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 #ifdef ENABLE_CHECKING
719 struct dom_walk_block_data *bd
720 = (struct dom_walk_block_data *)VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
722 /* We get cleared memory from the allocator, so if the memory is not
723 cleared, then we are re-using a previously allocated entry. In
724 that case, we can also re-use the underlying virtual arrays. Just
725 make sure we clear them before using them! */
728 if (bd->avail_exprs && VARRAY_ACTIVE_SIZE (bd->avail_exprs) > 0)
730 if (bd->const_and_copies && VARRAY_ACTIVE_SIZE (bd->const_and_copies) > 0)
732 if (bd->nonzero_vars && VARRAY_ACTIVE_SIZE (bd->nonzero_vars) > 0)
734 if (bd->stmts_to_rescan && VARRAY_ACTIVE_SIZE (bd->stmts_to_rescan) > 0)
736 if (bd->vrp_variables && VARRAY_ACTIVE_SIZE (bd->vrp_variables) > 0)
738 if (bd->block_defs && VARRAY_ACTIVE_SIZE (bd->block_defs) > 0)
744 /* Initialize local stacks for this optimizer and record equivalences
745 upon entry to BB. Equivalences can come from the edge traversed to
746 reach BB or they may come from PHI nodes at the start of BB. */
749 dom_opt_initialize_block (struct dom_walk_data *walk_data, basic_block bb)
751 if (dump_file && (dump_flags & TDF_DETAILS))
752 fprintf (dump_file, "\n\nOptimizing block #%d\n\n", bb->index);
754 record_equivalences_from_incoming_edge (walk_data, bb);
756 /* PHI nodes can create equivalences too. */
757 record_equivalences_from_phis (walk_data, bb);
760 /* Given an expression EXPR (a relational expression or a statement),
761 initialize the hash table element pointed by by ELEMENT. */
764 initialize_hash_element (tree expr, tree lhs, struct expr_hash_elt *element)
766 /* Hash table elements may be based on conditional expressions or statements.
768 For the former case, we have no annotation and we want to hash the
769 conditional expression. In the latter case we have an annotation and
770 we want to record the expression the statement evaluates. */
771 if (TREE_CODE_CLASS (TREE_CODE (expr)) == '<'
772 || TREE_CODE (expr) == TRUTH_NOT_EXPR)
777 else if (TREE_CODE (expr) == COND_EXPR)
779 element->ann = stmt_ann (expr);
780 element->rhs = COND_EXPR_COND (expr);
782 else if (TREE_CODE (expr) == SWITCH_EXPR)
784 element->ann = stmt_ann (expr);
785 element->rhs = SWITCH_COND (expr);
787 else if (TREE_CODE (expr) == RETURN_EXPR && TREE_OPERAND (expr, 0))
789 element->ann = stmt_ann (expr);
790 element->rhs = TREE_OPERAND (TREE_OPERAND (expr, 0), 1);
794 element->ann = stmt_ann (expr);
795 element->rhs = TREE_OPERAND (expr, 1);
799 element->hash = avail_expr_hash (element);
802 /* Remove all the expressions in LOCALS from TABLE, stopping when there are
803 LIMIT entries left in LOCALs. */
806 remove_local_expressions_from_table (varray_type locals,
813 /* Remove all the expressions made available in this block. */
814 while (VARRAY_ACTIVE_SIZE (locals) > limit)
816 struct expr_hash_elt element;
817 tree expr = VARRAY_TOP_TREE (locals);
820 initialize_hash_element (expr, NULL, &element);
821 htab_remove_elt_with_hash (table, &element, element.hash);
825 /* Use the SSA_NAMES in LOCALS to restore TABLE to its original
826 state, stopping when there are LIMIT entries left in LOCALs. */
829 restore_nonzero_vars_to_original_value (varray_type locals,
836 while (VARRAY_ACTIVE_SIZE (locals) > limit)
838 tree name = VARRAY_TOP_TREE (locals);
840 bitmap_clear_bit (table, SSA_NAME_VERSION (name));
844 /* Use the source/dest pairs in LOCALS to restore TABLE to its original
845 state, stopping when there are LIMIT entries left in LOCALs. */
848 restore_vars_to_original_value (varray_type locals,
855 while (VARRAY_ACTIVE_SIZE (locals) > limit)
857 tree prev_value, dest;
859 prev_value = VARRAY_TOP_TREE (locals);
861 dest = VARRAY_TOP_TREE (locals);
864 set_value_for (dest, prev_value, table);
868 /* Similar to restore_vars_to_original_value, except that it restores
869 CURRDEFS to its original value. */
871 restore_currdefs_to_original_value (varray_type locals, unsigned limit)
876 /* Restore CURRDEFS to its original state. */
877 while (VARRAY_ACTIVE_SIZE (locals) > limit)
879 tree tmp = VARRAY_TOP_TREE (locals);
884 /* If we recorded an SSA_NAME, then make the SSA_NAME the current
885 definition of its underlying variable. If we recorded anything
886 else, it must have been an _DECL node and its current reaching
887 definition must have been NULL. */
888 if (TREE_CODE (tmp) == SSA_NAME)
891 var = SSA_NAME_VAR (saved_def);
899 var_ann (var)->current_def = saved_def;
903 /* We have finished processing the dominator children of BB, perform
904 any finalization actions in preparation for leaving this node in
905 the dominator tree. */
908 dom_opt_finalize_block (struct dom_walk_data *walk_data, basic_block bb)
910 struct dom_walk_block_data *bd
911 = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
914 /* If we are at a leaf node in the dominator graph, see if we can thread
915 the edge from BB through its successor.
917 Do this before we remove entries from our equivalence tables. */
919 && ! bb->succ->succ_next
920 && (bb->succ->flags & EDGE_ABNORMAL) == 0
921 && (get_immediate_dominator (CDI_DOMINATORS, bb->succ->dest) != bb
922 || phi_nodes (bb->succ->dest)))
925 thread_across_edge (walk_data, bb->succ);
927 else if ((last = last_stmt (bb))
928 && TREE_CODE (last) == COND_EXPR
929 && (TREE_CODE_CLASS (TREE_CODE (COND_EXPR_COND (last))) == '<'
930 || TREE_CODE (COND_EXPR_COND (last)) == SSA_NAME)
932 && (bb->succ->flags & EDGE_ABNORMAL) == 0
933 && bb->succ->succ_next
934 && (bb->succ->succ_next->flags & EDGE_ABNORMAL) == 0
935 && ! bb->succ->succ_next->succ_next)
937 edge true_edge, false_edge;
938 tree cond, inverted = NULL;
939 enum tree_code cond_code;
941 extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
943 cond = COND_EXPR_COND (last);
944 cond_code = TREE_CODE (cond);
946 if (TREE_CODE_CLASS (cond_code) == '<')
947 inverted = invert_truthvalue (cond);
949 /* If the THEN arm is the end of a dominator tree or has PHI nodes,
950 then try to thread through its edge. */
951 if (get_immediate_dominator (CDI_DOMINATORS, true_edge->dest) != bb
952 || phi_nodes (true_edge->dest))
954 unsigned avail_expr_limit;
955 unsigned const_and_copies_limit;
956 unsigned currdefs_limit;
959 = bd->avail_exprs ? VARRAY_ACTIVE_SIZE (bd->avail_exprs) : 0;
960 const_and_copies_limit
961 = bd->const_and_copies ? VARRAY_ACTIVE_SIZE (bd->const_and_copies)
964 = bd->block_defs ? VARRAY_ACTIVE_SIZE (bd->block_defs) : 0;
966 /* Record any equivalences created by following this edge. */
967 if (TREE_CODE_CLASS (cond_code) == '<')
969 record_cond (cond, boolean_true_node, &bd->avail_exprs);
970 record_dominating_conditions (cond, &bd->avail_exprs);
971 record_cond (inverted, boolean_false_node, &bd->avail_exprs);
973 else if (cond_code == SSA_NAME)
974 record_const_or_copy (cond, boolean_true_node,
975 &bd->const_and_copies);
977 /* Now thread the edge. */
978 thread_across_edge (walk_data, true_edge);
980 /* And restore the various tables to their state before
981 we threaded this edge. */
982 remove_local_expressions_from_table (bd->avail_exprs,
985 restore_vars_to_original_value (bd->const_and_copies,
986 const_and_copies_limit,
988 restore_currdefs_to_original_value (bd->block_defs, currdefs_limit);
991 /* Similarly for the ELSE arm. */
992 if (get_immediate_dominator (CDI_DOMINATORS, false_edge->dest) != bb
993 || phi_nodes (false_edge->dest))
995 /* Record any equivalences created by following this edge. */
996 if (TREE_CODE_CLASS (cond_code) == '<')
998 record_cond (cond, boolean_false_node, &bd->avail_exprs);
999 record_cond (inverted, boolean_true_node, &bd->avail_exprs);
1000 record_dominating_conditions (inverted, &bd->avail_exprs);
1002 else if (cond_code == SSA_NAME)
1003 record_const_or_copy (cond, boolean_false_node,
1004 &bd->const_and_copies);
1006 thread_across_edge (walk_data, false_edge);
1008 /* No need to remove local expressions from our tables
1009 or restore vars to their original value as that will
1010 be done immediately below. */
1014 remove_local_expressions_from_table (bd->avail_exprs, 0, avail_exprs);
1015 restore_nonzero_vars_to_original_value (bd->nonzero_vars, 0, nonzero_vars);
1016 restore_vars_to_original_value (bd->const_and_copies, 0, const_and_copies);
1017 restore_currdefs_to_original_value (bd->block_defs, 0);
1019 /* Remove VRP records associated with this basic block. They are no
1022 To be efficient, we note which variables have had their values
1023 constrained in this block. So walk over each variable in the
1024 VRP_VARIABLEs array. */
1025 while (bd->vrp_variables && VARRAY_ACTIVE_SIZE (bd->vrp_variables) > 0)
1027 tree var = VARRAY_TOP_TREE (bd->vrp_variables);
1029 /* Each variable has a stack of value range records. We want to
1030 invalidate those associated with our basic block. So we walk
1031 the array backwards popping off records associated with our
1032 block. Once we hit a record not associated with our block
1034 varray_type var_vrp_records = VARRAY_GENERIC_PTR (vrp_data,
1035 SSA_NAME_VERSION (var));
1037 while (VARRAY_ACTIVE_SIZE (var_vrp_records) > 0)
1039 struct vrp_element *element
1040 = (struct vrp_element *)VARRAY_TOP_GENERIC_PTR (var_vrp_records);
1042 if (element->bb != bb)
1045 VARRAY_POP (var_vrp_records);
1048 VARRAY_POP (bd->vrp_variables);
1051 /* Re-scan operands in all statements that may have had new symbols
1053 while (bd->stmts_to_rescan && VARRAY_ACTIVE_SIZE (bd->stmts_to_rescan) > 0)
1055 tree stmt = VARRAY_TOP_TREE (bd->stmts_to_rescan);
1056 VARRAY_POP (bd->stmts_to_rescan);
1057 mark_new_vars_to_rename (stmt, vars_to_rename);
1061 /* PHI nodes can create equivalences too.
