1/* IPA visibility pass
2 Copyright (C) 2003-2017 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free
8Software Foundation; either version 3, or (at your option) any later
9version.
10
11GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12WARRANTY; without even the implied warranty of MERCHANTABILITY or
13FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14for more details.
15
16You should have received a copy of the GNU General Public License
17along 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
45 externally_visible flag is set for symbols that can not be privatized.
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"
79#include "function.h"
80#include "tree.h"
81#include "gimple-expr.h"
82#include "tree-pass.h"
83#include "cgraph.h"
84#include "calls.h"
85#include "varasm.h"
86#include "ipa-utils.h"
87#include "stringpool.h"
88#include "attribs.h"
89
90/* Return true when NODE can not be local. Worker for cgraph_local_node_p. */
91
92static bool
93non_local_p (struct cgraph_node *node, void *data ATTRIBUTE_UNUSED)
94{
95 return !(node->only_called_directly_or_aliased_p ()
96 /* i386 would need update to output thunk with local calling
97 conventions. */
98 && !node->thunk.thunk_p
99 && node->definition
100 && !DECL_EXTERNAL (node->decl)
101 && !lookup_attribute ("noipa", DECL_ATTRIBUTES (node->decl))
102 && !node->externally_visible
103 && !node->used_from_other_partition
104 && !node->in_other_partition
105 && node->get_availability () >= AVAIL_AVAILABLE);
106}
107
108/* Return true when function can be marked local. */
109
110bool
111cgraph_node::local_p (void)
112{
113 cgraph_node *n = ultimate_alias_target ();
114
115 if (n->thunk.thunk_p)
116 return n->callees->callee->local_p ();
117 return !n->call_for_symbol_thunks_and_aliases (non_local_p,
118 NULL, true);
119
120}
121
122/* A helper for comdat_can_be_unshared_p. */
123
124static bool
125comdat_can_be_unshared_p_1 (symtab_node *node)
126{
127 if (!node->externally_visible)
128 return true;
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 }
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
150 /* Non-readonly and volatile variables can not be duplicated. */
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.
161 Return true when turning COMDAT function static can not lead to wrong
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
167static bool
168comdat_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
189static bool
190cgraph_externally_visible_p (struct cgraph_node *node,
191 bool whole_program)
192{
193 while (node->transparent_alias && node->definition)
194 node = node->get_alias_target ();
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. */
206 if (DECL_BUILT_IN (node->decl))
207 return true;
208
209 /* If linker counts on us, we must preserve the function. */
210 if (node->used_from_object_file_p ())
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;
217 if (lookup_attribute ("noipa", DECL_ATTRIBUTES (node->decl)))
218 return true;
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;
225 /* When doing LTO or whole program, we can bring COMDAT functoins static.
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) */
229 if (((in_lto_p || whole_program) && !flag_incremental_link)
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. */
235 if ((in_lto_p && !flag_incremental_link)
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 if (node->instrumentation_clone
249 && MAIN_NAME_P (DECL_NAME (node->orig_decl)))
250 return true;
251
252 return false;
253}
254
255/* Return true when variable should be considered externally visible. */
256
257bool
258varpool_node::externally_visible_p (void)
259{
260 while (transparent_alias && definition)
261 return get_alias_target ()->externally_visible_p ();
262 if (DECL_EXTERNAL (decl))
263 return true;
264
265 if (!TREE_PUBLIC (decl))
266 return false;
267
268 /* If linker counts on us, we must preserve the function. */
269 if (used_from_object_file_p ())
270 return true;
271
272 /* Bringing TLS variables local may cause dynamic linker failures
273 on limits of static TLS vars. */
274 if (DECL_THREAD_LOCAL_P (decl)
275 && (DECL_TLS_MODEL (decl) != TLS_MODEL_EMULATED
276 && DECL_TLS_MODEL (decl) != TLS_MODEL_INITIAL_EXEC))
277 return true;
278
279 if (DECL_HARD_REGISTER (decl))
280 return true;
281 if (DECL_PRESERVE_P (decl))
282 return true;
283 if (lookup_attribute ("externally_visible",
284 DECL_ATTRIBUTES (decl)))
285 return true;
286 if (TARGET_DLLIMPORT_DECL_ATTRIBUTES
287 && lookup_attribute ("dllexport",
288 DECL_ATTRIBUTES (decl)))
289 return true;
290
291 /* See if we have linker information about symbol not being used or
292 if we need to make guess based on the declaration.
