2 Copyright 2009 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
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
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/>. */
23 #include "coretypes.h"
27 #include "ggc.h" /* lambda.h needs this */
28 #include "lambda.h" /* gcd */
30 #include "plugin-api.h"
31 #include "lto-streamer.h"
33 /* Vector to keep track of external variables we've seen so far. */
34 VEC(tree,gc) *lto_global_var_decls;
36 /* Symbol table entry. */
38 struct GTY(()) lto_symtab_entry_def
40 /* The symbol table entry key, an IDENTIFIER. */
42 /* The symbol table entry, a DECL. */
44 /* The cgraph node if decl is a function decl. Filled in during the
46 struct cgraph_node *node;
47 /* The varpool node if decl is a variable decl. Filled in during the
49 struct varpool_node *vnode;
50 /* LTO file-data and symbol resolution for this decl. */
51 struct lto_file_decl_data * GTY((skip (""))) file_data;
52 enum ld_plugin_symbol_resolution resolution;
53 /* Pointer to the next entry with the same key. Before decl merging
54 this links all symbols from the different TUs. After decl merging
55 this links merged but incompatible decls, thus all prevailing ones
57 struct lto_symtab_entry_def *next;
59 typedef struct lto_symtab_entry_def *lto_symtab_entry_t;
61 /* A poor man's symbol table. This hashes identifier to prevailing DECL
64 static GTY ((if_marked ("lto_symtab_entry_marked_p"),
65 param_is (struct lto_symtab_entry_def)))
66 htab_t lto_symtab_identifiers;
68 /* Return the hash value of an lto_symtab_entry_t object pointed to by P. */
71 lto_symtab_entry_hash (const void *p)
73 const struct lto_symtab_entry_def *base =
74 (const struct lto_symtab_entry_def *) p;
75 return htab_hash_string (IDENTIFIER_POINTER (base->id));
78 /* Return non-zero if P1 and P2 points to lto_symtab_entry_def structs
79 corresponding to the same symbol. */
82 lto_symtab_entry_eq (const void *p1, const void *p2)
84 const struct lto_symtab_entry_def *base1 =
85 (const struct lto_symtab_entry_def *) p1;
86 const struct lto_symtab_entry_def *base2 =
87 (const struct lto_symtab_entry_def *) p2;
88 return (base1->id == base2->id);
91 /* Returns non-zero if P points to an lto_symtab_entry_def struct that needs
92 to be marked for GC. */
95 lto_symtab_entry_marked_p (const void *p)
97 const struct lto_symtab_entry_def *base =
98 (const struct lto_symtab_entry_def *) p;
100 /* Keep this only if the decl or the chain is marked. */
101 return (ggc_marked_p (base->decl)
102 || (base->next && ggc_marked_p (base->next)));
105 /* Lazily initialize resolution hash tables. */
108 lto_symtab_maybe_init_hash_table (void)
110 if (lto_symtab_identifiers)
113 lto_symtab_identifiers =
114 htab_create_ggc (1021, lto_symtab_entry_hash,
115 lto_symtab_entry_eq, NULL);
118 /* Registers DECL with the LTO symbol table as having resolution RESOLUTION
119 and read from FILE_DATA. */
122 lto_symtab_register_decl (tree decl,
123 ld_plugin_symbol_resolution_t resolution,
124 struct lto_file_decl_data *file_data)
126 lto_symtab_entry_t new_entry;
129 /* Check that declarations reaching this function do not have
130 properties inconsistent with having external linkage. If any of
131 these asertions fail, then the object file reader has failed to
132 detect these cases and issue appropriate error messages. */
134 && TREE_PUBLIC (decl)
135 && (TREE_CODE (decl) == VAR_DECL
136 || TREE_CODE (decl) == FUNCTION_DECL)
137 && DECL_ASSEMBLER_NAME_SET_P (decl));
138 if (TREE_CODE (decl) == VAR_DECL
139 && DECL_INITIAL (decl))
140 gcc_assert (!DECL_EXTERNAL (decl)
141 || (TREE_STATIC (decl) && TREE_READONLY (decl)));
142 if (TREE_CODE (decl) == FUNCTION_DECL)