1063 Ignoring any alternatives which are the same as the result, if
1064 all the alternatives are equal, then the PHI node creates an
1067 Additionally, if all the PHI alternatives are known to have a nonzero
1068 value, then the result of this PHI is known to have a nonzero value,
1069 even if we do not know its exact value. */
1072 record_equivalences_from_phis (struct dom_walk_data *walk_data, basic_block bb)
1074 struct dom_walk_block_data *bd
1075 = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
1078 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1080 tree lhs = PHI_RESULT (phi);
1084 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1086 tree t = PHI_ARG_DEF (phi, i);
1088 if (TREE_CODE (t) == SSA_NAME || is_gimple_min_invariant (t))
1090 /* Ignore alternatives which are the same as our LHS. */
1091 if (operand_equal_p (lhs, t, 0))
1094 /* If we have not processed an alternative yet, then set
1095 RHS to this alternative. */
1098 /* If we have processed an alternative (stored in RHS), then
1099 see if it is equal to this one. If it isn't, then stop
1101 else if (! operand_equal_p (rhs, t, 0))
1108 /* If we had no interesting alternatives, then all the RHS alternatives
1109 must have been the same as LHS. */
1113 /* If we managed to iterate through each PHI alternative without
1114 breaking out of the loop, then we have a PHI which may create
1115 a useful equivalence. We do not need to record unwind data for
1116 this, since this is a true assignment and not an equivalence
1117 inferred from a comparison. All uses of this ssa name are dominated
1118 by this assignment, so unwinding just costs time and space. */
1119 if (i == PHI_NUM_ARGS (phi)
1120 && may_propagate_copy (lhs, rhs))
1121 set_value_for (lhs, rhs, const_and_copies);
1123 /* Now see if we know anything about the nonzero property for the
1124 result of this PHI. */
1125 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
1127 if (!PHI_ARG_NONZERO (phi, i))
1131 if (i == PHI_NUM_ARGS (phi))
1132 bitmap_set_bit (nonzero_vars, SSA_NAME_VERSION (PHI_RESULT (phi)));
1134 register_new_def (lhs, &bd->block_defs);
1138 /* Ignoring loop backedges, if BB has precisely one incoming edge then
1139 return that edge. Otherwise return NULL. */
1141 single_incoming_edge_ignoring_loop_edges (basic_block bb)
1146 for (e = bb->pred; e; e = e->pred_next)
1148 /* A loop back edge can be identified by the destination of
1149 the edge dominating the source of the edge. */
1150 if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
1153 /* If we have already seen a non-loop edge, then we must have
1154 multiple incoming non-loop edges and thus we return NULL. */
1158 /* This is the first non-loop incoming edge we have found. Record
1166 /* Record any equivalences created by the incoming edge to BB. If BB
1167 has more than one incoming edge, then no equivalence is created. */
1170 record_equivalences_from_incoming_edge (struct dom_walk_data *walk_data,
1175 struct eq_expr_value eq_expr_value;
1176 tree parent_block_last_stmt = NULL;
1177 struct dom_walk_block_data *bd
1178 = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
1180 /* If our parent block ended with a control statment, then we may be
1181 able to record some equivalences based on which outgoing edge from
1182 the parent was followed. */
1183 parent = get_immediate_dominator (CDI_DOMINATORS, bb);
1186 parent_block_last_stmt = last_stmt (parent);
1187 if (parent_block_last_stmt && !is_ctrl_stmt (parent_block_last_stmt))
1188 parent_block_last_stmt = NULL;
1191 eq_expr_value.src = NULL;
1192 eq_expr_value.dst = NULL;
1194 /* If we have a single predecessor (ignoring loop backedges), then extract
1195 EDGE_FLAGS from the single incoming edge. Otherwise just return as
1196 there is nothing to do. */
1198 && parent_block_last_stmt)
1200 edge e = single_incoming_edge_ignoring_loop_edges (bb);
1201 if (e && bb_for_stmt (parent_block_last_stmt) == e->src)
1202 edge_flags = e->flags;
1209 /* If our parent block ended in a COND_EXPR, add any equivalences
1210 created by the COND_EXPR to the hash table and initialize
1211 EQ_EXPR_VALUE appropriately.
1213 EQ_EXPR_VALUE is an assignment expression created when BB's immediate
1214 dominator ends in a COND_EXPR statement whose predicate is of the form
1215 'VAR == VALUE', where VALUE may be another variable or a constant.
1216 This is used to propagate VALUE on the THEN_CLAUSE of that
1217 conditional. This assignment is inserted in CONST_AND_COPIES so that
1218 the copy and constant propagator can find more propagation
1220 if (TREE_CODE (parent_block_last_stmt) == COND_EXPR
1221 && (edge_flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)))
1222 eq_expr_value = get_eq_expr_value (parent_block_last_stmt,
1223 (edge_flags & EDGE_TRUE_VALUE) != 0,
1226 &bd->vrp_variables);
1227 /* Similarly when the parent block ended in a SWITCH_EXPR.
1228 We can only know the value of the switch's condition if the dominator
1229 parent is also the only predecessor of this block. */
1230 else if (bb->pred->src == parent
1231 && TREE_CODE (parent_block_last_stmt) == SWITCH_EXPR)
1233 tree switch_cond = SWITCH_COND (parent_block_last_stmt);
1235 /* If the switch's condition is an SSA variable, then we may
1236 know its value at each of the case labels. */
1237 if (TREE_CODE (switch_cond) == SSA_NAME)
1239 tree switch_vec = SWITCH_LABELS (parent_block_last_stmt);
1240 size_t i, n = TREE_VEC_LENGTH (switch_vec);
1242 tree match_case = NULL_TREE;
1244 /* Search the case labels for those whose destination is
1245 the current basic block. */
1246 for (i = 0; i < n; ++i)
1248 tree elt = TREE_VEC_ELT (switch_vec, i);
1249 if (label_to_block (CASE_LABEL (elt)) == bb)
1251 if (++case_count > 1 || CASE_HIGH (elt))
1257 /* If we encountered precisely one CASE_LABEL_EXPR and it
1258 was not the default case, or a case range, then we know
1259 the exact value of SWITCH_COND which caused us to get to
1260 this block. Record that equivalence in EQ_EXPR_VALUE. */
1263 && CASE_LOW (match_case)
1264 && !CASE_HIGH (match_case))
1266 eq_expr_value.dst = switch_cond;
1267 eq_expr_value.src = fold_convert (TREE_TYPE (switch_cond),
1268 CASE_LOW (match_case));
1273 /* If EQ_EXPR_VALUE (VAR == VALUE) is given, register the VALUE as a
1274 new value for VAR, so that occurrences of VAR can be replaced with
1275 VALUE while re-writing the THEN arm of a COND_EXPR. */
1276 if (eq_expr_value.src && eq_expr_value.dst)
1277 record_equality (eq_expr_value.dst, eq_expr_value.src,
1278 &bd->const_and_copies);
1281 /* Dump SSA statistics on FILE. */
1284 dump_dominator_optimization_stats (FILE *file)
1288 fprintf (file, "Total number of statements: %6ld\n\n",
1289 opt_stats.num_stmts);
1290 fprintf (file, "Exprs considered for dominator optimizations: %6ld\n",
1291 opt_stats.num_exprs_considered);
1293 n_exprs = opt_stats.num_exprs_considered;
1297 fprintf (file, " Redundant expressions eliminated: %6ld (%.0f%%)\n",
1298 opt_stats.num_re, PERCENT (opt_stats.num_re,
1301 fprintf (file, "\nHash table statistics:\n");
1303 fprintf (file, " avail_exprs: ");
1304 htab_statistics (file, avail_exprs);
1308 /* Dump SSA statistics on stderr. */
1311 debug_dominator_optimization_stats (void)
1313 dump_dominator_optimization_stats (stderr);
1317 /* Dump statistics for the hash table HTAB. */
1320 htab_statistics (FILE *file, htab_t htab)
1322 fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
1323 (long) htab_size (htab),
1324 (long) htab_elements (htab),
1325 htab_collisions (htab));
1328 /* Record the fact that VAR has a nonzero value, though we may not know
1329 its exact value. Note that if VAR is already known to have a nonzero
1330 value, then we do nothing. */
1333 record_var_is_nonzero (tree var, varray_type *block_nonzero_vars_p)
1335 int indx = SSA_NAME_VERSION (var);
1337 if (bitmap_bit_p (nonzero_vars, indx))
1340 /* Mark it in the global table. */
1341 bitmap_set_bit (nonzero_vars, indx);
1343 /* Record this SSA_NAME so that we can reset the global table
1344 when we leave this block. */
1345 if (! *block_nonzero_vars_p)
1346 VARRAY_TREE_INIT (*block_nonzero_vars_p, 2, "block_nonzero_vars");
1347 VARRAY_PUSH_TREE (*block_nonzero_vars_p, var);
1350 /* Enter a statement into the true/false expression hash table indicating
1351 that the condition COND has the value VALUE. */
1354 record_cond (tree cond, tree value, varray_type *block_avail_exprs_p)
1356 struct expr_hash_elt *element = xmalloc (sizeof (struct expr_hash_elt));
1359 initialize_hash_element (cond, value, element);
1361 slot = htab_find_slot_with_hash (avail_exprs, (void *)element,
1362 element->hash, true);
1365 *slot = (void *) element;
1366 if (! *block_avail_exprs_p)
