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);
218 /* There are not supposed to be any outgoing edges from a node we
219 replace. Still this can happen for multiple instances of weak
221 for (e = node->callees; e; e = next)
223 next = e->next_callee;
224 cgraph_remove_edge (e);
229 struct cgraph_node *alias;
231 for (alias = node->same_body; alias; alias = alias->next)
232 if (DECL_ASSEMBLER_NAME_SET_P (alias->decl))
234 lto_symtab_entry_t se
235 = lto_symtab_get (DECL_ASSEMBLER_NAME (alias->decl));
237 for (; se; se = se->next)
238 if (se->node == node)
246 /* Finally remove the replaced node. */
247 cgraph_remove_node (node);
250 /* Replace the cgraph node NODE with PREVAILING_NODE in the cgraph, merging
251 all edges and removing the old node. */
254 lto_varpool_replace_node (struct varpool_node *vnode,
255 struct varpool_node *prevailing_node)
257 /* Merge node flags. */
260 gcc_assert (prevailing_node->analyzed);
261 varpool_mark_needed_node (prevailing_node);
263 gcc_assert (!vnode->finalized || prevailing_node->finalized);
264 gcc_assert (!vnode->analyzed || prevailing_node->analyzed);
266 /* Finally remove the replaced node. */
267 varpool_remove_node (vnode);
270 /* Merge two variable or function symbol table entries PREVAILING and ENTRY.
271 Return false if the symbols are not fully compatible and a diagnostic
272 should be emitted. */
275 lto_symtab_merge (lto_symtab_entry_t prevailing, lto_symtab_entry_t entry)
277 tree prevailing_decl = prevailing->decl;
278 tree decl = entry->decl;
279 tree prevailing_type, type;
281 /* Merge decl state in both directions, we may still end up using
283 TREE_ADDRESSABLE (prevailing_decl) |= TREE_ADDRESSABLE (decl);
284 TREE_ADDRESSABLE (decl) |= TREE_ADDRESSABLE (prevailing_decl);
286 /* The linker may ask us to combine two incompatible symbols.
287 Detect this case and notify the caller of required diagnostics. */
289 if (TREE_CODE (decl) == FUNCTION_DECL)
291 if (TREE_TYPE (prevailing_decl) != TREE_TYPE (decl))
292 /* If we don't have a merged type yet...sigh. The linker
293 wouldn't complain if the types were mismatched, so we
294 probably shouldn't either. Just use the type from
295 whichever decl appears to be associated with the
296 definition. If for some odd reason neither decl is, the
303 /* Now we exclusively deal with VAR_DECLs. */
305 /* Sharing a global symbol is a strong hint that two types are
306 compatible. We could use this information to complete
307 incomplete pointed-to types more aggressively here, ignoring
308 mismatches in both field and tag names. It's difficult though
309 to guarantee that this does not have side-effects on merging
310 more compatible types from other translation units though. */
312 /* We can tolerate differences in type qualification, the
313 qualification of the prevailing definition will prevail.
314 ??? In principle we might want to only warn for structurally
315 incompatible types here, but unless we have protective measures
316 for TBAA in place that would hide useful information. */
317 prevailing_type = TYPE_MAIN_VARIANT (TREE_TYPE (prevailing_decl));
318 type = TYPE_MAIN_VARIANT (TREE_TYPE (decl));
320 /* We have to register and fetch canonical types here as the global
321 fixup process didn't yet run. */
322 prevailing_type = gimple_register_type (prevailing_type);
323 type = gimple_register_type (type);
324 if (prevailing_type != type)
326 if (COMPLETE_TYPE_P (type))
329 /* If type is incomplete then avoid warnings in the cases
330 that TBAA handles just fine. */
332 if (TREE_CODE (prevailing_type) != TREE_CODE (type))
335 if (TREE_CODE (prevailing_type) == ARRAY_TYPE)
337 tree tem1 = TREE_TYPE (prevailing_type);
338 tree tem2 = TREE_TYPE (type);
339 while (TREE_CODE (tem1) == ARRAY_TYPE
340 && TREE_CODE (tem2) == ARRAY_TYPE)
342 tem1 = TREE_TYPE (tem1);
343 tem2 = TREE_TYPE (tem2);
346 if (TREE_CODE (tem1) != TREE_CODE (tem2))
349 if (gimple_register_type (tem1) != gimple_register_type (tem2))
353 /* Fallthru. Compatible enough. */
356 /* ??? We might want to emit a warning here if type qualification
357 differences were spotted. Do not do this unconditionally though. */
359 /* There is no point in comparing too many details of the decls here.
