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, 51 Franklin Street, Fifth Floor,
20 Boston, MA 02110-1301, 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
,heap
) *avail_exprs_stack
;
98 /* Stack of statements we need to rescan during finalization for newly
101 Statement rescanning must occur after the current block's available
102 expressions are removed from AVAIL_EXPRS. Else we may change the
103 hash code for an expression and be unable to find/remove it from
105 static VEC(tree
,heap
) *stmts_to_rescan
;
107 /* Structure for entries in the expression hash table.
109 This requires more memory for the hash table entries, but allows us
110 to avoid creating silly tree nodes and annotations for conditionals,
111 eliminates 2 global hash tables and two block local varrays.
113 It also allows us to reduce the number of hash table lookups we
114 have to perform in lookup_avail_expr and finally it allows us to
115 significantly reduce the number of calls into the hashing routine
120 /* The value (lhs) of this expression. */
123 /* The expression (rhs) we want to record. */
126 /* The stmt pointer if this element corresponds to a statement. */
129 /* The hash value for RHS/ann. */
133 /* Stack of dest,src pairs that need to be restored during finalization.
135 A NULL entry is used to mark the end of pairs which need to be
136 restored during finalization of this block. */
137 static VEC(tree
,heap
) *const_and_copies_stack
;
139 /* Bitmap of SSA_NAMEs known to have a nonzero value, even if we do not
140 know their exact value. */
141 static bitmap nonzero_vars
;
143 /* Bitmap of blocks that are scheduled to be threaded through. This
144 is used to communicate with thread_through_blocks. */
145 static bitmap threaded_blocks
;
147 /* Stack of SSA_NAMEs which need their NONZERO_VARS property cleared
148 when the current block is finalized.
150 A NULL entry is used to mark the end of names needing their
151 entry in NONZERO_VARS cleared during finalization of this block. */
152 static VEC(tree
,heap
) *nonzero_vars_stack
;
154 /* Track whether or not we have changed the control flow graph. */
155 static bool cfg_altered
;
157 /* Bitmap of blocks that have had EH statements cleaned. We should
158 remove their dead edges eventually. */
159 static bitmap need_eh_cleanup
;
161 /* Statistics for dominator optimizations. */
165 long num_exprs_considered
;
171 static struct opt_stats_d opt_stats
;
173 /* Value range propagation record. Each time we encounter a conditional
174 of the form SSA_NAME COND CONST we create a new vrp_element to record
175 how the condition affects the possible values SSA_NAME may have.
177 Each record contains the condition tested (COND), and the range of
178 values the variable may legitimately have if COND is true. Note the
179 range of values may be a smaller range than COND specifies if we have
180 recorded other ranges for this variable. Each record also contains the
181 block in which the range was recorded for invalidation purposes.
183 Note that the current known range is computed lazily. This allows us
184 to avoid the overhead of computing ranges which are never queried.
186 When we encounter a conditional, we look for records which constrain
187 the SSA_NAME used in the condition. In some cases those records allow
188 us to determine the condition's result at compile time. In other cases
189 they may allow us to simplify the condition.
191 We also use value ranges to do things like transform signed div/mod
192 operations into unsigned div/mod or to simplify ABS_EXPRs.
194 Simple experiments have shown these optimizations to not be all that
195 useful on switch statements (much to my surprise). So switch statement
196 optimizations are not performed.
198 Note carefully we do not propagate information through each statement
199 in the block. i.e., if we know variable X has a value defined of
200 [0, 25] and we encounter Y = X + 1, we do not track a value range
201 for Y (which would be [1, 26] if we cared). Similarly we do not
202 constrain values as we encounter narrowing typecasts, etc. */
206 /* The highest and lowest values the variable in COND may contain when
207 COND is true. Note this may not necessarily be the same values
208 tested by COND if the same variable was used in earlier conditionals.
210 Note this is computed lazily and thus can be NULL indicating that
211 the values have not been computed yet. */
215 /* The actual conditional we recorded. This is needed since we compute
219 /* The basic block where this record was created. We use this to determine
220 when to remove records. */
224 /* A hash table holding value range records (VRP_ELEMENTs) for a given
225 SSA_NAME. We used to use a varray indexed by SSA_NAME_VERSION, but
226 that gets awful wasteful, particularly since the density objects
227 with useful information is very low. */
228 static htab_t vrp_data
;
230 typedef struct vrp_element
*vrp_element_p
;
232 DEF_VEC_P(vrp_element_p
);
233 DEF_VEC_ALLOC_P(vrp_element_p
,heap
);
235 /* An entry in the VRP_DATA hash table. We record the variable and a
236 varray of VRP_ELEMENT records associated with that variable. */
240 VEC(vrp_element_p
,heap
) *records
;
243 /* Array of variables which have their values constrained by operations
244 in this basic block. We use this during finalization to know
245 which variables need their VRP data updated. */
247 /* Stack of SSA_NAMEs which had their values constrained by operations
248 in this basic block. During finalization of this block we use this
249 list to determine which variables need their VRP data updated.
251 A NULL entry marks the end of the SSA_NAMEs associated with this block. */
252 static VEC(tree
,heap
) *vrp_variables_stack
;
260 /* Local functions. */
261 static void optimize_stmt (struct dom_walk_data
*,
263 block_stmt_iterator
);
264 static tree
lookup_avail_expr (tree
, bool);
265 static hashval_t
vrp_hash (const void *);
266 static int vrp_eq (const void *, const void *);
267 static hashval_t
avail_expr_hash (const void *);
268 static hashval_t
real_avail_expr_hash (const void *);
269 static int avail_expr_eq (const void *, const void *);
270 static void htab_statistics (FILE *, htab_t
);
271 static void record_cond (tree
, tree
);
272 static void record_const_or_copy (tree
, tree
);
273 static void record_equality (tree
, tree
);
274 static tree
update_rhs_and_lookup_avail_expr (tree
, tree
, bool);
275 static tree
simplify_rhs_and_lookup_avail_expr (tree
, int);
276 static tree
simplify_cond_and_lookup_avail_expr (tree
, stmt_ann_t
, int);
277 static tree
simplify_switch_and_lookup_avail_expr (tree
, int);
278 static tree
find_equivalent_equality_comparison (tree
);
279 static void record_range (tree
, basic_block
);
280 static bool extract_range_from_cond (tree
, tree
*, tree
*, int *);
281 static void record_equivalences_from_phis (basic_block
);
282 static void record_equivalences_from_incoming_edge (basic_block
);
283 static bool eliminate_redundant_computations (tree
, stmt_ann_t
);
284 static void record_equivalences_from_stmt (tree
, int, stmt_ann_t
);
285 static void thread_across_edge (struct dom_walk_data
*, edge
);
286 static void dom_opt_finalize_block (struct dom_walk_data
*, basic_block
);
287 static void dom_opt_initialize_block (struct dom_walk_data
*, basic_block
);
288 static void propagate_to_outgoing_edges (struct dom_walk_data
*, basic_block
);
289 static void remove_local_expressions_from_table (void);
290 static void restore_vars_to_original_value (void);
291 static edge
single_incoming_edge_ignoring_loop_edges (basic_block
);
292 static void restore_nonzero_vars_to_original_value (void);
293 static inline bool unsafe_associative_fp_binop (tree
);
296 /* Local version of fold that doesn't introduce cruft. */
303 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
304 may have been added by fold, and "useless" type conversions that might
305 now be apparent due to propagation. */
306 STRIP_USELESS_TYPE_CONVERSION (t
);
311 /* Allocate an EDGE_INFO for edge E and attach it to E.
312 Return the new EDGE_INFO structure. */
314 static struct edge_info
*
315 allocate_edge_info (edge e
)
317 struct edge_info
*edge_info
;
319 edge_info
= xcalloc (1, sizeof (struct edge_info
));
325 /* Free all EDGE_INFO structures associated with edges in the CFG.
326 If a particular edge can be threaded, copy the redirection
327 target from the EDGE_INFO structure into the edge's AUX field
328 as required by code to update the CFG and SSA graph for
332 free_all_edge_infos (void)
340 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
342 struct edge_info
*edge_info
= e
->aux
;
346 e
->aux
= edge_info
->redirection_target
;
347 if (edge_info
->cond_equivalences
)
348 free (edge_info
->cond_equivalences
);
355 /* Free an instance of vrp_hash_elt. */
358 vrp_free (void *data
)
360 struct vrp_hash_elt
*elt
= data
;
361 struct VEC(vrp_element_p
,heap
) **vrp_elt
= &elt
->records
;
363 VEC_free (vrp_element_p
, heap
, *vrp_elt
);
367 /* Jump threading, redundancy elimination and const/copy propagation.
369 This pass may expose new symbols that need to be renamed into SSA. For
370 every new symbol exposed, its corresponding bit will be set in
374 tree_ssa_dominator_optimize (void)
376 struct dom_walk_data walk_data
;
378 struct loops loops_info
;
380 memset (&opt_stats
, 0, sizeof (opt_stats
));
382 /* Create our hash tables. */
383 avail_exprs
= htab_create (1024, real_avail_expr_hash
, avail_expr_eq
, free
);
384 vrp_data
= htab_create (ceil_log2 (num_ssa_names
), vrp_hash
, vrp_eq
,
386 avail_exprs_stack
= VEC_alloc (tree
, heap
, 20);
387 const_and_copies_stack
= VEC_alloc (tree
, heap
, 20);
388 nonzero_vars_stack
= VEC_alloc (tree
, heap
, 20);
389 vrp_variables_stack
= VEC_alloc (tree
, heap
, 20);
390 stmts_to_rescan
= VEC_alloc (tree
, heap
, 20);
391 nonzero_vars
= BITMAP_ALLOC (NULL
);
392 threaded_blocks
= BITMAP_ALLOC (NULL
);
393 need_eh_cleanup
= BITMAP_ALLOC (NULL
);
395 /* Setup callbacks for the generic dominator tree walker. */
396 walk_data
.walk_stmts_backward
= false;
397 walk_data
.dom_direction
= CDI_DOMINATORS
;
398 walk_data
.initialize_block_local_data
= NULL
;
399 walk_data
.before_dom_children_before_stmts
= dom_opt_initialize_block
;
400 walk_data
.before_dom_children_walk_stmts
= optimize_stmt
;
401 walk_data
.before_dom_children_after_stmts
= propagate_to_outgoing_edges
;
402 walk_data
.after_dom_children_before_stmts
= NULL
;
403 walk_data
.after_dom_children_walk_stmts
= NULL
;
404 walk_data
.after_dom_children_after_stmts
= dom_opt_finalize_block
;
405 /* Right now we only attach a dummy COND_EXPR to the global data pointer.
406 When we attach more stuff we'll need to fill this out with a real
408 walk_data
.global_data
= NULL
;
409 walk_data
.block_local_data_size
= 0;
410 walk_data
.interesting_blocks
= NULL
;
412 /* Now initialize the dominator walker. */
413 init_walk_dominator_tree (&walk_data
);
415 calculate_dominance_info (CDI_DOMINATORS
);
417 /* We need to know which edges exit loops so that we can
418 aggressively thread through loop headers to an exit
420 flow_loops_find (&loops_info
);
421 mark_loop_exit_edges (&loops_info
);
422 flow_loops_free (&loops_info
);
424 /* Clean up the CFG so that any forwarder blocks created by loop
425 canonicalization are removed. */
427 calculate_dominance_info (CDI_DOMINATORS
);
429 /* If we prove certain blocks are unreachable, then we want to
430 repeat the dominator optimization process as PHI nodes may
431 have turned into copies which allows better propagation of
432 values. So we repeat until we do not identify any new unreachable
436 /* Optimize the dominator tree. */
439 /* We need accurate information regarding back edges in the CFG
440 for jump threading. */
441 mark_dfs_back_edges ();
443 /* Recursively walk the dominator tree optimizing statements. */
444 walk_dominator_tree (&walk_data
, ENTRY_BLOCK_PTR
);
447 block_stmt_iterator bsi
;
451 for (bsi
= bsi_start (bb
); !bsi_end_p (bsi
); bsi_next (&bsi
))
453 update_stmt_if_modified (bsi_stmt (bsi
));
458 /* If we exposed any new variables, go ahead and put them into
459 SSA form now, before we handle jump threading. This simplifies
460 interactions between rewriting of _DECL nodes into SSA form
461 and rewriting SSA_NAME nodes into SSA form after block
462 duplication and CFG manipulation. */
463 update_ssa (TODO_update_ssa
);
465 free_all_edge_infos ();
467 /* Thread jumps, creating duplicate blocks as needed. */
468 cfg_altered
|= thread_through_all_blocks (threaded_blocks
);
470 /* Removal of statements may make some EH edges dead. Purge
471 such edges from the CFG as needed. */
472 if (!bitmap_empty_p (need_eh_cleanup
))
474 cfg_altered
|= tree_purge_all_dead_eh_edges (need_eh_cleanup
);
475 bitmap_zero (need_eh_cleanup
);
479 free_dominance_info (CDI_DOMINATORS
);
481 cfg_altered
= cleanup_tree_cfg ();
483 if (rediscover_loops_after_threading
)
485 /* Rerun basic loop analysis to discover any newly
486 created loops and update the set of exit edges. */
487 rediscover_loops_after_threading
= false;
488 flow_loops_find (&loops_info
);
489 mark_loop_exit_edges (&loops_info
);
490 flow_loops_free (&loops_info
);
492 /* Remove any forwarder blocks inserted by loop
493 header canonicalization. */
497 calculate_dominance_info (CDI_DOMINATORS
);
499 update_ssa (TODO_update_ssa
);
501 /* Reinitialize the various tables. */
502 bitmap_clear (nonzero_vars
);
503 bitmap_clear (threaded_blocks
);
504 htab_empty (avail_exprs
);
505 htab_empty (vrp_data
);
507 /* Finally, remove everything except invariants in SSA_NAME_VALUE.
