1 /* Forward propagation of expressions for single use variables.
2 Copyright (C) 2004, 2005, 2007, 2008, 2009 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3, or (at your option)
11 GCC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
22 #include "coretypes.h"
28 #include "basic-block.h"
30 #include "diagnostic.h"
31 #include "tree-flow.h"
32 #include "tree-pass.h"
33 #include "tree-dump.h"
34 #include "langhooks.h"
38 /* This pass propagates the RHS of assignment statements into use
39 sites of the LHS of the assignment. It's basically a specialized
40 form of tree combination. It is hoped all of this can disappear
41 when we have a generalized tree combiner.
43 One class of common cases we handle is forward propagating a single use
44 variable into a COND_EXPR.
48 if (x) goto ... else goto ...
50 Will be transformed into:
53 if (a COND b) goto ... else goto ...
55 Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
57 Or (assuming c1 and c2 are constants):
61 if (x EQ/NEQ c2) goto ... else goto ...
63 Will be transformed into:
66 if (a EQ/NEQ (c2 - c1)) goto ... else goto ...
68 Similarly for x = a - c1.
74 if (x) goto ... else goto ...
76 Will be transformed into:
79 if (a == 0) goto ... else goto ...
81 Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
82 For these cases, we propagate A into all, possibly more than one,
83 COND_EXPRs that use X.
89 if (x) goto ... else goto ...
91 Will be transformed into:
94 if (a != 0) goto ... else goto ...
96 (Assuming a is an integral type and x is a boolean or x is an
97 integral and a is a boolean.)
99 Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
100 For these cases, we propagate A into all, possibly more than one,
101 COND_EXPRs that use X.
103 In addition to eliminating the variable and the statement which assigns
104 a value to the variable, we may be able to later thread the jump without
105 adding insane complexity in the dominator optimizer.
107 Also note these transformations can cascade. We handle this by having
108 a worklist of COND_EXPR statements to examine. As we make a change to
109 a statement, we put it back on the worklist to examine on the next
110 iteration of the main loop.
112 A second class of propagation opportunities arises for ADDR_EXPR
123 ptr = (type1*)&type2var;
126 Will get turned into (if type1 and type2 are the same size
127 and neither have volatile on them):
128 res = VIEW_CONVERT_EXPR<type1>(type2var)
133 ptr2 = ptr + <constant>;
137 ptr2 = &x[constant/elementsize];
142 offset = index * element_size;
143 offset_p = (pointer) offset;
144 ptr2 = ptr + offset_p
146 Will get turned into:
154 Provided that decl has known alignment >= 2, will get turned into
158 We also propagate casts into SWITCH_EXPR and COND_EXPR conditions to
159 allow us to remove the cast and {NOT_EXPR,NEG_EXPR} into a subsequent
162 This will (of course) be extended as other needs arise. */
164 static bool forward_propagate_addr_expr (tree name
, tree rhs
);
166 /* Set to true if we delete EH edges during the optimization. */
167 static bool cfg_changed
;
169 static tree
rhs_to_tree (tree type
, gimple stmt
);
171 /* Get the next statement we can propagate NAME's value into skipping
172 trivial copies. Returns the statement that is suitable as a
173 propagation destination or NULL_TREE if there is no such one.
174 This only returns destinations in a single-use chain. FINAL_NAME_P
175 if non-NULL is written to the ssa name that represents the use. */
178 get_prop_dest_stmt (tree name
, tree
*final_name_p
)
184 /* If name has multiple uses, bail out. */
185 if (!single_imm_use (name
, &use
, &use_stmt
))
188 /* If this is not a trivial copy, we found it. */
189 if (!gimple_assign_ssa_name_copy_p (use_stmt
)
190 || gimple_assign_rhs1 (use_stmt
) != name
)
193 /* Continue searching uses of the copy destination. */
194 name
= gimple_assign_lhs (use_stmt
);
198 *final_name_p
= name
;
203 /* Get the statement we can propagate from into NAME skipping
204 trivial copies. Returns the statement which defines the
205 propagation source or NULL_TREE if there is no such one.
206 If SINGLE_USE_ONLY is set considers only sources which have
207 a single use chain up to NAME. If SINGLE_USE_P is non-null,
208 it is set to whether the chain to NAME is a single use chain
209 or not. SINGLE_USE_P is not written to if SINGLE_USE_ONLY is set. */
212 get_prop_source_stmt (tree name
, bool single_use_only
, bool *single_use_p
)
214 bool single_use
= true;
217 gimple def_stmt
= SSA_NAME_DEF_STMT (name
);
219 if (!has_single_use (name
))
226 /* If name is defined by a PHI node or is the default def, bail out. */
227 if (!is_gimple_assign (def_stmt
))
230 /* If def_stmt is not a simple copy, we possibly found it. */
231 if (!gimple_assign_ssa_name_copy_p (def_stmt
))
235 if (!single_use_only
&& single_use_p
)
236 *single_use_p
= single_use
;
238 /* We can look through pointer conversions in the search
239 for a useful stmt for the comparison folding. */
240 rhs
= gimple_assign_rhs1 (def_stmt
);
241 if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt
))
242 && TREE_CODE (rhs
) == SSA_NAME
243 && POINTER_TYPE_P (TREE_TYPE (gimple_assign_lhs (def_stmt
)))
244 && POINTER_TYPE_P (TREE_TYPE (rhs
)))
251 /* Continue searching the def of the copy source name. */
252 name
= gimple_assign_rhs1 (def_stmt
);
257 /* Checks if the destination ssa name in DEF_STMT can be used as
258 propagation source. Returns true if so, otherwise false. */
261 can_propagate_from (gimple def_stmt
)
266 gcc_assert (is_gimple_assign (def_stmt
));
268 /* If the rhs has side-effects we cannot propagate from it. */
269 if (gimple_has_volatile_ops (def_stmt
))
272 /* If the rhs is a load we cannot propagate from it. */
273 if (TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt
)) == tcc_reference
274 || TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt
)) == tcc_declaration
)
277 /* Constants can be always propagated. */
278 if (gimple_assign_single_p (def_stmt
)
