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 varray_type 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 varray_type 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 varray_type 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 varray_type 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 varray_type 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
 240 struct vrp_hash_elt
 241 {
 242   tree var;
 243   varray_type records;
 244 };
 245
 246 /* Array of variables which have their values constrained by operations
 247    in this basic block.  We use this during finalization to know
 248    which variables need their VRP data updated.  */
 249
 250 /* Stack of SSA_NAMEs which had their values constrainted by operations
 251    in this basic block.  During finalization of this block we use this
 252    list to determine which variables need their VRP data updated.
 253
 254    A NULL entry marks the end of the SSA_NAMEs associated with this block.  */
 255 static varray_type vrp_variables_stack;
 256
 257 struct eq_expr_value
 258 {
 259   tree src;
 260   tree dst;
 261 };
 262
 263 /* Local functions.  */
 264 static void optimize_stmt (struct dom_walk_data *,
 265                            basic_block bb,
 266                            block_stmt_iterator);
 267 static tree lookup_avail_expr (tree, bool);
 268 static hashval_t vrp_hash (const void *);
 269 static int vrp_eq (const void *, const void *);
 270 static hashval_t avail_expr_hash (const void *);
 271 static hashval_t real_avail_expr_hash (const void *);
 272 static int avail_expr_eq (const void *, const void *);
 273 static void htab_statistics (FILE *, htab_t);
 274 static void record_cond (tree, tree);
 275 static void record_const_or_copy (tree, tree);
 276 static void record_equality (tree, tree);
 277 static tree update_rhs_and_lookup_avail_expr (tree, tree, bool);
 278 static tree simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *,
 279                                                 tree, int);
 280 static tree simplify_cond_and_lookup_avail_expr (tree, stmt_ann_t, int);
 281 static tree simplify_switch_and_lookup_avail_expr (tree, int);
 282 static tree find_equivalent_equality_comparison (tree);
 283 static void record_range (tree, basic_block);
 284 static bool extract_range_from_cond (tree, tree *, tree *, int *);
 285 static void record_equivalences_from_phis (basic_block);
 286 static void record_equivalences_from_incoming_edge (basic_block);
 287 static bool eliminate_redundant_computations (struct dom_walk_data *,
 288                                               tree, stmt_ann_t);
 289 static void record_equivalences_from_stmt (tree, int, stmt_ann_t);
 290 static void thread_across_edge (struct dom_walk_data *, edge);
 291 static void dom_opt_finalize_block (struct dom_walk_data *, basic_block);
 292 static void dom_opt_initialize_block (struct dom_walk_data *, basic_block);
 293 static void propagate_to_outgoing_edges (struct dom_walk_data *, basic_block);
 294 static void remove_local_expressions_from_table (void);
 295 static void restore_vars_to_original_value (void);
 296 static void restore_currdefs_to_original_value (void);
 297 static void register_definitions_for_stmt (tree);
 298 static edge single_incoming_edge_ignoring_loop_edges (basic_block);
 299 static void restore_nonzero_vars_to_original_value (void);
 300 static inline bool unsafe_associative_fp_binop (tree);
 301
 302 /* Local version of fold that doesn't introduce cruft.  */
 303
 304 static tree
 305 local_fold (tree t)
 306 {
 307   t = fold (t);
 308
 309   /* Strip away useless type conversions.  Both the NON_LVALUE_EXPR that
 310      may have been added by fold, and "useless" type conversions that might
 311      now be apparent due to propagation.  */
 312   STRIP_USELESS_TYPE_CONVERSION (t);
 313
 314   return t;
 315 }
 316
 317 /* Allocate an EDGE_INFO for edge E and attach it to E.
 318    Return the new EDGE_INFO structure.  */
 319
 320 static struct edge_info *
 321 allocate_edge_info (edge e)
 322 {
 323   struct edge_info *edge_info;
 324
 325   edge_info = xcalloc (1, sizeof (struct edge_info));
 326
 327   e->aux = edge_info;
 328   return edge_info;
 329 }
 330
 331 /* Free all EDGE_INFO structures associated with edges in the CFG.
 332    If a particular edge can be threaded, copy the redirection
 333    target from the EDGE_INFO structure into the edge's AUX field
 334    as required by code to update the CFG and SSA graph for
 335    jump threading.  */
 336
 337 static void
 338 free_all_edge_infos (void)
 339 {
 340   basic_block bb;
 341   edge_iterator ei;
 342   edge e;
 343
 344   FOR_EACH_BB (bb)
 345     {
 346       FOR_EACH_EDGE (e, ei, bb->preds)
 347         {
 348          struct edge_info *edge_info = e->aux;
 349
 350           if (edge_info)
 351             {
 352               e->aux = edge_info->redirection_target;
 353               if (edge_info->cond_equivalences)
 354                 free (edge_info->cond_equivalences);
 355               free (edge_info);
 356             }
 357         }
 358     }
 359 }
 360
 361 /* Jump threading, redundancy elimination and const/copy propagation.
 362
 363    This pass may expose new symbols that need to be renamed into SSA.  For
 364    every new symbol exposed, its corresponding bit will be set in
 365    VARS_TO_RENAME.  */
 366
 367 static void
 368 tree_ssa_dominator_optimize (void)
 369 {
 370   struct dom_walk_data walk_data;
 371   unsigned int i;
 372
 373   memset (&opt_stats, 0, sizeof (opt_stats));
 374
 375   for (i = 0; i < num_referenced_vars; i++)
 376     var_ann (referenced_var (i))->current_def = NULL;
 377
 378   /* Mark loop edges so we avoid threading across loop boundaries.
 379      This may result in transforming natural loop into irreducible
 380      region.  */
 381   mark_dfs_back_edges ();
 382
 383   /* Create our hash tables.  */
 384   avail_exprs = htab_create (1024, real_avail_expr_hash, avail_expr_eq, free);
 385   vrp_data = htab_create (ceil_log2 (num_ssa_names), vrp_hash, vrp_eq, free);
 386   VARRAY_TREE_INIT (avail_exprs_stack, 20, "Available expression stack");
 387   VARRAY_TREE_INIT (block_defs_stack, 20, "Block DEFS stack");
 388   VARRAY_TREE_INIT (const_and_copies_stack, 20, "Block const_and_copies stack");
 389   VARRAY_TREE_INIT (nonzero_vars_stack, 20, "Block nonzero_vars stack");
 390   VARRAY_TREE_INIT (vrp_variables_stack, 20, "Block vrp_variables stack");
 391   VARRAY_TREE_INIT (stmts_to_rescan, 20, "Statements to rescan");
 392   nonzero_vars = BITMAP_XMALLOC ();
 393   need_eh_cleanup = BITMAP_XMALLOC ();
 394
 395   /* Setup callbacks for the generic dominator tree walker.  */
 396   walk_data.walk_stmts_backward = false;
 397   walk_data.dom_direction = CDI_DOMINATORS;
 398   walk_data.initialize_block_local_data = NULL;
 399   walk_data.before_dom_children_before_stmts = dom_opt_initialize_block;
 400   walk_data.before_dom_children_walk_stmts = optimize_stmt;
 401   walk_data.before_dom_children_after_stmts = propagate_to_outgoing_edges;
 402   walk_data.after_dom_children_before_stmts = NULL;
 403   walk_data.after_dom_children_walk_stmts = NULL;
 404   walk_data.after_dom_children_after_stmts = dom_opt_finalize_block;
 405   /* Right now we only attach a dummy COND_EXPR to the global data pointer.
 406      When we attach more stuff we'll need to fill this out with a real
 407      structure.  */
 408   walk_data.global_data = NULL;
 409   walk_data.block_local_data_size = 0;
 410
 411   /* Now initialize the dominator walker.  */
 412   init_walk_dominator_tree (&walk_data);
 413
 414   calculate_dominance_info (CDI_DOMINATORS);
 415
 416   /* If we prove certain blocks are unreachable, then we want to
 417      repeat the dominator optimization process as PHI nodes may
 418      have turned into copies which allows better propagation of
 419      values.  So we repeat until we do not identify any new unreachable
 420      blocks.  */
 421   do
 422     {
 423       /* Optimize the dominator tree.  */
 424       cfg_altered = false;
 425
 426       /* Recursively walk the dominator tree optimizing statements.  */
 427       walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
 428
 429       /* If we exposed any new variables, go ahead and put them into
 430          SSA form now, before we handle jump threading.  This simplifies
 431          interactions between rewriting of _DECL nodes into SSA form
 432          and rewriting SSA_NAME nodes into SSA form after block
 433          duplication and CFG manipulation.  */
 434       if (!bitmap_empty_p (vars_to_rename))
 435         {
 436           rewrite_into_ssa (false);
 437           bitmap_clear (vars_to_rename);
 438         }
 439
 440       free_all_edge_infos ();
 441
 442       /* Thread jumps, creating duplicate blocks as needed.  */
 443       cfg_altered = thread_through_all_blocks ();
 444
 445       /* Removal of statements may make some EH edges dead.  Purge
 446          such edges from the CFG as needed.  */
 447       if (!bitmap_empty_p (need_eh_cleanup))
 448         {
 449           cfg_altered |= tree_purge_all_dead_eh_edges (need_eh_cleanup);
 450           bitmap_zero (need_eh_cleanup);
 451         }
 452
 453       free_dominance_info (CDI_DOMINATORS);
 454       cfg_altered = cleanup_tree_cfg ();
 455       calculate_dominance_info (CDI_DOMINATORS);
 456
 457       rewrite_ssa_into_ssa ();
 458
 459       /* Reinitialize the various tables.  */
 460       bitmap_clear (nonzero_vars);
 461       htab_empty (avail_exprs);
 462       htab_empty (vrp_data);
 463
 464       for (i = 0; i < num_referenced_vars; i++)
 465         var_ann (referenced_var (i))->current_def = NULL;
 466     }
 467   while (cfg_altered);
 468
 469   /* Debugging dumps.  */
 470   if (dump_file && (dump_flags & TDF_STATS))
 471     dump_dominator_optimization_stats (dump_file);
 472
 473   /* We emptied the hash table earlier, now delete it completely.  */
 474   htab_delete (avail_exprs);
 475   htab_delete (vrp_data);
 476
 477   /* It is not necessary to clear CURRDEFS, REDIRECTION_EDGES, VRP_DATA,
 478      CONST_AND_COPIES, and NONZERO_VARS as they all get cleared at the bottom
 479      of the do-while loop above.  */
 480
 481   /* And finalize the dominator walker.  */
 482   fini_walk_dominator_tree (&walk_data);
 483
 484   /* Free nonzero_vars.  */
 485   BITMAP_XFREE (nonzero_vars);
 486   BITMAP_XFREE (need_eh_cleanup);
 487
 488   /* Finally, remove everything except invariants in SSA_NAME_VALUE.
 489
 490      Long term we will be able to let everything in SSA_NAME_VALUE
 491      persist.  However, for now, we know this is the safe thing to
 492      do.  */
 493   for (i = 0; i < num_ssa_names; i++)
 494     {
 495       tree name = ssa_name (i);
 496       tree value;
 497
 498       if (!name)
 499         continue;
 500
 501       value = SSA_NAME_VALUE (name);
 502       if (value && !is_gimple_min_invariant (value))
 503         SSA_NAME_VALUE (name) = NULL;
 504     }
 505 }
 506
 507 static bool
 508 gate_dominator (void)
 509 {
 510   return flag_tree_dom != 0;
 511 }
 512
 513 struct tree_opt_pass pass_dominator =
 514 {
 515   "dom",                                /* name */
 516   gate_dominator,                       /* gate */
 517   tree_ssa_dominator_optimize,          /* execute */
 518   NULL,                                 /* sub */
 519   NULL,                                 /* next */
 520   0,                                    /* static_pass_number */
 521   TV_TREE_SSA_DOMINATOR_OPTS,           /* tv_id */
 522   PROP_cfg | PROP_ssa | PROP_alias,     /* properties_required */
 523   0,                                    /* properties_provided */
 524   0,                                    /* properties_destroyed */
 525   0,                                    /* todo_flags_start */
 526   TODO_dump_func | TODO_rename_vars
 527     | TODO_verify_ssa,                  /* todo_flags_finish */
 528   0                                     /* letter */
 529 };
 530
 531
 532 /* We are exiting BB, see if the target block begins with a conditional
 533    jump which has a known value when reached via BB.  */
 534
 535 static void
 536 thread_across_edge (struct dom_walk_data *walk_data, edge e)
 537 {
 538   block_stmt_iterator bsi;
 539   tree stmt = NULL;
 540   tree phi;
 541
 542   /* Each PHI creates a temporary equivalence, record them.  */
 543   for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
 544     {
 545       tree src = PHI_ARG_DEF_FROM_EDGE (phi, e);
 546       tree dst = PHI_RESULT (phi);
 547       record_const_or_copy (dst, src);
 548       register_new_def (dst, &block_defs_stack);
 549     }
 550
 551   for (bsi = bsi_start (e->dest); ! bsi_end_p (bsi); bsi_next (&bsi))
 552     {
 553       tree lhs, cached_lhs;
 554
 555       stmt = bsi_stmt (bsi);
 556
 557       /* Ignore empty statements and labels.  */
 558       if (IS_EMPTY_STMT (stmt) || TREE_CODE (stmt) == LABEL_EXPR)
 559         continue;
 560
 561       /* If this is not a MODIFY_EXPR which sets an SSA_NAME to a new
 562          value, then stop our search here.  Ideally when we stop a
 563          search we stop on a COND_EXPR or SWITCH_EXPR.  */
 564       if (TREE_CODE (stmt) != MODIFY_EXPR
 565           || TREE_CODE (TREE_OPERAND (stmt, 0)) != SSA_NAME)
 566         break;
 567
 568       /* At this point we have a statement which assigns an RHS to an
 569          SSA_VAR on the LHS.  We want to prove that the RHS is already
 570          available and that its value is held in the current definition
 571          of the LHS -- meaning that this assignment is a NOP when
 572          reached via edge E.  */
 573       if (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME)
 574         cached_lhs = TREE_OPERAND (stmt, 1);
 575       else
 576         cached_lhs = lookup_avail_expr (stmt, false);
 577
 578       lhs = TREE_OPERAND (stmt, 0);
 579
 580       /* This can happen if we thread around to the start of a loop.  */
 581       if (lhs == cached_lhs)
 582         break;
 583
 584       /* If we did not find RHS in the hash table, then try again after
 585          temporarily const/copy propagating the operands.  */
 586       if (!cached_lhs)
 587         {
 588           /* Copy the operands.  */
 589           stmt_ann_t ann = stmt_ann (stmt);
 590           use_optype uses = USE_OPS (ann);
 591           vuse_optype vuses = VUSE_OPS (ann);
 592           tree *uses_copy = xcalloc (NUM_USES (uses),  sizeof (tree));
 593           tree *vuses_copy = xcalloc (NUM_VUSES (vuses), sizeof (tree));
 594           unsigned int i;
 595
 596           /* Make a copy of the uses into USES_COPY, then cprop into
 597              the use operands.  */
 598           for (i = 0; i < NUM_USES (uses); i++)
 599             {
 600               tree tmp = NULL;
 601
 602               uses_copy[i] = USE_OP (uses, i);
 603               if (TREE_CODE (USE_OP (uses, i)) == SSA_NAME)
 604                 tmp = SSA_NAME_VALUE (USE_OP (uses, i));
 605               if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
 606                 SET_USE_OP (uses, i, tmp);
 607             }
 608
 609           /* Similarly for virtual uses.  */
 610           for (i = 0; i < NUM_VUSES (vuses); i++)
 611             {
 612               tree tmp = NULL;
 613
 614               vuses_copy[i] = VUSE_OP (vuses, i);
 615               if (TREE_CODE (VUSE_OP (vuses, i)) == SSA_NAME)
 616                 tmp = SSA_NAME_VALUE (VUSE_OP (vuses, i));
 617               if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
 618                 SET_VUSE_OP (vuses, i, tmp);
 619             }
 620
 621           /* Try to lookup the new expression.  */
 622           cached_lhs = lookup_avail_expr (stmt, false);
 623
 624           /* Restore the statement's original uses/defs.  */
 625           for (i = 0; i < NUM_USES (uses); i++)
 626             SET_USE_OP (uses, i, uses_copy[i]);
 627
 628           for (i = 0; i < NUM_VUSES (vuses); i++)
 629             SET_VUSE_OP (vuses, i, vuses_copy[i]);
 630
 631           free (uses_copy);
 632           free (vuses_copy);
 633
 634           /* If we still did not find the expression in the hash table,
 635              then we can not ignore this statement.  */
 636           if (! cached_lhs)
 637             break;
 638         }
 639
 640       /* If the expression in the hash table was not assigned to an
 641          SSA_NAME, then we can not ignore this statement.  */
 642       if (TREE_CODE (cached_lhs) != SSA_NAME)
 643         break;
 644
 645       /* If we have different underlying variables, then we can not
 646          ignore this statement.  */
 647       if (SSA_NAME_VAR (cached_lhs) != SSA_NAME_VAR (lhs))
 648         break;
 649
 650       /* If CACHED_LHS does not represent the current value of the undering
 651          variable in CACHED_LHS/LHS, then we can not ignore this statement.  */
 652       if (var_ann (SSA_NAME_VAR (lhs))->current_def != cached_lhs)
 653         break;
 654
 655       /* If we got here, then we can ignore this statement and continue
 656          walking through the statements in the block looking for a threadable
