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"
37 #include "diagnostic.h"
39 #include "tree-dump.h"
40 #include "tree-flow.h"
43 #include "tree-pass.h"
44 #include "tree-ssa-propagate.h"
45 #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 /* Stack of SSA_NAMEs which need their NONZERO_VARS property cleared
145 when the current block is finalized.
147 A NULL entry is used to mark the end of names needing their
148 entry in NONZERO_VARS cleared during finalization of this block. */
149 static VEC(tree,heap) *nonzero_vars_stack;
151 /* Track whether or not we have changed the control flow graph. */
152 static bool cfg_altered;
154 /* Bitmap of blocks that have had EH statements cleaned. We should
155 remove their dead edges eventually. */
156 static bitmap need_eh_cleanup;
158 /* Statistics for dominator optimizations. */
162 long num_exprs_considered;
168 static struct opt_stats_d opt_stats;
170 /* Value range propagation record. Each time we encounter a conditional
171 of the form SSA_NAME COND CONST we create a new vrp_element to record
172 how the condition affects the possible values SSA_NAME may have.
174 Each record contains the condition tested (COND), and the range of
175 values the variable may legitimately have if COND is true. Note the
176 range of values may be a smaller range than COND specifies if we have
177 recorded other ranges for this variable. Each record also contains the
178 block in which the range was recorded for invalidation purposes.
180 Note that the current known range is computed lazily. This allows us
181 to avoid the overhead of computing ranges which are never queried.
183 When we encounter a conditional, we look for records which constrain
184 the SSA_NAME used in the condition. In some cases those records allow
185 us to determine the condition's result at compile time. In other cases
186 they may allow us to simplify the condition.
188 We also use value ranges to do things like transform signed div/mod
189 operations into unsigned div/mod or to simplify ABS_EXPRs.
191 Simple experiments have shown these optimizations to not be all that
192 useful on switch statements (much to my surprise). So switch statement
193 optimizations are not performed.
195 Note carefully we do not propagate information through each statement
196 in the block. i.e., if we know variable X has a value defined of
197 [0, 25] and we encounter Y = X + 1, we do not track a value range
198 for Y (which would be [1, 26] if we cared). Similarly we do not
199 constrain values as we encounter narrowing typecasts, etc. */
203 /* The highest and lowest values the variable in COND may contain when
204 COND is true. Note this may not necessarily be the same values
205 tested by COND if the same variable was used in earlier conditionals.
207 Note this is computed lazily and thus can be NULL indicating that
208 the values have not been computed yet. */
212 /* The actual conditional we recorded. This is needed since we compute
216 /* The basic block where this record was created. We use this to determine
217 when to remove records. */
221 /* A hash table holding value range records (VRP_ELEMENTs) for a given
222 SSA_NAME. We used to use a varray indexed by SSA_NAME_VERSION, but
223 that gets awful wasteful, particularly since the density objects
224 with useful information is very low. */
225 static htab_t vrp_data;
227 /* An entry in the VRP_DATA hash table. We record the variable and a
228 varray of VRP_ELEMENT records associated with that variable. */
235 /* Array of variables which have their values constrained by operations
236 in this basic block. We use this during finalization to know
237 which variables need their VRP data updated. */
239 /* Stack of SSA_NAMEs which had their values constrained by operations
240 in this basic block. During finalization of this block we use this
241 list to determine which variables need their VRP data updated.
243 A NULL entry marks the end of the SSA_NAMEs associated with this block. */
244 static VEC(tree,heap) *vrp_variables_stack;
252 /* Local functions. */
253 static void optimize_stmt (struct dom_walk_data *,
255 block_stmt_iterator);
256 static tree lookup_avail_expr (tree, bool);
257 static hashval_t vrp_hash (const void *);
258 static int vrp_eq (const void *, const void *);
259 static hashval_t avail_expr_hash (const void *);
260 static hashval_t real_avail_expr_hash (const void *);
261 static int avail_expr_eq (const void *, const void *);
262 static void htab_statistics (FILE *, htab_t);
263 static void record_cond (tree, tree);
264 static void record_const_or_copy (tree, tree);
265 static void record_equality (tree, tree);
266 static tree update_rhs_and_lookup_avail_expr (tree, tree, bool);
267 static tree simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *,
269 static tree simplify_cond_and_lookup_avail_expr (tree, stmt_ann_t, int);
270 static tree simplify_switch_and_lookup_avail_expr (tree, int);
271 static tree find_equivalent_equality_comparison (tree);
272 static void record_range (tree, basic_block);
273 static bool extract_range_from_cond (tree, tree *, tree *, int *);
274 static void record_equivalences_from_phis (basic_block);
275 static void record_equivalences_from_incoming_edge (basic_block);
276 static bool eliminate_redundant_computations (struct dom_walk_data *,
278 static void record_equivalences_from_stmt (tree, int, stmt_ann_t);
279 static void thread_across_edge (struct dom_walk_data *, edge);
280 static void dom_opt_finalize_block (struct dom_walk_data *, basic_block);
281 static void dom_opt_initialize_block (struct dom_walk_data *, basic_block);
282 static void propagate_to_outgoing_edges (struct dom_walk_data *, basic_block);
283 static void remove_local_expressions_from_table (void);
284 static void restore_vars_to_original_value (void);
285 static edge single_incoming_edge_ignoring_loop_edges (basic_block);
286 static void restore_nonzero_vars_to_original_value (void);
287 static inline bool unsafe_associative_fp_binop (tree);
290 /* Local version of fold that doesn't introduce cruft. */
297 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
298 may have been added by fold, and "useless" type conversions that might
299 now be apparent due to propagation. */
300 STRIP_USELESS_TYPE_CONVERSION (t);
305 /* Allocate an EDGE_INFO for edge E and attach it to E.
306 Return the new EDGE_INFO structure. */
308 static struct edge_info *
309 allocate_edge_info (edge e)
311 struct edge_info *edge_info;
313 edge_info = xcalloc (1, sizeof (struct edge_info));
319 /* Free all EDGE_INFO structures associated with edges in the CFG.
320 If a particular edge can be threaded, copy the redirection
321 target from the EDGE_INFO structure into the edge's AUX field
322 as required by code to update the CFG and SSA graph for
326 free_all_edge_infos (void)
334 FOR_EACH_EDGE (e, ei, bb->preds)
336 struct edge_info *edge_info = e->aux;
340 e->aux = edge_info->redirection_target;
341 if (edge_info->cond_equivalences)
342 free (edge_info->cond_equivalences);
349 /* Jump threading, redundancy elimination and const/copy propagation.
351 This pass may expose new symbols that need to be renamed into SSA. For
352 every new symbol exposed, its corresponding bit will be set in
356 tree_ssa_dominator_optimize (void)
358 struct dom_walk_data walk_data;
360 struct loops loops_info;
362 memset (&opt_stats, 0, sizeof (opt_stats));
364 /* Create our hash tables. */
365 avail_exprs = htab_create (1024, real_avail_expr_hash, avail_expr_eq, free);
366 vrp_data = htab_create (ceil_log2 (num_ssa_names), vrp_hash, vrp_eq, free);
367 avail_exprs_stack = VEC_alloc (tree, heap, 20);
368 const_and_copies_stack = VEC_alloc (tree, heap, 20);
369 nonzero_vars_stack = VEC_alloc (tree, heap, 20);
370 vrp_variables_stack = VEC_alloc (tree, heap, 20);
371 stmts_to_rescan = VEC_alloc (tree, heap, 20);
372 nonzero_vars = BITMAP_ALLOC (NULL);
373 need_eh_cleanup = BITMAP_ALLOC (NULL);
375 /* Setup callbacks for the generic dominator tree walker. */
376 walk_data.walk_stmts_backward = false;
377 walk_data.dom_direction = CDI_DOMINATORS;
378 walk_data.initialize_block_local_data = NULL;
379 walk_data.before_dom_children_before_stmts = dom_opt_initialize_block;
380 walk_data.before_dom_children_walk_stmts = optimize_stmt;
381 walk_data.before_dom_children_after_stmts = propagate_to_outgoing_edges;
382 walk_data.after_dom_children_before_stmts = NULL;
383 walk_data.after_dom_children_walk_stmts = NULL;
384 walk_data.after_dom_children_after_stmts = dom_opt_finalize_block;
385 /* Right now we only attach a dummy COND_EXPR to the global data pointer.
386 When we attach more stuff we'll need to fill this out with a real
388 walk_data.global_data = NULL;
389 walk_data.block_local_data_size = 0;
390 walk_data.interesting_blocks = NULL;
392 /* Now initialize the dominator walker. */
393 init_walk_dominator_tree (&walk_data);
395 calculate_dominance_info (CDI_DOMINATORS);
397 /* We need to know which edges exit loops so that we can
398 aggressively thread through loop headers to an exit
400 flow_loops_find (&loops_info);
401 mark_loop_exit_edges (&loops_info);
402 flow_loops_free (&loops_info);
404 /* Clean up the CFG so that any forwarder blocks created by loop
405 canonicalization are removed. */
407 calculate_dominance_info (CDI_DOMINATORS);
409 /* If we prove certain blocks are unreachable, then we want to
410 repeat the dominator optimization process as PHI nodes may
411 have turned into copies which allows better propagation of
412 values. So we repeat until we do not identify any new unreachable
416 /* Optimize the dominator tree. */
419 /* We need accurate information regarding back edges in the CFG
420 for jump threading. */
421 mark_dfs_back_edges ();
423 /* Recursively walk the dominator tree optimizing statements. */
424 walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
426 /* If we exposed any new variables, go ahead and put them into
427 SSA form now, before we handle jump threading. This simplifies
428 interactions between rewriting of _DECL nodes into SSA form
429 and rewriting SSA_NAME nodes into SSA form after block
430 duplication and CFG manipulation. */
431 update_ssa (TODO_update_ssa);
433 free_all_edge_infos ();
436 block_stmt_iterator bsi;
440 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
442 update_stmt_if_modified (bsi_stmt (bsi));
447 /* Thread jumps, creating duplicate blocks as needed. */
448 cfg_altered |= thread_through_all_blocks ();
450 /* Removal of statements may make some EH edges dead. Purge
451 such edges from the CFG as needed. */
452 if (!bitmap_empty_p (need_eh_cleanup))
454 cfg_altered |= tree_purge_all_dead_eh_edges (need_eh_cleanup);
455 bitmap_zero (need_eh_cleanup);
459 free_dominance_info (CDI_DOMINATORS);
461 cfg_altered = cleanup_tree_cfg ();
463 if (rediscover_loops_after_threading)
465 /* Rerun basic loop analysis to discover any newly
466 created loops and update the set of exit edges. */
467 rediscover_loops_after_threading = false;
468 flow_loops_find (&loops_info);
469 mark_loop_exit_edges (&loops_info);
470 flow_loops_free (&loops_info);
472 /* Remove any forwarder blocks inserted by loop
473 header canonicalization. */
477 calculate_dominance_info (CDI_DOMINATORS);
479 update_ssa (TODO_update_ssa);
481 /* Reinitialize the various tables. */
482 bitmap_clear (nonzero_vars);
483 htab_empty (avail_exprs);
484 htab_empty (vrp_data);
486 /* Finally, remove everything except invariants in SSA_NAME_VALUE.
488 This must be done before we iterate as we might have a
489 reference to an SSA_NAME which was removed by the call to
492 Long term we will be able to let everything in SSA_NAME_VALUE
493 persist. However, for now, we know this is the safe thing to do. */
494 for (i = 0; i < num_ssa_names; i++)
496 tree name = ssa_name (i);
502 value = SSA_NAME_VALUE (name);
503 if (value && !is_gimple_min_invariant (value))
504 SSA_NAME_VALUE (name) = NULL;
507 while (optimize > 1 && cfg_altered);
509 /* Debugging dumps. */
510 if (dump_file && (dump_flags & TDF_STATS))
511 dump_dominator_optimization_stats (dump_file);
513 /* We emptied the hash table earlier, now delete it completely. */
514 htab_delete (avail_exprs);
515 htab_delete (vrp_data);
517 /* It is not necessary to clear CURRDEFS, REDIRECTION_EDGES, VRP_DATA,
518 CONST_AND_COPIES, and NONZERO_VARS as they all get cleared at the bottom
519 of the do-while loop above. */
521 /* And finalize the dominator walker. */
522 fini_walk_dominator_tree (&walk_data);
524 /* Free nonzero_vars. */
525 BITMAP_FREE (nonzero_vars);
526 BITMAP_FREE (need_eh_cleanup);
528 VEC_free (tree, heap, avail_exprs_stack);
529 VEC_free (tree, heap, const_and_copies_stack);
530 VEC_free (tree, heap, nonzero_vars_stack);
531 VEC_free (tree, heap, vrp_variables_stack);
532 VEC_free (tree, heap, stmts_to_rescan);
536 gate_dominator (void)
538 return flag_tree_dom != 0;
541 struct tree_opt_pass pass_dominator =
544 gate_dominator, /* gate */
545 tree_ssa_dominator_optimize, /* execute */
548 0, /* static_pass_number */
549 TV_TREE_SSA_DOMINATOR_OPTS, /* tv_id */
550 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
551 0, /* properties_provided */
552 0, /* properties_destroyed */
553 0, /* todo_flags_start */
556 | TODO_verify_ssa, /* todo_flags_finish */
561 /* We are exiting E->src, see if E->dest ends with a conditional
562 jump which has a known value when reached via E.
