bc1876 NS |
16683 | @item -mprefergot |
16684 | @opindex mprefergot | |
16685 | When generating position-independent code, emit function calls using | |
16686 | the Global Offset Table instead of the Procedure Linkage Table. | |
9f85bca7 | 16687 | |
39bc1876 NS |
16688 | @item -musermode |
16689 | @opindex musermode | |
dc557046 R |
16690 | Don't generate privileged mode only code; implies -mno-inline-ic_invalidate |
16691 | if the inlined code would not work in user mode. | |
16692 | This is the default when the target is @code{sh-*-linux*}. | |
73a4d10b R |
16693 | |
16694 | @item -multcost=@var{number} | |
16695 | @opindex multcost=@var{number} | |
16696 | Set the cost to assume for a multiply insn. | |
16697 | ||
16698 | @item -mdiv=@var{strategy} | |
16699 | @opindex mdiv=@var{strategy} | |
16700 | Set the division strategy to use for SHmedia code. @var{strategy} must be | |
16701 | one of: call, call2, fp, inv, inv:minlat, inv20u, inv20l, inv:call, | |
16702 | inv:call2, inv:fp . | |
16703 | "fp" performs the operation in floating point. This has a very high latency, | |
16704 | but needs only a few instructions, so it might be a good choice if | |
30dc60c7 | 16705 | your code has enough easily exploitable ILP to allow the compiler to |
73a4d10b R |
16706 | schedule the floating point instructions together with other instructions. |
16707 | Division by zero causes a floating point exception. | |
16708 | "inv" uses integer operations to calculate the inverse of the divisor, | |
30dc60c7 | 16709 | and then multiplies the dividend with the inverse. This strategy allows |
73a4d10b R |
16710 | cse and hoisting of the inverse calculation. Division by zero calculates |
16711 | an unspecified result, but does not trap. | |
16712 | "inv:minlat" is a variant of "inv" where if no cse / hoisting opportunities | |
16713 | have been found, or if the entire operation has been hoisted to the same | |
16714 | place, the last stages of the inverse calculation are intertwined with the | |
16715 | final multiply to reduce the overall latency, at the expense of using a few | |
16716 | more instructions, and thus offering fewer scheduling opportunities with | |
16717 | other code. | |
16718 | "call" calls a library function that usually implements the inv:minlat | |
16719 | strategy. | |
16720 | This gives high code density for m5-*media-nofpu compilations. | |
16721 | "call2" uses a different entry point of the same library function, where it | |
16722 | assumes that a pointer to a lookup table has already been set up, which | |
16723 | exposes the pointer load to cse / code hoisting optimizations. | |
16724 | "inv:call", "inv:call2" and "inv:fp" all use the "inv" algorithm for initial | |
16725 | code generation, but if the code stays unoptimized, revert to the "call", | |
30dc60c7 | 16726 | "call2", or "fp" strategies, respectively. Note that the |
73a4d10b R |
16727 | potentially-trapping side effect of division by zero is carried by a |
16728 | separate instruction, so it is possible that all the integer instructions | |
16729 | are hoisted out, but the marker for the side effect stays where it is. | |
16730 | A recombination to fp operations or a call is not possible in that case. | |
16731 | "inv20u" and "inv20l" are variants of the "inv:minlat" strategy. In the case | |
16732 | that the inverse calculation was nor separated from the multiply, they speed | |
16733 | up division where the dividend fits into 20 bits (plus sign where applicable), | |
16734 | by inserting a test to skip a number of operations in this case; this test | |
30dc60c7 | 16735 | slows down the case of larger dividends. inv20u assumes the case of a such |
73a4d10b R |
16736 | a small dividend to be unlikely, and inv20l assumes it to be likely. |
16737 | ||
7a296495 CB |
16738 | @item -maccumulate-outgoing-args |
16739 | @opindex maccumulate-outgoing-args | |
16740 | Reserve space once for outgoing arguments in the function prologue rather | |
16741 | than around each call. Generally beneficial for performance and size. Also | |
16742 | needed for unwinding to avoid changing the stack frame around conditional code. | |
16743 | ||
73a4d10b R |
16744 | @item -mdivsi3_libfunc=@var{name} |
16745 | @opindex mdivsi3_libfunc=@var{name} | |
16746 | Set the name of the library function used for 32 bit signed division to | |
16747 | @var{name}. This only affect the name used in the call and inv:call | |
16748 | division strategies, and the compiler will still expect the same | |
16749 | sets of input/output/clobbered registers as if this option was not present. | |
16750 | ||
3217af3e KK |
16751 | @item -mfixed-range=@var{register-range} |
16752 | @opindex mfixed-range | |
16753 | Generate code treating the given register range as fixed registers. | |
16754 | A fixed register is one that the register allocator can not use. This is | |
16755 | useful when compiling kernel code. A register range is specified as | |
16756 | two registers separated by a dash. Multiple register ranges can be | |
16757 | specified separated by a comma. | |
16758 | ||
73a4d10b R |
16759 | @item -madjust-unroll |
16760 | @opindex madjust-unroll | |
16761 | Throttle unrolling to avoid thrashing target registers. | |
16762 | This option only has an effect if the gcc code base supports the | |
16763 | TARGET_ADJUST_UNROLL_MAX target hook. | |
16764 | ||
16765 | @item -mindexed-addressing | |
16766 | @opindex mindexed-addressing | |
16767 | Enable the use of the indexed addressing mode for SHmedia32/SHcompact. | |
16768 | This is only safe if the hardware and/or OS implement 32 bit wrap-around | |
16769 | semantics for the indexed addressing mode. The architecture allows the | |
16770 | implementation of processors with 64 bit MMU, which the OS could use to | |
30dc60c7 | 16771 | get 32 bit addressing, but since no current hardware implementation supports |
73a4d10b R |
16772 | this or any other way to make the indexed addressing mode safe to use in |
16773 | the 32 bit ABI, the default is -mno-indexed-addressing. | |
16774 | ||
16775 | @item -mgettrcost=@var{number} | |
16776 | @opindex mgettrcost=@var{number} | |
16777 | Set the cost assumed for the gettr instruction to @var{number}. | |
16778 | The default is 2 if @option{-mpt-fixed} is in effect, 100 otherwise. | |
16779 | ||
16780 | @item -mpt-fixed | |
16781 | @opindex mpt-fixed | |
16782 | Assume pt* instructions won't trap. This will generally generate better | |
16783 | scheduled code, but is unsafe on current hardware. The current architecture | |
16784 | definition says that ptabs and ptrel trap when the target anded with 3 is 3. | |
16785 | This has the unintentional effect of making it unsafe to schedule ptabs / | |
16786 | ptrel before a branch, or hoist it out of a loop. For example, | |
16787 | __do_global_ctors, a part of libgcc that runs constructors at program | |
78681dbd RS |
16788 | startup, calls functions in a list which is delimited by @minus{}1. With the |
16789 | -mpt-fixed option, the ptabs will be done before testing against @minus{}1. | |
73a4d10b | 16790 | That means that all the constructors will be run a bit quicker, but when |
30dc60c7 | 16791 | the loop comes to the end of the list, the program crashes because ptabs |
78681dbd | 16792 | loads @minus{}1 into a target register. Since this option is unsafe for any |
73a4d10b R |
16793 | hardware implementing the current architecture specification, the default |
16794 | is -mno-pt-fixed. Unless the user specifies a specific cost with | |
16795 | @option{-mgettrcost}, -mno-pt-fixed also implies @option{-mgettrcost=100}; | |
16796 | this deters register allocation using target registers for storing | |
16797 | ordinary integers. | |
16798 | ||
16799 | @item -minvalid-symbols | |
16800 | @opindex minvalid-symbols | |
16801 | Assume symbols might be invalid. Ordinary function symbols generated by | |
16802 | the compiler will always be valid to load with movi/shori/ptabs or | |
16803 | movi/shori/ptrel, but with assembler and/or linker tricks it is possible | |
16804 | to generate symbols that will cause ptabs / ptrel to trap. | |
16805 | This option is only meaningful when @option{-mno-pt-fixed} is in effect. | |
16806 | It will then prevent cross-basic-block cse, hoisting and most scheduling | |
16807 | of symbol loads. The default is @option{-mno-invalid-symbols}. | |
9f85bca7 JM |
16808 | @end table |
16809 | ||
c28aa982 RO |
16810 | @node Solaris 2 Options |
16811 | @subsection Solaris 2 Options | |
16812 | @cindex Solaris 2 options | |
16813 | ||
16814 | These @samp{-m} options are supported on Solaris 2: | |
16815 | ||
16816 | @table @gcctabopt | |
16817 | @item -mimpure-text | |
16818 | @opindex mimpure-text | |
16819 | @option{-mimpure-text}, used in addition to @option{-shared}, tells | |
16820 | the compiler to not pass @option{-z text} to the linker when linking a | |
16821 | shared object. Using this option, you can link position-dependent | |
16822 | code into a shared object. | |
16823 | ||
16824 | @option{-mimpure-text} suppresses the ``relocations remain against | |
16825 | allocatable but non-writable sections'' linker error message. | |
16826 | However, the necessary relocations will trigger copy-on-write, and the | |
16827 | shared object is not actually shared across processes. Instead of | |
16828 | using @option{-mimpure-text}, you should compile all source code with | |
16829 | @option{-fpic} or @option{-fPIC}. | |
16830 | ||
16831 | @end table | |
16832 | ||
16833 | These switches are supported in addition to the above on Solaris 2: | |
16834 | ||
16835 | @table @gcctabopt | |
16836 | @item -threads | |
16837 | @opindex threads | |
16838 | Add support for multithreading using the Solaris threads library. This | |
16839 | option sets flags for both the preprocessor and linker. This option does | |
16840 | not affect the thread safety of object code produced by the compiler or | |
16841 | that of libraries supplied with it. | |
16842 | ||
16843 | @item -pthreads | |
16844 | @opindex pthreads | |
16845 | Add support for multithreading using the POSIX threads library. This | |
16846 | option sets flags for both the preprocessor and linker. This option does | |
16847 | not affect the thread safety of object code produced by the compiler or | |
16848 | that of libraries supplied with it. | |
16849 | ||
16850 | @item -pthread | |
16851 | @opindex pthread | |
16852 | This is a synonym for @option{-pthreads}. | |
16853 | @end table | |
16854 | ||
39bc1876 NS |
16855 | @node SPARC Options |
16856 | @subsection SPARC Options | |
16857 | @cindex SPARC options | |
69a0611f | 16858 | |
39bc1876 | 16859 | These @samp{-m} options are supported on the SPARC: |
69a0611f GK |
16860 | |
16861 | @table @gcctabopt | |
39bc1876 NS |
16862 | @item -mno-app-regs |
16863 | @itemx -mapp-regs | |
16864 | @opindex mno-app-regs | |
16865 | @opindex mapp-regs | |
16866 | Specify @option{-mapp-regs} to generate output using the global registers | |
16867 | 2 through 4, which the SPARC SVR4 ABI reserves for applications. This | |
d14f5ecb | 16868 | is the default. |
69a0611f | 16869 | |
39bc1876 NS |
16870 | To be fully SVR4 ABI compliant at the cost of some performance loss, |
16871 | specify @option{-mno-app-regs}. You should compile libraries and system | |
16872 | software with this option. | |
70899148 | 16873 | |
39bc1876 NS |
16874 | @item -mfpu |
16875 | @itemx -mhard-float | |
16876 | @opindex mfpu | |
16877 | @opindex mhard-float | |
16878 | Generate output containing floating point instructions. This is the | |
16879 | default. | |
70899148 | 16880 | |
39bc1876 NS |
16881 | @item -mno-fpu |
16882 | @itemx -msoft-float | |
16883 | @opindex mno-fpu | |
16884 | @opindex msoft-float | |
16885 | Generate output containing library calls for floating point. | |
16886 | @strong{Warning:} the requisite libraries are not available for all SPARC | |
16887 | targets. Normally the facilities of the machine's usual C compiler are | |
16888 | used, but this cannot be done directly in cross-compilation. You must make | |
16889 | your own arrangements to provide suitable library functions for | |
16890 | cross-compilation. The embedded targets @samp{sparc-*-aout} and | |
16891 | @samp{sparclite-*-*} do provide software floating point support. | |
70899148 | 16892 | |
39bc1876 NS |
16893 | @option{-msoft-float} changes the calling convention in the output file; |
16894 | therefore, it is only useful if you compile @emph{all} of a program with | |
16895 | this option. In particular, you need to compile @file{libgcc.a}, the | |
16896 | library that comes with GCC, with @option{-msoft-float} in order for | |
16897 | this to work. | |
70899148 | 16898 | |
39bc1876 NS |
16899 | @item -mhard-quad-float |
16900 | @opindex mhard-quad-float | |
