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, 51 Franklin Street, Fifth Floor,
20 Boston, MA 02110-1301, 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"
47 /* This file implements optimizations on the dominator tree. */
50 /* Structure for recording edge equivalences as well as any pending
51 edge redirections during the dominator optimizer.
53 Computing and storing the edge equivalences instead of creating
54 them on-demand can save significant amounts of time, particularly
55 for pathological cases involving switch statements.
57 These structures live for a single iteration of the dominator
58 optimizer in the edge's AUX field. At the end of an iteration we
59 free each of these structures and update the AUX field to point
60 to any requested redirection target (the code for updating the
61 CFG and SSA graph for edge redirection expects redirection edge
62 targets to be in the AUX field for each edge. */
66 /* If this edge creates a simple equivalence, the LHS and RHS of
67 the equivalence will be stored here. */
71 /* Traversing an edge may also indicate one or more particular conditions
72 are true or false. The number of recorded conditions can vary, but
73 can be determined by the condition's code. So we have an array
74 and its maximum index rather than use a varray. */
75 tree *cond_equivalences;
76 unsigned int max_cond_equivalences;
78 /* If we can thread this edge this field records the new target. */
79 edge redirection_target;
83 /* Hash table with expressions made available during the renaming process.
84 When an assignment of the form X_i = EXPR is found, the statement is
85 stored in this table. If the same expression EXPR is later found on the
86 RHS of another statement, it is replaced with X_i (thus performing
87 global redundancy elimination). Similarly as we pass through conditionals
88 we record the conditional itself as having either a true or false value
90 static htab_t avail_exprs;
92 /* Stack of available expressions in AVAIL_EXPRs. Each block pushes any
93 expressions it enters into the hash table along with a marker entry
94 (null). When we finish processing the block, we pop off entries and
95 remove the expressions from the global hash table until we hit the
97 static VEC(tree,heap) *avail_exprs_stack;
99 /* Stack of statements we need to rescan during finalization for newly
102 Statement rescanning must occur after the current block's available
103 expressions are removed from AVAIL_EXPRS. Else we may change the
104 hash code for an expression and be unable to find/remove it from
106 static VEC(tree,heap) *stmts_to_rescan;
108 /* Structure for entries in the expression hash table.
110 This requires more memory for the hash table entries, but allows us
111 to avoid creating silly tree nodes and annotations for conditionals,
112 eliminates 2 global hash tables and two block local varrays.
114 It also allows us to reduce the number of hash table lookups we
115 have to perform in lookup_avail_expr and finally it allows us to
116 significantly reduce the number of calls into the hashing routine
121 /* The value (lhs) of this expression. */
124 /* The expression (rhs) we want to record. */
127 /* The stmt pointer if this element corresponds to a statement. */
130 /* The hash value for RHS/ann. */
134 /* Stack of dest,src pairs that need to be restored during finalization.
136 A NULL entry is used to mark the end of pairs which need to be
137 restored during finalization of this block. */
138 static VEC(tree,heap) *const_and_copies_stack;
140 /* Bitmap of SSA_NAMEs known to have a nonzero value, even if we do not
141 know their exact value. */
142 static bitmap nonzero_vars;
144 /* Bitmap of blocks that are scheduled to be threaded through. This
145 is used to communicate with thread_through_blocks. */
146 static bitmap threaded_blocks;
148 /* Stack of SSA_NAMEs which need their NONZERO_VARS property cleared
149 when the current block is finalized.
151 A NULL entry is used to mark the end of names needing their
152 entry in NONZERO_VARS cleared during finalization of this block. */
153 static VEC(tree,heap) *nonzero_vars_stack;
155 /* Track whether or not we have changed the control flow graph. */
156 static bool cfg_altered;
158 /* Bitmap of blocks that have had EH statements cleaned. We should
159 remove their dead edges eventually. */
160 static bitmap need_eh_cleanup;
162 /* Statistics for dominator optimizations. */
166 long num_exprs_considered;
173 static struct opt_stats_d opt_stats;
175 /* Value range propagation record. Each time we encounter a conditional
176 of the form SSA_NAME COND CONST we create a new vrp_element to record
177 how the condition affects the possible values SSA_NAME may have.
179 Each record contains the condition tested (COND), and the range of
180 values the variable may legitimately have if COND is true. Note the
181 range of values may be a smaller range than COND specifies if we have
182 recorded other ranges for this variable. Each record also contains the
183 block in which the range was recorded for invalidation purposes.
185 Note that the current known range is computed lazily. This allows us
186 to avoid the overhead of computing ranges which are never queried.
188 When we encounter a conditional, we look for records which constrain
189 the SSA_NAME used in the condition. In some cases those records allow
190 us to determine the condition's result at compile time. In other cases
191 they may allow us to simplify the condition.
193 We also use value ranges to do things like transform signed div/mod
194 operations into unsigned div/mod or to simplify ABS_EXPRs.
196 Simple experiments have shown these optimizations to not be all that
197 useful on switch statements (much to my surprise). So switch statement
198 optimizations are not performed.
200 Note carefully we do not propagate information through each statement
201 in the block. i.e., if we know variable X has a value defined of
202 [0, 25] and we encounter Y = X + 1, we do not track a value range
203 for Y (which would be [1, 26] if we cared). Similarly we do not
204 constrain values as we encounter narrowing typecasts, etc. */
208 /* The highest and lowest values the variable in COND may contain when
209 COND is true. Note this may not necessarily be the same values
210 tested by COND if the same variable was used in earlier conditionals.
212 Note this is computed lazily and thus can be NULL indicating that
213 the values have not been computed yet. */
217 /* The actual conditional we recorded. This is needed since we compute
221 /* The basic block where this record was created. We use this to determine
222 when to remove records. */
226 /* A hash table holding value range records (VRP_ELEMENTs) for a given
227 SSA_NAME. We used to use a varray indexed by SSA_NAME_VERSION, but
228 that gets awful wasteful, particularly since the density objects
229 with useful information is very low. */
230 static htab_t vrp_data;
232 typedef struct vrp_element *vrp_element_p;
234 DEF_VEC_P(vrp_element_p);
235 DEF_VEC_ALLOC_P(vrp_element_p,heap);
237 /* An entry in the VRP_DATA hash table. We record the variable and a
238 varray of VRP_ELEMENT records associated with that variable. */
242 VEC(vrp_element_p,heap) *records;
245 /* Array of variables which have their values constrained by operations
246 in this basic block. We use this during finalization to know
247 which variables need their VRP data updated. */
249 /* Stack of SSA_NAMEs which had their values constrained by operations
250 in this basic block. During finalization of this block we use this
251 list to determine which variables need their VRP data updated.
253 A NULL entry marks the end of the SSA_NAMEs associated with this block. */
254 static VEC(tree,heap) *vrp_variables_stack;
262 /* Local functions. */
263 static void optimize_stmt (struct dom_walk_data *,
265 block_stmt_iterator);
266 static tree lookup_avail_expr (tree, bool);
267 static hashval_t vrp_hash (const void *);
268 static int vrp_eq (const void *, const void *);
269 static hashval_t avail_expr_hash (const void *);
270 static hashval_t real_avail_expr_hash (const void *);
271 static int avail_expr_eq (const void *, const void *);
272 static void htab_statistics (FILE *, htab_t);
273 static void record_cond (tree, tree);
274 static void record_const_or_copy (tree, tree);
275 static void record_equality (tree, tree);
276 static tree simplify_cond_and_lookup_avail_expr (tree);
277 static void record_range (tree, basic_block);
278 static bool extract_range_from_cond (tree, tree *, tree *, int *);
279 static void record_equivalences_from_phis (basic_block);
280 static void record_equivalences_from_incoming_edge (basic_block);
281 static bool eliminate_redundant_computations (tree);
282 static void record_equivalences_from_stmt (tree, int, stmt_ann_t);
283 static void thread_across_edge (struct dom_walk_data *, edge);
284 static void dom_opt_finalize_block (struct dom_walk_data *, basic_block);
285 static void dom_opt_initialize_block (struct dom_walk_data *, basic_block);
286 static void propagate_to_outgoing_edges (struct dom_walk_data *, basic_block);
287 static void remove_local_expressions_from_table (void);
288 static void restore_vars_to_original_value (void);
289 static edge single_incoming_edge_ignoring_loop_edges (basic_block);
290 static void restore_nonzero_vars_to_original_value (void);
291 static inline bool unsafe_associative_fp_binop (tree);
294 /* Allocate an EDGE_INFO for edge E and attach it to E.
295 Return the new EDGE_INFO structure. */
297 static struct edge_info *
298 allocate_edge_info (edge e)
300 struct edge_info *edge_info;
302 edge_info = XCNEW (struct edge_info);
308 /* Free all EDGE_INFO structures associated with edges in the CFG.
309 If a particular edge can be threaded, copy the redirection
310 target from the EDGE_INFO structure into the edge's AUX field
311 as required by code to update the CFG and SSA graph for
315 free_all_edge_infos (void)
323 FOR_EACH_EDGE (e, ei, bb->preds)
325 struct edge_info *edge_info = (struct edge_info *) e->aux;
329 e->aux = edge_info->redirection_target;
330 if (edge_info->cond_equivalences)
331 free (edge_info->cond_equivalences);
338 /* Free an instance of vrp_hash_elt. */
341 vrp_free (void *data)
343 struct vrp_hash_elt *elt = (struct vrp_hash_elt *) data;
344 struct VEC(vrp_element_p,heap) **vrp_elt = &elt->records;
346 VEC_free (vrp_element_p, heap, *vrp_elt);
350 /* Jump threading, redundancy elimination and const/copy propagation.
352 This pass may expose new symbols that need to be renamed into SSA. For
353 every new symbol exposed, its corresponding bit will be set in
357 tree_ssa_dominator_optimize (void)
359 struct dom_walk_data walk_data;
361 struct loops loops_info;
363 memset (&opt_stats, 0, sizeof (opt_stats));
365 /* Create our hash tables. */
366 avail_exprs = htab_create (1024, real_avail_expr_hash, avail_expr_eq, free);
367 vrp_data = htab_create (ceil_log2 (num_ssa_names), vrp_hash, vrp_eq,
369 avail_exprs_stack = VEC_alloc (tree, heap, 20);
370 const_and_copies_stack = VEC_alloc (tree, heap, 20);
371 nonzero_vars_stack = VEC_alloc (tree, heap, 20);
372 vrp_variables_stack = VEC_alloc (tree, heap, 20);
373 stmts_to_rescan = VEC_alloc (tree, heap, 20);
374 nonzero_vars = BITMAP_ALLOC (NULL);
375 threaded_blocks = BITMAP_ALLOC (NULL);
376 need_eh_cleanup = BITMAP_ALLOC (NULL);
378 /* Setup callbacks for the generic dominator tree walker. */
379 walk_data.walk_stmts_backward = false;
380 walk_data.dom_direction = CDI_DOMINATORS;
381 walk_data.initialize_block_local_data = NULL;
382 walk_data.before_dom_children_before_stmts = dom_opt_initialize_block;
383 walk_data.before_dom_children_walk_stmts = optimize_stmt;
384 walk_data.before_dom_children_after_stmts = propagate_to_outgoing_edges;
385 walk_data.after_dom_children_before_stmts = NULL;
386 walk_data.after_dom_children_walk_stmts = NULL;
387 walk_data.after_dom_children_after_stmts = dom_opt_finalize_block;
388 /* Right now we only attach a dummy COND_EXPR to the global data pointer.
