1 /* SSA Dominator optimizations for trees
2 Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
3 Contributed by Diego Novillo <dnovillo@redhat.com>
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
24 #include "coretypes.h"
31 #include "basic-block.h"
36 #include "diagnostic.h"
38 #include "tree-dump.h"
39 #include "tree-flow.h"
42 #include "tree-pass.h"
43 #include "tree-ssa-propagate.h"
44 #include "langhooks.h"
46 /* This file implements optimizations on the dominator tree. */
49 /* Structure for recording edge equivalences as well as any pending
50 edge redirections during the dominator optimizer.
52 Computing and storing the edge equivalences instead of creating
53 them on-demand can save significant amounts of time, particularly
54 for pathological cases involving switch statements.
56 These structures live for a single iteration of the dominator
57 optimizer in the edge's AUX field. At the end of an iteration we
58 free each of these structures and update the AUX field to point
59 to any requested redirection target (the code for updating the
60 CFG and SSA graph for edge redirection expects redirection edge
61 targets to be in the AUX field for each edge. */
65 /* If this edge creates a simple equivalence, the LHS and RHS of
66 the equivalence will be stored here. */
70 /* Traversing an edge may also indicate one or more particular conditions
71 are true or false. The number of recorded conditions can vary, but
72 can be determined by the condition's code. So we have an array
73 and its maximum index rather than use a varray. */
74 tree
*cond_equivalences
;
75 unsigned int max_cond_equivalences
;
77 /* If we can thread this edge this field records the new target. */
78 edge redirection_target
;
82 /* Hash table with expressions made available during the renaming process.
83 When an assignment of the form X_i = EXPR is found, the statement is
84 stored in this table. If the same expression EXPR is later found on the
85 RHS of another statement, it is replaced with X_i (thus performing
86 global redundancy elimination). Similarly as we pass through conditionals
87 we record the conditional itself as having either a true or false value
89 static htab_t avail_exprs
;
91 /* Stack of available expressions in AVAIL_EXPRs. Each block pushes any
92 expressions it enters into the hash table along with a marker entry
93 (null). When we finish processing the block, we pop off entries and
94 remove the expressions from the global hash table until we hit the
96 static VEC(tree_on_heap
) *avail_exprs_stack
;
98 /* Stack of trees used to restore the global currdefs to its original
99 state after completing optimization of a block and its dominator children.
101 An SSA_NAME indicates that the current definition of the underlying
102 variable should be set to the given SSA_NAME.
104 A _DECL node indicates that the underlying variable has no current
107 A NULL node is used to mark the last node associated with the
109 static VEC(tree_on_heap
) *block_defs_stack
;
111 /* Stack of statements we need to rescan during finalization for newly
114 Statement rescanning must occur after the current block's available
115 expressions are removed from AVAIL_EXPRS. Else we may change the
116 hash code for an expression and be unable to find/remove it from
118 static VEC(tree_on_heap
) *stmts_to_rescan
;
120 /* Structure for entries in the expression hash table.
122 This requires more memory for the hash table entries, but allows us
123 to avoid creating silly tree nodes and annotations for conditionals,
124 eliminates 2 global hash tables and two block local varrays.
126 It also allows us to reduce the number of hash table lookups we
127 have to perform in lookup_avail_expr and finally it allows us to
128 significantly reduce the number of calls into the hashing routine
133 /* The value (lhs) of this expression. */
136 /* The expression (rhs) we want to record. */
139 /* The annotation if this element corresponds to a statement. */
142 /* The hash value for RHS/ann. */
146 /* Stack of dest,src pairs that need to be restored during finalization.
148 A NULL entry is used to mark the end of pairs which need to be
149 restored during finalization of this block. */
150 static VEC(tree_on_heap
) *const_and_copies_stack
;
152 /* Bitmap of SSA_NAMEs known to have a nonzero value, even if we do not
153 know their exact value. */
154 static bitmap nonzero_vars
;
156 /* Stack of SSA_NAMEs which need their NONZERO_VARS property cleared
157 when the current block is finalized.
159 A NULL entry is used to mark the end of names needing their
160 entry in NONZERO_VARS cleared during finalization of this block. */
161 static VEC(tree_on_heap
) *nonzero_vars_stack
;
163 /* Track whether or not we have changed the control flow graph. */
164 static bool cfg_altered
;
166 /* Bitmap of blocks that have had EH statements cleaned. We should
167 remove their dead edges eventually. */
168 static bitmap need_eh_cleanup
;
170 /* Statistics for dominator optimizations. */
174 long num_exprs_considered
;
178 static struct opt_stats_d opt_stats
;
180 /* Value range propagation record. Each time we encounter a conditional
181 of the form SSA_NAME COND CONST we create a new vrp_element to record
182 how the condition affects the possible values SSA_NAME may have.
184 Each record contains the condition tested (COND), and the the range of
185 values the variable may legitimately have if COND is true. Note the
186 range of values may be a smaller range than COND specifies if we have
187 recorded other ranges for this variable. Each record also contains the
188 block in which the range was recorded for invalidation purposes.
190 Note that the current known range is computed lazily. This allows us
191 to avoid the overhead of computing ranges which are never queried.
193 When we encounter a conditional, we look for records which constrain
194 the SSA_NAME used in the condition. In some cases those records allow
195 us to determine the condition's result at compile time. In other cases
196 they may allow us to simplify the condition.
198 We also use value ranges to do things like transform signed div/mod
199 operations into unsigned div/mod or to simplify ABS_EXPRs.
201 Simple experiments have shown these optimizations to not be all that
202 useful on switch statements (much to my surprise). So switch statement
203 optimizations are not performed.
205 Note carefully we do not propagate information through each statement
206 in the block. i.e., if we know variable X has a value defined of
207 [0, 25] and we encounter Y = X + 1, we do not track a value range
208 for Y (which would be [1, 26] if we cared). Similarly we do not
209 constrain values as we encounter narrowing typecasts, etc. */
213 /* The highest and lowest values the variable in COND may contain when
214 COND is true. Note this may not necessarily be the same values
215 tested by COND if the same variable was used in earlier conditionals.
217 Note this is computed lazily and thus can be NULL indicating that
218 the values have not been computed yet. */
222 /* The actual conditional we recorded. This is needed since we compute
226 /* The basic block where this record was created. We use this to determine
227 when to remove records. */
231 /* A hash table holding value range records (VRP_ELEMENTs) for a given
232 SSA_NAME. We used to use a varray indexed by SSA_NAME_VERSION, but
233 that gets awful wasteful, particularly since the density objects
234 with useful information is very low. */
235 static htab_t vrp_data
;
237 /* An entry in the VRP_DATA hash table. We record the variable and a
238 varray of VRP_ELEMENT records associated with that variable. */
245 /* Array of variables which have their values constrained by operations
246 in this basic block. We use this during finalization to know
247 which variables need their VRP data updated. */
249 /* Stack of SSA_NAMEs which had their values constrainted by operations
250 in this basic block. During finalization of this block we use this
251 list to determine which variables need their VRP data updated.
253 A NULL entry marks the end of the SSA_NAMEs associated with this block. */
254 static VEC(tree_on_heap
) *vrp_variables_stack
;
262 /* Local functions. */
263 static void optimize_stmt (struct dom_walk_data
*,
265 block_stmt_iterator
);
266 static tree
lookup_avail_expr (tree
, bool);
267 static hashval_t
vrp_hash (const void *);
268 static int vrp_eq (const void *, const void *);
269 static hashval_t
avail_expr_hash (const void *);
270 static hashval_t
real_avail_expr_hash (const void *);
271 static int avail_expr_eq (const void *, const void *);
272 static void htab_statistics (FILE *, htab_t
);
273 static void record_cond (tree
, tree
);
274 static void record_const_or_copy (tree
, tree
);
275 static void record_equality (tree
, tree
);
276 static tree
update_rhs_and_lookup_avail_expr (tree
, tree
, bool);
277 static tree
simplify_rhs_and_lookup_avail_expr (struct dom_walk_data
*,
279 static tree
simplify_cond_and_lookup_avail_expr (tree
, stmt_ann_t
, int);
280 static tree
simplify_switch_and_lookup_avail_expr (tree
, int);
281 static tree
find_equivalent_equality_comparison (tree
);
282 static void record_range (tree
, basic_block
);
283 static bool extract_range_from_cond (tree
, tree
*, tree
*, int *);
284 static void record_equivalences_from_phis (basic_block
);
285 static void record_equivalences_from_incoming_edge (basic_block
);
286 static bool eliminate_redundant_computations (struct dom_walk_data
*,
288 static void record_equivalences_from_stmt (tree
, int, stmt_ann_t
);
289 static void thread_across_edge (struct dom_walk_data
*, edge
);
290 static void dom_opt_finalize_block (struct dom_walk_data
*, basic_block
);
291 static void dom_opt_initialize_block (struct dom_walk_data
*, basic_block
);
292 static void propagate_to_outgoing_edges (struct dom_walk_data
*, basic_block
);
293 static void remove_local_expressions_from_table (void);
294 static void restore_vars_to_original_value (void);
295 static void restore_currdefs_to_original_value (void);
296 static void register_definitions_for_stmt (tree
);
297 static edge
single_incoming_edge_ignoring_loop_edges (basic_block
);
298 static void restore_nonzero_vars_to_original_value (void);
299 static inline bool unsafe_associative_fp_binop (tree
);
301 /* Local version of fold that doesn't introduce cruft. */
308 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
309 may have been added by fold, and "useless" type conversions that might
310 now be apparent due to propagation. */
311 STRIP_USELESS_TYPE_CONVERSION (t
);
316 /* Allocate an EDGE_INFO for edge E and attach it to E.
317 Return the new EDGE_INFO structure. */
319 static struct edge_info
*
320 allocate_edge_info (edge e
)
322 struct edge_info
*edge_info
;
324 edge_info
= xcalloc (1, sizeof (struct edge_info
));
330 /* Free all EDGE_INFO structures associated with edges in the CFG.
331 If a particular edge can be threaded, copy the redirection
332 target from the EDGE_INFO structure into the edge's AUX field
333 as required by code to update the CFG and SSA graph for
337 free_all_edge_infos (void)
345 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
347 struct edge_info
*edge_info
= e
->aux
;
351 e
->aux
= edge_info
->redirection_target
;
352 if (edge_info
->cond_equivalences
)
353 free (edge_info
->cond_equivalences
);
360 /* Jump threading, redundancy elimination and const/copy propagation.
362 This pass may expose new symbols that need to be renamed into SSA. For
363 every new symbol exposed, its corresponding bit will be set in
367 tree_ssa_dominator_optimize (void)
369 struct dom_walk_data walk_data
;
372 memset (&opt_stats
, 0, sizeof (opt_stats
));
374 for (i
= 0; i
< num_referenced_vars
; i
++)
375 var_ann (referenced_var (i
))->current_def
= NULL
;
377 /* Create our hash tables. */
378 avail_exprs
= htab_create (1024, real_avail_expr_hash
, avail_expr_eq
, free
);
379 vrp_data
= htab_create (ceil_log2 (num_ssa_names
), vrp_hash
, vrp_eq
, free
);
380 avail_exprs_stack
= VEC_alloc (tree_on_heap
, 20);
381 block_defs_stack
= VEC_alloc (tree_on_heap
, 20);
382 const_and_copies_stack
= VEC_alloc (tree_on_heap
, 20);
383 nonzero_vars_stack
= VEC_alloc (tree_on_heap
, 20);
384 vrp_variables_stack
= VEC_alloc (tree_on_heap
, 20);
385 stmts_to_rescan
= VEC_alloc (tree_on_heap
, 20);
386 nonzero_vars
= BITMAP_XMALLOC ();
387 need_eh_cleanup
= BITMAP_XMALLOC ();
389 /* Setup callbacks for the generic dominator tree walker. */
390 walk_data
.walk_stmts_backward
= false;
391 walk_data
.dom_direction
= CDI_DOMINATORS
;
392 walk_data
.initialize_block_local_data
= NULL
;
393 walk_data
.before_dom_children_before_stmts
= dom_opt_initialize_block
;
394 walk_data
.before_dom_children_walk_stmts
= optimize_stmt
;
395 walk_data
.before_dom_children_after_stmts
= propagate_to_outgoing_edges
;
396 walk_data
.after_dom_children_before_stmts
= NULL
;
397 walk_data
.after_dom_children_walk_stmts
= NULL
;
398 walk_data
.after_dom_children_after_stmts
= dom_opt_finalize_block
;
399 /* Right now we only attach a dummy COND_EXPR to the global data pointer.
400 When we attach more stuff we'll need to fill this out with a real
402 walk_data
.global_data
= NULL
;
403 walk_data
.block_local_data_size
= 0;
405 /* Now initialize the dominator walker. */
406 init_walk_dominator_tree (&walk_data
);
408 calculate_dominance_info (CDI_DOMINATORS
);
410 /* If we prove certain blocks are unreachable, then we want to
411 repeat the dominator optimization process as PHI nodes may
412 have turned into copies which allows better propagation of
413 values. So we repeat until we do not identify any new unreachable
417 /* Optimize the dominator tree. */
420 /* Recursively walk the dominator tree optimizing statements. */
421 walk_dominator_tree (&walk_data
, ENTRY_BLOCK_PTR
);
423 /* If we exposed any new variables, go ahead and put them into
424 SSA form now, before we handle jump threading. This simplifies
425 interactions between rewriting of _DECL nodes into SSA form
426 and rewriting SSA_NAME nodes into SSA form after block
427 duplication and CFG manipulation. */
428 if (!bitmap_empty_p (vars_to_rename
))
430 rewrite_into_ssa (false);
431 bitmap_clear (vars_to_rename
);
434 free_all_edge_infos ();
436 /* Thread jumps, creating duplicate blocks as needed. */
437 cfg_altered
= thread_through_all_blocks ();
439 /* Removal of statements may make some EH edges dead. Purge
440 such edges from the CFG as needed. */
441 if (!bitmap_empty_p (need_eh_cleanup
))
443 cfg_altered
|= tree_purge_all_dead_eh_edges (need_eh_cleanup
);
444 bitmap_zero (need_eh_cleanup
);
447 free_dominance_info (CDI_DOMINATORS
);
448 cfg_altered
= cleanup_tree_cfg ();
449 calculate_dominance_info (CDI_DOMINATORS
);
451 rewrite_ssa_into_ssa ();
453 /* Reinitialize the various tables. */
454 bitmap_clear (nonzero_vars
);
455 htab_empty (avail_exprs
);
456 htab_empty (vrp_data
);
458 for (i
= 0; i
< num_referenced_vars
; i
++)
459 var_ann (referenced_var (i
))->current_def
= NULL
;
463 /* Debugging dumps. */
464 if (dump_file
&& (dump_flags
& TDF_STATS
))
465 dump_dominator_optimization_stats (dump_file
);
467 /* We emptied the hash table earlier, now delete it completely. */
468 htab_delete (avail_exprs
);
469 htab_delete (vrp_data
);
471 /* It is not necessary to clear CURRDEFS, REDIRECTION_EDGES, VRP_DATA,
472 CONST_AND_COPIES, and NONZERO_VARS as they all get cleared at the bottom
473 of the do-while loop above. */
475 /* And finalize the dominator walker. */
476 fini_walk_dominator_tree (&walk_data
);
478 /* Free nonzero_vars. */
479 BITMAP_XFREE (nonzero_vars
);
480 BITMAP_XFREE (need_eh_cleanup
);
482 /* Finally, remove everything except invariants in SSA_NAME_VALUE.