 657          COND_EXPR.
 658
 659          We want to record an equivalence lhs = cache_lhs so that if
 660          the result of this statement is used later we can copy propagate
 661          suitably.  */
 662       record_const_or_copy (lhs, cached_lhs);
 663       register_new_def (lhs, &block_defs_stack);
 664     }
 665
 666   /* If we stopped at a COND_EXPR or SWITCH_EXPR, then see if we know which
 667      arm will be taken.  */
 668   if (stmt
 669       && (TREE_CODE (stmt) == COND_EXPR
 670           || TREE_CODE (stmt) == SWITCH_EXPR))
 671     {
 672       tree cond, cached_lhs;
 673       edge e1;
 674       edge_iterator ei;
 675
 676       /* Do not forward entry edges into the loop.  In the case loop
 677          has multiple entry edges we may end up in constructing irreducible
 678          region.
 679          ??? We may consider forwarding the edges in the case all incoming
 680          edges forward to the same destination block.  */
 681       if (!e->flags & EDGE_DFS_BACK)
 682         {
 683           FOR_EACH_EDGE (e1, ei, e->dest->preds)
 684             if (e1->flags & EDGE_DFS_BACK)
 685               break;
 686           if (e1)
 687             return;
 688         }
 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 (TREE_OPERAND (dummy_cond, 0), cond_code);
 734               TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 0) = op0;
 735               TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 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             cached_lhs = lookup_avail_expr (dummy_cond, false);
 743           if (!cached_lhs || ! is_gimple_min_invariant (cached_lhs))
 744             {
 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   VARRAY_PUSH_TREE (avail_exprs_stack, NULL_TREE);
 807   VARRAY_PUSH_TREE (block_defs_stack, NULL_TREE);
 808   VARRAY_PUSH_TREE (const_and_copies_stack, NULL_TREE);
 809   VARRAY_PUSH_TREE (nonzero_vars_stack, NULL_TREE);
 810   VARRAY_PUSH_TREE (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 (VARRAY_ACTIVE_SIZE (avail_exprs_stack) > 0)
 867     {
 868       struct expr_hash_elt element;
 869       tree expr = VARRAY_TOP_TREE (avail_exprs_stack);
 870       VARRAY_POP (avail_exprs_stack);
 871
 872       if (expr == NULL_TREE)
 873         break;
 874
 875       initialize_hash_element (expr, NULL, &element);
 876       htab_remove_elt_with_hash (avail_exprs, &element, element.hash);
 877     }
 878 }
 879
 880 /* Use the SSA_NAMES in LOCALS to restore TABLE to its original
 881    state, stopping when there are LIMIT entries left in LOCALs.  */
 882
 883 static void
 884 restore_nonzero_vars_to_original_value (void)
 885 {
 886   while (VARRAY_ACTIVE_SIZE (nonzero_vars_stack) > 0)
 887     {
 888       tree name = VARRAY_TOP_TREE (nonzero_vars_stack);
 889       VARRAY_POP (nonzero_vars_stack);
 890
 891       if (name == NULL)
 892         break;
 893
 894       bitmap_clear_bit (nonzero_vars, SSA_NAME_VERSION (name));
 895     }
 896 }
 897
 898 /* Use the source/dest pairs in CONST_AND_COPIES_STACK to restore
 899    CONST_AND_COPIES to its original state, stopping when we hit a
 900    NULL marker.  */
 901
 902 static void
 903 restore_vars_to_original_value (void)
 904 {
 905   while (VARRAY_ACTIVE_SIZE (const_and_copies_stack) > 0)
 906     {
 907       tree prev_value, dest;
 908
 909       dest = VARRAY_TOP_TREE (const_and_copies_stack);
 910       VARRAY_POP (const_and_copies_stack);
 911
 912       if (dest == NULL)
 913         break;
 914
 915       prev_value = VARRAY_TOP_TREE (const_and_copies_stack);
 916       VARRAY_POP (const_and_copies_stack);
 917
 918       SSA_NAME_VALUE (dest) =  prev_value;
 919     }
 920 }
 921
 922 /* Similar to restore_vars_to_original_value, except that it restores
 923    CURRDEFS to its original value.  */
 924 static void
 925 restore_currdefs_to_original_value (void)
 926 {
 927   /* Restore CURRDEFS to its original state.  */
 928   while (VARRAY_ACTIVE_SIZE (block_defs_stack) > 0)
 929     {
 930       tree tmp = VARRAY_TOP_TREE (block_defs_stack);
 931       tree saved_def, var;
 932
 933       VARRAY_POP (block_defs_stack);
 934
 935       if (tmp == NULL_TREE)
 936         break;
 937
 938       /* If we recorded an SSA_NAME, then make the SSA_NAME the current
 939          definition of its underlying variable.  If we recorded anything
 940          else, it must have been an _DECL node and its current reaching
 941          definition must have been NULL.  */
 942       if (TREE_CODE (tmp) == SSA_NAME)
 943         {
 944           saved_def = tmp;
 945           var = SSA_NAME_VAR (saved_def);
 946         }
 947       else
 948         {
 949           saved_def = NULL;
 950           var = tmp;
 951         }
 952
 953       var_ann (var)->current_def = saved_def;
 954     }
 955 }
 956
 957 /* We have finished processing the dominator children of BB, perform
 958    any finalization actions in preparation for leaving this node in
 959    the dominator tree.  */
 960
 961 static void
 962 dom_opt_finalize_block (struct dom_walk_data *walk_data, basic_block bb)
 963 {
 964   tree last;
 965
 966   /* If we are at a leaf node in the dominator graph, see if we can thread
 967      the edge from BB through its successor.
 968
 969      Do this before we remove entries from our equivalence tables.  */
 970   if (EDGE_COUNT (bb->succs) == 1
 971       && (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL) == 0
 972       && (get_immediate_dominator (CDI_DOMINATORS, EDGE_SUCC (bb, 0)->dest) != bb
 973           || phi_nodes (EDGE_SUCC (bb, 0)->dest)))
 974
 975     {
 976       thread_across_edge (walk_data, EDGE_SUCC (bb, 0));
 977     }
 978   else if ((last = last_stmt (bb))
 979            && TREE_CODE (last) == COND_EXPR
 980            && (COMPARISON_CLASS_P (COND_EXPR_COND (last))
 981                || TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME)
 982            && EDGE_COUNT (bb->succs) == 2
 983            && (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL) == 0
 984            && (EDGE_SUCC (bb, 1)->flags & EDGE_ABNORMAL) == 0)
 985     {
 986       edge true_edge, false_edge;
 987
 988       extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
 989
 990       /* If the THEN arm is the end of a dominator tree or has PHI nodes,
 991          then try to thread through its edge.  */
 992       if (get_immediate_dominator (CDI_DOMINATORS, true_edge->dest) != bb
 993           || phi_nodes (true_edge->dest))
 994         {
 995           struct edge_info *edge_info;
 996           unsigned int i;
 997
 998           /* Push a marker onto the available expression stack so that we
 999              unwind any expressions related to the TRUE arm before processing
1000              the false arm below.  */
1001           VARRAY_PUSH_TREE (avail_exprs_stack, NULL_TREE);
1002           VARRAY_PUSH_TREE (block_defs_stack, NULL_TREE);
1003           VARRAY_PUSH_TREE (const_and_copies_stack, NULL_TREE);
1004
1005           edge_info = true_edge->aux;
1006
1007           /* If we have info associated with this edge, record it into
1008              our equivalency tables.  */
1009           if (edge_info)
1010             {
1011               tree *cond_equivalences = edge_info->cond_equivalences;
1012               tree lhs = edge_info->lhs;
1013               tree rhs = edge_info->rhs;
1014
1015               /* If we have a simple NAME = VALUE equivalency record it.
1016                  Until the jump threading selection code improves, only
1017                  do this if both the name and value are SSA_NAMEs with
1018                  the same underlying variable to avoid missing threading
1019                  opportunities.  */
1020               if (lhs
1021                   && TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME
1022                   && TREE_CODE (edge_info->rhs) == SSA_NAME
1023                   && SSA_NAME_VAR (lhs) == SSA_NAME_VAR (rhs))
1024                 record_const_or_copy (lhs, rhs);
1025
1026               /* If we have 0 = COND or 1 = COND equivalences, record them
1027                  into our expression hash tables.  */
1028               if (cond_equivalences)
1029                 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1030                   {
1031                     tree expr = cond_equivalences[i];
1032                     tree value = cond_equivalences[i + 1];
1033
1034                     record_cond (expr, value);
1035                   }
1036             }
1037
1038           /* Now thread the edge.  */
1039           thread_across_edge (walk_data, true_edge);
1040
1041           /* And restore the various tables to their state before
1042              we threaded this edge.  */
1043           remove_local_expressions_from_table ();
1044           restore_vars_to_original_value ();
1045           restore_currdefs_to_original_value ();
1046         }
1047
1048       /* Similarly for the ELSE arm.  */
1049       if (get_immediate_dominator (CDI_DOMINATORS, false_edge->dest) != bb
1050           || phi_nodes (false_edge->dest))
1051         {
1052           struct edge_info *edge_info;
1053           unsigned int i;
1054
1055           edge_info = false_edge->aux;
1056
1057           /* If we have info associated with this edge, record it into
1058              our equivalency tables.  */
1059           if (edge_info)
1060             {
1061               tree *cond_equivalences = edge_info->cond_equivalences;
1062               tree lhs = edge_info->lhs;
1063               tree rhs = edge_info->rhs;
1064
1065               /* If we have a simple NAME = VALUE equivalency record it.
1066                  Until the jump threading selection code improves, only
1067                  do this if both the name and value are SSA_NAMEs with
1068                  the same underlying variable to avoid missing threading
1069                  opportunities.  */
1070               if (lhs
1071                   && TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME)
1072                 record_const_or_copy (lhs, rhs);
1073
1074               /* If we have 0 = COND or 1 = COND equivalences, record them
1075                  into our expression hash tables.  */
1076               if (cond_equivalences)
1077                 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1078                   {
1079                     tree expr = cond_equivalences[i];
1080                     tree value = cond_equivalences[i + 1];
1081
1082                     record_cond (expr, value);
1083                   }
1084             }
1085
1086           thread_across_edge (walk_data, false_edge);
1087
1088           /* No need to remove local expressions from our tables
1089              or restore vars to their original value as that will
1090              be done immediately below.  */
1091         }
1092     }
1093
1094   remove_local_expressions_from_table ();
1095   restore_nonzero_vars_to_original_value ();
1096   restore_vars_to_original_value ();
1097   restore_currdefs_to_original_value ();
1098
1099   /* Remove VRP records associated with this basic block.  They are no
1100      longer valid.
1101
1102      To be efficient, we note which variables have had their values
1103      constrained in this block.  So walk over each variable in the
1104      VRP_VARIABLEs array.  */
1105   while (VARRAY_ACTIVE_SIZE (vrp_variables_stack) > 0)
1106     {
1107       tree var = VARRAY_TOP_TREE (vrp_variables_stack);
1108       struct vrp_hash_elt vrp_hash_elt, *vrp_hash_elt_p;
1109       void **slot;
1110
1111       /* Each variable has a stack of value range records.  We want to
1112          invalidate those associated with our basic block.  So we walk
1113          the array backwards popping off records associated with our
1114          block.  Once we hit a record not associated with our block
1115          we are done.  */
1116       varray_type var_vrp_records;
1117
1118       VARRAY_POP (vrp_variables_stack);
1119
1120       if (var == NULL)
1121         break;
1122
1123       vrp_hash_elt.var = var;
1124       vrp_hash_elt.records = NULL;
1125
1126       slot = htab_find_slot (vrp_data, &vrp_hash_elt, NO_INSERT);
1127
1128       vrp_hash_elt_p = (struct vrp_hash_elt *) *slot;
1129       var_vrp_records = vrp_hash_elt_p->records;
1130
1131       while (VARRAY_ACTIVE_SIZE (var_vrp_records) > 0)
1132         {
1133           struct vrp_element *element
1134             = (struct vrp_element *)VARRAY_TOP_GENERIC_PTR (var_vrp_records);
1135
1136           if (element->bb != bb)
1137             break;
1138
1139           VARRAY_POP (var_vrp_records);
1140         }
1141     }
1142
1143   /* If we queued any statements to rescan in this block, then
1144      go ahead and rescan them now.  */
1145   while (VARRAY_ACTIVE_SIZE (stmts_to_rescan) > 0)
1146     {
1147       tree stmt = VARRAY_TOP_TREE (stmts_to_rescan);
1148       basic_block stmt_bb = bb_for_stmt (stmt);
1149
1150       if (stmt_bb != bb)
1151         break;
1152
1153       VARRAY_POP (stmts_to_rescan);
1154       mark_new_vars_to_rename (stmt, vars_to_rename);
1155     }
1156 }
1157
1158 /* PHI nodes can create equivalences too.