16901 | Generate output containing quad-word (long double) floating point | |
16902 | instructions. | |
70899148 | 16903 | |
39bc1876 NS |
16904 | @item -msoft-quad-float |
16905 | @opindex msoft-quad-float | |
16906 | Generate output containing library calls for quad-word (long double) | |
16907 | floating point instructions. The functions called are those specified | |
16908 | in the SPARC ABI@. This is the default. | |
70899148 | 16909 | |
39bc1876 NS |
16910 | As of this writing, there are no SPARC implementations that have hardware |
16911 | support for the quad-word floating point instructions. They all invoke | |
16912 | a trap handler for one of these instructions, and then the trap handler | |
16913 | emulates the effect of the instruction. Because of the trap handler overhead, | |
16914 | this is much slower than calling the ABI library routines. Thus the | |
16915 | @option{-msoft-quad-float} option is the default. | |
70899148 | 16916 | |
39bc1876 NS |
16917 | @item -mno-unaligned-doubles |
16918 | @itemx -munaligned-doubles | |
16919 | @opindex mno-unaligned-doubles | |
16920 | @opindex munaligned-doubles | |
16921 | Assume that doubles have 8 byte alignment. This is the default. | |
70899148 | 16922 | |
39bc1876 NS |
16923 | With @option{-munaligned-doubles}, GCC assumes that doubles have 8 byte |
16924 | alignment only if they are contained in another type, or if they have an | |
16925 | absolute address. Otherwise, it assumes they have 4 byte alignment. | |
16926 | Specifying this option avoids some rare compatibility problems with code | |
16927 | generated by other compilers. It is not the default because it results | |
16928 | in a performance loss, especially for floating point code. | |
70899148 | 16929 | |
39bc1876 NS |
16930 | @item -mno-faster-structs |
16931 | @itemx -mfaster-structs | |
16932 | @opindex mno-faster-structs | |
16933 | @opindex mfaster-structs | |
16934 | With @option{-mfaster-structs}, the compiler assumes that structures | |
16935 | should have 8 byte alignment. This enables the use of pairs of | |
16936 | @code{ldd} and @code{std} instructions for copies in structure | |
16937 | assignment, in place of twice as many @code{ld} and @code{st} pairs. | |
16938 | However, the use of this changed alignment directly violates the SPARC | |
16939 | ABI@. Thus, it's intended only for use on targets where the developer | |
16940 | acknowledges that their resulting code will not be directly in line with | |
16941 | the rules of the ABI@. | |
70899148 | 16942 | |
39bc1876 NS |
16943 | @item -mcpu=@var{cpu_type} |
16944 | @opindex mcpu | |
16945 | Set the instruction set, register set, and instruction scheduling parameters | |
16946 | for machine type @var{cpu_type}. Supported values for @var{cpu_type} are | |
16947 | @samp{v7}, @samp{cypress}, @samp{v8}, @samp{supersparc}, @samp{sparclite}, | |
16948 | @samp{f930}, @samp{f934}, @samp{hypersparc}, @samp{sparclite86x}, | |
4c837a1e | 16949 | @samp{sparclet}, @samp{tsc701}, @samp{v9}, @samp{ultrasparc}, |
9eeaed6e | 16950 | @samp{ultrasparc3}, @samp{niagara} and @samp{niagara2}. |
70899148 | 16951 | |
39bc1876 NS |
16952 | Default instruction scheduling parameters are used for values that select |
16953 | an architecture and not an implementation. These are @samp{v7}, @samp{v8}, | |
16954 | @samp{sparclite}, @samp{sparclet}, @samp{v9}. | |
70899148 | 16955 | |
39bc1876 NS |
16956 | Here is a list of each supported architecture and their supported |
16957 | implementations. | |
70899148 | 16958 | |
39bc1876 NS |
16959 | @smallexample |
16960 | v7: cypress | |
16961 | v8: supersparc, hypersparc | |
16962 | sparclite: f930, f934, sparclite86x | |
16963 | sparclet: tsc701 | |
9eeaed6e | 16964 | v9: ultrasparc, ultrasparc3, niagara, niagara2 |
39bc1876 | 16965 | @end smallexample |
70899148 | 16966 | |
39bc1876 NS |
16967 | By default (unless configured otherwise), GCC generates code for the V7 |
16968 | variant of the SPARC architecture. With @option{-mcpu=cypress}, the compiler | |
16969 | additionally optimizes it for the Cypress CY7C602 chip, as used in the | |
16970 | SPARCStation/SPARCServer 3xx series. This is also appropriate for the older | |
16971 | SPARCStation 1, 2, IPX etc. | |
70899148 | 16972 | |
39bc1876 NS |
16973 | With @option{-mcpu=v8}, GCC generates code for the V8 variant of the SPARC |
16974 | architecture. The only difference from V7 code is that the compiler emits | |
16975 | the integer multiply and integer divide instructions which exist in SPARC-V8 | |
16976 | but not in SPARC-V7. With @option{-mcpu=supersparc}, the compiler additionally | |
16977 | optimizes it for the SuperSPARC chip, as used in the SPARCStation 10, 1000 and | |
16978 | 2000 series. | |
70899148 | 16979 | |
39bc1876 NS |
16980 | With @option{-mcpu=sparclite}, GCC generates code for the SPARClite variant of |
16981 | the SPARC architecture. This adds the integer multiply, integer divide step | |
16982 | and scan (@code{ffs}) instructions which exist in SPARClite but not in SPARC-V7. | |
16983 | With @option{-mcpu=f930}, the compiler additionally optimizes it for the | |
8a36672b | 16984 | Fujitsu MB86930 chip, which is the original SPARClite, with no FPU@. With |
39bc1876 | 16985 | @option{-mcpu=f934}, the compiler additionally optimizes it for the Fujitsu |
8a36672b | 16986 | MB86934 chip, which is the more recent SPARClite with FPU@. |
70899148 | 16987 | |
39bc1876 NS |
16988 | With @option{-mcpu=sparclet}, GCC generates code for the SPARClet variant of |
16989 | the SPARC architecture. This adds the integer multiply, multiply/accumulate, | |
16990 | integer divide step and scan (@code{ffs}) instructions which exist in SPARClet | |
16991 | but not in SPARC-V7. With @option{-mcpu=tsc701}, the compiler additionally | |
16992 | optimizes it for the TEMIC SPARClet chip. | |
70899148 | 16993 | |
39bc1876 NS |
16994 | With @option{-mcpu=v9}, GCC generates code for the V9 variant of the SPARC |
16995 | architecture. This adds 64-bit integer and floating-point move instructions, | |
16996 | 3 additional floating-point condition code registers and conditional move | |
16997 | instructions. With @option{-mcpu=ultrasparc}, the compiler additionally | |
4c837a1e | 16998 | optimizes it for the Sun UltraSPARC I/II/IIi chips. With |
39bc1876 | 16999 | @option{-mcpu=ultrasparc3}, the compiler additionally optimizes it for the |
4c837a1e DM |
17000 | Sun UltraSPARC III/III+/IIIi/IIIi+/IV/IV+ chips. With |
17001 | @option{-mcpu=niagara}, the compiler additionally optimizes it for | |
9eeaed6e DM |
17002 | Sun UltraSPARC T1 chips. With @option{-mcpu=niagara2}, the compiler |
17003 | additionally optimizes it for Sun UltraSPARC T2 chips. | |
70899148 | 17004 | |
39bc1876 NS |
17005 | @item -mtune=@var{cpu_type} |
17006 | @opindex mtune | |
17007 | Set the instruction scheduling parameters for machine type | |
17008 | @var{cpu_type}, but do not set the instruction set or register set that the | |
17009 | option @option{-mcpu=@var{cpu_type}} would. | |
70899148 | 17010 | |
39bc1876 NS |
17011 | The same values for @option{-mcpu=@var{cpu_type}} can be used for |
17012 | @option{-mtune=@var{cpu_type}}, but the only useful values are those | |
17013 | that select a particular cpu implementation. Those are @samp{cypress}, | |
17014 | @samp{supersparc}, @samp{hypersparc}, @samp{f930}, @samp{f934}, | |
4c837a1e | 17015 | @samp{sparclite86x}, @samp{tsc701}, @samp{ultrasparc}, |
9eeaed6e | 17016 | @samp{ultrasparc3}, @samp{niagara}, and @samp{niagara2}. |
70899148 | 17017 | |
39bc1876 NS |
17018 | @item -mv8plus |
17019 | @itemx -mno-v8plus | |
17020 | @opindex mv8plus | |
17021 | @opindex mno-v8plus | |
8a36672b | 17022 | With @option{-mv8plus}, GCC generates code for the SPARC-V8+ ABI@. The |
39bc1876 NS |
17023 | difference from the V8 ABI is that the global and out registers are |
17024 | considered 64-bit wide. This is enabled by default on Solaris in 32-bit | |
17025 | mode for all SPARC-V9 processors. | |
70899148 | 17026 | |
39bc1876 NS |
17027 | @item -mvis |
17028 | @itemx -mno-vis | |
17029 | @opindex mvis | |
17030 | @opindex mno-vis | |
17031 | With @option{-mvis}, GCC generates code that takes advantage of the UltraSPARC | |
17032 | Visual Instruction Set extensions. The default is @option{-mno-vis}. | |
17033 | @end table | |
70899148 | 17034 | |
39bc1876 NS |
17035 | These @samp{-m} options are supported in addition to the above |
17036 | on SPARC-V9 processors in 64-bit environments: | |
70899148 | 17037 | |
39bc1876 NS |
17038 | @table @gcctabopt |
17039 | @item -mlittle-endian | |
17040 | @opindex mlittle-endian | |
8a36672b | 17041 | Generate code for a processor running in little-endian mode. It is only |
d4e1591f | 17042 | available for a few configurations and most notably not on Solaris and Linux. |
70899148 | 17043 | |
39bc1876 NS |
17044 | @item -m32 |
17045 | @itemx -m64 | |
17046 | @opindex m32 | |
17047 | @opindex m64 | |
17048 | Generate code for a 32-bit or 64-bit environment. | |
17049 | The 32-bit environment sets int, long and pointer to 32 bits. | |
17050 | The 64-bit environment sets int to 32 bits and long and pointer | |
17051 | to 64 bits. | |
70899148 | 17052 | |
39bc1876 NS |
17053 | @item -mcmodel=medlow |
17054 | @opindex mcmodel=medlow | |
17055 | Generate code for the Medium/Low code model: 64-bit addresses, programs | |
17056 | must be linked in the low 32 bits of memory. Programs can be statically | |
17057 | or dynamically linked. | |
70899148 | 17058 | |
39bc1876 NS |
17059 | @item -mcmodel=medmid |
17060 | @opindex mcmodel=medmid | |
17061 | Generate code for the Medium/Middle code model: 64-bit addresses, programs | |
17062 | must be linked in the low 44 bits of memory, the text and data segments must | |
17063 | be less than 2GB in size and the data segment must be located within 2GB of | |
17064 | the text segment. | |
70899148 | 17065 | |
39bc1876 NS |
17066 | @item -mcmodel=medany |
17067 | @opindex mcmodel=medany | |
17068 | Generate code for the Medium/Anywhere code model: 64-bit addresses, programs | |
17069 | may be linked anywhere in memory, the text and data segments must be less | |
17070 | than 2GB in size and the data segment must be located within 2GB of the | |
17071 | text segment. | |
70899148 | 17072 | |
39bc1876 NS |
17073 | @item -mcmodel=embmedany |
17074 | @opindex mcmodel=embmedany | |
17075 | Generate code for the Medium/Anywhere code model for embedded systems: | |
17076 | 64-bit addresses, the text and data segments must be less than 2GB in | |
17077 | size, both starting anywhere in memory (determined at link time). The | |
17078 | global register %g4 points to the base of the data segment. Programs | |
17079 | are statically linked and PIC is not supported. | |
70899148 | 17080 | |
39bc1876 NS |
17081 | @item -mstack-bias |
17082 | @itemx -mno-stack-bias | |
17083 | @opindex mstack-bias | |
17084 | @opindex mno-stack-bias | |
17085 | With @option{-mstack-bias}, GCC assumes that the stack pointer, and | |
17086 | frame pointer if present, are offset by @minus{}2047 which must be added back | |
17087 | when making stack frame references. This is the default in 64-bit mode. | |
17088 | Otherwise, assume no such offset is present. | |
17089 | @end table | |
70899148 | 17090 | |
85d9c13c TS |
17091 | @node SPU Options |
17092 | @subsection SPU Options | |
17093 | @cindex SPU options | |
17094 | ||
17095 | These @samp{-m} options are supported on the SPU: | |
17096 | ||
17097 | @table @gcctabopt | |
17098 | @item -mwarn-reloc | |
17099 | @itemx -merror-reloc | |
17100 | @opindex mwarn-reloc | |
17101 | @opindex merror-reloc | |
17102 | ||
17103 | The loader for SPU does not handle dynamic relocations. By default, GCC | |
17104 | will give an error when it generates code that requires a dynamic | |
17105 | relocation. @option{-mno-error-reloc} disables the error, | |
17106 | @option{-mwarn-reloc} will generate a warning instead. | |
17107 | ||
17108 | @item -msafe-dma | |
17109 | @itemx -munsafe-dma | |
17110 | @opindex msafe-dma | |
17111 | @opindex munsafe-dma | |
17112 | ||
17113 | Instructions which initiate or test completion of DMA must not be | |
17114 | reordered with respect to loads and stores of the memory which is being | |
17115 | accessed. Users typically address this problem using the volatile | |
17116 | keyword, but that can lead to inefficient code in places where the | |
17117 | memory is known to not change. Rather than mark the memory as volatile | |
17118 | we treat the DMA instructions as potentially effecting all memory. With | |
17119 | @option{-munsafe-dma} users must use the volatile keyword to protect | |
17120 | memory accesses. | |
17121 | ||
17122 | @item -mbranch-hints | |
17123 | @opindex mbranch-hints | |
17124 | ||
