1 /* Forward propagation of expressions for single use variables.
2 Copyright (C) 2004, 2005, 2007, 2008 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"
37 /* This pass propagates the RHS of assignment statements into use
38 sites of the LHS of the assignment. It's basically a specialized
39 form of tree combination. It is hoped all of this can disappear
40 when we have a generalized tree combiner.
42 Note carefully that after propagation the resulting statement
43 must still be a proper gimple statement. Right now we simply
44 only perform propagations we know will result in valid gimple
45 code. One day we'll want to generalize this code.
47 One class of common cases we handle is forward propagating a single use
48 variable into a COND_EXPR.
52 if (x) goto ... else goto ...
54 Will be transformed into:
57 if (a COND b) goto ... else goto ...
59 Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
61 Or (assuming c1 and c2 are constants):
65 if (x EQ/NEQ c2) goto ... else goto ...
67 Will be transformed into:
70 if (a EQ/NEQ (c2 - c1)) goto ... else goto ...
72 Similarly for x = a - c1.
78 if (x) goto ... else goto ...
80 Will be transformed into:
83 if (a == 0) goto ... else goto ...
85 Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
86 For these cases, we propagate A into all, possibly more than one,
87 COND_EXPRs that use X.
93 if (x) goto ... else goto ...
95 Will be transformed into:
98 if (a != 0) goto ... else goto ...
100 (Assuming a is an integral type and x is a boolean or x is an
101 integral and a is a boolean.)
103 Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
104 For these cases, we propagate A into all, possibly more than one,
105 COND_EXPRs that use X.
107 In addition to eliminating the variable and the statement which assigns
108 a value to the variable, we may be able to later thread the jump without
109 adding insane complexity in the dominator optimizer.
111 Also note these transformations can cascade. We handle this by having
112 a worklist of COND_EXPR statements to examine. As we make a change to
113 a statement, we put it back on the worklist to examine on the next
114 iteration of the main loop.
116 A second class of propagation opportunities arises for ADDR_EXPR
129 ptr2 = ptr + <constant>;
133 ptr2 = &x[constant/elementsize];
138 offset = index * element_size;
139 offset_p = (pointer) offset;
140 ptr2 = ptr + offset_p
142 Will get turned into:
146 We also propagate casts into SWITCH_EXPR and COND_EXPR conditions to
147 allow us to remove the cast and {NOT_EXPR,NEG_EXPR} into a subsequent
150 This will (of course) be extended as other needs arise. */
152 static bool forward_propagate_addr_expr (tree name, tree rhs);
154 /* Set to true if we delete EH edges during the optimization. */
155 static bool cfg_changed;
158 /* Get the next statement we can propagate NAME's value into skipping
159 trivial copies. Returns the statement that is suitable as a
160 propagation destination or NULL_TREE if there is no such one.
161 This only returns destinations in a single-use chain. FINAL_NAME_P
162 if non-NULL is written to the ssa name that represents the use. */
165 get_prop_dest_stmt (tree name, tree *final_name_p)
171 /* If name has multiple uses, bail out. */
172 if (!single_imm_use (name, &use, &use_stmt))
175 /* If this is not a trivial copy, we found it. */
176 if (TREE_CODE (use_stmt) != GIMPLE_MODIFY_STMT
177 || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) != SSA_NAME
178 || GIMPLE_STMT_OPERAND (use_stmt, 1) != name)
181 /* Continue searching uses of the copy destination. */
182 name = GIMPLE_STMT_OPERAND (use_stmt, 0);
186 *final_name_p = name;
191 /* Get the statement we can propagate from into NAME skipping
192 trivial copies. Returns the statement which defines the
193 propagation source or NULL_TREE if there is no such one.
