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,heap) *avail_exprs_stack;
98 /* Stack of statements we need to rescan during finalization for newly
101 Statement rescanning must occur after the current block's available
102 expressions are removed from AVAIL_EXPRS. Else we may change the
103 hash code for an expression and be unable to find/remove it from
105 static VEC(tree,heap) *stmts_to_rescan;
107 /* Structure for entries in the expression hash table.
109 This requires more memory for the hash table entries, but allows us
110 to avoid creating silly tree nodes and annotations for conditionals,
111 eliminates 2 global hash tables and two block local varrays.
113 It also allows us to reduce the number of hash table lookups we
114 have to perform in lookup_avail_expr and finally it allows us to
115 significantly reduce the number of calls into the hashing routine
120 /* The value (lhs) of this expression. */
123 /* The expression (rhs) we want to record. */
126 /* The stmt pointer if this element corresponds to a statement. */
129 /* The hash value for RHS/ann. */
133 /* Stack of dest,src pairs that need to be restored during finalization.
135 A NULL entry is used to mark the end of pairs which need to be
136 restored during finalization of this block. */
137 static VEC(tree,heap) *const_and_copies_stack;
139 /* Bitmap of SSA_NAMEs known to have a nonzero value, even if we do not
140 know their exact value. */
141 static bitmap nonzero_vars;
143 /* Bitmap of blocks that are scheduled to be threaded through. This
144 is used to communicate with thread_through_blocks. */
145 static bitmap threaded_blocks;
147 /* Stack of SSA_NAMEs which need their NONZERO_VARS property cleared
148 when the current block is finalized.
150 A NULL entry is used to mark the end of names needing their
151 entry in NONZERO_VARS cleared during finalization of this block. */
152 static VEC(tree,heap) *nonzero_vars_stack;
154 /* Track whether or not we have changed the control flow graph. */
155 static bool cfg_altered;
157 /* Bitmap of blocks that have had EH statements cleaned. We should
158 remove their dead edges eventually. */
159 static bitmap need_eh_cleanup;
161 /* Statistics for dominator optimizations. */
165 long num_exprs_considered;
171 static struct opt_stats_d opt_stats;
173 /* Value range propagation record. Each time we encounter a conditional
174 of the form SSA_NAME COND CONST we create a new vrp_element to record
175 how the condition affects the possible values SSA_NAME may have.
177 Each record contains the condition tested (COND), and the range of
178 values the variable may legitimately have if COND is true. Note the
179 range of values may be a smaller range than COND specifies if we have
180 recorded other ranges for this variable. Each record also contains the
181 block in which the range was recorded for invalidation purposes.
183 Note that the current known range is computed lazily. This allows us
184 to avoid the overhead of computing ranges which are never queried.
186 When we encounter a conditional, we look for records which constrain
187 the SSA_NAME used in the condition. In some cases those records allow
188 us to determine the condition's result at compile time. In other cases
189 they may allow us to simplify the condition.
191 We also use value ranges to do things like transform signed div/mod
192 operations into unsigned div/mod or to simplify ABS_EXPRs.
194 Simple experiments have shown these optimizations to not be all that
195 useful on switch statements (much to my surprise). So switch statement
196 optimizations are not performed.
198 Note carefully we do not propagate information through each statement
199 in the block. i.e., if we know variable X has a value defined of
200 [0, 25] and we encounter Y = X + 1, we do not track a value range
201 for Y (which would be [1, 26] if we cared). Similarly we do not
202 constrain values as we encounter narrowing typecasts, etc. */
206 /* The highest and lowest values the variable in COND may contain when
207 COND is true. Note this may not necessarily be the same values
208 tested by COND if the same variable was used in earlier conditionals.
210 Note this is computed lazily and thus can be NULL indicating that
211 the values have not been computed yet. */
215 /* The actual conditional we recorded. This is needed since we compute
219 /* The basic block where this record was created. We use this to determine
220 when to remove records. */
224 /* A hash table holding value range records (VRP_ELEMENTs) for a given
225 SSA_NAME. We used to use a varray indexed by SSA_NAME_VERSION, but
226 that gets awful wasteful, particularly since the density objects
227 with useful information is very low. */
228 static htab_t vrp_data;
230 typedef struct vrp_element *vrp_element_p;
232 DEF_VEC_P(vrp_element_p);
233 DEF_VEC_ALLOC_P(vrp_element_p,heap);
235 /* An entry in the VRP_DATA hash table. We record the variable and a
236 varray of VRP_ELEMENT records associated with that variable. */
240 VEC(vrp_element_p,heap) *records;
243 /* Array of variables which have their values constrained by operations
244 in this basic block. We use this during finalization to know
245 which variables need their VRP data updated. */
247 /* Stack of SSA_NAMEs which had their values constrained by operations
248 in this basic block. During finalization of this block we use this
249 list to determine which variables need their VRP data updated.
251 A NULL entry marks the end of the SSA_NAMEs associated with this block. */
252 static VEC(tree,heap) *vrp_variables_stack;
260 /* Local functions. */
261 static void optimize_stmt (struct dom_walk_data *,
263 block_stmt_iterator);
264 static tree lookup_avail_expr (tree, bool);
265 static hashval_t vrp_hash (const void *);
266 static int vrp_eq (const void *, const void *);
267 static hashval_t avail_expr_hash (const void *);
268 static hashval_t real_avail_expr_hash (const void *);
269 static int avail_expr_eq (const void *, const void *);
270 static void htab_statistics (FILE *, htab_t);
271 static void record_cond (tree, tree);
272 static void record_const_or_copy (tree, tree);
273 static void record_equality (tree, tree);
274 static tree update_rhs_and_lookup_avail_expr (tree, tree, bool);
275 static tree simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *,
277 static tree simplify_cond_and_lookup_avail_expr (tree, stmt_ann_t, int);
278 static tree simplify_switch_and_lookup_avail_expr (tree, int);
279 static tree find_equivalent_equality_comparison (tree);
280 static void record_range (tree, basic_block);
281 static bool extract_range_from_cond (tree, tree *, tree *, int *);
282 static void record_equivalences_from_phis (basic_block);
283 static void record_equivalences_from_incoming_edge (basic_block);
284 static bool eliminate_redundant_computations (struct dom_walk_data *,
286 static void record_equivalences_from_stmt (tree, int, stmt_ann_t);
287 static void thread_across_edge (struct dom_walk_data *, edge);
288 static void dom_opt_finalize_block (struct dom_walk_data *, basic_block);
289 static void dom_opt_initialize_block (struct dom_walk_data *, basic_block);
290 static void propagate_to_outgoing_edges (struct dom_walk_data *, basic_block);
291 static void remove_local_expressions_from_table (void);
292 static void restore_vars_to_original_value (void);
293 static edge single_incoming_edge_ignoring_loop_edges (basic_block);
294 static void restore_nonzero_vars_to_original_value (void);
295 static inline bool unsafe_associative_fp_binop (tree);
298 /* Local version of fold that doesn't introduce cruft. */
305 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
306 may have been added by fold, and "useless" type conversions that might
307 now be apparent due to propagation. */
308 STRIP_USELESS_TYPE_CONVERSION (t);
313 /* Allocate an EDGE_INFO for edge E and attach it to E.
314 Return the new EDGE_INFO structure. */
316 static struct edge_info *
317 allocate_edge_info (edge e)
319 struct edge_info *edge_info;
321 edge_info = xcalloc (1, sizeof (struct edge_info));
327 /* Free all EDGE_INFO structures associated with edges in the CFG.
328 If a particular edge can be threaded, copy the redirection
329 target from the EDGE_INFO structure into the edge's AUX field
330 as required by code to update the CFG and SSA graph for
334 free_all_edge_infos (void)
342 FOR_EACH_EDGE (e, ei, bb->preds)
344 struct edge_info *edge_info = e->aux;
348 e->aux = edge_info->redirection_target;
349 if (edge_info->cond_equivalences)
350 free (edge_info->cond_equivalences);
357 /* Free an instance of vrp_hash_elt. */
360 vrp_free (void *data)
362 struct vrp_hash_elt *elt = data;
363 struct VEC(vrp_element_p,heap) **vrp_elt = &elt->records;
365 VEC_free (vrp_element_p, heap, *vrp_elt);
369 /* Jump threading, redundancy elimination and const/copy propagation.
371 This pass may expose new symbols that need to be renamed into SSA. For
372 every new symbol exposed, its corresponding bit will be set in
376 tree_ssa_dominator_optimize (void)
378 struct dom_walk_data walk_data;
380 struct loops loops_info;
382 memset (&opt_stats, 0, sizeof (opt_stats));
384 /* Create our hash tables. */
385 avail_exprs = htab_create (1024, real_avail_expr_hash, avail_expr_eq, free);
386 vrp_data = htab_create (ceil_log2 (num_ssa_names), vrp_hash, vrp_eq,
388 avail_exprs_stack = VEC_alloc (tree, heap, 20);
389 const_and_copies_stack = VEC_alloc (tree, heap, 20);
390 nonzero_vars_stack = VEC_alloc (tree, heap, 20);
391 vrp_variables_stack = VEC_alloc (tree, heap, 20);
392 stmts_to_rescan = VEC_alloc (tree, heap, 20);
393 nonzero_vars = BITMAP_ALLOC (NULL);
394 threaded_blocks = BITMAP_ALLOC (NULL);
395 need_eh_cleanup = BITMAP_ALLOC (NULL);
397 /* Setup callbacks for the generic dominator tree walker. */
398 walk_data.walk_stmts_backward = false;
399 walk_data.dom_direction = CDI_DOMINATORS;
400 walk_data.initialize_block_local_data = NULL;
401 walk_data.before_dom_children_before_stmts = dom_opt_initialize_block;
402 walk_data.before_dom_children_walk_stmts = optimize_stmt;
403 walk_data.before_dom_children_after_stmts = propagate_to_outgoing_edges;
404 walk_data.after_dom_children_before_stmts = NULL;
405 walk_data.after_dom_children_walk_stmts = NULL;
406 walk_data.after_dom_children_after_stmts = dom_opt_finalize_block;
407 /* Right now we only attach a dummy COND_EXPR to the global data pointer.
408 When we attach more stuff we'll need to fill this out with a real
410 walk_data.global_data = NULL;
411 walk_data.block_local_data_size = 0;
412 walk_data.interesting_blocks = NULL;
414 /* Now initialize the dominator walker. */
415 init_walk_dominator_tree (&walk_data);
417 calculate_dominance_info (CDI_DOMINATORS);
419 /* We need to know which edges exit loops so that we can
420 aggressively thread through loop headers to an exit
422 flow_loops_find (&loops_info);
423 mark_loop_exit_edges (&loops_info);
424 flow_loops_free (&loops_info);
426 /* Clean up the CFG so that any forwarder blocks created by loop
427 canonicalization are removed. */
429 calculate_dominance_info (CDI_DOMINATORS);
431 /* If we prove certain blocks are unreachable, then we want to
432 repeat the dominator optimization process as PHI nodes may
433 have turned into copies which allows better propagation of
434 values. So we repeat until we do not identify any new unreachable
438 /* Optimize the dominator tree. */
441 /* We need accurate information regarding back edges in the CFG
442 for jump threading. */
443 mark_dfs_back_edges ();
445 /* Recursively walk the dominator tree optimizing statements. */
446 walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
449 block_stmt_iterator bsi;
453 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
455 update_stmt_if_modified (bsi_stmt (bsi));
460 /* If we exposed any new variables, go ahead and put them into
461 SSA form now, before we handle jump threading. This simplifies
462 interactions between rewriting of _DECL nodes into SSA form
463 and rewriting SSA_NAME nodes into SSA form after block
464 duplication and CFG manipulation. */
465 update_ssa (TODO_update_ssa);
467 free_all_edge_infos ();
469 /* Thread jumps, creating duplicate blocks as needed. */
470 cfg_altered |= thread_through_all_blocks (threaded_blocks);
472 /* Removal of statements may make some EH edges dead. Purge
473 such edges from the CFG as needed. */
474 if (!bitmap_empty_p (need_eh_cleanup))
476 cfg_altered |= tree_purge_all_dead_eh_edges (need_eh_cleanup);
477 bitmap_zero (need_eh_cleanup);
481 free_dominance_info (CDI_DOMINATORS);
483 cfg_altered = cleanup_tree_cfg ();
485 if (rediscover_loops_after_threading)
487 /* Rerun basic loop analysis to discover any newly
488 created loops and update the set of exit edges. */
489 rediscover_loops_after_threading = false;
490 flow_loops_find (&loops_info);
491 mark_loop_exit_edges (&loops_info);
492 flow_loops_free (&loops_info);
494 /* Remove any forwarder blocks inserted by loop
495 header canonicalization. */
499 calculate_dominance_info (CDI_DOMINATORS);
501 update_ssa (TODO_update_ssa);
503 /* Reinitialize the various tables. */
504 bitmap_clear (nonzero_vars);
505 bitmap_clear (threaded_blocks);
506 htab_empty (avail_exprs);
507 htab_empty (vrp_data);
509 /* Finally, remove everything except invariants in SSA_NAME_VALUE.
