gcc/varpool.c

   1 /* Callgraph handling code.
   2    Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2010, 2011
   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 (const_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 = CONST_CAST2 (tree, const_tree, 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) || in_lto_p));
 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->next)
 166     node->next->prev = node->prev;
 167   if (node->prev)
 168     node->prev->next = node->next;
 169   else
 170     {
 171       gcc_assert (varpool_nodes == node);
 172       varpool_nodes = node->next;
 173     }
 174   if (varpool_first_unanalyzed_node == node)
 175     varpool_first_unanalyzed_node = node->next_needed;
 176   if (node->next_needed)
 177     node->next_needed->prev_needed = node->prev_needed;
 178   else if (node->prev_needed)
 179     {
 180       gcc_assert (varpool_last_needed_node);
 181       varpool_last_needed_node = node->prev_needed;
 182     }
 183   if (node->prev_needed)
 184     node->prev_needed->next_needed = node->next_needed;
 185   else if (node->next_needed)
 186     {
 187       gcc_assert (varpool_nodes_queue == node);
 188       varpool_nodes_queue = node->next_needed;
 189     }
 190   if (node->same_comdat_group)
 191     {
 192       struct varpool_node *prev;
 193       for (prev = node->same_comdat_group;
 194            prev->same_comdat_group != node;
 195            prev = prev->same_comdat_group)
 196         ;
 197       if (node->same_comdat_group == prev)
 198         prev->same_comdat_group = NULL;
 199       else
 200         prev->same_comdat_group = node->same_comdat_group;
 201       node->same_comdat_group = NULL;
 202     }
 203   ipa_remove_all_references (&node->ref_list);
 204   ipa_remove_all_refering (&node->ref_list);
 205   ggc_free (node);
 206 }
 207
 208 /* Dump given cgraph node.  */
 209 void
 210 dump_varpool_node (FILE *f, struct varpool_node *node)
 211 {
 212   fprintf (f, "%s:", varpool_node_name (node));
 213   fprintf (f, " availability:%s",
 214            cgraph_function_flags_ready
 215            ? cgraph_availability_names[cgraph_variable_initializer_availability (node)]
 216            : "not-ready");
 217   if (DECL_ASSEMBLER_NAME_SET_P (node->decl))
 218     fprintf (f, " (asm: %s)", IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (node->decl)));
 219   if (DECL_INITIAL (node->decl))
 220     fprintf (f, " initialized");
 221   if (TREE_ASM_WRITTEN (node->decl))
 222     fprintf (f, " (asm written)");
 223   if (node->needed)
 224     fprintf (f, " needed");
 225   if (node->analyzed)
 226     fprintf (f, " analyzed");
 227   if (node->finalized)
 228     fprintf (f, " finalized");
 229   if (node->output)
 230     fprintf (f, " output");
 231   if (node->externally_visible)
 232     fprintf (f, " externally_visible");
 233   if (node->resolution != LDPR_UNKNOWN)
 234     fprintf (f, " %s",
 235              ld_plugin_symbol_resolution_names[(int)node->resolution]);
 236   if (node->in_other_partition)
 237     fprintf (f, " in_other_partition");
 238   else if (node->used_from_other_partition)
 239     fprintf (f, " used_from_other_partition");
 240   fprintf (f, "\n");
 241   fprintf (f, "  References: ");
 242   ipa_dump_references (f, &node->ref_list);
 243   fprintf (f, "  Refering this var: ");
 244   ipa_dump_refering (f, &node->ref_list);
 245 }
 246
 247 /* Dump the variable pool.  */
 248 void
 249 dump_varpool (FILE *f)
 250 {
 251   struct varpool_node *node;
 252
 253   fprintf (f, "variable pool:\n\n");
 254   for (node = varpool_nodes; node; node = node->next)
 255     dump_varpool_node (f, node);
 256 }
 257
 258 /* Dump the variable pool to stderr.  */
 259
 260 DEBUG_FUNCTION void
 261 debug_varpool (void)
 262 {