484 Long term we will be able to let everything in SSA_NAME_VALUE
485 persist. However, for now, we know this is the safe thing to
487 for (i
= 0; i
< num_ssa_names
; i
++)
489 tree name
= ssa_name (i
);
495 value
= SSA_NAME_VALUE (name
);
496 if (value
&& !is_gimple_min_invariant (value
))
497 SSA_NAME_VALUE (name
) = NULL
;
500 VEC_free (tree_on_heap
, block_defs_stack
);
501 VEC_free (tree_on_heap
, avail_exprs_stack
);
502 VEC_free (tree_on_heap
, const_and_copies_stack
);
503 VEC_free (tree_on_heap
, nonzero_vars_stack
);
504 VEC_free (tree_on_heap
, vrp_variables_stack
);
505 VEC_free (tree_on_heap
, stmts_to_rescan
);
509 gate_dominator (void)
511 return flag_tree_dom
!= 0;
514 struct tree_opt_pass pass_dominator
=
517 gate_dominator
, /* gate */
518 tree_ssa_dominator_optimize
, /* execute */
521 0, /* static_pass_number */
522 TV_TREE_SSA_DOMINATOR_OPTS
, /* tv_id */
523 PROP_cfg
| PROP_ssa
| PROP_alias
, /* properties_required */
524 0, /* properties_provided */
525 0, /* properties_destroyed */
526 0, /* todo_flags_start */
527 TODO_dump_func
| TODO_rename_vars
528 | TODO_verify_ssa
, /* todo_flags_finish */
533 /* We are exiting BB, see if the target block begins with a conditional
534 jump which has a known value when reached via BB. */
537 thread_across_edge (struct dom_walk_data
*walk_data
, edge e
)
539 block_stmt_iterator bsi
;
543 /* Each PHI creates a temporary equivalence, record them. */
544 for (phi
= phi_nodes (e
->dest
); phi
; phi
= PHI_CHAIN (phi
))
546 tree src
= PHI_ARG_DEF_FROM_EDGE (phi
, e
);
547 tree dst
= PHI_RESULT (phi
);
549 /* If the desired argument is not the same as this PHI's result
550 and it is set by a PHI in this block, then we can not thread
551 through this block. */
553 && TREE_CODE (src
) == SSA_NAME
554 && TREE_CODE (SSA_NAME_DEF_STMT (src
)) == PHI_NODE
555 && bb_for_stmt (SSA_NAME_DEF_STMT (src
)) == e
->dest
)
558 record_const_or_copy (dst
, src
);
559 register_new_def (dst
, &block_defs_stack
);
562 for (bsi
= bsi_start (e
->dest
); ! bsi_end_p (bsi
); bsi_next (&bsi
))
564 tree lhs
, cached_lhs
;
566 stmt
= bsi_stmt (bsi
);
568 /* Ignore empty statements and labels. */
569 if (IS_EMPTY_STMT (stmt
) || TREE_CODE (stmt
) == LABEL_EXPR
)
572 /* If this is not a MODIFY_EXPR which sets an SSA_NAME to a new
573 value, then stop our search here. Ideally when we stop a
574 search we stop on a COND_EXPR or SWITCH_EXPR. */
575 if (TREE_CODE (stmt
) != MODIFY_EXPR
576 || TREE_CODE (TREE_OPERAND (stmt
, 0)) != SSA_NAME
)
579 /* At this point we have a statement which assigns an RHS to an
580 SSA_VAR on the LHS. We want to prove that the RHS is already
581 available and that its value is held in the current definition
582 of the LHS -- meaning that this assignment is a NOP when
583 reached via edge E. */
584 if (TREE_CODE (TREE_OPERAND (stmt
, 1)) == SSA_NAME
)
585 cached_lhs
= TREE_OPERAND (stmt
, 1);
587 cached_lhs
= lookup_avail_expr (stmt
, false);
589 lhs
= TREE_OPERAND (stmt
, 0);
591 /* This can happen if we thread around to the start of a loop. */
592 if (lhs
== cached_lhs
)
595 /* If we did not find RHS in the hash table, then try again after
596 temporarily const/copy propagating the operands. */
599 /* Copy the operands. */
600 stmt_ann_t ann
= stmt_ann (stmt
);
601 use_optype uses
= USE_OPS (ann
);
602 vuse_optype vuses
= VUSE_OPS (ann
);
603 tree
*uses_copy
= xcalloc (NUM_USES (uses
), sizeof (tree
));
604 tree
*vuses_copy
= xcalloc (NUM_VUSES (vuses
), sizeof (tree
));
607 /* Make a copy of the uses into USES_COPY, then cprop into
609 for (i
= 0; i
< NUM_USES (uses
); i
++)
613 uses_copy
[i
] = USE_OP (uses
, i
);
614 if (TREE_CODE (USE_OP (uses
, i
)) == SSA_NAME
)
615 tmp
= SSA_NAME_VALUE (USE_OP (uses
, i
));
616 if (tmp
&& TREE_CODE (tmp
) != VALUE_HANDLE
)
617 SET_USE_OP (uses
, i
, tmp
);
620 /* Similarly for virtual uses. */
621 for (i
= 0; i
< NUM_VUSES (vuses
); i
++)
625 vuses_copy
[i
] = VUSE_OP (vuses
, i
);
626 if (TREE_CODE (VUSE_OP (vuses
, i
)) == SSA_NAME
)
627 tmp
= SSA_NAME_VALUE (VUSE_OP (vuses
, i
));
628 if (tmp
&& TREE_CODE (tmp
) != VALUE_HANDLE
)
629 SET_VUSE_OP (vuses
, i
, tmp
);
632 /* Try to lookup the new expression. */
633 cached_lhs
= lookup_avail_expr (stmt
, false);
635 /* Restore the statement's original uses/defs. */
636 for (i
= 0; i
< NUM_USES (uses
); i
++)
637 SET_USE_OP (uses
, i
, uses_copy
[i
]);
639 for (i
= 0; i
< NUM_VUSES (vuses
); i
++)
640 SET_VUSE_OP (vuses
, i
, vuses_copy
[i
]);
645 /* If we still did not find the expression in the hash table,
646 then we can not ignore this statement. */
651 /* If the expression in the hash table was not assigned to an
652 SSA_NAME, then we can not ignore this statement. */
653 if (TREE_CODE (cached_lhs
) != SSA_NAME
)
656 /* If we have different underlying variables, then we can not
657 ignore this statement. */
658 if (SSA_NAME_VAR (cached_lhs
) != SSA_NAME_VAR (lhs
))
661 /* If CACHED_LHS does not represent the current value of the underlying
662 variable in CACHED_LHS/LHS, then we can not ignore this statement. */
663 if (var_ann (SSA_NAME_VAR (lhs
))->current_def
!= cached_lhs
)
666 /* If we got here, then we can ignore this statement and continue
667 walking through the statements in the block looking for a threadable
670 We want to record an equivalence lhs = cache_lhs so that if
671 the result of this statement is used later we can copy propagate
673 record_const_or_copy (lhs
, cached_lhs
);
674 register_new_def (lhs
, &block_defs_stack
);
677 /* If we stopped at a COND_EXPR or SWITCH_EXPR, then see if we know which
678 arm will be taken. */
680 && (TREE_CODE (stmt
) == COND_EXPR
681 || TREE_CODE (stmt
) == SWITCH_EXPR
))
683 tree cond
, cached_lhs
;
685 /* Now temporarily cprop the operands and try to find the resulting
686 expression in the hash tables. */
687 if (TREE_CODE (stmt
) == COND_EXPR
)
688 cond
= COND_EXPR_COND (stmt
);
690 cond
= SWITCH_COND (stmt
);
692 if (COMPARISON_CLASS_P (cond
))
694 tree dummy_cond
, op0
, op1
;
695 enum tree_code cond_code
;
697 op0
= TREE_OPERAND (cond
, 0);
698 op1
= TREE_OPERAND (cond
, 1);
699 cond_code
= TREE_CODE (cond
);
701 /* Get the current value of both operands. */
702 if (TREE_CODE (op0
) == SSA_NAME
)
704 tree tmp
= SSA_NAME_VALUE (op0
);
705 if (tmp
&& TREE_CODE (tmp
) != VALUE_HANDLE
)
709 if (TREE_CODE (op1
) == SSA_NAME
)
711 tree tmp
= SSA_NAME_VALUE (op1
);
712 if (tmp
&& TREE_CODE (tmp
) != VALUE_HANDLE
)
716 /* Stuff the operator and operands into our dummy conditional
717 expression, creating the dummy conditional if necessary. */
718 dummy_cond
= walk_data
->global_data
;
721 dummy_cond
= build (cond_code
, boolean_type_node
, op0
, op1
);
722 dummy_cond
= build (COND_EXPR
, void_type_node
,
723 dummy_cond
, NULL
, NULL
);
724 walk_data
->global_data
= dummy_cond
;
728 TREE_SET_CODE (COND_EXPR_COND (dummy_cond
), cond_code
);
729 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 0) = op0
;
730 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 1) = op1
;
733 /* If the conditional folds to an invariant, then we are done,
734 otherwise look it up in the hash tables. */
735 cached_lhs
= local_fold (COND_EXPR_COND (dummy_cond
));
736 if (! is_gimple_min_invariant (cached_lhs
))
738 cached_lhs
= lookup_avail_expr (dummy_cond
, false);
739 if (!cached_lhs
|| ! is_gimple_min_invariant (cached_lhs
))
740 cached_lhs
= simplify_cond_and_lookup_avail_expr (dummy_cond
,
745 /* We can have conditionals which just test the state of a
746 variable rather than use a relational operator. These are
747 simpler to handle. */
748 else if (TREE_CODE (cond
) == SSA_NAME
)
751 cached_lhs
= SSA_NAME_VALUE (cached_lhs
);
752 if (cached_lhs
&& ! is_gimple_min_invariant (cached_lhs
))
756 cached_lhs
= lookup_avail_expr (stmt
, false);
760 edge taken_edge
= find_taken_edge (e
->dest
, cached_lhs
);
761 basic_block dest
= (taken_edge
? taken_edge
->dest
: NULL
);
766 /* If we have a known destination for the conditional, then
767 we can perform this optimization, which saves at least one
768 conditional jump each time it applies since we get to
769 bypass the conditional at our original destination. */
772 struct edge_info
*edge_info
;
774 update_bb_profile_for_threading (e
->dest
, EDGE_FREQUENCY (e
),
775 e
->count
, taken_edge
);
779 edge_info
= allocate_edge_info (e
);
780 edge_info
->redirection_target
= taken_edge
;
781 bb_ann (e
->dest
)->incoming_edge_threaded
= true;
788 /* Initialize local stacks for this optimizer and record equivalences
789 upon entry to BB. Equivalences can come from the edge traversed to
790 reach BB or they may come from PHI nodes at the start of BB. */
793 dom_opt_initialize_block (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
796 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
797 fprintf (dump_file
, "\n\nOptimizing block #%d\n\n", bb
->index
);
799 /* Push a marker on the stacks of local information so that we know how
800 far to unwind when we finalize this block. */
801 VEC_safe_push (tree_on_heap
, avail_exprs_stack
, NULL_TREE
);
802 VEC_safe_push (tree_on_heap
, block_defs_stack
, NULL_TREE
);
803 VEC_safe_push (tree_on_heap
, const_and_copies_stack
, NULL_TREE
);
804 VEC_safe_push (tree_on_heap
, nonzero_vars_stack
, NULL_TREE
);
805 VEC_safe_push (tree_on_heap
, vrp_variables_stack
, NULL_TREE
);
807 record_equivalences_from_incoming_edge (bb
);
809 /* PHI nodes can create equivalences too. */
810 record_equivalences_from_phis (bb
);
813 /* Given an expression EXPR (a relational expression or a statement),
814 initialize the hash table element pointed by by ELEMENT. */
817 initialize_hash_element (tree expr
, tree lhs
, struct expr_hash_elt
*element
)
819 /* Hash table elements may be based on conditional expressions or statements.