360 The type compatibility checks or the completing of types has properly
361 dealt with most issues. */
363 /* The following should all not invoke fatal errors as in non-LTO
364 mode the linker wouldn't complain either. Just emit warnings. */
366 /* Report a warning if user-specified alignments do not match. */
367 if ((DECL_USER_ALIGN (prevailing_decl) && DECL_USER_ALIGN (decl))
368 && DECL_ALIGN (prevailing_decl) < DECL_ALIGN (decl))
374 /* Return true if the symtab entry E can be replaced by another symtab
378 lto_symtab_resolve_replaceable_p (lto_symtab_entry_t e)
380 if (DECL_EXTERNAL (e->decl)
381 || DECL_COMDAT (e->decl)
382 || DECL_WEAK (e->decl))
385 if (TREE_CODE (e->decl) == VAR_DECL)
386 return (DECL_COMMON (e->decl)
387 || (!flag_no_common && !DECL_INITIAL (e->decl)));
392 /* Return true if the symtab entry E can be the prevailing one. */
395 lto_symtab_resolve_can_prevail_p (lto_symtab_entry_t e)
397 /* The C++ frontend ends up neither setting TREE_STATIC nor
398 DECL_EXTERNAL on virtual methods but only TREE_PUBLIC.
399 So do not reject !TREE_STATIC here but only DECL_EXTERNAL. */
400 if (DECL_EXTERNAL (e->decl))
403 /* For functions we need a non-discarded body. */
404 if (TREE_CODE (e->decl) == FUNCTION_DECL)
405 return (e->node && e->node->analyzed);
407 /* A variable should have a size. */
408 else if (TREE_CODE (e->decl) == VAR_DECL)
409 return (DECL_SIZE (e->decl) != NULL_TREE
410 /* The C++ frontend retains TREE_STATIC on the declaration
411 of foo_ in struct Foo { static Foo *foo_; }; but it is
412 not a definition. g++.dg/lto/20090315_0.C. */
413 && !DECL_EXTERNAL (e->decl));
418 /* Resolve the symbol with the candidates in the chain *SLOT and store
419 their resolutions. */
422 lto_symtab_resolve_symbols (void **slot)
424 lto_symtab_entry_t e;
425 lto_symtab_entry_t prevailing = NULL;
427 /* Always set e->node so that edges are updated to reflect decl merging. */
428 for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
430 if (TREE_CODE (e->decl) == FUNCTION_DECL)
431 e->node = cgraph_get_node (e->decl);
432 else if (TREE_CODE (e->decl) == VAR_DECL)
433 e->vnode = varpool_get_node (e->decl);
436 e = (lto_symtab_entry_t) *slot;
438 /* If the chain is already resolved there is nothing else to do. */
439 if (e->resolution != LDPR_UNKNOWN)
442 /* Find the single non-replaceable prevailing symbol and
443 diagnose ODR violations. */
444 for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
446 if (!lto_symtab_resolve_can_prevail_p (e))
448 e->resolution = LDPR_RESOLVED_IR;
452 /* Set a default resolution - the final prevailing one will get
454 e->resolution = LDPR_PREEMPTED_IR;
455 if (!lto_symtab_resolve_replaceable_p (e))
459 error_at (DECL_SOURCE_LOCATION (e->decl),
460 "%qD has already been defined", e->decl);
461 inform (DECL_SOURCE_LOCATION (prevailing->decl),
462 "previously defined here");
470 /* Do a second round choosing one from the replaceable prevailing decls. */
471 for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
473 if (e->resolution != LDPR_PREEMPTED_IR)
476 /* Choose the first function that can prevail as prevailing. */
