gcc/lto/lto-symtab.c

   1 /* LTO symbol table.
   2    Copyright (C) 2009-2015 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 "diagnostic-core.h"
  25 #include "hash-set.h"
  26 #include "machmode.h"
  27 #include "vec.h"
  28 #include "double-int.h"
  29 #include "input.h"
  30 #include "alias.h"
  31 #include "symtab.h"
  32 #include "options.h"
  33 #include "wide-int.h"
  34 #include "inchash.h"
  35 #include "tree.h"
  36 #include "fold-const.h"
  37 #include "predict.h"
  38 #include "tm.h"
  39 #include "hard-reg-set.h"
  40 #include "input.h"
  41 #include "function.h"
  42 #include "basic-block.h"
  43 #include "tree-ssa-alias.h"
  44 #include "internal-fn.h"
  45 #include "gimple-expr.h"
  46 #include "is-a.h"
  47 #include "gimple.h"
  48 #include "plugin-api.h"
  49 #include "hash-map.h"
  50 #include "ipa-ref.h"
  51 #include "cgraph.h"
  52 #include "lto-streamer.h"
  53 #include "ipa-utils.h"
  54 #include "alloc-pool.h"
  55 #include "symbol-summary.h"
  56 #include "ipa-prop.h"
  57 #include "ipa-inline.h"
  58 #include "builtins.h"
  59
  60 /* Replace the cgraph node NODE with PREVAILING_NODE in the cgraph, merging
  61    all edges and removing the old node.  */
  62
  63 static void
  64 lto_cgraph_replace_node (struct cgraph_node *node,
  65                          struct cgraph_node *prevailing_node)
  66 {
  67   struct cgraph_edge *e, *next;
  68   bool compatible_p;
  69
  70   if (symtab->dump_file)
  71     {
  72       fprintf (symtab->dump_file, "Replacing cgraph node %s/%i by %s/%i"
  73                " for symbol %s\n",
  74                node->name (), node->order,
  75                prevailing_node->name (),
  76                prevailing_node->order,
  77                IDENTIFIER_POINTER ((*targetm.asm_out.mangle_assembler_name)
  78                  (IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (node->decl)))));
  79     }
  80
  81   /* Merge node flags.  */
  82   if (node->force_output)
  83     prevailing_node->mark_force_output ();
  84   if (node->forced_by_abi)
  85     prevailing_node->forced_by_abi = true;
  86   if (node->address_taken)
  87     {
  88       gcc_assert (!prevailing_node->global.inlined_to);
  89       prevailing_node->mark_address_taken ();
  90     }
  91   if (node->definition && prevailing_node->definition)
  92     prevailing_node->merged = true;
  93
  94   /* Redirect all incoming edges.  */
  95   compatible_p
  96     = types_compatible_p (TREE_TYPE (TREE_TYPE (prevailing_node->decl)),
  97                           TREE_TYPE (TREE_TYPE (node->decl)));
  98   for (e = node->callers; e; e = next)
  99     {
 100       next = e->next_caller;
 101       e->redirect_callee (prevailing_node);
 102       /* If there is a mismatch between the supposed callee return type and
 103          the real one do not attempt to inline this function.
