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_copy_p (use_stmt)
190 || TREE_CODE (gimple_assign_lhs (use_stmt)) != SSA_NAME
191 || gimple_assign_rhs1 (use_stmt) != name)
194 /* Continue searching uses of the copy destination. */
195 name = gimple_assign_lhs (use_stmt);
199 *final_name_p = name;
204 /* Get the statement we can propagate from into NAME skipping
205 trivial copies. Returns the statement which defines the
206 propagation source or NULL_TREE if there is no such one.
207 If SINGLE_USE_ONLY is set considers only sources which have
208 a single use chain up to NAME. If SINGLE_USE_P is non-null,
209 it is set to whether the chain to NAME is a single use chain
210 or not. SINGLE_USE_P is not written to if SINGLE_USE_ONLY is set. */
213 get_prop_source_stmt (tree name, bool single_use_only, bool *single_use_p)
215 bool single_use = true;
218 gimple def_stmt = SSA_NAME_DEF_STMT (name);
220 if (!has_single_use (name))
227 /* If name is defined by a PHI node or is the default def, bail out. */
228 if (gimple_code (def_stmt) != GIMPLE_ASSIGN)
231 /* If name is not a simple copy destination, we found it. */
232 if (!gimple_assign_copy_p (def_stmt)
233 || TREE_CODE (gimple_assign_rhs1 (def_stmt)) != SSA_NAME)
237 if (!single_use_only && single_use_p)
238 *single_use_p = single_use;
240 /* We can look through pointer conversions in the search
241 for a useful stmt for the comparison folding. */
242 rhs = gimple_assign_rhs1 (def_stmt);
243 if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt))
244 && TREE_CODE (rhs) == SSA_NAME
245 && POINTER_TYPE_P (TREE_TYPE (gimple_assign_lhs (def_stmt)))
246 && POINTER_TYPE_P (TREE_TYPE (rhs)))
253 /* Continue searching the def of the copy source name. */
254 name = gimple_assign_rhs1 (def_stmt);
259 /* Checks if the destination ssa name in DEF_STMT can be used as
260 propagation source. Returns true if so, otherwise false. */
263 can_propagate_from (gimple def_stmt)
268 gcc_assert (is_gimple_assign (def_stmt));
269 /* If the rhs has side-effects we cannot propagate from it. */
270 if (gimple_has_volatile_ops (def_stmt))
273 /* If the rhs is a load we cannot propagate from it. */
274 if (TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt)) == tcc_reference
275 || TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt)) == tcc_declaration)
278 /* Constants can be always propagated. */
279 if (is_gimple_min_invariant
280 (rhs_to_tree (TREE_TYPE (gimple_assign_lhs (def_stmt)), def_stmt)))
283 /* We cannot propagate ssa names that occur in abnormal phi nodes. */
284 FOR_EACH_SSA_USE_OPERAND (use_p, def_stmt, iter, SSA_OP_USE)
285 if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (use_p)))
288 /* If the definition is a conversion of a pointer to a function type,
289 then we can not apply optimizations as some targets require
290 function pointers to be canonicalized and in this case this
291 optimization could eliminate a necessary canonicalization. */
292 if (is_gimple_assign (def_stmt)
293 && (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt))))
295 tree rhs = gimple_assign_rhs1 (def_stmt);
296 if (POINTER_TYPE_P (TREE_TYPE (rhs))
297 && TREE_CODE (TREE_TYPE (TREE_TYPE (rhs))) == FUNCTION_TYPE)
303 /* Remove a copy chain ending in NAME along the defs but not
304 further or including UP_TO_STMT. If NAME was replaced in
305 its only use then this function can be used to clean up
306 dead stmts. Returns true if UP_TO_STMT can be removed
307 as well, otherwise false. */
310 remove_prop_source_from_use (tree name, gimple up_to_stmt)
312 gimple_stmt_iterator gsi;
316 if (!has_zero_uses (name))
319 stmt = SSA_NAME_DEF_STMT (name);
320 if (stmt == up_to_stmt)
323 gsi = gsi_for_stmt (stmt);
325 gsi_remove (&gsi, true);
327 name = (gimple_assign_copy_p (stmt)) ? gimple_assign_rhs1 (stmt) : NULL;
328 } while (name && TREE_CODE (name) == SSA_NAME);
333 /* Return the rhs of a gimple_assign STMT in a form of a single tree,
334 converted to type TYPE.
