gcc/varpool.c

   1 /* Callgraph handling code.
   2    Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2010
   3    Free Software Foundation, Inc.
   4    Contributed by Jan Hubicka
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify it under
   9 the terms of the GNU General Public License as published by the Free
  10 Software Foundation; either version 3, or (at your option) any later
  11 version.
  12
  13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  15 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  16 for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GCC; see the file COPYING3.  If not see
  20 <http://www.gnu.org/licenses/>.  */
  21
  22 #include "config.h"
  23 #include "system.h"
  24 #include "coretypes.h"
  25 #include "tm.h"
  26 #include "tree.h"
  27 #include "cgraph.h"
  28 #include "langhooks.h"
  29 #include "diagnostic-core.h"
  30 #include "hashtab.h"
  31 #include "ggc.h"
  32 #include "timevar.h"
  33 #include "debug.h"
  34 #include "target.h"
  35 #include "output.h"
  36 #include "gimple.h"
  37 #include "tree-flow.h"
  38 #include "flags.h"
  39
  40 /*  This file contains basic routines manipulating variable pool.
  41
  42     Varpool acts as interface in between the front-end and middle-end
  43     and drives the decision process on what variables and when are
  44     going to be compiled.
  45
  46     The varpool nodes are allocated lazily for declarations
  47     either by frontend or at callgraph construction time.
  48     All variables supposed to be output into final file needs to be
  49     explicitly marked by frontend via VARPOOL_FINALIZE_DECL function.  */
  50
  51 /* Hash table used to convert declarations into nodes.  */
  52 static GTY((param_is (struct varpool_node))) htab_t varpool_hash;
  53
  54 /* The linked list of cgraph varpool nodes.
  55    Linked via node->next pointer.  */
  56 struct varpool_node *varpool_nodes;
  57
  58 /* Queue of cgraph nodes scheduled to be lowered and output.
  59    The queue is maintained via mark_needed_node, linked via node->next_needed
  60    pointer.
  61
  62    LAST_NEEDED_NODE points to the end of queue, so it can be
  63    maintained in forward order.  GTY is needed to make it friendly to
  64    PCH.
  65
  66    During compilation we construct the queue of needed variables
  67    twice: first time it is during cgraph construction, second time it is at the
  68    end of compilation in VARPOOL_REMOVE_UNREFERENCED_DECLS so we can avoid
  69    optimized out variables being output.
  70
  71    Each variable is thus first analyzed and then later possibly output.
  72    FIRST_UNANALYZED_NODE points to first node in queue that was not analyzed
  73    yet and is moved via VARPOOL_ANALYZE_PENDING_DECLS.  */
  74
  75 struct varpool_node *varpool_nodes_queue;
  76 static GTY(()) struct varpool_node *varpool_last_needed_node;
  77 static GTY(()) struct varpool_node *varpool_first_unanalyzed_node;
  78
  79 /* Lists all assembled variables to be sent to debugger output later on.  */
  80 static GTY(()) struct varpool_node *varpool_assembled_nodes_queue;
  81
  82 /* Return name of the node used in debug output.  */
  83 const char *
  84 varpool_node_name (struct varpool_node *node)
  85 {
  86   return lang_hooks.decl_printable_name (node->decl, 2);
  87 }
  88
  89 /* Returns a hash code for P.  */
  90 static hashval_t
  91 hash_varpool_node (const void *p)
  92 {
  93   const struct varpool_node *n = (const struct varpool_node *) p;
  94   return (hashval_t) DECL_UID (n->decl);
  95 }
  96
  97 /* Returns nonzero if P1 and P2 are equal.  */
  98 static int
  99 eq_varpool_node (const void *p1, const void *p2)
 100 {
 101   const struct varpool_node *n1 =
 102     (const struct varpool_node *) p1;
 103   const struct varpool_node *n2 =
 104     (const struct varpool_node *) p2;
 105   return DECL_UID (n1->decl) == DECL_UID (n2->decl);
 106 }
 107
 108 /* Return varpool node assigned to DECL without creating new one.  */
 109 struct varpool_node *
 110 varpool_get_node (tree decl)
 111 {
 112   struct varpool_node key, **slot;
 113
 114   gcc_assert (TREE_CODE (decl) == VAR_DECL
 115               && (TREE_STATIC (decl) || DECL_EXTERNAL (decl)));
 116
 117   if (!varpool_hash)
 118     return NULL;
 119   key.decl = decl;