389 When we attach more stuff we'll need to fill this out with a real
391 walk_data.global_data = NULL;
392 walk_data.block_local_data_size = 0;
393 walk_data.interesting_blocks = NULL;
395 /* Now initialize the dominator walker. */
396 init_walk_dominator_tree (&walk_data);
398 calculate_dominance_info (CDI_DOMINATORS);
400 /* We need to know which edges exit loops so that we can
401 aggressively thread through loop headers to an exit
403 flow_loops_find (&loops_info);
404 mark_loop_exit_edges (&loops_info);
405 flow_loops_free (&loops_info);
407 /* Clean up the CFG so that any forwarder blocks created by loop
408 canonicalization are removed. */
410 calculate_dominance_info (CDI_DOMINATORS);
412 /* If we prove certain blocks are unreachable, then we want to
413 repeat the dominator optimization process as PHI nodes may
414 have turned into copies which allows better propagation of
415 values. So we repeat until we do not identify any new unreachable
419 /* Optimize the dominator tree. */
422 /* We need accurate information regarding back edges in the CFG
423 for jump threading. */
424 mark_dfs_back_edges ();
426 /* Recursively walk the dominator tree optimizing statements. */
427 walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
430 block_stmt_iterator bsi;
434 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
436 update_stmt_if_modified (bsi_stmt (bsi));
441 /* If we exposed any new variables, go ahead and put them into
442 SSA form now, before we handle jump threading. This simplifies
443 interactions between rewriting of _DECL nodes into SSA form
444 and rewriting SSA_NAME nodes into SSA form after block
445 duplication and CFG manipulation. */
446 update_ssa (TODO_update_ssa);
448 free_all_edge_infos ();
450 /* Thread jumps, creating duplicate blocks as needed. */
451 cfg_altered |= thread_through_all_blocks (threaded_blocks);
453 /* Removal of statements may make some EH edges dead. Purge
454 such edges from the CFG as needed. */
455 if (!bitmap_empty_p (need_eh_cleanup))
457 cfg_altered |= tree_purge_all_dead_eh_edges (need_eh_cleanup);
458 bitmap_zero (need_eh_cleanup);
462 free_dominance_info (CDI_DOMINATORS);
464 /* Only iterate if we threaded jumps AND the CFG cleanup did
465 something interesting. Other cases generate far fewer
466 optimization opportunities and thus are not worth another
467 full DOM iteration. */
468 cfg_altered &= cleanup_tree_cfg ();
470 if (rediscover_loops_after_threading)
472 /* Rerun basic loop analysis to discover any newly
473 created loops and update the set of exit edges. */
474 rediscover_loops_after_threading = false;
475 flow_loops_find (&loops_info);
476 mark_loop_exit_edges (&loops_info);
477 flow_loops_free (&loops_info);
479 /* Remove any forwarder blocks inserted by loop
480 header canonicalization. */
484 calculate_dominance_info (CDI_DOMINATORS);
486 update_ssa (TODO_update_ssa);
488 /* Reinitialize the various tables. */
489 bitmap_clear (nonzero_vars);
490 bitmap_clear (threaded_blocks);
491 htab_empty (avail_exprs);
492 htab_empty (vrp_data);
494 /* Finally, remove everything except invariants in SSA_NAME_VALUE.
496 This must be done before we iterate as we might have a
497 reference to an SSA_NAME which was removed by the call to
500 Long term we will be able to let everything in SSA_NAME_VALUE
501 persist. However, for now, we know this is the safe thing to do. */
502 for (i = 0; i < num_ssa_names; i++)
504 tree name = ssa_name (i);
510 value = SSA_NAME_VALUE (name);
511 if (value && !is_gimple_min_invariant (value))
512 SSA_NAME_VALUE (name) = NULL;
515 opt_stats.num_iterations++;
517 while (optimize > 1 && cfg_altered);
519 /* Debugging dumps. */
520 if (dump_file && (dump_flags & TDF_STATS))
521 dump_dominator_optimization_stats (dump_file);
523 /* We emptied the hash table earlier, now delete it completely. */
524 htab_delete (avail_exprs);
525 htab_delete (vrp_data);
527 /* It is not necessary to clear CURRDEFS, REDIRECTION_EDGES, VRP_DATA,
528 CONST_AND_COPIES, and NONZERO_VARS as they all get cleared at the bottom
529 of the do-while loop above. */
531 /* And finalize the dominator walker. */
532 fini_walk_dominator_tree (&walk_data);
534 /* Free nonzero_vars. */
535 BITMAP_FREE (nonzero_vars);
536 BITMAP_FREE (threaded_blocks);
537 BITMAP_FREE (need_eh_cleanup);
539 VEC_free (tree, heap, avail_exprs_stack);
540 VEC_free (tree, heap, const_and_copies_stack);
541 VEC_free (tree, heap, nonzero_vars_stack);
542 VEC_free (tree, heap, vrp_variables_stack);
543 VEC_free (tree, heap, stmts_to_rescan);
547 gate_dominator (void)
549 return flag_tree_dom != 0;
552 struct tree_opt_pass pass_dominator =
555 gate_dominator, /* gate */
556 tree_ssa_dominator_optimize, /* execute */
559 0, /* static_pass_number */
560 TV_TREE_SSA_DOMINATOR_OPTS, /* tv_id */
561 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
562 0, /* properties_provided */
563 0, /* properties_destroyed */
564 0, /* todo_flags_start */
567 | TODO_verify_ssa, /* todo_flags_finish */
572 /* Given a stmt CONDSTMT containing a COND_EXPR, canonicalize the
573 COND_EXPR into a canonical form. */
576 canonicalize_comparison (tree condstmt)
578 tree cond = COND_EXPR_COND (condstmt);
581 enum tree_code code = TREE_CODE (cond);
583 if (!COMPARISON_CLASS_P (cond))
586 op0 = TREE_OPERAND (cond, 0);
587 op1 = TREE_OPERAND (cond, 1);
589 /* If it would be profitable to swap the operands, then do so to
590 canonicalize the statement, enabling better optimization.
592 By placing canonicalization of such expressions here we
593 transparently keep statements in canonical form, even
594 when the statement is modified. */
595 if (tree_swap_operands_p (op0, op1, false))
597 /* For relationals we need to swap the operands
598 and change the code. */
604 TREE_SET_CODE (cond, swap_tree_comparison (code));
605 swap_tree_operands (condstmt,
606 &TREE_OPERAND (cond, 0),
607 &TREE_OPERAND (cond, 1));
608 /* If one operand was in the operand cache, but the other is
609 not, because it is a constant, this is a case that the
610 internal updating code of swap_tree_operands can't handle
612 if (TREE_CODE_CLASS (TREE_CODE (op0))
613 != TREE_CODE_CLASS (TREE_CODE (op1)))
614 update_stmt (condstmt);
618 /* We are exiting E->src, see if E->dest ends with a conditional
619 jump which has a known value when reached via E.
621 Special care is necessary if E is a back edge in the CFG as we
622 will have already recorded equivalences for E->dest into our
623 various tables, including the result of the conditional at
624 the end of E->dest. Threading opportunities are severely
625 limited in that case to avoid short-circuiting the loop
628 Note it is quite common for the first block inside a loop to
629 end with a conditional which is either always true or always
630 false when reached via the loop backedge. Thus we do not want
631 to blindly disable threading across a loop backedge. */
634 thread_across_edge (struct dom_walk_data *walk_data, edge e)
636 block_stmt_iterator bsi;
643 /* If E->dest does not end with a conditional, then there is
645 bsi = bsi_last (e->dest);
648 || (TREE_CODE (bsi_stmt (bsi)) != COND_EXPR
649 && TREE_CODE (bsi_stmt (bsi)) != GOTO_EXPR
650 && TREE_CODE (bsi_stmt (bsi)) != SWITCH_EXPR))
653 /* The basic idea here is to use whatever knowledge we have
654 from our dominator walk to simplify statements in E->dest,
655 with the ultimate goal being to simplify the conditional
656 at the end of E->dest.
658 Note that we must undo any changes we make to the underlying
659 statements as the simplifications we are making are control
660 flow sensitive (ie, the simplifications are valid when we
661 traverse E, but may not be valid on other paths to E->dest. */
663 /* Each PHI creates a temporary equivalence, record them. Again
664 these are context sensitive equivalences and will be removed
666 for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
668 tree src = PHI_ARG_DEF_FROM_EDGE (phi, e);
669 tree dst = PHI_RESULT (phi);
671 /* Do not include virtual PHIs in our statement count as
672 they never generate code. */
673 if (is_gimple_reg (dst))
676 /* If the desired argument is not the same as this PHI's result
677 and it is set by a PHI in E->dest, then we can not thread
680 && TREE_CODE (src) == SSA_NAME
681 && TREE_CODE (SSA_NAME_DEF_STMT (src)) == PHI_NODE
682 && bb_for_stmt (SSA_NAME_DEF_STMT (src)) == e->dest)
685 record_const_or_copy (dst, src);
688 /* Try to simplify each statement in E->dest, ultimately leading to
689 a simplification of the COND_EXPR at the end of E->dest.
691 We might consider marking just those statements which ultimately
692 feed the COND_EXPR. It's not clear if the overhead of bookkeeping
693 would be recovered by trying to simplify fewer statements.
695 If we are able to simplify a statement into the form
696 SSA_NAME = (SSA_NAME | gimple invariant), then we can record
697 a context sensitive equivalency which may help us simplify
698 later statements in E->dest.
