1 /* SSA Dominator optimizations for trees
2 Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
3 Contributed by Diego Novillo <dnovillo@redhat.com>
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
24 #include "coretypes.h"
31 #include "basic-block.h"
37 #include "diagnostic.h"
39 #include "tree-dump.h"
40 #include "tree-flow.h"
43 #include "tree-pass.h"
44 #include "tree-ssa-propagate.h"
45 #include "langhooks.h"
47 /* This file implements optimizations on the dominator tree. */
50 /* Structure for recording edge equivalences as well as any pending
51 edge redirections during the dominator optimizer.
53 Computing and storing the edge equivalences instead of creating
54 them on-demand can save significant amounts of time, particularly
55 for pathological cases involving switch statements.
57 These structures live for a single iteration of the dominator
58 optimizer in the edge's AUX field. At the end of an iteration we
59 free each of these structures and update the AUX field to point
60 to any requested redirection target (the code for updating the
61 CFG and SSA graph for edge redirection expects redirection edge
62 targets to be in the AUX field for each edge. */
66 /* If this edge creates a simple equivalence, the LHS and RHS of
67 the equivalence will be stored here. */
71 /* Traversing an edge may also indicate one or more particular conditions
72 are true or false. The number of recorded conditions can vary, but
73 can be determined by the condition's code. So we have an array
74 and its maximum index rather than use a varray. */
75 tree
*cond_equivalences
;
76 unsigned int max_cond_equivalences
;
78 /* If we can thread this edge this field records the new target. */
79 edge redirection_target
;
83 /* Hash table with expressions made available during the renaming process.
84 When an assignment of the form X_i = EXPR is found, the statement is
85 stored in this table. If the same expression EXPR is later found on the
86 RHS of another statement, it is replaced with X_i (thus performing
87 global redundancy elimination). Similarly as we pass through conditionals
88 we record the conditional itself as having either a true or false value
90 static htab_t avail_exprs
;
92 /* Stack of available expressions in AVAIL_EXPRs. Each block pushes any
93 expressions it enters into the hash table along with a marker entry
94 (null). When we finish processing the block, we pop off entries and
95 remove the expressions from the global hash table until we hit the
97 static VEC(tree
,heap
) *avail_exprs_stack
;
99 /* Stack of statements we need to rescan during finalization for newly
102 Statement rescanning must occur after the current block's available
103 expressions are removed from AVAIL_EXPRS. Else we may change the
104 hash code for an expression and be unable to find/remove it from
106 static VEC(tree
,heap
) *stmts_to_rescan
;
108 /* Structure for entries in the expression hash table.
110 This requires more memory for the hash table entries, but allows us
111 to avoid creating silly tree nodes and annotations for conditionals,
112 eliminates 2 global hash tables and two block local varrays.
114 It also allows us to reduce the number of hash table lookups we
115 have to perform in lookup_avail_expr and finally it allows us to
116 significantly reduce the number of calls into the hashing routine
121 /* The value (lhs) of this expression. */
124 /* The expression (rhs) we want to record. */
127 /* The annotation if this element corresponds to a statement. */
130 /* The hash value for RHS/ann. */
134 /* Stack of dest,src pairs that need to be restored during finalization.
136 A NULL entry is used to mark the end of pairs which need to be
137 restored during finalization of this block. */
138 static VEC(tree
,heap
) *const_and_copies_stack
;
140 /* Bitmap of SSA_NAMEs known to have a nonzero value, even if we do not
141 know their exact value. */
142 static bitmap nonzero_vars
;
144 /* Stack of SSA_NAMEs which need their NONZERO_VARS property cleared
145 when the current block is finalized.
147 A NULL entry is used to mark the end of names needing their
148 entry in NONZERO_VARS cleared during finalization of this block. */
149 static VEC(tree
,heap
) *nonzero_vars_stack
;
151 /* Track whether or not we have changed the control flow graph. */
152 static bool cfg_altered
;
154 /* Bitmap of blocks that have had EH statements cleaned. We should
155 remove their dead edges eventually. */
156 static bitmap need_eh_cleanup
;
158 /* Statistics for dominator optimizations. */
162 long num_exprs_considered
;
168 static struct opt_stats_d opt_stats
;
170 /* Value range propagation record. Each time we encounter a conditional
171 of the form SSA_NAME COND CONST we create a new vrp_element to record
172 how the condition affects the possible values SSA_NAME may have.
174 Each record contains the condition tested (COND), and the range of
175 values the variable may legitimately have if COND is true. Note the
176 range of values may be a smaller range than COND specifies if we have
177 recorded other ranges for this variable. Each record also contains the
178 block in which the range was recorded for invalidation purposes.
180 Note that the current known range is computed lazily. This allows us
181 to avoid the overhead of computing ranges which are never queried.
183 When we encounter a conditional, we look for records which constrain
184 the SSA_NAME used in the condition. In some cases those records allow
185 us to determine the condition's result at compile time. In other cases
186 they may allow us to simplify the condition.
188 We also use value ranges to do things like transform signed div/mod
189 operations into unsigned div/mod or to simplify ABS_EXPRs.
191 Simple experiments have shown these optimizations to not be all that
192 useful on switch statements (much to my surprise). So switch statement
193 optimizations are not performed.
195 Note carefully we do not propagate information through each statement
196 in the block. i.e., if we know variable X has a value defined of
197 [0, 25] and we encounter Y = X + 1, we do not track a value range
198 for Y (which would be [1, 26] if we cared). Similarly we do not
199 constrain values as we encounter narrowing typecasts, etc. */
203 /* The highest and lowest values the variable in COND may contain when
204 COND is true. Note this may not necessarily be the same values
205 tested by COND if the same variable was used in earlier conditionals.
207 Note this is computed lazily and thus can be NULL indicating that
208 the values have not been computed yet. */
212 /* The actual conditional we recorded. This is needed since we compute
216 /* The basic block where this record was created. We use this to determine
217 when to remove records. */
221 /* A hash table holding value range records (VRP_ELEMENTs) for a given
222 SSA_NAME. We used to use a varray indexed by SSA_NAME_VERSION, but
223 that gets awful wasteful, particularly since the density objects
224 with useful information is very low. */
225 static htab_t vrp_data
;
227 /* An entry in the VRP_DATA hash table. We record the variable and a
228 varray of VRP_ELEMENT records associated with that variable. */
235 /* Array of variables which have their values constrained by operations
236 in this basic block. We use this during finalization to know
237 which variables need their VRP data updated. */
239 /* Stack of SSA_NAMEs which had their values constrained by operations
240 in this basic block. During finalization of this block we use this
241 list to determine which variables need their VRP data updated.
243 A NULL entry marks the end of the SSA_NAMEs associated with this block. */
244 static VEC(tree
,heap
) *vrp_variables_stack
;
252 /* Local functions. */
253 static void optimize_stmt (struct dom_walk_data
*,
255 block_stmt_iterator
);
256 static tree
lookup_avail_expr (tree
, bool);
257 static hashval_t
vrp_hash (const void *);
258 static int vrp_eq (const void *, const void *);
259 static hashval_t
avail_expr_hash (const void *);
260 static hashval_t
real_avail_expr_hash (const void *);
261 static int avail_expr_eq (const void *, const void *);
262 static void htab_statistics (FILE *, htab_t
);
263 static void record_cond (tree
, tree
);
264 static void record_const_or_copy (tree
, tree
);
265 static void record_equality (tree
, tree
);
266 static tree
update_rhs_and_lookup_avail_expr (tree
, tree
, bool);
267 static tree
simplify_rhs_and_lookup_avail_expr (struct dom_walk_data
*,
269 static tree
simplify_cond_and_lookup_avail_expr (tree
, stmt_ann_t
, int);
270 static tree
simplify_switch_and_lookup_avail_expr (tree
, int);
271 static tree
find_equivalent_equality_comparison (tree
);
272 static void record_range (tree
, basic_block
);
273 static bool extract_range_from_cond (tree
, tree
*, tree
*, int *);
274 static void record_equivalences_from_phis (basic_block
);
275 static void record_equivalences_from_incoming_edge (basic_block
);
276 static bool eliminate_redundant_computations (struct dom_walk_data
*,
278 static void record_equivalences_from_stmt (tree
, int, stmt_ann_t
);
279 static void thread_across_edge (struct dom_walk_data
*, edge
);
280 static void dom_opt_finalize_block (struct dom_walk_data
*, basic_block
);
281 static void dom_opt_initialize_block (struct dom_walk_data
*, basic_block
);
282 static void propagate_to_outgoing_edges (struct dom_walk_data
*, basic_block
);
283 static void remove_local_expressions_from_table (void);
284 static void restore_vars_to_original_value (void);
285 static edge
single_incoming_edge_ignoring_loop_edges (basic_block
);
286 static void restore_nonzero_vars_to_original_value (void);
287 static inline bool unsafe_associative_fp_binop (tree
);
290 /* Local version of fold that doesn't introduce cruft. */
297 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
298 may have been added by fold, and "useless" type conversions that might
299 now be apparent due to propagation. */
300 STRIP_USELESS_TYPE_CONVERSION (t
);
305 /* Allocate an EDGE_INFO for edge E and attach it to E.
306 Return the new EDGE_INFO structure. */
308 static struct edge_info
*
309 allocate_edge_info (edge e
)
311 struct edge_info
*edge_info
;
313 edge_info
= xcalloc (1, sizeof (struct edge_info
));
319 /* Free all EDGE_INFO structures associated with edges in the CFG.
320 If a particular edge can be threaded, copy the redirection
321 target from the EDGE_INFO structure into the edge's AUX field
322 as required by code to update the CFG and SSA graph for
326 free_all_edge_infos (void)
334 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
336 struct edge_info
*edge_info
= e
->aux
;
340 e
->aux
= edge_info
->redirection_target
;
341 if (edge_info
->cond_equivalences
)
342 free (edge_info
->cond_equivalences
);
349 /* Jump threading, redundancy elimination and const/copy propagation.
351 This pass may expose new symbols that need to be renamed into SSA. For
352 every new symbol exposed, its corresponding bit will be set in
356 tree_ssa_dominator_optimize (void)
358 struct dom_walk_data walk_data
;
360 struct loops loops_info
;
362 memset (&opt_stats
, 0, sizeof (opt_stats
));
364 /* Create our hash tables. */
365 avail_exprs
= htab_create (1024, real_avail_expr_hash
, avail_expr_eq
, free
);
366 vrp_data
= htab_create (ceil_log2 (num_ssa_names
), vrp_hash
, vrp_eq
, free
);
367 avail_exprs_stack
= VEC_alloc (tree
, heap
, 20);
368 const_and_copies_stack
= VEC_alloc (tree
, heap
, 20);
369 nonzero_vars_stack
= VEC_alloc (tree
, heap
, 20);
370 vrp_variables_stack
= VEC_alloc (tree
, heap
, 20);
371 stmts_to_rescan
= VEC_alloc (tree
, heap
, 20);
372 nonzero_vars
= BITMAP_ALLOC (NULL
);
373 need_eh_cleanup
= BITMAP_ALLOC (NULL
);
375 /* Setup callbacks for the generic dominator tree walker. */
376 walk_data
.walk_stmts_backward
= false;
377 walk_data
.dom_direction
= CDI_DOMINATORS
;
378 walk_data
.initialize_block_local_data
= NULL
;
379 walk_data
.before_dom_children_before_stmts
= dom_opt_initialize_block
;
380 walk_data
.before_dom_children_walk_stmts
= optimize_stmt
;
381 walk_data
.before_dom_children_after_stmts
= propagate_to_outgoing_edges
;
382 walk_data
.after_dom_children_before_stmts
= NULL
;
383 walk_data
.after_dom_children_walk_stmts
= NULL
;
384 walk_data
.after_dom_children_after_stmts
= dom_opt_finalize_block
;
385 /* Right now we only attach a dummy COND_EXPR to the global data pointer.
386 When we attach more stuff we'll need to fill this out with a real
388 walk_data
.global_data
= NULL
;
389 walk_data
.block_local_data_size
= 0;
390 walk_data
.interesting_blocks
= NULL
;
392 /* Now initialize the dominator walker. */
393 init_walk_dominator_tree (&walk_data
);
395 calculate_dominance_info (CDI_DOMINATORS
);
397 /* We need to know which edges exit loops so that we can
398 aggressively thread through loop headers to an exit
400 flow_loops_find (&loops_info
);
401 mark_loop_exit_edges (&loops_info
);
402 flow_loops_free (&loops_info
);
404 /* Clean up the CFG so that any forwarder blocks created by loop
405 canonicalization are removed. */
408 /* If we prove certain blocks are unreachable, then we want to
409 repeat the dominator optimization process as PHI nodes may
410 have turned into copies which allows better propagation of
411 values. So we repeat until we do not identify any new unreachable
415 /* Optimize the dominator tree. */
418 /* We need accurate information regarding back edges in the CFG
419 for jump threading. */
420 mark_dfs_back_edges ();
422 /* Recursively walk the dominator tree optimizing statements. */
423 walk_dominator_tree (&walk_data
, ENTRY_BLOCK_PTR
);
425 /* If we exposed any new variables, go ahead and put them into
426 SSA form now, before we handle jump threading. This simplifies
427 interactions between rewriting of _DECL nodes into SSA form
428 and rewriting SSA_NAME nodes into SSA form after block
429 duplication and CFG manipulation. */
430 update_ssa (TODO_update_ssa
);
432 free_all_edge_infos ();
435 block_stmt_iterator bsi
;
439 for (bsi
= bsi_start (bb
); !bsi_end_p (bsi
); bsi_next (&bsi
))
441 update_stmt_if_modified (bsi_stmt (bsi
));
445 /* Thread jumps, creating duplicate blocks as needed. */
446 cfg_altered
|= thread_through_all_blocks ();
448 /* Removal of statements may make some EH edges dead. Purge
449 such edges from the CFG as needed. */
450 if (!bitmap_empty_p (need_eh_cleanup
))
452 cfg_altered
|= tree_purge_all_dead_eh_edges (need_eh_cleanup
);
453 bitmap_zero (need_eh_cleanup
);
457 free_dominance_info (CDI_DOMINATORS
);
459 cfg_altered
= cleanup_tree_cfg ();
461 if (rediscover_loops_after_threading
)
463 /* Rerun basic loop analysis to discover any newly
464 created loops and update the set of exit edges. */
465 rediscover_loops_after_threading
= false;
466 flow_loops_find (&loops_info
);
467 mark_loop_exit_edges (&loops_info
);
468 flow_loops_free (&loops_info
);
470 /* Remove any forwarder blocks inserted by loop
471 header canonicalization. */
475 calculate_dominance_info (CDI_DOMINATORS
);
477 rewrite_ssa_into_ssa ();
479 /* Reinitialize the various tables. */
480 bitmap_clear (nonzero_vars
);
481 htab_empty (avail_exprs
);
482 htab_empty (vrp_data
);
484 /* Finally, remove everything except invariants in SSA_NAME_VALUE.
