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 "langhooks.h"
45 /* This file implements optimizations on the dominator tree. */
47 /* Hash table with expressions made available during the renaming process.
48 When an assignment of the form X_i = EXPR is found, the statement is
49 stored in this table. If the same expression EXPR is later found on the
50 RHS of another statement, it is replaced with X_i (thus performing
51 global redundancy elimination). Similarly as we pass through conditionals
52 we record the conditional itself as having either a true or false value
54 static htab_t avail_exprs;
56 /* Structure for entries in the expression hash table.
58 This requires more memory for the hash table entries, but allows us
59 to avoid creating silly tree nodes and annotations for conditionals,
60 eliminates 2 global hash tables and two block local varrays.
62 It also allows us to reduce the number of hash table lookups we
63 have to perform in lookup_avail_expr and finally it allows us to
64 significantly reduce the number of calls into the hashing routine
69 /* The value (lhs) of this expression. */
72 /* The expression (rhs) we want to record. */
75 /* The annotation if this element corresponds to a statement. */
78 /* The hash value for RHS/ann. */
82 /* Table of constant values and copies indexed by SSA name. When the
83 renaming pass finds an assignment of a constant (X_i = C) or a copy
84 assignment from another SSA variable (X_i = Y_j), it creates a mapping
85 between X_i and the RHS in this table. This mapping is used later on,
86 when renaming uses of X_i. If an assignment to X_i is found in this
87 table, instead of using X_i, we use the RHS of the statement stored in
88 this table (thus performing very simplistic copy and constant
90 static varray_type const_and_copies;
92 /* Bitmap of SSA_NAMEs known to have a nonzero value, even if we do not
93 know their exact value. */
94 static bitmap nonzero_vars;
96 /* Track whether or not we have changed the control flow graph. */
97 static bool cfg_altered;
99 /* Bitmap of blocks that have had EH statements cleaned. We should
100 remove their dead edges eventually. */
101 static bitmap need_eh_cleanup;
103 /* Statistics for dominator optimizations. */
107 long num_exprs_considered;
111 /* Value range propagation record. Each time we encounter a conditional
112 of the form SSA_NAME COND CONST we create a new vrp_element to record
113 how the condition affects the possible values SSA_NAME may have.
115 Each record contains the condition tested (COND), and the the range of
116 values the variable may legitimately have if COND is true. Note the
117 range of values may be a smaller range than COND specifies if we have
118 recorded other ranges for this variable. Each record also contains the
119 block in which the range was recorded for invalidation purposes.
121 Note that the current known range is computed lazily. This allows us
122 to avoid the overhead of computing ranges which are never queried.
124 When we encounter a conditional, we look for records which constrain
125 the SSA_NAME used in the condition. In some cases those records allow
126 us to determine the condition's result at compile time. In other cases
127 they may allow us to simplify the condition.
129 We also use value ranges to do things like transform signed div/mod
130 operations into unsigned div/mod or to simplify ABS_EXPRs.
132 Simple experiments have shown these optimizations to not be all that
133 useful on switch statements (much to my surprise). So switch statement
134 optimizations are not performed.
136 Note carefully we do not propagate information through each statement
137 in the block. ie, if we know variable X has a value defined of
138 [0, 25] and we encounter Y = X + 1, we do not track a value range
139 for Y (which would be [1, 26] if we cared). Similarly we do not
140 constrain values as we encounter narrowing typecasts, etc. */
144 /* The highest and lowest values the variable in COND may contain when
145 COND is true. Note this may not necessarily be the same values
146 tested by COND if the same variable was used in earlier conditionals.
148 Note this is computed lazily and thus can be NULL indicating that
149 the values have not been computed yet. */
153 /* The actual conditional we recorded. This is needed since we compute
157 /* The basic block where this record was created. We use this to determine
158 when to remove records. */
162 static struct opt_stats_d opt_stats;
164 /* A virtual array holding value range records for the variable identified
165 by the index, SSA_VERSION. */
166 static varray_type vrp_data;
168 /* Datastructure for block local data used during the dominator walk.
169 We maintain a stack of these as we recursively walk down the
172 struct dom_walk_block_data
174 /* Array of all the expressions entered into the global expression
175 hash table by this block. During finalization we use this array to
176 know what expressions to remove from the global expression hash
178 varray_type avail_exprs;
180 /* Array of dest, src pairs that need to be restored during finalization
181 into the global const/copies table during finalization. */
182 varray_type const_and_copies;
184 /* Similarly for the nonzero state of variables that needs to be
185 restored during finalization. */
186 varray_type nonzero_vars;
188 /* Array of statements we need to rescan during finalization for newly
189 exposed variables. */
190 varray_type stmts_to_rescan;
192 /* Array of variables which have their values constrained by operations
193 in this basic block. We use this during finalization to know
194 which variables need their VRP data updated. */
195 varray_type vrp_variables;
197 /* Array of tree pairs used to restore the global currdefs to its
198 original state after completing optimization of a block and its
199 dominator children. */
200 varray_type block_defs;
209 /* Local functions. */
210 static void optimize_stmt (struct dom_walk_data *,
212 block_stmt_iterator);
213 static inline tree get_value_for (tree, varray_type table);
214 static inline void set_value_for (tree, tree, varray_type table);
215 static tree lookup_avail_expr (tree, varray_type *, bool);
216 static struct eq_expr_value get_eq_expr_value (tree, int, varray_type *,
217 basic_block, varray_type *);
218 static hashval_t avail_expr_hash (const void *);
219 static hashval_t real_avail_expr_hash (const void *);
220 static int avail_expr_eq (const void *, const void *);
221 static void htab_statistics (FILE *, htab_t);
222 static void record_cond (tree, tree, varray_type *);
223 static void record_dominating_conditions (tree, varray_type *);
224 static void record_const_or_copy (tree, tree, varray_type *);
225 static void record_equality (tree, tree, varray_type *);
226 static tree update_rhs_and_lookup_avail_expr (tree, tree, varray_type *, bool);
227 static tree simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *,
229 static tree simplify_cond_and_lookup_avail_expr (tree, varray_type *,
231 static tree simplify_switch_and_lookup_avail_expr (tree, varray_type *, int);
232 static tree find_equivalent_equality_comparison (tree);
233 static void record_range (tree, basic_block, varray_type *);
234 static bool extract_range_from_cond (tree, tree *, tree *, int *);
235 static void record_equivalences_from_phis (struct dom_walk_data *, basic_block);
236 static void record_equivalences_from_incoming_edge (struct dom_walk_data *,
238 static bool eliminate_redundant_computations (struct dom_walk_data *,
240 static void record_equivalences_from_stmt (tree, varray_type *, varray_type *,
242 static void thread_across_edge (struct dom_walk_data *, edge);
243 static void dom_opt_finalize_block (struct dom_walk_data *, basic_block);
244 static void dom_opt_initialize_block_local_data (struct dom_walk_data *,
246 static void dom_opt_initialize_block (struct dom_walk_data *, basic_block);
247 static void cprop_into_phis (struct dom_walk_data *, basic_block);
248 static void remove_local_expressions_from_table (varray_type locals,
251 static void restore_vars_to_original_value (varray_type locals,
254 static void restore_currdefs_to_original_value (varray_type locals,
256 static void register_definitions_for_stmt (tree, varray_type *);
257 static edge single_incoming_edge_ignoring_loop_edges (basic_block);
259 /* Local version of fold that doesn't introduce cruft. */
266 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
267 may have been added by fold, and "useless" type conversions that might
268 now be apparent due to propagation. */
269 STRIP_USELESS_TYPE_CONVERSION (t);
274 /* Return the value associated with variable VAR in TABLE. */
277 get_value_for (tree var, varray_type table)
279 return VARRAY_TREE (table, SSA_NAME_VERSION (var));
282 /* Associate VALUE to variable VAR in TABLE. */
285 set_value_for (tree var, tree value, varray_type table)
287 VARRAY_TREE (table, SSA_NAME_VERSION (var)) = value;
290 /* Jump threading, redundancy elimination and const/copy propagation.
292 This pass may expose new symbols that need to be renamed into SSA. For
293 every new symbol exposed, its corresponding bit will be set in
297 tree_ssa_dominator_optimize (void)
299 struct dom_walk_data walk_data;
302 for (i = 0; i < num_referenced_vars; i++)
303 var_ann (referenced_var (i))->current_def = NULL;
305 /* Mark loop edges so we avoid threading across loop boundaries.
306 This may result in transforming natural loop into irreducible
308 mark_dfs_back_edges ();
310 /* Create our hash tables. */
311 avail_exprs = htab_create (1024, real_avail_expr_hash, avail_expr_eq, free);
312 VARRAY_TREE_INIT (const_and_copies, num_ssa_names, "const_and_copies");
313 nonzero_vars = BITMAP_XMALLOC ();
314 VARRAY_GENERIC_PTR_INIT (vrp_data, num_ssa_names, "vrp_data");
315 need_eh_cleanup = BITMAP_XMALLOC ();
317 /* Setup callbacks for the generic dominator tree walker. */
318 walk_data.walk_stmts_backward = false;
319 walk_data.dom_direction = CDI_DOMINATORS;
320 walk_data.initialize_block_local_data = dom_opt_initialize_block_local_data;
321 walk_data.before_dom_children_before_stmts = dom_opt_initialize_block;
322 walk_data.before_dom_children_walk_stmts = optimize_stmt;
323 walk_data.before_dom_children_after_stmts = cprop_into_phis;
324 walk_data.after_dom_children_before_stmts = NULL;
325 walk_data.after_dom_children_walk_stmts = NULL;
326 walk_data.after_dom_children_after_stmts = dom_opt_finalize_block;
327 /* Right now we only attach a dummy COND_EXPR to the global data pointer.
