gcc/tree-ssa-dom.c

   1 /* SSA Dominator optimizations for trees
   2    Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
   3    Contributed by Diego Novillo <dnovillo@redhat.com>
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 2, or (at your option)
  10 any later version.
  11
  12 GCC is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING.  If not, write to
  19 the Free Software Foundation, 59 Temple Place - Suite 330,
  20 Boston, MA 02111-1307, USA.  */
  21
  22 #include "config.h"
  23 #include "system.h"
  24 #include "coretypes.h"
  25 #include "tm.h"
  26 #include "tree.h"
  27 #include "flags.h"
  28 #include "rtl.h"
  29 #include "tm_p.h"
  30 #include "ggc.h"
  31 #include "basic-block.h"
  32 #include "output.h"
  33 #include "errors.h"
  34 #include "expr.h"
  35 #include "function.h"
  36 #include "diagnostic.h"
  37 #include "timevar.h"
  38 #include "tree-dump.h"
  39 #include "tree-flow.h"
  40 #include "domwalk.h"
  41 #include "real.h"
  42 #include "tree-pass.h"
  43 #include "tree-ssa-propagate.h"
  44 #include "langhooks.h"
  45
  46 /* This file implements optimizations on the dominator tree.  */
  47
  48
  49 /* Structure for recording edge equivalences as well as any pending
  50    edge redirections during the dominator optimizer.
  51
  52    Computing and storing the edge equivalences instead of creating
  53    them on-demand can save significant amounts of time, particularly
  54    for pathological cases involving switch statements.
  55
  56    These structures live for a single iteration of the dominator
  57    optimizer in the edge's AUX field.  At the end of an iteration we
  58    free each of these structures and update the AUX field to point
  59    to any requested redirection target (the code for updating the
  60    CFG and SSA graph for edge redirection expects redirection edge
  61    targets to be in the AUX field for each edge.  */
  62
  63 struct edge_info
  64 {
  65   /* If this edge creates a simple equivalence, the LHS and RHS of
  66      the equivalence will be stored here.  */
  67   tree lhs;
  68   tree rhs;
  69
  70   /* Traversing an edge may also indicate one or more particular conditions
  71      are true or false.  The number of recorded conditions can vary, but
  72      can be determined by the condition's code.  So we have an array
  73      and its maximum index rather than use a varray.  */
  74   tree *cond_equivalences;
  75   unsigned int max_cond_equivalences;
  76
  77   /* If we can thread this edge this field records the new target.  */
  78   edge redirection_target;
  79 };
  80
  81
  82 /* Hash table with expressions made available during the renaming process.
  83    When an assignment of the form X_i = EXPR is found, the statement is
  84    stored in this table.  If the same expression EXPR is later found on the
  85    RHS of another statement, it is replaced with X_i (thus performing
  86    global redundancy elimination).  Similarly as we pass through conditionals
  87    we record the conditional itself as having either a true or false value
  88    in this table.  */
  89 static htab_t avail_exprs;
  90
  91 /* Stack of available expressions in AVAIL_EXPRs.  Each block pushes any
  92    expressions it enters into the hash table along with a marker entry
  93    (null).  When we finish processing the block, we pop off entries and
  94    remove the expressions from the global hash table until we hit the
  95    marker.  */
  96 static VEC(tree_on_heap) *avail_exprs_stack;
  97
  98 /* Stack of trees used to restore the global currdefs to its original
  99    state after completing optimization of a block and its dominator children.
 100
 101    An SSA_NAME indicates that the current definition of the underlying
 102    variable should be set to the given SSA_NAME.
 103
 104    A _DECL node indicates that the underlying variable has no current
 105    definition.
 106
 107    A NULL node is used to mark the last node associated with the
 108    current block.  */
 109 static VEC(tree_on_heap) *block_defs_stack;
 110
 111 /* Stack of statements we need to rescan during finalization for newly
 112    exposed variables.
 113
 114    Statement rescanning must occur after the current block's available
 115    expressions are removed from AVAIL_EXPRS.  Else we may change the
 116    hash code for an expression and be unable to find/remove it from
 117    AVAIL_EXPRS.  */
 118 static VEC(tree_on_heap) *stmts_to_rescan;
 119
 120 /* Structure for entries in the expression hash table.
 121
 122    This requires more memory for the hash table entries, but allows us
 123    to avoid creating silly tree nodes and annotations for conditionals,
 124    eliminates 2 global hash tables and two block local varrays.
 125
 126    It also allows us to reduce the number of hash table lookups we
 127    have to perform in lookup_avail_expr and finally it allows us to
 128    significantly reduce the number of calls into the hashing routine
 129    itself.  */
 130
 131 struct expr_hash_elt
 132 {
 133   /* The value (lhs) of this expression.  */
 134   tree lhs;
 135
 136   /* The expression (rhs) we want to record.  */
 137   tree rhs;
 138
 139   /* The annotation if this element corresponds to a statement.  */
 140   stmt_ann_t ann;
 141
 142   /* The hash value for RHS/ann.  */
 143   hashval_t hash;
 144 };
 145
 146 /* Stack of dest,src pairs that need to be restored during finalization.
 147
 148    A NULL entry is used to mark the end of pairs which need to be
 149    restored during finalization of this block.  */
 150 static VEC(tree_on_heap) *const_and_copies_stack;
 151
 152 /* Bitmap of SSA_NAMEs known to have a nonzero value, even if we do not
 153    know their exact value.  */
 154 static bitmap nonzero_vars;
 155
 156 /* Stack of SSA_NAMEs which need their NONZERO_VARS property cleared
 157    when the current block is finalized.
 158
 159    A NULL entry is used to mark the end of names needing their
 160    entry in NONZERO_VARS cleared during finalization of this block.  */
 161 static VEC(tree_on_heap) *nonzero_vars_stack;
 162
 163 /* Track whether or not we have changed the control flow graph.  */
 164 static bool cfg_altered;
 165
 166 /* Bitmap of blocks that have had EH statements cleaned.  We should
 167    remove their dead edges eventually.  */
 168 static bitmap need_eh_cleanup;
 169
 170 /* Statistics for dominator optimizations.  */
 171 struct opt_stats_d
 172 {
 173   long num_stmts;
 174   long num_exprs_considered;
 175   long num_re;
 176 };
 177
 178 static struct opt_stats_d opt_stats;
 179
 180 /* Value range propagation record.  Each time we encounter a conditional
 181    of the form SSA_NAME COND CONST we create a new vrp_element to record
 182    how the condition affects the possible values SSA_NAME may have.
 183
 184    Each record contains the condition tested (COND), and the range of
 185    values the variable may legitimately have if COND is true.  Note the
 186    range of values may be a smaller range than COND specifies if we have
 187    recorded other ranges for this variable.  Each record also contains the
 188    block in which the range was recorded for invalidation purposes.
 189
 190    Note that the current known range is computed lazily.  This allows us
 191    to avoid the overhead of computing ranges which are never queried.
 192
 193    When we encounter a conditional, we look for records which constrain
 194    the SSA_NAME used in the condition.  In some cases those records allow
 195    us to determine the condition's result at compile time.  In other cases
 196    they may allow us to simplify the condition.
 197
 198    We also use value ranges to do things like transform signed div/mod
 199    operations into unsigned div/mod or to simplify ABS_EXPRs.
 200
 201    Simple experiments have shown these optimizations to not be all that
 202    useful on switch statements (much to my surprise).  So switch statement
 203    optimizations are not performed.
 204
 205    Note carefully we do not propagate information through each statement
 206    in the block.  i.e., if we know variable X has a value defined of
 207    [0, 25] and we encounter Y = X + 1, we do not track a value range
 208    for Y (which would be [1, 26] if we cared).  Similarly we do not
 209    constrain values as we encounter narrowing typecasts, etc.  */
 210
 211 struct vrp_element
 212 {
 213   /* The highest and lowest values the variable in COND may contain when
 214      COND is true.  Note this may not necessarily be the same values
 215      tested by COND if the same variable was used in earlier conditionals.
 216
 217      Note this is computed lazily and thus can be NULL indicating that
 218      the values have not been computed yet.  */
 219   tree low;
 220   tree high;
 221
 222   /* The actual conditional we recorded.  This is needed since we compute
 223      ranges lazily.  */
 224   tree cond;
 225
 226   /* The basic block where this record was created.  We use this to determine
 227      when to remove records.  */
 228   basic_block bb;
 229 };
 230
 231 /* A hash table holding value range records (VRP_ELEMENTs) for a given
 232    SSA_NAME.  We used to use a varray indexed by SSA_NAME_VERSION, but
 233    that gets awful wasteful, particularly since the density objects
 234    with useful information is very low.  */
 235 static htab_t vrp_data;
 236
 237 /* An entry in the VRP_DATA hash table.  We record the variable and a
 238    varray of VRP_ELEMENT records associated with that variable.  */
 239 struct vrp_hash_elt
 240 {
 241   tree var;
 242   varray_type records;
 243 };
 244
 245 /* Array of variables which have their values constrained by operations
 246    in this basic block.  We use this during finalization to know
 247    which variables need their VRP data updated.  */
 248
 249 /* Stack of SSA_NAMEs which had their values constrained by operations
 250    in this basic block.  During finalization of this block we use this
 251    list to determine which variables need their VRP data updated.
 252
 253    A NULL entry marks the end of the SSA_NAMEs associated with this block.  */
 254 static VEC(tree_on_heap) *vrp_variables_stack;
 255
 256 struct eq_expr_value
 257 {
 258   tree src;
 259   tree dst;
 260 };
 261
 262 /* Local functions.  */
 263 static void optimize_stmt (struct dom_walk_data *,
 264                            basic_block bb,
 265                            block_stmt_iterator);
 266 static tree lookup_avail_expr (tree, bool);
 267 static hashval_t vrp_hash (const void *);
 268 static int vrp_eq (const void *, const void *);
 269 static hashval_t avail_expr_hash (const void *);
 270 static hashval_t real_avail_expr_hash (const void *);
 271 static int avail_expr_eq (const void *, const void *);
 272 static void htab_statistics (FILE *, htab_t);
 273 static void record_cond (tree, tree);
 274 static void record_const_or_copy (tree, tree);
 275 static void record_equality (tree, tree);
 276 static tree update_rhs_and_lookup_avail_expr (tree, tree, bool);
 277 static tree simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *,
 278                                                 tree, int);
 279 static tree simplify_cond_and_lookup_avail_expr (tree, stmt_ann_t, int);
 280 static tree simplify_switch_and_lookup_avail_expr (tree, int);
 281 static tree find_equivalent_equality_comparison (tree);
 282 static void record_range (tree, basic_block);
 283 static bool extract_range_from_cond (tree, tree *, tree *, int *);
 284 static void record_equivalences_from_phis (basic_block);
 285 static void record_equivalences_from_incoming_edge (basic_block);
 286 static bool eliminate_redundant_computations (struct dom_walk_data *,
 287                                               tree, stmt_ann_t);
 288 static void record_equivalences_from_stmt (tree, int, stmt_ann_t);
 289 static void thread_across_edge (struct dom_walk_data *, edge);
 290 static void dom_opt_finalize_block (struct dom_walk_data *, basic_block);
 291 static void dom_opt_initialize_block (struct dom_walk_data *, basic_block);
 292 static void propagate_to_outgoing_edges (struct dom_walk_data *, basic_block);
 293 static void remove_local_expressions_from_table (void);
 294 static void restore_vars_to_original_value (void);
 295 static void restore_currdefs_to_original_value (void);
 296 static void register_definitions_for_stmt (tree);
 297 static edge single_incoming_edge_ignoring_loop_edges (basic_block);
 298 static void restore_nonzero_vars_to_original_value (void);
 299 static inline bool unsafe_associative_fp_binop (tree);
 300
 301 /* Local version of fold that doesn't introduce cruft.  */
 302
 303 static tree
 304 local_fold (tree t)
 305 {
 306   t = fold (t);
 307
 308   /* Strip away useless type conversions.  Both the NON_LVALUE_EXPR that
 309      may have been added by fold, and "useless" type conversions that might
 310      now be apparent due to propagation.  */
 311   STRIP_USELESS_TYPE_CONVERSION (t);
 312
 313   return t;
 314 }
 315
 316 /* Allocate an EDGE_INFO for edge E and attach it to E.
 317    Return the new EDGE_INFO structure.  */
 318
 319 static struct edge_info *
 320 allocate_edge_info (edge e)
 321 {
 322   struct edge_info *edge_info;
 323
 324   edge_info = xcalloc (1, sizeof (struct edge_info));
 325
 326   e->aux = edge_info;
 327   return edge_info;
 328 }
 329
 330 /* Free all EDGE_INFO structures associated with edges in the CFG.
 331    If a particular edge can be threaded, copy the redirection
 332    target from the EDGE_INFO structure into the edge's AUX field
 333    as required by code to update the CFG and SSA graph for
 334    jump threading.  */
 335
 336 static void
 337 free_all_edge_infos (void)
 338 {
 339   basic_block bb;
 340   edge_iterator ei;
 341   edge e;
 342
 343   FOR_EACH_BB (bb)
 344     {
 345       FOR_EACH_EDGE (e, ei, bb->preds)
 346         {
 347          struct edge_info *edge_info = e->aux;
 348
 349           if (edge_info)
 350             {
 351               e->aux = edge_info->redirection_target;
 352               if (edge_info->cond_equivalences)
 353                 free (edge_info->cond_equivalences);
 354               free (edge_info);
 355             }
 356         }
 357     }
 358 }
 359
 360 /* Jump threading, redundancy elimination and const/copy propagation.
 361
 362    This pass may expose new symbols that need to be renamed into SSA.  For
 363    every new symbol exposed, its corresponding bit will be set in
 364    VARS_TO_RENAME.  */
 365
 366 static void
 367 tree_ssa_dominator_optimize (void)
 368 {
 369   struct dom_walk_data walk_data;
 370   unsigned int i;
 371
 372   memset (&opt_stats, 0, sizeof (opt_stats));
 373
 374   for (i = 0; i < num_referenced_vars; i++)
 375     var_ann (referenced_var (i))->current_def = NULL;
 376
 377   /* Create our hash tables.  */
 378   avail_exprs = htab_create (1024, real_avail_expr_hash, avail_expr_eq, free);
 379   vrp_data = htab_create (ceil_log2 (num_ssa_names), vrp_hash, vrp_eq, free);
 380   avail_exprs_stack = VEC_alloc (tree_on_heap, 20);
 381   block_defs_stack = VEC_alloc (tree_on_heap, 20);
 382   const_and_copies_stack = VEC_alloc (tree_on_heap, 20);
 383   nonzero_vars_stack = VEC_alloc (tree_on_heap, 20);
 384   vrp_variables_stack = VEC_alloc (tree_on_heap, 20);
 385   stmts_to_rescan = VEC_alloc (tree_on_heap, 20);
 386   nonzero_vars = BITMAP_ALLOC (NULL);
 387   need_eh_cleanup = BITMAP_ALLOC (NULL);
 388
 389   /* Setup callbacks for the generic dominator tree walker.  */
 390   walk_data.walk_stmts_backward = false;
 391   walk_data.dom_direction = CDI_DOMINATORS;
 392   walk_data.initialize_block_local_data = NULL;
 393   walk_data.before_dom_children_before_stmts = dom_opt_initialize_block;
 394   walk_data.before_dom_children_walk_stmts = optimize_stmt;
 395   walk_data.before_dom_children_after_stmts = propagate_to_outgoing_edges;
 396   walk_data.after_dom_children_before_stmts = NULL;
 397   walk_data.after_dom_children_walk_stmts = NULL;
 398   walk_data.after_dom_children_after_stmts = dom_opt_finalize_block;
 399   /* Right now we only attach a dummy COND_EXPR to the global data pointer.
