2011-08-31 Tom de Vries <tom@codesourcery.com>
[official-gcc.git] / gcc / lto-symtab.c
blob3a7c783f770efb3da8aa9facfd9c4ffe3b70f9fb
1 /* LTO symbol table.
2 Copyright 2009, 2010 Free Software Foundation, Inc.
3 Contributed by CodeSourcery, Inc.
5 This file is part of GCC.
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.
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.
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/>. */
21 #include "config.h"
22 #include "system.h"
23 #include "coretypes.h"
24 #include "diagnostic-core.h"
25 #include "tree.h"
26 #include "gimple.h"
27 #include "ggc.h"
28 #include "hashtab.h"
29 #include "plugin-api.h"
30 #include "lto-streamer.h"
32 /* Vector to keep track of external variables we've seen so far. */
33 VEC(tree,gc) *lto_global_var_decls;
35 /* Symbol table entry. */
37 struct GTY(()) lto_symtab_entry_def
39 /* The symbol table entry key, an IDENTIFIER. */
40 tree id;
41 /* The symbol table entry, a DECL. */
42 tree decl;
43 /* The cgraph node if decl is a function decl. Filled in during the
44 merging process. */
45 struct cgraph_node *node;
46 /* The varpool node if decl is a variable decl. Filled in during the
47 merging process. */
48 struct varpool_node *vnode;
49 /* LTO file-data and symbol resolution for this decl. */
50 struct lto_file_decl_data * GTY((skip (""))) file_data;
51 enum ld_plugin_symbol_resolution resolution;
52 /* True when resolution was guessed and not read from the file. */
53 bool guessed;
54 /* Pointer to the next entry with the same key. Before decl merging
55 this links all symbols from the different TUs. After decl merging
56 this links merged but incompatible decls, thus all prevailing ones
57 remaining. */
58 struct lto_symtab_entry_def *next;
60 typedef struct lto_symtab_entry_def *lto_symtab_entry_t;
62 /* A poor man's symbol table. This hashes identifier to prevailing DECL
63 if there is one. */
65 static GTY ((if_marked ("lto_symtab_entry_marked_p"),
66 param_is (struct lto_symtab_entry_def)))
67 htab_t lto_symtab_identifiers;
69 /* Free symtab hashtable. */
71 void
72 lto_symtab_free (void)
74 htab_delete (lto_symtab_identifiers);
75 lto_symtab_identifiers = NULL;
78 /* Return the hash value of an lto_symtab_entry_t object pointed to by P. */
80 static hashval_t
81 lto_symtab_entry_hash (const void *p)
83 const struct lto_symtab_entry_def *base =
84 (const struct lto_symtab_entry_def *) p;
85 return IDENTIFIER_HASH_VALUE (base->id);
88 /* Return non-zero if P1 and P2 points to lto_symtab_entry_def structs
89 corresponding to the same symbol. */
91 static int
92 lto_symtab_entry_eq (const void *p1, const void *p2)
94 const struct lto_symtab_entry_def *base1 =
95 (const struct lto_symtab_entry_def *) p1;
96 const struct lto_symtab_entry_def *base2 =
97 (const struct lto_symtab_entry_def *) p2;
98 return (base1->id == base2->id);
101 /* Returns non-zero if P points to an lto_symtab_entry_def struct that needs
102 to be marked for GC. */
104 static int
105 lto_symtab_entry_marked_p (const void *p)
107 const struct lto_symtab_entry_def *base =
108 (const struct lto_symtab_entry_def *) p;
110 /* Keep this only if the common IDENTIFIER_NODE of the symtab chain
111 is marked which it will be if at least one of the DECLs in the
112 chain is marked. */
113 return ggc_marked_p (base->id);
116 /* Lazily initialize resolution hash tables. */
118 static void
119 lto_symtab_maybe_init_hash_table (void)
121 if (lto_symtab_identifiers)
122 return;
124 lto_symtab_identifiers =
125 htab_create_ggc (1021, lto_symtab_entry_hash,
126 lto_symtab_entry_eq, NULL);
