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3aea1f79 | 1 | @c Copyright (C) 1988-2014 Free Software Foundation, Inc. |
202d6e5f | 2 | @c This is part of the GCC manual. |
3 | @c For copying conditions, see the file gcc.texi. | |
4 | ||
5 | @node Target Macros | |
6 | @chapter Target Description Macros and Functions | |
7 | @cindex machine description macros | |
8 | @cindex target description macros | |
9 | @cindex macros, target description | |
10 | @cindex @file{tm.h} macros | |
11 | ||
12 | In addition to the file @file{@var{machine}.md}, a machine description | |
13 | includes a C header file conventionally given the name | |
14 | @file{@var{machine}.h} and a C source file named @file{@var{machine}.c}. | |
15 | The header file defines numerous macros that convey the information | |
16 | about the target machine that does not fit into the scheme of the | |
17 | @file{.md} file. The file @file{tm.h} should be a link to | |
18 | @file{@var{machine}.h}. The header file @file{config.h} includes | |
19 | @file{tm.h} and most compiler source files include @file{config.h}. The | |
20 | source file defines a variable @code{targetm}, which is a structure | |
21 | containing pointers to functions and data relating to the target | |
22 | machine. @file{@var{machine}.c} should also contain their definitions, | |
23 | if they are not defined elsewhere in GCC, and other functions called | |
24 | through the macros defined in the @file{.h} file. | |
25 | ||
26 | @menu | |
27 | * Target Structure:: The @code{targetm} variable. | |
28 | * Driver:: Controlling how the driver runs the compilation passes. | |
29 | * Run-time Target:: Defining @samp{-m} options like @option{-m68000} and @option{-m68020}. | |
30 | * Per-Function Data:: Defining data structures for per-function information. | |
31 | * Storage Layout:: Defining sizes and alignments of data. | |
32 | * Type Layout:: Defining sizes and properties of basic user data types. | |
33 | * Registers:: Naming and describing the hardware registers. | |
34 | * Register Classes:: Defining the classes of hardware registers. | |
202d6e5f | 35 | * Stack and Calling:: Defining which way the stack grows and by how much. |
36 | * Varargs:: Defining the varargs macros. | |
37 | * Trampolines:: Code set up at run time to enter a nested function. | |
38 | * Library Calls:: Controlling how library routines are implicitly called. | |
39 | * Addressing Modes:: Defining addressing modes valid for memory operands. | |
40 | * Anchored Addresses:: Defining how @option{-fsection-anchors} should work. | |
41 | * Condition Code:: Defining how insns update the condition code. | |
42 | * Costs:: Defining relative costs of different operations. | |
43 | * Scheduling:: Adjusting the behavior of the instruction scheduler. | |
44 | * Sections:: Dividing storage into text, data, and other sections. | |
45 | * PIC:: Macros for position independent code. | |
46 | * Assembler Format:: Defining how to write insns and pseudo-ops to output. | |
47 | * Debugging Info:: Defining the format of debugging output. | |
48 | * Floating Point:: Handling floating point for cross-compilers. | |
49 | * Mode Switching:: Insertion of mode-switching instructions. | |
50 | * Target Attributes:: Defining target-specific uses of @code{__attribute__}. | |
51 | * Emulated TLS:: Emulated TLS support. | |
52 | * MIPS Coprocessors:: MIPS coprocessor support and how to customize it. | |
53 | * PCH Target:: Validity checking for precompiled headers. | |
54 | * C++ ABI:: Controlling C++ ABI changes. | |
55 | * Named Address Spaces:: Adding support for named address spaces | |
56 | * Misc:: Everything else. | |
57 | @end menu | |
58 | ||
59 | @node Target Structure | |
60 | @section The Global @code{targetm} Variable | |
61 | @cindex target hooks | |
62 | @cindex target functions | |
63 | ||
64 | @deftypevar {struct gcc_target} targetm | |
65 | The target @file{.c} file must define the global @code{targetm} variable | |
66 | which contains pointers to functions and data relating to the target | |
67 | machine. The variable is declared in @file{target.h}; | |
68 | @file{target-def.h} defines the macro @code{TARGET_INITIALIZER} which is | |
69 | used to initialize the variable, and macros for the default initializers | |
70 | for elements of the structure. The @file{.c} file should override those | |
71 | macros for which the default definition is inappropriate. For example: | |
72 | @smallexample | |
73 | #include "target.h" | |
74 | #include "target-def.h" | |
75 | ||
76 | /* @r{Initialize the GCC target structure.} */ | |
77 | ||
78 | #undef TARGET_COMP_TYPE_ATTRIBUTES | |
79 | #define TARGET_COMP_TYPE_ATTRIBUTES @var{machine}_comp_type_attributes | |
80 | ||
81 | struct gcc_target targetm = TARGET_INITIALIZER; | |
82 | @end smallexample | |
83 | @end deftypevar | |
84 | ||
85 | Where a macro should be defined in the @file{.c} file in this manner to | |
86 | form part of the @code{targetm} structure, it is documented below as a | |
87 | ``Target Hook'' with a prototype. Many macros will change in future | |
88 | from being defined in the @file{.h} file to being part of the | |
89 | @code{targetm} structure. | |
90 | ||
c94b1d0e | 91 | Similarly, there is a @code{targetcm} variable for hooks that are |
92 | specific to front ends for C-family languages, documented as ``C | |
93 | Target Hook''. This is declared in @file{c-family/c-target.h}, the | |
851d9296 | 94 | initializer @code{TARGETCM_INITIALIZER} in |
c94b1d0e | 95 | @file{c-family/c-target-def.h}. If targets initialize @code{targetcm} |
96 | themselves, they should set @code{target_has_targetcm=yes} in | |
97 | @file{config.gcc}; otherwise a default definition is used. | |
98 | ||
3e87b980 | 99 | Similarly, there is a @code{targetm_common} variable for hooks that |
100 | are shared between the compiler driver and the compilers proper, | |
101 | documented as ``Common Target Hook''. This is declared in | |
102 | @file{common/common-target.h}, the initializer | |
103 | @code{TARGETM_COMMON_INITIALIZER} in | |
104 | @file{common/common-target-def.h}. If targets initialize | |
105 | @code{targetm_common} themselves, they should set | |
106 | @code{target_has_targetm_common=yes} in @file{config.gcc}; otherwise a | |
107 | default definition is used. | |
108 | ||
202d6e5f | 109 | @node Driver |
110 | @section Controlling the Compilation Driver, @file{gcc} | |
111 | @cindex driver | |
112 | @cindex controlling the compilation driver | |
113 | ||
114 | @c prevent bad page break with this line | |
115 | You can control the compilation driver. | |
116 | ||
202d6e5f | 117 | @defmac DRIVER_SELF_SPECS |
118 | A list of specs for the driver itself. It should be a suitable | |
119 | initializer for an array of strings, with no surrounding braces. | |
120 | ||
121 | The driver applies these specs to its own command line between loading | |
122 | default @file{specs} files (but not command-line specified ones) and | |
123 | choosing the multilib directory or running any subcommands. It | |
124 | applies them in the order given, so each spec can depend on the | |
125 | options added by earlier ones. It is also possible to remove options | |
126 | using @samp{%<@var{option}} in the usual way. | |
127 | ||
128 | This macro can be useful when a port has several interdependent target | |
129 | options. It provides a way of standardizing the command line so | |
130 | that the other specs are easier to write. | |
131 | ||
132 | Do not define this macro if it does not need to do anything. | |
133 | @end defmac | |
134 | ||
135 | @defmac OPTION_DEFAULT_SPECS | |
136 | A list of specs used to support configure-time default options (i.e.@: | |
137 | @option{--with} options) in the driver. It should be a suitable initializer | |
138 | for an array of structures, each containing two strings, without the | |
139 | outermost pair of surrounding braces. | |
140 | ||
141 | The first item in the pair is the name of the default. This must match | |
142 | the code in @file{config.gcc} for the target. The second item is a spec | |
143 | to apply if a default with this name was specified. The string | |
144 | @samp{%(VALUE)} in the spec will be replaced by the value of the default | |
145 | everywhere it occurs. | |
146 | ||
147 | The driver will apply these specs to its own command line between loading | |
148 | default @file{specs} files and processing @code{DRIVER_SELF_SPECS}, using | |
149 | the same mechanism as @code{DRIVER_SELF_SPECS}. | |
150 | ||
151 | Do not define this macro if it does not need to do anything. | |
152 | @end defmac | |
153 | ||
154 | @defmac CPP_SPEC | |
155 | A C string constant that tells the GCC driver program options to | |
156 | pass to CPP@. It can also specify how to translate options you | |
157 | give to GCC into options for GCC to pass to the CPP@. | |
158 | ||
159 | Do not define this macro if it does not need to do anything. | |
160 | @end defmac | |
161 | ||
162 | @defmac CPLUSPLUS_CPP_SPEC | |
163 | This macro is just like @code{CPP_SPEC}, but is used for C++, rather | |
164 | than C@. If you do not define this macro, then the value of | |
165 | @code{CPP_SPEC} (if any) will be used instead. | |
166 | @end defmac | |
167 | ||
168 | @defmac CC1_SPEC | |
169 | A C string constant that tells the GCC driver program options to | |
170 | pass to @code{cc1}, @code{cc1plus}, @code{f771}, and the other language | |
171 | front ends. | |
172 | It can also specify how to translate options you give to GCC into options | |
173 | for GCC to pass to front ends. | |
174 | ||
175 | Do not define this macro if it does not need to do anything. | |
176 | @end defmac | |
177 | ||
178 | @defmac CC1PLUS_SPEC | |
179 | A C string constant that tells the GCC driver program options to | |
180 | pass to @code{cc1plus}. It can also specify how to translate options you | |
181 | give to GCC into options for GCC to pass to the @code{cc1plus}. | |
182 | ||
183 | Do not define this macro if it does not need to do anything. | |
184 | Note that everything defined in CC1_SPEC is already passed to | |
185 | @code{cc1plus} so there is no need to duplicate the contents of | |
186 | CC1_SPEC in CC1PLUS_SPEC@. | |
187 | @end defmac | |
188 | ||
189 | @defmac ASM_SPEC | |
190 | A C string constant that tells the GCC driver program options to | |
191 | pass to the assembler. It can also specify how to translate options | |
192 | you give to GCC into options for GCC to pass to the assembler. | |
193 | See the file @file{sun3.h} for an example of this. | |
194 | ||
195 | Do not define this macro if it does not need to do anything. | |
196 | @end defmac | |
197 | ||
198 | @defmac ASM_FINAL_SPEC | |
199 | A C string constant that tells the GCC driver program how to | |
200 | run any programs which cleanup after the normal assembler. | |
201 | Normally, this is not needed. See the file @file{mips.h} for | |
202 | an example of this. | |
203 | ||
204 | Do not define this macro if it does not need to do anything. | |
205 | @end defmac | |
206 | ||
207 | @defmac AS_NEEDS_DASH_FOR_PIPED_INPUT | |
208 | Define this macro, with no value, if the driver should give the assembler | |
209 | an argument consisting of a single dash, @option{-}, to instruct it to | |
210 | read from its standard input (which will be a pipe connected to the | |
211 | output of the compiler proper). This argument is given after any | |
212 | @option{-o} option specifying the name of the output file. | |
213 | ||
214 | If you do not define this macro, the assembler is assumed to read its | |
215 | standard input if given no non-option arguments. If your assembler | |
216 | cannot read standard input at all, use a @samp{%@{pipe:%e@}} construct; | |
217 | see @file{mips.h} for instance. | |
218 | @end defmac | |
219 | ||
220 | @defmac LINK_SPEC | |
221 | A C string constant that tells the GCC driver program options to | |
222 | pass to the linker. It can also specify how to translate options you | |
223 | give to GCC into options for GCC to pass to the linker. | |
224 | ||
225 | Do not define this macro if it does not need to do anything. | |
226 | @end defmac | |
227 | ||
228 | @defmac LIB_SPEC | |
229 | Another C string constant used much like @code{LINK_SPEC}. The difference | |
230 | between the two is that @code{LIB_SPEC} is used at the end of the | |
231 | command given to the linker. | |
232 | ||
233 | If this macro is not defined, a default is provided that | |
234 | loads the standard C library from the usual place. See @file{gcc.c}. | |
235 | @end defmac | |
236 | ||
237 | @defmac LIBGCC_SPEC | |
238 | Another C string constant that tells the GCC driver program | |
239 | how and when to place a reference to @file{libgcc.a} into the | |
240 | linker command line. This constant is placed both before and after | |
241 | the value of @code{LIB_SPEC}. | |
242 | ||
243 | If this macro is not defined, the GCC driver provides a default that | |
244 | passes the string @option{-lgcc} to the linker. | |
245 | @end defmac | |
246 | ||
247 | @defmac REAL_LIBGCC_SPEC | |
248 | By default, if @code{ENABLE_SHARED_LIBGCC} is defined, the | |
249 | @code{LIBGCC_SPEC} is not directly used by the driver program but is | |
250 | instead modified to refer to different versions of @file{libgcc.a} | |
251 | depending on the values of the command line flags @option{-static}, | |
252 | @option{-shared}, @option{-static-libgcc}, and @option{-shared-libgcc}. On | |
253 | targets where these modifications are inappropriate, define | |
254 | @code{REAL_LIBGCC_SPEC} instead. @code{REAL_LIBGCC_SPEC} tells the | |
255 | driver how to place a reference to @file{libgcc} on the link command | |
256 | line, but, unlike @code{LIBGCC_SPEC}, it is used unmodified. | |
257 | @end defmac | |
258 | ||
259 | @defmac USE_LD_AS_NEEDED | |
260 | A macro that controls the modifications to @code{LIBGCC_SPEC} | |
261 | mentioned in @code{REAL_LIBGCC_SPEC}. If nonzero, a spec will be | |
8aaed91d | 262 | generated that uses @option{--as-needed} or equivalent options and the |
263 | shared @file{libgcc} in place of the | |
202d6e5f | 264 | static exception handler library, when linking without any of |
265 | @code{-static}, @code{-static-libgcc}, or @code{-shared-libgcc}. | |
266 | @end defmac | |
267 | ||
268 | @defmac LINK_EH_SPEC | |
269 | If defined, this C string constant is added to @code{LINK_SPEC}. | |
270 | When @code{USE_LD_AS_NEEDED} is zero or undefined, it also affects | |
271 | the modifications to @code{LIBGCC_SPEC} mentioned in | |
272 | @code{REAL_LIBGCC_SPEC}. | |
273 | @end defmac | |
274 | ||
275 | @defmac STARTFILE_SPEC | |
276 | Another C string constant used much like @code{LINK_SPEC}. The | |
277 | difference between the two is that @code{STARTFILE_SPEC} is used at | |
278 | the very beginning of the command given to the linker. | |
279 | ||
280 | If this macro is not defined, a default is provided that loads the | |
281 | standard C startup file from the usual place. See @file{gcc.c}. | |
282 | @end defmac | |
283 | ||
284 | @defmac ENDFILE_SPEC | |
285 | Another C string constant used much like @code{LINK_SPEC}. The | |
286 | difference between the two is that @code{ENDFILE_SPEC} is used at | |
287 | the very end of the command given to the linker. | |
288 | ||
289 | Do not define this macro if it does not need to do anything. | |
290 | @end defmac | |
291 | ||
292 | @defmac THREAD_MODEL_SPEC | |
293 | GCC @code{-v} will print the thread model GCC was configured to use. | |
294 | However, this doesn't work on platforms that are multilibbed on thread | |
295 | models, such as AIX 4.3. On such platforms, define | |
296 | @code{THREAD_MODEL_SPEC} such that it evaluates to a string without | |
297 | blanks that names one of the recognized thread models. @code{%*}, the | |
298 | default value of this macro, will expand to the value of | |
299 | @code{thread_file} set in @file{config.gcc}. | |
300 | @end defmac | |
301 | ||
302 | @defmac SYSROOT_SUFFIX_SPEC | |
303 | Define this macro to add a suffix to the target sysroot when GCC is | |
304 | configured with a sysroot. This will cause GCC to search for usr/lib, | |
305 | et al, within sysroot+suffix. | |
306 | @end defmac | |
307 | ||
308 | @defmac SYSROOT_HEADERS_SUFFIX_SPEC | |
309 | Define this macro to add a headers_suffix to the target sysroot when | |
310 | GCC is configured with a sysroot. This will cause GCC to pass the | |
311 | updated sysroot+headers_suffix to CPP, causing it to search for | |
312 | usr/include, et al, within sysroot+headers_suffix. | |
313 | @end defmac | |
314 | ||
315 | @defmac EXTRA_SPECS | |
316 | Define this macro to provide additional specifications to put in the | |
317 | @file{specs} file that can be used in various specifications like | |
318 | @code{CC1_SPEC}. | |
319 | ||
320 | The definition should be an initializer for an array of structures, | |
321 | containing a string constant, that defines the specification name, and a | |
322 | string constant that provides the specification. | |
323 | ||
324 | Do not define this macro if it does not need to do anything. | |
325 | ||
326 | @code{EXTRA_SPECS} is useful when an architecture contains several | |
327 | related targets, which have various @code{@dots{}_SPECS} which are similar | |
328 | to each other, and the maintainer would like one central place to keep | |
329 | these definitions. | |
330 | ||
331 | For example, the PowerPC System V.4 targets use @code{EXTRA_SPECS} to | |
332 | define either @code{_CALL_SYSV} when the System V calling sequence is | |
333 | used or @code{_CALL_AIX} when the older AIX-based calling sequence is | |
334 | used. | |
335 | ||
336 | The @file{config/rs6000/rs6000.h} target file defines: | |
337 | ||
338 | @smallexample | |
339 | #define EXTRA_SPECS \ | |
340 | @{ "cpp_sysv_default", CPP_SYSV_DEFAULT @}, | |
341 | ||
342 | #define CPP_SYS_DEFAULT "" | |
343 | @end smallexample | |
344 | ||
345 | The @file{config/rs6000/sysv.h} target file defines: | |
346 | @smallexample | |
347 | #undef CPP_SPEC | |
348 | #define CPP_SPEC \ | |
349 | "%@{posix: -D_POSIX_SOURCE @} \ | |
350 | %@{mcall-sysv: -D_CALL_SYSV @} \ | |
351 | %@{!mcall-sysv: %(cpp_sysv_default) @} \ | |
352 | %@{msoft-float: -D_SOFT_FLOAT@} %@{mcpu=403: -D_SOFT_FLOAT@}" | |
353 | ||
354 | #undef CPP_SYSV_DEFAULT | |
355 | #define CPP_SYSV_DEFAULT "-D_CALL_SYSV" | |
356 | @end smallexample | |
357 | ||
358 | while the @file{config/rs6000/eabiaix.h} target file defines | |
359 | @code{CPP_SYSV_DEFAULT} as: | |
360 | ||
361 | @smallexample | |
362 | #undef CPP_SYSV_DEFAULT | |
363 | #define CPP_SYSV_DEFAULT "-D_CALL_AIX" | |
364 | @end smallexample | |
365 | @end defmac | |
366 | ||
367 | @defmac LINK_LIBGCC_SPECIAL_1 | |
368 | Define this macro if the driver program should find the library | |
369 | @file{libgcc.a}. If you do not define this macro, the driver program will pass | |
370 | the argument @option{-lgcc} to tell the linker to do the search. | |
371 | @end defmac | |
372 | ||
373 | @defmac LINK_GCC_C_SEQUENCE_SPEC | |
374 | The sequence in which libgcc and libc are specified to the linker. | |
375 | By default this is @code{%G %L %G}. | |
376 | @end defmac | |
377 | ||
378 | @defmac LINK_COMMAND_SPEC | |
379 | A C string constant giving the complete command line need to execute the | |
380 | linker. When you do this, you will need to update your port each time a | |
381 | change is made to the link command line within @file{gcc.c}. Therefore, | |
382 | define this macro only if you need to completely redefine the command | |
383 | line for invoking the linker and there is no other way to accomplish | |
384 | the effect you need. Overriding this macro may be avoidable by overriding | |
385 | @code{LINK_GCC_C_SEQUENCE_SPEC} instead. | |
386 | @end defmac | |
387 | ||
3e87b980 | 388 | @hook TARGET_ALWAYS_STRIP_DOTDOT |
389 | ||
202d6e5f | 390 | @defmac MULTILIB_DEFAULTS |
391 | Define this macro as a C expression for the initializer of an array of | |
392 | string to tell the driver program which options are defaults for this | |
393 | target and thus do not need to be handled specially when using | |
394 | @code{MULTILIB_OPTIONS}. | |
395 | ||
396 | Do not define this macro if @code{MULTILIB_OPTIONS} is not defined in | |
397 | the target makefile fragment or if none of the options listed in | |
398 | @code{MULTILIB_OPTIONS} are set by default. | |
399 | @xref{Target Fragment}. | |
400 | @end defmac | |
401 | ||
402 | @defmac RELATIVE_PREFIX_NOT_LINKDIR | |
403 | Define this macro to tell @command{gcc} that it should only translate | |
404 | a @option{-B} prefix into a @option{-L} linker option if the prefix | |
405 | indicates an absolute file name. | |
406 | @end defmac | |
407 | ||
408 | @defmac MD_EXEC_PREFIX | |
409 | If defined, this macro is an additional prefix to try after | |
410 | @code{STANDARD_EXEC_PREFIX}. @code{MD_EXEC_PREFIX} is not searched | |
411 | when the compiler is built as a cross | |
412 | compiler. If you define @code{MD_EXEC_PREFIX}, then be sure to add it | |
413 | to the list of directories used to find the assembler in @file{configure.in}. | |
414 | @end defmac | |
415 | ||
416 | @defmac STANDARD_STARTFILE_PREFIX | |
417 | Define this macro as a C string constant if you wish to override the | |
418 | standard choice of @code{libdir} as the default prefix to | |
419 | try when searching for startup files such as @file{crt0.o}. | |
420 | @code{STANDARD_STARTFILE_PREFIX} is not searched when the compiler | |
421 | is built as a cross compiler. | |
422 | @end defmac | |
423 | ||
424 | @defmac STANDARD_STARTFILE_PREFIX_1 | |
425 | Define this macro as a C string constant if you wish to override the | |
426 | standard choice of @code{/lib} as a prefix to try after the default prefix | |
427 | when searching for startup files such as @file{crt0.o}. | |
428 | @code{STANDARD_STARTFILE_PREFIX_1} is not searched when the compiler | |
429 | is built as a cross compiler. | |
430 | @end defmac | |
431 | ||
432 | @defmac STANDARD_STARTFILE_PREFIX_2 | |
433 | Define this macro as a C string constant if you wish to override the | |
434 | standard choice of @code{/lib} as yet another prefix to try after the | |
435 | default prefix when searching for startup files such as @file{crt0.o}. | |
436 | @code{STANDARD_STARTFILE_PREFIX_2} is not searched when the compiler | |
437 | is built as a cross compiler. | |
438 | @end defmac | |
439 | ||
440 | @defmac MD_STARTFILE_PREFIX | |
441 | If defined, this macro supplies an additional prefix to try after the | |
442 | standard prefixes. @code{MD_EXEC_PREFIX} is not searched when the | |
443 | compiler is built as a cross compiler. | |
444 | @end defmac | |
445 | ||
446 | @defmac MD_STARTFILE_PREFIX_1 | |
447 | If defined, this macro supplies yet another prefix to try after the | |
448 | standard prefixes. It is not searched when the compiler is built as a | |
449 | cross compiler. | |
450 | @end defmac | |
451 | ||
452 | @defmac INIT_ENVIRONMENT | |
453 | Define this macro as a C string constant if you wish to set environment | |
454 | variables for programs called by the driver, such as the assembler and | |
455 | loader. The driver passes the value of this macro to @code{putenv} to | |
456 | initialize the necessary environment variables. | |
457 | @end defmac | |
458 | ||
459 | @defmac LOCAL_INCLUDE_DIR | |
460 | Define this macro as a C string constant if you wish to override the | |
461 | standard choice of @file{/usr/local/include} as the default prefix to | |
462 | try when searching for local header files. @code{LOCAL_INCLUDE_DIR} | |
638454a1 | 463 | comes before @code{NATIVE_SYSTEM_HEADER_DIR} (set in |
464 | @file{config.gcc}, normally @file{/usr/include}) in the search order. | |
202d6e5f | 465 | |
466 | Cross compilers do not search either @file{/usr/local/include} or its | |
467 | replacement. | |
468 | @end defmac | |
469 | ||
638454a1 | 470 | @defmac NATIVE_SYSTEM_HEADER_COMPONENT |
471 | The ``component'' corresponding to @code{NATIVE_SYSTEM_HEADER_DIR}. | |
202d6e5f | 472 | See @code{INCLUDE_DEFAULTS}, below, for the description of components. |
473 | If you do not define this macro, no component is used. | |
474 | @end defmac | |
475 | ||
476 | @defmac INCLUDE_DEFAULTS | |
477 | Define this macro if you wish to override the entire default search path | |
478 | for include files. For a native compiler, the default search path | |
479 | usually consists of @code{GCC_INCLUDE_DIR}, @code{LOCAL_INCLUDE_DIR}, | |
638454a1 | 480 | @code{GPLUSPLUS_INCLUDE_DIR}, and |
481 | @code{NATIVE_SYSTEM_HEADER_DIR}. In addition, @code{GPLUSPLUS_INCLUDE_DIR} | |
202d6e5f | 482 | and @code{GCC_INCLUDE_DIR} are defined automatically by @file{Makefile}, |
483 | and specify private search areas for GCC@. The directory | |
484 | @code{GPLUSPLUS_INCLUDE_DIR} is used only for C++ programs. | |
485 | ||
486 | The definition should be an initializer for an array of structures. | |
487 | Each array element should have four elements: the directory name (a | |
488 | string constant), the component name (also a string constant), a flag | |
489 | for C++-only directories, | |
490 | and a flag showing that the includes in the directory don't need to be | |
491 | wrapped in @code{extern @samp{C}} when compiling C++. Mark the end of | |
492 | the array with a null element. | |
493 | ||
494 | The component name denotes what GNU package the include file is part of, | |
495 | if any, in all uppercase letters. For example, it might be @samp{GCC} | |
496 | or @samp{BINUTILS}. If the package is part of a vendor-supplied | |
497 | operating system, code the component name as @samp{0}. | |
498 | ||
499 | For example, here is the definition used for VAX/VMS: | |
500 | ||
501 | @smallexample | |
502 | #define INCLUDE_DEFAULTS \ | |
503 | @{ \ | |
504 | @{ "GNU_GXX_INCLUDE:", "G++", 1, 1@}, \ | |
505 | @{ "GNU_CC_INCLUDE:", "GCC", 0, 0@}, \ | |
506 | @{ "SYS$SYSROOT:[SYSLIB.]", 0, 0, 0@}, \ | |
507 | @{ ".", 0, 0, 0@}, \ | |
508 | @{ 0, 0, 0, 0@} \ | |
509 | @} | |
510 | @end smallexample | |
511 | @end defmac | |
512 | ||
513 | Here is the order of prefixes tried for exec files: | |
514 | ||
515 | @enumerate | |
516 | @item | |
517 | Any prefixes specified by the user with @option{-B}. | |
518 | ||
519 | @item | |
520 | The environment variable @code{GCC_EXEC_PREFIX} or, if @code{GCC_EXEC_PREFIX} | |
15b474a2 | 521 | is not set and the compiler has not been installed in the configure-time |
202d6e5f | 522 | @var{prefix}, the location in which the compiler has actually been installed. |
523 | ||
524 | @item | |
525 | The directories specified by the environment variable @code{COMPILER_PATH}. | |
526 | ||
527 | @item | |
528 | The macro @code{STANDARD_EXEC_PREFIX}, if the compiler has been installed | |
15b474a2 | 529 | in the configured-time @var{prefix}. |
202d6e5f | 530 | |
531 | @item | |
15b474a2 | 532 | The location @file{/usr/libexec/gcc/}, but only if this is a native compiler. |
202d6e5f | 533 | |
534 | @item | |
15b474a2 | 535 | The location @file{/usr/lib/gcc/}, but only if this is a native compiler. |
202d6e5f | 536 | |
537 | @item | |
15b474a2 | 538 | The macro @code{MD_EXEC_PREFIX}, if defined, but only if this is a native |
202d6e5f | 539 | compiler. |
540 | @end enumerate | |
541 | ||
542 | Here is the order of prefixes tried for startfiles: | |
543 | ||
544 | @enumerate | |
545 | @item | |
546 | Any prefixes specified by the user with @option{-B}. | |
547 | ||
548 | @item | |
549 | The environment variable @code{GCC_EXEC_PREFIX} or its automatically determined | |
550 | value based on the installed toolchain location. | |
551 | ||
552 | @item | |
553 | The directories specified by the environment variable @code{LIBRARY_PATH} | |
554 | (or port-specific name; native only, cross compilers do not use this). | |
555 | ||
556 | @item | |
557 | The macro @code{STANDARD_EXEC_PREFIX}, but only if the toolchain is installed | |
15b474a2 | 558 | in the configured @var{prefix} or this is a native compiler. |
202d6e5f | 559 | |
560 | @item | |
561 | The location @file{/usr/lib/gcc/}, but only if this is a native compiler. | |
562 | ||
563 | @item | |
15b474a2 | 564 | The macro @code{MD_EXEC_PREFIX}, if defined, but only if this is a native |
202d6e5f | 565 | compiler. |
566 | ||
567 | @item | |
15b474a2 | 568 | The macro @code{MD_STARTFILE_PREFIX}, if defined, but only if this is a |
202d6e5f | 569 | native compiler, or we have a target system root. |
570 | ||
571 | @item | |
15b474a2 | 572 | The macro @code{MD_STARTFILE_PREFIX_1}, if defined, but only if this is a |
202d6e5f | 573 | native compiler, or we have a target system root. |
574 | ||
575 | @item | |
576 | The macro @code{STANDARD_STARTFILE_PREFIX}, with any sysroot modifications. | |
577 | If this path is relative it will be prefixed by @code{GCC_EXEC_PREFIX} and | |
578 | the machine suffix or @code{STANDARD_EXEC_PREFIX} and the machine suffix. | |
579 | ||
580 | @item | |
581 | The macro @code{STANDARD_STARTFILE_PREFIX_1}, but only if this is a native | |
582 | compiler, or we have a target system root. The default for this macro is | |
583 | @file{/lib/}. | |
584 | ||
585 | @item | |
586 | The macro @code{STANDARD_STARTFILE_PREFIX_2}, but only if this is a native | |
587 | compiler, or we have a target system root. The default for this macro is | |
588 | @file{/usr/lib/}. | |
589 | @end enumerate | |
590 | ||
591 | @node Run-time Target | |
592 | @section Run-time Target Specification | |
593 | @cindex run-time target specification | |
594 | @cindex predefined macros | |
595 | @cindex target specifications | |
596 | ||
597 | @c prevent bad page break with this line | |
598 | Here are run-time target specifications. | |
599 | ||
600 | @defmac TARGET_CPU_CPP_BUILTINS () | |
601 | This function-like macro expands to a block of code that defines | |
602 | built-in preprocessor macros and assertions for the target CPU, using | |
603 | the functions @code{builtin_define}, @code{builtin_define_std} and | |
604 | @code{builtin_assert}. When the front end | |
605 | calls this macro it provides a trailing semicolon, and since it has | |
606 | finished command line option processing your code can use those | |
607 | results freely. | |
608 | ||
609 | @code{builtin_assert} takes a string in the form you pass to the | |
610 | command-line option @option{-A}, such as @code{cpu=mips}, and creates | |
611 | the assertion. @code{builtin_define} takes a string in the form | |
612 | accepted by option @option{-D} and unconditionally defines the macro. | |
613 | ||
614 | @code{builtin_define_std} takes a string representing the name of an | |
615 | object-like macro. If it doesn't lie in the user's namespace, | |
616 | @code{builtin_define_std} defines it unconditionally. Otherwise, it | |
617 | defines a version with two leading underscores, and another version | |
618 | with two leading and trailing underscores, and defines the original | |
619 | only if an ISO standard was not requested on the command line. For | |
620 | example, passing @code{unix} defines @code{__unix}, @code{__unix__} | |
621 | and possibly @code{unix}; passing @code{_mips} defines @code{__mips}, | |
622 | @code{__mips__} and possibly @code{_mips}, and passing @code{_ABI64} | |
623 | defines only @code{_ABI64}. | |
624 | ||
625 | You can also test for the C dialect being compiled. The variable | |
626 | @code{c_language} is set to one of @code{clk_c}, @code{clk_cplusplus} | |
627 | or @code{clk_objective_c}. Note that if we are preprocessing | |
628 | assembler, this variable will be @code{clk_c} but the function-like | |
629 | macro @code{preprocessing_asm_p()} will return true, so you might want | |
630 | to check for that first. If you need to check for strict ANSI, the | |
631 | variable @code{flag_iso} can be used. The function-like macro | |
632 | @code{preprocessing_trad_p()} can be used to check for traditional | |
633 | preprocessing. | |
634 | @end defmac | |
635 | ||
636 | @defmac TARGET_OS_CPP_BUILTINS () | |
637 | Similarly to @code{TARGET_CPU_CPP_BUILTINS} but this macro is optional | |
638 | and is used for the target operating system instead. | |
639 | @end defmac | |
640 | ||
641 | @defmac TARGET_OBJFMT_CPP_BUILTINS () | |
642 | Similarly to @code{TARGET_CPU_CPP_BUILTINS} but this macro is optional | |
643 | and is used for the target object format. @file{elfos.h} uses this | |
644 | macro to define @code{__ELF__}, so you probably do not need to define | |
645 | it yourself. | |
646 | @end defmac | |
647 | ||
648 | @deftypevar {extern int} target_flags | |
649 | This variable is declared in @file{options.h}, which is included before | |
650 | any target-specific headers. | |
651 | @end deftypevar | |
652 | ||
653 | @hook TARGET_DEFAULT_TARGET_FLAGS | |
654 | This variable specifies the initial value of @code{target_flags}. | |
655 | Its default setting is 0. | |
656 | @end deftypevr | |
657 | ||
658 | @cindex optional hardware or system features | |
659 | @cindex features, optional, in system conventions | |
660 | ||
661 | @hook TARGET_HANDLE_OPTION | |
662 | This hook is called whenever the user specifies one of the | |
663 | target-specific options described by the @file{.opt} definition files | |
664 | (@pxref{Options}). It has the opportunity to do some option-specific | |
665 | processing and should return true if the option is valid. The default | |
666 | definition does nothing but return true. | |
667 | ||
fba5dd52 | 668 | @var{decoded} specifies the option and its arguments. @var{opts} and |
669 | @var{opts_set} are the @code{gcc_options} structures to be used for | |
670 | storing option state, and @var{loc} is the location at which the | |
671 | option was passed (@code{UNKNOWN_LOCATION} except for options passed | |
672 | via attributes). | |
202d6e5f | 673 | @end deftypefn |
674 | ||
675 | @hook TARGET_HANDLE_C_OPTION | |
676 | This target hook is called whenever the user specifies one of the | |
677 | target-specific C language family options described by the @file{.opt} | |
678 | definition files(@pxref{Options}). It has the opportunity to do some | |
679 | option-specific processing and should return true if the option is | |
680 | valid. The arguments are like for @code{TARGET_HANDLE_OPTION}. The | |
681 | default definition does nothing but return false. | |
682 | ||
683 | In general, you should use @code{TARGET_HANDLE_OPTION} to handle | |
684 | options. However, if processing an option requires routines that are | |
685 | only available in the C (and related language) front ends, then you | |
686 | should use @code{TARGET_HANDLE_C_OPTION} instead. | |
687 | @end deftypefn | |
688 | ||
1f6616ee | 689 | @hook TARGET_OBJC_CONSTRUCT_STRING_OBJECT |
690 | ||
ff6624bc | 691 | @hook TARGET_OBJC_DECLARE_UNRESOLVED_CLASS_REFERENCE |
692 | ||
693 | @hook TARGET_OBJC_DECLARE_CLASS_DEFINITION | |
694 | ||
1f6616ee | 695 | @hook TARGET_STRING_OBJECT_REF_TYPE_P |
696 | ||
697 | @hook TARGET_CHECK_STRING_OBJECT_FORMAT_ARG | |
d4238e8b | 698 | |
202d6e5f | 699 | @hook TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE |
202d6e5f | 700 | |
701 | @defmac C_COMMON_OVERRIDE_OPTIONS | |
4c834714 | 702 | This is similar to the @code{TARGET_OPTION_OVERRIDE} hook |
703 | but is only used in the C | |
202d6e5f | 704 | language frontends (C, Objective-C, C++, Objective-C++) and so can be |
705 | used to alter option flag variables which only exist in those | |
706 | frontends. | |
707 | @end defmac | |
708 | ||
c17f64cc | 709 | @hook TARGET_OPTION_OPTIMIZATION_TABLE |
202d6e5f | 710 | Some machines may desire to change what optimizations are performed for |
c17f64cc | 711 | various optimization levels. This variable, if defined, describes |
712 | options to enable at particular sets of optimization levels. These | |
713 | options are processed once | |
202d6e5f | 714 | just after the optimization level is determined and before the remainder |
c17f64cc | 715 | of the command options have been parsed, so may be overridden by other |
b59688ee | 716 | options passed explicitly. |
202d6e5f | 717 | |
c17f64cc | 718 | This processing is run once at program startup and when the optimization |
202d6e5f | 719 | options are changed via @code{#pragma GCC optimize} or by using the |
720 | @code{optimize} attribute. | |
c17f64cc | 721 | @end deftypevr |
202d6e5f | 722 | |
cc07c468 | 723 | @hook TARGET_OPTION_INIT_STRUCT |
724 | ||
686e2769 | 725 | @hook TARGET_OPTION_DEFAULT_PARAMS |
726 | ||
821d4118 | 727 | @defmac SWITCHABLE_TARGET |
728 | Some targets need to switch between substantially different subtargets | |
729 | during compilation. For example, the MIPS target has one subtarget for | |
730 | the traditional MIPS architecture and another for MIPS16. Source code | |
731 | can switch between these two subarchitectures using the @code{mips16} | |
732 | and @code{nomips16} attributes. | |
733 | ||
734 | Such subtargets can differ in things like the set of available | |
735 | registers, the set of available instructions, the costs of various | |
736 | operations, and so on. GCC caches a lot of this type of information | |
737 | in global variables, and recomputing them for each subtarget takes a | |
738 | significant amount of time. The compiler therefore provides a facility | |
739 | for maintaining several versions of the global variables and quickly | |
740 | switching between them; see @file{target-globals.h} for details. | |
741 | ||
742 | Define this macro to 1 if your target needs this facility. The default | |
743 | is 0. | |
744 | @end defmac | |
745 | ||
4c866b9b | 746 | @hook TARGET_FLOAT_EXCEPTIONS_ROUNDING_SUPPORTED_P |
747 | ||
202d6e5f | 748 | @node Per-Function Data |
749 | @section Defining data structures for per-function information. | |
750 | @cindex per-function data | |
751 | @cindex data structures | |
752 | ||
753 | If the target needs to store information on a per-function basis, GCC | |
754 | provides a macro and a couple of variables to allow this. Note, just | |
755 | using statics to store the information is a bad idea, since GCC supports | |
756 | nested functions, so you can be halfway through encoding one function | |
757 | when another one comes along. | |
758 | ||
759 | GCC defines a data structure called @code{struct function} which | |
760 | contains all of the data specific to an individual function. This | |
761 | structure contains a field called @code{machine} whose type is | |
762 | @code{struct machine_function *}, which can be used by targets to point | |
763 | to their own specific data. | |
764 | ||
765 | If a target needs per-function specific data it should define the type | |
766 | @code{struct machine_function} and also the macro @code{INIT_EXPANDERS}. | |
767 | This macro should be used to initialize the function pointer | |
768 | @code{init_machine_status}. This pointer is explained below. | |
769 | ||
770 | One typical use of per-function, target specific data is to create an | |
771 | RTX to hold the register containing the function's return address. This | |
772 | RTX can then be used to implement the @code{__builtin_return_address} | |
773 | function, for level 0. | |
774 | ||
775 | Note---earlier implementations of GCC used a single data area to hold | |
776 | all of the per-function information. Thus when processing of a nested | |
777 | function began the old per-function data had to be pushed onto a | |
778 | stack, and when the processing was finished, it had to be popped off the | |
779 | stack. GCC used to provide function pointers called | |
780 | @code{save_machine_status} and @code{restore_machine_status} to handle | |
781 | the saving and restoring of the target specific information. Since the | |
782 | single data area approach is no longer used, these pointers are no | |
783 | longer supported. | |
784 | ||
785 | @defmac INIT_EXPANDERS | |
786 | Macro called to initialize any target specific information. This macro | |
787 | is called once per function, before generation of any RTL has begun. | |
788 | The intention of this macro is to allow the initialization of the | |
789 | function pointer @code{init_machine_status}. | |
790 | @end defmac | |
791 | ||
792 | @deftypevar {void (*)(struct function *)} init_machine_status | |
793 | If this function pointer is non-@code{NULL} it will be called once per | |
794 | function, before function compilation starts, in order to allow the | |
795 | target to perform any target specific initialization of the | |
796 | @code{struct function} structure. It is intended that this would be | |
797 | used to initialize the @code{machine} of that structure. | |
798 | ||
799 | @code{struct machine_function} structures are expected to be freed by GC@. | |
800 | Generally, any memory that they reference must be allocated by using | |
801 | GC allocation, including the structure itself. | |
802 | @end deftypevar | |
803 | ||
804 | @node Storage Layout | |
805 | @section Storage Layout | |
806 | @cindex storage layout | |
807 | ||
808 | Note that the definitions of the macros in this table which are sizes or | |
809 | alignments measured in bits do not need to be constant. They can be C | |
810 | expressions that refer to static variables, such as the @code{target_flags}. | |
811 | @xref{Run-time Target}. | |
812 | ||
813 | @defmac BITS_BIG_ENDIAN | |
814 | Define this macro to have the value 1 if the most significant bit in a | |
815 | byte has the lowest number; otherwise define it to have the value zero. | |
816 | This means that bit-field instructions count from the most significant | |
817 | bit. If the machine has no bit-field instructions, then this must still | |
818 | be defined, but it doesn't matter which value it is defined to. This | |
819 | macro need not be a constant. | |
820 | ||
821 | This macro does not affect the way structure fields are packed into | |
822 | bytes or words; that is controlled by @code{BYTES_BIG_ENDIAN}. | |
823 | @end defmac | |
824 | ||
825 | @defmac BYTES_BIG_ENDIAN | |
826 | Define this macro to have the value 1 if the most significant byte in a | |
827 | word has the lowest number. This macro need not be a constant. | |
828 | @end defmac | |
829 | ||
830 | @defmac WORDS_BIG_ENDIAN | |
831 | Define this macro to have the value 1 if, in a multiword object, the | |
832 | most significant word has the lowest number. This applies to both | |
76c64076 | 833 | memory locations and registers; see @code{REG_WORDS_BIG_ENDIAN} if the |
834 | order of words in memory is not the same as the order in registers. This | |
202d6e5f | 835 | macro need not be a constant. |
836 | @end defmac | |
837 | ||
76c64076 | 838 | @defmac REG_WORDS_BIG_ENDIAN |
839 | On some machines, the order of words in a multiword object differs between | |
840 | registers in memory. In such a situation, define this macro to describe | |
841 | the order of words in a register. The macro @code{WORDS_BIG_ENDIAN} controls | |
842 | the order of words in memory. | |
843 | @end defmac | |
844 | ||
202d6e5f | 845 | @defmac FLOAT_WORDS_BIG_ENDIAN |
846 | Define this macro to have the value 1 if @code{DFmode}, @code{XFmode} or | |
847 | @code{TFmode} floating point numbers are stored in memory with the word | |
848 | containing the sign bit at the lowest address; otherwise define it to | |
849 | have the value 0. This macro need not be a constant. | |
850 | ||
851 | You need not define this macro if the ordering is the same as for | |
852 | multi-word integers. | |
853 | @end defmac | |
854 | ||
202d6e5f | 855 | @defmac BITS_PER_WORD |
856 | Number of bits in a word. If you do not define this macro, the default | |
857 | is @code{BITS_PER_UNIT * UNITS_PER_WORD}. | |
858 | @end defmac | |
859 | ||
860 | @defmac MAX_BITS_PER_WORD | |
861 | Maximum number of bits in a word. If this is undefined, the default is | |
862 | @code{BITS_PER_WORD}. Otherwise, it is the constant value that is the | |
863 | largest value that @code{BITS_PER_WORD} can have at run-time. | |
864 | @end defmac | |
865 | ||
866 | @defmac UNITS_PER_WORD | |
867 | Number of storage units in a word; normally the size of a general-purpose | |
868 | register, a power of two from 1 or 8. | |
869 | @end defmac | |
870 | ||
871 | @defmac MIN_UNITS_PER_WORD | |
872 | Minimum number of units in a word. If this is undefined, the default is | |
873 | @code{UNITS_PER_WORD}. Otherwise, it is the constant value that is the | |
874 | smallest value that @code{UNITS_PER_WORD} can have at run-time. | |
875 | @end defmac | |
876 | ||
202d6e5f | 877 | @defmac POINTER_SIZE |
878 | Width of a pointer, in bits. You must specify a value no wider than the | |
879 | width of @code{Pmode}. If it is not equal to the width of @code{Pmode}, | |
880 | you must define @code{POINTERS_EXTEND_UNSIGNED}. If you do not specify | |
881 | a value the default is @code{BITS_PER_WORD}. | |
882 | @end defmac | |
883 | ||
884 | @defmac POINTERS_EXTEND_UNSIGNED | |
885 | A C expression that determines how pointers should be extended from | |
886 | @code{ptr_mode} to either @code{Pmode} or @code{word_mode}. It is | |
887 | greater than zero if pointers should be zero-extended, zero if they | |
888 | should be sign-extended, and negative if some other sort of conversion | |
889 | is needed. In the last case, the extension is done by the target's | |
890 | @code{ptr_extend} instruction. | |
891 | ||
892 | You need not define this macro if the @code{ptr_mode}, @code{Pmode} | |
893 | and @code{word_mode} are all the same width. | |
894 | @end defmac | |
895 | ||
896 | @defmac PROMOTE_MODE (@var{m}, @var{unsignedp}, @var{type}) | |
897 | A macro to update @var{m} and @var{unsignedp} when an object whose type | |
898 | is @var{type} and which has the specified mode and signedness is to be | |
899 | stored in a register. This macro is only called when @var{type} is a | |
900 | scalar type. | |
901 | ||
902 | On most RISC machines, which only have operations that operate on a full | |
903 | register, define this macro to set @var{m} to @code{word_mode} if | |
904 | @var{m} is an integer mode narrower than @code{BITS_PER_WORD}. In most | |
905 | cases, only integer modes should be widened because wider-precision | |
906 | floating-point operations are usually more expensive than their narrower | |
907 | counterparts. | |
908 | ||
909 | For most machines, the macro definition does not change @var{unsignedp}. | |
910 | However, some machines, have instructions that preferentially handle | |
911 | either signed or unsigned quantities of certain modes. For example, on | |
912 | the DEC Alpha, 32-bit loads from memory and 32-bit add instructions | |
913 | sign-extend the result to 64 bits. On such machines, set | |
914 | @var{unsignedp} according to which kind of extension is more efficient. | |
915 | ||
916 | Do not define this macro if it would never modify @var{m}. | |
917 | @end defmac | |
918 | ||
919 | @hook TARGET_PROMOTE_FUNCTION_MODE | |
202d6e5f | 920 | |
921 | @defmac PARM_BOUNDARY | |
922 | Normal alignment required for function parameters on the stack, in | |
923 | bits. All stack parameters receive at least this much alignment | |
924 | regardless of data type. On most machines, this is the same as the | |
925 | size of an integer. | |
926 | @end defmac | |
927 | ||
928 | @defmac STACK_BOUNDARY | |
929 | Define this macro to the minimum alignment enforced by hardware for the | |
930 | stack pointer on this machine. The definition is a C expression for the | |
931 | desired alignment (measured in bits). This value is used as a default | |
932 | if @code{PREFERRED_STACK_BOUNDARY} is not defined. On most machines, | |
933 | this should be the same as @code{PARM_BOUNDARY}. | |
934 | @end defmac | |
935 | ||
936 | @defmac PREFERRED_STACK_BOUNDARY | |
937 | Define this macro if you wish to preserve a certain alignment for the | |
938 | stack pointer, greater than what the hardware enforces. The definition | |
939 | is a C expression for the desired alignment (measured in bits). This | |
940 | macro must evaluate to a value equal to or larger than | |
941 | @code{STACK_BOUNDARY}. | |
942 | @end defmac | |
943 | ||
944 | @defmac INCOMING_STACK_BOUNDARY | |
945 | Define this macro if the incoming stack boundary may be different | |
946 | from @code{PREFERRED_STACK_BOUNDARY}. This macro must evaluate | |
947 | to a value equal to or larger than @code{STACK_BOUNDARY}. | |
948 | @end defmac | |
949 | ||
950 | @defmac FUNCTION_BOUNDARY | |
951 | Alignment required for a function entry point, in bits. | |
952 | @end defmac | |
953 | ||
954 | @defmac BIGGEST_ALIGNMENT | |
955 | Biggest alignment that any data type can require on this machine, in | |
956 | bits. Note that this is not the biggest alignment that is supported, | |
957 | just the biggest alignment that, when violated, may cause a fault. | |
958 | @end defmac | |
959 | ||
960 | @defmac MALLOC_ABI_ALIGNMENT | |
961 | Alignment, in bits, a C conformant malloc implementation has to | |
962 | provide. If not defined, the default value is @code{BITS_PER_WORD}. | |
963 | @end defmac | |
964 | ||
965 | @defmac ATTRIBUTE_ALIGNED_VALUE | |
966 | Alignment used by the @code{__attribute__ ((aligned))} construct. If | |
967 | not defined, the default value is @code{BIGGEST_ALIGNMENT}. | |
968 | @end defmac | |
969 | ||
970 | @defmac MINIMUM_ATOMIC_ALIGNMENT | |
971 | If defined, the smallest alignment, in bits, that can be given to an | |
972 | object that can be referenced in one operation, without disturbing any | |
973 | nearby object. Normally, this is @code{BITS_PER_UNIT}, but may be larger | |
974 | on machines that don't have byte or half-word store operations. | |
975 | @end defmac | |
976 | ||
977 | @defmac BIGGEST_FIELD_ALIGNMENT | |
978 | Biggest alignment that any structure or union field can require on this | |
979 | machine, in bits. If defined, this overrides @code{BIGGEST_ALIGNMENT} for | |
980 | structure and union fields only, unless the field alignment has been set | |
981 | by the @code{__attribute__ ((aligned (@var{n})))} construct. | |
982 | @end defmac | |
983 | ||
984 | @defmac ADJUST_FIELD_ALIGN (@var{field}, @var{computed}) | |
985 | An expression for the alignment of a structure field @var{field} if the | |
986 | alignment computed in the usual way (including applying of | |
987 | @code{BIGGEST_ALIGNMENT} and @code{BIGGEST_FIELD_ALIGNMENT} to the | |
988 | alignment) is @var{computed}. It overrides alignment only if the | |
989 | field alignment has not been set by the | |
990 | @code{__attribute__ ((aligned (@var{n})))} construct. | |
991 | @end defmac | |
992 | ||
993 | @defmac MAX_STACK_ALIGNMENT | |
994 | Biggest stack alignment guaranteed by the backend. Use this macro | |
995 | to specify the maximum alignment of a variable on stack. | |
996 | ||
997 | If not defined, the default value is @code{STACK_BOUNDARY}. | |
998 | ||
999 | @c FIXME: The default should be @code{PREFERRED_STACK_BOUNDARY}. | |
1000 | @c But the fix for PR 32893 indicates that we can only guarantee | |
1001 | @c maximum stack alignment on stack up to @code{STACK_BOUNDARY}, not | |
1002 | @c @code{PREFERRED_STACK_BOUNDARY}, if stack alignment isn't supported. | |
1003 | @end defmac | |
1004 | ||
1005 | @defmac MAX_OFILE_ALIGNMENT | |
1006 | Biggest alignment supported by the object file format of this machine. | |
1007 | Use this macro to limit the alignment which can be specified using the | |
1008 | @code{__attribute__ ((aligned (@var{n})))} construct. If not defined, | |
1009 | the default value is @code{BIGGEST_ALIGNMENT}. | |
1010 | ||
1011 | On systems that use ELF, the default (in @file{config/elfos.h}) is | |
1012 | the largest supported 32-bit ELF section alignment representable on | |
3a4303e7 | 1013 | a 32-bit host e.g. @samp{(((uint64_t) 1 << 28) * 8)}. |
202d6e5f | 1014 | On 32-bit ELF the largest supported section alignment in bits is |
1015 | @samp{(0x80000000 * 8)}, but this is not representable on 32-bit hosts. | |
1016 | @end defmac | |
1017 | ||
1018 | @defmac DATA_ALIGNMENT (@var{type}, @var{basic-align}) | |
1019 | If defined, a C expression to compute the alignment for a variable in | |
1020 | the static store. @var{type} is the data type, and @var{basic-align} is | |
1021 | the alignment that the object would ordinarily have. The value of this | |
1022 | macro is used instead of that alignment to align the object. | |
1023 | ||
1024 | If this macro is not defined, then @var{basic-align} is used. | |
1025 | ||
1026 | @findex strcpy | |
1027 | One use of this macro is to increase alignment of medium-size data to | |
1028 | make it all fit in fewer cache lines. Another is to cause character | |
1029 | arrays to be word-aligned so that @code{strcpy} calls that copy | |
1030 | constants to character arrays can be done inline. | |
1031 | @end defmac | |
1032 | ||
a16734cd | 1033 | @defmac DATA_ABI_ALIGNMENT (@var{type}, @var{basic-align}) |
1034 | Similar to @code{DATA_ALIGNMENT}, but for the cases where the ABI mandates | |
1035 | some alignment increase, instead of optimization only purposes. E.g.@ | |
1036 | AMD x86-64 psABI says that variables with array type larger than 15 bytes | |
1037 | must be aligned to 16 byte boundaries. | |
1038 | ||
1039 | If this macro is not defined, then @var{basic-align} is used. | |
1040 | @end defmac | |
1041 | ||
202d6e5f | 1042 | @defmac CONSTANT_ALIGNMENT (@var{constant}, @var{basic-align}) |
