gcc/tree-ssanames.c

   1 /* Generic routines for manipulating SSA_NAME expressions
   2    Copyright (C) 2003-2020 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 #include "cfgloop.h"
  33 #include "tree-scalar-evolution.h"
  34
  35 /* Rewriting a function into SSA form can create a huge number of SSA_NAMEs,
  36    many of which may be thrown away shortly after their creation if jumps
  37    were threaded through PHI nodes.
  38
  39    While our garbage collection mechanisms will handle this situation, it
  40    is extremely wasteful to create nodes and throw them away, especially
  41    when the nodes can be reused.
  42
  43    For PR 8361, we can significantly reduce the number of nodes allocated
  44    and thus the total amount of memory allocated by managing SSA_NAMEs a
  45    little.  This additionally helps reduce the amount of work done by the
  46    garbage collector.  Similar results have been seen on a wider variety
  47    of tests (such as the compiler itself).
  48
  49    Right now we maintain our free list on a per-function basis.  It may
  50    or may not make sense to maintain the free list for the duration of
  51    a compilation unit.
  52
  53    External code should rely solely upon HIGHEST_SSA_VERSION and the
  54    externally defined functions.  External code should not know about
  55    the details of the free list management.
  56
  57    External code should also not assume the version number on nodes is
  58    monotonically increasing.  We reuse the version number when we
  59    reuse an SSA_NAME expression.  This helps keep arrays and bitmaps
  60    more compact.  */
  61
  62
  63 /* Version numbers with special meanings.  We start allocating new version
  64    numbers after the special ones.  */
  65 #define UNUSED_NAME_VERSION 0
  66
  67 unsigned int ssa_name_nodes_reused;
  68 unsigned int ssa_name_nodes_created;
  69
  70 #define FREE_SSANAMES(fun) (fun)->gimple_df->free_ssanames
  71 #define FREE_SSANAMES_QUEUE(fun) (fun)->gimple_df->free_ssanames_queue
  72
  73
  74 /* Initialize management of SSA_NAMEs to default SIZE.  If SIZE is
  75    zero use default.  */
  76
  77 void
  78 init_ssanames (struct function *fn, int size)
  79 {
  80   if (size < 50)
  81     size = 50;
  82
  83   vec_alloc (SSANAMES (fn), size);
  84
  85   /* Version 0 is special, so reserve the first slot in the table.  Though
  86      currently unused, we may use version 0 in alias analysis as part of
  87      the heuristics used to group aliases when the alias sets are too
  88      large.
  89
  90      We use vec::quick_push here because we know that SSA_NAMES has at
  91      least 50 elements reserved in it.  */
  92   SSANAMES (fn)->quick_push (NULL_TREE);
  93   FREE_SSANAMES (fn) = NULL;
  94   FREE_SSANAMES_QUEUE (fn) = NULL;
  95
  96   fn->gimple_df->ssa_renaming_needed = 0;
  97   fn->gimple_df->rename_vops = 0;
  98 }
  99
 100 /* Finalize management of SSA_NAMEs.  */
 101
 102 void
 103 fini_ssanames (struct function *fn)
 104 {
 105   vec_free (SSANAMES (fn));
 106   vec_free (FREE_SSANAMES (fn));
 107   vec_free (FREE_SSANAMES_QUEUE (fn));
 108 }
 109
 110 /* Dump some simple statistics regarding the re-use of SSA_NAME nodes.  */
 111
 112 void
 113 ssanames_print_statistics (void)
 114 {
 115   fprintf (stderr, "%-32s" PRsa (11) "\n", "SSA_NAME nodes allocated:",
 116            SIZE_AMOUNT (ssa_name_nodes_created));
 117   fprintf (stderr, "%-32s" PRsa (11) "\n", "SSA_NAME nodes reused:",
 118            SIZE_AMOUNT (ssa_name_nodes_reused));
 119 }
 120
 121 /* Verify the state of the SSA_NAME lists.
