1 /* SSA Dominator optimizations for trees
2 Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
3 Contributed by Diego Novillo <dnovillo@redhat.com>
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
24 #include "coretypes.h"
31 #include "basic-block.h"
36 #include "diagnostic.h"
38 #include "tree-dump.h"
39 #include "tree-flow.h"
42 #include "tree-pass.h"
43 #include "tree-ssa-propagate.h"
44 #include "langhooks.h"
46 /* This file implements optimizations on the dominator tree. */
49 /* Structure for recording edge equivalences as well as any pending
50 edge redirections during the dominator optimizer.
52 Computing and storing the edge equivalences instead of creating
53 them on-demand can save significant amounts of time, particularly
54 for pathological cases involving switch statements.
56 These structures live for a single iteration of the dominator
57 optimizer in the edge's AUX field. At the end of an iteration we
58 free each of these structures and update the AUX field to point
59 to any requested redirection target (the code for updating the
60 CFG and SSA graph for edge redirection expects redirection edge
61 targets to be in the AUX field for each edge. */
65 /* If this edge creates a simple equivalence, the LHS and RHS of
66 the equivalence will be stored here. */
70 /* Traversing an edge may also indicate one or more particular conditions
71 are true or false. The number of recorded conditions can vary, but
72 can be determined by the condition's code. So we have an array
73 and its maximum index rather than use a varray. */
74 tree *cond_equivalences;
75 unsigned int max_cond_equivalences;
77 /* If we can thread this edge this field records the new target. */
78 edge redirection_target;
82 /* Hash table with expressions made available during the renaming process.
83 When an assignment of the form X_i = EXPR is found, the statement is
84 stored in this table. If the same expression EXPR is later found on the
85 RHS of another statement, it is replaced with X_i (thus performing
86 global redundancy elimination). Similarly as we pass through conditionals
87 we record the conditional itself as having either a true or false value
89 static htab_t avail_exprs;
91 /* Stack of available expressions in AVAIL_EXPRs. Each block pushes any
92 expressions it enters into the hash table along with a marker entry
93 (null). When we finish processing the block, we pop off entries and
94 remove the expressions from the global hash table until we hit the
96 static varray_type avail_exprs_stack;
98 /* Stack of trees used to restore the global currdefs to its original
99 state after completing optimization of a block and its dominator children.
101 An SSA_NAME indicates that the current definition of the underlying
102 variable should be set to the given SSA_NAME.
104 A _DECL node indicates that the underlying variable has no current
107 A NULL node is used to mark the last node associated with the
109 VEC(tree_on_heap) *block_defs_stack;
111 /* FIXME: The other stacks should also be VEC(tree_on_heap). */
113 /* Stack of statements we need to rescan during finalization for newly
116 Statement rescanning must occur after the current block's available
117 expressions are removed from AVAIL_EXPRS. Else we may change the
118 hash code for an expression and be unable to find/remove it from
120 varray_type stmts_to_rescan;
122 /* Structure for entries in the expression hash table.
124 This requires more memory for the hash table entries, but allows us
125 to avoid creating silly tree nodes and annotations for conditionals,
126 eliminates 2 global hash tables and two block local varrays.
128 It also allows us to reduce the number of hash table lookups we
129 have to perform in lookup_avail_expr and finally it allows us to
130 significantly reduce the number of calls into the hashing routine
135 /* The value (lhs) of this expression. */
138 /* The expression (rhs) we want to record. */
141 /* The annotation if this element corresponds to a statement. */
144 /* The hash value for RHS/ann. */
148 /* Stack of dest,src pairs that need to be restored during finalization.
150 A NULL entry is used to mark the end of pairs which need to be
151 restored during finalization of this block. */
152 static varray_type const_and_copies_stack;
154 /* Bitmap of SSA_NAMEs known to have a nonzero value, even if we do not
155 know their exact value. */
156 static bitmap nonzero_vars;
158 /* Stack of SSA_NAMEs which need their NONZERO_VARS property cleared
159 when the current block is finalized.
161 A NULL entry is used to mark the end of names needing their
162 entry in NONZERO_VARS cleared during finalization of this block. */
163 static varray_type nonzero_vars_stack;
165 /* Track whether or not we have changed the control flow graph. */
166 static bool cfg_altered;
168 /* Bitmap of blocks that have had EH statements cleaned. We should
169 remove their dead edges eventually. */
170 static bitmap need_eh_cleanup;
172 /* Statistics for dominator optimizations. */
176 long num_exprs_considered;
180 static struct opt_stats_d opt_stats;
182 /* Value range propagation record. Each time we encounter a conditional
183 of the form SSA_NAME COND CONST we create a new vrp_element to record
184 how the condition affects the possible values SSA_NAME may have.
186 Each record contains the condition tested (COND), and the the range of
187 values the variable may legitimately have if COND is true. Note the
188 range of values may be a smaller range than COND specifies if we have
189 recorded other ranges for this variable. Each record also contains the
190 block in which the range was recorded for invalidation purposes.
192 Note that the current known range is computed lazily. This allows us
193 to avoid the overhead of computing ranges which are never queried.
195 When we encounter a conditional, we look for records which constrain
196 the SSA_NAME used in the condition. In some cases those records allow
197 us to determine the condition's result at compile time. In other cases
198 they may allow us to simplify the condition.
200 We also use value ranges to do things like transform signed div/mod
201 operations into unsigned div/mod or to simplify ABS_EXPRs.
203 Simple experiments have shown these optimizations to not be all that
204 useful on switch statements (much to my surprise). So switch statement
205 optimizations are not performed.
207 Note carefully we do not propagate information through each statement
208 in the block. i.e., if we know variable X has a value defined of
209 [0, 25] and we encounter Y = X + 1, we do not track a value range
210 for Y (which would be [1, 26] if we cared). Similarly we do not
211 constrain values as we encounter narrowing typecasts, etc. */
215 /* The highest and lowest values the variable in COND may contain when
216 COND is true. Note this may not necessarily be the same values
217 tested by COND if the same variable was used in earlier conditionals.
219 Note this is computed lazily and thus can be NULL indicating that
220 the values have not been computed yet. */
224 /* The actual conditional we recorded. This is needed since we compute
228 /* The basic block where this record was created. We use this to determine
229 when to remove records. */
233 /* A hash table holding value range records (VRP_ELEMENTs) for a given
234 SSA_NAME. We used to use a varray indexed by SSA_NAME_VERSION, but
235 that gets awful wasteful, particularly since the density objects
236 with useful information is very low. */
237 static htab_t vrp_data;
239 /* An entry in the VRP_DATA hash table. We record the variable and a
240 varray of VRP_ELEMENT records associated with that variable. */
248 /* Array of variables which have their values constrained by operations
249 in this basic block. We use this during finalization to know
250 which variables need their VRP data updated. */
252 /* Stack of SSA_NAMEs which had their values constrainted by operations
253 in this basic block. During finalization of this block we use this
254 list to determine which variables need their VRP data updated.
256 A NULL entry marks the end of the SSA_NAMEs associated with this block. */
257 static varray_type vrp_variables_stack;
265 /* Local functions. */
266 static void optimize_stmt (struct dom_walk_data *,
268 block_stmt_iterator);
269 static tree lookup_avail_expr (tree, bool);
270 static hashval_t vrp_hash (const void *);
271 static int vrp_eq (const void *, const void *);
272 static hashval_t avail_expr_hash (const void *);
273 static hashval_t real_avail_expr_hash (const void *);
274 static int avail_expr_eq (const void *, const void *);
275 static void htab_statistics (FILE *, htab_t);
276 static void record_cond (tree, tree);
277 static void record_const_or_copy (tree, tree);
278 static void record_equality (tree, tree);
279 static tree update_rhs_and_lookup_avail_expr (tree, tree, bool);
280 static tree simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *,
282 static tree simplify_cond_and_lookup_avail_expr (tree, stmt_ann_t, int);
283 static tree simplify_switch_and_lookup_avail_expr (tree, int);
284 static tree find_equivalent_equality_comparison (tree);
285 static void record_range (tree, basic_block);
286 static bool extract_range_from_cond (tree, tree *, tree *, int *);
287 static void record_equivalences_from_phis (basic_block);
288 static void record_equivalences_from_incoming_edge (basic_block);
289 static bool eliminate_redundant_computations (struct dom_walk_data *,
291 static void record_equivalences_from_stmt (tree, int, stmt_ann_t);
292 static void thread_across_edge (struct dom_walk_data *, edge);
293 static void dom_opt_finalize_block (struct dom_walk_data *, basic_block);
294 static void dom_opt_initialize_block (struct dom_walk_data *, basic_block);
295 static void propagate_to_outgoing_edges (struct dom_walk_data *, basic_block);
296 static void remove_local_expressions_from_table (void);
297 static void restore_vars_to_original_value (void);
298 static void restore_currdefs_to_original_value (void);
299 static void register_definitions_for_stmt (tree);
300 static edge single_incoming_edge_ignoring_loop_edges (basic_block);
301 static void restore_nonzero_vars_to_original_value (void);
302 static inline bool unsafe_associative_fp_binop (tree);
304 /* Local version of fold that doesn't introduce cruft. */
311 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
312 may have been added by fold, and "useless" type conversions that might
313 now be apparent due to propagation. */
314 STRIP_USELESS_TYPE_CONVERSION (t);
319 /* Allocate an EDGE_INFO for edge E and attach it to E.
320 Return the new EDGE_INFO structure. */
322 static struct edge_info *
323 allocate_edge_info (edge e)
325 struct edge_info *edge_info;
327 edge_info = xcalloc (1, sizeof (struct edge_info));
333 /* Free all EDGE_INFO structures associated with edges in the CFG.
334 If a particular edge can be threaded, copy the redirection
335 target from the EDGE_INFO structure into the edge's AUX field
336 as required by code to update the CFG and SSA graph for
340 free_all_edge_infos (void)
348 FOR_EACH_EDGE (e, ei, bb->preds)
350 struct edge_info *edge_info = e->aux;
354 e->aux = edge_info->redirection_target;
355 if (edge_info->cond_equivalences)
356 free (edge_info->cond_equivalences);
363 /* Jump threading, redundancy elimination and const/copy propagation.
365 This pass may expose new symbols that need to be renamed into SSA. For
366 every new symbol exposed, its corresponding bit will be set in
370 tree_ssa_dominator_optimize (void)
372 struct dom_walk_data walk_data;
375 memset (&opt_stats, 0, sizeof (opt_stats));
377 for (i = 0; i < num_referenced_vars; i++)
378 var_ann (referenced_var (i))->current_def = NULL;
380 /* Mark loop edges so we avoid threading across loop boundaries.
381 This may result in transforming natural loop into irreducible
383 mark_dfs_back_edges ();
385 /* Create our hash tables. */
386 avail_exprs = htab_create (1024, real_avail_expr_hash, avail_expr_eq, free);
387 vrp_data = htab_create (ceil_log2 (num_ssa_names), vrp_hash, vrp_eq, free);
388 VARRAY_TREE_INIT (avail_exprs_stack, 20, "Available expression stack");
389 block_defs_stack = VEC_alloc (tree_on_heap, 20);
390 VARRAY_TREE_INIT (const_and_copies_stack, 20, "Block const_and_copies stack");
391 VARRAY_TREE_INIT (nonzero_vars_stack, 20, "Block nonzero_vars stack");
392 VARRAY_TREE_INIT (vrp_variables_stack, 20, "Block vrp_variables stack");
393 VARRAY_TREE_INIT (stmts_to_rescan, 20, "Statements to rescan");
394 nonzero_vars = BITMAP_XMALLOC ();
395 need_eh_cleanup = BITMAP_XMALLOC ();
397 /* Setup callbacks for the generic dominator tree walker. */
398 walk_data.walk_stmts_backward = false;
399 walk_data.dom_direction = CDI_DOMINATORS;
400 walk_data.initialize_block_local_data = NULL;
401 walk_data.before_dom_children_before_stmts = dom_opt_initialize_block;
402 walk_data.before_dom_children_walk_stmts = optimize_stmt;
403 walk_data.before_dom_children_after_stmts = propagate_to_outgoing_edges;
404 walk_data.after_dom_children_before_stmts = NULL;
405 walk_data.after_dom_children_walk_stmts = NULL;
406 walk_data.after_dom_children_after_stmts = dom_opt_finalize_block;
407 /* Right now we only attach a dummy COND_EXPR to the global data pointer.