509 This must be done before we iterate as we might have a
510 reference to an SSA_NAME which was removed by the call to
513 Long term we will be able to let everything in SSA_NAME_VALUE
514 persist. However, for now, we know this is the safe thing to do. */
515 for (i
= 0; i
< num_ssa_names
; i
++)
517 tree name
= ssa_name (i
);
523 value
= SSA_NAME_VALUE (name
);
524 if (value
&& !is_gimple_min_invariant (value
))
525 SSA_NAME_VALUE (name
) = NULL
;
528 while (optimize
> 1 && cfg_altered
);
530 /* Debugging dumps. */
531 if (dump_file
&& (dump_flags
& TDF_STATS
))
532 dump_dominator_optimization_stats (dump_file
);
534 /* We emptied the hash table earlier, now delete it completely. */
535 htab_delete (avail_exprs
);
536 htab_delete (vrp_data
);
538 /* It is not necessary to clear CURRDEFS, REDIRECTION_EDGES, VRP_DATA,
539 CONST_AND_COPIES, and NONZERO_VARS as they all get cleared at the bottom
540 of the do-while loop above. */
542 /* And finalize the dominator walker. */
543 fini_walk_dominator_tree (&walk_data
);
545 /* Free nonzero_vars. */
546 BITMAP_FREE (nonzero_vars
);
547 BITMAP_FREE (threaded_blocks
);
548 BITMAP_FREE (need_eh_cleanup
);
550 VEC_free (tree
, heap
, avail_exprs_stack
);
551 VEC_free (tree
, heap
, const_and_copies_stack
);
552 VEC_free (tree
, heap
, nonzero_vars_stack
);
553 VEC_free (tree
, heap
, vrp_variables_stack
);
554 VEC_free (tree
, heap
, stmts_to_rescan
);
558 gate_dominator (void)
560 return flag_tree_dom
!= 0;
563 struct tree_opt_pass pass_dominator
=
566 gate_dominator
, /* gate */
567 tree_ssa_dominator_optimize
, /* execute */
570 0, /* static_pass_number */
571 TV_TREE_SSA_DOMINATOR_OPTS
, /* tv_id */
572 PROP_cfg
| PROP_ssa
| PROP_alias
, /* properties_required */
573 0, /* properties_provided */
574 0, /* properties_destroyed */
575 0, /* todo_flags_start */
578 | TODO_verify_ssa
, /* todo_flags_finish */
583 /* We are exiting E->src, see if E->dest ends with a conditional
584 jump which has a known value when reached via E.
586 Special care is necessary if E is a back edge in the CFG as we
587 will have already recorded equivalences for E->dest into our
588 various tables, including the result of the conditional at
589 the end of E->dest. Threading opportunities are severely
590 limited in that case to avoid short-circuiting the loop
593 Note it is quite common for the first block inside a loop to
594 end with a conditional which is either always true or always
595 false when reached via the loop backedge. Thus we do not want
596 to blindly disable threading across a loop backedge. */
599 thread_across_edge (struct dom_walk_data
*walk_data
, edge e
)
601 block_stmt_iterator bsi
;
605 /* If E->dest does not end with a conditional, then there is
607 bsi
= bsi_last (e
->dest
);
610 || (TREE_CODE (bsi_stmt (bsi
)) != COND_EXPR
611 && TREE_CODE (bsi_stmt (bsi
)) != GOTO_EXPR
612 && TREE_CODE (bsi_stmt (bsi
)) != SWITCH_EXPR
))
615 /* The basic idea here is to use whatever knowledge we have
616 from our dominator walk to simplify statements in E->dest,
617 with the ultimate goal being to simplify the conditional
618 at the end of E->dest.
620 Note that we must undo any changes we make to the underlying
621 statements as the simplifications we are making are control
622 flow sensitive (ie, the simplifications are valid when we
623 traverse E, but may not be valid on other paths to E->dest. */
625 /* Each PHI creates a temporary equivalence, record them. Again
626 these are context sensitive equivalences and will be removed
628 for (phi
= phi_nodes (e
->dest
); phi
; phi
= PHI_CHAIN (phi
))
630 tree src
= PHI_ARG_DEF_FROM_EDGE (phi
, e
);
631 tree dst
= PHI_RESULT (phi
);
633 /* If the desired argument is not the same as this PHI's result
634 and it is set by a PHI in E->dest, then we can not thread
637 && TREE_CODE (src
) == SSA_NAME
638 && TREE_CODE (SSA_NAME_DEF_STMT (src
)) == PHI_NODE
639 && bb_for_stmt (SSA_NAME_DEF_STMT (src
)) == e
->dest
)
642 record_const_or_copy (dst
, src
);
645 /* Try to simplify each statement in E->dest, ultimately leading to
646 a simplification of the COND_EXPR at the end of E->dest.
648 We might consider marking just those statements which ultimately
649 feed the COND_EXPR. It's not clear if the overhead of bookkeeping
650 would be recovered by trying to simplify fewer statements.
652 If we are able to simplify a statement into the form
653 SSA_NAME = (SSA_NAME | gimple invariant), then we can record
654 a context sensitive equivalency which may help us simplify
655 later statements in E->dest.
657 Failure to simplify into the form above merely means that the
658 statement provides no equivalences to help simplify later
659 statements. This does not prevent threading through E->dest. */
660 for (bsi
= bsi_start (e
->dest
); ! bsi_end_p (bsi
); bsi_next (&bsi
))
664 stmt
= bsi_stmt (bsi
);
666 /* Ignore empty statements and labels. */
667 if (IS_EMPTY_STMT (stmt
) || TREE_CODE (stmt
) == LABEL_EXPR
)
670 /* Safely handle threading across loop backedges. This is
671 over conservative, but still allows us to capture the
672 majority of the cases where we can thread across a loop
674 if ((e
->flags
& EDGE_DFS_BACK
) != 0
675 && TREE_CODE (stmt
) != COND_EXPR
676 && TREE_CODE (stmt
) != SWITCH_EXPR
)
679 /* If the statement has volatile operands, then we assume we
680 can not thread through this block. This is overly
681 conservative in some ways. */
682 if (TREE_CODE (stmt
) == ASM_EXPR
&& ASM_VOLATILE_P (stmt
))
685 /* If this is not a MODIFY_EXPR which sets an SSA_NAME to a new
686 value, then do not try to simplify this statement as it will
687 not simplify in any way that is helpful for jump threading. */
688 if (TREE_CODE (stmt
) != MODIFY_EXPR
689 || TREE_CODE (TREE_OPERAND (stmt
, 0)) != SSA_NAME
)
692 /* At this point we have a statement which assigns an RHS to an
693 SSA_VAR on the LHS. We want to try and simplify this statement
694 to expose more context sensitive equivalences which in turn may
695 allow us to simplify the condition at the end of the loop. */
696 if (TREE_CODE (TREE_OPERAND (stmt
, 1)) == SSA_NAME
)
697 cached_lhs
= TREE_OPERAND (stmt
, 1);
700 /* Copy the operands. */
704 unsigned int num
, i
= 0;
706 num
= NUM_SSA_OPERANDS (stmt
, (SSA_OP_USE
| SSA_OP_VUSE
));
707 copy
= xcalloc (num
, sizeof (tree
));
709 /* Make a copy of the uses & vuses into USES_COPY, then cprop into
711 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_USE
| SSA_OP_VUSE
)
714 tree use
= USE_FROM_PTR (use_p
);
717 if (TREE_CODE (use
) == SSA_NAME
)
718 tmp
= SSA_NAME_VALUE (use
);
719 if (tmp
&& TREE_CODE (tmp
) != VALUE_HANDLE
)
720 SET_USE (use_p
, tmp
);
723 /* Try to fold/lookup the new expression. Inserting the
724 expression into the hash table is unlikely to help
725 simplify anything later, so just query the hashtable. */
726 cached_lhs
= fold (TREE_OPERAND (stmt
, 1));
727 if (TREE_CODE (cached_lhs
) != SSA_NAME
728 && !is_gimple_min_invariant (cached_lhs
))
729 cached_lhs
= lookup_avail_expr (stmt
, false);
732 /* Restore the statement's original uses/defs. */
734 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_USE
| SSA_OP_VUSE
)
735 SET_USE (use_p
, copy
[i
++]);
740 /* Record the context sensitive equivalence if we were able
741 to simplify this statement. */
743 && (TREE_CODE (cached_lhs
) == SSA_NAME
744 || is_gimple_min_invariant (cached_lhs
)))
745 record_const_or_copy (TREE_OPERAND (stmt
, 0), cached_lhs
);
748 /* If we stopped at a COND_EXPR or SWITCH_EXPR, see if we know which arm
751 && (TREE_CODE (stmt
) == COND_EXPR
752 || TREE_CODE (stmt
) == GOTO_EXPR
753 || TREE_CODE (stmt
) == SWITCH_EXPR
))
755 tree cond
, cached_lhs
;
757 /* Now temporarily cprop the operands and try to find the resulting
758 expression in the hash tables. */
759 if (TREE_CODE (stmt
) == COND_EXPR
)
760 cond
= COND_EXPR_COND (stmt
);
761 else if (TREE_CODE (stmt
) == GOTO_EXPR
)
762 cond
= GOTO_DESTINATION (stmt
);
764 cond
= SWITCH_COND (stmt
);
766 if (COMPARISON_CLASS_P (cond
))
768 tree dummy_cond
, op0
, op1
;
769 enum tree_code cond_code
;
771 op0
= TREE_OPERAND (cond
, 0);
772 op1
= TREE_OPERAND (cond
, 1);
773 cond_code
= TREE_CODE (cond
);
775 /* Get the current value of both operands. */
776 if (TREE_CODE (op0
) == SSA_NAME
)
778 tree tmp
= SSA_NAME_VALUE (op0
);
779 if (tmp
&& TREE_CODE (tmp
) != VALUE_HANDLE
)
783 if (TREE_CODE (op1
) == SSA_NAME
)
785 tree tmp
= SSA_NAME_VALUE (op1
);
786 if (tmp
&& TREE_CODE (tmp
) != VALUE_HANDLE
)
790 /* Stuff the operator and operands into our dummy conditional
791 expression, creating the dummy conditional if necessary. */
792 dummy_cond
= walk_data
->global_data
;
795 dummy_cond
= build (cond_code
, boolean_type_node
, op0
, op1
);
796 dummy_cond
= build (COND_EXPR
, void_type_node
,
797 dummy_cond
, NULL
, NULL
);
798 walk_data
->global_data
= dummy_cond
;
802 TREE_SET_CODE (COND_EXPR_COND (dummy_cond
), cond_code
);
803 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 0) = op0
;
804 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 1) = op1
;
807 /* If the conditional folds to an invariant, then we are done,
808 otherwise look it up in the hash tables. */
809 cached_lhs
= local_fold (COND_EXPR_COND (dummy_cond
));
810 if (! is_gimple_min_invariant (cached_lhs
))
812 cached_lhs
= lookup_avail_expr (dummy_cond
, false);
813 if (!cached_lhs
|| ! is_gimple_min_invariant (cached_lhs
))
814 cached_lhs
= simplify_cond_and_lookup_avail_expr (dummy_cond
,
819 /* We can have conditionals which just test the state of a
820 variable rather than use a relational operator. These are
821 simpler to handle. */
822 else if (TREE_CODE (cond
) == SSA_NAME
)
825 cached_lhs
= SSA_NAME_VALUE (cached_lhs
);
826 if (cached_lhs
&& ! is_gimple_min_invariant (cached_lhs
))
830 cached_lhs
= lookup_avail_expr (stmt
, false);
834 edge taken_edge
= find_taken_edge (e
->dest
, cached_lhs
);
835 basic_block dest
= (taken_edge
? taken_edge
->dest
: NULL
);
840 /* If we have a known destination for the conditional, then
841 we can perform this optimization, which saves at least one
842 conditional jump each time it applies since we get to
843 bypass the conditional at our original destination. */
846 struct edge_info
*edge_info
;
848 update_bb_profile_for_threading (e
->dest
, EDGE_FREQUENCY (e
),
849 e
->count
, taken_edge
);
853 edge_info
= allocate_edge_info (e
);
854 edge_info
->redirection_target
= taken_edge
;
855 bitmap_set_bit (threaded_blocks
, e
->dest
->index
);
862 /* Initialize local stacks for this optimizer and record equivalences
863 upon entry to BB. Equivalences can come from the edge traversed to
864 reach BB or they may come from PHI nodes at the start of BB. */
867 dom_opt_initialize_block (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
870 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
871 fprintf (dump_file
, "\n\nOptimizing block #%d\n\n", bb
->index
);
873 /* Push a marker on the stacks of local information so that we know how
874 far to unwind when we finalize this block. */
875 VEC_safe_push (tree
, heap
, avail_exprs_stack
, NULL_TREE
);
876 VEC_safe_push (tree
, heap
, const_and_copies_stack
, NULL_TREE
);
877 VEC_safe_push (tree
, heap
, nonzero_vars_stack
, NULL_TREE
);
878 VEC_safe_push (tree
, heap
, vrp_variables_stack
, NULL_TREE
);
880 record_equivalences_from_incoming_edge (bb
);
882 /* PHI nodes can create equivalences too. */
883 record_equivalences_from_phis (bb
);
886 /* Given an expression EXPR (a relational expression or a statement),
887 initialize the hash table element pointed by by ELEMENT. */
890 initialize_hash_element (tree expr
, tree lhs
, struct expr_hash_elt
*element
)
892 /* Hash table elements may be based on conditional expressions or statements.