486 This must be done before we iterate as we might have a
487 reference to an SSA_NAME which was removed by the call to
488 rewrite_ssa_into_ssa.
490 Long term we will be able to let everything in SSA_NAME_VALUE
491 persist. However, for now, we know this is the safe thing to do. */
492 for (i
= 0; i
< num_ssa_names
; i
++)
494 tree name
= ssa_name (i
);
500 value
= SSA_NAME_VALUE (name
);
501 if (value
&& !is_gimple_min_invariant (value
))
502 SSA_NAME_VALUE (name
) = NULL
;
505 while (optimize
> 1 && cfg_altered
);
507 /* Debugging dumps. */
508 if (dump_file
&& (dump_flags
& TDF_STATS
))
509 dump_dominator_optimization_stats (dump_file
);
511 /* We emptied the hash table earlier, now delete it completely. */
512 htab_delete (avail_exprs
);
513 htab_delete (vrp_data
);
515 /* It is not necessary to clear CURRDEFS, REDIRECTION_EDGES, VRP_DATA,
516 CONST_AND_COPIES, and NONZERO_VARS as they all get cleared at the bottom
517 of the do-while loop above. */
519 /* And finalize the dominator walker. */
520 fini_walk_dominator_tree (&walk_data
);
522 /* Free nonzero_vars. */
523 BITMAP_FREE (nonzero_vars
);
524 BITMAP_FREE (need_eh_cleanup
);
526 VEC_free (tree
, heap
, avail_exprs_stack
);
527 VEC_free (tree
, heap
, const_and_copies_stack
);
528 VEC_free (tree
, heap
, nonzero_vars_stack
);
529 VEC_free (tree
, heap
, vrp_variables_stack
);
530 VEC_free (tree
, heap
, stmts_to_rescan
);
534 gate_dominator (void)
536 return flag_tree_dom
!= 0;
539 struct tree_opt_pass pass_dominator
=
542 gate_dominator
, /* gate */
543 tree_ssa_dominator_optimize
, /* execute */
546 0, /* static_pass_number */
547 TV_TREE_SSA_DOMINATOR_OPTS
, /* tv_id */
548 PROP_cfg
| PROP_ssa
| PROP_alias
, /* properties_required */
549 0, /* properties_provided */
550 0, /* properties_destroyed */
551 0, /* todo_flags_start */
554 | TODO_verify_ssa
, /* todo_flags_finish */
559 /* We are exiting E->src, see if E->dest ends with a conditional
560 jump which has a known value when reached via E.
562 Special care is necessary if E is a back edge in the CFG as we
563 will have already recorded equivalences for E->dest into our
564 various tables, including the result of the conditional at
565 the end of E->dest. Threading opportunities are severely
566 limited in that case to avoid short-circuiting the loop
569 Note it is quite common for the first block inside a loop to
570 end with a conditional which is either always true or always
571 false when reached via the loop backedge. Thus we do not want
572 to blindly disable threading across a loop backedge. */
575 thread_across_edge (struct dom_walk_data
*walk_data
, edge e
)
577 block_stmt_iterator bsi
;
581 /* If E->dest does not end with a conditional, then there is
583 bsi
= bsi_last (e
->dest
);
586 || (TREE_CODE (bsi_stmt (bsi
)) != COND_EXPR
587 && TREE_CODE (bsi_stmt (bsi
)) != GOTO_EXPR
588 && TREE_CODE (bsi_stmt (bsi
)) != SWITCH_EXPR
))
591 /* The basic idea here is to use whatever knowledge we have
592 from our dominator walk to simplify statements in E->dest,
593 with the ultimate goal being to simplify the conditional
594 at the end of E->dest.
596 Note that we must undo any changes we make to the underlying
597 statements as the simplifications we are making are control
598 flow sensitive (ie, the simplifications are valid when we
599 traverse E, but may not be valid on other paths to E->dest. */
601 /* Each PHI creates a temporary equivalence, record them. Again
602 these are context sensitive equivalences and will be removed
604 for (phi
= phi_nodes (e
->dest
); phi
; phi
= PHI_CHAIN (phi
))
606 tree src
= PHI_ARG_DEF_FROM_EDGE (phi
, e
);
607 tree dst
= PHI_RESULT (phi
);
609 /* If the desired argument is not the same as this PHI's result
610 and it is set by a PHI in E->dest, then we can not thread
613 && TREE_CODE (src
) == SSA_NAME
614 && TREE_CODE (SSA_NAME_DEF_STMT (src
)) == PHI_NODE
615 && bb_for_stmt (SSA_NAME_DEF_STMT (src
)) == e
->dest
)
618 record_const_or_copy (dst
, src
);
621 /* Try to simplify each statement in E->dest, ultimately leading to
622 a simplification of the COND_EXPR at the end of E->dest.
624 We might consider marking just those statements which ultimately
625 feed the COND_EXPR. It's not clear if the overhead of bookkeeping
626 would be recovered by trying to simplify fewer statements.
628 If we are able to simplify a statement into the form
629 SSA_NAME = (SSA_NAME | gimple invariant), then we can record
630 a context sensitive equivalency which may help us simplify
631 later statements in E->dest.
633 Failure to simplify into the form above merely means that the
634 statement provides no equivalences to help simplify later
635 statements. This does not prevent threading through E->dest. */
636 for (bsi
= bsi_start (e
->dest
); ! bsi_end_p (bsi
); bsi_next (&bsi
))
640 stmt
= bsi_stmt (bsi
);
642 /* Ignore empty statements and labels. */
643 if (IS_EMPTY_STMT (stmt
) || TREE_CODE (stmt
) == LABEL_EXPR
)
646 /* Safely handle threading across loop backedges. This is
647 over conservative, but still allows us to capture the
648 majority of the cases where we can thread across a loop
650 if ((e
->flags
& EDGE_DFS_BACK
) != 0
651 && TREE_CODE (stmt
) != COND_EXPR
652 && TREE_CODE (stmt
) != SWITCH_EXPR
)
655 /* If the statement has volatile operands, then we assume we
656 can not thread through this block. This is overly
657 conservative in some ways. */
658 if (TREE_CODE (stmt
) == ASM_EXPR
&& ASM_VOLATILE_P (stmt
))
661 /* If this is not a MODIFY_EXPR which sets an SSA_NAME to a new
662 value, then do not try to simplify this statement as it will
663 not simplify in any way that is helpful for jump threading. */
664 if (TREE_CODE (stmt
) != MODIFY_EXPR
665 || TREE_CODE (TREE_OPERAND (stmt
, 0)) != SSA_NAME
)
668 /* At this point we have a statement which assigns an RHS to an
669 SSA_VAR on the LHS. We want to try and simplify this statement
670 to expose more context sensitive equivalences which in turn may
671 allow us to simplify the condition at the end of the loop. */
672 if (TREE_CODE (TREE_OPERAND (stmt
, 1)) == SSA_NAME
)
673 cached_lhs
= TREE_OPERAND (stmt
, 1);
676 /* Copy the operands. */
677 stmt_ann_t ann
= stmt_ann (stmt
);
678 use_optype uses
= USE_OPS (ann
);
679 vuse_optype vuses
= VUSE_OPS (ann
);
680 tree
*uses_copy
= xmalloc (NUM_USES (uses
) * sizeof (tree
));
681 tree
*vuses_copy
= xmalloc (NUM_VUSES (vuses
) * sizeof (tree
));
684 /* Make a copy of the uses into USES_COPY, then cprop into
686 for (i
= 0; i
< NUM_USES (uses
); i
++)
690 uses_copy
[i
] = USE_OP (uses
, i
);
691 if (TREE_CODE (USE_OP (uses
, i
)) == SSA_NAME
)
692 tmp
= SSA_NAME_VALUE (USE_OP (uses
, i
));
693 if (tmp
&& TREE_CODE (tmp
) != VALUE_HANDLE
)
694 SET_USE_OP (uses
, i
, tmp
);
697 /* Similarly for virtual uses. */
698 for (i
= 0; i
< NUM_VUSES (vuses
); i
++)
702 vuses_copy
[i
] = VUSE_OP (vuses
, i
);
703 if (TREE_CODE (VUSE_OP (vuses
, i
)) == SSA_NAME
)
704 tmp
= SSA_NAME_VALUE (VUSE_OP (vuses
, i
));
705 if (tmp
&& TREE_CODE (tmp
) != VALUE_HANDLE
)
706 SET_VUSE_OP (vuses
, i
, tmp
);
709 /* Try to fold/lookup the new expression. Inserting the
710 expression into the hash table is unlikely to help
711 simplify anything later, so just query the hashtable. */
712 cached_lhs
= fold (TREE_OPERAND (stmt
, 1));
713 if (TREE_CODE (cached_lhs
) != SSA_NAME
714 && !is_gimple_min_invariant (cached_lhs
))
715 cached_lhs
= lookup_avail_expr (stmt
, false);
717 /* Restore the statement's original uses/defs. */
718 for (i
= 0; i
< NUM_USES (uses
); i
++)
719 SET_USE_OP (uses
, i
, uses_copy
[i
]);
721 for (i
= 0; i
< NUM_VUSES (vuses
); i
++)
722 SET_VUSE_OP (vuses
, i
, vuses_copy
[i
]);
728 /* Record the context sensitive equivalence if we were able
729 to simplify this statement. */
731 && (TREE_CODE (cached_lhs
) == SSA_NAME
732 || is_gimple_min_invariant (cached_lhs
)))
733 record_const_or_copy (TREE_OPERAND (stmt
, 0), cached_lhs
);
736 /* If we stopped at a COND_EXPR or SWITCH_EXPR, see if we know which arm
739 && (TREE_CODE (stmt
) == COND_EXPR
740 || TREE_CODE (stmt
) == GOTO_EXPR
741 || TREE_CODE (stmt
) == SWITCH_EXPR
))
743 tree cond
, cached_lhs
;
745 /* Now temporarily cprop the operands and try to find the resulting
746 expression in the hash tables. */
747 if (TREE_CODE (stmt
) == COND_EXPR
)
748 cond
= COND_EXPR_COND (stmt
);
749 else if (TREE_CODE (stmt
) == GOTO_EXPR
)
750 cond
= GOTO_DESTINATION (stmt
);
752 cond
= SWITCH_COND (stmt
);
754 if (COMPARISON_CLASS_P (cond
))
756 tree dummy_cond
, op0
, op1
;
757 enum tree_code cond_code
;
759 op0
= TREE_OPERAND (cond
, 0);
760 op1
= TREE_OPERAND (cond
, 1);
761 cond_code
= TREE_CODE (cond
);
763 /* Get the current value of both operands. */
764 if (TREE_CODE (op0
) == SSA_NAME
)
766 tree tmp
= SSA_NAME_VALUE (op0
);
767 if (tmp
&& TREE_CODE (tmp
) != VALUE_HANDLE
)
771 if (TREE_CODE (op1
) == SSA_NAME
)
773 tree tmp
= SSA_NAME_VALUE (op1
);
774 if (tmp
&& TREE_CODE (tmp
) != VALUE_HANDLE
)
778 /* Stuff the operator and operands into our dummy conditional
779 expression, creating the dummy conditional if necessary. */
780 dummy_cond
= walk_data
->global_data
;
783 dummy_cond
= build (cond_code
, boolean_type_node
, op0
, op1
);
784 dummy_cond
= build (COND_EXPR
, void_type_node
,
785 dummy_cond
, NULL
, NULL
);
786 walk_data
->global_data
= dummy_cond
;
790 TREE_SET_CODE (COND_EXPR_COND (dummy_cond
), cond_code
);
791 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 0) = op0
;
792 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 1) = op1
;
795 /* If the conditional folds to an invariant, then we are done,
796 otherwise look it up in the hash tables. */
797 cached_lhs
= local_fold (COND_EXPR_COND (dummy_cond
));
798 if (! is_gimple_min_invariant (cached_lhs
))
800 cached_lhs
= lookup_avail_expr (dummy_cond
, false);
801 if (!cached_lhs
|| ! is_gimple_min_invariant (cached_lhs
))
802 cached_lhs
= simplify_cond_and_lookup_avail_expr (dummy_cond
,
807 /* We can have conditionals which just test the state of a
808 variable rather than use a relational operator. These are
809 simpler to handle. */
810 else if (TREE_CODE (cond
) == SSA_NAME
)
813 cached_lhs
= SSA_NAME_VALUE (cached_lhs
);
814 if (cached_lhs
&& ! is_gimple_min_invariant (cached_lhs
))
818 cached_lhs
= lookup_avail_expr (stmt
, false);
822 edge taken_edge
= find_taken_edge (e
->dest
, cached_lhs
);
823 basic_block dest
= (taken_edge
? taken_edge
->dest
: NULL
);
828 /* If we have a known destination for the conditional, then
829 we can perform this optimization, which saves at least one
830 conditional jump each time it applies since we get to
831 bypass the conditional at our original destination. */
834 struct edge_info
*edge_info
;
836 update_bb_profile_for_threading (e
->dest
, EDGE_FREQUENCY (e
),
837 e
->count
, taken_edge
);
841 edge_info
= allocate_edge_info (e
);
842 edge_info
->redirection_target
= taken_edge
;
843 bb_ann (e
->dest
)->incoming_edge_threaded
= true;
850 /* Initialize local stacks for this optimizer and record equivalences
851 upon entry to BB. Equivalences can come from the edge traversed to
852 reach BB or they may come from PHI nodes at the start of BB. */
855 dom_opt_initialize_block (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
858 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
859 fprintf (dump_file
, "\n\nOptimizing block #%d\n\n", bb
->index
);
861 /* Push a marker on the stacks of local information so that we know how
862 far to unwind when we finalize this block. */
863 VEC_safe_push (tree
, heap
, avail_exprs_stack
, NULL_TREE
);
864 VEC_safe_push (tree
, heap
, const_and_copies_stack
, NULL_TREE
);
865 VEC_safe_push (tree
, heap
, nonzero_vars_stack
, NULL_TREE
);
866 VEC_safe_push (tree
, heap
, vrp_variables_stack
, NULL_TREE
);
868 record_equivalences_from_incoming_edge (bb
);
870 /* PHI nodes can create equivalences too. */
871 record_equivalences_from_phis (bb
);
874 /* Given an expression EXPR (a relational expression or a statement),
875 initialize the hash table element pointed by by ELEMENT. */
878 initialize_hash_element (tree expr
, tree lhs
, struct expr_hash_elt
*element
)
880 /* Hash table elements may be based on conditional expressions or statements.