143 gcc_assert (!DECL_ABSTRACT (decl));
145 new_entry = GGC_CNEW (struct lto_symtab_entry_def);
146 new_entry->id = DECL_ASSEMBLER_NAME (decl);
147 new_entry->decl = decl;
148 new_entry->resolution = resolution;
149 new_entry->file_data = file_data;
151 lto_symtab_maybe_init_hash_table ();
152 slot = htab_find_slot (lto_symtab_identifiers, new_entry, INSERT);
153 new_entry->next = (lto_symtab_entry_t) *slot;
157 /* Get the lto_symtab_entry_def struct associated with ID
160 static lto_symtab_entry_t
161 lto_symtab_get (tree id)
163 struct lto_symtab_entry_def temp;
166 lto_symtab_maybe_init_hash_table ();
168 slot = htab_find_slot (lto_symtab_identifiers, &temp, NO_INSERT);
169 return slot ? (lto_symtab_entry_t) *slot : NULL;
172 /* Get the linker resolution for DECL. */
174 enum ld_plugin_symbol_resolution
175 lto_symtab_get_resolution (tree decl)
177 lto_symtab_entry_t e;
179 gcc_assert (DECL_ASSEMBLER_NAME_SET_P (decl));
181 e = lto_symtab_get (DECL_ASSEMBLER_NAME (decl));
182 while (e && e->decl != decl)
187 return e->resolution;
191 /* Replace the cgraph node NODE with PREVAILING_NODE in the cgraph, merging
192 all edges and removing the old node. */
195 lto_cgraph_replace_node (struct cgraph_node *node,
196 struct cgraph_node *prevailing_node)
198 struct cgraph_edge *e, *next;
200 /* Merge node flags. */
202 cgraph_mark_needed_node (prevailing_node);
204 cgraph_mark_reachable_node (prevailing_node);
205 if (node->address_taken)
207 gcc_assert (!prevailing_node->global.inlined_to);
208 cgraph_mark_address_taken_node (prevailing_node);
211 /* Redirect all incoming edges. */
212 for (e = node->callers; e; e = next)
214 next = e->next_caller;
215 cgraph_redirect_edge_callee (e, prevailing_node);
220 struct cgraph_node *alias;
222 for (alias = node->same_body; alias; alias = alias->next)
223 if (DECL_ASSEMBLER_NAME_SET_P (alias->decl))
225 lto_symtab_entry_t se
226 = lto_symtab_get (DECL_ASSEMBLER_NAME (alias->decl));
228 for (; se; se = se->next)
229 if (se->node == node)
237 /* Finally remove the replaced node. */
238 cgraph_remove_node (node);
241 /* Replace the cgraph node NODE with PREVAILING_NODE in the cgraph, merging
242 all edges and removing the old node. */
245 lto_varpool_replace_node (struct varpool_node *vnode,
246 struct varpool_node *prevailing_node)
248 /* Merge node flags. */
251 gcc_assert (!vnode->analyzed || prevailing_node->analyzed);
252 varpool_mark_needed_node (prevailing_node);
254 /* Relink aliases. */
255 if (vnode->extra_name && !vnode->alias)
257 struct varpool_node *alias, *last;
258 for (alias = vnode->extra_name;
259 alias; alias = alias->next)
262 alias->extra_name = prevailing_node;
265 if (prevailing_node->extra_name)
267 last->next = prevailing_node->extra_name;
268 prevailing_node->extra_name->prev = last;
270 prevailing_node->extra_name = vnode->extra_name;
271 vnode->extra_name = NULL;
273 gcc_assert (!vnode->finalized || prevailing_node->finalized);
274 gcc_assert (!vnode->analyzed || prevailing_node->analyzed);
276 /* Finally remove the replaced node. */
277 varpool_remove_node (vnode);
280 /* Merge two variable or function symbol table entries PREVAILING and ENTRY.
281 Return false if the symbols are not fully compatible and a diagnostic
282 should be emitted. */
285 lto_symtab_merge (lto_symtab_entry_t prevailing, lto_symtab_entry_t entry)
287 tree prevailing_decl = prevailing->decl;
288 tree decl = entry->decl;
289 tree prevailing_type, type;
291 /* Merge decl state in both directions, we may still end up using
293 TREE_ADDRESSABLE (prevailing_decl) |= TREE_ADDRESSABLE (decl);
294 TREE_ADDRESSABLE (decl) |= TREE_ADDRESSABLE (prevailing_decl);
296 /* The linker may ask us to combine two incompatible symbols.
