gcc/varpool.c

   1 /* Callgraph handling code.
   2    Copyright (C) 2003-2013 Free Software Foundation, Inc.
   3    Contributed by Jan Hubicka
   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 "tm.h"
  25 #include "tree.h"
  26 #include "cgraph.h"
  27 #include "langhooks.h"
  28 #include "diagnostic-core.h"
  29 #include "hashtab.h"
  30 #include "ggc.h"
  31 #include "timevar.h"
  32 #include "debug.h"
  33 #include "target.h"
  34 #include "output.h"
  35 #include "gimple.h"
  36 #include "flags.h"
  37
  38 /* List of hooks triggered on varpool_node events.  */
  39 struct varpool_node_hook_list {
  40   varpool_node_hook hook;
  41   void *data;
  42   struct varpool_node_hook_list *next;
  43 };
  44
  45 /* List of hooks triggered when a node is removed.  */
  46 struct varpool_node_hook_list *first_varpool_node_removal_hook;
  47 /* List of hooks triggered when an variable is inserted.  */
  48 struct varpool_node_hook_list *first_varpool_variable_insertion_hook;
  49
  50 /* Register HOOK to be called with DATA on each removed node.  */
  51 struct varpool_node_hook_list *
  52 varpool_add_node_removal_hook (varpool_node_hook hook, void *data)
  53 {
  54   struct varpool_node_hook_list *entry;
  55   struct varpool_node_hook_list **ptr = &first_varpool_node_removal_hook;
  56
  57   entry = (struct varpool_node_hook_list *) xmalloc (sizeof (*entry));
  58   entry->hook = hook;
  59   entry->data = data;
  60   entry->next = NULL;
  61   while (*ptr)
  62     ptr = &(*ptr)->next;
  63   *ptr = entry;
  64   return entry;
  65 }
  66
  67 /* Remove ENTRY from the list of hooks called on removing nodes.  */
  68 void
  69 varpool_remove_node_removal_hook (struct varpool_node_hook_list *entry)
  70 {
  71   struct varpool_node_hook_list **ptr = &first_varpool_node_removal_hook;
  72
  73   while (*ptr != entry)
  74     ptr = &(*ptr)->next;
  75   *ptr = entry->next;
  76   free (entry);
  77 }
  78
  79 /* Call all node removal hooks.  */
  80 static void
  81 varpool_call_node_removal_hooks (struct varpool_node *node)
  82 {
  83   struct varpool_node_hook_list *entry = first_varpool_node_removal_hook;
  84   while (entry)
  85   {
  86     entry->hook (node, entry->data);
  87     entry = entry->next;
  88   }
  89 }
  90
  91 /* Register HOOK to be called with DATA on each inserted node.  */
  92 struct varpool_node_hook_list *
  93 varpool_add_variable_insertion_hook (varpool_node_hook hook, void *data)
  94 {
  95   struct varpool_node_hook_list *entry;
  96   struct varpool_node_hook_list **ptr = &first_varpool_variable_insertion_hook;
  97
  98   entry = (struct varpool_node_hook_list *) xmalloc (sizeof (*entry));
  99   entry->hook = hook;
 100   entry->data = data;
 101   entry->next = NULL;
 102   while (*ptr)
 103     ptr = &(*ptr)->next;
 104   *ptr = entry;
 105   return entry;
 106 }
 107
 108 /* Remove ENTRY from the list of hooks called on inserted nodes.  */
 109 void
 110 varpool_remove_variable_insertion_hook (struct varpool_node_hook_list *entry)
 111 {
 112   struct varpool_node_hook_list **ptr = &first_varpool_variable_insertion_hook;
 113
 114   while (*ptr != entry)
 115     ptr = &(*ptr)->next;
 116   *ptr = entry->next;
 117   free (entry);
 118 }
 119
 120 /* Call all node insertion hooks.  */
 121 void
 122 varpool_call_variable_insertion_hooks (struct varpool_node *node)
 123 {
 124   struct varpool_node_hook_list *entry = first_varpool_variable_insertion_hook;
 125   while (entry)
 126   {
 127     entry->hook (node, entry->data);
 128     entry = entry->next;
 129   }
 130 }
 131
 132 /* Allocate new callgraph node and insert it into basic data structures.  */
 133
 134 struct varpool_node *
 135 varpool_create_empty_node (void)
 136 {
 137   struct varpool_node *node = ggc_alloc_cleared_varpool_node ();
 138   node->type = SYMTAB_VARIABLE;
 139   return node;
 140 }
 141
 142 /* Return varpool node assigned to DECL.  Create new one when needed.  */
 143 struct varpool_node *
 144 varpool_node_for_decl (tree decl)
 145 {
 146   struct varpool_node *node = varpool_get_node (decl);
 147   gcc_checking_assert (TREE_CODE (decl) == VAR_DECL);
 148   if (node)
 149     return node;
 150
 151   node = varpool_create_empty_node ();
 152   node->decl = decl;
 153   symtab_register_node (node);
 154   return node;
 155 }
 156
 157 /* Remove node from the varpool.  */
 158 void
 159 varpool_remove_node (struct varpool_node *node)
 160 {
 161   tree init;
 162   varpool_call_node_removal_hooks (node);
 163   symtab_unregister_node (node);
 164
 165   /* Because we remove references from external functions before final compilation,
 166      we may end up removing useful constructors.