821 For the former case, we have no annotation and we want to hash the
822 conditional expression. In the latter case we have an annotation and
823 we want to record the expression the statement evaluates. */
824 if (COMPARISON_CLASS_P (expr
) || TREE_CODE (expr
) == TRUTH_NOT_EXPR
)
829 else if (TREE_CODE (expr
) == COND_EXPR
)
831 element
->ann
= stmt_ann (expr
);
832 element
->rhs
= COND_EXPR_COND (expr
);
834 else if (TREE_CODE (expr
) == SWITCH_EXPR
)
836 element
->ann
= stmt_ann (expr
);
837 element
->rhs
= SWITCH_COND (expr
);
839 else if (TREE_CODE (expr
) == RETURN_EXPR
&& TREE_OPERAND (expr
, 0))
841 element
->ann
= stmt_ann (expr
);
842 element
->rhs
= TREE_OPERAND (TREE_OPERAND (expr
, 0), 1);
846 element
->ann
= stmt_ann (expr
);
847 element
->rhs
= TREE_OPERAND (expr
, 1);
851 element
->hash
= avail_expr_hash (element
);
854 /* Remove all the expressions in LOCALS from TABLE, stopping when there are
855 LIMIT entries left in LOCALs. */
858 remove_local_expressions_from_table (void)
860 /* Remove all the expressions made available in this block. */
861 while (VEC_length (tree_on_heap
, avail_exprs_stack
) > 0)
863 struct expr_hash_elt element
;
864 tree expr
= VEC_pop (tree_on_heap
, avail_exprs_stack
);
866 if (expr
== NULL_TREE
)
869 initialize_hash_element (expr
, NULL
, &element
);
870 htab_remove_elt_with_hash (avail_exprs
, &element
, element
.hash
);
874 /* Use the SSA_NAMES in LOCALS to restore TABLE to its original
875 state, stopping when there are LIMIT entries left in LOCALs. */
878 restore_nonzero_vars_to_original_value (void)
880 while (VEC_length (tree_on_heap
, nonzero_vars_stack
) > 0)
882 tree name
= VEC_pop (tree_on_heap
, nonzero_vars_stack
);
887 bitmap_clear_bit (nonzero_vars
, SSA_NAME_VERSION (name
));
891 /* Use the source/dest pairs in CONST_AND_COPIES_STACK to restore
892 CONST_AND_COPIES to its original state, stopping when we hit a
896 restore_vars_to_original_value (void)
898 while (VEC_length (tree_on_heap
, const_and_copies_stack
) > 0)
900 tree prev_value
, dest
;
902 dest
= VEC_pop (tree_on_heap
, const_and_copies_stack
);
907 prev_value
= VEC_pop (tree_on_heap
, const_and_copies_stack
);
908 SSA_NAME_VALUE (dest
) = prev_value
;
912 /* Similar to restore_vars_to_original_value, except that it restores
913 CURRDEFS to its original value. */
915 restore_currdefs_to_original_value (void)
917 /* Restore CURRDEFS to its original state. */
918 while (VEC_length (tree_on_heap
, block_defs_stack
) > 0)
920 tree tmp
= VEC_pop (tree_on_heap
, block_defs_stack
);
923 if (tmp
== NULL_TREE
)
926 /* If we recorded an SSA_NAME, then make the SSA_NAME the current
927 definition of its underlying variable. If we recorded anything
928 else, it must have been an _DECL node and its current reaching
929 definition must have been NULL. */
930 if (TREE_CODE (tmp
) == SSA_NAME
)
933 var
= SSA_NAME_VAR (saved_def
);
941 var_ann (var
)->current_def
= saved_def
;
945 /* We have finished processing the dominator children of BB, perform
946 any finalization actions in preparation for leaving this node in
947 the dominator tree. */
950 dom_opt_finalize_block (struct dom_walk_data
*walk_data
, basic_block bb
)
954 /* If we are at a leaf node in the dominator tree, see if we can thread
955 the edge from BB through its successor.
957 Do this before we remove entries from our equivalence tables. */
958 if (EDGE_COUNT (bb
->succs
) == 1
959 && (EDGE_SUCC (bb
, 0)->flags
& EDGE_ABNORMAL
) == 0
960 && (get_immediate_dominator (CDI_DOMINATORS
, EDGE_SUCC (bb
, 0)->dest
) != bb
961 || phi_nodes (EDGE_SUCC (bb
, 0)->dest
)))
964 thread_across_edge (walk_data
, EDGE_SUCC (bb
, 0));
966 else if ((last
= last_stmt (bb
))
967 && TREE_CODE (last
) == COND_EXPR
968 && (COMPARISON_CLASS_P (COND_EXPR_COND (last
))
969 || TREE_CODE (COND_EXPR_COND (last
)) == SSA_NAME
)
970 && EDGE_COUNT (bb
->succs
) == 2
971 && (EDGE_SUCC (bb
, 0)->flags
& EDGE_ABNORMAL
) == 0
972 && (EDGE_SUCC (bb
, 1)->flags
& EDGE_ABNORMAL
) == 0)
974 edge true_edge
, false_edge
;
976 extract_true_false_edges_from_block (bb
, &true_edge
, &false_edge
);
978 /* If the THEN arm is the end of a dominator tree or has PHI nodes,
979 then try to thread through its edge. */
980 if (get_immediate_dominator (CDI_DOMINATORS
, true_edge
->dest
) != bb
981 || phi_nodes (true_edge
->dest
))
983 struct edge_info
*edge_info
;
986 /* Push a marker onto the available expression stack so that we
987 unwind any expressions related to the TRUE arm before processing
988 the false arm below. */
989 VEC_safe_push (tree_on_heap
, avail_exprs_stack
, NULL_TREE
);
990 VEC_safe_push (tree_on_heap
, block_defs_stack
, NULL_TREE
);
991 VEC_safe_push (tree_on_heap
, const_and_copies_stack
, NULL_TREE
);
993 edge_info
= true_edge
->aux
;
995 /* If we have info associated with this edge, record it into
996 our equivalency tables. */
999 tree
*cond_equivalences
= edge_info
->cond_equivalences
;
1000 tree lhs
= edge_info
->lhs
;
1001 tree rhs
= edge_info
->rhs
;
1003 /* If we have a simple NAME = VALUE equivalency record it.
1004 Until the jump threading selection code improves, only
1005 do this if both the name and value are SSA_NAMEs with
1006 the same underlying variable to avoid missing threading
1009 && TREE_CODE (COND_EXPR_COND (last
)) == SSA_NAME
1010 && TREE_CODE (edge_info
->rhs
) == SSA_NAME
1011 && SSA_NAME_VAR (lhs
) == SSA_NAME_VAR (rhs
))
1012 record_const_or_copy (lhs
, rhs
);
1014 /* If we have 0 = COND or 1 = COND equivalences, record them
1015 into our expression hash tables. */
1016 if (cond_equivalences
)
1017 for (i
= 0; i
< edge_info
->max_cond_equivalences
; i
+= 2)
1019 tree expr
= cond_equivalences
[i
];
1020 tree value
= cond_equivalences
[i
+ 1];
1022 record_cond (expr
, value
);
1026 /* Now thread the edge. */
1027 thread_across_edge (walk_data
, true_edge
);
1029 /* And restore the various tables to their state before
1030 we threaded this edge. */
1031 remove_local_expressions_from_table ();
1032 restore_vars_to_original_value ();
1033 restore_currdefs_to_original_value ();
1036 /* Similarly for the ELSE arm. */
1037 if (get_immediate_dominator (CDI_DOMINATORS
, false_edge
->dest
) != bb
1038 || phi_nodes (false_edge
->dest
))
1040 struct edge_info
*edge_info
;
1043 edge_info
= false_edge
->aux
;
1045 /* If we have info associated with this edge, record it into
1046 our equivalency tables. */
1049 tree
*cond_equivalences
= edge_info
->cond_equivalences
;
1050 tree lhs
= edge_info
->lhs
;
1051 tree rhs
= edge_info
->rhs
;
1053 /* If we have a simple NAME = VALUE equivalency record it.
1054 Until the jump threading selection code improves, only
1055 do this if both the name and value are SSA_NAMEs with
1056 the same underlying variable to avoid missing threading
1059 && TREE_CODE (COND_EXPR_COND (last
)) == SSA_NAME
)
1060 record_const_or_copy (lhs
, rhs
);
1062 /* If we have 0 = COND or 1 = COND equivalences, record them
1063 into our expression hash tables. */
1064 if (cond_equivalences
)
1065 for (i
= 0; i
< edge_info
->max_cond_equivalences
; i
+= 2)
1067 tree expr
= cond_equivalences
[i
];
1068 tree value
= cond_equivalences
[i
+ 1];
1070 record_cond (expr
, value
);
1074 thread_across_edge (walk_data
, false_edge
);
1076 /* No need to remove local expressions from our tables
1077 or restore vars to their original value as that will
1078 be done immediately below. */
1082 remove_local_expressions_from_table ();
1083 restore_nonzero_vars_to_original_value ();
1084 restore_vars_to_original_value ();
1085 restore_currdefs_to_original_value ();
1087 /* Remove VRP records associated with this basic block. They are no
1090 To be efficient, we note which variables have had their values
1091 constrained in this block. So walk over each variable in the
1092 VRP_VARIABLEs array. */
1093 while (VEC_length (tree_on_heap
, vrp_variables_stack
) > 0)
1095 tree var
= VEC_pop (tree_on_heap
, vrp_variables_stack
);
1096 struct vrp_hash_elt vrp_hash_elt
, *vrp_hash_elt_p
;
1099 /* Each variable has a stack of value range records. We want to
1100 invalidate those associated with our basic block. So we walk
1101 the array backwards popping off records associated with our
1102 block. Once we hit a record not associated with our block
1104 varray_type var_vrp_records
;
1109 vrp_hash_elt
.var
= var
;
1110 vrp_hash_elt
.records
= NULL
;
1112 slot
= htab_find_slot (vrp_data
, &vrp_hash_elt
, NO_INSERT
);
1114 vrp_hash_elt_p
= (struct vrp_hash_elt
*) *slot
;
1115 var_vrp_records
= vrp_hash_elt_p
->records
;
1117 while (VARRAY_ACTIVE_SIZE (var_vrp_records
) > 0)
1119 struct vrp_element
*element
1120 = (struct vrp_element
*)VARRAY_TOP_GENERIC_PTR (var_vrp_records
);
1122 if (element
->bb
!= bb
)
1125 VARRAY_POP (var_vrp_records
);
1129 /* If we queued any statements to rescan in this block, then
1130 go ahead and rescan them now. */
1131 while (VEC_length (tree_on_heap
, stmts_to_rescan
) > 0)
1133 tree stmt
= VEC_last (tree_on_heap
, stmts_to_rescan
);
1134 basic_block stmt_bb
= bb_for_stmt (stmt
);
1139 VEC_pop (tree_on_heap
, stmts_to_rescan
);
1140 mark_new_vars_to_rename (stmt
, vars_to_rename
);
1144 /* PHI nodes can create equivalences too.
1146 Ignoring any alternatives which are the same as the result, if
1147 all the alternatives are equal, then the PHI node creates an
1150 Additionally, if all the PHI alternatives are known to have a nonzero
1151 value, then the result of this PHI is known to have a nonzero value,
1152 even if we do not know its exact value. */
1155 record_equivalences_from_phis (basic_block bb
)
1159 for (phi
= phi_nodes (bb
); phi
; phi
= PHI_CHAIN (phi
))
1161 tree lhs
= PHI_RESULT (phi
);
1165 for (i
= 0; i
< PHI_NUM_ARGS (phi
); i
++)
1167 tree t
= PHI_ARG_DEF (phi
, i
);
1169 /* Ignore alternatives which are the same as our LHS. Since
1170 LHS is a PHI_RESULT, it is known to be a SSA_NAME, so we
1171 can simply compare pointers. */
1175 /* If we have not processed an alternative yet, then set
1176 RHS to this alternative. */
1179 /* If we have processed an alternative (stored in RHS), then
1180 see if it is equal to this one. If it isn't, then stop
1182 else if (! operand_equal_for_phi_arg_p (rhs
, t
))
1186 /* If we had no interesting alternatives, then all the RHS alternatives
1187 must have been the same as LHS. */
1191 /* If we managed to iterate through each PHI alternative without
1192 breaking out of the loop, then we have a PHI which may create
1193 a useful equivalence. We do not need to record unwind data for
1194 this, since this is a true assignment and not an equivalence
1195 inferred from a comparison. All uses of this ssa name are dominated
1196 by this assignment, so unwinding just costs time and space. */
1197 if (i
== PHI_NUM_ARGS (phi
)
1198 && may_propagate_copy (lhs
, rhs
))
1199 SSA_NAME_VALUE (lhs
) = rhs
;
1201 /* Now see if we know anything about the nonzero property for the
1202 result of this PHI. */
1203 for (i
= 0; i
< PHI_NUM_ARGS (phi
); i
++)
1205 if (!PHI_ARG_NONZERO (phi
, i
))
1209 if (i
== PHI_NUM_ARGS (phi
))
1210 bitmap_set_bit (nonzero_vars
, SSA_NAME_VERSION (PHI_RESULT (phi
)));
1212 register_new_def (lhs
, &block_defs_stack
);
1216 /* Ignoring loop backedges, if BB has precisely one incoming edge then
1217 return that edge. Otherwise return NULL. */
1219 single_incoming_edge_ignoring_loop_edges (basic_block bb
)
1225 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1227 /* A loop back edge can be identified by the destination of
1228 the edge dominating the source of the edge. */
1229 if (dominated_by_p (CDI_DOMINATORS
, e
->src
, e
->dest
))
1232 /* If we have already seen a non-loop edge, then we must have
1233 multiple incoming non-loop edges and thus we return NULL. */
1237 /* This is the first non-loop incoming edge we have found. Record
1245 /* Record any equivalences created by the incoming edge to BB. If BB
1246 has more than one incoming edge, then no equivalence is created. */
1249 record_equivalences_from_incoming_edge (basic_block bb
)
1253 struct edge_info
*edge_info
;
1255 /* If our parent block ended with a control statment, then we may be
1256 able to record some equivalences based on which outgoing edge from