279 && is_gimple_min_invariant (gimple_assign_rhs1 (def_stmt
)))
282 /* We cannot propagate ssa names that occur in abnormal phi nodes. */
283 FOR_EACH_SSA_USE_OPERAND (use_p
, def_stmt
, iter
, SSA_OP_USE
)
284 if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (use_p
)))
287 /* If the definition is a conversion of a pointer to a function type,
288 then we can not apply optimizations as some targets require
289 function pointers to be canonicalized and in this case this
290 optimization could eliminate a necessary canonicalization. */
291 if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt
)))
293 tree rhs
= gimple_assign_rhs1 (def_stmt
);
294 if (POINTER_TYPE_P (TREE_TYPE (rhs
))
295 && TREE_CODE (TREE_TYPE (TREE_TYPE (rhs
))) == FUNCTION_TYPE
)
302 /* Remove a copy chain ending in NAME along the defs but not
303 further or including UP_TO_STMT. If NAME was replaced in
304 its only use then this function can be used to clean up
305 dead stmts. Returns true if UP_TO_STMT can be removed
306 as well, otherwise false. */
309 remove_prop_source_from_use (tree name
, gimple up_to_stmt
)
311 gimple_stmt_iterator gsi
;
315 if (!has_zero_uses (name
))
318 stmt
= SSA_NAME_DEF_STMT (name
);
319 if (stmt
== up_to_stmt
)
322 gsi
= gsi_for_stmt (stmt
);
324 gsi_remove (&gsi
, true);
326 name
= (gimple_assign_copy_p (stmt
)) ? gimple_assign_rhs1 (stmt
) : NULL
;
327 } while (name
&& TREE_CODE (name
) == SSA_NAME
);
332 /* Return the rhs of a gimple_assign STMT in a form of a single tree,
333 converted to type TYPE.
335 This should disappear, but is needed so we can combine expressions and use
336 the fold() interfaces. Long term, we need to develop folding and combine
337 routines that deal with gimple exclusively . */
340 rhs_to_tree (tree type
, gimple stmt
)
342 location_t loc
= gimple_location (stmt
);
343 enum tree_code code
= gimple_assign_rhs_code (stmt
);
344 if (get_gimple_rhs_class (code
) == GIMPLE_BINARY_RHS
)
345 return fold_build2_loc (loc
, code
, type
, gimple_assign_rhs1 (stmt
),
346 gimple_assign_rhs2 (stmt
));
347 else if (get_gimple_rhs_class (code
) == GIMPLE_UNARY_RHS
)
348 return build1 (code
, type
, gimple_assign_rhs1 (stmt
));
349 else if (get_gimple_rhs_class (code
) == GIMPLE_SINGLE_RHS
)
350 return gimple_assign_rhs1 (stmt
);
355 /* Combine OP0 CODE OP1 in the context of a COND_EXPR. Returns
356 the folded result in a form suitable for COND_EXPR_COND or
357 NULL_TREE, if there is no suitable simplified form. If
358 INVARIANT_ONLY is true only gimple_min_invariant results are
359 considered simplified. */
362 combine_cond_expr_cond (location_t loc
, enum tree_code code
, tree type
,
363 tree op0
, tree op1
, bool invariant_only
)
367 gcc_assert (TREE_CODE_CLASS (code
) == tcc_comparison
);
369 t
= fold_binary_loc (loc
, code
, type
, op0
, op1
);
373 /* Require that we got a boolean type out if we put one in. */
374 gcc_assert (TREE_CODE (TREE_TYPE (t
)) == TREE_CODE (type
));
376 /* Canonicalize the combined condition for use in a COND_EXPR. */
377 t
= canonicalize_cond_expr_cond (t
);
379 /* Bail out if we required an invariant but didn't get one. */
380 if (!t
|| (invariant_only
&& !is_gimple_min_invariant (t
)))
386 /* Propagate from the ssa name definition statements of COND_EXPR
387 in GIMPLE_COND statement STMT into the conditional if that simplifies it.
388 Returns zero if no statement was changed, one if there were
389 changes and two if cfg_cleanup needs to run.
391 This must be kept in sync with forward_propagate_into_cond. */
394 forward_propagate_into_gimple_cond (gimple stmt
)
396 int did_something
= 0;
397 location_t loc
= gimple_location (stmt
);
400 tree tmp
= NULL_TREE
;
401 tree name
, rhs0
= NULL_TREE
, rhs1
= NULL_TREE
;
403 bool single_use0_p
= false, single_use1_p
= false;
404 enum tree_code code
= gimple_cond_code (stmt
);
406 /* We can do tree combining on SSA_NAME and comparison expressions. */
407 if (TREE_CODE_CLASS (gimple_cond_code (stmt
)) == tcc_comparison
408 && TREE_CODE (gimple_cond_lhs (stmt
)) == SSA_NAME
)
410 /* For comparisons use the first operand, that is likely to
411 simplify comparisons against constants. */
412 name
= gimple_cond_lhs (stmt
);
413 def_stmt
= get_prop_source_stmt (name
, false, &single_use0_p
);
414 if (def_stmt
&& can_propagate_from (def_stmt
))
416 tree op1
= gimple_cond_rhs (stmt
);
417 rhs0
= rhs_to_tree (TREE_TYPE (op1
), def_stmt
);
418 tmp
= combine_cond_expr_cond (loc
, code
, boolean_type_node
, rhs0
,
419 op1
, !single_use0_p
);
421 /* If that wasn't successful, try the second operand. */
423 && TREE_CODE (gimple_cond_rhs (stmt
)) == SSA_NAME
)
425 tree op0
= gimple_cond_lhs (stmt
);
426 name
= gimple_cond_rhs (stmt
);
427 def_stmt
= get_prop_source_stmt (name
, false, &single_use1_p
);
428 if (!def_stmt
|| !can_propagate_from (def_stmt
))
429 return did_something
;
431 rhs1
= rhs_to_tree (TREE_TYPE (op0
), def_stmt
);
432 tmp
= combine_cond_expr_cond (loc
, code
, boolean_type_node
, op0
,
433 rhs1
, !single_use1_p
);
435 /* If that wasn't successful either, try both operands. */
438 && rhs1
!= NULL_TREE
)
439 tmp
= combine_cond_expr_cond (loc
, code
, boolean_type_node
, rhs0
,
440 fold_convert_loc (loc
,
443 !(single_use0_p
&& single_use1_p
));
448 if (dump_file
&& tmp
)
450 tree cond
= build2 (gimple_cond_code (stmt
),
452 gimple_cond_lhs (stmt
),
453 gimple_cond_rhs (stmt
));
454 fprintf (dump_file
, " Replaced '");
455 print_generic_expr (dump_file
, cond
, 0);
456 fprintf (dump_file
, "' with '");
457 print_generic_expr (dump_file
, tmp
, 0);
458 fprintf (dump_file
, "'\n");
461 gimple_cond_set_condition_from_tree (stmt
, unshare_expr (tmp
));
464 /* Remove defining statements. */
465 remove_prop_source_from_use (name
, NULL
);
467 if (is_gimple_min_invariant (tmp
))
469 else if (did_something
== 0)
472 /* Continue combining. */
479 return did_something
;
483 /* Propagate from the ssa name definition statements of COND_EXPR
484 in the rhs of statement STMT into the conditional if that simplifies it.
