]>
Commit | Line | Data |
---|---|---|
e56b4594 | 1 | @c Copyright (C) 1988,1989,1992,1993,1994,1995,1996,1997,1998,1999,2000,2001 |
fed3cef0 | 2 | @c Free Software Foundation, Inc. |
feca2ed3 JW |
3 | @c This is part of the GCC manual. |
4 | @c For copying conditions, see the file gcc.texi. | |
5 | ||
6 | @node Target Macros | |
7 | @chapter Target Description Macros | |
8 | @cindex machine description macros | |
9 | @cindex target description macros | |
10 | @cindex macros, target description | |
11 | @cindex @file{tm.h} macros | |
12 | ||
13 | In addition to the file @file{@var{machine}.md}, a machine description | |
14 | includes a C header file conventionally given the name | |
15 | @file{@var{machine}.h}. This header file defines numerous macros | |
16 | that convey the information about the target machine that does not fit | |
17 | into the scheme of the @file{.md} file. The file @file{tm.h} should be | |
18 | a link to @file{@var{machine}.h}. The header file @file{config.h} | |
19 | includes @file{tm.h} and most compiler source files include | |
20 | @file{config.h}. | |
21 | ||
22 | @menu | |
23 | * Driver:: Controlling how the driver runs the compilation passes. | |
24 | * Run-time Target:: Defining @samp{-m} options like @samp{-m68000} and @samp{-m68020}. | |
414c4dc4 | 25 | * Per-Function Data:: Defining data structures for per-function information. |
feca2ed3 JW |
26 | * Storage Layout:: Defining sizes and alignments of data. |
27 | * Type Layout:: Defining sizes and properties of basic user data types. | |
28 | * Registers:: Naming and describing the hardware registers. | |
29 | * Register Classes:: Defining the classes of hardware registers. | |
30 | * Stack and Calling:: Defining which way the stack grows and by how much. | |
31 | * Varargs:: Defining the varargs macros. | |
32 | * Trampolines:: Code set up at run time to enter a nested function. | |
33 | * Library Calls:: Controlling how library routines are implicitly called. | |
34 | * Addressing Modes:: Defining addressing modes valid for memory operands. | |
35 | * Condition Code:: Defining how insns update the condition code. | |
36 | * Costs:: Defining relative costs of different operations. | |
37 | * Sections:: Dividing storage into text, data, and other sections. | |
38 | * PIC:: Macros for position independent code. | |
39 | * Assembler Format:: Defining how to write insns and pseudo-ops to output. | |
40 | * Debugging Info:: Defining the format of debugging output. | |
41 | * Cross-compilation:: Handling floating point for cross-compilers. | |
9f09b1f2 | 42 | * Mode Switching:: Insertion of mode-switching instructions. |
feca2ed3 JW |
43 | * Misc:: Everything else. |
44 | @end menu | |
45 | ||
46 | @node Driver | |
47 | @section Controlling the Compilation Driver, @file{gcc} | |
48 | @cindex driver | |
49 | @cindex controlling the compilation driver | |
50 | ||
51 | @c prevent bad page break with this line | |
52 | You can control the compilation driver. | |
53 | ||
54 | @table @code | |
55 | @findex SWITCH_TAKES_ARG | |
56 | @item SWITCH_TAKES_ARG (@var{char}) | |
57 | A C expression which determines whether the option @samp{-@var{char}} | |
58 | takes arguments. The value should be the number of arguments that | |
59 | option takes--zero, for many options. | |
60 | ||
61 | By default, this macro is defined as | |
62 | @code{DEFAULT_SWITCH_TAKES_ARG}, which handles the standard options | |
63 | properly. You need not define @code{SWITCH_TAKES_ARG} unless you | |
64 | wish to add additional options which take arguments. Any redefinition | |
65 | should call @code{DEFAULT_SWITCH_TAKES_ARG} and then check for | |
66 | additional options. | |
67 | ||
68 | @findex WORD_SWITCH_TAKES_ARG | |
69 | @item WORD_SWITCH_TAKES_ARG (@var{name}) | |
70 | A C expression which determines whether the option @samp{-@var{name}} | |
71 | takes arguments. The value should be the number of arguments that | |
72 | option takes--zero, for many options. This macro rather than | |
73 | @code{SWITCH_TAKES_ARG} is used for multi-character option names. | |
74 | ||
75 | By default, this macro is defined as | |
76 | @code{DEFAULT_WORD_SWITCH_TAKES_ARG}, which handles the standard options | |
77 | properly. You need not define @code{WORD_SWITCH_TAKES_ARG} unless you | |
78 | wish to add additional options which take arguments. Any redefinition | |
79 | should call @code{DEFAULT_WORD_SWITCH_TAKES_ARG} and then check for | |
80 | additional options. | |
81 | ||
88117d44 NC |
82 | @findex SWITCH_CURTAILS_COMPILATION |
83 | @item SWITCH_CURTAILS_COMPILATION (@var{char}) | |
84 | A C expression which determines whether the option @samp{-@var{char}} | |
85 | stops compilation before the generation of an executable. The value is | |
86 | boolean, non-zero if the option does stop an executable from being | |
87 | generated, zero otherwise. | |
88 | ||
89 | By default, this macro is defined as | |
90 | @code{DEFAULT_SWITCH_CURTAILS_COMPILATION}, which handles the standard | |
91 | options properly. You need not define | |
92 | @code{SWITCH_CURTAILS_COMPILATION} unless you wish to add additional | |
93 | options which affect the generation of an executable. Any redefinition | |
94 | should call @code{DEFAULT_SWITCH_CURTAILS_COMPILATION} and then check | |
95 | for additional options. | |
96 | ||
feca2ed3 JW |
97 | @findex SWITCHES_NEED_SPACES |
98 | @item SWITCHES_NEED_SPACES | |
99 | A string-valued C expression which enumerates the options for which | |
100 | the linker needs a space between the option and its argument. | |
101 | ||
102 | If this macro is not defined, the default value is @code{""}. | |
103 | ||
104 | @findex CPP_SPEC | |
105 | @item CPP_SPEC | |
a3a15b4d | 106 | A C string constant that tells the GCC driver program options to |
feca2ed3 | 107 | pass to CPP. It can also specify how to translate options you |
a3a15b4d | 108 | give to GCC into options for GCC to pass to the CPP. |
feca2ed3 JW |
109 | |
110 | Do not define this macro if it does not need to do anything. | |
111 | ||
a9374841 MM |
112 | @findex CPLUSPLUS_CPP_SPEC |
113 | @item CPLUSPLUS_CPP_SPEC | |
114 | This macro is just like @code{CPP_SPEC}, but is used for C++, rather | |
115 | than C. If you do not define this macro, then the value of | |
116 | @code{CPP_SPEC} (if any) will be used instead. | |
117 | ||
feca2ed3 JW |
118 | @findex NO_BUILTIN_SIZE_TYPE |
119 | @item NO_BUILTIN_SIZE_TYPE | |
120 | If this macro is defined, the preprocessor will not define the builtin macro | |
121 | @code{__SIZE_TYPE__}. The macro @code{__SIZE_TYPE__} must then be defined | |
122 | by @code{CPP_SPEC} instead. | |
123 | ||
124 | This should be defined if @code{SIZE_TYPE} depends on target dependent flags | |
125 | which are not accessible to the preprocessor. Otherwise, it should not | |
126 | be defined. | |
127 | ||
128 | @findex NO_BUILTIN_PTRDIFF_TYPE | |
129 | @item NO_BUILTIN_PTRDIFF_TYPE | |
130 | If this macro is defined, the preprocessor will not define the builtin macro | |
131 | @code{__PTRDIFF_TYPE__}. The macro @code{__PTRDIFF_TYPE__} must then be | |
132 | defined by @code{CPP_SPEC} instead. | |
133 | ||
134 | This should be defined if @code{PTRDIFF_TYPE} depends on target dependent flags | |
135 | which are not accessible to the preprocessor. Otherwise, it should not | |
0209c340 ZW |
136 | be defined. |
137 | ||
138 | @findex NO_BUILTIN_WCHAR_TYPE | |
139 | @item NO_BUILTIN_WCHAR_TYPE | |
140 | If this macro is defined, the preprocessor will not define the builtin macro | |
141 | @code{__WCHAR_TYPE__}. The macro @code{__WCHAR_TYPE__} must then be | |
142 | defined by @code{CPP_SPEC} instead. | |
143 | ||
144 | This should be defined if @code{WCHAR_TYPE} depends on target dependent flags | |
145 | which are not accessible to the preprocessor. Otherwise, it should not | |
feca2ed3 JW |
146 | be defined. |
147 | ||
1a67c7d3 JL |
148 | @findex NO_BUILTIN_WINT_TYPE |
149 | @item NO_BUILTIN_WINT_TYPE | |
150 | If this macro is defined, the preprocessor will not define the builtin macro | |
151 | @code{__WINT_TYPE__}. The macro @code{__WINT_TYPE__} must then be | |
152 | defined by @code{CPP_SPEC} instead. | |
153 | ||
154 | This should be defined if @code{WINT_TYPE} depends on target dependent flags | |
155 | which are not accessible to the preprocessor. Otherwise, it should not | |
156 | be defined. | |
157 | ||
feca2ed3 JW |
158 | @findex SIGNED_CHAR_SPEC |
159 | @item SIGNED_CHAR_SPEC | |
a3a15b4d | 160 | A C string constant that tells the GCC driver program options to |
feca2ed3 JW |
161 | pass to CPP. By default, this macro is defined to pass the option |
162 | @samp{-D__CHAR_UNSIGNED__} to CPP if @code{char} will be treated as | |
163 | @code{unsigned char} by @code{cc1}. | |
164 | ||
165 | Do not define this macro unless you need to override the default | |
166 | definition. | |
167 | ||
168 | @findex CC1_SPEC | |
169 | @item CC1_SPEC | |
a3a15b4d | 170 | A C string constant that tells the GCC driver program options to |
66519c70 JL |
171 | pass to @code{cc1}, @code{cc1plus}, @code{f771}, and the other language |
172 | front ends. | |
a3a15b4d JL |
173 | It can also specify how to translate options you give to GCC into options |
174 | for GCC to pass to front ends.. | |
feca2ed3 JW |
175 | |
176 | Do not define this macro if it does not need to do anything. | |
177 | ||
178 | @findex CC1PLUS_SPEC | |
179 | @item CC1PLUS_SPEC | |
a3a15b4d | 180 | A C string constant that tells the GCC driver program options to |
feca2ed3 | 181 | pass to @code{cc1plus}. It can also specify how to translate options you |
a3a15b4d | 182 | give to GCC into options for GCC to pass to the @code{cc1plus}. |
feca2ed3 JW |
183 | |
184 | Do not define this macro if it does not need to do anything. | |
1d96e5b4 FF |
185 | Note that everything defined in CC1_SPEC is already passed to |
186 | @code{cc1plus} so there is no need to duplicate the contents of | |
187 | CC1_SPEC in CC1PLUS_SPEC. | |
feca2ed3 JW |
188 | |
189 | @findex ASM_SPEC | |
190 | @item ASM_SPEC | |
a3a15b4d | 191 | A C string constant that tells the GCC driver program options to |
feca2ed3 | 192 | pass to the assembler. It can also specify how to translate options |
a3a15b4d | 193 | you give to GCC into options for GCC to pass to the assembler. |
feca2ed3 JW |
194 | See the file @file{sun3.h} for an example of this. |
195 | ||
196 | Do not define this macro if it does not need to do anything. | |
197 | ||
198 | @findex ASM_FINAL_SPEC | |
199 | @item ASM_FINAL_SPEC | |
a3a15b4d | 200 | A C string constant that tells the GCC driver program how to |
feca2ed3 JW |
201 | run any programs which cleanup after the normal assembler. |
202 | Normally, this is not needed. See the file @file{mips.h} for | |
203 | an example of this. | |
204 | ||
205 | Do not define this macro if it does not need to do anything. | |
206 | ||
207 | @findex LINK_SPEC | |
208 | @item LINK_SPEC | |
a3a15b4d | 209 | A C string constant that tells the GCC driver program options to |
feca2ed3 | 210 | pass to the linker. It can also specify how to translate options you |
a3a15b4d | 211 | give to GCC into options for GCC to pass to the linker. |
feca2ed3 JW |
212 | |
213 | Do not define this macro if it does not need to do anything. | |
214 | ||
215 | @findex LIB_SPEC | |
216 | @item LIB_SPEC | |
217 | Another C string constant used much like @code{LINK_SPEC}. The difference | |
218 | between the two is that @code{LIB_SPEC} is used at the end of the | |
219 | command given to the linker. | |
220 | ||
221 | If this macro is not defined, a default is provided that | |
222 | loads the standard C library from the usual place. See @file{gcc.c}. | |
223 | ||
224 | @findex LIBGCC_SPEC | |
225 | @item LIBGCC_SPEC | |
a3a15b4d | 226 | Another C string constant that tells the GCC driver program |
feca2ed3 JW |
227 | how and when to place a reference to @file{libgcc.a} into the |
228 | linker command line. This constant is placed both before and after | |
229 | the value of @code{LIB_SPEC}. | |
230 | ||
a3a15b4d | 231 | If this macro is not defined, the GCC driver provides a default that |
989b26a7 | 232 | passes the string @samp{-lgcc} to the linker. |
feca2ed3 JW |
233 | |
234 | @findex STARTFILE_SPEC | |
235 | @item STARTFILE_SPEC | |
236 | Another C string constant used much like @code{LINK_SPEC}. The | |
237 | difference between the two is that @code{STARTFILE_SPEC} is used at | |
238 | the very beginning of the command given to the linker. | |
239 | ||
240 | If this macro is not defined, a default is provided that loads the | |
241 | standard C startup file from the usual place. See @file{gcc.c}. | |
242 | ||
243 | @findex ENDFILE_SPEC | |
244 | @item ENDFILE_SPEC | |
245 | Another C string constant used much like @code{LINK_SPEC}. The | |
246 | difference between the two is that @code{ENDFILE_SPEC} is used at | |
247 | the very end of the command given to the linker. | |
248 | ||
249 | Do not define this macro if it does not need to do anything. | |
250 | ||
251 | @findex EXTRA_SPECS | |
252 | @item EXTRA_SPECS | |
253 | Define this macro to provide additional specifications to put in the | |
254 | @file{specs} file that can be used in various specifications like | |
255 | @code{CC1_SPEC}. | |
256 | ||
257 | The definition should be an initializer for an array of structures, | |
258 | containing a string constant, that defines the specification name, and a | |
259 | string constant that provides the specification. | |
260 | ||
261 | Do not define this macro if it does not need to do anything. | |
262 | ||
263 | @code{EXTRA_SPECS} is useful when an architecture contains several | |
264 | related targets, which have various @code{..._SPECS} which are similar | |
265 | to each other, and the maintainer would like one central place to keep | |
266 | these definitions. | |
267 | ||
268 | For example, the PowerPC System V.4 targets use @code{EXTRA_SPECS} to | |
269 | define either @code{_CALL_SYSV} when the System V calling sequence is | |
270 | used or @code{_CALL_AIX} when the older AIX-based calling sequence is | |
271 | used. | |
272 | ||
273 | The @file{config/rs6000/rs6000.h} target file defines: | |
274 | ||
275 | @example | |
276 | #define EXTRA_SPECS \ | |
277 | @{ "cpp_sysv_default", CPP_SYSV_DEFAULT @}, | |
278 | ||
279 | #define CPP_SYS_DEFAULT "" | |
280 | @end example | |
281 | ||
282 | The @file{config/rs6000/sysv.h} target file defines: | |
283 | @smallexample | |
284 | #undef CPP_SPEC | |
285 | #define CPP_SPEC \ | |
286 | "%@{posix: -D_POSIX_SOURCE @} \ | |
287 | %@{mcall-sysv: -D_CALL_SYSV @} %@{mcall-aix: -D_CALL_AIX @} \ | |
288 | %@{!mcall-sysv: %@{!mcall-aix: %(cpp_sysv_default) @}@} \ | |
289 | %@{msoft-float: -D_SOFT_FLOAT@} %@{mcpu=403: -D_SOFT_FLOAT@}" | |
290 | ||
291 | #undef CPP_SYSV_DEFAULT | |
292 | #define CPP_SYSV_DEFAULT "-D_CALL_SYSV" | |
293 | @end smallexample | |
294 | ||
295 | while the @file{config/rs6000/eabiaix.h} target file defines | |
296 | @code{CPP_SYSV_DEFAULT} as: | |
297 | ||
298 | @smallexample | |
299 | #undef CPP_SYSV_DEFAULT | |
300 | #define CPP_SYSV_DEFAULT "-D_CALL_AIX" | |
301 | @end smallexample | |
302 | ||
303 | @findex LINK_LIBGCC_SPECIAL | |
304 | @item LINK_LIBGCC_SPECIAL | |
305 | Define this macro if the driver program should find the library | |
306 | @file{libgcc.a} itself and should not pass @samp{-L} options to the | |
307 | linker. If you do not define this macro, the driver program will pass | |
308 | the argument @samp{-lgcc} to tell the linker to do the search and will | |
309 | pass @samp{-L} options to it. | |
310 | ||
311 | @findex LINK_LIBGCC_SPECIAL_1 | |
312 | @item LINK_LIBGCC_SPECIAL_1 | |
313 | Define this macro if the driver program should find the library | |
314 | @file{libgcc.a}. If you do not define this macro, the driver program will pass | |
315 | the argument @samp{-lgcc} to tell the linker to do the search. | |
316 | This macro is similar to @code{LINK_LIBGCC_SPECIAL}, except that it does | |
317 | not affect @samp{-L} options. | |
318 | ||
9ec36da5 JL |
319 | @findex LINK_COMMAND_SPEC |
320 | @item LINK_COMMAND_SPEC | |
321 | A C string constant giving the complete command line need to execute the | |
322 | linker. When you do this, you will need to update your port each time a | |
323 | change is made to the link command line within @file{gcc.c}. Therefore, | |
324 | define this macro only if you need to completely redefine the command | |
325 | line for invoking the linker and there is no other way to accomplish | |
326 | the effect you need. | |
327 | ||
feca2ed3 JW |
328 | @findex MULTILIB_DEFAULTS |
329 | @item MULTILIB_DEFAULTS | |
330 | Define this macro as a C expression for the initializer of an array of | |
331 | string to tell the driver program which options are defaults for this | |
332 | target and thus do not need to be handled specially when using | |
333 | @code{MULTILIB_OPTIONS}. | |
334 | ||
335 | Do not define this macro if @code{MULTILIB_OPTIONS} is not defined in | |
336 | the target makefile fragment or if none of the options listed in | |
337 | @code{MULTILIB_OPTIONS} are set by default. | |
338 | @xref{Target Fragment}. | |
339 | ||
340 | @findex RELATIVE_PREFIX_NOT_LINKDIR | |
341 | @item RELATIVE_PREFIX_NOT_LINKDIR | |
342 | Define this macro to tell @code{gcc} that it should only translate | |
343 | a @samp{-B} prefix into a @samp{-L} linker option if the prefix | |
344 | indicates an absolute file name. | |
345 | ||
346 | @findex STANDARD_EXEC_PREFIX | |
347 | @item STANDARD_EXEC_PREFIX | |
348 | Define this macro as a C string constant if you wish to override the | |
349 | standard choice of @file{/usr/local/lib/gcc-lib/} as the default prefix to | |
350 | try when searching for the executable files of the compiler. | |
351 | ||
352 | @findex MD_EXEC_PREFIX | |
353 | @item MD_EXEC_PREFIX | |
354 | If defined, this macro is an additional prefix to try after | |
355 | @code{STANDARD_EXEC_PREFIX}. @code{MD_EXEC_PREFIX} is not searched | |
356 | when the @samp{-b} option is used, or the compiler is built as a cross | |
5505263f JL |
357 | compiler. If you define @code{MD_EXEC_PREFIX}, then be sure to add it |
358 | to the list of directories used to find the assembler in @file{configure.in}. | |
feca2ed3 JW |
359 | |
360 | @findex STANDARD_STARTFILE_PREFIX | |
361 | @item STANDARD_STARTFILE_PREFIX | |
362 | Define this macro as a C string constant if you wish to override the | |
363 | standard choice of @file{/usr/local/lib/} as the default prefix to | |
364 | try when searching for startup files such as @file{crt0.o}. | |
365 | ||
366 | @findex MD_STARTFILE_PREFIX | |
367 | @item MD_STARTFILE_PREFIX | |
368 | If defined, this macro supplies an additional prefix to try after the | |
369 | standard prefixes. @code{MD_EXEC_PREFIX} is not searched when the | |
370 | @samp{-b} option is used, or when the compiler is built as a cross | |
371 | compiler. | |
372 | ||
373 | @findex MD_STARTFILE_PREFIX_1 | |
374 | @item MD_STARTFILE_PREFIX_1 | |
375 | If defined, this macro supplies yet another prefix to try after the | |
376 | standard prefixes. It is not searched when the @samp{-b} option is | |
377 | used, or when the compiler is built as a cross compiler. | |
378 | ||
379 | @findex INIT_ENVIRONMENT | |
380 | @item INIT_ENVIRONMENT | |
e9a25f70 | 381 | Define this macro as a C string constant if you wish to set environment |
feca2ed3 JW |
382 | variables for programs called by the driver, such as the assembler and |
383 | loader. The driver passes the value of this macro to @code{putenv} to | |
384 | initialize the necessary environment variables. | |
385 | ||
386 | @findex LOCAL_INCLUDE_DIR | |
387 | @item LOCAL_INCLUDE_DIR | |
388 | Define this macro as a C string constant if you wish to override the | |
389 | standard choice of @file{/usr/local/include} as the default prefix to | |
390 | try when searching for local header files. @code{LOCAL_INCLUDE_DIR} | |
391 | comes before @code{SYSTEM_INCLUDE_DIR} in the search order. | |
392 | ||
393 | Cross compilers do not use this macro and do not search either | |
394 | @file{/usr/local/include} or its replacement. | |
395 | ||
dc36ec2c RK |
396 | @findex MODIFY_TARGET_NAME |
397 | @item MODIFY_TARGET_NAME | |
398 | Define this macro if you with to define command-line switches that modify the | |
399 | default target name | |
400 | ||
401 | For each switch, you can include a string to be appended to the first | |
402 | part of the configuration name or a string to be deleted from the | |
403 | configuration name, if present. The definition should be an initializer | |
404 | for an array of structures. Each array element should have three | |
405 | elements: the switch name (a string constant, including the initial | |
406 | dash), one of the enumeration codes @code{ADD} or @code{DELETE} to | |
407 | indicate whether the string should be inserted or deleted, and the string | |
408 | to be inserted or deleted (a string constant). | |
409 | ||
410 | For example, on a machine where @samp{64} at the end of the | |
411 | configuration name denotes a 64-bit target and you want the @samp{-32} | |
412 | and @samp{-64} switches to select between 32- and 64-bit targets, you would | |
413 | code | |
414 | ||
415 | @smallexample | |
416 | #define MODIFY_TARGET_NAME \ | |
417 | @{ @{ "-32", DELETE, "64"@}, \ | |
418 | @{"-64", ADD, "64"@}@} | |
419 | @end smallexample | |
420 | ||
421 | ||
feca2ed3 JW |
422 | @findex SYSTEM_INCLUDE_DIR |
423 | @item SYSTEM_INCLUDE_DIR | |
424 | Define this macro as a C string constant if you wish to specify a | |
425 | system-specific directory to search for header files before the standard | |
426 | directory. @code{SYSTEM_INCLUDE_DIR} comes before | |
427 | @code{STANDARD_INCLUDE_DIR} in the search order. | |
428 | ||
429 | Cross compilers do not use this macro and do not search the directory | |
430 | specified. | |
431 | ||
432 | @findex STANDARD_INCLUDE_DIR | |
433 | @item STANDARD_INCLUDE_DIR | |
434 | Define this macro as a C string constant if you wish to override the | |
435 | standard choice of @file{/usr/include} as the default prefix to | |
436 | try when searching for header files. | |
437 | ||
438 | Cross compilers do not use this macro and do not search either | |
439 | @file{/usr/include} or its replacement. | |
440 | ||
e9a25f70 JL |
441 | @findex STANDARD_INCLUDE_COMPONENT |
442 | @item STANDARD_INCLUDE_COMPONENT | |
443 | The ``component'' corresponding to @code{STANDARD_INCLUDE_DIR}. | |
444 | See @code{INCLUDE_DEFAULTS}, below, for the description of components. | |
445 | If you do not define this macro, no component is used. | |
446 | ||
feca2ed3 JW |
447 | @findex INCLUDE_DEFAULTS |
448 | @item INCLUDE_DEFAULTS | |
449 | Define this macro if you wish to override the entire default search path | |
e9a25f70 JL |
450 | for include files. For a native compiler, the default search path |
451 | usually consists of @code{GCC_INCLUDE_DIR}, @code{LOCAL_INCLUDE_DIR}, | |
feca2ed3 JW |
452 | @code{SYSTEM_INCLUDE_DIR}, @code{GPLUSPLUS_INCLUDE_DIR}, and |
453 | @code{STANDARD_INCLUDE_DIR}. In addition, @code{GPLUSPLUS_INCLUDE_DIR} | |
454 | and @code{GCC_INCLUDE_DIR} are defined automatically by @file{Makefile}, | |
455 | and specify private search areas for GCC. The directory | |
456 | @code{GPLUSPLUS_INCLUDE_DIR} is used only for C++ programs. | |
457 | ||
458 | The definition should be an initializer for an array of structures. | |
e9a25f70 | 459 | Each array element should have four elements: the directory name (a |
9f6dc500 HPN |
460 | string constant), the component name (also a string constant), a flag |
461 | for C++-only directories, | |
e9a25f70 JL |
462 | and a flag showing that the includes in the directory don't need to be |
463 | wrapped in @code{extern @samp{C}} when compiling C++. Mark the end of | |
464 | the array with a null element. | |
465 | ||
466 | The component name denotes what GNU package the include file is part of, | |
467 | if any, in all upper-case letters. For example, it might be @samp{GCC} | |
9f6dc500 | 468 | or @samp{BINUTILS}. If the package is part of a vendor-supplied |
e9a25f70 JL |
469 | operating system, code the component name as @samp{0}. |
470 | ||
e9a25f70 | 471 | For example, here is the definition used for VAX/VMS: |
feca2ed3 JW |
472 | |
473 | @example | |
474 | #define INCLUDE_DEFAULTS \ | |
475 | @{ \ | |
e9a25f70 JL |
476 | @{ "GNU_GXX_INCLUDE:", "G++", 1, 1@}, \ |
477 | @{ "GNU_CC_INCLUDE:", "GCC", 0, 0@}, \ | |
478 | @{ "SYS$SYSROOT:[SYSLIB.]", 0, 0, 0@}, \ | |
479 | @{ ".", 0, 0, 0@}, \ | |
480 | @{ 0, 0, 0, 0@} \ | |
feca2ed3 JW |
481 | @} |
482 | @end example | |
483 | @end table | |
484 | ||
485 | Here is the order of prefixes tried for exec files: | |
486 | ||
487 | @enumerate | |
488 | @item | |
489 | Any prefixes specified by the user with @samp{-B}. | |
490 | ||
491 | @item | |
492 | The environment variable @code{GCC_EXEC_PREFIX}, if any. | |
493 | ||
494 | @item | |
495 | The directories specified by the environment variable @code{COMPILER_PATH}. | |
496 | ||
497 | @item | |
498 | The macro @code{STANDARD_EXEC_PREFIX}. | |
499 | ||
500 | @item | |
501 | @file{/usr/lib/gcc/}. | |
502 | ||
503 | @item | |
504 | The macro @code{MD_EXEC_PREFIX}, if any. | |
505 | @end enumerate | |
506 | ||
507 | Here is the order of prefixes tried for startfiles: | |
508 | ||
509 | @enumerate | |
510 | @item | |
511 | Any prefixes specified by the user with @samp{-B}. | |
512 | ||
513 | @item | |
514 | The environment variable @code{GCC_EXEC_PREFIX}, if any. | |
515 | ||
516 | @item | |
517 | The directories specified by the environment variable @code{LIBRARY_PATH} | |
512b62fb | 518 | (or port-specific name; native only, cross compilers do not use this). |
feca2ed3 JW |
519 | |
520 | @item | |
521 | The macro @code{STANDARD_EXEC_PREFIX}. | |
522 | ||
523 | @item | |
524 | @file{/usr/lib/gcc/}. | |
525 | ||
526 | @item | |
527 | The macro @code{MD_EXEC_PREFIX}, if any. | |
528 | ||
529 | @item | |
530 | The macro @code{MD_STARTFILE_PREFIX}, if any. | |
531 | ||
532 | @item | |
533 | The macro @code{STANDARD_STARTFILE_PREFIX}. | |
534 | ||
535 | @item | |
536 | @file{/lib/}. | |
537 | ||
538 | @item | |
539 | @file{/usr/lib/}. | |
540 | @end enumerate | |
541 | ||
542 | @node Run-time Target | |
543 | @section Run-time Target Specification | |
544 | @cindex run-time target specification | |
545 | @cindex predefined macros | |
546 | @cindex target specifications | |
547 | ||
548 | @c prevent bad page break with this line | |
549 | Here are run-time target specifications. | |
550 | ||
551 | @table @code | |
552 | @findex CPP_PREDEFINES | |
553 | @item CPP_PREDEFINES | |
554 | Define this to be a string constant containing @samp{-D} options to | |
555 | define the predefined macros that identify this machine and system. | |
5490d604 JM |
556 | These macros will be predefined unless the @option{-ansi} option (or a |
557 | @option{-std} option for strict ISO C conformance) is specified. | |
feca2ed3 JW |
558 | |
559 | In addition, a parallel set of macros are predefined, whose names are | |
560 | made by appending @samp{__} at the beginning and at the end. These | |
5490d604 JM |
561 | @samp{__} macros are permitted by the ISO standard, so they are |
562 | predefined regardless of whether @option{-ansi} or a @option{-std} option | |
563 | is specified. | |
feca2ed3 JW |
564 | |
565 | For example, on the Sun, one can use the following value: | |
566 | ||
567 | @smallexample | |
568 | "-Dmc68000 -Dsun -Dunix" | |
569 | @end smallexample | |
570 | ||
571 | The result is to define the macros @code{__mc68000__}, @code{__sun__} | |
572 | and @code{__unix__} unconditionally, and the macros @code{mc68000}, | |
573 | @code{sun} and @code{unix} provided @samp{-ansi} is not specified. | |
574 | ||
575 | @findex extern int target_flags | |
576 | @item extern int target_flags; | |
577 | This declaration should be present. | |
578 | ||
579 | @cindex optional hardware or system features | |
580 | @cindex features, optional, in system conventions | |
581 | @item TARGET_@dots{} | |
582 | This series of macros is to allow compiler command arguments to | |
583 | enable or disable the use of optional features of the target machine. | |
584 | For example, one machine description serves both the 68000 and | |
585 | the 68020; a command argument tells the compiler whether it should | |
586 | use 68020-only instructions or not. This command argument works | |
587 | by means of a macro @code{TARGET_68020} that tests a bit in | |
588 | @code{target_flags}. | |
589 | ||
590 | Define a macro @code{TARGET_@var{featurename}} for each such option. | |
9f6dc500 HPN |
591 | Its definition should test a bit in @code{target_flags}. It is |
592 | recommended that a helper macro @code{TARGET_MASK_@var{featurename}} | |
593 | is defined for each bit-value to test, and used in | |
594 | @code{TARGET_@var{featurename}} and @code{TARGET_SWITCHES}. For | |
595 | example: | |
feca2ed3 JW |
596 | |
597 | @smallexample | |
9f6dc500 HPN |
598 | #define TARGET_MASK_68020 1 |
599 | #define TARGET_68020 (target_flags & TARGET_MASK_68020) | |
feca2ed3 JW |
600 | @end smallexample |
601 | ||
602 | One place where these macros are used is in the condition-expressions | |
603 | of instruction patterns. Note how @code{TARGET_68020} appears | |
604 | frequently in the 68000 machine description file, @file{m68k.md}. | |
605 | Another place they are used is in the definitions of the other | |
606 | macros in the @file{@var{machine}.h} file. | |
607 | ||
608 | @findex TARGET_SWITCHES | |
609 | @item TARGET_SWITCHES | |
610 | This macro defines names of command options to set and clear | |
611 | bits in @code{target_flags}. Its definition is an initializer | |
612 | with a subgrouping for each command option. | |
613 | ||
614 | Each subgrouping contains a string constant, that defines the option | |
b8468bc7 NC |
615 | name, a number, which contains the bits to set in |
616 | @code{target_flags}, and a second string which is the description | |
617 | displayed by --help. If the number is negative then the bits specified | |
618 | by the number are cleared instead of being set. If the description | |
619 | string is present but empty, then no help information will be displayed | |
620 | for that option, but it will not count as an undocumented option. The | |
621 | actual option name is made by appending @samp{-m} to the specified name. | |
feca2ed3 JW |
622 | |
623 | One of the subgroupings should have a null string. The number in | |
624 | this grouping is the default value for @code{target_flags}. Any | |
625 | target options act starting with that value. | |
626 | ||
627 | Here is an example which defines @samp{-m68000} and @samp{-m68020} | |
628 | with opposite meanings, and picks the latter as the default: | |
629 | ||
630 | @smallexample | |
631 | #define TARGET_SWITCHES \ | |
9f6dc500 HPN |
632 | @{ @{ "68020", TARGET_MASK_68020, "" @}, \ |
633 | @{ "68000", -TARGET_MASK_68020, "Compile for the 68000" @}, \ | |
634 | @{ "", TARGET_MASK_68020, "" @}@} | |
feca2ed3 JW |
635 | @end smallexample |
636 | ||
637 | @findex TARGET_OPTIONS | |
638 | @item TARGET_OPTIONS | |
639 | This macro is similar to @code{TARGET_SWITCHES} but defines names of command | |
640 | options that have values. Its definition is an initializer with a | |
641 | subgrouping for each command option. | |
642 | ||
643 | Each subgrouping contains a string constant, that defines the fixed part | |
b8468bc7 NC |
644 | of the option name, the address of a variable, and a description string. |
645 | The variable, type @code{char *}, is set to the variable part of the | |
646 | given option if the fixed part matches. The actual option name is made | |
647 | by appending @samp{-m} to the specified name. | |
feca2ed3 JW |
648 | |
649 | Here is an example which defines @samp{-mshort-data-@var{number}}. If the | |
650 | given option is @samp{-mshort-data-512}, the variable @code{m88k_short_data} | |
651 | will be set to the string @code{"512"}. | |
652 | ||
653 | @smallexample | |
654 | extern char *m88k_short_data; | |
655 | #define TARGET_OPTIONS \ | |
b8468bc7 | 656 | @{ @{ "short-data-", &m88k_short_data, "Specify the size of the short data section" @} @} |
feca2ed3 JW |
657 | @end smallexample |
658 | ||
659 | @findex TARGET_VERSION | |
660 | @item TARGET_VERSION | |
661 | This macro is a C statement to print on @code{stderr} a string | |
662 | describing the particular machine description choice. Every machine | |
663 | description should define @code{TARGET_VERSION}. For example: | |
664 | ||
665 | @smallexample | |
666 | #ifdef MOTOROLA | |
667 | #define TARGET_VERSION \ | |
668 | fprintf (stderr, " (68k, Motorola syntax)"); | |
669 | #else | |
670 | #define TARGET_VERSION \ | |
671 | fprintf (stderr, " (68k, MIT syntax)"); | |
672 | #endif | |
673 | @end smallexample | |
674 | ||
675 | @findex OVERRIDE_OPTIONS | |
676 | @item OVERRIDE_OPTIONS | |
677 | Sometimes certain combinations of command options do not make sense on | |
678 | a particular target machine. You can define a macro | |
679 | @code{OVERRIDE_OPTIONS} to take account of this. This macro, if | |
680 | defined, is executed once just after all the command options have been | |
681 | parsed. | |
682 | ||
683 | Don't use this macro to turn on various extra optimizations for | |
684 | @samp{-O}. That is what @code{OPTIMIZATION_OPTIONS} is for. | |
685 | ||
686 | @findex OPTIMIZATION_OPTIONS | |
c6aded7c | 687 | @item OPTIMIZATION_OPTIONS (@var{level}, @var{size}) |
feca2ed3 JW |
688 | Some machines may desire to change what optimizations are performed for |
689 | various optimization levels. This macro, if defined, is executed once | |
690 | just after the optimization level is determined and before the remainder | |
691 | of the command options have been parsed. Values set in this macro are | |
692 | used as the default values for the other command line options. | |
693 | ||
694 | @var{level} is the optimization level specified; 2 if @samp{-O2} is | |
695 | specified, 1 if @samp{-O} is specified, and 0 if neither is specified. | |
696 | ||
c6aded7c AG |
697 | @var{size} is non-zero if @samp{-Os} is specified and zero otherwise. |
698 | ||
feca2ed3 JW |
699 | You should not use this macro to change options that are not |
700 | machine-specific. These should uniformly selected by the same | |
701 | optimization level on all supported machines. Use this macro to enable | |
702 | machine-specific optimizations. | |
703 | ||
704 | @strong{Do not examine @code{write_symbols} in | |
705 | this macro!} The debugging options are not supposed to alter the | |
706 | generated code. | |
707 | ||
708 | @findex CAN_DEBUG_WITHOUT_FP | |
709 | @item CAN_DEBUG_WITHOUT_FP | |
710 | Define this macro if debugging can be performed even without a frame | |
a3a15b4d | 711 | pointer. If this macro is defined, GCC will turn on the |
feca2ed3 JW |
712 | @samp{-fomit-frame-pointer} option whenever @samp{-O} is specified. |
713 | @end table | |
714 | ||
414c4dc4 NC |
715 | @node Per-Function Data |
716 | @section Defining data structures for per-function information. | |
717 | @cindex per-function data | |
718 | @cindex data structures | |
719 | ||
720 | If the target needs to store information on a per-function basis, GCC | |
721 | provides a macro and a couple of variables to allow this. Note, just | |
722 | using statics to store the information is a bad idea, since GCC supports | |
723 | nested functions, so you can be halfway through encoding one function | |
724 | when another one comes along. | |
725 | ||
726 | GCC defines a data structure called @code{struct function} which | |
727 | contains all of the data specific to an individual function. This | |
728 | structure contains a field called @code{machine} whose type is | |
729 | @code{struct machine_function *}, which can be used by targets to point | |
730 | to their own specific data. | |
731 | ||
732 | If a target needs per-function specific data it should define the type | |
733 | @code{struct machine_function} and also the macro | |
734 | @code{INIT_EXPANDERS}. This macro should be used to initialise some or | |
735 | all of the function pointers @code{init_machine_status}, | |
736 | @code{free_machine_status} and @code{mark_machine_status}. These | |
737 | pointers are explained below. | |
738 | ||
739 | One typical use of per-function, target specific data is to create an | |
740 | RTX to hold the register containing the function's return address. This | |
741 | RTX can then be used to implement the @code{__builtin_return_address} | |
742 | function, for level 0. | |
743 | ||
744 | Note - earlier implementations of GCC used a single data area to hold | |
745 | all of the per-function information. Thus when processing of a nested | |
746 | function began the old per-function data had to be pushed onto a | |
747 | stack, and when the processing was finished, it had to be popped off the | |
748 | stack. GCC used to provide function pointers called | |
749 | @code{save_machine_status} and @code{restore_machine_status} to handle | |
750 | the saving and restoring of the target specific information. Since the | |
751 | single data area approach is no longer used, these pointers are no | |
752 | longer supported. | |
753 | ||
754 | The macro and function pointers are described below. | |
755 | ||
756 | @table @code | |
757 | @findex INIT_EXPANDERS | |
758 | @item INIT_EXPANDERS | |
759 | Macro called to initialise any target specific information. This macro | |
760 | is called once per function, before generation of any RTL has begun. | |
761 | The intention of this macro is to allow the initialisation of the | |
762 | function pointers below. | |
763 | ||
764 | @findex init_machine_status | |
765 | @item init_machine_status | |
766 | This is a @code{void (*)(struct function *)} function pointer. If this | |
767 | pointer is non-NULL it will be called once per function, before function | |
768 | compilation starts, in order to allow the target to perform any target | |
769 | specific initialisation of the @code{struct function} structure. It is | |
770 | intended that this would be used to initialise the @code{machine} of | |
771 | that struture. | |
772 | ||
773 | @findex free_machine_status | |
774 | @item free_machine_status | |
775 | This is a @code{void (*)(struct function *)} function pointer. If this | |
776 | pointer is non-NULL it will be called once per function, after the | |
777 | function has been compiled, in order to allow any memory allocated | |
778 | during the @code{init_machine_status} function call to be freed. | |
779 | ||
780 | @findex mark_machine_status | |
781 | @item mark_machine_status | |
782 | This is a @code{void (*)(struct function *)} function pointer. If this | |
783 | pointer is non-NULL it will be called once per function in order to mark | |
784 | any data items in the @code{struct machine_function} structure which | |
785 | need garbage collection. | |
786 | ||
787 | @end table | |
788 | ||
feca2ed3 JW |
789 | @node Storage Layout |
790 | @section Storage Layout | |
791 | @cindex storage layout | |
792 | ||
793 | Note that the definitions of the macros in this table which are sizes or | |
794 | alignments measured in bits do not need to be constant. They can be C | |
795 | expressions that refer to static variables, such as the @code{target_flags}. | |
796 | @xref{Run-time Target}. | |
797 | ||
798 | @table @code | |
799 | @findex BITS_BIG_ENDIAN | |
800 | @item BITS_BIG_ENDIAN | |
801 | Define this macro to have the value 1 if the most significant bit in a | |
802 | byte has the lowest number; otherwise define it to have the value zero. | |
803 | This means that bit-field instructions count from the most significant | |
804 | bit. If the machine has no bit-field instructions, then this must still | |
805 | be defined, but it doesn't matter which value it is defined to. This | |
806 | macro need not be a constant. | |
807 | ||
808 | This macro does not affect the way structure fields are packed into | |
809 | bytes or words; that is controlled by @code{BYTES_BIG_ENDIAN}. | |
810 | ||
811 | @findex BYTES_BIG_ENDIAN | |
812 | @item BYTES_BIG_ENDIAN | |
813 | Define this macro to have the value 1 if the most significant byte in a | |
814 | word has the lowest number. This macro need not be a constant. | |
815 | ||
816 | @findex WORDS_BIG_ENDIAN | |
817 | @item WORDS_BIG_ENDIAN | |
818 | Define this macro to have the value 1 if, in a multiword object, the | |
819 | most significant word has the lowest number. This applies to both | |
a3a15b4d | 820 | memory locations and registers; GCC fundamentally assumes that the |
feca2ed3 JW |
821 | order of words in memory is the same as the order in registers. This |
822 | macro need not be a constant. | |
823 | ||
824 | @findex LIBGCC2_WORDS_BIG_ENDIAN | |
825 | @item LIBGCC2_WORDS_BIG_ENDIAN | |
826 | Define this macro if WORDS_BIG_ENDIAN is not constant. This must be a | |
827 | constant value with the same meaning as WORDS_BIG_ENDIAN, which will be | |
828 | used only when compiling libgcc2.c. Typically the value will be set | |
829 | based on preprocessor defines. | |
830 | ||
831 | @findex FLOAT_WORDS_BIG_ENDIAN | |
832 | @item FLOAT_WORDS_BIG_ENDIAN | |
833 | Define this macro to have the value 1 if @code{DFmode}, @code{XFmode} or | |
834 | @code{TFmode} floating point numbers are stored in memory with the word | |
835 | containing the sign bit at the lowest address; otherwise define it to | |
836 | have the value 0. This macro need not be a constant. | |
837 | ||
838 | You need not define this macro if the ordering is the same as for | |
839 | multi-word integers. | |
840 | ||
841 | @findex BITS_PER_UNIT | |
842 | @item BITS_PER_UNIT | |
843 | Define this macro to be the number of bits in an addressable storage | |
844 | unit (byte); normally 8. | |
845 | ||
846 | @findex BITS_PER_WORD | |
847 | @item BITS_PER_WORD | |
848 | Number of bits in a word; normally 32. | |
849 | ||
850 | @findex MAX_BITS_PER_WORD | |
851 | @item MAX_BITS_PER_WORD | |
852 | Maximum number of bits in a word. If this is undefined, the default is | |
853 | @code{BITS_PER_WORD}. Otherwise, it is the constant value that is the | |
854 | largest value that @code{BITS_PER_WORD} can have at run-time. | |
855 | ||
856 | @findex UNITS_PER_WORD | |
857 | @item UNITS_PER_WORD | |
858 | Number of storage units in a word; normally 4. | |
859 | ||
860 | @findex MIN_UNITS_PER_WORD | |
861 | @item MIN_UNITS_PER_WORD | |
862 | Minimum number of units in a word. If this is undefined, the default is | |
863 | @code{UNITS_PER_WORD}. Otherwise, it is the constant value that is the | |
864 | smallest value that @code{UNITS_PER_WORD} can have at run-time. | |
865 | ||
866 | @findex POINTER_SIZE | |
867 | @item POINTER_SIZE | |
868 | Width of a pointer, in bits. You must specify a value no wider than the | |
869 | width of @code{Pmode}. If it is not equal to the width of @code{Pmode}, | |
870 | you must define @code{POINTERS_EXTEND_UNSIGNED}. | |
871 | ||
872 | @findex POINTERS_EXTEND_UNSIGNED | |
873 | @item POINTERS_EXTEND_UNSIGNED | |
874 | A C expression whose value is nonzero if pointers that need to be | |
f5963e61 JL |
875 | extended from being @code{POINTER_SIZE} bits wide to @code{Pmode} are to |
876 | be zero-extended and zero if they are to be sign-extended. | |
feca2ed3 JW |
877 | |
878 | You need not define this macro if the @code{POINTER_SIZE} is equal | |
879 | to the width of @code{Pmode}. | |
880 | ||
881 | @findex PROMOTE_MODE | |
882 | @item PROMOTE_MODE (@var{m}, @var{unsignedp}, @var{type}) | |
883 | A macro to update @var{m} and @var{unsignedp} when an object whose type | |
884 | is @var{type} and which has the specified mode and signedness is to be | |
885 | stored in a register. This macro is only called when @var{type} is a | |
886 | scalar type. | |
887 | ||
888 | On most RISC machines, which only have operations that operate on a full | |
889 | register, define this macro to set @var{m} to @code{word_mode} if | |
890 | @var{m} is an integer mode narrower than @code{BITS_PER_WORD}. In most | |
891 | cases, only integer modes should be widened because wider-precision | |
892 | floating-point operations are usually more expensive than their narrower | |
893 | counterparts. | |
894 | ||
895 | For most machines, the macro definition does not change @var{unsignedp}. | |
896 | However, some machines, have instructions that preferentially handle | |
897 | either signed or unsigned quantities of certain modes. For example, on | |
898 | the DEC Alpha, 32-bit loads from memory and 32-bit add instructions | |
899 | sign-extend the result to 64 bits. On such machines, set | |
900 | @var{unsignedp} according to which kind of extension is more efficient. | |
901 | ||
902 | Do not define this macro if it would never modify @var{m}. | |
903 | ||
904 | @findex PROMOTE_FUNCTION_ARGS | |
905 | @item PROMOTE_FUNCTION_ARGS | |
906 | Define this macro if the promotion described by @code{PROMOTE_MODE} | |
907 | should also be done for outgoing function arguments. | |
908 | ||
909 | @findex PROMOTE_FUNCTION_RETURN | |
910 | @item PROMOTE_FUNCTION_RETURN | |
911 | Define this macro if the promotion described by @code{PROMOTE_MODE} | |
912 | should also be done for the return value of functions. | |
913 | ||
914 | If this macro is defined, @code{FUNCTION_VALUE} must perform the same | |
915 | promotions done by @code{PROMOTE_MODE}. | |
916 | ||
917 | @findex PROMOTE_FOR_CALL_ONLY | |
918 | @item PROMOTE_FOR_CALL_ONLY | |
919 | Define this macro if the promotion described by @code{PROMOTE_MODE} | |
920 | should @emph{only} be performed for outgoing function arguments or | |
921 | function return values, as specified by @code{PROMOTE_FUNCTION_ARGS} | |
922 | and @code{PROMOTE_FUNCTION_RETURN}, respectively. | |
923 | ||
924 | @findex PARM_BOUNDARY | |
925 | @item PARM_BOUNDARY | |
926 | Normal alignment required for function parameters on the stack, in | |
927 | bits. All stack parameters receive at least this much alignment | |
928 | regardless of data type. On most machines, this is the same as the | |
929 | size of an integer. | |
930 | ||
931 | @findex STACK_BOUNDARY | |
932 | @item STACK_BOUNDARY | |
c795bca9 BS |
933 | Define this macro if there is a guaranteed alignment for the stack |
934 | pointer on this machine. The definition is a C expression | |
935 | for the desired alignment (measured in bits). This value is used as a | |
936 | default if PREFERRED_STACK_BOUNDARY is not defined. | |
937 | ||
938 | @findex PREFERRED_STACK_BOUNDARY | |
939 | @item PREFERRED_STACK_BOUNDARY | |
feca2ed3 JW |
940 | Define this macro if you wish to preserve a certain alignment for |
941 | the stack pointer. The definition is a C expression | |
c795bca9 BS |
942 | for the desired alignment (measured in bits). If STACK_BOUNDARY is |
943 | also defined, this macro must evaluate to a value equal to or larger | |
944 | than STACK_BOUNDARY. | |
feca2ed3 | 945 | |
c795bca9 | 946 | @cindex @code{PUSH_ROUNDING}, interaction with @code{PREFERRED_STACK_BOUNDARY} |
feca2ed3 | 947 | If @code{PUSH_ROUNDING} is not defined, the stack will always be aligned |
c795bca9 BS |
948 | to the specified boundary. If @code{PUSH_ROUNDING} is defined and specifies |
949 | a less strict alignment than @code{PREFERRED_STACK_BOUNDARY}, the stack may | |
950 | be momentarily unaligned while pushing arguments. | |
feca2ed3 JW |
951 | |
952 | @findex FUNCTION_BOUNDARY | |
953 | @item FUNCTION_BOUNDARY | |
954 | Alignment required for a function entry point, in bits. | |
955 | ||
956 | @findex BIGGEST_ALIGNMENT | |
957 | @item BIGGEST_ALIGNMENT | |
958 | Biggest alignment that any data type can require on this machine, in bits. | |
959 | ||
861bb6c1 JL |
960 | @findex MINIMUM_ATOMIC_ALIGNMENT |
961 | @item MINIMUM_ATOMIC_ALIGNMENT | |
962 | If defined, the smallest alignment, in bits, that can be given to an | |
963 | object that can be referenced in one operation, without disturbing any | |
964 | nearby object. Normally, this is @code{BITS_PER_UNIT}, but may be larger | |
965 | on machines that don't have byte or half-word store operations. | |
966 | ||
feca2ed3 JW |
967 | @findex BIGGEST_FIELD_ALIGNMENT |
968 | @item BIGGEST_FIELD_ALIGNMENT | |
11cf4d18 JJ |
969 | Biggest alignment that any structure or union field can require on this |
970 | machine, in bits. If defined, this overrides @code{BIGGEST_ALIGNMENT} for | |
971 | structure and union fields only, unless the field alignment has been set | |
972 | by the @code{__attribute__ ((aligned (@var{n})))} construct. | |
feca2ed3 JW |
973 | |
974 | @findex ADJUST_FIELD_ALIGN | |
975 | @item ADJUST_FIELD_ALIGN (@var{field}, @var{computed}) | |
976 | An expression for the alignment of a structure field @var{field} if the | |
a3a15b4d | 977 | alignment computed in the usual way is @var{computed}. GCC uses |
feca2ed3 JW |
978 | this value instead of the value in @code{BIGGEST_ALIGNMENT} or |
979 | @code{BIGGEST_FIELD_ALIGNMENT}, if defined, for structure fields only. | |
980 | ||
981 | @findex MAX_OFILE_ALIGNMENT | |
982 | @item MAX_OFILE_ALIGNMENT | |
983 | Biggest alignment supported by the object file format of this machine. | |
984 | Use this macro to limit the alignment which can be specified using the | |
985 | @code{__attribute__ ((aligned (@var{n})))} construct. If not defined, | |
986 | the default value is @code{BIGGEST_ALIGNMENT}. | |
987 | ||
988 | @findex DATA_ALIGNMENT | |
989 | @item DATA_ALIGNMENT (@var{type}, @var{basic-align}) | |
a8d1550a | 990 | If defined, a C expression to compute the alignment for a variable in |
8a198bd2 JW |
991 | the static store. @var{type} is the data type, and @var{basic-align} is |
992 | the alignment that the object would ordinarily have. The value of this | |
feca2ed3 JW |
993 | macro is used instead of that alignment to align the object. |
994 | ||
995 | If this macro is not defined, then @var{basic-align} is used. | |
996 | ||
997 | @findex strcpy | |
998 | One use of this macro is to increase alignment of medium-size data to | |
999 | make it all fit in fewer cache lines. Another is to cause character | |
1000 | arrays to be word-aligned so that @code{strcpy} calls that copy | |
1001 | constants to character arrays can be done inline. | |
1002 | ||
1003 | @findex CONSTANT_ALIGNMENT | |
1004 | @item CONSTANT_ALIGNMENT (@var{constant}, @var{basic-align}) | |
1005 | If defined, a C expression to compute the alignment given to a constant | |
1006 | that is being placed in memory. @var{constant} is the constant and | |
1007 | @var{basic-align} is the alignment that the object would ordinarily | |
1008 | have. The value of this macro is used instead of that alignment to | |
1009 | align the object. | |
1010 | ||
1011 | If this macro is not defined, then @var{basic-align} is used. | |
1012 | ||
1013 | The typical use of this macro is to increase alignment for string | |
1014 | constants to be word aligned so that @code{strcpy} calls that copy | |
1015 | constants can be done inline. | |
1016 | ||
d16790f2 JW |
1017 | @findex LOCAL_ALIGNMENT |
1018 | @item LOCAL_ALIGNMENT (@var{type}, @var{basic-align}) | |
a8d1550a | 1019 | If defined, a C expression to compute the alignment for a variable in |
d16790f2 JW |
1020 | the local 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 | One use of this macro is to increase alignment of medium-size data to | |
1027 | make it all fit in fewer cache lines. | |
1028 | ||
feca2ed3 JW |
1029 | @findex EMPTY_FIELD_BOUNDARY |
1030 | @item EMPTY_FIELD_BOUNDARY | |
1031 | Alignment in bits to be given to a structure bit field that follows an | |
1032 | empty field such as @code{int : 0;}. | |
1033 | ||
1034 | Note that @code{PCC_BITFIELD_TYPE_MATTERS} also affects the alignment | |
1035 | that results from an empty field. | |
1036 | ||
1037 | @findex STRUCTURE_SIZE_BOUNDARY | |
1038 | @item STRUCTURE_SIZE_BOUNDARY | |
1039 | Number of bits which any structure or union's size must be a multiple of. | |
1040 | Each structure or union's size is rounded up to a multiple of this. | |
1041 | ||
1042 | If you do not define this macro, the default is the same as | |
1043 | @code{BITS_PER_UNIT}. | |
1044 | ||
1045 | @findex STRICT_ALIGNMENT | |
1046 | @item STRICT_ALIGNMENT | |
1047 | Define this macro to be the value 1 if instructions will fail to work | |
1048 | if given data not on the nominal alignment. If instructions will merely | |
1049 | go slower in that case, define this macro as 0. | |
1050 | ||
1051 | @findex PCC_BITFIELD_TYPE_MATTERS | |
1052 | @item PCC_BITFIELD_TYPE_MATTERS | |
1053 | Define this if you wish to imitate the way many other C compilers handle | |
1054 | alignment of bitfields and the structures that contain them. | |
1055 | ||
1056 | The behavior is that the type written for a bitfield (@code{int}, | |
1057 | @code{short}, or other integer type) imposes an alignment for the | |
1058 | entire structure, as if the structure really did contain an ordinary | |
1059 | field of that type. In addition, the bitfield is placed within the | |
1060 | structure so that it would fit within such a field, not crossing a | |
1061 | boundary for it. | |
1062 | ||
1063 | Thus, on most machines, a bitfield whose type is written as @code{int} | |
1064 | would not cross a four-byte boundary, and would force four-byte | |
1065 | alignment for the whole structure. (The alignment used may not be four | |
1066 | bytes; it is controlled by the other alignment parameters.) | |
1067 | ||
1068 | If the macro is defined, its definition should be a C expression; | |
1069 | a nonzero value for the expression enables this behavior. | |
1070 | ||
1071 | Note that if this macro is not defined, or its value is zero, some | |
1072 | bitfields may cross more than one alignment boundary. The compiler can | |
1073 | support such references if there are @samp{insv}, @samp{extv}, and | |
1074 | @samp{extzv} insns that can directly reference memory. | |
1075 | ||
1076 | The other known way of making bitfields work is to define | |
1077 | @code{STRUCTURE_SIZE_BOUNDARY} as large as @code{BIGGEST_ALIGNMENT}. | |
1078 | Then every structure can be accessed with fullwords. | |
1079 | ||
1080 | Unless the machine has bitfield instructions or you define | |
1081 | @code{STRUCTURE_SIZE_BOUNDARY} that way, you must define | |
1082 | @code{PCC_BITFIELD_TYPE_MATTERS} to have a nonzero value. | |
1083 | ||
a3a15b4d | 1084 | If your aim is to make GCC use the same conventions for laying out |
feca2ed3 JW |
1085 | bitfields as are used by another compiler, here is how to investigate |
1086 | what the other compiler does. Compile and run this program: | |
1087 | ||
1088 | @example | |
1089 | struct foo1 | |
1090 | @{ | |
1091 | char x; | |
1092 | char :0; | |
1093 | char y; | |
1094 | @}; | |
1095 | ||
1096 | struct foo2 | |
1097 | @{ | |
1098 | char x; | |
1099 | int :0; | |
1100 | char y; | |
1101 | @}; | |
1102 | ||
1103 | main () | |
1104 | @{ | |
1105 | printf ("Size of foo1 is %d\n", | |
1106 | sizeof (struct foo1)); | |
1107 | printf ("Size of foo2 is %d\n", | |
1108 | sizeof (struct foo2)); | |
1109 | exit (0); | |
1110 | @} | |
1111 | @end example | |
1112 | ||
1113 | If this prints 2 and 5, then the compiler's behavior is what you would | |
1114 | get from @code{PCC_BITFIELD_TYPE_MATTERS}. | |
1115 | ||
1116 | @findex BITFIELD_NBYTES_LIMITED | |
1117 | @item BITFIELD_NBYTES_LIMITED | |
1118 | Like PCC_BITFIELD_TYPE_MATTERS except that its effect is limited to | |
1119 | aligning a bitfield within the structure. | |
1120 | ||
31a02448 R |
1121 | @findex MEMBER_TYPE_FORCES_BLK |
1122 | @item MEMBER_TYPE_FORCES_BLK (@var{field}) | |
1123 | Return 1 if a structure or array containing @var{field} should be accessed using | |
9f6dc500 HPN |
1124 | @code{BLKMODE}. |
1125 | ||
1126 | Normally, this is not needed. See the file @file{c4x.h} for an example | |
1127 | of how to use this macro to prevent a structure having a floating point | |
1128 | field from being accessed in an integer mode. | |
1129 | ||
feca2ed3 | 1130 | @findex ROUND_TYPE_SIZE |
0003feb2 VM |
1131 | @item ROUND_TYPE_SIZE (@var{type}, @var{computed}, @var{specified}) |
1132 | Define this macro as an expression for the overall size of a type | |
1133 | (given by @var{type} as a tree node) when the size computed in the | |
1134 | usual way is @var{computed} and the alignment is @var{specified}. | |
feca2ed3 | 1135 | |
0003feb2 | 1136 | The default is to round @var{computed} up to a multiple of @var{specified}. |
feca2ed3 | 1137 | |
fed3cef0 RK |
1138 | @findex ROUND_TYPE_SIZE_UNIT |
1139 | @item ROUND_TYPE_SIZE_UNIT (@var{type}, @var{computed}, @var{specified}) | |
1140 | Similar to @code{ROUND_TYPE_SIZE}, but sizes and alignments are | |
1141 | specified in units (bytes). If you define @code{ROUND_TYPE_SIZE}, | |
1142 | you must also define this macro and they must be defined consistently | |
1143 | with each other. | |
1144 | ||
feca2ed3 | 1145 | @findex ROUND_TYPE_ALIGN |
0003feb2 VM |
1146 | @item ROUND_TYPE_ALIGN (@var{type}, @var{computed}, @var{specified}) |
1147 | Define this macro as an expression for the alignment of a type (given | |
1148 | by @var{type} as a tree node) if the alignment computed in the usual | |
1149 | way is @var{computed} and the alignment explicitly specified was | |
feca2ed3 JW |
1150 | @var{specified}. |
1151 | ||
1152 | The default is to use @var{specified} if it is larger; otherwise, use | |
1153 | the smaller of @var{computed} and @code{BIGGEST_ALIGNMENT} | |
1154 | ||
1155 | @findex MAX_FIXED_MODE_SIZE | |
1156 | @item MAX_FIXED_MODE_SIZE | |