293
294 Even if the linker clams the symbol is unused, never bring internal
295 symbols that are declared by user as used or externally visible.
296 This is needed for i.e. references from asm statements. */
297 if (used_from_object_file_p ())
298 return true;
299 if (resolution == LDPR_PREVAILING_DEF_IRONLY)
300 return false;
301
302 /* As a special case, the COMDAT virtual tables can be unshared.
303 In LTO mode turn vtables into static variables. The variable is readonly,
304 so this does not enable more optimization, but referring static var
305 is faster for dynamic linking. Also this match logic hidding vtables
306 from LTO symbol tables. */
307 if (((in_lto_p || flag_whole_program) && !flag_incremental_link)
308 && DECL_COMDAT (decl)
309 && comdat_can_be_unshared_p (this))
310 return false;
311
312 /* When doing link time optimizations, hidden symbols become local. */
313 if (in_lto_p && !flag_incremental_link
314 && (DECL_VISIBILITY (decl) == VISIBILITY_HIDDEN
315 || DECL_VISIBILITY (decl) == VISIBILITY_INTERNAL)
316 /* Be sure that node is defined in IR file, not in other object
317 file. In that case we don't set used_from_other_object_file. */
318 && definition)
319 ;
320 else if (!flag_whole_program)
321 return true;
322
323 /* Do not attempt to privatize COMDATS by default.
324 This would break linking with C++ libraries sharing
325 inline definitions.
326
327 FIXME: We can do so for readonly vars with no address taken and
328 possibly also for vtables since no direct pointer comparsion is done.
329 It might be interesting to do so to reduce linking overhead. */
330 if (DECL_COMDAT (decl) || DECL_WEAK (decl))
331 return true;
332 return false;
333}
334
335/* Return true if reference to NODE can be replaced by a local alias.
336 Local aliases save dynamic linking overhead and enable more optimizations.
337 */
338
339static bool
340can_replace_by_local_alias (symtab_node *node)
341{
342 /* If aliases aren't supported, we can't do replacement. */
343 if (!TARGET_SUPPORTS_ALIASES)
344 return false;
345
346 /* Weakrefs have a reason to be non-local. Be sure we do not replace
347 them. */
348 while (node->transparent_alias && node->definition && !node->weakref)
349 node = node->get_alias_target ();
350 if (node->weakref)
351 return false;
352
353 return (node->get_availability () > AVAIL_INTERPOSABLE
354 && !decl_binds_to_current_def_p (node->decl)
355 && !node->can_be_discarded_p ());
356}
357
358/* Return true if we can replace reference to NODE by local alias
359 within a virtual table. Generally we can replace function pointers
360 and virtual table pointers. */
361
362static bool
363can_replace_by_local_alias_in_vtable (symtab_node *node)
364{
365 if (is_a <varpool_node *> (node)
366 && !DECL_VIRTUAL_P (node->decl))
367 return false;
368 return can_replace_by_local_alias (node);
369}
370
371/* walk_tree callback that rewrites initializer references. */
372
373static tree
374update_vtable_references (tree *tp, int *walk_subtrees,
375 void *data ATTRIBUTE_UNUSED)
376{
377 if (VAR_OR_FUNCTION_DECL_P (*tp))
378 {
379 if (can_replace_by_local_alias_in_vtable (symtab_node::get (*tp)))
380 *tp = symtab_node::get (*tp)->noninterposable_alias ()->decl;
381 *walk_subtrees = 0;
382 }
383 else if (IS_TYPE_OR_DECL_P (*tp))
384 *walk_subtrees = 0;
385 return NULL;
386}
387
388/* In LTO we can remove COMDAT groups and weak symbols.
