Mercurial > hg > CbC > CbC_gcc

comparison gcc/lto-symtab.c @ 55:77e2b8dfacca gcc-4.4.5

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
update it from 4.4.3 to 4.5.0
author ryoma <e075725@ie.u-ryukyu.ac.jp>
date Fri, 12 Feb 2010 23:39:51 +0900
parents
children b7f97abdc517
comparison
equal deleted inserted replaced
52:c156f1bd5cd9 55:77e2b8dfacca
1 /* LTO symbol table.
2 Copyright 2009 Free Software Foundation, Inc.
3 Contributed by CodeSourcery, Inc.
4
5 This file is part of GCC.
6
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 3, or (at your option) any later
10 version.
11
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
20
21 #include "config.h"
22 #include "system.h"
23 #include "coretypes.h"
24 #include "toplev.h"
25 #include "tree.h"
26 #include "gimple.h"
27 #include "ggc.h" /* lambda.h needs this */
28 #include "lambda.h" /* gcd */
29 #include "hashtab.h"
30 #include "plugin-api.h"
31 #include "lto-streamer.h"
32
33 /* Vector to keep track of external variables we've seen so far. */
34 VEC(tree,gc) *lto_global_var_decls;
35
36 /* Symbol table entry. */
37
38 struct GTY(()) lto_symtab_entry_def
39 {
40 /* The symbol table entry key, an IDENTIFIER. */
41 tree id;
42 /* The symbol table entry, a DECL. */
43 tree decl;
44 /* The cgraph node if decl is a function decl. Filled in during the
45 merging process. */
46 struct cgraph_node *node;
47 /* LTO file-data and symbol resolution for this decl. */
48 struct lto_file_decl_data * GTY((skip (""))) file_data;
49 enum ld_plugin_symbol_resolution resolution;
50 /* Pointer to the next entry with the same key. Before decl merging
51 this links all symbols from the different TUs. After decl merging
52 this links merged but incompatible decls, thus all prevailing ones
53 remaining. */
54 struct lto_symtab_entry_def *next;
55 };
56 typedef struct lto_symtab_entry_def *lto_symtab_entry_t;
57
58 /* A poor man's symbol table. This hashes identifier to prevailing DECL
59 if there is one. */
60
61 static GTY ((if_marked ("lto_symtab_entry_marked_p"),
62 param_is (struct lto_symtab_entry_def)))
63 htab_t lto_symtab_identifiers;
64
65 /* Return the hash value of an lto_symtab_entry_t object pointed to by P. */
66
67 static hashval_t
68 lto_symtab_entry_hash (const void *p)
69 {
70 const struct lto_symtab_entry_def *base =
71 (const struct lto_symtab_entry_def *) p;
72 return htab_hash_string (IDENTIFIER_POINTER (base->id));
73 }
74
75 /* Return non-zero if P1 and P2 points to lto_symtab_entry_def structs
76 corresponding to the same symbol. */
77
78 static int
79 lto_symtab_entry_eq (const void *p1, const void *p2)
80 {
81 const struct lto_symtab_entry_def *base1 =
82 (const struct lto_symtab_entry_def *) p1;
83 const struct lto_symtab_entry_def *base2 =
84 (const struct lto_symtab_entry_def *) p2;
85 return (base1->id == base2->id);
86 }
87
88 /* Returns non-zero if P points to an lto_symtab_entry_def struct that needs
89 to be marked for GC. */
90
91 static int
92 lto_symtab_entry_marked_p (const void *p)
93 {
94 const struct lto_symtab_entry_def *base =
95 (const struct lto_symtab_entry_def *) p;
96
97 /* Keep this only if the decl or the chain is marked. */
98 return (ggc_marked_p (base->decl)
99 || (base->next && ggc_marked_p (base->next)));
100 }
101
102 /* Lazily initialize resolution hash tables. */
103
104 static void
105 lto_symtab_maybe_init_hash_table (void)
106 {
107 if (lto_symtab_identifiers)
108 return;
109
110 lto_symtab_identifiers =
111 htab_create_ggc (1021, lto_symtab_entry_hash,
112 lto_symtab_entry_eq, NULL);
113 }
114
115 /* Registers DECL with the LTO symbol table as having resolution RESOLUTION
116 and read from FILE_DATA. */
117
118 void