1043 | If defined, a C expression to compute the alignment given to a constant | |
1044 | that is being placed in memory. @var{constant} is the constant and | |
1045 | @var{basic-align} is the alignment that the object would ordinarily | |
1046 | have. The value of this macro is used instead of that alignment to | |
1047 | align the object. | |
1048 | ||
1049 | If this macro is not defined, then @var{basic-align} is used. | |
1050 | ||
1051 | The typical use of this macro is to increase alignment for string | |
1052 | constants to be word aligned so that @code{strcpy} calls that copy | |
1053 | constants can be done inline. | |
1054 | @end defmac | |
1055 | ||
1056 | @defmac LOCAL_ALIGNMENT (@var{type}, @var{basic-align}) | |
1057 | If defined, a C expression to compute the alignment for a variable in | |
1058 | the local store. @var{type} is the data type, and @var{basic-align} is | |
1059 | the alignment that the object would ordinarily have. The value of this | |
1060 | macro is used instead of that alignment to align the object. | |
1061 | ||
1062 | If this macro is not defined, then @var{basic-align} is used. | |
1063 | ||
1064 | One use of this macro is to increase alignment of medium-size data to | |
1065 | make it all fit in fewer cache lines. | |
c6e790c5 | 1066 | |
2f05705b | 1067 | If the value of this macro has a type, it should be an unsigned type. |
202d6e5f | 1068 | @end defmac |
1069 | ||
482a44fa | 1070 | @hook TARGET_VECTOR_ALIGNMENT |
1071 | ||
202d6e5f | 1072 | @defmac STACK_SLOT_ALIGNMENT (@var{type}, @var{mode}, @var{basic-align}) |
1073 | If defined, a C expression to compute the alignment for stack slot. | |
1074 | @var{type} is the data type, @var{mode} is the widest mode available, | |
1075 | and @var{basic-align} is the alignment that the slot would ordinarily | |
1076 | have. The value of this macro is used instead of that alignment to | |
1077 | align the slot. | |
1078 | ||
1079 | If this macro is not defined, then @var{basic-align} is used when | |
1080 | @var{type} is @code{NULL}. Otherwise, @code{LOCAL_ALIGNMENT} will | |
1081 | be used. | |
1082 | ||
1083 | This macro is to set alignment of stack slot to the maximum alignment | |
1084 | of all possible modes which the slot may have. | |
c6e790c5 | 1085 | |
2f05705b | 1086 | If the value of this macro has a type, it should be an unsigned type. |
202d6e5f | 1087 | @end defmac |
1088 | ||
1089 | @defmac LOCAL_DECL_ALIGNMENT (@var{decl}) | |
1090 | If defined, a C expression to compute the alignment for a local | |
1091 | variable @var{decl}. | |
1092 | ||
1093 | If this macro is not defined, then | |
1094 | @code{LOCAL_ALIGNMENT (TREE_TYPE (@var{decl}), DECL_ALIGN (@var{decl}))} | |
1095 | is used. | |
1096 | ||
1097 | One use of this macro is to increase alignment of medium-size data to | |
1098 | make it all fit in fewer cache lines. | |
c6e790c5 | 1099 | |
2f05705b | 1100 | If the value of this macro has a type, it should be an unsigned type. |
202d6e5f | 1101 | @end defmac |
1102 | ||
1103 | @defmac MINIMUM_ALIGNMENT (@var{exp}, @var{mode}, @var{align}) | |
1104 | If defined, a C expression to compute the minimum required alignment | |
1105 | for dynamic stack realignment purposes for @var{exp} (a type or decl), | |
1106 | @var{mode}, assuming normal alignment @var{align}. | |
1107 | ||
1108 | If this macro is not defined, then @var{align} will be used. | |
1109 | @end defmac | |
1110 | ||
1111 | @defmac EMPTY_FIELD_BOUNDARY | |
1112 | Alignment in bits to be given to a structure bit-field that follows an | |
1113 | empty field such as @code{int : 0;}. | |
1114 | ||
1115 | If @code{PCC_BITFIELD_TYPE_MATTERS} is true, it overrides this macro. | |
1116 | @end defmac | |
1117 | ||
1118 | @defmac STRUCTURE_SIZE_BOUNDARY | |
1119 | Number of bits which any structure or union's size must be a multiple of. | |
1120 | Each structure or union's size is rounded up to a multiple of this. | |
1121 | ||
1122 | If you do not define this macro, the default is the same as | |
1123 | @code{BITS_PER_UNIT}. | |
1124 | @end defmac | |
1125 | ||
1126 | @defmac STRICT_ALIGNMENT | |
1127 | Define this macro to be the value 1 if instructions will fail to work | |
1128 | if given data not on the nominal alignment. If instructions will merely | |
1129 | go slower in that case, define this macro as 0. | |
1130 | @end defmac | |
1131 | ||
1132 | @defmac PCC_BITFIELD_TYPE_MATTERS | |
1133 | Define this if you wish to imitate the way many other C compilers handle | |
1134 | alignment of bit-fields and the structures that contain them. | |
1135 | ||
1136 | The behavior is that the type written for a named bit-field (@code{int}, | |
1137 | @code{short}, or other integer type) imposes an alignment for the entire | |
1138 | structure, as if the structure really did contain an ordinary field of | |
1139 | that type. In addition, the bit-field is placed within the structure so | |
1140 | that it would fit within such a field, not crossing a boundary for it. | |
1141 | ||
1142 | Thus, on most machines, a named bit-field whose type is written as | |
1143 | @code{int} would not cross a four-byte boundary, and would force | |
1144 | four-byte alignment for the whole structure. (The alignment used may | |
1145 | not be four bytes; it is controlled by the other alignment parameters.) | |
1146 | ||
1147 | An unnamed bit-field will not affect the alignment of the containing | |
1148 | structure. | |
1149 | ||
1150 | If the macro is defined, its definition should be a C expression; | |
1151 | a nonzero value for the expression enables this behavior. | |
1152 | ||
1153 | Note that if this macro is not defined, or its value is zero, some | |
1154 | bit-fields may cross more than one alignment boundary. The compiler can | |
1155 | support such references if there are @samp{insv}, @samp{extv}, and | |
1156 | @samp{extzv} insns that can directly reference memory. | |
1157 | ||
1158 | The other known way of making bit-fields work is to define | |
1159 | @code{STRUCTURE_SIZE_BOUNDARY} as large as @code{BIGGEST_ALIGNMENT}. | |
1160 | Then every structure can be accessed with fullwords. | |
1161 | ||
1162 | Unless the machine has bit-field instructions or you define | |
1163 | @code{STRUCTURE_SIZE_BOUNDARY} that way, you must define | |
1164 | @code{PCC_BITFIELD_TYPE_MATTERS} to have a nonzero value. | |
1165 | ||
1166 | If your aim is to make GCC use the same conventions for laying out | |
1167 | bit-fields as are used by another compiler, here is how to investigate | |
1168 | what the other compiler does. Compile and run this program: | |
1169 | ||
1170 | @smallexample | |
1171 | struct foo1 | |
1172 | @{ | |
1173 | char x; | |
1174 | char :0; | |
1175 | char y; | |
1176 | @}; | |
1177 | ||
1178 | struct foo2 | |
1179 | @{ | |
1180 | char x; | |
1181 | int :0; | |
1182 | char y; | |
1183 | @}; | |
1184 | ||
1185 | main () | |
1186 | @{ | |
1187 | printf ("Size of foo1 is %d\n", | |
1188 | sizeof (struct foo1)); | |
1189 | printf ("Size of foo2 is %d\n", | |
1190 | sizeof (struct foo2)); | |
1191 | exit (0); | |
1192 | @} | |
1193 | @end smallexample | |
1194 | ||
1195 | If this prints 2 and 5, then the compiler's behavior is what you would | |
1196 | get from @code{PCC_BITFIELD_TYPE_MATTERS}. | |
1197 | @end defmac | |
1198 | ||
1199 | @defmac BITFIELD_NBYTES_LIMITED | |
1200 | Like @code{PCC_BITFIELD_TYPE_MATTERS} except that its effect is limited | |
1201 | to aligning a bit-field within the structure. | |
1202 | @end defmac | |
1203 | ||
1204 | @hook TARGET_ALIGN_ANON_BITFIELD | |
202d6e5f | 1205 | |
1206 | @hook TARGET_NARROW_VOLATILE_BITFIELD | |
202d6e5f | 1207 | |
f91ed644 | 1208 | @hook TARGET_MEMBER_TYPE_FORCES_BLK |
202d6e5f | 1209 | |
1210 | @defmac ROUND_TYPE_ALIGN (@var{type}, @var{computed}, @var{specified}) | |
1211 | Define this macro as an expression for the alignment of a type (given | |
1212 | by @var{type} as a tree node) if the alignment computed in the usual | |
1213 | way is @var{computed} and the alignment explicitly specified was | |
1214 | @var{specified}. | |
1215 | ||
1216 | The default is to use @var{specified} if it is larger; otherwise, use | |
1217 | the smaller of @var{computed} and @code{BIGGEST_ALIGNMENT} | |
1218 | @end defmac | |
1219 | ||
1220 | @defmac MAX_FIXED_MODE_SIZE | |
1221 | An integer expression for the size in bits of the largest integer | |
1222 | machine mode that should actually be used. All integer machine modes of | |
1223 | this size or smaller can be used for structures and unions with the | |
1224 | appropriate sizes. If this macro is undefined, @code{GET_MODE_BITSIZE | |
1225 | (DImode)} is assumed. | |
1226 | @end defmac | |
1227 | ||
1228 | @defmac STACK_SAVEAREA_MODE (@var{save_level}) | |
3754d046 | 1229 | If defined, an expression of type @code{machine_mode} that |
202d6e5f | 1230 | specifies the mode of the save area operand of a |
1231 | @code{save_stack_@var{level}} named pattern (@pxref{Standard Names}). | |
1232 | @var{save_level} is one of @code{SAVE_BLOCK}, @code{SAVE_FUNCTION}, or | |
1233 | @code{SAVE_NONLOCAL} and selects which of the three named patterns is | |
1234 | having its mode specified. | |
1235 | ||
1236 | You need not define this macro if it always returns @code{Pmode}. You | |
1237 | would most commonly define this macro if the | |
1238 | @code{save_stack_@var{level}} patterns need to support both a 32- and a | |
1239 | 64-bit mode. | |
1240 | @end defmac | |
1241 | ||
1242 | @defmac STACK_SIZE_MODE | |
3754d046 | 1243 | If defined, an expression of type @code{machine_mode} that |
202d6e5f | 1244 | specifies the mode of the size increment operand of an |
1245 | @code{allocate_stack} named pattern (@pxref{Standard Names}). | |
1246 | ||
1247 | You need not define this macro if it always returns @code{word_mode}. | |
1248 | You would most commonly define this macro if the @code{allocate_stack} | |
1249 | pattern needs to support both a 32- and a 64-bit mode. | |
1250 | @end defmac | |
1251 | ||
1252 | @hook TARGET_LIBGCC_CMP_RETURN_MODE | |
202d6e5f | 1253 | |
1254 | @hook TARGET_LIBGCC_SHIFT_COUNT_MODE | |
202d6e5f | 1255 | |
1256 | @hook TARGET_UNWIND_WORD_MODE | |
202d6e5f | 1257 | |
202d6e5f | 1258 | @hook TARGET_MS_BITFIELD_LAYOUT_P |
202d6e5f | 1259 | |
1260 | @hook TARGET_DECIMAL_FLOAT_SUPPORTED_P | |
202d6e5f | 1261 | |
1262 | @hook TARGET_FIXED_POINT_SUPPORTED_P | |
202d6e5f | 1263 | |
1264 | @hook TARGET_EXPAND_TO_RTL_HOOK | |
202d6e5f | 1265 | |
1266 | @hook TARGET_INSTANTIATE_DECLS | |
202d6e5f | 1267 | |
1268 | @hook TARGET_MANGLE_TYPE | |
202d6e5f | 1269 | |
1270 | @node Type Layout | |
1271 | @section Layout of Source Language Data Types | |
1272 | ||
1273 | These macros define the sizes and other characteristics of the standard | |
1274 | basic data types used in programs being compiled. Unlike the macros in | |
1275 | the previous section, these apply to specific features of C and related | |
1276 | languages, rather than to fundamental aspects of storage layout. | |
1277 | ||
1278 | @defmac INT_TYPE_SIZE | |
1279 | A C expression for the size in bits of the type @code{int} on the | |
1280 | target machine. If you don't define this, the default is one word. | |
1281 | @end defmac | |
1282 | ||
1283 | @defmac SHORT_TYPE_SIZE | |
1284 | A C expression for the size in bits of the type @code{short} on the | |
1285 | target machine. If you don't define this, the default is half a word. | |
1286 | (If this would be less than one storage unit, it is rounded up to one | |
1287 | unit.) | |
1288 | @end defmac | |
1289 | ||
1290 | @defmac LONG_TYPE_SIZE | |
1291 | A C expression for the size in bits of the type @code{long} on the | |
1292 | target machine. If you don't define this, the default is one word. | |
1293 | @end defmac | |
1294 | ||
1295 | @defmac ADA_LONG_TYPE_SIZE | |
1296 | On some machines, the size used for the Ada equivalent of the type | |
1297 | @code{long} by a native Ada compiler differs from that used by C@. In | |
1298 | that situation, define this macro to be a C expression to be used for | |
1299 | the size of that type. If you don't define this, the default is the | |
1300 | value of @code{LONG_TYPE_SIZE}. | |
1301 | @end defmac | |
1302 | ||
1303 | @defmac LONG_LONG_TYPE_SIZE | |
1304 | A C expression for the size in bits of the type @code{long long} on the | |
1305 | target machine. If you don't define this, the default is two | |
1306 | words. If you want to support GNU Ada on your machine, the value of this | |
1307 | macro must be at least 64. | |
1308 | @end defmac | |
1309 | ||
1310 | @defmac CHAR_TYPE_SIZE | |
1311 | A C expression for the size in bits of the type @code{char} on the | |
1312 | target machine. If you don't define this, the default is | |
1313 | @code{BITS_PER_UNIT}. | |
1314 | @end defmac | |
1315 | ||
1316 | @defmac BOOL_TYPE_SIZE | |
1317 | A C expression for the size in bits of the C++ type @code{bool} and | |
1318 | C99 type @code{_Bool} on the target machine. If you don't define | |
1319 | this, and you probably shouldn't, the default is @code{CHAR_TYPE_SIZE}. | |
1320 | @end defmac | |
1321 | ||
1322 | @defmac FLOAT_TYPE_SIZE | |
1323 | A C expression for the size in bits of the type @code{float} on the | |
1324 | target machine. If you don't define this, the default is one word. | |
1325 | @end defmac | |
1326 | ||
1327 | @defmac DOUBLE_TYPE_SIZE | |
1328 | A C expression for the size in bits of the type @code{double} on the | |
1329 | target machine. If you don't define this, the default is two | |
1330 | words. | |
1331 | @end defmac | |
1332 | ||
1333 | @defmac LONG_DOUBLE_TYPE_SIZE | |
1334 | A C expression for the size in bits of the type @code{long double} on | |
1335 | the target machine. If you don't define this, the default is two | |
1336 | words. | |
1337 | @end defmac | |
1338 | ||
1339 | @defmac SHORT_FRACT_TYPE_SIZE | |
1340 | A C expression for the size in bits of the type @code{short _Fract} on | |
1341 | the target machine. If you don't define this, the default is | |
1342 | @code{BITS_PER_UNIT}. | |
1343 | @end defmac | |
1344 | ||
1345 | @defmac FRACT_TYPE_SIZE | |
1346 | A C expression for the size in bits of the type @code{_Fract} on | |
1347 | the target machine. If you don't define this, the default is | |
1348 | @code{BITS_PER_UNIT * 2}. | |
1349 | @end defmac | |
1350 | ||
1351 | @defmac LONG_FRACT_TYPE_SIZE | |
1352 | A C expression for the size in bits of the type @code{long _Fract} on | |
1353 | the target machine. If you don't define this, the default is | |
1354 | @code{BITS_PER_UNIT * 4}. | |
1355 | @end defmac | |
1356 | ||
1357 | @defmac LONG_LONG_FRACT_TYPE_SIZE | |
1358 | A C expression for the size in bits of the type @code{long long _Fract} on | |
1359 | the target machine. If you don't define this, the default is | |
1360 | @code{BITS_PER_UNIT * 8}. | |
1361 | @end defmac | |
1362 | ||
1363 | @defmac SHORT_ACCUM_TYPE_SIZE | |
1364 | A C expression for the size in bits of the type @code{short _Accum} on | |
1365 | the target machine. If you don't define this, the default is | |
1366 | @code{BITS_PER_UNIT * 2}. | |
1367 | @end defmac | |
1368 | ||
1369 | @defmac ACCUM_TYPE_SIZE | |
1370 | A C expression for the size in bits of the type @code{_Accum} on | |
1371 | the target machine. If you don't define this, the default is | |
1372 | @code{BITS_PER_UNIT * 4}. | |
1373 | @end defmac | |
1374 | ||
1375 | @defmac LONG_ACCUM_TYPE_SIZE | |
1376 | A C expression for the size in bits of the type @code{long _Accum} on | |
1377 | the target machine. If you don't define this, the default is | |
1378 | @code{BITS_PER_UNIT * 8}. | |
1379 | @end defmac | |
1380 | ||
1381 | @defmac LONG_LONG_ACCUM_TYPE_SIZE | |
1382 | A C expression for the size in bits of the type @code{long long _Accum} on | |
1383 | the target machine. If you don't define this, the default is | |
1384 | @code{BITS_PER_UNIT * 16}. | |
1385 | @end defmac | |
1386 | ||
f308a9b2 | 1387 | @defmac LIBGCC2_GNU_PREFIX |
1388 | This macro corresponds to the @code{TARGET_LIBFUNC_GNU_PREFIX} target | |
1389 | hook and should be defined if that hook is overriden to be true. It | |
1390 | causes function names in libgcc to be changed to use a @code{__gnu_} | |
1391 | prefix for their name rather than the default @code{__}. A port which | |
1392 | uses this macro should also arrange to use @file{t-gnu-prefix} in | |
1393 | the libgcc @file{config.host}. | |
1394 | @end defmac | |
1395 | ||
202d6e5f | 1396 | @defmac TARGET_FLT_EVAL_METHOD |
1397 | A C expression for the value for @code{FLT_EVAL_METHOD} in @file{float.h}, | |
1398 | assuming, if applicable, that the floating-point control word is in its | |
1399 | default state. If you do not define this macro the value of | |
1400 | @code{FLT_EVAL_METHOD} will be zero. | |
1401 | @end defmac | |
1402 | ||
1403 | @defmac WIDEST_HARDWARE_FP_SIZE | |
1404 | A C expression for the size in bits of the widest floating-point format | |
1405 | supported by the hardware. If you define this macro, you must specify a | |
1406 | value less than or equal to the value of @code{LONG_DOUBLE_TYPE_SIZE}. | |
1407 | If you do not define this macro, the value of @code{LONG_DOUBLE_TYPE_SIZE} | |
1408 | is the default. | |
1409 | @end defmac | |
1410 | ||
1411 | @defmac DEFAULT_SIGNED_CHAR | |
1412 | An expression whose value is 1 or 0, according to whether the type | |
1413 | @code{char} should be signed or unsigned by default. The user can | |
1414 | always override this default with the options @option{-fsigned-char} | |
1415 | and @option{-funsigned-char}. | |
1416 | @end defmac | |
1417 | ||
1418 | @hook TARGET_DEFAULT_SHORT_ENUMS | |
202d6e5f | 1419 | |
1420 | @defmac SIZE_TYPE | |
1421 | A C expression for a string describing the name of the data type to use | |
1422 | for size values. The typedef name @code{size_t} is defined using the | |
1423 | contents of the string. | |
1424 | ||
1425 | The string can contain more than one keyword. If so, separate them with | |
1426 | spaces, and write first any length keyword, then @code{unsigned} if | |
1427 | appropriate, and finally @code{int}. The string must exactly match one | |
1428 | of the data type names defined in the function | |
816c3ff2 | 1429 | @code{c_common_nodes_and_builtins} in the file @file{c-family/c-common.c}. |
1430 | You may not omit @code{int} or change the order---that would cause the | |
1431 | compiler to crash on startup. | |
202d6e5f | 1432 | |
1433 | If you don't define this macro, the default is @code{"long unsigned | |
1434 | int"}. | |
1435 | @end defmac | |
1436 | ||
748e5d45 | 1437 | @defmac SIZETYPE |
1438 | GCC defines internal types (@code{sizetype}, @code{ssizetype}, | |
1439 | @code{bitsizetype} and @code{sbitsizetype}) for expressions | |
1440 | dealing with size. This macro is a C expression for a string describing | |
1441 | the name of the data type from which the precision of @code{sizetype} | |
1442 | is extracted. | |
1443 | ||
1444 | The string has the same restrictions as @code{SIZE_TYPE} string. | |
1445 | ||
1446 | If you don't define this macro, the default is @code{SIZE_TYPE}. | |
1447 | @end defmac | |
1448 | ||
202d6e5f | 1449 | @defmac PTRDIFF_TYPE |
1450 | A C expression for a string describing the name of the data type to use | |
1451 | for the result of subtracting two pointers. The typedef name | |
1452 | @code{ptrdiff_t} is defined using the contents of the string. See | |
1453 | @code{SIZE_TYPE} above for more information. | |
1454 | ||
1455 | If you don't define this macro, the default is @code{"long int"}. | |
1456 | @end defmac | |
1457 | ||
1458 | @defmac WCHAR_TYPE | |
1459 | A C expression for a string describing the name of the data type to use | |
1460 | for wide characters. The typedef name @code{wchar_t} is defined using | |
1461 | the contents of the string. See @code{SIZE_TYPE} above for more | |
1462 | information. | |
1463 | ||
1464 | If you don't define this macro, the default is @code{"int"}. | |
1465 | @end defmac | |
1466 | ||
1467 | @defmac WCHAR_TYPE_SIZE | |
1468 | A C expression for the size in bits of the data type for wide | |
1469 | characters. This is used in @code{cpp}, which cannot make use of | |
1470 | @code{WCHAR_TYPE}. | |
1471 | @end defmac | |
1472 | ||
1473 | @defmac WINT_TYPE | |
1474 | A C expression for a string describing the name of the data type to | |
1475 | use for wide characters passed to @code{printf} and returned from | |
1476 | @code{getwc}. The typedef name @code{wint_t} is defined using the | |
1477 | contents of the string. See @code{SIZE_TYPE} above for more | |
1478 | information. | |
1479 | ||
1480 | If you don't define this macro, the default is @code{"unsigned int"}. | |
1481 | @end defmac | |
1482 | ||
1483 | @defmac INTMAX_TYPE | |
1484 | A C expression for a string describing the name of the data type that | |
1485 | can represent any value of any standard or extended signed integer type. | |
1486 | The typedef name @code{intmax_t} is defined using the contents of the | |
1487 | string. See @code{SIZE_TYPE} above for more information. | |
1488 | ||
1489 | If you don't define this macro, the default is the first of | |
1490 | @code{"int"}, @code{"long int"}, or @code{"long long int"} that has as | |
1491 | much precision as @code{long long int}. | |
1492 | @end defmac | |
1493 | ||
1494 | @defmac UINTMAX_TYPE | |
1495 | A C expression for a string describing the name of the data type that | |
1496 | can represent any value of any standard or extended unsigned integer | |
1497 | type. The typedef name @code{uintmax_t} is defined using the contents | |
1498 | of the string. See @code{SIZE_TYPE} above for more information. | |
1499 | ||
1500 | If you don't define this macro, the default is the first of | |
1501 | @code{"unsigned int"}, @code{"long unsigned int"}, or @code{"long long | |
1502 | unsigned int"} that has as much precision as @code{long long unsigned | |
1503 | int}. | |
1504 | @end defmac | |
1505 | ||
1506 | @defmac SIG_ATOMIC_TYPE | |
1507 | @defmacx INT8_TYPE | |
1508 | @defmacx INT16_TYPE | |
1509 | @defmacx INT32_TYPE | |
1510 | @defmacx INT64_TYPE | |
1511 | @defmacx UINT8_TYPE | |
1512 | @defmacx UINT16_TYPE | |
1513 | @defmacx UINT32_TYPE | |
1514 | @defmacx UINT64_TYPE | |
1515 | @defmacx INT_LEAST8_TYPE | |
1516 | @defmacx INT_LEAST16_TYPE | |
1517 | @defmacx INT_LEAST32_TYPE | |
1518 | @defmacx INT_LEAST64_TYPE | |
1519 | @defmacx UINT_LEAST8_TYPE | |
1520 | @defmacx UINT_LEAST16_TYPE | |
1521 | @defmacx UINT_LEAST32_TYPE | |
1522 | @defmacx UINT_LEAST64_TYPE | |
1523 | @defmacx INT_FAST8_TYPE | |
1524 | @defmacx INT_FAST16_TYPE | |
1525 | @defmacx INT_FAST32_TYPE | |
1526 | @defmacx INT_FAST64_TYPE | |
1527 | @defmacx UINT_FAST8_TYPE | |
1528 | @defmacx UINT_FAST16_TYPE | |
1529 | @defmacx UINT_FAST32_TYPE | |
1530 | @defmacx UINT_FAST64_TYPE | |
1531 | @defmacx INTPTR_TYPE | |
1532 | @defmacx UINTPTR_TYPE | |
1533 | C expressions for the standard types @code{sig_atomic_t}, | |
1534 | @code{int8_t}, @code{int16_t}, @code{int32_t}, @code{int64_t}, | |
1535 | @code{uint8_t}, @code{uint16_t}, @code{uint32_t}, @code{uint64_t}, | |
1536 | @code{int_least8_t}, @code{int_least16_t}, @code{int_least32_t}, | |
1537 | @code{int_least64_t}, @code{uint_least8_t}, @code{uint_least16_t}, | |
1538 | @code{uint_least32_t}, @code{uint_least64_t}, @code{int_fast8_t}, | |
1539 | @code{int_fast16_t}, @code{int_fast32_t}, @code{int_fast64_t}, | |
1540 | @code{uint_fast8_t}, @code{uint_fast16_t}, @code{uint_fast32_t}, | |
1541 | @code{uint_fast64_t}, @code{intptr_t}, and @code{uintptr_t}. See | |
1542 | @code{SIZE_TYPE} above for more information. | |
1543 | ||
1544 | If any of these macros evaluates to a null pointer, the corresponding | |
1545 | type is not supported; if GCC is configured to provide | |
1546 | @code{<stdint.h>} in such a case, the header provided may not conform | |
1547 | to C99, depending on the type in question. The defaults for all of | |
1548 | these macros are null pointers. | |
1549 | @end defmac | |
1550 | ||
1551 | @defmac TARGET_PTRMEMFUNC_VBIT_LOCATION | |
1552 | The C++ compiler represents a pointer-to-member-function with a struct | |
1553 | that looks like: | |
1554 | ||
1555 | @smallexample | |
1556 | struct @{ | |
1557 | union @{ | |
1558 | void (*fn)(); | |
1559 | ptrdiff_t vtable_index; | |
1560 | @}; | |
1561 | ptrdiff_t delta; | |
1562 | @}; | |
1563 | @end smallexample | |
1564 | ||
1565 | @noindent | |
1566 | The C++ compiler must use one bit to indicate whether the function that | |
1567 | will be called through a pointer-to-member-function is virtual. | |
1568 | Normally, we assume that the low-order bit of a function pointer must | |
1569 | always be zero. Then, by ensuring that the vtable_index is odd, we can | |
1570 | distinguish which variant of the union is in use. But, on some | |
1571 | platforms function pointers can be odd, and so this doesn't work. In | |
1572 | that case, we use the low-order bit of the @code{delta} field, and shift | |
1573 | the remainder of the @code{delta} field to the left. | |
1574 | ||
1575 | GCC will automatically make the right selection about where to store | |
1576 | this bit using the @code{FUNCTION_BOUNDARY} setting for your platform. | |
1577 | However, some platforms such as ARM/Thumb have @code{FUNCTION_BOUNDARY} | |
1578 | set such that functions always start at even addresses, but the lowest | |
1579 | bit of pointers to functions indicate whether the function at that | |
1580 | address is in ARM or Thumb mode. If this is the case of your | |
1581 | architecture, you should define this macro to | |
1582 | @code{ptrmemfunc_vbit_in_delta}. | |
1583 | ||
1584 | In general, you should not have to define this macro. On architectures | |
1585 | in which function addresses are always even, according to | |
1586 | @code{FUNCTION_BOUNDARY}, GCC will automatically define this macro to | |
1587 | @code{ptrmemfunc_vbit_in_pfn}. | |
1588 | @end defmac | |
1589 | ||
1590 | @defmac TARGET_VTABLE_USES_DESCRIPTORS | |
1591 | Normally, the C++ compiler uses function pointers in vtables. This | |
1592 | macro allows the target to change to use ``function descriptors'' | |
1593 | instead. Function descriptors are found on targets for whom a | |
1594 | function pointer is actually a small data structure. Normally the | |
1595 | data structure consists of the actual code address plus a data | |
1596 | pointer to which the function's data is relative. | |
1597 | ||
1598 | If vtables are used, the value of this macro should be the number | |
1599 | of words that the function descriptor occupies. | |
1600 | @end defmac | |
1601 | ||
1602 | @defmac TARGET_VTABLE_ENTRY_ALIGN | |
1603 | By default, the vtable entries are void pointers, the so the alignment | |
1604 | is the same as pointer alignment. The value of this macro specifies | |
1605 | the alignment of the vtable entry in bits. It should be defined only | |
1606 | when special alignment is necessary. */ | |
1607 | @end defmac | |
1608 | ||
1609 | @defmac TARGET_VTABLE_DATA_ENTRY_DISTANCE | |
1610 | There are a few non-descriptor entries in the vtable at offsets below | |
1611 | zero. If these entries must be padded (say, to preserve the alignment | |
1612 | specified by @code{TARGET_VTABLE_ENTRY_ALIGN}), set this to the number | |
1613 | of words in each data entry. | |
1614 | @end defmac | |
1615 | ||
1616 | @node Registers | |
1617 | @section Register Usage | |
1618 | @cindex register usage | |
1619 | ||
1620 | This section explains how to describe what registers the target machine | |
1621 | has, and how (in general) they can be used. | |
1622 | ||
1623 | The description of which registers a specific instruction can use is | |
1624 | done with register classes; see @ref{Register Classes}. For information | |
1625 | on using registers to access a stack frame, see @ref{Frame Registers}. | |
1626 | For passing values in registers, see @ref{Register Arguments}. | |
1627 | For returning values in registers, see @ref{Scalar Return}. | |
1628 | ||
1629 | @menu | |
1630 | * Register Basics:: Number and kinds of registers. | |
1631 | * Allocation Order:: Order in which registers are allocated. | |
1632 | * Values in Registers:: What kinds of values each reg can hold. | |
1633 | * Leaf Functions:: Renumbering registers for leaf functions. | |
1634 | * Stack Registers:: Handling a register stack such as 80387. | |
1635 | @end menu | |
1636 | ||
1637 | @node Register Basics | |
1638 | @subsection Basic Characteristics of Registers | |
1639 | ||
1640 | @c prevent bad page break with this line | |
1641 | Registers have various characteristics. | |
1642 | ||
1643 | @defmac FIRST_PSEUDO_REGISTER | |
1644 | Number of hardware registers known to the compiler. They receive | |
1645 | numbers 0 through @code{FIRST_PSEUDO_REGISTER-1}; thus, the first | |
1646 | pseudo register's number really is assigned the number | |
1647 | @code{FIRST_PSEUDO_REGISTER}. | |
1648 | @end defmac | |
1649 | ||
1650 | @defmac FIXED_REGISTERS | |
1651 | @cindex fixed register | |
1652 | An initializer that says which registers are used for fixed purposes | |
1653 | all throughout the compiled code and are therefore not available for | |
1654 | general allocation. These would include the stack pointer, the frame | |
1655 | pointer (except on machines where that can be used as a general | |
1656 | register when no frame pointer is needed), the program counter on | |
1657 | machines where that is considered one of the addressable registers, | |
1658 | and any other numbered register with a standard use. | |
1659 | ||
1660 | This information is expressed as a sequence of numbers, separated by | |
1661 | commas and surrounded by braces. The @var{n}th number is 1 if | |
1662 | register @var{n} is fixed, 0 otherwise. | |
1663 | ||
1664 | The table initialized from this macro, and the table initialized by | |
1665 | the following one, may be overridden at run time either automatically, | |
1666 | by the actions of the macro @code{CONDITIONAL_REGISTER_USAGE}, or by | |
1667 | the user with the command options @option{-ffixed-@var{reg}}, | |
1668 | @option{-fcall-used-@var{reg}} and @option{-fcall-saved-@var{reg}}. | |
1669 | @end defmac | |
1670 | ||
1671 | @defmac CALL_USED_REGISTERS | |
1672 | @cindex call-used register | |
1673 | @cindex call-clobbered register | |
1674 | @cindex call-saved register | |
1675 | Like @code{FIXED_REGISTERS} but has 1 for each register that is | |
1676 | clobbered (in general) by function calls as well as for fixed | |
1677 | registers. This macro therefore identifies the registers that are not | |
1678 | available for general allocation of values that must live across | |
1679 | function calls. | |
1680 | ||
1681 | If a register has 0 in @code{CALL_USED_REGISTERS}, the compiler | |
1682 | automatically saves it on function entry and restores it on function | |
1683 | exit, if the register is used within the function. | |
1684 | @end defmac | |
1685 | ||
1686 | @defmac CALL_REALLY_USED_REGISTERS | |
1687 | @cindex call-used register | |
1688 | @cindex call-clobbered register | |
1689 | @cindex call-saved register | |
1690 | Like @code{CALL_USED_REGISTERS} except this macro doesn't require | |
1691 | that the entire set of @code{FIXED_REGISTERS} be included. | |
1692 | (@code{CALL_USED_REGISTERS} must be a superset of @code{FIXED_REGISTERS}). | |
1693 | This macro is optional. If not specified, it defaults to the value | |
1694 | of @code{CALL_USED_REGISTERS}. | |
1695 | @end defmac | |
1696 | ||
1697 | @defmac HARD_REGNO_CALL_PART_CLOBBERED (@var{regno}, @var{mode}) | |
1698 | @cindex call-used register | |
1699 | @cindex call-clobbered register | |
1700 | @cindex call-saved register | |
1701 | A C expression that is nonzero if it is not permissible to store a | |
1702 | value of mode @var{mode} in hard register number @var{regno} across a | |
1703 | call without some part of it being clobbered. For most machines this | |
1704 | macro need not be defined. It is only required for machines that do not | |
1705 | preserve the entire contents of a register across a call. | |
1706 | @end defmac | |
1707 | ||
1708 | @findex fixed_regs | |
1709 | @findex call_used_regs | |
1710 | @findex global_regs | |
1711 | @findex reg_names | |
1712 | @findex reg_class_contents | |
b2d7ede1 | 1713 | @hook TARGET_CONDITIONAL_REGISTER_USAGE |
202d6e5f | 1714 | |
1715 | @defmac INCOMING_REGNO (@var{out}) | |
1716 | Define this macro if the target machine has register windows. This C | |
1717 | expression returns the register number as seen by the called function | |
1718 | corresponding to the register number @var{out} as seen by the calling | |
1719 | function. Return @var{out} if register number @var{out} is not an | |
1720 | outbound register. | |
1721 | @end defmac | |
1722 | ||
1723 | @defmac OUTGOING_REGNO (@var{in}) | |
1724 | Define this macro if the target machine has register windows. This C | |
1725 | expression returns the register number as seen by the calling function | |
1726 | corresponding to the register number @var{in} as seen by the called | |
1727 | function. Return @var{in} if register number @var{in} is not an inbound | |
1728 | register. | |
1729 | @end defmac | |
1730 | ||
1731 | @defmac LOCAL_REGNO (@var{regno}) | |
1732 | Define this macro if the target machine has register windows. This C | |
1733 | expression returns true if the register is call-saved but is in the | |
1734 | register window. Unlike most call-saved registers, such registers | |
1735 | need not be explicitly restored on function exit or during non-local | |
1736 | gotos. | |
1737 | @end defmac | |
1738 | ||
1739 | @defmac PC_REGNUM | |
1740 | If the program counter has a register number, define this as that | |
1741 | register number. Otherwise, do not define it. | |
1742 | @end defmac | |
1743 | ||
1744 | @node Allocation Order | |
1745 | @subsection Order of Allocation of Registers | |
1746 | @cindex order of register allocation | |
1747 | @cindex register allocation order | |
1748 | ||
1749 | @c prevent bad page break with this line | |
1750 | Registers are allocated in order. | |
1751 | ||
1752 | @defmac REG_ALLOC_ORDER | |
1753 | If defined, an initializer for a vector of integers, containing the | |
1754 | numbers of hard registers in the order in which GCC should prefer | |
1755 | to use them (from most preferred to least). | |
1756 | ||
1757 | If this macro is not defined, registers are used lowest numbered first | |
1758 | (all else being equal). | |
1759 | ||
1760 | One use of this macro is on machines where the highest numbered | |
1761 | registers must always be saved and the save-multiple-registers | |
1762 | instruction supports only sequences of consecutive registers. On such | |
1763 | machines, define @code{REG_ALLOC_ORDER} to be an initializer that lists | |
1764 | the highest numbered allocable register first. | |
1765 | @end defmac | |
1766 | ||
1767 | @defmac ADJUST_REG_ALLOC_ORDER | |
1768 | A C statement (sans semicolon) to choose the order in which to allocate | |
1769 | hard registers for pseudo-registers local to a basic block. | |
1770 | ||
1771 | Store the desired register order in the array @code{reg_alloc_order}. | |
1772 | Element 0 should be the register to allocate first; element 1, the next | |
1773 | register; and so on. | |
1774 | ||
1775 | The macro body should not assume anything about the contents of | |
1776 | @code{reg_alloc_order} before execution of the macro. | |
1777 | ||
1778 | On most machines, it is not necessary to define this macro. | |
1779 | @end defmac | |
1780 | ||
1781 | @defmac HONOR_REG_ALLOC_ORDER | |
1782 | Normally, IRA tries to estimate the costs for saving a register in the | |
1783 | prologue and restoring it in the epilogue. This discourages it from | |
1784 | using call-saved registers. If a machine wants to ensure that IRA | |
1785 | allocates registers in the order given by REG_ALLOC_ORDER even if some | |
d44f2f7c | 1786 | call-saved registers appear earlier than call-used ones, then define this |
1787 | macro as a C expression to nonzero. Default is 0. | |
202d6e5f | 1788 | @end defmac |
1789 | ||
1790 | @defmac IRA_HARD_REGNO_ADD_COST_MULTIPLIER (@var{regno}) | |
1791 | In some case register allocation order is not enough for the | |
1792 | Integrated Register Allocator (@acronym{IRA}) to generate a good code. | |
1793 | If this macro is defined, it should return a floating point value | |
1794 | based on @var{regno}. The cost of using @var{regno} for a pseudo will | |
1795 | be increased by approximately the pseudo's usage frequency times the | |
1796 | value returned by this macro. Not defining this macro is equivalent | |
1797 | to having it always return @code{0.0}. | |
1798 | ||
1799 | On most machines, it is not necessary to define this macro. | |
1800 | @end defmac | |
1801 | ||
1802 | @node Values in Registers | |
1803 | @subsection How Values Fit in Registers | |
1804 | ||
1805 | This section discusses the macros that describe which kinds of values | |
1806 | (specifically, which machine modes) each register can hold, and how many | |
1807 | consecutive registers are needed for a given mode. | |
1808 | ||
1809 | @defmac HARD_REGNO_NREGS (@var{regno}, @var{mode}) | |
1810 | A C expression for the number of consecutive hard registers, starting | |
1811 | at register number @var{regno}, required to hold a value of mode | |
1812 | @var{mode}. This macro must never return zero, even if a register | |
1813 | cannot hold the requested mode - indicate that with HARD_REGNO_MODE_OK | |
1814 | and/or CANNOT_CHANGE_MODE_CLASS instead. | |
1815 | ||
1816 | On a machine where all registers are exactly one word, a suitable | |
1817 | definition of this macro is | |
1818 | ||
1819 | @smallexample | |
1820 | #define HARD_REGNO_NREGS(REGNO, MODE) \ | |
1821 | ((GET_MODE_SIZE (MODE) + UNITS_PER_WORD - 1) \ | |
1822 | / UNITS_PER_WORD) | |
1823 | @end smallexample | |
1824 | @end defmac | |
1825 | ||
1826 | @defmac HARD_REGNO_NREGS_HAS_PADDING (@var{regno}, @var{mode}) | |
1827 | A C expression that is nonzero if a value of mode @var{mode}, stored | |
1828 | in memory, ends with padding that causes it to take up more space than | |
1829 | in registers starting at register number @var{regno} (as determined by | |
1830 | multiplying GCC's notion of the size of the register when containing | |
1831 | this mode by the number of registers returned by | |
1832 | @code{HARD_REGNO_NREGS}). By default this is zero. | |
1833 | ||
1834 | For example, if a floating-point value is stored in three 32-bit | |
1835 | registers but takes up 128 bits in memory, then this would be | |
1836 | nonzero. | |
1837 | ||
1838 | This macros only needs to be defined if there are cases where | |
1839 | @code{subreg_get_info} | |
1840 | would otherwise wrongly determine that a @code{subreg} can be | |
1841 | represented by an offset to the register number, when in fact such a | |
1842 | @code{subreg} would contain some of the padding not stored in | |
1843 | registers and so not be representable. | |
1844 | @end defmac | |
1845 | ||
1846 | @defmac HARD_REGNO_NREGS_WITH_PADDING (@var{regno}, @var{mode}) | |
1847 | For values of @var{regno} and @var{mode} for which | |
1848 | @code{HARD_REGNO_NREGS_HAS_PADDING} returns nonzero, a C expression | |
1849 | returning the greater number of registers required to hold the value | |
1850 | including any padding. In the example above, the value would be four. | |
1851 | @end defmac | |
1852 | ||
1853 | @defmac REGMODE_NATURAL_SIZE (@var{mode}) | |
1854 | Define this macro if the natural size of registers that hold values | |
1855 | of mode @var{mode} is not the word size. It is a C expression that | |
1856 | should give the natural size in bytes for the specified mode. It is | |
1857 | used by the register allocator to try to optimize its results. This | |
1858 | happens for example on SPARC 64-bit where the natural size of | |
1859 | floating-point registers is still 32-bit. | |
1860 | @end defmac | |
1861 | ||
1862 | @defmac HARD_REGNO_MODE_OK (@var{regno}, @var{mode}) | |
1863 | A C expression that is nonzero if it is permissible to store a value | |
1864 | of mode @var{mode} in hard register number @var{regno} (or in several | |
1865 | registers starting with that one). For a machine where all registers | |
1866 | are equivalent, a suitable definition is | |
1867 | ||
1868 | @smallexample | |
1869 | #define HARD_REGNO_MODE_OK(REGNO, MODE) 1 | |
1870 | @end smallexample | |
1871 | ||
1872 | You need not include code to check for the numbers of fixed registers, | |
1873 | because the allocation mechanism considers them to be always occupied. | |
1874 | ||
1875 | @cindex register pairs | |
1876 | On some machines, double-precision values must be kept in even/odd | |
1877 | register pairs. You can implement that by defining this macro to reject | |
1878 | odd register numbers for such modes. | |
1879 | ||
1880 | The minimum requirement for a mode to be OK in a register is that the | |
1881 | @samp{mov@var{mode}} instruction pattern support moves between the | |
1882 | register and other hard register in the same class and that moving a | |
1883 | value into the register and back out not alter it. | |
1884 | ||
1885 | Since the same instruction used to move @code{word_mode} will work for | |
1886 | all narrower integer modes, it is not necessary on any machine for | |
1887 | @code{HARD_REGNO_MODE_OK} to distinguish between these modes, provided | |
1888 | you define patterns @samp{movhi}, etc., to take advantage of this. This | |
1889 | is useful because of the interaction between @code{HARD_REGNO_MODE_OK} | |
1890 | and @code{MODES_TIEABLE_P}; it is very desirable for all integer modes | |
1891 | to be tieable. | |
1892 | ||
1893 | Many machines have special registers for floating point arithmetic. | |
1894 | Often people assume that floating point machine modes are allowed only | |
1895 | in floating point registers. This is not true. Any registers that | |
1896 | can hold integers can safely @emph{hold} a floating point machine | |
1897 | mode, whether or not floating arithmetic can be done on it in those | |
1898 | registers. Integer move instructions can be used to move the values. | |
1899 | ||
1900 | On some machines, though, the converse is true: fixed-point machine | |
1901 | modes may not go in floating registers. This is true if the floating | |
1902 | registers normalize any value stored in them, because storing a | |
1903 | non-floating value there would garble it. In this case, | |
1904 | @code{HARD_REGNO_MODE_OK} should reject fixed-point machine modes in | |
1905 | floating registers. But if the floating registers do not automatically | |
1906 | normalize, if you can store any bit pattern in one and retrieve it | |
1907 | unchanged without a trap, then any machine mode may go in a floating | |
1908 | register, so you can define this macro to say so. | |
1909 | ||
1910 | The primary significance of special floating registers is rather that | |
1911 | they are the registers acceptable in floating point arithmetic | |
1912 | instructions. However, this is of no concern to | |
1913 | @code{HARD_REGNO_MODE_OK}. You handle it by writing the proper | |
1914 | constraints for those instructions. | |
1915 | ||
1916 | On some machines, the floating registers are especially slow to access, | |
1917 | so that it is better to store a value in a stack frame than in such a | |
1918 | register if floating point arithmetic is not being done. As long as the | |
1919 | floating registers are not in class @code{GENERAL_REGS}, they will not | |
1920 | be used unless some pattern's constraint asks for one. | |
1921 | @end defmac | |
1922 | ||
1923 | @defmac HARD_REGNO_RENAME_OK (@var{from}, @var{to}) | |
1924 | A C expression that is nonzero if it is OK to rename a hard register | |
1925 | @var{from} to another hard register @var{to}. | |
1926 | ||
1927 | One common use of this macro is to prevent renaming of a register to | |
1928 | another register that is not saved by a prologue in an interrupt | |
1929 | handler. | |
1930 | ||
1931 | The default is always nonzero. | |
1932 | @end defmac | |
1933 | ||
1934 | @defmac MODES_TIEABLE_P (@var{mode1}, @var{mode2}) | |
1935 | A C expression that is nonzero if a value of mode | |
1936 | @var{mode1} is accessible in mode @var{mode2} without copying. | |
1937 | ||
1938 | If @code{HARD_REGNO_MODE_OK (@var{r}, @var{mode1})} and | |
1939 | @code{HARD_REGNO_MODE_OK (@var{r}, @var{mode2})} are always the same for | |
1940 | any @var{r}, then @code{MODES_TIEABLE_P (@var{mode1}, @var{mode2})} | |
1941 | should be nonzero. If they differ for any @var{r}, you should define | |
1942 | this macro to return zero unless some other mechanism ensures the | |
1943 | accessibility of the value in a narrower mode. | |
1944 | ||
1945 | You should define this macro to return nonzero in as many cases as | |
1946 | possible since doing so will allow GCC to perform better register | |
1947 | allocation. | |
1948 | @end defmac | |
1949 | ||
1950 | @hook TARGET_HARD_REGNO_SCRATCH_OK | |
202d6e5f | 1951 | |
1952 | @defmac AVOID_CCMODE_COPIES | |
1953 | Define this macro if the compiler should avoid copies to/from @code{CCmode} | |
1954 | registers. You should only define this macro if support for copying to/from | |
1955 | @code{CCmode} is incomplete. | |
1956 | @end defmac | |
1957 | ||
1958 | @node Leaf Functions | |
1959 | @subsection Handling Leaf Functions | |
1960 | ||
1961 | @cindex leaf functions | |
1962 | @cindex functions, leaf | |
1963 | On some machines, a leaf function (i.e., one which makes no calls) can run | |
1964 | more efficiently if it does not make its own register window. Often this | |
1965 | means it is required to receive its arguments in the registers where they | |
1966 | are passed by the caller, instead of the registers where they would | |
1967 | normally arrive. | |
1968 | ||
1969 | The special treatment for leaf functions generally applies only when | |
1970 | other conditions are met; for example, often they may use only those | |
1971 | registers for its own variables and temporaries. We use the term ``leaf | |
1972 | function'' to mean a function that is suitable for this special | |
1973 | handling, so that functions with no calls are not necessarily ``leaf | |
1974 | functions''. | |
1975 | ||
1976 | GCC assigns register numbers before it knows whether the function is | |
1977 | suitable for leaf function treatment. So it needs to renumber the | |
1978 | registers in order to output a leaf function. The following macros | |
1979 | accomplish this. | |
1980 | ||
1981 | @defmac LEAF_REGISTERS | |
1982 | Name of a char vector, indexed by hard register number, which | |
1983 | contains 1 for a register that is allowable in a candidate for leaf | |
1984 | function treatment. | |
1985 | ||
1986 | If leaf function treatment involves renumbering the registers, then the | |
1987 | registers marked here should be the ones before renumbering---those that | |
1988 | GCC would ordinarily allocate. The registers which will actually be | |
1989 | used in the assembler code, after renumbering, should not be marked with 1 | |
1990 | in this vector. | |
1991 | ||
1992 | Define this macro only if the target machine offers a way to optimize | |
1993 | the treatment of leaf functions. | |
1994 | @end defmac | |
1995 | ||
1996 | @defmac LEAF_REG_REMAP (@var{regno}) | |
1997 | A C expression whose value is the register number to which @var{regno} | |
1998 | should be renumbered, when a function is treated as a leaf function. | |
1999 | ||
2000 | If @var{regno} is a register number which should not appear in a leaf | |
2001 | function before renumbering, then the expression should yield @minus{}1, which | |
2002 | will cause the compiler to abort. | |
2003 | ||
2004 | Define this macro only if the target machine offers a way to optimize the | |
2005 | treatment of leaf functions, and registers need to be renumbered to do | |
2006 | this. | |
2007 | @end defmac | |
2008 | ||
2009 | @findex current_function_is_leaf | |
2010 | @findex current_function_uses_only_leaf_regs | |
2011 | @code{TARGET_ASM_FUNCTION_PROLOGUE} and | |
2012 | @code{TARGET_ASM_FUNCTION_EPILOGUE} must usually treat leaf functions | |
2013 | specially. They can test the C variable @code{current_function_is_leaf} | |
2014 | which is nonzero for leaf functions. @code{current_function_is_leaf} is | |
2015 | set prior to local register allocation and is valid for the remaining | |
2016 | compiler passes. They can also test the C variable | |
2017 | @code{current_function_uses_only_leaf_regs} which is nonzero for leaf | |
2018 | functions which only use leaf registers. | |
2019 | @code{current_function_uses_only_leaf_regs} is valid after all passes | |
2020 | that modify the instructions have been run and is only useful if | |
2021 | @code{LEAF_REGISTERS} is defined. | |
2022 | @c changed this to fix overfull. ALSO: why the "it" at the beginning | |
2023 | @c of the next paragraph?! --mew 2feb93 | |
2024 | ||
2025 | @node Stack Registers | |
2026 | @subsection Registers That Form a Stack | |
2027 | ||
2028 | There are special features to handle computers where some of the | |
2029 | ``registers'' form a stack. Stack registers are normally written by | |
2030 | pushing onto the stack, and are numbered relative to the top of the | |
2031 | stack. | |
2032 | ||
2033 | Currently, GCC can only handle one group of stack-like registers, and | |
2034 | they must be consecutively numbered. Furthermore, the existing | |
2035 | support for stack-like registers is specific to the 80387 floating | |
2036 | point coprocessor. If you have a new architecture that uses | |
2037 | stack-like registers, you will need to do substantial work on | |
2038 | @file{reg-stack.c} and write your machine description to cooperate | |
2039 | with it, as well as defining these macros. | |
2040 | ||
2041 | @defmac STACK_REGS | |
2042 | Define this if the machine has any stack-like registers. | |
2043 | @end defmac | |
2044 | ||
2045 | @defmac STACK_REG_COVER_CLASS | |
2046 | This is a cover class containing the stack registers. Define this if | |
2047 | the machine has any stack-like registers. | |
2048 | @end defmac | |
2049 | ||
2050 | @defmac FIRST_STACK_REG | |
2051 | The number of the first stack-like register. This one is the top | |
2052 | of the stack. | |
2053 | @end defmac | |
2054 | ||
2055 | @defmac LAST_STACK_REG | |
2056 | The number of the last stack-like register. This one is the bottom of | |
2057 | the stack. | |
2058 | @end defmac | |
2059 | ||
2060 | @node Register Classes | |
2061 | @section Register Classes | |
2062 | @cindex register class definitions | |
2063 | @cindex class definitions, register | |
2064 | ||
2065 | On many machines, the numbered registers are not all equivalent. | |
2066 | For example, certain registers may not be allowed for indexed addressing; | |
2067 | certain registers may not be allowed in some instructions. These machine | |
2068 | restrictions are described to the compiler using @dfn{register classes}. | |
2069 | ||
2070 | You define a number of register classes, giving each one a name and saying | |
2071 | which of the registers belong to it. Then you can specify register classes | |
2072 | that are allowed as operands to particular instruction patterns. | |
2073 | ||
2074 | @findex ALL_REGS | |
2075 | @findex NO_REGS | |
2076 | In general, each register will belong to several classes. In fact, one | |
2077 | class must be named @code{ALL_REGS} and contain all the registers. Another | |
2078 | class must be named @code{NO_REGS} and contain no registers. Often the | |
2079 | union of two classes will be another class; however, this is not required. | |
2080 | ||
2081 | @findex GENERAL_REGS | |
2082 | One of the classes must be named @code{GENERAL_REGS}. There is nothing | |
2083 | terribly special about the name, but the operand constraint letters | |
2084 | @samp{r} and @samp{g} specify this class. If @code{GENERAL_REGS} is | |
2085 | the same as @code{ALL_REGS}, just define it as a macro which expands | |
2086 | to @code{ALL_REGS}. | |
2087 | ||
2088 | Order the classes so that if class @var{x} is contained in class @var{y} | |
2089 | then @var{x} has a lower class number than @var{y}. | |
2090 | ||
2091 | The way classes other than @code{GENERAL_REGS} are specified in operand | |
2092 | constraints is through machine-dependent operand constraint letters. | |
2093 | You can define such letters to correspond to various classes, then use | |
2094 | them in operand constraints. | |
2095 | ||
a4621139 | 2096 | You must define the narrowest register classes for allocatable |
2097 | registers, so that each class either has no subclasses, or that for | |
2098 | some mode, the move cost between registers within the class is | |
2099 | cheaper than moving a register in the class to or from memory | |
2100 | (@pxref{Costs}). | |
2101 | ||
202d6e5f | 2102 | You should define a class for the union of two classes whenever some |
2103 | instruction allows both classes. For example, if an instruction allows | |
2104 | either a floating point (coprocessor) register or a general register for a | |
2105 | certain operand, you should define a class @code{FLOAT_OR_GENERAL_REGS} | |
