gcc/tree-ssanames.c

   1 /* Generic routines for manipulating SSA_NAME expressions
   2    Copyright (C) 2003-2017 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 3, or (at your option)
   9 any later version.
  10
  11 GCC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20 #include "config.h"
  21 #include "system.h"
  22 #include "coretypes.h"
  23 #include "backend.h"
  24 #include "tree.h"
  25 #include "gimple.h"
  26 #include "tree-pass.h"
  27 #include "ssa.h"
  28 #include "gimple-iterator.h"
  29 #include "stor-layout.h"
  30 #include "tree-into-ssa.h"
  31 #include "tree-ssa.h"
  32
  33 /* Rewriting a function into SSA form can create a huge number of SSA_NAMEs,
  34    many of which may be thrown away shortly after their creation if jumps
  35    were threaded through PHI nodes.
  36
  37    While our garbage collection mechanisms will handle this situation, it
  38    is extremely wasteful to create nodes and throw them away, especially
  39    when the nodes can be reused.
  40
  41    For PR 8361, we can significantly reduce the number of nodes allocated
  42    and thus the total amount of memory allocated by managing SSA_NAMEs a
  43    little.  This additionally helps reduce the amount of work done by the
  44    garbage collector.  Similar results have been seen on a wider variety
  45    of tests (such as the compiler itself).
  46
  47    Right now we maintain our free list on a per-function basis.  It may
  48    or may not make sense to maintain the free list for the duration of
  49    a compilation unit.
  50
  51    External code should rely solely upon HIGHEST_SSA_VERSION and the
  52    externally defined functions.  External code should not know about
  53    the details of the free list management.
  54
  55    External code should also not assume the version number on nodes is
  56    monotonically increasing.  We reuse the version number when we
  57    reuse an SSA_NAME expression.  This helps keep arrays and bitmaps
  58    more compact.  */
  59
  60
  61 /* Version numbers with special meanings.  We start allocating new version
  62    numbers after the special ones.  */
  63 #define UNUSED_NAME_VERSION 0
  64
  65 unsigned int ssa_name_nodes_reused;
  66 unsigned int ssa_name_nodes_created;
  67
  68 #define FREE_SSANAMES(fun) (fun)->gimple_df->free_ssanames
  69 #define FREE_SSANAMES_QUEUE(fun) (fun)->gimple_df->free_ssanames_queue
  70
  71
  72 /* Initialize management of SSA_NAMEs to default SIZE.  If SIZE is
  73    zero use default.  */
  74
  75 void
  76 init_ssanames (struct function *fn, int size)
  77 {
  78   if (size < 50)
  79     size = 50;
  80
  81   vec_alloc (SSANAMES (fn), size);
  82
  83   /* Version 0 is special, so reserve the first slot in the table.  Though
  84      currently unused, we may use version 0 in alias analysis as part of
  85      the heuristics used to group aliases when the alias sets are too
  86      large.
  87
  88      We use vec::quick_push here because we know that SSA_NAMES has at
  89      least 50 elements reserved in it.  */
  90   SSANAMES (fn)->quick_push (NULL_TREE);
  91   FREE_SSANAMES (fn) = NULL;
  92   FREE_SSANAMES_QUEUE (fn) = NULL;
  93
  94   fn->gimple_df->ssa_renaming_needed = 0;
  95   fn->gimple_df->rename_vops = 0;
  96 }
  97
  98 /* Finalize management of SSA_NAMEs.  */
  99
 100 void
 101 fini_ssanames (struct function *fn)
 102 {
 103   vec_free (SSANAMES (fn));
 104   vec_free (FREE_SSANAMES (fn));
 105   vec_free (FREE_SSANAMES_QUEUE (fn));
 106 }
 107
 108 /* Dump some simple statistics regarding the re-use of SSA_NAME nodes.  */
 109
 110 void
 111 ssanames_print_statistics (void)
 112 {
 113   fprintf (stderr, "SSA_NAME nodes allocated: %u\n", ssa_name_nodes_created);
 114   fprintf (stderr, "SSA_NAME nodes reused: %u\n", ssa_name_nodes_reused);
 115 }
 116
 117 /* Verify the state of the SSA_NAME lists.