 400      When we attach more stuff we'll need to fill this out with a real
 401      structure.  */
 402   walk_data.global_data = NULL;
 403   walk_data.block_local_data_size = 0;
 404
 405   /* Now initialize the dominator walker.  */
 406   init_walk_dominator_tree (&walk_data);
 407
 408   calculate_dominance_info (CDI_DOMINATORS);
 409
 410   /* If we prove certain blocks are unreachable, then we want to
 411      repeat the dominator optimization process as PHI nodes may
 412      have turned into copies which allows better propagation of
 413      values.  So we repeat until we do not identify any new unreachable
 414      blocks.  */
 415   do
 416     {
 417       /* Optimize the dominator tree.  */
 418       cfg_altered = false;
 419
 420       /* Recursively walk the dominator tree optimizing statements.  */
 421       walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
 422
 423       /* If we exposed any new variables, go ahead and put them into
 424          SSA form now, before we handle jump threading.  This simplifies
 425          interactions between rewriting of _DECL nodes into SSA form
 426          and rewriting SSA_NAME nodes into SSA form after block
 427          duplication and CFG manipulation.  */
 428       if (!bitmap_empty_p (vars_to_rename))
 429         {
 430           rewrite_into_ssa (false);
 431           bitmap_clear (vars_to_rename);
 432         }
 433
 434       free_all_edge_infos ();
 435
 436       /* Thread jumps, creating duplicate blocks as needed.  */
 437       cfg_altered |= thread_through_all_blocks ();
 438
 439       /* Removal of statements may make some EH edges dead.  Purge
 440          such edges from the CFG as needed.  */
 441       if (!bitmap_empty_p (need_eh_cleanup))
 442         {
 443           cfg_altered |= tree_purge_all_dead_eh_edges (need_eh_cleanup);
 444           bitmap_zero (need_eh_cleanup);
 445         }
 446
 447       if (cfg_altered)
 448         free_dominance_info (CDI_DOMINATORS);
 449       cfg_altered |= cleanup_tree_cfg ();
 450       calculate_dominance_info (CDI_DOMINATORS);
 451
 452       rewrite_ssa_into_ssa ();
 453
 454       /* Reinitialize the various tables.  */
 455       bitmap_clear (nonzero_vars);
 456       htab_empty (avail_exprs);
 457       htab_empty (vrp_data);
 458
 459       for (i = 0; i < num_referenced_vars; i++)
 460         var_ann (referenced_var (i))->current_def = NULL;
 461
 462       /* Finally, remove everything except invariants in SSA_NAME_VALUE.
 463
 464          This must be done before we iterate as we might have a
 465          reference to an SSA_NAME which was removed by the call to
 466          rewrite_ssa_into_ssa.
 467
 468          Long term we will be able to let everything in SSA_NAME_VALUE
 469          persist.  However, for now, we know this is the safe thing to do.  */
 470       for (i = 0; i < num_ssa_names; i++)
 471         {
 472           tree name = ssa_name (i);
 473           tree value;
 474
 475           if (!name)
 476             continue;
 477
 478           value = SSA_NAME_VALUE (name);
 479           if (value && !is_gimple_min_invariant (value))
 480             SSA_NAME_VALUE (name) = NULL;
 481         }
 482     }
 483   while (optimize > 1 && cfg_altered);
 484
 485   /* Debugging dumps.  */
 486   if (dump_file && (dump_flags & TDF_STATS))
 487     dump_dominator_optimization_stats (dump_file);
 488
 489   /* We emptied the hash table earlier, now delete it completely.  */
 490   htab_delete (avail_exprs);
 491   htab_delete (vrp_data);
 492
 493   /* It is not necessary to clear CURRDEFS, REDIRECTION_EDGES, VRP_DATA,
 494      CONST_AND_COPIES, and NONZERO_VARS as they all get cleared at the bottom
 495      of the do-while loop above.  */
 496
 497   /* And finalize the dominator walker.  */
 498   fini_walk_dominator_tree (&walk_data);
 499
 500   /* Free nonzero_vars.  */
 501   BITMAP_FREE (nonzero_vars);
 502   BITMAP_FREE (need_eh_cleanup);
 503
 504   VEC_free (tree_on_heap, block_defs_stack);
 505   VEC_free (tree_on_heap, avail_exprs_stack);
 506   VEC_free (tree_on_heap, const_and_copies_stack);
 507   VEC_free (tree_on_heap, nonzero_vars_stack);
 508   VEC_free (tree_on_heap, vrp_variables_stack);
 509   VEC_free (tree_on_heap, stmts_to_rescan);
 510 }
 511
 512 static bool
 513 gate_dominator (void)
 514 {
 515   return flag_tree_dom != 0;
 516 }
 517
 518 struct tree_opt_pass pass_dominator =
 519 {
 520   "dom",                                /* name */
 521   gate_dominator,                       /* gate */
 522   tree_ssa_dominator_optimize,          /* execute */
 523   NULL,                                 /* sub */
 524   NULL,                                 /* next */
 525   0,                                    /* static_pass_number */
 526   TV_TREE_SSA_DOMINATOR_OPTS,           /* tv_id */
 527   PROP_cfg | PROP_ssa | PROP_alias,     /* properties_required */
 528   0,                                    /* properties_provided */
 529   0,                                    /* properties_destroyed */
 530   0,                                    /* todo_flags_start */
 531   TODO_dump_func | TODO_rename_vars
 532     | TODO_verify_ssa,                  /* todo_flags_finish */
 533   0                                     /* letter */
 534 };
 535
 536
 537 /* We are exiting BB, see if the target block begins with a conditional
 538    jump which has a known value when reached via BB.  */
 539
 540 static void
 541 thread_across_edge (struct dom_walk_data *walk_data, edge e)
 542 {
 543   block_stmt_iterator bsi;
 544   tree stmt = NULL;
 545   tree phi;
 546
 547   /* Each PHI creates a temporary equivalence, record them.  */
 548   for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
 549     {
 550       tree src = PHI_ARG_DEF_FROM_EDGE (phi, e);
 551       tree dst = PHI_RESULT (phi);
 552
 553       /* If the desired argument is not the same as this PHI's result
 554          and it is set by a PHI in this block, then we can not thread
 555          through this block.  */
 556       if (src != dst
 557           && TREE_CODE (src) == SSA_NAME
 558           && TREE_CODE (SSA_NAME_DEF_STMT (src)) == PHI_NODE
 559           && bb_for_stmt (SSA_NAME_DEF_STMT (src)) == e->dest)
 560         return;
 561
 562       record_const_or_copy (dst, src);
 563       register_new_def (dst, &block_defs_stack);
 564     }
 565
 566   for (bsi = bsi_start (e->dest); ! bsi_end_p (bsi); bsi_next (&bsi))
 567     {
 568       tree lhs, cached_lhs;
 569
 570       stmt = bsi_stmt (bsi);
 571
 572       /* Ignore empty statements and labels.  */
 573       if (IS_EMPTY_STMT (stmt) || TREE_CODE (stmt) == LABEL_EXPR)
 574         continue;
 575
 576       /* If this is not a MODIFY_EXPR which sets an SSA_NAME to a new
 577          value, then stop our search here.  Ideally when we stop a
 578          search we stop on a COND_EXPR or SWITCH_EXPR.  */
 579       if (TREE_CODE (stmt) != MODIFY_EXPR
 580           || TREE_CODE (TREE_OPERAND (stmt, 0)) != SSA_NAME)
 581         break;
 582
 583       /* At this point we have a statement which assigns an RHS to an
 584          SSA_VAR on the LHS.  We want to prove that the RHS is already
 585          available and that its value is held in the current definition
 586          of the LHS -- meaning that this assignment is a NOP when
 587          reached via edge E.  */
 588       if (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME)
 589         cached_lhs = TREE_OPERAND (stmt, 1);
 590       else
 591         cached_lhs = lookup_avail_expr (stmt, false);
 592
 593       lhs = TREE_OPERAND (stmt, 0);
 594
 595       /* This can happen if we thread around to the start of a loop.  */
 596       if (lhs == cached_lhs)
 597         break;
 598
 599       /* If we did not find RHS in the hash table, then try again after
 600          temporarily const/copy propagating the operands.  */
 601       if (!cached_lhs)
 602         {
 603           /* Copy the operands.  */
 604           stmt_ann_t ann = stmt_ann (stmt);
 605           use_optype uses = USE_OPS (ann);
 606           vuse_optype vuses = VUSE_OPS (ann);
 607           tree *uses_copy = xmalloc (NUM_USES (uses) * sizeof (tree));
 608           tree *vuses_copy = xmalloc (NUM_VUSES (vuses) * sizeof (tree));
 609           unsigned int i;
 610
 611           /* Make a copy of the uses into USES_COPY, then cprop into
 612              the use operands.  */
 613           for (i = 0; i < NUM_USES (uses); i++)
 614             {
 615               tree tmp = NULL;
 616
 617               uses_copy[i] = USE_OP (uses, i);
 618               if (TREE_CODE (USE_OP (uses, i)) == SSA_NAME)
 619                 tmp = SSA_NAME_VALUE (USE_OP (uses, i));
 620               if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
 621                 SET_USE_OP (uses, i, tmp);
 622             }
 623
 624           /* Similarly for virtual uses.  */
 625           for (i = 0; i < NUM_VUSES (vuses); i++)
 626             {
 627               tree tmp = NULL;
 628
 629               vuses_copy[i] = VUSE_OP (vuses, i);
 630               if (TREE_CODE (VUSE_OP (vuses, i)) == SSA_NAME)
 631                 tmp = SSA_NAME_VALUE (VUSE_OP (vuses, i));
 632               if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
 633                 SET_VUSE_OP (vuses, i, tmp);
 634             }
 635
 636           /* Try to lookup the new expression.  */
 637           cached_lhs = lookup_avail_expr (stmt, false);
 638
 639           /* Restore the statement's original uses/defs.  */
 640           for (i = 0; i < NUM_USES (uses); i++)
 641             SET_USE_OP (uses, i, uses_copy[i]);
 642
 643           for (i = 0; i < NUM_VUSES (vuses); i++)
 644             SET_VUSE_OP (vuses, i, vuses_copy[i]);
 645
 646           free (uses_copy);
 647           free (vuses_copy);
 648
 649           /* If we still did not find the expression in the hash table,
 650              then we can not ignore this statement.  */
 651           if (! cached_lhs)
 652             break;
 653         }
 654
 655       /* If the expression in the hash table was not assigned to an
 656          SSA_NAME, then we can not ignore this statement.  */
 657       if (TREE_CODE (cached_lhs) != SSA_NAME)
 658         break;
 659
 660       /* If we have different underlying variables, then we can not
 661          ignore this statement.  */
 662       if (SSA_NAME_VAR (cached_lhs) != SSA_NAME_VAR (lhs))
 663         break;
 664
 665       /* If CACHED_LHS does not represent the current value of the underlying
 666          variable in CACHED_LHS/LHS, then we can not ignore this statement.  */
 667       if (var_ann (SSA_NAME_VAR (lhs))->current_def != cached_lhs)
 668         break;
 669
 670       /* If we got here, then we can ignore this statement and continue
 671          walking through the statements in the block looking for a threadable
 672          COND_EXPR.
 673
 674          We want to record an equivalence lhs = cache_lhs so that if
 675          the result of this statement is used later we can copy propagate
 676          suitably.  */
 677       record_const_or_copy (lhs, cached_lhs);
 678       register_new_def (lhs, &block_defs_stack);
 679     }
 680
 681   /* If we stopped at a COND_EXPR or SWITCH_EXPR, then see if we know which
 682      arm will be taken.  */
 683   if (stmt
 684       && (TREE_CODE (stmt) == COND_EXPR
 685           || TREE_CODE (stmt) == SWITCH_EXPR))
 686     {
 687       tree cond, cached_lhs;
 688
 689       /* Now temporarily cprop the operands and try to find the resulting
 690          expression in the hash tables.  */
 691       if (TREE_CODE (stmt) == COND_EXPR)
 692         cond = COND_EXPR_COND (stmt);
 693       else
 694         cond = SWITCH_COND (stmt);
 695
 696       if (COMPARISON_CLASS_P (cond))
 697         {
 698           tree dummy_cond, op0, op1;
 699           enum tree_code cond_code;
 700
 701           op0 = TREE_OPERAND (cond, 0);
 702           op1 = TREE_OPERAND (cond, 1);
 703           cond_code = TREE_CODE (cond);
 704
 705           /* Get the current value of both operands.  */
 706           if (TREE_CODE (op0) == SSA_NAME)
 707             {
 708               tree tmp = SSA_NAME_VALUE (op0);
 709               if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
 710                 op0 = tmp;
 711             }
 712
 713           if (TREE_CODE (op1) == SSA_NAME)
 714             {
 715               tree tmp = SSA_NAME_VALUE (op1);
 716               if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
 717                 op1 = tmp;
 718             }
 719
 720           /* Stuff the operator and operands into our dummy conditional
 721              expression, creating the dummy conditional if necessary.  */
 722           dummy_cond = walk_data->global_data;
 723           if (! dummy_cond)
 724             {
 725               dummy_cond = build (cond_code, boolean_type_node, op0, op1);
 726               dummy_cond = build (COND_EXPR, void_type_node,
 727                                   dummy_cond, NULL, NULL);
 728               walk_data->global_data = dummy_cond;
 729             }
 730           else
 731             {
 732               TREE_SET_CODE (COND_EXPR_COND (dummy_cond), cond_code);
 733               TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op0;
 734               TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1) = op1;
 735             }
 736
 737           /* If the conditional folds to an invariant, then we are done,
 738              otherwise look it up in the hash tables.  */
 739           cached_lhs = local_fold (COND_EXPR_COND (dummy_cond));
 740           if (! is_gimple_min_invariant (cached_lhs))
 741             {
 742               cached_lhs = lookup_avail_expr (dummy_cond, false);
 743               if (!cached_lhs || ! is_gimple_min_invariant (cached_lhs))
 744                 cached_lhs = simplify_cond_and_lookup_avail_expr (dummy_cond,
 745                                                                   NULL,
 746                                                                   false);
 747             }
 748         }
 749       /* We can have conditionals which just test the state of a
 750          variable rather than use a relational operator.  These are
 751          simpler to handle.  */
 752       else if (TREE_CODE (cond) == SSA_NAME)
 753         {
 754           cached_lhs = cond;
 755           cached_lhs = SSA_NAME_VALUE (cached_lhs);
 756           if (cached_lhs && ! is_gimple_min_invariant (cached_lhs))
 757             cached_lhs = 0;
 758         }
 759       else
 760         cached_lhs = lookup_avail_expr (stmt, false);
 761
 762       if (cached_lhs)
 763         {
 764           edge taken_edge = find_taken_edge (e->dest, cached_lhs);
 765           basic_block dest = (taken_edge ? taken_edge->dest : NULL);
 766
 767           if (dest == e->dest)
 768             return;
 769
 770           /* If we have a known destination for the conditional, then
 771              we can perform this optimization, which saves at least one
 772              conditional jump each time it applies since we get to
 773              bypass the conditional at our original destination.  */
 774           if (dest)
 775             {
 776               struct edge_info *edge_info;
 777
 778               update_bb_profile_for_threading (e->dest, EDGE_FREQUENCY (e),
 779                                                e->count, taken_edge);
 780               if (e->aux)
 781                 edge_info = e->aux;
 782               else
 783                 edge_info = allocate_edge_info (e);
 784               edge_info->redirection_target = taken_edge;
 785               bb_ann (e->dest)->incoming_edge_threaded = true;
 786             }
 787         }
 788     }
 789 }
 790
 791
 792 /* Initialize local stacks for this optimizer and record equivalences
 793    upon entry to BB.  Equivalences can come from the edge traversed to
 794    reach BB or they may come from PHI nodes at the start of BB.  */
 795
 796 static void
 797 dom_opt_initialize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
 798                           basic_block bb)
 799 {
 800   if (dump_file && (dump_flags & TDF_DETAILS))
 801     fprintf (dump_file, "\n\nOptimizing block #%d\n\n", bb->index);
 802
 803   /* Push a marker on the stacks of local information so that we know how
 804      far to unwind when we finalize this block.  */
 805   VEC_safe_push (tree_on_heap, avail_exprs_stack, NULL_TREE);
 806   VEC_safe_push (tree_on_heap, block_defs_stack, NULL_TREE);
 807   VEC_safe_push (tree_on_heap, const_and_copies_stack, NULL_TREE);
 808   VEC_safe_push (tree_on_heap, nonzero_vars_stack, NULL_TREE);
 809   VEC_safe_push (tree_on_heap, vrp_variables_stack, NULL_TREE);
 810
 811   record_equivalences_from_incoming_edge (bb);
 812
 813   /* PHI nodes can create equivalences too.  */
 814   record_equivalences_from_phis (bb);
 815 }
 816
 817 /* Given an expression EXPR (a relational expression or a statement),
 818    initialize the hash table element pointed by by ELEMENT.  */
 819
 820 static void
 821 initialize_hash_element (tree expr, tree lhs, struct expr_hash_elt *element)
 822 {
 823   /* Hash table elements may be based on conditional expressions or statements.