1157 | An integer expression for the size in bits of the largest integer | |
1158 | machine mode that should actually be used. All integer machine modes of | |
1159 | this size or smaller can be used for structures and unions with the | |
1160 | appropriate sizes. If this macro is undefined, @code{GET_MODE_BITSIZE | |
1161 | (DImode)} is assumed. | |
1162 | ||
4061f623 BS |
1163 | @findex VECTOR_MODE_SUPPORTED_P |
1164 | @item VECTOR_MODE_SUPPORTED_P(@var{mode}) | |
1165 | Define this macro to be nonzero if the port is prepared to handle insns | |
1166 | involving vector mode @var{mode}. At the very least, it must have move | |
1167 | patterns for this mode. | |
1168 | ||
73c8090f DE |
1169 | @findex STACK_SAVEAREA_MODE |
1170 | @item STACK_SAVEAREA_MODE (@var{save_level}) | |
1171 | If defined, an expression of type @code{enum machine_mode} that | |
39403d82 DE |
1172 | specifies the mode of the save area operand of a |
1173 | @code{save_stack_@var{level}} named pattern (@pxref{Standard Names}). | |
1174 | @var{save_level} is one of @code{SAVE_BLOCK}, @code{SAVE_FUNCTION}, or | |
1175 | @code{SAVE_NONLOCAL} and selects which of the three named patterns is | |
1176 | having its mode specified. | |
73c8090f DE |
1177 | |
1178 | You need not define this macro if it always returns @code{Pmode}. You | |
1179 | would most commonly define this macro if the | |
1180 | @code{save_stack_@var{level}} patterns need to support both a 32- and a | |
1181 | 64-bit mode. | |
1182 | ||
39403d82 DE |
1183 | @findex STACK_SIZE_MODE |
1184 | @item STACK_SIZE_MODE | |
1185 | If defined, an expression of type @code{enum machine_mode} that | |
1186 | specifies the mode of the size increment operand of an | |
1187 | @code{allocate_stack} named pattern (@pxref{Standard Names}). | |
1188 | ||
1189 | You need not define this macro if it always returns @code{word_mode}. | |
1190 | You would most commonly define this macro if the @code{allocate_stack} | |
1191 | pattern needs to support both a 32- and a 64-bit mode. | |
1192 | ||
feca2ed3 JW |
1193 | @findex CHECK_FLOAT_VALUE |
1194 | @item CHECK_FLOAT_VALUE (@var{mode}, @var{value}, @var{overflow}) | |
1195 | A C statement to validate the value @var{value} (of type | |
1196 | @code{double}) for mode @var{mode}. This means that you check whether | |
1197 | @var{value} fits within the possible range of values for mode | |
1198 | @var{mode} on this target machine. The mode @var{mode} is always | |
1199 | a mode of class @code{MODE_FLOAT}. @var{overflow} is nonzero if | |
1200 | the value is already known to be out of range. | |
1201 | ||
1202 | If @var{value} is not valid or if @var{overflow} is nonzero, you should | |
1203 | set @var{overflow} to 1 and then assign some valid value to @var{value}. | |
1204 | Allowing an invalid value to go through the compiler can produce | |
1205 | incorrect assembler code which may even cause Unix assemblers to crash. | |
1206 | ||
1207 | This macro need not be defined if there is no work for it to do. | |
1208 | ||
1209 | @findex TARGET_FLOAT_FORMAT | |
1210 | @item TARGET_FLOAT_FORMAT | |
1211 | A code distinguishing the floating point format of the target machine. | |
1212 | There are three defined values: | |
1213 | ||
1214 | @table @code | |
1215 | @findex IEEE_FLOAT_FORMAT | |
1216 | @item IEEE_FLOAT_FORMAT | |
1217 | This code indicates IEEE floating point. It is the default; there is no | |
1218 | need to define this macro when the format is IEEE. | |
1219 | ||
1220 | @findex VAX_FLOAT_FORMAT | |
1221 | @item VAX_FLOAT_FORMAT | |
1222 | This code indicates the peculiar format used on the Vax. | |
1223 | ||
1224 | @findex UNKNOWN_FLOAT_FORMAT | |
1225 | @item UNKNOWN_FLOAT_FORMAT | |
1226 | This code indicates any other format. | |
1227 | @end table | |
1228 | ||
1229 | The value of this macro is compared with @code{HOST_FLOAT_FORMAT} | |
1230 | (@pxref{Config}) to determine whether the target machine has the same | |
1231 | format as the host machine. If any other formats are actually in use on | |
1232 | supported machines, new codes should be defined for them. | |
1233 | ||
1234 | The ordering of the component words of floating point values stored in | |
1235 | memory is controlled by @code{FLOAT_WORDS_BIG_ENDIAN} for the target | |
1236 | machine and @code{HOST_FLOAT_WORDS_BIG_ENDIAN} for the host. | |
e9a25f70 JL |
1237 | |
1238 | @findex DEFAULT_VTABLE_THUNKS | |
1239 | @item DEFAULT_VTABLE_THUNKS | |
a3a15b4d | 1240 | GCC supports two ways of implementing C++ vtables: traditional or with |
e9a25f70 JL |
1241 | so-called ``thunks''. The flag @samp{-fvtable-thunk} chooses between them. |
1242 | Define this macro to be a C expression for the default value of that flag. | |
a3a15b4d | 1243 | If @code{DEFAULT_VTABLE_THUNKS} is 0, GCC uses the traditional |
e9a25f70 JL |
1244 | implementation by default. The ``thunk'' implementation is more efficient |
1245 | (especially if you have provided an implementation of | |
1246 | @code{ASM_OUTPUT_MI_THUNK}, see @ref{Function Entry}), but is not binary | |
1247 | compatible with code compiled using the traditional implementation. | |
89bcce1b | 1248 | If you are writing a new port, define @code{DEFAULT_VTABLE_THUNKS} to 1. |
e9a25f70 JL |
1249 | |
1250 | If you do not define this macro, the default for @samp{-fvtable-thunk} is 0. | |
feca2ed3 JW |
1251 | @end table |
1252 | ||
1253 | @node Type Layout | |
1254 | @section Layout of Source Language Data Types | |
1255 | ||
1256 | These macros define the sizes and other characteristics of the standard | |
1257 | basic data types used in programs being compiled. Unlike the macros in | |
1258 | the previous section, these apply to specific features of C and related | |
1259 | languages, rather than to fundamental aspects of storage layout. | |
1260 | ||
1261 | @table @code | |
1262 | @findex INT_TYPE_SIZE | |
1263 | @item INT_TYPE_SIZE | |
1264 | A C expression for the size in bits of the type @code{int} on the | |
1265 | target machine. If you don't define this, the default is one word. | |
1266 | ||
1267 | @findex MAX_INT_TYPE_SIZE | |
1268 | @item MAX_INT_TYPE_SIZE | |
1269 | Maximum number for the size in bits of the type @code{int} on the target | |
1270 | machine. If this is undefined, the default is @code{INT_TYPE_SIZE}. | |
1271 | Otherwise, it is the constant value that is the largest value that | |
1272 | @code{INT_TYPE_SIZE} can have at run-time. This is used in @code{cpp}. | |
1273 | ||
1274 | @findex SHORT_TYPE_SIZE | |
1275 | @item SHORT_TYPE_SIZE | |
1276 | A C expression for the size in bits of the type @code{short} on the | |
1277 | target machine. If you don't define this, the default is half a word. | |
1278 | (If this would be less than one storage unit, it is rounded up to one | |
1279 | unit.) | |
1280 | ||
1281 | @findex LONG_TYPE_SIZE | |
1282 | @item LONG_TYPE_SIZE | |
1283 | A C expression for the size in bits of the type @code{long} on the | |
1284 | target machine. If you don't define this, the default is one word. | |
1285 | ||
1286 | @findex MAX_LONG_TYPE_SIZE | |
1287 | @item MAX_LONG_TYPE_SIZE | |
1288 | Maximum number for the size in bits of the type @code{long} on the | |
1289 | target machine. If this is undefined, the default is | |
1290 | @code{LONG_TYPE_SIZE}. Otherwise, it is the constant value that is the | |
1291 | largest value that @code{LONG_TYPE_SIZE} can have at run-time. This is | |
1292 | used in @code{cpp}. | |
1293 | ||
1294 | @findex LONG_LONG_TYPE_SIZE | |
1295 | @item LONG_LONG_TYPE_SIZE | |
1296 | A C expression for the size in bits of the type @code{long long} on the | |
1297 | target machine. If you don't define this, the default is two | |
047c1c92 | 1298 | words. If you want to support GNU Ada on your machine, the value of this |
feca2ed3 JW |
1299 | macro must be at least 64. |
1300 | ||
1301 | @findex CHAR_TYPE_SIZE | |
1302 | @item CHAR_TYPE_SIZE | |
1303 | A C expression for the size in bits of the type @code{char} on the | |
c294bd99 HPN |
1304 | target machine. If you don't define this, the default is |
1305 | @code{BITS_PER_UNIT}. | |
feca2ed3 JW |
1306 | |
1307 | @findex MAX_CHAR_TYPE_SIZE | |
1308 | @item MAX_CHAR_TYPE_SIZE | |
1309 | Maximum number for the size in bits of the type @code{char} on the | |
1310 | target machine. If this is undefined, the default is | |
1311 | @code{CHAR_TYPE_SIZE}. Otherwise, it is the constant value that is the | |
1312 | largest value that @code{CHAR_TYPE_SIZE} can have at run-time. This is | |
1313 | used in @code{cpp}. | |
1314 | ||
1315 | @findex FLOAT_TYPE_SIZE | |
1316 | @item FLOAT_TYPE_SIZE | |
1317 | A C expression for the size in bits of the type @code{float} on the | |
1318 | target machine. If you don't define this, the default is one word. | |
1319 | ||
1320 | @findex DOUBLE_TYPE_SIZE | |
1321 | @item DOUBLE_TYPE_SIZE | |
1322 | A C expression for the size in bits of the type @code{double} on the | |
1323 | target machine. If you don't define this, the default is two | |
1324 | words. | |
1325 | ||
1326 | @findex LONG_DOUBLE_TYPE_SIZE | |
1327 | @item LONG_DOUBLE_TYPE_SIZE | |
1328 | A C expression for the size in bits of the type @code{long double} on | |
1329 | the target machine. If you don't define this, the default is two | |
1330 | words. | |
1331 | ||
e9a25f70 JL |
1332 | @findex WIDEST_HARDWARE_FP_SIZE |
1333 | @item WIDEST_HARDWARE_FP_SIZE | |
1334 | A C expression for the size in bits of the widest floating-point format | |
1335 | supported by the hardware. If you define this macro, you must specify a | |
1336 | value less than or equal to the value of @code{LONG_DOUBLE_TYPE_SIZE}. | |
1337 | If you do not define this macro, the value of @code{LONG_DOUBLE_TYPE_SIZE} | |
1338 | is the default. | |
1339 | ||
feca2ed3 JW |
1340 | @findex DEFAULT_SIGNED_CHAR |
1341 | @item DEFAULT_SIGNED_CHAR | |
1342 | An expression whose value is 1 or 0, according to whether the type | |
1343 | @code{char} should be signed or unsigned by default. The user can | |
1344 | always override this default with the options @samp{-fsigned-char} | |
1345 | and @samp{-funsigned-char}. | |
1346 | ||
1347 | @findex DEFAULT_SHORT_ENUMS | |
1348 | @item DEFAULT_SHORT_ENUMS | |
1349 | A C expression to determine whether to give an @code{enum} type | |
1350 | only as many bytes as it takes to represent the range of possible values | |
1351 | of that type. A nonzero value means to do that; a zero value means all | |
1352 | @code{enum} types should be allocated like @code{int}. | |
1353 | ||
1354 | If you don't define the macro, the default is 0. | |
1355 | ||
1356 | @findex SIZE_TYPE | |
1357 | @item SIZE_TYPE | |
1358 | A C expression for a string describing the name of the data type to use | |
1359 | for size values. The typedef name @code{size_t} is defined using the | |
1360 | contents of the string. | |
1361 | ||
1362 | The string can contain more than one keyword. If so, separate them with | |
1363 | spaces, and write first any length keyword, then @code{unsigned} if | |
1364 | appropriate, and finally @code{int}. The string must exactly match one | |
1365 | of the data type names defined in the function | |
1366 | @code{init_decl_processing} in the file @file{c-decl.c}. You may not | |
1367 | omit @code{int} or change the order---that would cause the compiler to | |
1368 | crash on startup. | |
1369 | ||
1370 | If you don't define this macro, the default is @code{"long unsigned | |
1371 | int"}. | |
1372 | ||
1373 | @findex PTRDIFF_TYPE | |
1374 | @item PTRDIFF_TYPE | |
1375 | A C expression for a string describing the name of the data type to use | |
1376 | for the result of subtracting two pointers. The typedef name | |
1377 | @code{ptrdiff_t} is defined using the contents of the string. See | |
1378 | @code{SIZE_TYPE} above for more information. | |
1379 | ||
1380 | If you don't define this macro, the default is @code{"long int"}. | |
1381 | ||
1382 | @findex WCHAR_TYPE | |
1383 | @item WCHAR_TYPE | |
1384 | A C expression for a string describing the name of the data type to use | |
1385 | for wide characters. The typedef name @code{wchar_t} is defined using | |
1386 | the contents of the string. See @code{SIZE_TYPE} above for more | |
1387 | information. | |
1388 | ||
1389 | If you don't define this macro, the default is @code{"int"}. | |
1390 | ||
1391 | @findex WCHAR_TYPE_SIZE | |
1392 | @item WCHAR_TYPE_SIZE | |
1393 | A C expression for the size in bits of the data type for wide | |
1394 | characters. This is used in @code{cpp}, which cannot make use of | |
1395 | @code{WCHAR_TYPE}. | |
1396 | ||
1397 | @findex MAX_WCHAR_TYPE_SIZE | |
1398 | @item MAX_WCHAR_TYPE_SIZE | |
1399 | Maximum number for the size in bits of the data type for wide | |
1400 | characters. If this is undefined, the default is | |
1401 | @code{WCHAR_TYPE_SIZE}. Otherwise, it is the constant value that is the | |
1402 | largest value that @code{WCHAR_TYPE_SIZE} can have at run-time. This is | |
1403 | used in @code{cpp}. | |
1404 | ||
1a67c7d3 JL |
1405 | @findex WINT_TYPE |
1406 | @item WINT_TYPE | |
1407 | A C expression for a string describing the name of the data type to | |
1408 | use for wide characters passed to @code{printf} and returned from | |
1409 | @code{getwc}. The typedef name @code{wint_t} is defined using the | |
1410 | contents of the string. See @code{SIZE_TYPE} above for more | |
1411 | information. | |
1412 | ||
1413 | If you don't define this macro, the default is @code{"unsigned int"}. | |
1414 | ||
b15ad712 JM |
1415 | @findex INTMAX_TYPE |
1416 | @item INTMAX_TYPE | |
1417 | A C expression for a string describing the name of the data type that | |
1418 | can represent any value of any standard or extended signed integer type. | |
1419 | The typedef name @code{intmax_t} is defined using the contents of the | |
1420 | string. See @code{SIZE_TYPE} above for more information. | |
1421 | ||
1422 | If you don't define this macro, the default is the first of | |
1423 | @code{"int"}, @code{"long int"}, or @code{"long long int"} that has as | |
1424 | much precision as @code{long long int}. | |
1425 | ||
1426 | @findex UINTMAX_TYPE | |
1427 | @item UINTMAX_TYPE | |
1428 | A C expression for a string describing the name of the data type that | |
1429 | can represent any value of any standard or extended unsigned integer | |
1430 | type. The typedef name @code{uintmax_t} is defined using the contents | |
1431 | of the string. See @code{SIZE_TYPE} above for more information. | |
1432 | ||
1433 | If you don't define this macro, the default is the first of | |
1434 | @code{"unsigned int"}, @code{"long unsigned int"}, or @code{"long long | |
1435 | unsigned int"} that has as much precision as @code{long long unsigned | |
1436 | int}. | |
1437 | ||
feca2ed3 JW |
1438 | @findex OBJC_INT_SELECTORS |
1439 | @item OBJC_INT_SELECTORS | |
1440 | Define this macro if the type of Objective C selectors should be | |
1441 | @code{int}. | |
1442 | ||
1443 | If this macro is not defined, then selectors should have the type | |
1444 | @code{struct objc_selector *}. | |
1445 | ||
1446 | @findex OBJC_SELECTORS_WITHOUT_LABELS | |
1447 | @item OBJC_SELECTORS_WITHOUT_LABELS | |
1448 | Define this macro if the compiler can group all the selectors together | |
1449 | into a vector and use just one label at the beginning of the vector. | |
1450 | Otherwise, the compiler must give each selector its own assembler | |
1451 | label. | |
1452 | ||
1453 | On certain machines, it is important to have a separate label for each | |
1454 | selector because this enables the linker to eliminate duplicate selectors. | |
1455 | ||
1456 | @findex TARGET_BELL | |
1457 | @item TARGET_BELL | |
1458 | A C constant expression for the integer value for escape sequence | |
1459 | @samp{\a}. | |
1460 | ||
1461 | @findex TARGET_TAB | |
1462 | @findex TARGET_BS | |
1463 | @findex TARGET_NEWLINE | |
1464 | @item TARGET_BS | |
1465 | @itemx TARGET_TAB | |
1466 | @itemx TARGET_NEWLINE | |
1467 | C constant expressions for the integer values for escape sequences | |
1468 | @samp{\b}, @samp{\t} and @samp{\n}. | |
1469 | ||
1470 | @findex TARGET_VT | |
1471 | @findex TARGET_FF | |
1472 | @findex TARGET_CR | |
1473 | @item TARGET_VT | |
1474 | @itemx TARGET_FF | |
1475 | @itemx TARGET_CR | |
1476 | C constant expressions for the integer values for escape sequences | |
1477 | @samp{\v}, @samp{\f} and @samp{\r}. | |
1478 | @end table | |
1479 | ||
1480 | @node Registers | |
1481 | @section Register Usage | |
1482 | @cindex register usage | |
1483 | ||
1484 | This section explains how to describe what registers the target machine | |
1485 | has, and how (in general) they can be used. | |
1486 | ||
1487 | The description of which registers a specific instruction can use is | |
1488 | done with register classes; see @ref{Register Classes}. For information | |
1489 | on using registers to access a stack frame, see @ref{Frame Registers}. | |
1490 | For passing values in registers, see @ref{Register Arguments}. | |
1491 | For returning values in registers, see @ref{Scalar Return}. | |
1492 | ||
1493 | @menu | |
1494 | * Register Basics:: Number and kinds of registers. | |
1495 | * Allocation Order:: Order in which registers are allocated. | |
1496 | * Values in Registers:: What kinds of values each reg can hold. | |
1497 | * Leaf Functions:: Renumbering registers for leaf functions. | |
1498 | * Stack Registers:: Handling a register stack such as 80387. | |
feca2ed3 JW |
1499 | @end menu |
1500 | ||
1501 | @node Register Basics | |
1502 | @subsection Basic Characteristics of Registers | |
1503 | ||
1504 | @c prevent bad page break with this line | |
1505 | Registers have various characteristics. | |
1506 | ||
1507 | @table @code | |
1508 | @findex FIRST_PSEUDO_REGISTER | |
1509 | @item FIRST_PSEUDO_REGISTER | |
1510 | Number of hardware registers known to the compiler. They receive | |
1511 | numbers 0 through @code{FIRST_PSEUDO_REGISTER-1}; thus, the first | |
1512 | pseudo register's number really is assigned the number | |
1513 | @code{FIRST_PSEUDO_REGISTER}. | |
1514 | ||
1515 | @item FIXED_REGISTERS | |
1516 | @findex FIXED_REGISTERS | |
1517 | @cindex fixed register | |
1518 | An initializer that says which registers are used for fixed purposes | |
1519 | all throughout the compiled code and are therefore not available for | |
1520 | general allocation. These would include the stack pointer, the frame | |
1521 | pointer (except on machines where that can be used as a general | |
1522 | register when no frame pointer is needed), the program counter on | |
1523 | machines where that is considered one of the addressable registers, | |
1524 | and any other numbered register with a standard use. | |
1525 | ||
1526 | This information is expressed as a sequence of numbers, separated by | |
1527 | commas and surrounded by braces. The @var{n}th number is 1 if | |
1528 | register @var{n} is fixed, 0 otherwise. | |
1529 | ||
1530 | The table initialized from this macro, and the table initialized by | |
1531 | the following one, may be overridden at run time either automatically, | |
1532 | by the actions of the macro @code{CONDITIONAL_REGISTER_USAGE}, or by | |
1533 | the user with the command options @samp{-ffixed-@var{reg}}, | |
1534 | @samp{-fcall-used-@var{reg}} and @samp{-fcall-saved-@var{reg}}. | |
1535 | ||
1536 | @findex CALL_USED_REGISTERS | |
1537 | @item CALL_USED_REGISTERS | |
1538 | @cindex call-used register | |
1539 | @cindex call-clobbered register | |
1540 | @cindex call-saved register | |
1541 | Like @code{FIXED_REGISTERS} but has 1 for each register that is | |
1542 | clobbered (in general) by function calls as well as for fixed | |
1543 | registers. This macro therefore identifies the registers that are not | |
1544 | available for general allocation of values that must live across | |
1545 | function calls. | |
1546 | ||
1547 | If a register has 0 in @code{CALL_USED_REGISTERS}, the compiler | |
1548 | automatically saves it on function entry and restores it on function | |
1549 | exit, if the register is used within the function. | |
1550 | ||
1e326708 MH |
1551 | @findex HARD_REGNO_CALL_PART_CLOBBERED |
1552 | @item HARD_REGNO_CALL_PART_CLOBBERED (@var{regno}, @var{mode}) | |
1553 | @cindex call-used register | |
1554 | @cindex call-clobbered register | |
1555 | @cindex call-saved register | |
1556 | A C expression that is non-zero if it is not permissible to store a | |
1557 | value of mode @var{mode} in hard register number @var{regno} across a | |
1558 | call without some part of it being clobbered. For most machines this | |
1559 | macro need not be defined. It is only required for machines that do not | |
1560 | preserve the entire contents of a register across a call. | |
1561 | ||
feca2ed3 JW |
1562 | @findex CONDITIONAL_REGISTER_USAGE |
1563 | @findex fixed_regs | |
1564 | @findex call_used_regs | |
1565 | @item CONDITIONAL_REGISTER_USAGE | |
055177dc NC |
1566 | Zero or more C statements that may conditionally modify five variables |
1567 | @code{fixed_regs}, @code{call_used_regs}, @code{global_regs}, | |
1568 | (these three are of type @code{char []}), @code{reg_names} (of type | |
1569 | @code{const char * []}) and @code{reg_class_contents} (of type | |
1570 | @code{HARD_REG_SET}). | |
910bc42d | 1571 | Before the macro is called @code{fixed_regs}, @code{call_used_regs} |
055177dc NC |
1572 | @code{reg_class_contents} and @code{reg_names} have been initialized |
1573 | from @code{FIXED_REGISTERS}, @code{CALL_USED_REGISTERS}, | |
1574 | @code{REG_CLASS_CONTENTS} and @code{REGISTER_NAMES}, respectively, | |
910bc42d R |
1575 | @code{global_regs} has been cleared, and any @samp{-ffixed-@var{reg}}, |
1576 | @samp{-fcall-used-@var{reg}} and @samp{-fcall-saved-@var{reg}} command | |
1577 | options have been applied. | |
feca2ed3 JW |
1578 | |
1579 | This is necessary in case the fixed or call-clobbered registers depend | |
1580 | on target flags. | |
1581 | ||
1582 | You need not define this macro if it has no work to do. | |
1583 | ||
1584 | @cindex disabling certain registers | |
1585 | @cindex controlling register usage | |
1586 | If the usage of an entire class of registers depends on the target | |
1587 | flags, you may indicate this to GCC by using this macro to modify | |
1588 | @code{fixed_regs} and @code{call_used_regs} to 1 for each of the | |
1589 | registers in the classes which should not be used by GCC. Also define | |
1590 | the macro @code{REG_CLASS_FROM_LETTER} to return @code{NO_REGS} if it | |
1591 | is called with a letter for a class that shouldn't be used. | |
1592 | ||
1593 | (However, if this class is not included in @code{GENERAL_REGS} and all | |
1594 | of the insn patterns whose constraints permit this class are | |
1595 | controlled by target switches, then GCC will automatically avoid using | |
1596 | these registers when the target switches are opposed to them.) | |
1597 | ||
1598 | @findex NON_SAVING_SETJMP | |
1599 | @item NON_SAVING_SETJMP | |
1600 | If this macro is defined and has a nonzero value, it means that | |
1601 | @code{setjmp} and related functions fail to save the registers, or that | |
1602 | @code{longjmp} fails to restore them. To compensate, the compiler | |
1603 | avoids putting variables in registers in functions that use | |
1604 | @code{setjmp}. | |
1605 | ||
1606 | @findex INCOMING_REGNO | |
1607 | @item INCOMING_REGNO (@var{out}) | |
1608 | Define this macro if the target machine has register windows. This C | |
1609 | expression returns the register number as seen by the called function | |
1610 | corresponding to the register number @var{out} as seen by the calling | |
1611 | function. Return @var{out} if register number @var{out} is not an | |
1612 | outbound register. | |
1613 | ||
1614 | @findex OUTGOING_REGNO | |
1615 | @item OUTGOING_REGNO (@var{in}) | |
1616 | Define this macro if the target machine has register windows. This C | |
1617 | expression returns the register number as seen by the calling function | |
1618 | corresponding to the register number @var{in} as seen by the called | |
1619 | function. Return @var{in} if register number @var{in} is not an inbound | |
1620 | register. | |
1621 | ||
fa80e43d JL |
1622 | @findex LOCAL_REGNO |
1623 | @item LOCAL_REGNO (@var{regno}) | |
1624 | Define this macro if the target machine has register windows. This C | |
1625 | expression returns true if the register is call-saved but is in the | |
1626 | register window. Unlike most call-saved registers, such registers | |
1627 | need not be explicitly restored on function exit or during non-local | |
1628 | gotos. | |
1629 | ||
feca2ed3 JW |
1630 | @ignore |
1631 | @findex PC_REGNUM | |
1632 | @item PC_REGNUM | |
1633 | If the program counter has a register number, define this as that | |
1634 | register number. Otherwise, do not define it. | |
1635 | @end ignore | |
1636 | @end table | |
1637 | ||
1638 | @node Allocation Order | |
1639 | @subsection Order of Allocation of Registers | |
1640 | @cindex order of register allocation | |
1641 | @cindex register allocation order | |
1642 | ||
1643 | @c prevent bad page break with this line | |
1644 | Registers are allocated in order. | |
1645 | ||
1646 | @table @code | |
1647 | @findex REG_ALLOC_ORDER | |
1648 | @item REG_ALLOC_ORDER | |
1649 | If defined, an initializer for a vector of integers, containing the | |
a3a15b4d | 1650 | numbers of hard registers in the order in which GCC should prefer |
feca2ed3 JW |
1651 | to use them (from most preferred to least). |
1652 | ||
1653 | If this macro is not defined, registers are used lowest numbered first | |
1654 | (all else being equal). | |
1655 | ||
1656 | One use of this macro is on machines where the highest numbered | |
1657 | registers must always be saved and the save-multiple-registers | |
1658 | instruction supports only sequences of consecutive registers. On such | |
1659 | machines, define @code{REG_ALLOC_ORDER} to be an initializer that lists | |
956d6950 | 1660 | the highest numbered allocable register first. |
feca2ed3 JW |
1661 | |
1662 | @findex ORDER_REGS_FOR_LOCAL_ALLOC | |
1663 | @item ORDER_REGS_FOR_LOCAL_ALLOC | |
1664 | A C statement (sans semicolon) to choose the order in which to allocate | |
1665 | hard registers for pseudo-registers local to a basic block. | |
1666 | ||
1667 | Store the desired register order in the array @code{reg_alloc_order}. | |
1668 | Element 0 should be the register to allocate first; element 1, the next | |
1669 | register; and so on. | |
1670 | ||
1671 | The macro body should not assume anything about the contents of | |
1672 | @code{reg_alloc_order} before execution of the macro. | |
1673 | ||
1674 | On most machines, it is not necessary to define this macro. | |
1675 | @end table | |
1676 | ||
1677 | @node Values in Registers | |
1678 | @subsection How Values Fit in Registers | |
1679 | ||
1680 | This section discusses the macros that describe which kinds of values | |
1681 | (specifically, which machine modes) each register can hold, and how many | |
1682 | consecutive registers are needed for a given mode. | |
1683 | ||
1684 | @table @code | |
1685 | @findex HARD_REGNO_NREGS | |
1686 | @item HARD_REGNO_NREGS (@var{regno}, @var{mode}) | |
1687 | A C expression for the number of consecutive hard registers, starting | |
1688 | at register number @var{regno}, required to hold a value of mode | |
1689 | @var{mode}. | |
1690 | ||
1691 | On a machine where all registers are exactly one word, a suitable | |
1692 | definition of this macro is | |
1693 | ||
1694 | @smallexample | |
1695 | #define HARD_REGNO_NREGS(REGNO, MODE) \ | |
1696 | ((GET_MODE_SIZE (MODE) + UNITS_PER_WORD - 1) \ | |
32bd3974 | 1697 | / UNITS_PER_WORD) |
feca2ed3 JW |
1698 | @end smallexample |
1699 | ||
ce4d78eb RH |
1700 | @findex ALTER_HARD_SUBREG |
1701 | @item ALTER_HARD_SUBREG (@var{tgt_mode}, @var{word}, @var{src_mode}, @var{regno}) | |
1702 | A C expression that returns an adjusted hard register number for | |
1703 | ||
1704 | @smallexample | |
1705 | (subreg:@var{tgt_mode} (reg:@var{src_mode} @var{regno}) @var{word}) | |
1706 | @end smallexample | |
1707 | ||
1708 | This may be needed if the target machine has mixed sized big-endian | |
1709 | registers, like Sparc v9. | |
1710 | ||
feca2ed3 JW |
1711 | @findex HARD_REGNO_MODE_OK |
1712 | @item HARD_REGNO_MODE_OK (@var{regno}, @var{mode}) | |
1713 | A C expression that is nonzero if it is permissible to store a value | |
1714 | of mode @var{mode} in hard register number @var{regno} (or in several | |
1715 | registers starting with that one). For a machine where all registers | |
1716 | are equivalent, a suitable definition is | |
1717 | ||
1718 | @smallexample | |
1719 | #define HARD_REGNO_MODE_OK(REGNO, MODE) 1 | |
1720 | @end smallexample | |
1721 | ||
e9a25f70 JL |
1722 | You need not include code to check for the numbers of fixed registers, |
1723 | because the allocation mechanism considers them to be always occupied. | |
feca2ed3 JW |
1724 | |
1725 | @cindex register pairs | |
1726 | On some machines, double-precision values must be kept in even/odd | |
e9a25f70 JL |
1727 | register pairs. You can implement that by defining this macro to reject |
1728 | odd register numbers for such modes. | |
feca2ed3 JW |
1729 | |
1730 | The minimum requirement for a mode to be OK in a register is that the | |
1731 | @samp{mov@var{mode}} instruction pattern support moves between the | |
e9a25f70 JL |
1732 | register and other hard register in the same class and that moving a |
1733 | value into the register and back out not alter it. | |
feca2ed3 | 1734 | |
e9a25f70 JL |
1735 | Since the same instruction used to move @code{word_mode} will work for |
1736 | all narrower integer modes, it is not necessary on any machine for | |
feca2ed3 JW |
1737 | @code{HARD_REGNO_MODE_OK} to distinguish between these modes, provided |
1738 | you define patterns @samp{movhi}, etc., to take advantage of this. This | |
1739 | is useful because of the interaction between @code{HARD_REGNO_MODE_OK} | |
1740 | and @code{MODES_TIEABLE_P}; it is very desirable for all integer modes | |
1741 | to be tieable. | |
1742 | ||
1743 | Many machines have special registers for floating point arithmetic. | |
1744 | Often people assume that floating point machine modes are allowed only | |
1745 | in floating point registers. This is not true. Any registers that | |
1746 | can hold integers can safely @emph{hold} a floating point machine | |
1747 | mode, whether or not floating arithmetic can be done on it in those | |
1748 | registers. Integer move instructions can be used to move the values. | |
1749 | ||
1750 | On some machines, though, the converse is true: fixed-point machine | |
1751 | modes may not go in floating registers. This is true if the floating | |
1752 | registers normalize any value stored in them, because storing a | |
1753 | non-floating value there would garble it. In this case, | |
1754 | @code{HARD_REGNO_MODE_OK} should reject fixed-point machine modes in | |
1755 | floating registers. But if the floating registers do not automatically | |
1756 | normalize, if you can store any bit pattern in one and retrieve it | |
1757 | unchanged without a trap, then any machine mode may go in a floating | |
1758 | register, so you can define this macro to say so. | |
1759 | ||
1760 | The primary significance of special floating registers is rather that | |
1761 | they are the registers acceptable in floating point arithmetic | |
1762 | instructions. However, this is of no concern to | |
1763 | @code{HARD_REGNO_MODE_OK}. You handle it by writing the proper | |
1764 | constraints for those instructions. | |
1765 | ||
1766 | On some machines, the floating registers are especially slow to access, | |
1767 | so that it is better to store a value in a stack frame than in such a | |
1768 | register if floating point arithmetic is not being done. As long as the | |
1769 | floating registers are not in class @code{GENERAL_REGS}, they will not | |
1770 | be used unless some pattern's constraint asks for one. | |
1771 | ||
1772 | @findex MODES_TIEABLE_P | |
1773 | @item MODES_TIEABLE_P (@var{mode1}, @var{mode2}) | |
e9a25f70 | 1774 | A C expression that is nonzero if a value of mode |
956d6950 | 1775 | @var{mode1} is accessible in mode @var{mode2} without copying. |
feca2ed3 JW |
1776 | |
1777 | If @code{HARD_REGNO_MODE_OK (@var{r}, @var{mode1})} and | |
e9a25f70 JL |
1778 | @code{HARD_REGNO_MODE_OK (@var{r}, @var{mode2})} are always the same for |
1779 | any @var{r}, then @code{MODES_TIEABLE_P (@var{mode1}, @var{mode2})} | |
1780 | should be nonzero. If they differ for any @var{r}, you should define | |
1781 | this macro to return zero unless some other mechanism ensures the | |
956d6950 | 1782 | accessibility of the value in a narrower mode. |
e9a25f70 JL |
1783 | |
1784 | You should define this macro to return nonzero in as many cases as | |
a3a15b4d | 1785 | possible since doing so will allow GCC to perform better register |
e9a25f70 | 1786 | allocation. |
7506f491 DE |
1787 | |
1788 | @findex AVOID_CCMODE_COPIES | |
1789 | @item AVOID_CCMODE_COPIES | |
1790 | Define this macro if the compiler should avoid copies to/from @code{CCmode} | |
a89608cb | 1791 | registers. You should only define this macro if support for copying to/from |
7506f491 | 1792 | @code{CCmode} is incomplete. |
feca2ed3 JW |
1793 | @end table |
1794 | ||
1795 | @node Leaf Functions | |
1796 | @subsection Handling Leaf Functions | |
1797 | ||
1798 | @cindex leaf functions | |
1799 | @cindex functions, leaf | |
1800 | On some machines, a leaf function (i.e., one which makes no calls) can run | |
1801 | more efficiently if it does not make its own register window. Often this | |
1802 | means it is required to receive its arguments in the registers where they | |
1803 | are passed by the caller, instead of the registers where they would | |
1804 | normally arrive. | |
1805 | ||
1806 | The special treatment for leaf functions generally applies only when | |
1807 | other conditions are met; for example, often they may use only those | |
1808 | registers for its own variables and temporaries. We use the term ``leaf | |
1809 | function'' to mean a function that is suitable for this special | |
1810 | handling, so that functions with no calls are not necessarily ``leaf | |
1811 | functions''. | |
1812 | ||
a3a15b4d | 1813 | GCC assigns register numbers before it knows whether the function is |
feca2ed3 JW |
1814 | suitable for leaf function treatment. So it needs to renumber the |
1815 | registers in order to output a leaf function. The following macros | |
1816 | accomplish this. | |
1817 | ||
1818 | @table @code | |
1819 | @findex LEAF_REGISTERS | |
1820 | @item LEAF_REGISTERS | |
7d167afd | 1821 | Name of a char vector, indexed by hard register number, which |
feca2ed3 JW |
1822 | contains 1 for a register that is allowable in a candidate for leaf |
1823 | function treatment. | |
1824 | ||
1825 | If leaf function treatment involves renumbering the registers, then the | |
1826 | registers marked here should be the ones before renumbering---those that | |
a3a15b4d | 1827 | GCC would ordinarily allocate. The registers which will actually be |
feca2ed3 JW |
1828 | used in the assembler code, after renumbering, should not be marked with 1 |
1829 | in this vector. | |
1830 | ||
1831 | Define this macro only if the target machine offers a way to optimize | |
1832 | the treatment of leaf functions. | |
1833 | ||
1834 | @findex LEAF_REG_REMAP | |
1835 | @item LEAF_REG_REMAP (@var{regno}) | |
1836 | A C expression whose value is the register number to which @var{regno} | |
1837 | should be renumbered, when a function is treated as a leaf function. | |
1838 | ||
1839 | If @var{regno} is a register number which should not appear in a leaf | |
1840 | function before renumbering, then the expression should yield -1, which | |
1841 | will cause the compiler to abort. | |
1842 | ||
1843 | Define this macro only if the target machine offers a way to optimize the | |
1844 | treatment of leaf functions, and registers need to be renumbered to do | |
1845 | this. | |
1846 | @end table | |
1847 | ||
54ff41b7 JW |
1848 | @findex current_function_is_leaf |
1849 | @findex current_function_uses_only_leaf_regs | |
feca2ed3 | 1850 | Normally, @code{FUNCTION_PROLOGUE} and @code{FUNCTION_EPILOGUE} must |
54ff41b7 JW |
1851 | treat leaf functions specially. They can test the C variable |
1852 | @code{current_function_is_leaf} which is nonzero for leaf functions. | |
1853 | @code{current_function_is_leaf} is set prior to local register allocation | |
1854 | and is valid for the remaining compiler passes. They can also test the C | |
1855 | variable @code{current_function_uses_only_leaf_regs} which is nonzero for | |
1856 | leaf functions which only use leaf registers. | |
1857 | @code{current_function_uses_only_leaf_regs} is valid after reload and is | |
1858 | only useful if @code{LEAF_REGISTERS} is defined. | |
feca2ed3 JW |
1859 | @c changed this to fix overfull. ALSO: why the "it" at the beginning |
1860 | @c of the next paragraph?! --mew 2feb93 | |
1861 | ||
1862 | @node Stack Registers | |
1863 | @subsection Registers That Form a Stack | |
1864 | ||
1865 | There are special features to handle computers where some of the | |
1866 | ``registers'' form a stack, as in the 80387 coprocessor for the 80386. | |
1867 | Stack registers are normally written by pushing onto the stack, and are | |
1868 | numbered relative to the top of the stack. | |
1869 | ||
a3a15b4d | 1870 | Currently, GCC can only handle one group of stack-like registers, and |
feca2ed3 JW |
1871 | they must be consecutively numbered. |
1872 | ||
1873 | @table @code | |
1874 | @findex STACK_REGS | |
1875 | @item STACK_REGS | |
1876 | Define this if the machine has any stack-like registers. | |
1877 | ||
1878 | @findex FIRST_STACK_REG | |
1879 | @item FIRST_STACK_REG | |
1880 | The number of the first stack-like register. This one is the top | |
1881 | of the stack. | |
1882 | ||
1883 | @findex LAST_STACK_REG | |
1884 | @item LAST_STACK_REG | |
1885 | The number of the last stack-like register. This one is the bottom of | |
1886 | the stack. | |
1887 | @end table | |
1888 | ||
feca2ed3 JW |
1889 | @node Register Classes |
1890 | @section Register Classes | |
1891 | @cindex register class definitions | |
1892 | @cindex class definitions, register | |
1893 | ||
1894 | On many machines, the numbered registers are not all equivalent. | |
1895 | For example, certain registers may not be allowed for indexed addressing; | |
1896 | certain registers may not be allowed in some instructions. These machine | |
1897 | restrictions are described to the compiler using @dfn{register classes}. | |
1898 | ||
1899 | You define a number of register classes, giving each one a name and saying | |
1900 | which of the registers belong to it. Then you can specify register classes | |
1901 | that are allowed as operands to particular instruction patterns. | |
1902 | ||
1903 | @findex ALL_REGS | |
1904 | @findex NO_REGS | |
1905 | In general, each register will belong to several classes. In fact, one | |
1906 | class must be named @code{ALL_REGS} and contain all the registers. Another | |
1907 | class must be named @code{NO_REGS} and contain no registers. Often the | |
1908 | union of two classes will be another class; however, this is not required. | |
1909 | ||
1910 | @findex GENERAL_REGS | |
1911 | One of the classes must be named @code{GENERAL_REGS}. There is nothing | |
1912 | terribly special about the name, but the operand constraint letters | |
1913 | @samp{r} and @samp{g} specify this class. If @code{GENERAL_REGS} is | |
1914 | the same as @code{ALL_REGS}, just define it as a macro which expands | |
1915 | to @code{ALL_REGS}. | |
1916 | ||
1917 | Order the classes so that if class @var{x} is contained in class @var{y} | |
1918 | then @var{x} has a lower class number than @var{y}. | |
1919 | ||
1920 | The way classes other than @code{GENERAL_REGS} are specified in operand | |
1921 | constraints is through machine-dependent operand constraint letters. | |
1922 | You can define such letters to correspond to various classes, then use | |
1923 | them in operand constraints. | |
1924 | ||
1925 | You should define a class for the union of two classes whenever some | |
1926 | instruction allows both classes. For example, if an instruction allows | |
1927 | either a floating point (coprocessor) register or a general register for a | |
1928 | certain operand, you should define a class @code{FLOAT_OR_GENERAL_REGS} | |
1929 | which includes both of them. Otherwise you will get suboptimal code. | |
1930 | ||
1931 | You must also specify certain redundant information about the register | |
1932 | classes: for each class, which classes contain it and which ones are | |
1933 | contained in it; for each pair of classes, the largest class contained | |
1934 | in their union. | |
1935 | ||
1936 | When a value occupying several consecutive registers is expected in a | |
1937 | certain class, all the registers used must belong to that class. | |
1938 | Therefore, register classes cannot be used to enforce a requirement for | |
1939 | a register pair to start with an even-numbered register. The way to | |
1940 | specify this requirement is with @code{HARD_REGNO_MODE_OK}. | |
1941 | ||
1942 | Register classes used for input-operands of bitwise-and or shift | |
1943 | instructions have a special requirement: each such class must have, for | |
1944 | each fixed-point machine mode, a subclass whose registers can transfer that | |
1945 | mode to or from memory. For example, on some machines, the operations for | |
1946 | single-byte values (@code{QImode}) are limited to certain registers. When | |
1947 | this is so, each register class that is used in a bitwise-and or shift | |
1948 | instruction must have a subclass consisting of registers from which | |
1949 | single-byte values can be loaded or stored. This is so that | |
1950 | @code{PREFERRED_RELOAD_CLASS} can always have a possible value to return. | |
1951 | ||
1952 | @table @code | |
1953 | @findex enum reg_class | |
1954 | @item enum reg_class | |
1955 | An enumeral type that must be defined with all the register class names | |
1956 | as enumeral values. @code{NO_REGS} must be first. @code{ALL_REGS} | |
1957 | must be the last register class, followed by one more enumeral value, | |
1958 | @code{LIM_REG_CLASSES}, which is not a register class but rather | |
1959 | tells how many classes there are. | |
1960 | ||
1961 | Each register class has a number, which is the value of casting | |
1962 | the class name to type @code{int}. The number serves as an index | |
1963 | in many of the tables described below. | |
1964 | ||
1965 | @findex N_REG_CLASSES | |
1966 | @item N_REG_CLASSES | |
1967 | The number of distinct register classes, defined as follows: | |
1968 | ||
1969 | @example | |
1970 | #define N_REG_CLASSES (int) LIM_REG_CLASSES | |
1971 | @end example | |
1972 | ||
1973 | @findex REG_CLASS_NAMES | |
1974 | @item REG_CLASS_NAMES | |
1975 | An initializer containing the names of the register classes as C string | |
1976 | constants. These names are used in writing some of the debugging dumps. | |
1977 | ||
1978 | @findex REG_CLASS_CONTENTS | |
1979 | @item REG_CLASS_CONTENTS | |
1980 | An initializer containing the contents of the register classes, as integers | |
1981 | which are bit masks. The @var{n}th integer specifies the contents of class | |
1982 | @var{n}. The way the integer @var{mask} is interpreted is that | |
1983 | register @var{r} is in the class if @code{@var{mask} & (1 << @var{r})} is 1. | |
1984 | ||
1985 | When the machine has more than 32 registers, an integer does not suffice. | |
1986 | Then the integers are replaced by sub-initializers, braced groupings containing | |
1987 | several integers. Each sub-initializer must be suitable as an initializer | |
1988 | for the type @code{HARD_REG_SET} which is defined in @file{hard-reg-set.h}. | |
7c272079 MP |
1989 | In this situation, the first integer in each sub-initializer corresponds to |
1990 | registers 0 through 31, the second integer to registers 32 through 63, and | |
1991 | so on. | |
feca2ed3 JW |
1992 | |
1993 | @findex REGNO_REG_CLASS | |
1994 | @item REGNO_REG_CLASS (@var{regno}) | |
1995 | A C expression whose value is a register class containing hard register | |
1996 | @var{regno}. In general there is more than one such class; choose a class | |
1997 | which is @dfn{minimal}, meaning that no smaller class also contains the | |
1998 | register. | |
1999 | ||
2000 | @findex BASE_REG_CLASS | |
2001 | @item BASE_REG_CLASS | |
2002 | A macro whose definition is the name of the class to which a valid | |
2003 | base register must belong. A base register is one used in an address | |
2004 | which is the register value plus a displacement. | |
2005 | ||
2006 | @findex INDEX_REG_CLASS | |
2007 | @item INDEX_REG_CLASS | |
2008 | A macro whose definition is the name of the class to which a valid | |
2009 | index register must belong. An index register is one used in an | |
2010 | address where its value is either multiplied by a scale factor or | |
2011 | added to another register (as well as added to a displacement). | |
2012 | ||
2013 | @findex REG_CLASS_FROM_LETTER | |
2014 | @item REG_CLASS_FROM_LETTER (@var{char}) | |
2015 | A C expression which defines the machine-dependent operand constraint | |
2016 | letters for register classes. If @var{char} is such a letter, the | |
2017 | value should be the register class corresponding to it. Otherwise, | |
2018 | the value should be @code{NO_REGS}. The register letter @samp{r}, | |
2019 | corresponding to class @code{GENERAL_REGS}, will not be passed | |
2020 | to this macro; you do not need to handle it. | |
2021 | ||
2022 | @findex REGNO_OK_FOR_BASE_P | |
2023 | @item REGNO_OK_FOR_BASE_P (@var{num}) | |
2024 | A C expression which is nonzero if register number @var{num} is | |
2025 | suitable for use as a base register in operand addresses. It may be | |
2026 | either a suitable hard register or a pseudo register that has been | |
2027 | allocated such a hard register. | |
2028 | ||
861bb6c1 JL |
2029 | @findex REGNO_MODE_OK_FOR_BASE_P |
2030 | @item REGNO_MODE_OK_FOR_BASE_P (@var{num}, @var{mode}) | |
2031 | A C expression that is just like @code{REGNO_OK_FOR_BASE_P}, except that | |
2032 | that expression may examine the mode of the memory reference in | |
2033 | @var{mode}. You should define this macro if the mode of the memory | |
2034 | reference affects whether a register may be used as a base register. If | |
2035 | you define this macro, the compiler will use it instead of | |
2036 | @code{REGNO_OK_FOR_BASE_P}. | |
2037 | ||
feca2ed3 JW |
2038 | @findex REGNO_OK_FOR_INDEX_P |
2039 | @item REGNO_OK_FOR_INDEX_P (@var{num}) | |
2040 | A C expression which is nonzero if register number @var{num} is | |
2041 | suitable for use as an index register in operand addresses. It may be | |
2042 | either a suitable hard register or a pseudo register that has been | |
2043 | allocated such a hard register. | |
2044 | ||
2045 | The difference between an index register and a base register is that | |
2046 | the index register may be scaled. If an address involves the sum of | |
2047 | two registers, neither one of them scaled, then either one may be | |
2048 | labeled the ``base'' and the other the ``index''; but whichever | |
2049 | labeling is used must fit the machine's constraints of which registers | |
2050 | may serve in each capacity. The compiler will try both labelings, | |
2051 | looking for one that is valid, and will reload one or both registers | |
2052 | only if neither labeling works. | |
2053 | ||
2054 | @findex PREFERRED_RELOAD_CLASS | |
2055 | @item PREFERRED_RELOAD_CLASS (@var{x}, @var{class}) | |
2056 | A C expression that places additional restrictions on the register class | |
2057 | to use when it is necessary to copy value @var{x} into a register in class | |
2058 | @var{class}. The value is a register class; perhaps @var{class}, or perhaps | |
2059 | another, smaller class. On many machines, the following definition is | |
2060 | safe: | |
2061 | ||
2062 | @example | |
2063 | #define PREFERRED_RELOAD_CLASS(X,CLASS) CLASS | |
2064 | @end example | |
2065 | ||
2066 | Sometimes returning a more restrictive class makes better code. For | |
2067 | example, on the 68000, when @var{x} is an integer constant that is in range | |
2068 | for a @samp{moveq} instruction, the value of this macro is always | |
2069 | @code{DATA_REGS} as long as @var{class} includes the data registers. | |
2070 | Requiring a data register guarantees that a @samp{moveq} will be used. | |
2071 | ||
2072 | If @var{x} is a @code{const_double}, by returning @code{NO_REGS} | |
2073 | you can force @var{x} into a memory constant. This is useful on | |
2074 | certain machines where immediate floating values cannot be loaded into | |
2075 | certain kinds of registers. | |
2076 | ||
2077 | @findex PREFERRED_OUTPUT_RELOAD_CLASS | |
2078 | @item PREFERRED_OUTPUT_RELOAD_CLASS (@var{x}, @var{class}) | |
2079 | Like @code{PREFERRED_RELOAD_CLASS}, but for output reloads instead of | |
2080 | input reloads. If you don't define this macro, the default is to use | |
2081 | @var{class}, unchanged. | |
2082 | ||
2083 | @findex LIMIT_RELOAD_CLASS | |
2084 | @item LIMIT_RELOAD_CLASS (@var{mode}, @var{class}) | |
2085 | A C expression that places additional restrictions on the register class | |
2086 | to use when it is necessary to be able to hold a value of mode | |
2087 | @var{mode} in a reload register for which class @var{class} would | |
2088 | ordinarily be used. | |
2089 | ||
2090 | Unlike @code{PREFERRED_RELOAD_CLASS}, this macro should be used when | |
2091 | there are certain modes that simply can't go in certain reload classes. | |
2092 | ||
2093 | The value is a register class; perhaps @var{class}, or perhaps another, | |
2094 | smaller class. | |
2095 | ||
2096 | Don't define this macro unless the target machine has limitations which | |
2097 | require the macro to do something nontrivial. | |
2098 | ||
2099 | @findex SECONDARY_RELOAD_CLASS | |
2100 | @findex SECONDARY_INPUT_RELOAD_CLASS | |
2101 | @findex SECONDARY_OUTPUT_RELOAD_CLASS | |
2102 | @item SECONDARY_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) | |
2103 | @itemx SECONDARY_INPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) | |
2104 | @itemx SECONDARY_OUTPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) | |
2105 | Many machines have some registers that cannot be copied directly to or | |
2106 | from memory or even from other types of registers. An example is the | |
2107 | @samp{MQ} register, which on most machines, can only be copied to or | |
2108 | from general registers, but not memory. Some machines allow copying all | |
2109 | registers to and from memory, but require a scratch register for stores | |
2110 | to some memory locations (e.g., those with symbolic address on the RT, | |
2111 | and those with certain symbolic address on the Sparc when compiling | |
2112 | PIC). In some cases, both an intermediate and a scratch register are | |
2113 | required. | |
2114 | ||
2115 | You should define these macros to indicate to the reload phase that it may | |
2116 | need to allocate at least one register for a reload in addition to the | |
2117 | register to contain the data. Specifically, if copying @var{x} to a | |
2118 | register @var{class} in @var{mode} requires an intermediate register, | |
2119 | you should define @code{SECONDARY_INPUT_RELOAD_CLASS} to return the | |
2120 | largest register class all of whose registers can be used as | |
2121 | intermediate registers or scratch registers. | |
2122 | ||
2123 | If copying a register @var{class} in @var{mode} to @var{x} requires an | |
2124 | intermediate or scratch register, @code{SECONDARY_OUTPUT_RELOAD_CLASS} | |
2125 | should be defined to return the largest register class required. If the | |
2126 | requirements for input and output reloads are the same, the macro | |
2127 | @code{SECONDARY_RELOAD_CLASS} should be used instead of defining both | |
2128 | macros identically. | |
2129 | ||
2130 | The values returned by these macros are often @code{GENERAL_REGS}. | |
2131 | Return @code{NO_REGS} if no spare register is needed; i.e., if @var{x} | |
2132 | can be directly copied to or from a register of @var{class} in | |
2133 | @var{mode} without requiring a scratch register. Do not define this | |
2134 | macro if it would always return @code{NO_REGS}. | |
2135 | ||
2136 | If a scratch register is required (either with or without an | |
2137 | intermediate register), you should define patterns for | |
2138 | @samp{reload_in@var{m}} or @samp{reload_out@var{m}}, as required | |
2139 | (@pxref{Standard Names}. These patterns, which will normally be | |
2140 | implemented with a @code{define_expand}, should be similar to the | |
2141 | @samp{mov@var{m}} patterns, except that operand 2 is the scratch | |
2142 | register. | |
2143 | ||
2144 | Define constraints for the reload register and scratch register that | |
2145 | contain a single register class. If the original reload register (whose | |
2146 | class is @var{class}) can meet the constraint given in the pattern, the | |
2147 | value returned by these macros is used for the class of the scratch | |
2148 | register. Otherwise, two additional reload registers are required. | |
2149 | Their classes are obtained from the constraints in the insn pattern. | |
2150 | ||
2151 | @var{x} might be a pseudo-register or a @code{subreg} of a | |
2152 | pseudo-register, which could either be in a hard register or in memory. | |
2153 | Use @code{true_regnum} to find out; it will return -1 if the pseudo is | |
2154 | in memory and the hard register number if it is in a register. | |
2155 | ||
2156 | These macros should not be used in the case where a particular class of | |
2157 | registers can only be copied to memory and not to another class of | |
2158 | registers. In that case, secondary reload registers are not needed and | |
2159 | would not be helpful. Instead, a stack location must be used to perform | |
2160 | the copy and the @code{mov@var{m}} pattern should use memory as a | |
2161 | intermediate storage. This case often occurs between floating-point and | |
2162 | general registers. | |
2163 | ||
2164 | @findex SECONDARY_MEMORY_NEEDED | |
2165 | @item SECONDARY_MEMORY_NEEDED (@var{class1}, @var{class2}, @var{m}) | |
2166 | Certain machines have the property that some registers cannot be copied | |
2167 | to some other registers without using memory. Define this macro on | |
2168 | those machines to be a C expression that is non-zero if objects of mode | |
2169 | @var{m} in registers of @var{class1} can only be copied to registers of | |
2170 | class @var{class2} by storing a register of @var{class1} into memory | |
2171 | and loading that memory location into a register of @var{class2}. | |
2172 | ||
2173 | Do not define this macro if its value would always be zero. | |
2174 | ||
2175 | @findex SECONDARY_MEMORY_NEEDED_RTX | |
2176 | @item SECONDARY_MEMORY_NEEDED_RTX (@var{mode}) | |
2177 | Normally when @code{SECONDARY_MEMORY_NEEDED} is defined, the compiler | |
2178 | allocates a stack slot for a memory location needed for register copies. | |
2179 | If this macro is defined, the compiler instead uses the memory location | |
2180 | defined by this macro. | |
2181 | ||
2182 | Do not define this macro if you do not define | |
2183 | @code{SECONDARY_MEMORY_NEEDED}. | |
2184 | ||
2185 | @findex SECONDARY_MEMORY_NEEDED_MODE | |
2186 | @item SECONDARY_MEMORY_NEEDED_MODE (@var{mode}) | |
2187 | When the compiler needs a secondary memory location to copy between two | |
2188 | registers of mode @var{mode}, it normally allocates sufficient memory to | |
2189 | hold a quantity of @code{BITS_PER_WORD} bits and performs the store and | |
2190 | load operations in a mode that many bits wide and whose class is the | |
2191 | same as that of @var{mode}. | |
2192 | ||
2193 | This is right thing to do on most machines because it ensures that all | |
2194 | bits of the register are copied and prevents accesses to the registers | |
2195 | in a narrower mode, which some machines prohibit for floating-point | |
2196 | registers. | |
2197 | ||
2198 | However, this default behavior is not correct on some machines, such as | |
2199 | the DEC Alpha, that store short integers in floating-point registers | |
2200 | differently than in integer registers. On those machines, the default | |
2201 | widening will not work correctly and you must define this macro to | |
2202 | suppress that widening in some cases. See the file @file{alpha.h} for | |
2203 | details. | |
2204 | ||
2205 | Do not define this macro if you do not define | |
2206 | @code{SECONDARY_MEMORY_NEEDED} or if widening @var{mode} to a mode that | |
2207 | is @code{BITS_PER_WORD} bits wide is correct for your machine. | |
2208 | ||
2209 | @findex SMALL_REGISTER_CLASSES | |
2210 | @item SMALL_REGISTER_CLASSES | |
faa9eb19 BS |
2211 | On some machines, it is risky to let hard registers live across arbitrary |
2212 | insns. Typically, these machines have instructions that require values | |
2213 | to be in specific registers (like an accumulator), and reload will fail | |
2214 | if the required hard register is used for another purpose across such an | |
2215 | insn. | |
feca2ed3 | 2216 | |
861bb6c1 JL |
2217 | Define @code{SMALL_REGISTER_CLASSES} to be an expression with a non-zero |
2218 | value on these machines. When this macro has a non-zero value, the | |
faa9eb19 | 2219 | compiler will try to minimize the lifetime of hard registers. |