 263   dump_varpool (stderr);
 264 }
 265
 266 /* Given an assembler name, lookup node.  */
 267 struct varpool_node *
 268 varpool_node_for_asm (tree asmname)
 269 {
 270   struct varpool_node *node;
 271
 272   for (node = varpool_nodes; node ; node = node->next)
 273     if (decl_assembler_name_equal (node->decl, asmname))
 274       return node;
 275
 276   return NULL;
 277 }
 278
 279 /* Helper function for finalization code - add node into lists so it will
 280    be analyzed and compiled.  */
 281 static void
 282 varpool_enqueue_needed_node (struct varpool_node *node)
 283 {
 284   if (varpool_last_needed_node)
 285     {
 286       varpool_last_needed_node->next_needed = node;
 287       node->prev_needed = varpool_last_needed_node;
 288     }
 289   varpool_last_needed_node = node;
 290   node->next_needed = NULL;
 291   if (!varpool_nodes_queue)
 292     varpool_nodes_queue = node;
 293   if (!varpool_first_unanalyzed_node)
 294     varpool_first_unanalyzed_node = node;
 295   notice_global_symbol (node->decl);
 296 }
 297
 298 /* Notify finalize_compilation_unit that given node is reachable
 299    or needed.  */
 300 void
 301 varpool_mark_needed_node (struct varpool_node *node)
 302 {
 303   if (!node->needed && node->finalized
 304       && !TREE_ASM_WRITTEN (node->decl))
 305     varpool_enqueue_needed_node (node);
 306   node->needed = 1;
 307 }
 308
 309 /* Reset the queue of needed nodes.  */
 310 void
 311 varpool_reset_queue (void)
 312 {
 313   varpool_last_needed_node = NULL;
 314   varpool_nodes_queue = NULL;
 315   varpool_first_unanalyzed_node = NULL;
 316 }
 317
 318 /* Determine if variable DECL is needed.  That is, visible to something
 319    either outside this translation unit, something magic in the system
 320    configury */
 321 bool
 322 decide_is_variable_needed (struct varpool_node *node, tree decl)
 323 {
 324   /* If the user told us it is used, then it must be so.  */
 325   if (node->force_output)
 326     return true;
 327
 328   gcc_assert (!DECL_EXTERNAL (decl));
 329
 330   /* Externally visible variables must be output.  The exception is
 331      COMDAT variables that must be output only when they are needed.  */
 332   if (TREE_PUBLIC (decl)
 333       && !DECL_COMDAT (decl)
 334       && !DECL_EXTERNAL (decl))
 335     return true;
 336
 337   /* When not reordering top level variables, we have to assume that
 338      we are going to keep everything.  */
 339   if (!flag_toplevel_reorder)
 340     return true;
 341   return false;
 342 }
 343
 344 /* Return if DECL is constant and its initial value is known (so we can do
 345    constant folding using DECL_INITIAL (decl)).  */
 346
 347 bool
 348 const_value_known_p (tree decl)
 349 {
 350   if (TREE_CODE (decl) != VAR_DECL
 351       &&TREE_CODE (decl) != CONST_DECL)
 352     return false;
 353
 354   if (TREE_CODE (decl) == CONST_DECL
 355       || DECL_IN_CONSTANT_POOL (decl))
 356     return true;
 357
 358   gcc_assert (TREE_CODE (decl) == VAR_DECL);
 359
 360   if (!TREE_READONLY (decl) || TREE_THIS_VOLATILE (decl))
 361     return false;
 362
 363   /* Gimplifier takes away constructors of local vars  */
 364   if (!TREE_STATIC (decl) && !DECL_EXTERNAL (decl))
 365     return DECL_INITIAL (decl) != NULL;
 366
 367   gcc_assert (TREE_STATIC (decl) || DECL_EXTERNAL (decl));
 368
 369   /* Variables declared 'const' without an initializer
 370      have zero as the initializer if they may not be
 371      overridden at link or run time.  */
 372   if (!DECL_INITIAL (decl)
 373       && (DECL_EXTERNAL (decl)
 374           || decl_replaceable_p (decl)))
 375     return false;
 376
 377   /* Variables declared `const' with an initializer are considered
 378      to not be overwritable with different initializer by default.
