gcc/tree-emutls.c

   1 /* Lower TLS operations to emulation functions.
   2    Copyright (C) 2006, 2007, 2008, 2009, 2010
   3    Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it
   8 under the terms of the GNU General Public License as published by the
   9 Free Software Foundation; either version 3, or (at your option) any
  10 later version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT
  13 ANY 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 "tree.h"
  25 #include "gimple.h"
  26 #include "tree-pass.h"
  27 #include "tree-flow.h"
  28 #include "cgraph.h"
  29 #include "langhooks.h"
  30 #include "target.h"
  31 #include "targhooks.h"
  32 #include "tree-iterator.h"
  33
  34
  35 /* Whenever a target does not support thread-local storage (TLS) natively,
  36    we can emulate it with some run-time support in libgcc.  This will in
  37    turn rely on "keyed storage" a-la pthread_key_create; essentially all
  38    thread libraries provide such functionality.
  39
  40    In order to coordinate with the libgcc runtime, each TLS variable is
  41    described by a "control variable".  This control variable records the
  42    required size, alignment, and initial value of the TLS variable for
  43    instantiation at runtime.  It also stores an integer token to be used
  44    by the runtime to find the address of the variable within each thread.
  45
  46    On the compiler side, this means that we need to replace all instances
  47    of "tls_var" in the code with "*__emutls_get_addr(&control_var)".  We
  48    also need to eliminate "tls_var" from the symbol table and introduce
  49    "control_var".
  50
  51    We used to perform all of the transformations during conversion to rtl,
  52    and the variable substitutions magically within assemble_variable.
  53    However, this late fiddling of the symbol table conflicts with LTO and
  54    whole-program compilation.  Therefore we must now make all the changes
  55    to the symbol table early in the GIMPLE optimization path, before we
  56    write things out to LTO intermediate files.  */
  57
  58 /* These two vectors, once fully populated, are kept in lock-step so that
  59    the index of a TLS variable equals the index of its control variable in
  60    the other vector.  */
  61 static varpool_node_set tls_vars;
  62 static VEC(varpool_node_ptr, heap) *control_vars;
  63
  64 /* For the current basic block, an SSA_NAME that has computed the address
  65    of the TLS variable at the corresponding index.  */
  66 static VEC(tree, heap) *access_vars;
  67
  68 /* The type of the control structure, shared with the emutls.c runtime.  */
  69 static tree emutls_object_type;
  70
  71 #if !defined (NO_DOT_IN_LABEL)
  72 # define EMUTLS_SEPARATOR       "."
  73 #elif !defined (NO_DOLLAR_IN_LABEL)
  74 # define EMUTLS_SEPARATOR       "$"
  75 #else
  76 # define EMUTLS_SEPARATOR       "_"
  77 #endif
  78
  79 /* Create an IDENTIFIER_NODE by prefixing PREFIX to the
  80    IDENTIFIER_NODE NAME's name.  */
  81
  82 static tree
  83 prefix_name (const char *prefix, tree name)
  84 {
  85   unsigned plen = strlen (prefix);
  86   unsigned nlen = strlen (IDENTIFIER_POINTER (name));
  87   char *toname = (char *) alloca (plen + nlen + 1);
  88
  89   memcpy (toname, prefix, plen);
  90   memcpy (toname + plen, IDENTIFIER_POINTER (name), nlen + 1);
  91
  92   return get_identifier (toname);
  93 }
  94
  95 /* Create an identifier for the struct __emutls_object, given an identifier
  96    of the DECL_ASSEMBLY_NAME of the original object.  */
  97
  98 static tree
  99 get_emutls_object_name (tree name)
 100 {
 101   const char *prefix = (targetm.emutls.var_prefix