389 Either turn them into normal symbols or external symbol depending on
390 resolution info. */
391
392static void
393update_visibility_by_resolution_info (symtab_node * node)
394{
395 bool define;
396
397 if (!node->externally_visible
398 || (!DECL_WEAK (node->decl) && !DECL_ONE_ONLY (node->decl))
399 || node->resolution == LDPR_UNKNOWN)
400 return;
401
402 define = (node->resolution == LDPR_PREVAILING_DEF_IRONLY
403 || node->resolution == LDPR_PREVAILING_DEF
404 || node->resolution == LDPR_UNDEF
405 || node->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP);
406
407 /* The linker decisions ought to agree in the whole group. */
408 if (node->same_comdat_group)
409 for (symtab_node *next = node->same_comdat_group;
410 next != node; next = next->same_comdat_group)
411 {
412 if (!next->externally_visible || next->transparent_alias)
413 continue;
414
415 bool same_def
416 = define == (next->resolution == LDPR_PREVAILING_DEF_IRONLY
417 || next->resolution == LDPR_PREVAILING_DEF
418 || next->resolution == LDPR_UNDEF
419 || next->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP);
420 gcc_assert (in_lto_p || same_def);
421 if (!same_def)
422 return;
423 }
424
425 if (node->same_comdat_group)
426 for (symtab_node *next = node->same_comdat_group;
427 next != node; next = next->same_comdat_group)
428 {
429 /* During incremental linking we need to keep symbol weak for future
430 linking. We can still drop definition if we know non-LTO world
431 prevails. */
432 if (!flag_incremental_link)
433 {
434 DECL_WEAK (next->decl) = false;
435 next->set_comdat_group (NULL);
436 }
437 if (!define)
438 {
439 if (next->externally_visible)
440 DECL_EXTERNAL (next->decl) = true;
441 next->set_comdat_group (NULL);
442 }
443 }
444
445 /* During incremental linking we need to keep symbol weak for future
446 linking. We can still drop definition if we know non-LTO world prevails. */
447 if (!flag_incremental_link)
448 {
449 DECL_WEAK (node->decl) = false;
450 node->set_comdat_group (NULL);
451 node->dissolve_same_comdat_group_list ();
452 }
453 if (!define)
454 {
455 DECL_EXTERNAL (node->decl) = true;
456 node->set_comdat_group (NULL);
457 node->dissolve_same_comdat_group_list ();
458 }
459}
460
461/* Try to get rid of weakref. */
462
463static void
464optimize_weakref (symtab_node *node)
465{
466 bool strip_weakref = false;
467 bool static_alias = false;
468
469 gcc_assert (node->weakref);
470
471 /* Weakrefs with no target defined can not be optimized. */
472 if (!node->analyzed)
473 return;
474 symtab_node *target = node->get_alias_target ();
475
476 /* Weakrefs to weakrefs can be optimized only if target can be. */
477 if (target->weakref)
478 optimize_weakref (target);
479 if (target->weakref)
480 return;
481
482 /* If we have definition of weakref's target and we know it binds locally,
483 we can turn weakref to static alias. */
484 if (TARGET_SUPPORTS_ALIASES
485 && target->definition && decl_binds_to_current_def_p (target->decl))
486 strip_weakref = static_alias = true;
487 /* Otherwise we can turn weakref into transparent alias. This transformation
488 may break asm statements which directly refers to symbol name and expect
489 GNU as to translate it via .weakref directive. So do not optimize when
490 DECL_PRESERVED is set and .weakref is supported. */
491 else if ((!DECL_PRESERVE_P (target->decl)
492 || IDENTIFIER_TRANSPARENT_ALIAS (DECL_ASSEMBLER_NAME (node->decl)))
493 && !DECL_WEAK (target->decl)
494 && !DECL_EXTERNAL (target->decl)
495 && ((target->definition && !target->can_be_discarded_p ())
496 || target->resolution != LDPR_UNDEF))
497 strip_weakref = true;
498 if (!strip_weakref)
499 return;
500 node->weakref = false;
501 IDENTIFIER_TRANSPARENT_ALIAS (DECL_ASSEMBLER_NAME (node->decl)) = 0;
502 TREE_CHAIN (DECL_ASSEMBLER_NAME (node->decl)) = NULL_TREE;
503 DECL_ATTRIBUTES (node->decl) = remove_attribute ("weakref",
504 DECL_ATTRIBUTES
505 (node->decl));
506
507 if (dump_file)
508 fprintf (dump_file, "Optimizing weakref %s %s\n",
509 node->name(),
510 static_alias ? "as static alias" : "as transparent alias");
511
512 if (static_alias)
513 {
514 /* make_decl_local will shortcircuit if it doesn't see TREE_PUBLIC.