feca2ed3 | 2220 | |
861bb6c1 JL |
2221 | It is always safe to define this macro with a non-zero value, but if you |
2222 | unnecessarily define it, you will reduce the amount of optimizations | |
2223 | that can be performed in some cases. If you do not define this macro | |
2224 | with a non-zero value when it is required, the compiler will run out of | |
2225 | spill registers and print a fatal error message. For most machines, you | |
2226 | should not define this macro at all. | |
feca2ed3 JW |
2227 | |
2228 | @findex CLASS_LIKELY_SPILLED_P | |
2229 | @item CLASS_LIKELY_SPILLED_P (@var{class}) | |
2230 | A C expression whose value is nonzero if pseudos that have been assigned | |
2231 | to registers of class @var{class} would likely be spilled because | |
2232 | registers of @var{class} are needed for spill registers. | |
2233 | ||
2234 | The default value of this macro returns 1 if @var{class} has exactly one | |
2235 | register and zero otherwise. On most machines, this default should be | |
40687a9e | 2236 | used. Only define this macro to some other expression if pseudos |
feca2ed3 JW |
2237 | allocated by @file{local-alloc.c} end up in memory because their hard |
2238 | registers were needed for spill registers. If this macro returns nonzero | |
2239 | for those classes, those pseudos will only be allocated by | |
2240 | @file{global.c}, which knows how to reallocate the pseudo to another | |
2241 | register. If there would not be another register available for | |
2242 | reallocation, you should not change the definition of this macro since | |
2243 | the only effect of such a definition would be to slow down register | |
2244 | allocation. | |
2245 | ||
2246 | @findex CLASS_MAX_NREGS | |
2247 | @item CLASS_MAX_NREGS (@var{class}, @var{mode}) | |
2248 | A C expression for the maximum number of consecutive registers | |
2249 | of class @var{class} needed to hold a value of mode @var{mode}. | |
2250 | ||
2251 | This is closely related to the macro @code{HARD_REGNO_NREGS}. In fact, | |
2252 | the value of the macro @code{CLASS_MAX_NREGS (@var{class}, @var{mode})} | |
2253 | should be the maximum value of @code{HARD_REGNO_NREGS (@var{regno}, | |
2254 | @var{mode})} for all @var{regno} values in the class @var{class}. | |
2255 | ||
2256 | This macro helps control the handling of multiple-word values | |
2257 | in the reload pass. | |
2258 | ||
02188693 RH |
2259 | @item CLASS_CANNOT_CHANGE_MODE |
2260 | If defined, a C expression for a class that contains registers for | |
2261 | which the compiler may not change modes arbitrarily. | |
2262 | ||
2263 | @item CLASS_CANNOT_CHANGE_MODE_P(@var{from}, @var{to}) | |
2264 | A C expression that is true if, for a register in | |
2265 | @code{CLASS_CANNOT_CHANGE_MODE}, the requested mode punning is illegal. | |
feca2ed3 JW |
2266 | |
2267 | For the example, loading 32-bit integer or floating-point objects into | |
2268 | floating-point registers on the Alpha extends them to 64-bits. | |
2269 | Therefore loading a 64-bit object and then storing it as a 32-bit object | |
2270 | does not store the low-order 32-bits, as would be the case for a normal | |
02188693 RH |
2271 | register. Therefore, @file{alpha.h} defines @code{CLASS_CANNOT_CHANGE_MODE} |
2272 | as @code{FLOAT_REGS} and @code{CLASS_CANNOT_CHANGE_MODE_P} restricts | |
2273 | mode changes to same-size modes. | |
2274 | ||
2275 | Compare this to IA-64, which extends floating-point values to 82-bits, | |
2276 | and stores 64-bit integers in a different format than 64-bit doubles. | |
2277 | Therefore @code{CLASS_CANNOT_CHANGE_MODE_P} is always true. | |
feca2ed3 JW |
2278 | @end table |
2279 | ||
2280 | Three other special macros describe which operands fit which constraint | |
2281 | letters. | |
2282 | ||
2283 | @table @code | |
2284 | @findex CONST_OK_FOR_LETTER_P | |
2285 | @item CONST_OK_FOR_LETTER_P (@var{value}, @var{c}) | |
e119b68c MM |
2286 | A C expression that defines the machine-dependent operand constraint |
2287 | letters (@samp{I}, @samp{J}, @samp{K}, @dots{} @samp{P}) that specify | |
2288 | particular ranges of integer values. If @var{c} is one of those | |
2289 | letters, the expression should check that @var{value}, an integer, is in | |
2290 | the appropriate range and return 1 if so, 0 otherwise. If @var{c} is | |
2291 | not one of those letters, the value should be 0 regardless of | |
2292 | @var{value}. | |
feca2ed3 JW |
2293 | |
2294 | @findex CONST_DOUBLE_OK_FOR_LETTER_P | |
2295 | @item CONST_DOUBLE_OK_FOR_LETTER_P (@var{value}, @var{c}) | |
2296 | A C expression that defines the machine-dependent operand constraint | |
e119b68c MM |
2297 | letters that specify particular ranges of @code{const_double} values |
2298 | (@samp{G} or @samp{H}). | |
feca2ed3 JW |
2299 | |
2300 | If @var{c} is one of those letters, the expression should check that | |
2301 | @var{value}, an RTX of code @code{const_double}, is in the appropriate | |
2302 | range and return 1 if so, 0 otherwise. If @var{c} is not one of those | |
2303 | letters, the value should be 0 regardless of @var{value}. | |
2304 | ||
2305 | @code{const_double} is used for all floating-point constants and for | |
2306 | @code{DImode} fixed-point constants. A given letter can accept either | |
2307 | or both kinds of values. It can use @code{GET_MODE} to distinguish | |
2308 | between these kinds. | |
2309 | ||
2310 | @findex EXTRA_CONSTRAINT | |
2311 | @item EXTRA_CONSTRAINT (@var{value}, @var{c}) | |
2312 | A C expression that defines the optional machine-dependent constraint | |
c2cba7a9 RH |
2313 | letters that can be used to segregate specific types of operands, usually |
2314 | memory references, for the target machine. Any letter that is not | |
2315 | elsewhere defined and not matched by @code{REG_CLASS_FROM_LETTER} | |
2316 | may be used. Normally this macro will not be defined. | |
2317 | ||
2318 | If it is required for a particular target machine, it should return 1 | |
2319 | if @var{value} corresponds to the operand type represented by the | |
2320 | constraint letter @var{c}. If @var{c} is not defined as an extra | |
e119b68c | 2321 | constraint, the value returned should be 0 regardless of @var{value}. |
feca2ed3 | 2322 | |
c2cba7a9 RH |
2323 | For example, on the ROMP, load instructions cannot have their output |
2324 | in r0 if the memory reference contains a symbolic address. Constraint | |
2325 | letter @samp{Q} is defined as representing a memory address that does | |
feca2ed3 JW |
2326 | @emph{not} contain a symbolic address. An alternative is specified with |
2327 | a @samp{Q} constraint on the input and @samp{r} on the output. The next | |
2328 | alternative specifies @samp{m} on the input and a register class that | |
2329 | does not include r0 on the output. | |
2330 | @end table | |
2331 | ||
2332 | @node Stack and Calling | |
2333 | @section Stack Layout and Calling Conventions | |
2334 | @cindex calling conventions | |
2335 | ||
2336 | @c prevent bad page break with this line | |
2337 | This describes the stack layout and calling conventions. | |
2338 | ||
2339 | @menu | |
2340 | * Frame Layout:: | |
861bb6c1 | 2341 | * Stack Checking:: |
feca2ed3 JW |
2342 | * Frame Registers:: |
2343 | * Elimination:: | |
2344 | * Stack Arguments:: | |
2345 | * Register Arguments:: | |
2346 | * Scalar Return:: | |
2347 | * Aggregate Return:: | |
2348 | * Caller Saves:: | |
2349 | * Function Entry:: | |
2350 | * Profiling:: | |
b36f4ed3 | 2351 | * Inlining:: |
4cb1433c | 2352 | * Tail Calling:: |
feca2ed3 JW |
2353 | @end menu |
2354 | ||
2355 | @node Frame Layout | |
2356 | @subsection Basic Stack Layout | |
2357 | @cindex stack frame layout | |
2358 | @cindex frame layout | |
2359 | ||
2360 | @c prevent bad page break with this line | |
2361 | Here is the basic stack layout. | |
2362 | ||
2363 | @table @code | |
2364 | @findex STACK_GROWS_DOWNWARD | |
2365 | @item STACK_GROWS_DOWNWARD | |
2366 | Define this macro if pushing a word onto the stack moves the stack | |
2367 | pointer to a smaller address. | |
2368 | ||
2369 | When we say, ``define this macro if @dots{},'' it means that the | |
2370 | compiler checks this macro only with @code{#ifdef} so the precise | |
2371 | definition used does not matter. | |
2372 | ||
2373 | @findex FRAME_GROWS_DOWNWARD | |
2374 | @item FRAME_GROWS_DOWNWARD | |
2375 | Define this macro if the addresses of local variable slots are at negative | |
2376 | offsets from the frame pointer. | |
2377 | ||
2378 | @findex ARGS_GROW_DOWNWARD | |
2379 | @item ARGS_GROW_DOWNWARD | |
2380 | Define this macro if successive arguments to a function occupy decreasing | |
2381 | addresses on the stack. | |
2382 | ||
2383 | @findex STARTING_FRAME_OFFSET | |
2384 | @item STARTING_FRAME_OFFSET | |
2385 | Offset from the frame pointer to the first local variable slot to be allocated. | |
2386 | ||
2387 | If @code{FRAME_GROWS_DOWNWARD}, find the next slot's offset by | |
2388 | subtracting the first slot's length from @code{STARTING_FRAME_OFFSET}. | |
2389 | Otherwise, it is found by adding the length of the first slot to the | |
2390 | value @code{STARTING_FRAME_OFFSET}. | |
2391 | @c i'm not sure if the above is still correct.. had to change it to get | |
2392 | @c rid of an overfull. --mew 2feb93 | |
2393 | ||
2394 | @findex STACK_POINTER_OFFSET | |
2395 | @item STACK_POINTER_OFFSET | |
2396 | Offset from the stack pointer register to the first location at which | |
2397 | outgoing arguments are placed. If not specified, the default value of | |
2398 | zero is used. This is the proper value for most machines. | |
2399 | ||
2400 | If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above | |
2401 | the first location at which outgoing arguments are placed. | |
2402 | ||
2403 | @findex FIRST_PARM_OFFSET | |
2404 | @item FIRST_PARM_OFFSET (@var{fundecl}) | |
2405 | Offset from the argument pointer register to the first argument's | |
2406 | address. On some machines it may depend on the data type of the | |
2407 | function. | |
2408 | ||
2409 | If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above | |
2410 | the first argument's address. | |
2411 | ||
2412 | @findex STACK_DYNAMIC_OFFSET | |
2413 | @item STACK_DYNAMIC_OFFSET (@var{fundecl}) | |
2414 | Offset from the stack pointer register to an item dynamically allocated | |
2415 | on the stack, e.g., by @code{alloca}. | |
2416 | ||
2417 | The default value for this macro is @code{STACK_POINTER_OFFSET} plus the | |
2418 | length of the outgoing arguments. The default is correct for most | |
2419 | machines. See @file{function.c} for details. | |
2420 | ||
2421 | @findex DYNAMIC_CHAIN_ADDRESS | |
2422 | @item DYNAMIC_CHAIN_ADDRESS (@var{frameaddr}) | |
2423 | A C expression whose value is RTL representing the address in a stack | |
2424 | frame where the pointer to the caller's frame is stored. Assume that | |
2425 | @var{frameaddr} is an RTL expression for the address of the stack frame | |
2426 | itself. | |
2427 | ||
2428 | If you don't define this macro, the default is to return the value | |
2429 | of @var{frameaddr}---that is, the stack frame address is also the | |
2430 | address of the stack word that points to the previous frame. | |
2431 | ||
2432 | @findex SETUP_FRAME_ADDRESSES | |
0bc02db4 | 2433 | @item SETUP_FRAME_ADDRESSES |
feca2ed3 JW |
2434 | If defined, a C expression that produces the machine-specific code to |
2435 | setup the stack so that arbitrary frames can be accessed. For example, | |
2436 | on the Sparc, we must flush all of the register windows to the stack | |
0bc02db4 MS |
2437 | before we can access arbitrary stack frames. You will seldom need to |
2438 | define this macro. | |
2439 | ||
2440 | @findex BUILTIN_SETJMP_FRAME_VALUE | |
2441 | @item BUILTIN_SETJMP_FRAME_VALUE | |
2442 | If defined, a C expression that contains an rtx that is used to store | |
2443 | the address of the current frame into the built in @code{setjmp} buffer. | |
2444 | The default value, @code{virtual_stack_vars_rtx}, is correct for most | |
2445 | machines. One reason you may need to define this macro is if | |
2446 | @code{hard_frame_pointer_rtx} is the appropriate value on your machine. | |
feca2ed3 JW |
2447 | |
2448 | @findex RETURN_ADDR_RTX | |
2449 | @item RETURN_ADDR_RTX (@var{count}, @var{frameaddr}) | |
2450 | A C expression whose value is RTL representing the value of the return | |
861bb6c1 JL |
2451 | address for the frame @var{count} steps up from the current frame, after |
2452 | the prologue. @var{frameaddr} is the frame pointer of the @var{count} | |
2453 | frame, or the frame pointer of the @var{count} @minus{} 1 frame if | |
feca2ed3 JW |
2454 | @code{RETURN_ADDR_IN_PREVIOUS_FRAME} is defined. |
2455 | ||
e9a25f70 JL |
2456 | The value of the expression must always be the correct address when |
2457 | @var{count} is zero, but may be @code{NULL_RTX} if there is not way to | |
2458 | determine the return address of other frames. | |
2459 | ||
feca2ed3 JW |
2460 | @findex RETURN_ADDR_IN_PREVIOUS_FRAME |
2461 | @item RETURN_ADDR_IN_PREVIOUS_FRAME | |
2462 | Define this if the return address of a particular stack frame is accessed | |
2463 | from the frame pointer of the previous stack frame. | |
861bb6c1 JL |
2464 | |
2465 | @findex INCOMING_RETURN_ADDR_RTX | |
2466 | @item INCOMING_RETURN_ADDR_RTX | |
2467 | A C expression whose value is RTL representing the location of the | |
2468 | incoming return address at the beginning of any function, before the | |
2469 | prologue. This RTL is either a @code{REG}, indicating that the return | |
2470 | value is saved in @samp{REG}, or a @code{MEM} representing a location in | |
2471 | the stack. | |
2472 | ||
2473 | You only need to define this macro if you want to support call frame | |
2474 | debugging information like that provided by DWARF 2. | |
2475 | ||
2c849145 JM |
2476 | If this RTL is a @code{REG}, you should also define |
2477 | DWARF_FRAME_RETURN_COLUMN to @code{DWARF_FRAME_REGNUM (REGNO)}. | |
2478 | ||
861bb6c1 JL |
2479 | @findex INCOMING_FRAME_SP_OFFSET |
2480 | @item INCOMING_FRAME_SP_OFFSET | |
2481 | A C expression whose value is an integer giving the offset, in bytes, | |
2482 | from the value of the stack pointer register to the top of the stack | |
2483 | frame at the beginning of any function, before the prologue. The top of | |
2484 | the frame is defined to be the value of the stack pointer in the | |
2485 | previous frame, just before the call instruction. | |
2486 | ||
71038426 RH |
2487 | You only need to define this macro if you want to support call frame |
2488 | debugging information like that provided by DWARF 2. | |
2489 | ||
2490 | @findex ARG_POINTER_CFA_OFFSET | |
2c849145 | 2491 | @item ARG_POINTER_CFA_OFFSET (@var{fundecl}) |
71038426 RH |
2492 | A C expression whose value is an integer giving the offset, in bytes, |
2493 | from the argument pointer to the canonical frame address (cfa). The | |
2494 | final value should coincide with that calculated by | |
2495 | @code{INCOMING_FRAME_SP_OFFSET}. Which is unfortunately not usable | |
2496 | during virtual register instantiation. | |
2497 | ||
2c849145 JM |
2498 | The default value for this macro is @code{FIRST_PARM_OFFSET (fundecl)}, |
2499 | which is correct for most machines; in general, the arguments are found | |
208e52d9 JM |
2500 | immediately before the stack frame. Note that this is not the case on |
2501 | some targets that save registers into the caller's frame, such as SPARC | |
2502 | and rs6000, and so such targets need to define this macro. | |
2c849145 | 2503 | |
208e52d9 | 2504 | You only need to define this macro if the default is incorrect, and you |
2c849145 JM |
2505 | want to support call frame debugging information like that provided by |
2506 | DWARF 2. | |
512b62fb | 2507 | |
52a11cbf RH |
2508 | @findex EH_RETURN_DATA_REGNO |
2509 | @item EH_RETURN_DATA_REGNO (@var{N}) | |
2510 | A C expression whose value is the @var{N}th register number used for | |
2511 | data by exception handlers, or @code{INVALID_REGNUM} if fewer than | |
2512 | @var{N} registers are usable. | |
2513 | ||
2514 | The exception handling library routines communicate with the exception | |
2515 | handlers via a set of agreed upon registers. Ideally these registers | |
2516 | should be call-clobbered; it is possible to use call-saved registers, | |
2517 | but may negatively impact code size. The target must support at least | |
2518 | 2 data registers, but should define 4 if there are enough free registers. | |
2519 | ||
2520 | You must define this macro if you want to support call frame exception | |
2521 | handling like that provided by DWARF 2. | |
2522 | ||
2523 | @findex EH_RETURN_STACKADJ_RTX | |
2524 | @item EH_RETURN_STACKADJ_RTX | |
2525 | A C expression whose value is RTL representing a location in which | |
2526 | to store a stack adjustment to be applied before function return. | |
2527 | This is used to unwind the stack to an exception handler's call frame. | |
2528 | It will be assigned zero on code paths that return normally. | |
2529 | ||
2530 | Typically this is a call-clobbered hard register that is otherwise | |
2531 | untouched by the epilogue, but could also be a stack slot. | |
2532 | ||
2533 | You must define this macro if you want to support call frame exception | |
2534 | handling like that provided by DWARF 2. | |
2535 | ||
2536 | @findex EH_RETURN_HANDLER_RTX | |
2537 | @item EH_RETURN_HANDLER_RTX | |
2538 | A C expression whose value is RTL representing a location in which | |
2539 | to store the address of an exception handler to which we should | |
2540 | return. It will not be assigned on code paths that return normally. | |
2541 | ||
2542 | Typically this is the location in the call frame at which the normal | |
2543 | return address is stored. For targets that return by popping an | |
2544 | address off the stack, this might be a memory address just below | |
2545 | the @emph{target} call frame rather than inside the current call | |
2546 | frame. @code{EH_RETURN_STACKADJ_RTX} will have already been assigned, | |
2547 | so it may be used to calculate the location of the target call frame. | |
2548 | ||
2549 | Some targets have more complex requirements than storing to an | |
2550 | address calculable during initial code generation. In that case | |
2551 | the @code{eh_return} instruction pattern should be used instead. | |
2552 | ||
2553 | If you want to support call frame exception handling, you must | |
2554 | define either this macro or the @code{eh_return} instruction pattern. | |
2555 | ||
512b62fb JM |
2556 | @findex SMALL_STACK |
2557 | @item SMALL_STACK | |
2558 | Define this macro if the stack size for the target is very small. This | |
2559 | has the effect of disabling gcc's builtin @samp{alloca}, though | |
2560 | @samp{__builtin_alloca} is not affected. | |
861bb6c1 JL |
2561 | @end table |
2562 | ||
2563 | @node Stack Checking | |
2564 | @subsection Specifying How Stack Checking is Done | |
2565 | ||
a3a15b4d | 2566 | GCC will check that stack references are within the boundaries of |
861bb6c1 JL |
2567 | the stack, if the @samp{-fstack-check} is specified, in one of three ways: |
2568 | ||
2569 | @enumerate | |
2570 | @item | |
a3a15b4d | 2571 | If the value of the @code{STACK_CHECK_BUILTIN} macro is nonzero, GCC |
861bb6c1 JL |
2572 | will assume that you have arranged for stack checking to be done at |
2573 | appropriate places in the configuration files, e.g., in | |
a3a15b4d | 2574 | @code{FUNCTION_PROLOGUE}. GCC will do not other special processing. |
861bb6c1 JL |
2575 | |
2576 | @item | |
2577 | If @code{STACK_CHECK_BUILTIN} is zero and you defined a named pattern | |
a3a15b4d | 2578 | called @code{check_stack} in your @file{md} file, GCC will call that |
861bb6c1 JL |
2579 | pattern with one argument which is the address to compare the stack |
2580 | value against. You must arrange for this pattern to report an error if | |
2581 | the stack pointer is out of range. | |
2582 | ||
2583 | @item | |
a3a15b4d | 2584 | If neither of the above are true, GCC will generate code to periodically |
861bb6c1 JL |
2585 | ``probe'' the stack pointer using the values of the macros defined below. |
2586 | @end enumerate | |
2587 | ||
a3a15b4d | 2588 | Normally, you will use the default values of these macros, so GCC |
861bb6c1 JL |
2589 | will use the third approach. |
2590 | ||
2591 | @table @code | |
2592 | @findex STACK_CHECK_BUILTIN | |
2593 | @item STACK_CHECK_BUILTIN | |
2594 | A nonzero value if stack checking is done by the configuration files in a | |
2595 | machine-dependent manner. You should define this macro if stack checking | |
2596 | is require by the ABI of your machine or if you would like to have to stack | |
a3a15b4d | 2597 | checking in some more efficient way than GCC's portable approach. |
861bb6c1 JL |
2598 | The default value of this macro is zero. |
2599 | ||
2600 | @findex STACK_CHECK_PROBE_INTERVAL | |
2601 | @item STACK_CHECK_PROBE_INTERVAL | |
a3a15b4d | 2602 | An integer representing the interval at which GCC must generate stack |
861bb6c1 JL |
2603 | probe instructions. You will normally define this macro to be no larger |
2604 | than the size of the ``guard pages'' at the end of a stack area. The | |
2605 | default value of 4096 is suitable for most systems. | |
2606 | ||
2607 | @findex STACK_CHECK_PROBE_LOAD | |
2608 | @item STACK_CHECK_PROBE_LOAD | |
a3a15b4d JL |
2609 | A integer which is nonzero if GCC should perform the stack probe |
2610 | as a load instruction and zero if GCC should use a store instruction. | |
861bb6c1 JL |
2611 | The default is zero, which is the most efficient choice on most systems. |
2612 | ||
2613 | @findex STACK_CHECK_PROTECT | |
2614 | @item STACK_CHECK_PROTECT | |
2615 | The number of bytes of stack needed to recover from a stack overflow, | |
2616 | for languages where such a recovery is supported. The default value of | |
2617 | 75 words should be adequate for most machines. | |
2618 | ||
2619 | @findex STACK_CHECK_MAX_FRAME_SIZE | |
2620 | @item STACK_CHECK_MAX_FRAME_SIZE | |
a3a15b4d | 2621 | The maximum size of a stack frame, in bytes. GCC will generate probe |
861bb6c1 JL |
2622 | instructions in non-leaf functions to ensure at least this many bytes of |
2623 | stack are available. If a stack frame is larger than this size, stack | |
a3a15b4d JL |
2624 | checking will not be reliable and GCC will issue a warning. The |
2625 | default is chosen so that GCC only generates one instruction on most | |
861bb6c1 JL |
2626 | systems. You should normally not change the default value of this macro. |
2627 | ||
2628 | @findex STACK_CHECK_FIXED_FRAME_SIZE | |
2629 | @item STACK_CHECK_FIXED_FRAME_SIZE | |
a3a15b4d | 2630 | GCC uses this value to generate the above warning message. It |
861bb6c1 JL |
2631 | represents the amount of fixed frame used by a function, not including |
2632 | space for any callee-saved registers, temporaries and user variables. | |
2633 | You need only specify an upper bound for this amount and will normally | |
2634 | use the default of four words. | |
2635 | ||
2636 | @findex STACK_CHECK_MAX_VAR_SIZE | |
2637 | @item STACK_CHECK_MAX_VAR_SIZE | |
a3a15b4d | 2638 | The maximum size, in bytes, of an object that GCC will place in the |
861bb6c1 JL |
2639 | fixed area of the stack frame when the user specifies |
2640 | @samp{-fstack-check}. | |
a3a15b4d | 2641 | GCC computed the default from the values of the above macros and you will |
861bb6c1 | 2642 | normally not need to override that default. |
feca2ed3 JW |
2643 | @end table |
2644 | ||
2645 | @need 2000 | |
2646 | @node Frame Registers | |
2647 | @subsection Registers That Address the Stack Frame | |
2648 | ||
2649 | @c prevent bad page break with this line | |
2650 | This discusses registers that address the stack frame. | |
2651 | ||
2652 | @table @code | |
2653 | @findex STACK_POINTER_REGNUM | |
2654 | @item STACK_POINTER_REGNUM | |
2655 | The register number of the stack pointer register, which must also be a | |
2656 | fixed register according to @code{FIXED_REGISTERS}. On most machines, | |
2657 | the hardware determines which register this is. | |
2658 | ||
2659 | @findex FRAME_POINTER_REGNUM | |
2660 | @item FRAME_POINTER_REGNUM | |
2661 | The register number of the frame pointer register, which is used to | |
2662 | access automatic variables in the stack frame. On some machines, the | |
2663 | hardware determines which register this is. On other machines, you can | |
2664 | choose any register you wish for this purpose. | |
2665 | ||
2666 | @findex HARD_FRAME_POINTER_REGNUM | |
2667 | @item HARD_FRAME_POINTER_REGNUM | |
2668 | On some machines the offset between the frame pointer and starting | |
2669 | offset of the automatic variables is not known until after register | |
2670 | allocation has been done (for example, because the saved registers are | |
2671 | between these two locations). On those machines, define | |
2672 | @code{FRAME_POINTER_REGNUM} the number of a special, fixed register to | |
2673 | be used internally until the offset is known, and define | |
556e0f21 | 2674 | @code{HARD_FRAME_POINTER_REGNUM} to be the actual hard register number |
feca2ed3 JW |
2675 | used for the frame pointer. |
2676 | ||
2677 | You should define this macro only in the very rare circumstances when it | |
2678 | is not possible to calculate the offset between the frame pointer and | |
2679 | the automatic variables until after register allocation has been | |
2680 | completed. When this macro is defined, you must also indicate in your | |
2681 | definition of @code{ELIMINABLE_REGS} how to eliminate | |
2682 | @code{FRAME_POINTER_REGNUM} into either @code{HARD_FRAME_POINTER_REGNUM} | |
2683 | or @code{STACK_POINTER_REGNUM}. | |
2684 | ||
2685 | Do not define this macro if it would be the same as | |
2686 | @code{FRAME_POINTER_REGNUM}. | |
2687 | ||
2688 | @findex ARG_POINTER_REGNUM | |
2689 | @item ARG_POINTER_REGNUM | |
2690 | The register number of the arg pointer register, which is used to access | |
2691 | the function's argument list. On some machines, this is the same as the | |
2692 | frame pointer register. On some machines, the hardware determines which | |
2693 | register this is. On other machines, you can choose any register you | |
2694 | wish for this purpose. If this is not the same register as the frame | |
2695 | pointer register, then you must mark it as a fixed register according to | |
2696 | @code{FIXED_REGISTERS}, or arrange to be able to eliminate it | |
2697 | (@pxref{Elimination}). | |
2698 | ||
2699 | @findex RETURN_ADDRESS_POINTER_REGNUM | |
2700 | @item RETURN_ADDRESS_POINTER_REGNUM | |
2701 | The register number of the return address pointer register, which is used to | |
2702 | access the current function's return address from the stack. On some | |
2703 | machines, the return address is not at a fixed offset from the frame | |
2704 | pointer or stack pointer or argument pointer. This register can be defined | |
2705 | to point to the return address on the stack, and then be converted by | |
2706 | @code{ELIMINABLE_REGS} into either the frame pointer or stack pointer. | |
2707 | ||
2708 | Do not define this macro unless there is no other way to get the return | |
2709 | address from the stack. | |
2710 | ||
2711 | @findex STATIC_CHAIN_REGNUM | |
2712 | @findex STATIC_CHAIN_INCOMING_REGNUM | |
2713 | @item STATIC_CHAIN_REGNUM | |
2714 | @itemx STATIC_CHAIN_INCOMING_REGNUM | |
2715 | Register numbers used for passing a function's static chain pointer. If | |
2716 | register windows are used, the register number as seen by the called | |
2717 | function is @code{STATIC_CHAIN_INCOMING_REGNUM}, while the register | |
2718 | number as seen by the calling function is @code{STATIC_CHAIN_REGNUM}. If | |
2719 | these registers are the same, @code{STATIC_CHAIN_INCOMING_REGNUM} need | |
2720 | not be defined.@refill | |
2721 | ||
2722 | The static chain register need not be a fixed register. | |
2723 | ||
2724 | If the static chain is passed in memory, these macros should not be | |
2725 | defined; instead, the next two macros should be defined. | |
2726 | ||
2727 | @findex STATIC_CHAIN | |
2728 | @findex STATIC_CHAIN_INCOMING | |
2729 | @item STATIC_CHAIN | |
2730 | @itemx STATIC_CHAIN_INCOMING | |
2731 | If the static chain is passed in memory, these macros provide rtx giving | |
2732 | @code{mem} expressions that denote where they are stored. | |
2733 | @code{STATIC_CHAIN} and @code{STATIC_CHAIN_INCOMING} give the locations | |
2734 | as seen by the calling and called functions, respectively. Often the former | |
2735 | will be at an offset from the stack pointer and the latter at an offset from | |
2736 | the frame pointer.@refill | |
2737 | ||
2738 | @findex stack_pointer_rtx | |
2739 | @findex frame_pointer_rtx | |
2740 | @findex arg_pointer_rtx | |
2741 | The variables @code{stack_pointer_rtx}, @code{frame_pointer_rtx}, and | |
2742 | @code{arg_pointer_rtx} will have been initialized prior to the use of these | |
2743 | macros and should be used to refer to those items. | |
2744 | ||
2745 | If the static chain is passed in a register, the two previous macros should | |
2746 | be defined instead. | |
2747 | @end table | |
2748 | ||
2749 | @node Elimination | |
2750 | @subsection Eliminating Frame Pointer and Arg Pointer | |
2751 | ||
2752 | @c prevent bad page break with this line | |
2753 | This is about eliminating the frame pointer and arg pointer. | |
2754 | ||
2755 | @table @code | |
2756 | @findex FRAME_POINTER_REQUIRED | |
2757 | @item FRAME_POINTER_REQUIRED | |
2758 | A C expression which is nonzero if a function must have and use a frame | |
2759 | pointer. This expression is evaluated in the reload pass. If its value is | |
2760 | nonzero the function will have a frame pointer. | |
2761 | ||
2762 | The expression can in principle examine the current function and decide | |
2763 | according to the facts, but on most machines the constant 0 or the | |
2764 | constant 1 suffices. Use 0 when the machine allows code to be generated | |
2765 | with no frame pointer, and doing so saves some time or space. Use 1 | |
2766 | when there is no possible advantage to avoiding a frame pointer. | |
2767 | ||
2768 | In certain cases, the compiler does not know how to produce valid code | |
2769 | without a frame pointer. The compiler recognizes those cases and | |
2770 | automatically gives the function a frame pointer regardless of what | |
2771 | @code{FRAME_POINTER_REQUIRED} says. You don't need to worry about | |
2772 | them.@refill | |
2773 | ||
2774 | In a function that does not require a frame pointer, the frame pointer | |
2775 | register can be allocated for ordinary usage, unless you mark it as a | |
2776 | fixed register. See @code{FIXED_REGISTERS} for more information. | |
2777 | ||
2778 | @findex INITIAL_FRAME_POINTER_OFFSET | |
2779 | @findex get_frame_size | |
2780 | @item INITIAL_FRAME_POINTER_OFFSET (@var{depth-var}) | |
2781 | A C statement to store in the variable @var{depth-var} the difference | |
2782 | between the frame pointer and the stack pointer values immediately after | |
2783 | the function prologue. The value would be computed from information | |
2784 | such as the result of @code{get_frame_size ()} and the tables of | |
2785 | registers @code{regs_ever_live} and @code{call_used_regs}. | |
2786 | ||
2787 | If @code{ELIMINABLE_REGS} is defined, this macro will be not be used and | |
2788 | need not be defined. Otherwise, it must be defined even if | |
2789 | @code{FRAME_POINTER_REQUIRED} is defined to always be true; in that | |
2790 | case, you may set @var{depth-var} to anything. | |
2791 | ||
2792 | @findex ELIMINABLE_REGS | |
2793 | @item ELIMINABLE_REGS | |
2794 | If defined, this macro specifies a table of register pairs used to | |
2795 | eliminate unneeded registers that point into the stack frame. If it is not | |
2796 | defined, the only elimination attempted by the compiler is to replace | |
2797 | references to the frame pointer with references to the stack pointer. | |
2798 | ||
2799 | The definition of this macro is a list of structure initializations, each | |
2800 | of which specifies an original and replacement register. | |
2801 | ||
2802 | On some machines, the position of the argument pointer is not known until | |
2803 | the compilation is completed. In such a case, a separate hard register | |
2804 | must be used for the argument pointer. This register can be eliminated by | |
2805 | replacing it with either the frame pointer or the argument pointer, | |
2806 | depending on whether or not the frame pointer has been eliminated. | |
2807 | ||
2808 | In this case, you might specify: | |
2809 | @example | |
2810 | #define ELIMINABLE_REGS \ | |
2811 | @{@{ARG_POINTER_REGNUM, STACK_POINTER_REGNUM@}, \ | |
2812 | @{ARG_POINTER_REGNUM, FRAME_POINTER_REGNUM@}, \ | |
2813 | @{FRAME_POINTER_REGNUM, STACK_POINTER_REGNUM@}@} | |
2814 | @end example | |
2815 | ||
2816 | Note that the elimination of the argument pointer with the stack pointer is | |
2817 | specified first since that is the preferred elimination. | |
2818 | ||
2819 | @findex CAN_ELIMINATE | |
2820 | @item CAN_ELIMINATE (@var{from-reg}, @var{to-reg}) | |
2821 | A C expression that returns non-zero if the compiler is allowed to try | |
2822 | to replace register number @var{from-reg} with register number | |
2823 | @var{to-reg}. This macro need only be defined if @code{ELIMINABLE_REGS} | |
2824 | is defined, and will usually be the constant 1, since most of the cases | |
2825 | preventing register elimination are things that the compiler already | |
2826 | knows about. | |
2827 | ||
2828 | @findex INITIAL_ELIMINATION_OFFSET | |
2829 | @item INITIAL_ELIMINATION_OFFSET (@var{from-reg}, @var{to-reg}, @var{offset-var}) | |
2830 | This macro is similar to @code{INITIAL_FRAME_POINTER_OFFSET}. It | |
2831 | specifies the initial difference between the specified pair of | |
2832 | registers. This macro must be defined if @code{ELIMINABLE_REGS} is | |
2833 | defined. | |
2834 | ||
2835 | @findex LONGJMP_RESTORE_FROM_STACK | |
2836 | @item LONGJMP_RESTORE_FROM_STACK | |
2837 | Define this macro if the @code{longjmp} function restores registers from | |
2838 | the stack frames, rather than from those saved specifically by | |
2839 | @code{setjmp}. Certain quantities must not be kept in registers across | |
2840 | a call to @code{setjmp} on such machines. | |
2841 | @end table | |
2842 | ||
2843 | @node Stack Arguments | |
2844 | @subsection Passing Function Arguments on the Stack | |
2845 | @cindex arguments on stack | |
2846 | @cindex stack arguments | |
2847 | ||
2848 | The macros in this section control how arguments are passed | |
2849 | on the stack. See the following section for other macros that | |
2850 | control passing certain arguments in registers. | |
2851 | ||
2852 | @table @code | |
2853 | @findex PROMOTE_PROTOTYPES | |
2854 | @item PROMOTE_PROTOTYPES | |
7d473569 JJ |
2855 | A C expression whose value is nonzero if an argument declared in |
2856 | a prototype as an integral type smaller than @code{int} should | |
2857 | actually be passed as an @code{int}. In addition to avoiding | |
2858 | errors in certain cases of mismatch, it also makes for better | |
2859 | code on certain machines. If the macro is not defined in target | |
2860 | header files, it defaults to 0. | |
feca2ed3 | 2861 | |
f73ad30e JH |
2862 | @findex PUSH_ARGS |
2863 | @item PUSH_ARGS | |
2864 | A C expression. If nonzero, push insns will be used to pass | |
2865 | outgoing arguments. | |
2866 | If the target machine does not have a push instruction, set it to zero. | |
2867 | That directs GCC to use an alternate strategy: to | |
2868 | allocate the entire argument block and then store the arguments into | |
2869 | it. When PUSH_ARGS is nonzero, PUSH_ROUNDING must be defined too. | |
2870 | On some machines, the definition | |
2871 | ||
feca2ed3 JW |
2872 | @findex PUSH_ROUNDING |
2873 | @item PUSH_ROUNDING (@var{npushed}) | |
2874 | A C expression that is the number of bytes actually pushed onto the | |
2875 | stack when an instruction attempts to push @var{npushed} bytes. | |
feca2ed3 JW |
2876 | |
2877 | On some machines, the definition | |
2878 | ||
2879 | @example | |
2880 | #define PUSH_ROUNDING(BYTES) (BYTES) | |
2881 | @end example | |
2882 | ||
2883 | @noindent | |
2884 | will suffice. But on other machines, instructions that appear | |
2885 | to push one byte actually push two bytes in an attempt to maintain | |
2886 | alignment. Then the definition should be | |
2887 | ||
2888 | @example | |
2889 | #define PUSH_ROUNDING(BYTES) (((BYTES) + 1) & ~1) | |
2890 | @end example | |
2891 | ||
2892 | @findex ACCUMULATE_OUTGOING_ARGS | |
2893 | @findex current_function_outgoing_args_size | |
2894 | @item ACCUMULATE_OUTGOING_ARGS | |
f73ad30e | 2895 | A C expression. If nonzero, the maximum amount of space required for outgoing arguments |
feca2ed3 JW |
2896 | will be computed and placed into the variable |
2897 | @code{current_function_outgoing_args_size}. No space will be pushed | |
2898 | onto the stack for each call; instead, the function prologue should | |
2899 | increase the stack frame size by this amount. | |
2900 | ||
f73ad30e | 2901 | Setting both @code{PUSH_ARGS} and @code{ACCUMULATE_OUTGOING_ARGS} |
feca2ed3 JW |
2902 | is not proper. |
2903 | ||
2904 | @findex REG_PARM_STACK_SPACE | |
2905 | @item REG_PARM_STACK_SPACE (@var{fndecl}) | |
2906 | Define this macro if functions should assume that stack space has been | |
2907 | allocated for arguments even when their values are passed in | |
2908 | registers. | |
2909 | ||
2910 | The value of this macro is the size, in bytes, of the area reserved for | |
ab87f8c8 | 2911 | arguments passed in registers for the function represented by @var{fndecl}, |
a3a15b4d | 2912 | which can be zero if GCC is calling a library function. |
feca2ed3 JW |
2913 | |
2914 | This space can be allocated by the caller, or be a part of the | |
2915 | machine-dependent stack frame: @code{OUTGOING_REG_PARM_STACK_SPACE} says | |
2916 | which. | |
2917 | @c above is overfull. not sure what to do. --mew 5feb93 did | |
2918 | @c something, not sure if it looks good. --mew 10feb93 | |
2919 | ||
2920 | @findex MAYBE_REG_PARM_STACK_SPACE | |
2921 | @findex FINAL_REG_PARM_STACK_SPACE | |
2922 | @item MAYBE_REG_PARM_STACK_SPACE | |
2923 | @itemx FINAL_REG_PARM_STACK_SPACE (@var{const_size}, @var{var_size}) | |
2924 | Define these macros in addition to the one above if functions might | |
2925 | allocate stack space for arguments even when their values are passed | |
2926 | in registers. These should be used when the stack space allocated | |
2927 | for arguments in registers is not a simple constant independent of the | |
2928 | function declaration. | |
2929 | ||
2930 | The value of the first macro is the size, in bytes, of the area that | |
2931 | we should initially assume would be reserved for arguments passed in registers. | |
2932 | ||
2933 | The value of the second macro is the actual size, in bytes, of the area | |
2934 | that will be reserved for arguments passed in registers. This takes two | |
2935 | arguments: an integer representing the number of bytes of fixed sized | |
2936 | arguments on the stack, and a tree representing the number of bytes of | |
2937 | variable sized arguments on the stack. | |
2938 | ||
2939 | When these macros are defined, @code{REG_PARM_STACK_SPACE} will only be | |
2940 | called for libcall functions, the current function, or for a function | |
2941 | being called when it is known that such stack space must be allocated. | |
2942 | In each case this value can be easily computed. | |
2943 | ||
2944 | When deciding whether a called function needs such stack space, and how | |
a3a15b4d | 2945 | much space to reserve, GCC uses these two macros instead of |
feca2ed3 JW |
2946 | @code{REG_PARM_STACK_SPACE}. |
2947 | ||
2948 | @findex OUTGOING_REG_PARM_STACK_SPACE | |
2949 | @item OUTGOING_REG_PARM_STACK_SPACE | |
2950 | Define this if it is the responsibility of the caller to allocate the area | |
2951 | reserved for arguments passed in registers. | |
2952 | ||
2953 | If @code{ACCUMULATE_OUTGOING_ARGS} is defined, this macro controls | |
2954 | whether the space for these arguments counts in the value of | |
2955 | @code{current_function_outgoing_args_size}. | |
2956 | ||
2957 | @findex STACK_PARMS_IN_REG_PARM_AREA | |
2958 | @item STACK_PARMS_IN_REG_PARM_AREA | |
2959 | Define this macro if @code{REG_PARM_STACK_SPACE} is defined, but the | |
2960 | stack parameters don't skip the area specified by it. | |
2961 | @c i changed this, makes more sens and it should have taken care of the | |
2962 | @c overfull.. not as specific, tho. --mew 5feb93 | |
2963 | ||
2964 | Normally, when a parameter is not passed in registers, it is placed on the | |
2965 | stack beyond the @code{REG_PARM_STACK_SPACE} area. Defining this macro | |
2966 | suppresses this behavior and causes the parameter to be passed on the | |
2967 | stack in its natural location. | |
2968 | ||
2969 | @findex RETURN_POPS_ARGS | |
2970 | @item RETURN_POPS_ARGS (@var{fundecl}, @var{funtype}, @var{stack-size}) | |
2971 | A C expression that should indicate the number of bytes of its own | |
2972 | arguments that a function pops on returning, or 0 if the | |
2973 | function pops no arguments and the caller must therefore pop them all | |
2974 | after the function returns. | |
2975 | ||
2976 | @var{fundecl} is a C variable whose value is a tree node that describes | |
2977 | the function in question. Normally it is a node of type | |
2978 | @code{FUNCTION_DECL} that describes the declaration of the function. | |
2979 | From this you can obtain the DECL_MACHINE_ATTRIBUTES of the function. | |
2980 | ||
2981 | @var{funtype} is a C variable whose value is a tree node that | |
2982 | describes the function in question. Normally it is a node of type | |
2983 | @code{FUNCTION_TYPE} that describes the data type of the function. | |
2984 | From this it is possible to obtain the data types of the value and | |
2985 | arguments (if known). | |
2986 | ||
861bb6c1 | 2987 | When a call to a library function is being considered, @var{fundecl} |
feca2ed3 JW |
2988 | will contain an identifier node for the library function. Thus, if |
2989 | you need to distinguish among various library functions, you can do so | |
2990 | by their names. Note that ``library function'' in this context means | |
2991 | a function used to perform arithmetic, whose name is known specially | |
2992 | in the compiler and was not mentioned in the C code being compiled. | |
2993 | ||
2994 | @var{stack-size} is the number of bytes of arguments passed on the | |
2995 | stack. If a variable number of bytes is passed, it is zero, and | |
2996 | argument popping will always be the responsibility of the calling function. | |
2997 | ||
2998 | On the Vax, all functions always pop their arguments, so the definition | |
2999 | of this macro is @var{stack-size}. On the 68000, using the standard | |
3000 | calling convention, no functions pop their arguments, so the value of | |
3001 | the macro is always 0 in this case. But an alternative calling | |
3002 | convention is available in which functions that take a fixed number of | |
3003 | arguments pop them but other functions (such as @code{printf}) pop | |
3004 | nothing (the caller pops all). When this convention is in use, | |
3005 | @var{funtype} is examined to determine whether a function takes a fixed | |
3006 | number of arguments. | |
3007 | @end table | |
3008 | ||
3009 | @node Register Arguments | |
3010 | @subsection Passing Arguments in Registers | |
3011 | @cindex arguments in registers | |
3012 | @cindex registers arguments | |
3013 | ||
3014 | This section describes the macros which let you control how various | |
3015 | types of arguments are passed in registers or how they are arranged in | |
3016 | the stack. | |
3017 | ||
3018 | @table @code | |
3019 | @findex FUNCTION_ARG | |
3020 | @item FUNCTION_ARG (@var{cum}, @var{mode}, @var{type}, @var{named}) | |
3021 | A C expression that controls whether a function argument is passed | |
3022 | in a register, and which register. | |
3023 | ||
3024 | The arguments are @var{cum}, which summarizes all the previous | |
3025 | arguments; @var{mode}, the machine mode of the argument; @var{type}, | |
3026 | the data type of the argument as a tree node or 0 if that is not known | |
3027 | (which happens for C support library functions); and @var{named}, | |
3028 | which is 1 for an ordinary argument and 0 for nameless arguments that | |
3029 | correspond to @samp{@dots{}} in the called function's prototype. | |
3719d27b JO |
3030 | @var{type} can be an incomplete type if a syntax error has previously |
3031 | occurred. | |
feca2ed3 JW |
3032 | |
3033 | The value of the expression is usually either a @code{reg} RTX for the | |
3034 | hard register in which to pass the argument, or zero to pass the | |
3035 | argument on the stack. | |
3036 | ||
3037 | For machines like the Vax and 68000, where normally all arguments are | |
3038 | pushed, zero suffices as a definition. | |
3039 | ||
3040 | The value of the expression can also be a @code{parallel} RTX. This is | |
3041 | used when an argument is passed in multiple locations. The mode of the | |
3042 | of the @code{parallel} should be the mode of the entire argument. The | |
3043 | @code{parallel} holds any number of @code{expr_list} pairs; each one | |
f797c10b NC |
3044 | describes where part of the argument is passed. In each |
3045 | @code{expr_list} the first operand must be a @code{reg} RTX for the hard | |
3046 | register in which to pass this part of the argument, and the mode of the | |
3047 | register RTX indicates how large this part of the argument is. The | |
3048 | second operand of the @code{expr_list} is a @code{const_int} which gives | |
3049 | the offset in bytes into the entire argument of where this part starts. | |
3050 | As a special exception the first @code{expr_list} in the @code{parallel} | |
c980b85b NC |
3051 | RTX may have a first operand of zero. This indicates that the entire |
3052 | argument is also stored on the stack. | |
feca2ed3 JW |
3053 | |
3054 | @cindex @file{stdarg.h} and register arguments | |
5490d604 | 3055 | The usual way to make the ISO library @file{stdarg.h} work on a machine |
feca2ed3 JW |
3056 | where some arguments are usually passed in registers, is to cause |
3057 | nameless arguments to be passed on the stack instead. This is done | |
3058 | by making @code{FUNCTION_ARG} return 0 whenever @var{named} is 0. | |
3059 | ||
3060 | @cindex @code{MUST_PASS_IN_STACK}, and @code{FUNCTION_ARG} | |
3061 | @cindex @code{REG_PARM_STACK_SPACE}, and @code{FUNCTION_ARG} | |
3062 | You may use the macro @code{MUST_PASS_IN_STACK (@var{mode}, @var{type})} | |
3063 | in the definition of this macro to determine if this argument is of a | |
3064 | type that must be passed in the stack. If @code{REG_PARM_STACK_SPACE} | |
3065 | is not defined and @code{FUNCTION_ARG} returns non-zero for such an | |
3066 | argument, the compiler will abort. If @code{REG_PARM_STACK_SPACE} is | |
3067 | defined, the argument will be computed in the stack and then loaded into | |
3068 | a register. | |
3069 | ||
d9a4ee00 JL |
3070 | @findex MUST_PASS_IN_STACK |
3071 | @item MUST_PASS_IN_STACK (@var{mode}, @var{type}) | |
3072 | Define as a C expression that evaluates to nonzero if we do not know how | |
3073 | to pass TYPE solely in registers. The file @file{expr.h} defines a | |
3074 | definition that is usually appropriate, refer to @file{expr.h} for additional | |
3075 | documentation. | |
3076 | ||
feca2ed3 JW |
3077 | @findex FUNCTION_INCOMING_ARG |
3078 | @item FUNCTION_INCOMING_ARG (@var{cum}, @var{mode}, @var{type}, @var{named}) | |
3079 | Define this macro if the target machine has ``register windows'', so | |
3080 | that the register in which a function sees an arguments is not | |
3081 | necessarily the same as the one in which the caller passed the | |
3082 | argument. | |
3083 | ||
3084 | For such machines, @code{FUNCTION_ARG} computes the register in which | |
3085 | the caller passes the value, and @code{FUNCTION_INCOMING_ARG} should | |
3086 | be defined in a similar fashion to tell the function being called | |
3087 | where the arguments will arrive. | |
3088 | ||
3089 | If @code{FUNCTION_INCOMING_ARG} is not defined, @code{FUNCTION_ARG} | |
3090 | serves both purposes.@refill | |
3091 | ||
3092 | @findex FUNCTION_ARG_PARTIAL_NREGS | |
3093 | @item FUNCTION_ARG_PARTIAL_NREGS (@var{cum}, @var{mode}, @var{type}, @var{named}) | |
3094 | A C expression for the number of words, at the beginning of an | |
6b72173a | 3095 | argument, that must be put in registers. The value must be zero for |
feca2ed3 JW |
3096 | arguments that are passed entirely in registers or that are entirely |
3097 | pushed on the stack. | |
3098 | ||
3099 | On some machines, certain arguments must be passed partially in | |
3100 | registers and partially in memory. On these machines, typically the | |
3101 | first @var{n} words of arguments are passed in registers, and the rest | |
3102 | on the stack. If a multi-word argument (a @code{double} or a | |
3103 | structure) crosses that boundary, its first few words must be passed | |
3104 | in registers and the rest must be pushed. This macro tells the | |
3105 | compiler when this occurs, and how many of the words should go in | |
3106 | registers. | |
3107 | ||
3108 | @code{FUNCTION_ARG} for these arguments should return the first | |
3109 | register to be used by the caller for this argument; likewise | |
3110 | @code{FUNCTION_INCOMING_ARG}, for the called function. | |
3111 | ||
3112 | @findex FUNCTION_ARG_PASS_BY_REFERENCE | |
3113 | @item FUNCTION_ARG_PASS_BY_REFERENCE (@var{cum}, @var{mode}, @var{type}, @var{named}) | |
3114 | A C expression that indicates when an argument must be passed by reference. | |
3115 | If nonzero for an argument, a copy of that argument is made in memory and a | |
3116 | pointer to the argument is passed instead of the argument itself. | |
3117 | The pointer is passed in whatever way is appropriate for passing a pointer | |
3118 | to that type. | |
3119 | ||
3120 | On machines where @code{REG_PARM_STACK_SPACE} is not defined, a suitable | |
3121 | definition of this macro might be | |
3122 | @smallexample | |
3123 | #define FUNCTION_ARG_PASS_BY_REFERENCE\ | |
3124 | (CUM, MODE, TYPE, NAMED) \ | |
3125 | MUST_PASS_IN_STACK (MODE, TYPE) | |
3126 | @end smallexample | |
3127 | @c this is *still* too long. --mew 5feb93 | |
3128 | ||
3129 | @findex FUNCTION_ARG_CALLEE_COPIES | |
3130 | @item FUNCTION_ARG_CALLEE_COPIES (@var{cum}, @var{mode}, @var{type}, @var{named}) | |
3131 | If defined, a C expression that indicates when it is the called function's | |
3132 | responsibility to make a copy of arguments passed by invisible reference. | |
3133 | Normally, the caller makes a copy and passes the address of the copy to the | |
3134 | routine being called. When FUNCTION_ARG_CALLEE_COPIES is defined and is | |
3135 | nonzero, the caller does not make a copy. Instead, it passes a pointer to the | |
3136 | ``live'' value. The called function must not modify this value. If it can be | |
3137 | determined that the value won't be modified, it need not make a copy; | |
3138 | otherwise a copy must be made. | |
3139 | ||
3140 | @findex CUMULATIVE_ARGS | |
3141 | @item CUMULATIVE_ARGS | |
3142 | A C type for declaring a variable that is used as the first argument of | |
3143 | @code{FUNCTION_ARG} and other related values. For some target machines, | |
3144 | the type @code{int} suffices and can hold the number of bytes of | |
3145 | argument so far. | |
3146 | ||
3147 | There is no need to record in @code{CUMULATIVE_ARGS} anything about the | |
3148 | arguments that have been passed on the stack. The compiler has other | |
3149 | variables to keep track of that. For target machines on which all | |
3150 | arguments are passed on the stack, there is no need to store anything in | |
3151 | @code{CUMULATIVE_ARGS}; however, the data structure must exist and | |
3152 | should not be empty, so use @code{int}. | |
3153 | ||
3154 | @findex INIT_CUMULATIVE_ARGS | |
3155 | @item INIT_CUMULATIVE_ARGS (@var{cum}, @var{fntype}, @var{libname}, @var{indirect}) | |
3156 | A C statement (sans semicolon) for initializing the variable @var{cum} | |
3157 | for the state at the beginning of the argument list. The variable has | |
3158 | type @code{CUMULATIVE_ARGS}. The value of @var{fntype} is the tree node | |
3159 | for the data type of the function which will receive the args, or 0 | |
3160 | if the args are to a compiler support library function. The value of | |
3161 | @var{indirect} is nonzero when processing an indirect call, for example | |
3162 | a call through a function pointer. The value of @var{indirect} is zero | |
3163 | for a call to an explicitly named function, a library function call, or when | |
3164 | @code{INIT_CUMULATIVE_ARGS} is used to find arguments for the function | |
3165 | being compiled. | |
3166 | ||
3167 | When processing a call to a compiler support library function, | |
3168 | @var{libname} identifies which one. It is a @code{symbol_ref} rtx which | |
3169 | contains the name of the function, as a string. @var{libname} is 0 when | |
3170 | an ordinary C function call is being processed. Thus, each time this | |
3171 | macro is called, either @var{libname} or @var{fntype} is nonzero, but | |
3172 | never both of them at once. | |
3173 | ||
97fc4caf AO |
3174 | @findex INIT_CUMULATIVE_LIBCALL_ARGS |
3175 | @item INIT_CUMULATIVE_LIBCALL_ARGS (@var{cum}, @var{mode}, @var{libname}) | |
3176 | Like @code{INIT_CUMULATIVE_ARGS} but only used for outgoing libcalls, | |
3177 | it gets a @code{MODE} argument instead of @var{fntype}, that would be | |
3178 | @code{NULL}. @var{indirect} would always be zero, too. If this macro | |
3179 | is not defined, @code{INIT_CUMULATIVE_ARGS (cum, NULL_RTX, libname, | |
3180 | 0)} is used instead. | |
3181 | ||
feca2ed3 JW |
3182 | @findex INIT_CUMULATIVE_INCOMING_ARGS |
3183 | @item INIT_CUMULATIVE_INCOMING_ARGS (@var{cum}, @var{fntype}, @var{libname}) | |
3184 | Like @code{INIT_CUMULATIVE_ARGS} but overrides it for the purposes of | |
3185 | finding the arguments for the function being compiled. If this macro is | |
3186 | undefined, @code{INIT_CUMULATIVE_ARGS} is used instead. | |
3187 | ||
3188 | The value passed for @var{libname} is always 0, since library routines | |
a3a15b4d | 3189 | with special calling conventions are never compiled with GCC. The |
feca2ed3 JW |
3190 | argument @var{libname} exists for symmetry with |
3191 | @code{INIT_CUMULATIVE_ARGS}. | |
3192 | @c could use "this macro" in place of @code{INIT_CUMULATIVE_ARGS}, maybe. | |
3193 | @c --mew 5feb93 i switched the order of the sentences. --mew 10feb93 | |
3194 | ||
3195 | @findex FUNCTION_ARG_ADVANCE | |
3196 | @item FUNCTION_ARG_ADVANCE (@var{cum}, @var{mode}, @var{type}, @var{named}) | |
3197 | A C statement (sans semicolon) to update the summarizer variable | |
3198 | @var{cum} to advance past an argument in the argument list. The | |
3199 | values @var{mode}, @var{type} and @var{named} describe that argument. | |
3200 | Once this is done, the variable @var{cum} is suitable for analyzing | |
3201 | the @emph{following} argument with @code{FUNCTION_ARG}, etc.@refill | |
3202 | ||
3203 | This macro need not do anything if the argument in question was passed | |
3204 | on the stack. The compiler knows how to track the amount of stack space | |
3205 | used for arguments without any special help. | |
3206 | ||
3207 | @findex FUNCTION_ARG_PADDING | |
3208 | @item FUNCTION_ARG_PADDING (@var{mode}, @var{type}) | |
3209 | If defined, a C expression which determines whether, and in which direction, | |
3210 | to pad out an argument with extra space. The value should be of type | |
3211 | @code{enum direction}: either @code{upward} to pad above the argument, | |
3212 | @code{downward} to pad below, or @code{none} to inhibit padding. | |
3213 | ||
3214 | The @emph{amount} of padding is always just enough to reach the next | |
3215 | multiple of @code{FUNCTION_ARG_BOUNDARY}; this macro does not control | |
3216 | it. | |
3217 | ||
3218 | This macro has a default definition which is right for most systems. | |
3219 | For little-endian machines, the default is to pad upward. For | |
3220 | big-endian machines, the default is to pad downward for an argument of | |
3221 | constant size shorter than an @code{int}, and upward otherwise. | |
3222 | ||
5e4f6244 CP |
3223 | @findex PAD_VARARGS_DOWN |
3224 | @item PAD_VARARGS_DOWN | |
3225 | If defined, a C expression which determines whether the default | |
3226 | implementation of va_arg will attempt to pad down before reading the | |
3227 | next argument, if that argument is smaller than its aligned space as | |
3228 | controlled by @code{PARM_BOUNDARY}. If this macro is not defined, all such | |
3229 | arguments are padded down if @code{BYTES_BIG_ENDIAN} is true. | |
3230 | ||
feca2ed3 JW |
3231 | @findex FUNCTION_ARG_BOUNDARY |
3232 | @item FUNCTION_ARG_BOUNDARY (@var{mode}, @var{type}) | |
3233 | If defined, a C expression that gives the alignment boundary, in bits, | |
3234 | of an argument with the specified mode and type. If it is not defined, | |
3235 | @code{PARM_BOUNDARY} is used for all arguments. | |
3236 | ||
3237 | @findex FUNCTION_ARG_REGNO_P | |
3238 | @item FUNCTION_ARG_REGNO_P (@var{regno}) | |
3239 | A C expression that is nonzero if @var{regno} is the number of a hard | |
