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
127 ptr = (type1*)&type2var;
130 Will get turned into (if type1 and type2 are the same size
131 and neither have volatile on them):
132 res = VIEW_CONVERT_EXPR<type1>(type2var)
137 ptr2 = ptr + <constant>;
141 ptr2 = &x[constant/elementsize];
146 offset = index * element_size;
147 offset_p = (pointer) offset;
148 ptr2 = ptr + offset_p
150 Will get turned into:
154 We also propagate casts into SWITCH_EXPR and COND_EXPR conditions to
155 allow us to remove the cast and {NOT_EXPR,NEG_EXPR} into a subsequent
158 This will (of course) be extended as other needs arise. */
160 static bool forward_propagate_addr_expr (tree name, tree rhs);
162 /* Set to true if we delete EH edges during the optimization. */
163 static bool cfg_changed;
166 /* Get the next statement we can propagate NAME's value into skipping
167 trivial copies. Returns the statement that is suitable as a
168 propagation destination or NULL_TREE if there is no such one.
169 This only returns destinations in a single-use chain. FINAL_NAME_P
170 if non-NULL is written to the ssa name that represents the use. */
173 get_prop_dest_stmt (tree name, tree *final_name_p)
179 /* If name has multiple uses, bail out. */
180 if (!single_imm_use (name, &use, &use_stmt))
183 /* If this is not a trivial copy, we found it. */
184 if (TREE_CODE (use_stmt) != GIMPLE_MODIFY_STMT
185 || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) != SSA_NAME
186 || GIMPLE_STMT_OPERAND (use_stmt, 1) != name)
189 /* Continue searching uses of the copy destination. */
190 name = GIMPLE_STMT_OPERAND (use_stmt, 0);
194 *final_name_p = name;
199 /* Get the statement we can propagate from into NAME skipping
200 trivial copies. Returns the statement which defines the
201 propagation source or NULL_TREE if there is no such one.
202 If SINGLE_USE_ONLY is set considers only sources which have
203 a single use chain up to NAME. If SINGLE_USE_P is non-null,
204 it is set to whether the chain to NAME is a single use chain
205 or not. SINGLE_USE_P is not written to if SINGLE_USE_ONLY is set. */
208 get_prop_source_stmt (tree name, bool single_use_only, bool *single_use_p)
210 bool single_use = true;
213 tree def_stmt = SSA_NAME_DEF_STMT (name);
215 if (!has_single_use (name))
222 /* If name is defined by a PHI node or is the default def, bail out. */
223 if (TREE_CODE (def_stmt) != GIMPLE_MODIFY_STMT)
226 /* If name is not a simple copy destination, we found it. */
227 if (TREE_CODE (GIMPLE_STMT_OPERAND (def_stmt, 1)) != SSA_NAME)
231 if (!single_use_only && single_use_p)
232 *single_use_p = single_use;
234 /* We can look through pointer conversions in the search
235 for a useful stmt for the comparison folding. */
236 rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
237 if ((TREE_CODE (rhs) == NOP_EXPR
238 || TREE_CODE (rhs) == CONVERT_EXPR)
239 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
240 && POINTER_TYPE_P (TREE_TYPE (rhs))
241 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0))))
242 name = TREE_OPERAND (rhs, 0);
248 /* Continue searching the def of the copy source name. */
249 name = GIMPLE_STMT_OPERAND (def_stmt, 1);
