gcc/lto-symtab.c

   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   /* LTO file-data and symbol resolution for this decl.  */
  45   struct lto_file_decl_data * GTY((skip (""))) file_data;
  46   enum ld_plugin_symbol_resolution resolution;
  47   /* Pointer to the next entry with the same key.  Before decl merging
  48      this links all symbols from the different TUs.  After decl merging
  49      this links merged but incompatible decls, thus all prevailing ones
  50      remaining.  */
  51   struct lto_symtab_entry_def *next;
  52 };
  53 typedef struct lto_symtab_entry_def *lto_symtab_entry_t;
  54
  55 /* A poor man's symbol table. This hashes identifier to prevailing DECL
  56    if there is one. */
  57
  58 static GTY ((if_marked ("lto_symtab_entry_marked_p"),
  59              param_is (struct lto_symtab_entry_def)))
  60   htab_t lto_symtab_identifiers;
  61
  62 /* Return the hash value of an lto_symtab_entry_t object pointed to by P.  */
  63
  64 static hashval_t
  65 lto_symtab_entry_hash (const void *p)
  66 {
  67   const struct lto_symtab_entry_def *base =
  68     (const struct lto_symtab_entry_def *) p;
  69   return htab_hash_string (IDENTIFIER_POINTER (base->id));
  70 }
  71
  72 /* Return non-zero if P1 and P2 points to lto_symtab_entry_def structs
  73    corresponding to the same symbol.  */
  74
  75 static int
  76 lto_symtab_entry_eq (const void *p1, const void *p2)
  77 {
  78   const struct lto_symtab_entry_def *base1 =
  79      (const struct lto_symtab_entry_def *) p1;
  80   const struct lto_symtab_entry_def *base2 =
  81      (const struct lto_symtab_entry_def *) p2;
  82   return (base1->id == base2->id);
  83 }
  84
  85 /* Returns non-zero if P points to an lto_symtab_entry_def struct that needs
  86    to be marked for GC.  */
  87
  88 static int
  89 lto_symtab_entry_marked_p (const void *p)
  90 {
  91   const struct lto_symtab_entry_def *base =
  92      (const struct lto_symtab_entry_def *) p;
  93
  94   /* Keep this only if the decl or the chain is marked.  */
  95   return (ggc_marked_p (base->decl)
  96           || (base->next && ggc_marked_p (base->next)));
  97 }
  98
  99 /* Lazily initialize resolution hash tables.  */
 100
 101 static void
 102 lto_symtab_maybe_init_hash_table (void)
 103 {
 104   if (lto_symtab_identifiers)
 105     return;
 106
 107   lto_symtab_identifiers =
 108     htab_create_ggc (1021, lto_symtab_entry_hash,
 109                      lto_symtab_entry_eq, NULL);
 110 }
 111
 112 static bool maybe_merge_incomplete_and_complete_type (tree, tree);
 113
 114 /* Try to merge an incomplete type INCOMPLETE with a complete type
 115    COMPLETE of same kinds.
 116    Return true if they were merged, false otherwise.  */
 117
 118 static bool
 119 merge_incomplete_and_complete_type (tree incomplete, tree complete)
 120 {
 121   /* For merging array types do some extra sanity checking.  */
 122   if (TREE_CODE (incomplete) == ARRAY_TYPE
 123       && !maybe_merge_incomplete_and_complete_type (TREE_TYPE (incomplete),
 124                                                     TREE_TYPE (complete))
 125       && !gimple_types_compatible_p (TREE_TYPE (incomplete),
 126                                      TREE_TYPE (complete)))
 127     return false;
 128
 129   /* ??? Ideally we would do this by means of a common canonical type, but
 130      that's difficult as we do not have links from the canonical type
 131      back to all its children.  */
 132   gimple_force_type_merge (incomplete, complete);
 133
 134   return true;
 135 }
 136
 137 /* Try to merge a maybe complete / incomplete type pair TYPE1 and TYPE2.