119 lto_symtab_register_decl (tree decl,
120 ld_plugin_symbol_resolution_t resolution,
121 struct lto_file_decl_data *file_data)
122 {
123 lto_symtab_entry_t new_entry;
124 void **slot;
125
126 /* Check that declarations reaching this function do not have
127 properties inconsistent with having external linkage. If any of
128 these asertions fail, then the object file reader has failed to
129 detect these cases and issue appropriate error messages. */
130 gcc_assert (decl
131 && TREE_PUBLIC (decl)
132 && (TREE_CODE (decl) == VAR_DECL
133 || TREE_CODE (decl) == FUNCTION_DECL)
134 && DECL_ASSEMBLER_NAME_SET_P (decl));
135 if (TREE_CODE (decl) == VAR_DECL
136 && DECL_INITIAL (decl))
137 gcc_assert (!DECL_EXTERNAL (decl)
138 || (TREE_STATIC (decl) && TREE_READONLY (decl)));
139 if (TREE_CODE (decl) == FUNCTION_DECL)
140 gcc_assert (!DECL_ABSTRACT (decl));
141
142 new_entry = GGC_CNEW (struct lto_symtab_entry_def);
143 new_entry->id = DECL_ASSEMBLER_NAME (decl);
144 new_entry->decl = decl;
145 new_entry->resolution = resolution;
146 new_entry->file_data = file_data;
147
148 lto_symtab_maybe_init_hash_table ();
149 slot = htab_find_slot (lto_symtab_identifiers, new_entry, INSERT);
150 new_entry->next = (lto_symtab_entry_t) *slot;
151 *slot = new_entry;
152 }
153
154 /* Get the lto_symtab_entry_def struct associated with ID
155 if there is one. */
156
157 static lto_symtab_entry_t
158 lto_symtab_get (tree id)
159 {
160 struct lto_symtab_entry_def temp;
161 void **slot;
162
163 lto_symtab_maybe_init_hash_table ();
164 temp.id = id;
165 slot = htab_find_slot (lto_symtab_identifiers, &temp, NO_INSERT);
166 return slot ? (lto_symtab_entry_t) *slot : NULL;
167 }
168
169 /* Get the linker resolution for DECL. */
170
171 enum ld_plugin_symbol_resolution
172 lto_symtab_get_resolution (tree decl)
173 {
174 lto_symtab_entry_t e;
175
176 gcc_assert (DECL_ASSEMBLER_NAME_SET_P (decl));
177
178 e = lto_symtab_get (DECL_ASSEMBLER_NAME (decl));
179 while (e && e->decl != decl)
180 e = e->next;
181 if (!e)
182 return LDPR_UNKNOWN;
183
184 return e->resolution;
185 }
186
187
188 /* Replace the cgraph node NODE with PREVAILING_NODE in the cgraph, merging
189 all edges and removing the old node. */
190
191 static void
192 lto_cgraph_replace_node (struct cgraph_node *node,
193 struct cgraph_node *prevailing_node)
194 {
195 struct cgraph_edge *e, *next;
196
197 /* Merge node flags. */
198 if (node->needed)
199 cgraph_mark_needed_node (prevailing_node);
200 if (node->reachable)
201 cgraph_mark_reachable_node (prevailing_node);
202 if (node->address_taken)
203 {
204 gcc_assert (!prevailing_node->global.inlined_to);
205 cgraph_mark_address_taken_node (prevailing_node);
206 }
207
208 /* Redirect all incoming edges. */
209 for (e = node->callers; e; e = next)
210 {
211 next = e->next_caller;
212 cgraph_redirect_edge_callee (e, prevailing_node);
213 }
214
215 /* There are not supposed to be any outgoing edges from a node we
216 replace. Still this can happen for multiple instances of weak
217 functions. */
218 for (e = node->callees; e; e = next)
219 {
220 next = e->next_callee;
221 cgraph_remove_edge (e);
222 }
223
224 if (node->same_body)
225 {
226 struct cgraph_node *alias;
227
228 for (alias = node->same_body; alias; alias = alias->next)
229 if (DECL_ASSEMBLER_NAME_SET_P (alias->decl))
230 {
231 lto_symtab_entry_t se
232 = lto_symtab_get (DECL_ASSEMBLER_NAME (alias->decl));
233
234 for (; se; se = se->next)
235 if (se->node == node)
236 {
237 se->node = NULL;
238 break;
239 }
240 }
241 }
242
243 /* Finally remove the replaced node. */
244 cgraph_remove_node (node);
245 }
246
247 /* Merge two variable or function symbol table entries PREVAILING and ENTRY.