328 When we attach more stuff we'll need to fill this out with a real
330 walk_data.global_data = NULL;
331 walk_data.block_local_data_size = sizeof (struct dom_walk_block_data);
333 /* Now initialize the dominator walker. */
334 init_walk_dominator_tree (&walk_data);
336 calculate_dominance_info (CDI_DOMINATORS);
338 /* If we prove certain blocks are unreachable, then we want to
339 repeat the dominator optimization process as PHI nodes may
340 have turned into copies which allows better propagation of
341 values. So we repeat until we do not identify any new unreachable
345 /* Optimize the dominator tree. */
348 /* Recursively walk the dominator tree optimizing statements. */
349 walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
351 /* If we exposed any new variables, go ahead and put them into
352 SSA form now, before we handle jump threading. This simplifies
353 interactions between rewriting of _DECL nodes into SSA form
354 and rewriting SSA_NAME nodes into SSA form after block
355 duplication and CFG manipulation. */
356 if (bitmap_first_set_bit (vars_to_rename) >= 0)
358 rewrite_into_ssa (false);
359 bitmap_clear (vars_to_rename);
362 /* Thread jumps, creating duplicate blocks as needed. */
363 cfg_altered = thread_through_all_blocks ();
365 /* Removal of statements may make some EH edges dead. Purge
366 such edges from the CFG as needed. */
367 if (bitmap_first_set_bit (need_eh_cleanup) >= 0)
369 cfg_altered |= tree_purge_all_dead_eh_edges (need_eh_cleanup);
370 bitmap_zero (need_eh_cleanup);
373 free_dominance_info (CDI_DOMINATORS);
374 cfg_altered = cleanup_tree_cfg ();
375 calculate_dominance_info (CDI_DOMINATORS);
377 rewrite_ssa_into_ssa ();
379 if (VARRAY_ACTIVE_SIZE (const_and_copies) <= num_ssa_names)
381 VARRAY_GROW (const_and_copies, num_ssa_names);
382 VARRAY_GROW (vrp_data, num_ssa_names);
385 /* Reinitialize the various tables. */
386 bitmap_clear (nonzero_vars);
387 htab_empty (avail_exprs);
388 VARRAY_CLEAR (const_and_copies);
389 VARRAY_CLEAR (vrp_data);
391 for (i = 0; i < num_referenced_vars; i++)
392 var_ann (referenced_var (i))->current_def = NULL;
396 /* Debugging dumps. */
397 if (dump_file && (dump_flags & TDF_STATS))
398 dump_dominator_optimization_stats (dump_file);
400 /* We emptied the hash table earlier, now delete it completely. */
401 htab_delete (avail_exprs);
403 /* It is not necessary to clear CURRDEFS, REDIRECTION_EDGES, VRP_DATA,
404 CONST_AND_COPIES, and NONZERO_VARS as they all get cleared at the bottom
405 of the do-while loop above. */
407 /* And finalize the dominator walker. */
408 fini_walk_dominator_tree (&walk_data);
410 /* Free nonzero_vars. */
411 BITMAP_XFREE (nonzero_vars);
412 BITMAP_XFREE (need_eh_cleanup);
416 gate_dominator (void)
418 return flag_tree_dom != 0;
421 struct tree_opt_pass pass_dominator =
424 gate_dominator, /* gate */
425 tree_ssa_dominator_optimize, /* execute */
428 0, /* static_pass_number */
429 TV_TREE_SSA_DOMINATOR_OPTS, /* tv_id */
430 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
431 0, /* properties_provided */
432 0, /* properties_destroyed */
433 0, /* todo_flags_start */
434 TODO_dump_func | TODO_rename_vars
435 | TODO_verify_ssa, /* todo_flags_finish */
440 /* We are exiting BB, see if the target block begins with a conditional
441 jump which has a known value when reached via BB. */
444 thread_across_edge (struct dom_walk_data *walk_data, edge e)
446 struct dom_walk_block_data *bd
447 = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
448 block_stmt_iterator bsi;
452 /* Each PHI creates a temporary equivalence, record them. */
453 for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
455 tree src = PHI_ARG_DEF_FROM_EDGE (phi, e);
456 tree dst = PHI_RESULT (phi);
457 record_const_or_copy (dst, src, &bd->const_and_copies);
458 register_new_def (dst, &bd->block_defs);
461 for (bsi = bsi_start (e->dest); ! bsi_end_p (bsi); bsi_next (&bsi))
463 tree lhs, cached_lhs;
465 stmt = bsi_stmt (bsi);
467 /* Ignore empty statements and labels. */
468 if (IS_EMPTY_STMT (stmt) || TREE_CODE (stmt) == LABEL_EXPR)
471 /* If this is not a MODIFY_EXPR which sets an SSA_NAME to a new
472 value, then stop our search here. Ideally when we stop a
473 search we stop on a COND_EXPR or SWITCH_EXPR. */
474 if (TREE_CODE (stmt) != MODIFY_EXPR
475 || TREE_CODE (TREE_OPERAND (stmt, 0)) != SSA_NAME)
478 /* At this point we have a statement which assigns an RHS to an
479 SSA_VAR on the LHS. We want to prove that the RHS is already
480 available and that its value is held in the current definition
481 of the LHS -- meaning that this assignment is a NOP when
482 reached via edge E. */
483 if (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME)
484 cached_lhs = TREE_OPERAND (stmt, 1);
486 cached_lhs = lookup_avail_expr (stmt, NULL, false);
488 lhs = TREE_OPERAND (stmt, 0);
490 /* This can happen if we thread around to the start of a loop. */
491 if (lhs == cached_lhs)
494 /* If we did not find RHS in the hash table, then try again after
495 temporarily const/copy propagating the operands. */
498 /* Copy the operands. */
499 stmt_ann_t ann = stmt_ann (stmt);
500 use_optype uses = USE_OPS (ann);
501 vuse_optype vuses = VUSE_OPS (ann);
502 tree *uses_copy = xcalloc (NUM_USES (uses), sizeof (tree));
503 tree *vuses_copy = xcalloc (NUM_VUSES (vuses), sizeof (tree));
506 /* Make a copy of the uses into USES_COPY, then cprop into
508 for (i = 0; i < NUM_USES (uses); i++)
512 uses_copy[i] = USE_OP (uses, i);
513 if (TREE_CODE (USE_OP (uses, i)) == SSA_NAME)
514 tmp = get_value_for (USE_OP (uses, i), const_and_copies);
516 SET_USE_OP (uses, i, tmp);
519 /* Similarly for virtual uses. */
520 for (i = 0; i < NUM_VUSES (vuses); i++)
524 vuses_copy[i] = VUSE_OP (vuses, i);
525 if (TREE_CODE (VUSE_OP (vuses, i)) == SSA_NAME)
526 tmp = get_value_for (VUSE_OP (vuses, i), const_and_copies);
528 SET_VUSE_OP (vuses, i, tmp);
531 /* Try to lookup the new expression. */
532 cached_lhs = lookup_avail_expr (stmt, NULL, false);
534 /* Restore the statement's original uses/defs. */
535 for (i = 0; i < NUM_USES (uses); i++)
536 SET_USE_OP (uses, i, uses_copy[i]);
538 for (i = 0; i < NUM_VUSES (vuses); i++)
539 SET_VUSE_OP (vuses, i, vuses_copy[i]);
544 /* If we still did not find the expression in the hash table,
545 then we can not ignore this statement. */
550 /* If the expression in the hash table was not assigned to an
551 SSA_NAME, then we can not ignore this statement. */
552 if (TREE_CODE (cached_lhs) != SSA_NAME)
555 /* If we have different underlying variables, then we can not
556 ignore this statement. */
557 if (SSA_NAME_VAR (cached_lhs) != SSA_NAME_VAR (lhs))
560 /* If CACHED_LHS does not represent the current value of the undering
561 variable in CACHED_LHS/LHS, then we can not ignore this statement. */
562 if (var_ann (SSA_NAME_VAR (lhs))->current_def != cached_lhs)
565 /* If we got here, then we can ignore this statement and continue
566 walking through the statements in the block looking for a threadable
569 We want to record an equivalence lhs = cache_lhs so that if
570 the result of this statement is used later we can copy propagate
572 record_const_or_copy (lhs, cached_lhs, &bd->const_and_copies);
573 register_new_def (lhs, &bd->block_defs);
576 /* If we stopped at a COND_EXPR or SWITCH_EXPR, then see if we know which
577 arm will be taken. */
579 && (TREE_CODE (stmt) == COND_EXPR
580 || TREE_CODE (stmt) == SWITCH_EXPR))
582 tree cond, cached_lhs;
585 /* Do not forward entry edges into the loop. In the case loop
586 has multiple entry edges we may end up in constructing irreducible
588 ??? We may consider forwarding the edges in the case all incoming
589 edges forward to the same destination block. */
590 if (!e->flags & EDGE_DFS_BACK)
592 for (e1 = e->dest->pred; e; e = e->pred_next)
593 if (e1->flags & EDGE_DFS_BACK)
599 /* Now temporarily cprop the operands and try to find the resulting
600 expression in the hash tables. */
601 if (TREE_CODE (stmt) == COND_EXPR)
602 cond = COND_EXPR_COND (stmt);
604 cond = SWITCH_COND (stmt);
606 if (TREE_CODE_CLASS (TREE_CODE (cond)) == '<')
608 tree dummy_cond, op0, op1;
609 enum tree_code cond_code;
611 op0 = TREE_OPERAND (cond, 0);
612 op1 = TREE_OPERAND (cond, 1);
613 cond_code = TREE_CODE (cond);
615 /* Get the current value of both operands. */
616 if (TREE_CODE (op0) == SSA_NAME)
618 tree tmp = get_value_for (op0, const_and_copies);
623 if (TREE_CODE (op1) == SSA_NAME)
625 tree tmp = get_value_for (op1, const_and_copies);
630 /* Stuff the operator and operands into our dummy conditional
631 expression, creating the dummy conditional if necessary. */
632 dummy_cond = walk_data->global_data;
635 dummy_cond = build (cond_code, boolean_type_node, op0, op1);
636 dummy_cond = build (COND_EXPR, void_type_node,
637 dummy_cond, NULL, NULL);
638 walk_data->global_data = dummy_cond;
642 TREE_SET_CODE (TREE_OPERAND (dummy_cond, 0), cond_code);
643 TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 0) = op0;
644 TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 1) = op1;
647 /* If the conditional folds to an invariant, then we are done,
648 otherwise look it up in the hash tables. */
649 cached_lhs = local_fold (COND_EXPR_COND (dummy_cond));
650 if (! is_gimple_min_invariant (cached_lhs))
651 cached_lhs = lookup_avail_expr (dummy_cond, NULL, false);
652 if (!cached_lhs || ! is_gimple_min_invariant (cached_lhs))
654 cached_lhs = simplify_cond_and_lookup_avail_expr (dummy_cond,
660 /* We can have conditionals which just test the state of a
661 variable rather than use a relational operator. These are
662 simpler to handle. */
663 else if (TREE_CODE (cond) == SSA_NAME)
666 cached_lhs = get_value_for (cached_lhs, const_and_copies);
667 if (cached_lhs && ! is_gimple_min_invariant (cached_lhs))
671 cached_lhs = lookup_avail_expr (stmt, NULL, false);
675 edge taken_edge = find_taken_edge (e->dest, cached_lhs);
676 basic_block dest = (taken_edge ? taken_edge->dest : NULL);
681 /* If we have a known destination for the conditional, then
682 we can perform this optimization, which saves at least one
683 conditional jump each time it applies since we get to
684 bypass the conditional at our original destination. */
688 bb_ann (e->dest)->incoming_edge_threaded = true;
695 /* Initialize the local stacks.
697 AVAIL_EXPRS stores all the expressions made available in this block.
699 CONST_AND_COPIES stores var/value pairs to restore at the end of this
702 NONZERO_VARS stores the vars which have a nonzero value made in this
705 STMTS_TO_RESCAN is a list of statements we will rescan for operands.
707 VRP_VARIABLES is the list of variables which have had their values
708 constrained by an operation in this block.
710 These stacks are cleared in the finalization routine run for each
714 dom_opt_initialize_block_local_data (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
715 basic_block bb ATTRIBUTE_UNUSED,
716 bool recycled ATTRIBUTE_UNUSED)
718 struct dom_walk_block_data *bd
719 = (struct dom_walk_block_data *)VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
721 /* We get cleared memory from the allocator, so if the memory is not
722 cleared, then we are re-using a previously allocated entry. In
723 that case, we can also re-use the underlying virtual arrays. Just
724 make sure we clear them before using them! */
727 gcc_assert (!bd->avail_exprs
728 || VARRAY_ACTIVE_SIZE (bd->avail_exprs) == 0);
729 gcc_assert (!bd->const_and_copies
730 || VARRAY_ACTIVE_SIZE (bd->const_and_copies) == 0);
731 gcc_assert (!bd->nonzero_vars
732 || VARRAY_ACTIVE_SIZE (bd->nonzero_vars) == 0);
733 gcc_assert (!bd->stmts_to_rescan
734 || VARRAY_ACTIVE_SIZE (bd->stmts_to_rescan) == 0);
735 gcc_assert (!bd->vrp_variables
736 || VARRAY_ACTIVE_SIZE (bd->vrp_variables) == 0);
737 gcc_assert (!bd->block_defs
738 || VARRAY_ACTIVE_SIZE (bd->block_defs) == 0);
742 /* Initialize local stacks for this optimizer and record equivalences
743 upon entry to BB. Equivalences can come from the edge traversed to
744 reach BB or they may come from PHI nodes at the start of BB. */
747 dom_opt_initialize_block (struct dom_walk_data *walk_data, basic_block bb)
749 if (dump_file && (dump_flags & TDF_DETAILS))
750 fprintf (dump_file, "\n\nOptimizing block #%d\n\n", bb->index);
752 record_equivalences_from_incoming_edge (walk_data, bb);
754 /* PHI nodes can create equivalences too. */
755 record_equivalences_from_phis (walk_data, bb);
758 /* Given an expression EXPR (a relational expression or a statement),
759 initialize the hash table element pointed by by ELEMENT. */
762 initialize_hash_element (tree expr, tree lhs, struct expr_hash_elt *element)
764 /* Hash table elements may be based on conditional expressions or statements.
766 For the former case, we have no annotation and we want to hash the
767 conditional expression. In the latter case we have an annotation and
768 we want to record the expression the statement evaluates. */
769 if (TREE_CODE_CLASS (TREE_CODE (expr)) == '<'
770 || TREE_CODE (expr) == TRUTH_NOT_EXPR)
775 else if (TREE_CODE (expr) == COND_EXPR)
777 element->ann = stmt_ann (expr);
778 element->rhs = COND_EXPR_COND (expr);
780 else if (TREE_CODE (expr) == SWITCH_EXPR)
782 element->ann = stmt_ann (expr);
783 element->rhs = SWITCH_COND (expr);
785 else if (TREE_CODE (expr) == RETURN_EXPR && TREE_OPERAND (expr, 0))
787 element->ann = stmt_ann (expr);
788 element->rhs = TREE_OPERAND (TREE_OPERAND (expr, 0), 1);
792 element->ann = stmt_ann (expr);
793 element->rhs = TREE_OPERAND (expr, 1);
797 element->hash = avail_expr_hash (element);
800 /* Remove all the expressions in LOCALS from TABLE, stopping when there are
801 LIMIT entries left in LOCALs. */
804 remove_local_expressions_from_table (varray_type locals,
811 /* Remove all the expressions made available in this block. */
812 while (VARRAY_ACTIVE_SIZE (locals) > limit)
814 struct expr_hash_elt element;
815 tree expr = VARRAY_TOP_TREE (locals);
818 initialize_hash_element (expr, NULL, &element);
819 htab_remove_elt_with_hash (table, &element, element.hash);
823 /* Use the SSA_NAMES in LOCALS to restore TABLE to its original
824 state, stopping when there are LIMIT entries left in LOCALs. */
827 restore_nonzero_vars_to_original_value (varray_type locals,
834 while (VARRAY_ACTIVE_SIZE (locals) > limit)
836 tree name = VARRAY_TOP_TREE (locals);
838 bitmap_clear_bit (table, SSA_NAME_VERSION (name));
842 /* Use the source/dest pairs in LOCALS to restore TABLE to its original
843 state, stopping when there are LIMIT entries left in LOCALs. */
846 restore_vars_to_original_value (varray_type locals,
853 while (VARRAY_ACTIVE_SIZE (locals) > limit)
855 tree prev_value, dest;
857 prev_value = VARRAY_TOP_TREE (locals);
859 dest = VARRAY_TOP_TREE (locals);
862 set_value_for (dest, prev_value, table);
866 /* Similar to restore_vars_to_original_value, except that it restores
867 CURRDEFS to its original value. */
869 restore_currdefs_to_original_value (varray_type locals, unsigned limit)
874 /* Restore CURRDEFS to its original state. */
875 while (VARRAY_ACTIVE_SIZE (locals) > limit)
877 tree tmp = VARRAY_TOP_TREE (locals);
882 /* If we recorded an SSA_NAME, then make the SSA_NAME the current
883 definition of its underlying variable. If we recorded anything
884 else, it must have been an _DECL node and its current reaching
885 definition must have been NULL. */
886 if (TREE_CODE (tmp) == SSA_NAME)
889 var = SSA_NAME_VAR (saved_def);
897 var_ann (var)->current_def = saved_def;
901 /* We have finished processing the dominator children of BB, perform
902 any finalization actions in preparation for leaving this node in
903 the dominator tree. */
906 dom_opt_finalize_block (struct dom_walk_data *walk_data, basic_block bb)
908 struct dom_walk_block_data *bd
909 = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
912 /* If we are at a leaf node in the dominator graph, see if we can thread
913 the edge from BB through its successor.