 118
 119    There must be no duplicates on the free list.
 120    Every name on the free list must be marked as on the free list.
 121    Any name on the free list must not appear in the IL.
 122    No names can be leaked.  */
 123
 124 DEBUG_FUNCTION void
 125 verify_ssaname_freelists (struct function *fun)
 126 {
 127   if (!gimple_in_ssa_p (fun))
 128     return;
 129
 130   auto_bitmap names_in_il;
 131
 132   /* Walk the entire IL noting every SSA_NAME we see.  */
 133   basic_block bb;
 134   FOR_EACH_BB_FN (bb, fun)
 135     {
 136       tree t;
 137       /* First note the result and arguments of PHI nodes.  */
 138       for (gphi_iterator gsi = gsi_start_phis (bb);
 139            !gsi_end_p (gsi);
 140            gsi_next (&gsi))
 141         {
 142           gphi *phi = gsi.phi ();
 143           t = gimple_phi_result (phi);
 144           bitmap_set_bit (names_in_il, SSA_NAME_VERSION (t));
 145
 146           for (unsigned int i = 0; i < gimple_phi_num_args (phi); i++)
 147             {
 148               t = gimple_phi_arg_def (phi, i);
 149               if (TREE_CODE (t) == SSA_NAME)
 150                 bitmap_set_bit (names_in_il, SSA_NAME_VERSION (t));
 151             }
 152         }
 153
 154       /* Then note the operands of each statement.  */
 155       for (gimple_stmt_iterator gsi = gsi_start_bb (bb);
 156            !gsi_end_p (gsi);
 157            gsi_next (&gsi))
 158         {
 159           ssa_op_iter iter;
 160           gimple *stmt = gsi_stmt (gsi);
 161           FOR_EACH_SSA_TREE_OPERAND (t, stmt, iter, SSA_OP_ALL_OPERANDS)
 162             bitmap_set_bit (names_in_il, SSA_NAME_VERSION (t));
 163         }
 164     }
 165
 166   /* Now walk the free list noting what we find there and verifying
 167      there are no duplicates.  */
 168   auto_bitmap names_in_freelists;
 169   if (FREE_SSANAMES (fun))
 170     {
 171       for (unsigned int i = 0; i < FREE_SSANAMES (fun)->length (); i++)
 172         {
 173           tree t = (*FREE_SSANAMES (fun))[i];
 174
 175           /* Verify that the name is marked as being in the free list.  */
 176           gcc_assert (SSA_NAME_IN_FREE_LIST (t));
 177
 178           /* Verify the name has not already appeared in the free list and
 179              note it in the list of names found in the free list.  */
 180           gcc_assert (!bitmap_bit_p (names_in_freelists, SSA_NAME_VERSION (t)));
 181           bitmap_set_bit (names_in_freelists, SSA_NAME_VERSION (t));
 182         }
 183     }
 184
 185   /* Similarly for the names in the pending free list.  */
 186   if (FREE_SSANAMES_QUEUE (fun))
 187     {
 188       for (unsigned int i = 0; i < FREE_SSANAMES_QUEUE (fun)->length (); i++)
 189         {
 190           tree t = (*FREE_SSANAMES_QUEUE (fun))[i];
 191
 192           /* Verify that the name is marked as being in the free list.  */
 193           gcc_assert (SSA_NAME_IN_FREE_LIST (t));
 194
 195           /* Verify the name has not already appeared in the free list and
 196              note it in the list of names found in the free list.  */
 197           gcc_assert (!bitmap_bit_p (names_in_freelists, SSA_NAME_VERSION (t)));
 198           bitmap_set_bit (names_in_freelists, SSA_NAME_VERSION (t));
 199         }
 200     }
 201
 202   /* If any name appears in both the IL and the freelists, then
 203      something horrible has happened.  */
 204   bool intersect_p = bitmap_intersect_p (names_in_il, names_in_freelists);
 205   gcc_assert (!intersect_p);
 206
 207   /* Names can be queued up for release if there is an ssa update
 208      pending.  Pretend we saw them in the IL.  */
 209   if (names_to_release)
 210     bitmap_ior_into (names_in_il, names_to_release);
 211
 212   /* Function splitting can "lose" SSA_NAMEs in an effort to ensure that
 213      debug/non-debug compilations have the same SSA_NAMEs.  So for each
 214      lost SSA_NAME, see if it's likely one from that wart.  These will always
 215      be marked as default definitions.  So we loosely assume that anything
 216      marked as a default definition isn't leaked by pretending they are
 217      in the IL.  */
 218   for (unsigned int i = UNUSED_NAME_VERSION + 1; i < num_ssa_names; i++)
 219     if (ssa_name (i) && SSA_NAME_IS_DEFAULT_DEF (ssa_name (i)))
 220       bitmap_set_bit (names_in_il, i);
 221
 222   unsigned int i;
 223   bitmap_iterator bi;
 224   auto_bitmap all_names;
 225   bitmap_set_range (all_names, UNUSED_NAME_VERSION + 1, num_ssa_names - 1);
 226   bitmap_ior_into (names_in_il, names_in_freelists);
 227
 228   /* Any name not mentioned in the IL and not in the feelists
 229      has been leaked.  */
 230   EXECUTE_IF_AND_COMPL_IN_BITMAP(all_names, names_in_il,
 231                                  UNUSED_NAME_VERSION + 1, i, bi)
 232     gcc_assert (!ssa_name (i));
 233 }
 234
 235 /* Move all SSA_NAMEs from FREE_SSA_NAMES_QUEUE to FREE_SSA_NAMES.