700 Failure to simplify into the form above merely means that the
701 statement provides no equivalences to help simplify later
702 statements. This does not prevent threading through E->dest. */
703 max_stmt_count = PARAM_VALUE (PARAM_MAX_JUMP_THREAD_DUPLICATION_STMTS);
704 for (bsi = bsi_start (e->dest); ! bsi_end_p (bsi); bsi_next (&bsi))
706 tree cached_lhs = NULL;
708 stmt = bsi_stmt (bsi);
710 /* Ignore empty statements and labels. */
711 if (IS_EMPTY_STMT (stmt) || TREE_CODE (stmt) == LABEL_EXPR)
714 /* If duplicating this block is going to cause too much code
715 expansion, then do not thread through this block. */
717 if (stmt_count > max_stmt_count)
720 /* Safely handle threading across loop backedges. This is
721 over conservative, but still allows us to capture the
722 majority of the cases where we can thread across a loop
724 if ((e->flags & EDGE_DFS_BACK) != 0
725 && TREE_CODE (stmt) != COND_EXPR
726 && TREE_CODE (stmt) != SWITCH_EXPR)
729 /* If the statement has volatile operands, then we assume we
730 can not thread through this block. This is overly
731 conservative in some ways. */
732 if (TREE_CODE (stmt) == ASM_EXPR && ASM_VOLATILE_P (stmt))
735 /* If this is not a MODIFY_EXPR which sets an SSA_NAME to a new
736 value, then do not try to simplify this statement as it will
737 not simplify in any way that is helpful for jump threading. */
738 if (TREE_CODE (stmt) != MODIFY_EXPR
739 || TREE_CODE (TREE_OPERAND (stmt, 0)) != SSA_NAME)
742 /* At this point we have a statement which assigns an RHS to an
743 SSA_VAR on the LHS. We want to try and simplify this statement
744 to expose more context sensitive equivalences which in turn may
745 allow us to simplify the condition at the end of the loop. */
746 if (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME)
747 cached_lhs = TREE_OPERAND (stmt, 1);
750 /* Copy the operands. */
751 tree *copy, pre_fold_expr;
754 unsigned int num, i = 0;
756 num = NUM_SSA_OPERANDS (stmt, (SSA_OP_USE | SSA_OP_VUSE));
757 copy = XCNEWVEC (tree, num);
759 /* Make a copy of the uses & vuses into USES_COPY, then cprop into
761 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE | SSA_OP_VUSE)
764 tree use = USE_FROM_PTR (use_p);
767 if (TREE_CODE (use) == SSA_NAME)
768 tmp = SSA_NAME_VALUE (use);
769 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
770 SET_USE (use_p, tmp);
773 /* Try to fold/lookup the new expression. Inserting the
774 expression into the hash table is unlikely to help
775 Sadly, we have to handle conditional assignments specially
776 here, because fold expects all the operands of an expression
777 to be folded before the expression itself is folded, but we
778 can't just substitute the folded condition here. */
779 if (TREE_CODE (TREE_OPERAND (stmt, 1)) == COND_EXPR)
781 tree cond = COND_EXPR_COND (TREE_OPERAND (stmt, 1));
783 if (cond == boolean_true_node)
784 pre_fold_expr = COND_EXPR_THEN (TREE_OPERAND (stmt, 1));
785 else if (cond == boolean_false_node)
786 pre_fold_expr = COND_EXPR_ELSE (TREE_OPERAND (stmt, 1));
788 pre_fold_expr = TREE_OPERAND (stmt, 1);
791 pre_fold_expr = TREE_OPERAND (stmt, 1);
795 cached_lhs = fold (pre_fold_expr);
796 if (TREE_CODE (cached_lhs) != SSA_NAME
797 && !is_gimple_min_invariant (cached_lhs))
798 cached_lhs = lookup_avail_expr (stmt, false);
801 /* Restore the statement's original uses/defs. */
803 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE | SSA_OP_VUSE)
804 SET_USE (use_p, copy[i++]);
809 /* Record the context sensitive equivalence if we were able
810 to simplify this statement. */
812 && (TREE_CODE (cached_lhs) == SSA_NAME
813 || is_gimple_min_invariant (cached_lhs)))
814 record_const_or_copy (TREE_OPERAND (stmt, 0), cached_lhs);
817 /* If we stopped at a COND_EXPR or SWITCH_EXPR, see if we know which arm
820 && (TREE_CODE (stmt) == COND_EXPR
821 || TREE_CODE (stmt) == GOTO_EXPR
822 || TREE_CODE (stmt) == SWITCH_EXPR))
824 tree cond, cached_lhs;
826 /* Now temporarily cprop the operands and try to find the resulting
827 expression in the hash tables. */
828 if (TREE_CODE (stmt) == COND_EXPR)
830 canonicalize_comparison (stmt);
831 cond = COND_EXPR_COND (stmt);
833 else if (TREE_CODE (stmt) == GOTO_EXPR)
834 cond = GOTO_DESTINATION (stmt);
836 cond = SWITCH_COND (stmt);
838 if (COMPARISON_CLASS_P (cond))
840 tree dummy_cond, op0, op1;
841 enum tree_code cond_code;
843 op0 = TREE_OPERAND (cond, 0);
844 op1 = TREE_OPERAND (cond, 1);
845 cond_code = TREE_CODE (cond);
847 /* Get the current value of both operands. */
848 if (TREE_CODE (op0) == SSA_NAME)
850 tree tmp = SSA_NAME_VALUE (op0);
851 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
855 if (TREE_CODE (op1) == SSA_NAME)
857 tree tmp = SSA_NAME_VALUE (op1);
858 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
862 /* Stuff the operator and operands into our dummy conditional
863 expression, creating the dummy conditional if necessary. */
864 dummy_cond = (tree) walk_data->global_data;
867 dummy_cond = build2 (cond_code, boolean_type_node, op0, op1);
868 dummy_cond = build3 (COND_EXPR, void_type_node,
869 dummy_cond, NULL_TREE, NULL_TREE);
870 walk_data->global_data = dummy_cond;
874 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), cond_code);
875 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op0;
876 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1) = op1;
879 /* We absolutely do not care about any type conversions
880 we only care about a zero/nonzero value. */
881 cached_lhs = fold (COND_EXPR_COND (dummy_cond));
882 while (TREE_CODE (cached_lhs) == NOP_EXPR
883 || TREE_CODE (cached_lhs) == CONVERT_EXPR
884 || TREE_CODE (cached_lhs) == NON_LVALUE_EXPR)
885 cached_lhs = TREE_OPERAND (cached_lhs, 0);
887 if (! is_gimple_min_invariant (cached_lhs))
889 cached_lhs = lookup_avail_expr (dummy_cond, false);
890 if (!cached_lhs || ! is_gimple_min_invariant (cached_lhs))
891 cached_lhs = simplify_cond_and_lookup_avail_expr (dummy_cond);
894 /* We can have conditionals which just test the state of a
895 variable rather than use a relational operator. These are
896 simpler to handle. */
897 else if (TREE_CODE (cond) == SSA_NAME)
900 cached_lhs = SSA_NAME_VALUE (cached_lhs);
901 if (cached_lhs && ! is_gimple_min_invariant (cached_lhs))
905 cached_lhs = lookup_avail_expr (stmt, false);
909 edge taken_edge = find_taken_edge (e->dest, cached_lhs);
910 basic_block dest = (taken_edge ? taken_edge->dest : NULL);
915 /* If we have a known destination for the conditional, then
916 we can perform this optimization, which saves at least one
917 conditional jump each time it applies since we get to
918 bypass the conditional at our original destination. */
921 struct edge_info *edge_info;
924 edge_info = (struct edge_info *) e->aux;
926 edge_info = allocate_edge_info (e);
927 edge_info->redirection_target = taken_edge;
928 bitmap_set_bit (threaded_blocks, e->dest->index);
935 /* Initialize local stacks for this optimizer and record equivalences
936 upon entry to BB. Equivalences can come from the edge traversed to
937 reach BB or they may come from PHI nodes at the start of BB. */
940 dom_opt_initialize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
943 if (dump_file && (dump_flags & TDF_DETAILS))
944 fprintf (dump_file, "\n\nOptimizing block #%d\n\n", bb->index);
946 /* Push a marker on the stacks of local information so that we know how
947 far to unwind when we finalize this block. */
948 VEC_safe_push (tree, heap, avail_exprs_stack, NULL_TREE);
949 VEC_safe_push (tree, heap, const_and_copies_stack, NULL_TREE);
950 VEC_safe_push (tree, heap, nonzero_vars_stack, NULL_TREE);
951 VEC_safe_push (tree, heap, vrp_variables_stack, NULL_TREE);
953 record_equivalences_from_incoming_edge (bb);
955 /* PHI nodes can create equivalences too. */
956 record_equivalences_from_phis (bb);
959 /* Given an expression EXPR (a relational expression or a statement),
960 initialize the hash table element pointed to by ELEMENT. */
963 initialize_hash_element (tree expr, tree lhs, struct expr_hash_elt *element)
965 /* Hash table elements may be based on conditional expressions or statements.
967 For the former case, we have no annotation and we want to hash the
968 conditional expression. In the latter case we have an annotation and
969 we want to record the expression the statement evaluates. */
970 if (COMPARISON_CLASS_P (expr) || TREE_CODE (expr) == TRUTH_NOT_EXPR)
972 element->stmt = NULL;
975 else if (TREE_CODE (expr) == COND_EXPR)
977 element->stmt = expr;
978 element->rhs = COND_EXPR_COND (expr);
980 else if (TREE_CODE (expr) == SWITCH_EXPR)
982 element->stmt = expr;
983 element->rhs = SWITCH_COND (expr);
985 else if (TREE_CODE (expr) == RETURN_EXPR && TREE_OPERAND (expr, 0))
987 element->stmt = expr;
988 element->rhs = TREE_OPERAND (TREE_OPERAND (expr, 0), 1);
990 else if (TREE_CODE (expr) == GOTO_EXPR)
992 element->stmt = expr;
993 element->rhs = GOTO_DESTINATION (expr);
997 element->stmt = expr;
998 element->rhs = TREE_OPERAND (expr, 1);
1002 element->hash = avail_expr_hash (element);
1005 /* Remove all the expressions in LOCALS from TABLE, stopping when there are
1006 LIMIT entries left in LOCALs. */
1009 remove_local_expressions_from_table (void)
1011 /* Remove all the expressions made available in this block. */
1012 while (VEC_length (tree, avail_exprs_stack) > 0)
1014 struct expr_hash_elt element;
1015 tree expr = VEC_pop (tree, avail_exprs_stack);
1017 if (expr == NULL_TREE)
1020 initialize_hash_element (expr, NULL, &element);
1021 htab_remove_elt_with_hash (avail_exprs, &element, element.hash);
1025 /* Use the SSA_NAMES in LOCALS to restore TABLE to its original
1026 state, stopping when there are LIMIT entries left in LOCALs. */
1029 restore_nonzero_vars_to_original_value (void)
1031 while (VEC_length (tree, nonzero_vars_stack) > 0)
1033 tree name = VEC_pop (tree, nonzero_vars_stack);
1038 bitmap_clear_bit (nonzero_vars, SSA_NAME_VERSION (name));
1042 /* Use the source/dest pairs in CONST_AND_COPIES_STACK to restore
1043 CONST_AND_COPIES to its original state, stopping when we hit a
1047 restore_vars_to_original_value (void)
1049 while (VEC_length (tree, const_and_copies_stack) > 0)
1051 tree prev_value, dest;
1053 dest = VEC_pop (tree, const_and_copies_stack);
1058 prev_value = VEC_pop (tree, const_and_copies_stack);
1059 SSA_NAME_VALUE (dest) = prev_value;
1063 /* We have finished processing the dominator children of BB, perform
1064 any finalization actions in preparation for leaving this node in
1065 the dominator tree. */
1068 dom_opt_finalize_block (struct dom_walk_data *walk_data, basic_block bb)
1072 /* If we have an outgoing edge to a block with multiple incoming and
1073 outgoing edges, then we may be able to thread the edge. ie, we
1074 may be able to statically determine which of the outgoing edges
1075 will be traversed when the incoming edge from BB is traversed. */
1076 if (single_succ_p (bb)
1077 && (single_succ_edge (bb)->flags & EDGE_ABNORMAL) == 0
1078 && !single_pred_p (single_succ (bb))
1079 && !single_succ_p (single_succ (bb)))
1082 thread_across_edge (walk_data, single_succ_edge (bb));
1084 else if ((last = last_stmt (bb))
1085 && TREE_CODE (last) == COND_EXPR
1086 && (COMPARISON_CLASS_P (COND_EXPR_COND (last))
1087 || TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME)
1088 && EDGE_COUNT (bb->succs) == 2
1089 && (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL) == 0
1090 && (EDGE_SUCC (bb, 1)->flags & EDGE_ABNORMAL) == 0)
1092 edge true_edge, false_edge;
1094 extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
1096 /* Only try to thread the edge if it reaches a target block with
1097 more than one predecessor and more than one successor. */
1098 if (!single_pred_p (true_edge->dest) && !single_succ_p (true_edge->dest))
1100 struct edge_info *edge_info;
1103 /* Push a marker onto the available expression stack so that we
1104 unwind any expressions related to the TRUE arm before processing
1105 the false arm below. */
1106 VEC_safe_push (tree, heap, avail_exprs_stack, NULL_TREE);
1107 VEC_safe_push (tree, heap, const_and_copies_stack, NULL_TREE);
1109 edge_info = (struct edge_info *) true_edge->aux;
1111 /* If we have info associated with this edge, record it into
1112 our equivalency tables. */
1115 tree *cond_equivalences = edge_info->cond_equivalences;
1116 tree lhs = edge_info->lhs;
1117 tree rhs = edge_info->rhs;
1119 /* If we have a simple NAME = VALUE equivalency record it. */
1120 if (lhs && TREE_CODE (lhs) == SSA_NAME)
1121 record_const_or_copy (lhs, rhs);
1123 /* If we have 0 = COND or 1 = COND equivalences, record them
1124 into our expression hash tables. */
1125 if (cond_equivalences)
1126 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1128 tree expr = cond_equivalences[i];
1129 tree value = cond_equivalences[i + 1];
1131 record_cond (expr, value);
1135 /* Now thread the edge. */
1136 thread_across_edge (walk_data, true_edge);
1138 /* And restore the various tables to their state before
1139 we threaded this edge. */
1140 remove_local_expressions_from_table ();
1141 restore_vars_to_original_value ();
1144 /* Similarly for the ELSE arm. */
1145 if (!single_pred_p (false_edge->dest) && !single_succ_p (false_edge->dest))
1147 struct edge_info *edge_info;
1150 edge_info = (struct edge_info *) false_edge->aux;
1152 /* If we have info associated with this edge, record it into
1153 our equivalency tables. */
1156 tree *cond_equivalences = edge_info->cond_equivalences;
1157 tree lhs = edge_info->lhs;
1158 tree rhs = edge_info->rhs;
1160 /* If we have a simple NAME = VALUE equivalency record it. */
1161 if (lhs && TREE_CODE (lhs) == SSA_NAME)
1162 record_const_or_copy (lhs, rhs);
1164 /* If we have 0 = COND or 1 = COND equivalences, record them
1165 into our expression hash tables. */
1166 if (cond_equivalences)
1167 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1169 tree expr = cond_equivalences[i];
1170 tree value = cond_equivalences[i + 1];
1172 record_cond (expr, value);
1176 thread_across_edge (walk_data, false_edge);
1178 /* No need to remove local expressions from our tables
1179 or restore vars to their original value as that will
1180 be done immediately below. */
1184 remove_local_expressions_from_table ();
1185 restore_nonzero_vars_to_original_value ();
1186 restore_vars_to_original_value ();
1188 /* Remove VRP records associated with this basic block. They are no
1191 To be efficient, we note which variables have had their values
1192 constrained in this block. So walk over each variable in the
1193 VRP_VARIABLEs array. */
1194 while (VEC_length (tree, vrp_variables_stack) > 0)
1196 tree var = VEC_pop (tree, vrp_variables_stack);
1197 struct vrp_hash_elt vrp_hash_elt, *vrp_hash_elt_p;
1200 /* Each variable has a stack of value range records. We want to
1201 invalidate those associated with our basic block. So we walk
1202 the array backwards popping off records associated with our
1203 block. Once we hit a record not associated with our block
1205 VEC(vrp_element_p,heap) **var_vrp_records;
1210 vrp_hash_elt.var = var;
1211 vrp_hash_elt.records = NULL;
1213 slot = htab_find_slot (vrp_data, &vrp_hash_elt, NO_INSERT);
1215 vrp_hash_elt_p = (struct vrp_hash_elt *) *slot;
1216 var_vrp_records = &vrp_hash_elt_p->records;
1218 while (VEC_length (vrp_element_p, *var_vrp_records) > 0)
1220 struct vrp_element *element
1221 = VEC_last (vrp_element_p, *var_vrp_records);
1223 if (element->bb != bb)
1226 VEC_pop (vrp_element_p, *var_vrp_records);
1230 /* If we queued any statements to rescan in this block, then
1231 go ahead and rescan them now. */
1232 while (VEC_length (tree, stmts_to_rescan) > 0)
1234 tree stmt = VEC_last (tree, stmts_to_rescan);
1235 basic_block stmt_bb = bb_for_stmt (stmt);
1240 VEC_pop (tree, stmts_to_rescan);
1241 mark_new_vars_to_rename (stmt);
1245 /* PHI nodes can create equivalences too.