194 If SINGLE_USE_ONLY is set considers only sources which have
195 a single use chain up to NAME. If SINGLE_USE_P is non-null,
196 it is set to whether the chain to NAME is a single use chain
197 or not. SINGLE_USE_P is not written to if SINGLE_USE_ONLY is set. */
200 get_prop_source_stmt (tree name, bool single_use_only, bool *single_use_p)
202 bool single_use = true;
205 tree def_stmt = SSA_NAME_DEF_STMT (name);
207 if (!has_single_use (name))
214 /* If name is defined by a PHI node or is the default def, bail out. */
215 if (TREE_CODE (def_stmt) != GIMPLE_MODIFY_STMT)
218 /* If name is not a simple copy destination, we found it. */
219 if (TREE_CODE (GIMPLE_STMT_OPERAND (def_stmt, 1)) != SSA_NAME)
223 if (!single_use_only && single_use_p)
224 *single_use_p = single_use;
226 /* We can look through pointer conversions in the search
227 for a useful stmt for the comparison folding. */
228 rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
229 if ((TREE_CODE (rhs) == NOP_EXPR
230 || TREE_CODE (rhs) == CONVERT_EXPR)
231 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
232 && POINTER_TYPE_P (TREE_TYPE (rhs))
233 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0))))
234 name = TREE_OPERAND (rhs, 0);
240 /* Continue searching the def of the copy source name. */
241 name = GIMPLE_STMT_OPERAND (def_stmt, 1);
246 /* Checks if the destination ssa name in DEF_STMT can be used as
247 propagation source. Returns true if so, otherwise false. */
250 can_propagate_from (tree def_stmt)
252 tree rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
254 /* If the rhs has side-effects we cannot propagate from it. */
255 if (TREE_SIDE_EFFECTS (rhs))
258 /* If the rhs is a load we cannot propagate from it. */
259 if (REFERENCE_CLASS_P (rhs))
262 /* Constants can be always propagated. */
263 if (is_gimple_min_invariant (rhs))
266 /* We cannot propagate ssa names that occur in abnormal phi nodes. */
267 switch (TREE_CODE_LENGTH (TREE_CODE (rhs)))
270 if (TREE_OPERAND (rhs, 2) != NULL_TREE
271 && TREE_CODE (TREE_OPERAND (rhs, 2)) == SSA_NAME
272 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (rhs, 2)))
275 if (TREE_OPERAND (rhs, 1) != NULL_TREE
276 && TREE_CODE (TREE_OPERAND (rhs, 1)) == SSA_NAME
277 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (rhs, 1)))
280 if (TREE_OPERAND (rhs, 0) != NULL_TREE
281 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
282 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (rhs, 0)))
290 /* If the definition is a conversion of a pointer to a function type,
291 then we can not apply optimizations as some targets require function
292 pointers to be canonicalized and in this case this optimization could
293 eliminate a necessary canonicalization. */
294 if ((TREE_CODE (rhs) == NOP_EXPR
295 || TREE_CODE (rhs) == CONVERT_EXPR)
296 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0)))
297 && TREE_CODE (TREE_TYPE (TREE_TYPE
298 (TREE_OPERAND (rhs, 0)))) == FUNCTION_TYPE)
304 /* Remove a copy chain ending in NAME along the defs but not
305 further or including UP_TO_STMT. If NAME was replaced in
306 its only use then this function can be used to clean up
307 dead stmts. Returns true if UP_TO_STMT can be removed
308 as well, otherwise false. */
311 remove_prop_source_from_use (tree name, tree up_to_stmt)
313 block_stmt_iterator bsi;
317 if (!has_zero_uses (name))
320 stmt = SSA_NAME_DEF_STMT (name);
321 if (stmt == up_to_stmt)
324 bsi = bsi_for_stmt (stmt);
326 bsi_remove (&bsi, true);
328 name = GIMPLE_STMT_OPERAND (stmt, 1);
329 } while (TREE_CODE (name) == SSA_NAME);
334 /* Combine OP0 CODE OP1 in the context of a COND_EXPR. Returns
335 the folded result in a form suitable for COND_EXPR_COND or
336 NULL_TREE, if there is no suitable simplified form. If
337 INVARIANT_ONLY is true only gimple_min_invariant results are
338 considered simplified. */
341 combine_cond_expr_cond (enum tree_code code, tree type,
342 tree op0, tree op1, bool invariant_only)
346 gcc_assert (TREE_CODE_CLASS (code) == tcc_comparison);
348 t = fold_binary (code, type, op0, op1);
352 /* Require that we got a boolean type out if we put one in. */
353 gcc_assert (TREE_CODE (TREE_TYPE (t)) == TREE_CODE (type));
355 /* Canonicalize the combined condition for use in a COND_EXPR. */
356 t = canonicalize_cond_expr_cond (t);
358 /* Bail out if we required an invariant but didn't get one. */
361 && !is_gimple_min_invariant (t)))
367 /* Propagate from the ssa name definition statements of COND_EXPR
368 in statement STMT into the conditional if that simplifies it.
