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7aeffc5f | 1 | /* IPA visibility pass |
fbd26352 | 2 | Copyright (C) 2003-2019 Free Software Foundation, Inc. |
7aeffc5f | 3 | |
4 | This file is part of GCC. | |
5 | ||
6 | GCC is free software; you can redistribute it and/or modify it under | |
7 | the terms of the GNU General Public License as published by the Free | |
8 | Software Foundation; either version 3, or (at your option) any later | |
9 | version. | |
10 | ||
11 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
12 | WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
13 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
14 | for more details. | |
15 | ||
16 | You should have received a copy of the GNU General Public License | |
17 | along with GCC; see the file COPYING3. If not see | |
18 | <http://www.gnu.org/licenses/>. */ | |
19 | ||
20 | /* This file implements two related passes: | |
21 | ||
22 | - pass_data_ipa_function_and_variable_visibility run just after | |
23 | symbol table, references and callgraph are built | |
24 | ||
25 | - pass_data_ipa_function_and_variable_visibility run as first | |
26 | proper IPA pass (that is after early optimization, or, (with LTO) | |
27 | as a first pass done at link-time. | |
28 | ||
29 | Purpose of both passes is to set correctly visibility properties | |
30 | of all symbols. This includes: | |
31 | ||
32 | - Symbol privatization: | |
33 | ||
34 | Some symbols that are declared public by frontend may be | |
35 | turned local (either by -fwhole-program flag, by linker plugin feedback | |
36 | or by other reasons) | |
37 | ||
38 | - Discovery of local functions: | |
39 | ||
40 | A local function is one whose calls can occur only in the current | |
41 | compilation unit and all its calls are explicit, so we can change | |
42 | its calling convention. We simply mark all static functions whose | |
43 | address is not taken as local. | |
44 | ||
f4d3c071 | 45 | externally_visible flag is set for symbols that cannot be privatized. |
7aeffc5f | 46 | For privatized symbols we clear TREE_PUBLIC flag and dismantle comdat |
47 | group. | |
48 | ||
49 | - Dismantling of comdat groups: | |
50 | ||
51 | Comdat group represent a section that may be replaced by linker by | |
52 | a different copy of the same section from other unit. | |
53 | If we have resolution information (from linker plugin) and we know that | |
54 | a given comdat gorup is prevailing, we can dismantle it and turn symbols | |
55 | into normal symbols. If the resolution information says that the | |
56 | section was previaled by copy from non-LTO code, we can also dismantle | |
57 | it and turn all symbols into external. | |
58 | ||
59 | - Local aliases: | |
60 | ||
61 | Some symbols can be interposed by dynamic linker. Refering to these | |
62 | symbols is expensive, since it needs to be overwritable by the dynamic | |
63 | linker. In some cases we know that the interposition does not change | |
64 | semantic and we can always refer to a local copy (as in the case of | |
65 | inline function). In this case we produce a local alias and redirect | |
66 | calls to it. | |
67 | ||
68 | TODO: This should be done for references, too. | |
69 | ||
70 | - Removal of static ocnstructors and destructors that have no side effects. | |
71 | ||
72 | - Regularization of several oddities introduced by frontends that may | |
73 | be impractical later in the optimization queue. */ | |
74 | ||
75 | #include "config.h" | |
76 | #include "system.h" | |
77 | #include "coretypes.h" | |
78 | #include "tm.h" | |
1140c305 | 79 | #include "function.h" |
7c29e30e | 80 | #include "tree.h" |
81 | #include "gimple-expr.h" | |
7aeffc5f | 82 | #include "tree-pass.h" |
7c29e30e | 83 | #include "cgraph.h" |
7aeffc5f | 84 | #include "calls.h" |
825463d4 | 85 | #include "varasm.h" |
322f1ba9 | 86 | #include "ipa-utils.h" |
30a86690 | 87 | #include "stringpool.h" |
88 | #include "attribs.h" | |
7aeffc5f | 89 | |
f4d3c071 | 90 | /* Return true when NODE cannot be local. Worker for cgraph_local_node_p. */ |
7aeffc5f | 91 | |
c5e076fc | 92 | static bool |
93 | non_local_p (struct cgraph_node *node, void *data ATTRIBUTE_UNUSED) | |
7aeffc5f | 94 | { |
a09576fe | 95 | return !(node->only_called_directly_or_aliased_p () |
83582d71 | 96 | /* i386 would need update to output thunk with local calling |
280ce47d | 97 | conventions. */ |
a09576fe | 98 | && !node->thunk.thunk_p |
99 | && node->definition | |
100 | && !DECL_EXTERNAL (node->decl) | |
280ce47d | 101 | && !lookup_attribute ("noipa", DECL_ATTRIBUTES (node->decl)) |
a09576fe | 102 | && !node->externally_visible |
103 | && !node->used_from_other_partition | |
72db0954 | 104 | && !node->in_other_partition |
105 | && node->get_availability () >= AVAIL_AVAILABLE); | |
7aeffc5f | 106 | } |
107 | ||
108 | /* Return true when function can be marked local. */ | |
109 | ||
110 | bool | |
415d1b9a | 111 | cgraph_node::local_p (void) |
7aeffc5f | 112 | { |
415d1b9a | 113 | cgraph_node *n = ultimate_alias_target (); |