564 Special care is necessary if E is a back edge in the CFG as we
565 will have already recorded equivalences for E->dest into our
566 various tables, including the result of the conditional at
567 the end of E->dest. Threading opportunities are severely
568 limited in that case to avoid short-circuiting the loop
571 Note it is quite common for the first block inside a loop to
572 end with a conditional which is either always true or always
573 false when reached via the loop backedge. Thus we do not want
574 to blindly disable threading across a loop backedge. */
577 thread_across_edge (struct dom_walk_data *walk_data, edge e)
579 block_stmt_iterator bsi;
583 /* If E->dest does not end with a conditional, then there is
585 bsi = bsi_last (e->dest);
588 || (TREE_CODE (bsi_stmt (bsi)) != COND_EXPR
589 && TREE_CODE (bsi_stmt (bsi)) != GOTO_EXPR
590 && TREE_CODE (bsi_stmt (bsi)) != SWITCH_EXPR))
593 /* The basic idea here is to use whatever knowledge we have
594 from our dominator walk to simplify statements in E->dest,
595 with the ultimate goal being to simplify the conditional
596 at the end of E->dest.
598 Note that we must undo any changes we make to the underlying
599 statements as the simplifications we are making are control
600 flow sensitive (ie, the simplifications are valid when we
601 traverse E, but may not be valid on other paths to E->dest. */
603 /* Each PHI creates a temporary equivalence, record them. Again
604 these are context sensitive equivalences and will be removed
606 for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
608 tree src = PHI_ARG_DEF_FROM_EDGE (phi, e);
609 tree dst = PHI_RESULT (phi);
611 /* If the desired argument is not the same as this PHI's result
612 and it is set by a PHI in E->dest, then we can not thread
615 && TREE_CODE (src) == SSA_NAME
616 && TREE_CODE (SSA_NAME_DEF_STMT (src)) == PHI_NODE
617 && bb_for_stmt (SSA_NAME_DEF_STMT (src)) == e->dest)
620 record_const_or_copy (dst, src);
623 /* Try to simplify each statement in E->dest, ultimately leading to
624 a simplification of the COND_EXPR at the end of E->dest.
626 We might consider marking just those statements which ultimately
627 feed the COND_EXPR. It's not clear if the overhead of bookkeeping
628 would be recovered by trying to simplify fewer statements.
630 If we are able to simplify a statement into the form
631 SSA_NAME = (SSA_NAME | gimple invariant), then we can record
632 a context sensitive equivalency which may help us simplify
633 later statements in E->dest.
635 Failure to simplify into the form above merely means that the
636 statement provides no equivalences to help simplify later
637 statements. This does not prevent threading through E->dest. */
638 for (bsi = bsi_start (e->dest); ! bsi_end_p (bsi); bsi_next (&bsi))
642 stmt = bsi_stmt (bsi);
644 /* Ignore empty statements and labels. */
645 if (IS_EMPTY_STMT (stmt) || TREE_CODE (stmt) == LABEL_EXPR)
648 /* Safely handle threading across loop backedges. This is
649 over conservative, but still allows us to capture the
650 majority of the cases where we can thread across a loop
652 if ((e->flags & EDGE_DFS_BACK) != 0
653 && TREE_CODE (stmt) != COND_EXPR
654 && TREE_CODE (stmt) != SWITCH_EXPR)
657 /* If the statement has volatile operands, then we assume we
658 can not thread through this block. This is overly
659 conservative in some ways. */
660 if (TREE_CODE (stmt) == ASM_EXPR && ASM_VOLATILE_P (stmt))
663 /* If this is not a MODIFY_EXPR which sets an SSA_NAME to a new
664 value, then do not try to simplify this statement as it will
665 not simplify in any way that is helpful for jump threading. */
666 if (TREE_CODE (stmt) != MODIFY_EXPR
667 || TREE_CODE (TREE_OPERAND (stmt, 0)) != SSA_NAME)
670 /* At this point we have a statement which assigns an RHS to an
671 SSA_VAR on the LHS. We want to try and simplify this statement
672 to expose more context sensitive equivalences which in turn may
673 allow us to simplify the condition at the end of the loop. */
674 if (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME)
675 cached_lhs = TREE_OPERAND (stmt, 1);
678 /* Copy the operands. */
682 unsigned int num, i = 0;
684 num = NUM_SSA_OPERANDS (stmt, (SSA_OP_USE | SSA_OP_VUSE));
685 copy = xcalloc (num, sizeof (tree));
687 /* Make a copy of the uses & vuses into USES_COPY, then cprop into
689 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE | SSA_OP_VUSE)
692 tree use = USE_FROM_PTR (use_p);
695 if (TREE_CODE (use) == SSA_NAME)
696 tmp = SSA_NAME_VALUE (use);
697 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
698 SET_USE (use_p, tmp);
701 /* Try to fold/lookup the new expression. Inserting the
702 expression into the hash table is unlikely to help
703 simplify anything later, so just query the hashtable. */
704 cached_lhs = fold (TREE_OPERAND (stmt, 1));
705 if (TREE_CODE (cached_lhs) != SSA_NAME
706 && !is_gimple_min_invariant (cached_lhs))
707 cached_lhs = lookup_avail_expr (stmt, false);
710 /* Restore the statement's original uses/defs. */
712 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE | SSA_OP_VUSE)
713 SET_USE (use_p, copy[i++]);
718 /* Record the context sensitive equivalence if we were able
719 to simplify this statement. */
721 && (TREE_CODE (cached_lhs) == SSA_NAME
722 || is_gimple_min_invariant (cached_lhs)))
723 record_const_or_copy (TREE_OPERAND (stmt, 0), cached_lhs);
726 /* If we stopped at a COND_EXPR or SWITCH_EXPR, see if we know which arm
729 && (TREE_CODE (stmt) == COND_EXPR
730 || TREE_CODE (stmt) == GOTO_EXPR
731 || TREE_CODE (stmt) == SWITCH_EXPR))
733 tree cond, cached_lhs;
735 /* Now temporarily cprop the operands and try to find the resulting
736 expression in the hash tables. */
737 if (TREE_CODE (stmt) == COND_EXPR)
738 cond = COND_EXPR_COND (stmt);
739 else if (TREE_CODE (stmt) == GOTO_EXPR)
740 cond = GOTO_DESTINATION (stmt);
742 cond = SWITCH_COND (stmt);
744 if (COMPARISON_CLASS_P (cond))
746 tree dummy_cond, op0, op1;
747 enum tree_code cond_code;
749 op0 = TREE_OPERAND (cond, 0);
750 op1 = TREE_OPERAND (cond, 1);
751 cond_code = TREE_CODE (cond);
753 /* Get the current value of both operands. */
754 if (TREE_CODE (op0) == SSA_NAME)
756 tree tmp = SSA_NAME_VALUE (op0);
757 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
761 if (TREE_CODE (op1) == SSA_NAME)
763 tree tmp = SSA_NAME_VALUE (op1);
764 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
768 /* Stuff the operator and operands into our dummy conditional
769 expression, creating the dummy conditional if necessary. */
770 dummy_cond = walk_data->global_data;
773 dummy_cond = build (cond_code, boolean_type_node, op0, op1);
774 dummy_cond = build (COND_EXPR, void_type_node,
775 dummy_cond, NULL, NULL);
776 walk_data->global_data = dummy_cond;
780 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), cond_code);
781 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op0;
782 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1) = op1;
785 /* If the conditional folds to an invariant, then we are done,
786 otherwise look it up in the hash tables. */
787 cached_lhs = local_fold (COND_EXPR_COND (dummy_cond));
788 if (! is_gimple_min_invariant (cached_lhs))
790 cached_lhs = lookup_avail_expr (dummy_cond, false);
791 if (!cached_lhs || ! is_gimple_min_invariant (cached_lhs))
792 cached_lhs = simplify_cond_and_lookup_avail_expr (dummy_cond,
797 /* We can have conditionals which just test the state of a
798 variable rather than use a relational operator. These are
799 simpler to handle. */
800 else if (TREE_CODE (cond) == SSA_NAME)
803 cached_lhs = SSA_NAME_VALUE (cached_lhs);
804 if (cached_lhs && ! is_gimple_min_invariant (cached_lhs))
808 cached_lhs = lookup_avail_expr (stmt, false);
812 edge taken_edge = find_taken_edge (e->dest, cached_lhs);
813 basic_block dest = (taken_edge ? taken_edge->dest : NULL);
818 /* If we have a known destination for the conditional, then
819 we can perform this optimization, which saves at least one
820 conditional jump each time it applies since we get to
821 bypass the conditional at our original destination. */
824 struct edge_info *edge_info;
826 update_bb_profile_for_threading (e->dest, EDGE_FREQUENCY (e),
827 e->count, taken_edge);
831 edge_info = allocate_edge_info (e);
832 edge_info->redirection_target = taken_edge;
833 bb_ann (e->dest)->incoming_edge_threaded = true;
840 /* Initialize local stacks for this optimizer and record equivalences
841 upon entry to BB. Equivalences can come from the edge traversed to
842 reach BB or they may come from PHI nodes at the start of BB. */
845 dom_opt_initialize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
848 if (dump_file && (dump_flags & TDF_DETAILS))
849 fprintf (dump_file, "\n\nOptimizing block #%d\n\n", bb->index);
851 /* Push a marker on the stacks of local information so that we know how
852 far to unwind when we finalize this block. */
853 VEC_safe_push (tree, heap, avail_exprs_stack, NULL_TREE);
854 VEC_safe_push (tree, heap, const_and_copies_stack, NULL_TREE);
855 VEC_safe_push (tree, heap, nonzero_vars_stack, NULL_TREE);
856 VEC_safe_push (tree, heap, vrp_variables_stack, NULL_TREE);
858 record_equivalences_from_incoming_edge (bb);
860 /* PHI nodes can create equivalences too. */
861 record_equivalences_from_phis (bb);
864 /* Given an expression EXPR (a relational expression or a statement),
865 initialize the hash table element pointed by by ELEMENT. */
868 initialize_hash_element (tree expr, tree lhs, struct expr_hash_elt *element)
870 /* Hash table elements may be based on conditional expressions or statements.
872 For the former case, we have no annotation and we want to hash the
873 conditional expression. In the latter case we have an annotation and
874 we want to record the expression the statement evaluates. */
875 if (COMPARISON_CLASS_P (expr) || TREE_CODE (expr) == TRUTH_NOT_EXPR)
877 element->stmt = NULL;
880 else if (TREE_CODE (expr) == COND_EXPR)
882 element->stmt = expr;
883 element->rhs = COND_EXPR_COND (expr);
885 else if (TREE_CODE (expr) == SWITCH_EXPR)
887 element->stmt = expr;
888 element->rhs = SWITCH_COND (expr);
890 else if (TREE_CODE (expr) == RETURN_EXPR && TREE_OPERAND (expr, 0))
892 element->stmt = expr;
893 element->rhs = TREE_OPERAND (TREE_OPERAND (expr, 0), 1);
895 else if (TREE_CODE (expr) == GOTO_EXPR)
897 element->stmt = expr;
898 element->rhs = GOTO_DESTINATION (expr);
902 element->stmt = expr;
903 element->rhs = TREE_OPERAND (expr, 1);
907 element->hash = avail_expr_hash (element);
910 /* Remove all the expressions in LOCALS from TABLE, stopping when there are
911 LIMIT entries left in LOCALs. */
914 remove_local_expressions_from_table (void)
916 /* Remove all the expressions made available in this block. */
917 while (VEC_length (tree, avail_exprs_stack) > 0)
919 struct expr_hash_elt element;
920 tree expr = VEC_pop (tree, avail_exprs_stack);
922 if (expr == NULL_TREE)
925 initialize_hash_element (expr, NULL, &element);
926 htab_remove_elt_with_hash (avail_exprs, &element, element.hash);
930 /* Use the SSA_NAMES in LOCALS to restore TABLE to its original
931 state, stopping when there are LIMIT entries left in LOCALs. */
934 restore_nonzero_vars_to_original_value (void)
936 while (VEC_length (tree, nonzero_vars_stack) > 0)
938 tree name = VEC_pop (tree, nonzero_vars_stack);
943 bitmap_clear_bit (nonzero_vars, SSA_NAME_VERSION (name));
947 /* Use the source/dest pairs in CONST_AND_COPIES_STACK to restore
948 CONST_AND_COPIES to its original state, stopping when we hit a
952 restore_vars_to_original_value (void)
954 while (VEC_length (tree, const_and_copies_stack) > 0)
956 tree prev_value, dest;
958 dest = VEC_pop (tree, const_and_copies_stack);
963 prev_value = VEC_pop (tree, const_and_copies_stack);
964 SSA_NAME_VALUE (dest) = prev_value;
968 /* We have finished processing the dominator children of BB, perform
969 any finalization actions in preparation for leaving this node in
970 the dominator tree. */
973 dom_opt_finalize_block (struct dom_walk_data *walk_data, basic_block bb)
977 /* If we are at a leaf node in the dominator tree, see if we can thread
978 the edge from BB through its successor.