1159
1160    Ignoring any alternatives which are the same as the result, if
1161    all the alternatives are equal, then the PHI node creates an
1162    equivalence.
1163
1164    Additionally, if all the PHI alternatives are known to have a nonzero
1165    value, then the result of this PHI is known to have a nonzero value,
1166    even if we do not know its exact value.  */
1167
1168 static void
1169 record_equivalences_from_phis (basic_block bb)
1170 {
1171   tree phi;
1172
1173   for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1174     {
1175       tree lhs = PHI_RESULT (phi);
1176       tree rhs = NULL;
1177       int i;
1178
1179       for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1180         {
1181           tree t = PHI_ARG_DEF (phi, i);
1182
1183           if (TREE_CODE (t) == SSA_NAME || is_gimple_min_invariant (t))
1184             {
1185               /* Ignore alternatives which are the same as our LHS.  */
1186               if (operand_equal_p (lhs, t, 0))
1187                 continue;
1188
1189               /* If we have not processed an alternative yet, then set
1190                  RHS to this alternative.  */
1191               if (rhs == NULL)
1192                 rhs = t;
1193               /* If we have processed an alternative (stored in RHS), then
1194                  see if it is equal to this one.  If it isn't, then stop
1195                  the search.  */
1196               else if (! operand_equal_p (rhs, t, 0))
1197                 break;
1198             }
1199           else
1200             break;
1201         }
1202
1203       /* If we had no interesting alternatives, then all the RHS alternatives
1204          must have been the same as LHS.  */
1205       if (!rhs)
1206         rhs = lhs;
1207
1208       /* If we managed to iterate through each PHI alternative without
1209          breaking out of the loop, then we have a PHI which may create
1210          a useful equivalence.  We do not need to record unwind data for
1211          this, since this is a true assignment and not an equivalence
1212          inferred from a comparison.  All uses of this ssa name are dominated
1213          by this assignment, so unwinding just costs time and space.  */
1214       if (i == PHI_NUM_ARGS (phi)
1215           && may_propagate_copy (lhs, rhs))
1216         SSA_NAME_VALUE (lhs) = rhs;
1217
1218       /* Now see if we know anything about the nonzero property for the
1219          result of this PHI.  */
1220       for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1221         {
1222           if (!PHI_ARG_NONZERO (phi, i))
1223             break;
1224         }
1225
1226       if (i == PHI_NUM_ARGS (phi))
1227         bitmap_set_bit (nonzero_vars, SSA_NAME_VERSION (PHI_RESULT (phi)));
1228
1229       register_new_def (lhs, &block_defs_stack);
1230     }
1231 }
1232
1233 /* Ignoring loop backedges, if BB has precisely one incoming edge then
1234    return that edge.  Otherwise return NULL.  */
1235 static edge
1236 single_incoming_edge_ignoring_loop_edges (basic_block bb)
1237 {
1238   edge retval = NULL;
1239   edge e;
1240   edge_iterator ei;
1241
1242   FOR_EACH_EDGE (e, ei, bb->preds)
1243     {
1244       /* A loop back edge can be identified by the destination of
1245          the edge dominating the source of the edge.  */
1246       if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
1247         continue;
1248
1249       /* If we have already seen a non-loop edge, then we must have
1250          multiple incoming non-loop edges and thus we return NULL.  */
1251       if (retval)
1252         return NULL;
1253
1254       /* This is the first non-loop incoming edge we have found.  Record
1255          it.  */
1256       retval = e;
1257     }
1258
1259   return retval;
1260 }
1261
1262 /* Record any equivalences created by the incoming edge to BB.  If BB
1263    has more than one incoming edge, then no equivalence is created.  */
1264
1265 static void
1266 record_equivalences_from_incoming_edge (basic_block bb)
1267 {
1268   edge e;
1269   basic_block parent;
1270   struct edge_info *edge_info;
1271
1272   /* If our parent block ended with a control statment, then we may be
1273      able to record some equivalences based on which outgoing edge from
1274      the parent was followed.  */
1275   parent = get_immediate_dominator (CDI_DOMINATORS, bb);
1276
1277   e = single_incoming_edge_ignoring_loop_edges (bb);
1278
1279   /* If we had a single incoming edge from our parent block, then enter
1280      any data associated with the edge into our tables.  */
1281   if (e && e->src == parent)
1282     {
1283       unsigned int i;
1284
1285       edge_info = e->aux;
1286
1287       if (edge_info)
1288         {
1289           tree lhs = edge_info->lhs;
1290           tree rhs = edge_info->rhs;
1291           tree *cond_equivalences = edge_info->cond_equivalences;
1292
1293           if (lhs)
1294             record_equality (lhs, rhs);
1295
1296           if (cond_equivalences)
1297             {
1298               bool recorded_range = false;
1299               for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1300                 {
1301                   tree expr = cond_equivalences[i];
1302                   tree value = cond_equivalences[i + 1];
1303
1304                   record_cond (expr, value);
1305
1306                   /* For the first true equivalence, record range
1307                      information.  We only do this for the first
1308                      true equivalence as it should dominate any
1309                      later true equivalences.  */
1310                   if (! recorded_range
1311                       && COMPARISON_CLASS_P (expr)
1312                       && value == boolean_true_node
1313                       && TREE_CONSTANT (TREE_OPERAND (expr, 1)))
1314                     {
1315                       record_range (expr, bb);
1316                       recorded_range = true;
1317                     }
1318                 }
1319             }
1320         }
1321     }
1322 }
1323
1324 /* Dump SSA statistics on FILE.  */
1325
1326 void
1327 dump_dominator_optimization_stats (FILE *file)
1328 {
1329   long n_exprs;
1330
1331   fprintf (file, "Total number of statements:                   %6ld\n\n",
1332            opt_stats.num_stmts);
1333   fprintf (file, "Exprs considered for dominator optimizations: %6ld\n",
1334            opt_stats.num_exprs_considered);
1335
1336   n_exprs = opt_stats.num_exprs_considered;
1337   if (n_exprs == 0)
1338     n_exprs = 1;
1339
1340   fprintf (file, "    Redundant expressions eliminated:         %6ld (%.0f%%)\n",
1341            opt_stats.num_re, PERCENT (opt_stats.num_re,
1342                                       n_exprs));
1343
1344   fprintf (file, "\nHash table statistics:\n");
1345
1346   fprintf (file, "    avail_exprs: ");
1347   htab_statistics (file, avail_exprs);
1348 }
1349
1350
1351 /* Dump SSA statistics on stderr.  */
1352
1353 void
1354 debug_dominator_optimization_stats (void)
1355 {
1356   dump_dominator_optimization_stats (stderr);
1357 }
1358
1359
1360 /* Dump statistics for the hash table HTAB.  */
1361
1362 static void
1363 htab_statistics (FILE *file, htab_t htab)
1364 {
1365   fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
1366            (long) htab_size (htab),
1367            (long) htab_elements (htab),
1368            htab_collisions (htab));
1369 }
1370
1371 /* Record the fact that VAR has a nonzero value, though we may not know
1372    its exact value.  Note that if VAR is already known to have a nonzero
1373    value, then we do nothing.  */
1374
1375 static void
1376 record_var_is_nonzero (tree var)
1377 {
1378   int indx = SSA_NAME_VERSION (var);
1379
1380   if (bitmap_bit_p (nonzero_vars, indx))
1381     return;
1382
1383   /* Mark it in the global table.  */
1384   bitmap_set_bit (nonzero_vars, indx);
1385
1386   /* Record this SSA_NAME so that we can reset the global table
1387      when we leave this block.  */
1388   VARRAY_PUSH_TREE (nonzero_vars_stack, var);
1389 }
1390
1391 /* Enter a statement into the true/false expression hash table indicating
1392    that the condition COND has the value VALUE.  */
1393
1394 static void
1395 record_cond (tree cond, tree value)
1396 {
1397   struct expr_hash_elt *element = xmalloc (sizeof (struct expr_hash_elt));
1398   void **slot;
1399
1400   initialize_hash_element (cond, value, element);
1401
1402   slot = htab_find_slot_with_hash (avail_exprs, (void *)element,
1403                                    element->hash, true);
1404   if (*slot == NULL)
1405     {
1406       *slot = (void *) element;
1407       VARRAY_PUSH_TREE (avail_exprs_stack, cond);
1408     }
1409   else
1410     free (element);
1411 }
1412
1413 /* Build a new conditional using NEW_CODE, OP0 and OP1 and store
1414    the new conditional into *p, then store a boolean_true_node
1415    into the the *(p + 1).  */
1416
1417 static void
1418 build_and_record_new_cond (enum tree_code new_code, tree op0, tree op1, tree *p)
1419 {
1420   *p = build2 (new_code, boolean_type_node, op0, op1);
1421   p++;
1422   *p = boolean_true_node;
1423 }
1424
1425 /* Record that COND is true and INVERTED is false into the edge information
1426    structure.  Also record that any conditions dominated by COND are true
1427    as well.
1428
1429    For example, if a < b is true, then a <= b must also be true.  */
1430
1431 static void
1432 record_conditions (struct edge_info *edge_info, tree cond, tree inverted)
1433 {
1434   tree op0, op1;
1435
1436   if (!COMPARISON_CLASS_P (cond))
1437     return;
1438
1439   op0 = TREE_OPERAND (cond, 0);
1440   op1 = TREE_OPERAND (cond, 1);
1441
1442   switch (TREE_CODE (cond))
1443     {
1444     case LT_EXPR:
1445     case GT_EXPR:
1446       edge_info->max_cond_equivalences = 12;
1447       edge_info->cond_equivalences = xmalloc (12 * sizeof (tree));
1448       build_and_record_new_cond ((TREE_CODE (cond) == LT_EXPR
1449                                   ? LE_EXPR : GE_EXPR),
1450                                  op0, op1, &edge_info->cond_equivalences[4]);
1451       build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1452                                  &edge_info->cond_equivalences[6]);
1453       build_and_record_new_cond (NE_EXPR, op0, op1,
1454                                  &edge_info->cond_equivalences[8]);
1455       build_and_record_new_cond (LTGT_EXPR, op0, op1,
1456                                  &edge_info->cond_equivalences[10]);
1457       break;
1458
1459     case GE_EXPR:
1460     case LE_EXPR:
1461       edge_info->max_cond_equivalences = 6;
1462       edge_info->cond_equivalences = xmalloc (6 * sizeof (tree));
1463       build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1464                                  &edge_info->cond_equivalences[4]);
1465       break;
1466
1467     case EQ_EXPR:
1468       edge_info->max_cond_equivalences = 10;
1469       edge_info->cond_equivalences = xmalloc (10 * sizeof (tree));
1470       build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1471                                  &edge_info->cond_equivalences[4]);
1472       build_and_record_new_cond (LE_EXPR, op0, op1,
1473                                  &edge_info->cond_equivalences[6]);
1474       build_and_record_new_cond (GE_EXPR, op0, op1,
1475                                  &edge_info->cond_equivalences[8]);
1476       break;
1477
1478     case UNORDERED_EXPR:
1479       edge_info->max_cond_equivalences = 16;
1480       edge_info->cond_equivalences = xmalloc (16 * sizeof (tree));
1481       build_and_record_new_cond (NE_EXPR, op0, op1,
1482                                  &edge_info->cond_equivalences[4]);
1483       build_and_record_new_cond (UNLE_EXPR, op0, op1,
1484                                  &edge_info->cond_equivalences[6]);
1485       build_and_record_new_cond (UNGE_EXPR, op0, op1,
1486                                  &edge_info->cond_equivalences[8]);
1487       build_and_record_new_cond (UNEQ_EXPR, op0, op1,
1488                                  &edge_info->cond_equivalences[10]);
1489       build_and_record_new_cond (UNLT_EXPR, op0, op1,
1490                                  &edge_info->cond_equivalences[12]);
1491       build_and_record_new_cond (UNGT_EXPR, op0, op1,
1492                                  &edge_info->cond_equivalences[14]);
1493       break;
1494
1495     case UNLT_EXPR:
1496     case UNGT_EXPR:
1497       edge_info->max_cond_equivalences = 8;
1498       edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1499       build_and_record_new_cond ((TREE_CODE (cond) == UNLT_EXPR
1500                                   ? UNLE_EXPR : UNGE_EXPR),
1501                                  op0, op1, &edge_info->cond_equivalences[4]);
1502       build_and_record_new_cond (NE_EXPR, op0, op1,
1503                                  &edge_info->cond_equivalences[6]);
1504       break;
1505
1506     case UNEQ_EXPR:
1507       edge_info->max_cond_equivalences = 8;
1508       edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1509       build_and_record_new_cond (UNLE_EXPR, op0, op1,
1510                                  &edge_info->cond_equivalences[4]);
1511       build_and_record_new_cond (UNGE_EXPR, op0, op1,
1512                                  &edge_info->cond_equivalences[6]);
1513       break;
1514
1515     case LTGT_EXPR:
1516       edge_info->max_cond_equivalences = 8;
1517       edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1518       build_and_record_new_cond (NE_EXPR, op0, op1,
1519                                  &edge_info->cond_equivalences[4]);
1520       build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1521                                  &edge_info->cond_equivalences[6]);
1522       break;
1523
1524     default:
1525       edge_info->max_cond_equivalences = 4;
1526       edge_info->cond_equivalences = xmalloc (4 * sizeof (tree));
1527       break;
1528     }
1529
1530   /* Now store the original true and false conditions into the first
1531      two slots.  */
1532   edge_info->cond_equivalences[0] = cond;
1533   edge_info->cond_equivalences[1] = boolean_true_node;
1534   edge_info->cond_equivalences[2] = inverted;
1535   edge_info->cond_equivalences[3] = boolean_false_node;
1536 }
1537
1538 /* A helper function for record_const_or_copy and record_equality.
1539    Do the work of recording the value and undo info.  */
1540
1541 static void
1542 record_const_or_copy_1 (tree x, tree y, tree prev_x)
1543 {
1544   SSA_NAME_VALUE (x) = y;
1545
1546   VARRAY_PUSH_TREE (const_and_copies_stack, prev_x);
1547   VARRAY_PUSH_TREE (const_and_copies_stack, x);
1548 }
1549
1550
1551 /* Return the loop depth of the basic block of the defining statement of X.