1247 Ignoring any alternatives which are the same as the result, if
1248 all the alternatives are equal, then the PHI node creates an
1251 Additionally, if all the PHI alternatives are known to have a nonzero
1252 value, then the result of this PHI is known to have a nonzero value,
1253 even if we do not know its exact value. */
1256 record_equivalences_from_phis (basic_block bb)
1260 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1262 tree lhs = PHI_RESULT (phi);
1266 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1268 tree t = PHI_ARG_DEF (phi, i);
1270 /* Ignore alternatives which are the same as our LHS. Since
1271 LHS is a PHI_RESULT, it is known to be a SSA_NAME, so we
1272 can simply compare pointers. */
1276 /* If we have not processed an alternative yet, then set
1277 RHS to this alternative. */
1280 /* If we have processed an alternative (stored in RHS), then
1281 see if it is equal to this one. If it isn't, then stop
1283 else if (! operand_equal_for_phi_arg_p (rhs, t))
1287 /* If we had no interesting alternatives, then all the RHS alternatives
1288 must have been the same as LHS. */
1292 /* If we managed to iterate through each PHI alternative without
1293 breaking out of the loop, then we have a PHI which may create
1294 a useful equivalence. We do not need to record unwind data for
1295 this, since this is a true assignment and not an equivalence
1296 inferred from a comparison. All uses of this ssa name are dominated
1297 by this assignment, so unwinding just costs time and space. */
1298 if (i == PHI_NUM_ARGS (phi)
1299 && may_propagate_copy (lhs, rhs))
1300 SSA_NAME_VALUE (lhs) = rhs;
1302 /* Now see if we know anything about the nonzero property for the
1303 result of this PHI. */
1304 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1306 if (!PHI_ARG_NONZERO (phi, i))
1310 if (i == PHI_NUM_ARGS (phi))
1311 bitmap_set_bit (nonzero_vars, SSA_NAME_VERSION (PHI_RESULT (phi)));
1315 /* Ignoring loop backedges, if BB has precisely one incoming edge then
1316 return that edge. Otherwise return NULL. */
1318 single_incoming_edge_ignoring_loop_edges (basic_block bb)
1324 FOR_EACH_EDGE (e, ei, bb->preds)
1326 /* A loop back edge can be identified by the destination of
1327 the edge dominating the source of the edge. */
1328 if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
1331 /* If we have already seen a non-loop edge, then we must have
1332 multiple incoming non-loop edges and thus we return NULL. */
1336 /* This is the first non-loop incoming edge we have found. Record
1344 /* Record any equivalences created by the incoming edge to BB. If BB
1345 has more than one incoming edge, then no equivalence is created. */
1348 record_equivalences_from_incoming_edge (basic_block bb)
1352 struct edge_info *edge_info;
1354 /* If our parent block ended with a control statement, then we may be
1355 able to record some equivalences based on which outgoing edge from
1356 the parent was followed. */
1357 parent = get_immediate_dominator (CDI_DOMINATORS, bb);
1359 e = single_incoming_edge_ignoring_loop_edges (bb);
1361 /* If we had a single incoming edge from our parent block, then enter
1362 any data associated with the edge into our tables. */
1363 if (e && e->src == parent)
1367 edge_info = (struct edge_info *) e->aux;
1371 tree lhs = edge_info->lhs;
1372 tree rhs = edge_info->rhs;
1373 tree *cond_equivalences = edge_info->cond_equivalences;
1376 record_equality (lhs, rhs);
1378 if (cond_equivalences)
1380 bool recorded_range = false;
1381 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1383 tree expr = cond_equivalences[i];
1384 tree value = cond_equivalences[i + 1];
1386 record_cond (expr, value);
1388 /* For the first true equivalence, record range
1389 information. We only do this for the first
1390 true equivalence as it should dominate any
1391 later true equivalences. */
1392 if (! recorded_range
1393 && COMPARISON_CLASS_P (expr)
1394 && value == boolean_true_node
1395 && TREE_CONSTANT (TREE_OPERAND (expr, 1)))
1397 record_range (expr, bb);
1398 recorded_range = true;
1406 /* Dump SSA statistics on FILE. */
1409 dump_dominator_optimization_stats (FILE *file)
1413 fprintf (file, "Total number of statements: %6ld\n\n",
1414 opt_stats.num_stmts);
1415 fprintf (file, "Exprs considered for dominator optimizations: %6ld\n",
1416 opt_stats.num_exprs_considered);
1418 n_exprs = opt_stats.num_exprs_considered;
1422 fprintf (file, " Redundant expressions eliminated: %6ld (%.0f%%)\n",
1423 opt_stats.num_re, PERCENT (opt_stats.num_re,
1425 fprintf (file, " Constants propagated: %6ld\n",
1426 opt_stats.num_const_prop);
1427 fprintf (file, " Copies propagated: %6ld\n",
1428 opt_stats.num_copy_prop);
1430 fprintf (file, "\nTotal number of DOM iterations: %6ld\n",
1431 opt_stats.num_iterations);
1433 fprintf (file, "\nHash table statistics:\n");
1435 fprintf (file, " avail_exprs: ");
1436 htab_statistics (file, avail_exprs);
1440 /* Dump SSA statistics on stderr. */
1443 debug_dominator_optimization_stats (void)
1445 dump_dominator_optimization_stats (stderr);
1449 /* Dump statistics for the hash table HTAB. */
1452 htab_statistics (FILE *file, htab_t htab)
1454 fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
1455 (long) htab_size (htab),
1456 (long) htab_elements (htab),
1457 htab_collisions (htab));
1460 /* Record the fact that VAR has a nonzero value, though we may not know
1461 its exact value. Note that if VAR is already known to have a nonzero
1462 value, then we do nothing. */
1465 record_var_is_nonzero (tree var)
1467 int indx = SSA_NAME_VERSION (var);
1469 if (bitmap_bit_p (nonzero_vars, indx))
1472 /* Mark it in the global table. */
1473 bitmap_set_bit (nonzero_vars, indx);
1475 /* Record this SSA_NAME so that we can reset the global table
1476 when we leave this block. */
1477 VEC_safe_push (tree, heap, nonzero_vars_stack, var);
1480 /* Enter a statement into the true/false expression hash table indicating
1481 that the condition COND has the value VALUE. */
1484 record_cond (tree cond, tree value)
1486 struct expr_hash_elt *element = XCNEW (struct expr_hash_elt);
1489 initialize_hash_element (cond, value, element);
1491 slot = htab_find_slot_with_hash (avail_exprs, (void *)element,
1492 element->hash, INSERT);
1495 *slot = (void *) element;
1496 VEC_safe_push (tree, heap, avail_exprs_stack, cond);
1502 /* Build a new conditional using NEW_CODE, OP0 and OP1 and store
1503 the new conditional into *p, then store a boolean_true_node
1507 build_and_record_new_cond (enum tree_code new_code, tree op0, tree op1, tree *p)
1509 *p = build2 (new_code, boolean_type_node, op0, op1);
1511 *p = boolean_true_node;
1514 /* Record that COND is true and INVERTED is false into the edge information
1515 structure. Also record that any conditions dominated by COND are true
1518 For example, if a < b is true, then a <= b must also be true. */
1521 record_conditions (struct edge_info *edge_info, tree cond, tree inverted)
1525 if (!COMPARISON_CLASS_P (cond))
1528 op0 = TREE_OPERAND (cond, 0);
1529 op1 = TREE_OPERAND (cond, 1);
1531 switch (TREE_CODE (cond))
1535 edge_info->max_cond_equivalences = 12;
1536 edge_info->cond_equivalences = XNEWVEC (tree, 12);
1537 build_and_record_new_cond ((TREE_CODE (cond) == LT_EXPR
1538 ? LE_EXPR : GE_EXPR),
1539 op0, op1, &edge_info->cond_equivalences[4]);
1540 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1541 &edge_info->cond_equivalences[6]);
1542 build_and_record_new_cond (NE_EXPR, op0, op1,
1543 &edge_info->cond_equivalences[8]);
1544 build_and_record_new_cond (LTGT_EXPR, op0, op1,
1545 &edge_info->cond_equivalences[10]);
1550 edge_info->max_cond_equivalences = 6;
1551 edge_info->cond_equivalences = XNEWVEC (tree, 6);
1552 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1553 &edge_info->cond_equivalences[4]);
1557 edge_info->max_cond_equivalences = 10;
1558 edge_info->cond_equivalences = XNEWVEC (tree, 10);
1559 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1560 &edge_info->cond_equivalences[4]);
1561 build_and_record_new_cond (LE_EXPR, op0, op1,
1562 &edge_info->cond_equivalences[6]);
1563 build_and_record_new_cond (GE_EXPR, op0, op1,
1564 &edge_info->cond_equivalences[8]);
1567 case UNORDERED_EXPR:
1568 edge_info->max_cond_equivalences = 16;
1569 edge_info->cond_equivalences = XNEWVEC (tree, 16);
1570 build_and_record_new_cond (NE_EXPR, op0, op1,
1571 &edge_info->cond_equivalences[4]);
1572 build_and_record_new_cond (UNLE_EXPR, op0, op1,
1573 &edge_info->cond_equivalences[6]);
1574 build_and_record_new_cond (UNGE_EXPR, op0, op1,
1575 &edge_info->cond_equivalences[8]);
1576 build_and_record_new_cond (UNEQ_EXPR, op0, op1,
1577 &edge_info->cond_equivalences[10]);
1578 build_and_record_new_cond (UNLT_EXPR, op0, op1,
1579 &edge_info->cond_equivalences[12]);
1580 build_and_record_new_cond (UNGT_EXPR, op0, op1,
1581 &edge_info->cond_equivalences[14]);
1586 edge_info->max_cond_equivalences = 8;
1587 edge_info->cond_equivalences = XNEWVEC (tree, 8);
1588 build_and_record_new_cond ((TREE_CODE (cond) == UNLT_EXPR
1589 ? UNLE_EXPR : UNGE_EXPR),
1590 op0, op1, &edge_info->cond_equivalences[4]);
1591 build_and_record_new_cond (NE_EXPR, op0, op1,
1592 &edge_info->cond_equivalences[6]);
1596 edge_info->max_cond_equivalences = 8;
1597 edge_info->cond_equivalences = XNEWVEC (tree, 8);
1598 build_and_record_new_cond (UNLE_EXPR, op0, op1,
1599 &edge_info->cond_equivalences[4]);
1600 build_and_record_new_cond (UNGE_EXPR, op0, op1,
1601 &edge_info->cond_equivalences[6]);
1605 edge_info->max_cond_equivalences = 8;
1606 edge_info->cond_equivalences = XNEWVEC (tree, 8);
1607 build_and_record_new_cond (NE_EXPR, op0, op1,
1608 &edge_info->cond_equivalences[4]);
1609 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1610 &edge_info->cond_equivalences[6]);
1614 edge_info->max_cond_equivalences = 4;
1615 edge_info->cond_equivalences = XNEWVEC (tree, 4);
1619 /* Now store the original true and false conditions into the first
1621 edge_info->cond_equivalences[0] = cond;
1622 edge_info->cond_equivalences[1] = boolean_true_node;
1623 edge_info->cond_equivalences[2] = inverted;
1624 edge_info->cond_equivalences[3] = boolean_false_node;
1627 /* A helper function for record_const_or_copy and record_equality.