408 When we attach more stuff we'll need to fill this out with a real
410 walk_data.global_data = NULL;
411 walk_data.block_local_data_size = 0;
413 /* Now initialize the dominator walker. */
414 init_walk_dominator_tree (&walk_data);
416 calculate_dominance_info (CDI_DOMINATORS);
418 /* If we prove certain blocks are unreachable, then we want to
419 repeat the dominator optimization process as PHI nodes may
420 have turned into copies which allows better propagation of
421 values. So we repeat until we do not identify any new unreachable
425 /* Optimize the dominator tree. */
428 /* Recursively walk the dominator tree optimizing statements. */
429 walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
431 /* If we exposed any new variables, go ahead and put them into
432 SSA form now, before we handle jump threading. This simplifies
433 interactions between rewriting of _DECL nodes into SSA form
434 and rewriting SSA_NAME nodes into SSA form after block
435 duplication and CFG manipulation. */
436 if (!bitmap_empty_p (vars_to_rename))
438 rewrite_into_ssa (false);
439 bitmap_clear (vars_to_rename);
442 free_all_edge_infos ();
444 /* Thread jumps, creating duplicate blocks as needed. */
445 cfg_altered = thread_through_all_blocks ();
447 /* Removal of statements may make some EH edges dead. Purge
448 such edges from the CFG as needed. */
449 if (!bitmap_empty_p (need_eh_cleanup))
451 cfg_altered |= tree_purge_all_dead_eh_edges (need_eh_cleanup);
452 bitmap_zero (need_eh_cleanup);
455 free_dominance_info (CDI_DOMINATORS);
456 cfg_altered = cleanup_tree_cfg ();
457 calculate_dominance_info (CDI_DOMINATORS);
459 rewrite_ssa_into_ssa ();
461 /* Reinitialize the various tables. */
462 bitmap_clear (nonzero_vars);
463 htab_empty (avail_exprs);
464 htab_empty (vrp_data);
466 for (i = 0; i < num_referenced_vars; i++)
467 var_ann (referenced_var (i))->current_def = NULL;
471 /* Debugging dumps. */
472 if (dump_file && (dump_flags & TDF_STATS))
473 dump_dominator_optimization_stats (dump_file);
475 /* We emptied the hash table earlier, now delete it completely. */
476 htab_delete (avail_exprs);
477 htab_delete (vrp_data);
479 /* It is not necessary to clear CURRDEFS, REDIRECTION_EDGES, VRP_DATA,
480 CONST_AND_COPIES, and NONZERO_VARS as they all get cleared at the bottom
481 of the do-while loop above. */
483 /* And finalize the dominator walker. */
484 fini_walk_dominator_tree (&walk_data);
486 /* Free nonzero_vars. */
487 BITMAP_XFREE (nonzero_vars);
488 BITMAP_XFREE (need_eh_cleanup);
490 /* Finally, remove everything except invariants in SSA_NAME_VALUE.
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
495 for (i = 0; i < num_ssa_names; i++)
497 tree name = ssa_name (i);
503 value = SSA_NAME_VALUE (name);
504 if (value && !is_gimple_min_invariant (value))
505 SSA_NAME_VALUE (name) = NULL;
508 VEC_free (tree_on_heap, block_defs_stack);
509 block_defs_stack = NULL;
513 gate_dominator (void)
515 return flag_tree_dom != 0;
518 struct tree_opt_pass pass_dominator =
521 gate_dominator, /* gate */
522 tree_ssa_dominator_optimize, /* execute */
525 0, /* static_pass_number */
526 TV_TREE_SSA_DOMINATOR_OPTS, /* tv_id */
527 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
528 0, /* properties_provided */
529 0, /* properties_destroyed */
530 0, /* todo_flags_start */
531 TODO_dump_func | TODO_rename_vars
532 | TODO_verify_ssa, /* todo_flags_finish */
537 /* We are exiting BB, see if the target block begins with a conditional
538 jump which has a known value when reached via BB. */
541 thread_across_edge (struct dom_walk_data *walk_data, edge e)
543 block_stmt_iterator bsi;
547 /* Each PHI creates a temporary equivalence, record them. */
548 for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
550 tree src = PHI_ARG_DEF_FROM_EDGE (phi, e);
551 tree dst = PHI_RESULT (phi);
552 record_const_or_copy (dst, src);
553 register_new_def (dst, &block_defs_stack);
556 for (bsi = bsi_start (e->dest); ! bsi_end_p (bsi); bsi_next (&bsi))
558 tree lhs, cached_lhs;
560 stmt = bsi_stmt (bsi);
562 /* Ignore empty statements and labels. */
563 if (IS_EMPTY_STMT (stmt) || TREE_CODE (stmt) == LABEL_EXPR)
566 /* If this is not a MODIFY_EXPR which sets an SSA_NAME to a new
567 value, then stop our search here. Ideally when we stop a
568 search we stop on a COND_EXPR or SWITCH_EXPR. */
569 if (TREE_CODE (stmt) != MODIFY_EXPR
570 || TREE_CODE (TREE_OPERAND (stmt, 0)) != SSA_NAME)
573 /* At this point we have a statement which assigns an RHS to an
574 SSA_VAR on the LHS. We want to prove that the RHS is already
575 available and that its value is held in the current definition
576 of the LHS -- meaning that this assignment is a NOP when
577 reached via edge E. */
578 if (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME)
579 cached_lhs = TREE_OPERAND (stmt, 1);
581 cached_lhs = lookup_avail_expr (stmt, false);
583 lhs = TREE_OPERAND (stmt, 0);
585 /* This can happen if we thread around to the start of a loop. */
586 if (lhs == cached_lhs)
589 /* If we did not find RHS in the hash table, then try again after
590 temporarily const/copy propagating the operands. */
593 /* Copy the operands. */
594 stmt_ann_t ann = stmt_ann (stmt);
595 use_optype uses = USE_OPS (ann);
596 vuse_optype vuses = VUSE_OPS (ann);
597 tree *uses_copy = xcalloc (NUM_USES (uses), sizeof (tree));
598 tree *vuses_copy = xcalloc (NUM_VUSES (vuses), sizeof (tree));
601 /* Make a copy of the uses into USES_COPY, then cprop into
603 for (i = 0; i < NUM_USES (uses); i++)
607 uses_copy[i] = USE_OP (uses, i);
608 if (TREE_CODE (USE_OP (uses, i)) == SSA_NAME)
609 tmp = SSA_NAME_VALUE (USE_OP (uses, i));
610 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
611 SET_USE_OP (uses, i, tmp);
614 /* Similarly for virtual uses. */
615 for (i = 0; i < NUM_VUSES (vuses); i++)
619 vuses_copy[i] = VUSE_OP (vuses, i);
620 if (TREE_CODE (VUSE_OP (vuses, i)) == SSA_NAME)
621 tmp = SSA_NAME_VALUE (VUSE_OP (vuses, i));
622 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
623 SET_VUSE_OP (vuses, i, tmp);
626 /* Try to lookup the new expression. */
627 cached_lhs = lookup_avail_expr (stmt, false);
629 /* Restore the statement's original uses/defs. */
630 for (i = 0; i < NUM_USES (uses); i++)
631 SET_USE_OP (uses, i, uses_copy[i]);
633 for (i = 0; i < NUM_VUSES (vuses); i++)
634 SET_VUSE_OP (vuses, i, vuses_copy[i]);
639 /* If we still did not find the expression in the hash table,
640 then we can not ignore this statement. */
645 /* If the expression in the hash table was not assigned to an
646 SSA_NAME, then we can not ignore this statement. */
647 if (TREE_CODE (cached_lhs) != SSA_NAME)
650 /* If we have different underlying variables, then we can not
651 ignore this statement. */
652 if (SSA_NAME_VAR (cached_lhs) != SSA_NAME_VAR (lhs))
655 /* If CACHED_LHS does not represent the current value of the undering
656 variable in CACHED_LHS/LHS, then we can not ignore this statement. */
657 if (var_ann (SSA_NAME_VAR (lhs))->current_def != cached_lhs)
660 /* If we got here, then we can ignore this statement and continue
661 walking through the statements in the block looking for a threadable
664 We want to record an equivalence lhs = cache_lhs so that if
665 the result of this statement is used later we can copy propagate
667 record_const_or_copy (lhs, cached_lhs);
668 register_new_def (lhs, &block_defs_stack);
671 /* If we stopped at a COND_EXPR or SWITCH_EXPR, then see if we know which
672 arm will be taken. */
674 && (TREE_CODE (stmt) == COND_EXPR
675 || TREE_CODE (stmt) == SWITCH_EXPR))
677 tree cond, cached_lhs;
681 /* Do not forward entry edges into the loop. In the case loop
682 has multiple entry edges we may end up in constructing irreducible
684 ??? We may consider forwarding the edges in the case all incoming
685 edges forward to the same destination block. */
686 if (!e->flags & EDGE_DFS_BACK)
688 FOR_EACH_EDGE (e1, ei, e->dest->preds)
689 if (e1->flags & EDGE_DFS_BACK)
695 /* Now temporarily cprop the operands and try to find the resulting
696 expression in the hash tables. */
697 if (TREE_CODE (stmt) == COND_EXPR)
698 cond = COND_EXPR_COND (stmt);
700 cond = SWITCH_COND (stmt);
702 if (COMPARISON_CLASS_P (cond))
704 tree dummy_cond, op0, op1;
705 enum tree_code cond_code;
707 op0 = TREE_OPERAND (cond, 0);
708 op1 = TREE_OPERAND (cond, 1);
709 cond_code = TREE_CODE (cond);
711 /* Get the current value of both operands. */
712 if (TREE_CODE (op0) == SSA_NAME)
714 tree tmp = SSA_NAME_VALUE (op0);
715 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
719 if (TREE_CODE (op1) == SSA_NAME)
721 tree tmp = SSA_NAME_VALUE (op1);
722 if (tmp && TREE_CODE (tmp) != VALUE_HANDLE)
726 /* Stuff the operator and operands into our dummy conditional
727 expression, creating the dummy conditional if necessary. */
728 dummy_cond = walk_data->global_data;
731 dummy_cond = build (cond_code, boolean_type_node, op0, op1);
732 dummy_cond = build (COND_EXPR, void_type_node,
733 dummy_cond, NULL, NULL);
734 walk_data->global_data = dummy_cond;
738 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), cond_code);
739 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op0;
740 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1) = op1;
743 /* If the conditional folds to an invariant, then we are done,
744 otherwise look it up in the hash tables. */
745 cached_lhs = local_fold (COND_EXPR_COND (dummy_cond));
746 if (! is_gimple_min_invariant (cached_lhs))
747 cached_lhs = lookup_avail_expr (dummy_cond, false);
748 if (!cached_lhs || ! is_gimple_min_invariant (cached_lhs))
750 cached_lhs = simplify_cond_and_lookup_avail_expr (dummy_cond,
755 /* We can have conditionals which just test the state of a
756 variable rather than use a relational operator. These are
757 simpler to handle. */
758 else if (TREE_CODE (cond) == SSA_NAME)
761 cached_lhs = SSA_NAME_VALUE (cached_lhs);
762 if (cached_lhs && ! is_gimple_min_invariant (cached_lhs))
766 cached_lhs = lookup_avail_expr (stmt, false);
770 edge taken_edge = find_taken_edge (e->dest, cached_lhs);
771 basic_block dest = (taken_edge ? taken_edge->dest : NULL);
776 /* If we have a known destination for the conditional, then
777 we can perform this optimization, which saves at least one
778 conditional jump each time it applies since we get to
779 bypass the conditional at our original destination. */
782 struct edge_info *edge_info;
784 update_bb_profile_for_threading (e->dest, EDGE_FREQUENCY (e),
785 e->count, taken_edge);
789 edge_info = allocate_edge_info (e);
790 edge_info->redirection_target = taken_edge;
791 bb_ann (e->dest)->incoming_edge_threaded = true;
798 /* Initialize local stacks for this optimizer and record equivalences
799 upon entry to BB. Equivalences can come from the edge traversed to
800 reach BB or they may come from PHI nodes at the start of BB. */
803 dom_opt_initialize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
806 if (dump_file && (dump_flags & TDF_DETAILS))
807 fprintf (dump_file, "\n\nOptimizing block #%d\n\n", bb->index);
809 /* Push a marker on the stacks of local information so that we know how
810 far to unwind when we finalize this block. */
811 VARRAY_PUSH_TREE (avail_exprs_stack, NULL_TREE);
812 VEC_safe_push (tree_on_heap, block_defs_stack, NULL_TREE);
813 VARRAY_PUSH_TREE (const_and_copies_stack, NULL_TREE);
814 VARRAY_PUSH_TREE (nonzero_vars_stack, NULL_TREE);
815 VARRAY_PUSH_TREE (vrp_variables_stack, NULL_TREE);
817 record_equivalences_from_incoming_edge (bb);
819 /* PHI nodes can create equivalences too. */
820 record_equivalences_from_phis (bb);
823 /* Given an expression EXPR (a relational expression or a statement),
824 initialize the hash table element pointed by by ELEMENT. */
827 initialize_hash_element (tree expr, tree lhs, struct expr_hash_elt *element)
829 /* Hash table elements may be based on conditional expressions or statements.