 122
 123    There must be no duplicates on the free list.
 124    Every name on the free list must be marked as on the free list.
 125    Any name on the free list must not appear in the IL.
 126    No names can be leaked.  */
 127
 128 DEBUG_FUNCTION void
 129 verify_ssaname_freelists (struct function *fun)
 130 {
 131   if (!gimple_in_ssa_p (fun))
 132     return;
 133
 134   auto_bitmap names_in_il;
 135
 136   /* Walk the entire IL noting every SSA_NAME we see.  */
 137   basic_block bb;
 138   FOR_EACH_BB_FN (bb, fun)
 139     {
 140       tree t;
 141       /* First note the result and arguments of PHI nodes.  */
 142       for (gphi_iterator gsi = gsi_start_phis (bb);
 143            !gsi_end_p (gsi);
 144            gsi_next (&gsi))
 145         {
 146           gphi *phi = gsi.phi ();
 147           t = gimple_phi_result (phi);
 148           bitmap_set_bit (names_in_il, SSA_NAME_VERSION (t));
 149
 150           for (unsigned int i = 0; i < gimple_phi_num_args (phi); i++)
 151             {
 152               t = gimple_phi_arg_def (phi, i);
 153               if (TREE_CODE (t) == SSA_NAME)
 154                 bitmap_set_bit (names_in_il, SSA_NAME_VERSION (t));
 155             }
 156         }
 157
 158       /* Then note the operands of each statement.  */
 159       for (gimple_stmt_iterator gsi = gsi_start_bb (bb);
 160            !gsi_end_p (gsi);
 161            gsi_next (&gsi))
 162         {
 163           ssa_op_iter iter;
 164           gimple *stmt = gsi_stmt (gsi);
 165           FOR_EACH_SSA_TREE_OPERAND (t, stmt, iter, SSA_OP_ALL_OPERANDS)
 166             bitmap_set_bit (names_in_il, SSA_NAME_VERSION (t));
 167         }
 168     }
 169
 170   /* Now walk the free list noting what we find there and verifying
 171      there are no duplicates.  */
 172   auto_bitmap names_in_freelists;
 173   if (FREE_SSANAMES (fun))
 174     {
 175       for (unsigned int i = 0; i < FREE_SSANAMES (fun)->length (); i++)
 176         {
 177           tree t = (*FREE_SSANAMES (fun))[i];
 178
 179           /* Verify that the name is marked as being in the free list.  */
 180           gcc_assert (SSA_NAME_IN_FREE_LIST (t));
 181
 182           /* Verify the name has not already appeared in the free list and
 183              note it in the list of names found in the free list.  */
 184           gcc_assert (!bitmap_bit_p (names_in_freelists, SSA_NAME_VERSION (t)));
 185           bitmap_set_bit (names_in_freelists, SSA_NAME_VERSION (t));
 186         }
 187     }
 188
 189   /* Similarly for the names in the pending free list.  */
 190   if (FREE_SSANAMES_QUEUE (fun))
 191     {
 192       for (unsigned int i = 0; i < FREE_SSANAMES_QUEUE (fun)->length (); i++)
 193         {
 194           tree t = (*FREE_SSANAMES_QUEUE (fun))[i];
 195
 196           /* Verify that the name is marked as being in the free list.  */
 197           gcc_assert (SSA_NAME_IN_FREE_LIST (t));
 198
 199           /* Verify the name has not already appeared in the free list and
 200              note it in the list of names found in the free list.  */
 201           gcc_assert (!bitmap_bit_p (names_in_freelists, SSA_NAME_VERSION (t)));
 202           bitmap_set_bit (names_in_freelists, SSA_NAME_VERSION (t));
 203         }
 204     }
 205
 206   /* If any name appears in both the IL and the freelists, then
 207      something horrible has happened.  */
 208   bool intersect_p = bitmap_intersect_p (names_in_il, names_in_freelists);
 209   gcc_assert (!intersect_p);
 210
 211   /* Names can be queued up for release if there is an ssa update
 212      pending.  Pretend we saw them in the IL.  */
 213   if (names_to_release)
 214     bitmap_ior_into (names_in_il, names_to_release);
 215
 216   /* Function splitting can "lose" SSA_NAMEs in an effort to ensure that
 217      debug/non-debug compilations have the same SSA_NAMEs.  So for each
 218      lost SSA_NAME, see if it's likely one from that wart.  These will always
 219      be marked as default definitions.  So we loosely assume that anything
 220      marked as a default definition isn't leaked by pretending they are
 221      in the IL.  */
 222   for (unsigned int i = UNUSED_NAME_VERSION + 1; i < num_ssa_names; i++)
 223     if (ssa_name (i) && SSA_NAME_IS_DEFAULT_DEF (ssa_name (i)))
 224       bitmap_set_bit (names_in_il, i);
 225
 226   unsigned int i;
 227   bitmap_iterator bi;
 228   auto_bitmap all_names;
 229   bitmap_set_range (all_names, UNUSED_NAME_VERSION + 1, num_ssa_names - 1);
 230   bitmap_ior_into (names_in_il, names_in_freelists);
 231
 232   /* Any name not mentioned in the IL and not in the feelists
 233      has been leaked.  */
 234   EXECUTE_IF_AND_COMPL_IN_BITMAP(all_names, names_in_il,
 235                                  UNUSED_NAME_VERSION + 1, i, bi)
 236     gcc_assert (!ssa_name (i));
 237 }
 238
 239 /* Move all SSA_NAMEs from FREE_SSA_NAMES_QUEUE to FREE_SSA_NAMES.