 102                         ? targetm.emutls.var_prefix
 103                         : "__emutls_v" EMUTLS_SEPARATOR);
 104   return prefix_name (prefix, name);
 105 }
 106
 107 /* Create the fields of the type for the control variables.  Ordinarily
 108    this must match struct __emutls_object defined in emutls.c.  However
 109    this is a target hook so that VxWorks can define its own layout.  */
 110
 111 tree
 112 default_emutls_var_fields (tree type, tree *name ATTRIBUTE_UNUSED)
 113 {
 114   tree word_type_node, field, next_field;
 115
 116   field = build_decl (UNKNOWN_LOCATION,
 117                       FIELD_DECL, get_identifier ("__templ"), ptr_type_node);
 118   DECL_CONTEXT (field) = type;
 119   next_field = field;
 120
 121   field = build_decl (UNKNOWN_LOCATION,
 122                       FIELD_DECL, get_identifier ("__offset"),
 123                       ptr_type_node);
 124   DECL_CONTEXT (field) = type;
 125   DECL_CHAIN (field) = next_field;
 126   next_field = field;
 127
 128   word_type_node = lang_hooks.types.type_for_mode (word_mode, 1);
 129   field = build_decl (UNKNOWN_LOCATION,
 130                       FIELD_DECL, get_identifier ("__align"),
 131                       word_type_node);
 132   DECL_CONTEXT (field) = type;
 133   DECL_CHAIN (field) = next_field;
 134   next_field = field;
 135
 136   field = build_decl (UNKNOWN_LOCATION,
 137                       FIELD_DECL, get_identifier ("__size"), word_type_node);
 138   DECL_CONTEXT (field) = type;
 139   DECL_CHAIN (field) = next_field;
 140
 141   return field;
 142 }
 143
 144 /* Initialize emulated tls object TO, which refers to TLS variable DECL and
 145    is initialized by PROXY.  As above, this is the default implementation of
 146    a target hook overridden by VxWorks.  */
 147
 148 tree
 149 default_emutls_var_init (tree to, tree decl, tree proxy)
 150 {
 151   VEC(constructor_elt,gc) *v = VEC_alloc (constructor_elt, gc, 4);
 152   constructor_elt *elt;
 153   tree type = TREE_TYPE (to);
 154   tree field = TYPE_FIELDS (type);
 155
 156   elt = VEC_quick_push (constructor_elt, v, NULL);
 157   elt->index = field;
 158   elt->value = fold_convert (TREE_TYPE (field), DECL_SIZE_UNIT (decl));
 159
 160   elt = VEC_quick_push (constructor_elt, v, NULL);
 161   field = DECL_CHAIN (field);
 162   elt->index = field;
 163   elt->value = build_int_cst (TREE_TYPE (field),
 164                               DECL_ALIGN_UNIT (decl));
 165
 166   elt = VEC_quick_push (constructor_elt, v, NULL);
 167   field = DECL_CHAIN (field);
 168   elt->index = field;
 169   elt->value = null_pointer_node;
 170
 171   elt = VEC_quick_push (constructor_elt, v, NULL);
 172   field = DECL_CHAIN (field);
 173   elt->index = field;
 174   elt->value = proxy;
 175
 176   return build_constructor (type, v);
 177 }
 178
 179 /* Create the structure for struct __emutls_object.  This should match the
 180    structure at the top of emutls.c, modulo the union there.  */
 181
 182 static tree
 183 get_emutls_object_type (void)
 184 {
 185   tree type, type_name, field;
 186
 187   type = emutls_object_type;
 188   if (type)
 189     return type;
 190
 191   emutls_object_type = type = lang_hooks.types.make_type (RECORD_TYPE);
 192   type_name = NULL;
 193   field = targetm.emutls.var_fields (type, &type_name);
 194   if (!type_name)
 195     type_name = get_identifier ("__emutls_object");
 196   type_name = build_decl (UNKNOWN_LOCATION,
 197                           TYPE_DECL, type_name, type);
 198   TYPE_NAME (type) = type_name;
 199   TYPE_FIELDS (type) = field;
 200   layout_type (type);
 201
 202   return type;
 203 }
 204
 205 /* Create a read-only variable like DECL, with the same DECL_INITIAL.
