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38f8b050 | 1 | @c Copyright (C) 1988,1989,1992,1993,1994,1995,1996,1997,1998,1999,2000,2001, |
58cd1d70 | 2 | @c 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 |
38f8b050 JR |
3 | @c Free Software Foundation, Inc. |
4 | @c This is part of the GCC manual. | |
5 | @c For copying conditions, see the file gcc.texi. | |
6 | ||
7 | @node Target Macros | |
8 | @chapter Target Description Macros and Functions | |
9 | @cindex machine description macros | |
10 | @cindex target description macros | |
11 | @cindex macros, target description | |
12 | @cindex @file{tm.h} macros | |
13 | ||
14 | In addition to the file @file{@var{machine}.md}, a machine description | |
15 | includes a C header file conventionally given the name | |
16 | @file{@var{machine}.h} and a C source file named @file{@var{machine}.c}. | |
17 | The header file defines numerous macros that convey the information | |
18 | about the target machine that does not fit into the scheme of the | |
19 | @file{.md} file. The file @file{tm.h} should be a link to | |
20 | @file{@var{machine}.h}. The header file @file{config.h} includes | |
21 | @file{tm.h} and most compiler source files include @file{config.h}. The | |
22 | source file defines a variable @code{targetm}, which is a structure | |
23 | containing pointers to functions and data relating to the target | |
24 | machine. @file{@var{machine}.c} should also contain their definitions, | |
25 | if they are not defined elsewhere in GCC, and other functions called | |
26 | through the macros defined in the @file{.h} file. | |
27 | ||
28 | @menu | |
29 | * Target Structure:: The @code{targetm} variable. | |
30 | * Driver:: Controlling how the driver runs the compilation passes. | |
31 | * Run-time Target:: Defining @samp{-m} options like @option{-m68000} and @option{-m68020}. | |
32 | * Per-Function Data:: Defining data structures for per-function information. | |
33 | * Storage Layout:: Defining sizes and alignments of data. | |
34 | * Type Layout:: Defining sizes and properties of basic user data types. | |
35 | * Registers:: Naming and describing the hardware registers. | |
36 | * Register Classes:: Defining the classes of hardware registers. | |
37 | * Old Constraints:: The old way to define machine-specific constraints. | |
38 | * Stack and Calling:: Defining which way the stack grows and by how much. | |
39 | * Varargs:: Defining the varargs macros. | |
40 | * Trampolines:: Code set up at run time to enter a nested function. | |
41 | * Library Calls:: Controlling how library routines are implicitly called. | |
42 | * Addressing Modes:: Defining addressing modes valid for memory operands. | |
43 | * Anchored Addresses:: Defining how @option{-fsection-anchors} should work. | |
44 | * Condition Code:: Defining how insns update the condition code. | |
45 | * Costs:: Defining relative costs of different operations. | |
46 | * Scheduling:: Adjusting the behavior of the instruction scheduler. | |
47 | * Sections:: Dividing storage into text, data, and other sections. | |
48 | * PIC:: Macros for position independent code. | |
49 | * Assembler Format:: Defining how to write insns and pseudo-ops to output. | |
50 | * Debugging Info:: Defining the format of debugging output. | |
51 | * Floating Point:: Handling floating point for cross-compilers. | |
52 | * Mode Switching:: Insertion of mode-switching instructions. | |
53 | * Target Attributes:: Defining target-specific uses of @code{__attribute__}. | |
54 | * Emulated TLS:: Emulated TLS support. | |
55 | * MIPS Coprocessors:: MIPS coprocessor support and how to customize it. | |
56 | * PCH Target:: Validity checking for precompiled headers. | |
57 | * C++ ABI:: Controlling C++ ABI changes. | |
58 | * Named Address Spaces:: Adding support for named address spaces | |
59 | * Misc:: Everything else. | |
60 | @end menu | |
61 | ||
62 | @node Target Structure | |
63 | @section The Global @code{targetm} Variable | |
64 | @cindex target hooks | |
65 | @cindex target functions | |
66 | ||
67 | @deftypevar {struct gcc_target} targetm | |
68 | The target @file{.c} file must define the global @code{targetm} variable | |
69 | which contains pointers to functions and data relating to the target | |
70 | machine. The variable is declared in @file{target.h}; | |
71 | @file{target-def.h} defines the macro @code{TARGET_INITIALIZER} which is | |
72 | used to initialize the variable, and macros for the default initializers | |
73 | for elements of the structure. The @file{.c} file should override those | |
74 | macros for which the default definition is inappropriate. For example: | |
75 | @smallexample | |
76 | #include "target.h" | |
77 | #include "target-def.h" | |
78 | ||
79 | /* @r{Initialize the GCC target structure.} */ | |
80 | ||
81 | #undef TARGET_COMP_TYPE_ATTRIBUTES | |
82 | #define TARGET_COMP_TYPE_ATTRIBUTES @var{machine}_comp_type_attributes | |
83 | ||
84 | struct gcc_target targetm = TARGET_INITIALIZER; | |
85 | @end smallexample | |
86 | @end deftypevar | |
87 | ||
88 | Where a macro should be defined in the @file{.c} file in this manner to | |
89 | form part of the @code{targetm} structure, it is documented below as a | |
90 | ``Target Hook'' with a prototype. Many macros will change in future | |
91 | from being defined in the @file{.h} file to being part of the | |
92 | @code{targetm} structure. | |
93 | ||
acce4e77 JM |
94 | Similarly, there is a @code{targetcm} variable for hooks that are |
95 | specific to front ends for C-family languages, documented as ``C | |
96 | Target Hook''. This is declared in @file{c-family/c-target.h}, the | |
dd5a833e | 97 | initializer @code{TARGETCM_INITIALIZER} in |
acce4e77 JM |
98 | @file{c-family/c-target-def.h}. If targets initialize @code{targetcm} |
99 | themselves, they should set @code{target_has_targetcm=yes} in | |
100 | @file{config.gcc}; otherwise a default definition is used. | |
101 | ||
c49a6962 JM |
102 | Similarly, there is a @code{targetm_common} variable for hooks that |
103 | are shared between the compiler driver and the compilers proper, | |
104 | documented as ``Common Target Hook''. This is declared in | |
105 | @file{common/common-target.h}, the initializer | |
106 | @code{TARGETM_COMMON_INITIALIZER} in | |
107 | @file{common/common-target-def.h}. If targets initialize | |
108 | @code{targetm_common} themselves, they should set | |
109 | @code{target_has_targetm_common=yes} in @file{config.gcc}; otherwise a | |
110 | default definition is used. | |
111 | ||
38f8b050 JR |
112 | @node Driver |
113 | @section Controlling the Compilation Driver, @file{gcc} | |
114 | @cindex driver | |
115 | @cindex controlling the compilation driver | |
116 | ||
117 | @c prevent bad page break with this line | |
118 | You can control the compilation driver. | |
119 | ||
38f8b050 JR |
120 | @defmac DRIVER_SELF_SPECS |
121 | A list of specs for the driver itself. It should be a suitable | |
122 | initializer for an array of strings, with no surrounding braces. | |
123 | ||
124 | The driver applies these specs to its own command line between loading | |
125 | default @file{specs} files (but not command-line specified ones) and | |
126 | choosing the multilib directory or running any subcommands. It | |
127 | applies them in the order given, so each spec can depend on the | |
128 | options added by earlier ones. It is also possible to remove options | |
129 | using @samp{%<@var{option}} in the usual way. | |
130 | ||
131 | This macro can be useful when a port has several interdependent target | |
132 | options. It provides a way of standardizing the command line so | |
133 | that the other specs are easier to write. | |
134 | ||
135 | Do not define this macro if it does not need to do anything. | |
136 | @end defmac | |
137 | ||
138 | @defmac OPTION_DEFAULT_SPECS | |
139 | A list of specs used to support configure-time default options (i.e.@: | |
140 | @option{--with} options) in the driver. It should be a suitable initializer | |
141 | for an array of structures, each containing two strings, without the | |
142 | outermost pair of surrounding braces. | |
143 | ||
144 | The first item in the pair is the name of the default. This must match | |
145 | the code in @file{config.gcc} for the target. The second item is a spec | |
146 | to apply if a default with this name was specified. The string | |
147 | @samp{%(VALUE)} in the spec will be replaced by the value of the default | |
148 | everywhere it occurs. | |
149 | ||
150 | The driver will apply these specs to its own command line between loading | |
151 | default @file{specs} files and processing @code{DRIVER_SELF_SPECS}, using | |
152 | the same mechanism as @code{DRIVER_SELF_SPECS}. | |
153 | ||
154 | Do not define this macro if it does not need to do anything. | |
155 | @end defmac | |
156 | ||
157 | @defmac CPP_SPEC | |
158 | A C string constant that tells the GCC driver program options to | |
159 | pass to CPP@. It can also specify how to translate options you | |
160 | give to GCC into options for GCC to pass to the CPP@. | |
161 | ||
162 | Do not define this macro if it does not need to do anything. | |
163 | @end defmac | |
164 | ||
165 | @defmac CPLUSPLUS_CPP_SPEC | |
166 | This macro is just like @code{CPP_SPEC}, but is used for C++, rather | |
167 | than C@. If you do not define this macro, then the value of | |
168 | @code{CPP_SPEC} (if any) will be used instead. | |
169 | @end defmac | |
170 | ||
171 | @defmac CC1_SPEC | |
172 | A C string constant that tells the GCC driver program options to | |
173 | pass to @code{cc1}, @code{cc1plus}, @code{f771}, and the other language | |
174 | front ends. | |
175 | It can also specify how to translate options you give to GCC into options | |
176 | for GCC to pass to front ends. | |
177 | ||
178 | Do not define this macro if it does not need to do anything. | |
179 | @end defmac | |
180 | ||
181 | @defmac CC1PLUS_SPEC | |
182 | A C string constant that tells the GCC driver program options to | |
183 | pass to @code{cc1plus}. It can also specify how to translate options you | |
184 | give to GCC into options for GCC to pass to the @code{cc1plus}. | |
185 | ||
186 | Do not define this macro if it does not need to do anything. | |
187 | Note that everything defined in CC1_SPEC is already passed to | |
188 | @code{cc1plus} so there is no need to duplicate the contents of | |
189 | CC1_SPEC in CC1PLUS_SPEC@. | |
190 | @end defmac | |
191 | ||
192 | @defmac ASM_SPEC | |
193 | A C string constant that tells the GCC driver program options to | |
194 | pass to the assembler. It can also specify how to translate options | |
195 | you give to GCC into options for GCC to pass to the assembler. | |
196 | See the file @file{sun3.h} for an example of this. | |
197 | ||
198 | Do not define this macro if it does not need to do anything. | |
199 | @end defmac | |
200 | ||
201 | @defmac ASM_FINAL_SPEC | |
202 | A C string constant that tells the GCC driver program how to | |
203 | run any programs which cleanup after the normal assembler. | |
204 | Normally, this is not needed. See the file @file{mips.h} for | |
205 | an example of this. | |
206 | ||
207 | Do not define this macro if it does not need to do anything. | |
208 | @end defmac | |
209 | ||
210 | @defmac AS_NEEDS_DASH_FOR_PIPED_INPUT | |
211 | Define this macro, with no value, if the driver should give the assembler | |
212 | an argument consisting of a single dash, @option{-}, to instruct it to | |
213 | read from its standard input (which will be a pipe connected to the | |
214 | output of the compiler proper). This argument is given after any | |
215 | @option{-o} option specifying the name of the output file. | |
216 | ||
217 | If you do not define this macro, the assembler is assumed to read its | |
218 | standard input if given no non-option arguments. If your assembler | |
219 | cannot read standard input at all, use a @samp{%@{pipe:%e@}} construct; | |
220 | see @file{mips.h} for instance. | |
221 | @end defmac | |
222 | ||
223 | @defmac LINK_SPEC | |
224 | A C string constant that tells the GCC driver program options to | |
225 | pass to the linker. It can also specify how to translate options you | |
226 | give to GCC into options for GCC to pass to the linker. | |
227 | ||
228 | Do not define this macro if it does not need to do anything. | |
229 | @end defmac | |
230 | ||
231 | @defmac LIB_SPEC | |
232 | Another C string constant used much like @code{LINK_SPEC}. The difference | |
233 | between the two is that @code{LIB_SPEC} is used at the end of the | |
234 | command given to the linker. | |
235 | ||
236 | If this macro is not defined, a default is provided that | |
237 | loads the standard C library from the usual place. See @file{gcc.c}. | |
238 | @end defmac | |
239 | ||
240 | @defmac LIBGCC_SPEC | |
241 | Another C string constant that tells the GCC driver program | |
242 | how and when to place a reference to @file{libgcc.a} into the | |
243 | linker command line. This constant is placed both before and after | |
244 | the value of @code{LIB_SPEC}. | |
245 | ||
246 | If this macro is not defined, the GCC driver provides a default that | |
247 | passes the string @option{-lgcc} to the linker. | |
248 | @end defmac | |
249 | ||
250 | @defmac REAL_LIBGCC_SPEC | |
251 | By default, if @code{ENABLE_SHARED_LIBGCC} is defined, the | |
252 | @code{LIBGCC_SPEC} is not directly used by the driver program but is | |
253 | instead modified to refer to different versions of @file{libgcc.a} | |
254 | depending on the values of the command line flags @option{-static}, | |
255 | @option{-shared}, @option{-static-libgcc}, and @option{-shared-libgcc}. On | |
256 | targets where these modifications are inappropriate, define | |
257 | @code{REAL_LIBGCC_SPEC} instead. @code{REAL_LIBGCC_SPEC} tells the | |
258 | driver how to place a reference to @file{libgcc} on the link command | |
259 | line, but, unlike @code{LIBGCC_SPEC}, it is used unmodified. | |
260 | @end defmac | |
261 | ||
262 | @defmac USE_LD_AS_NEEDED | |
263 | A macro that controls the modifications to @code{LIBGCC_SPEC} | |
264 | mentioned in @code{REAL_LIBGCC_SPEC}. If nonzero, a spec will be | |
265 | generated that uses --as-needed and the shared libgcc in place of the | |
266 | static exception handler library, when linking without any of | |
267 | @code{-static}, @code{-static-libgcc}, or @code{-shared-libgcc}. | |
268 | @end defmac | |
269 | ||
270 | @defmac LINK_EH_SPEC | |
271 | If defined, this C string constant is added to @code{LINK_SPEC}. | |
272 | When @code{USE_LD_AS_NEEDED} is zero or undefined, it also affects | |
273 | the modifications to @code{LIBGCC_SPEC} mentioned in | |
274 | @code{REAL_LIBGCC_SPEC}. | |
275 | @end defmac | |
276 | ||
277 | @defmac STARTFILE_SPEC | |
278 | Another C string constant used much like @code{LINK_SPEC}. The | |
279 | difference between the two is that @code{STARTFILE_SPEC} is used at | |
280 | the very beginning of the command given to the linker. | |
281 | ||
282 | If this macro is not defined, a default is provided that loads the | |
283 | standard C startup file from the usual place. See @file{gcc.c}. | |
284 | @end defmac | |
285 | ||
286 | @defmac ENDFILE_SPEC | |
287 | Another C string constant used much like @code{LINK_SPEC}. The | |
288 | difference between the two is that @code{ENDFILE_SPEC} is used at | |
289 | the very end of the command given to the linker. | |
290 | ||
291 | Do not define this macro if it does not need to do anything. | |
292 | @end defmac | |
293 | ||
294 | @defmac THREAD_MODEL_SPEC | |
295 | GCC @code{-v} will print the thread model GCC was configured to use. | |
296 | However, this doesn't work on platforms that are multilibbed on thread | |
297 | models, such as AIX 4.3. On such platforms, define | |
298 | @code{THREAD_MODEL_SPEC} such that it evaluates to a string without | |
299 | blanks that names one of the recognized thread models. @code{%*}, the | |
300 | default value of this macro, will expand to the value of | |
301 | @code{thread_file} set in @file{config.gcc}. | |
302 | @end defmac | |
303 | ||
304 | @defmac SYSROOT_SUFFIX_SPEC | |
305 | Define this macro to add a suffix to the target sysroot when GCC is | |
306 | configured with a sysroot. This will cause GCC to search for usr/lib, | |
307 | et al, within sysroot+suffix. | |
308 | @end defmac | |
309 | ||
310 | @defmac SYSROOT_HEADERS_SUFFIX_SPEC | |
311 | Define this macro to add a headers_suffix to the target sysroot when | |
312 | GCC is configured with a sysroot. This will cause GCC to pass the | |
313 | updated sysroot+headers_suffix to CPP, causing it to search for | |
314 | usr/include, et al, within sysroot+headers_suffix. | |
315 | @end defmac | |
316 | ||
317 | @defmac EXTRA_SPECS | |
318 | Define this macro to provide additional specifications to put in the | |
319 | @file{specs} file that can be used in various specifications like | |
320 | @code{CC1_SPEC}. | |
321 | ||
322 | The definition should be an initializer for an array of structures, | |
323 | containing a string constant, that defines the specification name, and a | |
324 | string constant that provides the specification. | |
325 | ||
326 | Do not define this macro if it does not need to do anything. | |
327 | ||
328 | @code{EXTRA_SPECS} is useful when an architecture contains several | |
329 | related targets, which have various @code{@dots{}_SPECS} which are similar | |
330 | to each other, and the maintainer would like one central place to keep | |
331 | these definitions. | |
332 | ||
333 | For example, the PowerPC System V.4 targets use @code{EXTRA_SPECS} to | |
334 | define either @code{_CALL_SYSV} when the System V calling sequence is | |
335 | used or @code{_CALL_AIX} when the older AIX-based calling sequence is | |
336 | used. | |
337 | ||
338 | The @file{config/rs6000/rs6000.h} target file defines: | |
339 | ||
340 | @smallexample | |
341 | #define EXTRA_SPECS \ | |
342 | @{ "cpp_sysv_default", CPP_SYSV_DEFAULT @}, | |
343 | ||
344 | #define CPP_SYS_DEFAULT "" | |
345 | @end smallexample | |
346 | ||
347 | The @file{config/rs6000/sysv.h} target file defines: | |
348 | @smallexample | |
349 | #undef CPP_SPEC | |
350 | #define CPP_SPEC \ | |
351 | "%@{posix: -D_POSIX_SOURCE @} \ | |
352 | %@{mcall-sysv: -D_CALL_SYSV @} \ | |
353 | %@{!mcall-sysv: %(cpp_sysv_default) @} \ | |
354 | %@{msoft-float: -D_SOFT_FLOAT@} %@{mcpu=403: -D_SOFT_FLOAT@}" | |
355 | ||
356 | #undef CPP_SYSV_DEFAULT | |
357 | #define CPP_SYSV_DEFAULT "-D_CALL_SYSV" | |
358 | @end smallexample | |
359 | ||
360 | while the @file{config/rs6000/eabiaix.h} target file defines | |
361 | @code{CPP_SYSV_DEFAULT} as: | |
362 | ||
363 | @smallexample | |
364 | #undef CPP_SYSV_DEFAULT | |
365 | #define CPP_SYSV_DEFAULT "-D_CALL_AIX" | |
366 | @end smallexample | |
367 | @end defmac | |
368 | ||
369 | @defmac LINK_LIBGCC_SPECIAL_1 | |
370 | Define this macro if the driver program should find the library | |
371 | @file{libgcc.a}. If you do not define this macro, the driver program will pass | |
372 | the argument @option{-lgcc} to tell the linker to do the search. | |
373 | @end defmac | |
374 | ||
375 | @defmac LINK_GCC_C_SEQUENCE_SPEC | |
376 | The sequence in which libgcc and libc are specified to the linker. | |
377 | By default this is @code{%G %L %G}. | |
378 | @end defmac | |
379 | ||
380 | @defmac LINK_COMMAND_SPEC | |
381 | A C string constant giving the complete command line need to execute the | |
382 | linker. When you do this, you will need to update your port each time a | |
383 | change is made to the link command line within @file{gcc.c}. Therefore, | |
384 | define this macro only if you need to completely redefine the command | |
385 | line for invoking the linker and there is no other way to accomplish | |
386 | the effect you need. Overriding this macro may be avoidable by overriding | |
387 | @code{LINK_GCC_C_SEQUENCE_SPEC} instead. | |
388 | @end defmac | |
389 | ||
390 | @defmac LINK_ELIMINATE_DUPLICATE_LDIRECTORIES | |
391 | A nonzero value causes @command{collect2} to remove duplicate @option{-L@var{directory}} search | |
392 | directories from linking commands. Do not give it a nonzero value if | |
393 | removing duplicate search directories changes the linker's semantics. | |
394 | @end defmac | |
395 | ||
c49a6962 JM |
396 | @hook TARGET_ALWAYS_STRIP_DOTDOT |
397 | ||
38f8b050 JR |
398 | @defmac MULTILIB_DEFAULTS |
399 | Define this macro as a C expression for the initializer of an array of | |
400 | string to tell the driver program which options are defaults for this | |
401 | target and thus do not need to be handled specially when using | |
402 | @code{MULTILIB_OPTIONS}. | |
403 | ||
404 | Do not define this macro if @code{MULTILIB_OPTIONS} is not defined in | |
405 | the target makefile fragment or if none of the options listed in | |
406 | @code{MULTILIB_OPTIONS} are set by default. | |
407 | @xref{Target Fragment}. | |
408 | @end defmac | |
409 | ||
410 | @defmac RELATIVE_PREFIX_NOT_LINKDIR | |
411 | Define this macro to tell @command{gcc} that it should only translate | |
412 | a @option{-B} prefix into a @option{-L} linker option if the prefix | |
413 | indicates an absolute file name. | |
414 | @end defmac | |
415 | ||
416 | @defmac MD_EXEC_PREFIX | |
417 | If defined, this macro is an additional prefix to try after | |
418 | @code{STANDARD_EXEC_PREFIX}. @code{MD_EXEC_PREFIX} is not searched | |
419 | when the compiler is built as a cross | |
420 | compiler. If you define @code{MD_EXEC_PREFIX}, then be sure to add it | |
421 | to the list of directories used to find the assembler in @file{configure.in}. | |
422 | @end defmac | |
423 | ||
424 | @defmac STANDARD_STARTFILE_PREFIX | |
425 | Define this macro as a C string constant if you wish to override the | |
426 | standard choice of @code{libdir} as the default prefix to | |
427 | try when searching for startup files such as @file{crt0.o}. | |
428 | @code{STANDARD_STARTFILE_PREFIX} is not searched when the compiler | |
429 | is built as a cross compiler. | |
430 | @end defmac | |
431 | ||
432 | @defmac STANDARD_STARTFILE_PREFIX_1 | |
433 | Define this macro as a C string constant if you wish to override the | |
434 | standard choice of @code{/lib} as a prefix to try after the default prefix | |
435 | when searching for startup files such as @file{crt0.o}. | |
436 | @code{STANDARD_STARTFILE_PREFIX_1} is not searched when the compiler | |
437 | is built as a cross compiler. | |
438 | @end defmac | |
439 | ||
440 | @defmac STANDARD_STARTFILE_PREFIX_2 | |
441 | Define this macro as a C string constant if you wish to override the | |
442 | standard choice of @code{/lib} as yet another prefix to try after the | |
443 | default prefix when searching for startup files such as @file{crt0.o}. | |
444 | @code{STANDARD_STARTFILE_PREFIX_2} is not searched when the compiler | |
445 | is built as a cross compiler. | |
446 | @end defmac | |
447 | ||
448 | @defmac MD_STARTFILE_PREFIX | |
449 | If defined, this macro supplies an additional prefix to try after the | |
450 | standard prefixes. @code{MD_EXEC_PREFIX} is not searched when the | |
451 | compiler is built as a cross compiler. | |
452 | @end defmac | |
453 | ||
454 | @defmac MD_STARTFILE_PREFIX_1 | |
455 | If defined, this macro supplies yet another prefix to try after the | |
456 | standard prefixes. It is not searched when the compiler is built as a | |
457 | cross compiler. | |
458 | @end defmac | |
459 | ||
460 | @defmac INIT_ENVIRONMENT | |
461 | Define this macro as a C string constant if you wish to set environment | |
462 | variables for programs called by the driver, such as the assembler and | |
463 | loader. The driver passes the value of this macro to @code{putenv} to | |
464 | initialize the necessary environment variables. | |
465 | @end defmac | |
466 | ||
467 | @defmac LOCAL_INCLUDE_DIR | |
468 | Define this macro as a C string constant if you wish to override the | |
469 | standard choice of @file{/usr/local/include} as the default prefix to | |
470 | try when searching for local header files. @code{LOCAL_INCLUDE_DIR} | |
471 | comes before @code{SYSTEM_INCLUDE_DIR} in the search order. | |
472 | ||
473 | Cross compilers do not search either @file{/usr/local/include} or its | |
474 | replacement. | |
475 | @end defmac | |
476 | ||
477 | @defmac SYSTEM_INCLUDE_DIR | |
478 | Define this macro as a C string constant if you wish to specify a | |
479 | system-specific directory to search for header files before the standard | |
480 | directory. @code{SYSTEM_INCLUDE_DIR} comes before | |
481 | @code{STANDARD_INCLUDE_DIR} in the search order. | |
482 | ||
483 | Cross compilers do not use this macro and do not search the directory | |
484 | specified. | |
485 | @end defmac | |
486 | ||
487 | @defmac STANDARD_INCLUDE_DIR | |
488 | Define this macro as a C string constant if you wish to override the | |
489 | standard choice of @file{/usr/include} as the default prefix to | |
490 | try when searching for header files. | |
491 | ||
492 | Cross compilers ignore this macro and do not search either | |
493 | @file{/usr/include} or its replacement. | |
494 | @end defmac | |
495 | ||
496 | @defmac STANDARD_INCLUDE_COMPONENT | |
497 | The ``component'' corresponding to @code{STANDARD_INCLUDE_DIR}. | |
498 | See @code{INCLUDE_DEFAULTS}, below, for the description of components. | |
499 | If you do not define this macro, no component is used. | |
500 | @end defmac | |
501 | ||
502 | @defmac INCLUDE_DEFAULTS | |
503 | Define this macro if you wish to override the entire default search path | |
504 | for include files. For a native compiler, the default search path | |
505 | usually consists of @code{GCC_INCLUDE_DIR}, @code{LOCAL_INCLUDE_DIR}, | |
506 | @code{SYSTEM_INCLUDE_DIR}, @code{GPLUSPLUS_INCLUDE_DIR}, and | |
507 | @code{STANDARD_INCLUDE_DIR}. In addition, @code{GPLUSPLUS_INCLUDE_DIR} | |
508 | and @code{GCC_INCLUDE_DIR} are defined automatically by @file{Makefile}, | |
509 | and specify private search areas for GCC@. The directory | |
510 | @code{GPLUSPLUS_INCLUDE_DIR} is used only for C++ programs. | |
511 | ||
512 | The definition should be an initializer for an array of structures. | |
513 | Each array element should have four elements: the directory name (a | |
514 | string constant), the component name (also a string constant), a flag | |
515 | for C++-only directories, | |
516 | and a flag showing that the includes in the directory don't need to be | |
517 | wrapped in @code{extern @samp{C}} when compiling C++. Mark the end of | |
518 | the array with a null element. | |
519 | ||
520 | The component name denotes what GNU package the include file is part of, | |
521 | if any, in all uppercase letters. For example, it might be @samp{GCC} | |
522 | or @samp{BINUTILS}. If the package is part of a vendor-supplied | |
523 | operating system, code the component name as @samp{0}. | |
524 | ||
525 | For example, here is the definition used for VAX/VMS: | |
526 | ||
527 | @smallexample | |
528 | #define INCLUDE_DEFAULTS \ | |
529 | @{ \ | |
530 | @{ "GNU_GXX_INCLUDE:", "G++", 1, 1@}, \ | |
531 | @{ "GNU_CC_INCLUDE:", "GCC", 0, 0@}, \ | |
532 | @{ "SYS$SYSROOT:[SYSLIB.]", 0, 0, 0@}, \ | |
533 | @{ ".", 0, 0, 0@}, \ | |
534 | @{ 0, 0, 0, 0@} \ | |
535 | @} | |
536 | @end smallexample | |
537 | @end defmac | |
538 | ||
539 | Here is the order of prefixes tried for exec files: | |
540 | ||
541 | @enumerate | |
542 | @item | |
543 | Any prefixes specified by the user with @option{-B}. | |
544 | ||
545 | @item | |
546 | The environment variable @code{GCC_EXEC_PREFIX} or, if @code{GCC_EXEC_PREFIX} | |
ff2ce160 | 547 | is not set and the compiler has not been installed in the configure-time |
38f8b050 JR |
548 | @var{prefix}, the location in which the compiler has actually been installed. |
549 | ||
550 | @item | |
551 | The directories specified by the environment variable @code{COMPILER_PATH}. | |
552 | ||
553 | @item | |
554 | The macro @code{STANDARD_EXEC_PREFIX}, if the compiler has been installed | |
ff2ce160 | 555 | in the configured-time @var{prefix}. |
38f8b050 JR |
556 | |
557 | @item | |
ff2ce160 | 558 | The location @file{/usr/libexec/gcc/}, but only if this is a native compiler. |
38f8b050 JR |
559 | |
560 | @item | |
ff2ce160 | 561 | The location @file{/usr/lib/gcc/}, but only if this is a native compiler. |
38f8b050 JR |
562 | |
563 | @item | |
ff2ce160 | 564 | The macro @code{MD_EXEC_PREFIX}, if defined, but only if this is a native |
38f8b050 JR |
565 | compiler. |
566 | @end enumerate | |
567 | ||
568 | Here is the order of prefixes tried for startfiles: | |
569 | ||
570 | @enumerate | |
571 | @item | |
572 | Any prefixes specified by the user with @option{-B}. | |
573 | ||
574 | @item | |
575 | The environment variable @code{GCC_EXEC_PREFIX} or its automatically determined | |
576 | value based on the installed toolchain location. | |
577 | ||
578 | @item | |
579 | The directories specified by the environment variable @code{LIBRARY_PATH} | |
580 | (or port-specific name; native only, cross compilers do not use this). | |
581 | ||
582 | @item | |
583 | The macro @code{STANDARD_EXEC_PREFIX}, but only if the toolchain is installed | |
ff2ce160 | 584 | in the configured @var{prefix} or this is a native compiler. |
38f8b050 JR |
585 | |
586 | @item | |
587 | The location @file{/usr/lib/gcc/}, but only if this is a native compiler. | |
588 | ||
589 | @item | |
ff2ce160 | 590 | The macro @code{MD_EXEC_PREFIX}, if defined, but only if this is a native |
38f8b050 JR |
591 | compiler. |
592 | ||
593 | @item | |
ff2ce160 | 594 | The macro @code{MD_STARTFILE_PREFIX}, if defined, but only if this is a |
38f8b050 JR |
595 | native compiler, or we have a target system root. |
596 | ||
597 | @item | |
ff2ce160 | 598 | The macro @code{MD_STARTFILE_PREFIX_1}, if defined, but only if this is a |
38f8b050 JR |
599 | native compiler, or we have a target system root. |
600 | ||
601 | @item | |
602 | The macro @code{STANDARD_STARTFILE_PREFIX}, with any sysroot modifications. | |
603 | If this path is relative it will be prefixed by @code{GCC_EXEC_PREFIX} and | |
604 | the machine suffix or @code{STANDARD_EXEC_PREFIX} and the machine suffix. | |
605 | ||
606 | @item | |
607 | The macro @code{STANDARD_STARTFILE_PREFIX_1}, but only if this is a native | |
608 | compiler, or we have a target system root. The default for this macro is | |
609 | @file{/lib/}. | |
610 | ||
611 | @item | |
612 | The macro @code{STANDARD_STARTFILE_PREFIX_2}, but only if this is a native | |
613 | compiler, or we have a target system root. The default for this macro is | |
614 | @file{/usr/lib/}. | |
615 | @end enumerate | |
616 | ||
617 | @node Run-time Target | |
618 | @section Run-time Target Specification | |
619 | @cindex run-time target specification | |
620 | @cindex predefined macros | |
621 | @cindex target specifications | |
622 | ||
623 | @c prevent bad page break with this line | |
624 | Here are run-time target specifications. | |
625 | ||
626 | @defmac TARGET_CPU_CPP_BUILTINS () | |
627 | This function-like macro expands to a block of code that defines | |
628 | built-in preprocessor macros and assertions for the target CPU, using | |
629 | the functions @code{builtin_define}, @code{builtin_define_std} and | |
630 | @code{builtin_assert}. When the front end | |
631 | calls this macro it provides a trailing semicolon, and since it has | |
632 | finished command line option processing your code can use those | |
633 | results freely. | |
634 | ||
635 | @code{builtin_assert} takes a string in the form you pass to the | |
636 | command-line option @option{-A}, such as @code{cpu=mips}, and creates | |
637 | the assertion. @code{builtin_define} takes a string in the form | |
638 | accepted by option @option{-D} and unconditionally defines the macro. | |
639 | ||
640 | @code{builtin_define_std} takes a string representing the name of an | |
641 | object-like macro. If it doesn't lie in the user's namespace, | |
642 | @code{builtin_define_std} defines it unconditionally. Otherwise, it | |
643 | defines a version with two leading underscores, and another version | |
644 | with two leading and trailing underscores, and defines the original | |
645 | only if an ISO standard was not requested on the command line. For | |
646 | example, passing @code{unix} defines @code{__unix}, @code{__unix__} | |
647 | and possibly @code{unix}; passing @code{_mips} defines @code{__mips}, | |
648 | @code{__mips__} and possibly @code{_mips}, and passing @code{_ABI64} | |
649 | defines only @code{_ABI64}. | |
650 | ||
651 | You can also test for the C dialect being compiled. The variable | |
652 | @code{c_language} is set to one of @code{clk_c}, @code{clk_cplusplus} | |
653 | or @code{clk_objective_c}. Note that if we are preprocessing | |
654 | assembler, this variable will be @code{clk_c} but the function-like | |
655 | macro @code{preprocessing_asm_p()} will return true, so you might want | |
656 | to check for that first. If you need to check for strict ANSI, the | |
657 | variable @code{flag_iso} can be used. The function-like macro | |
658 | @code{preprocessing_trad_p()} can be used to check for traditional | |
659 | preprocessing. | |
660 | @end defmac | |
661 | ||
662 | @defmac TARGET_OS_CPP_BUILTINS () | |
663 | Similarly to @code{TARGET_CPU_CPP_BUILTINS} but this macro is optional | |
664 | and is used for the target operating system instead. | |
665 | @end defmac | |
666 | ||
667 | @defmac TARGET_OBJFMT_CPP_BUILTINS () | |
668 | Similarly to @code{TARGET_CPU_CPP_BUILTINS} but this macro is optional | |
669 | and is used for the target object format. @file{elfos.h} uses this | |
670 | macro to define @code{__ELF__}, so you probably do not need to define | |
671 | it yourself. | |
672 | @end defmac | |
673 | ||
674 | @deftypevar {extern int} target_flags | |
675 | This variable is declared in @file{options.h}, which is included before | |
676 | any target-specific headers. | |
677 | @end deftypevar | |
678 | ||
679 | @hook TARGET_DEFAULT_TARGET_FLAGS | |
680 | This variable specifies the initial value of @code{target_flags}. | |
681 | Its default setting is 0. | |
682 | @end deftypevr | |
683 | ||
684 | @cindex optional hardware or system features | |
685 | @cindex features, optional, in system conventions | |
686 | ||
687 | @hook TARGET_HANDLE_OPTION | |
688 | This hook is called whenever the user specifies one of the | |
689 | target-specific options described by the @file{.opt} definition files | |
690 | (@pxref{Options}). It has the opportunity to do some option-specific | |
691 | processing and should return true if the option is valid. The default | |
692 | definition does nothing but return true. | |
693 | ||
96e45421 JM |
694 | @var{decoded} specifies the option and its arguments. @var{opts} and |
695 | @var{opts_set} are the @code{gcc_options} structures to be used for | |
696 | storing option state, and @var{loc} is the location at which the | |
697 | option was passed (@code{UNKNOWN_LOCATION} except for options passed | |
698 | via attributes). | |
38f8b050 JR |
699 | @end deftypefn |
700 | ||
701 | @hook TARGET_HANDLE_C_OPTION | |
702 | This target hook is called whenever the user specifies one of the | |
703 | target-specific C language family options described by the @file{.opt} | |
704 | definition files(@pxref{Options}). It has the opportunity to do some | |
705 | option-specific processing and should return true if the option is | |
706 | valid. The arguments are like for @code{TARGET_HANDLE_OPTION}. The | |
707 | default definition does nothing but return false. | |
708 | ||
709 | In general, you should use @code{TARGET_HANDLE_OPTION} to handle | |
710 | options. However, if processing an option requires routines that are | |
711 | only available in the C (and related language) front ends, then you | |
712 | should use @code{TARGET_HANDLE_C_OPTION} instead. | |
713 | @end deftypefn | |
714 | ||
91ebb981 IS |
715 | @hook TARGET_OBJC_CONSTRUCT_STRING_OBJECT |
716 | ||
717 | @hook TARGET_STRING_OBJECT_REF_TYPE_P | |
718 | ||
719 | @hook TARGET_CHECK_STRING_OBJECT_FORMAT_ARG | |
26705988 | 720 | |
38f8b050 JR |
721 | @hook TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE |
722 | This target function is similar to the hook @code{TARGET_OPTION_OVERRIDE} | |
723 | but is called when the optimize level is changed via an attribute or | |
724 | pragma or when it is reset at the end of the code affected by the | |
725 | attribute or pragma. It is not called at the beginning of compilation | |
726 | when @code{TARGET_OPTION_OVERRIDE} is called so if you want to perform these | |
727 | actions then, you should have @code{TARGET_OPTION_OVERRIDE} call | |
728 | @code{TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE}. | |
729 | @end deftypefn | |
730 | ||
731 | @defmac C_COMMON_OVERRIDE_OPTIONS | |
c5387660 JM |
732 | This is similar to the @code{TARGET_OPTION_OVERRIDE} hook |
733 | but is only used in the C | |
38f8b050 JR |
734 | language frontends (C, Objective-C, C++, Objective-C++) and so can be |
735 | used to alter option flag variables which only exist in those | |
736 | frontends. | |
737 | @end defmac | |
738 | ||
3020190e | 739 | @hook TARGET_OPTION_OPTIMIZATION_TABLE |
38f8b050 | 740 | Some machines may desire to change what optimizations are performed for |
3020190e JM |
741 | various optimization levels. This variable, if defined, describes |
742 | options to enable at particular sets of optimization levels. These | |
743 | options are processed once | |
38f8b050 | 744 | just after the optimization level is determined and before the remainder |
3020190e | 745 | of the command options have been parsed, so may be overridden by other |
2b0d3573 | 746 | options passed explicitly. |
38f8b050 | 747 | |
3020190e | 748 | This processing is run once at program startup and when the optimization |
38f8b050 JR |
749 | options are changed via @code{#pragma GCC optimize} or by using the |
750 | @code{optimize} attribute. | |
3020190e | 751 | @end deftypevr |
38f8b050 | 752 | |
7e4aae92 JM |
753 | @hook TARGET_OPTION_INIT_STRUCT |
754 | ||
128dc8e2 JM |
755 | @hook TARGET_OPTION_DEFAULT_PARAMS |
756 | ||
3bd36029 RS |
757 | @defmac SWITCHABLE_TARGET |
758 | Some targets need to switch between substantially different subtargets | |
759 | during compilation. For example, the MIPS target has one subtarget for | |
760 | the traditional MIPS architecture and another for MIPS16. Source code | |
761 | can switch between these two subarchitectures using the @code{mips16} | |
762 | and @code{nomips16} attributes. | |
763 | ||
764 | Such subtargets can differ in things like the set of available | |
765 | registers, the set of available instructions, the costs of various | |
766 | operations, and so on. GCC caches a lot of this type of information | |
767 | in global variables, and recomputing them for each subtarget takes a | |
768 | significant amount of time. The compiler therefore provides a facility | |
769 | for maintaining several versions of the global variables and quickly | |
770 | switching between them; see @file{target-globals.h} for details. | |
771 | ||
772 | Define this macro to 1 if your target needs this facility. The default | |
773 | is 0. | |
774 | @end defmac | |
775 | ||
38f8b050 JR |
776 | @node Per-Function Data |
777 | @section Defining data structures for per-function information. | |
778 | @cindex per-function data | |
779 | @cindex data structures | |
780 | ||
781 | If the target needs to store information on a per-function basis, GCC | |
782 | provides a macro and a couple of variables to allow this. Note, just | |
783 | using statics to store the information is a bad idea, since GCC supports | |
784 | nested functions, so you can be halfway through encoding one function | |
785 | when another one comes along. | |
786 | ||
787 | GCC defines a data structure called @code{struct function} which | |
788 | contains all of the data specific to an individual function. This | |
789 | structure contains a field called @code{machine} whose type is | |
790 | @code{struct machine_function *}, which can be used by targets to point | |
791 | to their own specific data. | |
792 | ||
793 | If a target needs per-function specific data it should define the type | |
794 | @code{struct machine_function} and also the macro @code{INIT_EXPANDERS}. | |
795 | This macro should be used to initialize the function pointer | |
796 | @code{init_machine_status}. This pointer is explained below. | |
797 | ||
798 | One typical use of per-function, target specific data is to create an | |
799 | RTX to hold the register containing the function's return address. This | |
800 | RTX can then be used to implement the @code{__builtin_return_address} | |
801 | function, for level 0. | |
802 | ||
803 | Note---earlier implementations of GCC used a single data area to hold | |
804 | all of the per-function information. Thus when processing of a nested | |
805 | function began the old per-function data had to be pushed onto a | |
806 | stack, and when the processing was finished, it had to be popped off the | |
807 | stack. GCC used to provide function pointers called | |
808 | @code{save_machine_status} and @code{restore_machine_status} to handle | |
809 | the saving and restoring of the target specific information. Since the | |
810 | single data area approach is no longer used, these pointers are no | |
811 | longer supported. | |
812 | ||
813 | @defmac INIT_EXPANDERS | |
814 | Macro called to initialize any target specific information. This macro | |
815 | is called once per function, before generation of any RTL has begun. | |
816 | The intention of this macro is to allow the initialization of the | |
817 | function pointer @code{init_machine_status}. | |
818 | @end defmac | |
819 | ||
820 | @deftypevar {void (*)(struct function *)} init_machine_status | |
821 | If this function pointer is non-@code{NULL} it will be called once per | |
822 | function, before function compilation starts, in order to allow the | |
823 | target to perform any target specific initialization of the | |
824 | @code{struct function} structure. It is intended that this would be | |
825 | used to initialize the @code{machine} of that structure. | |
826 | ||
827 | @code{struct machine_function} structures are expected to be freed by GC@. | |
828 | Generally, any memory that they reference must be allocated by using | |
829 | GC allocation, including the structure itself. | |
830 | @end deftypevar | |
831 | ||
832 | @node Storage Layout | |
833 | @section Storage Layout | |
834 | @cindex storage layout | |
835 | ||
836 | Note that the definitions of the macros in this table which are sizes or | |
837 | alignments measured in bits do not need to be constant. They can be C | |
838 | expressions that refer to static variables, such as the @code{target_flags}. | |
839 | @xref{Run-time Target}. | |
840 | ||
841 | @defmac BITS_BIG_ENDIAN | |
842 | Define this macro to have the value 1 if the most significant bit in a | |
843 | byte has the lowest number; otherwise define it to have the value zero. | |
844 | This means that bit-field instructions count from the most significant | |
845 | bit. If the machine has no bit-field instructions, then this must still | |
846 | be defined, but it doesn't matter which value it is defined to. This | |
847 | macro need not be a constant. | |
848 | ||
849 | This macro does not affect the way structure fields are packed into | |
850 | bytes or words; that is controlled by @code{BYTES_BIG_ENDIAN}. | |
851 | @end defmac | |
852 | ||
853 | @defmac BYTES_BIG_ENDIAN | |
854 | Define this macro to have the value 1 if the most significant byte in a | |
855 | word has the lowest number. This macro need not be a constant. | |
856 | @end defmac | |
857 | ||
858 | @defmac WORDS_BIG_ENDIAN | |
859 | Define this macro to have the value 1 if, in a multiword object, the | |
860 | most significant word has the lowest number. This applies to both | |
c0a6a1ef BS |
861 | memory locations and registers; see @code{REG_WORDS_BIG_ENDIAN} if the |
862 | order of words in memory is not the same as the order in registers. This | |
38f8b050 JR |
863 | macro need not be a constant. |
864 | @end defmac | |
865 | ||
c0a6a1ef BS |
866 | @defmac REG_WORDS_BIG_ENDIAN |
867 | On some machines, the order of words in a multiword object differs between | |
868 | registers in memory. In such a situation, define this macro to describe | |
869 | the order of words in a register. The macro @code{WORDS_BIG_ENDIAN} controls | |
870 | the order of words in memory. | |
871 | @end defmac | |
872 | ||
38f8b050 JR |
873 | @defmac FLOAT_WORDS_BIG_ENDIAN |
874 | Define this macro to have the value 1 if @code{DFmode}, @code{XFmode} or | |
875 | @code{TFmode} floating point numbers are stored in memory with the word | |
876 | containing the sign bit at the lowest address; otherwise define it to | |
877 | have the value 0. This macro need not be a constant. | |
878 | ||
879 | You need not define this macro if the ordering is the same as for | |
880 | multi-word integers. | |
881 | @end defmac | |
882 | ||
883 | @defmac BITS_PER_UNIT | |
884 | Define this macro to be the number of bits in an addressable storage | |
885 | unit (byte). If you do not define this macro the default is 8. | |
886 | @end defmac | |
887 | ||
888 | @defmac BITS_PER_WORD | |
889 | Number of bits in a word. If you do not define this macro, the default | |
890 | is @code{BITS_PER_UNIT * UNITS_PER_WORD}. | |
891 | @end defmac | |
892 | ||
893 | @defmac MAX_BITS_PER_WORD | |
894 | Maximum number of bits in a word. If this is undefined, the default is | |
895 | @code{BITS_PER_WORD}. Otherwise, it is the constant value that is the | |
896 | largest value that @code{BITS_PER_WORD} can have at run-time. | |
897 | @end defmac | |
898 | ||
899 | @defmac UNITS_PER_WORD | |
900 | Number of storage units in a word; normally the size of a general-purpose | |
901 | register, a power of two from 1 or 8. | |
902 | @end defmac | |
903 | ||
904 | @defmac MIN_UNITS_PER_WORD | |
905 | Minimum number of units in a word. If this is undefined, the default is | |
906 | @code{UNITS_PER_WORD}. Otherwise, it is the constant value that is the | |
907 | smallest value that @code{UNITS_PER_WORD} can have at run-time. | |
908 | @end defmac | |
909 | ||
38f8b050 JR |
910 | @defmac POINTER_SIZE |
911 | Width of a pointer, in bits. You must specify a value no wider than the | |
912 | width of @code{Pmode}. If it is not equal to the width of @code{Pmode}, | |
913 | you must define @code{POINTERS_EXTEND_UNSIGNED}. If you do not specify | |
914 | a value the default is @code{BITS_PER_WORD}. | |
915 | @end defmac | |
916 | ||
917 | @defmac POINTERS_EXTEND_UNSIGNED | |
918 | A C expression that determines how pointers should be extended from | |
919 | @code{ptr_mode} to either @code{Pmode} or @code{word_mode}. It is | |
920 | greater than zero if pointers should be zero-extended, zero if they | |
921 | should be sign-extended, and negative if some other sort of conversion | |
922 | is needed. In the last case, the extension is done by the target's | |
923 | @code{ptr_extend} instruction. | |
924 | ||
925 | You need not define this macro if the @code{ptr_mode}, @code{Pmode} | |
926 | and @code{word_mode} are all the same width. | |
927 | @end defmac | |
928 | ||
929 | @defmac PROMOTE_MODE (@var{m}, @var{unsignedp}, @var{type}) | |
930 | A macro to update @var{m} and @var{unsignedp} when an object whose type | |
931 | is @var{type} and which has the specified mode and signedness is to be | |
932 | stored in a register. This macro is only called when @var{type} is a | |
933 | scalar type. | |
934 | ||
935 | On most RISC machines, which only have operations that operate on a full | |
936 | register, define this macro to set @var{m} to @code{word_mode} if | |
937 | @var{m} is an integer mode narrower than @code{BITS_PER_WORD}. In most | |
938 | cases, only integer modes should be widened because wider-precision | |
939 | floating-point operations are usually more expensive than their narrower | |
940 | counterparts. | |
941 | ||
942 | For most machines, the macro definition does not change @var{unsignedp}. | |
943 | However, some machines, have instructions that preferentially handle | |
944 | either signed or unsigned quantities of certain modes. For example, on | |
945 | the DEC Alpha, 32-bit loads from memory and 32-bit add instructions | |
946 | sign-extend the result to 64 bits. On such machines, set | |
947 | @var{unsignedp} according to which kind of extension is more efficient. | |
948 | ||
949 | Do not define this macro if it would never modify @var{m}. | |
950 | @end defmac | |
951 | ||
952 | @hook TARGET_PROMOTE_FUNCTION_MODE | |
953 | Like @code{PROMOTE_MODE}, but it is applied to outgoing function arguments or | |
954 | function return values. The target hook should return the new mode | |
955 | and possibly change @code{*@var{punsignedp}} if the promotion should | |
956 | change signedness. This function is called only for scalar @emph{or | |
957 | pointer} types. | |
958 | ||
959 | @var{for_return} allows to distinguish the promotion of arguments and | |
960 | return values. If it is @code{1}, a return value is being promoted and | |
961 | @code{TARGET_FUNCTION_VALUE} must perform the same promotions done here. | |
962 | If it is @code{2}, the returned mode should be that of the register in | |
963 | which an incoming parameter is copied, or the outgoing result is computed; | |
964 | then the hook should return the same mode as @code{promote_mode}, though | |
965 | the signedness may be different. | |
966 | ||
5e617be8 AK |
967 | @var{type} can be NULL when promoting function arguments of libcalls. |
968 | ||
38f8b050 JR |
969 | The default is to not promote arguments and return values. You can |
970 | also define the hook to @code{default_promote_function_mode_always_promote} | |
971 | if you would like to apply the same rules given by @code{PROMOTE_MODE}. | |
972 | @end deftypefn | |
973 | ||
974 | @defmac PARM_BOUNDARY | |
975 | Normal alignment required for function parameters on the stack, in | |
976 | bits. All stack parameters receive at least this much alignment | |
977 | regardless of data type. On most machines, this is the same as the | |
978 | size of an integer. | |
979 | @end defmac | |
980 | ||
981 | @defmac STACK_BOUNDARY | |
982 | Define this macro to the minimum alignment enforced by hardware for the | |
983 | stack pointer on this machine. The definition is a C expression for the | |
984 | desired alignment (measured in bits). This value is used as a default | |
985 | if @code{PREFERRED_STACK_BOUNDARY} is not defined. On most machines, | |
986 | this should be the same as @code{PARM_BOUNDARY}. | |
987 | @end defmac | |
988 | ||
989 | @defmac PREFERRED_STACK_BOUNDARY | |
990 | Define this macro if you wish to preserve a certain alignment for the | |
991 | stack pointer, greater than what the hardware enforces. The definition | |
992 | is a C expression for the desired alignment (measured in bits). This | |
993 | macro must evaluate to a value equal to or larger than | |
994 | @code{STACK_BOUNDARY}. | |
995 | @end defmac | |
996 | ||
997 | @defmac INCOMING_STACK_BOUNDARY | |
998 | Define this macro if the incoming stack boundary may be different | |
999 | from @code{PREFERRED_STACK_BOUNDARY}. This macro must evaluate | |
1000 | to a value equal to or larger than @code{STACK_BOUNDARY}. | |
1001 | @end defmac | |
1002 | ||
1003 | @defmac FUNCTION_BOUNDARY | |
1004 | Alignment required for a function entry point, in bits. | |
1005 | @end defmac | |
1006 | ||
1007 | @defmac BIGGEST_ALIGNMENT | |
1008 | Biggest alignment that any data type can require on this machine, in | |
1009 | bits. Note that this is not the biggest alignment that is supported, | |
1010 | just the biggest alignment that, when violated, may cause a fault. | |
1011 | @end defmac | |
1012 | ||
1013 | @defmac MALLOC_ABI_ALIGNMENT | |
1014 | Alignment, in bits, a C conformant malloc implementation has to | |
1015 | provide. If not defined, the default value is @code{BITS_PER_WORD}. | |
1016 | @end defmac | |
1017 | ||
1018 | @defmac ATTRIBUTE_ALIGNED_VALUE | |
1019 | Alignment used by the @code{__attribute__ ((aligned))} construct. If | |
1020 | not defined, the default value is @code{BIGGEST_ALIGNMENT}. | |
1021 | @end defmac | |
1022 | ||
1023 | @defmac MINIMUM_ATOMIC_ALIGNMENT | |
1024 | If defined, the smallest alignment, in bits, that can be given to an | |
1025 | object that can be referenced in one operation, without disturbing any | |
1026 | nearby object. Normally, this is @code{BITS_PER_UNIT}, but may be larger | |
1027 | on machines that don't have byte or half-word store operations. | |
1028 | @end defmac | |
1029 | ||
1030 | @defmac BIGGEST_FIELD_ALIGNMENT | |
1031 | Biggest alignment that any structure or union field can require on this | |
1032 | machine, in bits. If defined, this overrides @code{BIGGEST_ALIGNMENT} for | |
1033 | structure and union fields only, unless the field alignment has been set | |
1034 | by the @code{__attribute__ ((aligned (@var{n})))} construct. | |
1035 | @end defmac | |
1036 | ||
1037 | @defmac ADJUST_FIELD_ALIGN (@var{field}, @var{computed}) | |
1038 | An expression for the alignment of a structure field @var{field} if the | |
1039 | alignment computed in the usual way (including applying of | |
1040 | @code{BIGGEST_ALIGNMENT} and @code{BIGGEST_FIELD_ALIGNMENT} to the | |
1041 | alignment) is @var{computed}. It overrides alignment only if the | |
1042 | field alignment has not been set by the | |
1043 | @code{__attribute__ ((aligned (@var{n})))} construct. | |
1044 | @end defmac | |
1045 | ||
1046 | @defmac MAX_STACK_ALIGNMENT | |
1047 | Biggest stack alignment guaranteed by the backend. Use this macro | |
1048 | to specify the maximum alignment of a variable on stack. | |
1049 | ||
1050 | If not defined, the default value is @code{STACK_BOUNDARY}. | |
1051 | ||
1052 | @c FIXME: The default should be @code{PREFERRED_STACK_BOUNDARY}. | |
1053 | @c But the fix for PR 32893 indicates that we can only guarantee | |
1054 | @c maximum stack alignment on stack up to @code{STACK_BOUNDARY}, not | |
1055 | @c @code{PREFERRED_STACK_BOUNDARY}, if stack alignment isn't supported. | |
1056 | @end defmac | |
1057 | ||
1058 | @defmac MAX_OFILE_ALIGNMENT | |
1059 | Biggest alignment supported by the object file format of this machine. | |
1060 | Use this macro to limit the alignment which can be specified using the | |
1061 | @code{__attribute__ ((aligned (@var{n})))} construct. If not defined, | |
1062 | the default value is @code{BIGGEST_ALIGNMENT}. | |
1063 | ||
1064 | On systems that use ELF, the default (in @file{config/elfos.h}) is | |
1065 | the largest supported 32-bit ELF section alignment representable on | |
1066 | a 32-bit host e.g. @samp{(((unsigned HOST_WIDEST_INT) 1 << 28) * 8)}. | |
1067 | On 32-bit ELF the largest supported section alignment in bits is | |
1068 | @samp{(0x80000000 * 8)}, but this is not representable on 32-bit hosts. | |
1069 | @end defmac | |
1070 | ||
1071 | @defmac DATA_ALIGNMENT (@var{type}, @var{basic-align}) | |
1072 | If defined, a C expression to compute the alignment for a variable in | |
1073 | the static store. @var{type} is the data type, and @var{basic-align} is | |
1074 | the alignment that the object would ordinarily have. The value of this | |
1075 | macro is used instead of that alignment to align the object. | |
1076 | ||
1077 | If this macro is not defined, then @var{basic-align} is used. | |
1078 | ||
1079 | @findex strcpy | |
1080 | One use of this macro is to increase alignment of medium-size data to | |
1081 | make it all fit in fewer cache lines. Another is to cause character | |
1082 | arrays to be word-aligned so that @code{strcpy} calls that copy | |
1083 | constants to character arrays can be done inline. | |
1084 | @end defmac | |
1085 | ||
1086 | @defmac CONSTANT_ALIGNMENT (@var{constant}, @var{basic-align}) | |
1087 | If defined, a C expression to compute the alignment given to a constant | |
1088 | that is being placed in memory. @var{constant} is the constant and | |
1089 | @var{basic-align} is the alignment that the object would ordinarily | |
1090 | have. The value of this macro is used instead of that alignment to | |
1091 | align the object. | |
1092 | ||
1093 | If this macro is not defined, then @var{basic-align} is used. | |
1094 | ||
1095 | The typical use of this macro is to increase alignment for string | |
1096 | constants to be word aligned so that @code{strcpy} calls that copy | |
1097 | constants can be done inline. | |
1098 | @end defmac | |
1099 | ||
1100 | @defmac LOCAL_ALIGNMENT (@var{type}, @var{basic-align}) | |
1101 | If defined, a C expression to compute the alignment for a variable in | |
1102 | the local store. @var{type} is the data type, and @var{basic-align} is | |
1103 | the alignment that the object would ordinarily have. The value of this | |
1104 | macro is used instead of that alignment to align the object. | |
1105 | ||
1106 | If this macro is not defined, then @var{basic-align} is used. | |
1107 | ||
1108 | One use of this macro is to increase alignment of medium-size data to | |
1109 | make it all fit in fewer cache lines. | |
4a6336ad | 1110 | |
64ad7c99 | 1111 | If the value of this macro has a type, it should be an unsigned type. |
38f8b050 JR |
1112 | @end defmac |
1113 | ||
1114 | @defmac STACK_SLOT_ALIGNMENT (@var{type}, @var{mode}, @var{basic-align}) | |
1115 | If defined, a C expression to compute the alignment for stack slot. | |
1116 | @var{type} is the data type, @var{mode} is the widest mode available, | |
1117 | and @var{basic-align} is the alignment that the slot would ordinarily | |
1118 | have. The value of this macro is used instead of that alignment to | |
1119 | align the slot. | |
1120 | ||
1121 | If this macro is not defined, then @var{basic-align} is used when | |
1122 | @var{type} is @code{NULL}. Otherwise, @code{LOCAL_ALIGNMENT} will | |
1123 | be used. | |
1124 | ||
1125 | This macro is to set alignment of stack slot to the maximum alignment | |
1126 | of all possible modes which the slot may have. | |
4a6336ad | 1127 | |
64ad7c99 | 1128 | If the value of this macro has a type, it should be an unsigned type. |
38f8b050 JR |
1129 | @end defmac |
1130 | ||
1131 | @defmac LOCAL_DECL_ALIGNMENT (@var{decl}) | |
1132 | If defined, a C expression to compute the alignment for a local | |
1133 | variable @var{decl}. | |
1134 | ||
1135 | If this macro is not defined, then | |
1136 | @code{LOCAL_ALIGNMENT (TREE_TYPE (@var{decl}), DECL_ALIGN (@var{decl}))} | |
1137 | is used. | |
1138 | ||
1139 | One use of this macro is to increase alignment of medium-size data to | |
1140 | make it all fit in fewer cache lines. | |
4a6336ad | 1141 | |
64ad7c99 | 1142 | If the value of this macro has a type, it should be an unsigned type. |
38f8b050 JR |
1143 | @end defmac |
1144 | ||
1145 | @defmac MINIMUM_ALIGNMENT (@var{exp}, @var{mode}, @var{align}) | |
1146 | If defined, a C expression to compute the minimum required alignment | |
1147 | for dynamic stack realignment purposes for @var{exp} (a type or decl), | |
1148 | @var{mode}, assuming normal alignment @var{align}. | |
1149 | ||
1150 | If this macro is not defined, then @var{align} will be used. | |
1151 | @end defmac | |
1152 | ||
1153 | @defmac EMPTY_FIELD_BOUNDARY | |
1154 | Alignment in bits to be given to a structure bit-field that follows an | |
1155 | empty field such as @code{int : 0;}. | |
1156 | ||
1157 | If @code{PCC_BITFIELD_TYPE_MATTERS} is true, it overrides this macro. | |
1158 | @end defmac | |
1159 | ||
1160 | @defmac STRUCTURE_SIZE_BOUNDARY | |
1161 | Number of bits which any structure or union's size must be a multiple of. | |
1162 | Each structure or union's size is rounded up to a multiple of this. | |
1163 | ||
1164 | If you do not define this macro, the default is the same as | |
1165 | @code{BITS_PER_UNIT}. | |
1166 | @end defmac | |
1167 | ||
1168 | @defmac STRICT_ALIGNMENT | |
1169 | Define this macro to be the value 1 if instructions will fail to work | |
1170 | if given data not on the nominal alignment. If instructions will merely | |
1171 | go slower in that case, define this macro as 0. | |
1172 | @end defmac | |
1173 | ||
1174 | @defmac PCC_BITFIELD_TYPE_MATTERS | |
1175 | Define this if you wish to imitate the way many other C compilers handle | |
1176 | alignment of bit-fields and the structures that contain them. | |
1177 | ||
1178 | The behavior is that the type written for a named bit-field (@code{int}, | |
1179 | @code{short}, or other integer type) imposes an alignment for the entire | |
1180 | structure, as if the structure really did contain an ordinary field of | |
1181 | that type. In addition, the bit-field is placed within the structure so | |
1182 | that it would fit within such a field, not crossing a boundary for it. | |
1183 | ||
1184 | Thus, on most machines, a named bit-field whose type is written as | |
1185 | @code{int} would not cross a four-byte boundary, and would force | |
1186 | four-byte alignment for the whole structure. (The alignment used may | |
1187 | not be four bytes; it is controlled by the other alignment parameters.) | |
1188 | ||
1189 | An unnamed bit-field will not affect the alignment of the containing | |
1190 | structure. | |
1191 | ||
1192 | If the macro is defined, its definition should be a C expression; | |
1193 | a nonzero value for the expression enables this behavior. | |
1194 | ||
1195 | Note that if this macro is not defined, or its value is zero, some | |
1196 | bit-fields may cross more than one alignment boundary. The compiler can | |
1197 | support such references if there are @samp{insv}, @samp{extv}, and | |
1198 | @samp{extzv} insns that can directly reference memory. | |
1199 | ||
1200 | The other known way of making bit-fields work is to define | |
1201 | @code{STRUCTURE_SIZE_BOUNDARY} as large as @code{BIGGEST_ALIGNMENT}. | |
1202 | Then every structure can be accessed with fullwords. | |
1203 | ||
1204 | Unless the machine has bit-field instructions or you define | |
1205 | @code{STRUCTURE_SIZE_BOUNDARY} that way, you must define | |
1206 | @code{PCC_BITFIELD_TYPE_MATTERS} to have a nonzero value. | |
1207 | ||
1208 | If your aim is to make GCC use the same conventions for laying out | |
1209 | bit-fields as are used by another compiler, here is how to investigate | |
1210 | what the other compiler does. Compile and run this program: | |
1211 | ||
1212 | @smallexample | |
1213 | struct foo1 | |
1214 | @{ | |
1215 | char x; | |
1216 | char :0; | |
1217 | char y; | |
1218 | @}; | |
1219 | ||
1220 | struct foo2 | |
1221 | @{ | |
1222 | char x; | |
1223 | int :0; | |
1224 | char y; | |
1225 | @}; | |
1226 | ||
1227 | main () | |
1228 | @{ | |
1229 | printf ("Size of foo1 is %d\n", | |
1230 | sizeof (struct foo1)); | |
1231 | printf ("Size of foo2 is %d\n", | |
1232 | sizeof (struct foo2)); | |
1233 | exit (0); | |
1234 | @} | |
1235 | @end smallexample | |
1236 | ||
1237 | If this prints 2 and 5, then the compiler's behavior is what you would | |
1238 | get from @code{PCC_BITFIELD_TYPE_MATTERS}. | |
1239 | @end defmac | |
1240 | ||
1241 | @defmac BITFIELD_NBYTES_LIMITED | |
1242 | Like @code{PCC_BITFIELD_TYPE_MATTERS} except that its effect is limited | |
1243 | to aligning a bit-field within the structure. | |
1244 | @end defmac | |
1245 | ||
1246 | @hook TARGET_ALIGN_ANON_BITFIELD | |
1247 | When @code{PCC_BITFIELD_TYPE_MATTERS} is true this hook will determine | |
1248 | whether unnamed bitfields affect the alignment of the containing | |
1249 | structure. The hook should return true if the structure should inherit | |
1250 | the alignment requirements of an unnamed bitfield's type. | |
1251 | @end deftypefn | |
1252 | ||
1253 | @hook TARGET_NARROW_VOLATILE_BITFIELD | |
1254 | This target hook should return @code{true} if accesses to volatile bitfields | |
1255 | should use the narrowest mode possible. It should return @code{false} if | |
1256 | these accesses should use the bitfield container type. | |
1257 | ||
1258 | The default is @code{!TARGET_STRICT_ALIGN}. | |
1259 | @end deftypefn | |
1260 | ||
1261 | @defmac MEMBER_TYPE_FORCES_BLK (@var{field}, @var{mode}) | |
1262 | Return 1 if a structure or array containing @var{field} should be accessed using | |
1263 | @code{BLKMODE}. | |
1264 | ||
1265 | If @var{field} is the only field in the structure, @var{mode} is its | |
1266 | mode, otherwise @var{mode} is VOIDmode. @var{mode} is provided in the | |
1267 | case where structures of one field would require the structure's mode to | |
1268 | retain the field's mode. | |
1269 | ||
1270 | Normally, this is not needed. | |
1271 | @end defmac | |
1272 | ||
1273 | @defmac ROUND_TYPE_ALIGN (@var{type}, @var{computed}, @var{specified}) | |
1274 | Define this macro as an expression for the alignment of a type (given | |
1275 | by @var{type} as a tree node) if the alignment computed in the usual | |
1276 | way is @var{computed} and the alignment explicitly specified was | |
1277 | @var{specified}. | |
1278 | ||
1279 | The default is to use @var{specified} if it is larger; otherwise, use | |
1280 | the smaller of @var{computed} and @code{BIGGEST_ALIGNMENT} | |
1281 | @end defmac | |
1282 | ||
1283 | @defmac MAX_FIXED_MODE_SIZE | |
1284 | An integer expression for the size in bits of the largest integer | |
1285 | machine mode that should actually be used. All integer machine modes of | |
1286 | this size or smaller can be used for structures and unions with the | |
1287 | appropriate sizes. If this macro is undefined, @code{GET_MODE_BITSIZE | |
1288 | (DImode)} is assumed. | |
1289 | @end defmac | |
1290 | ||
1291 | @defmac STACK_SAVEAREA_MODE (@var{save_level}) | |
1292 | If defined, an expression of type @code{enum machine_mode} that | |
1293 | specifies the mode of the save area operand of a | |
1294 | @code{save_stack_@var{level}} named pattern (@pxref{Standard Names}). | |
1295 | @var{save_level} is one of @code{SAVE_BLOCK}, @code{SAVE_FUNCTION}, or | |
1296 | @code{SAVE_NONLOCAL} and selects which of the three named patterns is | |
1297 | having its mode specified. | |
1298 | ||
1299 | You need not define this macro if it always returns @code{Pmode}. You | |
1300 | would most commonly define this macro if the | |
1301 | @code{save_stack_@var{level}} patterns need to support both a 32- and a | |
1302 | 64-bit mode. | |
1303 | @end defmac | |
1304 | ||
1305 | @defmac STACK_SIZE_MODE | |
1306 | If defined, an expression of type @code{enum machine_mode} that | |
1307 | specifies the mode of the size increment operand of an | |
1308 | @code{allocate_stack} named pattern (@pxref{Standard Names}). | |
1309 | ||
1310 | You need not define this macro if it always returns @code{word_mode}. | |
1311 | You would most commonly define this macro if the @code{allocate_stack} | |
1312 | pattern needs to support both a 32- and a 64-bit mode. | |
1313 | @end defmac | |
1314 | ||
1315 | @hook TARGET_LIBGCC_CMP_RETURN_MODE | |
1316 | This target hook should return the mode to be used for the return value | |
1317 | of compare instructions expanded to libgcc calls. If not defined | |
1318 | @code{word_mode} is returned which is the right choice for a majority of | |
1319 | targets. | |
1320 | @end deftypefn | |
1321 | ||
1322 | @hook TARGET_LIBGCC_SHIFT_COUNT_MODE | |
1323 | This target hook should return the mode to be used for the shift count operand | |
1324 | of shift instructions expanded to libgcc calls. If not defined | |
1325 | @code{word_mode} is returned which is the right choice for a majority of | |
1326 | targets. | |
1327 | @end deftypefn | |
1328 | ||
1329 | @hook TARGET_UNWIND_WORD_MODE | |
1330 | Return machine mode to be used for @code{_Unwind_Word} type. | |
1331 | The default is to use @code{word_mode}. | |
1332 | @end deftypefn | |
1333 | ||
1334 | @defmac ROUND_TOWARDS_ZERO | |
1335 | If defined, this macro should be true if the prevailing rounding | |
1336 | mode is towards zero. | |
1337 | ||
1338 | Defining this macro only affects the way @file{libgcc.a} emulates | |
1339 | floating-point arithmetic. | |
1340 | ||
1341 | Not defining this macro is equivalent to returning zero. | |
1342 | @end defmac | |
1343 | ||
1344 | @defmac LARGEST_EXPONENT_IS_NORMAL (@var{size}) | |
1345 | This macro should return true if floats with @var{size} | |
1346 | bits do not have a NaN or infinity representation, but use the largest | |
1347 | exponent for normal numbers instead. | |
1348 | ||
1349 | Defining this macro only affects the way @file{libgcc.a} emulates | |
1350 | floating-point arithmetic. | |
1351 | ||
1352 | The default definition of this macro returns false for all sizes. | |
1353 | @end defmac | |
1354 | ||
1355 | @hook TARGET_MS_BITFIELD_LAYOUT_P | |
1356 | This target hook returns @code{true} if bit-fields in the given | |
1357 | @var{record_type} are to be laid out following the rules of Microsoft | |
1358 | Visual C/C++, namely: (i) a bit-field won't share the same storage | |
1359 | unit with the previous bit-field if their underlying types have | |
1360 | different sizes, and the bit-field will be aligned to the highest | |
1361 | alignment of the underlying types of itself and of the previous | |
1362 | bit-field; (ii) a zero-sized bit-field will affect the alignment of | |
1363 | the whole enclosing structure, even if it is unnamed; except that | |
1364 | (iii) a zero-sized bit-field will be disregarded unless it follows | |
1365 | another bit-field of nonzero size. If this hook returns @code{true}, | |
1366 | other macros that control bit-field layout are ignored. | |
1367 | ||
1368 | When a bit-field is inserted into a packed record, the whole size | |
1369 | of the underlying type is used by one or more same-size adjacent | |
1370 | bit-fields (that is, if its long:3, 32 bits is used in the record, | |
1371 | and any additional adjacent long bit-fields are packed into the same | |
1372 | chunk of 32 bits. However, if the size changes, a new field of that | |
1373 | size is allocated). In an unpacked record, this is the same as using | |
1374 | alignment, but not equivalent when packing. | |
1375 | ||
1376 | If both MS bit-fields and @samp{__attribute__((packed))} are used, | |
1377 | the latter will take precedence. If @samp{__attribute__((packed))} is | |
1378 | used on a single field when MS bit-fields are in use, it will take | |
1379 | precedence for that field, but the alignment of the rest of the structure | |
1380 | may affect its placement. | |
1381 | @end deftypefn | |
1382 | ||
1383 | @hook TARGET_DECIMAL_FLOAT_SUPPORTED_P | |
1384 | Returns true if the target supports decimal floating point. | |
1385 | @end deftypefn | |
1386 | ||
1387 | @hook TARGET_FIXED_POINT_SUPPORTED_P | |
1388 | Returns true if the target supports fixed-point arithmetic. | |
1389 | @end deftypefn | |
1390 | ||
1391 | @hook TARGET_EXPAND_TO_RTL_HOOK | |
1392 | This hook is called just before expansion into rtl, allowing the target | |
1393 | to perform additional initializations or analysis before the expansion. | |
1394 | For example, the rs6000 port uses it to allocate a scratch stack slot | |
1395 | for use in copying SDmode values between memory and floating point | |
1396 | registers whenever the function being expanded has any SDmode | |
1397 | usage. | |
1398 | @end deftypefn | |
1399 | ||
1400 | @hook TARGET_INSTANTIATE_DECLS | |
1401 | This hook allows the backend to perform additional instantiations on rtl | |
1402 | that are not actually in any insns yet, but will be later. | |
1403 | @end deftypefn | |
1404 | ||
1405 | @hook TARGET_MANGLE_TYPE | |
1406 | If your target defines any fundamental types, or any types your target | |
1407 | uses should be mangled differently from the default, define this hook | |
1408 | to return the appropriate encoding for these types as part of a C++ | |
1409 | mangled name. The @var{type} argument is the tree structure representing | |
1410 | the type to be mangled. The hook may be applied to trees which are | |
1411 | not target-specific fundamental types; it should return @code{NULL} | |
1412 | for all such types, as well as arguments it does not recognize. If the | |
1413 | return value is not @code{NULL}, it must point to a statically-allocated | |
1414 | string constant. | |
1415 | ||
1416 | Target-specific fundamental types might be new fundamental types or | |
1417 | qualified versions of ordinary fundamental types. Encode new | |
1418 | fundamental types as @samp{@w{u @var{n} @var{name}}}, where @var{name} | |
1419 | is the name used for the type in source code, and @var{n} is the | |
1420 | length of @var{name} in decimal. Encode qualified versions of | |
1421 | ordinary types as @samp{@w{U @var{n} @var{name} @var{code}}}, where | |
1422 | @var{name} is the name used for the type qualifier in source code, | |
1423 | @var{n} is the length of @var{name} as above, and @var{code} is the | |
1424 | code used to represent the unqualified version of this type. (See | |
1425 | @code{write_builtin_type} in @file{cp/mangle.c} for the list of | |
1426 | codes.) In both cases the spaces are for clarity; do not include any | |
1427 | spaces in your string. | |
1428 | ||
1429 | This hook is applied to types prior to typedef resolution. If the mangled | |
1430 | name for a particular type depends only on that type's main variant, you | |
1431 | can perform typedef resolution yourself using @code{TYPE_MAIN_VARIANT} | |
1432 | before mangling. | |
1433 | ||
1434 | The default version of this hook always returns @code{NULL}, which is | |
1435 | appropriate for a target that does not define any new fundamental | |
1436 | types. | |
1437 | @end deftypefn | |
1438 | ||
1439 | @node Type Layout | |
1440 | @section Layout of Source Language Data Types | |
1441 | ||
1442 | These macros define the sizes and other characteristics of the standard | |
1443 | basic data types used in programs being compiled. Unlike the macros in | |
1444 | the previous section, these apply to specific features of C and related | |
1445 | languages, rather than to fundamental aspects of storage layout. | |
1446 | ||
1447 | @defmac INT_TYPE_SIZE | |
1448 | A C expression for the size in bits of the type @code{int} on the | |
1449 | target machine. If you don't define this, the default is one word. | |
1450 | @end defmac | |
1451 | ||
1452 | @defmac SHORT_TYPE_SIZE | |
1453 | A C expression for the size in bits of the type @code{short} on the | |
1454 | target machine. If you don't define this, the default is half a word. | |
1455 | (If this would be less than one storage unit, it is rounded up to one | |
1456 | unit.) | |
1457 | @end defmac | |
1458 | ||
1459 | @defmac LONG_TYPE_SIZE | |
1460 | A C expression for the size in bits of the type @code{long} on the | |
1461 | target machine. If you don't define this, the default is one word. | |
1462 | @end defmac | |
1463 | ||
1464 | @defmac ADA_LONG_TYPE_SIZE | |
1465 | On some machines, the size used for the Ada equivalent of the type | |
1466 | @code{long} by a native Ada compiler differs from that used by C@. In | |
1467 | that situation, define this macro to be a C expression to be used for | |
1468 | the size of that type. If you don't define this, the default is the | |
1469 | value of @code{LONG_TYPE_SIZE}. | |
1470 | @end defmac | |
1471 | ||
1472 | @defmac LONG_LONG_TYPE_SIZE | |
1473 | A C expression for the size in bits of the type @code{long long} on the | |
1474 | target machine. If you don't define this, the default is two | |
1475 | words. If you want to support GNU Ada on your machine, the value of this | |
1476 | macro must be at least 64. | |
1477 | @end defmac | |
1478 | ||
1479 | @defmac CHAR_TYPE_SIZE | |
1480 | A C expression for the size in bits of the type @code{char} on the | |
1481 | target machine. If you don't define this, the default is | |
1482 | @code{BITS_PER_UNIT}. | |
1483 | @end defmac | |
1484 | ||
1485 | @defmac BOOL_TYPE_SIZE | |
1486 | A C expression for the size in bits of the C++ type @code{bool} and | |
1487 | C99 type @code{_Bool} on the target machine. If you don't define | |
1488 | this, and you probably shouldn't, the default is @code{CHAR_TYPE_SIZE}. | |
1489 | @end defmac | |
1490 | ||
1491 | @defmac FLOAT_TYPE_SIZE | |
1492 | A C expression for the size in bits of the type @code{float} on the | |
1493 | target machine. If you don't define this, the default is one word. | |
1494 | @end defmac | |
1495 | ||
1496 | @defmac DOUBLE_TYPE_SIZE | |
1497 | A C expression for the size in bits of the type @code{double} on the | |
1498 | target machine. If you don't define this, the default is two | |
1499 | words. | |