915 Do this before we remove entries from our equivalence tables. */
917 && ! bb->succ->succ_next
918 && (bb->succ->flags & EDGE_ABNORMAL) == 0
919 && (get_immediate_dominator (CDI_DOMINATORS, bb->succ->dest) != bb
920 || phi_nodes (bb->succ->dest)))
923 thread_across_edge (walk_data, bb->succ);
925 else if ((last = last_stmt (bb))
926 && TREE_CODE (last) == COND_EXPR
927 && (TREE_CODE_CLASS (TREE_CODE (COND_EXPR_COND (last))) == '<'
928 || TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME)
930 && (bb->succ->flags & EDGE_ABNORMAL) == 0
931 && bb->succ->succ_next
932 && (bb->succ->succ_next->flags & EDGE_ABNORMAL) == 0
933 && ! bb->succ->succ_next->succ_next)
935 edge true_edge, false_edge;
936 tree cond, inverted = NULL;
937 enum tree_code cond_code;
939 extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
941 cond = COND_EXPR_COND (last);
942 cond_code = TREE_CODE (cond);
944 if (TREE_CODE_CLASS (cond_code) == '<')
945 inverted = invert_truthvalue (cond);
947 /* If the THEN arm is the end of a dominator tree or has PHI nodes,
948 then try to thread through its edge. */
949 if (get_immediate_dominator (CDI_DOMINATORS, true_edge->dest) != bb
950 || phi_nodes (true_edge->dest))
952 unsigned avail_expr_limit;
953 unsigned const_and_copies_limit;
954 unsigned currdefs_limit;
957 = bd->avail_exprs ? VARRAY_ACTIVE_SIZE (bd->avail_exprs) : 0;
958 const_and_copies_limit
959 = bd->const_and_copies ? VARRAY_ACTIVE_SIZE (bd->const_and_copies)
962 = bd->block_defs ? VARRAY_ACTIVE_SIZE (bd->block_defs) : 0;
964 /* Record any equivalences created by following this edge. */
965 if (TREE_CODE_CLASS (cond_code) == '<')
967 record_cond (cond, boolean_true_node, &bd->avail_exprs);
968 record_dominating_conditions (cond, &bd->avail_exprs);
969 record_cond (inverted, boolean_false_node, &bd->avail_exprs);
971 else if (cond_code == SSA_NAME)
972 record_const_or_copy (cond, boolean_true_node,
973 &bd->const_and_copies);
975 /* Now thread the edge. */
976 thread_across_edge (walk_data, true_edge);
978 /* And restore the various tables to their state before
979 we threaded this edge. */
980 remove_local_expressions_from_table (bd->avail_exprs,
983 restore_vars_to_original_value (bd->const_and_copies,
984 const_and_copies_limit,
986 restore_currdefs_to_original_value (bd->block_defs, currdefs_limit);
989 /* Similarly for the ELSE arm. */
990 if (get_immediate_dominator (CDI_DOMINATORS, false_edge->dest) != bb
991 || phi_nodes (false_edge->dest))
993 /* Record any equivalences created by following this edge. */
994 if (TREE_CODE_CLASS (cond_code) == '<')
996 record_cond (cond, boolean_false_node, &bd->avail_exprs);
997 record_cond (inverted, boolean_true_node, &bd->avail_exprs);
998 record_dominating_conditions (inverted, &bd->avail_exprs);
1000 else if (cond_code == SSA_NAME)
1001 record_const_or_copy (cond, boolean_false_node,
1002 &bd->const_and_copies);
1004 thread_across_edge (walk_data, false_edge);
1006 /* No need to remove local expressions from our tables
1007 or restore vars to their original value as that will
1008 be done immediately below. */
1012 remove_local_expressions_from_table (bd->avail_exprs, 0, avail_exprs);
1013 restore_nonzero_vars_to_original_value (bd->nonzero_vars, 0, nonzero_vars);
1014 restore_vars_to_original_value (bd->const_and_copies, 0, const_and_copies);
1015 restore_currdefs_to_original_value (bd->block_defs, 0);
1017 /* Remove VRP records associated with this basic block. They are no
1020 To be efficient, we note which variables have had their values
1021 constrained in this block. So walk over each variable in the
1022 VRP_VARIABLEs array. */
1023 while (bd->vrp_variables && VARRAY_ACTIVE_SIZE (bd->vrp_variables) > 0)
1025 tree var = VARRAY_TOP_TREE (bd->vrp_variables);
1027 /* Each variable has a stack of value range records. We want to
1028 invalidate those associated with our basic block. So we walk
1029 the array backwards popping off records associated with our
1030 block. Once we hit a record not associated with our block
1032 varray_type var_vrp_records = VARRAY_GENERIC_PTR (vrp_data,
1033 SSA_NAME_VERSION (var));
1035 while (VARRAY_ACTIVE_SIZE (var_vrp_records) > 0)
1037 struct vrp_element *element
1038 = (struct vrp_element *)VARRAY_TOP_GENERIC_PTR (var_vrp_records);
1040 if (element->bb != bb)
1043 VARRAY_POP (var_vrp_records);
1046 VARRAY_POP (bd->vrp_variables);
1049 /* Re-scan operands in all statements that may have had new symbols
1051 while (bd->stmts_to_rescan && VARRAY_ACTIVE_SIZE (bd->stmts_to_rescan) > 0)
1053 tree stmt = VARRAY_TOP_TREE (bd->stmts_to_rescan);
1054 VARRAY_POP (bd->stmts_to_rescan);
1055 mark_new_vars_to_rename (stmt, vars_to_rename);
1059 /* PHI nodes can create equivalences too.
1061 Ignoring any alternatives which are the same as the result, if
1062 all the alternatives are equal, then the PHI node creates an
1065 Additionally, if all the PHI alternatives are known to have a nonzero
1066 value, then the result of this PHI is known to have a nonzero value,
1067 even if we do not know its exact value. */
1070 record_equivalences_from_phis (struct dom_walk_data *walk_data, basic_block bb)
1072 struct dom_walk_block_data *bd
1073 = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
1076 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1078 tree lhs = PHI_RESULT (phi);
1082 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1084 tree t = PHI_ARG_DEF (phi, i);
1086 if (TREE_CODE (t) == SSA_NAME || is_gimple_min_invariant (t))
1088 /* Ignore alternatives which are the same as our LHS. */
1089 if (operand_equal_p (lhs, t, 0))
1092 /* If we have not processed an alternative yet, then set
1093 RHS to this alternative. */
1096 /* If we have processed an alternative (stored in RHS), then
1097 see if it is equal to this one. If it isn't, then stop
1099 else if (! operand_equal_p (rhs, t, 0))
1106 /* If we had no interesting alternatives, then all the RHS alternatives
1107 must have been the same as LHS. */
1111 /* If we managed to iterate through each PHI alternative without
1112 breaking out of the loop, then we have a PHI which may create
1113 a useful equivalence. We do not need to record unwind data for
1114 this, since this is a true assignment and not an equivalence
1115 inferred from a comparison. All uses of this ssa name are dominated
1116 by this assignment, so unwinding just costs time and space. */
1117 if (i == PHI_NUM_ARGS (phi)
1118 && may_propagate_copy (lhs, rhs))
1119 set_value_for (lhs, rhs, const_and_copies);
1121 /* Now see if we know anything about the nonzero property for the
1122 result of this PHI. */
1123 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1125 if (!PHI_ARG_NONZERO (phi, i))
1129 if (i == PHI_NUM_ARGS (phi))
1130 bitmap_set_bit (nonzero_vars, SSA_NAME_VERSION (PHI_RESULT (phi)));
1132 register_new_def (lhs, &bd->block_defs);
1136 /* Ignoring loop backedges, if BB has precisely one incoming edge then
1137 return that edge. Otherwise return NULL. */
1139 single_incoming_edge_ignoring_loop_edges (basic_block bb)
1144 for (e = bb->pred; e; e = e->pred_next)
1146 /* A loop back edge can be identified by the destination of
1147 the edge dominating the source of the edge. */
1148 if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
1151 /* If we have already seen a non-loop edge, then we must have
1152 multiple incoming non-loop edges and thus we return NULL. */
1156 /* This is the first non-loop incoming edge we have found. Record
1164 /* Record any equivalences created by the incoming edge to BB. If BB
1165 has more than one incoming edge, then no equivalence is created. */
1168 record_equivalences_from_incoming_edge (struct dom_walk_data *walk_data,
1173 struct eq_expr_value eq_expr_value;
1174 tree parent_block_last_stmt = NULL;
1175 struct dom_walk_block_data *bd
1176 = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
1178 /* If our parent block ended with a control statment, then we may be
1179 able to record some equivalences based on which outgoing edge from
1180 the parent was followed. */
1181 parent = get_immediate_dominator (CDI_DOMINATORS, bb);
1184 parent_block_last_stmt = last_stmt (parent);
1185 if (parent_block_last_stmt && !is_ctrl_stmt (parent_block_last_stmt))
1186 parent_block_last_stmt = NULL;
1189 eq_expr_value.src = NULL;
1190 eq_expr_value.dst = NULL;
1192 /* If we have a single predecessor (ignoring loop backedges), then extract
1193 EDGE_FLAGS from the single incoming edge. Otherwise just return as
1194 there is nothing to do. */
1196 && parent_block_last_stmt)
1198 edge e = single_incoming_edge_ignoring_loop_edges (bb);
1199 if (e && bb_for_stmt (parent_block_last_stmt) == e->src)
1200 edge_flags = e->flags;
1207 /* If our parent block ended in a COND_EXPR, add any equivalences
1208 created by the COND_EXPR to the hash table and initialize
1209 EQ_EXPR_VALUE appropriately.
1211 EQ_EXPR_VALUE is an assignment expression created when BB's immediate
1212 dominator ends in a COND_EXPR statement whose predicate is of the form
1213 'VAR == VALUE', where VALUE may be another variable or a constant.
1214 This is used to propagate VALUE on the THEN_CLAUSE of that
1215 conditional. This assignment is inserted in CONST_AND_COPIES so that
1216 the copy and constant propagator can find more propagation
1218 if (TREE_CODE (parent_block_last_stmt) == COND_EXPR
1219 && (edge_flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)))
1220 eq_expr_value = get_eq_expr_value (parent_block_last_stmt,
1221 (edge_flags & EDGE_TRUE_VALUE) != 0,
1224 &bd->vrp_variables);
1225 /* Similarly when the parent block ended in a SWITCH_EXPR.