515 be sure it really clears the WEAK flag. */
516 TREE_PUBLIC (node->decl) = true;
517 node->make_decl_local ();
518 node->forced_by_abi = false;
519 node->resolution = LDPR_PREVAILING_DEF_IRONLY;
520 node->externally_visible = false;
521 gcc_assert (!DECL_WEAK (node->decl));
522 node->transparent_alias = false;
523 }
524 else
525 {
526 symtab->change_decl_assembler_name
527 (node->decl, DECL_ASSEMBLER_NAME (node->get_alias_target ()->decl));
528 node->transparent_alias = true;
529 node->copy_visibility_from (target);
530 }
531 gcc_assert (node->alias);
532}
533
534/* NODE is an externally visible definition, which we've discovered is
535 not needed externally. Make it local to this compilation. */
536
537static void
538localize_node (bool whole_program, symtab_node *node)
539{
540 gcc_assert (whole_program || in_lto_p || !TREE_PUBLIC (node->decl));
541
542 /* It is possible that one comdat group contains both hidden and non-hidden
543 symbols. In this case we can privatize all hidden symbol but we need
544 to keep non-hidden exported. */
545 if (node->same_comdat_group
546 && node->resolution == LDPR_PREVAILING_DEF_IRONLY)
547 {
548 symtab_node *next;
549 for (next = node->same_comdat_group;
550 next != node; next = next->same_comdat_group)
551 if (next->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP
552 || next->resolution == LDPR_PREVAILING_DEF)
553 break;
554 if (node != next)
555 {
556 if (!node->transparent_alias)
557 {
558 node->resolution = LDPR_PREVAILING_DEF_IRONLY;
559 node->make_decl_local ();
560 if (!flag_incremental_link)
561 node->unique_name |= true;
562 return;
563 }
564 }
565 }
566 /* For similar reason do not privatize whole comdat when seeing comdat
567 local. Wait for non-comdat symbol to be privatized first. */
568 if (node->comdat_local_p ())
569 return;
570
571 if (node->same_comdat_group && TREE_PUBLIC (node->decl))
572 {
573 for (symtab_node *next = node->same_comdat_group;
574 next != node; next = next->same_comdat_group)
575 {
576 next->set_comdat_group (NULL);
577 if (!next->alias)
578 next->set_section (NULL);
579 if (!next->transparent_alias)
580 next->make_decl_local ();
581 next->unique_name
582 |= ((next->resolution == LDPR_PREVAILING_DEF_IRONLY
583 || next->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP)
584 && TREE_PUBLIC (next->decl)
585 && !flag_incremental_link);
586 }
587
588 /* Now everything's localized, the grouping has no meaning, and
589 will cause crashes if we keep it around. */
590 node->dissolve_same_comdat_group_list ();
591 }
592
593 node->unique_name
594 |= ((node->resolution == LDPR_PREVAILING_DEF_IRONLY
595 || node->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP)
596 && TREE_PUBLIC (node->decl)
597 && !flag_incremental_link);
598
599 if (TREE_PUBLIC (node->decl))
600 node->set_comdat_group (NULL);
601 if (DECL_COMDAT (node->decl) && !node->alias)
602 node->set_section (NULL);
603 if (!node->transparent_alias)
604 {
605 node->resolution = LDPR_PREVAILING_DEF_IRONLY;
606 node->make_decl_local ();
607 }
608}
609
610/* Decide on visibility of all symbols. */
611
612static unsigned int
613function_and_variable_visibility (bool whole_program)
614{
615 struct cgraph_node *node;
616 varpool_node *vnode;
617
618 /* All aliases should be processed at this point. */
619 gcc_checking_assert (!alias_pairs || !alias_pairs->length ());
620
621#ifdef ASM_OUTPUT_DEF
622 FOR_EACH_DEFINED_FUNCTION (node)
623 {
624 if (node->get_availability () != AVAIL_INTERPOSABLE
625 || DECL_EXTERNAL (node->decl)
626 || node->has_aliases_p ())
627 continue;
628
629 cgraph_node *alias = 0;
630 for (cgraph_edge *e = node->callees; e; e = e->next_callee)
631 {
632 /* Recursive function calls usually can't be interposed. */
633
634 if (!e->recursive_p ())
635 continue;
636
637 if (!alias)
638 {
639 alias = dyn_cast<cgraph_node *> (node->noninterposable_alias ());
640 gcc_assert (alias && alias != node);
641 }
642
643 e->redirect_callee (alias);