 167      FIXME: We probably want to trace boundaries better.  */
 168   if ((init = ctor_for_folding (node->decl)) == error_mark_node)
 169     varpool_remove_initializer (node);
 170   else
 171     DECL_INITIAL (node->decl) = init;
 172   ggc_free (node);
 173 }
 174
 175 /* Renove node initializer when it is no longer needed.  */
 176 void
 177 varpool_remove_initializer (struct varpool_node *node)
 178 {
 179   if (DECL_INITIAL (node->decl)
 180       && !DECL_IN_CONSTANT_POOL (node->decl)
 181       /* Keep vtables for BINFO folding.  */
 182       && !DECL_VIRTUAL_P (node->decl)
 183       /* FIXME: http://gcc.gnu.org/PR55395 */
 184       && debug_info_level == DINFO_LEVEL_NONE
 185       /* When doing declaration merging we have duplicate
 186          entries for given decl.  Do not attempt to remove
 187          the boides, or we will end up remiving
 188          wrong one.  */
 189       && cgraph_state != CGRAPH_LTO_STREAMING)
 190     DECL_INITIAL (node->decl) = error_mark_node;
 191 }
 192
 193 /* Dump given cgraph node.  */
 194 void
 195 dump_varpool_node (FILE *f, struct varpool_node *node)
 196 {
 197   dump_symtab_base (f, node);
 198   fprintf (f, "  Availability: %s\n",
 199            cgraph_function_flags_ready
 200            ? cgraph_availability_names[cgraph_variable_initializer_availability (node)]
 201            : "not-ready");
 202   fprintf (f, "  Varpool flags:");
 203   if (DECL_INITIAL (node->decl))
 204     fprintf (f, " initialized");
 205   if (node->output)
 206     fprintf (f, " output");
 207   if (TREE_READONLY (node->decl))
 208     fprintf (f, " read-only");
 209   if (ctor_for_folding (node->decl) != error_mark_node)
 210     fprintf (f, " const-value-known");
 211   fprintf (f, "\n");
 212 }
 213
 214 /* Dump the variable pool.  */
 215 void
 216 dump_varpool (FILE *f)
 217 {
 218   struct varpool_node *node;
 219
 220   fprintf (f, "variable pool:\n\n");
 221   FOR_EACH_VARIABLE (node)
 222     dump_varpool_node (f, node);
 223 }
 224
 225 /* Dump the variable pool to stderr.  */
 226
 227 DEBUG_FUNCTION void
 228 debug_varpool (void)
 229 {
 230   dump_varpool (stderr);
 231 }
 232
 233 /* Given an assembler name, lookup node.  */
 234 struct varpool_node *
 235 varpool_node_for_asm (tree asmname)
 236 {
 237   if (symtab_node *node = symtab_node_for_asm (asmname))
 238     return dyn_cast <varpool_node> (node);
 239   else
 240     return NULL;
 241 }
 242
 243 /* Return if DECL is constant and its initial value is known (so we can do
 244    constant folding using DECL_INITIAL (decl)).