 120   slot = (struct varpool_node **)
 121     htab_find_slot (varpool_hash, &key, NO_INSERT);
 122   if (!slot)
 123     return NULL;
 124   return *slot;
 125 }
 126
 127 /* Return varpool node assigned to DECL.  Create new one when needed.  */
 128 struct varpool_node *
 129 varpool_node (tree decl)
 130 {
 131   struct varpool_node key, *node, **slot;
 132
 133   gcc_assert (TREE_CODE (decl) == VAR_DECL
 134               && (TREE_STATIC (decl) || DECL_EXTERNAL (decl)));
 135
 136   if (!varpool_hash)
 137     varpool_hash = htab_create_ggc (10, hash_varpool_node,
 138                                            eq_varpool_node, NULL);
 139   key.decl = decl;
 140   slot = (struct varpool_node **)
 141     htab_find_slot (varpool_hash, &key, INSERT);
 142   if (*slot)
 143     return *slot;
 144   node = ggc_alloc_cleared_varpool_node ();
 145   node->decl = decl;
 146   node->order = cgraph_order++;
 147   node->next = varpool_nodes;
 148   ipa_empty_ref_list (&node->ref_list);
 149   if (varpool_nodes)
 150     varpool_nodes->prev = node;
 151   varpool_nodes = node;
 152   *slot = node;
 153   return node;
 154 }
 155
 156 /* Remove node from the varpool.  */
 157 void
 158 varpool_remove_node (struct varpool_node *node)
 159 {
 160   void **slot;
 161   slot = htab_find_slot (varpool_hash, node, NO_INSERT);
 162   gcc_assert (*slot == node);
 163   htab_clear_slot (varpool_hash, slot);
 164   gcc_assert (!varpool_assembled_nodes_queue);
 165   if (!node->alias)
 166     while (node->extra_name)
 167       varpool_remove_node (node->extra_name);
 168   if (node->next)
 169     node->next->prev = node->prev;
 170   if (node->prev)
 171     node->prev->next = node->next;
 172   else
 173     {
 174       if (node->alias && node->extra_name)
 175         {
 176           gcc_assert (node->extra_name->extra_name == node);
 177           node->extra_name->extra_name = node->next;
 178         }
 179       else
 180         {
 181           gcc_assert (varpool_nodes == node);
 182           varpool_nodes = node->next;
 183         }
 184     }
 185   if (varpool_first_unanalyzed_node == node)
 186     varpool_first_unanalyzed_node = node->next_needed;
 187   if (node->next_needed)
 188     node->next_needed->prev_needed = node->prev_needed;
 189   else if (node->prev_needed)
 190     {
 191       gcc_assert (varpool_last_needed_node);
 192       varpool_last_needed_node = node->prev_needed;
 193     }
 194   if (node->prev_needed)
 195     node->prev_needed->next_needed = node->next_needed;
 196   else if (node->next_needed)
 197     {
 198       gcc_assert (varpool_nodes_queue == node);
 199       varpool_nodes_queue = node->next_needed;
 200     }
 201   if (node->same_comdat_group)
 202     {
 203       struct varpool_node *prev;
 204       for (prev = node->same_comdat_group;
 205            prev->same_comdat_group != node;
 206            prev = prev->same_comdat_group)
 207         ;
 208       if (node->same_comdat_group == prev)
 209         prev->same_comdat_group = NULL;
 210       else
 211         prev->same_comdat_group = node->same_comdat_group;
 212       node->same_comdat_group = NULL;
 213     }
 214   ipa_remove_all_references (&node->ref_list);
 215   ipa_remove_all_refering (&node->ref_list);
 216   ggc_free (node);
 217 }
 218
 219 /* Dump given cgraph node.  */
 220 void
 221 dump_varpool_node (FILE *f, struct varpool_node *node)
 222 {
 223   fprintf (f, "%s:", varpool_node_name (node));
 224   fprintf (f, " availability:%s",
 225            cgraph_function_flags_ready
 226            ? cgraph_availability_names[cgraph_variable_initializer_availability (node)]
 227            : "not-ready");
 228   if (DECL_ASSEMBLER_NAME_SET_P (node->decl))
 229     fprintf (f, " (asm: %s)", IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (node->decl)));
 230   if (DECL_INITIAL (node->decl))
 231     fprintf (f, " initialized");
 232   if (TREE_ASM_WRITTEN (node->decl))
 233     fprintf (f, " (asm written)");
 234   if (node->needed)
 235     fprintf (f, " needed");
 236   if (node->analyzed)
 237     fprintf (f, " analyzed");
 238   if (node->finalized)
 239     fprintf (f, " finalized");
 240   if (node->output)
 241     fprintf (f, " output");
 242   if (node->externally_visible)
 243     fprintf (f, " externally_visible");