3240 | register in which function arguments are sometimes passed. This does | |
3241 | @emph{not} include implicit arguments such as the static chain and | |
3242 | the structure-value address. On many machines, no registers can be | |
3243 | used for this purpose since all function arguments are pushed on the | |
3244 | stack. | |
bb1b857a GK |
3245 | |
3246 | @findex LOAD_ARGS_REVERSED | |
3247 | @item LOAD_ARGS_REVERSED | |
3248 | If defined, the order in which arguments are loaded into their | |
3249 | respective argument registers is reversed so that the last | |
4e5f1329 | 3250 | argument is loaded first. This macro only affects arguments |
bb1b857a GK |
3251 | passed in registers. |
3252 | ||
feca2ed3 JW |
3253 | @end table |
3254 | ||
3255 | @node Scalar Return | |
3256 | @subsection How Scalar Function Values Are Returned | |
3257 | @cindex return values in registers | |
3258 | @cindex values, returned by functions | |
3259 | @cindex scalars, returned as values | |
3260 | ||
3261 | This section discusses the macros that control returning scalars as | |
3262 | values---values that can fit in registers. | |
3263 | ||
3264 | @table @code | |
3265 | @findex TRADITIONAL_RETURN_FLOAT | |
3266 | @item TRADITIONAL_RETURN_FLOAT | |
3267 | Define this macro if @samp{-traditional} should not cause functions | |
3268 | declared to return @code{float} to convert the value to @code{double}. | |
3269 | ||
3270 | @findex FUNCTION_VALUE | |
3271 | @item FUNCTION_VALUE (@var{valtype}, @var{func}) | |
3272 | A C expression to create an RTX representing the place where a | |
3273 | function returns a value of data type @var{valtype}. @var{valtype} is | |
3274 | a tree node representing a data type. Write @code{TYPE_MODE | |
3275 | (@var{valtype})} to get the machine mode used to represent that type. | |
3276 | On many machines, only the mode is relevant. (Actually, on most | |
3277 | machines, scalar values are returned in the same place regardless of | |
3278 | mode).@refill | |
3279 | ||
3280 | The value of the expression is usually a @code{reg} RTX for the hard | |
3281 | register where the return value is stored. The value can also be a | |
3282 | @code{parallel} RTX, if the return value is in multiple places. See | |
3283 | @code{FUNCTION_ARG} for an explanation of the @code{parallel} form. | |
3284 | ||
3285 | If @code{PROMOTE_FUNCTION_RETURN} is defined, you must apply the same | |
3286 | promotion rules specified in @code{PROMOTE_MODE} if @var{valtype} is a | |
3287 | scalar type. | |
3288 | ||
3289 | If the precise function being called is known, @var{func} is a tree | |
3290 | node (@code{FUNCTION_DECL}) for it; otherwise, @var{func} is a null | |
3291 | pointer. This makes it possible to use a different value-returning | |
3292 | convention for specific functions when all their calls are | |
3293 | known.@refill | |
3294 | ||
3295 | @code{FUNCTION_VALUE} is not used for return vales with aggregate data | |
3296 | types, because these are returned in another way. See | |
3297 | @code{STRUCT_VALUE_REGNUM} and related macros, below. | |
3298 | ||
3299 | @findex FUNCTION_OUTGOING_VALUE | |
3300 | @item FUNCTION_OUTGOING_VALUE (@var{valtype}, @var{func}) | |
3301 | Define this macro if the target machine has ``register windows'' | |
3302 | so that the register in which a function returns its value is not | |
3303 | the same as the one in which the caller sees the value. | |
3304 | ||
3305 | For such machines, @code{FUNCTION_VALUE} computes the register in which | |
3306 | the caller will see the value. @code{FUNCTION_OUTGOING_VALUE} should be | |
3307 | defined in a similar fashion to tell the function where to put the | |
3308 | value.@refill | |
3309 | ||
3310 | If @code{FUNCTION_OUTGOING_VALUE} is not defined, | |
3311 | @code{FUNCTION_VALUE} serves both purposes.@refill | |
3312 | ||
3313 | @code{FUNCTION_OUTGOING_VALUE} is not used for return vales with | |
3314 | aggregate data types, because these are returned in another way. See | |
3315 | @code{STRUCT_VALUE_REGNUM} and related macros, below. | |
3316 | ||
3317 | @findex LIBCALL_VALUE | |
3318 | @item LIBCALL_VALUE (@var{mode}) | |
3319 | A C expression to create an RTX representing the place where a library | |
3320 | function returns a value of mode @var{mode}. If the precise function | |
3321 | being called is known, @var{func} is a tree node | |
3322 | (@code{FUNCTION_DECL}) for it; otherwise, @var{func} is a null | |
3323 | pointer. This makes it possible to use a different value-returning | |
3324 | convention for specific functions when all their calls are | |
3325 | known.@refill | |
3326 | ||
3327 | Note that ``library function'' in this context means a compiler | |
3328 | support routine, used to perform arithmetic, whose name is known | |
3329 | specially by the compiler and was not mentioned in the C code being | |
3330 | compiled. | |
3331 | ||
3332 | The definition of @code{LIBRARY_VALUE} need not be concerned aggregate | |
3333 | data types, because none of the library functions returns such types. | |
3334 | ||
3335 | @findex FUNCTION_VALUE_REGNO_P | |
3336 | @item FUNCTION_VALUE_REGNO_P (@var{regno}) | |
3337 | A C expression that is nonzero if @var{regno} is the number of a hard | |
3338 | register in which the values of called function may come back. | |
3339 | ||
3340 | A register whose use for returning values is limited to serving as the | |
3341 | second of a pair (for a value of type @code{double}, say) need not be | |
3342 | recognized by this macro. So for most machines, this definition | |
3343 | suffices: | |
3344 | ||
3345 | @example | |
3346 | #define FUNCTION_VALUE_REGNO_P(N) ((N) == 0) | |
3347 | @end example | |
3348 | ||
3349 | If the machine has register windows, so that the caller and the called | |
3350 | function use different registers for the return value, this macro | |
3351 | should recognize only the caller's register numbers. | |
3352 | ||
3353 | @findex APPLY_RESULT_SIZE | |
3354 | @item APPLY_RESULT_SIZE | |
3355 | Define this macro if @samp{untyped_call} and @samp{untyped_return} | |
3356 | need more space than is implied by @code{FUNCTION_VALUE_REGNO_P} for | |
3357 | saving and restoring an arbitrary return value. | |
3358 | @end table | |
3359 | ||
3360 | @node Aggregate Return | |
3361 | @subsection How Large Values Are Returned | |
3362 | @cindex aggregates as return values | |
3363 | @cindex large return values | |
3364 | @cindex returning aggregate values | |
3365 | @cindex structure value address | |
3366 | ||
3367 | When a function value's mode is @code{BLKmode} (and in some other | |
3368 | cases), the value is not returned according to @code{FUNCTION_VALUE} | |
3369 | (@pxref{Scalar Return}). Instead, the caller passes the address of a | |
3370 | block of memory in which the value should be stored. This address | |
3371 | is called the @dfn{structure value address}. | |
3372 | ||
3373 | This section describes how to control returning structure values in | |
3374 | memory. | |
3375 | ||
3376 | @table @code | |
3377 | @findex RETURN_IN_MEMORY | |
3378 | @item RETURN_IN_MEMORY (@var{type}) | |
3379 | A C expression which can inhibit the returning of certain function | |
3380 | values in registers, based on the type of value. A nonzero value says | |
3381 | to return the function value in memory, just as large structures are | |
3382 | always returned. Here @var{type} will be a C expression of type | |
3383 | @code{tree}, representing the data type of the value. | |
3384 | ||
3385 | Note that values of mode @code{BLKmode} must be explicitly handled | |
3386 | by this macro. Also, the option @samp{-fpcc-struct-return} | |
3387 | takes effect regardless of this macro. On most systems, it is | |
3388 | possible to leave the macro undefined; this causes a default | |
3389 | definition to be used, whose value is the constant 1 for @code{BLKmode} | |
3390 | values, and 0 otherwise. | |
3391 | ||
3392 | Do not use this macro to indicate that structures and unions should always | |
3393 | be returned in memory. You should instead use @code{DEFAULT_PCC_STRUCT_RETURN} | |
3394 | to indicate this. | |
3395 | ||
3396 | @findex DEFAULT_PCC_STRUCT_RETURN | |
3397 | @item DEFAULT_PCC_STRUCT_RETURN | |
3398 | Define this macro to be 1 if all structure and union return values must be | |
3399 | in memory. Since this results in slower code, this should be defined | |
3400 | only if needed for compatibility with other compilers or with an ABI. | |
3401 | If you define this macro to be 0, then the conventions used for structure | |
3402 | and union return values are decided by the @code{RETURN_IN_MEMORY} macro. | |
3403 | ||
3404 | If not defined, this defaults to the value 1. | |
3405 | ||
3406 | @findex STRUCT_VALUE_REGNUM | |
3407 | @item STRUCT_VALUE_REGNUM | |
3408 | If the structure value address is passed in a register, then | |
3409 | @code{STRUCT_VALUE_REGNUM} should be the number of that register. | |
3410 | ||
3411 | @findex STRUCT_VALUE | |
3412 | @item STRUCT_VALUE | |
3413 | If the structure value address is not passed in a register, define | |
3414 | @code{STRUCT_VALUE} as an expression returning an RTX for the place | |
3415 | where the address is passed. If it returns 0, the address is passed as | |
3416 | an ``invisible'' first argument. | |
3417 | ||
3418 | @findex STRUCT_VALUE_INCOMING_REGNUM | |
3419 | @item STRUCT_VALUE_INCOMING_REGNUM | |
3420 | On some architectures the place where the structure value address | |
3421 | is found by the called function is not the same place that the | |
3422 | caller put it. This can be due to register windows, or it could | |
3423 | be because the function prologue moves it to a different place. | |
3424 | ||
3425 | If the incoming location of the structure value address is in a | |
3426 | register, define this macro as the register number. | |
3427 | ||
3428 | @findex STRUCT_VALUE_INCOMING | |
3429 | @item STRUCT_VALUE_INCOMING | |
3430 | If the incoming location is not a register, then you should define | |
3431 | @code{STRUCT_VALUE_INCOMING} as an expression for an RTX for where the | |
3432 | called function should find the value. If it should find the value on | |
3433 | the stack, define this to create a @code{mem} which refers to the frame | |
3434 | pointer. A definition of 0 means that the address is passed as an | |
3435 | ``invisible'' first argument. | |
3436 | ||
3437 | @findex PCC_STATIC_STRUCT_RETURN | |
3438 | @item PCC_STATIC_STRUCT_RETURN | |
3439 | Define this macro if the usual system convention on the target machine | |
3440 | for returning structures and unions is for the called function to return | |
3441 | the address of a static variable containing the value. | |
3442 | ||
3443 | Do not define this if the usual system convention is for the caller to | |
3444 | pass an address to the subroutine. | |
3445 | ||
3446 | This macro has effect in @samp{-fpcc-struct-return} mode, but it does | |
3447 | nothing when you use @samp{-freg-struct-return} mode. | |
3448 | @end table | |
3449 | ||
3450 | @node Caller Saves | |
3451 | @subsection Caller-Saves Register Allocation | |
3452 | ||
a3a15b4d | 3453 | If you enable it, GCC can save registers around function calls. This |
feca2ed3 JW |
3454 | makes it possible to use call-clobbered registers to hold variables that |
3455 | must live across calls. | |
3456 | ||
3457 | @table @code | |
3458 | @findex DEFAULT_CALLER_SAVES | |
3459 | @item DEFAULT_CALLER_SAVES | |
3460 | Define this macro if function calls on the target machine do not preserve | |
3461 | any registers; in other words, if @code{CALL_USED_REGISTERS} has 1 | |
81610a0d HPN |
3462 | for all registers. When defined, this macro enables @samp{-fcaller-saves} |
3463 | by default for all optimization levels. It has no effect for optimization | |
3464 | levels 2 and higher, where @samp{-fcaller-saves} is the default. | |
feca2ed3 JW |
3465 | |
3466 | @findex CALLER_SAVE_PROFITABLE | |
3467 | @item CALLER_SAVE_PROFITABLE (@var{refs}, @var{calls}) | |
3468 | A C expression to determine whether it is worthwhile to consider placing | |
3469 | a pseudo-register in a call-clobbered hard register and saving and | |
3470 | restoring it around each function call. The expression should be 1 when | |
3471 | this is worth doing, and 0 otherwise. | |
3472 | ||
3473 | If you don't define this macro, a default is used which is good on most | |
3474 | machines: @code{4 * @var{calls} < @var{refs}}. | |
8d5c8167 JL |
3475 | |
3476 | @findex HARD_REGNO_CALLER_SAVE_MODE | |
3477 | @item HARD_REGNO_CALLER_SAVE_MODE (@var{regno}, @var{nregs}) | |
3478 | A C expression specifying which mode is required for saving @var{nregs} | |
3479 | of a pseudo-register in call-clobbered hard register @var{regno}. If | |
3480 | @var{regno} is unsuitable for caller save, @code{VOIDmode} should be | |
3481 | returned. For most machines this macro need not be defined since GCC | |
3482 | will select the smallest suitable mode. | |
feca2ed3 JW |
3483 | @end table |
3484 | ||
3485 | @node Function Entry | |
3486 | @subsection Function Entry and Exit | |
3487 | @cindex function entry and exit | |
3488 | @cindex prologue | |
3489 | @cindex epilogue | |
3490 | ||
3491 | This section describes the macros that output function entry | |
3492 | (@dfn{prologue}) and exit (@dfn{epilogue}) code. | |
3493 | ||
3494 | @table @code | |
3495 | @findex FUNCTION_PROLOGUE | |
3496 | @item FUNCTION_PROLOGUE (@var{file}, @var{size}) | |
3497 | A C compound statement that outputs the assembler code for entry to a | |
3498 | function. The prologue is responsible for setting up the stack frame, | |
3499 | initializing the frame pointer register, saving registers that must be | |
3500 | saved, and allocating @var{size} additional bytes of storage for the | |
3501 | local variables. @var{size} is an integer. @var{file} is a stdio | |
3502 | stream to which the assembler code should be output. | |
3503 | ||
3504 | The label for the beginning of the function need not be output by this | |
3505 | macro. That has already been done when the macro is run. | |
3506 | ||
3507 | @findex regs_ever_live | |
3508 | To determine which registers to save, the macro can refer to the array | |
3509 | @code{regs_ever_live}: element @var{r} is nonzero if hard register | |
3510 | @var{r} is used anywhere within the function. This implies the function | |
3511 | prologue should save register @var{r}, provided it is not one of the | |
3512 | call-used registers. (@code{FUNCTION_EPILOGUE} must likewise use | |
3513 | @code{regs_ever_live}.) | |
3514 | ||
3515 | On machines that have ``register windows'', the function entry code does | |
3516 | not save on the stack the registers that are in the windows, even if | |
3517 | they are supposed to be preserved by function calls; instead it takes | |
3518 | appropriate steps to ``push'' the register stack, if any non-call-used | |
3519 | registers are used in the function. | |
3520 | ||
3521 | @findex frame_pointer_needed | |
3522 | On machines where functions may or may not have frame-pointers, the | |
3523 | function entry code must vary accordingly; it must set up the frame | |
3524 | pointer if one is wanted, and not otherwise. To determine whether a | |
3525 | frame pointer is in wanted, the macro can refer to the variable | |
3526 | @code{frame_pointer_needed}. The variable's value will be 1 at run | |
3527 | time in a function that needs a frame pointer. @xref{Elimination}. | |
3528 | ||
3529 | The function entry code is responsible for allocating any stack space | |
3530 | required for the function. This stack space consists of the regions | |
3531 | listed below. In most cases, these regions are allocated in the | |
3532 | order listed, with the last listed region closest to the top of the | |
3533 | stack (the lowest address if @code{STACK_GROWS_DOWNWARD} is defined, and | |
3534 | the highest address if it is not defined). You can use a different order | |
3535 | for a machine if doing so is more convenient or required for | |
3536 | compatibility reasons. Except in cases where required by standard | |
3537 | or by a debugger, there is no reason why the stack layout used by GCC | |
3538 | need agree with that used by other compilers for a machine. | |
3539 | ||
3540 | @itemize @bullet | |
3541 | @item | |
3542 | @findex current_function_pretend_args_size | |
3543 | A region of @code{current_function_pretend_args_size} bytes of | |
3544 | uninitialized space just underneath the first argument arriving on the | |
3545 | stack. (This may not be at the very start of the allocated stack region | |
3546 | if the calling sequence has pushed anything else since pushing the stack | |
3547 | arguments. But usually, on such machines, nothing else has been pushed | |
3548 | yet, because the function prologue itself does all the pushing.) This | |
3549 | region is used on machines where an argument may be passed partly in | |
3550 | registers and partly in memory, and, in some cases to support the | |
3551 | features in @file{varargs.h} and @file{stdargs.h}. | |
3552 | ||
3553 | @item | |
3554 | An area of memory used to save certain registers used by the function. | |
3555 | The size of this area, which may also include space for such things as | |
3556 | the return address and pointers to previous stack frames, is | |
3557 | machine-specific and usually depends on which registers have been used | |
3558 | in the function. Machines with register windows often do not require | |
3559 | a save area. | |
3560 | ||
3561 | @item | |
3562 | A region of at least @var{size} bytes, possibly rounded up to an allocation | |
3563 | boundary, to contain the local variables of the function. On some machines, | |
3564 | this region and the save area may occur in the opposite order, with the | |
3565 | save area closer to the top of the stack. | |
3566 | ||
3567 | @item | |
3568 | @cindex @code{ACCUMULATE_OUTGOING_ARGS} and stack frames | |
3569 | Optionally, when @code{ACCUMULATE_OUTGOING_ARGS} is defined, a region of | |
3570 | @code{current_function_outgoing_args_size} bytes to be used for outgoing | |
3571 | argument lists of the function. @xref{Stack Arguments}. | |
3572 | @end itemize | |
3573 | ||
3574 | Normally, it is necessary for the macros @code{FUNCTION_PROLOGUE} and | |
3575 | @code{FUNCTION_EPILOGUE} to treat leaf functions specially. The C | |
54ff41b7 | 3576 | variable @code{current_function_is_leaf} is nonzero for such a function. |
feca2ed3 JW |
3577 | |
3578 | @findex EXIT_IGNORE_STACK | |
3579 | @item EXIT_IGNORE_STACK | |
3580 | Define this macro as a C expression that is nonzero if the return | |
3581 | instruction or the function epilogue ignores the value of the stack | |
3582 | pointer; in other words, if it is safe to delete an instruction to | |
3583 | adjust the stack pointer before a return from the function. | |
3584 | ||
3585 | Note that this macro's value is relevant only for functions for which | |
3586 | frame pointers are maintained. It is never safe to delete a final | |
3587 | stack adjustment in a function that has no frame pointer, and the | |
3588 | compiler knows this regardless of @code{EXIT_IGNORE_STACK}. | |
3589 | ||
3590 | @findex EPILOGUE_USES | |
3591 | @item EPILOGUE_USES (@var{regno}) | |
8760eaae | 3592 | Define this macro as a C expression that is nonzero for registers that are |
feca2ed3 JW |
3593 | used by the epilogue or the @samp{return} pattern. The stack and frame |
3594 | pointer registers are already be assumed to be used as needed. | |
3595 | ||
3596 | @findex FUNCTION_EPILOGUE | |
3597 | @item FUNCTION_EPILOGUE (@var{file}, @var{size}) | |
3598 | A C compound statement that outputs the assembler code for exit from a | |
3599 | function. The epilogue is responsible for restoring the saved | |
3600 | registers and stack pointer to their values when the function was | |
3601 | called, and returning control to the caller. This macro takes the | |
3602 | same arguments as the macro @code{FUNCTION_PROLOGUE}, and the | |
3603 | registers to restore are determined from @code{regs_ever_live} and | |
3604 | @code{CALL_USED_REGISTERS} in the same way. | |
3605 | ||
3606 | On some machines, there is a single instruction that does all the work | |
3607 | of returning from the function. On these machines, give that | |
3608 | instruction the name @samp{return} and do not define the macro | |
3609 | @code{FUNCTION_EPILOGUE} at all. | |
3610 | ||
3611 | Do not define a pattern named @samp{return} if you want the | |
3612 | @code{FUNCTION_EPILOGUE} to be used. If you want the target switches | |
3613 | to control whether return instructions or epilogues are used, define a | |
3614 | @samp{return} pattern with a validity condition that tests the target | |
3615 | switches appropriately. If the @samp{return} pattern's validity | |
3616 | condition is false, epilogues will be used. | |
3617 | ||
3618 | On machines where functions may or may not have frame-pointers, the | |
3619 | function exit code must vary accordingly. Sometimes the code for these | |
3620 | two cases is completely different. To determine whether a frame pointer | |
3621 | is wanted, the macro can refer to the variable | |
3622 | @code{frame_pointer_needed}. The variable's value will be 1 when compiling | |
3623 | a function that needs a frame pointer. | |
3624 | ||
3625 | Normally, @code{FUNCTION_PROLOGUE} and @code{FUNCTION_EPILOGUE} must | |
54ff41b7 JW |
3626 | treat leaf functions specially. The C variable @code{current_function_is_leaf} |
3627 | is nonzero for such a function. @xref{Leaf Functions}. | |
feca2ed3 JW |
3628 | |
3629 | On some machines, some functions pop their arguments on exit while | |
3630 | others leave that for the caller to do. For example, the 68020 when | |
3631 | given @samp{-mrtd} pops arguments in functions that take a fixed | |
3632 | number of arguments. | |
3633 | ||
3634 | @findex current_function_pops_args | |
3635 | Your definition of the macro @code{RETURN_POPS_ARGS} decides which | |
3636 | functions pop their own arguments. @code{FUNCTION_EPILOGUE} needs to | |
3637 | know what was decided. The variable that is called | |
3638 | @code{current_function_pops_args} is the number of bytes of its | |
3639 | arguments that a function should pop. @xref{Scalar Return}. | |
3640 | @c what is the "its arguments" in the above sentence referring to, pray | |
3641 | @c tell? --mew 5feb93 | |
3642 | ||
3643 | @findex DELAY_SLOTS_FOR_EPILOGUE | |
3644 | @item DELAY_SLOTS_FOR_EPILOGUE | |
3645 | Define this macro if the function epilogue contains delay slots to which | |
3646 | instructions from the rest of the function can be ``moved''. The | |
3647 | definition should be a C expression whose value is an integer | |
3648 | representing the number of delay slots there. | |
3649 | ||
3650 | @findex ELIGIBLE_FOR_EPILOGUE_DELAY | |
3651 | @item ELIGIBLE_FOR_EPILOGUE_DELAY (@var{insn}, @var{n}) | |
3652 | A C expression that returns 1 if @var{insn} can be placed in delay | |
3653 | slot number @var{n} of the epilogue. | |
3654 | ||
3655 | The argument @var{n} is an integer which identifies the delay slot now | |
3656 | being considered (since different slots may have different rules of | |
3657 | eligibility). It is never negative and is always less than the number | |
3658 | of epilogue delay slots (what @code{DELAY_SLOTS_FOR_EPILOGUE} returns). | |
3659 | If you reject a particular insn for a given delay slot, in principle, it | |
3660 | may be reconsidered for a subsequent delay slot. Also, other insns may | |
3661 | (at least in principle) be considered for the so far unfilled delay | |
3662 | slot. | |
3663 | ||
3664 | @findex current_function_epilogue_delay_list | |
3665 | @findex final_scan_insn | |
3666 | The insns accepted to fill the epilogue delay slots are put in an RTL | |
3667 | list made with @code{insn_list} objects, stored in the variable | |
3668 | @code{current_function_epilogue_delay_list}. The insn for the first | |
3669 | delay slot comes first in the list. Your definition of the macro | |
3670 | @code{FUNCTION_EPILOGUE} should fill the delay slots by outputting the | |
3671 | insns in this list, usually by calling @code{final_scan_insn}. | |
3672 | ||
3673 | You need not define this macro if you did not define | |
3674 | @code{DELAY_SLOTS_FOR_EPILOGUE}. | |
3675 | ||
3676 | @findex ASM_OUTPUT_MI_THUNK | |
3677 | @item ASM_OUTPUT_MI_THUNK (@var{file}, @var{thunk_fndecl}, @var{delta}, @var{function}) | |
3678 | A C compound statement that outputs the assembler code for a thunk | |
3679 | function, used to implement C++ virtual function calls with multiple | |
3680 | inheritance. The thunk acts as a wrapper around a virtual function, | |
3681 | adjusting the implicit object parameter before handing control off to | |
3682 | the real function. | |
3683 | ||
3684 | First, emit code to add the integer @var{delta} to the location that | |
3685 | contains the incoming first argument. Assume that this argument | |
3686 | contains a pointer, and is the one used to pass the @code{this} pointer | |
3687 | in C++. This is the incoming argument @emph{before} the function prologue, | |
3688 | e.g. @samp{%o0} on a sparc. The addition must preserve the values of | |
3689 | all other incoming arguments. | |
3690 | ||
3691 | After the addition, emit code to jump to @var{function}, which is a | |
3692 | @code{FUNCTION_DECL}. This is a direct pure jump, not a call, and does | |
3693 | not touch the return address. Hence returning from @var{FUNCTION} will | |
3694 | return to whoever called the current @samp{thunk}. | |
3695 | ||
3696 | The effect must be as if @var{function} had been called directly with | |
3697 | the adjusted first argument. This macro is responsible for emitting all | |
3698 | of the code for a thunk function; @code{FUNCTION_PROLOGUE} and | |
3699 | @code{FUNCTION_EPILOGUE} are not invoked. | |
3700 | ||
3701 | The @var{thunk_fndecl} is redundant. (@var{delta} and @var{function} | |
3702 | have already been extracted from it.) It might possibly be useful on | |
3703 | some targets, but probably not. | |
3704 | ||
861bb6c1 JL |
3705 | If you do not define this macro, the target-independent code in the C++ |
3706 | frontend will generate a less efficient heavyweight thunk that calls | |
3707 | @var{function} instead of jumping to it. The generic approach does | |
3708 | not support varargs. | |
feca2ed3 JW |
3709 | @end table |
3710 | ||
3711 | @node Profiling | |
3712 | @subsection Generating Code for Profiling | |
3713 | @cindex profiling, code generation | |
3714 | ||
3715 | These macros will help you generate code for profiling. | |
3716 | ||
3717 | @table @code | |
3718 | @findex FUNCTION_PROFILER | |
3719 | @item FUNCTION_PROFILER (@var{file}, @var{labelno}) | |
3720 | A C statement or compound statement to output to @var{file} some | |
3721 | assembler code to call the profiling subroutine @code{mcount}. | |
feca2ed3 JW |
3722 | |
3723 | @findex mcount | |
980e2067 JL |
3724 | The details of how @code{mcount} expects to be called are determined by |
3725 | your operating system environment, not by GCC. To figure them out, | |
3726 | compile a small program for profiling using the system's installed C | |
3727 | compiler and look at the assembler code that results. | |
3728 | ||
3729 | Older implementations of @code{mcount} expect the address of a counter | |
3730 | variable to be loaded into some register. The name of this variable is | |
3731 | @samp{LP} followed by the number @var{labelno}, so you would generate | |
3732 | the name using @samp{LP%d} in a @code{fprintf}. | |
3733 | ||
411707f4 CC |
3734 | @findex PROFILE_HOOK |
3735 | @item PROFILE_HOOK | |
3736 | A C statement or compound statement to output to @var{file} some assembly | |
3737 | code to call the profiling subroutine @code{mcount} even the target does | |
3738 | not support profiling. | |
3739 | ||
980e2067 JL |
3740 | @findex NO_PROFILE_COUNTERS |
3741 | @item NO_PROFILE_COUNTERS | |
3742 | Define this macro if the @code{mcount} subroutine on your system does | |
3743 | not need a counter variable allocated for each function. This is true | |
3744 | for almost all modern implementations. If you define this macro, you | |
3745 | must not use the @var{labelno} argument to @code{FUNCTION_PROFILER}. | |
feca2ed3 JW |
3746 | |
3747 | @findex PROFILE_BEFORE_PROLOGUE | |
3748 | @item PROFILE_BEFORE_PROLOGUE | |
3749 | Define this macro if the code for function profiling should come before | |
3750 | the function prologue. Normally, the profiling code comes after. | |
3751 | ||
3752 | @findex FUNCTION_BLOCK_PROFILER | |
3753 | @vindex profile_block_flag | |
3754 | @item FUNCTION_BLOCK_PROFILER (@var{file}, @var{labelno}) | |
3755 | A C statement or compound statement to output to @var{file} some | |
3756 | assembler code to initialize basic-block profiling for the current | |
3757 | object module. The global compile flag @code{profile_block_flag} | |
956d6950 | 3758 | distinguishes two profile modes. |
feca2ed3 JW |
3759 | |
3760 | @table @code | |
3761 | @findex __bb_init_func | |
3762 | @item profile_block_flag != 2 | |
3763 | Output code to call the subroutine @code{__bb_init_func} once per | |
3764 | object module, passing it as its sole argument the address of a block | |
3765 | allocated in the object module. | |
3766 | ||
3767 | The name of the block is a local symbol made with this statement: | |
3768 | ||
3769 | @smallexample | |
3770 | ASM_GENERATE_INTERNAL_LABEL (@var{buffer}, "LPBX", 0); | |
3771 | @end smallexample | |
3772 | ||
3773 | Of course, since you are writing the definition of | |
3774 | @code{ASM_GENERATE_INTERNAL_LABEL} as well as that of this macro, you | |
3775 | can take a short cut in the definition of this macro and use the name | |
3776 | that you know will result. | |
3777 | ||
3778 | The first word of this block is a flag which will be nonzero if the | |
3779 | object module has already been initialized. So test this word first, | |
3780 | and do not call @code{__bb_init_func} if the flag is | |
3781 | nonzero. BLOCK_OR_LABEL contains a unique number which may be used to | |
3782 | generate a label as a branch destination when @code{__bb_init_func} | |
3783 | will not be called. | |
3784 | ||
3785 | Described in assembler language, the code to be output looks like: | |
3786 | ||
3787 | @example | |
3788 | cmp (LPBX0),0 | |
3789 | bne local_label | |
3790 | parameter1 <- LPBX0 | |
3791 | call __bb_init_func | |
3792 | local_label: | |
3793 | @end example | |
3794 | ||
3795 | @findex __bb_init_trace_func | |
3796 | @item profile_block_flag == 2 | |
3797 | Output code to call the subroutine @code{__bb_init_trace_func} | |
3798 | and pass two parameters to it. The first parameter is the same as | |
3799 | for @code{__bb_init_func}. The second parameter is the number of the | |
3800 | first basic block of the function as given by BLOCK_OR_LABEL. Note | |
3801 | that @code{__bb_init_trace_func} has to be called, even if the object | |
3802 | module has been initialized already. | |
3803 | ||
3804 | Described in assembler language, the code to be output looks like: | |
3805 | @example | |
3806 | parameter1 <- LPBX0 | |
3807 | parameter2 <- BLOCK_OR_LABEL | |
3808 | call __bb_init_trace_func | |
3809 | @end example | |
3810 | @end table | |
3811 | ||
3812 | @findex BLOCK_PROFILER | |
3813 | @vindex profile_block_flag | |
3814 | @item BLOCK_PROFILER (@var{file}, @var{blockno}) | |
3815 | A C statement or compound statement to output to @var{file} some | |
3816 | assembler code to increment the count associated with the basic | |
3817 | block number @var{blockno}. The global compile flag | |
956d6950 | 3818 | @code{profile_block_flag} distinguishes two profile modes. |
feca2ed3 JW |
3819 | |
3820 | @table @code | |
3821 | @item profile_block_flag != 2 | |
3822 | Output code to increment the counter directly. Basic blocks are | |
3823 | numbered separately from zero within each compilation. The count | |
3824 | associated with block number @var{blockno} is at index | |
3825 | @var{blockno} in a vector of words; the name of this array is a local | |
3826 | symbol made with this statement: | |
3827 | ||
3828 | @smallexample | |
3829 | ASM_GENERATE_INTERNAL_LABEL (@var{buffer}, "LPBX", 2); | |
3830 | @end smallexample | |
3831 | ||
3832 | @c This paragraph is the same as one a few paragraphs up. | |
3833 | @c That is not an error. | |
3834 | Of course, since you are writing the definition of | |
3835 | @code{ASM_GENERATE_INTERNAL_LABEL} as well as that of this macro, you | |
3836 | can take a short cut in the definition of this macro and use the name | |
3837 | that you know will result. | |
3838 | ||
3839 | Described in assembler language, the code to be output looks like: | |
3840 | ||
3841 | @smallexample | |
3842 | inc (LPBX2+4*BLOCKNO) | |
3843 | @end smallexample | |
3844 | ||
3845 | @vindex __bb | |
3846 | @findex __bb_trace_func | |
3847 | @item profile_block_flag == 2 | |
3848 | Output code to initialize the global structure @code{__bb} and | |
3849 | call the function @code{__bb_trace_func}, which will increment the | |
3850 | counter. | |
3851 | ||
3852 | @code{__bb} consists of two words. In the first word, the current | |
3853 | basic block number, as given by BLOCKNO, has to be stored. In | |
3854 | the second word, the address of a block allocated in the object | |
3855 | module has to be stored. The address is given by the label created | |
3856 | with this statement: | |
3857 | ||
3858 | @smallexample | |
3859 | ASM_GENERATE_INTERNAL_LABEL (@var{buffer}, "LPBX", 0); | |
3860 | @end smallexample | |
3861 | ||
3862 | Described in assembler language, the code to be output looks like: | |
3863 | @example | |
3864 | move BLOCKNO -> (__bb) | |
3865 | move LPBX0 -> (__bb+4) | |
3866 | call __bb_trace_func | |
3867 | @end example | |
3868 | @end table | |
3869 | ||
3870 | @findex FUNCTION_BLOCK_PROFILER_EXIT | |
3871 | @findex __bb_trace_ret | |
3872 | @vindex profile_block_flag | |
3873 | @item FUNCTION_BLOCK_PROFILER_EXIT (@var{file}) | |
3874 | A C statement or compound statement to output to @var{file} | |
3875 | assembler code to call function @code{__bb_trace_ret}. The | |
3876 | assembler code should only be output | |
3877 | if the global compile flag @code{profile_block_flag} == 2. This | |
3878 | macro has to be used at every place where code for returning from | |
3879 | a function is generated (e.g. @code{FUNCTION_EPILOGUE}). Although | |
3880 | you have to write the definition of @code{FUNCTION_EPILOGUE} | |
3881 | as well, you have to define this macro to tell the compiler, that | |
3882 | the proper call to @code{__bb_trace_ret} is produced. | |
3883 | ||
3884 | @findex MACHINE_STATE_SAVE | |
3885 | @findex __bb_init_trace_func | |
3886 | @findex __bb_trace_func | |
3887 | @findex __bb_trace_ret | |
3888 | @item MACHINE_STATE_SAVE (@var{id}) | |
3889 | A C statement or compound statement to save all registers, which may | |
3890 | be clobbered by a function call, including condition codes. The | |
3891 | @code{asm} statement will be mostly likely needed to handle this | |
3892 | task. Local labels in the assembler code can be concatenated with the | |
8760eaae | 3893 | string @var{id}, to obtain a unique label name. |
feca2ed3 JW |
3894 | |
3895 | Registers or condition codes clobbered by @code{FUNCTION_PROLOGUE} or | |
3896 | @code{FUNCTION_EPILOGUE} must be saved in the macros | |
3897 | @code{FUNCTION_BLOCK_PROFILER}, @code{FUNCTION_BLOCK_PROFILER_EXIT} and | |
3898 | @code{BLOCK_PROFILER} prior calling @code{__bb_init_trace_func}, | |
3899 | @code{__bb_trace_ret} and @code{__bb_trace_func} respectively. | |
3900 | ||
3901 | @findex MACHINE_STATE_RESTORE | |
3902 | @findex __bb_init_trace_func | |
3903 | @findex __bb_trace_func | |
3904 | @findex __bb_trace_ret | |
3905 | @item MACHINE_STATE_RESTORE (@var{id}) | |
3906 | A C statement or compound statement to restore all registers, including | |
3907 | condition codes, saved by @code{MACHINE_STATE_SAVE}. | |
3908 | ||
3909 | Registers or condition codes clobbered by @code{FUNCTION_PROLOGUE} or | |
3910 | @code{FUNCTION_EPILOGUE} must be restored in the macros | |
3911 | @code{FUNCTION_BLOCK_PROFILER}, @code{FUNCTION_BLOCK_PROFILER_EXIT} and | |
3912 | @code{BLOCK_PROFILER} after calling @code{__bb_init_trace_func}, | |
3913 | @code{__bb_trace_ret} and @code{__bb_trace_func} respectively. | |
3914 | ||
3915 | @findex BLOCK_PROFILER_CODE | |
3916 | @item BLOCK_PROFILER_CODE | |
3917 | A C function or functions which are needed in the library to | |
3918 | support block profiling. | |
3919 | @end table | |
3920 | ||
b36f4ed3 NC |
3921 | @node Inlining |
3922 | @subsection Permitting inlining of functions with attributes | |
3923 | @cindex inlining | |
3924 | ||
3925 | By default if a function has a target specific attribute attached to it, | |
3926 | it will not be inlined. This behaviour can be overridden if the target | |
3927 | defines the @samp{FUNCTION_ATTRIBUTE_INLINABLE_P} macro. This macro | |
3928 | takes one argument, a @samp{DECL} describing the function. It should | |
3929 | return non-zero if the function can be inlined, otherwise it should | |
3930 | return 0. | |
3931 | ||
4cb1433c RH |
3932 | @node Tail Calling |
3933 | @subsection Permitting tail calls to functions | |
3934 | @cindex tail calls | |
3935 | @cindex sibling calls | |
3936 | ||
3937 | @table @code | |
3938 | @findex FUNCTION_OK_FOR_SIBCALL | |
3939 | @item FUNCTION_OK_FOR_SIBCALL (@var{decl}) | |
3940 | A C expression that evaluates to true if it is ok to perform a sibling | |
3941 | call to @var{decl}. | |
3942 | ||
3943 | It is not uncommon for limitations of calling conventions to prevent | |
3944 | tail calls to functions outside the current unit of translation, or | |
3945 | during PIC compilation. Use this macro to enforce these restrictions, | |
3946 | as the @code{sibcall} md pattern can not fail, or fall over to a | |
3947 | ``normal'' call. | |
3948 | @end table | |
3949 | ||
feca2ed3 JW |
3950 | @node Varargs |
3951 | @section Implementing the Varargs Macros | |
3952 | @cindex varargs implementation | |
3953 | ||
a3a15b4d | 3954 | GCC comes with an implementation of @file{varargs.h} and |
feca2ed3 JW |
3955 | @file{stdarg.h} that work without change on machines that pass arguments |
3956 | on the stack. Other machines require their own implementations of | |
3957 | varargs, and the two machine independent header files must have | |
3958 | conditionals to include it. | |
3959 | ||
5490d604 | 3960 | ISO @file{stdarg.h} differs from traditional @file{varargs.h} mainly in |
feca2ed3 JW |
3961 | the calling convention for @code{va_start}. The traditional |
3962 | implementation takes just one argument, which is the variable in which | |
5490d604 | 3963 | to store the argument pointer. The ISO implementation of |
feca2ed3 JW |
3964 | @code{va_start} takes an additional second argument. The user is |
3965 | supposed to write the last named argument of the function here. | |
3966 | ||
3967 | However, @code{va_start} should not use this argument. The way to find | |
3968 | the end of the named arguments is with the built-in functions described | |
3969 | below. | |
3970 | ||
3971 | @table @code | |
3972 | @findex __builtin_saveregs | |
3973 | @item __builtin_saveregs () | |
3974 | Use this built-in function to save the argument registers in memory so | |
5490d604 | 3975 | that the varargs mechanism can access them. Both ISO and traditional |
feca2ed3 JW |
3976 | versions of @code{va_start} must use @code{__builtin_saveregs}, unless |
3977 | you use @code{SETUP_INCOMING_VARARGS} (see below) instead. | |
3978 | ||
3979 | On some machines, @code{__builtin_saveregs} is open-coded under the | |
3980 | control of the macro @code{EXPAND_BUILTIN_SAVEREGS}. On other machines, | |
3981 | it calls a routine written in assembler language, found in | |
3982 | @file{libgcc2.c}. | |
3983 | ||
3984 | Code generated for the call to @code{__builtin_saveregs} appears at the | |
3985 | beginning of the function, as opposed to where the call to | |
3986 | @code{__builtin_saveregs} is written, regardless of what the code is. | |
3987 | This is because the registers must be saved before the function starts | |
3988 | to use them for its own purposes. | |
3989 | @c i rewrote the first sentence above to fix an overfull hbox. --mew | |
3990 | @c 10feb93 | |
3991 | ||
3992 | @findex __builtin_args_info | |
3993 | @item __builtin_args_info (@var{category}) | |
3994 | Use this built-in function to find the first anonymous arguments in | |
3995 | registers. | |
3996 | ||
3997 | In general, a machine may have several categories of registers used for | |
3998 | arguments, each for a particular category of data types. (For example, | |
3999 | on some machines, floating-point registers are used for floating-point | |
4000 | arguments while other arguments are passed in the general registers.) | |
4001 | To make non-varargs functions use the proper calling convention, you | |
4002 | have defined the @code{CUMULATIVE_ARGS} data type to record how many | |
4003 | registers in each category have been used so far | |
4004 | ||
4005 | @code{__builtin_args_info} accesses the same data structure of type | |
4006 | @code{CUMULATIVE_ARGS} after the ordinary argument layout is finished | |
4007 | with it, with @var{category} specifying which word to access. Thus, the | |
4008 | value indicates the first unused register in a given category. | |
4009 | ||
4010 | Normally, you would use @code{__builtin_args_info} in the implementation | |
4011 | of @code{va_start}, accessing each category just once and storing the | |
4012 | value in the @code{va_list} object. This is because @code{va_list} will | |
4013 | have to update the values, and there is no way to alter the | |
4014 | values accessed by @code{__builtin_args_info}. | |
4015 | ||
4016 | @findex __builtin_next_arg | |
4017 | @item __builtin_next_arg (@var{lastarg}) | |
4018 | This is the equivalent of @code{__builtin_args_info}, for stack | |
4019 | arguments. It returns the address of the first anonymous stack | |
4020 | argument, as type @code{void *}. If @code{ARGS_GROW_DOWNWARD}, it | |
4021 | returns the address of the location above the first anonymous stack | |
4022 | argument. Use it in @code{va_start} to initialize the pointer for | |
4023 | fetching arguments from the stack. Also use it in @code{va_start} to | |
4024 | verify that the second parameter @var{lastarg} is the last named argument | |
4025 | of the current function. | |
4026 | ||
4027 | @findex __builtin_classify_type | |
4028 | @item __builtin_classify_type (@var{object}) | |
4029 | Since each machine has its own conventions for which data types are | |
4030 | passed in which kind of register, your implementation of @code{va_arg} | |
4031 | has to embody these conventions. The easiest way to categorize the | |
4032 | specified data type is to use @code{__builtin_classify_type} together | |
4033 | with @code{sizeof} and @code{__alignof__}. | |
4034 | ||
4035 | @code{__builtin_classify_type} ignores the value of @var{object}, | |
4036 | considering only its data type. It returns an integer describing what | |
4037 | kind of type that is---integer, floating, pointer, structure, and so on. | |
4038 | ||
4039 | The file @file{typeclass.h} defines an enumeration that you can use to | |
4040 | interpret the values of @code{__builtin_classify_type}. | |
4041 | @end table | |
4042 | ||
4043 | These machine description macros help implement varargs: | |
4044 | ||
4045 | @table @code | |
4046 | @findex EXPAND_BUILTIN_SAVEREGS | |
d3707adb | 4047 | @item EXPAND_BUILTIN_SAVEREGS () |
feca2ed3 JW |
4048 | If defined, is a C expression that produces the machine-specific code |
4049 | for a call to @code{__builtin_saveregs}. This code will be moved to the | |
4050 | very beginning of the function, before any parameter access are made. | |
4051 | The return value of this function should be an RTX that contains the | |
4052 | value to use as the return of @code{__builtin_saveregs}. | |
4053 | ||
feca2ed3 | 4054 | @findex SETUP_INCOMING_VARARGS |
59d40964 | 4055 | @item SETUP_INCOMING_VARARGS (@var{args_so_far}, @var{mode}, @var{type}, @var{pretend_args_size}, @var{second_time}) |
feca2ed3 JW |
4056 | This macro offers an alternative to using @code{__builtin_saveregs} and |
4057 | defining the macro @code{EXPAND_BUILTIN_SAVEREGS}. Use it to store the | |
4058 | anonymous register arguments into the stack so that all the arguments | |
4059 | appear to have been passed consecutively on the stack. Once this is | |
4060 | done, you can use the standard implementation of varargs that works for | |
4061 | machines that pass all their arguments on the stack. | |
4062 | ||
4063 | The argument @var{args_so_far} is the @code{CUMULATIVE_ARGS} data | |
8760eaae | 4064 | structure, containing the values that are obtained after processing the |
feca2ed3 JW |
4065 | named arguments. The arguments @var{mode} and @var{type} describe the |
4066 | last named argument---its machine mode and its data type as a tree node. | |
4067 | ||
4068 | The macro implementation should do two things: first, push onto the | |
4069 | stack all the argument registers @emph{not} used for the named | |
4070 | arguments, and second, store the size of the data thus pushed into the | |
4071 | @code{int}-valued variable whose name is supplied as the argument | |
4072 | @var{pretend_args_size}. The value that you store here will serve as | |
4073 | additional offset for setting up the stack frame. | |
4074 | ||
4075 | Because you must generate code to push the anonymous arguments at | |
4076 | compile time without knowing their data types, | |
4077 | @code{SETUP_INCOMING_VARARGS} is only useful on machines that have just | |
4078 | a single category of argument register and use it uniformly for all data | |
4079 | types. | |
4080 | ||
4081 | If the argument @var{second_time} is nonzero, it means that the | |
4082 | arguments of the function are being analyzed for the second time. This | |
4083 | happens for an inline function, which is not actually compiled until the | |
4084 | end of the source file. The macro @code{SETUP_INCOMING_VARARGS} should | |
4085 | not generate any instructions in this case. | |
4086 | ||
4087 | @findex STRICT_ARGUMENT_NAMING | |
4088 | @item STRICT_ARGUMENT_NAMING | |
e5e809f4 JL |
4089 | Define this macro to be a nonzero value if the location where a function |
4090 | argument is passed depends on whether or not it is a named argument. | |
feca2ed3 JW |
4091 | |
4092 | This macro controls how the @var{named} argument to @code{FUNCTION_ARG} | |
e5e809f4 JL |
4093 | is set for varargs and stdarg functions. If this macro returns a |
4094 | nonzero value, the @var{named} argument is always true for named | |
4095 | arguments, and false for unnamed arguments. If it returns a value of | |
4096 | zero, but @code{SETUP_INCOMING_VARARGS} is defined, then all arguments | |
4097 | are treated as named. Otherwise, all named arguments except the last | |
4098 | are treated as named. | |
4099 | ||
4100 | You need not define this macro if it always returns zero. | |
9ab70a9b R |
4101 | |
4102 | @findex PRETEND_OUTGOING_VARARGS_NAMED | |
4103 | @item PRETEND_OUTGOING_VARARGS_NAMED | |
4104 | If you need to conditionally change ABIs so that one works with | |
4105 | @code{SETUP_INCOMING_VARARGS}, but the other works like neither | |
4106 | @code{SETUP_INCOMING_VARARGS} nor @code{STRICT_ARGUMENT_NAMING} was | |
4107 | defined, then define this macro to return nonzero if | |
4108 | @code{SETUP_INCOMING_VARARGS} is used, zero otherwise. | |
4109 | Otherwise, you should not define this macro. | |
feca2ed3 JW |
4110 | @end table |
4111 | ||
4112 | @node Trampolines | |
4113 | @section Trampolines for Nested Functions | |
4114 | @cindex trampolines for nested functions | |
4115 | @cindex nested functions, trampolines for | |
4116 | ||
4117 | A @dfn{trampoline} is a small piece of code that is created at run time | |
4118 | when the address of a nested function is taken. It normally resides on | |
4119 | the stack, in the stack frame of the containing function. These macros | |
a3a15b4d | 4120 | tell GCC how to generate code to allocate and initialize a |
feca2ed3 JW |
4121 | trampoline. |
4122 | ||
4123 | The instructions in the trampoline must do two things: load a constant | |
4124 | address into the static chain register, and jump to the real address of | |
4125 | the nested function. On CISC machines such as the m68k, this requires | |
4126 | two instructions, a move immediate and a jump. Then the two addresses | |
4127 | exist in the trampoline as word-long immediate operands. On RISC | |
4128 | machines, it is often necessary to load each address into a register in | |
4129 | two parts. Then pieces of each address form separate immediate | |
4130 | operands. | |
4131 | ||
4132 | The code generated to initialize the trampoline must store the variable | |
4133 | parts---the static chain value and the function address---into the | |
4134 | immediate operands of the instructions. On a CISC machine, this is | |
4135 | simply a matter of copying each address to a memory reference at the | |
4136 | proper offset from the start of the trampoline. On a RISC machine, it | |
4137 | may be necessary to take out pieces of the address and store them | |
4138 | separately. | |
4139 | ||
4140 | @table @code | |
4141 | @findex TRAMPOLINE_TEMPLATE | |
4142 | @item TRAMPOLINE_TEMPLATE (@var{file}) | |
4143 | A C statement to output, on the stream @var{file}, assembler code for a | |
4144 | block of data that contains the constant parts of a trampoline. This | |
4145 | code should not include a label---the label is taken care of | |
4146 | automatically. | |
4147 | ||
4148 | If you do not define this macro, it means no template is needed | |
4149 | for the target. Do not define this macro on systems where the block move | |
4150 | code to copy the trampoline into place would be larger than the code | |
4151 | to generate it on the spot. | |
4152 | ||
4153 | @findex TRAMPOLINE_SECTION | |
4154 | @item TRAMPOLINE_SECTION | |
4155 | The name of a subroutine to switch to the section in which the | |
4156 | trampoline template is to be placed (@pxref{Sections}). The default is | |
4157 | a value of @samp{readonly_data_section}, which places the trampoline in | |
4158 | the section containing read-only data. | |
4159 | ||
4160 | @findex TRAMPOLINE_SIZE | |
4161 | @item TRAMPOLINE_SIZE | |
4162 | A C expression for the size in bytes of the trampoline, as an integer. | |
4163 | ||
4164 | @findex TRAMPOLINE_ALIGNMENT | |
4165 | @item TRAMPOLINE_ALIGNMENT | |
4166 | Alignment required for trampolines, in bits. | |
4167 | ||
4168 | If you don't define this macro, the value of @code{BIGGEST_ALIGNMENT} | |
4169 | is used for aligning trampolines. | |
4170 | ||
4171 | @findex INITIALIZE_TRAMPOLINE | |
4172 | @item INITIALIZE_TRAMPOLINE (@var{addr}, @var{fnaddr}, @var{static_chain}) | |
4173 | A C statement to initialize the variable parts of a trampoline. | |
4174 | @var{addr} is an RTX for the address of the trampoline; @var{fnaddr} is | |
4175 | an RTX for the address of the nested function; @var{static_chain} is an | |
4176 | RTX for the static chain value that should be passed to the function | |
4177 | when it is called. | |
4178 | ||
b33493e3 AO |
4179 | @findex TRAMPOLINE_ADJUST_ADDRESS |
4180 | @item TRAMPOLINE_ADJUST_ADDRESS (@var{addr}) | |
4181 | A C statement that should perform any machine-specific adjustment in | |
4182 | the address of the trampoline. Its argument contains the address that | |
4183 | was passed to @code{INITIALIZE_TRAMPOLINE}. In case the address to be | |
4184 | used for a function call should be different from the address in which | |
4185 | the template was stored, the different address should be assigned to | |
4186 | @var{addr}. If this macro is not defined, @var{addr} will be used for | |
4187 | function calls. | |
4188 | ||
feca2ed3 JW |
4189 | @findex ALLOCATE_TRAMPOLINE |
4190 | @item ALLOCATE_TRAMPOLINE (@var{fp}) | |
4191 | A C expression to allocate run-time space for a trampoline. The | |
4192 | expression value should be an RTX representing a memory reference to the | |
4193 | space for the trampoline. | |
4194 | ||
4195 | @cindex @code{FUNCTION_EPILOGUE} and trampolines | |
4196 | @cindex @code{FUNCTION_PROLOGUE} and trampolines | |
4197 | If this macro is not defined, by default the trampoline is allocated as | |
4198 | a stack slot. This default is right for most machines. The exceptions | |
4199 | are machines where it is impossible to execute instructions in the stack | |
4200 | area. On such machines, you may have to implement a separate stack, | |
4201 | using this macro in conjunction with @code{FUNCTION_PROLOGUE} and | |
4202 | @code{FUNCTION_EPILOGUE}. | |
4203 | ||
4204 | @var{fp} points to a data structure, a @code{struct function}, which | |
4205 | describes the compilation status of the immediate containing function of | |
4206 | the function which the trampoline is for. Normally (when | |
4207 | @code{ALLOCATE_TRAMPOLINE} is not defined), the stack slot for the | |
4208 | trampoline is in the stack frame of this containing function. Other | |
4209 | allocation strategies probably must do something analogous with this | |
4210 | information. | |
4211 | @end table | |
4212 | ||
4213 | Implementing trampolines is difficult on many machines because they have | |
4214 | separate instruction and data caches. Writing into a stack location | |
4215 | fails to clear the memory in the instruction cache, so when the program | |
4216 | jumps to that location, it executes the old contents. | |
4217 | ||
4218 | Here are two possible solutions. One is to clear the relevant parts of | |
4219 | the instruction cache whenever a trampoline is set up. The other is to | |
4220 | make all trampolines identical, by having them jump to a standard | |
4221 | subroutine. The former technique makes trampoline execution faster; the | |
4222 | latter makes initialization faster. | |
4223 | ||
4224 | To clear the instruction cache when a trampoline is initialized, define | |
4225 | the following macros which describe the shape of the cache. | |
4226 | ||
4227 | @table @code | |
4228 | @findex INSN_CACHE_SIZE | |
4229 | @item INSN_CACHE_SIZE | |
4230 | The total size in bytes of the cache. | |
4231 | ||
4232 | @findex INSN_CACHE_LINE_WIDTH | |
4233 | @item INSN_CACHE_LINE_WIDTH | |
4234 | The length in bytes of each cache line. The cache is divided into cache | |
4235 | lines which are disjoint slots, each holding a contiguous chunk of data | |
4236 | fetched from memory. Each time data is brought into the cache, an | |
4237 | entire line is read at once. The data loaded into a cache line is | |
4238 | always aligned on a boundary equal to the line size. | |
4239 | ||
4240 | @findex INSN_CACHE_DEPTH | |
4241 | @item INSN_CACHE_DEPTH | |
4242 | The number of alternative cache lines that can hold any particular memory | |
4243 | location. | |
4244 | @end table | |
4245 | ||
4246 | Alternatively, if the machine has system calls or instructions to clear | |
4247 | the instruction cache directly, you can define the following macro. | |
4248 | ||
4249 | @table @code | |
4250 | @findex CLEAR_INSN_CACHE | |
4251 | @item CLEAR_INSN_CACHE (@var{BEG}, @var{END}) | |
4252 | If defined, expands to a C expression clearing the @emph{instruction | |
4253 | cache} in the specified interval. If it is not defined, and the macro | |
4254 | INSN_CACHE_SIZE is defined, some generic code is generated to clear the | |
4255 | cache. The definition of this macro would typically be a series of | |
4256 | @code{asm} statements. Both @var{BEG} and @var{END} are both pointer | |
4257 | expressions. | |
4258 | @end table | |
4259 | ||
4260 | To use a standard subroutine, define the following macro. In addition, | |
4261 | you must make sure that the instructions in a trampoline fill an entire | |
4262 | cache line with identical instructions, or else ensure that the | |
4263 | beginning of the trampoline code is always aligned at the same point in | |
4264 | its cache line. Look in @file{m68k.h} as a guide. | |
4265 | ||
4266 | @table @code | |
4267 | @findex TRANSFER_FROM_TRAMPOLINE | |
4268 | @item TRANSFER_FROM_TRAMPOLINE | |
4269 | Define this macro if trampolines need a special subroutine to do their | |
4270 | work. The macro should expand to a series of @code{asm} statements | |
a3a15b4d | 4271 | which will be compiled with GCC. They go in a library function named |
feca2ed3 JW |
4272 | @code{__transfer_from_trampoline}. |
4273 | ||
4274 | If you need to avoid executing the ordinary prologue code of a compiled | |
4275 | C function when you jump to the subroutine, you can do so by placing a | |
4276 | special label of your own in the assembler code. Use one @code{asm} | |
4277 | statement to generate an assembler label, and another to make the label | |
4278 | global. Then trampolines can use that label to jump directly to your | |
4279 | special assembler code. | |
4280 | @end table | |
4281 | ||
4282 | @node Library Calls | |
4283 | @section Implicit Calls to Library Routines | |
4284 | @cindex library subroutine names | |
4285 | @cindex @file{libgcc.a} | |
4286 | ||
4287 | @c prevent bad page break with this line | |
4288 | Here is an explanation of implicit calls to library routines. | |
4289 | ||
4290 | @table @code | |
4291 | @findex MULSI3_LIBCALL | |
4292 | @item MULSI3_LIBCALL | |
4293 | A C string constant giving the name of the function to call for | |