831 For the former case, we have no annotation and we want to hash the
832 conditional expression. In the latter case we have an annotation and
833 we want to record the expression the statement evaluates. */
834 if (COMPARISON_CLASS_P (expr) || TREE_CODE (expr) == TRUTH_NOT_EXPR)
839 else if (TREE_CODE (expr) == COND_EXPR)
841 element->ann = stmt_ann (expr);
842 element->rhs = COND_EXPR_COND (expr);
844 else if (TREE_CODE (expr) == SWITCH_EXPR)
846 element->ann = stmt_ann (expr);
847 element->rhs = SWITCH_COND (expr);
849 else if (TREE_CODE (expr) == RETURN_EXPR && TREE_OPERAND (expr, 0))
851 element->ann = stmt_ann (expr);
852 element->rhs = TREE_OPERAND (TREE_OPERAND (expr, 0), 1);
856 element->ann = stmt_ann (expr);
857 element->rhs = TREE_OPERAND (expr, 1);
861 element->hash = avail_expr_hash (element);
864 /* Remove all the expressions in LOCALS from TABLE, stopping when there are
865 LIMIT entries left in LOCALs. */
868 remove_local_expressions_from_table (void)
870 /* Remove all the expressions made available in this block. */
871 while (VARRAY_ACTIVE_SIZE (avail_exprs_stack) > 0)
873 struct expr_hash_elt element;
874 tree expr = VARRAY_TOP_TREE (avail_exprs_stack);
875 VARRAY_POP (avail_exprs_stack);
877 if (expr == NULL_TREE)
880 initialize_hash_element (expr, NULL, &element);
881 htab_remove_elt_with_hash (avail_exprs, &element, element.hash);
885 /* Use the SSA_NAMES in LOCALS to restore TABLE to its original
886 state, stopping when there are LIMIT entries left in LOCALs. */
889 restore_nonzero_vars_to_original_value (void)
891 while (VARRAY_ACTIVE_SIZE (nonzero_vars_stack) > 0)
893 tree name = VARRAY_TOP_TREE (nonzero_vars_stack);
894 VARRAY_POP (nonzero_vars_stack);
899 bitmap_clear_bit (nonzero_vars, SSA_NAME_VERSION (name));
903 /* Use the source/dest pairs in CONST_AND_COPIES_STACK to restore
904 CONST_AND_COPIES to its original state, stopping when we hit a
908 restore_vars_to_original_value (void)
910 while (VARRAY_ACTIVE_SIZE (const_and_copies_stack) > 0)
912 tree prev_value, dest;
914 dest = VARRAY_TOP_TREE (const_and_copies_stack);
915 VARRAY_POP (const_and_copies_stack);
920 prev_value = VARRAY_TOP_TREE (const_and_copies_stack);
921 VARRAY_POP (const_and_copies_stack);
923 SSA_NAME_VALUE (dest) = prev_value;
927 /* Similar to restore_vars_to_original_value, except that it restores
928 CURRDEFS to its original value. */
930 restore_currdefs_to_original_value (void)
932 /* Restore CURRDEFS to its original state. */
933 while (VEC_length (tree_on_heap, block_defs_stack) > 0)
935 tree tmp = VEC_pop (tree_on_heap, block_defs_stack);
938 if (tmp == NULL_TREE)
941 /* If we recorded an SSA_NAME, then make the SSA_NAME the current
942 definition of its underlying variable. If we recorded anything
943 else, it must have been an _DECL node and its current reaching
944 definition must have been NULL. */
945 if (TREE_CODE (tmp) == SSA_NAME)
948 var = SSA_NAME_VAR (saved_def);
956 var_ann (var)->current_def = saved_def;
960 /* We have finished processing the dominator children of BB, perform
961 any finalization actions in preparation for leaving this node in
962 the dominator tree. */
965 dom_opt_finalize_block (struct dom_walk_data *walk_data, basic_block bb)
969 /* If we are at a leaf node in the dominator graph, see if we can thread
970 the edge from BB through its successor.
972 Do this before we remove entries from our equivalence tables. */
973 if (EDGE_COUNT (bb->succs) == 1
974 && (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL) == 0
975 && (get_immediate_dominator (CDI_DOMINATORS, EDGE_SUCC (bb, 0)->dest) != bb
976 || phi_nodes (EDGE_SUCC (bb, 0)->dest)))
979 thread_across_edge (walk_data, EDGE_SUCC (bb, 0));
981 else if ((last = last_stmt (bb))
982 && TREE_CODE (last) == COND_EXPR
983 && (COMPARISON_CLASS_P (COND_EXPR_COND (last))
984 || TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME)
985 && EDGE_COUNT (bb->succs) == 2
986 && (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL) == 0
987 && (EDGE_SUCC (bb, 1)->flags & EDGE_ABNORMAL) == 0)
989 edge true_edge, false_edge;
991 extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
993 /* If the THEN arm is the end of a dominator tree or has PHI nodes,
994 then try to thread through its edge. */
995 if (get_immediate_dominator (CDI_DOMINATORS, true_edge->dest) != bb
996 || phi_nodes (true_edge->dest))
998 struct edge_info *edge_info;
1001 /* Push a marker onto the available expression stack so that we
1002 unwind any expressions related to the TRUE arm before processing
1003 the false arm below. */
1004 VARRAY_PUSH_TREE (avail_exprs_stack, NULL_TREE);
1005 VEC_safe_push (tree_on_heap, block_defs_stack, NULL_TREE);
1006 VARRAY_PUSH_TREE (const_and_copies_stack, NULL_TREE);
1008 edge_info = true_edge->aux;
1010 /* If we have info associated with this edge, record it into
1011 our equivalency tables. */
1014 tree *cond_equivalences = edge_info->cond_equivalences;
1015 tree lhs = edge_info->lhs;
1016 tree rhs = edge_info->rhs;
1018 /* If we have a simple NAME = VALUE equivalency record it.
1019 Until the jump threading selection code improves, only
1020 do this if both the name and value are SSA_NAMEs with
1021 the same underlying variable to avoid missing threading
1024 && TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME
1025 && TREE_CODE (edge_info->rhs) == SSA_NAME
1026 && SSA_NAME_VAR (lhs) == SSA_NAME_VAR (rhs))
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 ();
1048 restore_currdefs_to_original_value ();
1051 /* Similarly for the ELSE arm. */
1052 if (get_immediate_dominator (CDI_DOMINATORS, false_edge->dest) != bb
1053 || phi_nodes (false_edge->dest))
1055 struct edge_info *edge_info;
1058 edge_info = false_edge->aux;
1060 /* If we have info associated with this edge, record it into
1061 our equivalency tables. */
1064 tree *cond_equivalences = edge_info->cond_equivalences;
1065 tree lhs = edge_info->lhs;
1066 tree rhs = edge_info->rhs;
1068 /* If we have a simple NAME = VALUE equivalency record it.
1069 Until the jump threading selection code improves, only
1070 do this if both the name and value are SSA_NAMEs with
1071 the same underlying variable to avoid missing threading
1074 && TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME)
1075 record_const_or_copy (lhs, rhs);
1077 /* If we have 0 = COND or 1 = COND equivalences, record them
1078 into our expression hash tables. */
1079 if (cond_equivalences)
1080 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1082 tree expr = cond_equivalences[i];
1083 tree value = cond_equivalences[i + 1];
1085 record_cond (expr, value);
1089 thread_across_edge (walk_data, false_edge);
1091 /* No need to remove local expressions from our tables
1092 or restore vars to their original value as that will
1093 be done immediately below. */
1097 remove_local_expressions_from_table ();
1098 restore_nonzero_vars_to_original_value ();
1099 restore_vars_to_original_value ();
1100 restore_currdefs_to_original_value ();
1102 /* Remove VRP records associated with this basic block. They are no
1105 To be efficient, we note which variables have had their values
1106 constrained in this block. So walk over each variable in the
1107 VRP_VARIABLEs array. */
1108 while (VARRAY_ACTIVE_SIZE (vrp_variables_stack) > 0)
1110 tree var = VARRAY_TOP_TREE (vrp_variables_stack);
1111 struct vrp_hash_elt vrp_hash_elt, *vrp_hash_elt_p;
1114 /* Each variable has a stack of value range records. We want to
1115 invalidate those associated with our basic block. So we walk
1116 the array backwards popping off records associated with our
1117 block. Once we hit a record not associated with our block
1119 varray_type var_vrp_records;
1121 VARRAY_POP (vrp_variables_stack);
1126 vrp_hash_elt.var = var;
1127 vrp_hash_elt.records = NULL;
1129 slot = htab_find_slot (vrp_data, &vrp_hash_elt, NO_INSERT);
1131 vrp_hash_elt_p = (struct vrp_hash_elt *) *slot;
1132 var_vrp_records = vrp_hash_elt_p->records;
1134 while (VARRAY_ACTIVE_SIZE (var_vrp_records) > 0)
1136 struct vrp_element *element
1137 = (struct vrp_element *)VARRAY_TOP_GENERIC_PTR (var_vrp_records);
1139 if (element->bb != bb)
1142 VARRAY_POP (var_vrp_records);
1146 /* If we queued any statements to rescan in this block, then
1147 go ahead and rescan them now. */
1148 while (VARRAY_ACTIVE_SIZE (stmts_to_rescan) > 0)
1150 tree stmt = VARRAY_TOP_TREE (stmts_to_rescan);
1151 basic_block stmt_bb = bb_for_stmt (stmt);
1156 VARRAY_POP (stmts_to_rescan);
1157 mark_new_vars_to_rename (stmt, vars_to_rename);
1161 /* PHI nodes can create equivalences too.
1163 Ignoring any alternatives which are the same as the result, if
1164 all the alternatives are equal, then the PHI node creates an
1167 Additionally, if all the PHI alternatives are known to have a nonzero
1168 value, then the result of this PHI is known to have a nonzero value,
1169 even if we do not know its exact value. */
1172 record_equivalences_from_phis (basic_block bb)
1176 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1178 tree lhs = PHI_RESULT (phi);
1182 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1184 tree t = PHI_ARG_DEF (phi, i);
1186 if (TREE_CODE (t) == SSA_NAME || is_gimple_min_invariant (t))
1188 /* Ignore alternatives which are the same as our LHS. */
1189 if (operand_equal_p (lhs, t, 0))
1192 /* If we have not processed an alternative yet, then set
1193 RHS to this alternative. */
1196 /* If we have processed an alternative (stored in RHS), then
1197 see if it is equal to this one. If it isn't, then stop
1199 else if (! operand_equal_p (rhs, t, 0))
1206 /* If we had no interesting alternatives, then all the RHS alternatives
1207 must have been the same as LHS. */
1211 /* If we managed to iterate through each PHI alternative without
1212 breaking out of the loop, then we have a PHI which may create
1213 a useful equivalence. We do not need to record unwind data for
1214 this, since this is a true assignment and not an equivalence
1215 inferred from a comparison. All uses of this ssa name are dominated
1216 by this assignment, so unwinding just costs time and space. */
1217 if (i == PHI_NUM_ARGS (phi)
1218 && may_propagate_copy (lhs, rhs))
1219 SSA_NAME_VALUE (lhs) = rhs;
1221 /* Now see if we know anything about the nonzero property for the
1222 result of this PHI. */
1223 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1225 if (!PHI_ARG_NONZERO (phi, i))
1229 if (i == PHI_NUM_ARGS (phi))
1230 bitmap_set_bit (nonzero_vars, SSA_NAME_VERSION (PHI_RESULT (phi)));
1232 register_new_def (lhs, &block_defs_stack);
1236 /* Ignoring loop backedges, if BB has precisely one incoming edge then
1237 return that edge. Otherwise return NULL. */
1239 single_incoming_edge_ignoring_loop_edges (basic_block bb)
1245 FOR_EACH_EDGE (e, ei, bb->preds)
1247 /* A loop back edge can be identified by the destination of
1248 the edge dominating the source of the edge. */
1249 if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
1252 /* If we have already seen a non-loop edge, then we must have
1253 multiple incoming non-loop edges and thus we return NULL. */
1257 /* This is the first non-loop incoming edge we have found. Record
1265 /* Record any equivalences created by the incoming edge to BB. If BB
1266 has more than one incoming edge, then no equivalence is created. */
1269 record_equivalences_from_incoming_edge (basic_block bb)
1273 struct edge_info *edge_info;
1275 /* If our parent block ended with a control statment, then we may be
1276 able to record some equivalences based on which outgoing edge from
1277 the parent was followed. */
1278 parent = get_immediate_dominator (CDI_DOMINATORS, bb);
1280 e = single_incoming_edge_ignoring_loop_edges (bb);