 244   if (node->in_other_partition)
 245     fprintf (f, " in_other_partition");
 246   else if (node->used_from_other_partition)
 247     fprintf (f, " used_from_other_partition");
 248   fprintf (f, "\n");
 249   fprintf (f, "  References: ");
 250   ipa_dump_references (f, &node->ref_list);
 251   fprintf (f, "  Refering this var: ");
 252   ipa_dump_refering (f, &node->ref_list);
 253 }
 254
 255 /* Dump the variable pool.  */
 256 void
 257 dump_varpool (FILE *f)
 258 {
 259   struct varpool_node *node;
 260
 261   fprintf (f, "variable pool:\n\n");
 262   for (node = varpool_nodes; node; node = node->next)
 263     dump_varpool_node (f, node);
 264 }
 265
 266 /* Dump the variable pool to stderr.  */
 267
 268 DEBUG_FUNCTION void
 269 debug_varpool (void)
 270 {
 271   dump_varpool (stderr);
 272 }
 273
 274 /* Given an assembler name, lookup node.  */
 275 struct varpool_node *
 276 varpool_node_for_asm (tree asmname)
 277 {
 278   struct varpool_node *node;
 279
 280   for (node = varpool_nodes; node ; node = node->next)
 281     if (decl_assembler_name_equal (node->decl, asmname))
 282       return node;
 283
 284   return NULL;
 285 }
 286
 287 /* Helper function for finalization code - add node into lists so it will
 288    be analyzed and compiled.  */
 289 static void
 290 varpool_enqueue_needed_node (struct varpool_node *node)
 291 {
 292   if (varpool_last_needed_node)
 293     {
 294       varpool_last_needed_node->next_needed = node;
 295       node->prev_needed = varpool_last_needed_node;
 296     }
 297   varpool_last_needed_node = node;
 298   node->next_needed = NULL;
 299   if (!varpool_nodes_queue)
 300     varpool_nodes_queue = node;
 301   if (!varpool_first_unanalyzed_node)
 302     varpool_first_unanalyzed_node = node;
 303   notice_global_symbol (node->decl);
 304 }
 305
 306 /* Notify finalize_compilation_unit that given node is reachable
 307    or needed.  */
 308 void
 309 varpool_mark_needed_node (struct varpool_node *node)
 310 {
 311   if (node->alias && node->extra_name)
 312     node = node->extra_name;
 313   if (!node->needed && node->finalized
 314       && !TREE_ASM_WRITTEN (node->decl))
 315     varpool_enqueue_needed_node (node);
 316   node->needed = 1;
 317 }
 318
 319 /* Reset the queue of needed nodes.  */
 320 void
 321 varpool_reset_queue (void)
 322 {
 323   varpool_last_needed_node = NULL;
 324   varpool_nodes_queue = NULL;
 325   varpool_first_unanalyzed_node = NULL;
 326 }
 327
 328 /* Determine if variable DECL is needed.  That is, visible to something
 329    either outside this translation unit, something magic in the system
 330    configury */
 331 bool
 332 decide_is_variable_needed (struct varpool_node *node, tree decl)
 333 {
 334   if (node->used_from_other_partition)
 335     return true;
 336   /* If the user told us it is used, then it must be so.  */
 337   if ((node->externally_visible && !DECL_COMDAT (decl))
 338       || node->force_output)
 339     return true;
 340
 341   /* Externally visible variables must be output.  The exception is
 342      COMDAT variables that must be output only when they are needed.  */
 343   if (TREE_PUBLIC (decl)
 344       && !flag_whole_program
 345       && !flag_lto
 346       && !flag_whopr
 347       && !DECL_COMDAT (decl)
 348       && !DECL_EXTERNAL (decl))
 349     return true;
 350
 351   /* When not reordering top level variables, we have to assume that
 352      we are going to keep everything.  */
 353   if (flag_toplevel_reorder)
 354     return false;
 355
 356   /* We want to emit COMDAT variables only when absolutely necessary.  */
 357   if (DECL_COMDAT (decl))
 358     return false;
 359   return true;
 360 }
 361
 362 /* Return if DECL is constant and its initial value is known (so we can do
 363    constant folding using DECL_INITIAL (decl)).  */
 364
 365 bool
 366 const_value_known_p (tree decl)
 367 {
 368   struct varpool_node *vnode;
 369
 370   if (TREE_CODE (decl) != VAR_DECL
 371       &&TREE_CODE (decl) != CONST_DECL)
 372     return false;
 373
 374   if (TREE_CODE (decl) == CONST_DECL
 375       || DECL_IN_CONSTANT_POOL (decl))
 376     return true;
 377
 378   gcc_assert (TREE_CODE (decl) == VAR_DECL);
 379
 380   if (!TREE_READONLY (decl))
 381     return false;
 382