254 /* Checks if the destination ssa name in DEF_STMT can be used as
255 propagation source. Returns true if so, otherwise false. */
258 can_propagate_from (tree def_stmt)
260 tree rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
262 /* If the rhs has side-effects we cannot propagate from it. */
263 if (TREE_SIDE_EFFECTS (rhs))
266 /* If the rhs is a load we cannot propagate from it. */
267 if (REFERENCE_CLASS_P (rhs))
270 /* Constants can be always propagated. */
271 if (is_gimple_min_invariant (rhs))
274 /* We cannot propagate ssa names that occur in abnormal phi nodes. */
275 switch (TREE_CODE_LENGTH (TREE_CODE (rhs)))
278 if (TREE_OPERAND (rhs, 2) != NULL_TREE
279 && TREE_CODE (TREE_OPERAND (rhs, 2)) == SSA_NAME
280 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (rhs, 2)))
283 if (TREE_OPERAND (rhs, 1) != NULL_TREE
284 && TREE_CODE (TREE_OPERAND (rhs, 1)) == SSA_NAME
285 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (rhs, 1)))
288 if (TREE_OPERAND (rhs, 0) != NULL_TREE
289 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
290 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (rhs, 0)))
298 /* If the definition is a conversion of a pointer to a function type,
299 then we can not apply optimizations as some targets require function
300 pointers to be canonicalized and in this case this optimization could
301 eliminate a necessary canonicalization. */
302 if ((TREE_CODE (rhs) == NOP_EXPR
303 || TREE_CODE (rhs) == CONVERT_EXPR)
304 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0)))
305 && TREE_CODE (TREE_TYPE (TREE_TYPE
306 (TREE_OPERAND (rhs, 0)))) == FUNCTION_TYPE)
312 /* Remove a copy chain ending in NAME along the defs but not
313 further or including UP_TO_STMT. If NAME was replaced in
314 its only use then this function can be used to clean up
315 dead stmts. Returns true if UP_TO_STMT can be removed
316 as well, otherwise false. */
319 remove_prop_source_from_use (tree name, tree up_to_stmt)
321 block_stmt_iterator bsi;
325 if (!has_zero_uses (name))
328 stmt = SSA_NAME_DEF_STMT (name);
329 if (stmt == up_to_stmt)
332 bsi = bsi_for_stmt (stmt);
334 bsi_remove (&bsi, true);
336 name = GIMPLE_STMT_OPERAND (stmt, 1);
337 } while (TREE_CODE (name) == SSA_NAME);
342 /* Combine OP0 CODE OP1 in the context of a COND_EXPR. Returns
343 the folded result in a form suitable for COND_EXPR_COND or
344 NULL_TREE, if there is no suitable simplified form. If
345 INVARIANT_ONLY is true only gimple_min_invariant results are
346 considered simplified. */
349 combine_cond_expr_cond (enum tree_code code, tree type,
350 tree op0, tree op1, bool invariant_only)
354 gcc_assert (TREE_CODE_CLASS (code) == tcc_comparison);
356 t = fold_binary (code, type, op0, op1);
360 /* Require that we got a boolean type out if we put one in. */
361 gcc_assert (TREE_CODE (TREE_TYPE (t)) == TREE_CODE (type));
363 /* Canonicalize the combined condition for use in a COND_EXPR. */
364 t = canonicalize_cond_expr_cond (t);
366 /* Bail out if we required an invariant but didn't get one. */
369 && !is_gimple_min_invariant (t)))
375 /* Propagate from the ssa name definition statements of COND_EXPR
376 in statement STMT into the conditional if that simplifies it.