1367 VARRAY_TREE_INIT (*block_avail_exprs_p, 20, "block_avail_exprs");
1368 VARRAY_PUSH_TREE (*block_avail_exprs_p, cond);
1374 /* COND is a condition which is known to be true. Record variants of
1375 COND which must also be true.
1377 For example, if a < b is true, then a <= b must also be true. */
1380 record_dominating_conditions (tree cond, varray_type *block_avail_exprs_p)
1382 switch (TREE_CODE (cond))
1385 record_cond (build2 (LE_EXPR, boolean_type_node,
1386 TREE_OPERAND (cond, 0),
1387 TREE_OPERAND (cond, 1)),
1389 block_avail_exprs_p);
1390 record_cond (build2 (ORDERED_EXPR, boolean_type_node,
1391 TREE_OPERAND (cond, 0),
1392 TREE_OPERAND (cond, 1)),
1394 block_avail_exprs_p);
1395 record_cond (build2 (NE_EXPR, boolean_type_node,
1396 TREE_OPERAND (cond, 0),
1397 TREE_OPERAND (cond, 1)),
1399 block_avail_exprs_p);
1400 record_cond (build2 (LTGT_EXPR, boolean_type_node,
1401 TREE_OPERAND (cond, 0),
1402 TREE_OPERAND (cond, 1)),
1404 block_avail_exprs_p);
1408 record_cond (build2 (GE_EXPR, boolean_type_node,
1409 TREE_OPERAND (cond, 0),
1410 TREE_OPERAND (cond, 1)),
1412 block_avail_exprs_p);
1413 record_cond (build2 (ORDERED_EXPR, boolean_type_node,
1414 TREE_OPERAND (cond, 0),
1415 TREE_OPERAND (cond, 1)),
1417 block_avail_exprs_p);
1418 record_cond (build2 (NE_EXPR, boolean_type_node,
1419 TREE_OPERAND (cond, 0),
1420 TREE_OPERAND (cond, 1)),
1422 block_avail_exprs_p);
1423 record_cond (build2 (LTGT_EXPR, boolean_type_node,
1424 TREE_OPERAND (cond, 0),
1425 TREE_OPERAND (cond, 1)),
1427 block_avail_exprs_p);
1432 record_cond (build2 (ORDERED_EXPR, boolean_type_node,
1433 TREE_OPERAND (cond, 0),
1434 TREE_OPERAND (cond, 1)),
1436 block_avail_exprs_p);
1440 record_cond (build2 (ORDERED_EXPR, boolean_type_node,
1441 TREE_OPERAND (cond, 0),
1442 TREE_OPERAND (cond, 1)),
1444 block_avail_exprs_p);
1445 record_cond (build2 (LE_EXPR, boolean_type_node,
1446 TREE_OPERAND (cond, 0),
1447 TREE_OPERAND (cond, 1)),
1449 block_avail_exprs_p);
1450 record_cond (build2 (GE_EXPR, boolean_type_node,
1451 TREE_OPERAND (cond, 0),
1452 TREE_OPERAND (cond, 1)),
1454 block_avail_exprs_p);
1457 case UNORDERED_EXPR:
1458 record_cond (build2 (NE_EXPR, boolean_type_node,
1459 TREE_OPERAND (cond, 0),
1460 TREE_OPERAND (cond, 1)),
1462 block_avail_exprs_p);
1463 record_cond (build2 (UNLE_EXPR, boolean_type_node,
1464 TREE_OPERAND (cond, 0),
1465 TREE_OPERAND (cond, 1)),
1467 block_avail_exprs_p);
1468 record_cond (build2 (UNGE_EXPR, boolean_type_node,
1469 TREE_OPERAND (cond, 0),
1470 TREE_OPERAND (cond, 1)),
1472 block_avail_exprs_p);
1473 record_cond (build2 (UNEQ_EXPR, boolean_type_node,
1474 TREE_OPERAND (cond, 0),
1475 TREE_OPERAND (cond, 1)),
1477 block_avail_exprs_p);
1478 record_cond (build2 (UNLT_EXPR, boolean_type_node,
1479 TREE_OPERAND (cond, 0),
1480 TREE_OPERAND (cond, 1)),
1482 block_avail_exprs_p);
1483 record_cond (build2 (UNGT_EXPR, boolean_type_node,
1484 TREE_OPERAND (cond, 0),
1485 TREE_OPERAND (cond, 1)),
1487 block_avail_exprs_p);
1491 record_cond (build2 (UNLE_EXPR, boolean_type_node,
1492 TREE_OPERAND (cond, 0),
1493 TREE_OPERAND (cond, 1)),
1495 block_avail_exprs_p);
1496 record_cond (build2 (NE_EXPR, boolean_type_node,
1497 TREE_OPERAND (cond, 0),
1498 TREE_OPERAND (cond, 1)),
1500 block_avail_exprs_p);
1504 record_cond (build2 (UNGE_EXPR, boolean_type_node,
1505 TREE_OPERAND (cond, 0),
1506 TREE_OPERAND (cond, 1)),
1508 block_avail_exprs_p);
1509 record_cond (build2 (NE_EXPR, boolean_type_node,
1510 TREE_OPERAND (cond, 0),
1511 TREE_OPERAND (cond, 1)),
1513 block_avail_exprs_p);
1517 record_cond (build2 (UNLE_EXPR, boolean_type_node,
1518 TREE_OPERAND (cond, 0),
1519 TREE_OPERAND (cond, 1)),
1521 block_avail_exprs_p);
1522 record_cond (build2 (UNGE_EXPR, boolean_type_node,
1523 TREE_OPERAND (cond, 0),
1524 TREE_OPERAND (cond, 1)),
1526 block_avail_exprs_p);
1530 record_cond (build2 (NE_EXPR, boolean_type_node,
1531 TREE_OPERAND (cond, 0),
1532 TREE_OPERAND (cond, 1)),
1534 block_avail_exprs_p);
1535 record_cond (build2 (ORDERED_EXPR, boolean_type_node,
1536 TREE_OPERAND (cond, 0),
1537 TREE_OPERAND (cond, 1)),
1539 block_avail_exprs_p);
1546 /* A helper function for record_const_or_copy and record_equality.
1547 Do the work of recording the value and undo info. */
1550 record_const_or_copy_1 (tree x, tree y, tree prev_x,
1551 varray_type *block_const_and_copies_p)
1553 set_value_for (x, y, const_and_copies);
1555 if (!*block_const_and_copies_p)
1556 VARRAY_TREE_INIT (*block_const_and_copies_p, 2, "block_const_and_copies");
1557 VARRAY_PUSH_TREE (*block_const_and_copies_p, x);
1558 VARRAY_PUSH_TREE (*block_const_and_copies_p, prev_x);
1561 /* Record that X is equal to Y in const_and_copies. Record undo
1562 information in the block-local varray. */
1565 record_const_or_copy (tree x, tree y, varray_type *block_const_and_copies_p)
1567 tree prev_x = get_value_for (x, const_and_copies);
1569 if (TREE_CODE (y) == SSA_NAME)
1571 tree tmp = get_value_for (y, const_and_copies);
1576 record_const_or_copy_1 (x, y, prev_x, block_const_and_copies_p);
1579 /* Similarly, but assume that X and Y are the two operands of an EQ_EXPR.
1580 This constrains the cases in which we may treat this as assignment. */
1583 record_equality (tree x, tree y, varray_type *block_const_and_copies_p)
1585 tree prev_x = NULL, prev_y = NULL;
1587 if (TREE_CODE (x) == SSA_NAME)
1588 prev_x = get_value_for (x, const_and_copies);
1589 if (TREE_CODE (y) == SSA_NAME)
1590 prev_y = get_value_for (y, const_and_copies);
1592 /* If one of the previous values is invariant, then use that.
1593 Otherwise it doesn't matter which value we choose, just so
1594 long as we canonicalize on one value. */
1595 if (TREE_INVARIANT (y))
1597 else if (TREE_INVARIANT (x))
1598 prev_x = x, x = y, y = prev_x, prev_x = prev_y;
1599 else if (prev_x && TREE_INVARIANT (prev_x))
1600 x = y, y = prev_x, prev_x = prev_y;
1604 /* After the swapping, we must have one SSA_NAME. */
1605 if (TREE_CODE (x) != SSA_NAME)
1608 /* For IEEE, -0.0 == 0.0, so we don't necessarily know the sign of a
1609 variable compared against zero. If we're honoring signed zeros,
1610 then we cannot record this value unless we know that the value is
1612 if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (x)))
1613 && (TREE_CODE (y) != REAL_CST
1614 || REAL_VALUES_EQUAL (dconst0, TREE_REAL_CST (y))))
1617 record_const_or_copy_1 (x, y, prev_x, block_const_and_copies_p);
1620 /* STMT is a MODIFY_EXPR for which we were unable to find RHS in the
1621 hash tables. Try to simplify the RHS using whatever equivalences
1622 we may have recorded.
1624 If we are able to simplify the RHS, then lookup the simplified form in
1625 the hash table and return the result. Otherwise return NULL. */
1628 simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *walk_data,
1629 tree stmt, int insert)
1631 tree rhs = TREE_OPERAND (stmt, 1);
1632 enum tree_code rhs_code = TREE_CODE (rhs);
1634 struct dom_walk_block_data *bd
1635 = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
1637 /* If we have lhs = ~x, look and see if we earlier had x = ~y.
1638 In which case we can change this statement to be lhs = y.
1639 Which can then be copy propagated.
1641 Similarly for negation. */
1642 if ((rhs_code == BIT_NOT_EXPR || rhs_code == NEGATE_EXPR)
1643 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
1645 /* Get the definition statement for our RHS. */
1646 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1648 /* See if the RHS_DEF_STMT has the same form as our statement. */
1649 if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR
1650 && TREE_CODE (TREE_OPERAND (rhs_def_stmt, 1)) == rhs_code)
1652 tree rhs_def_operand;
1654 rhs_def_operand = TREE_OPERAND (TREE_OPERAND (rhs_def_stmt, 1), 0);
1656 /* Verify that RHS_DEF_OPERAND is a suitable SSA variable. */
1657 if (TREE_CODE (rhs_def_operand) == SSA_NAME
1658 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))
1659 result = update_rhs_and_lookup_avail_expr (stmt,
1666 /* If we have z = (x OP C1), see if we earlier had x = y OP C2.