485 Returns zero if no statement was changed, one if there were
486 changes and two if cfg_cleanup needs to run.
488 This must be kept in sync with forward_propagate_into_gimple_cond. */
491 forward_propagate_into_cond (gimple_stmt_iterator
*gsi_p
)
493 gimple stmt
= gsi_stmt (*gsi_p
);
494 location_t loc
= gimple_location (stmt
);
495 int did_something
= 0;
498 tree tmp
= NULL_TREE
;
499 tree cond
= gimple_assign_rhs1 (stmt
);
500 tree name
, rhs0
= NULL_TREE
, rhs1
= NULL_TREE
;
502 bool single_use0_p
= false, single_use1_p
= false;
504 /* We can do tree combining on SSA_NAME and comparison expressions. */
505 if (COMPARISON_CLASS_P (cond
)
506 && TREE_CODE (TREE_OPERAND (cond
, 0)) == SSA_NAME
)
508 /* For comparisons use the first operand, that is likely to
509 simplify comparisons against constants. */
510 name
= TREE_OPERAND (cond
, 0);
511 def_stmt
= get_prop_source_stmt (name
, false, &single_use0_p
);
512 if (def_stmt
&& can_propagate_from (def_stmt
))
514 tree op1
= TREE_OPERAND (cond
, 1);
515 rhs0
= rhs_to_tree (TREE_TYPE (op1
), def_stmt
);
516 tmp
= combine_cond_expr_cond (loc
, TREE_CODE (cond
),
518 rhs0
, op1
, !single_use0_p
);
520 /* If that wasn't successful, try the second operand. */
522 && TREE_CODE (TREE_OPERAND (cond
, 1)) == SSA_NAME
)
524 tree op0
= TREE_OPERAND (cond
, 0);
525 name
= TREE_OPERAND (cond
, 1);
526 def_stmt
= get_prop_source_stmt (name
, false, &single_use1_p
);
527 if (!def_stmt
|| !can_propagate_from (def_stmt
))
528 return did_something
;
530 rhs1
= rhs_to_tree (TREE_TYPE (op0
), def_stmt
);
531 tmp
= combine_cond_expr_cond (loc
, TREE_CODE (cond
),
533 op0
, rhs1
, !single_use1_p
);
535 /* If that wasn't successful either, try both operands. */
538 && rhs1
!= NULL_TREE
)
539 tmp
= combine_cond_expr_cond (loc
, TREE_CODE (cond
),
542 fold_convert_loc (loc
,
545 !(single_use0_p
&& single_use1_p
));
547 else if (TREE_CODE (cond
) == SSA_NAME
)
550 def_stmt
= get_prop_source_stmt (name
, true, NULL
);
551 if (def_stmt
|| !can_propagate_from (def_stmt
))
552 return did_something
;
554 rhs0
= gimple_assign_rhs1 (def_stmt
);
555 tmp
= combine_cond_expr_cond (loc
, NE_EXPR
, boolean_type_node
, rhs0
,
556 build_int_cst (TREE_TYPE (rhs0
), 0),
562 if (dump_file
&& tmp
)
564 fprintf (dump_file
, " Replaced '");
565 print_generic_expr (dump_file
, cond
, 0);
566 fprintf (dump_file
, "' with '");
567 print_generic_expr (dump_file
, tmp
, 0);
568 fprintf (dump_file
, "'\n");
571 gimple_assign_set_rhs_from_tree (gsi_p
, unshare_expr (tmp
));
572 stmt
= gsi_stmt (*gsi_p
);
575 /* Remove defining statements. */
576 remove_prop_source_from_use (name
, NULL
);
578 if (is_gimple_min_invariant (tmp
))
580 else if (did_something
== 0)
583 /* Continue combining. */
590 return did_something
;
593 /* We've just substituted an ADDR_EXPR into stmt. Update all the
594 relevant data structures to match. */
597 tidy_after_forward_propagate_addr (gimple stmt
)
599 /* We may have turned a trapping insn into a non-trapping insn. */
600 if (maybe_clean_or_replace_eh_stmt (stmt
, stmt
)
601 && gimple_purge_dead_eh_edges (gimple_bb (stmt
)))
604 if (TREE_CODE (gimple_assign_rhs1 (stmt
)) == ADDR_EXPR
)
605 recompute_tree_invariant_for_addr_expr (gimple_assign_rhs1 (stmt
));
608 /* DEF_RHS contains the address of the 0th element in an array.