 206    This will be used for initializing the emulated tls data area.  */
 207
 208 static tree
 209 get_emutls_init_templ_addr (tree decl)
 210 {
 211   tree name, to;
 212
 213   if (targetm.emutls.register_common && !DECL_INITIAL (decl)
 214       && !DECL_SECTION_NAME (decl))
 215     return null_pointer_node;
 216
 217   name = DECL_ASSEMBLER_NAME (decl);
 218   if (!targetm.emutls.tmpl_prefix || targetm.emutls.tmpl_prefix[0])
 219     {
 220       const char *prefix = (targetm.emutls.tmpl_prefix
 221                             ? targetm.emutls.tmpl_prefix
 222                             : "__emutls_t" EMUTLS_SEPARATOR);
 223       name = prefix_name (prefix, name);
 224     }
 225
 226   to = build_decl (DECL_SOURCE_LOCATION (decl),
 227                    VAR_DECL, name, TREE_TYPE (decl));
 228   SET_DECL_ASSEMBLER_NAME (to, DECL_NAME (to));
 229
 230   DECL_ARTIFICIAL (to) = 1;
 231   TREE_USED (to) = TREE_USED (decl);
 232   TREE_READONLY (to) = 1;
 233   DECL_IGNORED_P (to) = 1;
 234   DECL_CONTEXT (to) = DECL_CONTEXT (decl);
 235   DECL_SECTION_NAME (to) = DECL_SECTION_NAME (decl);
 236   DECL_PRESERVE_P (to) = DECL_PRESERVE_P (decl);
 237
 238   DECL_WEAK (to) = DECL_WEAK (decl);
 239   if (DECL_ONE_ONLY (decl))
 240     {
 241       make_decl_one_only (to, DECL_ASSEMBLER_NAME (to));
 242       TREE_STATIC (to) = TREE_STATIC (decl);
 243       TREE_PUBLIC (to) = TREE_PUBLIC (decl);
 244       DECL_VISIBILITY (to) = DECL_VISIBILITY (decl);
 245     }
 246   else
 247     TREE_STATIC (to) = 1;
 248
 249   DECL_VISIBILITY_SPECIFIED (to) = DECL_VISIBILITY_SPECIFIED (decl);
 250   DECL_INITIAL (to) = DECL_INITIAL (decl);
 251   DECL_INITIAL (decl) = NULL;
 252
 253   if (targetm.emutls.tmpl_section)
 254     {
 255       DECL_SECTION_NAME (to)
 256         = build_string (strlen (targetm.emutls.tmpl_section),
 257                         targetm.emutls.tmpl_section);
 258     }
 259
 260   /* Create varpool node for the new variable and finalize it if it is
 261      not external one.  */
 262   if (DECL_EXTERNAL (to))
 263     varpool_node (to);
 264   else
 265     varpool_finalize_decl (to);
 266   return build_fold_addr_expr (to);
 267 }
 268
 269 /* Create and return the control variable for the TLS variable DECL.  */
 270
 271 static tree
 272 new_emutls_decl (tree decl)
 273 {
 274   tree name, to;
 275
 276   name = DECL_ASSEMBLER_NAME (decl);
 277   to = build_decl (DECL_SOURCE_LOCATION (decl), VAR_DECL,
 278                    get_emutls_object_name (name),
 279                    get_emutls_object_type ());
 280
 281   SET_DECL_ASSEMBLER_NAME (to, DECL_NAME (to));
 282
 283   DECL_TLS_MODEL (to) = TLS_MODEL_EMULATED;
 284   DECL_ARTIFICIAL (to) = 1;
 285   DECL_IGNORED_P (to) = 1;
 286   TREE_READONLY (to) = 0;
 287   TREE_STATIC (to) = 1;
 288
 289   DECL_PRESERVE_P (to) = DECL_PRESERVE_P (decl);
 290   DECL_CONTEXT (to) = DECL_CONTEXT (decl);
 291   TREE_USED (to) = TREE_USED (decl);
 292   TREE_PUBLIC (to) = TREE_PUBLIC (decl);
 293   DECL_EXTERNAL (to) = DECL_EXTERNAL (decl);
 294   DECL_COMMON (to) = DECL_COMMON (decl);
 295   DECL_WEAK (to) = DECL_WEAK (decl);
 296   DECL_VISIBILITY (to) = DECL_VISIBILITY (decl);
 297   DECL_VISIBILITY_SPECIFIED (to) = DECL_VISIBILITY_SPECIFIED (decl);
 298   DECL_RESTRICTED_P (to) = DECL_RESTRICTED_P (decl);
 299   DECL_DLLIMPORT_P (to) = DECL_DLLIMPORT_P (decl);
 300
 301   DECL_ATTRIBUTES (to) = targetm.merge_decl_attributes (decl, to);
 302
 303   if (DECL_ONE_ONLY (decl))
 304     make_decl_one_only (to, DECL_ASSEMBLER_NAME (to));
 305