1667 If OP is associative, create and fold (y OP C2) OP C1 which
1668 should result in (y OP C3), use that as the RHS for the
1669 assignment. Add minus to this, as we handle it specially below. */
1670 if ((associative_tree_code (rhs_code) || rhs_code == MINUS_EXPR)
1671 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
1672 && is_gimple_min_invariant (TREE_OPERAND (rhs, 1)))
1674 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
1676 /* See if the RHS_DEF_STMT has the same form as our statement. */
1677 if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR)
1679 tree rhs_def_rhs = TREE_OPERAND (rhs_def_stmt, 1);
1680 enum tree_code rhs_def_code = TREE_CODE (rhs_def_rhs);
1682 if (rhs_code == rhs_def_code
1683 || (rhs_code == PLUS_EXPR && rhs_def_code == MINUS_EXPR)
1684 || (rhs_code == MINUS_EXPR && rhs_def_code == PLUS_EXPR))
1686 tree def_stmt_op0 = TREE_OPERAND (rhs_def_rhs, 0);
1687 tree def_stmt_op1 = TREE_OPERAND (rhs_def_rhs, 1);
1689 if (TREE_CODE (def_stmt_op0) == SSA_NAME
1690 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def_stmt_op0)
1691 && is_gimple_min_invariant (def_stmt_op1))
1693 tree outer_const = TREE_OPERAND (rhs, 1);
1694 tree type = TREE_TYPE (TREE_OPERAND (stmt, 0));
1697 /* If we care about correct floating point results, then
1698 don't fold x + c1 - c2. Note that we need to take both
1699 the codes and the signs to figure this out. */
1700 if (FLOAT_TYPE_P (type)
1701 && !flag_unsafe_math_optimizations
1702 && (rhs_def_code == PLUS_EXPR
1703 || rhs_def_code == MINUS_EXPR))
1707 neg ^= (rhs_code == MINUS_EXPR);
1708 neg ^= (rhs_def_code == MINUS_EXPR);
1709 neg ^= real_isneg (TREE_REAL_CST_PTR (outer_const));
1710 neg ^= real_isneg (TREE_REAL_CST_PTR (def_stmt_op1));
1713 goto dont_fold_assoc;
1716 /* Ho hum. So fold will only operate on the outermost
1717 thingy that we give it, so we have to build the new
1718 expression in two pieces. This requires that we handle
1719 combinations of plus and minus. */
1720 if (rhs_def_code != rhs_code)
1722 if (rhs_def_code == MINUS_EXPR)
1723 t = build (MINUS_EXPR, type, outer_const, def_stmt_op1);
1725 t = build (MINUS_EXPR, type, def_stmt_op1, outer_const);
1726 rhs_code = PLUS_EXPR;
1728 else if (rhs_def_code == MINUS_EXPR)
1729 t = build (PLUS_EXPR, type, def_stmt_op1, outer_const);
1731 t = build (rhs_def_code, type, def_stmt_op1, outer_const);
1733 t = build (rhs_code, type, def_stmt_op0, t);
1736 /* If the result is a suitable looking gimple expression,
1737 then use it instead of the original for STMT. */
1738 if (TREE_CODE (t) == SSA_NAME
1739 || (TREE_CODE_CLASS (TREE_CODE (t)) == '1'
1740 && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME)
1741 || ((TREE_CODE_CLASS (TREE_CODE (t)) == '2'
1742 || TREE_CODE_CLASS (TREE_CODE (t)) == '<')
1743 && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME
1744 && is_gimple_val (TREE_OPERAND (t, 1))))
1745 result = update_rhs_and_lookup_avail_expr
1746 (stmt, t, &bd->avail_exprs, insert);
1753 /* Transform TRUNC_DIV_EXPR and TRUNC_MOD_EXPR into RSHIFT_EXPR
1754 and BIT_AND_EXPR respectively if the first operand is greater
1755 than zero and the second operand is an exact power of two. */
1756 if ((rhs_code == TRUNC_DIV_EXPR || rhs_code == TRUNC_MOD_EXPR)
1757 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0)))
1758 && integer_pow2p (TREE_OPERAND (rhs, 1)))
1761 tree op = TREE_OPERAND (rhs, 0);
1763 if (TYPE_UNSIGNED (TREE_TYPE (op)))
1765 val = integer_one_node;
1769 tree dummy_cond = walk_data->global_data;
1773 dummy_cond = build (GT_EXPR, boolean_type_node,
1774 op, integer_zero_node);
1775 dummy_cond = build (COND_EXPR, void_type_node,
1776 dummy_cond, NULL, NULL);
1777 walk_data->global_data = dummy_cond;
1781 TREE_SET_CODE (TREE_OPERAND (dummy_cond, 0), GT_EXPR);
1782 TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 0) = op;
1783 TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 1)
1784 = integer_zero_node;
1786 val = simplify_cond_and_lookup_avail_expr (dummy_cond,
1791 if (val && integer_onep (val))
1794 tree op0 = TREE_OPERAND (rhs, 0);
1795 tree op1 = TREE_OPERAND (rhs, 1);
1797 if (rhs_code == TRUNC_DIV_EXPR)
1798 t = build (RSHIFT_EXPR, TREE_TYPE (op0), op0,
1799 build_int_cst (NULL_TREE, tree_log2 (op1)));
1801 t = build (BIT_AND_EXPR, TREE_TYPE (op0), op0,
1802 local_fold (build (MINUS_EXPR, TREE_TYPE (op1),
1803 op1, integer_one_node)));
1805 result = update_rhs_and_lookup_avail_expr (stmt, t,
1806 &bd->avail_exprs, insert);
1810 /* Transform ABS (X) into X or -X as appropriate. */
1811 if (rhs_code == ABS_EXPR
1812 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0))))
1815 tree op = TREE_OPERAND (rhs, 0);
1816 tree type = TREE_TYPE (op);
1818 if (TYPE_UNSIGNED (type))
1820 val = integer_zero_node;
1824 tree dummy_cond = walk_data->global_data;
1828 dummy_cond = build (LE_EXPR, boolean_type_node,
1829 op, integer_zero_node);
1830 dummy_cond = build (COND_EXPR, void_type_node,
1831 dummy_cond, NULL, NULL);
1832 walk_data->global_data = dummy_cond;
1836 TREE_SET_CODE (TREE_OPERAND (dummy_cond, 0), LE_EXPR);
1837 TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 0) = op;
1838 TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 1)
1839 = fold_convert (type, integer_zero_node);
1841 val = simplify_cond_and_lookup_avail_expr (dummy_cond,
1847 TREE_SET_CODE (TREE_OPERAND (dummy_cond, 0), GE_EXPR);
1848 TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 0) = op;
1849 TREE_OPERAND (TREE_OPERAND (dummy_cond, 0), 1)
1850 = fold_convert (type, integer_zero_node);
1852 val = simplify_cond_and_lookup_avail_expr (dummy_cond,
1858 if (integer_zerop (val))
1859 val = integer_one_node;
1860 else if (integer_onep (val))
1861 val = integer_zero_node;
1867 && (integer_onep (val) || integer_zerop (val)))
1871 if (integer_onep (val))
1872 t = build1 (NEGATE_EXPR, TREE_TYPE (op), op);
1876 result = update_rhs_and_lookup_avail_expr (stmt, t,
1877 &bd->avail_exprs, insert);
1881 /* Optimize *"foo" into 'f'. This is done here rather than
1882 in fold to avoid problems with stuff like &*"foo". */
1883 if (TREE_CODE (rhs) == INDIRECT_REF || TREE_CODE (rhs) == ARRAY_REF)
1885 tree t = fold_read_from_constant_string (rhs);
1888 result = update_rhs_and_lookup_avail_expr (stmt, t,
1889 &bd->avail_exprs, insert);
1895 /* COND is a condition of the form:
1897 x == const or x != const
1899 Look back to x's defining statement and see if x is defined as
1903 If const is unchanged if we convert it to type, then we can build
1904 the equivalent expression:
1907 y == const or y != const
1909 Which may allow further optimizations.
1911 Return the equivalent comparison or NULL if no such equivalent comparison
1915 find_equivalent_equality_comparison (tree cond)
1917 tree op0 = TREE_OPERAND (cond, 0);
1918 tree op1 = TREE_OPERAND (cond, 1);
1919 tree def_stmt = SSA_NAME_DEF_STMT (op0);
1921 /* OP0 might have been a parameter, so first make sure it
1922 was defined by a MODIFY_EXPR. */
1923 if (def_stmt && TREE_CODE (def_stmt) == MODIFY_EXPR)
1925 tree def_rhs = TREE_OPERAND (def_stmt, 1);
1927 /* Now make sure the RHS of the MODIFY_EXPR is a typecast. */
1928 if ((TREE_CODE (def_rhs) == NOP_EXPR
1929 || TREE_CODE (def_rhs) == CONVERT_EXPR)
1930 && TREE_CODE (TREE_OPERAND (def_rhs, 0)) == SSA_NAME)
1932 tree def_rhs_inner = TREE_OPERAND (def_rhs, 0);
1933 tree def_rhs_inner_type = TREE_TYPE (def_rhs_inner);
1936 if (TYPE_PRECISION (def_rhs_inner_type)
1937 > TYPE_PRECISION (TREE_TYPE (def_rhs)))
1940 /* What we want to prove is that if we convert OP1 to
1941 the type of the object inside the NOP_EXPR that the
1942 result is still equivalent to SRC.
1944 If that is true, the build and return new equivalent
1945 condition which uses the source of the typecast and the
1946 new constant (which has only changed its type). */
1947 new = build1 (TREE_CODE (def_rhs), def_rhs_inner_type, op1);
1948 new = local_fold (new);
1949 if (is_gimple_val (new) && tree_int_cst_equal (new, op1))
1950 return build (TREE_CODE (cond), TREE_TYPE (cond),
1951 def_rhs_inner, new);
1957 /* STMT is a COND_EXPR for which we could not trivially determine its
1958 result. This routine attempts to find equivalent forms of the
1959 condition which we may be able to optimize better. It also
1960 uses simple value range propagation to optimize conditionals. */
1963 simplify_cond_and_lookup_avail_expr (tree stmt,
1964 varray_type *block_avail_exprs_p,
1968 tree cond = COND_EXPR_COND (stmt);
1970 if (TREE_CODE_CLASS (TREE_CODE (cond)) == '<')
1972 tree op0 = TREE_OPERAND (cond, 0);
1973 tree op1 = TREE_OPERAND (cond, 1);
1975 if (TREE_CODE (op0) == SSA_NAME && is_gimple_min_invariant (op1))
1978 tree low, high, cond_low, cond_high;
1979 int lowequal, highequal, swapped, no_overlap, subset, cond_inverted;
1980 varray_type vrp_records;
1981 struct vrp_element *element;
1983 /* First see if we have test of an SSA_NAME against a constant
1984 where the SSA_NAME is defined by an earlier typecast which
1985 is irrelevant when performing tests against the given
1987 if (TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
1989 tree new_cond = find_equivalent_equality_comparison (cond);
1993 /* Update the statement to use the new equivalent
1995 COND_EXPR_COND (stmt) = new_cond;
1997 /* If this is not a real stmt, ann will be NULL and we
1998 avoid processing the operands. */
2002 /* Lookup the condition and return its known value if it
2004 new_cond = lookup_avail_expr (stmt, block_avail_exprs_p,
2009 /* The operands have changed, so update op0 and op1. */
2010 op0 = TREE_OPERAND (cond, 0);
2011 op1 = TREE_OPERAND (cond, 1);
2015 /* Consult the value range records for this variable (if they exist)
2016 to see if we can eliminate or simplify this conditional.
2018 Note two tests are necessary to determine no records exist.
2019 First we have to see if the virtual array exists, if it
2020 exists, then we have to check its active size.