129 /* Registers DECL with the LTO symbol table as having resolution RESOLUTION
130 and read from FILE_DATA. */
132 void
133 lto_symtab_register_decl (tree decl,
134 ld_plugin_symbol_resolution_t resolution,
135 struct lto_file_decl_data *file_data)
137 lto_symtab_entry_t new_entry;
138 void **slot;
140 /* Check that declarations reaching this function do not have
141 properties inconsistent with having external linkage. If any of
142 these asertions fail, then the object file reader has failed to
143 detect these cases and issue appropriate error messages. */
144 gcc_assert (decl
145 && TREE_PUBLIC (decl)
146 && (TREE_CODE (decl) == VAR_DECL
147 || TREE_CODE (decl) == FUNCTION_DECL)
148 && DECL_ASSEMBLER_NAME_SET_P (decl));
149 if (TREE_CODE (decl) == VAR_DECL
150 && DECL_INITIAL (decl))
151 gcc_assert (!DECL_EXTERNAL (decl)
152 || (TREE_STATIC (decl) && TREE_READONLY (decl)));
153 if (TREE_CODE (decl) == FUNCTION_DECL)
154 gcc_assert (!DECL_ABSTRACT (decl));
156 new_entry = ggc_alloc_cleared_lto_symtab_entry_def ();
157 new_entry->id = (*targetm.asm_out.mangle_assembler_name)
158 (IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl)));
159 new_entry->decl = decl;
160 new_entry->resolution = resolution;
161 new_entry->file_data = file_data;
163 lto_symtab_maybe_init_hash_table ();
164 slot = htab_find_slot (lto_symtab_identifiers, new_entry, INSERT);
165 new_entry->next = (lto_symtab_entry_t) *slot;
166 *slot = new_entry;
169 /* Get the lto_symtab_entry_def struct associated with ID
170 if there is one. */
172 static lto_symtab_entry_t
173 lto_symtab_get (tree id)
175 struct lto_symtab_entry_def temp;
176 void **slot;
178 lto_symtab_maybe_init_hash_table ();
179 temp.id = id;
180 slot = htab_find_slot (lto_symtab_identifiers, &temp, NO_INSERT);
181 return slot ? (lto_symtab_entry_t) *slot : NULL;
184 /* Get the linker resolution for DECL. */
186 enum ld_plugin_symbol_resolution
187 lto_symtab_get_resolution (tree decl)
189 lto_symtab_entry_t e;
191 gcc_assert (DECL_ASSEMBLER_NAME_SET_P (decl));
193 e = lto_symtab_get ((*targetm.asm_out.mangle_assembler_name)
194 (IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl))));
195 while (e && e->decl != decl)
196 e = e->next;
197 if (!e)
198 return LDPR_UNKNOWN;
200 return e->resolution;
204 /* Replace the cgraph node NODE with PREVAILING_NODE in the cgraph, merging
205 all edges and removing the old node. */
207 static void
208 lto_cgraph_replace_node (struct cgraph_node *node,
209 struct cgraph_node *prevailing_node)
211 struct cgraph_edge *e, *next;
212 bool compatible_p;
214 if (cgraph_dump_file)
216 fprintf (cgraph_dump_file, "Replacing cgraph node %s/%i by %s/%i"
217 " for symbol %s\n",
218 cgraph_node_name (node), node->uid,
219 cgraph_node_name (prevailing_node),
220 prevailing_node->uid,
221 IDENTIFIER_POINTER ((*targetm.asm_out.mangle_assembler_name)
222 (IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (node->decl)))));
225 /* Merge node flags. */
226 if (node->needed)
227 cgraph_mark_needed_node (prevailing_node);
228 if (node->reachable)
229 cgraph_mark_reachable_node (prevailing_node);
230 if (node->address_taken)
232 gcc_assert (!prevailing_node->global.inlined_to);
233 cgraph_mark_address_taken_node (prevailing_node);
236 /* Redirect all incoming edges. */
237 compatible_p
238 = types_compatible_p (TREE_TYPE (TREE_TYPE (prevailing_node->decl)),
239 TREE_TYPE (TREE_TYPE (node->decl)));
240 for (e = node->callers; e; e = next)
242 next = e->next_caller;
243 cgraph_redirect_edge_callee (e, prevailing_node);
244 /* If there is a mismatch between the supposed callee return type and
245 the real one do not attempt to inline this function.