297 Detect this case and notify the caller of required diagnostics. */
299 if (TREE_CODE (decl) == FUNCTION_DECL)
301 if (TREE_TYPE (prevailing_decl) != TREE_TYPE (decl))
302 /* If we don't have a merged type yet...sigh. The linker
303 wouldn't complain if the types were mismatched, so we
304 probably shouldn't either. Just use the type from
305 whichever decl appears to be associated with the
306 definition. If for some odd reason neither decl is, the
313 /* Now we exclusively deal with VAR_DECLs. */
315 /* Sharing a global symbol is a strong hint that two types are
316 compatible. We could use this information to complete
317 incomplete pointed-to types more aggressively here, ignoring
318 mismatches in both field and tag names. It's difficult though
319 to guarantee that this does not have side-effects on merging
320 more compatible types from other translation units though. */
322 /* We can tolerate differences in type qualification, the
323 qualification of the prevailing definition will prevail.
324 ??? In principle we might want to only warn for structurally
325 incompatible types here, but unless we have protective measures
326 for TBAA in place that would hide useful information. */
327 prevailing_type = TYPE_MAIN_VARIANT (TREE_TYPE (prevailing_decl));
328 type = TYPE_MAIN_VARIANT (TREE_TYPE (decl));
330 /* We have to register and fetch canonical types here as the global
331 fixup process didn't yet run. */
332 prevailing_type = gimple_register_type (prevailing_type);
333 type = gimple_register_type (type);
334 if (prevailing_type != type)
336 if (COMPLETE_TYPE_P (type))
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))
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))
359 if (gimple_register_type (tem1) != gimple_register_type (tem2))
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))
384 /* Return true if the symtab entry E can be replaced by another symtab
388 lto_symtab_resolve_replaceable_p (lto_symtab_entry_t e)
390 if (DECL_EXTERNAL (e->decl)
391 || DECL_COMDAT (e->decl)
392 || DECL_WEAK (e->decl))
395 if (TREE_CODE (e->decl) == VAR_DECL)
396 return (DECL_COMMON (e->decl)
397 || (!flag_no_common && !DECL_INITIAL (e->decl)));
402 /* Return true if the symtab entry E can be the prevailing one. */
405 lto_symtab_resolve_can_prevail_p (lto_symtab_entry_t e)
407 /* The C++ frontend ends up neither setting TREE_STATIC nor
408 DECL_EXTERNAL on virtual methods but only TREE_PUBLIC.
409 So do not reject !TREE_STATIC here but only DECL_EXTERNAL. */
410 if (DECL_EXTERNAL (e->decl))
413 /* For functions we need a non-discarded body. */
414 if (TREE_CODE (e->decl) == FUNCTION_DECL)
415 return (e->node && e->node->analyzed);
417 /* A variable should have a size. */
418 else if (TREE_CODE (e->decl) == VAR_DECL)
419 return (e->vnode && e->vnode->finalized);
424 /* Resolve the symbol with the candidates in the chain *SLOT and store
425 their resolutions. */
428 lto_symtab_resolve_symbols (void **slot)
430 lto_symtab_entry_t e;
431 lto_symtab_entry_t prevailing = NULL;
433 /* Always set e->node so that edges are updated to reflect decl merging. */
434 for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
436 if (TREE_CODE (e->decl) == FUNCTION_DECL)
437 e->node = cgraph_get_node (e->decl);
438 else if (TREE_CODE (e->decl) == VAR_DECL)
439 e->vnode = varpool_get_node (e->decl);
442 e = (lto_symtab_entry_t) *slot;
444 /* If the chain is already resolved there is nothing else to do. */