980 Do this before we remove entries from our equivalence tables. */
981 if (single_succ_p (bb)
982 && (single_succ_edge (bb)->flags & EDGE_ABNORMAL) == 0
983 && (get_immediate_dominator (CDI_DOMINATORS, single_succ (bb)) != bb
984 || phi_nodes (single_succ (bb))))
987 thread_across_edge (walk_data, single_succ_edge (bb));
989 else if ((last = last_stmt (bb))
990 && TREE_CODE (last) == COND_EXPR
991 && (COMPARISON_CLASS_P (COND_EXPR_COND (last))
992 || TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME)
993 && EDGE_COUNT (bb->succs) == 2
994 && (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL) == 0
995 && (EDGE_SUCC (bb, 1)->flags & EDGE_ABNORMAL) == 0)
997 edge true_edge, false_edge;
999 extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
1001 /* If the THEN arm is the end of a dominator tree or has PHI nodes,
1002 then try to thread through its edge. */
1003 if (get_immediate_dominator (CDI_DOMINATORS, true_edge->dest) != bb
1004 || phi_nodes (true_edge->dest))
1006 struct edge_info *edge_info;
1009 /* Push a marker onto the available expression stack so that we
1010 unwind any expressions related to the TRUE arm before processing
1011 the false arm below. */
1012 VEC_safe_push (tree, heap, avail_exprs_stack, NULL_TREE);
1013 VEC_safe_push (tree, heap, const_and_copies_stack, NULL_TREE);
1015 edge_info = true_edge->aux;
1017 /* If we have info associated with this edge, record it into
1018 our equivalency tables. */
1021 tree *cond_equivalences = edge_info->cond_equivalences;
1022 tree lhs = edge_info->lhs;
1023 tree rhs = edge_info->rhs;
1025 /* If we have a simple NAME = VALUE equivalency record it. */
1026 if (lhs && TREE_CODE (lhs) == SSA_NAME)
1027 record_const_or_copy (lhs, rhs);
1029 /* If we have 0 = COND or 1 = COND equivalences, record them
1030 into our expression hash tables. */
1031 if (cond_equivalences)
1032 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1034 tree expr = cond_equivalences[i];
1035 tree value = cond_equivalences[i + 1];
1037 record_cond (expr, value);
1041 /* Now thread the edge. */
1042 thread_across_edge (walk_data, true_edge);
1044 /* And restore the various tables to their state before
1045 we threaded this edge. */
1046 remove_local_expressions_from_table ();
1047 restore_vars_to_original_value ();
1050 /* Similarly for the ELSE arm. */
1051 if (get_immediate_dominator (CDI_DOMINATORS, false_edge->dest) != bb
1052 || phi_nodes (false_edge->dest))
1054 struct edge_info *edge_info;
1057 edge_info = false_edge->aux;
1059 /* If we have info associated with this edge, record it into
1060 our equivalency tables. */
1063 tree *cond_equivalences = edge_info->cond_equivalences;
1064 tree lhs = edge_info->lhs;
1065 tree rhs = edge_info->rhs;
1067 /* If we have a simple NAME = VALUE equivalency record it. */
1068 if (lhs && TREE_CODE (lhs) == SSA_NAME)
1069 record_const_or_copy (lhs, rhs);
1071 /* If we have 0 = COND or 1 = COND equivalences, record them
1072 into our expression hash tables. */
1073 if (cond_equivalences)
1074 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1076 tree expr = cond_equivalences[i];
1077 tree value = cond_equivalences[i + 1];
1079 record_cond (expr, value);
1083 thread_across_edge (walk_data, false_edge);
1085 /* No need to remove local expressions from our tables
1086 or restore vars to their original value as that will
1087 be done immediately below. */
1091 remove_local_expressions_from_table ();
1092 restore_nonzero_vars_to_original_value ();
1093 restore_vars_to_original_value ();
1095 /* Remove VRP records associated with this basic block. They are no
1098 To be efficient, we note which variables have had their values
1099 constrained in this block. So walk over each variable in the
1100 VRP_VARIABLEs array. */
1101 while (VEC_length (tree, vrp_variables_stack) > 0)
1103 tree var = VEC_pop (tree, vrp_variables_stack);
1104 struct vrp_hash_elt vrp_hash_elt, *vrp_hash_elt_p;
1107 /* Each variable has a stack of value range records. We want to
1108 invalidate those associated with our basic block. So we walk
1109 the array backwards popping off records associated with our
1110 block. Once we hit a record not associated with our block
1112 varray_type var_vrp_records;
1117 vrp_hash_elt.var = var;
1118 vrp_hash_elt.records = NULL;
1120 slot = htab_find_slot (vrp_data, &vrp_hash_elt, NO_INSERT);
1122 vrp_hash_elt_p = (struct vrp_hash_elt *) *slot;
1123 var_vrp_records = vrp_hash_elt_p->records;
1125 while (VARRAY_ACTIVE_SIZE (var_vrp_records) > 0)
1127 struct vrp_element *element
1128 = (struct vrp_element *)VARRAY_TOP_GENERIC_PTR (var_vrp_records);
1130 if (element->bb != bb)
1133 VARRAY_POP (var_vrp_records);
1137 /* If we queued any statements to rescan in this block, then
1138 go ahead and rescan them now. */
1139 while (VEC_length (tree, stmts_to_rescan) > 0)
1141 tree stmt = VEC_last (tree, stmts_to_rescan);
1142 basic_block stmt_bb = bb_for_stmt (stmt);
1147 VEC_pop (tree, stmts_to_rescan);
1148 mark_new_vars_to_rename (stmt);
1152 /* PHI nodes can create equivalences too.
1154 Ignoring any alternatives which are the same as the result, if
1155 all the alternatives are equal, then the PHI node creates an
1158 Additionally, if all the PHI alternatives are known to have a nonzero
1159 value, then the result of this PHI is known to have a nonzero value,
1160 even if we do not know its exact value. */
1163 record_equivalences_from_phis (basic_block bb)
1167 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1169 tree lhs = PHI_RESULT (phi);
1173 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1175 tree t = PHI_ARG_DEF (phi, i);
1177 /* Ignore alternatives which are the same as our LHS. Since
1178 LHS is a PHI_RESULT, it is known to be a SSA_NAME, so we
1179 can simply compare pointers. */
1183 /* If we have not processed an alternative yet, then set
1184 RHS to this alternative. */
1187 /* If we have processed an alternative (stored in RHS), then
1188 see if it is equal to this one. If it isn't, then stop
1190 else if (! operand_equal_for_phi_arg_p (rhs, t))
1194 /* If we had no interesting alternatives, then all the RHS alternatives
1195 must have been the same as LHS. */
1199 /* If we managed to iterate through each PHI alternative without
1200 breaking out of the loop, then we have a PHI which may create
1201 a useful equivalence. We do not need to record unwind data for
1202 this, since this is a true assignment and not an equivalence
1203 inferred from a comparison. All uses of this ssa name are dominated
1204 by this assignment, so unwinding just costs time and space. */
1205 if (i == PHI_NUM_ARGS (phi)
1206 && may_propagate_copy (lhs, rhs))
1207 SSA_NAME_VALUE (lhs) = rhs;
1209 /* Now see if we know anything about the nonzero property for the
1210 result of this PHI. */
1211 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1213 if (!PHI_ARG_NONZERO (phi, i))
1217 if (i == PHI_NUM_ARGS (phi))
1218 bitmap_set_bit (nonzero_vars, SSA_NAME_VERSION (PHI_RESULT (phi)));
1222 /* Ignoring loop backedges, if BB has precisely one incoming edge then
1223 return that edge. Otherwise return NULL. */
1225 single_incoming_edge_ignoring_loop_edges (basic_block bb)
1231 FOR_EACH_EDGE (e, ei, bb->preds)
1233 /* A loop back edge can be identified by the destination of
1234 the edge dominating the source of the edge. */
1235 if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
1238 /* If we have already seen a non-loop edge, then we must have
1239 multiple incoming non-loop edges and thus we return NULL. */
1243 /* This is the first non-loop incoming edge we have found. Record
1251 /* Record any equivalences created by the incoming edge to BB. If BB
1252 has more than one incoming edge, then no equivalence is created. */
1255 record_equivalences_from_incoming_edge (basic_block bb)
1259 struct edge_info *edge_info;
1261 /* If our parent block ended with a control statement, then we may be
1262 able to record some equivalences based on which outgoing edge from
1263 the parent was followed. */
1264 parent = get_immediate_dominator (CDI_DOMINATORS, bb);
1266 e = single_incoming_edge_ignoring_loop_edges (bb);
1268 /* If we had a single incoming edge from our parent block, then enter
1269 any data associated with the edge into our tables. */
1270 if (e && e->src == parent)
1278 tree lhs = edge_info->lhs;
1279 tree rhs = edge_info->rhs;
1280 tree *cond_equivalences = edge_info->cond_equivalences;
1283 record_equality (lhs, rhs);
1285 if (cond_equivalences)
1287 bool recorded_range = false;
1288 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1290 tree expr = cond_equivalences[i];
1291 tree value = cond_equivalences[i + 1];
1293 record_cond (expr, value);
1295 /* For the first true equivalence, record range
1296 information. We only do this for the first
1297 true equivalence as it should dominate any
1298 later true equivalences. */
1299 if (! recorded_range
1300 && COMPARISON_CLASS_P (expr)
1301 && value == boolean_true_node
1302 && TREE_CONSTANT (TREE_OPERAND (expr, 1)))
1304 record_range (expr, bb);
1305 recorded_range = true;
1313 /* Dump SSA statistics on FILE. */
1316 dump_dominator_optimization_stats (FILE *file)
1320 fprintf (file, "Total number of statements: %6ld\n\n",
1321 opt_stats.num_stmts);
1322 fprintf (file, "Exprs considered for dominator optimizations: %6ld\n",
1323 opt_stats.num_exprs_considered);
1325 n_exprs = opt_stats.num_exprs_considered;
1329 fprintf (file, " Redundant expressions eliminated: %6ld (%.0f%%)\n",
1330 opt_stats.num_re, PERCENT (opt_stats.num_re,
1332 fprintf (file, " Constants propagated: %6ld\n",
1333 opt_stats.num_const_prop);
1334 fprintf (file, " Copies propagated: %6ld\n",
1335 opt_stats.num_copy_prop);
1337 fprintf (file, "\nHash table statistics:\n");
1339 fprintf (file, " avail_exprs: ");
1340 htab_statistics (file, avail_exprs);
1344 /* Dump SSA statistics on stderr. */
1347 debug_dominator_optimization_stats (void)
1349 dump_dominator_optimization_stats (stderr);
1353 /* Dump statistics for the hash table HTAB. */
1356 htab_statistics (FILE *file, htab_t htab)
1358 fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
1359 (long) htab_size (htab),
1360 (long) htab_elements (htab),
1361 htab_collisions (htab));
1364 /* Record the fact that VAR has a nonzero value, though we may not know
1365 its exact value. Note that if VAR is already known to have a nonzero