882 For the former case, we have no annotation and we want to hash the
883 conditional expression. In the latter case we have an annotation and
884 we want to record the expression the statement evaluates. */
885 if (COMPARISON_CLASS_P (expr
) || TREE_CODE (expr
) == TRUTH_NOT_EXPR
)
890 else if (TREE_CODE (expr
) == COND_EXPR
)
892 element
->ann
= stmt_ann (expr
);
893 element
->rhs
= COND_EXPR_COND (expr
);
895 else if (TREE_CODE (expr
) == SWITCH_EXPR
)
897 element
->ann
= stmt_ann (expr
);
898 element
->rhs
= SWITCH_COND (expr
);
900 else if (TREE_CODE (expr
) == RETURN_EXPR
&& TREE_OPERAND (expr
, 0))
902 element
->ann
= stmt_ann (expr
);
903 element
->rhs
= TREE_OPERAND (TREE_OPERAND (expr
, 0), 1);
905 else if (TREE_CODE (expr
) == GOTO_EXPR
)
907 element
->ann
= stmt_ann (expr
);
908 element
->rhs
= GOTO_DESTINATION (expr
);
912 element
->ann
= stmt_ann (expr
);
913 element
->rhs
= TREE_OPERAND (expr
, 1);
917 element
->hash
= avail_expr_hash (element
);
920 /* Remove all the expressions in LOCALS from TABLE, stopping when there are
921 LIMIT entries left in LOCALs. */
924 remove_local_expressions_from_table (void)
926 /* Remove all the expressions made available in this block. */
927 while (VEC_length (tree
, avail_exprs_stack
) > 0)
929 struct expr_hash_elt element
;
930 tree expr
= VEC_pop (tree
, avail_exprs_stack
);
932 if (expr
== NULL_TREE
)
935 initialize_hash_element (expr
, NULL
, &element
);
936 htab_remove_elt_with_hash (avail_exprs
, &element
, element
.hash
);
940 /* Use the SSA_NAMES in LOCALS to restore TABLE to its original
941 state, stopping when there are LIMIT entries left in LOCALs. */
944 restore_nonzero_vars_to_original_value (void)
946 while (VEC_length (tree
, nonzero_vars_stack
) > 0)
948 tree name
= VEC_pop (tree
, nonzero_vars_stack
);
953 bitmap_clear_bit (nonzero_vars
, SSA_NAME_VERSION (name
));
957 /* Use the source/dest pairs in CONST_AND_COPIES_STACK to restore
958 CONST_AND_COPIES to its original state, stopping when we hit a
962 restore_vars_to_original_value (void)
964 while (VEC_length (tree
, const_and_copies_stack
) > 0)
966 tree prev_value
, dest
;
968 dest
= VEC_pop (tree
, const_and_copies_stack
);
973 prev_value
= VEC_pop (tree
, const_and_copies_stack
);
974 SSA_NAME_VALUE (dest
) = prev_value
;
978 /* We have finished processing the dominator children of BB, perform
979 any finalization actions in preparation for leaving this node in
980 the dominator tree. */
983 dom_opt_finalize_block (struct dom_walk_data
*walk_data
, basic_block bb
)
987 /* If we are at a leaf node in the dominator tree, see if we can thread
988 the edge from BB through its successor.
990 Do this before we remove entries from our equivalence tables. */
991 if (single_succ_p (bb
)
992 && (single_succ_edge (bb
)->flags
& EDGE_ABNORMAL
) == 0
993 && (get_immediate_dominator (CDI_DOMINATORS
, single_succ (bb
)) != bb
994 || phi_nodes (single_succ (bb
))))
997 thread_across_edge (walk_data
, single_succ_edge (bb
));
999 else if ((last
= last_stmt (bb
))
1000 && TREE_CODE (last
) == GOTO_EXPR
1001 && TREE_CODE (TREE_OPERAND (last
, 0)) == SSA_NAME
)
1006 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1008 thread_across_edge (walk_data
, e
);
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 varray_type 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 (VARRAY_ACTIVE_SIZE (var_vrp_records
) > 0)
1149 struct vrp_element
*element
1150 = (struct vrp_element
*)VARRAY_TOP_GENERIC_PTR (var_vrp_records
);
1152 if (element
->bb
!= bb
)
1155 VARRAY_POP (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
)));
1245 /* Ignoring loop backedges, if BB has precisely one incoming edge then
1246 return that edge. Otherwise return NULL. */
1248 single_incoming_edge_ignoring_loop_edges (basic_block bb
)
1254 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1256 /* A loop back edge can be identified by the destination of
1257 the edge dominating the source of the edge. */
1258 if (dominated_by_p (CDI_DOMINATORS
, e
->src
, e
->dest
))
1261 /* If we have already seen a non-loop edge, then we must have
1262 multiple incoming non-loop edges and thus we return NULL. */
1266 /* This is the first non-loop incoming edge we have found. Record
1274 /* Record any equivalences created by the incoming edge to BB. If BB
1275 has more than one incoming edge, then no equivalence is created. */
1278 record_equivalences_from_incoming_edge (basic_block bb
)
1282 struct edge_info
*edge_info
;
1284 /* If our parent block ended with a control statement, then we may be
1285 able to record some equivalences based on which outgoing edge from
1286 the parent was followed. */
1287 parent
= get_immediate_dominator (CDI_DOMINATORS
, bb
);
1289 e
= single_incoming_edge_ignoring_loop_edges (bb
);
1291 /* If we had a single incoming edge from our parent block, then enter
1292 any data associated with the edge into our tables. */
1293 if (e
&& e
->src
== parent
)
1301 tree lhs
= edge_info
->lhs
;
1302 tree rhs
= edge_info
->rhs
;
1303 tree
*cond_equivalences
= edge_info
->cond_equivalences
;
1306 record_equality (lhs
, rhs
);
1308 if (cond_equivalences
)
1310 bool recorded_range
= false;
1311 for (i
= 0; i
< edge_info
->max_cond_equivalences
; i
+= 2)
1313 tree expr
= cond_equivalences
[i
];
1314 tree value
= cond_equivalences
[i
+ 1];
1316 record_cond (expr
, value
);
1318 /* For the first true equivalence, record range
1319 information. We only do this for the first
1320 true equivalence as it should dominate any
1321 later true equivalences. */
1322 if (! recorded_range
1323 && COMPARISON_CLASS_P (expr
)
1324 && value
== boolean_true_node
1325 && TREE_CONSTANT (TREE_OPERAND (expr
, 1)))
1327 record_range (expr
, bb
);
1328 recorded_range
= true;
1336 /* Dump SSA statistics on FILE. */
1339 dump_dominator_optimization_stats (FILE *file
)
1343 fprintf (file
, "Total number of statements: %6ld\n\n",
1344 opt_stats
.num_stmts
);
1345 fprintf (file
, "Exprs considered for dominator optimizations: %6ld\n",
1346 opt_stats
.num_exprs_considered
);
1348 n_exprs
= opt_stats
.num_exprs_considered
;
1352 fprintf (file
, " Redundant expressions eliminated: %6ld (%.0f%%)\n",
1353 opt_stats
.num_re
, PERCENT (opt_stats
.num_re
,
1355 fprintf (file
, " Constants propagated: %6ld\n",
1356 opt_stats
.num_const_prop
);
1357 fprintf (file
, " Copies propagated: %6ld\n",
1358 opt_stats
.num_copy_prop
);
1360 fprintf (file
, "\nHash table statistics:\n");
1362 fprintf (file
, " avail_exprs: ");
1363 htab_statistics (file
, avail_exprs
);
1367 /* Dump SSA statistics on stderr. */
1370 debug_dominator_optimization_stats (void)
1372 dump_dominator_optimization_stats (stderr
);
1376 /* Dump statistics for the hash table HTAB. */
1379 htab_statistics (FILE *file
, htab_t htab
)
1381 fprintf (file
, "size %ld, %ld elements, %f collision/search ratio\n",
1382 (long) htab_size (htab
),
1383 (long) htab_elements (htab
),
1384 htab_collisions (htab
));
1387 /* Record the fact that VAR has a nonzero value, though we may not know
1388 its exact value. Note that if VAR is already known to have a nonzero
1389 value, then we do nothing. */
1392 record_var_is_nonzero (tree var
)
1394 int indx
= SSA_NAME_VERSION (var
);
1396 if (bitmap_bit_p (nonzero_vars
, indx
))
1399 /* Mark it in the global table. */
1400 bitmap_set_bit (nonzero_vars
, indx
);
1402 /* Record this SSA_NAME so that we can reset the global table
1403 when we leave this block. */
1404 VEC_safe_push (tree
, heap
, nonzero_vars_stack
, var
);
1407 /* Enter a statement into the true/false expression hash table indicating
1408 that the condition COND has the value VALUE. */
1411 record_cond (tree cond
, tree value
)
1413 struct expr_hash_elt
*element
= xmalloc (sizeof (struct expr_hash_elt
));
1416 initialize_hash_element (cond
, value
, element
);
1418 slot
= htab_find_slot_with_hash (avail_exprs
, (void *)element
,
1419 element
->hash
, INSERT
);
1422 *slot
= (void *) element
;
1423 VEC_safe_push (tree
, heap
, avail_exprs_stack
, cond
);
1429 /* Build a new conditional using NEW_CODE, OP0 and OP1 and store
1430 the new conditional into *p, then store a boolean_true_node
1434 build_and_record_new_cond (enum tree_code new_code
, tree op0
, tree op1
, tree
*p
)
1436 *p
= build2 (new_code
, boolean_type_node
, op0
, op1
);
1438 *p
= boolean_true_node
;
1441 /* Record that COND is true and INVERTED is false into the edge information
1442 structure. Also record that any conditions dominated by COND are true
1445 For example, if a < b is true, then a <= b must also be true. */
1448 record_conditions (struct edge_info
*edge_info
, tree cond
, tree inverted
)
1452 if (!COMPARISON_CLASS_P (cond
))
1455 op0
= TREE_OPERAND (cond
, 0);
1456 op1
= TREE_OPERAND (cond
, 1);
1458 switch (TREE_CODE (cond
))
1462 edge_info
->max_cond_equivalences
= 12;
1463 edge_info
->cond_equivalences
= xmalloc (12 * sizeof (tree
));
1464 build_and_record_new_cond ((TREE_CODE (cond
) == LT_EXPR
1465 ? LE_EXPR
: GE_EXPR
),
1466 op0
, op1
, &edge_info
->cond_equivalences
[4]);
1467 build_and_record_new_cond (ORDERED_EXPR
, op0
, op1
,
1468 &edge_info
->cond_equivalences
[6]);
1469 build_and_record_new_cond (NE_EXPR
, op0
, op1
,
1470 &edge_info
->cond_equivalences
[8]);
1471 build_and_record_new_cond (LTGT_EXPR
, op0
, op1
,
1472 &edge_info
->cond_equivalences
[10]);
1477 edge_info
->max_cond_equivalences
= 6;
1478 edge_info
->cond_equivalences
= xmalloc (6 * sizeof (tree
));
1479 build_and_record_new_cond (ORDERED_EXPR
, op0
, op1
,
1480 &edge_info
->cond_equivalences
[4]);
1484 edge_info
->max_cond_equivalences
= 10;
1485 edge_info
->cond_equivalences
= xmalloc (10 * sizeof (tree
));
1486 build_and_record_new_cond (ORDERED_EXPR
, op0
, op1
,
1487 &edge_info
->cond_equivalences
[4]);
1488 build_and_record_new_cond (LE_EXPR
, op0
, op1
,
1489 &edge_info
->cond_equivalences
[6]);
1490 build_and_record_new_cond (GE_EXPR
, op0
, op1
,
1491 &edge_info
->cond_equivalences
[8]);
1494 case UNORDERED_EXPR
:
1495 edge_info
->max_cond_equivalences
= 16;
1496 edge_info
->cond_equivalences
= xmalloc (16 * sizeof (tree
));
1497 build_and_record_new_cond (NE_EXPR
, op0
, op1
,
1498 &edge_info
->cond_equivalences
[4]);
1499 build_and_record_new_cond (UNLE_EXPR
, op0
, op1
,
1500 &edge_info
->cond_equivalences
[6]);
1501 build_and_record_new_cond (UNGE_EXPR
, op0
, op1
,
1502 &edge_info
->cond_equivalences
[8]);
1503 build_and_record_new_cond (UNEQ_EXPR
, op0
, op1
,
1504 &edge_info
->cond_equivalences
[10]);
1505 build_and_record_new_cond (UNLT_EXPR
, op0
, op1
,
1506 &edge_info
->cond_equivalences
[12]);
1507 build_and_record_new_cond (UNGT_EXPR
, op0
, op1
,
1508 &edge_info
->cond_equivalences
[14]);
1513 edge_info
->max_cond_equivalences
= 8;
1514 edge_info
->cond_equivalences
= xmalloc (8 * sizeof (tree
));
1515 build_and_record_new_cond ((TREE_CODE (cond
) == UNLT_EXPR
1516 ? UNLE_EXPR
: UNGE_EXPR
),
1517 op0
, op1
, &edge_info
->cond_equivalences
[4]);
1518 build_and_record_new_cond (NE_EXPR
, op0
, op1
,
1519 &edge_info
->cond_equivalences
[6]);
1523 edge_info
->max_cond_equivalences
= 8;
1524 edge_info
->cond_equivalences
= xmalloc (8 * sizeof (tree
));
1525 build_and_record_new_cond (UNLE_EXPR
, op0
, op1
,
1526 &edge_info
->cond_equivalences
[4]);
1527 build_and_record_new_cond (UNGE_EXPR
, op0
, op1
,
1528 &edge_info
->cond_equivalences
[6]);
1532 edge_info
->max_cond_equivalences
= 8;
1533 edge_info
->cond_equivalences
= xmalloc (8 * sizeof (tree
));
1534 build_and_record_new_cond (NE_EXPR
, op0
, op1
,
1535 &edge_info
->cond_equivalences
[4]);
1536 build_and_record_new_cond (ORDERED_EXPR
, op0
, op1
,
1537 &edge_info
->cond_equivalences
[6]);
1541 edge_info
->max_cond_equivalences
= 4;
1542 edge_info
->cond_equivalences
= xmalloc (4 * sizeof (tree
));
1546 /* Now store the original true and false conditions into the first
1548 edge_info
->cond_equivalences
[0] = cond
;
1549 edge_info
->cond_equivalences
[1] = boolean_true_node
;
1550 edge_info
->cond_equivalences
[2] = inverted
;
1551 edge_info
->cond_equivalences
[3] = boolean_false_node
;
1554 /* A helper function for record_const_or_copy and record_equality.
