1 /* SSA Dominator optimizations for trees
2 Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
3 Contributed by Diego Novillo <dnovillo@redhat.com>
5 This file is part of GCC.
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)
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.
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. */
24 #include "coretypes.h"
31 #include "basic-block.h"
36 #include "diagnostic.h"
38 #include "tree-dump.h"
39 #include "tree-flow.h"
42 #include "tree-pass.h"
43 #include "tree-ssa-propagate.h"
44 #include "langhooks.h"
46 /* This file implements optimizations on the dominator tree. */
49 /* Structure for recording edge equivalences as well as any pending
50 edge redirections during the dominator optimizer.
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.
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. */
65 /* If this edge creates a simple equivalence, the LHS and RHS of
66 the equivalence will be stored here. */
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;
77 /* If we can thread this edge this field records the new target. */
78 edge redirection_target;
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
89 static htab_t avail_exprs;
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
96 static VEC(tree_on_heap) *avail_exprs_stack;
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.
101 An SSA_NAME indicates that the current definition of the underlying
102 variable should be set to the given SSA_NAME.
104 A _DECL node indicates that the underlying variable has no current
107 A NULL node is used to mark the last node associated with the
109 static VEC(tree_on_heap) *block_defs_stack;
111 /* Stack of statements we need to rescan during finalization for newly
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
118 static VEC(tree_on_heap) *stmts_to_rescan;
120 /* Structure for entries in the expression hash table.
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.
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
133 /* The value (lhs) of this expression. */
136 /* The expression (rhs) we want to record. */
139 /* The annotation if this element corresponds to a statement. */
142 /* The hash value for RHS/ann. */
146 /* Stack of dest,src pairs that need to be restored during finalization.
148 A NULL entry is used to mark the end of pairs which need to be
149 restored during finalization of this block. */
150 static VEC(tree_on_heap) *const_and_copies_stack;
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;
156 /* Stack of SSA_NAMEs which need their NONZERO_VARS property cleared
157 when the current block is finalized.
159 A NULL entry is used to mark the end of names needing their
160 entry in NONZERO_VARS cleared during finalization of this block. */
161 static VEC(tree_on_heap) *nonzero_vars_stack;
163 /* Track whether or not we have changed the control flow graph. */
164 static bool cfg_altered;
166 /* Bitmap of blocks that have had EH statements cleaned. We should
167 remove their dead edges eventually. */
168 static bitmap need_eh_cleanup;
170 /* Statistics for dominator optimizations. */
174 long num_exprs_considered;
178 static struct opt_stats_d opt_stats;
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.
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.
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.
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.
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.
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.
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. */
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.
217 Note this is computed lazily and thus can be NULL indicating that
218 the values have not been computed yet. */
222 /* The actual conditional we recorded. This is needed since we compute
226 /* The basic block where this record was created. We use this to determine
227 when to remove records. */
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;
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. */
245 /* Array of variables which have their values constrained by operations
246 in this basic block. We use this during finalization to know
247 which variables need their VRP data updated. */
249 /* Stack of SSA_NAMEs which had their values constrainted by operations
250 in this basic block. During finalization of this block we use this
251 list to determine which variables need their VRP data updated.
253 A NULL entry marks the end of the SSA_NAMEs associated with this block. */
254 static VEC(tree_on_heap) *vrp_variables_stack;
262 /* Local functions. */
263 static void optimize_stmt (struct dom_walk_data *,
265 block_stmt_iterator);
266 static tree lookup_avail_expr (tree, bool);
267 static hashval_t vrp_hash (const void *);
268 static int vrp_eq (const void *, const void *);
269 static hashval_t avail_expr_hash (const void *);
270 static hashval_t real_avail_expr_hash (const void *);
271 static int avail_expr_eq (const void *, const void *);
272 static void htab_statistics (FILE *, htab_t);
273 static void record_cond (tree, tree);
274 static void record_const_or_copy (tree, tree);
275 static void record_equality (tree, tree);
276 static tree update_rhs_and_lookup_avail_expr (tree, tree, bool);
277 static tree simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *,
279 static tree simplify_cond_and_lookup_avail_expr (tree, stmt_ann_t, int);
280 static tree simplify_switch_and_lookup_avail_expr (tree, int);
281 static tree find_equivalent_equality_comparison (tree);
282 static void record_range (tree, basic_block);
283 static bool extract_range_from_cond (tree, tree *, tree *, int *);
284 static void record_equivalences_from_phis (basic_block);
285 static void record_equivalences_from_incoming_edge (basic_block);
286 static bool eliminate_redundant_computations (struct dom_walk_data *,
288 static void record_equivalences_from_stmt (tree, int, stmt_ann_t);
289 static void thread_across_edge (struct dom_walk_data *, edge);
290 static void dom_opt_finalize_block (struct dom_walk_data *, basic_block);
291 static void dom_opt_initialize_block (struct dom_walk_data *, basic_block);
292 static void propagate_to_outgoing_edges (struct dom_walk_data *, basic_block);
293 static void remove_local_expressions_from_table (void);
294 static void restore_vars_to_original_value (void);
295 static void restore_currdefs_to_original_value (void);
296 static void register_definitions_for_stmt (tree);
297 static edge single_incoming_edge_ignoring_loop_edges (basic_block);
298 static void restore_nonzero_vars_to_original_value (void);
299 static inline bool unsafe_associative_fp_binop (tree);
301 /* Local version of fold that doesn't introduce cruft. */
308 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
309 may have been added by fold, and "useless" type conversions that might
310 now be apparent due to propagation. */
311 STRIP_USELESS_TYPE_CONVERSION (t);
316 /* Allocate an EDGE_INFO for edge E and attach it to E.
317 Return the new EDGE_INFO structure. */
319 static struct edge_info *
320 allocate_edge_info (edge e)
322 struct edge_info *edge_info;
324 edge_info = xcalloc (1, sizeof (struct edge_info));
330 /* Free all EDGE_INFO structures associated with edges in the CFG.
331 If a particular edge can be threaded, copy the redirection
332 target from the EDGE_INFO structure into the edge's AUX field
333 as required by code to update the CFG and SSA graph for
337 free_all_edge_infos (void)
345 FOR_EACH_EDGE (e, ei, bb->preds)
347 struct edge_info *edge_info = e->aux;
351 e->aux = edge_info->redirection_target;
352 if (edge_info->cond_equivalences)
353 free (edge_info->cond_equivalences);
360 /* Jump threading, redundancy elimination and const/copy propagation.
362 This pass may expose new symbols that need to be renamed into SSA. For
363 every new symbol exposed, its corresponding bit will be set in
367 tree_ssa_dominator_optimize (void)
369 struct dom_walk_data walk_data;
372 memset (&opt_stats, 0, sizeof (opt_stats));
374 for (i = 0; i < num_referenced_vars; i++)
375 var_ann (referenced_var (i))->current_def = NULL;
377 /* Mark loop edges so we avoid threading across loop boundaries.
378 This may result in transforming natural loop into irreducible
380 mark_dfs_back_edges ();
382 /* Create our hash tables. */
383 avail_exprs = htab_create (1024, real_avail_expr_hash, avail_expr_eq, free);
384 vrp_data = htab_create (ceil_log2 (num_ssa_names), vrp_hash, vrp_eq, free);
385 avail_exprs_stack = VEC_alloc (tree_on_heap, 20);
386 block_defs_stack = VEC_alloc (tree_on_heap, 20);
387 const_and_copies_stack = VEC_alloc (tree_on_heap, 20);
388 nonzero_vars_stack = VEC_alloc (tree_on_heap, 20);
389 vrp_variables_stack = VEC_alloc (tree_on_heap, 20);
390 stmts_to_rescan = VEC_alloc (tree_on_heap, 20);
391 nonzero_vars = BITMAP_XMALLOC ();
392 need_eh_cleanup = BITMAP_XMALLOC ();
394 /* Setup callbacks for the generic dominator tree walker. */
395 walk_data.walk_stmts_backward = false;
396 walk_data.dom_direction = CDI_DOMINATORS;
397 walk_data.initialize_block_local_data = NULL;
398 walk_data.before_dom_children_before_stmts = dom_opt_initialize_block;
399 walk_data.before_dom_children_walk_stmts = optimize_stmt;
400 walk_data.before_dom_children_after_stmts = propagate_to_outgoing_edges;
401 walk_data.after_dom_children_before_stmts = NULL;
402 walk_data.after_dom_children_walk_stmts = NULL;
403 walk_data.after_dom_children_after_stmts = dom_opt_finalize_block;
404 /* Right now we only attach a dummy COND_EXPR to the global data pointer.
405 When we attach more stuff we'll need to fill this out with a real
407 walk_data.global_data = NULL;
408 walk_data.block_local_data_size = 0;
410 /* Now initialize the dominator walker. */
411 init_walk_dominator_tree (&walk_data);
413 calculate_dominance_info (CDI_DOMINATORS);
415 /* If we prove certain blocks are unreachable, then we want to
416 repeat the dominator optimization process as PHI nodes may
417 have turned into copies which allows better propagation of
418 values. So we repeat until we do not identify any new unreachable
422 /* Optimize the dominator tree. */
425 /* Recursively walk the dominator tree optimizing statements. */
426 walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
428 /* If we exposed any new variables, go ahead and put them into
429 SSA form now, before we handle jump threading. This simplifies
430 interactions between rewriting of _DECL nodes into SSA form
431 and rewriting SSA_NAME nodes into SSA form after block
432 duplication and CFG manipulation. */
433 if (!bitmap_empty_p (vars_to_rename))
435 rewrite_into_ssa (false);
436 bitmap_clear (vars_to_rename);
439 free_all_edge_infos ();
441 /* Thread jumps, creating duplicate blocks as needed. */
442 cfg_altered = thread_through_all_blocks ();
444 /* Removal of statements may make some EH edges dead. Purge
445 such edges from the CFG as needed. */
446 if (!bitmap_empty_p (need_eh_cleanup))
448 cfg_altered |= tree_purge_all_dead_eh_edges (need_eh_cleanup);
449 bitmap_zero (need_eh_cleanup);
452 free_dominance_info (CDI_DOMINATORS);
453 cfg_altered = cleanup_tree_cfg ();
454 calculate_dominance_info (CDI_DOMINATORS);
456 rewrite_ssa_into_ssa ();
458 /* Reinitialize the various tables. */
459 bitmap_clear (nonzero_vars);
460 htab_empty (avail_exprs);
461 htab_empty (vrp_data);
463 for (i = 0; i < num_referenced_vars; i++)
464 var_ann (referenced_var (i))->current_def = NULL;
468 /* Debugging dumps. */
469 if (dump_file && (dump_flags & TDF_STATS))
470 dump_dominator_optimization_stats (dump_file);
472 /* We emptied the hash table earlier, now delete it completely. */
473 htab_delete (avail_exprs);
474 htab_delete (vrp_data);
476 /* It is not necessary to clear CURRDEFS, REDIRECTION_EDGES, VRP_DATA,
477 CONST_AND_COPIES, and NONZERO_VARS as they all get cleared at the bottom
478 of the do-while loop above. */
480 /* And finalize the dominator walker. */
481 fini_walk_dominator_tree (&walk_data);
483 /* Free nonzero_vars. */
484 BITMAP_XFREE (nonzero_vars);
485 BITMAP_XFREE (need_eh_cleanup);
487 /* Finally, remove everything except invariants in SSA_NAME_VALUE.