 236
 237    We do not, but should have a mode to verify the state of the SSA_NAMEs
 238    lists.  In particular at this point every name must be in the IL,
 239    on the free list or in the queue.  Anything else is an error.  */
 240
 241 void
 242 flush_ssaname_freelist (void)
 243 {
 244   vec_safe_splice (FREE_SSANAMES (cfun), FREE_SSANAMES_QUEUE (cfun));
 245   vec_safe_truncate (FREE_SSANAMES_QUEUE (cfun), 0);
 246 }
 247
 248 /* Return an SSA_NAME node for variable VAR defined in statement STMT
 249    in function FN.  STMT may be an empty statement for artificial
 250    references (e.g., default definitions created when a variable is
 251    used without a preceding definition).  If VERISON is not zero then
 252    allocate the SSA name with that version.  */
 253
 254 tree
 255 make_ssa_name_fn (struct function *fn, tree var, gimple *stmt,
 256                   unsigned int version)
 257 {
 258   tree t;
 259   use_operand_p imm;
 260
 261   gcc_assert (VAR_P (var)
 262               || TREE_CODE (var) == PARM_DECL
 263               || TREE_CODE (var) == RESULT_DECL
 264               || (TYPE_P (var) && is_gimple_reg_type (var)));
 265
 266   /* Get the specified SSA name version.  */
 267   if (version != 0)
 268     {
 269       t = make_node (SSA_NAME);
 270       SSA_NAME_VERSION (t) = version;
 271       if (version >= SSANAMES (fn)->length ())
 272         vec_safe_grow_cleared (SSANAMES (fn), version + 1);
 273       gcc_assert ((*SSANAMES (fn))[version] == NULL);
 274       (*SSANAMES (fn))[version] = t;
 275       ssa_name_nodes_created++;
 276     }
 277   /* If our free list has an element, then use it.  */
 278   else if (!vec_safe_is_empty (FREE_SSANAMES (fn)))
 279     {
 280       t = FREE_SSANAMES (fn)->pop ();
 281       ssa_name_nodes_reused++;
 282
 283       /* The node was cleared out when we put it on the free list, so
 284          there is no need to do so again here.  */
 285       gcc_assert ((*SSANAMES (fn))[SSA_NAME_VERSION (t)] == NULL);
 286       (*SSANAMES (fn))[SSA_NAME_VERSION (t)] = t;
 287     }
 288   else
 289     {
 290       t = make_node (SSA_NAME);
 291       SSA_NAME_VERSION (t) = SSANAMES (fn)->length ();
 292       vec_safe_push (SSANAMES (fn), t);
 293       ssa_name_nodes_created++;
 294     }
 295
 296   if (TYPE_P (var))
 297     {
 298       TREE_TYPE (t) = TYPE_MAIN_VARIANT (var);
 299       SET_SSA_NAME_VAR_OR_IDENTIFIER (t, NULL_TREE);
 300     }
 301   else
 302     {
 303       TREE_TYPE (t) = TREE_TYPE (var);
 304       SET_SSA_NAME_VAR_OR_IDENTIFIER (t, var);
 305     }
 306   SSA_NAME_DEF_STMT (t) = stmt;
 307   if (POINTER_TYPE_P (TREE_TYPE (t)))
 308     SSA_NAME_PTR_INFO (t) = NULL;
 309   else
 310     SSA_NAME_RANGE_INFO (t) = NULL;
 311
 312   SSA_NAME_IN_FREE_LIST (t) = 0;
 313   SSA_NAME_IS_DEFAULT_DEF (t) = 0;
 314   imm = &(SSA_NAME_IMM_USE_NODE (t));
 315   imm->use = NULL;
 316   imm->prev = imm;
 317   imm->next = imm;
 318   imm->loc.ssa_name = t;
 319
 320   return t;
 321 }
 322
 323 /* Helper function for set_range_info.