7aeffc5f | 114 | |
7aeffc5f | 115 | if (n->thunk.thunk_p) |
a09576fe | 116 | return n->callees->callee->local_p (); |
c5e076fc | 117 | return !n->call_for_symbol_thunks_and_aliases (non_local_p, |
a09576fe | 118 | NULL, true); |
7aeffc5f | 119 | |
120 | } | |
121 | ||
7aeffc5f | 122 | /* A helper for comdat_can_be_unshared_p. */ |
123 | ||
124 | static bool | |
125 | comdat_can_be_unshared_p_1 (symtab_node *node) | |
126 | { | |
127 | if (!node->externally_visible) | |
128 | return true; | |
ce7711df | 129 | if (node->address_can_be_compared_p ()) |
130 | { | |
131 | struct ipa_ref *ref; | |
132 | ||
133 | for (unsigned int i = 0; node->iterate_referring (i, ref); i++) | |
134 | if (ref->address_matters_p ()) | |
135 | return false; | |
136 | } | |
7aeffc5f | 137 | |
138 | /* If the symbol is used in some weird way, better to not touch it. */ | |
139 | if (node->force_output) | |
140 | return false; | |
141 | ||
142 | /* Explicit instantiations needs to be output when possibly | |
143 | used externally. */ | |
144 | if (node->forced_by_abi | |
145 | && TREE_PUBLIC (node->decl) | |
146 | && (node->resolution != LDPR_PREVAILING_DEF_IRONLY | |
147 | && !flag_whole_program)) | |
148 | return false; | |
149 | ||
f4d3c071 | 150 | /* Non-readonly and volatile variables cannot be duplicated. */ |
7aeffc5f | 151 | if (is_a <varpool_node *> (node) |
152 | && (!TREE_READONLY (node->decl) | |
153 | || TREE_THIS_VOLATILE (node->decl))) | |
154 | return false; | |
155 | return true; | |
156 | } | |
157 | ||
158 | /* COMDAT functions must be shared only if they have address taken, | |
159 | otherwise we can produce our own private implementation with | |
160 | -fwhole-program. | |
f4d3c071 | 161 | Return true when turning COMDAT function static cannot lead to wrong |
7aeffc5f | 162 | code when the resulting object links with a library defining same COMDAT. |
163 | ||
164 | Virtual functions do have their addresses taken from the vtables, | |
165 | but in C++ there is no way to compare their addresses for equality. */ | |
166 | ||
167 | static bool | |
168 | comdat_can_be_unshared_p (symtab_node *node) | |
169 | { | |
170 | if (!comdat_can_be_unshared_p_1 (node)) | |
171 | return false; | |
172 | if (node->same_comdat_group) | |
173 | { | |
174 | symtab_node *next; | |
175 | ||
176 | /* If more than one function is in the same COMDAT group, it must | |
177 | be shared even if just one function in the comdat group has | |
178 | address taken. */ | |
179 | for (next = node->same_comdat_group; | |
180 | next != node; next = next->same_comdat_group) | |
181 | if (!comdat_can_be_unshared_p_1 (next)) | |
182 | return false; | |
183 | } | |
184 | return true; | |
185 | } | |
186 | ||
187 | /* Return true when function NODE should be considered externally visible. */ | |
188 | ||
189 | static bool | |
190 | cgraph_externally_visible_p (struct cgraph_node *node, | |
191 | bool whole_program) | |
192 | { | |
e0dec29d | 193 | while (node->transparent_alias && node->definition) |
194 | node = node->get_alias_target (); | |
7aeffc5f | 195 | if (!node->definition) |
196 | return false; | |
197 | if (!TREE_PUBLIC (node->decl) | |
198 | || DECL_EXTERNAL (node->decl)) | |
199 | return false; | |
200 | ||
201 | /* Do not try to localize built-in functions yet. One of problems is that we | |
202 | end up mangling their asm for WHOPR that makes it impossible to call them | |
203 | using the implicit built-in declarations anymore. Similarly this enables | |
204 | us to remove them as unreachable before actual calls may appear during | |
205 | expansion or folding. */ | |
a0e9bfbb | 206 | if (fndecl_built_in_p (node->decl)) |
7aeffc5f | 207 | return true; |
208 | ||
209 | /* If linker counts on us, we must preserve the function. */ | |
415d1b9a | 210 | if (node->used_from_object_file_p ()) |
7aeffc5f | 211 | return true; |
212 | if (DECL_PRESERVE_P (node->decl)) | |
213 | return true; | |
214 | if (lookup_attribute ("externally_visible", | |
215 | DECL_ATTRIBUTES (node->decl))) | |
216 | return true; | |
280ce47d | 217 | if (lookup_attribute ("noipa", DECL_ATTRIBUTES (node->decl))) |
218 | return true; | |
7aeffc5f | 219 | if (TARGET_DLLIMPORT_DECL_ATTRIBUTES |
220 | && lookup_attribute ("dllexport", | |
221 | DECL_ATTRIBUTES (node->decl))) | |
222 | return true; | |
223 | if (node->resolution == LDPR_PREVAILING_DEF_IRONLY) | |
224 | return false; | |
aca3df3b | 225 | /* When doing LTO or whole program, we can bring COMDAT functoins static. |
7aeffc5f | 226 | This improves code quality and we know we will duplicate them at most twice |
227 | (in the case that we are not using plugin and link with object file | |
228 | implementing same COMDAT) */ | |
4c4a180d | 229 | if (((in_lto_p || whole_program) && !flag_incremental_link) |
7aeffc5f | 230 | && DECL_COMDAT (node->decl) |
231 | && comdat_can_be_unshared_p (node)) | |
232 | return false; | |
233 | ||
234 | /* When doing link time optimizations, hidden symbols become local. */ | |
4c4a180d | 235 | if ((in_lto_p && !flag_incremental_link) |