15edf55e | 2106 | which includes both of them. Otherwise you will get suboptimal code, |
2107 | or even internal compiler errors when reload cannot find a register in the | |
851d9296 | 2108 | class computed via @code{reg_class_subunion}. |
202d6e5f | 2109 | |
2110 | You must also specify certain redundant information about the register | |
2111 | classes: for each class, which classes contain it and which ones are | |
2112 | contained in it; for each pair of classes, the largest class contained | |
2113 | in their union. | |
2114 | ||
2115 | When a value occupying several consecutive registers is expected in a | |
2116 | certain class, all the registers used must belong to that class. | |
2117 | Therefore, register classes cannot be used to enforce a requirement for | |
2118 | a register pair to start with an even-numbered register. The way to | |
2119 | specify this requirement is with @code{HARD_REGNO_MODE_OK}. | |
2120 | ||
2121 | Register classes used for input-operands of bitwise-and or shift | |
2122 | instructions have a special requirement: each such class must have, for | |
2123 | each fixed-point machine mode, a subclass whose registers can transfer that | |
2124 | mode to or from memory. For example, on some machines, the operations for | |
2125 | single-byte values (@code{QImode}) are limited to certain registers. When | |
2126 | this is so, each register class that is used in a bitwise-and or shift | |
2127 | instruction must have a subclass consisting of registers from which | |
2128 | single-byte values can be loaded or stored. This is so that | |
2129 | @code{PREFERRED_RELOAD_CLASS} can always have a possible value to return. | |
2130 | ||
2131 | @deftp {Data type} {enum reg_class} | |
2132 | An enumerated type that must be defined with all the register class names | |
2133 | as enumerated values. @code{NO_REGS} must be first. @code{ALL_REGS} | |
2134 | must be the last register class, followed by one more enumerated value, | |
2135 | @code{LIM_REG_CLASSES}, which is not a register class but rather | |
2136 | tells how many classes there are. | |
2137 | ||
2138 | Each register class has a number, which is the value of casting | |
2139 | the class name to type @code{int}. The number serves as an index | |
2140 | in many of the tables described below. | |
2141 | @end deftp | |
2142 | ||
2143 | @defmac N_REG_CLASSES | |
2144 | The number of distinct register classes, defined as follows: | |
2145 | ||
2146 | @smallexample | |
2147 | #define N_REG_CLASSES (int) LIM_REG_CLASSES | |
2148 | @end smallexample | |
2149 | @end defmac | |
2150 | ||
2151 | @defmac REG_CLASS_NAMES | |
2152 | An initializer containing the names of the register classes as C string | |
2153 | constants. These names are used in writing some of the debugging dumps. | |
2154 | @end defmac | |
2155 | ||
2156 | @defmac REG_CLASS_CONTENTS | |
2157 | An initializer containing the contents of the register classes, as integers | |
2158 | which are bit masks. The @var{n}th integer specifies the contents of class | |
2159 | @var{n}. The way the integer @var{mask} is interpreted is that | |
2160 | register @var{r} is in the class if @code{@var{mask} & (1 << @var{r})} is 1. | |
2161 | ||
2162 | When the machine has more than 32 registers, an integer does not suffice. | |
2163 | Then the integers are replaced by sub-initializers, braced groupings containing | |
2164 | several integers. Each sub-initializer must be suitable as an initializer | |
2165 | for the type @code{HARD_REG_SET} which is defined in @file{hard-reg-set.h}. | |
2166 | In this situation, the first integer in each sub-initializer corresponds to | |
2167 | registers 0 through 31, the second integer to registers 32 through 63, and | |
2168 | so on. | |
2169 | @end defmac | |
2170 | ||
2171 | @defmac REGNO_REG_CLASS (@var{regno}) | |
2172 | A C expression whose value is a register class containing hard register | |
2173 | @var{regno}. In general there is more than one such class; choose a class | |
2174 | which is @dfn{minimal}, meaning that no smaller class also contains the | |
2175 | register. | |
2176 | @end defmac | |
2177 | ||
2178 | @defmac BASE_REG_CLASS | |
2179 | A macro whose definition is the name of the class to which a valid | |
2180 | base register must belong. A base register is one used in an address | |
2181 | which is the register value plus a displacement. | |
2182 | @end defmac | |
2183 | ||
2184 | @defmac MODE_BASE_REG_CLASS (@var{mode}) | |
2185 | This is a variation of the @code{BASE_REG_CLASS} macro which allows | |
2186 | the selection of a base register in a mode dependent manner. If | |
2187 | @var{mode} is VOIDmode then it should return the same value as | |
2188 | @code{BASE_REG_CLASS}. | |
2189 | @end defmac | |
2190 | ||
2191 | @defmac MODE_BASE_REG_REG_CLASS (@var{mode}) | |
2192 | A C expression whose value is the register class to which a valid | |
2193 | base register must belong in order to be used in a base plus index | |
2194 | register address. You should define this macro if base plus index | |
2195 | addresses have different requirements than other base register uses. | |
2196 | @end defmac | |
2197 | ||
f8a8fc7b | 2198 | @defmac MODE_CODE_BASE_REG_CLASS (@var{mode}, @var{address_space}, @var{outer_code}, @var{index_code}) |
202d6e5f | 2199 | A C expression whose value is the register class to which a valid |
f8a8fc7b | 2200 | base register for a memory reference in mode @var{mode} to address |
2201 | space @var{address_space} must belong. @var{outer_code} and @var{index_code} | |
2202 | define the context in which the base register occurs. @var{outer_code} is | |
2203 | the code of the immediately enclosing expression (@code{MEM} for the top level | |
2204 | of an address, @code{ADDRESS} for something that occurs in an | |
202d6e5f | 2205 | @code{address_operand}). @var{index_code} is the code of the corresponding |
2206 | index expression if @var{outer_code} is @code{PLUS}; @code{SCRATCH} otherwise. | |
2207 | @end defmac | |
2208 | ||
2209 | @defmac INDEX_REG_CLASS | |
2210 | A macro whose definition is the name of the class to which a valid | |
2211 | index register must belong. An index register is one used in an | |
2212 | address where its value is either multiplied by a scale factor or | |
2213 | added to another register (as well as added to a displacement). | |
2214 | @end defmac | |
2215 | ||
2216 | @defmac REGNO_OK_FOR_BASE_P (@var{num}) | |
2217 | A C expression which is nonzero if register number @var{num} is | |
2218 | suitable for use as a base register in operand addresses. | |
202d6e5f | 2219 | @end defmac |
2220 | ||
2221 | @defmac REGNO_MODE_OK_FOR_BASE_P (@var{num}, @var{mode}) | |
2222 | A C expression that is just like @code{REGNO_OK_FOR_BASE_P}, except that | |
2223 | that expression may examine the mode of the memory reference in | |
2224 | @var{mode}. You should define this macro if the mode of the memory | |
2225 | reference affects whether a register may be used as a base register. If | |
2226 | you define this macro, the compiler will use it instead of | |
2227 | @code{REGNO_OK_FOR_BASE_P}. The mode may be @code{VOIDmode} for | |
2228 | addresses that appear outside a @code{MEM}, i.e., as an | |
2229 | @code{address_operand}. | |
202d6e5f | 2230 | @end defmac |
2231 | ||
2232 | @defmac REGNO_MODE_OK_FOR_REG_BASE_P (@var{num}, @var{mode}) | |
2233 | A C expression which is nonzero if register number @var{num} is suitable for | |
2234 | use as a base register in base plus index operand addresses, accessing | |
2235 | memory in mode @var{mode}. It may be either a suitable hard register or a | |
2236 | pseudo register that has been allocated such a hard register. You should | |
2237 | define this macro if base plus index addresses have different requirements | |
2238 | than other base register uses. | |
2239 | ||
2240 | Use of this macro is deprecated; please use the more general | |
2241 | @code{REGNO_MODE_CODE_OK_FOR_BASE_P}. | |
202d6e5f | 2242 | @end defmac |
2243 | ||
f8a8fc7b | 2244 | @defmac REGNO_MODE_CODE_OK_FOR_BASE_P (@var{num}, @var{mode}, @var{address_space}, @var{outer_code}, @var{index_code}) |
2245 | A C expression which is nonzero if register number @var{num} is | |
2246 | suitable for use as a base register in operand addresses, accessing | |
2247 | memory in mode @var{mode} in address space @var{address_space}. | |
2248 | This is similar to @code{REGNO_MODE_OK_FOR_BASE_P}, except | |
202d6e5f | 2249 | that that expression may examine the context in which the register |
2250 | appears in the memory reference. @var{outer_code} is the code of the | |
2251 | immediately enclosing expression (@code{MEM} if at the top level of the | |
2252 | address, @code{ADDRESS} for something that occurs in an | |
2253 | @code{address_operand}). @var{index_code} is the code of the | |
2254 | corresponding index expression if @var{outer_code} is @code{PLUS}; | |
2255 | @code{SCRATCH} otherwise. The mode may be @code{VOIDmode} for addresses | |
2256 | that appear outside a @code{MEM}, i.e., as an @code{address_operand}. | |
202d6e5f | 2257 | @end defmac |
2258 | ||
2259 | @defmac REGNO_OK_FOR_INDEX_P (@var{num}) | |
2260 | A C expression which is nonzero if register number @var{num} is | |
2261 | suitable for use as an index register in operand addresses. It may be | |
2262 | either a suitable hard register or a pseudo register that has been | |
2263 | allocated such a hard register. | |
2264 | ||
2265 | The difference between an index register and a base register is that | |
2266 | the index register may be scaled. If an address involves the sum of | |
2267 | two registers, neither one of them scaled, then either one may be | |
2268 | labeled the ``base'' and the other the ``index''; but whichever | |
2269 | labeling is used must fit the machine's constraints of which registers | |
2270 | may serve in each capacity. The compiler will try both labelings, | |
2271 | looking for one that is valid, and will reload one or both registers | |
2272 | only if neither labeling works. | |
202d6e5f | 2273 | @end defmac |
2274 | ||
d78118a3 | 2275 | @hook TARGET_PREFERRED_RENAME_CLASS |
2276 | ||
09a17585 | 2277 | @hook TARGET_PREFERRED_RELOAD_CLASS |
09a17585 | 2278 | |
202d6e5f | 2279 | @defmac PREFERRED_RELOAD_CLASS (@var{x}, @var{class}) |
2280 | A C expression that places additional restrictions on the register class | |
2281 | to use when it is necessary to copy value @var{x} into a register in class | |
2282 | @var{class}. The value is a register class; perhaps @var{class}, or perhaps | |
2283 | another, smaller class. On many machines, the following definition is | |
2284 | safe: | |
2285 | ||
2286 | @smallexample | |
2287 | #define PREFERRED_RELOAD_CLASS(X,CLASS) CLASS | |
2288 | @end smallexample | |
2289 | ||
2290 | Sometimes returning a more restrictive class makes better code. For | |
2291 | example, on the 68000, when @var{x} is an integer constant that is in range | |
2292 | for a @samp{moveq} instruction, the value of this macro is always | |
2293 | @code{DATA_REGS} as long as @var{class} includes the data registers. | |
2294 | Requiring a data register guarantees that a @samp{moveq} will be used. | |
2295 | ||
2296 | One case where @code{PREFERRED_RELOAD_CLASS} must not return | |
2297 | @var{class} is if @var{x} is a legitimate constant which cannot be | |
2298 | loaded into some register class. By returning @code{NO_REGS} you can | |
2299 | force @var{x} into a memory location. For example, rs6000 can load | |
2300 | immediate values into general-purpose registers, but does not have an | |
2301 | instruction for loading an immediate value into a floating-point | |
2302 | register, so @code{PREFERRED_RELOAD_CLASS} returns @code{NO_REGS} when | |
2303 | @var{x} is a floating-point constant. If the constant can't be loaded | |
2304 | into any kind of register, code generation will be better if | |
ca316360 | 2305 | @code{TARGET_LEGITIMATE_CONSTANT_P} makes the constant illegitimate instead |
2306 | of using @code{TARGET_PREFERRED_RELOAD_CLASS}. | |
202d6e5f | 2307 | |
2308 | If an insn has pseudos in it after register allocation, reload will go | |
2309 | through the alternatives and call repeatedly @code{PREFERRED_RELOAD_CLASS} | |
2310 | to find the best one. Returning @code{NO_REGS}, in this case, makes | |
2311 | reload add a @code{!} in front of the constraint: the x86 back-end uses | |
2312 | this feature to discourage usage of 387 registers when math is done in | |
2313 | the SSE registers (and vice versa). | |
2314 | @end defmac | |
2315 | ||
71db0d8b | 2316 | @hook TARGET_PREFERRED_OUTPUT_RELOAD_CLASS |
71db0d8b | 2317 | |
202d6e5f | 2318 | @defmac LIMIT_RELOAD_CLASS (@var{mode}, @var{class}) |
2319 | A C expression that places additional restrictions on the register class | |
2320 | to use when it is necessary to be able to hold a value of mode | |
2321 | @var{mode} in a reload register for which class @var{class} would | |
2322 | ordinarily be used. | |
2323 | ||
2324 | Unlike @code{PREFERRED_RELOAD_CLASS}, this macro should be used when | |
2325 | there are certain modes that simply can't go in certain reload classes. | |
2326 | ||
2327 | The value is a register class; perhaps @var{class}, or perhaps another, | |
2328 | smaller class. | |
2329 | ||
2330 | Don't define this macro unless the target machine has limitations which | |
2331 | require the macro to do something nontrivial. | |
2332 | @end defmac | |
2333 | ||
2334 | @hook TARGET_SECONDARY_RELOAD | |
202d6e5f | 2335 | |
2336 | @defmac SECONDARY_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) | |
2337 | @defmacx SECONDARY_INPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) | |
2338 | @defmacx SECONDARY_OUTPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) | |
2339 | These macros are obsolete, new ports should use the target hook | |
2340 | @code{TARGET_SECONDARY_RELOAD} instead. | |
2341 | ||
2342 | These are obsolete macros, replaced by the @code{TARGET_SECONDARY_RELOAD} | |
2343 | target hook. Older ports still define these macros to indicate to the | |
2344 | reload phase that it may | |
2345 | need to allocate at least one register for a reload in addition to the | |
2346 | register to contain the data. Specifically, if copying @var{x} to a | |
2347 | register @var{class} in @var{mode} requires an intermediate register, | |
2348 | you were supposed to define @code{SECONDARY_INPUT_RELOAD_CLASS} to return the | |
2349 | largest register class all of whose registers can be used as | |
2350 | intermediate registers or scratch registers. | |
2351 | ||
2352 | If copying a register @var{class} in @var{mode} to @var{x} requires an | |
2353 | intermediate or scratch register, @code{SECONDARY_OUTPUT_RELOAD_CLASS} | |
2354 | was supposed to be defined be defined to return the largest register | |
2355 | class required. If the | |
2356 | requirements for input and output reloads were the same, the macro | |
2357 | @code{SECONDARY_RELOAD_CLASS} should have been used instead of defining both | |
2358 | macros identically. | |
2359 | ||
2360 | The values returned by these macros are often @code{GENERAL_REGS}. | |
2361 | Return @code{NO_REGS} if no spare register is needed; i.e., if @var{x} | |
2362 | can be directly copied to or from a register of @var{class} in | |
2363 | @var{mode} without requiring a scratch register. Do not define this | |
2364 | macro if it would always return @code{NO_REGS}. | |
2365 | ||
2366 | If a scratch register is required (either with or without an | |
2367 | intermediate register), you were supposed to define patterns for | |
2368 | @samp{reload_in@var{m}} or @samp{reload_out@var{m}}, as required | |
2369 | (@pxref{Standard Names}. These patterns, which were normally | |
2370 | implemented with a @code{define_expand}, should be similar to the | |
2371 | @samp{mov@var{m}} patterns, except that operand 2 is the scratch | |
2372 | register. | |
2373 | ||
2374 | These patterns need constraints for the reload register and scratch | |
2375 | register that | |
2376 | contain a single register class. If the original reload register (whose | |
2377 | class is @var{class}) can meet the constraint given in the pattern, the | |
2378 | value returned by these macros is used for the class of the scratch | |
2379 | register. Otherwise, two additional reload registers are required. | |
2380 | Their classes are obtained from the constraints in the insn pattern. | |
2381 | ||
2382 | @var{x} might be a pseudo-register or a @code{subreg} of a | |
2383 | pseudo-register, which could either be in a hard register or in memory. | |
2384 | Use @code{true_regnum} to find out; it will return @minus{}1 if the pseudo is | |
2385 | in memory and the hard register number if it is in a register. | |
2386 | ||
2387 | These macros should not be used in the case where a particular class of | |
2388 | registers can only be copied to memory and not to another class of | |
2389 | registers. In that case, secondary reload registers are not needed and | |
2390 | would not be helpful. Instead, a stack location must be used to perform | |
2391 | the copy and the @code{mov@var{m}} pattern should use memory as an | |
2392 | intermediate storage. This case often occurs between floating-point and | |
2393 | general registers. | |
2394 | @end defmac | |
2395 | ||
2396 | @defmac SECONDARY_MEMORY_NEEDED (@var{class1}, @var{class2}, @var{m}) | |
2397 | Certain machines have the property that some registers cannot be copied | |
2398 | to some other registers without using memory. Define this macro on | |
2399 | those machines to be a C expression that is nonzero if objects of mode | |
2400 | @var{m} in registers of @var{class1} can only be copied to registers of | |
2401 | class @var{class2} by storing a register of @var{class1} into memory | |
2402 | and loading that memory location into a register of @var{class2}. | |
2403 | ||
2404 | Do not define this macro if its value would always be zero. | |
2405 | @end defmac | |
2406 | ||
2407 | @defmac SECONDARY_MEMORY_NEEDED_RTX (@var{mode}) | |
2408 | Normally when @code{SECONDARY_MEMORY_NEEDED} is defined, the compiler | |
2409 | allocates a stack slot for a memory location needed for register copies. | |
2410 | If this macro is defined, the compiler instead uses the memory location | |
2411 | defined by this macro. | |
2412 | ||
2413 | Do not define this macro if you do not define | |
2414 | @code{SECONDARY_MEMORY_NEEDED}. | |
2415 | @end defmac | |
2416 | ||
2417 | @defmac SECONDARY_MEMORY_NEEDED_MODE (@var{mode}) | |
2418 | When the compiler needs a secondary memory location to copy between two | |
2419 | registers of mode @var{mode}, it normally allocates sufficient memory to | |
2420 | hold a quantity of @code{BITS_PER_WORD} bits and performs the store and | |
2421 | load operations in a mode that many bits wide and whose class is the | |
2422 | same as that of @var{mode}. | |
2423 | ||
2424 | This is right thing to do on most machines because it ensures that all | |
2425 | bits of the register are copied and prevents accesses to the registers | |
2426 | in a narrower mode, which some machines prohibit for floating-point | |
2427 | registers. | |
2428 | ||
2429 | However, this default behavior is not correct on some machines, such as | |
2430 | the DEC Alpha, that store short integers in floating-point registers | |
2431 | differently than in integer registers. On those machines, the default | |
2432 | widening will not work correctly and you must define this macro to | |
2433 | suppress that widening in some cases. See the file @file{alpha.h} for | |
2434 | details. | |
2435 | ||
2436 | Do not define this macro if you do not define | |
2437 | @code{SECONDARY_MEMORY_NEEDED} or if widening @var{mode} to a mode that | |
2438 | is @code{BITS_PER_WORD} bits wide is correct for your machine. | |
2439 | @end defmac | |
2440 | ||
24dd0668 | 2441 | @hook TARGET_CLASS_LIKELY_SPILLED_P |
d3ba22dc | 2442 | |
2443 | @hook TARGET_CLASS_MAX_NREGS | |
24dd0668 | 2444 | |
202d6e5f | 2445 | @defmac CLASS_MAX_NREGS (@var{class}, @var{mode}) |
2446 | A C expression for the maximum number of consecutive registers | |
2447 | of class @var{class} needed to hold a value of mode @var{mode}. | |
2448 | ||
2449 | This is closely related to the macro @code{HARD_REGNO_NREGS}. In fact, | |
2450 | the value of the macro @code{CLASS_MAX_NREGS (@var{class}, @var{mode})} | |
2451 | should be the maximum value of @code{HARD_REGNO_NREGS (@var{regno}, | |
2452 | @var{mode})} for all @var{regno} values in the class @var{class}. | |
2453 | ||
2454 | This macro helps control the handling of multiple-word values | |
2455 | in the reload pass. | |
2456 | @end defmac | |
2457 | ||
2458 | @defmac CANNOT_CHANGE_MODE_CLASS (@var{from}, @var{to}, @var{class}) | |
2459 | If defined, a C expression that returns nonzero for a @var{class} for which | |
2460 | a change from mode @var{from} to mode @var{to} is invalid. | |
2461 | ||
2462 | For the example, loading 32-bit integer or floating-point objects into | |
2463 | floating-point registers on the Alpha extends them to 64 bits. | |
2464 | Therefore loading a 64-bit object and then storing it as a 32-bit object | |
2465 | does not store the low-order 32 bits, as would be the case for a normal | |
2466 | register. Therefore, @file{alpha.h} defines @code{CANNOT_CHANGE_MODE_CLASS} | |
2467 | as below: | |
2468 | ||
2469 | @smallexample | |
2470 | #define CANNOT_CHANGE_MODE_CLASS(FROM, TO, CLASS) \ | |
2471 | (GET_MODE_SIZE (FROM) != GET_MODE_SIZE (TO) \ | |
2472 | ? reg_classes_intersect_p (FLOAT_REGS, (CLASS)) : 0) | |
2473 | @end smallexample | |
2474 | @end defmac | |
2475 | ||
c6a6cdaa | 2476 | @hook TARGET_LRA_P |
2477 | ||
2478 | @hook TARGET_REGISTER_PRIORITY | |
2479 | ||
4a2ca8f3 | 2480 | @hook TARGET_REGISTER_USAGE_LEVELING_P |
2481 | ||
c6a6cdaa | 2482 | @hook TARGET_DIFFERENT_ADDR_DISPLACEMENT_P |
2483 | ||
2484 | @hook TARGET_SPILL_CLASS | |
2485 | ||
17f446a0 | 2486 | @hook TARGET_CSTORE_MODE |
2487 | ||
202d6e5f | 2488 | @node Stack and Calling |
2489 | @section Stack Layout and Calling Conventions | |
2490 | @cindex calling conventions | |
2491 | ||
2492 | @c prevent bad page break with this line | |
2493 | This describes the stack layout and calling conventions. | |
2494 | ||
2495 | @menu | |
2496 | * Frame Layout:: | |
2497 | * Exception Handling:: | |
2498 | * Stack Checking:: | |
2499 | * Frame Registers:: | |
2500 | * Elimination:: | |
2501 | * Stack Arguments:: | |
2502 | * Register Arguments:: | |
2503 | * Scalar Return:: | |
2504 | * Aggregate Return:: | |
2505 | * Caller Saves:: | |
2506 | * Function Entry:: | |
2507 | * Profiling:: | |
2508 | * Tail Calls:: | |
2509 | * Stack Smashing Protection:: | |
e9eaaa6a | 2510 | * Miscellaneous Register Hooks:: |
202d6e5f | 2511 | @end menu |
2512 | ||
2513 | @node Frame Layout | |
2514 | @subsection Basic Stack Layout | |
2515 | @cindex stack frame layout | |
2516 | @cindex frame layout | |
2517 | ||
2518 | @c prevent bad page break with this line | |
2519 | Here is the basic stack layout. | |
2520 | ||
2521 | @defmac STACK_GROWS_DOWNWARD | |
2522 | Define this macro if pushing a word onto the stack moves the stack | |
2523 | pointer to a smaller address. | |
2524 | ||
2525 | When we say, ``define this macro if @dots{}'', it means that the | |
2526 | compiler checks this macro only with @code{#ifdef} so the precise | |
2527 | definition used does not matter. | |
2528 | @end defmac | |
2529 | ||
2530 | @defmac STACK_PUSH_CODE | |
2531 | This macro defines the operation used when something is pushed | |
2532 | on the stack. In RTL, a push operation will be | |
2533 | @code{(set (mem (STACK_PUSH_CODE (reg sp))) @dots{})} | |
2534 | ||
2535 | The choices are @code{PRE_DEC}, @code{POST_DEC}, @code{PRE_INC}, | |
2536 | and @code{POST_INC}. Which of these is correct depends on | |
2537 | the stack direction and on whether the stack pointer points | |
2538 | to the last item on the stack or whether it points to the | |
2539 | space for the next item on the stack. | |
2540 | ||
2541 | The default is @code{PRE_DEC} when @code{STACK_GROWS_DOWNWARD} is | |
2542 | defined, which is almost always right, and @code{PRE_INC} otherwise, | |
2543 | which is often wrong. | |
2544 | @end defmac | |
2545 | ||
2546 | @defmac FRAME_GROWS_DOWNWARD | |
2547 | Define this macro to nonzero value if the addresses of local variable slots | |
2548 | are at negative offsets from the frame pointer. | |
2549 | @end defmac | |
2550 | ||
2551 | @defmac ARGS_GROW_DOWNWARD | |
2552 | Define this macro if successive arguments to a function occupy decreasing | |
2553 | addresses on the stack. | |
2554 | @end defmac | |
2555 | ||
2556 | @defmac STARTING_FRAME_OFFSET | |
2557 | Offset from the frame pointer to the first local variable slot to be allocated. | |
2558 | ||
2559 | If @code{FRAME_GROWS_DOWNWARD}, find the next slot's offset by | |
2560 | subtracting the first slot's length from @code{STARTING_FRAME_OFFSET}. | |
2561 | Otherwise, it is found by adding the length of the first slot to the | |
2562 | value @code{STARTING_FRAME_OFFSET}. | |
2563 | @c i'm not sure if the above is still correct.. had to change it to get | |
2564 | @c rid of an overfull. --mew 2feb93 | |
2565 | @end defmac | |
2566 | ||
2567 | @defmac STACK_ALIGNMENT_NEEDED | |
2568 | Define to zero to disable final alignment of the stack during reload. | |
2569 | The nonzero default for this macro is suitable for most ports. | |
2570 | ||
2571 | On ports where @code{STARTING_FRAME_OFFSET} is nonzero or where there | |
2572 | is a register save block following the local block that doesn't require | |
2573 | alignment to @code{STACK_BOUNDARY}, it may be beneficial to disable | |
2574 | stack alignment and do it in the backend. | |
2575 | @end defmac | |
2576 | ||
2577 | @defmac STACK_POINTER_OFFSET | |
2578 | Offset from the stack pointer register to the first location at which | |
2579 | outgoing arguments are placed. If not specified, the default value of | |
2580 | zero is used. This is the proper value for most machines. | |
2581 | ||
2582 | If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above | |
2583 | the first location at which outgoing arguments are placed. | |
2584 | @end defmac | |
2585 | ||
2586 | @defmac FIRST_PARM_OFFSET (@var{fundecl}) | |
2587 | Offset from the argument pointer register to the first argument's | |
2588 | address. On some machines it may depend on the data type of the | |
2589 | function. | |
2590 | ||
2591 | If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above | |
2592 | the first argument's address. | |
2593 | @end defmac | |
2594 | ||
2595 | @defmac STACK_DYNAMIC_OFFSET (@var{fundecl}) | |
2596 | Offset from the stack pointer register to an item dynamically allocated | |
2597 | on the stack, e.g., by @code{alloca}. | |
2598 | ||
2599 | The default value for this macro is @code{STACK_POINTER_OFFSET} plus the | |
2600 | length of the outgoing arguments. The default is correct for most | |
2601 | machines. See @file{function.c} for details. | |
2602 | @end defmac | |
2603 | ||
2604 | @defmac INITIAL_FRAME_ADDRESS_RTX | |
2605 | A C expression whose value is RTL representing the address of the initial | |
2606 | stack frame. This address is passed to @code{RETURN_ADDR_RTX} and | |
2607 | @code{DYNAMIC_CHAIN_ADDRESS}. If you don't define this macro, a reasonable | |
2608 | default value will be used. Define this macro in order to make frame pointer | |
2609 | elimination work in the presence of @code{__builtin_frame_address (count)} and | |
2610 | @code{__builtin_return_address (count)} for @code{count} not equal to zero. | |
2611 | @end defmac | |
2612 | ||
2613 | @defmac DYNAMIC_CHAIN_ADDRESS (@var{frameaddr}) | |
2614 | A C expression whose value is RTL representing the address in a stack | |
2615 | frame where the pointer to the caller's frame is stored. Assume that | |
2616 | @var{frameaddr} is an RTL expression for the address of the stack frame | |
2617 | itself. | |
2618 | ||
2619 | If you don't define this macro, the default is to return the value | |
2620 | of @var{frameaddr}---that is, the stack frame address is also the | |
2621 | address of the stack word that points to the previous frame. | |
2622 | @end defmac | |
2623 | ||
2624 | @defmac SETUP_FRAME_ADDRESSES | |
2625 | If defined, a C expression that produces the machine-specific code to | |
2626 | setup the stack so that arbitrary frames can be accessed. For example, | |
2627 | on the SPARC, we must flush all of the register windows to the stack | |
2628 | before we can access arbitrary stack frames. You will seldom need to | |
2629 | define this macro. | |
2630 | @end defmac | |
2631 | ||
2632 | @hook TARGET_BUILTIN_SETJMP_FRAME_VALUE | |
202d6e5f | 2633 | |
2634 | @defmac FRAME_ADDR_RTX (@var{frameaddr}) | |
2635 | A C expression whose value is RTL representing the value of the frame | |
2636 | address for the current frame. @var{frameaddr} is the frame pointer | |
2637 | of the current frame. This is used for __builtin_frame_address. | |
2638 | You need only define this macro if the frame address is not the same | |
2639 | as the frame pointer. Most machines do not need to define it. | |
2640 | @end defmac | |
2641 | ||
2642 | @defmac RETURN_ADDR_RTX (@var{count}, @var{frameaddr}) | |
2643 | A C expression whose value is RTL representing the value of the return | |
2644 | address for the frame @var{count} steps up from the current frame, after | |
2645 | the prologue. @var{frameaddr} is the frame pointer of the @var{count} | |
2646 | frame, or the frame pointer of the @var{count} @minus{} 1 frame if | |
2647 | @code{RETURN_ADDR_IN_PREVIOUS_FRAME} is defined. | |
2648 | ||
2649 | The value of the expression must always be the correct address when | |
2650 | @var{count} is zero, but may be @code{NULL_RTX} if there is no way to | |
2651 | determine the return address of other frames. | |
2652 | @end defmac | |
2653 | ||
2654 | @defmac RETURN_ADDR_IN_PREVIOUS_FRAME | |
2655 | Define this if the return address of a particular stack frame is accessed | |
2656 | from the frame pointer of the previous stack frame. | |
2657 | @end defmac | |
2658 | ||
2659 | @defmac INCOMING_RETURN_ADDR_RTX | |
2660 | A C expression whose value is RTL representing the location of the | |
2661 | incoming return address at the beginning of any function, before the | |
2662 | prologue. This RTL is either a @code{REG}, indicating that the return | |
2663 | value is saved in @samp{REG}, or a @code{MEM} representing a location in | |
2664 | the stack. | |
2665 | ||
2666 | You only need to define this macro if you want to support call frame | |
2667 | debugging information like that provided by DWARF 2. | |
2668 | ||
2669 | If this RTL is a @code{REG}, you should also define | |
2670 | @code{DWARF_FRAME_RETURN_COLUMN} to @code{DWARF_FRAME_REGNUM (REGNO)}. | |
2671 | @end defmac | |
2672 | ||
2673 | @defmac DWARF_ALT_FRAME_RETURN_COLUMN | |
2674 | A C expression whose value is an integer giving a DWARF 2 column | |
2675 | number that may be used as an alternative return column. The column | |
2676 | must not correspond to any gcc hard register (that is, it must not | |
2677 | be in the range of @code{DWARF_FRAME_REGNUM}). | |
2678 | ||
2679 | This macro can be useful if @code{DWARF_FRAME_RETURN_COLUMN} is set to a | |
2680 | general register, but an alternative column needs to be used for signal | |
2681 | frames. Some targets have also used different frame return columns | |
2682 | over time. | |
2683 | @end defmac | |
2684 | ||
2685 | @defmac DWARF_ZERO_REG | |
2686 | A C expression whose value is an integer giving a DWARF 2 register | |
2687 | number that is considered to always have the value zero. This should | |
2688 | only be defined if the target has an architected zero register, and | |
2689 | someone decided it was a good idea to use that register number to | |
2690 | terminate the stack backtrace. New ports should avoid this. | |
2691 | @end defmac | |
2692 | ||
2693 | @hook TARGET_DWARF_HANDLE_FRAME_UNSPEC | |
202d6e5f | 2694 | |
2695 | @defmac INCOMING_FRAME_SP_OFFSET | |
2696 | A C expression whose value is an integer giving the offset, in bytes, | |
2697 | from the value of the stack pointer register to the top of the stack | |
2698 | frame at the beginning of any function, before the prologue. The top of | |
2699 | the frame is defined to be the value of the stack pointer in the | |
2700 | previous frame, just before the call instruction. | |
2701 | ||
2702 | You only need to define this macro if you want to support call frame | |
2703 | debugging information like that provided by DWARF 2. | |
2704 | @end defmac | |
2705 | ||
2706 | @defmac ARG_POINTER_CFA_OFFSET (@var{fundecl}) | |
2707 | A C expression whose value is an integer giving the offset, in bytes, | |
2708 | from the argument pointer to the canonical frame address (cfa). The | |
2709 | final value should coincide with that calculated by | |
2710 | @code{INCOMING_FRAME_SP_OFFSET}. Which is unfortunately not usable | |
2711 | during virtual register instantiation. | |
2712 | ||
2713 | The default value for this macro is | |
2714 | @code{FIRST_PARM_OFFSET (fundecl) + crtl->args.pretend_args_size}, | |
2715 | which is correct for most machines; in general, the arguments are found | |
2716 | immediately before the stack frame. Note that this is not the case on | |
2717 | some targets that save registers into the caller's frame, such as SPARC | |
2718 | and rs6000, and so such targets need to define this macro. | |
2719 | ||
2720 | You only need to define this macro if the default is incorrect, and you | |
2721 | want to support call frame debugging information like that provided by | |
2722 | DWARF 2. | |
2723 | @end defmac | |
2724 | ||
2725 | @defmac FRAME_POINTER_CFA_OFFSET (@var{fundecl}) | |
2726 | If defined, a C expression whose value is an integer giving the offset | |
2727 | in bytes from the frame pointer to the canonical frame address (cfa). | |
2728 | The final value should coincide with that calculated by | |
2729 | @code{INCOMING_FRAME_SP_OFFSET}. | |
2730 | ||
2731 | Normally the CFA is calculated as an offset from the argument pointer, | |
2732 | via @code{ARG_POINTER_CFA_OFFSET}, but if the argument pointer is | |
2733 | variable due to the ABI, this may not be possible. If this macro is | |
2734 | defined, it implies that the virtual register instantiation should be | |
2735 | based on the frame pointer instead of the argument pointer. Only one | |
2736 | of @code{FRAME_POINTER_CFA_OFFSET} and @code{ARG_POINTER_CFA_OFFSET} | |
2737 | should be defined. | |
2738 | @end defmac | |
2739 | ||
2740 | @defmac CFA_FRAME_BASE_OFFSET (@var{fundecl}) | |
2741 | If defined, a C expression whose value is an integer giving the offset | |
2742 | in bytes from the canonical frame address (cfa) to the frame base used | |
2743 | in DWARF 2 debug information. The default is zero. A different value | |
2744 | may reduce the size of debug information on some ports. | |
2745 | @end defmac | |
2746 | ||
2747 | @node Exception Handling | |
2748 | @subsection Exception Handling Support | |
2749 | @cindex exception handling | |
2750 | ||
2751 | @defmac EH_RETURN_DATA_REGNO (@var{N}) | |
2752 | A C expression whose value is the @var{N}th register number used for | |
2753 | data by exception handlers, or @code{INVALID_REGNUM} if fewer than | |
2754 | @var{N} registers are usable. | |
2755 | ||
2756 | The exception handling library routines communicate with the exception | |
2757 | handlers via a set of agreed upon registers. Ideally these registers | |
2758 | should be call-clobbered; it is possible to use call-saved registers, | |
2759 | but may negatively impact code size. The target must support at least | |
2760 | 2 data registers, but should define 4 if there are enough free registers. | |
2761 | ||
2762 | You must define this macro if you want to support call frame exception | |
2763 | handling like that provided by DWARF 2. | |
2764 | @end defmac | |
2765 | ||
2766 | @defmac EH_RETURN_STACKADJ_RTX | |
2767 | A C expression whose value is RTL representing a location in which | |
2768 | to store a stack adjustment to be applied before function return. | |
2769 | This is used to unwind the stack to an exception handler's call frame. | |
2770 | It will be assigned zero on code paths that return normally. | |
2771 | ||
2772 | Typically this is a call-clobbered hard register that is otherwise | |
2773 | untouched by the epilogue, but could also be a stack slot. | |
2774 | ||
2775 | Do not define this macro if the stack pointer is saved and restored | |
2776 | by the regular prolog and epilog code in the call frame itself; in | |
2777 | this case, the exception handling library routines will update the | |
2778 | stack location to be restored in place. Otherwise, you must define | |
2779 | this macro if you want to support call frame exception handling like | |
2780 | that provided by DWARF 2. | |
2781 | @end defmac | |
2782 | ||
2783 | @defmac EH_RETURN_HANDLER_RTX | |
2784 | A C expression whose value is RTL representing a location in which | |
2785 | to store the address of an exception handler to which we should | |
2786 | return. It will not be assigned on code paths that return normally. | |
2787 | ||
2788 | Typically this is the location in the call frame at which the normal | |
2789 | return address is stored. For targets that return by popping an | |
2790 | address off the stack, this might be a memory address just below | |
2791 | the @emph{target} call frame rather than inside the current call | |
2792 | frame. If defined, @code{EH_RETURN_STACKADJ_RTX} will have already | |
2793 | been assigned, so it may be used to calculate the location of the | |
2794 | target call frame. | |
2795 | ||
2796 | Some targets have more complex requirements than storing to an | |
2797 | address calculable during initial code generation. In that case | |
2798 | the @code{eh_return} instruction pattern should be used instead. | |
2799 | ||
2800 | If you want to support call frame exception handling, you must | |
2801 | define either this macro or the @code{eh_return} instruction pattern. | |
2802 | @end defmac | |
2803 | ||
2804 | @defmac RETURN_ADDR_OFFSET | |
2805 | If defined, an integer-valued C expression for which rtl will be generated | |
2806 | to add it to the exception handler address before it is searched in the | |
2807 | exception handling tables, and to subtract it again from the address before | |
2808 | using it to return to the exception handler. | |
2809 | @end defmac | |
2810 | ||
2811 | @defmac ASM_PREFERRED_EH_DATA_FORMAT (@var{code}, @var{global}) | |
2812 | This macro chooses the encoding of pointers embedded in the exception | |
2813 | handling sections. If at all possible, this should be defined such | |
2814 | that the exception handling section will not require dynamic relocations, | |
2815 | and so may be read-only. | |
2816 | ||
2817 | @var{code} is 0 for data, 1 for code labels, 2 for function pointers. | |
2818 | @var{global} is true if the symbol may be affected by dynamic relocations. | |
2819 | The macro should return a combination of the @code{DW_EH_PE_*} defines | |
2820 | as found in @file{dwarf2.h}. | |
2821 | ||
2822 | If this macro is not defined, pointers will not be encoded but | |
2823 | represented directly. | |
2824 | @end defmac | |
2825 | ||
2826 | @defmac ASM_MAYBE_OUTPUT_ENCODED_ADDR_RTX (@var{file}, @var{encoding}, @var{size}, @var{addr}, @var{done}) | |
2827 | This macro allows the target to emit whatever special magic is required | |
2828 | to represent the encoding chosen by @code{ASM_PREFERRED_EH_DATA_FORMAT}. | |
2829 | Generic code takes care of pc-relative and indirect encodings; this must | |
2830 | be defined if the target uses text-relative or data-relative encodings. | |
2831 | ||
2832 | This is a C statement that branches to @var{done} if the format was | |
2833 | handled. @var{encoding} is the format chosen, @var{size} is the number | |
2834 | of bytes that the format occupies, @var{addr} is the @code{SYMBOL_REF} | |
2835 | to be emitted. | |
2836 | @end defmac | |
2837 | ||
202d6e5f | 2838 | @defmac MD_FALLBACK_FRAME_STATE_FOR (@var{context}, @var{fs}) |
2839 | This macro allows the target to add CPU and operating system specific | |
2840 | code to the call-frame unwinder for use when there is no unwind data | |
2841 | available. The most common reason to implement this macro is to unwind | |
2842 | through signal frames. | |
2843 | ||
2844 | This macro is called from @code{uw_frame_state_for} in | |
2845 | @file{unwind-dw2.c}, @file{unwind-dw2-xtensa.c} and | |
2846 | @file{unwind-ia64.c}. @var{context} is an @code{_Unwind_Context}; | |
2847 | @var{fs} is an @code{_Unwind_FrameState}. Examine @code{context->ra} | |
2848 | for the address of the code being executed and @code{context->cfa} for | |
2849 | the stack pointer value. If the frame can be decoded, the register | |
2850 | save addresses should be updated in @var{fs} and the macro should | |
2851 | evaluate to @code{_URC_NO_REASON}. If the frame cannot be decoded, | |
2852 | the macro should evaluate to @code{_URC_END_OF_STACK}. | |
2853 | ||
2854 | For proper signal handling in Java this macro is accompanied by | |
2855 | @code{MAKE_THROW_FRAME}, defined in @file{libjava/include/*-signal.h} headers. | |
2856 | @end defmac | |
2857 | ||
2858 | @defmac MD_HANDLE_UNWABI (@var{context}, @var{fs}) | |
2859 | This macro allows the target to add operating system specific code to the | |
2860 | call-frame unwinder to handle the IA-64 @code{.unwabi} unwinding directive, | |
2861 | usually used for signal or interrupt frames. | |
2862 | ||
c07f27fd | 2863 | This macro is called from @code{uw_update_context} in libgcc's |
2864 | @file{unwind-ia64.c}. @var{context} is an @code{_Unwind_Context}; | |
202d6e5f | 2865 | @var{fs} is an @code{_Unwind_FrameState}. Examine @code{fs->unwabi} |
2866 | for the abi and context in the @code{.unwabi} directive. If the | |
2867 | @code{.unwabi} directive can be handled, the register save addresses should | |
2868 | be updated in @var{fs}. | |
2869 | @end defmac | |
2870 | ||
2871 | @defmac TARGET_USES_WEAK_UNWIND_INFO | |
2872 | A C expression that evaluates to true if the target requires unwind | |
2873 | info to be given comdat linkage. Define it to be @code{1} if comdat | |
2874 | linkage is necessary. The default is @code{0}. | |
2875 | @end defmac | |
2876 | ||
2877 | @node Stack Checking | |
2878 | @subsection Specifying How Stack Checking is Done | |
2879 | ||
2880 | GCC will check that stack references are within the boundaries of the | |
2881 | stack, if the option @option{-fstack-check} is specified, in one of | |
2882 | three ways: | |
2883 | ||
2884 | @enumerate | |
2885 | @item | |
2886 | If the value of the @code{STACK_CHECK_BUILTIN} macro is nonzero, GCC | |
2887 | will assume that you have arranged for full stack checking to be done | |
2888 | at appropriate places in the configuration files. GCC will not do | |
2889 | other special processing. | |
2890 | ||
2891 | @item | |
2892 | If @code{STACK_CHECK_BUILTIN} is zero and the value of the | |
2893 | @code{STACK_CHECK_STATIC_BUILTIN} macro is nonzero, GCC will assume | |
2894 | that you have arranged for static stack checking (checking of the | |
2895 | static stack frame of functions) to be done at appropriate places | |
2896 | in the configuration files. GCC will only emit code to do dynamic | |
2897 | stack checking (checking on dynamic stack allocations) using the third | |
2898 | approach below. | |
2899 | ||
2900 | @item | |
2901 | If neither of the above are true, GCC will generate code to periodically | |
2902 | ``probe'' the stack pointer using the values of the macros defined below. | |
2903 | @end enumerate | |
2904 | ||
2905 | If neither STACK_CHECK_BUILTIN nor STACK_CHECK_STATIC_BUILTIN is defined, | |
2906 | GCC will change its allocation strategy for large objects if the option | |
2907 | @option{-fstack-check} is specified: they will always be allocated | |
2908 | dynamically if their size exceeds @code{STACK_CHECK_MAX_VAR_SIZE} bytes. | |
2909 | ||
2910 | @defmac STACK_CHECK_BUILTIN | |
2911 | A nonzero value if stack checking is done by the configuration files in a | |
2912 | machine-dependent manner. You should define this macro if stack checking | |
2913 | is required by the ABI of your machine or if you would like to do stack | |
2914 | checking in some more efficient way than the generic approach. The default | |
2915 | value of this macro is zero. | |
2916 | @end defmac | |
2917 | ||
2918 | @defmac STACK_CHECK_STATIC_BUILTIN | |
2919 | A nonzero value if static stack checking is done by the configuration files | |
2920 | in a machine-dependent manner. You should define this macro if you would | |
2921 | like to do static stack checking in some more efficient way than the generic | |
2922 | approach. The default value of this macro is zero. | |
2923 | @end defmac | |
2924 | ||
2925 | @defmac STACK_CHECK_PROBE_INTERVAL_EXP | |
2926 | An integer specifying the interval at which GCC must generate stack probe | |
2927 | instructions, defined as 2 raised to this integer. You will normally | |
2928 | define this macro so that the interval be no larger than the size of | |
2929 | the ``guard pages'' at the end of a stack area. The default value | |
2930 | of 12 (4096-byte interval) is suitable for most systems. | |
2931 | @end defmac | |
2932 | ||
2933 | @defmac STACK_CHECK_MOVING_SP | |
2934 | An integer which is nonzero if GCC should move the stack pointer page by page | |
2935 | when doing probes. This can be necessary on systems where the stack pointer | |
2936 | contains the bottom address of the memory area accessible to the executing | |
2937 | thread at any point in time. In this situation an alternate signal stack | |
2938 | is required in order to be able to recover from a stack overflow. The | |
2939 | default value of this macro is zero. | |
2940 | @end defmac | |
2941 | ||
2942 | @defmac STACK_CHECK_PROTECT | |
2943 | The number of bytes of stack needed to recover from a stack overflow, for | |
2944 | languages where such a recovery is supported. The default value of 75 words | |
2945 | with the @code{setjmp}/@code{longjmp}-based exception handling mechanism and | |
2946 | 8192 bytes with other exception handling mechanisms should be adequate for | |
2947 | most machines. | |
2948 | @end defmac | |
2949 | ||
2950 | The following macros are relevant only if neither STACK_CHECK_BUILTIN | |
2951 | nor STACK_CHECK_STATIC_BUILTIN is defined; you can omit them altogether | |
2952 | in the opposite case. | |
2953 | ||
2954 | @defmac STACK_CHECK_MAX_FRAME_SIZE | |
2955 | The maximum size of a stack frame, in bytes. GCC will generate probe | |
2956 | instructions in non-leaf functions to ensure at least this many bytes of | |
2957 | stack are available. If a stack frame is larger than this size, stack | |
2958 | checking will not be reliable and GCC will issue a warning. The | |
2959 | default is chosen so that GCC only generates one instruction on most | |
2960 | systems. You should normally not change the default value of this macro. | |
2961 | @end defmac | |
2962 | ||
2963 | @defmac STACK_CHECK_FIXED_FRAME_SIZE | |
2964 | GCC uses this value to generate the above warning message. It | |
2965 | represents the amount of fixed frame used by a function, not including | |
2966 | space for any callee-saved registers, temporaries and user variables. | |
2967 | You need only specify an upper bound for this amount and will normally | |
2968 | use the default of four words. | |
2969 | @end defmac | |
2970 | ||
2971 | @defmac STACK_CHECK_MAX_VAR_SIZE | |
2972 | The maximum size, in bytes, of an object that GCC will place in the | |
2973 | fixed area of the stack frame when the user specifies | |
2974 | @option{-fstack-check}. | |
2975 | GCC computed the default from the values of the above macros and you will | |
2976 | normally not need to override that default. | |
2977 | @end defmac | |
2978 | ||
2979 | @need 2000 | |
2980 | @node Frame Registers | |
2981 | @subsection Registers That Address the Stack Frame | |
2982 | ||
2983 | @c prevent bad page break with this line | |
2984 | This discusses registers that address the stack frame. | |
2985 | ||
2986 | @defmac STACK_POINTER_REGNUM | |
2987 | The register number of the stack pointer register, which must also be a | |
2988 | fixed register according to @code{FIXED_REGISTERS}. On most machines, | |
2989 | the hardware determines which register this is. | |
2990 | @end defmac | |
2991 | ||
2992 | @defmac FRAME_POINTER_REGNUM | |
2993 | The register number of the frame pointer register, which is used to | |
2994 | access automatic variables in the stack frame. On some machines, the | |
2995 | hardware determines which register this is. On other machines, you can | |
2996 | choose any register you wish for this purpose. | |
2997 | @end defmac | |
2998 | ||
2999 | @defmac HARD_FRAME_POINTER_REGNUM | |
3000 | On some machines the offset between the frame pointer and starting | |
3001 | offset of the automatic variables is not known until after register | |
3002 | allocation has been done (for example, because the saved registers are | |
3003 | between these two locations). On those machines, define | |
3004 | @code{FRAME_POINTER_REGNUM} the number of a special, fixed register to | |
3005 | be used internally until the offset is known, and define | |
3006 | @code{HARD_FRAME_POINTER_REGNUM} to be the actual hard register number | |
3007 | used for the frame pointer. | |
3008 | ||
3009 | You should define this macro only in the very rare circumstances when it | |
3010 | is not possible to calculate the offset between the frame pointer and | |
3011 | the automatic variables until after register allocation has been | |
3012 | completed. When this macro is defined, you must also indicate in your | |
3013 | definition of @code{ELIMINABLE_REGS} how to eliminate | |
3014 | @code{FRAME_POINTER_REGNUM} into either @code{HARD_FRAME_POINTER_REGNUM} | |
3015 | or @code{STACK_POINTER_REGNUM}. | |
3016 | ||
3017 | Do not define this macro if it would be the same as | |
3018 | @code{FRAME_POINTER_REGNUM}. | |
3019 | @end defmac | |
3020 | ||
3021 | @defmac ARG_POINTER_REGNUM | |
3022 | The register number of the arg pointer register, which is used to access | |
3023 | the function's argument list. On some machines, this is the same as the | |
3024 | frame pointer register. On some machines, the hardware determines which | |
3025 | register this is. On other machines, you can choose any register you | |
3026 | wish for this purpose. If this is not the same register as the frame | |
3027 | pointer register, then you must mark it as a fixed register according to | |
3028 | @code{FIXED_REGISTERS}, or arrange to be able to eliminate it | |
3029 | (@pxref{Elimination}). | |
3030 | @end defmac | |
3031 | ||
5ae82d58 | 3032 | @defmac HARD_FRAME_POINTER_IS_FRAME_POINTER |
3033 | Define this to a preprocessor constant that is nonzero if | |
3034 | @code{hard_frame_pointer_rtx} and @code{frame_pointer_rtx} should be | |
3035 | the same. The default definition is @samp{(HARD_FRAME_POINTER_REGNUM | |
3036 | == FRAME_POINTER_REGNUM)}; you only need to define this macro if that | |
3037 | definition is not suitable for use in preprocessor conditionals. | |
3038 | @end defmac | |
3039 | ||
3040 | @defmac HARD_FRAME_POINTER_IS_ARG_POINTER | |
3041 | Define this to a preprocessor constant that is nonzero if | |
3042 | @code{hard_frame_pointer_rtx} and @code{arg_pointer_rtx} should be the | |
3043 | same. The default definition is @samp{(HARD_FRAME_POINTER_REGNUM == | |
3044 | ARG_POINTER_REGNUM)}; you only need to define this macro if that | |
3045 | definition is not suitable for use in preprocessor conditionals. | |
3046 | @end defmac | |
3047 | ||
202d6e5f | 3048 | @defmac RETURN_ADDRESS_POINTER_REGNUM |
3049 | The register number of the return address pointer register, which is used to | |
3050 | access the current function's return address from the stack. On some | |
3051 | machines, the return address is not at a fixed offset from the frame | |
3052 | pointer or stack pointer or argument pointer. This register can be defined | |
3053 | to point to the return address on the stack, and then be converted by | |
3054 | @code{ELIMINABLE_REGS} into either the frame pointer or stack pointer. | |
3055 | ||
3056 | Do not define this macro unless there is no other way to get the return | |
3057 | address from the stack. | |
3058 | @end defmac | |
3059 | ||
3060 | @defmac STATIC_CHAIN_REGNUM | |
3061 | @defmacx STATIC_CHAIN_INCOMING_REGNUM | |
3062 | Register numbers used for passing a function's static chain pointer. If | |
3063 | register windows are used, the register number as seen by the called | |
3064 | function is @code{STATIC_CHAIN_INCOMING_REGNUM}, while the register | |
3065 | number as seen by the calling function is @code{STATIC_CHAIN_REGNUM}. If | |
3066 | these registers are the same, @code{STATIC_CHAIN_INCOMING_REGNUM} need | |
3067 | not be defined. | |
3068 | ||
3069 | The static chain register need not be a fixed register. | |
3070 | ||
3071 | If the static chain is passed in memory, these macros should not be | |