1552    This number should not be treated as absolutely correct because the loop
1553    information may not be completely up-to-date when dom runs.  However, it
1554    will be relatively correct, and as more passes are taught to keep loop info
1555    up to date, the result will become more and more accurate.  */
1556
1557 static int
1558 loop_depth_of_name (tree x)
1559 {
1560   tree defstmt;
1561   basic_block defbb;
1562
1563   /* If it's not an SSA_NAME, we have no clue where the definition is.  */
1564   if (TREE_CODE (x) != SSA_NAME)
1565     return 0;
1566
1567   /* Otherwise return the loop depth of the defining statement's bb.
1568      Note that there may not actually be a bb for this statement, if the
1569      ssa_name is live on entry.  */
1570   defstmt = SSA_NAME_DEF_STMT (x);
1571   defbb = bb_for_stmt (defstmt);
1572   if (!defbb)
1573     return 0;
1574
1575   return defbb->loop_depth;
1576 }
1577
1578
1579 /* Record that X is equal to Y in const_and_copies.  Record undo
1580    information in the block-local varray.  */
1581
1582 static void
1583 record_const_or_copy (tree x, tree y)
1584 {
1585   tree prev_x = SSA_NAME_VALUE (x);
1586
1587   if (TREE_CODE (y) == SSA_NAME)
1588     {
1589       tree tmp = SSA_NAME_VALUE (y);
1590       if (tmp)
1591         y = tmp;
1592     }
1593
1594   record_const_or_copy_1 (x, y, prev_x);
1595 }
1596
1597 /* Similarly, but assume that X and Y are the two operands of an EQ_EXPR.
1598    This constrains the cases in which we may treat this as assignment.  */
1599
1600 static void
1601 record_equality (tree x, tree y)
1602 {
1603   tree prev_x = NULL, prev_y = NULL;
1604
1605   if (TREE_CODE (x) == SSA_NAME)
1606     prev_x = SSA_NAME_VALUE (x);
1607   if (TREE_CODE (y) == SSA_NAME)
1608     prev_y = SSA_NAME_VALUE (y);
1609
1610   /* If one of the previous values is invariant, or invariant in more loops
1611      (by depth), then use that.
1612      Otherwise it doesn't matter which value we choose, just so
1613      long as we canonicalize on one value.  */
1614   if (TREE_INVARIANT (y))
1615     ;
1616   else if (TREE_INVARIANT (x) || (loop_depth_of_name (x) <= loop_depth_of_name (y)))
1617     prev_x = x, x = y, y = prev_x, prev_x = prev_y;
1618   else if (prev_x && TREE_INVARIANT (prev_x))
1619     x = y, y = prev_x, prev_x = prev_y;
1620   else if (prev_y && TREE_CODE (prev_y) != VALUE_HANDLE)
1621     y = prev_y;
1622
1623   /* After the swapping, we must have one SSA_NAME.  */
1624   if (TREE_CODE (x) != SSA_NAME)
1625     return;
1626
1627   /* For IEEE, -0.0 == 0.0, so we don't necessarily know the sign of a
1628      variable compared against zero.  If we're honoring signed zeros,
1629      then we cannot record this value unless we know that the value is
1630      nonzero.  */
1631   if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (x)))
1632       && (TREE_CODE (y) != REAL_CST
1633           || REAL_VALUES_EQUAL (dconst0, TREE_REAL_CST (y))))
1634     return;
1635
1636   record_const_or_copy_1 (x, y, prev_x);
1637 }
1638
1639 /* Return true, if it is ok to do folding of an associative expression.
1640    EXP is the tree for the associative expression.  */
1641
1642 static inline bool
1643 unsafe_associative_fp_binop (tree exp)
1644 {
1645   enum tree_code code = TREE_CODE (exp);
1646   return !(!flag_unsafe_math_optimizations
1647            && (code == MULT_EXPR || code == PLUS_EXPR)
1648            && FLOAT_TYPE_P (TREE_TYPE (exp)));
1649 }
1650
1651 /* STMT is a MODIFY_EXPR for which we were unable to find RHS in the
1652    hash tables.  Try to simplify the RHS using whatever equivalences
1653    we may have recorded.
1654
1655    If we are able to simplify the RHS, then lookup the simplified form in
1656    the hash table and return the result.  Otherwise return NULL.  */
1657
1658 static tree
1659 simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *walk_data,
1660                                     tree stmt, int insert)
1661 {
1662   tree rhs = TREE_OPERAND (stmt, 1);
1663   enum tree_code rhs_code = TREE_CODE (rhs);
1664   tree result = NULL;
1665
1666   /* If we have lhs = ~x, look and see if we earlier had x = ~y.
1667      In which case we can change this statement to be lhs = y.
1668      Which can then be copy propagated.
1669
1670      Similarly for negation.  */
1671   if ((rhs_code == BIT_NOT_EXPR || rhs_code == NEGATE_EXPR)
1672       && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
1673     {
1674       /* Get the definition statement for our RHS.  */
1675       tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1676
1677       /* See if the RHS_DEF_STMT has the same form as our statement.  */
1678       if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR
1679           && TREE_CODE (TREE_OPERAND (rhs_def_stmt, 1)) == rhs_code)
1680         {
1681           tree rhs_def_operand;
1682
1683           rhs_def_operand = TREE_OPERAND (TREE_OPERAND (rhs_def_stmt, 1), 0);
1684
1685           /* Verify that RHS_DEF_OPERAND is a suitable SSA variable.  */
1686           if (TREE_CODE (rhs_def_operand) == SSA_NAME
1687               && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))
1688             result = update_rhs_and_lookup_avail_expr (stmt,
1689                                                        rhs_def_operand,
1690                                                        insert);
1691         }
1692     }
1693
1694   /* If we have z = (x OP C1), see if we earlier had x = y OP C2.
1695      If OP is associative, create and fold (y OP C2) OP C1 which
1696      should result in (y OP C3), use that as the RHS for the
1697      assignment.  Add minus to this, as we handle it specially below.  */
1698   if ((associative_tree_code (rhs_code) || rhs_code == MINUS_EXPR)
1699       && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
1700       && is_gimple_min_invariant (TREE_OPERAND (rhs, 1)))
1701     {
1702       tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1703
1704       /* See if the RHS_DEF_STMT has the same form as our statement.  */
1705       if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR)
1706         {
1707           tree rhs_def_rhs = TREE_OPERAND (rhs_def_stmt, 1);
1708           enum tree_code rhs_def_code = TREE_CODE (rhs_def_rhs);
1709
1710           if ((rhs_code == rhs_def_code && unsafe_associative_fp_binop (rhs))
1711               || (rhs_code == PLUS_EXPR && rhs_def_code == MINUS_EXPR)
1712               || (rhs_code == MINUS_EXPR && rhs_def_code == PLUS_EXPR))
1713             {
1714               tree def_stmt_op0 = TREE_OPERAND (rhs_def_rhs, 0);
1715               tree def_stmt_op1 = TREE_OPERAND (rhs_def_rhs, 1);
1716
1717               if (TREE_CODE (def_stmt_op0) == SSA_NAME
1718                   && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def_stmt_op0)
1719                   && is_gimple_min_invariant (def_stmt_op1))
1720                 {
1721                   tree outer_const = TREE_OPERAND (rhs, 1);
1722                   tree type = TREE_TYPE (TREE_OPERAND (stmt, 0));
1723                   tree t;
1724
1725                   /* If we care about correct floating point results, then
1726                      don't fold x + c1 - c2.  Note that we need to take both
1727                      the codes and the signs to figure this out.  */
1728                   if (FLOAT_TYPE_P (type)
1729                       && !flag_unsafe_math_optimizations
1730                       && (rhs_def_code == PLUS_EXPR
1731                           || rhs_def_code == MINUS_EXPR))
1732                     {
1733                       bool neg = false;
1734
1735                       neg ^= (rhs_code == MINUS_EXPR);
1736                       neg ^= (rhs_def_code == MINUS_EXPR);
1737                       neg ^= real_isneg (TREE_REAL_CST_PTR (outer_const));
1738                       neg ^= real_isneg (TREE_REAL_CST_PTR (def_stmt_op1));
1739
1740                       if (neg)
1741                         goto dont_fold_assoc;
1742                     }
1743
1744                   /* Ho hum.  So fold will only operate on the outermost
1745                      thingy that we give it, so we have to build the new
1746                      expression in two pieces.  This requires that we handle
1747                      combinations of plus and minus.  */
1748                   if (rhs_def_code != rhs_code)
1749                     {
1750                       if (rhs_def_code == MINUS_EXPR)
1751                         t = build (MINUS_EXPR, type, outer_const, def_stmt_op1);
1752                       else
1753                         t = build (MINUS_EXPR, type, def_stmt_op1, outer_const);
1754                       rhs_code = PLUS_EXPR;
1755                     }
1756                   else if (rhs_def_code == MINUS_EXPR)
1757                     t = build (PLUS_EXPR, type, def_stmt_op1, outer_const);
1758                   else
1759                     t = build (rhs_def_code, type, def_stmt_op1, outer_const);
1760                   t = local_fold (t);
1761                   t = build (rhs_code, type, def_stmt_op0, t);
1762                   t = local_fold (t);
1763
1764                   /* If the result is a suitable looking gimple expression,
1765                      then use it instead of the original for STMT.  */
1766                   if (TREE_CODE (t) == SSA_NAME
1767                       || (UNARY_CLASS_P (t)
1768                           && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME)
1769                       || ((BINARY_CLASS_P (t) || COMPARISON_CLASS_P (t))
1770                           && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME
1771                           && is_gimple_val (TREE_OPERAND (t, 1))))
1772                     result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1773                 }
1774             }
1775         }
1776  dont_fold_assoc:;
1777     }
1778
1779   /* Transform TRUNC_DIV_EXPR and TRUNC_MOD_EXPR into RSHIFT_EXPR
1780      and BIT_AND_EXPR respectively if the first operand is greater
1781      than zero and the second operand is an exact power of two.  */
1782   if ((rhs_code == TRUNC_DIV_EXPR || rhs_code == TRUNC_MOD_EXPR)
1783       && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0)))
1784       && integer_pow2p (TREE_OPERAND (rhs, 1)))
1785     {
1786       tree val;
1787       tree op = TREE_OPERAND (rhs, 0);
1788
1789       if (TYPE_UNSIGNED (TREE_TYPE (op)))
1790         {
1791           val = integer_one_node;
1792         }
1793       else
1794         {
1795           tree dummy_cond = walk_data->global_data;
1796
1797           if (! dummy_cond)
1798             {
1799               dummy_cond = build (GT_EXPR, boolean_type_node,
1800                                   op, integer_zero_node);
1801               dummy_cond = build (COND_EXPR, void_type_node,
1802                                   dummy_cond, NULL, NULL);
1803               walk_data->global_data = dummy_cond;
1804             }
1805           else
1806             {
1807               TREE_SET_CODE (TREE_OPERAND (dummy_cond, 0), GT_EXPR);
1808               TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 0) = op;
1809               TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 1)
1810                 = integer_zero_node;
1811             }
1812           val = simplify_cond_and_lookup_avail_expr (dummy_cond, NULL, false);
1813         }
1814
1815       if (val && integer_onep (val))
1816         {
1817           tree t;
1818           tree op0 = TREE_OPERAND (rhs, 0);
1819           tree op1 = TREE_OPERAND (rhs, 1);
1820
1821           if (rhs_code == TRUNC_DIV_EXPR)
1822             t = build (RSHIFT_EXPR, TREE_TYPE (op0), op0,
1823                        build_int_cst (NULL_TREE, tree_log2 (op1)));
1824           else
1825             t = build (BIT_AND_EXPR, TREE_TYPE (op0), op0,
1826                        local_fold (build (MINUS_EXPR, TREE_TYPE (op1),
1827                                           op1, integer_one_node)));
1828
1829           result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1830         }
1831     }
1832
1833   /* Transform ABS (X) into X or -X as appropriate.  */
1834   if (rhs_code == ABS_EXPR
1835       && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0))))
1836     {
1837       tree val;
1838       tree op = TREE_OPERAND (rhs, 0);
1839       tree type = TREE_TYPE (op);
1840
1841       if (TYPE_UNSIGNED (type))
1842         {
1843           val = integer_zero_node;
1844         }
1845       else
1846         {
1847           tree dummy_cond = walk_data->global_data;
1848
1849           if (! dummy_cond)
1850             {
1851               dummy_cond = build (LE_EXPR, boolean_type_node,
1852                                   op, integer_zero_node);
1853               dummy_cond = build (COND_EXPR, void_type_node,
1854                                   dummy_cond, NULL, NULL);
1855               walk_data->global_data = dummy_cond;
1856             }
1857           else
1858             {
1859               TREE_SET_CODE (TREE_OPERAND (dummy_cond, 0), LE_EXPR);
1860               TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 0) = op;
1861               TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 1)
1862                 = build_int_cst (type, 0);
1863             }
1864           val = simplify_cond_and_lookup_avail_expr (dummy_cond, NULL, false);
1865
1866           if (!val)
1867             {
1868               TREE_SET_CODE (TREE_OPERAND (dummy_cond, 0), GE_EXPR);
1869               TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 0) = op;
1870               TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 1)
1871                 = build_int_cst (type, 0);
1872
1873               val = simplify_cond_and_lookup_avail_expr (dummy_cond,
1874                                                          NULL, false);
1875
1876               if (val)
1877                 {
1878                   if (integer_zerop (val))
1879                     val = integer_one_node;
1880                   else if (integer_onep (val))
1881                     val = integer_zero_node;
1882                 }
1883             }
1884         }
1885
1886       if (val
1887           && (integer_onep (val) || integer_zerop (val)))
1888         {
1889           tree t;
1890
1891           if (integer_onep (val))
1892             t = build1 (NEGATE_EXPR, TREE_TYPE (op), op);
1893           else
1894             t = op;
1895
1896           result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1897         }
1898     }
1899
1900   /* Optimize *"foo" into 'f'.  This is done here rather than
1901      in fold to avoid problems with stuff like &*"foo".  */
1902   if (TREE_CODE (rhs) == INDIRECT_REF || TREE_CODE (rhs) == ARRAY_REF)
1903     {
1904       tree t = fold_read_from_constant_string (rhs);
1905
1906       if (t)
1907         result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1908     }
1909
1910   return result;
1911 }
1912
1913 /* COND is a condition of the form:
1914
1915      x == const or x != const
1916
1917    Look back to x's defining statement and see if x is defined as
1918
1919      x = (type) y;
1920
1921    If const is unchanged if we convert it to type, then we can build
1922    the equivalent expression:
1923
1924
1925       y == const or y != const
1926
1927    Which may allow further optimizations.
1928
1929    Return the equivalent comparison or NULL if no such equivalent comparison
1930    was found.  */
1931
1932 static tree
1933 find_equivalent_equality_comparison (tree cond)
1934 {
1935   tree op0 = TREE_OPERAND (cond, 0);
1936   tree op1 = TREE_OPERAND (cond, 1);
1937   tree def_stmt = SSA_NAME_DEF_STMT (op0);
1938
1939   /* OP0 might have been a parameter, so first make sure it
1940      was defined by a MODIFY_EXPR.  */
1941   if (def_stmt && TREE_CODE (def_stmt) == MODIFY_EXPR)
1942     {
1943       tree def_rhs = TREE_OPERAND (def_stmt, 1);
1944
1945       /* Now make sure the RHS of the MODIFY_EXPR is a typecast.  */
1946       if ((TREE_CODE (def_rhs) == NOP_EXPR
1947            || TREE_CODE (def_rhs) == CONVERT_EXPR)
1948           && TREE_CODE (TREE_OPERAND (def_rhs, 0)) == SSA_NAME)
1949         {
1950           tree def_rhs_inner = TREE_OPERAND (def_rhs, 0);
1951           tree def_rhs_inner_type = TREE_TYPE (def_rhs_inner);
1952           tree new;
1953
1954           if (TYPE_PRECISION (def_rhs_inner_type)
1955               > TYPE_PRECISION (TREE_TYPE (def_rhs)))
1956             return NULL;
1957
1958           /* What we want to prove is that if we convert OP1 to
1959              the type of the object inside the NOP_EXPR that the
1960              result is still equivalent to SRC.