2022 Also note the vast majority of conditionals are not testing
2023 a variable which has had its range constrained by an earlier
2024 conditional. So this filter avoids a lot of unnecessary work. */
2025 vrp_records = VARRAY_GENERIC_PTR (vrp_data, SSA_NAME_VERSION (op0));
2026 if (vrp_records == NULL)
2029 limit = VARRAY_ACTIVE_SIZE (vrp_records);
2031 /* If we have no value range records for this variable, or we are
2032 unable to extract a range for this condition, then there is
2035 || ! extract_range_from_cond (cond, &cond_high,
2036 &cond_low, &cond_inverted))
2039 /* We really want to avoid unnecessary computations of range
2040 info. So all ranges are computed lazily; this avoids a
2041 lot of unnecessary work. ie, we record the conditional,
2042 but do not process how it constrains the variable's
2043 potential values until we know that processing the condition
2046 However, we do not want to have to walk a potentially long
2047 list of ranges, nor do we want to compute a variable's
2048 range more than once for a given path.
2050 Luckily, each time we encounter a conditional that can not
2051 be otherwise optimized we will end up here and we will
2052 compute the necessary range information for the variable
2053 used in this condition.
2055 Thus you can conclude that there will never be more than one
2056 conditional associated with a variable which has not been
2057 processed. So we never need to merge more than one new
2058 conditional into the current range.
2060 These properties also help us avoid unnecessary work. */
2062 = (struct vrp_element *)VARRAY_GENERIC_PTR (vrp_records, limit - 1);
2064 if (element->high && element->low)
2066 /* The last element has been processed, so there is no range
2067 merging to do, we can simply use the high/low values
2068 recorded in the last element. */
2070 high = element->high;
2074 tree tmp_high, tmp_low;
2077 /* The last element has not been processed. Process it now. */
2078 extract_range_from_cond (element->cond, &tmp_high,
2081 /* If this is the only element, then no merging is necessary,
2082 the high/low values from extract_range_from_cond are all
2091 /* Get the high/low value from the previous element. */
2092 struct vrp_element *prev
2093 = (struct vrp_element *)VARRAY_GENERIC_PTR (vrp_records,
2098 /* Merge in this element's range with the range from the
2101 The low value for the merged range is the maximum of
2102 the previous low value and the low value of this record.
2104 Similarly the high value for the merged range is the
2105 minimum of the previous high value and the high value of
2107 low = (tree_int_cst_compare (low, tmp_low) == 1
2109 high = (tree_int_cst_compare (high, tmp_high) == -1
2113 /* And record the computed range. */
2115 element->high = high;
2119 /* After we have constrained this variable's potential values,
2120 we try to determine the result of the given conditional.
2122 To simplify later tests, first determine if the current
2123 low value is the same low value as the conditional.
2124 Similarly for the current high value and the high value
2125 for the conditional. */
2126 lowequal = tree_int_cst_equal (low, cond_low);
2127 highequal = tree_int_cst_equal (high, cond_high);
2129 if (lowequal && highequal)
2130 return (cond_inverted ? boolean_false_node : boolean_true_node);
2132 /* To simplify the overlap/subset tests below we may want
2133 to swap the two ranges so that the larger of the two
2134 ranges occurs "first". */
2136 if (tree_int_cst_compare (low, cond_low) == 1
2138 && tree_int_cst_compare (cond_high, high) == 1))
2151 /* Now determine if there is no overlap in the ranges
2152 or if the second range is a subset of the first range. */
2153 no_overlap = tree_int_cst_lt (high, cond_low);
2154 subset = tree_int_cst_compare (cond_high, high) != 1;
2156 /* If there was no overlap in the ranges, then this conditional
2157 always has a false value (unless we had to invert this
2158 conditional, in which case it always has a true value). */
2160 return (cond_inverted ? boolean_true_node : boolean_false_node);
2162 /* If the current range is a subset of the condition's range,
2163 then this conditional always has a true value (unless we
2164 had to invert this conditional, in which case it always
2165 has a true value). */
2166 if (subset && swapped)
2167 return (cond_inverted ? boolean_false_node : boolean_true_node);
2169 /* We were unable to determine the result of the conditional.
2170 However, we may be able to simplify the conditional. First
2171 merge the ranges in the same manner as range merging above. */
2172 low = tree_int_cst_compare (low, cond_low) == 1 ? low : cond_low;
2173 high = tree_int_cst_compare (high, cond_high) == -1 ? high : cond_high;
2175 /* If the range has converged to a single point, then turn this
2176 into an equality comparison. */
2177 if (TREE_CODE (cond) != EQ_EXPR
2178 && TREE_CODE (cond) != NE_EXPR
2179 && tree_int_cst_equal (low, high))
2181 TREE_SET_CODE (cond, EQ_EXPR);
2182 TREE_OPERAND (cond, 1) = high;
2189 /* STMT is a SWITCH_EXPR for which we could not trivially determine its
2190 result. This routine attempts to find equivalent forms of the
2191 condition which we may be able to optimize better. */
2194 simplify_switch_and_lookup_avail_expr (tree stmt,
2195 varray_type *block_avail_exprs_p,
2198 tree cond = SWITCH_COND (stmt);
2201 /* The optimization that we really care about is removing unnecessary
2202 casts. That will let us do much better in propagating the inferred
2203 constant at the switch target. */
2204 if (TREE_CODE (cond) == SSA_NAME)
2206 def = SSA_NAME_DEF_STMT (cond);
2207 if (TREE_CODE (def) == MODIFY_EXPR)
2209 def = TREE_OPERAND (def, 1);
2210 if (TREE_CODE (def) == NOP_EXPR)
2215 def = TREE_OPERAND (def, 0);
2217 #ifdef ENABLE_CHECKING
2218 /* ??? Why was Jeff testing this? We are gimple... */
2219 if (!is_gimple_val (def))
2223 to = TREE_TYPE (cond);
2224 ti = TREE_TYPE (def);
2226 /* If we have an extension that preserves value, then we
2227 can copy the source value into the switch. */
2229 need_precision = TYPE_PRECISION (ti);
2231 if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
2233 else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
2234 need_precision += 1;
2235 if (TYPE_PRECISION (to) < need_precision)
2240 SWITCH_COND (stmt) = def;
2243 return lookup_avail_expr (stmt, block_avail_exprs_p, insert);
2253 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2254 known value for that SSA_NAME (or NULL if no value is known).
2256 NONZERO_VARS is the set SSA_NAMES known to have a nonzero value,
2257 even if we don't know their precise value.
2259 Propagate values from CONST_AND_COPIES and NONZERO_VARS into the PHI
2260 nodes of the successors of BB. */
2263 cprop_into_successor_phis (basic_block bb,
2264 varray_type const_and_copies,
2265 bitmap nonzero_vars)
2269 /* This can get rather expensive if the implementation is naive in
2270 how it finds the phi alternative associated with a particular edge. */
2271 for (e = bb->succ; e; e = e->succ_next)
2277 /* If this is an abnormal edge, then we do not want to copy propagate
2278 into the PHI alternative associated with this edge. */
2279 if (e->flags & EDGE_ABNORMAL)
2282 phi = phi_nodes (e->dest);
2286 /* There is no guarantee that for any two PHI nodes in a block that
2287 the phi alternative associated with a particular edge will be
2288 at the same index in the phi alternative array.
2290 However, it is very likely they will be the same. So we keep
2291 track of the index of the alternative where we found the edge in
2292 the previous phi node and check that index first in the next
2293 phi node. If that hint fails, then we actually search all
2295 phi_num_args = PHI_NUM_ARGS (phi);
2296 hint = phi_num_args;
2297 for ( ; phi; phi = PHI_CHAIN (phi))
2301 use_operand_p orig_p;
2304 /* If the hint is valid (!= phi_num_args), see if it points
2305 us to the desired phi alternative. */
2306 if (hint != phi_num_args && PHI_ARG_EDGE (phi, hint) == e)
2310 /* The hint was either invalid or did not point to the
2311 correct phi alternative. Search all the alternatives
2312 for the correct one. Update the hint. */
2313 for (i = 0; i < phi_num_args; i++)
2314 if (PHI_ARG_EDGE (phi, i) == e)
2319 #ifdef ENABLE_CHECKING
2320 /* If we did not find the proper alternative, then something is
2322 if (hint == phi_num_args)
2326 /* The alternative may be associated with a constant, so verify
2327 it is an SSA_NAME before doing anything with it. */
2328 orig_p = PHI_ARG_DEF_PTR (phi, hint);
2329 orig = USE_FROM_PTR (orig_p);
2330 if (TREE_CODE (orig) != SSA_NAME)
2333 /* If the alternative is known to have a nonzero value, record
2334 that fact in the PHI node itself for future use. */
2335 if (bitmap_bit_p (nonzero_vars, SSA_NAME_VERSION (orig)))
2336 PHI_ARG_NONZERO (phi, hint) = true;
2338 /* If we have *ORIG_P in our constant/copy table, then replace
2339 ORIG_P with its value in our constant/copy table. */
2340 new = VARRAY_TREE (const_and_copies, SSA_NAME_VERSION (orig));
2342 && (TREE_CODE (new) == SSA_NAME
2343 || is_gimple_min_invariant (new))
2344 && may_propagate_copy (orig, new))
2346 propagate_value (orig_p, new);
2353 /* Propagate known constants/copies into PHI nodes of BB's successor
2357 cprop_into_phis (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
2360 cprop_into_successor_phis (bb, const_and_copies, nonzero_vars);
2363 /* Search for redundant computations in STMT. If any are found, then
2364 replace them with the variable holding the result of the computation.