1366 value, then we do nothing. */
1369 record_var_is_nonzero (tree var)
1371 int indx = SSA_NAME_VERSION (var);
1373 if (bitmap_bit_p (nonzero_vars, indx))
1376 /* Mark it in the global table. */
1377 bitmap_set_bit (nonzero_vars, indx);
1379 /* Record this SSA_NAME so that we can reset the global table
1380 when we leave this block. */
1381 VEC_safe_push (tree, heap, nonzero_vars_stack, var);
1384 /* Enter a statement into the true/false expression hash table indicating
1385 that the condition COND has the value VALUE. */
1388 record_cond (tree cond, tree value)
1390 struct expr_hash_elt *element = xmalloc (sizeof (struct expr_hash_elt));
1393 initialize_hash_element (cond, value, element);
1395 slot = htab_find_slot_with_hash (avail_exprs, (void *)element,
1396 element->hash, INSERT);
1399 *slot = (void *) element;
1400 VEC_safe_push (tree, heap, avail_exprs_stack, cond);
1406 /* Build a new conditional using NEW_CODE, OP0 and OP1 and store
1407 the new conditional into *p, then store a boolean_true_node
1411 build_and_record_new_cond (enum tree_code new_code, tree op0, tree op1, tree *p)
1413 *p = build2 (new_code, boolean_type_node, op0, op1);
1415 *p = boolean_true_node;
1418 /* Record that COND is true and INVERTED is false into the edge information
1419 structure. Also record that any conditions dominated by COND are true
1422 For example, if a < b is true, then a <= b must also be true. */
1425 record_conditions (struct edge_info *edge_info, tree cond, tree inverted)
1429 if (!COMPARISON_CLASS_P (cond))
1432 op0 = TREE_OPERAND (cond, 0);
1433 op1 = TREE_OPERAND (cond, 1);
1435 switch (TREE_CODE (cond))
1439 edge_info->max_cond_equivalences = 12;
1440 edge_info->cond_equivalences = xmalloc (12 * sizeof (tree));
1441 build_and_record_new_cond ((TREE_CODE (cond) == LT_EXPR
1442 ? LE_EXPR : GE_EXPR),
1443 op0, op1, &edge_info->cond_equivalences[4]);
1444 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1445 &edge_info->cond_equivalences[6]);
1446 build_and_record_new_cond (NE_EXPR, op0, op1,
1447 &edge_info->cond_equivalences[8]);
1448 build_and_record_new_cond (LTGT_EXPR, op0, op1,
1449 &edge_info->cond_equivalences[10]);
1454 edge_info->max_cond_equivalences = 6;
1455 edge_info->cond_equivalences = xmalloc (6 * sizeof (tree));
1456 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1457 &edge_info->cond_equivalences[4]);
1461 edge_info->max_cond_equivalences = 10;
1462 edge_info->cond_equivalences = xmalloc (10 * sizeof (tree));
1463 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1464 &edge_info->cond_equivalences[4]);
1465 build_and_record_new_cond (LE_EXPR, op0, op1,
1466 &edge_info->cond_equivalences[6]);
1467 build_and_record_new_cond (GE_EXPR, op0, op1,
1468 &edge_info->cond_equivalences[8]);
1471 case UNORDERED_EXPR:
1472 edge_info->max_cond_equivalences = 16;
1473 edge_info->cond_equivalences = xmalloc (16 * sizeof (tree));
1474 build_and_record_new_cond (NE_EXPR, op0, op1,
1475 &edge_info->cond_equivalences[4]);
1476 build_and_record_new_cond (UNLE_EXPR, op0, op1,
1477 &edge_info->cond_equivalences[6]);
1478 build_and_record_new_cond (UNGE_EXPR, op0, op1,
1479 &edge_info->cond_equivalences[8]);
1480 build_and_record_new_cond (UNEQ_EXPR, op0, op1,
1481 &edge_info->cond_equivalences[10]);
1482 build_and_record_new_cond (UNLT_EXPR, op0, op1,
1483 &edge_info->cond_equivalences[12]);
1484 build_and_record_new_cond (UNGT_EXPR, op0, op1,
1485 &edge_info->cond_equivalences[14]);
1490 edge_info->max_cond_equivalences = 8;
1491 edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1492 build_and_record_new_cond ((TREE_CODE (cond) == UNLT_EXPR
1493 ? UNLE_EXPR : UNGE_EXPR),
1494 op0, op1, &edge_info->cond_equivalences[4]);
1495 build_and_record_new_cond (NE_EXPR, op0, op1,
1496 &edge_info->cond_equivalences[6]);
1500 edge_info->max_cond_equivalences = 8;
1501 edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1502 build_and_record_new_cond (UNLE_EXPR, op0, op1,
1503 &edge_info->cond_equivalences[4]);
1504 build_and_record_new_cond (UNGE_EXPR, op0, op1,
1505 &edge_info->cond_equivalences[6]);
1509 edge_info->max_cond_equivalences = 8;
1510 edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1511 build_and_record_new_cond (NE_EXPR, op0, op1,
1512 &edge_info->cond_equivalences[4]);
1513 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1514 &edge_info->cond_equivalences[6]);
1518 edge_info->max_cond_equivalences = 4;
1519 edge_info->cond_equivalences = xmalloc (4 * sizeof (tree));
1523 /* Now store the original true and false conditions into the first
1525 edge_info->cond_equivalences[0] = cond;
1526 edge_info->cond_equivalences[1] = boolean_true_node;
1527 edge_info->cond_equivalences[2] = inverted;
1528 edge_info->cond_equivalences[3] = boolean_false_node;
1531 /* A helper function for record_const_or_copy and record_equality.
1532 Do the work of recording the value and undo info. */
1535 record_const_or_copy_1 (tree x, tree y, tree prev_x)
1537 SSA_NAME_VALUE (x) = y;
1539 VEC_reserve (tree, heap, const_and_copies_stack, 2);
1540 VEC_quick_push (tree, const_and_copies_stack, prev_x);
1541 VEC_quick_push (tree, const_and_copies_stack, x);
1545 /* Return the loop depth of the basic block of the defining statement of X.
1546 This number should not be treated as absolutely correct because the loop
1547 information may not be completely up-to-date when dom runs. However, it
1548 will be relatively correct, and as more passes are taught to keep loop info
1549 up to date, the result will become more and more accurate. */
1552 loop_depth_of_name (tree x)
1557 /* If it's not an SSA_NAME, we have no clue where the definition is. */
1558 if (TREE_CODE (x) != SSA_NAME)
1561 /* Otherwise return the loop depth of the defining statement's bb.
1562 Note that there may not actually be a bb for this statement, if the
1563 ssa_name is live on entry. */
1564 defstmt = SSA_NAME_DEF_STMT (x);
1565 defbb = bb_for_stmt (defstmt);
1569 return defbb->loop_depth;
1573 /* Record that X is equal to Y in const_and_copies. Record undo
1574 information in the block-local vector. */
1577 record_const_or_copy (tree x, tree y)
1579 tree prev_x = SSA_NAME_VALUE (x);
1581 if (TREE_CODE (y) == SSA_NAME)
1583 tree tmp = SSA_NAME_VALUE (y);
1588 record_const_or_copy_1 (x, y, prev_x);
1591 /* Similarly, but assume that X and Y are the two operands of an EQ_EXPR.
1592 This constrains the cases in which we may treat this as assignment. */
1595 record_equality (tree x, tree y)
1597 tree prev_x = NULL, prev_y = NULL;
1599 if (TREE_CODE (x) == SSA_NAME)
1600 prev_x = SSA_NAME_VALUE (x);
1601 if (TREE_CODE (y) == SSA_NAME)
1602 prev_y = SSA_NAME_VALUE (y);
1604 /* If one of the previous values is invariant, or invariant in more loops
1605 (by depth), then use that.
1606 Otherwise it doesn't matter which value we choose, just so
1607 long as we canonicalize on one value. */
1608 if (TREE_INVARIANT (y))
1610 else if (TREE_INVARIANT (x) || (loop_depth_of_name (x) <= loop_depth_of_name (y)))
1611 prev_x = x, x = y, y = prev_x, prev_x = prev_y;
1612 else if (prev_x && TREE_INVARIANT (prev_x))
1613 x = y, y = prev_x, prev_x = prev_y;
1614 else if (prev_y && TREE_CODE (prev_y) != VALUE_HANDLE)
1617 /* After the swapping, we must have one SSA_NAME. */
1618 if (TREE_CODE (x) != SSA_NAME)
1621 /* For IEEE, -0.0 == 0.0, so we don't necessarily know the sign of a
1622 variable compared against zero. If we're honoring signed zeros,
1623 then we cannot record this value unless we know that the value is
1625 if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (x)))
1626 && (TREE_CODE (y) != REAL_CST
1627 || REAL_VALUES_EQUAL (dconst0, TREE_REAL_CST (y))))
1630 record_const_or_copy_1 (x, y, prev_x);
1633 /* Return true, if it is ok to do folding of an associative expression.
1634 EXP is the tree for the associative expression. */
1637 unsafe_associative_fp_binop (tree exp)
1639 enum tree_code code = TREE_CODE (exp);
1640 return !(!flag_unsafe_math_optimizations
1641 && (code == MULT_EXPR || code == PLUS_EXPR
1642 || code == MINUS_EXPR)
1643 && FLOAT_TYPE_P (TREE_TYPE (exp)));
1646 /* Returns true when STMT is a simple iv increment. It detects the
1647 following situation:
1649 i_1 = phi (..., i_2)
1650 i_2 = i_1 +/- ... */
1653 simple_iv_increment_p (tree stmt)
1655 tree lhs, rhs, preinc, phi;
1658 if (TREE_CODE (stmt) != MODIFY_EXPR)
1661 lhs = TREE_OPERAND (stmt, 0);
1662 if (TREE_CODE (lhs) != SSA_NAME)
1665 rhs = TREE_OPERAND (stmt, 1);
1667 if (TREE_CODE (rhs) != PLUS_EXPR
1668 && TREE_CODE (rhs) != MINUS_EXPR)
1671 preinc = TREE_OPERAND (rhs, 0);
1672 if (TREE_CODE (preinc) != SSA_NAME)
1675 phi = SSA_NAME_DEF_STMT (preinc);
1676 if (TREE_CODE (phi) != PHI_NODE)
1679 for (i = 0; i < (unsigned) PHI_NUM_ARGS (phi); i++)
1680 if (PHI_ARG_DEF (phi, i) == lhs)
1686 /* STMT is a MODIFY_EXPR for which we were unable to find RHS in the
1687 hash tables. Try to simplify the RHS using whatever equivalences
1688 we may have recorded.
1690 If we are able to simplify the RHS, then lookup the simplified form in
1691 the hash table and return the result. Otherwise return NULL. */
1694 simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *walk_data,
1695 tree stmt, int insert)
1697 tree rhs = TREE_OPERAND (stmt, 1);
1698 enum tree_code rhs_code = TREE_CODE (rhs);
1701 /* If we have lhs = ~x, look and see if we earlier had x = ~y.
1702 In which case we can change this statement to be lhs = y.
1703 Which can then be copy propagated.
1705 Similarly for negation. */
1706 if ((rhs_code == BIT_NOT_EXPR || rhs_code == NEGATE_EXPR)
1707 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
1709 /* Get the definition statement for our RHS. */
1710 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1712 /* See if the RHS_DEF_STMT has the same form as our statement. */
1713 if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR
1714 && TREE_CODE (TREE_OPERAND (rhs_def_stmt, 1)) == rhs_code)
1716 tree rhs_def_operand;
1718 rhs_def_operand = TREE_OPERAND (TREE_OPERAND (rhs_def_stmt, 1), 0);
1720 /* Verify that RHS_DEF_OPERAND is a suitable SSA variable. */
1721 if (TREE_CODE (rhs_def_operand) == SSA_NAME
1722 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))
1723 result = update_rhs_and_lookup_avail_expr (stmt,
1729 /* If we have z = (x OP C1), see if we earlier had x = y OP C2.