 240
 241    We do not, but should have a mode to verify the state of the SSA_NAMEs
 242    lists.  In particular at this point every name must be in the IL,
 243    on the free list or in the queue.  Anything else is an error.  */
 244
 245 void
 246 flush_ssaname_freelist (void)
 247 {
 248   /* If there were any SSA names released reset the SCEV cache.  */
 249   if (! vec_safe_is_empty (FREE_SSANAMES_QUEUE (cfun)))
 250     scev_reset_htab ();
 251   vec_safe_splice (FREE_SSANAMES (cfun), FREE_SSANAMES_QUEUE (cfun));
 252   vec_safe_truncate (FREE_SSANAMES_QUEUE (cfun), 0);
 253 }
 254
 255 /* Initialize SSA_NAME_IMM_USE_NODE of a SSA NAME.  */
 256
 257 void
 258 init_ssa_name_imm_use (tree name)
 259 {
 260   use_operand_p imm;
 261   imm = &(SSA_NAME_IMM_USE_NODE (name));
 262   imm->use = NULL;
 263   imm->prev = imm;
 264   imm->next = imm;
 265   imm->loc.ssa_name = name;
 266 }
 267
 268 /* Return an SSA_NAME node for variable VAR defined in statement STMT
 269    in function FN.  STMT may be an empty statement for artificial
 270    references (e.g., default definitions created when a variable is
 271    used without a preceding definition).  If VERISON is not zero then
 272    allocate the SSA name with that version.  */
 273
 274 tree
 275 make_ssa_name_fn (struct function *fn, tree var, gimple *stmt,
 276                   unsigned int version)
 277 {
 278   tree t;
 279   gcc_assert (VAR_P (var)
 280               || TREE_CODE (var) == PARM_DECL
 281               || TREE_CODE (var) == RESULT_DECL
 282               || (TYPE_P (var) && is_gimple_reg_type (var)));
 283
 284   /* Get the specified SSA name version.  */
 285   if (version != 0)
 286     {
 287       t = make_node (SSA_NAME);
 288       SSA_NAME_VERSION (t) = version;
 289       if (version >= SSANAMES (fn)->length ())
 290         vec_safe_grow_cleared (SSANAMES (fn), version + 1, true);
 291       gcc_assert ((*SSANAMES (fn))[version] == NULL);
 292       (*SSANAMES (fn))[version] = t;
 293       ssa_name_nodes_created++;
 294     }
 295   /* If our free list has an element, then use it.  */
 296   else if (!vec_safe_is_empty (FREE_SSANAMES (fn)))
 297     {
 298       t = FREE_SSANAMES (fn)->pop ();
 299       ssa_name_nodes_reused++;
 300
 301       /* The node was cleared out when we put it on the free list, so
 302          there is no need to do so again here.  */
 303       gcc_assert ((*SSANAMES (fn))[SSA_NAME_VERSION (t)] == NULL);
 304       (*SSANAMES (fn))[SSA_NAME_VERSION (t)] = t;
 305     }
 306   else
 307     {
 308       t = make_node (SSA_NAME);
 309       SSA_NAME_VERSION (t) = SSANAMES (fn)->length ();
 310       vec_safe_push (SSANAMES (fn), t);
 311       ssa_name_nodes_created++;
 312     }
 313
 314   if (TYPE_P (var))
 315     {
 316       TREE_TYPE (t) = TYPE_MAIN_VARIANT (var);
 317       SET_SSA_NAME_VAR_OR_IDENTIFIER (t, NULL_TREE);
 318     }
 319   else
 320     {
 321       TREE_TYPE (t) = TREE_TYPE (var);
 322       SET_SSA_NAME_VAR_OR_IDENTIFIER (t, var);
 323     }
 324   SSA_NAME_DEF_STMT (t) = stmt;
 325   if (POINTER_TYPE_P (TREE_TYPE (t)))
 326     SSA_NAME_PTR_INFO (t) = NULL;
 327   else
 328     SSA_NAME_RANGE_INFO (t) = NULL;
 329
 330   SSA_NAME_IN_FREE_LIST (t) = 0;
 331   SSA_NAME_IS_DEFAULT_DEF (t) = 0;
 332   init_ssa_name_imm_use (t);
 333
 334   return t;
 335 }
 336
 337 /* Helper function for set_range_info.