609 USE_STMT uses type of DEF_RHS to compute the address of an
610 arbitrary element within the array. The (variable) byte offset
611 of the element is contained in OFFSET.
613 We walk back through the use-def chains of OFFSET to verify that
614 it is indeed computing the offset of an element within the array
615 and extract the index corresponding to the given byte offset.
617 We then try to fold the entire address expression into a form
620 If we are successful, we replace the right hand side of USE_STMT
621 with the new address computation. */
624 forward_propagate_addr_into_variable_array_index (tree offset
,
626 gimple_stmt_iterator
*use_stmt_gsi
)
629 gimple offset_def
, use_stmt
= gsi_stmt (*use_stmt_gsi
);
632 tunit
= TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs
)));
633 if (!host_integerp (tunit
, 1))
636 /* Get the offset's defining statement. */
637 offset_def
= SSA_NAME_DEF_STMT (offset
);
639 /* Try to find an expression for a proper index. This is either a
640 multiplication expression by the element size or just the ssa name we came
641 along in case the element size is one. In that case, however, we do not
642 allow multiplications because they can be computing index to a higher
643 level dimension (PR 37861). */
644 if (integer_onep (tunit
))
646 if (is_gimple_assign (offset_def
)
647 && gimple_assign_rhs_code (offset_def
) == MULT_EXPR
)
654 /* The statement which defines OFFSET before type conversion
655 must be a simple GIMPLE_ASSIGN. */
656 if (!is_gimple_assign (offset_def
))
659 /* The RHS of the statement which defines OFFSET must be a
660 multiplication of an object by the size of the array elements.
661 This implicitly verifies that the size of the array elements
663 if (gimple_assign_rhs_code (offset_def
) == MULT_EXPR
664 && TREE_CODE (gimple_assign_rhs2 (offset_def
)) == INTEGER_CST
665 && tree_int_cst_equal (gimple_assign_rhs2 (offset_def
), tunit
))
667 /* The first operand to the MULT_EXPR is the desired index. */
668 index
= gimple_assign_rhs1 (offset_def
);
670 /* If we have idx * tunit + CST * tunit re-associate that. */
671 else if ((gimple_assign_rhs_code (offset_def
) == PLUS_EXPR
672 || gimple_assign_rhs_code (offset_def
) == MINUS_EXPR
)
673 && TREE_CODE (gimple_assign_rhs1 (offset_def
)) == SSA_NAME
674 && TREE_CODE (gimple_assign_rhs2 (offset_def
)) == INTEGER_CST
675 && (tmp
= div_if_zero_remainder (EXACT_DIV_EXPR
,
676 gimple_assign_rhs2 (offset_def
),
677 tunit
)) != NULL_TREE
)
679 gimple offset_def2
= SSA_NAME_DEF_STMT (gimple_assign_rhs1 (offset_def
));
680 if (is_gimple_assign (offset_def2
)
681 && gimple_assign_rhs_code (offset_def2
) == MULT_EXPR
682 && TREE_CODE (gimple_assign_rhs2 (offset_def2
)) == INTEGER_CST
683 && tree_int_cst_equal (gimple_assign_rhs2 (offset_def2
), tunit
))
685 index
= fold_build2 (gimple_assign_rhs_code (offset_def
),
687 gimple_assign_rhs1 (offset_def2
), tmp
);
696 /* Replace the pointer addition with array indexing. */
697 index
= force_gimple_operand_gsi (use_stmt_gsi
, index
, true, NULL_TREE
,
698 true, GSI_SAME_STMT
);
699 gimple_assign_set_rhs_from_tree (use_stmt_gsi
, unshare_expr (def_rhs
));
700 use_stmt
= gsi_stmt (*use_stmt_gsi
);
701 TREE_OPERAND (TREE_OPERAND (gimple_assign_rhs1 (use_stmt
), 0), 1)
704 /* That should have created gimple, so there is no need to
705 record information to undo the propagation. */
706 fold_stmt_inplace (use_stmt
);
707 tidy_after_forward_propagate_addr (use_stmt
);
711 /* NAME is a SSA_NAME representing DEF_RHS which is of the form
712 ADDR_EXPR <whatever>.
714 Try to forward propagate the ADDR_EXPR into the use USE_STMT.
715 Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
716 node or for recovery of array indexing from pointer arithmetic.
718 Return true if the propagation was successful (the propagation can
719 be not totally successful, yet things may have been changed). */
722 forward_propagate_addr_expr_1 (tree name
, tree def_rhs
,
723 gimple_stmt_iterator
*use_stmt_gsi
,
726 tree lhs
, rhs
, rhs2
, array_ref
;
728 gimple use_stmt
= gsi_stmt (*use_stmt_gsi
);
729 enum tree_code rhs_code
;
732 gcc_assert (TREE_CODE (def_rhs
) == ADDR_EXPR
);
734 lhs
= gimple_assign_lhs (use_stmt
);
735 rhs_code
= gimple_assign_rhs_code (use_stmt
);
736 rhs
= gimple_assign_rhs1 (use_stmt
);
738 /* Trivial cases. The use statement could be a trivial copy or a
739 useless conversion. Recurse to the uses of the lhs as copyprop does
740 not copy through different variant pointers and FRE does not catch
741 all useless conversions. Treat the case of a single-use name and
742 a conversion to def_rhs type separate, though. */
743 if (TREE_CODE (lhs
) == SSA_NAME
744 && ((rhs_code
== SSA_NAME
&& rhs
== name
)
745 || CONVERT_EXPR_CODE_P (rhs_code
)))
747 /* Only recurse if we don't deal with a single use or we cannot
748 do the propagation to the current statement. In particular
749 we can end up with a conversion needed for a non-invariant
750 address which we cannot do in a single statement. */
752 || (!useless_type_conversion_p (TREE_TYPE (lhs
), TREE_TYPE (def_rhs
))
753 && (!is_gimple_min_invariant (def_rhs
)
754 || (INTEGRAL_TYPE_P (TREE_TYPE (lhs
))
755 && POINTER_TYPE_P (TREE_TYPE (def_rhs
))
756 && (TYPE_PRECISION (TREE_TYPE (lhs
))
757 > TYPE_PRECISION (TREE_TYPE (def_rhs
)))))))
758 return forward_propagate_addr_expr (lhs
, def_rhs
);
760 gimple_assign_set_rhs1 (use_stmt
, unshare_expr (def_rhs
));
761 if (useless_type_conversion_p (TREE_TYPE (lhs
), TREE_TYPE (def_rhs
)))
762 gimple_assign_set_rhs_code (use_stmt
, TREE_CODE (def_rhs
));
764 gimple_assign_set_rhs_code (use_stmt
, NOP_EXPR
);
768 /* Now strip away any outer COMPONENT_REF/ARRAY_REF nodes from the LHS.