 324
 325    Store range information RANGE_TYPE, MIN, and MAX to tree ssa_name
 326    NAME.  */
 327
 328 void
 329 set_range_info_raw (tree name, enum value_range_type range_type,
 330                     const wide_int_ref &min, const wide_int_ref &max)
 331 {
 332   gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
 333   gcc_assert (range_type == VR_RANGE || range_type == VR_ANTI_RANGE);
 334   range_info_def *ri = SSA_NAME_RANGE_INFO (name);
 335   unsigned int precision = TYPE_PRECISION (TREE_TYPE (name));
 336
 337   /* Allocate if not available.  */
 338   if (ri == NULL)
 339     {
 340       size_t size = (sizeof (range_info_def)
 341                      + trailing_wide_ints <3>::extra_size (precision));
 342       ri = static_cast<range_info_def *> (ggc_internal_alloc (size));
 343       ri->ints.set_precision (precision);
 344       SSA_NAME_RANGE_INFO (name) = ri;
 345       ri->set_nonzero_bits (wi::shwi (-1, precision));
 346     }
 347
 348   /* Record the range type.  */
 349   if (SSA_NAME_RANGE_TYPE (name) != range_type)
 350     SSA_NAME_ANTI_RANGE_P (name) = (range_type == VR_ANTI_RANGE);
 351
 352   /* Set the values.  */
 353   ri->set_min (min);
 354   ri->set_max (max);
 355
 356   /* If it is a range, try to improve nonzero_bits from the min/max.  */
 357   if (range_type == VR_RANGE)
 358     {
 359       wide_int xorv = ri->get_min () ^ ri->get_max ();
 360       if (xorv != 0)
 361         xorv = wi::mask (precision - wi::clz (xorv), false, precision);
 362       ri->set_nonzero_bits (ri->get_nonzero_bits () & (ri->get_min () | xorv));
 363     }
 364 }
 365
 366 /* Store range information RANGE_TYPE, MIN, and MAX to tree ssa_name
 367    NAME while making sure we don't store useless range info.  */
 368
 369 void
 370 set_range_info (tree name, enum value_range_type range_type,
 371                 const wide_int_ref &min, const wide_int_ref &max)
 372 {
 373   gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
 374
 375   /* A range of the entire domain is really no range at all.  */
 376   tree type = TREE_TYPE (name);
 377   if (min == wi::min_value (TYPE_PRECISION (type), TYPE_SIGN (type))
 378       && max == wi::max_value (TYPE_PRECISION (type), TYPE_SIGN (type)))
 379     {
 380       range_info_def *ri = SSA_NAME_RANGE_INFO (name);
 381       if (ri == NULL)
 382         return;
 383       if (ri->get_nonzero_bits () == -1)
 384         {
 385           ggc_free (ri);
 386           SSA_NAME_RANGE_INFO (name) = NULL;
 387           return;
 388         }
 389     }
 390
 391   set_range_info_raw (name, range_type, min, max);
 392 }
 393
 394
 395 /* Gets range information MIN, MAX and returns enum value_range_type
 396    corresponding to tree ssa_name NAME.  enum value_range_type returned
 397    is used to determine if MIN and MAX are valid values.  */
 398
 399 enum value_range_type
 400 get_range_info (const_tree name, wide_int *min, wide_int *max)
 401 {
 402   gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
 403   gcc_assert (min && max);
 404   range_info_def *ri = SSA_NAME_RANGE_INFO (name);
 405
 406   /* Return VR_VARYING for SSA_NAMEs with NULL RANGE_INFO or SSA_NAMEs
 407      with integral types width > 2 * HOST_BITS_PER_WIDE_INT precision.  */
 408   if (!ri || (GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (name)))
 409               > 2 * HOST_BITS_PER_WIDE_INT))
 410     return VR_VARYING;
 411
 412   *min = ri->get_min ();
 413   *max = ri->get_max ();
 414   return SSA_NAME_RANGE_TYPE (name);
 415 }
 416
 417 /* Set nonnull attribute to pointer NAME.  */
 418
 419 void
 420 set_ptr_nonnull (tree name)
 421 {
 422   gcc_assert (POINTER_TYPE_P (TREE_TYPE (name)));
 423   struct ptr_info_def *pi = get_ptr_info (name);
 424   pi->pt.null = 0;
 425 }
 426
 427 /* Return nonnull attribute of pointer NAME.  */
 428 bool
 429 get_ptr_nonnull (const_tree name)
 430 {
 431   gcc_assert (POINTER_TYPE_P (TREE_TYPE (name)));
 432   struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
 433   if (pi == NULL)
 434     return false;
 435   /* TODO Now pt->null is conservatively set to true in PTA
 436      analysis. vrp is the only pass (including ipa-vrp)
 437      that clears pt.null via set_ptr_nonull when it knows
 438      for sure. PTA will preserves the pt.null value set by VRP.