248 Return false if the symbols are not fully compatible and a diagnostic
249 should be emitted. */
250
251 static bool
252 lto_symtab_merge (lto_symtab_entry_t prevailing, lto_symtab_entry_t entry)
253 {
254 tree prevailing_decl = prevailing->decl;
255 tree decl = entry->decl;
256 tree prevailing_type, type;
257
258 /* Merge decl state in both directions, we may still end up using
259 the new decl. */
260 TREE_ADDRESSABLE (prevailing_decl) |= TREE_ADDRESSABLE (decl);
261 TREE_ADDRESSABLE (decl) |= TREE_ADDRESSABLE (prevailing_decl);
262
263 /* The linker may ask us to combine two incompatible symbols.
264 Detect this case and notify the caller of required diagnostics. */
265
266 if (TREE_CODE (decl) == FUNCTION_DECL)
267 {
268 if (TREE_TYPE (prevailing_decl) != TREE_TYPE (decl))
269 /* If we don't have a merged type yet...sigh. The linker
270 wouldn't complain if the types were mismatched, so we
271 probably shouldn't either. Just use the type from
272 whichever decl appears to be associated with the
273 definition. If for some odd reason neither decl is, the
274 older one wins. */
275 (void) 0;
276
277 return true;
278 }
279
280 /* Now we exclusively deal with VAR_DECLs. */
281
282 /* Sharing a global symbol is a strong hint that two types are
283 compatible. We could use this information to complete
284 incomplete pointed-to types more aggressively here, ignoring
285 mismatches in both field and tag names. It's difficult though
286 to guarantee that this does not have side-effects on merging
287 more compatible types from other translation units though. */
288
289 /* We can tolerate differences in type qualification, the
290 qualification of the prevailing definition will prevail.
291 ??? In principle we might want to only warn for structurally
292 incompatible types here, but unless we have protective measures
293 for TBAA in place that would hide useful information. */
294 prevailing_type = TYPE_MAIN_VARIANT (TREE_TYPE (prevailing_decl));
295 type = TYPE_MAIN_VARIANT (TREE_TYPE (decl));
296
297 /* We have to register and fetch canonical types here as the global
298 fixup process didn't yet run. */
299 prevailing_type = gimple_register_type (prevailing_type);
300 type = gimple_register_type (type);
301 if (prevailing_type != type)
302 {
303 if (COMPLETE_TYPE_P (type))
304 return false;
305
306 /* If type is incomplete then avoid warnings in the cases
307 that TBAA handles just fine. */
308
309 if (TREE_CODE (prevailing_type) != TREE_CODE (type))
310 return false;
311
312 if (TREE_CODE (prevailing_type) == ARRAY_TYPE)
313 {
314 tree tem1 = TREE_TYPE (prevailing_type);
315 tree tem2 = TREE_TYPE (type);
316 while (TREE_CODE (tem1) == ARRAY_TYPE
317 && TREE_CODE (tem2) == ARRAY_TYPE)
318 {
319 tem1 = TREE_TYPE (tem1);
320 tem2 = TREE_TYPE (tem2);
321 }
322
323 if (TREE_CODE (tem1) != TREE_CODE (tem2))
324 return false;
325
326 if (gimple_register_type (tem1) != gimple_register_type (tem2))
327 return false;
328 }
329
330 /* Fallthru. Compatible enough. */
331 }
332
333 /* ??? We might want to emit a warning here if type qualification
334 differences were spotted. Do not do this unconditionally though. */
335
336 /* There is no point in comparing too many details of the decls here.
337 The type compatibility checks or the completing of types has properly
338 dealt with most issues. */
339
340 /* The following should all not invoke fatal errors as in non-LTO
341 mode the linker wouldn't complain either. Just emit warnings. */
342
343 /* Report a warning if user-specified alignments do not match. */
344 if ((DECL_USER_ALIGN (prevailing_decl) && DECL_USER_ALIGN (decl))
345 && DECL_ALIGN (prevailing_decl) < DECL_ALIGN (decl))
346 return false;
347
348 return true;
349 }
350
351 /* Return true if the symtab entry E can be replaced by another symtab
352 entry. */
353
354 static bool
355 lto_symtab_resolve_replaceable_p (lto_symtab_entry_t e)
356 {
357 if (DECL_EXTERNAL (e->decl)
358 || DECL_COMDAT (e->decl)
359 || DECL_WEAK (e->decl))
360 return true;
361
362 if (TREE_CODE (e->decl) == VAR_DECL)
363 return (DECL_COMMON (e->decl)
364 || (!flag_no_common && !DECL_INITIAL (e->decl)));
365
366 return false;
367 }
368
369 /* Return true if the symtab entry E can be the prevailing one. */
370
371 static bool
372 lto_symtab_resolve_can_prevail_p (lto_symtab_entry_t e)