 824
 825      For the former case, we have no annotation and we want to hash the
 826      conditional expression.  In the latter case we have an annotation and
 827      we want to record the expression the statement evaluates.  */
 828   if (COMPARISON_CLASS_P (expr) || TREE_CODE (expr) == TRUTH_NOT_EXPR)
 829     {
 830       element->ann = NULL;
 831       element->rhs = expr;
 832     }
 833   else if (TREE_CODE (expr) == COND_EXPR)
 834     {
 835       element->ann = stmt_ann (expr);
 836       element->rhs = COND_EXPR_COND (expr);
 837     }
 838   else if (TREE_CODE (expr) == SWITCH_EXPR)
 839     {
 840       element->ann = stmt_ann (expr);
 841       element->rhs = SWITCH_COND (expr);
 842     }
 843   else if (TREE_CODE (expr) == RETURN_EXPR && TREE_OPERAND (expr, 0))
 844     {
 845       element->ann = stmt_ann (expr);
 846       element->rhs = TREE_OPERAND (TREE_OPERAND (expr, 0), 1);
 847     }
 848   else
 849     {
 850       element->ann = stmt_ann (expr);
 851       element->rhs = TREE_OPERAND (expr, 1);
 852     }
 853
 854   element->lhs = lhs;
 855   element->hash = avail_expr_hash (element);
 856 }
 857
 858 /* Remove all the expressions in LOCALS from TABLE, stopping when there are
 859    LIMIT entries left in LOCALs.  */
 860
 861 static void
 862 remove_local_expressions_from_table (void)
 863 {
 864   /* Remove all the expressions made available in this block.  */
 865   while (VEC_length (tree_on_heap, avail_exprs_stack) > 0)
 866     {
 867       struct expr_hash_elt element;
 868       tree expr = VEC_pop (tree_on_heap, avail_exprs_stack);
 869
 870       if (expr == NULL_TREE)
 871         break;
 872
 873       initialize_hash_element (expr, NULL, &element);
 874       htab_remove_elt_with_hash (avail_exprs, &element, element.hash);
 875     }
 876 }
 877
 878 /* Use the SSA_NAMES in LOCALS to restore TABLE to its original
 879    state, stopping when there are LIMIT entries left in LOCALs.  */
 880
 881 static void
 882 restore_nonzero_vars_to_original_value (void)
 883 {
 884   while (VEC_length (tree_on_heap, nonzero_vars_stack) > 0)
 885     {
 886       tree name = VEC_pop (tree_on_heap, nonzero_vars_stack);
 887
 888       if (name == NULL)
 889         break;
 890
 891       bitmap_clear_bit (nonzero_vars, SSA_NAME_VERSION (name));
 892     }
 893 }
 894
 895 /* Use the source/dest pairs in CONST_AND_COPIES_STACK to restore
 896    CONST_AND_COPIES to its original state, stopping when we hit a
 897    NULL marker.  */
 898
 899 static void
 900 restore_vars_to_original_value (void)
 901 {
 902   while (VEC_length (tree_on_heap, const_and_copies_stack) > 0)
 903     {
 904       tree prev_value, dest;
 905
 906       dest = VEC_pop (tree_on_heap, const_and_copies_stack);
 907
 908       if (dest == NULL)
 909         break;
 910
 911       prev_value = VEC_pop (tree_on_heap, const_and_copies_stack);
 912       SSA_NAME_VALUE (dest) =  prev_value;
 913     }
 914 }
 915
 916 /* Similar to restore_vars_to_original_value, except that it restores
 917    CURRDEFS to its original value.  */
 918 static void
 919 restore_currdefs_to_original_value (void)
 920 {
 921   /* Restore CURRDEFS to its original state.  */
 922   while (VEC_length (tree_on_heap, block_defs_stack) > 0)
 923     {
 924       tree tmp = VEC_pop (tree_on_heap, block_defs_stack);
 925       tree saved_def, var;
 926
 927       if (tmp == NULL_TREE)
 928         break;
 929
 930       /* If we recorded an SSA_NAME, then make the SSA_NAME the current
 931          definition of its underlying variable.  If we recorded anything
 932          else, it must have been an _DECL node and its current reaching
 933          definition must have been NULL.  */
 934       if (TREE_CODE (tmp) == SSA_NAME)
 935         {
 936           saved_def = tmp;
 937           var = SSA_NAME_VAR (saved_def);
 938         }
 939       else
 940         {
 941           saved_def = NULL;
 942           var = tmp;
 943         }
 944
 945       var_ann (var)->current_def = saved_def;
 946     }
 947 }
 948
 949 /* We have finished processing the dominator children of BB, perform
 950    any finalization actions in preparation for leaving this node in
 951    the dominator tree.  */
 952
 953 static void
 954 dom_opt_finalize_block (struct dom_walk_data *walk_data, basic_block bb)
 955 {
 956   tree last;
 957
 958   /* If we are at a leaf node in the dominator tree, see if we can thread
 959      the edge from BB through its successor.
 960
 961      Do this before we remove entries from our equivalence tables.  */
 962   if (EDGE_COUNT (bb->succs) == 1
 963       && (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL) == 0
 964       && (get_immediate_dominator (CDI_DOMINATORS, EDGE_SUCC (bb, 0)->dest) != bb
 965           || phi_nodes (EDGE_SUCC (bb, 0)->dest)))
 966
 967     {
 968       thread_across_edge (walk_data, EDGE_SUCC (bb, 0));
 969     }
 970   else if ((last = last_stmt (bb))
 971            && TREE_CODE (last) == COND_EXPR
 972            && (COMPARISON_CLASS_P (COND_EXPR_COND (last))
 973                || TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME)
 974            && EDGE_COUNT (bb->succs) == 2
 975            && (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL) == 0
 976            && (EDGE_SUCC (bb, 1)->flags & EDGE_ABNORMAL) == 0)
 977     {
 978       edge true_edge, false_edge;
 979
 980       extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
 981
 982       /* If the THEN arm is the end of a dominator tree or has PHI nodes,
 983          then try to thread through its edge.  */
 984       if (get_immediate_dominator (CDI_DOMINATORS, true_edge->dest) != bb
 985           || phi_nodes (true_edge->dest))
 986         {
 987           struct edge_info *edge_info;
 988           unsigned int i;
 989
 990           /* Push a marker onto the available expression stack so that we
 991              unwind any expressions related to the TRUE arm before processing
 992              the false arm below.  */
 993           VEC_safe_push (tree_on_heap, avail_exprs_stack, NULL_TREE);
 994           VEC_safe_push (tree_on_heap, block_defs_stack, NULL_TREE);
 995           VEC_safe_push (tree_on_heap, const_and_copies_stack, NULL_TREE);
 996
 997           edge_info = true_edge->aux;
 998
 999           /* If we have info associated with this edge, record it into
1000              our equivalency tables.  */
1001           if (edge_info)
1002             {
1003               tree *cond_equivalences = edge_info->cond_equivalences;
1004               tree lhs = edge_info->lhs;
1005               tree rhs = edge_info->rhs;
1006
1007               /* If we have a simple NAME = VALUE equivalency record it.
1008                  Until the jump threading selection code improves, only
1009                  do this if both the name and value are SSA_NAMEs with
1010                  the same underlying variable to avoid missing threading
1011                  opportunities.  */
1012               if (lhs
1013                   && TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME
1014                   && TREE_CODE (edge_info->rhs) == SSA_NAME
1015                   && SSA_NAME_VAR (lhs) == SSA_NAME_VAR (rhs))
1016                 record_const_or_copy (lhs, rhs);
1017
1018               /* If we have 0 = COND or 1 = COND equivalences, record them
1019                  into our expression hash tables.  */
1020               if (cond_equivalences)
1021                 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1022                   {
1023                     tree expr = cond_equivalences[i];
1024                     tree value = cond_equivalences[i + 1];
1025
1026                     record_cond (expr, value);
1027                   }
1028             }
1029
1030           /* Now thread the edge.  */
1031           thread_across_edge (walk_data, true_edge);
1032
1033           /* And restore the various tables to their state before
1034              we threaded this edge.  */
1035           remove_local_expressions_from_table ();
1036           restore_vars_to_original_value ();
1037           restore_currdefs_to_original_value ();
1038         }
1039
1040       /* Similarly for the ELSE arm.  */
1041       if (get_immediate_dominator (CDI_DOMINATORS, false_edge->dest) != bb
1042           || phi_nodes (false_edge->dest))
1043         {
1044           struct edge_info *edge_info;
1045           unsigned int i;
1046
1047           edge_info = false_edge->aux;
1048
1049           /* If we have info associated with this edge, record it into
1050              our equivalency tables.  */
1051           if (edge_info)
1052             {
1053               tree *cond_equivalences = edge_info->cond_equivalences;
1054               tree lhs = edge_info->lhs;
1055               tree rhs = edge_info->rhs;
1056
1057               /* If we have a simple NAME = VALUE equivalency record it.
1058                  Until the jump threading selection code improves, only
1059                  do this if both the name and value are SSA_NAMEs with
1060                  the same underlying variable to avoid missing threading
1061                  opportunities.  */
1062               if (lhs
1063                   && TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME)
1064                 record_const_or_copy (lhs, rhs);
1065
1066               /* If we have 0 = COND or 1 = COND equivalences, record them
1067                  into our expression hash tables.  */
1068               if (cond_equivalences)
1069                 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1070                   {
1071                     tree expr = cond_equivalences[i];
1072                     tree value = cond_equivalences[i + 1];
1073
1074                     record_cond (expr, value);
1075                   }
1076             }
1077
1078           thread_across_edge (walk_data, false_edge);
1079
1080           /* No need to remove local expressions from our tables
1081              or restore vars to their original value as that will
1082              be done immediately below.  */
1083         }
1084     }
1085
1086   remove_local_expressions_from_table ();
1087   restore_nonzero_vars_to_original_value ();
1088   restore_vars_to_original_value ();
1089   restore_currdefs_to_original_value ();
1090
1091   /* Remove VRP records associated with this basic block.  They are no
1092      longer valid.
1093
1094      To be efficient, we note which variables have had their values
1095      constrained in this block.  So walk over each variable in the
1096      VRP_VARIABLEs array.  */
1097   while (VEC_length (tree_on_heap, vrp_variables_stack) > 0)
1098     {
1099       tree var = VEC_pop (tree_on_heap, vrp_variables_stack);
1100       struct vrp_hash_elt vrp_hash_elt, *vrp_hash_elt_p;
1101       void **slot;
1102
1103       /* Each variable has a stack of value range records.  We want to
1104          invalidate those associated with our basic block.  So we walk
1105          the array backwards popping off records associated with our
1106          block.  Once we hit a record not associated with our block
1107          we are done.  */
1108       varray_type var_vrp_records;
1109
1110       if (var == NULL)
1111         break;
1112
1113       vrp_hash_elt.var = var;
1114       vrp_hash_elt.records = NULL;
1115
1116       slot = htab_find_slot (vrp_data, &vrp_hash_elt, NO_INSERT);
1117
1118       vrp_hash_elt_p = (struct vrp_hash_elt *) *slot;
1119       var_vrp_records = vrp_hash_elt_p->records;
1120
1121       while (VARRAY_ACTIVE_SIZE (var_vrp_records) > 0)
1122         {
1123           struct vrp_element *element
1124             = (struct vrp_element *)VARRAY_TOP_GENERIC_PTR (var_vrp_records);
1125
1126           if (element->bb != bb)
1127             break;
1128
1129           VARRAY_POP (var_vrp_records);
1130         }
1131     }
1132
1133   /* If we queued any statements to rescan in this block, then
1134      go ahead and rescan them now.  */
1135   while (VEC_length (tree_on_heap, stmts_to_rescan) > 0)
1136     {
1137       tree stmt = VEC_last (tree_on_heap, stmts_to_rescan);
1138       basic_block stmt_bb = bb_for_stmt (stmt);
1139
1140       if (stmt_bb != bb)
1141         break;
1142
1143       VEC_pop (tree_on_heap, stmts_to_rescan);
1144       mark_new_vars_to_rename (stmt, vars_to_rename);
1145     }
1146 }
1147
1148 /* PHI nodes can create equivalences too.
1149
1150    Ignoring any alternatives which are the same as the result, if
1151    all the alternatives are equal, then the PHI node creates an
1152    equivalence.
1153
1154    Additionally, if all the PHI alternatives are known to have a nonzero
1155    value, then the result of this PHI is known to have a nonzero value,
1156    even if we do not know its exact value.  */
1157
1158 static void
1159 record_equivalences_from_phis (basic_block bb)
1160 {
1161   tree phi;
1162
1163   for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1164     {
1165       tree lhs = PHI_RESULT (phi);
1166       tree rhs = NULL;
1167       int i;
1168
1169       for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1170         {
1171           tree t = PHI_ARG_DEF (phi, i);
1172
1173           /* Ignore alternatives which are the same as our LHS.  Since
1174              LHS is a PHI_RESULT, it is known to be a SSA_NAME, so we
1175              can simply compare pointers.  */
1176           if (lhs == t)
1177             continue;
1178
1179           /* If we have not processed an alternative yet, then set
1180              RHS to this alternative.  */
1181           if (rhs == NULL)
1182             rhs = t;
1183           /* If we have processed an alternative (stored in RHS), then
1184              see if it is equal to this one.  If it isn't, then stop
1185              the search.  */
1186           else if (! operand_equal_for_phi_arg_p (rhs, t))
1187             break;
1188         }
1189
1190       /* If we had no interesting alternatives, then all the RHS alternatives
1191          must have been the same as LHS.  */
1192       if (!rhs)
1193         rhs = lhs;
1194
1195       /* If we managed to iterate through each PHI alternative without
1196          breaking out of the loop, then we have a PHI which may create
1197          a useful equivalence.  We do not need to record unwind data for
1198          this, since this is a true assignment and not an equivalence
1199          inferred from a comparison.  All uses of this ssa name are dominated
1200          by this assignment, so unwinding just costs time and space.  */
1201       if (i == PHI_NUM_ARGS (phi)
1202           && may_propagate_copy (lhs, rhs))
1203         SSA_NAME_VALUE (lhs) = rhs;
1204
1205       /* Now see if we know anything about the nonzero property for the
1206          result of this PHI.  */
1207       for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1208         {
1209           if (!PHI_ARG_NONZERO (phi, i))
1210             break;
1211         }
1212
1213       if (i == PHI_NUM_ARGS (phi))
1214         bitmap_set_bit (nonzero_vars, SSA_NAME_VERSION (PHI_RESULT (phi)));
1215
1216       register_new_def (lhs, &block_defs_stack);
1217     }
1218 }
1219
1220 /* Ignoring loop backedges, if BB has precisely one incoming edge then
1221    return that edge.  Otherwise return NULL.  */
1222 static edge
1223 single_incoming_edge_ignoring_loop_edges (basic_block bb)
1224 {
1225   edge retval = NULL;
1226   edge e;
1227   edge_iterator ei;
1228
1229   FOR_EACH_EDGE (e, ei, bb->preds)
1230     {
1231       /* A loop back edge can be identified by the destination of
1232          the edge dominating the source of the edge.  */
1233       if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
1234         continue;
1235
1236       /* If we have already seen a non-loop edge, then we must have
1237          multiple incoming non-loop edges and thus we return NULL.  */
1238       if (retval)
1239         return NULL;
1240
1241       /* This is the first non-loop incoming edge we have found.  Record
1242          it.  */
1243       retval = e;
1244     }
1245
1246   return retval;
1247 }
1248
1249 /* Record any equivalences created by the incoming edge to BB.  If BB
1250    has more than one incoming edge, then no equivalence is created.  */
1251
1252 static void
1253 record_equivalences_from_incoming_edge (basic_block bb)
1254 {
1255   edge e;
1256   basic_block parent;
1257   struct edge_info *edge_info;
1258
1259   /* If our parent block ended with a control statement, then we may be
1260      able to record some equivalences based on which outgoing edge from
1261      the parent was followed.  */
1262   parent = get_immediate_dominator (CDI_DOMINATORS, bb);
1263
1264   e = single_incoming_edge_ignoring_loop_edges (bb);
1265
1266   /* If we had a single incoming edge from our parent block, then enter
1267      any data associated with the edge into our tables.  */
1268   if (e && e->src == parent)
1269     {
1270       unsigned int i;
1271
1272       edge_info = e->aux;
1273
1274       if (edge_info)
1275         {
1276           tree lhs = edge_info->lhs;
1277           tree rhs = edge_info->rhs;
1278           tree *cond_equivalences = edge_info->cond_equivalences;
1279
1280           if (lhs)
1281             record_equality (lhs, rhs);
1282
1283           if (cond_equivalences)
1284             {
1285               bool recorded_range = false;
1286               for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1287                 {
1288                   tree expr = cond_equivalences[i];
1289                   tree value = cond_equivalences[i + 1];
1290
1291                   record_cond (expr, value);
1292
1293                   /* For the first true equivalence, record range
1294                      information.  We only do this for the first
1295                      true equivalence as it should dominate any
1296                      later true equivalences.  */
1297                   if (! recorded_range
1298                       && COMPARISON_CLASS_P (expr)
1299                       && value == boolean_true_node
1300                       && TREE_CONSTANT (TREE_OPERAND (expr, 1)))
1301                     {
1302                       record_range (expr, bb);
1303                       recorded_range = true;
1304                     }
1305                 }
1306             }
1307         }
1308     }
1309 }
1310
1311 /* Dump SSA statistics on FILE.  */
1312
1313 void
1314 dump_dominator_optimization_stats (FILE *file)
1315 {
1316   long n_exprs;
1317
1318   fprintf (file, "Total number of statements:                   %6ld\n\n",
1319            opt_stats.num_stmts);
1320   fprintf (file, "Exprs considered for dominator optimizations: %6ld\n",
1321            opt_stats.num_exprs_considered);
1322
1323   n_exprs = opt_stats.num_exprs_considered;
1324   if (n_exprs == 0)
1325     n_exprs = 1;
1326
1327   fprintf (file, "    Redundant expressions eliminated:         %6ld (%.0f%%)\n",
1328            opt_stats.num_re, PERCENT (opt_stats.num_re,
1329                                       n_exprs));
1330
1331   fprintf (file, "\nHash table statistics:\n");
1332
1333   fprintf (file, "    avail_exprs: ");
1334   htab_statistics (file, avail_exprs);
1335 }
1336
1337
1338 /* Dump SSA statistics on stderr.  */
1339
1340 void
1341 debug_dominator_optimization_stats (void)
1342 {
1343   dump_dominator_optimization_stats (stderr);
1344 }
1345
1346
1347 /* Dump statistics for the hash table HTAB.  */
1348
1349 static void
1350 htab_statistics (FILE *file, htab_t htab)
1351 {
1352   fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
1353            (long) htab_size (htab),
1354            (long) htab_elements (htab),
1355            htab_collisions (htab));
1356 }
1357
1358 /* Record the fact that VAR has a nonzero value, though we may not know
1359    its exact value.  Note that if VAR is already known to have a nonzero
1360    value, then we do nothing.  */
1361
1362 static void
1363 record_var_is_nonzero (tree var)
1364 {
1365   int indx = SSA_NAME_VERSION (var);
1366
1367   if (bitmap_bit_p (nonzero_vars, indx))
1368     return;
1369
1370   /* Mark it in the global table.  */
1371   bitmap_set_bit (nonzero_vars, indx);
1372
1373   /* Record this SSA_NAME so that we can reset the global table
1374      when we leave this block.  */
1375   VEC_safe_push (tree_on_heap, nonzero_vars_stack, var);
1376 }
1377
1378 /* Enter a statement into the true/false expression hash table indicating
1379    that the condition COND has the value VALUE.  */
1380
1381 static void
1382 record_cond (tree cond, tree value)
1383 {
1384   struct expr_hash_elt *element = xmalloc (sizeof (struct expr_hash_elt));
1385   void **slot;
1386
1387   initialize_hash_element (cond, value, element);
1388
1389   slot = htab_find_slot_with_hash (avail_exprs, (void *)element,
1390                                    element->hash, INSERT);
1391   if (*slot == NULL)
1392     {
1393       *slot = (void *) element;
1394       VEC_safe_push (tree_on_heap, avail_exprs_stack, cond);
1395     }
1396   else
1397     free (element);
1398 }
1399
1400 /* Build a new conditional using NEW_CODE, OP0 and OP1 and store
1401    the new conditional into *p, then store a boolean_true_node
1402    into *(p + 1).  */
1403
1404 static void
1405 build_and_record_new_cond (enum tree_code new_code, tree op0, tree op1, tree *p)
1406 {
1407   *p = build2 (new_code, boolean_type_node, op0, op1);
1408   p++;
1409   *p = boolean_true_node;
1410 }
1411
1412 /* Record that COND is true and INVERTED is false into the edge information
1413    structure.  Also record that any conditions dominated by COND are true
1414    as well.