1730 If OP is associative, create and fold (y OP C2) OP C1 which
1731 should result in (y OP C3), use that as the RHS for the
1732 assignment. Add minus to this, as we handle it specially below. */
1733 if ((associative_tree_code (rhs_code) || rhs_code == MINUS_EXPR)
1734 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
1735 && is_gimple_min_invariant (TREE_OPERAND (rhs, 1)))
1737 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1739 /* If the statement defines an induction variable, do not propagate
1740 its value, so that we do not create overlapping life ranges. */
1741 if (simple_iv_increment_p (rhs_def_stmt))
1742 goto dont_fold_assoc;
1744 /* See if the RHS_DEF_STMT has the same form as our statement. */
1745 if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR)
1747 tree rhs_def_rhs = TREE_OPERAND (rhs_def_stmt, 1);
1748 enum tree_code rhs_def_code = TREE_CODE (rhs_def_rhs);
1750 if ((rhs_code == rhs_def_code && unsafe_associative_fp_binop (rhs))
1751 || (rhs_code == PLUS_EXPR && rhs_def_code == MINUS_EXPR)
1752 || (rhs_code == MINUS_EXPR && rhs_def_code == PLUS_EXPR))
1754 tree def_stmt_op0 = TREE_OPERAND (rhs_def_rhs, 0);
1755 tree def_stmt_op1 = TREE_OPERAND (rhs_def_rhs, 1);
1757 if (TREE_CODE (def_stmt_op0) == SSA_NAME
1758 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def_stmt_op0)
1759 && is_gimple_min_invariant (def_stmt_op1))
1761 tree outer_const = TREE_OPERAND (rhs, 1);
1762 tree type = TREE_TYPE (TREE_OPERAND (stmt, 0));
1765 /* If we care about correct floating point results, then
1766 don't fold x + c1 - c2. Note that we need to take both
1767 the codes and the signs to figure this out. */
1768 if (FLOAT_TYPE_P (type)
1769 && !flag_unsafe_math_optimizations
1770 && (rhs_def_code == PLUS_EXPR
1771 || rhs_def_code == MINUS_EXPR))
1775 neg ^= (rhs_code == MINUS_EXPR);
1776 neg ^= (rhs_def_code == MINUS_EXPR);
1777 neg ^= real_isneg (TREE_REAL_CST_PTR (outer_const));
1778 neg ^= real_isneg (TREE_REAL_CST_PTR (def_stmt_op1));
1781 goto dont_fold_assoc;
1784 /* Ho hum. So fold will only operate on the outermost
1785 thingy that we give it, so we have to build the new
1786 expression in two pieces. This requires that we handle
1787 combinations of plus and minus. */
1788 if (rhs_def_code != rhs_code)
1790 if (rhs_def_code == MINUS_EXPR)
1791 t = build (MINUS_EXPR, type, outer_const, def_stmt_op1);
1793 t = build (MINUS_EXPR, type, def_stmt_op1, outer_const);
1794 rhs_code = PLUS_EXPR;
1796 else if (rhs_def_code == MINUS_EXPR)
1797 t = build (PLUS_EXPR, type, def_stmt_op1, outer_const);
1799 t = build (rhs_def_code, type, def_stmt_op1, outer_const);
1801 t = build (rhs_code, type, def_stmt_op0, t);
1804 /* If the result is a suitable looking gimple expression,
1805 then use it instead of the original for STMT. */
1806 if (TREE_CODE (t) == SSA_NAME
1807 || (UNARY_CLASS_P (t)
1808 && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME)
1809 || ((BINARY_CLASS_P (t) || COMPARISON_CLASS_P (t))
1810 && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME
1811 && is_gimple_val (TREE_OPERAND (t, 1))))
1812 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1819 /* Transform TRUNC_DIV_EXPR and TRUNC_MOD_EXPR into RSHIFT_EXPR
1820 and BIT_AND_EXPR respectively if the first operand is greater
1821 than zero and the second operand is an exact power of two. */
1822 if ((rhs_code == TRUNC_DIV_EXPR || rhs_code == TRUNC_MOD_EXPR)
1823 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0)))
1824 && integer_pow2p (TREE_OPERAND (rhs, 1)))
1827 tree op = TREE_OPERAND (rhs, 0);
1829 if (TYPE_UNSIGNED (TREE_TYPE (op)))
1831 val = integer_one_node;
1835 tree dummy_cond = walk_data->global_data;
1839 dummy_cond = build (GT_EXPR, boolean_type_node,
1840 op, integer_zero_node);
1841 dummy_cond = build (COND_EXPR, void_type_node,
1842 dummy_cond, NULL, NULL);
1843 walk_data->global_data = dummy_cond;
1847 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), GT_EXPR);
1848 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op;
1849 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1)
1850 = integer_zero_node;
1852 val = simplify_cond_and_lookup_avail_expr (dummy_cond, NULL, false);
1855 if (val && integer_onep (val))
1858 tree op0 = TREE_OPERAND (rhs, 0);
1859 tree op1 = TREE_OPERAND (rhs, 1);
1861 if (rhs_code == TRUNC_DIV_EXPR)
1862 t = build (RSHIFT_EXPR, TREE_TYPE (op0), op0,
1863 build_int_cst (NULL_TREE, tree_log2 (op1)));
1865 t = build (BIT_AND_EXPR, TREE_TYPE (op0), op0,
1866 local_fold (build (MINUS_EXPR, TREE_TYPE (op1),
1867 op1, integer_one_node)));
1869 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1873 /* Transform ABS (X) into X or -X as appropriate. */
1874 if (rhs_code == ABS_EXPR
1875 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0))))
1878 tree op = TREE_OPERAND (rhs, 0);
1879 tree type = TREE_TYPE (op);
1881 if (TYPE_UNSIGNED (type))
1883 val = integer_zero_node;
1887 tree dummy_cond = walk_data->global_data;
1891 dummy_cond = build (LE_EXPR, boolean_type_node,
1892 op, integer_zero_node);
1893 dummy_cond = build (COND_EXPR, void_type_node,
1894 dummy_cond, NULL, NULL);
1895 walk_data->global_data = dummy_cond;
1899 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), LE_EXPR);
1900 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op;
1901 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1)
1902 = build_int_cst (type, 0);
1904 val = simplify_cond_and_lookup_avail_expr (dummy_cond, NULL, false);
1908 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), GE_EXPR);
1909 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op;
1910 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1)
1911 = build_int_cst (type, 0);
1913 val = simplify_cond_and_lookup_avail_expr (dummy_cond,
1918 if (integer_zerop (val))
1919 val = integer_one_node;
1920 else if (integer_onep (val))
1921 val = integer_zero_node;
1927 && (integer_onep (val) || integer_zerop (val)))
1931 if (integer_onep (val))
1932 t = build1 (NEGATE_EXPR, TREE_TYPE (op), op);
1936 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1940 /* Optimize *"foo" into 'f'. This is done here rather than
1941 in fold to avoid problems with stuff like &*"foo". */
1942 if (TREE_CODE (rhs) == INDIRECT_REF || TREE_CODE (rhs) == ARRAY_REF)
1944 tree t = fold_read_from_constant_string (rhs);
1947 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1953 /* COND is a condition of the form:
1955 x == const or x != const
1957 Look back to x's defining statement and see if x is defined as
1961 If const is unchanged if we convert it to type, then we can build
1962 the equivalent expression:
1965 y == const or y != const
1967 Which may allow further optimizations.
1969 Return the equivalent comparison or NULL if no such equivalent comparison
1973 find_equivalent_equality_comparison (tree cond)
1975 tree op0 = TREE_OPERAND (cond, 0);
1976 tree op1 = TREE_OPERAND (cond, 1);
1977 tree def_stmt = SSA_NAME_DEF_STMT (op0);
1979 /* OP0 might have been a parameter, so first make sure it
1980 was defined by a MODIFY_EXPR. */
1981 if (def_stmt && TREE_CODE (def_stmt) == MODIFY_EXPR)
1983 tree def_rhs = TREE_OPERAND (def_stmt, 1);
1985 /* Now make sure the RHS of the MODIFY_EXPR is a typecast. */
1986 if ((TREE_CODE (def_rhs) == NOP_EXPR
1987 || TREE_CODE (def_rhs) == CONVERT_EXPR)
1988 && TREE_CODE (TREE_OPERAND (def_rhs, 0)) == SSA_NAME)
1990 tree def_rhs_inner = TREE_OPERAND (def_rhs, 0);
1991 tree def_rhs_inner_type = TREE_TYPE (def_rhs_inner);
1994 if (TYPE_PRECISION (def_rhs_inner_type)
1995 > TYPE_PRECISION (TREE_TYPE (def_rhs)))
1998 /* What we want to prove is that if we convert OP1 to
1999 the type of the object inside the NOP_EXPR that the
2000 result is still equivalent to SRC.
2002 If that is true, the build and return new equivalent
2003 condition which uses the source of the typecast and the
2004 new constant (which has only changed its type). */
2005 new = build1 (TREE_CODE (def_rhs), def_rhs_inner_type, op1);
2006 new = local_fold (new);
2007 if (is_gimple_val (new) && tree_int_cst_equal (new, op1))
2008 return build (TREE_CODE (cond), TREE_TYPE (cond),
2009 def_rhs_inner, new);
2015 /* STMT is a COND_EXPR for which we could not trivially determine its
2016 result. This routine attempts to find equivalent forms of the
2017 condition which we may be able to optimize better. It also
2018 uses simple value range propagation to optimize conditionals. */
2021 simplify_cond_and_lookup_avail_expr (tree stmt,
2025 tree cond = COND_EXPR_COND (stmt);
2027 if (COMPARISON_CLASS_P (cond))
2029 tree op0 = TREE_OPERAND (cond, 0);
2030 tree op1 = TREE_OPERAND (cond, 1);
2032 if (TREE_CODE (op0) == SSA_NAME && is_gimple_min_invariant (op1))
2035 tree low, high, cond_low, cond_high;
2036 int lowequal, highequal, swapped, no_overlap, subset, cond_inverted;
2037 varray_type vrp_records;
2038 struct vrp_element *element;
2039 struct vrp_hash_elt vrp_hash_elt, *vrp_hash_elt_p;
2042 /* First see if we have test of an SSA_NAME against a constant
2043 where the SSA_NAME is defined by an earlier typecast which
2044 is irrelevant when performing tests against the given
2046 if (TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
2048 tree new_cond = find_equivalent_equality_comparison (cond);
2052 /* Update the statement to use the new equivalent
2054 COND_EXPR_COND (stmt) = new_cond;
2056 /* If this is not a real stmt, ann will be NULL and we
2057 avoid processing the operands. */
2059 mark_stmt_modified (stmt);
2061 /* Lookup the condition and return its known value if it
2063 new_cond = lookup_avail_expr (stmt, insert);
2067 /* The operands have changed, so update op0 and op1. */
2068 op0 = TREE_OPERAND (cond, 0);
2069 op1 = TREE_OPERAND (cond, 1);
2073 /* Consult the value range records for this variable (if they exist)
2074 to see if we can eliminate or simplify this conditional.
2076 Note two tests are necessary to determine no records exist.
2077 First we have to see if the virtual array exists, if it
2078 exists, then we have to check its active size.
2080 Also note the vast majority of conditionals are not testing
2081 a variable which has had its range constrained by an earlier
2082 conditional. So this filter avoids a lot of unnecessary work. */
2083 vrp_hash_elt.var = op0;
2084 vrp_hash_elt.records = NULL;
2085 slot = htab_find_slot (vrp_data, &vrp_hash_elt, NO_INSERT);
2089 vrp_hash_elt_p = (struct vrp_hash_elt *) *slot;
2090 vrp_records = vrp_hash_elt_p->records;
2091 if (vrp_records == NULL)
2094 limit = VARRAY_ACTIVE_SIZE (vrp_records);
2096 /* If we have no value range records for this variable, or we are
2097 unable to extract a range for this condition, then there is
2100 || ! extract_range_from_cond (cond, &cond_high,
2101 &cond_low, &cond_inverted))
2104 /* We really want to avoid unnecessary computations of range
2105 info. So all ranges are computed lazily; this avoids a
2106 lot of unnecessary work. i.e., we record the conditional,
2107 but do not process how it constrains the variable's
2108 potential values until we know that processing the condition
2111 However, we do not want to have to walk a potentially long
2112 list of ranges, nor do we want to compute a variable's
2113 range more than once for a given path.
2115 Luckily, each time we encounter a conditional that can not
2116 be otherwise optimized we will end up here and we will
2117 compute the necessary range information for the variable
2118 used in this condition.
2120 Thus you can conclude that there will never be more than one
2121 conditional associated with a variable which has not been
2122 processed. So we never need to merge more than one new
2123 conditional into the current range.
2125 These properties also help us avoid unnecessary work. */
2127 = (struct vrp_element *)VARRAY_GENERIC_PTR (vrp_records, limit - 1);
2129 if (element->high && element->low)
2131 /* The last element has been processed, so there is no range
2132 merging to do, we can simply use the high/low values
2133 recorded in the last element. */
2135 high = element->high;
2139 tree tmp_high, tmp_low;
2142 /* The last element has not been processed. Process it now.
2143 record_range should ensure for cond inverted is not set.
2144 This call can only fail if cond is x < min or x > max,
2145 which fold should have optimized into false.
2146 If that doesn't happen, just pretend all values are
2148 if (! extract_range_from_cond (element->cond, &tmp_high,
2152 gcc_assert (dummy == 0);
2154 /* If this is the only element, then no merging is necessary,
2155 the high/low values from extract_range_from_cond are all
2164 /* Get the high/low value from the previous element. */
2165 struct vrp_element *prev
2166 = (struct vrp_element *)VARRAY_GENERIC_PTR (vrp_records,
2171 /* Merge in this element's range with the range from the
2174 The low value for the merged range is the maximum of
2175 the previous low value and the low value of this record.
2177 Similarly the high value for the merged range is the
2178 minimum of the previous high value and the high value of
2180 low = (low && tree_int_cst_compare (low, tmp_low) == 1
2182 high = (high && tree_int_cst_compare (high, tmp_high) == -1
2186 /* And record the computed range. */
2188 element->high = high;
2192 /* After we have constrained this variable's potential values,
2193 we try to determine the result of the given conditional.
2195 To simplify later tests, first determine if the current
2196 low value is the same low value as the conditional.
2197 Similarly for the current high value and the high value
2198 for the conditional. */
2199 lowequal = tree_int_cst_equal (low, cond_low);
2200 highequal = tree_int_cst_equal (high, cond_high);
2202 if (lowequal && highequal)
2203 return (cond_inverted ? boolean_false_node : boolean_true_node);
2205 /* To simplify the overlap/subset tests below we may want
2206 to swap the two ranges so that the larger of the two
2207 ranges occurs "first". */
2209 if (tree_int_cst_compare (low, cond_low) == 1
2211 && tree_int_cst_compare (cond_high, high) == 1))
2224 /* Now determine if there is no overlap in the ranges
2225 or if the second range is a subset of the first range. */
2226 no_overlap = tree_int_cst_lt (high, cond_low);
2227 subset = tree_int_cst_compare (cond_high, high) != 1;
2229 /* If there was no overlap in the ranges, then this conditional
2230 always has a false value (unless we had to invert this
2231 conditional, in which case it always has a true value). */
2233 return (cond_inverted ? boolean_true_node : boolean_false_node);
2235 /* If the current range is a subset of the condition's range,
2236 then this conditional always has a true value (unless we
2237 had to invert this conditional, in which case it always
2238 has a true value). */
2239 if (subset && swapped)
2240 return (cond_inverted ? boolean_false_node : boolean_true_node);
2242 /* We were unable to determine the result of the conditional.