894 For the former case, we have no annotation and we want to hash the
895 conditional expression. In the latter case we have an annotation and
896 we want to record the expression the statement evaluates. */
897 if (COMPARISON_CLASS_P (expr
) || TREE_CODE (expr
) == TRUTH_NOT_EXPR
)
899 element
->stmt
= NULL
;
902 else if (TREE_CODE (expr
) == COND_EXPR
)
904 element
->stmt
= expr
;
905 element
->rhs
= COND_EXPR_COND (expr
);
907 else if (TREE_CODE (expr
) == SWITCH_EXPR
)
909 element
->stmt
= expr
;
910 element
->rhs
= SWITCH_COND (expr
);
912 else if (TREE_CODE (expr
) == RETURN_EXPR
&& TREE_OPERAND (expr
, 0))
914 element
->stmt
= expr
;
915 element
->rhs
= TREE_OPERAND (TREE_OPERAND (expr
, 0), 1);
917 else if (TREE_CODE (expr
) == GOTO_EXPR
)
919 element
->stmt
= expr
;
920 element
->rhs
= GOTO_DESTINATION (expr
);
924 element
->stmt
= expr
;
925 element
->rhs
= TREE_OPERAND (expr
, 1);
929 element
->hash
= avail_expr_hash (element
);
932 /* Remove all the expressions in LOCALS from TABLE, stopping when there are
933 LIMIT entries left in LOCALs. */
936 remove_local_expressions_from_table (void)
938 /* Remove all the expressions made available in this block. */
939 while (VEC_length (tree
, avail_exprs_stack
) > 0)
941 struct expr_hash_elt element
;
942 tree expr
= VEC_pop (tree
, avail_exprs_stack
);
944 if (expr
== NULL_TREE
)
947 initialize_hash_element (expr
, NULL
, &element
);
948 htab_remove_elt_with_hash (avail_exprs
, &element
, element
.hash
);
952 /* Use the SSA_NAMES in LOCALS to restore TABLE to its original
953 state, stopping when there are LIMIT entries left in LOCALs. */
956 restore_nonzero_vars_to_original_value (void)
958 while (VEC_length (tree
, nonzero_vars_stack
) > 0)
960 tree name
= VEC_pop (tree
, nonzero_vars_stack
);
965 bitmap_clear_bit (nonzero_vars
, SSA_NAME_VERSION (name
));
969 /* Use the source/dest pairs in CONST_AND_COPIES_STACK to restore
970 CONST_AND_COPIES to its original state, stopping when we hit a
974 restore_vars_to_original_value (void)
976 while (VEC_length (tree
, const_and_copies_stack
) > 0)
978 tree prev_value
, dest
;
980 dest
= VEC_pop (tree
, const_and_copies_stack
);
985 prev_value
= VEC_pop (tree
, const_and_copies_stack
);
986 SSA_NAME_VALUE (dest
) = prev_value
;
990 /* We have finished processing the dominator children of BB, perform
991 any finalization actions in preparation for leaving this node in
992 the dominator tree. */
995 dom_opt_finalize_block (struct dom_walk_data
*walk_data
, basic_block bb
)
999 /* If we are at a leaf node in the dominator tree, see if we can thread
1000 the edge from BB through its successor.
1002 Do this before we remove entries from our equivalence tables. */
1003 if (single_succ_p (bb
)
1004 && (single_succ_edge (bb
)->flags
& EDGE_ABNORMAL
) == 0
1005 && (get_immediate_dominator (CDI_DOMINATORS
, single_succ (bb
)) != bb
1006 || phi_nodes (single_succ (bb
))))
1009 thread_across_edge (walk_data
, single_succ_edge (bb
));
1011 else if ((last
= last_stmt (bb
))
1012 && TREE_CODE (last
) == COND_EXPR
1013 && (COMPARISON_CLASS_P (COND_EXPR_COND (last
))
1014 || TREE_CODE (COND_EXPR_COND (last
)) == SSA_NAME
)
1015 && EDGE_COUNT (bb
->succs
) == 2
1016 && (EDGE_SUCC (bb
, 0)->flags
& EDGE_ABNORMAL
) == 0
1017 && (EDGE_SUCC (bb
, 1)->flags
& EDGE_ABNORMAL
) == 0)
1019 edge true_edge
, false_edge
;
1021 extract_true_false_edges_from_block (bb
, &true_edge
, &false_edge
);
1023 /* If the THEN arm is the end of a dominator tree or has PHI nodes,
1024 then try to thread through its edge. */
1025 if (get_immediate_dominator (CDI_DOMINATORS
, true_edge
->dest
) != bb
1026 || phi_nodes (true_edge
->dest
))
1028 struct edge_info
*edge_info
;
1031 /* Push a marker onto the available expression stack so that we
1032 unwind any expressions related to the TRUE arm before processing
1033 the false arm below. */
1034 VEC_safe_push (tree
, heap
, avail_exprs_stack
, NULL_TREE
);
1035 VEC_safe_push (tree
, heap
, const_and_copies_stack
, NULL_TREE
);
1037 edge_info
= true_edge
->aux
;
1039 /* If we have info associated with this edge, record it into
1040 our equivalency tables. */
1043 tree
*cond_equivalences
= edge_info
->cond_equivalences
;
1044 tree lhs
= edge_info
->lhs
;
1045 tree rhs
= edge_info
->rhs
;
1047 /* If we have a simple NAME = VALUE equivalency record it. */
1048 if (lhs
&& TREE_CODE (lhs
) == SSA_NAME
)
1049 record_const_or_copy (lhs
, rhs
);
1051 /* If we have 0 = COND or 1 = COND equivalences, record them
1052 into our expression hash tables. */
1053 if (cond_equivalences
)
1054 for (i
= 0; i
< edge_info
->max_cond_equivalences
; i
+= 2)
1056 tree expr
= cond_equivalences
[i
];
1057 tree value
= cond_equivalences
[i
+ 1];
1059 record_cond (expr
, value
);
1063 /* Now thread the edge. */
1064 thread_across_edge (walk_data
, true_edge
);
1066 /* And restore the various tables to their state before
1067 we threaded this edge. */
1068 remove_local_expressions_from_table ();
1069 restore_vars_to_original_value ();
1072 /* Similarly for the ELSE arm. */
1073 if (get_immediate_dominator (CDI_DOMINATORS
, false_edge
->dest
) != bb
1074 || phi_nodes (false_edge
->dest
))
1076 struct edge_info
*edge_info
;
1079 edge_info
= false_edge
->aux
;
1081 /* If we have info associated with this edge, record it into
1082 our equivalency tables. */
1085 tree
*cond_equivalences
= edge_info
->cond_equivalences
;
1086 tree lhs
= edge_info
->lhs
;
1087 tree rhs
= edge_info
->rhs
;
1089 /* If we have a simple NAME = VALUE equivalency record it. */
1090 if (lhs
&& TREE_CODE (lhs
) == SSA_NAME
)
1091 record_const_or_copy (lhs
, rhs
);
1093 /* If we have 0 = COND or 1 = COND equivalences, record them
1094 into our expression hash tables. */
1095 if (cond_equivalences
)
1096 for (i
= 0; i
< edge_info
->max_cond_equivalences
; i
+= 2)
1098 tree expr
= cond_equivalences
[i
];
1099 tree value
= cond_equivalences
[i
+ 1];
1101 record_cond (expr
, value
);
1105 thread_across_edge (walk_data
, false_edge
);
1107 /* No need to remove local expressions from our tables
1108 or restore vars to their original value as that will
1109 be done immediately below. */
1113 remove_local_expressions_from_table ();
1114 restore_nonzero_vars_to_original_value ();
1115 restore_vars_to_original_value ();
1117 /* Remove VRP records associated with this basic block. They are no
1120 To be efficient, we note which variables have had their values
1121 constrained in this block. So walk over each variable in the
1122 VRP_VARIABLEs array. */
1123 while (VEC_length (tree
, vrp_variables_stack
) > 0)
1125 tree var
= VEC_pop (tree
, vrp_variables_stack
);
1126 struct vrp_hash_elt vrp_hash_elt
, *vrp_hash_elt_p
;
1129 /* Each variable has a stack of value range records. We want to
1130 invalidate those associated with our basic block. So we walk
1131 the array backwards popping off records associated with our
1132 block. Once we hit a record not associated with our block
1134 VEC(vrp_element_p
,heap
) **var_vrp_records
;
1139 vrp_hash_elt
.var
= var
;
1140 vrp_hash_elt
.records
= NULL
;
1142 slot
= htab_find_slot (vrp_data
, &vrp_hash_elt
, NO_INSERT
);
1144 vrp_hash_elt_p
= (struct vrp_hash_elt
*) *slot
;
1145 var_vrp_records
= &vrp_hash_elt_p
->records
;
1147 while (VEC_length (vrp_element_p
, *var_vrp_records
) > 0)
1149 struct vrp_element
*element
1150 = VEC_last (vrp_element_p
, *var_vrp_records
);
1152 if (element
->bb
!= bb
)
1155 VEC_pop (vrp_element_p
, *var_vrp_records
);
1159 /* If we queued any statements to rescan in this block, then
1160 go ahead and rescan them now. */
1161 while (VEC_length (tree
, stmts_to_rescan
) > 0)
1163 tree stmt
= VEC_last (tree
, stmts_to_rescan
);
1164 basic_block stmt_bb
= bb_for_stmt (stmt
);
1169 VEC_pop (tree
, stmts_to_rescan
);
1170 mark_new_vars_to_rename (stmt
);
1174 /* PHI nodes can create equivalences too.
1176 Ignoring any alternatives which are the same as the result, if
1177 all the alternatives are equal, then the PHI node creates an
1180 Additionally, if all the PHI alternatives are known to have a nonzero
1181 value, then the result of this PHI is known to have a nonzero value,
1182 even if we do not know its exact value. */
1185 record_equivalences_from_phis (basic_block bb
)
1189 for (phi
= phi_nodes (bb
); phi
; phi
= PHI_CHAIN (phi
))
1191 tree lhs
= PHI_RESULT (phi
);
1195 for (i
= 0; i
< PHI_NUM_ARGS (phi
); i
++)
1197 tree t
= PHI_ARG_DEF (phi
, i
);
1199 /* Ignore alternatives which are the same as our LHS. Since
1200 LHS is a PHI_RESULT, it is known to be a SSA_NAME, so we
1201 can simply compare pointers. */
1205 /* If we have not processed an alternative yet, then set
1206 RHS to this alternative. */
1209 /* If we have processed an alternative (stored in RHS), then
1210 see if it is equal to this one. If it isn't, then stop
1212 else if (! operand_equal_for_phi_arg_p (rhs
, t
))
1216 /* If we had no interesting alternatives, then all the RHS alternatives
1217 must have been the same as LHS. */
1221 /* If we managed to iterate through each PHI alternative without
1222 breaking out of the loop, then we have a PHI which may create
1223 a useful equivalence. We do not need to record unwind data for
1224 this, since this is a true assignment and not an equivalence
1225 inferred from a comparison. All uses of this ssa name are dominated
1226 by this assignment, so unwinding just costs time and space. */
1227 if (i
== PHI_NUM_ARGS (phi
)
1228 && may_propagate_copy (lhs
, rhs
))
1229 SSA_NAME_VALUE (lhs
) = rhs
;
1231 /* Now see if we know anything about the nonzero property for the
1232 result of this PHI. */
1233 for (i
= 0; i
< PHI_NUM_ARGS (phi
); i
++)
1235 if (!PHI_ARG_NONZERO (phi
, i
))
1239 if (i
== PHI_NUM_ARGS (phi
))
1240 bitmap_set_bit (nonzero_vars
, SSA_NAME_VERSION (PHI_RESULT (phi
)));
1244 /* Ignoring loop backedges, if BB has precisely one incoming edge then
1245 return that edge. Otherwise return NULL. */
1247 single_incoming_edge_ignoring_loop_edges (basic_block bb
)
1253 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1255 /* A loop back edge can be identified by the destination of
1256 the edge dominating the source of the edge. */
1257 if (dominated_by_p (CDI_DOMINATORS
, e
->src
, e
->dest
))
1260 /* If we have already seen a non-loop edge, then we must have
1261 multiple incoming non-loop edges and thus we return NULL. */
1265 /* This is the first non-loop incoming edge we have found. Record
1273 /* Record any equivalences created by the incoming edge to BB. If BB
1274 has more than one incoming edge, then no equivalence is created. */
1277 record_equivalences_from_incoming_edge (basic_block bb
)
1281 struct edge_info
*edge_info
;
1283 /* If our parent block ended with a control statement, then we may be
1284 able to record some equivalences based on which outgoing edge from
1285 the parent was followed. */
1286 parent
= get_immediate_dominator (CDI_DOMINATORS
, bb
);
1288 e
= single_incoming_edge_ignoring_loop_edges (bb
);
1290 /* If we had a single incoming edge from our parent block, then enter
1291 any data associated with the edge into our tables. */
1292 if (e
&& e
->src
== parent
)
1300 tree lhs
= edge_info
->lhs
;
1301 tree rhs
= edge_info
->rhs
;
1302 tree
*cond_equivalences
= edge_info
->cond_equivalences
;
1305 record_equality (lhs
, rhs
);
1307 if (cond_equivalences
)
1309 bool recorded_range
= false;
1310 for (i
= 0; i
< edge_info
->max_cond_equivalences
; i
+= 2)
1312 tree expr
= cond_equivalences
[i
];
1313 tree value
= cond_equivalences
[i
+ 1];
1315 record_cond (expr
, value
);
1317 /* For the first true equivalence, record range
1318 information. We only do this for the first
1319 true equivalence as it should dominate any
1320 later true equivalences. */
1321 if (! recorded_range
1322 && COMPARISON_CLASS_P (expr
)
1323 && value
== boolean_true_node
1324 && TREE_CONSTANT (TREE_OPERAND (expr
, 1)))
1326 record_range (expr
, bb
);
1327 recorded_range
= true;