511 This must be done before we iterate as we might have a
512 reference to an SSA_NAME which was removed by the call to
515 Long term we will be able to let everything in SSA_NAME_VALUE
516 persist. However, for now, we know this is the safe thing to do. */
517 for (i = 0; i < num_ssa_names; i++)
519 tree name = ssa_name (i);
525 value = SSA_NAME_VALUE (name);
526 if (value && !is_gimple_min_invariant (value))
527 SSA_NAME_VALUE (name) = NULL;
530 while (optimize > 1 && cfg_altered);
532 /* Debugging dumps. */
533 if (dump_file && (dump_flags & TDF_STATS))
534 dump_dominator_optimization_stats (dump_file);
536 /* We emptied the hash table earlier, now delete it completely. */
537 htab_delete (avail_exprs);
538 htab_delete (vrp_data);
540 /* It is not necessary to clear CURRDEFS, REDIRECTION_EDGES, VRP_DATA,
541 CONST_AND_COPIES, and NONZERO_VARS as they all get cleared at the bottom
542 of the do-while loop above. */
544 /* And finalize the dominator walker. */
545 fini_walk_dominator_tree (&walk_data);
547 /* Free nonzero_vars. */
548 BITMAP_FREE (nonzero_vars);
549 BITMAP_FREE (threaded_blocks);
550 BITMAP_FREE (need_eh_cleanup);
552 VEC_free (tree, heap, avail_exprs_stack);
553 VEC_free (tree, heap, const_and_copies_stack);
554 VEC_free (tree, heap, nonzero_vars_stack);
555 VEC_free (tree, heap, vrp_variables_stack);
556 VEC_free (tree, heap, stmts_to_rescan);
560 gate_dominator (void)
562 return flag_tree_dom != 0;
565 struct tree_opt_pass pass_dominator =
568 gate_dominator, /* gate */
569 tree_ssa_dominator_optimize, /* execute */
572 0, /* static_pass_number */
573 TV_TREE_SSA_DOMINATOR_OPTS, /* tv_id */
574 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
575 0, /* properties_provided */
576 0, /* properties_destroyed */
577 0, /* todo_flags_start */
580 | TODO_verify_ssa, /* todo_flags_finish */
585 /* We are exiting E->src, see if E->dest ends with a conditional
586 jump which has a known value when reached via E.
588 Special care is necessary if E is a back edge in the CFG as we
589 will have already recorded equivalences for E->dest into our
590 various tables, including the result of the conditional at
591 the end of E->dest. Threading opportunities are severely
592 limited in that case to avoid short-circuiting the loop
595 Note it is quite common for the first block inside a loop to
596 end with a conditional which is either always true or always
597 false when reached via the loop backedge. Thus we do not want
598 to blindly disable threading across a loop backedge. */
601 thread_across_edge (struct dom_walk_data *walk_data, edge e)
603 block_stmt_iterator bsi;
607 /* If E->dest does not end with a conditional, then there is
609 bsi = bsi_last (e->dest);
612 || (TREE_CODE (bsi_stmt (bsi)) != COND_EXPR
613 && TREE_CODE (bsi_stmt (bsi)) != GOTO_EXPR
614 && TREE_CODE (bsi_stmt (bsi)) != SWITCH_EXPR))
617 /* The basic idea here is to use whatever knowledge we have
618 from our dominator walk to simplify statements in E->dest,
619 with the ultimate goal being to simplify the conditional
620 at the end of E->dest.
622 Note that we must undo any changes we make to the underlying
623 statements as the simplifications we are making are control
624 flow sensitive (ie, the simplifications are valid when we
625 traverse E, but may not be valid on other paths to E->dest. */
627 /* Each PHI creates a temporary equivalence, record them. Again
628 these are context sensitive equivalences and will be removed
630 for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
632 tree src = PHI_ARG_DEF_FROM_EDGE (phi, e);
633 tree dst = PHI_RESULT (phi);
635 /* If the desired argument is not the same as this PHI's result
636 and it is set by a PHI in E->dest, then we can not thread
639 && TREE_CODE (src) == SSA_NAME
640 && TREE_CODE (SSA_NAME_DEF_STMT (src)) == PHI_NODE
641 && bb_for_stmt (SSA_NAME_DEF_STMT (src)) == e->dest)
644 record_const_or_copy (dst, src);
647 /* Try to simplify each statement in E->dest, ultimately leading to
648 a simplification of the COND_EXPR at the end of E->dest.
650 We might consider marking just those statements which ultimately
651 feed the COND_EXPR. It's not clear if the overhead of bookkeeping
652 would be recovered by trying to simplify fewer statements.
654 If we are able to simplify a statement into the form
655 SSA_NAME = (SSA_NAME | gimple invariant), then we can record
656 a context sensitive equivalency which may help us simplify
657 later statements in E->dest.
659 Failure to simplify into the form above merely means that the
660 statement provides no equivalences to help simplify later
661 statements. This does not prevent threading through E->dest. */
662 for (bsi = bsi_start (e->dest); ! bsi_end_p (bsi); bsi_next (&bsi))
666 stmt = bsi_stmt (bsi);
668 /* Ignore empty statements and labels. */
669 if (IS_EMPTY_STMT (stmt) || TREE_CODE (stmt) == LABEL_EXPR)
672 /* Safely handle threading across loop backedges. This is
673 over conservative, but still allows us to capture the
674 majority of the cases where we can thread across a loop
676 if ((e->flags & EDGE_DFS_BACK) != 0
677 && TREE_CODE (stmt) != COND_EXPR
678 && TREE_CODE (stmt) != SWITCH_EXPR)
681 /* If the statement has volatile operands, then we assume we
682 can not thread through this block. This is overly
683 conservative in some ways. */
684 if (TREE_CODE (stmt) == ASM_EXPR && ASM_VOLATILE_P (stmt))
687 /* If this is not a MODIFY_EXPR which sets an SSA_NAME to a new
688 value, then do not try to simplify this statement as it will
689 not simplify in any way that is helpful for jump threading. */
690 if (TREE_CODE (stmt) != MODIFY_EXPR
691 || TREE_CODE (TREE_OPERAND (stmt, 0)) != SSA_NAME)
694 /* At this point we have a statement which assigns an RHS to an
695 SSA_VAR on the LHS. We want to try and simplify this statement
696 to expose more context sensitive equivalences which in turn may
697 allow us to simplify the condition at the end of the loop. */
698 if (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME)
699 cached_lhs = TREE_OPERAND (stmt, 1);
702 /* Copy the operands. */
706 unsigned int num, i = 0;
708 num = NUM_SSA_OPERANDS (stmt, (SSA_OP_USE | SSA_OP_VUSE));
709 copy = xcalloc (num, sizeof (tree));
711 /* Make a copy of the uses & vuses into USES_COPY, then cprop into
713 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE | SSA_OP_VUSE)
716 tree use = USE_FROM_PTR (use_p);
719 if (TREE_CODE (use) == SSA_NAME)
720 tmp = SSA_NAME_VALUE (use);
721 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
722 SET_USE (use_p, tmp);
725 /* Try to fold/lookup the new expression. Inserting the
726 expression into the hash table is unlikely to help
727 simplify anything later, so just query the hashtable. */
728 cached_lhs = fold (TREE_OPERAND (stmt, 1));
729 if (TREE_CODE (cached_lhs) != SSA_NAME
730 && !is_gimple_min_invariant (cached_lhs))
731 cached_lhs = lookup_avail_expr (stmt, false);
734 /* Restore the statement's original uses/defs. */
736 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE | SSA_OP_VUSE)
737 SET_USE (use_p, copy[i++]);
742 /* Record the context sensitive equivalence if we were able
743 to simplify this statement. */
745 && (TREE_CODE (cached_lhs) == SSA_NAME
746 || is_gimple_min_invariant (cached_lhs)))
747 record_const_or_copy (TREE_OPERAND (stmt, 0), cached_lhs);
750 /* If we stopped at a COND_EXPR or SWITCH_EXPR, see if we know which arm
753 && (TREE_CODE (stmt) == COND_EXPR
754 || TREE_CODE (stmt) == GOTO_EXPR
755 || TREE_CODE (stmt) == SWITCH_EXPR))
757 tree cond, cached_lhs;
759 /* Now temporarily cprop the operands and try to find the resulting
760 expression in the hash tables. */
761 if (TREE_CODE (stmt) == COND_EXPR)
762 cond = COND_EXPR_COND (stmt);
763 else if (TREE_CODE (stmt) == GOTO_EXPR)
764 cond = GOTO_DESTINATION (stmt);
766 cond = SWITCH_COND (stmt);
768 if (COMPARISON_CLASS_P (cond))
770 tree dummy_cond, op0, op1;
771 enum tree_code cond_code;
773 op0 = TREE_OPERAND (cond, 0);
774 op1 = TREE_OPERAND (cond, 1);
775 cond_code = TREE_CODE (cond);
777 /* Get the current value of both operands. */
778 if (TREE_CODE (op0) == SSA_NAME)
780 tree tmp = SSA_NAME_VALUE (op0);
781 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
785 if (TREE_CODE (op1) == SSA_NAME)
787 tree tmp = SSA_NAME_VALUE (op1);
788 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
792 /* Stuff the operator and operands into our dummy conditional
793 expression, creating the dummy conditional if necessary. */
794 dummy_cond = walk_data->global_data;
797 dummy_cond = build (cond_code, boolean_type_node, op0, op1);
798 dummy_cond = build (COND_EXPR, void_type_node,
799 dummy_cond, NULL, NULL);
800 walk_data->global_data = dummy_cond;
804 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), cond_code);
805 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op0;
806 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1) = op1;
809 /* If the conditional folds to an invariant, then we are done,
810 otherwise look it up in the hash tables. */
811 cached_lhs = local_fold (COND_EXPR_COND (dummy_cond));
812 if (! is_gimple_min_invariant (cached_lhs))
814 cached_lhs = lookup_avail_expr (dummy_cond, false);
815 if (!cached_lhs || ! is_gimple_min_invariant (cached_lhs))
816 cached_lhs = simplify_cond_and_lookup_avail_expr (dummy_cond,
821 /* We can have conditionals which just test the state of a
822 variable rather than use a relational operator. These are
823 simpler to handle. */
824 else if (TREE_CODE (cond) == SSA_NAME)
827 cached_lhs = SSA_NAME_VALUE (cached_lhs);
828 if (cached_lhs && ! is_gimple_min_invariant (cached_lhs))
832 cached_lhs = lookup_avail_expr (stmt, false);
836 edge taken_edge = find_taken_edge (e->dest, cached_lhs);
837 basic_block dest = (taken_edge ? taken_edge->dest : NULL);
842 /* If we have a known destination for the conditional, then
843 we can perform this optimization, which saves at least one
844 conditional jump each time it applies since we get to
845 bypass the conditional at our original destination. */
848 struct edge_info *edge_info;
850 update_bb_profile_for_threading (e->dest, EDGE_FREQUENCY (e),
851 e->count, taken_edge);
855 edge_info = allocate_edge_info (e);
856 edge_info->redirection_target = taken_edge;
857 bitmap_set_bit (threaded_blocks, e->dest->index);
864 /* Initialize local stacks for this optimizer and record equivalences
865 upon entry to BB. Equivalences can come from the edge traversed to
866 reach BB or they may come from PHI nodes at the start of BB. */
869 dom_opt_initialize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
872 if (dump_file && (dump_flags & TDF_DETAILS))
873 fprintf (dump_file, "\n\nOptimizing block #%d\n\n", bb->index);
875 /* Push a marker on the stacks of local information so that we know how
876 far to unwind when we finalize this block. */
877 VEC_safe_push (tree, heap, avail_exprs_stack, NULL_TREE);
878 VEC_safe_push (tree, heap, const_and_copies_stack, NULL_TREE);
879 VEC_safe_push (tree, heap, nonzero_vars_stack, NULL_TREE);
880 VEC_safe_push (tree, heap, vrp_variables_stack, NULL_TREE);
882 record_equivalences_from_incoming_edge (bb);
884 /* PHI nodes can create equivalences too. */
885 record_equivalences_from_phis (bb);
888 /* Given an expression EXPR (a relational expression or a statement),
889 initialize the hash table element pointed by by ELEMENT. */
892 initialize_hash_element (tree expr, tree lhs, struct expr_hash_elt *element)
894 /* Hash table elements may be based on conditional expressions or statements.