1500 | @end defmac | |
1501 | ||
1502 | @defmac LONG_DOUBLE_TYPE_SIZE | |
1503 | A C expression for the size in bits of the type @code{long double} on | |
1504 | the target machine. If you don't define this, the default is two | |
1505 | words. | |
1506 | @end defmac | |
1507 | ||
1508 | @defmac SHORT_FRACT_TYPE_SIZE | |
1509 | A C expression for the size in bits of the type @code{short _Fract} on | |
1510 | the target machine. If you don't define this, the default is | |
1511 | @code{BITS_PER_UNIT}. | |
1512 | @end defmac | |
1513 | ||
1514 | @defmac FRACT_TYPE_SIZE | |
1515 | A C expression for the size in bits of the type @code{_Fract} on | |
1516 | the target machine. If you don't define this, the default is | |
1517 | @code{BITS_PER_UNIT * 2}. | |
1518 | @end defmac | |
1519 | ||
1520 | @defmac LONG_FRACT_TYPE_SIZE | |
1521 | A C expression for the size in bits of the type @code{long _Fract} on | |
1522 | the target machine. If you don't define this, the default is | |
1523 | @code{BITS_PER_UNIT * 4}. | |
1524 | @end defmac | |
1525 | ||
1526 | @defmac LONG_LONG_FRACT_TYPE_SIZE | |
1527 | A C expression for the size in bits of the type @code{long long _Fract} on | |
1528 | the target machine. If you don't define this, the default is | |
1529 | @code{BITS_PER_UNIT * 8}. | |
1530 | @end defmac | |
1531 | ||
1532 | @defmac SHORT_ACCUM_TYPE_SIZE | |
1533 | A C expression for the size in bits of the type @code{short _Accum} on | |
1534 | the target machine. If you don't define this, the default is | |
1535 | @code{BITS_PER_UNIT * 2}. | |
1536 | @end defmac | |
1537 | ||
1538 | @defmac ACCUM_TYPE_SIZE | |
1539 | A C expression for the size in bits of the type @code{_Accum} on | |
1540 | the target machine. If you don't define this, the default is | |
1541 | @code{BITS_PER_UNIT * 4}. | |
1542 | @end defmac | |
1543 | ||
1544 | @defmac LONG_ACCUM_TYPE_SIZE | |
1545 | A C expression for the size in bits of the type @code{long _Accum} on | |
1546 | the target machine. If you don't define this, the default is | |
1547 | @code{BITS_PER_UNIT * 8}. | |
1548 | @end defmac | |
1549 | ||
1550 | @defmac LONG_LONG_ACCUM_TYPE_SIZE | |
1551 | A C expression for the size in bits of the type @code{long long _Accum} on | |
1552 | the target machine. If you don't define this, the default is | |
1553 | @code{BITS_PER_UNIT * 16}. | |
1554 | @end defmac | |
1555 | ||
1556 | @defmac LIBGCC2_LONG_DOUBLE_TYPE_SIZE | |
1557 | Define this macro if @code{LONG_DOUBLE_TYPE_SIZE} is not constant or | |
1558 | if you want routines in @file{libgcc2.a} for a size other than | |
1559 | @code{LONG_DOUBLE_TYPE_SIZE}. If you don't define this, the | |
1560 | default is @code{LONG_DOUBLE_TYPE_SIZE}. | |
1561 | @end defmac | |
1562 | ||
1563 | @defmac LIBGCC2_HAS_DF_MODE | |
a18bdccd | 1564 | Define this macro if neither @code{DOUBLE_TYPE_SIZE} nor |
38f8b050 JR |
1565 | @code{LIBGCC2_LONG_DOUBLE_TYPE_SIZE} is |
1566 | @code{DFmode} but you want @code{DFmode} routines in @file{libgcc2.a} | |
a18bdccd | 1567 | anyway. If you don't define this and either @code{DOUBLE_TYPE_SIZE} |
38f8b050 JR |
1568 | or @code{LIBGCC2_LONG_DOUBLE_TYPE_SIZE} is 64 then the default is 1, |
1569 | otherwise it is 0. | |
1570 | @end defmac | |
1571 | ||
1572 | @defmac LIBGCC2_HAS_XF_MODE | |
1573 | Define this macro if @code{LIBGCC2_LONG_DOUBLE_TYPE_SIZE} is not | |
1574 | @code{XFmode} but you want @code{XFmode} routines in @file{libgcc2.a} | |
1575 | anyway. If you don't define this and @code{LIBGCC2_LONG_DOUBLE_TYPE_SIZE} | |
1576 | is 80 then the default is 1, otherwise it is 0. | |
1577 | @end defmac | |
1578 | ||
1579 | @defmac LIBGCC2_HAS_TF_MODE | |
1580 | Define this macro if @code{LIBGCC2_LONG_DOUBLE_TYPE_SIZE} is not | |
1581 | @code{TFmode} but you want @code{TFmode} routines in @file{libgcc2.a} | |
1582 | anyway. If you don't define this and @code{LIBGCC2_LONG_DOUBLE_TYPE_SIZE} | |
1583 | is 128 then the default is 1, otherwise it is 0. | |
1584 | @end defmac | |
1585 | ||
cdbf4541 BS |
1586 | @defmac LIBGCC2_GNU_PREFIX |
1587 | This macro corresponds to the @code{TARGET_LIBFUNC_GNU_PREFIX} target | |
1588 | hook and should be defined if that hook is overriden to be true. It | |
1589 | causes function names in libgcc to be changed to use a @code{__gnu_} | |
1590 | prefix for their name rather than the default @code{__}. A port which | |
1591 | uses this macro should also arrange to use @file{t-gnu-prefix} in | |
1592 | the libgcc @file{config.host}. | |
1593 | @end defmac | |
1594 | ||
38f8b050 JR |
1595 | @defmac SF_SIZE |
1596 | @defmacx DF_SIZE | |
1597 | @defmacx XF_SIZE | |
1598 | @defmacx TF_SIZE | |
1599 | Define these macros to be the size in bits of the mantissa of | |
1600 | @code{SFmode}, @code{DFmode}, @code{XFmode} and @code{TFmode} values, | |
1601 | if the defaults in @file{libgcc2.h} are inappropriate. By default, | |
1602 | @code{FLT_MANT_DIG} is used for @code{SF_SIZE}, @code{LDBL_MANT_DIG} | |
1603 | for @code{XF_SIZE} and @code{TF_SIZE}, and @code{DBL_MANT_DIG} or | |
1604 | @code{LDBL_MANT_DIG} for @code{DF_SIZE} according to whether | |
a18bdccd | 1605 | @code{DOUBLE_TYPE_SIZE} or |
38f8b050 JR |
1606 | @code{LIBGCC2_LONG_DOUBLE_TYPE_SIZE} is 64. |
1607 | @end defmac | |
1608 | ||
1609 | @defmac TARGET_FLT_EVAL_METHOD | |
1610 | A C expression for the value for @code{FLT_EVAL_METHOD} in @file{float.h}, | |
1611 | assuming, if applicable, that the floating-point control word is in its | |
1612 | default state. If you do not define this macro the value of | |
1613 | @code{FLT_EVAL_METHOD} will be zero. | |
1614 | @end defmac | |
1615 | ||
1616 | @defmac WIDEST_HARDWARE_FP_SIZE | |
1617 | A C expression for the size in bits of the widest floating-point format | |
1618 | supported by the hardware. If you define this macro, you must specify a | |
1619 | value less than or equal to the value of @code{LONG_DOUBLE_TYPE_SIZE}. | |
1620 | If you do not define this macro, the value of @code{LONG_DOUBLE_TYPE_SIZE} | |
1621 | is the default. | |
1622 | @end defmac | |
1623 | ||
1624 | @defmac DEFAULT_SIGNED_CHAR | |
1625 | An expression whose value is 1 or 0, according to whether the type | |
1626 | @code{char} should be signed or unsigned by default. The user can | |
1627 | always override this default with the options @option{-fsigned-char} | |
1628 | and @option{-funsigned-char}. | |
1629 | @end defmac | |
1630 | ||
1631 | @hook TARGET_DEFAULT_SHORT_ENUMS | |
1632 | This target hook should return true if the compiler should give an | |
1633 | @code{enum} type only as many bytes as it takes to represent the range | |
1634 | of possible values of that type. It should return false if all | |
1635 | @code{enum} types should be allocated like @code{int}. | |
1636 | ||
1637 | The default is to return false. | |
1638 | @end deftypefn | |
1639 | ||
1640 | @defmac SIZE_TYPE | |
1641 | A C expression for a string describing the name of the data type to use | |
1642 | for size values. The typedef name @code{size_t} is defined using the | |
1643 | contents of the string. | |
1644 | ||
1645 | The string can contain more than one keyword. If so, separate them with | |
1646 | spaces, and write first any length keyword, then @code{unsigned} if | |
1647 | appropriate, and finally @code{int}. The string must exactly match one | |
1648 | of the data type names defined in the function | |
1649 | @code{init_decl_processing} in the file @file{c-decl.c}. You may not | |
1650 | omit @code{int} or change the order---that would cause the compiler to | |
1651 | crash on startup. | |
1652 | ||
1653 | If you don't define this macro, the default is @code{"long unsigned | |
1654 | int"}. | |
1655 | @end defmac | |
1656 | ||
1657 | @defmac PTRDIFF_TYPE | |
1658 | A C expression for a string describing the name of the data type to use | |
1659 | for the result of subtracting two pointers. The typedef name | |
1660 | @code{ptrdiff_t} is defined using the contents of the string. See | |
1661 | @code{SIZE_TYPE} above for more information. | |
1662 | ||
1663 | If you don't define this macro, the default is @code{"long int"}. | |
1664 | @end defmac | |
1665 | ||
1666 | @defmac WCHAR_TYPE | |
1667 | A C expression for a string describing the name of the data type to use | |
1668 | for wide characters. The typedef name @code{wchar_t} is defined using | |
1669 | the contents of the string. See @code{SIZE_TYPE} above for more | |
1670 | information. | |
1671 | ||
1672 | If you don't define this macro, the default is @code{"int"}. | |
1673 | @end defmac | |
1674 | ||
1675 | @defmac WCHAR_TYPE_SIZE | |
1676 | A C expression for the size in bits of the data type for wide | |
1677 | characters. This is used in @code{cpp}, which cannot make use of | |
1678 | @code{WCHAR_TYPE}. | |
1679 | @end defmac | |
1680 | ||
1681 | @defmac WINT_TYPE | |
1682 | A C expression for a string describing the name of the data type to | |
1683 | use for wide characters passed to @code{printf} and returned from | |
1684 | @code{getwc}. The typedef name @code{wint_t} is defined using the | |
1685 | contents of the string. See @code{SIZE_TYPE} above for more | |
1686 | information. | |
1687 | ||
1688 | If you don't define this macro, the default is @code{"unsigned int"}. | |
1689 | @end defmac | |
1690 | ||
1691 | @defmac INTMAX_TYPE | |
1692 | A C expression for a string describing the name of the data type that | |
1693 | can represent any value of any standard or extended signed integer type. | |
1694 | The typedef name @code{intmax_t} is defined using the contents of the | |
1695 | string. See @code{SIZE_TYPE} above for more information. | |
1696 | ||
1697 | If you don't define this macro, the default is the first of | |
1698 | @code{"int"}, @code{"long int"}, or @code{"long long int"} that has as | |
1699 | much precision as @code{long long int}. | |
1700 | @end defmac | |
1701 | ||
1702 | @defmac UINTMAX_TYPE | |
1703 | A C expression for a string describing the name of the data type that | |
1704 | can represent any value of any standard or extended unsigned integer | |
1705 | type. The typedef name @code{uintmax_t} is defined using the contents | |
1706 | of the string. See @code{SIZE_TYPE} above for more information. | |
1707 | ||
1708 | If you don't define this macro, the default is the first of | |
1709 | @code{"unsigned int"}, @code{"long unsigned int"}, or @code{"long long | |
1710 | unsigned int"} that has as much precision as @code{long long unsigned | |
1711 | int}. | |
1712 | @end defmac | |
1713 | ||
1714 | @defmac SIG_ATOMIC_TYPE | |
1715 | @defmacx INT8_TYPE | |
1716 | @defmacx INT16_TYPE | |
1717 | @defmacx INT32_TYPE | |
1718 | @defmacx INT64_TYPE | |
1719 | @defmacx UINT8_TYPE | |
1720 | @defmacx UINT16_TYPE | |
1721 | @defmacx UINT32_TYPE | |
1722 | @defmacx UINT64_TYPE | |
1723 | @defmacx INT_LEAST8_TYPE | |
1724 | @defmacx INT_LEAST16_TYPE | |
1725 | @defmacx INT_LEAST32_TYPE | |
1726 | @defmacx INT_LEAST64_TYPE | |
1727 | @defmacx UINT_LEAST8_TYPE | |
1728 | @defmacx UINT_LEAST16_TYPE | |
1729 | @defmacx UINT_LEAST32_TYPE | |
1730 | @defmacx UINT_LEAST64_TYPE | |
1731 | @defmacx INT_FAST8_TYPE | |
1732 | @defmacx INT_FAST16_TYPE | |
1733 | @defmacx INT_FAST32_TYPE | |
1734 | @defmacx INT_FAST64_TYPE | |
1735 | @defmacx UINT_FAST8_TYPE | |
1736 | @defmacx UINT_FAST16_TYPE | |
1737 | @defmacx UINT_FAST32_TYPE | |
1738 | @defmacx UINT_FAST64_TYPE | |
1739 | @defmacx INTPTR_TYPE | |
1740 | @defmacx UINTPTR_TYPE | |
1741 | C expressions for the standard types @code{sig_atomic_t}, | |
1742 | @code{int8_t}, @code{int16_t}, @code{int32_t}, @code{int64_t}, | |
1743 | @code{uint8_t}, @code{uint16_t}, @code{uint32_t}, @code{uint64_t}, | |
1744 | @code{int_least8_t}, @code{int_least16_t}, @code{int_least32_t}, | |
1745 | @code{int_least64_t}, @code{uint_least8_t}, @code{uint_least16_t}, | |
1746 | @code{uint_least32_t}, @code{uint_least64_t}, @code{int_fast8_t}, | |
1747 | @code{int_fast16_t}, @code{int_fast32_t}, @code{int_fast64_t}, | |
1748 | @code{uint_fast8_t}, @code{uint_fast16_t}, @code{uint_fast32_t}, | |
1749 | @code{uint_fast64_t}, @code{intptr_t}, and @code{uintptr_t}. See | |
1750 | @code{SIZE_TYPE} above for more information. | |
1751 | ||
1752 | If any of these macros evaluates to a null pointer, the corresponding | |
1753 | type is not supported; if GCC is configured to provide | |
1754 | @code{<stdint.h>} in such a case, the header provided may not conform | |
1755 | to C99, depending on the type in question. The defaults for all of | |
1756 | these macros are null pointers. | |
1757 | @end defmac | |
1758 | ||
1759 | @defmac TARGET_PTRMEMFUNC_VBIT_LOCATION | |
1760 | The C++ compiler represents a pointer-to-member-function with a struct | |
1761 | that looks like: | |
1762 | ||
1763 | @smallexample | |
1764 | struct @{ | |
1765 | union @{ | |
1766 | void (*fn)(); | |
1767 | ptrdiff_t vtable_index; | |
1768 | @}; | |
1769 | ptrdiff_t delta; | |
1770 | @}; | |
1771 | @end smallexample | |
1772 | ||
1773 | @noindent | |
1774 | The C++ compiler must use one bit to indicate whether the function that | |
1775 | will be called through a pointer-to-member-function is virtual. | |
1776 | Normally, we assume that the low-order bit of a function pointer must | |
1777 | always be zero. Then, by ensuring that the vtable_index is odd, we can | |
1778 | distinguish which variant of the union is in use. But, on some | |
1779 | platforms function pointers can be odd, and so this doesn't work. In | |
1780 | that case, we use the low-order bit of the @code{delta} field, and shift | |
1781 | the remainder of the @code{delta} field to the left. | |
1782 | ||
1783 | GCC will automatically make the right selection about where to store | |
1784 | this bit using the @code{FUNCTION_BOUNDARY} setting for your platform. | |
1785 | However, some platforms such as ARM/Thumb have @code{FUNCTION_BOUNDARY} | |
1786 | set such that functions always start at even addresses, but the lowest | |
1787 | bit of pointers to functions indicate whether the function at that | |
1788 | address is in ARM or Thumb mode. If this is the case of your | |
1789 | architecture, you should define this macro to | |
1790 | @code{ptrmemfunc_vbit_in_delta}. | |
1791 | ||
1792 | In general, you should not have to define this macro. On architectures | |
1793 | in which function addresses are always even, according to | |
1794 | @code{FUNCTION_BOUNDARY}, GCC will automatically define this macro to | |
1795 | @code{ptrmemfunc_vbit_in_pfn}. | |
1796 | @end defmac | |
1797 | ||
1798 | @defmac TARGET_VTABLE_USES_DESCRIPTORS | |
1799 | Normally, the C++ compiler uses function pointers in vtables. This | |
1800 | macro allows the target to change to use ``function descriptors'' | |
1801 | instead. Function descriptors are found on targets for whom a | |
1802 | function pointer is actually a small data structure. Normally the | |
1803 | data structure consists of the actual code address plus a data | |
1804 | pointer to which the function's data is relative. | |
1805 | ||
1806 | If vtables are used, the value of this macro should be the number | |
1807 | of words that the function descriptor occupies. | |
1808 | @end defmac | |
1809 | ||
1810 | @defmac TARGET_VTABLE_ENTRY_ALIGN | |
1811 | By default, the vtable entries are void pointers, the so the alignment | |
1812 | is the same as pointer alignment. The value of this macro specifies | |
1813 | the alignment of the vtable entry in bits. It should be defined only | |
1814 | when special alignment is necessary. */ | |
1815 | @end defmac | |
1816 | ||
1817 | @defmac TARGET_VTABLE_DATA_ENTRY_DISTANCE | |
1818 | There are a few non-descriptor entries in the vtable at offsets below | |
1819 | zero. If these entries must be padded (say, to preserve the alignment | |
1820 | specified by @code{TARGET_VTABLE_ENTRY_ALIGN}), set this to the number | |
1821 | of words in each data entry. | |
1822 | @end defmac | |
1823 | ||
1824 | @node Registers | |
1825 | @section Register Usage | |
1826 | @cindex register usage | |
1827 | ||
1828 | This section explains how to describe what registers the target machine | |
1829 | has, and how (in general) they can be used. | |
1830 | ||
1831 | The description of which registers a specific instruction can use is | |
1832 | done with register classes; see @ref{Register Classes}. For information | |
1833 | on using registers to access a stack frame, see @ref{Frame Registers}. | |
1834 | For passing values in registers, see @ref{Register Arguments}. | |
1835 | For returning values in registers, see @ref{Scalar Return}. | |
1836 | ||
1837 | @menu | |
1838 | * Register Basics:: Number and kinds of registers. | |
1839 | * Allocation Order:: Order in which registers are allocated. | |
1840 | * Values in Registers:: What kinds of values each reg can hold. | |
1841 | * Leaf Functions:: Renumbering registers for leaf functions. | |
1842 | * Stack Registers:: Handling a register stack such as 80387. | |
1843 | @end menu | |
1844 | ||
1845 | @node Register Basics | |
1846 | @subsection Basic Characteristics of Registers | |
1847 | ||
1848 | @c prevent bad page break with this line | |
1849 | Registers have various characteristics. | |
1850 | ||
1851 | @defmac FIRST_PSEUDO_REGISTER | |
1852 | Number of hardware registers known to the compiler. They receive | |
1853 | numbers 0 through @code{FIRST_PSEUDO_REGISTER-1}; thus, the first | |
1854 | pseudo register's number really is assigned the number | |
1855 | @code{FIRST_PSEUDO_REGISTER}. | |
1856 | @end defmac | |
1857 | ||
1858 | @defmac FIXED_REGISTERS | |
1859 | @cindex fixed register | |
1860 | An initializer that says which registers are used for fixed purposes | |
1861 | all throughout the compiled code and are therefore not available for | |
1862 | general allocation. These would include the stack pointer, the frame | |
1863 | pointer (except on machines where that can be used as a general | |
1864 | register when no frame pointer is needed), the program counter on | |
1865 | machines where that is considered one of the addressable registers, | |
1866 | and any other numbered register with a standard use. | |
1867 | ||
1868 | This information is expressed as a sequence of numbers, separated by | |
1869 | commas and surrounded by braces. The @var{n}th number is 1 if | |
1870 | register @var{n} is fixed, 0 otherwise. | |
1871 | ||
1872 | The table initialized from this macro, and the table initialized by | |
1873 | the following one, may be overridden at run time either automatically, | |
1874 | by the actions of the macro @code{CONDITIONAL_REGISTER_USAGE}, or by | |
1875 | the user with the command options @option{-ffixed-@var{reg}}, | |
1876 | @option{-fcall-used-@var{reg}} and @option{-fcall-saved-@var{reg}}. | |
1877 | @end defmac | |
1878 | ||
1879 | @defmac CALL_USED_REGISTERS | |
1880 | @cindex call-used register | |
1881 | @cindex call-clobbered register | |
1882 | @cindex call-saved register | |
1883 | Like @code{FIXED_REGISTERS} but has 1 for each register that is | |
1884 | clobbered (in general) by function calls as well as for fixed | |
1885 | registers. This macro therefore identifies the registers that are not | |
1886 | available for general allocation of values that must live across | |
1887 | function calls. | |
1888 | ||
1889 | If a register has 0 in @code{CALL_USED_REGISTERS}, the compiler | |
1890 | automatically saves it on function entry and restores it on function | |
1891 | exit, if the register is used within the function. | |
1892 | @end defmac | |
1893 | ||
1894 | @defmac CALL_REALLY_USED_REGISTERS | |
1895 | @cindex call-used register | |
1896 | @cindex call-clobbered register | |
1897 | @cindex call-saved register | |
1898 | Like @code{CALL_USED_REGISTERS} except this macro doesn't require | |
1899 | that the entire set of @code{FIXED_REGISTERS} be included. | |
1900 | (@code{CALL_USED_REGISTERS} must be a superset of @code{FIXED_REGISTERS}). | |
1901 | This macro is optional. If not specified, it defaults to the value | |
1902 | of @code{CALL_USED_REGISTERS}. | |
1903 | @end defmac | |
1904 | ||
1905 | @defmac HARD_REGNO_CALL_PART_CLOBBERED (@var{regno}, @var{mode}) | |
1906 | @cindex call-used register | |
1907 | @cindex call-clobbered register | |
1908 | @cindex call-saved register | |
1909 | A C expression that is nonzero if it is not permissible to store a | |
1910 | value of mode @var{mode} in hard register number @var{regno} across a | |
1911 | call without some part of it being clobbered. For most machines this | |
1912 | macro need not be defined. It is only required for machines that do not | |
1913 | preserve the entire contents of a register across a call. | |
1914 | @end defmac | |
1915 | ||
1916 | @findex fixed_regs | |
1917 | @findex call_used_regs | |
1918 | @findex global_regs | |
1919 | @findex reg_names | |
1920 | @findex reg_class_contents | |
5efd84c5 NF |
1921 | @hook TARGET_CONDITIONAL_REGISTER_USAGE |
1922 | This hook may conditionally modify five variables | |
38f8b050 JR |
1923 | @code{fixed_regs}, @code{call_used_regs}, @code{global_regs}, |
1924 | @code{reg_names}, and @code{reg_class_contents}, to take into account | |
1925 | any dependence of these register sets on target flags. The first three | |
1926 | of these are of type @code{char []} (interpreted as Boolean vectors). | |
1927 | @code{global_regs} is a @code{const char *[]}, and | |
1928 | @code{reg_class_contents} is a @code{HARD_REG_SET}. Before the macro is | |
1929 | called, @code{fixed_regs}, @code{call_used_regs}, | |
1930 | @code{reg_class_contents}, and @code{reg_names} have been initialized | |
1931 | from @code{FIXED_REGISTERS}, @code{CALL_USED_REGISTERS}, | |
1932 | @code{REG_CLASS_CONTENTS}, and @code{REGISTER_NAMES}, respectively. | |
1933 | @code{global_regs} has been cleared, and any @option{-ffixed-@var{reg}}, | |
1934 | @option{-fcall-used-@var{reg}} and @option{-fcall-saved-@var{reg}} | |
1935 | command options have been applied. | |
1936 | ||
38f8b050 JR |
1937 | @cindex disabling certain registers |
1938 | @cindex controlling register usage | |
1939 | If the usage of an entire class of registers depends on the target | |
1940 | flags, you may indicate this to GCC by using this macro to modify | |
1941 | @code{fixed_regs} and @code{call_used_regs} to 1 for each of the | |
1942 | registers in the classes which should not be used by GCC@. Also define | |
1943 | the macro @code{REG_CLASS_FROM_LETTER} / @code{REG_CLASS_FROM_CONSTRAINT} | |
1944 | to return @code{NO_REGS} if it | |
1945 | is called with a letter for a class that shouldn't be used. | |
1946 | ||
1947 | (However, if this class is not included in @code{GENERAL_REGS} and all | |
1948 | of the insn patterns whose constraints permit this class are | |
1949 | controlled by target switches, then GCC will automatically avoid using | |
1950 | these registers when the target switches are opposed to them.) | |
5efd84c5 | 1951 | @end deftypefn |
38f8b050 JR |
1952 | |
1953 | @defmac INCOMING_REGNO (@var{out}) | |
1954 | Define this macro if the target machine has register windows. This C | |
1955 | expression returns the register number as seen by the called function | |
1956 | corresponding to the register number @var{out} as seen by the calling | |
1957 | function. Return @var{out} if register number @var{out} is not an | |
1958 | outbound register. | |
1959 | @end defmac | |
1960 | ||
1961 | @defmac OUTGOING_REGNO (@var{in}) | |
1962 | Define this macro if the target machine has register windows. This C | |
1963 | expression returns the register number as seen by the calling function | |
1964 | corresponding to the register number @var{in} as seen by the called | |
1965 | function. Return @var{in} if register number @var{in} is not an inbound | |
1966 | register. | |
1967 | @end defmac | |
1968 | ||
1969 | @defmac LOCAL_REGNO (@var{regno}) | |
1970 | Define this macro if the target machine has register windows. This C | |
1971 | expression returns true if the register is call-saved but is in the | |
1972 | register window. Unlike most call-saved registers, such registers | |
1973 | need not be explicitly restored on function exit or during non-local | |
1974 | gotos. | |
1975 | @end defmac | |
1976 | ||
1977 | @defmac PC_REGNUM | |
1978 | If the program counter has a register number, define this as that | |
1979 | register number. Otherwise, do not define it. | |
1980 | @end defmac | |
1981 | ||
1982 | @node Allocation Order | |
1983 | @subsection Order of Allocation of Registers | |
1984 | @cindex order of register allocation | |
1985 | @cindex register allocation order | |
1986 | ||
1987 | @c prevent bad page break with this line | |
1988 | Registers are allocated in order. | |
1989 | ||
1990 | @defmac REG_ALLOC_ORDER | |
1991 | If defined, an initializer for a vector of integers, containing the | |
1992 | numbers of hard registers in the order in which GCC should prefer | |
1993 | to use them (from most preferred to least). | |
1994 | ||
1995 | If this macro is not defined, registers are used lowest numbered first | |
1996 | (all else being equal). | |
1997 | ||
1998 | One use of this macro is on machines where the highest numbered | |
1999 | registers must always be saved and the save-multiple-registers | |
2000 | instruction supports only sequences of consecutive registers. On such | |
2001 | machines, define @code{REG_ALLOC_ORDER} to be an initializer that lists | |
2002 | the highest numbered allocable register first. | |
2003 | @end defmac | |
2004 | ||
2005 | @defmac ADJUST_REG_ALLOC_ORDER | |
2006 | A C statement (sans semicolon) to choose the order in which to allocate | |
2007 | hard registers for pseudo-registers local to a basic block. | |
2008 | ||
2009 | Store the desired register order in the array @code{reg_alloc_order}. | |
2010 | Element 0 should be the register to allocate first; element 1, the next | |
2011 | register; and so on. | |
2012 | ||
2013 | The macro body should not assume anything about the contents of | |
2014 | @code{reg_alloc_order} before execution of the macro. | |
2015 | ||
2016 | On most machines, it is not necessary to define this macro. | |
2017 | @end defmac | |
2018 | ||
2019 | @defmac HONOR_REG_ALLOC_ORDER | |
2020 | Normally, IRA tries to estimate the costs for saving a register in the | |
2021 | prologue and restoring it in the epilogue. This discourages it from | |
2022 | using call-saved registers. If a machine wants to ensure that IRA | |
2023 | allocates registers in the order given by REG_ALLOC_ORDER even if some | |
2024 | call-saved registers appear earlier than call-used ones, this macro | |
2025 | should be defined. | |
2026 | @end defmac | |
2027 | ||
2028 | @defmac IRA_HARD_REGNO_ADD_COST_MULTIPLIER (@var{regno}) | |
2029 | In some case register allocation order is not enough for the | |
2030 | Integrated Register Allocator (@acronym{IRA}) to generate a good code. | |
2031 | If this macro is defined, it should return a floating point value | |
2032 | based on @var{regno}. The cost of using @var{regno} for a pseudo will | |
2033 | be increased by approximately the pseudo's usage frequency times the | |
2034 | value returned by this macro. Not defining this macro is equivalent | |
2035 | to having it always return @code{0.0}. | |
2036 | ||
2037 | On most machines, it is not necessary to define this macro. | |
2038 | @end defmac | |
2039 | ||
2040 | @node Values in Registers | |
2041 | @subsection How Values Fit in Registers | |
2042 | ||
2043 | This section discusses the macros that describe which kinds of values | |
2044 | (specifically, which machine modes) each register can hold, and how many | |
2045 | consecutive registers are needed for a given mode. | |
2046 | ||
2047 | @defmac HARD_REGNO_NREGS (@var{regno}, @var{mode}) | |
2048 | A C expression for the number of consecutive hard registers, starting | |
2049 | at register number @var{regno}, required to hold a value of mode | |
2050 | @var{mode}. This macro must never return zero, even if a register | |
2051 | cannot hold the requested mode - indicate that with HARD_REGNO_MODE_OK | |
2052 | and/or CANNOT_CHANGE_MODE_CLASS instead. | |
2053 | ||
2054 | On a machine where all registers are exactly one word, a suitable | |
2055 | definition of this macro is | |
2056 | ||
2057 | @smallexample | |
2058 | #define HARD_REGNO_NREGS(REGNO, MODE) \ | |
2059 | ((GET_MODE_SIZE (MODE) + UNITS_PER_WORD - 1) \ | |
2060 | / UNITS_PER_WORD) | |
2061 | @end smallexample | |
2062 | @end defmac | |
2063 | ||
2064 | @defmac HARD_REGNO_NREGS_HAS_PADDING (@var{regno}, @var{mode}) | |
2065 | A C expression that is nonzero if a value of mode @var{mode}, stored | |
2066 | in memory, ends with padding that causes it to take up more space than | |
2067 | in registers starting at register number @var{regno} (as determined by | |
2068 | multiplying GCC's notion of the size of the register when containing | |
2069 | this mode by the number of registers returned by | |
2070 | @code{HARD_REGNO_NREGS}). By default this is zero. | |
2071 | ||
2072 | For example, if a floating-point value is stored in three 32-bit | |
2073 | registers but takes up 128 bits in memory, then this would be | |
2074 | nonzero. | |
2075 | ||
2076 | This macros only needs to be defined if there are cases where | |
2077 | @code{subreg_get_info} | |
2078 | would otherwise wrongly determine that a @code{subreg} can be | |
2079 | represented by an offset to the register number, when in fact such a | |
2080 | @code{subreg} would contain some of the padding not stored in | |
2081 | registers and so not be representable. | |
2082 | @end defmac | |
2083 | ||
2084 | @defmac HARD_REGNO_NREGS_WITH_PADDING (@var{regno}, @var{mode}) | |
2085 | For values of @var{regno} and @var{mode} for which | |
2086 | @code{HARD_REGNO_NREGS_HAS_PADDING} returns nonzero, a C expression | |
2087 | returning the greater number of registers required to hold the value | |
2088 | including any padding. In the example above, the value would be four. | |
2089 | @end defmac | |
2090 | ||
2091 | @defmac REGMODE_NATURAL_SIZE (@var{mode}) | |
2092 | Define this macro if the natural size of registers that hold values | |
2093 | of mode @var{mode} is not the word size. It is a C expression that | |
2094 | should give the natural size in bytes for the specified mode. It is | |
2095 | used by the register allocator to try to optimize its results. This | |
2096 | happens for example on SPARC 64-bit where the natural size of | |
2097 | floating-point registers is still 32-bit. | |
2098 | @end defmac | |
2099 | ||
2100 | @defmac HARD_REGNO_MODE_OK (@var{regno}, @var{mode}) | |
2101 | A C expression that is nonzero if it is permissible to store a value | |
2102 | of mode @var{mode} in hard register number @var{regno} (or in several | |
2103 | registers starting with that one). For a machine where all registers | |
2104 | are equivalent, a suitable definition is | |
2105 | ||
2106 | @smallexample | |
2107 | #define HARD_REGNO_MODE_OK(REGNO, MODE) 1 | |
2108 | @end smallexample | |
2109 | ||
2110 | You need not include code to check for the numbers of fixed registers, | |
2111 | because the allocation mechanism considers them to be always occupied. | |
2112 | ||
2113 | @cindex register pairs | |
2114 | On some machines, double-precision values must be kept in even/odd | |
2115 | register pairs. You can implement that by defining this macro to reject | |
2116 | odd register numbers for such modes. | |
2117 | ||
2118 | The minimum requirement for a mode to be OK in a register is that the | |
2119 | @samp{mov@var{mode}} instruction pattern support moves between the | |
2120 | register and other hard register in the same class and that moving a | |
2121 | value into the register and back out not alter it. | |
2122 | ||
2123 | Since the same instruction used to move @code{word_mode} will work for | |
2124 | all narrower integer modes, it is not necessary on any machine for | |
2125 | @code{HARD_REGNO_MODE_OK} to distinguish between these modes, provided | |
2126 | you define patterns @samp{movhi}, etc., to take advantage of this. This | |
2127 | is useful because of the interaction between @code{HARD_REGNO_MODE_OK} | |
2128 | and @code{MODES_TIEABLE_P}; it is very desirable for all integer modes | |
2129 | to be tieable. | |
2130 | ||
2131 | Many machines have special registers for floating point arithmetic. | |
2132 | Often people assume that floating point machine modes are allowed only | |
2133 | in floating point registers. This is not true. Any registers that | |
2134 | can hold integers can safely @emph{hold} a floating point machine | |
2135 | mode, whether or not floating arithmetic can be done on it in those | |
2136 | registers. Integer move instructions can be used to move the values. | |
2137 | ||
2138 | On some machines, though, the converse is true: fixed-point machine | |
2139 | modes may not go in floating registers. This is true if the floating | |
2140 | registers normalize any value stored in them, because storing a | |
2141 | non-floating value there would garble it. In this case, | |
2142 | @code{HARD_REGNO_MODE_OK} should reject fixed-point machine modes in | |
2143 | floating registers. But if the floating registers do not automatically | |
2144 | normalize, if you can store any bit pattern in one and retrieve it | |
2145 | unchanged without a trap, then any machine mode may go in a floating | |
2146 | register, so you can define this macro to say so. | |
2147 | ||
2148 | The primary significance of special floating registers is rather that | |
2149 | they are the registers acceptable in floating point arithmetic | |
2150 | instructions. However, this is of no concern to | |
2151 | @code{HARD_REGNO_MODE_OK}. You handle it by writing the proper | |
2152 | constraints for those instructions. | |
2153 | ||
2154 | On some machines, the floating registers are especially slow to access, | |
2155 | so that it is better to store a value in a stack frame than in such a | |
2156 | register if floating point arithmetic is not being done. As long as the | |
2157 | floating registers are not in class @code{GENERAL_REGS}, they will not | |
2158 | be used unless some pattern's constraint asks for one. | |
2159 | @end defmac | |
2160 | ||
2161 | @defmac HARD_REGNO_RENAME_OK (@var{from}, @var{to}) | |
2162 | A C expression that is nonzero if it is OK to rename a hard register | |
2163 | @var{from} to another hard register @var{to}. | |
2164 | ||
2165 | One common use of this macro is to prevent renaming of a register to | |
2166 | another register that is not saved by a prologue in an interrupt | |
2167 | handler. | |
2168 | ||
2169 | The default is always nonzero. | |
2170 | @end defmac | |
2171 | ||
2172 | @defmac MODES_TIEABLE_P (@var{mode1}, @var{mode2}) | |
2173 | A C expression that is nonzero if a value of mode | |
2174 | @var{mode1} is accessible in mode @var{mode2} without copying. | |
2175 | ||
2176 | If @code{HARD_REGNO_MODE_OK (@var{r}, @var{mode1})} and | |
2177 | @code{HARD_REGNO_MODE_OK (@var{r}, @var{mode2})} are always the same for | |
2178 | any @var{r}, then @code{MODES_TIEABLE_P (@var{mode1}, @var{mode2})} | |
2179 | should be nonzero. If they differ for any @var{r}, you should define | |
2180 | this macro to return zero unless some other mechanism ensures the | |
2181 | accessibility of the value in a narrower mode. | |
2182 | ||
2183 | You should define this macro to return nonzero in as many cases as | |
2184 | possible since doing so will allow GCC to perform better register | |
2185 | allocation. | |
2186 | @end defmac | |
2187 | ||
2188 | @hook TARGET_HARD_REGNO_SCRATCH_OK | |
2189 | This target hook should return @code{true} if it is OK to use a hard register | |
2190 | @var{regno} as scratch reg in peephole2. | |
2191 | ||
2192 | One common use of this macro is to prevent using of a register that | |
2193 | is not saved by a prologue in an interrupt handler. | |
2194 | ||
2195 | The default version of this hook always returns @code{true}. | |
2196 | @end deftypefn | |
2197 | ||
2198 | @defmac AVOID_CCMODE_COPIES | |
2199 | Define this macro if the compiler should avoid copies to/from @code{CCmode} | |
2200 | registers. You should only define this macro if support for copying to/from | |
2201 | @code{CCmode} is incomplete. | |
2202 | @end defmac | |
2203 | ||
2204 | @node Leaf Functions | |
2205 | @subsection Handling Leaf Functions | |
2206 | ||
2207 | @cindex leaf functions | |
2208 | @cindex functions, leaf | |
2209 | On some machines, a leaf function (i.e., one which makes no calls) can run | |
2210 | more efficiently if it does not make its own register window. Often this | |
2211 | means it is required to receive its arguments in the registers where they | |
2212 | are passed by the caller, instead of the registers where they would | |
2213 | normally arrive. | |
2214 | ||
2215 | The special treatment for leaf functions generally applies only when | |
2216 | other conditions are met; for example, often they may use only those | |
2217 | registers for its own variables and temporaries. We use the term ``leaf | |
2218 | function'' to mean a function that is suitable for this special | |
2219 | handling, so that functions with no calls are not necessarily ``leaf | |
2220 | functions''. | |
2221 | ||
2222 | GCC assigns register numbers before it knows whether the function is | |
2223 | suitable for leaf function treatment. So it needs to renumber the | |
2224 | registers in order to output a leaf function. The following macros | |
2225 | accomplish this. | |
2226 | ||
2227 | @defmac LEAF_REGISTERS | |
2228 | Name of a char vector, indexed by hard register number, which | |
2229 | contains 1 for a register that is allowable in a candidate for leaf | |
2230 | function treatment. | |
2231 | ||
2232 | If leaf function treatment involves renumbering the registers, then the | |
2233 | registers marked here should be the ones before renumbering---those that | |
2234 | GCC would ordinarily allocate. The registers which will actually be | |
2235 | used in the assembler code, after renumbering, should not be marked with 1 | |
2236 | in this vector. | |
2237 | ||
2238 | Define this macro only if the target machine offers a way to optimize | |
2239 | the treatment of leaf functions. | |
2240 | @end defmac | |
2241 | ||
2242 | @defmac LEAF_REG_REMAP (@var{regno}) | |
2243 | A C expression whose value is the register number to which @var{regno} | |
2244 | should be renumbered, when a function is treated as a leaf function. | |
2245 | ||
2246 | If @var{regno} is a register number which should not appear in a leaf | |
2247 | function before renumbering, then the expression should yield @minus{}1, which | |
2248 | will cause the compiler to abort. | |
2249 | ||
2250 | Define this macro only if the target machine offers a way to optimize the | |
2251 | treatment of leaf functions, and registers need to be renumbered to do | |
2252 | this. | |
2253 | @end defmac | |
2254 | ||
2255 | @findex current_function_is_leaf | |
2256 | @findex current_function_uses_only_leaf_regs | |
2257 | @code{TARGET_ASM_FUNCTION_PROLOGUE} and | |
2258 | @code{TARGET_ASM_FUNCTION_EPILOGUE} must usually treat leaf functions | |
2259 | specially. They can test the C variable @code{current_function_is_leaf} | |
2260 | which is nonzero for leaf functions. @code{current_function_is_leaf} is | |
2261 | set prior to local register allocation and is valid for the remaining | |
2262 | compiler passes. They can also test the C variable | |
2263 | @code{current_function_uses_only_leaf_regs} which is nonzero for leaf | |
2264 | functions which only use leaf registers. | |
2265 | @code{current_function_uses_only_leaf_regs} is valid after all passes | |
2266 | that modify the instructions have been run and is only useful if | |
2267 | @code{LEAF_REGISTERS} is defined. | |
2268 | @c changed this to fix overfull. ALSO: why the "it" at the beginning | |
2269 | @c of the next paragraph?! --mew 2feb93 | |
2270 | ||
2271 | @node Stack Registers | |
2272 | @subsection Registers That Form a Stack | |
2273 | ||
2274 | There are special features to handle computers where some of the | |
2275 | ``registers'' form a stack. Stack registers are normally written by | |
2276 | pushing onto the stack, and are numbered relative to the top of the | |
2277 | stack. | |
2278 | ||
2279 | Currently, GCC can only handle one group of stack-like registers, and | |
2280 | they must be consecutively numbered. Furthermore, the existing | |
2281 | support for stack-like registers is specific to the 80387 floating | |
2282 | point coprocessor. If you have a new architecture that uses | |
2283 | stack-like registers, you will need to do substantial work on | |
2284 | @file{reg-stack.c} and write your machine description to cooperate | |
2285 | with it, as well as defining these macros. | |
2286 | ||
2287 | @defmac STACK_REGS | |
2288 | Define this if the machine has any stack-like registers. | |
2289 | @end defmac | |
2290 | ||
2291 | @defmac STACK_REG_COVER_CLASS | |
2292 | This is a cover class containing the stack registers. Define this if | |
2293 | the machine has any stack-like registers. | |
2294 | @end defmac | |
2295 | ||
2296 | @defmac FIRST_STACK_REG | |
2297 | The number of the first stack-like register. This one is the top | |
2298 | of the stack. | |
2299 | @end defmac | |
2300 | ||
2301 | @defmac LAST_STACK_REG | |
2302 | The number of the last stack-like register. This one is the bottom of | |
2303 | the stack. | |
2304 | @end defmac | |
2305 | ||
2306 | @node Register Classes | |
2307 | @section Register Classes | |
2308 | @cindex register class definitions | |
2309 | @cindex class definitions, register | |
2310 | ||
2311 | On many machines, the numbered registers are not all equivalent. | |
2312 | For example, certain registers may not be allowed for indexed addressing; | |
2313 | certain registers may not be allowed in some instructions. These machine | |
2314 | restrictions are described to the compiler using @dfn{register classes}. | |
2315 | ||
2316 | You define a number of register classes, giving each one a name and saying | |
2317 | which of the registers belong to it. Then you can specify register classes | |
2318 | that are allowed as operands to particular instruction patterns. | |
2319 | ||
2320 | @findex ALL_REGS | |
2321 | @findex NO_REGS | |
2322 | In general, each register will belong to several classes. In fact, one | |
2323 | class must be named @code{ALL_REGS} and contain all the registers. Another | |
2324 | class must be named @code{NO_REGS} and contain no registers. Often the | |
2325 | union of two classes will be another class; however, this is not required. | |
2326 | ||
2327 | @findex GENERAL_REGS | |
2328 | One of the classes must be named @code{GENERAL_REGS}. There is nothing | |
2329 | terribly special about the name, but the operand constraint letters | |
2330 | @samp{r} and @samp{g} specify this class. If @code{GENERAL_REGS} is | |
2331 | the same as @code{ALL_REGS}, just define it as a macro which expands | |
2332 | to @code{ALL_REGS}. | |
2333 | ||
2334 | Order the classes so that if class @var{x} is contained in class @var{y} | |
2335 | then @var{x} has a lower class number than @var{y}. | |
2336 | ||
2337 | The way classes other than @code{GENERAL_REGS} are specified in operand | |
2338 | constraints is through machine-dependent operand constraint letters. | |
2339 | You can define such letters to correspond to various classes, then use | |
2340 | them in operand constraints. | |
2341 | ||
6049a4c8 HPN |
2342 | You must define the narrowest register classes for allocatable |
2343 | registers, so that each class either has no subclasses, or that for | |
2344 | some mode, the move cost between registers within the class is | |
2345 | cheaper than moving a register in the class to or from memory | |
2346 | (@pxref{Costs}). | |
2347 | ||
38f8b050 JR |
2348 | You should define a class for the union of two classes whenever some |
2349 | instruction allows both classes. For example, if an instruction allows | |
2350 | either a floating point (coprocessor) register or a general register for a | |
2351 | certain operand, you should define a class @code{FLOAT_OR_GENERAL_REGS} | |
b899fd78 JR |
2352 | which includes both of them. Otherwise you will get suboptimal code, |
2353 | or even internal compiler errors when reload cannot find a register in the | |
dd5a833e | 2354 | class computed via @code{reg_class_subunion}. |
38f8b050 JR |
2355 | |
2356 | You must also specify certain redundant information about the register | |
2357 | classes: for each class, which classes contain it and which ones are | |
2358 | contained in it; for each pair of classes, the largest class contained | |
2359 | in their union. | |
2360 | ||
2361 | When a value occupying several consecutive registers is expected in a | |
2362 | certain class, all the registers used must belong to that class. | |
2363 | Therefore, register classes cannot be used to enforce a requirement for | |
2364 | a register pair to start with an even-numbered register. The way to | |
2365 | specify this requirement is with @code{HARD_REGNO_MODE_OK}. | |
2366 | ||
2367 | Register classes used for input-operands of bitwise-and or shift | |
2368 | instructions have a special requirement: each such class must have, for | |
2369 | each fixed-point machine mode, a subclass whose registers can transfer that | |
2370 | mode to or from memory. For example, on some machines, the operations for | |
2371 | single-byte values (@code{QImode}) are limited to certain registers. When | |
2372 | this is so, each register class that is used in a bitwise-and or shift | |
2373 | instruction must have a subclass consisting of registers from which | |
2374 | single-byte values can be loaded or stored. This is so that | |
2375 | @code{PREFERRED_RELOAD_CLASS} can always have a possible value to return. | |
2376 | ||
2377 | @deftp {Data type} {enum reg_class} | |
2378 | An enumerated type that must be defined with all the register class names | |
2379 | as enumerated values. @code{NO_REGS} must be first. @code{ALL_REGS} | |
2380 | must be the last register class, followed by one more enumerated value, | |
2381 | @code{LIM_REG_CLASSES}, which is not a register class but rather | |
2382 | tells how many classes there are. | |
2383 | ||
2384 | Each register class has a number, which is the value of casting | |
2385 | the class name to type @code{int}. The number serves as an index | |
2386 | in many of the tables described below. | |
2387 | @end deftp | |
2388 | ||
2389 | @defmac N_REG_CLASSES | |
2390 | The number of distinct register classes, defined as follows: | |
2391 | ||
2392 | @smallexample | |
2393 | #define N_REG_CLASSES (int) LIM_REG_CLASSES | |
2394 | @end smallexample | |
2395 | @end defmac | |
2396 | ||
2397 | @defmac REG_CLASS_NAMES | |
2398 | An initializer containing the names of the register classes as C string | |
2399 | constants. These names are used in writing some of the debugging dumps. | |
2400 | @end defmac | |
2401 | ||
2402 | @defmac REG_CLASS_CONTENTS | |
2403 | An initializer containing the contents of the register classes, as integers | |
2404 | which are bit masks. The @var{n}th integer specifies the contents of class | |
2405 | @var{n}. The way the integer @var{mask} is interpreted is that | |
2406 | register @var{r} is in the class if @code{@var{mask} & (1 << @var{r})} is 1. | |
2407 | ||
2408 | When the machine has more than 32 registers, an integer does not suffice. | |
2409 | Then the integers are replaced by sub-initializers, braced groupings containing | |
2410 | several integers. Each sub-initializer must be suitable as an initializer | |
2411 | for the type @code{HARD_REG_SET} which is defined in @file{hard-reg-set.h}. | |
2412 | In this situation, the first integer in each sub-initializer corresponds to | |
2413 | registers 0 through 31, the second integer to registers 32 through 63, and | |
2414 | so on. | |
2415 | @end defmac | |
2416 | ||
2417 | @defmac REGNO_REG_CLASS (@var{regno}) | |
2418 | A C expression whose value is a register class containing hard register | |
2419 | @var{regno}. In general there is more than one such class; choose a class | |
2420 | which is @dfn{minimal}, meaning that no smaller class also contains the | |
2421 | register. | |
2422 | @end defmac | |
2423 | ||
2424 | @defmac BASE_REG_CLASS | |
2425 | A macro whose definition is the name of the class to which a valid | |
2426 | base register must belong. A base register is one used in an address | |
2427 | which is the register value plus a displacement. | |
2428 | @end defmac | |
2429 | ||
2430 | @defmac MODE_BASE_REG_CLASS (@var{mode}) | |
2431 | This is a variation of the @code{BASE_REG_CLASS} macro which allows | |
2432 | the selection of a base register in a mode dependent manner. If | |
2433 | @var{mode} is VOIDmode then it should return the same value as | |
2434 | @code{BASE_REG_CLASS}. | |
2435 | @end defmac | |
2436 | ||
2437 | @defmac MODE_BASE_REG_REG_CLASS (@var{mode}) | |
2438 | A C expression whose value is the register class to which a valid | |
2439 | base register must belong in order to be used in a base plus index | |
2440 | register address. You should define this macro if base plus index | |
2441 | addresses have different requirements than other base register uses. | |
2442 | @end defmac | |
2443 | ||
2444 | @defmac MODE_CODE_BASE_REG_CLASS (@var{mode}, @var{outer_code}, @var{index_code}) | |
2445 | A C expression whose value is the register class to which a valid | |
2446 | base register must belong. @var{outer_code} and @var{index_code} define the | |
2447 | context in which the base register occurs. @var{outer_code} is the code of | |
2448 | the immediately enclosing expression (@code{MEM} for the top level of an | |
2449 | address, @code{ADDRESS} for something that occurs in an | |
2450 | @code{address_operand}). @var{index_code} is the code of the corresponding | |
2451 | index expression if @var{outer_code} is @code{PLUS}; @code{SCRATCH} otherwise. | |
2452 | @end defmac | |
2453 | ||
2454 | @defmac INDEX_REG_CLASS | |
2455 | A macro whose definition is the name of the class to which a valid | |
2456 | index register must belong. An index register is one used in an | |
2457 | address where its value is either multiplied by a scale factor or | |
2458 | added to another register (as well as added to a displacement). | |
2459 | @end defmac | |
2460 | ||
2461 | @defmac REGNO_OK_FOR_BASE_P (@var{num}) | |
2462 | A C expression which is nonzero if register number @var{num} is | |
2463 | suitable for use as a base register in operand addresses. | |
38f8b050 JR |
2464 | @end defmac |
2465 | ||
2466 | @defmac REGNO_MODE_OK_FOR_BASE_P (@var{num}, @var{mode}) | |
2467 | A C expression that is just like @code{REGNO_OK_FOR_BASE_P}, except that | |
2468 | that expression may examine the mode of the memory reference in | |
2469 | @var{mode}. You should define this macro if the mode of the memory | |
2470 | reference affects whether a register may be used as a base register. If | |
2471 | you define this macro, the compiler will use it instead of | |
2472 | @code{REGNO_OK_FOR_BASE_P}. The mode may be @code{VOIDmode} for | |
2473 | addresses that appear outside a @code{MEM}, i.e., as an | |
2474 | @code{address_operand}. | |
38f8b050 JR |
2475 | @end defmac |
2476 | ||
2477 | @defmac REGNO_MODE_OK_FOR_REG_BASE_P (@var{num}, @var{mode}) | |
2478 | A C expression which is nonzero if register number @var{num} is suitable for | |
2479 | use as a base register in base plus index operand addresses, accessing | |
2480 | memory in mode @var{mode}. It may be either a suitable hard register or a | |
2481 | pseudo register that has been allocated such a hard register. You should | |
2482 | define this macro if base plus index addresses have different requirements | |
2483 | than other base register uses. | |
2484 | ||
2485 | Use of this macro is deprecated; please use the more general | |
2486 | @code{REGNO_MODE_CODE_OK_FOR_BASE_P}. | |
38f8b050 JR |
2487 | @end defmac |
2488 | ||
2489 | @defmac REGNO_MODE_CODE_OK_FOR_BASE_P (@var{num}, @var{mode}, @var{outer_code}, @var{index_code}) | |
2490 | A C expression that is just like @code{REGNO_MODE_OK_FOR_BASE_P}, except | |
2491 | that that expression may examine the context in which the register | |
2492 | appears in the memory reference. @var{outer_code} is the code of the | |
2493 | immediately enclosing expression (@code{MEM} if at the top level of the | |
2494 | address, @code{ADDRESS} for something that occurs in an | |
2495 | @code{address_operand}). @var{index_code} is the code of the | |
2496 | corresponding index expression if @var{outer_code} is @code{PLUS}; | |
2497 | @code{SCRATCH} otherwise. The mode may be @code{VOIDmode} for addresses | |
2498 | that appear outside a @code{MEM}, i.e., as an @code{address_operand}. | |
38f8b050 JR |
2499 | @end defmac |
2500 | ||
2501 | @defmac REGNO_OK_FOR_INDEX_P (@var{num}) | |
2502 | A C expression which is nonzero if register number @var{num} is | |
2503 | suitable for use as an index register in operand addresses. It may be | |
2504 | either a suitable hard register or a pseudo register that has been | |
2505 | allocated such a hard register. | |
2506 | ||
2507 | The difference between an index register and a base register is that | |
2508 | the index register may be scaled. If an address involves the sum of | |
2509 | two registers, neither one of them scaled, then either one may be | |
2510 | labeled the ``base'' and the other the ``index''; but whichever | |
2511 | labeling is used must fit the machine's constraints of which registers | |
2512 | may serve in each capacity. The compiler will try both labelings, | |
2513 | looking for one that is valid, and will reload one or both registers | |
2514 | only if neither labeling works. | |
38f8b050 JR |
2515 | @end defmac |
2516 | ||
5f286f4a YQ |
2517 | @hook TARGET_PREFERRED_RENAME_CLASS |
2518 | ||
fba42e24 AS |
2519 | @hook TARGET_PREFERRED_RELOAD_CLASS |
2520 | A target hook that places additional restrictions on the register class | |
2521 | to use when it is necessary to copy value @var{x} into a register in class | |
2522 | @var{rclass}. The value is a register class; perhaps @var{rclass}, or perhaps | |
2523 | another, smaller class. | |
2524 | ||
2525 | The default version of this hook always returns value of @code{rclass} argument. | |
2526 | ||
2527 | Sometimes returning a more restrictive class makes better code. For | |
2528 | example, on the 68000, when @var{x} is an integer constant that is in range | |
2529 | for a @samp{moveq} instruction, the value of this macro is always | |
2530 | @code{DATA_REGS} as long as @var{rclass} includes the data registers. | |
2531 | Requiring a data register guarantees that a @samp{moveq} will be used. | |
2532 | ||
2533 | One case where @code{TARGET_PREFERRED_RELOAD_CLASS} must not return | |
2534 | @var{rclass} is if @var{x} is a legitimate constant which cannot be | |
2535 | loaded into some register class. By returning @code{NO_REGS} you can | |
2536 | force @var{x} into a memory location. For example, rs6000 can load | |
2537 | immediate values into general-purpose registers, but does not have an | |
2538 | instruction for loading an immediate value into a floating-point | |
2539 | register, so @code{TARGET_PREFERRED_RELOAD_CLASS} returns @code{NO_REGS} when | |
2540 | @var{x} is a floating-point constant. If the constant can't be loaded | |
2541 | into any kind of register, code generation will be better if | |
1a627b35 | 2542 | @code{TARGET_LEGITIMATE_CONSTANT_P} makes the constant illegitimate instead |
fba42e24 AS |
2543 | of using @code{TARGET_PREFERRED_RELOAD_CLASS}. |
2544 | ||
2545 | If an insn has pseudos in it after register allocation, reload will go | |
2546 | through the alternatives and call repeatedly @code{TARGET_PREFERRED_RELOAD_CLASS} | |
2547 | to find the best one. Returning @code{NO_REGS}, in this case, makes | |
2548 | reload add a @code{!} in front of the constraint: the x86 back-end uses | |
2549 | this feature to discourage usage of 387 registers when math is done in | |
2550 | the SSE registers (and vice versa). | |
2551 | @end deftypefn | |
2552 | ||
38f8b050 JR |
2553 | @defmac PREFERRED_RELOAD_CLASS (@var{x}, @var{class}) |
2554 | A C expression that places additional restrictions on the register class | |
2555 | to use when it is necessary to copy value @var{x} into a register in class | |
2556 | @var{class}. The value is a register class; perhaps @var{class}, or perhaps | |
2557 | another, smaller class. On many machines, the following definition is | |
2558 | safe: | |
2559 | ||
2560 | @smallexample | |
2561 | #define PREFERRED_RELOAD_CLASS(X,CLASS) CLASS | |
2562 | @end smallexample | |
2563 | ||
2564 | Sometimes returning a more restrictive class makes better code. For | |
2565 | example, on the 68000, when @var{x} is an integer constant that is in range | |
2566 | for a @samp{moveq} instruction, the value of this macro is always | |
2567 | @code{DATA_REGS} as long as @var{class} includes the data registers. | |
2568 | Requiring a data register guarantees that a @samp{moveq} will be used. | |
2569 | ||
2570 | One case where @code{PREFERRED_RELOAD_CLASS} must not return | |
2571 | @var{class} is if @var{x} is a legitimate constant which cannot be | |
2572 | loaded into some register class. By returning @code{NO_REGS} you can | |
2573 | force @var{x} into a memory location. For example, rs6000 can load | |
2574 | immediate values into general-purpose registers, but does not have an | |
2575 | instruction for loading an immediate value into a floating-point | |
2576 | register, so @code{PREFERRED_RELOAD_CLASS} returns @code{NO_REGS} when | |
2577 | @var{x} is a floating-point constant. If the constant can't be loaded | |
2578 | into any kind of register, code generation will be better if | |
1a627b35 RS |
2579 | @code{TARGET_LEGITIMATE_CONSTANT_P} makes the constant illegitimate instead |
2580 | of using @code{TARGET_PREFERRED_RELOAD_CLASS}. | |
38f8b050 JR |
2581 | |
2582 | If an insn has pseudos in it after register allocation, reload will go | |
2583 | through the alternatives and call repeatedly @code{PREFERRED_RELOAD_CLASS} | |
2584 | to find the best one. Returning @code{NO_REGS}, in this case, makes | |
2585 | reload add a @code{!} in front of the constraint: the x86 back-end uses | |
2586 | this feature to discourage usage of 387 registers when math is done in | |
2587 | the SSE registers (and vice versa). | |
2588 | @end defmac | |
2589 | ||
2590 | @defmac PREFERRED_OUTPUT_RELOAD_CLASS (@var{x}, @var{class}) | |
2591 | Like @code{PREFERRED_RELOAD_CLASS}, but for output reloads instead of | |
2592 | input reloads. If you don't define this macro, the default is to use | |
2593 | @var{class}, unchanged. | |
2594 | ||
2595 | You can also use @code{PREFERRED_OUTPUT_RELOAD_CLASS} to discourage | |
2596 | reload from using some alternatives, like @code{PREFERRED_RELOAD_CLASS}. | |
2597 | @end defmac | |
2598 | ||
abd26bfb AS |
2599 | @hook TARGET_PREFERRED_OUTPUT_RELOAD_CLASS |
2600 | Like @code{TARGET_PREFERRED_RELOAD_CLASS}, but for output reloads instead of | |
2601 | input reloads. | |
2602 | ||
2603 | The default version of this hook always returns value of @code{rclass} | |
2604 | argument. | |
2605 | ||
2606 | You can also use @code{TARGET_PREFERRED_OUTPUT_RELOAD_CLASS} to discourage | |
2607 | reload from using some alternatives, like @code{TARGET_PREFERRED_RELOAD_CLASS}. | |
2608 | @end deftypefn | |
2609 | ||
38f8b050 JR |
2610 | @defmac LIMIT_RELOAD_CLASS (@var{mode}, @var{class}) |
2611 | A C expression that places additional restrictions on the register class | |
2612 | to use when it is necessary to be able to hold a value of mode | |
2613 | @var{mode} in a reload register for which class @var{class} would | |
2614 | ordinarily be used. | |
2615 | ||
2616 | Unlike @code{PREFERRED_RELOAD_CLASS}, this macro should be used when | |
2617 | there are certain modes that simply can't go in certain reload classes. | |
2618 | ||
2619 | The value is a register class; perhaps @var{class}, or perhaps another, | |
2620 | smaller class. | |
2621 | ||
2622 | Don't define this macro unless the target machine has limitations which | |
2623 | require the macro to do something nontrivial. | |
2624 | @end defmac | |
2625 | ||
2626 | @hook TARGET_SECONDARY_RELOAD | |
2627 | Many machines have some registers that cannot be copied directly to or | |
2628 | from memory or even from other types of registers. An example is the | |
2629 | @samp{MQ} register, which on most machines, can only be copied to or | |
2630 | from general registers, but not memory. Below, we shall be using the | |
2631 | term 'intermediate register' when a move operation cannot be performed | |
2632 | directly, but has to be done by copying the source into the intermediate | |
2633 | register first, and then copying the intermediate register to the | |
2634 | destination. An intermediate register always has the same mode as | |
2635 | source and destination. Since it holds the actual value being copied, | |
2636 | reload might apply optimizations to re-use an intermediate register | |
2637 | and eliding the copy from the source when it can determine that the | |
2638 | intermediate register still holds the required value. | |
2639 | ||
2640 | Another kind of secondary reload is required on some machines which | |
2641 | allow copying all registers to and from memory, but require a scratch | |
2642 | register for stores to some memory locations (e.g., those with symbolic | |
2643 | address on the RT, and those with certain symbolic address on the SPARC | |
2644 | when compiling PIC)@. Scratch registers need not have the same mode | |
2645 | as the value being copied, and usually hold a different value than | |
2646 | that being copied. Special patterns in the md file are needed to | |
2647 | describe how the copy is performed with the help of the scratch register; | |
2648 | these patterns also describe the number, register class(es) and mode(s) | |
2649 | of the scratch register(s). | |
2650 | ||
2651 | In some cases, both an intermediate and a scratch register are required. | |
2652 | ||
2653 | For input reloads, this target hook is called with nonzero @var{in_p}, | |
2654 | and @var{x} is an rtx that needs to be copied to a register of class | |
2655 | @var{reload_class} in @var{reload_mode}. For output reloads, this target | |
2656 | hook is called with zero @var{in_p}, and a register of class @var{reload_class} | |
2657 | needs to be copied to rtx @var{x} in @var{reload_mode}. | |
2658 | ||
2659 | If copying a register of @var{reload_class} from/to @var{x} requires | |
2660 | an intermediate register, the hook @code{secondary_reload} should | |
2661 | return the register class required for this intermediate register. | |
2662 | If no intermediate register is required, it should return NO_REGS. | |
2663 | If more than one intermediate register is required, describe the one | |
2664 | that is closest in the copy chain to the reload register. | |
2665 | ||
2666 | If scratch registers are needed, you also have to describe how to | |
2667 | perform the copy from/to the reload register to/from this | |
2668 | closest intermediate register. Or if no intermediate register is | |
2669 | required, but still a scratch register is needed, describe the | |
2670 | copy from/to the reload register to/from the reload operand @var{x}. | |
2671 | ||
2672 | You do this by setting @code{sri->icode} to the instruction code of a pattern | |
2673 | in the md file which performs the move. Operands 0 and 1 are the output | |
2674 | and input of this copy, respectively. Operands from operand 2 onward are | |
2675 | for scratch operands. These scratch operands must have a mode, and a | |
2676 | single-register-class | |
2677 | @c [later: or memory] | |
2678 | output constraint. | |
2679 | ||
2680 | When an intermediate register is used, the @code{secondary_reload} | |
2681 | hook will be called again to determine how to copy the intermediate | |
2682 | register to/from the reload operand @var{x}, so your hook must also | |
2683 | have code to handle the register class of the intermediate operand. | |
2684 | ||
2685 | @c [For later: maybe we'll allow multi-alternative reload patterns - | |
2686 | @c the port maintainer could name a mov<mode> pattern that has clobbers - | |
2687 | @c and match the constraints of input and output to determine the required | |
2688 | @c alternative. A restriction would be that constraints used to match | |
2689 | @c against reloads registers would have to be written as register class | |
2690 | @c constraints, or we need a new target macro / hook that tells us if an | |
2691 | @c arbitrary constraint can match an unknown register of a given class. | |
2692 | @c Such a macro / hook would also be useful in other places.] | |
2693 | ||
2694 | ||
2695 | @var{x} might be a pseudo-register or a @code{subreg} of a | |
2696 | pseudo-register, which could either be in a hard register or in memory. | |
2697 | Use @code{true_regnum} to find out; it will return @minus{}1 if the pseudo is | |
2698 | in memory and the hard register number if it is in a register. | |
2699 | ||
2700 | Scratch operands in memory (constraint @code{"=m"} / @code{"=&m"}) are | |
2701 | currently not supported. For the time being, you will have to continue | |
2702 | to use @code{SECONDARY_MEMORY_NEEDED} for that purpose. | |
2703 | ||
2704 | @code{copy_cost} also uses this target hook to find out how values are | |
2705 | copied. If you want it to include some extra cost for the need to allocate | |
2706 | (a) scratch register(s), set @code{sri->extra_cost} to the additional cost. | |
2707 | Or if two dependent moves are supposed to have a lower cost than the sum | |
2708 | of the individual moves due to expected fortuitous scheduling and/or special | |
2709 | forwarding logic, you can set @code{sri->extra_cost} to a negative amount. | |
2710 | @end deftypefn | |
2711 | ||
2712 | @defmac SECONDARY_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) | |
2713 | @defmacx SECONDARY_INPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) | |
2714 | @defmacx SECONDARY_OUTPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) | |
2715 | These macros are obsolete, new ports should use the target hook | |
2716 | @code{TARGET_SECONDARY_RELOAD} instead. | |
2717 | ||
2718 | These are obsolete macros, replaced by the @code{TARGET_SECONDARY_RELOAD} | |
2719 | target hook. Older ports still define these macros to indicate to the | |
2720 | reload phase that it may | |
2721 | need to allocate at least one register for a reload in addition to the | |
2722 | register to contain the data. Specifically, if copying @var{x} to a | |
2723 | register @var{class} in @var{mode} requires an intermediate register, | |
2724 | you were supposed to define @code{SECONDARY_INPUT_RELOAD_CLASS} to return the | |
2725 | largest register class all of whose registers can be used as | |
2726 | intermediate registers or scratch registers. | |
2727 | ||
2728 | If copying a register @var{class} in @var{mode} to @var{x} requires an | |
2729 | intermediate or scratch register, @code{SECONDARY_OUTPUT_RELOAD_CLASS} | |
2730 | was supposed to be defined be defined to return the largest register | |
2731 | class required. If the | |
2732 | requirements for input and output reloads were the same, the macro | |
2733 | @code{SECONDARY_RELOAD_CLASS} should have been used instead of defining both | |
2734 | macros identically. | |
2735 | ||
2736 | The values returned by these macros are often @code{GENERAL_REGS}. | |
2737 | Return @code{NO_REGS} if no spare register is needed; i.e., if @var{x} | |
2738 | can be directly copied to or from a register of @var{class} in | |
2739 | @var{mode} without requiring a scratch register. Do not define this | |
2740 | macro if it would always return @code{NO_REGS}. | |
2741 | ||
2742 | If a scratch register is required (either with or without an | |
2743 | intermediate register), you were supposed to define patterns for | |
2744 | @samp{reload_in@var{m}} or @samp{reload_out@var{m}}, as required | |
2745 | (@pxref{Standard Names}. These patterns, which were normally | |
2746 | implemented with a @code{define_expand}, should be similar to the | |
2747 | @samp{mov@var{m}} patterns, except that operand 2 is the scratch | |
2748 | register. | |
2749 | ||
2750 | These patterns need constraints for the reload register and scratch | |
2751 | register that | |
2752 | contain a single register class. If the original reload register (whose | |
2753 | class is @var{class}) can meet the constraint given in the pattern, the | |
2754 | value returned by these macros is used for the class of the scratch | |
2755 | register. Otherwise, two additional reload registers are required. | |
2756 | Their classes are obtained from the constraints in the insn pattern. | |
2757 | ||
2758 | @var{x} might be a pseudo-register or a @code{subreg} of a | |
2759 | pseudo-register, which could either be in a hard register or in memory. | |
2760 | Use @code{true_regnum} to find out; it will return @minus{}1 if the pseudo is | |
2761 | in memory and the hard register number if it is in a register. | |
2762 | ||
2763 | These macros should not be used in the case where a particular class of | |
2764 | registers can only be copied to memory and not to another class of | |
2765 | registers. In that case, secondary reload registers are not needed and | |
2766 | would not be helpful. Instead, a stack location must be used to perform | |
2767 | the copy and the @code{mov@var{m}} pattern should use memory as an | |
2768 | intermediate storage. This case often occurs between floating-point and | |
2769 | general registers. | |
2770 | @end defmac | |
2771 | ||
2772 | @defmac SECONDARY_MEMORY_NEEDED (@var{class1}, @var{class2}, @var{m}) | |
2773 | Certain machines have the property that some registers cannot be copied | |
2774 | to some other registers without using memory. Define this macro on | |
2775 | those machines to be a C expression that is nonzero if objects of mode | |
2776 | @var{m} in registers of @var{class1} can only be copied to registers of | |
2777 | class @var{class2} by storing a register of @var{class1} into memory | |
2778 | and loading that memory location into a register of @var{class2}. | |
2779 | ||
2780 | Do not define this macro if its value would always be zero. | |
2781 | @end defmac | |
2782 | ||
2783 | @defmac SECONDARY_MEMORY_NEEDED_RTX (@var{mode}) | |
2784 | Normally when @code{SECONDARY_MEMORY_NEEDED} is defined, the compiler | |
2785 | allocates a stack slot for a memory location needed for register copies. | |
2786 | If this macro is defined, the compiler instead uses the memory location | |
2787 | defined by this macro. | |
2788 | ||
2789 | Do not define this macro if you do not define | |
2790 | @code{SECONDARY_MEMORY_NEEDED}. | |
2791 | @end defmac | |
2792 | ||
2793 | @defmac SECONDARY_MEMORY_NEEDED_MODE (@var{mode}) | |
2794 | When the compiler needs a secondary memory location to copy between two | |
2795 | registers of mode @var{mode}, it normally allocates sufficient memory to | |
2796 | hold a quantity of @code{BITS_PER_WORD} bits and performs the store and | |
2797 | load operations in a mode that many bits wide and whose class is the | |
2798 | same as that of @var{mode}. | |
2799 | ||
2800 | This is right thing to do on most machines because it ensures that all | |
2801 | bits of the register are copied and prevents accesses to the registers | |
2802 | in a narrower mode, which some machines prohibit for floating-point | |
2803 | registers. | |
2804 | ||
2805 | However, this default behavior is not correct on some machines, such as | |
2806 | the DEC Alpha, that store short integers in floating-point registers | |
2807 | differently than in integer registers. On those machines, the default | |
2808 | widening will not work correctly and you must define this macro to | |
2809 | suppress that widening in some cases. See the file @file{alpha.h} for | |
2810 | details. | |
2811 | ||
2812 | Do not define this macro if you do not define | |
2813 | @code{SECONDARY_MEMORY_NEEDED} or if widening @var{mode} to a mode that | |
2814 | is @code{BITS_PER_WORD} bits wide is correct for your machine. | |
2815 | @end defmac | |
2816 | ||
07b8f0a8 AS |
2817 | @hook TARGET_CLASS_LIKELY_SPILLED_P |
2818 | A target hook which returns @code{true} if pseudos that have been assigned | |
2819 | to registers of class @var{rclass} would likely be spilled because | |
2820 | registers of @var{rclass} are needed for spill registers. | |
2821 | ||
2822 | The default version of this target hook returns @code{true} if @var{rclass} | |
2823 | has exactly one register and @code{false} otherwise. On most machines, this | |
2824 | default should be used. Only use this target hook to some other expression | |
2825 | if pseudos allocated by @file{local-alloc.c} end up in memory because their | |
2826 | hard registers were needed for spill registers. If this target hook returns | |
2827 | @code{false} for those classes, those pseudos will only be allocated by | |
2828 | @file{global.c}, which knows how to reallocate the pseudo to another | |
2829 | register. If there would not be another register available for reallocation, | |
2830 | you should not change the implementation of this target hook since | |
2831 | the only effect of such implementation would be to slow down register | |
2832 | allocation. | |
2833 | @end deftypefn | |
2834 | ||
38f8b050 JR |
2835 | @defmac CLASS_MAX_NREGS (@var{class}, @var{mode}) |
2836 | A C expression for the maximum number of consecutive registers | |
2837 | of class @var{class} needed to hold a value of mode @var{mode}. | |
2838 | ||
2839 | This is closely related to the macro @code{HARD_REGNO_NREGS}. In fact, | |
2840 | the value of the macro @code{CLASS_MAX_NREGS (@var{class}, @var{mode})} | |
2841 | should be the maximum value of @code{HARD_REGNO_NREGS (@var{regno}, | |
2842 | @var{mode})} for all @var{regno} values in the class @var{class}. | |
2843 | ||
2844 | This macro helps control the handling of multiple-word values | |
2845 | in the reload pass. | |
2846 | @end defmac | |
2847 | ||
2848 | @defmac CANNOT_CHANGE_MODE_CLASS (@var{from}, @var{to}, @var{class}) | |
2849 | If defined, a C expression that returns nonzero for a @var{class} for which | |
2850 | a change from mode @var{from} to mode @var{to} is invalid. | |
2851 | ||
2852 | For the example, loading 32-bit integer or floating-point objects into | |
2853 | floating-point registers on the Alpha extends them to 64 bits. | |
2854 | Therefore loading a 64-bit object and then storing it as a 32-bit object | |
2855 | does not store the low-order 32 bits, as would be the case for a normal | |
2856 | register. Therefore, @file{alpha.h} defines @code{CANNOT_CHANGE_MODE_CLASS} | |
2857 | as below: | |
2858 | ||
2859 | @smallexample | |
2860 | #define CANNOT_CHANGE_MODE_CLASS(FROM, TO, CLASS) \ | |
2861 | (GET_MODE_SIZE (FROM) != GET_MODE_SIZE (TO) \ | |
2862 | ? reg_classes_intersect_p (FLOAT_REGS, (CLASS)) : 0) | |
2863 | @end smallexample | |
2864 | @end defmac | |
2865 | ||
38f8b050 JR |
2866 | @node Old Constraints |
2867 | @section Obsolete Macros for Defining Constraints | |
2868 | @cindex defining constraints, obsolete method | |
2869 | @cindex constraints, defining, obsolete method | |
2870 | ||
2871 | Machine-specific constraints can be defined with these macros instead | |
2872 | of the machine description constructs described in @ref{Define | |
2873 | Constraints}. This mechanism is obsolete. New ports should not use | |
2874 | it; old ports should convert to the new mechanism. | |
2875 | ||
2876 | @defmac CONSTRAINT_LEN (@var{char}, @var{str}) | |
2877 | For the constraint at the start of @var{str}, which starts with the letter | |
2878 | @var{c}, return the length. This allows you to have register class / | |
2879 | constant / extra constraints that are longer than a single letter; | |
2880 | you don't need to define this macro if you can do with single-letter | |
2881 | constraints only. The definition of this macro should use | |
2882 | DEFAULT_CONSTRAINT_LEN for all the characters that you don't want | |
2883 | to handle specially. | |
2884 | There are some sanity checks in genoutput.c that check the constraint lengths | |
2885 | for the md file, so you can also use this macro to help you while you are | |
2886 | transitioning from a byzantine single-letter-constraint scheme: when you | |
2887 | return a negative length for a constraint you want to re-use, genoutput | |
2888 | will complain about every instance where it is used in the md file. | |