 138    Return true if they were merged, false otherwise.  */
 139
 140 static bool
 141 maybe_merge_incomplete_and_complete_type (tree type1, tree type2)
 142 {
 143   bool res = false;
 144
 145   if (TREE_CODE (type1) != TREE_CODE (type2))
 146     return false;
 147
 148   if (!COMPLETE_TYPE_P (type1) && COMPLETE_TYPE_P (type2))
 149     res = merge_incomplete_and_complete_type (type1, type2);
 150   else if (COMPLETE_TYPE_P (type1) && !COMPLETE_TYPE_P (type2))
 151     res = merge_incomplete_and_complete_type (type2, type1);
 152
 153   /* Recurse on pointer targets.  */
 154   if (!res
 155       && POINTER_TYPE_P (type1)
 156       && POINTER_TYPE_P (type2))
 157     res = maybe_merge_incomplete_and_complete_type (TREE_TYPE (type1),
 158                                                     TREE_TYPE (type2));
 159
 160   return res;
 161 }
 162
 163 /* Check if OLD_DECL and NEW_DECL are compatible. */
 164
 165 static bool
 166 lto_symtab_compatible (tree old_decl, tree new_decl)
 167 {
 168   tree old_type, new_type;
 169
 170   if (TREE_CODE (old_decl) != TREE_CODE (new_decl))
 171     {
 172       switch (TREE_CODE (new_decl))
 173         {
 174         case VAR_DECL:
 175           gcc_assert (TREE_CODE (old_decl) == FUNCTION_DECL);
 176           error_at (DECL_SOURCE_LOCATION (new_decl),
 177                     "function %qD redeclared as variable", new_decl);
 178           inform (DECL_SOURCE_LOCATION (old_decl),
 179                   "previously declared here");
 180           return false;
 181
 182         case FUNCTION_DECL:
 183           gcc_assert (TREE_CODE (old_decl) == VAR_DECL);
 184           error_at (DECL_SOURCE_LOCATION (new_decl),
 185                     "variable %qD redeclared as function", new_decl);
 186           inform (DECL_SOURCE_LOCATION (old_decl),
 187                   "previously declared here");
 188           return false;
 189
 190         default:
 191           gcc_unreachable ();
 192         }
 193     }
 194
 195   if (TREE_CODE (new_decl) == FUNCTION_DECL)
 196     {
 197       if (!gimple_types_compatible_p (TREE_TYPE (old_decl),
 198                                       TREE_TYPE (new_decl)))
 199         /* If we don't have a merged type yet...sigh.  The linker
 200            wouldn't complain if the types were mismatched, so we
 201            probably shouldn't either.  Just use the type from
 202            whichever decl appears to be associated with the
 203            definition.  If for some odd reason neither decl is, the
 204            older one wins.  */
 205         (void) 0;
 206
 207       return true;
 208     }
 209
 210   /* Now we exclusively deal with VAR_DECLs.  */
 211
 212   /* Handle external declarations with incomplete type or pointed-to
 213      incomplete types by forcefully merging the types.
 214      ???  In principle all types involved in the two decls should
 215      be merged forcefully, for example without considering type or
 216      field names.  */
 217   old_type = TREE_TYPE (old_decl);
 218   new_type = TREE_TYPE (new_decl);
 219
 220   if (DECL_EXTERNAL (old_decl) || DECL_EXTERNAL (new_decl))
 221     maybe_merge_incomplete_and_complete_type (old_type, new_type);
 222   else if (POINTER_TYPE_P (old_type)
 223            && POINTER_TYPE_P (new_type))
 224     maybe_merge_incomplete_and_complete_type (TREE_TYPE (old_type),
 225                                               TREE_TYPE (new_type));
 226
 227   /* For array types we have to accept external declarations with
 228      different sizes than the actual definition (164.gzip).
 229      ???  We could emit a warning here.  */
 230   if (TREE_CODE (old_type) == TREE_CODE (new_type)
 231       && TREE_CODE (old_type) == ARRAY_TYPE
 232       && COMPLETE_TYPE_P (old_type)
 233       && COMPLETE_TYPE_P (new_type)
 234       && tree_int_cst_compare (TYPE_SIZE (old_type),
 235                                TYPE_SIZE (new_type)) != 0
 236       && gimple_types_compatible_p (TREE_TYPE (old_type),
 237                                     TREE_TYPE (new_type)))
 238     {
 239       /* If only one is external use the type of the non-external decl.