3072 | defined; instead, the @code{TARGET_STATIC_CHAIN} hook should be used. | |
3073 | @end defmac | |
3074 | ||
3075 | @hook TARGET_STATIC_CHAIN | |
202d6e5f | 3076 | |
3077 | @defmac DWARF_FRAME_REGISTERS | |
3078 | This macro specifies the maximum number of hard registers that can be | |
3079 | saved in a call frame. This is used to size data structures used in | |
3080 | DWARF2 exception handling. | |
3081 | ||
3082 | Prior to GCC 3.0, this macro was needed in order to establish a stable | |
3083 | exception handling ABI in the face of adding new hard registers for ISA | |
3084 | extensions. In GCC 3.0 and later, the EH ABI is insulated from changes | |
3085 | in the number of hard registers. Nevertheless, this macro can still be | |
3086 | used to reduce the runtime memory requirements of the exception handling | |
3087 | routines, which can be substantial if the ISA contains a lot of | |
3088 | registers that are not call-saved. | |
3089 | ||
3090 | If this macro is not defined, it defaults to | |
3091 | @code{FIRST_PSEUDO_REGISTER}. | |
3092 | @end defmac | |
3093 | ||
3094 | @defmac PRE_GCC3_DWARF_FRAME_REGISTERS | |
3095 | ||
3096 | This macro is similar to @code{DWARF_FRAME_REGISTERS}, but is provided | |
3097 | for backward compatibility in pre GCC 3.0 compiled code. | |
3098 | ||
3099 | If this macro is not defined, it defaults to | |
3100 | @code{DWARF_FRAME_REGISTERS}. | |
3101 | @end defmac | |
3102 | ||
3103 | @defmac DWARF_REG_TO_UNWIND_COLUMN (@var{regno}) | |
3104 | ||
3105 | Define this macro if the target's representation for dwarf registers | |
3106 | is different than the internal representation for unwind column. | |
3107 | Given a dwarf register, this macro should return the internal unwind | |
3108 | column number to use instead. | |
3109 | ||
3110 | See the PowerPC's SPE target for an example. | |
3111 | @end defmac | |
3112 | ||
3113 | @defmac DWARF_FRAME_REGNUM (@var{regno}) | |
3114 | ||
3115 | Define this macro if the target's representation for dwarf registers | |
3116 | used in .eh_frame or .debug_frame is different from that used in other | |
3117 | debug info sections. Given a GCC hard register number, this macro | |
3118 | should return the .eh_frame register number. The default is | |
3119 | @code{DBX_REGISTER_NUMBER (@var{regno})}. | |
3120 | ||
3121 | @end defmac | |
3122 | ||
3123 | @defmac DWARF2_FRAME_REG_OUT (@var{regno}, @var{for_eh}) | |
3124 | ||
3125 | Define this macro to map register numbers held in the call frame info | |
3126 | that GCC has collected using @code{DWARF_FRAME_REGNUM} to those that | |
3127 | should be output in .debug_frame (@code{@var{for_eh}} is zero) and | |
3128 | .eh_frame (@code{@var{for_eh}} is nonzero). The default is to | |
3129 | return @code{@var{regno}}. | |
3130 | ||
3131 | @end defmac | |
3132 | ||
e451a093 | 3133 | @defmac REG_VALUE_IN_UNWIND_CONTEXT |
3134 | ||
3135 | Define this macro if the target stores register values as | |
3136 | @code{_Unwind_Word} type in unwind context. It should be defined if | |
3137 | target register size is larger than the size of @code{void *}. The | |
3138 | default is to store register values as @code{void *} type. | |
3139 | ||
3140 | @end defmac | |
3141 | ||
3142 | @defmac ASSUME_EXTENDED_UNWIND_CONTEXT | |
3143 | ||
3144 | Define this macro to be 1 if the target always uses extended unwind | |
3145 | context with version, args_size and by_value fields. If it is undefined, | |
3146 | it will be defined to 1 when @code{REG_VALUE_IN_UNWIND_CONTEXT} is | |
3147 | defined and 0 otherwise. | |
3148 | ||
3149 | @end defmac | |
3150 | ||
202d6e5f | 3151 | @node Elimination |
3152 | @subsection Eliminating Frame Pointer and Arg Pointer | |
3153 | ||
3154 | @c prevent bad page break with this line | |
3155 | This is about eliminating the frame pointer and arg pointer. | |
3156 | ||
3157 | @hook TARGET_FRAME_POINTER_REQUIRED | |
202d6e5f | 3158 | |
3159 | @findex get_frame_size | |
3160 | @defmac INITIAL_FRAME_POINTER_OFFSET (@var{depth-var}) | |
3161 | A C statement to store in the variable @var{depth-var} the difference | |
3162 | between the frame pointer and the stack pointer values immediately after | |
3163 | the function prologue. The value would be computed from information | |
3164 | such as the result of @code{get_frame_size ()} and the tables of | |
3165 | registers @code{regs_ever_live} and @code{call_used_regs}. | |
3166 | ||
3167 | If @code{ELIMINABLE_REGS} is defined, this macro will be not be used and | |
3168 | need not be defined. Otherwise, it must be defined even if | |
3169 | @code{TARGET_FRAME_POINTER_REQUIRED} always returns true; in that | |
3170 | case, you may set @var{depth-var} to anything. | |
3171 | @end defmac | |
3172 | ||
3173 | @defmac ELIMINABLE_REGS | |
3174 | If defined, this macro specifies a table of register pairs used to | |
3175 | eliminate unneeded registers that point into the stack frame. If it is not | |
3176 | defined, the only elimination attempted by the compiler is to replace | |
3177 | references to the frame pointer with references to the stack pointer. | |
3178 | ||
3179 | The definition of this macro is a list of structure initializations, each | |
3180 | of which specifies an original and replacement register. | |
3181 | ||
3182 | On some machines, the position of the argument pointer is not known until | |
3183 | the compilation is completed. In such a case, a separate hard register | |
3184 | must be used for the argument pointer. This register can be eliminated by | |
3185 | replacing it with either the frame pointer or the argument pointer, | |
3186 | depending on whether or not the frame pointer has been eliminated. | |
3187 | ||
3188 | In this case, you might specify: | |
3189 | @smallexample | |
3190 | #define ELIMINABLE_REGS \ | |
3191 | @{@{ARG_POINTER_REGNUM, STACK_POINTER_REGNUM@}, \ | |
3192 | @{ARG_POINTER_REGNUM, FRAME_POINTER_REGNUM@}, \ | |
3193 | @{FRAME_POINTER_REGNUM, STACK_POINTER_REGNUM@}@} | |
3194 | @end smallexample | |
3195 | ||
3196 | Note that the elimination of the argument pointer with the stack pointer is | |
3197 | specified first since that is the preferred elimination. | |
3198 | @end defmac | |
3199 | ||
3200 | @hook TARGET_CAN_ELIMINATE | |
202d6e5f | 3201 | |
3202 | @defmac INITIAL_ELIMINATION_OFFSET (@var{from-reg}, @var{to-reg}, @var{offset-var}) | |
3203 | This macro is similar to @code{INITIAL_FRAME_POINTER_OFFSET}. It | |
3204 | specifies the initial difference between the specified pair of | |
3205 | registers. This macro must be defined if @code{ELIMINABLE_REGS} is | |
3206 | defined. | |
3207 | @end defmac | |
3208 | ||
3209 | @node Stack Arguments | |
3210 | @subsection Passing Function Arguments on the Stack | |
3211 | @cindex arguments on stack | |
3212 | @cindex stack arguments | |
3213 | ||
3214 | The macros in this section control how arguments are passed | |
3215 | on the stack. See the following section for other macros that | |
3216 | control passing certain arguments in registers. | |
3217 | ||
3218 | @hook TARGET_PROMOTE_PROTOTYPES | |
202d6e5f | 3219 | |
3220 | @defmac PUSH_ARGS | |
3221 | A C expression. If nonzero, push insns will be used to pass | |
3222 | outgoing arguments. | |
3223 | If the target machine does not have a push instruction, set it to zero. | |
3224 | That directs GCC to use an alternate strategy: to | |
3225 | allocate the entire argument block and then store the arguments into | |
3226 | it. When @code{PUSH_ARGS} is nonzero, @code{PUSH_ROUNDING} must be defined too. | |
3227 | @end defmac | |
3228 | ||
3229 | @defmac PUSH_ARGS_REVERSED | |
3230 | A C expression. If nonzero, function arguments will be evaluated from | |
3231 | last to first, rather than from first to last. If this macro is not | |
3232 | defined, it defaults to @code{PUSH_ARGS} on targets where the stack | |
3233 | and args grow in opposite directions, and 0 otherwise. | |
3234 | @end defmac | |
3235 | ||
3236 | @defmac PUSH_ROUNDING (@var{npushed}) | |
3237 | A C expression that is the number of bytes actually pushed onto the | |
3238 | stack when an instruction attempts to push @var{npushed} bytes. | |
3239 | ||
3240 | On some machines, the definition | |
3241 | ||
3242 | @smallexample | |
3243 | #define PUSH_ROUNDING(BYTES) (BYTES) | |
3244 | @end smallexample | |
3245 | ||
3246 | @noindent | |
3247 | will suffice. But on other machines, instructions that appear | |
3248 | to push one byte actually push two bytes in an attempt to maintain | |
3249 | alignment. Then the definition should be | |
3250 | ||
3251 | @smallexample | |
3252 | #define PUSH_ROUNDING(BYTES) (((BYTES) + 1) & ~1) | |
3253 | @end smallexample | |
c6e790c5 | 3254 | |
2f05705b | 3255 | If the value of this macro has a type, it should be an unsigned type. |
202d6e5f | 3256 | @end defmac |
3257 | ||
81e483dd | 3258 | @findex outgoing_args_size |
3259 | @findex crtl->outgoing_args_size | |
202d6e5f | 3260 | @defmac ACCUMULATE_OUTGOING_ARGS |
3261 | A C expression. If nonzero, the maximum amount of space required for outgoing arguments | |
81e483dd | 3262 | will be computed and placed into |
3263 | @code{crtl->outgoing_args_size}. No space will be pushed | |
202d6e5f | 3264 | onto the stack for each call; instead, the function prologue should |
3265 | increase the stack frame size by this amount. | |
3266 | ||
3267 | Setting both @code{PUSH_ARGS} and @code{ACCUMULATE_OUTGOING_ARGS} | |
3268 | is not proper. | |
3269 | @end defmac | |
3270 | ||
3271 | @defmac REG_PARM_STACK_SPACE (@var{fndecl}) | |
3272 | Define this macro if functions should assume that stack space has been | |
3273 | allocated for arguments even when their values are passed in | |
3274 | registers. | |
3275 | ||
3276 | The value of this macro is the size, in bytes, of the area reserved for | |
3277 | arguments passed in registers for the function represented by @var{fndecl}, | |
3278 | which can be zero if GCC is calling a library function. | |
3279 | The argument @var{fndecl} can be the FUNCTION_DECL, or the type itself | |
3280 | of the function. | |
3281 | ||
3282 | This space can be allocated by the caller, or be a part of the | |
3283 | machine-dependent stack frame: @code{OUTGOING_REG_PARM_STACK_SPACE} says | |
3284 | which. | |
3285 | @end defmac | |
3286 | @c above is overfull. not sure what to do. --mew 5feb93 did | |
3287 | @c something, not sure if it looks good. --mew 10feb93 | |
3288 | ||
02114c95 | 3289 | @defmac INCOMING_REG_PARM_STACK_SPACE (@var{fndecl}) |
3290 | Like @code{REG_PARM_STACK_SPACE}, but for incoming register arguments. | |
3291 | Define this macro if space guaranteed when compiling a function body | |
3292 | is different to space required when making a call, a situation that | |
3293 | can arise with K&R style function definitions. | |
3294 | @end defmac | |
3295 | ||
202d6e5f | 3296 | @defmac OUTGOING_REG_PARM_STACK_SPACE (@var{fntype}) |
3297 | Define this to a nonzero value if it is the responsibility of the | |
3298 | caller to allocate the area reserved for arguments passed in registers | |
3299 | when calling a function of @var{fntype}. @var{fntype} may be NULL | |
3300 | if the function called is a library function. | |
3301 | ||
3302 | If @code{ACCUMULATE_OUTGOING_ARGS} is defined, this macro controls | |
3303 | whether the space for these arguments counts in the value of | |
81e483dd | 3304 | @code{crtl->outgoing_args_size}. |
202d6e5f | 3305 | @end defmac |
3306 | ||
3307 | @defmac STACK_PARMS_IN_REG_PARM_AREA | |
3308 | Define this macro if @code{REG_PARM_STACK_SPACE} is defined, but the | |
3309 | stack parameters don't skip the area specified by it. | |
3310 | @c i changed this, makes more sens and it should have taken care of the | |
3311 | @c overfull.. not as specific, tho. --mew 5feb93 | |
3312 | ||
3313 | Normally, when a parameter is not passed in registers, it is placed on the | |
3314 | stack beyond the @code{REG_PARM_STACK_SPACE} area. Defining this macro | |
3315 | suppresses this behavior and causes the parameter to be passed on the | |
3316 | stack in its natural location. | |
3317 | @end defmac | |
3318 | ||
fe0b4016 | 3319 | @hook TARGET_RETURN_POPS_ARGS |
202d6e5f | 3320 | |
3321 | @defmac CALL_POPS_ARGS (@var{cum}) | |
3322 | A C expression that should indicate the number of bytes a call sequence | |
3323 | pops off the stack. It is added to the value of @code{RETURN_POPS_ARGS} | |
3324 | when compiling a function call. | |
3325 | ||
3326 | @var{cum} is the variable in which all arguments to the called function | |
3327 | have been accumulated. | |
3328 | ||
3329 | On certain architectures, such as the SH5, a call trampoline is used | |
3330 | that pops certain registers off the stack, depending on the arguments | |
3331 | that have been passed to the function. Since this is a property of the | |
3332 | call site, not of the called function, @code{RETURN_POPS_ARGS} is not | |
3333 | appropriate. | |
3334 | @end defmac | |
3335 | ||
3336 | @node Register Arguments | |
3337 | @subsection Passing Arguments in Registers | |
3338 | @cindex arguments in registers | |
3339 | @cindex registers arguments | |
3340 | ||
3341 | This section describes the macros which let you control how various | |
3342 | types of arguments are passed in registers or how they are arranged in | |
3343 | the stack. | |
3344 | ||
81bcd36c | 3345 | @hook TARGET_FUNCTION_ARG |
202d6e5f | 3346 | |
3347 | @hook TARGET_MUST_PASS_IN_STACK | |
202d6e5f | 3348 | |
81bcd36c | 3349 | @hook TARGET_FUNCTION_INCOMING_ARG |
202d6e5f | 3350 | |
a9d8ab38 | 3351 | @hook TARGET_USE_PSEUDO_PIC_REG |
3352 | ||
3353 | @hook TARGET_INIT_PIC_REG | |
3354 | ||
202d6e5f | 3355 | @hook TARGET_ARG_PARTIAL_BYTES |
202d6e5f | 3356 | |
b4c24d67 | 3357 | @hook TARGET_PASS_BY_REFERENCE |
202d6e5f | 3358 | |
3359 | @hook TARGET_CALLEE_COPIES | |
202d6e5f | 3360 | |
3361 | @defmac CUMULATIVE_ARGS | |
81bcd36c | 3362 | A C type for declaring a variable that is used as the first argument |
3363 | of @code{TARGET_FUNCTION_ARG} and other related values. For some | |
3364 | target machines, the type @code{int} suffices and can hold the number | |
3365 | of bytes of argument so far. | |
202d6e5f | 3366 | |
3367 | There is no need to record in @code{CUMULATIVE_ARGS} anything about the | |
3368 | arguments that have been passed on the stack. The compiler has other | |
3369 | variables to keep track of that. For target machines on which all | |
3370 | arguments are passed on the stack, there is no need to store anything in | |
3371 | @code{CUMULATIVE_ARGS}; however, the data structure must exist and | |
3372 | should not be empty, so use @code{int}. | |
3373 | @end defmac | |
3374 | ||
3375 | @defmac OVERRIDE_ABI_FORMAT (@var{fndecl}) | |
3376 | If defined, this macro is called before generating any code for a | |
3377 | function, but after the @var{cfun} descriptor for the function has been | |
3378 | created. The back end may use this macro to update @var{cfun} to | |
3379 | reflect an ABI other than that which would normally be used by default. | |
3380 | If the compiler is generating code for a compiler-generated function, | |
3381 | @var{fndecl} may be @code{NULL}. | |
3382 | @end defmac | |
3383 | ||
3384 | @defmac INIT_CUMULATIVE_ARGS (@var{cum}, @var{fntype}, @var{libname}, @var{fndecl}, @var{n_named_args}) | |
3385 | A C statement (sans semicolon) for initializing the variable | |
3386 | @var{cum} for the state at the beginning of the argument list. The | |
3387 | variable has type @code{CUMULATIVE_ARGS}. The value of @var{fntype} | |
3388 | is the tree node for the data type of the function which will receive | |
3389 | the args, or 0 if the args are to a compiler support library function. | |
3390 | For direct calls that are not libcalls, @var{fndecl} contain the | |
3391 | declaration node of the function. @var{fndecl} is also set when | |
3392 | @code{INIT_CUMULATIVE_ARGS} is used to find arguments for the function | |
3393 | being compiled. @var{n_named_args} is set to the number of named | |
3394 | arguments, including a structure return address if it is passed as a | |
3395 | parameter, when making a call. When processing incoming arguments, | |
3396 | @var{n_named_args} is set to @minus{}1. | |
3397 | ||
3398 | When processing a call to a compiler support library function, | |
3399 | @var{libname} identifies which one. It is a @code{symbol_ref} rtx which | |
3400 | contains the name of the function, as a string. @var{libname} is 0 when | |
3401 | an ordinary C function call is being processed. Thus, each time this | |
3402 | macro is called, either @var{libname} or @var{fntype} is nonzero, but | |
3403 | never both of them at once. | |
3404 | @end defmac | |
3405 | ||
3406 | @defmac INIT_CUMULATIVE_LIBCALL_ARGS (@var{cum}, @var{mode}, @var{libname}) | |
3407 | Like @code{INIT_CUMULATIVE_ARGS} but only used for outgoing libcalls, | |
3408 | it gets a @code{MODE} argument instead of @var{fntype}, that would be | |
3409 | @code{NULL}. @var{indirect} would always be zero, too. If this macro | |
3410 | is not defined, @code{INIT_CUMULATIVE_ARGS (cum, NULL_RTX, libname, | |
3411 | 0)} is used instead. | |
3412 | @end defmac | |
3413 | ||
3414 | @defmac INIT_CUMULATIVE_INCOMING_ARGS (@var{cum}, @var{fntype}, @var{libname}) | |
3415 | Like @code{INIT_CUMULATIVE_ARGS} but overrides it for the purposes of | |
3416 | finding the arguments for the function being compiled. If this macro is | |
3417 | undefined, @code{INIT_CUMULATIVE_ARGS} is used instead. | |
3418 | ||
3419 | The value passed for @var{libname} is always 0, since library routines | |
3420 | with special calling conventions are never compiled with GCC@. The | |
3421 | argument @var{libname} exists for symmetry with | |
3422 | @code{INIT_CUMULATIVE_ARGS}. | |
3423 | @c could use "this macro" in place of @code{INIT_CUMULATIVE_ARGS}, maybe. | |
3424 | @c --mew 5feb93 i switched the order of the sentences. --mew 10feb93 | |
3425 | @end defmac | |
3426 | ||
81bcd36c | 3427 | @hook TARGET_FUNCTION_ARG_ADVANCE |
202d6e5f | 3428 | |
3429 | @defmac FUNCTION_ARG_OFFSET (@var{mode}, @var{type}) | |
3430 | If defined, a C expression that is the number of bytes to add to the | |
3431 | offset of the argument passed in memory. This is needed for the SPU, | |
3432 | which passes @code{char} and @code{short} arguments in the preferred | |
3433 | slot that is in the middle of the quad word instead of starting at the | |
3434 | top. | |
3435 | @end defmac | |
3436 | ||
3437 | @defmac FUNCTION_ARG_PADDING (@var{mode}, @var{type}) | |
3438 | If defined, a C expression which determines whether, and in which direction, | |
3439 | to pad out an argument with extra space. The value should be of type | |
3440 | @code{enum direction}: either @code{upward} to pad above the argument, | |
3441 | @code{downward} to pad below, or @code{none} to inhibit padding. | |
3442 | ||
17bfc2bc | 3443 | The @emph{amount} of padding is not controlled by this macro, but by the |
3444 | target hook @code{TARGET_FUNCTION_ARG_ROUND_BOUNDARY}. It is | |
3445 | always just enough to reach the next multiple of that boundary. | |
202d6e5f | 3446 | |
3447 | This macro has a default definition which is right for most systems. | |
3448 | For little-endian machines, the default is to pad upward. For | |
3449 | big-endian machines, the default is to pad downward for an argument of | |
3450 | constant size shorter than an @code{int}, and upward otherwise. | |
3451 | @end defmac | |
3452 | ||
3453 | @defmac PAD_VARARGS_DOWN | |
3454 | If defined, a C expression which determines whether the default | |
3455 | implementation of va_arg will attempt to pad down before reading the | |
3456 | next argument, if that argument is smaller than its aligned space as | |
3457 | controlled by @code{PARM_BOUNDARY}. If this macro is not defined, all such | |
3458 | arguments are padded down if @code{BYTES_BIG_ENDIAN} is true. | |
3459 | @end defmac | |
3460 | ||
3461 | @defmac BLOCK_REG_PADDING (@var{mode}, @var{type}, @var{first}) | |
3462 | Specify padding for the last element of a block move between registers and | |
3463 | memory. @var{first} is nonzero if this is the only element. Defining this | |
3464 | macro allows better control of register function parameters on big-endian | |
3465 | machines, without using @code{PARALLEL} rtl. In particular, | |
3466 | @code{MUST_PASS_IN_STACK} need not test padding and mode of types in | |
3467 | registers, as there is no longer a "wrong" part of a register; For example, | |
3468 | a three byte aggregate may be passed in the high part of a register if so | |
3469 | required. | |
3470 | @end defmac | |
3471 | ||
bd99ba64 | 3472 | @hook TARGET_FUNCTION_ARG_BOUNDARY |
202d6e5f | 3473 | |
17bfc2bc | 3474 | @hook TARGET_FUNCTION_ARG_ROUND_BOUNDARY |
3475 | ||
202d6e5f | 3476 | @defmac FUNCTION_ARG_REGNO_P (@var{regno}) |
3477 | A C expression that is nonzero if @var{regno} is the number of a hard | |
3478 | register in which function arguments are sometimes passed. This does | |
3479 | @emph{not} include implicit arguments such as the static chain and | |
3480 | the structure-value address. On many machines, no registers can be | |
3481 | used for this purpose since all function arguments are pushed on the | |
3482 | stack. | |
3483 | @end defmac | |
3484 | ||
3485 | @hook TARGET_SPLIT_COMPLEX_ARG | |
202d6e5f | 3486 | |
3487 | @hook TARGET_BUILD_BUILTIN_VA_LIST | |
202d6e5f | 3488 | |
303ece6c | 3489 | @hook TARGET_ENUM_VA_LIST_P |
202d6e5f | 3490 | |
3491 | @hook TARGET_FN_ABI_VA_LIST | |
202d6e5f | 3492 | |
3493 | @hook TARGET_CANONICAL_VA_LIST_TYPE | |
202d6e5f | 3494 | |
3495 | @hook TARGET_GIMPLIFY_VA_ARG_EXPR | |
202d6e5f | 3496 | |
3497 | @hook TARGET_VALID_POINTER_MODE | |
202d6e5f | 3498 | |
be97d4b6 | 3499 | @hook TARGET_REF_MAY_ALIAS_ERRNO |
3500 | ||
202d6e5f | 3501 | @hook TARGET_SCALAR_MODE_SUPPORTED_P |
202d6e5f | 3502 | |
3503 | @hook TARGET_VECTOR_MODE_SUPPORTED_P | |
202d6e5f | 3504 | |
13d3ceb9 | 3505 | @hook TARGET_ARRAY_MODE_SUPPORTED_P |
3506 | ||
d5957f0d | 3507 | @hook TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P |
3508 | ||
202d6e5f | 3509 | @hook TARGET_SMALL_REGISTER_CLASSES_FOR_MODE_P |
202d6e5f | 3510 | |
a50372fe | 3511 | @hook TARGET_FLAGS_REGNUM |
3512 | ||
202d6e5f | 3513 | @node Scalar Return |
3514 | @subsection How Scalar Function Values Are Returned | |
3515 | @cindex return values in registers | |
3516 | @cindex values, returned by functions | |
3517 | @cindex scalars, returned as values | |
3518 | ||
3519 | This section discusses the macros that control returning scalars as | |
3520 | values---values that can fit in registers. | |
3521 | ||
3522 | @hook TARGET_FUNCTION_VALUE | |
3523 | ||
202d6e5f | 3524 | @defmac FUNCTION_VALUE (@var{valtype}, @var{func}) |
3525 | This macro has been deprecated. Use @code{TARGET_FUNCTION_VALUE} for | |
3526 | a new target instead. | |
3527 | @end defmac | |
3528 | ||
3529 | @defmac LIBCALL_VALUE (@var{mode}) | |
3530 | A C expression to create an RTX representing the place where a library | |
3531 | function returns a value of mode @var{mode}. | |
3532 | ||
3533 | Note that ``library function'' in this context means a compiler | |
3534 | support routine, used to perform arithmetic, whose name is known | |
3535 | specially by the compiler and was not mentioned in the C code being | |
3536 | compiled. | |
3537 | @end defmac | |
3538 | ||
3539 | @hook TARGET_LIBCALL_VALUE | |
202d6e5f | 3540 | |
3541 | @defmac FUNCTION_VALUE_REGNO_P (@var{regno}) | |
3542 | A C expression that is nonzero if @var{regno} is the number of a hard | |
3543 | register in which the values of called function may come back. | |
3544 | ||
3545 | A register whose use for returning values is limited to serving as the | |
3546 | second of a pair (for a value of type @code{double}, say) need not be | |
3547 | recognized by this macro. So for most machines, this definition | |
3548 | suffices: | |
3549 | ||
3550 | @smallexample | |
3551 | #define FUNCTION_VALUE_REGNO_P(N) ((N) == 0) | |
3552 | @end smallexample | |
3553 | ||
3554 | If the machine has register windows, so that the caller and the called | |
3555 | function use different registers for the return value, this macro | |
3556 | should recognize only the caller's register numbers. | |
3557 | ||
3558 | This macro has been deprecated. Use @code{TARGET_FUNCTION_VALUE_REGNO_P} | |
3559 | for a new target instead. | |
3560 | @end defmac | |
3561 | ||
3562 | @hook TARGET_FUNCTION_VALUE_REGNO_P | |
202d6e5f | 3563 | |
3564 | @defmac APPLY_RESULT_SIZE | |
3565 | Define this macro if @samp{untyped_call} and @samp{untyped_return} | |
3566 | need more space than is implied by @code{FUNCTION_VALUE_REGNO_P} for | |
3567 | saving and restoring an arbitrary return value. | |
3568 | @end defmac | |
3569 | ||
3570 | @hook TARGET_RETURN_IN_MSB | |
202d6e5f | 3571 | |
3572 | @node Aggregate Return | |
3573 | @subsection How Large Values Are Returned | |
3574 | @cindex aggregates as return values | |
3575 | @cindex large return values | |
3576 | @cindex returning aggregate values | |
3577 | @cindex structure value address | |
3578 | ||
3579 | When a function value's mode is @code{BLKmode} (and in some other | |
3580 | cases), the value is not returned according to | |
3581 | @code{TARGET_FUNCTION_VALUE} (@pxref{Scalar Return}). Instead, the | |
3582 | caller passes the address of a block of memory in which the value | |
3583 | should be stored. This address is called the @dfn{structure value | |
3584 | address}. | |
3585 | ||
3586 | This section describes how to control returning structure values in | |
3587 | memory. | |
3588 | ||
3589 | @hook TARGET_RETURN_IN_MEMORY | |
202d6e5f | 3590 | |
3591 | @defmac DEFAULT_PCC_STRUCT_RETURN | |
3592 | Define this macro to be 1 if all structure and union return values must be | |
3593 | in memory. Since this results in slower code, this should be defined | |
3594 | only if needed for compatibility with other compilers or with an ABI@. | |
3595 | If you define this macro to be 0, then the conventions used for structure | |
3596 | and union return values are decided by the @code{TARGET_RETURN_IN_MEMORY} | |
3597 | target hook. | |
3598 | ||
3599 | If not defined, this defaults to the value 1. | |
3600 | @end defmac | |
3601 | ||
3602 | @hook TARGET_STRUCT_VALUE_RTX | |
202d6e5f | 3603 | |
3604 | @defmac PCC_STATIC_STRUCT_RETURN | |
3605 | Define this macro if the usual system convention on the target machine | |
3606 | for returning structures and unions is for the called function to return | |
3607 | the address of a static variable containing the value. | |
3608 | ||
3609 | Do not define this if the usual system convention is for the caller to | |
3610 | pass an address to the subroutine. | |
3611 | ||
3612 | This macro has effect in @option{-fpcc-struct-return} mode, but it does | |
3613 | nothing when you use @option{-freg-struct-return} mode. | |
3614 | @end defmac | |
3615 | ||
4bac51c9 | 3616 | @hook TARGET_GET_RAW_RESULT_MODE |
3617 | ||
3618 | @hook TARGET_GET_RAW_ARG_MODE | |
3619 | ||
202d6e5f | 3620 | @node Caller Saves |
3621 | @subsection Caller-Saves Register Allocation | |
3622 | ||
3623 | If you enable it, GCC can save registers around function calls. This | |
3624 | makes it possible to use call-clobbered registers to hold variables that | |
3625 | must live across calls. | |
3626 | ||
202d6e5f | 3627 | @defmac HARD_REGNO_CALLER_SAVE_MODE (@var{regno}, @var{nregs}) |
3628 | A C expression specifying which mode is required for saving @var{nregs} | |
3629 | of a pseudo-register in call-clobbered hard register @var{regno}. If | |
3630 | @var{regno} is unsuitable for caller save, @code{VOIDmode} should be | |
3631 | returned. For most machines this macro need not be defined since GCC | |
3632 | will select the smallest suitable mode. | |
3633 | @end defmac | |
3634 | ||
3635 | @node Function Entry | |
3636 | @subsection Function Entry and Exit | |
3637 | @cindex function entry and exit | |
3638 | @cindex prologue | |
3639 | @cindex epilogue | |
3640 | ||
3641 | This section describes the macros that output function entry | |
3642 | (@dfn{prologue}) and exit (@dfn{epilogue}) code. | |
3643 | ||
3644 | @hook TARGET_ASM_FUNCTION_PROLOGUE | |
202d6e5f | 3645 | |
3646 | @hook TARGET_ASM_FUNCTION_END_PROLOGUE | |
202d6e5f | 3647 | |
3648 | @hook TARGET_ASM_FUNCTION_BEGIN_EPILOGUE | |
202d6e5f | 3649 | |
3650 | @hook TARGET_ASM_FUNCTION_EPILOGUE | |
202d6e5f | 3651 | |
3652 | @itemize @bullet | |
3653 | @item | |
81e483dd | 3654 | @findex pretend_args_size |
3655 | @findex crtl->args.pretend_args_size | |
3656 | A region of @code{crtl->args.pretend_args_size} bytes of | |
202d6e5f | 3657 | uninitialized space just underneath the first argument arriving on the |
3658 | stack. (This may not be at the very start of the allocated stack region | |
3659 | if the calling sequence has pushed anything else since pushing the stack | |
3660 | arguments. But usually, on such machines, nothing else has been pushed | |
3661 | yet, because the function prologue itself does all the pushing.) This | |
3662 | region is used on machines where an argument may be passed partly in | |
3663 | registers and partly in memory, and, in some cases to support the | |
3664 | features in @code{<stdarg.h>}. | |
3665 | ||
3666 | @item | |
3667 | An area of memory used to save certain registers used by the function. | |
3668 | The size of this area, which may also include space for such things as | |
3669 | the return address and pointers to previous stack frames, is | |
3670 | machine-specific and usually depends on which registers have been used | |
3671 | in the function. Machines with register windows often do not require | |
3672 | a save area. | |
3673 | ||
3674 | @item | |
3675 | A region of at least @var{size} bytes, possibly rounded up to an allocation | |
3676 | boundary, to contain the local variables of the function. On some machines, | |
3677 | this region and the save area may occur in the opposite order, with the | |
3678 | save area closer to the top of the stack. | |
3679 | ||
3680 | @item | |
3681 | @cindex @code{ACCUMULATE_OUTGOING_ARGS} and stack frames | |
3682 | Optionally, when @code{ACCUMULATE_OUTGOING_ARGS} is defined, a region of | |
81e483dd | 3683 | @code{crtl->outgoing_args_size} bytes to be used for outgoing |
202d6e5f | 3684 | argument lists of the function. @xref{Stack Arguments}. |
3685 | @end itemize | |
3686 | ||
3687 | @defmac EXIT_IGNORE_STACK | |
3688 | Define this macro as a C expression that is nonzero if the return | |
3689 | instruction or the function epilogue ignores the value of the stack | |
3690 | pointer; in other words, if it is safe to delete an instruction to | |
3691 | adjust the stack pointer before a return from the function. The | |
3692 | default is 0. | |
3693 | ||
3694 | Note that this macro's value is relevant only for functions for which | |
3695 | frame pointers are maintained. It is never safe to delete a final | |
3696 | stack adjustment in a function that has no frame pointer, and the | |
3697 | compiler knows this regardless of @code{EXIT_IGNORE_STACK}. | |
3698 | @end defmac | |
3699 | ||
3700 | @defmac EPILOGUE_USES (@var{regno}) | |
3701 | Define this macro as a C expression that is nonzero for registers that are | |
3702 | used by the epilogue or the @samp{return} pattern. The stack and frame | |
3703 | pointer registers are already assumed to be used as needed. | |
3704 | @end defmac | |
3705 | ||
3706 | @defmac EH_USES (@var{regno}) | |
3707 | Define this macro as a C expression that is nonzero for registers that are | |
3708 | used by the exception handling mechanism, and so should be considered live | |
3709 | on entry to an exception edge. | |
3710 | @end defmac | |
3711 | ||
202d6e5f | 3712 | @hook TARGET_ASM_OUTPUT_MI_THUNK |
202d6e5f | 3713 | |
3714 | @hook TARGET_ASM_CAN_OUTPUT_MI_THUNK | |
202d6e5f | 3715 | |
3716 | @node Profiling | |
3717 | @subsection Generating Code for Profiling | |
3718 | @cindex profiling, code generation | |
3719 | ||
3720 | These macros will help you generate code for profiling. | |
3721 | ||
3722 | @defmac FUNCTION_PROFILER (@var{file}, @var{labelno}) | |
3723 | A C statement or compound statement to output to @var{file} some | |
3724 | assembler code to call the profiling subroutine @code{mcount}. | |
3725 | ||
3726 | @findex mcount | |
3727 | The details of how @code{mcount} expects to be called are determined by | |
3728 | your operating system environment, not by GCC@. To figure them out, | |
3729 | compile a small program for profiling using the system's installed C | |
3730 | compiler and look at the assembler code that results. | |
3731 | ||
3732 | Older implementations of @code{mcount} expect the address of a counter | |
3733 | variable to be loaded into some register. The name of this variable is | |
3734 | @samp{LP} followed by the number @var{labelno}, so you would generate | |
3735 | the name using @samp{LP%d} in a @code{fprintf}. | |
3736 | @end defmac | |
3737 | ||
3738 | @defmac PROFILE_HOOK | |
3739 | A C statement or compound statement to output to @var{file} some assembly | |
3740 | code to call the profiling subroutine @code{mcount} even the target does | |
3741 | not support profiling. | |
3742 | @end defmac | |
3743 | ||
3744 | @defmac NO_PROFILE_COUNTERS | |
3745 | Define this macro to be an expression with a nonzero value if the | |
3746 | @code{mcount} subroutine on your system does not need a counter variable | |
3747 | allocated for each function. This is true for almost all modern | |
3748 | implementations. If you define this macro, you must not use the | |
3749 | @var{labelno} argument to @code{FUNCTION_PROFILER}. | |
3750 | @end defmac | |
3751 | ||
3752 | @defmac PROFILE_BEFORE_PROLOGUE | |
3753 | Define this macro if the code for function profiling should come before | |
3754 | the function prologue. Normally, the profiling code comes after. | |
3755 | @end defmac | |
3756 | ||
d44f2f7c | 3757 | @hook TARGET_KEEP_LEAF_WHEN_PROFILED |
3758 | ||
202d6e5f | 3759 | @node Tail Calls |
3760 | @subsection Permitting tail calls | |
3761 | @cindex tail calls | |
3762 | ||
3763 | @hook TARGET_FUNCTION_OK_FOR_SIBCALL | |
202d6e5f | 3764 | |
3765 | @hook TARGET_EXTRA_LIVE_ON_ENTRY | |
202d6e5f | 3766 | |
2e851bb8 | 3767 | @hook TARGET_SET_UP_BY_PROLOGUE |
3768 | ||
08c6cbd2 | 3769 | @hook TARGET_WARN_FUNC_RETURN |
3770 | ||
202d6e5f | 3771 | @node Stack Smashing Protection |
3772 | @subsection Stack smashing protection | |
3773 | @cindex stack smashing protection | |
3774 | ||
3775 | @hook TARGET_STACK_PROTECT_GUARD | |
202d6e5f | 3776 | |
3777 | @hook TARGET_STACK_PROTECT_FAIL | |
202d6e5f | 3778 | |
48b14f50 | 3779 | @hook TARGET_SUPPORTS_SPLIT_STACK |
3780 | ||
e9eaaa6a | 3781 | @node Miscellaneous Register Hooks |
3782 | @subsection Miscellaneous register hooks | |
3783 | @cindex miscellaneous register hooks | |
3784 | ||
3785 | @hook TARGET_CALL_FUSAGE_CONTAINS_NON_CALLEE_CLOBBERS | |
3786 | ||
202d6e5f | 3787 | @node Varargs |
3788 | @section Implementing the Varargs Macros | |
3789 | @cindex varargs implementation | |
3790 | ||
3791 | GCC comes with an implementation of @code{<varargs.h>} and | |
3792 | @code{<stdarg.h>} that work without change on machines that pass arguments | |
3793 | on the stack. Other machines require their own implementations of | |
3794 | varargs, and the two machine independent header files must have | |
3795 | conditionals to include it. | |
3796 | ||
3797 | ISO @code{<stdarg.h>} differs from traditional @code{<varargs.h>} mainly in | |
3798 | the calling convention for @code{va_start}. The traditional | |
3799 | implementation takes just one argument, which is the variable in which | |
3800 | to store the argument pointer. The ISO implementation of | |
3801 | @code{va_start} takes an additional second argument. The user is | |
3802 | supposed to write the last named argument of the function here. | |
3803 | ||
3804 | However, @code{va_start} should not use this argument. The way to find | |
3805 | the end of the named arguments is with the built-in functions described | |
3806 | below. | |
3807 | ||
3808 | @defmac __builtin_saveregs () | |
3809 | Use this built-in function to save the argument registers in memory so | |
3810 | that the varargs mechanism can access them. Both ISO and traditional | |
3811 | versions of @code{va_start} must use @code{__builtin_saveregs}, unless | |
3812 | you use @code{TARGET_SETUP_INCOMING_VARARGS} (see below) instead. | |
3813 | ||
3814 | On some machines, @code{__builtin_saveregs} is open-coded under the | |
3815 | control of the target hook @code{TARGET_EXPAND_BUILTIN_SAVEREGS}. On | |
3816 | other machines, it calls a routine written in assembler language, | |
3817 | found in @file{libgcc2.c}. | |
3818 | ||
3819 | Code generated for the call to @code{__builtin_saveregs} appears at the | |
3820 | beginning of the function, as opposed to where the call to | |
3821 | @code{__builtin_saveregs} is written, regardless of what the code is. | |
3822 | This is because the registers must be saved before the function starts | |
3823 | to use them for its own purposes. | |
3824 | @c i rewrote the first sentence above to fix an overfull hbox. --mew | |
3825 | @c 10feb93 | |
3826 | @end defmac | |
3827 | ||
202d6e5f | 3828 | @defmac __builtin_next_arg (@var{lastarg}) |
f739ab33 | 3829 | This builtin returns the address of the first anonymous stack |
202d6e5f | 3830 | argument, as type @code{void *}. If @code{ARGS_GROW_DOWNWARD}, it |
3831 | returns the address of the location above the first anonymous stack | |
3832 | argument. Use it in @code{va_start} to initialize the pointer for | |
3833 | fetching arguments from the stack. Also use it in @code{va_start} to | |
3834 | verify that the second parameter @var{lastarg} is the last named argument | |
3835 | of the current function. | |
3836 | @end defmac | |
3837 | ||
3838 | @defmac __builtin_classify_type (@var{object}) | |
3839 | Since each machine has its own conventions for which data types are | |
3840 | passed in which kind of register, your implementation of @code{va_arg} | |
3841 | has to embody these conventions. The easiest way to categorize the | |
3842 | specified data type is to use @code{__builtin_classify_type} together | |
3843 | with @code{sizeof} and @code{__alignof__}. | |
3844 | ||
3845 | @code{__builtin_classify_type} ignores the value of @var{object}, | |
3846 | considering only its data type. It returns an integer describing what | |
3847 | kind of type that is---integer, floating, pointer, structure, and so on. | |
3848 | ||
3849 | The file @file{typeclass.h} defines an enumeration that you can use to | |
3850 | interpret the values of @code{__builtin_classify_type}. | |
3851 | @end defmac | |
3852 | ||
3853 | These machine description macros help implement varargs: | |
3854 | ||
3855 | @hook TARGET_EXPAND_BUILTIN_SAVEREGS | |
202d6e5f | 3856 | |
3857 | @hook TARGET_SETUP_INCOMING_VARARGS | |
202d6e5f | 3858 | |
3859 | @hook TARGET_STRICT_ARGUMENT_NAMING | |
202d6e5f | 3860 | |
3861 | @hook TARGET_PRETEND_OUTGOING_VARARGS_NAMED | |
202d6e5f | 3862 | |
3863 | @node Trampolines | |
3864 | @section Trampolines for Nested Functions | |
3865 | @cindex trampolines for nested functions | |
3866 | @cindex nested functions, trampolines for | |
3867 | ||
3868 | A @dfn{trampoline} is a small piece of code that is created at run time | |
3869 | when the address of a nested function is taken. It normally resides on | |
3870 | the stack, in the stack frame of the containing function. These macros | |
3871 | tell GCC how to generate code to allocate and initialize a | |
3872 | trampoline. | |
3873 | ||
3874 | The instructions in the trampoline must do two things: load a constant | |
3875 | address into the static chain register, and jump to the real address of | |
3876 | the nested function. On CISC machines such as the m68k, this requires | |
3877 | two instructions, a move immediate and a jump. Then the two addresses | |
3878 | exist in the trampoline as word-long immediate operands. On RISC | |
3879 | machines, it is often necessary to load each address into a register in | |
3880 | two parts. Then pieces of each address form separate immediate | |
3881 | operands. | |
3882 | ||
3883 | The code generated to initialize the trampoline must store the variable | |
3884 | parts---the static chain value and the function address---into the | |
3885 | immediate operands of the instructions. On a CISC machine, this is | |
3886 | simply a matter of copying each address to a memory reference at the | |
3887 | proper offset from the start of the trampoline. On a RISC machine, it | |
3888 | may be necessary to take out pieces of the address and store them | |
3889 | separately. | |
3890 | ||
3891 | @hook TARGET_ASM_TRAMPOLINE_TEMPLATE | |
202d6e5f | 3892 | |
3893 | @defmac TRAMPOLINE_SECTION | |
3894 | Return the section into which the trampoline template is to be placed | |
3895 | (@pxref{Sections}). The default value is @code{readonly_data_section}. | |
3896 | @end defmac | |
3897 | ||
3898 | @defmac TRAMPOLINE_SIZE | |
3899 | A C expression for the size in bytes of the trampoline, as an integer. | |
3900 | @end defmac | |
3901 | ||
3902 | @defmac TRAMPOLINE_ALIGNMENT | |
3903 | Alignment required for trampolines, in bits. | |
3904 | ||
3905 | If you don't define this macro, the value of @code{FUNCTION_ALIGNMENT} | |
3906 | is used for aligning trampolines. | |
3907 | @end defmac | |
3908 | ||
3909 | @hook TARGET_TRAMPOLINE_INIT | |
202d6e5f | 3910 | |
3911 | @hook TARGET_TRAMPOLINE_ADJUST_ADDRESS | |
202d6e5f | 3912 | |
3913 | Implementing trampolines is difficult on many machines because they have | |
3914 | separate instruction and data caches. Writing into a stack location | |
3915 | fails to clear the memory in the instruction cache, so when the program | |
3916 | jumps to that location, it executes the old contents. | |
3917 | ||
3918 | Here are two possible solutions. One is to clear the relevant parts of | |
3919 | the instruction cache whenever a trampoline is set up. The other is to | |
3920 | make all trampolines identical, by having them jump to a standard | |
3921 | subroutine. The former technique makes trampoline execution faster; the | |
3922 | latter makes initialization faster. | |
3923 | ||
3924 | To clear the instruction cache when a trampoline is initialized, define | |
3925 | the following macro. | |
3926 | ||
3927 | @defmac CLEAR_INSN_CACHE (@var{beg}, @var{end}) | |
3928 | If defined, expands to a C expression clearing the @emph{instruction | |
3929 | cache} in the specified interval. The definition of this macro would | |
3930 | typically be a series of @code{asm} statements. Both @var{beg} and | |
3931 | @var{end} are both pointer expressions. | |
3932 | @end defmac | |
3933 | ||
202d6e5f | 3934 | To use a standard subroutine, define the following macro. In addition, |
3935 | you must make sure that the instructions in a trampoline fill an entire | |
3936 | cache line with identical instructions, or else ensure that the | |
3937 | beginning of the trampoline code is always aligned at the same point in | |
3938 | its cache line. Look in @file{m68k.h} as a guide. | |
3939 | ||
3940 | @defmac TRANSFER_FROM_TRAMPOLINE | |
3941 | Define this macro if trampolines need a special subroutine to do their | |
3942 | work. The macro should expand to a series of @code{asm} statements | |
3943 | which will be compiled with GCC@. They go in a library function named | |
3944 | @code{__transfer_from_trampoline}. | |
3945 | ||
3946 | If you need to avoid executing the ordinary prologue code of a compiled | |
3947 | C function when you jump to the subroutine, you can do so by placing a | |
3948 | special label of your own in the assembler code. Use one @code{asm} | |
3949 | statement to generate an assembler label, and another to make the label | |
3950 | global. Then trampolines can use that label to jump directly to your | |
3951 | special assembler code. | |
3952 | @end defmac | |
3953 | ||
3954 | @node Library Calls | |
3955 | @section Implicit Calls to Library Routines | |
3956 | @cindex library subroutine names | |
3957 | @cindex @file{libgcc.a} | |
3958 | ||
3959 | @c prevent bad page break with this line | |
3960 | Here is an explanation of implicit calls to library routines. | |
3961 | ||
3962 | @defmac DECLARE_LIBRARY_RENAMES | |
3963 | This macro, if defined, should expand to a piece of C code that will get | |
3964 | expanded when compiling functions for libgcc.a. It can be used to | |
3965 | provide alternate names for GCC's internal library functions if there | |
3966 | are ABI-mandated names that the compiler should provide. | |
3967 | @end defmac | |
3968 | ||
3969 | @findex set_optab_libfunc | |
3970 | @findex init_one_libfunc | |
3971 | @hook TARGET_INIT_LIBFUNCS | |
202d6e5f | 3972 | |
f308a9b2 | 3973 | @hook TARGET_LIBFUNC_GNU_PREFIX |
3974 | ||
202d6e5f | 3975 | @defmac FLOAT_LIB_COMPARE_RETURNS_BOOL (@var{mode}, @var{comparison}) |
3976 | This macro should return @code{true} if the library routine that | |
3977 | implements the floating point comparison operator @var{comparison} in | |
3978 | mode @var{mode} will return a boolean, and @var{false} if it will | |
3979 | return a tristate. | |
3980 | ||
3981 | GCC's own floating point libraries return tristates from the | |
3982 | comparison operators, so the default returns false always. Most ports | |
3983 | don't need to define this macro. | |
3984 | @end defmac | |
3985 | ||
3986 | @defmac TARGET_LIB_INT_CMP_BIASED | |
3987 | This macro should evaluate to @code{true} if the integer comparison | |
3988 | functions (like @code{__cmpdi2}) return 0 to indicate that the first | |
3989 | operand is smaller than the second, 1 to indicate that they are equal, | |
3990 | and 2 to indicate that the first operand is greater than the second. | |
3991 | If this macro evaluates to @code{false} the comparison functions return | |
3992 | @minus{}1, 0, and 1 instead of 0, 1, and 2. If the target uses the routines | |
3993 | in @file{libgcc.a}, you do not need to define this macro. | |
3994 | @end defmac | |
3995 | ||
b214253d | 3996 | @defmac TARGET_HAS_NO_HW_DIVIDE |
3997 | This macro should be defined if the target has no hardware divide | |
3998 | instructions. If this macro is defined, GCC will use an algorithm which | |
3999 | make use of simple logical and arithmetic operations for 64-bit | |
4000 | division. If the macro is not defined, GCC will use an algorithm which | |
4001 | make use of a 64-bit by 32-bit divide primitive. | |
4002 | @end defmac | |
4003 | ||
202d6e5f | 4004 | @cindex @code{EDOM}, implicit usage |
4005 | @findex matherr | |
4006 | @defmac TARGET_EDOM | |
4007 | The value of @code{EDOM} on the target machine, as a C integer constant | |
4008 | expression. If you don't define this macro, GCC does not attempt to | |
4009 | deposit the value of @code{EDOM} into @code{errno} directly. Look in | |
4010 | @file{/usr/include/errno.h} to find the value of @code{EDOM} on your | |
4011 | system. | |
4012 | ||
4013 | If you do not define @code{TARGET_EDOM}, then compiled code reports | |
4014 | domain errors by calling the library function and letting it report the | |
4015 | error. If mathematical functions on your system use @code{matherr} when | |
4016 | there is an error, then you should leave @code{TARGET_EDOM} undefined so | |
4017 | that @code{matherr} is used normally. | |
4018 | @end defmac | |
4019 | ||
4020 | @cindex @code{errno}, implicit usage | |
4021 | @defmac GEN_ERRNO_RTX | |
4022 | Define this macro as a C expression to create an rtl expression that | |
4023 | refers to the global ``variable'' @code{errno}. (On certain systems, | |
4024 | @code{errno} may not actually be a variable.) If you don't define this | |
4025 | macro, a reasonable default is used. | |
4026 | @end defmac | |
4027 | ||
30f690e0 | 4028 | @hook TARGET_LIBC_HAS_FUNCTION |
202d6e5f | 4029 | |
4030 | @defmac NEXT_OBJC_RUNTIME | |
3f3d5ad4 | 4031 | Set this macro to 1 to use the "NeXT" Objective-C message sending conventions |
4032 | by default. This calling convention involves passing the object, the selector | |
4033 | and the method arguments all at once to the method-lookup library function. | |
4034 | This is the usual setting when targeting Darwin/Mac OS X systems, which have | |
4035 | the NeXT runtime installed. | |
4036 | ||
4037 | If the macro is set to 0, the "GNU" Objective-C message sending convention | |
4038 | will be used by default. This convention passes just the object and the | |
4039 | selector to the method-lookup function, which returns a pointer to the method. | |
4040 | ||
4041 | In either case, it remains possible to select code-generation for the alternate | |
4042 | scheme, by means of compiler command line switches. | |
202d6e5f | 4043 | @end defmac |
4044 | ||
4045 | @node Addressing Modes | |
4046 | @section Addressing Modes | |
4047 | @cindex addressing modes | |
4048 | ||
4049 | @c prevent bad page break with this line | |
4050 | This is about addressing modes. | |
4051 | ||
4052 | @defmac HAVE_PRE_INCREMENT | |
4053 | @defmacx HAVE_PRE_DECREMENT | |
4054 | @defmacx HAVE_POST_INCREMENT | |
4055 | @defmacx HAVE_POST_DECREMENT | |
4056 | A C expression that is nonzero if the machine supports pre-increment, | |
4057 | pre-decrement, post-increment, or post-decrement addressing respectively. | |
4058 | @end defmac | |
4059 | ||
4060 | @defmac HAVE_PRE_MODIFY_DISP | |
4061 | @defmacx HAVE_POST_MODIFY_DISP | |
4062 | A C expression that is nonzero if the machine supports pre- or | |
4063 | post-address side-effect generation involving constants other than | |
4064 | the size of the memory operand. | |
4065 | @end defmac | |
4066 | ||
4067 | @defmac HAVE_PRE_MODIFY_REG | |
4068 | @defmacx HAVE_POST_MODIFY_REG | |
4069 | A C expression that is nonzero if the machine supports pre- or | |
4070 | post-address side-effect generation involving a register displacement. | |
4071 | @end defmac | |
4072 | ||
4073 | @defmac CONSTANT_ADDRESS_P (@var{x}) | |
4074 | A C expression that is 1 if the RTX @var{x} is a constant which | |
4075 | is a valid address. On most machines the default definition of | |
4076 | @code{(CONSTANT_P (@var{x}) && GET_CODE (@var{x}) != CONST_DOUBLE)} | |
4077 | is acceptable, but a few machines are more restrictive as to which | |
15b474a2 | 4078 | constant addresses are supported. |
202d6e5f | 4079 | @end defmac |
4080 | ||
4081 | @defmac CONSTANT_P (@var{x}) | |
4082 | @code{CONSTANT_P}, which is defined by target-independent code, | |
4083 | accepts integer-values expressions whose values are not explicitly | |
4084 | known, such as @code{symbol_ref}, @code{label_ref}, and @code{high} | |
4085 | expressions and @code{const} arithmetic expressions, in addition to | |
4086 | @code{const_int} and @code{const_double} expressions. | |
4087 | @end defmac | |
4088 | ||
4089 | @defmac MAX_REGS_PER_ADDRESS | |
4090 | A number, the maximum number of registers that can appear in a valid | |
4091 | memory address. Note that it is up to you to specify a value equal to | |
4092 | the maximum number that @code{TARGET_LEGITIMATE_ADDRESS_P} would ever | |
4093 | accept. | |
4094 | @end defmac | |
4095 | ||
4096 | @hook TARGET_LEGITIMATE_ADDRESS_P | |
202d6e5f | 4097 | |
4098 | @defmac TARGET_MEM_CONSTRAINT | |
4099 | A single character to be used instead of the default @code{'m'} | |
4100 | character for general memory addresses. This defines the constraint | |
4101 | letter which matches the memory addresses accepted by | |
4102 | @code{TARGET_LEGITIMATE_ADDRESS_P}. Define this macro if you want to | |
4103 | support new address formats in your back end without changing the | |
4104 | semantics of the @code{'m'} constraint. This is necessary in order to | |
4105 | preserve functionality of inline assembly constructs using the | |
4106 | @code{'m'} constraint. | |
4107 | @end defmac | |
4108 | ||
4109 | @defmac FIND_BASE_TERM (@var{x}) | |
4110 | A C expression to determine the base term of address @var{x}, | |
4111 | or to provide a simplified version of @var{x} from which @file{alias.c} | |
4112 | can easily find the base term. This macro is used in only two places: | |
4113 | @code{find_base_value} and @code{find_base_term} in @file{alias.c}. | |
4114 | ||
4115 | It is always safe for this macro to not be defined. It exists so | |
4116 | that alias analysis can understand machine-dependent addresses. | |
4117 | ||
4118 | The typical use of this macro is to handle addresses containing | |
4119 | a label_ref or symbol_ref within an UNSPEC@. | |
4120 | @end defmac | |
4121 | ||
4122 | @hook TARGET_LEGITIMIZE_ADDRESS | |
202d6e5f | 4123 | |
4124 | @defmac LEGITIMIZE_RELOAD_ADDRESS (@var{x}, @var{mode}, @var{opnum}, @var{type}, @var{ind_levels}, @var{win}) | |
4125 | A C compound statement that attempts to replace @var{x}, which is an address | |
4126 | that needs reloading, with a valid memory address for an operand of mode | |
4127 | @var{mode}. @var{win} will be a C statement label elsewhere in the code. | |
4128 | It is not necessary to define this macro, but it might be useful for | |
4129 | performance reasons. | |
4130 | ||
4131 | For example, on the i386, it is sometimes possible to use a single | |