 306   /* If we're not allowed to change the proxy object's alignment,
 307      pretend it has been set by the user.  */
 308   if (targetm.emutls.var_align_fixed)
 309     DECL_USER_ALIGN (to) = 1;
 310
 311   /* If the target wants the control variables grouped, do so.  */
 312   if (!DECL_COMMON (to) && targetm.emutls.var_section)
 313     {
 314       DECL_SECTION_NAME (to)
 315         = build_string (strlen (targetm.emutls.tmpl_section),
 316                         targetm.emutls.tmpl_section);
 317     }
 318
 319   /* If this variable is defined locally, then we need to initialize the
 320      control structure with size and alignment information.  Initialization
 321      of COMMON block variables happens elsewhere via a constructor.  */
 322   if (!DECL_EXTERNAL (to)
 323       && (!DECL_COMMON (to)
 324           || (DECL_INITIAL (decl)
 325               && DECL_INITIAL (decl) != error_mark_node)))
 326     {
 327       tree tmpl = get_emutls_init_templ_addr (decl);
 328       DECL_INITIAL (to) = targetm.emutls.var_init (to, decl, tmpl);
 329       record_references_in_initializer (to, false);
 330     }
 331
 332   /* Create varpool node for the new variable and finalize it if it is
 333      not external one.  */
 334   if (DECL_EXTERNAL (to))
 335     varpool_node (to);
 336   else
 337     varpool_finalize_decl (to);
 338   return to;
 339 }
 340
 341 /* Look up the index of the TLS variable DECL.  This index can then be
 342    used in both the control_vars and access_vars arrays.  */
 343
 344 static unsigned int
 345 emutls_index (tree decl)
 346 {
 347   varpool_node_set_iterator i;
 348
 349   i = varpool_node_set_find (tls_vars, varpool_get_node (decl));
 350   gcc_assert (i.index != ~0u);
 351
 352   return i.index;
 353 }
 354
 355 /* Look up the control variable for the TLS variable DECL.  */
 356
 357 static tree
 358 emutls_decl (tree decl)
 359 {
 360   struct varpool_node *var;
 361   unsigned int i;
 362
 363   i = emutls_index (decl);
 364   var = VEC_index (varpool_node_ptr, control_vars, i);
 365   return var->decl;
 366 }
 367
 368 /* Generate a call statement to initialize CONTROL_DECL for TLS_DECL.
 369    This only needs to happen for TLS COMMON variables; non-COMMON
 370    variables can be initialized statically.  Insert the generated
 371    call statement at the end of PSTMTS.  */
 372
 373 static void
 374 emutls_common_1 (tree tls_decl, tree control_decl, tree *pstmts)
 375 {
 376   tree x;
 377   tree word_type_node;
 378
 379   if (! DECL_COMMON (tls_decl)
 380       || (DECL_INITIAL (tls_decl)
 381           && DECL_INITIAL (tls_decl) != error_mark_node))
 382     return;
 383
 384   word_type_node = lang_hooks.types.type_for_mode (word_mode, 1);
 385
 386   x = build_call_expr (built_in_decls[BUILT_IN_EMUTLS_REGISTER_COMMON], 4,
 387                        build_fold_addr_expr (control_decl),
 388                        fold_convert (word_type_node,
 389                                      DECL_SIZE_UNIT (tls_decl)),
 390                        build_int_cst (word_type_node,
 391                                       DECL_ALIGN_UNIT (tls_decl)),
 392                        get_emutls_init_templ_addr (tls_decl));
 393
 394   append_to_statement_list (x, pstmts);
 395 }
 396
 397 struct lower_emutls_data
 398 {
 399   struct cgraph_node *cfun_node;
 400   struct cgraph_node *builtin_node;
 401   tree builtin_decl;
 402   basic_block bb;
 403   int bb_freq;
 404   location_t loc;
 405   gimple_seq seq;
 406 };
 407
 408 /* Given a TLS variable DECL, return an SSA_NAME holding its address.