1555 Do the work of recording the value and undo info. */
1558 record_const_or_copy_1 (tree x
, tree y
, tree prev_x
)
1560 SSA_NAME_VALUE (x
) = y
;
1562 VEC_reserve (tree
, heap
, const_and_copies_stack
, 2);
1563 VEC_quick_push (tree
, const_and_copies_stack
, prev_x
);
1564 VEC_quick_push (tree
, const_and_copies_stack
, x
);
1568 /* Return the loop depth of the basic block of the defining statement of X.
1569 This number should not be treated as absolutely correct because the loop
1570 information may not be completely up-to-date when dom runs. However, it
1571 will be relatively correct, and as more passes are taught to keep loop info
1572 up to date, the result will become more and more accurate. */
1575 loop_depth_of_name (tree x
)
1580 /* If it's not an SSA_NAME, we have no clue where the definition is. */
1581 if (TREE_CODE (x
) != SSA_NAME
)
1584 /* Otherwise return the loop depth of the defining statement's bb.
1585 Note that there may not actually be a bb for this statement, if the
1586 ssa_name is live on entry. */
1587 defstmt
= SSA_NAME_DEF_STMT (x
);
1588 defbb
= bb_for_stmt (defstmt
);
1592 return defbb
->loop_depth
;
1596 /* Record that X is equal to Y in const_and_copies. Record undo
1597 information in the block-local vector. */
1600 record_const_or_copy (tree x
, tree y
)
1602 tree prev_x
= SSA_NAME_VALUE (x
);
1604 if (TREE_CODE (y
) == SSA_NAME
)
1606 tree tmp
= SSA_NAME_VALUE (y
);
1611 record_const_or_copy_1 (x
, y
, prev_x
);
1614 /* Similarly, but assume that X and Y are the two operands of an EQ_EXPR.
1615 This constrains the cases in which we may treat this as assignment. */
1618 record_equality (tree x
, tree y
)
1620 tree prev_x
= NULL
, prev_y
= NULL
;
1622 if (TREE_CODE (x
) == SSA_NAME
)
1623 prev_x
= SSA_NAME_VALUE (x
);
1624 if (TREE_CODE (y
) == SSA_NAME
)
1625 prev_y
= SSA_NAME_VALUE (y
);
1627 /* If one of the previous values is invariant, or invariant in more loops
1628 (by depth), then use that.
1629 Otherwise it doesn't matter which value we choose, just so
1630 long as we canonicalize on one value. */
1631 if (TREE_INVARIANT (y
))
1633 else if (TREE_INVARIANT (x
) || (loop_depth_of_name (x
) <= loop_depth_of_name (y
)))
1634 prev_x
= x
, x
= y
, y
= prev_x
, prev_x
= prev_y
;
1635 else if (prev_x
&& TREE_INVARIANT (prev_x
))
1636 x
= y
, y
= prev_x
, prev_x
= prev_y
;
1637 else if (prev_y
&& TREE_CODE (prev_y
) != VALUE_HANDLE
)
1640 /* After the swapping, we must have one SSA_NAME. */
1641 if (TREE_CODE (x
) != SSA_NAME
)
1644 /* For IEEE, -0.0 == 0.0, so we don't necessarily know the sign of a
1645 variable compared against zero. If we're honoring signed zeros,
1646 then we cannot record this value unless we know that the value is
1648 if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (x
)))
1649 && (TREE_CODE (y
) != REAL_CST
1650 || REAL_VALUES_EQUAL (dconst0
, TREE_REAL_CST (y
))))
1653 record_const_or_copy_1 (x
, y
, prev_x
);
1656 /* Return true, if it is ok to do folding of an associative expression.
1657 EXP is the tree for the associative expression. */
1660 unsafe_associative_fp_binop (tree exp
)
1662 enum tree_code code
= TREE_CODE (exp
);
1663 return !(!flag_unsafe_math_optimizations
1664 && (code
== MULT_EXPR
|| code
== PLUS_EXPR
1665 || code
== MINUS_EXPR
)
1666 && FLOAT_TYPE_P (TREE_TYPE (exp
)));
1669 /* Returns true when STMT is a simple iv increment. It detects the
1670 following situation:
1672 i_1 = phi (..., i_2)
1673 i_2 = i_1 +/- ... */
1676 simple_iv_increment_p (tree stmt
)
1678 tree lhs
, rhs
, preinc
, phi
;
1681 if (TREE_CODE (stmt
) != MODIFY_EXPR
)
1684 lhs
= TREE_OPERAND (stmt
, 0);
1685 if (TREE_CODE (lhs
) != SSA_NAME
)
1688 rhs
= TREE_OPERAND (stmt
, 1);
1690 if (TREE_CODE (rhs
) != PLUS_EXPR
1691 && TREE_CODE (rhs
) != MINUS_EXPR
)
1694 preinc
= TREE_OPERAND (rhs
, 0);
1695 if (TREE_CODE (preinc
) != SSA_NAME
)
1698 phi
= SSA_NAME_DEF_STMT (preinc
);
1699 if (TREE_CODE (phi
) != PHI_NODE
)
1702 for (i
= 0; i
< (unsigned) PHI_NUM_ARGS (phi
); i
++)
1703 if (PHI_ARG_DEF (phi
, i
) == lhs
)
1709 /* STMT is a MODIFY_EXPR for which we were unable to find RHS in the
1710 hash tables. Try to simplify the RHS using whatever equivalences
1711 we may have recorded.
1713 If we are able to simplify the RHS, then lookup the simplified form in
1714 the hash table and return the result. Otherwise return NULL. */
1717 simplify_rhs_and_lookup_avail_expr (struct dom_walk_data
*walk_data
,
1718 tree stmt
, int insert
)
1720 tree rhs
= TREE_OPERAND (stmt
, 1);
1721 enum tree_code rhs_code
= TREE_CODE (rhs
);
1724 /* If we have lhs = ~x, look and see if we earlier had x = ~y.
1725 In which case we can change this statement to be lhs = y.
1726 Which can then be copy propagated.
1728 Similarly for negation. */
1729 if ((rhs_code
== BIT_NOT_EXPR
|| rhs_code
== NEGATE_EXPR
)
1730 && TREE_CODE (TREE_OPERAND (rhs
, 0)) == SSA_NAME
)
1732 /* Get the definition statement for our RHS. */
1733 tree rhs_def_stmt
= SSA_NAME_DEF_STMT (TREE_OPERAND (rhs
, 0));
1735 /* See if the RHS_DEF_STMT has the same form as our statement. */
1736 if (TREE_CODE (rhs_def_stmt
) == MODIFY_EXPR
1737 && TREE_CODE (TREE_OPERAND (rhs_def_stmt
, 1)) == rhs_code
)
1739 tree rhs_def_operand
;
1741 rhs_def_operand
= TREE_OPERAND (TREE_OPERAND (rhs_def_stmt
, 1), 0);
1743 /* Verify that RHS_DEF_OPERAND is a suitable SSA variable. */
1744 if (TREE_CODE (rhs_def_operand
) == SSA_NAME
1745 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand
))
1746 result
= update_rhs_and_lookup_avail_expr (stmt
,
1752 /* If we have z = (x OP C1), see if we earlier had x = y OP C2.
1753 If OP is associative, create and fold (y OP C2) OP C1 which
1754 should result in (y OP C3), use that as the RHS for the
1755 assignment. Add minus to this, as we handle it specially below. */
1756 if ((associative_tree_code (rhs_code
) || rhs_code
== MINUS_EXPR
)
1757 && TREE_CODE (TREE_OPERAND (rhs
, 0)) == SSA_NAME
1758 && is_gimple_min_invariant (TREE_OPERAND (rhs
, 1)))
1760 tree rhs_def_stmt
= SSA_NAME_DEF_STMT (TREE_OPERAND (rhs
, 0));
1762 /* If the statement defines an induction variable, do not propagate
1763 its value, so that we do not create overlapping life ranges. */
1764 if (simple_iv_increment_p (rhs_def_stmt
))
1765 goto dont_fold_assoc
;
1767 /* See if the RHS_DEF_STMT has the same form as our statement. */
1768 if (TREE_CODE (rhs_def_stmt
) == MODIFY_EXPR
)
1770 tree rhs_def_rhs
= TREE_OPERAND (rhs_def_stmt
, 1);
1771 enum tree_code rhs_def_code
= TREE_CODE (rhs_def_rhs
);
1773 if ((rhs_code
== rhs_def_code
&& unsafe_associative_fp_binop (rhs
))
1774 || (rhs_code
== PLUS_EXPR
&& rhs_def_code
== MINUS_EXPR
)
1775 || (rhs_code
== MINUS_EXPR
&& rhs_def_code
== PLUS_EXPR
))
1777 tree def_stmt_op0
= TREE_OPERAND (rhs_def_rhs
, 0);
1778 tree def_stmt_op1
= TREE_OPERAND (rhs_def_rhs
, 1);
1780 if (TREE_CODE (def_stmt_op0
) == SSA_NAME
1781 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def_stmt_op0
)
1782 && is_gimple_min_invariant (def_stmt_op1
))
1784 tree outer_const
= TREE_OPERAND (rhs
, 1);
1785 tree type
= TREE_TYPE (TREE_OPERAND (stmt
, 0));
1788 /* If we care about correct floating point results, then
1789 don't fold x + c1 - c2. Note that we need to take both
1790 the codes and the signs to figure this out. */
1791 if (FLOAT_TYPE_P (type
)
1792 && !flag_unsafe_math_optimizations
1793 && (rhs_def_code
== PLUS_EXPR
1794 || rhs_def_code
== MINUS_EXPR
))
1798 neg
^= (rhs_code
== MINUS_EXPR
);
1799 neg
^= (rhs_def_code
== MINUS_EXPR
);
1800 neg
^= real_isneg (TREE_REAL_CST_PTR (outer_const
));
1801 neg
^= real_isneg (TREE_REAL_CST_PTR (def_stmt_op1
));
1804 goto dont_fold_assoc
;
1807 /* Ho hum. So fold will only operate on the outermost
1808 thingy that we give it, so we have to build the new
1809 expression in two pieces. This requires that we handle
1810 combinations of plus and minus. */
1811 if (rhs_def_code
!= rhs_code
)
1813 if (rhs_def_code
== MINUS_EXPR
)
1814 t
= build (MINUS_EXPR
, type
, outer_const
, def_stmt_op1
);
1816 t
= build (MINUS_EXPR
, type
, def_stmt_op1
, outer_const
);
1817 rhs_code
= PLUS_EXPR
;
1819 else if (rhs_def_code
== MINUS_EXPR
)
1820 t
= build (PLUS_EXPR
, type
, def_stmt_op1
, outer_const
);
1822 t
= build (rhs_def_code
, type
, def_stmt_op1
, outer_const
);
1824 t
= build (rhs_code
, type
, def_stmt_op0
, t
);
1827 /* If the result is a suitable looking gimple expression,
1828 then use it instead of the original for STMT. */
1829 if (TREE_CODE (t
) == SSA_NAME
1830 || (UNARY_CLASS_P (t
)
1831 && TREE_CODE (TREE_OPERAND (t
, 0)) == SSA_NAME
)
1832 || ((BINARY_CLASS_P (t
) || COMPARISON_CLASS_P (t
))
1833 && TREE_CODE (TREE_OPERAND (t
, 0)) == SSA_NAME
1834 && is_gimple_val (TREE_OPERAND (t
, 1))))
1835 result
= update_rhs_and_lookup_avail_expr (stmt
, t
, insert
);
1842 /* Transform TRUNC_DIV_EXPR and TRUNC_MOD_EXPR into RSHIFT_EXPR
1843 and BIT_AND_EXPR respectively if the first operand is greater
1844 than zero and the second operand is an exact power of two. */
1845 if ((rhs_code
== TRUNC_DIV_EXPR
|| rhs_code
== TRUNC_MOD_EXPR
)
1846 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs
, 0)))
1847 && integer_pow2p (TREE_OPERAND (rhs
, 1)))
1850 tree op
= TREE_OPERAND (rhs
, 0);
1852 if (TYPE_UNSIGNED (TREE_TYPE (op
)))
1854 val
= integer_one_node
;
1858 tree dummy_cond
= walk_data
->global_data
;
1862 dummy_cond
= build (GT_EXPR
, boolean_type_node
,
1863 op
, integer_zero_node
);
1864 dummy_cond
= build (COND_EXPR
, void_type_node
,
1865 dummy_cond
, NULL
, NULL
);
1866 walk_data
->global_data
= dummy_cond
;
1870 TREE_SET_CODE (COND_EXPR_COND (dummy_cond
), GT_EXPR
);
1871 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 0) = op
;
1872 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 1)
1873 = integer_zero_node
;
1875 val
= simplify_cond_and_lookup_avail_expr (dummy_cond
, NULL
, false);
1878 if (val
&& integer_onep (val
))
1881 tree op0
= TREE_OPERAND (rhs
, 0);
1882 tree op1
= TREE_OPERAND (rhs
, 1);
1884 if (rhs_code
== TRUNC_DIV_EXPR
)
1885 t
= build (RSHIFT_EXPR
, TREE_TYPE (op0
), op0
,
1886 build_int_cst (NULL_TREE
, tree_log2 (op1
)));
1888 t
= build (BIT_AND_EXPR
, TREE_TYPE (op0
), op0
,
1889 local_fold (build (MINUS_EXPR
, TREE_TYPE (op1
),
1890 op1
, integer_one_node
)));
1892 result
= update_rhs_and_lookup_avail_expr (stmt
, t
, insert
);
1896 /* Transform ABS (X) into X or -X as appropriate. */
1897 if (rhs_code