4132 | reload register instead of two by reloading a sum of two pseudo | |
4133 | registers into a register. On the other hand, for number of RISC | |
4134 | processors offsets are limited so that often an intermediate address | |
4135 | needs to be generated in order to address a stack slot. By defining | |
4136 | @code{LEGITIMIZE_RELOAD_ADDRESS} appropriately, the intermediate addresses | |
4137 | generated for adjacent some stack slots can be made identical, and thus | |
4138 | be shared. | |
4139 | ||
4140 | @emph{Note}: This macro should be used with caution. It is necessary | |
4141 | to know something of how reload works in order to effectively use this, | |
4142 | and it is quite easy to produce macros that build in too much knowledge | |
4143 | of reload internals. | |
4144 | ||
4145 | @emph{Note}: This macro must be able to reload an address created by a | |
4146 | previous invocation of this macro. If it fails to handle such addresses | |
4147 | then the compiler may generate incorrect code or abort. | |
4148 | ||
4149 | @findex push_reload | |
4150 | The macro definition should use @code{push_reload} to indicate parts that | |
4151 | need reloading; @var{opnum}, @var{type} and @var{ind_levels} are usually | |
4152 | suitable to be passed unaltered to @code{push_reload}. | |
4153 | ||
4154 | The code generated by this macro must not alter the substructure of | |
4155 | @var{x}. If it transforms @var{x} into a more legitimate form, it | |
4156 | should assign @var{x} (which will always be a C variable) a new value. | |
4157 | This also applies to parts that you change indirectly by calling | |
4158 | @code{push_reload}. | |
4159 | ||
4160 | @findex strict_memory_address_p | |
4161 | The macro definition may use @code{strict_memory_address_p} to test if | |
4162 | the address has become legitimate. | |
4163 | ||
4164 | @findex copy_rtx | |
4165 | If you want to change only a part of @var{x}, one standard way of doing | |
4166 | this is to use @code{copy_rtx}. Note, however, that it unshares only a | |
4167 | single level of rtl. Thus, if the part to be changed is not at the | |
4168 | top level, you'll need to replace first the top level. | |
4169 | It is not necessary for this macro to come up with a legitimate | |
4170 | address; but often a machine-dependent strategy can generate better code. | |
4171 | @end defmac | |
4172 | ||
4173 | @hook TARGET_MODE_DEPENDENT_ADDRESS_P | |
202d6e5f | 4174 | |
ca316360 | 4175 | @hook TARGET_LEGITIMATE_CONSTANT_P |
202d6e5f | 4176 | |
4177 | @hook TARGET_DELEGITIMIZE_ADDRESS | |
202d6e5f | 4178 | |
202e7097 | 4179 | @hook TARGET_CONST_NOT_OK_FOR_DEBUG_P |
202e7097 | 4180 | |
202d6e5f | 4181 | @hook TARGET_CANNOT_FORCE_CONST_MEM |
202d6e5f | 4182 | |
4183 | @hook TARGET_USE_BLOCKS_FOR_CONSTANT_P | |
202d6e5f | 4184 | |
80d4c05f | 4185 | @hook TARGET_USE_BLOCKS_FOR_DECL_P |
80d4c05f | 4186 | |
707e3139 | 4187 | @hook TARGET_BUILTIN_RECIPROCAL |
202d6e5f | 4188 | |
4189 | @hook TARGET_VECTORIZE_BUILTIN_MASK_FOR_LOAD | |
202d6e5f | 4190 | |
202d6e5f | 4191 | @hook TARGET_VECTORIZE_BUILTIN_VECTORIZATION_COST |
202d6e5f | 4192 | |
4193 | @hook TARGET_VECTORIZE_VECTOR_ALIGNMENT_REACHABLE | |
202d6e5f | 4194 | |
428d5ecf | 4195 | @hook TARGET_VECTORIZE_VEC_PERM_CONST_OK |
202d6e5f | 4196 | |
4197 | @hook TARGET_VECTORIZE_BUILTIN_CONVERSION | |
202d6e5f | 4198 | |
4199 | @hook TARGET_VECTORIZE_BUILTIN_VECTORIZED_FUNCTION | |
202d6e5f | 4200 | |
4201 | @hook TARGET_VECTORIZE_SUPPORT_VECTOR_MISALIGNMENT | |
202d6e5f | 4202 | |
b24d851f | 4203 | @hook TARGET_VECTORIZE_PREFERRED_SIMD_MODE |
2101edf2 | 4204 | |
421b11b1 | 4205 | @hook TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_SIZES |
421b11b1 | 4206 | |
4db2b577 | 4207 | @hook TARGET_VECTORIZE_INIT_COST |
4208 | ||
4209 | @hook TARGET_VECTORIZE_ADD_STMT_COST | |
4210 | ||
4211 | @hook TARGET_VECTORIZE_FINISH_COST | |
4212 | ||
4213 | @hook TARGET_VECTORIZE_DESTROY_COST_DATA | |
4214 | ||
4c0315d0 | 4215 | @hook TARGET_VECTORIZE_BUILTIN_TM_LOAD |
4216 | ||
4217 | @hook TARGET_VECTORIZE_BUILTIN_TM_STORE | |
4218 | ||
16dfb112 | 4219 | @hook TARGET_VECTORIZE_BUILTIN_GATHER |
16dfb112 | 4220 | |
d09768a4 | 4221 | @hook TARGET_SIMD_CLONE_COMPUTE_VECSIZE_AND_SIMDLEN |
4222 | ||
4223 | @hook TARGET_SIMD_CLONE_ADJUST | |
4224 | ||
4225 | @hook TARGET_SIMD_CLONE_USABLE | |
4226 | ||
202d6e5f | 4227 | @node Anchored Addresses |
4228 | @section Anchored Addresses | |
4229 | @cindex anchored addresses | |
4230 | @cindex @option{-fsection-anchors} | |
4231 | ||
4232 | GCC usually addresses every static object as a separate entity. | |
4233 | For example, if we have: | |
4234 | ||
4235 | @smallexample | |
4236 | static int a, b, c; | |
4237 | int foo (void) @{ return a + b + c; @} | |
4238 | @end smallexample | |
4239 | ||
4240 | the code for @code{foo} will usually calculate three separate symbolic | |
4241 | addresses: those of @code{a}, @code{b} and @code{c}. On some targets, | |
4242 | it would be better to calculate just one symbolic address and access | |
4243 | the three variables relative to it. The equivalent pseudocode would | |
4244 | be something like: | |
4245 | ||
4246 | @smallexample | |
4247 | int foo (void) | |
4248 | @{ | |
4249 | register int *xr = &x; | |
4250 | return xr[&a - &x] + xr[&b - &x] + xr[&c - &x]; | |
4251 | @} | |
4252 | @end smallexample | |
4253 | ||
4254 | (which isn't valid C). We refer to shared addresses like @code{x} as | |
4255 | ``section anchors''. Their use is controlled by @option{-fsection-anchors}. | |
4256 | ||
4257 | The hooks below describe the target properties that GCC needs to know | |
4258 | in order to make effective use of section anchors. It won't use | |
4259 | section anchors at all unless either @code{TARGET_MIN_ANCHOR_OFFSET} | |
4260 | or @code{TARGET_MAX_ANCHOR_OFFSET} is set to a nonzero value. | |
4261 | ||
4262 | @hook TARGET_MIN_ANCHOR_OFFSET | |
202d6e5f | 4263 | |
4264 | @hook TARGET_MAX_ANCHOR_OFFSET | |
202d6e5f | 4265 | |
4266 | @hook TARGET_ASM_OUTPUT_ANCHOR | |
202d6e5f | 4267 | |
4268 | @hook TARGET_USE_ANCHORS_FOR_SYMBOL_P | |
202d6e5f | 4269 | |
4270 | @node Condition Code | |
4271 | @section Condition Code Status | |
4272 | @cindex condition code status | |
4273 | ||
4274 | The macros in this section can be split in two families, according to the | |
4275 | two ways of representing condition codes in GCC. | |
4276 | ||
4277 | The first representation is the so called @code{(cc0)} representation | |
4278 | (@pxref{Jump Patterns}), where all instructions can have an implicit | |
4279 | clobber of the condition codes. The second is the condition code | |
4280 | register representation, which provides better schedulability for | |
4281 | architectures that do have a condition code register, but on which | |
4282 | most instructions do not affect it. The latter category includes | |
4283 | most RISC machines. | |
4284 | ||
4285 | The implicit clobbering poses a strong restriction on the placement of | |
5b4ac966 | 4286 | the definition and use of the condition code. In the past the definition |
4287 | and use were always adjacent. However, recent changes to support trapping | |
4288 | arithmatic may result in the definition and user being in different blocks. | |
4289 | Thus, there may be a @code{NOTE_INSN_BASIC_BLOCK} between them. Additionally, | |
4290 | the definition may be the source of exception handling edges. | |
4291 | ||
4292 | These restrictions can prevent important | |
202d6e5f | 4293 | optimizations on some machines. For example, on the IBM RS/6000, there |
4294 | is a delay for taken branches unless the condition code register is set | |
4295 | three instructions earlier than the conditional branch. The instruction | |
4296 | scheduler cannot perform this optimization if it is not permitted to | |
4297 | separate the definition and use of the condition code register. | |
4298 | ||
4299 | For this reason, it is possible and suggested to use a register to | |
4300 | represent the condition code for new ports. If there is a specific | |
4301 | condition code register in the machine, use a hard register. If the | |
4302 | condition code or comparison result can be placed in any general register, | |
4303 | or if there are multiple condition registers, use a pseudo register. | |
4304 | Registers used to store the condition code value will usually have a mode | |
4305 | that is in class @code{MODE_CC}. | |
4306 | ||
4307 | Alternatively, you can use @code{BImode} if the comparison operator is | |
4308 | specified already in the compare instruction. In this case, you are not | |
4309 | interested in most macros in this section. | |
4310 | ||
4311 | @menu | |
4312 | * CC0 Condition Codes:: Old style representation of condition codes. | |
4313 | * MODE_CC Condition Codes:: Modern representation of condition codes. | |
202d6e5f | 4314 | @end menu |
4315 | ||
4316 | @node CC0 Condition Codes | |
4317 | @subsection Representation of condition codes using @code{(cc0)} | |
4318 | @findex cc0 | |
4319 | ||
4320 | @findex cc_status | |
4321 | The file @file{conditions.h} defines a variable @code{cc_status} to | |
4322 | describe how the condition code was computed (in case the interpretation of | |
4323 | the condition code depends on the instruction that it was set by). This | |
4324 | variable contains the RTL expressions on which the condition code is | |
4325 | currently based, and several standard flags. | |
4326 | ||
4327 | Sometimes additional machine-specific flags must be defined in the machine | |
4328 | description header file. It can also add additional machine-specific | |
4329 | information by defining @code{CC_STATUS_MDEP}. | |
4330 | ||
4331 | @defmac CC_STATUS_MDEP | |
4332 | C code for a data type which is used for declaring the @code{mdep} | |
4333 | component of @code{cc_status}. It defaults to @code{int}. | |
4334 | ||
4335 | This macro is not used on machines that do not use @code{cc0}. | |
4336 | @end defmac | |
4337 | ||
4338 | @defmac CC_STATUS_MDEP_INIT | |
4339 | A C expression to initialize the @code{mdep} field to ``empty''. | |
4340 | The default definition does nothing, since most machines don't use | |
4341 | the field anyway. If you want to use the field, you should probably | |
4342 | define this macro to initialize it. | |
4343 | ||
4344 | This macro is not used on machines that do not use @code{cc0}. | |
4345 | @end defmac | |
4346 | ||
4347 | @defmac NOTICE_UPDATE_CC (@var{exp}, @var{insn}) | |
4348 | A C compound statement to set the components of @code{cc_status} | |
4349 | appropriately for an insn @var{insn} whose body is @var{exp}. It is | |
4350 | this macro's responsibility to recognize insns that set the condition | |
4351 | code as a byproduct of other activity as well as those that explicitly | |
4352 | set @code{(cc0)}. | |
4353 | ||
4354 | This macro is not used on machines that do not use @code{cc0}. | |
4355 | ||
4356 | If there are insns that do not set the condition code but do alter | |
4357 | other machine registers, this macro must check to see whether they | |
4358 | invalidate the expressions that the condition code is recorded as | |
4359 | reflecting. For example, on the 68000, insns that store in address | |
4360 | registers do not set the condition code, which means that usually | |
4361 | @code{NOTICE_UPDATE_CC} can leave @code{cc_status} unaltered for such | |
4362 | insns. But suppose that the previous insn set the condition code | |
4363 | based on location @samp{a4@@(102)} and the current insn stores a new | |
4364 | value in @samp{a4}. Although the condition code is not changed by | |
4365 | this, it will no longer be true that it reflects the contents of | |
4366 | @samp{a4@@(102)}. Therefore, @code{NOTICE_UPDATE_CC} must alter | |
4367 | @code{cc_status} in this case to say that nothing is known about the | |
4368 | condition code value. | |
4369 | ||
4370 | The definition of @code{NOTICE_UPDATE_CC} must be prepared to deal | |
4371 | with the results of peephole optimization: insns whose patterns are | |
4372 | @code{parallel} RTXs containing various @code{reg}, @code{mem} or | |
4373 | constants which are just the operands. The RTL structure of these | |
4374 | insns is not sufficient to indicate what the insns actually do. What | |
4375 | @code{NOTICE_UPDATE_CC} should do when it sees one is just to run | |
4376 | @code{CC_STATUS_INIT}. | |
4377 | ||
4378 | A possible definition of @code{NOTICE_UPDATE_CC} is to call a function | |
4379 | that looks at an attribute (@pxref{Insn Attributes}) named, for example, | |
4380 | @samp{cc}. This avoids having detailed information about patterns in | |
4381 | two places, the @file{md} file and in @code{NOTICE_UPDATE_CC}. | |
4382 | @end defmac | |
4383 | ||
4384 | @node MODE_CC Condition Codes | |
4385 | @subsection Representation of condition codes using registers | |
4386 | @findex CCmode | |
4387 | @findex MODE_CC | |
4388 | ||
4389 | @defmac SELECT_CC_MODE (@var{op}, @var{x}, @var{y}) | |
4390 | On many machines, the condition code may be produced by other instructions | |
4391 | than compares, for example the branch can use directly the condition | |
4392 | code set by a subtract instruction. However, on some machines | |
4393 | when the condition code is set this way some bits (such as the overflow | |
4394 | bit) are not set in the same way as a test instruction, so that a different | |
4395 | branch instruction must be used for some conditional branches. When | |
4396 | this happens, use the machine mode of the condition code register to | |
4397 | record different formats of the condition code register. Modes can | |
4398 | also be used to record which compare instruction (e.g. a signed or an | |
4399 | unsigned comparison) produced the condition codes. | |
4400 | ||
4401 | If other modes than @code{CCmode} are required, add them to | |
4402 | @file{@var{machine}-modes.def} and define @code{SELECT_CC_MODE} to choose | |
4403 | a mode given an operand of a compare. This is needed because the modes | |
4404 | have to be chosen not only during RTL generation but also, for example, | |
4405 | by instruction combination. The result of @code{SELECT_CC_MODE} should | |
4406 | be consistent with the mode used in the patterns; for example to support | |
4407 | the case of the add on the SPARC discussed above, we have the pattern | |
4408 | ||
4409 | @smallexample | |
4410 | (define_insn "" | |
4411 | [(set (reg:CC_NOOV 0) | |
4412 | (compare:CC_NOOV | |
4413 | (plus:SI (match_operand:SI 0 "register_operand" "%r") | |
4414 | (match_operand:SI 1 "arith_operand" "rI")) | |
4415 | (const_int 0)))] | |
4416 | "" | |
4417 | "@dots{}") | |
4418 | @end smallexample | |
4419 | ||
4420 | @noindent | |
4421 | together with a @code{SELECT_CC_MODE} that returns @code{CC_NOOVmode} | |
4422 | for comparisons whose argument is a @code{plus}: | |
4423 | ||
4424 | @smallexample | |
4425 | #define SELECT_CC_MODE(OP,X,Y) \ | |
4426 | (GET_MODE_CLASS (GET_MODE (X)) == MODE_FLOAT \ | |
4427 | ? ((OP == EQ || OP == NE) ? CCFPmode : CCFPEmode) \ | |
4428 | : ((GET_CODE (X) == PLUS || GET_CODE (X) == MINUS \ | |
4429 | || GET_CODE (X) == NEG) \ | |
4430 | ? CC_NOOVmode : CCmode)) | |
4431 | @end smallexample | |
4432 | ||
4433 | Another reason to use modes is to retain information on which operands | |
4434 | were used by the comparison; see @code{REVERSIBLE_CC_MODE} later in | |
4435 | this section. | |
4436 | ||
4437 | You should define this macro if and only if you define extra CC modes | |
4438 | in @file{@var{machine}-modes.def}. | |
4439 | @end defmac | |
4440 | ||
f8e3aa87 | 4441 | @hook TARGET_CANONICALIZE_COMPARISON |
202d6e5f | 4442 | |
4443 | @defmac REVERSIBLE_CC_MODE (@var{mode}) | |
4444 | A C expression whose value is one if it is always safe to reverse a | |
4445 | comparison whose mode is @var{mode}. If @code{SELECT_CC_MODE} | |
4446 | can ever return @var{mode} for a floating-point inequality comparison, | |
4447 | then @code{REVERSIBLE_CC_MODE (@var{mode})} must be zero. | |
4448 | ||
4449 | You need not define this macro if it would always returns zero or if the | |
4450 | floating-point format is anything other than @code{IEEE_FLOAT_FORMAT}. | |
4451 | For example, here is the definition used on the SPARC, where floating-point | |
4452 | inequality comparisons are always given @code{CCFPEmode}: | |
4453 | ||
4454 | @smallexample | |
4455 | #define REVERSIBLE_CC_MODE(MODE) ((MODE) != CCFPEmode) | |
4456 | @end smallexample | |
4457 | @end defmac | |
4458 | ||
4459 | @defmac REVERSE_CONDITION (@var{code}, @var{mode}) | |
4460 | A C expression whose value is reversed condition code of the @var{code} for | |
4461 | comparison done in CC_MODE @var{mode}. The macro is used only in case | |
4462 | @code{REVERSIBLE_CC_MODE (@var{mode})} is nonzero. Define this macro in case | |
4463 | machine has some non-standard way how to reverse certain conditionals. For | |
4464 | instance in case all floating point conditions are non-trapping, compiler may | |
4465 | freely convert unordered compares to ordered one. Then definition may look | |
4466 | like: | |
4467 | ||
4468 | @smallexample | |
4469 | #define REVERSE_CONDITION(CODE, MODE) \ | |
4470 | ((MODE) != CCFPmode ? reverse_condition (CODE) \ | |
4471 | : reverse_condition_maybe_unordered (CODE)) | |
4472 | @end smallexample | |
4473 | @end defmac | |
4474 | ||
4475 | @hook TARGET_FIXED_CONDITION_CODE_REGS | |
202d6e5f | 4476 | |
4477 | @hook TARGET_CC_MODES_COMPATIBLE | |
202d6e5f | 4478 | |
202d6e5f | 4479 | @node Costs |
4480 | @section Describing Relative Costs of Operations | |
4481 | @cindex costs of instructions | |
4482 | @cindex relative costs | |
4483 | @cindex speed of instructions | |
4484 | ||
4485 | These macros let you describe the relative speed of various operations | |
4486 | on the target machine. | |
4487 | ||
4488 | @defmac REGISTER_MOVE_COST (@var{mode}, @var{from}, @var{to}) | |
4489 | A C expression for the cost of moving data of mode @var{mode} from a | |
4490 | register in class @var{from} to one in class @var{to}. The classes are | |
4491 | expressed using the enumeration values such as @code{GENERAL_REGS}. A | |
4492 | value of 2 is the default; other values are interpreted relative to | |
4493 | that. | |
4494 | ||
4495 | It is not required that the cost always equal 2 when @var{from} is the | |
4496 | same as @var{to}; on some machines it is expensive to move between | |
4497 | registers if they are not general registers. | |
4498 | ||
4499 | If reload sees an insn consisting of a single @code{set} between two | |
4500 | hard registers, and if @code{REGISTER_MOVE_COST} applied to their | |
4501 | classes returns a value of 2, reload does not check to ensure that the | |
4502 | constraints of the insn are met. Setting a cost of other than 2 will | |
4503 | allow reload to verify that the constraints are met. You should do this | |
4504 | if the @samp{mov@var{m}} pattern's constraints do not allow such copying. | |
4505 | ||
4506 | These macros are obsolete, new ports should use the target hook | |
4507 | @code{TARGET_REGISTER_MOVE_COST} instead. | |
4508 | @end defmac | |
4509 | ||
4510 | @hook TARGET_REGISTER_MOVE_COST | |
202d6e5f | 4511 | |
4512 | @defmac MEMORY_MOVE_COST (@var{mode}, @var{class}, @var{in}) | |
4513 | A C expression for the cost of moving data of mode @var{mode} between a | |
4514 | register of class @var{class} and memory; @var{in} is zero if the value | |
4515 | is to be written to memory, nonzero if it is to be read in. This cost | |
4516 | is relative to those in @code{REGISTER_MOVE_COST}. If moving between | |
4517 | registers and memory is more expensive than between two registers, you | |
4518 | should define this macro to express the relative cost. | |
4519 | ||
4520 | If you do not define this macro, GCC uses a default cost of 4 plus | |
4521 | the cost of copying via a secondary reload register, if one is | |
4522 | needed. If your machine requires a secondary reload register to copy | |
4523 | between memory and a register of @var{class} but the reload mechanism is | |
4524 | more complex than copying via an intermediate, define this macro to | |
4525 | reflect the actual cost of the move. | |
4526 | ||
4527 | GCC defines the function @code{memory_move_secondary_cost} if | |
4528 | secondary reloads are needed. It computes the costs due to copying via | |
4529 | a secondary register. If your machine copies from memory using a | |
4530 | secondary register in the conventional way but the default base value of | |
4531 | 4 is not correct for your machine, define this macro to add some other | |
4532 | value to the result of that function. The arguments to that function | |
4533 | are the same as to this macro. | |
4534 | ||
4535 | These macros are obsolete, new ports should use the target hook | |
4536 | @code{TARGET_MEMORY_MOVE_COST} instead. | |
4537 | @end defmac | |
4538 | ||
9de204fa | 4539 | @hook TARGET_MEMORY_MOVE_COST |
202d6e5f | 4540 | |
4541 | @defmac BRANCH_COST (@var{speed_p}, @var{predictable_p}) | |
b56a5220 | 4542 | A C expression for the cost of a branch instruction. A value of 1 is |
4543 | the default; other values are interpreted relative to that. Parameter | |
4544 | @var{speed_p} is true when the branch in question should be optimized | |
4545 | for speed. When it is false, @code{BRANCH_COST} should return a value | |
4546 | optimal for code size rather than performance. @var{predictable_p} is | |
4547 | true for well-predicted branches. On many architectures the | |
4548 | @code{BRANCH_COST} can be reduced then. | |
202d6e5f | 4549 | @end defmac |
4550 | ||
4551 | Here are additional macros which do not specify precise relative costs, | |
4552 | but only that certain actions are more expensive than GCC would | |
4553 | ordinarily expect. | |
4554 | ||
4555 | @defmac SLOW_BYTE_ACCESS | |
4556 | Define this macro as a C expression which is nonzero if accessing less | |
4557 | than a word of memory (i.e.@: a @code{char} or a @code{short}) is no | |
4558 | faster than accessing a word of memory, i.e., if such access | |
4559 | require more than one instruction or if there is no difference in cost | |
4560 | between byte and (aligned) word loads. | |
4561 | ||
4562 | When this macro is not defined, the compiler will access a field by | |
4563 | finding the smallest containing object; when it is defined, a fullword | |
4564 | load will be used if alignment permits. Unless bytes accesses are | |
4565 | faster than word accesses, using word accesses is preferable since it | |
4566 | may eliminate subsequent memory access if subsequent accesses occur to | |
4567 | other fields in the same word of the structure, but to different bytes. | |
4568 | @end defmac | |
4569 | ||
4570 | @defmac SLOW_UNALIGNED_ACCESS (@var{mode}, @var{alignment}) | |
4571 | Define this macro to be the value 1 if memory accesses described by the | |
4572 | @var{mode} and @var{alignment} parameters have a cost many times greater | |
4573 | than aligned accesses, for example if they are emulated in a trap | |
4574 | handler. | |
4575 | ||
4576 | When this macro is nonzero, the compiler will act as if | |
4577 | @code{STRICT_ALIGNMENT} were nonzero when generating code for block | |
4578 | moves. This can cause significantly more instructions to be produced. | |
4579 | Therefore, do not set this macro nonzero if unaligned accesses only add a | |
4580 | cycle or two to the time for a memory access. | |
4581 | ||
4582 | If the value of this macro is always zero, it need not be defined. If | |
4583 | this macro is defined, it should produce a nonzero value when | |
4584 | @code{STRICT_ALIGNMENT} is nonzero. | |
4585 | @end defmac | |
4586 | ||
4587 | @defmac MOVE_RATIO (@var{speed}) | |
4588 | The threshold of number of scalar memory-to-memory move insns, @emph{below} | |
4589 | which a sequence of insns should be generated instead of a | |
4590 | string move insn or a library call. Increasing the value will always | |
4591 | make code faster, but eventually incurs high cost in increased code size. | |
4592 | ||
4593 | Note that on machines where the corresponding move insn is a | |
4594 | @code{define_expand} that emits a sequence of insns, this macro counts | |
4595 | the number of such sequences. | |
4596 | ||
4597 | The parameter @var{speed} is true if the code is currently being | |
4598 | optimized for speed rather than size. | |
4599 | ||
4600 | If you don't define this, a reasonable default is used. | |
4601 | @end defmac | |
4602 | ||
4603 | @defmac MOVE_BY_PIECES_P (@var{size}, @var{alignment}) | |
4604 | A C expression used to determine whether @code{move_by_pieces} will be used to | |
4605 | copy a chunk of memory, or whether some other block move mechanism | |
4606 | will be used. Defaults to 1 if @code{move_by_pieces_ninsns} returns less | |
4607 | than @code{MOVE_RATIO}. | |
4608 | @end defmac | |
4609 | ||
4610 | @defmac MOVE_MAX_PIECES | |
4611 | A C expression used by @code{move_by_pieces} to determine the largest unit | |
4612 | a load or store used to copy memory is. Defaults to @code{MOVE_MAX}. | |
4613 | @end defmac | |
4614 | ||
4615 | @defmac CLEAR_RATIO (@var{speed}) | |
4616 | The threshold of number of scalar move insns, @emph{below} which a sequence | |
4617 | of insns should be generated to clear memory instead of a string clear insn | |
4618 | or a library call. Increasing the value will always make code faster, but | |
4619 | eventually incurs high cost in increased code size. | |
4620 | ||
4621 | The parameter @var{speed} is true if the code is currently being | |
4622 | optimized for speed rather than size. | |
4623 | ||
4624 | If you don't define this, a reasonable default is used. | |
4625 | @end defmac | |
4626 | ||
4627 | @defmac CLEAR_BY_PIECES_P (@var{size}, @var{alignment}) | |
4628 | A C expression used to determine whether @code{clear_by_pieces} will be used | |
4629 | to clear a chunk of memory, or whether some other block clear mechanism | |
4630 | will be used. Defaults to 1 if @code{move_by_pieces_ninsns} returns less | |
4631 | than @code{CLEAR_RATIO}. | |
4632 | @end defmac | |
4633 | ||
4634 | @defmac SET_RATIO (@var{speed}) | |
4635 | The threshold of number of scalar move insns, @emph{below} which a sequence | |
4636 | of insns should be generated to set memory to a constant value, instead of | |
15b474a2 | 4637 | a block set insn or a library call. |
202d6e5f | 4638 | Increasing the value will always make code faster, but |
4639 | eventually incurs high cost in increased code size. | |
4640 | ||
4641 | The parameter @var{speed} is true if the code is currently being | |
4642 | optimized for speed rather than size. | |
4643 | ||
4644 | If you don't define this, it defaults to the value of @code{MOVE_RATIO}. | |
4645 | @end defmac | |
4646 | ||
4647 | @defmac SET_BY_PIECES_P (@var{size}, @var{alignment}) | |
4648 | A C expression used to determine whether @code{store_by_pieces} will be | |
15b474a2 | 4649 | used to set a chunk of memory to a constant value, or whether some |
4650 | other mechanism will be used. Used by @code{__builtin_memset} when | |
202d6e5f | 4651 | storing values other than constant zero. |
4652 | Defaults to 1 if @code{move_by_pieces_ninsns} returns less | |
4653 | than @code{SET_RATIO}. | |
4654 | @end defmac | |
4655 | ||
4656 | @defmac STORE_BY_PIECES_P (@var{size}, @var{alignment}) | |
4657 | A C expression used to determine whether @code{store_by_pieces} will be | |
4658 | used to set a chunk of memory to a constant string value, or whether some | |
4659 | other mechanism will be used. Used by @code{__builtin_strcpy} when | |
4660 | called with a constant source string. | |
4661 | Defaults to 1 if @code{move_by_pieces_ninsns} returns less | |
4662 | than @code{MOVE_RATIO}. | |
4663 | @end defmac | |
4664 | ||
4665 | @defmac USE_LOAD_POST_INCREMENT (@var{mode}) | |
4666 | A C expression used to determine whether a load postincrement is a good | |
4667 | thing to use for a given mode. Defaults to the value of | |
4668 | @code{HAVE_POST_INCREMENT}. | |
4669 | @end defmac | |
4670 | ||
4671 | @defmac USE_LOAD_POST_DECREMENT (@var{mode}) | |
4672 | A C expression used to determine whether a load postdecrement is a good | |
4673 | thing to use for a given mode. Defaults to the value of | |
4674 | @code{HAVE_POST_DECREMENT}. | |
4675 | @end defmac | |
4676 | ||
4677 | @defmac USE_LOAD_PRE_INCREMENT (@var{mode}) | |
4678 | A C expression used to determine whether a load preincrement is a good | |
4679 | thing to use for a given mode. Defaults to the value of | |
4680 | @code{HAVE_PRE_INCREMENT}. | |
4681 | @end defmac | |
4682 | ||
4683 | @defmac USE_LOAD_PRE_DECREMENT (@var{mode}) | |
4684 | A C expression used to determine whether a load predecrement is a good | |
4685 | thing to use for a given mode. Defaults to the value of | |
4686 | @code{HAVE_PRE_DECREMENT}. | |
4687 | @end defmac | |
4688 | ||
4689 | @defmac USE_STORE_POST_INCREMENT (@var{mode}) | |
4690 | A C expression used to determine whether a store postincrement is a good | |
4691 | thing to use for a given mode. Defaults to the value of | |
4692 | @code{HAVE_POST_INCREMENT}. | |
4693 | @end defmac | |
4694 | ||
4695 | @defmac USE_STORE_POST_DECREMENT (@var{mode}) | |
4696 | A C expression used to determine whether a store postdecrement is a good | |
4697 | thing to use for a given mode. Defaults to the value of | |
4698 | @code{HAVE_POST_DECREMENT}. | |
4699 | @end defmac | |
4700 | ||
4701 | @defmac USE_STORE_PRE_INCREMENT (@var{mode}) | |
4702 | This macro is used to determine whether a store preincrement is a good | |
4703 | thing to use for a given mode. Defaults to the value of | |
4704 | @code{HAVE_PRE_INCREMENT}. | |
4705 | @end defmac | |
4706 | ||
4707 | @defmac USE_STORE_PRE_DECREMENT (@var{mode}) | |
4708 | This macro is used to determine whether a store predecrement is a good | |
4709 | thing to use for a given mode. Defaults to the value of | |
4710 | @code{HAVE_PRE_DECREMENT}. | |
4711 | @end defmac | |
4712 | ||
4713 | @defmac NO_FUNCTION_CSE | |
4714 | Define this macro if it is as good or better to call a constant | |
4715 | function address than to call an address kept in a register. | |
4716 | @end defmac | |
4717 | ||
802c6441 | 4718 | @defmac LOGICAL_OP_NON_SHORT_CIRCUIT |
4719 | Define this macro if a non-short-circuit operation produced by | |
4720 | @samp{fold_range_test ()} is optimal. This macro defaults to true if | |
4721 | @code{BRANCH_COST} is greater than or equal to the value 2. | |
4722 | @end defmac | |
4723 | ||
202d6e5f | 4724 | @hook TARGET_RTX_COSTS |
202d6e5f | 4725 | |
4726 | @hook TARGET_ADDRESS_COST | |
202d6e5f | 4727 | |
4728 | @node Scheduling | |
4729 | @section Adjusting the Instruction Scheduler | |
4730 | ||
4731 | The instruction scheduler may need a fair amount of machine-specific | |
4732 | adjustment in order to produce good code. GCC provides several target | |
4733 | hooks for this purpose. It is usually enough to define just a few of | |
4734 | them: try the first ones in this list first. | |
4735 | ||
4736 | @hook TARGET_SCHED_ISSUE_RATE | |
202d6e5f | 4737 | |
4738 | @hook TARGET_SCHED_VARIABLE_ISSUE | |
202d6e5f | 4739 | |
4740 | @hook TARGET_SCHED_ADJUST_COST | |
202d6e5f | 4741 | |
4742 | @hook TARGET_SCHED_ADJUST_PRIORITY | |
202d6e5f | 4743 | |
4744 | @hook TARGET_SCHED_REORDER | |
202d6e5f | 4745 | |
4746 | @hook TARGET_SCHED_REORDER2 | |
202d6e5f | 4747 | |
641b578b | 4748 | @hook TARGET_SCHED_MACRO_FUSION_P |
4749 | ||
4750 | @hook TARGET_SCHED_MACRO_FUSION_PAIR_P | |
4751 | ||
202d6e5f | 4752 | @hook TARGET_SCHED_DEPENDENCIES_EVALUATION_HOOK |
202d6e5f | 4753 | |
4754 | @hook TARGET_SCHED_INIT | |
202d6e5f | 4755 | |
4756 | @hook TARGET_SCHED_FINISH | |
202d6e5f | 4757 | |
4758 | @hook TARGET_SCHED_INIT_GLOBAL | |
202d6e5f | 4759 | |
4760 | @hook TARGET_SCHED_FINISH_GLOBAL | |
202d6e5f | 4761 | |
4762 | @hook TARGET_SCHED_DFA_PRE_CYCLE_INSN | |
202d6e5f | 4763 | |
4764 | @hook TARGET_SCHED_INIT_DFA_PRE_CYCLE_INSN | |
202d6e5f | 4765 | |
4766 | @hook TARGET_SCHED_DFA_POST_CYCLE_INSN | |
202d6e5f | 4767 | |
4768 | @hook TARGET_SCHED_INIT_DFA_POST_CYCLE_INSN | |
202d6e5f | 4769 | |
4770 | @hook TARGET_SCHED_DFA_PRE_ADVANCE_CYCLE | |
202d6e5f | 4771 | |
4772 | @hook TARGET_SCHED_DFA_POST_ADVANCE_CYCLE | |
202d6e5f | 4773 | |
4774 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD | |
202d6e5f | 4775 | |
4776 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD_GUARD | |
4777 | ||
44ad1e56 | 4778 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_BEGIN |
44ad1e56 | 4779 | |
4780 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_ISSUE | |
44ad1e56 | 4781 | |
4782 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_BACKTRACK | |
44ad1e56 | 4783 | |
4784 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_END | |
44ad1e56 | 4785 | |
4786 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_INIT | |
44ad1e56 | 4787 | |
4788 | @hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_FINI | |
44ad1e56 | 4789 | |
ec1842d2 | 4790 | @hook TARGET_SCHED_DFA_NEW_CYCLE |
202d6e5f | 4791 | |
4792 | @hook TARGET_SCHED_IS_COSTLY_DEPENDENCE | |
202d6e5f | 4793 | |
4794 | @hook TARGET_SCHED_H_I_D_EXTENDED | |
202d6e5f | 4795 | |
4796 | @hook TARGET_SCHED_ALLOC_SCHED_CONTEXT | |
202d6e5f | 4797 | |
4798 | @hook TARGET_SCHED_INIT_SCHED_CONTEXT | |
202d6e5f | 4799 | |
4800 | @hook TARGET_SCHED_SET_SCHED_CONTEXT | |
202d6e5f | 4801 | |
4802 | @hook TARGET_SCHED_CLEAR_SCHED_CONTEXT | |
202d6e5f | 4803 | |
4804 | @hook TARGET_SCHED_FREE_SCHED_CONTEXT | |
202d6e5f | 4805 | |
4806 | @hook TARGET_SCHED_SPECULATE_INSN | |
202d6e5f | 4807 | |
4808 | @hook TARGET_SCHED_NEEDS_BLOCK_P | |
202d6e5f | 4809 | |
4810 | @hook TARGET_SCHED_GEN_SPEC_CHECK | |
202d6e5f | 4811 | |
202d6e5f | 4812 | @hook TARGET_SCHED_SET_SCHED_FLAGS |
202d6e5f | 4813 | |
4814 | @hook TARGET_SCHED_SMS_RES_MII | |
202d6e5f | 4815 | |
0ac9454e | 4816 | @hook TARGET_SCHED_DISPATCH |
0ac9454e | 4817 | |
4818 | @hook TARGET_SCHED_DISPATCH_DO | |
0ac9454e | 4819 | |
6c2d9e41 | 4820 | @hook TARGET_SCHED_EXPOSED_PIPELINE |
4821 | ||
5b1c765d | 4822 | @hook TARGET_SCHED_REASSOCIATION_WIDTH |
4823 | ||
202d6e5f | 4824 | @node Sections |
4825 | @section Dividing the Output into Sections (Texts, Data, @dots{}) | |
4826 | @c the above section title is WAY too long. maybe cut the part between | |
4827 | @c the (...)? --mew 10feb93 | |
4828 | ||
4829 | An object file is divided into sections containing different types of | |
4830 | data. In the most common case, there are three sections: the @dfn{text | |
4831 | section}, which holds instructions and read-only data; the @dfn{data | |
4832 | section}, which holds initialized writable data; and the @dfn{bss | |
4833 | section}, which holds uninitialized data. Some systems have other kinds | |
4834 | of sections. | |
4835 | ||
4836 | @file{varasm.c} provides several well-known sections, such as | |
4837 | @code{text_section}, @code{data_section} and @code{bss_section}. | |
4838 | The normal way of controlling a @code{@var{foo}_section} variable | |
4839 | is to define the associated @code{@var{FOO}_SECTION_ASM_OP} macro, | |
4840 | as described below. The macros are only read once, when @file{varasm.c} | |
4841 | initializes itself, so their values must be run-time constants. | |
4842 | They may however depend on command-line flags. | |
4843 | ||
4844 | @emph{Note:} Some run-time files, such @file{crtstuff.c}, also make | |
4845 | use of the @code{@var{FOO}_SECTION_ASM_OP} macros, and expect them | |
4846 | to be string literals. | |
4847 | ||
4848 | Some assemblers require a different string to be written every time a | |
4849 | section is selected. If your assembler falls into this category, you | |
4850 | should define the @code{TARGET_ASM_INIT_SECTIONS} hook and use | |
4851 | @code{get_unnamed_section} to set up the sections. | |
4852 | ||
4853 | You must always create a @code{text_section}, either by defining | |
4854 | @code{TEXT_SECTION_ASM_OP} or by initializing @code{text_section} | |
4855 | in @code{TARGET_ASM_INIT_SECTIONS}. The same is true of | |
4856 | @code{data_section} and @code{DATA_SECTION_ASM_OP}. If you do not | |
4857 | create a distinct @code{readonly_data_section}, the default is to | |
4858 | reuse @code{text_section}. | |
4859 | ||
4860 | All the other @file{varasm.c} sections are optional, and are null | |
4861 | if the target does not provide them. | |
4862 | ||
4863 | @defmac TEXT_SECTION_ASM_OP | |
4864 | A C expression whose value is a string, including spacing, containing the | |
4865 | assembler operation that should precede instructions and read-only data. | |
4866 | Normally @code{"\t.text"} is right. | |
4867 | @end defmac | |
4868 | ||
4869 | @defmac HOT_TEXT_SECTION_NAME | |
4870 | If defined, a C string constant for the name of the section containing most | |
4871 | frequently executed functions of the program. If not defined, GCC will provide | |
4872 | a default definition if the target supports named sections. | |
4873 | @end defmac | |
4874 | ||
4875 | @defmac UNLIKELY_EXECUTED_TEXT_SECTION_NAME | |
4876 | If defined, a C string constant for the name of the section containing unlikely | |
4877 | executed functions in the program. | |
4878 | @end defmac | |
4879 | ||
4880 | @defmac DATA_SECTION_ASM_OP | |
4881 | A C expression whose value is a string, including spacing, containing the | |
4882 | assembler operation to identify the following data as writable initialized | |
4883 | data. Normally @code{"\t.data"} is right. | |
4884 | @end defmac | |
4885 | ||
4886 | @defmac SDATA_SECTION_ASM_OP | |
4887 | If defined, a C expression whose value is a string, including spacing, | |
4888 | containing the assembler operation to identify the following data as | |
4889 | initialized, writable small data. | |
4890 | @end defmac | |
4891 | ||
4892 | @defmac READONLY_DATA_SECTION_ASM_OP | |
4893 | A C expression whose value is a string, including spacing, containing the | |
4894 | assembler operation to identify the following data as read-only initialized | |
4895 | data. | |
4896 | @end defmac | |
4897 | ||
4898 | @defmac BSS_SECTION_ASM_OP | |
4899 | If defined, a C expression whose value is a string, including spacing, | |
4900 | containing the assembler operation to identify the following data as | |
fa8d6f0f | 4901 | uninitialized global data. If not defined, and |
4902 | @code{ASM_OUTPUT_ALIGNED_BSS} not defined, | |
202d6e5f | 4903 | uninitialized global data will be output in the data section if |
4904 | @option{-fno-common} is passed, otherwise @code{ASM_OUTPUT_COMMON} will be | |
4905 | used. | |
4906 | @end defmac | |
4907 | ||
4908 | @defmac SBSS_SECTION_ASM_OP | |
4909 | If defined, a C expression whose value is a string, including spacing, | |
4910 | containing the assembler operation to identify the following data as | |
4911 | uninitialized, writable small data. | |
4912 | @end defmac | |
4913 | ||
4914 | @defmac TLS_COMMON_ASM_OP | |
4915 | If defined, a C expression whose value is a string containing the | |
4916 | assembler operation to identify the following data as thread-local | |
4917 | common data. The default is @code{".tls_common"}. | |
4918 | @end defmac | |
4919 | ||
4920 | @defmac TLS_SECTION_ASM_FLAG | |
4921 | If defined, a C expression whose value is a character constant | |
4922 | containing the flag used to mark a section as a TLS section. The | |
4923 | default is @code{'T'}. | |
4924 | @end defmac | |
4925 | ||
4926 | @defmac INIT_SECTION_ASM_OP | |
4927 | If defined, a C expression whose value is a string, including spacing, | |
4928 | containing the assembler operation to identify the following data as | |
4929 | initialization code. If not defined, GCC will assume such a section does | |
4930 | not exist. This section has no corresponding @code{init_section} | |
4931 | variable; it is used entirely in runtime code. | |
4932 | @end defmac | |
4933 | ||
4934 | @defmac FINI_SECTION_ASM_OP | |
4935 | If defined, a C expression whose value is a string, including spacing, | |
4936 | containing the assembler operation to identify the following data as | |
4937 | finalization code. If not defined, GCC will assume such a section does | |
4938 | not exist. This section has no corresponding @code{fini_section} | |
4939 | variable; it is used entirely in runtime code. | |
4940 | @end defmac | |
4941 | ||
4942 | @defmac INIT_ARRAY_SECTION_ASM_OP | |
4943 | If defined, a C expression whose value is a string, including spacing, | |
4944 | containing the assembler operation to identify the following data as | |
4945 | part of the @code{.init_array} (or equivalent) section. If not | |
4946 | defined, GCC will assume such a section does not exist. Do not define | |
4947 | both this macro and @code{INIT_SECTION_ASM_OP}. | |
4948 | @end defmac | |
4949 | ||
4950 | @defmac FINI_ARRAY_SECTION_ASM_OP | |
4951 | If defined, a C expression whose value is a string, including spacing, | |
4952 | containing the assembler operation to identify the following data as | |
4953 | part of the @code{.fini_array} (or equivalent) section. If not | |
4954 | defined, GCC will assume such a section does not exist. Do not define | |
4955 | both this macro and @code{FINI_SECTION_ASM_OP}. | |
4956 | @end defmac | |
4957 | ||
4958 | @defmac CRT_CALL_STATIC_FUNCTION (@var{section_op}, @var{function}) | |
4959 | If defined, an ASM statement that switches to a different section | |
4960 | via @var{section_op}, calls @var{function}, and switches back to | |
4961 | the text section. This is used in @file{crtstuff.c} if | |
4962 | @code{INIT_SECTION_ASM_OP} or @code{FINI_SECTION_ASM_OP} to calls | |
4963 | to initialization and finalization functions from the init and fini | |
4964 | sections. By default, this macro uses a simple function call. Some | |
4965 | ports need hand-crafted assembly code to avoid dependencies on | |
4966 | registers initialized in the function prologue or to ensure that | |
4967 | constant pools don't end up too far way in the text section. | |
4968 | @end defmac | |
4969 | ||
4970 | @defmac TARGET_LIBGCC_SDATA_SECTION | |
4971 | If defined, a string which names the section into which small | |
4972 | variables defined in crtstuff and libgcc should go. This is useful | |
4973 | when the target has options for optimizing access to small data, and | |
4974 | you want the crtstuff and libgcc routines to be conservative in what | |
4975 | they expect of your application yet liberal in what your application | |
4976 | expects. For example, for targets with a @code{.sdata} section (like | |
4977 | MIPS), you could compile crtstuff with @code{-G 0} so that it doesn't | |
4978 | require small data support from your application, but use this macro | |
4979 | to put small data into @code{.sdata} so that your application can | |
4980 | access these variables whether it uses small data or not. | |
4981 | @end defmac | |
4982 | ||
4983 | @defmac FORCE_CODE_SECTION_ALIGN | |
4984 | If defined, an ASM statement that aligns a code section to some | |
4985 | arbitrary boundary. This is used to force all fragments of the | |
4986 | @code{.init} and @code{.fini} sections to have to same alignment | |
4987 | and thus prevent the linker from having to add any padding. | |
4988 | @end defmac | |
4989 | ||
4990 | @defmac JUMP_TABLES_IN_TEXT_SECTION | |
4991 | Define this macro to be an expression with a nonzero value if jump | |
4992 | tables (for @code{tablejump} insns) should be output in the text | |
4993 | section, along with the assembler instructions. Otherwise, the | |
4994 | readonly data section is used. | |
4995 | ||
4996 | This macro is irrelevant if there is no separate readonly data section. | |
4997 | @end defmac | |
4998 | ||
4999 | @hook TARGET_ASM_INIT_SECTIONS | |
202d6e5f | 5000 | |
5001 | @hook TARGET_ASM_RELOC_RW_MASK | |
202d6e5f | 5002 | |
5003 | @hook TARGET_ASM_SELECT_SECTION | |
202d6e5f | 5004 | |
5005 | @defmac USE_SELECT_SECTION_FOR_FUNCTIONS | |
5006 | Define this macro if you wish TARGET_ASM_SELECT_SECTION to be called | |
5007 | for @code{FUNCTION_DECL}s as well as for variables and constants. | |
5008 | ||
5009 | In the case of a @code{FUNCTION_DECL}, @var{reloc} will be zero if the | |
5010 | function has been determined to be likely to be called, and nonzero if | |
5011 | it is unlikely to be called. | |
5012 | @end defmac | |
5013 | ||
5014 | @hook TARGET_ASM_UNIQUE_SECTION | |
202d6e5f | 5015 | |
5016 | @hook TARGET_ASM_FUNCTION_RODATA_SECTION | |
202d6e5f | 5017 | |
6e71bd21 | 5018 | @hook TARGET_ASM_MERGEABLE_RODATA_PREFIX |
5019 | ||
e3ef604c | 5020 | @hook TARGET_ASM_TM_CLONE_TABLE_SECTION |
5021 | ||
202d6e5f | 5022 | @hook TARGET_ASM_SELECT_RTX_SECTION |
202d6e5f | 5023 | |
5024 | @hook TARGET_MANGLE_DECL_ASSEMBLER_NAME | |
202d6e5f | 5025 | |
5026 | @hook TARGET_ENCODE_SECTION_INFO | |
202d6e5f | 5027 | |
5028 | @hook TARGET_STRIP_NAME_ENCODING | |
202d6e5f | 5029 | |
5030 | @hook TARGET_IN_SMALL_DATA_P | |
202d6e5f | 5031 | |
5032 | @hook TARGET_HAVE_SRODATA_SECTION | |
202d6e5f | 5033 | |
8637d6a2 | 5034 | @hook TARGET_PROFILE_BEFORE_PROLOGUE |
5035 | ||
202d6e5f | 5036 | @hook TARGET_BINDS_LOCAL_P |
202d6e5f | 5037 | |
5038 | @hook TARGET_HAVE_TLS | |
202d6e5f | 5039 | |
5040 | ||
5041 | @node PIC | |
5042 | @section Position Independent Code | |
5043 | @cindex position independent code | |
5044 | @cindex PIC | |
5045 | ||
5046 | This section describes macros that help implement generation of position | |
5047 | independent code. Simply defining these macros is not enough to | |
5048 | generate valid PIC; you must also add support to the hook | |
5049 | @code{TARGET_LEGITIMATE_ADDRESS_P} and to the macro | |
5050 | @code{PRINT_OPERAND_ADDRESS}, as well as @code{LEGITIMIZE_ADDRESS}. You | |
5051 | must modify the definition of @samp{movsi} to do something appropriate | |
5052 | when the source operand contains a symbolic address. You may also | |
5053 | need to alter the handling of switch statements so that they use | |
5054 | relative addresses. | |
15b474a2 | 5055 | @c i rearranged the order of the macros above to try to force one of |
202d6e5f | 5056 | @c them to the next line, to eliminate an overfull hbox. --mew 10feb93 |
5057 | ||
5058 | @defmac PIC_OFFSET_TABLE_REGNUM | |
5059 | The register number of the register used to address a table of static | |
5060 | data addresses in memory. In some cases this register is defined by a | |
5061 | processor's ``application binary interface'' (ABI)@. When this macro | |
5062 | is defined, RTL is generated for this register once, as with the stack | |
5063 | pointer and frame pointer registers. If this macro is not defined, it | |
5064 | is up to the machine-dependent files to allocate such a register (if | |
5065 | necessary). Note that this register must be fixed when in use (e.g.@: | |
5066 | when @code{flag_pic} is true). | |
5067 | @end defmac | |
5068 | ||
5069 | @defmac PIC_OFFSET_TABLE_REG_CALL_CLOBBERED | |
260e669e | 5070 | A C expression that is nonzero if the register defined by |
5071 | @code{PIC_OFFSET_TABLE_REGNUM} is clobbered by calls. If not defined, | |
5072 | the default is zero. Do not define | |
202d6e5f | 5073 | this macro if @code{PIC_OFFSET_TABLE_REGNUM} is not defined. |
5074 | @end defmac | |
5075 | ||
5076 | @defmac LEGITIMATE_PIC_OPERAND_P (@var{x}) | |
5077 | A C expression that is nonzero if @var{x} is a legitimate immediate | |
5078 | operand on the target machine when generating position independent code. | |
5079 | You can assume that @var{x} satisfies @code{CONSTANT_P}, so you need not | |
5080 | check this. You can also assume @var{flag_pic} is true, so you need not | |
5081 | check it either. You need not define this macro if all constants | |
5082 | (including @code{SYMBOL_REF}) can be immediate operands when generating | |
5083 | position independent code. | |
5084 | @end defmac | |
5085 | ||
5086 | @node Assembler Format | |
5087 | @section Defining the Output Assembler Language | |
5088 | ||
5089 | This section describes macros whose principal purpose is to describe how | |
5090 | to write instructions in assembler language---rather than what the | |
5091 | instructions do. | |
5092 | ||
5093 | @menu | |
5094 | * File Framework:: Structural information for the assembler file. | |
5095 | * Data Output:: Output of constants (numbers, strings, addresses). | |
5096 | * Uninitialized Data:: Output of uninitialized variables. | |
5097 | * Label Output:: Output and generation of labels. | |
5098 | * Initialization:: General principles of initialization | |
5099 | and termination routines. | |
5100 | * Macros for Initialization:: | |
5101 | Specific macros that control the handling of | |
5102 | initialization and termination routines. | |
5103 | * Instruction Output:: Output of actual instructions. | |
5104 | * Dispatch Tables:: Output of jump tables. | |
5105 | * Exception Region Output:: Output of exception region code. | |
5106 | * Alignment Output:: Pseudo ops for alignment and skipping data. | |
5107 | @end menu | |
5108 | ||
5109 | @node File Framework | |
5110 | @subsection The Overall Framework of an Assembler File | |
5111 | @cindex assembler format | |
5112 | @cindex output of assembler code | |
5113 | ||
5114 | @c prevent bad page break with this line | |
5115 | This describes the overall framework of an assembly file. | |
5116 | ||
5117 | @findex default_file_start | |
5118 | @hook TARGET_ASM_FILE_START | |
202d6e5f | 5119 | |
5120 | @hook TARGET_ASM_FILE_START_APP_OFF | |
202d6e5f | 5121 | |
5122 | @hook TARGET_ASM_FILE_START_FILE_DIRECTIVE | |
202d6e5f | 5123 | |
5124 | @hook TARGET_ASM_FILE_END | |
202d6e5f | 5125 | |
5126 | @deftypefun void file_end_indicate_exec_stack () | |
5127 | Some systems use a common convention, the @samp{.note.GNU-stack} | |
5128 | special section, to indicate whether or not an object file relies on | |
5129 | the stack being executable. If your system uses this convention, you | |
5130 | should define @code{TARGET_ASM_FILE_END} to this function. If you | |
5131 | need to do other things in that hook, have your hook function call | |
5132 | this function. | |
5133 | @end deftypefun | |
5134 | ||
5135 | @hook TARGET_ASM_LTO_START | |
202d6e5f | 5136 | |
5137 | @hook TARGET_ASM_LTO_END | |
202d6e5f | 5138 | |
5139 | @hook TARGET_ASM_CODE_END | |
202d6e5f | 5140 | |
5141 | @defmac ASM_COMMENT_START | |
5142 | A C string constant describing how to begin a comment in the target | |
5143 | assembler language. The compiler assumes that the comment will end at | |
5144 | the end of the line. | |
5145 | @end defmac | |
5146 | ||
5147 | @defmac ASM_APP_ON | |
5148 | A C string constant for text to be output before each @code{asm} | |
5149 | statement or group of consecutive ones. Normally this is | |
5150 | @code{"#APP"}, which is a comment that has no effect on most | |
5151 | assemblers but tells the GNU assembler that it must check the lines | |
5152 | that follow for all valid assembler constructs. | |
5153 | @end defmac | |
5154 | ||
5155 | @defmac ASM_APP_OFF | |
5156 | A C string constant for text to be output after each @code{asm} | |
5157 | statement or group of consecutive ones. Normally this is | |
5158 | @code{"#NO_APP"}, which tells the GNU assembler to resume making the | |
5159 | time-saving assumptions that are valid for ordinary compiler output. | |
5160 | @end defmac | |
5161 | ||
5162 | @defmac ASM_OUTPUT_SOURCE_FILENAME (@var{stream}, @var{name}) | |
5163 | A C statement to output COFF information or DWARF debugging information | |
5164 | which indicates that filename @var{name} is the current source file to | |
5165 | the stdio stream @var{stream}. | |
5166 | ||
5167 | This macro need not be defined if the standard form of output | |
5168 | for the file format in use is appropriate. | |
5169 | @end defmac | |
5170 | ||
e2823fde | 5171 | @hook TARGET_ASM_OUTPUT_SOURCE_FILENAME |
5172 | ||
367b1459 | 5173 | @hook TARGET_ASM_OUTPUT_IDENT |
5174 | ||
202d6e5f | 5175 | @defmac OUTPUT_QUOTED_STRING (@var{stream}, @var{string}) |
5176 | A C statement to output the string @var{string} to the stdio stream | |
5177 | @var{stream}. If you do not call the function @code{output_quoted_string} | |
5178 | in your config files, GCC will only call it to output filenames to | |
5179 | the assembler source. So you can use it to canonicalize the format | |
5180 | of the filename using this macro. | |
5181 | @end defmac | |
5182 | ||
202d6e5f | 5183 | @hook TARGET_ASM_NAMED_SECTION |
202d6e5f | 5184 | |
3b73548b | 5185 | @hook TARGET_ASM_FUNCTION_SECTION |
3b73548b | 5186 | |
3b3edcd4 | 5187 | @hook TARGET_ASM_FUNCTION_SWITCHED_TEXT_SECTIONS |
5188 | ||
202d6e5f | 5189 | @hook TARGET_HAVE_NAMED_SECTIONS |
5190 | This flag is true if the target supports @code{TARGET_ASM_NAMED_SECTION}. | |
b213bf24 | 5191 | It must not be modified by command-line option processing. |
202d6e5f | 5192 | @end deftypevr |
5193 | ||
5194 | @anchor{TARGET_HAVE_SWITCHABLE_BSS_SECTIONS} | |
5195 | @hook TARGET_HAVE_SWITCHABLE_BSS_SECTIONS | |
202d6e5f | 5196 | |
5197 | @hook TARGET_SECTION_TYPE_FLAGS | |
202d6e5f | 5198 | |
5199 | @hook TARGET_ASM_RECORD_GCC_SWITCHES | |
202d6e5f | 5200 | |
5201 | @hook TARGET_ASM_RECORD_GCC_SWITCHES_SECTION | |
202d6e5f | 5202 | |
5203 | @need 2000 | |
5204 | @node Data Output | |