896 For the former case, we have no annotation and we want to hash the
897 conditional expression. In the latter case we have an annotation and
898 we want to record the expression the statement evaluates. */
899 if (COMPARISON_CLASS_P (expr) || TREE_CODE (expr) == TRUTH_NOT_EXPR)
901 element->stmt = NULL;
904 else if (TREE_CODE (expr) == COND_EXPR)
906 element->stmt = expr;
907 element->rhs = COND_EXPR_COND (expr);
909 else if (TREE_CODE (expr) == SWITCH_EXPR)
911 element->stmt = expr;
912 element->rhs = SWITCH_COND (expr);
914 else if (TREE_CODE (expr) == RETURN_EXPR && TREE_OPERAND (expr, 0))
916 element->stmt = expr;
917 element->rhs = TREE_OPERAND (TREE_OPERAND (expr, 0), 1);
919 else if (TREE_CODE (expr) == GOTO_EXPR)
921 element->stmt = expr;
922 element->rhs = GOTO_DESTINATION (expr);
926 element->stmt = expr;
927 element->rhs = TREE_OPERAND (expr, 1);
931 element->hash = avail_expr_hash (element);
934 /* Remove all the expressions in LOCALS from TABLE, stopping when there are
935 LIMIT entries left in LOCALs. */
938 remove_local_expressions_from_table (void)
940 /* Remove all the expressions made available in this block. */
941 while (VEC_length (tree, avail_exprs_stack) > 0)
943 struct expr_hash_elt element;
944 tree expr = VEC_pop (tree, avail_exprs_stack);
946 if (expr == NULL_TREE)
949 initialize_hash_element (expr, NULL, &element);
950 htab_remove_elt_with_hash (avail_exprs, &element, element.hash);
954 /* Use the SSA_NAMES in LOCALS to restore TABLE to its original
955 state, stopping when there are LIMIT entries left in LOCALs. */
958 restore_nonzero_vars_to_original_value (void)
960 while (VEC_length (tree, nonzero_vars_stack) > 0)
962 tree name = VEC_pop (tree, nonzero_vars_stack);
967 bitmap_clear_bit (nonzero_vars, SSA_NAME_VERSION (name));
971 /* Use the source/dest pairs in CONST_AND_COPIES_STACK to restore
972 CONST_AND_COPIES to its original state, stopping when we hit a
976 restore_vars_to_original_value (void)
978 while (VEC_length (tree, const_and_copies_stack) > 0)
980 tree prev_value, dest;
982 dest = VEC_pop (tree, const_and_copies_stack);
987 prev_value = VEC_pop (tree, const_and_copies_stack);
988 SSA_NAME_VALUE (dest) = prev_value;
992 /* We have finished processing the dominator children of BB, perform
993 any finalization actions in preparation for leaving this node in
994 the dominator tree. */
997 dom_opt_finalize_block (struct dom_walk_data *walk_data, basic_block bb)
1001 /* If we are at a leaf node in the dominator tree, see if we can thread
1002 the edge from BB through its successor.
1004 Do this before we remove entries from our equivalence tables. */
1005 if (single_succ_p (bb)
1006 && (single_succ_edge (bb)->flags & EDGE_ABNORMAL) == 0
1007 && (get_immediate_dominator (CDI_DOMINATORS, single_succ (bb)) != bb
1008 || phi_nodes (single_succ (bb))))
1011 thread_across_edge (walk_data, single_succ_edge (bb));
1013 else if ((last = last_stmt (bb))
1014 && TREE_CODE (last) == COND_EXPR
1015 && (COMPARISON_CLASS_P (COND_EXPR_COND (last))
1016 || TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME)
1017 && EDGE_COUNT (bb->succs) == 2
1018 && (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL) == 0
1019 && (EDGE_SUCC (bb, 1)->flags & EDGE_ABNORMAL) == 0)
1021 edge true_edge, false_edge;
1023 extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
1025 /* If the THEN arm is the end of a dominator tree or has PHI nodes,
1026 then try to thread through its edge. */
1027 if (get_immediate_dominator (CDI_DOMINATORS, true_edge->dest) != bb
1028 || phi_nodes (true_edge->dest))
1030 struct edge_info *edge_info;
1033 /* Push a marker onto the available expression stack so that we
1034 unwind any expressions related to the TRUE arm before processing
1035 the false arm below. */
1036 VEC_safe_push (tree, heap, avail_exprs_stack, NULL_TREE);
1037 VEC_safe_push (tree, heap, const_and_copies_stack, NULL_TREE);
1039 edge_info = true_edge->aux;
1041 /* If we have info associated with this edge, record it into
1042 our equivalency tables. */
1045 tree *cond_equivalences = edge_info->cond_equivalences;
1046 tree lhs = edge_info->lhs;
1047 tree rhs = edge_info->rhs;
1049 /* If we have a simple NAME = VALUE equivalency record it. */
1050 if (lhs && TREE_CODE (lhs) == SSA_NAME)
1051 record_const_or_copy (lhs, rhs);
1053 /* If we have 0 = COND or 1 = COND equivalences, record them
1054 into our expression hash tables. */
1055 if (cond_equivalences)
1056 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1058 tree expr = cond_equivalences[i];
1059 tree value = cond_equivalences[i + 1];
1061 record_cond (expr, value);
1065 /* Now thread the edge. */
1066 thread_across_edge (walk_data, true_edge);
1068 /* And restore the various tables to their state before
1069 we threaded this edge. */
1070 remove_local_expressions_from_table ();
1071 restore_vars_to_original_value ();
1074 /* Similarly for the ELSE arm. */
1075 if (get_immediate_dominator (CDI_DOMINATORS, false_edge->dest) != bb
1076 || phi_nodes (false_edge->dest))
1078 struct edge_info *edge_info;
1081 edge_info = false_edge->aux;
1083 /* If we have info associated with this edge, record it into
1084 our equivalency tables. */
1087 tree *cond_equivalences = edge_info->cond_equivalences;
1088 tree lhs = edge_info->lhs;
1089 tree rhs = edge_info->rhs;
1091 /* If we have a simple NAME = VALUE equivalency record it. */
1092 if (lhs && TREE_CODE (lhs) == SSA_NAME)
1093 record_const_or_copy (lhs, rhs);
1095 /* If we have 0 = COND or 1 = COND equivalences, record them
1096 into our expression hash tables. */
1097 if (cond_equivalences)
1098 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1100 tree expr = cond_equivalences[i];
1101 tree value = cond_equivalences[i + 1];
1103 record_cond (expr, value);
1107 thread_across_edge (walk_data, false_edge);
1109 /* No need to remove local expressions from our tables
1110 or restore vars to their original value as that will
1111 be done immediately below. */
1115 remove_local_expressions_from_table ();
1116 restore_nonzero_vars_to_original_value ();
1117 restore_vars_to_original_value ();
1119 /* Remove VRP records associated with this basic block. They are no
1122 To be efficient, we note which variables have had their values
1123 constrained in this block. So walk over each variable in the
1124 VRP_VARIABLEs array. */
1125 while (VEC_length (tree, vrp_variables_stack) > 0)
1127 tree var = VEC_pop (tree, vrp_variables_stack);
1128 struct vrp_hash_elt vrp_hash_elt, *vrp_hash_elt_p;
1131 /* Each variable has a stack of value range records. We want to
1132 invalidate those associated with our basic block. So we walk
1133 the array backwards popping off records associated with our
1134 block. Once we hit a record not associated with our block
1136 VEC(vrp_element_p,heap) **var_vrp_records;
1141 vrp_hash_elt.var = var;
1142 vrp_hash_elt.records = NULL;
1144 slot = htab_find_slot (vrp_data, &vrp_hash_elt, NO_INSERT);
1146 vrp_hash_elt_p = (struct vrp_hash_elt *) *slot;
1147 var_vrp_records = &vrp_hash_elt_p->records;
1149 while (VEC_length (vrp_element_p, *var_vrp_records) > 0)
1151 struct vrp_element *element
1152 = VEC_last (vrp_element_p, *var_vrp_records);
1154 if (element->bb != bb)
1157 VEC_pop (vrp_element_p, *var_vrp_records);
1161 /* If we queued any statements to rescan in this block, then
1162 go ahead and rescan them now. */
1163 while (VEC_length (tree, stmts_to_rescan) > 0)
1165 tree stmt = VEC_last (tree, stmts_to_rescan);
1166 basic_block stmt_bb = bb_for_stmt (stmt);
1171 VEC_pop (tree, stmts_to_rescan);
1172 mark_new_vars_to_rename (stmt);
1176 /* PHI nodes can create equivalences too.
1178 Ignoring any alternatives which are the same as the result, if
1179 all the alternatives are equal, then the PHI node creates an
1182 Additionally, if all the PHI alternatives are known to have a nonzero
1183 value, then the result of this PHI is known to have a nonzero value,
1184 even if we do not know its exact value. */
1187 record_equivalences_from_phis (basic_block bb)
1191 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1193 tree lhs = PHI_RESULT (phi);
1197 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1199 tree t = PHI_ARG_DEF (phi, i);
1201 /* Ignore alternatives which are the same as our LHS. Since
1202 LHS is a PHI_RESULT, it is known to be a SSA_NAME, so we
1203 can simply compare pointers. */
1207 /* If we have not processed an alternative yet, then set
1208 RHS to this alternative. */
1211 /* If we have processed an alternative (stored in RHS), then
1212 see if it is equal to this one. If it isn't, then stop
1214 else if (! operand_equal_for_phi_arg_p (rhs, t))
1218 /* If we had no interesting alternatives, then all the RHS alternatives
1219 must have been the same as LHS. */
1223 /* If we managed to iterate through each PHI alternative without
1224 breaking out of the loop, then we have a PHI which may create
1225 a useful equivalence. We do not need to record unwind data for
1226 this, since this is a true assignment and not an equivalence
1227 inferred from a comparison. All uses of this ssa name are dominated
1228 by this assignment, so unwinding just costs time and space. */
1229 if (i == PHI_NUM_ARGS (phi)
1230 && may_propagate_copy (lhs, rhs))
1231 SSA_NAME_VALUE (lhs) = rhs;
1233 /* Now see if we know anything about the nonzero property for the
1234 result of this PHI. */
1235 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1237 if (!PHI_ARG_NONZERO (phi, i))
1241 if (i == PHI_NUM_ARGS (phi))
1242 bitmap_set_bit (nonzero_vars, SSA_NAME_VERSION (PHI_RESULT (phi)));
1246 /* Ignoring loop backedges, if BB has precisely one incoming edge then
1247 return that edge. Otherwise return NULL. */
1249 single_incoming_edge_ignoring_loop_edges (basic_block bb)
1255 FOR_EACH_EDGE (e, ei, bb->preds)
1257 /* A loop back edge can be identified by the destination of
1258 the edge dominating the source of the edge. */
1259 if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
1262 /* If we have already seen a non-loop edge, then we must have
1263 multiple incoming non-loop edges and thus we return NULL. */
1267 /* This is the first non-loop incoming edge we have found. Record
1275 /* Record any equivalences created by the incoming edge to BB. If BB
1276 has more than one incoming edge, then no equivalence is created. */
1279 record_equivalences_from_incoming_edge (basic_block bb)
1283 struct edge_info *edge_info;
1285 /* If our parent block ended with a control statement, then we may be
1286 able to record some equivalences based on which outgoing edge from
1287 the parent was followed. */
1288 parent = get_immediate_dominator (CDI_DOMINATORS, bb);
1290 e = single_incoming_edge_ignoring_loop_edges (bb);
1292 /* If we had a single incoming edge from our parent block, then enter
1293 any data associated with the edge into our tables. */
1294 if (e && e->src == parent)
1302 tree lhs = edge_info->lhs;
1303 tree rhs = edge_info->rhs;
1304 tree *cond_equivalences = edge_info->cond_equivalences;
1307 record_equality (lhs, rhs);
1309 if (cond_equivalences)
1311 bool recorded_range = false;
1312 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1314 tree expr = cond_equivalences[i];
1315 tree value = cond_equivalences[i + 1];
1317 record_cond (expr, value);
1319 /* For the first true equivalence, record range
1320 information. We only do this for the first
1321 true equivalence as it should dominate any
1322 later true equivalences. */
1323 if (! recorded_range
1324 && COMPARISON_CLASS_P (expr)
1325 && value == boolean_true_node
1326 && TREE_CONSTANT (TREE_OPERAND (expr, 1)))
1328 record_range (expr, bb);