246 ??? We really need a way to match function signatures for ABI
247 compatibility and perform related promotions at inlining time. */
248 if (!compatible_p)
249 e->call_stmt_cannot_inline_p = 1;
251 /* Redirect incomming references. */
252 ipa_clone_refering (prevailing_node, NULL, &node->ref_list);
254 /* Finally remove the replaced node. */
255 cgraph_remove_node (node);
258 /* Replace the cgraph node NODE with PREVAILING_NODE in the cgraph, merging
259 all edges and removing the old node. */
261 static void
262 lto_varpool_replace_node (struct varpool_node *vnode,
263 struct varpool_node *prevailing_node)
265 /* Merge node flags. */
266 if (vnode->needed)
268 gcc_assert (!vnode->analyzed || prevailing_node->analyzed);
269 varpool_mark_needed_node (prevailing_node);
271 gcc_assert (!vnode->finalized || prevailing_node->finalized);
272 gcc_assert (!vnode->analyzed || prevailing_node->analyzed);
274 ipa_clone_refering (NULL, prevailing_node, &vnode->ref_list);
276 /* Be sure we can garbage collect the initializer. */
277 if (DECL_INITIAL (vnode->decl))
278 DECL_INITIAL (vnode->decl) = error_mark_node;
279 /* Finally remove the replaced node. */
280 varpool_remove_node (vnode);
283 /* Merge two variable or function symbol table entries PREVAILING and ENTRY.
284 Return false if the symbols are not fully compatible and a diagnostic
285 should be emitted. */
287 static bool
288 lto_symtab_merge (lto_symtab_entry_t prevailing, lto_symtab_entry_t entry)
290 tree prevailing_decl = prevailing->decl;
291 tree decl = entry->decl;
292 tree prevailing_type, type;
294 /* Merge decl state in both directions, we may still end up using
295 the new decl. */
296 TREE_ADDRESSABLE (prevailing_decl) |= TREE_ADDRESSABLE (decl);
297 TREE_ADDRESSABLE (decl) |= TREE_ADDRESSABLE (prevailing_decl);
299 /* The linker may ask us to combine two incompatible symbols.
300 Detect this case and notify the caller of required diagnostics. */
302 if (TREE_CODE (decl) == FUNCTION_DECL)
304 if (!types_compatible_p (TREE_TYPE (prevailing_decl),
305 TREE_TYPE (decl)))
306 /* If we don't have a merged type yet...sigh. The linker
307 wouldn't complain if the types were mismatched, so we
308 probably shouldn't either. Just use the type from
309 whichever decl appears to be associated with the
310 definition. If for some odd reason neither decl is, the
311 older one wins. */
312 (void) 0;
314 return true;
317 /* Now we exclusively deal with VAR_DECLs. */
319 /* Sharing a global symbol is a strong hint that two types are
320 compatible. We could use this information to complete
321 incomplete pointed-to types more aggressively here, ignoring
322 mismatches in both field and tag names. It's difficult though
323 to guarantee that this does not have side-effects on merging
324 more compatible types from other translation units though. */
326 /* We can tolerate differences in type qualification, the
327 qualification of the prevailing definition will prevail.