17125 | By default, GCC will generate a branch hint instruction to avoid | |
17126 | pipeline stalls for always taken or probably taken branches. A hint | |
17127 | will not be generated closer than 8 instructions away from its branch. | |
17128 | There is little reason to disable them, except for debugging purposes, | |
17129 | or to make an object a little bit smaller. | |
17130 | ||
17131 | @item -msmall-mem | |
17132 | @itemx -mlarge-mem | |
17133 | @opindex msmall-mem | |
17134 | @opindex mlarge-mem | |
17135 | ||
17136 | By default, GCC generates code assuming that addresses are never larger | |
17137 | than 18 bits. With @option{-mlarge-mem} code is generated that assumes | |
17138 | a full 32 bit address. | |
17139 | ||
cc8d70cd SL |
17140 | @item -mstdmain |
17141 | @opindex mstdmain | |
17142 | ||
17143 | By default, GCC links against startup code that assumes the SPU-style | |
17144 | main function interface (which has an unconventional parameter list). | |
17145 | With @option{-mstdmain}, GCC will link your program against startup | |
17146 | code that assumes a C99-style interface to @code{main}, including a | |
17147 | local copy of @code{argv} strings. | |
17148 | ||
32fb22af SL |
17149 | @item -mfixed-range=@var{register-range} |
17150 | @opindex mfixed-range | |
17151 | Generate code treating the given register range as fixed registers. | |
17152 | A fixed register is one that the register allocator can not use. This is | |
17153 | useful when compiling kernel code. A register range is specified as | |
17154 | two registers separated by a dash. Multiple register ranges can be | |
17155 | specified separated by a comma. | |
17156 | ||
299456f3 BE |
17157 | @item -mea32 |
17158 | @itemx -mea64 | |
17159 | @opindex mea32 | |
17160 | @opindex mea64 | |
17161 | Compile code assuming that pointers to the PPU address space accessed | |
17162 | via the @code{__ea} named address space qualifier are either 32 or 64 | |
17163 | bits wide. The default is 32 bits. As this is an ABI changing option, | |
17164 | all object code in an executable must be compiled with the same setting. | |
17165 | ||
17166 | @item -maddress-space-conversion | |
17167 | @itemx -mno-address-space-conversion | |
17168 | @opindex maddress-space-conversion | |
17169 | @opindex mno-address-space-conversion | |
17170 | Allow/disallow treating the @code{__ea} address space as superset | |
17171 | of the generic address space. This enables explicit type casts | |
17172 | between @code{__ea} and generic pointer as well as implicit | |
17173 | conversions of generic pointers to @code{__ea} pointers. The | |
17174 | default is to allow address space pointer conversions. | |
17175 | ||
17176 | @item -mcache-size=@var{cache-size} | |
17177 | @opindex mcache-size | |
17178 | This option controls the version of libgcc that the compiler links to an | |
17179 | executable and selects a software-managed cache for accessing variables | |
17180 | in the @code{__ea} address space with a particular cache size. Possible | |
17181 | options for @var{cache-size} are @samp{8}, @samp{16}, @samp{32}, @samp{64} | |
17182 | and @samp{128}. The default cache size is 64KB. | |
17183 | ||
17184 | @item -matomic-updates | |
17185 | @itemx -mno-atomic-updates | |
17186 | @opindex matomic-updates | |
17187 | @opindex mno-atomic-updates | |
17188 | This option controls the version of libgcc that the compiler links to an | |
17189 | executable and selects whether atomic updates to the software-managed | |
17190 | cache of PPU-side variables are used. If you use atomic updates, changes | |
17191 | to a PPU variable from SPU code using the @code{__ea} named address space | |
17192 | qualifier will not interfere with changes to other PPU variables residing | |
17193 | in the same cache line from PPU code. If you do not use atomic updates, | |
17194 | such interference may occur; however, writing back cache lines will be | |
17195 | more efficient. The default behavior is to use atomic updates. | |
17196 | ||
9dcc2e87 TS |
17197 | @item -mdual-nops |
17198 | @itemx -mdual-nops=@var{n} | |
17199 | @opindex mdual-nops | |
17200 | By default, GCC will insert nops to increase dual issue when it expects | |
17201 | it to increase performance. @var{n} can be a value from 0 to 10. A | |
17202 | smaller @var{n} will insert fewer nops. 10 is the default, 0 is the | |
17203 | same as @option{-mno-dual-nops}. Disabled with @option{-Os}. | |
17204 | ||
17205 | @item -mhint-max-nops=@var{n} | |
17206 | @opindex mhint-max-nops | |
17207 | Maximum number of nops to insert for a branch hint. A branch hint must | |
17208 | be at least 8 instructions away from the branch it is effecting. GCC | |
17209 | will insert up to @var{n} nops to enforce this, otherwise it will not | |
17210 | generate the branch hint. | |
17211 | ||
17212 | @item -mhint-max-distance=@var{n} | |
17213 | @opindex mhint-max-distance | |
17214 | The encoding of the branch hint instruction limits the hint to be within | |
17215 | 256 instructions of the branch it is effecting. By default, GCC makes | |
7a61cf6f | 17216 | sure it is within 125. |
9dcc2e87 TS |
17217 | |
17218 | @item -msafe-hints | |
17219 | @opindex msafe-hints | |
17220 | Work around a hardware bug which causes the SPU to stall indefinitely. | |
17221 | By default, GCC will insert the @code{hbrp} instruction to make sure | |
17222 | this stall won't happen. | |
17223 | ||
85d9c13c TS |
17224 | @end table |
17225 | ||
39bc1876 NS |
17226 | @node System V Options |
17227 | @subsection Options for System V | |
70899148 | 17228 | |
39bc1876 NS |
17229 | These additional options are available on System V Release 4 for |
17230 | compatibility with other compilers on those systems: | |
70899148 | 17231 | |
39bc1876 NS |
17232 | @table @gcctabopt |
17233 | @item -G | |
17234 | @opindex G | |
17235 | Create a shared object. | |
17236 | It is recommended that @option{-symbolic} or @option{-shared} be used instead. | |
70899148 | 17237 | |
39bc1876 NS |
17238 | @item -Qy |
17239 | @opindex Qy | |
17240 | Identify the versions of each tool used by the compiler, in a | |
17241 | @code{.ident} assembler directive in the output. | |
70899148 | 17242 | |
39bc1876 NS |
17243 | @item -Qn |
17244 | @opindex Qn | |
17245 | Refrain from adding @code{.ident} directives to the output file (this is | |
17246 | the default). | |
70899148 | 17247 | |
39bc1876 NS |
17248 | @item -YP,@var{dirs} |
17249 | @opindex YP | |
17250 | Search the directories @var{dirs}, and no others, for libraries | |
17251 | specified with @option{-l}. | |
70899148 | 17252 | |
39bc1876 NS |
17253 | @item -Ym,@var{dir} |
17254 | @opindex Ym | |
17255 | Look in the directory @var{dir} to find the M4 preprocessor. | |
17256 | The assembler uses this option. | |
17257 | @c This is supposed to go with a -Yd for predefined M4 macro files, but | |
17258 | @c the generic assembler that comes with Solaris takes just -Ym. | |
17259 | @end table | |
70899148 | 17260 | |
39bc1876 NS |
17261 | @node V850 Options |
17262 | @subsection V850 Options | |
17263 | @cindex V850 Options | |
70899148 | 17264 | |
39bc1876 | 17265 | These @samp{-m} options are defined for V850 implementations: |
70899148 | 17266 | |
39bc1876 NS |
17267 | @table @gcctabopt |
17268 | @item -mlong-calls | |
17269 | @itemx -mno-long-calls | |
17270 | @opindex mlong-calls | |
17271 | @opindex mno-long-calls | |
17272 | Treat all calls as being far away (near). If calls are assumed to be | |
17273 | far away, the compiler will always load the functions address up into a | |
17274 | register, and call indirect through the pointer. | |
70899148 | 17275 | |
39bc1876 NS |
17276 | @item -mno-ep |
17277 | @itemx -mep | |
17278 | @opindex mno-ep | |
17279 | @opindex mep | |
17280 | Do not optimize (do optimize) basic blocks that use the same index | |
17281 | pointer 4 or more times to copy pointer into the @code{ep} register, and | |
17282 | use the shorter @code{sld} and @code{sst} instructions. The @option{-mep} | |
17283 | option is on by default if you optimize. | |
70899148 | 17284 | |
39bc1876 NS |
17285 | @item -mno-prolog-function |
17286 | @itemx -mprolog-function | |
17287 | @opindex mno-prolog-function | |
17288 | @opindex mprolog-function | |
17289 | Do not use (do use) external functions to save and restore registers | |
17290 | at the prologue and epilogue of a function. The external functions | |
17291 | are slower, but use less code space if more than one function saves | |
17292 | the same number of registers. The @option{-mprolog-function} option | |
17293 | is on by default if you optimize. | |
70899148 | 17294 | |
39bc1876 NS |
17295 | @item -mspace |
17296 | @opindex mspace | |
17297 | Try to make the code as small as possible. At present, this just turns | |
17298 | on the @option{-mep} and @option{-mprolog-function} options. | |
70899148 | 17299 | |
39bc1876 NS |
17300 | @item -mtda=@var{n} |
17301 | @opindex mtda | |
17302 | Put static or global variables whose size is @var{n} bytes or less into | |
17303 | the tiny data area that register @code{ep} points to. The tiny data | |
17304 | area can hold up to 256 bytes in total (128 bytes for byte references). | |
70899148 | 17305 | |
39bc1876 NS |
17306 | @item -msda=@var{n} |
17307 | @opindex msda | |
17308 | Put static or global variables whose size is @var{n} bytes or less into | |
17309 | the small data area that register @code{gp} points to. The small data | |
17310 | area can hold up to 64 kilobytes. | |
70899148 | 17311 | |
39bc1876 NS |
17312 | @item -mzda=@var{n} |
17313 | @opindex mzda | |
17314 | Put static or global variables whose size is @var{n} bytes or less into | |
17315 | the first 32 kilobytes of memory. | |
70899148 | 17316 | |
39bc1876 NS |
17317 | @item -mv850 |
17318 | @opindex mv850 | |
17319 | Specify that the target processor is the V850. | |
70899148 | 17320 | |
39bc1876 NS |
17321 | @item -mbig-switch |
17322 | @opindex mbig-switch | |
17323 | Generate code suitable for big switch tables. Use this option only if | |
17324 | the assembler/linker complain about out of range branches within a switch | |
17325 | table. | |
70899148 | 17326 | |
39bc1876 NS |
17327 | @item -mapp-regs |
17328 | @opindex mapp-regs | |
17329 | This option will cause r2 and r5 to be used in the code generated by | |
17330 | the compiler. This setting is the default. | |
70899148 | 17331 | |
39bc1876 NS |
17332 | @item -mno-app-regs |
17333 | @opindex mno-app-regs | |
17334 | This option will cause r2 and r5 to be treated as fixed registers. | |
70899148 | 17335 | |
223a9d64 N |
17336 | @item -mv850e2v3 |
17337 | @opindex mv850e2v3 | |
17338 | Specify that the target processor is the V850E2V3. The preprocessor | |
17339 | constants @samp{__v850e2v3__} will be defined if | |
17340 | this option is used. | |
17341 | ||
17342 | @item -mv850e2 | |
17343 | @opindex mv850e2 | |
17344 | Specify that the target processor is the V850E2. The preprocessor | |
17345 | constants @samp{__v850e2__} will be defined if | |
17346 | ||
39bc1876 NS |
17347 | @item -mv850e1 |
17348 | @opindex mv850e1 | |
17349 | Specify that the target processor is the V850E1. The preprocessor | |
17350 | constants @samp{__v850e1__} and @samp{__v850e__} will be defined if | |
70899148 | 17351 | |
39bc1876 NS |
17352 | @item -mv850e |
17353 | @opindex mv850e | |
8a36672b | 17354 | Specify that the target processor is the V850E@. The preprocessor |
39bc1876 | 17355 | constant @samp{__v850e__} will be defined if this option is used. |
70899148 | 17356 | |
39bc1876 | 17357 | If neither @option{-mv850} nor @option{-mv850e} nor @option{-mv850e1} |
223a9d64 | 17358 | nor @option{-mv850e2} nor @option{-mv850e2v3} |
39bc1876 NS |
17359 | are defined then a default target processor will be chosen and the |
17360 | relevant @samp{__v850*__} preprocessor constant will be defined. | |
70899148 | 17361 | |
39bc1876 NS |
17362 | The preprocessor constants @samp{__v850} and @samp{__v851__} are always |
17363 | defined, regardless of which processor variant is the target. | |
70899148 | 17364 | |
39bc1876 NS |
17365 | @item -mdisable-callt |
17366 | @opindex mdisable-callt | |
17367 | This option will suppress generation of the CALLT instruction for the | |
223a9d64 | 17368 | v850e, v850e1, v850e2 and v850e2v3 flavors of the v850 architecture. The default is |
39bc1876 | 17369 | @option{-mno-disable-callt} which allows the CALLT instruction to be used. |
70899148 | 17370 | |
39bc1876 | 17371 | @end table |
70899148 | 17372 | |
39bc1876 NS |
17373 | @node VAX Options |
17374 | @subsection VAX Options | |
17375 | @cindex VAX options | |
70899148 | 17376 | |
39bc1876 | 17377 | These @samp{-m} options are defined for the VAX: |
70899148 | 17378 | |
39bc1876 NS |
17379 | @table @gcctabopt |
17380 | @item -munix | |