2889 | @end defmac | |
2890 | ||
2891 | @defmac REG_CLASS_FROM_LETTER (@var{char}) | |
2892 | A C expression which defines the machine-dependent operand constraint | |
2893 | letters for register classes. If @var{char} is such a letter, the | |
2894 | value should be the register class corresponding to it. Otherwise, | |
2895 | the value should be @code{NO_REGS}. The register letter @samp{r}, | |
2896 | corresponding to class @code{GENERAL_REGS}, will not be passed | |
2897 | to this macro; you do not need to handle it. | |
2898 | @end defmac | |
2899 | ||
2900 | @defmac REG_CLASS_FROM_CONSTRAINT (@var{char}, @var{str}) | |
2901 | Like @code{REG_CLASS_FROM_LETTER}, but you also get the constraint string | |
2902 | passed in @var{str}, so that you can use suffixes to distinguish between | |
2903 | different variants. | |
2904 | @end defmac | |
2905 | ||
2906 | @defmac CONST_OK_FOR_LETTER_P (@var{value}, @var{c}) | |
2907 | A C expression that defines the machine-dependent operand constraint | |
2908 | letters (@samp{I}, @samp{J}, @samp{K}, @dots{} @samp{P}) that specify | |
2909 | particular ranges of integer values. If @var{c} is one of those | |
2910 | letters, the expression should check that @var{value}, an integer, is in | |
2911 | the appropriate range and return 1 if so, 0 otherwise. If @var{c} is | |
2912 | not one of those letters, the value should be 0 regardless of | |
2913 | @var{value}. | |
2914 | @end defmac | |
2915 | ||
2916 | @defmac CONST_OK_FOR_CONSTRAINT_P (@var{value}, @var{c}, @var{str}) | |
2917 | Like @code{CONST_OK_FOR_LETTER_P}, but you also get the constraint | |
2918 | string passed in @var{str}, so that you can use suffixes to distinguish | |
2919 | between different variants. | |
2920 | @end defmac | |
2921 | ||
2922 | @defmac CONST_DOUBLE_OK_FOR_LETTER_P (@var{value}, @var{c}) | |
2923 | A C expression that defines the machine-dependent operand constraint | |
2924 | letters that specify particular ranges of @code{const_double} values | |
2925 | (@samp{G} or @samp{H}). | |
2926 | ||
2927 | If @var{c} is one of those letters, the expression should check that | |
2928 | @var{value}, an RTX of code @code{const_double}, is in the appropriate | |
2929 | range and return 1 if so, 0 otherwise. If @var{c} is not one of those | |
2930 | letters, the value should be 0 regardless of @var{value}. | |
2931 | ||
2932 | @code{const_double} is used for all floating-point constants and for | |
2933 | @code{DImode} fixed-point constants. A given letter can accept either | |
2934 | or both kinds of values. It can use @code{GET_MODE} to distinguish | |
2935 | between these kinds. | |
2936 | @end defmac | |
2937 | ||
2938 | @defmac CONST_DOUBLE_OK_FOR_CONSTRAINT_P (@var{value}, @var{c}, @var{str}) | |
2939 | Like @code{CONST_DOUBLE_OK_FOR_LETTER_P}, but you also get the constraint | |
2940 | string passed in @var{str}, so that you can use suffixes to distinguish | |
2941 | between different variants. | |
2942 | @end defmac | |
2943 | ||
2944 | @defmac EXTRA_CONSTRAINT (@var{value}, @var{c}) | |
2945 | A C expression that defines the optional machine-dependent constraint | |
2946 | letters that can be used to segregate specific types of operands, usually | |
2947 | memory references, for the target machine. Any letter that is not | |
2948 | elsewhere defined and not matched by @code{REG_CLASS_FROM_LETTER} / | |
2949 | @code{REG_CLASS_FROM_CONSTRAINT} | |
2950 | may be used. Normally this macro will not be defined. | |
2951 | ||
2952 | If it is required for a particular target machine, it should return 1 | |
2953 | if @var{value} corresponds to the operand type represented by the | |
2954 | constraint letter @var{c}. If @var{c} is not defined as an extra | |
2955 | constraint, the value returned should be 0 regardless of @var{value}. | |
2956 | ||
2957 | For example, on the ROMP, load instructions cannot have their output | |
2958 | in r0 if the memory reference contains a symbolic address. Constraint | |
2959 | letter @samp{Q} is defined as representing a memory address that does | |
2960 | @emph{not} contain a symbolic address. An alternative is specified with | |
2961 | a @samp{Q} constraint on the input and @samp{r} on the output. The next | |
2962 | alternative specifies @samp{m} on the input and a register class that | |
2963 | does not include r0 on the output. | |
2964 | @end defmac | |
2965 | ||
2966 | @defmac EXTRA_CONSTRAINT_STR (@var{value}, @var{c}, @var{str}) | |
2967 | Like @code{EXTRA_CONSTRAINT}, but you also get the constraint string passed | |
2968 | in @var{str}, so that you can use suffixes to distinguish between different | |
2969 | variants. | |
2970 | @end defmac | |
2971 | ||
2972 | @defmac EXTRA_MEMORY_CONSTRAINT (@var{c}, @var{str}) | |
2973 | A C expression that defines the optional machine-dependent constraint | |
2974 | letters, amongst those accepted by @code{EXTRA_CONSTRAINT}, that should | |
2975 | be treated like memory constraints by the reload pass. | |
2976 | ||
2977 | It should return 1 if the operand type represented by the constraint | |
2978 | at the start of @var{str}, the first letter of which is the letter @var{c}, | |
2979 | comprises a subset of all memory references including | |
2980 | all those whose address is simply a base register. This allows the reload | |
2981 | pass to reload an operand, if it does not directly correspond to the operand | |
2982 | type of @var{c}, by copying its address into a base register. | |
2983 | ||
2984 | For example, on the S/390, some instructions do not accept arbitrary | |
2985 | memory references, but only those that do not make use of an index | |
2986 | register. The constraint letter @samp{Q} is defined via | |
2987 | @code{EXTRA_CONSTRAINT} as representing a memory address of this type. | |
2988 | If the letter @samp{Q} is marked as @code{EXTRA_MEMORY_CONSTRAINT}, | |
2989 | a @samp{Q} constraint can handle any memory operand, because the | |
2990 | reload pass knows it can be reloaded by copying the memory address | |
2991 | into a base register if required. This is analogous to the way | |
2992 | an @samp{o} constraint can handle any memory operand. | |
2993 | @end defmac | |
2994 | ||
2995 | @defmac EXTRA_ADDRESS_CONSTRAINT (@var{c}, @var{str}) | |
2996 | A C expression that defines the optional machine-dependent constraint | |
2997 | letters, amongst those accepted by @code{EXTRA_CONSTRAINT} / | |
2998 | @code{EXTRA_CONSTRAINT_STR}, that should | |
2999 | be treated like address constraints by the reload pass. | |
3000 | ||
3001 | It should return 1 if the operand type represented by the constraint | |
3002 | at the start of @var{str}, which starts with the letter @var{c}, comprises | |
3003 | a subset of all memory addresses including | |
3004 | all those that consist of just a base register. This allows the reload | |
3005 | pass to reload an operand, if it does not directly correspond to the operand | |
3006 | type of @var{str}, by copying it into a base register. | |
3007 | ||
3008 | Any constraint marked as @code{EXTRA_ADDRESS_CONSTRAINT} can only | |
3009 | be used with the @code{address_operand} predicate. It is treated | |
3010 | analogously to the @samp{p} constraint. | |
3011 | @end defmac | |
3012 | ||
3013 | @node Stack and Calling | |
3014 | @section Stack Layout and Calling Conventions | |
3015 | @cindex calling conventions | |
3016 | ||
3017 | @c prevent bad page break with this line | |
3018 | This describes the stack layout and calling conventions. | |
3019 | ||
3020 | @menu | |
3021 | * Frame Layout:: | |
3022 | * Exception Handling:: | |
3023 | * Stack Checking:: | |
3024 | * Frame Registers:: | |
3025 | * Elimination:: | |
3026 | * Stack Arguments:: | |
3027 | * Register Arguments:: | |
3028 | * Scalar Return:: | |
3029 | * Aggregate Return:: | |
3030 | * Caller Saves:: | |
3031 | * Function Entry:: | |
3032 | * Profiling:: | |
3033 | * Tail Calls:: | |
3034 | * Stack Smashing Protection:: | |
3035 | @end menu | |
3036 | ||
3037 | @node Frame Layout | |
3038 | @subsection Basic Stack Layout | |
3039 | @cindex stack frame layout | |
3040 | @cindex frame layout | |
3041 | ||
3042 | @c prevent bad page break with this line | |
3043 | Here is the basic stack layout. | |
3044 | ||
3045 | @defmac STACK_GROWS_DOWNWARD | |
3046 | Define this macro if pushing a word onto the stack moves the stack | |
3047 | pointer to a smaller address. | |
3048 | ||
3049 | When we say, ``define this macro if @dots{}'', it means that the | |
3050 | compiler checks this macro only with @code{#ifdef} so the precise | |
3051 | definition used does not matter. | |
3052 | @end defmac | |
3053 | ||
3054 | @defmac STACK_PUSH_CODE | |
3055 | This macro defines the operation used when something is pushed | |
3056 | on the stack. In RTL, a push operation will be | |
3057 | @code{(set (mem (STACK_PUSH_CODE (reg sp))) @dots{})} | |
3058 | ||
3059 | The choices are @code{PRE_DEC}, @code{POST_DEC}, @code{PRE_INC}, | |
3060 | and @code{POST_INC}. Which of these is correct depends on | |
3061 | the stack direction and on whether the stack pointer points | |
3062 | to the last item on the stack or whether it points to the | |
3063 | space for the next item on the stack. | |
3064 | ||
3065 | The default is @code{PRE_DEC} when @code{STACK_GROWS_DOWNWARD} is | |
3066 | defined, which is almost always right, and @code{PRE_INC} otherwise, | |
3067 | which is often wrong. | |
3068 | @end defmac | |
3069 | ||
3070 | @defmac FRAME_GROWS_DOWNWARD | |
3071 | Define this macro to nonzero value if the addresses of local variable slots | |
3072 | are at negative offsets from the frame pointer. | |
3073 | @end defmac | |
3074 | ||
3075 | @defmac ARGS_GROW_DOWNWARD | |
3076 | Define this macro if successive arguments to a function occupy decreasing | |
3077 | addresses on the stack. | |
3078 | @end defmac | |
3079 | ||
3080 | @defmac STARTING_FRAME_OFFSET | |
3081 | Offset from the frame pointer to the first local variable slot to be allocated. | |
3082 | ||
3083 | If @code{FRAME_GROWS_DOWNWARD}, find the next slot's offset by | |
3084 | subtracting the first slot's length from @code{STARTING_FRAME_OFFSET}. | |
3085 | Otherwise, it is found by adding the length of the first slot to the | |
3086 | value @code{STARTING_FRAME_OFFSET}. | |
3087 | @c i'm not sure if the above is still correct.. had to change it to get | |
3088 | @c rid of an overfull. --mew 2feb93 | |
3089 | @end defmac | |
3090 | ||
3091 | @defmac STACK_ALIGNMENT_NEEDED | |
3092 | Define to zero to disable final alignment of the stack during reload. | |
3093 | The nonzero default for this macro is suitable for most ports. | |
3094 | ||
3095 | On ports where @code{STARTING_FRAME_OFFSET} is nonzero or where there | |
3096 | is a register save block following the local block that doesn't require | |
3097 | alignment to @code{STACK_BOUNDARY}, it may be beneficial to disable | |
3098 | stack alignment and do it in the backend. | |
3099 | @end defmac | |
3100 | ||
3101 | @defmac STACK_POINTER_OFFSET | |
3102 | Offset from the stack pointer register to the first location at which | |
3103 | outgoing arguments are placed. If not specified, the default value of | |
3104 | zero is used. This is the proper value for most machines. | |
3105 | ||
3106 | If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above | |
3107 | the first location at which outgoing arguments are placed. | |
3108 | @end defmac | |
3109 | ||
3110 | @defmac FIRST_PARM_OFFSET (@var{fundecl}) | |
3111 | Offset from the argument pointer register to the first argument's | |
3112 | address. On some machines it may depend on the data type of the | |
3113 | function. | |
3114 | ||
3115 | If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above | |
3116 | the first argument's address. | |
3117 | @end defmac | |
3118 | ||
3119 | @defmac STACK_DYNAMIC_OFFSET (@var{fundecl}) | |
3120 | Offset from the stack pointer register to an item dynamically allocated | |
3121 | on the stack, e.g., by @code{alloca}. | |
3122 | ||
3123 | The default value for this macro is @code{STACK_POINTER_OFFSET} plus the | |
3124 | length of the outgoing arguments. The default is correct for most | |
3125 | machines. See @file{function.c} for details. | |
3126 | @end defmac | |
3127 | ||
3128 | @defmac INITIAL_FRAME_ADDRESS_RTX | |
3129 | A C expression whose value is RTL representing the address of the initial | |
3130 | stack frame. This address is passed to @code{RETURN_ADDR_RTX} and | |
3131 | @code{DYNAMIC_CHAIN_ADDRESS}. If you don't define this macro, a reasonable | |
3132 | default value will be used. Define this macro in order to make frame pointer | |
3133 | elimination work in the presence of @code{__builtin_frame_address (count)} and | |
3134 | @code{__builtin_return_address (count)} for @code{count} not equal to zero. | |
3135 | @end defmac | |
3136 | ||
3137 | @defmac DYNAMIC_CHAIN_ADDRESS (@var{frameaddr}) | |
3138 | A C expression whose value is RTL representing the address in a stack | |
3139 | frame where the pointer to the caller's frame is stored. Assume that | |
3140 | @var{frameaddr} is an RTL expression for the address of the stack frame | |
3141 | itself. | |
3142 | ||
3143 | If you don't define this macro, the default is to return the value | |
3144 | of @var{frameaddr}---that is, the stack frame address is also the | |
3145 | address of the stack word that points to the previous frame. | |
3146 | @end defmac | |
3147 | ||
3148 | @defmac SETUP_FRAME_ADDRESSES | |
3149 | If defined, a C expression that produces the machine-specific code to | |
3150 | setup the stack so that arbitrary frames can be accessed. For example, | |
3151 | on the SPARC, we must flush all of the register windows to the stack | |
3152 | before we can access arbitrary stack frames. You will seldom need to | |
3153 | define this macro. | |
3154 | @end defmac | |
3155 | ||
3156 | @hook TARGET_BUILTIN_SETJMP_FRAME_VALUE | |
3157 | This target hook should return an rtx that is used to store | |
3158 | the address of the current frame into the built in @code{setjmp} buffer. | |
3159 | The default value, @code{virtual_stack_vars_rtx}, is correct for most | |
3160 | machines. One reason you may need to define this target hook is if | |
3161 | @code{hard_frame_pointer_rtx} is the appropriate value on your machine. | |
3162 | @end deftypefn | |
3163 | ||
3164 | @defmac FRAME_ADDR_RTX (@var{frameaddr}) | |
3165 | A C expression whose value is RTL representing the value of the frame | |
3166 | address for the current frame. @var{frameaddr} is the frame pointer | |
3167 | of the current frame. This is used for __builtin_frame_address. | |
3168 | You need only define this macro if the frame address is not the same | |
3169 | as the frame pointer. Most machines do not need to define it. | |
3170 | @end defmac | |
3171 | ||
3172 | @defmac RETURN_ADDR_RTX (@var{count}, @var{frameaddr}) | |
3173 | A C expression whose value is RTL representing the value of the return | |
3174 | address for the frame @var{count} steps up from the current frame, after | |
3175 | the prologue. @var{frameaddr} is the frame pointer of the @var{count} | |
3176 | frame, or the frame pointer of the @var{count} @minus{} 1 frame if | |
3177 | @code{RETURN_ADDR_IN_PREVIOUS_FRAME} is defined. | |
3178 | ||
3179 | The value of the expression must always be the correct address when | |
3180 | @var{count} is zero, but may be @code{NULL_RTX} if there is no way to | |
3181 | determine the return address of other frames. | |
3182 | @end defmac | |
3183 | ||
3184 | @defmac RETURN_ADDR_IN_PREVIOUS_FRAME | |
3185 | Define this if the return address of a particular stack frame is accessed | |
3186 | from the frame pointer of the previous stack frame. | |
3187 | @end defmac | |
3188 | ||
3189 | @defmac INCOMING_RETURN_ADDR_RTX | |
3190 | A C expression whose value is RTL representing the location of the | |
3191 | incoming return address at the beginning of any function, before the | |
3192 | prologue. This RTL is either a @code{REG}, indicating that the return | |
3193 | value is saved in @samp{REG}, or a @code{MEM} representing a location in | |
3194 | the stack. | |
3195 | ||
3196 | You only need to define this macro if you want to support call frame | |
3197 | debugging information like that provided by DWARF 2. | |
3198 | ||
3199 | If this RTL is a @code{REG}, you should also define | |
3200 | @code{DWARF_FRAME_RETURN_COLUMN} to @code{DWARF_FRAME_REGNUM (REGNO)}. | |
3201 | @end defmac | |
3202 | ||
3203 | @defmac DWARF_ALT_FRAME_RETURN_COLUMN | |
3204 | A C expression whose value is an integer giving a DWARF 2 column | |
3205 | number that may be used as an alternative return column. The column | |
3206 | must not correspond to any gcc hard register (that is, it must not | |
3207 | be in the range of @code{DWARF_FRAME_REGNUM}). | |
3208 | ||
3209 | This macro can be useful if @code{DWARF_FRAME_RETURN_COLUMN} is set to a | |
3210 | general register, but an alternative column needs to be used for signal | |
3211 | frames. Some targets have also used different frame return columns | |
3212 | over time. | |
3213 | @end defmac | |
3214 | ||
3215 | @defmac DWARF_ZERO_REG | |
3216 | A C expression whose value is an integer giving a DWARF 2 register | |
3217 | number that is considered to always have the value zero. This should | |
3218 | only be defined if the target has an architected zero register, and | |
3219 | someone decided it was a good idea to use that register number to | |
3220 | terminate the stack backtrace. New ports should avoid this. | |
3221 | @end defmac | |
3222 | ||
3223 | @hook TARGET_DWARF_HANDLE_FRAME_UNSPEC | |
3224 | This target hook allows the backend to emit frame-related insns that | |
3225 | contain UNSPECs or UNSPEC_VOLATILEs. The DWARF 2 call frame debugging | |
3226 | info engine will invoke it on insns of the form | |
3227 | @smallexample | |
3228 | (set (reg) (unspec [@dots{}] UNSPEC_INDEX)) | |
3229 | @end smallexample | |
3230 | and | |
3231 | @smallexample | |
3232 | (set (reg) (unspec_volatile [@dots{}] UNSPECV_INDEX)). | |
3233 | @end smallexample | |
3234 | to let the backend emit the call frame instructions. @var{label} is | |
3235 | the CFI label attached to the insn, @var{pattern} is the pattern of | |
3236 | the insn and @var{index} is @code{UNSPEC_INDEX} or @code{UNSPECV_INDEX}. | |
3237 | @end deftypefn | |
3238 | ||
3239 | @defmac INCOMING_FRAME_SP_OFFSET | |
3240 | A C expression whose value is an integer giving the offset, in bytes, | |
3241 | from the value of the stack pointer register to the top of the stack | |
3242 | frame at the beginning of any function, before the prologue. The top of | |
3243 | the frame is defined to be the value of the stack pointer in the | |
3244 | previous frame, just before the call instruction. | |
3245 | ||
3246 | You only need to define this macro if you want to support call frame | |
3247 | debugging information like that provided by DWARF 2. | |
3248 | @end defmac | |
3249 | ||
3250 | @defmac ARG_POINTER_CFA_OFFSET (@var{fundecl}) | |
3251 | A C expression whose value is an integer giving the offset, in bytes, | |
3252 | from the argument pointer to the canonical frame address (cfa). The | |
3253 | final value should coincide with that calculated by | |
3254 | @code{INCOMING_FRAME_SP_OFFSET}. Which is unfortunately not usable | |
3255 | during virtual register instantiation. | |
3256 | ||
3257 | The default value for this macro is | |
3258 | @code{FIRST_PARM_OFFSET (fundecl) + crtl->args.pretend_args_size}, | |
3259 | which is correct for most machines; in general, the arguments are found | |
3260 | immediately before the stack frame. Note that this is not the case on | |
3261 | some targets that save registers into the caller's frame, such as SPARC | |
3262 | and rs6000, and so such targets need to define this macro. | |
3263 | ||
3264 | You only need to define this macro if the default is incorrect, and you | |
3265 | want to support call frame debugging information like that provided by | |
3266 | DWARF 2. | |
3267 | @end defmac | |
3268 | ||
3269 | @defmac FRAME_POINTER_CFA_OFFSET (@var{fundecl}) | |
3270 | If defined, a C expression whose value is an integer giving the offset | |
3271 | in bytes from the frame pointer to the canonical frame address (cfa). | |
3272 | The final value should coincide with that calculated by | |
3273 | @code{INCOMING_FRAME_SP_OFFSET}. | |
3274 | ||
3275 | Normally the CFA is calculated as an offset from the argument pointer, | |
3276 | via @code{ARG_POINTER_CFA_OFFSET}, but if the argument pointer is | |
3277 | variable due to the ABI, this may not be possible. If this macro is | |
3278 | defined, it implies that the virtual register instantiation should be | |
3279 | based on the frame pointer instead of the argument pointer. Only one | |
3280 | of @code{FRAME_POINTER_CFA_OFFSET} and @code{ARG_POINTER_CFA_OFFSET} | |
3281 | should be defined. | |
3282 | @end defmac | |
3283 | ||
3284 | @defmac CFA_FRAME_BASE_OFFSET (@var{fundecl}) | |
3285 | If defined, a C expression whose value is an integer giving the offset | |
3286 | in bytes from the canonical frame address (cfa) to the frame base used | |
3287 | in DWARF 2 debug information. The default is zero. A different value | |
3288 | may reduce the size of debug information on some ports. | |
3289 | @end defmac | |
3290 | ||
3291 | @node Exception Handling | |
3292 | @subsection Exception Handling Support | |
3293 | @cindex exception handling | |
3294 | ||
3295 | @defmac EH_RETURN_DATA_REGNO (@var{N}) | |
3296 | A C expression whose value is the @var{N}th register number used for | |
3297 | data by exception handlers, or @code{INVALID_REGNUM} if fewer than | |
3298 | @var{N} registers are usable. | |
3299 | ||
3300 | The exception handling library routines communicate with the exception | |
3301 | handlers via a set of agreed upon registers. Ideally these registers | |
3302 | should be call-clobbered; it is possible to use call-saved registers, | |
3303 | but may negatively impact code size. The target must support at least | |
3304 | 2 data registers, but should define 4 if there are enough free registers. | |
3305 | ||
3306 | You must define this macro if you want to support call frame exception | |
3307 | handling like that provided by DWARF 2. | |
3308 | @end defmac | |
3309 | ||
3310 | @defmac EH_RETURN_STACKADJ_RTX | |
3311 | A C expression whose value is RTL representing a location in which | |
3312 | to store a stack adjustment to be applied before function return. | |
3313 | This is used to unwind the stack to an exception handler's call frame. | |
3314 | It will be assigned zero on code paths that return normally. | |
3315 | ||
3316 | Typically this is a call-clobbered hard register that is otherwise | |
3317 | untouched by the epilogue, but could also be a stack slot. | |
3318 | ||
3319 | Do not define this macro if the stack pointer is saved and restored | |
3320 | by the regular prolog and epilog code in the call frame itself; in | |
3321 | this case, the exception handling library routines will update the | |
3322 | stack location to be restored in place. Otherwise, you must define | |
3323 | this macro if you want to support call frame exception handling like | |
3324 | that provided by DWARF 2. | |
3325 | @end defmac | |
3326 | ||
3327 | @defmac EH_RETURN_HANDLER_RTX | |
3328 | A C expression whose value is RTL representing a location in which | |
3329 | to store the address of an exception handler to which we should | |
3330 | return. It will not be assigned on code paths that return normally. | |
3331 | ||
3332 | Typically this is the location in the call frame at which the normal | |
3333 | return address is stored. For targets that return by popping an | |
3334 | address off the stack, this might be a memory address just below | |
3335 | the @emph{target} call frame rather than inside the current call | |
3336 | frame. If defined, @code{EH_RETURN_STACKADJ_RTX} will have already | |
3337 | been assigned, so it may be used to calculate the location of the | |
3338 | target call frame. | |
3339 | ||
3340 | Some targets have more complex requirements than storing to an | |
3341 | address calculable during initial code generation. In that case | |
3342 | the @code{eh_return} instruction pattern should be used instead. | |
3343 | ||
3344 | If you want to support call frame exception handling, you must | |
3345 | define either this macro or the @code{eh_return} instruction pattern. | |
3346 | @end defmac | |
3347 | ||
3348 | @defmac RETURN_ADDR_OFFSET | |
3349 | If defined, an integer-valued C expression for which rtl will be generated | |
3350 | to add it to the exception handler address before it is searched in the | |
3351 | exception handling tables, and to subtract it again from the address before | |
3352 | using it to return to the exception handler. | |
3353 | @end defmac | |
3354 | ||
3355 | @defmac ASM_PREFERRED_EH_DATA_FORMAT (@var{code}, @var{global}) | |
3356 | This macro chooses the encoding of pointers embedded in the exception | |
3357 | handling sections. If at all possible, this should be defined such | |
3358 | that the exception handling section will not require dynamic relocations, | |
3359 | and so may be read-only. | |
3360 | ||
3361 | @var{code} is 0 for data, 1 for code labels, 2 for function pointers. | |
3362 | @var{global} is true if the symbol may be affected by dynamic relocations. | |
3363 | The macro should return a combination of the @code{DW_EH_PE_*} defines | |
3364 | as found in @file{dwarf2.h}. | |
3365 | ||
3366 | If this macro is not defined, pointers will not be encoded but | |
3367 | represented directly. | |
3368 | @end defmac | |
3369 | ||
3370 | @defmac ASM_MAYBE_OUTPUT_ENCODED_ADDR_RTX (@var{file}, @var{encoding}, @var{size}, @var{addr}, @var{done}) | |
3371 | This macro allows the target to emit whatever special magic is required | |
3372 | to represent the encoding chosen by @code{ASM_PREFERRED_EH_DATA_FORMAT}. | |
3373 | Generic code takes care of pc-relative and indirect encodings; this must | |
3374 | be defined if the target uses text-relative or data-relative encodings. | |
3375 | ||
3376 | This is a C statement that branches to @var{done} if the format was | |
3377 | handled. @var{encoding} is the format chosen, @var{size} is the number | |
3378 | of bytes that the format occupies, @var{addr} is the @code{SYMBOL_REF} | |
3379 | to be emitted. | |
3380 | @end defmac | |
3381 | ||
38f8b050 JR |
3382 | @defmac MD_FALLBACK_FRAME_STATE_FOR (@var{context}, @var{fs}) |
3383 | This macro allows the target to add CPU and operating system specific | |
3384 | code to the call-frame unwinder for use when there is no unwind data | |
3385 | available. The most common reason to implement this macro is to unwind | |
3386 | through signal frames. | |
3387 | ||
3388 | This macro is called from @code{uw_frame_state_for} in | |
3389 | @file{unwind-dw2.c}, @file{unwind-dw2-xtensa.c} and | |
3390 | @file{unwind-ia64.c}. @var{context} is an @code{_Unwind_Context}; | |
3391 | @var{fs} is an @code{_Unwind_FrameState}. Examine @code{context->ra} | |
3392 | for the address of the code being executed and @code{context->cfa} for | |
3393 | the stack pointer value. If the frame can be decoded, the register | |
3394 | save addresses should be updated in @var{fs} and the macro should | |
3395 | evaluate to @code{_URC_NO_REASON}. If the frame cannot be decoded, | |
3396 | the macro should evaluate to @code{_URC_END_OF_STACK}. | |
3397 | ||
3398 | For proper signal handling in Java this macro is accompanied by | |
3399 | @code{MAKE_THROW_FRAME}, defined in @file{libjava/include/*-signal.h} headers. | |
3400 | @end defmac | |
3401 | ||
3402 | @defmac MD_HANDLE_UNWABI (@var{context}, @var{fs}) | |
3403 | This macro allows the target to add operating system specific code to the | |
3404 | call-frame unwinder to handle the IA-64 @code{.unwabi} unwinding directive, | |
3405 | usually used for signal or interrupt frames. | |
3406 | ||
3407 | This macro is called from @code{uw_update_context} in @file{unwind-ia64.c}. | |
3408 | @var{context} is an @code{_Unwind_Context}; | |
3409 | @var{fs} is an @code{_Unwind_FrameState}. Examine @code{fs->unwabi} | |
3410 | for the abi and context in the @code{.unwabi} directive. If the | |
3411 | @code{.unwabi} directive can be handled, the register save addresses should | |
3412 | be updated in @var{fs}. | |
3413 | @end defmac | |
3414 | ||
3415 | @defmac TARGET_USES_WEAK_UNWIND_INFO | |
3416 | A C expression that evaluates to true if the target requires unwind | |
3417 | info to be given comdat linkage. Define it to be @code{1} if comdat | |
3418 | linkage is necessary. The default is @code{0}. | |
3419 | @end defmac | |
3420 | ||
3421 | @node Stack Checking | |
3422 | @subsection Specifying How Stack Checking is Done | |
3423 | ||
3424 | GCC will check that stack references are within the boundaries of the | |
3425 | stack, if the option @option{-fstack-check} is specified, in one of | |
3426 | three ways: | |
3427 | ||
3428 | @enumerate | |
3429 | @item | |
3430 | If the value of the @code{STACK_CHECK_BUILTIN} macro is nonzero, GCC | |
3431 | will assume that you have arranged for full stack checking to be done | |
3432 | at appropriate places in the configuration files. GCC will not do | |
3433 | other special processing. | |
3434 | ||
3435 | @item | |
3436 | If @code{STACK_CHECK_BUILTIN} is zero and the value of the | |
3437 | @code{STACK_CHECK_STATIC_BUILTIN} macro is nonzero, GCC will assume | |
3438 | that you have arranged for static stack checking (checking of the | |
3439 | static stack frame of functions) to be done at appropriate places | |
3440 | in the configuration files. GCC will only emit code to do dynamic | |
3441 | stack checking (checking on dynamic stack allocations) using the third | |
3442 | approach below. | |
3443 | ||
3444 | @item | |
3445 | If neither of the above are true, GCC will generate code to periodically | |
3446 | ``probe'' the stack pointer using the values of the macros defined below. | |
3447 | @end enumerate | |
3448 | ||
3449 | If neither STACK_CHECK_BUILTIN nor STACK_CHECK_STATIC_BUILTIN is defined, | |
3450 | GCC will change its allocation strategy for large objects if the option | |
3451 | @option{-fstack-check} is specified: they will always be allocated | |
3452 | dynamically if their size exceeds @code{STACK_CHECK_MAX_VAR_SIZE} bytes. | |
3453 | ||
3454 | @defmac STACK_CHECK_BUILTIN | |
3455 | A nonzero value if stack checking is done by the configuration files in a | |
3456 | machine-dependent manner. You should define this macro if stack checking | |
3457 | is required by the ABI of your machine or if you would like to do stack | |
3458 | checking in some more efficient way than the generic approach. The default | |
3459 | value of this macro is zero. | |
3460 | @end defmac | |
3461 | ||
3462 | @defmac STACK_CHECK_STATIC_BUILTIN | |
3463 | A nonzero value if static stack checking is done by the configuration files | |
3464 | in a machine-dependent manner. You should define this macro if you would | |
3465 | like to do static stack checking in some more efficient way than the generic | |
3466 | approach. The default value of this macro is zero. | |
3467 | @end defmac | |
3468 | ||
3469 | @defmac STACK_CHECK_PROBE_INTERVAL_EXP | |
3470 | An integer specifying the interval at which GCC must generate stack probe | |
3471 | instructions, defined as 2 raised to this integer. You will normally | |
3472 | define this macro so that the interval be no larger than the size of | |
3473 | the ``guard pages'' at the end of a stack area. The default value | |
3474 | of 12 (4096-byte interval) is suitable for most systems. | |
3475 | @end defmac | |
3476 | ||
3477 | @defmac STACK_CHECK_MOVING_SP | |
3478 | An integer which is nonzero if GCC should move the stack pointer page by page | |
3479 | when doing probes. This can be necessary on systems where the stack pointer | |
3480 | contains the bottom address of the memory area accessible to the executing | |
3481 | thread at any point in time. In this situation an alternate signal stack | |
3482 | is required in order to be able to recover from a stack overflow. The | |
3483 | default value of this macro is zero. | |
3484 | @end defmac | |
3485 | ||
3486 | @defmac STACK_CHECK_PROTECT | |
3487 | The number of bytes of stack needed to recover from a stack overflow, for | |
3488 | languages where such a recovery is supported. The default value of 75 words | |
3489 | with the @code{setjmp}/@code{longjmp}-based exception handling mechanism and | |
3490 | 8192 bytes with other exception handling mechanisms should be adequate for | |
3491 | most machines. | |
3492 | @end defmac | |
3493 | ||
3494 | The following macros are relevant only if neither STACK_CHECK_BUILTIN | |
3495 | nor STACK_CHECK_STATIC_BUILTIN is defined; you can omit them altogether | |
3496 | in the opposite case. | |
3497 | ||
3498 | @defmac STACK_CHECK_MAX_FRAME_SIZE | |
3499 | The maximum size of a stack frame, in bytes. GCC will generate probe | |
3500 | instructions in non-leaf functions to ensure at least this many bytes of | |
3501 | stack are available. If a stack frame is larger than this size, stack | |
3502 | checking will not be reliable and GCC will issue a warning. The | |
3503 | default is chosen so that GCC only generates one instruction on most | |
3504 | systems. You should normally not change the default value of this macro. | |
3505 | @end defmac | |
3506 | ||
3507 | @defmac STACK_CHECK_FIXED_FRAME_SIZE | |
3508 | GCC uses this value to generate the above warning message. It | |
3509 | represents the amount of fixed frame used by a function, not including | |
3510 | space for any callee-saved registers, temporaries and user variables. | |
3511 | You need only specify an upper bound for this amount and will normally | |
3512 | use the default of four words. | |
3513 | @end defmac | |
3514 | ||
3515 | @defmac STACK_CHECK_MAX_VAR_SIZE | |
3516 | The maximum size, in bytes, of an object that GCC will place in the | |
3517 | fixed area of the stack frame when the user specifies | |
3518 | @option{-fstack-check}. | |
3519 | GCC computed the default from the values of the above macros and you will | |
3520 | normally not need to override that default. | |
3521 | @end defmac | |
3522 | ||
3523 | @need 2000 | |
3524 | @node Frame Registers | |
3525 | @subsection Registers That Address the Stack Frame | |
3526 | ||
3527 | @c prevent bad page break with this line | |
3528 | This discusses registers that address the stack frame. | |
3529 | ||
3530 | @defmac STACK_POINTER_REGNUM | |
3531 | The register number of the stack pointer register, which must also be a | |
3532 | fixed register according to @code{FIXED_REGISTERS}. On most machines, | |
3533 | the hardware determines which register this is. | |
3534 | @end defmac | |
3535 | ||
3536 | @defmac FRAME_POINTER_REGNUM | |
3537 | The register number of the frame pointer register, which is used to | |
3538 | access automatic variables in the stack frame. On some machines, the | |
3539 | hardware determines which register this is. On other machines, you can | |
3540 | choose any register you wish for this purpose. | |
3541 | @end defmac | |
3542 | ||
3543 | @defmac HARD_FRAME_POINTER_REGNUM | |
3544 | On some machines the offset between the frame pointer and starting | |
3545 | offset of the automatic variables is not known until after register | |
3546 | allocation has been done (for example, because the saved registers are | |
3547 | between these two locations). On those machines, define | |
3548 | @code{FRAME_POINTER_REGNUM} the number of a special, fixed register to | |
3549 | be used internally until the offset is known, and define | |
3550 | @code{HARD_FRAME_POINTER_REGNUM} to be the actual hard register number | |
3551 | used for the frame pointer. | |
3552 | ||
3553 | You should define this macro only in the very rare circumstances when it | |
3554 | is not possible to calculate the offset between the frame pointer and | |
3555 | the automatic variables until after register allocation has been | |
3556 | completed. When this macro is defined, you must also indicate in your | |
3557 | definition of @code{ELIMINABLE_REGS} how to eliminate | |
3558 | @code{FRAME_POINTER_REGNUM} into either @code{HARD_FRAME_POINTER_REGNUM} | |
3559 | or @code{STACK_POINTER_REGNUM}. | |
3560 | ||
3561 | Do not define this macro if it would be the same as | |
3562 | @code{FRAME_POINTER_REGNUM}. | |
3563 | @end defmac | |
3564 | ||
3565 | @defmac ARG_POINTER_REGNUM | |
3566 | The register number of the arg pointer register, which is used to access | |
3567 | the function's argument list. On some machines, this is the same as the | |
3568 | frame pointer register. On some machines, the hardware determines which | |
3569 | register this is. On other machines, you can choose any register you | |
3570 | wish for this purpose. If this is not the same register as the frame | |
3571 | pointer register, then you must mark it as a fixed register according to | |
3572 | @code{FIXED_REGISTERS}, or arrange to be able to eliminate it | |
3573 | (@pxref{Elimination}). | |
3574 | @end defmac | |
3575 | ||
e3339d0f JM |
3576 | @defmac HARD_FRAME_POINTER_IS_FRAME_POINTER |
3577 | Define this to a preprocessor constant that is nonzero if | |
3578 | @code{hard_frame_pointer_rtx} and @code{frame_pointer_rtx} should be | |
3579 | the same. The default definition is @samp{(HARD_FRAME_POINTER_REGNUM | |
3580 | == FRAME_POINTER_REGNUM)}; you only need to define this macro if that | |
3581 | definition is not suitable for use in preprocessor conditionals. | |
3582 | @end defmac | |
3583 | ||
3584 | @defmac HARD_FRAME_POINTER_IS_ARG_POINTER | |
3585 | Define this to a preprocessor constant that is nonzero if | |
3586 | @code{hard_frame_pointer_rtx} and @code{arg_pointer_rtx} should be the | |
3587 | same. The default definition is @samp{(HARD_FRAME_POINTER_REGNUM == | |
3588 | ARG_POINTER_REGNUM)}; you only need to define this macro if that | |
3589 | definition is not suitable for use in preprocessor conditionals. | |
3590 | @end defmac | |
3591 | ||
38f8b050 JR |
3592 | @defmac RETURN_ADDRESS_POINTER_REGNUM |
3593 | The register number of the return address pointer register, which is used to | |
3594 | access the current function's return address from the stack. On some | |
3595 | machines, the return address is not at a fixed offset from the frame | |
3596 | pointer or stack pointer or argument pointer. This register can be defined | |
3597 | to point to the return address on the stack, and then be converted by | |
3598 | @code{ELIMINABLE_REGS} into either the frame pointer or stack pointer. | |
3599 | ||
3600 | Do not define this macro unless there is no other way to get the return | |
3601 | address from the stack. | |
3602 | @end defmac | |
3603 | ||
3604 | @defmac STATIC_CHAIN_REGNUM | |
3605 | @defmacx STATIC_CHAIN_INCOMING_REGNUM | |
3606 | Register numbers used for passing a function's static chain pointer. If | |
3607 | register windows are used, the register number as seen by the called | |
3608 | function is @code{STATIC_CHAIN_INCOMING_REGNUM}, while the register | |
3609 | number as seen by the calling function is @code{STATIC_CHAIN_REGNUM}. If | |
3610 | these registers are the same, @code{STATIC_CHAIN_INCOMING_REGNUM} need | |
3611 | not be defined. | |
3612 | ||
3613 | The static chain register need not be a fixed register. | |
3614 | ||
3615 | If the static chain is passed in memory, these macros should not be | |
3616 | defined; instead, the @code{TARGET_STATIC_CHAIN} hook should be used. | |
3617 | @end defmac | |
3618 | ||
3619 | @hook TARGET_STATIC_CHAIN | |
3620 | This hook replaces the use of @code{STATIC_CHAIN_REGNUM} et al for | |
3621 | targets that may use different static chain locations for different | |
3622 | nested functions. This may be required if the target has function | |
3623 | attributes that affect the calling conventions of the function and | |
3624 | those calling conventions use different static chain locations. | |
3625 | ||
3626 | The default version of this hook uses @code{STATIC_CHAIN_REGNUM} et al. | |
3627 | ||
3628 | If the static chain is passed in memory, this hook should be used to | |
3629 | provide rtx giving @code{mem} expressions that denote where they are stored. | |
3630 | Often the @code{mem} expression as seen by the caller will be at an offset | |
3631 | from the stack pointer and the @code{mem} expression as seen by the callee | |
3632 | will be at an offset from the frame pointer. | |
3633 | @findex stack_pointer_rtx | |
3634 | @findex frame_pointer_rtx | |
3635 | @findex arg_pointer_rtx | |
3636 | The variables @code{stack_pointer_rtx}, @code{frame_pointer_rtx}, and | |
3637 | @code{arg_pointer_rtx} will have been initialized and should be used | |
3638 | to refer to those items. | |
3639 | @end deftypefn | |
3640 | ||
3641 | @defmac DWARF_FRAME_REGISTERS | |
3642 | This macro specifies the maximum number of hard registers that can be | |
3643 | saved in a call frame. This is used to size data structures used in | |
3644 | DWARF2 exception handling. | |
3645 | ||
3646 | Prior to GCC 3.0, this macro was needed in order to establish a stable | |
3647 | exception handling ABI in the face of adding new hard registers for ISA | |
3648 | extensions. In GCC 3.0 and later, the EH ABI is insulated from changes | |
3649 | in the number of hard registers. Nevertheless, this macro can still be | |
3650 | used to reduce the runtime memory requirements of the exception handling | |
3651 | routines, which can be substantial if the ISA contains a lot of | |
3652 | registers that are not call-saved. | |
3653 | ||
3654 | If this macro is not defined, it defaults to | |
3655 | @code{FIRST_PSEUDO_REGISTER}. | |
3656 | @end defmac | |
3657 | ||
3658 | @defmac PRE_GCC3_DWARF_FRAME_REGISTERS | |
3659 | ||
3660 | This macro is similar to @code{DWARF_FRAME_REGISTERS}, but is provided | |
3661 | for backward compatibility in pre GCC 3.0 compiled code. | |
3662 | ||
3663 | If this macro is not defined, it defaults to | |
3664 | @code{DWARF_FRAME_REGISTERS}. | |
3665 | @end defmac | |
3666 | ||
3667 | @defmac DWARF_REG_TO_UNWIND_COLUMN (@var{regno}) | |
3668 | ||
3669 | Define this macro if the target's representation for dwarf registers | |
3670 | is different than the internal representation for unwind column. | |
3671 | Given a dwarf register, this macro should return the internal unwind | |
3672 | column number to use instead. | |
3673 | ||
3674 | See the PowerPC's SPE target for an example. | |
3675 | @end defmac | |
3676 | ||
3677 | @defmac DWARF_FRAME_REGNUM (@var{regno}) | |
3678 | ||
3679 | Define this macro if the target's representation for dwarf registers | |
3680 | used in .eh_frame or .debug_frame is different from that used in other | |
3681 | debug info sections. Given a GCC hard register number, this macro | |
3682 | should return the .eh_frame register number. The default is | |
3683 | @code{DBX_REGISTER_NUMBER (@var{regno})}. | |
3684 | ||
3685 | @end defmac | |
3686 | ||
3687 | @defmac DWARF2_FRAME_REG_OUT (@var{regno}, @var{for_eh}) | |
3688 | ||
3689 | Define this macro to map register numbers held in the call frame info | |
3690 | that GCC has collected using @code{DWARF_FRAME_REGNUM} to those that | |
3691 | should be output in .debug_frame (@code{@var{for_eh}} is zero) and | |
3692 | .eh_frame (@code{@var{for_eh}} is nonzero). The default is to | |
3693 | return @code{@var{regno}}. | |
3694 | ||
3695 | @end defmac | |
3696 | ||
3697 | @node Elimination | |
3698 | @subsection Eliminating Frame Pointer and Arg Pointer | |
3699 | ||
3700 | @c prevent bad page break with this line | |
3701 | This is about eliminating the frame pointer and arg pointer. | |
3702 | ||
3703 | @hook TARGET_FRAME_POINTER_REQUIRED | |
3704 | This target hook should return @code{true} if a function must have and use | |
3705 | a frame pointer. This target hook is called in the reload pass. If its return | |
3706 | value is @code{true} the function will have a frame pointer. | |
3707 | ||
3708 | This target hook can in principle examine the current function and decide | |
3709 | according to the facts, but on most machines the constant @code{false} or the | |
3710 | constant @code{true} suffices. Use @code{false} when the machine allows code | |
3711 | to be generated with no frame pointer, and doing so saves some time or space. | |
3712 | Use @code{true} when there is no possible advantage to avoiding a frame | |
3713 | pointer. | |
3714 | ||
3715 | In certain cases, the compiler does not know how to produce valid code | |
3716 | without a frame pointer. The compiler recognizes those cases and | |
3717 | automatically gives the function a frame pointer regardless of what | |
3718 | @code{TARGET_FRAME_POINTER_REQUIRED} returns. You don't need to worry about | |
3719 | them. | |
3720 | ||
3721 | In a function that does not require a frame pointer, the frame pointer | |
3722 | register can be allocated for ordinary usage, unless you mark it as a | |
3723 | fixed register. See @code{FIXED_REGISTERS} for more information. | |
3724 | ||
3725 | Default return value is @code{false}. | |
3726 | @end deftypefn | |
3727 | ||
3728 | @findex get_frame_size | |
3729 | @defmac INITIAL_FRAME_POINTER_OFFSET (@var{depth-var}) | |
3730 | A C statement to store in the variable @var{depth-var} the difference | |
3731 | between the frame pointer and the stack pointer values immediately after | |
3732 | the function prologue. The value would be computed from information | |
3733 | such as the result of @code{get_frame_size ()} and the tables of | |
3734 | registers @code{regs_ever_live} and @code{call_used_regs}. | |
3735 | ||
3736 | If @code{ELIMINABLE_REGS} is defined, this macro will be not be used and | |
3737 | need not be defined. Otherwise, it must be defined even if | |
3738 | @code{TARGET_FRAME_POINTER_REQUIRED} always returns true; in that | |
3739 | case, you may set @var{depth-var} to anything. | |
3740 | @end defmac | |
3741 | ||
3742 | @defmac ELIMINABLE_REGS | |
3743 | If defined, this macro specifies a table of register pairs used to | |
3744 | eliminate unneeded registers that point into the stack frame. If it is not | |
3745 | defined, the only elimination attempted by the compiler is to replace | |
3746 | references to the frame pointer with references to the stack pointer. | |
3747 | ||
3748 | The definition of this macro is a list of structure initializations, each | |
3749 | of which specifies an original and replacement register. | |
3750 | ||
3751 | On some machines, the position of the argument pointer is not known until | |
3752 | the compilation is completed. In such a case, a separate hard register | |
3753 | must be used for the argument pointer. This register can be eliminated by | |
3754 | replacing it with either the frame pointer or the argument pointer, | |
3755 | depending on whether or not the frame pointer has been eliminated. | |
3756 | ||
3757 | In this case, you might specify: | |
3758 | @smallexample | |
3759 | #define ELIMINABLE_REGS \ | |
3760 | @{@{ARG_POINTER_REGNUM, STACK_POINTER_REGNUM@}, \ | |
3761 | @{ARG_POINTER_REGNUM, FRAME_POINTER_REGNUM@}, \ | |
3762 | @{FRAME_POINTER_REGNUM, STACK_POINTER_REGNUM@}@} | |
3763 | @end smallexample | |
3764 | ||
3765 | Note that the elimination of the argument pointer with the stack pointer is | |
3766 | specified first since that is the preferred elimination. | |
3767 | @end defmac | |
3768 | ||
3769 | @hook TARGET_CAN_ELIMINATE | |
3770 | This target hook should returns @code{true} if the compiler is allowed to | |
3771 | try to replace register number @var{from_reg} with register number | |
3772 | @var{to_reg}. This target hook need only be defined if @code{ELIMINABLE_REGS} | |
3773 | is defined, and will usually be @code{true}, since most of the cases | |
3774 | preventing register elimination are things that the compiler already | |
3775 | knows about. | |
3776 | ||
3777 | Default return value is @code{true}. | |
3778 | @end deftypefn | |
3779 | ||
3780 | @defmac INITIAL_ELIMINATION_OFFSET (@var{from-reg}, @var{to-reg}, @var{offset-var}) | |
3781 | This macro is similar to @code{INITIAL_FRAME_POINTER_OFFSET}. It | |
3782 | specifies the initial difference between the specified pair of | |
3783 | registers. This macro must be defined if @code{ELIMINABLE_REGS} is | |
3784 | defined. | |
3785 | @end defmac | |
3786 | ||
3787 | @node Stack Arguments | |
3788 | @subsection Passing Function Arguments on the Stack | |
3789 | @cindex arguments on stack | |
3790 | @cindex stack arguments | |
3791 | ||
3792 | The macros in this section control how arguments are passed | |
3793 | on the stack. See the following section for other macros that | |
3794 | control passing certain arguments in registers. | |
3795 | ||
3796 | @hook TARGET_PROMOTE_PROTOTYPES | |
3797 | This target hook returns @code{true} if an argument declared in a | |
3798 | prototype as an integral type smaller than @code{int} should actually be | |
3799 | passed as an @code{int}. In addition to avoiding errors in certain | |
3800 | cases of mismatch, it also makes for better code on certain machines. | |
3801 | The default is to not promote prototypes. | |
3802 | @end deftypefn | |
3803 | ||
3804 | @defmac PUSH_ARGS | |
3805 | A C expression. If nonzero, push insns will be used to pass | |
3806 | outgoing arguments. | |
3807 | If the target machine does not have a push instruction, set it to zero. | |
3808 | That directs GCC to use an alternate strategy: to | |
3809 | allocate the entire argument block and then store the arguments into | |
3810 | it. When @code{PUSH_ARGS} is nonzero, @code{PUSH_ROUNDING} must be defined too. | |
3811 | @end defmac | |
3812 | ||
3813 | @defmac PUSH_ARGS_REVERSED | |
3814 | A C expression. If nonzero, function arguments will be evaluated from | |
3815 | last to first, rather than from first to last. If this macro is not | |
3816 | defined, it defaults to @code{PUSH_ARGS} on targets where the stack | |
3817 | and args grow in opposite directions, and 0 otherwise. | |
3818 | @end defmac | |
3819 | ||
3820 | @defmac PUSH_ROUNDING (@var{npushed}) | |
3821 | A C expression that is the number of bytes actually pushed onto the | |
3822 | stack when an instruction attempts to push @var{npushed} bytes. | |
3823 | ||
3824 | On some machines, the definition | |
3825 | ||
3826 | @smallexample | |
3827 | #define PUSH_ROUNDING(BYTES) (BYTES) | |
3828 | @end smallexample | |
3829 | ||
3830 | @noindent | |
3831 | will suffice. But on other machines, instructions that appear | |
3832 | to push one byte actually push two bytes in an attempt to maintain | |
3833 | alignment. Then the definition should be | |
3834 | ||
3835 | @smallexample | |
3836 | #define PUSH_ROUNDING(BYTES) (((BYTES) + 1) & ~1) | |
3837 | @end smallexample | |
4a6336ad | 3838 | |
64ad7c99 | 3839 | If the value of this macro has a type, it should be an unsigned type. |
38f8b050 JR |
3840 | @end defmac |
3841 | ||
3842 | @findex current_function_outgoing_args_size | |
3843 | @defmac ACCUMULATE_OUTGOING_ARGS | |
3844 | A C expression. If nonzero, the maximum amount of space required for outgoing arguments | |
3845 | will be computed and placed into the variable | |
3846 | @code{current_function_outgoing_args_size}. No space will be pushed | |
3847 | onto the stack for each call; instead, the function prologue should | |
3848 | increase the stack frame size by this amount. | |
3849 | ||
3850 | Setting both @code{PUSH_ARGS} and @code{ACCUMULATE_OUTGOING_ARGS} | |
3851 | is not proper. | |
3852 | @end defmac | |
3853 | ||
3854 | @defmac REG_PARM_STACK_SPACE (@var{fndecl}) | |
3855 | Define this macro if functions should assume that stack space has been | |
3856 | allocated for arguments even when their values are passed in | |
3857 | registers. | |
3858 | ||
3859 | The value of this macro is the size, in bytes, of the area reserved for | |
3860 | arguments passed in registers for the function represented by @var{fndecl}, | |
3861 | which can be zero if GCC is calling a library function. | |
3862 | The argument @var{fndecl} can be the FUNCTION_DECL, or the type itself | |
3863 | of the function. | |
3864 | ||
3865 | This space can be allocated by the caller, or be a part of the | |
3866 | machine-dependent stack frame: @code{OUTGOING_REG_PARM_STACK_SPACE} says | |
3867 | which. | |
3868 | @end defmac | |
3869 | @c above is overfull. not sure what to do. --mew 5feb93 did | |
3870 | @c something, not sure if it looks good. --mew 10feb93 | |
3871 | ||
3872 | @defmac OUTGOING_REG_PARM_STACK_SPACE (@var{fntype}) | |
3873 | Define this to a nonzero value if it is the responsibility of the | |
3874 | caller to allocate the area reserved for arguments passed in registers | |
3875 | when calling a function of @var{fntype}. @var{fntype} may be NULL | |
3876 | if the function called is a library function. | |
3877 | ||
3878 | If @code{ACCUMULATE_OUTGOING_ARGS} is defined, this macro controls | |
3879 | whether the space for these arguments counts in the value of | |
3880 | @code{current_function_outgoing_args_size}. | |
3881 | @end defmac | |
3882 | ||
3883 | @defmac STACK_PARMS_IN_REG_PARM_AREA | |
3884 | Define this macro if @code{REG_PARM_STACK_SPACE} is defined, but the | |
3885 | stack parameters don't skip the area specified by it. | |
3886 | @c i changed this, makes more sens and it should have taken care of the | |
3887 | @c overfull.. not as specific, tho. --mew 5feb93 | |
3888 | ||
3889 | Normally, when a parameter is not passed in registers, it is placed on the | |
3890 | stack beyond the @code{REG_PARM_STACK_SPACE} area. Defining this macro | |
3891 | suppresses this behavior and causes the parameter to be passed on the | |
3892 | stack in its natural location. | |
3893 | @end defmac | |
3894 | ||
893d13d5 | 3895 | @hook TARGET_RETURN_POPS_ARGS |
38f8b050 JR |
3896 | This target hook returns the number of bytes of its own arguments that |
3897 | a function pops on returning, or 0 if the function pops no arguments | |
3898 | and the caller must therefore pop them all after the function returns. | |
3899 | ||
3900 | @var{fundecl} is a C variable whose value is a tree node that describes | |
3901 | the function in question. Normally it is a node of type | |
3902 | @code{FUNCTION_DECL} that describes the declaration of the function. | |
3903 | From this you can obtain the @code{DECL_ATTRIBUTES} of the function. | |
3904 | ||
3905 | @var{funtype} is a C variable whose value is a tree node that | |
3906 | describes the function in question. Normally it is a node of type | |
3907 | @code{FUNCTION_TYPE} that describes the data type of the function. | |
3908 | From this it is possible to obtain the data types of the value and | |
3909 | arguments (if known). | |
3910 | ||
3911 | When a call to a library function is being considered, @var{fundecl} | |
3912 | will contain an identifier node for the library function. Thus, if | |
3913 | you need to distinguish among various library functions, you can do so | |
3914 | by their names. Note that ``library function'' in this context means | |
3915 | a function used to perform arithmetic, whose name is known specially | |
3916 | in the compiler and was not mentioned in the C code being compiled. | |
3917 | ||
893d13d5 | 3918 | @var{size} is the number of bytes of arguments passed on the |
38f8b050 JR |
3919 | stack. If a variable number of bytes is passed, it is zero, and |
3920 | argument popping will always be the responsibility of the calling function. | |
3921 | ||
3922 | On the VAX, all functions always pop their arguments, so the definition | |
893d13d5 | 3923 | of this macro is @var{size}. On the 68000, using the standard |
38f8b050 JR |
3924 | calling convention, no functions pop their arguments, so the value of |
3925 | the macro is always 0 in this case. But an alternative calling | |
3926 | convention is available in which functions that take a fixed number of | |
3927 | arguments pop them but other functions (such as @code{printf}) pop | |
3928 | nothing (the caller pops all). When this convention is in use, | |
3929 | @var{funtype} is examined to determine whether a function takes a fixed | |
3930 | number of arguments. | |
3931 | @end deftypefn | |
3932 | ||
3933 | @defmac CALL_POPS_ARGS (@var{cum}) | |
3934 | A C expression that should indicate the number of bytes a call sequence | |
3935 | pops off the stack. It is added to the value of @code{RETURN_POPS_ARGS} | |
3936 | when compiling a function call. | |
3937 | ||
3938 | @var{cum} is the variable in which all arguments to the called function | |
3939 | have been accumulated. | |
3940 | ||
3941 | On certain architectures, such as the SH5, a call trampoline is used | |
3942 | that pops certain registers off the stack, depending on the arguments | |
3943 | that have been passed to the function. Since this is a property of the | |
3944 | call site, not of the called function, @code{RETURN_POPS_ARGS} is not | |
3945 | appropriate. | |
3946 | @end defmac | |
3947 | ||
3948 | @node Register Arguments | |
3949 | @subsection Passing Arguments in Registers | |
3950 | @cindex arguments in registers | |
3951 | @cindex registers arguments | |
3952 | ||
3953 | This section describes the macros which let you control how various | |
3954 | types of arguments are passed in registers or how they are arranged in | |
3955 | the stack. | |
3956 | ||
b25b9e8f NF |
3957 | @hook TARGET_FUNCTION_ARG |
3958 | Return an RTX indicating whether a function argument is passed in a | |
3959 | register and if so, which register. | |
38f8b050 | 3960 | |
b25b9e8f | 3961 | The arguments are @var{ca}, which summarizes all the previous |
38f8b050 JR |
3962 | arguments; @var{mode}, the machine mode of the argument; @var{type}, |
3963 | the data type of the argument as a tree node or 0 if that is not known | |
3964 | (which happens for C support library functions); and @var{named}, | |
b25b9e8f NF |
3965 | which is @code{true} for an ordinary argument and @code{false} for |
3966 | nameless arguments that correspond to @samp{@dots{}} in the called | |
3967 | function's prototype. @var{type} can be an incomplete type if a | |
3968 | syntax error has previously occurred. | |
38f8b050 | 3969 | |
b25b9e8f NF |
3970 | The return value is usually either a @code{reg} RTX for the hard |
3971 | register in which to pass the argument, or zero to pass the argument | |
3972 | on the stack. | |
38f8b050 JR |
3973 | |
3974 | The value of the expression can also be a @code{parallel} RTX@. This is | |
3975 | used when an argument is passed in multiple locations. The mode of the | |
3976 | @code{parallel} should be the mode of the entire argument. The | |
3977 | @code{parallel} holds any number of @code{expr_list} pairs; each one | |
3978 | describes where part of the argument is passed. In each | |
3979 | @code{expr_list} the first operand must be a @code{reg} RTX for the hard | |
3980 | register in which to pass this part of the argument, and the mode of the | |
3981 | register RTX indicates how large this part of the argument is. The | |
3982 | second operand of the @code{expr_list} is a @code{const_int} which gives | |
3983 | the offset in bytes into the entire argument of where this part starts. | |
3984 | As a special exception the first @code{expr_list} in the @code{parallel} | |
3985 | RTX may have a first operand of zero. This indicates that the entire | |
3986 | argument is also stored on the stack. | |
3987 | ||
b25b9e8f | 3988 | The last time this hook is called, it is called with @code{MODE == |
38f8b050 JR |
3989 | VOIDmode}, and its result is passed to the @code{call} or @code{call_value} |
3990 | pattern as operands 2 and 3 respectively. | |
3991 | ||
3992 | @cindex @file{stdarg.h} and register arguments | |
b25b9e8f NF |
3993 | The usual way to make the ISO library @file{stdarg.h} work on a |
3994 | machine where some arguments are usually passed in registers, is to | |
3995 | cause nameless arguments to be passed on the stack instead. This is | |
3996 | done by making @code{TARGET_FUNCTION_ARG} return 0 whenever | |
3997 | @var{named} is @code{false}. | |
3998 | ||
3999 | @cindex @code{TARGET_MUST_PASS_IN_STACK}, and @code{TARGET_FUNCTION_ARG} | |
4000 | @cindex @code{REG_PARM_STACK_SPACE}, and @code{TARGET_FUNCTION_ARG} | |
38f8b050 JR |
4001 | You may use the hook @code{targetm.calls.must_pass_in_stack} |
4002 | in the definition of this macro to determine if this argument is of a | |
4003 | type that must be passed in the stack. If @code{REG_PARM_STACK_SPACE} | |
b25b9e8f | 4004 | is not defined and @code{TARGET_FUNCTION_ARG} returns nonzero for such an |
38f8b050 JR |
4005 | argument, the compiler will abort. If @code{REG_PARM_STACK_SPACE} is |
4006 | defined, the argument will be computed in the stack and then loaded into | |
4007 | a register. | |
b25b9e8f | 4008 | @end deftypefn |
38f8b050 JR |
4009 | |
4010 | @hook TARGET_MUST_PASS_IN_STACK | |
4011 | This target hook should return @code{true} if we should not pass @var{type} | |
4012 | solely in registers. The file @file{expr.h} defines a | |
4013 | definition that is usually appropriate, refer to @file{expr.h} for additional | |
4014 | documentation. | |
4015 | @end deftypefn | |
4016 | ||
b25b9e8f NF |
4017 | @hook TARGET_FUNCTION_INCOMING_ARG |
4018 | Define this hook if the target machine has ``register windows'', so | |
38f8b050 JR |
4019 | that the register in which a function sees an arguments is not |
4020 | necessarily the same as the one in which the caller passed the | |
4021 | argument. | |
4022 | ||
b25b9e8f NF |
4023 | For such machines, @code{TARGET_FUNCTION_ARG} computes the register in |
4024 | which the caller passes the value, and | |
4025 | @code{TARGET_FUNCTION_INCOMING_ARG} should be defined in a similar | |
4026 | fashion to tell the function being called where the arguments will | |
4027 | arrive. | |
38f8b050 | 4028 | |
b25b9e8f NF |
4029 | If @code{TARGET_FUNCTION_INCOMING_ARG} is not defined, |
4030 | @code{TARGET_FUNCTION_ARG} serves both purposes. | |
4031 | @end deftypefn | |
38f8b050 JR |
4032 | |
4033 | @hook TARGET_ARG_PARTIAL_BYTES | |
4034 | This target hook returns the number of bytes at the beginning of an | |
4035 | argument that must be put in registers. The value must be zero for | |
4036 | arguments that are passed entirely in registers or that are entirely | |
4037 | pushed on the stack. | |
4038 | ||
4039 | On some machines, certain arguments must be passed partially in | |
4040 | registers and partially in memory. On these machines, typically the | |
4041 | first few words of arguments are passed in registers, and the rest | |
4042 | on the stack. If a multi-word argument (a @code{double} or a | |
4043 | structure) crosses that boundary, its first few words must be passed | |
4044 | in registers and the rest must be pushed. This macro tells the | |
4045 | compiler when this occurs, and how many bytes should go in registers. | |
4046 | ||
b25b9e8f | 4047 | @code{TARGET_FUNCTION_ARG} for these arguments should return the first |
38f8b050 | 4048 | register to be used by the caller for this argument; likewise |
b25b9e8f | 4049 | @code{TARGET_FUNCTION_INCOMING_ARG}, for the called function. |
38f8b050 JR |
4050 | @end deftypefn |
4051 | ||
ec9f85e5 | 4052 | @hook TARGET_PASS_BY_REFERENCE |
38f8b050 JR |
4053 | This target hook should return @code{true} if an argument at the |
4054 | position indicated by @var{cum} should be passed by reference. This | |
4055 | predicate is queried after target independent reasons for being | |
4056 | passed by reference, such as @code{TREE_ADDRESSABLE (type)}. | |
4057 | ||
4058 | If the hook returns true, a copy of that argument is made in memory and a | |
4059 | pointer to the argument is passed instead of the argument itself. | |
4060 | The pointer is passed in whatever way is appropriate for passing a pointer | |
4061 | to that type. | |
4062 | @end deftypefn | |
4063 | ||
4064 | @hook TARGET_CALLEE_COPIES | |
4065 | The function argument described by the parameters to this hook is | |
4066 | known to be passed by reference. The hook should return true if the | |
4067 | function argument should be copied by the callee instead of copied | |
4068 | by the caller. | |
4069 | ||
4070 | For any argument for which the hook returns true, if it can be | |
4071 | determined that the argument is not modified, then a copy need | |
4072 | not be generated. | |
4073 | ||
4074 | The default version of this hook always returns false. | |
4075 | @end deftypefn | |
4076 | ||
4077 | @defmac CUMULATIVE_ARGS | |
b25b9e8f NF |
4078 | A C type for declaring a variable that is used as the first argument |
4079 | of @code{TARGET_FUNCTION_ARG} and other related values. For some | |
4080 | target machines, the type @code{int} suffices and can hold the number | |
4081 | of bytes of argument so far. | |
38f8b050 JR |
4082 | |
4083 | There is no need to record in @code{CUMULATIVE_ARGS} anything about the | |
4084 | arguments that have been passed on the stack. The compiler has other | |
4085 | variables to keep track of that. For target machines on which all | |
4086 | arguments are passed on the stack, there is no need to store anything in | |
4087 | @code{CUMULATIVE_ARGS}; however, the data structure must exist and | |
4088 | should not be empty, so use @code{int}. | |
4089 | @end defmac | |
4090 | ||
4091 | @defmac OVERRIDE_ABI_FORMAT (@var{fndecl}) | |
4092 | If defined, this macro is called before generating any code for a | |
4093 | function, but after the @var{cfun} descriptor for the function has been | |
4094 | created. The back end may use this macro to update @var{cfun} to | |
4095 | reflect an ABI other than that which would normally be used by default. | |
4096 | If the compiler is generating code for a compiler-generated function, | |
4097 | @var{fndecl} may be @code{NULL}. | |
4098 | @end defmac | |
4099 | ||
4100 | @defmac INIT_CUMULATIVE_ARGS (@var{cum}, @var{fntype}, @var{libname}, @var{fndecl}, @var{n_named_args}) | |
4101 | A C statement (sans semicolon) for initializing the variable | |
4102 | @var{cum} for the state at the beginning of the argument list. The | |
4103 | variable has type @code{CUMULATIVE_ARGS}. The value of @var{fntype} | |
4104 | is the tree node for the data type of the function which will receive | |
4105 | the args, or 0 if the args are to a compiler support library function. | |
4106 | For direct calls that are not libcalls, @var{fndecl} contain the | |
4107 | declaration node of the function. @var{fndecl} is also set when | |
4108 | @code{INIT_CUMULATIVE_ARGS} is used to find arguments for the function | |
4109 | being compiled. @var{n_named_args} is set to the number of named | |
4110 | arguments, including a structure return address if it is passed as a | |
4111 | parameter, when making a call. When processing incoming arguments, | |
4112 | @var{n_named_args} is set to @minus{}1. | |
4113 | ||
4114 | When processing a call to a compiler support library function, | |
4115 | @var{libname} identifies which one. It is a @code{symbol_ref} rtx which | |
4116 | contains the name of the function, as a string. @var{libname} is 0 when | |
4117 | an ordinary C function call is being processed. Thus, each time this | |
4118 | macro is called, either @var{libname} or @var{fntype} is nonzero, but | |
4119 | never both of them at once. | |
4120 | @end defmac | |
4121 | ||
4122 | @defmac INIT_CUMULATIVE_LIBCALL_ARGS (@var{cum}, @var{mode}, @var{libname}) | |
4123 | Like @code{INIT_CUMULATIVE_ARGS} but only used for outgoing libcalls, | |
4124 | it gets a @code{MODE} argument instead of @var{fntype}, that would be | |
4125 | @code{NULL}. @var{indirect} would always be zero, too. If this macro | |
4126 | is not defined, @code{INIT_CUMULATIVE_ARGS (cum, NULL_RTX, libname, | |
4127 | 0)} is used instead. | |
4128 | @end defmac | |
4129 | ||
4130 | @defmac INIT_CUMULATIVE_INCOMING_ARGS (@var{cum}, @var{fntype}, @var{libname}) | |
4131 | Like @code{INIT_CUMULATIVE_ARGS} but overrides it for the purposes of | |
4132 | finding the arguments for the function being compiled. If this macro is | |
4133 | undefined, @code{INIT_CUMULATIVE_ARGS} is used instead. | |
4134 | ||
4135 | The value passed for @var{libname} is always 0, since library routines | |
4136 | with special calling conventions are never compiled with GCC@. The | |
4137 | argument @var{libname} exists for symmetry with | |
4138 | @code{INIT_CUMULATIVE_ARGS}. | |
4139 | @c could use "this macro" in place of @code{INIT_CUMULATIVE_ARGS}, maybe. | |
4140 | @c --mew 5feb93 i switched the order of the sentences. --mew 10feb93 | |
4141 | @end defmac | |
4142 | ||
b25b9e8f NF |
4143 | @hook TARGET_FUNCTION_ARG_ADVANCE |
4144 | This hook updates the summarizer variable pointed to by @var{ca} to | |
4145 | advance past an argument in the argument list. The values @var{mode}, | |
4146 | @var{type} and @var{named} describe that argument. Once this is done, | |
4147 | the variable @var{cum} is suitable for analyzing the @emph{following} | |
4148 | argument with @code{TARGET_FUNCTION_ARG}, etc. | |
38f8b050 | 4149 | |
b25b9e8f | 4150 | This hook need not do anything if the argument in question was passed |
38f8b050 JR |
4151 | on the stack. The compiler knows how to track the amount of stack space |
4152 | used for arguments without any special help. | |
b25b9e8f | 4153 | @end deftypefn |
38f8b050 JR |
4154 | |
4155 | @defmac FUNCTION_ARG_OFFSET (@var{mode}, @var{type}) | |
4156 | If defined, a C expression that is the number of bytes to add to the | |
4157 | offset of the argument passed in memory. This is needed for the SPU, | |
4158 | which passes @code{char} and @code{short} arguments in the preferred | |
4159 | slot that is in the middle of the quad word instead of starting at the | |
4160 | top. | |
4161 | @end defmac | |
4162 | ||
4163 | @defmac FUNCTION_ARG_PADDING (@var{mode}, @var{type}) | |
4164 | If defined, a C expression which determines whether, and in which direction, | |
4165 | to pad out an argument with extra space. The value should be of type | |
4166 | @code{enum direction}: either @code{upward} to pad above the argument, | |
4167 | @code{downward} to pad below, or @code{none} to inhibit padding. | |
4168 | ||
123148b5 BS |
4169 | The @emph{amount} of padding is not controlled by this macro, but by the |
4170 | target hook @code{TARGET_FUNCTION_ARG_ROUND_BOUNDARY}. It is | |
4171 | always just enough to reach the next multiple of that boundary. | |
38f8b050 JR |
4172 | |
4173 | This macro has a default definition which is right for most systems. | |
4174 | For little-endian machines, the default is to pad upward. For | |
4175 | big-endian machines, the default is to pad downward for an argument of | |
4176 | constant size shorter than an @code{int}, and upward otherwise. | |
4177 | @end defmac | |
4178 | ||
4179 | @defmac PAD_VARARGS_DOWN | |
4180 | If defined, a C expression which determines whether the default | |
4181 | implementation of va_arg will attempt to pad down before reading the | |
4182 | next argument, if that argument is smaller than its aligned space as | |
4183 | controlled by @code{PARM_BOUNDARY}. If this macro is not defined, all such | |
4184 | arguments are padded down if @code{BYTES_BIG_ENDIAN} is true. | |
4185 | @end defmac | |
4186 | ||
4187 | @defmac BLOCK_REG_PADDING (@var{mode}, @var{type}, @var{first}) | |
4188 | Specify padding for the last element of a block move between registers and | |
4189 | memory. @var{first} is nonzero if this is the only element. Defining this | |
4190 | macro allows better control of register function parameters on big-endian | |
4191 | machines, without using @code{PARALLEL} rtl. In particular, | |
4192 | @code{MUST_PASS_IN_STACK} need not test padding and mode of types in | |
4193 | registers, as there is no longer a "wrong" part of a register; For example, | |
4194 | a three byte aggregate may be passed in the high part of a register if so | |
4195 | required. | |
4196 | @end defmac | |
4197 | ||
c2ed6cf8 | 4198 | @hook TARGET_FUNCTION_ARG_BOUNDARY |
2b0d3573 | 4199 | This hook returns the alignment boundary, in bits, of an argument |
c2ed6cf8 NF |
4200 | with the specified mode and type. The default hook returns |
4201 | @code{PARM_BOUNDARY} for all arguments. | |
4202 | @end deftypefn | |
38f8b050 | 4203 | |
123148b5 BS |
4204 | @hook TARGET_FUNCTION_ARG_ROUND_BOUNDARY |
4205 | ||
38f8b050 JR |
4206 | @defmac FUNCTION_ARG_REGNO_P (@var{regno}) |
4207 | A C expression that is nonzero if @var{regno} is the number of a hard | |
4208 | register in which function arguments are sometimes passed. This does | |
4209 | @emph{not} include implicit arguments such as the static chain and | |
4210 | the structure-value address. On many machines, no registers can be | |
4211 | used for this purpose since all function arguments are pushed on the | |
4212 | stack. | |
4213 | @end defmac | |
4214 | ||
4215 | @hook TARGET_SPLIT_COMPLEX_ARG | |
4216 | This hook should return true if parameter of type @var{type} are passed | |
4217 | as two scalar parameters. By default, GCC will attempt to pack complex | |
4218 | arguments into the target's word size. Some ABIs require complex arguments | |
4219 | to be split and treated as their individual components. For example, on | |
4220 | AIX64, complex floats should be passed in a pair of floating point | |
4221 | registers, even though a complex float would fit in one 64-bit floating | |
4222 | point register. | |
4223 | ||
4224 | The default value of this hook is @code{NULL}, which is treated as always | |
4225 | false. | |
4226 | @end deftypefn | |
4227 | ||
4228 | @hook TARGET_BUILD_BUILTIN_VA_LIST | |
4229 | This hook returns a type node for @code{va_list} for the target. | |
4230 | The default version of the hook returns @code{void*}. | |
4231 | @end deftypefn | |
4232 | ||
07a5b2bc | 4233 | @hook TARGET_ENUM_VA_LIST_P |
38f8b050 JR |
4234 | This target hook is used in function @code{c_common_nodes_and_builtins} |
4235 | to iterate through the target specific builtin types for va_list. The | |
4236 | variable @var{idx} is used as iterator. @var{pname} has to be a pointer | |
07a5b2bc | 4237 | to a @code{const char *} and @var{ptree} a pointer to a @code{tree} typed |
38f8b050 | 4238 | variable. |
07a5b2bc | 4239 | The arguments @var{pname} and @var{ptree} are used to store the result of |
38f8b050 JR |
4240 | this macro and are set to the name of the va_list builtin type and its |
4241 | internal type. | |
4242 | If the return value of this macro is zero, then there is no more element. | |
4243 | Otherwise the @var{IDX} should be increased for the next call of this | |
4244 | macro to iterate through all types. | |
4245 | @end deftypefn | |
4246 | ||
4247 | @hook TARGET_FN_ABI_VA_LIST | |
4248 | This hook returns the va_list type of the calling convention specified by | |
4249 | @var{fndecl}. | |
4250 | The default version of this hook returns @code{va_list_type_node}. | |
4251 | @end deftypefn | |
4252 | ||
4253 | @hook TARGET_CANONICAL_VA_LIST_TYPE | |
4254 | This hook returns the va_list type of the calling convention specified by the | |
4255 | type of @var{type}. If @var{type} is not a valid va_list type, it returns | |
4256 | @code{NULL_TREE}. | |
4257 | @end deftypefn | |
4258 | ||
4259 | @hook TARGET_GIMPLIFY_VA_ARG_EXPR | |
4260 | This hook performs target-specific gimplification of | |
4261 | @code{VA_ARG_EXPR}. The first two parameters correspond to the | |
4262 | arguments to @code{va_arg}; the latter two are as in | |
4263 | @code{gimplify.c:gimplify_expr}. | |
4264 | @end deftypefn | |
4265 | ||
4266 | @hook TARGET_VALID_POINTER_MODE | |
4267 | Define this to return nonzero if the port can handle pointers | |
4268 | with machine mode @var{mode}. The default version of this | |
4269 | hook returns true for both @code{ptr_mode} and @code{Pmode}. | |
4270 | @end deftypefn | |
4271 | ||
7352c013 RG |
4272 | @hook TARGET_REF_MAY_ALIAS_ERRNO |
4273 | ||
38f8b050 JR |
4274 | @hook TARGET_SCALAR_MODE_SUPPORTED_P |
4275 | Define this to return nonzero if the port is prepared to handle | |
4276 | insns involving scalar mode @var{mode}. For a scalar mode to be | |
4277 | considered supported, all the basic arithmetic and comparisons | |
4278 | must work. | |
4279 | ||
4280 | The default version of this hook returns true for any mode | |
4281 | required to handle the basic C types (as defined by the port). | |
4282 | Included here are the double-word arithmetic supported by the | |
4283 | code in @file{optabs.c}. | |
4284 | @end deftypefn | |
4285 | ||