1282 /* If we had a single incoming edge from our parent block, then enter
1283 any data associated with the edge into our tables. */
1284 if (e && e->src == parent)
1292 tree lhs = edge_info->lhs;
1293 tree rhs = edge_info->rhs;
1294 tree *cond_equivalences = edge_info->cond_equivalences;
1297 record_equality (lhs, rhs);
1299 if (cond_equivalences)
1301 bool recorded_range = false;
1302 for (i = 0; i < edge_info->max_cond_equivalences; i += 2)
1304 tree expr = cond_equivalences[i];
1305 tree value = cond_equivalences[i + 1];
1307 record_cond (expr, value);
1309 /* For the first true equivalence, record range
1310 information. We only do this for the first
1311 true equivalence as it should dominate any
1312 later true equivalences. */
1313 if (! recorded_range
1314 && COMPARISON_CLASS_P (expr)
1315 && value == boolean_true_node
1316 && TREE_CONSTANT (TREE_OPERAND (expr, 1)))
1318 record_range (expr, bb);
1319 recorded_range = true;
1327 /* Dump SSA statistics on FILE. */
1330 dump_dominator_optimization_stats (FILE *file)
1334 fprintf (file, "Total number of statements: %6ld\n\n",
1335 opt_stats.num_stmts);
1336 fprintf (file, "Exprs considered for dominator optimizations: %6ld\n",
1337 opt_stats.num_exprs_considered);
1339 n_exprs = opt_stats.num_exprs_considered;
1343 fprintf (file, " Redundant expressions eliminated: %6ld (%.0f%%)\n",
1344 opt_stats.num_re, PERCENT (opt_stats.num_re,
1347 fprintf (file, "\nHash table statistics:\n");
1349 fprintf (file, " avail_exprs: ");
1350 htab_statistics (file, avail_exprs);
1354 /* Dump SSA statistics on stderr. */
1357 debug_dominator_optimization_stats (void)
1359 dump_dominator_optimization_stats (stderr);
1363 /* Dump statistics for the hash table HTAB. */
1366 htab_statistics (FILE *file, htab_t htab)
1368 fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
1369 (long) htab_size (htab),
1370 (long) htab_elements (htab),
1371 htab_collisions (htab));
1374 /* Record the fact that VAR has a nonzero value, though we may not know
1375 its exact value. Note that if VAR is already known to have a nonzero
1376 value, then we do nothing. */
1379 record_var_is_nonzero (tree var)
1381 int indx = SSA_NAME_VERSION (var);
1383 if (bitmap_bit_p (nonzero_vars, indx))
1386 /* Mark it in the global table. */
1387 bitmap_set_bit (nonzero_vars, indx);
1389 /* Record this SSA_NAME so that we can reset the global table
1390 when we leave this block. */
1391 VARRAY_PUSH_TREE (nonzero_vars_stack, var);
1394 /* Enter a statement into the true/false expression hash table indicating
1395 that the condition COND has the value VALUE. */
1398 record_cond (tree cond, tree value)
1400 struct expr_hash_elt *element = xmalloc (sizeof (struct expr_hash_elt));
1403 initialize_hash_element (cond, value, element);
1405 slot = htab_find_slot_with_hash (avail_exprs, (void *)element,
1406 element->hash, true);
1409 *slot = (void *) element;
1410 VARRAY_PUSH_TREE (avail_exprs_stack, cond);
1416 /* Build a new conditional using NEW_CODE, OP0 and OP1 and store
1417 the new conditional into *p, then store a boolean_true_node
1418 into the the *(p + 1). */
1421 build_and_record_new_cond (enum tree_code new_code, tree op0, tree op1, tree *p)
1423 *p = build2 (new_code, boolean_type_node, op0, op1);
1425 *p = boolean_true_node;
1428 /* Record that COND is true and INVERTED is false into the edge information
1429 structure. Also record that any conditions dominated by COND are true
1432 For example, if a < b is true, then a <= b must also be true. */
1435 record_conditions (struct edge_info *edge_info, tree cond, tree inverted)
1439 if (!COMPARISON_CLASS_P (cond))
1442 op0 = TREE_OPERAND (cond, 0);
1443 op1 = TREE_OPERAND (cond, 1);
1445 switch (TREE_CODE (cond))
1449 edge_info->max_cond_equivalences = 12;
1450 edge_info->cond_equivalences = xmalloc (12 * sizeof (tree));
1451 build_and_record_new_cond ((TREE_CODE (cond) == LT_EXPR
1452 ? LE_EXPR : GE_EXPR),
1453 op0, op1, &edge_info->cond_equivalences[4]);
1454 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1455 &edge_info->cond_equivalences[6]);
1456 build_and_record_new_cond (NE_EXPR, op0, op1,
1457 &edge_info->cond_equivalences[8]);
1458 build_and_record_new_cond (LTGT_EXPR, op0, op1,
1459 &edge_info->cond_equivalences[10]);
1464 edge_info->max_cond_equivalences = 6;
1465 edge_info->cond_equivalences = xmalloc (6 * sizeof (tree));
1466 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1467 &edge_info->cond_equivalences[4]);
1471 edge_info->max_cond_equivalences = 10;
1472 edge_info->cond_equivalences = xmalloc (10 * sizeof (tree));
1473 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1474 &edge_info->cond_equivalences[4]);
1475 build_and_record_new_cond (LE_EXPR, op0, op1,
1476 &edge_info->cond_equivalences[6]);
1477 build_and_record_new_cond (GE_EXPR, op0, op1,
1478 &edge_info->cond_equivalences[8]);
1481 case UNORDERED_EXPR:
1482 edge_info->max_cond_equivalences = 16;
1483 edge_info->cond_equivalences = xmalloc (16 * sizeof (tree));
1484 build_and_record_new_cond (NE_EXPR, op0, op1,
1485 &edge_info->cond_equivalences[4]);
1486 build_and_record_new_cond (UNLE_EXPR, op0, op1,
1487 &edge_info->cond_equivalences[6]);
1488 build_and_record_new_cond (UNGE_EXPR, op0, op1,
1489 &edge_info->cond_equivalences[8]);
1490 build_and_record_new_cond (UNEQ_EXPR, op0, op1,
1491 &edge_info->cond_equivalences[10]);
1492 build_and_record_new_cond (UNLT_EXPR, op0, op1,
1493 &edge_info->cond_equivalences[12]);
1494 build_and_record_new_cond (UNGT_EXPR, op0, op1,
1495 &edge_info->cond_equivalences[14]);
1500 edge_info->max_cond_equivalences = 8;
1501 edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1502 build_and_record_new_cond ((TREE_CODE (cond) == UNLT_EXPR
1503 ? UNLE_EXPR : UNGE_EXPR),
1504 op0, op1, &edge_info->cond_equivalences[4]);
1505 build_and_record_new_cond (NE_EXPR, op0, op1,
1506 &edge_info->cond_equivalences[6]);
1510 edge_info->max_cond_equivalences = 8;
1511 edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1512 build_and_record_new_cond (UNLE_EXPR, op0, op1,
1513 &edge_info->cond_equivalences[4]);
1514 build_and_record_new_cond (UNGE_EXPR, op0, op1,
1515 &edge_info->cond_equivalences[6]);
1519 edge_info->max_cond_equivalences = 8;
1520 edge_info->cond_equivalences = xmalloc (8 * sizeof (tree));
1521 build_and_record_new_cond (NE_EXPR, op0, op1,
1522 &edge_info->cond_equivalences[4]);
1523 build_and_record_new_cond (ORDERED_EXPR, op0, op1,
1524 &edge_info->cond_equivalences[6]);
1528 edge_info->max_cond_equivalences = 4;
1529 edge_info->cond_equivalences = xmalloc (4 * sizeof (tree));
1533 /* Now store the original true and false conditions into the first
1535 edge_info->cond_equivalences[0] = cond;
1536 edge_info->cond_equivalences[1] = boolean_true_node;
1537 edge_info->cond_equivalences[2] = inverted;
1538 edge_info->cond_equivalences[3] = boolean_false_node;
1541 /* A helper function for record_const_or_copy and record_equality.
1542 Do the work of recording the value and undo info. */
1545 record_const_or_copy_1 (tree x, tree y, tree prev_x)
1547 SSA_NAME_VALUE (x) = y;
1549 VARRAY_PUSH_TREE (const_and_copies_stack, prev_x);
1550 VARRAY_PUSH_TREE (const_and_copies_stack, x);
1554 /* Return the loop depth of the basic block of the defining statement of X.
1555 This number should not be treated as absolutely correct because the loop
1556 information may not be completely up-to-date when dom runs. However, it
1557 will be relatively correct, and as more passes are taught to keep loop info
1558 up to date, the result will become more and more accurate. */
1561 loop_depth_of_name (tree x)
1566 /* If it's not an SSA_NAME, we have no clue where the definition is. */
1567 if (TREE_CODE (x) != SSA_NAME)
1570 /* Otherwise return the loop depth of the defining statement's bb.
1571 Note that there may not actually be a bb for this statement, if the
1572 ssa_name is live on entry. */
1573 defstmt = SSA_NAME_DEF_STMT (x);
1574 defbb = bb_for_stmt (defstmt);
1578 return defbb->loop_depth;
1582 /* Record that X is equal to Y in const_and_copies. Record undo
1583 information in the block-local varray. */
1586 record_const_or_copy (tree x, tree y)
1588 tree prev_x = SSA_NAME_VALUE (x);
1590 if (TREE_CODE (y) == SSA_NAME)
1592 tree tmp = SSA_NAME_VALUE (y);
1597 record_const_or_copy_1 (x, y, prev_x);
1600 /* Similarly, but assume that X and Y are the two operands of an EQ_EXPR.
1601 This constrains the cases in which we may treat this as assignment. */
1604 record_equality (tree x, tree y)
1606 tree prev_x = NULL, prev_y = NULL;
1608 if (TREE_CODE (x) == SSA_NAME)
1609 prev_x = SSA_NAME_VALUE (x);
1610 if (TREE_CODE (y) == SSA_NAME)
1611 prev_y = SSA_NAME_VALUE (y);
1613 /* If one of the previous values is invariant, or invariant in more loops
1614 (by depth), then use that.
1615 Otherwise it doesn't matter which value we choose, just so
1616 long as we canonicalize on one value. */
1617 if (TREE_INVARIANT (y))
1619 else if (TREE_INVARIANT (x) || (loop_depth_of_name (x) <= loop_depth_of_name (y)))
1620 prev_x = x, x = y, y = prev_x, prev_x = prev_y;
1621 else if (prev_x && TREE_INVARIANT (prev_x))
1622 x = y, y = prev_x, prev_x = prev_y;
1623 else if (prev_y && TREE_CODE (prev_y) != VALUE_HANDLE)
1626 /* After the swapping, we must have one SSA_NAME. */
1627 if (TREE_CODE (x) != SSA_NAME)
1630 /* For IEEE, -0.0 == 0.0, so we don't necessarily know the sign of a
1631 variable compared against zero. If we're honoring signed zeros,
1632 then we cannot record this value unless we know that the value is
1634 if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (x)))
1635 && (TREE_CODE (y) != REAL_CST
1636 || REAL_VALUES_EQUAL (dconst0, TREE_REAL_CST (y))))
1639 record_const_or_copy_1 (x, y, prev_x);
1642 /* Return true, if it is ok to do folding of an associative expression.
1643 EXP is the tree for the associative expression. */
1646 unsafe_associative_fp_binop (tree exp)
1648 enum tree_code code = TREE_CODE (exp);
1649 return !(!flag_unsafe_math_optimizations
1650 && (code == MULT_EXPR || code == PLUS_EXPR
1651 || code == MINUS_EXPR)
1652 && FLOAT_TYPE_P (TREE_TYPE (exp)));
1655 /* STMT is a MODIFY_EXPR for which we were unable to find RHS in the
1656 hash tables. Try to simplify the RHS using whatever equivalences
1657 we may have recorded.
1659 If we are able to simplify the RHS, then lookup the simplified form in
1660 the hash table and return the result. Otherwise return NULL. */
1663 simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *walk_data,
1664 tree stmt, int insert)
1666 tree rhs = TREE_OPERAND (stmt, 1);
1667 enum tree_code rhs_code = TREE_CODE (rhs);
1670 /* If we have lhs = ~x, look and see if we earlier had x = ~y.
1671 In which case we can change this statement to be lhs = y.
1672 Which can then be copy propagated.
1674 Similarly for negation. */
1675 if ((rhs_code == BIT_NOT_EXPR || rhs_code == NEGATE_EXPR)
1676 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
1678 /* Get the definition statement for our RHS. */
1679 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1681 /* See if the RHS_DEF_STMT has the same form as our statement. */
1682 if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR
1683 && TREE_CODE (TREE_OPERAND (rhs_def_stmt, 1)) == rhs_code)
1685 tree rhs_def_operand;
1687 rhs_def_operand = TREE_OPERAND (TREE_OPERAND (rhs_def_stmt, 1), 0);
1689 /* Verify that RHS_DEF_OPERAND is a suitable SSA variable. */
1690 if (TREE_CODE (rhs_def_operand) == SSA_NAME
1691 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))
1692 result = update_rhs_and_lookup_avail_expr (stmt,
1698 /* If we have z = (x OP C1), see if we earlier had x = y OP C2.