 338
 339    Store range information RANGE_TYPE, MIN, and MAX to tree ssa_name
 340    NAME.  */
 341
 342 void
 343 set_range_info_raw (tree name, enum value_range_kind range_type,
 344                     const wide_int_ref &min, const wide_int_ref &max)
 345 {
 346   gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
 347   gcc_assert (range_type == VR_RANGE || range_type == VR_ANTI_RANGE);
 348   range_info_def *ri = SSA_NAME_RANGE_INFO (name);
 349   unsigned int precision = TYPE_PRECISION (TREE_TYPE (name));
 350
 351   /* Allocate if not available.  */
 352   if (ri == NULL)
 353     {
 354       size_t size = (sizeof (range_info_def)
 355                      + trailing_wide_ints <3>::extra_size (precision));
 356       ri = static_cast<range_info_def *> (ggc_internal_alloc (size));
 357       ri->ints.set_precision (precision);
 358       SSA_NAME_RANGE_INFO (name) = ri;
 359       ri->set_nonzero_bits (wi::shwi (-1, precision));
 360     }
 361
 362   /* Record the range type.  */
 363   if (SSA_NAME_RANGE_TYPE (name) != range_type)
 364     SSA_NAME_ANTI_RANGE_P (name) = (range_type == VR_ANTI_RANGE);
 365
 366   /* Set the values.  */
 367   ri->set_min (min);
 368   ri->set_max (max);
 369
 370   /* If it is a range, try to improve nonzero_bits from the min/max.  */
 371   if (range_type == VR_RANGE)
 372     {
 373       wide_int xorv = ri->get_min () ^ ri->get_max ();
 374       if (xorv != 0)
 375         xorv = wi::mask (precision - wi::clz (xorv), false, precision);
 376       ri->set_nonzero_bits (ri->get_nonzero_bits () & (ri->get_min () | xorv));
 377     }
 378 }
 379
 380 /* Store range information RANGE_TYPE, MIN, and MAX to tree ssa_name
 381    NAME while making sure we don't store useless range info.  */
 382
 383 void
 384 set_range_info (tree name, enum value_range_kind range_type,
 385                 const wide_int_ref &min, const wide_int_ref &max)
 386 {
 387   gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
 388
 389   /* A range of the entire domain is really no range at all.  */
 390   tree type = TREE_TYPE (name);
 391   if (min == wi::min_value (TYPE_PRECISION (type), TYPE_SIGN (type))
 392       && max == wi::max_value (TYPE_PRECISION (type), TYPE_SIGN (type)))
 393     {
 394       range_info_def *ri = SSA_NAME_RANGE_INFO (name);
 395       if (ri == NULL)
 396         return;
 397       if (ri->get_nonzero_bits () == -1)
 398         {
 399           ggc_free (ri);
 400           SSA_NAME_RANGE_INFO (name) = NULL;
 401           return;
 402         }
 403     }
 404
 405   set_range_info_raw (name, range_type, min, max);
 406 }
 407
 408 /* Store range information for NAME from a value_range.  */
 409
 410 void
 411 set_range_info (tree name, const value_range &vr)
 412 {
 413   wide_int min = wi::to_wide (vr.min ());
 414   wide_int max = wi::to_wide (vr.max ());
 415   set_range_info (name, vr.kind (), min, max);
 416 }
 417
 418 /* Gets range information MIN, MAX and returns enum value_range_kind
 419    corresponding to tree ssa_name NAME.  enum value_range_kind returned
 420    is used to determine if MIN and MAX are valid values.  */
 421
 422 enum value_range_kind
 423 get_range_info (const_tree name, wide_int *min, wide_int *max)
 424 {
 425   gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
 426   gcc_assert (min && max);
 427   range_info_def *ri = SSA_NAME_RANGE_INFO (name);
 428
 429   /* Return VR_VARYING for SSA_NAMEs with NULL RANGE_INFO or SSA_NAMEs
 430      with integral types width > 2 * HOST_BITS_PER_WIDE_INT precision.  */
 431   if (!ri || (GET_MODE_PRECISION (SCALAR_INT_TYPE_MODE (TREE_TYPE (name)))
 432               > 2 * HOST_BITS_PER_WIDE_INT))
 433     return VR_VARYING;
 434
 435   *min = ri->get_min ();
 436   *max = ri->get_max ();
 437   return SSA_NAME_RANGE_TYPE (name);
 438 }
 439
 440 /* Gets range information corresponding to ssa_name NAME and stores it
 441    in a value_range VR.  Returns the value_range_kind.  */
 442
 443 enum value_range_kind
 444 get_range_info (const_tree name, irange &vr)
 445 {
 446   tree min, max;
 447   wide_int wmin, wmax;
 448   enum value_range_kind kind = get_range_info (name, &wmin, &wmax);
 449
 450   if (kind == VR_VARYING)
 451     vr.set_varying (TREE_TYPE (name));
 452   else if (kind == VR_UNDEFINED)
 453     vr.set_undefined ();
 454   else
 455     {
 456       min = wide_int_to_tree (TREE_TYPE (name), wmin);
 457       max = wide_int_to_tree (TREE_TYPE (name), wmax);
 458       vr.set (min, max, kind);
 459     }
 460   return kind;
 461 }
 462
 463 /* Set nonnull attribute to pointer NAME.  */
 464
 465 void
 466 set_ptr_nonnull (tree name)
 467 {
 468   gcc_assert (POINTER_TYPE_P (TREE_TYPE (name)));
 469   struct ptr_info_def *pi = get_ptr_info (name);
 470   pi->pt.null = 0;
 471 }
 472
 473 /* Return nonnull attribute of pointer NAME.  */
 474 bool
 475 get_ptr_nonnull (const_tree name)
 476 {
 477   gcc_assert (POINTER_TYPE_P (TREE_TYPE (name)));
 478   struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
 479   if (pi == NULL)
 480     return false;
 481   /* TODO Now pt->null is conservatively set to true in PTA
 482      analysis. vrp is the only pass (including ipa-vrp)
 483      that clears pt.null via set_ptr_nonull when it knows
 484      for sure. PTA will preserves the pt.null value set by VRP.