== ABS_EXPR
1898 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs
, 0))))
1901 tree op
= TREE_OPERAND (rhs
, 0);
1902 tree type
= TREE_TYPE (op
);
1904 if (TYPE_UNSIGNED (type
))
1906 val
= integer_zero_node
;
1910 tree dummy_cond
= walk_data
->global_data
;
1914 dummy_cond
= build (LE_EXPR
, boolean_type_node
,
1915 op
, integer_zero_node
);
1916 dummy_cond
= build (COND_EXPR
, void_type_node
,
1917 dummy_cond
, NULL
, NULL
);
1918 walk_data
->global_data
= dummy_cond
;
1922 TREE_SET_CODE (COND_EXPR_COND (dummy_cond
), LE_EXPR
);
1923 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 0) = op
;
1924 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 1)
1925 = build_int_cst (type
, 0);
1927 val
= simplify_cond_and_lookup_avail_expr (dummy_cond
, NULL
, false);
1931 TREE_SET_CODE (COND_EXPR_COND (dummy_cond
), GE_EXPR
);
1932 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 0) = op
;
1933 TREE_OPERAND (COND_EXPR_COND (dummy_cond
), 1)
1934 = build_int_cst (type
, 0);
1936 val
= simplify_cond_and_lookup_avail_expr (dummy_cond
,
1941 if (integer_zerop (val
))
1942 val
= integer_one_node
;
1943 else if (integer_onep (val
))
1944 val
= integer_zero_node
;
1950 && (integer_onep (val
) || integer_zerop (val
)))
1954 if (integer_onep (val
))
1955 t
= build1 (NEGATE_EXPR
, TREE_TYPE (op
), op
);
1959 result
= update_rhs_and_lookup_avail_expr (stmt
, t
, insert
);
1963 /* Optimize *"foo" into 'f'. This is done here rather than
1964 in fold to avoid problems with stuff like &*"foo". */
1965 if (TREE_CODE (rhs
) == INDIRECT_REF
|| TREE_CODE (rhs
) == ARRAY_REF
)
1967 tree t
= fold_read_from_constant_string (rhs
);
1970 result
= update_rhs_and_lookup_avail_expr (stmt
, t
, insert
);
1976 /* COND is a condition of the form:
1978 x == const or x != const
1980 Look back to x's defining statement and see if x is defined as
1984 If const is unchanged if we convert it to type, then we can build
1985 the equivalent expression:
1988 y == const or y != const
1990 Which may allow further optimizations.
1992 Return the equivalent comparison or NULL if no such equivalent comparison
1996 find_equivalent_equality_comparison (tree cond
)
1998 tree op0
= TREE_OPERAND (cond
, 0);
1999 tree op1
= TREE_OPERAND (cond
, 1);
2000 tree def_stmt
= SSA_NAME_DEF_STMT (op0
);
2002 /* OP0 might have been a parameter, so first make sure it
2003 was defined by a MODIFY_EXPR. */
2004 if (def_stmt
&& TREE_CODE (def_stmt
) == MODIFY_EXPR
)
2006 tree def_rhs
= TREE_OPERAND (def_stmt
, 1);
2008 /* Now make sure the RHS of the MODIFY_EXPR is a typecast. */
2009 if ((TREE_CODE (def_rhs
) == NOP_EXPR
2010 || TREE_CODE (def_rhs
) == CONVERT_EXPR
)
2011 && TREE_CODE (TREE_OPERAND (def_rhs
, 0)) == SSA_NAME
)
2013 tree def_rhs_inner
= TREE_OPERAND (def_rhs
, 0);
2014 tree def_rhs_inner_type
= TREE_TYPE (def_rhs_inner
);
2017 if (TYPE_PRECISION (def_rhs_inner_type
)
2018 > TYPE_PRECISION (TREE_TYPE (def_rhs
)))
2021 /* What we want to prove is that if we convert OP1 to
2022 the type of the object inside the NOP_EXPR that the
2023 result is still equivalent to SRC.
2025 If that is true, the build and return new equivalent
2026 condition which uses the source of the typecast and the
2027 new constant (which has only changed its type). */
2028 new = build1 (TREE_CODE (def_rhs
), def_rhs_inner_type
, op1
);
2029 new = local_fold (new);
2030 if (is_gimple_val (new) && tree_int_cst_equal (new, op1
))
2031 return build (TREE_CODE (cond
), TREE_TYPE (cond
),
2032 def_rhs_inner
, new);
2038 /* STMT is a COND_EXPR for which we could not trivially determine its
2039 result. This routine attempts to find equivalent forms of the
2040 condition which we may be able to optimize better. It also
2041 uses simple value range propagation to optimize conditionals. */
2044 simplify_cond_and_lookup_avail_expr (tree stmt
,
2048 tree cond
= COND_EXPR_COND (stmt
);
2050 if (COMPARISON_CLASS_P (cond
))
2052 tree op0
= TREE_OPERAND (cond
, 0);
2053 tree op1
= TREE_OPERAND (cond
, 1);
2055 if (TREE_CODE (op0
) == SSA_NAME
&& is_gimple_min_invariant (op1
))
2058 tree low
, high
, cond_low
, cond_high
;
2059 int lowequal
, highequal
, swapped
, no_overlap
, subset
, cond_inverted
;
2060 varray_type vrp_records
;
2061 struct vrp_element
*element
;
2062 struct vrp_hash_elt vrp_hash_elt
, *vrp_hash_elt_p
;
2065 /* First see if we have test of an SSA_NAME against a constant
2066 where the SSA_NAME is defined by an earlier typecast which
2067 is irrelevant when performing tests against the given
2069 if (TREE_CODE (cond
) == EQ_EXPR
|| TREE_CODE (cond
) == NE_EXPR
)
2071 tree new_cond
= find_equivalent_equality_comparison (cond
);
2075 /* Update the statement to use the new equivalent
2077 COND_EXPR_COND (stmt
) = new_cond
;
2079 /* If this is not a real stmt, ann will be NULL and we
2080 avoid processing the operands. */
2082 mark_stmt_modified (stmt
);
2084 /* Lookup the condition and return its known value if it
2086 new_cond
= lookup_avail_expr (stmt
, insert
);
2090 /* The operands have changed, so update op0 and op1. */
2091 op0
= TREE_OPERAND (cond
, 0);
2092 op1
= TREE_OPERAND (cond
, 1);
2096 /* Consult the value range records for this variable (if they exist)
2097 to see if we can eliminate or simplify this conditional.
2099 Note two tests are necessary to determine no records exist.
2100 First we have to see if the virtual array exists, if it
2101 exists, then we have to check its active size.
2103 Also note the vast majority of conditionals are not testing
2104 a variable which has had its range constrained by an earlier
2105 conditional. So this filter avoids a lot of unnecessary work. */
2106 vrp_hash_elt
.var
= op0
;
2107 vrp_hash_elt
.records
= NULL
;
2108 slot
= htab_find_slot (vrp_data
, &vrp_hash_elt
, NO_INSERT
);
2112 vrp_hash_elt_p
= (struct vrp_hash_elt
*) *slot
;
2113 vrp_records
= vrp_hash_elt_p
->records
;
2114 if (vrp_records
== NULL
)
2117 limit
= VARRAY_ACTIVE_SIZE (vrp_records
);
2119 /* If we have no value range records for this variable, or we are
2120 unable to extract a range for this condition, then there is
2123 || ! extract_range_from_cond (cond
, &cond_high
,
2124 &cond_low
, &cond_inverted
))
2127 /* We really want to avoid unnecessary computations of range
2128 info. So all ranges are computed lazily; this avoids a
2129 lot of unnecessary work. i.e., we record the conditional,
2130 but do not process how it constrains the variable's
2131 potential values until we know that processing the condition
2134 However, we do not want to have to walk a potentially long
2135 list of ranges, nor do we want to compute a variable's
2136 range more than once for a given path.
2138 Luckily, each time we encounter a conditional that can not
2139 be otherwise optimized we will end up here and we will
2140 compute the necessary range information for the variable
2141 used in this condition.
2143 Thus you can conclude that there will never be more than one
2144 conditional associated with a variable which has not been
2145 processed. So we never need to merge more than one new
2146 conditional into the current range.
2148 These properties also help us avoid unnecessary work. */
2150 = (struct vrp_element
*)VARRAY_GENERIC_PTR (vrp_records
, limit
- 1);
2152 if (element
->high
&& element
->low
)
2154 /* The last element has been processed, so there is no range
2155 merging to do, we can simply use the high/low values
2156 recorded in the last element. */
2158 high
= element
->high
;
2162 tree tmp_high
, tmp_low
;
2165 /* The last element has not been processed. Process it now.
2166 record_range should ensure for cond inverted is not set.
2167 This call can only fail if cond is x < min or x > max,
2168 which fold should have optimized into false.
2169 If that doesn't happen, just pretend all values are
2171 if (! extract_range_from_cond (element
->cond
, &tmp_high
,
2175 gcc_assert (dummy
== 0);
2177 /* If this is the only element, then no merging is necessary,
2178 the high/low values from extract_range_from_cond are all
2187 /* Get the high/low value from the previous element. */
2188 struct vrp_element
*prev
2189 = (struct vrp_element
*)VARRAY_GENERIC_PTR (vrp_records
,
2194 /* Merge in this element's range with the range from the
2197 The low value for the merged range is the maximum of
2198 the previous low value and the low value of this record.
2200 Similarly the high value for the merged range is the
2201 minimum of the previous high value and the high value of
2203 low
= (low
&& tree_int_cst_compare (low
, tmp_low
) == 1
2205 high
= (high
&& tree_int_cst_compare (high
, tmp_high
) == -1
2209 /* And record the computed range. */
2211 element
->high
= high
;
2215 /* After we have constrained this variable's potential values,
2216 we try to determine the result of the given conditional.
2218 To simplify later tests, first determine if the current
2219 low value is the same low value as the conditional.
2220 Similarly for the current high value and the high value
2221 for the conditional. */
2222 lowequal
= tree_int_cst_equal (low
, cond_low
);
2223 highequal
= tree_int_cst_equal (high
, cond_high
);
2225 if (lowequal
&& highequal
)
2226 return (cond_inverted
? boolean_false_node
: boolean_true_node
);
2228 /* To simplify the overlap/subset tests below we may want
2229 to swap the two ranges so that the larger of the two
2230 ranges occurs "first". */
2232 if (tree_int_cst_compare (low
, cond_low
) == 1
2234 && tree_int_cst_compare (cond_high
, high
) == 1))
2247 /* Now determine if there is no overlap in the ranges
2248 or if the second range is a subset of the first range. */
2249 no_overlap
= tree_int_cst_lt (high
, cond_low
);
2250 subset
= tree_int_cst_compare (cond_high
, high
) != 1;
2252 /* If there was no overlap in the ranges, then this conditional
2253 always has a false value (unless we had to invert this
2254 conditional, in which case it always has a true value). */
2256 return (cond_inverted
? boolean_true_node
: boolean_false_node
);
2258 /* If the current range is a subset of the condition's range,
2259 then this conditional always has a true value (unless we
2260 had to invert this conditional, in which case it always
2261 has a true value). */
2262 if (subset
&& swapped
)
2263 return (cond_inverted
? boolean_false_node
: boolean_true_node
);
2265 /* We were unable to determine the result of the conditional.