 104          ???  We really need a way to match function signatures for ABI
 105          compatibility and perform related promotions at inlining time.  */
 106       if (!compatible_p)
 107         e->call_stmt_cannot_inline_p = 1;
 108     }
 109   /* Redirect incomming references.  */
 110   prevailing_node->clone_referring (node);
 111
 112   /* Fix instrumentation references.  */
 113   if (node->instrumented_version)
 114     {
 115       gcc_assert (node->instrumentation_clone
 116                   == prevailing_node->instrumentation_clone);
 117       node->instrumented_version->instrumented_version = prevailing_node;
 118       if (!prevailing_node->instrumented_version)
 119         prevailing_node->instrumented_version = node->instrumented_version;
 120       /* Need to reset node->instrumented_version to NULL,
 121          otherwise node removal code would reset
 122          node->instrumented_version->instrumented_version.  */
 123       node->instrumented_version = NULL;
 124     }
 125
 126   ipa_merge_profiles (prevailing_node, node);
 127   lto_free_function_in_decl_state_for_node (node);
 128
 129   if (node->decl != prevailing_node->decl)
 130     node->release_body ();
 131
 132   /* Finally remove the replaced node.  */
 133   node->remove ();
 134 }
 135
 136 /* Replace the cgraph node NODE with PREVAILING_NODE in the cgraph, merging
 137    all edges and removing the old node.  */
 138
 139 static void
 140 lto_varpool_replace_node (varpool_node *vnode,
 141                           varpool_node *prevailing_node)
 142 {
 143   gcc_assert (!vnode->definition || prevailing_node->definition);
 144   gcc_assert (!vnode->analyzed || prevailing_node->analyzed);
 145
 146   prevailing_node->clone_referring (vnode);
 147   if (vnode->force_output)
 148     prevailing_node->force_output = true;
 149   if (vnode->forced_by_abi)
 150     prevailing_node->forced_by_abi = true;
 151
 152   /* Be sure we can garbage collect the initializer.  */
 153   if (DECL_INITIAL (vnode->decl)
 154       && vnode->decl != prevailing_node->decl)
 155     DECL_INITIAL (vnode->decl) = error_mark_node;
 156
 157   /* Check and report ODR violations on virtual tables.  */
 158   if (DECL_VIRTUAL_P (vnode->decl) || DECL_VIRTUAL_P (prevailing_node->decl))
 159     compare_virtual_tables (prevailing_node, vnode);
 160
 161   if (vnode->tls_model != prevailing_node->tls_model)
 162     {
 163       bool error = false;
 164
 165       /* Non-TLS and TLS never mix together.  Also emulated model is not
 166          compatible with anything else.  */
 167       if (prevailing_node->tls_model == TLS_MODEL_NONE
 168           || prevailing_node->tls_model == TLS_MODEL_EMULATED
 169           || vnode->tls_model == TLS_MODEL_NONE
 170           || vnode->tls_model == TLS_MODEL_EMULATED)
 171         error = true;
 172       /* Linked is silently supporting transitions
 173          GD -> IE, GD -> LE, LD -> LE, IE -> LE, LD -> IE.
 174          Do the same transitions and error out on others.  */
 175       else if ((prevailing_node->tls_model == TLS_MODEL_REAL
 176                 || prevailing_node->tls_model == TLS_MODEL_LOCAL_DYNAMIC)
 177                && (vnode->tls_model == TLS_MODEL_INITIAL_EXEC
 178                    || vnode->tls_model == TLS_MODEL_LOCAL_EXEC))
 179         prevailing_node->tls_model = vnode->tls_model;
 180       else if ((vnode->tls_model == TLS_MODEL_REAL
 181                 || vnode->tls_model == TLS_MODEL_LOCAL_DYNAMIC)
 182                && (prevailing_node->tls_model == TLS_MODEL_INITIAL_EXEC
 183                    || prevailing_node->tls_model == TLS_MODEL_LOCAL_EXEC))
 184         ;
 185       else if (prevailing_node->tls_model == TLS_MODEL_INITIAL_EXEC
 186                && vnode->tls_model == TLS_MODEL_LOCAL_EXEC)
 187         prevailing_node->tls_model = vnode->tls_model;
 188       else if (vnode->tls_model == TLS_MODEL_INITIAL_EXEC
 189                && prevailing_node->tls_model == TLS_MODEL_LOCAL_EXEC)
 190         ;
 191       else
 192         error = true;
 193       if (error)
 194         {
 195           error_at (DECL_SOURCE_LOCATION (vnode->decl),
 196                     "%qD is defined with tls model %s", vnode->decl, tls_model_names [vnode->tls_model]);
 197           inform (DECL_SOURCE_LOCATION (prevailing_node->decl),
 198                   "previously defined here as %s",
 199                   tls_model_names [prevailing_node->tls_model]);
 200         }
 201     }
 202   /* Finally remove the replaced node.  */
 203   vnode->remove ();
 204 }
 205
 206 /* Merge two variable or function symbol table entries PREVAILING and ENTRY.
 207    Return false if the symbols are not fully compatible and a diagnostic
 208    should be emitted.  */
 209
 210 static bool
 211 lto_symtab_merge (symtab_node *prevailing, symtab_node *entry)
 212 {
 213   tree prevailing_decl = prevailing->decl;
 214   tree decl = entry->decl;
 215   tree prevailing_type, type;
 216
 217   if (prevailing_decl == decl)
 218     return true;
 219
 220   /* Merge decl state in both directions, we may still end up using
 221      the new decl.  */
 222   TREE_ADDRESSABLE (prevailing_decl) |= TREE_ADDRESSABLE (decl);
 223   TREE_ADDRESSABLE (decl) |= TREE_ADDRESSABLE (prevailing_decl);
 224
 225   /* The linker may ask us to combine two incompatible symbols.