1335 /* Dump SSA statistics on FILE. */
1338 dump_dominator_optimization_stats (FILE *file
)
1342 fprintf (file
, "Total number of statements: %6ld\n\n",
1343 opt_stats
.num_stmts
);
1344 fprintf (file
, "Exprs considered for dominator optimizations: %6ld\n",
1345 opt_stats
.num_exprs_considered
);
1347 n_exprs
= opt_stats
.num_exprs_considered
;
1351 fprintf (file
, " Redundant expressions eliminated: %6ld (%.0f%%)\n",
1352 opt_stats
.num_re
, PERCENT (opt_stats
.num_re
,
1354 fprintf (file
, " Constants propagated: %6ld\n",
1355 opt_stats
.num_const_prop
);
1356 fprintf (file
, " Copies propagated: %6ld\n",
1357 opt_stats
.num_copy_prop
);
1359 fprintf (file
, "\nHash table statistics:\n");
1361 fprintf (file
, " avail_exprs: ");
1362 htab_statistics (file
, avail_exprs
);
1366 /* Dump SSA statistics on stderr. */
1369 debug_dominator_optimization_stats (void)
1371 dump_dominator_optimization_stats (stderr
);
1375 /* Dump statistics for the hash table HTAB. */
1378 htab_statistics (FILE *file
, htab_t htab
)
1380 fprintf (file
, "size %ld, %ld elements, %f collision/search ratio\n",
1381 (long) htab_size (htab
),
1382 (long) htab_elements (htab
),
1383 htab_collisions (htab
));
1386 /* Record the fact that VAR has a nonzero value, though we may not know
1387 its exact value. Note that if VAR is already known to have a nonzero
1388 value, then we do nothing. */
1391 record_var_is_nonzero (tree var
)
1393 int indx
= SSA_NAME_VERSION (var
);
1395 if (bitmap_bit_p (nonzero_vars
, indx
))
1398 /* Mark it in the global table. */
1399 bitmap_set_bit (nonzero_vars
, indx
);
1401 /* Record this SSA_NAME so that we can reset the global table
1402 when we leave this block. */
1403 VEC_safe_push (tree
, heap
, nonzero_vars_stack
, var
);
1406 /* Enter a statement into the true/false expression hash table indicating
1407 that the condition COND has the value VALUE. */
1410 record_cond (tree cond
, tree value
)
1412 struct expr_hash_elt
*element
= xmalloc (sizeof (struct expr_hash_elt
));
1415 initialize_hash_element (cond
, value
, element
);
1417 slot
= htab_find_slot_with_hash (avail_exprs
, (void *)element
,
1418 element
->hash
, INSERT
);
1421 *slot
= (void *) element
;
1422 VEC_safe_push (tree
, heap
, avail_exprs_stack
, cond
);
1428 /* Build a new conditional using NEW_CODE, OP0 and OP1 and store
1429 the new conditional into *p, then store a boolean_true_node
1433 build_and_record_new_cond (enum tree_code new_code
, tree op0
, tree op1
, tree
*p
)
1435 *p
= build2 (new_code
, boolean_type_node
, op0
, op1
);
1437 *p
= boolean_true_node
;
1440 /* Record that COND is true and INVERTED is false into the edge information
1441 structure. Also record that any conditions dominated by COND are true
1444 For example, if a < b is true, then a <= b must also be true. */
1447 record_conditions (struct edge_info
*edge_info
, tree cond
, tree inverted
)
1451 if (!COMPARISON_CLASS_P (cond
))
1454 op0
= TREE_OPERAND (cond
, 0);
1455 op1
= TREE_OPERAND (cond
, 1);
1457 switch (TREE_CODE (cond
))
1461 edge_info
->max_cond_equivalences
= 12;
1462 edge_info
->cond_equivalences
= xmalloc (12 * sizeof (tree
));
1463 build_and_record_new_cond ((TREE_CODE (cond
) == LT_EXPR
1464 ? LE_EXPR
: GE_EXPR
),
1465 op0
, op1
, &edge_info
->cond_equivalences
[4]);
1466 build_and_record_new_cond (ORDERED_EXPR
, op0
, op1
,
1467 &edge_info
->cond_equivalences
[6]);
1468 build_and_record_new_cond (NE_EXPR
, op0
, op1
,
1469 &edge_info
->cond_equivalences
[8]);
1470 build_and_record_new_cond (LTGT_EXPR
, op0
, op1
,
1471 &edge_info
->cond_equivalences
[10]);
1476 edge_info
->max_cond_equivalences
= 6;
1477 edge_info
->cond_equivalences
= xmalloc (6 * sizeof (tree
));
1478 build_and_record_new_cond (ORDERED_EXPR
, op0
, op1
,
1479 &edge_info
->cond_equivalences
[4]);
1483 edge_info
->max_cond_equivalences
= 10;
1484 edge_info
->cond_equivalences
= xmalloc (10 * sizeof (tree
));
1485 build_and_record_new_cond (ORDERED_EXPR
, op0
, op1
,
1486 &edge_info
->cond_equivalences
[4]);
1487 build_and_record_new_cond (LE_EXPR
, op0
, op1
,
1488 &edge_info
->cond_equivalences
[6]);
1489 build_and_record_new_cond (GE_EXPR
, op0
, op1
,
1490 &edge_info
->cond_equivalences
[8]);
1493 case UNORDERED_EXPR
:
1494 edge_info
->max_cond_equivalences
= 16;
1495 edge_info
->cond_equivalences
= xmalloc (16 * sizeof (tree
));
1496 build_and_record_new_cond (NE_EXPR
, op0
, op1
,
1497 &edge_info
->cond_equivalences
[4]);
1498 build_and_record_new_cond (UNLE_EXPR
, op0
, op1
,
1499 &edge_info
->cond_equivalences
[6]);
1500 build_and_record_new_cond (UNGE_EXPR
, op0
, op1
,
1501 &edge_info
->cond_equivalences
[8]);
1502 build_and_record_new_cond (UNEQ_EXPR
, op0
, op1
,
1503 &edge_info
->cond_equivalences
[10]);
1504 build_and_record_new_cond (UNLT_EXPR
, op0
, op1
,
1505 &edge_info
->cond_equivalences
[12]);
1506 build_and_record_new_cond (UNGT_EXPR
, op0
, op1
,
1507 &edge_info
->cond_equivalences
[14]);
1512 edge_info
->max_cond_equivalences
= 8;
1513 edge_info
->cond_equivalences
= xmalloc (8 * sizeof (tree
));
1514 build_and_record_new_cond ((TREE_CODE (cond
) == UNLT_EXPR
1515 ? UNLE_EXPR
: UNGE_EXPR
),
1516 op0
, op1
, &edge_info
->cond_equivalences
[4]);
1517 build_and_record_new_cond (NE_EXPR
, op0
, op1
,
1518 &edge_info
->cond_equivalences
[6]);
1522 edge_info
->max_cond_equivalences
= 8;
1523 edge_info
->cond_equivalences
= xmalloc (8 * sizeof (tree
));
1524 build_and_record_new_cond (UNLE_EXPR
, op0
, op1
,
1525 &edge_info
->cond_equivalences
[4]);
1526 build_and_record_new_cond (UNGE_EXPR
, op0
, op1
,
1527 &edge_info
->cond_equivalences
[6]);
1531 edge_info
->max_cond_equivalences
= 8;
1532 edge_info
->cond_equivalences
= xmalloc (8 * sizeof (tree
));
1533 build_and_record_new_cond (NE_EXPR
, op0
, op1
,
1534 &edge_info
->cond_equivalences
[4]);
1535 build_and_record_new_cond (ORDERED_EXPR
, op0
, op1
,
1536 &edge_info
->cond_equivalences
[6]);
1540 edge_info
->max_cond_equivalences
= 4;
1541 edge_info
->cond_equivalences
= xmalloc (4 * sizeof (tree
));
1545 /* Now store the original true and false conditions into the first
1547 edge_info
->cond_equivalences
[0] = cond
;
1548 edge_info
->cond_equivalences
[1] = boolean_true_node
;
1549 edge_info
->cond_equivalences
[2] = inverted
;
1550 edge_info
->cond_equivalences
[3] = boolean_false_node
;
1553 /* A helper function for record_const_or_copy and record_equality.
1554 Do the work of recording the value and undo info. */
1557 record_const_or_copy_1 (tree x
, tree y
, tree prev_x
)
1559 SSA_NAME_VALUE (x
) = y
;
1561 VEC_reserve (tree
, heap
, const_and_copies_stack
, 2);
1562 VEC_quick_push (tree
, const_and_copies_stack
, prev_x
);
1563 VEC_quick_push (tree
, const_and_copies_stack
, x
);
1567 /* Return the loop depth of the basic block of the defining statement of X.
1568 This number should not be treated as absolutely correct because the loop
1569 information may not be completely up-to-date when dom runs. However, it
1570 will be relatively correct, and as more passes are taught to keep loop info
1571 up to date, the result will become more and more accurate. */
1574 loop_depth_of_name (tree x
)
1579 /* If it's not an SSA_NAME, we have no clue where the definition is. */
1580 if (TREE_CODE (x
) != SSA_NAME
)
1583 /* Otherwise return the loop depth of the defining statement's bb.
1584 Note that there may not actually be a bb for this statement, if the
1585 ssa_name is live on entry. */
1586 defstmt
= SSA_NAME_DEF_STMT (x
);
1587 defbb
= bb_for_stmt (defstmt
);
1591 return defbb
->loop_depth
;
1595 /* Record that X is equal to Y in const_and_copies. Record undo
1596 information in the block-local vector. */
1599 record_const_or_copy (tree x
, tree y
)
1601 tree prev_x
= SSA_NAME_VALUE (x
);
1603 if (TREE_CODE (y
) == SSA_NAME
)
1605 tree tmp
= SSA_NAME_VALUE (y
);
1610 record_const_or_copy_1 (x
, y
, prev_x
);
1613 /* Similarly, but assume that X and Y are the two operands of an EQ_EXPR.
1614 This constrains the cases in which we may treat this as assignment. */
1617 record_equality (tree x
, tree y
)
1619 tree prev_x
= NULL
, prev_y
= NULL
;
1621 if (TREE_CODE (x
) == SSA_NAME
)
1622 prev_x
= SSA_NAME_VALUE (x
);
1623 if (TREE_CODE (y
) == SSA_NAME
)
1624 prev_y
= SSA_NAME_VALUE (y
);
1626 /* If one of the previous values is invariant, or invariant in more loops
1627 (by depth), then use that.
1628 Otherwise it doesn't matter which value we choose, just so
1629 long as we canonicalize on one value. */
1630 if (TREE_INVARIANT (y
))
1632 else if (TREE_INVARIANT (x
) || (loop_depth_of_name (x
) <= loop_depth_of_name (y
)))
1633 prev_x
= x
, x
= y
, y
= prev_x
, prev_x
= prev_y
;
1634 else if (prev_x
&& TREE_INVARIANT (prev_x
))
1635 x
= y
, y
= prev_x
, prev_x
= prev_y
;
1636 else if (prev_y
&& TREE_CODE (prev_y
) != VALUE_HANDLE
)
1639 /* After the swapping, we must have one SSA_NAME. */
1640 if (TREE_CODE (x
) != SSA_NAME
)
1643 /* For IEEE, -0.0 == 0.0, so we don't necessarily know the sign of a
1644 variable compared against zero. If we're honoring signed zeros,
1645 then we cannot record this value unless we know that the value is
1647 if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (x
)))
1648 && (TREE_CODE (y
) != REAL_CST
1649 || REAL_VALUES_EQUAL (dconst0
, TREE_REAL_CST (y
))))
1652 record_const_or_copy_1 (x
, y
, prev_x
);
1655 /* Return true, if it is ok to do folding of an associative expression.
1656 EXP is the tree for the associative expression. */
1659 unsafe_associative_fp_binop (tree exp
)
1661 enum tree_code code
= TREE_CODE (exp
);
1662 return !(!flag_unsafe_math_optimizations
1663 && (code
== MULT_EXPR
|| code
== PLUS_EXPR
1664 || code
== MINUS_EXPR
)
1665 && FLOAT_TYPE_P (TREE_TYPE (exp
)));
1668 /* Returns true when STMT is a simple iv increment. It detects the
1669 following situation:
1671 i_1 = phi (..., i_2)
1672 i_2 = i_1 +/- ... */
1675 simple_iv_increment_p (tree stmt
)
1677 tree lhs
, rhs
, preinc
, phi
;
1680 if (TREE_CODE (stmt
) != MODIFY_EXPR
)
1683 lhs
= TREE_OPERAND (stmt
, 0);
1684 if (TREE_CODE (lhs
) != SSA_NAME
)
1687 rhs
= TREE_OPERAND (stmt
, 1);
1689 if (TREE_CODE (rhs
) != PLUS_EXPR
1690 && TREE_CODE (rhs
) != MINUS_EXPR
)
1693 preinc
= TREE_OPERAND (rhs
, 0);
1694 if (TREE_CODE (preinc
) != SSA_NAME
)
1697 phi
= SSA_NAME_DEF_STMT (preinc
);
1698 if (TREE_CODE (phi
) != PHI_NODE
)
1701 for (i
= 0; i
< (unsigned) PHI_NUM_ARGS (phi
); i
++)
1702 if (PHI_ARG_DEF (phi
, i
) == lhs
)
1708 /* STMT is a MODIFY_EXPR for which we were unable to find RHS in the
1709 hash tables. Try to simplify the RHS using whatever equivalences
1710 we may have recorded.
1712 If we are able to simplify the RHS, then lookup the simplified form in
1713 the hash table and return the result. Otherwise return NULL. */
1716 simplify_rhs_and_lookup_avail_expr (tree stmt
, int insert
)
1718 tree rhs
= TREE_OPERAND (stmt
, 1);
1719 enum tree_code rhs_code
= TREE_CODE (rhs
);
1722 /* If we have lhs = ~x, look and see if we earlier had x = ~y.
1723 In which case we can change this statement to be lhs = y.
1724 Which can then be copy propagated.
1726 Similarly for negation. */
1727 if ((rhs_code
== BIT_NOT_EXPR
|| rhs_code
== NEGATE_EXPR
)
1728 && TREE_CODE (TREE_OPERAND (rhs
, 0)) == SSA_NAME
)
1730 /* Get the definition statement for our RHS. */
1731 tree rhs_def_stmt
= SSA_NAME_DEF_STMT (TREE_OPERAND (rhs
, 0));
1733 /* See if the RHS_DEF_STMT has the same form as our statement. */
1734 if (TREE_CODE (rhs_def_stmt
) == MODIFY_EXPR
1735 && TREE_CODE (TREE_OPERAND (rhs_def_stmt
, 1)) == rhs_code
)
1737 tree rhs_def_operand
;
1739 rhs_def_operand
= TREE_OPERAND (TREE_OPERAND (rhs_def_stmt
, 1), 0);
1741 /* Verify that RHS_DEF_OPERAND is a suitable SSA variable. */
1742 if (TREE_CODE (rhs_def_operand
) == SSA_NAME
1743 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand
))
1744 result
= update_rhs_and_lookup_avail_expr (stmt
,
1750 /* If we have z = (x OP C1), see if we earlier had x = y OP C2.