7aeffc5f | 236 | && (DECL_VISIBILITY (node->decl) == VISIBILITY_HIDDEN |
237 | || DECL_VISIBILITY (node->decl) == VISIBILITY_INTERNAL) | |
238 | /* Be sure that node is defined in IR file, not in other object | |
239 | file. In that case we don't set used_from_other_object_file. */ | |
240 | && node->definition) | |
241 | ; | |
242 | else if (!whole_program) | |
243 | return true; | |
244 | ||
245 | if (MAIN_NAME_P (DECL_NAME (node->decl))) | |
246 | return true; | |
247 | ||
248 | return false; | |
249 | } | |
250 | ||
97221fd7 | 251 | /* Return true when variable should be considered externally visible. */ |
7aeffc5f | 252 | |
253 | bool | |
97221fd7 | 254 | varpool_node::externally_visible_p (void) |
7aeffc5f | 255 | { |
e0dec29d | 256 | while (transparent_alias && definition) |
257 | return get_alias_target ()->externally_visible_p (); | |
97221fd7 | 258 | if (DECL_EXTERNAL (decl)) |
7aeffc5f | 259 | return true; |
260 | ||
97221fd7 | 261 | if (!TREE_PUBLIC (decl)) |
7aeffc5f | 262 | return false; |
263 | ||
264 | /* If linker counts on us, we must preserve the function. */ | |
97221fd7 | 265 | if (used_from_object_file_p ()) |
7aeffc5f | 266 | return true; |
267 | ||
78eb5b70 | 268 | /* Bringing TLS variables local may cause dynamic linker failures |
269 | on limits of static TLS vars. */ | |
270 | if (DECL_THREAD_LOCAL_P (decl) | |
271 | && (DECL_TLS_MODEL (decl) != TLS_MODEL_EMULATED | |
272 | && DECL_TLS_MODEL (decl) != TLS_MODEL_INITIAL_EXEC)) | |
273 | return true; | |
274 | ||
97221fd7 | 275 | if (DECL_HARD_REGISTER (decl)) |
7aeffc5f | 276 | return true; |
97221fd7 | 277 | if (DECL_PRESERVE_P (decl)) |
7aeffc5f | 278 | return true; |
279 | if (lookup_attribute ("externally_visible", | |
97221fd7 | 280 | DECL_ATTRIBUTES (decl))) |
7aeffc5f | 281 | return true; |
282 | if (TARGET_DLLIMPORT_DECL_ATTRIBUTES | |
283 | && lookup_attribute ("dllexport", | |
97221fd7 | 284 | DECL_ATTRIBUTES (decl))) |
7aeffc5f | 285 | return true; |
286 | ||
287 | /* See if we have linker information about symbol not being used or | |
288 | if we need to make guess based on the declaration. | |
289 | ||
290 | Even if the linker clams the symbol is unused, never bring internal | |
291 | symbols that are declared by user as used or externally visible. | |
292 | This is needed for i.e. references from asm statements. */ | |
97221fd7 | 293 | if (used_from_object_file_p ()) |
aca3df3b | 294 | return true; |
97221fd7 | 295 | if (resolution == LDPR_PREVAILING_DEF_IRONLY) |
7aeffc5f | 296 | return false; |
297 | ||
298 | /* As a special case, the COMDAT virtual tables can be unshared. | |
299 | In LTO mode turn vtables into static variables. The variable is readonly, | |
300 | so this does not enable more optimization, but referring static var | |
301 | is faster for dynamic linking. Also this match logic hidding vtables | |
302 | from LTO symbol tables. */ | |
4c4a180d | 303 | if (((in_lto_p || flag_whole_program) && !flag_incremental_link) |
97221fd7 | 304 | && DECL_COMDAT (decl) |
305 | && comdat_can_be_unshared_p (this)) | |
7aeffc5f | 306 | return false; |
307 | ||
308 | /* When doing link time optimizations, hidden symbols become local. */ | |
4c4a180d | 309 | if (in_lto_p && !flag_incremental_link |
97221fd7 | 310 | && (DECL_VISIBILITY (decl) == VISIBILITY_HIDDEN |
311 | || DECL_VISIBILITY (decl) == VISIBILITY_INTERNAL) | |
7aeffc5f | 312 | /* Be sure that node is defined in IR file, not in other object |
313 | file. In that case we don't set used_from_other_object_file. */ | |
97221fd7 | 314 | && definition) |
7aeffc5f | 315 | ; |
316 | else if (!flag_whole_program) | |
317 | return true; | |
318 | ||
319 | /* Do not attempt to privatize COMDATS by default. | |
320 | This would break linking with C++ libraries sharing | |
321 | inline definitions. | |
322 | ||
323 | FIXME: We can do so for readonly vars with no address taken and | |
324 | possibly also for vtables since no direct pointer comparsion is done. | |
325 | It might be interesting to do so to reduce linking overhead. */ | |
97221fd7 | 326 | if (DECL_COMDAT (decl) || DECL_WEAK (decl)) |
7aeffc5f | 327 | return true; |
328 | return false; | |
329 | } | |
330 | ||
331 | /* Return true if reference to NODE can be replaced by a local alias. | |
332 | Local aliases save dynamic linking overhead and enable more optimizations. | |
333 | */ | |
334 | ||
a865a0f2 | 335 | static bool |
7aeffc5f | 336 | can_replace_by_local_alias (symtab_node *node) |
337 | { | |
a865a0f2 | 338 | /* If aliases aren't supported, we can't do replacement. */ |
07b8a412 | 339 | if (!TARGET_SUPPORTS_ALIASES) |
340 | return false; | |
341 | ||
0325f3fd | 342 | /* Weakrefs have a reason to be non-local. Be sure we do not replace |
343 | them. */ | |
344 | while (node->transparent_alias && node->definition && !node->weakref) | |
345 | node = node->get_alias_target (); | |
346 | if (node->weakref) | |
347 | return false; | |
348 | ||
415d1b9a | 349 | return (node->get_availability () > AVAIL_INTERPOSABLE |
