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