 409    Append any new computation statements required to D->SEQ.  */
 410
 411 static tree
 412 gen_emutls_addr (tree decl, struct lower_emutls_data *d)
 413 {
 414   unsigned int index;
 415   tree addr;
 416
 417   /* Compute the address of the TLS variable with help from runtime.  */
 418   index = emutls_index (decl);
 419   addr = VEC_index (tree, access_vars, index);
 420   if (addr == NULL)
 421     {
 422       struct varpool_node *cvar;
 423       tree cdecl;
 424       gimple x;
 425
 426       cvar = VEC_index (varpool_node_ptr, control_vars, index);
 427       cdecl = cvar->decl;
 428       TREE_ADDRESSABLE (cdecl) = 1;
 429
 430       addr = create_tmp_var (build_pointer_type (TREE_TYPE (decl)), NULL);
 431       x = gimple_build_call (d->builtin_decl, 1, build_fold_addr_expr (cdecl));
 432       gimple_set_location (x, d->loc);
 433
 434       addr = make_ssa_name (addr, x);
 435       gimple_call_set_lhs (x, addr);
 436
 437       gimple_seq_add_stmt (&d->seq, x);
 438
 439       cgraph_create_edge (d->cfun_node, d->builtin_node, x,
 440                           d->bb->count, d->bb_freq);
 441
 442       /* We may be adding a new reference to a new variable to the function.
 443          This means we have to play with the ipa-reference web.  */
 444       ipa_record_reference (d->cfun_node, NULL, NULL, cvar, IPA_REF_ADDR, x);
 445
 446       /* Record this ssa_name for possible use later in the basic block.  */
 447       VEC_replace (tree, access_vars, index, addr);
 448     }
 449
 450   return addr;
 451 }
 452
 453 /* Callback for walk_gimple_op.  D = WI->INFO is a struct lower_emutls_data.
 454    Given an operand *PTR within D->STMT, if the operand references a TLS
 455    variable, then lower the reference to a call to the runtime.  Insert
 456    any new statements required into D->SEQ; the caller is responsible for
 457    placing those appropriately.  */
 458
 459 static tree
 460 lower_emutls_1 (tree *ptr, int *walk_subtrees, void *cb_data)
 461 {
 462   struct walk_stmt_info *wi = (struct walk_stmt_info *) cb_data;
 463   struct lower_emutls_data *d = (struct lower_emutls_data *) wi->info;
 464   tree t = *ptr;
 465   bool is_addr = false;
 466   tree addr;
 467
 468   *walk_subtrees = 0;
 469
 470   switch (TREE_CODE (t))
 471     {
 472     case ADDR_EXPR:
 473       /* If this is not a straight-forward "&var", but rather something
 474          like "&var.a", then we may need special handling.  */
 475       if (TREE_CODE (TREE_OPERAND (t, 0)) != VAR_DECL)
 476         {
 477           bool save_changed;
 478
 479           /* If we're allowed more than just is_gimple_val, continue.  */
 480           if (!wi->val_only)
 481             {
 482               *walk_subtrees = 1;
 483               return NULL_TREE;
 484             }
 485
 486           /* See if any substitution would be made.  */
 487           save_changed = wi->changed;
 488           wi->changed = false;
 489           wi->val_only = false;
 490           walk_tree (&TREE_OPERAND (t, 0), lower_emutls_1, wi, NULL);
 491           wi->val_only = true;
 492
 493           /* If so, then extract this entire sub-expression "&p->a" into a
 494              new assignment statement, and substitute yet another SSA_NAME.  */
 495           if (wi->changed)
 496             {
 497               gimple x;
 498
 499               addr = create_tmp_var (TREE_TYPE (t), NULL);
 500               x = gimple_build_assign (addr, t);
 501               gimple_set_location (x, d->loc);
 502