644 if (gimple_has_body_p (e->caller->decl))
645 {
646 push_cfun (DECL_STRUCT_FUNCTION (e->caller->decl));
647 e->redirect_call_stmt_to_callee ();
648 pop_cfun ();
649 }
650 }
651 }
652#endif
653
654 FOR_EACH_FUNCTION (node)
655 {
656 int flags = flags_from_decl_or_type (node->decl);
657
658 /* Optimize away PURE and CONST constructors and destructors. */
659 if (node->analyzed
660 && (DECL_STATIC_CONSTRUCTOR (node->decl)
661 || DECL_STATIC_DESTRUCTOR (node->decl))
662 && (flags & (ECF_CONST | ECF_PURE))
663 && !(flags & ECF_LOOPING_CONST_OR_PURE)
664 && opt_for_fn (node->decl, optimize))
665 {
666 DECL_STATIC_CONSTRUCTOR (node->decl) = 0;
667 DECL_STATIC_DESTRUCTOR (node->decl) = 0;
668 }
669
670 /* Frontends and alias code marks nodes as needed before parsing
671 is finished. We may end up marking as node external nodes
672 where this flag is meaningless strip it. */
673 if (DECL_EXTERNAL (node->decl) || !node->definition)
674 {
675 node->force_output = 0;
676 node->forced_by_abi = 0;
677 }
678
679 /* C++ FE on lack of COMDAT support create local COMDAT functions
680 (that ought to be shared but can not due to object format
681 limitations). It is necessary to keep the flag to make rest of C++ FE
682 happy. Clear the flag here to avoid confusion in middle-end. */
683 if (DECL_COMDAT (node->decl) && !TREE_PUBLIC (node->decl))
684 DECL_COMDAT (node->decl) = 0;
685
686 /* For external decls stop tracking same_comdat_group. It doesn't matter
687 what comdat group they are in when they won't be emitted in this TU.
688
689 An exception is LTO where we may end up with both external
690 and non-external declarations in the same comdat group in
691 the case declarations was not merged. */
692 if (node->same_comdat_group && DECL_EXTERNAL (node->decl) && !in_lto_p)
693 {
694 if (flag_checking)
695 {
696 for (symtab_node *n = node->same_comdat_group;
697 n != node;
698 n = n->same_comdat_group)
699 /* If at least one of same comdat group functions is external,
700 all of them have to be, otherwise it is a front-end bug. */
701 gcc_assert (DECL_EXTERNAL (n->decl));
702 }
703 node->dissolve_same_comdat_group_list ();
704 }
705 gcc_assert ((!DECL_WEAK (node->decl)
706 && !DECL_COMDAT (node->decl))
707 || TREE_PUBLIC (node->decl)
708 || node->weakref
709 || DECL_EXTERNAL (node->decl));
710 if (cgraph_externally_visible_p (node, whole_program))
711 {
712 gcc_assert (!node->global.inlined_to);
713 node->externally_visible = true;
714 }
715 else
716 {
717 node->externally_visible = false;
718 node->forced_by_abi = false;
719 }
720 if (!node->externally_visible
721 && node->definition && !node->weakref
722 && !DECL_EXTERNAL (node->decl))
723 localize_node (whole_program, node);
724
725 if (node->thunk.thunk_p
726 && !node->thunk.add_pointer_bounds_args
727 && TREE_PUBLIC (node->decl))
728 {
729 struct cgraph_node *decl_node = node;
730
731 decl_node = decl_node->callees->callee->function_symbol ();
732
733 /* Thunks have the same visibility as function they are attached to.
734 Make sure the C++ front end set this up properly. */
735 if (DECL_ONE_ONLY (decl_node->decl))
736 {
737 gcc_checking_assert (DECL_COMDAT (node->decl)
738 == DECL_COMDAT (decl_node->decl));
739 gcc_checking_assert (node->in_same_comdat_group_p (decl_node));
740 gcc_checking_assert (node->same_comdat_group);
741 }
742 node->forced_by_abi = decl_node->forced_by_abi;
743 if (DECL_EXTERNAL (decl_node->decl))
744 DECL_EXTERNAL (node->decl) = 1;
745 }
746
747 update_visibility_by_resolution_info (node);
748 if (node->weakref)
749 optimize_weakref (node);
750 }
751 FOR_EACH_DEFINED_FUNCTION (node)
752 {
753 if (!node->local.local)
754 node->local.local |= node->local_p ();
755
756 /* If we know that function can not be overwritten by a
757 different semantics and moreover its section can not be
758 discarded, replace all direct calls by calls to an
759 noninterposable alias. This make dynamic linking cheaper and
760 enable more optimization.