5205 | @subsection Output of Data | |
5206 | ||
5207 | ||
5208 | @hook TARGET_ASM_BYTE_OP | |
202d6e5f | 5209 | |
5210 | @hook TARGET_ASM_INTEGER | |
202d6e5f | 5211 | |
1282f299 | 5212 | @hook TARGET_ASM_OUTPUT_ADDR_CONST_EXTRA |
1282f299 | 5213 | |
202d6e5f | 5214 | @defmac ASM_OUTPUT_ASCII (@var{stream}, @var{ptr}, @var{len}) |
5215 | A C statement to output to the stdio stream @var{stream} an assembler | |
5216 | instruction to assemble a string constant containing the @var{len} | |
5217 | bytes at @var{ptr}. @var{ptr} will be a C expression of type | |
5218 | @code{char *} and @var{len} a C expression of type @code{int}. | |
5219 | ||
5220 | If the assembler has a @code{.ascii} pseudo-op as found in the | |
5221 | Berkeley Unix assembler, do not define the macro | |
5222 | @code{ASM_OUTPUT_ASCII}. | |
5223 | @end defmac | |
5224 | ||
5225 | @defmac ASM_OUTPUT_FDESC (@var{stream}, @var{decl}, @var{n}) | |
5226 | A C statement to output word @var{n} of a function descriptor for | |
5227 | @var{decl}. This must be defined if @code{TARGET_VTABLE_USES_DESCRIPTORS} | |
5228 | is defined, and is otherwise unused. | |
5229 | @end defmac | |
5230 | ||
5231 | @defmac CONSTANT_POOL_BEFORE_FUNCTION | |
5232 | You may define this macro as a C expression. You should define the | |
5233 | expression to have a nonzero value if GCC should output the constant | |
5234 | pool for a function before the code for the function, or a zero value if | |
5235 | GCC should output the constant pool after the function. If you do | |
5236 | not define this macro, the usual case, GCC will output the constant | |
5237 | pool before the function. | |
5238 | @end defmac | |
5239 | ||
5240 | @defmac ASM_OUTPUT_POOL_PROLOGUE (@var{file}, @var{funname}, @var{fundecl}, @var{size}) | |
5241 | A C statement to output assembler commands to define the start of the | |
5242 | constant pool for a function. @var{funname} is a string giving | |
5243 | the name of the function. Should the return type of the function | |
5244 | be required, it can be obtained via @var{fundecl}. @var{size} | |
5245 | is the size, in bytes, of the constant pool that will be written | |
5246 | immediately after this call. | |
5247 | ||
5248 | If no constant-pool prefix is required, the usual case, this macro need | |
5249 | not be defined. | |
5250 | @end defmac | |
5251 | ||
5252 | @defmac ASM_OUTPUT_SPECIAL_POOL_ENTRY (@var{file}, @var{x}, @var{mode}, @var{align}, @var{labelno}, @var{jumpto}) | |
5253 | A C statement (with or without semicolon) to output a constant in the | |
5254 | constant pool, if it needs special treatment. (This macro need not do | |
5255 | anything for RTL expressions that can be output normally.) | |
5256 | ||
5257 | The argument @var{file} is the standard I/O stream to output the | |
5258 | assembler code on. @var{x} is the RTL expression for the constant to | |
5259 | output, and @var{mode} is the machine mode (in case @var{x} is a | |
5260 | @samp{const_int}). @var{align} is the required alignment for the value | |
5261 | @var{x}; you should output an assembler directive to force this much | |
5262 | alignment. | |
5263 | ||
5264 | The argument @var{labelno} is a number to use in an internal label for | |
5265 | the address of this pool entry. The definition of this macro is | |
5266 | responsible for outputting the label definition at the proper place. | |
5267 | Here is how to do this: | |
5268 | ||
5269 | @smallexample | |
5270 | @code{(*targetm.asm_out.internal_label)} (@var{file}, "LC", @var{labelno}); | |
5271 | @end smallexample | |
5272 | ||
5273 | When you output a pool entry specially, you should end with a | |
5274 | @code{goto} to the label @var{jumpto}. This will prevent the same pool | |
5275 | entry from being output a second time in the usual manner. | |
5276 | ||
5277 | You need not define this macro if it would do nothing. | |
5278 | @end defmac | |
5279 | ||
5280 | @defmac ASM_OUTPUT_POOL_EPILOGUE (@var{file} @var{funname} @var{fundecl} @var{size}) | |
5281 | A C statement to output assembler commands to at the end of the constant | |
5282 | pool for a function. @var{funname} is a string giving the name of the | |
5283 | function. Should the return type of the function be required, you can | |
5284 | obtain it via @var{fundecl}. @var{size} is the size, in bytes, of the | |
5285 | constant pool that GCC wrote immediately before this call. | |
5286 | ||
5287 | If no constant-pool epilogue is required, the usual case, you need not | |
5288 | define this macro. | |
5289 | @end defmac | |
5290 | ||
5291 | @defmac IS_ASM_LOGICAL_LINE_SEPARATOR (@var{C}, @var{STR}) | |
5292 | Define this macro as a C expression which is nonzero if @var{C} is | |
5293 | used as a logical line separator by the assembler. @var{STR} points | |
5294 | to the position in the string where @var{C} was found; this can be used if | |
5295 | a line separator uses multiple characters. | |
5296 | ||
5297 | If you do not define this macro, the default is that only | |
5298 | the character @samp{;} is treated as a logical line separator. | |
5299 | @end defmac | |
5300 | ||
5301 | @hook TARGET_ASM_OPEN_PAREN | |
202d6e5f | 5302 | |
5303 | These macros are provided by @file{real.h} for writing the definitions | |
5304 | of @code{ASM_OUTPUT_DOUBLE} and the like: | |
5305 | ||
5306 | @defmac REAL_VALUE_TO_TARGET_SINGLE (@var{x}, @var{l}) | |
5307 | @defmacx REAL_VALUE_TO_TARGET_DOUBLE (@var{x}, @var{l}) | |
5308 | @defmacx REAL_VALUE_TO_TARGET_LONG_DOUBLE (@var{x}, @var{l}) | |
5309 | @defmacx REAL_VALUE_TO_TARGET_DECIMAL32 (@var{x}, @var{l}) | |
5310 | @defmacx REAL_VALUE_TO_TARGET_DECIMAL64 (@var{x}, @var{l}) | |
5311 | @defmacx REAL_VALUE_TO_TARGET_DECIMAL128 (@var{x}, @var{l}) | |
5312 | These translate @var{x}, of type @code{REAL_VALUE_TYPE}, to the | |
5313 | target's floating point representation, and store its bit pattern in | |
5314 | the variable @var{l}. For @code{REAL_VALUE_TO_TARGET_SINGLE} and | |
5315 | @code{REAL_VALUE_TO_TARGET_DECIMAL32}, this variable should be a | |
5316 | simple @code{long int}. For the others, it should be an array of | |
5317 | @code{long int}. The number of elements in this array is determined | |
5318 | by the size of the desired target floating point data type: 32 bits of | |
5319 | it go in each @code{long int} array element. Each array element holds | |
5320 | 32 bits of the result, even if @code{long int} is wider than 32 bits | |
5321 | on the host machine. | |
5322 | ||
5323 | The array element values are designed so that you can print them out | |
5324 | using @code{fprintf} in the order they should appear in the target | |
5325 | machine's memory. | |
5326 | @end defmac | |
5327 | ||
5328 | @node Uninitialized Data | |
5329 | @subsection Output of Uninitialized Variables | |
5330 | ||
5331 | Each of the macros in this section is used to do the whole job of | |
5332 | outputting a single uninitialized variable. | |
5333 | ||
5334 | @defmac ASM_OUTPUT_COMMON (@var{stream}, @var{name}, @var{size}, @var{rounded}) | |
5335 | A C statement (sans semicolon) to output to the stdio stream | |
5336 | @var{stream} the assembler definition of a common-label named | |
5337 | @var{name} whose size is @var{size} bytes. The variable @var{rounded} | |
5338 | is the size rounded up to whatever alignment the caller wants. It is | |
5339 | possible that @var{size} may be zero, for instance if a struct with no | |
5340 | other member than a zero-length array is defined. In this case, the | |
5341 | backend must output a symbol definition that allocates at least one | |
5342 | byte, both so that the address of the resulting object does not compare | |
5343 | equal to any other, and because some object formats cannot even express | |
5344 | the concept of a zero-sized common symbol, as that is how they represent | |
5345 | an ordinary undefined external. | |
5346 | ||
5347 | Use the expression @code{assemble_name (@var{stream}, @var{name})} to | |
5348 | output the name itself; before and after that, output the additional | |
5349 | assembler syntax for defining the name, and a newline. | |
5350 | ||
5351 | This macro controls how the assembler definitions of uninitialized | |
5352 | common global variables are output. | |
5353 | @end defmac | |
5354 | ||
5355 | @defmac ASM_OUTPUT_ALIGNED_COMMON (@var{stream}, @var{name}, @var{size}, @var{alignment}) | |
5356 | Like @code{ASM_OUTPUT_COMMON} except takes the required alignment as a | |
5357 | separate, explicit argument. If you define this macro, it is used in | |
5358 | place of @code{ASM_OUTPUT_COMMON}, and gives you more flexibility in | |
5359 | handling the required alignment of the variable. The alignment is specified | |
5360 | as the number of bits. | |
5361 | @end defmac | |
5362 | ||
5363 | @defmac ASM_OUTPUT_ALIGNED_DECL_COMMON (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) | |
5364 | Like @code{ASM_OUTPUT_ALIGNED_COMMON} except that @var{decl} of the | |
5365 | variable to be output, if there is one, or @code{NULL_TREE} if there | |
5366 | is no corresponding variable. If you define this macro, GCC will use it | |
5367 | in place of both @code{ASM_OUTPUT_COMMON} and | |
5368 | @code{ASM_OUTPUT_ALIGNED_COMMON}. Define this macro when you need to see | |
5369 | the variable's decl in order to chose what to output. | |
5370 | @end defmac | |
5371 | ||
fa8d6f0f | 5372 | @defmac ASM_OUTPUT_ALIGNED_BSS (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) |
202d6e5f | 5373 | A C statement (sans semicolon) to output to the stdio stream |
5374 | @var{stream} the assembler definition of uninitialized global @var{decl} named | |
fa8d6f0f | 5375 | @var{name} whose size is @var{size} bytes. The variable @var{alignment} |
5376 | is the alignment specified as the number of bits. | |
202d6e5f | 5377 | |
fa8d6f0f | 5378 | Try to use function @code{asm_output_aligned_bss} defined in file |
5379 | @file{varasm.c} when defining this macro. If unable, use the expression | |
202d6e5f | 5380 | @code{assemble_name (@var{stream}, @var{name})} to output the name itself; |
5381 | before and after that, output the additional assembler syntax for defining | |
5382 | the name, and a newline. | |
5383 | ||
fa8d6f0f | 5384 | There are two ways of handling global BSS@. One is to define this macro. |
202d6e5f | 5385 | The other is to have @code{TARGET_ASM_SELECT_SECTION} return a |
5386 | switchable BSS section (@pxref{TARGET_HAVE_SWITCHABLE_BSS_SECTIONS}). | |
5387 | You do not need to do both. | |
5388 | ||
5389 | Some languages do not have @code{common} data, and require a | |
5390 | non-common form of global BSS in order to handle uninitialized globals | |
5391 | efficiently. C++ is one example of this. However, if the target does | |
5392 | not support global BSS, the front end may choose to make globals | |
5393 | common in order to save space in the object file. | |
5394 | @end defmac | |
5395 | ||
202d6e5f | 5396 | @defmac ASM_OUTPUT_LOCAL (@var{stream}, @var{name}, @var{size}, @var{rounded}) |
5397 | A C statement (sans semicolon) to output to the stdio stream | |
5398 | @var{stream} the assembler definition of a local-common-label named | |
5399 | @var{name} whose size is @var{size} bytes. The variable @var{rounded} | |
5400 | is the size rounded up to whatever alignment the caller wants. | |
5401 | ||
5402 | Use the expression @code{assemble_name (@var{stream}, @var{name})} to | |
5403 | output the name itself; before and after that, output the additional | |
5404 | assembler syntax for defining the name, and a newline. | |
5405 | ||
5406 | This macro controls how the assembler definitions of uninitialized | |
5407 | static variables are output. | |
5408 | @end defmac | |
5409 | ||
5410 | @defmac ASM_OUTPUT_ALIGNED_LOCAL (@var{stream}, @var{name}, @var{size}, @var{alignment}) | |
5411 | Like @code{ASM_OUTPUT_LOCAL} except takes the required alignment as a | |
5412 | separate, explicit argument. If you define this macro, it is used in | |
5413 | place of @code{ASM_OUTPUT_LOCAL}, and gives you more flexibility in | |
5414 | handling the required alignment of the variable. The alignment is specified | |
5415 | as the number of bits. | |
5416 | @end defmac | |
5417 | ||
5418 | @defmac ASM_OUTPUT_ALIGNED_DECL_LOCAL (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) | |
5419 | Like @code{ASM_OUTPUT_ALIGNED_DECL} except that @var{decl} of the | |
5420 | variable to be output, if there is one, or @code{NULL_TREE} if there | |
5421 | is no corresponding variable. If you define this macro, GCC will use it | |
5422 | in place of both @code{ASM_OUTPUT_DECL} and | |
5423 | @code{ASM_OUTPUT_ALIGNED_DECL}. Define this macro when you need to see | |
5424 | the variable's decl in order to chose what to output. | |
5425 | @end defmac | |
5426 | ||
5427 | @node Label Output | |
5428 | @subsection Output and Generation of Labels | |
5429 | ||
5430 | @c prevent bad page break with this line | |
5431 | This is about outputting labels. | |
5432 | ||
5433 | @findex assemble_name | |
5434 | @defmac ASM_OUTPUT_LABEL (@var{stream}, @var{name}) | |
5435 | A C statement (sans semicolon) to output to the stdio stream | |
5436 | @var{stream} the assembler definition of a label named @var{name}. | |
5437 | Use the expression @code{assemble_name (@var{stream}, @var{name})} to | |
5438 | output the name itself; before and after that, output the additional | |
5439 | assembler syntax for defining the name, and a newline. A default | |
5440 | definition of this macro is provided which is correct for most systems. | |
5441 | @end defmac | |
5442 | ||
2761b7cb | 5443 | @defmac ASM_OUTPUT_FUNCTION_LABEL (@var{stream}, @var{name}, @var{decl}) |
5444 | A C statement (sans semicolon) to output to the stdio stream | |
5445 | @var{stream} the assembler definition of a label named @var{name} of | |
5446 | a function. | |
5447 | Use the expression @code{assemble_name (@var{stream}, @var{name})} to | |
5448 | output the name itself; before and after that, output the additional | |
5449 | assembler syntax for defining the name, and a newline. A default | |
5450 | definition of this macro is provided which is correct for most systems. | |
5451 | ||
5452 | If this macro is not defined, then the function name is defined in the | |
5453 | usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}). | |
5454 | @end defmac | |
5455 | ||
202d6e5f | 5456 | @findex assemble_name_raw |
5457 | @defmac ASM_OUTPUT_INTERNAL_LABEL (@var{stream}, @var{name}) | |
5458 | Identical to @code{ASM_OUTPUT_LABEL}, except that @var{name} is known | |
5459 | to refer to a compiler-generated label. The default definition uses | |
5460 | @code{assemble_name_raw}, which is like @code{assemble_name} except | |
5461 | that it is more efficient. | |
5462 | @end defmac | |
5463 | ||
5464 | @defmac SIZE_ASM_OP | |
5465 | A C string containing the appropriate assembler directive to specify the | |
5466 | size of a symbol, without any arguments. On systems that use ELF, the | |
5467 | default (in @file{config/elfos.h}) is @samp{"\t.size\t"}; on other | |
5468 | systems, the default is not to define this macro. | |
5469 | ||
5470 | Define this macro only if it is correct to use the default definitions | |
5471 | of @code{ASM_OUTPUT_SIZE_DIRECTIVE} and @code{ASM_OUTPUT_MEASURED_SIZE} | |
5472 | for your system. If you need your own custom definitions of those | |
5473 | macros, or if you do not need explicit symbol sizes at all, do not | |
5474 | define this macro. | |
5475 | @end defmac | |
5476 | ||
5477 | @defmac ASM_OUTPUT_SIZE_DIRECTIVE (@var{stream}, @var{name}, @var{size}) | |
5478 | A C statement (sans semicolon) to output to the stdio stream | |
5479 | @var{stream} a directive telling the assembler that the size of the | |
5480 | symbol @var{name} is @var{size}. @var{size} is a @code{HOST_WIDE_INT}. | |
5481 | If you define @code{SIZE_ASM_OP}, a default definition of this macro is | |
5482 | provided. | |
5483 | @end defmac | |
5484 | ||
5485 | @defmac ASM_OUTPUT_MEASURED_SIZE (@var{stream}, @var{name}) | |
5486 | A C statement (sans semicolon) to output to the stdio stream | |
5487 | @var{stream} a directive telling the assembler to calculate the size of | |
5488 | the symbol @var{name} by subtracting its address from the current | |
5489 | address. | |
5490 | ||
5491 | If you define @code{SIZE_ASM_OP}, a default definition of this macro is | |
5492 | provided. The default assumes that the assembler recognizes a special | |
5493 | @samp{.} symbol as referring to the current address, and can calculate | |
5494 | the difference between this and another symbol. If your assembler does | |
5495 | not recognize @samp{.} or cannot do calculations with it, you will need | |
5496 | to redefine @code{ASM_OUTPUT_MEASURED_SIZE} to use some other technique. | |
5497 | @end defmac | |
5498 | ||
75a15fa3 | 5499 | @defmac NO_DOLLAR_IN_LABEL |
5500 | Define this macro if the assembler does not accept the character | |
5501 | @samp{$} in label names. By default constructors and destructors in | |
5502 | G++ have @samp{$} in the identifiers. If this macro is defined, | |
5503 | @samp{.} is used instead. | |
5504 | @end defmac | |
5505 | ||
5506 | @defmac NO_DOT_IN_LABEL | |
5507 | Define this macro if the assembler does not accept the character | |
5508 | @samp{.} in label names. By default constructors and destructors in G++ | |
5509 | have names that use @samp{.}. If this macro is defined, these names | |
5510 | are rewritten to avoid @samp{.}. | |
5511 | @end defmac | |
5512 | ||
202d6e5f | 5513 | @defmac TYPE_ASM_OP |
5514 | A C string containing the appropriate assembler directive to specify the | |
5515 | type of a symbol, without any arguments. On systems that use ELF, the | |
5516 | default (in @file{config/elfos.h}) is @samp{"\t.type\t"}; on other | |
5517 | systems, the default is not to define this macro. | |
5518 | ||
5519 | Define this macro only if it is correct to use the default definition of | |
5520 | @code{ASM_OUTPUT_TYPE_DIRECTIVE} for your system. If you need your own | |
5521 | custom definition of this macro, or if you do not need explicit symbol | |
5522 | types at all, do not define this macro. | |
5523 | @end defmac | |
5524 | ||
5525 | @defmac TYPE_OPERAND_FMT | |
5526 | A C string which specifies (using @code{printf} syntax) the format of | |
5527 | the second operand to @code{TYPE_ASM_OP}. On systems that use ELF, the | |
5528 | default (in @file{config/elfos.h}) is @samp{"@@%s"}; on other systems, | |
5529 | the default is not to define this macro. | |
5530 | ||
5531 | Define this macro only if it is correct to use the default definition of | |
5532 | @code{ASM_OUTPUT_TYPE_DIRECTIVE} for your system. If you need your own | |
5533 | custom definition of this macro, or if you do not need explicit symbol | |
5534 | types at all, do not define this macro. | |
5535 | @end defmac | |
5536 | ||
5537 | @defmac ASM_OUTPUT_TYPE_DIRECTIVE (@var{stream}, @var{type}) | |
5538 | A C statement (sans semicolon) to output to the stdio stream | |
5539 | @var{stream} a directive telling the assembler that the type of the | |
5540 | symbol @var{name} is @var{type}. @var{type} is a C string; currently, | |
5541 | that string is always either @samp{"function"} or @samp{"object"}, but | |
5542 | you should not count on this. | |
5543 | ||
5544 | If you define @code{TYPE_ASM_OP} and @code{TYPE_OPERAND_FMT}, a default | |
5545 | definition of this macro is provided. | |
5546 | @end defmac | |
5547 | ||
5548 | @defmac ASM_DECLARE_FUNCTION_NAME (@var{stream}, @var{name}, @var{decl}) | |
5549 | A C statement (sans semicolon) to output to the stdio stream | |
5550 | @var{stream} any text necessary for declaring the name @var{name} of a | |
5551 | function which is being defined. This macro is responsible for | |
5552 | outputting the label definition (perhaps using | |
2761b7cb | 5553 | @code{ASM_OUTPUT_FUNCTION_LABEL}). The argument @var{decl} is the |
202d6e5f | 5554 | @code{FUNCTION_DECL} tree node representing the function. |
5555 | ||
5556 | If this macro is not defined, then the function name is defined in the | |
2761b7cb | 5557 | usual manner as a label (by means of @code{ASM_OUTPUT_FUNCTION_LABEL}). |
202d6e5f | 5558 | |
5559 | You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} in the definition | |
5560 | of this macro. | |
5561 | @end defmac | |
5562 | ||
5563 | @defmac ASM_DECLARE_FUNCTION_SIZE (@var{stream}, @var{name}, @var{decl}) | |
5564 | A C statement (sans semicolon) to output to the stdio stream | |
5565 | @var{stream} any text necessary for declaring the size of a function | |
5566 | which is being defined. The argument @var{name} is the name of the | |
5567 | function. The argument @var{decl} is the @code{FUNCTION_DECL} tree node | |
5568 | representing the function. | |
5569 | ||
5570 | If this macro is not defined, then the function size is not defined. | |
5571 | ||
5572 | You may wish to use @code{ASM_OUTPUT_MEASURED_SIZE} in the definition | |
5573 | of this macro. | |
5574 | @end defmac | |
5575 | ||
5576 | @defmac ASM_DECLARE_OBJECT_NAME (@var{stream}, @var{name}, @var{decl}) | |
5577 | A C statement (sans semicolon) to output to the stdio stream | |
5578 | @var{stream} any text necessary for declaring the name @var{name} of an | |
5579 | initialized variable which is being defined. This macro must output the | |
5580 | label definition (perhaps using @code{ASM_OUTPUT_LABEL}). The argument | |
5581 | @var{decl} is the @code{VAR_DECL} tree node representing the variable. | |
5582 | ||
5583 | If this macro is not defined, then the variable name is defined in the | |
5584 | usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}). | |
5585 | ||
5586 | You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} and/or | |
5587 | @code{ASM_OUTPUT_SIZE_DIRECTIVE} in the definition of this macro. | |
5588 | @end defmac | |
5589 | ||
8c38d114 | 5590 | @hook TARGET_ASM_DECLARE_CONSTANT_NAME |
202d6e5f | 5591 | |
5592 | @defmac ASM_DECLARE_REGISTER_GLOBAL (@var{stream}, @var{decl}, @var{regno}, @var{name}) | |
5593 | A C statement (sans semicolon) to output to the stdio stream | |
5594 | @var{stream} any text necessary for claiming a register @var{regno} | |
5595 | for a global variable @var{decl} with name @var{name}. | |
5596 | ||
5597 | If you don't define this macro, that is equivalent to defining it to do | |
5598 | nothing. | |
5599 | @end defmac | |
5600 | ||
5601 | @defmac ASM_FINISH_DECLARE_OBJECT (@var{stream}, @var{decl}, @var{toplevel}, @var{atend}) | |
5602 | A C statement (sans semicolon) to finish up declaring a variable name | |
5603 | once the compiler has processed its initializer fully and thus has had a | |
5604 | chance to determine the size of an array when controlled by an | |
5605 | initializer. This is used on systems where it's necessary to declare | |
5606 | something about the size of the object. | |
5607 | ||
5608 | If you don't define this macro, that is equivalent to defining it to do | |
5609 | nothing. | |
5610 | ||
5611 | You may wish to use @code{ASM_OUTPUT_SIZE_DIRECTIVE} and/or | |
5612 | @code{ASM_OUTPUT_MEASURED_SIZE} in the definition of this macro. | |
5613 | @end defmac | |
5614 | ||
5615 | @hook TARGET_ASM_GLOBALIZE_LABEL | |
202d6e5f | 5616 | |
5617 | @hook TARGET_ASM_GLOBALIZE_DECL_NAME | |
202d6e5f | 5618 | |
5619 | @defmac ASM_WEAKEN_LABEL (@var{stream}, @var{name}) | |
5620 | A C statement (sans semicolon) to output to the stdio stream | |
5621 | @var{stream} some commands that will make the label @var{name} weak; | |
5622 | that is, available for reference from other files but only used if | |
5623 | no other definition is available. Use the expression | |
5624 | @code{assemble_name (@var{stream}, @var{name})} to output the name | |
5625 | itself; before and after that, output the additional assembler syntax | |
5626 | for making that name weak, and a newline. | |
5627 | ||
5628 | If you don't define this macro or @code{ASM_WEAKEN_DECL}, GCC will not | |
5629 | support weak symbols and you should not define the @code{SUPPORTS_WEAK} | |
5630 | macro. | |
5631 | @end defmac | |
5632 | ||
5633 | @defmac ASM_WEAKEN_DECL (@var{stream}, @var{decl}, @var{name}, @var{value}) | |
5634 | Combines (and replaces) the function of @code{ASM_WEAKEN_LABEL} and | |
5635 | @code{ASM_OUTPUT_WEAK_ALIAS}, allowing access to the associated function | |
5636 | or variable decl. If @var{value} is not @code{NULL}, this C statement | |
5637 | should output to the stdio stream @var{stream} assembler code which | |
5638 | defines (equates) the weak symbol @var{name} to have the value | |
5639 | @var{value}. If @var{value} is @code{NULL}, it should output commands | |
5640 | to make @var{name} weak. | |
5641 | @end defmac | |
5642 | ||
5643 | @defmac ASM_OUTPUT_WEAKREF (@var{stream}, @var{decl}, @var{name}, @var{value}) | |
5644 | Outputs a directive that enables @var{name} to be used to refer to | |
5645 | symbol @var{value} with weak-symbol semantics. @code{decl} is the | |
5646 | declaration of @code{name}. | |
5647 | @end defmac | |
5648 | ||
5649 | @defmac SUPPORTS_WEAK | |
293c8430 | 5650 | A preprocessor constant expression which evaluates to true if the target |
5651 | supports weak symbols. | |
202d6e5f | 5652 | |
5653 | If you don't define this macro, @file{defaults.h} provides a default | |
5654 | definition. If either @code{ASM_WEAKEN_LABEL} or @code{ASM_WEAKEN_DECL} | |
293c8430 | 5655 | is defined, the default definition is @samp{1}; otherwise, it is @samp{0}. |
5656 | @end defmac | |
5657 | ||
5658 | @defmac TARGET_SUPPORTS_WEAK | |
5659 | A C expression which evaluates to true if the target supports weak symbols. | |
5660 | ||
5661 | If you don't define this macro, @file{defaults.h} provides a default | |
5662 | definition. The default definition is @samp{(SUPPORTS_WEAK)}. Define | |
5663 | this macro if you want to control weak symbol support with a compiler | |
5664 | flag such as @option{-melf}. | |
202d6e5f | 5665 | @end defmac |
5666 | ||
5667 | @defmac MAKE_DECL_ONE_ONLY (@var{decl}) | |
5668 | A C statement (sans semicolon) to mark @var{decl} to be emitted as a | |
5669 | public symbol such that extra copies in multiple translation units will | |
5670 | be discarded by the linker. Define this macro if your object file | |
5671 | format provides support for this concept, such as the @samp{COMDAT} | |
5672 | section flags in the Microsoft Windows PE/COFF format, and this support | |
5673 | requires changes to @var{decl}, such as putting it in a separate section. | |
5674 | @end defmac | |
5675 | ||
5676 | @defmac SUPPORTS_ONE_ONLY | |
5677 | A C expression which evaluates to true if the target supports one-only | |
5678 | semantics. | |
5679 | ||
5680 | If you don't define this macro, @file{varasm.c} provides a default | |
5681 | definition. If @code{MAKE_DECL_ONE_ONLY} is defined, the default | |
5682 | definition is @samp{1}; otherwise, it is @samp{0}. Define this macro if | |
5683 | you want to control one-only symbol support with a compiler flag, or if | |
5684 | setting the @code{DECL_ONE_ONLY} flag is enough to mark a declaration to | |
5685 | be emitted as one-only. | |
5686 | @end defmac | |
5687 | ||
5688 | @hook TARGET_ASM_ASSEMBLE_VISIBILITY | |
202d6e5f | 5689 | |
5690 | @defmac TARGET_WEAK_NOT_IN_ARCHIVE_TOC | |
5691 | A C expression that evaluates to true if the target's linker expects | |
5692 | that weak symbols do not appear in a static archive's table of contents. | |
5693 | The default is @code{0}. | |
5694 | ||
5695 | Leaving weak symbols out of an archive's table of contents means that, | |
5696 | if a symbol will only have a definition in one translation unit and | |
5697 | will have undefined references from other translation units, that | |
5698 | symbol should not be weak. Defining this macro to be nonzero will | |
5699 | thus have the effect that certain symbols that would normally be weak | |
5700 | (explicit template instantiations, and vtables for polymorphic classes | |
5701 | with noninline key methods) will instead be nonweak. | |
5702 | ||
5703 | The C++ ABI requires this macro to be zero. Define this macro for | |
5704 | targets where full C++ ABI compliance is impossible and where linker | |
5705 | restrictions require weak symbols to be left out of a static archive's | |
5706 | table of contents. | |
5707 | @end defmac | |
5708 | ||
5709 | @defmac ASM_OUTPUT_EXTERNAL (@var{stream}, @var{decl}, @var{name}) | |
5710 | A C statement (sans semicolon) to output to the stdio stream | |
5711 | @var{stream} any text necessary for declaring the name of an external | |
5712 | symbol named @var{name} which is referenced in this compilation but | |
5713 | not defined. The value of @var{decl} is the tree node for the | |
5714 | declaration. | |
5715 | ||
5716 | This macro need not be defined if it does not need to output anything. | |
5717 | The GNU assembler and most Unix assemblers don't require anything. | |
5718 | @end defmac | |
5719 | ||
5720 | @hook TARGET_ASM_EXTERNAL_LIBCALL | |
202d6e5f | 5721 | |
5722 | @hook TARGET_ASM_MARK_DECL_PRESERVED | |
202d6e5f | 5723 | |
5724 | @defmac ASM_OUTPUT_LABELREF (@var{stream}, @var{name}) | |
5725 | A C statement (sans semicolon) to output to the stdio stream | |
5726 | @var{stream} a reference in assembler syntax to a label named | |
5727 | @var{name}. This should add @samp{_} to the front of the name, if that | |
5728 | is customary on your operating system, as it is in most Berkeley Unix | |
5729 | systems. This macro is used in @code{assemble_name}. | |
5730 | @end defmac | |
5731 | ||
d86d364d | 5732 | @hook TARGET_MANGLE_ASSEMBLER_NAME |
5733 | ||
202d6e5f | 5734 | @defmac ASM_OUTPUT_SYMBOL_REF (@var{stream}, @var{sym}) |
5735 | A C statement (sans semicolon) to output a reference to | |
5736 | @code{SYMBOL_REF} @var{sym}. If not defined, @code{assemble_name} | |
5737 | will be used to output the name of the symbol. This macro may be used | |
5738 | to modify the way a symbol is referenced depending on information | |
5739 | encoded by @code{TARGET_ENCODE_SECTION_INFO}. | |
5740 | @end defmac | |
5741 | ||
5742 | @defmac ASM_OUTPUT_LABEL_REF (@var{stream}, @var{buf}) | |
5743 | A C statement (sans semicolon) to output a reference to @var{buf}, the | |
5744 | result of @code{ASM_GENERATE_INTERNAL_LABEL}. If not defined, | |
5745 | @code{assemble_name} will be used to output the name of the symbol. | |
5746 | This macro is not used by @code{output_asm_label}, or the @code{%l} | |
5747 | specifier that calls it; the intention is that this macro should be set | |
5748 | when it is necessary to output a label differently when its address is | |
5749 | being taken. | |
5750 | @end defmac | |
5751 | ||
5752 | @hook TARGET_ASM_INTERNAL_LABEL | |
202d6e5f | 5753 | |
5754 | @defmac ASM_OUTPUT_DEBUG_LABEL (@var{stream}, @var{prefix}, @var{num}) | |
5755 | A C statement to output to the stdio stream @var{stream} a debug info | |
5756 | label whose name is made from the string @var{prefix} and the number | |
5757 | @var{num}. This is useful for VLIW targets, where debug info labels | |
5758 | may need to be treated differently than branch target labels. On some | |
5759 | systems, branch target labels must be at the beginning of instruction | |
5760 | bundles, but debug info labels can occur in the middle of instruction | |
5761 | bundles. | |
5762 | ||
5763 | If this macro is not defined, then @code{(*targetm.asm_out.internal_label)} will be | |
5764 | used. | |
5765 | @end defmac | |
5766 | ||
5767 | @defmac ASM_GENERATE_INTERNAL_LABEL (@var{string}, @var{prefix}, @var{num}) | |
5768 | A C statement to store into the string @var{string} a label whose name | |
5769 | is made from the string @var{prefix} and the number @var{num}. | |
5770 | ||
5771 | This string, when output subsequently by @code{assemble_name}, should | |
5772 | produce the output that @code{(*targetm.asm_out.internal_label)} would produce | |
5773 | with the same @var{prefix} and @var{num}. | |
5774 | ||
5775 | If the string begins with @samp{*}, then @code{assemble_name} will | |
5776 | output the rest of the string unchanged. It is often convenient for | |
5777 | @code{ASM_GENERATE_INTERNAL_LABEL} to use @samp{*} in this way. If the | |
5778 | string doesn't start with @samp{*}, then @code{ASM_OUTPUT_LABELREF} gets | |
5779 | to output the string, and may change it. (Of course, | |
5780 | @code{ASM_OUTPUT_LABELREF} is also part of your machine description, so | |
5781 | you should know what it does on your machine.) | |
5782 | @end defmac | |
5783 | ||
5784 | @defmac ASM_FORMAT_PRIVATE_NAME (@var{outvar}, @var{name}, @var{number}) | |
5785 | A C expression to assign to @var{outvar} (which is a variable of type | |
5786 | @code{char *}) a newly allocated string made from the string | |
5787 | @var{name} and the number @var{number}, with some suitable punctuation | |
5788 | added. Use @code{alloca} to get space for the string. | |
5789 | ||
5790 | The string will be used as an argument to @code{ASM_OUTPUT_LABELREF} to | |
5791 | produce an assembler label for an internal static variable whose name is | |
5792 | @var{name}. Therefore, the string must be such as to result in valid | |
5793 | assembler code. The argument @var{number} is different each time this | |
5794 | macro is executed; it prevents conflicts between similarly-named | |
5795 | internal static variables in different scopes. | |
5796 | ||
5797 | Ideally this string should not be a valid C identifier, to prevent any | |
5798 | conflict with the user's own symbols. Most assemblers allow periods | |
5799 | or percent signs in assembler symbols; putting at least one of these | |
5800 | between the name and the number will suffice. | |
5801 | ||
5802 | If this macro is not defined, a default definition will be provided | |
5803 | which is correct for most systems. | |
5804 | @end defmac | |
5805 | ||
5806 | @defmac ASM_OUTPUT_DEF (@var{stream}, @var{name}, @var{value}) | |
5807 | A C statement to output to the stdio stream @var{stream} assembler code | |
5808 | which defines (equates) the symbol @var{name} to have the value @var{value}. | |
5809 | ||
5810 | @findex SET_ASM_OP | |
5811 | If @code{SET_ASM_OP} is defined, a default definition is provided which is | |
5812 | correct for most systems. | |
5813 | @end defmac | |
5814 | ||
5815 | @defmac ASM_OUTPUT_DEF_FROM_DECLS (@var{stream}, @var{decl_of_name}, @var{decl_of_value}) | |
5816 | A C statement to output to the stdio stream @var{stream} assembler code | |
5817 | which defines (equates) the symbol whose tree node is @var{decl_of_name} | |
5818 | to have the value of the tree node @var{decl_of_value}. This macro will | |
5819 | be used in preference to @samp{ASM_OUTPUT_DEF} if it is defined and if | |
5820 | the tree nodes are available. | |
5821 | ||
5822 | @findex SET_ASM_OP | |
5823 | If @code{SET_ASM_OP} is defined, a default definition is provided which is | |
5824 | correct for most systems. | |
5825 | @end defmac | |
5826 | ||
5827 | @defmac TARGET_DEFERRED_OUTPUT_DEFS (@var{decl_of_name}, @var{decl_of_value}) | |
5828 | A C statement that evaluates to true if the assembler code which defines | |
5829 | (equates) the symbol whose tree node is @var{decl_of_name} to have the value | |
5830 | of the tree node @var{decl_of_value} should be emitted near the end of the | |
5831 | current compilation unit. The default is to not defer output of defines. | |
5832 | This macro affects defines output by @samp{ASM_OUTPUT_DEF} and | |
5833 | @samp{ASM_OUTPUT_DEF_FROM_DECLS}. | |
5834 | @end defmac | |
5835 | ||
5836 | @defmac ASM_OUTPUT_WEAK_ALIAS (@var{stream}, @var{name}, @var{value}) | |
5837 | A C statement to output to the stdio stream @var{stream} assembler code | |
5838 | which defines (equates) the weak symbol @var{name} to have the value | |
5839 | @var{value}. If @var{value} is @code{NULL}, it defines @var{name} as | |
5840 | an undefined weak symbol. | |
5841 | ||
5842 | Define this macro if the target only supports weak aliases; define | |
5843 | @code{ASM_OUTPUT_DEF} instead if possible. | |
5844 | @end defmac | |
5845 | ||
5846 | @defmac OBJC_GEN_METHOD_LABEL (@var{buf}, @var{is_inst}, @var{class_name}, @var{cat_name}, @var{sel_name}) | |
5847 | Define this macro to override the default assembler names used for | |
5848 | Objective-C methods. | |
5849 | ||
5850 | The default name is a unique method number followed by the name of the | |
5851 | class (e.g.@: @samp{_1_Foo}). For methods in categories, the name of | |
5852 | the category is also included in the assembler name (e.g.@: | |
5853 | @samp{_1_Foo_Bar}). | |
5854 | ||
5855 | These names are safe on most systems, but make debugging difficult since | |
5856 | the method's selector is not present in the name. Therefore, particular | |
5857 | systems define other ways of computing names. | |
5858 | ||
5859 | @var{buf} is an expression of type @code{char *} which gives you a | |
5860 | buffer in which to store the name; its length is as long as | |
5861 | @var{class_name}, @var{cat_name} and @var{sel_name} put together, plus | |
5862 | 50 characters extra. | |
5863 | ||
5864 | The argument @var{is_inst} specifies whether the method is an instance | |
5865 | method or a class method; @var{class_name} is the name of the class; | |
5866 | @var{cat_name} is the name of the category (or @code{NULL} if the method is not | |
5867 | in a category); and @var{sel_name} is the name of the selector. | |
5868 | ||
5869 | On systems where the assembler can handle quoted names, you can use this | |
5870 | macro to provide more human-readable names. | |
5871 | @end defmac | |
5872 | ||
202d6e5f | 5873 | @node Initialization |
5874 | @subsection How Initialization Functions Are Handled | |
5875 | @cindex initialization routines | |
5876 | @cindex termination routines | |
5877 | @cindex constructors, output of | |
5878 | @cindex destructors, output of | |
5879 | ||
5880 | The compiled code for certain languages includes @dfn{constructors} | |
5881 | (also called @dfn{initialization routines})---functions to initialize | |
5882 | data in the program when the program is started. These functions need | |
5883 | to be called before the program is ``started''---that is to say, before | |
5884 | @code{main} is called. | |
5885 | ||
5886 | Compiling some languages generates @dfn{destructors} (also called | |
5887 | @dfn{termination routines}) that should be called when the program | |
5888 | terminates. | |
5889 | ||
5890 | To make the initialization and termination functions work, the compiler | |
5891 | must output something in the assembler code to cause those functions to | |
5892 | be called at the appropriate time. When you port the compiler to a new | |
5893 | system, you need to specify how to do this. | |
5894 | ||
5895 | There are two major ways that GCC currently supports the execution of | |
5896 | initialization and termination functions. Each way has two variants. | |
5897 | Much of the structure is common to all four variations. | |
5898 | ||
5899 | @findex __CTOR_LIST__ | |
5900 | @findex __DTOR_LIST__ | |
5901 | The linker must build two lists of these functions---a list of | |
5902 | initialization functions, called @code{__CTOR_LIST__}, and a list of | |
5903 | termination functions, called @code{__DTOR_LIST__}. | |
5904 | ||
5905 | Each list always begins with an ignored function pointer (which may hold | |
5906 | 0, @minus{}1, or a count of the function pointers after it, depending on | |
5907 | the environment). This is followed by a series of zero or more function | |
5908 | pointers to constructors (or destructors), followed by a function | |
5909 | pointer containing zero. | |
5910 | ||
5911 | Depending on the operating system and its executable file format, either | |
5912 | @file{crtstuff.c} or @file{libgcc2.c} traverses these lists at startup | |
5913 | time and exit time. Constructors are called in reverse order of the | |
5914 | list; destructors in forward order. | |
5915 | ||
5916 | The best way to handle static constructors works only for object file | |
5917 | formats which provide arbitrarily-named sections. A section is set | |
5918 | aside for a list of constructors, and another for a list of destructors. | |
5919 | Traditionally these are called @samp{.ctors} and @samp{.dtors}. Each | |
5920 | object file that defines an initialization function also puts a word in | |
5921 | the constructor section to point to that function. The linker | |
5922 | accumulates all these words into one contiguous @samp{.ctors} section. | |
5923 | Termination functions are handled similarly. | |
5924 | ||
5925 | This method will be chosen as the default by @file{target-def.h} if | |
5926 | @code{TARGET_ASM_NAMED_SECTION} is defined. A target that does not | |
5927 | support arbitrary sections, but does support special designated | |
5928 | constructor and destructor sections may define @code{CTORS_SECTION_ASM_OP} | |
5929 | and @code{DTORS_SECTION_ASM_OP} to achieve the same effect. | |
5930 | ||
5931 | When arbitrary sections are available, there are two variants, depending | |
5932 | upon how the code in @file{crtstuff.c} is called. On systems that | |
5933 | support a @dfn{.init} section which is executed at program startup, | |
5934 | parts of @file{crtstuff.c} are compiled into that section. The | |
5935 | program is linked by the @command{gcc} driver like this: | |
5936 | ||
5937 | @smallexample | |
5938 | ld -o @var{output_file} crti.o crtbegin.o @dots{} -lgcc crtend.o crtn.o | |
5939 | @end smallexample | |
5940 | ||
5941 | The prologue of a function (@code{__init}) appears in the @code{.init} | |
5942 | section of @file{crti.o}; the epilogue appears in @file{crtn.o}. Likewise | |
5943 | for the function @code{__fini} in the @dfn{.fini} section. Normally these | |
5944 | files are provided by the operating system or by the GNU C library, but | |
5945 | are provided by GCC for a few targets. | |
5946 | ||
5947 | The objects @file{crtbegin.o} and @file{crtend.o} are (for most targets) | |
5948 | compiled from @file{crtstuff.c}. They contain, among other things, code | |
5949 | fragments within the @code{.init} and @code{.fini} sections that branch | |
5950 | to routines in the @code{.text} section. The linker will pull all parts | |
5951 | of a section together, which results in a complete @code{__init} function | |
5952 | that invokes the routines we need at startup. | |
5953 | ||
5954 | To use this variant, you must define the @code{INIT_SECTION_ASM_OP} | |
5955 | macro properly. | |
5956 | ||
5957 | If no init section is available, when GCC compiles any function called | |
5958 | @code{main} (or more accurately, any function designated as a program | |
5959 | entry point by the language front end calling @code{expand_main_function}), | |
5960 | it inserts a procedure call to @code{__main} as the first executable code | |
5961 | after the function prologue. The @code{__main} function is defined | |
5962 | in @file{libgcc2.c} and runs the global constructors. | |
5963 | ||
5964 | In file formats that don't support arbitrary sections, there are again | |
5965 | two variants. In the simplest variant, the GNU linker (GNU @code{ld}) | |
5966 | and an `a.out' format must be used. In this case, | |
5967 | @code{TARGET_ASM_CONSTRUCTOR} is defined to produce a @code{.stabs} | |
5968 | entry of type @samp{N_SETT}, referencing the name @code{__CTOR_LIST__}, | |
5969 | and with the address of the void function containing the initialization | |
5970 | code as its value. The GNU linker recognizes this as a request to add | |
5971 | the value to a @dfn{set}; the values are accumulated, and are eventually | |
5972 | placed in the executable as a vector in the format described above, with | |
5973 | a leading (ignored) count and a trailing zero element. | |
5974 | @code{TARGET_ASM_DESTRUCTOR} is handled similarly. Since no init | |
5975 | section is available, the absence of @code{INIT_SECTION_ASM_OP} causes | |
5976 | the compilation of @code{main} to call @code{__main} as above, starting | |
5977 | the initialization process. | |
5978 | ||
5979 | The last variant uses neither arbitrary sections nor the GNU linker. | |
5980 | This is preferable when you want to do dynamic linking and when using | |
5981 | file formats which the GNU linker does not support, such as `ECOFF'@. In | |
5982 | this case, @code{TARGET_HAVE_CTORS_DTORS} is false, initialization and | |
5983 | termination functions are recognized simply by their names. This requires | |
5984 | an extra program in the linkage step, called @command{collect2}. This program | |
5985 | pretends to be the linker, for use with GCC; it does its job by running | |
5986 | the ordinary linker, but also arranges to include the vectors of | |
5987 | initialization and termination functions. These functions are called | |
5988 | via @code{__main} as described above. In order to use this method, | |
5989 | @code{use_collect2} must be defined in the target in @file{config.gcc}. | |
5990 | ||
5991 | @ifinfo | |
5992 | The following section describes the specific macros that control and | |
5993 | customize the handling of initialization and termination functions. | |
5994 | @end ifinfo | |
5995 | ||
5996 | @node Macros for Initialization | |
5997 | @subsection Macros Controlling Initialization Routines | |
5998 | ||
5999 | Here are the macros that control how the compiler handles initialization | |
6000 | and termination functions: | |
6001 | ||
6002 | @defmac INIT_SECTION_ASM_OP | |
6003 | If defined, a C string constant, including spacing, for the assembler | |
6004 | operation to identify the following data as initialization code. If not | |
6005 | defined, GCC will assume such a section does not exist. When you are | |
6006 | using special sections for initialization and termination functions, this | |
6007 | macro also controls how @file{crtstuff.c} and @file{libgcc2.c} arrange to | |
6008 | run the initialization functions. | |
6009 | @end defmac | |
6010 | ||
6011 | @defmac HAS_INIT_SECTION | |
6012 | If defined, @code{main} will not call @code{__main} as described above. | |
6013 | This macro should be defined for systems that control start-up code | |
6014 | on a symbol-by-symbol basis, such as OSF/1, and should not | |
6015 | be defined explicitly for systems that support @code{INIT_SECTION_ASM_OP}. | |
6016 | @end defmac | |
6017 | ||
6018 | @defmac LD_INIT_SWITCH | |
6019 | If defined, a C string constant for a switch that tells the linker that | |
6020 | the following symbol is an initialization routine. | |
6021 | @end defmac | |
6022 | ||
6023 | @defmac LD_FINI_SWITCH | |
6024 | If defined, a C string constant for a switch that tells the linker that | |
6025 | the following symbol is a finalization routine. | |
6026 | @end defmac | |
6027 | ||
6028 | @defmac COLLECT_SHARED_INIT_FUNC (@var{stream}, @var{func}) | |
6029 | If defined, a C statement that will write a function that can be | |
6030 | automatically called when a shared library is loaded. The function | |
6031 | should call @var{func}, which takes no arguments. If not defined, and | |
6032 | the object format requires an explicit initialization function, then a | |
6033 | function called @code{_GLOBAL__DI} will be generated. | |
6034 | ||
6035 | This function and the following one are used by collect2 when linking a | |
6036 | shared library that needs constructors or destructors, or has DWARF2 | |
6037 | exception tables embedded in the code. | |
6038 | @end defmac | |
6039 | ||
6040 | @defmac COLLECT_SHARED_FINI_FUNC (@var{stream}, @var{func}) | |
6041 | If defined, a C statement that will write a function that can be | |
6042 | automatically called when a shared library is unloaded. The function | |
6043 | should call @var{func}, which takes no arguments. If not defined, and | |
6044 | the object format requires an explicit finalization function, then a | |
6045 | function called @code{_GLOBAL__DD} will be generated. | |
6046 | @end defmac | |
6047 | ||
6048 | @defmac INVOKE__main | |
6049 | If defined, @code{main} will call @code{__main} despite the presence of | |
6050 | @code{INIT_SECTION_ASM_OP}. This macro should be defined for systems | |
6051 | where the init section is not actually run automatically, but is still | |
6052 | useful for collecting the lists of constructors and destructors. | |
6053 | @end defmac | |
6054 | ||
6055 | @defmac SUPPORTS_INIT_PRIORITY | |
6056 | If nonzero, the C++ @code{init_priority} attribute is supported and the | |
6057 | compiler should emit instructions to control the order of initialization | |
6058 | of objects. If zero, the compiler will issue an error message upon | |
6059 | encountering an @code{init_priority} attribute. | |
6060 | @end defmac | |
6061 | ||
6062 | @hook TARGET_HAVE_CTORS_DTORS | |
202d6e5f | 6063 | |
6064 | @hook TARGET_ASM_CONSTRUCTOR | |
202d6e5f | 6065 | |
6066 | @hook TARGET_ASM_DESTRUCTOR | |
202d6e5f | 6067 | |
6068 | If @code{TARGET_HAVE_CTORS_DTORS} is true, the initialization routine | |
6069 | generated for the generated object file will have static linkage. | |
6070 | ||
6071 | If your system uses @command{collect2} as the means of processing | |
6072 | constructors, then that program normally uses @command{nm} to scan | |
6073 | an object file for constructor functions to be called. | |
6074 | ||
6075 | On certain kinds of systems, you can define this macro to make | |
6076 | @command{collect2} work faster (and, in some cases, make it work at all): | |
6077 | ||
6078 | @defmac OBJECT_FORMAT_COFF | |
6079 | Define this macro if the system uses COFF (Common Object File Format) | |
6080 | object files, so that @command{collect2} can assume this format and scan | |
6081 | object files directly for dynamic constructor/destructor functions. | |
6082 | ||
6083 | This macro is effective only in a native compiler; @command{collect2} as | |
6084 | part of a cross compiler always uses @command{nm} for the target machine. | |
6085 | @end defmac | |
6086 | ||
6087 | @defmac REAL_NM_FILE_NAME | |
6088 | Define this macro as a C string constant containing the file name to use | |
6089 | to execute @command{nm}. The default is to search the path normally for | |
6090 | @command{nm}. | |
f369130e | 6091 | @end defmac |
6092 | ||
6093 | @defmac NM_FLAGS | |
6094 | @command{collect2} calls @command{nm} to scan object files for static | |
6095 | constructors and destructors and LTO info. By default, @option{-n} is | |
6096 | passed. Define @code{NM_FLAGS} to a C string constant if other options | |
b59688ee | 6097 | are needed to get the same output format as GNU @command{nm -n} |
f369130e | 6098 | produces. |
6099 | @end defmac | |
202d6e5f | 6100 | |
6101 | If your system supports shared libraries and has a program to list the | |
6102 | dynamic dependencies of a given library or executable, you can define | |
6103 | these macros to enable support for running initialization and | |
6104 | termination functions in shared libraries: | |
202d6e5f | 6105 | |
6106 | @defmac LDD_SUFFIX | |
6107 | Define this macro to a C string constant containing the name of the program | |
f369130e | 6108 | which lists dynamic dependencies, like @command{ldd} under SunOS 4. |
202d6e5f | 6109 | @end defmac |
6110 | ||
6111 | @defmac PARSE_LDD_OUTPUT (@var{ptr}) | |
6112 | Define this macro to be C code that extracts filenames from the output | |
6113 | of the program denoted by @code{LDD_SUFFIX}. @var{ptr} is a variable | |
6114 | of type @code{char *} that points to the beginning of a line of output | |
6115 | from @code{LDD_SUFFIX}. If the line lists a dynamic dependency, the | |
6116 | code must advance @var{ptr} to the beginning of the filename on that | |
6117 | line. Otherwise, it must set @var{ptr} to @code{NULL}. | |
6118 | @end defmac | |
6119 | ||
6120 | @defmac SHLIB_SUFFIX | |
6121 | Define this macro to a C string constant containing the default shared | |
6122 | library extension of the target (e.g., @samp{".so"}). @command{collect2} | |
6123 | strips version information after this suffix when generating global | |
6124 | constructor and destructor names. This define is only needed on targets | |
6125 | that use @command{collect2} to process constructors and destructors. | |
6126 | @end defmac | |
6127 | ||
6128 | @node Instruction Output | |
6129 | @subsection Output of Assembler Instructions | |
6130 | ||
6131 | @c prevent bad page break with this line | |
6132 | This describes assembler instruction output. | |
6133 | ||
6134 | @defmac REGISTER_NAMES | |
6135 | A C initializer containing the assembler's names for the machine | |
6136 | registers, each one as a C string constant. This is what translates | |
6137 | register numbers in the compiler into assembler language. | |
6138 | @end defmac | |
6139 | ||
6140 | @defmac ADDITIONAL_REGISTER_NAMES | |
6141 | If defined, a C initializer for an array of structures containing a name | |
6142 | and a register number. This macro defines additional names for hard | |
6143 | registers, thus allowing the @code{asm} option in declarations to refer | |
6144 | to registers using alternate names. | |
6145 | @end defmac | |
6146 | ||
ea26afd4 | 6147 | @defmac OVERLAPPING_REGISTER_NAMES |
6148 | If defined, a C initializer for an array of structures containing a | |
6149 | name, a register number and a count of the number of consecutive | |