2243 However, we may be able to simplify the conditional. First
2244 merge the ranges in the same manner as range merging above. */
2245 low = tree_int_cst_compare (low, cond_low) == 1 ? low : cond_low;
2246 high = tree_int_cst_compare (high, cond_high) == -1 ? high : cond_high;
2248 /* If the range has converged to a single point, then turn this
2249 into an equality comparison. */
2250 if (TREE_CODE (cond) != EQ_EXPR
2251 && TREE_CODE (cond) != NE_EXPR
2252 && tree_int_cst_equal (low, high))
2254 TREE_SET_CODE (cond, EQ_EXPR);
2255 TREE_OPERAND (cond, 1) = high;
2262 /* STMT is a SWITCH_EXPR for which we could not trivially determine its
2263 result. This routine attempts to find equivalent forms of the
2264 condition which we may be able to optimize better. */
2267 simplify_switch_and_lookup_avail_expr (tree stmt, int insert)
2269 tree cond = SWITCH_COND (stmt);
2272 /* The optimization that we really care about is removing unnecessary
2273 casts. That will let us do much better in propagating the inferred
2274 constant at the switch target. */
2275 if (TREE_CODE (cond) == SSA_NAME)
2277 def = SSA_NAME_DEF_STMT (cond);
2278 if (TREE_CODE (def) == MODIFY_EXPR)
2280 def = TREE_OPERAND (def, 1);
2281 if (TREE_CODE (def) == NOP_EXPR)
2286 def = TREE_OPERAND (def, 0);
2288 #ifdef ENABLE_CHECKING
2289 /* ??? Why was Jeff testing this? We are gimple... */
2290 gcc_assert (is_gimple_val (def));
2293 to = TREE_TYPE (cond);
2294 ti = TREE_TYPE (def);
2296 /* If we have an extension that preserves value, then we
2297 can copy the source value into the switch. */
2299 need_precision = TYPE_PRECISION (ti);
2301 if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
2303 else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
2304 need_precision += 1;
2305 if (TYPE_PRECISION (to) < need_precision)
2310 SWITCH_COND (stmt) = def;
2311 mark_stmt_modified (stmt);
2313 return lookup_avail_expr (stmt, insert);
2323 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2324 known value for that SSA_NAME (or NULL if no value is known).
2326 NONZERO_VARS is the set SSA_NAMES known to have a nonzero value,
2327 even if we don't know their precise value.
2329 Propagate values from CONST_AND_COPIES and NONZERO_VARS into the PHI
2330 nodes of the successors of BB. */
2333 cprop_into_successor_phis (basic_block bb, bitmap nonzero_vars)
2338 FOR_EACH_EDGE (e, ei, bb->succs)
2343 /* If this is an abnormal edge, then we do not want to copy propagate
2344 into the PHI alternative associated with this edge. */
2345 if (e->flags & EDGE_ABNORMAL)
2348 phi = phi_nodes (e->dest);
2353 for ( ; phi; phi = PHI_CHAIN (phi))
2356 use_operand_p orig_p;
2359 /* The alternative may be associated with a constant, so verify
2360 it is an SSA_NAME before doing anything with it. */
2361 orig_p = PHI_ARG_DEF_PTR (phi, indx);
2362 orig = USE_FROM_PTR (orig_p);
2363 if (TREE_CODE (orig) != SSA_NAME)
2366 /* If the alternative is known to have a nonzero value, record
2367 that fact in the PHI node itself for future use. */
2368 if (bitmap_bit_p (nonzero_vars, SSA_NAME_VERSION (orig)))
2369 PHI_ARG_NONZERO (phi, indx) = true;
2371 /* If we have *ORIG_P in our constant/copy table, then replace
2372 ORIG_P with its value in our constant/copy table. */
2373 new = SSA_NAME_VALUE (orig);
2376 && (TREE_CODE (new) == SSA_NAME
2377 || is_gimple_min_invariant (new))
2378 && may_propagate_copy (orig, new))
2379 propagate_value (orig_p, new);
2384 /* We have finished optimizing BB, record any information implied by
2385 taking a specific outgoing edge from BB. */
2388 record_edge_info (basic_block bb)
2390 block_stmt_iterator bsi = bsi_last (bb);
2391 struct edge_info *edge_info;
2393 if (! bsi_end_p (bsi))
2395 tree stmt = bsi_stmt (bsi);
2397 if (stmt && TREE_CODE (stmt) == SWITCH_EXPR)
2399 tree cond = SWITCH_COND (stmt);
2401 if (TREE_CODE (cond) == SSA_NAME)
2403 tree labels = SWITCH_LABELS (stmt);
2404 int i, n_labels = TREE_VEC_LENGTH (labels);
2405 tree *info = xcalloc (n_basic_blocks, sizeof (tree));
2409 for (i = 0; i < n_labels; i++)
2411 tree label = TREE_VEC_ELT (labels, i);
2412 basic_block target_bb = label_to_block (CASE_LABEL (label));
2414 if (CASE_HIGH (label)
2415 || !CASE_LOW (label)
2416 || info[target_bb->index])
2417 info[target_bb->index] = error_mark_node;
2419 info[target_bb->index] = label;
2422 FOR_EACH_EDGE (e, ei, bb->succs)
2424 basic_block target_bb = e->dest;
2425 tree node = info[target_bb->index];
2427 if (node != NULL && node != error_mark_node)
2429 tree x = fold_convert (TREE_TYPE (cond), CASE_LOW (node));
2430 edge_info = allocate_edge_info (e);
2431 edge_info->lhs = cond;
2439 /* A COND_EXPR may create equivalences too. */
2440 if (stmt && TREE_CODE (stmt) == COND_EXPR)
2442 tree cond = COND_EXPR_COND (stmt);
2446 extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
2448 /* If the conditional is a single variable 'X', record 'X = 1'
2449 for the true edge and 'X = 0' on the false edge. */
2450 if (SSA_VAR_P (cond))
2452 struct edge_info *edge_info;
2454 edge_info = allocate_edge_info (true_edge);
2455 edge_info->lhs = cond;
2456 edge_info->rhs = constant_boolean_node (1, TREE_TYPE (cond));
2458 edge_info = allocate_edge_info (false_edge);
2459 edge_info->lhs = cond;
2460 edge_info->rhs = constant_boolean_node (0, TREE_TYPE (cond));
2462 /* Equality tests may create one or two equivalences. */
2463 else if (COMPARISON_CLASS_P (cond))
2465 tree op0 = TREE_OPERAND (cond, 0);
2466 tree op1 = TREE_OPERAND (cond, 1);
2468 /* Special case comparing booleans against a constant as we
2469 know the value of OP0 on both arms of the branch. i.e., we
2470 can record an equivalence for OP0 rather than COND. */
2471 if ((TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
2472 && TREE_CODE (op0) == SSA_NAME
2473 && TREE_CODE (TREE_TYPE (op0)) == BOOLEAN_TYPE
2474 && is_gimple_min_invariant (op1))
2476 if (TREE_CODE (cond) == EQ_EXPR)
2478 edge_info = allocate_edge_info (true_edge);
2479 edge_info->lhs = op0;
2480 edge_info->rhs = (integer_zerop (op1)
2481 ? boolean_false_node
2482 : boolean_true_node);
2484 edge_info = allocate_edge_info (false_edge);
2485 edge_info->lhs = op0;
2486 edge_info->rhs = (integer_zerop (op1)
2488 : boolean_false_node);
2492 edge_info = allocate_edge_info (true_edge);
2493 edge_info->lhs = op0;
2494 edge_info->rhs = (integer_zerop (op1)
2496 : boolean_false_node);
2498 edge_info = allocate_edge_info (false_edge);
2499 edge_info->lhs = op0;
2500 edge_info->rhs = (integer_zerop (op1)
2501 ? boolean_false_node
2502 : boolean_true_node);
2506 else if (is_gimple_min_invariant (op0)
2507 && (TREE_CODE (op1) == SSA_NAME
2508 || is_gimple_min_invariant (op1)))
2510 tree inverted = invert_truthvalue (cond);
2511 struct edge_info *edge_info;
2513 edge_info = allocate_edge_info (true_edge);
2514 record_conditions (edge_info, cond, inverted);
2516 if (TREE_CODE (cond) == EQ_EXPR)
2518 edge_info->lhs = op1;
2519 edge_info->rhs = op0;
2522 edge_info = allocate_edge_info (false_edge);
2523 record_conditions (edge_info, inverted, cond);
2525 if (TREE_CODE (cond) == NE_EXPR)
2527 edge_info->lhs = op1;
2528 edge_info->rhs = op0;
2532 else if (TREE_CODE (op0) == SSA_NAME
2533 && (is_gimple_min_invariant (op1)
2534 || TREE_CODE (op1) == SSA_NAME))
2536 tree inverted = invert_truthvalue (cond);
2537 struct edge_info *edge_info;
2539 edge_info = allocate_edge_info (true_edge);
2540 record_conditions (edge_info, cond, inverted);
2542 if (TREE_CODE (cond) == EQ_EXPR)
2544 edge_info->lhs = op0;
2545 edge_info->rhs = op1;
2548 edge_info = allocate_edge_info (false_edge);
2549 record_conditions (edge_info, inverted, cond);
2551 if (TREE_CODE (cond) == NE_EXPR)
2553 edge_info->lhs = op0;
2554 edge_info->rhs = op1;
2559 /* ??? TRUTH_NOT_EXPR can create an equivalence too. */
2564 /* Propagate information from BB to its outgoing edges.
2566 This can include equivalency information implied by control statements
2567 at the end of BB and const/copy propagation into PHIs in BB's
2568 successor blocks. */
2571 propagate_to_outgoing_edges (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
2574 record_edge_info (bb);
2575 cprop_into_successor_phis (bb, nonzero_vars);
2578 /* Search for redundant computations in STMT. If any are found, then
2579 replace them with the variable holding the result of the computation.
2581 If safe, record this expression into the available expression hash
2585 eliminate_redundant_computations (struct dom_walk_data *walk_data,
2586 tree stmt, stmt_ann_t ann)
2588 tree *expr_p, def = NULL_TREE;
2591 bool retval = false;
2593 if (TREE_CODE (stmt) == MODIFY_EXPR)
2594 def = TREE_OPERAND (stmt, 0);
2596 /* Certain expressions on the RHS can be optimized away, but can not
2597 themselves be entered into the hash tables. */
2598 if (ann->makes_aliased_stores
2600 || TREE_CODE (def) != SSA_NAME
2601 || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def)
2602 || !ZERO_SSA_OPERANDS (stmt, SSA_OP_VMAYDEF)
2603 /* Do not record equivalences for increments of ivs. This would create
2604 overlapping live ranges for a very questionable gain. */
2605 || simple_iv_increment_p (stmt))
2608 /* Check if the expression has been computed before. */
2609 cached_lhs = lookup_avail_expr (stmt, insert);
2611 /* If this is an assignment and the RHS was not in the hash table,
2612 then try to simplify the RHS and lookup the new RHS in the
2614 if (! cached_lhs && TREE_CODE (stmt) == MODIFY_EXPR)
2615 cached_lhs = simplify_rhs_and_lookup_avail_expr (walk_data, stmt, insert);
2616 /* Similarly if this is a COND_EXPR and we did not find its
2617 expression in the hash table, simplify the condition and
2619 else if (! cached_lhs && TREE_CODE (stmt) == COND_EXPR)
2620 cached_lhs = simplify_cond_and_lookup_avail_expr (stmt, ann, insert);
2621 /* Similarly for a SWITCH_EXPR. */
2622 else if (!cached_lhs && TREE_CODE (stmt) == SWITCH_EXPR)
2623 cached_lhs = simplify_switch_and_lookup_avail_expr (stmt, insert);
2625 opt_stats.num_exprs_considered++;
2627 /* Get a pointer to the expression we are trying to optimize. */
2628 if (TREE_CODE (stmt) == COND_EXPR)
2629 expr_p = &COND_EXPR_COND (stmt);
2630 else if (TREE_CODE (stmt) == SWITCH_EXPR)
2631 expr_p = &SWITCH_COND (stmt);
2632 else if (TREE_CODE (stmt) == RETURN_EXPR && TREE_OPERAND (stmt, 0))
2633 expr_p = &TREE_OPERAND (TREE_OPERAND (stmt, 0), 1);
2635 expr_p = &TREE_OPERAND (stmt, 1);
2637 /* It is safe to ignore types here since we have already done
2638 type checking in the hashing and equality routines. In fact
2639 type checking here merely gets in the way of constant
2640 propagation. Also, make sure that it is safe to propagate
2641 CACHED_LHS into *EXPR_P. */
2643 && (TREE_CODE (cached_lhs) != SSA_NAME
2644 || may_propagate_copy (*expr_p, cached_lhs)))
2646 if (dump_file && (dump_flags & TDF_DETAILS))
2648 fprintf (dump_file, " Replaced redundant expr '");
2649 print_generic_expr (dump_file, *expr_p, dump_flags);
2650 fprintf (dump_file, "' with '");
2651 print_generic_expr (dump_file, cached_lhs, dump_flags);
2652 fprintf (dump_file, "'\n");
2657 #if defined ENABLE_CHECKING
2658 gcc_assert (TREE_CODE (cached_lhs) == SSA_NAME
2659 || is_gimple_min_invariant (cached_lhs));
2662 if (TREE_CODE (cached_lhs) == ADDR_EXPR
2663 || (POINTER_TYPE_P (TREE_TYPE (*expr_p))
2664 && is_gimple_min_invariant (cached_lhs)))
2667 propagate_tree_value (expr_p, cached_lhs);
2668 mark_stmt_modified (stmt);
2673 /* STMT, a MODIFY_EXPR, may create certain equivalences, in either
2674 the available expressions table or the const_and_copies table.