377 Returns zero if no statement was changed, one if there were
378 changes and two if cfg_cleanup needs to run. */
381 forward_propagate_into_cond (tree cond_expr, tree stmt)
383 int did_something = 0;
386 tree tmp = NULL_TREE;
387 tree cond = COND_EXPR_COND (cond_expr);
388 tree name, def_stmt, rhs0 = NULL_TREE, rhs1 = NULL_TREE;
389 bool single_use0_p = false, single_use1_p = false;
391 /* We can do tree combining on SSA_NAME and comparison expressions. */
392 if (COMPARISON_CLASS_P (cond)
393 && TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME)
395 /* For comparisons use the first operand, that is likely to
396 simplify comparisons against constants. */
397 name = TREE_OPERAND (cond, 0);
398 def_stmt = get_prop_source_stmt (name, false, &single_use0_p);
399 if (def_stmt != NULL_TREE
400 && can_propagate_from (def_stmt))
402 tree op1 = TREE_OPERAND (cond, 1);
403 rhs0 = GIMPLE_STMT_OPERAND (def_stmt, 1);
404 tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
405 fold_convert (TREE_TYPE (op1), rhs0),
406 op1, !single_use0_p);
408 /* If that wasn't successful, try the second operand. */
410 && TREE_CODE (TREE_OPERAND (cond, 1)) == SSA_NAME)
412 tree op0 = TREE_OPERAND (cond, 0);
413 name = TREE_OPERAND (cond, 1);
414 def_stmt = get_prop_source_stmt (name, false, &single_use1_p);
415 if (def_stmt == NULL_TREE
416 || !can_propagate_from (def_stmt))
417 return did_something;
419 rhs1 = GIMPLE_STMT_OPERAND (def_stmt, 1);
420 tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
422 fold_convert (TREE_TYPE (op0), rhs1),
425 /* If that wasn't successful either, try both operands. */
428 && rhs1 != NULL_TREE)
429 tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
431 fold_convert (TREE_TYPE (rhs0), rhs1),
432 !(single_use0_p && single_use1_p));
434 else if (TREE_CODE (cond) == SSA_NAME)
437 def_stmt = get_prop_source_stmt (name, true, NULL);
438 if (def_stmt == NULL_TREE
439 || !can_propagate_from (def_stmt))
440 return did_something;
442 rhs0 = GIMPLE_STMT_OPERAND (def_stmt, 1);
443 tmp = combine_cond_expr_cond (NE_EXPR, boolean_type_node, rhs0,
444 build_int_cst (TREE_TYPE (rhs0), 0),
450 if (dump_file && tmp)
452 fprintf (dump_file, " Replaced '");
453 print_generic_expr (dump_file, cond, 0);
454 fprintf (dump_file, "' with '");
455 print_generic_expr (dump_file, tmp, 0);
456 fprintf (dump_file, "'\n");
459 COND_EXPR_COND (cond_expr) = unshare_expr (tmp);
462 /* Remove defining statements. */
463 remove_prop_source_from_use (name, NULL);
465 if (is_gimple_min_invariant (tmp))
467 else if (did_something == 0)
470 /* Continue combining. */
477 return did_something;
480 /* We've just substituted an ADDR_EXPR into stmt. Update all the
481 relevant data structures to match. */
484 tidy_after_forward_propagate_addr (tree stmt)
486 /* We may have turned a trapping insn into a non-trapping insn. */
487 if (maybe_clean_or_replace_eh_stmt (stmt, stmt)
488 && tree_purge_dead_eh_edges (bb_for_stmt (stmt)))
491 if (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == ADDR_EXPR)
492 recompute_tree_invariant_for_addr_expr (GIMPLE_STMT_OPERAND (stmt, 1));
494 mark_symbols_for_renaming (stmt);
497 /* DEF_RHS contains the address of the 0th element in an array.
498 USE_STMT uses type of DEF_RHS to compute the address of an
499 arbitrary element within the array. The (variable) byte offset
500 of the element is contained in OFFSET.
502 We walk back through the use-def chains of OFFSET to verify that
503 it is indeed computing the offset of an element within the array
504 and extract the index corresponding to the given byte offset.
506 We then try to fold the entire address expression into a form
509 If we are successful, we replace the right hand side of USE_STMT
510 with the new address computation. */
513 forward_propagate_addr_into_variable_array_index (tree offset,
514 tree def_rhs, tree use_stmt)
518 /* Try to find an expression for a proper index. This is either
519 a multiplication expression by the element size or just the
520 ssa name we came along in case the element size is one. */
521 if (integer_onep (TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs)))))
525 /* Get the offset's defining statement. */
526 offset = SSA_NAME_DEF_STMT (offset);
528 /* The statement which defines OFFSET before type conversion
529 must be a simple GIMPLE_MODIFY_STMT. */
530 if (TREE_CODE (offset) != GIMPLE_MODIFY_STMT)
533 /* The RHS of the statement which defines OFFSET must be a
534 multiplication of an object by the size of the array elements.