17381 | @opindex munix | |
17382 | Do not output certain jump instructions (@code{aobleq} and so on) | |
17383 | that the Unix assembler for the VAX cannot handle across long | |
17384 | ranges. | |
70899148 | 17385 | |
39bc1876 NS |
17386 | @item -mgnu |
17387 | @opindex mgnu | |
17388 | Do output those jump instructions, on the assumption that you | |
17389 | will assemble with the GNU assembler. | |
70899148 | 17390 | |
39bc1876 NS |
17391 | @item -mg |
17392 | @opindex mg | |
17393 | Output code for g-format floating point numbers instead of d-format. | |
17394 | @end table | |
70899148 | 17395 | |
cd773ac4 RS |
17396 | @node VxWorks Options |
17397 | @subsection VxWorks Options | |
17398 | @cindex VxWorks Options | |
17399 | ||
17400 | The options in this section are defined for all VxWorks targets. | |
17401 | Options specific to the target hardware are listed with the other | |
17402 | options for that target. | |
17403 | ||
17404 | @table @gcctabopt | |
17405 | @item -mrtp | |
17406 | @opindex mrtp | |
17407 | GCC can generate code for both VxWorks kernels and real time processes | |
17408 | (RTPs). This option switches from the former to the latter. It also | |
17409 | defines the preprocessor macro @code{__RTP__}. | |
17410 | ||
17411 | @item -non-static | |
17412 | @opindex non-static | |
17413 | Link an RTP executable against shared libraries rather than static | |
17414 | libraries. The options @option{-static} and @option{-shared} can | |
17415 | also be used for RTPs (@pxref{Link Options}); @option{-static} | |
17416 | is the default. | |
17417 | ||
17418 | @item -Bstatic | |
17419 | @itemx -Bdynamic | |
17420 | @opindex Bstatic | |
17421 | @opindex Bdynamic | |
17422 | These options are passed down to the linker. They are defined for | |
17423 | compatibility with Diab. | |
17424 | ||
17425 | @item -Xbind-lazy | |
17426 | @opindex Xbind-lazy | |
17427 | Enable lazy binding of function calls. This option is equivalent to | |
17428 | @option{-Wl,-z,now} and is defined for compatibility with Diab. | |
17429 | ||
17430 | @item -Xbind-now | |
17431 | @opindex Xbind-now | |
17432 | Disable lazy binding of function calls. This option is the default and | |
17433 | is defined for compatibility with Diab. | |
17434 | @end table | |
17435 | ||
39bc1876 NS |
17436 | @node x86-64 Options |
17437 | @subsection x86-64 Options | |
17438 | @cindex x86-64 options | |
70899148 | 17439 | |
39bc1876 | 17440 | These are listed under @xref{i386 and x86-64 Options}. |
70899148 | 17441 | |
46994828 KT |
17442 | @node i386 and x86-64 Windows Options |
17443 | @subsection i386 and x86-64 Windows Options | |
17444 | @cindex i386 and x86-64 Windows Options | |
17445 | ||
17446 | These additional options are available for Windows targets: | |
17447 | ||
17448 | @table @gcctabopt | |
17449 | @item -mconsole | |
17450 | @opindex mconsole | |
17451 | This option is available for Cygwin and MinGW targets. It | |
17452 | specifies that a console application is to be generated, by | |
17453 | instructing the linker to set the PE header subsystem type | |
17454 | required for console applications. | |
c782f1dd | 17455 | This is the default behavior for Cygwin and MinGW targets. |
46994828 | 17456 | |
46994828 KT |
17457 | @item -mdll |
17458 | @opindex mdll | |
17459 | This option is available for Cygwin and MinGW targets. It | |
17460 | specifies that a DLL - a dynamic link library - is to be | |
17461 | generated, enabling the selection of the required runtime | |
17462 | startup object and entry point. | |
17463 | ||
17464 | @item -mnop-fun-dllimport | |
17465 | @opindex mnop-fun-dllimport | |
17466 | This option is available for Cygwin and MinGW targets. It | |
17467 | specifies that the dllimport attribute should be ignored. | |
17468 | ||
17469 | @item -mthread | |
17470 | @opindex mthread | |
17471 | This option is available for MinGW targets. It specifies | |
17472 | that MinGW-specific thread support is to be used. | |
17473 | ||
35091630 KT |
17474 | @item -municode |
17475 | @opindex municode | |
17476 | This option is available for mingw-w64 targets. It specifies | |
17477 | that the UNICODE macro is getting pre-defined and that the | |
a4ce9883 | 17478 | unicode capable runtime startup code is chosen. |
35091630 | 17479 | |
46994828 KT |
17480 | @item -mwin32 |
17481 | @opindex mwin32 | |
17482 | This option is available for Cygwin and MinGW targets. It | |
17483 | specifies that the typical Windows pre-defined macros are to | |
17484 | be set in the pre-processor, but does not influence the choice | |
17485 | of runtime library/startup code. | |
17486 | ||
17487 | @item -mwindows | |
17488 | @opindex mwindows | |
17489 | This option is available for Cygwin and MinGW targets. It | |
17490 | specifies that a GUI application is to be generated by | |
17491 | instructing the linker to set the PE header subsystem type | |
17492 | appropriately. | |
233215fe | 17493 | |
41ca8d08 KT |
17494 | @item -fno-set-stack-executable |
17495 | @opindex fno-set-stack-executable | |
17496 | This option is available for MinGW targets. It specifies that | |
17497 | the executable flag for stack used by nested functions isn't | |
17498 | set. This is necessary for binaries running in kernel mode of | |
17499 | Windows, as there the user32 API, which is used to set executable | |
17500 | privileges, isn't available. | |
17501 | ||
233215fe DK |
17502 | @item -mpe-aligned-commons |
17503 | @opindex mpe-aligned-commons | |
17504 | This option is available for Cygwin and MinGW targets. It | |
7a61cf6f | 17505 | specifies that the GNU extension to the PE file format that |
233215fe DK |
17506 | permits the correct alignment of COMMON variables should be |
17507 | used when generating code. It will be enabled by default if | |
17508 | GCC detects that the target assembler found during configuration | |
17509 | supports the feature. | |
46994828 KT |
17510 | @end table |
17511 | ||
6f401211 | 17512 | See also under @ref{i386 and x86-64 Options} for standard options. |
46994828 | 17513 | |
39bc1876 NS |
17514 | @node Xstormy16 Options |
17515 | @subsection Xstormy16 Options | |
17516 | @cindex Xstormy16 Options | |
70899148 | 17517 | |
39bc1876 | 17518 | These options are defined for Xstormy16: |
70899148 | 17519 | |
39bc1876 NS |
17520 | @table @gcctabopt |
17521 | @item -msim | |
17522 | @opindex msim | |
17523 | Choose startup files and linker script suitable for the simulator. | |
70899148 BS |
17524 | @end table |
17525 | ||
03984308 BW |
17526 | @node Xtensa Options |
17527 | @subsection Xtensa Options | |
17528 | @cindex Xtensa Options | |
17529 | ||
6cedbe44 | 17530 | These options are supported for Xtensa targets: |
03984308 BW |
17531 | |
17532 | @table @gcctabopt | |
f42f5a1b BW |
17533 | @item -mconst16 |
17534 | @itemx -mno-const16 | |
17535 | @opindex mconst16 | |
17536 | @opindex mno-const16 | |
6c2e8d1c BW |
17537 | Enable or disable use of @code{CONST16} instructions for loading |
17538 | constant values. The @code{CONST16} instruction is currently not a | |
17539 | standard option from Tensilica. When enabled, @code{CONST16} | |
17540 | instructions are always used in place of the standard @code{L32R} | |
17541 | instructions. The use of @code{CONST16} is enabled by default only if | |
17542 | the @code{L32R} instruction is not available. | |
17543 | ||
03984308 BW |
17544 | @item -mfused-madd |
17545 | @itemx -mno-fused-madd | |
17546 | @opindex mfused-madd | |
17547 | @opindex mno-fused-madd | |
17548 | Enable or disable use of fused multiply/add and multiply/subtract | |
17549 | instructions in the floating-point option. This has no effect if the | |
17550 | floating-point option is not also enabled. Disabling fused multiply/add | |
17551 | and multiply/subtract instructions forces the compiler to use separate | |
17552 | instructions for the multiply and add/subtract operations. This may be | |
17553 | desirable in some cases where strict IEEE 754-compliant results are | |
17554 | required: the fused multiply add/subtract instructions do not round the | |
17555 | intermediate result, thereby producing results with @emph{more} bits of | |
17556 | precision than specified by the IEEE standard. Disabling fused multiply | |
17557 | add/subtract instructions also ensures that the program output is not | |
17558 | sensitive to the compiler's ability to combine multiply and add/subtract | |
17559 | operations. | |
17560 | ||
66e58b33 BW |
17561 | @item -mserialize-volatile |
17562 | @itemx -mno-serialize-volatile | |
17563 | @opindex mserialize-volatile | |
17564 | @opindex mno-serialize-volatile | |
17565 | When this option is enabled, GCC inserts @code{MEMW} instructions before | |
17566 | @code{volatile} memory references to guarantee sequential consistency. | |
17567 | The default is @option{-mserialize-volatile}. Use | |
17568 | @option{-mno-serialize-volatile} to omit the @code{MEMW} instructions. | |
17569 | ||
1b408ba1 SA |
17570 | @item -mforce-no-pic |
17571 | @opindex mforce-no-pic | |
17572 | For targets, like GNU/Linux, where all user-mode Xtensa code must be | |
17573 | position-independent code (PIC), this option disables PIC for compiling | |
17574 | kernel code. | |
17575 | ||
03984308 BW |
17576 | @item -mtext-section-literals |
17577 | @itemx -mno-text-section-literals | |
17578 | @opindex mtext-section-literals | |
17579 | @opindex mno-text-section-literals | |
17580 | Control the treatment of literal pools. The default is | |
17581 | @option{-mno-text-section-literals}, which places literals in a separate | |
17582 | section in the output file. This allows the literal pool to be placed | |
17583 | in a data RAM/ROM, and it also allows the linker to combine literal | |
17584 | pools from separate object files to remove redundant literals and | |
17585 | improve code size. With @option{-mtext-section-literals}, the literals | |
17586 | are interspersed in the text section in order to keep them as close as | |
17587 | possible to their references. This may be necessary for large assembly | |
17588 | files. | |
17589 | ||
17590 | @item -mtarget-align | |
17591 | @itemx -mno-target-align | |
17592 | @opindex mtarget-align | |
17593 | @opindex mno-target-align | |
17594 | When this option is enabled, GCC instructs the assembler to | |
17595 | automatically align instructions to reduce branch penalties at the | |
17596 | expense of some code density. The assembler attempts to widen density | |
17597 | instructions to align branch targets and the instructions following call | |
17598 | instructions. If there are not enough preceding safe density | |
17599 | instructions to align a target, no widening will be performed. The | |
17600 | default is @option{-mtarget-align}. These options do not affect the | |
17601 | treatment of auto-aligned instructions like @code{LOOP}, which the | |
17602 | assembler will always align, either by widening density instructions or | |
17603 | by inserting no-op instructions. | |
17604 | ||
17605 | @item -mlongcalls | |
17606 | @itemx -mno-longcalls | |
17607 | @opindex mlongcalls | |
17608 | @opindex mno-longcalls | |
17609 | When this option is enabled, GCC instructs the assembler to translate | |
17610 | direct calls to indirect calls unless it can determine that the target | |
17611 | of a direct call is in the range allowed by the call instruction. This | |
17612 | translation typically occurs for calls to functions in other source | |
17613 | files. Specifically, the assembler translates a direct @code{CALL} | |
17614 | instruction into an @code{L32R} followed by a @code{CALLX} instruction. | |
17615 | The default is @option{-mno-longcalls}. This option should be used in | |
17616 | programs where the call target can potentially be out of range. This | |
17617 | option is implemented in the assembler, not the compiler, so the | |
17618 | assembly code generated by GCC will still show direct call | |
17619 | instructions---look at the disassembled object code to see the actual | |
17620 | instructions. Note that the assembler will use an indirect call for | |
17621 | every cross-file call, not just those that really will be out of range. | |
17622 | @end table | |
17623 | ||
39bc1876 NS |
17624 | @node zSeries Options |
17625 | @subsection zSeries Options | |
17626 | @cindex zSeries options | |
17627 | ||
17628 | These are listed under @xref{S/390 and zSeries Options}. | |
17629 | ||
74291a4b MM |
17630 | @node Code Gen Options |
17631 | @section Options for Code Generation Conventions | |
17632 | @cindex code generation conventions | |
17633 | @cindex options, code generation | |
17634 | @cindex run-time options | |
17635 | ||
17636 | These machine-independent options control the interface conventions | |
17637 | used in code generation. | |