328 ??? In principle we might want to only warn for structurally
329 incompatible types here, but unless we have protective measures
330 for TBAA in place that would hide useful information. */
331 prevailing_type = TYPE_MAIN_VARIANT (TREE_TYPE (prevailing_decl));
332 type = TYPE_MAIN_VARIANT (TREE_TYPE (decl));
334 if (!types_compatible_p (prevailing_type, type))
336 if (COMPLETE_TYPE_P (type))
337 return false;
339 /* If type is incomplete then avoid warnings in the cases
340 that TBAA handles just fine. */
342 if (TREE_CODE (prevailing_type) != TREE_CODE (type))
343 return false;
345 if (TREE_CODE (prevailing_type) == ARRAY_TYPE)
347 tree tem1 = TREE_TYPE (prevailing_type);
348 tree tem2 = TREE_TYPE (type);
349 while (TREE_CODE (tem1) == ARRAY_TYPE
350 && TREE_CODE (tem2) == ARRAY_TYPE)
352 tem1 = TREE_TYPE (tem1);
353 tem2 = TREE_TYPE (tem2);
356 if (TREE_CODE (tem1) != TREE_CODE (tem2))
357 return false;
359 if (!types_compatible_p (tem1, tem2))
360 return false;
363 /* Fallthru. Compatible enough. */
366 /* ??? We might want to emit a warning here if type qualification
367 differences were spotted. Do not do this unconditionally though. */
369 /* There is no point in comparing too many details of the decls here.
370 The type compatibility checks or the completing of types has properly
371 dealt with most issues. */
373 /* The following should all not invoke fatal errors as in non-LTO
374 mode the linker wouldn't complain either. Just emit warnings. */
376 /* Report a warning if user-specified alignments do not match. */
377 if ((DECL_USER_ALIGN (prevailing_decl) && DECL_USER_ALIGN (decl))
378 && DECL_ALIGN (prevailing_decl) < DECL_ALIGN (decl))
379 return false;
381 return true;
384 /* Return true if the symtab entry E can be replaced by another symtab
385 entry. */
387 static bool
388 lto_symtab_resolve_replaceable_p (lto_symtab_entry_t e)
390 if (DECL_EXTERNAL (e->decl)
391 || DECL_COMDAT (e->decl)
392 || DECL_ONE_ONLY (e->decl)
393 || DECL_WEAK (e->decl))
394 return true;
396 if (TREE_CODE (e->decl) == VAR_DECL)
397 return (DECL_COMMON (e->decl)
398 || (!flag_no_common && !DECL_INITIAL (e->decl)));
400 return false;
403 /* Return true if the symtab entry E can be the prevailing one. */
405 static bool
406 lto_symtab_resolve_can_prevail_p (lto_symtab_entry_t e)
408 /* The C++ frontend ends up neither setting TREE_STATIC nor
409 DECL_EXTERNAL on virtual methods but only TREE_PUBLIC.
410 So do not reject !TREE_STATIC here but only DECL_EXTERNAL. */
411 if (DECL_EXTERNAL (e->decl))
412 return false;
414 /* For functions we need a non-discarded body. */
415 if (TREE_CODE (e->decl) == FUNCTION_DECL)
416 return (e->node && e->node->analyzed);
418 else if (TREE_CODE (e->decl) == VAR_DECL)
420 if (!e->vnode)
421 return false;
422 return e->vnode->finalized;
425 gcc_unreachable ();
428 /* Resolve the symbol with the candidates in the chain *SLOT and store
429 their resolutions. */
431 static void
432 lto_symtab_resolve_symbols (void **slot)
434 lto_symtab_entry_t e;
435 lto_symtab_entry_t prevailing = NULL;
437 /* Always set e->node so that edges are updated to reflect decl merging. */
438 for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
440 if (TREE_CODE (e->decl) == FUNCTION_DECL)
441 e->node = cgraph_get_node (e->decl);
442 else if (TREE_CODE (e->decl) == VAR_DECL)
443 e->vnode = varpool_get_node (e->decl);
446 e = (lto_symtab_entry_t) *slot;
448 /* If the chain is already resolved there is nothing else to do. */
449 if (e->resolution != LDPR_UNKNOWN)
450 return;
452 /* Find the single non-replaceable prevailing symbol and
453 diagnose ODR violations. */
454 for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
456 if (!lto_symtab_resolve_can_prevail_p (e))
458 e->resolution = LDPR_RESOLVED_IR;
459 e->guessed = true;
460 continue;
463 /* Set a default resolution - the final prevailing one will get
464 adjusted later. */
465 e->resolution = LDPR_PREEMPTED_IR;
466 e->guessed = true;
467 if (!lto_symtab_resolve_replaceable_p (e))