4286 | @hook TARGET_VECTOR_MODE_SUPPORTED_P | |
4287 | Define this to return nonzero if the port is prepared to handle | |
4288 | insns involving vector mode @var{mode}. At the very least, it | |
4289 | must have move patterns for this mode. | |
4290 | @end deftypefn | |
4291 | ||
0f6d54f7 RS |
4292 | @hook TARGET_ARRAY_MODE_SUPPORTED_P |
4293 | ||
38f8b050 JR |
4294 | @hook TARGET_SMALL_REGISTER_CLASSES_FOR_MODE_P |
4295 | Define this to return nonzero for machine modes for which the port has | |
4296 | small register classes. If this target hook returns nonzero for a given | |
4297 | @var{mode}, the compiler will try to minimize the lifetime of registers | |
4298 | in @var{mode}. The hook may be called with @code{VOIDmode} as argument. | |
4299 | In this case, the hook is expected to return nonzero if it returns nonzero | |
4300 | for any mode. | |
4301 | ||
4302 | On some machines, it is risky to let hard registers live across arbitrary | |
4303 | insns. Typically, these machines have instructions that require values | |
4304 | to be in specific registers (like an accumulator), and reload will fail | |
4305 | if the required hard register is used for another purpose across such an | |
4306 | insn. | |
4307 | ||
4308 | Passes before reload do not know which hard registers will be used | |
4309 | in an instruction, but the machine modes of the registers set or used in | |
4310 | the instruction are already known. And for some machines, register | |
4311 | classes are small for, say, integer registers but not for floating point | |
4312 | registers. For example, the AMD x86-64 architecture requires specific | |
4313 | registers for the legacy x86 integer instructions, but there are many | |
4314 | SSE registers for floating point operations. On such targets, a good | |
4315 | strategy may be to return nonzero from this hook for @code{INTEGRAL_MODE_P} | |
4316 | machine modes but zero for the SSE register classes. | |
4317 | ||
2b0d3573 | 4318 | The default version of this hook returns false for any mode. It is always |
38f8b050 JR |
4319 | safe to redefine this hook to return with a nonzero value. But if you |
4320 | unnecessarily define it, you will reduce the amount of optimizations | |
4321 | that can be performed in some cases. If you do not define this hook | |
4322 | to return a nonzero value when it is required, the compiler will run out | |
4323 | of spill registers and print a fatal error message. | |
4324 | @end deftypefn | |
4325 | ||
e692f276 RH |
4326 | @hook TARGET_FLAGS_REGNUM |
4327 | ||
38f8b050 JR |
4328 | @node Scalar Return |
4329 | @subsection How Scalar Function Values Are Returned | |
4330 | @cindex return values in registers | |
4331 | @cindex values, returned by functions | |
4332 | @cindex scalars, returned as values | |
4333 | ||
4334 | This section discusses the macros that control returning scalars as | |
4335 | values---values that can fit in registers. | |
4336 | ||
4337 | @hook TARGET_FUNCTION_VALUE | |
4338 | ||
4339 | Define this to return an RTX representing the place where a function | |
4340 | returns or receives a value of data type @var{ret_type}, a tree node | |
4341 | representing a data type. @var{fn_decl_or_type} is a tree node | |
4342 | representing @code{FUNCTION_DECL} or @code{FUNCTION_TYPE} of a | |
4343 | function being called. If @var{outgoing} is false, the hook should | |
4344 | compute the register in which the caller will see the return value. | |
4345 | Otherwise, the hook should return an RTX representing the place where | |
4346 | a function returns a value. | |
4347 | ||
4348 | On many machines, only @code{TYPE_MODE (@var{ret_type})} is relevant. | |
4349 | (Actually, on most machines, scalar values are returned in the same | |
4350 | place regardless of mode.) The value of the expression is usually a | |
4351 | @code{reg} RTX for the hard register where the return value is stored. | |
4352 | The value can also be a @code{parallel} RTX, if the return value is in | |
b25b9e8f | 4353 | multiple places. See @code{TARGET_FUNCTION_ARG} for an explanation of the |
38f8b050 JR |
4354 | @code{parallel} form. Note that the callee will populate every |
4355 | location specified in the @code{parallel}, but if the first element of | |
4356 | the @code{parallel} contains the whole return value, callers will use | |
4357 | that element as the canonical location and ignore the others. The m68k | |
4358 | port uses this type of @code{parallel} to return pointers in both | |
4359 | @samp{%a0} (the canonical location) and @samp{%d0}. | |
4360 | ||
4361 | If @code{TARGET_PROMOTE_FUNCTION_RETURN} returns true, you must apply | |
4362 | the same promotion rules specified in @code{PROMOTE_MODE} if | |
4363 | @var{valtype} is a scalar type. | |
4364 | ||
4365 | If the precise function being called is known, @var{func} is a tree | |
4366 | node (@code{FUNCTION_DECL}) for it; otherwise, @var{func} is a null | |
4367 | pointer. This makes it possible to use a different value-returning | |
4368 | convention for specific functions when all their calls are | |
4369 | known. | |
4370 | ||
4371 | Some target machines have ``register windows'' so that the register in | |
4372 | which a function returns its value is not the same as the one in which | |
4373 | the caller sees the value. For such machines, you should return | |
4374 | different RTX depending on @var{outgoing}. | |
4375 | ||
4376 | @code{TARGET_FUNCTION_VALUE} is not used for return values with | |
4377 | aggregate data types, because these are returned in another way. See | |
4378 | @code{TARGET_STRUCT_VALUE_RTX} and related macros, below. | |
4379 | @end deftypefn | |
4380 | ||
4381 | @defmac FUNCTION_VALUE (@var{valtype}, @var{func}) | |
4382 | This macro has been deprecated. Use @code{TARGET_FUNCTION_VALUE} for | |
4383 | a new target instead. | |
4384 | @end defmac | |
4385 | ||
4386 | @defmac LIBCALL_VALUE (@var{mode}) | |
4387 | A C expression to create an RTX representing the place where a library | |
4388 | function returns a value of mode @var{mode}. | |
4389 | ||
4390 | Note that ``library function'' in this context means a compiler | |
4391 | support routine, used to perform arithmetic, whose name is known | |
4392 | specially by the compiler and was not mentioned in the C code being | |
4393 | compiled. | |
4394 | @end defmac | |
4395 | ||
4396 | @hook TARGET_LIBCALL_VALUE | |
4397 | Define this hook if the back-end needs to know the name of the libcall | |
ff2ce160 | 4398 | function in order to determine where the result should be returned. |
38f8b050 JR |
4399 | |
4400 | The mode of the result is given by @var{mode} and the name of the called | |
ff2ce160 | 4401 | library function is given by @var{fun}. The hook should return an RTX |
38f8b050 JR |
4402 | representing the place where the library function result will be returned. |
4403 | ||
4404 | If this hook is not defined, then LIBCALL_VALUE will be used. | |
4405 | @end deftypefn | |
4406 | ||
4407 | @defmac FUNCTION_VALUE_REGNO_P (@var{regno}) | |
4408 | A C expression that is nonzero if @var{regno} is the number of a hard | |
4409 | register in which the values of called function may come back. | |
4410 | ||
4411 | A register whose use for returning values is limited to serving as the | |
4412 | second of a pair (for a value of type @code{double}, say) need not be | |
4413 | recognized by this macro. So for most machines, this definition | |
4414 | suffices: | |
4415 | ||
4416 | @smallexample | |
4417 | #define FUNCTION_VALUE_REGNO_P(N) ((N) == 0) | |
4418 | @end smallexample | |
4419 | ||
4420 | If the machine has register windows, so that the caller and the called | |
4421 | function use different registers for the return value, this macro | |
4422 | should recognize only the caller's register numbers. | |
4423 | ||
4424 | This macro has been deprecated. Use @code{TARGET_FUNCTION_VALUE_REGNO_P} | |
4425 | for a new target instead. | |
4426 | @end defmac | |
4427 | ||
4428 | @hook TARGET_FUNCTION_VALUE_REGNO_P | |
4429 | A target hook that return @code{true} if @var{regno} is the number of a hard | |
4430 | register in which the values of called function may come back. | |
4431 | ||
4432 | A register whose use for returning values is limited to serving as the | |
4433 | second of a pair (for a value of type @code{double}, say) need not be | |
4434 | recognized by this target hook. | |
4435 | ||
4436 | If the machine has register windows, so that the caller and the called | |
4437 | function use different registers for the return value, this target hook | |
4438 | should recognize only the caller's register numbers. | |
4439 | ||
4440 | If this hook is not defined, then FUNCTION_VALUE_REGNO_P will be used. | |
4441 | @end deftypefn | |
4442 | ||
4443 | @defmac APPLY_RESULT_SIZE | |
4444 | Define this macro if @samp{untyped_call} and @samp{untyped_return} | |
4445 | need more space than is implied by @code{FUNCTION_VALUE_REGNO_P} for | |
4446 | saving and restoring an arbitrary return value. | |
4447 | @end defmac | |
4448 | ||
4449 | @hook TARGET_RETURN_IN_MSB | |
4450 | This hook should return true if values of type @var{type} are returned | |
4451 | at the most significant end of a register (in other words, if they are | |
4452 | padded at the least significant end). You can assume that @var{type} | |
4453 | is returned in a register; the caller is required to check this. | |
4454 | ||
4455 | Note that the register provided by @code{TARGET_FUNCTION_VALUE} must | |
4456 | be able to hold the complete return value. For example, if a 1-, 2- | |
4457 | or 3-byte structure is returned at the most significant end of a | |
4458 | 4-byte register, @code{TARGET_FUNCTION_VALUE} should provide an | |
4459 | @code{SImode} rtx. | |
4460 | @end deftypefn | |
4461 | ||
4462 | @node Aggregate Return | |
4463 | @subsection How Large Values Are Returned | |
4464 | @cindex aggregates as return values | |
4465 | @cindex large return values | |
4466 | @cindex returning aggregate values | |
4467 | @cindex structure value address | |
4468 | ||
4469 | When a function value's mode is @code{BLKmode} (and in some other | |
4470 | cases), the value is not returned according to | |
4471 | @code{TARGET_FUNCTION_VALUE} (@pxref{Scalar Return}). Instead, the | |
4472 | caller passes the address of a block of memory in which the value | |
4473 | should be stored. This address is called the @dfn{structure value | |
4474 | address}. | |
4475 | ||
4476 | This section describes how to control returning structure values in | |
4477 | memory. | |
4478 | ||
4479 | @hook TARGET_RETURN_IN_MEMORY | |
4480 | This target hook should return a nonzero value to say to return the | |
4481 | function value in memory, just as large structures are always returned. | |
4482 | Here @var{type} will be the data type of the value, and @var{fntype} | |
4483 | will be the type of the function doing the returning, or @code{NULL} for | |
4484 | libcalls. | |
4485 | ||
4486 | Note that values of mode @code{BLKmode} must be explicitly handled | |
4487 | by this function. Also, the option @option{-fpcc-struct-return} | |
4488 | takes effect regardless of this macro. On most systems, it is | |
4489 | possible to leave the hook undefined; this causes a default | |
4490 | definition to be used, whose value is the constant 1 for @code{BLKmode} | |
4491 | values, and 0 otherwise. | |
4492 | ||
4493 | Do not use this hook to indicate that structures and unions should always | |
4494 | be returned in memory. You should instead use @code{DEFAULT_PCC_STRUCT_RETURN} | |
4495 | to indicate this. | |
4496 | @end deftypefn | |
4497 | ||
4498 | @defmac DEFAULT_PCC_STRUCT_RETURN | |
4499 | Define this macro to be 1 if all structure and union return values must be | |
4500 | in memory. Since this results in slower code, this should be defined | |
4501 | only if needed for compatibility with other compilers or with an ABI@. | |
4502 | If you define this macro to be 0, then the conventions used for structure | |
4503 | and union return values are decided by the @code{TARGET_RETURN_IN_MEMORY} | |
4504 | target hook. | |
4505 | ||
4506 | If not defined, this defaults to the value 1. | |
4507 | @end defmac | |
4508 | ||
4509 | @hook TARGET_STRUCT_VALUE_RTX | |
4510 | This target hook should return the location of the structure value | |
4511 | address (normally a @code{mem} or @code{reg}), or 0 if the address is | |
4512 | passed as an ``invisible'' first argument. Note that @var{fndecl} may | |
4513 | be @code{NULL}, for libcalls. You do not need to define this target | |
4514 | hook if the address is always passed as an ``invisible'' first | |
4515 | argument. | |
4516 | ||
4517 | On some architectures the place where the structure value address | |
4518 | is found by the called function is not the same place that the | |
4519 | caller put it. This can be due to register windows, or it could | |
4520 | be because the function prologue moves it to a different place. | |
4521 | @var{incoming} is @code{1} or @code{2} when the location is needed in | |
4522 | the context of the called function, and @code{0} in the context of | |
4523 | the caller. | |
4524 | ||
4525 | If @var{incoming} is nonzero and the address is to be found on the | |
4526 | stack, return a @code{mem} which refers to the frame pointer. If | |
4527 | @var{incoming} is @code{2}, the result is being used to fetch the | |
4528 | structure value address at the beginning of a function. If you need | |
4529 | to emit adjusting code, you should do it at this point. | |
4530 | @end deftypefn | |
4531 | ||
4532 | @defmac PCC_STATIC_STRUCT_RETURN | |
4533 | Define this macro if the usual system convention on the target machine | |
4534 | for returning structures and unions is for the called function to return | |
4535 | the address of a static variable containing the value. | |
4536 | ||
4537 | Do not define this if the usual system convention is for the caller to | |
4538 | pass an address to the subroutine. | |
4539 | ||
4540 | This macro has effect in @option{-fpcc-struct-return} mode, but it does | |
4541 | nothing when you use @option{-freg-struct-return} mode. | |
4542 | @end defmac | |
4543 | ||
ffa88471 SE |
4544 | @hook TARGET_GET_RAW_RESULT_MODE |
4545 | ||
4546 | @hook TARGET_GET_RAW_ARG_MODE | |
4547 | ||
38f8b050 JR |
4548 | @node Caller Saves |
4549 | @subsection Caller-Saves Register Allocation | |
4550 | ||
4551 | If you enable it, GCC can save registers around function calls. This | |
4552 | makes it possible to use call-clobbered registers to hold variables that | |
4553 | must live across calls. | |
4554 | ||
4555 | @defmac CALLER_SAVE_PROFITABLE (@var{refs}, @var{calls}) | |
4556 | A C expression to determine whether it is worthwhile to consider placing | |
4557 | a pseudo-register in a call-clobbered hard register and saving and | |
4558 | restoring it around each function call. The expression should be 1 when | |
4559 | this is worth doing, and 0 otherwise. | |
4560 | ||
4561 | If you don't define this macro, a default is used which is good on most | |
4562 | machines: @code{4 * @var{calls} < @var{refs}}. | |
4563 | @end defmac | |
4564 | ||
4565 | @defmac HARD_REGNO_CALLER_SAVE_MODE (@var{regno}, @var{nregs}) | |
4566 | A C expression specifying which mode is required for saving @var{nregs} | |
4567 | of a pseudo-register in call-clobbered hard register @var{regno}. If | |
4568 | @var{regno} is unsuitable for caller save, @code{VOIDmode} should be | |
4569 | returned. For most machines this macro need not be defined since GCC | |
4570 | will select the smallest suitable mode. | |
4571 | @end defmac | |
4572 | ||
4573 | @node Function Entry | |
4574 | @subsection Function Entry and Exit | |
4575 | @cindex function entry and exit | |
4576 | @cindex prologue | |
4577 | @cindex epilogue | |
4578 | ||
4579 | This section describes the macros that output function entry | |
4580 | (@dfn{prologue}) and exit (@dfn{epilogue}) code. | |
4581 | ||
4582 | @hook TARGET_ASM_FUNCTION_PROLOGUE | |
4583 | If defined, a function that outputs the assembler code for entry to a | |
4584 | function. The prologue is responsible for setting up the stack frame, | |
4585 | initializing the frame pointer register, saving registers that must be | |
4586 | saved, and allocating @var{size} additional bytes of storage for the | |
4587 | local variables. @var{size} is an integer. @var{file} is a stdio | |
4588 | stream to which the assembler code should be output. | |
4589 | ||
4590 | The label for the beginning of the function need not be output by this | |
4591 | macro. That has already been done when the macro is run. | |
4592 | ||
4593 | @findex regs_ever_live | |
4594 | To determine which registers to save, the macro can refer to the array | |
4595 | @code{regs_ever_live}: element @var{r} is nonzero if hard register | |
4596 | @var{r} is used anywhere within the function. This implies the function | |
4597 | prologue should save register @var{r}, provided it is not one of the | |
4598 | call-used registers. (@code{TARGET_ASM_FUNCTION_EPILOGUE} must likewise use | |
4599 | @code{regs_ever_live}.) | |
4600 | ||
4601 | On machines that have ``register windows'', the function entry code does | |
4602 | not save on the stack the registers that are in the windows, even if | |
4603 | they are supposed to be preserved by function calls; instead it takes | |
4604 | appropriate steps to ``push'' the register stack, if any non-call-used | |
4605 | registers are used in the function. | |
4606 | ||
4607 | @findex frame_pointer_needed | |
4608 | On machines where functions may or may not have frame-pointers, the | |
4609 | function entry code must vary accordingly; it must set up the frame | |
4610 | pointer if one is wanted, and not otherwise. To determine whether a | |
4611 | frame pointer is in wanted, the macro can refer to the variable | |
4612 | @code{frame_pointer_needed}. The variable's value will be 1 at run | |
4613 | time in a function that needs a frame pointer. @xref{Elimination}. | |
4614 | ||
4615 | The function entry code is responsible for allocating any stack space | |
4616 | required for the function. This stack space consists of the regions | |
4617 | listed below. In most cases, these regions are allocated in the | |
4618 | order listed, with the last listed region closest to the top of the | |
4619 | stack (the lowest address if @code{STACK_GROWS_DOWNWARD} is defined, and | |
4620 | the highest address if it is not defined). You can use a different order | |
4621 | for a machine if doing so is more convenient or required for | |
4622 | compatibility reasons. Except in cases where required by standard | |
4623 | or by a debugger, there is no reason why the stack layout used by GCC | |
4624 | need agree with that used by other compilers for a machine. | |
4625 | @end deftypefn | |
4626 | ||
4627 | @hook TARGET_ASM_FUNCTION_END_PROLOGUE | |
4628 | If defined, a function that outputs assembler code at the end of a | |
4629 | prologue. This should be used when the function prologue is being | |
4630 | emitted as RTL, and you have some extra assembler that needs to be | |
4631 | emitted. @xref{prologue instruction pattern}. | |
4632 | @end deftypefn | |
4633 | ||
4634 | @hook TARGET_ASM_FUNCTION_BEGIN_EPILOGUE | |
4635 | If defined, a function that outputs assembler code at the start of an | |
4636 | epilogue. This should be used when the function epilogue is being | |
4637 | emitted as RTL, and you have some extra assembler that needs to be | |
4638 | emitted. @xref{epilogue instruction pattern}. | |
4639 | @end deftypefn | |
4640 | ||
4641 | @hook TARGET_ASM_FUNCTION_EPILOGUE | |
4642 | If defined, a function that outputs the assembler code for exit from a | |
4643 | function. The epilogue is responsible for restoring the saved | |
4644 | registers and stack pointer to their values when the function was | |
4645 | called, and returning control to the caller. This macro takes the | |
4646 | same arguments as the macro @code{TARGET_ASM_FUNCTION_PROLOGUE}, and the | |
4647 | registers to restore are determined from @code{regs_ever_live} and | |
4648 | @code{CALL_USED_REGISTERS} in the same way. | |
4649 | ||
4650 | On some machines, there is a single instruction that does all the work | |
4651 | of returning from the function. On these machines, give that | |
4652 | instruction the name @samp{return} and do not define the macro | |
4653 | @code{TARGET_ASM_FUNCTION_EPILOGUE} at all. | |
4654 | ||
4655 | Do not define a pattern named @samp{return} if you want the | |
4656 | @code{TARGET_ASM_FUNCTION_EPILOGUE} to be used. If you want the target | |
4657 | switches to control whether return instructions or epilogues are used, | |
4658 | define a @samp{return} pattern with a validity condition that tests the | |
4659 | target switches appropriately. If the @samp{return} pattern's validity | |
4660 | condition is false, epilogues will be used. | |
4661 | ||
4662 | On machines where functions may or may not have frame-pointers, the | |
4663 | function exit code must vary accordingly. Sometimes the code for these | |
4664 | two cases is completely different. To determine whether a frame pointer | |
4665 | is wanted, the macro can refer to the variable | |
4666 | @code{frame_pointer_needed}. The variable's value will be 1 when compiling | |
4667 | a function that needs a frame pointer. | |
4668 | ||
4669 | Normally, @code{TARGET_ASM_FUNCTION_PROLOGUE} and | |
4670 | @code{TARGET_ASM_FUNCTION_EPILOGUE} must treat leaf functions specially. | |
4671 | The C variable @code{current_function_is_leaf} is nonzero for such a | |
4672 | function. @xref{Leaf Functions}. | |
4673 | ||
4674 | On some machines, some functions pop their arguments on exit while | |
4675 | others leave that for the caller to do. For example, the 68020 when | |
4676 | given @option{-mrtd} pops arguments in functions that take a fixed | |
4677 | number of arguments. | |
4678 | ||
4679 | @findex current_function_pops_args | |
4680 | Your definition of the macro @code{RETURN_POPS_ARGS} decides which | |
4681 | functions pop their own arguments. @code{TARGET_ASM_FUNCTION_EPILOGUE} | |
4682 | needs to know what was decided. The number of bytes of the current | |
4683 | function's arguments that this function should pop is available in | |
4684 | @code{crtl->args.pops_args}. @xref{Scalar Return}. | |
4685 | @end deftypefn | |
4686 | ||
4687 | @itemize @bullet | |
4688 | @item | |
4689 | @findex current_function_pretend_args_size | |
4690 | A region of @code{current_function_pretend_args_size} bytes of | |
4691 | uninitialized space just underneath the first argument arriving on the | |
4692 | stack. (This may not be at the very start of the allocated stack region | |
4693 | if the calling sequence has pushed anything else since pushing the stack | |
4694 | arguments. But usually, on such machines, nothing else has been pushed | |
4695 | yet, because the function prologue itself does all the pushing.) This | |
4696 | region is used on machines where an argument may be passed partly in | |
4697 | registers and partly in memory, and, in some cases to support the | |
4698 | features in @code{<stdarg.h>}. | |
4699 | ||
4700 | @item | |
4701 | An area of memory used to save certain registers used by the function. | |
4702 | The size of this area, which may also include space for such things as | |
4703 | the return address and pointers to previous stack frames, is | |
4704 | machine-specific and usually depends on which registers have been used | |
4705 | in the function. Machines with register windows often do not require | |
4706 | a save area. | |
4707 | ||
4708 | @item | |
4709 | A region of at least @var{size} bytes, possibly rounded up to an allocation | |
4710 | boundary, to contain the local variables of the function. On some machines, | |
4711 | this region and the save area may occur in the opposite order, with the | |
4712 | save area closer to the top of the stack. | |
4713 | ||
4714 | @item | |
4715 | @cindex @code{ACCUMULATE_OUTGOING_ARGS} and stack frames | |
4716 | Optionally, when @code{ACCUMULATE_OUTGOING_ARGS} is defined, a region of | |
4717 | @code{current_function_outgoing_args_size} bytes to be used for outgoing | |
4718 | argument lists of the function. @xref{Stack Arguments}. | |
4719 | @end itemize | |
4720 | ||
4721 | @defmac EXIT_IGNORE_STACK | |
4722 | Define this macro as a C expression that is nonzero if the return | |
4723 | instruction or the function epilogue ignores the value of the stack | |
4724 | pointer; in other words, if it is safe to delete an instruction to | |
4725 | adjust the stack pointer before a return from the function. The | |
4726 | default is 0. | |
4727 | ||
4728 | Note that this macro's value is relevant only for functions for which | |
4729 | frame pointers are maintained. It is never safe to delete a final | |
4730 | stack adjustment in a function that has no frame pointer, and the | |
4731 | compiler knows this regardless of @code{EXIT_IGNORE_STACK}. | |
4732 | @end defmac | |
4733 | ||
4734 | @defmac EPILOGUE_USES (@var{regno}) | |
4735 | Define this macro as a C expression that is nonzero for registers that are | |
4736 | used by the epilogue or the @samp{return} pattern. The stack and frame | |
4737 | pointer registers are already assumed to be used as needed. | |
4738 | @end defmac | |
4739 | ||
4740 | @defmac EH_USES (@var{regno}) | |
4741 | Define this macro as a C expression that is nonzero for registers that are | |
4742 | used by the exception handling mechanism, and so should be considered live | |
4743 | on entry to an exception edge. | |
4744 | @end defmac | |
4745 | ||
4746 | @defmac DELAY_SLOTS_FOR_EPILOGUE | |
4747 | Define this macro if the function epilogue contains delay slots to which | |
4748 | instructions from the rest of the function can be ``moved''. The | |
4749 | definition should be a C expression whose value is an integer | |
4750 | representing the number of delay slots there. | |
4751 | @end defmac | |
4752 | ||
4753 | @defmac ELIGIBLE_FOR_EPILOGUE_DELAY (@var{insn}, @var{n}) | |
4754 | A C expression that returns 1 if @var{insn} can be placed in delay | |
4755 | slot number @var{n} of the epilogue. | |
4756 | ||
4757 | The argument @var{n} is an integer which identifies the delay slot now | |
4758 | being considered (since different slots may have different rules of | |
4759 | eligibility). It is never negative and is always less than the number | |
4760 | of epilogue delay slots (what @code{DELAY_SLOTS_FOR_EPILOGUE} returns). | |
4761 | If you reject a particular insn for a given delay slot, in principle, it | |
4762 | may be reconsidered for a subsequent delay slot. Also, other insns may | |
4763 | (at least in principle) be considered for the so far unfilled delay | |
4764 | slot. | |
4765 | ||
4766 | @findex current_function_epilogue_delay_list | |
4767 | @findex final_scan_insn | |
4768 | The insns accepted to fill the epilogue delay slots are put in an RTL | |
4769 | list made with @code{insn_list} objects, stored in the variable | |
4770 | @code{current_function_epilogue_delay_list}. The insn for the first | |
4771 | delay slot comes first in the list. Your definition of the macro | |
4772 | @code{TARGET_ASM_FUNCTION_EPILOGUE} should fill the delay slots by | |
4773 | outputting the insns in this list, usually by calling | |
4774 | @code{final_scan_insn}. | |
4775 | ||
4776 | You need not define this macro if you did not define | |
4777 | @code{DELAY_SLOTS_FOR_EPILOGUE}. | |
4778 | @end defmac | |
4779 | ||
4780 | @hook TARGET_ASM_OUTPUT_MI_THUNK | |
4781 | A function that outputs the assembler code for a thunk | |
4782 | function, used to implement C++ virtual function calls with multiple | |
4783 | inheritance. The thunk acts as a wrapper around a virtual function, | |
4784 | adjusting the implicit object parameter before handing control off to | |
4785 | the real function. | |
4786 | ||
4787 | First, emit code to add the integer @var{delta} to the location that | |
4788 | contains the incoming first argument. Assume that this argument | |
4789 | contains a pointer, and is the one used to pass the @code{this} pointer | |
4790 | in C++. This is the incoming argument @emph{before} the function prologue, | |
4791 | e.g.@: @samp{%o0} on a sparc. The addition must preserve the values of | |
4792 | all other incoming arguments. | |
4793 | ||
4794 | Then, if @var{vcall_offset} is nonzero, an additional adjustment should be | |
4795 | made after adding @code{delta}. In particular, if @var{p} is the | |
4796 | adjusted pointer, the following adjustment should be made: | |
4797 | ||
4798 | @smallexample | |
4799 | p += (*((ptrdiff_t **)p))[vcall_offset/sizeof(ptrdiff_t)] | |
4800 | @end smallexample | |
4801 | ||
4802 | After the additions, emit code to jump to @var{function}, which is a | |
4803 | @code{FUNCTION_DECL}. This is a direct pure jump, not a call, and does | |
4804 | not touch the return address. Hence returning from @var{FUNCTION} will | |
4805 | return to whoever called the current @samp{thunk}. | |
4806 | ||
4807 | The effect must be as if @var{function} had been called directly with | |
4808 | the adjusted first argument. This macro is responsible for emitting all | |
4809 | of the code for a thunk function; @code{TARGET_ASM_FUNCTION_PROLOGUE} | |
4810 | and @code{TARGET_ASM_FUNCTION_EPILOGUE} are not invoked. | |
4811 | ||
4812 | The @var{thunk_fndecl} is redundant. (@var{delta} and @var{function} | |
4813 | have already been extracted from it.) It might possibly be useful on | |
4814 | some targets, but probably not. | |
4815 | ||
4816 | If you do not define this macro, the target-independent code in the C++ | |
4817 | front end will generate a less efficient heavyweight thunk that calls | |
4818 | @var{function} instead of jumping to it. The generic approach does | |
4819 | not support varargs. | |
4820 | @end deftypefn | |
4821 | ||
4822 | @hook TARGET_ASM_CAN_OUTPUT_MI_THUNK | |
4823 | A function that returns true if TARGET_ASM_OUTPUT_MI_THUNK would be able | |
4824 | to output the assembler code for the thunk function specified by the | |
4825 | arguments it is passed, and false otherwise. In the latter case, the | |
4826 | generic approach will be used by the C++ front end, with the limitations | |
4827 | previously exposed. | |
4828 | @end deftypefn | |
4829 | ||
4830 | @node Profiling | |
4831 | @subsection Generating Code for Profiling | |
4832 | @cindex profiling, code generation | |
4833 | ||
4834 | These macros will help you generate code for profiling. | |
4835 | ||
4836 | @defmac FUNCTION_PROFILER (@var{file}, @var{labelno}) | |
4837 | A C statement or compound statement to output to @var{file} some | |
4838 | assembler code to call the profiling subroutine @code{mcount}. | |
4839 | ||
4840 | @findex mcount | |
4841 | The details of how @code{mcount} expects to be called are determined by | |
4842 | your operating system environment, not by GCC@. To figure them out, | |
4843 | compile a small program for profiling using the system's installed C | |
4844 | compiler and look at the assembler code that results. | |
4845 | ||
4846 | Older implementations of @code{mcount} expect the address of a counter | |
4847 | variable to be loaded into some register. The name of this variable is | |
4848 | @samp{LP} followed by the number @var{labelno}, so you would generate | |
4849 | the name using @samp{LP%d} in a @code{fprintf}. | |
4850 | @end defmac | |
4851 | ||
4852 | @defmac PROFILE_HOOK | |
4853 | A C statement or compound statement to output to @var{file} some assembly | |
4854 | code to call the profiling subroutine @code{mcount} even the target does | |
4855 | not support profiling. | |
4856 | @end defmac | |
4857 | ||
4858 | @defmac NO_PROFILE_COUNTERS | |
4859 | Define this macro to be an expression with a nonzero value if the | |
4860 | @code{mcount} subroutine on your system does not need a counter variable | |
4861 | allocated for each function. This is true for almost all modern | |
4862 | implementations. If you define this macro, you must not use the | |
4863 | @var{labelno} argument to @code{FUNCTION_PROFILER}. | |
4864 | @end defmac | |
4865 | ||
4866 | @defmac PROFILE_BEFORE_PROLOGUE | |
4867 | Define this macro if the code for function profiling should come before | |
4868 | the function prologue. Normally, the profiling code comes after. | |
4869 | @end defmac | |
4870 | ||
4871 | @node Tail Calls | |
4872 | @subsection Permitting tail calls | |
4873 | @cindex tail calls | |
4874 | ||
4875 | @hook TARGET_FUNCTION_OK_FOR_SIBCALL | |
4876 | True if it is ok to do sibling call optimization for the specified | |
4877 | call expression @var{exp}. @var{decl} will be the called function, | |
4878 | or @code{NULL} if this is an indirect call. | |
4879 | ||
4880 | It is not uncommon for limitations of calling conventions to prevent | |
4881 | tail calls to functions outside the current unit of translation, or | |
4882 | during PIC compilation. The hook is used to enforce these restrictions, | |
4883 | as the @code{sibcall} md pattern can not fail, or fall over to a | |
4884 | ``normal'' call. The criteria for successful sibling call optimization | |
4885 | may vary greatly between different architectures. | |
4886 | @end deftypefn | |
4887 | ||
4888 | @hook TARGET_EXTRA_LIVE_ON_ENTRY | |
4889 | Add any hard registers to @var{regs} that are live on entry to the | |
4890 | function. This hook only needs to be defined to provide registers that | |
4891 | cannot be found by examination of FUNCTION_ARG_REGNO_P, the callee saved | |
4892 | registers, STATIC_CHAIN_INCOMING_REGNUM, STATIC_CHAIN_REGNUM, | |
4893 | TARGET_STRUCT_VALUE_RTX, FRAME_POINTER_REGNUM, EH_USES, | |
4894 | FRAME_POINTER_REGNUM, ARG_POINTER_REGNUM, and the PIC_OFFSET_TABLE_REGNUM. | |
4895 | @end deftypefn | |
4896 | ||
4897 | @node Stack Smashing Protection | |
4898 | @subsection Stack smashing protection | |
4899 | @cindex stack smashing protection | |
4900 | ||
4901 | @hook TARGET_STACK_PROTECT_GUARD | |
4902 | This hook returns a @code{DECL} node for the external variable to use | |
4903 | for the stack protection guard. This variable is initialized by the | |
4904 | runtime to some random value and is used to initialize the guard value | |
4905 | that is placed at the top of the local stack frame. The type of this | |
4906 | variable must be @code{ptr_type_node}. | |
4907 | ||
4908 | The default version of this hook creates a variable called | |
4909 | @samp{__stack_chk_guard}, which is normally defined in @file{libgcc2.c}. | |
4910 | @end deftypefn | |
4911 | ||
4912 | @hook TARGET_STACK_PROTECT_FAIL | |
4913 | This hook returns a tree expression that alerts the runtime that the | |
4914 | stack protect guard variable has been modified. This expression should | |
4915 | involve a call to a @code{noreturn} function. | |
4916 | ||
4917 | The default version of this hook invokes a function called | |
4918 | @samp{__stack_chk_fail}, taking no arguments. This function is | |
4919 | normally defined in @file{libgcc2.c}. | |
4920 | @end deftypefn | |
4921 | ||
7458026b ILT |
4922 | @hook TARGET_SUPPORTS_SPLIT_STACK |
4923 | ||
38f8b050 JR |
4924 | @node Varargs |
4925 | @section Implementing the Varargs Macros | |
4926 | @cindex varargs implementation | |
4927 | ||
4928 | GCC comes with an implementation of @code{<varargs.h>} and | |
4929 | @code{<stdarg.h>} that work without change on machines that pass arguments | |
4930 | on the stack. Other machines require their own implementations of | |
4931 | varargs, and the two machine independent header files must have | |
4932 | conditionals to include it. | |
4933 | ||
4934 | ISO @code{<stdarg.h>} differs from traditional @code{<varargs.h>} mainly in | |
4935 | the calling convention for @code{va_start}. The traditional | |
4936 | implementation takes just one argument, which is the variable in which | |
4937 | to store the argument pointer. The ISO implementation of | |
4938 | @code{va_start} takes an additional second argument. The user is | |
4939 | supposed to write the last named argument of the function here. | |
4940 | ||
4941 | However, @code{va_start} should not use this argument. The way to find | |
4942 | the end of the named arguments is with the built-in functions described | |
4943 | below. | |
4944 | ||
4945 | @defmac __builtin_saveregs () | |
4946 | Use this built-in function to save the argument registers in memory so | |
4947 | that the varargs mechanism can access them. Both ISO and traditional | |
4948 | versions of @code{va_start} must use @code{__builtin_saveregs}, unless | |
4949 | you use @code{TARGET_SETUP_INCOMING_VARARGS} (see below) instead. | |
4950 | ||
4951 | On some machines, @code{__builtin_saveregs} is open-coded under the | |
4952 | control of the target hook @code{TARGET_EXPAND_BUILTIN_SAVEREGS}. On | |
4953 | other machines, it calls a routine written in assembler language, | |
4954 | found in @file{libgcc2.c}. | |
4955 | ||
4956 | Code generated for the call to @code{__builtin_saveregs} appears at the | |
4957 | beginning of the function, as opposed to where the call to | |
4958 | @code{__builtin_saveregs} is written, regardless of what the code is. | |
4959 | This is because the registers must be saved before the function starts | |
4960 | to use them for its own purposes. | |
4961 | @c i rewrote the first sentence above to fix an overfull hbox. --mew | |
4962 | @c 10feb93 | |
4963 | @end defmac | |
4964 | ||
38f8b050 | 4965 | @defmac __builtin_next_arg (@var{lastarg}) |
c59a0a1d | 4966 | This builtin returns the address of the first anonymous stack |
38f8b050 JR |
4967 | argument, as type @code{void *}. If @code{ARGS_GROW_DOWNWARD}, it |
4968 | returns the address of the location above the first anonymous stack | |
4969 | argument. Use it in @code{va_start} to initialize the pointer for | |
4970 | fetching arguments from the stack. Also use it in @code{va_start} to | |
4971 | verify that the second parameter @var{lastarg} is the last named argument | |
4972 | of the current function. | |
4973 | @end defmac | |
4974 | ||
4975 | @defmac __builtin_classify_type (@var{object}) | |
4976 | Since each machine has its own conventions for which data types are | |
4977 | passed in which kind of register, your implementation of @code{va_arg} | |
4978 | has to embody these conventions. The easiest way to categorize the | |
4979 | specified data type is to use @code{__builtin_classify_type} together | |
4980 | with @code{sizeof} and @code{__alignof__}. | |
4981 | ||
4982 | @code{__builtin_classify_type} ignores the value of @var{object}, | |
4983 | considering only its data type. It returns an integer describing what | |
4984 | kind of type that is---integer, floating, pointer, structure, and so on. | |
4985 | ||
4986 | The file @file{typeclass.h} defines an enumeration that you can use to | |
4987 | interpret the values of @code{__builtin_classify_type}. | |
4988 | @end defmac | |
4989 | ||
4990 | These machine description macros help implement varargs: | |
4991 | ||
4992 | @hook TARGET_EXPAND_BUILTIN_SAVEREGS | |
4993 | If defined, this hook produces the machine-specific code for a call to | |
4994 | @code{__builtin_saveregs}. This code will be moved to the very | |
4995 | beginning of the function, before any parameter access are made. The | |
4996 | return value of this function should be an RTX that contains the value | |
4997 | to use as the return of @code{__builtin_saveregs}. | |
4998 | @end deftypefn | |
4999 | ||
5000 | @hook TARGET_SETUP_INCOMING_VARARGS | |
5001 | This target hook offers an alternative to using | |
5002 | @code{__builtin_saveregs} and defining the hook | |
5003 | @code{TARGET_EXPAND_BUILTIN_SAVEREGS}. Use it to store the anonymous | |
5004 | register arguments into the stack so that all the arguments appear to | |
5005 | have been passed consecutively on the stack. Once this is done, you can | |
5006 | use the standard implementation of varargs that works for machines that | |
5007 | pass all their arguments on the stack. | |
5008 | ||
5009 | The argument @var{args_so_far} points to the @code{CUMULATIVE_ARGS} data | |
5010 | structure, containing the values that are obtained after processing the | |
5011 | named arguments. The arguments @var{mode} and @var{type} describe the | |
5012 | last named argument---its machine mode and its data type as a tree node. | |
5013 | ||
5014 | The target hook should do two things: first, push onto the stack all the | |
5015 | argument registers @emph{not} used for the named arguments, and second, | |
5016 | store the size of the data thus pushed into the @code{int}-valued | |
5017 | variable pointed to by @var{pretend_args_size}. The value that you | |
5018 | store here will serve as additional offset for setting up the stack | |
5019 | frame. | |
5020 | ||
5021 | Because you must generate code to push the anonymous arguments at | |
5022 | compile time without knowing their data types, | |
5023 | @code{TARGET_SETUP_INCOMING_VARARGS} is only useful on machines that | |
5024 | have just a single category of argument register and use it uniformly | |
5025 | for all data types. | |
5026 | ||
5027 | If the argument @var{second_time} is nonzero, it means that the | |
5028 | arguments of the function are being analyzed for the second time. This | |
5029 | happens for an inline function, which is not actually compiled until the | |
5030 | end of the source file. The hook @code{TARGET_SETUP_INCOMING_VARARGS} should | |
5031 | not generate any instructions in this case. | |
5032 | @end deftypefn | |
5033 | ||
5034 | @hook TARGET_STRICT_ARGUMENT_NAMING | |
5035 | Define this hook to return @code{true} if the location where a function | |
5036 | argument is passed depends on whether or not it is a named argument. | |
5037 | ||
b25b9e8f | 5038 | This hook controls how the @var{named} argument to @code{TARGET_FUNCTION_ARG} |
38f8b050 JR |
5039 | is set for varargs and stdarg functions. If this hook returns |
5040 | @code{true}, the @var{named} argument is always true for named | |
5041 | arguments, and false for unnamed arguments. If it returns @code{false}, | |
5042 | but @code{TARGET_PRETEND_OUTGOING_VARARGS_NAMED} returns @code{true}, | |
5043 | then all arguments are treated as named. Otherwise, all named arguments | |
5044 | except the last are treated as named. | |
5045 | ||
5046 | You need not define this hook if it always returns @code{false}. | |
5047 | @end deftypefn | |
5048 | ||
5049 | @hook TARGET_PRETEND_OUTGOING_VARARGS_NAMED | |
5050 | If you need to conditionally change ABIs so that one works with | |
5051 | @code{TARGET_SETUP_INCOMING_VARARGS}, but the other works like neither | |
5052 | @code{TARGET_SETUP_INCOMING_VARARGS} nor @code{TARGET_STRICT_ARGUMENT_NAMING} was | |
5053 | defined, then define this hook to return @code{true} if | |
5054 | @code{TARGET_SETUP_INCOMING_VARARGS} is used, @code{false} otherwise. | |
5055 | Otherwise, you should not define this hook. | |
5056 | @end deftypefn | |
5057 | ||
5058 | @node Trampolines | |
5059 | @section Trampolines for Nested Functions | |
5060 | @cindex trampolines for nested functions | |
5061 | @cindex nested functions, trampolines for | |
5062 | ||
5063 | A @dfn{trampoline} is a small piece of code that is created at run time | |
5064 | when the address of a nested function is taken. It normally resides on | |
5065 | the stack, in the stack frame of the containing function. These macros | |
5066 | tell GCC how to generate code to allocate and initialize a | |
5067 | trampoline. | |
5068 | ||
5069 | The instructions in the trampoline must do two things: load a constant | |
5070 | address into the static chain register, and jump to the real address of | |
5071 | the nested function. On CISC machines such as the m68k, this requires | |
5072 | two instructions, a move immediate and a jump. Then the two addresses | |
5073 | exist in the trampoline as word-long immediate operands. On RISC | |
5074 | machines, it is often necessary to load each address into a register in | |
5075 | two parts. Then pieces of each address form separate immediate | |
5076 | operands. | |
5077 | ||
5078 | The code generated to initialize the trampoline must store the variable | |
5079 | parts---the static chain value and the function address---into the | |
5080 | immediate operands of the instructions. On a CISC machine, this is | |
5081 | simply a matter of copying each address to a memory reference at the | |
5082 | proper offset from the start of the trampoline. On a RISC machine, it | |
5083 | may be necessary to take out pieces of the address and store them | |
5084 | separately. | |
5085 | ||
5086 | @hook TARGET_ASM_TRAMPOLINE_TEMPLATE | |
5087 | This hook is called by @code{assemble_trampoline_template} to output, | |
5088 | on the stream @var{f}, assembler code for a block of data that contains | |
5089 | the constant parts of a trampoline. This code should not include a | |
5090 | label---the label is taken care of automatically. | |
5091 | ||
5092 | If you do not define this hook, it means no template is needed | |
5093 | for the target. Do not define this hook on systems where the block move | |
5094 | code to copy the trampoline into place would be larger than the code | |
5095 | to generate it on the spot. | |
5096 | @end deftypefn | |
5097 | ||
5098 | @defmac TRAMPOLINE_SECTION | |
5099 | Return the section into which the trampoline template is to be placed | |
5100 | (@pxref{Sections}). The default value is @code{readonly_data_section}. | |
5101 | @end defmac | |
5102 | ||
5103 | @defmac TRAMPOLINE_SIZE | |
5104 | A C expression for the size in bytes of the trampoline, as an integer. | |
5105 | @end defmac | |
5106 | ||
5107 | @defmac TRAMPOLINE_ALIGNMENT | |
5108 | Alignment required for trampolines, in bits. | |
5109 | ||
5110 | If you don't define this macro, the value of @code{FUNCTION_ALIGNMENT} | |
5111 | is used for aligning trampolines. | |
5112 | @end defmac | |
5113 | ||
5114 | @hook TARGET_TRAMPOLINE_INIT | |
5115 | This hook is called to initialize a trampoline. | |
5116 | @var{m_tramp} is an RTX for the memory block for the trampoline; @var{fndecl} | |
5117 | is the @code{FUNCTION_DECL} for the nested function; @var{static_chain} is an | |
5118 | RTX for the static chain value that should be passed to the function | |
5119 | when it is called. | |
5120 | ||
5121 | If the target defines @code{TARGET_ASM_TRAMPOLINE_TEMPLATE}, then the | |
5122 | first thing this hook should do is emit a block move into @var{m_tramp} | |
5123 | from the memory block returned by @code{assemble_trampoline_template}. | |
ff2ce160 | 5124 | Note that the block move need only cover the constant parts of the |
38f8b050 JR |
5125 | trampoline. If the target isolates the variable parts of the trampoline |
5126 | to the end, not all @code{TRAMPOLINE_SIZE} bytes need be copied. | |
5127 | ||
5128 | If the target requires any other actions, such as flushing caches or | |
ff2ce160 | 5129 | enabling stack execution, these actions should be performed after |
38f8b050 JR |
5130 | initializing the trampoline proper. |
5131 | @end deftypefn | |
5132 | ||
5133 | @hook TARGET_TRAMPOLINE_ADJUST_ADDRESS | |
5134 | This hook should perform any machine-specific adjustment in | |
5135 | the address of the trampoline. Its argument contains the address of the | |
5136 | memory block that was passed to @code{TARGET_TRAMPOLINE_INIT}. In case | |
5137 | the address to be used for a function call should be different from the | |
5138 | address at which the template was stored, the different address should | |
5139 | be returned; otherwise @var{addr} should be returned unchanged. | |
5140 | If this hook is not defined, @var{addr} will be used for function calls. | |
5141 | @end deftypefn | |
5142 | ||
5143 | Implementing trampolines is difficult on many machines because they have | |
5144 | separate instruction and data caches. Writing into a stack location | |
5145 | fails to clear the memory in the instruction cache, so when the program | |
5146 | jumps to that location, it executes the old contents. | |
5147 | ||
5148 | Here are two possible solutions. One is to clear the relevant parts of | |
5149 | the instruction cache whenever a trampoline is set up. The other is to | |
5150 | make all trampolines identical, by having them jump to a standard | |
5151 | subroutine. The former technique makes trampoline execution faster; the | |
5152 | latter makes initialization faster. | |
5153 | ||
5154 | To clear the instruction cache when a trampoline is initialized, define | |
5155 | the following macro. | |
5156 | ||
5157 | @defmac CLEAR_INSN_CACHE (@var{beg}, @var{end}) | |
5158 | If defined, expands to a C expression clearing the @emph{instruction | |
5159 | cache} in the specified interval. The definition of this macro would | |
5160 | typically be a series of @code{asm} statements. Both @var{beg} and | |
5161 | @var{end} are both pointer expressions. | |
5162 | @end defmac | |
5163 | ||
38f8b050 JR |
5164 | To use a standard subroutine, define the following macro. In addition, |
5165 | you must make sure that the instructions in a trampoline fill an entire | |
5166 | cache line with identical instructions, or else ensure that the | |
5167 | beginning of the trampoline code is always aligned at the same point in | |
5168 | its cache line. Look in @file{m68k.h} as a guide. | |
5169 | ||
5170 | @defmac TRANSFER_FROM_TRAMPOLINE | |
5171 | Define this macro if trampolines need a special subroutine to do their | |
5172 | work. The macro should expand to a series of @code{asm} statements | |
5173 | which will be compiled with GCC@. They go in a library function named | |
5174 | @code{__transfer_from_trampoline}. | |
5175 | ||
5176 | If you need to avoid executing the ordinary prologue code of a compiled | |
5177 | C function when you jump to the subroutine, you can do so by placing a | |
5178 | special label of your own in the assembler code. Use one @code{asm} | |
5179 | statement to generate an assembler label, and another to make the label | |
5180 | global. Then trampolines can use that label to jump directly to your | |
5181 | special assembler code. | |
5182 | @end defmac | |
5183 | ||
5184 | @node Library Calls | |
5185 | @section Implicit Calls to Library Routines | |
5186 | @cindex library subroutine names | |
5187 | @cindex @file{libgcc.a} | |
5188 | ||
5189 | @c prevent bad page break with this line | |
5190 | Here is an explanation of implicit calls to library routines. | |
5191 | ||
5192 | @defmac DECLARE_LIBRARY_RENAMES | |
5193 | This macro, if defined, should expand to a piece of C code that will get | |
5194 | expanded when compiling functions for libgcc.a. It can be used to | |
5195 | provide alternate names for GCC's internal library functions if there | |
5196 | are ABI-mandated names that the compiler should provide. | |
5197 | @end defmac | |
5198 | ||
5199 | @findex set_optab_libfunc | |
5200 | @findex init_one_libfunc | |
5201 | @hook TARGET_INIT_LIBFUNCS | |
5202 | This hook should declare additional library routines or rename | |
5203 | existing ones, using the functions @code{set_optab_libfunc} and | |
5204 | @code{init_one_libfunc} defined in @file{optabs.c}. | |
5205 | @code{init_optabs} calls this macro after initializing all the normal | |
5206 | library routines. | |
5207 | ||
5208 | The default is to do nothing. Most ports don't need to define this hook. | |
5209 | @end deftypefn | |
5210 | ||
cdbf4541 BS |
5211 | @hook TARGET_LIBFUNC_GNU_PREFIX |
5212 | ||
38f8b050 JR |
5213 | @defmac FLOAT_LIB_COMPARE_RETURNS_BOOL (@var{mode}, @var{comparison}) |
5214 | This macro should return @code{true} if the library routine that | |
5215 | implements the floating point comparison operator @var{comparison} in | |
5216 | mode @var{mode} will return a boolean, and @var{false} if it will | |
5217 | return a tristate. | |
5218 | ||
5219 | GCC's own floating point libraries return tristates from the | |
5220 | comparison operators, so the default returns false always. Most ports | |
5221 | don't need to define this macro. | |
5222 | @end defmac | |
5223 | ||
5224 | @defmac TARGET_LIB_INT_CMP_BIASED | |
5225 | This macro should evaluate to @code{true} if the integer comparison | |
5226 | functions (like @code{__cmpdi2}) return 0 to indicate that the first | |
5227 | operand is smaller than the second, 1 to indicate that they are equal, | |
5228 | and 2 to indicate that the first operand is greater than the second. | |
5229 | If this macro evaluates to @code{false} the comparison functions return | |
5230 | @minus{}1, 0, and 1 instead of 0, 1, and 2. If the target uses the routines | |
5231 | in @file{libgcc.a}, you do not need to define this macro. | |
5232 | @end defmac | |
5233 | ||
38f8b050 JR |
5234 | @cindex @code{EDOM}, implicit usage |
5235 | @findex matherr | |
5236 | @defmac TARGET_EDOM | |
5237 | The value of @code{EDOM} on the target machine, as a C integer constant | |
5238 | expression. If you don't define this macro, GCC does not attempt to | |
5239 | deposit the value of @code{EDOM} into @code{errno} directly. Look in | |
5240 | @file{/usr/include/errno.h} to find the value of @code{EDOM} on your | |
5241 | system. | |
5242 | ||
5243 | If you do not define @code{TARGET_EDOM}, then compiled code reports | |
5244 | domain errors by calling the library function and letting it report the | |
5245 | error. If mathematical functions on your system use @code{matherr} when | |
5246 | there is an error, then you should leave @code{TARGET_EDOM} undefined so | |
5247 | that @code{matherr} is used normally. | |
5248 | @end defmac | |
5249 | ||
5250 | @cindex @code{errno}, implicit usage | |
5251 | @defmac GEN_ERRNO_RTX | |
5252 | Define this macro as a C expression to create an rtl expression that | |
5253 | refers to the global ``variable'' @code{errno}. (On certain systems, | |
5254 | @code{errno} may not actually be a variable.) If you don't define this | |
5255 | macro, a reasonable default is used. | |
5256 | @end defmac | |
5257 | ||
5258 | @cindex C99 math functions, implicit usage | |
5259 | @defmac TARGET_C99_FUNCTIONS | |
5260 | When this macro is nonzero, GCC will implicitly optimize @code{sin} calls into | |
5261 | @code{sinf} and similarly for other functions defined by C99 standard. The | |
5262 | default is zero because a number of existing systems lack support for these | |
5263 | functions in their runtime so this macro needs to be redefined to one on | |
5264 | systems that do support the C99 runtime. | |
5265 | @end defmac | |
5266 | ||
5267 | @cindex sincos math function, implicit usage | |
5268 | @defmac TARGET_HAS_SINCOS | |
5269 | When this macro is nonzero, GCC will implicitly optimize calls to @code{sin} | |
5270 | and @code{cos} with the same argument to a call to @code{sincos}. The | |
5271 | default is zero. The target has to provide the following functions: | |
5272 | @smallexample | |
5273 | void sincos(double x, double *sin, double *cos); | |
5274 | void sincosf(float x, float *sin, float *cos); | |
5275 | void sincosl(long double x, long double *sin, long double *cos); | |
5276 | @end smallexample | |
5277 | @end defmac | |
5278 | ||
5279 | @defmac NEXT_OBJC_RUNTIME | |
5280 | Define this macro to generate code for Objective-C message sending using | |
5281 | the calling convention of the NeXT system. This calling convention | |
5282 | involves passing the object, the selector and the method arguments all | |
5283 | at once to the method-lookup library function. | |
5284 | ||
5285 | The default calling convention passes just the object and the selector | |
5286 | to the lookup function, which returns a pointer to the method. | |
5287 | @end defmac | |
5288 | ||
5289 | @node Addressing Modes | |
5290 | @section Addressing Modes | |
5291 | @cindex addressing modes | |
5292 | ||
5293 | @c prevent bad page break with this line | |
5294 | This is about addressing modes. | |
5295 | ||
5296 | @defmac HAVE_PRE_INCREMENT | |
5297 | @defmacx HAVE_PRE_DECREMENT | |
5298 | @defmacx HAVE_POST_INCREMENT | |
5299 | @defmacx HAVE_POST_DECREMENT | |
5300 | A C expression that is nonzero if the machine supports pre-increment, | |
5301 | pre-decrement, post-increment, or post-decrement addressing respectively. | |
5302 | @end defmac | |
5303 | ||
5304 | @defmac HAVE_PRE_MODIFY_DISP | |
5305 | @defmacx HAVE_POST_MODIFY_DISP | |
5306 | A C expression that is nonzero if the machine supports pre- or | |
5307 | post-address side-effect generation involving constants other than | |
5308 | the size of the memory operand. | |
5309 | @end defmac | |
5310 | ||
5311 | @defmac HAVE_PRE_MODIFY_REG | |
5312 | @defmacx HAVE_POST_MODIFY_REG | |
5313 | A C expression that is nonzero if the machine supports pre- or | |
5314 | post-address side-effect generation involving a register displacement. | |
5315 | @end defmac | |
5316 | ||
5317 | @defmac CONSTANT_ADDRESS_P (@var{x}) | |
5318 | A C expression that is 1 if the RTX @var{x} is a constant which | |
5319 | is a valid address. On most machines the default definition of | |
5320 | @code{(CONSTANT_P (@var{x}) && GET_CODE (@var{x}) != CONST_DOUBLE)} | |
5321 | is acceptable, but a few machines are more restrictive as to which | |
ff2ce160 | 5322 | constant addresses are supported. |
38f8b050 JR |
5323 | @end defmac |
5324 | ||
5325 | @defmac CONSTANT_P (@var{x}) | |
5326 | @code{CONSTANT_P}, which is defined by target-independent code, | |
5327 | accepts integer-values expressions whose values are not explicitly | |
5328 | known, such as @code{symbol_ref}, @code{label_ref}, and @code{high} | |
5329 | expressions and @code{const} arithmetic expressions, in addition to | |
5330 | @code{const_int} and @code{const_double} expressions. | |
5331 | @end defmac | |
5332 | ||
5333 | @defmac MAX_REGS_PER_ADDRESS | |
5334 | A number, the maximum number of registers that can appear in a valid | |
5335 | memory address. Note that it is up to you to specify a value equal to | |
5336 | the maximum number that @code{TARGET_LEGITIMATE_ADDRESS_P} would ever | |
5337 | accept. | |
5338 | @end defmac | |
5339 | ||
5340 | @hook TARGET_LEGITIMATE_ADDRESS_P | |
5341 | A function that returns whether @var{x} (an RTX) is a legitimate memory | |
5342 | address on the target machine for a memory operand of mode @var{mode}. | |
5343 | ||
5344 | Legitimate addresses are defined in two variants: a strict variant and a | |
5345 | non-strict one. The @var{strict} parameter chooses which variant is | |
5346 | desired by the caller. | |
5347 | ||
5348 | The strict variant is used in the reload pass. It must be defined so | |
5349 | that any pseudo-register that has not been allocated a hard register is | |
5350 | considered a memory reference. This is because in contexts where some | |
5351 | kind of register is required, a pseudo-register with no hard register | |
5352 | must be rejected. For non-hard registers, the strict variant should look | |
5353 | up the @code{reg_renumber} array; it should then proceed using the hard | |
5354 | register number in the array, or treat the pseudo as a memory reference | |
5355 | if the array holds @code{-1}. | |
5356 | ||
5357 | The non-strict variant is used in other passes. It must be defined to | |
5358 | accept all pseudo-registers in every context where some kind of | |
5359 | register is required. | |
5360 | ||
5361 | Normally, constant addresses which are the sum of a @code{symbol_ref} | |
5362 | and an integer are stored inside a @code{const} RTX to mark them as | |
5363 | constant. Therefore, there is no need to recognize such sums | |
5364 | specifically as legitimate addresses. Normally you would simply | |
5365 | recognize any @code{const} as legitimate. | |
5366 | ||
5367 | Usually @code{PRINT_OPERAND_ADDRESS} is not prepared to handle constant | |
5368 | sums that are not marked with @code{const}. It assumes that a naked | |
5369 | @code{plus} indicates indexing. If so, then you @emph{must} reject such | |
5370 | naked constant sums as illegitimate addresses, so that none of them will | |
5371 | be given to @code{PRINT_OPERAND_ADDRESS}. | |
5372 | ||
5373 | @cindex @code{TARGET_ENCODE_SECTION_INFO} and address validation | |
5374 | On some machines, whether a symbolic address is legitimate depends on | |
5375 | the section that the address refers to. On these machines, define the | |
5376 | target hook @code{TARGET_ENCODE_SECTION_INFO} to store the information | |
5377 | into the @code{symbol_ref}, and then check for it here. When you see a | |
5378 | @code{const}, you will have to look inside it to find the | |
5379 | @code{symbol_ref} in order to determine the section. @xref{Assembler | |
5380 | Format}. | |
5381 | ||
5382 | @cindex @code{GO_IF_LEGITIMATE_ADDRESS} | |
5383 | Some ports are still using a deprecated legacy substitute for | |
5384 | this hook, the @code{GO_IF_LEGITIMATE_ADDRESS} macro. This macro | |
5385 | has this syntax: | |
5386 | ||
5387 | @example | |
5388 | #define GO_IF_LEGITIMATE_ADDRESS (@var{mode}, @var{x}, @var{label}) | |
5389 | @end example | |
5390 | ||
5391 | @noindent | |
5392 | and should @code{goto @var{label}} if the address @var{x} is a valid | |
5393 | address on the target machine for a memory operand of mode @var{mode}. | |
6f7b223b PK |
5394 | |
5395 | @findex REG_OK_STRICT | |
5396 | Compiler source files that want to use the strict variant of this | |
5397 | macro define the macro @code{REG_OK_STRICT}. You should use an | |
5398 | @code{#ifdef REG_OK_STRICT} conditional to define the strict variant in | |
5399 | that case and the non-strict variant otherwise. | |
5400 | ||
38f8b050 JR |
5401 | Using the hook is usually simpler because it limits the number of |
5402 | files that are recompiled when changes are made. | |
5403 | @end deftypefn | |
5404 | ||
5405 | @defmac TARGET_MEM_CONSTRAINT | |
5406 | A single character to be used instead of the default @code{'m'} | |
5407 | character for general memory addresses. This defines the constraint | |
5408 | letter which matches the memory addresses accepted by | |
5409 | @code{TARGET_LEGITIMATE_ADDRESS_P}. Define this macro if you want to | |
5410 | support new address formats in your back end without changing the | |
5411 | semantics of the @code{'m'} constraint. This is necessary in order to | |
5412 | preserve functionality of inline assembly constructs using the | |
5413 | @code{'m'} constraint. | |
5414 | @end defmac | |
5415 | ||
5416 | @defmac FIND_BASE_TERM (@var{x}) | |
5417 | A C expression to determine the base term of address @var{x}, | |
5418 | or to provide a simplified version of @var{x} from which @file{alias.c} | |
5419 | can easily find the base term. This macro is used in only two places: | |
5420 | @code{find_base_value} and @code{find_base_term} in @file{alias.c}. | |
5421 | ||
5422 | It is always safe for this macro to not be defined. It exists so | |
5423 | that alias analysis can understand machine-dependent addresses. | |
5424 | ||
5425 | The typical use of this macro is to handle addresses containing | |
5426 | a label_ref or symbol_ref within an UNSPEC@. | |
5427 | @end defmac | |
5428 | ||
5429 | @hook TARGET_LEGITIMIZE_ADDRESS | |
5430 | This hook is given an invalid memory address @var{x} for an | |
5431 | operand of mode @var{mode} and should try to return a valid memory | |
5432 | address. | |
5433 | ||
5434 | @findex break_out_memory_refs | |
5435 | @var{x} will always be the result of a call to @code{break_out_memory_refs}, | |
5436 | and @var{oldx} will be the operand that was given to that function to produce | |
5437 | @var{x}. | |
5438 | ||
5439 | The code of the hook should not alter the substructure of | |
5440 | @var{x}. If it transforms @var{x} into a more legitimate form, it | |
5441 | should return the new @var{x}. | |
5442 | ||
5443 | It is not necessary for this hook to come up with a legitimate address. | |
5444 | The compiler has standard ways of doing so in all cases. In fact, it | |
5445 | is safe to omit this hook or make it return @var{x} if it cannot find | |
5446 | a valid way to legitimize the address. But often a machine-dependent | |
5447 | strategy can generate better code. | |
5448 | @end deftypefn | |
5449 | ||
5450 | @defmac LEGITIMIZE_RELOAD_ADDRESS (@var{x}, @var{mode}, @var{opnum}, @var{type}, @var{ind_levels}, @var{win}) | |
5451 | A C compound statement that attempts to replace @var{x}, which is an address | |
5452 | that needs reloading, with a valid memory address for an operand of mode | |
5453 | @var{mode}. @var{win} will be a C statement label elsewhere in the code. | |
5454 | It is not necessary to define this macro, but it might be useful for | |
5455 | performance reasons. | |
5456 | ||
5457 | For example, on the i386, it is sometimes possible to use a single | |
5458 | reload register instead of two by reloading a sum of two pseudo | |
5459 | registers into a register. On the other hand, for number of RISC | |
5460 | processors offsets are limited so that often an intermediate address | |
5461 | needs to be generated in order to address a stack slot. By defining | |
5462 | @code{LEGITIMIZE_RELOAD_ADDRESS} appropriately, the intermediate addresses | |
5463 | generated for adjacent some stack slots can be made identical, and thus | |
5464 | be shared. | |
5465 | ||
5466 | @emph{Note}: This macro should be used with caution. It is necessary | |
5467 | to know something of how reload works in order to effectively use this, | |
5468 | and it is quite easy to produce macros that build in too much knowledge | |
5469 | of reload internals. | |
5470 | ||
5471 | @emph{Note}: This macro must be able to reload an address created by a | |
5472 | previous invocation of this macro. If it fails to handle such addresses | |
5473 | then the compiler may generate incorrect code or abort. | |
5474 | ||
5475 | @findex push_reload | |
5476 | The macro definition should use @code{push_reload} to indicate parts that | |
5477 | need reloading; @var{opnum}, @var{type} and @var{ind_levels} are usually | |
5478 | suitable to be passed unaltered to @code{push_reload}. | |
5479 | ||
5480 | The code generated by this macro must not alter the substructure of | |
5481 | @var{x}. If it transforms @var{x} into a more legitimate form, it | |
5482 | should assign @var{x} (which will always be a C variable) a new value. | |
5483 | This also applies to parts that you change indirectly by calling | |
5484 | @code{push_reload}. | |
5485 | ||
5486 | @findex strict_memory_address_p | |
5487 | The macro definition may use @code{strict_memory_address_p} to test if | |
5488 | the address has become legitimate. | |
5489 | ||
5490 | @findex copy_rtx | |
5491 | If you want to change only a part of @var{x}, one standard way of doing | |
5492 | this is to use @code{copy_rtx}. Note, however, that it unshares only a | |
5493 | single level of rtl. Thus, if the part to be changed is not at the | |
5494 | top level, you'll need to replace first the top level. | |
5495 | It is not necessary for this macro to come up with a legitimate | |
5496 | address; but often a machine-dependent strategy can generate better code. | |
5497 | @end defmac | |
5498 | ||
5499 | @hook TARGET_MODE_DEPENDENT_ADDRESS_P | |
5500 | This hook returns @code{true} if memory address @var{addr} can have | |
5501 | different meanings depending on the machine mode of the memory | |
5502 | reference it is used for or if the address is valid for some modes | |
5503 | but not others. | |
5504 | ||
5505 | Autoincrement and autodecrement addresses typically have mode-dependent | |
5506 | effects because the amount of the increment or decrement is the size | |
5507 | of the operand being addressed. Some machines have other mode-dependent | |
5508 | addresses. Many RISC machines have no mode-dependent addresses. | |
5509 | ||
5510 | You may assume that @var{addr} is a valid address for the machine. | |
5511 | ||
5512 | The default version of this hook returns @code{false}. | |
5513 | @end deftypefn | |
5514 | ||
5515 | @defmac GO_IF_MODE_DEPENDENT_ADDRESS (@var{addr}, @var{label}) | |
5516 | A C statement or compound statement with a conditional @code{goto | |
5517 | @var{label};} executed if memory address @var{x} (an RTX) can have | |
5518 | different meanings depending on the machine mode of the memory | |
5519 | reference it is used for or if the address is valid for some modes | |
5520 | but not others. | |
5521 | ||
5522 | Autoincrement and autodecrement addresses typically have mode-dependent | |
5523 | effects because the amount of the increment or decrement is the size | |
5524 | of the operand being addressed. Some machines have other mode-dependent | |
5525 | addresses. Many RISC machines have no mode-dependent addresses. | |
5526 | ||
5527 | You may assume that @var{addr} is a valid address for the machine. | |
5528 | ||
5529 | These are obsolete macros, replaced by the | |
5530 | @code{TARGET_MODE_DEPENDENT_ADDRESS_P} target hook. | |
5531 | @end defmac | |
5532 | ||
1a627b35 RS |
5533 | @hook TARGET_LEGITIMATE_CONSTANT_P |
5534 | This hook returns true if @var{x} is a legitimate constant for a | |
5535 | @var{mode}-mode immediate operand on the target machine. You can assume that | |
5536 | @var{x} satisfies @code{CONSTANT_P}, so you need not check this. | |
5537 | ||
5538 | The default definition returns true. | |
5539 | @end deftypefn | |
38f8b050 JR |
5540 | |
5541 | @hook TARGET_DELEGITIMIZE_ADDRESS | |
5542 | This hook is used to undo the possibly obfuscating effects of the | |
5543 | @code{LEGITIMIZE_ADDRESS} and @code{LEGITIMIZE_RELOAD_ADDRESS} target | |
5544 | macros. Some backend implementations of these macros wrap symbol | |
5545 | references inside an @code{UNSPEC} rtx to represent PIC or similar | |
5546 | addressing modes. This target hook allows GCC's optimizers to understand | |
5547 | the semantics of these opaque @code{UNSPEC}s by converting them back | |
5548 | into their original form. | |
5549 | @end deftypefn | |
5550 | ||
5551 | @hook TARGET_CANNOT_FORCE_CONST_MEM | |
5552 | This hook should return true if @var{x} is of a form that cannot (or | |
fbbf66e7 RS |
5553 | should not) be spilled to the constant pool. @var{mode} is the mode |
5554 | of @var{x}. | |
5555 | ||
5556 | The default version of this hook returns false. | |
38f8b050 JR |
5557 | |
5558 | The primary reason to define this hook is to prevent reload from | |
5559 | deciding that a non-legitimate constant would be better reloaded | |
5560 | from the constant pool instead of spilling and reloading a register | |
5561 | holding the constant. This restriction is often true of addresses | |
5562 | of TLS symbols for various targets. | |
5563 | @end deftypefn | |
5564 | ||
5565 | @hook TARGET_USE_BLOCKS_FOR_CONSTANT_P | |
5566 | This hook should return true if pool entries for constant @var{x} can | |
5567 | be placed in an @code{object_block} structure. @var{mode} is the mode | |
5568 | of @var{x}. | |
5569 | ||
5570 | The default version returns false for all constants. | |
5571 | @end deftypefn | |
5572 | ||
89356d17 | 5573 | @hook TARGET_BUILTIN_RECIPROCAL |
38f8b050 JR |
5574 | This hook should return the DECL of a function that implements reciprocal of |
5575 | the builtin function with builtin function code @var{fn}, or | |
5576 | @code{NULL_TREE} if such a function is not available. @var{md_fn} is true | |
5577 | when @var{fn} is a code of a machine-dependent builtin function. When | |
5578 | @var{sqrt} is true, additional optimizations that apply only to the reciprocal | |
5579 | of a square root function are performed, and only reciprocals of @code{sqrt} | |
5580 | function are valid. | |
5581 | @end deftypefn | |
5582 | ||
5583 | @hook TARGET_VECTORIZE_BUILTIN_MASK_FOR_LOAD | |
5584 | This hook should return the DECL of a function @var{f} that given an | |
5585 | address @var{addr} as an argument returns a mask @var{m} that can be | |
5586 | used to extract from two vectors the relevant data that resides in | |
5587 | @var{addr} in case @var{addr} is not properly aligned. | |
5588 | ||
5589 | The autovectorizer, when vectorizing a load operation from an address | |
5590 | @var{addr} that may be unaligned, will generate two vector loads from | |
5591 | the two aligned addresses around @var{addr}. It then generates a | |
5592 | @code{REALIGN_LOAD} operation to extract the relevant data from the | |
5593 | two loaded vectors. The first two arguments to @code{REALIGN_LOAD}, | |
5594 | @var{v1} and @var{v2}, are the two vectors, each of size @var{VS}, and | |
5595 | the third argument, @var{OFF}, defines how the data will be extracted | |
5596 | from these two vectors: if @var{OFF} is 0, then the returned vector is | |
5597 | @var{v2}; otherwise, the returned vector is composed from the last | |
5598 | @var{VS}-@var{OFF} elements of @var{v1} concatenated to the first | |
5599 | @var{OFF} elements of @var{v2}. | |
5600 | ||
5601 | If this hook is defined, the autovectorizer will generate a call | |
5602 | to @var{f} (using the DECL tree that this hook returns) and will | |
5603 | use the return value of @var{f} as the argument @var{OFF} to | |
5604 | @code{REALIGN_LOAD}. Therefore, the mask @var{m} returned by @var{f} | |
5605 | should comply with the semantics expected by @code{REALIGN_LOAD} | |
5606 | described above. | |
5607 | If this hook is not defined, then @var{addr} will be used as | |
5608 | the argument @var{OFF} to @code{REALIGN_LOAD}, in which case the low | |
5609 | log2(@var{VS}) @minus{} 1 bits of @var{addr} will be considered. | |
5610 | @end deftypefn | |
5611 | ||
5612 | @hook TARGET_VECTORIZE_BUILTIN_MUL_WIDEN_EVEN | |
5613 | This hook should return the DECL of a function @var{f} that implements | |
5614 | widening multiplication of the even elements of two input vectors of type @var{x}. | |
5615 | ||
5616 | If this hook is defined, the autovectorizer will use it along with the | |
5617 | @code{TARGET_VECTORIZE_BUILTIN_MUL_WIDEN_ODD} target hook when vectorizing | |
5618 | widening multiplication in cases that the order of the results does not have to be | |
5619 | preserved (e.g.@: used only by a reduction computation). Otherwise, the | |
5620 | @code{widen_mult_hi/lo} idioms will be used. | |
5621 | @end deftypefn | |
5622 | ||
5623 | @hook TARGET_VECTORIZE_BUILTIN_MUL_WIDEN_ODD | |
5624 | This hook should return the DECL of a function @var{f} that implements | |
5625 | widening multiplication of the odd elements of two input vectors of type @var{x}. | |
5626 | ||
5627 | If this hook is defined, the autovectorizer will use it along with the | |
5628 | @code{TARGET_VECTORIZE_BUILTIN_MUL_WIDEN_EVEN} target hook when vectorizing | |
5629 | widening multiplication in cases that the order of the results does not have to be | |
5630 | preserved (e.g.@: used only by a reduction computation). Otherwise, the | |
5631 | @code{widen_mult_hi/lo} idioms will be used. | |
5632 | @end deftypefn | |
5633 | ||
5634 | @hook TARGET_VECTORIZE_BUILTIN_VECTORIZATION_COST | |
5635 | Returns cost of different scalar or vector statements for vectorization cost model. | |
ff2ce160 | 5636 | For vector memory operations the cost may depend on type (@var{vectype}) and |
720f5239 | 5637 | misalignment value (@var{misalign}). |
38f8b050 JR |
5638 | @end deftypefn |
5639 | ||
5640 | @hook TARGET_VECTORIZE_VECTOR_ALIGNMENT_REACHABLE | |
5641 | Return true if vector alignment is reachable (by peeling N iterations) for the given type. | |
5642 | @end deftypefn | |
5643 | ||
5644 | @hook TARGET_VECTORIZE_BUILTIN_VEC_PERM | |
5645 | Target builtin that implements vector permute. | |
5646 | @end deftypefn | |
5647 | ||
5648 | @hook TARGET_VECTORIZE_BUILTIN_VEC_PERM_OK | |
5649 | Return true if a vector created for @code{builtin_vec_perm} is valid. | |
5650 | @end deftypefn | |
5651 | ||
5652 | @hook TARGET_VECTORIZE_BUILTIN_CONVERSION | |
5653 | This hook should return the DECL of a function that implements conversion of the | |
5654 | input vector of type @var{src_type} to type @var{dest_type}. | |
5655 | The value of @var{code} is one of the enumerators in @code{enum tree_code} and | |
5656 | specifies how the conversion is to be applied | |
5657 | (truncation, rounding, etc.). | |
5658 | ||
5659 | If this hook is defined, the autovectorizer will use the | |
5660 | @code{TARGET_VECTORIZE_BUILTIN_CONVERSION} target hook when vectorizing | |
5661 | conversion. Otherwise, it will return @code{NULL_TREE}. | |
5662 | @end deftypefn | |
5663 | ||
5664 | @hook TARGET_VECTORIZE_BUILTIN_VECTORIZED_FUNCTION | |
5665 | This hook should return the decl of a function that implements the | |
5666 | vectorized variant of the builtin function with builtin function code | |
5667 | @var{code} or @code{NULL_TREE} if such a function is not available. | |