 503               addr = make_ssa_name (addr, x);
 504               gimple_assign_set_lhs (x, addr);
 505
 506               gimple_seq_add_stmt (&d->seq, x);
 507
 508               *ptr = addr;
 509             }
 510           else
 511             wi->changed = save_changed;
 512
 513           return NULL_TREE;
 514         }
 515
 516       t = TREE_OPERAND (t, 0);
 517       is_addr = true;
 518       /* FALLTHRU */
 519
 520     case VAR_DECL:
 521       if (!DECL_THREAD_LOCAL_P (t))
 522         return NULL_TREE;
 523       break;
 524
 525     default:
 526       /* We're not interested in other decls or types, only subexpressions.  */
 527       if (EXPR_P (t))
 528         *walk_subtrees = 1;
 529       /* FALLTHRU */
 530
 531     case SSA_NAME:
 532       /* Special-case the return of SSA_NAME, since it's so common.  */
 533       return NULL_TREE;
 534     }
 535
 536   addr = gen_emutls_addr (t, d);
 537   if (is_addr)
 538     {
 539       /* Replace "&var" with "addr" in the statement.  */
 540       *ptr = addr;
 541     }
 542   else
 543     {
 544       /* Replace "var" with "*addr" in the statement.  */
 545       t = build2 (MEM_REF, TREE_TYPE (t), addr,
 546                   build_int_cst (TREE_TYPE (addr), 0));
 547       *ptr = t;
 548     }
 549
 550   wi->changed = true;
 551   return NULL_TREE;
 552 }
 553
 554 /* Lower all of the operands of STMT.  */
 555
 556 static void
 557 lower_emutls_stmt (gimple stmt, struct lower_emutls_data *d)
 558 {
 559   struct walk_stmt_info wi;
 560
 561   d->loc = gimple_location (stmt);
 562
 563   memset (&wi, 0, sizeof (wi));
 564   wi.info = d;
 565   wi.val_only = true;
 566   walk_gimple_op (stmt, lower_emutls_1, &wi);
 567
 568   if (wi.changed)
 569     update_stmt (stmt);
 570 }
 571
 572 /* Lower the I'th operand of PHI.  */
 573
 574 static void
 575 lower_emutls_phi_arg (gimple phi, unsigned int i, struct lower_emutls_data *d)
 576 {
 577   struct walk_stmt_info wi;
 578   struct phi_arg_d *pd = gimple_phi_arg (phi, i);
 579
 580   /* Early out for a very common case we don't care about.  */
 581   if (TREE_CODE (pd->def) == SSA_NAME)
 582     return;
 583
 584   d->loc = pd->locus;
 585
 586   memset (&wi, 0, sizeof (wi));
 587   wi.info = d;
 588   wi.val_only = true;
 589   walk_tree (&pd->def, lower_emutls_1, &wi, NULL);
 590
 591   /* For normal statements, we let update_stmt do its job.  But for phi
 592      nodes, we have to manipulate the immediate use list by hand.  */
 593   if (wi.changed)
 594     {
 595       gcc_assert (TREE_CODE (pd->def) == SSA_NAME);
 596       link_imm_use_stmt (&pd->imm_use, pd->def, phi);
 597     }
 598 }
 599
 600 /* Clear the ACCESS_VARS array, in order to begin a new block.  */
 601
 602 static inline void
 603 clear_access_vars (void)
 604 {
 605   memset (VEC_address (tree, access_vars), 0,
 606           VEC_length (tree, access_vars) * sizeof(tree));
 607 }
 608
 609 /* Lower the entire function NODE.  */
 610
 611 static void
 612 lower_emutls_function_body (struct cgraph_node *node)
 613 {
 614   struct lower_emutls_data d;
 615   bool any_edge_inserts = false;
 616
 617   current_function_decl = node->decl;
 618   push_cfun (DECL_STRUCT_FUNCTION (node->decl));
 619
 620   d.cfun_node = node;
 621   d.builtin_decl = built_in_decls[BUILT_IN_EMUTLS_GET_ADDRESS];
 622   /* This is where we introduce the declaration to the IL and so we have to
 623      create a node for it.  */
 624   d.builtin_node = cgraph_get_create_node (d.builtin_decl);
 625
 626   FOR_EACH_BB (d.bb)
 627     {