825463d4 | 350 | && !decl_binds_to_current_def_p (node->decl) |
415d1b9a | 351 | && !node->can_be_discarded_p ()); |
7aeffc5f | 352 | } |
353 | ||
a865a0f2 | 354 | /* Return true if we can replace reference to NODE by local alias |
b7cebaf8 | 355 | within a virtual table. Generally we can replace function pointers |
356 | and virtual table pointers. */ | |
357 | ||
a865a0f2 | 358 | static bool |
b7cebaf8 | 359 | can_replace_by_local_alias_in_vtable (symtab_node *node) |
360 | { | |
361 | if (is_a <varpool_node *> (node) | |
362 | && !DECL_VIRTUAL_P (node->decl)) | |
363 | return false; | |
364 | return can_replace_by_local_alias (node); | |
365 | } | |
366 | ||
367 | /* walk_tree callback that rewrites initializer references. */ | |
368 | ||
369 | static tree | |
ce7711df | 370 | update_vtable_references (tree *tp, int *walk_subtrees, |
371 | void *data ATTRIBUTE_UNUSED) | |
b7cebaf8 | 372 | { |
53e9c5c4 | 373 | if (VAR_OR_FUNCTION_DECL_P (*tp)) |
b7cebaf8 | 374 | { |
415d1b9a | 375 | if (can_replace_by_local_alias_in_vtable (symtab_node::get (*tp))) |
376 | *tp = symtab_node::get (*tp)->noninterposable_alias ()->decl; | |
b7cebaf8 | 377 | *walk_subtrees = 0; |
378 | } | |
379 | else if (IS_TYPE_OR_DECL_P (*tp)) | |
380 | *walk_subtrees = 0; | |
381 | return NULL; | |
382 | } | |
383 | ||
7aeffc5f | 384 | /* In LTO we can remove COMDAT groups and weak symbols. |
385 | Either turn them into normal symbols or external symbol depending on | |
386 | resolution info. */ | |
387 | ||
388 | static void | |
389 | update_visibility_by_resolution_info (symtab_node * node) | |
390 | { | |
391 | bool define; | |
392 | ||
393 | if (!node->externally_visible | |
394 | || (!DECL_WEAK (node->decl) && !DECL_ONE_ONLY (node->decl)) | |
aca3df3b | 395 | || node->resolution == LDPR_UNKNOWN) |
7aeffc5f | 396 | return; |
397 | ||
398 | define = (node->resolution == LDPR_PREVAILING_DEF_IRONLY | |
399 | || node->resolution == LDPR_PREVAILING_DEF | |
9b71510e | 400 | || node->resolution == LDPR_UNDEF |
7aeffc5f | 401 | || node->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP); |
402 | ||
403 | /* The linker decisions ought to agree in the whole group. */ | |
404 | if (node->same_comdat_group) | |
405 | for (symtab_node *next = node->same_comdat_group; | |
406 | next != node; next = next->same_comdat_group) | |
a0e59ca8 | 407 | { |
0325f3fd | 408 | if (!next->externally_visible || next->transparent_alias) |
a0e59ca8 | 409 | continue; |
410 | ||
411 | bool same_def | |
412 | = define == (next->resolution == LDPR_PREVAILING_DEF_IRONLY | |
413 | || next->resolution == LDPR_PREVAILING_DEF | |
414 | || next->resolution == LDPR_UNDEF | |
415 | || next->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP); | |
416 | gcc_assert (in_lto_p || same_def); | |
417 | if (!same_def) | |
418 | return; | |
419 | } | |
7aeffc5f | 420 | |
421 | if (node->same_comdat_group) | |
422 | for (symtab_node *next = node->same_comdat_group; | |
423 | next != node; next = next->same_comdat_group) | |
424 | { | |
4c4a180d | 425 | /* During incremental linking we need to keep symbol weak for future |
426 | linking. We can still drop definition if we know non-LTO world | |
427 | prevails. */ | |
428 | if (!flag_incremental_link) | |
429 | { | |
430 | DECL_WEAK (next->decl) = false; | |
431 | next->set_comdat_group (NULL); | |
432 | } | |
c7549d13 | 433 | if (!define) |
4c4a180d | 434 | { |
c7549d13 | 435 | if (next->externally_visible) |
436 | DECL_EXTERNAL (next->decl) = true; | |
4c4a180d | 437 | next->set_comdat_group (NULL); |
438 | } | |
7aeffc5f | 439 | } |
4c4a180d | 440 | |
441 | /* During incremental linking we need to keep symbol weak for future | |
442 | linking. We can still drop definition if we know non-LTO world prevails. */ | |
443 | if (!flag_incremental_link) | |
444 | { | |
445 | DECL_WEAK (node->decl) = false; | |
446 | node->set_comdat_group (NULL); | |
447 | node->dissolve_same_comdat_group_list (); | |
448 | } | |
7aeffc5f | 449 | if (!define) |
4c4a180d | 450 | { |
451 | DECL_EXTERNAL (node->decl) = true; | |
452 | node->set_comdat_group (NULL); | |
453 | node->dissolve_same_comdat_group_list (); | |
454 | } | |
7aeffc5f | 455 | } |
456 | ||
9b0e5d40 | 457 | /* Try to get rid of weakref. */ |
458 | ||
459 | static void | |
460 | optimize_weakref (symtab_node *node) | |
461 | { | |
9b0e5d40 | 462 | bool strip_weakref = false; |
463 | bool static_alias = false; | |
464 | ||
465 | gcc_assert (node->weakref); | |
466 | ||
f4d3c071 | 467 | /* Weakrefs with no target defined cannot be optimized. */ |
9b0e5d40 | 468 | if (!node->analyzed) |
469 | return; | |
470 | symtab_node *target = node->get_alias_target (); | |
471 | ||
472 | /* Weakrefs to weakrefs can be optimized only if target can be. */ | |
473 | if (target->weakref) | |
474 | optimize_weakref (target); | |
475 | if (target->weakref) | |
476 | return; | |
477 | ||
478 | /* If we have definition of weakref's target and we know it binds locally, | |
479 | we can turn weakref to static alias. */ | |
07b8a412 | 480 | if (TARGET_SUPPORTS_ALIASES |