 245    Return ERROR_MARK_NODE when value is unknown.  */
 246
 247 tree
 248 ctor_for_folding (tree decl)
 249 {
 250   struct varpool_node *node, *real_node;
 251   tree real_decl;
 252
 253   if (TREE_CODE (decl) != VAR_DECL
 254       && TREE_CODE (decl) != CONST_DECL)
 255     return error_mark_node;
 256
 257   if (TREE_CODE (decl) == CONST_DECL
 258       || DECL_IN_CONSTANT_POOL (decl))
 259     return DECL_INITIAL (decl);
 260
 261   if (TREE_THIS_VOLATILE (decl))
 262     return error_mark_node;
 263
 264   /* Do not care about automatic variables.  Those are never initialized
 265      anyway, because gimplifier exapnds the code*/
 266   if (!TREE_STATIC (decl) && !DECL_EXTERNAL (decl))
 267     {
 268       gcc_assert (!TREE_PUBLIC (decl));
 269       return error_mark_node;
 270     }
 271
 272   gcc_assert (TREE_CODE (decl) == VAR_DECL);
 273
 274   node = varpool_get_node (decl);
 275   if (node)
 276     {
 277       real_node = varpool_variable_node (node);
 278       real_decl = real_node->decl;
 279     }
 280   else
 281     real_decl = decl;
 282
 283   /* See if we are dealing with alias.
 284      In most cases alias is just alternative symbol pointing to a given
 285      constructor.  This allows us to use interposition rules of DECL
 286      constructor of REAL_NODE.  However weakrefs are special by being just
 287      alternative name of their target (if defined).  */
 288   if (decl != real_decl)
 289     {
 290       gcc_assert (!DECL_INITIAL (decl)
 291                   || DECL_INITIAL (decl) == error_mark_node);
 292       if (lookup_attribute ("weakref", DECL_ATTRIBUTES (decl)))
 293         {
 294           node = varpool_alias_target (node);
 295           decl = node->decl;
 296         }
 297     }
 298
 299   /* Vtables are defined by their types and must match no matter of interposition
 300      rules.  */
 301   if (DECL_VIRTUAL_P (real_decl))
 302     {
 303       gcc_checking_assert (TREE_READONLY (real_decl));
 304       return DECL_INITIAL (real_decl);
 305     }
 306
 307   /* If thre is no constructor, we have nothing to do.  */
 308   if (DECL_INITIAL (real_decl) == error_mark_node)
 309     return error_mark_node;
 310
 311   /* Non-readonly alias of readonly variable is also de-facto readonly,
 312      because the variable itself is in readonly section.
 313      We also honnor READONLY flag on alias assuming that user knows
 314      what he is doing.  */
 315   if (!TREE_READONLY (decl) && !TREE_READONLY (real_decl))
 316     return error_mark_node;
 317
 318   /* Variables declared 'const' without an initializer
 319      have zero as the initializer if they may not be
 320      overridden at link or run time.  */
 321   if (!DECL_INITIAL (real_decl)
 322       && (DECL_EXTERNAL (decl) || decl_replaceable_p (decl)))
 323     return error_mark_node;
 324
 325   /* Variables declared `const' with an initializer are considered
 326      to not be overwritable with different initializer by default.
 327
 328      ??? Previously we behaved so for scalar variables but not for array
 329      accesses.  */
 330   return DECL_INITIAL (real_decl);
 331 }
 332
 333 /* Add the variable DECL to the varpool.