2266 However, we may be able to simplify the conditional. First
2267 merge the ranges in the same manner as range merging above. */
2268 low
= tree_int_cst_compare (low
, cond_low
) == 1 ? low
: cond_low
;
2269 high
= tree_int_cst_compare (high
, cond_high
) == -1 ? high
: cond_high
;
2271 /* If the range has converged to a single point, then turn this
2272 into an equality comparison. */
2273 if (TREE_CODE (cond
) != EQ_EXPR
2274 && TREE_CODE (cond
) != NE_EXPR
2275 && tree_int_cst_equal (low
, high
))
2277 TREE_SET_CODE (cond
, EQ_EXPR
);
2278 TREE_OPERAND (cond
, 1) = high
;
2285 /* STMT is a SWITCH_EXPR for which we could not trivially determine its
2286 result. This routine attempts to find equivalent forms of the
2287 condition which we may be able to optimize better. */
2290 simplify_switch_and_lookup_avail_expr (tree stmt
, int insert
)
2292 tree cond
= SWITCH_COND (stmt
);
2295 /* The optimization that we really care about is removing unnecessary
2296 casts. That will let us do much better in propagating the inferred
2297 constant at the switch target. */
2298 if (TREE_CODE (cond
) == SSA_NAME
)
2300 def
= SSA_NAME_DEF_STMT (cond
);
2301 if (TREE_CODE (def
) == MODIFY_EXPR
)
2303 def
= TREE_OPERAND (def
, 1);
2304 if (TREE_CODE (def
) == NOP_EXPR
)
2309 def
= TREE_OPERAND (def
, 0);
2311 #ifdef ENABLE_CHECKING
2312 /* ??? Why was Jeff testing this? We are gimple... */
2313 gcc_assert (is_gimple_val (def
));
2316 to
= TREE_TYPE (cond
);
2317 ti
= TREE_TYPE (def
);
2319 /* If we have an extension that preserves value, then we
2320 can copy the source value into the switch. */
2322 need_precision
= TYPE_PRECISION (ti
);
2324 if (TYPE_UNSIGNED (to
) && !TYPE_UNSIGNED (ti
))
2326 else if (!TYPE_UNSIGNED (to
) && TYPE_UNSIGNED (ti
))
2327 need_precision
+= 1;
2328 if (TYPE_PRECISION (to
) < need_precision
)
2333 SWITCH_COND (stmt
) = def
;
2334 mark_stmt_modified (stmt
);
2336 return lookup_avail_expr (stmt
, insert
);
2346 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2347 known value for that SSA_NAME (or NULL if no value is known).
2349 NONZERO_VARS is the set SSA_NAMES known to have a nonzero value,
2350 even if we don't know their precise value.
2352 Propagate values from CONST_AND_COPIES and NONZERO_VARS into the PHI
2353 nodes of the successors of BB. */
2356 cprop_into_successor_phis (basic_block bb
, bitmap nonzero_vars
)
2361 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
2366 /* If this is an abnormal edge, then we do not want to copy propagate
2367 into the PHI alternative associated with this edge. */
2368 if (e
->flags
& EDGE_ABNORMAL
)
2371 phi
= phi_nodes (e
->dest
);
2376 for ( ; phi
; phi
= PHI_CHAIN (phi
))
2379 use_operand_p orig_p
;
2382 /* The alternative may be associated with a constant, so verify
2383 it is an SSA_NAME before doing anything with it. */
2384 orig_p
= PHI_ARG_DEF_PTR (phi
, indx
);
2385 orig
= USE_FROM_PTR (orig_p
);
2386 if (TREE_CODE (orig
) != SSA_NAME
)
2389 /* If the alternative is known to have a nonzero value, record
2390 that fact in the PHI node itself for future use. */
2391 if (bitmap_bit_p (nonzero_vars
, SSA_NAME_VERSION (orig
)))
2392 PHI_ARG_NONZERO (phi
, indx
) = true;
2394 /* If we have *ORIG_P in our constant/copy table, then replace
2395 ORIG_P with its value in our constant/copy table. */
2396 new = SSA_NAME_VALUE (orig
);
2399 && (TREE_CODE (new) == SSA_NAME
2400 || is_gimple_min_invariant (new))
2401 && may_propagate_copy (orig
, new))
2402 propagate_value (orig_p
, new);
2407 /* We have finished optimizing BB, record any information implied by
2408 taking a specific outgoing edge from BB. */
2411 record_edge_info (basic_block bb
)
2413 block_stmt_iterator bsi
= bsi_last (bb
);
2414 struct edge_info
*edge_info
;
2416 if (! bsi_end_p (bsi
))
2418 tree stmt
= bsi_stmt (bsi
);
2420 if (stmt
&& TREE_CODE (stmt
) == SWITCH_EXPR
)
2422 tree cond
= SWITCH_COND (stmt
);
2424 if (TREE_CODE (cond
) == SSA_NAME
)
2426 tree labels
= SWITCH_LABELS (stmt
);
2427 int i
, n_labels
= TREE_VEC_LENGTH (labels
);
2428 tree
*info
= xcalloc (n_basic_blocks
, sizeof (tree
));
2432 for (i
= 0; i
< n_labels
; i
++)
2434 tree label
= TREE_VEC_ELT (labels
, i
);
2435 basic_block target_bb
= label_to_block (CASE_LABEL (label
));
2437 if (CASE_HIGH (label
)
2438 || !CASE_LOW (label
)
2439 || info
[target_bb
->index
])
2440 info
[target_bb
->index
] = error_mark_node
;
2442 info
[target_bb
->index
] = label
;
2445 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
2447 basic_block target_bb
= e
->dest
;
2448 tree node
= info
[target_bb
->index
];
2450 if (node
!= NULL
&& node
!= error_mark_node
)
2452 tree x
= fold_convert (TREE_TYPE (cond
), CASE_LOW (node
));
2453 edge_info
= allocate_edge_info (e
);
2454 edge_info
->lhs
= cond
;
2462 /* A COND_EXPR may create equivalences too. */
2463 if (stmt
&& TREE_CODE (stmt
) == COND_EXPR
)
2465 tree cond
= COND_EXPR_COND (stmt
);
2469 extract_true_false_edges_from_block (bb
, &true_edge
, &false_edge
);
2471 /* If the conditional is a single variable 'X', record 'X = 1'
2472 for the true edge and 'X = 0' on the false edge. */
2473 if (SSA_VAR_P (cond
))
2475 struct edge_info
*edge_info
;
2477 edge_info
= allocate_edge_info (true_edge
);
2478 edge_info
->lhs
= cond
;
2479 edge_info
->rhs
= constant_boolean_node (1, TREE_TYPE (cond
));
2481 edge_info
= allocate_edge_info (false_edge
);
2482 edge_info
->lhs
= cond
;
2483 edge_info
->rhs
= constant_boolean_node (0, TREE_TYPE (cond
));
2485 /* Equality tests may create one or two equivalences. */
2486 else if (COMPARISON_CLASS_P (cond
))
2488 tree op0
= TREE_OPERAND (cond
, 0);
2489 tree op1
= TREE_OPERAND (cond
, 1);
2491 /* Special case comparing booleans against a constant as we
2492 know the value of OP0 on both arms of the branch. i.e., we
2493 can record an equivalence for OP0 rather than COND. */
2494 if ((TREE_CODE (cond
) == EQ_EXPR
|| TREE_CODE (cond
) == NE_EXPR
)
2495 && TREE_CODE (op0
) == SSA_NAME
2496 && TREE_CODE (TREE_TYPE (op0
)) == BOOLEAN_TYPE
2497 && is_gimple_min_invariant (op1
))
2499 if (TREE_CODE (cond
) == EQ_EXPR
)
2501 edge_info
= allocate_edge_info (true_edge
);
2502 edge_info
->lhs
= op0
;
2503 edge_info
->rhs
= (integer_zerop (op1
)
2504 ? boolean_false_node
2505 : boolean_true_node
);
2507 edge_info
= allocate_edge_info (false_edge
);
2508 edge_info
->lhs
= op0
;
2509 edge_info
->rhs
= (integer_zerop (op1
)
2511 : boolean_false_node
);
2515 edge_info
= allocate_edge_info (true_edge
);
2516 edge_info
->lhs
= op0
;
2517 edge_info
->rhs
= (integer_zerop (op1
)
2519 : boolean_false_node
);
2521 edge_info
= allocate_edge_info (false_edge
);
2522 edge_info
->lhs
= op0
;
2523 edge_info
->rhs
= (integer_zerop (op1
)
2524 ? boolean_false_node
2525 : boolean_true_node
);
2529 else if (is_gimple_min_invariant (op0
)
2530 && (TREE_CODE (op1
) == SSA_NAME
2531 || is_gimple_min_invariant (op1
)))
2533 tree inverted
= invert_truthvalue (cond
);
2534 struct edge_info
*edge_info
;
2536 edge_info
= allocate_edge_info (true_edge
);
2537 record_conditions (edge_info
, cond
, inverted
);
2539 if (TREE_CODE (cond
) == EQ_EXPR
)
2541 edge_info
->lhs
= op1
;
2542 edge_info
->rhs
= op0
;
2545 edge_info
= allocate_edge_info (false_edge
);
2546 record_conditions (edge_info
, inverted
, cond
);
2548 if (TREE_CODE (cond
) == NE_EXPR
)
2550 edge_info
->lhs
= op1
;
2551 edge_info
->rhs
= op0
;
2555 else if (TREE_CODE (op0
) == SSA_NAME
2556 && (is_gimple_min_invariant (op1
)
2557 || TREE_CODE (op1
) == SSA_NAME
))
2559 tree inverted
= invert_truthvalue (cond
);
2560 struct edge_info
*edge_info
;
2562 edge_info
= allocate_edge_info (true_edge
);
2563 record_conditions (edge_info
, cond
, inverted
);
2565 if (TREE_CODE (cond
) == EQ_EXPR
)
2567 edge_info
->lhs
= op0
;
2568 edge_info
->rhs
= op1
;
2571 edge_info
= allocate_edge_info (false_edge
);
2572 record_conditions (edge_info
, inverted
, cond
);
2574 if (TREE_CODE (cond
) == NE_EXPR
)
2576 edge_info
->lhs
= op0
;
2577 edge_info
->rhs
= op1
;
2582 /* ??? TRUTH_NOT_EXPR can create an equivalence too. */
2587 /* Propagate information from BB to its outgoing edges.
2589 This can include equivalency information implied by control statements
2590 at the end of BB and const/copy propagation into PHIs in BB's
2591 successor blocks. */
2594 propagate_to_outgoing_edges (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
2597 record_edge_info (bb
);
2598 cprop_into_successor_phis (bb
, nonzero_vars
);
2601 /* Search for redundant computations in STMT. If any are found, then
2602 replace them with the variable holding the result of the computation.
2604 If safe, record this expression into the available expression hash
2608 eliminate_redundant_computations (struct dom_walk_data
*walk_data
,
2609 tree stmt
, stmt_ann_t ann
)
2611 v_may_def_optype v_may_defs
= V_MAY_DEF_OPS (ann
);
2612 tree
*expr_p
, def
= NULL_TREE
;
2615 bool retval
= false;
2617 if (TREE_CODE (stmt
) == MODIFY_EXPR
)
2618 def
= TREE_OPERAND (stmt
, 0);
2620 /* Certain expressions on the RHS can be optimized away, but can not
2621 themselves be entered into the hash tables. */
2622 if (ann
->makes_aliased_stores
2624 || TREE_CODE (def
) != SSA_NAME
2625 || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def
)
2626 || NUM_V_MAY_DEFS (v_may_defs
) != 0
2627 /* Do not record equivalences for increments of ivs. This would create
2628 overlapping live ranges for a very questionable gain. */
2629 || simple_iv_increment_p (stmt
))
2632 /* Check if the expression has been computed before. */
2633 cached_lhs
= lookup_avail_expr (stmt
, insert
);
2635 /* If this is an assignment and the RHS was not in the hash table,
2636 then try to simplify the RHS and lookup the new RHS in the
2638 if (! cached_lhs
&& TREE_CODE (stmt
) == MODIFY_EXPR
)
2639 cached_lhs
= simplify_rhs_and_lookup_avail_expr (walk_data
, stmt
, insert
);
2640 /* Similarly if this is a COND_EXPR and we did not find its
2641 expression in the hash table, simplify the condition and
2643 else if (! cached_lhs
&& TREE_CODE (stmt
) == COND_EXPR
)
2644 cached_lhs
= simplify_cond_and_lookup_avail_expr (stmt
, ann
, insert
);
2645 /* Similarly for a SWITCH_EXPR. */
2646 else if (!cached_lhs
&& TREE_CODE (stmt
) == SWITCH_EXPR
)
2647 cached_lhs
= simplify_switch_and_lookup_avail_expr (stmt
, insert
);
2649 opt_stats
.num_exprs_considered
++;
2651 /* Get a pointer to the expression we are trying to optimize. */
2652 if (TREE_CODE (stmt
) == COND_EXPR
)
2653 expr_p
= &COND_EXPR_COND (stmt
);
2654 else if (TREE_CODE (stmt
) == SWITCH_EXPR
)
2655 expr_p
= &SWITCH_COND (stmt
);
2656 else if (TREE_CODE (stmt
) == RETURN_EXPR
&& TREE_OPERAND (stmt
, 0))
2657 expr_p
= &TREE_OPERAND (TREE_OPERAND (stmt
, 0), 1);
2659 expr_p
= &TREE_OPERAND (stmt
, 1);
2661 /* It is safe to ignore types here since we have already done
2662 type checking in the hashing and equality routines. In fact
2663 type checking here merely gets in the way of constant
2664 propagation. Also, make sure that it is safe to propagate
2665 CACHED_LHS into *EXPR_P. */
2667 && (TREE_CODE (cached_lhs
) != SSA_NAME
2668 || may_propagate_copy (*expr_p
, cached_lhs
)))
2670 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2672 fprintf (dump_file
, " Replaced redundant expr '");
2673 print_generic_expr (dump_file
, *expr_p
, dump_flags
);
2674 fprintf (dump_file
, "' with '");
2675 print_generic_expr (dump_file
, cached_lhs
, dump_flags
);
2676 fprintf (dump_file
, "'\n");
2681 #if defined ENABLE_CHECKING
2682 gcc_assert (TREE_CODE (cached_lhs
) == SSA_NAME
2683 || is_gimple_min_invariant (cached_lhs
));
2686 if (TREE_CODE (cached_lhs
) == ADDR_EXPR
2687 || (POINTER_TYPE_P (TREE_TYPE (*expr_p
))
2688 && is_gimple_min_invariant (cached_lhs
)))
2691 propagate_tree_value (expr_p
, cached_lhs
);
2692 mark_stmt_modified (stmt
);
2697 /* STMT, a MODIFY_EXPR, may create certain equivalences, in either
2698 the available expressions table or the const_and_copies table.