1751 If OP is associative, create and fold (y OP C2) OP C1 which
1752 should result in (y OP C3), use that as the RHS for the
1753 assignment. Add minus to this, as we handle it specially below. */
1754 if ((associative_tree_code (rhs_code
) || rhs_code
== MINUS_EXPR
)
1755 && TREE_CODE (TREE_OPERAND (rhs
, 0)) == SSA_NAME
1756 && is_gimple_min_invariant (TREE_OPERAND (rhs
, 1)))
1758 tree rhs_def_stmt
= SSA_NAME_DEF_STMT (TREE_OPERAND (rhs
, 0));
1760 /* If the statement defines an induction variable, do not propagate
1761 its value, so that we do not create overlapping life ranges. */
1762 if (simple_iv_increment_p (rhs_def_stmt
))
1763 goto dont_fold_assoc
;
1765 /* See if the RHS_DEF_STMT has the same form as our statement. */
1766 if (TREE_CODE (rhs_def_stmt
) == MODIFY_EXPR
)
1768 tree rhs_def_rhs
= TREE_OPERAND (rhs_def_stmt
, 1);
1769 enum tree_code rhs_def_code
= TREE_CODE (rhs_def_rhs
);
1771 if ((rhs_code
== rhs_def_code
&& unsafe_associative_fp_binop (rhs
))
1772 || (rhs_code
== PLUS_EXPR
&& rhs_def_code
== MINUS_EXPR
)
1773 || (rhs_code
== MINUS_EXPR
&& rhs_def_code
== PLUS_EXPR
))
1775 tree def_stmt_op0
= TREE_OPERAND (rhs_def_rhs
, 0);
1776 tree def_stmt_op1
= TREE_OPERAND (rhs_def_rhs
, 1);
1778 if (TREE_CODE (def_stmt_op0
) == SSA_NAME
1779 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def_stmt_op0
)
1780 && is_gimple_min_invariant (def_stmt_op1
))
1782 tree outer_const
= TREE_OPERAND (rhs
, 1);
1783 tree type
= TREE_TYPE (TREE_OPERAND (stmt
, 0));
1786 /* If we care about correct floating point results, then
1787 don't fold x + c1 - c2. Note that we need to take both
1788 the codes and the signs to figure this out. */
1789 if (FLOAT_TYPE_P (type
)
1790 && !flag_unsafe_math_optimizations
1791 && (rhs_def_code
== PLUS_EXPR
1792 || rhs_def_code
== MINUS_EXPR
))
1796 neg
^= (rhs_code
== MINUS_EXPR
);
1797 neg
^= (rhs_def_code
== MINUS_EXPR
);
1798 neg
^= real_isneg (TREE_REAL_CST_PTR (outer_const
));
1799 neg
^= real_isneg (TREE_REAL_CST_PTR (def_stmt_op1
));
1802 goto dont_fold_assoc
;
1805 /* Ho hum. So fold will only operate on the outermost
1806 thingy that we give it, so we have to build the new
1807 expression in two pieces. This requires that we handle
1808 combinations of plus and minus. */
1809 if (rhs_def_code
!= rhs_code
)
1811 if (rhs_def_code
== MINUS_EXPR
)
1812 t
= build (MINUS_EXPR
, type
, outer_const
, def_stmt_op1
);
1814 t
= build (MINUS_EXPR
, type
, def_stmt_op1
, outer_const
);
1815 rhs_code
= PLUS_EXPR
;
1817 else if (rhs_def_code
== MINUS_EXPR
)
1818 t
= build (PLUS_EXPR
, type
, def_stmt_op1
, outer_const
);
1820 t
= build (rhs_def_code
, type
, def_stmt_op1
, outer_const
);
1822 t
= build (rhs_code
, type
, def_stmt_op0
, t
);
1825 /* If the result is a suitable looking gimple expression,
1826 then use it instead of the original for STMT. */
1827 if (TREE_CODE (t
) == SSA_NAME
1828 || (UNARY_CLASS_P (t
)
1829 && TREE_CODE (TREE_OPERAND (t
, 0)) == SSA_NAME
)
1830 || ((BINARY_CLASS_P (t
) || COMPARISON_CLASS_P (t
))
1831 && TREE_CODE (TREE_OPERAND (t
, 0)) == SSA_NAME
1832 && is_gimple_val (TREE_OPERAND (t
, 1))))
1833 result
= update_rhs_and_lookup_avail_expr (stmt
, t
, insert
);
1840 /* Optimize *"foo" into 'f'. This is done here rather than
1841 in fold to avoid problems with stuff like &*"foo". */
1842 if (TREE_CODE (rhs
) == INDIRECT_REF
|| TREE_CODE (rhs
) == ARRAY_REF
)
1844 tree t
= fold_read_from_constant_string (rhs
);
1847 result
= update_rhs_and_lookup_avail_expr (stmt
, t
, insert
);
1853 /* COND is a condition of the form:
1855 x == const or x != const
1857 Look back to x's defining statement and see if x is defined as
1861 If const is unchanged if we convert it to type, then we can build
1862 the equivalent expression:
1865 y == const or y != const
1867 Which may allow further optimizations.
1869 Return the equivalent comparison or NULL if no such equivalent comparison
1873 find_equivalent_equality_comparison (tree cond
)
1875 tree op0
= TREE_OPERAND (cond
, 0);
1876 tree op1
= TREE_OPERAND (cond
, 1);
1877 tree def_stmt
= SSA_NAME_DEF_STMT (op0
);
1879 /* OP0 might have been a parameter, so first make sure it
1880 was defined by a MODIFY_EXPR. */
1881 if (def_stmt
&& TREE_CODE (def_stmt
) == MODIFY_EXPR
)
1883 tree def_rhs
= TREE_OPERAND (def_stmt
, 1);
1886 /* If either operand to the comparison is a pointer to
1887 a function, then we can not apply this optimization
1888 as some targets require function pointers to be
1889 canonicalized and in this case this optimization would
1890 eliminate a necessary canonicalization. */
1891 if ((POINTER_TYPE_P (TREE_TYPE (op0
))
1892 && TREE_CODE (TREE_TYPE (TREE_TYPE (op0
))) == FUNCTION_TYPE
)
1893 || (POINTER_TYPE_P (TREE_TYPE (op1
))
1894 && TREE_CODE (TREE_TYPE (TREE_TYPE (op1
))) == FUNCTION_TYPE
))
1897 /* Now make sure the RHS of the MODIFY_EXPR is a typecast. */
1898 if ((TREE_CODE (def_rhs
) == NOP_EXPR
1899 || TREE_CODE (def_rhs
) == CONVERT_EXPR
)
1900 && TREE_CODE (TREE_OPERAND (def_rhs
, 0)) == SSA_NAME
)
1902 tree def_rhs_inner
= TREE_OPERAND (def_rhs
, 0);
1903 tree def_rhs_inner_type
= TREE_TYPE (def_rhs_inner
);
1906 if (TYPE_PRECISION (def_rhs_inner_type
)
1907 > TYPE_PRECISION (TREE_TYPE (def_rhs
)))
1910 /* If the inner type of the conversion is a pointer to
1911 a function, then we can not apply this optimization
1912 as some targets require function pointers to be
1913 canonicalized. This optimization would result in
1914 canonicalization of the pointer when it was not originally
1916 if (POINTER_TYPE_P (def_rhs_inner_type
)
1917 && TREE_CODE (TREE_TYPE (def_rhs_inner_type
)) == FUNCTION_TYPE
)
1920 /* What we want to prove is that if we convert OP1 to
1921 the type of the object inside the NOP_EXPR that the
1922 result is still equivalent to SRC.
1924 If that is true, the build and return new equivalent
1925 condition which uses the source of the typecast and the
1926 new constant (which has only changed its type). */
1927 new = build1 (TREE_CODE (def_rhs
), def_rhs_inner_type
, op1
);
1928 new = local_fold (new);
1929 if (is_gimple_val (new) && tree_int_cst_equal (new, op1
))
1930 return build (TREE_CODE (cond
), TREE_TYPE (cond
),
1931 def_rhs_inner
, new);
1937 /* STMT is a COND_EXPR for which we could not trivially determine its
1938 result. This routine attempts to find equivalent forms of the
1939 condition which we may be able to optimize better. It also
1940 uses simple value range propagation to optimize conditionals. */
1943 simplify_cond_and_lookup_avail_expr (tree stmt
,
1947 tree cond
= COND_EXPR_COND (stmt
);
1949 if (COMPARISON_CLASS_P (cond
))
1951 tree op0
= TREE_OPERAND (cond
, 0);
1952 tree op1
= TREE_OPERAND (cond
, 1);
1954 if (TREE_CODE (op0
) == SSA_NAME
&& is_gimple_min_invariant (op1
))
1957 tree low
, high
, cond_low
, cond_high
;
1958 int lowequal
, highequal
, swapped
, no_overlap
, subset
, cond_inverted
;
1959 VEC(vrp_element_p
,heap
) **vrp_records
;
1960 struct vrp_element
*element
;
1961 struct vrp_hash_elt vrp_hash_elt
, *vrp_hash_elt_p
;
1964 /* First see if we have test of an SSA_NAME against a constant
1965 where the SSA_NAME is defined by an earlier typecast which
1966 is irrelevant when performing tests against the given
1968 if (TREE_CODE (cond
) == EQ_EXPR
|| TREE_CODE (cond
) == NE_EXPR
)
1970 tree new_cond
= find_equivalent_equality_comparison (cond
);
1974 /* Update the statement to use the new equivalent
1976 COND_EXPR_COND (stmt
) = new_cond
;
1978 /* If this is not a real stmt, ann will be NULL and we
1979 avoid processing the operands. */
1981 mark_stmt_modified (stmt
);
1983 /* Lookup the condition and return its known value if it
1985 new_cond
= lookup_avail_expr (stmt
, insert
);
1989 /* The operands have changed, so update op0 and op1. */
1990 op0
= TREE_OPERAND (cond
, 0);
1991 op1
= TREE_OPERAND (cond
, 1);
1995 /* Consult the value range records for this variable (if they exist)
1996 to see if we can eliminate or simplify this conditional.
1998 Note two tests are necessary to determine no records exist.
1999 First we have to see if the virtual array exists, if it
2000 exists, then we have to check its active size.
2002 Also note the vast majority of conditionals are not testing
2003 a variable which has had its range constrained by an earlier
2004 conditional. So this filter avoids a lot of unnecessary work. */
2005 vrp_hash_elt
.var
= op0
;
2006 vrp_hash_elt
.records
= NULL
;
2007 slot
= htab_find_slot (vrp_data
, &vrp_hash_elt
, NO_INSERT
);
2011 vrp_hash_elt_p
= (struct vrp_hash_elt
*) *slot
;
2012 vrp_records
= &vrp_hash_elt_p
->records
;
2014 limit
= VEC_length (vrp_element_p
, *vrp_records
);
2016 /* If we have no value range records for this variable, or we are
2017 unable to extract a range for this condition, then there is
2020 || ! extract_range_from_cond (cond
, &cond_high
,
2021 &cond_low
, &cond_inverted
))
2024 /* We really want to avoid unnecessary computations of range
2025 info. So all ranges are computed lazily; this avoids a
2026 lot of unnecessary work. i.e., we record the conditional,
2027 but do not process how it constrains the variable's
2028 potential values until we know that processing the condition
2031 However, we do not want to have to walk a potentially long
2032 list of ranges, nor do we want to compute a variable's
2033 range more than once for a given path.
2035 Luckily, each time we encounter a conditional that can not
2036 be otherwise optimized we will end up here and we will
2037 compute the necessary range information for the variable
2038 used in this condition.
2040 Thus you can conclude that there will never be more than one
2041 conditional associated with a variable which has not been
2042 processed. So we never need to merge more than one new
2043 conditional into the current range.
2045 These properties also help us avoid unnecessary work. */
2046 element
= VEC_last (vrp_element_p
, *vrp_records
);
2048 if (element
->high
&& element
->low
)
2050 /* The last element has been processed, so there is no range
2051 merging to do, we can simply use the high/low values
2052 recorded in the last element. */
2054 high
= element
->high
;
2058 tree tmp_high
, tmp_low
;
2061 /* The last element has not been processed. Process it now.
2062 record_range should ensure for cond inverted is not set.
2063 This call can only fail if cond is x < min or x > max,
2064 which fold should have optimized into false.
2065 If that doesn't happen, just pretend all values are
2067 if (! extract_range_from_cond (element
->cond
, &tmp_high
,
2071 gcc_assert (dummy
== 0);
2073 /* If this is the only element, then no merging is necessary,
2074 the high/low values from extract_range_from_cond are all
2083 /* Get the high/low value from the previous element. */
2084 struct vrp_element
*prev
2085 = VEC_index (vrp_element_p
, *vrp_records
, limit
- 2);
2089 /* Merge in this element's range with the range from the
2092 The low value for the merged range is the maximum of
2093 the previous low value and the low value of this record.
2095 Similarly the high value for the merged range is the
2096 minimum of the previous high value and the high value of
2098 low
= (low
&& tree_int_cst_compare (low
, tmp_low
) == 1
2100 high
= (high
&& tree_int_cst_compare (high
, tmp_high
) == -1
2104 /* And record the computed range. */
2106 element
->high
= high
;
2110 /* After we have constrained this variable's potential values,
2111 we try to determine the result of the given conditional.
2113 To simplify later tests, first determine if the current
2114 low value is the same low value as the conditional.