481 | && target->definition && decl_binds_to_current_def_p (target->decl)) | |
9b0e5d40 | 482 | strip_weakref = static_alias = true; |
483 | /* Otherwise we can turn weakref into transparent alias. This transformation | |
484 | may break asm statements which directly refers to symbol name and expect | |
485 | GNU as to translate it via .weakref directive. So do not optimize when | |
486 | DECL_PRESERVED is set and .weakref is supported. */ | |
487 | else if ((!DECL_PRESERVE_P (target->decl) | |
488 | || IDENTIFIER_TRANSPARENT_ALIAS (DECL_ASSEMBLER_NAME (node->decl))) | |
489 | && !DECL_WEAK (target->decl) | |
490 | && !DECL_EXTERNAL (target->decl) | |
491 | && ((target->definition && !target->can_be_discarded_p ()) | |
492 | || target->resolution != LDPR_UNDEF)) | |
493 | strip_weakref = true; | |
494 | if (!strip_weakref) | |
495 | return; | |
496 | node->weakref = false; | |
497 | IDENTIFIER_TRANSPARENT_ALIAS (DECL_ASSEMBLER_NAME (node->decl)) = 0; | |
498 | TREE_CHAIN (DECL_ASSEMBLER_NAME (node->decl)) = NULL_TREE; | |
499 | DECL_ATTRIBUTES (node->decl) = remove_attribute ("weakref", | |
500 | DECL_ATTRIBUTES | |
501 | (node->decl)); | |
502 | ||
503 | if (dump_file) | |
504 | fprintf (dump_file, "Optimizing weakref %s %s\n", | |
505 | node->name(), | |
506 | static_alias ? "as static alias" : "as transparent alias"); | |
507 | ||
508 | if (static_alias) | |
509 | { | |
510 | /* make_decl_local will shortcircuit if it doesn't see TREE_PUBLIC. | |
511 | be sure it really clears the WEAK flag. */ | |
512 | TREE_PUBLIC (node->decl) = true; | |
513 | node->make_decl_local (); | |
514 | node->forced_by_abi = false; | |
515 | node->resolution = LDPR_PREVAILING_DEF_IRONLY; | |
516 | node->externally_visible = false; | |
517 | gcc_assert (!DECL_WEAK (node->decl)); | |
518 | node->transparent_alias = false; | |
519 | } | |
520 | else | |
521 | { | |
522 | symtab->change_decl_assembler_name | |
523 | (node->decl, DECL_ASSEMBLER_NAME (node->get_alias_target ()->decl)); | |
524 | node->transparent_alias = true; | |
525 | node->copy_visibility_from (target); | |
526 | } | |
527 | gcc_assert (node->alias); | |
528 | } | |
529 | ||
83134006 | 530 | /* NODE is an externally visible definition, which we've discovered is |
531 | not needed externally. Make it local to this compilation. */ | |
532 | ||
533 | static void | |
534 | localize_node (bool whole_program, symtab_node *node) | |
535 | { | |
536 | gcc_assert (whole_program || in_lto_p || !TREE_PUBLIC (node->decl)); | |
537 | ||
83582d71 | 538 | /* It is possible that one comdat group contains both hidden and non-hidden |
539 | symbols. In this case we can privatize all hidden symbol but we need | |
540 | to keep non-hidden exported. */ | |
541 | if (node->same_comdat_group | |
b0c4bd4d | 542 | && (node->resolution == LDPR_PREVAILING_DEF_IRONLY |
543 | || node->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP)) | |
83582d71 | 544 | { |
545 | symtab_node *next; | |
546 | for (next = node->same_comdat_group; | |
547 | next != node; next = next->same_comdat_group) | |
548 | if (next->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP | |
549 | || next->resolution == LDPR_PREVAILING_DEF) | |
550 | break; | |
551 | if (node != next) | |
552 | { | |
553 | if (!node->transparent_alias) | |
554 | { | |
555 | node->resolution = LDPR_PREVAILING_DEF_IRONLY; | |
556 | node->make_decl_local (); | |
557 | if (!flag_incremental_link) | |
558 | node->unique_name |= true; | |
559 | return; | |
560 | } | |
561 | } | |
562 | } | |
563 | /* For similar reason do not privatize whole comdat when seeing comdat | |
564 | local. Wait for non-comdat symbol to be privatized first. */ | |
565 | if (node->comdat_local_p ()) | |
566 | return; | |
567 | ||
83134006 | 568 | if (node->same_comdat_group && TREE_PUBLIC (node->decl)) |
569 | { | |
570 | for (symtab_node *next = node->same_comdat_group; | |
571 | next != node; next = next->same_comdat_group) | |
572 | { | |
573 | next->set_comdat_group (NULL); | |
574 | if (!next->alias) | |
575 | next->set_section (NULL); | |
576 | if (!next->transparent_alias) | |
577 | next->make_decl_local (); | |
578 | next->unique_name | |
579 | |= ((next->resolution == LDPR_PREVAILING_DEF_IRONLY | |
580 | || next->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP) | |
581 | && TREE_PUBLIC (next->decl) | |
582 | && !flag_incremental_link); | |
583 | } | |
584 | ||
585 | /* Now everything's localized, the grouping has no meaning, and | |
586 | will cause crashes if we keep it around. */ | |
587 | node->dissolve_same_comdat_group_list (); | |
588 | } | |
589 | ||
590 | node->unique_name | |
591 | |= ((node->resolution == LDPR_PREVAILING_DEF_IRONLY | |
592 | || node->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP) | |
593 | && TREE_PUBLIC (node->decl) | |
594 | && !flag_incremental_link); | |
595 | ||
596 | if (TREE_PUBLIC (node->decl)) | |
597 | node->set_comdat_group (NULL); | |
598 | if (DECL_COMDAT (node->decl) && !node->alias) | |
599 | node->set_section (NULL); | |