 334    Unlike varpool_finalize_decl function is intended to be used
 335    by middle end and allows insertion of new variable at arbitrary point
 336    of compilation.  */
 337 void
 338 varpool_add_new_variable (tree decl)
 339 {
 340   struct varpool_node *node;
 341   varpool_finalize_decl (decl);
 342   node = varpool_node_for_decl (decl);
 343   varpool_call_variable_insertion_hooks (node);
 344   if (varpool_externally_visible_p (node))
 345     node->externally_visible = true;
 346 }
 347
 348 /* Return variable availability.  See cgraph.h for description of individual
 349    return values.  */
 350 enum availability
 351 cgraph_variable_initializer_availability (struct varpool_node *node)
 352 {
 353   gcc_assert (cgraph_function_flags_ready);
 354   if (!node->definition)
 355     return AVAIL_NOT_AVAILABLE;
 356   if (!TREE_PUBLIC (node->decl))
 357     return AVAIL_AVAILABLE;
 358   if (DECL_IN_CONSTANT_POOL (node->decl)
 359       || DECL_VIRTUAL_P (node->decl))
 360     return AVAIL_AVAILABLE;
 361   if (node->alias && node->weakref)
 362     {
 363       enum availability avail;
 364
 365       cgraph_variable_initializer_availability
 366               (varpool_variable_node (node, &avail));
 367       return avail;
 368     }
 369   /* If the variable can be overwritten, return OVERWRITABLE.  Takes
 370      care of at least one notable extension - the COMDAT variables
 371      used to share template instantiations in C++.  */
 372   if (decl_replaceable_p (node->decl)
 373       || DECL_EXTERNAL (node->decl))
 374     return AVAIL_OVERWRITABLE;
 375   return AVAIL_AVAILABLE;
 376 }
 377
 378 void
 379 varpool_analyze_node (struct varpool_node *node)
 380 {
 381   tree decl = node->decl;
 382
 383   /* When reading back varpool at LTO time, we re-construct the queue in order
 384      to have "needed" list right by inserting all needed nodes into varpool.
 385      We however don't want to re-analyze already analyzed nodes.  */
 386   if (!node->analyzed)
 387     {
 388       gcc_assert (!in_lto_p || cgraph_function_flags_ready);
 389       /* Compute the alignment early so function body expanders are
 390          already informed about increased alignment.  */
 391       align_variable (decl, 0);
 392     }
 393   if (node->alias)
 394     symtab_resolve_alias
 395        (node, varpool_get_node (node->alias_target));
 396   else if (DECL_INITIAL (decl))
 397     record_references_in_initializer (decl, node->analyzed);
 398   node->analyzed = true;
 399 }
 400
 401 /* Assemble thunks and aliases associated to NODE.  */
 402
 403 static void
 404 assemble_aliases (struct varpool_node *node)
 405 {
 406   int i;
 407   struct ipa_ref *ref;
 408   for (i = 0; ipa_ref_list_referring_iterate (&node->ref_list, i, ref); i++)
 409     if (ref->use == IPA_REF_ALIAS)
 410       {
 411         struct varpool_node *alias = ipa_ref_referring_varpool_node (ref);
 412         do_assemble_alias (alias->decl,
 413                            DECL_ASSEMBLER_NAME (node->decl));
 414         assemble_aliases (alias);
 415       }
 416 }
 417
 418 /* Output one variable, if necessary.  Return whether we output it.  */
 419
 420 bool
 421 varpool_assemble_decl (struct varpool_node *node)
 422 {
 423   tree decl = node->decl;
 424
 425   /* Aliases are outout when their target is produced or by
 426      output_weakrefs.  */
 427   if (node->alias)
 428     return false;
 429
 430   /* Constant pool is output from RTL land when the reference
 431      survive till this level.  */
 432   if (DECL_IN_CONSTANT_POOL (decl) && TREE_ASM_WRITTEN (decl))
 433     return false;
 434
 435   /* Decls with VALUE_EXPR should not be in the varpool at all.  They
 436      are not real variables, but just info for debugging and codegen.
 437      Unfortunately at the moment emutls is not updating varpool correctly
 438      after turning real vars into value_expr vars.  */
 439   if (DECL_HAS_VALUE_EXPR_P (decl)
 440       && !targetm.have_tls)
 441     return false;
 442
 443   /* Hard register vars do not need to be output.  */
 444   if (DECL_HARD_REGISTER (decl))
 445     return false;
 446
 447   gcc_checking_assert (!TREE_ASM_WRITTEN (decl)
 448                        && TREE_CODE (decl) == VAR_DECL
 449                        && !DECL_HAS_VALUE_EXPR_P (decl));
 450
 451   if (!node->in_other_partition
 452       && !DECL_EXTERNAL (decl))
 453     {
 454       assemble_variable (decl, 0, 1, 0);
 455       gcc_assert (TREE_ASM_WRITTEN (decl));
 456       node->definition = true;
 457       assemble_aliases (node);
 458       return true;
 459     }
 460
 461   return false;
 462 }
 463
 464 /* Add NODE to queue starting at FIRST.