 379
 380      ??? Previously we behaved so for scalar variables but not for array
 381      accesses.  */
 382   return true;
 383 }
 384
 385 /* Mark DECL as finalized.  By finalizing the declaration, frontend instruct the
 386    middle end to output the variable to asm file, if needed or externally
 387    visible.  */
 388 void
 389 varpool_finalize_decl (tree decl)
 390 {
 391   struct varpool_node *node = varpool_node (decl);
 392
 393   gcc_assert (TREE_STATIC (decl));
 394
 395   /* The first declaration of a variable that comes through this function
 396      decides whether it is global (in C, has external linkage)
 397      or local (in C, has internal linkage).  So do nothing more
 398      if this function has already run.  */
 399   if (node->finalized)
 400     {
 401       if (cgraph_global_info_ready)
 402         varpool_assemble_pending_decls ();
 403       return;
 404     }
 405   if (node->needed)
 406     varpool_enqueue_needed_node (node);
 407   node->finalized = true;
 408   if (TREE_THIS_VOLATILE (decl) || DECL_PRESERVE_P (decl))
 409     node->force_output = true;
 410
 411   if (decide_is_variable_needed (node, decl))
 412     varpool_mark_needed_node (node);
 413   if (cgraph_global_info_ready)
 414     varpool_assemble_pending_decls ();
 415 }
 416
 417 /* Add the variable DECL to the varpool.
 418    Unlike varpool_finalize_decl function is intended to be used
 419    by middle end and allows insertion of new variable at arbitrary point
 420    of compilation.  */
 421 void
 422 varpool_add_new_variable (tree decl)
 423 {
 424   struct varpool_node *node;
 425   varpool_finalize_decl (decl);
 426   node = varpool_node (decl);
 427   if (varpool_externally_visible_p (node, false))
 428     node->externally_visible = true;
 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 (!decl_replaceable_p (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 (node->alias && node->alias_of)
 478         {
 479           struct varpool_node *tgt = varpool_node (node->alias_of);
 480           if (!VEC_length (ipa_ref_t, node->ref_list.references))
 481             ipa_record_reference (NULL, node, NULL, tgt, IPA_REF_ALIAS, NULL);
 482           /* C++ FE sometimes change linkage flags after producing same body aliases.  */
 483           if (node->extra_name_alias)
 484             {
 485               DECL_WEAK (node->decl) = DECL_WEAK (node->alias_of);
 486               TREE_PUBLIC (node->decl) = TREE_PUBLIC (node->alias_of);
 487               DECL_VISIBILITY (node->decl) = DECL_VISIBILITY (node->alias_of);
 488               if (TREE_PUBLIC (node->decl))
 489                 {
 490                   DECL_COMDAT (node->decl) = DECL_COMDAT (node->alias_of);
 491                   DECL_COMDAT_GROUP (node->decl) = DECL_COMDAT_GROUP (node->alias_of);
 492                   if (DECL_ONE_ONLY (node->alias_of) && !node->same_comdat_group)
 493                     {
 494                       node->same_comdat_group = tgt;
 495                       if (!tgt->same_comdat_group)
 496                         tgt->same_comdat_group = node;
 497                       else
 498                         {
 499                           struct varpool_node *n;
 500                           for (n = tgt->same_comdat_group;
 501                                n->same_comdat_group != tgt;
 502                                n = n->same_comdat_group)
 503                             ;
 504                           n->same_comdat_group = node;
 505                         }
 506                     }
 507                 }
 508             }
 509         }
 510       else if (DECL_INITIAL (decl))
 511         record_references_in_initializer (decl, analyzed);
 512       if (node->same_comdat_group)
 513         {
 514           for (next = node->same_comdat_group;
 515                next != node;
 516                next = next->same_comdat_group)
 517             varpool_mark_needed_node (next);
 518         }
 519       changed = true;
 520     }
 521   timevar_pop (TV_VARPOOL);
 522   return changed;
 523 }
 524
 525 /* Assemble thunks and aliases asociated to NODE.  */
 526
 527 static void
 528 assemble_aliases (struct varpool_node *node)
 529 {
 530   int i;
 531   struct ipa_ref *ref;
 532   for (i = 0; ipa_ref_list_refering_iterate (&node->ref_list, i, ref); i++)
 533     if (ref->use == IPA_REF_ALIAS)
 534       {
 535         struct varpool_node *alias = ipa_ref_refering_varpool_node (ref);
 536         assemble_alias (alias->decl,
 537                         DECL_ASSEMBLER_NAME (alias->alias_of));
 538         assemble_aliases (alias);
 539       }
 540 }
 541
 542 /* Output one variable, if necessary.  Return whether we output it.  */
 543 bool
 544 varpool_assemble_decl (struct varpool_node *node)
 545 {
 546   tree decl = node->decl;
 547
 548   if (!TREE_ASM_WRITTEN (decl)
 549       && !node->alias
 550       && !node->in_other_partition
 551       && !DECL_EXTERNAL (decl)
 552       && (TREE_CODE (decl) != VAR_DECL || !DECL_HAS_VALUE_EXPR_P (decl)))
 553     {
 554       assemble_variable (decl, 0, 1, 0);
 555       if (TREE_ASM_WRITTEN (decl))
 556         {
 557           node->next_needed = varpool_assembled_nodes_queue;
 558           node->prev_needed = NULL;
 559           if (varpool_assembled_nodes_queue)
 560             varpool_assembled_nodes_queue->prev_needed = node;
 561           varpool_assembled_nodes_queue = node;
 562           node->finalized = 1;
 563           assemble_aliases (node);
 564           return true;
 565         }
 566     }
 567
 568   return false;
 569 }
 570
 571 /* Optimization of function bodies might've rendered some variables as
 572    unnecessary so we want to avoid these from being compiled.