17638 | ||
17639 | Most of them have both positive and negative forms; the negative form | |
630d3d5a | 17640 | of @option{-ffoo} would be @option{-fno-foo}. In the table below, only |
74291a4b MM |
17641 | one of the forms is listed---the one which is not the default. You |
17642 | can figure out the other form by either removing @samp{no-} or adding | |
17643 | it. | |
17644 | ||
2642624b | 17645 | @table @gcctabopt |
d4463dfc JQ |
17646 | @item -fbounds-check |
17647 | @opindex fbounds-check | |
17648 | For front-ends that support it, generate additional code to check that | |
17649 | indices used to access arrays are within the declared range. This is | |
dc5abe77 | 17650 | currently only supported by the Java and Fortran front-ends, where |
d4463dfc JQ |
17651 | this option defaults to true and false respectively. |
17652 | ||
17653 | @item -ftrapv | |
17654 | @opindex ftrapv | |
17655 | This option generates traps for signed overflow on addition, subtraction, | |
17656 | multiplication operations. | |
17657 | ||
4fa26a60 RS |
17658 | @item -fwrapv |
17659 | @opindex fwrapv | |
17660 | This option instructs the compiler to assume that signed arithmetic | |
17661 | overflow of addition, subtraction and multiplication wraps around | |
c0cbdbd9 | 17662 | using twos-complement representation. This flag enables some optimizations |
aa58883c | 17663 | and disables others. This option is enabled by default for the Java |
4fa26a60 RS |
17664 | front-end, as required by the Java language specification. |
17665 | ||
956d6950 | 17666 | @item -fexceptions |
cd3bb277 | 17667 | @opindex fexceptions |
767094dd | 17668 | Enable exception handling. Generates extra code needed to propagate |
f0523f02 | 17669 | exceptions. For some targets, this implies GCC will generate frame |
c5c76735 JL |
17670 | unwind information for all functions, which can produce significant data |
17671 | size overhead, although it does not affect execution. If you do not | |
f0523f02 | 17672 | specify this option, GCC will enable it by default for languages like |
90ecce3e | 17673 | C++ which normally require exception handling, and disable it for |
c5c76735 JL |
17674 | languages like C that do not normally require it. However, you may need |
17675 | to enable this option when compiling C code that needs to interoperate | |
17676 | properly with exception handlers written in C++. You may also wish to | |
17677 | disable this option if you are compiling older C++ programs that don't | |
17678 | use exception handling. | |
956d6950 | 17679 | |
6cfc0341 RH |
17680 | @item -fnon-call-exceptions |
17681 | @opindex fnon-call-exceptions | |
17682 | Generate code that allows trapping instructions to throw exceptions. | |
17683 | Note that this requires platform-specific runtime support that does | |
17684 | not exist everywhere. Moreover, it only allows @emph{trapping} | |
e979f9e8 | 17685 | instructions to throw exceptions, i.e.@: memory references or floating |
6cfc0341 RH |
17686 | point instructions. It does not allow exceptions to be thrown from |
17687 | arbitrary signal handlers such as @code{SIGALRM}. | |
17688 | ||
14a774a9 | 17689 | @item -funwind-tables |
cd3bb277 | 17690 | @opindex funwind-tables |
bedc7537 | 17691 | Similar to @option{-fexceptions}, except that it will just generate any needed |
14a774a9 RK |
17692 | static data, but will not affect the generated code in any other way. |
17693 | You will normally not enable this option; instead, a language processor | |
17694 | that needs this handling would enable it on your behalf. | |
17695 | ||
b932f770 | 17696 | @item -fasynchronous-unwind-tables |
2a9dc917 | 17697 | @opindex fasynchronous-unwind-tables |
b932f770 JH |
17698 | Generate unwind table in dwarf2 format, if supported by target machine. The |
17699 | table is exact at each instruction boundary, so it can be used for stack | |
17700 | unwinding from asynchronous events (such as debugger or garbage collector). | |
17701 | ||
74291a4b | 17702 | @item -fpcc-struct-return |
cd3bb277 | 17703 | @opindex fpcc-struct-return |
74291a4b MM |
17704 | Return ``short'' @code{struct} and @code{union} values in memory like |
17705 | longer ones, rather than in registers. This convention is less | |
17706 | efficient, but it has the advantage of allowing intercallability between | |
a9c60612 JJ |
17707 | GCC-compiled files and files compiled with other compilers, particularly |
17708 | the Portable C Compiler (pcc). | |
74291a4b MM |
17709 | |
17710 | The precise convention for returning structures in memory depends | |
17711 | on the target configuration macros. | |
17712 | ||
17713 | Short structures and unions are those whose size and alignment match | |
17714 | that of some integer type. | |
17715 | ||
a9c60612 JJ |
17716 | @strong{Warning:} code compiled with the @option{-fpcc-struct-return} |
17717 | switch is not binary compatible with code compiled with the | |
17718 | @option{-freg-struct-return} switch. | |
17719 | Use it to conform to a non-default application binary interface. | |
17720 | ||
74291a4b | 17721 | @item -freg-struct-return |
cd3bb277 | 17722 | @opindex freg-struct-return |
9c34dbbf ZW |
17723 | Return @code{struct} and @code{union} values in registers when possible. |
17724 | This is more efficient for small structures than | |
17725 | @option{-fpcc-struct-return}. | |
74291a4b | 17726 | |
9c34dbbf | 17727 | If you specify neither @option{-fpcc-struct-return} nor |
630d3d5a | 17728 | @option{-freg-struct-return}, GCC defaults to whichever convention is |
0c2d1a2a | 17729 | standard for the target. If there is no standard convention, GCC |
9c34dbbf ZW |
17730 | defaults to @option{-fpcc-struct-return}, except on targets where GCC is |
17731 | the principal compiler. In those cases, we can choose the standard, and | |
17732 | we chose the more efficient register return alternative. | |
74291a4b | 17733 | |
a9c60612 JJ |
17734 | @strong{Warning:} code compiled with the @option{-freg-struct-return} |
17735 | switch is not binary compatible with code compiled with the | |
17736 | @option{-fpcc-struct-return} switch. | |
17737 | Use it to conform to a non-default application binary interface. | |
17738 | ||
74291a4b | 17739 | @item -fshort-enums |
cd3bb277 | 17740 | @opindex fshort-enums |
74291a4b MM |
17741 | Allocate to an @code{enum} type only as many bytes as it needs for the |
17742 | declared range of possible values. Specifically, the @code{enum} type | |
17743 | will be equivalent to the smallest integer type which has enough room. | |
17744 | ||
a9c60612 JJ |
17745 | @strong{Warning:} the @option{-fshort-enums} switch causes GCC to generate |
17746 | code that is not binary compatible with code generated without that switch. | |
17747 | Use it to conform to a non-default application binary interface. | |
17748 | ||
74291a4b | 17749 | @item -fshort-double |
cd3bb277 | 17750 | @opindex fshort-double |
74291a4b MM |
17751 | Use the same size for @code{double} as for @code{float}. |
17752 | ||
a9c60612 JJ |
17753 | @strong{Warning:} the @option{-fshort-double} switch causes GCC to generate |
17754 | code that is not binary compatible with code generated without that switch. | |
17755 | Use it to conform to a non-default application binary interface. | |
17756 | ||
17757 | @item -fshort-wchar | |
17758 | @opindex fshort-wchar | |
17759 | Override the underlying type for @samp{wchar_t} to be @samp{short | |
17760 | unsigned int} instead of the default for the target. This option is | |
17761 | useful for building programs to run under WINE@. | |
17762 | ||
17763 | @strong{Warning:} the @option{-fshort-wchar} switch causes GCC to generate | |
17764 | code that is not binary compatible with code generated without that switch. | |
17765 | Use it to conform to a non-default application binary interface. | |
17766 | ||
74291a4b | 17767 | @item -fno-common |
cd3bb277 | 17768 | @opindex fno-common |
332459cd SL |
17769 | In C code, controls the placement of uninitialized global variables. |
17770 | Unix C compilers have traditionally permitted multiple definitions of | |
17771 | such variables in different compilation units by placing the variables | |
7a61cf6f NC |
17772 | in a common block. |
17773 | This is the behavior specified by @option{-fcommon}, and is the default | |
17774 | for GCC on most targets. | |
332459cd SL |
17775 | On the other hand, this behavior is not required by ISO C, and on some |
17776 | targets may carry a speed or code size penalty on variable references. | |
7a61cf6f | 17777 | The @option{-fno-common} option specifies that the compiler should place |
332459cd SL |
17778 | uninitialized global variables in the data section of the object file, |
17779 | rather than generating them as common blocks. | |
7a61cf6f | 17780 | This has the effect that if the same variable is declared |
332459cd SL |
17781 | (without @code{extern}) in two different compilations, |
17782 | you will get a multiple-definition error when you link them. | |
7a61cf6f NC |
17783 | In this case, you must compile with @option{-fcommon} instead. |
17784 | Compiling with @option{-fno-common} is useful on targets for which | |
332459cd SL |
17785 | it provides better performance, or if you wish to verify that the |
17786 | program will work on other systems which always treat uninitialized | |
17787 | variable declarations this way. | |
74291a4b MM |
17788 | |
17789 | @item -fno-ident | |
cd3bb277 | 17790 | @opindex fno-ident |
74291a4b MM |
17791 | Ignore the @samp{#ident} directive. |
17792 | ||
74291a4b | 17793 | @item -finhibit-size-directive |
cd3bb277 | 17794 | @opindex finhibit-size-directive |
74291a4b MM |
17795 | Don't output a @code{.size} assembler directive, or anything else that |
17796 | would cause trouble if the function is split in the middle, and the | |
17797 | two halves are placed at locations far apart in memory. This option is | |
17798 | used when compiling @file{crtstuff.c}; you should not need to use it | |
17799 | for anything else. | |
17800 | ||
17801 | @item -fverbose-asm | |
cd3bb277 | 17802 | @opindex fverbose-asm |
74291a4b MM |
17803 | Put extra commentary information in the generated assembly code to |
17804 | make it more readable. This option is generally only of use to those | |
17805 | who actually need to read the generated assembly code (perhaps while | |
17806 | debugging the compiler itself). | |
17807 | ||
630d3d5a | 17808 | @option{-fno-verbose-asm}, the default, causes the |
74291a4b MM |
17809 | extra information to be omitted and is useful when comparing two assembler |
17810 | files. | |
17811 | ||
e0d9d0dd NC |
17812 | @item -frecord-gcc-switches |
17813 | @opindex frecord-gcc-switches | |
17814 | This switch causes the command line that was used to invoke the | |
17815 | compiler to be recorded into the object file that is being created. | |
17816 | This switch is only implemented on some targets and the exact format | |
17817 | of the recording is target and binary file format dependent, but it | |
17818 | usually takes the form of a section containing ASCII text. This | |
17819 | switch is related to the @option{-fverbose-asm} switch, but that | |
17820 | switch only records information in the assembler output file as | |
17821 | comments, so it never reaches the object file. | |
17822 | ||
74291a4b | 17823 | @item -fpic |
cd3bb277 | 17824 | @opindex fpic |
74291a4b MM |
17825 | @cindex global offset table |
17826 | @cindex PIC | |
17827 | Generate position-independent code (PIC) suitable for use in a shared | |
17828 | library, if supported for the target machine. Such code accesses all | |
161d7b59 | 17829 | constant addresses through a global offset table (GOT)@. The dynamic |
861bb6c1 | 17830 | loader resolves the GOT entries when the program starts (the dynamic |
0c2d1a2a | 17831 | loader is not part of GCC; it is part of the operating system). If |
861bb6c1 JL |
17832 | the GOT size for the linked executable exceeds a machine-specific |
17833 | maximum size, you get an error message from the linker indicating that | |
630d3d5a | 17834 | @option{-fpic} does not work; in that case, recompile with @option{-fPIC} |
b6e69d94 | 17835 | instead. (These maximums are 8k on the SPARC and 32k |
861bb6c1 | 17836 | on the m68k and RS/6000. The 386 has no such limit.) |
74291a4b MM |
17837 | |
17838 | Position-independent code requires special support, and therefore works | |
0c2d1a2a | 17839 | only on certain machines. For the 386, GCC supports PIC for System V |
74291a4b MM |
17840 | but not for the Sun 386i. Code generated for the IBM RS/6000 is always |
17841 | position-independent. | |
17842 | ||
3d119f8f KG |
17843 | When this flag is set, the macros @code{__pic__} and @code{__PIC__} |
17844 | are defined to 1. | |
17845 | ||