1415
1416    For example, if a < b is true, then a <= b must also be true.  */
1417
1418 static void
1419 record_conditions (struct edge_info *edge_info, tree cond, tree inverted)
1420 {
1421   tree op0, op1;
1422
1423   if (!COMPARISON_CLASS_P (cond))
1424     return;
1425
1426   op0 = TREE_OPERAND (cond, 0);
1427   op1 = TREE_OPERAND (cond, 1);
1428
1429   switch (TREE_CODE (cond))
1430     {
1431     case LT_EXPR:
1432     case GT_EXPR:
1433       edge_info->max_cond_equivalences = 12;
1434       edge_info->cond_equivalences = xmalloc (12 * sizeof (tree));
1435       build_and_record_new_cond ((TREE_CODE (cond) == LT_EXPR
1436                                   ? LE_EXPR : GE_EXPR),
1437                                  op0, op1, &edge_info->cond_equivalences[4]);
1438       build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1439                                  &edge_info->cond_equivalences[6]);
1440       build_and_record_new_cond (NE_EXPR, op0, op1,
1441                                  &edge_info->cond_equivalences[8]);
1442       build_and_record_new_cond (LTGT_EXPR, op0, op1,
1443                                  &edge_info->cond_equivalences[10]);
1444       break;
1445
1446     case GE_EXPR:
1447     case LE_EXPR:
1448       edge_info->max_cond_equivalences = 6;
1449       edge_info->cond_equivalences = xmalloc (6 * sizeof (tree));
1450       build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1451                                  &edge_info->cond_equivalences[4]);
1452       break;
1453
1454     case EQ_EXPR:
1455       edge_info->max_cond_equivalences = 10;
1456       edge_info->cond_equivalences = xmalloc (10 * sizeof (tree));
1457       build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1458                                  &edge_info->cond_equivalences[4]);
1459       build_and_record_new_cond (LE_EXPR, op0, op1,
1460                                  &edge_info->cond_equivalences[6]);
1461       build_and_record_new_cond (GE_EXPR, op0, op1,
1462                                  &edge_info->cond_equivalences[8]);
1463       break;
1464
1465     case UNORDERED_EXPR:
1466       edge_info->max_cond_equivalences = 16;
1467       edge_info->cond_equivalences = xmalloc (16 * sizeof (tree));
1468       build_and_record_new_cond (NE_EXPR, op0, op1,
1469                                  &edge_info->cond_equivalences[4]);
1470       build_and_record_new_cond (UNLE_EXPR, op0, op1,
1471                                  &edge_info->cond_equivalences[6]);
1472       build_and_record_new_cond (UNGE_EXPR, op0, op1,
1473                                  &edge_info->cond_equivalences[8]);
1474       build_and_record_new_cond (UNEQ_EXPR, op0, op1,
1475                                  &edge_info->cond_equivalences[10]);
1476       build_and_record_new_cond (UNLT_EXPR, op0, op1,
1477                                  &edge_info->cond_equivalences[12]);
1478       build_and_record_new_cond (UNGT_EXPR, op0, op1,
1479                                  &edge_info->cond_equivalences[14]);
1480       break;
1481
1482     case UNLT_EXPR:
1483     case UNGT_EXPR:
1484       edge_info->max_cond_equivalences = 8;
1485       edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1486       build_and_record_new_cond ((TREE_CODE (cond) == UNLT_EXPR
1487                                   ? UNLE_EXPR : UNGE_EXPR),
1488                                  op0, op1, &edge_info->cond_equivalences[4]);
1489       build_and_record_new_cond (NE_EXPR, op0, op1,
1490                                  &edge_info->cond_equivalences[6]);
1491       break;
1492
1493     case UNEQ_EXPR:
1494       edge_info->max_cond_equivalences = 8;
1495       edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1496       build_and_record_new_cond (UNLE_EXPR, op0, op1,
1497                                  &edge_info->cond_equivalences[4]);
1498       build_and_record_new_cond (UNGE_EXPR, op0, op1,
1499                                  &edge_info->cond_equivalences[6]);
1500       break;
1501
1502     case LTGT_EXPR:
1503       edge_info->max_cond_equivalences = 8;
1504       edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1505       build_and_record_new_cond (NE_EXPR, op0, op1,
1506                                  &edge_info->cond_equivalences[4]);
1507       build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1508                                  &edge_info->cond_equivalences[6]);
1509       break;
1510
1511     default:
1512       edge_info->max_cond_equivalences = 4;
1513       edge_info->cond_equivalences = xmalloc (4 * sizeof (tree));
1514       break;
1515     }
1516
1517   /* Now store the original true and false conditions into the first
1518      two slots.  */
1519   edge_info->cond_equivalences[0] = cond;
1520   edge_info->cond_equivalences[1] = boolean_true_node;
1521   edge_info->cond_equivalences[2] = inverted;
1522   edge_info->cond_equivalences[3] = boolean_false_node;
1523 }
1524
1525 /* A helper function for record_const_or_copy and record_equality.
1526    Do the work of recording the value and undo info.  */
1527
1528 static void
1529 record_const_or_copy_1 (tree x, tree y, tree prev_x)
1530 {
1531   SSA_NAME_VALUE (x) = y;
1532
1533   VEC_safe_push (tree_on_heap, const_and_copies_stack, prev_x);
1534   VEC_safe_push (tree_on_heap, const_and_copies_stack, x);
1535 }
1536
1537
1538 /* Return the loop depth of the basic block of the defining statement of X.
1539    This number should not be treated as absolutely correct because the loop
1540    information may not be completely up-to-date when dom runs.  However, it
1541    will be relatively correct, and as more passes are taught to keep loop info
1542    up to date, the result will become more and more accurate.  */
1543
1544 static int
1545 loop_depth_of_name (tree x)
1546 {
1547   tree defstmt;
1548   basic_block defbb;
1549
1550   /* If it's not an SSA_NAME, we have no clue where the definition is.  */
1551   if (TREE_CODE (x) != SSA_NAME)
1552     return 0;
1553
1554   /* Otherwise return the loop depth of the defining statement's bb.
1555      Note that there may not actually be a bb for this statement, if the
1556      ssa_name is live on entry.  */
1557   defstmt = SSA_NAME_DEF_STMT (x);
1558   defbb = bb_for_stmt (defstmt);
1559   if (!defbb)
1560     return 0;
1561
1562   return defbb->loop_depth;
1563 }
1564
1565
1566 /* Record that X is equal to Y in const_and_copies.  Record undo
1567    information in the block-local vector.  */
1568
1569 static void
1570 record_const_or_copy (tree x, tree y)
1571 {
1572   tree prev_x = SSA_NAME_VALUE (x);
1573
1574   if (TREE_CODE (y) == SSA_NAME)
1575     {
1576       tree tmp = SSA_NAME_VALUE (y);
1577       if (tmp)
1578         y = tmp;
1579     }
1580
1581   record_const_or_copy_1 (x, y, prev_x);
1582 }
1583
1584 /* Similarly, but assume that X and Y are the two operands of an EQ_EXPR.
1585    This constrains the cases in which we may treat this as assignment.  */
1586
1587 static void
1588 record_equality (tree x, tree y)
1589 {
1590   tree prev_x = NULL, prev_y = NULL;
1591
1592   if (TREE_CODE (x) == SSA_NAME)
1593     prev_x = SSA_NAME_VALUE (x);
1594   if (TREE_CODE (y) == SSA_NAME)
1595     prev_y = SSA_NAME_VALUE (y);
1596
1597   /* If one of the previous values is invariant, or invariant in more loops
1598      (by depth), then use that.
1599      Otherwise it doesn't matter which value we choose, just so
1600      long as we canonicalize on one value.  */
1601   if (TREE_INVARIANT (y))
1602     ;
1603   else if (TREE_INVARIANT (x) || (loop_depth_of_name (x) <= loop_depth_of_name (y)))
1604     prev_x = x, x = y, y = prev_x, prev_x = prev_y;
1605   else if (prev_x && TREE_INVARIANT (prev_x))
1606     x = y, y = prev_x, prev_x = prev_y;
1607   else if (prev_y && TREE_CODE (prev_y) != VALUE_HANDLE)
1608     y = prev_y;
1609
1610   /* After the swapping, we must have one SSA_NAME.  */
1611   if (TREE_CODE (x) != SSA_NAME)
1612     return;
1613
1614   /* For IEEE, -0.0 == 0.0, so we don't necessarily know the sign of a
1615      variable compared against zero.  If we're honoring signed zeros,
1616      then we cannot record this value unless we know that the value is
1617      nonzero.  */
1618   if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (x)))
1619       && (TREE_CODE (y) != REAL_CST
1620           || REAL_VALUES_EQUAL (dconst0, TREE_REAL_CST (y))))
1621     return;
1622
1623   record_const_or_copy_1 (x, y, prev_x);
1624 }
1625
1626 /* Return true, if it is ok to do folding of an associative expression.
1627    EXP is the tree for the associative expression.  */
1628
1629 static inline bool
1630 unsafe_associative_fp_binop (tree exp)
1631 {
1632   enum tree_code code = TREE_CODE (exp);
1633   return !(!flag_unsafe_math_optimizations
1634            && (code == MULT_EXPR || code == PLUS_EXPR
1635                || code == MINUS_EXPR)
1636            && FLOAT_TYPE_P (TREE_TYPE (exp)));
1637 }
1638
1639 /* Returns true when STMT is a simple iv increment.  It detects the
1640    following situation:
1641
1642    i_1 = phi (..., i_2)
1643    i_2 = i_1 +/- ...  */
1644
1645 static bool
1646 simple_iv_increment_p (tree stmt)
1647 {
1648   tree lhs, rhs, preinc, phi;
1649   unsigned i;
1650
1651   if (TREE_CODE (stmt) != MODIFY_EXPR)
1652     return false;
1653
1654   lhs = TREE_OPERAND (stmt, 0);
1655   if (TREE_CODE (lhs) != SSA_NAME)
1656     return false;
1657
1658   rhs = TREE_OPERAND (stmt, 1);
1659
1660   if (TREE_CODE (rhs) != PLUS_EXPR
1661       && TREE_CODE (rhs) != MINUS_EXPR)
1662     return false;
1663
1664   preinc = TREE_OPERAND (rhs, 0);
1665   if (TREE_CODE (preinc) != SSA_NAME)
1666     return false;
1667
1668   phi = SSA_NAME_DEF_STMT (preinc);
1669   if (TREE_CODE (phi) != PHI_NODE)
1670     return false;
1671
1672   for (i = 0; i < (unsigned) PHI_NUM_ARGS (phi); i++)
1673     if (PHI_ARG_DEF (phi, i) == lhs)
1674       return true;
1675
1676   return false;
1677 }
1678
1679 /* STMT is a MODIFY_EXPR for which we were unable to find RHS in the
1680    hash tables.  Try to simplify the RHS using whatever equivalences
1681    we may have recorded.
1682
1683    If we are able to simplify the RHS, then lookup the simplified form in
1684    the hash table and return the result.  Otherwise return NULL.  */
1685
1686 static tree
1687 simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *walk_data,
1688                                     tree stmt, int insert)
1689 {
1690   tree rhs = TREE_OPERAND (stmt, 1);
1691   enum tree_code rhs_code = TREE_CODE (rhs);
1692   tree result = NULL;
1693
1694   /* If we have lhs = ~x, look and see if we earlier had x = ~y.
1695      In which case we can change this statement to be lhs = y.
1696      Which can then be copy propagated.
1697
1698      Similarly for negation.  */
1699   if ((rhs_code == BIT_NOT_EXPR || rhs_code == NEGATE_EXPR)
1700       && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
1701     {
1702       /* Get the definition statement for our RHS.  */
1703       tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1704
1705       /* See if the RHS_DEF_STMT has the same form as our statement.  */
1706       if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR
1707           && TREE_CODE (TREE_OPERAND (rhs_def_stmt, 1)) == rhs_code)
1708         {
1709           tree rhs_def_operand;
1710
1711           rhs_def_operand = TREE_OPERAND (TREE_OPERAND (rhs_def_stmt, 1), 0);
1712
1713           /* Verify that RHS_DEF_OPERAND is a suitable SSA variable.  */
1714           if (TREE_CODE (rhs_def_operand) == SSA_NAME
1715               && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))
1716             result = update_rhs_and_lookup_avail_expr (stmt,
1717                                                        rhs_def_operand,
1718                                                        insert);
1719         }
1720     }
1721
1722   /* If we have z = (x OP C1), see if we earlier had x = y OP C2.