 226      Detect this case and notify the caller of required diagnostics.  */
 227
 228   if (TREE_CODE (decl) == FUNCTION_DECL)
 229     {
 230       if (!types_compatible_p (TREE_TYPE (prevailing_decl),
 231                                TREE_TYPE (decl)))
 232         /* If we don't have a merged type yet...sigh.  The linker
 233            wouldn't complain if the types were mismatched, so we
 234            probably shouldn't either.  Just use the type from
 235            whichever decl appears to be associated with the
 236            definition.  If for some odd reason neither decl is, the
 237            older one wins.  */
 238         (void) 0;
 239
 240       return true;
 241     }
 242
 243   /* Now we exclusively deal with VAR_DECLs.  */
 244
 245   /* Sharing a global symbol is a strong hint that two types are
 246      compatible.  We could use this information to complete
 247      incomplete pointed-to types more aggressively here, ignoring
 248      mismatches in both field and tag names.  It's difficult though
 249      to guarantee that this does not have side-effects on merging
 250      more compatible types from other translation units though.  */
 251
 252   /* We can tolerate differences in type qualification, the
 253      qualification of the prevailing definition will prevail.
 254      ???  In principle we might want to only warn for structurally
 255      incompatible types here, but unless we have protective measures
 256      for TBAA in place that would hide useful information.  */
 257   prevailing_type = TYPE_MAIN_VARIANT (TREE_TYPE (prevailing_decl));
 258   type = TYPE_MAIN_VARIANT (TREE_TYPE (decl));
 259
 260   if (!types_compatible_p (prevailing_type, type))
 261     {
 262       if (COMPLETE_TYPE_P (type))
 263         return false;
 264
 265       /* If type is incomplete then avoid warnings in the cases
 266          that TBAA handles just fine.  */
 267
 268       if (TREE_CODE (prevailing_type) != TREE_CODE (type))
 269         return false;
 270
 271       if (TREE_CODE (prevailing_type) == ARRAY_TYPE)
 272         {
 273           tree tem1 = TREE_TYPE (prevailing_type);
 274           tree tem2 = TREE_TYPE (type);
 275           while (TREE_CODE (tem1) == ARRAY_TYPE
 276                  && TREE_CODE (tem2) == ARRAY_TYPE)
 277             {
 278               tem1 = TREE_TYPE (tem1);
 279               tem2 = TREE_TYPE (tem2);
 280             }
 281
 282           if (TREE_CODE (tem1) != TREE_CODE (tem2))
 283             return false;
 284
 285           if (!types_compatible_p (tem1, tem2))
 286             return false;
 287         }
 288
 289       /* Fallthru.  Compatible enough.  */
 290     }
 291
 292   /* ???  We might want to emit a warning here if type qualification
 293      differences were spotted.  Do not do this unconditionally though.  */
 294
 295   /* There is no point in comparing too many details of the decls here.
 296      The type compatibility checks or the completing of types has properly
 297      dealt with most issues.  */
 298
 299   /* The following should all not invoke fatal errors as in non-LTO
 300      mode the linker wouldn't complain either.  Just emit warnings.  */
 301
 302   /* Report a warning if user-specified alignments do not match.  */
 303   if ((DECL_USER_ALIGN (prevailing_decl) && DECL_USER_ALIGN (decl))
 304       && DECL_ALIGN (prevailing_decl) < DECL_ALIGN (decl))
 305     return false;
 306
 307   return true;
 308 }
 309
 310 /* Return true if the symtab entry E can be replaced by another symtab
 311    entry.  */
 312
 313 static bool
 314 lto_symtab_resolve_replaceable_p (symtab_node *e)
 315 {
 316   if (DECL_EXTERNAL (e->decl)
 317       || DECL_COMDAT (e->decl)
 318       || DECL_ONE_ONLY (e->decl)
 319       || DECL_WEAK (e->decl))
 320     return true;
 321
 322   if (TREE_CODE (e->decl) == VAR_DECL)
 323     return (DECL_COMMON (e->decl)
 324             || (!flag_no_common && !DECL_INITIAL (e->decl)));
 325
 326   return false;
 327 }
 328
 329 /* Return true, if the symbol E should be resolved by lto-symtab.