1628 Do the work of recording the value and undo info. */
1631 record_const_or_copy_1 (tree x, tree y, tree prev_x)
1633 SSA_NAME_VALUE (x) = y;
1635 VEC_reserve (tree, heap, const_and_copies_stack, 2);
1636 VEC_quick_push (tree, const_and_copies_stack, prev_x);
1637 VEC_quick_push (tree, const_and_copies_stack, x);
1641 /* Return the loop depth of the basic block of the defining statement of X.
1642 This number should not be treated as absolutely correct because the loop
1643 information may not be completely up-to-date when dom runs. However, it
1644 will be relatively correct, and as more passes are taught to keep loop info
1645 up to date, the result will become more and more accurate. */
1648 loop_depth_of_name (tree x)
1653 /* If it's not an SSA_NAME, we have no clue where the definition is. */
1654 if (TREE_CODE (x) != SSA_NAME)
1657 /* Otherwise return the loop depth of the defining statement's bb.
1658 Note that there may not actually be a bb for this statement, if the
1659 ssa_name is live on entry. */
1660 defstmt = SSA_NAME_DEF_STMT (x);
1661 defbb = bb_for_stmt (defstmt);
1665 return defbb->loop_depth;
1669 /* Record that X is equal to Y in const_and_copies. Record undo
1670 information in the block-local vector. */
1673 record_const_or_copy (tree x, tree y)
1675 tree prev_x = SSA_NAME_VALUE (x);
1677 if (TREE_CODE (y) == SSA_NAME)
1679 tree tmp = SSA_NAME_VALUE (y);
1684 record_const_or_copy_1 (x, y, prev_x);
1687 /* Similarly, but assume that X and Y are the two operands of an EQ_EXPR.
1688 This constrains the cases in which we may treat this as assignment. */
1691 record_equality (tree x, tree y)
1693 tree prev_x = NULL, prev_y = NULL;
1695 if (TREE_CODE (x) == SSA_NAME)
1696 prev_x = SSA_NAME_VALUE (x);
1697 if (TREE_CODE (y) == SSA_NAME)
1698 prev_y = SSA_NAME_VALUE (y);
1700 /* If one of the previous values is invariant, or invariant in more loops
1701 (by depth), then use that.
1702 Otherwise it doesn't matter which value we choose, just so
1703 long as we canonicalize on one value. */
1704 if (TREE_INVARIANT (y))
1706 else if (TREE_INVARIANT (x) || (loop_depth_of_name (x) <= loop_depth_of_name (y)))
1707 prev_x = x, x = y, y = prev_x, prev_x = prev_y;
1708 else if (prev_x && TREE_INVARIANT (prev_x))
1709 x = y, y = prev_x, prev_x = prev_y;
1710 else if (prev_y && TREE_CODE (prev_y) != VALUE_HANDLE)
1713 /* After the swapping, we must have one SSA_NAME. */
1714 if (TREE_CODE (x) != SSA_NAME)
1717 /* For IEEE, -0.0 == 0.0, so we don't necessarily know the sign of a
1718 variable compared against zero. If we're honoring signed zeros,
1719 then we cannot record this value unless we know that the value is
1721 if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (x)))
1722 && (TREE_CODE (y) != REAL_CST
1723 || REAL_VALUES_EQUAL (dconst0, TREE_REAL_CST (y))))
1726 record_const_or_copy_1 (x, y, prev_x);
1729 /* Return true, if it is ok to do folding of an associative expression.
1730 EXP is the tree for the associative expression. */
1733 unsafe_associative_fp_binop (tree exp)
1735 enum tree_code code = TREE_CODE (exp);
1736 return !(!flag_unsafe_math_optimizations
1737 && (code == MULT_EXPR || code == PLUS_EXPR
1738 || code == MINUS_EXPR)
1739 && FLOAT_TYPE_P (TREE_TYPE (exp)));
1742 /* Returns true when STMT is a simple iv increment. It detects the
1743 following situation:
1745 i_1 = phi (..., i_2)
1746 i_2 = i_1 +/- ... */
1749 simple_iv_increment_p (tree stmt)
1751 tree lhs, rhs, preinc, phi;
1754 if (TREE_CODE (stmt) != MODIFY_EXPR)
1757 lhs = TREE_OPERAND (stmt, 0);
1758 if (TREE_CODE (lhs) != SSA_NAME)
1761 rhs = TREE_OPERAND (stmt, 1);
1763 if (TREE_CODE (rhs) != PLUS_EXPR
1764 && TREE_CODE (rhs) != MINUS_EXPR)
1767 preinc = TREE_OPERAND (rhs, 0);
1768 if (TREE_CODE (preinc) != SSA_NAME)
1771 phi = SSA_NAME_DEF_STMT (preinc);
1772 if (TREE_CODE (phi) != PHI_NODE)
1775 for (i = 0; i < (unsigned) PHI_NUM_ARGS (phi); i++)
1776 if (PHI_ARG_DEF (phi, i) == lhs)
1782 /* STMT is a COND_EXPR for which we could not trivially determine its
1783 result. This routine attempts to find equivalent forms of the
1784 condition which we may be able to optimize better. It also
1785 uses simple value range propagation to optimize conditionals. */
1788 simplify_cond_and_lookup_avail_expr (tree stmt)
1790 tree cond = COND_EXPR_COND (stmt);
1792 if (COMPARISON_CLASS_P (cond))
1794 tree op0 = TREE_OPERAND (cond, 0);
1795 tree op1 = TREE_OPERAND (cond, 1);
1797 if (TREE_CODE (op0) == SSA_NAME && is_gimple_min_invariant (op1))
1800 tree low, high, cond_low, cond_high;
1801 int lowequal, highequal, swapped, no_overlap, subset, cond_inverted;
1802 VEC(vrp_element_p,heap) **vrp_records;
1803 struct vrp_element *element;
1804 struct vrp_hash_elt vrp_hash_elt, *vrp_hash_elt_p;
1807 /* Consult the value range records for this variable (if they exist)
1808 to see if we can eliminate or simplify this conditional.
1810 Note two tests are necessary to determine no records exist.
1811 First we have to see if the virtual array exists, if it
1812 exists, then we have to check its active size.
1814 Also note the vast majority of conditionals are not testing
1815 a variable which has had its range constrained by an earlier
1816 conditional. So this filter avoids a lot of unnecessary work. */
1817 vrp_hash_elt.var = op0;
1818 vrp_hash_elt.records = NULL;
1819 slot = htab_find_slot (vrp_data, &vrp_hash_elt, NO_INSERT);
1823 vrp_hash_elt_p = (struct vrp_hash_elt *) *slot;
1824 vrp_records = &vrp_hash_elt_p->records;
1826 limit = VEC_length (vrp_element_p, *vrp_records);
1828 /* If we have no value range records for this variable, or we are
1829 unable to extract a range for this condition, then there is
1832 || ! extract_range_from_cond (cond, &cond_high,
1833 &cond_low, &cond_inverted))
1836 /* We really want to avoid unnecessary computations of range
1837 info. So all ranges are computed lazily; this avoids a
1838 lot of unnecessary work. i.e., we record the conditional,
1839 but do not process how it constrains the variable's
1840 potential values until we know that processing the condition
1843 However, we do not want to have to walk a potentially long
1844 list of ranges, nor do we want to compute a variable's
1845 range more than once for a given path.
1847 Luckily, each time we encounter a conditional that can not
1848 be otherwise optimized we will end up here and we will
1849 compute the necessary range information for the variable
1850 used in this condition.
1852 Thus you can conclude that there will never be more than one
1853 conditional associated with a variable which has not been
1854 processed. So we never need to merge more than one new
1855 conditional into the current range.
1857 These properties also help us avoid unnecessary work. */
1858 element = VEC_last (vrp_element_p, *vrp_records);
1860 if (element->high && element->low)
1862 /* The last element has been processed, so there is no range
1863 merging to do, we can simply use the high/low values
1864 recorded in the last element. */
1866 high = element->high;
1870 tree tmp_high, tmp_low;
1873 /* The last element has not been processed. Process it now.
1874 record_range should ensure for cond inverted is not set.
1875 This call can only fail if cond is x < min or x > max,
1876 which fold should have optimized into false.
1877 If that doesn't happen, just pretend all values are
1879 if (! extract_range_from_cond (element->cond, &tmp_high,
1883 gcc_assert (dummy == 0);
1885 /* If this is the only element, then no merging is necessary,
1886 the high/low values from extract_range_from_cond are all
1895 /* Get the high/low value from the previous element. */
1896 struct vrp_element *prev
1897 = VEC_index (vrp_element_p, *vrp_records, limit - 2);
1901 /* Merge in this element's range with the range from the
1904 The low value for the merged range is the maximum of
1905 the previous low value and the low value of this record.
1907 Similarly the high value for the merged range is the
1908 minimum of the previous high value and the high value of
1910 low = (low && tree_int_cst_compare (low, tmp_low) == 1
1912 high = (high && tree_int_cst_compare (high, tmp_high) == -1
1916 /* And record the computed range. */
1918 element->high = high;
1922 /* After we have constrained this variable's potential values,
1923 we try to determine the result of the given conditional.
1925 To simplify later tests, first determine if the current
1926 low value is the same low value as the conditional.
1927 Similarly for the current high value and the high value
1928 for the conditional. */
1929 lowequal = tree_int_cst_equal (low, cond_low);
1930 highequal = tree_int_cst_equal (high, cond_high);
1932 if (lowequal && highequal)
1933 return (cond_inverted ? boolean_false_node : boolean_true_node);
1935 /* To simplify the overlap/subset tests below we may want
1936 to swap the two ranges so that the larger of the two
1937 ranges occurs "first". */
1939 if (tree_int_cst_compare (low, cond_low) == 1
1941 && tree_int_cst_compare (cond_high, high) == 1))
1954 /* Now determine if there is no overlap in the ranges
1955 or if the second range is a subset of the first range. */
1956 no_overlap = tree_int_cst_lt (high, cond_low);
1957 subset = tree_int_cst_compare (cond_high, high) != 1;
1959 /* If there was no overlap in the ranges, then this conditional
1960 always has a false value (unless we had to invert this
1961 conditional, in which case it always has a true value). */
1963 return (cond_inverted ? boolean_true_node : boolean_false_node);
1965 /* If the current range is a subset of the condition's range,
1966 then this conditional always has a true value (unless we
1967 had to invert this conditional, in which case it always
1968 has a true value). */
1969 if (subset && swapped)
1970 return (cond_inverted ? boolean_false_node : boolean_true_node);
1972 /* We were unable to determine the result of the conditional.