489 Long term we will be able to let everything in SSA_NAME_VALUE
490 persist. However, for now, we know this is the safe thing to
492 for (i = 0; i < num_ssa_names; i++)
494 tree name = ssa_name (i);
500 value = SSA_NAME_VALUE (name);
501 if (value && !is_gimple_min_invariant (value))
502 SSA_NAME_VALUE (name) = NULL;
505 VEC_free (tree_on_heap, block_defs_stack);
506 VEC_free (tree_on_heap, avail_exprs_stack);
507 VEC_free (tree_on_heap, const_and_copies_stack);
508 VEC_free (tree_on_heap, nonzero_vars_stack);
509 VEC_free (tree_on_heap, vrp_variables_stack);
510 VEC_free (tree_on_heap, stmts_to_rescan);
514 gate_dominator (void)
516 return flag_tree_dom != 0;
519 struct tree_opt_pass pass_dominator =
522 gate_dominator, /* gate */
523 tree_ssa_dominator_optimize, /* execute */
526 0, /* static_pass_number */
527 TV_TREE_SSA_DOMINATOR_OPTS, /* tv_id */
528 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
529 0, /* properties_provided */
530 0, /* properties_destroyed */
531 0, /* todo_flags_start */
532 TODO_dump_func | TODO_rename_vars
533 | TODO_verify_ssa, /* todo_flags_finish */
538 /* We are exiting BB, see if the target block begins with a conditional
539 jump which has a known value when reached via BB. */
542 thread_across_edge (struct dom_walk_data *walk_data, edge e)
544 block_stmt_iterator bsi;
548 /* Each PHI creates a temporary equivalence, record them. */
549 for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
551 tree src = PHI_ARG_DEF_FROM_EDGE (phi, e);
552 tree dst = PHI_RESULT (phi);
554 /* If the desired argument is not the same as this PHI's result
555 and it is set by a PHI in this block, then we can not thread
556 through this block. */
558 && TREE_CODE (src) == SSA_NAME
559 && TREE_CODE (SSA_NAME_DEF_STMT (src)) == PHI_NODE
560 && bb_for_stmt (SSA_NAME_DEF_STMT (src)) == e->dest)
563 record_const_or_copy (dst, src);
564 register_new_def (dst, &block_defs_stack);
567 for (bsi = bsi_start (e->dest); ! bsi_end_p (bsi); bsi_next (&bsi))
569 tree lhs, cached_lhs;
571 stmt = bsi_stmt (bsi);
573 /* Ignore empty statements and labels. */
574 if (IS_EMPTY_STMT (stmt) || TREE_CODE (stmt) == LABEL_EXPR)
577 /* If this is not a MODIFY_EXPR which sets an SSA_NAME to a new
578 value, then stop our search here. Ideally when we stop a
579 search we stop on a COND_EXPR or SWITCH_EXPR. */
580 if (TREE_CODE (stmt) != MODIFY_EXPR
581 || TREE_CODE (TREE_OPERAND (stmt, 0)) != SSA_NAME)
584 /* At this point we have a statement which assigns an RHS to an
585 SSA_VAR on the LHS. We want to prove that the RHS is already
586 available and that its value is held in the current definition
587 of the LHS -- meaning that this assignment is a NOP when
588 reached via edge E. */
589 if (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME)
590 cached_lhs = TREE_OPERAND (stmt, 1);
592 cached_lhs = lookup_avail_expr (stmt, false);
594 lhs = TREE_OPERAND (stmt, 0);
596 /* This can happen if we thread around to the start of a loop. */
597 if (lhs == cached_lhs)
600 /* If we did not find RHS in the hash table, then try again after
601 temporarily const/copy propagating the operands. */
604 /* Copy the operands. */
605 stmt_ann_t ann = stmt_ann (stmt);
606 use_optype uses = USE_OPS (ann);
607 vuse_optype vuses = VUSE_OPS (ann);
608 tree *uses_copy = xcalloc (NUM_USES (uses), sizeof (tree));
609 tree *vuses_copy = xcalloc (NUM_VUSES (vuses), sizeof (tree));
612 /* Make a copy of the uses into USES_COPY, then cprop into
614 for (i = 0; i < NUM_USES (uses); i++)
618 uses_copy[i] = USE_OP (uses, i);
619 if (TREE_CODE (USE_OP (uses, i)) == SSA_NAME)
620 tmp = SSA_NAME_VALUE (USE_OP (uses, i));
621 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
622 SET_USE_OP (uses, i, tmp);
625 /* Similarly for virtual uses. */
626 for (i = 0; i < NUM_VUSES (vuses); i++)
630 vuses_copy[i] = VUSE_OP (vuses, i);
631 if (TREE_CODE (VUSE_OP (vuses, i)) == SSA_NAME)
632 tmp = SSA_NAME_VALUE (VUSE_OP (vuses, i));
633 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
634 SET_VUSE_OP (vuses, i, tmp);
637 /* Try to lookup the new expression. */
638 cached_lhs = lookup_avail_expr (stmt, false);
640 /* Restore the statement's original uses/defs. */
641 for (i = 0; i < NUM_USES (uses); i++)
642 SET_USE_OP (uses, i, uses_copy[i]);
644 for (i = 0; i < NUM_VUSES (vuses); i++)
645 SET_VUSE_OP (vuses, i, vuses_copy[i]);
650 /* If we still did not find the expression in the hash table,
651 then we can not ignore this statement. */
656 /* If the expression in the hash table was not assigned to an
657 SSA_NAME, then we can not ignore this statement. */
658 if (TREE_CODE (cached_lhs) != SSA_NAME)
661 /* If we have different underlying variables, then we can not
662 ignore this statement. */
663 if (SSA_NAME_VAR (cached_lhs) != SSA_NAME_VAR (lhs))
666 /* If CACHED_LHS does not represent the current value of the underlying
667 variable in CACHED_LHS/LHS, then we can not ignore this statement. */
668 if (var_ann (SSA_NAME_VAR (lhs))->current_def != cached_lhs)
671 /* If we got here, then we can ignore this statement and continue
672 walking through the statements in the block looking for a threadable
675 We want to record an equivalence lhs = cache_lhs so that if
676 the result of this statement is used later we can copy propagate
678 record_const_or_copy (lhs, cached_lhs);
679 register_new_def (lhs, &block_defs_stack);
682 /* If we stopped at a COND_EXPR or SWITCH_EXPR, then see if we know which
683 arm will be taken. */
685 && (TREE_CODE (stmt) == COND_EXPR
686 || TREE_CODE (stmt) == SWITCH_EXPR))
688 tree cond, cached_lhs;
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);
695 cond = SWITCH_COND (stmt);
697 if (COMPARISON_CLASS_P (cond))
699 tree dummy_cond, op0, op1;
700 enum tree_code cond_code;
702 op0 = TREE_OPERAND (cond, 0);
703 op1 = TREE_OPERAND (cond, 1);
704 cond_code = TREE_CODE (cond);
706 /* Get the current value of both operands. */
707 if (TREE_CODE (op0) == SSA_NAME)
709 tree tmp = SSA_NAME_VALUE (op0);
710 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
714 if (TREE_CODE (op1) == SSA_NAME)
716 tree tmp = SSA_NAME_VALUE (op1);
717 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
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;
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;
733 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), cond_code);
734 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op0;
735 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1) = op1;
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))
743 cached_lhs = lookup_avail_expr (dummy_cond, false);
744 if (!cached_lhs || ! is_gimple_min_invariant (cached_lhs))
745 cached_lhs = simplify_cond_and_lookup_avail_expr (dummy_cond,
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)
756 cached_lhs = SSA_NAME_VALUE (cached_lhs);
757 if (cached_lhs && ! is_gimple_min_invariant (cached_lhs))
761 cached_lhs = lookup_avail_expr (stmt, false);
765 edge taken_edge = find_taken_edge (e->dest, cached_lhs);
766 basic_block dest = (taken_edge ? taken_edge->dest : NULL);
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. */
777 struct edge_info *edge_info;
779 update_bb_profile_for_threading (e->dest, EDGE_FREQUENCY (e),
780 e->count, taken_edge);
784 edge_info = allocate_edge_info (e);
785 edge_info->redirection_target = taken_edge;
786 bb_ann (e->dest)->incoming_edge_threaded = true;
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. */
798 dom_opt_initialize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
801 if (dump_file && (dump_flags & TDF_DETAILS))
802 fprintf (dump_file, "\n\nOptimizing block #%d\n\n", bb->index);
804 /* Push a marker on the stacks of local information so that we know how
805 far to unwind when we finalize this block. */
806 VEC_safe_push (tree_on_heap, avail_exprs_stack, NULL_TREE);
807 VEC_safe_push (tree_on_heap, block_defs_stack, NULL_TREE);
808 VEC_safe_push (tree_on_heap, const_and_copies_stack, NULL_TREE);
809 VEC_safe_push (tree_on_heap, nonzero_vars_stack, NULL_TREE);
810 VEC_safe_push (tree_on_heap, vrp_variables_stack, NULL_TREE);
812 record_equivalences_from_incoming_edge (bb);
814 /* PHI nodes can create equivalences too. */
815 record_equivalences_from_phis (bb);
818 /* Given an expression EXPR (a relational expression or a statement),
819 initialize the hash table element pointed by by ELEMENT. */
822 initialize_hash_element (tree expr, tree lhs, struct expr_hash_elt *element)
824 /* Hash table elements may be based on conditional expressions or statements.
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)
834 else if (TREE_CODE (expr) == COND_EXPR)
836 element->ann = stmt_ann (expr);
837 element->rhs = COND_EXPR_COND (expr);
839 else if (TREE_CODE (expr) == SWITCH_EXPR)
841 element->ann = stmt_ann (expr);
842 element->rhs = SWITCH_COND (expr);
844 else if (TREE_CODE (expr) == RETURN_EXPR && TREE_OPERAND (expr, 0))
846 element->ann = stmt_ann (expr);
847 element->rhs = TREE_OPERAND (TREE_OPERAND (expr, 0), 1);
851 element->ann = stmt_ann (expr);
852 element->rhs = TREE_OPERAND (expr, 1);
856 element->hash = avail_expr_hash (element);
859 /* Remove all the expressions in LOCALS from TABLE, stopping when there are
860 LIMIT entries left in LOCALs. */
863 remove_local_expressions_from_table (void)
865 /* Remove all the expressions made available in this block. */
866 while (VEC_length (tree_on_heap, avail_exprs_stack) > 0)
868 struct expr_hash_elt element;
869 tree expr = VEC_pop (tree_on_heap, avail_exprs_stack);
871 if (expr == NULL_TREE)
874 initialize_hash_element (expr, NULL, &element);
875 htab_remove_elt_with_hash (avail_exprs, &element, element.hash);
879 /* Use the SSA_NAMES in LOCALS to restore TABLE to its original
880 state, stopping when there are LIMIT entries left in LOCALs. */
883 restore_nonzero_vars_to_original_value (void)
885 while (VEC_length (tree_on_heap, nonzero_vars_stack) > 0)
887 tree name = VEC_pop (tree_on_heap, nonzero_vars_stack);
892 bitmap_clear_bit (nonzero_vars, SSA_NAME_VERSION (name));
896 /* Use the source/dest pairs in CONST_AND_COPIES_STACK to restore
897 CONST_AND_COPIES to its original state, stopping when we hit a
901 restore_vars_to_original_value (void)
903 while (VEC_length (tree_on_heap, const_and_copies_stack) > 0)
905 tree prev_value, dest;
907 dest = VEC_pop (tree_on_heap, const_and_copies_stack);
912 prev_value = VEC_pop (tree_on_heap, const_and_copies_stack);
913 SSA_NAME_VALUE (dest) = prev_value;
917 /* Similar to restore_vars_to_original_value, except that it restores
918 CURRDEFS to its original value. */
920 restore_currdefs_to_original_value (void)
922 /* Restore CURRDEFS to its original state. */
923 while (VEC_length (tree_on_heap, block_defs_stack) > 0)
925 tree tmp = VEC_pop (tree_on_heap, block_defs_stack);
928 if (tmp == NULL_TREE)
931 /* If we recorded an SSA_NAME, then make the SSA_NAME the current
932 definition of its underlying variable. If we recorded anything
933 else, it must have been an _DECL node and its current reaching
934 definition must have been NULL. */
935 if (TREE_CODE (tmp) == SSA_NAME)
938 var = SSA_NAME_VAR (saved_def);
946 var_ann (var)->current_def = saved_def;
950 /* We have finished processing the dominator children of BB, perform
951 any finalization actions in preparation for leaving this node in
952 the dominator tree. */
955 dom_opt_finalize_block (struct dom_walk_data *walk_data, basic_block bb)
959 /* If we are at a leaf node in the dominator tree, see if we can thread
960 the edge from BB through its successor.
962 Do this before we remove entries from our equivalence tables. */
963 if (EDGE_COUNT (bb->succs) == 1
964 && (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL) == 0
965 && (get_immediate_dominator (CDI_DOMINATORS, EDGE_SUCC (bb, 0)->dest) != bb
966 || phi_nodes (EDGE_SUCC (bb, 0)->dest)))
969 thread_across_edge (walk_data, EDGE_SUCC (bb, 0));
971 else if ((last = last_stmt (bb))
972 && TREE_CODE (last) == COND_EXPR
973 && (COMPARISON_CLASS_P (COND_EXPR_COND (last))
974 || TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME)
975 && EDGE_COUNT (bb->succs) == 2
976 && (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL) == 0
977 && (EDGE_SUCC (bb, 1)->flags & EDGE_ABNORMAL) == 0)
979 edge true_edge, false_edge;
981 extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
983 /* If the THEN arm is the end of a dominator tree or has PHI nodes,
984 then try to thread through its edge. */
985 if (get_immediate_dominator (CDI_DOMINATORS, true_edge->dest) != bb
986 || phi_nodes (true_edge->dest))
988 struct edge_info *edge_info;
991 /* Push a marker onto the available expression stack so that we
992 unwind any expressions related to the TRUE arm before processing
993 the false arm below. */
994 VEC_safe_push (tree_on_heap, avail_exprs_stack, NULL_TREE);
995 VEC_safe_push (tree_on_heap, block_defs_stack, NULL_TREE);
996 VEC_safe_push (tree_on_heap, const_and_copies_stack, NULL_TREE);
998 edge_info = true_edge->aux;
1000 /* If we have info associated with this edge, record it into
1001 our equivalency tables. */
1004 tree *cond_equivalences = edge_info->cond_equivalences;
1005 tree lhs = edge_info->lhs;
1006 tree rhs = edge_info->rhs;
1008 /* If we have a simple NAME = VALUE equivalency record it.