6150 | machine registers the name overlaps. This macro defines additional | |
6151 | names for hard registers, thus allowing the @code{asm} option in | |
6152 | declarations to refer to registers using alternate names. Unlike | |
6153 | @code{ADDITIONAL_REGISTER_NAMES}, this macro should be used when the | |
6154 | register name implies multiple underlying registers. | |
6155 | ||
6156 | This macro should be used when it is important that a clobber in an | |
6157 | @code{asm} statement clobbers all the underlying values implied by the | |
6158 | register name. For example, on ARM, clobbering the double-precision | |
6159 | VFP register ``d0'' implies clobbering both single-precision registers | |
6160 | ``s0'' and ``s1''. | |
6161 | @end defmac | |
6162 | ||
202d6e5f | 6163 | @defmac ASM_OUTPUT_OPCODE (@var{stream}, @var{ptr}) |
6164 | Define this macro if you are using an unusual assembler that | |
6165 | requires different names for the machine instructions. | |
6166 | ||
6167 | The definition is a C statement or statements which output an | |
6168 | assembler instruction opcode to the stdio stream @var{stream}. The | |
6169 | macro-operand @var{ptr} is a variable of type @code{char *} which | |
6170 | points to the opcode name in its ``internal'' form---the form that is | |
6171 | written in the machine description. The definition should output the | |
6172 | opcode name to @var{stream}, performing any translation you desire, and | |
6173 | increment the variable @var{ptr} to point at the end of the opcode | |
6174 | so that it will not be output twice. | |
6175 | ||
6176 | In fact, your macro definition may process less than the entire opcode | |
6177 | name, or more than the opcode name; but if you want to process text | |
6178 | that includes @samp{%}-sequences to substitute operands, you must take | |
6179 | care of the substitution yourself. Just be sure to increment | |
6180 | @var{ptr} over whatever text should not be output normally. | |
6181 | ||
6182 | @findex recog_data.operand | |
6183 | If you need to look at the operand values, they can be found as the | |
6184 | elements of @code{recog_data.operand}. | |
6185 | ||
6186 | If the macro definition does nothing, the instruction is output | |
6187 | in the usual way. | |
6188 | @end defmac | |
6189 | ||
6190 | @defmac FINAL_PRESCAN_INSN (@var{insn}, @var{opvec}, @var{noperands}) | |
6191 | If defined, a C statement to be executed just prior to the output of | |
6192 | assembler code for @var{insn}, to modify the extracted operands so | |
6193 | they will be output differently. | |
6194 | ||
6195 | Here the argument @var{opvec} is the vector containing the operands | |
6196 | extracted from @var{insn}, and @var{noperands} is the number of | |
6197 | elements of the vector which contain meaningful data for this insn. | |
6198 | The contents of this vector are what will be used to convert the insn | |
6199 | template into assembler code, so you can change the assembler output | |
6200 | by changing the contents of the vector. | |
6201 | ||
6202 | This macro is useful when various assembler syntaxes share a single | |
6203 | file of instruction patterns; by defining this macro differently, you | |
6204 | can cause a large class of instructions to be output differently (such | |
6205 | as with rearranged operands). Naturally, variations in assembler | |
6206 | syntax affecting individual insn patterns ought to be handled by | |
6207 | writing conditional output routines in those patterns. | |
6208 | ||
6209 | If this macro is not defined, it is equivalent to a null statement. | |
6210 | @end defmac | |
6211 | ||
6212 | @hook TARGET_ASM_FINAL_POSTSCAN_INSN | |
202d6e5f | 6213 | |
6214 | @defmac PRINT_OPERAND (@var{stream}, @var{x}, @var{code}) | |
6215 | A C compound statement to output to stdio stream @var{stream} the | |
6216 | assembler syntax for an instruction operand @var{x}. @var{x} is an | |
6217 | RTL expression. | |
6218 | ||
6219 | @var{code} is a value that can be used to specify one of several ways | |
6220 | of printing the operand. It is used when identical operands must be | |
6221 | printed differently depending on the context. @var{code} comes from | |
6222 | the @samp{%} specification that was used to request printing of the | |
6223 | operand. If the specification was just @samp{%@var{digit}} then | |
6224 | @var{code} is 0; if the specification was @samp{%@var{ltr} | |
6225 | @var{digit}} then @var{code} is the ASCII code for @var{ltr}. | |
6226 | ||
6227 | @findex reg_names | |
6228 | If @var{x} is a register, this macro should print the register's name. | |
6229 | The names can be found in an array @code{reg_names} whose type is | |
6230 | @code{char *[]}. @code{reg_names} is initialized from | |
6231 | @code{REGISTER_NAMES}. | |
6232 | ||
6233 | When the machine description has a specification @samp{%@var{punct}} | |
6234 | (a @samp{%} followed by a punctuation character), this macro is called | |
6235 | with a null pointer for @var{x} and the punctuation character for | |
6236 | @var{code}. | |
6237 | @end defmac | |
6238 | ||
6239 | @defmac PRINT_OPERAND_PUNCT_VALID_P (@var{code}) | |
6240 | A C expression which evaluates to true if @var{code} is a valid | |
6241 | punctuation character for use in the @code{PRINT_OPERAND} macro. If | |
6242 | @code{PRINT_OPERAND_PUNCT_VALID_P} is not defined, it means that no | |
6243 | punctuation characters (except for the standard one, @samp{%}) are used | |
6244 | in this way. | |
6245 | @end defmac | |
6246 | ||
6247 | @defmac PRINT_OPERAND_ADDRESS (@var{stream}, @var{x}) | |
6248 | A C compound statement to output to stdio stream @var{stream} the | |
6249 | assembler syntax for an instruction operand that is a memory reference | |
6250 | whose address is @var{x}. @var{x} is an RTL expression. | |
6251 | ||
6252 | @cindex @code{TARGET_ENCODE_SECTION_INFO} usage | |
6253 | On some machines, the syntax for a symbolic address depends on the | |
6254 | section that the address refers to. On these machines, define the hook | |
6255 | @code{TARGET_ENCODE_SECTION_INFO} to store the information into the | |
6256 | @code{symbol_ref}, and then check for it here. @xref{Assembler | |
6257 | Format}. | |
6258 | @end defmac | |
6259 | ||
6260 | @findex dbr_sequence_length | |
6261 | @defmac DBR_OUTPUT_SEQEND (@var{file}) | |
6262 | A C statement, to be executed after all slot-filler instructions have | |
6263 | been output. If necessary, call @code{dbr_sequence_length} to | |
6264 | determine the number of slots filled in a sequence (zero if not | |
6265 | currently outputting a sequence), to decide how many no-ops to output, | |
6266 | or whatever. | |
6267 | ||
6268 | Don't define this macro if it has nothing to do, but it is helpful in | |
6269 | reading assembly output if the extent of the delay sequence is made | |
6270 | explicit (e.g.@: with white space). | |
6271 | @end defmac | |
6272 | ||
6273 | @findex final_sequence | |
6274 | Note that output routines for instructions with delay slots must be | |
6275 | prepared to deal with not being output as part of a sequence | |
6276 | (i.e.@: when the scheduling pass is not run, or when no slot fillers could be | |
6277 | found.) The variable @code{final_sequence} is null when not | |
6278 | processing a sequence, otherwise it contains the @code{sequence} rtx | |
6279 | being output. | |
6280 | ||
6281 | @findex asm_fprintf | |
6282 | @defmac REGISTER_PREFIX | |
6283 | @defmacx LOCAL_LABEL_PREFIX | |
6284 | @defmacx USER_LABEL_PREFIX | |
6285 | @defmacx IMMEDIATE_PREFIX | |
6286 | If defined, C string expressions to be used for the @samp{%R}, @samp{%L}, | |
6287 | @samp{%U}, and @samp{%I} options of @code{asm_fprintf} (see | |
6288 | @file{final.c}). These are useful when a single @file{md} file must | |
6289 | support multiple assembler formats. In that case, the various @file{tm.h} | |
6290 | files can define these macros differently. | |
6291 | @end defmac | |
6292 | ||
6293 | @defmac ASM_FPRINTF_EXTENSIONS (@var{file}, @var{argptr}, @var{format}) | |
6294 | If defined this macro should expand to a series of @code{case} | |
6295 | statements which will be parsed inside the @code{switch} statement of | |
6296 | the @code{asm_fprintf} function. This allows targets to define extra | |
6297 | printf formats which may useful when generating their assembler | |
6298 | statements. Note that uppercase letters are reserved for future | |
6299 | generic extensions to asm_fprintf, and so are not available to target | |
6300 | specific code. The output file is given by the parameter @var{file}. | |
6301 | The varargs input pointer is @var{argptr} and the rest of the format | |
6302 | string, starting the character after the one that is being switched | |
6303 | upon, is pointed to by @var{format}. | |
6304 | @end defmac | |
6305 | ||
6306 | @defmac ASSEMBLER_DIALECT | |
6307 | If your target supports multiple dialects of assembler language (such as | |
6308 | different opcodes), define this macro as a C expression that gives the | |
6309 | numeric index of the assembler language dialect to use, with zero as the | |
6310 | first variant. | |
6311 | ||
6312 | If this macro is defined, you may use constructs of the form | |
6313 | @smallexample | |
6314 | @samp{@{option0|option1|option2@dots{}@}} | |
6315 | @end smallexample | |
6316 | @noindent | |
6317 | in the output templates of patterns (@pxref{Output Template}) or in the | |
6318 | first argument of @code{asm_fprintf}. This construct outputs | |
6319 | @samp{option0}, @samp{option1}, @samp{option2}, etc., if the value of | |
6320 | @code{ASSEMBLER_DIALECT} is zero, one, two, etc. Any special characters | |
6321 | within these strings retain their usual meaning. If there are fewer | |
6322 | alternatives within the braces than the value of | |
82353beb | 6323 | @code{ASSEMBLER_DIALECT}, the construct outputs nothing. If it's needed |
6324 | to print curly braces or @samp{|} character in assembler output directly, | |
6325 | @samp{%@{}, @samp{%@}} and @samp{%|} can be used. | |
202d6e5f | 6326 | |
6327 | If you do not define this macro, the characters @samp{@{}, @samp{|} and | |
6328 | @samp{@}} do not have any special meaning when used in templates or | |
6329 | operands to @code{asm_fprintf}. | |
6330 | ||
6331 | Define the macros @code{REGISTER_PREFIX}, @code{LOCAL_LABEL_PREFIX}, | |
6332 | @code{USER_LABEL_PREFIX} and @code{IMMEDIATE_PREFIX} if you can express | |
6333 | the variations in assembler language syntax with that mechanism. Define | |
6334 | @code{ASSEMBLER_DIALECT} and use the @samp{@{option0|option1@}} syntax | |
6335 | if the syntax variant are larger and involve such things as different | |
6336 | opcodes or operand order. | |
6337 | @end defmac | |
6338 | ||
6339 | @defmac ASM_OUTPUT_REG_PUSH (@var{stream}, @var{regno}) | |
6340 | A C expression to output to @var{stream} some assembler code | |
6341 | which will push hard register number @var{regno} onto the stack. | |
6342 | The code need not be optimal, since this macro is used only when | |
6343 | profiling. | |
6344 | @end defmac | |
6345 | ||
6346 | @defmac ASM_OUTPUT_REG_POP (@var{stream}, @var{regno}) | |
6347 | A C expression to output to @var{stream} some assembler code | |
6348 | which will pop hard register number @var{regno} off of the stack. | |
6349 | The code need not be optimal, since this macro is used only when | |
6350 | profiling. | |
6351 | @end defmac | |
6352 | ||
6353 | @node Dispatch Tables | |
6354 | @subsection Output of Dispatch Tables | |
6355 | ||
6356 | @c prevent bad page break with this line | |
6357 | This concerns dispatch tables. | |
6358 | ||
6359 | @cindex dispatch table | |
6360 | @defmac ASM_OUTPUT_ADDR_DIFF_ELT (@var{stream}, @var{body}, @var{value}, @var{rel}) | |
6361 | A C statement to output to the stdio stream @var{stream} an assembler | |
6362 | pseudo-instruction to generate a difference between two labels. | |
6363 | @var{value} and @var{rel} are the numbers of two internal labels. The | |
6364 | definitions of these labels are output using | |
6365 | @code{(*targetm.asm_out.internal_label)}, and they must be printed in the same | |
6366 | way here. For example, | |
6367 | ||
6368 | @smallexample | |
6369 | fprintf (@var{stream}, "\t.word L%d-L%d\n", | |
6370 | @var{value}, @var{rel}) | |
6371 | @end smallexample | |
6372 | ||
6373 | You must provide this macro on machines where the addresses in a | |
6374 | dispatch table are relative to the table's own address. If defined, GCC | |
6375 | will also use this macro on all machines when producing PIC@. | |
6376 | @var{body} is the body of the @code{ADDR_DIFF_VEC}; it is provided so that the | |
6377 | mode and flags can be read. | |
6378 | @end defmac | |
6379 | ||
6380 | @defmac ASM_OUTPUT_ADDR_VEC_ELT (@var{stream}, @var{value}) | |
6381 | This macro should be provided on machines where the addresses | |
6382 | in a dispatch table are absolute. | |
6383 | ||
6384 | The definition should be a C statement to output to the stdio stream | |
6385 | @var{stream} an assembler pseudo-instruction to generate a reference to | |
6386 | a label. @var{value} is the number of an internal label whose | |
6387 | definition is output using @code{(*targetm.asm_out.internal_label)}. | |
6388 | For example, | |
6389 | ||
6390 | @smallexample | |
6391 | fprintf (@var{stream}, "\t.word L%d\n", @var{value}) | |
6392 | @end smallexample | |
6393 | @end defmac | |
6394 | ||
6395 | @defmac ASM_OUTPUT_CASE_LABEL (@var{stream}, @var{prefix}, @var{num}, @var{table}) | |
6396 | Define this if the label before a jump-table needs to be output | |
6397 | specially. The first three arguments are the same as for | |
6398 | @code{(*targetm.asm_out.internal_label)}; the fourth argument is the | |
9ddbb404 | 6399 | jump-table which follows (a @code{jump_table_data} containing an |
202d6e5f | 6400 | @code{addr_vec} or @code{addr_diff_vec}). |
6401 | ||
6402 | This feature is used on system V to output a @code{swbeg} statement | |
6403 | for the table. | |
6404 | ||
6405 | If this macro is not defined, these labels are output with | |
6406 | @code{(*targetm.asm_out.internal_label)}. | |
6407 | @end defmac | |
6408 | ||
6409 | @defmac ASM_OUTPUT_CASE_END (@var{stream}, @var{num}, @var{table}) | |
6410 | Define this if something special must be output at the end of a | |
6411 | jump-table. The definition should be a C statement to be executed | |
6412 | after the assembler code for the table is written. It should write | |
6413 | the appropriate code to stdio stream @var{stream}. The argument | |
6414 | @var{table} is the jump-table insn, and @var{num} is the label-number | |
6415 | of the preceding label. | |
6416 | ||
6417 | If this macro is not defined, nothing special is output at the end of | |
6418 | the jump-table. | |
6419 | @end defmac | |
6420 | ||
6421 | @hook TARGET_ASM_EMIT_UNWIND_LABEL | |
202d6e5f | 6422 | |
6423 | @hook TARGET_ASM_EMIT_EXCEPT_TABLE_LABEL | |
202d6e5f | 6424 | |
37966699 | 6425 | @hook TARGET_ASM_EMIT_EXCEPT_PERSONALITY |
6426 | ||
202d6e5f | 6427 | @hook TARGET_ASM_UNWIND_EMIT |
202d6e5f | 6428 | |
f3e8e368 | 6429 | @hook TARGET_ASM_UNWIND_EMIT_BEFORE_INSN |
6430 | ||
202d6e5f | 6431 | @node Exception Region Output |
6432 | @subsection Assembler Commands for Exception Regions | |
6433 | ||
6434 | @c prevent bad page break with this line | |
6435 | ||
6436 | This describes commands marking the start and the end of an exception | |
6437 | region. | |
6438 | ||
6439 | @defmac EH_FRAME_SECTION_NAME | |
6440 | If defined, a C string constant for the name of the section containing | |
6441 | exception handling frame unwind information. If not defined, GCC will | |
6442 | provide a default definition if the target supports named sections. | |
6443 | @file{crtstuff.c} uses this macro to switch to the appropriate section. | |
6444 | ||
6445 | You should define this symbol if your target supports DWARF 2 frame | |
6446 | unwind information and the default definition does not work. | |
6447 | @end defmac | |
6448 | ||
6449 | @defmac EH_FRAME_IN_DATA_SECTION | |
6450 | If defined, DWARF 2 frame unwind information will be placed in the | |
6451 | data section even though the target supports named sections. This | |
6452 | might be necessary, for instance, if the system linker does garbage | |
6453 | collection and sections cannot be marked as not to be collected. | |
6454 | ||
6455 | Do not define this macro unless @code{TARGET_ASM_NAMED_SECTION} is | |
6456 | also defined. | |
6457 | @end defmac | |
6458 | ||
6459 | @defmac EH_TABLES_CAN_BE_READ_ONLY | |
6460 | Define this macro to 1 if your target is such that no frame unwind | |
6461 | information encoding used with non-PIC code will ever require a | |
6462 | runtime relocation, but the linker may not support merging read-only | |
6463 | and read-write sections into a single read-write section. | |
6464 | @end defmac | |
6465 | ||
6466 | @defmac MASK_RETURN_ADDR | |
6467 | An rtx used to mask the return address found via @code{RETURN_ADDR_RTX}, so | |
6468 | that it does not contain any extraneous set bits in it. | |
6469 | @end defmac | |
6470 | ||
6471 | @defmac DWARF2_UNWIND_INFO | |
6472 | Define this macro to 0 if your target supports DWARF 2 frame unwind | |
6473 | information, but it does not yet work with exception handling. | |
6474 | Otherwise, if your target supports this information (if it defines | |
d8555e79 | 6475 | @code{INCOMING_RETURN_ADDR_RTX} and @code{OBJECT_FORMAT_ELF}), |
6476 | GCC will provide a default definition of 1. | |
cc7d6aed | 6477 | @end defmac |
202d6e5f | 6478 | |
cc7d6aed | 6479 | @hook TARGET_EXCEPT_UNWIND_INFO |
6480 | This hook defines the mechanism that will be used for exception handling | |
6481 | by the target. If the target has ABI specified unwind tables, the hook | |
6482 | should return @code{UI_TARGET}. If the target is to use the | |
6483 | @code{setjmp}/@code{longjmp}-based exception handling scheme, the hook | |
6484 | should return @code{UI_SJLJ}. If the target supports DWARF 2 frame unwind | |
6485 | information, the hook should return @code{UI_DWARF2}. | |
202d6e5f | 6486 | |
cc7d6aed | 6487 | A target may, if exceptions are disabled, choose to return @code{UI_NONE}. |
6488 | This may end up simplifying other parts of target-specific code. The | |
6489 | default implementation of this hook never returns @code{UI_NONE}. | |
202d6e5f | 6490 | |
cc7d6aed | 6491 | Note that the value returned by this hook should be constant. It should |
b213bf24 | 6492 | not depend on anything except the command-line switches described by |
6493 | @var{opts}. In particular, the | |
cc7d6aed | 6494 | setting @code{UI_SJLJ} must be fixed at compiler start-up as C pre-processor |
6495 | macros and builtin functions related to exception handling are set up | |
6496 | depending on this setting. | |
6497 | ||
6498 | The default implementation of the hook first honors the | |
6499 | @option{--enable-sjlj-exceptions} configure option, then | |
b213bf24 | 6500 | @code{DWARF2_UNWIND_INFO}, and finally defaults to @code{UI_SJLJ}. If |
6501 | @code{DWARF2_UNWIND_INFO} depends on command-line options, the target | |
6502 | must define this hook so that @var{opts} is used correctly. | |
cc7d6aed | 6503 | @end deftypefn |
202d6e5f | 6504 | |
6505 | @hook TARGET_UNWIND_TABLES_DEFAULT | |
6506 | This variable should be set to @code{true} if the target ABI requires unwinding | |
b213bf24 | 6507 | tables even when exceptions are not used. It must not be modified by |
6508 | command-line option processing. | |
202d6e5f | 6509 | @end deftypevr |
6510 | ||
202d6e5f | 6511 | @defmac DONT_USE_BUILTIN_SETJMP |
6512 | Define this macro to 1 if the @code{setjmp}/@code{longjmp}-based scheme | |
6513 | should use the @code{setjmp}/@code{longjmp} functions from the C library | |
6514 | instead of the @code{__builtin_setjmp}/@code{__builtin_longjmp} machinery. | |
6515 | @end defmac | |
6516 | ||
91bb968b | 6517 | @defmac JMP_BUF_SIZE |
6518 | This macro has no effect unless @code{DONT_USE_BUILTIN_SETJMP} is also | |
6519 | defined. Define this macro if the default size of @code{jmp_buf} buffer | |
6520 | for the @code{setjmp}/@code{longjmp}-based exception handling mechanism | |
6521 | is not large enough, or if it is much too large. | |
6522 | The default size is @code{FIRST_PSEUDO_REGISTER * sizeof(void *)}. | |
6523 | @end defmac | |
6524 | ||
202d6e5f | 6525 | @defmac DWARF_CIE_DATA_ALIGNMENT |
6526 | This macro need only be defined if the target might save registers in the | |
6527 | function prologue at an offset to the stack pointer that is not aligned to | |
6528 | @code{UNITS_PER_WORD}. The definition should be the negative minimum | |
6529 | alignment if @code{STACK_GROWS_DOWNWARD} is defined, and the positive | |
6530 | minimum alignment otherwise. @xref{SDB and DWARF}. Only applicable if | |
6531 | the target supports DWARF 2 frame unwind information. | |
6532 | @end defmac | |
6533 | ||
6534 | @hook TARGET_TERMINATE_DW2_EH_FRAME_INFO | |
202d6e5f | 6535 | |
6536 | @hook TARGET_DWARF_REGISTER_SPAN | |
202d6e5f | 6537 | |
d626297e | 6538 | @hook TARGET_DWARF_FRAME_REG_MODE |
6539 | ||
202d6e5f | 6540 | @hook TARGET_INIT_DWARF_REG_SIZES_EXTRA |
202d6e5f | 6541 | |
6542 | @hook TARGET_ASM_TTYPE | |
202d6e5f | 6543 | |
6544 | @hook TARGET_ARM_EABI_UNWINDER | |
202d6e5f | 6545 | |
6546 | @node Alignment Output | |
6547 | @subsection Assembler Commands for Alignment | |
6548 | ||
6549 | @c prevent bad page break with this line | |
6550 | This describes commands for alignment. | |
6551 | ||
6552 | @defmac JUMP_ALIGN (@var{label}) | |
6553 | The alignment (log base 2) to put in front of @var{label}, which is | |
6554 | a common destination of jumps and has no fallthru incoming edge. | |
6555 | ||
6556 | This macro need not be defined if you don't want any special alignment | |
6557 | to be done at such a time. Most machine descriptions do not currently | |
6558 | define the macro. | |
6559 | ||
6560 | Unless it's necessary to inspect the @var{label} parameter, it is better | |
6561 | to set the variable @var{align_jumps} in the target's | |
6562 | @code{TARGET_OPTION_OVERRIDE}. Otherwise, you should try to honor the user's | |
6563 | selection in @var{align_jumps} in a @code{JUMP_ALIGN} implementation. | |
6564 | @end defmac | |
6565 | ||
ae2b9f1f | 6566 | @hook TARGET_ASM_JUMP_ALIGN_MAX_SKIP |
ae2b9f1f | 6567 | |
202d6e5f | 6568 | @defmac LABEL_ALIGN_AFTER_BARRIER (@var{label}) |
6569 | The alignment (log base 2) to put in front of @var{label}, which follows | |
6570 | a @code{BARRIER}. | |
6571 | ||
6572 | This macro need not be defined if you don't want any special alignment | |
6573 | to be done at such a time. Most machine descriptions do not currently | |
6574 | define the macro. | |
6575 | @end defmac | |
6576 | ||
ae2b9f1f | 6577 | @hook TARGET_ASM_LABEL_ALIGN_AFTER_BARRIER_MAX_SKIP |
202d6e5f | 6578 | |
6579 | @defmac LOOP_ALIGN (@var{label}) | |
720b223d | 6580 | The alignment (log base 2) to put in front of @var{label} that heads |
6581 | a frequently executed basic block (usually the header of a loop). | |
202d6e5f | 6582 | |
6583 | This macro need not be defined if you don't want any special alignment | |
6584 | to be done at such a time. Most machine descriptions do not currently | |
6585 | define the macro. | |
6586 | ||
6587 | Unless it's necessary to inspect the @var{label} parameter, it is better | |
6588 | to set the variable @code{align_loops} in the target's | |
6589 | @code{TARGET_OPTION_OVERRIDE}. Otherwise, you should try to honor the user's | |
6590 | selection in @code{align_loops} in a @code{LOOP_ALIGN} implementation. | |
6591 | @end defmac | |
6592 | ||
ae2b9f1f | 6593 | @hook TARGET_ASM_LOOP_ALIGN_MAX_SKIP |
202d6e5f | 6594 | |
6595 | @defmac LABEL_ALIGN (@var{label}) | |
6596 | The alignment (log base 2) to put in front of @var{label}. | |
6597 | If @code{LABEL_ALIGN_AFTER_BARRIER} / @code{LOOP_ALIGN} specify a different alignment, | |
6598 | the maximum of the specified values is used. | |
6599 | ||
6600 | Unless it's necessary to inspect the @var{label} parameter, it is better | |
6601 | to set the variable @code{align_labels} in the target's | |
6602 | @code{TARGET_OPTION_OVERRIDE}. Otherwise, you should try to honor the user's | |
6603 | selection in @code{align_labels} in a @code{LABEL_ALIGN} implementation. | |
6604 | @end defmac | |
6605 | ||
ae2b9f1f | 6606 | @hook TARGET_ASM_LABEL_ALIGN_MAX_SKIP |
202d6e5f | 6607 | |
6608 | @defmac ASM_OUTPUT_SKIP (@var{stream}, @var{nbytes}) | |
6609 | A C statement to output to the stdio stream @var{stream} an assembler | |
6610 | instruction to advance the location counter by @var{nbytes} bytes. | |
6611 | Those bytes should be zero when loaded. @var{nbytes} will be a C | |
6612 | expression of type @code{unsigned HOST_WIDE_INT}. | |
6613 | @end defmac | |
6614 | ||
6615 | @defmac ASM_NO_SKIP_IN_TEXT | |
6616 | Define this macro if @code{ASM_OUTPUT_SKIP} should not be used in the | |
6617 | text section because it fails to put zeros in the bytes that are skipped. | |
6618 | This is true on many Unix systems, where the pseudo--op to skip bytes | |
6619 | produces no-op instructions rather than zeros when used in the text | |
6620 | section. | |
6621 | @end defmac | |
6622 | ||
6623 | @defmac ASM_OUTPUT_ALIGN (@var{stream}, @var{power}) | |
6624 | A C statement to output to the stdio stream @var{stream} an assembler | |
6625 | command to advance the location counter to a multiple of 2 to the | |
6626 | @var{power} bytes. @var{power} will be a C expression of type @code{int}. | |
6627 | @end defmac | |
6628 | ||
6629 | @defmac ASM_OUTPUT_ALIGN_WITH_NOP (@var{stream}, @var{power}) | |
6630 | Like @code{ASM_OUTPUT_ALIGN}, except that the ``nop'' instruction is used | |
6631 | for padding, if necessary. | |
6632 | @end defmac | |
6633 | ||
6634 | @defmac ASM_OUTPUT_MAX_SKIP_ALIGN (@var{stream}, @var{power}, @var{max_skip}) | |
6635 | A C statement to output to the stdio stream @var{stream} an assembler | |
6636 | command to advance the location counter to a multiple of 2 to the | |
6637 | @var{power} bytes, but only if @var{max_skip} or fewer bytes are needed to | |
6638 | satisfy the alignment request. @var{power} and @var{max_skip} will be | |
6639 | a C expression of type @code{int}. | |
6640 | @end defmac | |
6641 | ||
6642 | @need 3000 | |
6643 | @node Debugging Info | |
6644 | @section Controlling Debugging Information Format | |
6645 | ||
6646 | @c prevent bad page break with this line | |
6647 | This describes how to specify debugging information. | |
6648 | ||
6649 | @menu | |
6650 | * All Debuggers:: Macros that affect all debugging formats uniformly. | |
6651 | * DBX Options:: Macros enabling specific options in DBX format. | |
6652 | * DBX Hooks:: Hook macros for varying DBX format. | |
6653 | * File Names and DBX:: Macros controlling output of file names in DBX format. | |
6654 | * SDB and DWARF:: Macros for SDB (COFF) and DWARF formats. | |
6655 | * VMS Debug:: Macros for VMS debug format. | |
6656 | @end menu | |
6657 | ||
6658 | @node All Debuggers | |
6659 | @subsection Macros Affecting All Debugging Formats | |
6660 | ||
6661 | @c prevent bad page break with this line | |
6662 | These macros affect all debugging formats. | |
6663 | ||
6664 | @defmac DBX_REGISTER_NUMBER (@var{regno}) | |
6665 | A C expression that returns the DBX register number for the compiler | |
6666 | register number @var{regno}. In the default macro provided, the value | |
6667 | of this expression will be @var{regno} itself. But sometimes there are | |
6668 | some registers that the compiler knows about and DBX does not, or vice | |
6669 | versa. In such cases, some register may need to have one number in the | |
6670 | compiler and another for DBX@. | |
6671 | ||
6672 | If two registers have consecutive numbers inside GCC, and they can be | |
6673 | used as a pair to hold a multiword value, then they @emph{must} have | |
6674 | consecutive numbers after renumbering with @code{DBX_REGISTER_NUMBER}. | |
6675 | Otherwise, debuggers will be unable to access such a pair, because they | |
6676 | expect register pairs to be consecutive in their own numbering scheme. | |
6677 | ||
6678 | If you find yourself defining @code{DBX_REGISTER_NUMBER} in way that | |
6679 | does not preserve register pairs, then what you must do instead is | |
6680 | redefine the actual register numbering scheme. | |
6681 | @end defmac | |
6682 | ||
6683 | @defmac DEBUGGER_AUTO_OFFSET (@var{x}) | |
6684 | A C expression that returns the integer offset value for an automatic | |
6685 | variable having address @var{x} (an RTL expression). The default | |
6686 | computation assumes that @var{x} is based on the frame-pointer and | |
6687 | gives the offset from the frame-pointer. This is required for targets | |
6688 | that produce debugging output for DBX or COFF-style debugging output | |
6689 | for SDB and allow the frame-pointer to be eliminated when the | |
6690 | @option{-g} options is used. | |
6691 | @end defmac | |
6692 | ||
6693 | @defmac DEBUGGER_ARG_OFFSET (@var{offset}, @var{x}) | |
6694 | A C expression that returns the integer offset value for an argument | |
6695 | having address @var{x} (an RTL expression). The nominal offset is | |
6696 | @var{offset}. | |
6697 | @end defmac | |
6698 | ||
6699 | @defmac PREFERRED_DEBUGGING_TYPE | |
6700 | A C expression that returns the type of debugging output GCC should | |
6701 | produce when the user specifies just @option{-g}. Define | |
6702 | this if you have arranged for GCC to support more than one format of | |
6703 | debugging output. Currently, the allowable values are @code{DBX_DEBUG}, | |
6704 | @code{SDB_DEBUG}, @code{DWARF_DEBUG}, @code{DWARF2_DEBUG}, | |
6705 | @code{XCOFF_DEBUG}, @code{VMS_DEBUG}, and @code{VMS_AND_DWARF2_DEBUG}. | |
6706 | ||
6707 | When the user specifies @option{-ggdb}, GCC normally also uses the | |
6708 | value of this macro to select the debugging output format, but with two | |
6709 | exceptions. If @code{DWARF2_DEBUGGING_INFO} is defined, GCC uses the | |
6710 | value @code{DWARF2_DEBUG}. Otherwise, if @code{DBX_DEBUGGING_INFO} is | |
6711 | defined, GCC uses @code{DBX_DEBUG}. | |
6712 | ||
6713 | The value of this macro only affects the default debugging output; the | |
6714 | user can always get a specific type of output by using @option{-gstabs}, | |
6715 | @option{-gcoff}, @option{-gdwarf-2}, @option{-gxcoff}, or @option{-gvms}. | |
6716 | @end defmac | |
6717 | ||
6718 | @node DBX Options | |
6719 | @subsection Specific Options for DBX Output | |
6720 | ||
6721 | @c prevent bad page break with this line | |
6722 | These are specific options for DBX output. | |
6723 | ||
6724 | @defmac DBX_DEBUGGING_INFO | |
6725 | Define this macro if GCC should produce debugging output for DBX | |
6726 | in response to the @option{-g} option. | |
6727 | @end defmac | |
6728 | ||
6729 | @defmac XCOFF_DEBUGGING_INFO | |
6730 | Define this macro if GCC should produce XCOFF format debugging output | |
6731 | in response to the @option{-g} option. This is a variant of DBX format. | |
6732 | @end defmac | |
6733 | ||
6734 | @defmac DEFAULT_GDB_EXTENSIONS | |
6735 | Define this macro to control whether GCC should by default generate | |
6736 | GDB's extended version of DBX debugging information (assuming DBX-format | |
6737 | debugging information is enabled at all). If you don't define the | |
6738 | macro, the default is 1: always generate the extended information | |
6739 | if there is any occasion to. | |
6740 | @end defmac | |
6741 | ||
6742 | @defmac DEBUG_SYMS_TEXT | |
6743 | Define this macro if all @code{.stabs} commands should be output while | |
6744 | in the text section. | |
6745 | @end defmac | |
6746 | ||
6747 | @defmac ASM_STABS_OP | |
6748 | A C string constant, including spacing, naming the assembler pseudo op to | |
6749 | use instead of @code{"\t.stabs\t"} to define an ordinary debugging symbol. | |
6750 | If you don't define this macro, @code{"\t.stabs\t"} is used. This macro | |
6751 | applies only to DBX debugging information format. | |
6752 | @end defmac | |
6753 | ||
6754 | @defmac ASM_STABD_OP | |
6755 | A C string constant, including spacing, naming the assembler pseudo op to | |
6756 | use instead of @code{"\t.stabd\t"} to define a debugging symbol whose | |
6757 | value is the current location. If you don't define this macro, | |
6758 | @code{"\t.stabd\t"} is used. This macro applies only to DBX debugging | |
6759 | information format. | |
6760 | @end defmac | |
6761 | ||
6762 | @defmac ASM_STABN_OP | |
6763 | A C string constant, including spacing, naming the assembler pseudo op to | |
6764 | use instead of @code{"\t.stabn\t"} to define a debugging symbol with no | |
6765 | name. If you don't define this macro, @code{"\t.stabn\t"} is used. This | |
6766 | macro applies only to DBX debugging information format. | |
6767 | @end defmac | |
6768 | ||
6769 | @defmac DBX_NO_XREFS | |
6770 | Define this macro if DBX on your system does not support the construct | |
6771 | @samp{xs@var{tagname}}. On some systems, this construct is used to | |
6772 | describe a forward reference to a structure named @var{tagname}. | |
6773 | On other systems, this construct is not supported at all. | |
6774 | @end defmac | |
6775 | ||
6776 | @defmac DBX_CONTIN_LENGTH | |
6777 | A symbol name in DBX-format debugging information is normally | |
6778 | continued (split into two separate @code{.stabs} directives) when it | |
6779 | exceeds a certain length (by default, 80 characters). On some | |
6780 | operating systems, DBX requires this splitting; on others, splitting | |
6781 | must not be done. You can inhibit splitting by defining this macro | |
6782 | with the value zero. You can override the default splitting-length by | |
6783 | defining this macro as an expression for the length you desire. | |
6784 | @end defmac | |
6785 | ||
6786 | @defmac DBX_CONTIN_CHAR | |
6787 | Normally continuation is indicated by adding a @samp{\} character to | |
6788 | the end of a @code{.stabs} string when a continuation follows. To use | |
6789 | a different character instead, define this macro as a character | |
6790 | constant for the character you want to use. Do not define this macro | |
6791 | if backslash is correct for your system. | |
6792 | @end defmac | |
6793 | ||
6794 | @defmac DBX_STATIC_STAB_DATA_SECTION | |
6795 | Define this macro if it is necessary to go to the data section before | |
6796 | outputting the @samp{.stabs} pseudo-op for a non-global static | |
6797 | variable. | |
6798 | @end defmac | |
6799 | ||
6800 | @defmac DBX_TYPE_DECL_STABS_CODE | |
6801 | The value to use in the ``code'' field of the @code{.stabs} directive | |
6802 | for a typedef. The default is @code{N_LSYM}. | |
6803 | @end defmac | |
6804 | ||
6805 | @defmac DBX_STATIC_CONST_VAR_CODE | |
6806 | The value to use in the ``code'' field of the @code{.stabs} directive | |
6807 | for a static variable located in the text section. DBX format does not | |
6808 | provide any ``right'' way to do this. The default is @code{N_FUN}. | |
6809 | @end defmac | |
6810 | ||
6811 | @defmac DBX_REGPARM_STABS_CODE | |
6812 | The value to use in the ``code'' field of the @code{.stabs} directive | |
6813 | for a parameter passed in registers. DBX format does not provide any | |
6814 | ``right'' way to do this. The default is @code{N_RSYM}. | |
6815 | @end defmac | |
6816 | ||
6817 | @defmac DBX_REGPARM_STABS_LETTER | |
6818 | The letter to use in DBX symbol data to identify a symbol as a parameter | |
6819 | passed in registers. DBX format does not customarily provide any way to | |
6820 | do this. The default is @code{'P'}. | |
6821 | @end defmac | |
6822 | ||
6823 | @defmac DBX_FUNCTION_FIRST | |
6824 | Define this macro if the DBX information for a function and its | |
6825 | arguments should precede the assembler code for the function. Normally, | |
6826 | in DBX format, the debugging information entirely follows the assembler | |
6827 | code. | |
6828 | @end defmac | |
6829 | ||
6830 | @defmac DBX_BLOCKS_FUNCTION_RELATIVE | |
6831 | Define this macro, with value 1, if the value of a symbol describing | |
6832 | the scope of a block (@code{N_LBRAC} or @code{N_RBRAC}) should be | |
6833 | relative to the start of the enclosing function. Normally, GCC uses | |
6834 | an absolute address. | |
6835 | @end defmac | |
6836 | ||
6837 | @defmac DBX_LINES_FUNCTION_RELATIVE | |
6838 | Define this macro, with value 1, if the value of a symbol indicating | |
6839 | the current line number (@code{N_SLINE}) should be relative to the | |
6840 | start of the enclosing function. Normally, GCC uses an absolute address. | |
6841 | @end defmac | |
6842 | ||
6843 | @defmac DBX_USE_BINCL | |
6844 | Define this macro if GCC should generate @code{N_BINCL} and | |
6845 | @code{N_EINCL} stabs for included header files, as on Sun systems. This | |
6846 | macro also directs GCC to output a type number as a pair of a file | |
6847 | number and a type number within the file. Normally, GCC does not | |
6848 | generate @code{N_BINCL} or @code{N_EINCL} stabs, and it outputs a single | |
6849 | number for a type number. | |
6850 | @end defmac | |
6851 | ||
6852 | @node DBX Hooks | |
6853 | @subsection Open-Ended Hooks for DBX Format | |
6854 | ||
6855 | @c prevent bad page break with this line | |
6856 | These are hooks for DBX format. | |
6857 | ||
202d6e5f | 6858 | @defmac DBX_OUTPUT_SOURCE_LINE (@var{stream}, @var{line}, @var{counter}) |
6859 | A C statement to output DBX debugging information before code for line | |
6860 | number @var{line} of the current source file to the stdio stream | |
6861 | @var{stream}. @var{counter} is the number of time the macro was | |
6862 | invoked, including the current invocation; it is intended to generate | |
6863 | unique labels in the assembly output. | |
6864 | ||
6865 | This macro should not be defined if the default output is correct, or | |
6866 | if it can be made correct by defining @code{DBX_LINES_FUNCTION_RELATIVE}. | |
6867 | @end defmac | |
6868 | ||
6869 | @defmac NO_DBX_FUNCTION_END | |
6870 | Some stabs encapsulation formats (in particular ECOFF), cannot handle the | |
6871 | @code{.stabs "",N_FUN,,0,0,Lscope-function-1} gdb dbx extension construct. | |
6872 | On those machines, define this macro to turn this feature off without | |
6873 | disturbing the rest of the gdb extensions. | |
6874 | @end defmac | |
6875 | ||
6876 | @defmac NO_DBX_BNSYM_ENSYM | |
6877 | Some assemblers cannot handle the @code{.stabd BNSYM/ENSYM,0,0} gdb dbx | |
6878 | extension construct. On those machines, define this macro to turn this | |
6879 | feature off without disturbing the rest of the gdb extensions. | |
6880 | @end defmac | |
6881 | ||
6882 | @node File Names and DBX | |
6883 | @subsection File Names in DBX Format | |
6884 | ||
6885 | @c prevent bad page break with this line | |
6886 | This describes file names in DBX format. | |
6887 | ||
6888 | @defmac DBX_OUTPUT_MAIN_SOURCE_FILENAME (@var{stream}, @var{name}) | |
6889 | A C statement to output DBX debugging information to the stdio stream | |
6890 | @var{stream}, which indicates that file @var{name} is the main source | |
6891 | file---the file specified as the input file for compilation. | |
6892 | This macro is called only once, at the beginning of compilation. | |
6893 | ||
6894 | This macro need not be defined if the standard form of output | |
6895 | for DBX debugging information is appropriate. | |
6896 | ||
6897 | It may be necessary to refer to a label equal to the beginning of the | |
6898 | text section. You can use @samp{assemble_name (stream, ltext_label_name)} | |
6899 | to do so. If you do this, you must also set the variable | |
6900 | @var{used_ltext_label_name} to @code{true}. | |
6901 | @end defmac | |
6902 | ||
6903 | @defmac NO_DBX_MAIN_SOURCE_DIRECTORY | |
6904 | Define this macro, with value 1, if GCC should not emit an indication | |
6905 | of the current directory for compilation and current source language at | |
6906 | the beginning of the file. | |
6907 | @end defmac | |
6908 | ||
6909 | @defmac NO_DBX_GCC_MARKER | |
6910 | Define this macro, with value 1, if GCC should not emit an indication | |
6911 | that this object file was compiled by GCC@. The default is to emit | |
6912 | an @code{N_OPT} stab at the beginning of every source file, with | |
6913 | @samp{gcc2_compiled.} for the string and value 0. | |
6914 | @end defmac | |
6915 | ||
6916 | @defmac DBX_OUTPUT_MAIN_SOURCE_FILE_END (@var{stream}, @var{name}) | |
6917 | A C statement to output DBX debugging information at the end of | |
6918 | compilation of the main source file @var{name}. Output should be | |
6919 | written to the stdio stream @var{stream}. | |
6920 | ||
6921 | If you don't define this macro, nothing special is output at the end | |
6922 | of compilation, which is correct for most machines. | |
6923 | @end defmac | |
6924 | ||
6925 | @defmac DBX_OUTPUT_NULL_N_SO_AT_MAIN_SOURCE_FILE_END | |
6926 | Define this macro @emph{instead of} defining | |
6927 | @code{DBX_OUTPUT_MAIN_SOURCE_FILE_END}, if what needs to be output at | |
6928 | the end of compilation is an @code{N_SO} stab with an empty string, | |
6929 | whose value is the highest absolute text address in the file. | |
6930 | @end defmac | |
6931 | ||
6932 | @need 2000 | |
6933 | @node SDB and DWARF | |
6934 | @subsection Macros for SDB and DWARF Output | |
6935 | ||
6936 | @c prevent bad page break with this line | |
6937 | Here are macros for SDB and DWARF output. | |
6938 | ||
6939 | @defmac SDB_DEBUGGING_INFO | |
6940 | Define this macro if GCC should produce COFF-style debugging output | |
6941 | for SDB in response to the @option{-g} option. | |
6942 | @end defmac | |
6943 | ||
6944 | @defmac DWARF2_DEBUGGING_INFO | |
6945 | Define this macro if GCC should produce dwarf version 2 format | |
6946 | debugging output in response to the @option{-g} option. | |
6947 | ||
6948 | @hook TARGET_DWARF_CALLING_CONVENTION | |
202d6e5f | 6949 | |
6950 | To support optional call frame debugging information, you must also | |
6951 | define @code{INCOMING_RETURN_ADDR_RTX} and either set | |
6952 | @code{RTX_FRAME_RELATED_P} on the prologue insns if you use RTL for the | |
6953 | prologue, or call @code{dwarf2out_def_cfa} and @code{dwarf2out_reg_save} | |
6954 | as appropriate from @code{TARGET_ASM_FUNCTION_PROLOGUE} if you don't. | |
6955 | @end defmac | |
6956 | ||
6957 | @defmac DWARF2_FRAME_INFO | |
6958 | Define this macro to a nonzero value if GCC should always output | |
cc7d6aed | 6959 | Dwarf 2 frame information. If @code{TARGET_EXCEPT_UNWIND_INFO} |
6960 | (@pxref{Exception Region Output}) returns @code{UI_DWARF2}, and | |
6961 | exceptions are enabled, GCC will output this information not matter | |
6962 | how you define @code{DWARF2_FRAME_INFO}. | |
202d6e5f | 6963 | @end defmac |
6964 | ||
cc7d6aed | 6965 | @hook TARGET_DEBUG_UNWIND_INFO |
cc7d6aed | 6966 | |
202d6e5f | 6967 | @defmac DWARF2_ASM_LINE_DEBUG_INFO |
6968 | Define this macro to be a nonzero value if the assembler can generate Dwarf 2 | |
6969 | line debug info sections. This will result in much more compact line number | |
6970 | tables, and hence is desirable if it works. | |
6971 | @end defmac | |
6972 | ||
1651aa77 | 6973 | @hook TARGET_WANT_DEBUG_PUB_SECTIONS |
6974 | ||
effa044f | 6975 | @hook TARGET_FORCE_AT_COMP_DIR |
6976 | ||
8a42230a | 6977 | @hook TARGET_DELAY_SCHED2 |
6978 | ||
6979 | @hook TARGET_DELAY_VARTRACK | |
6980 | ||
202d6e5f | 6981 | @defmac ASM_OUTPUT_DWARF_DELTA (@var{stream}, @var{size}, @var{label1}, @var{label2}) |
6982 | A C statement to issue assembly directives that create a difference | |
6983 | @var{lab1} minus @var{lab2}, using an integer of the given @var{size}. | |
6984 | @end defmac | |
6985 | ||
6986 | @defmac ASM_OUTPUT_DWARF_VMS_DELTA (@var{stream}, @var{size}, @var{label1}, @var{label2}) | |
6987 | A C statement to issue assembly directives that create a difference | |
6988 | between the two given labels in system defined units, e.g. instruction | |
6989 | slots on IA64 VMS, using an integer of the given size. | |
6990 | @end defmac | |
6991 | ||
6992 | @defmac ASM_OUTPUT_DWARF_OFFSET (@var{stream}, @var{size}, @var{label}, @var{section}) | |
6993 | A C statement to issue assembly directives that create a | |
6994 | section-relative reference to the given @var{label}, using an integer of the | |
6995 | given @var{size}. The label is known to be defined in the given @var{section}. | |
6996 | @end defmac | |
6997 | ||
6998 | @defmac ASM_OUTPUT_DWARF_PCREL (@var{stream}, @var{size}, @var{label}) | |
6999 | A C statement to issue assembly directives that create a self-relative | |
7000 | reference to the given @var{label}, using an integer of the given @var{size}. | |
7001 | @end defmac | |
7002 | ||
7003 | @defmac ASM_OUTPUT_DWARF_TABLE_REF (@var{label}) | |
7004 | A C statement to issue assembly directives that create a reference to | |
7005 | the DWARF table identifier @var{label} from the current section. This | |
7006 | is used on some systems to avoid garbage collecting a DWARF table which | |
7007 | is referenced by a function. | |
7008 | @end defmac | |
7009 | ||
7010 | @hook TARGET_ASM_OUTPUT_DWARF_DTPREL | |
202d6e5f | 7011 | |
7012 | @defmac PUT_SDB_@dots{} | |
7013 | Define these macros to override the assembler syntax for the special | |
7014 | SDB assembler directives. See @file{sdbout.c} for a list of these | |
7015 | macros and their arguments. If the standard syntax is used, you need | |
7016 | not define them yourself. | |
7017 | @end defmac | |
7018 | ||
7019 | @defmac SDB_DELIM | |
7020 | Some assemblers do not support a semicolon as a delimiter, even between | |
7021 | SDB assembler directives. In that case, define this macro to be the | |
7022 | delimiter to use (usually @samp{\n}). It is not necessary to define | |
7023 | a new set of @code{PUT_SDB_@var{op}} macros if this is the only change | |
7024 | required. | |
7025 | @end defmac | |
7026 | ||
7027 | @defmac SDB_ALLOW_UNKNOWN_REFERENCES | |
7028 | Define this macro to allow references to unknown structure, | |
7029 | union, or enumeration tags to be emitted. Standard COFF does not | |
7030 | allow handling of unknown references, MIPS ECOFF has support for | |
7031 | it. | |
7032 | @end defmac | |
7033 | ||
7034 | @defmac SDB_ALLOW_FORWARD_REFERENCES | |
7035 | Define this macro to allow references to structure, union, or | |
7036 | enumeration tags that have not yet been seen to be handled. Some | |
7037 | assemblers choke if forward tags are used, while some require it. | |
7038 | @end defmac | |
7039 | ||
7040 | @defmac SDB_OUTPUT_SOURCE_LINE (@var{stream}, @var{line}) | |
7041 | A C statement to output SDB debugging information before code for line | |
7042 | number @var{line} of the current source file to the stdio stream | |
7043 | @var{stream}. The default is to emit an @code{.ln} directive. | |
7044 | @end defmac | |
7045 | ||
7046 | @need 2000 | |
7047 | @node VMS Debug | |
7048 | @subsection Macros for VMS Debug Format | |
7049 | ||
7050 | @c prevent bad page break with this line | |
7051 | Here are macros for VMS debug format. | |
7052 | ||
7053 | @defmac VMS_DEBUGGING_INFO | |
7054 | Define this macro if GCC should produce debugging output for VMS | |
7055 | in response to the @option{-g} option. The default behavior for VMS | |
7056 | is to generate minimal debug info for a traceback in the absence of | |
7057 | @option{-g} unless explicitly overridden with @option{-g0}. This | |
02e53c17 | 7058 | behavior is controlled by @code{TARGET_OPTION_OPTIMIZATION} and |
202d6e5f | 7059 | @code{TARGET_OPTION_OVERRIDE}. |
7060 | @end defmac | |
7061 | ||
7062 | @node Floating Point | |
7063 | @section Cross Compilation and Floating Point | |
7064 | @cindex cross compilation and floating point | |
7065 | @cindex floating point and cross compilation | |
7066 | ||
7067 | While all modern machines use twos-complement representation for integers, | |
7068 | there are a variety of representations for floating point numbers. This | |
7069 | means that in a cross-compiler the representation of floating point numbers | |
7070 | in the compiled program may be different from that used in the machine | |
7071 | doing the compilation. | |
7072 | ||
7073 | Because different representation systems may offer different amounts of | |
7074 | range and precision, all floating point constants must be represented in | |
7075 | the target machine's format. Therefore, the cross compiler cannot | |
7076 | safely use the host machine's floating point arithmetic; it must emulate | |
7077 | the target's arithmetic. To ensure consistency, GCC always uses | |
7078 | emulation to work with floating point values, even when the host and | |
7079 | target floating point formats are identical. | |
7080 | ||
7081 | The following macros are provided by @file{real.h} for the compiler to | |
7082 | use. All parts of the compiler which generate or optimize | |
7083 | floating-point calculations must use these macros. They may evaluate | |
7084 | their operands more than once, so operands must not have side effects. | |
7085 | ||
7086 | @defmac REAL_VALUE_TYPE | |
7087 | The C data type to be used to hold a floating point value in the target | |
7088 | machine's format. Typically this is a @code{struct} containing an | |
7089 | array of @code{HOST_WIDE_INT}, but all code should treat it as an opaque | |
7090 | quantity. | |
7091 | @end defmac | |
7092 | ||
7093 | @deftypefn Macro int REAL_VALUES_EQUAL (REAL_VALUE_TYPE @var{x}, REAL_VALUE_TYPE @var{y}) | |
7094 | Compares for equality the two values, @var{x} and @var{y}. If the target | |
7095 | floating point format supports negative zeroes and/or NaNs, | |
7096 | @samp{REAL_VALUES_EQUAL (-0.0, 0.0)} is true, and | |
7097 | @samp{REAL_VALUES_EQUAL (NaN, NaN)} is false. | |
7098 | @end deftypefn | |
7099 | ||
7100 | @deftypefn Macro int REAL_VALUES_LESS (REAL_VALUE_TYPE @var{x}, REAL_VALUE_TYPE @var{y}) | |
7101 | Tests whether @var{x} is less than @var{y}. | |
7102 | @end deftypefn | |
7103 | ||
7104 | @deftypefn Macro HOST_WIDE_INT REAL_VALUE_FIX (REAL_VALUE_TYPE @var{x}) | |
7105 | Truncates @var{x} to a signed integer, rounding toward zero. | |
7106 | @end deftypefn | |
7107 | ||
7108 | @deftypefn Macro {unsigned HOST_WIDE_INT} REAL_VALUE_UNSIGNED_FIX (REAL_VALUE_TYPE @var{x}) | |
7109 | Truncates @var{x} to an unsigned integer, rounding toward zero. If | |
7110 | @var{x} is negative, returns zero. | |
7111 | @end deftypefn | |
7112 | ||
3754d046 | 7113 | @deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_ATOF (const char *@var{string}, machine_mode @var{mode}) |
202d6e5f | 7114 | Converts @var{string} into a floating point number in the target machine's |
7115 | representation for mode @var{mode}. This routine can handle both | |
7116 | decimal and hexadecimal floating point constants, using the syntax | |
7117 | defined by the C language for both. | |
7118 | @end deftypefn | |
7119 | ||
7120 | @deftypefn Macro int REAL_VALUE_NEGATIVE (REAL_VALUE_TYPE @var{x}) | |
7121 | Returns 1 if @var{x} is negative (including negative zero), 0 otherwise. | |
7122 | @end deftypefn | |
7123 | ||
7124 | @deftypefn Macro int REAL_VALUE_ISINF (REAL_VALUE_TYPE @var{x}) | |
7125 | Determines whether @var{x} represents infinity (positive or negative). | |
7126 | @end deftypefn | |
7127 | ||
7128 | @deftypefn Macro int REAL_VALUE_ISNAN (REAL_VALUE_TYPE @var{x}) | |
7129 | Determines whether @var{x} represents a ``NaN'' (not-a-number). | |
7130 | @end deftypefn | |
7131 | ||
7132 | @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}) | |
7133 | Calculates an arithmetic operation on the two floating point values | |
7134 | @var{x} and @var{y}, storing the result in @var{output} (which must be a | |
7135 | variable). | |
7136 | ||
7137 | The operation to be performed is specified by @var{code}. Only the | |
7138 | following codes are supported: @code{PLUS_EXPR}, @code{MINUS_EXPR}, | |
7139 | @code{MULT_EXPR}, @code{RDIV_EXPR}, @code{MAX_EXPR}, @code{MIN_EXPR}. | |
7140 | ||
7141 | If @code{REAL_ARITHMETIC} is asked to evaluate division by zero and the | |
7142 | target's floating point format cannot represent infinity, it will call | |
7143 | @code{abort}. Callers should check for this situation first, using | |
7144 | @code{MODE_HAS_INFINITIES}. @xref{Storage Layout}. | |
7145 | @end deftypefn | |
7146 | ||
7147 | @deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_NEGATE (REAL_VALUE_TYPE @var{x}) | |
7148 | Returns the negative of the floating point value @var{x}. | |
7149 | @end deftypefn | |
7150 | ||
7151 | @deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_ABS (REAL_VALUE_TYPE @var{x}) | |
7152 | Returns the absolute value of @var{x}. | |
7153 | @end deftypefn | |
7154 | ||
202d6e5f | 7155 | @node Mode Switching |
7156 | @section Mode Switching Instructions | |
7157 | @cindex mode switching | |
7158 | The following macros control mode switching optimizations: | |
7159 | ||
7160 | @defmac OPTIMIZE_MODE_SWITCHING (@var{entity}) | |
7161 | Define this macro if the port needs extra instructions inserted for mode | |
7162 | switching in an optimizing compilation. | |
7163 | ||