369 Returns zero if no statement was changed, one if there were
370 changes and two if cfg_cleanup needs to run. */
373 forward_propagate_into_cond (tree cond_expr, tree stmt)
375 int did_something = 0;
378 tree tmp = NULL_TREE;
379 tree cond = COND_EXPR_COND (cond_expr);
380 tree name, def_stmt, rhs0 = NULL_TREE, rhs1 = NULL_TREE;
381 bool single_use0_p = false, single_use1_p = false;
383 /* We can do tree combining on SSA_NAME and comparison expressions. */
384 if (COMPARISON_CLASS_P (cond)
385 && TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME)
387 /* For comparisons use the first operand, that is likely to
388 simplify comparisons against constants. */
389 name = TREE_OPERAND (cond, 0);
390 def_stmt = get_prop_source_stmt (name, false, &single_use0_p);
391 if (def_stmt != NULL_TREE
392 && can_propagate_from (def_stmt))
394 tree op1 = TREE_OPERAND (cond, 1);
395 rhs0 = GIMPLE_STMT_OPERAND (def_stmt, 1);
396 tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
397 fold_convert (TREE_TYPE (op1), rhs0),
398 op1, !single_use0_p);
400 /* If that wasn't successful, try the second operand. */
402 && TREE_CODE (TREE_OPERAND (cond, 1)) == SSA_NAME)
404 tree op0 = TREE_OPERAND (cond, 0);
405 name = TREE_OPERAND (cond, 1);
406 def_stmt = get_prop_source_stmt (name, false, &single_use1_p);
407 if (def_stmt == NULL_TREE
408 || !can_propagate_from (def_stmt))
409 return did_something;
411 rhs1 = GIMPLE_STMT_OPERAND (def_stmt, 1);
412 tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
414 fold_convert (TREE_TYPE (op0), rhs1),
417 /* If that wasn't successful either, try both operands. */
420 && rhs1 != NULL_TREE)
421 tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
423 fold_convert (TREE_TYPE (rhs0), rhs1),
424 !(single_use0_p && single_use1_p));
426 else if (TREE_CODE (cond) == SSA_NAME)
429 def_stmt = get_prop_source_stmt (name, true, NULL);
430 if (def_stmt == NULL_TREE
431 || !can_propagate_from (def_stmt))
432 return did_something;
434 rhs0 = GIMPLE_STMT_OPERAND (def_stmt, 1);
435 tmp = combine_cond_expr_cond (NE_EXPR, boolean_type_node, rhs0,
436 build_int_cst (TREE_TYPE (rhs0), 0),
442 if (dump_file && tmp)
444 fprintf (dump_file, " Replaced '");
445 print_generic_expr (dump_file, cond, 0);
446 fprintf (dump_file, "' with '");
447 print_generic_expr (dump_file, tmp, 0);
448 fprintf (dump_file, "'\n");
451 COND_EXPR_COND (cond_expr) = unshare_expr (tmp);
454 /* Remove defining statements. */
455 remove_prop_source_from_use (name, NULL);
457 if (is_gimple_min_invariant (tmp))
459 else if (did_something == 0)
462 /* Continue combining. */
469 return did_something;
472 /* We've just substituted an ADDR_EXPR into stmt. Update all the
473 relevant data structures to match. */
476 tidy_after_forward_propagate_addr (tree stmt)
478 /* We may have turned a trapping insn into a non-trapping insn. */
479 if (maybe_clean_or_replace_eh_stmt (stmt, stmt)
480 && tree_purge_dead_eh_edges (bb_for_stmt (stmt)))
483 if (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == ADDR_EXPR)
484 recompute_tree_invariant_for_addr_expr (GIMPLE_STMT_OPERAND (stmt, 1));
486 mark_symbols_for_renaming (stmt);
489 /* DEF_RHS contains the address of the 0th element in an array.