74291a4b | 17846 | @item -fPIC |
cd3bb277 | 17847 | @opindex fPIC |
74291a4b MM |
17848 | If supported for the target machine, emit position-independent code, |
17849 | suitable for dynamic linking and avoiding any limit on the size of the | |
068d4f38 BE |
17850 | global offset table. This option makes a difference on the m68k, |
17851 | PowerPC and SPARC@. | |
74291a4b MM |
17852 | |
17853 | Position-independent code requires special support, and therefore works | |
17854 | only on certain machines. | |
17855 | ||
3d119f8f KG |
17856 | When this flag is set, the macros @code{__pic__} and @code{__PIC__} |
17857 | are defined to 2. | |
17858 | ||
24a4dd31 JJ |
17859 | @item -fpie |
17860 | @itemx -fPIE | |
17861 | @opindex fpie | |
17862 | @opindex fPIE | |
17863 | These options are similar to @option{-fpic} and @option{-fPIC}, but | |
17864 | generated position independent code can be only linked into executables. | |
17865 | Usually these options are used when @option{-pie} GCC option will be | |
17866 | used during linking. | |
17867 | ||
7c0ffd09 RS |
17868 | @option{-fpie} and @option{-fPIE} both define the macros |
17869 | @code{__pie__} and @code{__PIE__}. The macros have the value 1 | |
17870 | for @option{-fpie} and 2 for @option{-fPIE}. | |
17871 | ||
82c0180d JM |
17872 | @item -fno-jump-tables |
17873 | @opindex fno-jump-tables | |
17874 | Do not use jump tables for switch statements even where it would be | |
17875 | more efficient than other code generation strategies. This option is | |
17876 | of use in conjunction with @option{-fpic} or @option{-fPIC} for | |
17877 | building code which forms part of a dynamic linker and cannot | |
17878 | reference the address of a jump table. On some targets, jump tables | |
17879 | do not require a GOT and this option is not needed. | |
17880 | ||
74291a4b | 17881 | @item -ffixed-@var{reg} |
cd3bb277 | 17882 | @opindex ffixed |
74291a4b MM |
17883 | Treat the register named @var{reg} as a fixed register; generated code |
17884 | should never refer to it (except perhaps as a stack pointer, frame | |
17885 | pointer or in some other fixed role). | |
17886 | ||
17887 | @var{reg} must be the name of a register. The register names accepted | |
17888 | are machine-specific and are defined in the @code{REGISTER_NAMES} | |
17889 | macro in the machine description macro file. | |
17890 | ||
17891 | This flag does not have a negative form, because it specifies a | |
17892 | three-way choice. | |
17893 | ||
17894 | @item -fcall-used-@var{reg} | |
cd3bb277 | 17895 | @opindex fcall-used |
956d6950 | 17896 | Treat the register named @var{reg} as an allocable register that is |
74291a4b MM |
17897 | clobbered by function calls. It may be allocated for temporaries or |
17898 | variables that do not live across a call. Functions compiled this way | |
17899 | will not save and restore the register @var{reg}. | |
17900 | ||
cb2fdc84 GRK |
17901 | It is an error to used this flag with the frame pointer or stack pointer. |
17902 | Use of this flag for other registers that have fixed pervasive roles in | |
17903 | the machine's execution model will produce disastrous results. | |
74291a4b MM |
17904 | |
17905 | This flag does not have a negative form, because it specifies a | |
17906 | three-way choice. | |
17907 | ||
17908 | @item -fcall-saved-@var{reg} | |
cd3bb277 | 17909 | @opindex fcall-saved |
956d6950 | 17910 | Treat the register named @var{reg} as an allocable register saved by |
74291a4b MM |
17911 | functions. It may be allocated even for temporaries or variables that |
17912 | live across a call. Functions compiled this way will save and restore | |
17913 | the register @var{reg} if they use it. | |
17914 | ||
cb2fdc84 GRK |
17915 | It is an error to used this flag with the frame pointer or stack pointer. |
17916 | Use of this flag for other registers that have fixed pervasive roles in | |
17917 | the machine's execution model will produce disastrous results. | |
74291a4b MM |
17918 | |
17919 | A different sort of disaster will result from the use of this flag for | |
17920 | a register in which function values may be returned. | |
17921 | ||
17922 | This flag does not have a negative form, because it specifies a | |
17923 | three-way choice. | |
17924 | ||
467cecf3 | 17925 | @item -fpack-struct[=@var{n}] |
cd3bb277 | 17926 | @opindex fpack-struct |
467cecf3 | 17927 | Without a value specified, pack all structure members together without |
8a36672b | 17928 | holes. When a value is specified (which must be a small power of two), pack |
467cecf3 JB |
17929 | structure members according to this value, representing the maximum |
17930 | alignment (that is, objects with default alignment requirements larger than | |
17931 | this will be output potentially unaligned at the next fitting location. | |
a9c60612 JJ |
17932 | |
17933 | @strong{Warning:} the @option{-fpack-struct} switch causes GCC to generate | |
17934 | code that is not binary compatible with code generated without that switch. | |
3364c33b | 17935 | Additionally, it makes the code suboptimal. |
a9c60612 | 17936 | Use it to conform to a non-default application binary interface. |
74291a4b | 17937 | |
07417085 | 17938 | @item -finstrument-functions |
cd3bb277 | 17939 | @opindex finstrument-functions |
07417085 KR |
17940 | Generate instrumentation calls for entry and exit to functions. Just |
17941 | after function entry and just before function exit, the following | |
17942 | profiling functions will be called with the address of the current | |
17943 | function and its call site. (On some platforms, | |
17944 | @code{__builtin_return_address} does not work beyond the current | |
17945 | function, so the call site information may not be available to the | |
17946 | profiling functions otherwise.) | |
17947 | ||
3ab51846 | 17948 | @smallexample |
310668e8 JM |
17949 | void __cyg_profile_func_enter (void *this_fn, |
17950 | void *call_site); | |
17951 | void __cyg_profile_func_exit (void *this_fn, | |
17952 | void *call_site); | |
3ab51846 | 17953 | @end smallexample |
07417085 KR |
17954 | |
17955 | The first argument is the address of the start of the current function, | |
17956 | which may be looked up exactly in the symbol table. | |
17957 | ||
17958 | This instrumentation is also done for functions expanded inline in other | |
17959 | functions. The profiling calls will indicate where, conceptually, the | |
17960 | inline function is entered and exited. This means that addressable | |
17961 | versions of such functions must be available. If all your uses of a | |
17962 | function are expanded inline, this may mean an additional expansion of | |
17963 | code size. If you use @samp{extern inline} in your C code, an | |
17964 | addressable version of such functions must be provided. (This is | |
17965 | normally the case anyways, but if you get lucky and the optimizer always | |
17966 | expands the functions inline, you might have gotten away without | |
17967 | providing static copies.) | |
17968 | ||
17969 | A function may be given the attribute @code{no_instrument_function}, in | |
17970 | which case this instrumentation will not be done. This can be used, for | |
17971 | example, for the profiling functions listed above, high-priority | |
17972 | interrupt routines, and any functions from which the profiling functions | |
17973 | cannot safely be called (perhaps signal handlers, if the profiling | |
17974 | routines generate output or allocate memory). | |
17975 | ||
8d5a7d1f ILT |
17976 | @item -finstrument-functions-exclude-file-list=@var{file},@var{file},@dots{} |
17977 | @opindex finstrument-functions-exclude-file-list | |
17978 | ||
17979 | Set the list of functions that are excluded from instrumentation (see | |
17980 | the description of @code{-finstrument-functions}). If the file that | |
17981 | contains a function definition matches with one of @var{file}, then | |
17982 | that function is not instrumented. The match is done on substrings: | |
17983 | if the @var{file} parameter is a substring of the file name, it is | |
17984 | considered to be a match. | |
17985 | ||
ab940b73 RW |
17986 | For example: |
17987 | ||
17988 | @smallexample | |
17989 | -finstrument-functions-exclude-file-list=/bits/stl,include/sys | |
17990 | @end smallexample | |
17991 | ||
17992 | @noindent | |
8d5a7d1f ILT |
17993 | will exclude any inline function defined in files whose pathnames |
17994 | contain @code{/bits/stl} or @code{include/sys}. | |
17995 | ||
17996 | If, for some reason, you want to include letter @code{','} in one of | |
17997 | @var{sym}, write @code{'\,'}. For example, | |
17998 | @code{-finstrument-functions-exclude-file-list='\,\,tmp'} | |
17999 | (note the single quote surrounding the option). | |
18000 | ||
18001 | @item -finstrument-functions-exclude-function-list=@var{sym},@var{sym},@dots{} | |
18002 | @opindex finstrument-functions-exclude-function-list | |
18003 | ||
18004 | This is similar to @code{-finstrument-functions-exclude-file-list}, | |
18005 | but this option sets the list of function names to be excluded from | |
18006 | instrumentation. The function name to be matched is its user-visible | |
18007 | name, such as @code{vector<int> blah(const vector<int> &)}, not the | |
18008 | internal mangled name (e.g., @code{_Z4blahRSt6vectorIiSaIiEE}). The | |
18009 | match is done on substrings: if the @var{sym} parameter is a substring | |
4f1e4960 JM |
18010 | of the function name, it is considered to be a match. For C99 and C++ |
18011 | extended identifiers, the function name must be given in UTF-8, not | |
18012 | using universal character names. | |
8d5a7d1f | 18013 | |
861bb6c1 | 18014 | @item -fstack-check |
cd3bb277 | 18015 | @opindex fstack-check |
861bb6c1 JL |
18016 | Generate code to verify that you do not go beyond the boundary of the |
18017 | stack. You should specify this flag if you are running in an | |
18018 | environment with multiple threads, but only rarely need to specify it in | |
18019 | a single-threaded environment since stack overflow is automatically | |
18020 | detected on nearly all systems if there is only one stack. | |
18021 | ||
a157febd | 18022 | Note that this switch does not actually cause checking to be done; the |
b38f3813 EB |
18023 | operating system or the language runtime must do that. The switch causes |
18024 | generation of code to ensure that they see the stack being extended. | |
18025 | ||
18026 | You can additionally specify a string parameter: @code{no} means no | |
18027 | checking, @code{generic} means force the use of old-style checking, | |
18028 | @code{specific} means use the best checking method and is equivalent | |
18029 | to bare @option{-fstack-check}. | |
18030 | ||
18031 | Old-style checking is a generic mechanism that requires no specific | |
18032 | target support in the compiler but comes with the following drawbacks: | |
18033 | ||
18034 | @enumerate | |
18035 | @item | |
18036 | Modified allocation strategy for large objects: they will always be | |
18037 | allocated dynamically if their size exceeds a fixed threshold. | |
18038 | ||
18039 | @item | |
18040 | Fixed limit on the size of the static frame of functions: when it is | |
18041 | topped by a particular function, stack checking is not reliable and | |
18042 | a warning is issued by the compiler. | |
18043 | ||
18044 | @item | |
18045 | Inefficiency: because of both the modified allocation strategy and the | |
18046 | generic implementation, the performances of the code are hampered. | |
18047 | @end enumerate | |
18048 | ||
18049 | Note that old-style stack checking is also the fallback method for | |
18050 | @code{specific} if no target support has been added in the compiler. | |
a157febd GK |
18051 | |
18052 | @item -fstack-limit-register=@var{reg} | |
18053 | @itemx -fstack-limit-symbol=@var{sym} | |
18054 | @itemx -fno-stack-limit | |
cd3bb277 JM |
18055 | @opindex fstack-limit-register |
18056 | @opindex fstack-limit-symbol | |
18057 | @opindex fno-stack-limit | |
a157febd GK |
18058 | Generate code to ensure that the stack does not grow beyond a certain value, |
18059 | either the value of a register or the address of a symbol. If the stack | |
18060 | would grow beyond the value, a signal is raised. For most targets, | |
18061 | the signal is raised before the stack overruns the boundary, so | |
18062 | it is possible to catch the signal without taking special precautions. | |
18063 | ||
9c34dbbf ZW |
18064 | For instance, if the stack starts at absolute address @samp{0x80000000} |
18065 | and grows downwards, you can use the flags | |
18066 | @option{-fstack-limit-symbol=__stack_limit} and | |
18067 | @option{-Wl,--defsym,__stack_limit=0x7ffe0000} to enforce a stack limit | |
18068 | of 128KB@. Note that this may only work with the GNU linker. | |