1226 We can only know the value of the switch's condition if the dominator
1227 parent is also the only predecessor of this block. */
1228 else if (bb->pred->src == parent
1229 && TREE_CODE (parent_block_last_stmt) == SWITCH_EXPR)
1231 tree switch_cond = SWITCH_COND (parent_block_last_stmt);
1233 /* If the switch's condition is an SSA variable, then we may
1234 know its value at each of the case labels. */
1235 if (TREE_CODE (switch_cond) == SSA_NAME)
1237 tree switch_vec = SWITCH_LABELS (parent_block_last_stmt);
1238 size_t i, n = TREE_VEC_LENGTH (switch_vec);
1240 tree match_case = NULL_TREE;
1242 /* Search the case labels for those whose destination is
1243 the current basic block. */
1244 for (i = 0; i < n; ++i)
1246 tree elt = TREE_VEC_ELT (switch_vec, i);
1247 if (label_to_block (CASE_LABEL (elt)) == bb)
1249 if (++case_count > 1 || CASE_HIGH (elt))
1255 /* If we encountered precisely one CASE_LABEL_EXPR and it
1256 was not the default case, or a case range, then we know
1257 the exact value of SWITCH_COND which caused us to get to
1258 this block. Record that equivalence in EQ_EXPR_VALUE. */
1261 && CASE_LOW (match_case)
1262 && !CASE_HIGH (match_case))
1264 eq_expr_value.dst = switch_cond;
1265 eq_expr_value.src = fold_convert (TREE_TYPE (switch_cond),
1266 CASE_LOW (match_case));
1271 /* If EQ_EXPR_VALUE (VAR == VALUE) is given, register the VALUE as a
1272 new value for VAR, so that occurrences of VAR can be replaced with
1273 VALUE while re-writing the THEN arm of a COND_EXPR. */
1274 if (eq_expr_value.src && eq_expr_value.dst)
1275 record_equality (eq_expr_value.dst, eq_expr_value.src,
1276 &bd->const_and_copies);
1279 /* Dump SSA statistics on FILE. */
1282 dump_dominator_optimization_stats (FILE *file)
1286 fprintf (file, "Total number of statements: %6ld\n\n",
1287 opt_stats.num_stmts);
1288 fprintf (file, "Exprs considered for dominator optimizations: %6ld\n",
1289 opt_stats.num_exprs_considered);
1291 n_exprs = opt_stats.num_exprs_considered;
1295 fprintf (file, " Redundant expressions eliminated: %6ld (%.0f%%)\n",
1296 opt_stats.num_re, PERCENT (opt_stats.num_re,
1299 fprintf (file, "\nHash table statistics:\n");
1301 fprintf (file, " avail_exprs: ");
1302 htab_statistics (file, avail_exprs);
1306 /* Dump SSA statistics on stderr. */
1309 debug_dominator_optimization_stats (void)
1311 dump_dominator_optimization_stats (stderr);
1315 /* Dump statistics for the hash table HTAB. */
1318 htab_statistics (FILE *file, htab_t htab)
1320 fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
1321 (long) htab_size (htab),
1322 (long) htab_elements (htab),
1323 htab_collisions (htab));
1326 /* Record the fact that VAR has a nonzero value, though we may not know
1327 its exact value. Note that if VAR is already known to have a nonzero
1328 value, then we do nothing. */
1331 record_var_is_nonzero (tree var, varray_type *block_nonzero_vars_p)
1333 int indx = SSA_NAME_VERSION (var);
1335 if (bitmap_bit_p (nonzero_vars, indx))
1338 /* Mark it in the global table. */
1339 bitmap_set_bit (nonzero_vars, indx);
1341 /* Record this SSA_NAME so that we can reset the global table
1342 when we leave this block. */
1343 if (! *block_nonzero_vars_p)
1344 VARRAY_TREE_INIT (*block_nonzero_vars_p, 2, "block_nonzero_vars");
1345 VARRAY_PUSH_TREE (*block_nonzero_vars_p, var);
1348 /* Enter a statement into the true/false expression hash table indicating
1349 that the condition COND has the value VALUE. */
1352 record_cond (tree cond, tree value, varray_type *block_avail_exprs_p)
1354 struct expr_hash_elt *element = xmalloc (sizeof (struct expr_hash_elt));
1357 initialize_hash_element (cond, value, element);
1359 slot = htab_find_slot_with_hash (avail_exprs, (void *)element,
1360 element->hash, true);
1363 *slot = (void *) element;
1364 if (! *block_avail_exprs_p)
1365 VARRAY_TREE_INIT (*block_avail_exprs_p, 20, "block_avail_exprs");
1366 VARRAY_PUSH_TREE (*block_avail_exprs_p, cond);
1372 /* COND is a condition which is known to be true. Record variants of
1373 COND which must also be true.
1375 For example, if a < b is true, then a <= b must also be true. */
1378 record_dominating_conditions (tree cond, varray_type *block_avail_exprs_p)
1380 switch (TREE_CODE (cond))
1383 record_cond (build2 (LE_EXPR, boolean_type_node,
1384 TREE_OPERAND (cond, 0),
1385 TREE_OPERAND (cond, 1)),
1387 block_avail_exprs_p);
1388 record_cond (build2 (ORDERED_EXPR, boolean_type_node,
1389 TREE_OPERAND (cond, 0),
1390 TREE_OPERAND (cond, 1)),
1392 block_avail_exprs_p);
1393 record_cond (build2 (NE_EXPR, boolean_type_node,
1394 TREE_OPERAND (cond, 0),
1395 TREE_OPERAND (cond, 1)),
1397 block_avail_exprs_p);
1398 record_cond (build2 (LTGT_EXPR, boolean_type_node,
1399 TREE_OPERAND (cond, 0),
1400 TREE_OPERAND (cond, 1)),
1402 block_avail_exprs_p);
1406 record_cond (build2 (GE_EXPR, boolean_type_node,
1407 TREE_OPERAND (cond, 0),
1408 TREE_OPERAND (cond, 1)),
1410 block_avail_exprs_p);
1411 record_cond (build2 (ORDERED_EXPR, boolean_type_node,
1412 TREE_OPERAND (cond, 0),
1413 TREE_OPERAND (cond, 1)),
1415 block_avail_exprs_p);
1416 record_cond (build2 (NE_EXPR, boolean_type_node,
1417 TREE_OPERAND (cond, 0),
1418 TREE_OPERAND (cond, 1)),
1420 block_avail_exprs_p);
1421 record_cond (build2 (LTGT_EXPR, boolean_type_node,
1422 TREE_OPERAND (cond, 0),
1423 TREE_OPERAND (cond, 1)),
1425 block_avail_exprs_p);
1430 record_cond (build2 (ORDERED_EXPR, boolean_type_node,
1431 TREE_OPERAND (cond, 0),
1432 TREE_OPERAND (cond, 1)),
1434 block_avail_exprs_p);
1438 record_cond (build2 (ORDERED_EXPR, boolean_type_node,
1439 TREE_OPERAND (cond, 0),
1440 TREE_OPERAND (cond, 1)),
1442 block_avail_exprs_p);
1443 record_cond (build2 (LE_EXPR, boolean_type_node,
1444 TREE_OPERAND (cond, 0),
1445 TREE_OPERAND (cond, 1)),
1447 block_avail_exprs_p);
1448 record_cond (build2 (GE_EXPR, boolean_type_node,
1449 TREE_OPERAND (cond, 0),
1450 TREE_OPERAND (cond, 1)),
1452 block_avail_exprs_p);
1455 case UNORDERED_EXPR:
1456 record_cond (build2 (NE_EXPR, boolean_type_node,
1457 TREE_OPERAND (cond, 0),
1458 TREE_OPERAND (cond, 1)),
1460 block_avail_exprs_p);
1461 record_cond (build2 (UNLE_EXPR, boolean_type_node,
1462 TREE_OPERAND (cond, 0),
1463 TREE_OPERAND (cond, 1)),
1465 block_avail_exprs_p);
1466 record_cond (build2 (UNGE_EXPR, boolean_type_node,
1467 TREE_OPERAND (cond, 0),
1468 TREE_OPERAND (cond, 1)),
1470 block_avail_exprs_p);
1471 record_cond (build2 (UNEQ_EXPR, boolean_type_node,
1472 TREE_OPERAND (cond, 0),
1473 TREE_OPERAND (cond, 1)),
1475 block_avail_exprs_p);
1476 record_cond (build2 (UNLT_EXPR, boolean_type_node,
1477 TREE_OPERAND (cond, 0),
1478 TREE_OPERAND (cond, 1)),
1480 block_avail_exprs_p);
1481 record_cond (build2 (UNGT_EXPR, boolean_type_node,
1482 TREE_OPERAND (cond, 0),
1483 TREE_OPERAND (cond, 1)),
1485 block_avail_exprs_p);
1489 record_cond (build2 (UNLE_EXPR, boolean_type_node,
1490 TREE_OPERAND (cond, 0),
1491 TREE_OPERAND (cond, 1)),
1493 block_avail_exprs_p);
1494 record_cond (build2 (NE_EXPR, boolean_type_node,
1495 TREE_OPERAND (cond, 0),
1496 TREE_OPERAND (cond, 1)),
1498 block_avail_exprs_p);
1502 record_cond (build2 (UNGE_EXPR, boolean_type_node,
1503 TREE_OPERAND (cond, 0),
1504 TREE_OPERAND (cond, 1)),
1506 block_avail_exprs_p);
1507 record_cond (build2 (NE_EXPR, boolean_type_node,
1508 TREE_OPERAND (cond, 0),
1509 TREE_OPERAND (cond, 1)),
1511 block_avail_exprs_p);
1515 record_cond (build2 (UNLE_EXPR, boolean_type_node,
1516 TREE_OPERAND (cond, 0),
1517 TREE_OPERAND (cond, 1)),
1519 block_avail_exprs_p);
1520 record_cond (build2 (UNGE_EXPR, boolean_type_node,
1521 TREE_OPERAND (cond, 0),
1522 TREE_OPERAND (cond, 1)),
1524 block_avail_exprs_p);
1528 record_cond (build2 (NE_EXPR, boolean_type_node,
1529 TREE_OPERAND (cond, 0),
1530 TREE_OPERAND (cond, 1)),
1532 block_avail_exprs_p);
1533 record_cond (build2 (ORDERED_EXPR, boolean_type_node,
1534 TREE_OPERAND (cond, 0),
1535 TREE_OPERAND (cond, 1)),
1537 block_avail_exprs_p);
1544 /* A helper function for record_const_or_copy and record_equality.
1545 Do the work of recording the value and undo info. */
1548 record_const_or_copy_1 (tree x, tree y, tree prev_x,
1549 varray_type *block_const_and_copies_p)
1551 set_value_for (x, y, const_and_copies);
1553 if (!*block_const_and_copies_p)
1554 VARRAY_TREE_INIT (*block_const_and_copies_p, 2, "block_const_and_copies");
1555 VARRAY_PUSH_TREE (*block_const_and_copies_p, x);
1556 VARRAY_PUSH_TREE (*block_const_and_copies_p, prev_x);
1559 /* Record that X is equal to Y in const_and_copies. Record undo
1560 information in the block-local varray. */
1563 record_const_or_copy (tree x, tree y, varray_type *block_const_and_copies_p)
1565 tree prev_x = get_value_for (x, const_and_copies);
1567 if (TREE_CODE (y) == SSA_NAME)
1569 tree tmp = get_value_for (y, const_and_copies);
1574 record_const_or_copy_1 (x, y, prev_x, block_const_and_copies_p);
1577 /* Similarly, but assume that X and Y are the two operands of an EQ_EXPR.
1578 This constrains the cases in which we may treat this as assignment. */
1581 record_equality (tree x, tree y, varray_type *block_const_and_copies_p)
1583 tree prev_x = NULL, prev_y = NULL;
1585 if (TREE_CODE (x) == SSA_NAME)
1586 prev_x = get_value_for (x, const_and_copies);
1587 if (TREE_CODE (y) == SSA_NAME)
1588 prev_y = get_value_for (y, const_and_copies);
1590 /* If one of the previous values is invariant, then use that.
1591 Otherwise it doesn't matter which value we choose, just so
1592 long as we canonicalize on one value. */
1593 if (TREE_INVARIANT (y))
1595 else if (TREE_INVARIANT (x))
1596 prev_x = x, x = y, y = prev_x, prev_x = prev_y;
1597 else if (prev_x && TREE_INVARIANT (prev_x))
1598 x = y, y = prev_x, prev_x = prev_y;
1602 /* After the swapping, we must have one SSA_NAME. */
1603 if (TREE_CODE (x) != SSA_NAME)
1606 /* For IEEE, -0.0 == 0.0, so we don't necessarily know the sign of a
1607 variable compared against zero. If we're honoring signed zeros,
1608 then we cannot record this value unless we know that the value is
1610 if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (x)))
1611 && (TREE_CODE (y) != REAL_CST
1612 || REAL_VALUES_EQUAL (dconst0, TREE_REAL_CST (y))))
1615 record_const_or_copy_1 (x, y, prev_x, block_const_and_copies_p);
1618 /* STMT is a MODIFY_EXPR for which we were unable to find RHS in the
1619 hash tables. Try to simplify the RHS using whatever equivalences
1620 we may have recorded.
1622 If we are able to simplify the RHS, then lookup the simplified form in
1623 the hash table and return the result. Otherwise return NULL. */
1626 simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *walk_data,
1627 tree stmt, int insert)
1629 tree rhs = TREE_OPERAND (stmt, 1);
1630 enum tree_code rhs_code = TREE_CODE (rhs);
1632 struct dom_walk_block_data *bd
1633 = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
1635 /* If we have lhs = ~x, look and see if we earlier had x = ~y.
1636 In which case we can change this statement to be lhs = y.
1637 Which can then be copy propagated.
1639 Similarly for negation. */
1640 if ((rhs_code == BIT_NOT_EXPR || rhs_code == NEGATE_EXPR)
1641 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
1643 /* Get the definition statement for our RHS. */
1644 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1646 /* See if the RHS_DEF_STMT has the same form as our statement. */
1647 if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR
1648 && TREE_CODE (TREE_OPERAND (rhs_def_stmt, 1)) == rhs_code)
1650 tree rhs_def_operand;
1652 rhs_def_operand = TREE_OPERAND (TREE_OPERAND (rhs_def_stmt, 1), 0);
1654 /* Verify that RHS_DEF_OPERAND is a suitable SSA variable. */
1655 if (TREE_CODE (rhs_def_operand) == SSA_NAME
1656 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))
1657 result = update_rhs_and_lookup_avail_expr (stmt,
1664 /* If we have z = (x OP C1), see if we earlier had x = y OP C2.