1329 recorded_range = true;
1337 /* Dump SSA statistics on FILE. */
1340 dump_dominator_optimization_stats (FILE *file)
1344 fprintf (file, "Total number of statements: %6ld\n\n",
1345 opt_stats.num_stmts);
1346 fprintf (file, "Exprs considered for dominator optimizations: %6ld\n",
1347 opt_stats.num_exprs_considered);
1349 n_exprs = opt_stats.num_exprs_considered;
1353 fprintf (file, " Redundant expressions eliminated: %6ld (%.0f%%)\n",
1354 opt_stats.num_re, PERCENT (opt_stats.num_re,
1356 fprintf (file, " Constants propagated: %6ld\n",
1357 opt_stats.num_const_prop);
1358 fprintf (file, " Copies propagated: %6ld\n",
1359 opt_stats.num_copy_prop);
1361 fprintf (file, "\nHash table statistics:\n");
1363 fprintf (file, " avail_exprs: ");
1364 htab_statistics (file, avail_exprs);
1368 /* Dump SSA statistics on stderr. */
1371 debug_dominator_optimization_stats (void)
1373 dump_dominator_optimization_stats (stderr);
1377 /* Dump statistics for the hash table HTAB. */
1380 htab_statistics (FILE *file, htab_t htab)
1382 fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
1383 (long) htab_size (htab),
1384 (long) htab_elements (htab),
1385 htab_collisions (htab));
1388 /* Record the fact that VAR has a nonzero value, though we may not know
1389 its exact value. Note that if VAR is already known to have a nonzero
1390 value, then we do nothing. */
1393 record_var_is_nonzero (tree var)
1395 int indx = SSA_NAME_VERSION (var);
1397 if (bitmap_bit_p (nonzero_vars, indx))
1400 /* Mark it in the global table. */
1401 bitmap_set_bit (nonzero_vars, indx);
1403 /* Record this SSA_NAME so that we can reset the global table
1404 when we leave this block. */
1405 VEC_safe_push (tree, heap, nonzero_vars_stack, var);
1408 /* Enter a statement into the true/false expression hash table indicating
1409 that the condition COND has the value VALUE. */
1412 record_cond (tree cond, tree value)
1414 struct expr_hash_elt *element = xmalloc (sizeof (struct expr_hash_elt));
1417 initialize_hash_element (cond, value, element);
1419 slot = htab_find_slot_with_hash (avail_exprs, (void *)element,
1420 element->hash, INSERT);
1423 *slot = (void *) element;
1424 VEC_safe_push (tree, heap, avail_exprs_stack, cond);
1430 /* Build a new conditional using NEW_CODE, OP0 and OP1 and store
1431 the new conditional into *p, then store a boolean_true_node
1435 build_and_record_new_cond (enum tree_code new_code, tree op0, tree op1, tree *p)
1437 *p = build2 (new_code, boolean_type_node, op0, op1);
1439 *p = boolean_true_node;
1442 /* Record that COND is true and INVERTED is false into the edge information
1443 structure. Also record that any conditions dominated by COND are true
1446 For example, if a < b is true, then a <= b must also be true. */
1449 record_conditions (struct edge_info *edge_info, tree cond, tree inverted)
1453 if (!COMPARISON_CLASS_P (cond))
1456 op0 = TREE_OPERAND (cond, 0);
1457 op1 = TREE_OPERAND (cond, 1);
1459 switch (TREE_CODE (cond))
1463 edge_info->max_cond_equivalences = 12;
1464 edge_info->cond_equivalences = xmalloc (12 * sizeof (tree));
1465 build_and_record_new_cond ((TREE_CODE (cond) == LT_EXPR
1466 ? LE_EXPR : GE_EXPR),
1467 op0, op1, &edge_info->cond_equivalences[4]);
1468 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1469 &edge_info->cond_equivalences[6]);
1470 build_and_record_new_cond (NE_EXPR, op0, op1,
1471 &edge_info->cond_equivalences[8]);
1472 build_and_record_new_cond (LTGT_EXPR, op0, op1,
1473 &edge_info->cond_equivalences[10]);
1478 edge_info->max_cond_equivalences = 6;
1479 edge_info->cond_equivalences = xmalloc (6 * sizeof (tree));
1480 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1481 &edge_info->cond_equivalences[4]);
1485 edge_info->max_cond_equivalences = 10;
1486 edge_info->cond_equivalences = xmalloc (10 * sizeof (tree));
1487 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1488 &edge_info->cond_equivalences[4]);
1489 build_and_record_new_cond (LE_EXPR, op0, op1,
1490 &edge_info->cond_equivalences[6]);
1491 build_and_record_new_cond (GE_EXPR, op0, op1,
1492 &edge_info->cond_equivalences[8]);
1495 case UNORDERED_EXPR:
1496 edge_info->max_cond_equivalences = 16;
1497 edge_info->cond_equivalences = xmalloc (16 * sizeof (tree));
1498 build_and_record_new_cond (NE_EXPR, op0, op1,
1499 &edge_info->cond_equivalences[4]);
1500 build_and_record_new_cond (UNLE_EXPR, op0, op1,
1501 &edge_info->cond_equivalences[6]);
1502 build_and_record_new_cond (UNGE_EXPR, op0, op1,
1503 &edge_info->cond_equivalences[8]);
1504 build_and_record_new_cond (UNEQ_EXPR, op0, op1,
1505 &edge_info->cond_equivalences[10]);
1506 build_and_record_new_cond (UNLT_EXPR, op0, op1,
1507 &edge_info->cond_equivalences[12]);
1508 build_and_record_new_cond (UNGT_EXPR, op0, op1,
1509 &edge_info->cond_equivalences[14]);
1514 edge_info->max_cond_equivalences = 8;
1515 edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1516 build_and_record_new_cond ((TREE_CODE (cond) == UNLT_EXPR
1517 ? UNLE_EXPR : UNGE_EXPR),
1518 op0, op1, &edge_info->cond_equivalences[4]);
1519 build_and_record_new_cond (NE_EXPR, op0, op1,
1520 &edge_info->cond_equivalences[6]);
1524 edge_info->max_cond_equivalences = 8;
1525 edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1526 build_and_record_new_cond (UNLE_EXPR, op0, op1,
1527 &edge_info->cond_equivalences[4]);
1528 build_and_record_new_cond (UNGE_EXPR, op0, op1,
1529 &edge_info->cond_equivalences[6]);
1533 edge_info->max_cond_equivalences = 8;
1534 edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1535 build_and_record_new_cond (NE_EXPR, op0, op1,
1536 &edge_info->cond_equivalences[4]);
1537 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1538 &edge_info->cond_equivalences[6]);
1542 edge_info->max_cond_equivalences = 4;
1543 edge_info->cond_equivalences = xmalloc (4 * sizeof (tree));
1547 /* Now store the original true and false conditions into the first
1549 edge_info->cond_equivalences[0] = cond;
1550 edge_info->cond_equivalences[1] = boolean_true_node;
1551 edge_info->cond_equivalences[2] = inverted;
1552 edge_info->cond_equivalences[3] = boolean_false_node;
1555 /* A helper function for record_const_or_copy and record_equality.
1556 Do the work of recording the value and undo info. */
1559 record_const_or_copy_1 (tree x, tree y, tree prev_x)
1561 SSA_NAME_VALUE (x) = y;
1563 VEC_reserve (tree, heap, const_and_copies_stack, 2);
1564 VEC_quick_push (tree, const_and_copies_stack, prev_x);
1565 VEC_quick_push (tree, const_and_copies_stack, x);
1569 /* Return the loop depth of the basic block of the defining statement of X.
1570 This number should not be treated as absolutely correct because the loop
1571 information may not be completely up-to-date when dom runs. However, it
1572 will be relatively correct, and as more passes are taught to keep loop info
1573 up to date, the result will become more and more accurate. */
1576 loop_depth_of_name (tree x)
1581 /* If it's not an SSA_NAME, we have no clue where the definition is. */
1582 if (TREE_CODE (x) != SSA_NAME)
1585 /* Otherwise return the loop depth of the defining statement's bb.
1586 Note that there may not actually be a bb for this statement, if the
1587 ssa_name is live on entry. */
1588 defstmt = SSA_NAME_DEF_STMT (x);
1589 defbb = bb_for_stmt (defstmt);
1593 return defbb->loop_depth;
1597 /* Record that X is equal to Y in const_and_copies. Record undo
1598 information in the block-local vector. */
1601 record_const_or_copy (tree x, tree y)
1603 tree prev_x = SSA_NAME_VALUE (x);
1605 if (TREE_CODE (y) == SSA_NAME)
1607 tree tmp = SSA_NAME_VALUE (y);
1612 record_const_or_copy_1 (x, y, prev_x);
1615 /* Similarly, but assume that X and Y are the two operands of an EQ_EXPR.
1616 This constrains the cases in which we may treat this as assignment. */
1619 record_equality (tree x, tree y)
1621 tree prev_x = NULL, prev_y = NULL;
1623 if (TREE_CODE (x) == SSA_NAME)
1624 prev_x = SSA_NAME_VALUE (x);
1625 if (TREE_CODE (y) == SSA_NAME)
1626 prev_y = SSA_NAME_VALUE (y);
1628 /* If one of the previous values is invariant, or invariant in more loops
1629 (by depth), then use that.
1630 Otherwise it doesn't matter which value we choose, just so
1631 long as we canonicalize on one value. */
1632 if (TREE_INVARIANT (y))
1634 else if (TREE_INVARIANT (x) || (loop_depth_of_name (x) <= loop_depth_of_name (y)))
1635 prev_x = x, x = y, y = prev_x, prev_x = prev_y;
1636 else if (prev_x && TREE_INVARIANT (prev_x))
1637 x = y, y = prev_x, prev_x = prev_y;
1638 else if (prev_y && TREE_CODE (prev_y) != VALUE_HANDLE)
1641 /* After the swapping, we must have one SSA_NAME. */
1642 if (TREE_CODE (x) != SSA_NAME)
1645 /* For IEEE, -0.0 == 0.0, so we don't necessarily know the sign of a
1646 variable compared against zero. If we're honoring signed zeros,
1647 then we cannot record this value unless we know that the value is
1649 if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (x)))
1650 && (TREE_CODE (y) != REAL_CST
1651 || REAL_VALUES_EQUAL (dconst0, TREE_REAL_CST (y))))
1654 record_const_or_copy_1 (x, y, prev_x);
1657 /* Return true, if it is ok to do folding of an associative expression.
1658 EXP is the tree for the associative expression. */
1661 unsafe_associative_fp_binop (tree exp)
1663 enum tree_code code = TREE_CODE (exp);
1664 return !(!flag_unsafe_math_optimizations
1665 && (code == MULT_EXPR || code == PLUS_EXPR
1666 || code == MINUS_EXPR)
1667 && FLOAT_TYPE_P (TREE_TYPE (exp)));
1670 /* Returns true when STMT is a simple iv increment. It detects the
1671 following situation:
1673 i_1 = phi (..., i_2)
1674 i_2 = i_1 +/- ... */
1677 simple_iv_increment_p (tree stmt)
1679 tree lhs, rhs, preinc, phi;
1682 if (TREE_CODE (stmt) != MODIFY_EXPR)
1685 lhs = TREE_OPERAND (stmt, 0);
1686 if (TREE_CODE (lhs) != SSA_NAME)
1689 rhs = TREE_OPERAND (stmt, 1);
1691 if (TREE_CODE (rhs) != PLUS_EXPR
1692 && TREE_CODE (rhs) != MINUS_EXPR)
1695 preinc = TREE_OPERAND (rhs, 0);
1696 if (TREE_CODE (preinc) != SSA_NAME)
1699 phi = SSA_NAME_DEF_STMT (preinc);
1700 if (TREE_CODE (phi) != PHI_NODE)
1703 for (i = 0; i < (unsigned) PHI_NUM_ARGS (phi); i++)
1704 if (PHI_ARG_DEF (phi, i) == lhs)
1710 /* STMT is a MODIFY_EXPR for which we were unable to find RHS in the
1711 hash tables. Try to simplify the RHS using whatever equivalences
1712 we may have recorded.
1714 If we are able to simplify the RHS, then lookup the simplified form in
1715 the hash table and return the result. Otherwise return NULL. */
1718 simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *walk_data,
1719 tree stmt, int insert)
1721 tree rhs = TREE_OPERAND (stmt, 1);
1722 enum tree_code rhs_code = TREE_CODE (rhs);
1725 /* If we have lhs = ~x, look and see if we earlier had x = ~y.
1726 In which case we can change this statement to be lhs = y.
1727 Which can then be copy propagated.
1729 Similarly for negation. */
1730 if ((rhs_code == BIT_NOT_EXPR || rhs_code == NEGATE_EXPR)
1731 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
1733 /* Get the definition statement for our RHS. */
1734 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1736 /* See if the RHS_DEF_STMT has the same form as our statement. */
1737 if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR
1738 && TREE_CODE (TREE_OPERAND (rhs_def_stmt, 1)) == rhs_code)
1740 tree rhs_def_operand;
1742 rhs_def_operand = TREE_OPERAND (TREE_OPERAND (rhs_def_stmt, 1), 0);
1744 /* Verify that RHS_DEF_OPERAND is a suitable SSA variable. */
1745 if (TREE_CODE (rhs_def_operand) == SSA_NAME
1746 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))
1747 result = update_rhs_and_lookup_avail_expr (stmt,
1753 /* If we have z = (x OP C1), see if we earlier had x = y OP C2.