 383   /* Gimplifier takes away constructors of local vars  */
 384   if (!TREE_STATIC (decl) && !DECL_EXTERNAL (decl))
 385     return DECL_INITIAL (decl) != NULL;
 386
 387   gcc_assert (TREE_STATIC (decl) || DECL_EXTERNAL (decl));
 388
 389   /* In WHOPR mode we can put variable into one partition
 390      and make it external in the other partition.  In this
 391      case we still know the value, but it can't be determined
 392      from DECL flags.  For this reason we keep const_value_known
 393      flag in varpool nodes.  */
 394   if ((vnode = varpool_get_node (decl))
 395       && vnode->const_value_known)
 396     return true;
 397
 398   /* Variables declared 'const' without an initializer
 399      have zero as the initializer if they may not be
 400      overridden at link or run time.  */
 401   if (!DECL_INITIAL (decl)
 402       && (DECL_EXTERNAL (decl)
 403           || DECL_REPLACEABLE_P (decl)))
 404     return false;
 405
 406   /* Variables declared `const' with an initializer are considered
 407      to not be overwritable with different initializer by default.
 408
 409      ??? Previously we behaved so for scalar variables but not for array
 410      accesses.  */
 411   return true;
 412 }
 413
 414 /* Mark DECL as finalized.  By finalizing the declaration, frontend instruct the
 415    middle end to output the variable to asm file, if needed or externally
 416    visible.  */
 417 void
 418 varpool_finalize_decl (tree decl)
 419 {
 420   struct varpool_node *node = varpool_node (decl);
 421
 422   gcc_assert (TREE_STATIC (decl));
 423
 424   /* The first declaration of a variable that comes through this function
 425      decides whether it is global (in C, has external linkage)
 426      or local (in C, has internal linkage).  So do nothing more
 427      if this function has already run.  */
 428   if (node->finalized)
 429     {
 430       if (cgraph_global_info_ready)
 431         varpool_assemble_pending_decls ();
 432       return;
 433     }
 434   if (node->needed)
 435     varpool_enqueue_needed_node (node);
 436   node->finalized = true;
 437   if (TREE_THIS_VOLATILE (decl) || DECL_PRESERVE_P (decl))
 438     node->force_output = true;
 439
 440   if (decide_is_variable_needed (node, decl))
 441     varpool_mark_needed_node (node);
 442   /* Since we reclaim unreachable nodes at the end of every language
 443      level unit, we need to be conservative about possible entry points
 444      there.  */
 445   else if (TREE_PUBLIC (decl) && !DECL_COMDAT (decl) && !DECL_EXTERNAL (decl))
 446     varpool_mark_needed_node (node);
 447   node->const_value_known |= const_value_known_p (node->decl);
 448   if (cgraph_global_info_ready)
 449     varpool_assemble_pending_decls ();
 450 }
 451
 452 /* Return variable availability.  See cgraph.h for description of individual
 453    return values.  */
 454 enum availability
 455 cgraph_variable_initializer_availability (struct varpool_node *node)
 456 {
 457   gcc_assert (cgraph_function_flags_ready);
 458   if (!node->finalized)
 459     return AVAIL_NOT_AVAILABLE;
 460   if (!TREE_PUBLIC (node->decl))
 461     return AVAIL_AVAILABLE;
 462   /* If the variable can be overwritten, return OVERWRITABLE.  Takes
 463      care of at least two notable extensions - the COMDAT variables
 464      used to share template instantiations in C++.  */
 465   if (!(*targetm.binds_local_p) (node->decl) && !DECL_COMDAT (node->decl))
 466     return AVAIL_OVERWRITABLE;
 467   return AVAIL_AVAILABLE;
 468 }
 469
 470 /* Walk the decls we marked as necessary and see if they reference new
 471    variables or functions and add them into the worklists.  */
 472 bool
 473 varpool_analyze_pending_decls (void)
 474 {
 475   bool changed = false;
 476
 477   timevar_push (TV_VARPOOL);
 478   while (varpool_first_unanalyzed_node)
 479     {
 480       struct varpool_node *node = varpool_first_unanalyzed_node, *next;
 481       tree decl = node->decl;
 482       bool analyzed = node->analyzed;
 483
 484       varpool_first_unanalyzed_node->analyzed = true;
 485
 486       varpool_first_unanalyzed_node = varpool_first_unanalyzed_node->next_needed;
 487
 488       /* When reading back varpool at LTO time, we re-construct the queue in order
 489          to have "needed" list right by inserting all needed nodes into varpool.