 485
 486      When PTA analysis is improved, pt.anything, pt.nonlocal
 487      and pt.escaped may also has to be considered before
 488      deciding that pointer cannot point to NULL.  */
 489   return !pi->pt.null;
 490 }
 491
 492 /* Change non-zero bits bitmask of NAME.  */
 493
 494 void
 495 set_nonzero_bits (tree name, const wide_int_ref &mask)
 496 {
 497   gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
 498   if (SSA_NAME_RANGE_INFO (name) == NULL)
 499     {
 500       if (mask == -1)
 501         return;
 502       set_range_info_raw (name, VR_RANGE,
 503                           wi::to_wide (TYPE_MIN_VALUE (TREE_TYPE (name))),
 504                           wi::to_wide (TYPE_MAX_VALUE (TREE_TYPE (name))));
 505     }
 506   range_info_def *ri = SSA_NAME_RANGE_INFO (name);
 507   ri->set_nonzero_bits (mask);
 508 }
 509
 510 /* Return a widest_int with potentially non-zero bits in SSA_NAME
 511    NAME, the constant for INTEGER_CST, or -1 if unknown.  */
 512
 513 wide_int
 514 get_nonzero_bits (const_tree name)
 515 {
 516   if (TREE_CODE (name) == INTEGER_CST)
 517     return wi::to_wide (name);
 518
 519   /* Use element_precision instead of TYPE_PRECISION so complex and
 520      vector types get a non-zero precision.  */
 521   unsigned int precision = element_precision (TREE_TYPE (name));
 522   if (POINTER_TYPE_P (TREE_TYPE (name)))
 523     {
 524       struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
 525       if (pi && pi->align)
 526         return wi::shwi (-(HOST_WIDE_INT) pi->align
 527                          | (HOST_WIDE_INT) pi->misalign, precision);
 528       return wi::shwi (-1, precision);
 529     }
 530
 531   range_info_def *ri = SSA_NAME_RANGE_INFO (name);
 532   if (!ri)
 533     return wi::shwi (-1, precision);
 534
 535   return ri->get_nonzero_bits ();
 536 }
 537
 538 /* Return TRUE is OP, an SSA_NAME has a range of values [0..1], false
 539    otherwise.
 540
 541    This can be because it is a boolean type, any unsigned integral
 542    type with a single bit of precision, or has known range of [0..1]
 543    via VRP analysis.  */
 544
 545 bool
 546 ssa_name_has_boolean_range (tree op)
 547 {
 548   gcc_assert (TREE_CODE (op) == SSA_NAME);
 549
 550   /* Boolean types always have a range [0..1].  */
 551   if (TREE_CODE (TREE_TYPE (op)) == BOOLEAN_TYPE)
 552     return true;
 553
 554   /* An integral type with a single bit of precision.  */
 555   if (INTEGRAL_TYPE_P (TREE_TYPE (op))
 556       && TYPE_UNSIGNED (TREE_TYPE (op))
 557       && TYPE_PRECISION (TREE_TYPE (op)) == 1)
 558     return true;
 559
 560   /* An integral type with more precision, but the object
 561      only takes on values [0..1] as determined by VRP
 562      analysis.  */
 563   if (INTEGRAL_TYPE_P (TREE_TYPE (op))
 564       && (TYPE_PRECISION (TREE_TYPE (op)) > 1)
 565       && wi::eq_p (get_nonzero_bits (op), 1))
 566     return true;
 567
 568   return false;
 569 }
 570
 571 /* We no longer need the SSA_NAME expression VAR, release it so that
 572    it may be reused.
 573
 574    Note it is assumed that no calls to make_ssa_name will be made
 575    until all uses of the ssa name are released and that the only
 576    use of the SSA_NAME expression is to check its SSA_NAME_VAR.  All
 577    other fields must be assumed clobbered.  */
 578
 579 void
 580 release_ssa_name_fn (struct function *fn, tree var)
 581 {
 582   if (!var)
 583     return;
 584
 585   /* Never release the default definition for a symbol.  It's a
 586      special SSA name that should always exist once it's created.  */
 587   if (SSA_NAME_IS_DEFAULT_DEF (var))
 588     return;
 589
 590   /* If VAR has been registered for SSA updating, don't remove it.