1009 Until the jump threading selection code improves, only
1010 do this if both the name and value are SSA_NAMEs with
1011 the same underlying variable to avoid missing threading
1014 && TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME
1015 && TREE_CODE (edge_info->rhs) == SSA_NAME
1016 && SSA_NAME_VAR (lhs) == SSA_NAME_VAR (rhs))
1017 record_const_or_copy (lhs, rhs);
1019 /* If we have 0 = COND or 1 = COND equivalences, record them
1020 into our expression hash tables. */
1021 if (cond_equivalences)
1022 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1024 tree expr = cond_equivalences[i];
1025 tree value = cond_equivalences[i + 1];
1027 record_cond (expr, value);
1031 /* Now thread the edge. */
1032 thread_across_edge (walk_data, true_edge);
1034 /* And restore the various tables to their state before
1035 we threaded this edge. */
1036 remove_local_expressions_from_table ();
1037 restore_vars_to_original_value ();
1038 restore_currdefs_to_original_value ();
1041 /* Similarly for the ELSE arm. */
1042 if (get_immediate_dominator (CDI_DOMINATORS, false_edge->dest) != bb
1043 || phi_nodes (false_edge->dest))
1045 struct edge_info *edge_info;
1048 edge_info = false_edge->aux;
1050 /* If we have info associated with this edge, record it into
1051 our equivalency tables. */
1054 tree *cond_equivalences = edge_info->cond_equivalences;
1055 tree lhs = edge_info->lhs;
1056 tree rhs = edge_info->rhs;
1058 /* If we have a simple NAME = VALUE equivalency record it.
1059 Until the jump threading selection code improves, only
1060 do this if both the name and value are SSA_NAMEs with
1061 the same underlying variable to avoid missing threading
1064 && TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME)
1065 record_const_or_copy (lhs, rhs);
1067 /* If we have 0 = COND or 1 = COND equivalences, record them
1068 into our expression hash tables. */
1069 if (cond_equivalences)
1070 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1072 tree expr = cond_equivalences[i];
1073 tree value = cond_equivalences[i + 1];
1075 record_cond (expr, value);
1079 thread_across_edge (walk_data, false_edge);
1081 /* No need to remove local expressions from our tables
1082 or restore vars to their original value as that will
1083 be done immediately below. */
1087 remove_local_expressions_from_table ();
1088 restore_nonzero_vars_to_original_value ();
1089 restore_vars_to_original_value ();
1090 restore_currdefs_to_original_value ();
1092 /* Remove VRP records associated with this basic block. They are no
1095 To be efficient, we note which variables have had their values
1096 constrained in this block. So walk over each variable in the
1097 VRP_VARIABLEs array. */
1098 while (VEC_length (tree_on_heap, vrp_variables_stack) > 0)
1100 tree var = VEC_pop (tree_on_heap, vrp_variables_stack);
1101 struct vrp_hash_elt vrp_hash_elt, *vrp_hash_elt_p;
1104 /* Each variable has a stack of value range records. We want to
1105 invalidate those associated with our basic block. So we walk
1106 the array backwards popping off records associated with our
1107 block. Once we hit a record not associated with our block
1109 varray_type var_vrp_records;
1114 vrp_hash_elt.var = var;
1115 vrp_hash_elt.records = NULL;
1117 slot = htab_find_slot (vrp_data, &vrp_hash_elt, NO_INSERT);
1119 vrp_hash_elt_p = (struct vrp_hash_elt *) *slot;
1120 var_vrp_records = vrp_hash_elt_p->records;
1122 while (VARRAY_ACTIVE_SIZE (var_vrp_records) > 0)
1124 struct vrp_element *element
1125 = (struct vrp_element *)VARRAY_TOP_GENERIC_PTR (var_vrp_records);
1127 if (element->bb != bb)
1130 VARRAY_POP (var_vrp_records);
1134 /* If we queued any statements to rescan in this block, then
1135 go ahead and rescan them now. */
1136 while (VEC_length (tree_on_heap, stmts_to_rescan) > 0)
1138 tree stmt = VEC_last (tree_on_heap, stmts_to_rescan);
1139 basic_block stmt_bb = bb_for_stmt (stmt);
1144 VEC_pop (tree_on_heap, stmts_to_rescan);
1145 mark_new_vars_to_rename (stmt, vars_to_rename);
1149 /* PHI nodes can create equivalences too.
1151 Ignoring any alternatives which are the same as the result, if
1152 all the alternatives are equal, then the PHI node creates an
1155 Additionally, if all the PHI alternatives are known to have a nonzero
1156 value, then the result of this PHI is known to have a nonzero value,
1157 even if we do not know its exact value. */
1160 record_equivalences_from_phis (basic_block bb)
1164 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1166 tree lhs = PHI_RESULT (phi);
1170 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1172 tree t = PHI_ARG_DEF (phi, i);
1174 /* Ignore alternatives which are the same as our LHS. Since
1175 LHS is a PHI_RESULT, it is known to be a SSA_NAME, so we
1176 can simply compare pointers. */
1180 /* If we have not processed an alternative yet, then set
1181 RHS to this alternative. */
1184 /* If we have processed an alternative (stored in RHS), then
1185 see if it is equal to this one. If it isn't, then stop
1187 else if (! operand_equal_for_phi_arg_p (rhs, t))
1191 /* If we had no interesting alternatives, then all the RHS alternatives
1192 must have been the same as LHS. */
1196 /* If we managed to iterate through each PHI alternative without
1197 breaking out of the loop, then we have a PHI which may create
1198 a useful equivalence. We do not need to record unwind data for
1199 this, since this is a true assignment and not an equivalence
1200 inferred from a comparison. All uses of this ssa name are dominated
1201 by this assignment, so unwinding just costs time and space. */
1202 if (i == PHI_NUM_ARGS (phi)
1203 && may_propagate_copy (lhs, rhs))
1204 SSA_NAME_VALUE (lhs) = rhs;
1206 /* Now see if we know anything about the nonzero property for the
1207 result of this PHI. */
1208 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1210 if (!PHI_ARG_NONZERO (phi, i))
1214 if (i == PHI_NUM_ARGS (phi))
1215 bitmap_set_bit (nonzero_vars, SSA_NAME_VERSION (PHI_RESULT (phi)));
1217 register_new_def (lhs, &block_defs_stack);
1221 /* Ignoring loop backedges, if BB has precisely one incoming edge then
1222 return that edge. Otherwise return NULL. */
1224 single_incoming_edge_ignoring_loop_edges (basic_block bb)
1230 FOR_EACH_EDGE (e, ei, bb->preds)
1232 /* A loop back edge can be identified by the destination of
1233 the edge dominating the source of the edge. */
1234 if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
1237 /* If we have already seen a non-loop edge, then we must have
1238 multiple incoming non-loop edges and thus we return NULL. */
1242 /* This is the first non-loop incoming edge we have found. Record
1250 /* Record any equivalences created by the incoming edge to BB. If BB
1251 has more than one incoming edge, then no equivalence is created. */
1254 record_equivalences_from_incoming_edge (basic_block bb)
1258 struct edge_info *edge_info;
1260 /* If our parent block ended with a control statment, then we may be
1261 able to record some equivalences based on which outgoing edge from
1262 the parent was followed. */
1263 parent = get_immediate_dominator (CDI_DOMINATORS, bb);
1265 e = single_incoming_edge_ignoring_loop_edges (bb);
1267 /* If we had a single incoming edge from our parent block, then enter
1268 any data associated with the edge into our tables. */
1269 if (e && e->src == parent)
1277 tree lhs = edge_info->lhs;
1278 tree rhs = edge_info->rhs;
1279 tree *cond_equivalences = edge_info->cond_equivalences;
1282 record_equality (lhs, rhs);
1284 if (cond_equivalences)
1286 bool recorded_range = false;
1287 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1289 tree expr = cond_equivalences[i];
1290 tree value = cond_equivalences[i + 1];
1292 record_cond (expr, value);
1294 /* For the first true equivalence, record range
1295 information. We only do this for the first
1296 true equivalence as it should dominate any
1297 later true equivalences. */
1298 if (! recorded_range
1299 && COMPARISON_CLASS_P (expr)
1300 && value == boolean_true_node
1301 && TREE_CONSTANT (TREE_OPERAND (expr, 1)))
1303 record_range (expr, bb);
1304 recorded_range = true;
1312 /* Dump SSA statistics on FILE. */
1315 dump_dominator_optimization_stats (FILE *file)
1319 fprintf (file, "Total number of statements: %6ld\n\n",
1320 opt_stats.num_stmts);
1321 fprintf (file, "Exprs considered for dominator optimizations: %6ld\n",
1322 opt_stats.num_exprs_considered);
1324 n_exprs = opt_stats.num_exprs_considered;
1328 fprintf (file, " Redundant expressions eliminated: %6ld (%.0f%%)\n",
1329 opt_stats.num_re, PERCENT (opt_stats.num_re,
1332 fprintf (file, "\nHash table statistics:\n");
1334 fprintf (file, " avail_exprs: ");
1335 htab_statistics (file, avail_exprs);
1339 /* Dump SSA statistics on stderr. */
1342 debug_dominator_optimization_stats (void)
1344 dump_dominator_optimization_stats (stderr);
1348 /* Dump statistics for the hash table HTAB. */
1351 htab_statistics (FILE *file, htab_t htab)
1353 fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
1354 (long) htab_size (htab),
1355 (long) htab_elements (htab),
1356 htab_collisions (htab));
1359 /* Record the fact that VAR has a nonzero value, though we may not know
1360 its exact value. Note that if VAR is already known to have a nonzero
1361 value, then we do nothing. */
1364 record_var_is_nonzero (tree var)
1366 int indx = SSA_NAME_VERSION (var);
1368 if (bitmap_bit_p (nonzero_vars, indx))
1371 /* Mark it in the global table. */
1372 bitmap_set_bit (nonzero_vars, indx);
1374 /* Record this SSA_NAME so that we can reset the global table
1375 when we leave this block. */
1376 VEC_safe_push (tree_on_heap, nonzero_vars_stack, var);
1379 /* Enter a statement into the true/false expression hash table indicating
1380 that the condition COND has the value VALUE. */
1383 record_cond (tree cond, tree value)
1385 struct expr_hash_elt *element = xmalloc (sizeof (struct expr_hash_elt));
1388 initialize_hash_element (cond, value, element);
1390 slot = htab_find_slot_with_hash (avail_exprs, (void *)element,
1391 element->hash, true);
1394 *slot = (void *) element;
1395 VEC_safe_push (tree_on_heap, avail_exprs_stack, cond);
1401 /* Build a new conditional using NEW_CODE, OP0 and OP1 and store
1402 the new conditional into *p, then store a boolean_true_node
1403 into the the *(p + 1). */
1406 build_and_record_new_cond (enum tree_code new_code, tree op0, tree op1, tree *p)
1408 *p = build2 (new_code, boolean_type_node, op0, op1);
1410 *p = boolean_true_node;
1413 /* Record that COND is true and INVERTED is false into the edge information
1414 structure. Also record that any conditions dominated by COND are true
1417 For example, if a < b is true, then a <= b must also be true. */
1420 record_conditions (struct edge_info *edge_info, tree cond, tree inverted)
1424 if (!COMPARISON_CLASS_P (cond))
1427 op0 = TREE_OPERAND (cond, 0);
1428 op1 = TREE_OPERAND (cond, 1);
1430 switch (TREE_CODE (cond))
1434 edge_info->max_cond_equivalences = 12;
1435 edge_info->cond_equivalences = xmalloc (12 * sizeof (tree));
1436 build_and_record_new_cond ((TREE_CODE (cond) == LT_EXPR
1437 ? LE_EXPR : GE_EXPR),
1438 op0, op1, &edge_info->cond_equivalences[4]);
1439 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1440 &edge_info->cond_equivalences[6]);
1441 build_and_record_new_cond (NE_EXPR, op0, op1,
1442 &edge_info->cond_equivalences[8]);
1443 build_and_record_new_cond (LTGT_EXPR, op0, op1,
1444 &edge_info->cond_equivalences[10]);
1449 edge_info->max_cond_equivalences = 6;
1450 edge_info->cond_equivalences = xmalloc (6 * sizeof (tree));
1451 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1452 &edge_info->cond_equivalences[4]);
1456 edge_info->max_cond_equivalences = 10;
1457 edge_info->cond_equivalences = xmalloc (10 * sizeof (tree));
1458 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1459 &edge_info->cond_equivalences[4]);
1460 build_and_record_new_cond (LE_EXPR, op0, op1,
1461 &edge_info->cond_equivalences[6]);
1462 build_and_record_new_cond (GE_EXPR, op0, op1,
1463 &edge_info->cond_equivalences[8]);
1466 case UNORDERED_EXPR:
1467 edge_info->max_cond_equivalences = 16;
1468 edge_info->cond_equivalences = xmalloc (16 * sizeof (tree));
1469 build_and_record_new_cond (NE_EXPR, op0, op1,
1470 &edge_info->cond_equivalences[4]);
1471 build_and_record_new_cond (UNLE_EXPR, op0, op1,
1472 &edge_info->cond_equivalences[6]);
1473 build_and_record_new_cond (UNGE_EXPR, op0, op1,
1474 &edge_info->cond_equivalences[8]);
1475 build_and_record_new_cond (UNEQ_EXPR, op0, op1,
1476 &edge_info->cond_equivalences[10]);
1477 build_and_record_new_cond (UNLT_EXPR, op0, op1,
1478 &edge_info->cond_equivalences[12]);
1479 build_and_record_new_cond (UNGT_EXPR, op0, op1,
1480 &edge_info->cond_equivalences[14]);
1485 edge_info->max_cond_equivalences = 8;
1486 edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1487 build_and_record_new_cond ((TREE_CODE (cond) == UNLT_EXPR
1488 ? UNLE_EXPR : UNGE_EXPR),
1489 op0, op1, &edge_info->cond_equivalences[4]);
1490 build_and_record_new_cond (NE_EXPR, op0, op1,
1491 &edge_info->cond_equivalences[6]);
1495 edge_info->max_cond_equivalences = 8;
1496 edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1497 build_and_record_new_cond (UNLE_EXPR, op0, op1,
1498 &edge_info->cond_equivalences[4]);
1499 build_and_record_new_cond (UNGE_EXPR, op0, op1,
1500 &edge_info->cond_equivalences[6]);
1504 edge_info->max_cond_equivalences = 8;
1505 edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1506 build_and_record_new_cond (NE_EXPR, op0, op1,
1507 &edge_info->cond_equivalences[4]);
1508 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1509 &edge_info->cond_equivalences[6]);
1513 edge_info->max_cond_equivalences = 4;
1514 edge_info->cond_equivalences = xmalloc (4 * sizeof (tree));
1518 /* Now store the original true and false conditions into the first
1520 edge_info->cond_equivalences[0] = cond;
1521 edge_info->cond_equivalences[1] = boolean_true_node;
1522 edge_info->cond_equivalences[2] = inverted;
1523 edge_info->cond_equivalences[3] = boolean_false_node;
1526 /* A helper function for record_const_or_copy and record_equality.