490 USE_STMT uses type of DEF_RHS to compute the address of an
491 arbitrary element within the array. The (variable) byte offset
492 of the element is contained in OFFSET.
494 We walk back through the use-def chains of OFFSET to verify that
495 it is indeed computing the offset of an element within the array
496 and extract the index corresponding to the given byte offset.
498 We then try to fold the entire address expression into a form
501 If we are successful, we replace the right hand side of USE_STMT
502 with the new address computation. */
505 forward_propagate_addr_into_variable_array_index (tree offset,
506 tree def_rhs, tree use_stmt)
510 /* Try to find an expression for a proper index. This is either
511 a multiplication expression by the element size or just the
512 ssa name we came along in case the element size is one. */
513 if (integer_onep (TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs)))))
517 /* Get the offset's defining statement. */
518 offset = SSA_NAME_DEF_STMT (offset);
520 /* The statement which defines OFFSET before type conversion
521 must be a simple GIMPLE_MODIFY_STMT. */
522 if (TREE_CODE (offset) != GIMPLE_MODIFY_STMT)
525 /* The RHS of the statement which defines OFFSET must be a
526 multiplication of an object by the size of the array elements.
527 This implicitly verifies that the size of the array elements
529 offset = GIMPLE_STMT_OPERAND (offset, 1);
530 if (TREE_CODE (offset) != MULT_EXPR
531 || TREE_CODE (TREE_OPERAND (offset, 1)) != INTEGER_CST
532 || !simple_cst_equal (TREE_OPERAND (offset, 1),
533 TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs)))))
536 /* The first operand to the MULT_EXPR is the desired index. */
537 index = TREE_OPERAND (offset, 0);
540 /* Replace the pointer addition with array indexing. */
541 GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (def_rhs);
542 TREE_OPERAND (TREE_OPERAND (GIMPLE_STMT_OPERAND (use_stmt, 1), 0), 1)
545 /* That should have created gimple, so there is no need to
546 record information to undo the propagation. */
547 fold_stmt_inplace (use_stmt);
548 tidy_after_forward_propagate_addr (use_stmt);
552 /* NAME is a SSA_NAME representing DEF_RHS which is of the form
553 ADDR_EXPR <whatever>.
555 Try to forward propagate the ADDR_EXPR into the use USE_STMT.
556 Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
557 node or for recovery of array indexing from pointer arithmetic.
559 Return true if the propagation was successful (the propagation can
560 be not totally successful, yet things may have been changed). */
563 forward_propagate_addr_expr_1 (tree name, tree def_rhs, tree use_stmt,
566 tree lhs, rhs, array_ref;
569 gcc_assert (TREE_CODE (def_rhs) == ADDR_EXPR);
571 lhs = GIMPLE_STMT_OPERAND (use_stmt, 0);
572 rhs = GIMPLE_STMT_OPERAND (use_stmt, 1);
574 /* Trivial cases. The use statement could be a trivial copy or a
575 useless conversion. Recurse to the uses of the lhs as copyprop does
576 not copy through different variant pointers and FRE does not catch
577 all useless conversions. Treat the case of a single-use name and
578 a conversion to def_rhs type separate, though. */
579 if (TREE_CODE (lhs) == SSA_NAME
581 || TREE_CODE (rhs) == NOP_EXPR
582 || TREE_CODE (rhs) == CONVERT_EXPR)
583 && useless_type_conversion_p (TREE_TYPE (rhs), TREE_TYPE (def_rhs)))
585 /* Only recurse if we don't deal with a single use. */
587 return forward_propagate_addr_expr (lhs, def_rhs);
589 GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (def_rhs);
593 /* Now strip away any outer COMPONENT_REF/ARRAY_REF nodes from the LHS.