1257 the parent was followed. */
1258 parent
= get_immediate_dominator (CDI_DOMINATORS
, bb
);
1260 e
= single_incoming_edge_ignoring_loop_edges (bb
);
1262 /* If we had a single incoming edge from our parent block, then enter
1263 any data associated with the edge into our tables. */
1264 if (e
&& e
->src
== parent
)
1272 tree lhs
= edge_info
->lhs
;
1273 tree rhs
= edge_info
->rhs
;
1274 tree
*cond_equivalences
= edge_info
->cond_equivalences
;
1277 record_equality (lhs
, rhs
);
1279 if (cond_equivalences
)
1281 bool recorded_range
= false;
1282 for (i
= 0; i
< edge_info
->max_cond_equivalences
; i
+= 2)
1284 tree expr
= cond_equivalences
[i
];
1285 tree value
= cond_equivalences
[i
+ 1];
1287 record_cond (expr
, value
);
1289 /* For the first true equivalence, record range
1290 information. We only do this for the first
1291 true equivalence as it should dominate any
1292 later true equivalences. */
1293 if (! recorded_range
1294 && COMPARISON_CLASS_P (expr
)
1295 && value
== boolean_true_node
1296 && TREE_CONSTANT (TREE_OPERAND (expr
, 1)))
1298 record_range (expr
, bb
);
1299 recorded_range
= true;
1307 /* Dump SSA statistics on FILE. */
1310 dump_dominator_optimization_stats (FILE *file
)
1314 fprintf (file
, "Total number of statements: %6ld\n\n",
1315 opt_stats
.num_stmts
);
1316 fprintf (file
, "Exprs considered for dominator optimizations: %6ld\n",
1317 opt_stats
.num_exprs_considered
);
1319 n_exprs
= opt_stats
.num_exprs_considered
;
1323 fprintf (file
, " Redundant expressions eliminated: %6ld (%.0f%%)\n",
1324 opt_stats
.num_re
, PERCENT (opt_stats
.num_re
,
1327 fprintf (file
, "\nHash table statistics:\n");
1329 fprintf (file
, " avail_exprs: ");
1330 htab_statistics (file
, avail_exprs
);
1334 /* Dump SSA statistics on stderr. */
1337 debug_dominator_optimization_stats (void)
1339 dump_dominator_optimization_stats (stderr
);
1343 /* Dump statistics for the hash table HTAB. */
1346 htab_statistics (FILE *file
, htab_t htab
)
1348 fprintf (file
, "size %ld, %ld elements, %f collision/search ratio\n",
1349 (long) htab_size (htab
),
1350 (long) htab_elements (htab
),
1351 htab_collisions (htab
));
1354 /* Record the fact that VAR has a nonzero value, though we may not know
1355 its exact value. Note that if VAR is already known to have a nonzero
1356 value, then we do nothing. */
1359 record_var_is_nonzero (tree var
)
1361 int indx
= SSA_NAME_VERSION (var
);
1363 if (bitmap_bit_p (nonzero_vars
, indx
))
1366 /* Mark it in the global table. */
1367 bitmap_set_bit (nonzero_vars
, indx
);
1369 /* Record this SSA_NAME so that we can reset the global table
1370 when we leave this block. */
1371 VEC_safe_push (tree_on_heap
, nonzero_vars_stack
, var
);
1374 /* Enter a statement into the true/false expression hash table indicating
1375 that the condition COND has the value VALUE. */
1378 record_cond (tree cond
, tree value
)
1380 struct expr_hash_elt
*element
= xmalloc (sizeof (struct expr_hash_elt
));
1383 initialize_hash_element (cond
, value
, element
);
1385 slot
= htab_find_slot_with_hash (avail_exprs
, (void *)element
,
1386 element
->hash
, true);
1389 *slot
= (void *) element
;
1390 VEC_safe_push (tree_on_heap
, avail_exprs_stack
, cond
);
1396 /* Build a new conditional using NEW_CODE, OP0 and OP1 and store
1397 the new conditional into *p, then store a boolean_true_node
1398 into the the *(p + 1). */
1401 build_and_record_new_cond (enum tree_code new_code
, tree op0
, tree op1
, tree
*p
)
1403 *p
= build2 (new_code
, boolean_type_node
, op0
, op1
);
1405 *p
= boolean_true_node
;
1408 /* Record that COND is true and INVERTED is false into the edge information
1409 structure. Also record that any conditions dominated by COND are true
1412 For example, if a < b is true, then a <= b must also be true. */
1415 record_conditions (struct edge_info
*edge_info
, tree cond
, tree inverted
)
1419 if (!COMPARISON_CLASS_P (cond
))
1422 op0
= TREE_OPERAND (cond
, 0);
1423 op1
= TREE_OPERAND (cond
, 1);
1425 switch (TREE_CODE (cond
))
1429 edge_info
->max_cond_equivalences
= 12;
1430 edge_info
->cond_equivalences
= xmalloc (12 * sizeof (tree
));
1431 build_and_record_new_cond ((TREE_CODE (cond
) == LT_EXPR
1432 ? LE_EXPR
: GE_EXPR
),
1433 op0
, op1
, &edge_info
->cond_equivalences
[4]);
1434 build_and_record_new_cond (ORDERED_EXPR
, op0
, op1
,
1435 &edge_info
->cond_equivalences
[6]);
1436 build_and_record_new_cond (NE_EXPR
, op0
, op1
,
1437 &edge_info
->cond_equivalences
[8]);
1438 build_and_record_new_cond (LTGT_EXPR
, op0
, op1
,
1439 &edge_info
->cond_equivalences
[10]);
1444 edge_info
->max_cond_equivalences
= 6;
1445 edge_info
->cond_equivalences
= xmalloc (6 * sizeof (tree
));
1446 build_and_record_new_cond (ORDERED_EXPR
, op0
, op1
,
1447 &edge_info
->cond_equivalences
[4]);
1451 edge_info
->max_cond_equivalences
= 10;
1452 edge_info
->cond_equivalences
= xmalloc (10 * sizeof (tree
));
1453 build_and_record_new_cond (ORDERED_EXPR
, op0
, op1
,
1454 &edge_info
->cond_equivalences
[4]);
1455 build_and_record_new_cond (LE_EXPR
, op0
, op1
,
1456 &edge_info
->cond_equivalences
[6]);
1457 build_and_record_new_cond (GE_EXPR
, op0
, op1
,
1458 &edge_info
->cond_equivalences
[8]);
1461 case UNORDERED_EXPR
:
1462 edge_info
->max_cond_equivalences
= 16;
1463 edge_info
->cond_equivalences
= xmalloc (16 * sizeof (tree
));
1464 build_and_record_new_cond (NE_EXPR
, op0
, op1
,
1465 &edge_info
->cond_equivalences
[4]);
1466 build_and_record_new_cond (UNLE_EXPR
, op0
, op1
,
1467 &edge_info
->cond_equivalences
[6]);
1468 build_and_record_new_cond (UNGE_EXPR
, op0
, op1
,
1469 &edge_info
->cond_equivalences
[8]);
1470 build_and_record_new_cond (UNEQ_EXPR
, op0
, op1
,
1471 &edge_info
->cond_equivalences
[10]);
1472 build_and_record_new_cond (UNLT_EXPR
, op0
, op1
,
1473 &edge_info
->cond_equivalences
[12]);
1474 build_and_record_new_cond (UNGT_EXPR
, op0
, op1
,
1475 &edge_info
->cond_equivalences
[14]);
1480 edge_info
->max_cond_equivalences
= 8;
1481 edge_info
->cond_equivalences
= xmalloc (8 * sizeof (tree
));
1482 build_and_record_new_cond ((TREE_CODE (cond
) == UNLT_EXPR
1483 ? UNLE_EXPR
: UNGE_EXPR
),
1484 op0
, op1
, &edge_info
->cond_equivalences
[4]);
1485 build_and_record_new_cond (NE_EXPR
, op0
, op1
,
1486 &edge_info
->cond_equivalences
[6]);
1490 edge_info
->max_cond_equivalences
= 8;
1491 edge_info
->cond_equivalences
= xmalloc (8 * sizeof (tree
));
1492 build_and_record_new_cond (UNLE_EXPR
, op0
, op1
,
1493 &edge_info
->cond_equivalences
[4]);
1494 build_and_record_new_cond (UNGE_EXPR
, op0
, op1
,
1495 &edge_info
->cond_equivalences
[6]);
1499 edge_info
->max_cond_equivalences
= 8;
1500 edge_info
->cond_equivalences
= xmalloc (8 * sizeof (tree
));
1501 build_and_record_new_cond (NE_EXPR
, op0
, op1
,
1502 &edge_info
->cond_equivalences
[4]);
1503 build_and_record_new_cond (ORDERED_EXPR
, op0
, op1
,
1504 &edge_info
->cond_equivalences
[6]);
1508 edge_info
->max_cond_equivalences
= 4;
1509 edge_info
->cond_equivalences
= xmalloc (4 * sizeof (tree
));
1513 /* Now store the original true and false conditions into the first
1515 edge_info
->cond_equivalences
[0] = cond
;
1516 edge_info
->cond_equivalences
[1] = boolean_true_node
;
1517 edge_info
->cond_equivalences
[2] = inverted
;
1518 edge_info
->cond_equivalences
[3] = boolean_false_node
;
1521 /* A helper function for record_const_or_copy and record_equality.
1522 Do the work of recording the value and undo info. */
1525 record_const_or_copy_1 (tree x
, tree y
, tree prev_x
)
1527 SSA_NAME_VALUE (x
) = y
;
1529 VEC_safe_push (tree_on_heap
, const_and_copies_stack
, prev_x
);
1530 VEC_safe_push (tree_on_heap
, const_and_copies_stack
, x
);
1534 /* Return the loop depth of the basic block of the defining statement of X.
1535 This number should not be treated as absolutely correct because the loop
1536 information may not be completely up-to-date when dom runs. However, it
1537 will be relatively correct, and as more passes are taught to keep loop info
1538 up to date, the result will become more and more accurate. */
1541 loop_depth_of_name (tree x
)
1546 /* If it's not an SSA_NAME, we have no clue where the definition is. */
1547 if (TREE_CODE (x
) != SSA_NAME
)
1550 /* Otherwise return the loop depth of the defining statement's bb.
1551 Note that there may not actually be a bb for this statement, if the
1552 ssa_name is live on entry. */
1553 defstmt
= SSA_NAME_DEF_STMT (x
);
1554 defbb
= bb_for_stmt (defstmt
);
1558 return defbb
->loop_depth
;
1562 /* Record that X is equal to Y in const_and_copies. Record undo
1563 information in the block-local vector. */
1566 record_const_or_copy (tree x
, tree y
)
1568 tree prev_x
= SSA_NAME_VALUE (x
);
1570 if (TREE_CODE (y
) == SSA_NAME
)
1572 tree tmp
= SSA_NAME_VALUE (y
);
1577 record_const_or_copy_1 (x
, y
, prev_x
);
1580 /* Similarly, but assume that X and Y are the two operands of an EQ_EXPR.
1581 This constrains the cases in which we may treat this as assignment. */
1584 record_equality (tree x
, tree y
)
1586 tree prev_x
= NULL
, prev_y
= NULL
;
1588 if (TREE_CODE (x
) == SSA_NAME
)
1589 prev_x
= SSA_NAME_VALUE (x
);
1590 if (TREE_CODE (y
) == SSA_NAME
)
1591 prev_y
= SSA_NAME_VALUE (y
);
1593 /* If one of the previous values is invariant, or invariant in more loops
1594 (by depth), then use that.
1595 Otherwise it doesn't matter which value we choose, just so
1596 long as we canonicalize on one value. */
1597 if (TREE_INVARIANT (y
))
1599 else if (TREE_INVARIANT (x
) || (loop_depth_of_name (x
) <= loop_depth_of_name (y
)))
1600 prev_x
= x
, x
= y
, y
= prev_x
, prev_x
= prev_y
;
1601 else if (prev_x
&& TREE_INVARIANT (prev_x
))
1602 x
= y
, y
= prev_x
, prev_x
= prev_y
;
1603 else if (prev_y
&& TREE_CODE (prev_y
) != VALUE_HANDLE
)
1606 /* After the swapping, we must have one SSA_NAME. */
1607 if (TREE_CODE (x
) != SSA_NAME
)
1610 /* For IEEE, -0.0 == 0.0, so we don't necessarily know the sign of a
1611 variable compared against zero. If we're honoring signed zeros,
1612 then we cannot record this value unless we know that the value is
1614 if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (x
)))
1615 && (TREE_CODE (y
) != REAL_CST
1616 || REAL_VALUES_EQUAL (dconst0
, TREE_REAL_CST (y
))))
1619 record_const_or_copy_1 (x
, y
, prev_x
);
1622 /* Return true, if it is ok to do folding of an associative expression.
1623 EXP is the tree for the associative expression. */
1626 unsafe_associative_fp_binop (tree exp
)
1628 enum tree_code code
= TREE_CODE (exp
);
1629 return !(!flag_unsafe_math_optimizations
1630 && (code
== MULT_EXPR
|| code
== PLUS_EXPR
1631 || code
== MINUS_EXPR
)
1632 && FLOAT_TYPE_P (TREE_TYPE (exp
)));
1635 /* STMT is a MODIFY_EXPR for which we were unable to find RHS in the
1636 hash tables. Try to simplify the RHS using whatever equivalences
1637 we may have recorded.
1639 If we are able to simplify the RHS, then lookup the simplified form in
1640 the hash table and return the result. Otherwise return NULL. */
1643 simplify_rhs_and_lookup_avail_expr (struct dom_walk_data
*walk_data
,
1644 tree stmt
, int insert
)
1646 tree rhs
= TREE_OPERAND (stmt
, 1);
1647 enum tree_code rhs_code
= TREE_CODE (rhs
);
1650 /* If we have lhs = ~x, look and see if we earlier had x = ~y.
1651 In which case we can change this statement to be lhs = y.
1652 Which can then be copy propagated.
1654 Similarly for negation. */
1655 if ((rhs_code
== BIT_NOT_EXPR
|| rhs_code
== NEGATE_EXPR
)
1656 && TREE_CODE (TREE_OPERAND (rhs
, 0)) == SSA_NAME
)
1658 /* Get the definition statement for our RHS. */
1659 tree rhs_def_stmt
= SSA_NAME_DEF_STMT (TREE_OPERAND (rhs
, 0));
1661 /* See if the RHS_DEF_STMT has the same form as our statement. */
1662 if (TREE_CODE (rhs_def_stmt
) == MODIFY_EXPR
1663 && TREE_CODE (TREE_OPERAND (rhs_def_stmt
, 1)) == rhs_code
)
1665 tree rhs_def_operand
;
1667 rhs_def_operand
= TREE_OPERAND (TREE_OPERAND (rhs_def_stmt
, 1), 0);
1669 /* Verify that RHS_DEF_OPERAND is a suitable SSA variable. */
1670 if (TREE_CODE (rhs_def_operand
) == SSA_NAME
1671 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand
))
1672 result
= update_rhs_and_lookup_avail_expr (stmt
,
1678 /* If we have z = (x OP C1), see if we earlier had x = y OP C2.