1754 If OP is associative, create and fold (y OP C2) OP C1 which
1755 should result in (y OP C3), use that as the RHS for the
1756 assignment. Add minus to this, as we handle it specially below. */
1757 if ((associative_tree_code (rhs_code) || rhs_code == MINUS_EXPR)
1758 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
1759 && is_gimple_min_invariant (TREE_OPERAND (rhs, 1)))
1761 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1763 /* If the statement defines an induction variable, do not propagate
1764 its value, so that we do not create overlapping life ranges. */
1765 if (simple_iv_increment_p (rhs_def_stmt))
1766 goto dont_fold_assoc;
1768 /* See if the RHS_DEF_STMT has the same form as our statement. */
1769 if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR)
1771 tree rhs_def_rhs = TREE_OPERAND (rhs_def_stmt, 1);
1772 enum tree_code rhs_def_code = TREE_CODE (rhs_def_rhs);
1774 if ((rhs_code == rhs_def_code && unsafe_associative_fp_binop (rhs))
1775 || (rhs_code == PLUS_EXPR && rhs_def_code == MINUS_EXPR)
1776 || (rhs_code == MINUS_EXPR && rhs_def_code == PLUS_EXPR))
1778 tree def_stmt_op0 = TREE_OPERAND (rhs_def_rhs, 0);
1779 tree def_stmt_op1 = TREE_OPERAND (rhs_def_rhs, 1);
1781 if (TREE_CODE (def_stmt_op0) == SSA_NAME
1782 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def_stmt_op0)
1783 && is_gimple_min_invariant (def_stmt_op1))
1785 tree outer_const = TREE_OPERAND (rhs, 1);
1786 tree type = TREE_TYPE (TREE_OPERAND (stmt, 0));
1789 /* If we care about correct floating point results, then
1790 don't fold x + c1 - c2. Note that we need to take both
1791 the codes and the signs to figure this out. */
1792 if (FLOAT_TYPE_P (type)
1793 && !flag_unsafe_math_optimizations
1794 && (rhs_def_code == PLUS_EXPR
1795 || rhs_def_code == MINUS_EXPR))
1799 neg ^= (rhs_code == MINUS_EXPR);
1800 neg ^= (rhs_def_code == MINUS_EXPR);
1801 neg ^= real_isneg (TREE_REAL_CST_PTR (outer_const));
1802 neg ^= real_isneg (TREE_REAL_CST_PTR (def_stmt_op1));
1805 goto dont_fold_assoc;
1808 /* Ho hum. So fold will only operate on the outermost
1809 thingy that we give it, so we have to build the new
1810 expression in two pieces. This requires that we handle
1811 combinations of plus and minus. */
1812 if (rhs_def_code != rhs_code)
1814 if (rhs_def_code == MINUS_EXPR)
1815 t = build (MINUS_EXPR, type, outer_const, def_stmt_op1);
1817 t = build (MINUS_EXPR, type, def_stmt_op1, outer_const);
1818 rhs_code = PLUS_EXPR;
1820 else if (rhs_def_code == MINUS_EXPR)
1821 t = build (PLUS_EXPR, type, def_stmt_op1, outer_const);
1823 t = build (rhs_def_code, type, def_stmt_op1, outer_const);
1825 t = build (rhs_code, type, def_stmt_op0, t);
1828 /* If the result is a suitable looking gimple expression,
1829 then use it instead of the original for STMT. */
1830 if (TREE_CODE (t) == SSA_NAME
1831 || (UNARY_CLASS_P (t)
1832 && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME)
1833 || ((BINARY_CLASS_P (t) || COMPARISON_CLASS_P (t))
1834 && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME
1835 && is_gimple_val (TREE_OPERAND (t, 1))))
1836 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1843 /* Transform TRUNC_DIV_EXPR and TRUNC_MOD_EXPR into RSHIFT_EXPR
1844 and BIT_AND_EXPR respectively if the first operand is greater
1845 than zero and the second operand is an exact power of two. */
1846 if ((rhs_code == TRUNC_DIV_EXPR || rhs_code == TRUNC_MOD_EXPR)
1847 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0)))
1848 && integer_pow2p (TREE_OPERAND (rhs, 1)))
1851 tree op = TREE_OPERAND (rhs, 0);
1853 if (TYPE_UNSIGNED (TREE_TYPE (op)))
1855 val = integer_one_node;
1859 tree dummy_cond = walk_data->global_data;
1863 dummy_cond = build (GT_EXPR, boolean_type_node,
1864 op, integer_zero_node);
1865 dummy_cond = build (COND_EXPR, void_type_node,
1866 dummy_cond, NULL, NULL);
1867 walk_data->global_data = dummy_cond;
1871 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), GT_EXPR);
1872 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op;
1873 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1)
1874 = integer_zero_node;
1876 val = simplify_cond_and_lookup_avail_expr (dummy_cond, NULL, false);
1879 if (val && integer_onep (val))
1882 tree op0 = TREE_OPERAND (rhs, 0);
1883 tree op1 = TREE_OPERAND (rhs, 1);
1885 if (rhs_code == TRUNC_DIV_EXPR)
1886 t = build (RSHIFT_EXPR, TREE_TYPE (op0), op0,
1887 build_int_cst (NULL_TREE, tree_log2 (op1)));
1889 t = build (BIT_AND_EXPR, TREE_TYPE (op0), op0,
1890 local_fold (build (MINUS_EXPR, TREE_TYPE (op1),
1891 op1, integer_one_node)));
1893 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1897 /* Transform ABS (X) into X or -X as appropriate. */
1898 if (rhs_code == ABS_EXPR
1899 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0))))
1902 tree op = TREE_OPERAND (rhs, 0);
1903 tree type = TREE_TYPE (op);
1905 if (TYPE_UNSIGNED (type))
1907 val = integer_zero_node;
1911 tree dummy_cond = walk_data->global_data;
1915 dummy_cond = build (LE_EXPR, boolean_type_node,
1916 op, integer_zero_node);
1917 dummy_cond = build (COND_EXPR, void_type_node,
1918 dummy_cond, NULL, NULL);
1919 walk_data->global_data = dummy_cond;
1923 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), LE_EXPR);
1924 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op;
1925 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1)
1926 = build_int_cst (type, 0);
1928 val = simplify_cond_and_lookup_avail_expr (dummy_cond, NULL, false);
1932 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), GE_EXPR);
1933 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op;
1934 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1)
1935 = build_int_cst (type, 0);
1937 val = simplify_cond_and_lookup_avail_expr (dummy_cond,
1942 if (integer_zerop (val))
1943 val = integer_one_node;
1944 else if (integer_onep (val))
1945 val = integer_zero_node;
1951 && (integer_onep (val) || integer_zerop (val)))
1955 if (integer_onep (val))
1956 t = build1 (NEGATE_EXPR, TREE_TYPE (op), op);
1960 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1964 /* Optimize *"foo" into 'f'. This is done here rather than
1965 in fold to avoid problems with stuff like &*"foo". */
1966 if (TREE_CODE (rhs) == INDIRECT_REF || TREE_CODE (rhs) == ARRAY_REF)
1968 tree t = fold_read_from_constant_string (rhs);
1971 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1977 /* COND is a condition of the form:
1979 x == const or x != const
1981 Look back to x's defining statement and see if x is defined as
1985 If const is unchanged if we convert it to type, then we can build
1986 the equivalent expression:
1989 y == const or y != const
1991 Which may allow further optimizations.
1993 Return the equivalent comparison or NULL if no such equivalent comparison
1997 find_equivalent_equality_comparison (tree cond)
1999 tree op0 = TREE_OPERAND (cond, 0);
2000 tree op1 = TREE_OPERAND (cond, 1);
2001 tree def_stmt = SSA_NAME_DEF_STMT (op0);
2003 /* OP0 might have been a parameter, so first make sure it
2004 was defined by a MODIFY_EXPR. */
2005 if (def_stmt && TREE_CODE (def_stmt) == MODIFY_EXPR)
2007 tree def_rhs = TREE_OPERAND (def_stmt, 1);
2009 /* Now make sure the RHS of the MODIFY_EXPR is a typecast. */
2010 if ((TREE_CODE (def_rhs) == NOP_EXPR
2011 || TREE_CODE (def_rhs) == CONVERT_EXPR)
2012 && TREE_CODE (TREE_OPERAND (def_rhs, 0)) == SSA_NAME)
2014 tree def_rhs_inner = TREE_OPERAND (def_rhs, 0);
2015 tree def_rhs_inner_type = TREE_TYPE (def_rhs_inner);
2018 if (TYPE_PRECISION (def_rhs_inner_type)
2019 > TYPE_PRECISION (TREE_TYPE (def_rhs)))
2022 /* What we want to prove is that if we convert OP1 to
2023 the type of the object inside the NOP_EXPR that the
2024 result is still equivalent to SRC.
2026 If that is true, the build and return new equivalent
2027 condition which uses the source of the typecast and the
2028 new constant (which has only changed its type). */
2029 new = build1 (TREE_CODE (def_rhs), def_rhs_inner_type, op1);
2030 new = local_fold (new);
2031 if (is_gimple_val (new) && tree_int_cst_equal (new, op1))
2032 return build (TREE_CODE (cond), TREE_TYPE (cond),
2033 def_rhs_inner, new);
2039 /* STMT is a COND_EXPR for which we could not trivially determine its
2040 result. This routine attempts to find equivalent forms of the
2041 condition which we may be able to optimize better. It also
2042 uses simple value range propagation to optimize conditionals. */
2045 simplify_cond_and_lookup_avail_expr (tree stmt,
2049 tree cond = COND_EXPR_COND (stmt);
2051 if (COMPARISON_CLASS_P (cond))
2053 tree op0 = TREE_OPERAND (cond, 0);
2054 tree op1 = TREE_OPERAND (cond, 1);
2056 if (TREE_CODE (op0) == SSA_NAME && is_gimple_min_invariant (op1))
2059 tree low, high, cond_low, cond_high;
2060 int lowequal, highequal, swapped, no_overlap, subset, cond_inverted;
2061 VEC(vrp_element_p,heap) **vrp_records;
2062 struct vrp_element *element;
2063 struct vrp_hash_elt vrp_hash_elt, *vrp_hash_elt_p;
2066 /* First see if we have test of an SSA_NAME against a constant
2067 where the SSA_NAME is defined by an earlier typecast which
2068 is irrelevant when performing tests against the given
2070 if (TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
2072 tree new_cond = find_equivalent_equality_comparison (cond);
2076 /* Update the statement to use the new equivalent
2078 COND_EXPR_COND (stmt) = new_cond;
2080 /* If this is not a real stmt, ann will be NULL and we
2081 avoid processing the operands. */
2083 mark_stmt_modified (stmt);
2085 /* Lookup the condition and return its known value if it
2087 new_cond = lookup_avail_expr (stmt, insert);
2091 /* The operands have changed, so update op0 and op1. */
2092 op0 = TREE_OPERAND (cond, 0);
2093 op1 = TREE_OPERAND (cond, 1);
2097 /* Consult the value range records for this variable (if they exist)
2098 to see if we can eliminate or simplify this conditional.
2100 Note two tests are necessary to determine no records exist.
2101 First we have to see if the virtual array exists, if it
2102 exists, then we have to check its active size.
2104 Also note the vast majority of conditionals are not testing
2105 a variable which has had its range constrained by an earlier
2106 conditional. So this filter avoids a lot of unnecessary work. */
2107 vrp_hash_elt.var = op0;
2108 vrp_hash_elt.records = NULL;
2109 slot = htab_find_slot (vrp_data, &vrp_hash_elt, NO_INSERT);
2113 vrp_hash_elt_p = (struct vrp_hash_elt *) *slot;
2114 vrp_records = &vrp_hash_elt_p->records;
2116 limit = VEC_length (vrp_element_p, *vrp_records);
2118 /* If we have no value range records for this variable, or we are
2119 unable to extract a range for this condition, then there is
2122 || ! extract_range_from_cond (cond, &cond_high,
2123 &cond_low, &cond_inverted))
2126 /* We really want to avoid unnecessary computations of range
2127 info. So all ranges are computed lazily; this avoids a
2128 lot of unnecessary work. i.e., we record the conditional,
2129 but do not process how it constrains the variable's
2130 potential values until we know that processing the condition
2133 However, we do not want to have to walk a potentially long
2134 list of ranges, nor do we want to compute a variable's
2135 range more than once for a given path.
2137 Luckily, each time we encounter a conditional that can not
2138 be otherwise optimized we will end up here and we will
2139 compute the necessary range information for the variable
2140 used in this condition.
2142 Thus you can conclude that there will never be more than one
2143 conditional associated with a variable which has not been
2144 processed. So we never need to merge more than one new
2145 conditional into the current range.
2147 These properties also help us avoid unnecessary work. */
2148 element = VEC_last (vrp_element_p, *vrp_records);
2150 if (element->high && element->low)
2152 /* The last element has been processed, so there is no range
2153 merging to do, we can simply use the high/low values
2154 recorded in the last element. */
2156 high = element->high;
2160 tree tmp_high, tmp_low;
2163 /* The last element has not been processed. Process it now.
2164 record_range should ensure for cond inverted is not set.
2165 This call can only fail if cond is x < min or x > max,
2166 which fold should have optimized into false.
2167 If that doesn't happen, just pretend all values are
2169 if (! extract_range_from_cond (element->cond, &tmp_high,
2173 gcc_assert (dummy == 0);
2175 /* If this is the only element, then no merging is necessary,
2176 the high/low values from extract_range_from_cond are all
2185 /* Get the high/low value from the previous element. */
2186 struct vrp_element *prev
2187 = VEC_index (vrp_element_p, *vrp_records, limit - 2);
2191 /* Merge in this element's range with the range from the
2194 The low value for the merged range is the maximum of
2195 the previous low value and the low value of this record.
2197 Similarly the high value for the merged range is the
2198 minimum of the previous high value and the high value of
2200 low = (low && tree_int_cst_compare (low, tmp_low) == 1
2202 high = (high && tree_int_cst_compare (high, tmp_high) == -1
2206 /* And record the computed range. */
2208 element->high = high;
2212 /* After we have constrained this variable's potential values,
2213 we try to determine the result of the given conditional.
2215 To simplify later tests, first determine if the current
2216 low value is the same low value as the conditional.