2699 Detect and record those equivalences. */
2702 record_equivalences_from_stmt (tree stmt
,
2706 tree lhs
= TREE_OPERAND (stmt
, 0);
2707 enum tree_code lhs_code
= TREE_CODE (lhs
);
2710 if (lhs_code
== SSA_NAME
)
2712 tree rhs
= TREE_OPERAND (stmt
, 1);
2714 /* Strip away any useless type conversions. */
2715 STRIP_USELESS_TYPE_CONVERSION (rhs
);
2717 /* If the RHS of the assignment is a constant or another variable that
2718 may be propagated, register it in the CONST_AND_COPIES table. We
2719 do not need to record unwind data for this, since this is a true
2720 assignment and not an equivalence inferred from a comparison. All
2721 uses of this ssa name are dominated by this assignment, so unwinding
2722 just costs time and space. */
2724 && (TREE_CODE (rhs
) == SSA_NAME
2725 || is_gimple_min_invariant (rhs
)))
2726 SSA_NAME_VALUE (lhs
) = rhs
;
2728 if (expr_computes_nonzero (rhs
))
2729 record_var_is_nonzero (lhs
);
2732 /* Look at both sides for pointer dereferences. If we find one, then
2733 the pointer must be nonnull and we can enter that equivalence into
2735 if (flag_delete_null_pointer_checks
)
2736 for (i
= 0; i
< 2; i
++)
2738 tree t
= TREE_OPERAND (stmt
, i
);
2740 /* Strip away any COMPONENT_REFs. */
2741 while (TREE_CODE (t
) == COMPONENT_REF
)
2742 t
= TREE_OPERAND (t
, 0);
2744 /* Now see if this is a pointer dereference. */
2745 if (INDIRECT_REF_P (t
))
2747 tree op
= TREE_OPERAND (t
, 0);
2749 /* If the pointer is a SSA variable, then enter new
2750 equivalences into the hash table. */
2751 while (TREE_CODE (op
) == SSA_NAME
)
2753 tree def
= SSA_NAME_DEF_STMT (op
);
2755 record_var_is_nonzero (op
);
2757 /* And walk up the USE-DEF chains noting other SSA_NAMEs
2758 which are known to have a nonzero value. */
2760 && TREE_CODE (def
) == MODIFY_EXPR
2761 && TREE_CODE (TREE_OPERAND (def
, 1)) == NOP_EXPR
)
2762 op
= TREE_OPERAND (TREE_OPERAND (def
, 1), 0);
2769 /* A memory store, even an aliased store, creates a useful
2770 equivalence. By exchanging the LHS and RHS, creating suitable
2771 vops and recording the result in the available expression table,
2772 we may be able to expose more redundant loads. */
2773 if (!ann
->has_volatile_ops
2774 && (TREE_CODE (TREE_OPERAND (stmt
, 1)) == SSA_NAME
2775 || is_gimple_min_invariant (TREE_OPERAND (stmt
, 1)))
2776 && !is_gimple_reg (lhs
))
2778 tree rhs
= TREE_OPERAND (stmt
, 1);
2781 /* FIXME: If the LHS of the assignment is a bitfield and the RHS
2782 is a constant, we need to adjust the constant to fit into the
2783 type of the LHS. If the LHS is a bitfield and the RHS is not
2784 a constant, then we can not record any equivalences for this
2785 statement since we would need to represent the widening or
2786 narrowing of RHS. This fixes gcc.c-torture/execute/921016-1.c
2787 and should not be necessary if GCC represented bitfields
2789 if (lhs_code
== COMPONENT_REF
2790 && DECL_BIT_FIELD (TREE_OPERAND (lhs
, 1)))
2792 if (TREE_CONSTANT (rhs
))
2793 rhs
= widen_bitfield (rhs
, TREE_OPERAND (lhs
, 1), lhs
);
2797 /* If the value overflowed, then we can not use this equivalence. */
2798 if (rhs
&& ! is_gimple_min_invariant (rhs
))
2804 /* Build a new statement with the RHS and LHS exchanged. */
2805 new = build (MODIFY_EXPR
, TREE_TYPE (stmt
), rhs
, lhs
);
2807 create_ssa_artficial_load_stmt (&(ann
->operands
), new);
2809 /* Finally enter the statement into the available expression
2811 lookup_avail_expr (new, true);
2816 /* Replace *OP_P in STMT with any known equivalent value for *OP_P from
2817 CONST_AND_COPIES. */
2820 cprop_operand (tree stmt
, use_operand_p op_p
)
2822 bool may_have_exposed_new_symbols
= false;
2824 tree op
= USE_FROM_PTR (op_p
);
2826 /* If the operand has a known constant value or it is known to be a
2827 copy of some other variable, use the value or copy stored in
2828 CONST_AND_COPIES. */
2829 val
= SSA_NAME_VALUE (op
);
2830 if (val
&& val
!= op
&& TREE_CODE (val
) != VALUE_HANDLE
)
2832 tree op_type
, val_type
;
2834 /* Do not change the base variable in the virtual operand
2835 tables. That would make it impossible to reconstruct
2836 the renamed virtual operand if we later modify this
2837 statement. Also only allow the new value to be an SSA_NAME
2838 for propagation into virtual operands. */
2839 if (!is_gimple_reg (op
)
2840 && (TREE_CODE (val
) != SSA_NAME
2841 || is_gimple_reg (val
)
2842 || get_virtual_var (val
) != get_virtual_var (op
)))
2845 /* Do not replace hard register operands in asm statements. */
2846 if (TREE_CODE (stmt
) == ASM_EXPR
2847 && !may_propagate_copy_into_asm (op
))
2850 /* Get the toplevel type of each operand. */
2851 op_type
= TREE_TYPE (op
);
2852 val_type
= TREE_TYPE (val
);
2854 /* While both types are pointers, get the type of the object
2856 while (POINTER_TYPE_P (op_type
) && POINTER_TYPE_P (val_type
))
2858 op_type
= TREE_TYPE (op_type
);
2859 val_type
= TREE_TYPE (val_type
);
2862 /* Make sure underlying types match before propagating a constant by
2863 converting the constant to the proper type. Note that convert may
2864 return a non-gimple expression, in which case we ignore this
2865 propagation opportunity. */
2866 if (TREE_CODE (val
) != SSA_NAME
)
2868 if (!lang_hooks
.types_compatible_p (op_type
, val_type
))
2870 val
= fold_convert (TREE_TYPE (op
), val
);
2871 if (!is_gimple_min_invariant (val
))
2876 /* Certain operands are not allowed to be copy propagated due
2877 to their interaction with exception handling and some GCC
2879 else if (!may_propagate_copy (op
, val
))
2882 /* Do not propagate copies if the propagated value is at a deeper loop
2883 depth than the propagatee. Otherwise, this may move loop variant
2884 variables outside of their loops and prevent coalescing
2885 opportunities. If the value was loop invariant, it will be hoisted
2886 by LICM and exposed for copy propagation. */
2887 if (loop_depth_of_name (val
) > loop_depth_of_name (op
))
2891 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2893 fprintf (dump_file
, " Replaced '");
2894 print_generic_expr (dump_file
, op
, dump_flags
);
2895 fprintf (dump_file
, "' with %s '",
2896 (TREE_CODE (val
) != SSA_NAME
? "constant" : "variable"));
2897 print_generic_expr (dump_file
, val
, dump_flags
);
2898 fprintf (dump_file
, "'\n");
2901 /* If VAL is an ADDR_EXPR or a constant of pointer type, note
2902 that we may have exposed a new symbol for SSA renaming. */
2903 if (TREE_CODE (val
) == ADDR_EXPR
2904 || (POINTER_TYPE_P (TREE_TYPE (op
))
2905 && is_gimple_min_invariant (val
)))
2906 may_have_exposed_new_symbols
= true;
2908 if (TREE_CODE (val
) != SSA_NAME
)
2909 opt_stats
.num_const_prop
++;
2911 opt_stats
.num_copy_prop
++;
2913 propagate_value (op_p
, val
);
2915 /* And note that we modified this statement. This is now
2916 safe, even if we changed virtual operands since we will
2917 rescan the statement and rewrite its operands again. */
2918 mark_stmt_modified (stmt
);
2920 return may_have_exposed_new_symbols
;
2923 /* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
2924 known value for that SSA_NAME (or NULL if no value is known).
2926 Propagate values from CONST_AND_COPIES into the uses, vuses and
2927 v_may_def_ops of STMT. */
2930 cprop_into_stmt (tree stmt
)
2932 bool may_have_exposed_new_symbols
= false;
2937 FOR_EACH_SSA_USE_OPERAND (op_p
, stmt
, iter
, SSA_OP_ALL_USES
)
2939 if (TREE_CODE (USE_FROM_PTR (op_p
)) == SSA_NAME
)
2940 may_have_exposed_new_symbols
|= cprop_operand (stmt
, op_p
);
2943 if (may_have_exposed_new_symbols
)
2945 rhs
= get_rhs (stmt
);
2946 if (rhs
&& TREE_CODE (rhs
) == ADDR_EXPR
)
2947 recompute_tree_invarant_for_addr_expr (rhs
);
2950 return may_have_exposed_new_symbols
;
2954 /* Optimize the statement pointed by iterator SI.
2956 We try to perform some simplistic global redundancy elimination and
2957 constant propagation:
2959 1- To detect global redundancy, we keep track of expressions that have
2960 been computed in this block and its dominators. If we find that the
2961 same expression is computed more than once, we eliminate repeated
2962 computations by using the target of the first one.
2964 2- Constant values and copy assignments. This is used to do very
2965 simplistic constant and copy propagation. When a constant or copy
2966 assignment is found, we map the value on the RHS of the assignment to
2967 the variable in the LHS in the CONST_AND_COPIES table. */
2970 optimize_stmt (struct dom_walk_data
*walk_data
, basic_block bb
,
2971 block_stmt_iterator si
)
2975 bool may_optimize_p
;
2976 bool may_have_exposed_new_symbols
= false;
2978 stmt
= bsi_stmt (si
);
2980 update_stmt_if_modified (stmt
);
2981 ann
= stmt_ann (stmt
);
2982 opt_stats
.num_stmts
++;
2983 may_have_exposed_new_symbols
= false;
2985 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2987 fprintf (dump_file
, "Optimizing statement ");
2988 print_generic_stmt (dump_file
, stmt
, TDF_SLIM
);
2991 /* Const/copy propagate into USES, VUSES and the RHS of V_MAY_DEFs. */
2992 may_have_exposed_new_symbols
= cprop_into_stmt (stmt
);
2994 /* If the statement has been modified with constant replacements,
2995 fold its RHS before checking for redundant computations. */
2998 /* Try to fold the statement making sure that STMT is kept
3000 if (fold_stmt (bsi_stmt_ptr (si
)))
3002 stmt
= bsi_stmt (si
);
3003 ann
= stmt_ann (stmt
);
3005 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3007 fprintf (dump_file
, " Folded to: ");
3008 print_generic_stmt (dump_file
, stmt
, TDF_SLIM
);
3012 /* Constant/copy propagation above may change the set of
3013 virtual operands associated with this statement. Folding
3014 may remove the need for some virtual operands.
3016 Indicate we will need to rescan and rewrite the statement. */
3017 may_have_exposed_new_symbols
= true;
3020 /* Check for redundant computations. Do this optimization only
3021 for assignments that have no volatile ops and conditionals. */
3022 may_optimize_p
= (!ann
->has_volatile_ops
3023 && ((TREE_CODE (stmt
) == RETURN_EXPR
3024 && TREE_OPERAND (stmt
, 0)
3025 && TREE_CODE (TREE_OPERAND (stmt
, 0)) == MODIFY_EXPR
3026 && ! (TREE_SIDE_EFFECTS
3027 (TREE_OPERAND (TREE_OPERAND (stmt
, 0), 1))))
3028 || (TREE_CODE (stmt
) == MODIFY_EXPR
3029 && ! TREE_SIDE_EFFECTS (TREE_OPERAND (stmt
, 1)))
3030 || TREE_CODE (stmt
) == COND_EXPR
3031 || TREE_CODE (stmt
) == SWITCH_EXPR
));
3034 may_have_exposed_new_symbols
3035 |= eliminate_redundant_computations (walk_data
, stmt
, ann
);
3037 /* Record any additional equivalences created by this statement. */
3038 if (TREE_CODE (stmt
) == MODIFY_EXPR
)
3039 record_equivalences_from_stmt (stmt
,
3043 /* If STMT is a COND_EXPR and it was modified, then we may know
3044 where it goes. If that is the case, then mark the CFG as altered.
3046 This will cause us to later call remove_unreachable_blocks and
3047 cleanup_tree_cfg when it is safe to do so. It is not safe to
3048 clean things up here since removal of edges and such can trigger
3049 the removal of PHI nodes, which in turn can release SSA_NAMEs to
3052 That's all fine and good, except that once SSA_NAMEs are released
3053 to the manager, we must not call create_ssa_name until all references
3054 to released SSA_NAMEs have been eliminated.
3056 All references to the deleted SSA_NAMEs can not be eliminated until
3057 we remove unreachable blocks.