1679 If OP is associative, create and fold (y OP C2) OP C1 which
1680 should result in (y OP C3), use that as the RHS for the
1681 assignment. Add minus to this, as we handle it specially below. */
1682 if ((associative_tree_code (rhs_code
) || rhs_code
== MINUS_EXPR
)
1683 && TREE_CODE (TREE_OPERAND (rhs
, 0)) == SSA_NAME
1684 && is_gimple_min_invariant (TREE_OPERAND (rhs
, 1)))
1686 tree rhs_def_stmt
= SSA_NAME_DEF_STMT (TREE_OPERAND (rhs
, 0));
1688 /* See if the RHS_DEF_STMT has the same form as our statement. */
1689 if (TREE_CODE (rhs_def_stmt
) == MODIFY_EXPR
)
1691 tree rhs_def_rhs
= TREE_OPERAND (rhs_def_stmt
, 1);
1692 enum tree_code rhs_def_code
= TREE_CODE (rhs_def_rhs
);
1694 if ((rhs_code
== rhs_def_code
&& unsafe_associative_fp_binop (rhs
))
1695 || (rhs_code
== PLUS_EXPR
&& rhs_def_code
== MINUS_EXPR
)
1696 || (rhs_code
== MINUS_EXPR
&& rhs_def_code
== PLUS_EXPR
))
1698 tree def_stmt_op0
= TREE_OPERAND (rhs_def_rhs
, 0);
1699 tree def_stmt_op1
= TREE_OPERAND (rhs_def_rhs
, 1);
1701 if (TREE_CODE (def_stmt_op0
) == SSA_NAME
1702 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def_stmt_op0
)
1703 && is_gimple_min_invariant (def_stmt_op1
))
1705 tree outer_const
= TREE_OPERAND (rhs
, 1);
1706 tree type
= TREE_TYPE (TREE_OPERAND (stmt
, 0));
1709 /* If we care about correct floating point results, then
1710 don't fold x + c1 - c2. Note that we need to take both
1711 the codes and the signs to figure this out. */
1712 if (FLOAT_TYPE_P (type
)
1713 && !flag_unsafe_math_optimizations
1714 && (rhs_def_code
== PLUS_EXPR
1715 || rhs_def_code
== MINUS_EXPR
))
1719 neg
^= (rhs_code
== MINUS_EXPR
);
1720 neg
^= (rhs_def_code
== MINUS_EXPR
);
1721 neg
^= real_isneg (TREE_REAL_CST_PTR (outer_const
));
1722 neg
^= real_isneg (TREE_REAL_CST_PTR (def_stmt_op1
));
1725 goto dont_fold_assoc
;
1728 /* Ho hum. So fold will only operate on the outermost
1729 thingy that we give it, so we have to build the new
1730 expression in two pieces. This requires that we handle
1731 combinations of plus and minus. */
1732 if (rhs_def_code
!= rhs_code
)
1734 if (rhs_def_code
== MINUS_EXPR
)
1735 t
= build (MINUS_EXPR
, type
, outer_const
, def_stmt_op1
);
1737 t
= build (MINUS_EXPR
, type
, def_stmt_op1
, outer_const
);
1738 rhs_code
= PLUS_EXPR
;
1740 else if (rhs_def_code
== MINUS_EXPR
)
1741 t
= build (PLUS_EXPR
, type
, def_stmt_op1
, outer_const
);
1743 t
= build (rhs_def_code
, type
, def_stmt_op1
, outer_const
);
1745 t
= build (rhs_code
, type
, def_stmt_op0
, t
);
1748 /* If the result is a suitable looking gimple expression,
1749 then use it instead of the original for STMT. */
1750 if (TREE_CODE (t
) == SSA_NAME
1751 || (UNARY_CLASS_P (t
)
1752 && TREE_CODE (TREE_OPERAND (t
, 0)) == SSA_NAME
)
1753 || ((BINARY_CLASS_P (t
) || COMPARISON_CLASS_P (t
))
1754 && TREE_CODE (TREE_OPERAND (t
, 0)) == SSA_NAME
1755 && is_gimple_val (TREE_OPERAND (t
, 1))))
1756 result
= update_rhs_and_lookup_avail_expr (stmt
, t
, insert
);
1763 /* Transform TRUNC_DIV_EXPR and TRUNC_MOD_EXPR into RSHIFT_EXPR
1764 and BIT_AND_EXPR respectively if the first operand is greater
1765 than zero and the second operand is an exact power of two. */
1766 if ((rhs_code
== TRUNC_DIV_EXPR
|| rhs_code
== TRUNC_MOD_EXPR
)
1767 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs
, 0)))
1768 && integer_pow2p (TREE_OPERAND (rhs
, 1)))
1771 tree op
= TREE_OPERAND (rhs
, 0);
1773 if (TYPE_UNSIGNED (TREE_TYPE (op
)))
1775 val
= integer_one_node
;
1779 tree dummy_cond
= walk_data
->global_data
;
1783 dummy_cond
= build (GT_EXPR
, boolean_type_node
,
1784 op
, integer_zero_node
);
1785 dummy_cond
= build (COND_EXPR
, void_type_node
,
1786 dummy_cond
, NULL
, NULL
);
1787 walk_data
->global_data
= dummy_cond
;
1791 TREE_SET_CODE (COND_EXPR_COND (dummy_cond
), GT_EXPR
);
1792 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 0) = op
;
1793 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 1)
1794 = integer_zero_node
;
1796 val
= simplify_cond_and_lookup_avail_expr (dummy_cond
, NULL
, false);
1799 if (val
&& integer_onep (val
))
1802 tree op0
= TREE_OPERAND (rhs
, 0);
1803 tree op1
= TREE_OPERAND (rhs
, 1);
1805 if (rhs_code
== TRUNC_DIV_EXPR
)
1806 t
= build (RSHIFT_EXPR
, TREE_TYPE (op0
), op0
,
1807 build_int_cst (NULL_TREE
, tree_log2 (op1
)));
1809 t
= build (BIT_AND_EXPR
, TREE_TYPE (op0
), op0
,
1810 local_fold (build (MINUS_EXPR
, TREE_TYPE (op1
),
1811 op1
, integer_one_node
)));
1813 result
= update_rhs_and_lookup_avail_expr (stmt
, t
, insert
);
1817 /* Transform ABS (X) into X or -X as appropriate. */
1818 if (rhs_code
== ABS_EXPR
1819 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs
, 0))))
1822 tree op
= TREE_OPERAND (rhs
, 0);
1823 tree type
= TREE_TYPE (op
);
1825 if (TYPE_UNSIGNED (type
))
1827 val
= integer_zero_node
;
1831 tree dummy_cond
= walk_data
->global_data
;
1835 dummy_cond
= build (LE_EXPR
, boolean_type_node
,
1836 op
, integer_zero_node
);
1837 dummy_cond
= build (COND_EXPR
, void_type_node
,
1838 dummy_cond
, NULL
, NULL
);
1839 walk_data
->global_data
= dummy_cond
;
1843 TREE_SET_CODE (COND_EXPR_COND (dummy_cond
), LE_EXPR
);
1844 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 0) = op
;
1845 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 1)
1846 = build_int_cst (type
, 0);
1848 val
= simplify_cond_and_lookup_avail_expr (dummy_cond
, NULL
, false);
1852 TREE_SET_CODE (COND_EXPR_COND (dummy_cond
), GE_EXPR
);
1853 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 0) = op
;
1854 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 1)
1855 = build_int_cst (type
, 0);
1857 val
= simplify_cond_and_lookup_avail_expr (dummy_cond
,
1862 if (integer_zerop (val
))
1863 val
= integer_one_node
;
1864 else if (integer_onep (val
))
1865 val
= integer_zero_node
;
1871 && (integer_onep (val
) || integer_zerop (val
)))
1875 if (integer_onep (val
))
1876 t
= build1 (NEGATE_EXPR
, TREE_TYPE (op
), op
);
1880 result
= update_rhs_and_lookup_avail_expr (stmt
, t
, insert
);
1884 /* Optimize *"foo" into 'f'. This is done here rather than
1885 in fold to avoid problems with stuff like &*"foo". */
1886 if (TREE_CODE (rhs
) == INDIRECT_REF
|| TREE_CODE (rhs
) == ARRAY_REF
)
1888 tree t
= fold_read_from_constant_string (rhs
);
1891 result
= update_rhs_and_lookup_avail_expr (stmt
, t
, insert
);
1897 /* COND is a condition of the form:
1899 x == const or x != const
1901 Look back to x's defining statement and see if x is defined as
1905 If const is unchanged if we convert it to type, then we can build
1906 the equivalent expression:
1909 y == const or y != const
1911 Which may allow further optimizations.
1913 Return the equivalent comparison or NULL if no such equivalent comparison
1917 find_equivalent_equality_comparison (tree cond
)
1919 tree op0
= TREE_OPERAND (cond
, 0);
1920 tree op1
= TREE_OPERAND (cond
, 1);
1921 tree def_stmt
= SSA_NAME_DEF_STMT (op0
);
1923 /* OP0 might have been a parameter, so first make sure it
1924 was defined by a MODIFY_EXPR. */
1925 if (def_stmt
&& TREE_CODE (def_stmt
) == MODIFY_EXPR
)
1927 tree def_rhs
= TREE_OPERAND (def_stmt
, 1);
1929 /* Now make sure the RHS of the MODIFY_EXPR is a typecast. */
1930 if ((TREE_CODE (def_rhs
) == NOP_EXPR
1931 || TREE_CODE (def_rhs
) == CONVERT_EXPR
)
1932 && TREE_CODE (TREE_OPERAND (def_rhs
, 0)) == SSA_NAME
)
1934 tree def_rhs_inner
= TREE_OPERAND (def_rhs
, 0);
1935 tree def_rhs_inner_type
= TREE_TYPE (def_rhs_inner
);
1938 if (TYPE_PRECISION (def_rhs_inner_type
)
1939 > TYPE_PRECISION (TREE_TYPE (def_rhs
)))
1942 /* What we want to prove is that if we convert OP1 to
1943 the type of the object inside the NOP_EXPR that the
1944 result is still equivalent to SRC.
1946 If that is true, the build and return new equivalent
1947 condition which uses the source of the typecast and the
1948 new constant (which has only changed its type). */
1949 new = build1 (TREE_CODE (def_rhs
), def_rhs_inner_type
, op1
);
1950 new = local_fold (new);
1951 if (is_gimple_val (new) && tree_int_cst_equal (new, op1
))
1952 return build (TREE_CODE (cond
), TREE_TYPE (cond
),
1953 def_rhs_inner
, new);
1959 /* STMT is a COND_EXPR for which we could not trivially determine its
1960 result. This routine attempts to find equivalent forms of the
1961 condition which we may be able to optimize better. It also
1962 uses simple value range propagation to optimize conditionals. */
1965 simplify_cond_and_lookup_avail_expr (tree stmt
,
1969 tree cond
= COND_EXPR_COND (stmt
);
1971 if (COMPARISON_CLASS_P (cond
))
1973 tree op0
= TREE_OPERAND (cond
, 0);
1974 tree op1
= TREE_OPERAND (cond
, 1);
1976 if (TREE_CODE (op0
) == SSA_NAME
&& is_gimple_min_invariant (op1
))
1979 tree low
, high
, cond_low
, cond_high
;
1980 int lowequal
, highequal
, swapped
, no_overlap
, subset
, cond_inverted
;
1981 varray_type vrp_records
;
1982 struct vrp_element
*element
;
1983 struct vrp_hash_elt vrp_hash_elt
, *vrp_hash_elt_p
;
1986 /* First see if we have test of an SSA_NAME against a constant
1987 where the SSA_NAME is defined by an earlier typecast which
1988 is irrelevant when performing tests against the given
1990 if (TREE_CODE (cond
) == EQ_EXPR
|| TREE_CODE (cond
) == NE_EXPR
)
1992 tree new_cond
= find_equivalent_equality_comparison (cond
);
1996 /* Update the statement to use the new equivalent
1998 COND_EXPR_COND (stmt
) = new_cond
;
2000 /* If this is not a real stmt, ann will be NULL and we
2001 avoid processing the operands. */
2005 /* Lookup the condition and return its known value if it
2007 new_cond
= lookup_avail_expr (stmt
, insert
);
2011 /* The operands have changed, so update op0 and op1. */
2012 op0
= TREE_OPERAND (cond
, 0);
2013 op1
= TREE_OPERAND (cond
, 1);
2017 /* Consult the value range records for this variable (if they exist)
2018 to see if we can eliminate or simplify this conditional.
2020 Note two tests are necessary to determine no records exist.
2021 First we have to see if the virtual array exists, if it
2022 exists, then we have to check its active size.
2024 Also note the vast majority of conditionals are not testing
2025 a variable which has had its range constrained by an earlier
2026 conditional. So this filter avoids a lot of unnecessary work. */
2027 vrp_hash_elt
.var
= op0
;
2028 vrp_hash_elt
.records
= NULL
;
2029 slot
= htab_find_slot (vrp_data
, &vrp_hash_elt
, NO_INSERT
);
2033 vrp_hash_elt_p
= (struct vrp_hash_elt
*) *slot
;
2034 vrp_records
= vrp_hash_elt_p
->records
;
2035 if (vrp_records
== NULL
)
2038 limit
= VARRAY_ACTIVE_SIZE (vrp_records
);
2040 /* If we have no value range records for this variable, or we are
2041 unable to extract a range for this condition, then there is
2044 || ! extract_range_from_cond (cond
, &cond_high
,
2045 &cond_low
, &cond_inverted
))
2048 /* We really want to avoid unnecessary computations of range
2049 info. So all ranges are computed lazily; this avoids a
2050 lot of unnecessary work. i.e., we record the conditional,
2051 but do not process how it constrains the variable's
2052 potential values until we know that processing the condition
2055 However, we do not want to have to walk a potentially long
2056 list of ranges, nor do we want to compute a variable's
2057 range more than once for a given path.
2059 Luckily, each time we encounter a conditional that can not
2060 be otherwise optimized we will end up here and we will
2061 compute the necessary range information for the variable
2062 used in this condition.
2064 Thus you can conclude that there will never be more than one
2065 conditional associated with a variable which has not been
2066 processed. So we never need to merge more than one new
2067 conditional into the current range.
2069 These properties also help us avoid unnecessary work. */
2071 = (struct vrp_element
*)VARRAY_GENERIC_PTR (vrp_records
, limit
- 1);
2073 if (element
->high
&& element
->low
)
2075 /* The last element has been processed, so there is no range
2076 merging to do, we can simply use the high/low values
2077 recorded in the last element. */
2079 high
= element
->high
;
2083 tree tmp_high
, tmp_low
;
2086 /* The last element has not been processed. Process it now.
2087 record_range should ensure for cond inverted is not set.
2088 This call can only fail if cond is x < min or x > max,
2089 which fold should have optimized into false.
2090 If that doesn't happen, just pretend all values are
2092 if (! extract_range_from_cond (element
->cond
, &tmp_high
,
2096 gcc_assert (dummy
== 0);
2098 /* If this is the only element, then no merging is necessary,
2099 the high/low values from extract_range_from_cond are all
2108 /* Get the high/low value from the previous element. */
2109 struct vrp_element
*prev
2110 = (struct vrp_element
*)VARRAY_GENERIC_PTR (vrp_records
,
2115 /* Merge in this element's range with the range from the
2118 The low value for the merged range is the maximum of
2119 the previous low value and the low value of this record.
2121 Similarly the high value for the merged range is the
2122 minimum of the previous high value and the high value of
2124 low
= (tree_int_cst_compare (low
, tmp_low
) == 1
2126 high
= (tree_int_cst_compare (high
, tmp_high
) == -1
2130 /* And record the computed range. */
2132 element
->high
= high
;
2136 /* After we have constrained this variable's potential values,
2137 we try to determine the result of the given conditional.
2139 To simplify later tests, first determine if the current
2140 low value is the same low value as the conditional.