2675 Detect and record those equivalences. */
2678 record_equivalences_from_stmt (tree stmt,
2682 tree lhs = TREE_OPERAND (stmt, 0);
2683 enum tree_code lhs_code = TREE_CODE (lhs);
2686 if (lhs_code == SSA_NAME)
2688 tree rhs = TREE_OPERAND (stmt, 1);
2690 /* Strip away any useless type conversions. */
2691 STRIP_USELESS_TYPE_CONVERSION (rhs);
2693 /* If the RHS of the assignment is a constant or another variable that
2694 may be propagated, register it in the CONST_AND_COPIES table. We
2695 do not need to record unwind data for this, since this is a true
2696 assignment and not an equivalence inferred from a comparison. All
2697 uses of this ssa name are dominated by this assignment, so unwinding
2698 just costs time and space. */
2700 && (TREE_CODE (rhs) == SSA_NAME
2701 || is_gimple_min_invariant (rhs)))
2702 SSA_NAME_VALUE (lhs) = rhs;
2704 if (expr_computes_nonzero (rhs))
2705 record_var_is_nonzero (lhs);
2708 /* Look at both sides for pointer dereferences. If we find one, then
2709 the pointer must be nonnull and we can enter that equivalence into
2711 if (flag_delete_null_pointer_checks)
2712 for (i = 0; i < 2; i++)
2714 tree t = TREE_OPERAND (stmt, i);
2716 /* Strip away any COMPONENT_REFs. */
2717 while (TREE_CODE (t) == COMPONENT_REF)
2718 t = TREE_OPERAND (t, 0);
2720 /* Now see if this is a pointer dereference. */
2721 if (INDIRECT_REF_P (t))
2723 tree op = TREE_OPERAND (t, 0);
2725 /* If the pointer is a SSA variable, then enter new
2726 equivalences into the hash table. */
2727 while (TREE_CODE (op) == SSA_NAME)
2729 tree def = SSA_NAME_DEF_STMT (op);
2731 record_var_is_nonzero (op);
2733 /* And walk up the USE-DEF chains noting other SSA_NAMEs
2734 which are known to have a nonzero value. */
2736 && TREE_CODE (def) == MODIFY_EXPR
2737 && TREE_CODE (TREE_OPERAND (def, 1)) == NOP_EXPR)
2738 op = TREE_OPERAND (TREE_OPERAND (def, 1), 0);
2745 /* A memory store, even an aliased store, creates a useful
2746 equivalence. By exchanging the LHS and RHS, creating suitable
2747 vops and recording the result in the available expression table,
2748 we may be able to expose more redundant loads. */
2749 if (!ann->has_volatile_ops
2750 && (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME
2751 || is_gimple_min_invariant (TREE_OPERAND (stmt, 1)))
2752 && !is_gimple_reg (lhs))
2754 tree rhs = TREE_OPERAND (stmt, 1);
2757 /* FIXME: If the LHS of the assignment is a bitfield and the RHS
2758 is a constant, we need to adjust the constant to fit into the
2759 type of the LHS. If the LHS is a bitfield and the RHS is not
2760 a constant, then we can not record any equivalences for this
2761 statement since we would need to represent the widening or
2762 narrowing of RHS. This fixes gcc.c-torture/execute/921016-1.c
2763 and should not be necessary if GCC represented bitfields
2765 if (lhs_code == COMPONENT_REF
2766 && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1)))
2768 if (TREE_CONSTANT (rhs))
2769 rhs = widen_bitfield (rhs, TREE_OPERAND (lhs, 1), lhs);
2773 /* If the value overflowed, then we can not use this equivalence. */
2774 if (rhs && ! is_gimple_min_invariant (rhs))
2780 /* Build a new statement with the RHS and LHS exchanged. */
2781 new = build (MODIFY_EXPR, TREE_TYPE (stmt), rhs, lhs);
2783 create_ssa_artficial_load_stmt (new, stmt);
2785 /* Finally enter the statement into the available expression
2787 lookup_avail_expr (new, true);
2792 /* Replace *OP_P in STMT with any known equivalent value for *OP_P from
2793 CONST_AND_COPIES. */
2796 cprop_operand (tree stmt, use_operand_p op_p)
2798 bool may_have_exposed_new_symbols = false;
2800 tree op = USE_FROM_PTR (op_p);
2802 /* If the operand has a known constant value or it is known to be a
2803 copy of some other variable, use the value or copy stored in
2804 CONST_AND_COPIES. */
2805 val = SSA_NAME_VALUE (op);
2806 if (val && val != op && TREE_CODE (val) != VALUE_HANDLE)
2808 tree op_type, val_type;
2810 /* Do not change the base variable in the virtual operand
2811 tables. That would make it impossible to reconstruct
2812 the renamed virtual operand if we later modify this
2813 statement. Also only allow the new value to be an SSA_NAME
2814 for propagation into virtual operands. */
2815 if (!is_gimple_reg (op)
2816 && (TREE_CODE (val) != SSA_NAME
2817 || is_gimple_reg (val)
2818 || get_virtual_var (val) != get_virtual_var (op)))
2821 /* Do not replace hard register operands in asm statements. */
2822 if (TREE_CODE (stmt) == ASM_EXPR
2823 && !may_propagate_copy_into_asm (op))
2826 /* Get the toplevel type of each operand. */
2827 op_type = TREE_TYPE (op);
2828 val_type = TREE_TYPE (val);
2830 /* While both types are pointers, get the type of the object
2832 while (POINTER_TYPE_P (op_type) && POINTER_TYPE_P (val_type))
2834 op_type = TREE_TYPE (op_type);
2835 val_type = TREE_TYPE (val_type);
2838 /* Make sure underlying types match before propagating a constant by
2839 converting the constant to the proper type. Note that convert may
2840 return a non-gimple expression, in which case we ignore this
2841 propagation opportunity. */
2842 if (TREE_CODE (val) != SSA_NAME)
2844 if (!lang_hooks.types_compatible_p (op_type, val_type))
2846 val = fold_convert (TREE_TYPE (op), val);
2847 if (!is_gimple_min_invariant (val))
2852 /* Certain operands are not allowed to be copy propagated due
2853 to their interaction with exception handling and some GCC
2855 else if (!may_propagate_copy (op, val))
2858 /* Do not propagate copies if the propagated value is at a deeper loop
2859 depth than the propagatee. Otherwise, this may move loop variant
2860 variables outside of their loops and prevent coalescing
2861 opportunities. If the value was loop invariant, it will be hoisted
2862 by LICM and exposed for copy propagation. */
2863 if (loop_depth_of_name (val) > loop_depth_of_name (op))
2867 if (dump_file && (dump_flags & TDF_DETAILS))
2869 fprintf (dump_file, " Replaced '");
2870 print_generic_expr (dump_file, op, dump_flags);
2871 fprintf (dump_file, "' with %s '",
2872 (TREE_CODE (val) != SSA_NAME ? "constant" : "variable"));
2873 print_generic_expr (dump_file, val, dump_flags);
2874 fprintf (dump_file, "'\n");
2877 /* If VAL is an ADDR_EXPR or a constant of pointer type, note
2878 that we may have exposed a new symbol for SSA renaming. */
2879 if (TREE_CODE (val) == ADDR_EXPR
2880 || (POINTER_TYPE_P (TREE_TYPE (op))
2881 && is_gimple_min_invariant (val)))
2882 may_have_exposed_new_symbols = true;
2884 if (TREE_CODE (val) != SSA_NAME)
2885 opt_stats.num_const_prop++;
2887 opt_stats.num_copy_prop++;
2889 propagate_value (op_p, val);
2891 /* And note that we modified this statement. This is now
2892 safe, even if we changed virtual operands since we will
2893 rescan the statement and rewrite its operands again. */
2894 mark_stmt_modified (stmt);
2896 return may_have_exposed_new_symbols;
2899 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2900 known value for that SSA_NAME (or NULL if no value is known).
2902 Propagate values from CONST_AND_COPIES into the uses, vuses and
2903 v_may_def_ops of STMT. */
2906 cprop_into_stmt (tree stmt)
2908 bool may_have_exposed_new_symbols = false;
2913 FOR_EACH_SSA_USE_OPERAND (op_p, stmt, iter, SSA_OP_ALL_USES)
2915 if (TREE_CODE (USE_FROM_PTR (op_p)) == SSA_NAME)
2916 may_have_exposed_new_symbols |= cprop_operand (stmt, op_p);
2919 if (may_have_exposed_new_symbols)
2921 rhs = get_rhs (stmt);
2922 if (rhs && TREE_CODE (rhs) == ADDR_EXPR)
2923 recompute_tree_invarant_for_addr_expr (rhs);
2926 return may_have_exposed_new_symbols;
2930 /* Optimize the statement pointed by iterator SI.
2932 We try to perform some simplistic global redundancy elimination and
2933 constant propagation:
2935 1- To detect global redundancy, we keep track of expressions that have
2936 been computed in this block and its dominators. If we find that the
2937 same expression is computed more than once, we eliminate repeated
2938 computations by using the target of the first one.
2940 2- Constant values and copy assignments. This is used to do very
2941 simplistic constant and copy propagation. When a constant or copy
2942 assignment is found, we map the value on the RHS of the assignment to
2943 the variable in the LHS in the CONST_AND_COPIES table. */
2946 optimize_stmt (struct dom_walk_data *walk_data, basic_block bb,
2947 block_stmt_iterator si)
2950 tree stmt, old_stmt;
2951 bool may_optimize_p;
2952 bool may_have_exposed_new_symbols = false;
2954 old_stmt = stmt = bsi_stmt (si);
2956 update_stmt_if_modified (stmt);
2957 ann = stmt_ann (stmt);
2958 opt_stats.num_stmts++;
2959 may_have_exposed_new_symbols = false;
2961 if (dump_file && (dump_flags & TDF_DETAILS))
2963 fprintf (dump_file, "Optimizing statement ");
2964 print_generic_stmt (dump_file, stmt, TDF_SLIM);
2967 /* Const/copy propagate into USES, VUSES and the RHS of V_MAY_DEFs. */
2968 may_have_exposed_new_symbols = cprop_into_stmt (stmt);
2970 /* If the statement has been modified with constant replacements,
2971 fold its RHS before checking for redundant computations. */
2974 /* Try to fold the statement making sure that STMT is kept
2976 if (fold_stmt (bsi_stmt_ptr (si)))
2978 stmt = bsi_stmt (si);
2979 ann = stmt_ann (stmt);
2981 if (dump_file && (dump_flags & TDF_DETAILS))
2983 fprintf (dump_file, " Folded to: ");
2984 print_generic_stmt (dump_file, stmt, TDF_SLIM);
2988 /* Constant/copy propagation above may change the set of
2989 virtual operands associated with this statement. Folding
2990 may remove the need for some virtual operands.
2992 Indicate we will need to rescan and rewrite the statement. */
2993 may_have_exposed_new_symbols = true;
2996 /* Check for redundant computations. Do this optimization only
2997 for assignments that have no volatile ops and conditionals. */
2998 may_optimize_p = (!ann->has_volatile_ops
2999 && ((TREE_CODE (stmt) == RETURN_EXPR
3000 && TREE_OPERAND (stmt, 0)
3001 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR
3002 && ! (TREE_SIDE_EFFECTS
3003 (TREE_OPERAND (TREE_OPERAND (stmt, 0), 1))))
3004 || (TREE_CODE (stmt) == MODIFY_EXPR
3005 && ! TREE_SIDE_EFFECTS (TREE_OPERAND (stmt, 1)))
3006 || TREE_CODE (stmt) == COND_EXPR
3007 || TREE_CODE (stmt) == SWITCH_EXPR));
3010 may_have_exposed_new_symbols
3011 |= eliminate_redundant_computations (walk_data, stmt, ann);
3013 /* Record any additional equivalences created by this statement. */
3014 if (TREE_CODE (stmt) == MODIFY_EXPR)
3015 record_equivalences_from_stmt (stmt,
3019 /* If STMT is a COND_EXPR and it was modified, then we may know
3020 where it goes. If that is the case, then mark the CFG as altered.