 628       gimple_stmt_iterator gsi;
 629       unsigned int i, nedge;
 630
 631       /* Lower each of the PHI nodes of the block, as we may have
 632          propagated &tlsvar into a PHI argument.  These loops are
 633          arranged so that we process each edge at once, and each
 634          PHI argument for that edge.  */
 635       if (!gimple_seq_empty_p (phi_nodes (d.bb)))
 636         {
 637           /* The calls will be inserted on the edges, and the frequencies
 638              will be computed during the commit process.  */
 639           d.bb_freq = 0;
 640
 641           nedge = EDGE_COUNT (d.bb->preds);
 642           for (i = 0; i < nedge; ++i)
 643             {
 644               edge e = EDGE_PRED (d.bb, i);
 645
 646               /* We can re-use any SSA_NAME created on this edge.  */
 647               clear_access_vars ();
 648               d.seq = NULL;
 649
 650               for (gsi = gsi_start_phis (d.bb);
 651                    !gsi_end_p (gsi);
 652                    gsi_next (&gsi))
 653                 lower_emutls_phi_arg (gsi_stmt (gsi), i, &d);
 654
 655               /* Insert all statements generated by all phi nodes for this
 656                  particular edge all at once.  */
 657               if (d.seq)
 658                 {
 659                   gsi_insert_seq_on_edge (e, d.seq);
 660                   any_edge_inserts = true;
 661                 }
 662             }
 663         }
 664
 665       d.bb_freq = compute_call_stmt_bb_frequency (current_function_decl, d.bb);
 666
 667       /* We can re-use any SSA_NAME created during this basic block.  */
 668       clear_access_vars ();
 669
 670       /* Lower each of the statements of the block.  */
 671       for (gsi = gsi_start_bb (d.bb); !gsi_end_p (gsi); gsi_next (&gsi))
 672         {
 673           d.seq = NULL;
 674           lower_emutls_stmt (gsi_stmt (gsi), &d);
 675
 676           /* If any new statements were created, insert them immediately
 677              before the first use.  This prevents variable lifetimes from
 678              becoming unnecessarily long.  */
 679           if (d.seq)
 680             gsi_insert_seq_before (&gsi, d.seq, GSI_SAME_STMT);
 681         }
 682     }
 683
 684   if (any_edge_inserts)
 685     gsi_commit_edge_inserts ();
 686
 687   pop_cfun ();
 688   current_function_decl = NULL;
 689 }
 690
 691 /* Main entry point to the tls lowering pass.  */
 692
 693 static unsigned int
 694 ipa_lower_emutls (void)
 695 {
 696   struct varpool_node *var;
 697   struct cgraph_node *func;
 698   bool any_aliases = false;
 699   tree ctor_body = NULL;
 700   unsigned int i, n_tls;
 701
 702   tls_vars = varpool_node_set_new ();
 703
 704   /* Examine all global variables for TLS variables.  */
 705   for (var = varpool_nodes; var ; var = var->next)
 706     if (DECL_THREAD_LOCAL_P (var->decl))
 707       {
 708         gcc_checking_assert (TREE_STATIC (var->decl)
 709                              || DECL_EXTERNAL (var->decl));
 710         varpool_node_set_add (tls_vars, var);
 711       }
 712
 713   /* If we found no TLS variables, then there is no further work to do.  */
 714   if (tls_vars->nodes == NULL)
 715     {
 716       tls_vars = NULL;
 717       if (dump_file)
 718         fprintf (dump_file, "No TLS variables found.\n");
 719       return 0;
 720     }
 721
 722   /* Allocate the on-the-side arrays that share indicies with the TLS vars.  */
 723   n_tls = VEC_length (varpool_node_ptr, tls_vars->nodes);
 724   control_vars = VEC_alloc (varpool_node_ptr, heap, n_tls);