2366 If safe, record this expression into the available expression hash
2370 eliminate_redundant_computations (struct dom_walk_data *walk_data,
2371 tree stmt, stmt_ann_t ann)
2373 v_may_def_optype v_may_defs = V_MAY_DEF_OPS (ann);
2374 tree *expr_p, def = NULL_TREE;
2377 bool retval = false;
2378 struct dom_walk_block_data *bd
2379 = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
2381 if (TREE_CODE (stmt) == MODIFY_EXPR)
2382 def = TREE_OPERAND (stmt, 0);
2384 /* Certain expressions on the RHS can be optimized away, but can not
2385 themselves be entered into the hash tables. */
2386 if (ann->makes_aliased_stores
2388 || TREE_CODE (def) != SSA_NAME
2389 || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def)
2390 || NUM_V_MAY_DEFS (v_may_defs) != 0)
2393 /* Check if the expression has been computed before. */
2394 cached_lhs = lookup_avail_expr (stmt, &bd->avail_exprs, insert);
2396 /* If this is an assignment and the RHS was not in the hash table,
2397 then try to simplify the RHS and lookup the new RHS in the
2399 if (! cached_lhs && TREE_CODE (stmt) == MODIFY_EXPR)
2400 cached_lhs = simplify_rhs_and_lookup_avail_expr (walk_data,
2403 /* Similarly if this is a COND_EXPR and we did not find its
2404 expression in the hash table, simplify the condition and
2406 else if (! cached_lhs && TREE_CODE (stmt) == COND_EXPR)
2407 cached_lhs = simplify_cond_and_lookup_avail_expr (stmt,
2411 /* Similarly for a SWITCH_EXPR. */
2412 else if (!cached_lhs && TREE_CODE (stmt) == SWITCH_EXPR)
2413 cached_lhs = simplify_switch_and_lookup_avail_expr (stmt,
2417 opt_stats.num_exprs_considered++;
2419 /* Get a pointer to the expression we are trying to optimize. */
2420 if (TREE_CODE (stmt) == COND_EXPR)
2421 expr_p = &COND_EXPR_COND (stmt);
2422 else if (TREE_CODE (stmt) == SWITCH_EXPR)
2423 expr_p = &SWITCH_COND (stmt);
2424 else if (TREE_CODE (stmt) == RETURN_EXPR && TREE_OPERAND (stmt, 0))
2425 expr_p = &TREE_OPERAND (TREE_OPERAND (stmt, 0), 1);
2427 expr_p = &TREE_OPERAND (stmt, 1);
2429 /* It is safe to ignore types here since we have already done
2430 type checking in the hashing and equality routines. In fact
2431 type checking here merely gets in the way of constant
2432 propagation. Also, make sure that it is safe to propagate
2433 CACHED_LHS into *EXPR_P. */
2435 && (TREE_CODE (cached_lhs) != SSA_NAME
2436 || may_propagate_copy (*expr_p, cached_lhs)))
2438 if (dump_file && (dump_flags & TDF_DETAILS))
2440 fprintf (dump_file, " Replaced redundant expr '");
2441 print_generic_expr (dump_file, *expr_p, dump_flags);
2442 fprintf (dump_file, "' with '");
2443 print_generic_expr (dump_file, cached_lhs, dump_flags);
2444 fprintf (dump_file, "'\n");
2449 #if defined ENABLE_CHECKING
2450 if (TREE_CODE (cached_lhs) != SSA_NAME
2451 && !is_gimple_min_invariant (cached_lhs))
2455 if (TREE_CODE (cached_lhs) == ADDR_EXPR
2456 || (POINTER_TYPE_P (TREE_TYPE (*expr_p))
2457 && is_gimple_min_invariant (cached_lhs)))
2460 propagate_tree_value (expr_p, cached_lhs);
2466 /* STMT, a MODIFY_EXPR, may create certain equivalences, in either
2467 the available expressions table or the const_and_copies table.
2468 Detect and record those equivalences. */
2471 record_equivalences_from_stmt (tree stmt,
2472 varray_type *block_avail_exprs_p,
2473 varray_type *block_nonzero_vars_p,
2477 tree lhs = TREE_OPERAND (stmt, 0);
2478 enum tree_code lhs_code = TREE_CODE (lhs);
2481 if (lhs_code == SSA_NAME)
2483 tree rhs = TREE_OPERAND (stmt, 1);
2485 /* Strip away any useless type conversions. */
2486 STRIP_USELESS_TYPE_CONVERSION (rhs);
2488 /* If the RHS of the assignment is a constant or another variable that
2489 may be propagated, register it in the CONST_AND_COPIES table. We
2490 do not need to record unwind data for this, since this is a true
2491 assignment and not an equivalence inferred from a comparison. All
2492 uses of this ssa name are dominated by this assignment, so unwinding
2493 just costs time and space. */
2495 && (TREE_CODE (rhs) == SSA_NAME
2496 || is_gimple_min_invariant (rhs)))
2497 set_value_for (lhs, rhs, const_and_copies);
2499 /* alloca never returns zero and the address of a non-weak symbol
2500 is never zero. NOP_EXPRs and CONVERT_EXPRs can be completely
2501 stripped as they do not affect this equivalence. */
2502 while (TREE_CODE (rhs) == NOP_EXPR
2503 || TREE_CODE (rhs) == CONVERT_EXPR)
2504 rhs = TREE_OPERAND (rhs, 0);
2506 if (alloca_call_p (rhs)
2507 || (TREE_CODE (rhs) == ADDR_EXPR
2508 && DECL_P (TREE_OPERAND (rhs, 0))
2509 && ! DECL_WEAK (TREE_OPERAND (rhs, 0))))
2510 record_var_is_nonzero (lhs, block_nonzero_vars_p);
2512 /* IOR of any value with a nonzero value will result in a nonzero
2513 value. Even if we do not know the exact result recording that
2514 the result is nonzero is worth the effort. */
2515 if (TREE_CODE (rhs) == BIT_IOR_EXPR
2516 && integer_nonzerop (TREE_OPERAND (rhs, 1)))
2517 record_var_is_nonzero (lhs, block_nonzero_vars_p);
2520 /* Look at both sides for pointer dereferences. If we find one, then
2521 the pointer must be nonnull and we can enter that equivalence into
2523 if (flag_delete_null_pointer_checks)
2524 for (i = 0; i < 2; i++)
2526 tree t = TREE_OPERAND (stmt, i);
2528 /* Strip away any COMPONENT_REFs. */
2529 while (TREE_CODE (t) == COMPONENT_REF)
2530 t = TREE_OPERAND (t, 0);
2532 /* Now see if this is a pointer dereference. */
2533 if (TREE_CODE (t) == INDIRECT_REF)
2535 tree op = TREE_OPERAND (t, 0);
2537 /* If the pointer is a SSA variable, then enter new
2538 equivalences into the hash table. */
2539 while (TREE_CODE (op) == SSA_NAME)
2541 tree def = SSA_NAME_DEF_STMT (op);
2543 record_var_is_nonzero (op, block_nonzero_vars_p);
2545 /* And walk up the USE-DEF chains noting other SSA_NAMEs
2546 which are known to have a nonzero value. */
2548 && TREE_CODE (def) == MODIFY_EXPR
2549 && TREE_CODE (TREE_OPERAND (def, 1)) == NOP_EXPR)
2550 op = TREE_OPERAND (TREE_OPERAND (def, 1), 0);
2557 /* A memory store, even an aliased store, creates a useful
2558 equivalence. By exchanging the LHS and RHS, creating suitable
2559 vops and recording the result in the available expression table,
2560 we may be able to expose more redundant loads. */
2561 if (!ann->has_volatile_ops
2562 && (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME
2563 || is_gimple_min_invariant (TREE_OPERAND (stmt, 1)))
2564 && !is_gimple_reg (lhs))
2566 tree rhs = TREE_OPERAND (stmt, 1);
2569 /* FIXME: If the LHS of the assignment is a bitfield and the RHS
2570 is a constant, we need to adjust the constant to fit into the
2571 type of the LHS. If the LHS is a bitfield and the RHS is not
2572 a constant, then we can not record any equivalences for this
2573 statement since we would need to represent the widening or
2574 narrowing of RHS. This fixes gcc.c-torture/execute/921016-1.c
2575 and should not be necessary if GCC represented bitfields
2577 if (lhs_code == COMPONENT_REF
2578 && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1)))
2580 if (TREE_CONSTANT (rhs))
2581 rhs = widen_bitfield (rhs, TREE_OPERAND (lhs, 1), lhs);
2585 /* If the value overflowed, then we can not use this equivalence. */
2586 if (rhs && ! is_gimple_min_invariant (rhs))
2592 /* Build a new statement with the RHS and LHS exchanged. */
2593 new = build (MODIFY_EXPR, TREE_TYPE (stmt), rhs, lhs);
2595 create_ssa_artficial_load_stmt (&(ann->operands), new);
2597 /* Finally enter the statement into the available expression
2599 lookup_avail_expr (new, block_avail_exprs_p, true);
2604 /* Replace *OP_P in STMT with any known equivalent value for *OP_P from
2605 CONST_AND_COPIES. */
2608 cprop_operand (tree stmt, use_operand_p op_p, varray_type const_and_copies)
2610 bool may_have_exposed_new_symbols = false;
2612 tree op = USE_FROM_PTR (op_p);
2614 /* If the operand has a known constant value or it is known to be a
2615 copy of some other variable, use the value or copy stored in
2616 CONST_AND_COPIES. */
2617 val = VARRAY_TREE (const_and_copies, SSA_NAME_VERSION (op));
2620 tree op_type, val_type;
2622 /* Do not change the base variable in the virtual operand
2623 tables. That would make it impossible to reconstruct
2624 the renamed virtual operand if we later modify this
2625 statement. Also only allow the new value to be an SSA_NAME
2626 for propagation into virtual operands. */
2627 if (!is_gimple_reg (op)
2628 && (get_virtual_var (val) != get_virtual_var (op)
2629 || TREE_CODE (val) != SSA_NAME))
2632 /* Get the toplevel type of each operand. */
2633 op_type = TREE_TYPE (op);
2634 val_type = TREE_TYPE (val);
2636 /* While both types are pointers, get the type of the object
2638 while (POINTER_TYPE_P (op_type) && POINTER_TYPE_P (val_type))
2640 op_type = TREE_TYPE (op_type);
2641 val_type = TREE_TYPE (val_type);
2644 /* Make sure underlying types match before propagating a constant by
2645 converting the constant to the proper type. Note that convert may
2646 return a non-gimple expression, in which case we ignore this
2647 propagation opportunity. */
2648 if (TREE_CODE (val) != SSA_NAME)
2650 if (!lang_hooks.types_compatible_p (op_type, val_type))
2652 val = fold_convert (TREE_TYPE (op), val);
2653 if (!is_gimple_min_invariant (val))
2658 /* Certain operands are not allowed to be copy propagated due
2659 to their interaction with exception handling and some GCC
2661 else if (!may_propagate_copy (op, val))
2665 if (dump_file && (dump_flags & TDF_DETAILS))
2667 fprintf (dump_file, " Replaced '");
2668 print_generic_expr (dump_file, op, dump_flags);
2669 fprintf (dump_file, "' with %s '",
2670 (TREE_CODE (val) != SSA_NAME ? "constant" : "variable"));
2671 print_generic_expr (dump_file, val, dump_flags);
2672 fprintf (dump_file, "'\n");
2675 /* If VAL is an ADDR_EXPR or a constant of pointer type, note
2676 that we may have exposed a new symbol for SSA renaming. */
2677 if (TREE_CODE (val) == ADDR_EXPR
2678 || (POINTER_TYPE_P (TREE_TYPE (op))
2679 && is_gimple_min_invariant (val)))
2680 may_have_exposed_new_symbols = true;
2682 propagate_value (op_p, val);
2684 /* And note that we modified this statement. This is now
2685 safe, even if we changed virtual operands since we will
2686 rescan the statement and rewrite its operands again. */
2689 return may_have_exposed_new_symbols;
2692 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2693 known value for that SSA_NAME (or NULL if no value is known).