1961
1962              If that is true, the build and return new equivalent
1963              condition which uses the source of the typecast and the
1964              new constant (which has only changed its type).  */
1965           new = build1 (TREE_CODE (def_rhs), def_rhs_inner_type, op1);
1966           new = local_fold (new);
1967           if (is_gimple_val (new) && tree_int_cst_equal (new, op1))
1968             return build (TREE_CODE (cond), TREE_TYPE (cond),
1969                           def_rhs_inner, new);
1970         }
1971     }
1972   return NULL;
1973 }
1974
1975 /* STMT is a COND_EXPR for which we could not trivially determine its
1976    result.  This routine attempts to find equivalent forms of the
1977    condition which we may be able to optimize better.  It also
1978    uses simple value range propagation to optimize conditionals.  */
1979
1980 static tree
1981 simplify_cond_and_lookup_avail_expr (tree stmt,
1982                                      stmt_ann_t ann,
1983                                      int insert)
1984 {
1985   tree cond = COND_EXPR_COND (stmt);
1986
1987   if (COMPARISON_CLASS_P (cond))
1988     {
1989       tree op0 = TREE_OPERAND (cond, 0);
1990       tree op1 = TREE_OPERAND (cond, 1);
1991
1992       if (TREE_CODE (op0) == SSA_NAME && is_gimple_min_invariant (op1))
1993         {
1994           int limit;
1995           tree low, high, cond_low, cond_high;
1996           int lowequal, highequal, swapped, no_overlap, subset, cond_inverted;
1997           varray_type vrp_records;
1998           struct vrp_element *element;
1999           struct vrp_hash_elt vrp_hash_elt, *vrp_hash_elt_p;
2000           void **slot;
2001
2002           /* First see if we have test of an SSA_NAME against a constant
2003              where the SSA_NAME is defined by an earlier typecast which
2004              is irrelevant when performing tests against the given
2005              constant.  */
2006           if (TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
2007             {
2008               tree new_cond = find_equivalent_equality_comparison (cond);
2009
2010               if (new_cond)
2011                 {
2012                   /* Update the statement to use the new equivalent
2013                      condition.  */
2014                   COND_EXPR_COND (stmt) = new_cond;
2015
2016                   /* If this is not a real stmt, ann will be NULL and we
2017                      avoid processing the operands.  */
2018                   if (ann)
2019                     modify_stmt (stmt);
2020
2021                   /* Lookup the condition and return its known value if it
2022                      exists.  */
2023                   new_cond = lookup_avail_expr (stmt, insert);
2024                   if (new_cond)
2025                     return new_cond;
2026
2027                   /* The operands have changed, so update op0 and op1.  */
2028                   op0 = TREE_OPERAND (cond, 0);
2029                   op1 = TREE_OPERAND (cond, 1);
2030                 }
2031             }
2032
2033           /* Consult the value range records for this variable (if they exist)
2034              to see if we can eliminate or simplify this conditional.
2035
2036              Note two tests are necessary to determine no records exist.
2037              First we have to see if the virtual array exists, if it
2038              exists, then we have to check its active size.
2039
2040              Also note the vast majority of conditionals are not testing
2041              a variable which has had its range constrained by an earlier
2042              conditional.  So this filter avoids a lot of unnecessary work.  */
2043           vrp_hash_elt.var = op0;
2044           vrp_hash_elt.records = NULL;
2045           slot = htab_find_slot (vrp_data, &vrp_hash_elt, NO_INSERT);
2046           if (slot == NULL)
2047             return NULL;
2048
2049           vrp_hash_elt_p = (struct vrp_hash_elt *) *slot;
2050           vrp_records = vrp_hash_elt_p->records;
2051           if (vrp_records == NULL)
2052             return NULL;
2053
2054           limit = VARRAY_ACTIVE_SIZE (vrp_records);
2055
2056           /* If we have no value range records for this variable, or we are
2057              unable to extract a range for this condition, then there is
2058              nothing to do.  */
2059           if (limit == 0
2060               || ! extract_range_from_cond (cond, &cond_high,
2061                                             &cond_low, &cond_inverted))
2062             return NULL;
2063
2064           /* We really want to avoid unnecessary computations of range
2065              info.  So all ranges are computed lazily; this avoids a
2066              lot of unnecessary work.  i.e., we record the conditional,
2067              but do not process how it constrains the variable's
2068              potential values until we know that processing the condition
2069              could be helpful.
2070
2071              However, we do not want to have to walk a potentially long
2072              list of ranges, nor do we want to compute a variable's
2073              range more than once for a given path.
2074
2075              Luckily, each time we encounter a conditional that can not
2076              be otherwise optimized we will end up here and we will
2077              compute the necessary range information for the variable
2078              used in this condition.
2079
2080              Thus you can conclude that there will never be more than one
2081              conditional associated with a variable which has not been
2082              processed.  So we never need to merge more than one new
2083              conditional into the current range.
2084
2085              These properties also help us avoid unnecessary work.  */
2086            element
2087              = (struct vrp_element *)VARRAY_GENERIC_PTR (vrp_records, limit - 1);
2088
2089           if (element->high && element->low)
2090             {
2091               /* The last element has been processed, so there is no range
2092                  merging to do, we can simply use the high/low values
2093                  recorded in the last element.  */
2094               low = element->low;
2095               high = element->high;
2096             }
2097           else
2098             {
2099               tree tmp_high, tmp_low;
2100               int dummy;
2101
2102               /* The last element has not been processed.  Process it now.  */
2103               extract_range_from_cond (element->cond, &tmp_high,
2104                                        &tmp_low, &dummy);
2105
2106               /* If this is the only element, then no merging is necessary,
2107                  the high/low values from extract_range_from_cond are all
2108                  we need.  */
2109               if (limit == 1)
2110                 {
2111                   low = tmp_low;
2112                   high = tmp_high;
2113                 }
2114               else
2115                 {
2116                   /* Get the high/low value from the previous element.  */
2117                   struct vrp_element *prev
2118                     = (struct vrp_element *)VARRAY_GENERIC_PTR (vrp_records,
2119                                                                 limit - 2);
2120                   low = prev->low;
2121                   high = prev->high;
2122
2123                   /* Merge in this element's range with the range from the
2124                      previous element.
2125
2126                      The low value for the merged range is the maximum of
2127                      the previous low value and the low value of this record.
2128
2129                      Similarly the high value for the merged range is the
2130                      minimum of the previous high value and the high value of
2131                      this record.  */
2132                   low = (tree_int_cst_compare (low, tmp_low) == 1
2133                          ? low : tmp_low);
2134                   high = (tree_int_cst_compare (high, tmp_high) == -1
2135                           ? high : tmp_high);
2136                 }
2137
2138               /* And record the computed range.  */
2139               element->low = low;
2140               element->high = high;
2141
2142             }
2143
2144           /* After we have constrained this variable's potential values,
2145              we try to determine the result of the given conditional.
2146
2147              To simplify later tests, first determine if the current
2148              low value is the same low value as the conditional.
2149              Similarly for the current high value and the high value
2150              for the conditional.  */
2151           lowequal = tree_int_cst_equal (low, cond_low);
2152           highequal = tree_int_cst_equal (high, cond_high);
2153
2154           if (lowequal && highequal)
2155             return (cond_inverted ? boolean_false_node : boolean_true_node);
2156
2157           /* To simplify the overlap/subset tests below we may want
2158              to swap the two ranges so that the larger of the two
2159              ranges occurs "first".  */
2160           swapped = 0;
2161           if (tree_int_cst_compare (low, cond_low) == 1
2162               || (lowequal
2163                   && tree_int_cst_compare (cond_high, high) == 1))
2164             {
2165               tree temp;
2166
2167               swapped = 1;
2168               temp = low;
2169               low = cond_low;
2170               cond_low = temp;
2171               temp = high;
2172               high = cond_high;
2173               cond_high = temp;
2174             }
2175
2176           /* Now determine if there is no overlap in the ranges
2177              or if the second range is a subset of the first range.  */
2178           no_overlap = tree_int_cst_lt (high, cond_low);
2179           subset = tree_int_cst_compare (cond_high, high) != 1;
2180
2181           /* If there was no overlap in the ranges, then this conditional
2182              always has a false value (unless we had to invert this
2183              conditional, in which case it always has a true value).  */
2184           if (no_overlap)
2185             return (cond_inverted ? boolean_true_node : boolean_false_node);
2186
2187           /* If the current range is a subset of the condition's range,
2188              then this conditional always has a true value (unless we
2189              had to invert this conditional, in which case it always
2190              has a true value).  */
2191           if (subset && swapped)
2192             return (cond_inverted ? boolean_false_node : boolean_true_node);
2193
2194           /* We were unable to determine the result of the conditional.
2195              However, we may be able to simplify the conditional.  First
2196              merge the ranges in the same manner as range merging above.  */
2197           low = tree_int_cst_compare (low, cond_low) == 1 ? low : cond_low;
2198           high = tree_int_cst_compare (high, cond_high) == -1 ? high : cond_high;
2199
2200           /* If the range has converged to a single point, then turn this
2201              into an equality comparison.  */
2202           if (TREE_CODE (cond) != EQ_EXPR
2203               && TREE_CODE (cond) != NE_EXPR
2204               && tree_int_cst_equal (low, high))
2205             {
2206               TREE_SET_CODE (cond, EQ_EXPR);
2207               TREE_OPERAND (cond, 1) = high;
2208             }
2209         }
2210     }
2211   return 0;
2212 }
2213
2214 /* STMT is a SWITCH_EXPR for which we could not trivially determine its
2215    result.  This routine attempts to find equivalent forms of the
2216    condition which we may be able to optimize better.  */
2217
2218 static tree
2219 simplify_switch_and_lookup_avail_expr (tree stmt, int insert)
2220 {
2221   tree cond = SWITCH_COND (stmt);
2222   tree def, to, ti;
2223
2224   /* The optimization that we really care about is removing unnecessary
2225      casts.  That will let us do much better in propagating the inferred
2226      constant at the switch target.  */
2227   if (TREE_CODE (cond) == SSA_NAME)
2228     {
2229       def = SSA_NAME_DEF_STMT (cond);
2230       if (TREE_CODE (def) == MODIFY_EXPR)
2231         {
2232           def = TREE_OPERAND (def, 1);
2233           if (TREE_CODE (def) == NOP_EXPR)
2234             {
2235               int need_precision;
2236               bool fail;
2237
2238               def = TREE_OPERAND (def, 0);
2239
2240 #ifdef ENABLE_CHECKING
2241               /* ??? Why was Jeff testing this?  We are gimple...  */
2242               gcc_assert (is_gimple_val (def));
2243 #endif
2244
2245               to = TREE_TYPE (cond);
2246               ti = TREE_TYPE (def);
2247
2248               /* If we have an extension that preserves value, then we
2249                  can copy the source value into the switch.  */
2250
2251               need_precision = TYPE_PRECISION (ti);
2252               fail = false;
2253               if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
2254                 fail = true;
2255               else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
2256                 need_precision += 1;
2257               if (TYPE_PRECISION (to) < need_precision)
2258                 fail = true;
2259
2260               if (!fail)
2261                 {
2262                   SWITCH_COND (stmt) = def;
2263                   modify_stmt (stmt);
2264
2265                   return lookup_avail_expr (stmt, insert);
2266                 }
2267             }
2268         }
2269     }
2270
2271   return 0;
2272 }
2273
2274
2275 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2276    known value for that SSA_NAME (or NULL if no value is known).
2277
2278    NONZERO_VARS is the set SSA_NAMES known to have a nonzero value,
2279    even if we don't know their precise value.
2280
2281    Propagate values from CONST_AND_COPIES and NONZERO_VARS into the PHI
2282    nodes of the successors of BB.  */
2283
2284 static void
2285 cprop_into_successor_phis (basic_block bb, bitmap nonzero_vars)
2286 {
2287   edge e;
2288   edge_iterator ei;
2289
2290   /* This can get rather expensive if the implementation is naive in
2291      how it finds the phi alternative associated with a particular edge.  */
2292   FOR_EACH_EDGE (e, ei, bb->succs)
2293     {
2294       tree phi;
2295       int phi_num_args;
2296       int hint;
2297
2298       /* If this is an abnormal edge, then we do not want to copy propagate
2299          into the PHI alternative associated with this edge.  */
2300       if (e->flags & EDGE_ABNORMAL)
2301         continue;
2302
2303       phi = phi_nodes (e->dest);
2304       if (! phi)
2305         continue;
2306
2307       /* There is no guarantee that for any two PHI nodes in a block that
2308          the phi alternative associated with a particular edge will be
2309          at the same index in the phi alternative array.