469 if (prevailing)
471 error_at (DECL_SOURCE_LOCATION (e->decl),
472 "%qD has already been defined", e->decl);
473 inform (DECL_SOURCE_LOCATION (prevailing->decl),
474 "previously defined here");
476 prevailing = e;
479 if (prevailing)
480 goto found;
482 /* Do a second round choosing one from the replaceable prevailing decls. */
483 for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
485 if (e->resolution != LDPR_PREEMPTED_IR)
486 continue;
488 /* Choose the first function that can prevail as prevailing. */
489 if (TREE_CODE (e->decl) == FUNCTION_DECL)
491 prevailing = e;
492 break;
495 /* From variables that can prevail choose the largest one. */
496 if (!prevailing
497 || tree_int_cst_lt (DECL_SIZE (prevailing->decl),
498 DECL_SIZE (e->decl)))
499 prevailing = e;
502 if (!prevailing)
503 return;
505 found:
506 /* If current lto files represent the whole program,
507 it is correct to use LDPR_PREVALING_DEF_IRONLY.
508 If current lto files are part of whole program, internal
509 resolver doesn't know if it is LDPR_PREVAILING_DEF
510 or LDPR_PREVAILING_DEF_IRONLY. Use IRONLY conforms to
511 using -fwhole-program. Otherwise, it doesn't
512 matter using either LDPR_PREVAILING_DEF or
513 LDPR_PREVAILING_DEF_IRONLY
515 FIXME: above workaround due to gold plugin makes some
516 variables IRONLY, which are indeed PREVAILING_DEF in
517 resolution file. These variables still need manual
518 externally_visible attribute. */
519 prevailing->resolution = LDPR_PREVAILING_DEF_IRONLY;
520 prevailing->guessed = true;
523 /* Merge all decls in the symbol table chain to the prevailing decl and
524 issue diagnostics about type mismatches. If DIAGNOSED_P is true
525 do not issue further diagnostics.*/
527 static void
528 lto_symtab_merge_decls_2 (void **slot, bool diagnosed_p)
530 lto_symtab_entry_t prevailing, e;
531 VEC(tree, heap) *mismatches = NULL;
532 unsigned i;
533 tree decl;
535 /* Nothing to do for a single entry. */
536 prevailing = (lto_symtab_entry_t) *slot;
537 if (!prevailing->next)
538 return;
540 /* Try to merge each entry with the prevailing one. */
541 for (e = prevailing->next; e; e = e->next)
543 if (!lto_symtab_merge (prevailing, e)
544 && !diagnosed_p)
545 VEC_safe_push (tree, heap, mismatches, e->decl);
547 if (VEC_empty (tree, mismatches))
548 return;
550 /* Diagnose all mismatched re-declarations. */
551 FOR_EACH_VEC_ELT (tree, mismatches, i, decl)
553 if (!types_compatible_p (TREE_TYPE (prevailing->decl), TREE_TYPE (decl)))
554 diagnosed_p |= warning_at (DECL_SOURCE_LOCATION (decl), 0,
555 "type of %qD does not match original "
556 "declaration", decl);
558 else if ((DECL_USER_ALIGN (prevailing->decl) && DECL_USER_ALIGN (decl))
559 && DECL_ALIGN (prevailing->decl) < DECL_ALIGN (decl))
561 diagnosed_p |= warning_at (DECL_SOURCE_LOCATION (decl), 0,
562 "alignment of %qD is bigger than "
563 "original declaration", decl);
566 if (diagnosed_p)
567 inform (DECL_SOURCE_LOCATION (prevailing->decl),
568 "previously declared here");
570 VEC_free (tree, heap, mismatches);
573 /* Helper to process the decl chain for the symbol table entry *SLOT. */
575 static int
576 lto_symtab_merge_decls_1 (void **slot, void *data ATTRIBUTE_UNUSED)
578 lto_symtab_entry_t e, prevailing;
579 bool diagnosed_p = false;
581 /* Compute the symbol resolutions. This is a no-op when using the
582 linker plugin. */
583 lto_symtab_resolve_symbols (slot);
585 /* Find the prevailing decl. */
586 for (prevailing = (lto_symtab_entry_t) *slot;
587 prevailing
588 && prevailing->resolution != LDPR_PREVAILING_DEF_IRONLY
589 && prevailing->resolution != LDPR_PREVAILING_DEF;
590 prevailing = prevailing->next)
593 /* Assert it's the only one. */
594 if (prevailing)
595 for (e = prevailing->next; e; e = e->next)
597 if (e->resolution == LDPR_PREVAILING_DEF_IRONLY
598 || e->resolution == LDPR_PREVAILING_DEF)
599 fatal_error ("multiple prevailing defs for %qE",
600 DECL_NAME (prevailing->decl));
603 /* If there's not a prevailing symbol yet it's an external reference.