 591      After update_ssa has run, the name will be released.  */
 592   if (name_registered_for_update_p (var))
 593     {
 594       release_ssa_name_after_update_ssa (var);
 595       return;
 596     }
 597
 598   /* release_ssa_name can be called multiple times on a single SSA_NAME.
 599      However, it should only end up on our free list one time.   We
 600      keep a status bit in the SSA_NAME node itself to indicate it has
 601      been put on the free list.
 602
 603      Note that once on the freelist you cannot reference the SSA_NAME's
 604      defining statement.  */
 605   if (! SSA_NAME_IN_FREE_LIST (var))
 606     {
 607       int saved_ssa_name_version = SSA_NAME_VERSION (var);
 608       use_operand_p imm = &(SSA_NAME_IMM_USE_NODE (var));
 609
 610       if (MAY_HAVE_DEBUG_BIND_STMTS)
 611         insert_debug_temp_for_var_def (NULL, var);
 612
 613       if (flag_checking)
 614         verify_imm_links (stderr, var);
 615       while (imm->next != imm)
 616         delink_imm_use (imm->next);
 617
 618       (*SSANAMES (fn))[SSA_NAME_VERSION (var)] = NULL_TREE;
 619       memset (var, 0, tree_size (var));
 620
 621       imm->prev = imm;
 622       imm->next = imm;
 623       imm->loc.ssa_name = var;
 624
 625       /* First put back the right tree node so that the tree checking
 626          macros do not complain.  */
 627       TREE_SET_CODE (var, SSA_NAME);
 628
 629       /* Restore the version number.  */
 630       SSA_NAME_VERSION (var) = saved_ssa_name_version;
 631
 632       /* Note this SSA_NAME is now in the first list.  */
 633       SSA_NAME_IN_FREE_LIST (var) = 1;
 634
 635       /* Put in a non-NULL TREE_TYPE so dumping code will not ICE
 636          if it happens to come along a released SSA name and tries
 637          to inspect its type.  */
 638       TREE_TYPE (var) = error_mark_node;
 639
 640       /* And finally queue it so that it will be put on the free list.  */
 641       vec_safe_push (FREE_SSANAMES_QUEUE (fn), var);
 642     }
 643 }
 644
 645 /* If the alignment of the pointer described by PI is known, return true and
 646    store the alignment and the deviation from it into *ALIGNP and *MISALIGNP
 647    respectively.  Otherwise return false.  */
 648
 649 bool
 650 get_ptr_info_alignment (struct ptr_info_def *pi, unsigned int *alignp,
 651                         unsigned int *misalignp)
 652 {
 653   if (pi->align)
 654     {
 655       *alignp = pi->align;
 656       *misalignp = pi->misalign;
 657       return true;
 658     }
 659   else
 660     return false;
 661 }
 662
 663 /* State that the pointer described by PI has unknown alignment.  */
 664
 665 void
 666 mark_ptr_info_alignment_unknown (struct ptr_info_def *pi)
 667 {
 668   pi->align = 0;
 669   pi->misalign = 0;
 670 }
 671
 672 /* Store the power-of-two byte alignment and the deviation from that
 673    alignment of pointer described by PI to ALIOGN and MISALIGN
 674    respectively.  */
 675
 676 void
 677 set_ptr_info_alignment (struct ptr_info_def *pi, unsigned int align,
 678                             unsigned int misalign)
 679 {
 680   gcc_checking_assert (align != 0);
 681   gcc_assert ((align & (align - 1)) == 0);
 682   gcc_assert ((misalign & ~(align - 1)) == 0);
 683
 684   pi->align = align;
 685   pi->misalign = misalign;
 686 }
 687
 688 /* If pointer described by PI has known alignment, increase its known
 689    misalignment by INCREMENT modulo its current alignment.  */
 690
 691 void
 692 adjust_ptr_info_misalignment (struct ptr_info_def *pi, poly_uint64 increment)
 693 {
 694   if (pi->align != 0)
 695     {
 696       increment += pi->misalign;
 697       if (!known_misalignment (increment, pi->align, &pi->misalign))
 698         {
 699           pi->align = known_alignment (increment);
 700           pi->misalign = 0;
 701         }
 702     }
 703 }
 704
 705 /* Return the alias information associated with pointer T.  It creates a
 706    new instance if none existed.  */
 707