2310
2311          However, it is very likely they will be the same.  So we keep
2312          track of the index of the alternative where we found the edge in
2313          the previous phi node and check that index first in the next
2314          phi node.  If that hint fails, then we actually search all
2315          the entries.  */
2316       phi_num_args = PHI_NUM_ARGS (phi);
2317       hint = phi_num_args;
2318       for ( ; phi; phi = PHI_CHAIN (phi))
2319         {
2320           int i;
2321           tree new;
2322           use_operand_p orig_p;
2323           tree orig;
2324
2325           /* If the hint is valid (!= phi_num_args), see if it points
2326              us to the desired phi alternative.  */
2327           if (hint != phi_num_args && PHI_ARG_EDGE (phi, hint) == e)
2328             ;
2329           else
2330             {
2331               /* The hint was either invalid or did not point to the
2332                  correct phi alternative.  Search all the alternatives
2333                  for the correct one.  Update the hint.  */
2334               for (i = 0; i < phi_num_args; i++)
2335                 if (PHI_ARG_EDGE (phi, i) == e)
2336                   break;
2337               hint = i;
2338             }
2339
2340           /* If we did not find the proper alternative, then something is
2341              horribly wrong.  */
2342           gcc_assert (hint != phi_num_args);
2343
2344           /* The alternative may be associated with a constant, so verify
2345              it is an SSA_NAME before doing anything with it.  */
2346           orig_p = PHI_ARG_DEF_PTR (phi, hint);
2347           orig = USE_FROM_PTR (orig_p);
2348           if (TREE_CODE (orig) != SSA_NAME)
2349             continue;
2350
2351           /* If the alternative is known to have a nonzero value, record
2352              that fact in the PHI node itself for future use.  */
2353           if (bitmap_bit_p (nonzero_vars, SSA_NAME_VERSION (orig)))
2354             PHI_ARG_NONZERO (phi, hint) = true;
2355
2356           /* If we have *ORIG_P in our constant/copy table, then replace
2357              ORIG_P with its value in our constant/copy table.  */
2358           new = SSA_NAME_VALUE (orig);
2359           if (new
2360               && (TREE_CODE (new) == SSA_NAME
2361                   || is_gimple_min_invariant (new))
2362               && may_propagate_copy (orig, new))
2363             {
2364               propagate_value (orig_p, new);
2365             }
2366         }
2367     }
2368 }
2369
2370 /* We have finished optimizing BB, record any information implied by
2371    taking a specific outgoing edge from BB.  */
2372
2373 static void
2374 record_edge_info (basic_block bb)
2375 {
2376   block_stmt_iterator bsi = bsi_last (bb);
2377   struct edge_info *edge_info;
2378
2379   if (! bsi_end_p (bsi))
2380     {
2381       tree stmt = bsi_stmt (bsi);
2382
2383       if (stmt && TREE_CODE (stmt) == SWITCH_EXPR)
2384         {
2385           tree cond = SWITCH_COND (stmt);
2386
2387           if (TREE_CODE (cond) == SSA_NAME)
2388             {
2389               tree labels = SWITCH_LABELS (stmt);
2390               int i, n_labels = TREE_VEC_LENGTH (labels);
2391               tree *info = xcalloc (n_basic_blocks, sizeof (tree));
2392               edge e;
2393               edge_iterator ei;
2394
2395               for (i = 0; i < n_labels; i++)
2396                 {
2397                   tree label = TREE_VEC_ELT (labels, i);
2398                   basic_block target_bb = label_to_block (CASE_LABEL (label));
2399
2400                   if (CASE_HIGH (label)
2401                       || !CASE_LOW (label)
2402                       || info[target_bb->index])
2403                     info[target_bb->index] = error_mark_node;
2404                   else
2405                     info[target_bb->index] = label;
2406                 }
2407
2408               FOR_EACH_EDGE (e, ei, bb->succs)
2409                 {
2410                   basic_block target_bb = e->dest;
2411                   tree node = info[target_bb->index];
2412
2413                   if (node != NULL && node != error_mark_node)
2414                     {
2415                       tree x = fold_convert (TREE_TYPE (cond), CASE_LOW (node));
2416                       edge_info = allocate_edge_info (e);
2417                       edge_info->lhs = cond;
2418                       edge_info->rhs = x;
2419                     }
2420                 }
2421               free (info);
2422             }
2423         }
2424
2425       /* A COND_EXPR may create equivalences too.  */
2426       if (stmt && TREE_CODE (stmt) == COND_EXPR)
2427         {
2428           tree cond = COND_EXPR_COND (stmt);
2429           edge true_edge;
2430           edge false_edge;
2431
2432           extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
2433
2434           /* If the conditional is a single variable 'X', record 'X = 1'
2435              for the true edge and 'X = 0' on the false edge.  */
2436           if (SSA_VAR_P (cond))
2437             {
2438               struct edge_info *edge_info;
2439
2440               edge_info = allocate_edge_info (true_edge);
2441               edge_info->lhs = cond;
2442               edge_info->rhs = constant_boolean_node (1, TREE_TYPE (cond));
2443
2444               edge_info = allocate_edge_info (false_edge);
2445               edge_info->lhs = cond;
2446               edge_info->rhs = constant_boolean_node (0, TREE_TYPE (cond));
2447             }
2448           /* Equality tests may create one or two equivalences.  */
2449           else if (COMPARISON_CLASS_P (cond))
2450             {
2451               tree op0 = TREE_OPERAND (cond, 0);
2452               tree op1 = TREE_OPERAND (cond, 1);
2453
2454               /* Special case comparing booleans against a constant as we
2455                  know the value of OP0 on both arms of the branch.  i.e., we
2456                  can record an equivalence for OP0 rather than COND.  */
2457               if ((TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
2458                   && TREE_CODE (op0) == SSA_NAME
2459                   && TREE_CODE (TREE_TYPE (op0)) == BOOLEAN_TYPE
2460                   && is_gimple_min_invariant (op1))
2461                 {
2462                   if (TREE_CODE (cond) == EQ_EXPR)
2463                     {
2464                       edge_info = allocate_edge_info (true_edge);
2465                       edge_info->lhs = op0;
2466                       edge_info->rhs = (integer_zerop (op1)
2467                                             ? boolean_false_node
2468                                             : boolean_true_node);
2469
2470                       edge_info = allocate_edge_info (false_edge);
2471                       edge_info->lhs = op0;
2472                       edge_info->rhs = (integer_zerop (op1)
2473                                             ? boolean_true_node
2474                                             : boolean_false_node);
2475                     }
2476                   else
2477                     {
2478                       edge_info = allocate_edge_info (true_edge);
2479                       edge_info->lhs = op0;
2480                       edge_info->rhs = (integer_zerop (op1)
2481                                             ? boolean_true_node
2482                                             : boolean_false_node);
2483
2484                       edge_info = allocate_edge_info (false_edge);
2485                       edge_info->lhs = op0;
2486                       edge_info->rhs = (integer_zerop (op1)
2487                                             ? boolean_false_node
2488                                             : boolean_true_node);
2489                     }
2490                 }
2491
2492               if (is_gimple_min_invariant (op0)
2493                   && (TREE_CODE (op1) == SSA_NAME
2494                        || is_gimple_min_invariant (op1)))
2495                 {
2496                   tree inverted = invert_truthvalue (cond);
2497                   struct edge_info *edge_info;
2498
2499                   edge_info = allocate_edge_info (true_edge);
2500                   record_conditions (edge_info, cond, inverted);
2501
2502                   if (TREE_CODE (cond) == EQ_EXPR)
2503                     {
2504                       edge_info->lhs = op1;
2505                       edge_info->rhs = op0;
2506                     }
2507
2508                   edge_info = allocate_edge_info (false_edge);
2509                   record_conditions (edge_info, inverted, cond);
2510
2511                   if (TREE_CODE (cond) == NE_EXPR)
2512                     {
2513                       edge_info->lhs = op1;
2514                       edge_info->rhs = op0;
2515                     }
2516                 }
2517
2518               if (TREE_CODE (op0) == SSA_NAME
2519                   && (is_gimple_min_invariant (op1)
2520                       || TREE_CODE (op1) == SSA_NAME))
2521                 {
2522                   tree inverted = invert_truthvalue (cond);
2523                   struct edge_info *edge_info;
2524
2525                   edge_info = allocate_edge_info (true_edge);
2526                   record_conditions (edge_info, cond, inverted);
2527
2528                   if (TREE_CODE (cond) == EQ_EXPR)
2529                     {
2530                       edge_info->lhs = op0;
2531                       edge_info->rhs = op1;
2532                     }
2533
2534                   edge_info = allocate_edge_info (false_edge);
2535                   record_conditions (edge_info, inverted, cond);
2536
2537                   if (TREE_CODE (cond) == NE_EXPR)
2538                     {
2539                       edge_info->lhs = op0;
2540                       edge_info->rhs = op1;
2541                     }
2542                 }
2543             }
2544
2545           /* ??? TRUTH_NOT_EXPR can create an equivalence too.  */
2546         }
2547     }
2548 }
2549
2550 /* Propagate information from BB to its outgoing edges.
2551
2552    This can include equivalency information implied by control statements
2553    at the end of BB and const/copy propagation into PHIs in BB's
2554    successor blocks.  */
2555
2556 static void
2557 propagate_to_outgoing_edges (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
2558                              basic_block bb)
2559 {
2560
2561   record_edge_info (bb);
2562   cprop_into_successor_phis (bb, nonzero_vars);
2563 }
2564
2565 /* Search for redundant computations in STMT.  If any are found, then
2566    replace them with the variable holding the result of the computation.
2567
2568    If safe, record this expression into the available expression hash
2569    table.  */
2570
2571 static bool
2572 eliminate_redundant_computations (struct dom_walk_data *walk_data,
2573                                   tree stmt, stmt_ann_t ann)
2574 {
2575   v_may_def_optype v_may_defs = V_MAY_DEF_OPS (ann);
2576   tree *expr_p, def = NULL_TREE;
2577   bool insert = true;
2578   tree cached_lhs;
2579   bool retval = false;
2580
2581   if (TREE_CODE (stmt) == MODIFY_EXPR)
2582     def = TREE_OPERAND (stmt, 0);
2583
2584   /* Certain expressions on the RHS can be optimized away, but can not
2585      themselves be entered into the hash tables.  */
2586   if (ann->makes_aliased_stores
2587       || ! def
2588       || TREE_CODE (def) != SSA_NAME
2589       || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def)
2590       || NUM_V_MAY_DEFS (v_may_defs) != 0)
2591     insert = false;
2592
2593   /* Check if the expression has been computed before.  */
2594   cached_lhs = lookup_avail_expr (stmt, insert);
2595
2596   /* If this is an assignment and the RHS was not in the hash table,
2597      then try to simplify the RHS and lookup the new RHS in the
2598      hash table.  */
2599   if (! cached_lhs && TREE_CODE (stmt) == MODIFY_EXPR)
2600     cached_lhs = simplify_rhs_and_lookup_avail_expr (walk_data, stmt, insert);
2601   /* Similarly if this is a COND_EXPR and we did not find its
2602      expression in the hash table, simplify the condition and
2603      try again.  */
2604   else if (! cached_lhs && TREE_CODE (stmt) == COND_EXPR)
2605     cached_lhs = simplify_cond_and_lookup_avail_expr (stmt, ann, insert);
2606   /* Similarly for a SWITCH_EXPR.  */
2607   else if (!cached_lhs && TREE_CODE (stmt) == SWITCH_EXPR)
2608     cached_lhs = simplify_switch_and_lookup_avail_expr (stmt, insert);
2609
2610   opt_stats.num_exprs_considered++;
2611
2612   /* Get a pointer to the expression we are trying to optimize.  */
2613   if (TREE_CODE (stmt) == COND_EXPR)
2614     expr_p = &COND_EXPR_COND (stmt);
2615   else if (TREE_CODE (stmt) == SWITCH_EXPR)
2616     expr_p = &SWITCH_COND (stmt);
2617   else if (TREE_CODE (stmt) == RETURN_EXPR && TREE_OPERAND (stmt, 0))
2618     expr_p = &TREE_OPERAND (TREE_OPERAND (stmt, 0), 1);
2619   else
2620     expr_p = &TREE_OPERAND (stmt, 1);
2621
2622   /* It is safe to ignore types here since we have already done
2623      type checking in the hashing and equality routines.  In fact
2624      type checking here merely gets in the way of constant
2625      propagation.  Also, make sure that it is safe to propagate
2626      CACHED_LHS into *EXPR_P.  */
2627   if (cached_lhs
2628       && (TREE_CODE (cached_lhs) != SSA_NAME
2629           || may_propagate_copy (*expr_p, cached_lhs)))
2630     {
2631       if (dump_file && (dump_flags & TDF_DETAILS))
2632         {
2633           fprintf (dump_file, "  Replaced redundant expr '");
2634           print_generic_expr (dump_file, *expr_p, dump_flags);
2635           fprintf (dump_file, "' with '");
2636           print_generic_expr (dump_file, cached_lhs, dump_flags);
2637            fprintf (dump_file, "'\n");
2638         }
2639
2640       opt_stats.num_re++;
2641
2642 #if defined ENABLE_CHECKING
2643       gcc_assert (TREE_CODE (cached_lhs) == SSA_NAME
2644                   || is_gimple_min_invariant (cached_lhs));
2645 #endif
2646
2647       if (TREE_CODE (cached_lhs) == ADDR_EXPR
2648           || (POINTER_TYPE_P (TREE_TYPE (*expr_p))
2649               && is_gimple_min_invariant (cached_lhs)))
2650         retval = true;
2651
2652       propagate_tree_value (expr_p, cached_lhs);
2653       modify_stmt (stmt);
2654     }
2655   return retval;
2656 }
2657
2658 /* STMT, a MODIFY_EXPR, may create certain equivalences, in either
2659    the available expressions table or the const_and_copies table.