3059 We can not remove unreachable blocks until after we have completed
3060 any queued jump threading.
3062 We can not complete any queued jump threads until we have taken
3063 appropriate variables out of SSA form. Taking variables out of
3064 SSA form can call create_ssa_name and thus we lose.
3066 Ultimately I suspect we're going to need to change the interface
3067 into the SSA_NAME manager. */
3073 if (TREE_CODE (stmt
) == COND_EXPR
)
3074 val
= COND_EXPR_COND (stmt
);
3075 else if (TREE_CODE (stmt
) == SWITCH_EXPR
)
3076 val
= SWITCH_COND (stmt
);
3078 if (val
&& TREE_CODE (val
) == INTEGER_CST
&& find_taken_edge (bb
, val
))
3081 /* If we simplified a statement in such a way as to be shown that it
3082 cannot trap, update the eh information and the cfg to match. */
3083 if (maybe_clean_eh_stmt (stmt
))
3085 bitmap_set_bit (need_eh_cleanup
, bb
->index
);
3086 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3087 fprintf (dump_file
, " Flagged to clear EH edges.\n");
3091 if (may_have_exposed_new_symbols
)
3092 VEC_safe_push (tree
, heap
, stmts_to_rescan
, bsi_stmt (si
));
3095 /* Replace the RHS of STMT with NEW_RHS. If RHS can be found in the
3096 available expression hashtable, then return the LHS from the hash
3099 If INSERT is true, then we also update the available expression
3100 hash table to account for the changes made to STMT. */
3103 update_rhs_and_lookup_avail_expr (tree stmt
, tree new_rhs
, bool insert
)
3105 tree cached_lhs
= NULL
;
3107 /* Remove the old entry from the hash table. */
3110 struct expr_hash_elt element
;
3112 initialize_hash_element (stmt
, NULL
, &element
);
3113 htab_remove_elt_with_hash (avail_exprs
, &element
, element
.hash
);
3116 /* Now update the RHS of the assignment. */
3117 TREE_OPERAND (stmt
, 1) = new_rhs
;
3119 /* Now lookup the updated statement in the hash table. */
3120 cached_lhs
= lookup_avail_expr (stmt
, insert
);
3122 /* We have now called lookup_avail_expr twice with two different
3123 versions of this same statement, once in optimize_stmt, once here.
3125 We know the call in optimize_stmt did not find an existing entry
3126 in the hash table, so a new entry was created. At the same time
3127 this statement was pushed onto the AVAIL_EXPRS_STACK vector.
3129 If this call failed to find an existing entry on the hash table,
3130 then the new version of this statement was entered into the
3131 hash table. And this statement was pushed onto BLOCK_AVAIL_EXPR
3132 for the second time. So there are two copies on BLOCK_AVAIL_EXPRs
3134 If this call succeeded, we still have one copy of this statement
3135 on the BLOCK_AVAIL_EXPRs vector.
3137 For both cases, we need to pop the most recent entry off the
3138 BLOCK_AVAIL_EXPRs vector. For the case where we never found this
3139 statement in the hash tables, that will leave precisely one
3140 copy of this statement on BLOCK_AVAIL_EXPRs. For the case where
3141 we found a copy of this statement in the second hash table lookup
3142 we want _no_ copies of this statement in BLOCK_AVAIL_EXPRs. */
3144 VEC_pop (tree
, avail_exprs_stack
);
3146 /* And make sure we record the fact that we modified this
3148 mark_stmt_modified (stmt
);
3153 /* Search for an existing instance of STMT in the AVAIL_EXPRS table. If
3154 found, return its LHS. Otherwise insert STMT in the table and return
3157 Also, when an expression is first inserted in the AVAIL_EXPRS table, it
3158 is also added to the stack pointed by BLOCK_AVAIL_EXPRS_P, so that they
3159 can be removed when we finish processing this block and its children.
3161 NOTE: This function assumes that STMT is a MODIFY_EXPR node that
3162 contains no CALL_EXPR on its RHS and makes no volatile nor
3163 aliased references. */
3166 lookup_avail_expr (tree stmt
, bool insert
)
3171 struct expr_hash_elt
*element
= xmalloc (sizeof (struct expr_hash_elt
));
3173 lhs
= TREE_CODE (stmt
) == MODIFY_EXPR
? TREE_OPERAND (stmt
, 0) : NULL
;
3175 initialize_hash_element (stmt
, lhs
, element
);
3177 /* Don't bother remembering constant assignments and copy operations.
3178 Constants and copy operations are handled by the constant/copy propagator
3179 in optimize_stmt. */
3180 if (TREE_CODE (element
->rhs
) == SSA_NAME
3181 || is_gimple_min_invariant (element
->rhs
))
3187 /* If this is an equality test against zero, see if we have recorded a
3188 nonzero value for the variable in question. */
3189 if ((TREE_CODE (element
->rhs
) == EQ_EXPR
3190 || TREE_CODE (element
->rhs
) == NE_EXPR
)
3191 && TREE_CODE (TREE_OPERAND (element
->rhs
, 0)) == SSA_NAME
3192 && integer_zerop (TREE_OPERAND (element
->rhs
, 1)))
3194 int indx
= SSA_NAME_VERSION (TREE_OPERAND (element
->rhs
, 0));
3196 if (bitmap_bit_p (nonzero_vars
, indx
))
3198 tree t
= element
->rhs
;
3201 if (TREE_CODE (t
) == EQ_EXPR
)
3202 return boolean_false_node
;
3204 return boolean_true_node
;
3208 /* Finally try to find the expression in the main expression hash table. */
3209 slot
= htab_find_slot_with_hash (avail_exprs
, element
, element
->hash
,
3210 (insert
? INSERT
: NO_INSERT
));
3219 *slot
= (void *) element
;
3220 VEC_safe_push (tree
, heap
, avail_exprs_stack
,
3221 stmt
? stmt
: element
->rhs
);
3225 /* Extract the LHS of the assignment so that it can be used as the current
3226 definition of another variable. */
3227 lhs
= ((struct expr_hash_elt
*)*slot
)->lhs
;
3229 /* See if the LHS appears in the CONST_AND_COPIES table. If it does, then
3230 use the value from the const_and_copies table. */
3231 if (TREE_CODE (lhs
) == SSA_NAME
)
3233 temp
= SSA_NAME_VALUE (lhs
);
3234 if (temp
&& TREE_CODE (temp
) != VALUE_HANDLE
)
3242 /* Given a condition COND, record into HI_P, LO_P and INVERTED_P the
3243 range of values that result in the conditional having a true value.
3245 Return true if we are successful in extracting a range from COND and
3246 false if we are unsuccessful. */
3249 extract_range_from_cond (tree cond
, tree
*hi_p
, tree
*lo_p
, int *inverted_p
)
3251 tree op1
= TREE_OPERAND (cond
, 1);
3252 tree high
, low
, type
;
3255 type
= TREE_TYPE (op1
);
3257 /* Experiments have shown that it's rarely, if ever useful to
3258 record ranges for enumerations. Presumably this is due to
3259 the fact that they're rarely used directly. They are typically
3260 cast into an integer type and used that way. */
3261 if (TREE_CODE (type
) != INTEGER_TYPE
3262 /* We don't know how to deal with types with variable bounds. */
3263 || TREE_CODE (TYPE_MIN_VALUE (type
)) != INTEGER_CST
3264 || TREE_CODE (TYPE_MAX_VALUE (type
)) != INTEGER_CST
)
3267 switch (TREE_CODE (cond
))
3281 high
= TYPE_MAX_VALUE (type
);
3286 high
= TYPE_MAX_VALUE (type
);
3287 if (!tree_int_cst_lt (op1
, high
))
3289 low
= int_const_binop (PLUS_EXPR
, op1
, integer_one_node
, 1);
3295 low
= TYPE_MIN_VALUE (type
);
3300 low
= TYPE_MIN_VALUE (type
);
3301 if (!tree_int_cst_lt (low
, op1
))
3303 high
= int_const_binop (MINUS_EXPR
, op1
, integer_one_node
, 1);
3313 *inverted_p
= inverted
;
3317 /* Record a range created by COND for basic block BB. */
3320 record_range (tree cond
, basic_block bb
)
3322 enum tree_code code
= TREE_CODE (cond
);
3324 /* We explicitly ignore NE_EXPRs and all the unordered comparisons.
3325 They rarely allow for meaningful range optimizations and significantly
3326 complicate the implementation. */
3327 if ((code
== LT_EXPR
|| code
== LE_EXPR
|| code
== GT_EXPR
3328 || code
== GE_EXPR
|| code
== EQ_EXPR
)
3329 && TREE_CODE (TREE_TYPE (TREE_OPERAND (cond
, 1))) == INTEGER_TYPE
)
3331 struct vrp_hash_elt
*vrp_hash_elt
;
3332 struct vrp_element
*element
;
3333 varray_type
*vrp_records_p
;
3337 vrp_hash_elt
= xmalloc (sizeof (struct vrp_hash_elt
));
3338 vrp_hash_elt
->var
= TREE_OPERAND (cond
, 0);
3339 vrp_hash_elt
->records
= NULL
;
3340 slot
= htab_find_slot (vrp_data
, vrp_hash_elt
, INSERT
);
3343 *slot
= (void *) vrp_hash_elt
;
3345 free (vrp_hash_elt
);
3347 vrp_hash_elt
= (struct vrp_hash_elt
*) *slot
;
3348 vrp_records_p
= &vrp_hash_elt
->records
;
3350 element
= ggc_alloc (sizeof (struct vrp_element
));
3351 element
->low
= NULL
;
3352 element
->high
= NULL
;
3353 element
->cond
= cond
;
3356 if (*vrp_records_p
== NULL
)
3357 VARRAY_GENERIC_PTR_INIT (*vrp_records_p
, 2, "vrp records");
3359 VARRAY_PUSH_GENERIC_PTR (*vrp_records_p
, element
);
3360 VEC_safe_push (tree
, heap
, vrp_variables_stack
, TREE_OPERAND (cond
, 0));
3364 /* Hashing and equality functions for VRP_DATA.
3366 Since this hash table is addressed by SSA_NAMEs, we can hash on
3367 their version number and equality can be determined with a
3368 pointer comparison. */
3371 vrp_hash (const void *p
)
3373 tree var
= ((struct vrp_hash_elt
*)p
)->var
;
3375 return SSA_NAME_VERSION (var
);
3379 vrp_eq (const void *p1
, const void *p2
)
3381 tree var1
= ((struct vrp_hash_elt
*)p1
)->var
;
3382 tree var2
= ((struct vrp_hash_elt
*)p2
)->var
;
3384 return var1
== var2
;
3387 /* Hashing and equality functions for AVAIL_EXPRS. The table stores
3388 MODIFY_EXPR statements. We compute a value number for expressions using
3389 the code of the expression and the SSA numbers of its operands. */
3392 avail_expr_hash (const void *p
)
3394 stmt_ann_t ann
= ((struct expr_hash_elt
*)p
)->ann
;
3395 tree rhs
= ((struct expr_hash_elt
*)p
)->rhs
;
3400 /* iterative_hash_expr knows how to deal with any expression and
3401 deals with commutative operators as well, so just use it instead
3402 of duplicating such complexities here. */
3403 val
= iterative_hash_expr (rhs
, val
);
3405 /* If the hash table entry is not associated with a statement, then we
3406 can just hash the expression and not worry about virtual operands
3411 /* Add the SSA version numbers of every vuse operand. This is important
3412 because compound variables like arrays are not renamed in the
3413 operands. Rather, the rename is done on the virtual variable
3414 representing all the elements of the array. */
3415 vuses
= VUSE_OPS (ann
);
3416 for (i
= 0; i
< NUM_VUSES (vuses
); i
++)
3417 val
= iterative_hash_expr (VUSE_OP (vuses
, i
), val
);
3423 real_avail_expr_hash (const void *p
)
3425 return ((const struct expr_hash_elt
*)p
)->hash
;
3429 avail_expr_eq (const void *p1
, const void *p2
)
3431 stmt_ann_t ann1
= ((struct expr_hash_elt
*)p1
)->ann
;
3432 tree rhs1
= ((struct expr_hash_elt
*)p1
)->rhs
;
3433 stmt_ann_t ann2
= ((struct expr_hash_elt
*)p2
)->ann
;
3434 tree rhs2
= ((struct expr_hash_elt
*)p2
)->rhs
;
3436 /* If they are the same physical expression, return true. */
3437 if (rhs1
== rhs2
&& ann1
== ann2
)
3440 /* If their codes are not equal, then quit now. */
3441 if (TREE_CODE (rhs1
) != TREE_CODE (rhs2
))
3444 /* In case of a collision, both RHS have to be identical and have the
3445 same VUSE operands. */
3446 if ((TREE_TYPE (rhs1
) == TREE_TYPE (rhs2
)
3447 || lang_hooks
.types_compatible_p (TREE_TYPE (rhs1
), TREE_TYPE (rhs2
)))
3448 && operand_equal_p (rhs1
, rhs2
, OEP_PURE_SAME
))
3450 vuse_optype ops1
= NULL
;
3451 vuse_optype ops2
= NULL
;
3452 size_t num_ops1
= 0;
3453 size_t num_ops2
= 0;
3458 ops1
= VUSE_OPS (ann1
);
3459 num_ops1
= NUM_VUSES (ops1
);
3464 ops2
= VUSE_OPS (ann2
);
3465 num_ops2
= NUM_VUSES (ops2
);
3468 /* If the number of virtual uses is different, then we consider
3470 if (num_ops1
!= num_ops2
)
3473 for (i
= 0; i
< num_ops1
; i
++)
3474 if (VUSE_OP (ops1
, i
) != VUSE_OP (ops2
, i
))
3477 gcc_assert (((struct expr_hash_elt
*)p1
)->hash
3478 == ((struct expr_hash_elt
*)p2
)->hash
);