600 | if (!node->transparent_alias) | |
601 | { | |
602 | node->resolution = LDPR_PREVAILING_DEF_IRONLY; | |
603 | node->make_decl_local (); | |
604 | } | |
605 | } | |
606 | ||
7aeffc5f | 607 | /* Decide on visibility of all symbols. */ |
608 | ||
609 | static unsigned int | |
610 | function_and_variable_visibility (bool whole_program) | |
611 | { | |
612 | struct cgraph_node *node; | |
613 | varpool_node *vnode; | |
614 | ||
c8f03f88 | 615 | /* All aliases should be processed at this point. */ |
7aeffc5f | 616 | gcc_checking_assert (!alias_pairs || !alias_pairs->length ()); |
617 | ||
c8f03f88 | 618 | #ifdef ASM_OUTPUT_DEF |
322f1ba9 | 619 | FOR_EACH_DEFINED_FUNCTION (node) |
620 | { | |
621 | if (node->get_availability () != AVAIL_INTERPOSABLE | |
622 | || DECL_EXTERNAL (node->decl) | |
05128b32 | 623 | || node->has_aliases_p () |
624 | || lookup_attribute ("noipa", DECL_ATTRIBUTES (node->decl))) | |
322f1ba9 | 625 | continue; |
626 | ||
627 | cgraph_node *alias = 0; | |
628 | for (cgraph_edge *e = node->callees; e; e = e->next_callee) | |
629 | { | |
630 | /* Recursive function calls usually can't be interposed. */ | |
631 | ||
632 | if (!e->recursive_p ()) | |
633 | continue; | |
634 | ||
635 | if (!alias) | |
c8f03f88 | 636 | { |
322f1ba9 | 637 | alias = dyn_cast<cgraph_node *> (node->noninterposable_alias ()); |
638 | gcc_assert (alias && alias != node); | |
639 | } | |
640 | ||
641 | e->redirect_callee (alias); | |
642 | if (gimple_has_body_p (e->caller->decl)) | |
c8f03f88 | 643 | { |
322f1ba9 | 644 | push_cfun (DECL_STRUCT_FUNCTION (e->caller->decl)); |
645 | e->redirect_call_stmt_to_callee (); | |
c8f03f88 | 646 | pop_cfun (); |
322f1ba9 | 647 | } |
648 | } | |
649 | } | |
c8f03f88 | 650 | #endif |
651 | ||
7aeffc5f | 652 | FOR_EACH_FUNCTION (node) |
653 | { | |
654 | int flags = flags_from_decl_or_type (node->decl); | |
655 | ||
656 | /* Optimize away PURE and CONST constructors and destructors. */ | |
5f4e4f36 | 657 | if (node->analyzed |
658 | && (DECL_STATIC_CONSTRUCTOR (node->decl) | |
587101b8 | 659 | || DECL_STATIC_DESTRUCTOR (node->decl)) |
7aeffc5f | 660 | && (flags & (ECF_CONST | ECF_PURE)) |
5f4e4f36 | 661 | && !(flags & ECF_LOOPING_CONST_OR_PURE) |
662 | && opt_for_fn (node->decl, optimize)) | |
7aeffc5f | 663 | { |
664 | DECL_STATIC_CONSTRUCTOR (node->decl) = 0; | |
665 | DECL_STATIC_DESTRUCTOR (node->decl) = 0; | |
666 | } | |
667 | ||
dc824618 | 668 | /* Frontends and alias code marks nodes as needed before parsing |
669 | is finished. We may end up marking as node external nodes | |
670 | where this flag is meaningless strip it. */ | |
7aeffc5f | 671 | if (DECL_EXTERNAL (node->decl) || !node->definition) |
672 | { | |
673 | node->force_output = 0; | |
674 | node->forced_by_abi = 0; | |
675 | } | |
676 | ||
677 | /* C++ FE on lack of COMDAT support create local COMDAT functions | |
f4d3c071 | 678 | (that ought to be shared but cannot due to object format |
7aeffc5f | 679 | limitations). It is necessary to keep the flag to make rest of C++ FE |
680 | happy. Clear the flag here to avoid confusion in middle-end. */ | |
681 | if (DECL_COMDAT (node->decl) && !TREE_PUBLIC (node->decl)) | |
682 | DECL_COMDAT (node->decl) = 0; | |
683 | ||
684 | /* For external decls stop tracking same_comdat_group. It doesn't matter | |
7b3390b4 | 685 | what comdat group they are in when they won't be emitted in this TU. |
686 | ||
687 | An exception is LTO where we may end up with both external | |
688 | and non-external declarations in the same comdat group in | |
689 | the case declarations was not merged. */ | |
690 | if (node->same_comdat_group && DECL_EXTERNAL (node->decl) && !in_lto_p) | |
7aeffc5f | 691 | { |
382ecba7 | 692 | if (flag_checking) |
693 | { | |
694 | for (symtab_node *n = node->same_comdat_group; | |
695 | n != node; | |
696 | n = n->same_comdat_group) | |
697 | /* If at least one of same comdat group functions is external, | |
698 | all of them have to be, otherwise it is a front-end bug. */ | |
699 | gcc_assert (DECL_EXTERNAL (n->decl)); | |
700 | } | |
415d1b9a | 701 | node->dissolve_same_comdat_group_list (); |
7aeffc5f | 702 | } |
703 | gcc_assert ((!DECL_WEAK (node->decl) | |
aca3df3b | 704 | && !DECL_COMDAT (node->decl)) |
7aeffc5f | 705 | || TREE_PUBLIC (node->decl) |
706 | || node->weakref | |
707 | || DECL_EXTERNAL (node->decl)); | |
708 | if (cgraph_externally_visible_p (node, whole_program)) | |
709 | { | |
710 | gcc_assert (!node->global.inlined_to); | |
711 | node->externally_visible = true; | |
712 | } | |
713 | else | |
714 | { | |
715 | node->externally_visible = false; | |
716 | node->forced_by_abi = false; | |
717 | } | |
718 | if (!node->externally_visible | |
719 | && node->definition && !node->weakref | |
720 | && !DECL_EXTERNAL (node->decl)) | |
83134006 | 721 | localize_node (whole_program, node); |
7aeffc5f | 722 | |
723 | if (node->thunk.thunk_p | |
724 | && TREE_PUBLIC (node->decl)) | |
725 | { | |
726 | struct cgraph_node *decl_node = node; | |
727 | ||