 439
 440      When PTA analysis is improved, pt.anything, pt.nonlocal
 441      and pt.escaped may also has to be considered before
 442      deciding that pointer cannot point to NULL.  */
 443   return !pi->pt.null;
 444 }
 445
 446 /* Change non-zero bits bitmask of NAME.  */
 447
 448 void
 449 set_nonzero_bits (tree name, const wide_int_ref &mask)
 450 {
 451   gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
 452   if (SSA_NAME_RANGE_INFO (name) == NULL)
 453     {
 454       if (mask == -1)
 455         return;
 456       set_range_info_raw (name, VR_RANGE,
 457                           TYPE_MIN_VALUE (TREE_TYPE (name)),
 458                           TYPE_MAX_VALUE (TREE_TYPE (name)));
 459     }
 460   range_info_def *ri = SSA_NAME_RANGE_INFO (name);
 461   ri->set_nonzero_bits (mask);
 462 }
 463
 464 /* Return a widest_int with potentially non-zero bits in SSA_NAME
 465    NAME, the constant for INTEGER_CST, or -1 if unknown.  */
 466
 467 wide_int
 468 get_nonzero_bits (const_tree name)
 469 {
 470   if (TREE_CODE (name) == INTEGER_CST)
 471     return name;
 472
 473   unsigned int precision = TYPE_PRECISION (TREE_TYPE (name));
 474   if (POINTER_TYPE_P (TREE_TYPE (name)))
 475     {
 476       struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
 477       if (pi && pi->align)
 478         return wi::shwi (-(HOST_WIDE_INT) pi->align
 479                          | (HOST_WIDE_INT) pi->misalign, precision);
 480       return wi::shwi (-1, precision);
 481     }
 482
 483   range_info_def *ri = SSA_NAME_RANGE_INFO (name);
 484   if (!ri)
 485     return wi::shwi (-1, precision);
 486
 487   return ri->get_nonzero_bits ();
 488 }
 489
 490 /* Return TRUE is OP, an SSA_NAME has a range of values [0..1], false
 491    otherwise.
 492
 493    This can be because it is a boolean type, any unsigned integral
 494    type with a single bit of precision, or has known range of [0..1]
 495    via VRP analysis.  */
 496
 497 bool
 498 ssa_name_has_boolean_range (tree op)
 499 {
 500   gcc_assert (TREE_CODE (op) == SSA_NAME);
 501
 502   /* Boolean types always have a range [0..1].  */
 503   if (TREE_CODE (TREE_TYPE (op)) == BOOLEAN_TYPE)
 504     return true;
 505
 506   /* An integral type with a single bit of precision.  */
 507   if (INTEGRAL_TYPE_P (TREE_TYPE (op))
 508       && TYPE_UNSIGNED (TREE_TYPE (op))
 509       && TYPE_PRECISION (TREE_TYPE (op)) == 1)
 510     return true;
 511
 512   /* An integral type with more precision, but the object
 513      only takes on values [0..1] as determined by VRP
 514      analysis.  */
 515   if (INTEGRAL_TYPE_P (TREE_TYPE (op))
 516       && (TYPE_PRECISION (TREE_TYPE (op)) > 1)
 517       && wi::eq_p (get_nonzero_bits (op), 1))
 518     return true;
 519
 520   return false;
 521 }
 522
 523 /* We no longer need the SSA_NAME expression VAR, release it so that
 524    it may be reused.
 525
 526    Note it is assumed that no calls to make_ssa_name will be made
 527    until all uses of the ssa name are released and that the only
 528    use of the SSA_NAME expression is to check its SSA_NAME_VAR.  All
 529    other fields must be assumed clobbered.  */
 530
 531 void
 532 release_ssa_name_fn (struct function *fn, tree var)
 533 {
 534   if (!var)
 535     return;
 536
 537   /* Never release the default definition for a symbol.  It's a
 538      special SSA name that should always exist once it's created.  */
 539   if (SSA_NAME_IS_DEFAULT_DEF (var))
 540     return;
 541
 542   /* If VAR has been registered for SSA updating, don't remove it.
 543      After update_ssa has run, the name will be released.  */
 544   if (name_registered_for_update_p (var))
 545     {
 546       release_ssa_name_after_update_ssa (var);
 547       return;
 548     }
 549
 550   /* release_ssa_name can be called multiple times on a single SSA_NAME.