373 {
374 /* The C++ frontend ends up neither setting TREE_STATIC nor
375 DECL_EXTERNAL on virtual methods but only TREE_PUBLIC.
376 So do not reject !TREE_STATIC here but only DECL_EXTERNAL. */
377 if (DECL_EXTERNAL (e->decl))
378 return false;
379
380 /* For functions we need a non-discarded body. */
381 if (TREE_CODE (e->decl) == FUNCTION_DECL)
382 return (e->node && e->node->analyzed);
383
384 /* A variable should have a size. */
385 else if (TREE_CODE (e->decl) == VAR_DECL)
386 return (DECL_SIZE (e->decl) != NULL_TREE
387 /* The C++ frontend retains TREE_STATIC on the declaration
388 of foo_ in struct Foo { static Foo *foo_; }; but it is
389 not a definition. g++.dg/lto/20090315_0.C. */
390 && !DECL_EXTERNAL (e->decl));
391
392 gcc_unreachable ();
393 }
394
395 /* Resolve the symbol with the candidates in the chain *SLOT and store
396 their resolutions. */
397
398 static void
399 lto_symtab_resolve_symbols (void **slot)
400 {
401 lto_symtab_entry_t e;
402 lto_symtab_entry_t prevailing = NULL;
403
404 /* Always set e->node so that edges are updated to reflect decl merging. */
405 for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
406 {
407 if (TREE_CODE (e->decl) == FUNCTION_DECL)
408 e->node = cgraph_get_node (e->decl);
409 }
410
411 e = (lto_symtab_entry_t) *slot;
412
413 /* If the chain is already resolved there is nothing else to do. */
414 if (e->resolution != LDPR_UNKNOWN)
415 return;
416
417 /* Find the single non-replaceable prevailing symbol and
418 diagnose ODR violations. */
419 for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
420 {
421 if (!lto_symtab_resolve_can_prevail_p (e))
422 {
423 e->resolution = LDPR_RESOLVED_IR;
424 continue;
425 }
426
427 /* Set a default resolution - the final prevailing one will get
428 adjusted later. */
429 e->resolution = LDPR_PREEMPTED_IR;
430 if (!lto_symtab_resolve_replaceable_p (e))
431 {
432 if (prevailing)
433 {
434 error_at (DECL_SOURCE_LOCATION (e->decl),
435 "%qD has already been defined", e->decl);
436 inform (DECL_SOURCE_LOCATION (prevailing->decl),
437 "previously defined here");
438 }
439 prevailing = e;
440 }
441 }
442 if (prevailing)
443 goto found;
444
445 /* Do a second round choosing one from the replaceable prevailing decls. */
446 for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
447 {
448 if (e->resolution != LDPR_PREEMPTED_IR)
449 continue;
450
451 /* Choose the first function that can prevail as prevailing. */
452 if (TREE_CODE (e->decl) == FUNCTION_DECL)
453 {
454 prevailing = e;
455 break;
456 }
457
458 /* From variables that can prevail choose the largest one. */
459 if (!prevailing
460 || tree_int_cst_lt (DECL_SIZE (prevailing->decl),
461 DECL_SIZE (e->decl)))
462 prevailing = e;
463 }
464
465 if (!prevailing)
466 return;
467
468 found:
469 if (TREE_CODE (prevailing->decl) == VAR_DECL
470 && TREE_READONLY (prevailing->decl))
471 prevailing->resolution = LDPR_PREVAILING_DEF_IRONLY;
472 else