769 ADDR_EXPR will not appear on the LHS. */
770 lhsp
= gimple_assign_lhs_ptr (use_stmt
);
771 while (handled_component_p (*lhsp
))
772 lhsp
= &TREE_OPERAND (*lhsp
, 0);
775 /* Now see if the LHS node is an INDIRECT_REF using NAME. If so,
776 propagate the ADDR_EXPR into the use of NAME and fold the result. */
777 if (TREE_CODE (lhs
) == INDIRECT_REF
778 && TREE_OPERAND (lhs
, 0) == name
)
780 if (may_propagate_address_into_dereference (def_rhs
, lhs
)
781 && (lhsp
!= gimple_assign_lhs_ptr (use_stmt
)
782 || useless_type_conversion_p
783 (TREE_TYPE (TREE_OPERAND (def_rhs
, 0)), TREE_TYPE (rhs
))))
785 *lhsp
= unshare_expr (TREE_OPERAND (def_rhs
, 0));
786 fold_stmt_inplace (use_stmt
);
787 tidy_after_forward_propagate_addr (use_stmt
);
789 /* Continue propagating into the RHS if this was not the only use. */
794 /* We can have a struct assignment dereferencing our name twice.
795 Note that we didn't propagate into the lhs to not falsely
796 claim we did when propagating into the rhs. */
800 /* Strip away any outer COMPONENT_REF, ARRAY_REF or ADDR_EXPR
801 nodes from the RHS. */
802 rhsp
= gimple_assign_rhs1_ptr (use_stmt
);
803 while (handled_component_p (*rhsp
)
804 || TREE_CODE (*rhsp
) == ADDR_EXPR
)
805 rhsp
= &TREE_OPERAND (*rhsp
, 0);
808 /* Now see if the RHS node is an INDIRECT_REF using NAME. If so,
809 propagate the ADDR_EXPR into the use of NAME and fold the result. */
810 if (TREE_CODE (rhs
) == INDIRECT_REF
811 && TREE_OPERAND (rhs
, 0) == name
812 && may_propagate_address_into_dereference (def_rhs
, rhs
))
814 *rhsp
= unshare_expr (TREE_OPERAND (def_rhs
, 0));
815 fold_stmt_inplace (use_stmt
);
816 tidy_after_forward_propagate_addr (use_stmt
);
820 /* Now see if the RHS node is an INDIRECT_REF using NAME. If so,
821 propagate the ADDR_EXPR into the use of NAME and try to
822 create a VCE and fold the result. */
823 if (TREE_CODE (rhs
) == INDIRECT_REF
824 && TREE_OPERAND (rhs
, 0) == name
825 && TYPE_SIZE (TREE_TYPE (rhs
))
826 && TYPE_SIZE (TREE_TYPE (TREE_OPERAND (def_rhs
, 0)))
827 /* Function decls should not be used for VCE either as it could be a
828 function descriptor that we want and not the actual function code. */
829 && TREE_CODE (TREE_OPERAND (def_rhs
, 0)) != FUNCTION_DECL
830 /* We should not convert volatile loads to non volatile loads. */
831 && !TYPE_VOLATILE (TREE_TYPE (rhs
))
832 && !TYPE_VOLATILE (TREE_TYPE (TREE_OPERAND (def_rhs
, 0)))
833 && operand_equal_p (TYPE_SIZE (TREE_TYPE (rhs
)),
834 TYPE_SIZE (TREE_TYPE (TREE_OPERAND (def_rhs
, 0))), 0))
836 tree def_rhs_base
, new_rhs
= unshare_expr (TREE_OPERAND (def_rhs
, 0));
837 new_rhs
= fold_build1 (VIEW_CONVERT_EXPR
, TREE_TYPE (rhs
), new_rhs
);
838 if (TREE_CODE (new_rhs
) != VIEW_CONVERT_EXPR
)
840 /* If we have folded the VIEW_CONVERT_EXPR then the result is only
841 valid if we can replace the whole rhs of the use statement. */
842 if (rhs
!= gimple_assign_rhs1 (use_stmt
))
844 new_rhs
= force_gimple_operand_gsi (use_stmt_gsi
, new_rhs
, true, NULL
,
846 gimple_assign_set_rhs1 (use_stmt
, new_rhs
);
847 tidy_after_forward_propagate_addr (use_stmt
);
850 /* If the defining rhs comes from an indirect reference, then do not
851 convert into a VIEW_CONVERT_EXPR. */
852 def_rhs_base
= TREE_OPERAND (def_rhs
, 0);
853 while (handled_component_p (def_rhs_base
))
854 def_rhs_base
= TREE_OPERAND (def_rhs_base
, 0);
855 if (!INDIRECT_REF_P (def_rhs_base
))
857 /* We may have arbitrary VIEW_CONVERT_EXPRs in a nested component
858 reference. Place it there and fold the thing. */
860 fold_stmt_inplace (use_stmt
);
861 tidy_after_forward_propagate_addr (use_stmt
);
866 /* If the use of the ADDR_EXPR is not a POINTER_PLUS_EXPR, there
868 if (gimple_assign_rhs_code (use_stmt
) != POINTER_PLUS_EXPR
869 || gimple_assign_rhs1 (use_stmt
) != name
)
872 /* The remaining cases are all for turning pointer arithmetic into
873 array indexing. They only apply when we have the address of
874 element zero in an array. If that is not the case then there
876 array_ref
= TREE_OPERAND (def_rhs
, 0);
877 if (TREE_CODE (array_ref
) != ARRAY_REF
878 || TREE_CODE (TREE_TYPE (TREE_OPERAND (array_ref
, 0))) != ARRAY_TYPE
879 || TREE_CODE (TREE_OPERAND (array_ref
, 1)) != INTEGER_CST
)
882 rhs2
= gimple_assign_rhs2 (use_stmt
);
883 /* Try to optimize &x[C1] p+ C2 where C2 is a multiple of the size
884 of the elements in X into &x[C1 + C2/element size]. */
885 if (TREE_CODE (rhs2
) == INTEGER_CST
)
887 tree new_rhs
= maybe_fold_stmt_addition (gimple_location (use_stmt
),
892 tree type
= TREE_TYPE (gimple_assign_lhs (use_stmt
));