 725   access_vars = VEC_alloc (tree, heap, n_tls);
 726   VEC_safe_grow (tree, heap, access_vars, n_tls);
 727
 728   /* Create the control variables for each TLS variable.  */
 729   FOR_EACH_VEC_ELT (varpool_node_ptr, tls_vars->nodes, i, var)
 730     {
 731       tree cdecl;
 732       struct varpool_node *cvar;
 733
 734       var = VEC_index (varpool_node_ptr, tls_vars->nodes, i);
 735       cdecl = new_emutls_decl (var->decl);
 736
 737       cvar = varpool_get_node (cdecl);
 738       VEC_quick_push (varpool_node_ptr, control_vars, cvar);
 739
 740       if (var->alias)
 741         {
 742           any_aliases = true;
 743           cvar->alias = true;
 744         }
 745       else
 746         {
 747           /* Make sure the COMMON block control variable gets initialized.
 748              Note that there's no point in doing this for aliases; we only
 749              need to do this once for the main variable.  */
 750           emutls_common_1 (var->decl, cdecl, &ctor_body);
 751         }
 752
 753       /* Indicate that the value of the TLS variable may be found elsewhere,
 754          preventing the variable from re-appearing in the GIMPLE.  We cheat
 755          and use the control variable here (rather than a full call_expr),
 756          which is special-cased inside the DWARF2 output routines.  */
 757       SET_DECL_VALUE_EXPR (var->decl, cdecl);
 758       DECL_HAS_VALUE_EXPR_P (var->decl) = 1;
 759     }
 760
 761   /* If there were any aliases, then frob the alias_pairs vector.  */
 762   if (any_aliases)
 763     {
 764       alias_pair *p;
 765       FOR_EACH_VEC_ELT (alias_pair, alias_pairs, i, p)
 766         if (DECL_THREAD_LOCAL_P (p->decl))
 767           {
 768             p->decl = emutls_decl (p->decl);
 769             p->target = get_emutls_object_name (p->target);
 770           }
 771     }
 772
 773   /* Adjust all uses of TLS variables within the function bodies.  */
 774   for (func = cgraph_nodes; func; func = func->next)
 775     if (func->reachable && func->lowered)
 776       lower_emutls_function_body (func);
 777
 778   /* Generate the constructor for any COMMON control variables created.  */
 779   if (ctor_body)
 780     cgraph_build_static_cdtor ('I', ctor_body, DEFAULT_INIT_PRIORITY);
 781
 782   VEC_free (varpool_node_ptr, heap, control_vars);
 783   VEC_free (tree, heap, access_vars);
 784   tls_vars = NULL;
 785
 786   return TODO_dump_func | TODO_ggc_collect | TODO_verify_all;
 787 }
 788
 789 /* If the target supports TLS natively, we need do nothing here.  */
 790
 791 static bool
 792 gate_emutls (void)
 793 {
 794   return !targetm.have_tls;
 795 }
 796
 797 struct simple_ipa_opt_pass pass_ipa_lower_emutls =
 798 {
 799  {
 800   SIMPLE_IPA_PASS,
 801   "emutls",                             /* name */
 802   gate_emutls,                          /* gate */
 803   ipa_lower_emutls,                     /* execute */
 804   NULL,                                 /* sub */
 805   NULL,                                 /* next */
 806   0,                                    /* static_pass_number */
 807   TV_IPA_OPT,                           /* tv_id */
 808   PROP_cfg | PROP_ssa,                  /* properties_required */
 809   0,                                    /* properties_provided */
 810   0,                                    /* properties_destroyed */
 811   0,                                    /* todo_flags_start */
 812   0,                                    /* todo_flags_finish */
 813  }
 814 };