1699 If OP is associative, create and fold (y OP C2) OP C1 which
1700 should result in (y OP C3), use that as the RHS for the
1701 assignment. Add minus to this, as we handle it specially below. */
1702 if ((associative_tree_code (rhs_code) || rhs_code == MINUS_EXPR)
1703 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
1704 && is_gimple_min_invariant (TREE_OPERAND (rhs, 1)))
1706 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1708 /* See if the RHS_DEF_STMT has the same form as our statement. */
1709 if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR)
1711 tree rhs_def_rhs = TREE_OPERAND (rhs_def_stmt, 1);
1712 enum tree_code rhs_def_code = TREE_CODE (rhs_def_rhs);
1714 if ((rhs_code == rhs_def_code && unsafe_associative_fp_binop (rhs))
1715 || (rhs_code == PLUS_EXPR && rhs_def_code == MINUS_EXPR)
1716 || (rhs_code == MINUS_EXPR && rhs_def_code == PLUS_EXPR))
1718 tree def_stmt_op0 = TREE_OPERAND (rhs_def_rhs, 0);
1719 tree def_stmt_op1 = TREE_OPERAND (rhs_def_rhs, 1);
1721 if (TREE_CODE (def_stmt_op0) == SSA_NAME
1722 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def_stmt_op0)
1723 && is_gimple_min_invariant (def_stmt_op1))
1725 tree outer_const = TREE_OPERAND (rhs, 1);
1726 tree type = TREE_TYPE (TREE_OPERAND (stmt, 0));
1729 /* If we care about correct floating point results, then
1730 don't fold x + c1 - c2. Note that we need to take both
1731 the codes and the signs to figure this out. */
1732 if (FLOAT_TYPE_P (type)
1733 && !flag_unsafe_math_optimizations
1734 && (rhs_def_code == PLUS_EXPR
1735 || rhs_def_code == MINUS_EXPR))
1739 neg ^= (rhs_code == MINUS_EXPR);
1740 neg ^= (rhs_def_code == MINUS_EXPR);
1741 neg ^= real_isneg (TREE_REAL_CST_PTR (outer_const));
1742 neg ^= real_isneg (TREE_REAL_CST_PTR (def_stmt_op1));
1745 goto dont_fold_assoc;
1748 /* Ho hum. So fold will only operate on the outermost
1749 thingy that we give it, so we have to build the new
1750 expression in two pieces. This requires that we handle
1751 combinations of plus and minus. */
1752 if (rhs_def_code != rhs_code)
1754 if (rhs_def_code == MINUS_EXPR)
1755 t = build (MINUS_EXPR, type, outer_const, def_stmt_op1);
1757 t = build (MINUS_EXPR, type, def_stmt_op1, outer_const);
1758 rhs_code = PLUS_EXPR;
1760 else if (rhs_def_code == MINUS_EXPR)
1761 t = build (PLUS_EXPR, type, def_stmt_op1, outer_const);
1763 t = build (rhs_def_code, type, def_stmt_op1, outer_const);
1765 t = build (rhs_code, type, def_stmt_op0, t);
1768 /* If the result is a suitable looking gimple expression,
1769 then use it instead of the original for STMT. */
1770 if (TREE_CODE (t) == SSA_NAME
1771 || (UNARY_CLASS_P (t)
1772 && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME)
1773 || ((BINARY_CLASS_P (t) || COMPARISON_CLASS_P (t))
1774 && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME
1775 && is_gimple_val (TREE_OPERAND (t, 1))))
1776 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1783 /* Transform TRUNC_DIV_EXPR and TRUNC_MOD_EXPR into RSHIFT_EXPR
1784 and BIT_AND_EXPR respectively if the first operand is greater
1785 than zero and the second operand is an exact power of two. */
1786 if ((rhs_code == TRUNC_DIV_EXPR || rhs_code == TRUNC_MOD_EXPR)
1787 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0)))
1788 && integer_pow2p (TREE_OPERAND (rhs, 1)))
1791 tree op = TREE_OPERAND (rhs, 0);
1793 if (TYPE_UNSIGNED (TREE_TYPE (op)))
1795 val = integer_one_node;
1799 tree dummy_cond = walk_data->global_data;
1803 dummy_cond = build (GT_EXPR, boolean_type_node,
1804 op, integer_zero_node);
1805 dummy_cond = build (COND_EXPR, void_type_node,
1806 dummy_cond, NULL, NULL);
1807 walk_data->global_data = dummy_cond;
1811 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), GT_EXPR);
1812 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op;
1813 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1)
1814 = integer_zero_node;
1816 val = simplify_cond_and_lookup_avail_expr (dummy_cond, NULL, false);
1819 if (val && integer_onep (val))
1822 tree op0 = TREE_OPERAND (rhs, 0);
1823 tree op1 = TREE_OPERAND (rhs, 1);
1825 if (rhs_code == TRUNC_DIV_EXPR)
1826 t = build (RSHIFT_EXPR, TREE_TYPE (op0), op0,
1827 build_int_cst (NULL_TREE, tree_log2 (op1)));
1829 t = build (BIT_AND_EXPR, TREE_TYPE (op0), op0,
1830 local_fold (build (MINUS_EXPR, TREE_TYPE (op1),
1831 op1, integer_one_node)));
1833 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1837 /* Transform ABS (X) into X or -X as appropriate. */
1838 if (rhs_code == ABS_EXPR
1839 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0))))
1842 tree op = TREE_OPERAND (rhs, 0);
1843 tree type = TREE_TYPE (op);
1845 if (TYPE_UNSIGNED (type))
1847 val = integer_zero_node;
1851 tree dummy_cond = walk_data->global_data;
1855 dummy_cond = build (LE_EXPR, boolean_type_node,
1856 op, integer_zero_node);
1857 dummy_cond = build (COND_EXPR, void_type_node,
1858 dummy_cond, NULL, NULL);
1859 walk_data->global_data = dummy_cond;
1863 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), LE_EXPR);
1864 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op;
1865 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1)
1866 = build_int_cst (type, 0);
1868 val = simplify_cond_and_lookup_avail_expr (dummy_cond, NULL, false);
1872 TREE_SET_CODE (COND_EXPR_COND (dummy_cond), GE_EXPR);
1873 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 0) = op;
1874 TREE_OPERAND (COND_EXPR_COND (dummy_cond), 1)
1875 = build_int_cst (type, 0);
1877 val = simplify_cond_and_lookup_avail_expr (dummy_cond,
1882 if (integer_zerop (val))
1883 val = integer_one_node;
1884 else if (integer_onep (val))
1885 val = integer_zero_node;
1891 && (integer_onep (val) || integer_zerop (val)))
1895 if (integer_onep (val))
1896 t = build1 (NEGATE_EXPR, TREE_TYPE (op), op);
1900 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1904 /* Optimize *"foo" into 'f'. This is done here rather than
1905 in fold to avoid problems with stuff like &*"foo". */
1906 if (TREE_CODE (rhs) == INDIRECT_REF || TREE_CODE (rhs) == ARRAY_REF)
1908 tree t = fold_read_from_constant_string (rhs);
1911 result = update_rhs_and_lookup_avail_expr (stmt, t, insert);
1917 /* COND is a condition of the form:
1919 x == const or x != const
1921 Look back to x's defining statement and see if x is defined as
1925 If const is unchanged if we convert it to type, then we can build
1926 the equivalent expression:
1929 y == const or y != const
1931 Which may allow further optimizations.
1933 Return the equivalent comparison or NULL if no such equivalent comparison
1937 find_equivalent_equality_comparison (tree cond)
1939 tree op0 = TREE_OPERAND (cond, 0);
1940 tree op1 = TREE_OPERAND (cond, 1);
1941 tree def_stmt = SSA_NAME_DEF_STMT (op0);
1943 /* OP0 might have been a parameter, so first make sure it
1944 was defined by a MODIFY_EXPR. */
1945 if (def_stmt && TREE_CODE (def_stmt) == MODIFY_EXPR)
1947 tree def_rhs = TREE_OPERAND (def_stmt, 1);
1949 /* Now make sure the RHS of the MODIFY_EXPR is a typecast. */
1950 if ((TREE_CODE (def_rhs) == NOP_EXPR
1951 || TREE_CODE (def_rhs) == CONVERT_EXPR)
1952 && TREE_CODE (TREE_OPERAND (def_rhs, 0)) == SSA_NAME)
1954 tree def_rhs_inner = TREE_OPERAND (def_rhs, 0);
1955 tree def_rhs_inner_type = TREE_TYPE (def_rhs_inner);
1958 if (TYPE_PRECISION (def_rhs_inner_type)
1959 > TYPE_PRECISION (TREE_TYPE (def_rhs)))
1962 /* What we want to prove is that if we convert OP1 to
1963 the type of the object inside the NOP_EXPR that the
1964 result is still equivalent to SRC.
1966 If that is true, the build and return new equivalent
1967 condition which uses the source of the typecast and the
1968 new constant (which has only changed its type). */
1969 new = build1 (TREE_CODE (def_rhs), def_rhs_inner_type, op1);
1970 new = local_fold (new);
1971 if (is_gimple_val (new) && tree_int_cst_equal (new, op1))
1972 return build (TREE_CODE (cond), TREE_TYPE (cond),
1973 def_rhs_inner, new);
1979 /* STMT is a COND_EXPR for which we could not trivially determine its
1980 result. This routine attempts to find equivalent forms of the
1981 condition which we may be able to optimize better. It also
1982 uses simple value range propagation to optimize conditionals. */
1985 simplify_cond_and_lookup_avail_expr (tree stmt,
1989 tree cond = COND_EXPR_COND (stmt);
1991 if (COMPARISON_CLASS_P (cond))
1993 tree op0 = TREE_OPERAND (cond, 0);
1994 tree op1 = TREE_OPERAND (cond, 1);
1996 if (TREE_CODE (op0) == SSA_NAME && is_gimple_min_invariant (op1))
1999 tree low, high, cond_low, cond_high;
2000 int lowequal, highequal, swapped, no_overlap, subset, cond_inverted;
2001 varray_type vrp_records;
2002 struct vrp_element *element;
2003 struct vrp_hash_elt vrp_hash_elt, *vrp_hash_elt_p;
2006 /* First see if we have test of an SSA_NAME against a constant
2007 where the SSA_NAME is defined by an earlier typecast which
2008 is irrelevant when performing tests against the given
2010 if (TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
2012 tree new_cond = find_equivalent_equality_comparison (cond);
2016 /* Update the statement to use the new equivalent
2018 COND_EXPR_COND (stmt) = new_cond;
2020 /* If this is not a real stmt, ann will be NULL and we
2021 avoid processing the operands. */
2025 /* Lookup the condition and return its known value if it
2027 new_cond = lookup_avail_expr (stmt, insert);
2031 /* The operands have changed, so update op0 and op1. */
2032 op0 = TREE_OPERAND (cond, 0);
2033 op1 = TREE_OPERAND (cond, 1);
2037 /* Consult the value range records for this variable (if they exist)
2038 to see if we can eliminate or simplify this conditional.
2040 Note two tests are necessary to determine no records exist.
2041 First we have to see if the virtual array exists, if it
2042 exists, then we have to check its active size.
2044 Also note the vast majority of conditionals are not testing
2045 a variable which has had its range constrained by an earlier
2046 conditional. So this filter avoids a lot of unnecessary work. */
2047 vrp_hash_elt.var = op0;
2048 vrp_hash_elt.records = NULL;
2049 slot = htab_find_slot (vrp_data, &vrp_hash_elt, NO_INSERT);
2053 vrp_hash_elt_p = (struct vrp_hash_elt *) *slot;
2054 vrp_records = vrp_hash_elt_p->records;
2055 if (vrp_records == NULL)
2058 limit = VARRAY_ACTIVE_SIZE (vrp_records);
2060 /* If we have no value range records for this variable, or we are
2061 unable to extract a range for this condition, then there is
2064 || ! extract_range_from_cond (cond, &cond_high,
2065 &cond_low, &cond_inverted))
2068 /* We really want to avoid unnecessary computations of range
2069 info. So all ranges are computed lazily; this avoids a
2070 lot of unnecessary work. i.e., we record the conditional,
2071 but do not process how it constrains the variable's
2072 potential values until we know that processing the condition
2075 However, we do not want to have to walk a potentially long
2076 list of ranges, nor do we want to compute a variable's
2077 range more than once for a given path.
2079 Luckily, each time we encounter a conditional that can not
2080 be otherwise optimized we will end up here and we will
2081 compute the necessary range information for the variable
2082 used in this condition.
2084 Thus you can conclude that there will never be more than one
2085 conditional associated with a variable which has not been
2086 processed. So we never need to merge more than one new
2087 conditional into the current range.
2089 These properties also help us avoid unnecessary work. */
2091 = (struct vrp_element *)VARRAY_GENERIC_PTR (vrp_records, limit - 1);
2093 if (element->high && element->low)
2095 /* The last element has been processed, so there is no range
2096 merging to do, we can simply use the high/low values
2097 recorded in the last element. */
2099 high = element->high;
2103 tree tmp_high, tmp_low;
2106 /* The last element has not been processed. Process it now. */
2107 extract_range_from_cond (element->cond, &tmp_high,
2110 /* If this is the only element, then no merging is necessary,
2111 the high/low values from extract_range_from_cond are all
2120 /* Get the high/low value from the previous element. */
2121 struct vrp_element *prev
2122 = (struct vrp_element *)VARRAY_GENERIC_PTR (vrp_records,
2127 /* Merge in this element's range with the range from the
2130 The low value for the merged range is the maximum of
2131 the previous low value and the low value of this record.
2133 Similarly the high value for the merged range is the
2134 minimum of the previous high value and the high value of
2136 low = (tree_int_cst_compare (low, tmp_low) == 1
2138 high = (tree_int_cst_compare (high, tmp_high) == -1
2142 /* And record the computed range. */
2144 element->high = high;
2148 /* After we have constrained this variable's potential values,
2149 we try to determine the result of the given conditional.
2151 To simplify later tests, first determine if the current
2152 low value is the same low value as the conditional.
2153 Similarly for the current high value and the high value
2154 for the conditional. */
2155 lowequal = tree_int_cst_equal (low, cond_low);
2156 highequal = tree_int_cst_equal (high, cond_high);
2158 if (lowequal && highequal)
2159 return (cond_inverted ? boolean_false_node : boolean_true_node);
2161 /* To simplify the overlap/subset tests below we may want
2162 to swap the two ranges so that the larger of the two
2163 ranges occurs "first". */
2165 if (tree_int_cst_compare (low, cond_low) == 1
2167 && tree_int_cst_compare (cond_high, high) == 1))
2180 /* Now determine if there is no overlap in the ranges
2181 or if the second range is a subset of the first range. */
2182 no_overlap = tree_int_cst_lt (high, cond_low);
2183 subset = tree_int_cst_compare (cond_high, high) != 1;
2185 /* If there was no overlap in the ranges, then this conditional
2186 always has a false value (unless we had to invert this
2187 conditional, in which case it always has a true value). */
2189 return (cond_inverted ? boolean_true_node : boolean_false_node);
2191 /* If the current range is a subset of the condition's range,
2192 then this conditional always has a true value (unless we
2193 had to invert this conditional, in which case it always
2194 has a true value). */
2195 if (subset && swapped)
2196 return (cond_inverted ? boolean_false_node : boolean_true_node);
2198 /* We were unable to determine the result of the conditional.