4294 | multiplication of one signed full-word by another. If you do not | |
4295 | define this macro, the default name is used, which is @code{__mulsi3}, | |
4296 | a function defined in @file{libgcc.a}. | |
4297 | ||
4298 | @findex DIVSI3_LIBCALL | |
4299 | @item DIVSI3_LIBCALL | |
4300 | A C string constant giving the name of the function to call for | |
4301 | division of one signed full-word by another. If you do not define | |
4302 | this macro, the default name is used, which is @code{__divsi3}, a | |
4303 | function defined in @file{libgcc.a}. | |
4304 | ||
4305 | @findex UDIVSI3_LIBCALL | |
4306 | @item UDIVSI3_LIBCALL | |
4307 | A C string constant giving the name of the function to call for | |
4308 | division of one unsigned full-word by another. If you do not define | |
4309 | this macro, the default name is used, which is @code{__udivsi3}, a | |
4310 | function defined in @file{libgcc.a}. | |
4311 | ||
4312 | @findex MODSI3_LIBCALL | |
4313 | @item MODSI3_LIBCALL | |
4314 | A C string constant giving the name of the function to call for the | |
4315 | remainder in division of one signed full-word by another. If you do | |
4316 | not define this macro, the default name is used, which is | |
4317 | @code{__modsi3}, a function defined in @file{libgcc.a}. | |
4318 | ||
4319 | @findex UMODSI3_LIBCALL | |
4320 | @item UMODSI3_LIBCALL | |
4321 | A C string constant giving the name of the function to call for the | |
4322 | remainder in division of one unsigned full-word by another. If you do | |
4323 | not define this macro, the default name is used, which is | |
4324 | @code{__umodsi3}, a function defined in @file{libgcc.a}. | |
4325 | ||
4326 | @findex MULDI3_LIBCALL | |
4327 | @item MULDI3_LIBCALL | |
4328 | A C string constant giving the name of the function to call for | |
4329 | multiplication of one signed double-word by another. If you do not | |
4330 | define this macro, the default name is used, which is @code{__muldi3}, | |
4331 | a function defined in @file{libgcc.a}. | |
4332 | ||
4333 | @findex DIVDI3_LIBCALL | |
4334 | @item DIVDI3_LIBCALL | |
4335 | A C string constant giving the name of the function to call for | |
4336 | division of one signed double-word by another. If you do not define | |
4337 | this macro, the default name is used, which is @code{__divdi3}, a | |
4338 | function defined in @file{libgcc.a}. | |
4339 | ||
4340 | @findex UDIVDI3_LIBCALL | |
4341 | @item UDIVDI3_LIBCALL | |
4342 | A C string constant giving the name of the function to call for | |
4343 | division of one unsigned full-word by another. If you do not define | |
4344 | this macro, the default name is used, which is @code{__udivdi3}, a | |
4345 | function defined in @file{libgcc.a}. | |
4346 | ||
4347 | @findex MODDI3_LIBCALL | |
4348 | @item MODDI3_LIBCALL | |
4349 | A C string constant giving the name of the function to call for the | |
4350 | remainder in division of one signed double-word by another. If you do | |
4351 | not define this macro, the default name is used, which is | |
4352 | @code{__moddi3}, a function defined in @file{libgcc.a}. | |
4353 | ||
4354 | @findex UMODDI3_LIBCALL | |
4355 | @item UMODDI3_LIBCALL | |
4356 | A C string constant giving the name of the function to call for the | |
4357 | remainder in division of one unsigned full-word by another. If you do | |
4358 | not define this macro, the default name is used, which is | |
4359 | @code{__umoddi3}, a function defined in @file{libgcc.a}. | |
4360 | ||
4361 | @findex INIT_TARGET_OPTABS | |
4362 | @item INIT_TARGET_OPTABS | |
4363 | Define this macro as a C statement that declares additional library | |
4364 | routines renames existing ones. @code{init_optabs} calls this macro after | |
4365 | initializing all the normal library routines. | |
4366 | ||
c5c60e15 BS |
4367 | @findex FLOAT_LIB_COMPARE_RETURNS_BOOL (@var{mode}, @var{comparison}) |
4368 | @item FLOAT_LIB_COMPARE_RETURNS_BOOL | |
4369 | Define this macro as a C statement that returns nonzero if a call to | |
4370 | the floating point comparison library function will return a boolean | |
4371 | value that indicates the result of the comparison. It should return | |
4372 | zero if one of gcc's own libgcc functions is called. | |
4373 | ||
4374 | Most ports don't need to define this macro. | |
4375 | ||
feca2ed3 JW |
4376 | @findex TARGET_EDOM |
4377 | @cindex @code{EDOM}, implicit usage | |
4378 | @item TARGET_EDOM | |
4379 | The value of @code{EDOM} on the target machine, as a C integer constant | |
a3a15b4d | 4380 | expression. If you don't define this macro, GCC does not attempt to |
feca2ed3 JW |
4381 | deposit the value of @code{EDOM} into @code{errno} directly. Look in |
4382 | @file{/usr/include/errno.h} to find the value of @code{EDOM} on your | |
4383 | system. | |
4384 | ||
4385 | If you do not define @code{TARGET_EDOM}, then compiled code reports | |
4386 | domain errors by calling the library function and letting it report the | |
4387 | error. If mathematical functions on your system use @code{matherr} when | |
4388 | there is an error, then you should leave @code{TARGET_EDOM} undefined so | |
4389 | that @code{matherr} is used normally. | |
4390 | ||
4391 | @findex GEN_ERRNO_RTX | |
4392 | @cindex @code{errno}, implicit usage | |
4393 | @item GEN_ERRNO_RTX | |
4394 | Define this macro as a C expression to create an rtl expression that | |
4395 | refers to the global ``variable'' @code{errno}. (On certain systems, | |
4396 | @code{errno} may not actually be a variable.) If you don't define this | |
4397 | macro, a reasonable default is used. | |
4398 | ||
4399 | @findex TARGET_MEM_FUNCTIONS | |
4400 | @cindex @code{bcopy}, implicit usage | |
4401 | @cindex @code{memcpy}, implicit usage | |
4402 | @cindex @code{bzero}, implicit usage | |
4403 | @cindex @code{memset}, implicit usage | |
4404 | @item TARGET_MEM_FUNCTIONS | |
5490d604 JM |
4405 | Define this macro if GCC should generate calls to the ISO C |
4406 | (and System V) library functions @code{memcpy} and @code{memset} | |
feca2ed3 JW |
4407 | rather than the BSD functions @code{bcopy} and @code{bzero}. |
4408 | ||
4409 | @findex LIBGCC_NEEDS_DOUBLE | |
4410 | @item LIBGCC_NEEDS_DOUBLE | |
4411 | Define this macro if only @code{float} arguments cannot be passed to | |
4412 | library routines (so they must be converted to @code{double}). This | |
4413 | macro affects both how library calls are generated and how the library | |
4414 | routines in @file{libgcc1.c} accept their arguments. It is useful on | |
4415 | machines where floating and fixed point arguments are passed | |
4416 | differently, such as the i860. | |
4417 | ||
4418 | @findex FLOAT_ARG_TYPE | |
4419 | @item FLOAT_ARG_TYPE | |
4420 | Define this macro to override the type used by the library routines to | |
4421 | pick up arguments of type @code{float}. (By default, they use a union | |
4422 | of @code{float} and @code{int}.) | |
4423 | ||
4424 | The obvious choice would be @code{float}---but that won't work with | |
4425 | traditional C compilers that expect all arguments declared as @code{float} | |
4426 | to arrive as @code{double}. To avoid this conversion, the library routines | |
4427 | ask for the value as some other type and then treat it as a @code{float}. | |
4428 | ||
4429 | On some systems, no other type will work for this. For these systems, | |
4430 | you must use @code{LIBGCC_NEEDS_DOUBLE} instead, to force conversion of | |
4431 | the values @code{double} before they are passed. | |
4432 | ||
4433 | @findex FLOATIFY | |
4434 | @item FLOATIFY (@var{passed-value}) | |
4435 | Define this macro to override the way library routines redesignate a | |
4436 | @code{float} argument as a @code{float} instead of the type it was | |
4437 | passed as. The default is an expression which takes the @code{float} | |
4438 | field of the union. | |
4439 | ||
4440 | @findex FLOAT_VALUE_TYPE | |
4441 | @item FLOAT_VALUE_TYPE | |
4442 | Define this macro to override the type used by the library routines to | |
4443 | return values that ought to have type @code{float}. (By default, they | |
4444 | use @code{int}.) | |
4445 | ||
4446 | The obvious choice would be @code{float}---but that won't work with | |
4447 | traditional C compilers gratuitously convert values declared as | |
4448 | @code{float} into @code{double}. | |
4449 | ||
4450 | @findex INTIFY | |
4451 | @item INTIFY (@var{float-value}) | |
4452 | Define this macro to override the way the value of a | |
4453 | @code{float}-returning library routine should be packaged in order to | |
4454 | return it. These functions are actually declared to return type | |
4455 | @code{FLOAT_VALUE_TYPE} (normally @code{int}). | |
4456 | ||
4457 | These values can't be returned as type @code{float} because traditional | |
4458 | C compilers would gratuitously convert the value to a @code{double}. | |
4459 | ||
4460 | A local variable named @code{intify} is always available when the macro | |
4461 | @code{INTIFY} is used. It is a union of a @code{float} field named | |
4462 | @code{f} and a field named @code{i} whose type is | |
4463 | @code{FLOAT_VALUE_TYPE} or @code{int}. | |
4464 | ||
4465 | If you don't define this macro, the default definition works by copying | |
4466 | the value through that union. | |
4467 | ||
4468 | @findex nongcc_SI_type | |
4469 | @item nongcc_SI_type | |
4470 | Define this macro as the name of the data type corresponding to | |
4471 | @code{SImode} in the system's own C compiler. | |
4472 | ||
4473 | You need not define this macro if that type is @code{long int}, as it usually | |
4474 | is. | |
4475 | ||
4476 | @findex nongcc_word_type | |
4477 | @item nongcc_word_type | |
4478 | Define this macro as the name of the data type corresponding to the | |
4479 | word_mode in the system's own C compiler. | |
4480 | ||
4481 | You need not define this macro if that type is @code{long int}, as it usually | |
4482 | is. | |
4483 | ||
4484 | @findex perform_@dots{} | |
4485 | @item perform_@dots{} | |
4486 | Define these macros to supply explicit C statements to carry out various | |
4487 | arithmetic operations on types @code{float} and @code{double} in the | |
4488 | library routines in @file{libgcc1.c}. See that file for a full list | |
4489 | of these macros and their arguments. | |
4490 | ||
4491 | On most machines, you don't need to define any of these macros, because | |
4492 | the C compiler that comes with the system takes care of doing them. | |
4493 | ||
4494 | @findex NEXT_OBJC_RUNTIME | |
4495 | @item NEXT_OBJC_RUNTIME | |
4496 | Define this macro to generate code for Objective C message sending using | |
4497 | the calling convention of the NeXT system. This calling convention | |
4498 | involves passing the object, the selector and the method arguments all | |
4499 | at once to the method-lookup library function. | |
4500 | ||
4501 | The default calling convention passes just the object and the selector | |
4502 | to the lookup function, which returns a pointer to the method. | |
4503 | @end table | |
4504 | ||
4505 | @node Addressing Modes | |
4506 | @section Addressing Modes | |
4507 | @cindex addressing modes | |
4508 | ||
4509 | @c prevent bad page break with this line | |
4510 | This is about addressing modes. | |
4511 | ||
4512 | @table @code | |
feca2ed3 | 4513 | @findex HAVE_PRE_INCREMENT |
feca2ed3 | 4514 | @findex HAVE_PRE_DECREMENT |
7a6bd5ae JL |
4515 | @findex HAVE_POST_INCREMENT |
4516 | @findex HAVE_POST_DECREMENT | |
feca2ed3 | 4517 | @item HAVE_PRE_INCREMENT |
feca2ed3 | 4518 | @itemx HAVE_PRE_DECREMENT |
7a6bd5ae JL |
4519 | @itemx HAVE_POST_INCREMENT |
4520 | @itemx HAVE_POST_DECREMENT | |
4521 | A C expression that is non-zero if the machine supports pre-increment, | |
4522 | pre-decrement, post-increment, or post-decrement addressing respectively. | |
feca2ed3 | 4523 | |
864bcaa7 | 4524 | @findex HAVE_POST_MODIFY_DISP |
864bcaa7 JL |
4525 | @findex HAVE_PRE_MODIFY_DISP |
4526 | @item HAVE_PRE_MODIFY_DISP | |
7a6bd5ae JL |
4527 | @itemx HAVE_POST_MODIFY_DISP |
4528 | A C expression that is non-zero if the machine supports pre- or | |
4529 | post-address side-effect generation involving constants other than | |
4530 | the size of the memory operand. | |
864bcaa7 JL |
4531 | |
4532 | @findex HAVE_POST_MODIFY_REG | |
864bcaa7 JL |
4533 | @findex HAVE_PRE_MODIFY_REG |
4534 | @item HAVE_PRE_MODIFY_REG | |
7a6bd5ae JL |
4535 | @itemx HAVE_POST_MODIFY_REG |
4536 | A C expression that is non-zero if the machine supports pre- or | |
4537 | post-address side-effect generation involving a register displacement. | |
864bcaa7 | 4538 | |
feca2ed3 JW |
4539 | @findex CONSTANT_ADDRESS_P |
4540 | @item CONSTANT_ADDRESS_P (@var{x}) | |
4541 | A C expression that is 1 if the RTX @var{x} is a constant which | |
4542 | is a valid address. On most machines, this can be defined as | |
4543 | @code{CONSTANT_P (@var{x})}, but a few machines are more restrictive | |
4544 | in which constant addresses are supported. | |
4545 | ||
4546 | @findex CONSTANT_P | |
4547 | @code{CONSTANT_P} accepts integer-values expressions whose values are | |
4548 | not explicitly known, such as @code{symbol_ref}, @code{label_ref}, and | |
4549 | @code{high} expressions and @code{const} arithmetic expressions, in | |
4550 | addition to @code{const_int} and @code{const_double} expressions. | |
4551 | ||
4552 | @findex MAX_REGS_PER_ADDRESS | |
4553 | @item MAX_REGS_PER_ADDRESS | |
4554 | A number, the maximum number of registers that can appear in a valid | |
4555 | memory address. Note that it is up to you to specify a value equal to | |
4556 | the maximum number that @code{GO_IF_LEGITIMATE_ADDRESS} would ever | |
4557 | accept. | |
4558 | ||
4559 | @findex GO_IF_LEGITIMATE_ADDRESS | |
4560 | @item GO_IF_LEGITIMATE_ADDRESS (@var{mode}, @var{x}, @var{label}) | |
4561 | A C compound statement with a conditional @code{goto @var{label};} | |
4562 | executed if @var{x} (an RTX) is a legitimate memory address on the | |
4563 | target machine for a memory operand of mode @var{mode}. | |
4564 | ||
4565 | It usually pays to define several simpler macros to serve as | |
4566 | subroutines for this one. Otherwise it may be too complicated to | |
4567 | understand. | |
4568 | ||
4569 | This macro must exist in two variants: a strict variant and a | |
4570 | non-strict one. The strict variant is used in the reload pass. It | |
4571 | must be defined so that any pseudo-register that has not been | |
4572 | allocated a hard register is considered a memory reference. In | |
4573 | contexts where some kind of register is required, a pseudo-register | |
4574 | with no hard register must be rejected. | |
4575 | ||
4576 | The non-strict variant is used in other passes. It must be defined to | |
4577 | accept all pseudo-registers in every context where some kind of | |
4578 | register is required. | |
4579 | ||
4580 | @findex REG_OK_STRICT | |
4581 | Compiler source files that want to use the strict variant of this | |
4582 | macro define the macro @code{REG_OK_STRICT}. You should use an | |
4583 | @code{#ifdef REG_OK_STRICT} conditional to define the strict variant | |
4584 | in that case and the non-strict variant otherwise. | |
4585 | ||
4586 | Subroutines to check for acceptable registers for various purposes (one | |
4587 | for base registers, one for index registers, and so on) are typically | |
4588 | among the subroutines used to define @code{GO_IF_LEGITIMATE_ADDRESS}. | |
4589 | Then only these subroutine macros need have two variants; the higher | |
4590 | levels of macros may be the same whether strict or not.@refill | |
4591 | ||
4592 | Normally, constant addresses which are the sum of a @code{symbol_ref} | |
4593 | and an integer are stored inside a @code{const} RTX to mark them as | |
4594 | constant. Therefore, there is no need to recognize such sums | |
4595 | specifically as legitimate addresses. Normally you would simply | |
4596 | recognize any @code{const} as legitimate. | |
4597 | ||
4598 | Usually @code{PRINT_OPERAND_ADDRESS} is not prepared to handle constant | |
4599 | sums that are not marked with @code{const}. It assumes that a naked | |
4600 | @code{plus} indicates indexing. If so, then you @emph{must} reject such | |
4601 | naked constant sums as illegitimate addresses, so that none of them will | |
4602 | be given to @code{PRINT_OPERAND_ADDRESS}. | |
4603 | ||
4604 | @cindex @code{ENCODE_SECTION_INFO} and address validation | |
4605 | On some machines, whether a symbolic address is legitimate depends on | |
4606 | the section that the address refers to. On these machines, define the | |
4607 | macro @code{ENCODE_SECTION_INFO} to store the information into the | |
4608 | @code{symbol_ref}, and then check for it here. When you see a | |
4609 | @code{const}, you will have to look inside it to find the | |
4610 | @code{symbol_ref} in order to determine the section. @xref{Assembler | |
4611 | Format}. | |
4612 | ||
4613 | @findex saveable_obstack | |
4614 | The best way to modify the name string is by adding text to the | |
4615 | beginning, with suitable punctuation to prevent any ambiguity. Allocate | |
4616 | the new name in @code{saveable_obstack}. You will have to modify | |
4617 | @code{ASM_OUTPUT_LABELREF} to remove and decode the added text and | |
4618 | output the name accordingly, and define @code{STRIP_NAME_ENCODING} to | |
4619 | access the original name string. | |
4620 | ||
4621 | You can check the information stored here into the @code{symbol_ref} in | |
4622 | the definitions of the macros @code{GO_IF_LEGITIMATE_ADDRESS} and | |
4623 | @code{PRINT_OPERAND_ADDRESS}. | |
4624 | ||
4625 | @findex REG_OK_FOR_BASE_P | |
4626 | @item REG_OK_FOR_BASE_P (@var{x}) | |
4627 | A C expression that is nonzero if @var{x} (assumed to be a @code{reg} | |
4628 | RTX) is valid for use as a base register. For hard registers, it | |
4629 | should always accept those which the hardware permits and reject the | |
4630 | others. Whether the macro accepts or rejects pseudo registers must be | |
4631 | controlled by @code{REG_OK_STRICT} as described above. This usually | |
4632 | requires two variant definitions, of which @code{REG_OK_STRICT} | |
4633 | controls the one actually used. | |
4634 | ||
861bb6c1 JL |
4635 | @findex REG_MODE_OK_FOR_BASE_P |
4636 | @item REG_MODE_OK_FOR_BASE_P (@var{x}, @var{mode}) | |
4637 | A C expression that is just like @code{REG_OK_FOR_BASE_P}, except that | |
4638 | that expression may examine the mode of the memory reference in | |
4639 | @var{mode}. You should define this macro if the mode of the memory | |
4640 | reference affects whether a register may be used as a base register. If | |
4641 | you define this macro, the compiler will use it instead of | |
4642 | @code{REG_OK_FOR_BASE_P}. | |
4643 | ||
feca2ed3 JW |
4644 | @findex REG_OK_FOR_INDEX_P |
4645 | @item REG_OK_FOR_INDEX_P (@var{x}) | |
4646 | A C expression that is nonzero if @var{x} (assumed to be a @code{reg} | |
4647 | RTX) is valid for use as an index register. | |
4648 | ||
4649 | The difference between an index register and a base register is that | |
4650 | the index register may be scaled. If an address involves the sum of | |
4651 | two registers, neither one of them scaled, then either one may be | |
4652 | labeled the ``base'' and the other the ``index''; but whichever | |
4653 | labeling is used must fit the machine's constraints of which registers | |
4654 | may serve in each capacity. The compiler will try both labelings, | |
4655 | looking for one that is valid, and will reload one or both registers | |
4656 | only if neither labeling works. | |
4657 | ||
b949ea8b JW |
4658 | @findex FIND_BASE_TERM |
4659 | @item FIND_BASE_TERM (@var{x}) | |
4660 | A C expression to determine the base term of address @var{x}. | |
4661 | This macro is used in only one place: `find_base_term' in alias.c. | |
4662 | ||
4663 | It is always safe for this macro to not be defined. It exists so | |
4664 | that alias analysis can understand machine-dependent addresses. | |
4665 | ||
4666 | The typical use of this macro is to handle addresses containing | |
4667 | a label_ref or symbol_ref within an UNSPEC. | |
4668 | ||
feca2ed3 JW |
4669 | @findex LEGITIMIZE_ADDRESS |
4670 | @item LEGITIMIZE_ADDRESS (@var{x}, @var{oldx}, @var{mode}, @var{win}) | |
4671 | A C compound statement that attempts to replace @var{x} with a valid | |
4672 | memory address for an operand of mode @var{mode}. @var{win} will be a | |
4673 | C statement label elsewhere in the code; the macro definition may use | |
4674 | ||
4675 | @example | |
4676 | GO_IF_LEGITIMATE_ADDRESS (@var{mode}, @var{x}, @var{win}); | |
4677 | @end example | |
4678 | ||
4679 | @noindent | |
4680 | to avoid further processing if the address has become legitimate. | |
4681 | ||
4682 | @findex break_out_memory_refs | |
4683 | @var{x} will always be the result of a call to @code{break_out_memory_refs}, | |
4684 | and @var{oldx} will be the operand that was given to that function to produce | |
4685 | @var{x}. | |
4686 | ||
4687 | The code generated by this macro should not alter the substructure of | |
4688 | @var{x}. If it transforms @var{x} into a more legitimate form, it | |
4689 | should assign @var{x} (which will always be a C variable) a new value. | |
4690 | ||
4691 | It is not necessary for this macro to come up with a legitimate | |
4692 | address. The compiler has standard ways of doing so in all cases. In | |
4693 | fact, it is safe for this macro to do nothing. But often a | |
4694 | machine-dependent strategy can generate better code. | |
4695 | ||
a9a2595b JR |
4696 | @findex LEGITIMIZE_RELOAD_ADDRESS |
4697 | @item LEGITIMIZE_RELOAD_ADDRESS (@var{x}, @var{mode}, @var{opnum}, @var{type}, @var{ind_levels}, @var{win}) | |
4698 | A C compound statement that attempts to replace @var{x}, which is an address | |
4699 | that needs reloading, with a valid memory address for an operand of mode | |
4700 | @var{mode}. @var{win} will be a C statement label elsewhere in the code. | |
4701 | It is not necessary to define this macro, but it might be useful for | |
4702 | performance reasons. | |
4703 | ||
4704 | For example, on the i386, it is sometimes possible to use a single | |
4705 | reload register instead of two by reloading a sum of two pseudo | |
4706 | registers into a register. On the other hand, for number of RISC | |
4707 | processors offsets are limited so that often an intermediate address | |
4708 | needs to be generated in order to address a stack slot. By defining | |
4709 | LEGITIMIZE_RELOAD_ADDRESS appropriately, the intermediate addresses | |
4710 | generated for adjacent some stack slots can be made identical, and thus | |
4711 | be shared. | |
4712 | ||
39bdfaa0 RH |
4713 | @emph{Note}: This macro should be used with caution. It is necessary |
4714 | to know something of how reload works in order to effectively use this, | |
4715 | and it is quite easy to produce macros that build in too much knowledge | |
4716 | of reload internals. | |
a9a2595b | 4717 | |
5f0c590d JL |
4718 | @emph{Note}: This macro must be able to reload an address created by a |
4719 | previous invocation of this macro. If it fails to handle such addresses | |
4720 | then the compiler may generate incorrect code or abort. | |
4721 | ||
a9a2595b | 4722 | @findex push_reload |
39bdfaa0 RH |
4723 | The macro definition should use @code{push_reload} to indicate parts that |
4724 | need reloading; @var{opnum}, @var{type} and @var{ind_levels} are usually | |
4725 | suitable to be passed unaltered to @code{push_reload}. | |
a9a2595b | 4726 | |
39bdfaa0 | 4727 | The code generated by this macro must not alter the substructure of |
a9a2595b JR |
4728 | @var{x}. If it transforms @var{x} into a more legitimate form, it |
4729 | should assign @var{x} (which will always be a C variable) a new value. | |
4730 | This also applies to parts that you change indirectly by calling | |
4731 | @code{push_reload}. | |
4732 | ||
39bdfaa0 RH |
4733 | @findex strict_memory_address_p |
4734 | The macro definition may use @code{strict_memory_address_p} to test if | |
4735 | the address has become legitimate. | |
4736 | ||
a9a2595b JR |
4737 | @findex copy_rtx |
4738 | If you want to change only a part of @var{x}, one standard way of doing | |
4739 | this is to use @code{copy_rtx}. Note, however, that is unshares only a | |
4740 | single level of rtl. Thus, if the part to be changed is not at the | |
4741 | top level, you'll need to replace first the top leve | |
4742 | It is not necessary for this macro to come up with a legitimate | |
4743 | address; but often a machine-dependent strategy can generate better code. | |
4744 | ||
feca2ed3 JW |
4745 | @findex GO_IF_MODE_DEPENDENT_ADDRESS |
4746 | @item GO_IF_MODE_DEPENDENT_ADDRESS (@var{addr}, @var{label}) | |
4747 | A C statement or compound statement with a conditional @code{goto | |
4748 | @var{label};} executed if memory address @var{x} (an RTX) can have | |
4749 | different meanings depending on the machine mode of the memory | |
4750 | reference it is used for or if the address is valid for some modes | |
4751 | but not others. | |
4752 | ||
4753 | Autoincrement and autodecrement addresses typically have mode-dependent | |
4754 | effects because the amount of the increment or decrement is the size | |
4755 | of the operand being addressed. Some machines have other mode-dependent | |
4756 | addresses. Many RISC machines have no mode-dependent addresses. | |
4757 | ||
4758 | You may assume that @var{addr} is a valid address for the machine. | |
4759 | ||
4760 | @findex LEGITIMATE_CONSTANT_P | |
4761 | @item LEGITIMATE_CONSTANT_P (@var{x}) | |
4762 | A C expression that is nonzero if @var{x} is a legitimate constant for | |
4763 | an immediate operand on the target machine. You can assume that | |
4764 | @var{x} satisfies @code{CONSTANT_P}, so you need not check this. In fact, | |
4765 | @samp{1} is a suitable definition for this macro on machines where | |
4766 | anything @code{CONSTANT_P} is valid.@refill | |
4767 | @end table | |
4768 | ||
4769 | @node Condition Code | |
4770 | @section Condition Code Status | |
4771 | @cindex condition code status | |
4772 | ||
4773 | @c prevent bad page break with this line | |
4774 | This describes the condition code status. | |
4775 | ||
4776 | @findex cc_status | |
4777 | The file @file{conditions.h} defines a variable @code{cc_status} to | |
4778 | describe how the condition code was computed (in case the interpretation of | |
4779 | the condition code depends on the instruction that it was set by). This | |
4780 | variable contains the RTL expressions on which the condition code is | |
4781 | currently based, and several standard flags. | |
4782 | ||
4783 | Sometimes additional machine-specific flags must be defined in the machine | |
4784 | description header file. It can also add additional machine-specific | |
4785 | information by defining @code{CC_STATUS_MDEP}. | |
4786 | ||
4787 | @table @code | |
4788 | @findex CC_STATUS_MDEP | |
4789 | @item CC_STATUS_MDEP | |
4790 | C code for a data type which is used for declaring the @code{mdep} | |
4791 | component of @code{cc_status}. It defaults to @code{int}. | |
4792 | ||
4793 | This macro is not used on machines that do not use @code{cc0}. | |
4794 | ||
4795 | @findex CC_STATUS_MDEP_INIT | |
4796 | @item CC_STATUS_MDEP_INIT | |
4797 | A C expression to initialize the @code{mdep} field to ``empty''. | |
4798 | The default definition does nothing, since most machines don't use | |
4799 | the field anyway. If you want to use the field, you should probably | |
4800 | define this macro to initialize it. | |
4801 | ||
4802 | This macro is not used on machines that do not use @code{cc0}. | |
4803 | ||
4804 | @findex NOTICE_UPDATE_CC | |
4805 | @item NOTICE_UPDATE_CC (@var{exp}, @var{insn}) | |
4806 | A C compound statement to set the components of @code{cc_status} | |
4807 | appropriately for an insn @var{insn} whose body is @var{exp}. It is | |
4808 | this macro's responsibility to recognize insns that set the condition | |
4809 | code as a byproduct of other activity as well as those that explicitly | |
4810 | set @code{(cc0)}. | |
4811 | ||
4812 | This macro is not used on machines that do not use @code{cc0}. | |
4813 | ||
4814 | If there are insns that do not set the condition code but do alter | |
4815 | other machine registers, this macro must check to see whether they | |
4816 | invalidate the expressions that the condition code is recorded as | |
4817 | reflecting. For example, on the 68000, insns that store in address | |
4818 | registers do not set the condition code, which means that usually | |
4819 | @code{NOTICE_UPDATE_CC} can leave @code{cc_status} unaltered for such | |
4820 | insns. But suppose that the previous insn set the condition code | |
4821 | based on location @samp{a4@@(102)} and the current insn stores a new | |
4822 | value in @samp{a4}. Although the condition code is not changed by | |
4823 | this, it will no longer be true that it reflects the contents of | |
4824 | @samp{a4@@(102)}. Therefore, @code{NOTICE_UPDATE_CC} must alter | |
4825 | @code{cc_status} in this case to say that nothing is known about the | |
4826 | condition code value. | |
4827 | ||
4828 | The definition of @code{NOTICE_UPDATE_CC} must be prepared to deal | |
4829 | with the results of peephole optimization: insns whose patterns are | |
4830 | @code{parallel} RTXs containing various @code{reg}, @code{mem} or | |
4831 | constants which are just the operands. The RTL structure of these | |
4832 | insns is not sufficient to indicate what the insns actually do. What | |
4833 | @code{NOTICE_UPDATE_CC} should do when it sees one is just to run | |
4834 | @code{CC_STATUS_INIT}. | |
4835 | ||
4836 | A possible definition of @code{NOTICE_UPDATE_CC} is to call a function | |
4837 | that looks at an attribute (@pxref{Insn Attributes}) named, for example, | |
4838 | @samp{cc}. This avoids having detailed information about patterns in | |
4839 | two places, the @file{md} file and in @code{NOTICE_UPDATE_CC}. | |
4840 | ||
4841 | @findex EXTRA_CC_MODES | |
4842 | @item EXTRA_CC_MODES | |
aa0b4465 ZW |
4843 | A list of additional modes for condition code values in registers |
4844 | (@pxref{Jump Patterns}). This macro should expand to a sequence of | |
4845 | calls of the macro @code{CC} separated by white space. @code{CC} takes | |
4846 | two arguments. The first is the enumeration name of the mode, which | |
4847 | should begin with @samp{CC} and end with @samp{mode}. The second is a C | |
4848 | string giving the printable name of the mode; it should be the same as | |
4849 | the first argument, but with the trailing @samp{mode} removed. | |
feca2ed3 | 4850 | |
aa0b4465 | 4851 | You should only define this macro if additional modes are required. |
feca2ed3 | 4852 | |
aa0b4465 | 4853 | A sample definition of @code{EXTRA_CC_MODES} is: |
feca2ed3 | 4854 | @smallexample |
aa0b4465 ZW |
4855 | #define EXTRA_CC_MODES \ |
4856 | CC(CC_NOOVmode, "CC_NOOV") \ | |
4857 | CC(CCFPmode, "CCFP") \ | |
4858 | CC(CCFPEmode, "CCFPE") | |
feca2ed3 JW |
4859 | @end smallexample |
4860 | ||
feca2ed3 JW |
4861 | @findex SELECT_CC_MODE |
4862 | @item SELECT_CC_MODE (@var{op}, @var{x}, @var{y}) | |
4863 | Returns a mode from class @code{MODE_CC} to be used when comparison | |
4864 | operation code @var{op} is applied to rtx @var{x} and @var{y}. For | |
4865 | example, on the Sparc, @code{SELECT_CC_MODE} is defined as (see | |
4866 | @pxref{Jump Patterns} for a description of the reason for this | |
4867 | definition) | |
4868 | ||
4869 | @smallexample | |
4870 | #define SELECT_CC_MODE(OP,X,Y) \ | |
4871 | (GET_MODE_CLASS (GET_MODE (X)) == MODE_FLOAT \ | |
4872 | ? ((OP == EQ || OP == NE) ? CCFPmode : CCFPEmode) \ | |
4873 | : ((GET_CODE (X) == PLUS || GET_CODE (X) == MINUS \ | |
4874 | || GET_CODE (X) == NEG) \ | |
4875 | ? CC_NOOVmode : CCmode)) | |
4876 | @end smallexample | |
4877 | ||
4878 | You need not define this macro if @code{EXTRA_CC_MODES} is not defined. | |
4879 | ||
4880 | @findex CANONICALIZE_COMPARISON | |
4881 | @item CANONICALIZE_COMPARISON (@var{code}, @var{op0}, @var{op1}) | |
8760eaae | 4882 | On some machines not all possible comparisons are defined, but you can |
feca2ed3 JW |
4883 | convert an invalid comparison into a valid one. For example, the Alpha |
4884 | does not have a @code{GT} comparison, but you can use an @code{LT} | |
4885 | comparison instead and swap the order of the operands. | |
4886 | ||
4887 | On such machines, define this macro to be a C statement to do any | |
4888 | required conversions. @var{code} is the initial comparison code | |
4889 | and @var{op0} and @var{op1} are the left and right operands of the | |
4890 | comparison, respectively. You should modify @var{code}, @var{op0}, and | |
4891 | @var{op1} as required. | |
4892 | ||
a3a15b4d | 4893 | GCC will not assume that the comparison resulting from this macro is |
feca2ed3 JW |
4894 | valid but will see if the resulting insn matches a pattern in the |
4895 | @file{md} file. | |
4896 | ||
4897 | You need not define this macro if it would never change the comparison | |
4898 | code or operands. | |
4899 | ||
4900 | @findex REVERSIBLE_CC_MODE | |
4901 | @item REVERSIBLE_CC_MODE (@var{mode}) | |
4902 | A C expression whose value is one if it is always safe to reverse a | |
4903 | comparison whose mode is @var{mode}. If @code{SELECT_CC_MODE} | |
4904 | can ever return @var{mode} for a floating-point inequality comparison, | |
4905 | then @code{REVERSIBLE_CC_MODE (@var{mode})} must be zero. | |
4906 | ||
4907 | You need not define this macro if it would always returns zero or if the | |
4908 | floating-point format is anything other than @code{IEEE_FLOAT_FORMAT}. | |
4909 | For example, here is the definition used on the Sparc, where floating-point | |
4910 | inequality comparisons are always given @code{CCFPEmode}: | |
4911 | ||
4912 | @smallexample | |
4913 | #define REVERSIBLE_CC_MODE(MODE) ((MODE) != CCFPEmode) | |
4914 | @end smallexample | |
4915 | ||
9e7adcb3 JH |
4916 | @findex REVERSE_CONDITION (@var{code}, @var{mode}) |
4917 | A C expression whose value is reversed condition code of the @var{code} for | |
4918 | comparison done in CC_MODE @var{mode}. The macro is used only in case | |
4919 | @code{REVERSIBLE_CC_MODE (@var{mode})} is nonzero. Define this macro in case | |
4920 | machine has some non-standard way how to reverse certain conditionals. For | |
4921 | instance in case all floating point conditions are non-trapping, compiler may | |
4922 | freely convert unordered compares to ordered one. Then definition may look | |
4923 | like: | |
4924 | ||
4925 | @smallexample | |
4926 | #define REVERSE_CONDITION(CODE, MODE) \ | |
4927 | ((MODE) != CCFPmode ? reverse_condtion (CODE) \ | |
4928 | : reverse_condition_maybe_unordered (CODE)) | |
4929 | @end smallexample | |
4930 | ||
7e6d8ba1 AH |
4931 | @findex REVERSE_CONDEXEC_PREDICATES_P |
4932 | @item REVERSE_CONDEXEC_PREDICATES_P (@var{code1}, @var{code2}) | |
4933 | A C expression that returns true if the conditional execution predicate | |
4934 | @var{code1} is the inverse of @var{code2} and vice versa. Define this to | |
4935 | return 0 if the target has conditional execution predicates that cannot be | |
a43f528e AH |
4936 | reversed safely. If no expansion is specified, this macro is defined as |
4937 | follows: | |
7e6d8ba1 AH |
4938 | |
4939 | @smallexample | |
4940 | #define REVERSE_CONDEXEC_PREDICATES_P (x, y) ((x) == reverse_condition (y)) | |
4941 | @end smallexample | |
4942 | ||
feca2ed3 JW |
4943 | @end table |
4944 | ||
4945 | @node Costs | |
4946 | @section Describing Relative Costs of Operations | |
4947 | @cindex costs of instructions | |
4948 | @cindex relative costs | |
4949 | @cindex speed of instructions | |
4950 | ||
4951 | These macros let you describe the relative speed of various operations | |
4952 | on the target machine. | |
4953 | ||
4954 | @table @code | |
4955 | @findex CONST_COSTS | |
4956 | @item CONST_COSTS (@var{x}, @var{code}, @var{outer_code}) | |
4957 | A part of a C @code{switch} statement that describes the relative costs | |
4958 | of constant RTL expressions. It must contain @code{case} labels for | |
4959 | expression codes @code{const_int}, @code{const}, @code{symbol_ref}, | |
4960 | @code{label_ref} and @code{const_double}. Each case must ultimately | |
4961 | reach a @code{return} statement to return the relative cost of the use | |
4962 | of that kind of constant value in an expression. The cost may depend on | |
4963 | the precise value of the constant, which is available for examination in | |
4964 | @var{x}, and the rtx code of the expression in which it is contained, | |
4965 | found in @var{outer_code}. | |
4966 | ||
4967 | @var{code} is the expression code---redundant, since it can be | |
4968 | obtained with @code{GET_CODE (@var{x})}. | |
4969 | ||
4970 | @findex RTX_COSTS | |
4971 | @findex COSTS_N_INSNS | |
4972 | @item RTX_COSTS (@var{x}, @var{code}, @var{outer_code}) | |
4973 | Like @code{CONST_COSTS} but applies to nonconstant RTL expressions. | |
4974 | This can be used, for example, to indicate how costly a multiply | |
4975 | instruction is. In writing this macro, you can use the construct | |
4976 | @code{COSTS_N_INSNS (@var{n})} to specify a cost equal to @var{n} fast | |
4977 | instructions. @var{outer_code} is the code of the expression in which | |
4978 | @var{x} is contained. | |
4979 | ||
4980 | This macro is optional; do not define it if the default cost assumptions | |
4981 | are adequate for the target machine. | |
4982 | ||
8625fab5 KG |
4983 | @findex DEFAULT_RTX_COSTS |
4984 | @item DEFAULT_RTX_COSTS (@var{x}, @var{code}, @var{outer_code}) | |
4985 | This macro, if defined, is called for any case not handled by the | |
4986 | @code{RTX_COSTS} or @code{CONST_COSTS} macros. This eliminates the need | |
4987 | to put case labels into the macro, but the code, or any functions it | |
4988 | calls, must assume that the RTL in @var{x} could be of any type that has | |
4989 | not already been handled. The arguments are the same as for | |
4990 | @code{RTX_COSTS}, and the macro should execute a return statement giving | |
4991 | the cost of any RTL expressions that it can handle. The default cost | |
4992 | calculation is used for any RTL for which this macro does not return a | |
4993 | value. | |
4994 | ||
4995 | This macro is optional; do not define it if the default cost assumptions | |
4996 | are adequate for the target machine. | |
4997 | ||
feca2ed3 JW |
4998 | @findex ADDRESS_COST |
4999 | @item ADDRESS_COST (@var{address}) | |
5000 | An expression giving the cost of an addressing mode that contains | |
5001 | @var{address}. If not defined, the cost is computed from | |
5002 | the @var{address} expression and the @code{CONST_COSTS} values. | |
5003 | ||
5004 | For most CISC machines, the default cost is a good approximation of the | |
5005 | true cost of the addressing mode. However, on RISC machines, all | |
5006 | instructions normally have the same length and execution time. Hence | |
5007 | all addresses will have equal costs. | |
5008 | ||
5009 | In cases where more than one form of an address is known, the form with | |
5010 | the lowest cost will be used. If multiple forms have the same, lowest, | |
5011 | cost, the one that is the most complex will be used. | |
5012 | ||
5013 | For example, suppose an address that is equal to the sum of a register | |
5014 | and a constant is used twice in the same basic block. When this macro | |
5015 | is not defined, the address will be computed in a register and memory | |
5016 | references will be indirect through that register. On machines where | |
5017 | the cost of the addressing mode containing the sum is no higher than | |
5018 | that of a simple indirect reference, this will produce an additional | |
5019 | instruction and possibly require an additional register. Proper | |
5020 | specification of this macro eliminates this overhead for such machines. | |
5021 | ||
5022 | Similar use of this macro is made in strength reduction of loops. | |
5023 | ||
5024 | @var{address} need not be valid as an address. In such a case, the cost | |
5025 | is not relevant and can be any value; invalid addresses need not be | |
5026 | assigned a different cost. | |
5027 | ||
5028 | On machines where an address involving more than one register is as | |
5029 | cheap as an address computation involving only one register, defining | |
5030 | @code{ADDRESS_COST} to reflect this can cause two registers to be live | |
5031 | over a region of code where only one would have been if | |
5032 | @code{ADDRESS_COST} were not defined in that manner. This effect should | |
5033 | be considered in the definition of this macro. Equivalent costs should | |
5034 | probably only be given to addresses with different numbers of registers | |
5035 | on machines with lots of registers. | |
5036 | ||
5037 | This macro will normally either not be defined or be defined as a | |
5038 | constant. | |
5039 | ||
5040 | @findex REGISTER_MOVE_COST | |
e56b4594 AO |
5041 | @item REGISTER_MOVE_COST (@var{mode}, @var{from}, @var{to}) |
5042 | A C expression for the cost of moving data of mode @var{mode} from a | |
5043 | register in class @var{from} to one in class @var{to}. The classes are | |
5044 | expressed using the enumeration values such as @code{GENERAL_REGS}. A | |
5045 | value of 2 is the default; other values are interpreted relative to | |
5046 | that. | |
feca2ed3 JW |
5047 | |
5048 | It is not required that the cost always equal 2 when @var{from} is the | |
5049 | same as @var{to}; on some machines it is expensive to move between | |
5050 | registers if they are not general registers. | |
5051 | ||
5052 | If reload sees an insn consisting of a single @code{set} between two | |
5053 | hard registers, and if @code{REGISTER_MOVE_COST} applied to their | |
5054 | classes returns a value of 2, reload does not check to ensure that the | |
5055 | constraints of the insn are met. Setting a cost of other than 2 will | |
5056 | allow reload to verify that the constraints are met. You should do this | |
5057 | if the @samp{mov@var{m}} pattern's constraints do not allow such copying. | |
5058 | ||
5059 | @findex MEMORY_MOVE_COST | |
cbd5b9a2 KR |
5060 | @item MEMORY_MOVE_COST (@var{mode}, @var{class}, @var{in}) |
5061 | A C expression for the cost of moving data of mode @var{mode} between a | |
5062 | register of class @var{class} and memory; @var{in} is zero if the value | |
473fe49b KR |
5063 | is to be written to memory, non-zero if it is to be read in. This cost |
5064 | is relative to those in @code{REGISTER_MOVE_COST}. If moving between | |
5065 | registers and memory is more expensive than between two registers, you | |
5066 | should define this macro to express the relative cost. | |
5067 | ||
a3a15b4d | 5068 | If you do not define this macro, GCC uses a default cost of 4 plus |
38e01259 | 5069 | the cost of copying via a secondary reload register, if one is |
473fe49b KR |
5070 | needed. If your machine requires a secondary reload register to copy |
5071 | between memory and a register of @var{class} but the reload mechanism is | |
5072 | more complex than copying via an intermediate, define this macro to | |
5073 | reflect the actual cost of the move. | |
5074 | ||
a3a15b4d | 5075 | GCC defines the function @code{memory_move_secondary_cost} if |
473fe49b KR |
5076 | secondary reloads are needed. It computes the costs due to copying via |
5077 | a secondary register. If your machine copies from memory using a | |
5078 | secondary register in the conventional way but the default base value of | |
5079 | 4 is not correct for your machine, define this macro to add some other | |
5080 | value to the result of that function. The arguments to that function | |
5081 | are the same as to this macro. | |
cbd5b9a2 | 5082 | |
feca2ed3 JW |
5083 | @findex BRANCH_COST |
5084 | @item BRANCH_COST | |
5085 | A C expression for the cost of a branch instruction. A value of 1 is | |
5086 | the default; other values are interpreted relative to that. | |
5087 | @end table | |
5088 | ||
5089 | Here are additional macros which do not specify precise relative costs, | |
a3a15b4d | 5090 | but only that certain actions are more expensive than GCC would |
feca2ed3 JW |
5091 | ordinarily expect. |
5092 | ||
5093 | @table @code | |
5094 | @findex SLOW_BYTE_ACCESS | |
5095 | @item SLOW_BYTE_ACCESS | |
5096 | Define this macro as a C expression which is nonzero if accessing less | |
5097 | than a word of memory (i.e. a @code{char} or a @code{short}) is no | |
5098 | faster than accessing a word of memory, i.e., if such access | |
5099 | require more than one instruction or if there is no difference in cost | |
5100 | between byte and (aligned) word loads. | |
5101 | ||
5102 | When this macro is not defined, the compiler will access a field by | |
5103 | finding the smallest containing object; when it is defined, a fullword | |
5104 | load will be used if alignment permits. Unless bytes accesses are | |
5105 | faster than word accesses, using word accesses is preferable since it | |
5106 | may eliminate subsequent memory access if subsequent accesses occur to | |
5107 | other fields in the same word of the structure, but to different bytes. | |
5108 | ||
5109 | @findex SLOW_ZERO_EXTEND | |
5110 | @item SLOW_ZERO_EXTEND | |
5111 | Define this macro if zero-extension (of a @code{char} or @code{short} | |
5112 | to an @code{int}) can be done faster if the destination is a register | |
5113 | that is known to be zero. | |
5114 | ||
5115 | If you define this macro, you must have instruction patterns that | |
5116 | recognize RTL structures like this: | |
5117 | ||
5118 | @smallexample | |
5119 | (set (strict_low_part (subreg:QI (reg:SI @dots{}) 0)) @dots{}) | |
5120 | @end smallexample | |
5121 | ||
5122 | @noindent | |
5123 | and likewise for @code{HImode}. | |
5124 | ||
5125 | @findex SLOW_UNALIGNED_ACCESS | |
5fad8ebf DE |
5126 | @item SLOW_UNALIGNED_ACCESS (@var{mode}, @var{alignment}) |
5127 | Define this macro to be the value 1 if memory accesses described by the | |
5128 | @var{mode} and @var{alignment} parameters have a cost many times greater | |
5129 | than aligned accesses, for example if they are emulated in a trap | |
5130 | handler. | |
feca2ed3 JW |
5131 | |
5132 | When this macro is non-zero, the compiler will act as if | |
5133 | @code{STRICT_ALIGNMENT} were non-zero when generating code for block | |
5134 | moves. This can cause significantly more instructions to be produced. | |
5135 | Therefore, do not set this macro non-zero if unaligned accesses only add a | |
5136 | cycle or two to the time for a memory access. | |
5137 | ||
6be57663 DE |
5138 | If the value of this macro is always zero, it need not be defined. If |
5139 | this macro is defined, it should produce a non-zero value when | |
5140 | @code{STRICT_ALIGNMENT} is non-zero. | |
feca2ed3 JW |
5141 | |
5142 | @findex DONT_REDUCE_ADDR | |
5143 | @item DONT_REDUCE_ADDR | |
5144 | Define this macro to inhibit strength reduction of memory addresses. | |
5145 | (On some machines, such strength reduction seems to do harm rather | |
5146 | than good.) | |
5147 | ||
5148 | @findex MOVE_RATIO | |
5149 | @item MOVE_RATIO | |
9862dea9 | 5150 | The threshold of number of scalar memory-to-memory move insns, @emph{below} |
c5c76735 | 5151 | which a sequence of insns should be generated instead of a |
feca2ed3 JW |
5152 | string move insn or a library call. Increasing the value will always |
5153 | make code faster, but eventually incurs high cost in increased code size. | |
5154 | ||
c5c76735 JL |
5155 | Note that on machines where the corresponding move insn is a |
5156 | @code{define_expand} that emits a sequence of insns, this macro counts | |
5157 | the number of such sequences. | |
9862dea9 | 5158 | |
feca2ed3 JW |
5159 | If you don't define this, a reasonable default is used. |
5160 | ||
fbe1758d AM |
5161 | @findex MOVE_BY_PIECES_P |
5162 | @item MOVE_BY_PIECES_P (@var{size}, @var{alignment}) | |
5163 | A C expression used to determine whether @code{move_by_pieces} will be used to | |
5164 | copy a chunk of memory, or whether some other block move mechanism | |
6e01bd94 | 5165 | will be used. Defaults to 1 if @code{move_by_pieces_ninsns} returns less |
fbe1758d AM |
5166 | than @code{MOVE_RATIO}. |
5167 | ||
5168 | @findex MOVE_MAX_PIECES | |
5169 | @item MOVE_MAX_PIECES | |
5170 | A C expression used by @code{move_by_pieces} to determine the largest unit | |
6e01bd94 | 5171 | a load or store used to copy memory is. Defaults to @code{MOVE_MAX}. |
fbe1758d AM |
5172 | |
5173 | @findex USE_LOAD_POST_INCREMENT | |
5174 | @item USE_LOAD_POST_INCREMENT (@var{mode}) | |
6e01bd94 MH |
5175 | A C expression used to determine whether a load postincrement is a good |
5176 | thing to use for a given mode. Defaults to the value of | |
5177 | @code{HAVE_POST_INCREMENT}. | |
5178 | ||
5179 | @findex USE_LOAD_POST_DECREMENT | |
5180 | @item USE_LOAD_POST_DECREMENT (@var{mode}) | |
5181 | A C expression used to determine whether a load postdecrement is a good | |
5182 | thing to use for a given mode. Defaults to the value of | |
5183 | @code{HAVE_POST_DECREMENT}. | |
fbe1758d AM |
5184 | |
5185 | @findex USE_LOAD_PRE_INCREMENT | |
5186 | @item USE_LOAD_PRE_INCREMENT (@var{mode}) | |
6e01bd94 MH |
5187 | A C expression used to determine whether a load preincrement is a good |
5188 | thing to use for a given mode. Defaults to the value of | |
5189 | @code{HAVE_PRE_INCREMENT}. | |
5190 | ||
5191 | @findex USE_LOAD_PRE_DECREMENT | |
5192 | @item USE_LOAD_PRE_DECREMENT (@var{mode}) | |
5193 | A C expression used to determine whether a load predecrement is a good | |
5194 | thing to use for a given mode. Defaults to the value of | |
5195 | @code{HAVE_PRE_DECREMENT}. | |
fbe1758d AM |
5196 | |
5197 | @findex USE_STORE_POST_INCREMENT | |
5198 | @item USE_STORE_POST_INCREMENT (@var{mode}) | |
6e01bd94 MH |
5199 | A C expression used to determine whether a store postincrement is a good |
5200 | thing to use for a given mode. Defaults to the value of | |
5201 | @code{HAVE_POST_INCREMENT}. | |
5202 | ||
5203 | @findex USE_STORE_POST_DECREMENT | |
5204 | @item USE_STORE_POST_DECREMENT (@var{mode}) | |
5205 | A C expression used to determine whether a store postdeccrement is a good | |
5206 | thing to use for a given mode. Defaults to the value of | |
5207 | @code{HAVE_POST_DECREMENT}. | |
fbe1758d AM |
5208 | |
5209 | @findex USE_STORE_PRE_INCREMENT | |
5210 | @item USE_STORE_PRE_INCREMENT (@var{mode}) | |
6e01bd94 MH |
5211 | This macro is used to determine whether a store preincrement is a good |
5212 | thing to use for a given mode. Defaults to the value of | |
5213 | @code{HAVE_PRE_INCREMENT}. | |
5214 | ||
5215 | @findex USE_STORE_PRE_DECREMENT | |
5216 | @item USE_STORE_PRE_DECREMENT (@var{mode}) | |
5217 | This macro is used to determine whether a store predecrement is a good | |
5218 | thing to use for a given mode. Defaults to the value of | |
5219 | @code{HAVE_PRE_DECREMENT}. | |
fbe1758d | 5220 | |
feca2ed3 JW |
5221 | @findex NO_FUNCTION_CSE |
5222 | @item NO_FUNCTION_CSE | |
5223 | Define this macro if it is as good or better to call a constant | |
5224 | function address than to call an address kept in a register. | |
5225 | ||
5226 | @findex NO_RECURSIVE_FUNCTION_CSE | |
5227 | @item NO_RECURSIVE_FUNCTION_CSE | |
5228 | Define this macro if it is as good or better for a function to call | |
5229 | itself with an explicit address than to call an address kept in a | |
5230 | register. | |
5231 | ||
5232 | @findex ADJUST_COST | |
5233 | @item ADJUST_COST (@var{insn}, @var{link}, @var{dep_insn}, @var{cost}) | |
5234 | A C statement (sans semicolon) to update the integer variable @var{cost} | |
5235 | based on the relationship between @var{insn} that is dependent on | |
5236 | @var{dep_insn} through the dependence @var{link}. The default is to | |
5237 | make no adjustment to @var{cost}. This can be used for example to | |
5238 | specify to the scheduler that an output- or anti-dependence does not | |
5239 | incur the same cost as a data-dependence. | |
5240 | ||
5241 | @findex ADJUST_PRIORITY | |
5242 | @item ADJUST_PRIORITY (@var{insn}) | |
5243 | A C statement (sans semicolon) to update the integer scheduling | |
5244 | priority @code{INSN_PRIORITY(@var{insn})}. Reduce the priority | |
5245 | to execute the @var{insn} earlier, increase the priority to execute | |
5246 | @var{insn} later. Do not define this macro if you do not need to | |
5247 | adjust the scheduling priorities of insns. | |
5248 | @end table | |
5249 | ||
5250 | @node Sections | |
5251 | @section Dividing the Output into Sections (Texts, Data, @dots{}) | |
5252 | @c the above section title is WAY too long. maybe cut the part between | |
5253 | @c the (...)? --mew 10feb93 | |
5254 | ||
5255 | An object file is divided into sections containing different types of | |
5256 | data. In the most common case, there are three sections: the @dfn{text | |
5257 | section}, which holds instructions and read-only data; the @dfn{data | |
5258 | section}, which holds initialized writable data; and the @dfn{bss | |
5259 | section}, which holds uninitialized data. Some systems have other kinds | |
5260 | of sections. | |
5261 | ||
5262 | The compiler must tell the assembler when to switch sections. These | |
5263 | macros control what commands to output to tell the assembler this. You | |
5264 | can also define additional sections. | |
5265 | ||
5266 | @table @code | |
5267 | @findex TEXT_SECTION_ASM_OP | |
5268 | @item TEXT_SECTION_ASM_OP | |
047c1c92 HPN |
5269 | A C expression whose value is a string, including spacing, containing the |
5270 | assembler operation that should precede instructions and read-only data. | |
5271 | Normally @code{"\t.text"} is right. | |
feca2ed3 JW |
5272 | |
5273 | @findex DATA_SECTION_ASM_OP | |
5274 | @item DATA_SECTION_ASM_OP | |
047c1c92 HPN |
5275 | A C expression whose value is a string, including spacing, containing the |
5276 | assembler operation to identify the following data as writable initialized | |
5277 | data. Normally @code{"\t.data"} is right. | |
feca2ed3 JW |
5278 | |
5279 | @findex SHARED_SECTION_ASM_OP | |
5280 | @item SHARED_SECTION_ASM_OP | |
047c1c92 HPN |
5281 | If defined, a C expression whose value is a string, including spacing, |
5282 | containing the assembler operation to identify the following data as | |
5283 | shared data. If not defined, @code{DATA_SECTION_ASM_OP} will be used. | |
feca2ed3 JW |
5284 | |
5285 | @findex BSS_SECTION_ASM_OP | |
5286 | @item BSS_SECTION_ASM_OP | |
047c1c92 HPN |
5287 | If defined, a C expression whose value is a string, including spacing, |
5288 | containing the assembler operation to identify the following data as | |
5289 | uninitialized global data. If not defined, and neither | |
5290 | @code{ASM_OUTPUT_BSS} nor @code{ASM_OUTPUT_ALIGNED_BSS} are defined, | |
5291 | uninitialized global data will be output in the data section if | |
5292 | @samp{-fno-common} is passed, otherwise @code{ASM_OUTPUT_COMMON} will be | |
5293 | used. | |
feca2ed3 JW |
5294 | |
5295 | @findex SHARED_BSS_SECTION_ASM_OP | |
5296 | @item SHARED_BSS_SECTION_ASM_OP | |
047c1c92 HPN |
5297 | If defined, a C expression whose value is a string, including spacing, |
5298 | containing the assembler operation to identify the following data as | |
5299 | uninitialized global shared data. If not defined, and | |
5300 | @code{BSS_SECTION_ASM_OP} is, the latter will be used. | |
feca2ed3 JW |
5301 | |
5302 | @findex INIT_SECTION_ASM_OP | |
5303 | @item INIT_SECTION_ASM_OP | |
047c1c92 HPN |
5304 | If defined, a C expression whose value is a string, including spacing, |
5305 | containing the assembler operation to identify the following data as | |
5306 | initialization code. If not defined, GCC will assume such a section does | |
5307 | not exist. | |
feca2ed3 | 5308 | |
1b2dd04a AO |
5309 | @findex FINI_SECTION_ASM_OP |
5310 | @item FINI_SECTION_ASM_OP | |
047c1c92 HPN |
5311 | If defined, a C expression whose value is a string, including spacing, |
5312 | containing the assembler operation to identify the following data as | |
5313 | finalization code. If not defined, GCC will assume such a section does | |
5314 | not exist. | |
1b2dd04a AO |
5315 | |
5316 | @findex CRT_CALL_STATIC_FUNCTION | |
5317 | @item CRT_CALL_STATIC_FUNCTION | |
5318 | If defined, a C statement that calls the function named as the sole | |
5319 | argument of this macro. This is used in @file{crtstuff.c} if | |
5320 | @code{INIT_SECTION_ASM_OP} or @code{FINI_SECTION_ASM_OP} to calls to | |
5321 | initialization and finalization functions from the init and fini | |
5322 | sections. By default, this macro is a simple function call. Some | |
5323 | ports need hand-crafted assembly code to avoid dependencies on | |
5324 | registers initialized in the function prologue or to ensure that | |
5325 | constant pools don't end up too far way in the text section. | |
5326 | ||
feca2ed3 JW |
5327 | @findex EXTRA_SECTIONS |
5328 | @findex in_text | |
5329 | @findex in_data | |
5330 | @item EXTRA_SECTIONS | |
5331 | A list of names for sections other than the standard two, which are | |
5332 | @code{in_text} and @code{in_data}. You need not define this macro | |
5333 | on a system with no other sections (that GCC needs to use). | |
5334 | ||
5335 | @findex EXTRA_SECTION_FUNCTIONS | |
5336 | @findex text_section | |
5337 | @findex data_section | |
5338 | @item EXTRA_SECTION_FUNCTIONS | |
5339 | One or more functions to be defined in @file{varasm.c}. These | |