2141 Similarly for the current high value and the high value
2142 for the conditional. */
2143 lowequal
= tree_int_cst_equal (low
, cond_low
);
2144 highequal
= tree_int_cst_equal (high
, cond_high
);
2146 if (lowequal
&& highequal
)
2147 return (cond_inverted
? boolean_false_node
: boolean_true_node
);
2149 /* To simplify the overlap/subset tests below we may want
2150 to swap the two ranges so that the larger of the two
2151 ranges occurs "first". */
2153 if (tree_int_cst_compare (low
, cond_low
) == 1
2155 && tree_int_cst_compare (cond_high
, high
) == 1))
2168 /* Now determine if there is no overlap in the ranges
2169 or if the second range is a subset of the first range. */
2170 no_overlap
= tree_int_cst_lt (high
, cond_low
);
2171 subset
= tree_int_cst_compare (cond_high
, high
) != 1;
2173 /* If there was no overlap in the ranges, then this conditional
2174 always has a false value (unless we had to invert this
2175 conditional, in which case it always has a true value). */
2177 return (cond_inverted
? boolean_true_node
: boolean_false_node
);
2179 /* If the current range is a subset of the condition's range,
2180 then this conditional always has a true value (unless we
2181 had to invert this conditional, in which case it always
2182 has a true value). */
2183 if (subset
&& swapped
)
2184 return (cond_inverted
? boolean_false_node
: boolean_true_node
);
2186 /* We were unable to determine the result of the conditional.
2187 However, we may be able to simplify the conditional. First
2188 merge the ranges in the same manner as range merging above. */
2189 low
= tree_int_cst_compare (low
, cond_low
) == 1 ? low
: cond_low
;
2190 high
= tree_int_cst_compare (high
, cond_high
) == -1 ? high
: cond_high
;
2192 /* If the range has converged to a single point, then turn this
2193 into an equality comparison. */
2194 if (TREE_CODE (cond
) != EQ_EXPR
2195 && TREE_CODE (cond
) != NE_EXPR
2196 && tree_int_cst_equal (low
, high
))
2198 TREE_SET_CODE (cond
, EQ_EXPR
);
2199 TREE_OPERAND (cond
, 1) = high
;
2206 /* STMT is a SWITCH_EXPR for which we could not trivially determine its
2207 result. This routine attempts to find equivalent forms of the
2208 condition which we may be able to optimize better. */
2211 simplify_switch_and_lookup_avail_expr (tree stmt
, int insert
)
2213 tree cond
= SWITCH_COND (stmt
);
2216 /* The optimization that we really care about is removing unnecessary
2217 casts. That will let us do much better in propagating the inferred
2218 constant at the switch target. */
2219 if (TREE_CODE (cond
) == SSA_NAME
)
2221 def
= SSA_NAME_DEF_STMT (cond
);
2222 if (TREE_CODE (def
) == MODIFY_EXPR
)
2224 def
= TREE_OPERAND (def
, 1);
2225 if (TREE_CODE (def
) == NOP_EXPR
)
2230 def
= TREE_OPERAND (def
, 0);
2232 #ifdef ENABLE_CHECKING
2233 /* ??? Why was Jeff testing this? We are gimple... */
2234 gcc_assert (is_gimple_val (def
));
2237 to
= TREE_TYPE (cond
);
2238 ti
= TREE_TYPE (def
);
2240 /* If we have an extension that preserves value, then we
2241 can copy the source value into the switch. */
2243 need_precision
= TYPE_PRECISION (ti
);
2245 if (TYPE_UNSIGNED (to
) && !TYPE_UNSIGNED (ti
))
2247 else if (!TYPE_UNSIGNED (to
) && TYPE_UNSIGNED (ti
))
2248 need_precision
+= 1;
2249 if (TYPE_PRECISION (to
) < need_precision
)
2254 SWITCH_COND (stmt
) = def
;
2257 return lookup_avail_expr (stmt
, insert
);
2267 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2268 known value for that SSA_NAME (or NULL if no value is known).
2270 NONZERO_VARS is the set SSA_NAMES known to have a nonzero value,
2271 even if we don't know their precise value.
2273 Propagate values from CONST_AND_COPIES and NONZERO_VARS into the PHI
2274 nodes of the successors of BB. */
2277 cprop_into_successor_phis (basic_block bb
, bitmap nonzero_vars
)
2282 /* This can get rather expensive if the implementation is naive in
2283 how it finds the phi alternative associated with a particular edge. */
2284 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
2289 /* If this is an abnormal edge, then we do not want to copy propagate
2290 into the PHI alternative associated with this edge. */
2291 if (e
->flags
& EDGE_ABNORMAL
)
2294 phi
= phi_nodes (e
->dest
);
2299 for ( ; phi
; phi
= PHI_CHAIN (phi
))
2302 use_operand_p orig_p
;
2305 /* The alternative may be associated with a constant, so verify
2306 it is an SSA_NAME before doing anything with it. */
2307 orig_p
= PHI_ARG_DEF_PTR (phi
, indx
);
2308 orig
= USE_FROM_PTR (orig_p
);
2309 if (TREE_CODE (orig
) != SSA_NAME
)
2312 /* If the alternative is known to have a nonzero value, record
2313 that fact in the PHI node itself for future use. */
2314 if (bitmap_bit_p (nonzero_vars
, SSA_NAME_VERSION (orig
)))
2315 PHI_ARG_NONZERO (phi
, indx
) = true;
2317 /* If we have *ORIG_P in our constant/copy table, then replace
2318 ORIG_P with its value in our constant/copy table. */
2319 new = SSA_NAME_VALUE (orig
);
2321 && (TREE_CODE (new) == SSA_NAME
2322 || is_gimple_min_invariant (new))
2323 && may_propagate_copy (orig
, new))
2325 propagate_value (orig_p
, new);
2331 /* We have finished optimizing BB, record any information implied by
2332 taking a specific outgoing edge from BB. */
2335 record_edge_info (basic_block bb
)
2337 block_stmt_iterator bsi
= bsi_last (bb
);
2338 struct edge_info
*edge_info
;
2340 if (! bsi_end_p (bsi
))
2342 tree stmt
= bsi_stmt (bsi
);
2344 if (stmt
&& TREE_CODE (stmt
) == SWITCH_EXPR
)
2346 tree cond
= SWITCH_COND (stmt
);
2348 if (TREE_CODE (cond
) == SSA_NAME
)
2350 tree labels
= SWITCH_LABELS (stmt
);
2351 int i
, n_labels
= TREE_VEC_LENGTH (labels
);
2352 tree
*info
= xcalloc (n_basic_blocks
, sizeof (tree
));
2356 for (i
= 0; i
< n_labels
; i
++)
2358 tree label
= TREE_VEC_ELT (labels
, i
);
2359 basic_block target_bb
= label_to_block (CASE_LABEL (label
));
2361 if (CASE_HIGH (label
)
2362 || !CASE_LOW (label
)
2363 || info
[target_bb
->index
])
2364 info
[target_bb
->index
] = error_mark_node
;
2366 info
[target_bb
->index
] = label
;
2369 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
2371 basic_block target_bb
= e
->dest
;
2372 tree node
= info
[target_bb
->index
];
2374 if (node
!= NULL
&& node
!= error_mark_node
)
2376 tree x
= fold_convert (TREE_TYPE (cond
), CASE_LOW (node
));
2377 edge_info
= allocate_edge_info (e
);
2378 edge_info
->lhs
= cond
;
2386 /* A COND_EXPR may create equivalences too. */
2387 if (stmt
&& TREE_CODE (stmt
) == COND_EXPR
)
2389 tree cond
= COND_EXPR_COND (stmt
);
2393 extract_true_false_edges_from_block (bb
, &true_edge
, &false_edge
);
2395 /* If the conditional is a single variable 'X', record 'X = 1'
2396 for the true edge and 'X = 0' on the false edge. */
2397 if (SSA_VAR_P (cond
))
2399 struct edge_info
*edge_info
;
2401 edge_info
= allocate_edge_info (true_edge
);
2402 edge_info
->lhs
= cond
;
2403 edge_info
->rhs
= constant_boolean_node (1, TREE_TYPE (cond
));
2405 edge_info
= allocate_edge_info (false_edge
);
2406 edge_info
->lhs
= cond
;
2407 edge_info
->rhs
= constant_boolean_node (0, TREE_TYPE (cond
));
2409 /* Equality tests may create one or two equivalences. */
2410 else if (COMPARISON_CLASS_P (cond
))
2412 tree op0
= TREE_OPERAND (cond
, 0);
2413 tree op1
= TREE_OPERAND (cond
, 1);
2415 /* Special case comparing booleans against a constant as we
2416 know the value of OP0 on both arms of the branch. i.e., we
2417 can record an equivalence for OP0 rather than COND. */
2418 if ((TREE_CODE (cond
) == EQ_EXPR
|| TREE_CODE (cond
) == NE_EXPR
)
2419 && TREE_CODE (op0
) == SSA_NAME
2420 && TREE_CODE (TREE_TYPE (op0
)) == BOOLEAN_TYPE
2421 && is_gimple_min_invariant (op1
))
2423 if (TREE_CODE (cond
) == EQ_EXPR
)
2425 edge_info
= allocate_edge_info (true_edge
);
2426 edge_info
->lhs
= op0
;
2427 edge_info
->rhs
= (integer_zerop (op1
)
2428 ? boolean_false_node
2429 : boolean_true_node
);
2431 edge_info
= allocate_edge_info (false_edge
);
2432 edge_info
->lhs
= op0
;
2433 edge_info
->rhs
= (integer_zerop (op1
)
2435 : boolean_false_node
);
2439 edge_info
= allocate_edge_info (true_edge
);
2440 edge_info
->lhs
= op0
;
2441 edge_info
->rhs
= (integer_zerop (op1
)
2443 : boolean_false_node
);
2445 edge_info
= allocate_edge_info (false_edge
);
2446 edge_info
->lhs
= op0
;
2447 edge_info
->rhs
= (integer_zerop (op1
)
2448 ? boolean_false_node
2449 : boolean_true_node
);
2453 else if (is_gimple_min_invariant (op0
)
2454 && (TREE_CODE (op1
) == SSA_NAME
2455 || is_gimple_min_invariant (op1
)))
2457 tree inverted
= invert_truthvalue (cond
);
2458 struct edge_info
*edge_info
;
2460 edge_info
= allocate_edge_info (true_edge
);
2461 record_conditions (edge_info
, cond
, inverted
);
2463 if (TREE_CODE (cond
) == EQ_EXPR
)
2465 edge_info
->lhs
= op1
;
2466 edge_info
->rhs
= op0
;
2469 edge_info
= allocate_edge_info (false_edge
);
2470 record_conditions (edge_info
, inverted
, cond
);
2472 if (TREE_CODE (cond
) == NE_EXPR
)
2474 edge_info
->lhs
= op1
;
2475 edge_info
->rhs
= op0
;
2479 else if (TREE_CODE (op0
) == SSA_NAME
2480 && (is_gimple_min_invariant (op1
)
2481 || TREE_CODE (op1
) == SSA_NAME
))
2483 tree inverted
= invert_truthvalue (cond
);
2484 struct edge_info
*edge_info
;
2486 edge_info
= allocate_edge_info (true_edge
);
2487 record_conditions (edge_info
, cond
, inverted
);
2489 if (TREE_CODE (cond
) == EQ_EXPR
)
2491 edge_info
->lhs
= op0
;
2492 edge_info
->rhs
= op1
;
2495 edge_info
= allocate_edge_info (false_edge
);
2496 record_conditions (edge_info
, inverted
, cond
);
2498 if (TREE_CODE (cond
) == NE_EXPR
)
2500 edge_info
->lhs
= op0
;
2501 edge_info
->rhs
= op1
;
2506 /* ??? TRUTH_NOT_EXPR can create an equivalence too. */
2511 /* Propagate information from BB to its outgoing edges.
2513 This can include equivalency information implied by control statements
2514 at the end of BB and const/copy propagation into PHIs in BB's
2515 successor blocks. */
2518 propagate_to_outgoing_edges (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
2522 record_edge_info (bb
);
2523 cprop_into_successor_phis (bb
, nonzero_vars
);
2526 /* Search for redundant computations in STMT. If any are found, then
2527 replace them with the variable holding the result of the computation.
2529 If safe, record this expression into the available expression hash
2533 eliminate_redundant_computations (struct dom_walk_data
*walk_data
,
2534 tree stmt
, stmt_ann_t ann
)
2536 v_may_def_optype v_may_defs
= V_MAY_DEF_OPS (ann
);
2537 tree
*expr_p
, def
= NULL_TREE
;
2540 bool retval
= false;
2542 if (TREE_CODE (stmt
) == MODIFY_EXPR
)
2543 def
= TREE_OPERAND (stmt
, 0);
2545 /* Certain expressions on the RHS can be optimized away, but can not
2546 themselves be entered into the hash tables. */
2547 if (ann
->makes_aliased_stores
2549 || TREE_CODE (def
) != SSA_NAME
2550 || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def
)
2551 || NUM_V_MAY_DEFS (v_may_defs
) != 0)
2554 /* Check if the expression has been computed before. */
2555 cached_lhs
= lookup_avail_expr (stmt
, insert
);
2557 /* If this is an assignment and the RHS was not in the hash table,
2558 then try to simplify the RHS and lookup the new RHS in the
2560 if (! cached_lhs
&& TREE_CODE (stmt
) == MODIFY_EXPR
)
2561 cached_lhs
= simplify_rhs_and_lookup_avail_expr (walk_data
, stmt
, insert
);
2562 /* Similarly if this is a COND_EXPR and we did not find its
2563 expression in the hash table, simplify the condition and
2565 else if (! cached_lhs
&& TREE_CODE (stmt
) == COND_EXPR
)
2566 cached_lhs
= simplify_cond_and_lookup_avail_expr (stmt
, ann
, insert
);
2567 /* Similarly for a SWITCH_EXPR. */
2568 else if (!cached_lhs
&& TREE_CODE (stmt
) == SWITCH_EXPR
)
2569 cached_lhs
= simplify_switch_and_lookup_avail_expr (stmt
, insert
);
2571 opt_stats
.num_exprs_considered
++;
2573 /* Get a pointer to the expression we are trying to optimize. */
2574 if (TREE_CODE (stmt
) == COND_EXPR
)
2575 expr_p
= &COND_EXPR_COND (stmt
);
2576 else if (TREE_CODE (stmt
) == SWITCH_EXPR
)
2577 expr_p
= &SWITCH_COND (stmt
);
2578 else if (TREE_CODE (stmt
) == RETURN_EXPR
&& TREE_OPERAND (stmt
, 0))
2579 expr_p
= &TREE_OPERAND (TREE_OPERAND (stmt
, 0), 1);
2581 expr_p
= &TREE_OPERAND (stmt
, 1);
2583 /* It is safe to ignore types here since we have already done
2584 type checking in the hashing and equality routines. In fact
2585 type checking here merely gets in the way of constant
2586 propagation. Also, make sure that it is safe to propagate
2587 CACHED_LHS into *EXPR_P. */
2589 && (TREE_CODE (cached_lhs
) != SSA_NAME
2590 || may_propagate_copy (*expr_p
, cached_lhs
)))
2592 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2594 fprintf (dump_file
, " Replaced redundant expr '");
2595 print_generic_expr (dump_file
, *expr_p
, dump_flags
);
2596 fprintf (dump_file
, "' with '");
2597 print_generic_expr (dump_file
, cached_lhs
, dump_flags
);
2598 fprintf (dump_file
, "'\n");
2603 #if defined ENABLE_CHECKING
2604 gcc_assert (TREE_CODE (cached_lhs
) == SSA_NAME
2605 || is_gimple_min_invariant (cached_lhs
));
2608 if (TREE_CODE (cached_lhs
) == ADDR_EXPR
2609 || (POINTER_TYPE_P (TREE_TYPE (*expr_p
))
2610 && is_gimple_min_invariant (cached_lhs
)))
2613 propagate_tree_value (expr_p
, cached_lhs
);
2619 /* STMT, a MODIFY_EXPR, may create certain equivalences, in either
2620 the available expressions table or the const_and_copies table.
