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 NODE is constant and its initial value is known (so we can do
 363    constant folding).  The decision depends on whole program decisions
 364    and can not be recomputed at ltrans stage for variables from other
 365    partitions.  For this reason the new value should be always combined
 366    with the previous knowledge.  */
 367
 368 bool
 369 varpool_decide_const_value_known (struct varpool_node *node)
 370 {
 371   tree decl = node->decl;
 372
 373   gcc_assert (TREE_STATIC (decl) || DECL_EXTERNAL (decl));
 374   gcc_assert (TREE_CODE (decl) == VAR_DECL);
 375   if (!TREE_READONLY (decl))
 376     return false;
 377   /* Variables declared 'const' without an initializer
 378      have zero as the initializer if they may not be
 379      overridden at link or run time.  */
 380   if (!DECL_INITIAL (decl)
 381       && (DECL_EXTERNAL (decl)
 382           || DECL_REPLACEABLE_P (decl)))
 383     return false;
 384
 385   /* Variables declared `const' with an initializer are considered
 386      to not be overwritable with different initializer by default.
 387
 388      ??? Previously we behaved so for scalar variables but not for array
 389      accesses.  */
 390   return true;
 391 }
 392
 393 /* Mark DECL as finalized.  By finalizing the declaration, frontend instruct the
 394    middle end to output the variable to asm file, if needed or externally
 395    visible.  */
 396 void
 397 varpool_finalize_decl (tree decl)
 398 {
 399   struct varpool_node *node = varpool_node (decl);
 400
 401   gcc_assert (TREE_STATIC (decl));
 402
 403   /* The first declaration of a variable that comes through this function
 404      decides whether it is global (in C, has external linkage)
 405      or local (in C, has internal linkage).  So do nothing more
 406      if this function has already run.  */
 407   if (node->finalized)
 408     {
 409       if (cgraph_global_info_ready)
 410         varpool_assemble_pending_decls ();
 411       return;
 412     }
 413   if (node->needed)
 414     varpool_enqueue_needed_node (node);
 415   node->finalized = true;
 416   if (TREE_THIS_VOLATILE (decl) || DECL_PRESERVE_P (decl))
 417     node->force_output = true;
 418
 419   if (decide_is_variable_needed (node, decl))
 420     varpool_mark_needed_node (node);
 421   /* Since we reclaim unreachable nodes at the end of every language
 422      level unit, we need to be conservative about possible entry points
 423      there.  */
 424   else if (TREE_PUBLIC (decl) && !DECL_COMDAT (decl) && !DECL_EXTERNAL (decl))
 425     varpool_mark_needed_node (node);
 426   node->const_value_known |= varpool_decide_const_value_known (node);
 427   if (cgraph_global_info_ready)
 428     varpool_assemble_pending_decls ();
 429 }
 430
 431 /* Return variable availability.  See cgraph.h for description of individual
 432    return values.  */
 433 enum availability
 434 cgraph_variable_initializer_availability (struct varpool_node *node)
 435 {
 436   gcc_assert (cgraph_function_flags_ready);
 437   if (!node->finalized)
 438     return AVAIL_NOT_AVAILABLE;
 439   if (!TREE_PUBLIC (node->decl))
 440     return AVAIL_AVAILABLE;
 441   /* If the variable can be overwritten, return OVERWRITABLE.  Takes
 442      care of at least two notable extensions - the COMDAT variables
 443      used to share template instantiations in C++.  */
 444   if (!(*targetm.binds_local_p) (node->decl) && !DECL_COMDAT (node->decl))
 445     return AVAIL_OVERWRITABLE;
 446   return AVAIL_AVAILABLE;
 447 }
 448
 449 /* Walk the decls we marked as necessary and see if they reference new
 450    variables or functions and add them into the worklists.  */
 451 bool
 452 varpool_analyze_pending_decls (void)
 453 {
 454   bool changed = false;
 455
 456   timevar_push (TV_VARPOOL);
 457   while (varpool_first_unanalyzed_node)
 458     {
 459       struct varpool_node *node = varpool_first_unanalyzed_node, *next;
 460       tree decl = node->decl;
 461       bool analyzed = node->analyzed;
 462
 463       varpool_first_unanalyzed_node->analyzed = true;
 464
 465       varpool_first_unanalyzed_node = varpool_first_unanalyzed_node->next_needed;
 466
 467       /* When reading back varpool at LTO time, we re-construct the queue in order
 468          to have "needed" list right by inserting all needed nodes into varpool.