1723      If OP is associative, create and fold (y OP C2) OP C1 which
1724      should result in (y OP C3), use that as the RHS for the
1725      assignment.  Add minus to this, as we handle it specially below.  */
1726   if ((associative_tree_code (rhs_code) || rhs_code == MINUS_EXPR)
1727       && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
1728       && is_gimple_min_invariant (TREE_OPERAND (rhs, 1)))
1729     {
1730       tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1731
1732       /* If the statement defines an induction variable, do not propagate
1733          its value, so that we do not create overlapping life ranges.  */
1734       if (simple_iv_increment_p (rhs_def_stmt))
1735         goto dont_fold_assoc;
1736
1737       /* See if the RHS_DEF_STMT has the same form as our statement.  */
1738       if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR)
1739         {
1740           tree rhs_def_rhs = TREE_OPERAND (rhs_def_stmt, 1);
1741           enum tree_code rhs_def_code = TREE_CODE (rhs_def_rhs);
1742
1743           if ((rhs_code == rhs_def_code && unsafe_associative_fp_binop (rhs))
1744               || (rhs_code == PLUS_EXPR && rhs_def_code == MINUS_EXPR)
1745               || (rhs_code == MINUS_EXPR && rhs_def_code == PLUS_EXPR))
1746             {
1747               tree def_stmt_op0 = TREE_OPERAND (rhs_def_rhs, 0);
1748               tree def_stmt_op1 = TREE_OPERAND (rhs_def_rhs, 1);
1749
1750               if (TREE_CODE (def_stmt_op0) == SSA_NAME
1751                   && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def_stmt_op0)
1752                   && is_gimple_min_invariant (def_stmt_op1))
1753                 {
1754                   tree outer_const = TREE_OPERAND (rhs, 1);
1755                   tree type = TREE_TYPE (TREE_OPERAND (stmt, 0));
1756                   tree t;
1757
1758                   /* If we care about correct floating point results, then
1759                      don't fold x + c1 - c2.  Note that we need to take both
1760                      the codes and the signs to figure this out.  */
1761                   if (FLOAT_TYPE_P (type)
1762                       && !flag_unsafe_math_optimizations
1763                       && (rhs_def_code == PLUS_EXPR
1764                           || rhs_def_code == MINUS_EXPR))
1765                     {
1766                       bool neg = false;
1767
1768                       neg ^= (rhs_code == MINUS_EXPR);
1769                       neg ^= (rhs_def_code == MINUS_EXPR);
1770                       neg ^= real_isneg (TREE_REAL_CST_PTR (outer_const));
1771                       neg ^= real_isneg (TREE_REAL_CST_PTR (def_stmt_op1));
1772
1773                       if (neg)
1774                         goto dont_fold_assoc;
1775                     }
1776
1777                   /* Ho hum.  So fold will only operate on the outermost
1778                      thingy that we give it, so we have to build the new
1779                      expression in two pieces.  This requires that we handle
1780                      combinations of plus and minus.  */
1781                   if (rhs_def_code != rhs_code)
1782                     {
1783                       if (rhs_def_code == MINUS_EXPR)
1784                         t = build (MINUS_EXPR, type, outer_const, def_stmt_op1);
1785                       else
1786                         t = build (MINUS_EXPR, type, def_stmt_op1, outer_const);
1787                       rhs_code = PLUS_EXPR;
1788                     }
1789                   else if (rhs_def_code == MINUS_EXPR)
1790                     t = build (PLUS_EXPR, type, def_stmt_op1, outer_const);
1791                   else
1792                     t = build (rhs_def_code, type, def_stmt_op1, outer_const);
1793                   t = local_fold (t);
1794                   t = build (rhs_code, type, def_stmt_op0, t);
1795                   t = local_fold (t);
1796
1797                   /* If the result is a suitable looking gimple expression,
1798                      then use it instead of the original for STMT.  */
1799                   if (TREE_CODE (t) == SSA_NAME
1800                       || (UNARY_CLASS_P (t)
1801                           && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME)
1802                       || ((BINARY_CLASS_P (t) || COMPARISON_CLASS_P (t))
1803                           && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME
1804                           && is_gimple_val (TREE_OPERAND (t, 1))))
1805                     result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1806                 }
1807             }
1808         }
1809  dont_fold_assoc:;
1810     }
1811
1812   /* Transform TRUNC_DIV_EXPR and TRUNC_MOD_EXPR into RSHIFT_EXPR
1813      and BIT_AND_EXPR respectively if the first operand is greater
1814      than zero and the second operand is an exact power of two.  */
1815   if ((rhs_code == TRUNC_DIV_EXPR || rhs_code == TRUNC_MOD_EXPR)
1816       && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0)))
1817       && integer_pow2p (TREE_OPERAND (rhs, 1)))
1818     {
1819       tree val;
1820       tree op = TREE_OPERAND (rhs, 0);
1821
1822       if (TYPE_UNSIGNED (TREE_TYPE (op)))
1823         {
1824           val = integer_one_node;
1825         }
1826       else
1827         {
1828           tree dummy_cond = walk_data->global_data;
1829
1830           if (! dummy_cond)
1831             {
1832               dummy_cond = build (GT_EXPR, boolean_type_node,
1833                                   op, integer_zero_node);
1834               dummy_cond = build (COND_EXPR, void_type_node,
1835                                   dummy_cond, NULL, NULL);
1836               walk_data->global_data = dummy_cond;
1837             }
1838           else
1839             {
1840               TREE_SET_CODE (COND_EXPR_COND (dummy_cond), GT_EXPR);
1841               TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op;
1842               TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1)
1843                 = integer_zero_node;
1844             }
1845           val = simplify_cond_and_lookup_avail_expr (dummy_cond, NULL, false);
1846         }
1847
1848       if (val && integer_onep (val))
1849         {
1850           tree t;
1851           tree op0 = TREE_OPERAND (rhs, 0);
1852           tree op1 = TREE_OPERAND (rhs, 1);
1853
1854           if (rhs_code == TRUNC_DIV_EXPR)
1855             t = build (RSHIFT_EXPR, TREE_TYPE (op0), op0,
1856                        build_int_cst (NULL_TREE, tree_log2 (op1)));
1857           else
1858             t = build (BIT_AND_EXPR, TREE_TYPE (op0), op0,
1859                        local_fold (build (MINUS_EXPR, TREE_TYPE (op1),
1860                                           op1, integer_one_node)));
1861
1862           result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1863         }
1864     }
1865
1866   /* Transform ABS (X) into X or -X as appropriate.  */
1867   if (rhs_code == ABS_EXPR
1868       && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0))))
1869     {
1870       tree val;
1871       tree op = TREE_OPERAND (rhs, 0);
1872       tree type = TREE_TYPE (op);
1873
1874       if (TYPE_UNSIGNED (type))
1875         {
1876           val = integer_zero_node;
1877         }
1878       else
1879         {
1880           tree dummy_cond = walk_data->global_data;
1881
1882           if (! dummy_cond)
1883             {
1884               dummy_cond = build (LE_EXPR, boolean_type_node,
1885                                   op, integer_zero_node);
1886               dummy_cond = build (COND_EXPR, void_type_node,
1887                                   dummy_cond, NULL, NULL);
1888               walk_data->global_data = dummy_cond;
1889             }
1890           else
1891             {
1892               TREE_SET_CODE (COND_EXPR_COND (dummy_cond), LE_EXPR);
1893               TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op;
1894               TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1)
1895                 = build_int_cst (type, 0);
1896             }
1897           val = simplify_cond_and_lookup_avail_expr (dummy_cond, NULL, false);
1898
1899           if (!val)
1900             {
1901               TREE_SET_CODE (COND_EXPR_COND (dummy_cond), GE_EXPR);
1902               TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op;
1903               TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1)
1904                 = build_int_cst (type, 0);
1905
1906               val = simplify_cond_and_lookup_avail_expr (dummy_cond,
1907                                                          NULL, false);
1908
1909               if (val)
1910                 {
1911                   if (integer_zerop (val))
1912                     val = integer_one_node;
1913                   else if (integer_onep (val))
1914                     val = integer_zero_node;
1915                 }
1916             }
1917         }
1918
1919       if (val
1920           && (integer_onep (val) || integer_zerop (val)))
1921         {
1922           tree t;
1923
1924           if (integer_onep (val))
1925             t = build1 (NEGATE_EXPR, TREE_TYPE (op), op);
1926           else
1927             t = op;
1928
1929           result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1930         }
1931     }
1932
1933   /* Optimize *"foo" into 'f'.  This is done here rather than
1934      in fold to avoid problems with stuff like &*"foo".  */
1935   if (TREE_CODE (rhs) == INDIRECT_REF || TREE_CODE (rhs) == ARRAY_REF)
1936     {
1937       tree t = fold_read_from_constant_string (rhs);
1938
1939       if (t)
1940         result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1941     }
1942
1943   return result;
1944 }
1945
1946 /* COND is a condition of the form:
1947
1948      x == const or x != const
1949
1950    Look back to x's defining statement and see if x is defined as
1951
1952      x = (type) y;
1953
1954    If const is unchanged if we convert it to type, then we can build
1955    the equivalent expression:
1956
1957
1958       y == const or y != const
1959
1960    Which may allow further optimizations.
1961
1962    Return the equivalent comparison or NULL if no such equivalent comparison
1963    was found.  */
1964
1965 static tree
1966 find_equivalent_equality_comparison (tree cond)
1967 {
1968   tree op0 = TREE_OPERAND (cond, 0);
1969   tree op1 = TREE_OPERAND (cond, 1);
1970   tree def_stmt = SSA_NAME_DEF_STMT (op0);
1971
1972   /* OP0 might have been a parameter, so first make sure it
1973      was defined by a MODIFY_EXPR.  */
1974   if (def_stmt && TREE_CODE (def_stmt) == MODIFY_EXPR)
1975     {
1976       tree def_rhs = TREE_OPERAND (def_stmt, 1);
1977
1978       /* Now make sure the RHS of the MODIFY_EXPR is a typecast.  */
1979       if ((TREE_CODE (def_rhs) == NOP_EXPR
1980            || TREE_CODE (def_rhs) == CONVERT_EXPR)
1981           && TREE_CODE (TREE_OPERAND (def_rhs, 0)) == SSA_NAME)
1982         {
1983           tree def_rhs_inner = TREE_OPERAND (def_rhs, 0);
1984           tree def_rhs_inner_type = TREE_TYPE (def_rhs_inner);
1985           tree new;
1986
1987           if (TYPE_PRECISION (def_rhs_inner_type)
1988               > TYPE_PRECISION (TREE_TYPE (def_rhs)))
1989             return NULL;
1990
1991           /* What we want to prove is that if we convert OP1 to
1992              the type of the object inside the NOP_EXPR that the
1993              result is still equivalent to SRC.
1994
1995              If that is true, the build and return new equivalent
1996              condition which uses the source of the typecast and the
1997              new constant (which has only changed its type).  */
1998           new = build1 (TREE_CODE (def_rhs), def_rhs_inner_type, op1);
1999           new = local_fold (new);
2000           if (is_gimple_val (new) && tree_int_cst_equal (new, op1))
2001             return build (TREE_CODE (cond), TREE_TYPE (cond),
2002                           def_rhs_inner, new);
2003         }
2004     }
2005   return NULL;
2006 }
2007
2008 /* STMT is a COND_EXPR for which we could not trivially determine its
2009    result.  This routine attempts to find equivalent forms of the
2010    condition which we may be able to optimize better.  It also
2011    uses simple value range propagation to optimize conditionals.  */
2012
2013 static tree
2014 simplify_cond_and_lookup_avail_expr (tree stmt,
2015                                      stmt_ann_t ann,
2016                                      int insert)
2017 {
2018   tree cond = COND_EXPR_COND (stmt);
2019
2020   if (COMPARISON_CLASS_P (cond))
2021     {
2022       tree op0 = TREE_OPERAND (cond, 0);
2023       tree op1 = TREE_OPERAND (cond, 1);
2024
2025       if (TREE_CODE (op0) == SSA_NAME && is_gimple_min_invariant (op1))
2026         {
2027           int limit;
2028           tree low, high, cond_low, cond_high;
2029           int lowequal, highequal, swapped, no_overlap, subset, cond_inverted;
2030           varray_type vrp_records;
2031           struct vrp_element *element;
2032           struct vrp_hash_elt vrp_hash_elt, *vrp_hash_elt_p;
2033           void **slot;
2034
2035           /* First see if we have test of an SSA_NAME against a constant
2036              where the SSA_NAME is defined by an earlier typecast which
2037              is irrelevant when performing tests against the given
2038              constant.  */
2039           if (TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
2040             {
2041               tree new_cond = find_equivalent_equality_comparison (cond);
2042
2043               if (new_cond)
2044                 {
2045                   /* Update the statement to use the new equivalent
2046                      condition.  */
2047                   COND_EXPR_COND (stmt) = new_cond;
2048
2049                   /* If this is not a real stmt, ann will be NULL and we
2050                      avoid processing the operands.  */
2051                   if (ann)
2052                     modify_stmt (stmt);
2053
2054                   /* Lookup the condition and return its known value if it
2055                      exists.  */
2056                   new_cond = lookup_avail_expr (stmt, insert);
2057                   if (new_cond)
2058                     return new_cond;
2059
2060                   /* The operands have changed, so update op0 and op1.  */
2061                   op0 = TREE_OPERAND (cond, 0);
2062                   op1 = TREE_OPERAND (cond, 1);
2063                 }
2064             }
2065
2066           /* Consult the value range records for this variable (if they exist)
2067              to see if we can eliminate or simplify this conditional.
2068
2069              Note two tests are necessary to determine no records exist.
2070              First we have to see if the virtual array exists, if it
2071              exists, then we have to check its active size.
2072
2073              Also note the vast majority of conditionals are not testing
2074              a variable which has had its range constrained by an earlier
2075              conditional.  So this filter avoids a lot of unnecessary work.  */
2076           vrp_hash_elt.var = op0;
2077           vrp_hash_elt.records = NULL;
2078           slot = htab_find_slot (vrp_data, &vrp_hash_elt, NO_INSERT);
2079           if (slot == NULL)
2080             return NULL;
2081
2082           vrp_hash_elt_p = (struct vrp_hash_elt *) *slot;
2083           vrp_records = vrp_hash_elt_p->records;
2084           if (vrp_records == NULL)
2085             return NULL;
2086
2087           limit = VARRAY_ACTIVE_SIZE (vrp_records);
2088
2089           /* If we have no value range records for this variable, or we are
2090              unable to extract a range for this condition, then there is
2091              nothing to do.  */
2092           if (limit == 0
2093               || ! extract_range_from_cond (cond, &cond_high,
2094                                             &cond_low, &cond_inverted))
2095             return NULL;
2096
2097           /* We really want to avoid unnecessary computations of range
2098              info.  So all ranges are computed lazily; this avoids a
2099              lot of unnecessary work.  i.e., we record the conditional,
2100              but do not process how it constrains the variable's
2101              potential values until we know that processing the condition
2102              could be helpful.
2103
2104              However, we do not want to have to walk a potentially long
2105              list of ranges, nor do we want to compute a variable's
2106              range more than once for a given path.
2107
2108              Luckily, each time we encounter a conditional that can not
2109              be otherwise optimized we will end up here and we will
2110              compute the necessary range information for the variable
2111              used in this condition.
2112
2113              Thus you can conclude that there will never be more than one
2114              conditional associated with a variable which has not been
2115              processed.  So we never need to merge more than one new
2116              conditional into the current range.
2117
2118              These properties also help us avoid unnecessary work.  */
2119            element
2120              = (struct vrp_element *)VARRAY_GENERIC_PTR (vrp_records, limit - 1);
2121
2122           if (element->high && element->low)
2123             {
2124               /* The last element has been processed, so there is no range
2125                  merging to do, we can simply use the high/low values
2126                  recorded in the last element.  */
2127               low = element->low;
2128               high = element->high;
2129             }
2130           else
2131             {
2132               tree tmp_high, tmp_low;
2133               int dummy;
2134
2135               /* The last element has not been processed.  Process it now.
2136                  record_range should ensure for cond inverted is not set.
2137                  This call can only fail if cond is x < min or x > max,
2138                  which fold should have optimized into false.
2139                  If that doesn't happen, just pretend all values are
2140                  in the range.  */
2141               if (! extract_range_from_cond (element->cond, &tmp_high,
2142                                              &tmp_low, &dummy))
2143                 gcc_unreachable ();
2144               else
2145                 gcc_assert (dummy == 0);
2146
2147               /* If this is the only element, then no merging is necessary,
2148                  the high/low values from extract_range_from_cond are all
2149                  we need.  */
2150               if (limit == 1)
2151                 {
2152                   low = tmp_low;
2153                   high = tmp_high;
2154                 }
2155               else
2156                 {
2157                   /* Get the high/low value from the previous element.  */
2158                   struct vrp_element *prev
2159                     = (struct vrp_element *)VARRAY_GENERIC_PTR (vrp_records,
2160                                                                 limit - 2);
2161                   low = prev->low;
2162                   high = prev->high;
2163
2164                   /* Merge in this element's range with the range from the
2165                      previous element.
2166
2167                      The low value for the merged range is the maximum of
2168                      the previous low value and the low value of this record.
2169
2170                      Similarly the high value for the merged range is the
2171                      minimum of the previous high value and the high value of
2172                      this record.  */
2173                   low = (tree_int_cst_compare (low, tmp_low) == 1
2174                          ? low : tmp_low);
2175                   high = (tree_int_cst_compare (high, tmp_high) == -1
2176                           ? high : tmp_high);
2177                 }
2178
2179               /* And record the computed range.  */
2180               element->low = low;
2181               element->high = high;
2182
2183             }
2184
2185           /* After we have constrained this variable's potential values,
2186              we try to determine the result of the given conditional.
2187
2188              To simplify later tests, first determine if the current
2189              low value is the same low value as the conditional.