535 This implicitly verifies that the size of the array elements
537 offset = GIMPLE_STMT_OPERAND (offset, 1);
538 if (TREE_CODE (offset) != MULT_EXPR
539 || TREE_CODE (TREE_OPERAND (offset, 1)) != INTEGER_CST
540 || !simple_cst_equal (TREE_OPERAND (offset, 1),
541 TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs)))))
544 /* The first operand to the MULT_EXPR is the desired index. */
545 index = TREE_OPERAND (offset, 0);
548 /* Replace the pointer addition with array indexing. */
549 GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (def_rhs);
550 TREE_OPERAND (TREE_OPERAND (GIMPLE_STMT_OPERAND (use_stmt, 1), 0), 1)
553 /* That should have created gimple, so there is no need to
554 record information to undo the propagation. */
555 fold_stmt_inplace (use_stmt);
556 tidy_after_forward_propagate_addr (use_stmt);
560 /* NAME is a SSA_NAME representing DEF_RHS which is of the form
561 ADDR_EXPR <whatever>.
563 Try to forward propagate the ADDR_EXPR into the use USE_STMT.
564 Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
565 node or for recovery of array indexing from pointer arithmetic.
567 Return true if the propagation was successful (the propagation can
568 be not totally successful, yet things may have been changed). */
571 forward_propagate_addr_expr_1 (tree name, tree def_rhs, tree use_stmt,
574 tree lhs, rhs, array_ref;
577 gcc_assert (TREE_CODE (def_rhs) == ADDR_EXPR);
579 lhs = GIMPLE_STMT_OPERAND (use_stmt, 0);
580 rhs = GIMPLE_STMT_OPERAND (use_stmt, 1);
582 /* Trivial cases. The use statement could be a trivial copy or a
583 useless conversion. Recurse to the uses of the lhs as copyprop does
584 not copy through different variant pointers and FRE does not catch
585 all useless conversions. Treat the case of a single-use name and
586 a conversion to def_rhs type separate, though. */
587 if (TREE_CODE (lhs) == SSA_NAME
589 || TREE_CODE (rhs) == NOP_EXPR
590 || TREE_CODE (rhs) == CONVERT_EXPR)
591 && useless_type_conversion_p (TREE_TYPE (rhs), TREE_TYPE (def_rhs)))
593 /* Only recurse if we don't deal with a single use. */
595 return forward_propagate_addr_expr (lhs, def_rhs);
597 GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (def_rhs);
601 /* Now strip away any outer COMPONENT_REF/ARRAY_REF nodes from the LHS.
602 ADDR_EXPR will not appear on the LHS. */
603 lhsp = &GIMPLE_STMT_OPERAND (use_stmt, 0);
604 while (handled_component_p (*lhsp))
605 lhsp = &TREE_OPERAND (*lhsp, 0);
608 /* Now see if the LHS node is an INDIRECT_REF using NAME. If so,
609 propagate the ADDR_EXPR into the use of NAME and fold the result. */
610 if (TREE_CODE (lhs) == INDIRECT_REF
611 && TREE_OPERAND (lhs, 0) == name
612 && useless_type_conversion_p (TREE_TYPE (TREE_OPERAND (lhs, 0)),
614 /* ??? This looks redundant, but is required for bogus types
615 that can sometimes occur. */
616 && useless_type_conversion_p (TREE_TYPE (lhs),
617 TREE_TYPE (TREE_OPERAND (def_rhs, 0))))
619 *lhsp = unshare_expr (TREE_OPERAND (def_rhs, 0));
620 fold_stmt_inplace (use_stmt);
621 tidy_after_forward_propagate_addr (use_stmt);
623 /* Continue propagating into the RHS if this was not the only use. */
628 /* Strip away any outer COMPONENT_REF, ARRAY_REF or ADDR_EXPR
629 nodes from the RHS. */
630 rhsp = &GIMPLE_STMT_OPERAND (use_stmt, 1);
631 while (handled_component_p (*rhsp)
632 || TREE_CODE (*rhsp) == ADDR_EXPR)
633 rhsp = &TREE_OPERAND (*rhsp, 0);
636 /* Now see if the RHS node is an INDIRECT_REF using NAME. If so,
637 propagate the ADDR_EXPR into the use of NAME and fold the result. */
638 if (TREE_CODE (rhs) == INDIRECT_REF
639 && TREE_OPERAND (rhs, 0) == name