2217 Similarly for the current high value and the high value
2218 for the conditional. */
2219 lowequal = tree_int_cst_equal (low, cond_low);
2220 highequal = tree_int_cst_equal (high, cond_high);
2222 if (lowequal && highequal)
2223 return (cond_inverted ? boolean_false_node : boolean_true_node);
2225 /* To simplify the overlap/subset tests below we may want
2226 to swap the two ranges so that the larger of the two
2227 ranges occurs "first". */
2229 if (tree_int_cst_compare (low, cond_low) == 1
2231 && tree_int_cst_compare (cond_high, high) == 1))
2244 /* Now determine if there is no overlap in the ranges
2245 or if the second range is a subset of the first range. */
2246 no_overlap = tree_int_cst_lt (high, cond_low);
2247 subset = tree_int_cst_compare (cond_high, high) != 1;
2249 /* If there was no overlap in the ranges, then this conditional
2250 always has a false value (unless we had to invert this
2251 conditional, in which case it always has a true value). */
2253 return (cond_inverted ? boolean_true_node : boolean_false_node);
2255 /* If the current range is a subset of the condition's range,
2256 then this conditional always has a true value (unless we
2257 had to invert this conditional, in which case it always
2258 has a true value). */
2259 if (subset && swapped)
2260 return (cond_inverted ? boolean_false_node : boolean_true_node);
2262 /* We were unable to determine the result of the conditional.
2263 However, we may be able to simplify the conditional. First
2264 merge the ranges in the same manner as range merging above. */
2265 low = tree_int_cst_compare (low, cond_low) == 1 ? low : cond_low;
2266 high = tree_int_cst_compare (high, cond_high) == -1 ? high : cond_high;
2268 /* If the range has converged to a single point, then turn this
2269 into an equality comparison. */
2270 if (TREE_CODE (cond) != EQ_EXPR
2271 && TREE_CODE (cond) != NE_EXPR
2272 && tree_int_cst_equal (low, high))
2274 TREE_SET_CODE (cond, EQ_EXPR);
2275 TREE_OPERAND (cond, 1) = high;
2282 /* STMT is a SWITCH_EXPR for which we could not trivially determine its
2283 result. This routine attempts to find equivalent forms of the
2284 condition which we may be able to optimize better. */
2287 simplify_switch_and_lookup_avail_expr (tree stmt, int insert)
2289 tree cond = SWITCH_COND (stmt);
2292 /* The optimization that we really care about is removing unnecessary
2293 casts. That will let us do much better in propagating the inferred
2294 constant at the switch target. */
2295 if (TREE_CODE (cond) == SSA_NAME)
2297 def = SSA_NAME_DEF_STMT (cond);
2298 if (TREE_CODE (def) == MODIFY_EXPR)
2300 def = TREE_OPERAND (def, 1);
2301 if (TREE_CODE (def) == NOP_EXPR)
2306 def = TREE_OPERAND (def, 0);
2308 #ifdef ENABLE_CHECKING
2309 /* ??? Why was Jeff testing this? We are gimple... */
2310 gcc_assert (is_gimple_val (def));
2313 to = TREE_TYPE (cond);
2314 ti = TREE_TYPE (def);
2316 /* If we have an extension that preserves value, then we
2317 can copy the source value into the switch. */
2319 need_precision = TYPE_PRECISION (ti);
2321 if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
2323 else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
2324 need_precision += 1;
2325 if (TYPE_PRECISION (to) < need_precision)
2330 SWITCH_COND (stmt) = def;
2331 mark_stmt_modified (stmt);
2333 return lookup_avail_expr (stmt, insert);
2343 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2344 known value for that SSA_NAME (or NULL if no value is known).
2346 NONZERO_VARS is the set SSA_NAMES known to have a nonzero value,
2347 even if we don't know their precise value.
2349 Propagate values from CONST_AND_COPIES and NONZERO_VARS into the PHI
2350 nodes of the successors of BB. */
2353 cprop_into_successor_phis (basic_block bb, bitmap nonzero_vars)
2358 FOR_EACH_EDGE (e, ei, bb->succs)
2363 /* If this is an abnormal edge, then we do not want to copy propagate
2364 into the PHI alternative associated with this edge. */
2365 if (e->flags & EDGE_ABNORMAL)
2368 phi = phi_nodes (e->dest);
2373 for ( ; phi; phi = PHI_CHAIN (phi))
2376 use_operand_p orig_p;
2379 /* The alternative may be associated with a constant, so verify
2380 it is an SSA_NAME before doing anything with it. */
2381 orig_p = PHI_ARG_DEF_PTR (phi, indx);
2382 orig = USE_FROM_PTR (orig_p);
2383 if (TREE_CODE (orig) != SSA_NAME)
2386 /* If the alternative is known to have a nonzero value, record
2387 that fact in the PHI node itself for future use. */
2388 if (bitmap_bit_p (nonzero_vars, SSA_NAME_VERSION (orig)))
2389 PHI_ARG_NONZERO (phi, indx) = true;
2391 /* If we have *ORIG_P in our constant/copy table, then replace
2392 ORIG_P with its value in our constant/copy table. */
2393 new = SSA_NAME_VALUE (orig);
2396 && (TREE_CODE (new) == SSA_NAME
2397 || is_gimple_min_invariant (new))
2398 && may_propagate_copy (orig, new))
2399 propagate_value (orig_p, new);
2404 /* We have finished optimizing BB, record any information implied by
2405 taking a specific outgoing edge from BB. */
2408 record_edge_info (basic_block bb)
2410 block_stmt_iterator bsi = bsi_last (bb);
2411 struct edge_info *edge_info;
2413 if (! bsi_end_p (bsi))
2415 tree stmt = bsi_stmt (bsi);
2417 if (stmt && TREE_CODE (stmt) == SWITCH_EXPR)
2419 tree cond = SWITCH_COND (stmt);
2421 if (TREE_CODE (cond) == SSA_NAME)
2423 tree labels = SWITCH_LABELS (stmt);
2424 int i, n_labels = TREE_VEC_LENGTH (labels);
2425 tree *info = xcalloc (last_basic_block, sizeof (tree));
2429 for (i = 0; i < n_labels; i++)
2431 tree label = TREE_VEC_ELT (labels, i);
2432 basic_block target_bb = label_to_block (CASE_LABEL (label));
2434 if (CASE_HIGH (label)
2435 || !CASE_LOW (label)
2436 || info[target_bb->index])
2437 info[target_bb->index] = error_mark_node;
2439 info[target_bb->index] = label;
2442 FOR_EACH_EDGE (e, ei, bb->succs)
2444 basic_block target_bb = e->dest;
2445 tree node = info[target_bb->index];
2447 if (node != NULL && node != error_mark_node)
2449 tree x = fold_convert (TREE_TYPE (cond), CASE_LOW (node));
2450 edge_info = allocate_edge_info (e);
2451 edge_info->lhs = cond;
2459 /* A COND_EXPR may create equivalences too. */
2460 if (stmt && TREE_CODE (stmt) == COND_EXPR)
2462 tree cond = COND_EXPR_COND (stmt);
2466 extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
2468 /* If the conditional is a single variable 'X', record 'X = 1'
2469 for the true edge and 'X = 0' on the false edge. */
2470 if (SSA_VAR_P (cond))
2472 struct edge_info *edge_info;
2474 edge_info = allocate_edge_info (true_edge);
2475 edge_info->lhs = cond;
2476 edge_info->rhs = constant_boolean_node (1, TREE_TYPE (cond));
2478 edge_info = allocate_edge_info (false_edge);
2479 edge_info->lhs = cond;
2480 edge_info->rhs = constant_boolean_node (0, TREE_TYPE (cond));
2482 /* Equality tests may create one or two equivalences. */
2483 else if (COMPARISON_CLASS_P (cond))
2485 tree op0 = TREE_OPERAND (cond, 0);
2486 tree op1 = TREE_OPERAND (cond, 1);
2488 /* Special case comparing booleans against a constant as we
2489 know the value of OP0 on both arms of the branch. i.e., we
2490 can record an equivalence for OP0 rather than COND. */
2491 if ((TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
2492 && TREE_CODE (op0) == SSA_NAME
2493 && TREE_CODE (TREE_TYPE (op0)) == BOOLEAN_TYPE
2494 && is_gimple_min_invariant (op1))
2496 if (TREE_CODE (cond) == EQ_EXPR)
2498 edge_info = allocate_edge_info (true_edge);
2499 edge_info->lhs = op0;
2500 edge_info->rhs = (integer_zerop (op1)
2501 ? boolean_false_node
2502 : boolean_true_node);
2504 edge_info = allocate_edge_info (false_edge);
2505 edge_info->lhs = op0;
2506 edge_info->rhs = (integer_zerop (op1)
2508 : boolean_false_node);
2512 edge_info = allocate_edge_info (true_edge);
2513 edge_info->lhs = op0;
2514 edge_info->rhs = (integer_zerop (op1)
2516 : boolean_false_node);
2518 edge_info = allocate_edge_info (false_edge);
2519 edge_info->lhs = op0;
2520 edge_info->rhs = (integer_zerop (op1)
2521 ? boolean_false_node
2522 : boolean_true_node);
2526 else if (is_gimple_min_invariant (op0)
2527 && (TREE_CODE (op1) == SSA_NAME
2528 || is_gimple_min_invariant (op1)))
2530 tree inverted = invert_truthvalue (cond);
2531 struct edge_info *edge_info;
2533 edge_info = allocate_edge_info (true_edge);
2534 record_conditions (edge_info, cond, inverted);
2536 if (TREE_CODE (cond) == EQ_EXPR)
2538 edge_info->lhs = op1;
2539 edge_info->rhs = op0;
2542 edge_info = allocate_edge_info (false_edge);
2543 record_conditions (edge_info, inverted, cond);
2545 if (TREE_CODE (cond) == NE_EXPR)
2547 edge_info->lhs = op1;
2548 edge_info->rhs = op0;
2552 else if (TREE_CODE (op0) == SSA_NAME
2553 && (is_gimple_min_invariant (op1)
2554 || TREE_CODE (op1) == SSA_NAME))
2556 tree inverted = invert_truthvalue (cond);
2557 struct edge_info *edge_info;
2559 edge_info = allocate_edge_info (true_edge);
2560 record_conditions (edge_info, cond, inverted);
2562 if (TREE_CODE (cond) == EQ_EXPR)
2564 edge_info->lhs = op0;
2565 edge_info->rhs = op1;
2568 edge_info = allocate_edge_info (false_edge);
2569 record_conditions (edge_info, inverted, cond);
2571 if (TREE_CODE (cond) == NE_EXPR)
2573 edge_info->lhs = op0;
2574 edge_info->rhs = op1;
2579 /* ??? TRUTH_NOT_EXPR can create an equivalence too. */
2584 /* Propagate information from BB to its outgoing edges.
2586 This can include equivalency information implied by control statements
2587 at the end of BB and const/copy propagation into PHIs in BB's
2588 successor blocks. */
2591 propagate_to_outgoing_edges (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
2594 record_edge_info (bb);
2595 cprop_into_successor_phis (bb, nonzero_vars);
2598 /* Search for redundant computations in STMT. If any are found, then
2599 replace them with the variable holding the result of the computation.
2601 If safe, record this expression into the available expression hash
2605 eliminate_redundant_computations (struct dom_walk_data *walk_data,
2606 tree stmt, stmt_ann_t ann)
2608 tree *expr_p, def = NULL_TREE;
2611 bool retval = false;
2613 if (TREE_CODE (stmt) == MODIFY_EXPR)
2614 def = TREE_OPERAND (stmt, 0);
2616 /* Certain expressions on the RHS can be optimized away, but can not
2617 themselves be entered into the hash tables. */
2618 if (ann->makes_aliased_stores
2620 || TREE_CODE (def) != SSA_NAME
2621 || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def)
2622 || !ZERO_SSA_OPERANDS (stmt, SSA_OP_VMAYDEF)
2623 /* Do not record equivalences for increments of ivs. This would create
2624 overlapping live ranges for a very questionable gain. */
2625 || simple_iv_increment_p (stmt))
2628 /* Check if the expression has been computed before. */
2629 cached_lhs = lookup_avail_expr (stmt, insert);
2631 /* If this is an assignment and the RHS was not in the hash table,
2632 then try to simplify the RHS and lookup the new RHS in the
2634 if (! cached_lhs && TREE_CODE (stmt) == MODIFY_EXPR)
2635 cached_lhs = simplify_rhs_and_lookup_avail_expr (walk_data, stmt, insert);
2636 /* Similarly if this is a COND_EXPR and we did not find its
2637 expression in the hash table, simplify the condition and
2639 else if (! cached_lhs && TREE_CODE (stmt) == COND_EXPR)
2640 cached_lhs = simplify_cond_and_lookup_avail_expr (stmt, ann, insert);
2641 /* Similarly for a SWITCH_EXPR. */
2642 else if (!cached_lhs && TREE_CODE (stmt) == SWITCH_EXPR)
2643 cached_lhs = simplify_switch_and_lookup_avail_expr (stmt, insert);
2645 opt_stats.num_exprs_considered++;
2647 /* Get a pointer to the expression we are trying to optimize. */
2648 if (TREE_CODE (stmt) == COND_EXPR)
2649 expr_p = &COND_EXPR_COND (stmt);
2650 else if (TREE_CODE (stmt) == SWITCH_EXPR)
2651 expr_p = &SWITCH_COND (stmt);
2652 else if (TREE_CODE (stmt) == RETURN_EXPR && TREE_OPERAND (stmt, 0))
2653 expr_p = &TREE_OPERAND (TREE_OPERAND (stmt, 0), 1);
2655 expr_p = &TREE_OPERAND (stmt, 1);
2657 /* It is safe to ignore types here since we have already done
2658 type checking in the hashing and equality routines. In fact
2659 type checking here merely gets in the way of constant
2660 propagation. Also, make sure that it is safe to propagate
2661 CACHED_LHS into *EXPR_P. */
2663 && (TREE_CODE (cached_lhs) != SSA_NAME
2664 || may_propagate_copy (*expr_p, cached_lhs)))
2666 if (dump_file && (dump_flags & TDF_DETAILS))
2668 fprintf (dump_file, " Replaced redundant expr '");
2669 print_generic_expr (dump_file, *expr_p, dump_flags);
2670 fprintf (dump_file, "' with '");
2671 print_generic_expr (dump_file, cached_lhs, dump_flags);
2672 fprintf (dump_file, "'\n");
2677 #if defined ENABLE_CHECKING
2678 gcc_assert (TREE_CODE (cached_lhs) == SSA_NAME
2679 || is_gimple_min_invariant (cached_lhs));
2682 if (TREE_CODE (cached_lhs) == ADDR_EXPR
2683 || (POINTER_TYPE_P (TREE_TYPE (*expr_p))
2684 && is_gimple_min_invariant (cached_lhs)))
2687 propagate_tree_value (expr_p, cached_lhs);
2688 mark_stmt_modified (stmt);
2693 /* STMT, a MODIFY_EXPR, may create certain equivalences, in either
2694 the available expressions table or the const_and_copies table.