1527 Do the work of recording the value and undo info. */
1530 record_const_or_copy_1 (tree x, tree y, tree prev_x)
1532 SSA_NAME_VALUE (x) = y;
1534 VEC_safe_push (tree_on_heap, const_and_copies_stack, prev_x);
1535 VEC_safe_push (tree_on_heap, const_and_copies_stack, x);
1539 /* Return the loop depth of the basic block of the defining statement of X.
1540 This number should not be treated as absolutely correct because the loop
1541 information may not be completely up-to-date when dom runs. However, it
1542 will be relatively correct, and as more passes are taught to keep loop info
1543 up to date, the result will become more and more accurate. */
1546 loop_depth_of_name (tree x)
1551 /* If it's not an SSA_NAME, we have no clue where the definition is. */
1552 if (TREE_CODE (x) != SSA_NAME)
1555 /* Otherwise return the loop depth of the defining statement's bb.
1556 Note that there may not actually be a bb for this statement, if the
1557 ssa_name is live on entry. */
1558 defstmt = SSA_NAME_DEF_STMT (x);
1559 defbb = bb_for_stmt (defstmt);
1563 return defbb->loop_depth;
1567 /* Record that X is equal to Y in const_and_copies. Record undo
1568 information in the block-local vector. */
1571 record_const_or_copy (tree x, tree y)
1573 tree prev_x = SSA_NAME_VALUE (x);
1575 if (TREE_CODE (y) == SSA_NAME)
1577 tree tmp = SSA_NAME_VALUE (y);
1582 record_const_or_copy_1 (x, y, prev_x);
1585 /* Similarly, but assume that X and Y are the two operands of an EQ_EXPR.
1586 This constrains the cases in which we may treat this as assignment. */
1589 record_equality (tree x, tree y)
1591 tree prev_x = NULL, prev_y = NULL;
1593 if (TREE_CODE (x) == SSA_NAME)
1594 prev_x = SSA_NAME_VALUE (x);
1595 if (TREE_CODE (y) == SSA_NAME)
1596 prev_y = SSA_NAME_VALUE (y);
1598 /* If one of the previous values is invariant, or invariant in more loops
1599 (by depth), then use that.
1600 Otherwise it doesn't matter which value we choose, just so
1601 long as we canonicalize on one value. */
1602 if (TREE_INVARIANT (y))
1604 else if (TREE_INVARIANT (x) || (loop_depth_of_name (x) <= loop_depth_of_name (y)))
1605 prev_x = x, x = y, y = prev_x, prev_x = prev_y;
1606 else if (prev_x && TREE_INVARIANT (prev_x))
1607 x = y, y = prev_x, prev_x = prev_y;
1608 else if (prev_y && TREE_CODE (prev_y) != VALUE_HANDLE)
1611 /* After the swapping, we must have one SSA_NAME. */
1612 if (TREE_CODE (x) != SSA_NAME)
1615 /* For IEEE, -0.0 == 0.0, so we don't necessarily know the sign of a
1616 variable compared against zero. If we're honoring signed zeros,
1617 then we cannot record this value unless we know that the value is
1619 if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (x)))
1620 && (TREE_CODE (y) != REAL_CST
1621 || REAL_VALUES_EQUAL (dconst0, TREE_REAL_CST (y))))
1624 record_const_or_copy_1 (x, y, prev_x);
1627 /* Return true, if it is ok to do folding of an associative expression.
1628 EXP is the tree for the associative expression. */
1631 unsafe_associative_fp_binop (tree exp)
1633 enum tree_code code = TREE_CODE (exp);
1634 return !(!flag_unsafe_math_optimizations
1635 && (code == MULT_EXPR || code == PLUS_EXPR
1636 || code == MINUS_EXPR)
1637 && FLOAT_TYPE_P (TREE_TYPE (exp)));
1640 /* STMT is a MODIFY_EXPR for which we were unable to find RHS in the
1641 hash tables. Try to simplify the RHS using whatever equivalences
1642 we may have recorded.
1644 If we are able to simplify the RHS, then lookup the simplified form in
1645 the hash table and return the result. Otherwise return NULL. */
1648 simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *walk_data,
1649 tree stmt, int insert)
1651 tree rhs = TREE_OPERAND (stmt, 1);
1652 enum tree_code rhs_code = TREE_CODE (rhs);
1655 /* If we have lhs = ~x, look and see if we earlier had x = ~y.
1656 In which case we can change this statement to be lhs = y.
1657 Which can then be copy propagated.
1659 Similarly for negation. */
1660 if ((rhs_code == BIT_NOT_EXPR || rhs_code == NEGATE_EXPR)
1661 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
1663 /* Get the definition statement for our RHS. */
1664 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1666 /* See if the RHS_DEF_STMT has the same form as our statement. */
1667 if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR
1668 && TREE_CODE (TREE_OPERAND (rhs_def_stmt, 1)) == rhs_code)
1670 tree rhs_def_operand;
1672 rhs_def_operand = TREE_OPERAND (TREE_OPERAND (rhs_def_stmt, 1), 0);
1674 /* Verify that RHS_DEF_OPERAND is a suitable SSA variable. */
1675 if (TREE_CODE (rhs_def_operand) == SSA_NAME
1676 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))
1677 result = update_rhs_and_lookup_avail_expr (stmt,
1683 /* If we have z = (x OP C1), see if we earlier had x = y OP C2.
1684 If OP is associative, create and fold (y OP C2) OP C1 which
1685 should result in (y OP C3), use that as the RHS for the
1686 assignment. Add minus to this, as we handle it specially below. */
1687 if ((associative_tree_code (rhs_code) || rhs_code == MINUS_EXPR)
1688 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
1689 && is_gimple_min_invariant (TREE_OPERAND (rhs, 1)))
1691 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1693 /* See if the RHS_DEF_STMT has the same form as our statement. */
1694 if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR)
1696 tree rhs_def_rhs = TREE_OPERAND (rhs_def_stmt, 1);
1697 enum tree_code rhs_def_code = TREE_CODE (rhs_def_rhs);
1699 if ((rhs_code == rhs_def_code && unsafe_associative_fp_binop (rhs))
1700 || (rhs_code == PLUS_EXPR && rhs_def_code == MINUS_EXPR)
1701 || (rhs_code == MINUS_EXPR && rhs_def_code == PLUS_EXPR))
1703 tree def_stmt_op0 = TREE_OPERAND (rhs_def_rhs, 0);
1704 tree def_stmt_op1 = TREE_OPERAND (rhs_def_rhs, 1);
1706 if (TREE_CODE (def_stmt_op0) == SSA_NAME
1707 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def_stmt_op0)
1708 && is_gimple_min_invariant (def_stmt_op1))
1710 tree outer_const = TREE_OPERAND (rhs, 1);
1711 tree type = TREE_TYPE (TREE_OPERAND (stmt, 0));
1714 /* If we care about correct floating point results, then
1715 don't fold x + c1 - c2. Note that we need to take both
1716 the codes and the signs to figure this out. */
1717 if (FLOAT_TYPE_P (type)
1718 && !flag_unsafe_math_optimizations
1719 && (rhs_def_code == PLUS_EXPR
1720 || rhs_def_code == MINUS_EXPR))
1724 neg ^= (rhs_code == MINUS_EXPR);
1725 neg ^= (rhs_def_code == MINUS_EXPR);
1726 neg ^= real_isneg (TREE_REAL_CST_PTR (outer_const));
1727 neg ^= real_isneg (TREE_REAL_CST_PTR (def_stmt_op1));
1730 goto dont_fold_assoc;
1733 /* Ho hum. So fold will only operate on the outermost
1734 thingy that we give it, so we have to build the new
1735 expression in two pieces. This requires that we handle
1736 combinations of plus and minus. */
1737 if (rhs_def_code != rhs_code)
1739 if (rhs_def_code == MINUS_EXPR)
1740 t = build (MINUS_EXPR, type, outer_const, def_stmt_op1);
1742 t = build (MINUS_EXPR, type, def_stmt_op1, outer_const);
1743 rhs_code = PLUS_EXPR;
1745 else if (rhs_def_code == MINUS_EXPR)
1746 t = build (PLUS_EXPR, type, def_stmt_op1, outer_const);
1748 t = build (rhs_def_code, type, def_stmt_op1, outer_const);
1750 t = build (rhs_code, type, def_stmt_op0, t);
1753 /* If the result is a suitable looking gimple expression,
1754 then use it instead of the original for STMT. */
1755 if (TREE_CODE (t) == SSA_NAME
1756 || (UNARY_CLASS_P (t)
1757 && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME)
1758 || ((BINARY_CLASS_P (t) || COMPARISON_CLASS_P (t))
1759 && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME
1760 && is_gimple_val (TREE_OPERAND (t, 1))))
1761 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1768 /* Transform TRUNC_DIV_EXPR and TRUNC_MOD_EXPR into RSHIFT_EXPR
1769 and BIT_AND_EXPR respectively if the first operand is greater
1770 than zero and the second operand is an exact power of two. */
1771 if ((rhs_code == TRUNC_DIV_EXPR || rhs_code == TRUNC_MOD_EXPR)
1772 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0)))
1773 && integer_pow2p (TREE_OPERAND (rhs, 1)))
1776 tree op = TREE_OPERAND (rhs, 0);
1778 if (TYPE_UNSIGNED (TREE_TYPE (op)))
1780 val = integer_one_node;
1784 tree dummy_cond = walk_data->global_data;
1788 dummy_cond = build (GT_EXPR, boolean_type_node,
1789 op, integer_zero_node);
1790 dummy_cond = build (COND_EXPR, void_type_node,
1791 dummy_cond, NULL, NULL);
1792 walk_data->global_data = dummy_cond;
1796 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), GT_EXPR);
1797 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op;
1798 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1)
1799 = integer_zero_node;
1801 val = simplify_cond_and_lookup_avail_expr (dummy_cond, NULL, false);
1804 if (val && integer_onep (val))
1807 tree op0 = TREE_OPERAND (rhs, 0);
1808 tree op1 = TREE_OPERAND (rhs, 1);
1810 if (rhs_code == TRUNC_DIV_EXPR)
1811 t = build (RSHIFT_EXPR, TREE_TYPE (op0), op0,
1812 build_int_cst (NULL_TREE, tree_log2 (op1)));
1814 t = build (BIT_AND_EXPR, TREE_TYPE (op0), op0,
1815 local_fold (build (MINUS_EXPR, TREE_TYPE (op1),
1816 op1, integer_one_node)));
1818 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1822 /* Transform ABS (X) into X or -X as appropriate. */
1823 if (rhs_code == ABS_EXPR
1824 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0))))
1827 tree op = TREE_OPERAND (rhs, 0);
1828 tree type = TREE_TYPE (op);
1830 if (TYPE_UNSIGNED (type))
1832 val = integer_zero_node;
1836 tree dummy_cond = walk_data->global_data;
1840 dummy_cond = build (LE_EXPR, boolean_type_node,
1841 op, integer_zero_node);
1842 dummy_cond = build (COND_EXPR, void_type_node,
1843 dummy_cond, NULL, NULL);
1844 walk_data->global_data = dummy_cond;
1848 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), LE_EXPR);
1849 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op;
1850 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1)
1851 = build_int_cst (type, 0);
1853 val = simplify_cond_and_lookup_avail_expr (dummy_cond, NULL, false);
1857 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), GE_EXPR);
1858 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op;
1859 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1)
1860 = build_int_cst (type, 0);
1862 val = simplify_cond_and_lookup_avail_expr (dummy_cond,
1867 if (integer_zerop (val))
1868 val = integer_one_node;
1869 else if (integer_onep (val))
1870 val = integer_zero_node;
1876 && (integer_onep (val) || integer_zerop (val)))
1880 if (integer_onep (val))
1881 t = build1 (NEGATE_EXPR, TREE_TYPE (op), op);
1885 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1889 /* Optimize *"foo" into 'f'. This is done here rather than
1890 in fold to avoid problems with stuff like &*"foo". */
1891 if (TREE_CODE (rhs) == INDIRECT_REF || TREE_CODE (rhs) == ARRAY_REF)
1893 tree t = fold_read_from_constant_string (rhs);
1896 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1902 /* COND is a condition of the form:
1904 x == const or x != const
1906 Look back to x's defining statement and see if x is defined as
1910 If const is unchanged if we convert it to type, then we can build
1911 the equivalent expression:
1914 y == const or y != const
1916 Which may allow further optimizations.
1918 Return the equivalent comparison or NULL if no such equivalent comparison
1922 find_equivalent_equality_comparison (tree cond)
1924 tree op0 = TREE_OPERAND (cond, 0);
1925 tree op1 = TREE_OPERAND (cond, 1);
1926 tree def_stmt = SSA_NAME_DEF_STMT (op0);
1928 /* OP0 might have been a parameter, so first make sure it
1929 was defined by a MODIFY_EXPR. */
1930 if (def_stmt && TREE_CODE (def_stmt) == MODIFY_EXPR)
1932 tree def_rhs = TREE_OPERAND (def_stmt, 1);
1934 /* Now make sure the RHS of the MODIFY_EXPR is a typecast. */
1935 if ((TREE_CODE (def_rhs) == NOP_EXPR
1936 || TREE_CODE (def_rhs) == CONVERT_EXPR)
1937 && TREE_CODE (TREE_OPERAND (def_rhs, 0)) == SSA_NAME)
1939 tree def_rhs_inner = TREE_OPERAND (def_rhs, 0);
1940 tree def_rhs_inner_type = TREE_TYPE (def_rhs_inner);
1943 if (TYPE_PRECISION (def_rhs_inner_type)
1944 > TYPE_PRECISION (TREE_TYPE (def_rhs)))
1947 /* What we want to prove is that if we convert OP1 to
1948 the type of the object inside the NOP_EXPR that the
1949 result is still equivalent to SRC.
1951 If that is true, the build and return new equivalent
1952 condition which uses the source of the typecast and the
1953 new constant (which has only changed its type). */
1954 new = build1 (TREE_CODE (def_rhs), def_rhs_inner_type, op1);
1955 new = local_fold (new);
1956 if (is_gimple_val (new) && tree_int_cst_equal (new, op1))
1957 return build (TREE_CODE (cond), TREE_TYPE (cond),
1958 def_rhs_inner, new);
1964 /* STMT is a COND_EXPR for which we could not trivially determine its
1965 result. This routine attempts to find equivalent forms of the
1966 condition which we may be able to optimize better. It also
1967 uses simple value range propagation to optimize conditionals. */
1970 simplify_cond_and_lookup_avail_expr (tree stmt,
1974 tree cond = COND_EXPR_COND (stmt);
1976 if (COMPARISON_CLASS_P (cond))
1978 tree op0 = TREE_OPERAND (cond, 0);
1979 tree op1 = TREE_OPERAND (cond, 1);
1981 if (TREE_CODE (op0) == SSA_NAME && is_gimple_min_invariant (op1))
1984 tree low, high, cond_low, cond_high;
1985 int lowequal, highequal, swapped, no_overlap, subset, cond_inverted;
1986 varray_type vrp_records;
1987 struct vrp_element *element;
1988 struct vrp_hash_elt vrp_hash_elt, *vrp_hash_elt_p;
1991 /* First see if we have test of an SSA_NAME against a constant
1992 where the SSA_NAME is defined by an earlier typecast which
1993 is irrelevant when performing tests against the given
1995 if (TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
1997 tree new_cond = find_equivalent_equality_comparison (cond);
2001 /* Update the statement to use the new equivalent
2003 COND_EXPR_COND (stmt) = new_cond;
2005 /* If this is not a real stmt, ann will be NULL and we
2006 avoid processing the operands. */
2010 /* Lookup the condition and return its known value if it
2012 new_cond = lookup_avail_expr (stmt, insert);
2016 /* The operands have changed, so update op0 and op1. */
2017 op0 = TREE_OPERAND (cond, 0);
2018 op1 = TREE_OPERAND (cond, 1);
2022 /* Consult the value range records for this variable (if they exist)
2023 to see if we can eliminate or simplify this conditional.
2025 Note two tests are necessary to determine no records exist.
2026 First we have to see if the virtual array exists, if it
2027 exists, then we have to check its active size.
2029 Also note the vast majority of conditionals are not testing
2030 a variable which has had its range constrained by an earlier
2031 conditional. So this filter avoids a lot of unnecessary work. */
2032 vrp_hash_elt.var = op0;
2033 vrp_hash_elt.records = NULL;
2034 slot = htab_find_slot (vrp_data, &vrp_hash_elt, NO_INSERT);
2038 vrp_hash_elt_p = (struct vrp_hash_elt *) *slot;
2039 vrp_records = vrp_hash_elt_p->records;
2040 if (vrp_records == NULL)
2043 limit = VARRAY_ACTIVE_SIZE (vrp_records);
2045 /* If we have no value range records for this variable, or we are
2046 unable to extract a range for this condition, then there is
2049 || ! extract_range_from_cond (cond, &cond_high,
2050 &cond_low, &cond_inverted))
2053 /* We really want to avoid unnecessary computations of range
2054 info. So all ranges are computed lazily; this avoids a
2055 lot of unnecessary work. i.e., we record the conditional,
2056 but do not process how it constrains the variable's
2057 potential values until we know that processing the condition
2060 However, we do not want to have to walk a potentially long
2061 list of ranges, nor do we want to compute a variable's
2062 range more than once for a given path.
2064 Luckily, each time we encounter a conditional that can not
2065 be otherwise optimized we will end up here and we will
2066 compute the necessary range information for the variable
2067 used in this condition.
2069 Thus you can conclude that there will never be more than one
2070 conditional associated with a variable which has not been
2071 processed. So we never need to merge more than one new
2072 conditional into the current range.
2074 These properties also help us avoid unnecessary work. */
2076 = (struct vrp_element *)VARRAY_GENERIC_PTR (vrp_records, limit - 1);
2078 if (element->high && element->low)
2080 /* The last element has been processed, so there is no range
2081 merging to do, we can simply use the high/low values
2082 recorded in the last element. */
2084 high = element->high;
2088 tree tmp_high, tmp_low;
2091 /* The last element has not been processed. Process it now.
2092 record_range should ensure for cond inverted is not set.
2093 This call can only fail if cond is x < min or x > max,
2094 which fold should have optimized into false.
2095 If that doesn't happen, just pretend all values are
2097 if (! extract_range_from_cond (element->cond, &tmp_high,
2101 gcc_assert (dummy == 0);
2103 /* If this is the only element, then no merging is necessary,
2104 the high/low values from extract_range_from_cond are all
2113 /* Get the high/low value from the previous element. */
2114 struct vrp_element *prev
2115 = (struct vrp_element *)VARRAY_GENERIC_PTR (vrp_records,
2120 /* Merge in this element's range with the range from the
2123 The low value for the merged range is the maximum of
2124 the previous low value and the low value of this record.
2126 Similarly the high value for the merged range is the
2127 minimum of the previous high value and the high value of
2129 low = (tree_int_cst_compare (low, tmp_low) == 1
2131 high = (tree_int_cst_compare (high, tmp_high) == -1
2135 /* And record the computed range. */
2137 element->high = high;
2141 /* After we have constrained this variable's potential values,
2142 we try to determine the result of the given conditional.
2144 To simplify later tests, first determine if the current
2145 low value is the same low value as the conditional.
2146 Similarly for the current high value and the high value
2147 for the conditional. */
2148 lowequal = tree_int_cst_equal (low, cond_low);
2149 highequal = tree_int_cst_equal (high, cond_high);
2151 if (lowequal && highequal)
2152 return (cond_inverted ? boolean_false_node : boolean_true_node);
2154 /* To simplify the overlap/subset tests below we may want
2155 to swap the two ranges so that the larger of the two
2156 ranges occurs "first". */
2158 if (tree_int_cst_compare (low, cond_low) == 1
2160 && tree_int_cst_compare (cond_high, high) == 1))
2173 /* Now determine if there is no overlap in the ranges
2174 or if the second range is a subset of the first range. */
2175 no_overlap = tree_int_cst_lt (high, cond_low);
2176 subset = tree_int_cst_compare (cond_high, high) != 1;
2178 /* If there was no overlap in the ranges, then this conditional
2179 always has a false value (unless we had to invert this
2180 conditional, in which case it always has a true value). */
2182 return (cond_inverted ? boolean_true_node : boolean_false_node);
2184 /* If the current range is a subset of the condition's range,
2185 then this conditional always has a true value (unless we
2186 had to invert this conditional, in which case it always
2187 has a true value). */
2188 if (subset && swapped)
2189 return (cond_inverted ? boolean_false_node : boolean_true_node);
2191 /* We were unable to determine the result of the conditional.
2192 However, we may be able to simplify the conditional. First
2193 merge the ranges in the same manner as range merging above. */
2194 low = tree_int_cst_compare (low, cond_low) == 1 ? low : cond_low;
2195 high = tree_int_cst_compare (high, cond_high) == -1 ? high : cond_high;
2197 /* If the range has converged to a single point, then turn this
2198 into an equality comparison. */
2199 if (TREE_CODE (cond) != EQ_EXPR
2200 && TREE_CODE (cond) != NE_EXPR
2201 && tree_int_cst_equal (low, high))
2203 TREE_SET_CODE (cond, EQ_EXPR);
2204 TREE_OPERAND (cond, 1) = high;
2211 /* STMT is a SWITCH_EXPR for which we could not trivially determine its
2212 result. This routine attempts to find equivalent forms of the
2213 condition which we may be able to optimize better. */
2216 simplify_switch_and_lookup_avail_expr (tree stmt, int insert)
2218 tree cond = SWITCH_COND (stmt);
2221 /* The optimization that we really care about is removing unnecessary
2222 casts. That will let us do much better in propagating the inferred
2223 constant at the switch target. */
2224 if (TREE_CODE (cond) == SSA_NAME)
2226 def = SSA_NAME_DEF_STMT (cond);
2227 if (TREE_CODE (def) == MODIFY_EXPR)
2229 def = TREE_OPERAND (def, 1);
2230 if (TREE_CODE (def) == NOP_EXPR)
2235 def = TREE_OPERAND (def, 0);
2237 #ifdef ENABLE_CHECKING
2238 /* ??? Why was Jeff testing this? We are gimple... */
2239 gcc_assert (is_gimple_val (def));
2242 to = TREE_TYPE (cond);
2243 ti = TREE_TYPE (def);
2245 /* If we have an extension that preserves value, then we
2246 can copy the source value into the switch. */
2248 need_precision = TYPE_PRECISION (ti);
2250 if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
2252 else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
2253 need_precision += 1;
2254 if (TYPE_PRECISION (to) < need_precision)
2259 SWITCH_COND (stmt) = def;
2262 return lookup_avail_expr (stmt, insert);
2272 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2273 known value for that SSA_NAME (or NULL if no value is known).