 240          Else use the larger one and also adjust the decl size.
 241          ???  Directional merging would allow us to simply pick the
 242          larger one instead of rewriting it.  */
 243       if (DECL_EXTERNAL (old_decl) ^ DECL_EXTERNAL (new_decl))
 244         {
 245           if (DECL_EXTERNAL (old_decl))
 246             TREE_TYPE (old_decl) = new_type;
 247           else if (DECL_EXTERNAL (new_decl))
 248             TREE_TYPE (new_decl) = old_type;
 249         }
 250       else
 251         {
 252           if (tree_int_cst_compare (TYPE_SIZE (old_type),
 253                                     TYPE_SIZE (new_type)) < 0)
 254             {
 255               TREE_TYPE (old_decl) = new_type;
 256               DECL_SIZE (old_decl) = DECL_SIZE (new_decl);
 257               DECL_SIZE_UNIT (old_decl) = DECL_SIZE_UNIT (new_decl);
 258             }
 259           else
 260             {
 261               TREE_TYPE (new_decl) = old_type;
 262               DECL_SIZE (new_decl) = DECL_SIZE (old_decl);
 263               DECL_SIZE_UNIT (new_decl) = DECL_SIZE_UNIT (old_decl);
 264             }
 265         }
 266     }
 267
 268   /* We can tolerate differences in type qualification, the
 269      qualification of the prevailing definition will prevail.  */
 270   old_type = TYPE_MAIN_VARIANT (TREE_TYPE (old_decl));
 271   new_type = TYPE_MAIN_VARIANT (TREE_TYPE (new_decl));
 272   if (!gimple_types_compatible_p (old_type, new_type))
 273     {
 274       if (warning_at (DECL_SOURCE_LOCATION (new_decl), 0,
 275                       "type of %qD does not match original declaration",
 276                       new_decl))
 277         inform (DECL_SOURCE_LOCATION (old_decl),
 278                 "previously declared here");
 279       return false;
 280     }
 281
 282   /* ???  We might want to emit a warning here if type qualification
 283      differences were spotted.  Do not do this unconditionally though.  */
 284
 285   /* There is no point in comparing too many details of the decls here.
 286      The type compatibility checks or the completing of types has properly
 287      dealt with most issues.  */
 288
 289   /* The following should all not invoke fatal errors as in non-LTO
 290      mode the linker wouldn't complain either.  Just emit warnings.  */
 291
 292   /* Report a warning if user-specified alignments do not match.  */
 293   if ((DECL_USER_ALIGN (old_decl) && DECL_USER_ALIGN (new_decl))
 294       && DECL_ALIGN (old_decl) != DECL_ALIGN (new_decl))
 295     {
 296       warning_at (DECL_SOURCE_LOCATION (new_decl), 0,
 297                   "alignment of %qD does not match original declaration",
 298                   new_decl);
 299       inform (DECL_SOURCE_LOCATION (old_decl), "previously declared here");
 300       return false;
 301     }
 302
 303   return true;
 304 }
 305
 306 /* Registers DECL with the LTO symbol table as having resolution RESOLUTION
 307    and read from FILE_DATA. */
 308
 309 void
 310 lto_symtab_register_decl (tree decl,
 311                           ld_plugin_symbol_resolution_t resolution,
 312                           struct lto_file_decl_data *file_data)
 313 {
 314   lto_symtab_entry_t new_entry;
 315   void **slot;
 316
 317   /* Check that declarations reaching this function do not have