2621 Detect and record those equivalences. */
2624 record_equivalences_from_stmt (tree stmt
,
2628 tree lhs
= TREE_OPERAND (stmt
, 0);
2629 enum tree_code lhs_code
= TREE_CODE (lhs
);
2632 if (lhs_code
== SSA_NAME
)
2634 tree rhs
= TREE_OPERAND (stmt
, 1);
2636 /* Strip away any useless type conversions. */
2637 STRIP_USELESS_TYPE_CONVERSION (rhs
);
2639 /* If the RHS of the assignment is a constant or another variable that
2640 may be propagated, register it in the CONST_AND_COPIES table. We
2641 do not need to record unwind data for this, since this is a true
2642 assignment and not an equivalence inferred from a comparison. All
2643 uses of this ssa name are dominated by this assignment, so unwinding
2644 just costs time and space. */
2646 && (TREE_CODE (rhs
) == SSA_NAME
2647 || is_gimple_min_invariant (rhs
)))
2648 SSA_NAME_VALUE (lhs
) = rhs
;
2650 /* alloca never returns zero and the address of a non-weak symbol
2651 is never zero. NOP_EXPRs and CONVERT_EXPRs can be completely
2652 stripped as they do not affect this equivalence. */
2653 while (TREE_CODE (rhs
) == NOP_EXPR
2654 || TREE_CODE (rhs
) == CONVERT_EXPR
)
2655 rhs
= TREE_OPERAND (rhs
, 0);
2657 if (alloca_call_p (rhs
)
2658 || (TREE_CODE (rhs
) == ADDR_EXPR
2659 && DECL_P (TREE_OPERAND (rhs
, 0))
2660 && ! DECL_WEAK (TREE_OPERAND (rhs
, 0))))
2661 record_var_is_nonzero (lhs
);
2663 /* IOR of any value with a nonzero value will result in a nonzero
2664 value. Even if we do not know the exact result recording that
2665 the result is nonzero is worth the effort. */
2666 if (TREE_CODE (rhs
) == BIT_IOR_EXPR
2667 && integer_nonzerop (TREE_OPERAND (rhs
, 1)))
2668 record_var_is_nonzero (lhs
);
2671 /* Look at both sides for pointer dereferences. If we find one, then
2672 the pointer must be nonnull and we can enter that equivalence into
2674 if (flag_delete_null_pointer_checks
)
2675 for (i
= 0; i
< 2; i
++)
2677 tree t
= TREE_OPERAND (stmt
, i
);
2679 /* Strip away any COMPONENT_REFs. */
2680 while (TREE_CODE (t
) == COMPONENT_REF
)
2681 t
= TREE_OPERAND (t
, 0);
2683 /* Now see if this is a pointer dereference. */
2684 if (INDIRECT_REF_P (t
))
2686 tree op
= TREE_OPERAND (t
, 0);
2688 /* If the pointer is a SSA variable, then enter new
2689 equivalences into the hash table. */
2690 while (TREE_CODE (op
) == SSA_NAME
)
2692 tree def
= SSA_NAME_DEF_STMT (op
);
2694 record_var_is_nonzero (op
);
2696 /* And walk up the USE-DEF chains noting other SSA_NAMEs
2697 which are known to have a nonzero value. */
2699 && TREE_CODE (def
) == MODIFY_EXPR
2700 && TREE_CODE (TREE_OPERAND (def
, 1)) == NOP_EXPR
)
2701 op
= TREE_OPERAND (TREE_OPERAND (def
, 1), 0);
2708 /* A memory store, even an aliased store, creates a useful
2709 equivalence. By exchanging the LHS and RHS, creating suitable
2710 vops and recording the result in the available expression table,
2711 we may be able to expose more redundant loads. */
2712 if (!ann
->has_volatile_ops
2713 && (TREE_CODE (TREE_OPERAND (stmt
, 1)) == SSA_NAME
2714 || is_gimple_min_invariant (TREE_OPERAND (stmt
, 1)))
2715 && !is_gimple_reg (lhs
))
2717 tree rhs
= TREE_OPERAND (stmt
, 1);
2720 /* FIXME: If the LHS of the assignment is a bitfield and the RHS
2721 is a constant, we need to adjust the constant to fit into the
2722 type of the LHS. If the LHS is a bitfield and the RHS is not
2723 a constant, then we can not record any equivalences for this
2724 statement since we would need to represent the widening or
2725 narrowing of RHS. This fixes gcc.c-torture/execute/921016-1.c
2726 and should not be necessary if GCC represented bitfields
2728 if (lhs_code
== COMPONENT_REF
2729 && DECL_BIT_FIELD (TREE_OPERAND (lhs
, 1)))
2731 if (TREE_CONSTANT (rhs
))
2732 rhs
= widen_bitfield (rhs
, TREE_OPERAND (lhs
, 1), lhs
);
2736 /* If the value overflowed, then we can not use this equivalence. */
2737 if (rhs
&& ! is_gimple_min_invariant (rhs
))
2743 /* Build a new statement with the RHS and LHS exchanged. */
2744 new = build (MODIFY_EXPR
, TREE_TYPE (stmt
), rhs
, lhs
);
2746 create_ssa_artficial_load_stmt (&(ann
->operands
), new);
2748 /* Finally enter the statement into the available expression
2750 lookup_avail_expr (new, true);
2755 /* Replace *OP_P in STMT with any known equivalent value for *OP_P from
2756 CONST_AND_COPIES. */
2759 cprop_operand (tree stmt
, use_operand_p op_p
)
2761 bool may_have_exposed_new_symbols
= false;
2763 tree op
= USE_FROM_PTR (op_p
);
2765 /* If the operand has a known constant value or it is known to be a
2766 copy of some other variable, use the value or copy stored in
2767 CONST_AND_COPIES. */
2768 val
= SSA_NAME_VALUE (op
);
2769 if (val
&& TREE_CODE (val
) != VALUE_HANDLE
)
2771 tree op_type
, val_type
;
2773 /* Do not change the base variable in the virtual operand
2774 tables. That would make it impossible to reconstruct
2775 the renamed virtual operand if we later modify this
2776 statement. Also only allow the new value to be an SSA_NAME
2777 for propagation into virtual operands. */
2778 if (!is_gimple_reg (op
)
2779 && (get_virtual_var (val
) != get_virtual_var (op
)
2780 || TREE_CODE (val
) != SSA_NAME
))
2783 /* Do not replace hard register operands in asm statements. */
2784 if (TREE_CODE (stmt
) == ASM_EXPR
2785 && !may_propagate_copy_into_asm (op
))
2788 /* Get the toplevel type of each operand. */
2789 op_type
= TREE_TYPE (op
);
2790 val_type
= TREE_TYPE (val
);
2792 /* While both types are pointers, get the type of the object
2794 while (POINTER_TYPE_P (op_type
) && POINTER_TYPE_P (val_type
))
2796 op_type
= TREE_TYPE (op_type
);
2797 val_type
= TREE_TYPE (val_type
);
2800 /* Make sure underlying types match before propagating a constant by
2801 converting the constant to the proper type. Note that convert may
2802 return a non-gimple expression, in which case we ignore this
2803 propagation opportunity. */
2804 if (TREE_CODE (val
) != SSA_NAME
)
2806 if (!lang_hooks
.types_compatible_p (op_type
, val_type
))
2808 val
= fold_convert (TREE_TYPE (op
), val
);
2809 if (!is_gimple_min_invariant (val
))
2814 /* Certain operands are not allowed to be copy propagated due
2815 to their interaction with exception handling and some GCC
2817 else if (!may_propagate_copy (op
, val
))
2821 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2823 fprintf (dump_file
, " Replaced '");
2824 print_generic_expr (dump_file
, op
, dump_flags
);
2825 fprintf (dump_file
, "' with %s '",
2826 (TREE_CODE (val
) != SSA_NAME
? "constant" : "variable"));
2827 print_generic_expr (dump_file
, val
, dump_flags
);
2828 fprintf (dump_file
, "'\n");
2831 /* If VAL is an ADDR_EXPR or a constant of pointer type, note
2832 that we may have exposed a new symbol for SSA renaming. */
2833 if (TREE_CODE (val
) == ADDR_EXPR
2834 || (POINTER_TYPE_P (TREE_TYPE (op
))
2835 && is_gimple_min_invariant (val
)))
2836 may_have_exposed_new_symbols
= true;
2838 propagate_value (op_p
, val
);
2840 /* And note that we modified this statement. This is now
2841 safe, even if we changed virtual operands since we will
2842 rescan the statement and rewrite its operands again. */
2845 return may_have_exposed_new_symbols
;
2848 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2849 known value for that SSA_NAME (or NULL if no value is known).
2851 Propagate values from CONST_AND_COPIES into the uses, vuses and
2852 v_may_def_ops of STMT. */
2855 cprop_into_stmt (tree stmt
)
2857 bool may_have_exposed_new_symbols
= false;
2862 FOR_EACH_SSA_USE_OPERAND (op_p
, stmt
, iter
, SSA_OP_ALL_USES
)
2864 if (TREE_CODE (USE_FROM_PTR (op_p
)) == SSA_NAME
)
2865 may_have_exposed_new_symbols
|= cprop_operand (stmt
, op_p
);
2868 if (may_have_exposed_new_symbols
)
2870 rhs
= get_rhs (stmt
);
2871 if (rhs
&& TREE_CODE (rhs
) == ADDR_EXPR
)
2872 recompute_tree_invarant_for_addr_expr (rhs
);
2875 return may_have_exposed_new_symbols
;
2879 /* Optimize the statement pointed by iterator SI.
2881 We try to perform some simplistic global redundancy elimination and
2882 constant propagation:
2884 1- To detect global redundancy, we keep track of expressions that have
2885 been computed in this block and its dominators. If we find that the
2886 same expression is computed more than once, we eliminate repeated
2887 computations by using the target of the first one.
2889 2- Constant values and copy assignments. This is used to do very
2890 simplistic constant and copy propagation. When a constant or copy
2891 assignment is found, we map the value on the RHS of the assignment to
2892 the variable in the LHS in the CONST_AND_COPIES table. */
2895 optimize_stmt (struct dom_walk_data
*walk_data
, basic_block bb
,
2896 block_stmt_iterator si
)
2900 bool may_optimize_p
;
2901 bool may_have_exposed_new_symbols
= false;
2903 stmt
= bsi_stmt (si
);
2905 get_stmt_operands (stmt
);
2906 ann
= stmt_ann (stmt
);
2907 opt_stats
.num_stmts
++;
2908 may_have_exposed_new_symbols
= false;
2910 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2912 fprintf (dump_file
, "Optimizing statement ");
2913 print_generic_stmt (dump_file
, stmt
, TDF_SLIM
);
2916 /* Const/copy propagate into USES, VUSES and the RHS of V_MAY_DEFs. */
2917 may_have_exposed_new_symbols
= cprop_into_stmt (stmt
);
2919 /* If the statement has been modified with constant replacements,
2920 fold its RHS before checking for redundant computations. */
2923 /* Try to fold the statement making sure that STMT is kept
2925 if (fold_stmt (bsi_stmt_ptr (si
)))
2927 stmt
= bsi_stmt (si
);
2928 ann
= stmt_ann (stmt
);
2930 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2932 fprintf (dump_file
, " Folded to: ");
2933 print_generic_stmt (dump_file
, stmt
, TDF_SLIM
);
2937 /* Constant/copy propagation above may change the set of
2938 virtual operands associated with this statement. Folding
2939 may remove the need for some virtual operands.
2941 Indicate we will need to rescan and rewrite the statement. */
2942 may_have_exposed_new_symbols
= true;
2945 /* Check for redundant computations. Do this optimization only
2946 for assignments that have no volatile ops and conditionals. */
2947 may_optimize_p
= (!ann
->has_volatile_ops
2948 && ((TREE_CODE (stmt
) == RETURN_EXPR
2949 && TREE_OPERAND (stmt
, 0)
2950 && TREE_CODE (TREE_OPERAND (stmt
, 0)) == MODIFY_EXPR
2951 && ! (TREE_SIDE_EFFECTS
2952 (TREE_OPERAND (TREE_OPERAND (stmt
, 0), 1))))
2953 || (TREE_CODE (stmt
) == MODIFY_EXPR
2954 && ! TREE_SIDE_EFFECTS (TREE_OPERAND (stmt
, 1)))
2955 || TREE_CODE (stmt
) == COND_EXPR
2956 || TREE_CODE (stmt
) == SWITCH_EXPR
));
2959 may_have_exposed_new_symbols
2960 |= eliminate_redundant_computations (walk_data
, stmt
, ann
);
2962 /* Record any additional equivalences created by this statement. */
2963 if (TREE_CODE (stmt
) == MODIFY_EXPR
)
2964 record_equivalences_from_stmt (stmt
,
2968 register_definitions_for_stmt (stmt
);
2970 /* If STMT is a COND_EXPR and it was modified, then we may know
2971 where it goes. If that is the case, then mark the CFG as altered.