2695 Propagate values from CONST_AND_COPIES into the uses, vuses and
2696 v_may_def_ops of STMT. */
2699 cprop_into_stmt (tree stmt, varray_type const_and_copies)
2701 bool may_have_exposed_new_symbols = false;
2705 FOR_EACH_SSA_USE_OPERAND (op_p, stmt, iter, SSA_OP_ALL_USES)
2707 if (TREE_CODE (USE_FROM_PTR (op_p)) == SSA_NAME)
2708 may_have_exposed_new_symbols
2709 |= cprop_operand (stmt, op_p, const_and_copies);
2712 return may_have_exposed_new_symbols;
2716 /* Optimize the statement pointed by iterator SI.
2718 We try to perform some simplistic global redundancy elimination and
2719 constant propagation:
2721 1- To detect global redundancy, we keep track of expressions that have
2722 been computed in this block and its dominators. If we find that the
2723 same expression is computed more than once, we eliminate repeated
2724 computations by using the target of the first one.
2726 2- Constant values and copy assignments. This is used to do very
2727 simplistic constant and copy propagation. When a constant or copy
2728 assignment is found, we map the value on the RHS of the assignment to
2729 the variable in the LHS in the CONST_AND_COPIES table. */
2732 optimize_stmt (struct dom_walk_data *walk_data, basic_block bb,
2733 block_stmt_iterator si)
2737 bool may_optimize_p;
2738 bool may_have_exposed_new_symbols = false;
2739 struct dom_walk_block_data *bd
2740 = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
2742 stmt = bsi_stmt (si);
2744 get_stmt_operands (stmt);
2745 ann = stmt_ann (stmt);
2746 opt_stats.num_stmts++;
2747 may_have_exposed_new_symbols = false;
2749 if (dump_file && (dump_flags & TDF_DETAILS))
2751 fprintf (dump_file, "Optimizing statement ");
2752 print_generic_stmt (dump_file, stmt, TDF_SLIM);
2755 /* Const/copy propagate into USES, VUSES and the RHS of V_MAY_DEFs. */
2756 may_have_exposed_new_symbols = cprop_into_stmt (stmt, const_and_copies);
2758 /* If the statement has been modified with constant replacements,
2759 fold its RHS before checking for redundant computations. */
2762 /* Try to fold the statement making sure that STMT is kept
2764 if (fold_stmt (bsi_stmt_ptr (si)))
2766 stmt = bsi_stmt (si);
2767 ann = stmt_ann (stmt);
2769 if (dump_file && (dump_flags & TDF_DETAILS))
2771 fprintf (dump_file, " Folded to: ");
2772 print_generic_stmt (dump_file, stmt, TDF_SLIM);
2776 /* Constant/copy propagation above may change the set of
2777 virtual operands associated with this statement. Folding
2778 may remove the need for some virtual operands.
2780 Indicate we will need to rescan and rewrite the statement. */
2781 may_have_exposed_new_symbols = true;
2784 /* Check for redundant computations. Do this optimization only
2785 for assignments that have no volatile ops and conditionals. */
2786 may_optimize_p = (!ann->has_volatile_ops
2787 && ((TREE_CODE (stmt) == RETURN_EXPR
2788 && TREE_OPERAND (stmt, 0)
2789 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR
2790 && ! (TREE_SIDE_EFFECTS
2791 (TREE_OPERAND (TREE_OPERAND (stmt, 0), 1))))
2792 || (TREE_CODE (stmt) == MODIFY_EXPR
2793 && ! TREE_SIDE_EFFECTS (TREE_OPERAND (stmt, 1)))
2794 || TREE_CODE (stmt) == COND_EXPR
2795 || TREE_CODE (stmt) == SWITCH_EXPR));
2798 may_have_exposed_new_symbols
2799 |= eliminate_redundant_computations (walk_data, stmt, ann);
2801 /* Record any additional equivalences created by this statement. */
2802 if (TREE_CODE (stmt) == MODIFY_EXPR)
2803 record_equivalences_from_stmt (stmt,
2809 register_definitions_for_stmt (stmt, &bd->block_defs);
2811 /* If STMT is a COND_EXPR and it was modified, then we may know
2812 where it goes. If that is the case, then mark the CFG as altered.
2814 This will cause us to later call remove_unreachable_blocks and
2815 cleanup_tree_cfg when it is safe to do so. It is not safe to
2816 clean things up here since removal of edges and such can trigger
2817 the removal of PHI nodes, which in turn can release SSA_NAMEs to
2820 That's all fine and good, except that once SSA_NAMEs are released
2821 to the manager, we must not call create_ssa_name until all references
2822 to released SSA_NAMEs have been eliminated.
2824 All references to the deleted SSA_NAMEs can not be eliminated until
2825 we remove unreachable blocks.
2827 We can not remove unreachable blocks until after we have completed
2828 any queued jump threading.
2830 We can not complete any queued jump threads until we have taken
2831 appropriate variables out of SSA form. Taking variables out of
2832 SSA form can call create_ssa_name and thus we lose.
2834 Ultimately I suspect we're going to need to change the interface
2835 into the SSA_NAME manager. */
2841 if (TREE_CODE (stmt) == COND_EXPR)
2842 val = COND_EXPR_COND (stmt);
2843 else if (TREE_CODE (stmt) == SWITCH_EXPR)
2844 val = SWITCH_COND (stmt);
2846 if (val && TREE_CODE (val) == INTEGER_CST && find_taken_edge (bb, val))
2849 /* If we simplified a statement in such a way as to be shown that it
2850 cannot trap, update the eh information and the cfg to match. */
2851 if (maybe_clean_eh_stmt (stmt))
2853 bitmap_set_bit (need_eh_cleanup, bb->index);
2854 if (dump_file && (dump_flags & TDF_DETAILS))
2855 fprintf (dump_file, " Flagged to clear EH edges.\n");
2859 if (may_have_exposed_new_symbols)
2861 if (! bd->stmts_to_rescan)
2862 VARRAY_TREE_INIT (bd->stmts_to_rescan, 20, "stmts_to_rescan");
2863 VARRAY_PUSH_TREE (bd->stmts_to_rescan, bsi_stmt (si));
2867 /* Replace the RHS of STMT with NEW_RHS. If RHS can be found in the
2868 available expression hashtable, then return the LHS from the hash
2871 If INSERT is true, then we also update the available expression
2872 hash table to account for the changes made to STMT. */
2875 update_rhs_and_lookup_avail_expr (tree stmt, tree new_rhs,
2876 varray_type *block_avail_exprs_p,
2879 tree cached_lhs = NULL;
2881 /* Remove the old entry from the hash table. */
2884 struct expr_hash_elt element;
2886 initialize_hash_element (stmt, NULL, &element);
2887 htab_remove_elt_with_hash (avail_exprs, &element, element.hash);
2890 /* Now update the RHS of the assignment. */
2891 TREE_OPERAND (stmt, 1) = new_rhs;
2893 /* Now lookup the updated statement in the hash table. */
2894 cached_lhs = lookup_avail_expr (stmt, block_avail_exprs_p, insert);
2896 /* We have now called lookup_avail_expr twice with two different
2897 versions of this same statement, once in optimize_stmt, once here.
2899 We know the call in optimize_stmt did not find an existing entry
2900 in the hash table, so a new entry was created. At the same time
2901 this statement was pushed onto the BLOCK_AVAIL_EXPRS varray.
2903 If this call failed to find an existing entry on the hash table,
2904 then the new version of this statement was entered into the
2905 hash table. And this statement was pushed onto BLOCK_AVAIL_EXPR
2906 for the second time. So there are two copies on BLOCK_AVAIL_EXPRs
2908 If this call succeeded, we still have one copy of this statement
2909 on the BLOCK_AVAIL_EXPRs varray.
2911 For both cases, we need to pop the most recent entry off the
2912 BLOCK_AVAIL_EXPRs varray. For the case where we never found this
2913 statement in the hash tables, that will leave precisely one
2914 copy of this statement on BLOCK_AVAIL_EXPRs. For the case where
2915 we found a copy of this statement in the second hash table lookup
2916 we want _no_ copies of this statement in BLOCK_AVAIL_EXPRs. */
2918 VARRAY_POP (*block_avail_exprs_p);
2920 /* And make sure we record the fact that we modified this
2927 /* Search for an existing instance of STMT in the AVAIL_EXPRS table. If
2928 found, return its LHS. Otherwise insert STMT in the table and return
2931 Also, when an expression is first inserted in the AVAIL_EXPRS table, it
2932 is also added to the stack pointed by BLOCK_AVAIL_EXPRS_P, so that they
2933 can be removed when we finish processing this block and its children.
2935 NOTE: This function assumes that STMT is a MODIFY_EXPR node that
2936 contains no CALL_EXPR on its RHS and makes no volatile nor
2937 aliased references. */
2940 lookup_avail_expr (tree stmt, varray_type *block_avail_exprs_p, bool insert)
2945 struct expr_hash_elt *element = xcalloc (sizeof (struct expr_hash_elt), 1);
2947 lhs = TREE_CODE (stmt) == MODIFY_EXPR ? TREE_OPERAND (stmt, 0) : NULL;
2949 initialize_hash_element (stmt, lhs, element);
2951 /* Don't bother remembering constant assignments and copy operations.
2952 Constants and copy operations are handled by the constant/copy propagator
2953 in optimize_stmt. */
2954 if (TREE_CODE (element->rhs) == SSA_NAME
2955 || is_gimple_min_invariant (element->rhs))
2961 /* If this is an equality test against zero, see if we have recorded a
2962 nonzero value for the variable in question. */
2963 if ((TREE_CODE (element->rhs) == EQ_EXPR
2964 || TREE_CODE (element->rhs) == NE_EXPR)
2965 && TREE_CODE (TREE_OPERAND (element->rhs, 0)) == SSA_NAME
2966 && integer_zerop (TREE_OPERAND (element->rhs, 1)))
2968 int indx = SSA_NAME_VERSION (TREE_OPERAND (element->rhs, 0));
2970 if (bitmap_bit_p (nonzero_vars, indx))
2972 tree t = element->rhs;
2975 if (TREE_CODE (t) == EQ_EXPR)
2976 return boolean_false_node;
2978 return boolean_true_node;
2982 /* Finally try to find the expression in the main expression hash table. */
2983 slot = htab_find_slot_with_hash (avail_exprs, element, element->hash,
2984 (insert ? INSERT : NO_INSERT));
2993 *slot = (void *) element;
2994 if (! *block_avail_exprs_p)
2995 VARRAY_TREE_INIT (*block_avail_exprs_p, 20, "block_avail_exprs");
2996 VARRAY_PUSH_TREE (*block_avail_exprs_p, stmt ? stmt : element->rhs);
3000 /* Extract the LHS of the assignment so that it can be used as the current
3001 definition of another variable. */
3002 lhs = ((struct expr_hash_elt *)*slot)->lhs;
3004 /* See if the LHS appears in the CONST_AND_COPIES table. If it does, then
3005 use the value from the const_and_copies table. */
3006 if (TREE_CODE (lhs) == SSA_NAME)
3008 temp = get_value_for (lhs, const_and_copies);
3017 /* Given a condition COND, record into HI_P, LO_P and INVERTED_P the
3018 range of values that result in the conditional having a true value.