1665 If OP is associative, create and fold (y OP C2) OP C1 which
1666 should result in (y OP C3), use that as the RHS for the
1667 assignment. Add minus to this, as we handle it specially below. */
1668 if ((associative_tree_code (rhs_code) || rhs_code == MINUS_EXPR)
1669 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
1670 && is_gimple_min_invariant (TREE_OPERAND (rhs, 1)))
1672 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1674 /* See if the RHS_DEF_STMT has the same form as our statement. */
1675 if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR)
1677 tree rhs_def_rhs = TREE_OPERAND (rhs_def_stmt, 1);
1678 enum tree_code rhs_def_code = TREE_CODE (rhs_def_rhs);
1680 if (rhs_code == rhs_def_code
1681 || (rhs_code == PLUS_EXPR && rhs_def_code == MINUS_EXPR)
1682 || (rhs_code == MINUS_EXPR && rhs_def_code == PLUS_EXPR))
1684 tree def_stmt_op0 = TREE_OPERAND (rhs_def_rhs, 0);
1685 tree def_stmt_op1 = TREE_OPERAND (rhs_def_rhs, 1);
1687 if (TREE_CODE (def_stmt_op0) == SSA_NAME
1688 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def_stmt_op0)
1689 && is_gimple_min_invariant (def_stmt_op1))
1691 tree outer_const = TREE_OPERAND (rhs, 1);
1692 tree type = TREE_TYPE (TREE_OPERAND (stmt, 0));
1695 /* If we care about correct floating point results, then
1696 don't fold x + c1 - c2. Note that we need to take both
1697 the codes and the signs to figure this out. */
1698 if (FLOAT_TYPE_P (type)
1699 && !flag_unsafe_math_optimizations
1700 && (rhs_def_code == PLUS_EXPR
1701 || rhs_def_code == MINUS_EXPR))
1705 neg ^= (rhs_code == MINUS_EXPR);
1706 neg ^= (rhs_def_code == MINUS_EXPR);
1707 neg ^= real_isneg (TREE_REAL_CST_PTR (outer_const));
1708 neg ^= real_isneg (TREE_REAL_CST_PTR (def_stmt_op1));
1711 goto dont_fold_assoc;
1714 /* Ho hum. So fold will only operate on the outermost
1715 thingy that we give it, so we have to build the new
1716 expression in two pieces. This requires that we handle
1717 combinations of plus and minus. */
1718 if (rhs_def_code != rhs_code)
1720 if (rhs_def_code == MINUS_EXPR)
1721 t = build (MINUS_EXPR, type, outer_const, def_stmt_op1);
1723 t = build (MINUS_EXPR, type, def_stmt_op1, outer_const);
1724 rhs_code = PLUS_EXPR;
1726 else if (rhs_def_code == MINUS_EXPR)
1727 t = build (PLUS_EXPR, type, def_stmt_op1, outer_const);
1729 t = build (rhs_def_code, type, def_stmt_op1, outer_const);
1731 t = build (rhs_code, type, def_stmt_op0, t);
1734 /* If the result is a suitable looking gimple expression,
1735 then use it instead of the original for STMT. */
1736 if (TREE_CODE (t) == SSA_NAME
1737 || (TREE_CODE_CLASS (TREE_CODE (t)) == '1'
1738 && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME)
1739 || ((TREE_CODE_CLASS (TREE_CODE (t)) == '2'
1740 || TREE_CODE_CLASS (TREE_CODE (t)) == '<')
1741 && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME
1742 && is_gimple_val (TREE_OPERAND (t, 1))))
1743 result = update_rhs_and_lookup_avail_expr
1744 (stmt, t, &bd->avail_exprs, insert);
1751 /* Transform TRUNC_DIV_EXPR and TRUNC_MOD_EXPR into RSHIFT_EXPR
1752 and BIT_AND_EXPR respectively if the first operand is greater
1753 than zero and the second operand is an exact power of two. */
1754 if ((rhs_code == TRUNC_DIV_EXPR || rhs_code == TRUNC_MOD_EXPR)
1755 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0)))
1756 && integer_pow2p (TREE_OPERAND (rhs, 1)))
1759 tree op = TREE_OPERAND (rhs, 0);
1761 if (TYPE_UNSIGNED (TREE_TYPE (op)))
1763 val = integer_one_node;
1767 tree dummy_cond = walk_data->global_data;
1771 dummy_cond = build (GT_EXPR, boolean_type_node,
1772 op, integer_zero_node);
1773 dummy_cond = build (COND_EXPR, void_type_node,
1774 dummy_cond, NULL, NULL);
1775 walk_data->global_data = dummy_cond;
1779 TREE_SET_CODE (TREE_OPERAND (dummy_cond, 0), GT_EXPR);
1780 TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 0) = op;
1781 TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 1)
1782 = integer_zero_node;
1784 val = simplify_cond_and_lookup_avail_expr (dummy_cond,
1789 if (val && integer_onep (val))
1792 tree op0 = TREE_OPERAND (rhs, 0);
1793 tree op1 = TREE_OPERAND (rhs, 1);
1795 if (rhs_code == TRUNC_DIV_EXPR)
1796 t = build (RSHIFT_EXPR, TREE_TYPE (op0), op0,
1797 build_int_cst (NULL_TREE, tree_log2 (op1)));
1799 t = build (BIT_AND_EXPR, TREE_TYPE (op0), op0,
1800 local_fold (build (MINUS_EXPR, TREE_TYPE (op1),
1801 op1, integer_one_node)));
1803 result = update_rhs_and_lookup_avail_expr (stmt, t,
1804 &bd->avail_exprs, insert);
1808 /* Transform ABS (X) into X or -X as appropriate. */
1809 if (rhs_code == ABS_EXPR
1810 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0))))
1813 tree op = TREE_OPERAND (rhs, 0);
1814 tree type = TREE_TYPE (op);
1816 if (TYPE_UNSIGNED (type))
1818 val = integer_zero_node;
1822 tree dummy_cond = walk_data->global_data;
1826 dummy_cond = build (LE_EXPR, boolean_type_node,
1827 op, integer_zero_node);
1828 dummy_cond = build (COND_EXPR, void_type_node,
1829 dummy_cond, NULL, NULL);
1830 walk_data->global_data = dummy_cond;
1834 TREE_SET_CODE (TREE_OPERAND (dummy_cond, 0), LE_EXPR);
1835 TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 0) = op;
1836 TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 1)
1837 = build_int_cst (type, 0);
1839 val = simplify_cond_and_lookup_avail_expr (dummy_cond,
1845 TREE_SET_CODE (TREE_OPERAND (dummy_cond, 0), GE_EXPR);
1846 TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 0) = op;
1847 TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 1)
1848 = build_int_cst (type, 0);
1850 val = simplify_cond_and_lookup_avail_expr (dummy_cond,
1856 if (integer_zerop (val))
1857 val = integer_one_node;
1858 else if (integer_onep (val))
1859 val = integer_zero_node;
1865 && (integer_onep (val) || integer_zerop (val)))
1869 if (integer_onep (val))
1870 t = build1 (NEGATE_EXPR, TREE_TYPE (op), op);
1874 result = update_rhs_and_lookup_avail_expr (stmt, t,
1875 &bd->avail_exprs, insert);
1879 /* Optimize *"foo" into 'f'. This is done here rather than
1880 in fold to avoid problems with stuff like &*"foo". */
1881 if (TREE_CODE (rhs) == INDIRECT_REF || TREE_CODE (rhs) == ARRAY_REF)
1883 tree t = fold_read_from_constant_string (rhs);
1886 result = update_rhs_and_lookup_avail_expr (stmt, t,
1887 &bd->avail_exprs, insert);
1893 /* COND is a condition of the form:
1895 x == const or x != const
1897 Look back to x's defining statement and see if x is defined as
1901 If const is unchanged if we convert it to type, then we can build
1902 the equivalent expression:
1905 y == const or y != const
1907 Which may allow further optimizations.
1909 Return the equivalent comparison or NULL if no such equivalent comparison
1913 find_equivalent_equality_comparison (tree cond)
1915 tree op0 = TREE_OPERAND (cond, 0);
1916 tree op1 = TREE_OPERAND (cond, 1);
1917 tree def_stmt = SSA_NAME_DEF_STMT (op0);
1919 /* OP0 might have been a parameter, so first make sure it
1920 was defined by a MODIFY_EXPR. */
1921 if (def_stmt && TREE_CODE (def_stmt) == MODIFY_EXPR)
1923 tree def_rhs = TREE_OPERAND (def_stmt, 1);
1925 /* Now make sure the RHS of the MODIFY_EXPR is a typecast. */
1926 if ((TREE_CODE (def_rhs) == NOP_EXPR
1927 || TREE_CODE (def_rhs) == CONVERT_EXPR)
1928 && TREE_CODE (TREE_OPERAND (def_rhs, 0)) == SSA_NAME)
1930 tree def_rhs_inner = TREE_OPERAND (def_rhs, 0);
1931 tree def_rhs_inner_type = TREE_TYPE (def_rhs_inner);
1934 if (TYPE_PRECISION (def_rhs_inner_type)
1935 > TYPE_PRECISION (TREE_TYPE (def_rhs)))
1938 /* What we want to prove is that if we convert OP1 to
1939 the type of the object inside the NOP_EXPR that the
1940 result is still equivalent to SRC.
1942 If that is true, the build and return new equivalent
1943 condition which uses the source of the typecast and the
1944 new constant (which has only changed its type). */
1945 new = build1 (TREE_CODE (def_rhs), def_rhs_inner_type, op1);
1946 new = local_fold (new);
1947 if (is_gimple_val (new) && tree_int_cst_equal (new, op1))
1948 return build (TREE_CODE (cond), TREE_TYPE (cond),
1949 def_rhs_inner, new);
1955 /* STMT is a COND_EXPR for which we could not trivially determine its
1956 result. This routine attempts to find equivalent forms of the
1957 condition which we may be able to optimize better. It also
1958 uses simple value range propagation to optimize conditionals. */
1961 simplify_cond_and_lookup_avail_expr (tree stmt,
1962 varray_type *block_avail_exprs_p,
1966 tree cond = COND_EXPR_COND (stmt);
1968 if (TREE_CODE_CLASS (TREE_CODE (cond)) == '<')
1970 tree op0 = TREE_OPERAND (cond, 0);
1971 tree op1 = TREE_OPERAND (cond, 1);
1973 if (TREE_CODE (op0) == SSA_NAME && is_gimple_min_invariant (op1))
1976 tree low, high, cond_low, cond_high;
1977 int lowequal, highequal, swapped, no_overlap, subset, cond_inverted;
1978 varray_type vrp_records;
1979 struct vrp_element *element;
1981 /* First see if we have test of an SSA_NAME against a constant
1982 where the SSA_NAME is defined by an earlier typecast which
1983 is irrelevant when performing tests against the given
1985 if (TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
1987 tree new_cond = find_equivalent_equality_comparison (cond);
1991 /* Update the statement to use the new equivalent
1993 COND_EXPR_COND (stmt) = new_cond;
1995 /* If this is not a real stmt, ann will be NULL and we
1996 avoid processing the operands. */
2000 /* Lookup the condition and return its known value if it
2002 new_cond = lookup_avail_expr (stmt, block_avail_exprs_p,
2007 /* The operands have changed, so update op0 and op1. */
2008 op0 = TREE_OPERAND (cond, 0);
2009 op1 = TREE_OPERAND (cond, 1);
2013 /* Consult the value range records for this variable (if they exist)
2014 to see if we can eliminate or simplify this conditional.
2016 Note two tests are necessary to determine no records exist.
2017 First we have to see if the virtual array exists, if it
2018 exists, then we have to check its active size.
2020 Also note the vast majority of conditionals are not testing
2021 a variable which has had its range constrained by an earlier
2022 conditional. So this filter avoids a lot of unnecessary work. */
2023 vrp_records = VARRAY_GENERIC_PTR (vrp_data, SSA_NAME_VERSION (op0));
2024 if (vrp_records == NULL)
2027 limit = VARRAY_ACTIVE_SIZE (vrp_records);
2029 /* If we have no value range records for this variable, or we are
2030 unable to extract a range for this condition, then there is
2033 || ! extract_range_from_cond (cond, &cond_high,
2034 &cond_low, &cond_inverted))
2037 /* We really want to avoid unnecessary computations of range
2038 info. So all ranges are computed lazily; this avoids a
2039 lot of unnecessary work. ie, we record the conditional,
2040 but do not process how it constrains the variable's
2041 potential values until we know that processing the condition
2044 However, we do not want to have to walk a potentially long
2045 list of ranges, nor do we want to compute a variable's
2046 range more than once for a given path.
2048 Luckily, each time we encounter a conditional that can not
2049 be otherwise optimized we will end up here and we will
2050 compute the necessary range information for the variable
2051 used in this condition.
2053 Thus you can conclude that there will never be more than one
2054 conditional associated with a variable which has not been
2055 processed. So we never need to merge more than one new
2056 conditional into the current range.
2058 These properties also help us avoid unnecessary work. */
2060 = (struct vrp_element *)VARRAY_GENERIC_PTR (vrp_records, limit - 1);
2062 if (element->high && element->low)
2064 /* The last element has been processed, so there is no range
2065 merging to do, we can simply use the high/low values
2066 recorded in the last element. */
2068 high = element->high;
2072 tree tmp_high, tmp_low;
2075 /* The last element has not been processed. Process it now. */
2076 extract_range_from_cond (element->cond, &tmp_high,
2079 /* If this is the only element, then no merging is necessary,
2080 the high/low values from extract_range_from_cond are all
2089 /* Get the high/low value from the previous element. */
2090 struct vrp_element *prev
2091 = (struct vrp_element *)VARRAY_GENERIC_PTR (vrp_records,
2096 /* Merge in this element's range with the range from the
2099 The low value for the merged range is the maximum of
2100 the previous low value and the low value of this record.