893 new_rhs
= unshare_expr (new_rhs
);
894 if (!useless_type_conversion_p (type
, TREE_TYPE (new_rhs
)))
896 if (!is_gimple_min_invariant (new_rhs
))
897 new_rhs
= force_gimple_operand_gsi (use_stmt_gsi
, new_rhs
,
899 true, GSI_SAME_STMT
);
900 new_rhs
= fold_convert (type
, new_rhs
);
902 gimple_assign_set_rhs_from_tree (use_stmt_gsi
, new_rhs
);
903 use_stmt
= gsi_stmt (*use_stmt_gsi
);
904 update_stmt (use_stmt
);
905 tidy_after_forward_propagate_addr (use_stmt
);
910 /* Try to optimize &x[0] p+ OFFSET where OFFSET is defined by
911 converting a multiplication of an index by the size of the
912 array elements, then the result is converted into the proper
913 type for the arithmetic. */
914 if (TREE_CODE (rhs2
) == SSA_NAME
915 && integer_zerop (TREE_OPERAND (array_ref
, 1))
916 && useless_type_conversion_p (TREE_TYPE (name
), TREE_TYPE (def_rhs
))
917 /* Avoid problems with IVopts creating PLUS_EXPRs with a
918 different type than their operands. */
919 && useless_type_conversion_p (TREE_TYPE (lhs
), TREE_TYPE (def_rhs
)))
920 return forward_propagate_addr_into_variable_array_index (rhs2
, def_rhs
,
925 /* STMT is a statement of the form SSA_NAME = ADDR_EXPR <whatever>.
927 Try to forward propagate the ADDR_EXPR into all uses of the SSA_NAME.
928 Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
929 node or for recovery of array indexing from pointer arithmetic.
930 Returns true, if all uses have been propagated into. */
933 forward_propagate_addr_expr (tree name
, tree rhs
)
935 int stmt_loop_depth
= gimple_bb (SSA_NAME_DEF_STMT (name
))->loop_depth
;
936 imm_use_iterator iter
;
939 bool single_use_p
= has_single_use (name
);
941 FOR_EACH_IMM_USE_STMT (use_stmt
, iter
, name
)
946 /* If the use is not in a simple assignment statement, then
947 there is nothing we can do. */
948 if (gimple_code (use_stmt
) != GIMPLE_ASSIGN
)
954 /* If the use is in a deeper loop nest, then we do not want
955 to propagate the ADDR_EXPR into the loop as that is likely
956 adding expression evaluations into the loop. */
957 if (gimple_bb (use_stmt
)->loop_depth
> stmt_loop_depth
)
964 gimple_stmt_iterator gsi
= gsi_for_stmt (use_stmt
);
965 result
= forward_propagate_addr_expr_1 (name
, rhs
, &gsi
,
967 /* If the use has moved to a different statement adjust
968 the update machinery for the old statement too. */
969 if (use_stmt
!= gsi_stmt (gsi
))
971 update_stmt (use_stmt
);
972 use_stmt
= gsi_stmt (gsi
);
975 update_stmt (use_stmt
);
979 /* Remove intermediate now unused copy and conversion chains. */
980 use_rhs
= gimple_assign_rhs1 (use_stmt
);
982 && TREE_CODE (gimple_assign_lhs (use_stmt
)) == SSA_NAME
983 && TREE_CODE (use_rhs
) == SSA_NAME
984 && has_zero_uses (gimple_assign_lhs (use_stmt
)))
986 gimple_stmt_iterator gsi
= gsi_for_stmt (use_stmt
);
987 release_defs (use_stmt
);
988 gsi_remove (&gsi
, true);
995 /* Forward propagate the comparison defined in STMT like
996 cond_1 = x CMP y to uses of the form
1000 Returns true if stmt is now unused. */
1003 forward_propagate_comparison (gimple stmt
)
1005 tree name
= gimple_assign_lhs (stmt
);
1007 tree tmp
= NULL_TREE
;
1009 /* Don't propagate ssa names that occur in abnormal phis. */
1010 if ((TREE_CODE (gimple_assign_rhs1 (stmt
)) == SSA_NAME
1011 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_assign_rhs1 (stmt
)))
1012 || (TREE_CODE (gimple_assign_rhs2 (stmt
)) == SSA_NAME
1013 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_assign_rhs2 (stmt
))))
1016 /* Do not un-cse comparisons. But propagate through copies. */
1017 use_stmt
= get_prop_dest_stmt (name
, &name
);
1021 /* Conversion of the condition result to another integral type. */
1022 if (is_gimple_assign (use_stmt
)
1023 && (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (use_stmt
))
1024 || TREE_CODE_CLASS (gimple_assign_rhs_code (use_stmt
))
1026 || gimple_assign_rhs_code (use_stmt
) == TRUTH_NOT_EXPR
)
1027 && INTEGRAL_TYPE_P (TREE_TYPE (gimple_assign_lhs (use_stmt
))))
1029 tree lhs
= gimple_assign_lhs (use_stmt
);
1031 /* We can propagate the condition into a conversion. */
1032 if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (use_stmt
)))
1034 /* Avoid using fold here as that may create a COND_EXPR with
1035 non-boolean condition as canonical form. */
1036 tmp
= build2 (gimple_assign_rhs_code (stmt
), TREE_TYPE (lhs
),
1037 gimple_assign_rhs1 (stmt
), gimple_assign_rhs2 (stmt
));
1039 /* We can propagate the condition into X op CST where op
1040 is EQ_EXPR or NE_EXPR and CST is either one or zero. */
1041 else if (TREE_CODE_CLASS (gimple_assign_rhs_code (use_stmt