2190              Similarly for the current high value and the high value
2191              for the conditional.  */
2192           lowequal = tree_int_cst_equal (low, cond_low);
2193           highequal = tree_int_cst_equal (high, cond_high);
2194
2195           if (lowequal && highequal)
2196             return (cond_inverted ? boolean_false_node : boolean_true_node);
2197
2198           /* To simplify the overlap/subset tests below we may want
2199              to swap the two ranges so that the larger of the two
2200              ranges occurs "first".  */
2201           swapped = 0;
2202           if (tree_int_cst_compare (low, cond_low) == 1
2203               || (lowequal
2204                   && tree_int_cst_compare (cond_high, high) == 1))
2205             {
2206               tree temp;
2207
2208               swapped = 1;
2209               temp = low;
2210               low = cond_low;
2211               cond_low = temp;
2212               temp = high;
2213               high = cond_high;
2214               cond_high = temp;
2215             }
2216
2217           /* Now determine if there is no overlap in the ranges
2218              or if the second range is a subset of the first range.  */
2219           no_overlap = tree_int_cst_lt (high, cond_low);
2220           subset = tree_int_cst_compare (cond_high, high) != 1;
2221
2222           /* If there was no overlap in the ranges, then this conditional
2223              always has a false value (unless we had to invert this
2224              conditional, in which case it always has a true value).  */
2225           if (no_overlap)
2226             return (cond_inverted ? boolean_true_node : boolean_false_node);
2227
2228           /* If the current range is a subset of the condition's range,
2229              then this conditional always has a true value (unless we
2230              had to invert this conditional, in which case it always
2231              has a true value).  */
2232           if (subset && swapped)
2233             return (cond_inverted ? boolean_false_node : boolean_true_node);
2234
2235           /* We were unable to determine the result of the conditional.
2236              However, we may be able to simplify the conditional.  First
2237              merge the ranges in the same manner as range merging above.  */
2238           low = tree_int_cst_compare (low, cond_low) == 1 ? low : cond_low;
2239           high = tree_int_cst_compare (high, cond_high) == -1 ? high : cond_high;
2240
2241           /* If the range has converged to a single point, then turn this
2242              into an equality comparison.  */
2243           if (TREE_CODE (cond) != EQ_EXPR
2244               && TREE_CODE (cond) != NE_EXPR
2245               && tree_int_cst_equal (low, high))
2246             {
2247               TREE_SET_CODE (cond, EQ_EXPR);
2248               TREE_OPERAND (cond, 1) = high;
2249             }
2250         }
2251     }
2252   return 0;
2253 }
2254
2255 /* STMT is a SWITCH_EXPR for which we could not trivially determine its
2256    result.  This routine attempts to find equivalent forms of the
2257    condition which we may be able to optimize better.  */
2258
2259 static tree
2260 simplify_switch_and_lookup_avail_expr (tree stmt, int insert)
2261 {
2262   tree cond = SWITCH_COND (stmt);
2263   tree def, to, ti;
2264
2265   /* The optimization that we really care about is removing unnecessary
2266      casts.  That will let us do much better in propagating the inferred
2267      constant at the switch target.  */
2268   if (TREE_CODE (cond) == SSA_NAME)
2269     {
2270       def = SSA_NAME_DEF_STMT (cond);
2271       if (TREE_CODE (def) == MODIFY_EXPR)
2272         {
2273           def = TREE_OPERAND (def, 1);
2274           if (TREE_CODE (def) == NOP_EXPR)
2275             {
2276               int need_precision;
2277               bool fail;
2278
2279               def = TREE_OPERAND (def, 0);
2280
2281 #ifdef ENABLE_CHECKING
2282               /* ??? Why was Jeff testing this?  We are gimple...  */
2283               gcc_assert (is_gimple_val (def));
2284 #endif
2285
2286               to = TREE_TYPE (cond);
2287               ti = TREE_TYPE (def);
2288
2289               /* If we have an extension that preserves value, then we
2290                  can copy the source value into the switch.  */
2291
2292               need_precision = TYPE_PRECISION (ti);
2293               fail = false;
2294               if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
2295                 fail = true;
2296               else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
2297                 need_precision += 1;
2298               if (TYPE_PRECISION (to) < need_precision)
2299                 fail = true;
2300
2301               if (!fail)
2302                 {
2303                   SWITCH_COND (stmt) = def;
2304                   modify_stmt (stmt);
2305
2306                   return lookup_avail_expr (stmt, insert);
2307                 }
2308             }
2309         }
2310     }
2311
2312   return 0;
2313 }
2314
2315
2316 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2317    known value for that SSA_NAME (or NULL if no value is known).
2318
2319    NONZERO_VARS is the set SSA_NAMES known to have a nonzero value,
2320    even if we don't know their precise value.
2321
2322    Propagate values from CONST_AND_COPIES and NONZERO_VARS into the PHI
2323    nodes of the successors of BB.  */
2324
2325 static void
2326 cprop_into_successor_phis (basic_block bb, bitmap nonzero_vars)
2327 {
2328   edge e;
2329   edge_iterator ei;
2330
2331   /* This can get rather expensive if the implementation is naive in
2332      how it finds the phi alternative associated with a particular edge.  */
2333   FOR_EACH_EDGE (e, ei, bb->succs)
2334     {
2335       tree phi;
2336       int indx;
2337
2338       /* If this is an abnormal edge, then we do not want to copy propagate
2339          into the PHI alternative associated with this edge.  */
2340       if (e->flags & EDGE_ABNORMAL)
2341         continue;
2342
2343       phi = phi_nodes (e->dest);
2344       if (! phi)
2345         continue;
2346
2347       indx = e->dest_idx;
2348       for ( ; phi; phi = PHI_CHAIN (phi))
2349         {
2350           tree new;
2351           use_operand_p orig_p;
2352           tree orig;
2353
2354           /* The alternative may be associated with a constant, so verify
2355              it is an SSA_NAME before doing anything with it.  */
2356           orig_p = PHI_ARG_DEF_PTR (phi, indx);
2357           orig = USE_FROM_PTR (orig_p);
2358           if (TREE_CODE (orig) != SSA_NAME)
2359             continue;
2360
2361           /* If the alternative is known to have a nonzero value, record
2362              that fact in the PHI node itself for future use.  */
2363           if (bitmap_bit_p (nonzero_vars, SSA_NAME_VERSION (orig)))
2364             PHI_ARG_NONZERO (phi, indx) = true;
2365
2366           /* If we have *ORIG_P in our constant/copy table, then replace
2367              ORIG_P with its value in our constant/copy table.  */
2368           new = SSA_NAME_VALUE (orig);
2369           if (new
2370               && (TREE_CODE (new) == SSA_NAME
2371                   || is_gimple_min_invariant (new))
2372               && may_propagate_copy (orig, new))
2373             {
2374               propagate_value (orig_p, new);
2375             }
2376         }
2377     }
2378 }
2379
2380 /* We have finished optimizing BB, record any information implied by
2381    taking a specific outgoing edge from BB.  */
2382
2383 static void
2384 record_edge_info (basic_block bb)
2385 {
2386   block_stmt_iterator bsi = bsi_last (bb);
2387   struct edge_info *edge_info;
2388
2389   if (! bsi_end_p (bsi))
2390     {
2391       tree stmt = bsi_stmt (bsi);
2392
2393       if (stmt && TREE_CODE (stmt) == SWITCH_EXPR)
2394         {
2395           tree cond = SWITCH_COND (stmt);
2396
2397           if (TREE_CODE (cond) == SSA_NAME)
2398             {
2399               tree labels = SWITCH_LABELS (stmt);
2400               int i, n_labels = TREE_VEC_LENGTH (labels);
2401               tree *info = xcalloc (n_basic_blocks, sizeof (tree));
2402               edge e;
2403               edge_iterator ei;
2404
2405               for (i = 0; i < n_labels; i++)
2406                 {
2407                   tree label = TREE_VEC_ELT (labels, i);
2408                   basic_block target_bb = label_to_block (CASE_LABEL (label));
2409
2410                   if (CASE_HIGH (label)
2411                       || !CASE_LOW (label)
2412                       || info[target_bb->index])
2413                     info[target_bb->index] = error_mark_node;
2414                   else
2415                     info[target_bb->index] = label;
2416                 }
2417
2418               FOR_EACH_EDGE (e, ei, bb->succs)
2419                 {
2420                   basic_block target_bb = e->dest;
2421                   tree node = info[target_bb->index];
2422
2423                   if (node != NULL && node != error_mark_node)
2424                     {
2425                       tree x = fold_convert (TREE_TYPE (cond), CASE_LOW (node));
2426                       edge_info = allocate_edge_info (e);
2427                       edge_info->lhs = cond;
2428                       edge_info->rhs = x;
2429                     }
2430                 }
2431               free (info);
2432             }
2433         }
2434
2435       /* A COND_EXPR may create equivalences too.  */
2436       if (stmt && TREE_CODE (stmt) == COND_EXPR)
2437         {
2438           tree cond = COND_EXPR_COND (stmt);
2439           edge true_edge;
2440           edge false_edge;
2441
2442           extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
2443
2444           /* If the conditional is a single variable 'X', record 'X = 1'
2445              for the true edge and 'X = 0' on the false edge.  */
2446           if (SSA_VAR_P (cond))
2447             {
2448               struct edge_info *edge_info;
2449
2450               edge_info = allocate_edge_info (true_edge);
2451               edge_info->lhs = cond;
2452               edge_info->rhs = constant_boolean_node (1, TREE_TYPE (cond));
2453
2454               edge_info = allocate_edge_info (false_edge);
2455               edge_info->lhs = cond;
2456               edge_info->rhs = constant_boolean_node (0, TREE_TYPE (cond));
2457             }
2458           /* Equality tests may create one or two equivalences.  */
2459           else if (COMPARISON_CLASS_P (cond))
2460             {
2461               tree op0 = TREE_OPERAND (cond, 0);
2462               tree op1 = TREE_OPERAND (cond, 1);
2463
2464               /* Special case comparing booleans against a constant as we
2465                  know the value of OP0 on both arms of the branch.  i.e., we
2466                  can record an equivalence for OP0 rather than COND.  */
2467               if ((TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
2468                   && TREE_CODE (op0) == SSA_NAME
2469                   && TREE_CODE (TREE_TYPE (op0)) == BOOLEAN_TYPE
2470                   && is_gimple_min_invariant (op1))
2471                 {
2472                   if (TREE_CODE (cond) == EQ_EXPR)
2473                     {
2474                       edge_info = allocate_edge_info (true_edge);
2475                       edge_info->lhs = op0;
2476                       edge_info->rhs = (integer_zerop (op1)
2477                                             ? boolean_false_node
2478                                             : boolean_true_node);
2479
2480                       edge_info = allocate_edge_info (false_edge);
2481                       edge_info->lhs = op0;
2482                       edge_info->rhs = (integer_zerop (op1)
2483                                             ? boolean_true_node
2484                                             : boolean_false_node);
2485                     }
2486                   else
2487                     {
2488                       edge_info = allocate_edge_info (true_edge);
2489                       edge_info->lhs = op0;
2490                       edge_info->rhs = (integer_zerop (op1)
2491                                             ? boolean_true_node
2492                                             : boolean_false_node);
2493
2494                       edge_info = allocate_edge_info (false_edge);
2495                       edge_info->lhs = op0;
2496                       edge_info->rhs = (integer_zerop (op1)
2497                                             ? boolean_false_node
2498                                             : boolean_true_node);
2499                     }
2500                 }
2501
2502               else if (is_gimple_min_invariant (op0)
2503                        && (TREE_CODE (op1) == SSA_NAME
2504                            || is_gimple_min_invariant (op1)))
2505                 {
2506                   tree inverted = invert_truthvalue (cond);
2507                   struct edge_info *edge_info;
2508
2509                   edge_info = allocate_edge_info (true_edge);
2510                   record_conditions (edge_info, cond, inverted);
2511
2512                   if (TREE_CODE (cond) == EQ_EXPR)
2513                     {
2514                       edge_info->lhs = op1;
2515                       edge_info->rhs = op0;
2516                     }
2517
2518                   edge_info = allocate_edge_info (false_edge);
2519                   record_conditions (edge_info, inverted, cond);
2520
2521                   if (TREE_CODE (cond) == NE_EXPR)
2522                     {
2523                       edge_info->lhs = op1;
2524                       edge_info->rhs = op0;
2525                     }
2526                 }
2527
2528               else if (TREE_CODE (op0) == SSA_NAME
2529                        && (is_gimple_min_invariant (op1)
2530                            || TREE_CODE (op1) == SSA_NAME))
2531                 {
2532                   tree inverted = invert_truthvalue (cond);
2533                   struct edge_info *edge_info;
2534
2535                   edge_info = allocate_edge_info (true_edge);
2536                   record_conditions (edge_info, cond, inverted);
2537
2538                   if (TREE_CODE (cond) == EQ_EXPR)
2539                     {
2540                       edge_info->lhs = op0;
2541                       edge_info->rhs = op1;
2542                     }
2543
2544                   edge_info = allocate_edge_info (false_edge);
2545                   record_conditions (edge_info, inverted, cond);
2546
2547                   if (TREE_CODE (cond) == NE_EXPR)
2548                     {
2549                       edge_info->lhs = op0;
2550                       edge_info->rhs = op1;
2551                     }
2552                 }
2553             }
2554
2555           /* ??? TRUTH_NOT_EXPR can create an equivalence too.  */
2556         }
2557     }
2558 }
2559
2560 /* Propagate information from BB to its outgoing edges.
2561
2562    This can include equivalency information implied by control statements
2563    at the end of BB and const/copy propagation into PHIs in BB's
2564    successor blocks.  */
2565
2566 static void
2567 propagate_to_outgoing_edges (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
2568                              basic_block bb)
2569 {
2570
2571   record_edge_info (bb);
2572   cprop_into_successor_phis (bb, nonzero_vars);
2573 }
2574
2575 /* Search for redundant computations in STMT.  If any are found, then
2576    replace them with the variable holding the result of the computation.
2577
2578    If safe, record this expression into the available expression hash
2579    table.  */
2580
2581 static bool
2582 eliminate_redundant_computations (struct dom_walk_data *walk_data,
2583                                   tree stmt, stmt_ann_t ann)
2584 {
2585   v_may_def_optype v_may_defs = V_MAY_DEF_OPS (ann);
2586   tree *expr_p, def = NULL_TREE;
2587   bool insert = true;
2588   tree cached_lhs;
2589   bool retval = false;
2590
2591   if (TREE_CODE (stmt) == MODIFY_EXPR)
2592     def = TREE_OPERAND (stmt, 0);
2593
2594   /* Certain expressions on the RHS can be optimized away, but can not
2595      themselves be entered into the hash tables.  */
2596   if (ann->makes_aliased_stores
2597       || ! def
2598       || TREE_CODE (def) != SSA_NAME
2599       || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def)
2600       || NUM_V_MAY_DEFS (v_may_defs) != 0
2601       /* Do not record equivalences for increments of ivs.  This would create
2602          overlapping live ranges for a very questionable gain.  */
2603       || simple_iv_increment_p (stmt))
2604     insert = false;
2605
2606   /* Check if the expression has been computed before.  */
2607   cached_lhs = lookup_avail_expr (stmt, insert);
2608
2609   /* If this is an assignment and the RHS was not in the hash table,
2610      then try to simplify the RHS and lookup the new RHS in the
2611      hash table.  */
2612   if (! cached_lhs && TREE_CODE (stmt) == MODIFY_EXPR)
2613     cached_lhs = simplify_rhs_and_lookup_avail_expr (walk_data, stmt, insert);
2614   /* Similarly if this is a COND_EXPR and we did not find its
2615      expression in the hash table, simplify the condition and
2616      try again.  */
2617   else if (! cached_lhs && TREE_CODE (stmt) == COND_EXPR)
2618     cached_lhs = simplify_cond_and_lookup_avail_expr (stmt, ann, insert);
2619   /* Similarly for a SWITCH_EXPR.  */
2620   else if (!cached_lhs && TREE_CODE (stmt) == SWITCH_EXPR)
2621     cached_lhs = simplify_switch_and_lookup_avail_expr (stmt, insert);
2622
2623   opt_stats.num_exprs_considered++;
2624
2625   /* Get a pointer to the expression we are trying to optimize.  */
2626   if (TREE_CODE (stmt) == COND_EXPR)
2627     expr_p = &COND_EXPR_COND (stmt);
2628   else if (TREE_CODE (stmt) == SWITCH_EXPR)
2629     expr_p = &SWITCH_COND (stmt);
2630   else if (TREE_CODE (stmt) == RETURN_EXPR && TREE_OPERAND (stmt, 0))
2631     expr_p = &TREE_OPERAND (TREE_OPERAND (stmt, 0), 1);
2632   else
2633     expr_p = &TREE_OPERAND (stmt, 1);
2634
2635   /* It is safe to ignore types here since we have already done
2636      type checking in the hashing and equality routines.  In fact
2637      type checking here merely gets in the way of constant
2638      propagation.  Also, make sure that it is safe to propagate
2639      CACHED_LHS into *EXPR_P.  */
2640   if (cached_lhs
2641       && (TREE_CODE (cached_lhs) != SSA_NAME
2642           || may_propagate_copy (*expr_p, cached_lhs)))
2643     {
2644       if (dump_file && (dump_flags & TDF_DETAILS))
2645         {
2646           fprintf (dump_file, "  Replaced redundant expr '");
2647           print_generic_expr (dump_file, *expr_p, dump_flags);
2648           fprintf (dump_file, "' with '");
2649           print_generic_expr (dump_file, cached_lhs, dump_flags);
2650            fprintf (dump_file, "'\n");
2651         }
2652
2653       opt_stats.num_re++;
2654
2655 #if defined ENABLE_CHECKING
2656       gcc_assert (TREE_CODE (cached_lhs) == SSA_NAME
2657                   || is_gimple_min_invariant (cached_lhs));
2658 #endif
2659
2660       if (TREE_CODE (cached_lhs) == ADDR_EXPR
2661           || (POINTER_TYPE_P (TREE_TYPE (*expr_p))
2662               && is_gimple_min_invariant (cached_lhs)))
2663         retval = true;
2664
2665       propagate_tree_value (expr_p, cached_lhs);
2666       modify_stmt (stmt);
2667     }
2668   return retval;
2669 }
2670
2671 /* STMT, a MODIFY_EXPR, may create certain equivalences, in either
2672    the available expressions table or the const_and_copies table.