 490          We however don't want to re-analyze already analyzed nodes.  */
 491       if (!analyzed)
 492         {
 493           gcc_assert (!in_lto_p || cgraph_function_flags_ready);
 494           /* Compute the alignment early so function body expanders are
 495              already informed about increased alignment.  */
 496           align_variable (decl, 0);
 497         }
 498       if (DECL_INITIAL (decl))
 499         record_references_in_initializer (decl, analyzed);
 500       if (node->same_comdat_group)
 501         {
 502           for (next = node->same_comdat_group;
 503                next != node;
 504                next = next->same_comdat_group)
 505             varpool_mark_needed_node (next);
 506         }
 507       changed = true;
 508     }
 509   timevar_pop (TV_VARPOOL);
 510   return changed;
 511 }
 512
 513 /* Output one variable, if necessary.  Return whether we output it.  */
 514 bool
 515 varpool_assemble_decl (struct varpool_node *node)
 516 {
 517   tree decl = node->decl;
 518
 519   if (!TREE_ASM_WRITTEN (decl)
 520       && !node->alias
 521       && !node->in_other_partition
 522       && !DECL_EXTERNAL (decl)
 523       && (TREE_CODE (decl) != VAR_DECL || !DECL_HAS_VALUE_EXPR_P (decl)))
 524     {
 525       assemble_variable (decl, 0, 1, 0);
 526       if (TREE_ASM_WRITTEN (decl))
 527         {
 528           struct varpool_node *alias;
 529
 530           node->next_needed = varpool_assembled_nodes_queue;
 531           node->prev_needed = NULL;
 532           if (varpool_assembled_nodes_queue)
 533             varpool_assembled_nodes_queue->prev_needed = node;
 534           varpool_assembled_nodes_queue = node;
 535           node->finalized = 1;
 536
 537           /* Also emit any extra name aliases.  */
 538           for (alias = node->extra_name; alias; alias = alias->next)
 539             {
 540               /* Update linkage fields in case they've changed.  */
 541               DECL_WEAK (alias->decl) = DECL_WEAK (decl);
 542               TREE_PUBLIC (alias->decl) = TREE_PUBLIC (decl);
 543               DECL_VISIBILITY (alias->decl) = DECL_VISIBILITY (decl);
 544               assemble_alias (alias->decl, DECL_ASSEMBLER_NAME (decl));
 545             }
 546
 547           return true;
 548         }
 549     }
 550
 551   return false;
 552 }
 553
 554 /* Optimization of function bodies might've rendered some variables as
 555    unnecessary so we want to avoid these from being compiled.
 556
 557    This is done by pruning the queue and keeping only the variables that
 558    really appear needed (ie they are either externally visible or referenced
 559    by compiled function). Re-doing the reachability analysis on variables
 560    brings back the remaining variables referenced by these.  */
 561 void
 562 varpool_remove_unreferenced_decls (void)
 563 {
 564   struct varpool_node *next, *node = varpool_nodes_queue;
 565
 566   varpool_reset_queue ();
 567
 568   if (seen_error ())
 569     return;
 570
 571   while (node)
 572     {
 573       tree decl = node->decl;
 574       next = node->next_needed;
 575       node->needed = 0;
 576
 577       if (node->finalized
 578           && (decide_is_variable_needed (node, decl)
 579               /* ??? Cgraph does not yet rule the world with an iron hand,
 580                  and does not control the emission of debug information.