2660    Detect and record those equivalences.  */
2661
2662 static void
2663 record_equivalences_from_stmt (tree stmt,
2664                                int may_optimize_p,
2665                                stmt_ann_t ann)
2666 {
2667   tree lhs = TREE_OPERAND (stmt, 0);
2668   enum tree_code lhs_code = TREE_CODE (lhs);
2669   int i;
2670
2671   if (lhs_code == SSA_NAME)
2672     {
2673       tree rhs = TREE_OPERAND (stmt, 1);
2674
2675       /* Strip away any useless type conversions.  */
2676       STRIP_USELESS_TYPE_CONVERSION (rhs);
2677
2678       /* If the RHS of the assignment is a constant or another variable that
2679          may be propagated, register it in the CONST_AND_COPIES table.  We
2680          do not need to record unwind data for this, since this is a true
2681          assignment and not an equivalence inferred from a comparison.  All
2682          uses of this ssa name are dominated by this assignment, so unwinding
2683          just costs time and space.  */
2684       if (may_optimize_p
2685           && (TREE_CODE (rhs) == SSA_NAME
2686               || is_gimple_min_invariant (rhs)))
2687         SSA_NAME_VALUE (lhs) = rhs;
2688
2689       /* alloca never returns zero and the address of a non-weak symbol
2690          is never zero.  NOP_EXPRs and CONVERT_EXPRs can be completely
2691          stripped as they do not affect this equivalence.  */
2692       while (TREE_CODE (rhs) == NOP_EXPR
2693              || TREE_CODE (rhs) == CONVERT_EXPR)
2694         rhs = TREE_OPERAND (rhs, 0);
2695
2696       if (alloca_call_p (rhs)
2697           || (TREE_CODE (rhs) == ADDR_EXPR
2698               && DECL_P (TREE_OPERAND (rhs, 0))
2699               && ! DECL_WEAK (TREE_OPERAND (rhs, 0))))
2700         record_var_is_nonzero (lhs);
2701
2702       /* IOR of any value with a nonzero value will result in a nonzero
2703          value.  Even if we do not know the exact result recording that
2704          the result is nonzero is worth the effort.  */
2705       if (TREE_CODE (rhs) == BIT_IOR_EXPR
2706           && integer_nonzerop (TREE_OPERAND (rhs, 1)))
2707         record_var_is_nonzero (lhs);
2708     }
2709
2710   /* Look at both sides for pointer dereferences.  If we find one, then
2711      the pointer must be nonnull and we can enter that equivalence into
2712      the hash tables.  */
2713   if (flag_delete_null_pointer_checks)
2714     for (i = 0; i < 2; i++)
2715       {
2716         tree t = TREE_OPERAND (stmt, i);
2717
2718         /* Strip away any COMPONENT_REFs.  */
2719         while (TREE_CODE (t) == COMPONENT_REF)
2720           t = TREE_OPERAND (t, 0);
2721
2722         /* Now see if this is a pointer dereference.  */
2723         if (INDIRECT_REF_P (t))
2724           {
2725             tree op = TREE_OPERAND (t, 0);
2726
2727             /* If the pointer is a SSA variable, then enter new
2728                equivalences into the hash table.  */
2729             while (TREE_CODE (op) == SSA_NAME)
2730               {
2731                 tree def = SSA_NAME_DEF_STMT (op);
2732
2733                 record_var_is_nonzero (op);
2734
2735                 /* And walk up the USE-DEF chains noting other SSA_NAMEs
2736                    which are known to have a nonzero value.  */
2737                 if (def
2738                     && TREE_CODE (def) == MODIFY_EXPR
2739                     && TREE_CODE (TREE_OPERAND (def, 1)) == NOP_EXPR)
2740                   op = TREE_OPERAND (TREE_OPERAND (def, 1), 0);
2741                 else
2742                   break;
2743               }
2744           }
2745       }
2746
2747   /* A memory store, even an aliased store, creates a useful
2748      equivalence.  By exchanging the LHS and RHS, creating suitable
2749      vops and recording the result in the available expression table,
2750      we may be able to expose more redundant loads.  */
2751   if (!ann->has_volatile_ops
2752       && (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME
2753           || is_gimple_min_invariant (TREE_OPERAND (stmt, 1)))
2754       && !is_gimple_reg (lhs))
2755     {
2756       tree rhs = TREE_OPERAND (stmt, 1);
2757       tree new;
2758
2759       /* FIXME: If the LHS of the assignment is a bitfield and the RHS
2760          is a constant, we need to adjust the constant to fit into the
2761          type of the LHS.  If the LHS is a bitfield and the RHS is not
2762          a constant, then we can not record any equivalences for this
2763          statement since we would need to represent the widening or
2764          narrowing of RHS.  This fixes gcc.c-torture/execute/921016-1.c
2765          and should not be necessary if GCC represented bitfields
2766          properly.  */
2767       if (lhs_code == COMPONENT_REF
2768           && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1)))
2769         {
2770           if (TREE_CONSTANT (rhs))
2771             rhs = widen_bitfield (rhs, TREE_OPERAND (lhs, 1), lhs);
2772           else
2773             rhs = NULL;
2774
2775           /* If the value overflowed, then we can not use this equivalence.  */
2776           if (rhs && ! is_gimple_min_invariant (rhs))
2777             rhs = NULL;
2778         }
2779
2780       if (rhs)
2781         {
2782           /* Build a new statement with the RHS and LHS exchanged.  */
2783           new = build (MODIFY_EXPR, TREE_TYPE (stmt), rhs, lhs);
2784
2785           create_ssa_artficial_load_stmt (&(ann->operands), new);
2786
2787           /* Finally enter the statement into the available expression
2788              table.  */
2789           lookup_avail_expr (new, true);
2790         }
2791     }
2792 }
2793
2794 /* Replace *OP_P in STMT with any known equivalent value for *OP_P from
2795    CONST_AND_COPIES.  */
2796
2797 static bool
2798 cprop_operand (tree stmt, use_operand_p op_p)
2799 {
2800   bool may_have_exposed_new_symbols = false;
2801   tree val;
2802   tree op = USE_FROM_PTR (op_p);
2803
2804   /* If the operand has a known constant value or it is known to be a
2805      copy of some other variable, use the value or copy stored in
2806      CONST_AND_COPIES.  */
2807   val = SSA_NAME_VALUE (op);
2808   if (val && TREE_CODE (val) != VALUE_HANDLE)
2809     {
2810       tree op_type, val_type;
2811
2812       /* Do not change the base variable in the virtual operand
2813          tables.  That would make it impossible to reconstruct
2814          the renamed virtual operand if we later modify this
2815          statement.  Also only allow the new value to be an SSA_NAME
2816          for propagation into virtual operands.  */
2817       if (!is_gimple_reg (op)
2818           && (get_virtual_var (val) != get_virtual_var (op)
2819               || TREE_CODE (val) != SSA_NAME))
2820         return false;
2821
2822       /* Do not replace hard register operands in asm statements.  */
2823       if (TREE_CODE (stmt) == ASM_EXPR
2824           && !may_propagate_copy_into_asm (op))
2825         return false;
2826
2827       /* Get the toplevel type of each operand.  */
2828       op_type = TREE_TYPE (op);
2829       val_type = TREE_TYPE (val);
2830
2831       /* While both types are pointers, get the type of the object
2832          pointed to.  */
2833       while (POINTER_TYPE_P (op_type) && POINTER_TYPE_P (val_type))
2834         {
2835           op_type = TREE_TYPE (op_type);
2836           val_type = TREE_TYPE (val_type);
2837         }
2838
2839       /* Make sure underlying types match before propagating a constant by
2840          converting the constant to the proper type.  Note that convert may
2841          return a non-gimple expression, in which case we ignore this
2842          propagation opportunity.  */
2843       if (TREE_CODE (val) != SSA_NAME)
2844         {
2845           if (!lang_hooks.types_compatible_p (op_type, val_type))
2846             {
2847               val = fold_convert (TREE_TYPE (op), val);
2848               if (!is_gimple_min_invariant (val))
2849                 return false;
2850             }
2851         }
2852
2853       /* Certain operands are not allowed to be copy propagated due
2854          to their interaction with exception handling and some GCC
2855          extensions.  */
2856       else if (!may_propagate_copy (op, val))
2857         return false;
2858
2859       /* Dump details.  */
2860       if (dump_file && (dump_flags & TDF_DETAILS))
2861         {
2862           fprintf (dump_file, "  Replaced '");
2863           print_generic_expr (dump_file, op, dump_flags);
2864           fprintf (dump_file, "' with %s '",
2865                    (TREE_CODE (val) != SSA_NAME ? "constant" : "variable"));
2866           print_generic_expr (dump_file, val, dump_flags);
2867           fprintf (dump_file, "'\n");
2868         }
2869
2870       /* If VAL is an ADDR_EXPR or a constant of pointer type, note
2871          that we may have exposed a new symbol for SSA renaming.  */
2872       if (TREE_CODE (val) == ADDR_EXPR
2873           || (POINTER_TYPE_P (TREE_TYPE (op))
2874               && is_gimple_min_invariant (val)))
2875         may_have_exposed_new_symbols = true;
2876
2877       propagate_value (op_p, val);
2878
2879       /* And note that we modified this statement.  This is now
2880          safe, even if we changed virtual operands since we will
2881          rescan the statement and rewrite its operands again.  */
2882       modify_stmt (stmt);
2883     }
2884   return may_have_exposed_new_symbols;
2885 }
2886
2887 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2888    known value for that SSA_NAME (or NULL if no value is known).
2889
2890    Propagate values from CONST_AND_COPIES into the uses, vuses and
2891    v_may_def_ops of STMT.  */
2892
2893 static bool
2894 cprop_into_stmt (tree stmt)
2895 {
2896   bool may_have_exposed_new_symbols = false;
2897   use_operand_p op_p;
2898   ssa_op_iter iter;
2899   tree rhs;
2900
2901   FOR_EACH_SSA_USE_OPERAND (op_p, stmt, iter, SSA_OP_ALL_USES)
2902     {
2903       if (TREE_CODE (USE_FROM_PTR (op_p)) == SSA_NAME)
2904         may_have_exposed_new_symbols |= cprop_operand (stmt, op_p);
2905     }
2906
2907   if (may_have_exposed_new_symbols)
2908     {
2909       rhs = get_rhs (stmt);
2910       if (rhs && TREE_CODE (rhs) == ADDR_EXPR)
2911         recompute_tree_invarant_for_addr_expr (rhs);
2912     }
2913
2914   return may_have_exposed_new_symbols;
2915 }
2916
2917
2918 /* Optimize the statement pointed by iterator SI.
2919
2920    We try to perform some simplistic global redundancy elimination and
2921    constant propagation:
2922
2923    1- To detect global redundancy, we keep track of expressions that have
2924       been computed in this block and its dominators.  If we find that the
2925       same expression is computed more than once, we eliminate repeated
2926       computations by using the target of the first one.
2927
2928    2- Constant values and copy assignments.  This is used to do very
2929       simplistic constant and copy propagation.  When a constant or copy
2930       assignment is found, we map the value on the RHS of the assignment to
2931       the variable in the LHS in the CONST_AND_COPIES table.  */
2932
2933 static void
2934 optimize_stmt (struct dom_walk_data *walk_data, basic_block bb,
2935                block_stmt_iterator si)
2936 {
2937   stmt_ann_t ann;
2938   tree stmt;
2939   bool may_optimize_p;
2940   bool may_have_exposed_new_symbols = false;
2941
2942   stmt = bsi_stmt (si);
2943
2944   get_stmt_operands (stmt);
2945   ann = stmt_ann (stmt);
2946   opt_stats.num_stmts++;
2947   may_have_exposed_new_symbols = false;
2948
2949   if (dump_file && (dump_flags & TDF_DETAILS))
2950     {
2951       fprintf (dump_file, "Optimizing statement ");
2952       print_generic_stmt (dump_file, stmt, TDF_SLIM);
2953     }
2954
2955   /* Const/copy propagate into USES, VUSES and the RHS of V_MAY_DEFs.  */
2956   may_have_exposed_new_symbols = cprop_into_stmt (stmt);
2957
2958   /* If the statement has been modified with constant replacements,
2959      fold its RHS before checking for redundant computations.  */
2960   if (ann->modified)
2961     {
2962       /* Try to fold the statement making sure that STMT is kept
2963          up to date.  */
2964       if (fold_stmt (bsi_stmt_ptr (si)))
2965         {
2966           stmt = bsi_stmt (si);
2967           ann = stmt_ann (stmt);
2968
2969           if (dump_file && (dump_flags & TDF_DETAILS))
2970             {
2971               fprintf (dump_file, "  Folded to: ");
2972               print_generic_stmt (dump_file, stmt, TDF_SLIM);
2973             }
2974         }
2975
2976       /* Constant/copy propagation above may change the set of
2977          virtual operands associated with this statement.  Folding
2978          may remove the need for some virtual operands.
2979
2980          Indicate we will need to rescan and rewrite the statement.  */
2981       may_have_exposed_new_symbols = true;
2982     }
2983
2984   /* Check for redundant computations.  Do this optimization only
2985      for assignments that have no volatile ops and conditionals.  */
2986   may_optimize_p = (!ann->has_volatile_ops
2987                     && ((TREE_CODE (stmt) == RETURN_EXPR
2988                          && TREE_OPERAND (stmt, 0)
2989                          && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR
2990                          && ! (TREE_SIDE_EFFECTS
2991                                (TREE_OPERAND (TREE_OPERAND (stmt, 0), 1))))
2992                         || (TREE_CODE (stmt) == MODIFY_EXPR
2993                             && ! TREE_SIDE_EFFECTS (TREE_OPERAND (stmt, 1)))
2994                         || TREE_CODE (stmt) == COND_EXPR
2995                         || TREE_CODE (stmt) == SWITCH_EXPR));
2996
2997   if (may_optimize_p)
2998     may_have_exposed_new_symbols
2999       |= eliminate_redundant_computations (walk_data, stmt, ann);
3000
3001   /* Record any additional equivalences created by this statement.  */
3002   if (TREE_CODE (stmt) == MODIFY_EXPR)
3003     record_equivalences_from_stmt (stmt,
3004                                    may_optimize_p,
3005                                    ann);
3006
3007   register_definitions_for_stmt (stmt);
3008
3009   /* If STMT is a COND_EXPR and it was modified, then we may know
3010      where it goes.  If that is the case, then mark the CFG as altered.
3011
3012      This will cause us to later call remove_unreachable_blocks and
3013      cleanup_tree_cfg when it is safe to do so.  It is not safe to
3014      clean things up here since removal of edges and such can trigger
3015      the removal of PHI nodes, which in turn can release SSA_NAMEs to
3016      the manager.
3017
3018      That's all fine and good, except that once SSA_NAMEs are released
3019      to the manager, we must not call create_ssa_name until all references
3020      to released SSA_NAMEs have been eliminated.
3021
3022      All references to the deleted SSA_NAMEs can not be eliminated until
3023      we remove unreachable blocks.
3024
3025      We can not remove unreachable blocks until after we have completed
3026      any queued jump threading.
3027
3028      We can not complete any queued jump threads until we have taken
3029      appropriate variables out of SSA form.  Taking variables out of
3030      SSA form can call create_ssa_name and thus we lose.
3031
3032      Ultimately I suspect we're going to need to change the interface
3033      into the SSA_NAME manager.  */
3034
3035   if (ann->modified)
3036     {
3037       tree val = NULL;
3038
3039       if (TREE_CODE (stmt) == COND_EXPR)
3040         val = COND_EXPR_COND (stmt);
3041       else if (TREE_CODE (stmt) == SWITCH_EXPR)
3042         val = SWITCH_COND (stmt);
3043
3044       if (val && TREE_CODE (val) == INTEGER_CST && find_taken_edge (bb, val))
3045         cfg_altered = true;
3046
3047       /* If we simplified a statement in such a way as to be shown that it
3048          cannot trap, update the eh information and the cfg to match.  */
3049       if (maybe_clean_eh_stmt (stmt))
3050         {
3051           bitmap_set_bit (need_eh_cleanup, bb->index);
3052           if (dump_file && (dump_flags & TDF_DETAILS))
3053             fprintf (dump_file, "  Flagged to clear EH edges.\n");
3054         }
3055     }
3056
3057   if (may_have_exposed_new_symbols)
3058     VARRAY_PUSH_TREE (stmts_to_rescan, bsi_stmt (si));
3059 }
3060
3061 /* Replace the RHS of STMT with NEW_RHS.  If RHS can be found in the
3062    available expression hashtable, then return the LHS from the hash
3063    table.