640 && useless_type_conversion_p (TREE_TYPE (TREE_OPERAND (rhs, 0)),
642 /* ??? This looks redundant, but is required for bogus types
643 that can sometimes occur. */
644 && useless_type_conversion_p (TREE_TYPE (rhs),
645 TREE_TYPE (TREE_OPERAND (def_rhs, 0))))
647 *rhsp = unshare_expr (TREE_OPERAND (def_rhs, 0));
648 fold_stmt_inplace (use_stmt);
649 tidy_after_forward_propagate_addr (use_stmt);
653 /* Now see if the RHS node is an INDIRECT_REF using NAME. If so,
654 propagate the ADDR_EXPR into the use of NAME and try to
655 create a VCE and fold the result. */
656 if (TREE_CODE (rhs) == INDIRECT_REF
657 && TREE_OPERAND (rhs, 0) == name
658 && TYPE_SIZE (TREE_TYPE (rhs))
659 && TYPE_SIZE (TREE_TYPE (TREE_OPERAND (def_rhs, 0)))
660 /* Function decls should not be used for VCE either as it could be
661 a function descriptor that we want and not the actual function code. */
662 && TREE_CODE (TREE_OPERAND (def_rhs, 0)) != FUNCTION_DECL
663 /* We should not convert volatile loads to non volatile loads. */
664 && !TYPE_VOLATILE (TREE_TYPE (rhs))
665 && !TYPE_VOLATILE (TREE_TYPE (TREE_OPERAND (def_rhs, 0)))
666 && operand_equal_p (TYPE_SIZE (TREE_TYPE (rhs)),
667 TYPE_SIZE (TREE_TYPE (TREE_OPERAND (def_rhs, 0))), 0))
670 tree new_rhs = unshare_expr (TREE_OPERAND (def_rhs, 0));
671 new_rhs = fold_build1 (VIEW_CONVERT_EXPR, TREE_TYPE (rhs), new_rhs);
672 /* If we have folded the VCE, then we have to create a new statement. */
673 if (TREE_CODE (new_rhs) != VIEW_CONVERT_EXPR)
675 block_stmt_iterator bsi = bsi_for_stmt (use_stmt);
676 new_rhs = force_gimple_operand_bsi (&bsi, new_rhs, true, NULL, true, BSI_SAME_STMT);
677 /* As we change the deference to a SSA_NAME, we need to return false to make sure that
678 the statement does not get removed. */
682 fold_stmt_inplace (use_stmt);
683 tidy_after_forward_propagate_addr (use_stmt);
687 /* If the use of the ADDR_EXPR is not a POINTER_PLUS_EXPR, there
689 if (TREE_CODE (rhs) != POINTER_PLUS_EXPR
690 || TREE_OPERAND (rhs, 0) != name)
693 /* The remaining cases are all for turning pointer arithmetic into
694 array indexing. They only apply when we have the address of
695 element zero in an array. If that is not the case then there
697 array_ref = TREE_OPERAND (def_rhs, 0);
698 if (TREE_CODE (array_ref) != ARRAY_REF
699 || TREE_CODE (TREE_TYPE (TREE_OPERAND (array_ref, 0))) != ARRAY_TYPE
700 || !integer_zerop (TREE_OPERAND (array_ref, 1)))
703 /* Try to optimize &x[0] p+ C where C is a multiple of the size
704 of the elements in X into &x[C/element size]. */
705 if (TREE_CODE (TREE_OPERAND (rhs, 1)) == INTEGER_CST)
707 tree orig = unshare_expr (rhs);
708 TREE_OPERAND (rhs, 0) = unshare_expr (def_rhs);
710 /* If folding succeeds, then we have just exposed new variables
711 in USE_STMT which will need to be renamed. If folding fails,
712 then we need to put everything back the way it was. */
713 if (fold_stmt_inplace (use_stmt))
715 tidy_after_forward_propagate_addr (use_stmt);
720 GIMPLE_STMT_OPERAND (use_stmt, 1) = orig;
721 update_stmt (use_stmt);
726 /* Try to optimize &x[0] p+ OFFSET where OFFSET is defined by
727 converting a multiplication of an index by the size of the
728 array elements, then the result is converted into the proper
729 type for the arithmetic. */
730 if (TREE_CODE (TREE_OPERAND (rhs, 1)) == SSA_NAME
731 /* Avoid problems with IVopts creating PLUS_EXPRs with a
732 different type than their operands. */
733 && useless_type_conversion_p (TREE_TYPE (rhs), TREE_TYPE (name)))
737 res = forward_propagate_addr_into_variable_array_index (TREE_OPERAND (rhs, 1),
744 /* STMT is a statement of the form SSA_NAME = ADDR_EXPR <whatever>.