2695 Detect and record those equivalences. */
2698 record_equivalences_from_stmt (tree stmt,
2702 tree lhs = TREE_OPERAND (stmt, 0);
2703 enum tree_code lhs_code = TREE_CODE (lhs);
2706 if (lhs_code == SSA_NAME)
2708 tree rhs = TREE_OPERAND (stmt, 1);
2710 /* Strip away any useless type conversions. */
2711 STRIP_USELESS_TYPE_CONVERSION (rhs);
2713 /* If the RHS of the assignment is a constant or another variable that
2714 may be propagated, register it in the CONST_AND_COPIES table. We
2715 do not need to record unwind data for this, since this is a true
2716 assignment and not an equivalence inferred from a comparison. All
2717 uses of this ssa name are dominated by this assignment, so unwinding
2718 just costs time and space. */
2720 && (TREE_CODE (rhs) == SSA_NAME
2721 || is_gimple_min_invariant (rhs)))
2722 SSA_NAME_VALUE (lhs) = rhs;
2724 if (expr_computes_nonzero (rhs))
2725 record_var_is_nonzero (lhs);
2728 /* Look at both sides for pointer dereferences. If we find one, then
2729 the pointer must be nonnull and we can enter that equivalence into
2731 if (flag_delete_null_pointer_checks)
2732 for (i = 0; i < 2; i++)
2734 tree t = TREE_OPERAND (stmt, i);
2736 /* Strip away any COMPONENT_REFs. */
2737 while (TREE_CODE (t) == COMPONENT_REF)
2738 t = TREE_OPERAND (t, 0);
2740 /* Now see if this is a pointer dereference. */
2741 if (INDIRECT_REF_P (t))
2743 tree op = TREE_OPERAND (t, 0);
2745 /* If the pointer is a SSA variable, then enter new
2746 equivalences into the hash table. */
2747 while (TREE_CODE (op) == SSA_NAME)
2749 tree def = SSA_NAME_DEF_STMT (op);
2751 record_var_is_nonzero (op);
2753 /* And walk up the USE-DEF chains noting other SSA_NAMEs
2754 which are known to have a nonzero value. */
2756 && TREE_CODE (def) == MODIFY_EXPR
2757 && TREE_CODE (TREE_OPERAND (def, 1)) == NOP_EXPR)
2758 op = TREE_OPERAND (TREE_OPERAND (def, 1), 0);
2765 /* A memory store, even an aliased store, creates a useful
2766 equivalence. By exchanging the LHS and RHS, creating suitable
2767 vops and recording the result in the available expression table,
2768 we may be able to expose more redundant loads. */
2769 if (!ann->has_volatile_ops
2770 && (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME
2771 || is_gimple_min_invariant (TREE_OPERAND (stmt, 1)))
2772 && !is_gimple_reg (lhs))
2774 tree rhs = TREE_OPERAND (stmt, 1);
2777 /* FIXME: If the LHS of the assignment is a bitfield and the RHS
2778 is a constant, we need to adjust the constant to fit into the
2779 type of the LHS. If the LHS is a bitfield and the RHS is not
2780 a constant, then we can not record any equivalences for this
2781 statement since we would need to represent the widening or
2782 narrowing of RHS. This fixes gcc.c-torture/execute/921016-1.c
2783 and should not be necessary if GCC represented bitfields
2785 if (lhs_code == COMPONENT_REF
2786 && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1)))
2788 if (TREE_CONSTANT (rhs))
2789 rhs = widen_bitfield (rhs, TREE_OPERAND (lhs, 1), lhs);
2793 /* If the value overflowed, then we can not use this equivalence. */
2794 if (rhs && ! is_gimple_min_invariant (rhs))
2800 /* Build a new statement with the RHS and LHS exchanged. */
2801 new = build (MODIFY_EXPR, TREE_TYPE (stmt), rhs, lhs);
2803 create_ssa_artficial_load_stmt (new, stmt);
2805 /* Finally enter the statement into the available expression
2807 lookup_avail_expr (new, true);
2812 /* Replace *OP_P in STMT with any known equivalent value for *OP_P from
2813 CONST_AND_COPIES. */
2816 cprop_operand (tree stmt, use_operand_p op_p)
2818 bool may_have_exposed_new_symbols = false;
2820 tree op = USE_FROM_PTR (op_p);
2822 /* If the operand has a known constant value or it is known to be a
2823 copy of some other variable, use the value or copy stored in
2824 CONST_AND_COPIES. */
2825 val = SSA_NAME_VALUE (op);
2826 if (val && val != op && TREE_CODE (val) != VALUE_HANDLE)
2828 tree op_type, val_type;
2830 /* Do not change the base variable in the virtual operand
2831 tables. That would make it impossible to reconstruct
2832 the renamed virtual operand if we later modify this
2833 statement. Also only allow the new value to be an SSA_NAME
2834 for propagation into virtual operands. */
2835 if (!is_gimple_reg (op)
2836 && (TREE_CODE (val) != SSA_NAME
2837 || is_gimple_reg (val)
2838 || get_virtual_var (val) != get_virtual_var (op)))
2841 /* Do not replace hard register operands in asm statements. */
2842 if (TREE_CODE (stmt) == ASM_EXPR
2843 && !may_propagate_copy_into_asm (op))
2846 /* Get the toplevel type of each operand. */
2847 op_type = TREE_TYPE (op);
2848 val_type = TREE_TYPE (val);
2850 /* While both types are pointers, get the type of the object
2852 while (POINTER_TYPE_P (op_type) && POINTER_TYPE_P (val_type))
2854 op_type = TREE_TYPE (op_type);
2855 val_type = TREE_TYPE (val_type);
2858 /* Make sure underlying types match before propagating a constant by
2859 converting the constant to the proper type. Note that convert may
2860 return a non-gimple expression, in which case we ignore this
2861 propagation opportunity. */
2862 if (TREE_CODE (val) != SSA_NAME)
2864 if (!lang_hooks.types_compatible_p (op_type, val_type))
2866 val = fold_convert (TREE_TYPE (op), val);
2867 if (!is_gimple_min_invariant (val))
2872 /* Certain operands are not allowed to be copy propagated due
2873 to their interaction with exception handling and some GCC
2875 else if (!may_propagate_copy (op, val))
2878 /* Do not propagate copies if the propagated value is at a deeper loop
2879 depth than the propagatee. Otherwise, this may move loop variant
2880 variables outside of their loops and prevent coalescing
2881 opportunities. If the value was loop invariant, it will be hoisted
2882 by LICM and exposed for copy propagation. */
2883 if (loop_depth_of_name (val) > loop_depth_of_name (op))
2887 if (dump_file && (dump_flags & TDF_DETAILS))
2889 fprintf (dump_file, " Replaced '");
2890 print_generic_expr (dump_file, op, dump_flags);
2891 fprintf (dump_file, "' with %s '",
2892 (TREE_CODE (val) != SSA_NAME ? "constant" : "variable"));
2893 print_generic_expr (dump_file, val, dump_flags);
2894 fprintf (dump_file, "'\n");
2897 /* If VAL is an ADDR_EXPR or a constant of pointer type, note
2898 that we may have exposed a new symbol for SSA renaming. */
2899 if (TREE_CODE (val) == ADDR_EXPR
2900 || (POINTER_TYPE_P (TREE_TYPE (op))
2901 && is_gimple_min_invariant (val)))
2902 may_have_exposed_new_symbols = true;
2904 if (TREE_CODE (val) != SSA_NAME)
2905 opt_stats.num_const_prop++;
2907 opt_stats.num_copy_prop++;
2909 propagate_value (op_p, val);
2911 /* And note that we modified this statement. This is now
2912 safe, even if we changed virtual operands since we will
2913 rescan the statement and rewrite its operands again. */
2914 mark_stmt_modified (stmt);
2916 return may_have_exposed_new_symbols;
2919 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2920 known value for that SSA_NAME (or NULL if no value is known).
2922 Propagate values from CONST_AND_COPIES into the uses, vuses and
2923 v_may_def_ops of STMT. */
2926 cprop_into_stmt (tree stmt)
2928 bool may_have_exposed_new_symbols = false;
2932 FOR_EACH_SSA_USE_OPERAND (op_p, stmt, iter, SSA_OP_ALL_USES)
2934 if (TREE_CODE (USE_FROM_PTR (op_p)) == SSA_NAME)
2935 may_have_exposed_new_symbols |= cprop_operand (stmt, op_p);
2938 return may_have_exposed_new_symbols;
2942 /* Optimize the statement pointed by iterator SI.
2944 We try to perform some simplistic global redundancy elimination and
2945 constant propagation:
2947 1- To detect global redundancy, we keep track of expressions that have
2948 been computed in this block and its dominators. If we find that the
2949 same expression is computed more than once, we eliminate repeated
2950 computations by using the target of the first one.
2952 2- Constant values and copy assignments. This is used to do very
2953 simplistic constant and copy propagation. When a constant or copy
2954 assignment is found, we map the value on the RHS of the assignment to
2955 the variable in the LHS in the CONST_AND_COPIES table. */
2958 optimize_stmt (struct dom_walk_data *walk_data, basic_block bb,
2959 block_stmt_iterator si)
2962 tree stmt, old_stmt;
2963 bool may_optimize_p;
2964 bool may_have_exposed_new_symbols = false;
2966 old_stmt = stmt = bsi_stmt (si);
2968 update_stmt_if_modified (stmt);
2969 ann = stmt_ann (stmt);
2970 opt_stats.num_stmts++;
2971 may_have_exposed_new_symbols = false;
2973 if (dump_file && (dump_flags & TDF_DETAILS))
2975 fprintf (dump_file, "Optimizing statement ");
2976 print_generic_stmt (dump_file, stmt, TDF_SLIM);
2979 /* Const/copy propagate into USES, VUSES and the RHS of V_MAY_DEFs. */
2980 may_have_exposed_new_symbols = cprop_into_stmt (stmt);
2982 /* If the statement has been modified with constant replacements,
2983 fold its RHS before checking for redundant computations. */
2988 /* Try to fold the statement making sure that STMT is kept
2990 if (fold_stmt (bsi_stmt_ptr (si)))
2992 stmt = bsi_stmt (si);
2993 ann = stmt_ann (stmt);
2995 if (dump_file && (dump_flags & TDF_DETAILS))
2997 fprintf (dump_file, " Folded to: ");
2998 print_generic_stmt (dump_file, stmt, TDF_SLIM);
3002 rhs = get_rhs (stmt);
3003 if (rhs && TREE_CODE (rhs) == ADDR_EXPR)
3004 recompute_tree_invarant_for_addr_expr (rhs);
3006 /* Constant/copy propagation above may change the set of
3007 virtual operands associated with this statement. Folding
3008 may remove the need for some virtual operands.
3010 Indicate we will need to rescan and rewrite the statement. */
3011 may_have_exposed_new_symbols = true;
3014 /* Check for redundant computations. Do this optimization only
3015 for assignments that have no volatile ops and conditionals. */
3016 may_optimize_p = (!ann->has_volatile_ops
3017 && ((TREE_CODE (stmt) == RETURN_EXPR
3018 && TREE_OPERAND (stmt, 0)
3019 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR
3020 && ! (TREE_SIDE_EFFECTS
3021 (TREE_OPERAND (TREE_OPERAND (stmt, 0), 1))))
3022 || (TREE_CODE (stmt) == MODIFY_EXPR
3023 && ! TREE_SIDE_EFFECTS (TREE_OPERAND (stmt, 1)))
3024 || TREE_CODE (stmt) == COND_EXPR
3025 || TREE_CODE (stmt) == SWITCH_EXPR));
3028 may_have_exposed_new_symbols
3029 |= eliminate_redundant_computations (walk_data, stmt, ann);
3031 /* Record any additional equivalences created by this statement. */
3032 if (TREE_CODE (stmt) == MODIFY_EXPR)
3033 record_equivalences_from_stmt (stmt,
3037 /* If STMT is a COND_EXPR and it was modified, then we may know
3038 where it goes. If that is the case, then mark the CFG as altered.