 551      However, it should only end up on our free list one time.   We
 552      keep a status bit in the SSA_NAME node itself to indicate it has
 553      been put on the free list.
 554
 555      Note that once on the freelist you can not reference the SSA_NAME's
 556      defining statement.  */
 557   if (! SSA_NAME_IN_FREE_LIST (var))
 558     {
 559       tree saved_ssa_name_var = SSA_NAME_VAR (var);
 560       int saved_ssa_name_version = SSA_NAME_VERSION (var);
 561       use_operand_p imm = &(SSA_NAME_IMM_USE_NODE (var));
 562
 563       if (MAY_HAVE_DEBUG_STMTS)
 564         insert_debug_temp_for_var_def (NULL, var);
 565
 566       if (flag_checking)
 567         verify_imm_links (stderr, var);
 568       while (imm->next != imm)
 569         delink_imm_use (imm->next);
 570
 571       (*SSANAMES (fn))[SSA_NAME_VERSION (var)] = NULL_TREE;
 572       memset (var, 0, tree_size (var));
 573
 574       imm->prev = imm;
 575       imm->next = imm;
 576       imm->loc.ssa_name = var;
 577
 578       /* First put back the right tree node so that the tree checking
 579          macros do not complain.  */
 580       TREE_SET_CODE (var, SSA_NAME);
 581
 582       /* Restore the version number.  */
 583       SSA_NAME_VERSION (var) = saved_ssa_name_version;
 584
 585       /* Hopefully this can go away once we have the new incremental
 586          SSA updating code installed.  */
 587       SET_SSA_NAME_VAR_OR_IDENTIFIER (var, saved_ssa_name_var);
 588
 589       /* Note this SSA_NAME is now in the first list.  */
 590       SSA_NAME_IN_FREE_LIST (var) = 1;
 591
 592       /* And finally queue it so that it will be put on the free list.  */
 593       vec_safe_push (FREE_SSANAMES_QUEUE (fn), var);
 594     }
 595 }
 596
 597 /* If the alignment of the pointer described by PI is known, return true and
 598    store the alignment and the deviation from it into *ALIGNP and *MISALIGNP
 599    respectively.  Otherwise return false.  */
 600
 601 bool
 602 get_ptr_info_alignment (struct ptr_info_def *pi, unsigned int *alignp,
 603                         unsigned int *misalignp)
 604 {
 605   if (pi->align)
 606     {
 607       *alignp = pi->align;
 608       *misalignp = pi->misalign;
 609       return true;
 610     }
 611   else
 612     return false;
 613 }
 614
 615 /* State that the pointer described by PI has unknown alignment.  */
 616
 617 void
 618 mark_ptr_info_alignment_unknown (struct ptr_info_def *pi)
 619 {
 620   pi->align = 0;
 621   pi->misalign = 0;
 622 }
 623
 624 /* Store the power-of-two byte alignment and the deviation from that
 625    alignment of pointer described by PI to ALIOGN and MISALIGN
 626    respectively.  */
 627
 628 void
 629 set_ptr_info_alignment (struct ptr_info_def *pi, unsigned int align,
 630                             unsigned int misalign)
 631 {
 632   gcc_checking_assert (align != 0);
 633   gcc_assert ((align & (align - 1)) == 0);
 634   gcc_assert ((misalign & ~(align - 1)) == 0);
 635
 636   pi->align = align;
 637   pi->misalign = misalign;
 638 }
 639
 640 /* If pointer described by PI has known alignment, increase its known
 641    misalignment by INCREMENT modulo its current alignment.  */
 642
 643 void
 644 adjust_ptr_info_misalignment (struct ptr_info_def *pi,
 645                               unsigned int increment)
 646 {
 647   if (pi->align != 0)
 648     {
 649       pi->misalign += increment;
 650       pi->misalign &= (pi->align - 1);
 651     }
 652 }
 653
 654 /* Return the alias information associated with pointer T.  It creates a
 655    new instance if none existed.  */
 656
 657 struct ptr_info_def *
 658 get_ptr_info (tree t)
 659 {
 660   struct ptr_info_def *pi;
 661
 662   gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
 663
 664   pi = SSA_NAME_PTR_INFO (t);