604 Happens a lot during ltrans. Choose the first symbol with a
605 cgraph or a varpool node. */
606 if (!prevailing)
608 prevailing = (lto_symtab_entry_t) *slot;
609 /* For functions choose one with a cgraph node. */
610 if (TREE_CODE (prevailing->decl) == FUNCTION_DECL)
611 while (!prevailing->node
612 && prevailing->next)
613 prevailing = prevailing->next;
614 /* For variables chose with a priority variant with vnode
615 attached (i.e. from unit where external declaration of
616 variable is actually used).
617 When there are multiple variants, chose one with size.
618 This is needed for C++ typeinfos, for example in
619 lto/20081204-1 there are typeifos in both units, just
620 one of them do have size. */
621 if (TREE_CODE (prevailing->decl) == VAR_DECL)
623 for (e = prevailing->next; e; e = e->next)
624 if ((!prevailing->vnode && e->vnode)
625 || ((prevailing->vnode != NULL) == (e->vnode != NULL)
626 && !COMPLETE_TYPE_P (TREE_TYPE (prevailing->decl))
627 && COMPLETE_TYPE_P (TREE_TYPE (e->decl))))
628 prevailing = e;
632 /* Move it first in the list. */
633 if ((lto_symtab_entry_t) *slot != prevailing)
635 for (e = (lto_symtab_entry_t) *slot; e->next != prevailing; e = e->next)
637 e->next = prevailing->next;
638 prevailing->next = (lto_symtab_entry_t) *slot;
639 *slot = (void *) prevailing;
642 /* Record the prevailing variable. */
643 if (TREE_CODE (prevailing->decl) == VAR_DECL)
644 VEC_safe_push (tree, gc, lto_global_var_decls, prevailing->decl);
646 /* Diagnose mismatched objects. */
647 for (e = prevailing->next; e; e = e->next)
649 if (TREE_CODE (prevailing->decl) == TREE_CODE (e->decl))
650 continue;
652 switch (TREE_CODE (prevailing->decl))
654 case VAR_DECL:
655 gcc_assert (TREE_CODE (e->decl) == FUNCTION_DECL);
656 error_at (DECL_SOURCE_LOCATION (e->decl),
657 "variable %qD redeclared as function", prevailing->decl);
658 break;
660 case FUNCTION_DECL:
661 gcc_assert (TREE_CODE (e->decl) == VAR_DECL);
662 error_at (DECL_SOURCE_LOCATION (e->decl),
663 "function %qD redeclared as variable", prevailing->decl);
664 break;
666 default:
667 gcc_unreachable ();
670 diagnosed_p = true;
672 if (diagnosed_p)
673 inform (DECL_SOURCE_LOCATION (prevailing->decl),
674 "previously declared here");
676 /* Merge the chain to the single prevailing decl and diagnose
677 mismatches. */
678 lto_symtab_merge_decls_2 (slot, diagnosed_p);
680 /* Store resolution decision into the callgraph.
681 In LTRANS don't overwrite information we stored into callgraph at
682 WPA stage.
684 Do not bother to store guessed decisions. Generic code knows how
685 to handle UNKNOWN relocation well.