2115 Similarly for the current high value and the high value
2116 for the conditional. */
2117 lowequal
= tree_int_cst_equal (low
, cond_low
);
2118 highequal
= tree_int_cst_equal (high
, cond_high
);
2120 if (lowequal
&& highequal
)
2121 return (cond_inverted
? boolean_false_node
: boolean_true_node
);
2123 /* To simplify the overlap/subset tests below we may want
2124 to swap the two ranges so that the larger of the two
2125 ranges occurs "first". */
2127 if (tree_int_cst_compare (low
, cond_low
) == 1
2129 && tree_int_cst_compare (cond_high
, high
) == 1))
2142 /* Now determine if there is no overlap in the ranges
2143 or if the second range is a subset of the first range. */
2144 no_overlap
= tree_int_cst_lt (high
, cond_low
);
2145 subset
= tree_int_cst_compare (cond_high
, high
) != 1;
2147 /* If there was no overlap in the ranges, then this conditional
2148 always has a false value (unless we had to invert this
2149 conditional, in which case it always has a true value). */
2151 return (cond_inverted
? boolean_true_node
: boolean_false_node
);
2153 /* If the current range is a subset of the condition's range,
2154 then this conditional always has a true value (unless we
2155 had to invert this conditional, in which case it always
2156 has a true value). */
2157 if (subset
&& swapped
)
2158 return (cond_inverted
? boolean_false_node
: boolean_true_node
);
2160 /* We were unable to determine the result of the conditional.
2161 However, we may be able to simplify the conditional. First
2162 merge the ranges in the same manner as range merging above. */
2163 low
= tree_int_cst_compare (low
, cond_low
) == 1 ? low
: cond_low
;
2164 high
= tree_int_cst_compare (high
, cond_high
) == -1 ? high
: cond_high
;
2166 /* If the range has converged to a single point, then turn this
2167 into an equality comparison. */
2168 if (TREE_CODE (cond
) != EQ_EXPR
2169 && TREE_CODE (cond
) != NE_EXPR
2170 && tree_int_cst_equal (low
, high
))
2172 TREE_SET_CODE (cond
, EQ_EXPR
);
2173 TREE_OPERAND (cond
, 1) = high
;
2180 /* STMT is a SWITCH_EXPR for which we could not trivially determine its
2181 result. This routine attempts to find equivalent forms of the
2182 condition which we may be able to optimize better. */
2185 simplify_switch_and_lookup_avail_expr (tree stmt
, int insert
)
2187 tree cond
= SWITCH_COND (stmt
);
2190 /* The optimization that we really care about is removing unnecessary
2191 casts. That will let us do much better in propagating the inferred
2192 constant at the switch target. */
2193 if (TREE_CODE (cond
) == SSA_NAME
)
2195 def
= SSA_NAME_DEF_STMT (cond
);
2196 if (TREE_CODE (def
) == MODIFY_EXPR
)
2198 def
= TREE_OPERAND (def
, 1);
2199 if (TREE_CODE (def
) == NOP_EXPR
)
2204 def
= TREE_OPERAND (def
, 0);
2206 #ifdef ENABLE_CHECKING
2207 /* ??? Why was Jeff testing this? We are gimple... */
2208 gcc_assert (is_gimple_val (def
));
2211 to
= TREE_TYPE (cond
);
2212 ti
= TREE_TYPE (def
);
2214 /* If we have an extension that preserves value, then we
2215 can copy the source value into the switch. */
2217 need_precision
= TYPE_PRECISION (ti
);
2219 if (TYPE_UNSIGNED (to
) && !TYPE_UNSIGNED (ti
))
2221 else if (!TYPE_UNSIGNED (to
) && TYPE_UNSIGNED (ti
))
2222 need_precision
+= 1;
2223 if (TYPE_PRECISION (to
) < need_precision
)
2228 SWITCH_COND (stmt
) = def
;
2229 mark_stmt_modified (stmt
);
2231 return lookup_avail_expr (stmt
, insert
);
2241 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2242 known value for that SSA_NAME (or NULL if no value is known).
2244 NONZERO_VARS is the set SSA_NAMES known to have a nonzero value,
2245 even if we don't know their precise value.
2247 Propagate values from CONST_AND_COPIES and NONZERO_VARS into the PHI
2248 nodes of the successors of BB. */
2251 cprop_into_successor_phis (basic_block bb
, bitmap nonzero_vars
)
2256 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
2261 /* If this is an abnormal edge, then we do not want to copy propagate
2262 into the PHI alternative associated with this edge. */
2263 if (e
->flags
& EDGE_ABNORMAL
)
2266 phi
= phi_nodes (e
->dest
);
2271 for ( ; phi
; phi
= PHI_CHAIN (phi
))
2274 use_operand_p orig_p
;
2277 /* The alternative may be associated with a constant, so verify
2278 it is an SSA_NAME before doing anything with it. */
2279 orig_p
= PHI_ARG_DEF_PTR (phi
, indx
);
2280 orig
= USE_FROM_PTR (orig_p
);
2281 if (TREE_CODE (orig
) != SSA_NAME
)
2284 /* If the alternative is known to have a nonzero value, record
2285 that fact in the PHI node itself for future use. */
2286 if (bitmap_bit_p (nonzero_vars
, SSA_NAME_VERSION (orig
)))
2287 PHI_ARG_NONZERO (phi
, indx
) = true;
2289 /* If we have *ORIG_P in our constant/copy table, then replace
2290 ORIG_P with its value in our constant/copy table. */
2291 new = SSA_NAME_VALUE (orig
);
2294 && (TREE_CODE (new) == SSA_NAME
2295 || is_gimple_min_invariant (new))
2296 && may_propagate_copy (orig
, new))
2297 propagate_value (orig_p
, new);
2302 /* We have finished optimizing BB, record any information implied by
2303 taking a specific outgoing edge from BB. */
2306 record_edge_info (basic_block bb
)
2308 block_stmt_iterator bsi
= bsi_last (bb
);
2309 struct edge_info
*edge_info
;
2311 if (! bsi_end_p (bsi
))
2313 tree stmt
= bsi_stmt (bsi
);
2315 if (stmt
&& TREE_CODE (stmt
) == SWITCH_EXPR
)
2317 tree cond
= SWITCH_COND (stmt
);
2319 if (TREE_CODE (cond
) == SSA_NAME
)
2321 tree labels
= SWITCH_LABELS (stmt
);
2322 int i
, n_labels
= TREE_VEC_LENGTH (labels
);
2323 tree
*info
= xcalloc (last_basic_block
, sizeof (tree
));
2327 for (i
= 0; i
< n_labels
; i
++)
2329 tree label
= TREE_VEC_ELT (labels
, i
);
2330 basic_block target_bb
= label_to_block (CASE_LABEL (label
));
2332 if (CASE_HIGH (label
)
2333 || !CASE_LOW (label
)
2334 || info
[target_bb
->index
])
2335 info
[target_bb
->index
] = error_mark_node
;
2337 info
[target_bb
->index
] = label
;
2340 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
2342 basic_block target_bb
= e
->dest
;
2343 tree node
= info
[target_bb
->index
];
2345 if (node
!= NULL
&& node
!= error_mark_node
)
2347 tree x
= fold_convert (TREE_TYPE (cond
), CASE_LOW (node
));
2348 edge_info
= allocate_edge_info (e
);
2349 edge_info
->lhs
= cond
;
2357 /* A COND_EXPR may create equivalences too. */
2358 if (stmt
&& TREE_CODE (stmt
) == COND_EXPR
)
2360 tree cond
= COND_EXPR_COND (stmt
);
2364 extract_true_false_edges_from_block (bb
, &true_edge
, &false_edge
);
2366 /* If the conditional is a single variable 'X', record 'X = 1'
2367 for the true edge and 'X = 0' on the false edge. */
2368 if (SSA_VAR_P (cond
))
2370 struct edge_info
*edge_info
;
2372 edge_info
= allocate_edge_info (true_edge
);
2373 edge_info
->lhs
= cond
;
2374 edge_info
->rhs
= constant_boolean_node (1, TREE_TYPE (cond
));
2376 edge_info
= allocate_edge_info (false_edge
);
2377 edge_info
->lhs
= cond
;
2378 edge_info
->rhs
= constant_boolean_node (0, TREE_TYPE (cond
));
2380 /* Equality tests may create one or two equivalences. */
2381 else if (COMPARISON_CLASS_P (cond
))
2383 tree op0
= TREE_OPERAND (cond
, 0);
2384 tree op1
= TREE_OPERAND (cond
, 1);
2386 /* Special case comparing booleans against a constant as we
2387 know the value of OP0 on both arms of the branch. i.e., we
2388 can record an equivalence for OP0 rather than COND. */
2389 if ((TREE_CODE (cond
) == EQ_EXPR
|| TREE_CODE (cond
) == NE_EXPR
)
2390 && TREE_CODE (op0
) == SSA_NAME
2391 && TREE_CODE (TREE_TYPE (op0
)) == BOOLEAN_TYPE
2392 && is_gimple_min_invariant (op1
))
2394 if (TREE_CODE (cond
) == EQ_EXPR
)
2396 edge_info
= allocate_edge_info (true_edge
);
2397 edge_info
->lhs
= op0
;
2398 edge_info
->rhs
= (integer_zerop (op1
)
2399 ? boolean_false_node
2400 : boolean_true_node
);
2402 edge_info
= allocate_edge_info (false_edge
);
2403 edge_info
->lhs
= op0
;
2404 edge_info
->rhs
= (integer_zerop (op1
)
2406 : boolean_false_node
);
2410 edge_info
= allocate_edge_info (true_edge
);
2411 edge_info
->lhs
= op0
;
2412 edge_info
->rhs
= (integer_zerop (op1
)
2414 : boolean_false_node
);
2416 edge_info
= allocate_edge_info (false_edge
);
2417 edge_info
->lhs
= op0
;
2418 edge_info
->rhs
= (integer_zerop (op1
)
2419 ? boolean_false_node
2420 : boolean_true_node
);
2424 else if (is_gimple_min_invariant (op0
)
2425 && (TREE_CODE (op1
) == SSA_NAME
2426 || is_gimple_min_invariant (op1
)))
2428 tree inverted
= invert_truthvalue (cond
);
2429 struct edge_info
*edge_info
;
2431 edge_info
= allocate_edge_info (true_edge
);
2432 record_conditions (edge_info
, cond
, inverted
);
2434 if (TREE_CODE (cond
) == EQ_EXPR
)
2436 edge_info
->lhs
= op1
;
2437 edge_info
->rhs
= op0
;
2440 edge_info
= allocate_edge_info (false_edge
);
2441 record_conditions (edge_info
, inverted
, cond
);
2443 if (TREE_CODE (cond
) == NE_EXPR
)
2445 edge_info
->lhs
= op1
;
2446 edge_info
->rhs
= op0
;
2450 else if (TREE_CODE (op0
) == SSA_NAME
2451 && (is_gimple_min_invariant (op1
)
2452 || TREE_CODE (op1
) == SSA_NAME
))
2454 tree inverted
= invert_truthvalue (cond
);
2455 struct edge_info
*edge_info
;
2457 edge_info
= allocate_edge_info (true_edge
);
2458 record_conditions (edge_info
, cond
, inverted
);
2460 if (TREE_CODE (cond
) == EQ_EXPR
)
2462 edge_info
->lhs
= op0
;
2463 edge_info
->rhs
= op1
;
2466 edge_info
= allocate_edge_info (false_edge
);
2467 record_conditions (edge_info
, inverted
, cond
);
2469 if (TREE_CODE (cond
) == NE_EXPR
)
2471 edge_info
->lhs
= op0
;
2472 edge_info
->rhs
= op1
;
2477 /* ??? TRUTH_NOT_EXPR can create an equivalence too. */
2482 /* Propagate information from BB to its outgoing edges.
2484 This can include equivalency information implied by control statements
2485 at the end of BB and const/copy propagation into PHIs in BB's
2486 successor blocks. */
2489 propagate_to_outgoing_edges (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
2492 record_edge_info (bb
);
2493 cprop_into_successor_phis (bb
, nonzero_vars
);
2496 /* Search for redundant computations in STMT. If any are found, then
2497 replace them with the variable holding the result of the computation.
2499 If safe, record this expression into the available expression hash
2503 eliminate_redundant_computations (tree stmt
, stmt_ann_t ann
)
2505 tree
*expr_p
, def
= NULL_TREE
;
2508 bool retval
= false;
2509 bool modify_expr_p
= false;
2511 if (TREE_CODE (stmt
) == MODIFY_EXPR
)
2512 def
= TREE_OPERAND (stmt
, 0);
2514 /* Certain expressions on the RHS can be optimized away, but can not
2515 themselves be entered into the hash tables. */
2516 if (ann
->makes_aliased_stores
2518 || TREE_CODE (def
) != SSA_NAME
2519 || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def
)
2520 || !ZERO_SSA_OPERANDS (stmt
, SSA_OP_VMAYDEF
)
2521 /* Do not record equivalences for increments of ivs. This would create
2522 overlapping live ranges for a very questionable gain. */
2523 || simple_iv_increment_p (stmt
))
2526 /* Check if the expression has been computed before. */
2527 cached_lhs
= lookup_avail_expr (stmt
, insert
);
2529 /* If this is an assignment and the RHS was not in the hash table,
2530 then try to simplify the RHS and lookup the new RHS in the
2532 if (! cached_lhs
&& TREE_CODE (stmt
) == MODIFY_EXPR
)
2533 cached_lhs
= simplify_rhs_and_lookup_avail_expr (stmt
, insert
);
2534 /* Similarly if this is a COND_EXPR and we did not find its
2535 expression in the hash table, simplify the condition and
2537 else if (! cached_lhs
&& TREE_CODE (stmt
) == COND_EXPR
)
2538 cached_lhs
= simplify_cond_and_lookup_avail_expr (stmt
, ann
, insert
);
2539 /* Similarly for a SWITCH_EXPR. */
2540 else if (!cached_lhs
&& TREE_CODE (stmt
) == SWITCH_EXPR
)
2541 cached_lhs
= simplify_switch_and_lookup_avail_expr (stmt
, insert
);
2543 opt_stats
.num_exprs_considered
++;
2545 /* Get a pointer to the expression we are trying to optimize. */
2546 if (TREE_CODE (stmt
) == COND_EXPR
)
2547 expr_p
= &COND_EXPR_COND (stmt
);
2548 else if (TREE_CODE (stmt
) == SWITCH_EXPR
)
2549 expr_p
= &SWITCH_COND (stmt
);
2550 else if (TREE_CODE (stmt
) == RETURN_EXPR
&& TREE_OPERAND (stmt
, 0))
2552 expr_p
= &TREE_OPERAND (TREE_OPERAND (stmt
, 0), 1);
2553 modify_expr_p
= true;
2557 expr_p
= &TREE_OPERAND (stmt
, 1);
2558 modify_expr_p
= true;
2561 /* It is safe to ignore types here since we have already done
2562 type checking in the hashing and equality routines. In fact
2563 type checking here merely gets in the way of constant
2564 propagation. Also, make sure that it is safe to propagate
2565 CACHED_LHS into *EXPR_P. */
2567 && ((TREE_CODE (cached_lhs
) != SSA_NAME
2569 || tree_ssa_useless_type_conversion_1 (TREE_TYPE (*expr_p
),
2570 TREE_TYPE (cached_lhs
))))
2571 || may_propagate_copy (*expr_p
, cached_lhs
)))
2573 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2575 fprintf (dump_file
, " Replaced redundant expr '");
2576 print_generic_expr (dump_file
, *expr_p
, dump_flags
);
2577 fprintf (dump_file
, "' with '");
2578 print_generic_expr (dump_file
, cached_lhs
, dump_flags
);
2579 fprintf (dump_file
, "'\n");
2584 #if defined ENABLE_CHECKING
2585 gcc_assert (TREE_CODE (cached_lhs
) == SSA_NAME
2586 || is_gimple_min_invariant (cached_lhs
));
2589 if (TREE_CODE (cached_lhs
) == ADDR_EXPR
2590 || (POINTER_TYPE_P (TREE_TYPE (*expr_p
))
2591 && is_gimple_min_invariant (cached_lhs
)))
2595 && !tree_ssa_useless_type_conversion_1 (TREE_TYPE (*expr_p
),
2596 TREE_TYPE (cached_lhs
)))
2597 cached_lhs
= fold_convert (TREE_TYPE (*expr_p
), cached_lhs
);
2599 propagate_tree_value (expr_p
, cached_lhs
);
2600 mark_stmt_modified (stmt
);
2605 /* STMT, a MODIFY_EXPR, may create certain equivalences, in either
2606 the available expressions table or the const_and_copies table.