477 if (TREE_CODE (e->decl) == FUNCTION_DECL)
483 /* From variables that can prevail choose the largest one. */
485 || tree_int_cst_lt (DECL_SIZE (prevailing->decl),
486 DECL_SIZE (e->decl)))
494 if (TREE_CODE (prevailing->decl) == VAR_DECL
495 && TREE_READONLY (prevailing->decl))
496 prevailing->resolution = LDPR_PREVAILING_DEF_IRONLY;
498 prevailing->resolution = LDPR_PREVAILING_DEF;
501 /* Merge all decls in the symbol table chain to the prevailing decl and
502 issue diagnostics about type mismatches. */
505 lto_symtab_merge_decls_2 (void **slot)
507 lto_symtab_entry_t prevailing, e;
508 VEC(tree, heap) *mismatches = NULL;
511 bool diagnosed_p = false;
513 /* Nothing to do for a single entry. */
514 prevailing = (lto_symtab_entry_t) *slot;
515 if (!prevailing->next)
518 /* Try to merge each entry with the prevailing one. */
519 for (e = prevailing->next; e; e = e->next)
521 if (!lto_symtab_merge (prevailing, e))
522 VEC_safe_push (tree, heap, mismatches, e->decl);
524 if (VEC_empty (tree, mismatches))
527 /* Diagnose all mismatched re-declarations. */
528 for (i = 0; VEC_iterate (tree, mismatches, i, decl); ++i)
530 if (TREE_TYPE (prevailing->decl) != TREE_TYPE (decl))
531 diagnosed_p |= warning_at (DECL_SOURCE_LOCATION (decl), 0,
532 "type of %qD does not match original "
533 "declaration", decl);
535 else if ((DECL_USER_ALIGN (prevailing->decl) && DECL_USER_ALIGN (decl))
536 && DECL_ALIGN (prevailing->decl) < DECL_ALIGN (decl))
538 diagnosed_p |= warning_at (DECL_SOURCE_LOCATION (decl), 0,
539 "alignment of %qD is bigger than "
540 "original declaration", decl);
544 inform (DECL_SOURCE_LOCATION (prevailing->decl),
545 "previously declared here");
547 VEC_free (tree, heap, mismatches);
550 /* Helper to process the decl chain for the symbol table entry *SLOT. */
553 lto_symtab_merge_decls_1 (void **slot, void *data ATTRIBUTE_UNUSED)
555 lto_symtab_entry_t e, prevailing;
556 bool diagnosed_p = false;
558 /* Compute the symbol resolutions. This is a no-op when using the
560 lto_symtab_resolve_symbols (slot);
562 /* Find the prevailing decl. */
563 for (prevailing = (lto_symtab_entry_t) *slot;
565 && prevailing->resolution != LDPR_PREVAILING_DEF_IRONLY
566 && prevailing->resolution != LDPR_PREVAILING_DEF;
567 prevailing = prevailing->next)
570 /* Assert it's the only one. */
572 for (e = prevailing->next; e; e = e->next)
573 gcc_assert (e->resolution != LDPR_PREVAILING_DEF_IRONLY
574 && e->resolution != LDPR_PREVAILING_DEF);
576 /* If there's not a prevailing symbol yet it's an external reference.
577 Happens a lot during ltrans. Choose the first symbol with a
578 cgraph or a varpool node. */
581 prevailing = (lto_symtab_entry_t) *slot;
582 /* For functions choose one with a cgraph node. */
583 if (TREE_CODE (prevailing->decl) == FUNCTION_DECL)
584 while (!prevailing->node
586 prevailing = prevailing->next;
587 if (TREE_CODE (prevailing->decl) == VAR_DECL)
588 while (!prevailing->vnode
590 prevailing = prevailing->next;
591 /* We do not stream varpool nodes, so the first decl has to
592 be good enough for now.