2673    Detect and record those equivalences.  */
2674
2675 static void
2676 record_equivalences_from_stmt (tree stmt,
2677                                int may_optimize_p,
2678                                stmt_ann_t ann)
2679 {
2680   tree lhs = TREE_OPERAND (stmt, 0);
2681   enum tree_code lhs_code = TREE_CODE (lhs);
2682   int i;
2683
2684   if (lhs_code == SSA_NAME)
2685     {
2686       tree rhs = TREE_OPERAND (stmt, 1);
2687
2688       /* Strip away any useless type conversions.  */
2689       STRIP_USELESS_TYPE_CONVERSION (rhs);
2690
2691       /* If the RHS of the assignment is a constant or another variable that
2692          may be propagated, register it in the CONST_AND_COPIES table.  We
2693          do not need to record unwind data for this, since this is a true
2694          assignment and not an equivalence inferred from a comparison.  All
2695          uses of this ssa name are dominated by this assignment, so unwinding
2696          just costs time and space.  */
2697       if (may_optimize_p
2698           && (TREE_CODE (rhs) == SSA_NAME
2699               || is_gimple_min_invariant (rhs)))
2700         SSA_NAME_VALUE (lhs) = rhs;
2701
2702       /* alloca never returns zero and the address of a non-weak symbol
2703          is never zero.  NOP_EXPRs and CONVERT_EXPRs can be completely
2704          stripped as they do not affect this equivalence.  */
2705       while (TREE_CODE (rhs) == NOP_EXPR
2706              || TREE_CODE (rhs) == CONVERT_EXPR)
2707         rhs = TREE_OPERAND (rhs, 0);
2708
2709       if (alloca_call_p (rhs)
2710           || (TREE_CODE (rhs) == ADDR_EXPR
2711               && DECL_P (TREE_OPERAND (rhs, 0))
2712               && ! DECL_WEAK (TREE_OPERAND (rhs, 0))))
2713         record_var_is_nonzero (lhs);
2714
2715       /* IOR of any value with a nonzero value will result in a nonzero
2716          value.  Even if we do not know the exact result recording that
2717          the result is nonzero is worth the effort.  */
2718       if (TREE_CODE (rhs) == BIT_IOR_EXPR
2719           && integer_nonzerop (TREE_OPERAND (rhs, 1)))
2720         record_var_is_nonzero (lhs);
2721     }
2722
2723   /* Look at both sides for pointer dereferences.  If we find one, then
2724      the pointer must be nonnull and we can enter that equivalence into
2725      the hash tables.  */
2726   if (flag_delete_null_pointer_checks)
2727     for (i = 0; i < 2; i++)
2728       {
2729         tree t = TREE_OPERAND (stmt, i);
2730
2731         /* Strip away any COMPONENT_REFs.  */
2732         while (TREE_CODE (t) == COMPONENT_REF)
2733           t = TREE_OPERAND (t, 0);
2734
2735         /* Now see if this is a pointer dereference.  */
2736         if (INDIRECT_REF_P (t))
2737           {
2738             tree op = TREE_OPERAND (t, 0);
2739
2740             /* If the pointer is a SSA variable, then enter new
2741                equivalences into the hash table.  */
2742             while (TREE_CODE (op) == SSA_NAME)
2743               {
2744                 tree def = SSA_NAME_DEF_STMT (op);
2745
2746                 record_var_is_nonzero (op);
2747
2748                 /* And walk up the USE-DEF chains noting other SSA_NAMEs
2749                    which are known to have a nonzero value.  */
2750                 if (def
2751                     && TREE_CODE (def) == MODIFY_EXPR
2752                     && TREE_CODE (TREE_OPERAND (def, 1)) == NOP_EXPR)
2753                   op = TREE_OPERAND (TREE_OPERAND (def, 1), 0);
2754                 else
2755                   break;
2756               }
2757           }
2758       }
2759
2760   /* A memory store, even an aliased store, creates a useful
2761      equivalence.  By exchanging the LHS and RHS, creating suitable
2762      vops and recording the result in the available expression table,
2763      we may be able to expose more redundant loads.  */
2764   if (!ann->has_volatile_ops
2765       && (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME
2766           || is_gimple_min_invariant (TREE_OPERAND (stmt, 1)))
2767       && !is_gimple_reg (lhs))
2768     {
2769       tree rhs = TREE_OPERAND (stmt, 1);
2770       tree new;
2771
2772       /* FIXME: If the LHS of the assignment is a bitfield and the RHS
2773          is a constant, we need to adjust the constant to fit into the
2774          type of the LHS.  If the LHS is a bitfield and the RHS is not
2775          a constant, then we can not record any equivalences for this
2776          statement since we would need to represent the widening or
2777          narrowing of RHS.  This fixes gcc.c-torture/execute/921016-1.c
2778          and should not be necessary if GCC represented bitfields
2779          properly.  */
2780       if (lhs_code == COMPONENT_REF
2781           && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1)))
2782         {
2783           if (TREE_CONSTANT (rhs))
2784             rhs = widen_bitfield (rhs, TREE_OPERAND (lhs, 1), lhs);
2785           else
2786             rhs = NULL;
2787
2788           /* If the value overflowed, then we can not use this equivalence.  */
2789           if (rhs && ! is_gimple_min_invariant (rhs))
2790             rhs = NULL;
2791         }
2792
2793       if (rhs)
2794         {
2795           /* Build a new statement with the RHS and LHS exchanged.  */
2796           new = build (MODIFY_EXPR, TREE_TYPE (stmt), rhs, lhs);
2797
2798           create_ssa_artficial_load_stmt (&(ann->operands), new);
2799
2800           /* Finally enter the statement into the available expression
2801              table.  */
2802           lookup_avail_expr (new, true);
2803         }
2804     }
2805 }
2806
2807 /* Replace *OP_P in STMT with any known equivalent value for *OP_P from
2808    CONST_AND_COPIES.  */
2809
2810 static bool
2811 cprop_operand (tree stmt, use_operand_p op_p)
2812 {
2813   bool may_have_exposed_new_symbols = false;
2814   tree val;
2815   tree op = USE_FROM_PTR (op_p);
2816
2817   /* If the operand has a known constant value or it is known to be a
2818      copy of some other variable, use the value or copy stored in
2819      CONST_AND_COPIES.  */
2820   val = SSA_NAME_VALUE (op);
2821   if (val && TREE_CODE (val) != VALUE_HANDLE)
2822     {
2823       tree op_type, val_type;
2824
2825       /* Do not change the base variable in the virtual operand
2826          tables.  That would make it impossible to reconstruct
2827          the renamed virtual operand if we later modify this
2828          statement.  Also only allow the new value to be an SSA_NAME
2829          for propagation into virtual operands.  */
2830       if (!is_gimple_reg (op)
2831           && (get_virtual_var (val) != get_virtual_var (op)
2832               || TREE_CODE (val) != SSA_NAME))
2833         return false;
2834
2835       /* Do not replace hard register operands in asm statements.  */
2836       if (TREE_CODE (stmt) == ASM_EXPR
2837           && !may_propagate_copy_into_asm (op))
2838         return false;
2839
2840       /* Get the toplevel type of each operand.  */
2841       op_type = TREE_TYPE (op);
2842       val_type = TREE_TYPE (val);
2843
2844       /* While both types are pointers, get the type of the object
2845          pointed to.  */
2846       while (POINTER_TYPE_P (op_type) && POINTER_TYPE_P (val_type))
2847         {
2848           op_type = TREE_TYPE (op_type);
2849           val_type = TREE_TYPE (val_type);
2850         }
2851
2852       /* Make sure underlying types match before propagating a constant by
2853          converting the constant to the proper type.  Note that convert may
2854          return a non-gimple expression, in which case we ignore this
2855          propagation opportunity.  */
2856       if (TREE_CODE (val) != SSA_NAME)
2857         {
2858           if (!lang_hooks.types_compatible_p (op_type, val_type))
2859             {
2860               val = fold_convert (TREE_TYPE (op), val);
2861               if (!is_gimple_min_invariant (val))
2862                 return false;
2863             }
2864         }
2865
2866       /* Certain operands are not allowed to be copy propagated due
2867          to their interaction with exception handling and some GCC
2868          extensions.  */
2869       else if (!may_propagate_copy (op, val))
2870         return false;
2871
2872       /* Do not propagate copies if the propagated value is at a deeper loop
2873          depth than the propagatee.  Otherwise, this may move loop variant
2874          variables outside of their loops and prevent coalescing
2875          opportunities.  If the value was loop invariant, it will be hoisted
2876          by LICM and exposed for copy propagation.  */
2877       if (loop_depth_of_name (val) > loop_depth_of_name (op))
2878         return false;
2879
2880       /* Dump details.  */
2881       if (dump_file && (dump_flags & TDF_DETAILS))
2882         {
2883           fprintf (dump_file, "  Replaced '");
2884           print_generic_expr (dump_file, op, dump_flags);
2885           fprintf (dump_file, "' with %s '",
2886                    (TREE_CODE (val) != SSA_NAME ? "constant" : "variable"));
2887           print_generic_expr (dump_file, val, dump_flags);
2888           fprintf (dump_file, "'\n");
2889         }
2890
2891       /* If VAL is an ADDR_EXPR or a constant of pointer type, note
2892          that we may have exposed a new symbol for SSA renaming.  */
2893       if (TREE_CODE (val) == ADDR_EXPR
2894           || (POINTER_TYPE_P (TREE_TYPE (op))
2895               && is_gimple_min_invariant (val)))
2896         may_have_exposed_new_symbols = true;
2897
2898       propagate_value (op_p, val);
2899
2900       /* And note that we modified this statement.  This is now
2901          safe, even if we changed virtual operands since we will
2902          rescan the statement and rewrite its operands again.  */
2903       modify_stmt (stmt);
2904     }
2905   return may_have_exposed_new_symbols;
2906 }
2907
2908 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2909    known value for that SSA_NAME (or NULL if no value is known).
2910
2911    Propagate values from CONST_AND_COPIES into the uses, vuses and
2912    v_may_def_ops of STMT.  */
2913
2914 static bool
2915 cprop_into_stmt (tree stmt)
2916 {
2917   bool may_have_exposed_new_symbols = false;
2918   use_operand_p op_p;
2919   ssa_op_iter iter;
2920   tree rhs;
2921
2922   FOR_EACH_SSA_USE_OPERAND (op_p, stmt, iter, SSA_OP_ALL_USES)
2923     {
2924       if (TREE_CODE (USE_FROM_PTR (op_p)) == SSA_NAME)
2925         may_have_exposed_new_symbols |= cprop_operand (stmt, op_p);
2926     }
2927
2928   if (may_have_exposed_new_symbols)
2929     {
2930       rhs = get_rhs (stmt);
2931       if (rhs && TREE_CODE (rhs) == ADDR_EXPR)
2932         recompute_tree_invarant_for_addr_expr (rhs);
2933     }
2934
2935   return may_have_exposed_new_symbols;
2936 }
2937
2938
2939 /* Optimize the statement pointed by iterator SI.
2940
2941    We try to perform some simplistic global redundancy elimination and
2942    constant propagation:
2943
2944    1- To detect global redundancy, we keep track of expressions that have
2945       been computed in this block and its dominators.  If we find that the
2946       same expression is computed more than once, we eliminate repeated
2947       computations by using the target of the first one.
2948
2949    2- Constant values and copy assignments.  This is used to do very
2950       simplistic constant and copy propagation.  When a constant or copy
2951       assignment is found, we map the value on the RHS of the assignment to
2952       the variable in the LHS in the CONST_AND_COPIES table.  */
2953
2954 static void
2955 optimize_stmt (struct dom_walk_data *walk_data, basic_block bb,
2956                block_stmt_iterator si)
2957 {
2958   stmt_ann_t ann;
2959   tree stmt;
2960   bool may_optimize_p;
2961   bool may_have_exposed_new_symbols = false;
2962
2963   stmt = bsi_stmt (si);
2964
2965   get_stmt_operands (stmt);
2966   ann = stmt_ann (stmt);
2967   opt_stats.num_stmts++;
2968   may_have_exposed_new_symbols = false;
2969
2970   if (dump_file && (dump_flags & TDF_DETAILS))
2971     {
2972       fprintf (dump_file, "Optimizing statement ");
2973       print_generic_stmt (dump_file, stmt, TDF_SLIM);
2974     }
2975
2976   /* Const/copy propagate into USES, VUSES and the RHS of V_MAY_DEFs.  */
2977   may_have_exposed_new_symbols = cprop_into_stmt (stmt);
2978
2979   /* If the statement has been modified with constant replacements,
2980      fold its RHS before checking for redundant computations.  */
2981   if (ann->modified)
2982     {
2983       /* Try to fold the statement making sure that STMT is kept
2984          up to date.  */
2985       if (fold_stmt (bsi_stmt_ptr (si)))
2986         {
2987           stmt = bsi_stmt (si);
2988           ann = stmt_ann (stmt);
2989
2990           if (dump_file && (dump_flags & TDF_DETAILS))
2991             {
2992               fprintf (dump_file, "  Folded to: ");
2993               print_generic_stmt (dump_file, stmt, TDF_SLIM);
2994             }
2995         }
2996
2997       /* Constant/copy propagation above may change the set of
2998          virtual operands associated with this statement.  Folding
2999          may remove the need for some virtual operands.
3000
3001          Indicate we will need to rescan and rewrite the statement.  */
3002       may_have_exposed_new_symbols = true;
3003     }
3004
3005   /* Check for redundant computations.  Do this optimization only
3006      for assignments that have no volatile ops and conditionals.  */
3007   may_optimize_p = (!ann->has_volatile_ops
3008                     && ((TREE_CODE (stmt) == RETURN_EXPR
3009                          && TREE_OPERAND (stmt, 0)
3010                          && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR
3011                          && ! (TREE_SIDE_EFFECTS
3012                                (TREE_OPERAND (TREE_OPERAND (stmt, 0), 1))))
3013                         || (TREE_CODE (stmt) == MODIFY_EXPR
3014                             && ! TREE_SIDE_EFFECTS (TREE_OPERAND (stmt, 1)))
3015                         || TREE_CODE (stmt) == COND_EXPR
3016                         || TREE_CODE (stmt) == SWITCH_EXPR));
3017
3018   if (may_optimize_p)
3019     may_have_exposed_new_symbols
3020       |= eliminate_redundant_computations (walk_data, stmt, ann);
3021
3022   /* Record any additional equivalences created by this statement.  */
3023   if (TREE_CODE (stmt) == MODIFY_EXPR)
3024     record_equivalences_from_stmt (stmt,
3025                                    may_optimize_p,
3026                                    ann);
3027
3028   register_definitions_for_stmt (stmt);
3029
3030   /* If STMT is a COND_EXPR and it was modified, then we may know
3031      where it goes.  If that is the case, then mark the CFG as altered.
3032
3033      This will cause us to later call remove_unreachable_blocks and
3034      cleanup_tree_cfg when it is safe to do so.  It is not safe to
3035      clean things up here since removal of edges and such can trigger
3036      the removal of PHI nodes, which in turn can release SSA_NAMEs to
3037      the manager.
3038
3039      That's all fine and good, except that once SSA_NAMEs are released
3040      to the manager, we must not call create_ssa_name until all references
3041      to released SSA_NAMEs have been eliminated.
3042
3043      All references to the deleted SSA_NAMEs can not be eliminated until
3044      we remove unreachable blocks.
3045
3046      We can not remove unreachable blocks until after we have completed
3047      any queued jump threading.