687 The problem with storing guessed decision is whether to use
688 PREVAILING_DEF or PREVAILING_DEF_IRONLY. First one would disable
689 some whole program optimizations, while ther second would imply
690 to many whole program assumptions. */
691 if (prevailing->node && !flag_ltrans && !prevailing->guessed)
692 prevailing->node->resolution = prevailing->resolution;
693 else if (prevailing->vnode && !flag_ltrans && !prevailing->guessed)
694 prevailing->vnode->resolution = prevailing->resolution;
695 return 1;
698 /* Resolve and merge all symbol table chains to a prevailing decl. */
700 void
701 lto_symtab_merge_decls (void)
703 lto_symtab_maybe_init_hash_table ();
704 htab_traverse (lto_symtab_identifiers, lto_symtab_merge_decls_1, NULL);
707 /* Helper to process the decl chain for the symbol table entry *SLOT. */
709 static int
710 lto_symtab_merge_cgraph_nodes_1 (void **slot, void *data ATTRIBUTE_UNUSED)
712 lto_symtab_entry_t e, prevailing = (lto_symtab_entry_t) *slot;
714 if (!prevailing->next)
715 return 1;
717 /* Replace the cgraph node of each entry with the prevailing one. */
718 for (e = prevailing->next; e; e = e->next)
720 if (e->node != NULL)
722 /* In case we prevail funcion by an alias, we can run into case
723 that the alias has no cgraph node attached, since it was
724 previously unused. Create the node. */
725 if (!prevailing->node)
727 prevailing->node = cgraph_create_node (prevailing->decl);
728 prevailing->node->alias = true;
730 lto_cgraph_replace_node (e->node, prevailing->node);
732 if (e->vnode != NULL)
734 if (!prevailing->vnode)
736 prevailing->vnode = varpool_node (prevailing->decl);
737 prevailing->vnode->alias = true;
739 lto_varpool_replace_node (e->vnode, prevailing->vnode);
743 /* Drop all but the prevailing decl from the symtab. */
744 prevailing->next = NULL;
746 return 1;
749 /* Merge cgraph nodes according to the symbol merging done by
750 lto_symtab_merge_decls. */
752 void
753 lto_symtab_merge_cgraph_nodes (void)
755 struct cgraph_node *node;
756 struct varpool_node *vnode;
757 lto_symtab_maybe_init_hash_table ();
758 htab_traverse (lto_symtab_identifiers, lto_symtab_merge_cgraph_nodes_1, NULL);
760 for (node = cgraph_nodes; node; node = node->next)
761 if ((node->thunk.thunk_p || node->alias)
762 && node->thunk.alias)
763 node->thunk.alias = lto_symtab_prevailing_decl (node->thunk.alias);
764 for (vnode = varpool_nodes; vnode; vnode = vnode->next)
765 if (vnode->alias_of)
766 vnode->alias_of = lto_symtab_prevailing_decl (vnode->alias_of);
769 /* Given the decl DECL, return the prevailing decl with the same name. */
771 tree
772 lto_symtab_prevailing_decl (tree decl)
774 lto_symtab_entry_t ret;
776 /* Builtins and local symbols are their own prevailing decl. */
777 if (!TREE_PUBLIC (decl) || is_builtin_fn (decl))
778 return decl;
780 /* DECL_ABSTRACTs are their own prevailng decl. */
781 if (TREE_CODE (decl) == FUNCTION_DECL && DECL_ABSTRACT (decl))
782 return decl;
784 /* Ensure DECL_ASSEMBLER_NAME will not set assembler name. */
785 gcc_assert (DECL_ASSEMBLER_NAME_SET_P (decl));
787 /* Walk through the list of candidates and return the one we merged to. */
788 ret = lto_symtab_get ((*targetm.asm_out.mangle_assembler_name)
789 (IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl))));
790 if (!ret)
791 return NULL_TREE;
793 return ret->decl;
796 #include "gt-lto-symtab.h"