5340 | functions should do jobs analogous to those of @code{text_section} and | |
5341 | @code{data_section}, for your additional sections. Do not define this | |
5342 | macro if you do not define @code{EXTRA_SECTIONS}. | |
5343 | ||
5344 | @findex READONLY_DATA_SECTION | |
5345 | @item READONLY_DATA_SECTION | |
5346 | On most machines, read-only variables, constants, and jump tables are | |
5347 | placed in the text section. If this is not the case on your machine, | |
5348 | this macro should be defined to be the name of a function (either | |
5349 | @code{data_section} or a function defined in @code{EXTRA_SECTIONS}) that | |
5350 | switches to the section to be used for read-only items. | |
5351 | ||
5352 | If these items should be placed in the text section, this macro should | |
5353 | not be defined. | |
5354 | ||
5355 | @findex SELECT_SECTION | |
5356 | @item SELECT_SECTION (@var{exp}, @var{reloc}) | |
5357 | A C statement or statements to switch to the appropriate section for | |
5358 | output of @var{exp}. You can assume that @var{exp} is either a | |
5359 | @code{VAR_DECL} node or a constant of some sort. @var{reloc} | |
5360 | indicates whether the initial value of @var{exp} requires link-time | |
5361 | relocations. Select the section by calling @code{text_section} or one | |
5362 | of the alternatives for other sections. | |
5363 | ||
5364 | Do not define this macro if you put all read-only variables and | |
5365 | constants in the read-only data section (usually the text section). | |
5366 | ||
5367 | @findex SELECT_RTX_SECTION | |
5368 | @item SELECT_RTX_SECTION (@var{mode}, @var{rtx}) | |
5369 | A C statement or statements to switch to the appropriate section for | |
5370 | output of @var{rtx} in mode @var{mode}. You can assume that @var{rtx} | |
5371 | is some kind of constant in RTL. The argument @var{mode} is redundant | |
5372 | except in the case of a @code{const_int} rtx. Select the section by | |
5373 | calling @code{text_section} or one of the alternatives for other | |
5374 | sections. | |
5375 | ||
5376 | Do not define this macro if you put all constants in the read-only | |
5377 | data section. | |
5378 | ||
5379 | @findex JUMP_TABLES_IN_TEXT_SECTION | |
5380 | @item JUMP_TABLES_IN_TEXT_SECTION | |
75197b37 BS |
5381 | Define this macro to be an expression with a non-zero value if jump |
5382 | tables (for @code{tablejump} insns) should be output in the text | |
5383 | section, along with the assembler instructions. Otherwise, the | |
5384 | readonly data section is used. | |
feca2ed3 JW |
5385 | |
5386 | This macro is irrelevant if there is no separate readonly data section. | |
5387 | ||
5388 | @findex ENCODE_SECTION_INFO | |
5389 | @item ENCODE_SECTION_INFO (@var{decl}) | |
5390 | Define this macro if references to a symbol must be treated differently | |
5391 | depending on something about the variable or function named by the | |
5392 | symbol (such as what section it is in). | |
5393 | ||
5394 | The macro definition, if any, is executed immediately after the rtl for | |
5395 | @var{decl} has been created and stored in @code{DECL_RTL (@var{decl})}. | |
5396 | The value of the rtl will be a @code{mem} whose address is a | |
5397 | @code{symbol_ref}. | |
5398 | ||
5399 | @cindex @code{SYMBOL_REF_FLAG}, in @code{ENCODE_SECTION_INFO} | |
5400 | The usual thing for this macro to do is to record a flag in the | |
5401 | @code{symbol_ref} (such as @code{SYMBOL_REF_FLAG}) or to store a | |
5402 | modified name string in the @code{symbol_ref} (if one bit is not enough | |
5403 | information). | |
5404 | ||
5405 | @findex STRIP_NAME_ENCODING | |
5406 | @item STRIP_NAME_ENCODING (@var{var}, @var{sym_name}) | |
5407 | Decode @var{sym_name} and store the real name part in @var{var}, sans | |
5408 | the characters that encode section info. Define this macro if | |
5409 | @code{ENCODE_SECTION_INFO} alters the symbol's name string. | |
5410 | ||
e9a25f70 | 5411 | @findex UNIQUE_SECTION_P |
861bb6c1 JL |
5412 | @item UNIQUE_SECTION_P (@var{decl}) |
5413 | A C expression which evaluates to true if @var{decl} should be placed | |
5414 | into a unique section for some target-specific reason. If you do not | |
5415 | define this macro, the default is @samp{0}. Note that the flag | |
5416 | @samp{-ffunction-sections} will also cause functions to be placed into | |
5417 | unique sections. | |
5418 | ||
feca2ed3 | 5419 | @findex UNIQUE_SECTION |
861bb6c1 JL |
5420 | @item UNIQUE_SECTION (@var{decl}, @var{reloc}) |
5421 | A C statement to build up a unique section name, expressed as a | |
5422 | STRING_CST node, and assign it to @samp{DECL_SECTION_NAME (@var{decl})}. | |
5423 | @var{reloc} indicates whether the initial value of @var{exp} requires | |
a3a15b4d | 5424 | link-time relocations. If you do not define this macro, GCC will use |
a56e7c08 NC |
5425 | the symbol name prefixed by @samp{.} as the section name. Note - this |
5426 | macro can now be called for unitialised data items as well as | |
5427 | initialised data and functions. | |
feca2ed3 JW |
5428 | @end table |
5429 | ||
5430 | @node PIC | |
5431 | @section Position Independent Code | |
5432 | @cindex position independent code | |
5433 | @cindex PIC | |
5434 | ||
5435 | This section describes macros that help implement generation of position | |
5436 | independent code. Simply defining these macros is not enough to | |
5437 | generate valid PIC; you must also add support to the macros | |
5438 | @code{GO_IF_LEGITIMATE_ADDRESS} and @code{PRINT_OPERAND_ADDRESS}, as | |
5439 | well as @code{LEGITIMIZE_ADDRESS}. You must modify the definition of | |
5440 | @samp{movsi} to do something appropriate when the source operand | |
5441 | contains a symbolic address. You may also need to alter the handling of | |
5442 | switch statements so that they use relative addresses. | |
5443 | @c i rearranged the order of the macros above to try to force one of | |
5444 | @c them to the next line, to eliminate an overfull hbox. --mew 10feb93 | |
5445 | ||
5446 | @table @code | |
5447 | @findex PIC_OFFSET_TABLE_REGNUM | |
5448 | @item PIC_OFFSET_TABLE_REGNUM | |
5449 | The register number of the register used to address a table of static | |
5450 | data addresses in memory. In some cases this register is defined by a | |
5451 | processor's ``application binary interface'' (ABI). When this macro | |
5452 | is defined, RTL is generated for this register once, as with the stack | |
5453 | pointer and frame pointer registers. If this macro is not defined, it | |
5454 | is up to the machine-dependent files to allocate such a register (if | |
5455 | necessary). | |
5456 | ||
5457 | @findex PIC_OFFSET_TABLE_REG_CALL_CLOBBERED | |
5458 | @item PIC_OFFSET_TABLE_REG_CALL_CLOBBERED | |
5459 | Define this macro if the register defined by | |
5460 | @code{PIC_OFFSET_TABLE_REGNUM} is clobbered by calls. Do not define | |
ed4db1ee | 5461 | this macro if @code{PIC_OFFSET_TABLE_REGNUM} is not defined. |
feca2ed3 JW |
5462 | |
5463 | @findex FINALIZE_PIC | |
5464 | @item FINALIZE_PIC | |
5465 | By generating position-independent code, when two different programs (A | |
5466 | and B) share a common library (libC.a), the text of the library can be | |
5467 | shared whether or not the library is linked at the same address for both | |
5468 | programs. In some of these environments, position-independent code | |
5469 | requires not only the use of different addressing modes, but also | |
5470 | special code to enable the use of these addressing modes. | |
5471 | ||
5472 | The @code{FINALIZE_PIC} macro serves as a hook to emit these special | |
5473 | codes once the function is being compiled into assembly code, but not | |
5474 | before. (It is not done before, because in the case of compiling an | |
5475 | inline function, it would lead to multiple PIC prologues being | |
5476 | included in functions which used inline functions and were compiled to | |
5477 | assembly language.) | |
5478 | ||
5479 | @findex LEGITIMATE_PIC_OPERAND_P | |
5480 | @item LEGITIMATE_PIC_OPERAND_P (@var{x}) | |
5481 | A C expression that is nonzero if @var{x} is a legitimate immediate | |
5482 | operand on the target machine when generating position independent code. | |
5483 | You can assume that @var{x} satisfies @code{CONSTANT_P}, so you need not | |
5484 | check this. You can also assume @var{flag_pic} is true, so you need not | |
5485 | check it either. You need not define this macro if all constants | |
5486 | (including @code{SYMBOL_REF}) can be immediate operands when generating | |
5487 | position independent code. | |
5488 | @end table | |
5489 | ||
5490 | @node Assembler Format | |
5491 | @section Defining the Output Assembler Language | |
5492 | ||
5493 | This section describes macros whose principal purpose is to describe how | |
5494 | to write instructions in assembler language--rather than what the | |
5495 | instructions do. | |
5496 | ||
5497 | @menu | |
5498 | * File Framework:: Structural information for the assembler file. | |
5499 | * Data Output:: Output of constants (numbers, strings, addresses). | |
5500 | * Uninitialized Data:: Output of uninitialized variables. | |
5501 | * Label Output:: Output and generation of labels. | |
5502 | * Initialization:: General principles of initialization | |
5503 | and termination routines. | |
5504 | * Macros for Initialization:: | |
5505 | Specific macros that control the handling of | |
5506 | initialization and termination routines. | |
5507 | * Instruction Output:: Output of actual instructions. | |
5508 | * Dispatch Tables:: Output of jump tables. | |
5509 | * Exception Region Output:: Output of exception region code. | |
5510 | * Alignment Output:: Pseudo ops for alignment and skipping data. | |
5511 | @end menu | |
5512 | ||
5513 | @node File Framework | |
5514 | @subsection The Overall Framework of an Assembler File | |
5515 | @cindex assembler format | |
5516 | @cindex output of assembler code | |
5517 | ||
5518 | @c prevent bad page break with this line | |
5519 | This describes the overall framework of an assembler file. | |
5520 | ||
5521 | @table @code | |
5522 | @findex ASM_FILE_START | |
5523 | @item ASM_FILE_START (@var{stream}) | |
5524 | A C expression which outputs to the stdio stream @var{stream} | |
5525 | some appropriate text to go at the start of an assembler file. | |
5526 | ||
5527 | Normally this macro is defined to output a line containing | |
5528 | @samp{#NO_APP}, which is a comment that has no effect on most | |
5529 | assemblers but tells the GNU assembler that it can save time by not | |
5530 | checking for certain assembler constructs. | |
5531 | ||
5532 | On systems that use SDB, it is necessary to output certain commands; | |
5533 | see @file{attasm.h}. | |
5534 | ||
5535 | @findex ASM_FILE_END | |
5536 | @item ASM_FILE_END (@var{stream}) | |
5537 | A C expression which outputs to the stdio stream @var{stream} | |
5538 | some appropriate text to go at the end of an assembler file. | |
5539 | ||
5540 | If this macro is not defined, the default is to output nothing | |
5541 | special at the end of the file. Most systems don't require any | |
5542 | definition. | |
5543 | ||
5544 | On systems that use SDB, it is necessary to output certain commands; | |
5545 | see @file{attasm.h}. | |
5546 | ||
5547 | @findex ASM_IDENTIFY_GCC | |
5548 | @item ASM_IDENTIFY_GCC (@var{file}) | |
5549 | A C statement to output assembler commands which will identify | |
a3a15b4d | 5550 | the object file as having been compiled with GCC (or another |
feca2ed3 JW |
5551 | GNU compiler). |
5552 | ||
5553 | If you don't define this macro, the string @samp{gcc_compiled.:} | |
5554 | is output. This string is calculated to define a symbol which, | |
5555 | on BSD systems, will never be defined for any other reason. | |
5556 | GDB checks for the presence of this symbol when reading the | |
5557 | symbol table of an executable. | |
5558 | ||
5559 | On non-BSD systems, you must arrange communication with GDB in | |
5560 | some other fashion. If GDB is not used on your system, you can | |
5561 | define this macro with an empty body. | |
5562 | ||
5563 | @findex ASM_COMMENT_START | |
5564 | @item ASM_COMMENT_START | |
5565 | A C string constant describing how to begin a comment in the target | |
5566 | assembler language. The compiler assumes that the comment will end at | |
5567 | the end of the line. | |
5568 | ||
5569 | @findex ASM_APP_ON | |
5570 | @item ASM_APP_ON | |
5571 | A C string constant for text to be output before each @code{asm} | |
5572 | statement or group of consecutive ones. Normally this is | |
5573 | @code{"#APP"}, which is a comment that has no effect on most | |
5574 | assemblers but tells the GNU assembler that it must check the lines | |
5575 | that follow for all valid assembler constructs. | |
5576 | ||
5577 | @findex ASM_APP_OFF | |
5578 | @item ASM_APP_OFF | |
5579 | A C string constant for text to be output after each @code{asm} | |
5580 | statement or group of consecutive ones. Normally this is | |
5581 | @code{"#NO_APP"}, which tells the GNU assembler to resume making the | |
5582 | time-saving assumptions that are valid for ordinary compiler output. | |
5583 | ||
5584 | @findex ASM_OUTPUT_SOURCE_FILENAME | |
5585 | @item ASM_OUTPUT_SOURCE_FILENAME (@var{stream}, @var{name}) | |
5586 | A C statement to output COFF information or DWARF debugging information | |
5587 | which indicates that filename @var{name} is the current source file to | |
5588 | the stdio stream @var{stream}. | |
5589 | ||
5590 | This macro need not be defined if the standard form of output | |
5591 | for the file format in use is appropriate. | |
5592 | ||
e9a25f70 | 5593 | @findex OUTPUT_QUOTED_STRING |
8760eaae | 5594 | @item OUTPUT_QUOTED_STRING (@var{stream}, @var{string}) |
e9a25f70 JL |
5595 | A C statement to output the string @var{string} to the stdio stream |
5596 | @var{stream}. If you do not call the function @code{output_quoted_string} | |
a3a15b4d | 5597 | in your config files, GCC will only call it to output filenames to |
e9a25f70 JL |
5598 | the assembler source. So you can use it to canonicalize the format |
5599 | of the filename using this macro. | |
5600 | ||
feca2ed3 JW |
5601 | @findex ASM_OUTPUT_SOURCE_LINE |
5602 | @item ASM_OUTPUT_SOURCE_LINE (@var{stream}, @var{line}) | |
5603 | A C statement to output DBX or SDB debugging information before code | |
5604 | for line number @var{line} of the current source file to the | |
5605 | stdio stream @var{stream}. | |
5606 | ||
5607 | This macro need not be defined if the standard form of debugging | |
5608 | information for the debugger in use is appropriate. | |
5609 | ||
5610 | @findex ASM_OUTPUT_IDENT | |
5611 | @item ASM_OUTPUT_IDENT (@var{stream}, @var{string}) | |
5612 | A C statement to output something to the assembler file to handle a | |
5613 | @samp{#ident} directive containing the text @var{string}. If this | |
5614 | macro is not defined, nothing is output for a @samp{#ident} directive. | |
5615 | ||
5616 | @findex ASM_OUTPUT_SECTION_NAME | |
861bb6c1 | 5617 | @item ASM_OUTPUT_SECTION_NAME (@var{stream}, @var{decl}, @var{name}, @var{reloc}) |
feca2ed3 JW |
5618 | A C statement to output something to the assembler file to switch to section |
5619 | @var{name} for object @var{decl} which is either a @code{FUNCTION_DECL}, a | |
861bb6c1 JL |
5620 | @code{VAR_DECL} or @code{NULL_TREE}. @var{reloc} |
5621 | indicates whether the initial value of @var{exp} requires link-time | |
231db5f4 MM |
5622 | relocations. The string given by @var{name} will always be the |
5623 | canonical version stored in the global stringpool. | |
5624 | ||
5625 | Some target formats do not support arbitrary sections. Do not define | |
5626 | this macro in such cases. | |
feca2ed3 JW |
5627 | |
5628 | At present this macro is only used to support section attributes. | |
5629 | When this macro is undefined, section attributes are disabled. | |
5630 | ||
5631 | @findex OBJC_PROLOGUE | |
5632 | @item OBJC_PROLOGUE | |
5633 | A C statement to output any assembler statements which are required to | |
5634 | precede any Objective C object definitions or message sending. The | |
5635 | statement is executed only when compiling an Objective C program. | |
5636 | @end table | |
5637 | ||
5638 | @need 2000 | |
5639 | @node Data Output | |
5640 | @subsection Output of Data | |
5641 | ||
5642 | @c prevent bad page break with this line | |
5643 | This describes data output. | |
5644 | ||
5645 | @table @code | |
5646 | @findex ASM_OUTPUT_LONG_DOUBLE | |
5647 | @findex ASM_OUTPUT_DOUBLE | |
5648 | @findex ASM_OUTPUT_FLOAT | |
5649 | @item ASM_OUTPUT_LONG_DOUBLE (@var{stream}, @var{value}) | |
5650 | @itemx ASM_OUTPUT_DOUBLE (@var{stream}, @var{value}) | |
5651 | @itemx ASM_OUTPUT_FLOAT (@var{stream}, @var{value}) | |
5652 | @itemx ASM_OUTPUT_THREE_QUARTER_FLOAT (@var{stream}, @var{value}) | |
5653 | @itemx ASM_OUTPUT_SHORT_FLOAT (@var{stream}, @var{value}) | |
5654 | @itemx ASM_OUTPUT_BYTE_FLOAT (@var{stream}, @var{value}) | |
5655 | A C statement to output to the stdio stream @var{stream} an assembler | |
5656 | instruction to assemble a floating-point constant of @code{TFmode}, | |
5657 | @code{DFmode}, @code{SFmode}, @code{TQFmode}, @code{HFmode}, or | |
5658 | @code{QFmode}, respectively, whose value is @var{value}. @var{value} | |
5659 | will be a C expression of type @code{REAL_VALUE_TYPE}. Macros such as | |
5660 | @code{REAL_VALUE_TO_TARGET_DOUBLE} are useful for writing these | |
5661 | definitions. | |
5662 | ||
5663 | @findex ASM_OUTPUT_QUADRUPLE_INT | |
5664 | @findex ASM_OUTPUT_DOUBLE_INT | |
5665 | @findex ASM_OUTPUT_INT | |
5666 | @findex ASM_OUTPUT_SHORT | |
5667 | @findex ASM_OUTPUT_CHAR | |
5668 | @findex output_addr_const | |
5669 | @item ASM_OUTPUT_QUADRUPLE_INT (@var{stream}, @var{exp}) | |
5670 | @itemx ASM_OUTPUT_DOUBLE_INT (@var{stream}, @var{exp}) | |
5671 | @itemx ASM_OUTPUT_INT (@var{stream}, @var{exp}) | |
5672 | @itemx ASM_OUTPUT_SHORT (@var{stream}, @var{exp}) | |
5673 | @itemx ASM_OUTPUT_CHAR (@var{stream}, @var{exp}) | |
5674 | A C statement to output to the stdio stream @var{stream} an assembler | |
5675 | instruction to assemble an integer of 16, 8, 4, 2 or 1 bytes, | |
5676 | respectively, whose value is @var{value}. The argument @var{exp} will | |
5677 | be an RTL expression which represents a constant value. Use | |
5678 | @samp{output_addr_const (@var{stream}, @var{exp})} to output this value | |
5679 | as an assembler expression.@refill | |
5680 | ||
5681 | For sizes larger than @code{UNITS_PER_WORD}, if the action of a macro | |
5682 | would be identical to repeatedly calling the macro corresponding to | |
5683 | a size of @code{UNITS_PER_WORD}, once for each word, you need not define | |
5684 | the macro. | |
5685 | ||
422be3c3 AO |
5686 | @findex OUTPUT_ADDR_CONST_EXTRA |
5687 | @item OUTPUT_ADDR_CONST_EXTRA (@var{stream}, @var{x}, @var{fail}) | |
5688 | A C statement to recognize @var{rtx} patterns that | |
5689 | @code{output_addr_const} can't deal with, and output assembly code to | |
5690 | @var{stream} corresponding to the pattern @var{x}. This may be used to | |
5691 | allow machine-dependent @code{UNSPEC}s to appear within constants. | |
5692 | ||
5693 | If @code{OUTPUT_ADDR_CONST_EXTRA} fails to recognize a pattern, it must | |
5694 | @code{goto fail}, so that a standard error message is printed. If it | |
5695 | prints an error message itself, by calling, for example, | |
5696 | @code{output_operand_lossage}, it may just complete normally. | |
5697 | ||
feca2ed3 JW |
5698 | @findex ASM_OUTPUT_BYTE |
5699 | @item ASM_OUTPUT_BYTE (@var{stream}, @var{value}) | |
5700 | A C statement to output to the stdio stream @var{stream} an assembler | |
5701 | instruction to assemble a single byte containing the number @var{value}. | |
5702 | ||
5703 | @findex ASM_BYTE_OP | |
5704 | @item ASM_BYTE_OP | |
047c1c92 HPN |
5705 | A C string constant, including spacing, giving the pseudo-op to use for a |
5706 | sequence of single-byte constants. If this macro is not defined, the | |
5707 | default is @code{"\t.byte\t"}. | |
feca2ed3 | 5708 | |
1a7519ff RH |
5709 | @findex UNALIGNED_SHORT_ASM_OP |
5710 | @findex UNALIGNED_INT_ASM_OP | |
5711 | @findex UNALIGNED_DOUBLE_INT_ASM_OP | |
5712 | @item UNALIGNED_SHORT_ASM_OP | |
5713 | @itemx UNALIGNED_INT_ASM_OP | |
5714 | @itemx UNALIGNED_DOUBLE_INT_ASM_OP | |
5715 | A C string constant, including spacing, giving the pseudo-op to use | |
5716 | to assemble 16, 32, and 64 bit integers respectively @emph{without} | |
5717 | adding implicit padding or alignment. These macros are required if | |
5718 | DWARF 2 frame unwind is used. On ELF systems, these will default | |
5719 | to @code{.2byte}, @code{.4byte}, and @code{.8byte}.@refill | |
5720 | ||
feca2ed3 JW |
5721 | @findex ASM_OUTPUT_ASCII |
5722 | @item ASM_OUTPUT_ASCII (@var{stream}, @var{ptr}, @var{len}) | |
5723 | A C statement to output to the stdio stream @var{stream} an assembler | |
5724 | instruction to assemble a string constant containing the @var{len} | |
5725 | bytes at @var{ptr}. @var{ptr} will be a C expression of type | |
5726 | @code{char *} and @var{len} a C expression of type @code{int}. | |
5727 | ||
5728 | If the assembler has a @code{.ascii} pseudo-op as found in the | |
5729 | Berkeley Unix assembler, do not define the macro | |
5730 | @code{ASM_OUTPUT_ASCII}. | |
5731 | ||
861bb6c1 JL |
5732 | @findex CONSTANT_POOL_BEFORE_FUNCTION |
5733 | @item CONSTANT_POOL_BEFORE_FUNCTION | |
5734 | You may define this macro as a C expression. You should define the | |
a3a15b4d | 5735 | expression to have a non-zero value if GCC should output the constant |
861bb6c1 | 5736 | pool for a function before the code for the function, or a zero value if |
a3a15b4d JL |
5737 | GCC should output the constant pool after the function. If you do |
5738 | not define this macro, the usual case, GCC will output the constant | |
861bb6c1 JL |
5739 | pool before the function. |
5740 | ||
feca2ed3 | 5741 | @findex ASM_OUTPUT_POOL_PROLOGUE |
8760eaae | 5742 | @item ASM_OUTPUT_POOL_PROLOGUE (@var{file}, @var{funname}, @var{fundecl}, @var{size}) |
feca2ed3 JW |
5743 | A C statement to output assembler commands to define the start of the |
5744 | constant pool for a function. @var{funname} is a string giving | |
5745 | the name of the function. Should the return type of the function | |
5746 | be required, it can be obtained via @var{fundecl}. @var{size} | |
5747 | is the size, in bytes, of the constant pool that will be written | |
5748 | immediately after this call. | |
5749 | ||
5750 | If no constant-pool prefix is required, the usual case, this macro need | |
5751 | not be defined. | |
5752 | ||
5753 | @findex ASM_OUTPUT_SPECIAL_POOL_ENTRY | |
5754 | @item ASM_OUTPUT_SPECIAL_POOL_ENTRY (@var{file}, @var{x}, @var{mode}, @var{align}, @var{labelno}, @var{jumpto}) | |
5755 | A C statement (with or without semicolon) to output a constant in the | |
5756 | constant pool, if it needs special treatment. (This macro need not do | |
5757 | anything for RTL expressions that can be output normally.) | |
5758 | ||
5759 | The argument @var{file} is the standard I/O stream to output the | |
5760 | assembler code on. @var{x} is the RTL expression for the constant to | |
5761 | output, and @var{mode} is the machine mode (in case @var{x} is a | |
5762 | @samp{const_int}). @var{align} is the required alignment for the value | |
5763 | @var{x}; you should output an assembler directive to force this much | |
5764 | alignment. | |
5765 | ||
5766 | The argument @var{labelno} is a number to use in an internal label for | |
5767 | the address of this pool entry. The definition of this macro is | |
5768 | responsible for outputting the label definition at the proper place. | |
5769 | Here is how to do this: | |
5770 | ||
5771 | @example | |
5772 | ASM_OUTPUT_INTERNAL_LABEL (@var{file}, "LC", @var{labelno}); | |
5773 | @end example | |
5774 | ||
5775 | When you output a pool entry specially, you should end with a | |
5776 | @code{goto} to the label @var{jumpto}. This will prevent the same pool | |
5777 | entry from being output a second time in the usual manner. | |
5778 | ||
5779 | You need not define this macro if it would do nothing. | |
5780 | ||
861bb6c1 JL |
5781 | @findex CONSTANT_AFTER_FUNCTION_P |
5782 | @item CONSTANT_AFTER_FUNCTION_P (@var{exp}) | |
5783 | Define this macro as a C expression which is nonzero if the constant | |
5784 | @var{exp}, of type @code{tree}, should be output after the code for a | |
5785 | function. The compiler will normally output all constants before the | |
5786 | function; you need not define this macro if this is OK. | |
5787 | ||
5788 | @findex ASM_OUTPUT_POOL_EPILOGUE | |
5789 | @item ASM_OUTPUT_POOL_EPILOGUE (@var{file} @var{funname} @var{fundecl} @var{size}) | |
5790 | A C statement to output assembler commands to at the end of the constant | |
5791 | pool for a function. @var{funname} is a string giving the name of the | |
5792 | function. Should the return type of the function be required, you can | |
5793 | obtain it via @var{fundecl}. @var{size} is the size, in bytes, of the | |
a3a15b4d | 5794 | constant pool that GCC wrote immediately before this call. |
861bb6c1 JL |
5795 | |
5796 | If no constant-pool epilogue is required, the usual case, you need not | |
5797 | define this macro. | |
5798 | ||
feca2ed3 JW |
5799 | @findex IS_ASM_LOGICAL_LINE_SEPARATOR |
5800 | @item IS_ASM_LOGICAL_LINE_SEPARATOR (@var{C}) | |
5801 | Define this macro as a C expression which is nonzero if @var{C} is | |
5802 | used as a logical line separator by the assembler. | |
5803 | ||
5804 | If you do not define this macro, the default is that only | |
5805 | the character @samp{;} is treated as a logical line separator. | |
5806 | ||
5807 | ||
5808 | @findex ASM_OPEN_PAREN | |
5809 | @findex ASM_CLOSE_PAREN | |
5810 | @item ASM_OPEN_PAREN | |
5811 | @itemx ASM_CLOSE_PAREN | |
a8d1550a | 5812 | These macros are defined as C string constants, describing the syntax |
feca2ed3 JW |
5813 | in the assembler for grouping arithmetic expressions. The following |
5814 | definitions are correct for most assemblers: | |
5815 | ||
5816 | @example | |
5817 | #define ASM_OPEN_PAREN "(" | |
5818 | #define ASM_CLOSE_PAREN ")" | |
5819 | @end example | |
5820 | @end table | |
5821 | ||
5822 | These macros are provided by @file{real.h} for writing the definitions | |
5823 | of @code{ASM_OUTPUT_DOUBLE} and the like: | |
5824 | ||
5825 | @table @code | |
5826 | @item REAL_VALUE_TO_TARGET_SINGLE (@var{x}, @var{l}) | |
5827 | @itemx REAL_VALUE_TO_TARGET_DOUBLE (@var{x}, @var{l}) | |
5828 | @itemx REAL_VALUE_TO_TARGET_LONG_DOUBLE (@var{x}, @var{l}) | |
5829 | @findex REAL_VALUE_TO_TARGET_SINGLE | |
5830 | @findex REAL_VALUE_TO_TARGET_DOUBLE | |
5831 | @findex REAL_VALUE_TO_TARGET_LONG_DOUBLE | |
5832 | These translate @var{x}, of type @code{REAL_VALUE_TYPE}, to the target's | |
5833 | floating point representation, and store its bit pattern in the array of | |
5834 | @code{long int} whose address is @var{l}. The number of elements in the | |
5835 | output array is determined by the size of the desired target floating | |
5836 | point data type: 32 bits of it go in each @code{long int} array | |
5837 | element. Each array element holds 32 bits of the result, even if | |
5838 | @code{long int} is wider than 32 bits on the host machine. | |
5839 | ||
5840 | The array element values are designed so that you can print them out | |
5841 | using @code{fprintf} in the order they should appear in the target | |
5842 | machine's memory. | |
5843 | ||
5844 | @item REAL_VALUE_TO_DECIMAL (@var{x}, @var{format}, @var{string}) | |
5845 | @findex REAL_VALUE_TO_DECIMAL | |
5846 | This macro converts @var{x}, of type @code{REAL_VALUE_TYPE}, to a | |
5847 | decimal number and stores it as a string into @var{string}. | |
5848 | You must pass, as @var{string}, the address of a long enough block | |
5849 | of space to hold the result. | |
5850 | ||
5851 | The argument @var{format} is a @code{printf}-specification that serves | |
5852 | as a suggestion for how to format the output string. | |
5853 | @end table | |
5854 | ||
5855 | @node Uninitialized Data | |
5856 | @subsection Output of Uninitialized Variables | |
5857 | ||
5858 | Each of the macros in this section is used to do the whole job of | |
5859 | outputting a single uninitialized variable. | |
5860 | ||
5861 | @table @code | |
5862 | @findex ASM_OUTPUT_COMMON | |
5863 | @item ASM_OUTPUT_COMMON (@var{stream}, @var{name}, @var{size}, @var{rounded}) | |
5864 | A C statement (sans semicolon) to output to the stdio stream | |
5865 | @var{stream} the assembler definition of a common-label named | |
5866 | @var{name} whose size is @var{size} bytes. The variable @var{rounded} | |
5867 | is the size rounded up to whatever alignment the caller wants. | |
5868 | ||
5869 | Use the expression @code{assemble_name (@var{stream}, @var{name})} to | |
5870 | output the name itself; before and after that, output the additional | |
5871 | assembler syntax for defining the name, and a newline. | |
5872 | ||
5873 | This macro controls how the assembler definitions of uninitialized | |
5874 | common global variables are output. | |
5875 | ||
5876 | @findex ASM_OUTPUT_ALIGNED_COMMON | |
5877 | @item ASM_OUTPUT_ALIGNED_COMMON (@var{stream}, @var{name}, @var{size}, @var{alignment}) | |
5878 | Like @code{ASM_OUTPUT_COMMON} except takes the required alignment as a | |
5879 | separate, explicit argument. If you define this macro, it is used in | |
5880 | place of @code{ASM_OUTPUT_COMMON}, and gives you more flexibility in | |
5881 | handling the required alignment of the variable. The alignment is specified | |
5882 | as the number of bits. | |
5883 | ||
e9a25f70 JL |
5884 | @findex ASM_OUTPUT_ALIGNED_DECL_COMMON |
5885 | @item ASM_OUTPUT_ALIGNED_DECL_COMMON (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) | |
5886 | Like @code{ASM_OUTPUT_ALIGNED_COMMON} except that @var{decl} of the | |
5887 | variable to be output, if there is one, or @code{NULL_TREE} if there | |
8760eaae | 5888 | is no corresponding variable. If you define this macro, GCC will use it |
e9a25f70 JL |
5889 | in place of both @code{ASM_OUTPUT_COMMON} and |
5890 | @code{ASM_OUTPUT_ALIGNED_COMMON}. Define this macro when you need to see | |
5891 | the variable's decl in order to chose what to output. | |
5892 | ||
feca2ed3 JW |
5893 | @findex ASM_OUTPUT_SHARED_COMMON |
5894 | @item ASM_OUTPUT_SHARED_COMMON (@var{stream}, @var{name}, @var{size}, @var{rounded}) | |
5895 | If defined, it is similar to @code{ASM_OUTPUT_COMMON}, except that it | |
5896 | is used when @var{name} is shared. If not defined, @code{ASM_OUTPUT_COMMON} | |
5897 | will be used. | |
5898 | ||
5899 | @findex ASM_OUTPUT_BSS | |
5900 | @item ASM_OUTPUT_BSS (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{rounded}) | |
5901 | A C statement (sans semicolon) to output to the stdio stream | |
5902 | @var{stream} the assembler definition of uninitialized global @var{decl} named | |
5903 | @var{name} whose size is @var{size} bytes. The variable @var{rounded} | |
5904 | is the size rounded up to whatever alignment the caller wants. | |
5905 | ||
5906 | Try to use function @code{asm_output_bss} defined in @file{varasm.c} when | |
5907 | defining this macro. If unable, use the expression | |
5908 | @code{assemble_name (@var{stream}, @var{name})} to output the name itself; | |
5909 | before and after that, output the additional assembler syntax for defining | |
5910 | the name, and a newline. | |
5911 | ||
5912 | This macro controls how the assembler definitions of uninitialized global | |
5913 | variables are output. This macro exists to properly support languages like | |
5914 | @code{c++} which do not have @code{common} data. However, this macro currently | |
5915 | is not defined for all targets. If this macro and | |
5916 | @code{ASM_OUTPUT_ALIGNED_BSS} are not defined then @code{ASM_OUTPUT_COMMON} | |
e9a25f70 JL |
5917 | or @code{ASM_OUTPUT_ALIGNED_COMMON} or |
5918 | @code{ASM_OUTPUT_ALIGNED_DECL_COMMON} is used. | |
feca2ed3 JW |
5919 | |
5920 | @findex ASM_OUTPUT_ALIGNED_BSS | |
5921 | @item ASM_OUTPUT_ALIGNED_BSS (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) | |
5922 | Like @code{ASM_OUTPUT_BSS} except takes the required alignment as a | |
5923 | separate, explicit argument. If you define this macro, it is used in | |
5924 | place of @code{ASM_OUTPUT_BSS}, and gives you more flexibility in | |
5925 | handling the required alignment of the variable. The alignment is specified | |
5926 | as the number of bits. | |
5927 | ||
5928 | Try to use function @code{asm_output_aligned_bss} defined in file | |
5929 | @file{varasm.c} when defining this macro. | |
5930 | ||
5931 | @findex ASM_OUTPUT_SHARED_BSS | |
5932 | @item ASM_OUTPUT_SHARED_BSS (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{rounded}) | |
5933 | If defined, it is similar to @code{ASM_OUTPUT_BSS}, except that it | |
5934 | is used when @var{name} is shared. If not defined, @code{ASM_OUTPUT_BSS} | |
5935 | will be used. | |
5936 | ||
5937 | @findex ASM_OUTPUT_LOCAL | |
5938 | @item ASM_OUTPUT_LOCAL (@var{stream}, @var{name}, @var{size}, @var{rounded}) | |
5939 | A C statement (sans semicolon) to output to the stdio stream | |
5940 | @var{stream} the assembler definition of a local-common-label named | |
5941 | @var{name} whose size is @var{size} bytes. The variable @var{rounded} | |
5942 | is the size rounded up to whatever alignment the caller wants. | |
5943 | ||
5944 | Use the expression @code{assemble_name (@var{stream}, @var{name})} to | |
5945 | output the name itself; before and after that, output the additional | |
5946 | assembler syntax for defining the name, and a newline. | |
5947 | ||
5948 | This macro controls how the assembler definitions of uninitialized | |
5949 | static variables are output. | |
5950 | ||
5951 | @findex ASM_OUTPUT_ALIGNED_LOCAL | |
5952 | @item ASM_OUTPUT_ALIGNED_LOCAL (@var{stream}, @var{name}, @var{size}, @var{alignment}) | |
5953 | Like @code{ASM_OUTPUT_LOCAL} except takes the required alignment as a | |
5954 | separate, explicit argument. If you define this macro, it is used in | |
5955 | place of @code{ASM_OUTPUT_LOCAL}, and gives you more flexibility in | |
5956 | handling the required alignment of the variable. The alignment is specified | |
5957 | as the number of bits. | |
5958 | ||
e9a25f70 JL |
5959 | @findex ASM_OUTPUT_ALIGNED_DECL_LOCAL |
5960 | @item ASM_OUTPUT_ALIGNED_DECL_LOCAL (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) | |
5961 | Like @code{ASM_OUTPUT_ALIGNED_DECL} except that @var{decl} of the | |
5962 | variable to be output, if there is one, or @code{NULL_TREE} if there | |
8760eaae | 5963 | is no corresponding variable. If you define this macro, GCC will use it |
e9a25f70 JL |
5964 | in place of both @code{ASM_OUTPUT_DECL} and |
5965 | @code{ASM_OUTPUT_ALIGNED_DECL}. Define this macro when you need to see | |
5966 | the variable's decl in order to chose what to output. | |
5967 | ||
feca2ed3 JW |
5968 | @findex ASM_OUTPUT_SHARED_LOCAL |
5969 | @item ASM_OUTPUT_SHARED_LOCAL (@var{stream}, @var{name}, @var{size}, @var{rounded}) | |
5970 | If defined, it is similar to @code{ASM_OUTPUT_LOCAL}, except that it | |
5971 | is used when @var{name} is shared. If not defined, @code{ASM_OUTPUT_LOCAL} | |
5972 | will be used. | |
5973 | @end table | |
5974 | ||
5975 | @node Label Output | |
5976 | @subsection Output and Generation of Labels | |
5977 | ||
5978 | @c prevent bad page break with this line | |
5979 | This is about outputting labels. | |
5980 | ||
5981 | @table @code | |
5982 | @findex ASM_OUTPUT_LABEL | |
5983 | @findex assemble_name | |
5984 | @item ASM_OUTPUT_LABEL (@var{stream}, @var{name}) | |
5985 | A C statement (sans semicolon) to output to the stdio stream | |
5986 | @var{stream} the assembler definition of a label named @var{name}. | |
5987 | Use the expression @code{assemble_name (@var{stream}, @var{name})} to | |
5988 | output the name itself; before and after that, output the additional | |
5989 | assembler syntax for defining the name, and a newline. | |
5990 | ||
5991 | @findex ASM_DECLARE_FUNCTION_NAME | |
5992 | @item ASM_DECLARE_FUNCTION_NAME (@var{stream}, @var{name}, @var{decl}) | |
5993 | A C statement (sans semicolon) to output to the stdio stream | |
5994 | @var{stream} any text necessary for declaring the name @var{name} of a | |
5995 | function which is being defined. This macro is responsible for | |
5996 | outputting the label definition (perhaps using | |
5997 | @code{ASM_OUTPUT_LABEL}). The argument @var{decl} is the | |
5998 | @code{FUNCTION_DECL} tree node representing the function. | |
5999 | ||
6000 | If this macro is not defined, then the function name is defined in the | |
6001 | usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}). | |
6002 | ||
6003 | @findex ASM_DECLARE_FUNCTION_SIZE | |
6004 | @item ASM_DECLARE_FUNCTION_SIZE (@var{stream}, @var{name}, @var{decl}) | |
6005 | A C statement (sans semicolon) to output to the stdio stream | |
6006 | @var{stream} any text necessary for declaring the size of a function | |
6007 | which is being defined. The argument @var{name} is the name of the | |
6008 | function. The argument @var{decl} is the @code{FUNCTION_DECL} tree node | |
6009 | representing the function. | |
6010 | ||
6011 | If this macro is not defined, then the function size is not defined. | |
6012 | ||
6013 | @findex ASM_DECLARE_OBJECT_NAME | |
6014 | @item ASM_DECLARE_OBJECT_NAME (@var{stream}, @var{name}, @var{decl}) | |
6015 | A C statement (sans semicolon) to output to the stdio stream | |
6016 | @var{stream} any text necessary for declaring the name @var{name} of an | |
6017 | initialized variable which is being defined. This macro must output the | |
6018 | label definition (perhaps using @code{ASM_OUTPUT_LABEL}). The argument | |
6019 | @var{decl} is the @code{VAR_DECL} tree node representing the variable. | |
6020 | ||
6021 | If this macro is not defined, then the variable name is defined in the | |
6022 | usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}). | |
6023 | ||
1cb36a98 RH |
6024 | @findex ASM_DECLARE_REGISTER_GLOBAL |
6025 | @item ASM_DECLARE_REGISTER_GLOBAL (@var{stream}, @var{decl}, @var{regno}, @var{name}) | |
6026 | A C statement (sans semicolon) to output to the stdio stream | |
6027 | @var{stream} any text necessary for claiming a register @var{regno} | |
6028 | for a global variable @var{decl} with name @var{name}. | |
6029 | ||
6030 | If you don't define this macro, that is equivalent to defining it to do | |
6031 | nothing. | |
6032 | ||
feca2ed3 JW |
6033 | @findex ASM_FINISH_DECLARE_OBJECT |
6034 | @item ASM_FINISH_DECLARE_OBJECT (@var{stream}, @var{decl}, @var{toplevel}, @var{atend}) | |
6035 | A C statement (sans semicolon) to finish up declaring a variable name | |
6036 | once the compiler has processed its initializer fully and thus has had a | |
6037 | chance to determine the size of an array when controlled by an | |
6038 | initializer. This is used on systems where it's necessary to declare | |
6039 | something about the size of the object. | |
6040 | ||
6041 | If you don't define this macro, that is equivalent to defining it to do | |
6042 | nothing. | |
6043 | ||
6044 | @findex ASM_GLOBALIZE_LABEL | |
6045 | @item ASM_GLOBALIZE_LABEL (@var{stream}, @var{name}) | |
6046 | A C statement (sans semicolon) to output to the stdio stream | |
6047 | @var{stream} some commands that will make the label @var{name} global; | |
6048 | that is, available for reference from other files. Use the expression | |
6049 | @code{assemble_name (@var{stream}, @var{name})} to output the name | |
6050 | itself; before and after that, output the additional assembler syntax | |
6051 | for making that name global, and a newline. | |
6052 | ||
6053 | @findex ASM_WEAKEN_LABEL | |
6054 | @item ASM_WEAKEN_LABEL | |
6055 | A C statement (sans semicolon) to output to the stdio stream | |
6056 | @var{stream} some commands that will make the label @var{name} weak; | |
6057 | that is, available for reference from other files but only used if | |
6058 | no other definition is available. Use the expression | |
6059 | @code{assemble_name (@var{stream}, @var{name})} to output the name | |
6060 | itself; before and after that, output the additional assembler syntax | |
6061 | for making that name weak, and a newline. | |
6062 | ||
a3a15b4d | 6063 | If you don't define this macro, GCC will not support weak |
feca2ed3 JW |
6064 | symbols and you should not define the @code{SUPPORTS_WEAK} macro. |
6065 | ||
6066 | @findex SUPPORTS_WEAK | |
6067 | @item SUPPORTS_WEAK | |
6068 | A C expression which evaluates to true if the target supports weak symbols. | |
6069 | ||
6070 | If you don't define this macro, @file{defaults.h} provides a default | |
6071 | definition. If @code{ASM_WEAKEN_LABEL} is defined, the default | |
6072 | definition is @samp{1}; otherwise, it is @samp{0}. Define this macro if | |
6073 | you want to control weak symbol support with a compiler flag such as | |
6074 | @samp{-melf}. | |
6075 | ||
6076 | @findex MAKE_DECL_ONE_ONLY (@var{decl}) | |
6077 | @item MAKE_DECL_ONE_ONLY | |
6078 | A C statement (sans semicolon) to mark @var{decl} to be emitted as a | |
6079 | public symbol such that extra copies in multiple translation units will | |
6080 | be discarded by the linker. Define this macro if your object file | |
6081 | format provides support for this concept, such as the @samp{COMDAT} | |
6082 | section flags in the Microsoft Windows PE/COFF format, and this support | |
6083 | requires changes to @var{decl}, such as putting it in a separate section. | |
6084 | ||
e9a25f70 JL |
6085 | @findex SUPPORTS_ONE_ONLY |
6086 | @item SUPPORTS_ONE_ONLY | |
feca2ed3 JW |
6087 | A C expression which evaluates to true if the target supports one-only |
6088 | semantics. | |
6089 | ||
6090 | If you don't define this macro, @file{varasm.c} provides a default | |
6091 | definition. If @code{MAKE_DECL_ONE_ONLY} is defined, the default | |
6092 | definition is @samp{1}; otherwise, it is @samp{0}. Define this macro if | |
e9a25f70 | 6093 | you want to control one-only symbol support with a compiler flag, or if |
feca2ed3 JW |
6094 | setting the @code{DECL_ONE_ONLY} flag is enough to mark a declaration to |
6095 | be emitted as one-only. | |
6096 | ||
6097 | @findex ASM_OUTPUT_EXTERNAL | |
6098 | @item ASM_OUTPUT_EXTERNAL (@var{stream}, @var{decl}, @var{name}) | |
6099 | A C statement (sans semicolon) to output to the stdio stream | |
6100 | @var{stream} any text necessary for declaring the name of an external | |
6101 | symbol named @var{name} which is referenced in this compilation but | |
6102 | not defined. The value of @var{decl} is the tree node for the | |
6103 | declaration. | |
6104 | ||
6105 | This macro need not be defined if it does not need to output anything. | |
6106 | The GNU assembler and most Unix assemblers don't require anything. | |
6107 | ||
6108 | @findex ASM_OUTPUT_EXTERNAL_LIBCALL | |
6109 | @item ASM_OUTPUT_EXTERNAL_LIBCALL (@var{stream}, @var{symref}) | |
6110 | A C statement (sans semicolon) to output on @var{stream} an assembler | |
6111 | pseudo-op to declare a library function name external. The name of the | |
6112 | library function is given by @var{symref}, which has type @code{rtx} and | |
6113 | is a @code{symbol_ref}. | |
6114 | ||
6115 | This macro need not be defined if it does not need to output anything. | |
6116 | The GNU assembler and most Unix assemblers don't require anything. | |
6117 | ||
6118 | @findex ASM_OUTPUT_LABELREF | |
6119 | @item ASM_OUTPUT_LABELREF (@var{stream}, @var{name}) | |
6120 | A C statement (sans semicolon) to output to the stdio stream | |
6121 | @var{stream} a reference in assembler syntax to a label named | |
6122 | @var{name}. This should add @samp{_} to the front of the name, if that | |
6123 | is customary on your operating system, as it is in most Berkeley Unix | |
6124 | systems. This macro is used in @code{assemble_name}. | |
6125 | ||
6126 | @ignore @c Seems not to exist anymore. | |
6127 | @findex ASM_OUTPUT_LABELREF_AS_INT | |
6128 | @item ASM_OUTPUT_LABELREF_AS_INT (@var{file}, @var{label}) | |
6129 | Define this macro for systems that use the program @code{collect2}. | |
6130 | The definition should be a C statement to output a word containing | |
6131 | a reference to the label @var{label}. | |
6132 | @end ignore | |
6133 | ||
99c8c61c AO |
6134 | @findex ASM_OUTPUT_SYMBOL_REF |
6135 | @item ASM_OUTPUT_SYMBOL_REF (@var{stream}, @var{sym}) | |
6136 | A C statement (sans semicolon) to output a reference to | |
6137 | @code{SYMBOL_REF} @var{sym}. If not defined, @code{assemble_output} | |
6138 | will be used to output the name of the symbol. This macro may be used | |
6139 | to modify the way a symbol is referenced depending on information | |
6140 | encoded by @code{ENCODE_SECTION_INFO}. | |
6141 | ||
feca2ed3 JW |
6142 | @findex ASM_OUTPUT_INTERNAL_LABEL |
6143 | @item ASM_OUTPUT_INTERNAL_LABEL (@var{stream}, @var{prefix}, @var{num}) | |
6144 | A C statement to output to the stdio stream @var{stream} a label whose | |
6145 | name is made from the string @var{prefix} and the number @var{num}. | |
6146 | ||
6147 | It is absolutely essential that these labels be distinct from the labels | |
6148 | used for user-level functions and variables. Otherwise, certain programs | |
6149 | will have name conflicts with internal labels. | |
6150 | ||
6151 | It is desirable to exclude internal labels from the symbol table of the | |
6152 | object file. Most assemblers have a naming convention for labels that | |
6153 | should be excluded; on many systems, the letter @samp{L} at the | |
6154 | beginning of a label has this effect. You should find out what | |
6155 | convention your system uses, and follow it. | |
6156 | ||
6157 | The usual definition of this macro is as follows: | |
6158 | ||
6159 | @example | |
6160 | fprintf (@var{stream}, "L%s%d:\n", @var{prefix}, @var{num}) | |
6161 | @end example | |
6162 | ||
8215347e JW |
6163 | @findex ASM_OUTPUT_DEBUG_LABEL |
6164 | @item ASM_OUTPUT_DEBUG_LABEL (@var{stream}, @var{prefix}, @var{num}) | |
6165 | A C statement to output to the stdio stream @var{stream} a debug info | |
6166 | label whose name is made from the string @var{prefix} and the number | |
6167 | @var{num}. This is useful for VLIW targets, where debug info labels | |
6168 | may need to be treated differently than branch target labels. On some | |
6169 | systems, branch target labels must be at the beginning of instruction | |
6170 | bundles, but debug info labels can occur in the middle of instruction | |
6171 | bundles. | |
6172 | ||
6173 | If this macro is not defined, then @code{ASM_OUTPUT_INTERNAL_LABEL} will be | |
6174 | used. | |
6175 | ||
8cd0faaf CM |
6176 | @findex ASM_OUTPUT_ALTERNATE_LABEL_NAME |
6177 | @item ASM_OUTPUT_ALTERNATE_LABEL_NAME (@var{stream}, @var{string}) | |
6178 | A C statement to output to the stdio stream @var{stream} the string | |
6179 | @var{string}. | |
6180 | ||
6181 | The default definition of this macro is as follows: | |
6182 | ||
6183 | @example | |
6184 | fprintf (@var{stream}, "%s:\n", LABEL_ALTERNATE_NAME (INSN)) | |
6185 | @end example | |
6186 | ||
feca2ed3 JW |
6187 | @findex ASM_GENERATE_INTERNAL_LABEL |
6188 | @item ASM_GENERATE_INTERNAL_LABEL (@var{string}, @var{prefix}, @var{num}) | |
6189 | A C statement to store into the string @var{string} a label whose name | |
6190 | is made from the string @var{prefix} and the number @var{num}. | |
6191 | ||
6192 | This string, when output subsequently by @code{assemble_name}, should | |
6193 | produce the output that @code{ASM_OUTPUT_INTERNAL_LABEL} would produce | |
6194 | with the same @var{prefix} and @var{num}. | |
6195 | ||
6196 | If the string begins with @samp{*}, then @code{assemble_name} will | |
6197 | output the rest of the string unchanged. It is often convenient for | |
6198 | @code{ASM_GENERATE_INTERNAL_LABEL} to use @samp{*} in this way. If the | |
6199 | string doesn't start with @samp{*}, then @code{ASM_OUTPUT_LABELREF} gets | |
6200 | to output the string, and may change it. (Of course, | |
6201 | @code{ASM_OUTPUT_LABELREF} is also part of your machine description, so | |
6202 | you should know what it does on your machine.) | |
6203 | ||
6204 | @findex ASM_FORMAT_PRIVATE_NAME | |
6205 | @item ASM_FORMAT_PRIVATE_NAME (@var{outvar}, @var{name}, @var{number}) | |
6206 | A C expression to assign to @var{outvar} (which is a variable of type | |
6207 | @code{char *}) a newly allocated string made from the string | |
6208 | @var{name} and the number @var{number}, with some suitable punctuation | |
6209 | added. Use @code{alloca} to get space for the string. | |
6210 | ||
6211 | The string will be used as an argument to @code{ASM_OUTPUT_LABELREF} to | |
6212 | produce an assembler label for an internal static variable whose name is | |
6213 | @var{name}. Therefore, the string must be such as to result in valid | |
6214 | assembler code. The argument @var{number} is different each time this | |
6215 | macro is executed; it prevents conflicts between similarly-named | |
6216 | internal static variables in different scopes. | |
6217 | ||
6218 | Ideally this string should not be a valid C identifier, to prevent any | |
6219 | conflict with the user's own symbols. Most assemblers allow periods | |
6220 | or percent signs in assembler symbols; putting at least one of these | |
6221 | between the name and the number will suffice. | |
6222 | ||
6223 | @findex ASM_OUTPUT_DEF | |
6224 | @item ASM_OUTPUT_DEF (@var{stream}, @var{name}, @var{value}) | |
6225 | A C statement to output to the stdio stream @var{stream} assembler code | |
6226 | which defines (equates) the symbol @var{name} to have the value @var{value}. | |
6227 | ||
203cb4ef | 6228 | @findex SET_ASM_OP |
feca2ed3 JW |
6229 | If SET_ASM_OP is defined, a default definition is provided which is |
6230 | correct for most systems. | |
810e3c45 | 6231 | |
e4faf1eb | 6232 | @findex ASM_OUTPUT_DEF_FROM_DECLS |
8760eaae | 6233 | @item ASM_OUTPUT_DEF_FROM_DECLS (@var{stream}, @var{decl_of_name}, @var{decl_of_value}) |
e4faf1eb | 6234 | A C statement to output to the stdio stream @var{stream} assembler code |
3b7a2e58 | 6235 | which defines (equates) the symbol whose tree node is @var{decl_of_name} |
e4faf1eb NC |
6236 | to have the value of the tree node @var{decl_of_value}. This macro will |
6237 | be used in preference to @samp{ASM_OUTPUT_DEF} if it is defined and if | |
6238 | the tree nodes are available. | |
6239 | ||
956d6950 JL |
6240 | @findex ASM_OUTPUT_DEFINE_LABEL_DIFFERENCE_SYMBOL |
6241 | @item ASM_OUTPUT_DEFINE_LABEL_DIFFERENCE_SYMBOL (@var{stream}, @var{symbol}, @var{high}, @var{low}) | |
6242 | A C statement to output to the stdio stream @var{stream} assembler code | |
6243 | which defines (equates) the symbol @var{symbol} to have a value equal to | |
6244 | the difference of the two symbols @var{high} and @var{low}, i.e. | |
a3a15b4d | 6245 | @var{high} minus @var{low}. GCC guarantees that the symbols @var{high} |
956d6950 JL |
6246 | and @var{low} are already known by the assembler so that the difference |
6247 | resolves into a constant. | |
6248 | ||
203cb4ef | 6249 | @findex SET_ASM_OP |
956d6950 JL |
6250 | If SET_ASM_OP is defined, a default definition is provided which is |
6251 | correct for most systems. | |
6252 | ||
810e3c45 JM |
6253 | @findex ASM_OUTPUT_WEAK_ALIAS |
6254 | @item ASM_OUTPUT_WEAK_ALIAS (@var{stream}, @var{name}, @var{value}) | |
6255 | A C statement to output to the stdio stream @var{stream} assembler code | |
6256 | which defines (equates) the weak symbol @var{name} to have the value | |
6257 | @var{value}. | |
6258 | ||
6259 | Define this macro if the target only supports weak aliases; define | |
6260 | ASM_OUTPUT_DEF instead if possible. | |
6261 | ||
feca2ed3 JW |
6262 | @findex OBJC_GEN_METHOD_LABEL |
6263 | @item OBJC_GEN_METHOD_LABEL (@var{buf}, @var{is_inst}, @var{class_name}, @var{cat_name}, @var{sel_name}) | |
6264 | Define this macro to override the default assembler names used for | |
6265 | Objective C methods. | |
6266 | ||
6267 | The default name is a unique method number followed by the name of the | |
6268 | class (e.g.@: @samp{_1_Foo}). For methods in categories, the name of | |
6269 | the category is also included in the assembler name (e.g.@: | |
6270 | @samp{_1_Foo_Bar}). | |
6271 | ||
6272 | These names are safe on most systems, but make debugging difficult since | |
6273 | the method's selector is not present in the name. Therefore, particular | |
6274 | systems define other ways of computing names. | |
6275 | ||
6276 | @var{buf} is an expression of type @code{char *} which gives you a | |
6277 | buffer in which to store the name; its length is as long as | |
6278 | @var{class_name}, @var{cat_name} and @var{sel_name} put together, plus | |
6279 | 50 characters extra. | |
6280 | ||
6281 | The argument @var{is_inst} specifies whether the method is an instance | |
6282 | method or a class method; @var{class_name} is the name of the class; | |
6283 | @var{cat_name} is the name of the category (or NULL if the method is not | |
6284 | in a category); and @var{sel_name} is the name of the selector. | |
6285 | ||
6286 | On systems where the assembler can handle quoted names, you can use this | |
6287 | macro to provide more human-readable names. | |
6288 | @end table | |
6289 | ||
6290 | @node Initialization | |
6291 | @subsection How Initialization Functions Are Handled | |
6292 | @cindex initialization routines | |
6293 | @cindex termination routines | |
6294 | @cindex constructors, output of | |
6295 | @cindex destructors, output of | |
6296 | ||
6297 | The compiled code for certain languages includes @dfn{constructors} | |
6298 | (also called @dfn{initialization routines})---functions to initialize | |
6299 | data in the program when the program is started. These functions need | |
6300 | to be called before the program is ``started''---that is to say, before | |
6301 | @code{main} is called. | |
6302 | ||
6303 | Compiling some languages generates @dfn{destructors} (also called | |
6304 | @dfn{termination routines}) that should be called when the program | |
6305 | terminates. | |
6306 | ||
6307 | To make the initialization and termination functions work, the compiler | |
6308 | must output something in the assembler code to cause those functions to | |
6309 | be called at the appropriate time. When you port the compiler to a new | |
6310 | system, you need to specify how to do this. | |
6311 | ||
6312 | There are two major ways that GCC currently supports the execution of | |
6313 | initialization and termination functions. Each way has two variants. | |
6314 | Much of the structure is common to all four variations. | |
6315 | ||
6316 | @findex __CTOR_LIST__ | |
6317 | @findex __DTOR_LIST__ | |
6318 | The linker must build two lists of these functions---a list of | |
6319 | initialization functions, called @code{__CTOR_LIST__}, and a list of | |
6320 | termination functions, called @code{__DTOR_LIST__}. | |
6321 | ||
6322 | Each list always begins with an ignored function pointer (which may hold | |
6323 | 0, @minus{}1, or a count of the function pointers after it, depending on | |
6324 | the environment). This is followed by a series of zero or more function | |
6325 | pointers to constructors (or destructors), followed by a function | |
6326 | pointer containing zero. | |
6327 | ||
6328 | Depending on the operating system and its executable file format, either | |
6329 | @file{crtstuff.c} or @file{libgcc2.c} traverses these lists at startup | |
6330 | time and exit time. Constructors are called in reverse order of the | |
6331 | list; destructors in forward order. | |
6332 | ||
6333 | The best way to handle static constructors works only for object file | |
6334 | formats which provide arbitrarily-named sections. A section is set | |
6335 | aside for a list of constructors, and another for a list of destructors. | |
6336 | Traditionally these are called @samp{.ctors} and @samp{.dtors}. Each | |
6337 | object file that defines an initialization function also puts a word in | |
6338 | the constructor section to point to that function. The linker | |
6339 | accumulates all these words into one contiguous @samp{.ctors} section. | |
6340 | Termination functions are handled similarly. | |
6341 | ||
6342 | To use this method, you need appropriate definitions of the macros | |
6343 | @code{ASM_OUTPUT_CONSTRUCTOR} and @code{ASM_OUTPUT_DESTRUCTOR}. Usually | |
6344 | you can get them by including @file{svr4.h}. | |
6345 | ||
6346 | When arbitrary sections are available, there are two variants, depending | |
6347 | upon how the code in @file{crtstuff.c} is called. On systems that | |
6348 | support an @dfn{init} section which is executed at program startup, | |
6349 | parts of @file{crtstuff.c} are compiled into that section. The | |
6350 | program is linked by the @code{gcc} driver like this: | |
6351 | ||
6352 | @example | |
6353 | ld -o @var{output_file} crtbegin.o @dots{} crtend.o -lgcc | |
6354 | @end example | |
6355 | ||
6356 | The head of a function (@code{__do_global_ctors}) appears in the init | |
6357 | section of @file{crtbegin.o}; the remainder of the function appears in | |
6358 | the init section of @file{crtend.o}. The linker will pull these two | |
6359 | parts of the section together, making a whole function. If any of the | |
6360 | user's object files linked into the middle of it contribute code, then that | |