445 if (e->resolution != LDPR_UNKNOWN)
448 /* Find the single non-replaceable prevailing symbol and
449 diagnose ODR violations. */
450 for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
452 if (!lto_symtab_resolve_can_prevail_p (e))
454 e->resolution = LDPR_RESOLVED_IR;
458 /* Set a default resolution - the final prevailing one will get
460 e->resolution = LDPR_PREEMPTED_IR;
461 if (!lto_symtab_resolve_replaceable_p (e))
465 error_at (DECL_SOURCE_LOCATION (e->decl),
466 "%qD has already been defined", e->decl);
467 inform (DECL_SOURCE_LOCATION (prevailing->decl),
468 "previously defined here");
476 /* Do a second round choosing one from the replaceable prevailing decls. */
477 for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
479 if (e->resolution != LDPR_PREEMPTED_IR)
482 /* Choose the first function that can prevail as prevailing. */
483 if (TREE_CODE (e->decl) == FUNCTION_DECL)
489 /* From variables that can prevail choose the largest one. */
491 || tree_int_cst_lt (DECL_SIZE (prevailing->decl),
492 DECL_SIZE (e->decl)))
500 if (TREE_CODE (prevailing->decl) == VAR_DECL
501 && TREE_READONLY (prevailing->decl))
502 prevailing->resolution = LDPR_PREVAILING_DEF_IRONLY;
504 prevailing->resolution = LDPR_PREVAILING_DEF;
507 /* Merge all decls in the symbol table chain to the prevailing decl and
508 issue diagnostics about type mismatches. */
511 lto_symtab_merge_decls_2 (void **slot)
513 lto_symtab_entry_t prevailing, e;
514 VEC(tree, heap) *mismatches = NULL;
517 bool diagnosed_p = false;
519 /* Nothing to do for a single entry. */
520 prevailing = (lto_symtab_entry_t) *slot;
521 if (!prevailing->next)
524 /* Try to merge each entry with the prevailing one. */
525 for (e = prevailing->next; e; e = e->next)
527 if (!lto_symtab_merge (prevailing, e))
528 VEC_safe_push (tree, heap, mismatches, e->decl);
530 if (VEC_empty (tree, mismatches))
533 /* Diagnose all mismatched re-declarations. */
534 for (i = 0; VEC_iterate (tree, mismatches, i, decl); ++i)
536 if (TREE_TYPE (prevailing->decl) != TREE_TYPE (decl))
537 diagnosed_p |= warning_at (DECL_SOURCE_LOCATION (decl), 0,
538 "type of %qD does not match original "
539 "declaration", decl);
541 else if ((DECL_USER_ALIGN (prevailing->decl) && DECL_USER_ALIGN (decl))
542 && DECL_ALIGN (prevailing->decl) < DECL_ALIGN (decl))
544 diagnosed_p |= warning_at (DECL_SOURCE_LOCATION (decl), 0,
545 "alignment of %qD is bigger than "
546 "original declaration", decl);
550 inform (DECL_SOURCE_LOCATION (prevailing->decl),
551 "previously declared here");
553 VEC_free (tree, heap, mismatches);
556 /* Helper to process the decl chain for the symbol table entry *SLOT. */
559 lto_symtab_merge_decls_1 (void **slot, void *data ATTRIBUTE_UNUSED)
561 lto_symtab_entry_t e, prevailing;
562 bool diagnosed_p = false;
564 /* Compute the symbol resolutions. This is a no-op when using the
566 lto_symtab_resolve_symbols (slot);
568 /* Find the prevailing decl. */
569 for (prevailing = (lto_symtab_entry_t) *slot;
571 && prevailing->resolution != LDPR_PREVAILING_DEF_IRONLY
572 && prevailing->resolution != LDPR_PREVAILING_DEF;
573 prevailing = prevailing->next)
576 /* Assert it's the only one. */
578 for (e = prevailing->next; e; e = e->next)
579 gcc_assert (e->resolution != LDPR_PREVAILING_DEF_IRONLY
580 && e->resolution != LDPR_PREVAILING_DEF);
582 /* If there's not a prevailing symbol yet it's an external reference.