3022 This will cause us to later call remove_unreachable_blocks and
3023 cleanup_tree_cfg when it is safe to do so. It is not safe to
3024 clean things up here since removal of edges and such can trigger
3025 the removal of PHI nodes, which in turn can release SSA_NAMEs to
3028 That's all fine and good, except that once SSA_NAMEs are released
3029 to the manager, we must not call create_ssa_name until all references
3030 to released SSA_NAMEs have been eliminated.
3032 All references to the deleted SSA_NAMEs can not be eliminated until
3033 we remove unreachable blocks.
3035 We can not remove unreachable blocks until after we have completed
3036 any queued jump threading.
3038 We can not complete any queued jump threads until we have taken
3039 appropriate variables out of SSA form. Taking variables out of
3040 SSA form can call create_ssa_name and thus we lose.
3042 Ultimately I suspect we're going to need to change the interface
3043 into the SSA_NAME manager. */
3049 if (TREE_CODE (stmt) == COND_EXPR)
3050 val = COND_EXPR_COND (stmt);
3051 else if (TREE_CODE (stmt) == SWITCH_EXPR)
3052 val = SWITCH_COND (stmt);
3054 if (val && TREE_CODE (val) == INTEGER_CST && find_taken_edge (bb, val))
3057 /* If we simplified a statement in such a way as to be shown that it
3058 cannot trap, update the eh information and the cfg to match. */
3059 if (maybe_clean_or_replace_eh_stmt (old_stmt, stmt))
3061 bitmap_set_bit (need_eh_cleanup, bb->index);
3062 if (dump_file && (dump_flags & TDF_DETAILS))
3063 fprintf (dump_file, " Flagged to clear EH edges.\n");
3067 if (may_have_exposed_new_symbols)
3068 VEC_safe_push (tree, heap, stmts_to_rescan, bsi_stmt (si));
3071 /* Replace the RHS of STMT with NEW_RHS. If RHS can be found in the
3072 available expression hashtable, then return the LHS from the hash
3075 If INSERT is true, then we also update the available expression
3076 hash table to account for the changes made to STMT. */
3079 update_rhs_and_lookup_avail_expr (tree stmt, tree new_rhs, bool insert)
3081 tree cached_lhs = NULL;
3083 /* Remove the old entry from the hash table. */
3086 struct expr_hash_elt element;
3088 initialize_hash_element (stmt, NULL, &element);
3089 htab_remove_elt_with_hash (avail_exprs, &element, element.hash);
3092 /* Now update the RHS of the assignment. */
3093 TREE_OPERAND (stmt, 1) = new_rhs;
3095 /* Now lookup the updated statement in the hash table. */
3096 cached_lhs = lookup_avail_expr (stmt, insert);
3098 /* We have now called lookup_avail_expr twice with two different
3099 versions of this same statement, once in optimize_stmt, once here.
3101 We know the call in optimize_stmt did not find an existing entry
3102 in the hash table, so a new entry was created. At the same time
3103 this statement was pushed onto the AVAIL_EXPRS_STACK vector.
3105 If this call failed to find an existing entry on the hash table,
3106 then the new version of this statement was entered into the
3107 hash table. And this statement was pushed onto BLOCK_AVAIL_EXPR
3108 for the second time. So there are two copies on BLOCK_AVAIL_EXPRs
3110 If this call succeeded, we still have one copy of this statement
3111 on the BLOCK_AVAIL_EXPRs vector.
3113 For both cases, we need to pop the most recent entry off the
3114 BLOCK_AVAIL_EXPRs vector. For the case where we never found this
3115 statement in the hash tables, that will leave precisely one
3116 copy of this statement on BLOCK_AVAIL_EXPRs. For the case where
3117 we found a copy of this statement in the second hash table lookup
3118 we want _no_ copies of this statement in BLOCK_AVAIL_EXPRs. */
3120 VEC_pop (tree, avail_exprs_stack);
3122 /* And make sure we record the fact that we modified this
3124 mark_stmt_modified (stmt);
3129 /* Search for an existing instance of STMT in the AVAIL_EXPRS table. If
3130 found, return its LHS. Otherwise insert STMT in the table and return
3133 Also, when an expression is first inserted in the AVAIL_EXPRS table, it
3134 is also added to the stack pointed by BLOCK_AVAIL_EXPRS_P, so that they
3135 can be removed when we finish processing this block and its children.
3137 NOTE: This function assumes that STMT is a MODIFY_EXPR node that
3138 contains no CALL_EXPR on its RHS and makes no volatile nor
3139 aliased references. */
3142 lookup_avail_expr (tree stmt, bool insert)
3147 struct expr_hash_elt *element = xmalloc (sizeof (struct expr_hash_elt));
3149 lhs = TREE_CODE (stmt) == MODIFY_EXPR ? TREE_OPERAND (stmt, 0) : NULL;
3151 initialize_hash_element (stmt, lhs, element);
3153 /* Don't bother remembering constant assignments and copy operations.
3154 Constants and copy operations are handled by the constant/copy propagator
3155 in optimize_stmt. */
3156 if (TREE_CODE (element->rhs) == SSA_NAME
3157 || is_gimple_min_invariant (element->rhs))
3163 /* If this is an equality test against zero, see if we have recorded a
3164 nonzero value for the variable in question. */
3165 if ((TREE_CODE (element->rhs) == EQ_EXPR
3166 || TREE_CODE (element->rhs) == NE_EXPR)
3167 && TREE_CODE (TREE_OPERAND (element->rhs, 0)) == SSA_NAME
3168 && integer_zerop (TREE_OPERAND (element->rhs, 1)))
3170 int indx = SSA_NAME_VERSION (TREE_OPERAND (element->rhs, 0));
3172 if (bitmap_bit_p (nonzero_vars, indx))
3174 tree t = element->rhs;
3177 if (TREE_CODE (t) == EQ_EXPR)
3178 return boolean_false_node;
3180 return boolean_true_node;
3184 /* Finally try to find the expression in the main expression hash table. */
3185 slot = htab_find_slot_with_hash (avail_exprs, element, element->hash,
3186 (insert ? INSERT : NO_INSERT));
3195 *slot = (void *) element;
3196 VEC_safe_push (tree, heap, avail_exprs_stack,
3197 stmt ? stmt : element->rhs);
3201 /* Extract the LHS of the assignment so that it can be used as the current
3202 definition of another variable. */
3203 lhs = ((struct expr_hash_elt *)*slot)->lhs;
3205 /* See if the LHS appears in the CONST_AND_COPIES table. If it does, then
3206 use the value from the const_and_copies table. */
3207 if (TREE_CODE (lhs) == SSA_NAME)
3209 temp = SSA_NAME_VALUE (lhs);
3210 if (temp && TREE_CODE (temp) != VALUE_HANDLE)
3218 /* Given a condition COND, record into HI_P, LO_P and INVERTED_P the
3219 range of values that result in the conditional having a true value.
3221 Return true if we are successful in extracting a range from COND and
3222 false if we are unsuccessful. */
3225 extract_range_from_cond (tree cond, tree *hi_p, tree *lo_p, int *inverted_p)
3227 tree op1 = TREE_OPERAND (cond, 1);
3228 tree high, low, type;
3231 type = TREE_TYPE (op1);
3233 /* Experiments have shown that it's rarely, if ever useful to
3234 record ranges for enumerations. Presumably this is due to
3235 the fact that they're rarely used directly. They are typically
3236 cast into an integer type and used that way. */
3237 if (TREE_CODE (type) != INTEGER_TYPE
3238 /* We don't know how to deal with types with variable bounds. */
3239 || TREE_CODE (TYPE_MIN_VALUE (type)) != INTEGER_CST
3240 || TREE_CODE (TYPE_MAX_VALUE (type)) != INTEGER_CST)
3243 switch (TREE_CODE (cond))
3257 high = TYPE_MAX_VALUE (type);
3262 high = TYPE_MAX_VALUE (type);
3263 if (!tree_int_cst_lt (op1, high))
3265 low = int_const_binop (PLUS_EXPR, op1, integer_one_node, 1);
3271 low = TYPE_MIN_VALUE (type);
3276 low = TYPE_MIN_VALUE (type);
3277 if (!tree_int_cst_lt (low, op1))
3279 high = int_const_binop (MINUS_EXPR, op1, integer_one_node, 1);
3289 *inverted_p = inverted;
3293 /* Record a range created by COND for basic block BB. */
3296 record_range (tree cond, basic_block bb)
3298 enum tree_code code = TREE_CODE (cond);
3300 /* We explicitly ignore NE_EXPRs and all the unordered comparisons.
3301 They rarely allow for meaningful range optimizations and significantly
3302 complicate the implementation. */
3303 if ((code == LT_EXPR || code == LE_EXPR || code == GT_EXPR
3304 || code == GE_EXPR || code == EQ_EXPR)
3305 && TREE_CODE (TREE_TYPE (TREE_OPERAND (cond, 1))) == INTEGER_TYPE)
3307 struct vrp_hash_elt *vrp_hash_elt;
3308 struct vrp_element *element;
3309 varray_type *vrp_records_p;
3313 vrp_hash_elt = xmalloc (sizeof (struct vrp_hash_elt));
3314 vrp_hash_elt->var = TREE_OPERAND (cond, 0);
3315 vrp_hash_elt->records = NULL;
3316 slot = htab_find_slot (vrp_data, vrp_hash_elt, INSERT);
3319 *slot = (void *) vrp_hash_elt;
3321 free (vrp_hash_elt);
3323 vrp_hash_elt = (struct vrp_hash_elt *) *slot;
3324 vrp_records_p = &vrp_hash_elt->records;
3326 element = ggc_alloc (sizeof (struct vrp_element));
3327 element->low = NULL;
3328 element->high = NULL;
3329 element->cond = cond;
3332 if (*vrp_records_p == NULL)
3333 VARRAY_GENERIC_PTR_INIT (*vrp_records_p, 2, "vrp records");
3335 VARRAY_PUSH_GENERIC_PTR (*vrp_records_p, element);
3336 VEC_safe_push (tree, heap, vrp_variables_stack, TREE_OPERAND (cond, 0));
3340 /* Hashing and equality functions for VRP_DATA.
3342 Since this hash table is addressed by SSA_NAMEs, we can hash on
3343 their version number and equality can be determined with a
3344 pointer comparison. */
3347 vrp_hash (const void *p)
3349 tree var = ((struct vrp_hash_elt *)p)->var;
3351 return SSA_NAME_VERSION (var);
3355 vrp_eq (const void *p1, const void *p2)
3357 tree var1 = ((struct vrp_hash_elt *)p1)->var;
3358 tree var2 = ((struct vrp_hash_elt *)p2)->var;
3360 return var1 == var2;
3363 /* Hashing and equality functions for AVAIL_EXPRS. The table stores
3364 MODIFY_EXPR statements. We compute a value number for expressions using
3365 the code of the expression and the SSA numbers of its operands. */
3368 avail_expr_hash (const void *p)
3370 tree stmt = ((struct expr_hash_elt *)p)->stmt;
3371 tree rhs = ((struct expr_hash_elt *)p)->rhs;
3376 /* iterative_hash_expr knows how to deal with any expression and
3377 deals with commutative operators as well, so just use it instead
3378 of duplicating such complexities here. */
3379 val = iterative_hash_expr (rhs, val);
3381 /* If the hash table entry is not associated with a statement, then we
3382 can just hash the expression and not worry about virtual operands
3384 if (!stmt || !stmt_ann (stmt))
3387 /* Add the SSA version numbers of every vuse operand. This is important
3388 because compound variables like arrays are not renamed in the
3389 operands. Rather, the rename is done on the virtual variable
3390 representing all the elements of the array. */
3391 FOR_EACH_SSA_TREE_OPERAND (vuse, stmt, iter, SSA_OP_VUSE)
3392 val = iterative_hash_expr (vuse, val);
3398 real_avail_expr_hash (const void *p)
3400 return ((const struct expr_hash_elt *)p)->hash;
3404 avail_expr_eq (const void *p1, const void *p2)
3406 tree stmt1 = ((struct expr_hash_elt *)p1)->stmt;
3407 tree rhs1 = ((struct expr_hash_elt *)p1)->rhs;
3408 tree stmt2 = ((struct expr_hash_elt *)p2)->stmt;
3409 tree rhs2 = ((struct expr_hash_elt *)p2)->rhs;
3411 /* If they are the same physical expression, return true. */
3412 if (rhs1 == rhs2 && stmt1 == stmt2)
3415 /* If their codes are not equal, then quit now. */
3416 if (TREE_CODE (rhs1) != TREE_CODE (rhs2))
3419 /* In case of a collision, both RHS have to be identical and have the
3420 same VUSE operands. */
3421 if ((TREE_TYPE (rhs1) == TREE_TYPE (rhs2)
3422 || lang_hooks.types_compatible_p (TREE_TYPE (rhs1), TREE_TYPE (rhs2)))
3423 && operand_equal_p (rhs1, rhs2, OEP_PURE_SAME))
3425 bool ret = compare_ssa_operands_equal (stmt1, stmt2, SSA_OP_VUSE);
3426 gcc_assert (!ret || ((struct expr_hash_elt *)p1)->hash
3427 == ((struct expr_hash_elt *)p2)->hash);