5668 | The value of @var{fndecl} is the builtin function declaration. The | |
5669 | return type of the vectorized function shall be of vector type | |
5670 | @var{vec_type_out} and the argument types should be @var{vec_type_in}. | |
5671 | @end deftypefn | |
5672 | ||
5673 | @hook TARGET_VECTORIZE_SUPPORT_VECTOR_MISALIGNMENT | |
5674 | This hook should return true if the target supports misaligned vector | |
5675 | store/load of a specific factor denoted in the @var{misalignment} | |
5676 | parameter. The vector store/load should be of machine mode @var{mode} and | |
5677 | the elements in the vectors should be of type @var{type}. @var{is_packed} | |
5678 | parameter is true if the memory access is defined in a packed struct. | |
5679 | @end deftypefn | |
5680 | ||
cc4b5170 RG |
5681 | @hook TARGET_VECTORIZE_PREFERRED_SIMD_MODE |
5682 | This hook should return the preferred mode for vectorizing scalar | |
5683 | mode @var{mode}. The default is | |
5684 | equal to @code{word_mode}, because the vectorizer can do some | |
26983c22 L |
5685 | transformations even in absence of specialized @acronym{SIMD} hardware. |
5686 | @end deftypefn | |
5687 | ||
767f865f RG |
5688 | @hook TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_SIZES |
5689 | This hook should return a mask of sizes that should be iterated over | |
5690 | after trying to autovectorize using the vector size derived from the | |
5691 | mode returned by @code{TARGET_VECTORIZE_PREFERRED_SIMD_MODE}. | |
5692 | The default is zero which means to not iterate over other vector sizes. | |
5693 | @end deftypefn | |
5694 | ||
38f8b050 JR |
5695 | @node Anchored Addresses |
5696 | @section Anchored Addresses | |
5697 | @cindex anchored addresses | |
5698 | @cindex @option{-fsection-anchors} | |
5699 | ||
5700 | GCC usually addresses every static object as a separate entity. | |
5701 | For example, if we have: | |
5702 | ||
5703 | @smallexample | |
5704 | static int a, b, c; | |
5705 | int foo (void) @{ return a + b + c; @} | |
5706 | @end smallexample | |
5707 | ||
5708 | the code for @code{foo} will usually calculate three separate symbolic | |
5709 | addresses: those of @code{a}, @code{b} and @code{c}. On some targets, | |
5710 | it would be better to calculate just one symbolic address and access | |
5711 | the three variables relative to it. The equivalent pseudocode would | |
5712 | be something like: | |
5713 | ||
5714 | @smallexample | |
5715 | int foo (void) | |
5716 | @{ | |
5717 | register int *xr = &x; | |
5718 | return xr[&a - &x] + xr[&b - &x] + xr[&c - &x]; | |
5719 | @} | |
5720 | @end smallexample | |
5721 | ||
5722 | (which isn't valid C). We refer to shared addresses like @code{x} as | |
5723 | ``section anchors''. Their use is controlled by @option{-fsection-anchors}. | |
5724 | ||
5725 | The hooks below describe the target properties that GCC needs to know | |
5726 | in order to make effective use of section anchors. It won't use | |
5727 | section anchors at all unless either @code{TARGET_MIN_ANCHOR_OFFSET} | |
5728 | or @code{TARGET_MAX_ANCHOR_OFFSET} is set to a nonzero value. | |
5729 | ||
5730 | @hook TARGET_MIN_ANCHOR_OFFSET | |
5731 | The minimum offset that should be applied to a section anchor. | |
5732 | On most targets, it should be the smallest offset that can be | |
5733 | applied to a base register while still giving a legitimate address | |
5734 | for every mode. The default value is 0. | |
5735 | @end deftypevr | |
5736 | ||
5737 | @hook TARGET_MAX_ANCHOR_OFFSET | |
5738 | Like @code{TARGET_MIN_ANCHOR_OFFSET}, but the maximum (inclusive) | |
5739 | offset that should be applied to section anchors. The default | |
5740 | value is 0. | |
5741 | @end deftypevr | |
5742 | ||
5743 | @hook TARGET_ASM_OUTPUT_ANCHOR | |
5744 | Write the assembly code to define section anchor @var{x}, which is a | |
5745 | @code{SYMBOL_REF} for which @samp{SYMBOL_REF_ANCHOR_P (@var{x})} is true. | |
5746 | The hook is called with the assembly output position set to the beginning | |
5747 | of @code{SYMBOL_REF_BLOCK (@var{x})}. | |
5748 | ||
5749 | If @code{ASM_OUTPUT_DEF} is available, the hook's default definition uses | |
5750 | it to define the symbol as @samp{. + SYMBOL_REF_BLOCK_OFFSET (@var{x})}. | |
5751 | If @code{ASM_OUTPUT_DEF} is not available, the hook's default definition | |
5752 | is @code{NULL}, which disables the use of section anchors altogether. | |
5753 | @end deftypefn | |
5754 | ||
5755 | @hook TARGET_USE_ANCHORS_FOR_SYMBOL_P | |
5756 | Return true if GCC should attempt to use anchors to access @code{SYMBOL_REF} | |
5757 | @var{x}. You can assume @samp{SYMBOL_REF_HAS_BLOCK_INFO_P (@var{x})} and | |
5758 | @samp{!SYMBOL_REF_ANCHOR_P (@var{x})}. | |
5759 | ||
5760 | The default version is correct for most targets, but you might need to | |
5761 | intercept this hook to handle things like target-specific attributes | |
5762 | or target-specific sections. | |
5763 | @end deftypefn | |
5764 | ||
5765 | @node Condition Code | |
5766 | @section Condition Code Status | |
5767 | @cindex condition code status | |
5768 | ||
5769 | The macros in this section can be split in two families, according to the | |
5770 | two ways of representing condition codes in GCC. | |
5771 | ||
5772 | The first representation is the so called @code{(cc0)} representation | |
5773 | (@pxref{Jump Patterns}), where all instructions can have an implicit | |
5774 | clobber of the condition codes. The second is the condition code | |
5775 | register representation, which provides better schedulability for | |
5776 | architectures that do have a condition code register, but on which | |
5777 | most instructions do not affect it. The latter category includes | |
5778 | most RISC machines. | |
5779 | ||
5780 | The implicit clobbering poses a strong restriction on the placement of | |
5781 | the definition and use of the condition code, which need to be in adjacent | |
5782 | insns for machines using @code{(cc0)}. This can prevent important | |
5783 | optimizations on some machines. For example, on the IBM RS/6000, there | |
5784 | is a delay for taken branches unless the condition code register is set | |
5785 | three instructions earlier than the conditional branch. The instruction | |
5786 | scheduler cannot perform this optimization if it is not permitted to | |
5787 | separate the definition and use of the condition code register. | |
5788 | ||
5789 | For this reason, it is possible and suggested to use a register to | |
5790 | represent the condition code for new ports. If there is a specific | |
5791 | condition code register in the machine, use a hard register. If the | |
5792 | condition code or comparison result can be placed in any general register, | |
5793 | or if there are multiple condition registers, use a pseudo register. | |
5794 | Registers used to store the condition code value will usually have a mode | |
5795 | that is in class @code{MODE_CC}. | |
5796 | ||
5797 | Alternatively, you can use @code{BImode} if the comparison operator is | |
5798 | specified already in the compare instruction. In this case, you are not | |
5799 | interested in most macros in this section. | |
5800 | ||
5801 | @menu | |
5802 | * CC0 Condition Codes:: Old style representation of condition codes. | |
5803 | * MODE_CC Condition Codes:: Modern representation of condition codes. | |
ac7eb5c6 | 5804 | * Cond Exec Macros:: Macros to control conditional execution. |
38f8b050 JR |
5805 | @end menu |
5806 | ||
5807 | @node CC0 Condition Codes | |
5808 | @subsection Representation of condition codes using @code{(cc0)} | |
5809 | @findex cc0 | |
5810 | ||
5811 | @findex cc_status | |
5812 | The file @file{conditions.h} defines a variable @code{cc_status} to | |
5813 | describe how the condition code was computed (in case the interpretation of | |
5814 | the condition code depends on the instruction that it was set by). This | |
5815 | variable contains the RTL expressions on which the condition code is | |
5816 | currently based, and several standard flags. | |
5817 | ||
5818 | Sometimes additional machine-specific flags must be defined in the machine | |
5819 | description header file. It can also add additional machine-specific | |
5820 | information by defining @code{CC_STATUS_MDEP}. | |
5821 | ||
5822 | @defmac CC_STATUS_MDEP | |
5823 | C code for a data type which is used for declaring the @code{mdep} | |
5824 | component of @code{cc_status}. It defaults to @code{int}. | |
5825 | ||
5826 | This macro is not used on machines that do not use @code{cc0}. | |
5827 | @end defmac | |
5828 | ||
5829 | @defmac CC_STATUS_MDEP_INIT | |
5830 | A C expression to initialize the @code{mdep} field to ``empty''. | |
5831 | The default definition does nothing, since most machines don't use | |
5832 | the field anyway. If you want to use the field, you should probably | |
5833 | define this macro to initialize it. | |
5834 | ||
5835 | This macro is not used on machines that do not use @code{cc0}. | |
5836 | @end defmac | |
5837 | ||
5838 | @defmac NOTICE_UPDATE_CC (@var{exp}, @var{insn}) | |
5839 | A C compound statement to set the components of @code{cc_status} | |
5840 | appropriately for an insn @var{insn} whose body is @var{exp}. It is | |
5841 | this macro's responsibility to recognize insns that set the condition | |
5842 | code as a byproduct of other activity as well as those that explicitly | |
5843 | set @code{(cc0)}. | |
5844 | ||
5845 | This macro is not used on machines that do not use @code{cc0}. | |
5846 | ||
5847 | If there are insns that do not set the condition code but do alter | |
5848 | other machine registers, this macro must check to see whether they | |
5849 | invalidate the expressions that the condition code is recorded as | |
5850 | reflecting. For example, on the 68000, insns that store in address | |
5851 | registers do not set the condition code, which means that usually | |
5852 | @code{NOTICE_UPDATE_CC} can leave @code{cc_status} unaltered for such | |
5853 | insns. But suppose that the previous insn set the condition code | |
5854 | based on location @samp{a4@@(102)} and the current insn stores a new | |
5855 | value in @samp{a4}. Although the condition code is not changed by | |
5856 | this, it will no longer be true that it reflects the contents of | |
5857 | @samp{a4@@(102)}. Therefore, @code{NOTICE_UPDATE_CC} must alter | |
5858 | @code{cc_status} in this case to say that nothing is known about the | |
5859 | condition code value. | |
5860 | ||
5861 | The definition of @code{NOTICE_UPDATE_CC} must be prepared to deal | |
5862 | with the results of peephole optimization: insns whose patterns are | |
5863 | @code{parallel} RTXs containing various @code{reg}, @code{mem} or | |
5864 | constants which are just the operands. The RTL structure of these | |
5865 | insns is not sufficient to indicate what the insns actually do. What | |
5866 | @code{NOTICE_UPDATE_CC} should do when it sees one is just to run | |
5867 | @code{CC_STATUS_INIT}. | |
5868 | ||
5869 | A possible definition of @code{NOTICE_UPDATE_CC} is to call a function | |
5870 | that looks at an attribute (@pxref{Insn Attributes}) named, for example, | |
5871 | @samp{cc}. This avoids having detailed information about patterns in | |
5872 | two places, the @file{md} file and in @code{NOTICE_UPDATE_CC}. | |
5873 | @end defmac | |
5874 | ||
5875 | @node MODE_CC Condition Codes | |
5876 | @subsection Representation of condition codes using registers | |
5877 | @findex CCmode | |
5878 | @findex MODE_CC | |
5879 | ||
5880 | @defmac SELECT_CC_MODE (@var{op}, @var{x}, @var{y}) | |
5881 | On many machines, the condition code may be produced by other instructions | |
5882 | than compares, for example the branch can use directly the condition | |
5883 | code set by a subtract instruction. However, on some machines | |
5884 | when the condition code is set this way some bits (such as the overflow | |
5885 | bit) are not set in the same way as a test instruction, so that a different | |
5886 | branch instruction must be used for some conditional branches. When | |
5887 | this happens, use the machine mode of the condition code register to | |
5888 | record different formats of the condition code register. Modes can | |
5889 | also be used to record which compare instruction (e.g. a signed or an | |
5890 | unsigned comparison) produced the condition codes. | |
5891 | ||
5892 | If other modes than @code{CCmode} are required, add them to | |
5893 | @file{@var{machine}-modes.def} and define @code{SELECT_CC_MODE} to choose | |
5894 | a mode given an operand of a compare. This is needed because the modes | |
5895 | have to be chosen not only during RTL generation but also, for example, | |
5896 | by instruction combination. The result of @code{SELECT_CC_MODE} should | |
5897 | be consistent with the mode used in the patterns; for example to support | |
5898 | the case of the add on the SPARC discussed above, we have the pattern | |
5899 | ||
5900 | @smallexample | |
5901 | (define_insn "" | |
5902 | [(set (reg:CC_NOOV 0) | |
5903 | (compare:CC_NOOV | |
5904 | (plus:SI (match_operand:SI 0 "register_operand" "%r") | |
5905 | (match_operand:SI 1 "arith_operand" "rI")) | |
5906 | (const_int 0)))] | |
5907 | "" | |
5908 | "@dots{}") | |
5909 | @end smallexample | |
5910 | ||
5911 | @noindent | |
5912 | together with a @code{SELECT_CC_MODE} that returns @code{CC_NOOVmode} | |
5913 | for comparisons whose argument is a @code{plus}: | |
5914 | ||
5915 | @smallexample | |
5916 | #define SELECT_CC_MODE(OP,X,Y) \ | |
5917 | (GET_MODE_CLASS (GET_MODE (X)) == MODE_FLOAT \ | |
5918 | ? ((OP == EQ || OP == NE) ? CCFPmode : CCFPEmode) \ | |
5919 | : ((GET_CODE (X) == PLUS || GET_CODE (X) == MINUS \ | |
5920 | || GET_CODE (X) == NEG) \ | |
5921 | ? CC_NOOVmode : CCmode)) | |
5922 | @end smallexample | |
5923 | ||
5924 | Another reason to use modes is to retain information on which operands | |
5925 | were used by the comparison; see @code{REVERSIBLE_CC_MODE} later in | |
5926 | this section. | |
5927 | ||
5928 | You should define this macro if and only if you define extra CC modes | |
5929 | in @file{@var{machine}-modes.def}. | |
5930 | @end defmac | |
5931 | ||
5932 | @defmac CANONICALIZE_COMPARISON (@var{code}, @var{op0}, @var{op1}) | |
5933 | On some machines not all possible comparisons are defined, but you can | |
5934 | convert an invalid comparison into a valid one. For example, the Alpha | |
5935 | does not have a @code{GT} comparison, but you can use an @code{LT} | |
5936 | comparison instead and swap the order of the operands. | |
5937 | ||
5938 | On such machines, define this macro to be a C statement to do any | |
5939 | required conversions. @var{code} is the initial comparison code | |
5940 | and @var{op0} and @var{op1} are the left and right operands of the | |
5941 | comparison, respectively. You should modify @var{code}, @var{op0}, and | |
5942 | @var{op1} as required. | |
5943 | ||
5944 | GCC will not assume that the comparison resulting from this macro is | |
5945 | valid but will see if the resulting insn matches a pattern in the | |
5946 | @file{md} file. | |
5947 | ||
5948 | You need not define this macro if it would never change the comparison | |
5949 | code or operands. | |
5950 | @end defmac | |
5951 | ||
5952 | @defmac REVERSIBLE_CC_MODE (@var{mode}) | |
5953 | A C expression whose value is one if it is always safe to reverse a | |
5954 | comparison whose mode is @var{mode}. If @code{SELECT_CC_MODE} | |
5955 | can ever return @var{mode} for a floating-point inequality comparison, | |
5956 | then @code{REVERSIBLE_CC_MODE (@var{mode})} must be zero. | |
5957 | ||
5958 | You need not define this macro if it would always returns zero or if the | |
5959 | floating-point format is anything other than @code{IEEE_FLOAT_FORMAT}. | |
5960 | For example, here is the definition used on the SPARC, where floating-point | |
5961 | inequality comparisons are always given @code{CCFPEmode}: | |
5962 | ||
5963 | @smallexample | |
5964 | #define REVERSIBLE_CC_MODE(MODE) ((MODE) != CCFPEmode) | |
5965 | @end smallexample | |
5966 | @end defmac | |
5967 | ||
5968 | @defmac REVERSE_CONDITION (@var{code}, @var{mode}) | |
5969 | A C expression whose value is reversed condition code of the @var{code} for | |
5970 | comparison done in CC_MODE @var{mode}. The macro is used only in case | |
5971 | @code{REVERSIBLE_CC_MODE (@var{mode})} is nonzero. Define this macro in case | |
5972 | machine has some non-standard way how to reverse certain conditionals. For | |
5973 | instance in case all floating point conditions are non-trapping, compiler may | |
5974 | freely convert unordered compares to ordered one. Then definition may look | |
5975 | like: | |
5976 | ||
5977 | @smallexample | |
5978 | #define REVERSE_CONDITION(CODE, MODE) \ | |
5979 | ((MODE) != CCFPmode ? reverse_condition (CODE) \ | |
5980 | : reverse_condition_maybe_unordered (CODE)) | |
5981 | @end smallexample | |
5982 | @end defmac | |
5983 | ||
5984 | @hook TARGET_FIXED_CONDITION_CODE_REGS | |
5985 | On targets which do not use @code{(cc0)}, and which use a hard | |
5986 | register rather than a pseudo-register to hold condition codes, the | |
5987 | regular CSE passes are often not able to identify cases in which the | |
5988 | hard register is set to a common value. Use this hook to enable a | |
5989 | small pass which optimizes such cases. This hook should return true | |
5990 | to enable this pass, and it should set the integers to which its | |
5991 | arguments point to the hard register numbers used for condition codes. | |
5992 | When there is only one such register, as is true on most systems, the | |
5993 | integer pointed to by @var{p2} should be set to | |
5994 | @code{INVALID_REGNUM}. | |
5995 | ||
5996 | The default version of this hook returns false. | |
5997 | @end deftypefn | |
5998 | ||
5999 | @hook TARGET_CC_MODES_COMPATIBLE | |
6000 | On targets which use multiple condition code modes in class | |
6001 | @code{MODE_CC}, it is sometimes the case that a comparison can be | |
6002 | validly done in more than one mode. On such a system, define this | |
6003 | target hook to take two mode arguments and to return a mode in which | |
6004 | both comparisons may be validly done. If there is no such mode, | |
6005 | return @code{VOIDmode}. | |
6006 | ||
6007 | The default version of this hook checks whether the modes are the | |
6008 | same. If they are, it returns that mode. If they are different, it | |
6009 | returns @code{VOIDmode}. | |
6010 | @end deftypefn | |
6011 | ||
ac7eb5c6 | 6012 | @node Cond Exec Macros |
38f8b050 JR |
6013 | @subsection Macros to control conditional execution |
6014 | @findex conditional execution | |
6015 | @findex predication | |
6016 | ||
6017 | There is one macro that may need to be defined for targets | |
6018 | supporting conditional execution, independent of how they | |
6019 | represent conditional branches. | |
6020 | ||
6021 | @defmac REVERSE_CONDEXEC_PREDICATES_P (@var{op1}, @var{op2}) | |
6022 | A C expression that returns true if the conditional execution predicate | |
6023 | @var{op1}, a comparison operation, is the inverse of @var{op2} and vice | |
6024 | versa. Define this to return 0 if the target has conditional execution | |
6025 | predicates that cannot be reversed safely. There is no need to validate | |
6026 | that the arguments of op1 and op2 are the same, this is done separately. | |
6027 | If no expansion is specified, this macro is defined as follows: | |
6028 | ||
6029 | @smallexample | |
6030 | #define REVERSE_CONDEXEC_PREDICATES_P (x, y) \ | |
6031 | (GET_CODE ((x)) == reversed_comparison_code ((y), NULL)) | |
6032 | @end smallexample | |
6033 | @end defmac | |
6034 | ||
6035 | @node Costs | |
6036 | @section Describing Relative Costs of Operations | |
6037 | @cindex costs of instructions | |
6038 | @cindex relative costs | |
6039 | @cindex speed of instructions | |
6040 | ||
6041 | These macros let you describe the relative speed of various operations | |
6042 | on the target machine. | |
6043 | ||
6044 | @defmac REGISTER_MOVE_COST (@var{mode}, @var{from}, @var{to}) | |
6045 | A C expression for the cost of moving data of mode @var{mode} from a | |
6046 | register in class @var{from} to one in class @var{to}. The classes are | |
6047 | expressed using the enumeration values such as @code{GENERAL_REGS}. A | |
6048 | value of 2 is the default; other values are interpreted relative to | |
6049 | that. | |
6050 | ||
6051 | It is not required that the cost always equal 2 when @var{from} is the | |
6052 | same as @var{to}; on some machines it is expensive to move between | |
6053 | registers if they are not general registers. | |
6054 | ||
6055 | If reload sees an insn consisting of a single @code{set} between two | |
6056 | hard registers, and if @code{REGISTER_MOVE_COST} applied to their | |
6057 | classes returns a value of 2, reload does not check to ensure that the | |
6058 | constraints of the insn are met. Setting a cost of other than 2 will | |
6059 | allow reload to verify that the constraints are met. You should do this | |
6060 | if the @samp{mov@var{m}} pattern's constraints do not allow such copying. | |
6061 | ||
6062 | These macros are obsolete, new ports should use the target hook | |
6063 | @code{TARGET_REGISTER_MOVE_COST} instead. | |
6064 | @end defmac | |
6065 | ||
6066 | @hook TARGET_REGISTER_MOVE_COST | |
6067 | This target hook should return the cost of moving data of mode @var{mode} | |
6068 | from a register in class @var{from} to one in class @var{to}. The classes | |
6069 | are expressed using the enumeration values such as @code{GENERAL_REGS}. | |
6070 | A value of 2 is the default; other values are interpreted relative to | |
6071 | that. | |
6072 | ||
6073 | It is not required that the cost always equal 2 when @var{from} is the | |
6074 | same as @var{to}; on some machines it is expensive to move between | |
6075 | registers if they are not general registers. | |
6076 | ||
6077 | If reload sees an insn consisting of a single @code{set} between two | |
6078 | hard registers, and if @code{TARGET_REGISTER_MOVE_COST} applied to their | |
6079 | classes returns a value of 2, reload does not check to ensure that the | |
6080 | constraints of the insn are met. Setting a cost of other than 2 will | |
6081 | allow reload to verify that the constraints are met. You should do this | |
6082 | if the @samp{mov@var{m}} pattern's constraints do not allow such copying. | |
6083 | ||
6084 | The default version of this function returns 2. | |
6085 | @end deftypefn | |
6086 | ||
6087 | @defmac MEMORY_MOVE_COST (@var{mode}, @var{class}, @var{in}) | |
6088 | A C expression for the cost of moving data of mode @var{mode} between a | |
6089 | register of class @var{class} and memory; @var{in} is zero if the value | |
6090 | is to be written to memory, nonzero if it is to be read in. This cost | |
6091 | is relative to those in @code{REGISTER_MOVE_COST}. If moving between | |
6092 | registers and memory is more expensive than between two registers, you | |
6093 | should define this macro to express the relative cost. | |
6094 | ||
6095 | If you do not define this macro, GCC uses a default cost of 4 plus | |
6096 | the cost of copying via a secondary reload register, if one is | |
6097 | needed. If your machine requires a secondary reload register to copy | |
6098 | between memory and a register of @var{class} but the reload mechanism is | |
6099 | more complex than copying via an intermediate, define this macro to | |
6100 | reflect the actual cost of the move. | |
6101 | ||
6102 | GCC defines the function @code{memory_move_secondary_cost} if | |
6103 | secondary reloads are needed. It computes the costs due to copying via | |
6104 | a secondary register. If your machine copies from memory using a | |
6105 | secondary register in the conventional way but the default base value of | |
6106 | 4 is not correct for your machine, define this macro to add some other | |
6107 | value to the result of that function. The arguments to that function | |
6108 | are the same as to this macro. | |
6109 | ||
6110 | These macros are obsolete, new ports should use the target hook | |
6111 | @code{TARGET_MEMORY_MOVE_COST} instead. | |
6112 | @end defmac | |
6113 | ||
911852ff | 6114 | @hook TARGET_MEMORY_MOVE_COST |
38f8b050 | 6115 | This target hook should return the cost of moving data of mode @var{mode} |
911852ff | 6116 | between a register of class @var{rclass} and memory; @var{in} is @code{false} |
38f8b050 JR |
6117 | if the value is to be written to memory, @code{true} if it is to be read in. |
6118 | This cost is relative to those in @code{TARGET_REGISTER_MOVE_COST}. | |
6119 | If moving between registers and memory is more expensive than between two | |
6120 | registers, you should add this target hook to express the relative cost. | |
6121 | ||
6122 | If you do not add this target hook, GCC uses a default cost of 4 plus | |
6123 | the cost of copying via a secondary reload register, if one is | |
6124 | needed. If your machine requires a secondary reload register to copy | |
911852ff | 6125 | between memory and a register of @var{rclass} but the reload mechanism is |
38f8b050 JR |
6126 | more complex than copying via an intermediate, use this target hook to |
6127 | reflect the actual cost of the move. | |
6128 | ||
6129 | GCC defines the function @code{memory_move_secondary_cost} if | |
6130 | secondary reloads are needed. It computes the costs due to copying via | |
6131 | a secondary register. If your machine copies from memory using a | |
6132 | secondary register in the conventional way but the default base value of | |
6133 | 4 is not correct for your machine, use this target hook to add some other | |
6134 | value to the result of that function. The arguments to that function | |
6135 | are the same as to this target hook. | |
6136 | @end deftypefn | |
6137 | ||
6138 | @defmac BRANCH_COST (@var{speed_p}, @var{predictable_p}) | |
525d13b0 MS |
6139 | A C expression for the cost of a branch instruction. A value of 1 is |
6140 | the default; other values are interpreted relative to that. Parameter | |
6141 | @var{speed_p} is true when the branch in question should be optimized | |
6142 | for speed. When it is false, @code{BRANCH_COST} should return a value | |
6143 | optimal for code size rather than performance. @var{predictable_p} is | |
6144 | true for well-predicted branches. On many architectures the | |
6145 | @code{BRANCH_COST} can be reduced then. | |
38f8b050 JR |
6146 | @end defmac |
6147 | ||
6148 | Here are additional macros which do not specify precise relative costs, | |
6149 | but only that certain actions are more expensive than GCC would | |
6150 | ordinarily expect. | |
6151 | ||
6152 | @defmac SLOW_BYTE_ACCESS | |
6153 | Define this macro as a C expression which is nonzero if accessing less | |
6154 | than a word of memory (i.e.@: a @code{char} or a @code{short}) is no | |
6155 | faster than accessing a word of memory, i.e., if such access | |
6156 | require more than one instruction or if there is no difference in cost | |
6157 | between byte and (aligned) word loads. | |
6158 | ||
6159 | When this macro is not defined, the compiler will access a field by | |
6160 | finding the smallest containing object; when it is defined, a fullword | |
6161 | load will be used if alignment permits. Unless bytes accesses are | |
6162 | faster than word accesses, using word accesses is preferable since it | |
6163 | may eliminate subsequent memory access if subsequent accesses occur to | |
6164 | other fields in the same word of the structure, but to different bytes. | |
6165 | @end defmac | |
6166 | ||
6167 | @defmac SLOW_UNALIGNED_ACCESS (@var{mode}, @var{alignment}) | |
6168 | Define this macro to be the value 1 if memory accesses described by the | |
6169 | @var{mode} and @var{alignment} parameters have a cost many times greater | |
6170 | than aligned accesses, for example if they are emulated in a trap | |
6171 | handler. | |
6172 | ||
6173 | When this macro is nonzero, the compiler will act as if | |
6174 | @code{STRICT_ALIGNMENT} were nonzero when generating code for block | |
6175 | moves. This can cause significantly more instructions to be produced. | |
6176 | Therefore, do not set this macro nonzero if unaligned accesses only add a | |
6177 | cycle or two to the time for a memory access. | |
6178 | ||
6179 | If the value of this macro is always zero, it need not be defined. If | |
6180 | this macro is defined, it should produce a nonzero value when | |
6181 | @code{STRICT_ALIGNMENT} is nonzero. | |
6182 | @end defmac | |
6183 | ||
6184 | @defmac MOVE_RATIO (@var{speed}) | |
6185 | The threshold of number of scalar memory-to-memory move insns, @emph{below} | |
6186 | which a sequence of insns should be generated instead of a | |
6187 | string move insn or a library call. Increasing the value will always | |
6188 | make code faster, but eventually incurs high cost in increased code size. | |
6189 | ||
6190 | Note that on machines where the corresponding move insn is a | |
6191 | @code{define_expand} that emits a sequence of insns, this macro counts | |
6192 | the number of such sequences. | |
6193 | ||
6194 | The parameter @var{speed} is true if the code is currently being | |
6195 | optimized for speed rather than size. | |
6196 | ||
6197 | If you don't define this, a reasonable default is used. | |
6198 | @end defmac | |
6199 | ||
6200 | @defmac MOVE_BY_PIECES_P (@var{size}, @var{alignment}) | |
6201 | A C expression used to determine whether @code{move_by_pieces} will be used to | |
6202 | copy a chunk of memory, or whether some other block move mechanism | |
6203 | will be used. Defaults to 1 if @code{move_by_pieces_ninsns} returns less | |
6204 | than @code{MOVE_RATIO}. | |
6205 | @end defmac | |
6206 | ||
6207 | @defmac MOVE_MAX_PIECES | |
6208 | A C expression used by @code{move_by_pieces} to determine the largest unit | |
6209 | a load or store used to copy memory is. Defaults to @code{MOVE_MAX}. | |
6210 | @end defmac | |
6211 | ||
6212 | @defmac CLEAR_RATIO (@var{speed}) | |
6213 | The threshold of number of scalar move insns, @emph{below} which a sequence | |
6214 | of insns should be generated to clear memory instead of a string clear insn | |
6215 | or a library call. Increasing the value will always make code faster, but | |
6216 | eventually incurs high cost in increased code size. | |
6217 | ||
6218 | The parameter @var{speed} is true if the code is currently being | |
6219 | optimized for speed rather than size. | |
6220 | ||
6221 | If you don't define this, a reasonable default is used. | |
6222 | @end defmac | |
6223 | ||
6224 | @defmac CLEAR_BY_PIECES_P (@var{size}, @var{alignment}) | |
6225 | A C expression used to determine whether @code{clear_by_pieces} will be used | |
6226 | to clear a chunk of memory, or whether some other block clear mechanism | |
6227 | will be used. Defaults to 1 if @code{move_by_pieces_ninsns} returns less | |
6228 | than @code{CLEAR_RATIO}. | |
6229 | @end defmac | |
6230 | ||
6231 | @defmac SET_RATIO (@var{speed}) | |
6232 | The threshold of number of scalar move insns, @emph{below} which a sequence | |
6233 | of insns should be generated to set memory to a constant value, instead of | |
ff2ce160 | 6234 | a block set insn or a library call. |
38f8b050 JR |
6235 | Increasing the value will always make code faster, but |
6236 | eventually incurs high cost in increased code size. | |
6237 | ||
6238 | The parameter @var{speed} is true if the code is currently being | |
6239 | optimized for speed rather than size. | |
6240 | ||
6241 | If you don't define this, it defaults to the value of @code{MOVE_RATIO}. | |
6242 | @end defmac | |
6243 | ||
6244 | @defmac SET_BY_PIECES_P (@var{size}, @var{alignment}) | |
6245 | A C expression used to determine whether @code{store_by_pieces} will be | |
ff2ce160 MS |
6246 | used to set a chunk of memory to a constant value, or whether some |
6247 | other mechanism will be used. Used by @code{__builtin_memset} when | |
38f8b050 JR |
6248 | storing values other than constant zero. |
6249 | Defaults to 1 if @code{move_by_pieces_ninsns} returns less | |
6250 | than @code{SET_RATIO}. | |
6251 | @end defmac | |
6252 | ||
6253 | @defmac STORE_BY_PIECES_P (@var{size}, @var{alignment}) | |
6254 | A C expression used to determine whether @code{store_by_pieces} will be | |
6255 | used to set a chunk of memory to a constant string value, or whether some | |
6256 | other mechanism will be used. Used by @code{__builtin_strcpy} when | |
6257 | called with a constant source string. | |
6258 | Defaults to 1 if @code{move_by_pieces_ninsns} returns less | |
6259 | than @code{MOVE_RATIO}. | |
6260 | @end defmac | |
6261 | ||
6262 | @defmac USE_LOAD_POST_INCREMENT (@var{mode}) | |
6263 | A C expression used to determine whether a load postincrement is a good | |
6264 | thing to use for a given mode. Defaults to the value of | |
6265 | @code{HAVE_POST_INCREMENT}. | |
6266 | @end defmac | |
6267 | ||
6268 | @defmac USE_LOAD_POST_DECREMENT (@var{mode}) | |
6269 | A C expression used to determine whether a load postdecrement is a good | |
6270 | thing to use for a given mode. Defaults to the value of | |
6271 | @code{HAVE_POST_DECREMENT}. | |
6272 | @end defmac | |
6273 | ||
6274 | @defmac USE_LOAD_PRE_INCREMENT (@var{mode}) | |
6275 | A C expression used to determine whether a load preincrement is a good | |
6276 | thing to use for a given mode. Defaults to the value of | |
6277 | @code{HAVE_PRE_INCREMENT}. | |
6278 | @end defmac | |
6279 | ||
6280 | @defmac USE_LOAD_PRE_DECREMENT (@var{mode}) | |
6281 | A C expression used to determine whether a load predecrement is a good | |
6282 | thing to use for a given mode. Defaults to the value of | |
6283 | @code{HAVE_PRE_DECREMENT}. | |
6284 | @end defmac | |
6285 | ||
6286 | @defmac USE_STORE_POST_INCREMENT (@var{mode}) | |
6287 | A C expression used to determine whether a store postincrement is a good | |
6288 | thing to use for a given mode. Defaults to the value of | |
6289 | @code{HAVE_POST_INCREMENT}. | |
6290 | @end defmac | |
6291 | ||
6292 | @defmac USE_STORE_POST_DECREMENT (@var{mode}) | |
6293 | A C expression used to determine whether a store postdecrement is a good | |
6294 | thing to use for a given mode. Defaults to the value of | |
6295 | @code{HAVE_POST_DECREMENT}. | |
6296 | @end defmac | |
6297 | ||
6298 | @defmac USE_STORE_PRE_INCREMENT (@var{mode}) | |
6299 | This macro is used to determine whether a store preincrement is a good | |
6300 | thing to use for a given mode. Defaults to the value of | |
6301 | @code{HAVE_PRE_INCREMENT}. | |
6302 | @end defmac | |
6303 | ||
6304 | @defmac USE_STORE_PRE_DECREMENT (@var{mode}) | |
6305 | This macro is used to determine whether a store predecrement is a good | |
6306 | thing to use for a given mode. Defaults to the value of | |
6307 | @code{HAVE_PRE_DECREMENT}. | |
6308 | @end defmac | |
6309 | ||
6310 | @defmac NO_FUNCTION_CSE | |
6311 | Define this macro if it is as good or better to call a constant | |
6312 | function address than to call an address kept in a register. | |
6313 | @end defmac | |
6314 | ||
6315 | @defmac RANGE_TEST_NON_SHORT_CIRCUIT | |
6316 | Define this macro if a non-short-circuit operation produced by | |
6317 | @samp{fold_range_test ()} is optimal. This macro defaults to true if | |
6318 | @code{BRANCH_COST} is greater than or equal to the value 2. | |
6319 | @end defmac | |
6320 | ||
6321 | @hook TARGET_RTX_COSTS | |
6322 | This target hook describes the relative costs of RTL expressions. | |
6323 | ||
6324 | The cost may depend on the precise form of the expression, which is | |
6325 | available for examination in @var{x}, and the rtx code of the expression | |
6326 | in which it is contained, found in @var{outer_code}. @var{code} is the | |
6327 | expression code---redundant, since it can be obtained with | |
6328 | @code{GET_CODE (@var{x})}. | |
6329 | ||
6330 | In implementing this hook, you can use the construct | |
6331 | @code{COSTS_N_INSNS (@var{n})} to specify a cost equal to @var{n} fast | |
6332 | instructions. | |
6333 | ||
6334 | On entry to the hook, @code{*@var{total}} contains a default estimate | |
6335 | for the cost of the expression. The hook should modify this value as | |
6336 | necessary. Traditionally, the default costs are @code{COSTS_N_INSNS (5)} | |
6337 | for multiplications, @code{COSTS_N_INSNS (7)} for division and modulus | |
6338 | operations, and @code{COSTS_N_INSNS (1)} for all other operations. | |
6339 | ||
6340 | When optimizing for code size, i.e.@: when @code{speed} is | |
6341 | false, this target hook should be used to estimate the relative | |
6342 | size cost of an expression, again relative to @code{COSTS_N_INSNS}. | |
6343 | ||
6344 | The hook returns true when all subexpressions of @var{x} have been | |
6345 | processed, and false when @code{rtx_cost} should recurse. | |
6346 | @end deftypefn | |
6347 | ||
6348 | @hook TARGET_ADDRESS_COST | |
6349 | This hook computes the cost of an addressing mode that contains | |
6350 | @var{address}. If not defined, the cost is computed from | |
6351 | the @var{address} expression and the @code{TARGET_RTX_COST} hook. | |
6352 | ||
6353 | For most CISC machines, the default cost is a good approximation of the | |
6354 | true cost of the addressing mode. However, on RISC machines, all | |
6355 | instructions normally have the same length and execution time. Hence | |
6356 | all addresses will have equal costs. | |
6357 | ||
6358 | In cases where more than one form of an address is known, the form with | |
6359 | the lowest cost will be used. If multiple forms have the same, lowest, | |
6360 | cost, the one that is the most complex will be used. | |
6361 | ||
6362 | For example, suppose an address that is equal to the sum of a register | |
6363 | and a constant is used twice in the same basic block. When this macro | |
6364 | is not defined, the address will be computed in a register and memory | |
6365 | references will be indirect through that register. On machines where | |
6366 | the cost of the addressing mode containing the sum is no higher than | |
6367 | that of a simple indirect reference, this will produce an additional | |
6368 | instruction and possibly require an additional register. Proper | |
6369 | specification of this macro eliminates this overhead for such machines. | |
6370 | ||
6371 | This hook is never called with an invalid address. | |
6372 | ||
6373 | On machines where an address involving more than one register is as | |
6374 | cheap as an address computation involving only one register, defining | |
6375 | @code{TARGET_ADDRESS_COST} to reflect this can cause two registers to | |
6376 | be live over a region of code where only one would have been if | |
6377 | @code{TARGET_ADDRESS_COST} were not defined in that manner. This effect | |
6378 | should be considered in the definition of this macro. Equivalent costs | |
6379 | should probably only be given to addresses with different numbers of | |
6380 | registers on machines with lots of registers. | |
6381 | @end deftypefn | |
6382 | ||
6383 | @node Scheduling | |
6384 | @section Adjusting the Instruction Scheduler | |
6385 | ||
6386 | The instruction scheduler may need a fair amount of machine-specific | |
6387 | adjustment in order to produce good code. GCC provides several target | |
6388 | hooks for this purpose. It is usually enough to define just a few of | |
6389 | them: try the first ones in this list first. | |
6390 | ||
6391 | @hook TARGET_SCHED_ISSUE_RATE | |
6392 | This hook returns the maximum number of instructions that can ever | |
6393 | issue at the same time on the target machine. The default is one. | |
6394 | Although the insn scheduler can define itself the possibility of issue | |
6395 | an insn on the same cycle, the value can serve as an additional | |
6396 | constraint to issue insns on the same simulated processor cycle (see | |
6397 | hooks @samp{TARGET_SCHED_REORDER} and @samp{TARGET_SCHED_REORDER2}). | |
6398 | This value must be constant over the entire compilation. If you need | |
6399 | it to vary depending on what the instructions are, you must use | |
6400 | @samp{TARGET_SCHED_VARIABLE_ISSUE}. | |
6401 | @end deftypefn | |
6402 | ||
6403 | @hook TARGET_SCHED_VARIABLE_ISSUE | |
6404 | This hook is executed by the scheduler after it has scheduled an insn | |
6405 | from the ready list. It should return the number of insns which can | |
6406 | still be issued in the current cycle. The default is | |
6407 | @samp{@w{@var{more} - 1}} for insns other than @code{CLOBBER} and | |
6408 | @code{USE}, which normally are not counted against the issue rate. | |
6409 | You should define this hook if some insns take more machine resources | |
6410 | than others, so that fewer insns can follow them in the same cycle. | |
6411 | @var{file} is either a null pointer, or a stdio stream to write any | |
6412 | debug output to. @var{verbose} is the verbose level provided by | |
6413 | @option{-fsched-verbose-@var{n}}. @var{insn} is the instruction that | |
6414 | was scheduled. | |
6415 | @end deftypefn | |
6416 | ||
6417 | @hook TARGET_SCHED_ADJUST_COST | |
6418 | This function corrects the value of @var{cost} based on the | |
6419 | relationship between @var{insn} and @var{dep_insn} through the | |
6420 | dependence @var{link}. It should return the new value. The default | |
6421 | is to make no adjustment to @var{cost}. This can be used for example | |
6422 | to specify to the scheduler using the traditional pipeline description | |
6423 | that an output- or anti-dependence does not incur the same cost as a | |
6424 | data-dependence. If the scheduler using the automaton based pipeline | |
6425 | description, the cost of anti-dependence is zero and the cost of | |
6426 | output-dependence is maximum of one and the difference of latency | |
6427 | times of the first and the second insns. If these values are not | |
6428 | acceptable, you could use the hook to modify them too. See also | |
6429 | @pxref{Processor pipeline description}. | |
6430 | @end deftypefn | |
6431 | ||
6432 | @hook TARGET_SCHED_ADJUST_PRIORITY | |
6433 | This hook adjusts the integer scheduling priority @var{priority} of | |
6434 | @var{insn}. It should return the new priority. Increase the priority to | |
6435 | execute @var{insn} earlier, reduce the priority to execute @var{insn} | |
6436 | later. Do not define this hook if you do not need to adjust the | |
6437 | scheduling priorities of insns. | |
6438 | @end deftypefn | |
6439 | ||
6440 | @hook TARGET_SCHED_REORDER | |
6441 | This hook is executed by the scheduler after it has scheduled the ready | |
6442 | list, to allow the machine description to reorder it (for example to | |
6443 | combine two small instructions together on @samp{VLIW} machines). | |
6444 | @var{file} is either a null pointer, or a stdio stream to write any | |
6445 | debug output to. @var{verbose} is the verbose level provided by | |
6446 | @option{-fsched-verbose-@var{n}}. @var{ready} is a pointer to the ready | |
6447 | list of instructions that are ready to be scheduled. @var{n_readyp} is | |
6448 | a pointer to the number of elements in the ready list. The scheduler | |
6449 | reads the ready list in reverse order, starting with | |
6450 | @var{ready}[@var{*n_readyp} @minus{} 1] and going to @var{ready}[0]. @var{clock} | |
6451 | is the timer tick of the scheduler. You may modify the ready list and | |
6452 | the number of ready insns. The return value is the number of insns that | |
6453 | can issue this cycle; normally this is just @code{issue_rate}. See also | |
6454 | @samp{TARGET_SCHED_REORDER2}. | |
6455 | @end deftypefn | |
6456 | ||
6457 | @hook TARGET_SCHED_REORDER2 | |
6458 | Like @samp{TARGET_SCHED_REORDER}, but called at a different time. That | |
6459 | function is called whenever the scheduler starts a new cycle. This one | |
6460 | is called once per iteration over a cycle, immediately after | |
6461 | @samp{TARGET_SCHED_VARIABLE_ISSUE}; it can reorder the ready list and | |
6462 | return the number of insns to be scheduled in the same cycle. Defining | |
6463 | this hook can be useful if there are frequent situations where | |
6464 | scheduling one insn causes other insns to become ready in the same | |
6465 | cycle. These other insns can then be taken into account properly. | |
6466 | @end deftypefn | |
6467 | ||
6468 | @hook TARGET_SCHED_DEPENDENCIES_EVALUATION_HOOK | |
6469 | This hook is called after evaluation forward dependencies of insns in | |
6470 | chain given by two parameter values (@var{head} and @var{tail} | |
6471 | correspondingly) but before insns scheduling of the insn chain. For | |
6472 | example, it can be used for better insn classification if it requires | |
6473 | analysis of dependencies. This hook can use backward and forward | |
6474 | dependencies of the insn scheduler because they are already | |
6475 | calculated. | |
6476 | @end deftypefn | |
6477 | ||
6478 | @hook TARGET_SCHED_INIT | |
6479 | This hook is executed by the scheduler at the beginning of each block of | |
6480 | instructions that are to be scheduled. @var{file} is either a null | |
6481 | pointer, or a stdio stream to write any debug output to. @var{verbose} | |
6482 | is the verbose level provided by @option{-fsched-verbose-@var{n}}. | |
6483 | @var{max_ready} is the maximum number of insns in the current scheduling | |
6484 | region that can be live at the same time. This can be used to allocate | |
6485 | scratch space if it is needed, e.g.@: by @samp{TARGET_SCHED_REORDER}. | |
6486 | @end deftypefn | |
6487 | ||
6488 | @hook TARGET_SCHED_FINISH | |
6489 | This hook is executed by the scheduler at the end of each block of | |
6490 | instructions that are to be scheduled. It can be used to perform | |
6491 | cleanup of any actions done by the other scheduling hooks. @var{file} | |
6492 | is either a null pointer, or a stdio stream to write any debug output | |
6493 | to. @var{verbose} is the verbose level provided by | |
6494 | @option{-fsched-verbose-@var{n}}. | |
6495 | @end deftypefn | |
6496 | ||
6497 | @hook TARGET_SCHED_INIT_GLOBAL | |
6498 | This hook is executed by the scheduler after function level initializations. | |
6499 | @var{file} is either a null pointer, or a stdio stream to write any debug output to. | |
6500 | @var{verbose} is the verbose level provided by @option{-fsched-verbose-@var{n}}. | |
6501 | @var{old_max_uid} is the maximum insn uid when scheduling begins. | |
6502 | @end deftypefn | |
6503 | ||
6504 | @hook TARGET_SCHED_FINISH_GLOBAL | |
6505 | This is the cleanup hook corresponding to @code{TARGET_SCHED_INIT_GLOBAL}. | |
6506 | @var{file} is either a null pointer, or a stdio stream to write any debug output to. | |
6507 | @var{verbose} is the verbose level provided by @option{-fsched-verbose-@var{n}}. | |
6508 | @end deftypefn | |
6509 | ||
6510 | @hook TARGET_SCHED_DFA_PRE_CYCLE_INSN | |
6511 | The hook returns an RTL insn. The automaton state used in the | |
6512 | pipeline hazard recognizer is changed as if the insn were scheduled | |
6513 | when the new simulated processor cycle starts. Usage of the hook may | |
6514 | simplify the automaton pipeline description for some @acronym{VLIW} | |
6515 | processors. If the hook is defined, it is used only for the automaton | |
6516 | based pipeline description. The default is not to change the state | |
6517 | when the new simulated processor cycle starts. | |
6518 | @end deftypefn | |
6519 | ||
6520 | @hook TARGET_SCHED_INIT_DFA_PRE_CYCLE_INSN | |
6521 | The hook can be used to initialize data used by the previous hook. | |
6522 | @end deftypefn | |
6523 | ||
6524 | @hook TARGET_SCHED_DFA_POST_CYCLE_INSN | |
6525 | The hook is analogous to @samp{TARGET_SCHED_DFA_PRE_CYCLE_INSN} but used | |
6526 | to changed the state as if the insn were scheduled when the new | |
6527 | simulated processor cycle finishes. | |
6528 | @end deftypefn | |
6529 | ||
6530 | @hook TARGET_SCHED_INIT_DFA_POST_CYCLE_INSN | |
6531 | The hook is analogous to @samp{TARGET_SCHED_INIT_DFA_PRE_CYCLE_INSN} but | |
6532 | used to initialize data used by the previous hook. | |
6533 | @end deftypefn | |
6534 | ||
6535 | @hook TARGET_SCHED_DFA_PRE_ADVANCE_CYCLE | |
6536 | The hook to notify target that the current simulated cycle is about to finish. | |
6537 | The hook is analogous to @samp{TARGET_SCHED_DFA_PRE_CYCLE_INSN} but used | |
6538 | to change the state in more complicated situations - e.g., when advancing | |
6539 | state on a single insn is not enough. | |
6540 | @end deftypefn | |
6541 | ||
6542 | @hook TARGET_SCHED_DFA_POST_ADVANCE_CYCLE | |
6543 | The hook to notify target that new simulated cycle has just started. | |
6544 | The hook is analogous to @samp{TARGET_SCHED_DFA_POST_CYCLE_INSN} but used | |
6545 | to change the state in more complicated situations - e.g., when advancing | |
6546 | state on a single insn is not enough. | |
6547 | @end deftypefn | |
6548 | ||
6549 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD | |
6550 | This hook controls better choosing an insn from the ready insn queue | |
6551 | for the @acronym{DFA}-based insn scheduler. Usually the scheduler | |
6552 | chooses the first insn from the queue. If the hook returns a positive | |
6553 | value, an additional scheduler code tries all permutations of | |
6554 | @samp{TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD ()} | |
6555 | subsequent ready insns to choose an insn whose issue will result in | |
6556 | maximal number of issued insns on the same cycle. For the | |
6557 | @acronym{VLIW} processor, the code could actually solve the problem of | |
6558 | packing simple insns into the @acronym{VLIW} insn. Of course, if the | |
6559 | rules of @acronym{VLIW} packing are described in the automaton. | |
6560 | ||
6561 | This code also could be used for superscalar @acronym{RISC} | |
6562 | processors. Let us consider a superscalar @acronym{RISC} processor | |
6563 | with 3 pipelines. Some insns can be executed in pipelines @var{A} or | |
6564 | @var{B}, some insns can be executed only in pipelines @var{B} or | |
6565 | @var{C}, and one insn can be executed in pipeline @var{B}. The | |
6566 | processor may issue the 1st insn into @var{A} and the 2nd one into | |
6567 | @var{B}. In this case, the 3rd insn will wait for freeing @var{B} | |
6568 | until the next cycle. If the scheduler issues the 3rd insn the first, | |
6569 | the processor could issue all 3 insns per cycle. | |
6570 | ||
6571 | Actually this code demonstrates advantages of the automaton based | |
6572 | pipeline hazard recognizer. We try quickly and easy many insn | |
6573 | schedules to choose the best one. | |
6574 | ||
6575 | The default is no multipass scheduling. | |
6576 | @end deftypefn | |
6577 | ||
6578 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD_GUARD | |
6579 | ||
6580 | This hook controls what insns from the ready insn queue will be | |
6581 | considered for the multipass insn scheduling. If the hook returns | |
6582 | zero for @var{insn}, the insn will be not chosen to | |
6583 | be issued. | |
6584 | ||
6585 | The default is that any ready insns can be chosen to be issued. | |
6586 | @end deftypefn | |
6587 | ||
894fd6f2 MK |
6588 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_BEGIN |
6589 | This hook prepares the target backend for a new round of multipass | |
6590 | scheduling. | |
6591 | @end deftypefn | |
6592 | ||
6593 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_ISSUE | |
6594 | This hook is called when multipass scheduling evaluates instruction INSN. | |
6595 | @end deftypefn | |
6596 | ||
6597 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_BACKTRACK | |
6598 | This is called when multipass scheduling backtracks from evaluation of | |
6599 | an instruction. | |
6600 | @end deftypefn | |
6601 | ||
6602 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_END | |
6603 | This hook notifies the target about the result of the concluded current | |
6604 | round of multipass scheduling. | |
6605 | @end deftypefn | |
6606 | ||
6607 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_INIT | |
2b0d3573 | 6608 | This hook initializes target-specific data used in multipass scheduling. |
894fd6f2 MK |
6609 | @end deftypefn |
6610 | ||
6611 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_FINI | |
2b0d3573 | 6612 | This hook finalizes target-specific data used in multipass scheduling. |
894fd6f2 MK |
6613 | @end deftypefn |
6614 | ||
c06bbdf7 | 6615 | @hook TARGET_SCHED_DFA_NEW_CYCLE |
38f8b050 JR |
6616 | This hook is called by the insn scheduler before issuing @var{insn} |
6617 | on cycle @var{clock}. If the hook returns nonzero, | |
6618 | @var{insn} is not issued on this processor cycle. Instead, | |
6619 | the processor cycle is advanced. If *@var{sort_p} | |
6620 | is zero, the insn ready queue is not sorted on the new cycle | |
6621 | start as usually. @var{dump} and @var{verbose} specify the file and | |
6622 | verbosity level to use for debugging output. | |
6623 | @var{last_clock} and @var{clock} are, respectively, the | |
6624 | processor cycle on which the previous insn has been issued, | |
6625 | and the current processor cycle. | |
6626 | @end deftypefn | |
6627 | ||
6628 | @hook TARGET_SCHED_IS_COSTLY_DEPENDENCE | |
6629 | This hook is used to define which dependences are considered costly by | |
6630 | the target, so costly that it is not advisable to schedule the insns that | |
6631 | are involved in the dependence too close to one another. The parameters | |
6632 | to this hook are as follows: The first parameter @var{_dep} is the dependence | |
6633 | being evaluated. The second parameter @var{cost} is the cost of the | |
6634 | dependence as estimated by the scheduler, and the third | |
6635 | parameter @var{distance} is the distance in cycles between the two insns. | |
6636 | The hook returns @code{true} if considering the distance between the two | |
6637 | insns the dependence between them is considered costly by the target, | |
6638 | and @code{false} otherwise. | |
6639 | ||
6640 | Defining this hook can be useful in multiple-issue out-of-order machines, | |
6641 | where (a) it's practically hopeless to predict the actual data/resource | |
6642 | delays, however: (b) there's a better chance to predict the actual grouping | |
6643 | that will be formed, and (c) correctly emulating the grouping can be very | |
6644 | important. In such targets one may want to allow issuing dependent insns | |
6645 | closer to one another---i.e., closer than the dependence distance; however, | |
6646 | not in cases of ``costly dependences'', which this hooks allows to define. | |
6647 | @end deftypefn | |
6648 | ||
6649 | @hook TARGET_SCHED_H_I_D_EXTENDED | |
6650 | This hook is called by the insn scheduler after emitting a new instruction to | |
6651 | the instruction stream. The hook notifies a target backend to extend its | |
6652 | per instruction data structures. | |
6653 | @end deftypefn | |
6654 | ||
6655 | @hook TARGET_SCHED_ALLOC_SCHED_CONTEXT | |
6656 | Return a pointer to a store large enough to hold target scheduling context. | |
6657 | @end deftypefn | |
6658 | ||
6659 | @hook TARGET_SCHED_INIT_SCHED_CONTEXT | |
6660 | Initialize store pointed to by @var{tc} to hold target scheduling context. | |
6661 | It @var{clean_p} is true then initialize @var{tc} as if scheduler is at the | |
6662 | beginning of the block. Otherwise, copy the current context into @var{tc}. | |
6663 | @end deftypefn | |
6664 | ||
6665 | @hook TARGET_SCHED_SET_SCHED_CONTEXT | |
6666 | Copy target scheduling context pointed to by @var{tc} to the current context. | |
6667 | @end deftypefn | |
6668 | ||
6669 | @hook TARGET_SCHED_CLEAR_SCHED_CONTEXT | |
6670 | Deallocate internal data in target scheduling context pointed to by @var{tc}. | |
6671 | @end deftypefn | |
6672 | ||
6673 | @hook TARGET_SCHED_FREE_SCHED_CONTEXT | |
6674 | Deallocate a store for target scheduling context pointed to by @var{tc}. | |
6675 | @end deftypefn | |
6676 | ||
6677 | @hook TARGET_SCHED_SPECULATE_INSN | |
6678 | This hook is called by the insn scheduler when @var{insn} has only | |
6679 | speculative dependencies and therefore can be scheduled speculatively. | |
6680 | The hook is used to check if the pattern of @var{insn} has a speculative | |
6681 | version and, in case of successful check, to generate that speculative | |
6682 | pattern. The hook should return 1, if the instruction has a speculative form, | |
6683 | or @minus{}1, if it doesn't. @var{request} describes the type of requested | |
6684 | speculation. If the return value equals 1 then @var{new_pat} is assigned | |
6685 | the generated speculative pattern. | |
6686 | @end deftypefn | |
6687 | ||
6688 | @hook TARGET_SCHED_NEEDS_BLOCK_P | |
6689 | This hook is called by the insn scheduler during generation of recovery code | |
6690 | for @var{insn}. It should return @code{true}, if the corresponding check | |
6691 | instruction should branch to recovery code, or @code{false} otherwise. | |
6692 | @end deftypefn | |
6693 | ||
6694 | @hook TARGET_SCHED_GEN_SPEC_CHECK | |
6695 | This hook is called by the insn scheduler to generate a pattern for recovery | |
6696 | check instruction. If @var{mutate_p} is zero, then @var{insn} is a | |
6697 | speculative instruction for which the check should be generated. | |
6698 | @var{label} is either a label of a basic block, where recovery code should | |
6699 | be emitted, or a null pointer, when requested check doesn't branch to | |
6700 | recovery code (a simple check). If @var{mutate_p} is nonzero, then | |
6701 | a pattern for a branchy check corresponding to a simple check denoted by | |
6702 | @var{insn} should be generated. In this case @var{label} can't be null. | |
6703 | @end deftypefn | |
6704 | ||
6705 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD_GUARD_SPEC | |
6706 | This hook is used as a workaround for | |
6707 | @samp{TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD_GUARD} not being | |
6708 | called on the first instruction of the ready list. The hook is used to | |
6709 | discard speculative instructions that stand first in the ready list from | |
6710 | being scheduled on the current cycle. If the hook returns @code{false}, | |
6711 | @var{insn} will not be chosen to be issued. | |
6712 | For non-speculative instructions, | |
6713 | the hook should always return @code{true}. For example, in the ia64 backend | |
6714 | the hook is used to cancel data speculative insns when the ALAT table | |
6715 | is nearly full. | |
6716 | @end deftypefn | |
6717 | ||
6718 | @hook TARGET_SCHED_SET_SCHED_FLAGS | |
6719 | This hook is used by the insn scheduler to find out what features should be | |
6720 | enabled/used. | |
6721 | The structure *@var{spec_info} should be filled in by the target. | |
6722 | The structure describes speculation types that can be used in the scheduler. | |
6723 | @end deftypefn | |
6724 | ||
6725 | @hook TARGET_SCHED_SMS_RES_MII | |
6726 | This hook is called by the swing modulo scheduler to calculate a | |
6727 | resource-based lower bound which is based on the resources available in | |
6728 | the machine and the resources required by each instruction. The target | |
6729 | backend can use @var{g} to calculate such bound. A very simple lower | |
6730 | bound will be used in case this hook is not implemented: the total number | |
6731 | of instructions divided by the issue rate. | |
6732 | @end deftypefn | |
6733 | ||
7942e47e RY |
6734 | @hook TARGET_SCHED_DISPATCH |
6735 | This hook is called by Haifa Scheduler. It returns true if dispatch scheduling | |
6736 | is supported in hardware and the condition specified in the parameter is true. | |
6737 | @end deftypefn | |
6738 | ||
6739 | @hook TARGET_SCHED_DISPATCH_DO | |
6740 | This hook is called by Haifa Scheduler. It performs the operation specified | |
6741 | in its second parameter. | |
6742 | @end deftypefn | |
6743 | ||
b0bd15f7 BS |
6744 | @hook TARGET_SCHED_EXPOSED_PIPELINE |
6745 | ||
38f8b050 JR |
6746 | @node Sections |
6747 | @section Dividing the Output into Sections (Texts, Data, @dots{}) | |
6748 | @c the above section title is WAY too long. maybe cut the part between | |
6749 | @c the (...)? --mew 10feb93 | |
6750 | ||
6751 | An object file is divided into sections containing different types of | |
6752 | data. In the most common case, there are three sections: the @dfn{text | |
6753 | section}, which holds instructions and read-only data; the @dfn{data | |
6754 | section}, which holds initialized writable data; and the @dfn{bss | |
6755 | section}, which holds uninitialized data. Some systems have other kinds | |
6756 | of sections. | |
6757 | ||
6758 | @file{varasm.c} provides several well-known sections, such as | |
6759 | @code{text_section}, @code{data_section} and @code{bss_section}. | |
6760 | The normal way of controlling a @code{@var{foo}_section} variable | |
6761 | is to define the associated @code{@var{FOO}_SECTION_ASM_OP} macro, | |
6762 | as described below. The macros are only read once, when @file{varasm.c} | |
6763 | initializes itself, so their values must be run-time constants. | |
6764 | They may however depend on command-line flags. | |
6765 | ||
6766 | @emph{Note:} Some run-time files, such @file{crtstuff.c}, also make | |
6767 | use of the @code{@var{FOO}_SECTION_ASM_OP} macros, and expect them | |
6768 | to be string literals. | |
6769 | ||
6770 | Some assemblers require a different string to be written every time a | |
6771 | section is selected. If your assembler falls into this category, you | |
6772 | should define the @code{TARGET_ASM_INIT_SECTIONS} hook and use | |
6773 | @code{get_unnamed_section} to set up the sections. | |
6774 | ||
6775 | You must always create a @code{text_section}, either by defining | |
6776 | @code{TEXT_SECTION_ASM_OP} or by initializing @code{text_section} | |
6777 | in @code{TARGET_ASM_INIT_SECTIONS}. The same is true of | |
6778 | @code{data_section} and @code{DATA_SECTION_ASM_OP}. If you do not | |
6779 | create a distinct @code{readonly_data_section}, the default is to | |
6780 | reuse @code{text_section}. | |
6781 | ||
6782 | All the other @file{varasm.c} sections are optional, and are null | |
6783 | if the target does not provide them. | |
6784 | ||
6785 | @defmac TEXT_SECTION_ASM_OP | |
6786 | A C expression whose value is a string, including spacing, containing the | |
6787 | assembler operation that should precede instructions and read-only data. | |
6788 | Normally @code{"\t.text"} is right. | |
6789 | @end defmac | |
6790 | ||
6791 | @defmac HOT_TEXT_SECTION_NAME | |
6792 | If defined, a C string constant for the name of the section containing most | |
6793 | frequently executed functions of the program. If not defined, GCC will provide | |
6794 | a default definition if the target supports named sections. | |
6795 | @end defmac | |
6796 | ||
6797 | @defmac UNLIKELY_EXECUTED_TEXT_SECTION_NAME | |
6798 | If defined, a C string constant for the name of the section containing unlikely | |
6799 | executed functions in the program. | |
6800 | @end defmac | |
6801 | ||
6802 | @defmac DATA_SECTION_ASM_OP | |
6803 | A C expression whose value is a string, including spacing, containing the | |
6804 | assembler operation to identify the following data as writable initialized | |
6805 | data. Normally @code{"\t.data"} is right. | |
6806 | @end defmac | |
6807 | ||
6808 | @defmac SDATA_SECTION_ASM_OP | |
6809 | If defined, a C expression whose value is a string, including spacing, | |
6810 | containing the assembler operation to identify the following data as | |
6811 | initialized, writable small data. | |
6812 | @end defmac | |
6813 | ||
6814 | @defmac READONLY_DATA_SECTION_ASM_OP | |
6815 | A C expression whose value is a string, including spacing, containing the | |
6816 | assembler operation to identify the following data as read-only initialized | |
6817 | data. | |
6818 | @end defmac | |
6819 | ||
6820 | @defmac BSS_SECTION_ASM_OP | |
6821 | If defined, a C expression whose value is a string, including spacing, | |
6822 | containing the assembler operation to identify the following data as | |
07c5f94e AS |
6823 | uninitialized global data. If not defined, and |
6824 | @code{ASM_OUTPUT_ALIGNED_BSS} not defined, | |
38f8b050 JR |
6825 | uninitialized global data will be output in the data section if |
6826 | @option{-fno-common} is passed, otherwise @code{ASM_OUTPUT_COMMON} will be | |
6827 | used. | |
6828 | @end defmac | |
6829 | ||
6830 | @defmac SBSS_SECTION_ASM_OP | |
6831 | If defined, a C expression whose value is a string, including spacing, | |
6832 | containing the assembler operation to identify the following data as | |
6833 | uninitialized, writable small data. | |
6834 | @end defmac | |
6835 | ||
6836 | @defmac TLS_COMMON_ASM_OP | |
6837 | If defined, a C expression whose value is a string containing the | |
6838 | assembler operation to identify the following data as thread-local | |
6839 | common data. The default is @code{".tls_common"}. | |
6840 | @end defmac | |
6841 | ||
6842 | @defmac TLS_SECTION_ASM_FLAG | |
6843 | If defined, a C expression whose value is a character constant | |
6844 | containing the flag used to mark a section as a TLS section. The | |
6845 | default is @code{'T'}. | |
6846 | @end defmac | |
6847 | ||
6848 | @defmac INIT_SECTION_ASM_OP | |
6849 | If defined, a C expression whose value is a string, including spacing, | |
6850 | containing the assembler operation to identify the following data as | |
6851 | initialization code. If not defined, GCC will assume such a section does | |
6852 | not exist. This section has no corresponding @code{init_section} | |
6853 | variable; it is used entirely in runtime code. | |
6854 | @end defmac | |
6855 | ||
6856 | @defmac FINI_SECTION_ASM_OP | |
6857 | If defined, a C expression whose value is a string, including spacing, | |
6858 | containing the assembler operation to identify the following data as | |
6859 | finalization code. If not defined, GCC will assume such a section does | |
6860 | not exist. This section has no corresponding @code{fini_section} | |
6861 | variable; it is used entirely in runtime code. | |
6862 | @end defmac | |
6863 | ||
6864 | @defmac INIT_ARRAY_SECTION_ASM_OP | |
6865 | If defined, a C expression whose value is a string, including spacing, | |
6866 | containing the assembler operation to identify the following data as | |
6867 | part of the @code{.init_array} (or equivalent) section. If not | |
6868 | defined, GCC will assume such a section does not exist. Do not define | |
6869 | both this macro and @code{INIT_SECTION_ASM_OP}. | |
6870 | @end defmac | |
6871 | ||
6872 | @defmac FINI_ARRAY_SECTION_ASM_OP | |
6873 | If defined, a C expression whose value is a string, including spacing, | |
6874 | containing the assembler operation to identify the following data as | |
6875 | part of the @code{.fini_array} (or equivalent) section. If not | |
6876 | defined, GCC will assume such a section does not exist. Do not define | |
6877 | both this macro and @code{FINI_SECTION_ASM_OP}. | |
6878 | @end defmac | |
6879 | ||
6880 | @defmac CRT_CALL_STATIC_FUNCTION (@var{section_op}, @var{function}) | |
6881 | If defined, an ASM statement that switches to a different section | |
6882 | via @var{section_op}, calls @var{function}, and switches back to | |
6883 | the text section. This is used in @file{crtstuff.c} if | |
6884 | @code{INIT_SECTION_ASM_OP} or @code{FINI_SECTION_ASM_OP} to calls | |
6885 | to initialization and finalization functions from the init and fini | |
6886 | sections. By default, this macro uses a simple function call. Some | |
6887 | ports need hand-crafted assembly code to avoid dependencies on | |
6888 | registers initialized in the function prologue or to ensure that | |
6889 | constant pools don't end up too far way in the text section. | |
6890 | @end defmac | |
6891 | ||
6892 | @defmac TARGET_LIBGCC_SDATA_SECTION | |
6893 | If defined, a string which names the section into which small | |
6894 | variables defined in crtstuff and libgcc should go. This is useful | |
6895 | when the target has options for optimizing access to small data, and | |
6896 | you want the crtstuff and libgcc routines to be conservative in what | |
6897 | they expect of your application yet liberal in what your application | |
6898 | expects. For example, for targets with a @code{.sdata} section (like | |
6899 | MIPS), you could compile crtstuff with @code{-G 0} so that it doesn't | |
6900 | require small data support from your application, but use this macro | |
6901 | to put small data into @code{.sdata} so that your application can | |
6902 | access these variables whether it uses small data or not. | |
6903 | @end defmac | |
6904 | ||
6905 | @defmac FORCE_CODE_SECTION_ALIGN | |
6906 | If defined, an ASM statement that aligns a code section to some | |
6907 | arbitrary boundary. This is used to force all fragments of the | |
6908 | @code{.init} and @code{.fini} sections to have to same alignment | |
6909 | and thus prevent the linker from having to add any padding. | |
6910 | @end defmac | |
6911 | ||
6912 | @defmac JUMP_TABLES_IN_TEXT_SECTION | |
6913 | Define this macro to be an expression with a nonzero value if jump | |
6914 | tables (for @code{tablejump} insns) should be output in the text | |
6915 | section, along with the assembler instructions. Otherwise, the | |
6916 | readonly data section is used. | |
6917 | ||
6918 | This macro is irrelevant if there is no separate readonly data section. | |
6919 | @end defmac | |
6920 | ||
6921 | @hook TARGET_ASM_INIT_SECTIONS | |
6922 | Define this hook if you need to do something special to set up the | |
6923 | @file{varasm.c} sections, or if your target has some special sections | |
6924 | of its own that you need to create. | |
6925 | ||
6926 | GCC calls this hook after processing the command line, but before writing | |
6927 | any assembly code, and before calling any of the section-returning hooks | |
6928 | described below. | |
6929 | @end deftypefn | |
6930 | ||
6931 | @hook TARGET_ASM_RELOC_RW_MASK | |
6932 | Return a mask describing how relocations should be treated when | |
6933 | selecting sections. Bit 1 should be set if global relocations | |
6934 | should be placed in a read-write section; bit 0 should be set if | |
6935 | local relocations should be placed in a read-write section. | |
6936 | ||
6937 | The default version of this function returns 3 when @option{-fpic} | |
6938 | is in effect, and 0 otherwise. The hook is typically redefined | |
6939 | when the target cannot support (some kinds of) dynamic relocations | |
6940 | in read-only sections even in executables. | |
6941 | @end deftypefn | |
6942 | ||
6943 | @hook TARGET_ASM_SELECT_SECTION | |
6944 | Return the section into which @var{exp} should be placed. You can | |
6945 | assume that @var{exp} is either a @code{VAR_DECL} node or a constant of | |
6946 | some sort. @var{reloc} indicates whether the initial value of @var{exp} | |
6947 | requires link-time relocations. Bit 0 is set when variable contains | |
6948 | local relocations only, while bit 1 is set for global relocations. | |
6949 | @var{align} is the constant alignment in bits. | |
6950 | ||
6951 | The default version of this function takes care of putting read-only | |
6952 | variables in @code{readonly_data_section}. | |
6953 | ||
6954 | See also @var{USE_SELECT_SECTION_FOR_FUNCTIONS}. | |
6955 | @end deftypefn | |
6956 | ||
6957 | @defmac USE_SELECT_SECTION_FOR_FUNCTIONS | |
6958 | Define this macro if you wish TARGET_ASM_SELECT_SECTION to be called | |
6959 | for @code{FUNCTION_DECL}s as well as for variables and constants. | |
6960 | ||
6961 | In the case of a @code{FUNCTION_DECL}, @var{reloc} will be zero if the | |
6962 | function has been determined to be likely to be called, and nonzero if | |
6963 | it is unlikely to be called. | |
6964 | @end defmac | |
6965 | ||
6966 | @hook TARGET_ASM_UNIQUE_SECTION | |
6967 | Build up a unique section name, expressed as a @code{STRING_CST} node, | |
6968 | and assign it to @samp{DECL_SECTION_NAME (@var{decl})}. | |
6969 | As with @code{TARGET_ASM_SELECT_SECTION}, @var{reloc} indicates whether | |
6970 | the initial value of @var{exp} requires link-time relocations. | |
6971 | ||
6972 | The default version of this function appends the symbol name to the | |
6973 | ELF section name that would normally be used for the symbol. For | |
6974 | example, the function @code{foo} would be placed in @code{.text.foo}. | |
6975 | Whatever the actual target object format, this is often good enough. | |
6976 | @end deftypefn | |
6977 | ||
6978 | @hook TARGET_ASM_FUNCTION_RODATA_SECTION | |
6979 | Return the readonly data section associated with | |
6980 | @samp{DECL_SECTION_NAME (@var{decl})}. | |
6981 | The default version of this function selects @code{.gnu.linkonce.r.name} if | |
6982 | the function's section is @code{.gnu.linkonce.t.name}, @code{.rodata.name} | |
6983 | if function is in @code{.text.name}, and the normal readonly-data section | |
6984 | otherwise. | |
6985 | @end deftypefn | |
6986 | ||
727a65e6 BS |
6987 | @hook TARGET_ASM_MERGEABLE_RODATA_PREFIX |
6988 | ||
38f8b050 JR |
6989 | @hook TARGET_ASM_SELECT_RTX_SECTION |
6990 | Return the section into which a constant @var{x}, of mode @var{mode}, | |
6991 | should be placed. You can assume that @var{x} is some kind of | |
6992 | constant in RTL@. The argument @var{mode} is redundant except in the | |
6993 | case of a @code{const_int} rtx. @var{align} is the constant alignment | |
6994 | in bits. | |
6995 | ||
6996 | The default version of this function takes care of putting symbolic | |
6997 | constants in @code{flag_pic} mode in @code{data_section} and everything | |
6998 | else in @code{readonly_data_section}. | |
6999 | @end deftypefn | |
7000 | ||
7001 | @hook TARGET_MANGLE_DECL_ASSEMBLER_NAME | |
7002 | Define this hook if you need to postprocess the assembler name generated | |
7003 | by target-independent code. The @var{id} provided to this hook will be | |
7004 | the computed name (e.g., the macro @code{DECL_NAME} of the @var{decl} in C, | |
7005 | or the mangled name of the @var{decl} in C++). The return value of the | |
7006 | hook is an @code{IDENTIFIER_NODE} for the appropriate mangled name on | |
7007 | your target system. The default implementation of this hook just | |
7008 | returns the @var{id} provided. | |
7009 | @end deftypefn | |
7010 | ||
7011 | @hook TARGET_ENCODE_SECTION_INFO | |
7012 | Define this hook if references to a symbol or a constant must be | |
7013 | treated differently depending on something about the variable or | |
7014 | function named by the symbol (such as what section it is in). | |
7015 | ||
7016 | The hook is executed immediately after rtl has been created for | |
7017 | @var{decl}, which may be a variable or function declaration or | |
7018 | an entry in the constant pool. In either case, @var{rtl} is the | |
7019 | rtl in question. Do @emph{not} use @code{DECL_RTL (@var{decl})} | |
7020 | in this hook; that field may not have been initialized yet. | |
7021 | ||
7022 | In the case of a constant, it is safe to assume that the rtl is | |
7023 | a @code{mem} whose address is a @code{symbol_ref}. Most decls | |
7024 | will also have this form, but that is not guaranteed. Global | |
7025 | register variables, for instance, will have a @code{reg} for their | |
7026 | rtl. (Normally the right thing to do with such unusual rtl is | |
7027 | leave it alone.) | |
7028 | ||
7029 | The @var{new_decl_p} argument will be true if this is the first time | |
7030 | that @code{TARGET_ENCODE_SECTION_INFO} has been invoked on this decl. It will | |
7031 | be false for subsequent invocations, which will happen for duplicate | |
7032 | declarations. Whether or not anything must be done for the duplicate | |
7033 | declaration depends on whether the hook examines @code{DECL_ATTRIBUTES}. | |
7034 | @var{new_decl_p} is always true when the hook is called for a constant. | |
7035 | ||
7036 | @cindex @code{SYMBOL_REF_FLAG}, in @code{TARGET_ENCODE_SECTION_INFO} | |
7037 | The usual thing for this hook to do is to record flags in the | |
7038 | @code{symbol_ref}, using @code{SYMBOL_REF_FLAG} or @code{SYMBOL_REF_FLAGS}. | |
7039 | Historically, the name string was modified if it was necessary to | |
7040 | encode more than one bit of information, but this practice is now | |
7041 | discouraged; use @code{SYMBOL_REF_FLAGS}. | |
7042 | ||
7043 | The default definition of this hook, @code{default_encode_section_info} | |
7044 | in @file{varasm.c}, sets a number of commonly-useful bits in | |