336 This should disappear, but is needed so we can combine expressions and use
337 the fold() interfaces. Long term, we need to develop folding and combine
338 routines that deal with gimple exclusively . */
341 rhs_to_tree (tree type, gimple 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 (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 (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 (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;
399 tree tmp = NULL_TREE;
400 tree name, rhs0 = NULL_TREE, rhs1 = NULL_TREE;
402 bool single_use0_p = false, single_use1_p = false;
403 enum tree_code code = gimple_cond_code (stmt);
405 /* We can do tree combining on SSA_NAME and comparison expressions. */
406 if (TREE_CODE_CLASS (gimple_cond_code (stmt)) == tcc_comparison
407 && TREE_CODE (gimple_cond_lhs (stmt)) == SSA_NAME)
409 /* For comparisons use the first operand, that is likely to
410 simplify comparisons against constants. */
411 name = gimple_cond_lhs (stmt);
412 def_stmt = get_prop_source_stmt (name, false, &single_use0_p);
413 if (def_stmt && can_propagate_from (def_stmt))
415 tree op1 = gimple_cond_rhs (stmt);
416 rhs0 = rhs_to_tree (TREE_TYPE (op1), def_stmt);
417 tmp = combine_cond_expr_cond (code, boolean_type_node, rhs0,
418 op1, !single_use0_p);
420 /* If that wasn't successful, try the second operand. */
422 && TREE_CODE (gimple_cond_rhs (stmt)) == SSA_NAME)
424 tree op0 = gimple_cond_lhs (stmt);
425 name = gimple_cond_rhs (stmt);
426 def_stmt = get_prop_source_stmt (name, false, &single_use1_p);
427 if (!def_stmt || !can_propagate_from (def_stmt))
428 return did_something;
430 rhs1 = rhs_to_tree (TREE_TYPE (op0), def_stmt);
431 tmp = combine_cond_expr_cond (code, boolean_type_node, op0, rhs1,
434 /* If that wasn't successful either, try both operands. */
437 && rhs1 != NULL_TREE)
438 tmp = combine_cond_expr_cond (code, boolean_type_node, rhs0,
439 fold_convert (TREE_TYPE (rhs0), rhs1),
440 !(single_use0_p && single_use1_p));
445 if (dump_file && tmp)
447 tree cond = build2 (gimple_cond_code (stmt),
449 gimple_cond_lhs (stmt),
450 gimple_cond_rhs (stmt));
451 fprintf (dump_file, " Replaced '");
452 print_generic_expr (dump_file, cond, 0);
453 fprintf (dump_file, "' with '");
454 print_generic_expr (dump_file, tmp, 0);
455 fprintf (dump_file, "'\n");
458 gimple_cond_set_condition_from_tree (stmt, unshare_expr (tmp));
461 /* Remove defining statements. */
462 remove_prop_source_from_use (name, NULL);
464 if (is_gimple_min_invariant (tmp))
466 else if (did_something == 0)
469 /* Continue combining. */
476 return did_something;
480 /* Propagate from the ssa name definition statements of COND_EXPR
481 in the rhs of statement STMT into the conditional if that simplifies it.
482 Returns zero if no statement was changed, one if there were
483 changes and two if cfg_cleanup needs to run.
485 This must be kept in sync with forward_propagate_into_gimple_cond. */
488 forward_propagate_into_cond (gimple_stmt_iterator *gsi_p)
490 gimple stmt = gsi_stmt (*gsi_p);
491 int did_something = 0;
494 tree tmp = NULL_TREE;
495 tree cond = gimple_assign_rhs1 (stmt);
496 tree name, rhs0 = NULL_TREE, rhs1 = NULL_TREE;
498 bool single_use0_p = false, single_use1_p = false;
500 /* We can do tree combining on SSA_NAME and comparison expressions. */
501 if (COMPARISON_CLASS_P (cond)
502 && TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME)
504 /* For comparisons use the first operand, that is likely to
505 simplify comparisons against constants. */
506 name = TREE_OPERAND (cond, 0);
507 def_stmt = get_prop_source_stmt (name, false, &single_use0_p);
508 if (def_stmt && can_propagate_from (def_stmt))
510 tree op1 = TREE_OPERAND (cond, 1);
511 rhs0 = rhs_to_tree (TREE_TYPE (op1), def_stmt);
512 tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
513 rhs0, op1, !single_use0_p);
515 /* If that wasn't successful, try the second operand. */
517 && TREE_CODE (TREE_OPERAND (cond, 1)) == SSA_NAME)
519 tree op0 = TREE_OPERAND (cond, 0);
520 name = TREE_OPERAND (cond, 1);
521 def_stmt = get_prop_source_stmt (name, false, &single_use1_p);
522 if (!def_stmt || !can_propagate_from (def_stmt))
523 return did_something;
525 rhs1 = rhs_to_tree (TREE_TYPE (op0), def_stmt);
526 tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
527 op0, rhs1, !single_use1_p);
529 /* If that wasn't successful either, try both operands. */
532 && rhs1 != NULL_TREE)
533 tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