 708 struct ptr_info_def *
 709 get_ptr_info (tree t)
 710 {
 711   struct ptr_info_def *pi;
 712
 713   gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
 714
 715   pi = SSA_NAME_PTR_INFO (t);
 716   if (pi == NULL)
 717     {
 718       pi = ggc_cleared_alloc<ptr_info_def> ();
 719       pt_solution_reset (&pi->pt);
 720       mark_ptr_info_alignment_unknown (pi);
 721       SSA_NAME_PTR_INFO (t) = pi;
 722     }
 723
 724   return pi;
 725 }
 726
 727
 728 /* Creates a new SSA name using the template NAME tobe defined by
 729    statement STMT in function FN.  */
 730
 731 tree
 732 copy_ssa_name_fn (struct function *fn, tree name, gimple *stmt)
 733 {
 734   tree new_name;
 735
 736   if (SSA_NAME_VAR (name))
 737     new_name = make_ssa_name_fn (fn, SSA_NAME_VAR (name), stmt);
 738   else
 739     {
 740       new_name = make_ssa_name_fn (fn, TREE_TYPE (name), stmt);
 741       SET_SSA_NAME_VAR_OR_IDENTIFIER (new_name, SSA_NAME_IDENTIFIER (name));
 742     }
 743
 744   return new_name;
 745 }
 746
 747
 748 /* Creates a duplicate of the ptr_info_def at PTR_INFO for use by
 749    the SSA name NAME.  */
 750
 751 void
 752 duplicate_ssa_name_ptr_info (tree name, struct ptr_info_def *ptr_info)
 753 {
 754   struct ptr_info_def *new_ptr_info;
 755
 756   gcc_assert (POINTER_TYPE_P (TREE_TYPE (name)));
 757   gcc_assert (!SSA_NAME_PTR_INFO (name));
 758
 759   if (!ptr_info)
 760     return;
 761
 762   new_ptr_info = ggc_alloc<ptr_info_def> ();
 763   *new_ptr_info = *ptr_info;
 764
 765   SSA_NAME_PTR_INFO (name) = new_ptr_info;
 766 }
 767
 768 /* Creates a duplicate of the range_info_def at RANGE_INFO of type
 769    RANGE_TYPE for use by the SSA name NAME.  */
 770 void
 771 duplicate_ssa_name_range_info (tree name, enum value_range_kind range_type,
 772                                struct range_info_def *range_info)
 773 {
 774   struct range_info_def *new_range_info;
 775
 776   gcc_assert (!POINTER_TYPE_P (TREE_TYPE (name)));
 777   gcc_assert (!SSA_NAME_RANGE_INFO (name));
 778
 779   if (!range_info)
 780     return;
 781
 782   unsigned int precision = TYPE_PRECISION (TREE_TYPE (name));
 783   size_t size = (sizeof (range_info_def)
 784                  + trailing_wide_ints <3>::extra_size (precision));
 785   new_range_info = static_cast<range_info_def *> (ggc_internal_alloc (size));
 786   memcpy (new_range_info, range_info, size);
 787
 788   gcc_assert (range_type == VR_RANGE || range_type == VR_ANTI_RANGE);
 789   SSA_NAME_ANTI_RANGE_P (name) = (range_type == VR_ANTI_RANGE);
 790   SSA_NAME_RANGE_INFO (name) = new_range_info;
 791 }
 792
 793
 794
 795 /* Creates a duplicate of a ssa name NAME tobe defined by statement STMT
 796    in function FN.  */
 797
 798 tree
 799 duplicate_ssa_name_fn (struct function *fn, tree name, gimple *stmt)
 800 {
 801   tree new_name = copy_ssa_name_fn (fn, name, stmt);
 802   if (POINTER_TYPE_P (TREE_TYPE (name)))
 803     {
 804       struct ptr_info_def *old_ptr_info = SSA_NAME_PTR_INFO (name);
 805
 806       if (old_ptr_info)
 807         duplicate_ssa_name_ptr_info (new_name, old_ptr_info);
 808     }
 809   else
 810     {
 811       struct range_info_def *old_range_info = SSA_NAME_RANGE_INFO (name);
 812
 813       if (old_range_info)
 814         duplicate_ssa_name_range_info (new_name, SSA_NAME_RANGE_TYPE (name),
 815                                        old_range_info);
 816     }
 817
 818   return new_name;
 819 }
 820
 821
 822 /* Reset all flow sensitive data on NAME such as range-info, nonzero
 823    bits and alignment.  */
 824
 825 void
 826 reset_flow_sensitive_info (tree name)
 827 {
 828   if (POINTER_TYPE_P (TREE_TYPE (name)))
 829     {
 830       /* points-to info is not flow-sensitive.  */
 831       if (SSA_NAME_PTR_INFO (name))
 832         {
 833           /* [E]VRP can derive context sensitive alignment info and
 834              non-nullness properties.  We must reset both.  */
 835           mark_ptr_info_alignment_unknown (SSA_NAME_PTR_INFO (name));