2102 Similarly the high value for the merged range is the
2103 minimum of the previous high value and the high value of
2105 low = (tree_int_cst_compare (low, tmp_low) == 1
2107 high = (tree_int_cst_compare (high, tmp_high) == -1
2111 /* And record the computed range. */
2113 element->high = high;
2117 /* After we have constrained this variable's potential values,
2118 we try to determine the result of the given conditional.
2120 To simplify later tests, first determine if the current
2121 low value is the same low value as the conditional.
2122 Similarly for the current high value and the high value
2123 for the conditional. */
2124 lowequal = tree_int_cst_equal (low, cond_low);
2125 highequal = tree_int_cst_equal (high, cond_high);
2127 if (lowequal && highequal)
2128 return (cond_inverted ? boolean_false_node : boolean_true_node);
2130 /* To simplify the overlap/subset tests below we may want
2131 to swap the two ranges so that the larger of the two
2132 ranges occurs "first". */
2134 if (tree_int_cst_compare (low, cond_low) == 1
2136 && tree_int_cst_compare (cond_high, high) == 1))
2149 /* Now determine if there is no overlap in the ranges
2150 or if the second range is a subset of the first range. */
2151 no_overlap = tree_int_cst_lt (high, cond_low);
2152 subset = tree_int_cst_compare (cond_high, high) != 1;
2154 /* If there was no overlap in the ranges, then this conditional
2155 always has a false value (unless we had to invert this
2156 conditional, in which case it always has a true value). */
2158 return (cond_inverted ? boolean_true_node : boolean_false_node);
2160 /* If the current range is a subset of the condition's range,
2161 then this conditional always has a true value (unless we
2162 had to invert this conditional, in which case it always
2163 has a true value). */
2164 if (subset && swapped)
2165 return (cond_inverted ? boolean_false_node : boolean_true_node);
2167 /* We were unable to determine the result of the conditional.
2168 However, we may be able to simplify the conditional. First
2169 merge the ranges in the same manner as range merging above. */
2170 low = tree_int_cst_compare (low, cond_low) == 1 ? low : cond_low;
2171 high = tree_int_cst_compare (high, cond_high) == -1 ? high : cond_high;
2173 /* If the range has converged to a single point, then turn this
2174 into an equality comparison. */
2175 if (TREE_CODE (cond) != EQ_EXPR
2176 && TREE_CODE (cond) != NE_EXPR
2177 && tree_int_cst_equal (low, high))
2179 TREE_SET_CODE (cond, EQ_EXPR);
2180 TREE_OPERAND (cond, 1) = high;
2187 /* STMT is a SWITCH_EXPR for which we could not trivially determine its
2188 result. This routine attempts to find equivalent forms of the
2189 condition which we may be able to optimize better. */
2192 simplify_switch_and_lookup_avail_expr (tree stmt,
2193 varray_type *block_avail_exprs_p,
2196 tree cond = SWITCH_COND (stmt);
2199 /* The optimization that we really care about is removing unnecessary
2200 casts. That will let us do much better in propagating the inferred
2201 constant at the switch target. */
2202 if (TREE_CODE (cond) == SSA_NAME)
2204 def = SSA_NAME_DEF_STMT (cond);
2205 if (TREE_CODE (def) == MODIFY_EXPR)
2207 def = TREE_OPERAND (def, 1);
2208 if (TREE_CODE (def) == NOP_EXPR)
2213 def = TREE_OPERAND (def, 0);
2215 #ifdef ENABLE_CHECKING
2216 /* ??? Why was Jeff testing this? We are gimple... */
2217 gcc_assert (is_gimple_val (def));
2220 to = TREE_TYPE (cond);
2221 ti = TREE_TYPE (def);
2223 /* If we have an extension that preserves value, then we
2224 can copy the source value into the switch. */
2226 need_precision = TYPE_PRECISION (ti);
2228 if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
2230 else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
2231 need_precision += 1;
2232 if (TYPE_PRECISION (to) < need_precision)
2237 SWITCH_COND (stmt) = def;
2240 return lookup_avail_expr (stmt, block_avail_exprs_p, insert);
2250 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2251 known value for that SSA_NAME (or NULL if no value is known).
2253 NONZERO_VARS is the set SSA_NAMES known to have a nonzero value,
2254 even if we don't know their precise value.
2256 Propagate values from CONST_AND_COPIES and NONZERO_VARS into the PHI
2257 nodes of the successors of BB. */
2260 cprop_into_successor_phis (basic_block bb,
2261 varray_type const_and_copies,
2262 bitmap nonzero_vars)
2266 /* This can get rather expensive if the implementation is naive in
2267 how it finds the phi alternative associated with a particular edge. */
2268 for (e = bb->succ; e; e = e->succ_next)
2274 /* If this is an abnormal edge, then we do not want to copy propagate
2275 into the PHI alternative associated with this edge. */
2276 if (e->flags & EDGE_ABNORMAL)
2279 phi = phi_nodes (e->dest);
2283 /* There is no guarantee that for any two PHI nodes in a block that
2284 the phi alternative associated with a particular edge will be
2285 at the same index in the phi alternative array.
2287 However, it is very likely they will be the same. So we keep
2288 track of the index of the alternative where we found the edge in
2289 the previous phi node and check that index first in the next
2290 phi node. If that hint fails, then we actually search all
2292 phi_num_args = PHI_NUM_ARGS (phi);
2293 hint = phi_num_args;
2294 for ( ; phi; phi = PHI_CHAIN (phi))
2298 use_operand_p orig_p;
2301 /* If the hint is valid (!= phi_num_args), see if it points
2302 us to the desired phi alternative. */
2303 if (hint != phi_num_args && PHI_ARG_EDGE (phi, hint) == e)
2307 /* The hint was either invalid or did not point to the
2308 correct phi alternative. Search all the alternatives
2309 for the correct one. Update the hint. */
2310 for (i = 0; i < phi_num_args; i++)
2311 if (PHI_ARG_EDGE (phi, i) == e)
2316 /* If we did not find the proper alternative, then something is
2318 gcc_assert (hint != phi_num_args);
2320 /* The alternative may be associated with a constant, so verify
2321 it is an SSA_NAME before doing anything with it. */
2322 orig_p = PHI_ARG_DEF_PTR (phi, hint);
2323 orig = USE_FROM_PTR (orig_p);
2324 if (TREE_CODE (orig) != SSA_NAME)
2327 /* If the alternative is known to have a nonzero value, record
2328 that fact in the PHI node itself for future use. */
2329 if (bitmap_bit_p (nonzero_vars, SSA_NAME_VERSION (orig)))
2330 PHI_ARG_NONZERO (phi, hint) = true;
2332 /* If we have *ORIG_P in our constant/copy table, then replace
2333 ORIG_P with its value in our constant/copy table. */
2334 new = VARRAY_TREE (const_and_copies, SSA_NAME_VERSION (orig));
2336 && (TREE_CODE (new) == SSA_NAME
2337 || is_gimple_min_invariant (new))
2338 && may_propagate_copy (orig, new))
2340 propagate_value (orig_p, new);
2347 /* Propagate known constants/copies into PHI nodes of BB's successor
2351 cprop_into_phis (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
2354 cprop_into_successor_phis (bb, const_and_copies, nonzero_vars);
2357 /* Search for redundant computations in STMT. If any are found, then
2358 replace them with the variable holding the result of the computation.
2360 If safe, record this expression into the available expression hash
2364 eliminate_redundant_computations (struct dom_walk_data *walk_data,
2365 tree stmt, stmt_ann_t ann)
2367 v_may_def_optype v_may_defs = V_MAY_DEF_OPS (ann);
2368 tree *expr_p, def = NULL_TREE;
2371 bool retval = false;
2372 struct dom_walk_block_data *bd
2373 = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
2375 if (TREE_CODE (stmt) == MODIFY_EXPR)
2376 def = TREE_OPERAND (stmt, 0);
2378 /* Certain expressions on the RHS can be optimized away, but can not
2379 themselves be entered into the hash tables. */
2380 if (ann->makes_aliased_stores
2382 || TREE_CODE (def) != SSA_NAME
2383 || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def)
2384 || NUM_V_MAY_DEFS (v_may_defs) != 0)
2387 /* Check if the expression has been computed before. */
2388 cached_lhs = lookup_avail_expr (stmt, &bd->avail_exprs, insert);
2390 /* If this is an assignment and the RHS was not in the hash table,
2391 then try to simplify the RHS and lookup the new RHS in the
2393 if (! cached_lhs && TREE_CODE (stmt) == MODIFY_EXPR)
2394 cached_lhs = simplify_rhs_and_lookup_avail_expr (walk_data,
2397 /* Similarly if this is a COND_EXPR and we did not find its
2398 expression in the hash table, simplify the condition and
2400 else if (! cached_lhs && TREE_CODE (stmt) == COND_EXPR)
2401 cached_lhs = simplify_cond_and_lookup_avail_expr (stmt,
2405 /* Similarly for a SWITCH_EXPR. */
2406 else if (!cached_lhs && TREE_CODE (stmt) == SWITCH_EXPR)
2407 cached_lhs = simplify_switch_and_lookup_avail_expr (stmt,
2411 opt_stats.num_exprs_considered++;
2413 /* Get a pointer to the expression we are trying to optimize. */
2414 if (TREE_CODE (stmt) == COND_EXPR)
2415 expr_p = &COND_EXPR_COND (stmt);
2416 else if (TREE_CODE (stmt) == SWITCH_EXPR)
2417 expr_p = &SWITCH_COND (stmt);
2418 else if (TREE_CODE (stmt) == RETURN_EXPR && TREE_OPERAND (stmt, 0))
2419 expr_p = &TREE_OPERAND (TREE_OPERAND (stmt, 0), 1);
2421 expr_p = &TREE_OPERAND (stmt, 1);
2423 /* It is safe to ignore types here since we have already done
2424 type checking in the hashing and equality routines. In fact
2425 type checking here merely gets in the way of constant
2426 propagation. Also, make sure that it is safe to propagate
2427 CACHED_LHS into *EXPR_P. */
2429 && (TREE_CODE (cached_lhs) != SSA_NAME
2430 || may_propagate_copy (*expr_p, cached_lhs)))
2432 if (dump_file && (dump_flags & TDF_DETAILS))
2434 fprintf (dump_file, " Replaced redundant expr '");
2435 print_generic_expr (dump_file, *expr_p, dump_flags);
2436 fprintf (dump_file, "' with '");
2437 print_generic_expr (dump_file, cached_lhs, dump_flags);
2438 fprintf (dump_file, "'\n");
2443 #if defined ENABLE_CHECKING
2444 gcc_assert (TREE_CODE (cached_lhs) == SSA_NAME
2445 || is_gimple_min_invariant (cached_lhs));
2448 if (TREE_CODE (cached_lhs) == ADDR_EXPR
2449 || (POINTER_TYPE_P (TREE_TYPE (*expr_p))
2450 && is_gimple_min_invariant (cached_lhs)))
2453 propagate_tree_value (expr_p, cached_lhs);
2459 /* STMT, a MODIFY_EXPR, may create certain equivalences, in either
2460 the available expressions table or the const_and_copies table.