 469          We however don't want to re-analyze already analyzed nodes.  */
 470       if (!analyzed)
 471         {
 472           gcc_assert (!in_lto_p || cgraph_function_flags_ready);
 473           /* Compute the alignment early so function body expanders are
 474              already informed about increased alignment.  */
 475           align_variable (decl, 0);
 476         }
 477       if (DECL_INITIAL (decl))
 478         record_references_in_initializer (decl, analyzed);
 479       if (node->same_comdat_group)
 480         {
 481           for (next = node->same_comdat_group;
 482                next != node;
 483                next = next->same_comdat_group)
 484             varpool_mark_needed_node (next);
 485         }
 486       changed = true;
 487     }
 488   timevar_pop (TV_VARPOOL);
 489   return changed;
 490 }
 491
 492 /* Output one variable, if necessary.  Return whether we output it.  */
 493 bool
 494 varpool_assemble_decl (struct varpool_node *node)
 495 {
 496   tree decl = node->decl;
 497
 498   if (!TREE_ASM_WRITTEN (decl)
 499       && !node->alias
 500       && !node->in_other_partition
 501       && !DECL_EXTERNAL (decl)
 502       && (TREE_CODE (decl) != VAR_DECL || !DECL_HAS_VALUE_EXPR_P (decl)))
 503     {
 504       assemble_variable (decl, 0, 1, 0);
 505       if (TREE_ASM_WRITTEN (decl))
 506         {
 507           struct varpool_node *alias;
 508
 509           node->next_needed = varpool_assembled_nodes_queue;
 510           node->prev_needed = NULL;
 511           if (varpool_assembled_nodes_queue)
 512             varpool_assembled_nodes_queue->prev_needed = node;
 513           varpool_assembled_nodes_queue = node;
 514           node->finalized = 1;
 515
 516           /* Also emit any extra name aliases.  */
 517           for (alias = node->extra_name; alias; alias = alias->next)
 518             {
 519               /* Update linkage fields in case they've changed.  */
 520               DECL_WEAK (alias->decl) = DECL_WEAK (decl);
 521               TREE_PUBLIC (alias->decl) = TREE_PUBLIC (decl);
 522               DECL_VISIBILITY (alias->decl) = DECL_VISIBILITY (decl);
 523               assemble_alias (alias->decl, DECL_ASSEMBLER_NAME (decl));
 524             }
 525
 526           return true;
 527         }
 528     }
 529
 530   return false;
 531 }
 532
 533 /* Optimization of function bodies might've rendered some variables as
 534    unnecessary so we want to avoid these from being compiled.
 535
 536    This is done by pruning the queue and keeping only the variables that
 537    really appear needed (ie they are either externally visible or referenced
 538    by compiled function). Re-doing the reachability analysis on variables
 539    brings back the remaining variables referenced by these.  */
 540 void
 541 varpool_remove_unreferenced_decls (void)
 542 {
 543   struct varpool_node *next, *node = varpool_nodes_queue;
 544
 545   varpool_reset_queue ();
 546
 547   if (seen_error ())
 548     return;
 549
 550   while (node)
 551     {
 552       tree decl = node->decl;
 553       next = node->next_needed;
 554       node->needed = 0;
 555
 556       if (node->finalized
 557           && (decide_is_variable_needed (node, decl)
 558               /* ??? Cgraph does not yet rule the world with an iron hand,
 559                  and does not control the emission of debug information.