 330    Those are all external symbols and all real symbols that are not static (we
 331    handle renaming of static later in partitioning).  */
 332
 333 static bool
 334 lto_symtab_symbol_p (symtab_node *e)
 335 {
 336   if (!TREE_PUBLIC (e->decl) && !DECL_EXTERNAL (e->decl))
 337     return false;
 338   return e->real_symbol_p ();
 339 }
 340
 341 /* Return true if the symtab entry E can be the prevailing one.  */
 342
 343 static bool
 344 lto_symtab_resolve_can_prevail_p (symtab_node *e)
 345 {
 346   if (!lto_symtab_symbol_p (e))
 347     return false;
 348
 349   /* The C++ frontend ends up neither setting TREE_STATIC nor
 350      DECL_EXTERNAL on virtual methods but only TREE_PUBLIC.
 351      So do not reject !TREE_STATIC here but only DECL_EXTERNAL.  */
 352   if (DECL_EXTERNAL (e->decl))
 353     return false;
 354
 355   return e->definition;
 356 }
 357
 358 /* Resolve the symbol with the candidates in the chain *SLOT and store
 359    their resolutions.  */
 360
 361 static symtab_node *
 362 lto_symtab_resolve_symbols (symtab_node *first)
 363 {
 364   symtab_node *e;
 365   symtab_node *prevailing = NULL;
 366
 367   /* Always set e->node so that edges are updated to reflect decl merging. */
 368   for (e = first; e; e = e->next_sharing_asm_name)
 369     if (lto_symtab_symbol_p (e)
 370         && (e->resolution == LDPR_PREVAILING_DEF_IRONLY
 371             || e->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP
 372             || e->resolution == LDPR_PREVAILING_DEF))
 373       {
 374         prevailing = e;
 375         break;
 376       }
 377
 378   /* If the chain is already resolved there is nothing else to do.  */
 379   if (prevailing)
 380     {
 381       /* Assert it's the only one.  */
 382       for (e = prevailing->next_sharing_asm_name; e; e = e->next_sharing_asm_name)
 383         if (lto_symtab_symbol_p (e)
 384             && (e->resolution == LDPR_PREVAILING_DEF_IRONLY
 385                 || e->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP
 386                 || e->resolution == LDPR_PREVAILING_DEF))
 387           fatal_error (input_location, "multiple prevailing defs for %qE",
 388                        DECL_NAME (prevailing->decl));
 389       return prevailing;
 390     }
 391
 392   /* Find the single non-replaceable prevailing symbol and
 393      diagnose ODR violations.  */
 394   for (e = first; e; e = e->next_sharing_asm_name)
 395     {
 396       if (!lto_symtab_resolve_can_prevail_p (e))
 397         continue;
 398
 399       /* If we have a non-replaceable definition it prevails.  */
 400       if (!lto_symtab_resolve_replaceable_p (e))
 401         {
 402           if (prevailing)
 403             {
 404               error_at (DECL_SOURCE_LOCATION (e->decl),
 405                         "%qD has already been defined", e->decl);
 406               inform (DECL_SOURCE_LOCATION (prevailing->decl),
 407                       "previously defined here");
 408             }
 409           prevailing = e;
 410         }
 411     }
 412   if (prevailing)
 413     return prevailing;
 414
 415   /* Do a second round choosing one from the replaceable prevailing decls.  */
 416   for (e = first; e; e = e->next_sharing_asm_name)
 417     {
 418       if (!lto_symtab_resolve_can_prevail_p (e))
 419         continue;
 420
 421       /* Choose the first function that can prevail as prevailing.  */
 422       if (TREE_CODE (e->decl) == FUNCTION_DECL)
 423         {
 424           prevailing = e;
 425           break;
 426         }
 427
 428       /* From variables that can prevail choose the largest one.  */
 429       if (!prevailing
 430           || tree_int_cst_lt (DECL_SIZE (prevailing->decl),
 431                               DECL_SIZE (e->decl))
 432           /* When variables are equivalent try to chose one that has useful
 433              DECL_INITIAL.  This makes sense for keyed vtables that are
 434              DECL_EXTERNAL but initialized.  In units that do not need them
 435              we replace the initializer by error_mark_node to conserve
 436              memory.