 465    The queue is linked via AUX pointers and terminated by pointer to 1.  */
 466
 467 static void
 468 enqueue_node (struct varpool_node *node, struct varpool_node **first)
 469 {
 470   if (node->aux)
 471     return;
 472   gcc_checking_assert (*first);
 473   node->aux = *first;
 474   *first = node;
 475 }
 476
 477 /* Optimization of function bodies might've rendered some variables as
 478    unnecessary so we want to avoid these from being compiled.  Re-do
 479    reachability starting from variables that are either externally visible
 480    or was referred from the asm output routines.  */
 481
 482 static void
 483 varpool_remove_unreferenced_decls (void)
 484 {
 485   struct varpool_node *next, *node;
 486   struct varpool_node *first = (struct varpool_node *)(void *)1;
 487   int i;
 488   struct ipa_ref *ref;
 489
 490   if (seen_error ())
 491     return;
 492
 493   if (cgraph_dump_file)
 494     fprintf (cgraph_dump_file, "Trivially needed variables:");
 495   FOR_EACH_DEFINED_VARIABLE (node)
 496     {
 497       if (node->analyzed
 498           && (!varpool_can_remove_if_no_refs (node)
 499               /* We just expanded all function bodies.  See if any of
 500                  them needed the variable.  */
 501               || DECL_RTL_SET_P (node->decl)))
 502         {
 503           enqueue_node (node, &first);
 504           if (cgraph_dump_file)
 505             fprintf (cgraph_dump_file, " %s", varpool_node_asm_name (node));
 506         }
 507     }
 508   while (first != (struct varpool_node *)(void *)1)
 509     {
 510       node = first;
 511       first = (struct varpool_node *)first->aux;
 512
 513       if (node->same_comdat_group)
 514         {
 515           symtab_node *next;
 516           for (next = node->same_comdat_group;
 517                next != node;
 518                next = next->same_comdat_group)
 519             {
 520               varpool_node *vnext = dyn_cast <varpool_node> (next);
 521               if (vnext && vnext->analyzed)
 522                 enqueue_node (vnext, &first);
 523             }
 524         }
 525       for (i = 0; ipa_ref_list_reference_iterate (&node->ref_list, i, ref); i++)
 526         {
 527           varpool_node *vnode = dyn_cast <varpool_node> (ref->referred);
 528           if (vnode
 529               && (!DECL_EXTERNAL (ref->referred->decl)
 530                   || vnode->alias)
 531               && vnode->analyzed)
 532             enqueue_node (vnode, &first);
 533         }
 534     }
 535   if (cgraph_dump_file)
 536     fprintf (cgraph_dump_file, "\nRemoving variables:");
 537   for (node = varpool_first_defined_variable (); node; node = next)
 538     {
 539       next = varpool_next_defined_variable (node);
 540       if (!node->aux)
 541         {
 542           if (cgraph_dump_file)
 543             fprintf (cgraph_dump_file, " %s", varpool_node_asm_name (node));
 544           varpool_remove_node (node);
 545         }
 546     }
 547   if (cgraph_dump_file)
 548     fprintf (cgraph_dump_file, "\n");
 549 }
 550
 551 /* For variables in named sections make sure get_variable_section
 552    is called before we switch to those sections.  Then section
 553    conflicts between read-only and read-only requiring relocations
 554    sections can be resolved.  */
 555 void
 556 varpool_finalize_named_section_flags (struct varpool_node *node)
 557 {
 558   if (!TREE_ASM_WRITTEN (node->decl)
 559       && !node->alias
 560       && !node->in_other_partition
 561       && !DECL_EXTERNAL (node->decl)
 562       && TREE_CODE (node->decl) == VAR_DECL
 563       && !DECL_HAS_VALUE_EXPR_P (node->decl)
 564       && DECL_SECTION_NAME (node->decl))
 565     get_variable_section (node->decl, false);
 566 }
 567
 568 /* Output all variables enqueued to be assembled.  */
 569 bool
 570 varpool_output_variables (void)
 571 {