 836           SSA_NAME_PTR_INFO (name)->pt.null = 1;
 837         }
 838     }
 839   else
 840     SSA_NAME_RANGE_INFO (name) = NULL;
 841 }
 842
 843 /* Clear all flow sensitive data from all statements and PHI definitions
 844    in BB.  */
 845
 846 void
 847 reset_flow_sensitive_info_in_bb (basic_block bb)
 848 {
 849   for (gimple_stmt_iterator gsi = gsi_start_bb (bb); !gsi_end_p (gsi);
 850        gsi_next (&gsi))
 851     {
 852       gimple *stmt = gsi_stmt (gsi);
 853       ssa_op_iter i;
 854       tree op;
 855       FOR_EACH_SSA_TREE_OPERAND (op, stmt, i, SSA_OP_DEF)
 856         reset_flow_sensitive_info (op);
 857     }
 858
 859   for (gphi_iterator gsi = gsi_start_phis (bb); !gsi_end_p (gsi);
 860        gsi_next (&gsi))
 861     {
 862       tree phi_def = gimple_phi_result (gsi.phi ());
 863       reset_flow_sensitive_info (phi_def);
 864     }
 865 }
 866
 867 /* Release all the SSA_NAMEs created by STMT.  */
 868
 869 void
 870 release_defs (gimple *stmt)
 871 {
 872   tree def;
 873   ssa_op_iter iter;
 874
 875   FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
 876     if (TREE_CODE (def) == SSA_NAME)
 877       release_ssa_name (def);
 878 }
 879
 880
 881 /* Replace the symbol associated with SSA_NAME with SYM.  */
 882
 883 void
 884 replace_ssa_name_symbol (tree ssa_name, tree sym)
 885 {
 886   SET_SSA_NAME_VAR_OR_IDENTIFIER (ssa_name, sym);
 887   TREE_TYPE (ssa_name) = TREE_TYPE (sym);
 888 }
 889
 890 /* Release the vector of free SSA_NAMEs and compact the vector of SSA_NAMEs
 891    that are live.  */
 892
 893 static void
 894 release_free_names_and_compact_live_names (function *fun)
 895 {
 896   unsigned i, j;
 897   int n = vec_safe_length (FREE_SSANAMES (fun));
 898
 899   /* Now release the freelist.  */
 900   vec_free (FREE_SSANAMES (fun));
 901
 902   /* And compact the SSA number space.  We make sure to not change the
 903      relative order of SSA versions.  */
 904   for (i = 1, j = 1; i < fun->gimple_df->ssa_names->length (); ++i)
 905     {
 906       tree name = ssa_name (i);
 907       if (name)
 908         {
 909           if (i != j)
 910             {
 911               SSA_NAME_VERSION (name) = j;
 912               (*fun->gimple_df->ssa_names)[j] = name;
 913             }
 914           j++;
 915         }
 916     }
 917   fun->gimple_df->ssa_names->truncate (j);
 918
 919   statistics_counter_event (fun, "SSA names released", n);
 920   statistics_counter_event (fun, "SSA name holes removed", i - j);
 921   if (dump_file)
 922     fprintf (dump_file, "Released %i names, %.2f%%, removed %i holes\n",
 923              n, n * 100.0 / num_ssa_names, i - j);
 924 }
 925
 926 /* Return SSA names that are unused to GGC memory and compact the SSA
 927    version namespace.  This is used to keep footprint of compiler during
 928    interprocedural optimization.  */
 929
 930 namespace {
 931
 932 const pass_data pass_data_release_ssa_names =
 933 {
 934   GIMPLE_PASS, /* type */
 935   "release_ssa", /* name */
 936   OPTGROUP_NONE, /* optinfo_flags */
 937   TV_TREE_SSA_OTHER, /* tv_id */
 938   PROP_ssa, /* properties_required */
 939   0, /* properties_provided */
 940   0, /* properties_destroyed */
 941   TODO_remove_unused_locals, /* todo_flags_start */
 942   0, /* todo_flags_finish */
 943 };
 944
 945 class pass_release_ssa_names : public gimple_opt_pass
 946 {
 947 public:
 948   pass_release_ssa_names (gcc::context *ctxt)
 949     : gimple_opt_pass (pass_data_release_ssa_names, ctxt)
 950   {}
 951
 952   /* opt_pass methods: */
 953   virtual unsigned int execute (function *);
 954
 955 }; // class pass_release_ssa_names
 956
 957 unsigned int
 958 pass_release_ssa_names::execute (function *fun)
 959 {
 960   release_free_names_and_compact_live_names (fun);
 961   return 0;
 962 }
 963
 964 } // anon namespace
 965
 966 gimple_opt_pass *
 967 make_pass_release_ssa_names (gcc::context *ctxt)
 968 {
 969   return new pass_release_ssa_names (ctxt);
 970 }