 581                  After a variable has its DECL_RTL set, we must assume that
 582                  it may be referenced by the debug information, and we can
 583                  no longer elide it.  */
 584               || DECL_RTL_SET_P (decl)))
 585         varpool_mark_needed_node (node);
 586
 587       node = next;
 588     }
 589   /* Make sure we mark alias targets as used targets.  */
 590   finish_aliases_1 ();
 591   varpool_analyze_pending_decls ();
 592 }
 593
 594 /* Output all variables enqueued to be assembled.  */
 595 bool
 596 varpool_assemble_pending_decls (void)
 597 {
 598   bool changed = false;
 599
 600   if (seen_error ())
 601     return false;
 602
 603   timevar_push (TV_VAROUT);
 604   /* EH might mark decls as needed during expansion.  This should be safe since
 605      we don't create references to new function, but it should not be used
 606      elsewhere.  */
 607   varpool_analyze_pending_decls ();
 608
 609   while (varpool_nodes_queue)
 610     {
 611       struct varpool_node *node = varpool_nodes_queue;
 612
 613       varpool_nodes_queue = varpool_nodes_queue->next_needed;
 614       if (varpool_assemble_decl (node))
 615         changed = true;
 616       else
 617         {
 618           node->prev_needed = NULL;
 619           node->next_needed = NULL;
 620         }
 621     }
 622   /* varpool_nodes_queue is now empty, clear the pointer to the last element
 623      in the queue.  */
 624   varpool_last_needed_node = NULL;
 625   timevar_pop (TV_VAROUT);
 626   return changed;
 627 }
 628
 629 /* Remove all elements from the queue so we can re-use it for debug output.  */
 630 void
 631 varpool_empty_needed_queue (void)
 632 {
 633   /* EH might mark decls as needed during expansion.  This should be safe since
 634      we don't create references to new function, but it should not be used
 635      elsewhere.  */
 636   varpool_analyze_pending_decls ();
 637
 638   while (varpool_nodes_queue)
 639     {
 640       struct varpool_node *node = varpool_nodes_queue;
 641       varpool_nodes_queue = varpool_nodes_queue->next_needed;
 642       node->next_needed = NULL;
 643       node->prev_needed = NULL;
 644     }
 645   /* varpool_nodes_queue is now empty, clear the pointer to the last element
 646      in the queue.  */
 647   varpool_last_needed_node = NULL;
 648 }
 649
 650 /* Create a new global variable of type TYPE.  */
 651 tree
 652 add_new_static_var (tree type)
 653 {
 654   tree new_decl;
 655   struct varpool_node *new_node;
 656
 657   new_decl = create_tmp_var (type, NULL);
 658   DECL_NAME (new_decl) = create_tmp_var_name (NULL);
 659   TREE_READONLY (new_decl) = 0;
 660   TREE_STATIC (new_decl) = 1;
 661   TREE_USED (new_decl) = 1;
 662   DECL_CONTEXT (new_decl) = NULL_TREE;
 663   DECL_ABSTRACT (new_decl) = 0;
 664   lang_hooks.dup_lang_specific_decl (new_decl);
 665   create_var_ann (new_decl);
 666   new_node = varpool_node (new_decl);
 667   varpool_mark_needed_node (new_node);
 668   add_referenced_var (new_decl);
 669   varpool_finalize_decl (new_decl);
 670
 671   return new_node->decl;
 672 }
 673
 674 /* Attempt to mark ALIAS as an alias to DECL.  Return TRUE if successful.
 675    Extra name aliases are output whenever DECL is output.  */
 676
 677 bool
 678 varpool_extra_name_alias (tree alias, tree decl)
 679 {
 680   struct varpool_node key, *alias_node, *decl_node, **slot;
 681
 682 #ifndef ASM_OUTPUT_DEF
 683   /* If aliases aren't supported by the assembler, fail.  */
 684   return false;
 685 #endif
 686
 687   gcc_assert (TREE_CODE (decl) == VAR_DECL);
 688   gcc_assert (TREE_CODE (alias) == VAR_DECL);
 689   /* Make sure the hash table has been created.  */
 690   decl_node = varpool_node (decl);
 691
 692   key.decl = alias;
 693
 694   slot = (struct varpool_node **) htab_find_slot (varpool_hash, &key, INSERT);
 695
 696   /* If the varpool_node has been already created, fail.  */
 697   if (*slot)
 698     return false;
 699
 700   alias_node = ggc_alloc_cleared_varpool_node ();
 701   alias_node->decl = alias;
 702   alias_node->alias = 1;
 703   alias_node->extra_name = decl_node;
 704   alias_node->next = decl_node->extra_name;
 705   ipa_empty_ref_list (&alias_node->ref_list);
 706   if (decl_node->extra_name)
 707     decl_node->extra_name->prev = alias_node;
 708   decl_node->extra_name = alias_node;
 709   *slot = alias_node;
 710   return true;
 711 }
 712
 713 #include "gt-varpool.h"