746 Try to forward propagate the ADDR_EXPR into all uses of the SSA_NAME.
747 Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
748 node or for recovery of array indexing from pointer arithmetic.
749 Returns true, if all uses have been propagated into. */
752 forward_propagate_addr_expr (tree name, tree rhs)
754 int stmt_loop_depth = bb_for_stmt (SSA_NAME_DEF_STMT (name))->loop_depth;
755 imm_use_iterator iter;
758 bool single_use_p = has_single_use (name);
760 FOR_EACH_IMM_USE_STMT (use_stmt, iter, name)
765 /* If the use is not in a simple assignment statement, then
766 there is nothing we can do. */
767 if (TREE_CODE (use_stmt) != GIMPLE_MODIFY_STMT)
773 /* If the use is in a deeper loop nest, then we do not want
774 to propagate the ADDR_EXPR into the loop as that is likely
775 adding expression evaluations into the loop. */
776 if (bb_for_stmt (use_stmt)->loop_depth > stmt_loop_depth)
782 push_stmt_changes (&use_stmt);
784 result = forward_propagate_addr_expr_1 (name, rhs, use_stmt,
788 pop_stmt_changes (&use_stmt);
790 /* Remove intermediate now unused copy and conversion chains. */
791 use_rhs = GIMPLE_STMT_OPERAND (use_stmt, 1);
793 && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME
794 && (TREE_CODE (use_rhs) == SSA_NAME
795 || ((TREE_CODE (use_rhs) == NOP_EXPR
796 || TREE_CODE (use_rhs) == CONVERT_EXPR)
797 && TREE_CODE (TREE_OPERAND (use_rhs, 0)) == SSA_NAME)))
799 block_stmt_iterator bsi = bsi_for_stmt (use_stmt);
800 release_defs (use_stmt);
801 bsi_remove (&bsi, true);
808 /* Forward propagate the comparison COND defined in STMT like
809 cond_1 = x CMP y to uses of the form
813 Returns true if stmt is now unused. */
816 forward_propagate_comparison (tree cond, tree stmt)
818 tree name = GIMPLE_STMT_OPERAND (stmt, 0);
819 tree use_stmt, tmp = NULL_TREE;
821 /* Don't propagate ssa names that occur in abnormal phis. */
822 if ((TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME
823 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (cond, 0)))
824 || (TREE_CODE (TREE_OPERAND (cond, 1)) == SSA_NAME
825 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (cond, 1))))
828 /* Do not un-cse comparisons. But propagate through copies. */
829 use_stmt = get_prop_dest_stmt (name, &name);
830 if (use_stmt == NULL_TREE)
833 /* Conversion of the condition result to another integral type. */
834 if (TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
835 && (TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == CONVERT_EXPR
836 || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == NOP_EXPR
837 || COMPARISON_CLASS_P (GIMPLE_STMT_OPERAND (use_stmt, 1))
838 || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == TRUTH_NOT_EXPR)
839 && INTEGRAL_TYPE_P (TREE_TYPE (GIMPLE_STMT_OPERAND (use_stmt, 0))))
841 tree lhs = GIMPLE_STMT_OPERAND (use_stmt, 0);
842 tree rhs = GIMPLE_STMT_OPERAND (use_stmt, 1);
844 /* We can propagate the condition into a conversion. */
845 if (TREE_CODE (rhs) == CONVERT_EXPR
846 || TREE_CODE (rhs) == NOP_EXPR)
848 /* Avoid using fold here as that may create a COND_EXPR with
849 non-boolean condition as canonical form. */
850 tmp = build2 (TREE_CODE (cond), TREE_TYPE (lhs),
851 TREE_OPERAND (cond, 0), TREE_OPERAND (cond, 1));
853 /* We can propagate the condition into X op CST where op