1973 However, we may be able to simplify the conditional. First
1974 merge the ranges in the same manner as range merging above. */
1975 low = tree_int_cst_compare (low, cond_low) == 1 ? low : cond_low;
1976 high = tree_int_cst_compare (high, cond_high) == -1 ? high : cond_high;
1978 /* If the range has converged to a single point, then turn this
1979 into an equality comparison. */
1980 if (TREE_CODE (cond) != EQ_EXPR
1981 && TREE_CODE (cond) != NE_EXPR
1982 && tree_int_cst_equal (low, high))
1984 TREE_SET_CODE (cond, EQ_EXPR);
1985 TREE_OPERAND (cond, 1) = high;
1992 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
1993 known value for that SSA_NAME (or NULL if no value is known).
1995 NONZERO_VARS is the set SSA_NAMES known to have a nonzero value,
1996 even if we don't know their precise value.
1998 Propagate values from CONST_AND_COPIES and NONZERO_VARS into the PHI
1999 nodes of the successors of BB. */
2002 cprop_into_successor_phis (basic_block bb, bitmap nonzero_vars)
2007 FOR_EACH_EDGE (e, ei, bb->succs)
2012 /* If this is an abnormal edge, then we do not want to copy propagate
2013 into the PHI alternative associated with this edge. */
2014 if (e->flags & EDGE_ABNORMAL)
2017 phi = phi_nodes (e->dest);
2022 for ( ; phi; phi = PHI_CHAIN (phi))
2025 use_operand_p orig_p;
2028 /* The alternative may be associated with a constant, so verify
2029 it is an SSA_NAME before doing anything with it. */
2030 orig_p = PHI_ARG_DEF_PTR (phi, indx);
2031 orig = USE_FROM_PTR (orig_p);
2032 if (TREE_CODE (orig) != SSA_NAME)
2035 /* If the alternative is known to have a nonzero value, record
2036 that fact in the PHI node itself for future use. */
2037 if (bitmap_bit_p (nonzero_vars, SSA_NAME_VERSION (orig)))
2038 PHI_ARG_NONZERO (phi, indx) = true;
2040 /* If we have *ORIG_P in our constant/copy table, then replace
2041 ORIG_P with its value in our constant/copy table. */
2042 new = SSA_NAME_VALUE (orig);
2045 && (TREE_CODE (new) == SSA_NAME
2046 || is_gimple_min_invariant (new))
2047 && may_propagate_copy (orig, new))
2048 propagate_value (orig_p, new);
2053 /* We have finished optimizing BB, record any information implied by
2054 taking a specific outgoing edge from BB. */
2057 record_edge_info (basic_block bb)
2059 block_stmt_iterator bsi = bsi_last (bb);
2060 struct edge_info *edge_info;
2062 if (! bsi_end_p (bsi))
2064 tree stmt = bsi_stmt (bsi);
2066 if (stmt && TREE_CODE (stmt) == SWITCH_EXPR)
2068 tree cond = SWITCH_COND (stmt);
2070 if (TREE_CODE (cond) == SSA_NAME)
2072 tree labels = SWITCH_LABELS (stmt);
2073 int i, n_labels = TREE_VEC_LENGTH (labels);
2074 tree *info = XCNEWVEC (tree, last_basic_block);
2078 for (i = 0; i < n_labels; i++)
2080 tree label = TREE_VEC_ELT (labels, i);
2081 basic_block target_bb = label_to_block (CASE_LABEL (label));
2083 if (CASE_HIGH (label)
2084 || !CASE_LOW (label)
2085 || info[target_bb->index])
2086 info[target_bb->index] = error_mark_node;
2088 info[target_bb->index] = label;
2091 FOR_EACH_EDGE (e, ei, bb->succs)
2093 basic_block target_bb = e->dest;
2094 tree node = info[target_bb->index];
2096 if (node != NULL && node != error_mark_node)
2098 tree x = fold_convert (TREE_TYPE (cond), CASE_LOW (node));
2099 edge_info = allocate_edge_info (e);
2100 edge_info->lhs = cond;
2108 /* A COND_EXPR may create equivalences too. */
2109 if (stmt && TREE_CODE (stmt) == COND_EXPR)
2111 tree cond = COND_EXPR_COND (stmt);
2115 extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
2117 /* If the conditional is a single variable 'X', record 'X = 1'
2118 for the true edge and 'X = 0' on the false edge. */
2119 if (SSA_VAR_P (cond))
2121 struct edge_info *edge_info;
2123 edge_info = allocate_edge_info (true_edge);
2124 edge_info->lhs = cond;
2125 edge_info->rhs = constant_boolean_node (1, TREE_TYPE (cond));
2127 edge_info = allocate_edge_info (false_edge);
2128 edge_info->lhs = cond;
2129 edge_info->rhs = constant_boolean_node (0, TREE_TYPE (cond));
2131 /* Equality tests may create one or two equivalences. */
2132 else if (COMPARISON_CLASS_P (cond))
2134 tree op0 = TREE_OPERAND (cond, 0);
2135 tree op1 = TREE_OPERAND (cond, 1);
2137 /* Special case comparing booleans against a constant as we
2138 know the value of OP0 on both arms of the branch. i.e., we
2139 can record an equivalence for OP0 rather than COND. */
2140 if ((TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
2141 && TREE_CODE (op0) == SSA_NAME
2142 && TREE_CODE (TREE_TYPE (op0)) == BOOLEAN_TYPE
2143 && is_gimple_min_invariant (op1))
2145 if (TREE_CODE (cond) == EQ_EXPR)
2147 edge_info = allocate_edge_info (true_edge);
2148 edge_info->lhs = op0;
2149 edge_info->rhs = (integer_zerop (op1)
2150 ? boolean_false_node
2151 : boolean_true_node);
2153 edge_info = allocate_edge_info (false_edge);
2154 edge_info->lhs = op0;
2155 edge_info->rhs = (integer_zerop (op1)
2157 : boolean_false_node);
2161 edge_info = allocate_edge_info (true_edge);
2162 edge_info->lhs = op0;
2163 edge_info->rhs = (integer_zerop (op1)
2165 : boolean_false_node);
2167 edge_info = allocate_edge_info (false_edge);
2168 edge_info->lhs = op0;
2169 edge_info->rhs = (integer_zerop (op1)
2170 ? boolean_false_node
2171 : boolean_true_node);
2175 else if (is_gimple_min_invariant (op0)
2176 && (TREE_CODE (op1) == SSA_NAME
2177 || is_gimple_min_invariant (op1)))
2179 tree inverted = invert_truthvalue (cond);
2180 struct edge_info *edge_info;
2182 edge_info = allocate_edge_info (true_edge);
2183 record_conditions (edge_info, cond, inverted);
2185 if (TREE_CODE (cond) == EQ_EXPR)
2187 edge_info->lhs = op1;
2188 edge_info->rhs = op0;
2191 edge_info = allocate_edge_info (false_edge);
2192 record_conditions (edge_info, inverted, cond);
2194 if (TREE_CODE (cond) == NE_EXPR)
2196 edge_info->lhs = op1;
2197 edge_info->rhs = op0;
2201 else if (TREE_CODE (op0) == SSA_NAME
2202 && (is_gimple_min_invariant (op1)
2203 || TREE_CODE (op1) == SSA_NAME))
2205 tree inverted = invert_truthvalue (cond);
2206 struct edge_info *edge_info;
2208 edge_info = allocate_edge_info (true_edge);
2209 record_conditions (edge_info, cond, inverted);
2211 if (TREE_CODE (cond) == EQ_EXPR)
2213 edge_info->lhs = op0;
2214 edge_info->rhs = op1;
2217 edge_info = allocate_edge_info (false_edge);
2218 record_conditions (edge_info, inverted, cond);
2220 if (TREE_CODE (cond) == NE_EXPR)
2222 edge_info->lhs = op0;
2223 edge_info->rhs = op1;
2228 /* ??? TRUTH_NOT_EXPR can create an equivalence too. */
2233 /* Propagate information from BB to its outgoing edges.
2235 This can include equivalency information implied by control statements
2236 at the end of BB and const/copy propagation into PHIs in BB's
2237 successor blocks. */
2240 propagate_to_outgoing_edges (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
2243 record_edge_info (bb);
2244 cprop_into_successor_phis (bb, nonzero_vars);
2247 /* Search for redundant computations in STMT. If any are found, then
2248 replace them with the variable holding the result of the computation.
2250 If safe, record this expression into the available expression hash
2254 eliminate_redundant_computations (tree stmt)
2256 tree *expr_p, def = NULL_TREE;
2259 bool retval = false;
2260 bool modify_expr_p = false;
2262 if (TREE_CODE (stmt) == MODIFY_EXPR)
2263 def = TREE_OPERAND (stmt, 0);
2265 /* Certain expressions on the RHS can be optimized away, but can not
2266 themselves be entered into the hash tables. */
2268 || TREE_CODE (def) != SSA_NAME
2269 || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def)
2270 || !ZERO_SSA_OPERANDS (stmt, SSA_OP_VMAYDEF)
2271 /* Do not record equivalences for increments of ivs. This would create
2272 overlapping live ranges for a very questionable gain. */
2273 || simple_iv_increment_p (stmt))
2276 /* Check if the expression has been computed before. */
2277 cached_lhs = lookup_avail_expr (stmt, insert);
2279 /* If this is a COND_EXPR and we did not find its expression in
2280 the hash table, simplify the condition and try again. */
2281 if (! cached_lhs && TREE_CODE (stmt) == COND_EXPR)
2282 cached_lhs = simplify_cond_and_lookup_avail_expr (stmt);
2284 opt_stats.num_exprs_considered++;
2286 /* Get a pointer to the expression we are trying to optimize. */
2287 if (TREE_CODE (stmt) == COND_EXPR)
2288 expr_p = &COND_EXPR_COND (stmt);
2289 else if (TREE_CODE (stmt) == SWITCH_EXPR)
2290 expr_p = &SWITCH_COND (stmt);
2291 else if (TREE_CODE (stmt) == RETURN_EXPR && TREE_OPERAND (stmt, 0))
2293 expr_p = &TREE_OPERAND (TREE_OPERAND (stmt, 0), 1);
2294 modify_expr_p = true;
2298 expr_p = &TREE_OPERAND (stmt, 1);
2299 modify_expr_p = true;
2302 /* It is safe to ignore types here since we have already done
2303 type checking in the hashing and equality routines. In fact
2304 type checking here merely gets in the way of constant
2305 propagation. Also, make sure that it is safe to propagate
2306 CACHED_LHS into *EXPR_P. */
2308 && ((TREE_CODE (cached_lhs) != SSA_NAME
2310 || tree_ssa_useless_type_conversion_1 (TREE_TYPE (*expr_p),
2311 TREE_TYPE (cached_lhs))))
2312 || may_propagate_copy (*expr_p, cached_lhs)))
2314 if (dump_file && (dump_flags & TDF_DETAILS))
2316 fprintf (dump_file, " Replaced redundant expr '");
2317 print_generic_expr (dump_file, *expr_p, dump_flags);
2318 fprintf (dump_file, "' with '");
2319 print_generic_expr (dump_file, cached_lhs, dump_flags);
2320 fprintf (dump_file, "'\n");
2325 #if defined ENABLE_CHECKING
2326 gcc_assert (TREE_CODE (cached_lhs) == SSA_NAME
2327 || is_gimple_min_invariant (cached_lhs));
2330 if (TREE_CODE (cached_lhs) == ADDR_EXPR
2331 || (POINTER_TYPE_P (TREE_TYPE (*expr_p))
2332 && is_gimple_min_invariant (cached_lhs)))
2336 && !tree_ssa_useless_type_conversion_1 (TREE_TYPE (*expr_p),
2337 TREE_TYPE (cached_lhs)))
2338 cached_lhs = fold_convert (TREE_TYPE (*expr_p), cached_lhs);
2340 propagate_tree_value (expr_p, cached_lhs);
2341 mark_stmt_modified (stmt);
2346 /* STMT, a MODIFY_EXPR, may create certain equivalences, in either
2347 the available expressions table or the const_and_copies table.