 573
 574    This is done by pruning the queue and keeping only the variables that
 575    really appear needed (ie they are either externally visible or referenced
 576    by compiled function). Re-doing the reachability analysis on variables
 577    brings back the remaining variables referenced by these.  */
 578 void
 579 varpool_remove_unreferenced_decls (void)
 580 {
 581   struct varpool_node *next, *node = varpool_nodes_queue;
 582
 583   varpool_reset_queue ();
 584
 585   if (seen_error ())
 586     return;
 587
 588   while (node)
 589     {
 590       next = node->next_needed;
 591       node->needed = 0;
 592
 593       if (node->analyzed
 594           && (!varpool_can_remove_if_no_refs (node)
 595               /* We just expanded all function bodies.  See if any of
 596                  them needed the variable.  */
 597               || DECL_RTL_SET_P (node->decl)))
 598         varpool_mark_needed_node (node);
 599
 600       node = next;
 601     }
 602   /* Make sure we mark alias targets as used targets.  */
 603   finish_aliases_1 ();
 604   varpool_analyze_pending_decls ();
 605 }
 606
 607 /* For variables in named sections make sure get_variable_section
 608    is called before we switch to those sections.  Then section
 609    conflicts between read-only and read-only requiring relocations
 610    sections can be resolved.  */
 611 void
 612 varpool_finalize_named_section_flags (struct varpool_node *node)
 613 {
 614   if (!TREE_ASM_WRITTEN (node->decl)
 615       && !node->alias
 616       && !node->in_other_partition
 617       && !DECL_EXTERNAL (node->decl)
 618       && TREE_CODE (node->decl) == VAR_DECL
 619       && !DECL_HAS_VALUE_EXPR_P (node->decl)
 620       && DECL_SECTION_NAME (node->decl))
 621     get_variable_section (node->decl, false);
 622 }
 623
 624 /* Output all variables enqueued to be assembled.  */
 625 bool
 626 varpool_assemble_pending_decls (void)
 627 {
 628   bool changed = false;
 629   struct varpool_node *node;
 630
 631   if (seen_error ())
 632     return false;
 633
 634   timevar_push (TV_VAROUT);
 635   /* EH might mark decls as needed during expansion.  This should be safe since
 636      we don't create references to new function, but it should not be used
 637      elsewhere.  */
 638   varpool_analyze_pending_decls ();
 639
 640   for (node = varpool_nodes_queue; node; node = node->next_needed)
 641     varpool_finalize_named_section_flags (node);
 642
 643   while (varpool_nodes_queue)
 644     {
 645       struct varpool_node *node = varpool_nodes_queue;
 646
 647       varpool_nodes_queue = varpool_nodes_queue->next_needed;
 648       if (varpool_assemble_decl (node))
 649         changed = true;
 650       else
 651         {
 652           node->prev_needed = NULL;
 653           node->next_needed = NULL;
 654         }
 655     }
 656   /* varpool_nodes_queue is now empty, clear the pointer to the last element
 657      in the queue.  */
 658   varpool_last_needed_node = NULL;
 659   timevar_pop (TV_VAROUT);
 660   return changed;
 661 }
 662
 663 /* Remove all elements from the queue so we can re-use it for debug output.  */
 664 void
 665 varpool_empty_needed_queue (void)
 666 {
 667   /* EH might mark decls as needed during expansion.  This should be safe since
 668      we don't create references to new function, but it should not be used
 669      elsewhere.  */
 670   varpool_analyze_pending_decls ();
 671
 672   while (varpool_nodes_queue)
 673     {
 674       struct varpool_node *node = varpool_nodes_queue;
 675       varpool_nodes_queue = varpool_nodes_queue->next_needed;
 676       node->next_needed = NULL;
 677       node->prev_needed = NULL;
 678     }
 679   /* varpool_nodes_queue is now empty, clear the pointer to the last element