854 is EQ_EXRP or NE_EXPR and CST is either one or zero. */
855 else if (COMPARISON_CLASS_P (rhs)
856 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
857 && TREE_CODE (TREE_OPERAND (rhs, 1)) == INTEGER_CST)
859 enum tree_code code = TREE_CODE (rhs);
860 tree cst = TREE_OPERAND (rhs, 1);
862 tmp = combine_cond_expr_cond (code, TREE_TYPE (lhs),
863 fold_convert (TREE_TYPE (cst), cond),
865 if (tmp == NULL_TREE)
868 /* We can propagate the condition into a statement that
869 computes the logical negation of the comparison result. */
870 else if (TREE_CODE (rhs) == TRUTH_NOT_EXPR)
872 tree type = TREE_TYPE (TREE_OPERAND (cond, 0));
873 bool nans = HONOR_NANS (TYPE_MODE (type));
875 code = invert_tree_comparison (TREE_CODE (cond), nans);
876 if (code == ERROR_MARK)
879 tmp = build2 (code, TREE_TYPE (lhs), TREE_OPERAND (cond, 0),
880 TREE_OPERAND (cond, 1));
885 GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (tmp);
886 update_stmt (use_stmt);
888 /* Remove defining statements. */
889 remove_prop_source_from_use (name, stmt);
891 if (dump_file && (dump_flags & TDF_DETAILS))
893 fprintf (dump_file, " Replaced '");
894 print_generic_expr (dump_file, rhs, dump_flags);
895 fprintf (dump_file, "' with '");
896 print_generic_expr (dump_file, tmp, dump_flags);
897 fprintf (dump_file, "'\n");
906 /* If we have lhs = ~x (STMT), look and see if earlier we had x = ~y.
907 If so, we can change STMT into lhs = y which can later be copy
908 propagated. Similarly for negation.
910 This could trivially be formulated as a forward propagation
911 to immediate uses. However, we already had an implementation
912 from DOM which used backward propagation via the use-def links.
914 It turns out that backward propagation is actually faster as
915 there's less work to do for each NOT/NEG expression we find.
916 Backwards propagation needs to look at the statement in a single
917 backlink. Forward propagation needs to look at potentially more
918 than one forward link. */
921 simplify_not_neg_expr (tree stmt)
923 tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
924 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
926 /* See if the RHS_DEF_STMT has the same form as our statement. */
927 if (TREE_CODE (rhs_def_stmt) == GIMPLE_MODIFY_STMT
928 && TREE_CODE (GIMPLE_STMT_OPERAND (rhs_def_stmt, 1)) == TREE_CODE (rhs))
930 tree rhs_def_operand =
931 TREE_OPERAND (GIMPLE_STMT_OPERAND (rhs_def_stmt, 1), 0);
933 /* Verify that RHS_DEF_OPERAND is a suitable SSA_NAME. */
934 if (TREE_CODE (rhs_def_operand) == SSA_NAME
935 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))
937 GIMPLE_STMT_OPERAND (stmt, 1) = rhs_def_operand;
943 /* STMT is a SWITCH_EXPR for which we attempt to find equivalent forms of
944 the condition which we may be able to optimize better. */
947 simplify_switch_expr (tree stmt)
949 tree cond = SWITCH_COND (stmt);
952 /* The optimization that we really care about is removing unnecessary
953 casts. That will let us do much better in propagating the inferred
954 constant at the switch target. */
955 if (TREE_CODE (cond) == SSA_NAME)
957 def = SSA_NAME_DEF_STMT (cond);
958 if (TREE_CODE (def) == GIMPLE_MODIFY_STMT)
960 def = GIMPLE_STMT_OPERAND (def, 1);
961 if (TREE_CODE (def) == NOP_EXPR)
966 def = TREE_OPERAND (def, 0);