))
1043 && TREE_CODE (gimple_assign_rhs1 (use_stmt
)) == SSA_NAME
1044 && TREE_CODE (gimple_assign_rhs2 (use_stmt
)) == INTEGER_CST
)
1046 enum tree_code code
= gimple_assign_rhs_code (use_stmt
);
1047 tree cst
= gimple_assign_rhs2 (use_stmt
);
1050 cond
= build2 (gimple_assign_rhs_code (stmt
),
1052 gimple_assign_rhs1 (stmt
),
1053 gimple_assign_rhs2 (stmt
));
1055 tmp
= combine_cond_expr_cond (gimple_location (use_stmt
),
1056 code
, TREE_TYPE (lhs
),
1058 if (tmp
== NULL_TREE
)
1061 /* We can propagate the condition into a statement that
1062 computes the logical negation of the comparison result. */
1063 else if (gimple_assign_rhs_code (use_stmt
) == TRUTH_NOT_EXPR
)
1065 tree type
= TREE_TYPE (gimple_assign_rhs1 (stmt
));
1066 bool nans
= HONOR_NANS (TYPE_MODE (type
));
1067 enum tree_code code
;
1068 code
= invert_tree_comparison (gimple_assign_rhs_code (stmt
), nans
);
1069 if (code
== ERROR_MARK
)
1072 tmp
= build2 (code
, TREE_TYPE (lhs
), gimple_assign_rhs1 (stmt
),
1073 gimple_assign_rhs2 (stmt
));
1079 gimple_stmt_iterator gsi
= gsi_for_stmt (use_stmt
);
1080 gimple_assign_set_rhs_from_tree (&gsi
, unshare_expr (tmp
));
1081 use_stmt
= gsi_stmt (gsi
);
1082 update_stmt (use_stmt
);
1085 /* Remove defining statements. */
1086 remove_prop_source_from_use (name
, stmt
);
1088 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1090 tree old_rhs
= rhs_to_tree (TREE_TYPE (gimple_assign_lhs (stmt
)),
1092 fprintf (dump_file
, " Replaced '");
1093 print_generic_expr (dump_file
, old_rhs
, dump_flags
);
1094 fprintf (dump_file
, "' with '");
1095 print_generic_expr (dump_file
, tmp
, dump_flags
);
1096 fprintf (dump_file
, "'\n");
1105 /* If we have lhs = ~x (STMT), look and see if earlier we had x = ~y.
1106 If so, we can change STMT into lhs = y which can later be copy
1107 propagated. Similarly for negation.
1109 This could trivially be formulated as a forward propagation
1110 to immediate uses. However, we already had an implementation
1111 from DOM which used backward propagation via the use-def links.
1113 It turns out that backward propagation is actually faster as
1114 there's less work to do for each NOT/NEG expression we find.
1115 Backwards propagation needs to look at the statement in a single
1116 backlink. Forward propagation needs to look at potentially more
1117 than one forward link. */
1120 simplify_not_neg_expr (gimple_stmt_iterator
*gsi_p
)
1122 gimple stmt
= gsi_stmt (*gsi_p
);
1123 tree rhs
= gimple_assign_rhs1 (stmt
);
1124 gimple rhs_def_stmt
= SSA_NAME_DEF_STMT (rhs
);
1126 /* See if the RHS_DEF_STMT has the same form as our statement. */
1127 if (is_gimple_assign (rhs_def_stmt
)
1128 && gimple_assign_rhs_code (rhs_def_stmt
) == gimple_assign_rhs_code (stmt
))
1130 tree rhs_def_operand
= gimple_assign_rhs1 (rhs_def_stmt
);
1132 /* Verify that RHS_DEF_OPERAND is a suitable SSA_NAME. */
1133 if (TREE_CODE (rhs_def_operand
) == SSA_NAME
1134 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand
))
1136 gimple_assign_set_rhs_from_tree (gsi_p
, rhs_def_operand
);
1137 stmt
= gsi_stmt (*gsi_p
);
1143 /* STMT is a SWITCH_EXPR for which we attempt to find equivalent forms of
1144 the condition which we may be able to optimize better. */
1147 simplify_gimple_switch (gimple stmt
)
1149 tree cond
= gimple_switch_index (stmt
);
1153 /* The optimization that we really care about is removing unnecessary
1154 casts. That will let us do much better in propagating the inferred
1155 constant at the switch target. */
1156 if (TREE_CODE (cond
) == SSA_NAME
)
1158 def_stmt
= SSA_NAME_DEF_STMT (cond
);
1159 if (is_gimple_assign (def_stmt
))
1161 if (gimple_assign_rhs_code (def_stmt
) == NOP_EXPR
)
1166 def
= gimple_assign_rhs1 (def_stmt
);
1168 #ifdef ENABLE_CHECKING
1169 /* ??? Why was Jeff testing this? We are gimple... */
1170 gcc_assert (is_gimple_val (def
));
1173 to
= TREE_TYPE (cond
);
1174 ti
= TREE_TYPE (def
);
1176 /* If we have an extension that preserves value, then we
1177 can copy the source value into the switch. */
1179 need_precision
= TYPE_PRECISION (ti
);
1181 if (! INTEGRAL_TYPE_P (ti
))
1183 else if (TYPE_UNSIGNED (to
) && !TYPE_UNSIGNED (ti
))
1185 else if (!TYPE_UNSIGNED (to
) && TYPE_UNSIGNED (ti
))
1186 need_precision
+= 1;
1187 if (TYPE_PRECISION (to
) < need_precision
)
1192 gimple_switch_set_index (stmt
, def
);
1200 /* Run bitwise and assignments throug the folder. If the first argument is an
1201 ssa name that is itself a result of a typecast of an ADDR_EXPR to an
1202 integer, feed the ADDR_EXPR to the folder rather than the ssa name.