2973 This will cause us to later call remove_unreachable_blocks and
2974 cleanup_tree_cfg when it is safe to do so. It is not safe to
2975 clean things up here since removal of edges and such can trigger
2976 the removal of PHI nodes, which in turn can release SSA_NAMEs to
2979 That's all fine and good, except that once SSA_NAMEs are released
2980 to the manager, we must not call create_ssa_name until all references
2981 to released SSA_NAMEs have been eliminated.
2983 All references to the deleted SSA_NAMEs can not be eliminated until
2984 we remove unreachable blocks.
2986 We can not remove unreachable blocks until after we have completed
2987 any queued jump threading.
2989 We can not complete any queued jump threads until we have taken
2990 appropriate variables out of SSA form. Taking variables out of
2991 SSA form can call create_ssa_name and thus we lose.
2993 Ultimately I suspect we're going to need to change the interface
2994 into the SSA_NAME manager. */
3000 if (TREE_CODE (stmt
) == COND_EXPR
)
3001 val
= COND_EXPR_COND (stmt
);
3002 else if (TREE_CODE (stmt
) == SWITCH_EXPR
)
3003 val
= SWITCH_COND (stmt
);
3005 if (val
&& TREE_CODE (val
) == INTEGER_CST
&& find_taken_edge (bb
, val
))
3008 /* If we simplified a statement in such a way as to be shown that it
3009 cannot trap, update the eh information and the cfg to match. */
3010 if (maybe_clean_eh_stmt (stmt
))
3012 bitmap_set_bit (need_eh_cleanup
, bb
->index
);
3013 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3014 fprintf (dump_file
, " Flagged to clear EH edges.\n");
3018 if (may_have_exposed_new_symbols
)
3019 VEC_safe_push (tree_on_heap
, stmts_to_rescan
, bsi_stmt (si
));
3022 /* Replace the RHS of STMT with NEW_RHS. If RHS can be found in the
3023 available expression hashtable, then return the LHS from the hash
3026 If INSERT is true, then we also update the available expression
3027 hash table to account for the changes made to STMT. */
3030 update_rhs_and_lookup_avail_expr (tree stmt
, tree new_rhs
, bool insert
)
3032 tree cached_lhs
= NULL
;
3034 /* Remove the old entry from the hash table. */
3037 struct expr_hash_elt element
;
3039 initialize_hash_element (stmt
, NULL
, &element
);
3040 htab_remove_elt_with_hash (avail_exprs
, &element
, element
.hash
);
3043 /* Now update the RHS of the assignment. */
3044 TREE_OPERAND (stmt
, 1) = new_rhs
;
3046 /* Now lookup the updated statement in the hash table. */
3047 cached_lhs
= lookup_avail_expr (stmt
, insert
);
3049 /* We have now called lookup_avail_expr twice with two different
3050 versions of this same statement, once in optimize_stmt, once here.
3052 We know the call in optimize_stmt did not find an existing entry
3053 in the hash table, so a new entry was created. At the same time
3054 this statement was pushed onto the AVAIL_EXPRS_STACK vector.
3056 If this call failed to find an existing entry on the hash table,
3057 then the new version of this statement was entered into the
3058 hash table. And this statement was pushed onto BLOCK_AVAIL_EXPR
3059 for the second time. So there are two copies on BLOCK_AVAIL_EXPRs
3061 If this call succeeded, we still have one copy of this statement
3062 on the BLOCK_AVAIL_EXPRs vector.
3064 For both cases, we need to pop the most recent entry off the
3065 BLOCK_AVAIL_EXPRs vector. For the case where we never found this
3066 statement in the hash tables, that will leave precisely one
3067 copy of this statement on BLOCK_AVAIL_EXPRs. For the case where
3068 we found a copy of this statement in the second hash table lookup
3069 we want _no_ copies of this statement in BLOCK_AVAIL_EXPRs. */
3071 VEC_pop (tree_on_heap
, avail_exprs_stack
);
3073 /* And make sure we record the fact that we modified this
3080 /* Search for an existing instance of STMT in the AVAIL_EXPRS table. If
3081 found, return its LHS. Otherwise insert STMT in the table and return
3084 Also, when an expression is first inserted in the AVAIL_EXPRS table, it
3085 is also added to the stack pointed by BLOCK_AVAIL_EXPRS_P, so that they
3086 can be removed when we finish processing this block and its children.
3088 NOTE: This function assumes that STMT is a MODIFY_EXPR node that
3089 contains no CALL_EXPR on its RHS and makes no volatile nor
3090 aliased references. */
3093 lookup_avail_expr (tree stmt
, bool insert
)
3098 struct expr_hash_elt
*element
= xcalloc (sizeof (struct expr_hash_elt
), 1);
3100 lhs
= TREE_CODE (stmt
) == MODIFY_EXPR
? TREE_OPERAND (stmt
, 0) : NULL
;
3102 initialize_hash_element (stmt
, lhs
, element
);
3104 /* Don't bother remembering constant assignments and copy operations.
3105 Constants and copy operations are handled by the constant/copy propagator
3106 in optimize_stmt. */
3107 if (TREE_CODE (element
->rhs
) == SSA_NAME
3108 || is_gimple_min_invariant (element
->rhs
))
3114 /* If this is an equality test against zero, see if we have recorded a
3115 nonzero value for the variable in question. */
3116 if ((TREE_CODE (element
->rhs
) == EQ_EXPR
3117 || TREE_CODE (element
->rhs
) == NE_EXPR
)
3118 && TREE_CODE (TREE_OPERAND (element
->rhs
, 0)) == SSA_NAME
3119 && integer_zerop (TREE_OPERAND (element
->rhs
, 1)))
3121 int indx
= SSA_NAME_VERSION (TREE_OPERAND (element
->rhs
, 0));
3123 if (bitmap_bit_p (nonzero_vars
, indx
))
3125 tree t
= element
->rhs
;
3128 if (TREE_CODE (t
) == EQ_EXPR
)
3129 return boolean_false_node
;
3131 return boolean_true_node
;
3135 /* Finally try to find the expression in the main expression hash table. */
3136 slot
= htab_find_slot_with_hash (avail_exprs
, element
, element
->hash
,
3137 (insert
? INSERT
: NO_INSERT
));
3146 *slot
= (void *) element
;
3147 VEC_safe_push (tree_on_heap
, avail_exprs_stack
,
3148 stmt
? stmt
: element
->rhs
);
3152 /* Extract the LHS of the assignment so that it can be used as the current
3153 definition of another variable. */
3154 lhs
= ((struct expr_hash_elt
*)*slot
)->lhs
;
3156 /* See if the LHS appears in the CONST_AND_COPIES table. If it does, then
3157 use the value from the const_and_copies table. */
3158 if (TREE_CODE (lhs
) == SSA_NAME
)
3160 temp
= SSA_NAME_VALUE (lhs
);
3161 if (temp
&& TREE_CODE (temp
) != VALUE_HANDLE
)
3169 /* Given a condition COND, record into HI_P, LO_P and INVERTED_P the
3170 range of values that result in the conditional having a true value.
3172 Return true if we are successful in extracting a range from COND and
3173 false if we are unsuccessful. */
3176 extract_range_from_cond (tree cond
, tree
*hi_p
, tree
*lo_p
, int *inverted_p
)
3178 tree op1
= TREE_OPERAND (cond
, 1);
3179 tree high
, low
, type
;
3182 /* Experiments have shown that it's rarely, if ever useful to
3183 record ranges for enumerations. Presumably this is due to
3184 the fact that they're rarely used directly. They are typically
3185 cast into an integer type and used that way. */
3186 if (TREE_CODE (TREE_TYPE (op1
)) != INTEGER_TYPE
)
3189 type
= TREE_TYPE (op1
);
3191 switch (TREE_CODE (cond
))
3205 high
= TYPE_MAX_VALUE (type
);
3210 high
= TYPE_MAX_VALUE (type
);
3211 if (!tree_int_cst_lt (op1
, high
))
3213 low
= int_const_binop (PLUS_EXPR
, op1
, integer_one_node
, 1);
3219 low
= TYPE_MIN_VALUE (type
);
3224 low
= TYPE_MIN_VALUE (type
);
3225 if (!tree_int_cst_lt (low
, op1
))
3227 high
= int_const_binop (MINUS_EXPR
, op1
, integer_one_node
, 1);
3237 *inverted_p
= inverted
;
3241 /* Record a range created by COND for basic block BB. */
3244 record_range (tree cond
, basic_block bb
)
3246 enum tree_code code
= TREE_CODE (cond
);
3248 /* We explicitly ignore NE_EXPRs and all the unordered comparisons.
3249 They rarely allow for meaningful range optimizations and significantly
3250 complicate the implementation. */
3251 if ((code
== LT_EXPR
|| code
== LE_EXPR
|| code
== GT_EXPR
3252 || code
== GE_EXPR
|| code
== EQ_EXPR
)
3253 && TREE_CODE (TREE_TYPE (TREE_OPERAND (cond
, 1))) == INTEGER_TYPE
)
3255 struct vrp_hash_elt
*vrp_hash_elt
;
3256 struct vrp_element
*element
;
3257 varray_type
*vrp_records_p
;
3261 vrp_hash_elt
= xmalloc (sizeof (struct vrp_hash_elt
));
3262 vrp_hash_elt
->var
= TREE_OPERAND (cond
, 0);
3263 vrp_hash_elt
->records
= NULL
;
3264 slot
= htab_find_slot (vrp_data
, vrp_hash_elt
, INSERT
);
3267 *slot
= (void *) vrp_hash_elt
;
3269 free (vrp_hash_elt
);
3271 vrp_hash_elt
= (struct vrp_hash_elt
*) *slot
;
3272 vrp_records_p
= &vrp_hash_elt
->records
;
3274 element
= ggc_alloc (sizeof (struct vrp_element
));
3275 element
->low
= NULL
;
3276 element
->high
= NULL
;
3277 element
->cond
= cond
;
3280 if (*vrp_records_p
== NULL
)
3281 VARRAY_GENERIC_PTR_INIT (*vrp_records_p
, 2, "vrp records");
3283 VARRAY_PUSH_GENERIC_PTR (*vrp_records_p
, element
);
3284 VEC_safe_push (tree_on_heap
, vrp_variables_stack
, TREE_OPERAND (cond
, 0));
3288 /* Hashing and equality functions for VRP_DATA.
3290 Since this hash table is addressed by SSA_NAMEs, we can hash on
3291 their version number and equality can be determined with a
3292 pointer comparison. */
3295 vrp_hash (const void *p
)
3297 tree var
= ((struct vrp_hash_elt
*)p
)->var
;
3299 return SSA_NAME_VERSION (var
);
3303 vrp_eq (const void *p1
, const void *p2
)
3305 tree var1
= ((struct vrp_hash_elt
*)p1
)->var
;
3306 tree var2
= ((struct vrp_hash_elt
*)p2
)->var
;
3308 return var1
== var2
;
3311 /* Hashing and equality functions for AVAIL_EXPRS. The table stores
3312 MODIFY_EXPR statements. We compute a value number for expressions using
3313 the code of the expression and the SSA numbers of its operands. */
3316 avail_expr_hash (const void *p
)
3318 stmt_ann_t ann
= ((struct expr_hash_elt
*)p
)->ann
;
3319 tree rhs
= ((struct expr_hash_elt
*)p
)->rhs
;
3324 /* iterative_hash_expr knows how to deal with any expression and
3325 deals with commutative operators as well, so just use it instead
3326 of duplicating such complexities here. */
3327 val
= iterative_hash_expr (rhs
, val
);
3329 /* If the hash table entry is not associated with a statement, then we
3330 can just hash the expression and not worry about virtual operands
3335 /* Add the SSA version numbers of every vuse operand. This is important
3336 because compound variables like arrays are not renamed in the
3337 operands. Rather, the rename is done on the virtual variable
3338 representing all the elements of the array. */
3339 vuses
= VUSE_OPS (ann
);
3340 for (i
= 0; i
< NUM_VUSES (vuses
); i
++)
3341 val
= iterative_hash_expr (VUSE_OP (vuses
, i
), val
);
3347 real_avail_expr_hash (const void *p
)
3349 return ((const struct expr_hash_elt
*)p
)->hash
;
3353 avail_expr_eq (const void *p1
, const void *p2
)
3355 stmt_ann_t ann1
= ((struct expr_hash_elt
*)p1
)->ann
;
3356 tree rhs1
= ((struct expr_hash_elt
*)p1
)->rhs
;
3357 stmt_ann_t ann2
= ((struct expr_hash_elt
*)p2
)->ann
;
3358 tree rhs2
= ((struct expr_hash_elt
*)p2
)->rhs
;
3360 /* If they are the same physical expression, return true. */
3361 if (rhs1
== rhs2
&& ann1
== ann2
)
3364 /* If their codes are not equal, then quit now. */
3365 if (TREE_CODE (rhs1
) != TREE_CODE (rhs2
))
3368 /* In case of a collision, both RHS have to be identical and have the
3369 same VUSE operands. */
3370 if ((TREE_TYPE (rhs1
) == TREE_TYPE (rhs2
)
3371 || lang_hooks
.types_compatible_p (TREE_TYPE (rhs1
), TREE_TYPE (rhs2
)))
3372 && operand_equal_p (rhs1
, rhs2
, OEP_PURE_SAME
))
3374 vuse_optype ops1
= NULL
;
3375 vuse_optype ops2
= NULL
;
3376 size_t num_ops1
= 0;
3377 size_t num_ops2
= 0;
3382 ops1
= VUSE_OPS (ann1
);
3383 num_ops1
= NUM_VUSES (ops1
);
3388 ops2
= VUSE_OPS (ann2
);
3389 num_ops2
= NUM_VUSES (ops2
);
3392 /* If the number of virtual uses is different, then we consider
3394 if (num_ops1
!= num_ops2
)
3397 for (i
= 0; i
< num_ops1
; i
++)
3398 if (VUSE_OP (ops1
, i
) != VUSE_OP (ops2
, i
))
3401 gcc_assert (((struct expr_hash_elt
*)p1
)->hash
3402 == ((struct expr_hash_elt
*)p2
)->hash
);
3409 /* Given STMT and a pointer to the block local definitions BLOCK_DEFS_P,
3410 register register all objects set by this statement into BLOCK_DEFS_P
3414 register_definitions_for_stmt (tree stmt
)
3419 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_ALL_DEFS
)
3422 /* FIXME: We shouldn't be registering new defs if the variable
3423 doesn't need to be renamed. */
3424 register_new_def (def
, &block_defs_stack
);