2348 Detect and record those equivalences. */
2351 record_equivalences_from_stmt (tree stmt,
2355 tree lhs = TREE_OPERAND (stmt, 0);
2356 enum tree_code lhs_code = TREE_CODE (lhs);
2359 if (lhs_code == SSA_NAME)
2361 tree rhs = TREE_OPERAND (stmt, 1);
2363 /* Strip away any useless type conversions. */
2364 STRIP_USELESS_TYPE_CONVERSION (rhs);
2366 /* If the RHS of the assignment is a constant or another variable that
2367 may be propagated, register it in the CONST_AND_COPIES table. We
2368 do not need to record unwind data for this, since this is a true
2369 assignment and not an equivalence inferred from a comparison. All
2370 uses of this ssa name are dominated by this assignment, so unwinding
2371 just costs time and space. */
2373 && (TREE_CODE (rhs) == SSA_NAME
2374 || is_gimple_min_invariant (rhs)))
2375 SSA_NAME_VALUE (lhs) = rhs;
2377 if (tree_expr_nonzero_p (rhs))
2378 record_var_is_nonzero (lhs);
2381 /* Look at both sides for pointer dereferences. If we find one, then
2382 the pointer must be nonnull and we can enter that equivalence into
2384 if (flag_delete_null_pointer_checks)
2385 for (i = 0; i < 2; i++)
2387 tree t = TREE_OPERAND (stmt, i);
2389 /* Strip away any COMPONENT_REFs. */
2390 while (TREE_CODE (t) == COMPONENT_REF)
2391 t = TREE_OPERAND (t, 0);
2393 /* Now see if this is a pointer dereference. */
2394 if (INDIRECT_REF_P (t))
2396 tree op = TREE_OPERAND (t, 0);
2398 /* If the pointer is a SSA variable, then enter new
2399 equivalences into the hash table. */
2400 while (TREE_CODE (op) == SSA_NAME)
2402 tree def = SSA_NAME_DEF_STMT (op);
2404 record_var_is_nonzero (op);
2406 /* And walk up the USE-DEF chains noting other SSA_NAMEs
2407 which are known to have a nonzero value. */
2409 && TREE_CODE (def) == MODIFY_EXPR
2410 && TREE_CODE (TREE_OPERAND (def, 1)) == NOP_EXPR)
2411 op = TREE_OPERAND (TREE_OPERAND (def, 1), 0);
2418 /* A memory store, even an aliased store, creates a useful
2419 equivalence. By exchanging the LHS and RHS, creating suitable
2420 vops and recording the result in the available expression table,
2421 we may be able to expose more redundant loads. */
2422 if (!ann->has_volatile_ops
2423 && (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME
2424 || is_gimple_min_invariant (TREE_OPERAND (stmt, 1)))
2425 && !is_gimple_reg (lhs))
2427 tree rhs = TREE_OPERAND (stmt, 1);
2430 /* FIXME: If the LHS of the assignment is a bitfield and the RHS
2431 is a constant, we need to adjust the constant to fit into the
2432 type of the LHS. If the LHS is a bitfield and the RHS is not
2433 a constant, then we can not record any equivalences for this
2434 statement since we would need to represent the widening or
2435 narrowing of RHS. This fixes gcc.c-torture/execute/921016-1.c
2436 and should not be necessary if GCC represented bitfields
2438 if (lhs_code == COMPONENT_REF
2439 && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1)))
2441 if (TREE_CONSTANT (rhs))
2442 rhs = widen_bitfield (rhs, TREE_OPERAND (lhs, 1), lhs);
2446 /* If the value overflowed, then we can not use this equivalence. */
2447 if (rhs && ! is_gimple_min_invariant (rhs))
2453 /* Build a new statement with the RHS and LHS exchanged. */
2454 new = build2 (MODIFY_EXPR, TREE_TYPE (stmt), rhs, lhs);
2456 create_ssa_artficial_load_stmt (new, stmt);
2458 /* Finally enter the statement into the available expression
2460 lookup_avail_expr (new, true);
2465 /* Replace *OP_P in STMT with any known equivalent value for *OP_P from
2466 CONST_AND_COPIES. */
2469 cprop_operand (tree stmt, use_operand_p op_p)
2471 bool may_have_exposed_new_symbols = false;
2473 tree op = USE_FROM_PTR (op_p);
2475 /* If the operand has a known constant value or it is known to be a
2476 copy of some other variable, use the value or copy stored in
2477 CONST_AND_COPIES. */
2478 val = SSA_NAME_VALUE (op);
2479 if (val && val != op && TREE_CODE (val) != VALUE_HANDLE)
2481 tree op_type, val_type;
2483 /* Do not change the base variable in the virtual operand
2484 tables. That would make it impossible to reconstruct
2485 the renamed virtual operand if we later modify this
2486 statement. Also only allow the new value to be an SSA_NAME
2487 for propagation into virtual operands. */
2488 if (!is_gimple_reg (op)
2489 && (TREE_CODE (val) != SSA_NAME
2490 || is_gimple_reg (val)
2491 || get_virtual_var (val) != get_virtual_var (op)))
2494 /* Do not replace hard register operands in asm statements. */
2495 if (TREE_CODE (stmt) == ASM_EXPR
2496 && !may_propagate_copy_into_asm (op))
2499 /* Get the toplevel type of each operand. */
2500 op_type = TREE_TYPE (op);
2501 val_type = TREE_TYPE (val);
2503 /* While both types are pointers, get the type of the object
2505 while (POINTER_TYPE_P (op_type) && POINTER_TYPE_P (val_type))
2507 op_type = TREE_TYPE (op_type);
2508 val_type = TREE_TYPE (val_type);
2511 /* Make sure underlying types match before propagating a constant by
2512 converting the constant to the proper type. Note that convert may
2513 return a non-gimple expression, in which case we ignore this
2514 propagation opportunity. */
2515 if (TREE_CODE (val) != SSA_NAME)
2517 if (!lang_hooks.types_compatible_p (op_type, val_type))
2519 val = fold_convert (TREE_TYPE (op), val);
2520 if (!is_gimple_min_invariant (val))
2525 /* Certain operands are not allowed to be copy propagated due
2526 to their interaction with exception handling and some GCC
2528 else if (!may_propagate_copy (op, val))
2531 /* Do not propagate copies if the propagated value is at a deeper loop
2532 depth than the propagatee. Otherwise, this may move loop variant
2533 variables outside of their loops and prevent coalescing
2534 opportunities. If the value was loop invariant, it will be hoisted
2535 by LICM and exposed for copy propagation. */
2536 if (loop_depth_of_name (val) > loop_depth_of_name (op))
2540 if (dump_file && (dump_flags & TDF_DETAILS))
2542 fprintf (dump_file, " Replaced '");
2543 print_generic_expr (dump_file, op, dump_flags);
2544 fprintf (dump_file, "' with %s '",
2545 (TREE_CODE (val) != SSA_NAME ? "constant" : "variable"));
2546 print_generic_expr (dump_file, val, dump_flags);
2547 fprintf (dump_file, "'\n");
2550 /* If VAL is an ADDR_EXPR or a constant of pointer type, note
2551 that we may have exposed a new symbol for SSA renaming. */
2552 if (TREE_CODE (val) == ADDR_EXPR
2553 || (POINTER_TYPE_P (TREE_TYPE (op))
2554 && is_gimple_min_invariant (val)))
2555 may_have_exposed_new_symbols = true;
2557 if (TREE_CODE (val) != SSA_NAME)
2558 opt_stats.num_const_prop++;
2560 opt_stats.num_copy_prop++;
2562 propagate_value (op_p, val);
2564 /* And note that we modified this statement. This is now
2565 safe, even if we changed virtual operands since we will
2566 rescan the statement and rewrite its operands again. */
2567 mark_stmt_modified (stmt);
2569 return may_have_exposed_new_symbols;
2572 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2573 known value for that SSA_NAME (or NULL if no value is known).
2575 Propagate values from CONST_AND_COPIES into the uses, vuses and
2576 v_may_def_ops of STMT. */
2579 cprop_into_stmt (tree stmt)
2581 bool may_have_exposed_new_symbols = false;
2585 FOR_EACH_SSA_USE_OPERAND (op_p, stmt, iter, SSA_OP_ALL_USES)
2587 if (TREE_CODE (USE_FROM_PTR (op_p)) == SSA_NAME)
2588 may_have_exposed_new_symbols |= cprop_operand (stmt, op_p);
2591 return may_have_exposed_new_symbols;
2595 /* Optimize the statement pointed to by iterator SI.
2597 We try to perform some simplistic global redundancy elimination and
2598 constant propagation:
2600 1- To detect global redundancy, we keep track of expressions that have
2601 been computed in this block and its dominators. If we find that the
2602 same expression is computed more than once, we eliminate repeated
2603 computations by using the target of the first one.
2605 2- Constant values and copy assignments. This is used to do very
2606 simplistic constant and copy propagation. When a constant or copy
2607 assignment is found, we map the value on the RHS of the assignment to
2608 the variable in the LHS in the CONST_AND_COPIES table. */
2611 optimize_stmt (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
2612 basic_block bb, block_stmt_iterator si)
2615 tree stmt, old_stmt;
2616 bool may_optimize_p;
2617 bool may_have_exposed_new_symbols = false;
2619 old_stmt = stmt = bsi_stmt (si);
2621 if (TREE_CODE (stmt) == COND_EXPR)
2622 canonicalize_comparison (stmt);
2624 update_stmt_if_modified (stmt);
2625 ann = stmt_ann (stmt);
2626 opt_stats.num_stmts++;
2627 may_have_exposed_new_symbols = false;
2629 if (dump_file && (dump_flags & TDF_DETAILS))
2631 fprintf (dump_file, "Optimizing statement ");
2632 print_generic_stmt (dump_file, stmt, TDF_SLIM);
2635 /* Const/copy propagate into USES, VUSES and the RHS of V_MAY_DEFs. */
2636 may_have_exposed_new_symbols = cprop_into_stmt (stmt);
2638 /* If the statement has been modified with constant replacements,
2639 fold its RHS before checking for redundant computations. */
2644 /* Try to fold the statement making sure that STMT is kept
2646 if (fold_stmt (bsi_stmt_ptr (si)))
2648 stmt = bsi_stmt (si);
2649 ann = stmt_ann (stmt);
2651 if (dump_file && (dump_flags & TDF_DETAILS))
2653 fprintf (dump_file, " Folded to: ");
2654 print_generic_stmt (dump_file, stmt, TDF_SLIM);
2658 rhs = get_rhs (stmt);
2659 if (rhs && TREE_CODE (rhs) == ADDR_EXPR)
2660 recompute_tree_invariant_for_addr_expr (rhs);
2662 /* Constant/copy propagation above may change the set of
2663 virtual operands associated with this statement. Folding
2664 may remove the need for some virtual operands.
2666 Indicate we will need to rescan and rewrite the statement. */
2667 may_have_exposed_new_symbols = true;
2670 /* Check for redundant computations. Do this optimization only
2671 for assignments that have no volatile ops and conditionals. */
2672 may_optimize_p = (!ann->has_volatile_ops
2673 && ((TREE_CODE (stmt) == RETURN_EXPR
2674 && TREE_OPERAND (stmt, 0)
2675 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR
2676 && ! (TREE_SIDE_EFFECTS
2677 (TREE_OPERAND (TREE_OPERAND (stmt, 0), 1))))
2678 || (TREE_CODE (stmt) == MODIFY_EXPR
2679 && ! TREE_SIDE_EFFECTS (TREE_OPERAND (stmt, 1)))
2680 || TREE_CODE (stmt) == COND_EXPR
2681 || TREE_CODE (stmt) == SWITCH_EXPR));
2684 may_have_exposed_new_symbols |= eliminate_redundant_computations (stmt);
2686 /* Record any additional equivalences created by this statement. */
2687 if (TREE_CODE (stmt) == MODIFY_EXPR)
2688 record_equivalences_from_stmt (stmt,
2692 /* If STMT is a COND_EXPR and it was modified, then we may know
2693 where it goes. If that is the case, then mark the CFG as altered.