594 ADDR_EXPR will not appear on the LHS. */
595 lhsp = &GIMPLE_STMT_OPERAND (use_stmt, 0);
596 while (handled_component_p (*lhsp))
597 lhsp = &TREE_OPERAND (*lhsp, 0);
600 /* Now see if the LHS node is an INDIRECT_REF using NAME. If so,
601 propagate the ADDR_EXPR into the use of NAME and fold the result. */
602 if (TREE_CODE (lhs) == INDIRECT_REF
603 && TREE_OPERAND (lhs, 0) == name
604 /* This will not allow stripping const qualification from
605 pointers which we want to allow specifically here to clean up
606 the IL for initialization of constant objects. */
607 && (useless_type_conversion_p (TREE_TYPE (TREE_OPERAND (lhs, 0)),
609 /* So explicitly check for this here. */
610 || (TYPE_QUALS (TREE_TYPE (TREE_TYPE (TREE_OPERAND (lhs, 0))))
611 ^ TYPE_QUALS (TREE_TYPE (TREE_TYPE (def_rhs)))) == TYPE_QUAL_CONST)
612 /* ??? This looks redundant, but is required for bogus types
613 that can sometimes occur. */
614 && useless_type_conversion_p (TREE_TYPE (lhs),
615 TREE_TYPE (TREE_OPERAND (def_rhs, 0))))
617 *lhsp = unshare_expr (TREE_OPERAND (def_rhs, 0));
618 fold_stmt_inplace (use_stmt);
619 tidy_after_forward_propagate_addr (use_stmt);
621 /* Continue propagating into the RHS if this was not the only use. */
626 /* Strip away any outer COMPONENT_REF, ARRAY_REF or ADDR_EXPR
627 nodes from the RHS. */
628 rhsp = &GIMPLE_STMT_OPERAND (use_stmt, 1);
629 while (handled_component_p (*rhsp)
630 || TREE_CODE (*rhsp) == ADDR_EXPR)
631 rhsp = &TREE_OPERAND (*rhsp, 0);
634 /* Now see if the RHS node is an INDIRECT_REF using NAME. If so,
635 propagate the ADDR_EXPR into the use of NAME and fold the result. */
636 if (TREE_CODE (rhs) == INDIRECT_REF
637 && TREE_OPERAND (rhs, 0) == name
638 /* ??? This doesn't allow stripping const qualification to
639 streamline the IL for reads from non-constant objects. */
640 && (useless_type_conversion_p (TREE_TYPE (TREE_OPERAND (rhs, 0)),
642 /* So explicitly check for this here. */
643 || (TYPE_QUALS (TREE_TYPE (TREE_TYPE (TREE_OPERAND (rhs, 0))))
644 ^ TYPE_QUALS (TREE_TYPE (TREE_TYPE (def_rhs)))) == TYPE_QUAL_CONST)
645 && useless_type_conversion_p (TREE_TYPE (rhs),
646 TREE_TYPE (TREE_OPERAND (def_rhs, 0))))
648 *rhsp = unshare_expr (TREE_OPERAND (def_rhs, 0));
649 fold_stmt_inplace (use_stmt);
650 tidy_after_forward_propagate_addr (use_stmt);
654 /* If the use of the ADDR_EXPR is not a POINTER_PLUS_EXPR, there
656 if (TREE_CODE (rhs) != POINTER_PLUS_EXPR
657 || TREE_OPERAND (rhs, 0) != name)
660 /* The remaining cases are all for turning pointer arithmetic into
661 array indexing. They only apply when we have the address of
662 element zero in an array. If that is not the case then there
664 array_ref = TREE_OPERAND (def_rhs, 0);
665 if (TREE_CODE (array_ref) != ARRAY_REF
666 || TREE_CODE (TREE_TYPE (TREE_OPERAND (array_ref, 0))) != ARRAY_TYPE
667 || !integer_zerop (TREE_OPERAND (array_ref, 1)))
670 /* Try to optimize &x[0] p+ C where C is a multiple of the size
671 of the elements in X into &x[C/element size]. */
672 if (TREE_CODE (TREE_OPERAND (rhs, 1)) == INTEGER_CST)
674 tree orig = unshare_expr (rhs);
675 TREE_OPERAND (rhs, 0) = unshare_expr (def_rhs);
677 /* If folding succeeds, then we have just exposed new variables
678 in USE_STMT which will need to be renamed. If folding fails,
679 then we need to put everything back the way it was. */
680 if (fold_stmt_inplace (use_stmt))
682 tidy_after_forward_propagate_addr (use_stmt);
687 GIMPLE_STMT_OPERAND (use_stmt, 1) = orig;
688 update_stmt (use_stmt);
693 /* Try to optimize &x[0] p+ OFFSET where OFFSET is defined by
694 converting a multiplication of an index by the size of the
695 array elements, then the result is converted into the proper
696 type for the arithmetic. */
697 if (TREE_CODE (TREE_OPERAND (rhs, 1)) == SSA_NAME
698 /* Avoid problems with IVopts creating PLUS_EXPRs with a
699 different type than their operands. */
700 && useless_type_conversion_p (TREE_TYPE (rhs), TREE_TYPE (name)))
704 res = forward_propagate_addr_into_variable_array_index (TREE_OPERAND (rhs, 1),
711 /* STMT is a statement of the form SSA_NAME = ADDR_EXPR <whatever>.