 437
 438              We know that the vtable is keyed outside the LTO unit - otherwise
 439              the keyed instance would prevail.  We still can preserve useful
 440              info in the initializer.  */
 441           || (DECL_SIZE (prevailing->decl) == DECL_SIZE (e->decl)
 442               && (DECL_INITIAL (e->decl)
 443                   && DECL_INITIAL (e->decl) != error_mark_node)
 444               && (!DECL_INITIAL (prevailing->decl)
 445                   || DECL_INITIAL (prevailing->decl) == error_mark_node)))
 446         prevailing = e;
 447     }
 448
 449   return prevailing;
 450 }
 451
 452 /* Merge all decls in the symbol table chain to the prevailing decl and
 453    issue diagnostics about type mismatches.  If DIAGNOSED_P is true
 454    do not issue further diagnostics.*/
 455
 456 static void
 457 lto_symtab_merge_decls_2 (symtab_node *first, bool diagnosed_p)
 458 {
 459   symtab_node *prevailing;
 460   symtab_node *e;
 461   vec<tree> mismatches = vNULL;
 462   unsigned i;
 463   tree decl;
 464
 465   /* Nothing to do for a single entry.  */
 466   prevailing = first;
 467   if (!prevailing->next_sharing_asm_name)
 468     return;
 469
 470   /* Try to merge each entry with the prevailing one.  */
 471   for (e = prevailing->next_sharing_asm_name;
 472        e; e = e->next_sharing_asm_name)
 473     if (TREE_PUBLIC (e->decl))
 474       {
 475         if (!lto_symtab_merge (prevailing, e)
 476             && !diagnosed_p)
 477           mismatches.safe_push (e->decl);
 478       }
 479   if (mismatches.is_empty ())
 480     return;
 481
 482   /* Diagnose all mismatched re-declarations.  */
 483   FOR_EACH_VEC_ELT (mismatches, i, decl)
 484     {
 485       if (!types_compatible_p (TREE_TYPE (prevailing->decl),
 486                                TREE_TYPE (decl)))
 487         diagnosed_p |= warning_at (DECL_SOURCE_LOCATION (decl), 0,
 488                                    "type of %qD does not match original "
 489                                    "declaration", decl);
 490
 491       else if ((DECL_USER_ALIGN (prevailing->decl)
 492                 && DECL_USER_ALIGN (decl))
 493                && DECL_ALIGN (prevailing->decl) < DECL_ALIGN (decl))
 494         {
 495           diagnosed_p |= warning_at (DECL_SOURCE_LOCATION (decl), 0,
 496                                      "alignment of %qD is bigger than "
 497                                      "original declaration", decl);
 498         }
 499     }
 500   if (diagnosed_p)
 501     inform (DECL_SOURCE_LOCATION (prevailing->decl),
 502             "previously declared here");
 503
 504   mismatches.release ();
 505 }
 506
 507 /* Helper to process the decl chain for the symbol table entry *SLOT.  */
 508
 509 static void
 510 lto_symtab_merge_decls_1 (symtab_node *first)
 511 {
 512   symtab_node *e;
 513   symtab_node *prevailing;
 514   bool diagnosed_p = false;
 515
 516   if (symtab->dump_file)
 517     {
 518       fprintf (symtab->dump_file, "Merging nodes for %s. Candidates:\n",
 519                first->asm_name ());
 520       for (e = first; e; e = e->next_sharing_asm_name)
 521         if (TREE_PUBLIC (e->decl))
 522           e->dump (symtab->dump_file);
 523     }
 524
 525   /* Compute the symbol resolutions.  This is a no-op when using the
 526      linker plugin and resolution was decided by the linker.  */
 527   prevailing = lto_symtab_resolve_symbols (first);
 528
 529   /* If there's not a prevailing symbol yet it's an external reference.
 530      Happens a lot during ltrans.  Choose the first symbol with a
 531      cgraph or a varpool node.  */
 532   if (!prevailing)
 533     {
 534       for (prevailing = first;
 535            prevailing; prevailing = prevailing->next_sharing_asm_name)
 536         if (lto_symtab_symbol_p (prevailing))
 537           break;
 538       if (!prevailing)
 539         return;
 540       /* For variables chose with a priority variant with vnode
 541          attached (i.e. from unit where external declaration of
 542          variable is actually used).