7045 | @code{SYMBOL_REF_FLAGS}. Check whether the default does what you need | |
7046 | before overriding it. | |
7047 | @end deftypefn | |
7048 | ||
7049 | @hook TARGET_STRIP_NAME_ENCODING | |
7050 | Decode @var{name} and return the real name part, sans | |
7051 | the characters that @code{TARGET_ENCODE_SECTION_INFO} | |
7052 | may have added. | |
7053 | @end deftypefn | |
7054 | ||
7055 | @hook TARGET_IN_SMALL_DATA_P | |
7056 | Returns true if @var{exp} should be placed into a ``small data'' section. | |
7057 | The default version of this hook always returns false. | |
7058 | @end deftypefn | |
7059 | ||
7060 | @hook TARGET_HAVE_SRODATA_SECTION | |
7061 | Contains the value true if the target places read-only | |
7062 | ``small data'' into a separate section. The default value is false. | |
7063 | @end deftypevr | |
7064 | ||
3c5273a9 KT |
7065 | @hook TARGET_PROFILE_BEFORE_PROLOGUE |
7066 | ||
38f8b050 JR |
7067 | @hook TARGET_BINDS_LOCAL_P |
7068 | Returns true if @var{exp} names an object for which name resolution | |
7069 | rules must resolve to the current ``module'' (dynamic shared library | |
7070 | or executable image). | |
7071 | ||
7072 | The default version of this hook implements the name resolution rules | |
7073 | for ELF, which has a looser model of global name binding than other | |
7074 | currently supported object file formats. | |
7075 | @end deftypefn | |
7076 | ||
7077 | @hook TARGET_HAVE_TLS | |
7078 | Contains the value true if the target supports thread-local storage. | |
7079 | The default value is false. | |
7080 | @end deftypevr | |
7081 | ||
7082 | ||
7083 | @node PIC | |
7084 | @section Position Independent Code | |
7085 | @cindex position independent code | |
7086 | @cindex PIC | |
7087 | ||
7088 | This section describes macros that help implement generation of position | |
7089 | independent code. Simply defining these macros is not enough to | |
7090 | generate valid PIC; you must also add support to the hook | |
7091 | @code{TARGET_LEGITIMATE_ADDRESS_P} and to the macro | |
7092 | @code{PRINT_OPERAND_ADDRESS}, as well as @code{LEGITIMIZE_ADDRESS}. You | |
7093 | must modify the definition of @samp{movsi} to do something appropriate | |
7094 | when the source operand contains a symbolic address. You may also | |
7095 | need to alter the handling of switch statements so that they use | |
7096 | relative addresses. | |
ff2ce160 | 7097 | @c i rearranged the order of the macros above to try to force one of |
38f8b050 JR |
7098 | @c them to the next line, to eliminate an overfull hbox. --mew 10feb93 |
7099 | ||
7100 | @defmac PIC_OFFSET_TABLE_REGNUM | |
7101 | The register number of the register used to address a table of static | |
7102 | data addresses in memory. In some cases this register is defined by a | |
7103 | processor's ``application binary interface'' (ABI)@. When this macro | |
7104 | is defined, RTL is generated for this register once, as with the stack | |
7105 | pointer and frame pointer registers. If this macro is not defined, it | |
7106 | is up to the machine-dependent files to allocate such a register (if | |
7107 | necessary). Note that this register must be fixed when in use (e.g.@: | |
7108 | when @code{flag_pic} is true). | |
7109 | @end defmac | |
7110 | ||
7111 | @defmac PIC_OFFSET_TABLE_REG_CALL_CLOBBERED | |
f8fe0a4a JM |
7112 | A C expression that is nonzero if the register defined by |
7113 | @code{PIC_OFFSET_TABLE_REGNUM} is clobbered by calls. If not defined, | |
7114 | the default is zero. Do not define | |
38f8b050 JR |
7115 | this macro if @code{PIC_OFFSET_TABLE_REGNUM} is not defined. |
7116 | @end defmac | |
7117 | ||
7118 | @defmac LEGITIMATE_PIC_OPERAND_P (@var{x}) | |
7119 | A C expression that is nonzero if @var{x} is a legitimate immediate | |
7120 | operand on the target machine when generating position independent code. | |
7121 | You can assume that @var{x} satisfies @code{CONSTANT_P}, so you need not | |
7122 | check this. You can also assume @var{flag_pic} is true, so you need not | |
7123 | check it either. You need not define this macro if all constants | |
7124 | (including @code{SYMBOL_REF}) can be immediate operands when generating | |
7125 | position independent code. | |
7126 | @end defmac | |
7127 | ||
7128 | @node Assembler Format | |
7129 | @section Defining the Output Assembler Language | |
7130 | ||
7131 | This section describes macros whose principal purpose is to describe how | |
7132 | to write instructions in assembler language---rather than what the | |
7133 | instructions do. | |
7134 | ||
7135 | @menu | |
7136 | * File Framework:: Structural information for the assembler file. | |
7137 | * Data Output:: Output of constants (numbers, strings, addresses). | |
7138 | * Uninitialized Data:: Output of uninitialized variables. | |
7139 | * Label Output:: Output and generation of labels. | |
7140 | * Initialization:: General principles of initialization | |
7141 | and termination routines. | |
7142 | * Macros for Initialization:: | |
7143 | Specific macros that control the handling of | |
7144 | initialization and termination routines. | |
7145 | * Instruction Output:: Output of actual instructions. | |
7146 | * Dispatch Tables:: Output of jump tables. | |
7147 | * Exception Region Output:: Output of exception region code. | |
7148 | * Alignment Output:: Pseudo ops for alignment and skipping data. | |
7149 | @end menu | |
7150 | ||
7151 | @node File Framework | |
7152 | @subsection The Overall Framework of an Assembler File | |
7153 | @cindex assembler format | |
7154 | @cindex output of assembler code | |
7155 | ||
7156 | @c prevent bad page break with this line | |
7157 | This describes the overall framework of an assembly file. | |
7158 | ||
7159 | @findex default_file_start | |
7160 | @hook TARGET_ASM_FILE_START | |
7161 | Output to @code{asm_out_file} any text which the assembler expects to | |
7162 | find at the beginning of a file. The default behavior is controlled | |
7163 | by two flags, documented below. Unless your target's assembler is | |
7164 | quite unusual, if you override the default, you should call | |
7165 | @code{default_file_start} at some point in your target hook. This | |
7166 | lets other target files rely on these variables. | |
7167 | @end deftypefn | |
7168 | ||
7169 | @hook TARGET_ASM_FILE_START_APP_OFF | |
7170 | If this flag is true, the text of the macro @code{ASM_APP_OFF} will be | |
7171 | printed as the very first line in the assembly file, unless | |
7172 | @option{-fverbose-asm} is in effect. (If that macro has been defined | |
7173 | to the empty string, this variable has no effect.) With the normal | |
7174 | definition of @code{ASM_APP_OFF}, the effect is to notify the GNU | |
7175 | assembler that it need not bother stripping comments or extra | |
7176 | whitespace from its input. This allows it to work a bit faster. | |
7177 | ||
7178 | The default is false. You should not set it to true unless you have | |
7179 | verified that your port does not generate any extra whitespace or | |
7180 | comments that will cause GAS to issue errors in NO_APP mode. | |
7181 | @end deftypevr | |
7182 | ||
7183 | @hook TARGET_ASM_FILE_START_FILE_DIRECTIVE | |
7184 | If this flag is true, @code{output_file_directive} will be called | |
7185 | for the primary source file, immediately after printing | |
7186 | @code{ASM_APP_OFF} (if that is enabled). Most ELF assemblers expect | |
7187 | this to be done. The default is false. | |
7188 | @end deftypevr | |
7189 | ||
7190 | @hook TARGET_ASM_FILE_END | |
7191 | Output to @code{asm_out_file} any text which the assembler expects | |
7192 | to find at the end of a file. The default is to output nothing. | |
7193 | @end deftypefn | |
7194 | ||
7195 | @deftypefun void file_end_indicate_exec_stack () | |
7196 | Some systems use a common convention, the @samp{.note.GNU-stack} | |
7197 | special section, to indicate whether or not an object file relies on | |
7198 | the stack being executable. If your system uses this convention, you | |
7199 | should define @code{TARGET_ASM_FILE_END} to this function. If you | |
7200 | need to do other things in that hook, have your hook function call | |
7201 | this function. | |
7202 | @end deftypefun | |
7203 | ||
7204 | @hook TARGET_ASM_LTO_START | |
7205 | Output to @code{asm_out_file} any text which the assembler expects | |
7206 | to find at the start of an LTO section. The default is to output | |
7207 | nothing. | |
7208 | @end deftypefn | |
7209 | ||
7210 | @hook TARGET_ASM_LTO_END | |
7211 | Output to @code{asm_out_file} any text which the assembler expects | |
7212 | to find at the end of an LTO section. The default is to output | |
7213 | nothing. | |
7214 | @end deftypefn | |
7215 | ||
7216 | @hook TARGET_ASM_CODE_END | |
7217 | Output to @code{asm_out_file} any text which is needed before emitting | |
7218 | unwind info and debug info at the end of a file. Some targets emit | |
7219 | here PIC setup thunks that cannot be emitted at the end of file, | |
7220 | because they couldn't have unwind info then. The default is to output | |
7221 | nothing. | |
7222 | @end deftypefn | |
7223 | ||
7224 | @defmac ASM_COMMENT_START | |
7225 | A C string constant describing how to begin a comment in the target | |
7226 | assembler language. The compiler assumes that the comment will end at | |
7227 | the end of the line. | |
7228 | @end defmac | |
7229 | ||
7230 | @defmac ASM_APP_ON | |
7231 | A C string constant for text to be output before each @code{asm} | |
7232 | statement or group of consecutive ones. Normally this is | |
7233 | @code{"#APP"}, which is a comment that has no effect on most | |
7234 | assemblers but tells the GNU assembler that it must check the lines | |
7235 | that follow for all valid assembler constructs. | |
7236 | @end defmac | |
7237 | ||
7238 | @defmac ASM_APP_OFF | |
7239 | A C string constant for text to be output after each @code{asm} | |
7240 | statement or group of consecutive ones. Normally this is | |
7241 | @code{"#NO_APP"}, which tells the GNU assembler to resume making the | |
7242 | time-saving assumptions that are valid for ordinary compiler output. | |
7243 | @end defmac | |
7244 | ||
7245 | @defmac ASM_OUTPUT_SOURCE_FILENAME (@var{stream}, @var{name}) | |
7246 | A C statement to output COFF information or DWARF debugging information | |
7247 | which indicates that filename @var{name} is the current source file to | |
7248 | the stdio stream @var{stream}. | |
7249 | ||
7250 | This macro need not be defined if the standard form of output | |
7251 | for the file format in use is appropriate. | |
7252 | @end defmac | |
7253 | ||
b5f5d41d AS |
7254 | @hook TARGET_ASM_OUTPUT_SOURCE_FILENAME |
7255 | ||
38f8b050 JR |
7256 | @defmac OUTPUT_QUOTED_STRING (@var{stream}, @var{string}) |
7257 | A C statement to output the string @var{string} to the stdio stream | |
7258 | @var{stream}. If you do not call the function @code{output_quoted_string} | |
7259 | in your config files, GCC will only call it to output filenames to | |
7260 | the assembler source. So you can use it to canonicalize the format | |
7261 | of the filename using this macro. | |
7262 | @end defmac | |
7263 | ||
7264 | @defmac ASM_OUTPUT_IDENT (@var{stream}, @var{string}) | |
7265 | A C statement to output something to the assembler file to handle a | |
7266 | @samp{#ident} directive containing the text @var{string}. If this | |
7267 | macro is not defined, nothing is output for a @samp{#ident} directive. | |
7268 | @end defmac | |
7269 | ||
7270 | @hook TARGET_ASM_NAMED_SECTION | |
7271 | Output assembly directives to switch to section @var{name}. The section | |
7272 | should have attributes as specified by @var{flags}, which is a bit mask | |
7273 | of the @code{SECTION_*} flags defined in @file{output.h}. If @var{decl} | |
7274 | is non-NULL, it is the @code{VAR_DECL} or @code{FUNCTION_DECL} with which | |
7275 | this section is associated. | |
7276 | @end deftypefn | |
7277 | ||
f16d3f39 JH |
7278 | @hook TARGET_ASM_FUNCTION_SECTION |
7279 | Return preferred text (sub)section for function @var{decl}. | |
7280 | Main purpose of this function is to separate cold, normal and hot | |
ff2ce160 | 7281 | functions. @var{startup} is true when function is known to be used only |
f16d3f39 JH |
7282 | at startup (from static constructors or it is @code{main()}). |
7283 | @var{exit} is true when function is known to be used only at exit | |
7284 | (from static destructors). | |
7285 | Return NULL if function should go to default text section. | |
7286 | @end deftypefn | |
7287 | ||
14d11d40 IS |
7288 | @hook TARGET_ASM_FUNCTION_SWITCHED_TEXT_SECTIONS |
7289 | ||
38f8b050 JR |
7290 | @hook TARGET_HAVE_NAMED_SECTIONS |
7291 | This flag is true if the target supports @code{TARGET_ASM_NAMED_SECTION}. | |
d5fabb58 | 7292 | It must not be modified by command-line option processing. |
38f8b050 JR |
7293 | @end deftypevr |
7294 | ||
7295 | @anchor{TARGET_HAVE_SWITCHABLE_BSS_SECTIONS} | |
7296 | @hook TARGET_HAVE_SWITCHABLE_BSS_SECTIONS | |
7297 | This flag is true if we can create zeroed data by switching to a BSS | |
7298 | section and then using @code{ASM_OUTPUT_SKIP} to allocate the space. | |
7299 | This is true on most ELF targets. | |
7300 | @end deftypevr | |
7301 | ||
7302 | @hook TARGET_SECTION_TYPE_FLAGS | |
7303 | Choose a set of section attributes for use by @code{TARGET_ASM_NAMED_SECTION} | |
7304 | based on a variable or function decl, a section name, and whether or not the | |
7305 | declaration's initializer may contain runtime relocations. @var{decl} may be | |
7306 | null, in which case read-write data should be assumed. | |
7307 | ||
7308 | The default version of this function handles choosing code vs data, | |
7309 | read-only vs read-write data, and @code{flag_pic}. You should only | |
7310 | need to override this if your target has special flags that might be | |
7311 | set via @code{__attribute__}. | |
7312 | @end deftypefn | |
7313 | ||
7314 | @hook TARGET_ASM_RECORD_GCC_SWITCHES | |
7315 | Provides the target with the ability to record the gcc command line | |
7316 | switches that have been passed to the compiler, and options that are | |
7317 | enabled. The @var{type} argument specifies what is being recorded. | |
7318 | It can take the following values: | |
7319 | ||
7320 | @table @gcctabopt | |
7321 | @item SWITCH_TYPE_PASSED | |
7322 | @var{text} is a command line switch that has been set by the user. | |
7323 | ||
7324 | @item SWITCH_TYPE_ENABLED | |
7325 | @var{text} is an option which has been enabled. This might be as a | |
7326 | direct result of a command line switch, or because it is enabled by | |
7327 | default or because it has been enabled as a side effect of a different | |
7328 | command line switch. For example, the @option{-O2} switch enables | |
7329 | various different individual optimization passes. | |
7330 | ||
7331 | @item SWITCH_TYPE_DESCRIPTIVE | |
7332 | @var{text} is either NULL or some descriptive text which should be | |
7333 | ignored. If @var{text} is NULL then it is being used to warn the | |
7334 | target hook that either recording is starting or ending. The first | |
7335 | time @var{type} is SWITCH_TYPE_DESCRIPTIVE and @var{text} is NULL, the | |
7336 | warning is for start up and the second time the warning is for | |
7337 | wind down. This feature is to allow the target hook to make any | |
7338 | necessary preparations before it starts to record switches and to | |
7339 | perform any necessary tidying up after it has finished recording | |
7340 | switches. | |
7341 | ||
7342 | @item SWITCH_TYPE_LINE_START | |
7343 | This option can be ignored by this target hook. | |
7344 | ||
7345 | @item SWITCH_TYPE_LINE_END | |
7346 | This option can be ignored by this target hook. | |
7347 | @end table | |
7348 | ||
7349 | The hook's return value must be zero. Other return values may be | |
7350 | supported in the future. | |
7351 | ||
7352 | By default this hook is set to NULL, but an example implementation is | |
7353 | provided for ELF based targets. Called @var{elf_record_gcc_switches}, | |
7354 | it records the switches as ASCII text inside a new, string mergeable | |
7355 | section in the assembler output file. The name of the new section is | |
7356 | provided by the @code{TARGET_ASM_RECORD_GCC_SWITCHES_SECTION} target | |
7357 | hook. | |
7358 | @end deftypefn | |
7359 | ||
7360 | @hook TARGET_ASM_RECORD_GCC_SWITCHES_SECTION | |
7361 | This is the name of the section that will be created by the example | |
7362 | ELF implementation of the @code{TARGET_ASM_RECORD_GCC_SWITCHES} target | |
7363 | hook. | |
7364 | @end deftypevr | |
7365 | ||
7366 | @need 2000 | |
7367 | @node Data Output | |
7368 | @subsection Output of Data | |
7369 | ||
7370 | ||
7371 | @hook TARGET_ASM_BYTE_OP | |
7372 | @deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_HI_OP | |
7373 | @deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_SI_OP | |
7374 | @deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_DI_OP | |
7375 | @deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_TI_OP | |
7376 | @deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_HI_OP | |
7377 | @deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_SI_OP | |
7378 | @deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_DI_OP | |
7379 | @deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_TI_OP | |
7380 | These hooks specify assembly directives for creating certain kinds | |
7381 | of integer object. The @code{TARGET_ASM_BYTE_OP} directive creates a | |
7382 | byte-sized object, the @code{TARGET_ASM_ALIGNED_HI_OP} one creates an | |
7383 | aligned two-byte object, and so on. Any of the hooks may be | |
7384 | @code{NULL}, indicating that no suitable directive is available. | |
7385 | ||
7386 | The compiler will print these strings at the start of a new line, | |
7387 | followed immediately by the object's initial value. In most cases, | |
7388 | the string should contain a tab, a pseudo-op, and then another tab. | |
7389 | @end deftypevr | |
7390 | ||
7391 | @hook TARGET_ASM_INTEGER | |
7392 | The @code{assemble_integer} function uses this hook to output an | |
7393 | integer object. @var{x} is the object's value, @var{size} is its size | |
7394 | in bytes and @var{aligned_p} indicates whether it is aligned. The | |
7395 | function should return @code{true} if it was able to output the | |
7396 | object. If it returns false, @code{assemble_integer} will try to | |
7397 | split the object into smaller parts. | |
7398 | ||
7399 | The default implementation of this hook will use the | |
7400 | @code{TARGET_ASM_BYTE_OP} family of strings, returning @code{false} | |
7401 | when the relevant string is @code{NULL}. | |
7402 | @end deftypefn | |
7403 | ||
6cbd8875 AS |
7404 | @hook TARGET_ASM_OUTPUT_ADDR_CONST_EXTRA |
7405 | A target hook to recognize @var{rtx} patterns that @code{output_addr_const} | |
7406 | can't deal with, and output assembly code to @var{file} corresponding to | |
7407 | the pattern @var{x}. This may be used to allow machine-dependent | |
7408 | @code{UNSPEC}s to appear within constants. | |
7409 | ||
7410 | If target hook fails to recognize a pattern, it must return @code{false}, | |
7411 | so that a standard error message is printed. If it prints an error message | |
7412 | itself, by calling, for example, @code{output_operand_lossage}, it may just | |
7413 | return @code{true}. | |
7414 | @end deftypefn | |
7415 | ||
38f8b050 JR |
7416 | @defmac OUTPUT_ADDR_CONST_EXTRA (@var{stream}, @var{x}, @var{fail}) |
7417 | A C statement to recognize @var{rtx} patterns that | |
7418 | @code{output_addr_const} can't deal with, and output assembly code to | |
7419 | @var{stream} corresponding to the pattern @var{x}. This may be used to | |
7420 | allow machine-dependent @code{UNSPEC}s to appear within constants. | |
7421 | ||
7422 | If @code{OUTPUT_ADDR_CONST_EXTRA} fails to recognize a pattern, it must | |
7423 | @code{goto fail}, so that a standard error message is printed. If it | |
7424 | prints an error message itself, by calling, for example, | |
7425 | @code{output_operand_lossage}, it may just complete normally. | |
7426 | @end defmac | |
7427 | ||
7428 | @defmac ASM_OUTPUT_ASCII (@var{stream}, @var{ptr}, @var{len}) | |
7429 | A C statement to output to the stdio stream @var{stream} an assembler | |
7430 | instruction to assemble a string constant containing the @var{len} | |
7431 | bytes at @var{ptr}. @var{ptr} will be a C expression of type | |
7432 | @code{char *} and @var{len} a C expression of type @code{int}. | |
7433 | ||
7434 | If the assembler has a @code{.ascii} pseudo-op as found in the | |
7435 | Berkeley Unix assembler, do not define the macro | |
7436 | @code{ASM_OUTPUT_ASCII}. | |
7437 | @end defmac | |
7438 | ||
7439 | @defmac ASM_OUTPUT_FDESC (@var{stream}, @var{decl}, @var{n}) | |
7440 | A C statement to output word @var{n} of a function descriptor for | |
7441 | @var{decl}. This must be defined if @code{TARGET_VTABLE_USES_DESCRIPTORS} | |
7442 | is defined, and is otherwise unused. | |
7443 | @end defmac | |
7444 | ||
7445 | @defmac CONSTANT_POOL_BEFORE_FUNCTION | |
7446 | You may define this macro as a C expression. You should define the | |
7447 | expression to have a nonzero value if GCC should output the constant | |
7448 | pool for a function before the code for the function, or a zero value if | |
7449 | GCC should output the constant pool after the function. If you do | |
7450 | not define this macro, the usual case, GCC will output the constant | |
7451 | pool before the function. | |
7452 | @end defmac | |
7453 | ||
7454 | @defmac ASM_OUTPUT_POOL_PROLOGUE (@var{file}, @var{funname}, @var{fundecl}, @var{size}) | |
7455 | A C statement to output assembler commands to define the start of the | |
7456 | constant pool for a function. @var{funname} is a string giving | |
7457 | the name of the function. Should the return type of the function | |
7458 | be required, it can be obtained via @var{fundecl}. @var{size} | |
7459 | is the size, in bytes, of the constant pool that will be written | |
7460 | immediately after this call. | |
7461 | ||
7462 | If no constant-pool prefix is required, the usual case, this macro need | |
7463 | not be defined. | |
7464 | @end defmac | |
7465 | ||
7466 | @defmac ASM_OUTPUT_SPECIAL_POOL_ENTRY (@var{file}, @var{x}, @var{mode}, @var{align}, @var{labelno}, @var{jumpto}) | |
7467 | A C statement (with or without semicolon) to output a constant in the | |
7468 | constant pool, if it needs special treatment. (This macro need not do | |
7469 | anything for RTL expressions that can be output normally.) | |
7470 | ||
7471 | The argument @var{file} is the standard I/O stream to output the | |
7472 | assembler code on. @var{x} is the RTL expression for the constant to | |
7473 | output, and @var{mode} is the machine mode (in case @var{x} is a | |
7474 | @samp{const_int}). @var{align} is the required alignment for the value | |
7475 | @var{x}; you should output an assembler directive to force this much | |
7476 | alignment. | |
7477 | ||
7478 | The argument @var{labelno} is a number to use in an internal label for | |
7479 | the address of this pool entry. The definition of this macro is | |
7480 | responsible for outputting the label definition at the proper place. | |
7481 | Here is how to do this: | |
7482 | ||
7483 | @smallexample | |
7484 | @code{(*targetm.asm_out.internal_label)} (@var{file}, "LC", @var{labelno}); | |
7485 | @end smallexample | |
7486 | ||
7487 | When you output a pool entry specially, you should end with a | |
7488 | @code{goto} to the label @var{jumpto}. This will prevent the same pool | |
7489 | entry from being output a second time in the usual manner. | |
7490 | ||
7491 | You need not define this macro if it would do nothing. | |
7492 | @end defmac | |
7493 | ||
7494 | @defmac ASM_OUTPUT_POOL_EPILOGUE (@var{file} @var{funname} @var{fundecl} @var{size}) | |
7495 | A C statement to output assembler commands to at the end of the constant | |
7496 | pool for a function. @var{funname} is a string giving the name of the | |
7497 | function. Should the return type of the function be required, you can | |
7498 | obtain it via @var{fundecl}. @var{size} is the size, in bytes, of the | |
7499 | constant pool that GCC wrote immediately before this call. | |
7500 | ||
7501 | If no constant-pool epilogue is required, the usual case, you need not | |
7502 | define this macro. | |
7503 | @end defmac | |
7504 | ||
7505 | @defmac IS_ASM_LOGICAL_LINE_SEPARATOR (@var{C}, @var{STR}) | |
7506 | Define this macro as a C expression which is nonzero if @var{C} is | |
7507 | used as a logical line separator by the assembler. @var{STR} points | |
7508 | to the position in the string where @var{C} was found; this can be used if | |
7509 | a line separator uses multiple characters. | |
7510 | ||
7511 | If you do not define this macro, the default is that only | |
7512 | the character @samp{;} is treated as a logical line separator. | |
7513 | @end defmac | |
7514 | ||
7515 | @hook TARGET_ASM_OPEN_PAREN | |
7516 | These target hooks are C string constants, describing the syntax in the | |
7517 | assembler for grouping arithmetic expressions. If not overridden, they | |
7518 | default to normal parentheses, which is correct for most assemblers. | |
7519 | @end deftypevr | |
7520 | ||
7521 | These macros are provided by @file{real.h} for writing the definitions | |
7522 | of @code{ASM_OUTPUT_DOUBLE} and the like: | |
7523 | ||
7524 | @defmac REAL_VALUE_TO_TARGET_SINGLE (@var{x}, @var{l}) | |
7525 | @defmacx REAL_VALUE_TO_TARGET_DOUBLE (@var{x}, @var{l}) | |
7526 | @defmacx REAL_VALUE_TO_TARGET_LONG_DOUBLE (@var{x}, @var{l}) | |
7527 | @defmacx REAL_VALUE_TO_TARGET_DECIMAL32 (@var{x}, @var{l}) | |
7528 | @defmacx REAL_VALUE_TO_TARGET_DECIMAL64 (@var{x}, @var{l}) | |
7529 | @defmacx REAL_VALUE_TO_TARGET_DECIMAL128 (@var{x}, @var{l}) | |
7530 | These translate @var{x}, of type @code{REAL_VALUE_TYPE}, to the | |
7531 | target's floating point representation, and store its bit pattern in | |
7532 | the variable @var{l}. For @code{REAL_VALUE_TO_TARGET_SINGLE} and | |
7533 | @code{REAL_VALUE_TO_TARGET_DECIMAL32}, this variable should be a | |
7534 | simple @code{long int}. For the others, it should be an array of | |
7535 | @code{long int}. The number of elements in this array is determined | |
7536 | by the size of the desired target floating point data type: 32 bits of | |
7537 | it go in each @code{long int} array element. Each array element holds | |
7538 | 32 bits of the result, even if @code{long int} is wider than 32 bits | |
7539 | on the host machine. | |
7540 | ||
7541 | The array element values are designed so that you can print them out | |
7542 | using @code{fprintf} in the order they should appear in the target | |
7543 | machine's memory. | |
7544 | @end defmac | |
7545 | ||
7546 | @node Uninitialized Data | |
7547 | @subsection Output of Uninitialized Variables | |
7548 | ||
7549 | Each of the macros in this section is used to do the whole job of | |
7550 | outputting a single uninitialized variable. | |
7551 | ||
7552 | @defmac ASM_OUTPUT_COMMON (@var{stream}, @var{name}, @var{size}, @var{rounded}) | |
7553 | A C statement (sans semicolon) to output to the stdio stream | |
7554 | @var{stream} the assembler definition of a common-label named | |
7555 | @var{name} whose size is @var{size} bytes. The variable @var{rounded} | |
7556 | is the size rounded up to whatever alignment the caller wants. It is | |
7557 | possible that @var{size} may be zero, for instance if a struct with no | |
7558 | other member than a zero-length array is defined. In this case, the | |
7559 | backend must output a symbol definition that allocates at least one | |
7560 | byte, both so that the address of the resulting object does not compare | |
7561 | equal to any other, and because some object formats cannot even express | |
7562 | the concept of a zero-sized common symbol, as that is how they represent | |
7563 | an ordinary undefined external. | |
7564 | ||
7565 | Use the expression @code{assemble_name (@var{stream}, @var{name})} to | |
7566 | output the name itself; before and after that, output the additional | |
7567 | assembler syntax for defining the name, and a newline. | |
7568 | ||
7569 | This macro controls how the assembler definitions of uninitialized | |
7570 | common global variables are output. | |
7571 | @end defmac | |
7572 | ||
7573 | @defmac ASM_OUTPUT_ALIGNED_COMMON (@var{stream}, @var{name}, @var{size}, @var{alignment}) | |
7574 | Like @code{ASM_OUTPUT_COMMON} except takes the required alignment as a | |
7575 | separate, explicit argument. If you define this macro, it is used in | |
7576 | place of @code{ASM_OUTPUT_COMMON}, and gives you more flexibility in | |
7577 | handling the required alignment of the variable. The alignment is specified | |
7578 | as the number of bits. | |
7579 | @end defmac | |
7580 | ||
7581 | @defmac ASM_OUTPUT_ALIGNED_DECL_COMMON (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) | |
7582 | Like @code{ASM_OUTPUT_ALIGNED_COMMON} except that @var{decl} of the | |
7583 | variable to be output, if there is one, or @code{NULL_TREE} if there | |
7584 | is no corresponding variable. If you define this macro, GCC will use it | |
7585 | in place of both @code{ASM_OUTPUT_COMMON} and | |
7586 | @code{ASM_OUTPUT_ALIGNED_COMMON}. Define this macro when you need to see | |
7587 | the variable's decl in order to chose what to output. | |
7588 | @end defmac | |
7589 | ||
07c5f94e | 7590 | @defmac ASM_OUTPUT_ALIGNED_BSS (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) |
38f8b050 JR |
7591 | A C statement (sans semicolon) to output to the stdio stream |
7592 | @var{stream} the assembler definition of uninitialized global @var{decl} named | |
07c5f94e AS |
7593 | @var{name} whose size is @var{size} bytes. The variable @var{alignment} |
7594 | is the alignment specified as the number of bits. | |
38f8b050 | 7595 | |
07c5f94e AS |
7596 | Try to use function @code{asm_output_aligned_bss} defined in file |
7597 | @file{varasm.c} when defining this macro. If unable, use the expression | |
38f8b050 JR |
7598 | @code{assemble_name (@var{stream}, @var{name})} to output the name itself; |
7599 | before and after that, output the additional assembler syntax for defining | |
7600 | the name, and a newline. | |
7601 | ||
07c5f94e | 7602 | There are two ways of handling global BSS@. One is to define this macro. |
38f8b050 JR |
7603 | The other is to have @code{TARGET_ASM_SELECT_SECTION} return a |
7604 | switchable BSS section (@pxref{TARGET_HAVE_SWITCHABLE_BSS_SECTIONS}). | |
7605 | You do not need to do both. | |
7606 | ||
7607 | Some languages do not have @code{common} data, and require a | |
7608 | non-common form of global BSS in order to handle uninitialized globals | |
7609 | efficiently. C++ is one example of this. However, if the target does | |
7610 | not support global BSS, the front end may choose to make globals | |
7611 | common in order to save space in the object file. | |
7612 | @end defmac | |
7613 | ||
38f8b050 JR |
7614 | @defmac ASM_OUTPUT_LOCAL (@var{stream}, @var{name}, @var{size}, @var{rounded}) |
7615 | A C statement (sans semicolon) to output to the stdio stream | |
7616 | @var{stream} the assembler definition of a local-common-label named | |
7617 | @var{name} whose size is @var{size} bytes. The variable @var{rounded} | |
7618 | is the size rounded up to whatever alignment the caller wants. | |
7619 | ||
7620 | Use the expression @code{assemble_name (@var{stream}, @var{name})} to | |
7621 | output the name itself; before and after that, output the additional | |
7622 | assembler syntax for defining the name, and a newline. | |
7623 | ||
7624 | This macro controls how the assembler definitions of uninitialized | |
7625 | static variables are output. | |
7626 | @end defmac | |
7627 | ||
7628 | @defmac ASM_OUTPUT_ALIGNED_LOCAL (@var{stream}, @var{name}, @var{size}, @var{alignment}) | |
7629 | Like @code{ASM_OUTPUT_LOCAL} except takes the required alignment as a | |
7630 | separate, explicit argument. If you define this macro, it is used in | |
7631 | place of @code{ASM_OUTPUT_LOCAL}, and gives you more flexibility in | |
7632 | handling the required alignment of the variable. The alignment is specified | |
7633 | as the number of bits. | |
7634 | @end defmac | |
7635 | ||
7636 | @defmac ASM_OUTPUT_ALIGNED_DECL_LOCAL (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) | |
7637 | Like @code{ASM_OUTPUT_ALIGNED_DECL} except that @var{decl} of the | |
7638 | variable to be output, if there is one, or @code{NULL_TREE} if there | |
7639 | is no corresponding variable. If you define this macro, GCC will use it | |
7640 | in place of both @code{ASM_OUTPUT_DECL} and | |
7641 | @code{ASM_OUTPUT_ALIGNED_DECL}. Define this macro when you need to see | |
7642 | the variable's decl in order to chose what to output. | |
7643 | @end defmac | |
7644 | ||
7645 | @node Label Output | |
7646 | @subsection Output and Generation of Labels | |
7647 | ||
7648 | @c prevent bad page break with this line | |
7649 | This is about outputting labels. | |
7650 | ||
7651 | @findex assemble_name | |
7652 | @defmac ASM_OUTPUT_LABEL (@var{stream}, @var{name}) | |
7653 | A C statement (sans semicolon) to output to the stdio stream | |
7654 | @var{stream} the assembler definition of a label named @var{name}. | |
7655 | Use the expression @code{assemble_name (@var{stream}, @var{name})} to | |
7656 | output the name itself; before and after that, output the additional | |
7657 | assembler syntax for defining the name, and a newline. A default | |
7658 | definition of this macro is provided which is correct for most systems. | |
7659 | @end defmac | |
7660 | ||
135a687e KT |
7661 | @defmac ASM_OUTPUT_FUNCTION_LABEL (@var{stream}, @var{name}, @var{decl}) |
7662 | A C statement (sans semicolon) to output to the stdio stream | |
7663 | @var{stream} the assembler definition of a label named @var{name} of | |
7664 | a function. | |
7665 | Use the expression @code{assemble_name (@var{stream}, @var{name})} to | |
7666 | output the name itself; before and after that, output the additional | |
7667 | assembler syntax for defining the name, and a newline. A default | |
7668 | definition of this macro is provided which is correct for most systems. | |
7669 | ||
7670 | If this macro is not defined, then the function name is defined in the | |
7671 | usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}). | |
7672 | @end defmac | |
7673 | ||
38f8b050 JR |
7674 | @findex assemble_name_raw |
7675 | @defmac ASM_OUTPUT_INTERNAL_LABEL (@var{stream}, @var{name}) | |
7676 | Identical to @code{ASM_OUTPUT_LABEL}, except that @var{name} is known | |
7677 | to refer to a compiler-generated label. The default definition uses | |
7678 | @code{assemble_name_raw}, which is like @code{assemble_name} except | |
7679 | that it is more efficient. | |
7680 | @end defmac | |
7681 | ||
7682 | @defmac SIZE_ASM_OP | |
7683 | A C string containing the appropriate assembler directive to specify the | |
7684 | size of a symbol, without any arguments. On systems that use ELF, the | |
7685 | default (in @file{config/elfos.h}) is @samp{"\t.size\t"}; on other | |
7686 | systems, the default is not to define this macro. | |
7687 | ||
7688 | Define this macro only if it is correct to use the default definitions | |
7689 | of @code{ASM_OUTPUT_SIZE_DIRECTIVE} and @code{ASM_OUTPUT_MEASURED_SIZE} | |
7690 | for your system. If you need your own custom definitions of those | |
7691 | macros, or if you do not need explicit symbol sizes at all, do not | |
7692 | define this macro. | |
7693 | @end defmac | |
7694 | ||
7695 | @defmac ASM_OUTPUT_SIZE_DIRECTIVE (@var{stream}, @var{name}, @var{size}) | |
7696 | A C statement (sans semicolon) to output to the stdio stream | |
7697 | @var{stream} a directive telling the assembler that the size of the | |
7698 | symbol @var{name} is @var{size}. @var{size} is a @code{HOST_WIDE_INT}. | |
7699 | If you define @code{SIZE_ASM_OP}, a default definition of this macro is | |
7700 | provided. | |
7701 | @end defmac | |
7702 | ||
7703 | @defmac ASM_OUTPUT_MEASURED_SIZE (@var{stream}, @var{name}) | |
7704 | A C statement (sans semicolon) to output to the stdio stream | |
7705 | @var{stream} a directive telling the assembler to calculate the size of | |
7706 | the symbol @var{name} by subtracting its address from the current | |
7707 | address. | |
7708 | ||
7709 | If you define @code{SIZE_ASM_OP}, a default definition of this macro is | |
7710 | provided. The default assumes that the assembler recognizes a special | |
7711 | @samp{.} symbol as referring to the current address, and can calculate | |
7712 | the difference between this and another symbol. If your assembler does | |
7713 | not recognize @samp{.} or cannot do calculations with it, you will need | |
7714 | to redefine @code{ASM_OUTPUT_MEASURED_SIZE} to use some other technique. | |
7715 | @end defmac | |
7716 | ||
7717 | @defmac TYPE_ASM_OP | |
7718 | A C string containing the appropriate assembler directive to specify the | |
7719 | type of a symbol, without any arguments. On systems that use ELF, the | |
7720 | default (in @file{config/elfos.h}) is @samp{"\t.type\t"}; on other | |
7721 | systems, the default is not to define this macro. | |
7722 | ||
7723 | Define this macro only if it is correct to use the default definition of | |
7724 | @code{ASM_OUTPUT_TYPE_DIRECTIVE} for your system. If you need your own | |
7725 | custom definition of this macro, or if you do not need explicit symbol | |
7726 | types at all, do not define this macro. | |
7727 | @end defmac | |
7728 | ||
7729 | @defmac TYPE_OPERAND_FMT | |
7730 | A C string which specifies (using @code{printf} syntax) the format of | |
7731 | the second operand to @code{TYPE_ASM_OP}. On systems that use ELF, the | |
7732 | default (in @file{config/elfos.h}) is @samp{"@@%s"}; on other systems, | |
7733 | the default is not to define this macro. | |
7734 | ||
7735 | Define this macro only if it is correct to use the default definition of | |
7736 | @code{ASM_OUTPUT_TYPE_DIRECTIVE} for your system. If you need your own | |
7737 | custom definition of this macro, or if you do not need explicit symbol | |
7738 | types at all, do not define this macro. | |
7739 | @end defmac | |
7740 | ||
7741 | @defmac ASM_OUTPUT_TYPE_DIRECTIVE (@var{stream}, @var{type}) | |
7742 | A C statement (sans semicolon) to output to the stdio stream | |
7743 | @var{stream} a directive telling the assembler that the type of the | |
7744 | symbol @var{name} is @var{type}. @var{type} is a C string; currently, | |
7745 | that string is always either @samp{"function"} or @samp{"object"}, but | |
7746 | you should not count on this. | |
7747 | ||
7748 | If you define @code{TYPE_ASM_OP} and @code{TYPE_OPERAND_FMT}, a default | |
7749 | definition of this macro is provided. | |
7750 | @end defmac | |
7751 | ||
7752 | @defmac ASM_DECLARE_FUNCTION_NAME (@var{stream}, @var{name}, @var{decl}) | |
7753 | A C statement (sans semicolon) to output to the stdio stream | |
7754 | @var{stream} any text necessary for declaring the name @var{name} of a | |
7755 | function which is being defined. This macro is responsible for | |
7756 | outputting the label definition (perhaps using | |
135a687e | 7757 | @code{ASM_OUTPUT_FUNCTION_LABEL}). The argument @var{decl} is the |
38f8b050 JR |
7758 | @code{FUNCTION_DECL} tree node representing the function. |
7759 | ||
7760 | If this macro is not defined, then the function name is defined in the | |
135a687e | 7761 | usual manner as a label (by means of @code{ASM_OUTPUT_FUNCTION_LABEL}). |
38f8b050 JR |
7762 | |
7763 | You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} in the definition | |
7764 | of this macro. | |
7765 | @end defmac | |
7766 | ||
7767 | @defmac ASM_DECLARE_FUNCTION_SIZE (@var{stream}, @var{name}, @var{decl}) | |
7768 | A C statement (sans semicolon) to output to the stdio stream | |
7769 | @var{stream} any text necessary for declaring the size of a function | |
7770 | which is being defined. The argument @var{name} is the name of the | |
7771 | function. The argument @var{decl} is the @code{FUNCTION_DECL} tree node | |
7772 | representing the function. | |
7773 | ||
7774 | If this macro is not defined, then the function size is not defined. | |
7775 | ||
7776 | You may wish to use @code{ASM_OUTPUT_MEASURED_SIZE} in the definition | |
7777 | of this macro. | |
7778 | @end defmac | |
7779 | ||
7780 | @defmac ASM_DECLARE_OBJECT_NAME (@var{stream}, @var{name}, @var{decl}) | |
7781 | A C statement (sans semicolon) to output to the stdio stream | |
7782 | @var{stream} any text necessary for declaring the name @var{name} of an | |
7783 | initialized variable which is being defined. This macro must output the | |
7784 | label definition (perhaps using @code{ASM_OUTPUT_LABEL}). The argument | |
7785 | @var{decl} is the @code{VAR_DECL} tree node representing the variable. | |
7786 | ||
7787 | If this macro is not defined, then the variable name is defined in the | |
7788 | usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}). | |
7789 | ||
7790 | You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} and/or | |
7791 | @code{ASM_OUTPUT_SIZE_DIRECTIVE} in the definition of this macro. | |
7792 | @end defmac | |
7793 | ||
ad78130c | 7794 | @hook TARGET_ASM_DECLARE_CONSTANT_NAME |
38f8b050 JR |
7795 | A target hook to output to the stdio stream @var{file} any text necessary |
7796 | for declaring the name @var{name} of a constant which is being defined. This | |
7797 | target hook is responsible for outputting the label definition (perhaps using | |
7798 | @code{assemble_label}). The argument @var{exp} is the value of the constant, | |
7799 | and @var{size} is the size of the constant in bytes. The @var{name} | |
7800 | will be an internal label. | |
7801 | ||
7802 | The default version of this target hook, define the @var{name} in the | |
7803 | usual manner as a label (by means of @code{assemble_label}). | |
7804 | ||
7805 | You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} in this target hook. | |
7806 | @end deftypefn | |
7807 | ||
7808 | @defmac ASM_DECLARE_REGISTER_GLOBAL (@var{stream}, @var{decl}, @var{regno}, @var{name}) | |
7809 | A C statement (sans semicolon) to output to the stdio stream | |
7810 | @var{stream} any text necessary for claiming a register @var{regno} | |
7811 | for a global variable @var{decl} with name @var{name}. | |
7812 | ||
7813 | If you don't define this macro, that is equivalent to defining it to do | |
7814 | nothing. | |
7815 | @end defmac | |
7816 | ||
7817 | @defmac ASM_FINISH_DECLARE_OBJECT (@var{stream}, @var{decl}, @var{toplevel}, @var{atend}) | |
7818 | A C statement (sans semicolon) to finish up declaring a variable name | |
7819 | once the compiler has processed its initializer fully and thus has had a | |
7820 | chance to determine the size of an array when controlled by an | |
7821 | initializer. This is used on systems where it's necessary to declare | |
7822 | something about the size of the object. | |
7823 | ||
7824 | If you don't define this macro, that is equivalent to defining it to do | |
7825 | nothing. | |
7826 | ||
7827 | You may wish to use @code{ASM_OUTPUT_SIZE_DIRECTIVE} and/or | |
7828 | @code{ASM_OUTPUT_MEASURED_SIZE} in the definition of this macro. | |
7829 | @end defmac | |
7830 | ||
7831 | @hook TARGET_ASM_GLOBALIZE_LABEL | |
7832 | This target hook is a function to output to the stdio stream | |
7833 | @var{stream} some commands that will make the label @var{name} global; | |
7834 | that is, available for reference from other files. | |
7835 | ||
7836 | The default implementation relies on a proper definition of | |
7837 | @code{GLOBAL_ASM_OP}. | |
7838 | @end deftypefn | |
7839 | ||
7840 | @hook TARGET_ASM_GLOBALIZE_DECL_NAME | |
7841 | This target hook is a function to output to the stdio stream | |
7842 | @var{stream} some commands that will make the name associated with @var{decl} | |
7843 | global; that is, available for reference from other files. | |
7844 | ||
7845 | The default implementation uses the TARGET_ASM_GLOBALIZE_LABEL target hook. | |
7846 | @end deftypefn | |
7847 | ||
7848 | @defmac ASM_WEAKEN_LABEL (@var{stream}, @var{name}) | |
7849 | A C statement (sans semicolon) to output to the stdio stream | |
7850 | @var{stream} some commands that will make the label @var{name} weak; | |
7851 | that is, available for reference from other files but only used if | |
7852 | no other definition is available. Use the expression | |
7853 | @code{assemble_name (@var{stream}, @var{name})} to output the name | |
7854 | itself; before and after that, output the additional assembler syntax | |
7855 | for making that name weak, and a newline. | |
7856 | ||
7857 | If you don't define this macro or @code{ASM_WEAKEN_DECL}, GCC will not | |
7858 | support weak symbols and you should not define the @code{SUPPORTS_WEAK} | |
7859 | macro. | |
7860 | @end defmac | |
7861 | ||
7862 | @defmac ASM_WEAKEN_DECL (@var{stream}, @var{decl}, @var{name}, @var{value}) | |
7863 | Combines (and replaces) the function of @code{ASM_WEAKEN_LABEL} and | |
7864 | @code{ASM_OUTPUT_WEAK_ALIAS}, allowing access to the associated function | |
7865 | or variable decl. If @var{value} is not @code{NULL}, this C statement | |
7866 | should output to the stdio stream @var{stream} assembler code which | |
7867 | defines (equates) the weak symbol @var{name} to have the value | |
7868 | @var{value}. If @var{value} is @code{NULL}, it should output commands | |
7869 | to make @var{name} weak. | |
7870 | @end defmac | |
7871 | ||
7872 | @defmac ASM_OUTPUT_WEAKREF (@var{stream}, @var{decl}, @var{name}, @var{value}) | |
7873 | Outputs a directive that enables @var{name} to be used to refer to | |
7874 | symbol @var{value} with weak-symbol semantics. @code{decl} is the | |
7875 | declaration of @code{name}. | |
7876 | @end defmac | |
7877 | ||
7878 | @defmac SUPPORTS_WEAK | |
74b90fe2 JDA |
7879 | A preprocessor constant expression which evaluates to true if the target |
7880 | supports weak symbols. | |
38f8b050 JR |
7881 | |
7882 | If you don't define this macro, @file{defaults.h} provides a default | |
7883 | definition. If either @code{ASM_WEAKEN_LABEL} or @code{ASM_WEAKEN_DECL} | |
74b90fe2 JDA |
7884 | is defined, the default definition is @samp{1}; otherwise, it is @samp{0}. |
7885 | @end defmac | |
7886 | ||
7887 | @defmac TARGET_SUPPORTS_WEAK | |
7888 | A C expression which evaluates to true if the target supports weak symbols. | |
7889 | ||
7890 | If you don't define this macro, @file{defaults.h} provides a default | |
7891 | definition. The default definition is @samp{(SUPPORTS_WEAK)}. Define | |
7892 | this macro if you want to control weak symbol support with a compiler | |
7893 | flag such as @option{-melf}. | |
38f8b050 JR |
7894 | @end defmac |
7895 | ||
7896 | @defmac MAKE_DECL_ONE_ONLY (@var{decl}) | |
7897 | A C statement (sans semicolon) to mark @var{decl} to be emitted as a | |
7898 | public symbol such that extra copies in multiple translation units will | |
7899 | be discarded by the linker. Define this macro if your object file | |
7900 | format provides support for this concept, such as the @samp{COMDAT} | |
7901 | section flags in the Microsoft Windows PE/COFF format, and this support | |
7902 | requires changes to @var{decl}, such as putting it in a separate section. | |
7903 | @end defmac | |
7904 | ||
7905 | @defmac SUPPORTS_ONE_ONLY | |
7906 | A C expression which evaluates to true if the target supports one-only | |
7907 | semantics. | |
7908 | ||
7909 | If you don't define this macro, @file{varasm.c} provides a default | |
7910 | definition. If @code{MAKE_DECL_ONE_ONLY} is defined, the default | |
7911 | definition is @samp{1}; otherwise, it is @samp{0}. Define this macro if | |
7912 | you want to control one-only symbol support with a compiler flag, or if | |
7913 | setting the @code{DECL_ONE_ONLY} flag is enough to mark a declaration to | |
7914 | be emitted as one-only. | |
7915 | @end defmac | |
7916 | ||
7917 | @hook TARGET_ASM_ASSEMBLE_VISIBILITY | |
7918 | This target hook is a function to output to @var{asm_out_file} some | |
7919 | commands that will make the symbol(s) associated with @var{decl} have | |
7920 | hidden, protected or internal visibility as specified by @var{visibility}. | |
7921 | @end deftypefn | |
7922 | ||
7923 | @defmac TARGET_WEAK_NOT_IN_ARCHIVE_TOC | |
7924 | A C expression that evaluates to true if the target's linker expects | |
7925 | that weak symbols do not appear in a static archive's table of contents. | |
7926 | The default is @code{0}. | |
7927 | ||
7928 | Leaving weak symbols out of an archive's table of contents means that, | |
7929 | if a symbol will only have a definition in one translation unit and | |
7930 | will have undefined references from other translation units, that | |
7931 | symbol should not be weak. Defining this macro to be nonzero will | |
7932 | thus have the effect that certain symbols that would normally be weak | |
7933 | (explicit template instantiations, and vtables for polymorphic classes | |
7934 | with noninline key methods) will instead be nonweak. | |
7935 | ||
7936 | The C++ ABI requires this macro to be zero. Define this macro for | |
7937 | targets where full C++ ABI compliance is impossible and where linker | |
7938 | restrictions require weak symbols to be left out of a static archive's | |
7939 | table of contents. | |
7940 | @end defmac | |
7941 | ||
7942 | @defmac ASM_OUTPUT_EXTERNAL (@var{stream}, @var{decl}, @var{name}) | |
7943 | A C statement (sans semicolon) to output to the stdio stream | |
7944 | @var{stream} any text necessary for declaring the name of an external | |
7945 | symbol named @var{name} which is referenced in this compilation but | |
7946 | not defined. The value of @var{decl} is the tree node for the | |
7947 | declaration. | |
7948 | ||
7949 | This macro need not be defined if it does not need to output anything. | |
7950 | The GNU assembler and most Unix assemblers don't require anything. | |
7951 | @end defmac | |
7952 | ||
7953 | @hook TARGET_ASM_EXTERNAL_LIBCALL | |
7954 | This target hook is a function to output to @var{asm_out_file} an assembler | |
7955 | pseudo-op to declare a library function name external. The name of the | |
7956 | library function is given by @var{symref}, which is a @code{symbol_ref}. | |
7957 | @end deftypefn | |
7958 | ||
7959 | @hook TARGET_ASM_MARK_DECL_PRESERVED | |
7960 | This target hook is a function to output to @var{asm_out_file} an assembler | |
7961 | directive to annotate @var{symbol} as used. The Darwin target uses the | |
7962 | .no_dead_code_strip directive. | |
7963 | @end deftypefn | |
7964 | ||
7965 | @defmac ASM_OUTPUT_LABELREF (@var{stream}, @var{name}) | |
7966 | A C statement (sans semicolon) to output to the stdio stream | |
7967 | @var{stream} a reference in assembler syntax to a label named | |
7968 | @var{name}. This should add @samp{_} to the front of the name, if that | |
7969 | is customary on your operating system, as it is in most Berkeley Unix | |
7970 | systems. This macro is used in @code{assemble_name}. | |
7971 | @end defmac | |
7972 | ||
77754180 DK |
7973 | @hook TARGET_MANGLE_ASSEMBLER_NAME |
7974 | ||
38f8b050 JR |
7975 | @defmac ASM_OUTPUT_SYMBOL_REF (@var{stream}, @var{sym}) |
7976 | A C statement (sans semicolon) to output a reference to | |
7977 | @code{SYMBOL_REF} @var{sym}. If not defined, @code{assemble_name} | |
7978 | will be used to output the name of the symbol. This macro may be used | |
7979 | to modify the way a symbol is referenced depending on information | |
7980 | encoded by @code{TARGET_ENCODE_SECTION_INFO}. | |
7981 | @end defmac | |
7982 | ||
7983 | @defmac ASM_OUTPUT_LABEL_REF (@var{stream}, @var{buf}) | |
7984 | A C statement (sans semicolon) to output a reference to @var{buf}, the | |
7985 | result of @code{ASM_GENERATE_INTERNAL_LABEL}. If not defined, | |
7986 | @code{assemble_name} will be used to output the name of the symbol. | |
7987 | This macro is not used by @code{output_asm_label}, or the @code{%l} | |
7988 | specifier that calls it; the intention is that this macro should be set | |
7989 | when it is necessary to output a label differently when its address is | |
7990 | being taken. | |
7991 | @end defmac | |
7992 | ||
7993 | @hook TARGET_ASM_INTERNAL_LABEL | |
7994 | A function to output to the stdio stream @var{stream} a label whose | |
7995 | name is made from the string @var{prefix} and the number @var{labelno}. | |
7996 | ||
7997 | It is absolutely essential that these labels be distinct from the labels | |
7998 | used for user-level functions and variables. Otherwise, certain programs | |
7999 | will have name conflicts with internal labels. | |
8000 | ||
8001 | It is desirable to exclude internal labels from the symbol table of the | |
8002 | object file. Most assemblers have a naming convention for labels that | |
8003 | should be excluded; on many systems, the letter @samp{L} at the | |
8004 | beginning of a label has this effect. You should find out what | |
8005 | convention your system uses, and follow it. | |
8006 | ||
8007 | The default version of this function utilizes @code{ASM_GENERATE_INTERNAL_LABEL}. | |
8008 | @end deftypefn | |
8009 | ||
8010 | @defmac ASM_OUTPUT_DEBUG_LABEL (@var{stream}, @var{prefix}, @var{num}) | |
8011 | A C statement to output to the stdio stream @var{stream} a debug info | |
8012 | label whose name is made from the string @var{prefix} and the number | |
8013 | @var{num}. This is useful for VLIW targets, where debug info labels | |
8014 | may need to be treated differently than branch target labels. On some | |
8015 | systems, branch target labels must be at the beginning of instruction | |
8016 | bundles, but debug info labels can occur in the middle of instruction | |
8017 | bundles. | |
8018 | ||
8019 | If this macro is not defined, then @code{(*targetm.asm_out.internal_label)} will be | |
8020 | used. | |
8021 | @end defmac | |
8022 | ||
8023 | @defmac ASM_GENERATE_INTERNAL_LABEL (@var{string}, @var{prefix}, @var{num}) | |
8024 | A C statement to store into the string @var{string} a label whose name | |
8025 | is made from the string @var{prefix} and the number @var{num}. | |
8026 | ||
8027 | This string, when output subsequently by @code{assemble_name}, should | |
8028 | produce the output that @code{(*targetm.asm_out.internal_label)} would produce | |
8029 | with the same @var{prefix} and @var{num}. | |
8030 | ||
8031 | If the string begins with @samp{*}, then @code{assemble_name} will | |
8032 | output the rest of the string unchanged. It is often convenient for | |
8033 | @code{ASM_GENERATE_INTERNAL_LABEL} to use @samp{*} in this way. If the | |
8034 | string doesn't start with @samp{*}, then @code{ASM_OUTPUT_LABELREF} gets | |
8035 | to output the string, and may change it. (Of course, | |
8036 | @code{ASM_OUTPUT_LABELREF} is also part of your machine description, so | |
8037 | you should know what it does on your machine.) | |
8038 | @end defmac | |
8039 | ||
8040 | @defmac ASM_FORMAT_PRIVATE_NAME (@var{outvar}, @var{name}, @var{number}) | |
8041 | A C expression to assign to @var{outvar} (which is a variable of type | |
8042 | @code{char *}) a newly allocated string made from the string | |
8043 | @var{name} and the number @var{number}, with some suitable punctuation | |
8044 | added. Use @code{alloca} to get space for the string. | |
8045 | ||
8046 | The string will be used as an argument to @code{ASM_OUTPUT_LABELREF} to | |
8047 | produce an assembler label for an internal static variable whose name is | |
8048 | @var{name}. Therefore, the string must be such as to result in valid | |
8049 | assembler code. The argument @var{number} is different each time this | |
8050 | macro is executed; it prevents conflicts between similarly-named | |
8051 | internal static variables in different scopes. | |
8052 | ||
8053 | Ideally this string should not be a valid C identifier, to prevent any | |
8054 | conflict with the user's own symbols. Most assemblers allow periods | |
8055 | or percent signs in assembler symbols; putting at least one of these | |
8056 | between the name and the number will suffice. | |
8057 | ||
8058 | If this macro is not defined, a default definition will be provided | |
8059 | which is correct for most systems. | |
8060 | @end defmac | |
8061 | ||
8062 | @defmac ASM_OUTPUT_DEF (@var{stream}, @var{name}, @var{value}) | |
8063 | A C statement to output to the stdio stream @var{stream} assembler code | |
8064 | which defines (equates) the symbol @var{name} to have the value @var{value}. | |
8065 | ||
8066 | @findex SET_ASM_OP | |
8067 | If @code{SET_ASM_OP} is defined, a default definition is provided which is | |
8068 | correct for most systems. | |
8069 | @end defmac | |
8070 | ||
8071 | @defmac ASM_OUTPUT_DEF_FROM_DECLS (@var{stream}, @var{decl_of_name}, @var{decl_of_value}) | |
8072 | A C statement to output to the stdio stream @var{stream} assembler code | |
8073 | which defines (equates) the symbol whose tree node is @var{decl_of_name} | |
8074 | to have the value of the tree node @var{decl_of_value}. This macro will | |
8075 | be used in preference to @samp{ASM_OUTPUT_DEF} if it is defined and if | |
8076 | the tree nodes are available. | |
8077 | ||
8078 | @findex SET_ASM_OP | |
8079 | If @code{SET_ASM_OP} is defined, a default definition is provided which is | |
8080 | correct for most systems. | |
8081 | @end defmac | |
8082 | ||
8083 | @defmac TARGET_DEFERRED_OUTPUT_DEFS (@var{decl_of_name}, @var{decl_of_value}) | |
8084 | A C statement that evaluates to true if the assembler code which defines | |
8085 | (equates) the symbol whose tree node is @var{decl_of_name} to have the value | |
8086 | of the tree node @var{decl_of_value} should be emitted near the end of the | |
8087 | current compilation unit. The default is to not defer output of defines. | |
8088 | This macro affects defines output by @samp{ASM_OUTPUT_DEF} and | |
8089 | @samp{ASM_OUTPUT_DEF_FROM_DECLS}. | |
8090 | @end defmac | |
8091 | ||
8092 | @defmac ASM_OUTPUT_WEAK_ALIAS (@var{stream}, @var{name}, @var{value}) | |
8093 | A C statement to output to the stdio stream @var{stream} assembler code | |
8094 | which defines (equates) the weak symbol @var{name} to have the value | |
8095 | @var{value}. If @var{value} is @code{NULL}, it defines @var{name} as | |
8096 | an undefined weak symbol. | |
8097 | ||
8098 | Define this macro if the target only supports weak aliases; define | |
8099 | @code{ASM_OUTPUT_DEF} instead if possible. | |
8100 | @end defmac | |
8101 | ||
8102 | @defmac OBJC_GEN_METHOD_LABEL (@var{buf}, @var{is_inst}, @var{class_name}, @var{cat_name}, @var{sel_name}) | |
8103 | Define this macro to override the default assembler names used for | |
8104 | Objective-C methods. | |
8105 | ||
8106 | The default name is a unique method number followed by the name of the | |
8107 | class (e.g.@: @samp{_1_Foo}). For methods in categories, the name of | |
8108 | the category is also included in the assembler name (e.g.@: | |
8109 | @samp{_1_Foo_Bar}). | |
8110 | ||
8111 | These names are safe on most systems, but make debugging difficult since | |
8112 | the method's selector is not present in the name. Therefore, particular | |
8113 | systems define other ways of computing names. | |
8114 | ||
8115 | @var{buf} is an expression of type @code{char *} which gives you a | |
8116 | buffer in which to store the name; its length is as long as | |
8117 | @var{class_name}, @var{cat_name} and @var{sel_name} put together, plus | |
8118 | 50 characters extra. | |
8119 | ||
8120 | The argument @var{is_inst} specifies whether the method is an instance | |
8121 | method or a class method; @var{class_name} is the name of the class; | |
8122 | @var{cat_name} is the name of the category (or @code{NULL} if the method is not | |
8123 | in a category); and @var{sel_name} is the name of the selector. | |
8124 | ||
8125 | On systems where the assembler can handle quoted names, you can use this | |
8126 | macro to provide more human-readable names. | |
8127 | @end defmac | |
8128 | ||
8129 | @defmac ASM_DECLARE_CLASS_REFERENCE (@var{stream}, @var{name}) | |
8130 | A C statement (sans semicolon) to output to the stdio stream | |
8131 | @var{stream} commands to declare that the label @var{name} is an | |
8132 | Objective-C class reference. This is only needed for targets whose | |
8133 | linkers have special support for NeXT-style runtimes. | |
8134 | @end defmac | |
8135 | ||
8136 | @defmac ASM_DECLARE_UNRESOLVED_REFERENCE (@var{stream}, @var{name}) | |
8137 | A C statement (sans semicolon) to output to the stdio stream | |
8138 | @var{stream} commands to declare that the label @var{name} is an | |
8139 | unresolved Objective-C class reference. This is only needed for targets | |
8140 | whose linkers have special support for NeXT-style runtimes. | |
8141 | @end defmac | |
8142 | ||
8143 | @node Initialization | |
8144 | @subsection How Initialization Functions Are Handled | |
8145 | @cindex initialization routines | |
8146 | @cindex termination routines | |
8147 | @cindex constructors, output of | |
8148 | @cindex destructors, output of | |
8149 | ||
8150 | The compiled code for certain languages includes @dfn{constructors} | |
8151 | (also called @dfn{initialization routines})---functions to initialize | |
8152 | data in the program when the program is started. These functions need | |
8153 | to be called before the program is ``started''---that is to say, before | |
8154 | @code{main} is called. | |
8155 | ||
8156 | Compiling some languages generates @dfn{destructors} (also called | |
8157 | @dfn{termination routines}) that should be called when the program | |
8158 | terminates. | |
8159 | ||
8160 | To make the initialization and termination functions work, the compiler | |
8161 | must output something in the assembler code to cause those functions to | |
8162 | be called at the appropriate time. When you port the compiler to a new | |
8163 | system, you need to specify how to do this. | |
8164 | ||
8165 | There are two major ways that GCC currently supports the execution of | |
8166 | initialization and termination functions. Each way has two variants. | |
8167 | Much of the structure is common to all four variations. | |
8168 | ||
8169 | @findex __CTOR_LIST__ | |
8170 | @findex __DTOR_LIST__ | |
8171 | The linker must build two lists of these functions---a list of | |
8172 | initialization functions, called @code{__CTOR_LIST__}, and a list of | |
8173 | termination functions, called @code{__DTOR_LIST__}. | |
8174 | ||
8175 | Each list always begins with an ignored function pointer (which may hold | |
8176 | 0, @minus{}1, or a count of the function pointers after it, depending on | |
8177 | the environment). This is followed by a series of zero or more function | |
8178 | pointers to constructors (or destructors), followed by a function | |
8179 | pointer containing zero. | |
8180 | ||
8181 | Depending on the operating system and its executable file format, either | |
8182 | @file{crtstuff.c} or @file{libgcc2.c} traverses these lists at startup | |
8183 | time and exit time. Constructors are called in reverse order of the | |
8184 | list; destructors in forward order. | |
8185 | ||
8186 | The best way to handle static constructors works only for object file | |
8187 | formats which provide arbitrarily-named sections. A section is set | |
8188 | aside for a list of constructors, and another for a list of destructors. | |
8189 | Traditionally these are called @samp{.ctors} and @samp{.dtors}. Each | |
8190 | object file that defines an initialization function also puts a word in | |
8191 | the constructor section to point to that function. The linker | |
8192 | accumulates all these words into one contiguous @samp{.ctors} section. | |
8193 | Termination functions are handled similarly. | |
8194 | ||
8195 | This method will be chosen as the default by @file{target-def.h} if | |
8196 | @code{TARGET_ASM_NAMED_SECTION} is defined. A target that does not | |
8197 | support arbitrary sections, but does support special designated | |
8198 | constructor and destructor sections may define @code{CTORS_SECTION_ASM_OP} | |
8199 | and @code{DTORS_SECTION_ASM_OP} to achieve the same effect. | |
8200 | ||
8201 | When arbitrary sections are available, there are two variants, depending | |
8202 | upon how the code in @file{crtstuff.c} is called. On systems that | |
8203 | support a @dfn{.init} section which is executed at program startup, | |
8204 | parts of @file{crtstuff.c} are compiled into that section. The | |
8205 | program is linked by the @command{gcc} driver like this: | |
8206 | ||
8207 | @smallexample | |
8208 | ld -o @var{output_file} crti.o crtbegin.o @dots{} -lgcc crtend.o crtn.o | |
8209 | @end smallexample | |
8210 | ||
8211 | The prologue of a function (@code{__init}) appears in the @code{.init} | |
8212 | section of @file{crti.o}; the epilogue appears in @file{crtn.o}. Likewise | |
8213 | for the function @code{__fini} in the @dfn{.fini} section. Normally these | |
8214 | files are provided by the operating system or by the GNU C library, but | |
8215 | are provided by GCC for a few targets. | |
8216 | ||
8217 | The objects @file{crtbegin.o} and @file{crtend.o} are (for most targets) | |
8218 | compiled from @file{crtstuff.c}. They contain, among other things, code | |
8219 | fragments within the @code{.init} and @code{.fini} sections that branch | |
8220 | to routines in the @code{.text} section. The linker will pull all parts | |
8221 | of a section together, which results in a complete @code{__init} function | |
8222 | that invokes the routines we need at startup. | |
8223 | ||
8224 | To use this variant, you must define the @code{INIT_SECTION_ASM_OP} | |
8225 | macro properly. | |
8226 | ||
8227 | If no init section is available, when GCC compiles any function called | |
8228 | @code{main} (or more accurately, any function designated as a program | |
8229 | entry point by the language front end calling @code{expand_main_function}), | |
8230 | it inserts a procedure call to @code{__main} as the first executable code | |
8231 | after the function prologue. The @code{__main} function is defined | |
8232 | in @file{libgcc2.c} and runs the global constructors. | |
8233 | ||
8234 | In file formats that don't support arbitrary sections, there are again | |
8235 | two variants. In the simplest variant, the GNU linker (GNU @code{ld}) | |
8236 | and an `a.out' format must be used. In this case, | |
8237 | @code{TARGET_ASM_CONSTRUCTOR} is defined to produce a @code{.stabs} | |
8238 | entry of type @samp{N_SETT}, referencing the name @code{__CTOR_LIST__}, | |
8239 | and with the address of the void function containing the initialization | |
8240 | code as its value. The GNU linker recognizes this as a request to add | |
8241 | the value to a @dfn{set}; the values are accumulated, and are eventually | |
8242 | placed in the executable as a vector in the format described above, with | |
8243 | a leading (ignored) count and a trailing zero element. | |
8244 | @code{TARGET_ASM_DESTRUCTOR} is handled similarly. Since no init | |
8245 | section is available, the absence of @code{INIT_SECTION_ASM_OP} causes | |
8246 | the compilation of @code{main} to call @code{__main} as above, starting | |
8247 | the initialization process. | |
8248 | ||
8249 | The last variant uses neither arbitrary sections nor the GNU linker. | |
8250 | This is preferable when you want to do dynamic linking and when using | |
8251 | file formats which the GNU linker does not support, such as `ECOFF'@. In | |
8252 | this case, @code{TARGET_HAVE_CTORS_DTORS} is false, initialization and | |
8253 | termination functions are recognized simply by their names. This requires | |
8254 | an extra program in the linkage step, called @command{collect2}. This program | |
8255 | pretends to be the linker, for use with GCC; it does its job by running | |
8256 | the ordinary linker, but also arranges to include the vectors of | |
8257 | initialization and termination functions. These functions are called | |
8258 | via @code{__main} as described above. In order to use this method, | |
8259 | @code{use_collect2} must be defined in the target in @file{config.gcc}. | |
8260 | ||
8261 | @ifinfo | |
8262 | The following section describes the specific macros that control and | |
8263 | customize the handling of initialization and termination functions. | |
8264 | @end ifinfo | |
8265 | ||
8266 | @node Macros for Initialization | |
8267 | @subsection Macros Controlling Initialization Routines | |
8268 | ||
8269 | Here are the macros that control how the compiler handles initialization | |
8270 | and termination functions: | |
8271 | ||
8272 | @defmac INIT_SECTION_ASM_OP | |
8273 | If defined, a C string constant, including spacing, for the assembler | |
8274 | operation to identify the following data as initialization code. If not | |
8275 | defined, GCC will assume such a section does not exist. When you are | |
8276 | using special sections for initialization and termination functions, this | |
8277 | macro also controls how @file{crtstuff.c} and @file{libgcc2.c} arrange to | |
8278 | run the initialization functions. | |
8279 | @end defmac | |
8280 | ||
8281 | @defmac HAS_INIT_SECTION | |
8282 | If defined, @code{main} will not call @code{__main} as described above. | |
8283 | This macro should be defined for systems that control start-up code | |
8284 | on a symbol-by-symbol basis, such as OSF/1, and should not | |
8285 | be defined explicitly for systems that support @code{INIT_SECTION_ASM_OP}. | |
8286 | @end defmac | |
8287 | ||
8288 | @defmac LD_INIT_SWITCH | |
8289 | If defined, a C string constant for a switch that tells the linker that | |
8290 | the following symbol is an initialization routine. | |
8291 | @end defmac | |
8292 | ||
8293 | @defmac LD_FINI_SWITCH | |
8294 | If defined, a C string constant for a switch that tells the linker that | |
8295 | the following symbol is a finalization routine. | |
8296 | @end defmac | |
8297 | ||
8298 | @defmac COLLECT_SHARED_INIT_FUNC (@var{stream}, @var{func}) | |
8299 | If defined, a C statement that will write a function that can be | |
8300 | automatically called when a shared library is loaded. The function | |
8301 | should call @var{func}, which takes no arguments. If not defined, and | |
8302 | the object format requires an explicit initialization function, then a | |
8303 | function called @code{_GLOBAL__DI} will be generated. | |
8304 | ||
8305 | This function and the following one are used by collect2 when linking a | |
8306 | shared library that needs constructors or destructors, or has DWARF2 | |
8307 | exception tables embedded in the code. | |
8308 | @end defmac | |
8309 | ||
8310 | @defmac COLLECT_SHARED_FINI_FUNC (@var{stream}, @var{func}) | |
8311 | If defined, a C statement that will write a function that can be | |
8312 | automatically called when a shared library is unloaded. The function | |
8313 | should call @var{func}, which takes no arguments. If not defined, and | |
8314 | the object format requires an explicit finalization function, then a | |
8315 | function called @code{_GLOBAL__DD} will be generated. | |
8316 | @end defmac | |
8317 | ||
8318 | @defmac INVOKE__main | |
8319 | If defined, @code{main} will call @code{__main} despite the presence of | |
8320 | @code{INIT_SECTION_ASM_OP}. This macro should be defined for systems | |
8321 | where the init section is not actually run automatically, but is still | |
8322 | useful for collecting the lists of constructors and destructors. | |
8323 | @end defmac | |
8324 | ||
8325 | @defmac SUPPORTS_INIT_PRIORITY | |
8326 | If nonzero, the C++ @code{init_priority} attribute is supported and the | |
8327 | compiler should emit instructions to control the order of initialization | |
8328 | of objects. If zero, the compiler will issue an error message upon | |
8329 | encountering an @code{init_priority} attribute. | |
8330 | @end defmac | |
8331 | ||
8332 | @hook TARGET_HAVE_CTORS_DTORS | |
8333 | This value is true if the target supports some ``native'' method of | |
8334 | collecting constructors and destructors to be run at startup and exit. | |
8335 | It is false if we must use @command{collect2}. | |
8336 | @end deftypevr | |
8337 | ||
8338 | @hook TARGET_ASM_CONSTRUCTOR | |
8339 | If defined, a function that outputs assembler code to arrange to call | |
8340 | the function referenced by @var{symbol} at initialization time. | |
8341 | ||
8342 | Assume that @var{symbol} is a @code{SYMBOL_REF} for a function taking | |
8343 | no arguments and with no return value. If the target supports initialization | |
8344 | priorities, @var{priority} is a value between 0 and @code{MAX_INIT_PRIORITY}; | |
8345 | otherwise it must be @code{DEFAULT_INIT_PRIORITY}. | |
8346 | ||
8347 | If this macro is not defined by the target, a suitable default will | |
8348 | be chosen if (1) the target supports arbitrary section names, (2) the | |
8349 | target defines @code{CTORS_SECTION_ASM_OP}, or (3) @code{USE_COLLECT2} | |
8350 | is not defined. | |
8351 | @end deftypefn | |
8352 | ||
8353 | @hook TARGET_ASM_DESTRUCTOR | |
8354 | This is like @code{TARGET_ASM_CONSTRUCTOR} but used for termination | |
8355 | functions rather than initialization functions. | |
8356 | @end deftypefn | |
8357 | ||
8358 | If @code{TARGET_HAVE_CTORS_DTORS} is true, the initialization routine | |
8359 | generated for the generated object file will have static linkage. | |
8360 | ||
8361 | If your system uses @command{collect2} as the means of processing | |
8362 | constructors, then that program normally uses @command{nm} to scan | |
8363 | an object file for constructor functions to be called. | |
8364 | ||
8365 | On certain kinds of systems, you can define this macro to make | |
8366 | @command{collect2} work faster (and, in some cases, make it work at all): | |
8367 | ||
8368 | @defmac OBJECT_FORMAT_COFF | |
8369 | Define this macro if the system uses COFF (Common Object File Format) | |
8370 | object files, so that @command{collect2} can assume this format and scan | |
8371 | object files directly for dynamic constructor/destructor functions. | |
8372 | ||
8373 | This macro is effective only in a native compiler; @command{collect2} as | |
8374 | part of a cross compiler always uses @command{nm} for the target machine. | |
8375 | @end defmac | |
8376 | ||
8377 | @defmac REAL_NM_FILE_NAME | |
8378 | Define this macro as a C string constant containing the file name to use | |
8379 | to execute @command{nm}. The default is to search the path normally for | |
8380 | @command{nm}. | |
3e794bfe RO |
8381 | @end defmac |
8382 | ||
8383 | @defmac NM_FLAGS | |
8384 | @command{collect2} calls @command{nm} to scan object files for static | |
8385 | constructors and destructors and LTO info. By default, @option{-n} is | |
8386 | passed. Define @code{NM_FLAGS} to a C string constant if other options | |
2b0d3573 | 8387 | are needed to get the same output format as GNU @command{nm -n} |
3e794bfe RO |
8388 | produces. |
8389 | @end defmac | |
38f8b050 JR |
8390 | |
8391 | If your system supports shared libraries and has a program to list the | |
8392 | dynamic dependencies of a given library or executable, you can define | |
8393 | these macros to enable support for running initialization and | |
8394 | termination functions in shared libraries: | |
38f8b050 JR |
8395 | |
8396 | @defmac LDD_SUFFIX | |
8397 | Define this macro to a C string constant containing the name of the program | |
3e794bfe | 8398 | which lists dynamic dependencies, like @command{ldd} under SunOS 4. |
38f8b050 JR |
8399 | @end defmac |
8400 | ||
8401 | @defmac PARSE_LDD_OUTPUT (@var{ptr}) | |
8402 | Define this macro to be C code that extracts filenames from the output | |
8403 | of the program denoted by @code{LDD_SUFFIX}. @var{ptr} is a variable | |
8404 | of type @code{char *} that points to the beginning of a line of output | |
8405 | from @code{LDD_SUFFIX}. If the line lists a dynamic dependency, the | |
8406 | code must advance @var{ptr} to the beginning of the filename on that | |
8407 | line. Otherwise, it must set @var{ptr} to @code{NULL}. | |
8408 | @end defmac | |
8409 | ||
8410 | @defmac SHLIB_SUFFIX | |
8411 | Define this macro to a C string constant containing the default shared | |
8412 | library extension of the target (e.g., @samp{".so"}). @command{collect2} | |
8413 | strips version information after this suffix when generating global | |
8414 | constructor and destructor names. This define is only needed on targets | |