3048
3049      We can not complete any queued jump threads until we have taken
3050      appropriate variables out of SSA form.  Taking variables out of
3051      SSA form can call create_ssa_name and thus we lose.
3052
3053      Ultimately I suspect we're going to need to change the interface
3054      into the SSA_NAME manager.  */
3055
3056   if (ann->modified)
3057     {
3058       tree val = NULL;
3059
3060       if (TREE_CODE (stmt) == COND_EXPR)
3061         val = COND_EXPR_COND (stmt);
3062       else if (TREE_CODE (stmt) == SWITCH_EXPR)
3063         val = SWITCH_COND (stmt);
3064
3065       if (val && TREE_CODE (val) == INTEGER_CST && find_taken_edge (bb, val))
3066         cfg_altered = true;
3067
3068       /* If we simplified a statement in such a way as to be shown that it
3069          cannot trap, update the eh information and the cfg to match.  */
3070       if (maybe_clean_eh_stmt (stmt))
3071         {
3072           bitmap_set_bit (need_eh_cleanup, bb->index);
3073           if (dump_file && (dump_flags & TDF_DETAILS))
3074             fprintf (dump_file, "  Flagged to clear EH edges.\n");
3075         }
3076     }
3077
3078   if (may_have_exposed_new_symbols)
3079     VEC_safe_push (tree_on_heap, stmts_to_rescan, bsi_stmt (si));
3080 }
3081
3082 /* Replace the RHS of STMT with NEW_RHS.  If RHS can be found in the
3083    available expression hashtable, then return the LHS from the hash
3084    table.
3085
3086    If INSERT is true, then we also update the available expression
3087    hash table to account for the changes made to STMT.  */
3088
3089 static tree
3090 update_rhs_and_lookup_avail_expr (tree stmt, tree new_rhs, bool insert)
3091 {
3092   tree cached_lhs = NULL;
3093
3094   /* Remove the old entry from the hash table.  */
3095   if (insert)
3096     {
3097       struct expr_hash_elt element;
3098
3099       initialize_hash_element (stmt, NULL, &element);
3100       htab_remove_elt_with_hash (avail_exprs, &element, element.hash);
3101     }
3102
3103   /* Now update the RHS of the assignment.  */
3104   TREE_OPERAND (stmt, 1) = new_rhs;
3105
3106   /* Now lookup the updated statement in the hash table.  */
3107   cached_lhs = lookup_avail_expr (stmt, insert);
3108
3109   /* We have now called lookup_avail_expr twice with two different
3110      versions of this same statement, once in optimize_stmt, once here.
3111
3112      We know the call in optimize_stmt did not find an existing entry
3113      in the hash table, so a new entry was created.  At the same time
3114      this statement was pushed onto the AVAIL_EXPRS_STACK vector.
3115
3116      If this call failed to find an existing entry on the hash table,
3117      then the new version of this statement was entered into the
3118      hash table.  And this statement was pushed onto BLOCK_AVAIL_EXPR
3119      for the second time.  So there are two copies on BLOCK_AVAIL_EXPRs
3120
3121      If this call succeeded, we still have one copy of this statement
3122      on the BLOCK_AVAIL_EXPRs vector.
3123
3124      For both cases, we need to pop the most recent entry off the
3125      BLOCK_AVAIL_EXPRs vector.  For the case where we never found this
3126      statement in the hash tables, that will leave precisely one
3127      copy of this statement on BLOCK_AVAIL_EXPRs.  For the case where
3128      we found a copy of this statement in the second hash table lookup
3129      we want _no_ copies of this statement in BLOCK_AVAIL_EXPRs.  */
3130   if (insert)
3131     VEC_pop (tree_on_heap, avail_exprs_stack);
3132
3133   /* And make sure we record the fact that we modified this
3134      statement.  */
3135   modify_stmt (stmt);
3136
3137   return cached_lhs;
3138 }
3139
3140 /* Search for an existing instance of STMT in the AVAIL_EXPRS table.  If
3141    found, return its LHS. Otherwise insert STMT in the table and return
3142    NULL_TREE.
3143
3144    Also, when an expression is first inserted in the AVAIL_EXPRS table, it
3145    is also added to the stack pointed by BLOCK_AVAIL_EXPRS_P, so that they
3146    can be removed when we finish processing this block and its children.
3147
3148    NOTE: This function assumes that STMT is a MODIFY_EXPR node that
3149    contains no CALL_EXPR on its RHS and makes no volatile nor
3150    aliased references.  */
3151
3152 static tree
3153 lookup_avail_expr (tree stmt, bool insert)
3154 {
3155   void **slot;
3156   tree lhs;
3157   tree temp;
3158   struct expr_hash_elt *element = xmalloc (sizeof (struct expr_hash_elt));
3159
3160   lhs = TREE_CODE (stmt) == MODIFY_EXPR ? TREE_OPERAND (stmt, 0) : NULL;
3161
3162   initialize_hash_element (stmt, lhs, element);
3163
3164   /* Don't bother remembering constant assignments and copy operations.
3165      Constants and copy operations are handled by the constant/copy propagator
3166      in optimize_stmt.  */
3167   if (TREE_CODE (element->rhs) == SSA_NAME
3168       || is_gimple_min_invariant (element->rhs))
3169     {
3170       free (element);
3171       return NULL_TREE;
3172     }
3173
3174   /* If this is an equality test against zero, see if we have recorded a
3175      nonzero value for the variable in question.  */
3176   if ((TREE_CODE (element->rhs) == EQ_EXPR
3177        || TREE_CODE  (element->rhs) == NE_EXPR)
3178       && TREE_CODE (TREE_OPERAND (element->rhs, 0)) == SSA_NAME
3179       && integer_zerop (TREE_OPERAND (element->rhs, 1)))
3180     {
3181       int indx = SSA_NAME_VERSION (TREE_OPERAND (element->rhs, 0));
3182
3183       if (bitmap_bit_p (nonzero_vars, indx))
3184         {
3185           tree t = element->rhs;
3186           free (element);
3187
3188           if (TREE_CODE (t) == EQ_EXPR)
3189             return boolean_false_node;
3190           else
3191             return boolean_true_node;
3192         }
3193     }
3194
3195   /* Finally try to find the expression in the main expression hash table.  */
3196   slot = htab_find_slot_with_hash (avail_exprs, element, element->hash,
3197                                    (insert ? INSERT : NO_INSERT));
3198   if (slot == NULL)
3199     {
3200       free (element);
3201       return NULL_TREE;
3202     }
3203
3204   if (*slot == NULL)
3205     {
3206       *slot = (void *) element;
3207       VEC_safe_push (tree_on_heap, avail_exprs_stack,
3208                      stmt ? stmt : element->rhs);
3209       return NULL_TREE;
3210     }
3211
3212   /* Extract the LHS of the assignment so that it can be used as the current
3213      definition of another variable.  */
3214   lhs = ((struct expr_hash_elt *)*slot)->lhs;
3215
3216   /* See if the LHS appears in the CONST_AND_COPIES table.  If it does, then
3217      use the value from the const_and_copies table.  */
3218   if (TREE_CODE (lhs) == SSA_NAME)
3219     {
3220       temp = SSA_NAME_VALUE (lhs);
3221       if (temp && TREE_CODE (temp) != VALUE_HANDLE)
3222         lhs = temp;
3223     }
3224
3225   free (element);
3226   return lhs;
3227 }
3228
3229 /* Given a condition COND, record into HI_P, LO_P and INVERTED_P the
3230    range of values that result in the conditional having a true value.
3231
3232    Return true if we are successful in extracting a range from COND and
3233    false if we are unsuccessful.  */
3234
3235 static bool
3236 extract_range_from_cond (tree cond, tree *hi_p, tree *lo_p, int *inverted_p)
3237 {
3238   tree op1 = TREE_OPERAND (cond, 1);
3239   tree high, low, type;
3240   int inverted;
3241
3242   type = TREE_TYPE (op1);
3243
3244   /* Experiments have shown that it's rarely, if ever useful to
3245      record ranges for enumerations.  Presumably this is due to
3246      the fact that they're rarely used directly.  They are typically
3247      cast into an integer type and used that way.  */
3248   if (TREE_CODE (type) != INTEGER_TYPE
3249       /* We don't know how to deal with types with variable bounds.  */
3250       || TREE_CODE (TYPE_MIN_VALUE (type)) != INTEGER_CST
3251       || TREE_CODE (TYPE_MAX_VALUE (type)) != INTEGER_CST)
3252     return 0;
3253
3254   switch (TREE_CODE (cond))
3255     {
3256     case EQ_EXPR:
3257       high = low = op1;
3258       inverted = 0;
3259       break;
3260
3261     case NE_EXPR:
3262       high = low = op1;
3263       inverted = 1;
3264       break;
3265
3266     case GE_EXPR:
3267       low = op1;
3268       high = TYPE_MAX_VALUE (type);
3269       inverted = 0;
3270       break;
3271
3272     case GT_EXPR:
3273       high = TYPE_MAX_VALUE (type);
3274       if (!tree_int_cst_lt (op1, high))
3275         return 0;
3276       low = int_const_binop (PLUS_EXPR, op1, integer_one_node, 1);
3277       inverted = 0;
3278       break;
3279
3280     case LE_EXPR:
3281       high = op1;
3282       low = TYPE_MIN_VALUE (type);
3283       inverted = 0;
3284       break;
3285
3286     case LT_EXPR:
3287       low = TYPE_MIN_VALUE (type);
3288       if (!tree_int_cst_lt (low, op1))
3289         return 0;
3290       high = int_const_binop (MINUS_EXPR, op1, integer_one_node, 1);
3291       inverted = 0;
3292       break;
3293
3294     default:
3295       return 0;
3296     }
3297
3298   *hi_p = high;
3299   *lo_p = low;
3300   *inverted_p = inverted;
3301   return 1;
3302 }
3303
3304 /* Record a range created by COND for basic block BB.  */
3305
3306 static void
3307 record_range (tree cond, basic_block bb)
3308 {
3309   enum tree_code code = TREE_CODE (cond);
3310
3311   /* We explicitly ignore NE_EXPRs and all the unordered comparisons.
3312      They rarely allow for meaningful range optimizations and significantly
3313      complicate the implementation.  */
3314   if ((code == LT_EXPR || code == LE_EXPR || code == GT_EXPR
3315        || code == GE_EXPR || code == EQ_EXPR)
3316       && TREE_CODE (TREE_TYPE (TREE_OPERAND (cond, 1))) == INTEGER_TYPE)
3317     {
3318       struct vrp_hash_elt *vrp_hash_elt;
3319       struct vrp_element *element;
3320       varray_type *vrp_records_p;
3321       void **slot;
3322
3323
3324       vrp_hash_elt = xmalloc (sizeof (struct vrp_hash_elt));
3325       vrp_hash_elt->var = TREE_OPERAND (cond, 0);
3326       vrp_hash_elt->records = NULL;
3327       slot = htab_find_slot (vrp_data, vrp_hash_elt, INSERT);
3328
3329       if (*slot == NULL)
3330         *slot = (void *) vrp_hash_elt;
3331       else
3332         free (vrp_hash_elt);
3333
3334       vrp_hash_elt = (struct vrp_hash_elt *) *slot;
3335       vrp_records_p = &vrp_hash_elt->records;
3336
3337       element = ggc_alloc (sizeof (struct vrp_element));
3338       element->low = NULL;
3339       element->high = NULL;
3340       element->cond = cond;
3341       element->bb = bb;
3342
3343       if (*vrp_records_p == NULL)
3344         VARRAY_GENERIC_PTR_INIT (*vrp_records_p, 2, "vrp records");
3345
3346       VARRAY_PUSH_GENERIC_PTR (*vrp_records_p, element);
3347       VEC_safe_push (tree_on_heap, vrp_variables_stack, TREE_OPERAND (cond, 0));
3348     }
3349 }
3350
3351 /* Hashing and equality functions for VRP_DATA.
3352
3353    Since this hash table is addressed by SSA_NAMEs, we can hash on
3354    their version number and equality can be determined with a
3355    pointer comparison.  */
3356
3357 static hashval_t
3358 vrp_hash (const void *p)
3359 {
3360   tree var = ((struct vrp_hash_elt *)p)->var;
3361
3362   return SSA_NAME_VERSION (var);
3363 }
3364
3365 static int
3366 vrp_eq (const void *p1, const void *p2)
3367 {
3368   tree var1 = ((struct vrp_hash_elt *)p1)->var;
3369   tree var2 = ((struct vrp_hash_elt *)p2)->var;
3370
3371   return var1 == var2;
3372 }
3373
3374 /* Hashing and equality functions for AVAIL_EXPRS.  The table stores
3375    MODIFY_EXPR statements.  We compute a value number for expressions using
3376    the code of the expression and the SSA numbers of its operands.  */
3377
3378 static hashval_t
3379 avail_expr_hash (const void *p)
3380 {
3381   stmt_ann_t ann = ((struct expr_hash_elt *)p)->ann;
3382   tree rhs = ((struct expr_hash_elt *)p)->rhs;
3383   hashval_t val = 0;
3384   size_t i;
3385   vuse_optype vuses;
3386
3387   /* iterative_hash_expr knows how to deal with any expression and
3388      deals with commutative operators as well, so just use it instead
3389      of duplicating such complexities here.  */
3390   val = iterative_hash_expr (rhs, val);
3391
3392   /* If the hash table entry is not associated with a statement, then we
3393      can just hash the expression and not worry about virtual operands
3394      and such.  */
3395   if (!ann)
3396     return val;
3397
3398   /* Add the SSA version numbers of every vuse operand.  This is important
3399      because compound variables like arrays are not renamed in the
3400      operands.  Rather, the rename is done on the virtual variable
3401      representing all the elements of the array.  */
3402   vuses = VUSE_OPS (ann);
3403   for (i = 0; i < NUM_VUSES (vuses); i++)
3404     val = iterative_hash_expr (VUSE_OP (vuses, i), val);
3405
3406   return val;
3407 }
3408
3409 static hashval_t
3410 real_avail_expr_hash (const void *p)
3411 {
3412   return ((const struct expr_hash_elt *)p)->hash;
3413 }
3414
3415 static int
3416 avail_expr_eq (const void *p1, const void *p2)
3417 {
3418   stmt_ann_t ann1 = ((struct expr_hash_elt *)p1)->ann;
3419   tree rhs1 = ((struct expr_hash_elt *)p1)->rhs;
3420   stmt_ann_t ann2 = ((struct expr_hash_elt *)p2)->ann;
3421   tree rhs2 = ((struct expr_hash_elt *)p2)->rhs;
3422
3423   /* If they are the same physical expression, return true.  */
3424   if (rhs1 == rhs2 && ann1 == ann2)
3425     return true;
3426
3427   /* If their codes are not equal, then quit now.  */
3428   if (TREE_CODE (rhs1) != TREE_CODE (rhs2))
3429     return false;
3430
3431   /* In case of a collision, both RHS have to be identical and have the
3432      same VUSE operands.  */
3433   if ((TREE_TYPE (rhs1) == TREE_TYPE (rhs2)
3434        || lang_hooks.types_compatible_p (TREE_TYPE (rhs1), TREE_TYPE (rhs2)))
3435       && operand_equal_p (rhs1, rhs2, OEP_PURE_SAME))
3436     {
3437       vuse_optype ops1 = NULL;
3438       vuse_optype ops2 = NULL;
3439       size_t num_ops1 = 0;
3440       size_t num_ops2 = 0;
3441       size_t i;
3442
3443       if (ann1)
3444         {
3445           ops1 = VUSE_OPS (ann1);
3446           num_ops1 = NUM_VUSES (ops1);
3447         }
3448
3449       if (ann2)
3450         {
3451           ops2 = VUSE_OPS (ann2);
3452           num_ops2 = NUM_VUSES (ops2);
3453         }
3454
3455       /* If the number of virtual uses is different, then we consider
3456          them not equal.  */
3457       if (num_ops1 != num_ops2)
3458         return false;
3459
3460       for (i = 0; i < num_ops1; i++)
3461         if (VUSE_OP (ops1, i) != VUSE_OP (ops2, i))
3462           return false;
3463
3464       gcc_assert (((struct expr_hash_elt *)p1)->hash
3465                   == ((struct expr_hash_elt *)p2)->hash);
3466       return true;
3467     }
3468
3469   return false;
3470 }
3471
3472 /* Given STMT and a pointer to the block local definitions BLOCK_DEFS_P,
3473    register register all objects set by this statement into BLOCK_DEFS_P
3474    and CURRDEFS.  */
3475
3476 static void
3477 register_definitions_for_stmt (tree stmt)
3478 {
3479   tree def;
3480   ssa_op_iter iter;
3481
3482   FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
3483     {
3484
3485       /* FIXME: We shouldn't be registering new defs if the variable
3486          doesn't need to be renamed.  */
3487       register_new_def (def, &block_defs_stack);
3488     }
3489 }
3490