 543          When there are multiple variants, chose one with size.
 544          This is needed for C++ typeinfos, for example in
 545          lto/20081204-1 there are typeifos in both units, just
 546          one of them do have size.  */
 547       if (TREE_CODE (prevailing->decl) == VAR_DECL)
 548         {
 549           for (e = prevailing->next_sharing_asm_name;
 550                e; e = e->next_sharing_asm_name)
 551             if (!COMPLETE_TYPE_P (TREE_TYPE (prevailing->decl))
 552                 && COMPLETE_TYPE_P (TREE_TYPE (e->decl))
 553                 && lto_symtab_symbol_p (e))
 554               prevailing = e;
 555         }
 556       /* For variables prefer the non-builtin if one is available.  */
 557       else if (TREE_CODE (prevailing->decl) == FUNCTION_DECL)
 558         {
 559           for (e = first; e; e = e->next_sharing_asm_name)
 560             if (TREE_CODE (e->decl) == FUNCTION_DECL
 561                 && !DECL_BUILT_IN (e->decl)
 562                 && lto_symtab_symbol_p (e))
 563               {
 564                 prevailing = e;
 565                 break;
 566               }
 567         }
 568     }
 569
 570   symtab->symtab_prevail_in_asm_name_hash (prevailing);
 571
 572   /* Diagnose mismatched objects.  */
 573   for (e = prevailing->next_sharing_asm_name;
 574        e; e = e->next_sharing_asm_name)
 575     {
 576       if (TREE_CODE (prevailing->decl)
 577           == TREE_CODE (e->decl))
 578         continue;
 579       if (!lto_symtab_symbol_p (e))
 580         continue;
 581
 582       switch (TREE_CODE (prevailing->decl))
 583         {
 584         case VAR_DECL:
 585           gcc_assert (TREE_CODE (e->decl) == FUNCTION_DECL);
 586           error_at (DECL_SOURCE_LOCATION (e->decl),
 587                     "variable %qD redeclared as function",
 588                     prevailing->decl);
 589           break;
 590
 591         case FUNCTION_DECL:
 592           gcc_assert (TREE_CODE (e->decl) == VAR_DECL);
 593           error_at (DECL_SOURCE_LOCATION (e->decl),
 594                     "function %qD redeclared as variable",
 595                     prevailing->decl);
 596           break;
 597
 598         default:
 599           gcc_unreachable ();
 600         }
 601
 602       diagnosed_p = true;
 603     }
 604   if (diagnosed_p)
 605       inform (DECL_SOURCE_LOCATION (prevailing->decl),
 606               "previously declared here");
 607
 608   /* Merge the chain to the single prevailing decl and diagnose
 609      mismatches.  */
 610   lto_symtab_merge_decls_2 (prevailing, diagnosed_p);
 611
 612   if (symtab->dump_file)
 613     {
 614       fprintf (symtab->dump_file, "After resolution:\n");
 615       for (e = prevailing; e; e = e->next_sharing_asm_name)
 616         e->dump (symtab->dump_file);
 617     }
 618 }
 619
 620 /* Resolve and merge all symbol table chains to a prevailing decl.  */
 621
 622 void
 623 lto_symtab_merge_decls (void)
 624 {
 625   symtab_node *node;
 626
 627   /* Populate assembler name hash.   */
 628   symtab->symtab_initialize_asm_name_hash ();
 629
 630   FOR_EACH_SYMBOL (node)
 631     if (!node->previous_sharing_asm_name
 632         && node->next_sharing_asm_name)
 633       lto_symtab_merge_decls_1 (node);
 634 }
 635
 636 /* Helper to process the decl chain for the symbol table entry *SLOT.  */
 637
 638 static void
 639 lto_symtab_merge_symbols_1 (symtab_node *prevailing)
 640 {
 641   symtab_node *e;
 642   symtab_node *next;
 643
 644   /* Replace the cgraph node of each entry with the prevailing one.  */
 645   for (e = prevailing->next_sharing_asm_name; e;
 646        e = next)
 647     {
 648       next = e->next_sharing_asm_name;
 649
 650       if (!lto_symtab_symbol_p (e))
 651         continue;
 652       cgraph_node *ce = dyn_cast <cgraph_node *> (e);
 653       if (ce && !DECL_BUILT_IN (e->decl))
 654         lto_cgraph_replace_node (ce, dyn_cast<cgraph_node *> (prevailing));
 655       if (varpool_node *ve = dyn_cast <varpool_node *> (e))
 656         lto_varpool_replace_node (ve, dyn_cast<varpool_node *> (prevailing));
 657     }
 658
 659   return;
 660 }
 661
 662 /* Merge cgraph nodes according to the symbol merging done by
 663    lto_symtab_merge_decls.  */
 664
 665 void
 666 lto_symtab_merge_symbols (void)
 667 {
 668   symtab_node *node;
 669
 670   if (!flag_ltrans)
 671     {
 672       symtab->symtab_initialize_asm_name_hash ();
 673
 674       /* Do the actual merging.