713 Try to forward propagate the ADDR_EXPR into all uses of the SSA_NAME.
714 Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
715 node or for recovery of array indexing from pointer arithmetic.
716 Returns true, if all uses have been propagated into. */
719 forward_propagate_addr_expr (tree name, tree rhs)
721 int stmt_loop_depth = bb_for_stmt (SSA_NAME_DEF_STMT (name))->loop_depth;
722 imm_use_iterator iter;
725 bool single_use_p = has_single_use (name);
727 FOR_EACH_IMM_USE_STMT (use_stmt, iter, name)
732 /* If the use is not in a simple assignment statement, then
733 there is nothing we can do. */
734 if (TREE_CODE (use_stmt) != GIMPLE_MODIFY_STMT)
740 /* If the use is in a deeper loop nest, then we do not want
741 to propagate the ADDR_EXPR into the loop as that is likely
742 adding expression evaluations into the loop. */
743 if (bb_for_stmt (use_stmt)->loop_depth > stmt_loop_depth)
749 push_stmt_changes (&use_stmt);
751 result = forward_propagate_addr_expr_1 (name, rhs, use_stmt,
755 pop_stmt_changes (&use_stmt);
757 /* Remove intermediate now unused copy and conversion chains. */
758 use_rhs = GIMPLE_STMT_OPERAND (use_stmt, 1);
760 && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME
761 && (TREE_CODE (use_rhs) == SSA_NAME
762 || ((TREE_CODE (use_rhs) == NOP_EXPR
763 || TREE_CODE (use_rhs) == CONVERT_EXPR)
764 && TREE_CODE (TREE_OPERAND (use_rhs, 0)) == SSA_NAME)))
766 block_stmt_iterator bsi = bsi_for_stmt (use_stmt);
767 release_defs (use_stmt);
768 bsi_remove (&bsi, true);
775 /* Forward propagate the comparison COND defined in STMT like
776 cond_1 = x CMP y to uses of the form
780 Returns true if stmt is now unused. */
783 forward_propagate_comparison (tree cond, tree stmt)
785 tree name = GIMPLE_STMT_OPERAND (stmt, 0);
786 tree use_stmt, tmp = NULL_TREE;
788 /* Don't propagate ssa names that occur in abnormal phis. */
789 if ((TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME
790 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (cond, 0)))
791 || (TREE_CODE (TREE_OPERAND (cond, 1)) == SSA_NAME
792 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (cond, 1))))
795 /* Do not un-cse comparisons. But propagate through copies. */
796 use_stmt = get_prop_dest_stmt (name, &name);
797 if (use_stmt == NULL_TREE)
800 /* Conversion of the condition result to another integral type. */
801 if (TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
802 && (TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == CONVERT_EXPR
803 || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == NOP_EXPR
804 || COMPARISON_CLASS_P (GIMPLE_STMT_OPERAND (use_stmt, 1))
805 || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == TRUTH_NOT_EXPR)
806 && INTEGRAL_TYPE_P (TREE_TYPE (GIMPLE_STMT_OPERAND (use_stmt, 0))))
808 tree lhs = GIMPLE_STMT_OPERAND (use_stmt, 0);
809 tree rhs = GIMPLE_STMT_OPERAND (use_stmt, 1);
811 /* We can propagate the condition into a conversion. */
812 if (TREE_CODE (rhs) == CONVERT_EXPR
813 || TREE_CODE (rhs) == NOP_EXPR)
815 /* Avoid using fold here as that may create a COND_EXPR with
816 non-boolean condition as canonical form. */
817 tmp = build2 (TREE_CODE (cond), TREE_TYPE (lhs),
818 TREE_OPERAND (cond, 0), TREE_OPERAND (cond, 1));
820 /* We can propagate the condition into X op CST where op