761
762 TODO: We can also update virtual tables. */
763 if (node->callers
764 && can_replace_by_local_alias (node))
765 {
766 cgraph_node *alias = dyn_cast<cgraph_node *>
767 (node->noninterposable_alias ());
768
769 if (alias && alias != node)
770 {
771 while (node->callers)
772 {
773 struct cgraph_edge *e = node->callers;
774
775 e->redirect_callee (alias);
776 if (gimple_has_body_p (e->caller->decl))
777 {
778 push_cfun (DECL_STRUCT_FUNCTION (e->caller->decl));
779 e->redirect_call_stmt_to_callee ();
780 pop_cfun ();
781 }
782 }
783 }
784 }
785 }
786 FOR_EACH_VARIABLE (vnode)
787 {
788 /* weak flag makes no sense on local variables. */
789 gcc_assert (!DECL_WEAK (vnode->decl)
790 || vnode->weakref
791 || TREE_PUBLIC (vnode->decl)
792 || DECL_EXTERNAL (vnode->decl));
793 /* In several cases declarations can not be common:
794
795 - when declaration has initializer
796 - when it is in weak
797 - when it has specific section
798 - when it resides in non-generic address space.
799 - if declaration is local, it will get into .local common section
800 so common flag is not needed. Frontends still produce these in
801 certain cases, such as for:
802
803 static int a __attribute__ ((common))
804
805 Canonicalize things here and clear the redundant flag. */
806 if (DECL_COMMON (vnode->decl)
807 && (!(TREE_PUBLIC (vnode->decl)
808 || DECL_EXTERNAL (vnode->decl))
809 || (DECL_INITIAL (vnode->decl)
810 && DECL_INITIAL (vnode->decl) != error_mark_node)
811 || DECL_WEAK (vnode->decl)
812 || DECL_SECTION_NAME (vnode->decl) != NULL
813 || ! (ADDR_SPACE_GENERIC_P
814 (TYPE_ADDR_SPACE (TREE_TYPE (vnode->decl))))))
815 DECL_COMMON (vnode->decl) = 0;
816 if (vnode->weakref)
817 optimize_weakref (vnode);
818 }
819 FOR_EACH_DEFINED_VARIABLE (vnode)
820 {
821 if (!vnode->definition)
822 continue;
823 if (vnode->externally_visible_p ())
824 vnode->externally_visible = true;
825 else
826 {
827 vnode->externally_visible = false;
828 vnode->forced_by_abi = false;
829 }
830 if (lookup_attribute ("no_reorder",
831 DECL_ATTRIBUTES (vnode->decl)))
832 vnode->no_reorder = 1;
833
834 if (!vnode->externally_visible
835 && !vnode->transparent_alias
836 && !DECL_EXTERNAL (vnode->decl))
837 localize_node (whole_program, vnode);
838
839 update_visibility_by_resolution_info (vnode);
840
841 /* Update virtual tables to point to local aliases where possible. */
842 if (DECL_VIRTUAL_P (vnode->decl)
843 && !DECL_EXTERNAL (vnode->decl))
844 {
845 int i;
846 struct ipa_ref *ref;
847 bool found = false;
848
849 /* See if there is something to update. */
850 for (i = 0; vnode->iterate_reference (i, ref); i++)
851 if (ref->use == IPA_REF_ADDR
852 && can_replace_by_local_alias_in_vtable (ref->referred))
853 {
854 found = true;
855 break;
856 }
857 if (found)
858 {
859 hash_set<tree> visited_nodes;
860
861 vnode->get_constructor ();
862 walk_tree (&DECL_INITIAL (vnode->decl),
863 update_vtable_references, NULL, &visited_nodes);
864 vnode->remove_all_references ();
865 record_references_in_initializer (vnode->decl, false);
866 }
867 }
868 }
869
870 if (dump_file)
871 {
872 fprintf (dump_file, "\nMarking local functions:");
873 FOR_EACH_DEFINED_FUNCTION (node)
874 if (node->local.local)
875 fprintf (dump_file, " %s", node->name ());
876 fprintf (dump_file, "\n\n");
877 fprintf (dump_file, "\nMarking externally visible functions:");
878 FOR_EACH_DEFINED_FUNCTION (node)
879 if (node->externally_visible)