 675          At this point we invalidate hash translating decls into symtab nodes
 676          because after removing one of duplicate decls the hash is not correcly
 677          updated to the ohter dupliate.  */
 678       FOR_EACH_SYMBOL (node)
 679         if (lto_symtab_symbol_p (node)
 680             && node->next_sharing_asm_name
 681             && !node->previous_sharing_asm_name)
 682           lto_symtab_merge_symbols_1 (node);
 683
 684       /* Resolve weakref aliases whose target are now in the compilation unit.
 685          also re-populate the hash translating decls into symtab nodes*/
 686       FOR_EACH_SYMBOL (node)
 687         {
 688           cgraph_node *cnode, *cnode2;
 689           varpool_node *vnode;
 690           symtab_node *node2;
 691
 692           if (!node->analyzed && node->alias_target)
 693             {
 694               symtab_node *tgt = symtab_node::get_for_asmname (node->alias_target);
 695               gcc_assert (node->weakref);
 696               if (tgt)
 697                 node->resolve_alias (tgt);
 698             }
 699           node->aux = NULL;
 700
 701           if (!(cnode = dyn_cast <cgraph_node *> (node))
 702               || !cnode->clone_of
 703               || cnode->clone_of->decl != cnode->decl)
 704             {
 705               /* Builtins are not merged via decl merging.  It is however
 706                  possible that tree merging unified the declaration.  We
 707                  do not want duplicate entries in symbol table.  */
 708               if (cnode && DECL_BUILT_IN (node->decl)
 709                   && (cnode2 = cgraph_node::get (node->decl))
 710                   && cnode2 != cnode)
 711                 lto_cgraph_replace_node (cnode2, cnode);
 712
 713               /* The user defined assembler variables are also not unified by their
 714                  symbol name (since it is irrelevant), but we need to unify symbol
 715                  nodes if tree merging occured.  */
 716               if ((vnode = dyn_cast <varpool_node *> (node))
 717                   && DECL_HARD_REGISTER (vnode->decl)
 718                   && (node2 = symtab_node::get (vnode->decl))
 719                   && node2 != node)
 720                 lto_varpool_replace_node (dyn_cast <varpool_node *> (node2),
 721                                           vnode);
 722
 723
 724               /* Abstract functions may have duplicated cgraph nodes attached;
 725                  remove them.  */
 726               else if (cnode && DECL_ABSTRACT_P (cnode->decl)
 727                        && (cnode2 = cgraph_node::get (node->decl))
 728                        && cnode2 != cnode)
 729                 cnode2->remove ();
 730
 731               node->decl->decl_with_vis.symtab_node = node;
 732             }
 733         }
 734     }
 735 }
 736
 737 /* Given the decl DECL, return the prevailing decl with the same name. */
 738
 739 tree
 740 lto_symtab_prevailing_decl (tree decl)
 741 {
 742   symtab_node *ret;
 743
 744   /* Builtins and local symbols are their own prevailing decl.  */
 745   if ((!TREE_PUBLIC (decl) && !DECL_EXTERNAL (decl)) || is_builtin_fn (decl))
 746     return decl;
 747
 748   /* DECL_ABSTRACT_Ps are their own prevailing decl.  */
 749   if (TREE_CODE (decl) == FUNCTION_DECL && DECL_ABSTRACT_P (decl))
 750     return decl;
 751
 752   /* Likewise builtins are their own prevailing decl.  This preserves
 753      non-builtin vs. builtin uses from compile-time.  */
 754   if (TREE_CODE (decl) == FUNCTION_DECL && DECL_BUILT_IN (decl))
 755     return decl;
 756
 757   /* Ensure DECL_ASSEMBLER_NAME will not set assembler name.  */
 758   gcc_assert (DECL_ASSEMBLER_NAME_SET_P (decl));
 759
 760   /* Walk through the list of candidates and return the one we merged to.  */
 761   ret = symtab_node::get_for_asmname (DECL_ASSEMBLER_NAME (decl));
 762   if (!ret)
 763     return decl;
 764
 765   return ret->decl;
 766 }