473 prevailing->resolution = LDPR_PREVAILING_DEF;
474 }
475
476 /* Merge all decls in the symbol table chain to the prevailing decl and
477 issue diagnostics about type mismatches. */
478
479 static void
480 lto_symtab_merge_decls_2 (void **slot)
481 {
482 lto_symtab_entry_t prevailing, e;
483 VEC(tree, heap) *mismatches = NULL;
484 unsigned i;
485 tree decl;
486 bool diagnosed_p = false;
487
488 /* Nothing to do for a single entry. */
489 prevailing = (lto_symtab_entry_t) *slot;
490 if (!prevailing->next)
491 return;
492
493 /* Try to merge each entry with the prevailing one. */
494 for (e = prevailing->next; e; e = e->next)
495 {
496 if (!lto_symtab_merge (prevailing, e))
497 VEC_safe_push (tree, heap, mismatches, e->decl);
498 }
499 if (VEC_empty (tree, mismatches))
500 return;
501
502 /* Diagnose all mismatched re-declarations. */
503 for (i = 0; VEC_iterate (tree, mismatches, i, decl); ++i)
504 {
505 if (TREE_TYPE (prevailing->decl) != TREE_TYPE (decl))
506 diagnosed_p |= warning_at (DECL_SOURCE_LOCATION (decl), 0,
507 "type of %qD does not match original "
508 "declaration", decl);
509
510 else if ((DECL_USER_ALIGN (prevailing->decl) && DECL_USER_ALIGN (decl))
511 && DECL_ALIGN (prevailing->decl) < DECL_ALIGN (decl))
512 {
513 diagnosed_p |= warning_at (DECL_SOURCE_LOCATION (decl), 0,
514 "alignment of %qD is bigger than "
515 "original declaration", decl);
516 }
517 }
518 if (diagnosed_p)
519 inform (DECL_SOURCE_LOCATION (prevailing->decl),
520 "previously declared here");
521
522 VEC_free (tree, heap, mismatches);
523 }
524
525 /* Helper to process the decl chain for the symbol table entry *SLOT. */
526
527 static int
528 lto_symtab_merge_decls_1 (void **slot, void *data ATTRIBUTE_UNUSED)
529 {
530 lto_symtab_entry_t e, prevailing;
531 bool diagnosed_p = false;
532
533 /* Compute the symbol resolutions. This is a no-op when using the
534 linker plugin. */
535 lto_symtab_resolve_symbols (slot);
536
537 /* Find the prevailing decl. */
538 for (prevailing = (lto_symtab_entry_t) *slot;
539 prevailing
540 && prevailing->resolution != LDPR_PREVAILING_DEF_IRONLY
541 && prevailing->resolution != LDPR_PREVAILING_DEF;
542 prevailing = prevailing->next)
543 ;
544
545 /* Assert it's the only one. */
546 if (prevailing)
547 for (e = prevailing->next; e; e = e->next)
548 gcc_assert (e->resolution != LDPR_PREVAILING_DEF_IRONLY
549 && e->resolution != LDPR_PREVAILING_DEF);
550
551 /* If there's not a prevailing symbol yet it's an external reference.
552 Happens a lot during ltrans. Choose the first symbol with a
553 cgraph or a varpool node. */
554 if (!prevailing)
555 {
556 prevailing = (lto_symtab_entry_t) *slot;
557 /* For functions choose one with a cgraph node. */
558 if (TREE_CODE (prevailing->decl) == FUNCTION_DECL)
559 while (!prevailing->node
560 && prevailing->next)
561 prevailing = prevailing->next;
562 /* We do not stream varpool nodes, so the first decl has to
563 be good enough for now.