2275 NONZERO_VARS is the set SSA_NAMES known to have a nonzero value,
2276 even if we don't know their precise value.
2278 Propagate values from CONST_AND_COPIES and NONZERO_VARS into the PHI
2279 nodes of the successors of BB. */
2282 cprop_into_successor_phis (basic_block bb, bitmap nonzero_vars)
2287 /* This can get rather expensive if the implementation is naive in
2288 how it finds the phi alternative associated with a particular edge. */
2289 FOR_EACH_EDGE (e, ei, bb->succs)
2294 /* If this is an abnormal edge, then we do not want to copy propagate
2295 into the PHI alternative associated with this edge. */
2296 if (e->flags & EDGE_ABNORMAL)
2299 phi = phi_nodes (e->dest);
2304 for ( ; phi; phi = PHI_CHAIN (phi))
2307 use_operand_p orig_p;
2310 /* The alternative may be associated with a constant, so verify
2311 it is an SSA_NAME before doing anything with it. */
2312 orig_p = PHI_ARG_DEF_PTR (phi, indx);
2313 orig = USE_FROM_PTR (orig_p);
2314 if (TREE_CODE (orig) != SSA_NAME)
2317 /* If the alternative is known to have a nonzero value, record
2318 that fact in the PHI node itself for future use. */
2319 if (bitmap_bit_p (nonzero_vars, SSA_NAME_VERSION (orig)))
2320 PHI_ARG_NONZERO (phi, indx) = true;
2322 /* If we have *ORIG_P in our constant/copy table, then replace
2323 ORIG_P with its value in our constant/copy table. */
2324 new = SSA_NAME_VALUE (orig);
2326 && (TREE_CODE (new) == SSA_NAME
2327 || is_gimple_min_invariant (new))
2328 && may_propagate_copy (orig, new))
2330 propagate_value (orig_p, new);
2336 /* We have finished optimizing BB, record any information implied by
2337 taking a specific outgoing edge from BB. */
2340 record_edge_info (basic_block bb)
2342 block_stmt_iterator bsi = bsi_last (bb);
2343 struct edge_info *edge_info;
2345 if (! bsi_end_p (bsi))
2347 tree stmt = bsi_stmt (bsi);
2349 if (stmt && TREE_CODE (stmt) == SWITCH_EXPR)
2351 tree cond = SWITCH_COND (stmt);
2353 if (TREE_CODE (cond) == SSA_NAME)
2355 tree labels = SWITCH_LABELS (stmt);
2356 int i, n_labels = TREE_VEC_LENGTH (labels);
2357 tree *info = xcalloc (n_basic_blocks, sizeof (tree));
2361 for (i = 0; i < n_labels; i++)
2363 tree label = TREE_VEC_ELT (labels, i);
2364 basic_block target_bb = label_to_block (CASE_LABEL (label));
2366 if (CASE_HIGH (label)
2367 || !CASE_LOW (label)
2368 || info[target_bb->index])
2369 info[target_bb->index] = error_mark_node;
2371 info[target_bb->index] = label;
2374 FOR_EACH_EDGE (e, ei, bb->succs)
2376 basic_block target_bb = e->dest;
2377 tree node = info[target_bb->index];
2379 if (node != NULL && node != error_mark_node)
2381 tree x = fold_convert (TREE_TYPE (cond), CASE_LOW (node));
2382 edge_info = allocate_edge_info (e);
2383 edge_info->lhs = cond;
2391 /* A COND_EXPR may create equivalences too. */
2392 if (stmt && TREE_CODE (stmt) == COND_EXPR)
2394 tree cond = COND_EXPR_COND (stmt);
2398 extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
2400 /* If the conditional is a single variable 'X', record 'X = 1'
2401 for the true edge and 'X = 0' on the false edge. */
2402 if (SSA_VAR_P (cond))
2404 struct edge_info *edge_info;
2406 edge_info = allocate_edge_info (true_edge);
2407 edge_info->lhs = cond;
2408 edge_info->rhs = constant_boolean_node (1, TREE_TYPE (cond));
2410 edge_info = allocate_edge_info (false_edge);
2411 edge_info->lhs = cond;
2412 edge_info->rhs = constant_boolean_node (0, TREE_TYPE (cond));
2414 /* Equality tests may create one or two equivalences. */
2415 else if (COMPARISON_CLASS_P (cond))
2417 tree op0 = TREE_OPERAND (cond, 0);
2418 tree op1 = TREE_OPERAND (cond, 1);
2420 /* Special case comparing booleans against a constant as we
2421 know the value of OP0 on both arms of the branch. i.e., we
2422 can record an equivalence for OP0 rather than COND. */
2423 if ((TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
2424 && TREE_CODE (op0) == SSA_NAME
2425 && TREE_CODE (TREE_TYPE (op0)) == BOOLEAN_TYPE
2426 && is_gimple_min_invariant (op1))
2428 if (TREE_CODE (cond) == EQ_EXPR)
2430 edge_info = allocate_edge_info (true_edge);
2431 edge_info->lhs = op0;
2432 edge_info->rhs = (integer_zerop (op1)
2433 ? boolean_false_node
2434 : boolean_true_node);
2436 edge_info = allocate_edge_info (false_edge);
2437 edge_info->lhs = op0;
2438 edge_info->rhs = (integer_zerop (op1)
2440 : boolean_false_node);
2444 edge_info = allocate_edge_info (true_edge);
2445 edge_info->lhs = op0;
2446 edge_info->rhs = (integer_zerop (op1)
2448 : boolean_false_node);
2450 edge_info = allocate_edge_info (false_edge);
2451 edge_info->lhs = op0;
2452 edge_info->rhs = (integer_zerop (op1)
2453 ? boolean_false_node
2454 : boolean_true_node);
2458 else if (is_gimple_min_invariant (op0)
2459 && (TREE_CODE (op1) == SSA_NAME
2460 || is_gimple_min_invariant (op1)))
2462 tree inverted = invert_truthvalue (cond);
2463 struct edge_info *edge_info;
2465 edge_info = allocate_edge_info (true_edge);
2466 record_conditions (edge_info, cond, inverted);
2468 if (TREE_CODE (cond) == EQ_EXPR)
2470 edge_info->lhs = op1;
2471 edge_info->rhs = op0;
2474 edge_info = allocate_edge_info (false_edge);
2475 record_conditions (edge_info, inverted, cond);
2477 if (TREE_CODE (cond) == NE_EXPR)
2479 edge_info->lhs = op1;
2480 edge_info->rhs = op0;
2484 else if (TREE_CODE (op0) == SSA_NAME
2485 && (is_gimple_min_invariant (op1)
2486 || TREE_CODE (op1) == SSA_NAME))
2488 tree inverted = invert_truthvalue (cond);
2489 struct edge_info *edge_info;
2491 edge_info = allocate_edge_info (true_edge);
2492 record_conditions (edge_info, cond, inverted);
2494 if (TREE_CODE (cond) == EQ_EXPR)
2496 edge_info->lhs = op0;
2497 edge_info->rhs = op1;
2500 edge_info = allocate_edge_info (false_edge);
2501 record_conditions (edge_info, inverted, cond);
2503 if (TREE_CODE (cond) == NE_EXPR)
2505 edge_info->lhs = op0;
2506 edge_info->rhs = op1;
2511 /* ??? TRUTH_NOT_EXPR can create an equivalence too. */
2516 /* Propagate information from BB to its outgoing edges.
2518 This can include equivalency information implied by control statements
2519 at the end of BB and const/copy propagation into PHIs in BB's
2520 successor blocks. */
2523 propagate_to_outgoing_edges (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
2527 record_edge_info (bb);
2528 cprop_into_successor_phis (bb, nonzero_vars);
2531 /* Search for redundant computations in STMT. If any are found, then
2532 replace them with the variable holding the result of the computation.
2534 If safe, record this expression into the available expression hash
2538 eliminate_redundant_computations (struct dom_walk_data *walk_data,
2539 tree stmt, stmt_ann_t ann)
2541 v_may_def_optype v_may_defs = V_MAY_DEF_OPS (ann);
2542 tree *expr_p, def = NULL_TREE;
2545 bool retval = false;
2547 if (TREE_CODE (stmt) == MODIFY_EXPR)
2548 def = TREE_OPERAND (stmt, 0);
2550 /* Certain expressions on the RHS can be optimized away, but can not
2551 themselves be entered into the hash tables. */
2552 if (ann->makes_aliased_stores
2554 || TREE_CODE (def) != SSA_NAME
2555 || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def)
2556 || NUM_V_MAY_DEFS (v_may_defs) != 0)
2559 /* Check if the expression has been computed before. */
2560 cached_lhs = lookup_avail_expr (stmt, insert);
2562 /* If this is an assignment and the RHS was not in the hash table,
2563 then try to simplify the RHS and lookup the new RHS in the
2565 if (! cached_lhs && TREE_CODE (stmt) == MODIFY_EXPR)
2566 cached_lhs = simplify_rhs_and_lookup_avail_expr (walk_data, stmt, insert);
2567 /* Similarly if this is a COND_EXPR and we did not find its
2568 expression in the hash table, simplify the condition and
2570 else if (! cached_lhs && TREE_CODE (stmt) == COND_EXPR)
2571 cached_lhs = simplify_cond_and_lookup_avail_expr (stmt, ann, insert);
2572 /* Similarly for a SWITCH_EXPR. */
2573 else if (!cached_lhs && TREE_CODE (stmt) == SWITCH_EXPR)
2574 cached_lhs = simplify_switch_and_lookup_avail_expr (stmt, insert);
2576 opt_stats.num_exprs_considered++;
2578 /* Get a pointer to the expression we are trying to optimize. */
2579 if (TREE_CODE (stmt) == COND_EXPR)
2580 expr_p = &COND_EXPR_COND (stmt);
2581 else if (TREE_CODE (stmt) == SWITCH_EXPR)
2582 expr_p = &SWITCH_COND (stmt);
2583 else if (TREE_CODE (stmt) == RETURN_EXPR && TREE_OPERAND (stmt, 0))
2584 expr_p = &TREE_OPERAND (TREE_OPERAND (stmt, 0), 1);
2586 expr_p = &TREE_OPERAND (stmt, 1);
2588 /* It is safe to ignore types here since we have already done
2589 type checking in the hashing and equality routines. In fact
2590 type checking here merely gets in the way of constant
2591 propagation. Also, make sure that it is safe to propagate
2592 CACHED_LHS into *EXPR_P. */
2594 && (TREE_CODE (cached_lhs) != SSA_NAME
2595 || may_propagate_copy (*expr_p, cached_lhs)))
2597 if (dump_file && (dump_flags & TDF_DETAILS))
2599 fprintf (dump_file, " Replaced redundant expr '");
2600 print_generic_expr (dump_file, *expr_p, dump_flags);
2601 fprintf (dump_file, "' with '");
2602 print_generic_expr (dump_file, cached_lhs, dump_flags);
2603 fprintf (dump_file, "'\n");
2608 #if defined ENABLE_CHECKING
2609 gcc_assert (TREE_CODE (cached_lhs) == SSA_NAME
2610 || is_gimple_min_invariant (cached_lhs));
2613 if (TREE_CODE (cached_lhs) == ADDR_EXPR
2614 || (POINTER_TYPE_P (TREE_TYPE (*expr_p))
2615 && is_gimple_min_invariant (cached_lhs)))
2618 propagate_tree_value (expr_p, cached_lhs);
2624 /* STMT, a MODIFY_EXPR, may create certain equivalences, in either
2625 the available expressions table or the const_and_copies table.