2607 Detect and record those equivalences. */
2610 record_equivalences_from_stmt (tree stmt
,
2614 tree lhs
= TREE_OPERAND (stmt
, 0);
2615 enum tree_code lhs_code
= TREE_CODE (lhs
);
2618 if (lhs_code
== SSA_NAME
)
2620 tree rhs
= TREE_OPERAND (stmt
, 1);
2622 /* Strip away any useless type conversions. */
2623 STRIP_USELESS_TYPE_CONVERSION (rhs
);
2625 /* If the RHS of the assignment is a constant or another variable that
2626 may be propagated, register it in the CONST_AND_COPIES table. We
2627 do not need to record unwind data for this, since this is a true
2628 assignment and not an equivalence inferred from a comparison. All
2629 uses of this ssa name are dominated by this assignment, so unwinding
2630 just costs time and space. */
2632 && (TREE_CODE (rhs
) == SSA_NAME
2633 || is_gimple_min_invariant (rhs
)))
2634 SSA_NAME_VALUE (lhs
) = rhs
;
2636 if (expr_computes_nonzero (rhs
))
2637 record_var_is_nonzero (lhs
);
2640 /* Look at both sides for pointer dereferences. If we find one, then
2641 the pointer must be nonnull and we can enter that equivalence into
2643 if (flag_delete_null_pointer_checks
)
2644 for (i
= 0; i
< 2; i
++)
2646 tree t
= TREE_OPERAND (stmt
, i
);
2648 /* Strip away any COMPONENT_REFs. */
2649 while (TREE_CODE (t
) == COMPONENT_REF
)
2650 t
= TREE_OPERAND (t
, 0);
2652 /* Now see if this is a pointer dereference. */
2653 if (INDIRECT_REF_P (t
))
2655 tree op
= TREE_OPERAND (t
, 0);
2657 /* If the pointer is a SSA variable, then enter new
2658 equivalences into the hash table. */
2659 while (TREE_CODE (op
) == SSA_NAME
)
2661 tree def
= SSA_NAME_DEF_STMT (op
);
2663 record_var_is_nonzero (op
);
2665 /* And walk up the USE-DEF chains noting other SSA_NAMEs
2666 which are known to have a nonzero value. */
2668 && TREE_CODE (def
) == MODIFY_EXPR
2669 && TREE_CODE (TREE_OPERAND (def
, 1)) == NOP_EXPR
)
2670 op
= TREE_OPERAND (TREE_OPERAND (def
, 1), 0);
2677 /* A memory store, even an aliased store, creates a useful
2678 equivalence. By exchanging the LHS and RHS, creating suitable
2679 vops and recording the result in the available expression table,
2680 we may be able to expose more redundant loads. */
2681 if (!ann
->has_volatile_ops
2682 && (TREE_CODE (TREE_OPERAND (stmt
, 1)) == SSA_NAME
2683 || is_gimple_min_invariant (TREE_OPERAND (stmt
, 1)))
2684 && !is_gimple_reg (lhs
))
2686 tree rhs
= TREE_OPERAND (stmt
, 1);
2689 /* FIXME: If the LHS of the assignment is a bitfield and the RHS
2690 is a constant, we need to adjust the constant to fit into the
2691 type of the LHS. If the LHS is a bitfield and the RHS is not
2692 a constant, then we can not record any equivalences for this
2693 statement since we would need to represent the widening or
2694 narrowing of RHS. This fixes gcc.c-torture/execute/921016-1.c
2695 and should not be necessary if GCC represented bitfields
2697 if (lhs_code
== COMPONENT_REF
2698 && DECL_BIT_FIELD (TREE_OPERAND (lhs
, 1)))
2700 if (TREE_CONSTANT (rhs
))
2701 rhs
= widen_bitfield (rhs
, TREE_OPERAND (lhs
, 1), lhs
);
2705 /* If the value overflowed, then we can not use this equivalence. */
2706 if (rhs
&& ! is_gimple_min_invariant (rhs
))
2712 /* Build a new statement with the RHS and LHS exchanged. */
2713 new = build (MODIFY_EXPR
, TREE_TYPE (stmt
), rhs
, lhs
);
2715 create_ssa_artficial_load_stmt (new, stmt
);
2717 /* Finally enter the statement into the available expression
2719 lookup_avail_expr (new, true);
2724 /* Replace *OP_P in STMT with any known equivalent value for *OP_P from
2725 CONST_AND_COPIES. */
2728 cprop_operand (tree stmt
, use_operand_p op_p
)
2730 bool may_have_exposed_new_symbols
= false;
2732 tree op
= USE_FROM_PTR (op_p
);
2734 /* If the operand has a known constant value or it is known to be a
2735 copy of some other variable, use the value or copy stored in
2736 CONST_AND_COPIES. */
2737 val
= SSA_NAME_VALUE (op
);
2738 if (val
&& val
!= op
&& TREE_CODE (val
) != VALUE_HANDLE
)
2740 tree op_type
, val_type
;
2742 /* Do not change the base variable in the virtual operand
2743 tables. That would make it impossible to reconstruct
2744 the renamed virtual operand if we later modify this
2745 statement. Also only allow the new value to be an SSA_NAME
2746 for propagation into virtual operands. */
2747 if (!is_gimple_reg (op
)
2748 && (TREE_CODE (val
) != SSA_NAME
2749 || is_gimple_reg (val
)
2750 || get_virtual_var (val
) != get_virtual_var (op
)))
2753 /* Do not replace hard register operands in asm statements. */
2754 if (TREE_CODE (stmt
) == ASM_EXPR
2755 && !may_propagate_copy_into_asm (op
))
2758 /* Get the toplevel type of each operand. */
2759 op_type
= TREE_TYPE (op
);
2760 val_type
= TREE_TYPE (val
);
2762 /* While both types are pointers, get the type of the object
2764 while (POINTER_TYPE_P (op_type
) && POINTER_TYPE_P (val_type
))
2766 op_type
= TREE_TYPE (op_type
);
2767 val_type
= TREE_TYPE (val_type
);
2770 /* Make sure underlying types match before propagating a constant by
2771 converting the constant to the proper type. Note that convert may
2772 return a non-gimple expression, in which case we ignore this
2773 propagation opportunity. */
2774 if (TREE_CODE (val
) != SSA_NAME
)
2776 if (!lang_hooks
.types_compatible_p (op_type
, val_type
))
2778 val
= fold_convert (TREE_TYPE (op
), val
);
2779 if (!is_gimple_min_invariant (val
))
2784 /* Certain operands are not allowed to be copy propagated due
2785 to their interaction with exception handling and some GCC
2787 else if (!may_propagate_copy (op
, val
))
2790 /* Do not propagate copies if the propagated value is at a deeper loop
2791 depth than the propagatee. Otherwise, this may move loop variant
2792 variables outside of their loops and prevent coalescing
2793 opportunities. If the value was loop invariant, it will be hoisted
2794 by LICM and exposed for copy propagation. */
2795 if (loop_depth_of_name (val
) > loop_depth_of_name (op
))
2799 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2801 fprintf (dump_file
, " Replaced '");
2802 print_generic_expr (dump_file
, op
, dump_flags
);
2803 fprintf (dump_file
, "' with %s '",
2804 (TREE_CODE (val
) != SSA_NAME
? "constant" : "variable"));
2805 print_generic_expr (dump_file
, val
, dump_flags
);
2806 fprintf (dump_file
, "'\n");
2809 /* If VAL is an ADDR_EXPR or a constant of pointer type, note
2810 that we may have exposed a new symbol for SSA renaming. */
2811 if (TREE_CODE (val
) == ADDR_EXPR
2812 || (POINTER_TYPE_P (TREE_TYPE (op
))
2813 && is_gimple_min_invariant (val
)))
2814 may_have_exposed_new_symbols
= true;
2816 if (TREE_CODE (val
) != SSA_NAME
)
2817 opt_stats
.num_const_prop
++;
2819 opt_stats
.num_copy_prop
++;
2821 propagate_value (op_p
, val
);
2823 /* And note that we modified this statement. This is now
2824 safe, even if we changed virtual operands since we will
2825 rescan the statement and rewrite its operands again. */
2826 mark_stmt_modified (stmt
);
2828 return may_have_exposed_new_symbols
;
2831 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2832 known value for that SSA_NAME (or NULL if no value is known).
2834 Propagate values from CONST_AND_COPIES into the uses, vuses and
2835 v_may_def_ops of STMT. */
2838 cprop_into_stmt (tree stmt
)
2840 bool may_have_exposed_new_symbols
= false;
2844 FOR_EACH_SSA_USE_OPERAND (op_p
, stmt
, iter
, SSA_OP_ALL_USES
)
2846 if (TREE_CODE (USE_FROM_PTR (op_p
)) == SSA_NAME
)
2847 may_have_exposed_new_symbols
|= cprop_operand (stmt
, op_p
);
2850 return may_have_exposed_new_symbols
;
2854 /* Optimize the statement pointed by iterator SI.
2856 We try to perform some simplistic global redundancy elimination and
2857 constant propagation:
2859 1- To detect global redundancy, we keep track of expressions that have
2860 been computed in this block and its dominators. If we find that the
2861 same expression is computed more than once, we eliminate repeated
2862 computations by using the target of the first one.
2864 2- Constant values and copy assignments. This is used to do very
2865 simplistic constant and copy propagation. When a constant or copy
2866 assignment is found, we map the value on the RHS of the assignment to
2867 the variable in the LHS in the CONST_AND_COPIES table. */
2870 optimize_stmt (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
2871 basic_block bb
, block_stmt_iterator si
)
2874 tree stmt
, old_stmt
;
2875 bool may_optimize_p
;
2876 bool may_have_exposed_new_symbols
= false;
2878 old_stmt
= stmt
= bsi_stmt (si
);
2880 update_stmt_if_modified (stmt
);
2881 ann
= stmt_ann (stmt
);
2882 opt_stats
.num_stmts
++;
2883 may_have_exposed_new_symbols
= false;
2885 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2887 fprintf (dump_file
, "Optimizing statement ");
2888 print_generic_stmt (dump_file
, stmt
, TDF_SLIM
);
2891 /* Const/copy propagate into USES, VUSES and the RHS of V_MAY_DEFs. */
2892 may_have_exposed_new_symbols
= cprop_into_stmt (stmt
);
2894 /* If the statement has been modified with constant replacements,
2895 fold its RHS before checking for redundant computations. */
2900 /* Try to fold the statement making sure that STMT is kept
2902 if (fold_stmt (bsi_stmt_ptr (si
)))
2904 stmt
= bsi_stmt (si
);
2905 ann
= stmt_ann (stmt
);
2907 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2909 fprintf (dump_file
, " Folded to: ");
2910 print_generic_stmt (dump_file
, stmt
, TDF_SLIM
);
2914 rhs
= get_rhs (stmt
);
2915 if (rhs
&& TREE_CODE (rhs
) == ADDR_EXPR
)
2916 recompute_tree_invarant_for_addr_expr (rhs
);
2918 /* Constant/copy propagation above may change the set of
2919 virtual operands associated with this statement. Folding
2920 may remove the need for some virtual operands.
2922 Indicate we will need to rescan and rewrite the statement. */
2923 may_have_exposed_new_symbols
= true;
2926 /* Check for redundant computations. Do this optimization only
2927 for assignments that have no volatile ops and conditionals. */
2928 may_optimize_p
= (!ann
->has_volatile_ops
2929 && ((TREE_CODE (stmt
) == RETURN_EXPR
2930 && TREE_OPERAND (stmt
, 0)
2931 && TREE_CODE (TREE_OPERAND (stmt
, 0)) == MODIFY_EXPR
2932 && ! (TREE_SIDE_EFFECTS
2933 (TREE_OPERAND (TREE_OPERAND (stmt
, 0), 1))))
2934 || (TREE_CODE (stmt
) == MODIFY_EXPR
2935 && ! TREE_SIDE_EFFECTS (TREE_OPERAND (stmt
, 1)))
2936 || TREE_CODE (stmt
) == COND_EXPR
2937 || TREE_CODE (stmt
) == SWITCH_EXPR
));
2940 may_have_exposed_new_symbols
2941 |= eliminate_redundant_computations (stmt
, ann
);
2943 /* Record any additional equivalences created by this statement. */
2944 if (TREE_CODE (stmt
) == MODIFY_EXPR
)
2945 record_equivalences_from_stmt (stmt
,
2949 /* If STMT is a COND_EXPR and it was modified, then we may know
2950 where it goes. If that is the case, then mark the CFG as altered.