a157febd | 18069 | |
7458026b ILT |
18070 | @item -fsplit-stack |
18071 | @opindex fsplit-stack | |
18072 | Generate code to automatically split the stack before it overflows. | |
18073 | The resulting program has a discontiguous stack which can only | |
18074 | overflow if the program is unable to allocate any more memory. This | |
18075 | is most useful when running threaded programs, as it is no longer | |
18076 | necessary to calculate a good stack size to use for each thread. This | |
18077 | is currently only implemented for the i386 and x86_64 backends running | |
18078 | GNU/Linux. | |
18079 | ||
18080 | When code compiled with @option{-fsplit-stack} calls code compiled | |
18081 | without @option{-fsplit-stack}, there may not be much stack space | |
18082 | available for the latter code to run. If compiling all code, | |
18083 | including library code, with @option{-fsplit-stack} is not an option, | |
18084 | then the linker can fix up these calls so that the code compiled | |
18085 | without @option{-fsplit-stack} always has a large stack. Support for | |
18086 | this is implemented in the gold linker in GNU binutils release 2.21 | |
18087 | and later. | |
18088 | ||
19283265 | 18089 | @item -fleading-underscore |
cd3bb277 | 18090 | @opindex fleading-underscore |
695ac33f | 18091 | This option and its counterpart, @option{-fno-leading-underscore}, forcibly |
19283265 RH |
18092 | change the way C symbols are represented in the object file. One use |
18093 | is to help link with legacy assembly code. | |
18094 | ||
a9c60612 JJ |
18095 | @strong{Warning:} the @option{-fleading-underscore} switch causes GCC to |
18096 | generate code that is not binary compatible with code generated without that | |
18097 | switch. Use it to conform to a non-default application binary interface. | |
18098 | Not all targets provide complete support for this switch. | |
3d78f2e9 RH |
18099 | |
18100 | @item -ftls-model=@var{model} | |
d228aace | 18101 | @opindex ftls-model |
3d78f2e9 RH |
18102 | Alter the thread-local storage model to be used (@pxref{Thread-Local}). |
18103 | The @var{model} argument should be one of @code{global-dynamic}, | |
18104 | @code{local-dynamic}, @code{initial-exec} or @code{local-exec}. | |
18105 | ||
18106 | The default without @option{-fpic} is @code{initial-exec}; with | |
18107 | @option{-fpic} the default is @code{global-dynamic}. | |
d7afec4b ND |
18108 | |
18109 | @item -fvisibility=@var{default|internal|hidden|protected} | |
18110 | @opindex fvisibility | |
78466c0e | 18111 | Set the default ELF image symbol visibility to the specified option---all |
27ef2cdd | 18112 | symbols will be marked with this unless overridden within the code. |
d7afec4b | 18113 | Using this feature can very substantially improve linking and |
27ef2cdd | 18114 | load times of shared object libraries, produce more optimized |
d7afec4b ND |
18115 | code, provide near-perfect API export and prevent symbol clashes. |
18116 | It is @strong{strongly} recommended that you use this in any shared objects | |
18117 | you distribute. | |
f0eb93a8 | 18118 | |
d7afec4b ND |
18119 | Despite the nomenclature, @code{default} always means public ie; |
18120 | available to be linked against from outside the shared object. | |
18121 | @code{protected} and @code{internal} are pretty useless in real-world | |
18122 | usage so the only other commonly used option will be @code{hidden}. | |
78466c0e JM |
18123 | The default if @option{-fvisibility} isn't specified is |
18124 | @code{default}, i.e., make every | |
18125 | symbol public---this causes the same behavior as previous versions of | |
8a36672b | 18126 | GCC@. |
f0eb93a8 | 18127 | |
d7afec4b ND |
18128 | A good explanation of the benefits offered by ensuring ELF |
18129 | symbols have the correct visibility is given by ``How To Write | |
18130 | Shared Libraries'' by Ulrich Drepper (which can be found at | |
78466c0e | 18131 | @w{@uref{http://people.redhat.com/~drepper/}})---however a superior |
d7afec4b ND |
18132 | solution made possible by this option to marking things hidden when |
18133 | the default is public is to make the default hidden and mark things | |
8a36672b | 18134 | public. This is the norm with DLL's on Windows and with @option{-fvisibility=hidden} |
d7afec4b ND |
18135 | and @code{__attribute__ ((visibility("default")))} instead of |
18136 | @code{__declspec(dllexport)} you get almost identical semantics with | |
8a36672b | 18137 | identical syntax. This is a great boon to those working with |
d7afec4b ND |
18138 | cross-platform projects. |
18139 | ||
18140 | For those adding visibility support to existing code, you may find | |
8a36672b | 18141 | @samp{#pragma GCC visibility} of use. This works by you enclosing |
d7afec4b ND |
18142 | the declarations you wish to set visibility for with (for example) |
18143 | @samp{#pragma GCC visibility push(hidden)} and | |
be1b1c9b L |
18144 | @samp{#pragma GCC visibility pop}. |
18145 | Bear in mind that symbol visibility should be viewed @strong{as | |
d7afec4b ND |
18146 | part of the API interface contract} and thus all new code should |
18147 | always specify visibility when it is not the default ie; declarations | |
18148 | only for use within the local DSO should @strong{always} be marked explicitly | |
78466c0e | 18149 | as hidden as so to avoid PLT indirection overheads---making this |
d7afec4b ND |
18150 | abundantly clear also aids readability and self-documentation of the code. |
18151 | Note that due to ISO C++ specification requirements, operator new and | |
18152 | operator delete must always be of default visibility. | |
18153 | ||
46bdbc00 GK |
18154 | Be aware that headers from outside your project, in particular system |
18155 | headers and headers from any other library you use, may not be | |
18156 | expecting to be compiled with visibility other than the default. You | |
18157 | may need to explicitly say @samp{#pragma GCC visibility push(default)} | |
18158 | before including any such headers. | |
18159 | ||
b9e75696 JM |
18160 | @samp{extern} declarations are not affected by @samp{-fvisibility}, so |
18161 | a lot of code can be recompiled with @samp{-fvisibility=hidden} with | |
18162 | no modifications. However, this means that calls to @samp{extern} | |
18163 | functions with no explicit visibility will use the PLT, so it is more | |
18164 | effective to use @samp{__attribute ((visibility))} and/or | |
18165 | @samp{#pragma GCC visibility} to tell the compiler which @samp{extern} | |
18166 | declarations should be treated as hidden. | |
18167 | ||
18168 | Note that @samp{-fvisibility} does affect C++ vague linkage | |
18169 | entities. This means that, for instance, an exception class that will | |
18170 | be thrown between DSOs must be explicitly marked with default | |
18171 | visibility so that the @samp{type_info} nodes will be unified between | |
18172 | the DSOs. | |
18173 | ||
ce84fa41 | 18174 | An overview of these techniques, their benefits and how to use them |
ab940b73 | 18175 | is at @uref{http://gcc.gnu.org/@/wiki/@/Visibility}. |
ce84fa41 | 18176 | |
6a78b724 | 18177 | @item -fstrict-volatile-bitfields |
c1721efb | 18178 | @opindex fstrict-volatile-bitfields |
6a78b724 DD |
18179 | This option should be used if accesses to volatile bitfields (or other |
18180 | structure fields, although the compiler usually honors those types | |
0d600fce JZ |
18181 | anyway) should use a single access of the width of the |
18182 | field's type, aligned to a natural alignment if possible. For | |
6a78b724 DD |
18183 | example, targets with memory-mapped peripheral registers might require |
18184 | all such accesses to be 16 bits wide; with this flag the user could | |
18185 | declare all peripheral bitfields as ``unsigned short'' (assuming short | |
18186 | is 16 bits on these targets) to force GCC to use 16 bit accesses | |
18187 | instead of, perhaps, a more efficient 32 bit access. | |
18188 | ||
18189 | If this option is disabled, the compiler will use the most efficient | |
18190 | instruction. In the previous example, that might be a 32-bit load | |
18191 | instruction, even though that will access bytes that do not contain | |
18192 | any portion of the bitfield, or memory-mapped registers unrelated to | |
18193 | the one being updated. | |
18194 | ||
0d600fce | 18195 | If the target requires strict alignment, and honoring the field |
6a78b724 | 18196 | type would require violating this alignment, a warning is issued. |
0d600fce JZ |
18197 | If the field has @code{packed} attribute, the access is done without |
18198 | honoring the field type. If the field doesn't have @code{packed} | |
18199 | attribute, the access is done honoring the field type. In both cases, | |
18200 | GCC assumes that the user knows something about the target hardware | |
18201 | that it is unaware of. | |
6a78b724 DD |
18202 | |
18203 | The default value of this option is determined by the application binary | |
18204 | interface for the target processor. | |
18205 | ||
74291a4b MM |
18206 | @end table |
18207 | ||
ee457005 JM |
18208 | @c man end |
18209 | ||
74291a4b | 18210 | @node Environment Variables |
0c2d1a2a | 18211 | @section Environment Variables Affecting GCC |
74291a4b MM |
18212 | @cindex environment variables |
18213 | ||
ee457005 | 18214 | @c man begin ENVIRONMENT |
0c2d1a2a JB |
18215 | This section describes several environment variables that affect how GCC |
18216 | operates. Some of them work by specifying directories or prefixes to use | |
767094dd | 18217 | when searching for various kinds of files. Some are used to specify other |
46103ab4 | 18218 | aspects of the compilation environment. |
74291a4b | 18219 | |
74291a4b | 18220 | Note that you can also specify places to search using options such as |
630d3d5a | 18221 | @option{-B}, @option{-I} and @option{-L} (@pxref{Directory Options}). These |
74291a4b | 18222 | take precedence over places specified using environment variables, which |
161d7b59 | 18223 | in turn take precedence over those specified by the configuration of GCC@. |
b11cc610 JM |
18224 | @xref{Driver,, Controlling the Compilation Driver @file{gcc}, gccint, |
18225 | GNU Compiler Collection (GCC) Internals}. | |
74291a4b | 18226 | |
bedc7537 | 18227 | @table @env |
ab87f8c8 JL |
18228 | @item LANG |
18229 | @itemx LC_CTYPE | |
18230 | @c @itemx LC_COLLATE | |
18231 | @itemx LC_MESSAGES | |
18232 | @c @itemx LC_MONETARY | |
18233 | @c @itemx LC_NUMERIC | |
18234 | @c @itemx LC_TIME | |
18235 | @itemx LC_ALL | |
18236 | @findex LANG | |
18237 | @findex LC_CTYPE | |
18238 | @c @findex LC_COLLATE | |
18239 | @findex LC_MESSAGES | |
18240 | @c @findex LC_MONETARY | |
18241 | @c @findex LC_NUMERIC | |
18242 | @c @findex LC_TIME | |
18243 | @findex LC_ALL | |
18244 | @cindex locale | |
0c2d1a2a JB |
18245 | These environment variables control the way that GCC uses |
18246 | localization information that allow GCC to work with different | |
18247 | national conventions. GCC inspects the locale categories | |
bedc7537 | 18248 | @env{LC_CTYPE} and @env{LC_MESSAGES} if it has been configured to do |
ab87f8c8 | 18249 | so. These locale categories can be set to any value supported by your |
0e6d31fb JM |
18250 | installation. A typical value is @samp{en_GB.UTF-8} for English in the United |
18251 | Kingdom encoded in UTF-8. | |
ab87f8c8 | 18252 | |
bedc7537 | 18253 | The @env{LC_CTYPE} environment variable specifies character |
0c2d1a2a | 18254 | classification. GCC uses it to determine the character boundaries in |
ab87f8c8 JL |
18255 | a string; this is needed for some multibyte encodings that contain quote |
18256 | and escape characters that would otherwise be interpreted as a string | |
18257 | end or escape. | |
18258 | ||
bedc7537 | 18259 | The @env{LC_MESSAGES} environment variable specifies the language to |
ab87f8c8 JL |
18260 | use in diagnostic messages. |
18261 | ||
bedc7537 NC |
18262 | If the @env{LC_ALL} environment variable is set, it overrides the value |
18263 | of @env{LC_CTYPE} and @env{LC_MESSAGES}; otherwise, @env{LC_CTYPE} | |
18264 | and @env{LC_MESSAGES} default to the value of the @env{LANG} | |
0c2d1a2a | 18265 | environment variable. If none of these variables are set, GCC |
ab87f8c8 JL |
18266 | defaults to traditional C English behavior. |
18267 | ||
74291a4b MM |
18268 | @item TMPDIR |
18269 | @findex TMPDIR | |
bedc7537 | 18270 | If @env{TMPDIR} is set, it specifies the directory to use for temporary |
0c2d1a2a | 18271 | files. GCC uses temporary files to hold the output of one stage of |
74291a4b MM |
18272 | compilation which is to be used as input to the next stage: for example, |
18273 | the output of the preprocessor, which is the input to the compiler | |
18274 | proper. | |
18275 | ||