 572   bool changed = false;
 573   struct varpool_node *node;
 574
 575   if (seen_error ())
 576     return false;
 577
 578   varpool_remove_unreferenced_decls ();
 579
 580   timevar_push (TV_VAROUT);
 581
 582   FOR_EACH_DEFINED_VARIABLE (node)
 583     varpool_finalize_named_section_flags (node);
 584
 585   FOR_EACH_DEFINED_VARIABLE (node)
 586     if (varpool_assemble_decl (node))
 587       changed = true;
 588   timevar_pop (TV_VAROUT);
 589   return changed;
 590 }
 591
 592 /* Create a new global variable of type TYPE.  */
 593 tree
 594 add_new_static_var (tree type)
 595 {
 596   tree new_decl;
 597   struct varpool_node *new_node;
 598
 599   new_decl = create_tmp_var_raw (type, NULL);
 600   DECL_NAME (new_decl) = create_tmp_var_name (NULL);
 601   TREE_READONLY (new_decl) = 0;
 602   TREE_STATIC (new_decl) = 1;
 603   TREE_USED (new_decl) = 1;
 604   DECL_CONTEXT (new_decl) = NULL_TREE;
 605   DECL_ABSTRACT (new_decl) = 0;
 606   lang_hooks.dup_lang_specific_decl (new_decl);
 607   new_node = varpool_node_for_decl (new_decl);
 608   varpool_finalize_decl (new_decl);
 609
 610   return new_node->decl;
 611 }
 612
 613 /* Attempt to mark ALIAS as an alias to DECL.  Return TRUE if successful.
 614    Extra name aliases are output whenever DECL is output.  */
 615
 616 struct varpool_node *
 617 varpool_create_variable_alias (tree alias, tree decl)
 618 {
 619   struct varpool_node *alias_node;
 620
 621   gcc_assert (TREE_CODE (decl) == VAR_DECL);
 622   gcc_assert (TREE_CODE (alias) == VAR_DECL);
 623   alias_node = varpool_node_for_decl (alias);
 624   alias_node->alias = true;
 625   alias_node->definition = true;
 626   alias_node->alias_target = decl;
 627   if (lookup_attribute ("weakref", DECL_ATTRIBUTES (alias)) != NULL)
 628     alias_node->weakref = true;
 629   return alias_node;
 630 }
 631
 632 /* Attempt to mark ALIAS as an alias to DECL.  Return TRUE if successful.
 633    Extra name aliases are output whenever DECL is output.  */
 634
 635 struct varpool_node *
 636 varpool_extra_name_alias (tree alias, tree decl)
 637 {
 638   struct varpool_node *alias_node;
 639
 640 #ifndef ASM_OUTPUT_DEF
 641   /* If aliases aren't supported by the assembler, fail.  */
 642   return NULL;
 643 #endif
 644   alias_node = varpool_create_variable_alias (alias, decl);
 645   alias_node->cpp_implicit_alias = true;
 646
 647   /* Extra name alias mechanizm creates aliases really late
 648      via DECL_ASSEMBLER_NAME mechanizm.
 649      This is unfortunate because they are not going through the
 650      standard channels.  Ensure they get output.  */
 651   if (cpp_implicit_aliases_done)
 652     symtab_resolve_alias (alias_node,
 653                           varpool_node_for_decl (decl));
 654   return alias_node;
 655 }
 656
 657 /* Call calback on NODE and aliases associated to NODE.
 658    When INCLUDE_OVERWRITABLE is false, overwritable aliases and thunks are
 659    skipped. */
 660
 661 bool
 662 varpool_for_node_and_aliases (struct varpool_node *node,
 663                               bool (*callback) (struct varpool_node *, void *),
 664                               void *data,
 665                               bool include_overwritable)
 666 {
 667   int i;
 668   struct ipa_ref *ref;
 669
 670   if (callback (node, data))
 671     return true;
 672   for (i = 0; ipa_ref_list_referring_iterate (&node->ref_list, i, ref); i++)
 673     if (ref->use == IPA_REF_ALIAS)
 674       {
 675         struct varpool_node *alias = ipa_ref_referring_varpool_node (ref);
 676         if (include_overwritable
 677             || cgraph_variable_initializer_availability (alias) > AVAIL_OVERWRITABLE)
 678           if (varpool_for_node_and_aliases (alias, callback, data,
 679                                            include_overwritable))
 680             return true;
 681       }
 682   return false;
 683 }