415d1b9a | 728 | decl_node = decl_node->callees->callee->function_symbol (); |
7aeffc5f | 729 | |
730 | /* Thunks have the same visibility as function they are attached to. | |
731 | Make sure the C++ front end set this up properly. */ | |
732 | if (DECL_ONE_ONLY (decl_node->decl)) | |
733 | { | |
734 | gcc_checking_assert (DECL_COMDAT (node->decl) | |
735 | == DECL_COMDAT (decl_node->decl)); | |
415d1b9a | 736 | gcc_checking_assert (node->in_same_comdat_group_p (decl_node)); |
7aeffc5f | 737 | gcc_checking_assert (node->same_comdat_group); |
738 | } | |
739 | node->forced_by_abi = decl_node->forced_by_abi; | |
740 | if (DECL_EXTERNAL (decl_node->decl)) | |
741 | DECL_EXTERNAL (node->decl) = 1; | |
742 | } | |
743 | ||
744 | update_visibility_by_resolution_info (node); | |
9b0e5d40 | 745 | if (node->weakref) |
746 | optimize_weakref (node); | |
7aeffc5f | 747 | } |
748 | FOR_EACH_DEFINED_FUNCTION (node) | |
749 | { | |
e3f2be84 | 750 | if (!node->local.local) |
751 | node->local.local |= node->local_p (); | |
7aeffc5f | 752 | |
f4d3c071 | 753 | /* If we know that function cannot be overwritten by a |
754 | different semantics and moreover its section cannot be | |
a865a0f2 | 755 | discarded, replace all direct calls by calls to an |
756 | noninterposable alias. This make dynamic linking cheaper and | |
757 | enable more optimization. | |
7aeffc5f | 758 | |
759 | TODO: We can also update virtual tables. */ | |
4696e459 | 760 | if (node->callers |
4696e459 | 761 | && can_replace_by_local_alias (node)) |
7aeffc5f | 762 | { |
415d1b9a | 763 | cgraph_node *alias = dyn_cast<cgraph_node *> |
764 | (node->noninterposable_alias ()); | |
7aeffc5f | 765 | |
766 | if (alias && alias != node) | |
767 | { | |
768 | while (node->callers) | |
769 | { | |
770 | struct cgraph_edge *e = node->callers; | |
771 | ||
35ee1c66 | 772 | e->redirect_callee (alias); |
7aeffc5f | 773 | if (gimple_has_body_p (e->caller->decl)) |
774 | { | |
775 | push_cfun (DECL_STRUCT_FUNCTION (e->caller->decl)); | |
35ee1c66 | 776 | e->redirect_call_stmt_to_callee (); |
7aeffc5f | 777 | pop_cfun (); |
778 | } | |
779 | } | |
780 | } | |
781 | } | |
782 | } | |
783 | FOR_EACH_VARIABLE (vnode) | |
784 | { | |
785 | /* weak flag makes no sense on local variables. */ | |
786 | gcc_assert (!DECL_WEAK (vnode->decl) | |
787 | || vnode->weakref | |
788 | || TREE_PUBLIC (vnode->decl) | |
789 | || DECL_EXTERNAL (vnode->decl)); | |
f4d3c071 | 790 | /* In several cases declarations cannot be common: |
7aeffc5f | 791 | |
792 | - when declaration has initializer | |
793 | - when it is in weak | |
794 | - when it has specific section | |
795 | - when it resides in non-generic address space. | |
796 | - if declaration is local, it will get into .local common section | |
797 | so common flag is not needed. Frontends still produce these in | |
798 | certain cases, such as for: | |
799 | ||
800 | static int a __attribute__ ((common)) | |
801 | ||
802 | Canonicalize things here and clear the redundant flag. */ | |
803 | if (DECL_COMMON (vnode->decl) | |
804 | && (!(TREE_PUBLIC (vnode->decl) | |
805 | || DECL_EXTERNAL (vnode->decl)) | |
806 | || (DECL_INITIAL (vnode->decl) | |
807 | && DECL_INITIAL (vnode->decl) != error_mark_node) | |
808 | || DECL_WEAK (vnode->decl) | |
809 | || DECL_SECTION_NAME (vnode->decl) != NULL | |
810 | || ! (ADDR_SPACE_GENERIC_P | |
811 | (TYPE_ADDR_SPACE (TREE_TYPE (vnode->decl)))))) | |
812 | DECL_COMMON (vnode->decl) = 0; | |
9b0e5d40 | 813 | if (vnode->weakref) |
814 | optimize_weakref (vnode); | |
7aeffc5f | 815 | } |
816 | FOR_EACH_DEFINED_VARIABLE (vnode) | |
817 | { | |
818 | if (!vnode->definition) | |
819 | continue; | |
97221fd7 | 820 | if (vnode->externally_visible_p ()) |
7aeffc5f | 821 | vnode->externally_visible = true; |
822 | else | |
823 | { | |
824 | vnode->externally_visible = false; | |
825 | vnode->forced_by_abi = false; | |
826 | } | |
6b722052 | 827 | if (lookup_attribute ("no_reorder", |
828 | DECL_ATTRIBUTES (vnode->decl))) | |
829 | vnode->no_reorder = 1; | |
83134006 | 830 | |
7aeffc5f | 831 | if (!vnode->externally_visible |
83582d71 | 832 | && !vnode->transparent_alias |
833 | && !DECL_EXTERNAL (vnode->decl)) | |
83134006 | 834 | localize_node (whole_program, vnode); |
7aeffc5f | 835 | |
7aeffc5f | 836 | update_visibility_by_resolution_info (vnode); |
b7cebaf8 | 837 | |
6f24ab3b | 838 | /* Update virtual tables to point to local aliases where possible. */ |
b7cebaf8 | 839 | if (DECL_VIRTUAL_P (vnode->decl) |
24833914 | 840 | && !DECL_EXTERNAL (vnode->decl)) |
b7cebaf8 | 841 | { |
842 | int i; | |
843 | struct ipa_ref *ref; | |
844 | bool found = false; | |
845 | ||
846 | /* See if there is something to update. */ | |
58da8146 | 847 | for (i = 0; vnode->iterate_reference (i, ref); i++) |
b7cebaf8 | 848 | if (ref->use == IPA_REF_ADDR |
849 | && can_replace_by_local_alias_in_vtable (ref->referred)) | |
850 | { | |
851 | found = true; | |
852 | break; | |
853 | } | |
854 | if (found) | |
855 | { | |
431205b7 | 856 | hash_set<tree> visited_nodes; |
afb0d513 | 857 | |