18276 | @item GCC_EXEC_PREFIX | |
18277 | @findex GCC_EXEC_PREFIX | |
bedc7537 | 18278 | If @env{GCC_EXEC_PREFIX} is set, it specifies a prefix to use in the |
74291a4b MM |
18279 | names of the subprograms executed by the compiler. No slash is added |
18280 | when this prefix is combined with the name of a subprogram, but you can | |
18281 | specify a prefix that ends with a slash if you wish. | |
18282 | ||
f0523f02 | 18283 | If @env{GCC_EXEC_PREFIX} is not set, GCC will attempt to figure out |
0deb20df TT |
18284 | an appropriate prefix to use based on the pathname it was invoked with. |
18285 | ||
0c2d1a2a | 18286 | If GCC cannot find the subprogram using the specified prefix, it |
74291a4b MM |
18287 | tries looking in the usual places for the subprogram. |
18288 | ||
bedc7537 | 18289 | The default value of @env{GCC_EXEC_PREFIX} is |
fe037b8a CD |
18290 | @file{@var{prefix}/lib/gcc/} where @var{prefix} is the prefix to |
18291 | the installed compiler. In many cases @var{prefix} is the value | |
74291a4b MM |
18292 | of @code{prefix} when you ran the @file{configure} script. |
18293 | ||
630d3d5a | 18294 | Other prefixes specified with @option{-B} take precedence over this prefix. |
74291a4b MM |
18295 | |
18296 | This prefix is also used for finding files such as @file{crt0.o} that are | |
18297 | used for linking. | |
18298 | ||
18299 | In addition, the prefix is used in an unusual way in finding the | |
18300 | directories to search for header files. For each of the standard | |
8e5f33ff | 18301 | directories whose name normally begins with @samp{/usr/local/lib/gcc} |
bedc7537 | 18302 | (more precisely, with the value of @env{GCC_INCLUDE_DIR}), GCC tries |
74291a4b | 18303 | replacing that beginning with the specified prefix to produce an |
630d3d5a | 18304 | alternate directory name. Thus, with @option{-Bfoo/}, GCC will search |
74291a4b MM |
18305 | @file{foo/bar} where it would normally search @file{/usr/local/lib/bar}. |
18306 | These alternate directories are searched first; the standard directories | |
cb7ad97b EC |
18307 | come next. If a standard directory begins with the configured |
18308 | @var{prefix} then the value of @var{prefix} is replaced by | |
fe037b8a | 18309 | @env{GCC_EXEC_PREFIX} when looking for header files. |
74291a4b MM |
18310 | |
18311 | @item COMPILER_PATH | |
18312 | @findex COMPILER_PATH | |
bedc7537 NC |
18313 | The value of @env{COMPILER_PATH} is a colon-separated list of |
18314 | directories, much like @env{PATH}. GCC tries the directories thus | |
74291a4b | 18315 | specified when searching for subprograms, if it can't find the |
bedc7537 | 18316 | subprograms using @env{GCC_EXEC_PREFIX}. |
74291a4b MM |
18317 | |
18318 | @item LIBRARY_PATH | |
18319 | @findex LIBRARY_PATH | |
bedc7537 NC |
18320 | The value of @env{LIBRARY_PATH} is a colon-separated list of |
18321 | directories, much like @env{PATH}. When configured as a native compiler, | |
0c2d1a2a | 18322 | GCC tries the directories thus specified when searching for special |
bedc7537 | 18323 | linker files, if it can't find them using @env{GCC_EXEC_PREFIX}. Linking |
0c2d1a2a | 18324 | using GCC also uses these directories when searching for ordinary |
630d3d5a JM |
18325 | libraries for the @option{-l} option (but directories specified with |
18326 | @option{-L} come first). | |
74291a4b | 18327 | |
56f48ce9 DB |
18328 | @item LANG |
18329 | @findex LANG | |
18330 | @cindex locale definition | |
767094dd | 18331 | This variable is used to pass locale information to the compiler. One way in |
56f48ce9 DB |
18332 | which this information is used is to determine the character set to be used |
18333 | when character literals, string literals and comments are parsed in C and C++. | |
18334 | When the compiler is configured to allow multibyte characters, | |
bedc7537 | 18335 | the following values for @env{LANG} are recognized: |
56f48ce9 | 18336 | |
2642624b | 18337 | @table @samp |
56f48ce9 DB |
18338 | @item C-JIS |
18339 | Recognize JIS characters. | |
18340 | @item C-SJIS | |
18341 | Recognize SJIS characters. | |
18342 | @item C-EUCJP | |
18343 | Recognize EUCJP characters. | |
18344 | @end table | |
18345 | ||
bedc7537 | 18346 | If @env{LANG} is not defined, or if it has some other value, then the |
56f48ce9 DB |
18347 | compiler will use mblen and mbtowc as defined by the default locale to |
18348 | recognize and translate multibyte characters. | |
74291a4b MM |
18349 | @end table |
18350 | ||
40adaa27 NB |
18351 | @noindent |
18352 | Some additional environments variables affect the behavior of the | |
18353 | preprocessor. | |
18354 | ||
18355 | @include cppenv.texi | |
18356 | ||
9d86bffc JM |
18357 | @c man end |
18358 | ||
17211ab5 GK |
18359 | @node Precompiled Headers |
18360 | @section Using Precompiled Headers | |
18361 | @cindex precompiled headers | |
18362 | @cindex speed of compilation | |
18363 | ||
18364 | Often large projects have many header files that are included in every | |
18365 | source file. The time the compiler takes to process these header files | |
18366 | over and over again can account for nearly all of the time required to | |
18367 | build the project. To make builds faster, GCC allows users to | |
18368 | `precompile' a header file; then, if builds can use the precompiled | |
18369 | header file they will be much faster. | |
18370 | ||
18371 | To create a precompiled header file, simply compile it as you would any | |
18372 | other file, if necessary using the @option{-x} option to make the driver | |
18373 | treat it as a C or C++ header file. You will probably want to use a | |
18374 | tool like @command{make} to keep the precompiled header up-to-date when | |
18375 | the headers it contains change. | |
18376 | ||
18377 | A precompiled header file will be searched for when @code{#include} is | |
18378 | seen in the compilation. As it searches for the included file | |
24726b96 | 18379 | (@pxref{Search Path,,Search Path,cpp,The C Preprocessor}) the |
17211ab5 GK |
18380 | compiler looks for a precompiled header in each directory just before it |
18381 | looks for the include file in that directory. The name searched for is | |
d8fad4ea | 18382 | the name specified in the @code{#include} with @samp{.gch} appended. If |
17211ab5 GK |
18383 | the precompiled header file can't be used, it is ignored. |
18384 | ||
18385 | For instance, if you have @code{#include "all.h"}, and you have | |
d8fad4ea | 18386 | @file{all.h.gch} in the same directory as @file{all.h}, then the |
17211ab5 GK |
18387 | precompiled header file will be used if possible, and the original |
18388 | header will be used otherwise. | |
18389 | ||
18390 | Alternatively, you might decide to put the precompiled header file in a | |
18391 | directory and use @option{-I} to ensure that directory is searched | |
18392 | before (or instead of) the directory containing the original header. | |
18393 | Then, if you want to check that the precompiled header file is always | |
18394 | used, you can put a file of the same name as the original header in this | |
18395 | directory containing an @code{#error} command. | |
18396 | ||
18397 | This also works with @option{-include}. So yet another way to use | |
18398 | precompiled headers, good for projects not designed with precompiled | |
18399 | header files in mind, is to simply take most of the header files used by | |
18400 | a project, include them from another header file, precompile that header | |
18401 | file, and @option{-include} the precompiled header. If the header files | |
18402 | have guards against multiple inclusion, they will be skipped because | |
18403 | they've already been included (in the precompiled header). | |
18404 | ||
18405 | If you need to precompile the same header file for different | |
18406 | languages, targets, or compiler options, you can instead make a | |
d8fad4ea | 18407 | @emph{directory} named like @file{all.h.gch}, and put each precompiled |
54e109ed GK |
18408 | header in the directory, perhaps using @option{-o}. It doesn't matter |
18409 | what you call the files in the directory, every precompiled header in | |
18410 | the directory will be considered. The first precompiled header | |
18411 | encountered in the directory that is valid for this compilation will | |
18412 | be used; they're searched in no particular order. | |
17211ab5 GK |
18413 | |
18414 | There are many other possibilities, limited only by your imagination, | |
18415 | good sense, and the constraints of your build system. | |
18416 | ||
18417 | A precompiled header file can be used only when these conditions apply: | |
18418 | ||
18419 | @itemize | |
18420 | @item | |
18421 | Only one precompiled header can be used in a particular compilation. | |
54e109ed | 18422 | |
17211ab5 GK |
18423 | @item |
18424 | A precompiled header can't be used once the first C token is seen. You | |
18425 | can have preprocessor directives before a precompiled header; you can | |
18426 | even include a precompiled header from inside another header, so long as | |
18427 | there are no C tokens before the @code{#include}. | |
54e109ed | 18428 | |
17211ab5 GK |
18429 | @item |
18430 | The precompiled header file must be produced for the same language as | |
18431 | the current compilation. You can't use a C precompiled header for a C++ | |
18432 | compilation. | |
54e109ed | 18433 | |
17211ab5 | 18434 | @item |
3fd30b88 GK |
18435 | The precompiled header file must have been produced by the same compiler |
18436 | binary as the current compilation is using. | |
54e109ed | 18437 | |
17211ab5 | 18438 | @item |
54e109ed GK |
18439 | Any macros defined before the precompiled header is included must |
18440 | either be defined in the same way as when the precompiled header was | |
18441 | generated, or must not affect the precompiled header, which usually | |
0bdcd332 | 18442 | means that they don't appear in the precompiled header at all. |
54e109ed GK |
18443 | |
18444 | The @option{-D} option is one way to define a macro before a | |
18445 | precompiled header is included; using a @code{#define} can also do it. | |
18446 | There are also some options that define macros implicitly, like | |
18447 | @option{-O} and @option{-Wdeprecated}; the same rule applies to macros | |
18448 | defined this way. | |
18449 | ||
18450 | @item If debugging information is output when using the precompiled | |
18451 | header, using @option{-g} or similar, the same kind of debugging information | |
18452 | must have been output when building the precompiled header. However, | |
18453 | a precompiled header built using @option{-g} can be used in a compilation | |
18454 | when no debugging information is being output. | |
18455 | ||
18456 | @item The same @option{-m} options must generally be used when building | |
18457 | and using the precompiled header. @xref{Submodel Options}, | |
18458 | for any cases where this rule is relaxed. | |
18459 | ||
18460 | @item Each of the following options must be the same when building and using | |
18461 | the precompiled header: | |
18462 | ||
d6cc6ec9 | 18463 | @gccoptlist{-fexceptions} |
54e109ed | 18464 | |
17211ab5 | 18465 | @item |
54e109ed GK |
18466 | Some other command-line options starting with @option{-f}, |
18467 | @option{-p}, or @option{-O} must be defined in the same way as when | |
18468 | the precompiled header was generated. At present, it's not clear | |
18469 | which options are safe to change and which are not; the safest choice | |
18470 | is to use exactly the same options when generating and using the | |
18471 | precompiled header. The following are known to be safe: | |
18472 | ||
78681dbd RS |
18473 | @gccoptlist{-fmessage-length= -fpreprocessed -fsched-interblock @gol |
18474 | -fsched-spec -fsched-spec-load -fsched-spec-load-dangerous @gol | |
18475 | -fsched-verbose=<number> -fschedule-insns -fvisibility= @gol | |
3fd30b88 | 18476 | -pedantic-errors} |
54e109ed | 18477 | |
17211ab5 GK |
18478 | @end itemize |
18479 | ||
54e109ed GK |
18480 | For all of these except the last, the compiler will automatically |
18481 | ignore the precompiled header if the conditions aren't met. If you | |
18482 | find an option combination that doesn't work and doesn't cause the | |
18483 | precompiled header to be ignored, please consider filing a bug report, | |
18484 | see @ref{Bugs}. | |
17211ab5 | 18485 | |
c0d578e6 | 18486 | If you do use differing options when generating and using the |
83c99486 KH |
18487 | precompiled header, the actual behavior will be a mixture of the |
18488 | behavior for the options. For instance, if you use @option{-g} to | |
c0d578e6 GK |
18489 | generate the precompiled header but not when using it, you may or may |
18490 | not get debugging information for routines in the precompiled header. |