 665   if (pi == NULL)
 666     {
 667       pi = ggc_cleared_alloc<ptr_info_def> ();
 668       pt_solution_reset (&pi->pt);
 669       mark_ptr_info_alignment_unknown (pi);
 670       SSA_NAME_PTR_INFO (t) = pi;
 671     }
 672
 673   return pi;
 674 }
 675
 676
 677 /* Creates a new SSA name using the template NAME tobe defined by
 678    statement STMT in function FN.  */
 679
 680 tree
 681 copy_ssa_name_fn (struct function *fn, tree name, gimple *stmt)
 682 {
 683   tree new_name;
 684
 685   if (SSA_NAME_VAR (name))
 686     new_name = make_ssa_name_fn (fn, SSA_NAME_VAR (name), stmt);
 687   else
 688     {
 689       new_name = make_ssa_name_fn (fn, TREE_TYPE (name), stmt);
 690       SET_SSA_NAME_VAR_OR_IDENTIFIER (new_name, SSA_NAME_IDENTIFIER (name));
 691     }
 692
 693   return new_name;
 694 }
 695
 696
 697 /* Creates a duplicate of the ptr_info_def at PTR_INFO for use by
 698    the SSA name NAME.  */
 699
 700 void
 701 duplicate_ssa_name_ptr_info (tree name, struct ptr_info_def *ptr_info)
 702 {
 703   struct ptr_info_def *new_ptr_info;
 704
 705   gcc_assert (POINTER_TYPE_P (TREE_TYPE (name)));
 706   gcc_assert (!SSA_NAME_PTR_INFO (name));
 707
 708   if (!ptr_info)
 709     return;
 710
 711   new_ptr_info = ggc_alloc<ptr_info_def> ();
 712   *new_ptr_info = *ptr_info;
 713
 714   SSA_NAME_PTR_INFO (name) = new_ptr_info;
 715 }
 716
 717 /* Creates a duplicate of the range_info_def at RANGE_INFO of type
 718    RANGE_TYPE for use by the SSA name NAME.  */
 719 void
 720 duplicate_ssa_name_range_info (tree name, enum value_range_type range_type,
 721                                struct range_info_def *range_info)
 722 {
 723   struct range_info_def *new_range_info;
 724
 725   gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
 726   gcc_assert (!SSA_NAME_RANGE_INFO (name));
 727
 728   if (!range_info)
 729     return;
 730
 731   unsigned int precision = TYPE_PRECISION (TREE_TYPE (name));
 732   size_t size = (sizeof (range_info_def)
 733                  + trailing_wide_ints <3>::extra_size (precision));
 734   new_range_info = static_cast<range_info_def *> (ggc_internal_alloc (size));
 735   memcpy (new_range_info, range_info, size);
 736
 737   gcc_assert (range_type == VR_RANGE || range_type == VR_ANTI_RANGE);
 738   SSA_NAME_ANTI_RANGE_P (name) = (range_type == VR_ANTI_RANGE);
 739   SSA_NAME_RANGE_INFO (name) = new_range_info;
 740 }
 741
 742
 743
 744 /* Creates a duplicate of a ssa name NAME tobe defined by statement STMT
 745    in function FN.  */
 746
 747 tree
 748 duplicate_ssa_name_fn (struct function *fn, tree name, gimple *stmt)
 749 {
 750   tree new_name = copy_ssa_name_fn (fn, name, stmt);
 751   if (POINTER_TYPE_P (TREE_TYPE (name)))
 752     {
 753       struct ptr_info_def *old_ptr_info = SSA_NAME_PTR_INFO (name);
 754
 755       if (old_ptr_info)
 756         duplicate_ssa_name_ptr_info (new_name, old_ptr_info);
 757     }
 758   else
 759     {
 760       struct range_info_def *old_range_info = SSA_NAME_RANGE_INFO (name);
 761
 762       if (old_range_info)
 763         duplicate_ssa_name_range_info (new_name, SSA_NAME_RANGE_TYPE (name),
 764                                        old_range_info);
 765     }
 766
 767   return new_name;
 768 }
 769
 770
 771 /* Reset all flow sensitive data on NAME such as range-info, nonzero
 772    bits and alignment.  */
 773
 774 void
 775 reset_flow_sensitive_info (tree name)
 776 {
 777   if (POINTER_TYPE_P (TREE_TYPE (name)))
 778     {
 779       /* points-to info is not flow-sensitive.  */
 780       if (SSA_NAME_PTR_INFO (name))
 781         mark_ptr_info_alignment_unknown (SSA_NAME_PTR_INFO (name));
 782     }
 783   else
 784     SSA_NAME_RANGE_INFO (name) = NULL;
 785 }
 786
 787 /* Clear all flow sensitive data from all statements and PHI definitions