968 #ifdef ENABLE_CHECKING
969 /* ??? Why was Jeff testing this? We are gimple... */
970 gcc_assert (is_gimple_val (def));
973 to = TREE_TYPE (cond);
974 ti = TREE_TYPE (def);
976 /* If we have an extension that preserves value, then we
977 can copy the source value into the switch. */
979 need_precision = TYPE_PRECISION (ti);
981 if (! INTEGRAL_TYPE_P (ti))
983 else if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
985 else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
987 if (TYPE_PRECISION (to) < need_precision)
992 SWITCH_COND (stmt) = def;
1000 /* Main entry point for the forward propagation optimizer. */
1003 tree_ssa_forward_propagate_single_use_vars (void)
1006 unsigned int todoflags = 0;
1008 cfg_changed = false;
1012 block_stmt_iterator bsi;
1014 /* Note we update BSI within the loop as necessary. */
1015 for (bsi = bsi_start (bb); !bsi_end_p (bsi); )
1017 tree stmt = bsi_stmt (bsi);
1019 /* If this statement sets an SSA_NAME to an address,
1020 try to propagate the address into the uses of the SSA_NAME. */
1021 if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
1023 tree lhs = GIMPLE_STMT_OPERAND (stmt, 0);
1024 tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
1027 if (TREE_CODE (lhs) != SSA_NAME)
1033 if (TREE_CODE (rhs) == ADDR_EXPR
1034 /* Handle pointer conversions on invariant addresses
1035 as well, as this is valid gimple. */
1036 || ((TREE_CODE (rhs) == NOP_EXPR
1037 || TREE_CODE (rhs) == CONVERT_EXPR)
1038 && TREE_CODE (TREE_OPERAND (rhs, 0)) == ADDR_EXPR
1039 && POINTER_TYPE_P (TREE_TYPE (rhs))))
1042 if (!stmt_references_abnormal_ssa_name (stmt)
1043 && forward_propagate_addr_expr (lhs, rhs))
1045 release_defs (stmt);
1046 todoflags |= TODO_remove_unused_locals;
1047 bsi_remove (&bsi, true);
1052 else if ((TREE_CODE (rhs) == BIT_NOT_EXPR
1053 || TREE_CODE (rhs) == NEGATE_EXPR)
1054 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
1056 simplify_not_neg_expr (stmt);
1059 else if (TREE_CODE (rhs) == COND_EXPR)
1062 fold_defer_overflow_warnings ();
1063 did_something = forward_propagate_into_cond (rhs, stmt);
1064 if (did_something == 2)
1066 fold_undefer_overflow_warnings (!TREE_NO_WARNING (rhs)
1067 && did_something, stmt, WARN_STRICT_OVERFLOW_CONDITIONAL);
1070 else if (COMPARISON_CLASS_P (rhs))
1072 if (forward_propagate_comparison (rhs, stmt))
1074 release_defs (stmt);
1075 todoflags |= TODO_remove_unused_locals;
1076 bsi_remove (&bsi, true);
1084 else if (TREE_CODE (stmt) == SWITCH_EXPR)
1086 simplify_switch_expr (stmt);
1089 else if (TREE_CODE (stmt) == COND_EXPR)
1092 fold_defer_overflow_warnings ();
1093 did_something = forward_propagate_into_cond (stmt, stmt);
1094 if (did_something == 2)
1096 fold_undefer_overflow_warnings (did_something, stmt,
1097 WARN_STRICT_OVERFLOW_CONDITIONAL);
1106 todoflags |= TODO_cleanup_cfg;
1112 gate_forwprop (void)
1117 struct gimple_opt_pass pass_forwprop =
1121 "forwprop", /* name */
1122 gate_forwprop, /* gate */
1123 tree_ssa_forward_propagate_single_use_vars, /* execute */
1126 0, /* static_pass_number */
1127 TV_TREE_FORWPROP, /* tv_id */
1128 PROP_cfg | PROP_ssa, /* properties_required */
1129 0, /* properties_provided */
1130 0, /* properties_destroyed */
1131 0, /* todo_flags_start */
1135 | TODO_verify_ssa /* todo_flags_finish */