 680      in the queue.  */
 681   varpool_last_needed_node = NULL;
 682 }
 683
 684 /* Create a new global variable of type TYPE.  */
 685 tree
 686 add_new_static_var (tree type)
 687 {
 688   tree new_decl;
 689   struct varpool_node *new_node;
 690
 691   new_decl = create_tmp_var (type, NULL);
 692   DECL_NAME (new_decl) = create_tmp_var_name (NULL);
 693   TREE_READONLY (new_decl) = 0;
 694   TREE_STATIC (new_decl) = 1;
 695   TREE_USED (new_decl) = 1;
 696   DECL_CONTEXT (new_decl) = NULL_TREE;
 697   DECL_ABSTRACT (new_decl) = 0;
 698   lang_hooks.dup_lang_specific_decl (new_decl);
 699   create_var_ann (new_decl);
 700   new_node = varpool_node (new_decl);
 701   varpool_mark_needed_node (new_node);
 702   add_referenced_var (new_decl);
 703   varpool_finalize_decl (new_decl);
 704
 705   return new_node->decl;
 706 }
 707
 708 /* Attempt to mark ALIAS as an alias to DECL.  Return TRUE if successful.
 709    Extra name aliases are output whenever DECL is output.  */
 710
 711 struct varpool_node *
 712 varpool_create_variable_alias (tree alias, tree decl)
 713 {
 714   struct varpool_node *alias_node;
 715
 716   gcc_assert (TREE_CODE (decl) == VAR_DECL);
 717   gcc_assert (TREE_CODE (alias) == VAR_DECL);
 718   alias_node = varpool_node (alias);
 719   alias_node->alias = 1;
 720   if (!DECL_EXTERNAL (alias))
 721     alias_node->finalized = 1;
 722   alias_node->alias_of = decl;
 723   if ((!DECL_EXTERNAL (alias)
 724        && decide_is_variable_needed (alias_node, alias))
 725       || alias_node->needed)
 726     varpool_mark_needed_node (alias_node);
 727   return alias_node;
 728 }
 729
 730 /* Attempt to mark ALIAS as an alias to DECL.  Return TRUE if successful.
 731    Extra name aliases are output whenever DECL is output.  */
 732
 733 struct varpool_node *
 734 varpool_extra_name_alias (tree alias, tree decl)
 735 {
 736   struct varpool_node *alias_node;
 737
 738 #ifndef ASM_OUTPUT_DEF
 739   /* If aliases aren't supported by the assembler, fail.  */
 740   return NULL;
 741 #endif
 742   alias_node = varpool_create_variable_alias (alias, decl);
 743   alias_node->extra_name_alias = true;
 744   return alias_node;
 745 }
 746
 747 /* Return true when NODE is known to be used from other (non-LTO) object file.
 748    Known only when doing LTO via linker plugin.  */
 749
 750 bool
 751 varpool_used_from_object_file_p (struct varpool_node *node)
 752 {
 753   if (!TREE_PUBLIC (node->decl))
 754     return false;
 755   if (resolution_used_from_other_file_p (node->resolution))
 756     return true;
 757   return false;
 758 }
 759
 760 /* Call calback on NODE and aliases asociated to NODE.
 761    When INCLUDE_OVERWRITABLE is false, overwritable aliases and thunks are
 762    skipped. */
 763
 764 bool
 765 varpool_for_node_and_aliases (struct varpool_node *node,
 766                               bool (*callback) (struct varpool_node *, void *),
 767                               void *data,
 768                               bool include_overwritable)
 769 {
 770   int i;
 771   struct ipa_ref *ref;
 772
 773   if (callback (node, data))
 774     return true;
 775   for (i = 0; ipa_ref_list_refering_iterate (&node->ref_list, i, ref); i++)
 776     if (ref->use == IPA_REF_ALIAS)
 777       {
 778         struct varpool_node *alias = ipa_ref_refering_varpool_node (ref);
 779         if (include_overwritable
 780             || cgraph_variable_initializer_availability (alias) > AVAIL_OVERWRITABLE)
 781           if (varpool_for_node_and_aliases (alias, callback, data,
 782                                            include_overwritable))
 783             return true;
 784       }
 785   return false;
 786 }
 787 #include "gt-varpool.h"