3040 This will cause us to later call remove_unreachable_blocks and
3041 cleanup_tree_cfg when it is safe to do so. It is not safe to
3042 clean things up here since removal of edges and such can trigger
3043 the removal of PHI nodes, which in turn can release SSA_NAMEs to
3046 That's all fine and good, except that once SSA_NAMEs are released
3047 to the manager, we must not call create_ssa_name until all references
3048 to released SSA_NAMEs have been eliminated.
3050 All references to the deleted SSA_NAMEs can not be eliminated until
3051 we remove unreachable blocks.
3053 We can not remove unreachable blocks until after we have completed
3054 any queued jump threading.
3056 We can not complete any queued jump threads until we have taken
3057 appropriate variables out of SSA form. Taking variables out of
3058 SSA form can call create_ssa_name and thus we lose.
3060 Ultimately I suspect we're going to need to change the interface
3061 into the SSA_NAME manager. */
3067 if (TREE_CODE (stmt) == COND_EXPR)
3068 val = COND_EXPR_COND (stmt);
3069 else if (TREE_CODE (stmt) == SWITCH_EXPR)
3070 val = SWITCH_COND (stmt);
3072 if (val && TREE_CODE (val) == INTEGER_CST && find_taken_edge (bb, val))
3075 /* If we simplified a statement in such a way as to be shown that it
3076 cannot trap, update the eh information and the cfg to match. */
3077 if (maybe_clean_or_replace_eh_stmt (old_stmt, stmt))
3079 bitmap_set_bit (need_eh_cleanup, bb->index);
3080 if (dump_file && (dump_flags & TDF_DETAILS))
3081 fprintf (dump_file, " Flagged to clear EH edges.\n");
3085 if (may_have_exposed_new_symbols)
3086 VEC_safe_push (tree, heap, stmts_to_rescan, bsi_stmt (si));
3089 /* Replace the RHS of STMT with NEW_RHS. If RHS can be found in the
3090 available expression hashtable, then return the LHS from the hash
3093 If INSERT is true, then we also update the available expression
3094 hash table to account for the changes made to STMT. */
3097 update_rhs_and_lookup_avail_expr (tree stmt, tree new_rhs, bool insert)
3099 tree cached_lhs = NULL;
3101 /* Remove the old entry from the hash table. */
3104 struct expr_hash_elt element;
3106 initialize_hash_element (stmt, NULL, &element);
3107 htab_remove_elt_with_hash (avail_exprs, &element, element.hash);
3110 /* Now update the RHS of the assignment. */
3111 TREE_OPERAND (stmt, 1) = new_rhs;
3113 /* Now lookup the updated statement in the hash table. */
3114 cached_lhs = lookup_avail_expr (stmt, insert);
3116 /* We have now called lookup_avail_expr twice with two different
3117 versions of this same statement, once in optimize_stmt, once here.
3119 We know the call in optimize_stmt did not find an existing entry
3120 in the hash table, so a new entry was created. At the same time
3121 this statement was pushed onto the AVAIL_EXPRS_STACK vector.
3123 If this call failed to find an existing entry on the hash table,
3124 then the new version of this statement was entered into the
3125 hash table. And this statement was pushed onto BLOCK_AVAIL_EXPR
3126 for the second time. So there are two copies on BLOCK_AVAIL_EXPRs
3128 If this call succeeded, we still have one copy of this statement
3129 on the BLOCK_AVAIL_EXPRs vector.
3131 For both cases, we need to pop the most recent entry off the
3132 BLOCK_AVAIL_EXPRs vector. For the case where we never found this
3133 statement in the hash tables, that will leave precisely one
3134 copy of this statement on BLOCK_AVAIL_EXPRs. For the case where
3135 we found a copy of this statement in the second hash table lookup
3136 we want _no_ copies of this statement in BLOCK_AVAIL_EXPRs. */
3138 VEC_pop (tree, avail_exprs_stack);
3140 /* And make sure we record the fact that we modified this
3142 mark_stmt_modified (stmt);
3147 /* Search for an existing instance of STMT in the AVAIL_EXPRS table. If
3148 found, return its LHS. Otherwise insert STMT in the table and return
3151 Also, when an expression is first inserted in the AVAIL_EXPRS table, it
3152 is also added to the stack pointed by BLOCK_AVAIL_EXPRS_P, so that they
3153 can be removed when we finish processing this block and its children.
3155 NOTE: This function assumes that STMT is a MODIFY_EXPR node that
3156 contains no CALL_EXPR on its RHS and makes no volatile nor
3157 aliased references. */
3160 lookup_avail_expr (tree stmt, bool insert)
3165 struct expr_hash_elt *element = xmalloc (sizeof (struct expr_hash_elt));
3167 lhs = TREE_CODE (stmt) == MODIFY_EXPR ? TREE_OPERAND (stmt, 0) : NULL;
3169 initialize_hash_element (stmt, lhs, element);
3171 /* Don't bother remembering constant assignments and copy operations.
3172 Constants and copy operations are handled by the constant/copy propagator
3173 in optimize_stmt. */
3174 if (TREE_CODE (element->rhs) == SSA_NAME
3175 || is_gimple_min_invariant (element->rhs))
3181 /* If this is an equality test against zero, see if we have recorded a
3182 nonzero value for the variable in question. */
3183 if ((TREE_CODE (element->rhs) == EQ_EXPR
3184 || TREE_CODE (element->rhs) == NE_EXPR)
3185 && TREE_CODE (TREE_OPERAND (element->rhs, 0)) == SSA_NAME
3186 && integer_zerop (TREE_OPERAND (element->rhs, 1)))
3188 int indx = SSA_NAME_VERSION (TREE_OPERAND (element->rhs, 0));
3190 if (bitmap_bit_p (nonzero_vars, indx))
3192 tree t = element->rhs;
3195 if (TREE_CODE (t) == EQ_EXPR)
3196 return boolean_false_node;
3198 return boolean_true_node;
3202 /* Finally try to find the expression in the main expression hash table. */
3203 slot = htab_find_slot_with_hash (avail_exprs, element, element->hash,
3204 (insert ? INSERT : NO_INSERT));
3213 *slot = (void *) element;
3214 VEC_safe_push (tree, heap, avail_exprs_stack,
3215 stmt ? stmt : element->rhs);
3219 /* Extract the LHS of the assignment so that it can be used as the current
3220 definition of another variable. */
3221 lhs = ((struct expr_hash_elt *)*slot)->lhs;
3223 /* See if the LHS appears in the CONST_AND_COPIES table. If it does, then
3224 use the value from the const_and_copies table. */
3225 if (TREE_CODE (lhs) == SSA_NAME)
3227 temp = SSA_NAME_VALUE (lhs);
3228 if (temp && TREE_CODE (temp) != VALUE_HANDLE)
3236 /* Given a condition COND, record into HI_P, LO_P and INVERTED_P the
3237 range of values that result in the conditional having a true value.
3239 Return true if we are successful in extracting a range from COND and
3240 false if we are unsuccessful. */
3243 extract_range_from_cond (tree cond, tree *hi_p, tree *lo_p, int *inverted_p)
3245 tree op1 = TREE_OPERAND (cond, 1);
3246 tree high, low, type;
3249 type = TREE_TYPE (op1);
3251 /* Experiments have shown that it's rarely, if ever useful to
3252 record ranges for enumerations. Presumably this is due to
3253 the fact that they're rarely used directly. They are typically
3254 cast into an integer type and used that way. */
3255 if (TREE_CODE (type) != INTEGER_TYPE
3256 /* We don't know how to deal with types with variable bounds. */
3257 || TREE_CODE (TYPE_MIN_VALUE (type)) != INTEGER_CST
3258 || TREE_CODE (TYPE_MAX_VALUE (type)) != INTEGER_CST)
3261 switch (TREE_CODE (cond))
3275 high = TYPE_MAX_VALUE (type);
3280 high = TYPE_MAX_VALUE (type);
3281 if (!tree_int_cst_lt (op1, high))
3283 low = int_const_binop (PLUS_EXPR, op1, integer_one_node, 1);
3289 low = TYPE_MIN_VALUE (type);
3294 low = TYPE_MIN_VALUE (type);
3295 if (!tree_int_cst_lt (low, op1))
3297 high = int_const_binop (MINUS_EXPR, op1, integer_one_node, 1);
3307 *inverted_p = inverted;
3311 /* Record a range created by COND for basic block BB. */
3314 record_range (tree cond, basic_block bb)
3316 enum tree_code code = TREE_CODE (cond);
3318 /* We explicitly ignore NE_EXPRs and all the unordered comparisons.
3319 They rarely allow for meaningful range optimizations and significantly
3320 complicate the implementation. */
3321 if ((code == LT_EXPR || code == LE_EXPR || code == GT_EXPR
3322 || code == GE_EXPR || code == EQ_EXPR)
3323 && TREE_CODE (TREE_TYPE (TREE_OPERAND (cond, 1))) == INTEGER_TYPE)
3325 struct vrp_hash_elt *vrp_hash_elt;
3326 struct vrp_element *element;
3327 VEC(vrp_element_p,heap) **vrp_records_p;
3331 vrp_hash_elt = xmalloc (sizeof (struct vrp_hash_elt));
3332 vrp_hash_elt->var = TREE_OPERAND (cond, 0);
3333 vrp_hash_elt->records = NULL;
3334 slot = htab_find_slot (vrp_data, vrp_hash_elt, INSERT);
3337 *slot = (void *) vrp_hash_elt;
3339 vrp_free (vrp_hash_elt);
3341 vrp_hash_elt = (struct vrp_hash_elt *) *slot;
3342 vrp_records_p = &vrp_hash_elt->records;
3344 element = ggc_alloc (sizeof (struct vrp_element));
3345 element->low = NULL;
3346 element->high = NULL;
3347 element->cond = cond;
3350 VEC_safe_push (vrp_element_p, heap, *vrp_records_p, element);
3351 VEC_safe_push (tree, heap, vrp_variables_stack, TREE_OPERAND (cond, 0));
3355 /* Hashing and equality functions for VRP_DATA.
3357 Since this hash table is addressed by SSA_NAMEs, we can hash on
3358 their version number and equality can be determined with a
3359 pointer comparison. */
3362 vrp_hash (const void *p)
3364 tree var = ((struct vrp_hash_elt *)p)->var;
3366 return SSA_NAME_VERSION (var);
3370 vrp_eq (const void *p1, const void *p2)
3372 tree var1 = ((struct vrp_hash_elt *)p1)->var;
3373 tree var2 = ((struct vrp_hash_elt *)p2)->var;
3375 return var1 == var2;
3378 /* Hashing and equality functions for AVAIL_EXPRS. The table stores
3379 MODIFY_EXPR statements. We compute a value number for expressions using
3380 the code of the expression and the SSA numbers of its operands. */
3383 avail_expr_hash (const void *p)
3385 tree stmt = ((struct expr_hash_elt *)p)->stmt;
3386 tree rhs = ((struct expr_hash_elt *)p)->rhs;
3391 /* iterative_hash_expr knows how to deal with any expression and
3392 deals with commutative operators as well, so just use it instead
3393 of duplicating such complexities here. */
3394 val = iterative_hash_expr (rhs, val);
3396 /* If the hash table entry is not associated with a statement, then we
3397 can just hash the expression and not worry about virtual operands
3399 if (!stmt || !stmt_ann (stmt))
3402 /* Add the SSA version numbers of every vuse operand. This is important
3403 because compound variables like arrays are not renamed in the
3404 operands. Rather, the rename is done on the virtual variable
3405 representing all the elements of the array. */
3406 FOR_EACH_SSA_TREE_OPERAND (vuse, stmt, iter, SSA_OP_VUSE)
3407 val = iterative_hash_expr (vuse, val);
3413 real_avail_expr_hash (const void *p)
3415 return ((const struct expr_hash_elt *)p)->hash;
3419 avail_expr_eq (const void *p1, const void *p2)
3421 tree stmt1 = ((struct expr_hash_elt *)p1)->stmt;
3422 tree rhs1 = ((struct expr_hash_elt *)p1)->rhs;
3423 tree stmt2 = ((struct expr_hash_elt *)p2)->stmt;
3424 tree rhs2 = ((struct expr_hash_elt *)p2)->rhs;
3426 /* If they are the same physical expression, return true. */
3427 if (rhs1 == rhs2 && stmt1 == stmt2)
3430 /* If their codes are not equal, then quit now. */
3431 if (TREE_CODE (rhs1) != TREE_CODE (rhs2))
3434 /* In case of a collision, both RHS have to be identical and have the
3435 same VUSE operands. */
3436 if ((TREE_TYPE (rhs1) == TREE_TYPE (rhs2)
3437 || lang_hooks.types_compatible_p (TREE_TYPE (rhs1), TREE_TYPE (rhs2)))
3438 && operand_equal_p (rhs1, rhs2, OEP_PURE_SAME))
3440 bool ret = compare_ssa_operands_equal (stmt1, stmt2, SSA_OP_VUSE);
3441 gcc_assert (!ret || ((struct expr_hash_elt *)p1)->hash
3442 == ((struct expr_hash_elt *)p2)->hash);