3020 Return true if we are successful in extracting a range from COND and
3021 false if we are unsuccessful. */
3024 extract_range_from_cond (tree cond, tree *hi_p, tree *lo_p, int *inverted_p)
3026 tree op1 = TREE_OPERAND (cond, 1);
3027 tree high, low, type;
3030 /* Experiments have shown that it's rarely, if ever useful to
3031 record ranges for enumerations. Presumably this is due to
3032 the fact that they're rarely used directly. They are typically
3033 cast into an integer type and used that way. */
3034 if (TREE_CODE (TREE_TYPE (op1)) != INTEGER_TYPE)
3037 type = TREE_TYPE (op1);
3039 switch (TREE_CODE (cond))
3053 high = TYPE_MAX_VALUE (type);
3058 low = int_const_binop (PLUS_EXPR, op1, integer_one_node, 1);
3059 high = TYPE_MAX_VALUE (type);
3065 low = TYPE_MIN_VALUE (type);
3070 high = int_const_binop (MINUS_EXPR, op1, integer_one_node, 1);
3071 low = TYPE_MIN_VALUE (type);
3081 *inverted_p = inverted;
3085 /* Record a range created by COND for basic block BB. */
3088 record_range (tree cond, basic_block bb, varray_type *vrp_variables_p)
3090 /* We explicitly ignore NE_EXPRs. They rarely allow for meaningful
3091 range optimizations and significantly complicate the implementation. */
3092 if (TREE_CODE_CLASS (TREE_CODE (cond)) == '<'
3093 && TREE_CODE (cond) != NE_EXPR
3094 && TREE_CODE (TREE_TYPE (TREE_OPERAND (cond, 1))) == INTEGER_TYPE)
3096 struct vrp_element *element = ggc_alloc (sizeof (struct vrp_element));
3097 int ssa_version = SSA_NAME_VERSION (TREE_OPERAND (cond, 0));
3099 varray_type *vrp_records_p
3100 = (varray_type *)&VARRAY_GENERIC_PTR (vrp_data, ssa_version);
3102 element->low = NULL;
3103 element->high = NULL;
3104 element->cond = cond;
3107 if (*vrp_records_p == NULL)
3109 VARRAY_GENERIC_PTR_INIT (*vrp_records_p, 2, "vrp records");
3110 VARRAY_GENERIC_PTR (vrp_data, ssa_version) = *vrp_records_p;
3113 VARRAY_PUSH_GENERIC_PTR (*vrp_records_p, element);
3114 if (! *vrp_variables_p)
3115 VARRAY_TREE_INIT (*vrp_variables_p, 2, "vrp_variables");
3116 VARRAY_PUSH_TREE (*vrp_variables_p, TREE_OPERAND (cond, 0));
3120 /* Given a conditional statement IF_STMT, return the assignment 'X = Y'
3121 known to be true depending on which arm of IF_STMT is taken.
3123 Not all conditional statements will result in a useful assignment.
3124 Return NULL_TREE in that case.
3126 Also enter into the available expression table statements of
3133 This allows us to lookup the condition in a dominated block and
3134 get back a constant indicating if the condition is true. */
3136 static struct eq_expr_value
3137 get_eq_expr_value (tree if_stmt,
3139 varray_type *block_avail_exprs_p,
3141 varray_type *vrp_variables_p)
3144 struct eq_expr_value retval;
3146 cond = COND_EXPR_COND (if_stmt);
3150 /* If the conditional is a single variable 'X', return 'X = 1' for
3151 the true arm and 'X = 0' on the false arm. */
3152 if (TREE_CODE (cond) == SSA_NAME)
3155 retval.src = constant_boolean_node (true_arm, TREE_TYPE (cond));
3159 /* If we have a comparison expression, then record its result into
3160 the available expression table. */
3161 if (TREE_CODE_CLASS (TREE_CODE (cond)) == '<')
3163 tree op0 = TREE_OPERAND (cond, 0);
3164 tree op1 = TREE_OPERAND (cond, 1);
3166 /* Special case comparing booleans against a constant as we know
3167 the value of OP0 on both arms of the branch. ie, we can record
3168 an equivalence for OP0 rather than COND. */
3169 if ((TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
3170 && TREE_CODE (op0) == SSA_NAME
3171 && TREE_CODE (TREE_TYPE (op0)) == BOOLEAN_TYPE
3172 && is_gimple_min_invariant (op1))
3174 if ((TREE_CODE (cond) == EQ_EXPR && true_arm)
3175 || (TREE_CODE (cond) == NE_EXPR && ! true_arm))
3181 if (integer_zerop (op1))
3182 retval.src = boolean_true_node;
3184 retval.src = boolean_false_node;
3190 if (TREE_CODE (op0) == SSA_NAME
3191 && (is_gimple_min_invariant (op1) || TREE_CODE (op1) == SSA_NAME))
3193 tree inverted = invert_truthvalue (cond);
3195 /* When we find an available expression in the hash table, we replace
3196 the expression with the LHS of the statement in the hash table.
3198 So, we want to build statements such as "1 = <condition>" on the
3199 true arm and "0 = <condition>" on the false arm. That way if we
3200 find the expression in the table, we will replace it with its
3201 known constant value. Also insert inversions of the result and
3202 condition into the hash table. */
3205 record_cond (cond, boolean_true_node, block_avail_exprs_p);
3206 record_dominating_conditions (cond, block_avail_exprs_p);
3207 record_cond (inverted, boolean_false_node, block_avail_exprs_p);
3209 if (TREE_CONSTANT (op1))
3210 record_range (cond, bb, vrp_variables_p);
3212 /* If the conditional is of the form 'X == Y', return 'X = Y'
3213 for the true arm. */
3214 if (TREE_CODE (cond) == EQ_EXPR)
3224 record_cond (inverted, boolean_true_node, block_avail_exprs_p);
3225 record_dominating_conditions (inverted, block_avail_exprs_p);
3226 record_cond (cond, boolean_false_node, block_avail_exprs_p);
3228 if (TREE_CONSTANT (op1))
3229 record_range (inverted, bb, vrp_variables_p);
3231 /* If the conditional is of the form 'X != Y', return 'X = Y'
3232 for the false arm. */
3233 if (TREE_CODE (cond) == NE_EXPR)
3246 /* Hashing and equality functions for AVAIL_EXPRS. The table stores
3247 MODIFY_EXPR statements. We compute a value number for expressions using
3248 the code of the expression and the SSA numbers of its operands. */
3251 avail_expr_hash (const void *p)
3253 stmt_ann_t ann = ((struct expr_hash_elt *)p)->ann;
3254 tree rhs = ((struct expr_hash_elt *)p)->rhs;
3259 /* iterative_hash_expr knows how to deal with any expression and
3260 deals with commutative operators as well, so just use it instead
3261 of duplicating such complexities here. */
3262 val = iterative_hash_expr (rhs, val);
3264 /* If the hash table entry is not associated with a statement, then we
3265 can just hash the expression and not worry about virtual operands
3270 /* Add the SSA version numbers of every vuse operand. This is important
3271 because compound variables like arrays are not renamed in the
3272 operands. Rather, the rename is done on the virtual variable
3273 representing all the elements of the array. */
3274 vuses = VUSE_OPS (ann);
3275 for (i = 0; i < NUM_VUSES (vuses); i++)
3276 val = iterative_hash_expr (VUSE_OP (vuses, i), val);
3282 real_avail_expr_hash (const void *p)
3284 return ((const struct expr_hash_elt *)p)->hash;
3288 avail_expr_eq (const void *p1, const void *p2)
3290 stmt_ann_t ann1 = ((struct expr_hash_elt *)p1)->ann;
3291 tree rhs1 = ((struct expr_hash_elt *)p1)->rhs;
3292 stmt_ann_t ann2 = ((struct expr_hash_elt *)p2)->ann;
3293 tree rhs2 = ((struct expr_hash_elt *)p2)->rhs;
3295 /* If they are the same physical expression, return true. */
3296 if (rhs1 == rhs2 && ann1 == ann2)
3299 /* If their codes are not equal, then quit now. */
3300 if (TREE_CODE (rhs1) != TREE_CODE (rhs2))
3303 /* In case of a collision, both RHS have to be identical and have the
3304 same VUSE operands. */
3305 if ((TREE_TYPE (rhs1) == TREE_TYPE (rhs2)
3306 || lang_hooks.types_compatible_p (TREE_TYPE (rhs1), TREE_TYPE (rhs2)))
3307 && operand_equal_p (rhs1, rhs2, OEP_PURE_SAME))
3309 vuse_optype ops1 = NULL;
3310 vuse_optype ops2 = NULL;
3311 size_t num_ops1 = 0;
3312 size_t num_ops2 = 0;
3317 ops1 = VUSE_OPS (ann1);
3318 num_ops1 = NUM_VUSES (ops1);
3323 ops2 = VUSE_OPS (ann2);
3324 num_ops2 = NUM_VUSES (ops2);
3327 /* If the number of virtual uses is different, then we consider
3329 if (num_ops1 != num_ops2)
3332 for (i = 0; i < num_ops1; i++)
3333 if (VUSE_OP (ops1, i) != VUSE_OP (ops2, i))
3336 #ifdef ENABLE_CHECKING
3337 if (((struct expr_hash_elt *)p1)->hash
3338 != ((struct expr_hash_elt *)p2)->hash)
3347 /* Given STMT and a pointer to the block local definitions BLOCK_DEFS_P,
3348 register register all objects set by this statement into BLOCK_DEFS_P
3352 register_definitions_for_stmt (tree stmt, varray_type *block_defs_p)
3357 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
3360 /* FIXME: We shouldn't be registering new defs if the variable
3361 doesn't need to be renamed. */
3362 register_new_def (def, block_defs_p);