2952 This will cause us to later call remove_unreachable_blocks and
2953 cleanup_tree_cfg when it is safe to do so. It is not safe to
2954 clean things up here since removal of edges and such can trigger
2955 the removal of PHI nodes, which in turn can release SSA_NAMEs to
2958 That's all fine and good, except that once SSA_NAMEs are released
2959 to the manager, we must not call create_ssa_name until all references
2960 to released SSA_NAMEs have been eliminated.
2962 All references to the deleted SSA_NAMEs can not be eliminated until
2963 we remove unreachable blocks.
2965 We can not remove unreachable blocks until after we have completed
2966 any queued jump threading.
2968 We can not complete any queued jump threads until we have taken
2969 appropriate variables out of SSA form. Taking variables out of
2970 SSA form can call create_ssa_name and thus we lose.
2972 Ultimately I suspect we're going to need to change the interface
2973 into the SSA_NAME manager. */
2979 if (TREE_CODE (stmt
) == COND_EXPR
)
2980 val
= COND_EXPR_COND (stmt
);
2981 else if (TREE_CODE (stmt
) == SWITCH_EXPR
)
2982 val
= SWITCH_COND (stmt
);
2984 if (val
&& TREE_CODE (val
) == INTEGER_CST
&& find_taken_edge (bb
, val
))
2987 /* If we simplified a statement in such a way as to be shown that it
2988 cannot trap, update the eh information and the cfg to match. */
2989 if (maybe_clean_or_replace_eh_stmt (old_stmt
, stmt
))
2991 bitmap_set_bit (need_eh_cleanup
, bb
->index
);
2992 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2993 fprintf (dump_file
, " Flagged to clear EH edges.\n");
2997 if (may_have_exposed_new_symbols
)
2998 VEC_safe_push (tree
, heap
, stmts_to_rescan
, bsi_stmt (si
));
3001 /* Replace the RHS of STMT with NEW_RHS. If RHS can be found in the
3002 available expression hashtable, then return the LHS from the hash
3005 If INSERT is true, then we also update the available expression
3006 hash table to account for the changes made to STMT. */
3009 update_rhs_and_lookup_avail_expr (tree stmt
, tree new_rhs
, bool insert
)
3011 tree cached_lhs
= NULL
;
3013 /* Remove the old entry from the hash table. */
3016 struct expr_hash_elt element
;
3018 initialize_hash_element (stmt
, NULL
, &element
);
3019 htab_remove_elt_with_hash (avail_exprs
, &element
, element
.hash
);
3022 /* Now update the RHS of the assignment. */
3023 TREE_OPERAND (stmt
, 1) = new_rhs
;
3025 /* Now lookup the updated statement in the hash table. */
3026 cached_lhs
= lookup_avail_expr (stmt
, insert
);
3028 /* We have now called lookup_avail_expr twice with two different
3029 versions of this same statement, once in optimize_stmt, once here.
3031 We know the call in optimize_stmt did not find an existing entry
3032 in the hash table, so a new entry was created. At the same time
3033 this statement was pushed onto the AVAIL_EXPRS_STACK vector.
3035 If this call failed to find an existing entry on the hash table,
3036 then the new version of this statement was entered into the
3037 hash table. And this statement was pushed onto BLOCK_AVAIL_EXPR
3038 for the second time. So there are two copies on BLOCK_AVAIL_EXPRs
3040 If this call succeeded, we still have one copy of this statement
3041 on the BLOCK_AVAIL_EXPRs vector.
3043 For both cases, we need to pop the most recent entry off the
3044 BLOCK_AVAIL_EXPRs vector. For the case where we never found this
3045 statement in the hash tables, that will leave precisely one
3046 copy of this statement on BLOCK_AVAIL_EXPRs. For the case where
3047 we found a copy of this statement in the second hash table lookup
3048 we want _no_ copies of this statement in BLOCK_AVAIL_EXPRs. */
3050 VEC_pop (tree
, avail_exprs_stack
);
3052 /* And make sure we record the fact that we modified this
3054 mark_stmt_modified (stmt
);
3059 /* Search for an existing instance of STMT in the AVAIL_EXPRS table. If
3060 found, return its LHS. Otherwise insert STMT in the table and return
3063 Also, when an expression is first inserted in the AVAIL_EXPRS table, it
3064 is also added to the stack pointed by BLOCK_AVAIL_EXPRS_P, so that they
3065 can be removed when we finish processing this block and its children.
3067 NOTE: This function assumes that STMT is a MODIFY_EXPR node that
3068 contains no CALL_EXPR on its RHS and makes no volatile nor
3069 aliased references. */
3072 lookup_avail_expr (tree stmt
, bool insert
)
3077 struct expr_hash_elt
*element
= xmalloc (sizeof (struct expr_hash_elt
));
3079 lhs
= TREE_CODE (stmt
) == MODIFY_EXPR
? TREE_OPERAND (stmt
, 0) : NULL
;
3081 initialize_hash_element (stmt
, lhs
, element
);
3083 /* Don't bother remembering constant assignments and copy operations.
3084 Constants and copy operations are handled by the constant/copy propagator
3085 in optimize_stmt. */
3086 if (TREE_CODE (element
->rhs
) == SSA_NAME
3087 || is_gimple_min_invariant (element
->rhs
))
3093 /* If this is an equality test against zero, see if we have recorded a
3094 nonzero value for the variable in question. */
3095 if ((TREE_CODE (element
->rhs
) == EQ_EXPR
3096 || TREE_CODE (element
->rhs
) == NE_EXPR
)
3097 && TREE_CODE (TREE_OPERAND (element
->rhs
, 0)) == SSA_NAME
3098 && integer_zerop (TREE_OPERAND (element
->rhs
, 1)))
3100 int indx
= SSA_NAME_VERSION (TREE_OPERAND (element
->rhs
, 0));
3102 if (bitmap_bit_p (nonzero_vars
, indx
))
3104 tree t
= element
->rhs
;
3106 return constant_boolean_node (TREE_CODE (t
) != EQ_EXPR
,
3107 TREE_TYPE (element
->rhs
));
3111 /* Finally try to find the expression in the main expression hash table. */
3112 slot
= htab_find_slot_with_hash (avail_exprs
, element
, element
->hash
,
3113 (insert
? INSERT
: NO_INSERT
));
3122 *slot
= (void *) element
;
3123 VEC_safe_push (tree
, heap
, avail_exprs_stack
,
3124 stmt
? stmt
: element
->rhs
);
3128 /* Extract the LHS of the assignment so that it can be used as the current
3129 definition of another variable. */
3130 lhs
= ((struct expr_hash_elt
*)*slot
)->lhs
;
3132 /* See if the LHS appears in the CONST_AND_COPIES table. If it does, then
3133 use the value from the const_and_copies table. */
3134 if (TREE_CODE (lhs
) == SSA_NAME
)
3136 temp
= SSA_NAME_VALUE (lhs
);
3137 if (temp
&& TREE_CODE (temp
) != VALUE_HANDLE
)
3145 /* Given a condition COND, record into HI_P, LO_P and INVERTED_P the
3146 range of values that result in the conditional having a true value.
3148 Return true if we are successful in extracting a range from COND and
3149 false if we are unsuccessful. */
3152 extract_range_from_cond (tree cond
, tree
*hi_p
, tree
*lo_p
, int *inverted_p
)
3154 tree op1
= TREE_OPERAND (cond
, 1);
3155 tree high
, low
, type
;
3158 type
= TREE_TYPE (op1
);
3160 /* Experiments have shown that it's rarely, if ever useful to
3161 record ranges for enumerations. Presumably this is due to
3162 the fact that they're rarely used directly. They are typically
3163 cast into an integer type and used that way. */
3164 if (TREE_CODE (type
) != INTEGER_TYPE
3165 /* We don't know how to deal with types with variable bounds. */
3166 || TREE_CODE (TYPE_MIN_VALUE (type
)) != INTEGER_CST
3167 || TREE_CODE (TYPE_MAX_VALUE (type
)) != INTEGER_CST
)
3170 switch (TREE_CODE (cond
))
3184 high
= TYPE_MAX_VALUE (type
);
3189 high
= TYPE_MAX_VALUE (type
);
3190 if (!tree_int_cst_lt (op1
, high
))
3192 low
= int_const_binop (PLUS_EXPR
, op1
, integer_one_node
, 1);
3198 low
= TYPE_MIN_VALUE (type
);
3203 low
= TYPE_MIN_VALUE (type
);
3204 if (!tree_int_cst_lt (low
, op1
))
3206 high
= int_const_binop (MINUS_EXPR
, op1
, integer_one_node
, 1);
3216 *inverted_p
= inverted
;
3220 /* Record a range created by COND for basic block BB. */
3223 record_range (tree cond
, basic_block bb
)
3225 enum tree_code code
= TREE_CODE (cond
);
3227 /* We explicitly ignore NE_EXPRs and all the unordered comparisons.
3228 They rarely allow for meaningful range optimizations and significantly
3229 complicate the implementation. */
3230 if ((code
== LT_EXPR
|| code
== LE_EXPR
|| code
== GT_EXPR
3231 || code
== GE_EXPR
|| code
== EQ_EXPR
)
3232 && TREE_CODE (TREE_TYPE (TREE_OPERAND (cond
, 1))) == INTEGER_TYPE
)
3234 struct vrp_hash_elt
*vrp_hash_elt
;
3235 struct vrp_element
*element
;
3236 VEC(vrp_element_p
,heap
) **vrp_records_p
;
3240 vrp_hash_elt
= xmalloc (sizeof (struct vrp_hash_elt
));
3241 vrp_hash_elt
->var
= TREE_OPERAND (cond
, 0);
3242 vrp_hash_elt
->records
= NULL
;
3243 slot
= htab_find_slot (vrp_data
, vrp_hash_elt
, INSERT
);
3246 *slot
= (void *) vrp_hash_elt
;
3248 vrp_free (vrp_hash_elt
);
3250 vrp_hash_elt
= (struct vrp_hash_elt
*) *slot
;
3251 vrp_records_p
= &vrp_hash_elt
->records
;
3253 element
= ggc_alloc (sizeof (struct vrp_element
));
3254 element
->low
= NULL
;
3255 element
->high
= NULL
;
3256 element
->cond
= cond
;
3259 VEC_safe_push (vrp_element_p
, heap
, *vrp_records_p
, element
);
3260 VEC_safe_push (tree
, heap
, vrp_variables_stack
, TREE_OPERAND (cond
, 0));
3264 /* Hashing and equality functions for VRP_DATA.
3266 Since this hash table is addressed by SSA_NAMEs, we can hash on
3267 their version number and equality can be determined with a
3268 pointer comparison. */
3271 vrp_hash (const void *p
)
3273 tree var
= ((struct vrp_hash_elt
*)p
)->var
;
3275 return SSA_NAME_VERSION (var
);
3279 vrp_eq (const void *p1
, const void *p2
)
3281 tree var1
= ((struct vrp_hash_elt
*)p1
)->var
;
3282 tree var2
= ((struct vrp_hash_elt
*)p2
)->var
;
3284 return var1
== var2
;
3287 /* Hashing and equality functions for AVAIL_EXPRS. The table stores
3288 MODIFY_EXPR statements. We compute a value number for expressions using
3289 the code of the expression and the SSA numbers of its operands. */
3292 avail_expr_hash (const void *p
)
3294 tree stmt
= ((struct expr_hash_elt
*)p
)->stmt
;
3295 tree rhs
= ((struct expr_hash_elt
*)p
)->rhs
;
3300 /* iterative_hash_expr knows how to deal with any expression and
3301 deals with commutative operators as well, so just use it instead
3302 of duplicating such complexities here. */
3303 val
= iterative_hash_expr (rhs
, val
);
3305 /* If the hash table entry is not associated with a statement, then we
3306 can just hash the expression and not worry about virtual operands
3308 if (!stmt
|| !stmt_ann (stmt
))
3311 /* Add the SSA version numbers of every vuse operand. This is important
3312 because compound variables like arrays are not renamed in the
3313 operands. Rather, the rename is done on the virtual variable
3314 representing all the elements of the array. */
3315 FOR_EACH_SSA_TREE_OPERAND (vuse
, stmt
, iter
, SSA_OP_VUSE
)
3316 val
= iterative_hash_expr (vuse
, val
);
3322 real_avail_expr_hash (const void *p
)
3324 return ((const struct expr_hash_elt
*)p
)->hash
;
3328 avail_expr_eq (const void *p1
, const void *p2
)
3330 tree stmt1
= ((struct expr_hash_elt
*)p1
)->stmt
;
3331 tree rhs1
= ((struct expr_hash_elt
*)p1
)->rhs
;
3332 tree stmt2
= ((struct expr_hash_elt
*)p2
)->stmt
;
3333 tree rhs2
= ((struct expr_hash_elt
*)p2
)->rhs
;
3335 /* If they are the same physical expression, return true. */
3336 if (rhs1
== rhs2
&& stmt1
== stmt2
)
3339 /* If their codes are not equal, then quit now. */
3340 if (TREE_CODE (rhs1
) != TREE_CODE (rhs2
))
3343 /* In case of a collision, both RHS have to be identical and have the
3344 same VUSE operands. */
3345 if ((TREE_TYPE (rhs1
) == TREE_TYPE (rhs2
)
3346 || lang_hooks
.types_compatible_p (TREE_TYPE (rhs1
), TREE_TYPE (rhs2
)))
3347 && operand_equal_p (rhs1
, rhs2
, OEP_PURE_SAME
))
3349 bool ret
= compare_ssa_operands_equal (stmt1
, stmt2
, SSA_OP_VUSE
);
3350 gcc_assert (!ret
|| ((struct expr_hash_elt
*)p1
)->hash
3351 == ((struct expr_hash_elt
*)p2
)->hash
);