 788    in BB.  */
 789
 790 void
 791 reset_flow_sensitive_info_in_bb (basic_block bb)
 792 {
 793   for (gimple_stmt_iterator gsi = gsi_start_bb (bb); !gsi_end_p (gsi);
 794        gsi_next (&gsi))
 795     {
 796       gimple *stmt = gsi_stmt (gsi);
 797       ssa_op_iter i;
 798       tree op;
 799       FOR_EACH_SSA_TREE_OPERAND (op, stmt, i, SSA_OP_DEF)
 800         reset_flow_sensitive_info (op);
 801     }
 802
 803   for (gphi_iterator gsi = gsi_start_phis (bb); !gsi_end_p (gsi);
 804        gsi_next (&gsi))
 805     {
 806       tree phi_def = gimple_phi_result (gsi.phi ());
 807       reset_flow_sensitive_info (phi_def);
 808     }
 809 }
 810
 811 /* Release all the SSA_NAMEs created by STMT.  */
 812
 813 void
 814 release_defs (gimple *stmt)
 815 {
 816   tree def;
 817   ssa_op_iter iter;
 818
 819   FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
 820     if (TREE_CODE (def) == SSA_NAME)
 821       release_ssa_name (def);
 822 }
 823
 824
 825 /* Replace the symbol associated with SSA_NAME with SYM.  */
 826
 827 void
 828 replace_ssa_name_symbol (tree ssa_name, tree sym)
 829 {
 830   SET_SSA_NAME_VAR_OR_IDENTIFIER (ssa_name, sym);
 831   TREE_TYPE (ssa_name) = TREE_TYPE (sym);
 832 }
 833
 834 /* Release the vector of free SSA_NAMEs and compact the vector of SSA_NAMEs
 835    that are live.  */
 836
 837 static void
 838 release_free_names_and_compact_live_names (function *fun)
 839 {
 840   unsigned i, j;
 841   int n = vec_safe_length (FREE_SSANAMES (fun));
 842
 843   /* Now release the freelist.  */
 844   vec_free (FREE_SSANAMES (fun));
 845
 846   /* And compact the SSA number space.  We make sure to not change the
 847      relative order of SSA versions.  */
 848   for (i = 1, j = 1; i < fun->gimple_df->ssa_names->length (); ++i)
 849     {
 850       tree name = ssa_name (i);
 851       if (name)
 852         {
 853           if (i != j)
 854             {
 855               SSA_NAME_VERSION (name) = j;
 856               (*fun->gimple_df->ssa_names)[j] = name;
 857             }
 858           j++;
 859         }
 860     }
 861   fun->gimple_df->ssa_names->truncate (j);
 862
 863   statistics_counter_event (fun, "SSA names released", n);
 864   statistics_counter_event (fun, "SSA name holes removed", i - j);
 865   if (dump_file)
 866     fprintf (dump_file, "Released %i names, %.2f%%, removed %i holes\n",
 867              n, n * 100.0 / num_ssa_names, i - j);
 868 }
 869
 870 /* Return SSA names that are unused to GGC memory and compact the SSA
 871    version namespace.  This is used to keep footprint of compiler during
 872    interprocedural optimization.  */
 873
 874 namespace {
 875
 876 const pass_data pass_data_release_ssa_names =
 877 {
 878   GIMPLE_PASS, /* type */
 879   "release_ssa", /* name */
 880   OPTGROUP_NONE, /* optinfo_flags */
 881   TV_TREE_SSA_OTHER, /* tv_id */
 882   PROP_ssa, /* properties_required */
 883   0, /* properties_provided */
 884   0, /* properties_destroyed */
 885   TODO_remove_unused_locals, /* todo_flags_start */
 886   0, /* todo_flags_finish */
 887 };
 888
 889 class pass_release_ssa_names : public gimple_opt_pass
 890 {
 891 public:
 892   pass_release_ssa_names (gcc::context *ctxt)
 893     : gimple_opt_pass (pass_data_release_ssa_names, ctxt)
 894   {}
 895
 896   /* opt_pass methods: */
 897   virtual unsigned int execute (function *);
 898
 899 }; // class pass_release_ssa_names
 900
 901 unsigned int
 902 pass_release_ssa_names::execute (function *fun)
 903 {
 904   release_free_names_and_compact_live_names (fun);
 905   return 0;
 906 }
 907
 908 } // anon namespace
 909
 910 gimple_opt_pass *
 911 make_pass_release_ssa_names (gcc::context *ctxt)
 912 {
 913   return new pass_release_ssa_names (ctxt);
 914 }