 318      properties inconsistent with having external linkage.  If any of
 319      these asertions fail, then the object file reader has failed to
 320      detect these cases and issue appropriate error messages.  */
 321   gcc_assert (decl
 322               && TREE_PUBLIC (decl)
 323               && (TREE_CODE (decl) == VAR_DECL
 324                   || TREE_CODE (decl) == FUNCTION_DECL)
 325               && DECL_ASSEMBLER_NAME_SET_P (decl));
 326   if (TREE_CODE (decl) == VAR_DECL)
 327     gcc_assert (!(DECL_EXTERNAL (decl) && DECL_INITIAL (decl)));
 328   if (TREE_CODE (decl) == FUNCTION_DECL)
 329     gcc_assert (!DECL_ABSTRACT (decl));
 330
 331   new_entry = GGC_CNEW (struct lto_symtab_entry_def);
 332   new_entry->id = DECL_ASSEMBLER_NAME (decl);
 333   new_entry->decl = decl;
 334   new_entry->resolution = resolution;
 335   new_entry->file_data = file_data;
 336
 337   lto_symtab_maybe_init_hash_table ();
 338   slot = htab_find_slot (lto_symtab_identifiers, new_entry, INSERT);
 339   new_entry->next = (lto_symtab_entry_t) *slot;
 340   *slot = new_entry;
 341 }
 342
 343 /* Get the lto_symtab_entry_def struct associated with ID
 344    if there is one.  */
 345
 346 static lto_symtab_entry_t
 347 lto_symtab_get (tree id)
 348 {
 349   struct lto_symtab_entry_def temp;
 350   void **slot;
 351
 352   lto_symtab_maybe_init_hash_table ();
 353   temp.id = id;
 354   slot = htab_find_slot (lto_symtab_identifiers, &temp, NO_INSERT);
 355   return slot ? (lto_symtab_entry_t) *slot : NULL;
 356 }
 357
 358 /* Get the linker resolution for DECL.  */
 359
 360 enum ld_plugin_symbol_resolution
 361 lto_symtab_get_resolution (tree decl)
 362 {
 363   lto_symtab_entry_t e;
 364
 365   gcc_assert (DECL_ASSEMBLER_NAME_SET_P (decl));
 366
 367   e = lto_symtab_get (DECL_ASSEMBLER_NAME (decl));
 368   while (e && e->decl != decl)
 369     e = e->next;
 370   if (!e)
 371     return LDPR_UNKNOWN;
 372
 373   return e->resolution;
 374 }
 375
 376 /* Replace the cgraph node OLD_NODE with NEW_NODE in the cgraph, merging
 377    all edges and removing the old node.  */
 378
 379 static void
 380 lto_cgraph_replace_node (struct cgraph_node *old_node,
 381                          struct cgraph_node *new_node)
 382 {
 383   struct cgraph_edge *e, *next;
 384
 385   /* Merge node flags.  */
 386   if (old_node->needed)
 387     cgraph_mark_needed_node (new_node);
 388   if (old_node->reachable)
 389     cgraph_mark_reachable_node (new_node);
 390   if (old_node->address_taken)
 391     cgraph_mark_address_taken_node (new_node);
 392
 393   /* Redirect all incoming edges.  */
 394   for (e = old_node->callers; e; e = next)
 395     {
 396       next = e->next_caller;
 397       cgraph_redirect_edge_callee (e, new_node);
 398     }
 399
 400   /* There are not supposed to be any outgoing edges from a node we
 401      replace.  Still this can happen for multiple instances of weak
 402      functions.
 403      ???  For now do what the old code did.  Do not create edges for them.  */
 404   for (e = old_node->callees; e; e = next)
 405     {
 406       next = e->next_callee;
 407       cgraph_remove_edge (e);
 408     }
 409
 410   /* Finally remove the replaced node.  */
 411   cgraph_remove_node (old_node);
 412 }
 413
 414 /* Merge two variable or function symbol table entries ENTRY1 and ENTRY2.