6361 | code will be executed as part of the body of @code{__do_global_ctors}. | |
6362 | ||
6363 | To use this variant, you must define the @code{INIT_SECTION_ASM_OP} | |
6364 | macro properly. | |
6365 | ||
6366 | If no init section is available, do not define | |
6367 | @code{INIT_SECTION_ASM_OP}. Then @code{__do_global_ctors} is built into | |
6368 | the text section like all other functions, and resides in | |
6369 | @file{libgcc.a}. When GCC compiles any function called @code{main}, it | |
6370 | inserts a procedure call to @code{__main} as the first executable code | |
6371 | after the function prologue. The @code{__main} function, also defined | |
6372 | in @file{libgcc2.c}, simply calls @file{__do_global_ctors}. | |
6373 | ||
6374 | In file formats that don't support arbitrary sections, there are again | |
6375 | two variants. In the simplest variant, the GNU linker (GNU @code{ld}) | |
6376 | and an `a.out' format must be used. In this case, | |
6377 | @code{ASM_OUTPUT_CONSTRUCTOR} is defined to produce a @code{.stabs} | |
6378 | entry of type @samp{N_SETT}, referencing the name @code{__CTOR_LIST__}, | |
6379 | and with the address of the void function containing the initialization | |
6380 | code as its value. The GNU linker recognizes this as a request to add | |
6381 | the value to a ``set''; the values are accumulated, and are eventually | |
6382 | placed in the executable as a vector in the format described above, with | |
6383 | a leading (ignored) count and a trailing zero element. | |
6384 | @code{ASM_OUTPUT_DESTRUCTOR} is handled similarly. Since no init | |
6385 | section is available, the absence of @code{INIT_SECTION_ASM_OP} causes | |
6386 | the compilation of @code{main} to call @code{__main} as above, starting | |
6387 | the initialization process. | |
6388 | ||
6389 | The last variant uses neither arbitrary sections nor the GNU linker. | |
6390 | This is preferable when you want to do dynamic linking and when using | |
6391 | file formats which the GNU linker does not support, such as `ECOFF'. In | |
6392 | this case, @code{ASM_OUTPUT_CONSTRUCTOR} does not produce an | |
6393 | @code{N_SETT} symbol; initialization and termination functions are | |
6394 | recognized simply by their names. This requires an extra program in the | |
6395 | linkage step, called @code{collect2}. This program pretends to be the | |
a3a15b4d | 6396 | linker, for use with GCC; it does its job by running the ordinary |
feca2ed3 JW |
6397 | linker, but also arranges to include the vectors of initialization and |
6398 | termination functions. These functions are called via @code{__main} as | |
6399 | described above. | |
6400 | ||
6401 | Choosing among these configuration options has been simplified by a set | |
6402 | of operating-system-dependent files in the @file{config} subdirectory. | |
6403 | These files define all of the relevant parameters. Usually it is | |
6404 | sufficient to include one into your specific machine-dependent | |
6405 | configuration file. These files are: | |
6406 | ||
6407 | @table @file | |
6408 | @item aoutos.h | |
6409 | For operating systems using the `a.out' format. | |
6410 | ||
6411 | @item next.h | |
6412 | For operating systems using the `MachO' format. | |
6413 | ||
6414 | @item svr3.h | |
6415 | For System V Release 3 and similar systems using `COFF' format. | |
6416 | ||
6417 | @item svr4.h | |
6418 | For System V Release 4 and similar systems using `ELF' format. | |
6419 | ||
6420 | @item vms.h | |
6421 | For the VMS operating system. | |
6422 | @end table | |
6423 | ||
6424 | @ifinfo | |
6425 | The following section describes the specific macros that control and | |
6426 | customize the handling of initialization and termination functions. | |
6427 | @end ifinfo | |
6428 | ||
6429 | @node Macros for Initialization | |
6430 | @subsection Macros Controlling Initialization Routines | |
6431 | ||
6432 | Here are the macros that control how the compiler handles initialization | |
6433 | and termination functions: | |
6434 | ||
6435 | @table @code | |
6436 | @findex INIT_SECTION_ASM_OP | |
6437 | @item INIT_SECTION_ASM_OP | |
047c1c92 HPN |
6438 | If defined, a C string constant, including spacing, for the assembler |
6439 | operation to identify the following data as initialization code. If not | |
6440 | defined, GCC will assume such a section does not exist. When you are | |
6441 | using special sections for initialization and termination functions, this | |
6442 | macro also controls how @file{crtstuff.c} and @file{libgcc2.c} arrange to | |
6443 | run the initialization functions. | |
feca2ed3 JW |
6444 | |
6445 | @item HAS_INIT_SECTION | |
6446 | @findex HAS_INIT_SECTION | |
6447 | If defined, @code{main} will not call @code{__main} as described above. | |
6448 | This macro should be defined for systems that control the contents of the | |
6449 | init section on a symbol-by-symbol basis, such as OSF/1, and should not | |
6450 | be defined explicitly for systems that support | |
6451 | @code{INIT_SECTION_ASM_OP}. | |
6452 | ||
6453 | @item LD_INIT_SWITCH | |
6454 | @findex LD_INIT_SWITCH | |
6455 | If defined, a C string constant for a switch that tells the linker that | |
6456 | the following symbol is an initialization routine. | |
6457 | ||
6458 | @item LD_FINI_SWITCH | |
6459 | @findex LD_FINI_SWITCH | |
6460 | If defined, a C string constant for a switch that tells the linker that | |
6461 | the following symbol is a finalization routine. | |
6462 | ||
6463 | @item INVOKE__main | |
6464 | @findex INVOKE__main | |
6465 | If defined, @code{main} will call @code{__main} despite the presence of | |
6466 | @code{INIT_SECTION_ASM_OP}. This macro should be defined for systems | |
6467 | where the init section is not actually run automatically, but is still | |
6468 | useful for collecting the lists of constructors and destructors. | |
6469 | ||
ea4f1fce JO |
6470 | @item SUPPORTS_INIT_PRIORITY |
6471 | @findex SUPPORTS_INIT_PRIORITY | |
6472 | If nonzero, the C++ @code{init_priority} attribute is supported and the | |
6473 | compiler should emit instructions to control the order of initialization | |
6474 | of objects. If zero, the compiler will issue an error message upon | |
6475 | encountering an @code{init_priority} attribute. | |
6476 | ||
feca2ed3 JW |
6477 | @item ASM_OUTPUT_CONSTRUCTOR (@var{stream}, @var{name}) |
6478 | @findex ASM_OUTPUT_CONSTRUCTOR | |
6479 | Define this macro as a C statement to output on the stream @var{stream} | |
6480 | the assembler code to arrange to call the function named @var{name} at | |
6481 | initialization time. | |
6482 | ||
6483 | Assume that @var{name} is the name of a C function generated | |
6484 | automatically by the compiler. This function takes no arguments. Use | |
6485 | the function @code{assemble_name} to output the name @var{name}; this | |
6486 | performs any system-specific syntactic transformations such as adding an | |
6487 | underscore. | |
6488 | ||
6489 | If you don't define this macro, nothing special is output to arrange to | |
6490 | call the function. This is correct when the function will be called in | |
6491 | some other manner---for example, by means of the @code{collect2} program, | |
6492 | which looks through the symbol table to find these functions by their | |
6493 | names. | |
6494 | ||
6495 | @item ASM_OUTPUT_DESTRUCTOR (@var{stream}, @var{name}) | |
6496 | @findex ASM_OUTPUT_DESTRUCTOR | |
6497 | This is like @code{ASM_OUTPUT_CONSTRUCTOR} but used for termination | |
6498 | functions rather than initialization functions. | |
14686fcd JL |
6499 | |
6500 | When @code{ASM_OUTPUT_CONSTRUCTOR} and @code{ASM_OUTPUT_DESTRUCTOR} are | |
3b7a2e58 | 6501 | defined, the initialization routine generated for the generated object |
14686fcd | 6502 | file will have static linkage. |
feca2ed3 JW |
6503 | @end table |
6504 | ||
6505 | If your system uses @code{collect2} as the means of processing | |
6506 | constructors, then that program normally uses @code{nm} to scan an | |
14686fcd JL |
6507 | object file for constructor functions to be called. On such systems you |
6508 | must not define @code{ASM_OUTPUT_CONSTRUCTOR} and @code{ASM_OUTPUT_DESTRUCTOR} | |
6509 | as the object file's initialization routine must have global scope. | |
6510 | ||
6511 | On certain kinds of systems, you can define these macros to make | |
6512 | @code{collect2} work faster (and, in some cases, make it work at all): | |
feca2ed3 JW |
6513 | |
6514 | @table @code | |
6515 | @findex OBJECT_FORMAT_COFF | |
6516 | @item OBJECT_FORMAT_COFF | |
6517 | Define this macro if the system uses COFF (Common Object File Format) | |
6518 | object files, so that @code{collect2} can assume this format and scan | |
6519 | object files directly for dynamic constructor/destructor functions. | |
6520 | ||
6521 | @findex OBJECT_FORMAT_ROSE | |
6522 | @item OBJECT_FORMAT_ROSE | |
6523 | Define this macro if the system uses ROSE format object files, so that | |
6524 | @code{collect2} can assume this format and scan object files directly | |
6525 | for dynamic constructor/destructor functions. | |
6526 | ||
6527 | These macros are effective only in a native compiler; @code{collect2} as | |
6528 | part of a cross compiler always uses @code{nm} for the target machine. | |
6529 | ||
6530 | @findex REAL_NM_FILE_NAME | |
6531 | @item REAL_NM_FILE_NAME | |
6532 | Define this macro as a C string constant containing the file name to use | |
6533 | to execute @code{nm}. The default is to search the path normally for | |
6534 | @code{nm}. | |
6535 | ||
6536 | If your system supports shared libraries and has a program to list the | |
6537 | dynamic dependencies of a given library or executable, you can define | |
6538 | these macros to enable support for running initialization and | |
6539 | termination functions in shared libraries: | |
6540 | ||
6541 | @findex LDD_SUFFIX | |
6542 | @item LDD_SUFFIX | |
6543 | Define this macro to a C string constant containing the name of the | |
6544 | program which lists dynamic dependencies, like @code{"ldd"} under SunOS 4. | |
6545 | ||
6546 | @findex PARSE_LDD_OUTPUT | |
6547 | @item PARSE_LDD_OUTPUT (@var{PTR}) | |
6548 | Define this macro to be C code that extracts filenames from the output | |
6549 | of the program denoted by @code{LDD_SUFFIX}. @var{PTR} is a variable | |
6550 | of type @code{char *} that points to the beginning of a line of output | |
6551 | from @code{LDD_SUFFIX}. If the line lists a dynamic dependency, the | |
6552 | code must advance @var{PTR} to the beginning of the filename on that | |
6553 | line. Otherwise, it must set @var{PTR} to @code{NULL}. | |
6554 | ||
6555 | @end table | |
6556 | ||
6557 | @node Instruction Output | |
6558 | @subsection Output of Assembler Instructions | |
6559 | ||
6560 | @c prevent bad page break with this line | |
6561 | This describes assembler instruction output. | |
6562 | ||
6563 | @table @code | |
6564 | @findex REGISTER_NAMES | |
6565 | @item REGISTER_NAMES | |
6566 | A C initializer containing the assembler's names for the machine | |
6567 | registers, each one as a C string constant. This is what translates | |
6568 | register numbers in the compiler into assembler language. | |
6569 | ||
6570 | @findex ADDITIONAL_REGISTER_NAMES | |
6571 | @item ADDITIONAL_REGISTER_NAMES | |
6572 | If defined, a C initializer for an array of structures containing a name | |
6573 | and a register number. This macro defines additional names for hard | |
6574 | registers, thus allowing the @code{asm} option in declarations to refer | |
6575 | to registers using alternate names. | |
6576 | ||
6577 | @findex ASM_OUTPUT_OPCODE | |
6578 | @item ASM_OUTPUT_OPCODE (@var{stream}, @var{ptr}) | |
6579 | Define this macro if you are using an unusual assembler that | |
6580 | requires different names for the machine instructions. | |
6581 | ||
6582 | The definition is a C statement or statements which output an | |
6583 | assembler instruction opcode to the stdio stream @var{stream}. The | |
6584 | macro-operand @var{ptr} is a variable of type @code{char *} which | |
6585 | points to the opcode name in its ``internal'' form---the form that is | |
6586 | written in the machine description. The definition should output the | |
6587 | opcode name to @var{stream}, performing any translation you desire, and | |
6588 | increment the variable @var{ptr} to point at the end of the opcode | |
6589 | so that it will not be output twice. | |
6590 | ||
6591 | In fact, your macro definition may process less than the entire opcode | |
6592 | name, or more than the opcode name; but if you want to process text | |
6593 | that includes @samp{%}-sequences to substitute operands, you must take | |
6594 | care of the substitution yourself. Just be sure to increment | |
6595 | @var{ptr} over whatever text should not be output normally. | |
6596 | ||
6597 | @findex recog_operand | |
6598 | If you need to look at the operand values, they can be found as the | |
6599 | elements of @code{recog_operand}. | |
6600 | ||
6601 | If the macro definition does nothing, the instruction is output | |
6602 | in the usual way. | |
6603 | ||
6604 | @findex FINAL_PRESCAN_INSN | |
6605 | @item FINAL_PRESCAN_INSN (@var{insn}, @var{opvec}, @var{noperands}) | |
6606 | If defined, a C statement to be executed just prior to the output of | |
6607 | assembler code for @var{insn}, to modify the extracted operands so | |
6608 | they will be output differently. | |
6609 | ||
6610 | Here the argument @var{opvec} is the vector containing the operands | |
6611 | extracted from @var{insn}, and @var{noperands} is the number of | |
6612 | elements of the vector which contain meaningful data for this insn. | |
6613 | The contents of this vector are what will be used to convert the insn | |
6614 | template into assembler code, so you can change the assembler output | |
6615 | by changing the contents of the vector. | |
6616 | ||
6617 | This macro is useful when various assembler syntaxes share a single | |
6618 | file of instruction patterns; by defining this macro differently, you | |
6619 | can cause a large class of instructions to be output differently (such | |
6620 | as with rearranged operands). Naturally, variations in assembler | |
6621 | syntax affecting individual insn patterns ought to be handled by | |
6622 | writing conditional output routines in those patterns. | |
6623 | ||
6624 | If this macro is not defined, it is equivalent to a null statement. | |
6625 | ||
6626 | @findex FINAL_PRESCAN_LABEL | |
6627 | @item FINAL_PRESCAN_LABEL | |
6628 | If defined, @code{FINAL_PRESCAN_INSN} will be called on each | |
6629 | @code{CODE_LABEL}. In that case, @var{opvec} will be a null pointer and | |
6630 | @var{noperands} will be zero. | |
6631 | ||
6632 | @findex PRINT_OPERAND | |
6633 | @item PRINT_OPERAND (@var{stream}, @var{x}, @var{code}) | |
6634 | A C compound statement to output to stdio stream @var{stream} the | |
6635 | assembler syntax for an instruction operand @var{x}. @var{x} is an | |
6636 | RTL expression. | |
6637 | ||
6638 | @var{code} is a value that can be used to specify one of several ways | |
6639 | of printing the operand. It is used when identical operands must be | |
6640 | printed differently depending on the context. @var{code} comes from | |
6641 | the @samp{%} specification that was used to request printing of the | |
6642 | operand. If the specification was just @samp{%@var{digit}} then | |
6643 | @var{code} is 0; if the specification was @samp{%@var{ltr} | |
6644 | @var{digit}} then @var{code} is the ASCII code for @var{ltr}. | |
6645 | ||
6646 | @findex reg_names | |
6647 | If @var{x} is a register, this macro should print the register's name. | |
6648 | The names can be found in an array @code{reg_names} whose type is | |
6649 | @code{char *[]}. @code{reg_names} is initialized from | |
6650 | @code{REGISTER_NAMES}. | |
6651 | ||
6652 | When the machine description has a specification @samp{%@var{punct}} | |
6653 | (a @samp{%} followed by a punctuation character), this macro is called | |
6654 | with a null pointer for @var{x} and the punctuation character for | |
6655 | @var{code}. | |
6656 | ||
6657 | @findex PRINT_OPERAND_PUNCT_VALID_P | |
6658 | @item PRINT_OPERAND_PUNCT_VALID_P (@var{code}) | |
6659 | A C expression which evaluates to true if @var{code} is a valid | |
6660 | punctuation character for use in the @code{PRINT_OPERAND} macro. If | |
6661 | @code{PRINT_OPERAND_PUNCT_VALID_P} is not defined, it means that no | |
6662 | punctuation characters (except for the standard one, @samp{%}) are used | |
6663 | in this way. | |
6664 | ||
6665 | @findex PRINT_OPERAND_ADDRESS | |
6666 | @item PRINT_OPERAND_ADDRESS (@var{stream}, @var{x}) | |
6667 | A C compound statement to output to stdio stream @var{stream} the | |
6668 | assembler syntax for an instruction operand that is a memory reference | |
6669 | whose address is @var{x}. @var{x} is an RTL expression. | |
6670 | ||
6671 | @cindex @code{ENCODE_SECTION_INFO} usage | |
6672 | On some machines, the syntax for a symbolic address depends on the | |
6673 | section that the address refers to. On these machines, define the macro | |
6674 | @code{ENCODE_SECTION_INFO} to store the information into the | |
6675 | @code{symbol_ref}, and then check for it here. @xref{Assembler Format}. | |
6676 | ||
6677 | @findex DBR_OUTPUT_SEQEND | |
6678 | @findex dbr_sequence_length | |
6679 | @item DBR_OUTPUT_SEQEND(@var{file}) | |
6680 | A C statement, to be executed after all slot-filler instructions have | |
6681 | been output. If necessary, call @code{dbr_sequence_length} to | |
6682 | determine the number of slots filled in a sequence (zero if not | |
6683 | currently outputting a sequence), to decide how many no-ops to output, | |
6684 | or whatever. | |
6685 | ||
6686 | Don't define this macro if it has nothing to do, but it is helpful in | |
6687 | reading assembly output if the extent of the delay sequence is made | |
6688 | explicit (e.g. with white space). | |
6689 | ||
6690 | @findex final_sequence | |
6691 | Note that output routines for instructions with delay slots must be | |
6692 | prepared to deal with not being output as part of a sequence (i.e. | |
6693 | when the scheduling pass is not run, or when no slot fillers could be | |
6694 | found.) The variable @code{final_sequence} is null when not | |
6695 | processing a sequence, otherwise it contains the @code{sequence} rtx | |
6696 | being output. | |
6697 | ||
6698 | @findex REGISTER_PREFIX | |
6699 | @findex LOCAL_LABEL_PREFIX | |
6700 | @findex USER_LABEL_PREFIX | |
6701 | @findex IMMEDIATE_PREFIX | |
6702 | @findex asm_fprintf | |
6703 | @item REGISTER_PREFIX | |
6704 | @itemx LOCAL_LABEL_PREFIX | |
6705 | @itemx USER_LABEL_PREFIX | |
6706 | @itemx IMMEDIATE_PREFIX | |
6707 | If defined, C string expressions to be used for the @samp{%R}, @samp{%L}, | |
6708 | @samp{%U}, and @samp{%I} options of @code{asm_fprintf} (see | |
6709 | @file{final.c}). These are useful when a single @file{md} file must | |
6710 | support multiple assembler formats. In that case, the various @file{tm.h} | |
6711 | files can define these macros differently. | |
6712 | ||
fe0503ea NC |
6713 | @item ASM_FPRINTF_EXTENSIONS(@var{file}, @var{argptr}, @var{format}) |
6714 | @findex ASM_FPRINTF_EXTENSIONS | |
3b7a2e58 | 6715 | If defined this macro should expand to a series of @code{case} |
fe0503ea NC |
6716 | statements which will be parsed inside the @code{switch} statement of |
6717 | the @code{asm_fprintf} function. This allows targets to define extra | |
6718 | printf formats which may useful when generating their assembler | |
3b7a2e58 | 6719 | statements. Note that upper case letters are reserved for future |
fe0503ea NC |
6720 | generic extensions to asm_fprintf, and so are not available to target |
6721 | specific code. The output file is given by the parameter @var{file}. | |
6722 | The varargs input pointer is @var{argptr} and the rest of the format | |
6723 | string, starting the character after the one that is being switched | |
6724 | upon, is pointed to by @var{format}. | |
6725 | ||
feca2ed3 JW |
6726 | @findex ASSEMBLER_DIALECT |
6727 | @item ASSEMBLER_DIALECT | |
6728 | If your target supports multiple dialects of assembler language (such as | |
6729 | different opcodes), define this macro as a C expression that gives the | |
6730 | numeric index of the assembler language dialect to use, with zero as the | |
6731 | first variant. | |
6732 | ||
6733 | If this macro is defined, you may use constructs of the form | |
6734 | @samp{@{option0|option1|option2@dots{}@}} in the output | |
6735 | templates of patterns (@pxref{Output Template}) or in the first argument | |
6736 | of @code{asm_fprintf}. This construct outputs @samp{option0}, | |
6737 | @samp{option1} or @samp{option2}, etc., if the value of | |
6738 | @code{ASSEMBLER_DIALECT} is zero, one or two, etc. Any special | |
6739 | characters within these strings retain their usual meaning. | |
6740 | ||
6741 | If you do not define this macro, the characters @samp{@{}, @samp{|} and | |
6742 | @samp{@}} do not have any special meaning when used in templates or | |
6743 | operands to @code{asm_fprintf}. | |
6744 | ||
6745 | Define the macros @code{REGISTER_PREFIX}, @code{LOCAL_LABEL_PREFIX}, | |
6746 | @code{USER_LABEL_PREFIX} and @code{IMMEDIATE_PREFIX} if you can express | |
e5e809f4 | 6747 | the variations in assembler language syntax with that mechanism. Define |
feca2ed3 JW |
6748 | @code{ASSEMBLER_DIALECT} and use the @samp{@{option0|option1@}} syntax |
6749 | if the syntax variant are larger and involve such things as different | |
6750 | opcodes or operand order. | |
6751 | ||
6752 | @findex ASM_OUTPUT_REG_PUSH | |
6753 | @item ASM_OUTPUT_REG_PUSH (@var{stream}, @var{regno}) | |
6754 | A C expression to output to @var{stream} some assembler code | |
6755 | which will push hard register number @var{regno} onto the stack. | |
6756 | The code need not be optimal, since this macro is used only when | |
6757 | profiling. | |
6758 | ||
6759 | @findex ASM_OUTPUT_REG_POP | |
6760 | @item ASM_OUTPUT_REG_POP (@var{stream}, @var{regno}) | |
6761 | A C expression to output to @var{stream} some assembler code | |
6762 | which will pop hard register number @var{regno} off of the stack. | |
6763 | The code need not be optimal, since this macro is used only when | |
6764 | profiling. | |
6765 | @end table | |
6766 | ||
6767 | @node Dispatch Tables | |
6768 | @subsection Output of Dispatch Tables | |
6769 | ||
6770 | @c prevent bad page break with this line | |
6771 | This concerns dispatch tables. | |
6772 | ||
6773 | @table @code | |
6774 | @cindex dispatch table | |
6775 | @findex ASM_OUTPUT_ADDR_DIFF_ELT | |
33f7f353 | 6776 | @item ASM_OUTPUT_ADDR_DIFF_ELT (@var{stream}, @var{body}, @var{value}, @var{rel}) |
feca2ed3 JW |
6777 | A C statement to output to the stdio stream @var{stream} an assembler |
6778 | pseudo-instruction to generate a difference between two labels. | |
6779 | @var{value} and @var{rel} are the numbers of two internal labels. The | |
6780 | definitions of these labels are output using | |
6781 | @code{ASM_OUTPUT_INTERNAL_LABEL}, and they must be printed in the same | |
6782 | way here. For example, | |
6783 | ||
6784 | @example | |
6785 | fprintf (@var{stream}, "\t.word L%d-L%d\n", | |
6786 | @var{value}, @var{rel}) | |
6787 | @end example | |
6788 | ||
6789 | You must provide this macro on machines where the addresses in a | |
6790 | dispatch table are relative to the table's own address. If defined, GNU | |
6791 | CC will also use this macro on all machines when producing PIC. | |
33f7f353 JR |
6792 | @var{body} is the body of the ADDR_DIFF_VEC; it is provided so that the |
6793 | mode and flags can be read. | |
feca2ed3 JW |
6794 | |
6795 | @findex ASM_OUTPUT_ADDR_VEC_ELT | |
6796 | @item ASM_OUTPUT_ADDR_VEC_ELT (@var{stream}, @var{value}) | |
6797 | This macro should be provided on machines where the addresses | |
6798 | in a dispatch table are absolute. | |
6799 | ||
6800 | The definition should be a C statement to output to the stdio stream | |
6801 | @var{stream} an assembler pseudo-instruction to generate a reference to | |
6802 | a label. @var{value} is the number of an internal label whose | |
6803 | definition is output using @code{ASM_OUTPUT_INTERNAL_LABEL}. | |
6804 | For example, | |
6805 | ||
6806 | @example | |
6807 | fprintf (@var{stream}, "\t.word L%d\n", @var{value}) | |
6808 | @end example | |
6809 | ||
6810 | @findex ASM_OUTPUT_CASE_LABEL | |
6811 | @item ASM_OUTPUT_CASE_LABEL (@var{stream}, @var{prefix}, @var{num}, @var{table}) | |
6812 | Define this if the label before a jump-table needs to be output | |
6813 | specially. The first three arguments are the same as for | |
6814 | @code{ASM_OUTPUT_INTERNAL_LABEL}; the fourth argument is the | |
6815 | jump-table which follows (a @code{jump_insn} containing an | |
6816 | @code{addr_vec} or @code{addr_diff_vec}). | |
6817 | ||
6818 | This feature is used on system V to output a @code{swbeg} statement | |
6819 | for the table. | |
6820 | ||
6821 | If this macro is not defined, these labels are output with | |
6822 | @code{ASM_OUTPUT_INTERNAL_LABEL}. | |
6823 | ||
6824 | @findex ASM_OUTPUT_CASE_END | |
6825 | @item ASM_OUTPUT_CASE_END (@var{stream}, @var{num}, @var{table}) | |
6826 | Define this if something special must be output at the end of a | |
6827 | jump-table. The definition should be a C statement to be executed | |
6828 | after the assembler code for the table is written. It should write | |
6829 | the appropriate code to stdio stream @var{stream}. The argument | |
6830 | @var{table} is the jump-table insn, and @var{num} is the label-number | |
6831 | of the preceding label. | |
6832 | ||
6833 | If this macro is not defined, nothing special is output at the end of | |
6834 | the jump-table. | |
6835 | @end table | |
6836 | ||
6837 | @node Exception Region Output | |
6838 | @subsection Assembler Commands for Exception Regions | |
6839 | ||
6840 | @c prevent bad page break with this line | |
6841 | ||
6842 | This describes commands marking the start and the end of an exception | |
6843 | region. | |
6844 | ||
6845 | @table @code | |
6846 | @findex ASM_OUTPUT_EH_REGION_BEG | |
6847 | @item ASM_OUTPUT_EH_REGION_BEG () | |
6848 | A C expression to output text to mark the start of an exception region. | |
6849 | ||
6850 | This macro need not be defined on most platforms. | |
6851 | ||
6852 | @findex ASM_OUTPUT_EH_REGION_END | |
6853 | @item ASM_OUTPUT_EH_REGION_END () | |
6854 | A C expression to output text to mark the end of an exception region. | |
6855 | ||
6856 | This macro need not be defined on most platforms. | |
6857 | ||
0021b564 JM |
6858 | @findex EXCEPTION_SECTION |
6859 | @item EXCEPTION_SECTION () | |
6860 | A C expression to switch to the section in which the main | |
6861 | exception table is to be placed (@pxref{Sections}). The default is a | |
6862 | section named @code{.gcc_except_table} on machines that support named | |
6863 | sections via @code{ASM_OUTPUT_SECTION_NAME}, otherwise if @samp{-fpic} | |
6864 | or @samp{-fPIC} is in effect, the @code{data_section}, otherwise the | |
6865 | @code{readonly_data_section}. | |
6866 | ||
6867 | @findex EH_FRAME_SECTION_ASM_OP | |
6868 | @item EH_FRAME_SECTION_ASM_OP | |
047c1c92 HPN |
6869 | If defined, a C string constant, including spacing, for the assembler |
6870 | operation to switch to the section for exception handling frame unwind | |
6871 | information. If not defined, GCC will provide a default definition if the | |
6872 | target supports named sections. @file{crtstuff.c} uses this macro to | |
6873 | switch to the appropriate section. | |
0021b564 JM |
6874 | |
6875 | You should define this symbol if your target supports DWARF 2 frame | |
6876 | unwind information and the default definition does not work. | |
6877 | ||
feca2ed3 JW |
6878 | @findex OMIT_EH_TABLE |
6879 | @item OMIT_EH_TABLE () | |
6880 | A C expression that is nonzero if the normal exception table output | |
6881 | should be omitted. | |
6882 | ||
6883 | This macro need not be defined on most platforms. | |
6884 | ||
6885 | @findex EH_TABLE_LOOKUP | |
6886 | @item EH_TABLE_LOOKUP () | |
6887 | Alternate runtime support for looking up an exception at runtime and | |
6888 | finding the associated handler, if the default method won't work. | |
6889 | ||
6890 | This macro need not be defined on most platforms. | |
6891 | ||
6892 | @findex DOESNT_NEED_UNWINDER | |
6893 | @item DOESNT_NEED_UNWINDER | |
6894 | A C expression that decides whether or not the current function needs to | |
6895 | have a function unwinder generated for it. See the file @code{except.c} | |
6896 | for details on when to define this, and how. | |
6897 | ||
6898 | @findex MASK_RETURN_ADDR | |
6899 | @item MASK_RETURN_ADDR | |
6900 | An rtx used to mask the return address found via RETURN_ADDR_RTX, so | |
6901 | that it does not contain any extraneous set bits in it. | |
0021b564 JM |
6902 | |
6903 | @findex DWARF2_UNWIND_INFO | |
6904 | @item DWARF2_UNWIND_INFO | |
6905 | Define this macro to 0 if your target supports DWARF 2 frame unwind | |
6906 | information, but it does not yet work with exception handling. | |
6907 | Otherwise, if your target supports this information (if it defines | |
6908 | @samp{INCOMING_RETURN_ADDR_RTX} and either @samp{UNALIGNED_INT_ASM_OP} | |
6909 | or @samp{OBJECT_FORMAT_ELF}), GCC will provide a default definition of | |
6910 | 1. | |
6911 | ||
6912 | If this macro is defined to 1, the DWARF 2 unwinder will be the default | |
6913 | exception handling mechanism; otherwise, setjmp/longjmp will be used by | |
6914 | default. | |
6915 | ||
6916 | If this macro is defined to anything, the DWARF 2 unwinder will be used | |
6917 | instead of inline unwinders and __unwind_function in the non-setjmp case. | |
6918 | ||
27c35f4b HPN |
6919 | @findex DWARF_CIE_DATA_ALIGNMENT |
6920 | @item DWARF_CIE_DATA_ALIGNMENT | |
6921 | This macro need only be defined if the target might save registers in the | |
6922 | function prologue at an offset to the stack pointer that is not aligned to | |
6923 | @code{UNITS_PER_WORD}. The definition should be the negative minimum | |
6924 | alignment if @code{STACK_GROWS_DOWNWARD} is defined, and the positive | |
6925 | minimum alignment otherwise. @xref{SDB and DWARF}. Only applicable if | |
6926 | the target supports DWARF 2 frame unwind information. | |
6927 | ||
feca2ed3 JW |
6928 | @end table |
6929 | ||
6930 | @node Alignment Output | |
6931 | @subsection Assembler Commands for Alignment | |
6932 | ||
6933 | @c prevent bad page break with this line | |
6934 | This describes commands for alignment. | |
6935 | ||
6936 | @table @code | |
fc470718 R |
6937 | @findex LABEL_ALIGN_AFTER_BARRIER |
6938 | @item LABEL_ALIGN_AFTER_BARRIER (@var{label}) | |
6939 | The alignment (log base 2) to put in front of @var{label}, which follows | |
6940 | a BARRIER. | |
feca2ed3 JW |
6941 | |
6942 | This macro need not be defined if you don't want any special alignment | |
6943 | to be done at such a time. Most machine descriptions do not currently | |
6944 | define the macro. | |
6945 | ||
efa3896a GK |
6946 | Unless it's necessary to inspect the @var{label} parameter, it is better |
6947 | to set the variable @var{align_jumps} in the target's | |
6948 | @code{OVERRIDE_OPTIONS}. Otherwise, you should try to honour the user's | |
6949 | selection in @var{align_jumps} in a @code{LABEL_ALIGN_AFTER_BARRIER} | |
6950 | implementation. | |
6951 | ||
6952 | @findex LABEL_ALIGN_AFTER_BARRIER_MAX_SKIP | |
6953 | @item LABEL_ALIGN_AFTER_BARRIER_MAX_SKIP | |
6954 | The maximum number of bytes to skip when applying | |
6955 | @code{LABEL_ALIGN_AFTER_BARRIER}. This works only if | |
6956 | @code{ASM_OUTPUT_MAX_SKIP_ALIGN} is defined. | |
6957 | ||
fc470718 R |
6958 | @findex LOOP_ALIGN |
6959 | @item LOOP_ALIGN (@var{label}) | |
6960 | The alignment (log base 2) to put in front of @var{label}, which follows | |
6961 | a NOTE_INSN_LOOP_BEG note. | |
feca2ed3 JW |
6962 | |
6963 | This macro need not be defined if you don't want any special alignment | |
6964 | to be done at such a time. Most machine descriptions do not currently | |
6965 | define the macro. | |
6966 | ||
efa3896a GK |
6967 | Unless it's necessary to inspect the @var{label} parameter, it is better |
6968 | to set the variable @var{align_loops} in the target's | |
6969 | @code{OVERRIDE_OPTIONS}. Otherwise, you should try to honour the user's | |
6970 | selection in @var{align_loops} in a @code{LOOP_ALIGN} implementation. | |
6971 | ||
6972 | @findex LOOP_ALIGN_MAX_SKIP | |
6973 | @item LOOP_ALIGN_MAX_SKIP | |
6974 | The maximum number of bytes to skip when applying @code{LOOP_ALIGN}. | |
6975 | This works only if @code{ASM_OUTPUT_MAX_SKIP_ALIGN} is defined. | |
6976 | ||
fc470718 R |
6977 | @findex LABEL_ALIGN |
6978 | @item LABEL_ALIGN (@var{label}) | |
6979 | The alignment (log base 2) to put in front of @var{label}. | |
6980 | If LABEL_ALIGN_AFTER_BARRIER / LOOP_ALIGN specify a different alignment, | |
6981 | the maximum of the specified values is used. | |
6982 | ||
efa3896a GK |
6983 | Unless it's necessary to inspect the @var{label} parameter, it is better |
6984 | to set the variable @var{align_labels} in the target's | |
6985 | @code{OVERRIDE_OPTIONS}. Otherwise, you should try to honour the user's | |
6986 | selection in @var{align_labels} in a @code{LABEL_ALIGN} implementation. | |
6987 | ||
6988 | @findex LABEL_ALIGN_MAX_SKIP | |
6989 | @item LABEL_ALIGN_MAX_SKIP | |
6990 | The maximum number of bytes to skip when applying @code{LABEL_ALIGN}. | |
6991 | This works only if @code{ASM_OUTPUT_MAX_SKIP_ALIGN} is defined. | |
6992 | ||
feca2ed3 JW |
6993 | @findex ASM_OUTPUT_SKIP |
6994 | @item ASM_OUTPUT_SKIP (@var{stream}, @var{nbytes}) | |
6995 | A C statement to output to the stdio stream @var{stream} an assembler | |
6996 | instruction to advance the location counter by @var{nbytes} bytes. | |
6997 | Those bytes should be zero when loaded. @var{nbytes} will be a C | |
6998 | expression of type @code{int}. | |
6999 | ||
7000 | @findex ASM_NO_SKIP_IN_TEXT | |
7001 | @item ASM_NO_SKIP_IN_TEXT | |
7002 | Define this macro if @code{ASM_OUTPUT_SKIP} should not be used in the | |
556e0f21 | 7003 | text section because it fails to put zeros in the bytes that are skipped. |
feca2ed3 JW |
7004 | This is true on many Unix systems, where the pseudo--op to skip bytes |
7005 | produces no-op instructions rather than zeros when used in the text | |
7006 | section. | |
7007 | ||
7008 | @findex ASM_OUTPUT_ALIGN | |
7009 | @item ASM_OUTPUT_ALIGN (@var{stream}, @var{power}) | |
7010 | A C statement to output to the stdio stream @var{stream} an assembler | |
7011 | command to advance the location counter to a multiple of 2 to the | |
7012 | @var{power} bytes. @var{power} will be a C expression of type @code{int}. | |
26f63a77 JL |
7013 | |
7014 | @findex ASM_OUTPUT_MAX_SKIP_ALIGN | |
7015 | @item ASM_OUTPUT_MAX_SKIP_ALIGN (@var{stream}, @var{power}, @var{max_skip}) | |
7016 | A C statement to output to the stdio stream @var{stream} an assembler | |
7017 | command to advance the location counter to a multiple of 2 to the | |
7018 | @var{power} bytes, but only if @var{max_skip} or fewer bytes are needed to | |
7019 | satisfy the alignment request. @var{power} and @var{max_skip} will be | |
7020 | a C expression of type @code{int}. | |
feca2ed3 JW |
7021 | @end table |
7022 | ||
7023 | @need 3000 | |
7024 | @node Debugging Info | |
7025 | @section Controlling Debugging Information Format | |
7026 | ||
7027 | @c prevent bad page break with this line | |
7028 | This describes how to specify debugging information. | |
7029 | ||
7030 | @menu | |
7031 | * All Debuggers:: Macros that affect all debugging formats uniformly. | |
7032 | * DBX Options:: Macros enabling specific options in DBX format. | |
7033 | * DBX Hooks:: Hook macros for varying DBX format. | |
7034 | * File Names and DBX:: Macros controlling output of file names in DBX format. | |
7035 | * SDB and DWARF:: Macros for SDB (COFF) and DWARF formats. | |
7036 | @end menu | |
7037 | ||
7038 | @node All Debuggers | |
7039 | @subsection Macros Affecting All Debugging Formats | |
7040 | ||
7041 | @c prevent bad page break with this line | |
7042 | These macros affect all debugging formats. | |
7043 | ||
7044 | @table @code | |
7045 | @findex DBX_REGISTER_NUMBER | |
7046 | @item DBX_REGISTER_NUMBER (@var{regno}) | |
7047 | A C expression that returns the DBX register number for the compiler | |
7048 | register number @var{regno}. In simple cases, the value of this | |
7049 | expression may be @var{regno} itself. But sometimes there are some | |
7050 | registers that the compiler knows about and DBX does not, or vice | |
7051 | versa. In such cases, some register may need to have one number in | |
7052 | the compiler and another for DBX. | |
7053 | ||
a3a15b4d | 7054 | If two registers have consecutive numbers inside GCC, and they can be |
feca2ed3 JW |
7055 | used as a pair to hold a multiword value, then they @emph{must} have |
7056 | consecutive numbers after renumbering with @code{DBX_REGISTER_NUMBER}. | |
7057 | Otherwise, debuggers will be unable to access such a pair, because they | |
7058 | expect register pairs to be consecutive in their own numbering scheme. | |
7059 | ||
7060 | If you find yourself defining @code{DBX_REGISTER_NUMBER} in way that | |
7061 | does not preserve register pairs, then what you must do instead is | |
7062 | redefine the actual register numbering scheme. | |
7063 | ||
7064 | @findex DEBUGGER_AUTO_OFFSET | |
7065 | @item DEBUGGER_AUTO_OFFSET (@var{x}) | |
7066 | A C expression that returns the integer offset value for an automatic | |
7067 | variable having address @var{x} (an RTL expression). The default | |
7068 | computation assumes that @var{x} is based on the frame-pointer and | |
7069 | gives the offset from the frame-pointer. This is required for targets | |
7070 | that produce debugging output for DBX or COFF-style debugging output | |
7071 | for SDB and allow the frame-pointer to be eliminated when the | |
7072 | @samp{-g} options is used. | |
7073 | ||
7074 | @findex DEBUGGER_ARG_OFFSET | |
7075 | @item DEBUGGER_ARG_OFFSET (@var{offset}, @var{x}) | |
7076 | A C expression that returns the integer offset value for an argument | |
7077 | having address @var{x} (an RTL expression). The nominal offset is | |
7078 | @var{offset}. | |
7079 | ||
7080 | @findex PREFERRED_DEBUGGING_TYPE | |
7081 | @item PREFERRED_DEBUGGING_TYPE | |
a3a15b4d | 7082 | A C expression that returns the type of debugging output GCC should |
e5e809f4 | 7083 | produce when the user specifies just @samp{-g}. Define |
a3a15b4d | 7084 | this if you have arranged for GCC to support more than one format of |
e5e809f4 | 7085 | debugging output. Currently, the allowable values are @code{DBX_DEBUG}, |
f3ff3f4a JM |
7086 | @code{SDB_DEBUG}, @code{DWARF_DEBUG}, @code{DWARF2_DEBUG}, and |
7087 | @code{XCOFF_DEBUG}. | |
feca2ed3 | 7088 | |
a3a15b4d | 7089 | When the user specifies @samp{-ggdb}, GCC normally also uses the |
e5e809f4 JL |
7090 | value of this macro to select the debugging output format, but with two |
7091 | exceptions. If @code{DWARF2_DEBUGGING_INFO} is defined and | |
a3a15b4d | 7092 | @code{LINKER_DOES_NOT_WORK_WITH_DWARF2} is not defined, GCC uses the |
e5e809f4 | 7093 | value @code{DWARF2_DEBUG}. Otherwise, if @code{DBX_DEBUGGING_INFO} is |
a3a15b4d | 7094 | defined, GCC uses @code{DBX_DEBUG}. |
deabc777 | 7095 | |
feca2ed3 JW |
7096 | The value of this macro only affects the default debugging output; the |
7097 | user can always get a specific type of output by using @samp{-gstabs}, | |
f3ff3f4a | 7098 | @samp{-gcoff}, @samp{-gdwarf-1}, @samp{-gdwarf-2}, or @samp{-gxcoff}. |
feca2ed3 JW |
7099 | @end table |
7100 | ||
7101 | @node DBX Options | |
7102 | @subsection Specific Options for DBX Output | |
7103 | ||
7104 | @c prevent bad page break with this line | |
7105 | These are specific options for DBX output. | |
7106 | ||
7107 | @table @code | |
7108 | @findex DBX_DEBUGGING_INFO | |
7109 | @item DBX_DEBUGGING_INFO | |
a3a15b4d | 7110 | Define this macro if GCC should produce debugging output for DBX |
feca2ed3 JW |
7111 | in response to the @samp{-g} option. |
7112 | ||
7113 | @findex XCOFF_DEBUGGING_INFO | |
7114 | @item XCOFF_DEBUGGING_INFO | |
a3a15b4d | 7115 | Define this macro if GCC should produce XCOFF format debugging output |
feca2ed3 JW |
7116 | in response to the @samp{-g} option. This is a variant of DBX format. |
7117 | ||
7118 | @findex DEFAULT_GDB_EXTENSIONS | |
7119 | @item DEFAULT_GDB_EXTENSIONS | |
a3a15b4d | 7120 | Define this macro to control whether GCC should by default generate |
feca2ed3 JW |
7121 | GDB's extended version of DBX debugging information (assuming DBX-format |
7122 | debugging information is enabled at all). If you don't define the | |
7123 | macro, the default is 1: always generate the extended information | |
7124 | if there is any occasion to. | |
7125 | ||
7126 | @findex DEBUG_SYMS_TEXT | |
7127 | @item DEBUG_SYMS_TEXT | |
7128 | Define this macro if all @code{.stabs} commands should be output while | |
7129 | in the text section. | |
7130 | ||
7131 | @findex ASM_STABS_OP | |
7132 | @item ASM_STABS_OP | |
047c1c92 HPN |
7133 | A C string constant, including spacing, naming the assembler pseudo op to |
7134 | use instead of @code{"\t.stabs\t"} to define an ordinary debugging symbol. | |
7135 | If you don't define this macro, @code{"\t.stabs\t"} is used. This macro | |
7136 | applies only to DBX debugging information format. | |
feca2ed3 JW |
7137 | |
7138 | @findex ASM_STABD_OP | |
7139 | @item ASM_STABD_OP | |
047c1c92 HPN |
7140 | A C string constant, including spacing, naming the assembler pseudo op to |
7141 | use instead of @code{"\t.stabd\t"} to define a debugging symbol whose | |
7142 | value is the current location. If you don't define this macro, | |
7143 | @code{"\t.stabd\t"} is used. This macro applies only to DBX debugging | |
7144 | information format. | |
feca2ed3 JW |
7145 | |
7146 | @findex ASM_STABN_OP | |
7147 | @item ASM_STABN_OP | |
047c1c92 HPN |
7148 | A C string constant, including spacing, naming the assembler pseudo op to |
7149 | use instead of @code{"\t.stabn\t"} to define a debugging symbol with no | |
7150 | name. If you don't define this macro, @code{"\t.stabn\t"} is used. This | |
7151 | macro applies only to DBX debugging information format. | |
feca2ed3 JW |
7152 | |
7153 | @findex DBX_NO_XREFS | |
7154 | @item DBX_NO_XREFS | |
7155 | Define this macro if DBX on your system does not support the construct | |
7156 | @samp{xs@var{tagname}}. On some systems, this construct is used to | |
7157 | describe a forward reference to a structure named @var{tagname}. | |
7158 | On other systems, this construct is not supported at all. | |
7159 | ||
7160 | @findex DBX_CONTIN_LENGTH | |
7161 | @item DBX_CONTIN_LENGTH | |
7162 | A symbol name in DBX-format debugging information is normally | |
7163 | continued (split into two separate @code{.stabs} directives) when it | |
7164 | exceeds a certain length (by default, 80 characters). On some | |
7165 | operating systems, DBX requires this splitting; on others, splitting | |
7166 | must not be done. You can inhibit splitting by defining this macro | |
7167 | with the value zero. You can override the default splitting-length by | |
7168 | defining this macro as an expression for the length you desire. | |
7169 | ||
7170 | @findex DBX_CONTIN_CHAR | |
7171 | @item DBX_CONTIN_CHAR | |
7172 | Normally continuation is indicated by adding a @samp{\} character to | |
7173 | the end of a @code{.stabs} string when a continuation follows. To use | |
7174 | a different character instead, define this macro as a character | |
7175 | constant for the character you want to use. Do not define this macro | |
7176 | if backslash is correct for your system. | |
7177 | ||
7178 | @findex DBX_STATIC_STAB_DATA_SECTION | |
7179 | @item DBX_STATIC_STAB_DATA_SECTION | |
7180 | Define this macro if it is necessary to go to the data section before | |
7181 | outputting the @samp{.stabs} pseudo-op for a non-global static | |
7182 | variable. | |
7183 | ||
7184 | @findex DBX_TYPE_DECL_STABS_CODE | |
7185 | @item DBX_TYPE_DECL_STABS_CODE | |
7186 | The value to use in the ``code'' field of the @code{.stabs} directive | |
7187 | for a typedef. The default is @code{N_LSYM}. | |
7188 | ||
7189 | @findex DBX_STATIC_CONST_VAR_CODE | |
7190 | @item DBX_STATIC_CONST_VAR_CODE | |
7191 | The value to use in the ``code'' field of the @code{.stabs} directive | |
7192 | for a static variable located in the text section. DBX format does not | |
7193 | provide any ``right'' way to do this. The default is @code{N_FUN}. | |
7194 | ||
7195 | @findex DBX_REGPARM_STABS_CODE | |
7196 | @item DBX_REGPARM_STABS_CODE | |
7197 | The value to use in the ``code'' field of the @code{.stabs} directive | |
7198 | for a parameter passed in registers. DBX format does not provide any | |
7199 | ``right'' way to do this. The default is @code{N_RSYM}. | |
7200 | ||
7201 | @findex DBX_REGPARM_STABS_LETTER | |
7202 | @item DBX_REGPARM_STABS_LETTER | |
7203 | The letter to use in DBX symbol data to identify a symbol as a parameter | |
7204 | passed in registers. DBX format does not customarily provide any way to | |
7205 | do this. The default is @code{'P'}. | |
7206 | ||
7207 | @findex DBX_MEMPARM_STABS_LETTER | |
7208 | @item DBX_MEMPARM_STABS_LETTER | |
7209 | The letter to use in DBX symbol data to identify a symbol as a stack | |
7210 | parameter. The default is @code{'p'}. | |
7211 | ||
7212 | @findex DBX_FUNCTION_FIRST | |
7213 | @item DBX_FUNCTION_FIRST | |
7214 | Define this macro if the DBX information for a function and its | |
7215 | arguments should precede the assembler code for the function. Normally, | |
7216 | in DBX format, the debugging information entirely follows the assembler | |
7217 | code. | |
7218 | ||
7219 | @findex DBX_LBRAC_FIRST | |
7220 | @item DBX_LBRAC_FIRST | |
7221 | Define this macro if the @code{N_LBRAC} symbol for a block should | |
7222 | precede the debugging information for variables and functions defined in | |
7223 | that block. Normally, in DBX format, the @code{N_LBRAC} symbol comes | |
7224 | first. | |
7225 | ||
7226 | @findex DBX_BLOCKS_FUNCTION_RELATIVE | |
7227 | @item DBX_BLOCKS_FUNCTION_RELATIVE | |
7228 | Define this macro if the value of a symbol describing the scope of a | |
7229 | block (@code{N_LBRAC} or @code{N_RBRAC}) should be relative to the start | |
7230 | of the enclosing function. Normally, GNU C uses an absolute address. | |
7231 | ||
7232 | @findex DBX_USE_BINCL | |
7233 | @item DBX_USE_BINCL | |
7234 | Define this macro if GNU C should generate @code{N_BINCL} and | |
7235 | @code{N_EINCL} stabs for included header files, as on Sun systems. This | |
7236 | macro also directs GNU C to output a type number as a pair of a file | |
7237 | number and a type number within the file. Normally, GNU C does not | |
7238 | generate @code{N_BINCL} or @code{N_EINCL} stabs, and it outputs a single | |
7239 | number for a type number. | |
7240 | @end table | |
7241 | ||
7242 | @node DBX Hooks | |
7243 | @subsection Open-Ended Hooks for DBX Format | |
7244 | ||
7245 | @c prevent bad page break with this line | |
7246 | These are hooks for DBX format. | |
7247 | ||
7248 | @table @code | |
7249 | @findex DBX_OUTPUT_LBRAC | |
7250 | @item DBX_OUTPUT_LBRAC (@var{stream}, @var{name}) | |
7251 | Define this macro to say how to output to @var{stream} the debugging | |
7252 | information for the start of a scope level for variable names. The | |
7253 | argument @var{name} is the name of an assembler symbol (for use with | |
7254 | @code{assemble_name}) whose value is the address where the scope begins. | |
7255 | ||
7256 | @findex DBX_OUTPUT_RBRAC | |
7257 | @item DBX_OUTPUT_RBRAC (@var{stream}, @var{name}) | |
7258 | Like @code{DBX_OUTPUT_LBRAC}, but for the end of a scope level. | |
7259 | ||
7260 | @findex DBX_OUTPUT_ENUM | |
7261 | @item DBX_OUTPUT_ENUM (@var{stream}, @var{type}) | |
7262 | Define this macro if the target machine requires special handling to | |
7263 | output an enumeration type. The definition should be a C statement | |
7264 | (sans semicolon) to output the appropriate information to @var{stream} | |
7265 | for the type @var{type}. | |
7266 | ||
7267 | @findex DBX_OUTPUT_FUNCTION_END | |
7268 | @item DBX_OUTPUT_FUNCTION_END (@var{stream}, @var{function}) | |
7269 | Define this macro if the target machine requires special output at the | |
7270 | end of the debugging information for a function. The definition should | |
7271 | be a C statement (sans semicolon) to output the appropriate information | |
7272 | to @var{stream}. @var{function} is the @code{FUNCTION_DECL} node for | |
7273 | the function. | |
7274 | ||
7275 | @findex DBX_OUTPUT_STANDARD_TYPES | |
7276 | @item DBX_OUTPUT_STANDARD_TYPES (@var{syms}) | |
7277 | Define this macro if you need to control the order of output of the | |
7278 | standard data types at the beginning of compilation. The argument | |
7279 | @var{syms} is a @code{tree} which is a chain of all the predefined | |
7280 | global symbols, including names of data types. | |
7281 | ||
7282 | Normally, DBX output starts with definitions of the types for integers | |
7283 | and characters, followed by all the other predefined types of the | |
7284 | particular language in no particular order. | |
7285 | ||
7286 | On some machines, it is necessary to output different particular types | |
7287 | first. To do this, define @code{DBX_OUTPUT_STANDARD_TYPES} to output | |
7288 | those symbols in the necessary order. Any predefined types that you | |
7289 | don't explicitly output will be output afterward in no particular order. | |
7290 | ||
7291 | Be careful not to define this macro so that it works only for C. There | |
7292 | are no global variables to access most of the built-in types, because | |
7293 | another language may have another set of types. The way to output a | |
7294 | particular type is to look through @var{syms} to see if you can find it. | |
7295 | Here is an example: | |
7296 | ||
7297 | @smallexample | |
7298 | @{ | |
7299 | tree decl; | |
7300 | for (decl = syms; decl; decl = TREE_CHAIN (decl)) | |
7301 | if (!strcmp (IDENTIFIER_POINTER (DECL_NAME (decl)), | |
7302 | "long int")) | |
7303 | dbxout_symbol (decl); | |
7304 | @dots{} | |
7305 | @} | |
7306 | @end smallexample | |
7307 | ||
7308 | @noindent | |
7309 | This does nothing if the expected type does not exist. | |
7310 | ||
7311 | See the function @code{init_decl_processing} in @file{c-decl.c} to find | |
7312 | the names to use for all the built-in C types. | |
7313 | ||
7314 | Here is another way of finding a particular type: | |
7315 | ||
7316 | @c this is still overfull. --mew 10feb93 | |
7317 | @smallexample | |
7318 | @{ | |
7319 | tree decl; | |
7320 | for (decl = syms; decl; decl = TREE_CHAIN (decl)) | |
7321 | if (TREE_CODE (decl) == TYPE_DECL | |
7322 | && (TREE_CODE (TREE_TYPE (decl)) | |
7323 | == INTEGER_CST) | |
7324 | && TYPE_PRECISION (TREE_TYPE (decl)) == 16 | |
7325 | && TYPE_UNSIGNED (TREE_TYPE (decl))) | |
7326 | @group | |
7327 | /* @r{This must be @code{unsigned short}.} */ | |
7328 | dbxout_symbol (decl); | |
7329 | @dots{} | |
7330 | @} | |
7331 | @end group | |
7332 | @end smallexample | |
7333 | ||
7334 | @findex NO_DBX_FUNCTION_END | |
7335 | @item NO_DBX_FUNCTION_END | |
7336 | Some stabs encapsulation formats (in particular ECOFF), cannot handle the | |
7337 | @code{.stabs "",N_FUN,,0,0,Lscope-function-1} gdb dbx extention construct. | |
7338 | On those machines, define this macro to turn this feature off without | |
7339 | disturbing the rest of the gdb extensions. | |
7340 | ||
7341 | @end table | |
7342 | ||
7343 | @node File Names and DBX | |
7344 | @subsection File Names in DBX Format | |
7345 | ||
7346 | @c prevent bad page break with this line | |
7347 | This describes file names in DBX format. | |
7348 | ||
7349 | @table @code | |
7350 | @findex DBX_WORKING_DIRECTORY | |
7351 | @item DBX_WORKING_DIRECTORY | |
7352 | Define this if DBX wants to have the current directory recorded in each | |
7353 | object file. | |
7354 | ||
7355 | Note that the working directory is always recorded if GDB extensions are | |
7356 | enabled. | |
7357 | ||
7358 | @findex DBX_OUTPUT_MAIN_SOURCE_FILENAME | |
7359 | @item DBX_OUTPUT_MAIN_SOURCE_FILENAME (@var{stream}, @var{name}) | |
7360 | A C statement to output DBX debugging information to the stdio stream | |
7361 | @var{stream} which indicates that file @var{name} is the main source | |
7362 | file---the file specified as the input file for compilation. | |
7363 | This macro is called only once, at the beginning of compilation. | |
7364 | ||
7365 | This macro need not be defined if the standard form of output | |
7366 | for DBX debugging information is appropriate. | |
7367 | ||
7368 | @findex DBX_OUTPUT_MAIN_SOURCE_DIRECTORY | |
7369 | @item DBX_OUTPUT_MAIN_SOURCE_DIRECTORY (@var{stream}, @var{name}) | |
7370 | A C statement to output DBX debugging information to the stdio stream | |
7371 | @var{stream} which indicates that the current directory during | |
7372 | compilation is named @var{name}. | |
7373 | ||
7374 | This macro need not be defined if the standard form of output | |
7375 | for DBX debugging information is appropriate. | |
7376 | ||
7377 | @findex DBX_OUTPUT_MAIN_SOURCE_FILE_END | |
7378 | @item DBX_OUTPUT_MAIN_SOURCE_FILE_END (@var{stream}, @var{name}) | |
7379 | A C statement to output DBX debugging information at the end of | |
7380 | compilation of the main source file @var{name}. | |
7381 | ||
7382 | If you don't define this macro, nothing special is output at the end | |
7383 | of compilation, which is correct for most machines. | |
7384 | ||
7385 | @findex DBX_OUTPUT_SOURCE_FILENAME | |
7386 | @item DBX_OUTPUT_SOURCE_FILENAME (@var{stream}, @var{name}) | |
7387 | A C statement to output DBX debugging information to the stdio stream | |
7388 | @var{stream} which indicates that file @var{name} is the current source | |
7389 | file. This output is generated each time input shifts to a different | |
7390 | source file as a result of @samp{#include}, the end of an included file, | |
7391 | or a @samp{#line} command. | |
7392 | ||
7393 | This macro need not be defined if the standard form of output | |
7394 | for DBX debugging information is appropriate. | |
7395 | @end table | |
7396 | ||
7397 | @need 2000 | |
7398 | @node SDB and DWARF | |
7399 | @subsection Macros for SDB and DWARF Output | |
7400 | ||
7401 | @c prevent bad page break with this line | |
7402 | Here are macros for SDB and DWARF output. | |
7403 | ||
7404 | @table @code | |
7405 | @findex SDB_DEBUGGING_INFO | |
7406 | @item SDB_DEBUGGING_INFO | |
a3a15b4d | 7407 | Define this macro if GCC should produce COFF-style debugging output |
feca2ed3 JW |
7408 | for SDB in response to the @samp{-g} option. |
7409 | ||
7410 | @findex DWARF_DEBUGGING_INFO | |
7411 | @item DWARF_DEBUGGING_INFO | |
a3a15b4d | 7412 | Define this macro if GCC should produce dwarf format debugging output |
feca2ed3 JW |
7413 | in response to the @samp{-g} option. |
7414 | ||
f3ff3f4a JM |
7415 | @findex DWARF2_DEBUGGING_INFO |
7416 | @item DWARF2_DEBUGGING_INFO | |
a3a15b4d | 7417 | Define this macro if GCC should produce dwarf version 2 format |
f3ff3f4a JM |
7418 | debugging output in response to the @samp{-g} option. |
7419 | ||
861bb6c1 JL |
7420 | To support optional call frame debugging information, you must also |
7421 | define @code{INCOMING_RETURN_ADDR_RTX} and either set | |
7422 | @code{RTX_FRAME_RELATED_P} on the prologue insns if you use RTL for the | |
7423 | prologue, or call @code{dwarf2out_def_cfa} and @code{dwarf2out_reg_save} | |
7424 | as appropriate from @code{FUNCTION_PROLOGUE} if you don't. | |
7425 | ||
9ec36da5 JL |
7426 | @findex DWARF2_FRAME_INFO |
7427 | @item DWARF2_FRAME_INFO | |
a3a15b4d | 7428 | Define this macro to a nonzero value if GCC should always output |
9ec36da5 | 7429 | Dwarf 2 frame information. If @code{DWARF2_UNWIND_INFO} |
a3a15b4d | 7430 | (@pxref{Exception Region Output} is nonzero, GCC will output this |
9ec36da5 JL |
7431 | information not matter how you define @code{DWARF2_FRAME_INFO}. |
7432 | ||
deabc777 PE |
7433 | @findex LINKER_DOES_NOT_WORK_WITH_DWARF2 |
7434 | @item LINKER_DOES_NOT_WORK_WITH_DWARF2 | |
e5e809f4 | 7435 | Define this macro if the linker does not work with Dwarf version 2. |
a3a15b4d | 7436 | Normally, if the user specifies only @samp{-ggdb} GCC will use Dwarf |
e5e809f4 JL |
7437 | version 2 if available; this macro disables this. See the description |
7438 | of the @code{PREFERRED_DEBUGGING_TYPE} macro for more details. | |
deabc777 | 7439 | |
b366352b MM |
7440 | @findex DWARF2_GENERATE_TEXT_SECTION_LABEL |
7441 | @item DWARF2_GENERATE_TEXT_SECTION_LABEL | |
7442 | By default, the Dwarf 2 debugging information generator will generate a | |
7443 | label to mark the beginning of the text section. If it is better simply | |
7444 | to use the name of the text section itself, rather than an explicit label, | |
7445 | to indicate the beginning of the text section, define this macro to zero. | |
7446 | ||
b2244e22 JW |
7447 | @findex DWARF2_ASM_LINE_DEBUG_INFO |
7448 | @item DWARF2_ASM_LINE_DEBUG_INFO | |
7449 | Define this macro to be a nonzero value if the assembler can generate Dwarf 2 | |
7450 | line debug info sections. This will result in much more compact line number | |
7451 | tables, and hence is desirable if it works. | |
7452 | ||
feca2ed3 JW |