2199 However, we may be able to simplify the conditional. First
2200 merge the ranges in the same manner as range merging above. */
2201 low = tree_int_cst_compare (low, cond_low) == 1 ? low : cond_low;
2202 high = tree_int_cst_compare (high, cond_high) == -1 ? high : cond_high;
2204 /* If the range has converged to a single point, then turn this
2205 into an equality comparison. */
2206 if (TREE_CODE (cond) != EQ_EXPR
2207 && TREE_CODE (cond) != NE_EXPR
2208 && tree_int_cst_equal (low, high))
2210 TREE_SET_CODE (cond, EQ_EXPR);
2211 TREE_OPERAND (cond, 1) = high;
2218 /* STMT is a SWITCH_EXPR for which we could not trivially determine its
2219 result. This routine attempts to find equivalent forms of the
2220 condition which we may be able to optimize better. */
2223 simplify_switch_and_lookup_avail_expr (tree stmt, int insert)
2225 tree cond = SWITCH_COND (stmt);
2228 /* The optimization that we really care about is removing unnecessary
2229 casts. That will let us do much better in propagating the inferred
2230 constant at the switch target. */
2231 if (TREE_CODE (cond) == SSA_NAME)
2233 def = SSA_NAME_DEF_STMT (cond);
2234 if (TREE_CODE (def) == MODIFY_EXPR)
2236 def = TREE_OPERAND (def, 1);
2237 if (TREE_CODE (def) == NOP_EXPR)
2242 def = TREE_OPERAND (def, 0);
2244 #ifdef ENABLE_CHECKING
2245 /* ??? Why was Jeff testing this? We are gimple... */
2246 gcc_assert (is_gimple_val (def));
2249 to = TREE_TYPE (cond);
2250 ti = TREE_TYPE (def);
2252 /* If we have an extension that preserves value, then we
2253 can copy the source value into the switch. */
2255 need_precision = TYPE_PRECISION (ti);
2257 if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
2259 else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
2260 need_precision += 1;
2261 if (TYPE_PRECISION (to) < need_precision)
2266 SWITCH_COND (stmt) = def;
2269 return lookup_avail_expr (stmt, insert);
2279 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2280 known value for that SSA_NAME (or NULL if no value is known).
2282 NONZERO_VARS is the set SSA_NAMES known to have a nonzero value,
2283 even if we don't know their precise value.
2285 Propagate values from CONST_AND_COPIES and NONZERO_VARS into the PHI
2286 nodes of the successors of BB. */
2289 cprop_into_successor_phis (basic_block bb, bitmap nonzero_vars)
2294 /* This can get rather expensive if the implementation is naive in
2295 how it finds the phi alternative associated with a particular edge. */
2296 FOR_EACH_EDGE (e, ei, bb->succs)
2302 /* If this is an abnormal edge, then we do not want to copy propagate
2303 into the PHI alternative associated with this edge. */
2304 if (e->flags & EDGE_ABNORMAL)
2307 phi = phi_nodes (e->dest);
2311 /* There is no guarantee that for any two PHI nodes in a block that
2312 the phi alternative associated with a particular edge will be
2313 at the same index in the phi alternative array.
2315 However, it is very likely they will be the same. So we keep
2316 track of the index of the alternative where we found the edge in
2317 the previous phi node and check that index first in the next
2318 phi node. If that hint fails, then we actually search all
2320 phi_num_args = PHI_NUM_ARGS (phi);
2321 hint = phi_num_args;
2322 for ( ; phi; phi = PHI_CHAIN (phi))
2326 use_operand_p orig_p;
2329 /* If the hint is valid (!= phi_num_args), see if it points
2330 us to the desired phi alternative. */
2331 if (hint != phi_num_args && PHI_ARG_EDGE (phi, hint) == e)
2335 /* The hint was either invalid or did not point to the
2336 correct phi alternative. Search all the alternatives
2337 for the correct one. Update the hint. */
2338 for (i = 0; i < phi_num_args; i++)
2339 if (PHI_ARG_EDGE (phi, i) == e)
2344 /* If we did not find the proper alternative, then something is
2346 gcc_assert (hint != phi_num_args);
2348 /* The alternative may be associated with a constant, so verify
2349 it is an SSA_NAME before doing anything with it. */
2350 orig_p = PHI_ARG_DEF_PTR (phi, hint);
2351 orig = USE_FROM_PTR (orig_p);
2352 if (TREE_CODE (orig) != SSA_NAME)
2355 /* If the alternative is known to have a nonzero value, record
2356 that fact in the PHI node itself for future use. */
2357 if (bitmap_bit_p (nonzero_vars, SSA_NAME_VERSION (orig)))
2358 PHI_ARG_NONZERO (phi, hint) = true;
2360 /* If we have *ORIG_P in our constant/copy table, then replace
2361 ORIG_P with its value in our constant/copy table. */
2362 new = SSA_NAME_VALUE (orig);
2364 && (TREE_CODE (new) == SSA_NAME
2365 || is_gimple_min_invariant (new))
2366 && may_propagate_copy (orig, new))
2368 propagate_value (orig_p, new);
2374 /* We have finished optimizing BB, record any information implied by
2375 taking a specific outgoing edge from BB. */
2378 record_edge_info (basic_block bb)
2380 block_stmt_iterator bsi = bsi_last (bb);
2381 struct edge_info *edge_info;
2383 if (! bsi_end_p (bsi))
2385 tree stmt = bsi_stmt (bsi);
2387 if (stmt && TREE_CODE (stmt) == SWITCH_EXPR)
2389 tree cond = SWITCH_COND (stmt);
2391 if (TREE_CODE (cond) == SSA_NAME)
2393 tree labels = SWITCH_LABELS (stmt);
2394 int i, n_labels = TREE_VEC_LENGTH (labels);
2395 tree *info = xcalloc (n_basic_blocks, sizeof (tree));
2399 for (i = 0; i < n_labels; i++)
2401 tree label = TREE_VEC_ELT (labels, i);
2402 basic_block target_bb = label_to_block (CASE_LABEL (label));
2404 if (CASE_HIGH (label)
2405 || !CASE_LOW (label)
2406 || info[target_bb->index])
2407 info[target_bb->index] = error_mark_node;
2409 info[target_bb->index] = label;
2412 FOR_EACH_EDGE (e, ei, bb->succs)
2414 basic_block target_bb = e->dest;
2415 tree node = info[target_bb->index];
2417 if (node != NULL && node != error_mark_node)
2419 tree x = fold_convert (TREE_TYPE (cond), CASE_LOW (node));
2420 edge_info = allocate_edge_info (e);
2421 edge_info->lhs = cond;
2429 /* A COND_EXPR may create equivalences too. */
2430 if (stmt && TREE_CODE (stmt) == COND_EXPR)
2432 tree cond = COND_EXPR_COND (stmt);
2436 extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
2438 /* If the conditional is a single variable 'X', record 'X = 1'
2439 for the true edge and 'X = 0' on the false edge. */
2440 if (SSA_VAR_P (cond))
2442 struct edge_info *edge_info;
2444 edge_info = allocate_edge_info (true_edge);
2445 edge_info->lhs = cond;
2446 edge_info->rhs = constant_boolean_node (1, TREE_TYPE (cond));
2448 edge_info = allocate_edge_info (false_edge);
2449 edge_info->lhs = cond;
2450 edge_info->rhs = constant_boolean_node (0, TREE_TYPE (cond));
2452 /* Equality tests may create one or two equivalences. */
2453 else if (COMPARISON_CLASS_P (cond))
2455 tree op0 = TREE_OPERAND (cond, 0);
2456 tree op1 = TREE_OPERAND (cond, 1);
2458 /* Special case comparing booleans against a constant as we
2459 know the value of OP0 on both arms of the branch. i.e., we
2460 can record an equivalence for OP0 rather than COND. */
2461 if ((TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
2462 && TREE_CODE (op0) == SSA_NAME
2463 && TREE_CODE (TREE_TYPE (op0)) == BOOLEAN_TYPE
2464 && is_gimple_min_invariant (op1))
2466 if (TREE_CODE (cond) == EQ_EXPR)
2468 edge_info = allocate_edge_info (true_edge);
2469 edge_info->lhs = op0;
2470 edge_info->rhs = (integer_zerop (op1)
2471 ? boolean_false_node
2472 : boolean_true_node);
2474 edge_info = allocate_edge_info (false_edge);
2475 edge_info->lhs = op0;
2476 edge_info->rhs = (integer_zerop (op1)
2478 : boolean_false_node);
2482 edge_info = allocate_edge_info (true_edge);
2483 edge_info->lhs = op0;
2484 edge_info->rhs = (integer_zerop (op1)
2486 : boolean_false_node);
2488 edge_info = allocate_edge_info (false_edge);
2489 edge_info->lhs = op0;
2490 edge_info->rhs = (integer_zerop (op1)
2491 ? boolean_false_node
2492 : boolean_true_node);
2496 if (is_gimple_min_invariant (op0)
2497 && (TREE_CODE (op1) == SSA_NAME
2498 || is_gimple_min_invariant (op1)))
2500 tree inverted = invert_truthvalue (cond);
2501 struct edge_info *edge_info;
2503 edge_info = allocate_edge_info (true_edge);
2504 record_conditions (edge_info, cond, inverted);
2506 if (TREE_CODE (cond) == EQ_EXPR)
2508 edge_info->lhs = op1;
2509 edge_info->rhs = op0;
2512 edge_info = allocate_edge_info (false_edge);
2513 record_conditions (edge_info, inverted, cond);
2515 if (TREE_CODE (cond) == NE_EXPR)
2517 edge_info->lhs = op1;
2518 edge_info->rhs = op0;
2522 if (TREE_CODE (op0) == SSA_NAME
2523 && (is_gimple_min_invariant (op1)
2524 || TREE_CODE (op1) == SSA_NAME))
2526 tree inverted = invert_truthvalue (cond);
2527 struct edge_info *edge_info;
2529 edge_info = allocate_edge_info (true_edge);
2530 record_conditions (edge_info, cond, inverted);
2532 if (TREE_CODE (cond) == EQ_EXPR)
2534 edge_info->lhs = op0;
2535 edge_info->rhs = op1;
2538 edge_info = allocate_edge_info (false_edge);
2539 record_conditions (edge_info, inverted, cond);
2541 if (TREE_CODE (cond) == NE_EXPR)
2543 edge_info->lhs = op0;
2544 edge_info->rhs = op1;
2549 /* ??? TRUTH_NOT_EXPR can create an equivalence too. */
2554 /* Propagate information from BB to its outgoing edges.
2556 This can include equivalency information implied by control statements
2557 at the end of BB and const/copy propagation into PHIs in BB's
2558 successor blocks. */
2561 propagate_to_outgoing_edges (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
2565 record_edge_info (bb);
2566 cprop_into_successor_phis (bb, nonzero_vars);
2569 /* Search for redundant computations in STMT. If any are found, then
2570 replace them with the variable holding the result of the computation.
2572 If safe, record this expression into the available expression hash
2576 eliminate_redundant_computations (struct dom_walk_data *walk_data,
2577 tree stmt, stmt_ann_t ann)
2579 v_may_def_optype v_may_defs = V_MAY_DEF_OPS (ann);
2580 tree *expr_p, def = NULL_TREE;
2583 bool retval = false;
2585 if (TREE_CODE (stmt) == MODIFY_EXPR)
2586 def = TREE_OPERAND (stmt, 0);
2588 /* Certain expressions on the RHS can be optimized away, but can not
2589 themselves be entered into the hash tables. */
2590 if (ann->makes_aliased_stores
2592 || TREE_CODE (def) != SSA_NAME
2593 || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def)
2594 || NUM_V_MAY_DEFS (v_may_defs) != 0)
2597 /* Check if the expression has been computed before. */
2598 cached_lhs = lookup_avail_expr (stmt, insert);
2600 /* If this is an assignment and the RHS was not in the hash table,
2601 then try to simplify the RHS and lookup the new RHS in the
2603 if (! cached_lhs && TREE_CODE (stmt) == MODIFY_EXPR)
2604 cached_lhs = simplify_rhs_and_lookup_avail_expr (walk_data, stmt, insert);
2605 /* Similarly if this is a COND_EXPR and we did not find its
2606 expression in the hash table, simplify the condition and
2608 else if (! cached_lhs && TREE_CODE (stmt) == COND_EXPR)
2609 cached_lhs = simplify_cond_and_lookup_avail_expr (stmt, ann, insert);
2610 /* Similarly for a SWITCH_EXPR. */
2611 else if (!cached_lhs && TREE_CODE (stmt) == SWITCH_EXPR)
2612 cached_lhs = simplify_switch_and_lookup_avail_expr (stmt, insert);
2614 opt_stats.num_exprs_considered++;
2616 /* Get a pointer to the expression we are trying to optimize. */
2617 if (TREE_CODE (stmt) == COND_EXPR)
2618 expr_p = &COND_EXPR_COND (stmt);
2619 else if (TREE_CODE (stmt) == SWITCH_EXPR)
2620 expr_p = &SWITCH_COND (stmt);
2621 else if (TREE_CODE (stmt) == RETURN_EXPR && TREE_OPERAND (stmt, 0))
2622 expr_p = &TREE_OPERAND (TREE_OPERAND (stmt, 0), 1);
2624 expr_p = &TREE_OPERAND (stmt, 1);
2626 /* It is safe to ignore types here since we have already done
2627 type checking in the hashing and equality routines. In fact
2628 type checking here merely gets in the way of constant
2629 propagation. Also, make sure that it is safe to propagate
2630 CACHED_LHS into *EXPR_P. */
2632 && (TREE_CODE (cached_lhs) != SSA_NAME
2633 || may_propagate_copy (*expr_p, cached_lhs)))
2635 if (dump_file && (dump_flags & TDF_DETAILS))
2637 fprintf (dump_file, " Replaced redundant expr '");
2638 print_generic_expr (dump_file, *expr_p, dump_flags);
2639 fprintf (dump_file, "' with '");
2640 print_generic_expr (dump_file, cached_lhs, dump_flags);
2641 fprintf (dump_file, "'\n");
2646 #if defined ENABLE_CHECKING
2647 gcc_assert (TREE_CODE (cached_lhs) == SSA_NAME
2648 || is_gimple_min_invariant (cached_lhs));
2651 if (TREE_CODE (cached_lhs) == ADDR_EXPR
2652 || (POINTER_TYPE_P (TREE_TYPE (*expr_p))
2653 && is_gimple_min_invariant (cached_lhs)))
2656 propagate_tree_value (expr_p, cached_lhs);
2662 /* STMT, a MODIFY_EXPR, may create certain equivalences, in either
2663 the available expressions table or the const_and_copies table.