 415    Return the prevailing one or NULL if a merge is not possible.  */
 416
 417 static lto_symtab_entry_t
 418 lto_symtab_merge (lto_symtab_entry_t entry1, lto_symtab_entry_t entry2)
 419 {
 420   tree old_decl = entry1->decl;
 421   tree new_decl = entry2->decl;
 422   ld_plugin_symbol_resolution_t old_resolution = entry1->resolution;
 423   ld_plugin_symbol_resolution_t new_resolution = entry2->resolution;
 424   struct cgraph_node *old_node = NULL;
 425   struct cgraph_node *new_node = NULL;
 426
 427   /* Give ODR violation errors.  */
 428   if (new_resolution == LDPR_PREVAILING_DEF
 429       || new_resolution == LDPR_PREVAILING_DEF_IRONLY)
 430     {
 431       if ((old_resolution == LDPR_PREVAILING_DEF
 432            || old_resolution == LDPR_PREVAILING_DEF_IRONLY)
 433           && (old_resolution != new_resolution || flag_no_common))
 434         {
 435           error_at (DECL_SOURCE_LOCATION (new_decl),
 436                     "%qD has already been defined", new_decl);
 437           inform (DECL_SOURCE_LOCATION (old_decl),
 438                   "previously defined here");
 439           return NULL;
 440         }
 441     }
 442
 443   /* The linker may ask us to combine two incompatible symbols.  */
 444   if (!lto_symtab_compatible (old_decl, new_decl))
 445     return NULL;
 446
 447   if (TREE_CODE (old_decl) == FUNCTION_DECL)
 448     old_node = cgraph_get_node (old_decl);
 449   if (TREE_CODE (new_decl) == FUNCTION_DECL)
 450     new_node = cgraph_get_node (new_decl);
 451
 452   /* Merge decl state in both directions, we may still end up using
 453      the new decl.  */
 454   TREE_ADDRESSABLE (old_decl) |= TREE_ADDRESSABLE (new_decl);
 455   TREE_ADDRESSABLE (new_decl) |= TREE_ADDRESSABLE (old_decl);
 456
 457   gcc_assert (new_resolution != LDPR_UNKNOWN
 458               && new_resolution != LDPR_UNDEF
 459               && old_resolution != LDPR_UNKNOWN
 460               && old_resolution != LDPR_UNDEF);
 461
 462   if (new_resolution == LDPR_PREVAILING_DEF
 463       || new_resolution == LDPR_PREVAILING_DEF_IRONLY
 464       || (!old_node && new_node))
 465     {
 466       gcc_assert ((!old_node && new_node)
 467                   || old_resolution == LDPR_PREEMPTED_IR
 468                   || old_resolution ==  LDPR_RESOLVED_IR
 469                   || (old_resolution == new_resolution && !flag_no_common));
 470       if (old_node)
 471         lto_cgraph_replace_node (old_node, new_node);
 472       /* Choose new_decl, entry2.  */
 473       return entry2;
 474     }
 475
 476   if (new_resolution == LDPR_PREEMPTED_REG
 477       || new_resolution == LDPR_RESOLVED_EXEC
 478       || new_resolution == LDPR_RESOLVED_DYN)
 479     gcc_assert (old_resolution == LDPR_PREEMPTED_REG
 480                 || old_resolution == LDPR_RESOLVED_EXEC
 481                 || old_resolution == LDPR_RESOLVED_DYN);
 482
 483   if (new_resolution == LDPR_PREEMPTED_IR
 484       || new_resolution == LDPR_RESOLVED_IR)
 485     gcc_assert (old_resolution == LDPR_PREVAILING_DEF
 486                 || old_resolution == LDPR_PREVAILING_DEF_IRONLY
 487                 || old_resolution == LDPR_PREEMPTED_IR
 488                 || old_resolution == LDPR_RESOLVED_IR);
 489
 490   if (new_node)
 491     lto_cgraph_replace_node (new_node, old_node);
 492
 493   /* Choose old_decl, entry1.  */
 494   return entry1;
 495 }
 496
 497 /* Resolve the symbol with the candidates in the chain *SLOT and store
 498    their resolutions.  */
 499
 500 static void
 501 lto_symtab_resolve_symbols (void **slot)
 502 {
 503   lto_symtab_entry_t e = (lto_symtab_entry_t) *slot;
 504
 505   /* If the chain is already resolved there is nothing to do.  */
 506   if (e->resolution != LDPR_UNKNOWN)
 507     return;
 508
 509   /* This is a poor mans resolver.  */