564 ??? For QOI choose a variable with readonly initializer
565 if there is one. This matches C++
566 struct Foo { static const int i = 1; }; without a real
567 definition. */
568 if (TREE_CODE (prevailing->decl) == VAR_DECL)
569 while (!(TREE_READONLY (prevailing->decl)
570 && DECL_INITIAL (prevailing->decl))
571 && prevailing->next)
572 prevailing = prevailing->next;
573 }
574
575 /* Move it first in the list. */
576 if ((lto_symtab_entry_t) *slot != prevailing)
577 {
578 for (e = (lto_symtab_entry_t) *slot; e->next != prevailing; e = e->next)
579 ;
580 e->next = prevailing->next;
581 prevailing->next = (lto_symtab_entry_t) *slot;
582 *slot = (void *) prevailing;
583 }
584
585 /* Record the prevailing variable. */
586 if (TREE_CODE (prevailing->decl) == VAR_DECL)
587 VEC_safe_push (tree, gc, lto_global_var_decls, prevailing->decl);
588
589 /* Diagnose mismatched objects. */
590 for (e = prevailing->next; e; e = e->next)
591 {
592 if (TREE_CODE (prevailing->decl) == TREE_CODE (e->decl))
593 continue;
594
595 switch (TREE_CODE (prevailing->decl))
596 {
597 case VAR_DECL:
598 gcc_assert (TREE_CODE (e->decl) == FUNCTION_DECL);
599 error_at (DECL_SOURCE_LOCATION (e->decl),
600 "variable %qD redeclared as function", prevailing->decl);
601 break;
602
603 case FUNCTION_DECL:
604 gcc_assert (TREE_CODE (e->decl) == VAR_DECL);
605 error_at (DECL_SOURCE_LOCATION (e->decl),
606 "function %qD redeclared as variable", prevailing->decl);
607 break;
608
609 default:
610 gcc_unreachable ();
611 }
612
613 diagnosed_p = true;
614 }
615 if (diagnosed_p)
616 inform (DECL_SOURCE_LOCATION (prevailing->decl),
617 "previously declared here");
618
619 /* Register and adjust types of the entries. */
620 for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
621 TREE_TYPE (e->decl) = gimple_register_type (TREE_TYPE (e->decl));
622
623 /* Merge the chain to the single prevailing decl and diagnose
624 mismatches. */
625 lto_symtab_merge_decls_2 (slot);
626
627 /* Drop all but the prevailing decl from the symtab. */
628 if (TREE_CODE (prevailing->decl) != FUNCTION_DECL)
629 prevailing->next = NULL;
630
631 return 1;
632 }
633
634 /* Resolve and merge all symbol table chains to a prevailing decl. */
635
636 void
637 lto_symtab_merge_decls (void)
638 {
639 lto_symtab_maybe_init_hash_table ();
640 htab_traverse (lto_symtab_identifiers, lto_symtab_merge_decls_1, NULL);
641 }
642
643 /* Helper to process the decl chain for the symbol table entry *SLOT. */
644
645 static int
646 lto_symtab_merge_cgraph_nodes_1 (void **slot, void *data ATTRIBUTE_UNUSED)
647 {
648 lto_symtab_entry_t e, prevailing = (lto_symtab_entry_t) *slot;
649
650 if (!prevailing->next)
651 return 1;
652
653 gcc_assert (TREE_CODE (prevailing->decl) == FUNCTION_DECL);
654
655 /* Replace the cgraph node of each entry with the prevailing one. */
656 for (e = prevailing->next; e; e = e->next)
657 {
658 if (e->node != NULL)
659 {
660 if (e->node->decl != e->decl && e->node->same_body)
661 {
662 struct cgraph_node *alias;
663
664 for (alias = e->node->same_body; alias; alias = alias->next)
665 if (alias->decl == e->decl)
666 break;
667 if (alias)
668 {
669 cgraph_remove_same_body_alias (alias);
670 continue;
671 }
672 }
673 lto_cgraph_replace_node (e->node, prevailing->node);
674 }
675 }
676
677 /* Drop all but the prevailing decl from the symtab. */
678 prevailing->next = NULL;
679
680 return 1;
681 }
682
683 /* Merge cgraph nodes according to the symbol merging done by
684 lto_symtab_merge_decls. */
685
686 void
687 lto_symtab_merge_cgraph_nodes (void)
688 {
689 lto_symtab_maybe_init_hash_table ();
690 htab_traverse (lto_symtab_identifiers, lto_symtab_merge_cgraph_nodes_1, NULL);
691 }
692
693 /* Given the decl DECL, return the prevailing decl with the same name. */
694
695 tree
696 lto_symtab_prevailing_decl (tree decl)
697 {
698 lto_symtab_entry_t ret;
699
700 /* Builtins and local symbols are their own prevailing decl. */
701 if (!TREE_PUBLIC (decl) || is_builtin_fn (decl))
702 return decl;
703
704 /* DECL_ABSTRACTs are their own prevailng decl. */
705 if (TREE_CODE (decl) == FUNCTION_DECL && DECL_ABSTRACT (decl))
706 return decl;
707
708 /* Ensure DECL_ASSEMBLER_NAME will not set assembler name. */
709 gcc_assert (DECL_ASSEMBLER_NAME_SET_P (decl));
710
711 /* Walk through the list of candidates and return the one we merged to. */
712 ret = lto_symtab_get (DECL_ASSEMBLER_NAME (decl));
713 if (!ret)
714 return NULL_TREE;
715
716 return ret->decl;
717 }
718
719 #include "gt-lto-symtab.h"