1206 simplify_bitwise_and (gimple_stmt_iterator
*gsi
, gimple stmt
)
1209 tree arg1
= gimple_assign_rhs1 (stmt
);
1210 tree arg2
= gimple_assign_rhs2 (stmt
);
1212 if (TREE_CODE (arg2
) != INTEGER_CST
)
1215 if (TREE_CODE (arg1
) == SSA_NAME
&& !SSA_NAME_IS_DEFAULT_DEF (arg1
))
1217 gimple def
= SSA_NAME_DEF_STMT (arg1
);
1219 if (gimple_assign_cast_p (def
)
1220 && INTEGRAL_TYPE_P (gimple_expr_type (def
)))
1222 tree op
= gimple_assign_rhs1 (def
);
1224 if (TREE_CODE (op
) == ADDR_EXPR
)
1229 res
= fold_binary_loc (gimple_location (stmt
),
1230 BIT_AND_EXPR
, TREE_TYPE (gimple_assign_lhs (stmt
)),
1232 if (res
&& is_gimple_min_invariant (res
))
1234 gimple_assign_set_rhs_from_tree (gsi
, res
);
1240 /* Main entry point for the forward propagation optimizer. */
1243 tree_ssa_forward_propagate_single_use_vars (void)
1246 unsigned int todoflags
= 0;
1248 cfg_changed
= false;
1252 gimple_stmt_iterator gsi
;
1254 /* Note we update GSI within the loop as necessary. */
1255 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); )
1257 gimple stmt
= gsi_stmt (gsi
);
1259 /* If this statement sets an SSA_NAME to an address,
1260 try to propagate the address into the uses of the SSA_NAME. */
1261 if (is_gimple_assign (stmt
))
1263 tree lhs
= gimple_assign_lhs (stmt
);
1264 tree rhs
= gimple_assign_rhs1 (stmt
);
1266 if (TREE_CODE (lhs
) != SSA_NAME
)
1272 if (gimple_assign_rhs_code (stmt
) == ADDR_EXPR
1273 /* Handle pointer conversions on invariant addresses
1274 as well, as this is valid gimple. */
1275 || (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (stmt
))
1276 && TREE_CODE (rhs
) == ADDR_EXPR
1277 && POINTER_TYPE_P (TREE_TYPE (lhs
))))
1280 if (!stmt_references_abnormal_ssa_name (stmt
)
1281 && forward_propagate_addr_expr (lhs
, rhs
))
1283 release_defs (stmt
);
1284 todoflags
|= TODO_remove_unused_locals
;
1285 gsi_remove (&gsi
, true);
1290 else if (gimple_assign_rhs_code (stmt
) == POINTER_PLUS_EXPR
1291 && is_gimple_min_invariant (rhs
))
1293 /* Make sure to fold &a[0] + off_1 here. */
1294 fold_stmt_inplace (stmt
);
1296 if (gimple_assign_rhs_code (stmt
) == POINTER_PLUS_EXPR
)
1299 else if ((gimple_assign_rhs_code (stmt
) == BIT_NOT_EXPR
1300 || gimple_assign_rhs_code (stmt
) == NEGATE_EXPR
)
1301 && TREE_CODE (rhs
) == SSA_NAME
)
1303 simplify_not_neg_expr (&gsi
);
1306 else if (gimple_assign_rhs_code (stmt
) == COND_EXPR
)
1308 /* In this case the entire COND_EXPR is in rhs1. */
1310 fold_defer_overflow_warnings ();
1311 did_something
= forward_propagate_into_cond (&gsi
);
1312 stmt
= gsi_stmt (gsi
);
1313 if (did_something
== 2)
1315 fold_undefer_overflow_warnings (!TREE_NO_WARNING (rhs
)
1316 && did_something
, stmt
, WARN_STRICT_OVERFLOW_CONDITIONAL
);
1319 else if (TREE_CODE_CLASS (gimple_assign_rhs_code (stmt
))
1322 if (forward_propagate_comparison (stmt
))
1324 release_defs (stmt
);
1325 todoflags
|= TODO_remove_unused_locals
;
1326 gsi_remove (&gsi
, true);
1331 else if (gimple_assign_rhs_code (stmt
) == BIT_AND_EXPR
)
1333 simplify_bitwise_and (&gsi
, stmt
);
1339 else if (gimple_code (stmt
) == GIMPLE_SWITCH
)
1341 simplify_gimple_switch (stmt
);
1344 else if (gimple_code (stmt
) == GIMPLE_COND
)
1347 fold_defer_overflow_warnings ();
1348 did_something
= forward_propagate_into_gimple_cond (stmt
);
1349 if (did_something
== 2)
1351 fold_undefer_overflow_warnings (did_something
, stmt
,
1352 WARN_STRICT_OVERFLOW_CONDITIONAL
);
1361 todoflags
|= TODO_cleanup_cfg
;
1367 gate_forwprop (void)
1369 return flag_tree_forwprop
;
1372 struct gimple_opt_pass pass_forwprop
=
1376 "forwprop", /* name */
1377 gate_forwprop
, /* gate */
1378 tree_ssa_forward_propagate_single_use_vars
, /* execute */
1381 0, /* static_pass_number */
1382 TV_TREE_FORWPROP
, /* tv_id */
1383 PROP_cfg
| PROP_ssa
, /* properties_required */
1384 0, /* properties_provided */
1385 0, /* properties_destroyed */
1386 0, /* todo_flags_start */
1390 | TODO_verify_ssa
/* todo_flags_finish */