 510   for (; e; e = e->next)
 511     {
 512       gcc_assert (e->resolution == LDPR_UNKNOWN);
 513       if (DECL_EXTERNAL (e->decl)
 514           || (TREE_CODE (e->decl) == FUNCTION_DECL
 515               && !cgraph_get_node (e->decl)))
 516         e->resolution = LDPR_RESOLVED_IR;
 517       else
 518         {
 519           if (TREE_READONLY (e->decl))
 520             e->resolution = LDPR_PREVAILING_DEF_IRONLY;
 521           else
 522             e->resolution = LDPR_PREVAILING_DEF;
 523         }
 524     }
 525 }
 526
 527 /* Merge one symbol table chain to a (set of) prevailing decls.  */
 528
 529 static void
 530 lto_symtab_merge_decls_2 (void **slot)
 531 {
 532   lto_symtab_entry_t e2, e1;
 533
 534   /* Nothing to do for a single entry.  */
 535   e1 = (lto_symtab_entry_t) *slot;
 536   if (!e1->next)
 537     return;
 538
 539   /* Try to merge each entry with each other entry.  In case of a
 540      single prevailing decl this is linear.  */
 541 restart:
 542   for (; e1; e1 = e1->next)
 543     for (e2 = e1->next; e2; e2 = e2->next)
 544       {
 545         lto_symtab_entry_t prevailing = lto_symtab_merge (e1, e2);
 546         if (prevailing == e1)
 547           {
 548             lto_symtab_entry_t tmp = prevailing;
 549             while (tmp->next != e2)
 550               tmp = tmp->next;
 551             tmp->next = e2->next;
 552             e2->next = NULL;
 553             e2 = tmp;
 554           }
 555         else if (prevailing == e2)
 556           {
 557             lto_symtab_entry_t tmp = (lto_symtab_entry_t) *slot;
 558             if (tmp == e1)
 559               {
 560                 *slot = e1->next;
 561                 tmp = e1->next;
 562               }
 563             else
 564               {
 565                 while (tmp->next != e1)
 566                   tmp = tmp->next;
 567                 tmp->next = e1->next;
 568               }
 569             e1->next = NULL;
 570             e1 = tmp;
 571             goto restart;
 572           }
 573       }
 574 }
 575
 576 /* Fixup the chain of prevailing variable decls *SLOT that are commonized
 577    during link-time.  */
 578
 579 static void
 580 lto_symtab_fixup_var_decls (void **slot)
 581 {
 582   lto_symtab_entry_t e = (lto_symtab_entry_t) *slot;
 583   tree size = bitsize_zero_node;
 584
 585   /* Find the largest prevailing decl and move it to the front of the chain.
 586      This is the decl we will output as representative for the common
 587      section.  */
 588   size = bitsize_zero_node;
 589   if (e->resolution == LDPR_PREVAILING_DEF_IRONLY
 590       || e->resolution == LDPR_PREVAILING_DEF)
 591     size = DECL_SIZE (e->decl);
 592   for (; e->next;)
 593     {
 594       lto_symtab_entry_t next = e->next;
 595       if ((next->resolution == LDPR_PREVAILING_DEF_IRONLY
 596            || next->resolution == LDPR_PREVAILING_DEF)
 597           && tree_int_cst_lt (size, DECL_SIZE (next->decl)))
 598         {
 599           size = DECL_SIZE (next->decl);
 600           e->next = next->next;
 601           next->next = (lto_symtab_entry_t) *slot;
 602           *slot = next;
 603         }
 604       else
 605         e = next;
 606     }
 607
 608   /* Mark everything apart from the first var as written out.  */
 609   e = (lto_symtab_entry_t) *slot;
 610   for (e = e->next; e; e = e->next)
 611     TREE_ASM_WRITTEN (e->decl) = true;
 612 }
 613
 614 /* Helper to process the decl chain for the symbol table entry *SLOT.  */
 615
 616 static int
 617 lto_symtab_merge_decls_1 (void **slot, void *data ATTRIBUTE_UNUSED)
 618 {
 619   lto_symtab_entry_t e;
 620
 621   /* Compute the symbol resolutions.  */
 622   lto_symtab_resolve_symbols (slot);
 623
 624   /* Register and adjust types of the entries.  */