8415 | that use @command{collect2} to process constructors and destructors. | |
8416 | @end defmac | |
8417 | ||
8418 | @node Instruction Output | |
8419 | @subsection Output of Assembler Instructions | |
8420 | ||
8421 | @c prevent bad page break with this line | |
8422 | This describes assembler instruction output. | |
8423 | ||
8424 | @defmac REGISTER_NAMES | |
8425 | A C initializer containing the assembler's names for the machine | |
8426 | registers, each one as a C string constant. This is what translates | |
8427 | register numbers in the compiler into assembler language. | |
8428 | @end defmac | |
8429 | ||
8430 | @defmac ADDITIONAL_REGISTER_NAMES | |
8431 | If defined, a C initializer for an array of structures containing a name | |
8432 | and a register number. This macro defines additional names for hard | |
8433 | registers, thus allowing the @code{asm} option in declarations to refer | |
8434 | to registers using alternate names. | |
8435 | @end defmac | |
8436 | ||
0c6d290e RE |
8437 | @defmac OVERLAPPING_REGISTER_NAMES |
8438 | If defined, a C initializer for an array of structures containing a | |
8439 | name, a register number and a count of the number of consecutive | |
8440 | machine registers the name overlaps. This macro defines additional | |
8441 | names for hard registers, thus allowing the @code{asm} option in | |
8442 | declarations to refer to registers using alternate names. Unlike | |
8443 | @code{ADDITIONAL_REGISTER_NAMES}, this macro should be used when the | |
8444 | register name implies multiple underlying registers. | |
8445 | ||
8446 | This macro should be used when it is important that a clobber in an | |
8447 | @code{asm} statement clobbers all the underlying values implied by the | |
8448 | register name. For example, on ARM, clobbering the double-precision | |
8449 | VFP register ``d0'' implies clobbering both single-precision registers | |
8450 | ``s0'' and ``s1''. | |
8451 | @end defmac | |
8452 | ||
38f8b050 JR |
8453 | @defmac ASM_OUTPUT_OPCODE (@var{stream}, @var{ptr}) |
8454 | Define this macro if you are using an unusual assembler that | |
8455 | requires different names for the machine instructions. | |
8456 | ||
8457 | The definition is a C statement or statements which output an | |
8458 | assembler instruction opcode to the stdio stream @var{stream}. The | |
8459 | macro-operand @var{ptr} is a variable of type @code{char *} which | |
8460 | points to the opcode name in its ``internal'' form---the form that is | |
8461 | written in the machine description. The definition should output the | |
8462 | opcode name to @var{stream}, performing any translation you desire, and | |
8463 | increment the variable @var{ptr} to point at the end of the opcode | |
8464 | so that it will not be output twice. | |
8465 | ||
8466 | In fact, your macro definition may process less than the entire opcode | |
8467 | name, or more than the opcode name; but if you want to process text | |
8468 | that includes @samp{%}-sequences to substitute operands, you must take | |
8469 | care of the substitution yourself. Just be sure to increment | |
8470 | @var{ptr} over whatever text should not be output normally. | |
8471 | ||
8472 | @findex recog_data.operand | |
8473 | If you need to look at the operand values, they can be found as the | |
8474 | elements of @code{recog_data.operand}. | |
8475 | ||
8476 | If the macro definition does nothing, the instruction is output | |
8477 | in the usual way. | |
8478 | @end defmac | |
8479 | ||
8480 | @defmac FINAL_PRESCAN_INSN (@var{insn}, @var{opvec}, @var{noperands}) | |
8481 | If defined, a C statement to be executed just prior to the output of | |
8482 | assembler code for @var{insn}, to modify the extracted operands so | |
8483 | they will be output differently. | |
8484 | ||
8485 | Here the argument @var{opvec} is the vector containing the operands | |
8486 | extracted from @var{insn}, and @var{noperands} is the number of | |
8487 | elements of the vector which contain meaningful data for this insn. | |
8488 | The contents of this vector are what will be used to convert the insn | |
8489 | template into assembler code, so you can change the assembler output | |
8490 | by changing the contents of the vector. | |
8491 | ||
8492 | This macro is useful when various assembler syntaxes share a single | |
8493 | file of instruction patterns; by defining this macro differently, you | |
8494 | can cause a large class of instructions to be output differently (such | |
8495 | as with rearranged operands). Naturally, variations in assembler | |
8496 | syntax affecting individual insn patterns ought to be handled by | |
8497 | writing conditional output routines in those patterns. | |
8498 | ||
8499 | If this macro is not defined, it is equivalent to a null statement. | |
8500 | @end defmac | |
8501 | ||
8502 | @hook TARGET_ASM_FINAL_POSTSCAN_INSN | |
8503 | If defined, this target hook is a function which is executed just after the | |
8504 | output of assembler code for @var{insn}, to change the mode of the assembler | |
8505 | if necessary. | |
8506 | ||
8507 | Here the argument @var{opvec} is the vector containing the operands | |
8508 | extracted from @var{insn}, and @var{noperands} is the number of | |
8509 | elements of the vector which contain meaningful data for this insn. | |
8510 | The contents of this vector are what was used to convert the insn | |
8511 | template into assembler code, so you can change the assembler mode | |
8512 | by checking the contents of the vector. | |
8513 | @end deftypefn | |
8514 | ||
8515 | @defmac PRINT_OPERAND (@var{stream}, @var{x}, @var{code}) | |
8516 | A C compound statement to output to stdio stream @var{stream} the | |
8517 | assembler syntax for an instruction operand @var{x}. @var{x} is an | |
8518 | RTL expression. | |
8519 | ||
8520 | @var{code} is a value that can be used to specify one of several ways | |
8521 | of printing the operand. It is used when identical operands must be | |
8522 | printed differently depending on the context. @var{code} comes from | |
8523 | the @samp{%} specification that was used to request printing of the | |
8524 | operand. If the specification was just @samp{%@var{digit}} then | |
8525 | @var{code} is 0; if the specification was @samp{%@var{ltr} | |
8526 | @var{digit}} then @var{code} is the ASCII code for @var{ltr}. | |
8527 | ||
8528 | @findex reg_names | |
8529 | If @var{x} is a register, this macro should print the register's name. | |
8530 | The names can be found in an array @code{reg_names} whose type is | |
8531 | @code{char *[]}. @code{reg_names} is initialized from | |
8532 | @code{REGISTER_NAMES}. | |
8533 | ||
8534 | When the machine description has a specification @samp{%@var{punct}} | |
8535 | (a @samp{%} followed by a punctuation character), this macro is called | |
8536 | with a null pointer for @var{x} and the punctuation character for | |
8537 | @var{code}. | |
8538 | @end defmac | |
8539 | ||
8540 | @defmac PRINT_OPERAND_PUNCT_VALID_P (@var{code}) | |
8541 | A C expression which evaluates to true if @var{code} is a valid | |
8542 | punctuation character for use in the @code{PRINT_OPERAND} macro. If | |
8543 | @code{PRINT_OPERAND_PUNCT_VALID_P} is not defined, it means that no | |
8544 | punctuation characters (except for the standard one, @samp{%}) are used | |
8545 | in this way. | |
8546 | @end defmac | |
8547 | ||
8548 | @defmac PRINT_OPERAND_ADDRESS (@var{stream}, @var{x}) | |
8549 | A C compound statement to output to stdio stream @var{stream} the | |
8550 | assembler syntax for an instruction operand that is a memory reference | |
8551 | whose address is @var{x}. @var{x} is an RTL expression. | |
8552 | ||
8553 | @cindex @code{TARGET_ENCODE_SECTION_INFO} usage | |
8554 | On some machines, the syntax for a symbolic address depends on the | |
8555 | section that the address refers to. On these machines, define the hook | |
8556 | @code{TARGET_ENCODE_SECTION_INFO} to store the information into the | |
8557 | @code{symbol_ref}, and then check for it here. @xref{Assembler | |
8558 | Format}. | |
8559 | @end defmac | |
8560 | ||
8561 | @findex dbr_sequence_length | |
8562 | @defmac DBR_OUTPUT_SEQEND (@var{file}) | |
8563 | A C statement, to be executed after all slot-filler instructions have | |
8564 | been output. If necessary, call @code{dbr_sequence_length} to | |
8565 | determine the number of slots filled in a sequence (zero if not | |
8566 | currently outputting a sequence), to decide how many no-ops to output, | |
8567 | or whatever. | |
8568 | ||
8569 | Don't define this macro if it has nothing to do, but it is helpful in | |
8570 | reading assembly output if the extent of the delay sequence is made | |
8571 | explicit (e.g.@: with white space). | |
8572 | @end defmac | |
8573 | ||
8574 | @findex final_sequence | |
8575 | Note that output routines for instructions with delay slots must be | |
8576 | prepared to deal with not being output as part of a sequence | |
8577 | (i.e.@: when the scheduling pass is not run, or when no slot fillers could be | |
8578 | found.) The variable @code{final_sequence} is null when not | |
8579 | processing a sequence, otherwise it contains the @code{sequence} rtx | |
8580 | being output. | |
8581 | ||
8582 | @findex asm_fprintf | |
8583 | @defmac REGISTER_PREFIX | |
8584 | @defmacx LOCAL_LABEL_PREFIX | |
8585 | @defmacx USER_LABEL_PREFIX | |
8586 | @defmacx IMMEDIATE_PREFIX | |
8587 | If defined, C string expressions to be used for the @samp{%R}, @samp{%L}, | |
8588 | @samp{%U}, and @samp{%I} options of @code{asm_fprintf} (see | |
8589 | @file{final.c}). These are useful when a single @file{md} file must | |
8590 | support multiple assembler formats. In that case, the various @file{tm.h} | |
8591 | files can define these macros differently. | |
8592 | @end defmac | |
8593 | ||
8594 | @defmac ASM_FPRINTF_EXTENSIONS (@var{file}, @var{argptr}, @var{format}) | |
8595 | If defined this macro should expand to a series of @code{case} | |
8596 | statements which will be parsed inside the @code{switch} statement of | |
8597 | the @code{asm_fprintf} function. This allows targets to define extra | |
8598 | printf formats which may useful when generating their assembler | |
8599 | statements. Note that uppercase letters are reserved for future | |
8600 | generic extensions to asm_fprintf, and so are not available to target | |
8601 | specific code. The output file is given by the parameter @var{file}. | |
8602 | The varargs input pointer is @var{argptr} and the rest of the format | |
8603 | string, starting the character after the one that is being switched | |
8604 | upon, is pointed to by @var{format}. | |
8605 | @end defmac | |
8606 | ||
8607 | @defmac ASSEMBLER_DIALECT | |
8608 | If your target supports multiple dialects of assembler language (such as | |
8609 | different opcodes), define this macro as a C expression that gives the | |
8610 | numeric index of the assembler language dialect to use, with zero as the | |
8611 | first variant. | |
8612 | ||
8613 | If this macro is defined, you may use constructs of the form | |
8614 | @smallexample | |
8615 | @samp{@{option0|option1|option2@dots{}@}} | |
8616 | @end smallexample | |
8617 | @noindent | |
8618 | in the output templates of patterns (@pxref{Output Template}) or in the | |
8619 | first argument of @code{asm_fprintf}. This construct outputs | |
8620 | @samp{option0}, @samp{option1}, @samp{option2}, etc., if the value of | |
8621 | @code{ASSEMBLER_DIALECT} is zero, one, two, etc. Any special characters | |
8622 | within these strings retain their usual meaning. If there are fewer | |
8623 | alternatives within the braces than the value of | |
8624 | @code{ASSEMBLER_DIALECT}, the construct outputs nothing. | |
8625 | ||
8626 | If you do not define this macro, the characters @samp{@{}, @samp{|} and | |
8627 | @samp{@}} do not have any special meaning when used in templates or | |
8628 | operands to @code{asm_fprintf}. | |
8629 | ||
8630 | Define the macros @code{REGISTER_PREFIX}, @code{LOCAL_LABEL_PREFIX}, | |
8631 | @code{USER_LABEL_PREFIX} and @code{IMMEDIATE_PREFIX} if you can express | |
8632 | the variations in assembler language syntax with that mechanism. Define | |
8633 | @code{ASSEMBLER_DIALECT} and use the @samp{@{option0|option1@}} syntax | |
8634 | if the syntax variant are larger and involve such things as different | |
8635 | opcodes or operand order. | |
8636 | @end defmac | |
8637 | ||
8638 | @defmac ASM_OUTPUT_REG_PUSH (@var{stream}, @var{regno}) | |
8639 | A C expression to output to @var{stream} some assembler code | |
8640 | which will push hard register number @var{regno} onto the stack. | |
8641 | The code need not be optimal, since this macro is used only when | |
8642 | profiling. | |
8643 | @end defmac | |
8644 | ||
8645 | @defmac ASM_OUTPUT_REG_POP (@var{stream}, @var{regno}) | |
8646 | A C expression to output to @var{stream} some assembler code | |
8647 | which will pop hard register number @var{regno} off of the stack. | |
8648 | The code need not be optimal, since this macro is used only when | |
8649 | profiling. | |
8650 | @end defmac | |
8651 | ||
8652 | @node Dispatch Tables | |
8653 | @subsection Output of Dispatch Tables | |
8654 | ||
8655 | @c prevent bad page break with this line | |
8656 | This concerns dispatch tables. | |
8657 | ||
8658 | @cindex dispatch table | |
8659 | @defmac ASM_OUTPUT_ADDR_DIFF_ELT (@var{stream}, @var{body}, @var{value}, @var{rel}) | |
8660 | A C statement to output to the stdio stream @var{stream} an assembler | |
8661 | pseudo-instruction to generate a difference between two labels. | |
8662 | @var{value} and @var{rel} are the numbers of two internal labels. The | |
8663 | definitions of these labels are output using | |
8664 | @code{(*targetm.asm_out.internal_label)}, and they must be printed in the same | |
8665 | way here. For example, | |
8666 | ||
8667 | @smallexample | |
8668 | fprintf (@var{stream}, "\t.word L%d-L%d\n", | |
8669 | @var{value}, @var{rel}) | |
8670 | @end smallexample | |
8671 | ||
8672 | You must provide this macro on machines where the addresses in a | |
8673 | dispatch table are relative to the table's own address. If defined, GCC | |
8674 | will also use this macro on all machines when producing PIC@. | |
8675 | @var{body} is the body of the @code{ADDR_DIFF_VEC}; it is provided so that the | |
8676 | mode and flags can be read. | |
8677 | @end defmac | |
8678 | ||
8679 | @defmac ASM_OUTPUT_ADDR_VEC_ELT (@var{stream}, @var{value}) | |
8680 | This macro should be provided on machines where the addresses | |
8681 | in a dispatch table are absolute. | |
8682 | ||
8683 | The definition should be a C statement to output to the stdio stream | |
8684 | @var{stream} an assembler pseudo-instruction to generate a reference to | |
8685 | a label. @var{value} is the number of an internal label whose | |
8686 | definition is output using @code{(*targetm.asm_out.internal_label)}. | |
8687 | For example, | |
8688 | ||
8689 | @smallexample | |
8690 | fprintf (@var{stream}, "\t.word L%d\n", @var{value}) | |
8691 | @end smallexample | |
8692 | @end defmac | |
8693 | ||
8694 | @defmac ASM_OUTPUT_CASE_LABEL (@var{stream}, @var{prefix}, @var{num}, @var{table}) | |
8695 | Define this if the label before a jump-table needs to be output | |
8696 | specially. The first three arguments are the same as for | |
8697 | @code{(*targetm.asm_out.internal_label)}; the fourth argument is the | |
8698 | jump-table which follows (a @code{jump_insn} containing an | |
8699 | @code{addr_vec} or @code{addr_diff_vec}). | |
8700 | ||
8701 | This feature is used on system V to output a @code{swbeg} statement | |
8702 | for the table. | |
8703 | ||
8704 | If this macro is not defined, these labels are output with | |
8705 | @code{(*targetm.asm_out.internal_label)}. | |
8706 | @end defmac | |
8707 | ||
8708 | @defmac ASM_OUTPUT_CASE_END (@var{stream}, @var{num}, @var{table}) | |
8709 | Define this if something special must be output at the end of a | |
8710 | jump-table. The definition should be a C statement to be executed | |
8711 | after the assembler code for the table is written. It should write | |
8712 | the appropriate code to stdio stream @var{stream}. The argument | |
8713 | @var{table} is the jump-table insn, and @var{num} is the label-number | |
8714 | of the preceding label. | |
8715 | ||
8716 | If this macro is not defined, nothing special is output at the end of | |
8717 | the jump-table. | |
8718 | @end defmac | |
8719 | ||
8720 | @hook TARGET_ASM_EMIT_UNWIND_LABEL | |
8721 | This target hook emits a label at the beginning of each FDE@. It | |
8722 | should be defined on targets where FDEs need special labels, and it | |
8723 | should write the appropriate label, for the FDE associated with the | |
8724 | function declaration @var{decl}, to the stdio stream @var{stream}. | |
8725 | The third argument, @var{for_eh}, is a boolean: true if this is for an | |
8726 | exception table. The fourth argument, @var{empty}, is a boolean: | |
8727 | true if this is a placeholder label for an omitted FDE@. | |
8728 | ||
8729 | The default is that FDEs are not given nonlocal labels. | |
8730 | @end deftypefn | |
8731 | ||
8732 | @hook TARGET_ASM_EMIT_EXCEPT_TABLE_LABEL | |
8733 | This target hook emits a label at the beginning of the exception table. | |
8734 | It should be defined on targets where it is desirable for the table | |
8735 | to be broken up according to function. | |
8736 | ||
8737 | The default is that no label is emitted. | |
8738 | @end deftypefn | |
8739 | ||
a68b5e52 RH |
8740 | @hook TARGET_ASM_EMIT_EXCEPT_PERSONALITY |
8741 | ||
38f8b050 JR |
8742 | @hook TARGET_ASM_UNWIND_EMIT |
8743 | This target hook emits assembly directives required to unwind the | |
f0a0390e RH |
8744 | given instruction. This is only used when @code{TARGET_EXCEPT_UNWIND_INFO} |
8745 | returns @code{UI_TARGET}. | |
38f8b050 JR |
8746 | @end deftypefn |
8747 | ||
3bc6b3e6 RH |
8748 | @hook TARGET_ASM_UNWIND_EMIT_BEFORE_INSN |
8749 | ||
38f8b050 JR |
8750 | @node Exception Region Output |
8751 | @subsection Assembler Commands for Exception Regions | |
8752 | ||
8753 | @c prevent bad page break with this line | |
8754 | ||
8755 | This describes commands marking the start and the end of an exception | |
8756 | region. | |
8757 | ||
8758 | @defmac EH_FRAME_SECTION_NAME | |
8759 | If defined, a C string constant for the name of the section containing | |
8760 | exception handling frame unwind information. If not defined, GCC will | |
8761 | provide a default definition if the target supports named sections. | |
8762 | @file{crtstuff.c} uses this macro to switch to the appropriate section. | |
8763 | ||
8764 | You should define this symbol if your target supports DWARF 2 frame | |
8765 | unwind information and the default definition does not work. | |
8766 | @end defmac | |
8767 | ||
8768 | @defmac EH_FRAME_IN_DATA_SECTION | |
8769 | If defined, DWARF 2 frame unwind information will be placed in the | |
8770 | data section even though the target supports named sections. This | |
8771 | might be necessary, for instance, if the system linker does garbage | |
8772 | collection and sections cannot be marked as not to be collected. | |
8773 | ||
8774 | Do not define this macro unless @code{TARGET_ASM_NAMED_SECTION} is | |
8775 | also defined. | |
8776 | @end defmac | |
8777 | ||
8778 | @defmac EH_TABLES_CAN_BE_READ_ONLY | |
8779 | Define this macro to 1 if your target is such that no frame unwind | |
8780 | information encoding used with non-PIC code will ever require a | |
8781 | runtime relocation, but the linker may not support merging read-only | |
8782 | and read-write sections into a single read-write section. | |
8783 | @end defmac | |
8784 | ||
8785 | @defmac MASK_RETURN_ADDR | |
8786 | An rtx used to mask the return address found via @code{RETURN_ADDR_RTX}, so | |
8787 | that it does not contain any extraneous set bits in it. | |
8788 | @end defmac | |
8789 | ||
8790 | @defmac DWARF2_UNWIND_INFO | |
8791 | Define this macro to 0 if your target supports DWARF 2 frame unwind | |
8792 | information, but it does not yet work with exception handling. | |
8793 | Otherwise, if your target supports this information (if it defines | |
f0a0390e RH |
8794 | @code{INCOMING_RETURN_ADDR_RTX} and either @code{UNALIGNED_INT_ASM_OP} |
8795 | or @code{OBJECT_FORMAT_ELF}), GCC will provide a default definition of 1. | |
8796 | @end defmac | |
38f8b050 | 8797 | |
f0a0390e RH |
8798 | @hook TARGET_EXCEPT_UNWIND_INFO |
8799 | This hook defines the mechanism that will be used for exception handling | |
8800 | by the target. If the target has ABI specified unwind tables, the hook | |
8801 | should return @code{UI_TARGET}. If the target is to use the | |
8802 | @code{setjmp}/@code{longjmp}-based exception handling scheme, the hook | |
8803 | should return @code{UI_SJLJ}. If the target supports DWARF 2 frame unwind | |
8804 | information, the hook should return @code{UI_DWARF2}. | |
38f8b050 | 8805 | |
f0a0390e RH |
8806 | A target may, if exceptions are disabled, choose to return @code{UI_NONE}. |
8807 | This may end up simplifying other parts of target-specific code. The | |
8808 | default implementation of this hook never returns @code{UI_NONE}. | |
38f8b050 | 8809 | |
f0a0390e | 8810 | Note that the value returned by this hook should be constant. It should |
d5fabb58 JM |
8811 | not depend on anything except the command-line switches described by |
8812 | @var{opts}. In particular, the | |
f0a0390e RH |
8813 | setting @code{UI_SJLJ} must be fixed at compiler start-up as C pre-processor |
8814 | macros and builtin functions related to exception handling are set up | |
8815 | depending on this setting. | |
8816 | ||
8817 | The default implementation of the hook first honors the | |
8818 | @option{--enable-sjlj-exceptions} configure option, then | |
d5fabb58 JM |
8819 | @code{DWARF2_UNWIND_INFO}, and finally defaults to @code{UI_SJLJ}. If |
8820 | @code{DWARF2_UNWIND_INFO} depends on command-line options, the target | |
8821 | must define this hook so that @var{opts} is used correctly. | |
f0a0390e | 8822 | @end deftypefn |
38f8b050 JR |
8823 | |
8824 | @hook TARGET_UNWIND_TABLES_DEFAULT | |
8825 | This variable should be set to @code{true} if the target ABI requires unwinding | |
d5fabb58 JM |
8826 | tables even when exceptions are not used. It must not be modified by |
8827 | command-line option processing. | |
38f8b050 JR |
8828 | @end deftypevr |
8829 | ||
38f8b050 JR |
8830 | @defmac DONT_USE_BUILTIN_SETJMP |
8831 | Define this macro to 1 if the @code{setjmp}/@code{longjmp}-based scheme | |
8832 | should use the @code{setjmp}/@code{longjmp} functions from the C library | |
8833 | instead of the @code{__builtin_setjmp}/@code{__builtin_longjmp} machinery. | |
8834 | @end defmac | |
8835 | ||
8836 | @defmac DWARF_CIE_DATA_ALIGNMENT | |
8837 | This macro need only be defined if the target might save registers in the | |
8838 | function prologue at an offset to the stack pointer that is not aligned to | |
8839 | @code{UNITS_PER_WORD}. The definition should be the negative minimum | |
8840 | alignment if @code{STACK_GROWS_DOWNWARD} is defined, and the positive | |
8841 | minimum alignment otherwise. @xref{SDB and DWARF}. Only applicable if | |
8842 | the target supports DWARF 2 frame unwind information. | |
8843 | @end defmac | |
8844 | ||
8845 | @hook TARGET_TERMINATE_DW2_EH_FRAME_INFO | |
8846 | Contains the value true if the target should add a zero word onto the | |
8847 | end of a Dwarf-2 frame info section when used for exception handling. | |
8848 | Default value is false if @code{EH_FRAME_SECTION_NAME} is defined, and | |
8849 | true otherwise. | |
8850 | @end deftypevr | |
8851 | ||
8852 | @hook TARGET_DWARF_REGISTER_SPAN | |
8853 | Given a register, this hook should return a parallel of registers to | |
8854 | represent where to find the register pieces. Define this hook if the | |
8855 | register and its mode are represented in Dwarf in non-contiguous | |
8856 | locations, or if the register should be represented in more than one | |
8857 | register in Dwarf. Otherwise, this hook should return @code{NULL_RTX}. | |
8858 | If not defined, the default is to return @code{NULL_RTX}. | |
8859 | @end deftypefn | |
8860 | ||
8861 | @hook TARGET_INIT_DWARF_REG_SIZES_EXTRA | |
8862 | If some registers are represented in Dwarf-2 unwind information in | |
8863 | multiple pieces, define this hook to fill in information about the | |
8864 | sizes of those pieces in the table used by the unwinder at runtime. | |
8865 | It will be called by @code{expand_builtin_init_dwarf_reg_sizes} after | |
8866 | filling in a single size corresponding to each hard register; | |
8867 | @var{address} is the address of the table. | |
8868 | @end deftypefn | |
8869 | ||
8870 | @hook TARGET_ASM_TTYPE | |
8871 | This hook is used to output a reference from a frame unwinding table to | |
8872 | the type_info object identified by @var{sym}. It should return @code{true} | |
8873 | if the reference was output. Returning @code{false} will cause the | |
8874 | reference to be output using the normal Dwarf2 routines. | |
8875 | @end deftypefn | |
8876 | ||
8877 | @hook TARGET_ARM_EABI_UNWINDER | |
8878 | This flag should be set to @code{true} on targets that use an ARM EABI | |
8879 | based unwinding library, and @code{false} on other targets. This effects | |
8880 | the format of unwinding tables, and how the unwinder in entered after | |
8881 | running a cleanup. The default is @code{false}. | |
8882 | @end deftypevr | |
8883 | ||
8884 | @node Alignment Output | |
8885 | @subsection Assembler Commands for Alignment | |
8886 | ||
8887 | @c prevent bad page break with this line | |
8888 | This describes commands for alignment. | |
8889 | ||
8890 | @defmac JUMP_ALIGN (@var{label}) | |
8891 | The alignment (log base 2) to put in front of @var{label}, which is | |
8892 | a common destination of jumps and has no fallthru incoming edge. | |
8893 | ||
8894 | This macro need not be defined if you don't want any special alignment | |
8895 | to be done at such a time. Most machine descriptions do not currently | |
8896 | define the macro. | |
8897 | ||
8898 | Unless it's necessary to inspect the @var{label} parameter, it is better | |
8899 | to set the variable @var{align_jumps} in the target's | |
8900 | @code{TARGET_OPTION_OVERRIDE}. Otherwise, you should try to honor the user's | |
8901 | selection in @var{align_jumps} in a @code{JUMP_ALIGN} implementation. | |
8902 | @end defmac | |
8903 | ||
ad0c4c36 DD |
8904 | @hook TARGET_ASM_JUMP_ALIGN_MAX_SKIP |
8905 | The maximum number of bytes to skip before @var{label} when applying | |
8906 | @code{JUMP_ALIGN}. This works only if | |
8907 | @code{ASM_OUTPUT_MAX_SKIP_ALIGN} is defined. | |
8908 | @end deftypefn | |
8909 | ||
38f8b050 JR |
8910 | @defmac LABEL_ALIGN_AFTER_BARRIER (@var{label}) |
8911 | The alignment (log base 2) to put in front of @var{label}, which follows | |
8912 | a @code{BARRIER}. | |
8913 | ||
8914 | This macro need not be defined if you don't want any special alignment | |
8915 | to be done at such a time. Most machine descriptions do not currently | |
8916 | define the macro. | |
8917 | @end defmac | |
8918 | ||
ad0c4c36 DD |
8919 | @hook TARGET_ASM_LABEL_ALIGN_AFTER_BARRIER_MAX_SKIP |
8920 | The maximum number of bytes to skip before @var{label} when applying | |
38f8b050 JR |
8921 | @code{LABEL_ALIGN_AFTER_BARRIER}. This works only if |
8922 | @code{ASM_OUTPUT_MAX_SKIP_ALIGN} is defined. | |
ad0c4c36 | 8923 | @end deftypefn |
38f8b050 JR |
8924 | |
8925 | @defmac LOOP_ALIGN (@var{label}) | |
8926 | The alignment (log base 2) to put in front of @var{label}, which follows | |
8927 | a @code{NOTE_INSN_LOOP_BEG} note. | |
8928 | ||
8929 | This macro need not be defined if you don't want any special alignment | |
8930 | to be done at such a time. Most machine descriptions do not currently | |
8931 | define the macro. | |
8932 | ||
8933 | Unless it's necessary to inspect the @var{label} parameter, it is better | |
8934 | to set the variable @code{align_loops} in the target's | |
8935 | @code{TARGET_OPTION_OVERRIDE}. Otherwise, you should try to honor the user's | |
8936 | selection in @code{align_loops} in a @code{LOOP_ALIGN} implementation. | |
8937 | @end defmac | |
8938 | ||
ad0c4c36 DD |
8939 | @hook TARGET_ASM_LOOP_ALIGN_MAX_SKIP |
8940 | The maximum number of bytes to skip when applying @code{LOOP_ALIGN} to | |
8941 | @var{label}. This works only if @code{ASM_OUTPUT_MAX_SKIP_ALIGN} is | |
8942 | defined. | |
8943 | @end deftypefn | |
38f8b050 JR |
8944 | |
8945 | @defmac LABEL_ALIGN (@var{label}) | |
8946 | The alignment (log base 2) to put in front of @var{label}. | |
8947 | If @code{LABEL_ALIGN_AFTER_BARRIER} / @code{LOOP_ALIGN} specify a different alignment, | |
8948 | the maximum of the specified values is used. | |
8949 | ||
8950 | Unless it's necessary to inspect the @var{label} parameter, it is better | |
8951 | to set the variable @code{align_labels} in the target's | |
8952 | @code{TARGET_OPTION_OVERRIDE}. Otherwise, you should try to honor the user's | |
8953 | selection in @code{align_labels} in a @code{LABEL_ALIGN} implementation. | |
8954 | @end defmac | |
8955 | ||
ad0c4c36 DD |
8956 | @hook TARGET_ASM_LABEL_ALIGN_MAX_SKIP |
8957 | The maximum number of bytes to skip when applying @code{LABEL_ALIGN} | |
8958 | to @var{label}. This works only if @code{ASM_OUTPUT_MAX_SKIP_ALIGN} | |
8959 | is defined. | |
8960 | @end deftypefn | |
38f8b050 JR |
8961 | |
8962 | @defmac ASM_OUTPUT_SKIP (@var{stream}, @var{nbytes}) | |
8963 | A C statement to output to the stdio stream @var{stream} an assembler | |
8964 | instruction to advance the location counter by @var{nbytes} bytes. | |
8965 | Those bytes should be zero when loaded. @var{nbytes} will be a C | |
8966 | expression of type @code{unsigned HOST_WIDE_INT}. | |
8967 | @end defmac | |
8968 | ||
8969 | @defmac ASM_NO_SKIP_IN_TEXT | |
8970 | Define this macro if @code{ASM_OUTPUT_SKIP} should not be used in the | |
8971 | text section because it fails to put zeros in the bytes that are skipped. | |
8972 | This is true on many Unix systems, where the pseudo--op to skip bytes | |
8973 | produces no-op instructions rather than zeros when used in the text | |
8974 | section. | |
8975 | @end defmac | |
8976 | ||
8977 | @defmac ASM_OUTPUT_ALIGN (@var{stream}, @var{power}) | |
8978 | A C statement to output to the stdio stream @var{stream} an assembler | |
8979 | command to advance the location counter to a multiple of 2 to the | |
8980 | @var{power} bytes. @var{power} will be a C expression of type @code{int}. | |
8981 | @end defmac | |
8982 | ||
8983 | @defmac ASM_OUTPUT_ALIGN_WITH_NOP (@var{stream}, @var{power}) | |
8984 | Like @code{ASM_OUTPUT_ALIGN}, except that the ``nop'' instruction is used | |
8985 | for padding, if necessary. | |
8986 | @end defmac | |
8987 | ||
8988 | @defmac ASM_OUTPUT_MAX_SKIP_ALIGN (@var{stream}, @var{power}, @var{max_skip}) | |
8989 | A C statement to output to the stdio stream @var{stream} an assembler | |
8990 | command to advance the location counter to a multiple of 2 to the | |
8991 | @var{power} bytes, but only if @var{max_skip} or fewer bytes are needed to | |
8992 | satisfy the alignment request. @var{power} and @var{max_skip} will be | |
8993 | a C expression of type @code{int}. | |
8994 | @end defmac | |
8995 | ||
8996 | @need 3000 | |
8997 | @node Debugging Info | |
8998 | @section Controlling Debugging Information Format | |
8999 | ||
9000 | @c prevent bad page break with this line | |
9001 | This describes how to specify debugging information. | |
9002 | ||
9003 | @menu | |
9004 | * All Debuggers:: Macros that affect all debugging formats uniformly. | |
9005 | * DBX Options:: Macros enabling specific options in DBX format. | |
9006 | * DBX Hooks:: Hook macros for varying DBX format. | |
9007 | * File Names and DBX:: Macros controlling output of file names in DBX format. | |
9008 | * SDB and DWARF:: Macros for SDB (COFF) and DWARF formats. | |
9009 | * VMS Debug:: Macros for VMS debug format. | |
9010 | @end menu | |
9011 | ||
9012 | @node All Debuggers | |
9013 | @subsection Macros Affecting All Debugging Formats | |
9014 | ||
9015 | @c prevent bad page break with this line | |
9016 | These macros affect all debugging formats. | |
9017 | ||
9018 | @defmac DBX_REGISTER_NUMBER (@var{regno}) | |
9019 | A C expression that returns the DBX register number for the compiler | |
9020 | register number @var{regno}. In the default macro provided, the value | |
9021 | of this expression will be @var{regno} itself. But sometimes there are | |
9022 | some registers that the compiler knows about and DBX does not, or vice | |
9023 | versa. In such cases, some register may need to have one number in the | |
9024 | compiler and another for DBX@. | |
9025 | ||
9026 | If two registers have consecutive numbers inside GCC, and they can be | |
9027 | used as a pair to hold a multiword value, then they @emph{must} have | |
9028 | consecutive numbers after renumbering with @code{DBX_REGISTER_NUMBER}. | |
9029 | Otherwise, debuggers will be unable to access such a pair, because they | |
9030 | expect register pairs to be consecutive in their own numbering scheme. | |
9031 | ||
9032 | If you find yourself defining @code{DBX_REGISTER_NUMBER} in way that | |
9033 | does not preserve register pairs, then what you must do instead is | |
9034 | redefine the actual register numbering scheme. | |
9035 | @end defmac | |
9036 | ||
9037 | @defmac DEBUGGER_AUTO_OFFSET (@var{x}) | |
9038 | A C expression that returns the integer offset value for an automatic | |
9039 | variable having address @var{x} (an RTL expression). The default | |
9040 | computation assumes that @var{x} is based on the frame-pointer and | |
9041 | gives the offset from the frame-pointer. This is required for targets | |
9042 | that produce debugging output for DBX or COFF-style debugging output | |
9043 | for SDB and allow the frame-pointer to be eliminated when the | |
9044 | @option{-g} options is used. | |
9045 | @end defmac | |
9046 | ||
9047 | @defmac DEBUGGER_ARG_OFFSET (@var{offset}, @var{x}) | |
9048 | A C expression that returns the integer offset value for an argument | |
9049 | having address @var{x} (an RTL expression). The nominal offset is | |
9050 | @var{offset}. | |
9051 | @end defmac | |
9052 | ||
9053 | @defmac PREFERRED_DEBUGGING_TYPE | |
9054 | A C expression that returns the type of debugging output GCC should | |
9055 | produce when the user specifies just @option{-g}. Define | |
9056 | this if you have arranged for GCC to support more than one format of | |
9057 | debugging output. Currently, the allowable values are @code{DBX_DEBUG}, | |
9058 | @code{SDB_DEBUG}, @code{DWARF_DEBUG}, @code{DWARF2_DEBUG}, | |
9059 | @code{XCOFF_DEBUG}, @code{VMS_DEBUG}, and @code{VMS_AND_DWARF2_DEBUG}. | |
9060 | ||
9061 | When the user specifies @option{-ggdb}, GCC normally also uses the | |
9062 | value of this macro to select the debugging output format, but with two | |
9063 | exceptions. If @code{DWARF2_DEBUGGING_INFO} is defined, GCC uses the | |
9064 | value @code{DWARF2_DEBUG}. Otherwise, if @code{DBX_DEBUGGING_INFO} is | |
9065 | defined, GCC uses @code{DBX_DEBUG}. | |
9066 | ||
9067 | The value of this macro only affects the default debugging output; the | |
9068 | user can always get a specific type of output by using @option{-gstabs}, | |
9069 | @option{-gcoff}, @option{-gdwarf-2}, @option{-gxcoff}, or @option{-gvms}. | |
9070 | @end defmac | |
9071 | ||
9072 | @node DBX Options | |
9073 | @subsection Specific Options for DBX Output | |
9074 | ||
9075 | @c prevent bad page break with this line | |
9076 | These are specific options for DBX output. | |
9077 | ||
9078 | @defmac DBX_DEBUGGING_INFO | |
9079 | Define this macro if GCC should produce debugging output for DBX | |
9080 | in response to the @option{-g} option. | |
9081 | @end defmac | |
9082 | ||
9083 | @defmac XCOFF_DEBUGGING_INFO | |
9084 | Define this macro if GCC should produce XCOFF format debugging output | |
9085 | in response to the @option{-g} option. This is a variant of DBX format. | |
9086 | @end defmac | |
9087 | ||
9088 | @defmac DEFAULT_GDB_EXTENSIONS | |
9089 | Define this macro to control whether GCC should by default generate | |
9090 | GDB's extended version of DBX debugging information (assuming DBX-format | |
9091 | debugging information is enabled at all). If you don't define the | |
9092 | macro, the default is 1: always generate the extended information | |
9093 | if there is any occasion to. | |
9094 | @end defmac | |
9095 | ||
9096 | @defmac DEBUG_SYMS_TEXT | |
9097 | Define this macro if all @code{.stabs} commands should be output while | |
9098 | in the text section. | |
9099 | @end defmac | |
9100 | ||
9101 | @defmac ASM_STABS_OP | |
9102 | A C string constant, including spacing, naming the assembler pseudo op to | |
9103 | use instead of @code{"\t.stabs\t"} to define an ordinary debugging symbol. | |
9104 | If you don't define this macro, @code{"\t.stabs\t"} is used. This macro | |
9105 | applies only to DBX debugging information format. | |
9106 | @end defmac | |
9107 | ||
9108 | @defmac ASM_STABD_OP | |
9109 | A C string constant, including spacing, naming the assembler pseudo op to | |
9110 | use instead of @code{"\t.stabd\t"} to define a debugging symbol whose | |
9111 | value is the current location. If you don't define this macro, | |
9112 | @code{"\t.stabd\t"} is used. This macro applies only to DBX debugging | |
9113 | information format. | |
9114 | @end defmac | |
9115 | ||
9116 | @defmac ASM_STABN_OP | |
9117 | A C string constant, including spacing, naming the assembler pseudo op to | |
9118 | use instead of @code{"\t.stabn\t"} to define a debugging symbol with no | |
9119 | name. If you don't define this macro, @code{"\t.stabn\t"} is used. This | |
9120 | macro applies only to DBX debugging information format. | |
9121 | @end defmac | |
9122 | ||
9123 | @defmac DBX_NO_XREFS | |
9124 | Define this macro if DBX on your system does not support the construct | |
9125 | @samp{xs@var{tagname}}. On some systems, this construct is used to | |
9126 | describe a forward reference to a structure named @var{tagname}. | |
9127 | On other systems, this construct is not supported at all. | |
9128 | @end defmac | |
9129 | ||
9130 | @defmac DBX_CONTIN_LENGTH | |
9131 | A symbol name in DBX-format debugging information is normally | |
9132 | continued (split into two separate @code{.stabs} directives) when it | |
9133 | exceeds a certain length (by default, 80 characters). On some | |
9134 | operating systems, DBX requires this splitting; on others, splitting | |
9135 | must not be done. You can inhibit splitting by defining this macro | |
9136 | with the value zero. You can override the default splitting-length by | |
9137 | defining this macro as an expression for the length you desire. | |
9138 | @end defmac | |
9139 | ||
9140 | @defmac DBX_CONTIN_CHAR | |
9141 | Normally continuation is indicated by adding a @samp{\} character to | |
9142 | the end of a @code{.stabs} string when a continuation follows. To use | |
9143 | a different character instead, define this macro as a character | |
9144 | constant for the character you want to use. Do not define this macro | |
9145 | if backslash is correct for your system. | |
9146 | @end defmac | |
9147 | ||
9148 | @defmac DBX_STATIC_STAB_DATA_SECTION | |
9149 | Define this macro if it is necessary to go to the data section before | |
9150 | outputting the @samp{.stabs} pseudo-op for a non-global static | |
9151 | variable. | |
9152 | @end defmac | |
9153 | ||
9154 | @defmac DBX_TYPE_DECL_STABS_CODE | |
9155 | The value to use in the ``code'' field of the @code{.stabs} directive | |
9156 | for a typedef. The default is @code{N_LSYM}. | |
9157 | @end defmac | |
9158 | ||
9159 | @defmac DBX_STATIC_CONST_VAR_CODE | |
9160 | The value to use in the ``code'' field of the @code{.stabs} directive | |
9161 | for a static variable located in the text section. DBX format does not | |
9162 | provide any ``right'' way to do this. The default is @code{N_FUN}. | |
9163 | @end defmac | |
9164 | ||
9165 | @defmac DBX_REGPARM_STABS_CODE | |
9166 | The value to use in the ``code'' field of the @code{.stabs} directive | |
9167 | for a parameter passed in registers. DBX format does not provide any | |
9168 | ``right'' way to do this. The default is @code{N_RSYM}. | |
9169 | @end defmac | |
9170 | ||
9171 | @defmac DBX_REGPARM_STABS_LETTER | |
9172 | The letter to use in DBX symbol data to identify a symbol as a parameter | |
9173 | passed in registers. DBX format does not customarily provide any way to | |
9174 | do this. The default is @code{'P'}. | |
9175 | @end defmac | |
9176 | ||
9177 | @defmac DBX_FUNCTION_FIRST | |
9178 | Define this macro if the DBX information for a function and its | |
9179 | arguments should precede the assembler code for the function. Normally, | |
9180 | in DBX format, the debugging information entirely follows the assembler | |
9181 | code. | |
9182 | @end defmac | |
9183 | ||
9184 | @defmac DBX_BLOCKS_FUNCTION_RELATIVE | |
9185 | Define this macro, with value 1, if the value of a symbol describing | |
9186 | the scope of a block (@code{N_LBRAC} or @code{N_RBRAC}) should be | |
9187 | relative to the start of the enclosing function. Normally, GCC uses | |
9188 | an absolute address. | |
9189 | @end defmac | |
9190 | ||
9191 | @defmac DBX_LINES_FUNCTION_RELATIVE | |
9192 | Define this macro, with value 1, if the value of a symbol indicating | |
9193 | the current line number (@code{N_SLINE}) should be relative to the | |
9194 | start of the enclosing function. Normally, GCC uses an absolute address. | |
9195 | @end defmac | |
9196 | ||
9197 | @defmac DBX_USE_BINCL | |
9198 | Define this macro if GCC should generate @code{N_BINCL} and | |
9199 | @code{N_EINCL} stabs for included header files, as on Sun systems. This | |
9200 | macro also directs GCC to output a type number as a pair of a file | |
9201 | number and a type number within the file. Normally, GCC does not | |
9202 | generate @code{N_BINCL} or @code{N_EINCL} stabs, and it outputs a single | |
9203 | number for a type number. | |
9204 | @end defmac | |
9205 | ||
9206 | @node DBX Hooks | |
9207 | @subsection Open-Ended Hooks for DBX Format | |
9208 | ||
9209 | @c prevent bad page break with this line | |
9210 | These are hooks for DBX format. | |
9211 | ||
9212 | @defmac DBX_OUTPUT_LBRAC (@var{stream}, @var{name}) | |
9213 | Define this macro to say how to output to @var{stream} the debugging | |
9214 | information for the start of a scope level for variable names. The | |
9215 | argument @var{name} is the name of an assembler symbol (for use with | |
9216 | @code{assemble_name}) whose value is the address where the scope begins. | |
9217 | @end defmac | |
9218 | ||
9219 | @defmac DBX_OUTPUT_RBRAC (@var{stream}, @var{name}) | |
9220 | Like @code{DBX_OUTPUT_LBRAC}, but for the end of a scope level. | |
9221 | @end defmac | |
9222 | ||
9223 | @defmac DBX_OUTPUT_NFUN (@var{stream}, @var{lscope_label}, @var{decl}) | |
9224 | Define this macro if the target machine requires special handling to | |
9225 | output an @code{N_FUN} entry for the function @var{decl}. | |
9226 | @end defmac | |
9227 | ||
9228 | @defmac DBX_OUTPUT_SOURCE_LINE (@var{stream}, @var{line}, @var{counter}) | |
9229 | A C statement to output DBX debugging information before code for line | |
9230 | number @var{line} of the current source file to the stdio stream | |
9231 | @var{stream}. @var{counter} is the number of time the macro was | |
9232 | invoked, including the current invocation; it is intended to generate | |
9233 | unique labels in the assembly output. | |
9234 | ||
9235 | This macro should not be defined if the default output is correct, or | |
9236 | if it can be made correct by defining @code{DBX_LINES_FUNCTION_RELATIVE}. | |
9237 | @end defmac | |
9238 | ||
9239 | @defmac NO_DBX_FUNCTION_END | |
9240 | Some stabs encapsulation formats (in particular ECOFF), cannot handle the | |
9241 | @code{.stabs "",N_FUN,,0,0,Lscope-function-1} gdb dbx extension construct. | |
9242 | On those machines, define this macro to turn this feature off without | |
9243 | disturbing the rest of the gdb extensions. | |
9244 | @end defmac | |
9245 | ||
9246 | @defmac NO_DBX_BNSYM_ENSYM | |
9247 | Some assemblers cannot handle the @code{.stabd BNSYM/ENSYM,0,0} gdb dbx | |
9248 | extension construct. On those machines, define this macro to turn this | |
9249 | feature off without disturbing the rest of the gdb extensions. | |
9250 | @end defmac | |
9251 | ||
9252 | @node File Names and DBX | |
9253 | @subsection File Names in DBX Format | |
9254 | ||
9255 | @c prevent bad page break with this line | |
9256 | This describes file names in DBX format. | |
9257 | ||
9258 | @defmac DBX_OUTPUT_MAIN_SOURCE_FILENAME (@var{stream}, @var{name}) | |
9259 | A C statement to output DBX debugging information to the stdio stream | |
9260 | @var{stream}, which indicates that file @var{name} is the main source | |
9261 | file---the file specified as the input file for compilation. | |
9262 | This macro is called only once, at the beginning of compilation. | |
9263 | ||
9264 | This macro need not be defined if the standard form of output | |
9265 | for DBX debugging information is appropriate. | |
9266 | ||
9267 | It may be necessary to refer to a label equal to the beginning of the | |
9268 | text section. You can use @samp{assemble_name (stream, ltext_label_name)} | |
9269 | to do so. If you do this, you must also set the variable | |
9270 | @var{used_ltext_label_name} to @code{true}. | |
9271 | @end defmac | |
9272 | ||
9273 | @defmac NO_DBX_MAIN_SOURCE_DIRECTORY | |
9274 | Define this macro, with value 1, if GCC should not emit an indication | |
9275 | of the current directory for compilation and current source language at | |
9276 | the beginning of the file. | |
9277 | @end defmac | |
9278 | ||
9279 | @defmac NO_DBX_GCC_MARKER | |
9280 | Define this macro, with value 1, if GCC should not emit an indication | |
9281 | that this object file was compiled by GCC@. The default is to emit | |
9282 | an @code{N_OPT} stab at the beginning of every source file, with | |
9283 | @samp{gcc2_compiled.} for the string and value 0. | |
9284 | @end defmac | |
9285 | ||
9286 | @defmac DBX_OUTPUT_MAIN_SOURCE_FILE_END (@var{stream}, @var{name}) | |
9287 | A C statement to output DBX debugging information at the end of | |
9288 | compilation of the main source file @var{name}. Output should be | |
9289 | written to the stdio stream @var{stream}. | |
9290 | ||
9291 | If you don't define this macro, nothing special is output at the end | |
9292 | of compilation, which is correct for most machines. | |
9293 | @end defmac | |
9294 | ||
9295 | @defmac DBX_OUTPUT_NULL_N_SO_AT_MAIN_SOURCE_FILE_END | |
9296 | Define this macro @emph{instead of} defining | |
9297 | @code{DBX_OUTPUT_MAIN_SOURCE_FILE_END}, if what needs to be output at | |
9298 | the end of compilation is an @code{N_SO} stab with an empty string, | |
9299 | whose value is the highest absolute text address in the file. | |
9300 | @end defmac | |
9301 | ||
9302 | @need 2000 | |
9303 | @node SDB and DWARF | |
9304 | @subsection Macros for SDB and DWARF Output | |
9305 | ||
9306 | @c prevent bad page break with this line | |
9307 | Here are macros for SDB and DWARF output. | |
9308 | ||
9309 | @defmac SDB_DEBUGGING_INFO | |
9310 | Define this macro if GCC should produce COFF-style debugging output | |
9311 | for SDB in response to the @option{-g} option. | |
9312 | @end defmac | |
9313 | ||
9314 | @defmac DWARF2_DEBUGGING_INFO | |
9315 | Define this macro if GCC should produce dwarf version 2 format | |
9316 | debugging output in response to the @option{-g} option. | |
9317 | ||
9318 | @hook TARGET_DWARF_CALLING_CONVENTION | |
9319 | Define this to enable the dwarf attribute @code{DW_AT_calling_convention} to | |
9320 | be emitted for each function. Instead of an integer return the enum | |
9321 | value for the @code{DW_CC_} tag. | |
9322 | @end deftypefn | |
9323 | ||
9324 | To support optional call frame debugging information, you must also | |
9325 | define @code{INCOMING_RETURN_ADDR_RTX} and either set | |
9326 | @code{RTX_FRAME_RELATED_P} on the prologue insns if you use RTL for the | |
9327 | prologue, or call @code{dwarf2out_def_cfa} and @code{dwarf2out_reg_save} | |
9328 | as appropriate from @code{TARGET_ASM_FUNCTION_PROLOGUE} if you don't. | |
9329 | @end defmac | |
9330 | ||
9331 | @defmac DWARF2_FRAME_INFO | |
9332 | Define this macro to a nonzero value if GCC should always output | |
f0a0390e RH |
9333 | Dwarf 2 frame information. If @code{TARGET_EXCEPT_UNWIND_INFO} |
9334 | (@pxref{Exception Region Output}) returns @code{UI_DWARF2}, and | |
9335 | exceptions are enabled, GCC will output this information not matter | |
9336 | how you define @code{DWARF2_FRAME_INFO}. | |
38f8b050 JR |
9337 | @end defmac |
9338 | ||
f0a0390e RH |
9339 | @hook TARGET_DEBUG_UNWIND_INFO |
9340 | This hook defines the mechanism that will be used for describing frame | |
9341 | unwind information to the debugger. Normally the hook will return | |
9342 | @code{UI_DWARF2} if DWARF 2 debug information is enabled, and | |
9343 | return @code{UI_NONE} otherwise. | |
9344 | ||
9345 | A target may return @code{UI_DWARF2} even when DWARF 2 debug information | |
9346 | is disabled in order to always output DWARF 2 frame information. | |
9347 | ||
9348 | A target may return @code{UI_TARGET} if it has ABI specified unwind tables. | |
9349 | This will suppress generation of the normal debug frame unwind information. | |
9350 | @end deftypefn | |
9351 | ||
38f8b050 JR |
9352 | @defmac DWARF2_ASM_LINE_DEBUG_INFO |
9353 | Define this macro to be a nonzero value if the assembler can generate Dwarf 2 | |
9354 | line debug info sections. This will result in much more compact line number | |
9355 | tables, and hence is desirable if it works. | |
9356 | @end defmac | |
9357 | ||
9730bc27 TT |
9358 | @hook TARGET_WANT_DEBUG_PUB_SECTIONS |
9359 | ||
2ba42841 AO |
9360 | @hook TARGET_DELAY_SCHED2 |
9361 | ||
9362 | @hook TARGET_DELAY_VARTRACK | |
9363 | ||
38f8b050 JR |
9364 | @defmac ASM_OUTPUT_DWARF_DELTA (@var{stream}, @var{size}, @var{label1}, @var{label2}) |
9365 | A C statement to issue assembly directives that create a difference | |
9366 | @var{lab1} minus @var{lab2}, using an integer of the given @var{size}. | |
9367 | @end defmac | |
9368 | ||
9369 | @defmac ASM_OUTPUT_DWARF_VMS_DELTA (@var{stream}, @var{size}, @var{label1}, @var{label2}) | |
9370 | A C statement to issue assembly directives that create a difference | |
9371 | between the two given labels in system defined units, e.g. instruction | |
9372 | slots on IA64 VMS, using an integer of the given size. | |
9373 | @end defmac | |
9374 | ||
9375 | @defmac ASM_OUTPUT_DWARF_OFFSET (@var{stream}, @var{size}, @var{label}, @var{section}) | |
9376 | A C statement to issue assembly directives that create a | |
9377 | section-relative reference to the given @var{label}, using an integer of the | |
9378 | given @var{size}. The label is known to be defined in the given @var{section}. | |
9379 | @end defmac | |
9380 | ||
9381 | @defmac ASM_OUTPUT_DWARF_PCREL (@var{stream}, @var{size}, @var{label}) | |
9382 | A C statement to issue assembly directives that create a self-relative | |
9383 | reference to the given @var{label}, using an integer of the given @var{size}. | |
9384 | @end defmac | |
9385 | ||
9386 | @defmac ASM_OUTPUT_DWARF_TABLE_REF (@var{label}) | |
9387 | A C statement to issue assembly directives that create a reference to | |
9388 | the DWARF table identifier @var{label} from the current section. This | |
9389 | is used on some systems to avoid garbage collecting a DWARF table which | |
9390 | is referenced by a function. | |
9391 | @end defmac | |
9392 | ||
9393 | @hook TARGET_ASM_OUTPUT_DWARF_DTPREL | |
9394 | If defined, this target hook is a function which outputs a DTP-relative | |
9395 | reference to the given TLS symbol of the specified size. | |
9396 | @end deftypefn | |
9397 | ||
9398 | @defmac PUT_SDB_@dots{} | |
9399 | Define these macros to override the assembler syntax for the special | |
9400 | SDB assembler directives. See @file{sdbout.c} for a list of these | |
9401 | macros and their arguments. If the standard syntax is used, you need | |
9402 | not define them yourself. | |
9403 | @end defmac | |
9404 | ||
9405 | @defmac SDB_DELIM | |
9406 | Some assemblers do not support a semicolon as a delimiter, even between | |
9407 | SDB assembler directives. In that case, define this macro to be the | |
9408 | delimiter to use (usually @samp{\n}). It is not necessary to define | |
9409 | a new set of @code{PUT_SDB_@var{op}} macros if this is the only change | |
9410 | required. | |
9411 | @end defmac | |
9412 | ||
9413 | @defmac SDB_ALLOW_UNKNOWN_REFERENCES | |
9414 | Define this macro to allow references to unknown structure, | |
9415 | union, or enumeration tags to be emitted. Standard COFF does not | |
9416 | allow handling of unknown references, MIPS ECOFF has support for | |
9417 | it. | |
9418 | @end defmac | |
9419 | ||
9420 | @defmac SDB_ALLOW_FORWARD_REFERENCES | |
9421 | Define this macro to allow references to structure, union, or | |
9422 | enumeration tags that have not yet been seen to be handled. Some | |
9423 | assemblers choke if forward tags are used, while some require it. | |
9424 | @end defmac | |
9425 | ||
9426 | @defmac SDB_OUTPUT_SOURCE_LINE (@var{stream}, @var{line}) | |
9427 | A C statement to output SDB debugging information before code for line | |
9428 | number @var{line} of the current source file to the stdio stream | |
9429 | @var{stream}. The default is to emit an @code{.ln} directive. | |
9430 | @end defmac | |
9431 | ||
9432 | @need 2000 | |
9433 | @node VMS Debug | |
9434 | @subsection Macros for VMS Debug Format | |
9435 | ||
9436 | @c prevent bad page break with this line | |
9437 | Here are macros for VMS debug format. | |
9438 | ||
9439 | @defmac VMS_DEBUGGING_INFO | |
9440 | Define this macro if GCC should produce debugging output for VMS | |
9441 | in response to the @option{-g} option. The default behavior for VMS | |
9442 | is to generate minimal debug info for a traceback in the absence of | |
9443 | @option{-g} unless explicitly overridden with @option{-g0}. This | |
fac0f722 | 9444 | behavior is controlled by @code{TARGET_OPTION_OPTIMIZATION} and |
38f8b050 JR |
9445 | @code{TARGET_OPTION_OVERRIDE}. |
9446 | @end defmac | |
9447 | ||
9448 | @node Floating Point | |
9449 | @section Cross Compilation and Floating Point | |
9450 | @cindex cross compilation and floating point | |
9451 | @cindex floating point and cross compilation | |
9452 | ||
9453 | While all modern machines use twos-complement representation for integers, | |
9454 | there are a variety of representations for floating point numbers. This | |
9455 | means that in a cross-compiler the representation of floating point numbers | |
9456 | in the compiled program may be different from that used in the machine | |
9457 | doing the compilation. | |
9458 | ||
9459 | Because different representation systems may offer different amounts of | |
9460 | range and precision, all floating point constants must be represented in | |
9461 | the target machine's format. Therefore, the cross compiler cannot | |
9462 | safely use the host machine's floating point arithmetic; it must emulate | |
9463 | the target's arithmetic. To ensure consistency, GCC always uses | |
9464 | emulation to work with floating point values, even when the host and | |
9465 | target floating point formats are identical. | |
9466 | ||
9467 | The following macros are provided by @file{real.h} for the compiler to | |
9468 | use. All parts of the compiler which generate or optimize | |
9469 | floating-point calculations must use these macros. They may evaluate | |
9470 | their operands more than once, so operands must not have side effects. | |
9471 | ||
9472 | @defmac REAL_VALUE_TYPE | |
9473 | The C data type to be used to hold a floating point value in the target | |
9474 | machine's format. Typically this is a @code{struct} containing an | |
9475 | array of @code{HOST_WIDE_INT}, but all code should treat it as an opaque | |
9476 | quantity. | |
9477 | @end defmac | |
9478 | ||
9479 | @deftypefn Macro int REAL_VALUES_EQUAL (REAL_VALUE_TYPE @var{x}, REAL_VALUE_TYPE @var{y}) | |
9480 | Compares for equality the two values, @var{x} and @var{y}. If the target | |
9481 | floating point format supports negative zeroes and/or NaNs, | |
9482 | @samp{REAL_VALUES_EQUAL (-0.0, 0.0)} is true, and | |
9483 | @samp{REAL_VALUES_EQUAL (NaN, NaN)} is false. | |
9484 | @end deftypefn | |
9485 | ||
9486 | @deftypefn Macro int REAL_VALUES_LESS (REAL_VALUE_TYPE @var{x}, REAL_VALUE_TYPE @var{y}) | |
9487 | Tests whether @var{x} is less than @var{y}. | |
9488 | @end deftypefn | |
9489 | ||
9490 | @deftypefn Macro HOST_WIDE_INT REAL_VALUE_FIX (REAL_VALUE_TYPE @var{x}) | |
9491 | Truncates @var{x} to a signed integer, rounding toward zero. | |
9492 | @end deftypefn | |
9493 | ||
9494 | @deftypefn Macro {unsigned HOST_WIDE_INT} REAL_VALUE_UNSIGNED_FIX (REAL_VALUE_TYPE @var{x}) | |
9495 | Truncates @var{x} to an unsigned integer, rounding toward zero. If | |
9496 | @var{x} is negative, returns zero. | |
9497 | @end deftypefn | |
9498 | ||
9499 | @deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_ATOF (const char *@var{string}, enum machine_mode @var{mode}) | |
9500 | Converts @var{string} into a floating point number in the target machine's | |
9501 | representation for mode @var{mode}. This routine can handle both | |
9502 | decimal and hexadecimal floating point constants, using the syntax | |
9503 | defined by the C language for both. | |
9504 | @end deftypefn | |
9505 | ||
9506 | @deftypefn Macro int REAL_VALUE_NEGATIVE (REAL_VALUE_TYPE @var{x}) | |
9507 | Returns 1 if @var{x} is negative (including negative zero), 0 otherwise. | |
9508 | @end deftypefn | |
9509 | ||
9510 | @deftypefn Macro int REAL_VALUE_ISINF (REAL_VALUE_TYPE @var{x}) | |
9511 | Determines whether @var{x} represents infinity (positive or negative). | |
9512 | @end deftypefn | |
9513 | ||
9514 | @deftypefn Macro int REAL_VALUE_ISNAN (REAL_VALUE_TYPE @var{x}) | |
9515 | Determines whether @var{x} represents a ``NaN'' (not-a-number). | |
9516 | @end deftypefn | |
9517 | ||
9518 | @deftypefn Macro void REAL_ARITHMETIC (REAL_VALUE_TYPE @var{output}, enum tree_code @var{code}, REAL_VALUE_TYPE @var{x}, REAL_VALUE_TYPE @var{y}) | |
9519 | Calculates an arithmetic operation on the two floating point values | |
9520 | @var{x} and @var{y}, storing the result in @var{output} (which must be a | |
9521 | variable). | |
9522 | ||
9523 | The operation to be performed is specified by @var{code}. Only the | |
9524 | following codes are supported: @code{PLUS_EXPR}, @code{MINUS_EXPR}, | |
9525 | @code{MULT_EXPR}, @code{RDIV_EXPR}, @code{MAX_EXPR}, @code{MIN_EXPR}. | |
9526 | ||
9527 | If @code{REAL_ARITHMETIC} is asked to evaluate division by zero and the | |
9528 | target's floating point format cannot represent infinity, it will call | |
9529 | @code{abort}. Callers should check for this situation first, using | |
9530 | @code{MODE_HAS_INFINITIES}. @xref{Storage Layout}. | |
9531 | @end deftypefn | |
9532 | ||
9533 | @deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_NEGATE (REAL_VALUE_TYPE @var{x}) | |
9534 | Returns the negative of the floating point value @var{x}. | |
9535 | @end deftypefn | |
9536 | ||
9537 | @deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_ABS (REAL_VALUE_TYPE @var{x}) | |
9538 | Returns the absolute value of @var{x}. | |
9539 | @end deftypefn | |
9540 | ||
9541 | @deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_TRUNCATE (REAL_VALUE_TYPE @var{mode}, enum machine_mode @var{x}) | |
9542 | Truncates the floating point value @var{x} to fit in @var{mode}. The | |
9543 | return value is still a full-size @code{REAL_VALUE_TYPE}, but it has an | |
9544 | appropriate bit pattern to be output as a floating constant whose | |
9545 | precision accords with mode @var{mode}. | |
9546 | @end deftypefn | |
9547 | ||
9548 | @deftypefn Macro void REAL_VALUE_TO_INT (HOST_WIDE_INT @var{low}, HOST_WIDE_INT @var{high}, REAL_VALUE_TYPE @var{x}) | |
9549 | Converts a floating point value @var{x} into a double-precision integer | |
9550 | which is then stored into @var{low} and @var{high}. If the value is not | |
9551 | integral, it is truncated. | |
9552 | @end deftypefn | |
9553 | ||
9554 | @deftypefn Macro void REAL_VALUE_FROM_INT (REAL_VALUE_TYPE @var{x}, HOST_WIDE_INT @var{low}, HOST_WIDE_INT @var{high}, enum machine_mode @var{mode}) | |
9555 | Converts a double-precision integer found in @var{low} and @var{high}, | |
9556 | into a floating point value which is then stored into @var{x}. The | |
9557 | value is truncated to fit in mode @var{mode}. | |
9558 | @end deftypefn | |
9559 | ||
9560 | @node Mode Switching | |
9561 | @section Mode Switching Instructions | |
9562 | @cindex mode switching | |
9563 | The following macros control mode switching optimizations: | |
9564 | ||
9565 | @defmac OPTIMIZE_MODE_SWITCHING (@var{entity}) | |
9566 | Define this macro if the port needs extra instructions inserted for mode | |
9567 | switching in an optimizing compilation. | |
9568 | ||
9569 | For an example, the SH4 can perform both single and double precision | |
9570 | floating point operations, but to perform a single precision operation, | |
9571 | the FPSCR PR bit has to be cleared, while for a double precision | |
9572 | operation, this bit has to be set. Changing the PR bit requires a general | |
9573 | purpose register as a scratch register, hence these FPSCR sets have to | |
9574 | be inserted before reload, i.e.@: you can't put this into instruction emitting | |
9575 | or @code{TARGET_MACHINE_DEPENDENT_REORG}. | |
9576 | ||
9577 | You can have multiple entities that are mode-switched, and select at run time | |
9578 | which entities actually need it. @code{OPTIMIZE_MODE_SWITCHING} should | |
9579 | return nonzero for any @var{entity} that needs mode-switching. | |
9580 | If you define this macro, you also have to define | |
9581 | @code{NUM_MODES_FOR_MODE_SWITCHING}, @code{MODE_NEEDED}, | |
9582 | @code{MODE_PRIORITY_TO_MODE} and @code{EMIT_MODE_SET}. | |
9583 | @code{MODE_AFTER}, @code{MODE_ENTRY}, and @code{MODE_EXIT} | |
9584 | are optional. | |
9585 | @end defmac | |
9586 | ||
9587 | @defmac NUM_MODES_FOR_MODE_SWITCHING | |
9588 | If you define @code{OPTIMIZE_MODE_SWITCHING}, you have to define this as | |
9589 | initializer for an array of integers. Each initializer element | |
9590 | N refers to an entity that needs mode switching, and specifies the number | |
9591 | of different modes that might need to be set for this entity. | |
9592 | The position of the initializer in the initializer---starting counting at | |
9593 | zero---determines the integer that is used to refer to the mode-switched | |
9594 | entity in question. | |
9595 | In macros that take mode arguments / yield a mode result, modes are | |
9596 | represented as numbers 0 @dots{} N @minus{} 1. N is used to specify that no mode | |
9597 | switch is needed / supplied. | |
9598 | @end defmac | |
9599 | ||
9600 | @defmac MODE_NEEDED (@var{entity}, @var{insn}) | |
9601 | @var{entity} is an integer specifying a mode-switched entity. If | |
9602 | @code{OPTIMIZE_MODE_SWITCHING} is defined, you must define this macro to | |
9603 | return an integer value not larger than the corresponding element in | |
9604 | @code{NUM_MODES_FOR_MODE_SWITCHING}, to denote the mode that @var{entity} must | |
9605 | be switched into prior to the execution of @var{insn}. | |
9606 | @end defmac | |
9607 | ||
9608 | @defmac MODE_AFTER (@var{mode}, @var{insn}) | |
9609 | If this macro is defined, it is evaluated for every @var{insn} during | |
9610 | mode switching. It determines the mode that an insn results in (if | |
9611 | different from the incoming mode). | |
9612 | @end defmac | |
9613 | ||
9614 | @defmac MODE_ENTRY (@var{entity}) | |
9615 | If this macro is defined, it is evaluated for every @var{entity} that needs | |
9616 | mode switching. It should evaluate to an integer, which is a mode that | |
9617 | @var{entity} is assumed to be switched to at function entry. If @code{MODE_ENTRY} | |
9618 | is defined then @code{MODE_EXIT} must be defined. | |
9619 | @end defmac | |
9620 | ||
9621 | @defmac MODE_EXIT (@var{entity}) | |
9622 | If this macro is defined, it is evaluated for every @var{entity} that needs | |
9623 | mode switching. It should evaluate to an integer, which is a mode that | |
9624 | @var{entity} is assumed to be switched to at function exit. If @code{MODE_EXIT} | |
9625 | is defined then @code{MODE_ENTRY} must be defined. | |
9626 | @end defmac | |
9627 | ||
9628 | @defmac MODE_PRIORITY_TO_MODE (@var{entity}, @var{n}) | |
9629 | This macro specifies the order in which modes for @var{entity} are processed. | |
9630 | 0 is the highest priority, @code{NUM_MODES_FOR_MODE_SWITCHING[@var{entity}] - 1} the | |
9631 | lowest. The value of the macro should be an integer designating a mode | |
9632 | for @var{entity}. For any fixed @var{entity}, @code{mode_priority_to_mode} | |
9633 | (@var{entity}, @var{n}) shall be a bijection in 0 @dots{} | |
9634 | @code{num_modes_for_mode_switching[@var{entity}] - 1}. | |
9635 | @end defmac | |
9636 | ||
9637 | @defmac EMIT_MODE_SET (@var{entity}, @var{mode}, @var{hard_regs_live}) | |
9638 | Generate one or more insns to set @var{entity} to @var{mode}. | |
9639 | @var{hard_reg_live} is the set of hard registers live at the point where | |
9640 | the insn(s) are to be inserted. | |
9641 | @end defmac | |
9642 | ||
9643 | @node Target Attributes | |
9644 | @section Defining target-specific uses of @code{__attribute__} | |
9645 | @cindex target attributes | |
9646 | @cindex machine attributes | |
9647 | @cindex attributes, target-specific | |
9648 | ||
9649 | Target-specific attributes may be defined for functions, data and types. | |
9650 | These are described using the following target hooks; they also need to | |
9651 | be documented in @file{extend.texi}. | |
9652 | ||
9653 | @hook TARGET_ATTRIBUTE_TABLE | |
9654 | If defined, this target hook points to an array of @samp{struct | |
9655 | attribute_spec} (defined in @file{tree.h}) specifying the machine | |
9656 | specific attributes for this target and some of the restrictions on the | |
9657 | entities to which these attributes are applied and the arguments they | |
9658 | take. | |
9659 | @end deftypevr | |
9660 | ||
9661 | @hook TARGET_ATTRIBUTE_TAKES_IDENTIFIER_P | |
9662 | If defined, this target hook is a function which returns true if the | |
9663 | machine-specific attribute named @var{name} expects an identifier | |
9664 | given as its first argument to be passed on as a plain identifier, not | |
9665 | subjected to name lookup. If this is not defined, the default is | |
9666 | false for all machine-specific attributes. | |
9667 | @end deftypefn | |
9668 | ||
9669 | @hook TARGET_COMP_TYPE_ATTRIBUTES | |
9670 | If defined, this target hook is a function which returns zero if the attributes on | |
9671 | @var{type1} and @var{type2} are incompatible, one if they are compatible, | |
9672 | and two if they are nearly compatible (which causes a warning to be | |
9673 | generated). If this is not defined, machine-specific attributes are | |
9674 | supposed always to be compatible. | |
9675 | @end deftypefn | |
9676 | ||
9677 | @hook TARGET_SET_DEFAULT_TYPE_ATTRIBUTES | |
9678 | If defined, this target hook is a function which assigns default attributes to | |
9679 | the newly defined @var{type}. | |
9680 | @end deftypefn | |
9681 | ||
9682 | @hook TARGET_MERGE_TYPE_ATTRIBUTES | |
9683 | Define this target hook if the merging of type attributes needs special | |
9684 | handling. If defined, the result is a list of the combined | |
9685 | @code{TYPE_ATTRIBUTES} of @var{type1} and @var{type2}. It is assumed | |
9686 | that @code{comptypes} has already been called and returned 1. This | |
9687 | function may call @code{merge_attributes} to handle machine-independent | |
9688 | merging. | |
9689 | @end deftypefn | |
9690 | ||
9691 | @hook TARGET_MERGE_DECL_ATTRIBUTES | |
9692 | Define this target hook if the merging of decl attributes needs special | |
9693 | handling. If defined, the result is a list of the combined | |
9694 | @code{DECL_ATTRIBUTES} of @var{olddecl} and @var{newdecl}. | |
9695 | @var{newdecl} is a duplicate declaration of @var{olddecl}. Examples of | |
9696 | when this is needed are when one attribute overrides another, or when an | |
9697 | attribute is nullified by a subsequent definition. This function may | |
9698 | call @code{merge_attributes} to handle machine-independent merging. | |
9699 | ||
9700 | @findex TARGET_DLLIMPORT_DECL_ATTRIBUTES | |
9701 | If the only target-specific handling you require is @samp{dllimport} | |
9702 | for Microsoft Windows targets, you should define the macro | |
9703 | @code{TARGET_DLLIMPORT_DECL_ATTRIBUTES} to @code{1}. The compiler | |
9704 | will then define a function called | |
9705 | @code{merge_dllimport_decl_attributes} which can then be defined as | |
9706 | the expansion of @code{TARGET_MERGE_DECL_ATTRIBUTES}. You can also | |
9707 | add @code{handle_dll_attribute} in the attribute table for your port | |
9708 | to perform initial processing of the @samp{dllimport} and | |
9709 | @samp{dllexport} attributes. This is done in @file{i386/cygwin.h} and | |
9710 | @file{i386/i386.c}, for example. | |
9711 | @end deftypefn | |
9712 | ||
9713 | @hook TARGET_VALID_DLLIMPORT_ATTRIBUTE_P | |
9714 | ||
9715 | @defmac TARGET_DECLSPEC | |
9716 | Define this macro to a nonzero value if you want to treat | |
9717 | @code{__declspec(X)} as equivalent to @code{__attribute((X))}. By | |
9718 | default, this behavior is enabled only for targets that define | |
9719 | @code{TARGET_DLLIMPORT_DECL_ATTRIBUTES}. The current implementation | |
9720 | of @code{__declspec} is via a built-in macro, but you should not rely | |
9721 | on this implementation detail. | |
9722 | @end defmac | |
9723 | ||
9724 | @hook TARGET_INSERT_ATTRIBUTES | |
9725 | Define this target hook if you want to be able to add attributes to a decl | |
9726 | when it is being created. This is normally useful for back ends which | |
9727 | wish to implement a pragma by using the attributes which correspond to | |
9728 | the pragma's effect. The @var{node} argument is the decl which is being | |
9729 | created. The @var{attr_ptr} argument is a pointer to the attribute list | |
9730 | for this decl. The list itself should not be modified, since it may be | |
9731 | shared with other decls, but attributes may be chained on the head of | |
9732 | the list and @code{*@var{attr_ptr}} modified to point to the new | |
9733 | attributes, or a copy of the list may be made if further changes are | |
9734 | needed. | |
9735 | @end deftypefn | |
9736 | ||
9737 | @hook TARGET_FUNCTION_ATTRIBUTE_INLINABLE_P | |
9738 | @cindex inlining | |
9739 | This target hook returns @code{true} if it is ok to inline @var{fndecl} | |
9740 | into the current function, despite its having target-specific | |
9741 | attributes, @code{false} otherwise. By default, if a function has a | |
9742 | target specific attribute attached to it, it will not be inlined. | |
9743 | @end deftypefn | |
9744 | ||
9745 | @hook TARGET_OPTION_VALID_ATTRIBUTE_P | |
9746 | This hook is called to parse the @code{attribute(option("..."))}, and | |
9747 | it allows the function to set different target machine compile time | |
9748 | options for the current function that might be different than the | |
9749 | options specified on the command line. The hook should return | |
9750 | @code{true} if the options are valid. | |
9751 | ||
9752 | The hook should set the @var{DECL_FUNCTION_SPECIFIC_TARGET} field in | |
9753 | the function declaration to hold a pointer to a target specific | |
9754 | @var{struct cl_target_option} structure. | |
9755 | @end deftypefn | |
9756 | ||
9757 | @hook TARGET_OPTION_SAVE | |
9758 | This hook is called to save any additional target specific information | |
9759 | in the @var{struct cl_target_option} structure for function specific | |
9760 | options. | |
9761 | @xref{Option file format}. | |
9762 | @end deftypefn | |
9763 | ||
9764 | @hook TARGET_OPTION_RESTORE | |
9765 | This hook is called to restore any additional target specific | |
9766 | information in the @var{struct cl_target_option} structure for | |
9767 | function specific options. | |
9768 | @end deftypefn | |
9769 | ||
9770 | @hook TARGET_OPTION_PRINT | |
9771 | This hook is called to print any additional target specific | |
9772 | information in the @var{struct cl_target_option} structure for | |
9773 | function specific options. | |
9774 | @end deftypefn | |
9775 | ||
56cb42ea | 9776 | @hook TARGET_OPTION_PRAGMA_PARSE |
38f8b050 JR |
9777 | This target hook parses the options for @code{#pragma GCC option} to |
9778 | set the machine specific options for functions that occur later in the | |
9779 | input stream. The options should be the same as handled by the | |
56cb42ea | 9780 | @code{TARGET_OPTION_VALID_ATTRIBUTE_P} hook. |
38f8b050 JR |
9781 | @end deftypefn |
9782 | ||
9783 | @hook TARGET_OPTION_OVERRIDE | |
9784 | Sometimes certain combinations of command options do not make sense on | |
9785 | a particular target machine. You can override the hook | |
9786 | @code{TARGET_OPTION_OVERRIDE} to take account of this. This hooks is called | |
9787 | once just after all the command options have been parsed. | |
9788 | ||
9789 | Don't use this hook to turn on various extra optimizations for | |
fac0f722 | 9790 | @option{-O}. That is what @code{TARGET_OPTION_OPTIMIZATION} is for. |
38f8b050 JR |
9791 | |
9792 | If you need to do something whenever the optimization level is | |
9793 | changed via the optimize attribute or pragma, see | |
9794 | @code{TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE} | |
9795 | @end deftypefn | |
9796 | ||
9797 | @hook TARGET_CAN_INLINE_P | |
9798 | This target hook returns @code{false} if the @var{caller} function | |
9799 | cannot inline @var{callee}, based on target specific information. By | |
9800 | default, inlining is not allowed if the callee function has function | |
9801 | specific target options and the caller does not use the same options. | |
9802 | @end deftypefn | |
9803 | ||
9804 | @node Emulated TLS | |
9805 | @section Emulating TLS | |
9806 | @cindex Emulated TLS | |
9807 | ||
9808 | For targets whose psABI does not provide Thread Local Storage via | |
9809 | specific relocations and instruction sequences, an emulation layer is | |
9810 | used. A set of target hooks allows this emulation layer to be | |
9811 | configured for the requirements of a particular target. For instance | |
9812 | the psABI may in fact specify TLS support in terms of an emulation | |
9813 | layer. | |
9814 | ||
9815 | The emulation layer works by creating a control object for every TLS | |
9816 | object. To access the TLS object, a lookup function is provided | |
9817 | which, when given the address of the control object, will return the | |
9818 | address of the current thread's instance of the TLS object. | |
9819 | ||
9820 | @hook TARGET_EMUTLS_GET_ADDRESS | |
9821 | Contains the name of the helper function that uses a TLS control | |
9822 | object to locate a TLS instance. The default causes libgcc's | |
9823 | emulated TLS helper function to be used. | |
9824 | @end deftypevr | |
9825 | ||
9826 | @hook TARGET_EMUTLS_REGISTER_COMMON | |
9827 | Contains the name of the helper function that should be used at | |
9828 | program startup to register TLS objects that are implicitly | |
9829 | initialized to zero. If this is @code{NULL}, all TLS objects will | |
9830 | have explicit initializers. The default causes libgcc's emulated TLS | |
9831 | registration function to be used. | |
9832 | @end deftypevr | |
9833 | ||
9834 | @hook TARGET_EMUTLS_VAR_SECTION | |
9835 | Contains the name of the section in which TLS control variables should | |
9836 | be placed. The default of @code{NULL} allows these to be placed in | |
9837 | any section. | |
9838 | @end deftypevr | |
9839 | ||
9840 | @hook TARGET_EMUTLS_TMPL_SECTION | |
9841 | Contains the name of the section in which TLS initializers should be | |
9842 | placed. The default of @code{NULL} allows these to be placed in any | |
9843 | section. | |
9844 | @end deftypevr | |
9845 | ||
9846 | @hook TARGET_EMUTLS_VAR_PREFIX | |