593 ??? For QOI choose a variable with readonly initializer
594 if there is one. This matches C++
595 struct Foo { static const int i = 1; }; without a real
597 if (TREE_CODE (prevailing->decl) == VAR_DECL)
598 while (!(TREE_READONLY (prevailing->decl)
599 && DECL_INITIAL (prevailing->decl))
601 prevailing = prevailing->next;
604 /* Move it first in the list. */
605 if ((lto_symtab_entry_t) *slot != prevailing)
607 for (e = (lto_symtab_entry_t) *slot; e->next != prevailing; e = e->next)
609 e->next = prevailing->next;
610 prevailing->next = (lto_symtab_entry_t) *slot;
611 *slot = (void *) prevailing;
614 /* Record the prevailing variable. */
615 if (TREE_CODE (prevailing->decl) == VAR_DECL)
616 VEC_safe_push (tree, gc, lto_global_var_decls, prevailing->decl);
618 /* Diagnose mismatched objects. */
619 for (e = prevailing->next; e; e = e->next)
621 if (TREE_CODE (prevailing->decl) == TREE_CODE (e->decl))
624 switch (TREE_CODE (prevailing->decl))
627 gcc_assert (TREE_CODE (e->decl) == FUNCTION_DECL);
628 error_at (DECL_SOURCE_LOCATION (e->decl),
629 "variable %qD redeclared as function", prevailing->decl);
633 gcc_assert (TREE_CODE (e->decl) == VAR_DECL);
634 error_at (DECL_SOURCE_LOCATION (e->decl),
635 "function %qD redeclared as variable", prevailing->decl);
645 inform (DECL_SOURCE_LOCATION (prevailing->decl),
646 "previously declared here");
648 /* Register and adjust types of the entries. */
649 for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
650 TREE_TYPE (e->decl) = gimple_register_type (TREE_TYPE (e->decl));
652 /* Merge the chain to the single prevailing decl and diagnose
654 lto_symtab_merge_decls_2 (slot);
656 /* Drop all but the prevailing decl from the symtab. */
657 if (TREE_CODE (prevailing->decl) != FUNCTION_DECL
658 && TREE_CODE (prevailing->decl) != VAR_DECL)
659 prevailing->next = NULL;
664 /* Resolve and merge all symbol table chains to a prevailing decl. */
667 lto_symtab_merge_decls (void)
669 lto_symtab_maybe_init_hash_table ();
670 htab_traverse (lto_symtab_identifiers, lto_symtab_merge_decls_1, NULL);
673 /* Helper to process the decl chain for the symbol table entry *SLOT. */
676 lto_symtab_merge_cgraph_nodes_1 (void **slot, void *data ATTRIBUTE_UNUSED)
678 lto_symtab_entry_t e, prevailing = (lto_symtab_entry_t) *slot;
680 if (!prevailing->next)
683 /* Replace the cgraph node of each entry with the prevailing one. */
684 for (e = prevailing->next; e; e = e->next)
688 if (e->node->decl != e->decl && e->node->same_body)
690 struct cgraph_node *alias;
692 for (alias = e->node->same_body; alias; alias = alias->next)
693 if (alias->decl == e->decl)
697 cgraph_remove_same_body_alias (alias);
701 lto_cgraph_replace_node (e->node, prevailing->node);
703 if (e->vnode != NULL)
704 lto_varpool_replace_node (e->vnode, prevailing->vnode);
707 /* Drop all but the prevailing decl from the symtab. */
708 prevailing->next = NULL;
713 /* Merge cgraph nodes according to the symbol merging done by
714 lto_symtab_merge_decls. */
717 lto_symtab_merge_cgraph_nodes (void)
719 lto_symtab_maybe_init_hash_table ();
720 htab_traverse (lto_symtab_identifiers, lto_symtab_merge_cgraph_nodes_1, NULL);
723 /* Given the decl DECL, return the prevailing decl with the same name. */
726 lto_symtab_prevailing_decl (tree decl)
728 lto_symtab_entry_t ret;
730 /* Builtins and local symbols are their own prevailing decl. */
731 if (!TREE_PUBLIC (decl) || is_builtin_fn (decl))
734 /* DECL_ABSTRACTs are their own prevailng decl. */
735 if (TREE_CODE (decl) == FUNCTION_DECL && DECL_ABSTRACT (decl))
738 /* Ensure DECL_ASSEMBLER_NAME will not set assembler name. */
739 gcc_assert (DECL_ASSEMBLER_NAME_SET_P (decl));
741 /* Walk through the list of candidates and return the one we merged to. */
742 ret = lto_symtab_get (DECL_ASSEMBLER_NAME (decl));
749 #include "gt-lto-symtab.h"