 625   for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
 626     TREE_TYPE (e->decl) = gimple_register_type (TREE_TYPE (e->decl));
 627
 628   /* Merge the chain to a (hopefully) single prevailing decl.  */
 629   lto_symtab_merge_decls_2 (slot);
 630
 631   /* ???  Ideally we should delay all diagnostics until this point to
 632      avoid duplicates.  */
 633
 634   /* All done for FUNCTION_DECLs.  */
 635   e = (lto_symtab_entry_t) *slot;
 636   if (TREE_CODE (e->decl) == FUNCTION_DECL)
 637     return 1;
 638
 639   /* Fixup variables in case there are multiple prevailing ones.  */
 640   if (e->next)
 641     lto_symtab_fixup_var_decls (slot);
 642
 643   /* Insert all variable decls into the global variable decl vector.  */
 644   for (e = (lto_symtab_entry_t) *slot; e; e = e->next)
 645     VEC_safe_push (tree, gc, lto_global_var_decls, e->decl);
 646
 647   return 1;
 648 }
 649
 650 /* Resolve and merge all symbol table chains to a prevailing decl.  */
 651
 652 void
 653 lto_symtab_merge_decls (void)
 654 {
 655   lto_symtab_maybe_init_hash_table ();
 656   htab_traverse (lto_symtab_identifiers, lto_symtab_merge_decls_1, NULL);
 657 }
 658
 659
 660 /* Given the decl DECL, return the prevailing decl with the same name. */
 661
 662 tree
 663 lto_symtab_prevailing_decl (tree decl)
 664 {
 665   lto_symtab_entry_t ret;
 666
 667   /* Builtins and local symbols are their own prevailing decl.  */
 668   if (!TREE_PUBLIC (decl) || is_builtin_fn (decl))
 669     return decl;
 670
 671   /* DECL_ABSTRACTs are their own prevailng decl.  */
 672   if (TREE_CODE (decl) == FUNCTION_DECL && DECL_ABSTRACT (decl))
 673     return decl;
 674
 675   /* Ensure DECL_ASSEMBLER_NAME will not set assembler name.  */
 676   gcc_assert (DECL_ASSEMBLER_NAME_SET_P (decl));
 677
 678   /* Walk through the list of candidates and return the one we merged to.  */
 679   ret = lto_symtab_get (DECL_ASSEMBLER_NAME (decl));
 680   if (!ret)
 681     return NULL_TREE;
 682
 683   /* If there is only one candidate return it.  */
 684   if (ret->next == NULL)
 685     return ret->decl;
 686
 687   /* If there are multiple decls to choose from find the one we merged
 688      with and return that.  */
 689   while (ret)
 690     {
 691       if (gimple_types_compatible_p (TREE_TYPE (decl), TREE_TYPE (ret->decl)))
 692         return ret->decl;
 693
 694       ret = ret->next;
 695     }
 696
 697   gcc_unreachable ();
 698 }
 699
 700 /* Remove any storage used to store resolution of DECL.  */
 701
 702 void
 703 lto_symtab_clear_resolution (tree decl)
 704 {
 705   struct lto_symtab_entry_def temp;
 706   lto_symtab_entry_t head;
 707   void **slot;
 708
 709   if (!TREE_PUBLIC (decl))
 710     return;
 711
 712   /* LTO FIXME: There should be no DECL_ABSTRACT in the middle end. */
 713   if (TREE_CODE (decl) == FUNCTION_DECL && DECL_ABSTRACT (decl))
 714     return;
 715
 716   gcc_assert (DECL_ASSEMBLER_NAME_SET_P (decl));
 717
 718   lto_symtab_maybe_init_hash_table ();
 719   temp.id = DECL_ASSEMBLER_NAME (decl);
 720   slot = htab_find_slot (lto_symtab_identifiers, &temp, NO_INSERT);
 721   if (!*slot)
 722     return;
 723
 724   head = (lto_symtab_entry_t) *slot;
 725   if (head->decl == decl)
 726     {
 727       if (head->next)
 728         {
 729           *slot = head->next;
 730           head->next = NULL;
 731         }
 732       else
 733         htab_remove_elt (lto_symtab_identifiers, &temp);
 734     }
 735   else
 736     {
 737       lto_symtab_entry_t e;
 738       while (head->next && head->next->decl != decl)
 739         head = head->next;
 740       if (head->next)
 741         {
 742           e = head->next;
 743           head->next = e->next;
 744           e->next = NULL;
 745         }
 746     }
 747 }
 748
 749 #include "gt-lto-symtab.h"