2626 Detect and record those equivalences. */
2629 record_equivalences_from_stmt (tree stmt,
2633 tree lhs = TREE_OPERAND (stmt, 0);
2634 enum tree_code lhs_code = TREE_CODE (lhs);
2637 if (lhs_code == SSA_NAME)
2639 tree rhs = TREE_OPERAND (stmt, 1);
2641 /* Strip away any useless type conversions. */
2642 STRIP_USELESS_TYPE_CONVERSION (rhs);
2644 /* If the RHS of the assignment is a constant or another variable that
2645 may be propagated, register it in the CONST_AND_COPIES table. We
2646 do not need to record unwind data for this, since this is a true
2647 assignment and not an equivalence inferred from a comparison. All
2648 uses of this ssa name are dominated by this assignment, so unwinding
2649 just costs time and space. */
2651 && (TREE_CODE (rhs) == SSA_NAME
2652 || is_gimple_min_invariant (rhs)))
2653 SSA_NAME_VALUE (lhs) = rhs;
2655 /* alloca never returns zero and the address of a non-weak symbol
2656 is never zero. NOP_EXPRs and CONVERT_EXPRs can be completely
2657 stripped as they do not affect this equivalence. */
2658 while (TREE_CODE (rhs) == NOP_EXPR
2659 || TREE_CODE (rhs) == CONVERT_EXPR)
2660 rhs = TREE_OPERAND (rhs, 0);
2662 if (alloca_call_p (rhs)
2663 || (TREE_CODE (rhs) == ADDR_EXPR
2664 && DECL_P (TREE_OPERAND (rhs, 0))
2665 && ! DECL_WEAK (TREE_OPERAND (rhs, 0))))
2666 record_var_is_nonzero (lhs);
2668 /* IOR of any value with a nonzero value will result in a nonzero
2669 value. Even if we do not know the exact result recording that
2670 the result is nonzero is worth the effort. */
2671 if (TREE_CODE (rhs) == BIT_IOR_EXPR
2672 && integer_nonzerop (TREE_OPERAND (rhs, 1)))
2673 record_var_is_nonzero (lhs);
2676 /* Look at both sides for pointer dereferences. If we find one, then
2677 the pointer must be nonnull and we can enter that equivalence into
2679 if (flag_delete_null_pointer_checks)
2680 for (i = 0; i < 2; i++)
2682 tree t = TREE_OPERAND (stmt, i);
2684 /* Strip away any COMPONENT_REFs. */
2685 while (TREE_CODE (t) == COMPONENT_REF)
2686 t = TREE_OPERAND (t, 0);
2688 /* Now see if this is a pointer dereference. */
2689 if (INDIRECT_REF_P (t))
2691 tree op = TREE_OPERAND (t, 0);
2693 /* If the pointer is a SSA variable, then enter new
2694 equivalences into the hash table. */
2695 while (TREE_CODE (op) == SSA_NAME)
2697 tree def = SSA_NAME_DEF_STMT (op);
2699 record_var_is_nonzero (op);
2701 /* And walk up the USE-DEF chains noting other SSA_NAMEs
2702 which are known to have a nonzero value. */
2704 && TREE_CODE (def) == MODIFY_EXPR
2705 && TREE_CODE (TREE_OPERAND (def, 1)) == NOP_EXPR)
2706 op = TREE_OPERAND (TREE_OPERAND (def, 1), 0);
2713 /* A memory store, even an aliased store, creates a useful
2714 equivalence. By exchanging the LHS and RHS, creating suitable
2715 vops and recording the result in the available expression table,
2716 we may be able to expose more redundant loads. */
2717 if (!ann->has_volatile_ops
2718 && (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME
2719 || is_gimple_min_invariant (TREE_OPERAND (stmt, 1)))
2720 && !is_gimple_reg (lhs))
2722 tree rhs = TREE_OPERAND (stmt, 1);
2725 /* FIXME: If the LHS of the assignment is a bitfield and the RHS
2726 is a constant, we need to adjust the constant to fit into the
2727 type of the LHS. If the LHS is a bitfield and the RHS is not
2728 a constant, then we can not record any equivalences for this
2729 statement since we would need to represent the widening or
2730 narrowing of RHS. This fixes gcc.c-torture/execute/921016-1.c
2731 and should not be necessary if GCC represented bitfields
2733 if (lhs_code == COMPONENT_REF
2734 && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1)))
2736 if (TREE_CONSTANT (rhs))
2737 rhs = widen_bitfield (rhs, TREE_OPERAND (lhs, 1), lhs);
2741 /* If the value overflowed, then we can not use this equivalence. */
2742 if (rhs && ! is_gimple_min_invariant (rhs))
2748 /* Build a new statement with the RHS and LHS exchanged. */
2749 new = build (MODIFY_EXPR, TREE_TYPE (stmt), rhs, lhs);
2751 create_ssa_artficial_load_stmt (&(ann->operands), new);
2753 /* Finally enter the statement into the available expression
2755 lookup_avail_expr (new, true);
2760 /* Replace *OP_P in STMT with any known equivalent value for *OP_P from
2761 CONST_AND_COPIES. */
2764 cprop_operand (tree stmt, use_operand_p op_p)
2766 bool may_have_exposed_new_symbols = false;
2768 tree op = USE_FROM_PTR (op_p);
2770 /* If the operand has a known constant value or it is known to be a
2771 copy of some other variable, use the value or copy stored in
2772 CONST_AND_COPIES. */
2773 val = SSA_NAME_VALUE (op);
2774 if (val && TREE_CODE (val) != VALUE_HANDLE)
2776 tree op_type, val_type;
2778 /* Do not change the base variable in the virtual operand
2779 tables. That would make it impossible to reconstruct
2780 the renamed virtual operand if we later modify this
2781 statement. Also only allow the new value to be an SSA_NAME
2782 for propagation into virtual operands. */
2783 if (!is_gimple_reg (op)
2784 && (get_virtual_var (val) != get_virtual_var (op)
2785 || TREE_CODE (val) != SSA_NAME))
2788 /* Do not replace hard register operands in asm statements. */
2789 if (TREE_CODE (stmt) == ASM_EXPR
2790 && !may_propagate_copy_into_asm (op))
2793 /* Get the toplevel type of each operand. */
2794 op_type = TREE_TYPE (op);
2795 val_type = TREE_TYPE (val);
2797 /* While both types are pointers, get the type of the object
2799 while (POINTER_TYPE_P (op_type) && POINTER_TYPE_P (val_type))
2801 op_type = TREE_TYPE (op_type);
2802 val_type = TREE_TYPE (val_type);
2805 /* Make sure underlying types match before propagating a constant by
2806 converting the constant to the proper type. Note that convert may
2807 return a non-gimple expression, in which case we ignore this
2808 propagation opportunity. */
2809 if (TREE_CODE (val) != SSA_NAME)
2811 if (!lang_hooks.types_compatible_p (op_type, val_type))
2813 val = fold_convert (TREE_TYPE (op), val);
2814 if (!is_gimple_min_invariant (val))
2819 /* Certain operands are not allowed to be copy propagated due
2820 to their interaction with exception handling and some GCC
2822 else if (!may_propagate_copy (op, val))
2826 if (dump_file && (dump_flags & TDF_DETAILS))
2828 fprintf (dump_file, " Replaced '");
2829 print_generic_expr (dump_file, op, dump_flags);
2830 fprintf (dump_file, "' with %s '",
2831 (TREE_CODE (val) != SSA_NAME ? "constant" : "variable"));
2832 print_generic_expr (dump_file, val, dump_flags);
2833 fprintf (dump_file, "'\n");
2836 /* If VAL is an ADDR_EXPR or a constant of pointer type, note
2837 that we may have exposed a new symbol for SSA renaming. */
2838 if (TREE_CODE (val) == ADDR_EXPR
2839 || (POINTER_TYPE_P (TREE_TYPE (op))
2840 && is_gimple_min_invariant (val)))
2841 may_have_exposed_new_symbols = true;
2843 propagate_value (op_p, val);
2845 /* And note that we modified this statement. This is now
2846 safe, even if we changed virtual operands since we will
2847 rescan the statement and rewrite its operands again. */
2850 return may_have_exposed_new_symbols;
2853 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2854 known value for that SSA_NAME (or NULL if no value is known).
2856 Propagate values from CONST_AND_COPIES into the uses, vuses and
2857 v_may_def_ops of STMT. */
2860 cprop_into_stmt (tree stmt)
2862 bool may_have_exposed_new_symbols = false;
2867 FOR_EACH_SSA_USE_OPERAND (op_p, stmt, iter, SSA_OP_ALL_USES)
2869 if (TREE_CODE (USE_FROM_PTR (op_p)) == SSA_NAME)
2870 may_have_exposed_new_symbols |= cprop_operand (stmt, op_p);
2873 if (may_have_exposed_new_symbols)
2875 rhs = get_rhs (stmt);
2876 if (rhs && TREE_CODE (rhs) == ADDR_EXPR)
2877 recompute_tree_invarant_for_addr_expr (rhs);
2880 return may_have_exposed_new_symbols;
2884 /* Optimize the statement pointed by iterator SI.
2886 We try to perform some simplistic global redundancy elimination and
2887 constant propagation:
2889 1- To detect global redundancy, we keep track of expressions that have
2890 been computed in this block and its dominators. If we find that the
2891 same expression is computed more than once, we eliminate repeated
2892 computations by using the target of the first one.
2894 2- Constant values and copy assignments. This is used to do very
2895 simplistic constant and copy propagation. When a constant or copy
2896 assignment is found, we map the value on the RHS of the assignment to
2897 the variable in the LHS in the CONST_AND_COPIES table. */
2900 optimize_stmt (struct dom_walk_data *walk_data, basic_block bb,
2901 block_stmt_iterator si)
2905 bool may_optimize_p;
2906 bool may_have_exposed_new_symbols = false;
2908 stmt = bsi_stmt (si);
2910 get_stmt_operands (stmt);
2911 ann = stmt_ann (stmt);
2912 opt_stats.num_stmts++;
2913 may_have_exposed_new_symbols = false;
2915 if (dump_file && (dump_flags & TDF_DETAILS))
2917 fprintf (dump_file, "Optimizing statement ");
2918 print_generic_stmt (dump_file, stmt, TDF_SLIM);
2921 /* Const/copy propagate into USES, VUSES and the RHS of V_MAY_DEFs. */
2922 may_have_exposed_new_symbols = cprop_into_stmt (stmt);
2924 /* If the statement has been modified with constant replacements,
2925 fold its RHS before checking for redundant computations. */
2928 /* Try to fold the statement making sure that STMT is kept
2930 if (fold_stmt (bsi_stmt_ptr (si)))
2932 stmt = bsi_stmt (si);
2933 ann = stmt_ann (stmt);
2935 if (dump_file && (dump_flags & TDF_DETAILS))
2937 fprintf (dump_file, " Folded to: ");
2938 print_generic_stmt (dump_file, stmt, TDF_SLIM);
2942 /* Constant/copy propagation above may change the set of
2943 virtual operands associated with this statement. Folding
2944 may remove the need for some virtual operands.
2946 Indicate we will need to rescan and rewrite the statement. */
2947 may_have_exposed_new_symbols = true;
2950 /* Check for redundant computations. Do this optimization only
2951 for assignments that have no volatile ops and conditionals. */
2952 may_optimize_p = (!ann->has_volatile_ops
2953 && ((TREE_CODE (stmt) == RETURN_EXPR
2954 && TREE_OPERAND (stmt, 0)
2955 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR
2956 && ! (TREE_SIDE_EFFECTS
2957 (TREE_OPERAND (TREE_OPERAND (stmt, 0), 1))))
2958 || (TREE_CODE (stmt) == MODIFY_EXPR
2959 && ! TREE_SIDE_EFFECTS (TREE_OPERAND (stmt, 1)))
2960 || TREE_CODE (stmt) == COND_EXPR
2961 || TREE_CODE (stmt) == SWITCH_EXPR));
2964 may_have_exposed_new_symbols
2965 |= eliminate_redundant_computations (walk_data, stmt, ann);
2967 /* Record any additional equivalences created by this statement. */
2968 if (TREE_CODE (stmt) == MODIFY_EXPR)
2969 record_equivalences_from_stmt (stmt,
2973 register_definitions_for_stmt (stmt);
2975 /* If STMT is a COND_EXPR and it was modified, then we may know
2976 where it goes. If that is the case, then mark the CFG as altered.
2978 This will cause us to later call remove_unreachable_blocks and
2979 cleanup_tree_cfg when it is safe to do so. It is not safe to
2980 clean things up here since removal of edges and such can trigger
2981 the removal of PHI nodes, which in turn can release SSA_NAMEs to
2984 That's all fine and good, except that once SSA_NAMEs are released
2985 to the manager, we must not call create_ssa_name until all references
2986 to released SSA_NAMEs have been eliminated.
2988 All references to the deleted SSA_NAMEs can not be eliminated until
2989 we remove unreachable blocks.
2991 We can not remove unreachable blocks until after we have completed
2992 any queued jump threading.