2664 Detect and record those equivalences. */
2667 record_equivalences_from_stmt (tree stmt,
2671 tree lhs = TREE_OPERAND (stmt, 0);
2672 enum tree_code lhs_code = TREE_CODE (lhs);
2675 if (lhs_code == SSA_NAME)
2677 tree rhs = TREE_OPERAND (stmt, 1);
2679 /* Strip away any useless type conversions. */
2680 STRIP_USELESS_TYPE_CONVERSION (rhs);
2682 /* If the RHS of the assignment is a constant or another variable that
2683 may be propagated, register it in the CONST_AND_COPIES table. We
2684 do not need to record unwind data for this, since this is a true
2685 assignment and not an equivalence inferred from a comparison. All
2686 uses of this ssa name are dominated by this assignment, so unwinding
2687 just costs time and space. */
2689 && (TREE_CODE (rhs) == SSA_NAME
2690 || is_gimple_min_invariant (rhs)))
2691 SSA_NAME_VALUE (lhs) = rhs;
2693 /* alloca never returns zero and the address of a non-weak symbol
2694 is never zero. NOP_EXPRs and CONVERT_EXPRs can be completely
2695 stripped as they do not affect this equivalence. */
2696 while (TREE_CODE (rhs) == NOP_EXPR
2697 || TREE_CODE (rhs) == CONVERT_EXPR)
2698 rhs = TREE_OPERAND (rhs, 0);
2700 if (alloca_call_p (rhs)
2701 || (TREE_CODE (rhs) == ADDR_EXPR
2702 && DECL_P (TREE_OPERAND (rhs, 0))
2703 && ! DECL_WEAK (TREE_OPERAND (rhs, 0))))
2704 record_var_is_nonzero (lhs);
2706 /* IOR of any value with a nonzero value will result in a nonzero
2707 value. Even if we do not know the exact result recording that
2708 the result is nonzero is worth the effort. */
2709 if (TREE_CODE (rhs) == BIT_IOR_EXPR
2710 && integer_nonzerop (TREE_OPERAND (rhs, 1)))
2711 record_var_is_nonzero (lhs);
2714 /* Look at both sides for pointer dereferences. If we find one, then
2715 the pointer must be nonnull and we can enter that equivalence into
2717 if (flag_delete_null_pointer_checks)
2718 for (i = 0; i < 2; i++)
2720 tree t = TREE_OPERAND (stmt, i);
2722 /* Strip away any COMPONENT_REFs. */
2723 while (TREE_CODE (t) == COMPONENT_REF)
2724 t = TREE_OPERAND (t, 0);
2726 /* Now see if this is a pointer dereference. */
2727 if (INDIRECT_REF_P (t))
2729 tree op = TREE_OPERAND (t, 0);
2731 /* If the pointer is a SSA variable, then enter new
2732 equivalences into the hash table. */
2733 while (TREE_CODE (op) == SSA_NAME)
2735 tree def = SSA_NAME_DEF_STMT (op);
2737 record_var_is_nonzero (op);
2739 /* And walk up the USE-DEF chains noting other SSA_NAMEs
2740 which are known to have a nonzero value. */
2742 && TREE_CODE (def) == MODIFY_EXPR
2743 && TREE_CODE (TREE_OPERAND (def, 1)) == NOP_EXPR)
2744 op = TREE_OPERAND (TREE_OPERAND (def, 1), 0);
2751 /* A memory store, even an aliased store, creates a useful
2752 equivalence. By exchanging the LHS and RHS, creating suitable
2753 vops and recording the result in the available expression table,
2754 we may be able to expose more redundant loads. */
2755 if (!ann->has_volatile_ops
2756 && (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME
2757 || is_gimple_min_invariant (TREE_OPERAND (stmt, 1)))
2758 && !is_gimple_reg (lhs))
2760 tree rhs = TREE_OPERAND (stmt, 1);
2763 /* FIXME: If the LHS of the assignment is a bitfield and the RHS
2764 is a constant, we need to adjust the constant to fit into the
2765 type of the LHS. If the LHS is a bitfield and the RHS is not
2766 a constant, then we can not record any equivalences for this
2767 statement since we would need to represent the widening or
2768 narrowing of RHS. This fixes gcc.c-torture/execute/921016-1.c
2769 and should not be necessary if GCC represented bitfields
2771 if (lhs_code == COMPONENT_REF
2772 && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1)))
2774 if (TREE_CONSTANT (rhs))
2775 rhs = widen_bitfield (rhs, TREE_OPERAND (lhs, 1), lhs);
2779 /* If the value overflowed, then we can not use this equivalence. */
2780 if (rhs && ! is_gimple_min_invariant (rhs))
2786 /* Build a new statement with the RHS and LHS exchanged. */
2787 new = build (MODIFY_EXPR, TREE_TYPE (stmt), rhs, lhs);
2789 create_ssa_artficial_load_stmt (&(ann->operands), new);
2791 /* Finally enter the statement into the available expression
2793 lookup_avail_expr (new, true);
2798 /* Replace *OP_P in STMT with any known equivalent value for *OP_P from
2799 CONST_AND_COPIES. */
2802 cprop_operand (tree stmt, use_operand_p op_p)
2804 bool may_have_exposed_new_symbols = false;
2806 tree op = USE_FROM_PTR (op_p);
2808 /* If the operand has a known constant value or it is known to be a
2809 copy of some other variable, use the value or copy stored in
2810 CONST_AND_COPIES. */
2811 val = SSA_NAME_VALUE (op);
2812 if (val && TREE_CODE (val) != VALUE_HANDLE)
2814 tree op_type, val_type;
2816 /* Do not change the base variable in the virtual operand
2817 tables. That would make it impossible to reconstruct
2818 the renamed virtual operand if we later modify this
2819 statement. Also only allow the new value to be an SSA_NAME
2820 for propagation into virtual operands. */
2821 if (!is_gimple_reg (op)
2822 && (get_virtual_var (val) != get_virtual_var (op)
2823 || TREE_CODE (val) != SSA_NAME))
2826 /* Do not replace hard register operands in asm statements. */
2827 if (TREE_CODE (stmt) == ASM_EXPR
2828 && !may_propagate_copy_into_asm (op))
2831 /* Get the toplevel type of each operand. */
2832 op_type = TREE_TYPE (op);
2833 val_type = TREE_TYPE (val);
2835 /* While both types are pointers, get the type of the object
2837 while (POINTER_TYPE_P (op_type) && POINTER_TYPE_P (val_type))
2839 op_type = TREE_TYPE (op_type);
2840 val_type = TREE_TYPE (val_type);
2843 /* Make sure underlying types match before propagating a constant by
2844 converting the constant to the proper type. Note that convert may
2845 return a non-gimple expression, in which case we ignore this
2846 propagation opportunity. */
2847 if (TREE_CODE (val) != SSA_NAME)
2849 if (!lang_hooks.types_compatible_p (op_type, val_type))
2851 val = fold_convert (TREE_TYPE (op), val);
2852 if (!is_gimple_min_invariant (val))
2857 /* Certain operands are not allowed to be copy propagated due
2858 to their interaction with exception handling and some GCC
2860 else if (!may_propagate_copy (op, val))
2864 if (dump_file && (dump_flags & TDF_DETAILS))
2866 fprintf (dump_file, " Replaced '");
2867 print_generic_expr (dump_file, op, dump_flags);
2868 fprintf (dump_file, "' with %s '",
2869 (TREE_CODE (val) != SSA_NAME ? "constant" : "variable"));
2870 print_generic_expr (dump_file, val, dump_flags);
2871 fprintf (dump_file, "'\n");
2874 /* If VAL is an ADDR_EXPR or a constant of pointer type, note
2875 that we may have exposed a new symbol for SSA renaming. */
2876 if (TREE_CODE (val) == ADDR_EXPR
2877 || (POINTER_TYPE_P (TREE_TYPE (op))
2878 && is_gimple_min_invariant (val)))
2879 may_have_exposed_new_symbols = true;
2881 propagate_value (op_p, val);
2883 /* And note that we modified this statement. This is now
2884 safe, even if we changed virtual operands since we will
2885 rescan the statement and rewrite its operands again. */
2888 return may_have_exposed_new_symbols;
2891 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2892 known value for that SSA_NAME (or NULL if no value is known).
2894 Propagate values from CONST_AND_COPIES into the uses, vuses and
2895 v_may_def_ops of STMT. */
2898 cprop_into_stmt (tree stmt)
2900 bool may_have_exposed_new_symbols = false;
2905 FOR_EACH_SSA_USE_OPERAND (op_p, stmt, iter, SSA_OP_ALL_USES)
2907 if (TREE_CODE (USE_FROM_PTR (op_p)) == SSA_NAME)
2908 may_have_exposed_new_symbols |= cprop_operand (stmt, op_p);
2911 if (may_have_exposed_new_symbols)
2913 rhs = get_rhs (stmt);
2914 if (rhs && TREE_CODE (rhs) == ADDR_EXPR)
2915 recompute_tree_invarant_for_addr_expr (rhs);
2918 return may_have_exposed_new_symbols;
2922 /* Optimize the statement pointed by iterator SI.
2924 We try to perform some simplistic global redundancy elimination and
2925 constant propagation:
2927 1- To detect global redundancy, we keep track of expressions that have
2928 been computed in this block and its dominators. If we find that the
2929 same expression is computed more than once, we eliminate repeated
2930 computations by using the target of the first one.
2932 2- Constant values and copy assignments. This is used to do very
2933 simplistic constant and copy propagation. When a constant or copy
2934 assignment is found, we map the value on the RHS of the assignment to
2935 the variable in the LHS in the CONST_AND_COPIES table. */
2938 optimize_stmt (struct dom_walk_data *walk_data, basic_block bb,
2939 block_stmt_iterator si)
2943 bool may_optimize_p;
2944 bool may_have_exposed_new_symbols = false;
2946 stmt = bsi_stmt (si);
2948 get_stmt_operands (stmt);
2949 ann = stmt_ann (stmt);
2950 opt_stats.num_stmts++;
2951 may_have_exposed_new_symbols = false;
2953 if (dump_file && (dump_flags & TDF_DETAILS))
2955 fprintf (dump_file, "Optimizing statement ");
2956 print_generic_stmt (dump_file, stmt, TDF_SLIM);
2959 /* Const/copy propagate into USES, VUSES and the RHS of V_MAY_DEFs. */
2960 may_have_exposed_new_symbols = cprop_into_stmt (stmt);
2962 /* If the statement has been modified with constant replacements,
2963 fold its RHS before checking for redundant computations. */
2966 /* Try to fold the statement making sure that STMT is kept
2968 if (fold_stmt (bsi_stmt_ptr (si)))
2970 stmt = bsi_stmt (si);
2971 ann = stmt_ann (stmt);
2973 if (dump_file && (dump_flags & TDF_DETAILS))
2975 fprintf (dump_file, " Folded to: ");
2976 print_generic_stmt (dump_file, stmt, TDF_SLIM);
2980 /* Constant/copy propagation above may change the set of
2981 virtual operands associated with this statement. Folding
2982 may remove the need for some virtual operands.
2984 Indicate we will need to rescan and rewrite the statement. */
2985 may_have_exposed_new_symbols = true;
2988 /* Check for redundant computations. Do this optimization only
2989 for assignments that have no volatile ops and conditionals. */
2990 may_optimize_p = (!ann->has_volatile_ops
2991 && ((TREE_CODE (stmt) == RETURN_EXPR
2992 && TREE_OPERAND (stmt, 0)
2993 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR
2994 && ! (TREE_SIDE_EFFECTS
2995 (TREE_OPERAND (TREE_OPERAND (stmt, 0), 1))))
2996 || (TREE_CODE (stmt) == MODIFY_EXPR
2997 && ! TREE_SIDE_EFFECTS (TREE_OPERAND (stmt, 1)))
2998 || TREE_CODE (stmt) == COND_EXPR
2999 || TREE_CODE (stmt) == SWITCH_EXPR));
3002 may_have_exposed_new_symbols
3003 |= eliminate_redundant_computations (walk_data, stmt, ann);
3005 /* Record any additional equivalences created by this statement. */
3006 if (TREE_CODE (stmt) == MODIFY_EXPR)
3007 record_equivalences_from_stmt (stmt,
3011 register_definitions_for_stmt (stmt);
3013 /* If STMT is a COND_EXPR and it was modified, then we may know
3014 where it goes. If that is the case, then mark the CFG as altered.
3016 This will cause us to later call remove_unreachable_blocks and
3017 cleanup_tree_cfg when it is safe to do so. It is not safe to
3018 clean things up here since removal of edges and such can trigger
3019 the removal of PHI nodes, which in turn can release SSA_NAMEs to
3022 That's all fine and good, except that once SSA_NAMEs are released
3023 to the manager, we must not call create_ssa_name until all references
3024 to released SSA_NAMEs have been eliminated.