2695 This will cause us to later call remove_unreachable_blocks and
2696 cleanup_tree_cfg when it is safe to do so. It is not safe to
2697 clean things up here since removal of edges and such can trigger
2698 the removal of PHI nodes, which in turn can release SSA_NAMEs to
2701 That's all fine and good, except that once SSA_NAMEs are released
2702 to the manager, we must not call create_ssa_name until all references
2703 to released SSA_NAMEs have been eliminated.
2705 All references to the deleted SSA_NAMEs can not be eliminated until
2706 we remove unreachable blocks.
2708 We can not remove unreachable blocks until after we have completed
2709 any queued jump threading.
2711 We can not complete any queued jump threads until we have taken
2712 appropriate variables out of SSA form. Taking variables out of
2713 SSA form can call create_ssa_name and thus we lose.
2715 Ultimately I suspect we're going to need to change the interface
2716 into the SSA_NAME manager. */
2722 if (TREE_CODE (stmt) == COND_EXPR)
2723 val = COND_EXPR_COND (stmt);
2724 else if (TREE_CODE (stmt) == SWITCH_EXPR)
2725 val = SWITCH_COND (stmt);
2727 if (val && TREE_CODE (val) == INTEGER_CST && find_taken_edge (bb, val))
2730 /* If we simplified a statement in such a way as to be shown that it
2731 cannot trap, update the eh information and the cfg to match. */
2732 if (maybe_clean_or_replace_eh_stmt (old_stmt, stmt))
2734 bitmap_set_bit (need_eh_cleanup, bb->index);
2735 if (dump_file && (dump_flags & TDF_DETAILS))
2736 fprintf (dump_file, " Flagged to clear EH edges.\n");
2740 if (may_have_exposed_new_symbols)
2741 VEC_safe_push (tree, heap, stmts_to_rescan, bsi_stmt (si));
2744 /* Search for an existing instance of STMT in the AVAIL_EXPRS table. If
2745 found, return its LHS. Otherwise insert STMT in the table and return
2748 Also, when an expression is first inserted in the AVAIL_EXPRS table, it
2749 is also added to the stack pointed to by BLOCK_AVAIL_EXPRS_P, so that they
2750 can be removed when we finish processing this block and its children.
2752 NOTE: This function assumes that STMT is a MODIFY_EXPR node that
2753 contains no CALL_EXPR on its RHS and makes no volatile nor
2754 aliased references. */
2757 lookup_avail_expr (tree stmt, bool insert)
2762 struct expr_hash_elt *element = XNEW (struct expr_hash_elt);
2764 lhs = TREE_CODE (stmt) == MODIFY_EXPR ? TREE_OPERAND (stmt, 0) : NULL;
2766 initialize_hash_element (stmt, lhs, element);
2768 /* Don't bother remembering constant assignments and copy operations.
2769 Constants and copy operations are handled by the constant/copy propagator
2770 in optimize_stmt. */
2771 if (TREE_CODE (element->rhs) == SSA_NAME
2772 || is_gimple_min_invariant (element->rhs))
2778 /* If this is an equality test against zero, see if we have recorded a
2779 nonzero value for the variable in question. */
2780 if ((TREE_CODE (element->rhs) == EQ_EXPR
2781 || TREE_CODE (element->rhs) == NE_EXPR)
2782 && TREE_CODE (TREE_OPERAND (element->rhs, 0)) == SSA_NAME
2783 && integer_zerop (TREE_OPERAND (element->rhs, 1)))
2785 int indx = SSA_NAME_VERSION (TREE_OPERAND (element->rhs, 0));
2787 if (bitmap_bit_p (nonzero_vars, indx))
2789 tree t = element->rhs;
2791 return constant_boolean_node (TREE_CODE (t) != EQ_EXPR,
2796 /* Finally try to find the expression in the main expression hash table. */
2797 slot = htab_find_slot_with_hash (avail_exprs, element, element->hash,
2798 (insert ? INSERT : NO_INSERT));
2807 *slot = (void *) element;
2808 VEC_safe_push (tree, heap, avail_exprs_stack,
2809 stmt ? stmt : element->rhs);
2813 /* Extract the LHS of the assignment so that it can be used as the current
2814 definition of another variable. */
2815 lhs = ((struct expr_hash_elt *)*slot)->lhs;
2817 /* See if the LHS appears in the CONST_AND_COPIES table. If it does, then
2818 use the value from the const_and_copies table. */
2819 if (TREE_CODE (lhs) == SSA_NAME)
2821 temp = SSA_NAME_VALUE (lhs);
2822 if (temp && TREE_CODE (temp) != VALUE_HANDLE)
2830 /* Given a condition COND, record into HI_P, LO_P and INVERTED_P the
2831 range of values that result in the conditional having a true value.
2833 Return true if we are successful in extracting a range from COND and
2834 false if we are unsuccessful. */
2837 extract_range_from_cond (tree cond, tree *hi_p, tree *lo_p, int *inverted_p)
2839 tree op1 = TREE_OPERAND (cond, 1);
2840 tree high, low, type;
2843 type = TREE_TYPE (op1);
2845 /* Experiments have shown that it's rarely, if ever useful to
2846 record ranges for enumerations. Presumably this is due to
2847 the fact that they're rarely used directly. They are typically
2848 cast into an integer type and used that way. */
2849 if (TREE_CODE (type) != INTEGER_TYPE)
2852 switch (TREE_CODE (cond))
2867 /* Get the highest value of the type. If not a constant, use that
2868 of its base type, if it has one. */
2869 high = TYPE_MAX_VALUE (type);
2870 if (TREE_CODE (high) != INTEGER_CST && TREE_TYPE (type))
2871 high = TYPE_MAX_VALUE (TREE_TYPE (type));
2876 high = TYPE_MAX_VALUE (type);
2877 if (TREE_CODE (high) != INTEGER_CST && TREE_TYPE (type))
2878 high = TYPE_MAX_VALUE (TREE_TYPE (type));
2879 if (!tree_int_cst_lt (op1, high))
2881 low = int_const_binop (PLUS_EXPR, op1, integer_one_node, 1);
2887 low = TYPE_MIN_VALUE (type);
2888 if (TREE_CODE (low) != INTEGER_CST && TREE_TYPE (type))
2889 low = TYPE_MIN_VALUE (TREE_TYPE (type));
2894 low = TYPE_MIN_VALUE (type);
2895 if (TREE_CODE (low) != INTEGER_CST && TREE_TYPE (type))
2896 low = TYPE_MIN_VALUE (TREE_TYPE (type));
2897 if (!tree_int_cst_lt (low, op1))
2899 high = int_const_binop (MINUS_EXPR, op1, integer_one_node, 1);
2909 *inverted_p = inverted;
2913 /* Record a range created by COND for basic block BB. */
2916 record_range (tree cond, basic_block bb)
2918 enum tree_code code = TREE_CODE (cond);
2920 /* We explicitly ignore NE_EXPRs and all the unordered comparisons.
2921 They rarely allow for meaningful range optimizations and significantly
2922 complicate the implementation. */
2923 if ((code == LT_EXPR || code == LE_EXPR || code == GT_EXPR
2924 || code == GE_EXPR || code == EQ_EXPR)
2925 && TREE_CODE (TREE_TYPE (TREE_OPERAND (cond, 1))) == INTEGER_TYPE)
2927 struct vrp_hash_elt *vrp_hash_elt;
2928 struct vrp_element *element;
2929 VEC(vrp_element_p,heap) **vrp_records_p;
2933 vrp_hash_elt = XNEW (struct vrp_hash_elt);
2934 vrp_hash_elt->var = TREE_OPERAND (cond, 0);
2935 vrp_hash_elt->records = NULL;
2936 slot = htab_find_slot (vrp_data, vrp_hash_elt, INSERT);
2939 *slot = (void *) vrp_hash_elt;
2941 vrp_free (vrp_hash_elt);
2943 vrp_hash_elt = (struct vrp_hash_elt *) *slot;
2944 vrp_records_p = &vrp_hash_elt->records;
2946 element = GGC_NEW (struct vrp_element);
2947 element->low = NULL;
2948 element->high = NULL;
2949 element->cond = cond;
2952 VEC_safe_push (vrp_element_p, heap, *vrp_records_p, element);
2953 VEC_safe_push (tree, heap, vrp_variables_stack, TREE_OPERAND (cond, 0));
2957 /* Hashing and equality functions for VRP_DATA.
2959 Since this hash table is addressed by SSA_NAMEs, we can hash on
2960 their version number and equality can be determined with a
2961 pointer comparison. */
2964 vrp_hash (const void *p)
2966 tree var = ((struct vrp_hash_elt *)p)->var;
2968 return SSA_NAME_VERSION (var);
2972 vrp_eq (const void *p1, const void *p2)
2974 tree var1 = ((struct vrp_hash_elt *)p1)->var;
2975 tree var2 = ((struct vrp_hash_elt *)p2)->var;
2977 return var1 == var2;
2980 /* Hashing and equality functions for AVAIL_EXPRS. The table stores
2981 MODIFY_EXPR statements. We compute a value number for expressions using
2982 the code of the expression and the SSA numbers of its operands. */
2985 avail_expr_hash (const void *p)
2987 tree stmt = ((struct expr_hash_elt *)p)->stmt;
2988 tree rhs = ((struct expr_hash_elt *)p)->rhs;
2993 /* iterative_hash_expr knows how to deal with any expression and
2994 deals with commutative operators as well, so just use it instead
2995 of duplicating such complexities here. */
2996 val = iterative_hash_expr (rhs, val);
2998 /* If the hash table entry is not associated with a statement, then we
2999 can just hash the expression and not worry about virtual operands
3001 if (!stmt || !stmt_ann (stmt))
3004 /* Add the SSA version numbers of every vuse operand. This is important
3005 because compound variables like arrays are not renamed in the
3006 operands. Rather, the rename is done on the virtual variable
3007 representing all the elements of the array. */
3008 FOR_EACH_SSA_TREE_OPERAND (vuse, stmt, iter, SSA_OP_VUSE)
3009 val = iterative_hash_expr (vuse, val);
3015 real_avail_expr_hash (const void *p)
3017 return ((const struct expr_hash_elt *)p)->hash;
3021 avail_expr_eq (const void *p1, const void *p2)
3023 tree stmt1 = ((struct expr_hash_elt *)p1)->stmt;
3024 tree rhs1 = ((struct expr_hash_elt *)p1)->rhs;
3025 tree stmt2 = ((struct expr_hash_elt *)p2)->stmt;
3026 tree rhs2 = ((struct expr_hash_elt *)p2)->rhs;
3028 /* If they are the same physical expression, return true. */
3029 if (rhs1 == rhs2 && stmt1 == stmt2)
3032 /* If their codes are not equal, then quit now. */
3033 if (TREE_CODE (rhs1) != TREE_CODE (rhs2))
3036 /* In case of a collision, both RHS have to be identical and have the
3037 same VUSE operands. */
3038 if ((TREE_TYPE (rhs1) == TREE_TYPE (rhs2)
3039 || lang_hooks.types_compatible_p (TREE_TYPE (rhs1), TREE_TYPE (rhs2)))
3040 && operand_equal_p (rhs1, rhs2, OEP_PURE_SAME))
3042 bool ret = compare_ssa_operands_equal (stmt1, stmt2, SSA_OP_VUSE);
3043 gcc_assert (!ret || ((struct expr_hash_elt *)p1)->hash
3044 == ((struct expr_hash_elt *)p2)->hash);