2994 We can not complete any queued jump threads until we have taken
2995 appropriate variables out of SSA form. Taking variables out of
2996 SSA form can call create_ssa_name and thus we lose.
2998 Ultimately I suspect we're going to need to change the interface
2999 into the SSA_NAME manager. */
3005 if (TREE_CODE (stmt) == COND_EXPR)
3006 val = COND_EXPR_COND (stmt);
3007 else if (TREE_CODE (stmt) == SWITCH_EXPR)
3008 val = SWITCH_COND (stmt);
3010 if (val && TREE_CODE (val) == INTEGER_CST && find_taken_edge (bb, val))
3013 /* If we simplified a statement in such a way as to be shown that it
3014 cannot trap, update the eh information and the cfg to match. */
3015 if (maybe_clean_eh_stmt (stmt))
3017 bitmap_set_bit (need_eh_cleanup, bb->index);
3018 if (dump_file && (dump_flags & TDF_DETAILS))
3019 fprintf (dump_file, " Flagged to clear EH edges.\n");
3023 if (may_have_exposed_new_symbols)
3024 VEC_safe_push (tree_on_heap, stmts_to_rescan, bsi_stmt (si));
3027 /* Replace the RHS of STMT with NEW_RHS. If RHS can be found in the
3028 available expression hashtable, then return the LHS from the hash
3031 If INSERT is true, then we also update the available expression
3032 hash table to account for the changes made to STMT. */
3035 update_rhs_and_lookup_avail_expr (tree stmt, tree new_rhs, bool insert)
3037 tree cached_lhs = NULL;
3039 /* Remove the old entry from the hash table. */
3042 struct expr_hash_elt element;
3044 initialize_hash_element (stmt, NULL, &element);
3045 htab_remove_elt_with_hash (avail_exprs, &element, element.hash);
3048 /* Now update the RHS of the assignment. */
3049 TREE_OPERAND (stmt, 1) = new_rhs;
3051 /* Now lookup the updated statement in the hash table. */
3052 cached_lhs = lookup_avail_expr (stmt, insert);
3054 /* We have now called lookup_avail_expr twice with two different
3055 versions of this same statement, once in optimize_stmt, once here.
3057 We know the call in optimize_stmt did not find an existing entry
3058 in the hash table, so a new entry was created. At the same time
3059 this statement was pushed onto the AVAIL_EXPRS_STACK vector.
3061 If this call failed to find an existing entry on the hash table,
3062 then the new version of this statement was entered into the
3063 hash table. And this statement was pushed onto BLOCK_AVAIL_EXPR
3064 for the second time. So there are two copies on BLOCK_AVAIL_EXPRs
3066 If this call succeeded, we still have one copy of this statement
3067 on the BLOCK_AVAIL_EXPRs vector.
3069 For both cases, we need to pop the most recent entry off the
3070 BLOCK_AVAIL_EXPRs vector. For the case where we never found this
3071 statement in the hash tables, that will leave precisely one
3072 copy of this statement on BLOCK_AVAIL_EXPRs. For the case where
3073 we found a copy of this statement in the second hash table lookup
3074 we want _no_ copies of this statement in BLOCK_AVAIL_EXPRs. */
3076 VEC_pop (tree_on_heap, avail_exprs_stack);
3078 /* And make sure we record the fact that we modified this
3085 /* Search for an existing instance of STMT in the AVAIL_EXPRS table. If
3086 found, return its LHS. Otherwise insert STMT in the table and return
3089 Also, when an expression is first inserted in the AVAIL_EXPRS table, it
3090 is also added to the stack pointed by BLOCK_AVAIL_EXPRS_P, so that they
3091 can be removed when we finish processing this block and its children.
3093 NOTE: This function assumes that STMT is a MODIFY_EXPR node that
3094 contains no CALL_EXPR on its RHS and makes no volatile nor
3095 aliased references. */
3098 lookup_avail_expr (tree stmt, bool insert)
3103 struct expr_hash_elt *element = xcalloc (sizeof (struct expr_hash_elt), 1);
3105 lhs = TREE_CODE (stmt) == MODIFY_EXPR ? TREE_OPERAND (stmt, 0) : NULL;
3107 initialize_hash_element (stmt, lhs, element);
3109 /* Don't bother remembering constant assignments and copy operations.
3110 Constants and copy operations are handled by the constant/copy propagator
3111 in optimize_stmt. */
3112 if (TREE_CODE (element->rhs) == SSA_NAME
3113 || is_gimple_min_invariant (element->rhs))
3119 /* If this is an equality test against zero, see if we have recorded a
3120 nonzero value for the variable in question. */
3121 if ((TREE_CODE (element->rhs) == EQ_EXPR
3122 || TREE_CODE (element->rhs) == NE_EXPR)
3123 && TREE_CODE (TREE_OPERAND (element->rhs, 0)) == SSA_NAME
3124 && integer_zerop (TREE_OPERAND (element->rhs, 1)))
3126 int indx = SSA_NAME_VERSION (TREE_OPERAND (element->rhs, 0));
3128 if (bitmap_bit_p (nonzero_vars, indx))
3130 tree t = element->rhs;
3133 if (TREE_CODE (t) == EQ_EXPR)
3134 return boolean_false_node;
3136 return boolean_true_node;
3140 /* Finally try to find the expression in the main expression hash table. */
3141 slot = htab_find_slot_with_hash (avail_exprs, element, element->hash,
3142 (insert ? INSERT : NO_INSERT));
3151 *slot = (void *) element;
3152 VEC_safe_push (tree_on_heap, avail_exprs_stack,
3153 stmt ? stmt : element->rhs);
3157 /* Extract the LHS of the assignment so that it can be used as the current
3158 definition of another variable. */
3159 lhs = ((struct expr_hash_elt *)*slot)->lhs;
3161 /* See if the LHS appears in the CONST_AND_COPIES table. If it does, then
3162 use the value from the const_and_copies table. */
3163 if (TREE_CODE (lhs) == SSA_NAME)
3165 temp = SSA_NAME_VALUE (lhs);
3166 if (temp && TREE_CODE (temp) != VALUE_HANDLE)
3174 /* Given a condition COND, record into HI_P, LO_P and INVERTED_P the
3175 range of values that result in the conditional having a true value.
3177 Return true if we are successful in extracting a range from COND and
3178 false if we are unsuccessful. */
3181 extract_range_from_cond (tree cond, tree *hi_p, tree *lo_p, int *inverted_p)
3183 tree op1 = TREE_OPERAND (cond, 1);
3184 tree high, low, type;
3187 /* Experiments have shown that it's rarely, if ever useful to
3188 record ranges for enumerations. Presumably this is due to
3189 the fact that they're rarely used directly. They are typically
3190 cast into an integer type and used that way. */
3191 if (TREE_CODE (TREE_TYPE (op1)) != INTEGER_TYPE)
3194 type = TREE_TYPE (op1);
3196 switch (TREE_CODE (cond))
3210 high = TYPE_MAX_VALUE (type);
3215 high = TYPE_MAX_VALUE (type);
3216 if (!tree_int_cst_lt (op1, high))
3218 low = int_const_binop (PLUS_EXPR, op1, integer_one_node, 1);
3224 low = TYPE_MIN_VALUE (type);
3229 low = TYPE_MIN_VALUE (type);
3230 if (!tree_int_cst_lt (low, op1))
3232 high = int_const_binop (MINUS_EXPR, op1, integer_one_node, 1);
3242 *inverted_p = inverted;
3246 /* Record a range created by COND for basic block BB. */
3249 record_range (tree cond, basic_block bb)
3251 enum tree_code code = TREE_CODE (cond);
3253 /* We explicitly ignore NE_EXPRs and all the unordered comparisons.
3254 They rarely allow for meaningful range optimizations and significantly
3255 complicate the implementation. */
3256 if ((code == LT_EXPR || code == LE_EXPR || code == GT_EXPR
3257 || code == GE_EXPR || code == EQ_EXPR)
3258 && TREE_CODE (TREE_TYPE (TREE_OPERAND (cond, 1))) == INTEGER_TYPE)
3260 struct vrp_hash_elt *vrp_hash_elt;
3261 struct vrp_element *element;
3262 varray_type *vrp_records_p;
3266 vrp_hash_elt = xmalloc (sizeof (struct vrp_hash_elt));
3267 vrp_hash_elt->var = TREE_OPERAND (cond, 0);
3268 vrp_hash_elt->records = NULL;
3269 slot = htab_find_slot (vrp_data, vrp_hash_elt, INSERT);
3272 *slot = (void *) vrp_hash_elt;
3274 free (vrp_hash_elt);
3276 vrp_hash_elt = (struct vrp_hash_elt *) *slot;
3277 vrp_records_p = &vrp_hash_elt->records;
3279 element = ggc_alloc (sizeof (struct vrp_element));
3280 element->low = NULL;
3281 element->high = NULL;
3282 element->cond = cond;
3285 if (*vrp_records_p == NULL)
3286 VARRAY_GENERIC_PTR_INIT (*vrp_records_p, 2, "vrp records");
3288 VARRAY_PUSH_GENERIC_PTR (*vrp_records_p, element);
3289 VEC_safe_push (tree_on_heap, vrp_variables_stack, TREE_OPERAND (cond, 0));
3293 /* Hashing and equality functions for VRP_DATA.
3295 Since this hash table is addressed by SSA_NAMEs, we can hash on
3296 their version number and equality can be determined with a
3297 pointer comparison. */
3300 vrp_hash (const void *p)
3302 tree var = ((struct vrp_hash_elt *)p)->var;
3304 return SSA_NAME_VERSION (var);
3308 vrp_eq (const void *p1, const void *p2)
3310 tree var1 = ((struct vrp_hash_elt *)p1)->var;
3311 tree var2 = ((struct vrp_hash_elt *)p2)->var;
3313 return var1 == var2;
3316 /* Hashing and equality functions for AVAIL_EXPRS. The table stores
3317 MODIFY_EXPR statements. We compute a value number for expressions using
3318 the code of the expression and the SSA numbers of its operands. */
3321 avail_expr_hash (const void *p)
3323 stmt_ann_t ann = ((struct expr_hash_elt *)p)->ann;
3324 tree rhs = ((struct expr_hash_elt *)p)->rhs;
3329 /* iterative_hash_expr knows how to deal with any expression and
3330 deals with commutative operators as well, so just use it instead
3331 of duplicating such complexities here. */
3332 val = iterative_hash_expr (rhs, val);
3334 /* If the hash table entry is not associated with a statement, then we
3335 can just hash the expression and not worry about virtual operands
3340 /* Add the SSA version numbers of every vuse operand. This is important
3341 because compound variables like arrays are not renamed in the
3342 operands. Rather, the rename is done on the virtual variable
3343 representing all the elements of the array. */
3344 vuses = VUSE_OPS (ann);
3345 for (i = 0; i < NUM_VUSES (vuses); i++)
3346 val = iterative_hash_expr (VUSE_OP (vuses, i), val);
3352 real_avail_expr_hash (const void *p)
3354 return ((const struct expr_hash_elt *)p)->hash;
3358 avail_expr_eq (const void *p1, const void *p2)
3360 stmt_ann_t ann1 = ((struct expr_hash_elt *)p1)->ann;
3361 tree rhs1 = ((struct expr_hash_elt *)p1)->rhs;
3362 stmt_ann_t ann2 = ((struct expr_hash_elt *)p2)->ann;
3363 tree rhs2 = ((struct expr_hash_elt *)p2)->rhs;
3365 /* If they are the same physical expression, return true. */
3366 if (rhs1 == rhs2 && ann1 == ann2)
3369 /* If their codes are not equal, then quit now. */
3370 if (TREE_CODE (rhs1) != TREE_CODE (rhs2))
3373 /* In case of a collision, both RHS have to be identical and have the
3374 same VUSE operands. */
3375 if ((TREE_TYPE (rhs1) == TREE_TYPE (rhs2)
3376 || lang_hooks.types_compatible_p (TREE_TYPE (rhs1), TREE_TYPE (rhs2)))
3377 && operand_equal_p (rhs1, rhs2, OEP_PURE_SAME))
3379 vuse_optype ops1 = NULL;
3380 vuse_optype ops2 = NULL;
3381 size_t num_ops1 = 0;
3382 size_t num_ops2 = 0;
3387 ops1 = VUSE_OPS (ann1);
3388 num_ops1 = NUM_VUSES (ops1);
3393 ops2 = VUSE_OPS (ann2);
3394 num_ops2 = NUM_VUSES (ops2);
3397 /* If the number of virtual uses is different, then we consider
3399 if (num_ops1 != num_ops2)
3402 for (i = 0; i < num_ops1; i++)
3403 if (VUSE_OP (ops1, i) != VUSE_OP (ops2, i))
3406 gcc_assert (((struct expr_hash_elt *)p1)->hash
3407 == ((struct expr_hash_elt *)p2)->hash);
3414 /* Given STMT and a pointer to the block local definitions BLOCK_DEFS_P,
3415 register register all objects set by this statement into BLOCK_DEFS_P
3419 register_definitions_for_stmt (tree stmt)
3424 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
3427 /* FIXME: We shouldn't be registering new defs if the variable
3428 doesn't need to be renamed. */
3429 register_new_def (def, &block_defs_stack);