2461 Detect and record those equivalences. */
2464 record_equivalences_from_stmt (tree stmt,
2465 varray_type *block_avail_exprs_p,
2466 varray_type *block_nonzero_vars_p,
2470 tree lhs = TREE_OPERAND (stmt, 0);
2471 enum tree_code lhs_code = TREE_CODE (lhs);
2474 if (lhs_code == SSA_NAME)
2476 tree rhs = TREE_OPERAND (stmt, 1);
2478 /* Strip away any useless type conversions. */
2479 STRIP_USELESS_TYPE_CONVERSION (rhs);
2481 /* If the RHS of the assignment is a constant or another variable that
2482 may be propagated, register it in the CONST_AND_COPIES table. We
2483 do not need to record unwind data for this, since this is a true
2484 assignment and not an equivalence inferred from a comparison. All
2485 uses of this ssa name are dominated by this assignment, so unwinding
2486 just costs time and space. */
2488 && (TREE_CODE (rhs) == SSA_NAME
2489 || is_gimple_min_invariant (rhs)))
2490 set_value_for (lhs, rhs, const_and_copies);
2492 /* alloca never returns zero and the address of a non-weak symbol
2493 is never zero. NOP_EXPRs and CONVERT_EXPRs can be completely
2494 stripped as they do not affect this equivalence. */
2495 while (TREE_CODE (rhs) == NOP_EXPR
2496 || TREE_CODE (rhs) == CONVERT_EXPR)
2497 rhs = TREE_OPERAND (rhs, 0);
2499 if (alloca_call_p (rhs)
2500 || (TREE_CODE (rhs) == ADDR_EXPR
2501 && DECL_P (TREE_OPERAND (rhs, 0))
2502 && ! DECL_WEAK (TREE_OPERAND (rhs, 0))))
2503 record_var_is_nonzero (lhs, block_nonzero_vars_p);
2505 /* IOR of any value with a nonzero value will result in a nonzero
2506 value. Even if we do not know the exact result recording that
2507 the result is nonzero is worth the effort. */
2508 if (TREE_CODE (rhs) == BIT_IOR_EXPR
2509 && integer_nonzerop (TREE_OPERAND (rhs, 1)))
2510 record_var_is_nonzero (lhs, block_nonzero_vars_p);
2513 /* Look at both sides for pointer dereferences. If we find one, then
2514 the pointer must be nonnull and we can enter that equivalence into
2516 if (flag_delete_null_pointer_checks)
2517 for (i = 0; i < 2; i++)
2519 tree t = TREE_OPERAND (stmt, i);
2521 /* Strip away any COMPONENT_REFs. */
2522 while (TREE_CODE (t) == COMPONENT_REF)
2523 t = TREE_OPERAND (t, 0);
2525 /* Now see if this is a pointer dereference. */
2526 if (TREE_CODE (t) == INDIRECT_REF)
2528 tree op = TREE_OPERAND (t, 0);
2530 /* If the pointer is a SSA variable, then enter new
2531 equivalences into the hash table. */
2532 while (TREE_CODE (op) == SSA_NAME)
2534 tree def = SSA_NAME_DEF_STMT (op);
2536 record_var_is_nonzero (op, block_nonzero_vars_p);
2538 /* And walk up the USE-DEF chains noting other SSA_NAMEs
2539 which are known to have a nonzero value. */
2541 && TREE_CODE (def) == MODIFY_EXPR
2542 && TREE_CODE (TREE_OPERAND (def, 1)) == NOP_EXPR)
2543 op = TREE_OPERAND (TREE_OPERAND (def, 1), 0);
2550 /* A memory store, even an aliased store, creates a useful
2551 equivalence. By exchanging the LHS and RHS, creating suitable
2552 vops and recording the result in the available expression table,
2553 we may be able to expose more redundant loads. */
2554 if (!ann->has_volatile_ops
2555 && (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME
2556 || is_gimple_min_invariant (TREE_OPERAND (stmt, 1)))
2557 && !is_gimple_reg (lhs))
2559 tree rhs = TREE_OPERAND (stmt, 1);
2562 /* FIXME: If the LHS of the assignment is a bitfield and the RHS
2563 is a constant, we need to adjust the constant to fit into the
2564 type of the LHS. If the LHS is a bitfield and the RHS is not
2565 a constant, then we can not record any equivalences for this
2566 statement since we would need to represent the widening or
2567 narrowing of RHS. This fixes gcc.c-torture/execute/921016-1.c
2568 and should not be necessary if GCC represented bitfields
2570 if (lhs_code == COMPONENT_REF
2571 && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1)))
2573 if (TREE_CONSTANT (rhs))
2574 rhs = widen_bitfield (rhs, TREE_OPERAND (lhs, 1), lhs);
2578 /* If the value overflowed, then we can not use this equivalence. */
2579 if (rhs && ! is_gimple_min_invariant (rhs))
2585 /* Build a new statement with the RHS and LHS exchanged. */
2586 new = build (MODIFY_EXPR, TREE_TYPE (stmt), rhs, lhs);
2588 create_ssa_artficial_load_stmt (&(ann->operands), new);
2590 /* Finally enter the statement into the available expression
2592 lookup_avail_expr (new, block_avail_exprs_p, true);
2597 /* Replace *OP_P in STMT with any known equivalent value for *OP_P from
2598 CONST_AND_COPIES. */
2601 cprop_operand (tree stmt, use_operand_p op_p, varray_type const_and_copies)
2603 bool may_have_exposed_new_symbols = false;
2605 tree op = USE_FROM_PTR (op_p);
2607 /* If the operand has a known constant value or it is known to be a
2608 copy of some other variable, use the value or copy stored in
2609 CONST_AND_COPIES. */
2610 val = VARRAY_TREE (const_and_copies, SSA_NAME_VERSION (op));
2613 tree op_type, val_type;
2615 /* Do not change the base variable in the virtual operand
2616 tables. That would make it impossible to reconstruct
2617 the renamed virtual operand if we later modify this
2618 statement. Also only allow the new value to be an SSA_NAME
2619 for propagation into virtual operands. */
2620 if (!is_gimple_reg (op)
2621 && (get_virtual_var (val) != get_virtual_var (op)
2622 || TREE_CODE (val) != SSA_NAME))
2625 /* Get the toplevel type of each operand. */
2626 op_type = TREE_TYPE (op);
2627 val_type = TREE_TYPE (val);
2629 /* While both types are pointers, get the type of the object
2631 while (POINTER_TYPE_P (op_type) && POINTER_TYPE_P (val_type))
2633 op_type = TREE_TYPE (op_type);
2634 val_type = TREE_TYPE (val_type);
2637 /* Make sure underlying types match before propagating a constant by
2638 converting the constant to the proper type. Note that convert may
2639 return a non-gimple expression, in which case we ignore this
2640 propagation opportunity. */
2641 if (TREE_CODE (val) != SSA_NAME)
2643 if (!lang_hooks.types_compatible_p (op_type, val_type))
2645 val = fold_convert (TREE_TYPE (op), val);
2646 if (!is_gimple_min_invariant (val))
2651 /* Certain operands are not allowed to be copy propagated due
2652 to their interaction with exception handling and some GCC
2654 else if (!may_propagate_copy (op, val))
2658 if (dump_file && (dump_flags & TDF_DETAILS))
2660 fprintf (dump_file, " Replaced '");
2661 print_generic_expr (dump_file, op, dump_flags);
2662 fprintf (dump_file, "' with %s '",
2663 (TREE_CODE (val) != SSA_NAME ? "constant" : "variable"));
2664 print_generic_expr (dump_file, val, dump_flags);
2665 fprintf (dump_file, "'\n");
2668 /* If VAL is an ADDR_EXPR or a constant of pointer type, note
2669 that we may have exposed a new symbol for SSA renaming. */
2670 if (TREE_CODE (val) == ADDR_EXPR
2671 || (POINTER_TYPE_P (TREE_TYPE (op))
2672 && is_gimple_min_invariant (val)))
2673 may_have_exposed_new_symbols = true;
2675 propagate_value (op_p, val);
2677 /* And note that we modified this statement. This is now
2678 safe, even if we changed virtual operands since we will
2679 rescan the statement and rewrite its operands again. */
2682 return may_have_exposed_new_symbols;
2685 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2686 known value for that SSA_NAME (or NULL if no value is known).
2688 Propagate values from CONST_AND_COPIES into the uses, vuses and
2689 v_may_def_ops of STMT. */
2692 cprop_into_stmt (tree stmt, varray_type const_and_copies)
2694 bool may_have_exposed_new_symbols = false;
2698 FOR_EACH_SSA_USE_OPERAND (op_p, stmt, iter, SSA_OP_ALL_USES)
2700 if (TREE_CODE (USE_FROM_PTR (op_p)) == SSA_NAME)
2701 may_have_exposed_new_symbols
2702 |= cprop_operand (stmt, op_p, const_and_copies);
2705 return may_have_exposed_new_symbols;
2709 /* Optimize the statement pointed by iterator SI.
2711 We try to perform some simplistic global redundancy elimination and
2712 constant propagation:
2714 1- To detect global redundancy, we keep track of expressions that have
2715 been computed in this block and its dominators. If we find that the
2716 same expression is computed more than once, we eliminate repeated
2717 computations by using the target of the first one.
2719 2- Constant values and copy assignments. This is used to do very
2720 simplistic constant and copy propagation. When a constant or copy
2721 assignment is found, we map the value on the RHS of the assignment to
2722 the variable in the LHS in the CONST_AND_COPIES table. */
2725 optimize_stmt (struct dom_walk_data *walk_data, basic_block bb,
2726 block_stmt_iterator si)
2730 bool may_optimize_p;
2731 bool may_have_exposed_new_symbols = false;
2732 struct dom_walk_block_data *bd
2733 = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
2735 stmt = bsi_stmt (si);
2737 get_stmt_operands (stmt);
2738 ann = stmt_ann (stmt);
2739 opt_stats.num_stmts++;
2740 may_have_exposed_new_symbols = false;
2742 if (dump_file && (dump_flags & TDF_DETAILS))
2744 fprintf (dump_file, "Optimizing statement ");
2745 print_generic_stmt (dump_file, stmt, TDF_SLIM);
2748 /* Const/copy propagate into USES, VUSES and the RHS of V_MAY_DEFs. */
2749 may_have_exposed_new_symbols = cprop_into_stmt (stmt, const_and_copies);
2751 /* If the statement has been modified with constant replacements,
2752 fold its RHS before checking for redundant computations. */
2755 /* Try to fold the statement making sure that STMT is kept
2757 if (fold_stmt (bsi_stmt_ptr (si)))
2759 stmt = bsi_stmt (si);
2760 ann = stmt_ann (stmt);
2762 if (dump_file && (dump_flags & TDF_DETAILS))
2764 fprintf (dump_file, " Folded to: ");
2765 print_generic_stmt (dump_file, stmt, TDF_SLIM);
2769 /* Constant/copy propagation above may change the set of
2770 virtual operands associated with this statement. Folding
2771 may remove the need for some virtual operands.
2773 Indicate we will need to rescan and rewrite the statement. */
2774 may_have_exposed_new_symbols = true;
2777 /* Check for redundant computations. Do this optimization only
2778 for assignments that have no volatile ops and conditionals. */
2779 may_optimize_p = (!ann->has_volatile_ops
2780 && ((TREE_CODE (stmt) == RETURN_EXPR
2781 && TREE_OPERAND (stmt, 0)
2782 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR
2783 && ! (TREE_SIDE_EFFECTS
2784 (TREE_OPERAND (TREE_OPERAND (stmt, 0), 1))))
2785 || (TREE_CODE (stmt) == MODIFY_EXPR
2786 && ! TREE_SIDE_EFFECTS (TREE_OPERAND (stmt, 1)))
2787 || TREE_CODE (stmt) == COND_EXPR
2788 || TREE_CODE (stmt) == SWITCH_EXPR));
2791 may_have_exposed_new_symbols
2792 |= eliminate_redundant_computations (walk_data, stmt, ann);
2794 /* Record any additional equivalences created by this statement. */
2795 if (TREE_CODE (stmt) == MODIFY_EXPR)
2796 record_equivalences_from_stmt (stmt,
2802 register_definitions_for_stmt (stmt, &bd->block_defs);
2804 /* If STMT is a COND_EXPR and it was modified, then we may know
2805 where it goes. If that is the case, then mark the CFG as altered.
2807 This will cause us to later call remove_unreachable_blocks and
2808 cleanup_tree_cfg when it is safe to do so. It is not safe to
2809 clean things up here since removal of edges and such can trigger
2810 the removal of PHI nodes, which in turn can release SSA_NAMEs to
2813 That's all fine and good, except that once SSA_NAMEs are released
2814 to the manager, we must not call create_ssa_name until all references
2815 to released SSA_NAMEs have been eliminated.
2817 All references to the deleted SSA_NAMEs can not be eliminated until
2818 we remove unreachable blocks.
2820 We can not remove unreachable blocks until after we have completed
2821 any queued jump threading.
2823 We can not complete any queued jump threads until we have taken
2824 appropriate variables out of SSA form. Taking variables out of
2825 SSA form can call create_ssa_name and thus we lose.
2827 Ultimately I suspect we're going to need to change the interface
2828 into the SSA_NAME manager. */
2834 if (TREE_CODE (stmt) == COND_EXPR)
2835 val = COND_EXPR_COND (stmt);
2836 else if (TREE_CODE (stmt) == SWITCH_EXPR)
2837 val = SWITCH_COND (stmt);
2839 if (val && TREE_CODE (val) == INTEGER_CST && find_taken_edge (bb, val))
2842 /* If we simplified a statement in such a way as to be shown that it
2843 cannot trap, update the eh information and the cfg to match. */
2844 if (maybe_clean_eh_stmt (stmt))
2846 bitmap_set_bit (need_eh_cleanup, bb->index);
2847 if (dump_file && (dump_flags & TDF_DETAILS))
2848 fprintf (dump_file, " Flagged to clear EH edges.\n");
2852 if (may_have_exposed_new_symbols)
2854 if (! bd->stmts_to_rescan)
2855 VARRAY_TREE_INIT (bd->stmts_to_rescan, 20, "stmts_to_rescan");
2856 VARRAY_PUSH_TREE (bd->stmts_to_rescan, bsi_stmt (si));
2860 /* Replace the RHS of STMT with NEW_RHS. If RHS can be found in the
2861 available expression hashtable, then return the LHS from the hash
2864 If INSERT is true, then we also update the available expression
2865 hash table to account for the changes made to STMT. */
2868 update_rhs_and_lookup_avail_expr (tree stmt, tree new_rhs,
2869 varray_type *block_avail_exprs_p,
2872 tree cached_lhs = NULL;
2874 /* Remove the old entry from the hash table. */
2877 struct expr_hash_elt element;
2879 initialize_hash_element (stmt, NULL, &element);
2880 htab_remove_elt_with_hash (avail_exprs, &element, element.hash);
2883 /* Now update the RHS of the assignment. */
2884 TREE_OPERAND (stmt, 1) = new_rhs;
2886 /* Now lookup the updated statement in the hash table. */
2887 cached_lhs = lookup_avail_expr (stmt, block_avail_exprs_p, insert);
2889 /* We have now called lookup_avail_expr twice with two different
2890 versions of this same statement, once in optimize_stmt, once here.
2892 We know the call in optimize_stmt did not find an existing entry
2893 in the hash table, so a new entry was created. At the same time
2894 this statement was pushed onto the BLOCK_AVAIL_EXPRS varray.
2896 If this call failed to find an existing entry on the hash table,
2897 then the new version of this statement was entered into the
2898 hash table. And this statement was pushed onto BLOCK_AVAIL_EXPR
2899 for the second time. So there are two copies on BLOCK_AVAIL_EXPRs
2901 If this call succeeded, we still have one copy of this statement
2902 on the BLOCK_AVAIL_EXPRs varray.