7453 | @findex PUT_SDB_@dots{} |
7454 | @item PUT_SDB_@dots{} | |
7455 | Define these macros to override the assembler syntax for the special | |
7456 | SDB assembler directives. See @file{sdbout.c} for a list of these | |
7457 | macros and their arguments. If the standard syntax is used, you need | |
7458 | not define them yourself. | |
7459 | ||
7460 | @findex SDB_DELIM | |
7461 | @item SDB_DELIM | |
7462 | Some assemblers do not support a semicolon as a delimiter, even between | |
7463 | SDB assembler directives. In that case, define this macro to be the | |
7464 | delimiter to use (usually @samp{\n}). It is not necessary to define | |
7465 | a new set of @code{PUT_SDB_@var{op}} macros if this is the only change | |
7466 | required. | |
7467 | ||
7468 | @findex SDB_GENERATE_FAKE | |
7469 | @item SDB_GENERATE_FAKE | |
7470 | Define this macro to override the usual method of constructing a dummy | |
7471 | name for anonymous structure and union types. See @file{sdbout.c} for | |
7472 | more information. | |
7473 | ||
7474 | @findex SDB_ALLOW_UNKNOWN_REFERENCES | |
7475 | @item SDB_ALLOW_UNKNOWN_REFERENCES | |
7476 | Define this macro to allow references to unknown structure, | |
7477 | union, or enumeration tags to be emitted. Standard COFF does not | |
7478 | allow handling of unknown references, MIPS ECOFF has support for | |
7479 | it. | |
7480 | ||
7481 | @findex SDB_ALLOW_FORWARD_REFERENCES | |
7482 | @item SDB_ALLOW_FORWARD_REFERENCES | |
7483 | Define this macro to allow references to structure, union, or | |
7484 | enumeration tags that have not yet been seen to be handled. Some | |
7485 | assemblers choke if forward tags are used, while some require it. | |
7486 | @end table | |
7487 | ||
7488 | @node Cross-compilation | |
7489 | @section Cross Compilation and Floating Point | |
7490 | @cindex cross compilation and floating point | |
7491 | @cindex floating point and cross compilation | |
7492 | ||
7493 | While all modern machines use 2's complement representation for integers, | |
7494 | there are a variety of representations for floating point numbers. This | |
7495 | means that in a cross-compiler the representation of floating point numbers | |
7496 | in the compiled program may be different from that used in the machine | |
7497 | doing the compilation. | |
7498 | ||
7499 | @findex atof | |
7500 | Because different representation systems may offer different amounts of | |
7501 | range and precision, the cross compiler cannot safely use the host | |
7502 | machine's floating point arithmetic. Therefore, floating point constants | |
7503 | must be represented in the target machine's format. This means that the | |
7504 | cross compiler cannot use @code{atof} to parse a floating point constant; | |
7505 | it must have its own special routine to use instead. Also, constant | |
7506 | folding must emulate the target machine's arithmetic (or must not be done | |
7507 | at all). | |
7508 | ||
7509 | The macros in the following table should be defined only if you are cross | |
7510 | compiling between different floating point formats. | |
7511 | ||
7512 | Otherwise, don't define them. Then default definitions will be set up which | |
7513 | use @code{double} as the data type, @code{==} to test for equality, etc. | |
7514 | ||
7515 | You don't need to worry about how many times you use an operand of any | |
7516 | of these macros. The compiler never uses operands which have side effects. | |
7517 | ||
7518 | @table @code | |
7519 | @findex REAL_VALUE_TYPE | |
7520 | @item REAL_VALUE_TYPE | |
7521 | A macro for the C data type to be used to hold a floating point value | |
7522 | in the target machine's format. Typically this would be a | |
7523 | @code{struct} containing an array of @code{int}. | |
7524 | ||
7525 | @findex REAL_VALUES_EQUAL | |
7526 | @item REAL_VALUES_EQUAL (@var{x}, @var{y}) | |
7527 | A macro for a C expression which compares for equality the two values, | |
7528 | @var{x} and @var{y}, both of type @code{REAL_VALUE_TYPE}. | |
7529 | ||
7530 | @findex REAL_VALUES_LESS | |
7531 | @item REAL_VALUES_LESS (@var{x}, @var{y}) | |
7532 | A macro for a C expression which tests whether @var{x} is less than | |
7533 | @var{y}, both values being of type @code{REAL_VALUE_TYPE} and | |
7534 | interpreted as floating point numbers in the target machine's | |
7535 | representation. | |
7536 | ||
7537 | @findex REAL_VALUE_LDEXP | |
7538 | @findex ldexp | |
7539 | @item REAL_VALUE_LDEXP (@var{x}, @var{scale}) | |
7540 | A macro for a C expression which performs the standard library | |
7541 | function @code{ldexp}, but using the target machine's floating point | |
7542 | representation. Both @var{x} and the value of the expression have | |
7543 | type @code{REAL_VALUE_TYPE}. The second argument, @var{scale}, is an | |
7544 | integer. | |
7545 | ||
7546 | @findex REAL_VALUE_FIX | |
7547 | @item REAL_VALUE_FIX (@var{x}) | |
7548 | A macro whose definition is a C expression to convert the target-machine | |
7549 | floating point value @var{x} to a signed integer. @var{x} has type | |
7550 | @code{REAL_VALUE_TYPE}. | |
7551 | ||
7552 | @findex REAL_VALUE_UNSIGNED_FIX | |
7553 | @item REAL_VALUE_UNSIGNED_FIX (@var{x}) | |
7554 | A macro whose definition is a C expression to convert the target-machine | |
7555 | floating point value @var{x} to an unsigned integer. @var{x} has type | |
7556 | @code{REAL_VALUE_TYPE}. | |
7557 | ||
7558 | @findex REAL_VALUE_RNDZINT | |
7559 | @item REAL_VALUE_RNDZINT (@var{x}) | |
7560 | A macro whose definition is a C expression to round the target-machine | |
7561 | floating point value @var{x} towards zero to an integer value (but still | |
7562 | as a floating point number). @var{x} has type @code{REAL_VALUE_TYPE}, | |
7563 | and so does the value. | |
7564 | ||
7565 | @findex REAL_VALUE_UNSIGNED_RNDZINT | |
7566 | @item REAL_VALUE_UNSIGNED_RNDZINT (@var{x}) | |
7567 | A macro whose definition is a C expression to round the target-machine | |
7568 | floating point value @var{x} towards zero to an unsigned integer value | |
7569 | (but still represented as a floating point number). @var{x} has type | |
7570 | @code{REAL_VALUE_TYPE}, and so does the value. | |
7571 | ||
7572 | @findex REAL_VALUE_ATOF | |
7573 | @item REAL_VALUE_ATOF (@var{string}, @var{mode}) | |
7574 | A macro for a C expression which converts @var{string}, an expression of | |
7575 | type @code{char *}, into a floating point number in the target machine's | |
7576 | representation for mode @var{mode}. The value has type | |
7577 | @code{REAL_VALUE_TYPE}. | |
7578 | ||
7579 | @findex REAL_INFINITY | |
7580 | @item REAL_INFINITY | |
7581 | Define this macro if infinity is a possible floating point value, and | |
7582 | therefore division by 0 is legitimate. | |
7583 | ||
7584 | @findex REAL_VALUE_ISINF | |
7585 | @findex isinf | |
7586 | @item REAL_VALUE_ISINF (@var{x}) | |
7587 | A macro for a C expression which determines whether @var{x}, a floating | |
7588 | point value, is infinity. The value has type @code{int}. | |
7589 | By default, this is defined to call @code{isinf}. | |
7590 | ||
7591 | @findex REAL_VALUE_ISNAN | |
7592 | @findex isnan | |
7593 | @item REAL_VALUE_ISNAN (@var{x}) | |
7594 | A macro for a C expression which determines whether @var{x}, a floating | |
7595 | point value, is a ``nan'' (not-a-number). The value has type | |
7596 | @code{int}. By default, this is defined to call @code{isnan}. | |
7597 | @end table | |
7598 | ||
7599 | @cindex constant folding and floating point | |
7600 | Define the following additional macros if you want to make floating | |
7601 | point constant folding work while cross compiling. If you don't | |
7602 | define them, cross compilation is still possible, but constant folding | |
7603 | will not happen for floating point values. | |
7604 | ||
7605 | @table @code | |
7606 | @findex REAL_ARITHMETIC | |
7607 | @item REAL_ARITHMETIC (@var{output}, @var{code}, @var{x}, @var{y}) | |
7608 | A macro for a C statement which calculates an arithmetic operation of | |
7609 | the two floating point values @var{x} and @var{y}, both of type | |
7610 | @code{REAL_VALUE_TYPE} in the target machine's representation, to | |
7611 | produce a result of the same type and representation which is stored | |
7612 | in @var{output} (which will be a variable). | |
7613 | ||
7614 | The operation to be performed is specified by @var{code}, a tree code | |
7615 | which will always be one of the following: @code{PLUS_EXPR}, | |
7616 | @code{MINUS_EXPR}, @code{MULT_EXPR}, @code{RDIV_EXPR}, | |
7617 | @code{MAX_EXPR}, @code{MIN_EXPR}.@refill | |
7618 | ||
7619 | @cindex overflow while constant folding | |
7620 | The expansion of this macro is responsible for checking for overflow. | |
7621 | If overflow happens, the macro expansion should execute the statement | |
7622 | @code{return 0;}, which indicates the inability to perform the | |
7623 | arithmetic operation requested. | |
7624 | ||
7625 | @findex REAL_VALUE_NEGATE | |
7626 | @item REAL_VALUE_NEGATE (@var{x}) | |
7627 | A macro for a C expression which returns the negative of the floating | |
7628 | point value @var{x}. Both @var{x} and the value of the expression | |
7629 | have type @code{REAL_VALUE_TYPE} and are in the target machine's | |
7630 | floating point representation. | |
7631 | ||
7632 | There is no way for this macro to report overflow, since overflow | |
7633 | can't happen in the negation operation. | |
7634 | ||
7635 | @findex REAL_VALUE_TRUNCATE | |
7636 | @item REAL_VALUE_TRUNCATE (@var{mode}, @var{x}) | |
7637 | A macro for a C expression which converts the floating point value | |
7638 | @var{x} to mode @var{mode}. | |
7639 | ||
7640 | Both @var{x} and the value of the expression are in the target machine's | |
7641 | floating point representation and have type @code{REAL_VALUE_TYPE}. | |
7642 | However, the value should have an appropriate bit pattern to be output | |
7643 | properly as a floating constant whose precision accords with mode | |
7644 | @var{mode}. | |
7645 | ||
7646 | There is no way for this macro to report overflow. | |
7647 | ||
7648 | @findex REAL_VALUE_TO_INT | |
7649 | @item REAL_VALUE_TO_INT (@var{low}, @var{high}, @var{x}) | |
7650 | A macro for a C expression which converts a floating point value | |
7651 | @var{x} into a double-precision integer which is then stored into | |
7652 | @var{low} and @var{high}, two variables of type @var{int}. | |
7653 | ||
7654 | @item REAL_VALUE_FROM_INT (@var{x}, @var{low}, @var{high}, @var{mode}) | |
7655 | @findex REAL_VALUE_FROM_INT | |
7656 | A macro for a C expression which converts a double-precision integer | |
7657 | found in @var{low} and @var{high}, two variables of type @var{int}, | |
7658 | into a floating point value which is then stored into @var{x}. | |
7659 | The value is in the target machine's representation for mode @var{mode} | |
7660 | and has the type @code{REAL_VALUE_TYPE}. | |
7661 | @end table | |
7662 | ||
9f09b1f2 R |
7663 | @node Mode Switching |
7664 | @section Mode Switching Instructions | |
7665 | @cindex mode switching | |
7666 | The following macros control mode switching optimizations: | |
7667 | ||
7668 | @table @code | |
7669 | @findex OPTIMIZE_MODE_SWITCHING | |
7670 | @item OPTIMIZE_MODE_SWITCHING (@var{entity}) | |
7671 | Define this macro if the port needs extra instructions inserted for mode | |
7672 | switching in an optimizing compilation. | |
7673 | ||
7674 | For an example, the SH4 can perform both single and double precision | |
7675 | floating point operations, but to perform a single precision operation, | |
7676 | the FPSCR PR bit has to be cleared, while for a double precision | |
7677 | operation, this bit has to be set. Changing the PR bit requires a general | |
7678 | purpose register as a scratch register, hence these FPSCR sets have to | |
7679 | be inserted before reload, i.e. you can't put this into instruction emitting | |
7680 | or MACHINE_DEPENDENT_REORG. | |
7681 | ||
7682 | You can have multiple entities that are mode-switched, and select at run time | |
7683 | which entities actually need it. @code{OPTIMIZE_MODE_SWITCHING} should | |
7684 | return non-zero for any @var{entity} that that needs mode-switching. | |
7685 | If you define this macro, you also have to define | |
7686 | @code{NUM_MODES_FOR_MODE_SWITCHING}, @code{MODE_NEEDED}, | |
7687 | @code{MODE_PRIORITY_TO_MODE} and @code{EMIT_MODE_SET}. | |
1270c255 | 7688 | @code{NORMAL_MODE} is optional. |
9f09b1f2 R |
7689 | |
7690 | @findex NUM_MODES_FOR_MODE_SWITCHING | |
7691 | @item NUM_MODES_FOR_MODE_SWITCHING | |
7692 | If you define @code{OPTIMIZE_MODE_SWITCHING}, you have to define this as | |
7693 | initializer for an array of integers. Each initializer element | |
7694 | N refers to an entity that needs mode switching, and specifies the number | |
7695 | of different modes that might need to be set for this entity. | |
7696 | The position of the initializer in the initializer - starting counting at | |
7697 | zero - determines the integer that is used to refer to the mode-switched | |
7698 | entity in question. | |
7699 | In macros that take mode arguments / yield a mode result, modes are | |
7700 | represented as numbers 0 .. N - 1. N is used to specify that no mode | |
7701 | switch is needed / supplied. | |
7702 | ||
9f09b1f2 R |
7703 | @findex MODE_NEEDED |
7704 | @item MODE_NEEDED (@var{entity}, @var{insn}) | |
7705 | @var{entity} is an integer specifying a mode-switched entity. If | |
7706 | @code{OPTIMIZE_MODE_SWITCHING} is defined, you must define this macro to | |
7707 | return an integer value not larger than the corresponding element in | |
7708 | NUM_MODES_FOR_MODE_SWITCHING, to denote the mode that @var{entity} must | |
7709 | be switched into prior to the execution of INSN. | |
7710 | ||
1270c255 CP |
7711 | @findex NORMAL_MODE |
7712 | @item NORMAL_MODE (@var{entity}) | |
9f09b1f2 R |
7713 | If this macro is defined, it is evaluated for every @var{entity} that needs |
7714 | mode switching. It should evaluate to an integer, which is a mode that | |
1270c255 | 7715 | @var{entity} is assumed to be switched to at function entry and exit. |
9f09b1f2 R |
7716 | |
7717 | @findex MODE_PRIORITY_TO_MODE | |
7718 | @item MODE_PRIORITY_TO_MODE (@var{entity}, @var{n}) | |
7719 | This macro specifies the order in which modes for ENTITY are processed. | |
7720 | 0 is the highest priority, NUM_MODES_FOR_MODE_SWITCHING[ENTITY] - 1 the | |
7721 | lowest. The value of the macro should be an integer designating a mode | |
7722 | for ENTITY. For any fixed @var{entity}, @code{mode_priority_to_mode} | |
7723 | (@var{entity}, @var{n}) shall be a bijection in 0 .. | |
7724 | @code{num_modes_for_mode_switching}[@var{entity}] - 1 . | |
7725 | ||
7726 | @findex EMIT_MODE_SET | |
7727 | @item EMIT_MODE_SET (@var{entity}, @var{mode}, @var{hard_regs_live}) | |
7728 | Generate one or more insns to set @var{entity} to @var{mode}. | |
7729 | @var{hard_reg_live} is the set of hard registers live at the point where | |
7730 | the insn(s) are to be inserted. | |
7731 | @end table | |
7732 | ||
feca2ed3 JW |
7733 | @node Misc |
7734 | @section Miscellaneous Parameters | |
7735 | @cindex parameters, miscellaneous | |
7736 | ||
7737 | @c prevent bad page break with this line | |
7738 | Here are several miscellaneous parameters. | |
7739 | ||
7740 | @table @code | |
7741 | @item PREDICATE_CODES | |
7742 | @findex PREDICATE_CODES | |
7743 | Define this if you have defined special-purpose predicates in the file | |
7744 | @file{@var{machine}.c}. This macro is called within an initializer of an | |
7745 | array of structures. The first field in the structure is the name of a | |
7746 | predicate and the second field is an array of rtl codes. For each | |
7747 | predicate, list all rtl codes that can be in expressions matched by the | |
7748 | predicate. The list should have a trailing comma. Here is an example | |
7749 | of two entries in the list for a typical RISC machine: | |
7750 | ||
7751 | @smallexample | |
7752 | #define PREDICATE_CODES \ | |
7753 | @{"gen_reg_rtx_operand", @{SUBREG, REG@}@}, \ | |
7754 | @{"reg_or_short_cint_operand", @{SUBREG, REG, CONST_INT@}@}, | |
7755 | @end smallexample | |
7756 | ||
7757 | Defining this macro does not affect the generated code (however, | |
7758 | incorrect definitions that omit an rtl code that may be matched by the | |
7759 | predicate can cause the compiler to malfunction). Instead, it allows | |
7760 | the table built by @file{genrecog} to be more compact and efficient, | |
7761 | thus speeding up the compiler. The most important predicates to include | |
556e0f21 | 7762 | in the list specified by this macro are those used in the most insn |
feca2ed3 JW |
7763 | patterns. |
7764 | ||
975d393a AO |
7765 | For each predicate function named in @var{PREDICATE_CODES}, a |
7766 | declaration will be generated in @file{insn-codes.h}. | |
7767 | ||
8fe0ca0c RH |
7768 | @item SPECIAL_MODE_PREDICATES |
7769 | @findex SPECIAL_MODE_PREDICATES | |
7770 | Define this if you have special predicates that know special things | |
7771 | about modes. Genrecog will warn about certain forms of | |
7772 | @code{match_operand} without a mode; if the operand predicate is | |
7773 | listed in @code{SPECIAL_MODE_PREDICATES}, the warning will be | |
7774 | suppressed. | |
7775 | ||
7776 | Here is an example from the IA-32 port (@code{ext_register_operand} | |
7777 | specially checks for @code{HImode} or @code{SImode} in preparation | |
7778 | for a byte extraction from @code{%ah} etc.). | |
7779 | ||
7780 | @smallexample | |
7781 | #define SPECIAL_MODE_PREDICATES \ | |
7782 | "ext_register_operand", | |
7783 | @end smallexample | |
7784 | ||
feca2ed3 JW |
7785 | @findex CASE_VECTOR_MODE |
7786 | @item CASE_VECTOR_MODE | |
7787 | An alias for a machine mode name. This is the machine mode that | |
7788 | elements of a jump-table should have. | |
7789 | ||
33f7f353 JR |
7790 | @findex CASE_VECTOR_SHORTEN_MODE |
7791 | @item CASE_VECTOR_SHORTEN_MODE (@var{min_offset}, @var{max_offset}, @var{body}) | |
7792 | Optional: return the preferred mode for an @code{addr_diff_vec} | |
7793 | when the minimum and maximum offset are known. If you define this, | |
7794 | it enables extra code in branch shortening to deal with @code{addr_diff_vec}. | |
7795 | To make this work, you also have to define INSN_ALIGN and | |
7796 | make the alignment for @code{addr_diff_vec} explicit. | |
391aaa6b | 7797 | The @var{body} argument is provided so that the offset_unsigned and scale |
33f7f353 JR |
7798 | flags can be updated. |
7799 | ||
feca2ed3 JW |
7800 | @findex CASE_VECTOR_PC_RELATIVE |
7801 | @item CASE_VECTOR_PC_RELATIVE | |
18543a22 ILT |
7802 | Define this macro to be a C expression to indicate when jump-tables |
7803 | should contain relative addresses. If jump-tables never contain | |
7804 | relative addresses, then you need not define this macro. | |
feca2ed3 JW |
7805 | |
7806 | @findex CASE_DROPS_THROUGH | |
7807 | @item CASE_DROPS_THROUGH | |
7808 | Define this if control falls through a @code{case} insn when the index | |
7809 | value is out of range. This means the specified default-label is | |
7810 | actually ignored by the @code{case} insn proper. | |
7811 | ||
7812 | @findex CASE_VALUES_THRESHOLD | |
7813 | @item CASE_VALUES_THRESHOLD | |
7814 | Define this to be the smallest number of different values for which it | |
7815 | is best to use a jump-table instead of a tree of conditional branches. | |
7816 | The default is four for machines with a @code{casesi} instruction and | |
7817 | five otherwise. This is best for most machines. | |
7818 | ||
7819 | @findex WORD_REGISTER_OPERATIONS | |
7820 | @item WORD_REGISTER_OPERATIONS | |
7821 | Define this macro if operations between registers with integral mode | |
7822 | smaller than a word are always performed on the entire register. | |
7823 | Most RISC machines have this property and most CISC machines do not. | |
7824 | ||
7825 | @findex LOAD_EXTEND_OP | |
7826 | @item LOAD_EXTEND_OP (@var{mode}) | |
7827 | Define this macro to be a C expression indicating when insns that read | |
7828 | memory in @var{mode}, an integral mode narrower than a word, set the | |
7829 | bits outside of @var{mode} to be either the sign-extension or the | |
7830 | zero-extension of the data read. Return @code{SIGN_EXTEND} for values | |
7831 | of @var{mode} for which the | |
7832 | insn sign-extends, @code{ZERO_EXTEND} for which it zero-extends, and | |
7833 | @code{NIL} for other modes. | |
7834 | ||
7835 | This macro is not called with @var{mode} non-integral or with a width | |
7836 | greater than or equal to @code{BITS_PER_WORD}, so you may return any | |
7837 | value in this case. Do not define this macro if it would always return | |
7838 | @code{NIL}. On machines where this macro is defined, you will normally | |
7839 | define it as the constant @code{SIGN_EXTEND} or @code{ZERO_EXTEND}. | |
7840 | ||
77643ab8 MM |
7841 | @findex SHORT_IMMEDIATES_SIGN_EXTEND |
7842 | @item SHORT_IMMEDIATES_SIGN_EXTEND | |
7843 | Define this macro if loading short immediate values into registers sign | |
7844 | extends. | |
7845 | ||
feca2ed3 JW |
7846 | @findex IMPLICIT_FIX_EXPR |
7847 | @item IMPLICIT_FIX_EXPR | |
7848 | An alias for a tree code that should be used by default for conversion | |
7849 | of floating point values to fixed point. Normally, | |
7850 | @code{FIX_ROUND_EXPR} is used.@refill | |
7851 | ||
7852 | @findex FIXUNS_TRUNC_LIKE_FIX_TRUNC | |
7853 | @item FIXUNS_TRUNC_LIKE_FIX_TRUNC | |
7854 | Define this macro if the same instructions that convert a floating | |
7855 | point number to a signed fixed point number also convert validly to an | |
7856 | unsigned one. | |
7857 | ||
7858 | @findex EASY_DIV_EXPR | |
7859 | @item EASY_DIV_EXPR | |
7860 | An alias for a tree code that is the easiest kind of division to | |
7861 | compile code for in the general case. It may be | |
7862 | @code{TRUNC_DIV_EXPR}, @code{FLOOR_DIV_EXPR}, @code{CEIL_DIV_EXPR} or | |
7863 | @code{ROUND_DIV_EXPR}. These four division operators differ in how | |
7864 | they round the result to an integer. @code{EASY_DIV_EXPR} is used | |
7865 | when it is permissible to use any of those kinds of division and the | |
7866 | choice should be made on the basis of efficiency.@refill | |
7867 | ||
7868 | @findex MOVE_MAX | |
7869 | @item MOVE_MAX | |
7870 | The maximum number of bytes that a single instruction can move quickly | |
7871 | between memory and registers or between two memory locations. | |
7872 | ||
7873 | @findex MAX_MOVE_MAX | |
7874 | @item MAX_MOVE_MAX | |
7875 | The maximum number of bytes that a single instruction can move quickly | |
7876 | between memory and registers or between two memory locations. If this | |
7877 | is undefined, the default is @code{MOVE_MAX}. Otherwise, it is the | |
7878 | constant value that is the largest value that @code{MOVE_MAX} can have | |
7879 | at run-time. | |
7880 | ||
7881 | @findex SHIFT_COUNT_TRUNCATED | |
7882 | @item SHIFT_COUNT_TRUNCATED | |
7883 | A C expression that is nonzero if on this machine the number of bits | |
7884 | actually used for the count of a shift operation is equal to the number | |
7885 | of bits needed to represent the size of the object being shifted. When | |
7886 | this macro is non-zero, the compiler will assume that it is safe to omit | |
7887 | a sign-extend, zero-extend, and certain bitwise `and' instructions that | |
7888 | truncates the count of a shift operation. On machines that have | |
7889 | instructions that act on bitfields at variable positions, which may | |
7890 | include `bit test' instructions, a nonzero @code{SHIFT_COUNT_TRUNCATED} | |
7891 | also enables deletion of truncations of the values that serve as | |
7892 | arguments to bitfield instructions. | |
7893 | ||
7894 | If both types of instructions truncate the count (for shifts) and | |
7895 | position (for bitfield operations), or if no variable-position bitfield | |
7896 | instructions exist, you should define this macro. | |
7897 | ||
7898 | However, on some machines, such as the 80386 and the 680x0, truncation | |
7899 | only applies to shift operations and not the (real or pretended) | |
7900 | bitfield operations. Define @code{SHIFT_COUNT_TRUNCATED} to be zero on | |
7901 | such machines. Instead, add patterns to the @file{md} file that include | |
7902 | the implied truncation of the shift instructions. | |
7903 | ||
7904 | You need not define this macro if it would always have the value of zero. | |
7905 | ||
7906 | @findex TRULY_NOOP_TRUNCATION | |
7907 | @item TRULY_NOOP_TRUNCATION (@var{outprec}, @var{inprec}) | |
7908 | A C expression which is nonzero if on this machine it is safe to | |
7909 | ``convert'' an integer of @var{inprec} bits to one of @var{outprec} | |
7910 | bits (where @var{outprec} is smaller than @var{inprec}) by merely | |
7911 | operating on it as if it had only @var{outprec} bits. | |
7912 | ||
7913 | On many machines, this expression can be 1. | |
7914 | ||
7915 | @c rearranged this, removed the phrase "it is reported that". this was | |
7916 | @c to fix an overfull hbox. --mew 10feb93 | |
7917 | When @code{TRULY_NOOP_TRUNCATION} returns 1 for a pair of sizes for | |
7918 | modes for which @code{MODES_TIEABLE_P} is 0, suboptimal code can result. | |
7919 | If this is the case, making @code{TRULY_NOOP_TRUNCATION} return 0 in | |
7920 | such cases may improve things. | |
7921 | ||
7922 | @findex STORE_FLAG_VALUE | |
7923 | @item STORE_FLAG_VALUE | |
7924 | A C expression describing the value returned by a comparison operator | |
7925 | with an integral mode and stored by a store-flag instruction | |
7926 | (@samp{s@var{cond}}) when the condition is true. This description must | |
7927 | apply to @emph{all} the @samp{s@var{cond}} patterns and all the | |
7928 | comparison operators whose results have a @code{MODE_INT} mode. | |
7929 | ||
7930 | A value of 1 or -1 means that the instruction implementing the | |
7931 | comparison operator returns exactly 1 or -1 when the comparison is true | |
7932 | and 0 when the comparison is false. Otherwise, the value indicates | |
7933 | which bits of the result are guaranteed to be 1 when the comparison is | |
7934 | true. This value is interpreted in the mode of the comparison | |
7935 | operation, which is given by the mode of the first operand in the | |
7936 | @samp{s@var{cond}} pattern. Either the low bit or the sign bit of | |
7937 | @code{STORE_FLAG_VALUE} be on. Presently, only those bits are used by | |
7938 | the compiler. | |
7939 | ||
7940 | If @code{STORE_FLAG_VALUE} is neither 1 or -1, the compiler will | |
7941 | generate code that depends only on the specified bits. It can also | |
7942 | replace comparison operators with equivalent operations if they cause | |
7943 | the required bits to be set, even if the remaining bits are undefined. | |
7944 | For example, on a machine whose comparison operators return an | |
7945 | @code{SImode} value and where @code{STORE_FLAG_VALUE} is defined as | |
7946 | @samp{0x80000000}, saying that just the sign bit is relevant, the | |
7947 | expression | |
7948 | ||
7949 | @smallexample | |
7950 | (ne:SI (and:SI @var{x} (const_int @var{power-of-2})) (const_int 0)) | |
7951 | @end smallexample | |
7952 | ||
7953 | @noindent | |
7954 | can be converted to | |
7955 | ||
7956 | @smallexample | |
7957 | (ashift:SI @var{x} (const_int @var{n})) | |
7958 | @end smallexample | |
7959 | ||
7960 | @noindent | |
7961 | where @var{n} is the appropriate shift count to move the bit being | |
7962 | tested into the sign bit. | |
7963 | ||
7964 | There is no way to describe a machine that always sets the low-order bit | |
7965 | for a true value, but does not guarantee the value of any other bits, | |
7966 | but we do not know of any machine that has such an instruction. If you | |
a3a15b4d | 7967 | are trying to port GCC to such a machine, include an instruction to |
feca2ed3 JW |
7968 | perform a logical-and of the result with 1 in the pattern for the |
7969 | comparison operators and let us know | |
7970 | @ifset USING | |
7971 | (@pxref{Bug Reporting,,How to Report Bugs}). | |
7972 | @end ifset | |
7973 | @ifclear USING | |
7974 | (@pxref{Bug Reporting,,How to Report Bugs,gcc.info,Using GCC}). | |
7975 | @end ifclear | |
7976 | ||
7977 | Often, a machine will have multiple instructions that obtain a value | |
7978 | from a comparison (or the condition codes). Here are rules to guide the | |
7979 | choice of value for @code{STORE_FLAG_VALUE}, and hence the instructions | |
7980 | to be used: | |
7981 | ||
7982 | @itemize @bullet | |
7983 | @item | |
7984 | Use the shortest sequence that yields a valid definition for | |
7985 | @code{STORE_FLAG_VALUE}. It is more efficient for the compiler to | |
7986 | ``normalize'' the value (convert it to, e.g., 1 or 0) than for the | |
7987 | comparison operators to do so because there may be opportunities to | |
7988 | combine the normalization with other operations. | |
7989 | ||
7990 | @item | |
7991 | For equal-length sequences, use a value of 1 or -1, with -1 being | |
7992 | slightly preferred on machines with expensive jumps and 1 preferred on | |
7993 | other machines. | |
7994 | ||
7995 | @item | |
7996 | As a second choice, choose a value of @samp{0x80000001} if instructions | |
7997 | exist that set both the sign and low-order bits but do not define the | |
7998 | others. | |
7999 | ||
8000 | @item | |
8001 | Otherwise, use a value of @samp{0x80000000}. | |
8002 | @end itemize | |
8003 | ||
8004 | Many machines can produce both the value chosen for | |
8005 | @code{STORE_FLAG_VALUE} and its negation in the same number of | |
8006 | instructions. On those machines, you should also define a pattern for | |
8007 | those cases, e.g., one matching | |
8008 | ||
8009 | @smallexample | |
8010 | (set @var{A} (neg:@var{m} (ne:@var{m} @var{B} @var{C}))) | |
8011 | @end smallexample | |
8012 | ||
8013 | Some machines can also perform @code{and} or @code{plus} operations on | |
8014 | condition code values with less instructions than the corresponding | |
8015 | @samp{s@var{cond}} insn followed by @code{and} or @code{plus}. On those | |
8016 | machines, define the appropriate patterns. Use the names @code{incscc} | |
8017 | and @code{decscc}, respectively, for the patterns which perform | |
8018 | @code{plus} or @code{minus} operations on condition code values. See | |
8019 | @file{rs6000.md} for some examples. The GNU Superoptizer can be used to | |
8020 | find such instruction sequences on other machines. | |
8021 | ||
8022 | You need not define @code{STORE_FLAG_VALUE} if the machine has no store-flag | |
8023 | instructions. | |
8024 | ||
8025 | @findex FLOAT_STORE_FLAG_VALUE | |
12530dbe RH |
8026 | @item FLOAT_STORE_FLAG_VALUE (@var{mode}) |
8027 | A C expression that gives a non-zero @code{REAL_VALUE_TYPE} value that is | |
feca2ed3 JW |
8028 | returned when comparison operators with floating-point results are true. |
8029 | Define this macro on machine that have comparison operations that return | |
8030 | floating-point values. If there are no such operations, do not define | |
8031 | this macro. | |
8032 | ||
8033 | @findex Pmode | |
8034 | @item Pmode | |
8035 | An alias for the machine mode for pointers. On most machines, define | |
8036 | this to be the integer mode corresponding to the width of a hardware | |
8037 | pointer; @code{SImode} on 32-bit machine or @code{DImode} on 64-bit machines. | |
8038 | On some machines you must define this to be one of the partial integer | |
8039 | modes, such as @code{PSImode}. | |
8040 | ||
8041 | The width of @code{Pmode} must be at least as large as the value of | |
8042 | @code{POINTER_SIZE}. If it is not equal, you must define the macro | |
8043 | @code{POINTERS_EXTEND_UNSIGNED} to specify how pointers are extended | |
8044 | to @code{Pmode}. | |
8045 | ||
8046 | @findex FUNCTION_MODE | |
8047 | @item FUNCTION_MODE | |
8048 | An alias for the machine mode used for memory references to functions | |
8049 | being called, in @code{call} RTL expressions. On most machines this | |
8050 | should be @code{QImode}. | |
8051 | ||
8052 | @findex INTEGRATE_THRESHOLD | |
8053 | @item INTEGRATE_THRESHOLD (@var{decl}) | |
8054 | A C expression for the maximum number of instructions above which the | |
8055 | function @var{decl} should not be inlined. @var{decl} is a | |
8056 | @code{FUNCTION_DECL} node. | |
8057 | ||
8058 | The default definition of this macro is 64 plus 8 times the number of | |
8059 | arguments that the function accepts. Some people think a larger | |
8060 | threshold should be used on RISC machines. | |
8061 | ||
8062 | @findex SCCS_DIRECTIVE | |
8063 | @item SCCS_DIRECTIVE | |
8064 | Define this if the preprocessor should ignore @code{#sccs} directives | |
8065 | and print no error message. | |
8066 | ||
8067 | @findex NO_IMPLICIT_EXTERN_C | |
8068 | @item NO_IMPLICIT_EXTERN_C | |
8069 | Define this macro if the system header files support C++ as well as C. | |
8070 | This macro inhibits the usual method of using system header files in | |
8071 | C++, which is to pretend that the file's contents are enclosed in | |
8072 | @samp{extern "C" @{@dots{}@}}. | |
8073 | ||
8074 | @findex HANDLE_PRAGMA | |
8b97c5f8 ZW |
8075 | @item HANDLE_PRAGMA (@var{getc}, @var{ungetc}, @var{name}) |
8076 | This macro is no longer supported. You must use | |
8077 | @code{REGISTER_TARGET_PRAGMAS} instead. | |
8078 | ||
8079 | @findex REGISTER_TARGET_PRAGMAS | |
feca2ed3 JW |
8080 | @findex #pragma |
8081 | @findex pragma | |
8b97c5f8 ZW |
8082 | @item REGISTER_TARGET_PRAGMAS (@var{pfile}) |
8083 | Define this macro if you want to implement any target-specific pragmas. | |
8084 | If defined, it is a C expression which makes a series of calls to the | |
8085 | @code{cpp_register_pragma} and/or @code{cpp_register_pragma_space} | |
8086 | functions. The @var{pfile} argument is the first argument to supply to | |
8087 | these functions. The macro may also do setup required for the pragmas. | |
8088 | ||
8089 | The primary reason to define this macro is to provide compatibility with | |
8090 | other compilers for the same target. In general, we discourage | |
8091 | definition of target-specific pragmas for GCC. | |
feca2ed3 | 8092 | |
3b7a2e58 | 8093 | If the pragma can be implemented by attributes then the macro |
f09db6e0 NC |
8094 | @samp{INSERT_ATTRIBUTES} might be a useful one to define as well. |
8095 | ||
8b97c5f8 ZW |
8096 | Preprocessor macros that appear on pragma lines are not expanded. All |
8097 | @samp{#pragma} directives that do not match any registered pragma are | |
8098 | silently ignored, unless the user specifies @samp{-Wunknown-pragmas}. | |
8099 | ||
8100 | @deftypefun void cpp_register_pragma (cpp_reader *@var{pfile}, const char *@var{space}, const char *@var{name}, void (*@var{callback}) (cpp_reader *)) | |
8101 | ||
8102 | Each call to @code{cpp_register_pragma} establishes one pragma. The | |
8103 | @var{callback} routine will be called when the preprocessor encounters a | |
8104 | pragma of the form | |
8105 | ||
8106 | @smallexample | |
8107 | #pragma [@var{space}] @var{name} @dots{} | |
8108 | @end smallexample | |
8109 | ||
8110 | @var{space} must have been the subject of a previous call to | |
8111 | @code{cpp_register_pragma_space}, or else be a null pointer. The | |
8112 | callback routine receives @var{pfile} as its first argument, but must | |
8113 | not use it for anything (this may change in the future). It may read | |
8114 | any text after the @var{name} by making calls to @code{c_lex}. Text | |
8115 | which is not read by the callback will be silently ignored. | |
8116 | ||
8117 | Note that both @var{space} and @var{name} are case sensitive. | |
8118 | ||
8119 | For an example use of this routine, see @file{c4x.h} and the callback | |
8120 | routines defined in @file{c4x.c}. | |
aac69a49 NC |
8121 | |
8122 | Note that the use of @code{c_lex} is specific to the C and C++ | |
8123 | compilers. It will not work in the Java or Fortran compilers, or any | |
8124 | other language compilers for that matter. Thus if @code{c_lex} is going | |
8125 | to be called from target-specific code, it must only be done so when | |
8126 | building hte C and C++ compilers. This can be done by defining the | |
8127 | variables @code{c_target_objs} and @code{cxx_target_objs} in the | |
8128 | target entry in the @code{config.gcc} file. These variables should name | |
8129 | the target-specific, language-specific object file which contains the | |
8130 | code that uses @code{c_lex}. Note it will also be necessary to add a | |
8131 | rule to the makefile fragment pointed to by @code{tmake_file} that shows | |
8132 | how to build this object file. | |
8b97c5f8 ZW |
8133 | @end deftypefun |
8134 | ||
8135 | @deftypefun void cpp_register_pragma_space (cpp_reader *@var{pfile}, const char *@var{space}) | |
8136 | This routine establishes a namespace for pragmas, which will be | |
8137 | registered by subsequent calls to @code{cpp_register_pragma}. For | |
8138 | example, pragmas defined by the C standard are in the @samp{STDC} | |
8139 | namespace, and pragmas specific to GCC are in the @samp{GCC} namespace. | |
8140 | ||
8141 | For an example use of this routine in a target header, see @file{v850.h}. | |
8142 | @end deftypefun | |
f09db6e0 | 8143 | |
e2af664c NC |
8144 | @findex HANDLE_SYSV_PRAGMA |
8145 | @findex #pragma | |
8146 | @findex pragma | |
8147 | @item HANDLE_SYSV_PRAGMA | |
8148 | Define this macro (to a value of 1) if you want the System V style | |
8149 | pragmas @samp{#pragma pack(<n>)} and @samp{#pragma weak <name> | |
8150 | [=<value>]} to be supported by gcc. | |
8151 | ||
8152 | The pack pragma specifies the maximum alignment (in bytes) of fields | |
8153 | within a structure, in much the same way as the @samp{__aligned__} and | |
8154 | @samp{__packed__} @code{__attribute__}s do. A pack value of zero resets | |
8155 | the behaviour to the default. | |
8156 | ||
8157 | The weak pragma only works if @code{SUPPORTS_WEAK} and | |
8158 | @code{ASM_WEAKEN_LABEL} are defined. If enabled it allows the creation | |
8159 | of specifically named weak labels, optionally with a value. | |
8160 | ||
8161 | @findex HANDLE_PRAGMA_PACK_PUSH_POP | |
8162 | @findex #pragma | |
8163 | @findex pragma | |
8164 | @item HANDLE_PRAGMA_PACK_PUSH_POP | |
8165 | Define this macro (to a value of 1) if you want to support the Win32 | |
8166 | style pragmas @samp{#pragma pack(push,<n>)} and @samp{#pragma | |
8167 | pack(pop)}. The pack(push,<n>) pragma specifies the maximum alignment | |
8168 | (in bytes) of fields within a structure, in much the same way as the | |
8169 | @samp{__aligned__} and @samp{__packed__} @code{__attribute__}s do. A | |
8170 | pack value of zero resets the behaviour to the default. Successive | |
8171 | invocations of this pragma cause the previous values to be stacked, so | |
8172 | that invocations of @samp{#pragma pack(pop)} will return to the previous | |
8173 | value. | |
8174 | ||
feca2ed3 JW |
8175 | @findex VALID_MACHINE_DECL_ATTRIBUTE |
8176 | @item VALID_MACHINE_DECL_ATTRIBUTE (@var{decl}, @var{attributes}, @var{identifier}, @var{args}) | |
8177 | If defined, a C expression whose value is nonzero if @var{identifier} with | |
8178 | arguments @var{args} is a valid machine specific attribute for @var{decl}. | |
8179 | The attributes in @var{attributes} have previously been assigned to @var{decl}. | |
8180 | ||
8181 | @findex VALID_MACHINE_TYPE_ATTRIBUTE | |
8182 | @item VALID_MACHINE_TYPE_ATTRIBUTE (@var{type}, @var{attributes}, @var{identifier}, @var{args}) | |
8183 | If defined, a C expression whose value is nonzero if @var{identifier} with | |
8184 | arguments @var{args} is a valid machine specific attribute for @var{type}. | |
8185 | The attributes in @var{attributes} have previously been assigned to @var{type}. | |
8186 | ||
8187 | @findex COMP_TYPE_ATTRIBUTES | |
8188 | @item COMP_TYPE_ATTRIBUTES (@var{type1}, @var{type2}) | |
8189 | If defined, a C expression whose value is zero if the attributes on | |
8190 | @var{type1} and @var{type2} are incompatible, one if they are compatible, | |
8191 | and two if they are nearly compatible (which causes a warning to be | |
8192 | generated). | |
8193 | ||
8194 | @findex SET_DEFAULT_TYPE_ATTRIBUTES | |
8195 | @item SET_DEFAULT_TYPE_ATTRIBUTES (@var{type}) | |
8196 | If defined, a C statement that assigns default attributes to | |
8197 | newly defined @var{type}. | |
8198 | ||
d9525bec BK |
8199 | @findex MERGE_MACHINE_TYPE_ATTRIBUTES |
8200 | @item MERGE_MACHINE_TYPE_ATTRIBUTES (@var{type1}, @var{type2}) | |
8201 | Define this macro if the merging of type attributes needs special handling. | |
8202 | If defined, the result is a list of the combined TYPE_ATTRIBUTES of | |
8203 | @var{type1} and @var{type2}. It is assumed that comptypes has already been | |
8204 | called and returned 1. | |
8205 | ||
8206 | @findex MERGE_MACHINE_DECL_ATTRIBUTES | |
8207 | @item MERGE_MACHINE_DECL_ATTRIBUTES (@var{olddecl}, @var{newdecl}) | |
8208 | Define this macro if the merging of decl attributes needs special handling. | |
8209 | If defined, the result is a list of the combined DECL_MACHINE_ATTRIBUTES of | |
8210 | @var{olddecl} and @var{newdecl}. @var{newdecl} is a duplicate declaration | |
8211 | of @var{olddecl}. Examples of when this is needed are when one attribute | |
8212 | overrides another, or when an attribute is nullified by a subsequent | |
8213 | definition. | |
8214 | ||
f09db6e0 NC |
8215 | @findex INSERT_ATTRIBUTES |
8216 | @item INSERT_ATTRIBUTES (@var{node}, @var{attr_ptr}, @var{prefix_ptr}) | |
8217 | Define this macro if you want to be able to add attributes to a decl | |
8218 | when it is being created. This is normally useful for backends which | |
8219 | wish to implement a pragma by using the attributes which correspond to | |
8220 | the pragma's effect. The @var{node} argument is the decl which is being | |
8221 | created. The @var{attr_ptr} argument is a pointer to the attribute list | |
8222 | for this decl. The @var{prefix_ptr} is a pointer to the list of | |
8223 | attributes that have appeared after the specifiers and modifiers of the | |
8224 | declaration, but before the declaration proper. | |
8225 | ||
9ec36da5 JL |
8226 | @findex SET_DEFAULT_DECL_ATTRIBUTES |
8227 | @item SET_DEFAULT_DECL_ATTRIBUTES (@var{decl}, @var{attributes}) | |
8228 | If defined, a C statement that assigns default attributes to | |
8229 | newly defined @var{decl}. | |
8230 | ||
feca2ed3 JW |
8231 | @findex DOLLARS_IN_IDENTIFIERS |
8232 | @item DOLLARS_IN_IDENTIFIERS | |
8233 | Define this macro to control use of the character @samp{$} in identifier | |
37d13a29 | 8234 | names. 0 means @samp{$} is not allowed by default; 1 means it is allowed. |
feca2ed3 | 8235 | 1 is the default; there is no need to define this macro in that case. |
37d13a29 | 8236 | This macro controls the compiler proper; it does not affect the preprocessor. |
feca2ed3 JW |
8237 | |
8238 | @findex NO_DOLLAR_IN_LABEL | |
8239 | @item NO_DOLLAR_IN_LABEL | |
8240 | Define this macro if the assembler does not accept the character | |
8241 | @samp{$} in label names. By default constructors and destructors in | |
8242 | G++ have @samp{$} in the identifiers. If this macro is defined, | |
8243 | @samp{.} is used instead. | |
8244 | ||
8245 | @findex NO_DOT_IN_LABEL | |
8246 | @item NO_DOT_IN_LABEL | |
8247 | Define this macro if the assembler does not accept the character | |
8248 | @samp{.} in label names. By default constructors and destructors in G++ | |
8249 | have names that use @samp{.}. If this macro is defined, these names | |
8250 | are rewritten to avoid @samp{.}. | |
8251 | ||
8252 | @findex DEFAULT_MAIN_RETURN | |
8253 | @item DEFAULT_MAIN_RETURN | |
8254 | Define this macro if the target system expects every program's @code{main} | |
8255 | function to return a standard ``success'' value by default (if no other | |
8256 | value is explicitly returned). | |
8257 | ||
8258 | The definition should be a C statement (sans semicolon) to generate the | |
8259 | appropriate rtl instructions. It is used only when compiling the end of | |
8260 | @code{main}. | |
8261 | ||
c063dc98 JM |
8262 | @item NEED_ATEXIT |
8263 | @findex NEED_ATEXIT | |
8264 | Define this if the target system lacks the function @code{atexit} | |
5490d604 | 8265 | from the ISO C standard. If this macro is defined, a default definition |
c063dc98 JM |
8266 | will be provided to support C++. If @code{ON_EXIT} is not defined, |
8267 | a default @code{exit} function will also be provided. | |
8268 | ||
8269 | @item ON_EXIT | |
8270 | @findex ON_EXIT | |
8271 | Define this macro if the target has another way to implement atexit | |
8272 | functionality without replacing @code{exit}. For instance, SunOS 4 has | |
8273 | a similar @code{on_exit} library function. | |
8274 | ||
8275 | The definition should be a functional macro which can be used just like | |
8276 | the @code{atexit} function. | |
feca2ed3 JW |
8277 | |
8278 | @item EXIT_BODY | |
8279 | @findex EXIT_BODY | |
8280 | Define this if your @code{exit} function needs to do something | |
8281 | besides calling an external function @code{_cleanup} before | |
8282 | terminating with @code{_exit}. The @code{EXIT_BODY} macro is | |
9e9b9afe JM |
8283 | only needed if @code{NEED_ATEXIT} is defined and @code{ON_EXIT} is not |
8284 | defined. | |
feca2ed3 JW |
8285 | |
8286 | @findex INSN_SETS_ARE_DELAYED | |
8287 | @item INSN_SETS_ARE_DELAYED (@var{insn}) | |
8288 | Define this macro as a C expression that is nonzero if it is safe for the | |
8289 | delay slot scheduler to place instructions in the delay slot of @var{insn}, | |
8290 | even if they appear to use a resource set or clobbered in @var{insn}. | |
a3a15b4d | 8291 | @var{insn} is always a @code{jump_insn} or an @code{insn}; GCC knows that |
feca2ed3 JW |
8292 | every @code{call_insn} has this behavior. On machines where some @code{insn} |
8293 | or @code{jump_insn} is really a function call and hence has this behavior, | |
8294 | you should define this macro. | |
8295 | ||
8296 | You need not define this macro if it would always return zero. | |
8297 | ||
8298 | @findex INSN_REFERENCES_ARE_DELAYED | |
8299 | @item INSN_REFERENCES_ARE_DELAYED (@var{insn}) | |
8300 | Define this macro as a C expression that is nonzero if it is safe for the | |
8301 | delay slot scheduler to place instructions in the delay slot of @var{insn}, | |
8302 | even if they appear to set or clobber a resource referenced in @var{insn}. | |
8303 | @var{insn} is always a @code{jump_insn} or an @code{insn}. On machines where | |
8304 | some @code{insn} or @code{jump_insn} is really a function call and its operands | |
8305 | are registers whose use is actually in the subroutine it calls, you should | |
8306 | define this macro. Doing so allows the delay slot scheduler to move | |
8307 | instructions which copy arguments into the argument registers into the delay | |
8308 | slot of @var{insn}. | |
8309 | ||
8310 | You need not define this macro if it would always return zero. | |
8311 | ||
8312 | @findex MACHINE_DEPENDENT_REORG | |
8313 | @item MACHINE_DEPENDENT_REORG (@var{insn}) | |
8314 | In rare cases, correct code generation requires extra machine | |
8315 | dependent processing between the second jump optimization pass and | |
8316 | delayed branch scheduling. On those machines, define this macro as a C | |
8317 | statement to act on the code starting at @var{insn}. | |
8318 | ||
861bb6c1 JL |
8319 | @findex MULTIPLE_SYMBOL_SPACES |
8320 | @item MULTIPLE_SYMBOL_SPACES | |
8321 | Define this macro if in some cases global symbols from one translation | |
8322 | unit may not be bound to undefined symbols in another translation unit | |
8323 | without user intervention. For instance, under Microsoft Windows | |
8324 | symbols must be explicitly imported from shared libraries (DLLs). | |
8325 | ||
57bcb97a RH |
8326 | @findex MD_ASM_CLOBBERS |
8327 | @item MD_ASM_CLOBBERS | |
8328 | A C statement that adds to @var{CLOBBERS} @code{STRING_CST} trees for | |
8329 | any hard regs the port wishes to automatically clobber for all asms. | |
8330 | ||
70cfa7ad MM |
8331 | @findex ISSUE_RATE |
8332 | @item ISSUE_RATE | |
8333 | A C expression that returns how many instructions can be issued at the | |
a89608cb | 8334 | same time if the machine is a superscalar machine. |
70cfa7ad | 8335 | |
e4da5f6d | 8336 | @findex MD_SCHED_INIT |
79c2ffde | 8337 | @item MD_SCHED_INIT (@var{file}, @var{verbose}, @var{max_ready}) |
a89608cb | 8338 | A C statement which is executed by the scheduler at the |
e4da5f6d MM |
8339 | beginning of each block of instructions that are to be scheduled. |
8340 | @var{file} is either a null pointer, or a stdio stream to write any | |
8341 | debug output to. @var{verbose} is the verbose level provided by | |
79c2ffde BS |
8342 | @samp{-fsched-verbose-}@var{n}. @var{max_ready} is the maximum number |
8343 | of insns in the current scheduling region that can be live at the same | |
8344 | time. This can be used to allocate scratch space if it is needed. | |
8345 | ||
8346 | @findex MD_SCHED_FINISH | |
8347 | @item MD_SCHED_FINISH (@var{file}, @var{verbose}) | |
8348 | A C statement which is executed by the scheduler at the end of each block | |
8349 | of instructions that are to be scheduled. It can be used to perform | |
8350 | cleanup of any actions done by the other scheduling macros. | |
8351 | @var{file} is either a null pointer, or a stdio stream to write any | |
8352 | debug output to. @var{verbose} is the verbose level provided by | |
e4da5f6d MM |
8353 | @samp{-fsched-verbose-}@var{n}. |
8354 | ||
8355 | @findex MD_SCHED_REORDER | |
8760eaae | 8356 | @item MD_SCHED_REORDER (@var{file}, @var{verbose}, @var{ready}, @var{n_ready}, @var{clock}, @var{can_issue_more}) |
a89608cb | 8357 | A C statement which is executed by the scheduler after it |
e4da5f6d MM |
8358 | has scheduled the ready list to allow the machine description to reorder |
8359 | it (for example to combine two small instructions together on | |
8360 | @samp{VLIW} machines). @var{file} is either a null pointer, or a stdio | |
8361 | stream to write any debug output to. @var{verbose} is the verbose level | |
8362 | provided by @samp{-fsched-verbose-}@var{n}. @var{ready} is a pointer to | |
8363 | the ready list of instructions that are ready to be scheduled. | |
8364 | @var{n_ready} is the number of elements in the ready list. The | |
8365 | scheduler reads the ready list in reverse order, starting with | |
197043f5 RH |
8366 | @var{ready}[@var{n_ready}-1] and going to @var{ready}[0]. @var{clock} |
8367 | is the timer tick of the scheduler. @var{can_issue_more} is an output | |
8368 | parameter that is set to the number of insns that can issue this clock; | |
79c2ffde BS |
8369 | normally this is just @code{issue_rate}. See also @samp{MD_SCHED_REORDER2}. |
8370 | ||
8371 | @findex MD_SCHED_REORDER2 | |
8372 | @item MD_SCHED_REORDER2 (@var{file}, @var{verbose}, @var{ready}, @var{n_ready}, @var{clock}, @var{can_issue_more}) | |
8373 | Like @samp{MD_SCHED_REORDER}, but called at a different time. While the | |
8374 | @samp{MD_SCHED_REORDER} macro is called whenever the scheduler starts a | |
8375 | new cycle, this macro is used immediately after @samp{MD_SCHED_VARIABLE_ISSUE} | |
8376 | is called; it can reorder the ready list and set @var{can_issue_more} to | |
8377 | determine whether there are more insns to be scheduled in the same cycle. | |
8378 | Defining this macro can be useful if there are frequent situations where | |
8379 | scheduling one insn causes other insns to become ready in the same cycle, | |
8380 | these other insns can then be taken into account properly. | |
e4da5f6d MM |
8381 | |
8382 | @findex MD_SCHED_VARIABLE_ISSUE | |
8383 | @item MD_SCHED_VARIABLE_ISSUE (@var{file}, @var{verbose}, @var{insn}, @var{more}) | |
a89608cb | 8384 | A C statement which is executed by the scheduler after it |
e4da5f6d MM |
8385 | has scheduled an insn from the ready list. @var{file} is either a null |
8386 | pointer, or a stdio stream to write any debug output to. @var{verbose} | |
8387 | is the verbose level provided by @samp{-fsched-verbose-}@var{n}. | |
8388 | @var{insn} is the instruction that was scheduled. @var{more} is the | |
8389 | number of instructions that can be issued in the current cycle. The | |
8390 | @samp{MD_SCHED_VARIABLE_ISSUE} macro is responsible for updating the | |
8391 | value of @var{more} (typically by @var{more}--). | |
8392 | ||
dbecbbe4 JL |
8393 | @findex MAX_INTEGER_COMPUTATION_MODE |
8394 | @item MAX_INTEGER_COMPUTATION_MODE | |
8395 | Define this to the largest integer machine mode which can be used for | |
8396 | operations other than load, store and copy operations. | |
8397 | ||
8398 | You need only define this macro if the target holds values larger than | |
8399 | @code{word_mode} in general purpose registers. Most targets should not define | |
8400 | this macro. | |
f89223a9 | 8401 | |
71d718e0 JM |
8402 | @findex MATH_LIBRARY |
8403 | @item MATH_LIBRARY | |
8404 | Define this macro as a C string constant for the linker argument to link | |
8405 | in the system math library, or @samp{""} if the target does not have a | |
8406 | separate math library. | |
8407 | ||
8408 | You need only define this macro if the default of @samp{"-lm"} is wrong. | |
512b62fb JM |
8409 | |
8410 | @findex LIBRARY_PATH_ENV | |
8411 | @item LIBRARY_PATH_ENV | |
8412 | Define this macro as a C string constant for the environment variable that | |
8413 | specifies where the linker should look for libraries. | |
8414 | ||
8415 | You need only define this macro if the default of @samp{"LIBRARY_PATH"} | |
8416 | is wrong. | |
e09d24ff R |
8417 | |
8418 | @findex TARGET_HAS_F_SETLKW | |
8419 | @item TARGET_HAS_F_SETLKW | |
7c714ee1 | 8420 | Define this macro if the target supports file locking with fcntl / F_SETLKW. |
e09d24ff R |
8421 | Note that this functionality is part of POSIX. |
8422 | Defining @code{TARGET_HAS_F_SETLKW} will enable the test coverage code | |
8423 | to use file locking when exiting a program, which avoids race conditions | |
8424 | if the program has forked. | |
0c99ec5c RH |
8425 | |
8426 | @findex MAX_CONDITIONAL_EXECUTE | |
8427 | @item MAX_CONDITIONAL_EXECUTE | |
8428 | ||
8429 | A C expression for the maximum number of instructions to execute via | |
8430 | conditional execution instructions instead of a branch. A value of | |
8431 | @code{BRANCH_COST}+1 is the default if the machine does not use cc0, and | |
8432 | 1 if it does use cc0. | |
90280148 MM |
8433 | |
8434 | @findex IFCVT_MODIFY_TESTS | |
8435 | @item IFCVT_MODIFY_TESTS | |
8436 | A C expression to modify the tests in @code{TRUE_EXPR}, and | |
8437 | @code{FALSE_EXPPR} for use in converting insns in @code{TEST_BB}, | |
8438 | @code{THEN_BB}, @code{ELSE_BB}, and @code{JOIN_BB} basic blocks to | |
8439 | conditional execution. Set either @code{TRUE_EXPR} or @code{FALSE_EXPR} | |
8440 | to a null pointer if the tests cannot be converted. | |
8441 | ||
8442 | @findex IFCVT_MODIFY_INSN | |
8443 | @item IFCVT_MODIFY_INSN | |
8444 | A C expression to modify the @code{PATTERN} of an @code{INSN} that is to | |
8445 | be converted to conditional execution format. | |
8446 | ||
8447 | @findex IFCVT_MODIFY_FINAL | |
8448 | @item IFCVT_MODIFY_FINAL | |
8449 | A C expression to perform any final machine dependent modifications in | |
8450 | converting code to conditional execution in the basic blocks | |
8451 | @code{TEST_BB}, @code{THEN_BB}, @code{ELSE_BB}, and @code{JOIN_BB}. | |
8452 | ||
8453 | @findex IFCVT_MODIFY_CANCEL | |
8454 | @item IFCVT_MODIFY_CANCEL | |
8455 | A C expression to cancel any machine dependent modifications in | |
8456 | converting code to conditional execution in the basic blocks | |
8457 | @code{TEST_BB}, @code{THEN_BB}, @code{ELSE_BB}, and @code{JOIN_BB}. | |
4a1d48f6 BS |
8458 | |
8459 | @findex MD_INIT_BUILTINS | |
8460 | @item MD_INIT_BUILTINS | |
8461 | Define this macro if you have any machine-specific builtin functions that | |
8462 | need to be defined. It should be a C expression that performs the | |
8463 | necessary setup. | |
8464 | ||
8465 | Machine specific builtins can be useful to expand special machine | |
8466 | instructions that would otherwise not normally be generated because | |
8467 | they have no equivalent in the source language (for example, SIMD vector | |
8468 | instructions or prefetch instructions). | |
8469 | ||
8470 | To create a builtin function, call the function @code{builtin_function} | |
8471 | which is defined by the language frontend. You can use any type nodes set | |
8472 | up by @code{build_common_tree_nodes} and @code{build_common_tree_nodes_2}; | |
8473 | only language frontends that use these two functions will use | |
8474 | @samp{MD_INIT_BUILTINS}. | |
8475 | ||
8476 | @findex MD_EXPAND_BUILTIN | |
8477 | @item MD_EXPAND_BUILTIN(@var{exp}, @var{target}, @var{subtarget}, @var{mode}, @var{ignore}) | |
8478 | ||
8479 | Expand a call to a machine specific builtin that was set up by | |
8480 | @samp{MD_INIT_BUILTINS}. @var{exp} is the expression for the function call; | |
8481 | the result should go to @var{target} if that is convenient, and have mode | |
8482 | @var{mode} if that is convenient. @var{subtarget} may be used as the target | |
8483 | for computing one of @var{exp}'s operands. @var{ignore} is nonzero if the value | |
8484 | is to be ignored. | |
8485 | This macro should return the result of the call to the builtin. | |
8486 | ||
feca2ed3 | 8487 | @end table |