9847 | Contains the prefix to be prepended to TLS control variable names. | |
9848 | The default of @code{NULL} uses a target-specific prefix. | |
9849 | @end deftypevr | |
9850 | ||
9851 | @hook TARGET_EMUTLS_TMPL_PREFIX | |
9852 | Contains the prefix to be prepended to TLS initializer objects. The | |
9853 | default of @code{NULL} uses a target-specific prefix. | |
9854 | @end deftypevr | |
9855 | ||
9856 | @hook TARGET_EMUTLS_VAR_FIELDS | |
9857 | Specifies a function that generates the FIELD_DECLs for a TLS control | |
9858 | object type. @var{type} is the RECORD_TYPE the fields are for and | |
9859 | @var{name} should be filled with the structure tag, if the default of | |
9860 | @code{__emutls_object} is unsuitable. The default creates a type suitable | |
9861 | for libgcc's emulated TLS function. | |
9862 | @end deftypefn | |
9863 | ||
9864 | @hook TARGET_EMUTLS_VAR_INIT | |
9865 | Specifies a function that generates the CONSTRUCTOR to initialize a | |
9866 | TLS control object. @var{var} is the TLS control object, @var{decl} | |
9867 | is the TLS object and @var{tmpl_addr} is the address of the | |
9868 | initializer. The default initializes libgcc's emulated TLS control object. | |
9869 | @end deftypefn | |
9870 | ||
9871 | @hook TARGET_EMUTLS_VAR_ALIGN_FIXED | |
9872 | Specifies whether the alignment of TLS control variable objects is | |
9873 | fixed and should not be increased as some backends may do to optimize | |
9874 | single objects. The default is false. | |
9875 | @end deftypevr | |
9876 | ||
9877 | @hook TARGET_EMUTLS_DEBUG_FORM_TLS_ADDRESS | |
9878 | Specifies whether a DWARF @code{DW_OP_form_tls_address} location descriptor | |
9879 | may be used to describe emulated TLS control objects. | |
9880 | @end deftypevr | |
9881 | ||
9882 | @node MIPS Coprocessors | |
9883 | @section Defining coprocessor specifics for MIPS targets. | |
9884 | @cindex MIPS coprocessor-definition macros | |
9885 | ||
9886 | The MIPS specification allows MIPS implementations to have as many as 4 | |
9887 | coprocessors, each with as many as 32 private registers. GCC supports | |
9888 | accessing these registers and transferring values between the registers | |
9889 | and memory using asm-ized variables. For example: | |
9890 | ||
9891 | @smallexample | |
9892 | register unsigned int cp0count asm ("c0r1"); | |
9893 | unsigned int d; | |
9894 | ||
9895 | d = cp0count + 3; | |
9896 | @end smallexample | |
9897 | ||
9898 | (``c0r1'' is the default name of register 1 in coprocessor 0; alternate | |
9899 | names may be added as described below, or the default names may be | |
9900 | overridden entirely in @code{SUBTARGET_CONDITIONAL_REGISTER_USAGE}.) | |
9901 | ||
9902 | Coprocessor registers are assumed to be epilogue-used; sets to them will | |
9903 | be preserved even if it does not appear that the register is used again | |
9904 | later in the function. | |
9905 | ||
9906 | Another note: according to the MIPS spec, coprocessor 1 (if present) is | |
9907 | the FPU@. One accesses COP1 registers through standard mips | |
9908 | floating-point support; they are not included in this mechanism. | |
9909 | ||
9910 | There is one macro used in defining the MIPS coprocessor interface which | |
9911 | you may want to override in subtargets; it is described below. | |
9912 | ||
9913 | @defmac ALL_COP_ADDITIONAL_REGISTER_NAMES | |
9914 | A comma-separated list (with leading comma) of pairs describing the | |
9915 | alternate names of coprocessor registers. The format of each entry should be | |
9916 | @smallexample | |
9917 | @{ @var{alternatename}, @var{register_number}@} | |
9918 | @end smallexample | |
9919 | Default: empty. | |
9920 | @end defmac | |
9921 | ||
9922 | @node PCH Target | |
9923 | @section Parameters for Precompiled Header Validity Checking | |
9924 | @cindex parameters, precompiled headers | |
9925 | ||
9926 | @hook TARGET_GET_PCH_VALIDITY | |
9927 | This hook returns a pointer to the data needed by | |
9928 | @code{TARGET_PCH_VALID_P} and sets | |
9929 | @samp{*@var{sz}} to the size of the data in bytes. | |
9930 | @end deftypefn | |
9931 | ||
9932 | @hook TARGET_PCH_VALID_P | |
9933 | This hook checks whether the options used to create a PCH file are | |
9934 | compatible with the current settings. It returns @code{NULL} | |
9935 | if so and a suitable error message if not. Error messages will | |
9936 | be presented to the user and must be localized using @samp{_(@var{msg})}. | |
9937 | ||
9938 | @var{data} is the data that was returned by @code{TARGET_GET_PCH_VALIDITY} | |
9939 | when the PCH file was created and @var{sz} is the size of that data in bytes. | |
9940 | It's safe to assume that the data was created by the same version of the | |
9941 | compiler, so no format checking is needed. | |
9942 | ||
9943 | The default definition of @code{default_pch_valid_p} should be | |
9944 | suitable for most targets. | |
9945 | @end deftypefn | |
9946 | ||
9947 | @hook TARGET_CHECK_PCH_TARGET_FLAGS | |
9948 | If this hook is nonnull, the default implementation of | |
9949 | @code{TARGET_PCH_VALID_P} will use it to check for compatible values | |
9950 | of @code{target_flags}. @var{pch_flags} specifies the value that | |
9951 | @code{target_flags} had when the PCH file was created. The return | |
9952 | value is the same as for @code{TARGET_PCH_VALID_P}. | |
9953 | @end deftypefn | |
9954 | ||
9955 | @node C++ ABI | |
9956 | @section C++ ABI parameters | |
9957 | @cindex parameters, c++ abi | |
9958 | ||
9959 | @hook TARGET_CXX_GUARD_TYPE | |
9960 | Define this hook to override the integer type used for guard variables. | |
9961 | These are used to implement one-time construction of static objects. The | |
9962 | default is long_long_integer_type_node. | |
9963 | @end deftypefn | |
9964 | ||
9965 | @hook TARGET_CXX_GUARD_MASK_BIT | |
9966 | This hook determines how guard variables are used. It should return | |
9967 | @code{false} (the default) if the first byte should be used. A return value of | |
9968 | @code{true} indicates that only the least significant bit should be used. | |
9969 | @end deftypefn | |
9970 | ||
9971 | @hook TARGET_CXX_GET_COOKIE_SIZE | |
9972 | This hook returns the size of the cookie to use when allocating an array | |
9973 | whose elements have the indicated @var{type}. Assumes that it is already | |
9974 | known that a cookie is needed. The default is | |
9975 | @code{max(sizeof (size_t), alignof(type))}, as defined in section 2.7 of the | |
9976 | IA64/Generic C++ ABI@. | |
9977 | @end deftypefn | |
9978 | ||
9979 | @hook TARGET_CXX_COOKIE_HAS_SIZE | |
9980 | This hook should return @code{true} if the element size should be stored in | |
9981 | array cookies. The default is to return @code{false}. | |
9982 | @end deftypefn | |
9983 | ||
9984 | @hook TARGET_CXX_IMPORT_EXPORT_CLASS | |
9985 | If defined by a backend this hook allows the decision made to export | |
9986 | class @var{type} to be overruled. Upon entry @var{import_export} | |
9987 | will contain 1 if the class is going to be exported, @minus{}1 if it is going | |
9988 | to be imported and 0 otherwise. This function should return the | |
9989 | modified value and perform any other actions necessary to support the | |
9990 | backend's targeted operating system. | |
9991 | @end deftypefn | |
9992 | ||
9993 | @hook TARGET_CXX_CDTOR_RETURNS_THIS | |
9994 | This hook should return @code{true} if constructors and destructors return | |
9995 | the address of the object created/destroyed. The default is to return | |
9996 | @code{false}. | |
9997 | @end deftypefn | |
9998 | ||
9999 | @hook TARGET_CXX_KEY_METHOD_MAY_BE_INLINE | |
10000 | This hook returns true if the key method for a class (i.e., the method | |
10001 | which, if defined in the current translation unit, causes the virtual | |
10002 | table to be emitted) may be an inline function. Under the standard | |
10003 | Itanium C++ ABI the key method may be an inline function so long as | |
10004 | the function is not declared inline in the class definition. Under | |
10005 | some variants of the ABI, an inline function can never be the key | |
10006 | method. The default is to return @code{true}. | |
10007 | @end deftypefn | |
10008 | ||
10009 | @hook TARGET_CXX_DETERMINE_CLASS_DATA_VISIBILITY | |
10010 | ||
10011 | @hook TARGET_CXX_CLASS_DATA_ALWAYS_COMDAT | |
10012 | This hook returns true (the default) if virtual tables and other | |
10013 | similar implicit class data objects are always COMDAT if they have | |
10014 | external linkage. If this hook returns false, then class data for | |
10015 | classes whose virtual table will be emitted in only one translation | |
10016 | unit will not be COMDAT. | |
10017 | @end deftypefn | |
10018 | ||
10019 | @hook TARGET_CXX_LIBRARY_RTTI_COMDAT | |
10020 | This hook returns true (the default) if the RTTI information for | |
10021 | the basic types which is defined in the C++ runtime should always | |
10022 | be COMDAT, false if it should not be COMDAT. | |
10023 | @end deftypefn | |
10024 | ||
10025 | @hook TARGET_CXX_USE_AEABI_ATEXIT | |
10026 | This hook returns true if @code{__aeabi_atexit} (as defined by the ARM EABI) | |
10027 | should be used to register static destructors when @option{-fuse-cxa-atexit} | |
10028 | is in effect. The default is to return false to use @code{__cxa_atexit}. | |
10029 | @end deftypefn | |
10030 | ||
10031 | @hook TARGET_CXX_USE_ATEXIT_FOR_CXA_ATEXIT | |
10032 | This hook returns true if the target @code{atexit} function can be used | |
10033 | in the same manner as @code{__cxa_atexit} to register C++ static | |
10034 | destructors. This requires that @code{atexit}-registered functions in | |
10035 | shared libraries are run in the correct order when the libraries are | |
10036 | unloaded. The default is to return false. | |
10037 | @end deftypefn | |
10038 | ||
10039 | @hook TARGET_CXX_ADJUST_CLASS_AT_DEFINITION | |
10040 | ||
10041 | @node Named Address Spaces | |
10042 | @section Adding support for named address spaces | |
10043 | @cindex named address spaces | |
10044 | ||
10045 | The draft technical report of the ISO/IEC JTC1 S22 WG14 N1275 | |
10046 | standards committee, @cite{Programming Languages - C - Extensions to | |
10047 | support embedded processors}, specifies a syntax for embedded | |
10048 | processors to specify alternate address spaces. You can configure a | |
10049 | GCC port to support section 5.1 of the draft report to add support for | |
10050 | address spaces other than the default address space. These address | |
10051 | spaces are new keywords that are similar to the @code{volatile} and | |
10052 | @code{const} type attributes. | |
10053 | ||
10054 | Pointers to named address spaces can have a different size than | |
10055 | pointers to the generic address space. | |
10056 | ||
10057 | For example, the SPU port uses the @code{__ea} address space to refer | |
10058 | to memory in the host processor, rather than memory local to the SPU | |
10059 | processor. Access to memory in the @code{__ea} address space involves | |
10060 | issuing DMA operations to move data between the host processor and the | |
10061 | local processor memory address space. Pointers in the @code{__ea} | |
10062 | address space are either 32 bits or 64 bits based on the | |
10063 | @option{-mea32} or @option{-mea64} switches (native SPU pointers are | |
10064 | always 32 bits). | |
10065 | ||
10066 | Internally, address spaces are represented as a small integer in the | |
10067 | range 0 to 15 with address space 0 being reserved for the generic | |
10068 | address space. | |
10069 | ||
10070 | To register a named address space qualifier keyword with the C front end, | |
10071 | the target may call the @code{c_register_addr_space} routine. For example, | |
10072 | the SPU port uses the following to declare @code{__ea} as the keyword for | |
10073 | named address space #1: | |
10074 | @smallexample | |
10075 | #define ADDR_SPACE_EA 1 | |
10076 | c_register_addr_space ("__ea", ADDR_SPACE_EA); | |
10077 | @end smallexample | |
10078 | ||
10079 | @hook TARGET_ADDR_SPACE_POINTER_MODE | |
10080 | Define this to return the machine mode to use for pointers to | |
10081 | @var{address_space} if the target supports named address spaces. | |
10082 | The default version of this hook returns @code{ptr_mode} for the | |
10083 | generic address space only. | |
10084 | @end deftypefn | |
10085 | ||
10086 | @hook TARGET_ADDR_SPACE_ADDRESS_MODE | |
10087 | Define this to return the machine mode to use for addresses in | |
10088 | @var{address_space} if the target supports named address spaces. | |
10089 | The default version of this hook returns @code{Pmode} for the | |
10090 | generic address space only. | |
10091 | @end deftypefn | |
10092 | ||
10093 | @hook TARGET_ADDR_SPACE_VALID_POINTER_MODE | |
10094 | Define this to return nonzero if the port can handle pointers | |
10095 | with machine mode @var{mode} to address space @var{as}. This target | |
10096 | hook is the same as the @code{TARGET_VALID_POINTER_MODE} target hook, | |
10097 | except that it includes explicit named address space support. The default | |
10098 | version of this hook returns true for the modes returned by either the | |
10099 | @code{TARGET_ADDR_SPACE_POINTER_MODE} or @code{TARGET_ADDR_SPACE_ADDRESS_MODE} | |
10100 | target hooks for the given address space. | |
10101 | @end deftypefn | |
10102 | ||
10103 | @hook TARGET_ADDR_SPACE_LEGITIMATE_ADDRESS_P | |
10104 | Define this to return true if @var{exp} is a valid address for mode | |
10105 | @var{mode} in the named address space @var{as}. The @var{strict} | |
10106 | parameter says whether strict addressing is in effect after reload has | |
10107 | finished. This target hook is the same as the | |
10108 | @code{TARGET_LEGITIMATE_ADDRESS_P} target hook, except that it includes | |
10109 | explicit named address space support. | |
10110 | @end deftypefn | |
10111 | ||
10112 | @hook TARGET_ADDR_SPACE_LEGITIMIZE_ADDRESS | |
10113 | Define this to modify an invalid address @var{x} to be a valid address | |
10114 | with mode @var{mode} in the named address space @var{as}. This target | |
10115 | hook is the same as the @code{TARGET_LEGITIMIZE_ADDRESS} target hook, | |
10116 | except that it includes explicit named address space support. | |
10117 | @end deftypefn | |
10118 | ||
10119 | @hook TARGET_ADDR_SPACE_SUBSET_P | |
10120 | Define this to return whether the @var{subset} named address space is | |
10121 | contained within the @var{superset} named address space. Pointers to | |
10122 | a named address space that is a subset of another named address space | |
10123 | will be converted automatically without a cast if used together in | |
10124 | arithmetic operations. Pointers to a superset address space can be | |
10125 | converted to pointers to a subset address space via explicit casts. | |
10126 | @end deftypefn | |
10127 | ||
10128 | @hook TARGET_ADDR_SPACE_CONVERT | |
10129 | Define this to convert the pointer expression represented by the RTL | |
10130 | @var{op} with type @var{from_type} that points to a named address | |
10131 | space to a new pointer expression with type @var{to_type} that points | |
10132 | to a different named address space. When this hook it called, it is | |
10133 | guaranteed that one of the two address spaces is a subset of the other, | |
10134 | as determined by the @code{TARGET_ADDR_SPACE_SUBSET_P} target hook. | |
10135 | @end deftypefn | |
10136 | ||
10137 | @node Misc | |
10138 | @section Miscellaneous Parameters | |
10139 | @cindex parameters, miscellaneous | |
10140 | ||
10141 | @c prevent bad page break with this line | |
10142 | Here are several miscellaneous parameters. | |
10143 | ||
10144 | @defmac HAS_LONG_COND_BRANCH | |
10145 | Define this boolean macro to indicate whether or not your architecture | |
10146 | has conditional branches that can span all of memory. It is used in | |
10147 | conjunction with an optimization that partitions hot and cold basic | |
10148 | blocks into separate sections of the executable. If this macro is | |
10149 | set to false, gcc will convert any conditional branches that attempt | |
10150 | to cross between sections into unconditional branches or indirect jumps. | |
10151 | @end defmac | |
10152 | ||
10153 | @defmac HAS_LONG_UNCOND_BRANCH | |
10154 | Define this boolean macro to indicate whether or not your architecture | |
10155 | has unconditional branches that can span all of memory. It is used in | |
10156 | conjunction with an optimization that partitions hot and cold basic | |
10157 | blocks into separate sections of the executable. If this macro is | |
10158 | set to false, gcc will convert any unconditional branches that attempt | |
10159 | to cross between sections into indirect jumps. | |
10160 | @end defmac | |
10161 | ||
10162 | @defmac CASE_VECTOR_MODE | |
10163 | An alias for a machine mode name. This is the machine mode that | |
10164 | elements of a jump-table should have. | |
10165 | @end defmac | |
10166 | ||
10167 | @defmac CASE_VECTOR_SHORTEN_MODE (@var{min_offset}, @var{max_offset}, @var{body}) | |
10168 | Optional: return the preferred mode for an @code{addr_diff_vec} | |
10169 | when the minimum and maximum offset are known. If you define this, | |
10170 | it enables extra code in branch shortening to deal with @code{addr_diff_vec}. | |
10171 | To make this work, you also have to define @code{INSN_ALIGN} and | |
10172 | make the alignment for @code{addr_diff_vec} explicit. | |
10173 | The @var{body} argument is provided so that the offset_unsigned and scale | |
10174 | flags can be updated. | |
10175 | @end defmac | |
10176 | ||
10177 | @defmac CASE_VECTOR_PC_RELATIVE | |
10178 | Define this macro to be a C expression to indicate when jump-tables | |
10179 | should contain relative addresses. You need not define this macro if | |
10180 | jump-tables never contain relative addresses, or jump-tables should | |
10181 | contain relative addresses only when @option{-fPIC} or @option{-fPIC} | |
10182 | is in effect. | |
10183 | @end defmac | |
10184 | ||
10185 | @hook TARGET_CASE_VALUES_THRESHOLD | |
10186 | This function return the smallest number of different values for which it | |
10187 | is best to use a jump-table instead of a tree of conditional branches. | |
10188 | The default is four for machines with a @code{casesi} instruction and | |
10189 | five otherwise. This is best for most machines. | |
10190 | @end deftypefn | |
10191 | ||
10192 | @defmac CASE_USE_BIT_TESTS | |
10193 | Define this macro to be a C expression to indicate whether C switch | |
10194 | statements may be implemented by a sequence of bit tests. This is | |
10195 | advantageous on processors that can efficiently implement left shift | |
10196 | of 1 by the number of bits held in a register, but inappropriate on | |
10197 | targets that would require a loop. By default, this macro returns | |
10198 | @code{true} if the target defines an @code{ashlsi3} pattern, and | |
10199 | @code{false} otherwise. | |
10200 | @end defmac | |
10201 | ||
10202 | @defmac WORD_REGISTER_OPERATIONS | |
10203 | Define this macro if operations between registers with integral mode | |
10204 | smaller than a word are always performed on the entire register. | |
10205 | Most RISC machines have this property and most CISC machines do not. | |
10206 | @end defmac | |
10207 | ||
10208 | @defmac LOAD_EXTEND_OP (@var{mem_mode}) | |
10209 | Define this macro to be a C expression indicating when insns that read | |
10210 | memory in @var{mem_mode}, an integral mode narrower than a word, set the | |
10211 | bits outside of @var{mem_mode} to be either the sign-extension or the | |
10212 | zero-extension of the data read. Return @code{SIGN_EXTEND} for values | |
10213 | of @var{mem_mode} for which the | |
10214 | insn sign-extends, @code{ZERO_EXTEND} for which it zero-extends, and | |
10215 | @code{UNKNOWN} for other modes. | |
10216 | ||
10217 | This macro is not called with @var{mem_mode} non-integral or with a width | |
10218 | greater than or equal to @code{BITS_PER_WORD}, so you may return any | |
10219 | value in this case. Do not define this macro if it would always return | |
10220 | @code{UNKNOWN}. On machines where this macro is defined, you will normally | |
10221 | define it as the constant @code{SIGN_EXTEND} or @code{ZERO_EXTEND}. | |
10222 | ||
10223 | You may return a non-@code{UNKNOWN} value even if for some hard registers | |
10224 | the sign extension is not performed, if for the @code{REGNO_REG_CLASS} | |
10225 | of these hard registers @code{CANNOT_CHANGE_MODE_CLASS} returns nonzero | |
10226 | when the @var{from} mode is @var{mem_mode} and the @var{to} mode is any | |
10227 | integral mode larger than this but not larger than @code{word_mode}. | |
10228 | ||
10229 | You must return @code{UNKNOWN} if for some hard registers that allow this | |
10230 | mode, @code{CANNOT_CHANGE_MODE_CLASS} says that they cannot change to | |
10231 | @code{word_mode}, but that they can change to another integral mode that | |
10232 | is larger then @var{mem_mode} but still smaller than @code{word_mode}. | |
10233 | @end defmac | |
10234 | ||
10235 | @defmac SHORT_IMMEDIATES_SIGN_EXTEND | |
10236 | Define this macro if loading short immediate values into registers sign | |
10237 | extends. | |
10238 | @end defmac | |
10239 | ||
10240 | @defmac FIXUNS_TRUNC_LIKE_FIX_TRUNC | |
10241 | Define this macro if the same instructions that convert a floating | |
10242 | point number to a signed fixed point number also convert validly to an | |
10243 | unsigned one. | |
10244 | @end defmac | |
10245 | ||
10246 | @hook TARGET_MIN_DIVISIONS_FOR_RECIP_MUL | |
10247 | When @option{-ffast-math} is in effect, GCC tries to optimize | |
10248 | divisions by the same divisor, by turning them into multiplications by | |
10249 | the reciprocal. This target hook specifies the minimum number of divisions | |
10250 | that should be there for GCC to perform the optimization for a variable | |
10251 | of mode @var{mode}. The default implementation returns 3 if the machine | |
10252 | has an instruction for the division, and 2 if it does not. | |
10253 | @end deftypefn | |
10254 | ||
10255 | @defmac MOVE_MAX | |
10256 | The maximum number of bytes that a single instruction can move quickly | |
10257 | between memory and registers or between two memory locations. | |
10258 | @end defmac | |
10259 | ||
10260 | @defmac MAX_MOVE_MAX | |
10261 | The maximum number of bytes that a single instruction can move quickly | |
10262 | between memory and registers or between two memory locations. If this | |
10263 | is undefined, the default is @code{MOVE_MAX}. Otherwise, it is the | |
10264 | constant value that is the largest value that @code{MOVE_MAX} can have | |
10265 | at run-time. | |
10266 | @end defmac | |
10267 | ||
10268 | @defmac SHIFT_COUNT_TRUNCATED | |
10269 | A C expression that is nonzero if on this machine the number of bits | |
10270 | actually used for the count of a shift operation is equal to the number | |
10271 | of bits needed to represent the size of the object being shifted. When | |
10272 | this macro is nonzero, the compiler will assume that it is safe to omit | |
10273 | a sign-extend, zero-extend, and certain bitwise `and' instructions that | |
10274 | truncates the count of a shift operation. On machines that have | |
10275 | instructions that act on bit-fields at variable positions, which may | |
10276 | include `bit test' instructions, a nonzero @code{SHIFT_COUNT_TRUNCATED} | |
10277 | also enables deletion of truncations of the values that serve as | |
10278 | arguments to bit-field instructions. | |
10279 | ||
10280 | If both types of instructions truncate the count (for shifts) and | |
10281 | position (for bit-field operations), or if no variable-position bit-field | |
10282 | instructions exist, you should define this macro. | |
10283 | ||
10284 | However, on some machines, such as the 80386 and the 680x0, truncation | |
10285 | only applies to shift operations and not the (real or pretended) | |
10286 | bit-field operations. Define @code{SHIFT_COUNT_TRUNCATED} to be zero on | |
10287 | such machines. Instead, add patterns to the @file{md} file that include | |
10288 | the implied truncation of the shift instructions. | |
10289 | ||
10290 | You need not define this macro if it would always have the value of zero. | |
10291 | @end defmac | |
10292 | ||
10293 | @anchor{TARGET_SHIFT_TRUNCATION_MASK} | |
10294 | @hook TARGET_SHIFT_TRUNCATION_MASK | |
10295 | This function describes how the standard shift patterns for @var{mode} | |
10296 | deal with shifts by negative amounts or by more than the width of the mode. | |
10297 | @xref{shift patterns}. | |
10298 | ||
10299 | On many machines, the shift patterns will apply a mask @var{m} to the | |
10300 | shift count, meaning that a fixed-width shift of @var{x} by @var{y} is | |
10301 | equivalent to an arbitrary-width shift of @var{x} by @var{y & m}. If | |
10302 | this is true for mode @var{mode}, the function should return @var{m}, | |
10303 | otherwise it should return 0. A return value of 0 indicates that no | |
10304 | particular behavior is guaranteed. | |
10305 | ||
10306 | Note that, unlike @code{SHIFT_COUNT_TRUNCATED}, this function does | |
10307 | @emph{not} apply to general shift rtxes; it applies only to instructions | |
10308 | that are generated by the named shift patterns. | |
10309 | ||
10310 | The default implementation of this function returns | |
10311 | @code{GET_MODE_BITSIZE (@var{mode}) - 1} if @code{SHIFT_COUNT_TRUNCATED} | |
10312 | and 0 otherwise. This definition is always safe, but if | |
10313 | @code{SHIFT_COUNT_TRUNCATED} is false, and some shift patterns | |
10314 | nevertheless truncate the shift count, you may get better code | |
10315 | by overriding it. | |
10316 | @end deftypefn | |
10317 | ||
10318 | @defmac TRULY_NOOP_TRUNCATION (@var{outprec}, @var{inprec}) | |
10319 | A C expression which is nonzero if on this machine it is safe to | |
10320 | ``convert'' an integer of @var{inprec} bits to one of @var{outprec} | |
10321 | bits (where @var{outprec} is smaller than @var{inprec}) by merely | |
10322 | operating on it as if it had only @var{outprec} bits. | |
10323 | ||
10324 | On many machines, this expression can be 1. | |
10325 | ||
10326 | @c rearranged this, removed the phrase "it is reported that". this was | |
10327 | @c to fix an overfull hbox. --mew 10feb93 | |
10328 | When @code{TRULY_NOOP_TRUNCATION} returns 1 for a pair of sizes for | |
10329 | modes for which @code{MODES_TIEABLE_P} is 0, suboptimal code can result. | |
10330 | If this is the case, making @code{TRULY_NOOP_TRUNCATION} return 0 in | |
10331 | such cases may improve things. | |
10332 | @end defmac | |
10333 | ||
10334 | @hook TARGET_MODE_REP_EXTENDED | |
10335 | The representation of an integral mode can be such that the values | |
10336 | are always extended to a wider integral mode. Return | |
10337 | @code{SIGN_EXTEND} if values of @var{mode} are represented in | |
10338 | sign-extended form to @var{rep_mode}. Return @code{UNKNOWN} | |
10339 | otherwise. (Currently, none of the targets use zero-extended | |
10340 | representation this way so unlike @code{LOAD_EXTEND_OP}, | |
10341 | @code{TARGET_MODE_REP_EXTENDED} is expected to return either | |
10342 | @code{SIGN_EXTEND} or @code{UNKNOWN}. Also no target extends | |
10343 | @var{mode} to @var{rep_mode} so that @var{rep_mode} is not the next | |
10344 | widest integral mode and currently we take advantage of this fact.) | |
10345 | ||
10346 | Similarly to @code{LOAD_EXTEND_OP} you may return a non-@code{UNKNOWN} | |
10347 | value even if the extension is not performed on certain hard registers | |
10348 | as long as for the @code{REGNO_REG_CLASS} of these hard registers | |
10349 | @code{CANNOT_CHANGE_MODE_CLASS} returns nonzero. | |
10350 | ||
10351 | Note that @code{TARGET_MODE_REP_EXTENDED} and @code{LOAD_EXTEND_OP} | |
10352 | describe two related properties. If you define | |
10353 | @code{TARGET_MODE_REP_EXTENDED (mode, word_mode)} you probably also want | |
10354 | to define @code{LOAD_EXTEND_OP (mode)} to return the same type of | |
10355 | extension. | |
10356 | ||
10357 | In order to enforce the representation of @code{mode}, | |
10358 | @code{TRULY_NOOP_TRUNCATION} should return false when truncating to | |
10359 | @code{mode}. | |
10360 | @end deftypefn | |
10361 | ||
10362 | @defmac STORE_FLAG_VALUE | |
10363 | A C expression describing the value returned by a comparison operator | |
10364 | with an integral mode and stored by a store-flag instruction | |
10365 | (@samp{cstore@var{mode}4}) when the condition is true. This description must | |
10366 | apply to @emph{all} the @samp{cstore@var{mode}4} patterns and all the | |
10367 | comparison operators whose results have a @code{MODE_INT} mode. | |
10368 | ||
10369 | A value of 1 or @minus{}1 means that the instruction implementing the | |
10370 | comparison operator returns exactly 1 or @minus{}1 when the comparison is true | |
10371 | and 0 when the comparison is false. Otherwise, the value indicates | |
10372 | which bits of the result are guaranteed to be 1 when the comparison is | |
10373 | true. This value is interpreted in the mode of the comparison | |
10374 | operation, which is given by the mode of the first operand in the | |
10375 | @samp{cstore@var{mode}4} pattern. Either the low bit or the sign bit of | |
10376 | @code{STORE_FLAG_VALUE} be on. Presently, only those bits are used by | |
10377 | the compiler. | |
10378 | ||
10379 | If @code{STORE_FLAG_VALUE} is neither 1 or @minus{}1, the compiler will | |
10380 | generate code that depends only on the specified bits. It can also | |
10381 | replace comparison operators with equivalent operations if they cause | |
10382 | the required bits to be set, even if the remaining bits are undefined. | |
10383 | For example, on a machine whose comparison operators return an | |
10384 | @code{SImode} value and where @code{STORE_FLAG_VALUE} is defined as | |
10385 | @samp{0x80000000}, saying that just the sign bit is relevant, the | |
10386 | expression | |
10387 | ||
10388 | @smallexample | |
10389 | (ne:SI (and:SI @var{x} (const_int @var{power-of-2})) (const_int 0)) | |
10390 | @end smallexample | |
10391 | ||
10392 | @noindent | |
10393 | can be converted to | |
10394 | ||
10395 | @smallexample | |
10396 | (ashift:SI @var{x} (const_int @var{n})) | |
10397 | @end smallexample | |
10398 | ||
10399 | @noindent | |
10400 | where @var{n} is the appropriate shift count to move the bit being | |
10401 | tested into the sign bit. | |
10402 | ||
10403 | There is no way to describe a machine that always sets the low-order bit | |
10404 | for a true value, but does not guarantee the value of any other bits, | |
10405 | but we do not know of any machine that has such an instruction. If you | |
10406 | are trying to port GCC to such a machine, include an instruction to | |
10407 | perform a logical-and of the result with 1 in the pattern for the | |
10408 | comparison operators and let us know at @email{gcc@@gcc.gnu.org}. | |
10409 | ||
10410 | Often, a machine will have multiple instructions that obtain a value | |
10411 | from a comparison (or the condition codes). Here are rules to guide the | |
10412 | choice of value for @code{STORE_FLAG_VALUE}, and hence the instructions | |
10413 | to be used: | |
10414 | ||
10415 | @itemize @bullet | |
10416 | @item | |
10417 | Use the shortest sequence that yields a valid definition for | |
10418 | @code{STORE_FLAG_VALUE}. It is more efficient for the compiler to | |
10419 | ``normalize'' the value (convert it to, e.g., 1 or 0) than for the | |
10420 | comparison operators to do so because there may be opportunities to | |
10421 | combine the normalization with other operations. | |
10422 | ||
10423 | @item | |
10424 | For equal-length sequences, use a value of 1 or @minus{}1, with @minus{}1 being | |
10425 | slightly preferred on machines with expensive jumps and 1 preferred on | |
10426 | other machines. | |
10427 | ||
10428 | @item | |
10429 | As a second choice, choose a value of @samp{0x80000001} if instructions | |
10430 | exist that set both the sign and low-order bits but do not define the | |
10431 | others. | |
10432 | ||
10433 | @item | |
10434 | Otherwise, use a value of @samp{0x80000000}. | |
10435 | @end itemize | |
10436 | ||
10437 | Many machines can produce both the value chosen for | |
10438 | @code{STORE_FLAG_VALUE} and its negation in the same number of | |
10439 | instructions. On those machines, you should also define a pattern for | |
10440 | those cases, e.g., one matching | |
10441 | ||
10442 | @smallexample | |
10443 | (set @var{A} (neg:@var{m} (ne:@var{m} @var{B} @var{C}))) | |
10444 | @end smallexample | |
10445 | ||
10446 | Some machines can also perform @code{and} or @code{plus} operations on | |
10447 | condition code values with less instructions than the corresponding | |
10448 | @samp{cstore@var{mode}4} insn followed by @code{and} or @code{plus}. On those | |
10449 | machines, define the appropriate patterns. Use the names @code{incscc} | |
10450 | and @code{decscc}, respectively, for the patterns which perform | |
10451 | @code{plus} or @code{minus} operations on condition code values. See | |
2b0d3573 | 10452 | @file{rs6000.md} for some examples. The GNU Superoptimizer can be used to |
38f8b050 JR |
10453 | find such instruction sequences on other machines. |
10454 | ||
10455 | If this macro is not defined, the default value, 1, is used. You need | |
10456 | not define @code{STORE_FLAG_VALUE} if the machine has no store-flag | |
10457 | instructions, or if the value generated by these instructions is 1. | |
10458 | @end defmac | |
10459 | ||
10460 | @defmac FLOAT_STORE_FLAG_VALUE (@var{mode}) | |
10461 | A C expression that gives a nonzero @code{REAL_VALUE_TYPE} value that is | |
10462 | returned when comparison operators with floating-point results are true. | |
10463 | Define this macro on machines that have comparison operations that return | |
10464 | floating-point values. If there are no such operations, do not define | |
10465 | this macro. | |
10466 | @end defmac | |
10467 | ||
10468 | @defmac VECTOR_STORE_FLAG_VALUE (@var{mode}) | |
10469 | A C expression that gives a rtx representing the nonzero true element | |
10470 | for vector comparisons. The returned rtx should be valid for the inner | |
10471 | mode of @var{mode} which is guaranteed to be a vector mode. Define | |
10472 | this macro on machines that have vector comparison operations that | |
10473 | return a vector result. If there are no such operations, do not define | |
10474 | this macro. Typically, this macro is defined as @code{const1_rtx} or | |
10475 | @code{constm1_rtx}. This macro may return @code{NULL_RTX} to prevent | |
10476 | the compiler optimizing such vector comparison operations for the | |
10477 | given mode. | |
10478 | @end defmac | |
10479 | ||
10480 | @defmac CLZ_DEFINED_VALUE_AT_ZERO (@var{mode}, @var{value}) | |
10481 | @defmacx CTZ_DEFINED_VALUE_AT_ZERO (@var{mode}, @var{value}) | |
10482 | A C expression that indicates whether the architecture defines a value | |
ff2ce160 | 10483 | for @code{clz} or @code{ctz} with a zero operand. |
38f8b050 JR |
10484 | A result of @code{0} indicates the value is undefined. |
10485 | If the value is defined for only the RTL expression, the macro should | |
10486 | evaluate to @code{1}; if the value applies also to the corresponding optab | |
10487 | entry (which is normally the case if it expands directly into | |
ff2ce160 | 10488 | the corresponding RTL), then the macro should evaluate to @code{2}. |
38f8b050 | 10489 | In the cases where the value is defined, @var{value} should be set to |
ff2ce160 | 10490 | this value. |
38f8b050 JR |
10491 | |
10492 | If this macro is not defined, the value of @code{clz} or | |
10493 | @code{ctz} at zero is assumed to be undefined. | |
10494 | ||
10495 | This macro must be defined if the target's expansion for @code{ffs} | |
10496 | relies on a particular value to get correct results. Otherwise it | |
10497 | is not necessary, though it may be used to optimize some corner cases, and | |
10498 | to provide a default expansion for the @code{ffs} optab. | |
10499 | ||
10500 | Note that regardless of this macro the ``definedness'' of @code{clz} | |
10501 | and @code{ctz} at zero do @emph{not} extend to the builtin functions | |
10502 | visible to the user. Thus one may be free to adjust the value at will | |
10503 | to match the target expansion of these operations without fear of | |
10504 | breaking the API@. | |
10505 | @end defmac | |
10506 | ||
10507 | @defmac Pmode | |
10508 | An alias for the machine mode for pointers. On most machines, define | |
10509 | this to be the integer mode corresponding to the width of a hardware | |
10510 | pointer; @code{SImode} on 32-bit machine or @code{DImode} on 64-bit machines. | |
10511 | On some machines you must define this to be one of the partial integer | |
10512 | modes, such as @code{PSImode}. | |
10513 | ||
10514 | The width of @code{Pmode} must be at least as large as the value of | |
10515 | @code{POINTER_SIZE}. If it is not equal, you must define the macro | |
10516 | @code{POINTERS_EXTEND_UNSIGNED} to specify how pointers are extended | |
10517 | to @code{Pmode}. | |
10518 | @end defmac | |
10519 | ||
10520 | @defmac FUNCTION_MODE | |
10521 | An alias for the machine mode used for memory references to functions | |
10522 | being called, in @code{call} RTL expressions. On most CISC machines, | |
ff2ce160 | 10523 | where an instruction can begin at any byte address, this should be |
38f8b050 JR |
10524 | @code{QImode}. On most RISC machines, where all instructions have fixed |
10525 | size and alignment, this should be a mode with the same size and alignment | |
10526 | as the machine instruction words - typically @code{SImode} or @code{HImode}. | |
10527 | @end defmac | |
10528 | ||
10529 | @defmac STDC_0_IN_SYSTEM_HEADERS | |
10530 | In normal operation, the preprocessor expands @code{__STDC__} to the | |
10531 | constant 1, to signify that GCC conforms to ISO Standard C@. On some | |
10532 | hosts, like Solaris, the system compiler uses a different convention, | |
10533 | where @code{__STDC__} is normally 0, but is 1 if the user specifies | |
10534 | strict conformance to the C Standard. | |
10535 | ||
10536 | Defining @code{STDC_0_IN_SYSTEM_HEADERS} makes GNU CPP follows the host | |
10537 | convention when processing system header files, but when processing user | |
10538 | files @code{__STDC__} will always expand to 1. | |
10539 | @end defmac | |
10540 | ||
10541 | @defmac NO_IMPLICIT_EXTERN_C | |
10542 | Define this macro if the system header files support C++ as well as C@. | |
10543 | This macro inhibits the usual method of using system header files in | |
10544 | C++, which is to pretend that the file's contents are enclosed in | |
10545 | @samp{extern "C" @{@dots{}@}}. | |
10546 | @end defmac | |
10547 | ||
10548 | @findex #pragma | |
10549 | @findex pragma | |
10550 | @defmac REGISTER_TARGET_PRAGMAS () | |
10551 | Define this macro if you want to implement any target-specific pragmas. | |
10552 | If defined, it is a C expression which makes a series of calls to | |
10553 | @code{c_register_pragma} or @code{c_register_pragma_with_expansion} | |
10554 | for each pragma. The macro may also do any | |
10555 | setup required for the pragmas. | |
10556 | ||
10557 | The primary reason to define this macro is to provide compatibility with | |
10558 | other compilers for the same target. In general, we discourage | |
10559 | definition of target-specific pragmas for GCC@. | |
10560 | ||
10561 | If the pragma can be implemented by attributes then you should consider | |
10562 | defining the target hook @samp{TARGET_INSERT_ATTRIBUTES} as well. | |
10563 | ||
10564 | Preprocessor macros that appear on pragma lines are not expanded. All | |
10565 | @samp{#pragma} directives that do not match any registered pragma are | |
10566 | silently ignored, unless the user specifies @option{-Wunknown-pragmas}. | |
10567 | @end defmac | |
10568 | ||
10569 | @deftypefun void c_register_pragma (const char *@var{space}, const char *@var{name}, void (*@var{callback}) (struct cpp_reader *)) | |
10570 | @deftypefunx void c_register_pragma_with_expansion (const char *@var{space}, const char *@var{name}, void (*@var{callback}) (struct cpp_reader *)) | |
10571 | ||
10572 | Each call to @code{c_register_pragma} or | |
10573 | @code{c_register_pragma_with_expansion} establishes one pragma. The | |
10574 | @var{callback} routine will be called when the preprocessor encounters a | |
10575 | pragma of the form | |
10576 | ||
10577 | @smallexample | |
10578 | #pragma [@var{space}] @var{name} @dots{} | |
10579 | @end smallexample | |
10580 | ||
10581 | @var{space} is the case-sensitive namespace of the pragma, or | |
10582 | @code{NULL} to put the pragma in the global namespace. The callback | |
10583 | routine receives @var{pfile} as its first argument, which can be passed | |
10584 | on to cpplib's functions if necessary. You can lex tokens after the | |
10585 | @var{name} by calling @code{pragma_lex}. Tokens that are not read by the | |
10586 | callback will be silently ignored. The end of the line is indicated by | |
10587 | a token of type @code{CPP_EOF}. Macro expansion occurs on the | |
10588 | arguments of pragmas registered with | |
10589 | @code{c_register_pragma_with_expansion} but not on the arguments of | |
10590 | pragmas registered with @code{c_register_pragma}. | |
10591 | ||
10592 | Note that the use of @code{pragma_lex} is specific to the C and C++ | |
10593 | compilers. It will not work in the Java or Fortran compilers, or any | |
10594 | other language compilers for that matter. Thus if @code{pragma_lex} is going | |
10595 | to be called from target-specific code, it must only be done so when | |
10596 | building the C and C++ compilers. This can be done by defining the | |
10597 | variables @code{c_target_objs} and @code{cxx_target_objs} in the | |
10598 | target entry in the @file{config.gcc} file. These variables should name | |
10599 | the target-specific, language-specific object file which contains the | |
10600 | code that uses @code{pragma_lex}. Note it will also be necessary to add a | |
10601 | rule to the makefile fragment pointed to by @code{tmake_file} that shows | |
10602 | how to build this object file. | |
10603 | @end deftypefun | |
10604 | ||
38f8b050 | 10605 | @defmac HANDLE_PRAGMA_PACK_WITH_EXPANSION |
24a57808 | 10606 | Define this macro if macros should be expanded in the |
38f8b050 JR |
10607 | arguments of @samp{#pragma pack}. |
10608 | @end defmac | |
10609 | ||
10610 | @hook TARGET_HANDLE_PRAGMA_EXTERN_PREFIX | |
10611 | ||
10612 | @defmac TARGET_DEFAULT_PACK_STRUCT | |
10613 | If your target requires a structure packing default other than 0 (meaning | |
10614 | the machine default), define this macro to the necessary value (in bytes). | |
10615 | This must be a value that would also be valid to use with | |
10616 | @samp{#pragma pack()} (that is, a small power of two). | |
10617 | @end defmac | |
10618 | ||
10619 | @defmac DOLLARS_IN_IDENTIFIERS | |
10620 | Define this macro to control use of the character @samp{$} in | |
10621 | identifier names for the C family of languages. 0 means @samp{$} is | |
10622 | not allowed by default; 1 means it is allowed. 1 is the default; | |
10623 | there is no need to define this macro in that case. | |
10624 | @end defmac | |
10625 | ||
10626 | @defmac NO_DOLLAR_IN_LABEL | |
10627 | Define this macro if the assembler does not accept the character | |
10628 | @samp{$} in label names. By default constructors and destructors in | |
10629 | G++ have @samp{$} in the identifiers. If this macro is defined, | |
10630 | @samp{.} is used instead. | |
10631 | @end defmac | |
10632 | ||
10633 | @defmac NO_DOT_IN_LABEL | |
10634 | Define this macro if the assembler does not accept the character | |
10635 | @samp{.} in label names. By default constructors and destructors in G++ | |
10636 | have names that use @samp{.}. If this macro is defined, these names | |
10637 | are rewritten to avoid @samp{.}. | |
10638 | @end defmac | |
10639 | ||
10640 | @defmac INSN_SETS_ARE_DELAYED (@var{insn}) | |
10641 | Define this macro as a C expression that is nonzero if it is safe for the | |
10642 | delay slot scheduler to place instructions in the delay slot of @var{insn}, | |
10643 | even if they appear to use a resource set or clobbered in @var{insn}. | |
10644 | @var{insn} is always a @code{jump_insn} or an @code{insn}; GCC knows that | |
10645 | every @code{call_insn} has this behavior. On machines where some @code{insn} | |
10646 | or @code{jump_insn} is really a function call and hence has this behavior, | |
10647 | you should define this macro. | |
10648 | ||
10649 | You need not define this macro if it would always return zero. | |
10650 | @end defmac | |
10651 | ||
10652 | @defmac INSN_REFERENCES_ARE_DELAYED (@var{insn}) | |
10653 | Define this macro as a C expression that is nonzero if it is safe for the | |
10654 | delay slot scheduler to place instructions in the delay slot of @var{insn}, | |
10655 | even if they appear to set or clobber a resource referenced in @var{insn}. | |
10656 | @var{insn} is always a @code{jump_insn} or an @code{insn}. On machines where | |
10657 | some @code{insn} or @code{jump_insn} is really a function call and its operands | |
10658 | are registers whose use is actually in the subroutine it calls, you should | |
10659 | define this macro. Doing so allows the delay slot scheduler to move | |
10660 | instructions which copy arguments into the argument registers into the delay | |
10661 | slot of @var{insn}. | |
10662 | ||
10663 | You need not define this macro if it would always return zero. | |
10664 | @end defmac | |
10665 | ||
10666 | @defmac MULTIPLE_SYMBOL_SPACES | |
10667 | Define this macro as a C expression that is nonzero if, in some cases, | |
10668 | global symbols from one translation unit may not be bound to undefined | |
10669 | symbols in another translation unit without user intervention. For | |
10670 | instance, under Microsoft Windows symbols must be explicitly imported | |
10671 | from shared libraries (DLLs). | |
10672 | ||
10673 | You need not define this macro if it would always evaluate to zero. | |
10674 | @end defmac | |
10675 | ||
10676 | @hook TARGET_MD_ASM_CLOBBERS | |
10677 | This target hook should add to @var{clobbers} @code{STRING_CST} trees for | |
10678 | any hard regs the port wishes to automatically clobber for an asm. | |
10679 | It should return the result of the last @code{tree_cons} used to add a | |
10680 | clobber. The @var{outputs}, @var{inputs} and @var{clobber} lists are the | |
10681 | corresponding parameters to the asm and may be inspected to avoid | |
10682 | clobbering a register that is an input or output of the asm. You can use | |
10683 | @code{tree_overlaps_hard_reg_set}, declared in @file{tree.h}, to test | |
10684 | for overlap with regards to asm-declared registers. | |
10685 | @end deftypefn | |
10686 | ||
10687 | @defmac MATH_LIBRARY | |
10688 | Define this macro as a C string constant for the linker argument to link | |
d9d16a19 JM |
10689 | in the system math library, minus the initial @samp{"-l"}, or |
10690 | @samp{""} if the target does not have a | |
38f8b050 JR |
10691 | separate math library. |
10692 | ||
d9d16a19 | 10693 | You need only define this macro if the default of @samp{"m"} is wrong. |
38f8b050 JR |
10694 | @end defmac |
10695 | ||
10696 | @defmac LIBRARY_PATH_ENV | |
10697 | Define this macro as a C string constant for the environment variable that | |
10698 | specifies where the linker should look for libraries. | |
10699 | ||
10700 | You need only define this macro if the default of @samp{"LIBRARY_PATH"} | |
10701 | is wrong. | |
10702 | @end defmac | |
10703 | ||
10704 | @defmac TARGET_POSIX_IO | |
10705 | Define this macro if the target supports the following POSIX@ file | |
10706 | functions, access, mkdir and file locking with fcntl / F_SETLKW@. | |
10707 | Defining @code{TARGET_POSIX_IO} will enable the test coverage code | |
10708 | to use file locking when exiting a program, which avoids race conditions | |
10709 | if the program has forked. It will also create directories at run-time | |
10710 | for cross-profiling. | |
10711 | @end defmac | |
10712 | ||
10713 | @defmac MAX_CONDITIONAL_EXECUTE | |
10714 | ||
10715 | A C expression for the maximum number of instructions to execute via | |
10716 | conditional execution instructions instead of a branch. A value of | |
10717 | @code{BRANCH_COST}+1 is the default if the machine does not use cc0, and | |
10718 | 1 if it does use cc0. | |
10719 | @end defmac | |
10720 | ||
10721 | @defmac IFCVT_MODIFY_TESTS (@var{ce_info}, @var{true_expr}, @var{false_expr}) | |
10722 | Used if the target needs to perform machine-dependent modifications on the | |
10723 | conditionals used for turning basic blocks into conditionally executed code. | |
10724 | @var{ce_info} points to a data structure, @code{struct ce_if_block}, which | |
10725 | contains information about the currently processed blocks. @var{true_expr} | |
10726 | and @var{false_expr} are the tests that are used for converting the | |
10727 | then-block and the else-block, respectively. Set either @var{true_expr} or | |
10728 | @var{false_expr} to a null pointer if the tests cannot be converted. | |
10729 | @end defmac | |
10730 | ||
10731 | @defmac IFCVT_MODIFY_MULTIPLE_TESTS (@var{ce_info}, @var{bb}, @var{true_expr}, @var{false_expr}) | |
10732 | Like @code{IFCVT_MODIFY_TESTS}, but used when converting more complicated | |
10733 | if-statements into conditions combined by @code{and} and @code{or} operations. | |
10734 | @var{bb} contains the basic block that contains the test that is currently | |
10735 | being processed and about to be turned into a condition. | |
10736 | @end defmac | |
10737 | ||
10738 | @defmac IFCVT_MODIFY_INSN (@var{ce_info}, @var{pattern}, @var{insn}) | |
10739 | A C expression to modify the @var{PATTERN} of an @var{INSN} that is to | |
10740 | be converted to conditional execution format. @var{ce_info} points to | |
10741 | a data structure, @code{struct ce_if_block}, which contains information | |
10742 | about the currently processed blocks. | |
10743 | @end defmac | |
10744 | ||
10745 | @defmac IFCVT_MODIFY_FINAL (@var{ce_info}) | |
10746 | A C expression to perform any final machine dependent modifications in | |
10747 | converting code to conditional execution. The involved basic blocks | |
10748 | can be found in the @code{struct ce_if_block} structure that is pointed | |
10749 | to by @var{ce_info}. | |
10750 | @end defmac | |
10751 | ||
10752 | @defmac IFCVT_MODIFY_CANCEL (@var{ce_info}) | |
10753 | A C expression to cancel any machine dependent modifications in | |
10754 | converting code to conditional execution. The involved basic blocks | |
10755 | can be found in the @code{struct ce_if_block} structure that is pointed | |
10756 | to by @var{ce_info}. | |
10757 | @end defmac | |
10758 | ||
10759 | @defmac IFCVT_INIT_EXTRA_FIELDS (@var{ce_info}) | |
10760 | A C expression to initialize any extra fields in a @code{struct ce_if_block} | |
10761 | structure, which are defined by the @code{IFCVT_EXTRA_FIELDS} macro. | |
10762 | @end defmac | |
10763 | ||
10764 | @defmac IFCVT_EXTRA_FIELDS | |
10765 | If defined, it should expand to a set of field declarations that will be | |
10766 | added to the @code{struct ce_if_block} structure. These should be initialized | |
10767 | by the @code{IFCVT_INIT_EXTRA_FIELDS} macro. | |
10768 | @end defmac | |
10769 | ||
10770 | @hook TARGET_MACHINE_DEPENDENT_REORG | |
10771 | If non-null, this hook performs a target-specific pass over the | |
10772 | instruction stream. The compiler will run it at all optimization levels, | |
10773 | just before the point at which it normally does delayed-branch scheduling. | |
10774 | ||
10775 | The exact purpose of the hook varies from target to target. Some use | |
10776 | it to do transformations that are necessary for correctness, such as | |
10777 | laying out in-function constant pools or avoiding hardware hazards. | |
10778 | Others use it as an opportunity to do some machine-dependent optimizations. | |
10779 | ||
10780 | You need not implement the hook if it has nothing to do. The default | |
10781 | definition is null. | |
10782 | @end deftypefn | |
10783 | ||
10784 | @hook TARGET_INIT_BUILTINS | |
10785 | Define this hook if you have any machine-specific built-in functions | |
10786 | that need to be defined. It should be a function that performs the | |
10787 | necessary setup. | |
10788 | ||
10789 | Machine specific built-in functions can be useful to expand special machine | |
10790 | instructions that would otherwise not normally be generated because | |
10791 | they have no equivalent in the source language (for example, SIMD vector | |
10792 | instructions or prefetch instructions). | |
10793 | ||
10794 | To create a built-in function, call the function | |
10795 | @code{lang_hooks.builtin_function} | |
10796 | which is defined by the language front end. You can use any type nodes set | |
1a072294 | 10797 | up by @code{build_common_tree_nodes}; |
38f8b050 JR |
10798 | only language front ends that use those two functions will call |
10799 | @samp{TARGET_INIT_BUILTINS}. | |
10800 | @end deftypefn | |
10801 | ||
10802 | @hook TARGET_BUILTIN_DECL | |
10803 | Define this hook if you have any machine-specific built-in functions | |
10804 | that need to be defined. It should be a function that returns the | |
10805 | builtin function declaration for the builtin function code @var{code}. | |
10806 | If there is no such builtin and it cannot be initialized at this time | |
10807 | if @var{initialize_p} is true the function should return @code{NULL_TREE}. | |
10808 | If @var{code} is out of range the function should return | |
10809 | @code{error_mark_node}. | |
10810 | @end deftypefn | |
10811 | ||
10812 | @hook TARGET_EXPAND_BUILTIN | |
10813 | ||
10814 | Expand a call to a machine specific built-in function that was set up by | |
10815 | @samp{TARGET_INIT_BUILTINS}. @var{exp} is the expression for the | |
10816 | function call; the result should go to @var{target} if that is | |
10817 | convenient, and have mode @var{mode} if that is convenient. | |
10818 | @var{subtarget} may be used as the target for computing one of | |
10819 | @var{exp}'s operands. @var{ignore} is nonzero if the value is to be | |
10820 | ignored. This function should return the result of the call to the | |
10821 | built-in function. | |
10822 | @end deftypefn | |
10823 | ||
d66f5459 | 10824 | @hook TARGET_RESOLVE_OVERLOADED_BUILTIN |
38f8b050 JR |
10825 | Select a replacement for a machine specific built-in function that |
10826 | was set up by @samp{TARGET_INIT_BUILTINS}. This is done | |
10827 | @emph{before} regular type checking, and so allows the target to | |
10828 | implement a crude form of function overloading. @var{fndecl} is the | |
10829 | declaration of the built-in function. @var{arglist} is the list of | |
10830 | arguments passed to the built-in function. The result is a | |
10831 | complete expression that implements the operation, usually | |
10832 | another @code{CALL_EXPR}. | |
10833 | @var{arglist} really has type @samp{VEC(tree,gc)*} | |
10834 | @end deftypefn | |
10835 | ||
08914aaa | 10836 | @hook TARGET_FOLD_BUILTIN |
38f8b050 JR |
10837 | Fold a call to a machine specific built-in function that was set up by |
10838 | @samp{TARGET_INIT_BUILTINS}. @var{fndecl} is the declaration of the | |
10839 | built-in function. @var{n_args} is the number of arguments passed to | |
10840 | the function; the arguments themselves are pointed to by @var{argp}. | |
10841 | The result is another tree containing a simplified expression for the | |
10842 | call's result. If @var{ignore} is true the value will be ignored. | |
10843 | @end deftypefn | |
10844 | ||
10845 | @hook TARGET_INVALID_WITHIN_DOLOOP | |
10846 | ||
10847 | Take an instruction in @var{insn} and return NULL if it is valid within a | |
10848 | low-overhead loop, otherwise return a string explaining why doloop | |
10849 | could not be applied. | |
10850 | ||
10851 | Many targets use special registers for low-overhead looping. For any | |
10852 | instruction that clobbers these this function should return a string indicating | |
10853 | the reason why the doloop could not be applied. | |
10854 | By default, the RTL loop optimizer does not use a present doloop pattern for | |
10855 | loops containing function calls or branch on table instructions. | |
10856 | @end deftypefn | |
10857 | ||
10858 | @defmac MD_CAN_REDIRECT_BRANCH (@var{branch1}, @var{branch2}) | |
10859 | ||
10860 | Take a branch insn in @var{branch1} and another in @var{branch2}. | |
10861 | Return true if redirecting @var{branch1} to the destination of | |
10862 | @var{branch2} is possible. | |
10863 | ||
10864 | On some targets, branches may have a limited range. Optimizing the | |
10865 | filling of delay slots can result in branches being redirected, and this | |
10866 | may in turn cause a branch offset to overflow. | |
10867 | @end defmac | |
10868 | ||
10869 | @hook TARGET_COMMUTATIVE_P | |
10870 | This target hook returns @code{true} if @var{x} is considered to be commutative. | |
10871 | Usually, this is just COMMUTATIVE_P (@var{x}), but the HP PA doesn't consider | |
10872 | PLUS to be commutative inside a MEM@. @var{outer_code} is the rtx code | |
10873 | of the enclosing rtl, if known, otherwise it is UNKNOWN. | |
10874 | @end deftypefn | |
10875 | ||
10876 | @hook TARGET_ALLOCATE_INITIAL_VALUE | |
10877 | ||
10878 | When the initial value of a hard register has been copied in a pseudo | |
10879 | register, it is often not necessary to actually allocate another register | |
10880 | to this pseudo register, because the original hard register or a stack slot | |
10881 | it has been saved into can be used. @code{TARGET_ALLOCATE_INITIAL_VALUE} | |
10882 | is called at the start of register allocation once for each hard register | |
10883 | that had its initial value copied by using | |
10884 | @code{get_func_hard_reg_initial_val} or @code{get_hard_reg_initial_val}. | |
10885 | Possible values are @code{NULL_RTX}, if you don't want | |
10886 | to do any special allocation, a @code{REG} rtx---that would typically be | |
10887 | the hard register itself, if it is known not to be clobbered---or a | |
10888 | @code{MEM}. | |
10889 | If you are returning a @code{MEM}, this is only a hint for the allocator; | |
10890 | it might decide to use another register anyways. | |
10891 | You may use @code{current_function_leaf_function} in the hook, functions | |
10892 | that use @code{REG_N_SETS}, to determine if the hard | |
10893 | register in question will not be clobbered. | |
10894 | The default value of this hook is @code{NULL}, which disables any special | |
10895 | allocation. | |
10896 | @end deftypefn | |
10897 | ||
10898 | @hook TARGET_UNSPEC_MAY_TRAP_P | |
10899 | This target hook returns nonzero if @var{x}, an @code{unspec} or | |
10900 | @code{unspec_volatile} operation, might cause a trap. Targets can use | |
10901 | this hook to enhance precision of analysis for @code{unspec} and | |
10902 | @code{unspec_volatile} operations. You may call @code{may_trap_p_1} | |
10903 | to analyze inner elements of @var{x} in which case @var{flags} should be | |
10904 | passed along. | |
10905 | @end deftypefn | |
10906 | ||
10907 | @hook TARGET_SET_CURRENT_FUNCTION | |
ff2ce160 | 10908 | The compiler invokes this hook whenever it changes its current function |
38f8b050 JR |
10909 | context (@code{cfun}). You can define this function if |
10910 | the back end needs to perform any initialization or reset actions on a | |
10911 | per-function basis. For example, it may be used to implement function | |
10912 | attributes that affect register usage or code generation patterns. | |
10913 | The argument @var{decl} is the declaration for the new function context, | |
10914 | and may be null to indicate that the compiler has left a function context | |
10915 | and is returning to processing at the top level. | |
10916 | The default hook function does nothing. | |
10917 | ||
10918 | GCC sets @code{cfun} to a dummy function context during initialization of | |
10919 | some parts of the back end. The hook function is not invoked in this | |
10920 | situation; you need not worry about the hook being invoked recursively, | |
10921 | or when the back end is in a partially-initialized state. | |
10922 | @code{cfun} might be @code{NULL} to indicate processing at top level, | |
10923 | outside of any function scope. | |
10924 | @end deftypefn | |
10925 | ||
10926 | @defmac TARGET_OBJECT_SUFFIX | |
10927 | Define this macro to be a C string representing the suffix for object | |
10928 | files on your target machine. If you do not define this macro, GCC will | |
10929 | use @samp{.o} as the suffix for object files. | |
10930 | @end defmac | |
10931 | ||
10932 | @defmac TARGET_EXECUTABLE_SUFFIX | |
10933 | Define this macro to be a C string representing the suffix to be | |
10934 | automatically added to executable files on your target machine. If you | |
10935 | do not define this macro, GCC will use the null string as the suffix for | |
10936 | executable files. | |
10937 | @end defmac | |
10938 | ||
10939 | @defmac COLLECT_EXPORT_LIST | |
10940 | If defined, @code{collect2} will scan the individual object files | |
10941 | specified on its command line and create an export list for the linker. | |
10942 | Define this macro for systems like AIX, where the linker discards | |
10943 | object files that are not referenced from @code{main} and uses export | |
10944 | lists. | |
10945 | @end defmac | |
10946 | ||
10947 | @defmac MODIFY_JNI_METHOD_CALL (@var{mdecl}) | |
10948 | Define this macro to a C expression representing a variant of the | |
10949 | method call @var{mdecl}, if Java Native Interface (JNI) methods | |
10950 | must be invoked differently from other methods on your target. | |
10951 | For example, on 32-bit Microsoft Windows, JNI methods must be invoked using | |
10952 | the @code{stdcall} calling convention and this macro is then | |
10953 | defined as this expression: | |
10954 | ||
10955 | @smallexample | |
10956 | build_type_attribute_variant (@var{mdecl}, | |
10957 | build_tree_list | |
10958 | (get_identifier ("stdcall"), | |
10959 | NULL)) | |
10960 | @end smallexample | |
10961 | @end defmac | |
10962 | ||
10963 | @hook TARGET_CANNOT_MODIFY_JUMPS_P | |
10964 | This target hook returns @code{true} past the point in which new jump | |
10965 | instructions could be created. On machines that require a register for | |
10966 | every jump such as the SHmedia ISA of SH5, this point would typically be | |
10967 | reload, so this target hook should be defined to a function such as: | |
10968 | ||
10969 | @smallexample | |
10970 | static bool | |
10971 | cannot_modify_jumps_past_reload_p () | |
10972 | @{ | |
10973 | return (reload_completed || reload_in_progress); | |
10974 | @} | |
10975 | @end smallexample | |
10976 | @end deftypefn | |
10977 | ||
10978 | @hook TARGET_BRANCH_TARGET_REGISTER_CLASS | |
10979 | This target hook returns a register class for which branch target register | |
10980 | optimizations should be applied. All registers in this class should be | |
10981 | usable interchangeably. After reload, registers in this class will be | |
10982 | re-allocated and loads will be hoisted out of loops and be subjected | |
10983 | to inter-block scheduling. | |
10984 | @end deftypefn | |
10985 | ||
10986 | @hook TARGET_BRANCH_TARGET_REGISTER_CALLEE_SAVED | |
10987 | Branch target register optimization will by default exclude callee-saved | |
10988 | registers | |
10989 | that are not already live during the current function; if this target hook | |
10990 | returns true, they will be included. The target code must than make sure | |
10991 | that all target registers in the class returned by | |
10992 | @samp{TARGET_BRANCH_TARGET_REGISTER_CLASS} that might need saving are | |
10993 | saved. @var{after_prologue_epilogue_gen} indicates if prologues and | |
10994 | epilogues have already been generated. Note, even if you only return | |
10995 | true when @var{after_prologue_epilogue_gen} is false, you still are likely | |
10996 | to have to make special provisions in @code{INITIAL_ELIMINATION_OFFSET} | |
10997 | to reserve space for caller-saved target registers. | |
10998 | @end deftypefn | |
10999 | ||
11000 | @hook TARGET_HAVE_CONDITIONAL_EXECUTION | |
11001 | This target hook returns true if the target supports conditional execution. | |
11002 | This target hook is required only when the target has several different | |
11003 | modes and they have different conditional execution capability, such as ARM. | |
11004 | @end deftypefn | |
11005 | ||
11006 | @hook TARGET_LOOP_UNROLL_ADJUST | |
11007 | This target hook returns a new value for the number of times @var{loop} | |
11008 | should be unrolled. The parameter @var{nunroll} is the number of times | |
11009 | the loop is to be unrolled. The parameter @var{loop} is a pointer to | |
11010 | the loop, which is going to be checked for unrolling. This target hook | |
11011 | is required only when the target has special constraints like maximum | |
11012 | number of memory accesses. | |
11013 | @end deftypefn | |
11014 | ||
11015 | @defmac POWI_MAX_MULTS | |
11016 | If defined, this macro is interpreted as a signed integer C expression | |
11017 | that specifies the maximum number of floating point multiplications | |
11018 | that should be emitted when expanding exponentiation by an integer | |
11019 | constant inline. When this value is defined, exponentiation requiring | |
11020 | more than this number of multiplications is implemented by calling the | |
11021 | system library's @code{pow}, @code{powf} or @code{powl} routines. | |
11022 | The default value places no upper bound on the multiplication count. | |
11023 | @end defmac | |
11024 | ||
11025 | @deftypefn Macro void TARGET_EXTRA_INCLUDES (const char *@var{sysroot}, const char *@var{iprefix}, int @var{stdinc}) | |
11026 | This target hook should register any extra include files for the | |
11027 | target. The parameter @var{stdinc} indicates if normal include files | |
11028 | are present. The parameter @var{sysroot} is the system root directory. | |
11029 | The parameter @var{iprefix} is the prefix for the gcc directory. | |
11030 | @end deftypefn | |
11031 | ||
11032 | @deftypefn Macro void TARGET_EXTRA_PRE_INCLUDES (const char *@var{sysroot}, const char *@var{iprefix}, int @var{stdinc}) | |
11033 | This target hook should register any extra include files for the | |
11034 | target before any standard headers. The parameter @var{stdinc} | |
11035 | indicates if normal include files are present. The parameter | |
11036 | @var{sysroot} is the system root directory. The parameter | |
11037 | @var{iprefix} is the prefix for the gcc directory. | |
11038 | @end deftypefn | |
11039 | ||
11040 | @deftypefn Macro void TARGET_OPTF (char *@var{path}) | |
11041 | This target hook should register special include paths for the target. | |
11042 | The parameter @var{path} is the include to register. On Darwin | |
11043 | systems, this is used for Framework includes, which have semantics | |
11044 | that are different from @option{-I}. | |
11045 | @end deftypefn | |
11046 | ||
11047 | @defmac bool TARGET_USE_LOCAL_THUNK_ALIAS_P (tree @var{fndecl}) | |
11048 | This target macro returns @code{true} if it is safe to use a local alias | |
11049 | for a virtual function @var{fndecl} when constructing thunks, | |
11050 | @code{false} otherwise. By default, the macro returns @code{true} for all | |
11051 | functions, if a target supports aliases (i.e.@: defines | |
11052 | @code{ASM_OUTPUT_DEF}), @code{false} otherwise, | |
11053 | @end defmac | |
11054 | ||
11055 | @defmac TARGET_FORMAT_TYPES | |
11056 | If defined, this macro is the name of a global variable containing | |
11057 | target-specific format checking information for the @option{-Wformat} | |
11058 | option. The default is to have no target-specific format checks. | |
11059 | @end defmac | |
11060 | ||
11061 | @defmac TARGET_N_FORMAT_TYPES | |
11062 | If defined, this macro is the number of entries in | |
11063 | @code{TARGET_FORMAT_TYPES}. | |
11064 | @end defmac | |
11065 | ||
11066 | @defmac TARGET_OVERRIDES_FORMAT_ATTRIBUTES | |
11067 | If defined, this macro is the name of a global variable containing | |
11068 | target-specific format overrides for the @option{-Wformat} option. The | |
11069 | default is to have no target-specific format overrides. If defined, | |
11070 | @code{TARGET_FORMAT_TYPES} must be defined, too. | |
11071 | @end defmac | |
11072 | ||
11073 | @defmac TARGET_OVERRIDES_FORMAT_ATTRIBUTES_COUNT | |
11074 | If defined, this macro specifies the number of entries in | |
11075 | @code{TARGET_OVERRIDES_FORMAT_ATTRIBUTES}. | |
11076 | @end defmac | |
11077 | ||
11078 | @defmac TARGET_OVERRIDES_FORMAT_INIT | |
11079 | If defined, this macro specifies the optional initialization | |
11080 | routine for target specific customizations of the system printf | |
11081 | and scanf formatter settings. | |
11082 | @end defmac | |
11083 | ||
11084 | @hook TARGET_RELAXED_ORDERING | |
11085 | If set to @code{true}, means that the target's memory model does not | |
11086 | guarantee that loads which do not depend on one another will access | |
11087 | main memory in the order of the instruction stream; if ordering is | |
11088 | important, an explicit memory barrier must be used. This is true of | |
11089 | many recent processors which implement a policy of ``relaxed,'' | |
11090 | ``weak,'' or ``release'' memory consistency, such as Alpha, PowerPC, | |
11091 | and ia64. The default is @code{false}. | |
11092 | @end deftypevr | |
11093 | ||
11094 | @hook TARGET_INVALID_ARG_FOR_UNPROTOTYPED_FN | |
11095 | If defined, this macro returns the diagnostic message when it is | |
11096 | illegal to pass argument @var{val} to function @var{funcdecl} | |
11097 | with prototype @var{typelist}. | |
11098 | @end deftypefn | |
11099 | ||
11100 | @hook TARGET_INVALID_CONVERSION | |
11101 | If defined, this macro returns the diagnostic message when it is | |
11102 | invalid to convert from @var{fromtype} to @var{totype}, or @code{NULL} | |
11103 | if validity should be determined by the front end. | |
11104 | @end deftypefn | |
11105 | ||
11106 | @hook TARGET_INVALID_UNARY_OP | |
11107 | If defined, this macro returns the diagnostic message when it is | |
11108 | invalid to apply operation @var{op} (where unary plus is denoted by | |
11109 | @code{CONVERT_EXPR}) to an operand of type @var{type}, or @code{NULL} | |
11110 | if validity should be determined by the front end. | |
11111 | @end deftypefn | |
11112 | ||
11113 | @hook TARGET_INVALID_BINARY_OP | |
11114 | If defined, this macro returns the diagnostic message when it is | |
11115 | invalid to apply operation @var{op} to operands of types @var{type1} | |
11116 | and @var{type2}, or @code{NULL} if validity should be determined by | |
11117 | the front end. | |
11118 | @end deftypefn | |
11119 | ||
11120 | @hook TARGET_INVALID_PARAMETER_TYPE | |
11121 | If defined, this macro returns the diagnostic message when it is | |
ff2ce160 | 11122 | invalid for functions to include parameters of type @var{type}, |
38f8b050 JR |
11123 | or @code{NULL} if validity should be determined by |
11124 | the front end. This is currently used only by the C and C++ front ends. | |
11125 | @end deftypefn | |
11126 | ||
11127 | @hook TARGET_INVALID_RETURN_TYPE | |
11128 | If defined, this macro returns the diagnostic message when it is | |
ff2ce160 | 11129 | invalid for functions to have return type @var{type}, |
38f8b050 JR |
11130 | or @code{NULL} if validity should be determined by |
11131 | the front end. This is currently used only by the C and C++ front ends. | |
11132 | @end deftypefn | |
11133 | ||
11134 | @hook TARGET_PROMOTED_TYPE | |
ff2ce160 MS |
11135 | If defined, this target hook returns the type to which values of |
11136 | @var{type} should be promoted when they appear in expressions, | |
38f8b050 JR |
11137 | analogous to the integer promotions, or @code{NULL_TREE} to use the |
11138 | front end's normal promotion rules. This hook is useful when there are | |
11139 | target-specific types with special promotion rules. | |
11140 | This is currently used only by the C and C++ front ends. | |
11141 | @end deftypefn | |
11142 | ||
11143 | @hook TARGET_CONVERT_TO_TYPE | |
ff2ce160 MS |
11144 | If defined, this hook returns the result of converting @var{expr} to |
11145 | @var{type}. It should return the converted expression, | |
38f8b050 | 11146 | or @code{NULL_TREE} to apply the front end's normal conversion rules. |
ff2ce160 | 11147 | This hook is useful when there are target-specific types with special |
38f8b050 JR |
11148 | conversion rules. |
11149 | This is currently used only by the C and C++ front ends. | |
11150 | @end deftypefn | |
11151 | ||
11152 | @defmac TARGET_USE_JCR_SECTION | |
11153 | This macro determines whether to use the JCR section to register Java | |
11154 | classes. By default, TARGET_USE_JCR_SECTION is defined to 1 if both | |
11155 | SUPPORTS_WEAK and TARGET_HAVE_NAMED_SECTIONS are true, else 0. | |
11156 | @end defmac | |
11157 | ||
11158 | @defmac OBJC_JBLEN | |
11159 | This macro determines the size of the objective C jump buffer for the | |
11160 | NeXT runtime. By default, OBJC_JBLEN is defined to an innocuous value. | |
11161 | @end defmac | |
11162 | ||
11163 | @defmac LIBGCC2_UNWIND_ATTRIBUTE | |
11164 | Define this macro if any target-specific attributes need to be attached | |
ff2ce160 | 11165 | to the functions in @file{libgcc} that provide low-level support for |
38f8b050 JR |
11166 | call stack unwinding. It is used in declarations in @file{unwind-generic.h} |
11167 | and the associated definitions of those functions. | |
11168 | @end defmac | |
11169 | ||
11170 | @hook TARGET_UPDATE_STACK_BOUNDARY | |
11171 | Define this macro to update the current function stack boundary if | |
11172 | necessary. | |
11173 | @end deftypefn | |
11174 | ||
11175 | @hook TARGET_GET_DRAP_RTX | |
11176 | This hook should return an rtx for Dynamic Realign Argument Pointer (DRAP) if a | |
11177 | different argument pointer register is needed to access the function's | |
11178 | argument list due to stack realignment. Return @code{NULL} if no DRAP | |
11179 | is needed. | |
11180 | @end deftypefn | |
11181 | ||
11182 | @hook TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS | |
11183 | When optimization is disabled, this hook indicates whether or not | |
11184 | arguments should be allocated to stack slots. Normally, GCC allocates | |
11185 | stacks slots for arguments when not optimizing in order to make | |
11186 | debugging easier. However, when a function is declared with | |
11187 | @code{__attribute__((naked))}, there is no stack frame, and the compiler | |
11188 | cannot safely move arguments from the registers in which they are passed | |
11189 | to the stack. Therefore, this hook should return true in general, but | |
11190 | false for naked functions. The default implementation always returns true. | |
11191 | @end deftypefn | |
11192 | ||
11193 | @hook TARGET_CONST_ANCHOR | |
11194 | On some architectures it can take multiple instructions to synthesize | |
11195 | a constant. If there is another constant already in a register that | |
11196 | is close enough in value then it is preferable that the new constant | |
11197 | is computed from this register using immediate addition or | |
11198 | subtraction. We accomplish this through CSE. Besides the value of | |
11199 | the constant we also add a lower and an upper constant anchor to the | |
11200 | available expressions. These are then queried when encountering new | |
11201 | constants. The anchors are computed by rounding the constant up and | |
11202 | down to a multiple of the value of @code{TARGET_CONST_ANCHOR}. | |
11203 | @code{TARGET_CONST_ANCHOR} should be the maximum positive value | |
11204 | accepted by immediate-add plus one. We currently assume that the | |
11205 | value of @code{TARGET_CONST_ANCHOR} is a power of 2. For example, on | |
11206 | MIPS, where add-immediate takes a 16-bit signed value, | |
11207 | @code{TARGET_CONST_ANCHOR} is set to @samp{0x8000}. The default value | |
11208 | is zero, which disables this optimization. @end deftypevr |