821 is EQ_EXRP or NE_EXPR and CST is either one or zero. */
822 else if (COMPARISON_CLASS_P (rhs)
823 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
824 && TREE_CODE (TREE_OPERAND (rhs, 1)) == INTEGER_CST)
826 enum tree_code code = TREE_CODE (rhs);
827 tree cst = TREE_OPERAND (rhs, 1);
829 tmp = combine_cond_expr_cond (code, TREE_TYPE (lhs),
830 fold_convert (TREE_TYPE (cst), cond),
832 if (tmp == NULL_TREE)
835 /* We can propagate the condition into a statement that
836 computes the logical negation of the comparison result. */
837 else if (TREE_CODE (rhs) == TRUTH_NOT_EXPR)
839 tree type = TREE_TYPE (TREE_OPERAND (cond, 0));
840 bool nans = HONOR_NANS (TYPE_MODE (type));
842 code = invert_tree_comparison (TREE_CODE (cond), nans);
843 if (code == ERROR_MARK)
846 tmp = build2 (code, TREE_TYPE (lhs), TREE_OPERAND (cond, 0),
847 TREE_OPERAND (cond, 1));
852 GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (tmp);
853 update_stmt (use_stmt);
855 /* Remove defining statements. */
856 remove_prop_source_from_use (name, stmt);
858 if (dump_file && (dump_flags & TDF_DETAILS))
860 fprintf (dump_file, " Replaced '");
861 print_generic_expr (dump_file, rhs, dump_flags);
862 fprintf (dump_file, "' with '");
863 print_generic_expr (dump_file, tmp, dump_flags);
864 fprintf (dump_file, "'\n");
873 /* If we have lhs = ~x (STMT), look and see if earlier we had x = ~y.
874 If so, we can change STMT into lhs = y which can later be copy
875 propagated. Similarly for negation.
877 This could trivially be formulated as a forward propagation
878 to immediate uses. However, we already had an implementation
879 from DOM which used backward propagation via the use-def links.
881 It turns out that backward propagation is actually faster as
882 there's less work to do for each NOT/NEG expression we find.
883 Backwards propagation needs to look at the statement in a single
884 backlink. Forward propagation needs to look at potentially more
885 than one forward link. */
888 simplify_not_neg_expr (tree stmt)
890 tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
891 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
893 /* See if the RHS_DEF_STMT has the same form as our statement. */
894 if (TREE_CODE (rhs_def_stmt) == GIMPLE_MODIFY_STMT
895 && TREE_CODE (GIMPLE_STMT_OPERAND (rhs_def_stmt, 1)) == TREE_CODE (rhs))
897 tree rhs_def_operand =
898 TREE_OPERAND (GIMPLE_STMT_OPERAND (rhs_def_stmt, 1), 0);
900 /* Verify that RHS_DEF_OPERAND is a suitable SSA_NAME. */
901 if (TREE_CODE (rhs_def_operand) == SSA_NAME
902 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))
904 GIMPLE_STMT_OPERAND (stmt, 1) = rhs_def_operand;
910 /* STMT is a SWITCH_EXPR for which we attempt to find equivalent forms of
911 the condition which we may be able to optimize better. */
914 simplify_switch_expr (tree stmt)
916 tree cond = SWITCH_COND (stmt);
919 /* The optimization that we really care about is removing unnecessary
920 casts. That will let us do much better in propagating the inferred
921 constant at the switch target. */
922 if (TREE_CODE (cond) == SSA_NAME)
924 def = SSA_NAME_DEF_STMT (cond);
925 if (TREE_CODE (def) == GIMPLE_MODIFY_STMT)
927 def = GIMPLE_STMT_OPERAND (def, 1);
928 if (TREE_CODE (def) == NOP_EXPR)