583 Happens a lot during ltrans. Choose the first symbol with a
584 cgraph or a varpool node. */
587 prevailing = (lto_symtab_entry_t) *slot;
588 /* For functions choose one with a cgraph node. */
589 if (TREE_CODE (prevailing->decl) == FUNCTION_DECL)
590 while (!prevailing->node
592 prevailing = prevailing->next;
593 if (TREE_CODE (prevailing->decl) == VAR_DECL)
594 while (!prevailing->vnode
596 prevailing = prevailing->next;
599 /* Move it first in the list. */
600 if ((lto_symtab_entry_t) *slot != prevailing)
602 for (e = (lto_symtab_entry_t) *slot; e->next != prevailing; e = e->next)
604 e->next = prevailing->next;
605 prevailing->next = (lto_symtab_entry_t) *slot;
606 *slot = (void *) prevailing;
609 /* Record the prevailing variable. */
610 if (TREE_CODE (prevailing->decl) == VAR_DECL)
611 VEC_safe_push (tree, gc, lto_global_var_decls, prevailing->decl);
613 /* Diagnose mismatched objects. */
614 for (e = prevailing->next; e; e = e->next)
616 if (TREE_CODE (prevailing->decl) == TREE_CODE (e->decl))
619 switch (TREE_CODE (prevailing->decl))
622 gcc_assert (TREE_CODE (e->decl) == FUNCTION_DECL);
623 error_at (DECL_SOURCE_LOCATION (e->decl),
624 "variable %qD redeclared as function", prevailing->decl);
628 gcc_assert (TREE_CODE (e->decl) == VAR_DECL);
629 error_at (DECL_SOURCE_LOCATION (e->decl),
630 "function %qD redeclared as variable", prevailing->decl);
640 inform (DECL_SOURCE_LOCATION (prevailing->decl),
641 "previously declared here");
643 /* Register and adjust types of the entries. */
644 for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
645 TREE_TYPE (e->decl) = gimple_register_type (TREE_TYPE (e->decl));
647 /* Merge the chain to the single prevailing decl and diagnose
649 lto_symtab_merge_decls_2 (slot);
651 /* Drop all but the prevailing decl from the symtab. */
652 if (TREE_CODE (prevailing->decl) != FUNCTION_DECL
653 && TREE_CODE (prevailing->decl) != VAR_DECL)
654 prevailing->next = NULL;
659 /* Resolve and merge all symbol table chains to a prevailing decl. */
662 lto_symtab_merge_decls (void)
664 lto_symtab_maybe_init_hash_table ();
665 htab_traverse (lto_symtab_identifiers, lto_symtab_merge_decls_1, NULL);
668 /* Helper to process the decl chain for the symbol table entry *SLOT. */
671 lto_symtab_merge_cgraph_nodes_1 (void **slot, void *data ATTRIBUTE_UNUSED)
673 lto_symtab_entry_t e, prevailing = (lto_symtab_entry_t) *slot;
675 if (!prevailing->next)
678 /* Replace the cgraph node of each entry with the prevailing one. */
679 for (e = prevailing->next; e; e = e->next)
683 if (e->node->decl != e->decl && e->node->same_body)
685 struct cgraph_node *alias;
687 for (alias = e->node->same_body; alias; alias = alias->next)
688 if (alias->decl == e->decl)
692 cgraph_remove_same_body_alias (alias);
696 lto_cgraph_replace_node (e->node, prevailing->node);
698 if (e->vnode != NULL)
699 lto_varpool_replace_node (e->vnode, prevailing->vnode);
702 /* Drop all but the prevailing decl from the symtab. */
703 prevailing->next = NULL;
708 /* Merge cgraph nodes according to the symbol merging done by
709 lto_symtab_merge_decls. */
712 lto_symtab_merge_cgraph_nodes (void)
714 lto_symtab_maybe_init_hash_table ();
715 htab_traverse (lto_symtab_identifiers, lto_symtab_merge_cgraph_nodes_1, NULL);
718 /* Given the decl DECL, return the prevailing decl with the same name. */
721 lto_symtab_prevailing_decl (tree decl)
723 lto_symtab_entry_t ret;
725 /* Builtins and local symbols are their own prevailing decl. */
726 if (!TREE_PUBLIC (decl) || is_builtin_fn (decl))
729 /* DECL_ABSTRACTs are their own prevailng decl. */
730 if (TREE_CODE (decl) == FUNCTION_DECL && DECL_ABSTRACT (decl))
733 /* Ensure DECL_ASSEMBLER_NAME will not set assembler name. */
734 gcc_assert (DECL_ASSEMBLER_NAME_SET_P (decl));
736 /* Walk through the list of candidates and return the one we merged to. */
737 ret = lto_symtab_get (DECL_ASSEMBLER_NAME (decl));
744 #include "gt-lto-symtab.h"