 560                  After a variable has its DECL_RTL set, we must assume that
 561                  it may be referenced by the debug information, and we can
 562                  no longer elide it.  */
 563               || DECL_RTL_SET_P (decl)))
 564         varpool_mark_needed_node (node);
 565
 566       node = next;
 567     }
 568   /* Make sure we mark alias targets as used targets.  */
 569   finish_aliases_1 ();
 570   varpool_analyze_pending_decls ();
 571 }
 572
 573 /* Output all variables enqueued to be assembled.  */
 574 bool
 575 varpool_assemble_pending_decls (void)
 576 {
 577   bool changed = false;
 578
 579   if (seen_error ())
 580     return false;
 581
 582   timevar_push (TV_VAROUT);
 583   /* EH might mark decls as needed during expansion.  This should be safe since
 584      we don't create references to new function, but it should not be used
 585      elsewhere.  */
 586   varpool_analyze_pending_decls ();
 587
 588   while (varpool_nodes_queue)
 589     {
 590       struct varpool_node *node = varpool_nodes_queue;
 591
 592       varpool_nodes_queue = varpool_nodes_queue->next_needed;
 593       if (varpool_assemble_decl (node))
 594         changed = true;
 595       else
 596         {
 597           node->prev_needed = NULL;
 598           node->next_needed = NULL;
 599         }
 600     }
 601   /* varpool_nodes_queue is now empty, clear the pointer to the last element
 602      in the queue.  */
 603   varpool_last_needed_node = NULL;
 604   timevar_pop (TV_VAROUT);
 605   return changed;
 606 }
 607
 608 /* Remove all elements from the queue so we can re-use it for debug output.  */
 609 void
 610 varpool_empty_needed_queue (void)
 611 {
 612   /* EH might mark decls as needed during expansion.  This should be safe since
 613      we don't create references to new function, but it should not be used
 614      elsewhere.  */
 615   varpool_analyze_pending_decls ();
 616
 617   while (varpool_nodes_queue)
 618     {
 619       struct varpool_node *node = varpool_nodes_queue;
 620       varpool_nodes_queue = varpool_nodes_queue->next_needed;
 621       node->next_needed = NULL;
 622       node->prev_needed = NULL;
 623     }
 624   /* varpool_nodes_queue is now empty, clear the pointer to the last element
 625      in the queue.  */
 626   varpool_last_needed_node = NULL;
 627 }
 628
 629 /* Create a new global variable of type TYPE.  */
 630 tree
 631 add_new_static_var (tree type)
 632 {
 633   tree new_decl;
 634   struct varpool_node *new_node;
 635
 636   new_decl = create_tmp_var (type, NULL);
 637   DECL_NAME (new_decl) = create_tmp_var_name (NULL);
 638   TREE_READONLY (new_decl) = 0;
 639   TREE_STATIC (new_decl) = 1;
 640   TREE_USED (new_decl) = 1;
 641   DECL_CONTEXT (new_decl) = NULL_TREE;
 642   DECL_ABSTRACT (new_decl) = 0;
 643   lang_hooks.dup_lang_specific_decl (new_decl);
 644   create_var_ann (new_decl);
 645   new_node = varpool_node (new_decl);
 646   varpool_mark_needed_node (new_node);
 647   add_referenced_var (new_decl);
 648   varpool_finalize_decl (new_decl);
 649
 650   return new_node->decl;
 651 }
 652
 653 /* Attempt to mark ALIAS as an alias to DECL.  Return TRUE if successful.
 654    Extra name aliases are output whenever DECL is output.  */
 655
 656 bool
 657 varpool_extra_name_alias (tree alias, tree decl)
 658 {
 659   struct varpool_node key, *alias_node, *decl_node, **slot;
 660
 661 #ifndef ASM_OUTPUT_DEF
 662   /* If aliases aren't supported by the assembler, fail.  */
 663   return false;
 664 #endif
 665
 666   gcc_assert (TREE_CODE (decl) == VAR_DECL);
 667   gcc_assert (TREE_CODE (alias) == VAR_DECL);
 668   /* Make sure the hash table has been created.  */
 669   decl_node = varpool_node (decl);
 670
 671   key.decl = alias;
 672
 673   slot = (struct varpool_node **) htab_find_slot (varpool_hash, &key, INSERT);
 674
 675   /* If the varpool_node has been already created, fail.  */
 676   if (*slot)
 677     return false;
 678
 679   alias_node = ggc_alloc_cleared_varpool_node ();
 680   alias_node->decl = alias;
 681   alias_node->alias = 1;
 682   alias_node->extra_name = decl_node;
 683   alias_node->next = decl_node->extra_name;
 684   ipa_empty_ref_list (&alias_node->ref_list);
 685   if (decl_node->extra_name)
 686     decl_node->extra_name->prev = alias_node;
 687   decl_node->extra_name = alias_node;
 688   *slot = alias_node;
 689   return true;
 690 }
 691
 692 #include "gt-varpool.h"