3026 All references to the deleted SSA_NAMEs can not be eliminated until
3027 we remove unreachable blocks.
3029 We can not remove unreachable blocks until after we have completed
3030 any queued jump threading.
3032 We can not complete any queued jump threads until we have taken
3033 appropriate variables out of SSA form. Taking variables out of
3034 SSA form can call create_ssa_name and thus we lose.
3036 Ultimately I suspect we're going to need to change the interface
3037 into the SSA_NAME manager. */
3043 if (TREE_CODE (stmt) == COND_EXPR)
3044 val = COND_EXPR_COND (stmt);
3045 else if (TREE_CODE (stmt) == SWITCH_EXPR)
3046 val = SWITCH_COND (stmt);
3048 if (val && TREE_CODE (val) == INTEGER_CST && find_taken_edge (bb, val))
3051 /* If we simplified a statement in such a way as to be shown that it
3052 cannot trap, update the eh information and the cfg to match. */
3053 if (maybe_clean_eh_stmt (stmt))
3055 bitmap_set_bit (need_eh_cleanup, bb->index);
3056 if (dump_file && (dump_flags & TDF_DETAILS))
3057 fprintf (dump_file, " Flagged to clear EH edges.\n");
3061 if (may_have_exposed_new_symbols)
3062 VARRAY_PUSH_TREE (stmts_to_rescan, bsi_stmt (si));
3065 /* Replace the RHS of STMT with NEW_RHS. If RHS can be found in the
3066 available expression hashtable, then return the LHS from the hash
3069 If INSERT is true, then we also update the available expression
3070 hash table to account for the changes made to STMT. */
3073 update_rhs_and_lookup_avail_expr (tree stmt, tree new_rhs, bool insert)
3075 tree cached_lhs = NULL;
3077 /* Remove the old entry from the hash table. */
3080 struct expr_hash_elt element;
3082 initialize_hash_element (stmt, NULL, &element);
3083 htab_remove_elt_with_hash (avail_exprs, &element, element.hash);
3086 /* Now update the RHS of the assignment. */
3087 TREE_OPERAND (stmt, 1) = new_rhs;
3089 /* Now lookup the updated statement in the hash table. */
3090 cached_lhs = lookup_avail_expr (stmt, insert);
3092 /* We have now called lookup_avail_expr twice with two different
3093 versions of this same statement, once in optimize_stmt, once here.
3095 We know the call in optimize_stmt did not find an existing entry
3096 in the hash table, so a new entry was created. At the same time
3097 this statement was pushed onto the BLOCK_AVAIL_EXPRS varray.
3099 If this call failed to find an existing entry on the hash table,
3100 then the new version of this statement was entered into the
3101 hash table. And this statement was pushed onto BLOCK_AVAIL_EXPR
3102 for the second time. So there are two copies on BLOCK_AVAIL_EXPRs
3104 If this call succeeded, we still have one copy of this statement
3105 on the BLOCK_AVAIL_EXPRs varray.
3107 For both cases, we need to pop the most recent entry off the
3108 BLOCK_AVAIL_EXPRs varray. For the case where we never found this
3109 statement in the hash tables, that will leave precisely one
3110 copy of this statement on BLOCK_AVAIL_EXPRs. For the case where
3111 we found a copy of this statement in the second hash table lookup
3112 we want _no_ copies of this statement in BLOCK_AVAIL_EXPRs. */
3114 VARRAY_POP (avail_exprs_stack);
3116 /* And make sure we record the fact that we modified this
3123 /* Search for an existing instance of STMT in the AVAIL_EXPRS table. If
3124 found, return its LHS. Otherwise insert STMT in the table and return
3127 Also, when an expression is first inserted in the AVAIL_EXPRS table, it
3128 is also added to the stack pointed by BLOCK_AVAIL_EXPRS_P, so that they
3129 can be removed when we finish processing this block and its children.
3131 NOTE: This function assumes that STMT is a MODIFY_EXPR node that
3132 contains no CALL_EXPR on its RHS and makes no volatile nor
3133 aliased references. */
3136 lookup_avail_expr (tree stmt, bool insert)
3141 struct expr_hash_elt *element = xcalloc (sizeof (struct expr_hash_elt), 1);
3143 lhs = TREE_CODE (stmt) == MODIFY_EXPR ? TREE_OPERAND (stmt, 0) : NULL;
3145 initialize_hash_element (stmt, lhs, element);
3147 /* Don't bother remembering constant assignments and copy operations.
3148 Constants and copy operations are handled by the constant/copy propagator
3149 in optimize_stmt. */
3150 if (TREE_CODE (element->rhs) == SSA_NAME
3151 || is_gimple_min_invariant (element->rhs))
3157 /* If this is an equality test against zero, see if we have recorded a
3158 nonzero value for the variable in question. */
3159 if ((TREE_CODE (element->rhs) == EQ_EXPR
3160 || TREE_CODE (element->rhs) == NE_EXPR)
3161 && TREE_CODE (TREE_OPERAND (element->rhs, 0)) == SSA_NAME
3162 && integer_zerop (TREE_OPERAND (element->rhs, 1)))
3164 int indx = SSA_NAME_VERSION (TREE_OPERAND (element->rhs, 0));
3166 if (bitmap_bit_p (nonzero_vars, indx))
3168 tree t = element->rhs;
3171 if (TREE_CODE (t) == EQ_EXPR)
3172 return boolean_false_node;
3174 return boolean_true_node;
3178 /* Finally try to find the expression in the main expression hash table. */
3179 slot = htab_find_slot_with_hash (avail_exprs, element, element->hash,
3180 (insert ? INSERT : NO_INSERT));
3189 *slot = (void *) element;
3190 VARRAY_PUSH_TREE (avail_exprs_stack, stmt ? stmt : element->rhs);
3194 /* Extract the LHS of the assignment so that it can be used as the current
3195 definition of another variable. */
3196 lhs = ((struct expr_hash_elt *)*slot)->lhs;
3198 /* See if the LHS appears in the CONST_AND_COPIES table. If it does, then
3199 use the value from the const_and_copies table. */
3200 if (TREE_CODE (lhs) == SSA_NAME)
3202 temp = SSA_NAME_VALUE (lhs);
3203 if (temp && TREE_CODE (temp) != VALUE_HANDLE)
3211 /* Given a condition COND, record into HI_P, LO_P and INVERTED_P the
3212 range of values that result in the conditional having a true value.
3214 Return true if we are successful in extracting a range from COND and
3215 false if we are unsuccessful. */
3218 extract_range_from_cond (tree cond, tree *hi_p, tree *lo_p, int *inverted_p)
3220 tree op1 = TREE_OPERAND (cond, 1);
3221 tree high, low, type;
3224 /* Experiments have shown that it's rarely, if ever useful to
3225 record ranges for enumerations. Presumably this is due to
3226 the fact that they're rarely used directly. They are typically
3227 cast into an integer type and used that way. */
3228 if (TREE_CODE (TREE_TYPE (op1)) != INTEGER_TYPE)
3231 type = TREE_TYPE (op1);
3233 switch (TREE_CODE (cond))
3247 high = TYPE_MAX_VALUE (type);
3252 low = int_const_binop (PLUS_EXPR, op1, integer_one_node, 1);
3253 high = TYPE_MAX_VALUE (type);
3259 low = TYPE_MIN_VALUE (type);
3264 high = int_const_binop (MINUS_EXPR, op1, integer_one_node, 1);
3265 low = TYPE_MIN_VALUE (type);
3275 *inverted_p = inverted;
3279 /* Record a range created by COND for basic block BB. */
3282 record_range (tree cond, basic_block bb)
3284 enum tree_code code = TREE_CODE (cond);
3286 /* We explicitly ignore NE_EXPRs and all the unordered comparisons.
3287 They rarely allow for meaningful range optimizations and significantly
3288 complicate the implementation. */
3289 if ((code == LT_EXPR || code == LE_EXPR || code == GT_EXPR
3290 || code == GE_EXPR || code == EQ_EXPR)
3291 && TREE_CODE (TREE_TYPE (TREE_OPERAND (cond, 1))) == INTEGER_TYPE)
3293 struct vrp_hash_elt *vrp_hash_elt;
3294 struct vrp_element *element;
3295 varray_type *vrp_records_p;
3299 vrp_hash_elt = xmalloc (sizeof (struct vrp_hash_elt));
3300 vrp_hash_elt->var = TREE_OPERAND (cond, 0);
3301 vrp_hash_elt->records = NULL;
3302 slot = htab_find_slot (vrp_data, vrp_hash_elt, INSERT);
3305 *slot = (void *) vrp_hash_elt;
3307 free (vrp_hash_elt);
3309 vrp_hash_elt = (struct vrp_hash_elt *) *slot;
3310 vrp_records_p = &vrp_hash_elt->records;
3312 element = ggc_alloc (sizeof (struct vrp_element));
3313 element->low = NULL;
3314 element->high = NULL;
3315 element->cond = cond;
3318 if (*vrp_records_p == NULL)
3319 VARRAY_GENERIC_PTR_INIT (*vrp_records_p, 2, "vrp records");
3321 VARRAY_PUSH_GENERIC_PTR (*vrp_records_p, element);
3322 VARRAY_PUSH_TREE (vrp_variables_stack, TREE_OPERAND (cond, 0));
3326 /* Hashing and equality functions for VRP_DATA.
3328 Since this hash table is addressed by SSA_NAMEs, we can hash on
3329 their version number and equality can be determined with a
3330 pointer comparison. */
3333 vrp_hash (const void *p)
3335 tree var = ((struct vrp_hash_elt *)p)->var;
3337 return SSA_NAME_VERSION (var);
3341 vrp_eq (const void *p1, const void *p2)
3343 tree var1 = ((struct vrp_hash_elt *)p1)->var;
3344 tree var2 = ((struct vrp_hash_elt *)p2)->var;
3346 return var1 == var2;
3349 /* Hashing and equality functions for AVAIL_EXPRS. The table stores
3350 MODIFY_EXPR statements. We compute a value number for expressions using
3351 the code of the expression and the SSA numbers of its operands. */
3354 avail_expr_hash (const void *p)
3356 stmt_ann_t ann = ((struct expr_hash_elt *)p)->ann;
3357 tree rhs = ((struct expr_hash_elt *)p)->rhs;
3362 /* iterative_hash_expr knows how to deal with any expression and
3363 deals with commutative operators as well, so just use it instead
3364 of duplicating such complexities here. */
3365 val = iterative_hash_expr (rhs, val);
3367 /* If the hash table entry is not associated with a statement, then we
3368 can just hash the expression and not worry about virtual operands
3373 /* Add the SSA version numbers of every vuse operand. This is important
3374 because compound variables like arrays are not renamed in the
3375 operands. Rather, the rename is done on the virtual variable
3376 representing all the elements of the array. */
3377 vuses = VUSE_OPS (ann);
3378 for (i = 0; i < NUM_VUSES (vuses); i++)
3379 val = iterative_hash_expr (VUSE_OP (vuses, i), val);
3385 real_avail_expr_hash (const void *p)
3387 return ((const struct expr_hash_elt *)p)->hash;
3391 avail_expr_eq (const void *p1, const void *p2)
3393 stmt_ann_t ann1 = ((struct expr_hash_elt *)p1)->ann;
3394 tree rhs1 = ((struct expr_hash_elt *)p1)->rhs;
3395 stmt_ann_t ann2 = ((struct expr_hash_elt *)p2)->ann;
3396 tree rhs2 = ((struct expr_hash_elt *)p2)->rhs;
3398 /* If they are the same physical expression, return true. */
3399 if (rhs1 == rhs2 && ann1 == ann2)
3402 /* If their codes are not equal, then quit now. */
3403 if (TREE_CODE (rhs1) != TREE_CODE (rhs2))
3406 /* In case of a collision, both RHS have to be identical and have the
3407 same VUSE operands. */
3408 if ((TREE_TYPE (rhs1) == TREE_TYPE (rhs2)
3409 || lang_hooks.types_compatible_p (TREE_TYPE (rhs1), TREE_TYPE (rhs2)))
3410 && operand_equal_p (rhs1, rhs2, OEP_PURE_SAME))
3412 vuse_optype ops1 = NULL;
3413 vuse_optype ops2 = NULL;
3414 size_t num_ops1 = 0;
3415 size_t num_ops2 = 0;
3420 ops1 = VUSE_OPS (ann1);
3421 num_ops1 = NUM_VUSES (ops1);
3426 ops2 = VUSE_OPS (ann2);
3427 num_ops2 = NUM_VUSES (ops2);
3430 /* If the number of virtual uses is different, then we consider
3432 if (num_ops1 != num_ops2)
3435 for (i = 0; i < num_ops1; i++)
3436 if (VUSE_OP (ops1, i) != VUSE_OP (ops2, i))
3439 gcc_assert (((struct expr_hash_elt *)p1)->hash
3440 == ((struct expr_hash_elt *)p2)->hash);
3447 /* Given STMT and a pointer to the block local definitions BLOCK_DEFS_P,
3448 register register all objects set by this statement into BLOCK_DEFS_P
3452 register_definitions_for_stmt (tree stmt)
3457 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
3460 /* FIXME: We shouldn't be registering new defs if the variable
3461 doesn't need to be renamed. */
3462 register_new_def (def, &block_defs_stack);