97221fd7 | 858 | vnode->get_constructor (); |
b7cebaf8 | 859 | walk_tree (&DECL_INITIAL (vnode->decl), |
431205b7 | 860 | update_vtable_references, NULL, &visited_nodes); |
51ce5652 | 861 | vnode->remove_all_references (); |
b7cebaf8 | 862 | record_references_in_initializer (vnode->decl, false); |
863 | } | |
864 | } | |
7aeffc5f | 865 | } |
866 | ||
867 | if (dump_file) | |
868 | { | |
869 | fprintf (dump_file, "\nMarking local functions:"); | |
870 | FOR_EACH_DEFINED_FUNCTION (node) | |
871 | if (node->local.local) | |
872 | fprintf (dump_file, " %s", node->name ()); | |
873 | fprintf (dump_file, "\n\n"); | |
874 | fprintf (dump_file, "\nMarking externally visible functions:"); | |
875 | FOR_EACH_DEFINED_FUNCTION (node) | |
876 | if (node->externally_visible) | |
877 | fprintf (dump_file, " %s", node->name ()); | |
878 | fprintf (dump_file, "\n\n"); | |
879 | fprintf (dump_file, "\nMarking externally visible variables:"); | |
880 | FOR_EACH_DEFINED_VARIABLE (vnode) | |
881 | if (vnode->externally_visible) | |
882 | fprintf (dump_file, " %s", vnode->name ()); | |
883 | fprintf (dump_file, "\n\n"); | |
884 | } | |
35ee1c66 | 885 | symtab->function_flags_ready = true; |
7aeffc5f | 886 | return 0; |
887 | } | |
888 | ||
889 | /* Local function pass handling visibilities. This happens before LTO streaming | |
890 | so in particular -fwhole-program should be ignored at this level. */ | |
891 | ||
7620bc82 | 892 | namespace { |
893 | ||
894 | const pass_data pass_data_ipa_function_and_variable_visibility = | |
7aeffc5f | 895 | { |
896 | SIMPLE_IPA_PASS, /* type */ | |
897 | "visibility", /* name */ | |
898 | OPTGROUP_NONE, /* optinfo_flags */ | |
7aeffc5f | 899 | TV_CGRAPHOPT, /* tv_id */ |
900 | 0, /* properties_required */ | |
901 | 0, /* properties_provided */ | |
902 | 0, /* properties_destroyed */ | |
903 | 0, /* todo_flags_start */ | |
904 | ( TODO_remove_functions | TODO_dump_symtab ), /* todo_flags_finish */ | |
905 | }; | |
906 | ||
907 | /* Bring functions local at LTO time with -fwhole-program. */ | |
908 | ||
909 | static unsigned int | |
910 | whole_program_function_and_variable_visibility (void) | |
911 | { | |
912 | function_and_variable_visibility (flag_whole_program); | |
5f4e4f36 | 913 | if (optimize || in_lto_p) |
8c8b8b86 | 914 | ipa_discover_variable_flags (); |
7aeffc5f | 915 | return 0; |
916 | } | |
917 | ||
7620bc82 | 918 | } // anon namespace |
919 | ||
920 | namespace { | |
921 | ||
922 | const pass_data pass_data_ipa_whole_program_visibility = | |
7aeffc5f | 923 | { |
924 | IPA_PASS, /* type */ | |
925 | "whole-program", /* name */ | |
926 | OPTGROUP_NONE, /* optinfo_flags */ | |
7aeffc5f | 927 | TV_CGRAPHOPT, /* tv_id */ |
928 | 0, /* properties_required */ | |
929 | 0, /* properties_provided */ | |
930 | 0, /* properties_destroyed */ | |
931 | 0, /* todo_flags_start */ | |
932 | ( TODO_remove_functions | TODO_dump_symtab ), /* todo_flags_finish */ | |
933 | }; | |
934 | ||
7620bc82 | 935 | class pass_ipa_whole_program_visibility : public ipa_opt_pass_d |
7aeffc5f | 936 | { |
937 | public: | |
938 | pass_ipa_whole_program_visibility (gcc::context *ctxt) | |
939 | : ipa_opt_pass_d (pass_data_ipa_whole_program_visibility, ctxt, | |
940 | NULL, /* generate_summary */ | |
941 | NULL, /* write_summary */ | |
942 | NULL, /* read_summary */ | |
943 | NULL, /* write_optimization_summary */ | |
944 | NULL, /* read_optimization_summary */ | |
945 | NULL, /* stmt_fixup */ | |
946 | 0, /* function_transform_todo_flags_start */ | |
947 | NULL, /* function_transform */ | |
948 | NULL) /* variable_transform */ | |
949 | {} | |
950 | ||
951 | /* opt_pass methods: */ | |
952 | ||
953 | virtual bool gate (function *) | |
954 | { | |
955 | /* Do not re-run on ltrans stage. */ | |
956 | return !flag_ltrans; | |
957 | } | |
958 | virtual unsigned int execute (function *) | |
959 | { | |
960 | return whole_program_function_and_variable_visibility (); | |
961 | } | |
962 | ||
963 | }; // class pass_ipa_whole_program_visibility | |
964 | ||
7620bc82 | 965 | } // anon namespace |
966 | ||
7aeffc5f | 967 | ipa_opt_pass_d * |
968 | make_pass_ipa_whole_program_visibility (gcc::context *ctxt) | |
969 | { | |
970 | return new pass_ipa_whole_program_visibility (ctxt); | |
971 | } | |
972 | ||
973 | class pass_ipa_function_and_variable_visibility : public simple_ipa_opt_pass | |
974 | { | |
975 | public: | |
976 | pass_ipa_function_and_variable_visibility (gcc::context *ctxt) | |
977 | : simple_ipa_opt_pass (pass_data_ipa_function_and_variable_visibility, | |
978 | ctxt) | |
979 | {} | |
980 | ||
981 | /* opt_pass methods: */ | |
982 | virtual unsigned int execute (function *) | |
983 | { | |
984 | return function_and_variable_visibility (flag_whole_program && !flag_lto); | |
985 | } | |
986 | ||
987 | }; // class pass_ipa_function_and_variable_visibility | |
988 | ||
989 | simple_ipa_opt_pass * | |
990 | make_pass_ipa_function_and_variable_visibility (gcc::context *ctxt) | |
991 | { | |
992 | return new pass_ipa_function_and_variable_visibility (ctxt); | |
993 | } |