880 fprintf (dump_file, " %s", node->name ());
881 fprintf (dump_file, "\n\n");
882 fprintf (dump_file, "\nMarking externally visible variables:");
883 FOR_EACH_DEFINED_VARIABLE (vnode)
884 if (vnode->externally_visible)
885 fprintf (dump_file, " %s", vnode->name ());
886 fprintf (dump_file, "\n\n");
887 }
888 symtab->function_flags_ready = true;
889 return 0;
890}
891
892/* Local function pass handling visibilities. This happens before LTO streaming
893 so in particular -fwhole-program should be ignored at this level. */
894
895namespace {
896
897const pass_data pass_data_ipa_function_and_variable_visibility =
898{
899 SIMPLE_IPA_PASS, /* type */
900 "visibility", /* name */
901 OPTGROUP_NONE, /* optinfo_flags */
902 TV_CGRAPHOPT, /* tv_id */
903 0, /* properties_required */
904 0, /* properties_provided */
905 0, /* properties_destroyed */
906 0, /* todo_flags_start */
907 ( TODO_remove_functions | TODO_dump_symtab ), /* todo_flags_finish */
908};
909
910/* Bring functions local at LTO time with -fwhole-program. */
911
912static unsigned int
913whole_program_function_and_variable_visibility (void)
914{
915 function_and_variable_visibility (flag_whole_program);
916 if (optimize || in_lto_p)
917 ipa_discover_readonly_nonaddressable_vars ();
918 return 0;
919}
920
921} // anon namespace
922
923namespace {
924
925const pass_data pass_data_ipa_whole_program_visibility =
926{
927 IPA_PASS, /* type */
928 "whole-program", /* name */
929 OPTGROUP_NONE, /* optinfo_flags */
930 TV_CGRAPHOPT, /* tv_id */
931 0, /* properties_required */
932 0, /* properties_provided */
933 0, /* properties_destroyed */
934 0, /* todo_flags_start */
935 ( TODO_remove_functions | TODO_dump_symtab ), /* todo_flags_finish */
936};
937
938class pass_ipa_whole_program_visibility : public ipa_opt_pass_d
939{
940public:
941 pass_ipa_whole_program_visibility (gcc::context *ctxt)
942 : ipa_opt_pass_d (pass_data_ipa_whole_program_visibility, ctxt,
943 NULL, /* generate_summary */
944 NULL, /* write_summary */
945 NULL, /* read_summary */
946 NULL, /* write_optimization_summary */
947 NULL, /* read_optimization_summary */
948 NULL, /* stmt_fixup */
949 0, /* function_transform_todo_flags_start */
950 NULL, /* function_transform */
951 NULL) /* variable_transform */
952 {}
953
954 /* opt_pass methods: */
955
956 virtual bool gate (function *)
957 {
958 /* Do not re-run on ltrans stage. */
959 return !flag_ltrans;
960 }
961 virtual unsigned int execute (function *)
962 {
963 return whole_program_function_and_variable_visibility ();
964 }
965
966}; // class pass_ipa_whole_program_visibility
967
968} // anon namespace
969
970ipa_opt_pass_d *
971make_pass_ipa_whole_program_visibility (gcc::context *ctxt)
972{
973 return new pass_ipa_whole_program_visibility (ctxt);
974}
975
976class pass_ipa_function_and_variable_visibility : public simple_ipa_opt_pass
977{
978public:
979 pass_ipa_function_and_variable_visibility (gcc::context *ctxt)
980 : simple_ipa_opt_pass (pass_data_ipa_function_and_variable_visibility,
981 ctxt)
982 {}
983
984 /* opt_pass methods: */
985 virtual unsigned int execute (function *)
986 {
987 return function_and_variable_visibility (flag_whole_program && !flag_lto);
988 }
989
990}; // class pass_ipa_function_and_variable_visibility
991
992simple_ipa_opt_pass *
993make_pass_ipa_function_and_variable_visibility (gcc::context *ctxt)
994{
995 return new pass_ipa_function_and_variable_visibility (ctxt);
996}
997