933 def = TREE_OPERAND (def, 0);
935 #ifdef ENABLE_CHECKING
936 /* ??? Why was Jeff testing this? We are gimple... */
937 gcc_assert (is_gimple_val (def));
940 to = TREE_TYPE (cond);
941 ti = TREE_TYPE (def);
943 /* If we have an extension that preserves value, then we
944 can copy the source value into the switch. */
946 need_precision = TYPE_PRECISION (ti);
948 if (! INTEGRAL_TYPE_P (ti))
950 else if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
952 else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
954 if (TYPE_PRECISION (to) < need_precision)
959 SWITCH_COND (stmt) = def;
967 /* Main entry point for the forward propagation optimizer. */
970 tree_ssa_forward_propagate_single_use_vars (void)
973 unsigned int todoflags = 0;
979 block_stmt_iterator bsi;
981 /* Note we update BSI within the loop as necessary. */
982 for (bsi = bsi_start (bb); !bsi_end_p (bsi); )
984 tree stmt = bsi_stmt (bsi);
986 /* If this statement sets an SSA_NAME to an address,
987 try to propagate the address into the uses of the SSA_NAME. */
988 if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
990 tree lhs = GIMPLE_STMT_OPERAND (stmt, 0);
991 tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
994 if (TREE_CODE (lhs) != SSA_NAME)
1000 if (TREE_CODE (rhs) == ADDR_EXPR
1001 /* Handle pointer conversions on invariant addresses
1002 as well, as this is valid gimple. */
1003 || ((TREE_CODE (rhs) == NOP_EXPR
1004 || TREE_CODE (rhs) == CONVERT_EXPR)
1005 && TREE_CODE (TREE_OPERAND (rhs, 0)) == ADDR_EXPR
1006 && POINTER_TYPE_P (TREE_TYPE (rhs))))
1009 if (!stmt_references_abnormal_ssa_name (stmt)
1010 && forward_propagate_addr_expr (lhs, rhs))
1012 release_defs (stmt);
1013 todoflags |= TODO_remove_unused_locals;
1014 bsi_remove (&bsi, true);
1019 else if ((TREE_CODE (rhs) == BIT_NOT_EXPR
1020 || TREE_CODE (rhs) == NEGATE_EXPR)
1021 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
1023 simplify_not_neg_expr (stmt);
1026 else if (TREE_CODE (rhs) == COND_EXPR)
1029 fold_defer_overflow_warnings ();
1030 did_something = forward_propagate_into_cond (rhs, stmt);
1031 if (did_something == 2)
1033 fold_undefer_overflow_warnings (!TREE_NO_WARNING (rhs)
1034 && did_something, stmt, WARN_STRICT_OVERFLOW_CONDITIONAL);
1037 else if (COMPARISON_CLASS_P (rhs))
1039 if (forward_propagate_comparison (rhs, stmt))
1041 release_defs (stmt);
1042 todoflags |= TODO_remove_unused_locals;
1043 bsi_remove (&bsi, true);
1051 else if (TREE_CODE (stmt) == SWITCH_EXPR)
1053 simplify_switch_expr (stmt);
1056 else if (TREE_CODE (stmt) == COND_EXPR)
1059 fold_defer_overflow_warnings ();
1060 did_something = forward_propagate_into_cond (stmt, stmt);
1061 if (did_something == 2)
1063 fold_undefer_overflow_warnings (did_something, stmt,
1064 WARN_STRICT_OVERFLOW_CONDITIONAL);
1073 todoflags |= TODO_cleanup_cfg;
1079 gate_forwprop (void)
1084 struct gimple_opt_pass pass_forwprop =
1088 "forwprop", /* name */
1089 gate_forwprop, /* gate */
1090 tree_ssa_forward_propagate_single_use_vars, /* execute */
1093 0, /* static_pass_number */
1094 TV_TREE_FORWPROP, /* tv_id */
1095 PROP_cfg | PROP_ssa, /* properties_required */
1096 0, /* properties_provided */
1097 0, /* properties_destroyed */
1098 0, /* todo_flags_start */
1102 | TODO_verify_ssa /* todo_flags_finish */