gcc/tree-ssa-dom.c

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