3064
3065    If INSERT is true, then we also update the available expression
3066    hash table to account for the changes made to STMT.  */
3067
3068 static tree
3069 update_rhs_and_lookup_avail_expr (tree stmt, tree new_rhs, bool insert)
3070 {
3071   tree cached_lhs = NULL;
3072
3073   /* Remove the old entry from the hash table.  */
3074   if (insert)
3075     {
3076       struct expr_hash_elt element;
3077
3078       initialize_hash_element (stmt, NULL, &element);
3079       htab_remove_elt_with_hash (avail_exprs, &element, element.hash);
3080     }
3081
3082   /* Now update the RHS of the assignment.  */
3083   TREE_OPERAND (stmt, 1) = new_rhs;
3084
3085   /* Now lookup the updated statement in the hash table.  */
3086   cached_lhs = lookup_avail_expr (stmt, insert);
3087
3088   /* We have now called lookup_avail_expr twice with two different
3089      versions of this same statement, once in optimize_stmt, once here.
3090
3091      We know the call in optimize_stmt did not find an existing entry
3092      in the hash table, so a new entry was created.  At the same time
3093      this statement was pushed onto the BLOCK_AVAIL_EXPRS varray.
3094
3095      If this call failed to find an existing entry on the hash table,
3096      then the new version of this statement was entered into the
3097      hash table.  And this statement was pushed onto BLOCK_AVAIL_EXPR
3098      for the second time.  So there are two copies on BLOCK_AVAIL_EXPRs
3099
3100      If this call succeeded, we still have one copy of this statement
3101      on the BLOCK_AVAIL_EXPRs varray.
3102
3103      For both cases, we need to pop the most recent entry off the
3104      BLOCK_AVAIL_EXPRs varray.  For the case where we never found this
3105      statement in the hash tables, that will leave precisely one
3106      copy of this statement on BLOCK_AVAIL_EXPRs.  For the case where
3107      we found a copy of this statement in the second hash table lookup
3108      we want _no_ copies of this statement in BLOCK_AVAIL_EXPRs.  */
3109   if (insert)
3110     VARRAY_POP (avail_exprs_stack);
3111
3112   /* And make sure we record the fact that we modified this
3113      statement.  */
3114   modify_stmt (stmt);
3115
3116   return cached_lhs;
3117 }
3118
3119 /* Search for an existing instance of STMT in the AVAIL_EXPRS table.  If
3120    found, return its LHS. Otherwise insert STMT in the table and return
3121    NULL_TREE.
3122
3123    Also, when an expression is first inserted in the AVAIL_EXPRS table, it
3124    is also added to the stack pointed by BLOCK_AVAIL_EXPRS_P, so that they
3125    can be removed when we finish processing this block and its children.
3126
3127    NOTE: This function assumes that STMT is a MODIFY_EXPR node that
3128    contains no CALL_EXPR on its RHS and makes no volatile nor
3129    aliased references.  */
3130
3131 static tree
3132 lookup_avail_expr (tree stmt, bool insert)
3133 {
3134   void **slot;
3135   tree lhs;
3136   tree temp;
3137   struct expr_hash_elt *element = xcalloc (sizeof (struct expr_hash_elt), 1);
3138
3139   lhs = TREE_CODE (stmt) == MODIFY_EXPR ? TREE_OPERAND (stmt, 0) : NULL;
3140
3141   initialize_hash_element (stmt, lhs, element);
3142
3143   /* Don't bother remembering constant assignments and copy operations.
3144      Constants and copy operations are handled by the constant/copy propagator
3145      in optimize_stmt.  */
3146   if (TREE_CODE (element->rhs) == SSA_NAME
3147       || is_gimple_min_invariant (element->rhs))
3148     {
3149       free (element);
3150       return NULL_TREE;
3151     }
3152
3153   /* If this is an equality test against zero, see if we have recorded a
3154      nonzero value for the variable in question.  */
3155   if ((TREE_CODE (element->rhs) == EQ_EXPR
3156        || TREE_CODE  (element->rhs) == NE_EXPR)
3157       && TREE_CODE (TREE_OPERAND (element->rhs, 0)) == SSA_NAME
3158       && integer_zerop (TREE_OPERAND (element->rhs, 1)))
3159     {
3160       int indx = SSA_NAME_VERSION (TREE_OPERAND (element->rhs, 0));
3161
3162       if (bitmap_bit_p (nonzero_vars, indx))
3163         {
3164           tree t = element->rhs;
3165           free (element);
3166
3167           if (TREE_CODE (t) == EQ_EXPR)
3168             return boolean_false_node;
3169           else
3170             return boolean_true_node;
3171         }
3172     }
3173
3174   /* Finally try to find the expression in the main expression hash table.  */
3175   slot = htab_find_slot_with_hash (avail_exprs, element, element->hash,
3176                                    (insert ? INSERT : NO_INSERT));
3177   if (slot == NULL)
3178     {
3179       free (element);
3180       return NULL_TREE;
3181     }
3182
3183   if (*slot == NULL)
3184     {
3185       *slot = (void *) element;
3186       VARRAY_PUSH_TREE (avail_exprs_stack, stmt ? stmt : element->rhs);
3187       return NULL_TREE;
3188     }
3189
3190   /* Extract the LHS of the assignment so that it can be used as the current
3191      definition of another variable.  */
3192   lhs = ((struct expr_hash_elt *)*slot)->lhs;
3193
3194   /* See if the LHS appears in the CONST_AND_COPIES table.  If it does, then
3195      use the value from the const_and_copies table.  */
3196   if (TREE_CODE (lhs) == SSA_NAME)
3197     {
3198       temp = SSA_NAME_VALUE (lhs);
3199       if (temp && TREE_CODE (temp) != VALUE_HANDLE)
3200         lhs = temp;
3201     }
3202
3203   free (element);
3204   return lhs;
3205 }
3206
3207 /* Given a condition COND, record into HI_P, LO_P and INVERTED_P the
3208    range of values that result in the conditional having a true value.
3209
3210    Return true if we are successful in extracting a range from COND and
3211    false if we are unsuccessful.  */
3212
3213 static bool
3214 extract_range_from_cond (tree cond, tree *hi_p, tree *lo_p, int *inverted_p)
3215 {
3216   tree op1 = TREE_OPERAND (cond, 1);
3217   tree high, low, type;
3218   int inverted;
3219
3220   /* Experiments have shown that it's rarely, if ever useful to
3221      record ranges for enumerations.  Presumably this is due to
3222      the fact that they're rarely used directly.  They are typically
3223      cast into an integer type and used that way.  */
3224   if (TREE_CODE (TREE_TYPE (op1)) != INTEGER_TYPE)
3225     return 0;
3226
3227   type = TREE_TYPE (op1);
3228
3229   switch (TREE_CODE (cond))
3230     {
3231     case EQ_EXPR:
3232       high = low = op1;
3233       inverted = 0;
3234       break;
3235
3236     case NE_EXPR:
3237       high = low = op1;
3238       inverted = 1;
3239       break;
3240
3241     case GE_EXPR:
3242       low = op1;
3243       high = TYPE_MAX_VALUE (type);
3244       inverted = 0;
3245       break;
3246
3247     case GT_EXPR:
3248       low = int_const_binop (PLUS_EXPR, op1, integer_one_node, 1);
3249       high = TYPE_MAX_VALUE (type);
3250       inverted = 0;
3251       break;
3252
3253     case LE_EXPR:
3254       high = op1;
3255       low = TYPE_MIN_VALUE (type);
3256       inverted = 0;
3257       break;
3258
3259     case LT_EXPR:
3260       high = int_const_binop (MINUS_EXPR, op1, integer_one_node, 1);
3261       low = TYPE_MIN_VALUE (type);
3262       inverted = 0;
3263       break;
3264
3265     default:
3266       return 0;
3267     }
3268
3269   *hi_p = high;
3270   *lo_p = low;
3271   *inverted_p = inverted;
3272   return 1;
3273 }
3274
3275 /* Record a range created by COND for basic block BB.  */
3276
3277 static void
3278 record_range (tree cond, basic_block bb)
3279 {
3280   enum tree_code code = TREE_CODE (cond);
3281
3282   /* We explicitly ignore NE_EXPRs and all the unordered comparisons.
3283      They rarely allow for meaningful range optimizations and significantly
3284      complicate the implementation.  */
3285   if ((code == LT_EXPR || code == LE_EXPR || code == GT_EXPR
3286        || code == GE_EXPR || code == EQ_EXPR)
3287       && TREE_CODE (TREE_TYPE (TREE_OPERAND (cond, 1))) == INTEGER_TYPE)
3288     {
3289       struct vrp_hash_elt *vrp_hash_elt;
3290       struct vrp_element *element;
3291       varray_type *vrp_records_p;
3292       void **slot;
3293
3294
3295       vrp_hash_elt = xmalloc (sizeof (struct vrp_hash_elt));
3296       vrp_hash_elt->var = TREE_OPERAND (cond, 0);
3297       vrp_hash_elt->records = NULL;
3298       slot = htab_find_slot (vrp_data, vrp_hash_elt, INSERT);
3299
3300       if (*slot == NULL)
3301         *slot = (void *) vrp_hash_elt;
3302       else
3303         free (vrp_hash_elt);
3304
3305       vrp_hash_elt = (struct vrp_hash_elt *) *slot;
3306       vrp_records_p = &vrp_hash_elt->records;
3307
3308       element = ggc_alloc (sizeof (struct vrp_element));
3309       element->low = NULL;
3310       element->high = NULL;
3311       element->cond = cond;
3312       element->bb = bb;
3313
3314       if (*vrp_records_p == NULL)
3315         VARRAY_GENERIC_PTR_INIT (*vrp_records_p, 2, "vrp records");
3316
3317       VARRAY_PUSH_GENERIC_PTR (*vrp_records_p, element);
3318       VARRAY_PUSH_TREE (vrp_variables_stack, TREE_OPERAND (cond, 0));
3319     }
3320 }
3321
3322 /* Hashing and equality functions for VRP_DATA.
3323
3324    Since this hash table is addressed by SSA_NAMEs, we can hash on
3325    their version number and equality can be determined with a
3326    pointer comparison.  */
3327
3328 static hashval_t
3329 vrp_hash (const void *p)
3330 {
3331   tree var = ((struct vrp_hash_elt *)p)->var;
3332
3333   return SSA_NAME_VERSION (var);
3334 }
3335
3336 static int
3337 vrp_eq (const void *p1, const void *p2)
3338 {
3339   tree var1 = ((struct vrp_hash_elt *)p1)->var;
3340   tree var2 = ((struct vrp_hash_elt *)p2)->var;
3341
3342   return var1 == var2;
3343 }
3344
3345 /* Hashing and equality functions for AVAIL_EXPRS.  The table stores
3346    MODIFY_EXPR statements.  We compute a value number for expressions using
3347    the code of the expression and the SSA numbers of its operands.  */
3348
3349 static hashval_t
3350 avail_expr_hash (const void *p)
3351 {
3352   stmt_ann_t ann = ((struct expr_hash_elt *)p)->ann;
3353   tree rhs = ((struct expr_hash_elt *)p)->rhs;
3354   hashval_t val = 0;
3355   size_t i;
3356   vuse_optype vuses;
3357
3358   /* iterative_hash_expr knows how to deal with any expression and
3359      deals with commutative operators as well, so just use it instead
3360      of duplicating such complexities here.  */
3361   val = iterative_hash_expr (rhs, val);
3362
3363   /* If the hash table entry is not associated with a statement, then we
3364      can just hash the expression and not worry about virtual operands
3365      and such.  */
3366   if (!ann)
3367     return val;
3368
3369   /* Add the SSA version numbers of every vuse operand.  This is important
3370      because compound variables like arrays are not renamed in the
3371      operands.  Rather, the rename is done on the virtual variable
3372      representing all the elements of the array.  */
3373   vuses = VUSE_OPS (ann);
3374   for (i = 0; i < NUM_VUSES (vuses); i++)
3375     val = iterative_hash_expr (VUSE_OP (vuses, i), val);
3376
3377   return val;
3378 }
3379
3380 static hashval_t
3381 real_avail_expr_hash (const void *p)
3382 {
3383   return ((const struct expr_hash_elt *)p)->hash;
3384 }
3385
3386 static int
3387 avail_expr_eq (const void *p1, const void *p2)
3388 {
3389   stmt_ann_t ann1 = ((struct expr_hash_elt *)p1)->ann;
3390   tree rhs1 = ((struct expr_hash_elt *)p1)->rhs;
3391   stmt_ann_t ann2 = ((struct expr_hash_elt *)p2)->ann;
3392   tree rhs2 = ((struct expr_hash_elt *)p2)->rhs;
3393
3394   /* If they are the same physical expression, return true.  */
3395   if (rhs1 == rhs2 && ann1 == ann2)
3396     return true;
3397
3398   /* If their codes are not equal, then quit now.  */
3399   if (TREE_CODE (rhs1) != TREE_CODE (rhs2))
3400     return false;
3401
3402   /* In case of a collision, both RHS have to be identical and have the
3403      same VUSE operands.  */
3404   if ((TREE_TYPE (rhs1) == TREE_TYPE (rhs2)
3405        || lang_hooks.types_compatible_p (TREE_TYPE (rhs1), TREE_TYPE (rhs2)))
3406       && operand_equal_p (rhs1, rhs2, OEP_PURE_SAME))
3407     {
3408       vuse_optype ops1 = NULL;
3409       vuse_optype ops2 = NULL;
3410       size_t num_ops1 = 0;
3411       size_t num_ops2 = 0;
3412       size_t i;
3413
3414       if (ann1)
3415         {
3416           ops1 = VUSE_OPS (ann1);
3417           num_ops1 = NUM_VUSES (ops1);
3418         }
3419
3420       if (ann2)
3421         {
3422           ops2 = VUSE_OPS (ann2);
3423           num_ops2 = NUM_VUSES (ops2);
3424         }
3425
3426       /* If the number of virtual uses is different, then we consider
3427          them not equal.  */
3428       if (num_ops1 != num_ops2)
3429         return false;
3430
3431       for (i = 0; i < num_ops1; i++)
3432         if (VUSE_OP (ops1, i) != VUSE_OP (ops2, i))
3433           return false;
3434
3435       gcc_assert (((struct expr_hash_elt *)p1)->hash
3436                   == ((struct expr_hash_elt *)p2)->hash);
3437       return true;
3438     }
3439
3440   return false;
3441 }
3442
3443 /* Given STMT and a pointer to the block local definitions BLOCK_DEFS_P,
3444    register register all objects set by this statement into BLOCK_DEFS_P
3445    and CURRDEFS.  */
3446
3447 static void
3448 register_definitions_for_stmt (tree stmt)
3449 {
3450   tree def;
3451   ssa_op_iter iter;
3452
3453   FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
3454     {
3455
3456       /* FIXME: We shouldn't be registering new defs if the variable
3457          doesn't need to be renamed.  */
3458       register_new_def (def, &block_defs_stack);
3459     }
3460 }
3461