7164 | For an example, the SH4 can perform both single and double precision | |
7165 | floating point operations, but to perform a single precision operation, | |
7166 | the FPSCR PR bit has to be cleared, while for a double precision | |
7167 | operation, this bit has to be set. Changing the PR bit requires a general | |
7168 | purpose register as a scratch register, hence these FPSCR sets have to | |
7169 | be inserted before reload, i.e.@: you can't put this into instruction emitting | |
7170 | or @code{TARGET_MACHINE_DEPENDENT_REORG}. | |
7171 | ||
7172 | You can have multiple entities that are mode-switched, and select at run time | |
7173 | which entities actually need it. @code{OPTIMIZE_MODE_SWITCHING} should | |
7174 | return nonzero for any @var{entity} that needs mode-switching. | |
7175 | If you define this macro, you also have to define | |
cea19dab | 7176 | @code{NUM_MODES_FOR_MODE_SWITCHING}, @code{TARGET_MODE_NEEDED}, |
7177 | @code{TARGET_MODE_PRIORITY} and @code{TARGET_MODE_EMIT}. | |
7178 | @code{TARGET_MODE_AFTER}, @code{TARGET_MODE_ENTRY}, and @code{TARGET_MODE_EXIT} | |
202d6e5f | 7179 | are optional. |
7180 | @end defmac | |
7181 | ||
7182 | @defmac NUM_MODES_FOR_MODE_SWITCHING | |
7183 | If you define @code{OPTIMIZE_MODE_SWITCHING}, you have to define this as | |
7184 | initializer for an array of integers. Each initializer element | |
7185 | N refers to an entity that needs mode switching, and specifies the number | |
7186 | of different modes that might need to be set for this entity. | |
7187 | The position of the initializer in the initializer---starting counting at | |
7188 | zero---determines the integer that is used to refer to the mode-switched | |
7189 | entity in question. | |
7190 | In macros that take mode arguments / yield a mode result, modes are | |
7191 | represented as numbers 0 @dots{} N @minus{} 1. N is used to specify that no mode | |
7192 | switch is needed / supplied. | |
7193 | @end defmac | |
7194 | ||
cea19dab | 7195 | @hook TARGET_MODE_EMIT |
202d6e5f | 7196 | |
cea19dab | 7197 | @hook TARGET_MODE_NEEDED |
202d6e5f | 7198 | |
cea19dab | 7199 | @hook TARGET_MODE_AFTER |
202d6e5f | 7200 | |
cea19dab | 7201 | @hook TARGET_MODE_ENTRY |
202d6e5f | 7202 | |
cea19dab | 7203 | @hook TARGET_MODE_EXIT |
202d6e5f | 7204 | |
cea19dab | 7205 | @hook TARGET_MODE_PRIORITY |
202d6e5f | 7206 | |
7207 | @node Target Attributes | |
7208 | @section Defining target-specific uses of @code{__attribute__} | |
7209 | @cindex target attributes | |
7210 | @cindex machine attributes | |
7211 | @cindex attributes, target-specific | |
7212 | ||
7213 | Target-specific attributes may be defined for functions, data and types. | |
7214 | These are described using the following target hooks; they also need to | |
7215 | be documented in @file{extend.texi}. | |
7216 | ||
7217 | @hook TARGET_ATTRIBUTE_TABLE | |
202d6e5f | 7218 | |
7219 | @hook TARGET_ATTRIBUTE_TAKES_IDENTIFIER_P | |
202d6e5f | 7220 | |
7221 | @hook TARGET_COMP_TYPE_ATTRIBUTES | |
202d6e5f | 7222 | |
7223 | @hook TARGET_SET_DEFAULT_TYPE_ATTRIBUTES | |
202d6e5f | 7224 | |
7225 | @hook TARGET_MERGE_TYPE_ATTRIBUTES | |
202d6e5f | 7226 | |
7227 | @hook TARGET_MERGE_DECL_ATTRIBUTES | |
202d6e5f | 7228 | |
7229 | @hook TARGET_VALID_DLLIMPORT_ATTRIBUTE_P | |
7230 | ||
7231 | @defmac TARGET_DECLSPEC | |
7232 | Define this macro to a nonzero value if you want to treat | |
7233 | @code{__declspec(X)} as equivalent to @code{__attribute((X))}. By | |
7234 | default, this behavior is enabled only for targets that define | |
7235 | @code{TARGET_DLLIMPORT_DECL_ATTRIBUTES}. The current implementation | |
7236 | of @code{__declspec} is via a built-in macro, but you should not rely | |
7237 | on this implementation detail. | |
7238 | @end defmac | |
7239 | ||
7240 | @hook TARGET_INSERT_ATTRIBUTES | |
202d6e5f | 7241 | |
7242 | @hook TARGET_FUNCTION_ATTRIBUTE_INLINABLE_P | |
202d6e5f | 7243 | |
7244 | @hook TARGET_OPTION_VALID_ATTRIBUTE_P | |
202d6e5f | 7245 | |
7246 | @hook TARGET_OPTION_SAVE | |
202d6e5f | 7247 | |
7248 | @hook TARGET_OPTION_RESTORE | |
202d6e5f | 7249 | |
7250 | @hook TARGET_OPTION_PRINT | |
202d6e5f | 7251 | |
04f989af | 7252 | @hook TARGET_OPTION_PRAGMA_PARSE |
202d6e5f | 7253 | |
7254 | @hook TARGET_OPTION_OVERRIDE | |
202d6e5f | 7255 | |
cc8ef84f | 7256 | @hook TARGET_OPTION_FUNCTION_VERSIONS |
cc8ef84f | 7257 | |
202d6e5f | 7258 | @hook TARGET_CAN_INLINE_P |
202d6e5f | 7259 | |
7260 | @node Emulated TLS | |
7261 | @section Emulating TLS | |
7262 | @cindex Emulated TLS | |
7263 | ||
7264 | For targets whose psABI does not provide Thread Local Storage via | |
7265 | specific relocations and instruction sequences, an emulation layer is | |
7266 | used. A set of target hooks allows this emulation layer to be | |
7267 | configured for the requirements of a particular target. For instance | |
7268 | the psABI may in fact specify TLS support in terms of an emulation | |
7269 | layer. | |
7270 | ||
7271 | The emulation layer works by creating a control object for every TLS | |
7272 | object. To access the TLS object, a lookup function is provided | |
7273 | which, when given the address of the control object, will return the | |
7274 | address of the current thread's instance of the TLS object. | |
7275 | ||
7276 | @hook TARGET_EMUTLS_GET_ADDRESS | |
202d6e5f | 7277 | |
7278 | @hook TARGET_EMUTLS_REGISTER_COMMON | |
202d6e5f | 7279 | |
7280 | @hook TARGET_EMUTLS_VAR_SECTION | |
202d6e5f | 7281 | |
7282 | @hook TARGET_EMUTLS_TMPL_SECTION | |
202d6e5f | 7283 | |
7284 | @hook TARGET_EMUTLS_VAR_PREFIX | |
202d6e5f | 7285 | |
7286 | @hook TARGET_EMUTLS_TMPL_PREFIX | |
202d6e5f | 7287 | |
7288 | @hook TARGET_EMUTLS_VAR_FIELDS | |
202d6e5f | 7289 | |
7290 | @hook TARGET_EMUTLS_VAR_INIT | |
202d6e5f | 7291 | |
7292 | @hook TARGET_EMUTLS_VAR_ALIGN_FIXED | |
202d6e5f | 7293 | |
7294 | @hook TARGET_EMUTLS_DEBUG_FORM_TLS_ADDRESS | |
202d6e5f | 7295 | |
7296 | @node MIPS Coprocessors | |
7297 | @section Defining coprocessor specifics for MIPS targets. | |
7298 | @cindex MIPS coprocessor-definition macros | |
7299 | ||
7300 | The MIPS specification allows MIPS implementations to have as many as 4 | |
7301 | coprocessors, each with as many as 32 private registers. GCC supports | |
7302 | accessing these registers and transferring values between the registers | |
7303 | and memory using asm-ized variables. For example: | |
7304 | ||
7305 | @smallexample | |
7306 | register unsigned int cp0count asm ("c0r1"); | |
7307 | unsigned int d; | |
7308 | ||
7309 | d = cp0count + 3; | |
7310 | @end smallexample | |
7311 | ||
7312 | (``c0r1'' is the default name of register 1 in coprocessor 0; alternate | |
7313 | names may be added as described below, or the default names may be | |
7314 | overridden entirely in @code{SUBTARGET_CONDITIONAL_REGISTER_USAGE}.) | |
7315 | ||
7316 | Coprocessor registers are assumed to be epilogue-used; sets to them will | |
7317 | be preserved even if it does not appear that the register is used again | |
7318 | later in the function. | |
7319 | ||
7320 | Another note: according to the MIPS spec, coprocessor 1 (if present) is | |
7321 | the FPU@. One accesses COP1 registers through standard mips | |
7322 | floating-point support; they are not included in this mechanism. | |
7323 | ||
202d6e5f | 7324 | @node PCH Target |
7325 | @section Parameters for Precompiled Header Validity Checking | |
7326 | @cindex parameters, precompiled headers | |
7327 | ||
7328 | @hook TARGET_GET_PCH_VALIDITY | |
202d6e5f | 7329 | |
7330 | @hook TARGET_PCH_VALID_P | |
202d6e5f | 7331 | |
7332 | @hook TARGET_CHECK_PCH_TARGET_FLAGS | |
202d6e5f | 7333 | |
e5d92c9b | 7334 | @hook TARGET_PREPARE_PCH_SAVE |
7335 | ||
202d6e5f | 7336 | @node C++ ABI |
7337 | @section C++ ABI parameters | |
7338 | @cindex parameters, c++ abi | |
7339 | ||
7340 | @hook TARGET_CXX_GUARD_TYPE | |
202d6e5f | 7341 | |
7342 | @hook TARGET_CXX_GUARD_MASK_BIT | |
202d6e5f | 7343 | |
7344 | @hook TARGET_CXX_GET_COOKIE_SIZE | |
202d6e5f | 7345 | |
7346 | @hook TARGET_CXX_COOKIE_HAS_SIZE | |
202d6e5f | 7347 | |
7348 | @hook TARGET_CXX_IMPORT_EXPORT_CLASS | |
202d6e5f | 7349 | |
7350 | @hook TARGET_CXX_CDTOR_RETURNS_THIS | |
202d6e5f | 7351 | |
7352 | @hook TARGET_CXX_KEY_METHOD_MAY_BE_INLINE | |
202d6e5f | 7353 | |
7354 | @hook TARGET_CXX_DETERMINE_CLASS_DATA_VISIBILITY | |
7355 | ||
7356 | @hook TARGET_CXX_CLASS_DATA_ALWAYS_COMDAT | |
202d6e5f | 7357 | |
7358 | @hook TARGET_CXX_LIBRARY_RTTI_COMDAT | |
202d6e5f | 7359 | |
7360 | @hook TARGET_CXX_USE_AEABI_ATEXIT | |
202d6e5f | 7361 | |
7362 | @hook TARGET_CXX_USE_ATEXIT_FOR_CXA_ATEXIT | |
202d6e5f | 7363 | |
7364 | @hook TARGET_CXX_ADJUST_CLASS_AT_DEFINITION | |
7365 | ||
7bfdbc17 | 7366 | @hook TARGET_CXX_DECL_MANGLING_CONTEXT |
7367 | ||
202d6e5f | 7368 | @node Named Address Spaces |
7369 | @section Adding support for named address spaces | |
7370 | @cindex named address spaces | |
7371 | ||
7372 | The draft technical report of the ISO/IEC JTC1 S22 WG14 N1275 | |
7373 | standards committee, @cite{Programming Languages - C - Extensions to | |
7374 | support embedded processors}, specifies a syntax for embedded | |
7375 | processors to specify alternate address spaces. You can configure a | |
7376 | GCC port to support section 5.1 of the draft report to add support for | |
7377 | address spaces other than the default address space. These address | |
7378 | spaces are new keywords that are similar to the @code{volatile} and | |
7379 | @code{const} type attributes. | |
7380 | ||
7381 | Pointers to named address spaces can have a different size than | |
7382 | pointers to the generic address space. | |
7383 | ||
7384 | For example, the SPU port uses the @code{__ea} address space to refer | |
7385 | to memory in the host processor, rather than memory local to the SPU | |
7386 | processor. Access to memory in the @code{__ea} address space involves | |
7387 | issuing DMA operations to move data between the host processor and the | |
7388 | local processor memory address space. Pointers in the @code{__ea} | |
7389 | address space are either 32 bits or 64 bits based on the | |
7390 | @option{-mea32} or @option{-mea64} switches (native SPU pointers are | |
7391 | always 32 bits). | |
7392 | ||
7393 | Internally, address spaces are represented as a small integer in the | |
7394 | range 0 to 15 with address space 0 being reserved for the generic | |
7395 | address space. | |
7396 | ||
7397 | To register a named address space qualifier keyword with the C front end, | |
7398 | the target may call the @code{c_register_addr_space} routine. For example, | |
7399 | the SPU port uses the following to declare @code{__ea} as the keyword for | |
7400 | named address space #1: | |
7401 | @smallexample | |
7402 | #define ADDR_SPACE_EA 1 | |
7403 | c_register_addr_space ("__ea", ADDR_SPACE_EA); | |
7404 | @end smallexample | |
7405 | ||
7406 | @hook TARGET_ADDR_SPACE_POINTER_MODE | |
202d6e5f | 7407 | |
7408 | @hook TARGET_ADDR_SPACE_ADDRESS_MODE | |
202d6e5f | 7409 | |
7410 | @hook TARGET_ADDR_SPACE_VALID_POINTER_MODE | |
202d6e5f | 7411 | |
7412 | @hook TARGET_ADDR_SPACE_LEGITIMATE_ADDRESS_P | |
202d6e5f | 7413 | |
7414 | @hook TARGET_ADDR_SPACE_LEGITIMIZE_ADDRESS | |
202d6e5f | 7415 | |
7416 | @hook TARGET_ADDR_SPACE_SUBSET_P | |
202d6e5f | 7417 | |
7418 | @hook TARGET_ADDR_SPACE_CONVERT | |
202d6e5f | 7419 | |
7420 | @node Misc | |
7421 | @section Miscellaneous Parameters | |
7422 | @cindex parameters, miscellaneous | |
7423 | ||
7424 | @c prevent bad page break with this line | |
7425 | Here are several miscellaneous parameters. | |
7426 | ||
7427 | @defmac HAS_LONG_COND_BRANCH | |
7428 | Define this boolean macro to indicate whether or not your architecture | |
7429 | has conditional branches that can span all of memory. It is used in | |
7430 | conjunction with an optimization that partitions hot and cold basic | |
7431 | blocks into separate sections of the executable. If this macro is | |
7432 | set to false, gcc will convert any conditional branches that attempt | |
7433 | to cross between sections into unconditional branches or indirect jumps. | |
7434 | @end defmac | |
7435 | ||
7436 | @defmac HAS_LONG_UNCOND_BRANCH | |
7437 | Define this boolean macro to indicate whether or not your architecture | |
7438 | has unconditional branches that can span all of memory. It is used in | |
7439 | conjunction with an optimization that partitions hot and cold basic | |
7440 | blocks into separate sections of the executable. If this macro is | |
7441 | set to false, gcc will convert any unconditional branches that attempt | |
7442 | to cross between sections into indirect jumps. | |
7443 | @end defmac | |
7444 | ||
7445 | @defmac CASE_VECTOR_MODE | |
7446 | An alias for a machine mode name. This is the machine mode that | |
7447 | elements of a jump-table should have. | |
7448 | @end defmac | |
7449 | ||
7450 | @defmac CASE_VECTOR_SHORTEN_MODE (@var{min_offset}, @var{max_offset}, @var{body}) | |
7451 | Optional: return the preferred mode for an @code{addr_diff_vec} | |
7452 | when the minimum and maximum offset are known. If you define this, | |
7453 | it enables extra code in branch shortening to deal with @code{addr_diff_vec}. | |
7454 | To make this work, you also have to define @code{INSN_ALIGN} and | |
7455 | make the alignment for @code{addr_diff_vec} explicit. | |
7456 | The @var{body} argument is provided so that the offset_unsigned and scale | |
7457 | flags can be updated. | |
7458 | @end defmac | |
7459 | ||
7460 | @defmac CASE_VECTOR_PC_RELATIVE | |
7461 | Define this macro to be a C expression to indicate when jump-tables | |
7462 | should contain relative addresses. You need not define this macro if | |
7463 | jump-tables never contain relative addresses, or jump-tables should | |
7464 | contain relative addresses only when @option{-fPIC} or @option{-fPIC} | |
7465 | is in effect. | |
7466 | @end defmac | |
7467 | ||
7468 | @hook TARGET_CASE_VALUES_THRESHOLD | |
202d6e5f | 7469 | |
202d6e5f | 7470 | @defmac WORD_REGISTER_OPERATIONS |
7471 | Define this macro if operations between registers with integral mode | |
7472 | smaller than a word are always performed on the entire register. | |
7473 | Most RISC machines have this property and most CISC machines do not. | |
7474 | @end defmac | |
7475 | ||
7476 | @defmac LOAD_EXTEND_OP (@var{mem_mode}) | |
7477 | Define this macro to be a C expression indicating when insns that read | |
7478 | memory in @var{mem_mode}, an integral mode narrower than a word, set the | |
7479 | bits outside of @var{mem_mode} to be either the sign-extension or the | |
7480 | zero-extension of the data read. Return @code{SIGN_EXTEND} for values | |
7481 | of @var{mem_mode} for which the | |
7482 | insn sign-extends, @code{ZERO_EXTEND} for which it zero-extends, and | |
7483 | @code{UNKNOWN} for other modes. | |
7484 | ||
7485 | This macro is not called with @var{mem_mode} non-integral or with a width | |
7486 | greater than or equal to @code{BITS_PER_WORD}, so you may return any | |
7487 | value in this case. Do not define this macro if it would always return | |
7488 | @code{UNKNOWN}. On machines where this macro is defined, you will normally | |
7489 | define it as the constant @code{SIGN_EXTEND} or @code{ZERO_EXTEND}. | |
7490 | ||
7491 | You may return a non-@code{UNKNOWN} value even if for some hard registers | |
7492 | the sign extension is not performed, if for the @code{REGNO_REG_CLASS} | |
7493 | of these hard registers @code{CANNOT_CHANGE_MODE_CLASS} returns nonzero | |
7494 | when the @var{from} mode is @var{mem_mode} and the @var{to} mode is any | |
7495 | integral mode larger than this but not larger than @code{word_mode}. | |
7496 | ||
7497 | You must return @code{UNKNOWN} if for some hard registers that allow this | |
7498 | mode, @code{CANNOT_CHANGE_MODE_CLASS} says that they cannot change to | |
7499 | @code{word_mode}, but that they can change to another integral mode that | |
7500 | is larger then @var{mem_mode} but still smaller than @code{word_mode}. | |
7501 | @end defmac | |
7502 | ||
7503 | @defmac SHORT_IMMEDIATES_SIGN_EXTEND | |
7504 | Define this macro if loading short immediate values into registers sign | |
7505 | extends. | |
7506 | @end defmac | |
7507 | ||
202d6e5f | 7508 | @hook TARGET_MIN_DIVISIONS_FOR_RECIP_MUL |
202d6e5f | 7509 | |
7510 | @defmac MOVE_MAX | |
7511 | The maximum number of bytes that a single instruction can move quickly | |
7512 | between memory and registers or between two memory locations. | |
7513 | @end defmac | |
7514 | ||
7515 | @defmac MAX_MOVE_MAX | |
7516 | The maximum number of bytes that a single instruction can move quickly | |
7517 | between memory and registers or between two memory locations. If this | |
7518 | is undefined, the default is @code{MOVE_MAX}. Otherwise, it is the | |
7519 | constant value that is the largest value that @code{MOVE_MAX} can have | |
7520 | at run-time. | |
7521 | @end defmac | |
7522 | ||
7523 | @defmac SHIFT_COUNT_TRUNCATED | |
7524 | A C expression that is nonzero if on this machine the number of bits | |
7525 | actually used for the count of a shift operation is equal to the number | |
7526 | of bits needed to represent the size of the object being shifted. When | |
7527 | this macro is nonzero, the compiler will assume that it is safe to omit | |
7528 | a sign-extend, zero-extend, and certain bitwise `and' instructions that | |
7529 | truncates the count of a shift operation. On machines that have | |
7530 | instructions that act on bit-fields at variable positions, which may | |
7531 | include `bit test' instructions, a nonzero @code{SHIFT_COUNT_TRUNCATED} | |
7532 | also enables deletion of truncations of the values that serve as | |
7533 | arguments to bit-field instructions. | |
7534 | ||
7535 | If both types of instructions truncate the count (for shifts) and | |
7536 | position (for bit-field operations), or if no variable-position bit-field | |
7537 | instructions exist, you should define this macro. | |
7538 | ||
7539 | However, on some machines, such as the 80386 and the 680x0, truncation | |
7540 | only applies to shift operations and not the (real or pretended) | |
7541 | bit-field operations. Define @code{SHIFT_COUNT_TRUNCATED} to be zero on | |
7542 | such machines. Instead, add patterns to the @file{md} file that include | |
7543 | the implied truncation of the shift instructions. | |
7544 | ||
7545 | You need not define this macro if it would always have the value of zero. | |
7546 | @end defmac | |
7547 | ||
7548 | @anchor{TARGET_SHIFT_TRUNCATION_MASK} | |
7549 | @hook TARGET_SHIFT_TRUNCATION_MASK | |
202d6e5f | 7550 | |
7551 | @defmac TRULY_NOOP_TRUNCATION (@var{outprec}, @var{inprec}) | |
7552 | A C expression which is nonzero if on this machine it is safe to | |
7553 | ``convert'' an integer of @var{inprec} bits to one of @var{outprec} | |
7554 | bits (where @var{outprec} is smaller than @var{inprec}) by merely | |
7555 | operating on it as if it had only @var{outprec} bits. | |
7556 | ||
7557 | On many machines, this expression can be 1. | |
7558 | ||
7559 | @c rearranged this, removed the phrase "it is reported that". this was | |
7560 | @c to fix an overfull hbox. --mew 10feb93 | |
7561 | When @code{TRULY_NOOP_TRUNCATION} returns 1 for a pair of sizes for | |
7562 | modes for which @code{MODES_TIEABLE_P} is 0, suboptimal code can result. | |
7563 | If this is the case, making @code{TRULY_NOOP_TRUNCATION} return 0 in | |
7564 | such cases may improve things. | |
7565 | @end defmac | |
7566 | ||
7567 | @hook TARGET_MODE_REP_EXTENDED | |
202d6e5f | 7568 | |
7569 | @defmac STORE_FLAG_VALUE | |
7570 | A C expression describing the value returned by a comparison operator | |
7571 | with an integral mode and stored by a store-flag instruction | |
7572 | (@samp{cstore@var{mode}4}) when the condition is true. This description must | |
7573 | apply to @emph{all} the @samp{cstore@var{mode}4} patterns and all the | |
7574 | comparison operators whose results have a @code{MODE_INT} mode. | |
7575 | ||
7576 | A value of 1 or @minus{}1 means that the instruction implementing the | |
7577 | comparison operator returns exactly 1 or @minus{}1 when the comparison is true | |
7578 | and 0 when the comparison is false. Otherwise, the value indicates | |
7579 | which bits of the result are guaranteed to be 1 when the comparison is | |
7580 | true. This value is interpreted in the mode of the comparison | |
7581 | operation, which is given by the mode of the first operand in the | |
7582 | @samp{cstore@var{mode}4} pattern. Either the low bit or the sign bit of | |
7583 | @code{STORE_FLAG_VALUE} be on. Presently, only those bits are used by | |
7584 | the compiler. | |
7585 | ||
7586 | If @code{STORE_FLAG_VALUE} is neither 1 or @minus{}1, the compiler will | |
7587 | generate code that depends only on the specified bits. It can also | |
7588 | replace comparison operators with equivalent operations if they cause | |
7589 | the required bits to be set, even if the remaining bits are undefined. | |
7590 | For example, on a machine whose comparison operators return an | |
7591 | @code{SImode} value and where @code{STORE_FLAG_VALUE} is defined as | |
7592 | @samp{0x80000000}, saying that just the sign bit is relevant, the | |
7593 | expression | |
7594 | ||
7595 | @smallexample | |
7596 | (ne:SI (and:SI @var{x} (const_int @var{power-of-2})) (const_int 0)) | |
7597 | @end smallexample | |
7598 | ||
7599 | @noindent | |
7600 | can be converted to | |
7601 | ||
7602 | @smallexample | |
7603 | (ashift:SI @var{x} (const_int @var{n})) | |
7604 | @end smallexample | |
7605 | ||
7606 | @noindent | |
7607 | where @var{n} is the appropriate shift count to move the bit being | |
7608 | tested into the sign bit. | |
7609 | ||
7610 | There is no way to describe a machine that always sets the low-order bit | |
7611 | for a true value, but does not guarantee the value of any other bits, | |
7612 | but we do not know of any machine that has such an instruction. If you | |
7613 | are trying to port GCC to such a machine, include an instruction to | |
7614 | perform a logical-and of the result with 1 in the pattern for the | |
7615 | comparison operators and let us know at @email{gcc@@gcc.gnu.org}. | |
7616 | ||
7617 | Often, a machine will have multiple instructions that obtain a value | |
7618 | from a comparison (or the condition codes). Here are rules to guide the | |
7619 | choice of value for @code{STORE_FLAG_VALUE}, and hence the instructions | |
7620 | to be used: | |
7621 | ||
7622 | @itemize @bullet | |
7623 | @item | |
7624 | Use the shortest sequence that yields a valid definition for | |
7625 | @code{STORE_FLAG_VALUE}. It is more efficient for the compiler to | |
7626 | ``normalize'' the value (convert it to, e.g., 1 or 0) than for the | |
7627 | comparison operators to do so because there may be opportunities to | |
7628 | combine the normalization with other operations. | |
7629 | ||
7630 | @item | |
7631 | For equal-length sequences, use a value of 1 or @minus{}1, with @minus{}1 being | |
7632 | slightly preferred on machines with expensive jumps and 1 preferred on | |
7633 | other machines. | |
7634 | ||
7635 | @item | |
7636 | As a second choice, choose a value of @samp{0x80000001} if instructions | |
7637 | exist that set both the sign and low-order bits but do not define the | |
7638 | others. | |
7639 | ||
7640 | @item | |
7641 | Otherwise, use a value of @samp{0x80000000}. | |
7642 | @end itemize | |
7643 | ||
7644 | Many machines can produce both the value chosen for | |
7645 | @code{STORE_FLAG_VALUE} and its negation in the same number of | |
7646 | instructions. On those machines, you should also define a pattern for | |
7647 | those cases, e.g., one matching | |
7648 | ||
7649 | @smallexample | |
7650 | (set @var{A} (neg:@var{m} (ne:@var{m} @var{B} @var{C}))) | |
7651 | @end smallexample | |
7652 | ||
7653 | Some machines can also perform @code{and} or @code{plus} operations on | |
7654 | condition code values with less instructions than the corresponding | |
7655 | @samp{cstore@var{mode}4} insn followed by @code{and} or @code{plus}. On those | |
7656 | machines, define the appropriate patterns. Use the names @code{incscc} | |
7657 | and @code{decscc}, respectively, for the patterns which perform | |
7658 | @code{plus} or @code{minus} operations on condition code values. See | |
b59688ee | 7659 | @file{rs6000.md} for some examples. The GNU Superoptimizer can be used to |
202d6e5f | 7660 | find such instruction sequences on other machines. |
7661 | ||
7662 | If this macro is not defined, the default value, 1, is used. You need | |
7663 | not define @code{STORE_FLAG_VALUE} if the machine has no store-flag | |
7664 | instructions, or if the value generated by these instructions is 1. | |
7665 | @end defmac | |
7666 | ||
7667 | @defmac FLOAT_STORE_FLAG_VALUE (@var{mode}) | |
7668 | A C expression that gives a nonzero @code{REAL_VALUE_TYPE} value that is | |
7669 | returned when comparison operators with floating-point results are true. | |
7670 | Define this macro on machines that have comparison operations that return | |
7671 | floating-point values. If there are no such operations, do not define | |
7672 | this macro. | |
7673 | @end defmac | |
7674 | ||
7675 | @defmac VECTOR_STORE_FLAG_VALUE (@var{mode}) | |
7676 | A C expression that gives a rtx representing the nonzero true element | |
7677 | for vector comparisons. The returned rtx should be valid for the inner | |
7678 | mode of @var{mode} which is guaranteed to be a vector mode. Define | |
7679 | this macro on machines that have vector comparison operations that | |
7680 | return a vector result. If there are no such operations, do not define | |
7681 | this macro. Typically, this macro is defined as @code{const1_rtx} or | |
7682 | @code{constm1_rtx}. This macro may return @code{NULL_RTX} to prevent | |
7683 | the compiler optimizing such vector comparison operations for the | |
7684 | given mode. | |
7685 | @end defmac | |
7686 | ||
7687 | @defmac CLZ_DEFINED_VALUE_AT_ZERO (@var{mode}, @var{value}) | |
7688 | @defmacx CTZ_DEFINED_VALUE_AT_ZERO (@var{mode}, @var{value}) | |
7689 | A C expression that indicates whether the architecture defines a value | |
15b474a2 | 7690 | for @code{clz} or @code{ctz} with a zero operand. |
202d6e5f | 7691 | A result of @code{0} indicates the value is undefined. |
7692 | If the value is defined for only the RTL expression, the macro should | |
7693 | evaluate to @code{1}; if the value applies also to the corresponding optab | |
7694 | entry (which is normally the case if it expands directly into | |
15b474a2 | 7695 | the corresponding RTL), then the macro should evaluate to @code{2}. |
202d6e5f | 7696 | In the cases where the value is defined, @var{value} should be set to |
15b474a2 | 7697 | this value. |
202d6e5f | 7698 | |
7699 | If this macro is not defined, the value of @code{clz} or | |
7700 | @code{ctz} at zero is assumed to be undefined. | |
7701 | ||
7702 | This macro must be defined if the target's expansion for @code{ffs} | |
7703 | relies on a particular value to get correct results. Otherwise it | |
7704 | is not necessary, though it may be used to optimize some corner cases, and | |
7705 | to provide a default expansion for the @code{ffs} optab. | |
7706 | ||
7707 | Note that regardless of this macro the ``definedness'' of @code{clz} | |
7708 | and @code{ctz} at zero do @emph{not} extend to the builtin functions | |
7709 | visible to the user. Thus one may be free to adjust the value at will | |
7710 | to match the target expansion of these operations without fear of | |
7711 | breaking the API@. | |
7712 | @end defmac | |
7713 | ||
7714 | @defmac Pmode | |
7715 | An alias for the machine mode for pointers. On most machines, define | |
7716 | this to be the integer mode corresponding to the width of a hardware | |
7717 | pointer; @code{SImode} on 32-bit machine or @code{DImode} on 64-bit machines. | |
7718 | On some machines you must define this to be one of the partial integer | |
7719 | modes, such as @code{PSImode}. | |
7720 | ||
7721 | The width of @code{Pmode} must be at least as large as the value of | |
7722 | @code{POINTER_SIZE}. If it is not equal, you must define the macro | |
7723 | @code{POINTERS_EXTEND_UNSIGNED} to specify how pointers are extended | |
7724 | to @code{Pmode}. | |
7725 | @end defmac | |
7726 | ||
7727 | @defmac FUNCTION_MODE | |
7728 | An alias for the machine mode used for memory references to functions | |
7729 | being called, in @code{call} RTL expressions. On most CISC machines, | |
15b474a2 | 7730 | where an instruction can begin at any byte address, this should be |
202d6e5f | 7731 | @code{QImode}. On most RISC machines, where all instructions have fixed |
7732 | size and alignment, this should be a mode with the same size and alignment | |
7733 | as the machine instruction words - typically @code{SImode} or @code{HImode}. | |
7734 | @end defmac | |
7735 | ||
7736 | @defmac STDC_0_IN_SYSTEM_HEADERS | |
7737 | In normal operation, the preprocessor expands @code{__STDC__} to the | |
7738 | constant 1, to signify that GCC conforms to ISO Standard C@. On some | |
7739 | hosts, like Solaris, the system compiler uses a different convention, | |
7740 | where @code{__STDC__} is normally 0, but is 1 if the user specifies | |
7741 | strict conformance to the C Standard. | |
7742 | ||
7743 | Defining @code{STDC_0_IN_SYSTEM_HEADERS} makes GNU CPP follows the host | |
7744 | convention when processing system header files, but when processing user | |
7745 | files @code{__STDC__} will always expand to 1. | |
7746 | @end defmac | |
7747 | ||
6adc88f8 | 7748 | @hook TARGET_C_PREINCLUDE |
7749 | ||
f9f68d35 | 7750 | @hook TARGET_CXX_IMPLICIT_EXTERN_C |
7751 | ||
202d6e5f | 7752 | @defmac NO_IMPLICIT_EXTERN_C |
7753 | Define this macro if the system header files support C++ as well as C@. | |
7754 | This macro inhibits the usual method of using system header files in | |
7755 | C++, which is to pretend that the file's contents are enclosed in | |
7756 | @samp{extern "C" @{@dots{}@}}. | |
7757 | @end defmac | |
7758 | ||
7759 | @findex #pragma | |
7760 | @findex pragma | |
7761 | @defmac REGISTER_TARGET_PRAGMAS () | |
7762 | Define this macro if you want to implement any target-specific pragmas. | |
7763 | If defined, it is a C expression which makes a series of calls to | |
7764 | @code{c_register_pragma} or @code{c_register_pragma_with_expansion} | |
7765 | for each pragma. The macro may also do any | |
7766 | setup required for the pragmas. | |
7767 | ||
7768 | The primary reason to define this macro is to provide compatibility with | |
7769 | other compilers for the same target. In general, we discourage | |
7770 | definition of target-specific pragmas for GCC@. | |
7771 | ||
7772 | If the pragma can be implemented by attributes then you should consider | |
7773 | defining the target hook @samp{TARGET_INSERT_ATTRIBUTES} as well. | |
7774 | ||
7775 | Preprocessor macros that appear on pragma lines are not expanded. All | |
7776 | @samp{#pragma} directives that do not match any registered pragma are | |
7777 | silently ignored, unless the user specifies @option{-Wunknown-pragmas}. | |
7778 | @end defmac | |
7779 | ||
7780 | @deftypefun void c_register_pragma (const char *@var{space}, const char *@var{name}, void (*@var{callback}) (struct cpp_reader *)) | |
7781 | @deftypefunx void c_register_pragma_with_expansion (const char *@var{space}, const char *@var{name}, void (*@var{callback}) (struct cpp_reader *)) | |
7782 | ||
7783 | Each call to @code{c_register_pragma} or | |
7784 | @code{c_register_pragma_with_expansion} establishes one pragma. The | |
7785 | @var{callback} routine will be called when the preprocessor encounters a | |
7786 | pragma of the form | |
7787 | ||
7788 | @smallexample | |
7789 | #pragma [@var{space}] @var{name} @dots{} | |
7790 | @end smallexample | |
7791 | ||
7792 | @var{space} is the case-sensitive namespace of the pragma, or | |
7793 | @code{NULL} to put the pragma in the global namespace. The callback | |
7794 | routine receives @var{pfile} as its first argument, which can be passed | |
7795 | on to cpplib's functions if necessary. You can lex tokens after the | |
7796 | @var{name} by calling @code{pragma_lex}. Tokens that are not read by the | |
7797 | callback will be silently ignored. The end of the line is indicated by | |
7798 | a token of type @code{CPP_EOF}. Macro expansion occurs on the | |
7799 | arguments of pragmas registered with | |
7800 | @code{c_register_pragma_with_expansion} but not on the arguments of | |
7801 | pragmas registered with @code{c_register_pragma}. | |
7802 | ||
7803 | Note that the use of @code{pragma_lex} is specific to the C and C++ | |
7804 | compilers. It will not work in the Java or Fortran compilers, or any | |
7805 | other language compilers for that matter. Thus if @code{pragma_lex} is going | |
7806 | to be called from target-specific code, it must only be done so when | |
7807 | building the C and C++ compilers. This can be done by defining the | |
7808 | variables @code{c_target_objs} and @code{cxx_target_objs} in the | |
7809 | target entry in the @file{config.gcc} file. These variables should name | |
7810 | the target-specific, language-specific object file which contains the | |
7811 | code that uses @code{pragma_lex}. Note it will also be necessary to add a | |
7812 | rule to the makefile fragment pointed to by @code{tmake_file} that shows | |
7813 | how to build this object file. | |
7814 | @end deftypefun | |
7815 | ||
202d6e5f | 7816 | @defmac HANDLE_PRAGMA_PACK_WITH_EXPANSION |
3e0e49f2 | 7817 | Define this macro if macros should be expanded in the |
202d6e5f | 7818 | arguments of @samp{#pragma pack}. |
7819 | @end defmac | |
7820 | ||
202d6e5f | 7821 | @defmac TARGET_DEFAULT_PACK_STRUCT |
7822 | If your target requires a structure packing default other than 0 (meaning | |
7823 | the machine default), define this macro to the necessary value (in bytes). | |
7824 | This must be a value that would also be valid to use with | |
7825 | @samp{#pragma pack()} (that is, a small power of two). | |
7826 | @end defmac | |
7827 | ||
7828 | @defmac DOLLARS_IN_IDENTIFIERS | |
7829 | Define this macro to control use of the character @samp{$} in | |
7830 | identifier names for the C family of languages. 0 means @samp{$} is | |
7831 | not allowed by default; 1 means it is allowed. 1 is the default; | |
7832 | there is no need to define this macro in that case. | |
7833 | @end defmac | |
7834 | ||
202d6e5f | 7835 | @defmac INSN_SETS_ARE_DELAYED (@var{insn}) |
7836 | Define this macro as a C expression that is nonzero if it is safe for the | |
7837 | delay slot scheduler to place instructions in the delay slot of @var{insn}, | |
7838 | even if they appear to use a resource set or clobbered in @var{insn}. | |
7839 | @var{insn} is always a @code{jump_insn} or an @code{insn}; GCC knows that | |
7840 | every @code{call_insn} has this behavior. On machines where some @code{insn} | |
7841 | or @code{jump_insn} is really a function call and hence has this behavior, | |
7842 | you should define this macro. | |
7843 | ||
7844 | You need not define this macro if it would always return zero. | |
7845 | @end defmac | |
7846 | ||
7847 | @defmac INSN_REFERENCES_ARE_DELAYED (@var{insn}) | |
7848 | Define this macro as a C expression that is nonzero if it is safe for the | |
7849 | delay slot scheduler to place instructions in the delay slot of @var{insn}, | |
7850 | even if they appear to set or clobber a resource referenced in @var{insn}. | |
7851 | @var{insn} is always a @code{jump_insn} or an @code{insn}. On machines where | |
7852 | some @code{insn} or @code{jump_insn} is really a function call and its operands | |
7853 | are registers whose use is actually in the subroutine it calls, you should | |
7854 | define this macro. Doing so allows the delay slot scheduler to move | |
7855 | instructions which copy arguments into the argument registers into the delay | |
7856 | slot of @var{insn}. | |
7857 | ||
7858 | You need not define this macro if it would always return zero. | |
7859 | @end defmac | |
7860 | ||
7861 | @defmac MULTIPLE_SYMBOL_SPACES | |
7862 | Define this macro as a C expression that is nonzero if, in some cases, | |
7863 | global symbols from one translation unit may not be bound to undefined | |
7864 | symbols in another translation unit without user intervention. For | |
7865 | instance, under Microsoft Windows symbols must be explicitly imported | |
7866 | from shared libraries (DLLs). | |
7867 | ||
7868 | You need not define this macro if it would always evaluate to zero. | |
7869 | @end defmac | |
7870 | ||
7871 | @hook TARGET_MD_ASM_CLOBBERS | |
202d6e5f | 7872 | |
7873 | @defmac MATH_LIBRARY | |
7874 | Define this macro as a C string constant for the linker argument to link | |
cb22f930 | 7875 | in the system math library, minus the initial @samp{"-l"}, or |
7876 | @samp{""} if the target does not have a | |
202d6e5f | 7877 | separate math library. |
7878 | ||
cb22f930 | 7879 | You need only define this macro if the default of @samp{"m"} is wrong. |
202d6e5f | 7880 | @end defmac |
7881 | ||
7882 | @defmac LIBRARY_PATH_ENV | |
7883 | Define this macro as a C string constant for the environment variable that | |
7884 | specifies where the linker should look for libraries. | |
7885 | ||
7886 | You need only define this macro if the default of @samp{"LIBRARY_PATH"} | |
7887 | is wrong. | |
7888 | @end defmac | |
7889 | ||
7890 | @defmac TARGET_POSIX_IO | |
7891 | Define this macro if the target supports the following POSIX@ file | |
7892 | functions, access, mkdir and file locking with fcntl / F_SETLKW@. | |
7893 | Defining @code{TARGET_POSIX_IO} will enable the test coverage code | |
7894 | to use file locking when exiting a program, which avoids race conditions | |
7895 | if the program has forked. It will also create directories at run-time | |
7896 | for cross-profiling. | |
7897 | @end defmac | |
7898 | ||
7899 | @defmac MAX_CONDITIONAL_EXECUTE | |
7900 | ||
7901 | A C expression for the maximum number of instructions to execute via | |
7902 | conditional execution instructions instead of a branch. A value of | |
7903 | @code{BRANCH_COST}+1 is the default if the machine does not use cc0, and | |
7904 | 1 if it does use cc0. | |
7905 | @end defmac | |
7906 | ||
7907 | @defmac IFCVT_MODIFY_TESTS (@var{ce_info}, @var{true_expr}, @var{false_expr}) | |
7908 | Used if the target needs to perform machine-dependent modifications on the | |
7909 | conditionals used for turning basic blocks into conditionally executed code. | |
7910 | @var{ce_info} points to a data structure, @code{struct ce_if_block}, which | |
7911 | contains information about the currently processed blocks. @var{true_expr} | |
7912 | and @var{false_expr} are the tests that are used for converting the | |
7913 | then-block and the else-block, respectively. Set either @var{true_expr} or | |
7914 | @var{false_expr} to a null pointer if the tests cannot be converted. | |
7915 | @end defmac | |
7916 | ||
7917 | @defmac IFCVT_MODIFY_MULTIPLE_TESTS (@var{ce_info}, @var{bb}, @var{true_expr}, @var{false_expr}) | |
7918 | Like @code{IFCVT_MODIFY_TESTS}, but used when converting more complicated | |
7919 | if-statements into conditions combined by @code{and} and @code{or} operations. | |
7920 | @var{bb} contains the basic block that contains the test that is currently | |
7921 | being processed and about to be turned into a condition. | |
7922 | @end defmac | |
7923 | ||
7924 | @defmac IFCVT_MODIFY_INSN (@var{ce_info}, @var{pattern}, @var{insn}) | |
7925 | A C expression to modify the @var{PATTERN} of an @var{INSN} that is to | |
7926 | be converted to conditional execution format. @var{ce_info} points to | |
7927 | a data structure, @code{struct ce_if_block}, which contains information | |
7928 | about the currently processed blocks. | |
7929 | @end defmac | |
7930 | ||
7931 | @defmac IFCVT_MODIFY_FINAL (@var{ce_info}) | |
7932 | A C expression to perform any final machine dependent modifications in | |
7933 | converting code to conditional execution. The involved basic blocks | |
7934 | can be found in the @code{struct ce_if_block} structure that is pointed | |
7935 | to by @var{ce_info}. | |
7936 | @end defmac | |
7937 | ||
7938 | @defmac IFCVT_MODIFY_CANCEL (@var{ce_info}) | |
7939 | A C expression to cancel any machine dependent modifications in | |
7940 | converting code to conditional execution. The involved basic blocks | |
7941 | can be found in the @code{struct ce_if_block} structure that is pointed | |
7942 | to by @var{ce_info}. | |
7943 | @end defmac | |
7944 | ||
e2ca32a4 | 7945 | @defmac IFCVT_MACHDEP_INIT (@var{ce_info}) |
7946 | A C expression to initialize any machine specific data for if-conversion | |
7947 | of the if-block in the @code{struct ce_if_block} structure that is pointed | |
7948 | to by @var{ce_info}. | |
202d6e5f | 7949 | @end defmac |
7950 | ||
7951 | @hook TARGET_MACHINE_DEPENDENT_REORG | |
202d6e5f | 7952 | |
7953 | @hook TARGET_INIT_BUILTINS | |
202d6e5f | 7954 | |
7955 | @hook TARGET_BUILTIN_DECL | |
202d6e5f | 7956 | |
7957 | @hook TARGET_EXPAND_BUILTIN | |
7958 | ||
00a1fec8 | 7959 | @hook TARGET_RESOLVE_OVERLOADED_BUILTIN |
202d6e5f | 7960 | |
bf084459 | 7961 | @hook TARGET_FOLD_BUILTIN |
202d6e5f | 7962 | |
29cad3b6 | 7963 | @hook TARGET_GIMPLE_FOLD_BUILTIN |
7964 | ||
cc8ef84f | 7965 | @hook TARGET_COMPARE_VERSION_PRIORITY |
cc8ef84f | 7966 | |
7967 | @hook TARGET_GET_FUNCTION_VERSIONS_DISPATCHER | |
cc8ef84f | 7968 | |
7969 | @hook TARGET_GENERATE_VERSION_DISPATCHER_BODY | |
cc8ef84f | 7970 | |
a04a7bec | 7971 | @hook TARGET_CAN_USE_DOLOOP_P |
7972 | ||
202d6e5f | 7973 | @hook TARGET_INVALID_WITHIN_DOLOOP |
7974 | ||
2a29bc01 | 7975 | @hook TARGET_LEGITIMATE_COMBINED_INSN |
7976 | ||
202d6e5f | 7977 | @defmac MD_CAN_REDIRECT_BRANCH (@var{branch1}, @var{branch2}) |
7978 | ||
7979 | Take a branch insn in @var{branch1} and another in @var{branch2}. | |
7980 | Return true if redirecting @var{branch1} to the destination of | |
7981 | @var{branch2} is possible. | |
7982 | ||
7983 | On some targets, branches may have a limited range. Optimizing the | |
7984 | filling of delay slots can result in branches being redirected, and this | |
7985 | may in turn cause a branch offset to overflow. | |
7986 | @end defmac | |
7987 | ||
c7b4d9b2 | 7988 | @hook TARGET_CAN_FOLLOW_JUMP |
7989 | ||
202d6e5f | 7990 | @hook TARGET_COMMUTATIVE_P |
202d6e5f | 7991 | |
7992 | @hook TARGET_ALLOCATE_INITIAL_VALUE | |
7993 | ||
202d6e5f | 7994 | @hook TARGET_UNSPEC_MAY_TRAP_P |
202d6e5f | 7995 | |
7996 | @hook TARGET_SET_CURRENT_FUNCTION | |
202d6e5f | 7997 | |
7998 | @defmac TARGET_OBJECT_SUFFIX | |
7999 | Define this macro to be a C string representing the suffix for object | |
8000 | files on your target machine. If you do not define this macro, GCC will | |
8001 | use @samp{.o} as the suffix for object files. | |
8002 | @end defmac | |
8003 | ||
8004 | @defmac TARGET_EXECUTABLE_SUFFIX | |
8005 | Define this macro to be a C string representing the suffix to be | |
8006 | automatically added to executable files on your target machine. If you | |
8007 | do not define this macro, GCC will use the null string as the suffix for | |
8008 | executable files. | |
8009 | @end defmac | |
8010 | ||
8011 | @defmac COLLECT_EXPORT_LIST | |
8012 | If defined, @code{collect2} will scan the individual object files | |
8013 | specified on its command line and create an export list for the linker. | |
8014 | Define this macro for systems like AIX, where the linker discards | |
8015 | object files that are not referenced from @code{main} and uses export | |
8016 | lists. | |
8017 | @end defmac | |
8018 | ||
8019 | @defmac MODIFY_JNI_METHOD_CALL (@var{mdecl}) | |
8020 | Define this macro to a C expression representing a variant of the | |
8021 | method call @var{mdecl}, if Java Native Interface (JNI) methods | |
8022 | must be invoked differently from other methods on your target. | |
8023 | For example, on 32-bit Microsoft Windows, JNI methods must be invoked using | |
8024 | the @code{stdcall} calling convention and this macro is then | |
8025 | defined as this expression: | |
8026 | ||
8027 | @smallexample | |
8028 | build_type_attribute_variant (@var{mdecl}, | |
8029 | build_tree_list | |
8030 | (get_identifier ("stdcall"), | |
8031 | NULL)) | |
8032 | @end smallexample | |
8033 | @end defmac | |
8034 | ||
8035 | @hook TARGET_CANNOT_MODIFY_JUMPS_P | |
202d6e5f | 8036 | |
8037 | @hook TARGET_BRANCH_TARGET_REGISTER_CLASS | |
202d6e5f | 8038 | |
8039 | @hook TARGET_BRANCH_TARGET_REGISTER_CALLEE_SAVED | |
202d6e5f | 8040 | |
8041 | @hook TARGET_HAVE_CONDITIONAL_EXECUTION | |
202d6e5f | 8042 | |
8043 | @hook TARGET_LOOP_UNROLL_ADJUST | |
202d6e5f | 8044 | |
8045 | @defmac POWI_MAX_MULTS | |
8046 | If defined, this macro is interpreted as a signed integer C expression | |
8047 | that specifies the maximum number of floating point multiplications | |
8048 | that should be emitted when expanding exponentiation by an integer | |
8049 | constant inline. When this value is defined, exponentiation requiring | |
8050 | more than this number of multiplications is implemented by calling the | |
8051 | system library's @code{pow}, @code{powf} or @code{powl} routines. | |
8052 | The default value places no upper bound on the multiplication count. | |
8053 | @end defmac | |
8054 | ||
8055 | @deftypefn Macro void TARGET_EXTRA_INCLUDES (const char *@var{sysroot}, const char *@var{iprefix}, int @var{stdinc}) | |
8056 | This target hook should register any extra include files for the | |
8057 | target. The parameter @var{stdinc} indicates if normal include files | |
8058 | are present. The parameter @var{sysroot} is the system root directory. | |
8059 | The parameter @var{iprefix} is the prefix for the gcc directory. | |
8060 | @end deftypefn | |
8061 | ||
8062 | @deftypefn Macro void TARGET_EXTRA_PRE_INCLUDES (const char *@var{sysroot}, const char *@var{iprefix}, int @var{stdinc}) | |
8063 | This target hook should register any extra include files for the | |
8064 | target before any standard headers. The parameter @var{stdinc} | |
8065 | indicates if normal include files are present. The parameter | |
8066 | @var{sysroot} is the system root directory. The parameter | |
8067 | @var{iprefix} is the prefix for the gcc directory. | |
8068 | @end deftypefn | |
8069 | ||
8070 | @deftypefn Macro void TARGET_OPTF (char *@var{path}) | |
8071 | This target hook should register special include paths for the target. | |
8072 | The parameter @var{path} is the include to register. On Darwin | |
8073 | systems, this is used for Framework includes, which have semantics | |
8074 | that are different from @option{-I}. | |
8075 | @end deftypefn | |
8076 | ||
8077 | @defmac bool TARGET_USE_LOCAL_THUNK_ALIAS_P (tree @var{fndecl}) | |
8078 | This target macro returns @code{true} if it is safe to use a local alias | |
8079 | for a virtual function @var{fndecl} when constructing thunks, | |
8080 | @code{false} otherwise. By default, the macro returns @code{true} for all | |
8081 | functions, if a target supports aliases (i.e.@: defines | |
8082 | @code{ASM_OUTPUT_DEF}), @code{false} otherwise, | |
8083 | @end defmac | |
8084 | ||
8085 | @defmac TARGET_FORMAT_TYPES | |
8086 | If defined, this macro is the name of a global variable containing | |
8087 | target-specific format checking information for the @option{-Wformat} | |
8088 | option. The default is to have no target-specific format checks. | |
8089 | @end defmac | |
8090 | ||
8091 | @defmac TARGET_N_FORMAT_TYPES | |
8092 | If defined, this macro is the number of entries in | |
8093 | @code{TARGET_FORMAT_TYPES}. | |
8094 | @end defmac | |
8095 | ||
8096 | @defmac TARGET_OVERRIDES_FORMAT_ATTRIBUTES | |
8097 | If defined, this macro is the name of a global variable containing | |
8098 | target-specific format overrides for the @option{-Wformat} option. The | |
8099 | default is to have no target-specific format overrides. If defined, | |
8100 | @code{TARGET_FORMAT_TYPES} must be defined, too. | |
8101 | @end defmac | |
8102 | ||
8103 | @defmac TARGET_OVERRIDES_FORMAT_ATTRIBUTES_COUNT | |
8104 | If defined, this macro specifies the number of entries in | |
8105 | @code{TARGET_OVERRIDES_FORMAT_ATTRIBUTES}. | |
8106 | @end defmac | |
8107 | ||
8108 | @defmac TARGET_OVERRIDES_FORMAT_INIT | |
8109 | If defined, this macro specifies the optional initialization | |
8110 | routine for target specific customizations of the system printf | |
8111 | and scanf formatter settings. | |
8112 | @end defmac | |
8113 | ||
8114 | @hook TARGET_RELAXED_ORDERING | |
202d6e5f | 8115 | |
8116 | @hook TARGET_INVALID_ARG_FOR_UNPROTOTYPED_FN | |
202d6e5f | 8117 | |
8118 | @hook TARGET_INVALID_CONVERSION | |
202d6e5f | 8119 | |
8120 | @hook TARGET_INVALID_UNARY_OP | |
202d6e5f | 8121 | |
8122 | @hook TARGET_INVALID_BINARY_OP | |
202d6e5f | 8123 | |
8124 | @hook TARGET_INVALID_PARAMETER_TYPE | |
202d6e5f | 8125 | |
8126 | @hook TARGET_INVALID_RETURN_TYPE | |
202d6e5f | 8127 | |
8128 | @hook TARGET_PROMOTED_TYPE | |
202d6e5f | 8129 | |
8130 | @hook TARGET_CONVERT_TO_TYPE | |
202d6e5f | 8131 | |
8132 | @defmac TARGET_USE_JCR_SECTION | |
8133 | This macro determines whether to use the JCR section to register Java | |
8134 | classes. By default, TARGET_USE_JCR_SECTION is defined to 1 if both | |
8135 | SUPPORTS_WEAK and TARGET_HAVE_NAMED_SECTIONS are true, else 0. | |
8136 | @end defmac | |
8137 | ||
8138 | @defmac OBJC_JBLEN | |
8139 | This macro determines the size of the objective C jump buffer for the | |
8140 | NeXT runtime. By default, OBJC_JBLEN is defined to an innocuous value. | |
8141 | @end defmac | |
8142 | ||
8143 | @defmac LIBGCC2_UNWIND_ATTRIBUTE | |
8144 | Define this macro if any target-specific attributes need to be attached | |
15b474a2 | 8145 | to the functions in @file{libgcc} that provide low-level support for |
202d6e5f | 8146 | call stack unwinding. It is used in declarations in @file{unwind-generic.h} |
8147 | and the associated definitions of those functions. | |
8148 | @end defmac | |
8149 | ||
8150 | @hook TARGET_UPDATE_STACK_BOUNDARY | |
202d6e5f | 8151 | |
8152 | @hook TARGET_GET_DRAP_RTX | |
202d6e5f | 8153 | |
8154 | @hook TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS | |
202d6e5f | 8155 | |
8156 | @hook TARGET_CONST_ANCHOR | |
df1680c8 | 8157 | |
7ad5fd20 | 8158 | @hook TARGET_ASAN_SHADOW_OFFSET |
8159 | ||
7f738025 | 8160 | @hook TARGET_MEMMODEL_CHECK |
7f738025 | 8161 | |
df1680c8 | 8162 | @hook TARGET_ATOMIC_TEST_AND_SET_TRUEVAL |
df9f2e40 | 8163 | |
8164 | @hook TARGET_HAS_IFUNC_P | |
e913b5cd | 8165 | |
1e6e32b6 | 8166 | @hook TARGET_ATOMIC_ALIGN_FOR_MODE |
8167 | ||
b560fabd | 8168 | @hook TARGET_ATOMIC_ASSIGN_EXPAND_FENV |
55af3bae | 8169 | |
e913b5cd | 8170 | @defmac TARGET_SUPPORTS_WIDE_INT |
8171 | ||
8172 | On older ports, large integers are stored in @code{CONST_DOUBLE} rtl | |
a342dbb2 | 8173 | objects. Newer ports define @code{TARGET_SUPPORTS_WIDE_INT} to be nonzero |
8174 | to indicate that large integers are stored in | |
e913b5cd | 8175 | @code{CONST_WIDE_INT} rtl objects. The @code{CONST_WIDE_INT} allows |
8176 | very large integer constants to be represented. @code{CONST_DOUBLE} | |
a342dbb2 | 8177 | is limited to twice the size of the host's @code{HOST_WIDE_INT} |
e913b5cd | 8178 | representation. |
8179 | ||
8180 | Converting a port mostly requires looking for the places where | |
a342dbb2 | 8181 | @code{CONST_DOUBLE}s are used with @code{VOIDmode} and replacing that |
e913b5cd | 8182 | code with code that accesses @code{CONST_WIDE_INT}s. @samp{"grep -i |
8183 | const_double"} at the port level gets you to 95% of the changes that | |
8184 | need to be made. There are a few places that require a deeper look. | |
8185 | ||
8186 | @itemize @bullet | |
8187 | @item | |
8188 | There is no equivalent to @code{hval} and @code{lval} for | |
8189 | @code{CONST_WIDE_INT}s. This would be difficult to express in the md | |
8190 | language since there are a variable number of elements. | |
8191 | ||
8192 | Most ports only check that @code{hval} is either 0 or -1 to see if the | |
8193 | value is small. As mentioned above, this will no longer be necessary | |
8194 | since small constants are always @code{CONST_INT}. Of course there | |
8195 | are still a few exceptions, the alpha's constraint used by the zap | |
8196 | instruction certainly requires careful examination by C code. | |
8197 | However, all the current code does is pass the hval and lval to C | |
8198 | code, so evolving the c code to look at the @code{CONST_WIDE_INT} is | |
8199 | not really a large change. | |
8200 | ||
8201 | @item | |
8202 | Because there is no standard template that ports use to materialize | |
8203 | constants, there is likely to be some futzing that is unique to each | |
8204 | port in this code. | |
8205 | ||
8206 | @item | |
8207 | The rtx costs may have to be adjusted to properly account for larger | |
8208 | constants that are represented as @code{CONST_WIDE_INT}. | |
8209 | @end itemize | |
8210 | ||
a342dbb2 | 8211 | All and all it does not take long to convert ports that the |
e913b5cd | 8212 | maintainer is familiar with. |
8213 | ||
8214 | @end defmac |