2904 For both cases, we need to pop the most recent entry off the
2905 BLOCK_AVAIL_EXPRs varray. For the case where we never found this
2906 statement in the hash tables, that will leave precisely one
2907 copy of this statement on BLOCK_AVAIL_EXPRs. For the case where
2908 we found a copy of this statement in the second hash table lookup
2909 we want _no_ copies of this statement in BLOCK_AVAIL_EXPRs. */
2911 VARRAY_POP (*block_avail_exprs_p);
2913 /* And make sure we record the fact that we modified this
2920 /* Search for an existing instance of STMT in the AVAIL_EXPRS table. If
2921 found, return its LHS. Otherwise insert STMT in the table and return
2924 Also, when an expression is first inserted in the AVAIL_EXPRS table, it
2925 is also added to the stack pointed by BLOCK_AVAIL_EXPRS_P, so that they
2926 can be removed when we finish processing this block and its children.
2928 NOTE: This function assumes that STMT is a MODIFY_EXPR node that
2929 contains no CALL_EXPR on its RHS and makes no volatile nor
2930 aliased references. */
2933 lookup_avail_expr (tree stmt, varray_type *block_avail_exprs_p, bool insert)
2938 struct expr_hash_elt *element = xcalloc (sizeof (struct expr_hash_elt), 1);
2940 lhs = TREE_CODE (stmt) == MODIFY_EXPR ? TREE_OPERAND (stmt, 0) : NULL;
2942 initialize_hash_element (stmt, lhs, element);
2944 /* Don't bother remembering constant assignments and copy operations.
2945 Constants and copy operations are handled by the constant/copy propagator
2946 in optimize_stmt. */
2947 if (TREE_CODE (element->rhs) == SSA_NAME
2948 || is_gimple_min_invariant (element->rhs))
2954 /* If this is an equality test against zero, see if we have recorded a
2955 nonzero value for the variable in question. */
2956 if ((TREE_CODE (element->rhs) == EQ_EXPR
2957 || TREE_CODE (element->rhs) == NE_EXPR)
2958 && TREE_CODE (TREE_OPERAND (element->rhs, 0)) == SSA_NAME
2959 && integer_zerop (TREE_OPERAND (element->rhs, 1)))
2961 int indx = SSA_NAME_VERSION (TREE_OPERAND (element->rhs, 0));
2963 if (bitmap_bit_p (nonzero_vars, indx))
2965 tree t = element->rhs;
2968 if (TREE_CODE (t) == EQ_EXPR)
2969 return boolean_false_node;
2971 return boolean_true_node;
2975 /* Finally try to find the expression in the main expression hash table. */
2976 slot = htab_find_slot_with_hash (avail_exprs, element, element->hash,
2977 (insert ? INSERT : NO_INSERT));
2986 *slot = (void *) element;
2987 if (! *block_avail_exprs_p)
2988 VARRAY_TREE_INIT (*block_avail_exprs_p, 20, "block_avail_exprs");
2989 VARRAY_PUSH_TREE (*block_avail_exprs_p, stmt ? stmt : element->rhs);
2993 /* Extract the LHS of the assignment so that it can be used as the current
2994 definition of another variable. */
2995 lhs = ((struct expr_hash_elt *)*slot)->lhs;
2997 /* See if the LHS appears in the CONST_AND_COPIES table. If it does, then
2998 use the value from the const_and_copies table. */
2999 if (TREE_CODE (lhs) == SSA_NAME)
3001 temp = get_value_for (lhs, const_and_copies);
3010 /* Given a condition COND, record into HI_P, LO_P and INVERTED_P the
3011 range of values that result in the conditional having a true value.
3013 Return true if we are successful in extracting a range from COND and
3014 false if we are unsuccessful. */
3017 extract_range_from_cond (tree cond, tree *hi_p, tree *lo_p, int *inverted_p)
3019 tree op1 = TREE_OPERAND (cond, 1);
3020 tree high, low, type;
3023 /* Experiments have shown that it's rarely, if ever useful to
3024 record ranges for enumerations. Presumably this is due to
3025 the fact that they're rarely used directly. They are typically
3026 cast into an integer type and used that way. */
3027 if (TREE_CODE (TREE_TYPE (op1)) != INTEGER_TYPE)
3030 type = TREE_TYPE (op1);
3032 switch (TREE_CODE (cond))
3046 high = TYPE_MAX_VALUE (type);
3051 low = int_const_binop (PLUS_EXPR, op1, integer_one_node, 1);
3052 high = TYPE_MAX_VALUE (type);
3058 low = TYPE_MIN_VALUE (type);
3063 high = int_const_binop (MINUS_EXPR, op1, integer_one_node, 1);
3064 low = TYPE_MIN_VALUE (type);
3074 *inverted_p = inverted;
3078 /* Record a range created by COND for basic block BB. */
3081 record_range (tree cond, basic_block bb, varray_type *vrp_variables_p)
3083 /* We explicitly ignore NE_EXPRs. They rarely allow for meaningful
3084 range optimizations and significantly complicate the implementation. */
3085 if (TREE_CODE_CLASS (TREE_CODE (cond)) == '<'
3086 && TREE_CODE (cond) != NE_EXPR
3087 && TREE_CODE (TREE_TYPE (TREE_OPERAND (cond, 1))) == INTEGER_TYPE)
3089 struct vrp_element *element = ggc_alloc (sizeof (struct vrp_element));
3090 int ssa_version = SSA_NAME_VERSION (TREE_OPERAND (cond, 0));
3092 varray_type *vrp_records_p
3093 = (varray_type *)&VARRAY_GENERIC_PTR (vrp_data, ssa_version);
3095 element->low = NULL;
3096 element->high = NULL;
3097 element->cond = cond;
3100 if (*vrp_records_p == NULL)
3102 VARRAY_GENERIC_PTR_INIT (*vrp_records_p, 2, "vrp records");
3103 VARRAY_GENERIC_PTR (vrp_data, ssa_version) = *vrp_records_p;
3106 VARRAY_PUSH_GENERIC_PTR (*vrp_records_p, element);
3107 if (! *vrp_variables_p)
3108 VARRAY_TREE_INIT (*vrp_variables_p, 2, "vrp_variables");
3109 VARRAY_PUSH_TREE (*vrp_variables_p, TREE_OPERAND (cond, 0));
3113 /* Given a conditional statement IF_STMT, return the assignment 'X = Y'
3114 known to be true depending on which arm of IF_STMT is taken.
3116 Not all conditional statements will result in a useful assignment.
3117 Return NULL_TREE in that case.
3119 Also enter into the available expression table statements of
3126 This allows us to lookup the condition in a dominated block and
3127 get back a constant indicating if the condition is true. */
3129 static struct eq_expr_value
3130 get_eq_expr_value (tree if_stmt,
3132 varray_type *block_avail_exprs_p,
3134 varray_type *vrp_variables_p)
3137 struct eq_expr_value retval;
3139 cond = COND_EXPR_COND (if_stmt);
3143 /* If the conditional is a single variable 'X', return 'X = 1' for
3144 the true arm and 'X = 0' on the false arm. */
3145 if (TREE_CODE (cond) == SSA_NAME)
3148 retval.src = constant_boolean_node (true_arm, TREE_TYPE (cond));
3152 /* If we have a comparison expression, then record its result into
3153 the available expression table. */
3154 if (TREE_CODE_CLASS (TREE_CODE (cond)) == '<')
3156 tree op0 = TREE_OPERAND (cond, 0);
3157 tree op1 = TREE_OPERAND (cond, 1);
3159 /* Special case comparing booleans against a constant as we know
3160 the value of OP0 on both arms of the branch. ie, we can record
3161 an equivalence for OP0 rather than COND. */
3162 if ((TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
3163 && TREE_CODE (op0) == SSA_NAME
3164 && TREE_CODE (TREE_TYPE (op0)) == BOOLEAN_TYPE
3165 && is_gimple_min_invariant (op1))
3167 if ((TREE_CODE (cond) == EQ_EXPR && true_arm)
3168 || (TREE_CODE (cond) == NE_EXPR && ! true_arm))
3174 if (integer_zerop (op1))
3175 retval.src = boolean_true_node;
3177 retval.src = boolean_false_node;
3183 if (TREE_CODE (op0) == SSA_NAME
3184 && (is_gimple_min_invariant (op1) || TREE_CODE (op1) == SSA_NAME))
3186 tree inverted = invert_truthvalue (cond);
3188 /* When we find an available expression in the hash table, we replace
3189 the expression with the LHS of the statement in the hash table.
3191 So, we want to build statements such as "1 = <condition>" on the
3192 true arm and "0 = <condition>" on the false arm. That way if we
3193 find the expression in the table, we will replace it with its
3194 known constant value. Also insert inversions of the result and
3195 condition into the hash table. */
3198 record_cond (cond, boolean_true_node, block_avail_exprs_p);
3199 record_dominating_conditions (cond, block_avail_exprs_p);
3200 record_cond (inverted, boolean_false_node, block_avail_exprs_p);
3202 if (TREE_CONSTANT (op1))
3203 record_range (cond, bb, vrp_variables_p);
3205 /* If the conditional is of the form 'X == Y', return 'X = Y'
3206 for the true arm. */
3207 if (TREE_CODE (cond) == EQ_EXPR)
3217 record_cond (inverted, boolean_true_node, block_avail_exprs_p);
3218 record_dominating_conditions (inverted, block_avail_exprs_p);
3219 record_cond (cond, boolean_false_node, block_avail_exprs_p);
3221 if (TREE_CONSTANT (op1))
3222 record_range (inverted, bb, vrp_variables_p);
3224 /* If the conditional is of the form 'X != Y', return 'X = Y'
3225 for the false arm. */
3226 if (TREE_CODE (cond) == NE_EXPR)
3239 /* Hashing and equality functions for AVAIL_EXPRS. The table stores
3240 MODIFY_EXPR statements. We compute a value number for expressions using
3241 the code of the expression and the SSA numbers of its operands. */
3244 avail_expr_hash (const void *p)
3246 stmt_ann_t ann = ((struct expr_hash_elt *)p)->ann;
3247 tree rhs = ((struct expr_hash_elt *)p)->rhs;
3252 /* iterative_hash_expr knows how to deal with any expression and
3253 deals with commutative operators as well, so just use it instead
3254 of duplicating such complexities here. */
3255 val = iterative_hash_expr (rhs, val);
3257 /* If the hash table entry is not associated with a statement, then we
3258 can just hash the expression and not worry about virtual operands
3263 /* Add the SSA version numbers of every vuse operand. This is important
3264 because compound variables like arrays are not renamed in the
3265 operands. Rather, the rename is done on the virtual variable
3266 representing all the elements of the array. */
3267 vuses = VUSE_OPS (ann);
3268 for (i = 0; i < NUM_VUSES (vuses); i++)
3269 val = iterative_hash_expr (VUSE_OP (vuses, i), val);
3275 real_avail_expr_hash (const void *p)
3277 return ((const struct expr_hash_elt *)p)->hash;
3281 avail_expr_eq (const void *p1, const void *p2)
3283 stmt_ann_t ann1 = ((struct expr_hash_elt *)p1)->ann;
3284 tree rhs1 = ((struct expr_hash_elt *)p1)->rhs;
3285 stmt_ann_t ann2 = ((struct expr_hash_elt *)p2)->ann;
3286 tree rhs2 = ((struct expr_hash_elt *)p2)->rhs;
3288 /* If they are the same physical expression, return true. */
3289 if (rhs1 == rhs2 && ann1 == ann2)
3292 /* If their codes are not equal, then quit now. */
3293 if (TREE_CODE (rhs1) != TREE_CODE (rhs2))
3296 /* In case of a collision, both RHS have to be identical and have the
3297 same VUSE operands. */
3298 if ((TREE_TYPE (rhs1) == TREE_TYPE (rhs2)
3299 || lang_hooks.types_compatible_p (TREE_TYPE (rhs1), TREE_TYPE (rhs2)))
3300 && operand_equal_p (rhs1, rhs2, OEP_PURE_SAME))
3302 vuse_optype ops1 = NULL;
3303 vuse_optype ops2 = NULL;
3304 size_t num_ops1 = 0;
3305 size_t num_ops2 = 0;
3310 ops1 = VUSE_OPS (ann1);
3311 num_ops1 = NUM_VUSES (ops1);
3316 ops2 = VUSE_OPS (ann2);
3317 num_ops2 = NUM_VUSES (ops2);
3320 /* If the number of virtual uses is different, then we consider
3322 if (num_ops1 != num_ops2)
3325 for (i = 0; i < num_ops1; i++)
3326 if (VUSE_OP (ops1, i) != VUSE_OP (ops2, i))
3329 gcc_assert (((struct expr_hash_elt *)p1)->hash
3330 == ((struct expr_hash_elt *)p2)->hash);
3337 /* Given STMT and a pointer to the block local definitions BLOCK_DEFS_P,
3338 register register all objects set by this statement into BLOCK_DEFS_P
3342 register_definitions_for_stmt (tree stmt, varray_type *block_defs_p)
3347 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
3350 /* FIXME: We shouldn't be registering new defs if the variable
3351 doesn't need to be renamed. */
3352 register_new_def (def, block_defs_p);