534 rhs0, fold_convert (TREE_TYPE (rhs0),
536 !(single_use0_p && single_use1_p));
538 else if (TREE_CODE (cond) == SSA_NAME)
541 def_stmt = get_prop_source_stmt (name, true, NULL);
542 if (def_stmt || !can_propagate_from (def_stmt))
543 return did_something;
545 rhs0 = gimple_assign_rhs1 (def_stmt);
546 tmp = combine_cond_expr_cond (NE_EXPR, boolean_type_node, rhs0,
547 build_int_cst (TREE_TYPE (rhs0), 0),
553 if (dump_file && tmp)
555 fprintf (dump_file, " Replaced '");
556 print_generic_expr (dump_file, cond, 0);
557 fprintf (dump_file, "' with '");
558 print_generic_expr (dump_file, tmp, 0);
559 fprintf (dump_file, "'\n");
562 gimple_assign_set_rhs_from_tree (gsi_p, unshare_expr (tmp));
563 stmt = gsi_stmt (*gsi_p);
566 /* Remove defining statements. */
567 remove_prop_source_from_use (name, NULL);
569 if (is_gimple_min_invariant (tmp))
571 else if (did_something == 0)
574 /* Continue combining. */
581 return did_something;
584 /* We've just substituted an ADDR_EXPR into stmt. Update all the
585 relevant data structures to match. */
588 tidy_after_forward_propagate_addr (gimple stmt)
590 /* We may have turned a trapping insn into a non-trapping insn. */
591 if (maybe_clean_or_replace_eh_stmt (stmt, stmt)
592 && gimple_purge_dead_eh_edges (gimple_bb (stmt)))
595 if (TREE_CODE (gimple_assign_rhs1 (stmt)) == ADDR_EXPR)
596 recompute_tree_invariant_for_addr_expr (gimple_assign_rhs1 (stmt));
598 mark_symbols_for_renaming (stmt);
601 /* DEF_RHS contains the address of the 0th element in an array.
602 USE_STMT uses type of DEF_RHS to compute the address of an
603 arbitrary element within the array. The (variable) byte offset
604 of the element is contained in OFFSET.
606 We walk back through the use-def chains of OFFSET to verify that
607 it is indeed computing the offset of an element within the array
608 and extract the index corresponding to the given byte offset.
610 We then try to fold the entire address expression into a form
613 If we are successful, we replace the right hand side of USE_STMT
614 with the new address computation. */
617 forward_propagate_addr_into_variable_array_index (tree offset,
619 gimple_stmt_iterator *use_stmt_gsi)
622 gimple offset_def, use_stmt = gsi_stmt (*use_stmt_gsi);
625 tunit = TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs)));
626 if (!host_integerp (tunit, 1))
629 /* Get the offset's defining statement. */
630 offset_def = SSA_NAME_DEF_STMT (offset);
632 /* Try to find an expression for a proper index. This is either a
633 multiplication expression by the element size or just the ssa name we came
634 along in case the element size is one. In that case, however, we do not
635 allow multiplications because they can be computing index to a higher
636 level dimension (PR 37861). */
637 if (integer_onep (tunit))
639 if (is_gimple_assign (offset_def)
640 && gimple_assign_rhs_code (offset_def) == MULT_EXPR)
647 /* The statement which defines OFFSET before type conversion
648 must be a simple GIMPLE_ASSIGN. */
649 if (!is_gimple_assign (offset_def))
652 /* The RHS of the statement which defines OFFSET must be a
653 multiplication of an object by the size of the array elements.
654 This implicitly verifies that the size of the array elements
656 if (gimple_assign_rhs_code (offset_def) == MULT_EXPR
657 && TREE_CODE (gimple_assign_rhs2 (offset_def)) == INTEGER_CST
658 && tree_int_cst_equal (gimple_assign_rhs2 (offset_def), tunit))
660 /* The first operand to the MULT_EXPR is the desired index. */
661 index = gimple_assign_rhs1 (offset_def);
663 /* If we have idx * tunit + CST * tunit re-associate that. */
664 else if ((gimple_assign_rhs_code (offset_def) == PLUS_EXPR
665 || gimple_assign_rhs_code (offset_def) == MINUS_EXPR)
666 && TREE_CODE (gimple_assign_rhs1 (offset_def)) == SSA_NAME
667 && TREE_CODE (gimple_assign_rhs2 (offset_def)) == INTEGER_CST
668 && (tmp = div_if_zero_remainder (EXACT_DIV_EXPR,
669 gimple_assign_rhs2 (offset_def),
670 tunit)) != NULL_TREE)
672 gimple offset_def2 = SSA_NAME_DEF_STMT (gimple_assign_rhs1 (offset_def));
673 if (gimple_assign_rhs_code (offset_def2) == MULT_EXPR
674 && TREE_CODE (gimple_assign_rhs2 (offset_def2)) == INTEGER_CST
675 && tree_int_cst_equal (gimple_assign_rhs2 (offset_def2), tunit))
677 index = fold_build2 (gimple_assign_rhs_code (offset_def),
679 gimple_assign_rhs1 (offset_def2), tmp);
688 /* Replace the pointer addition with array indexing. */
689 index = force_gimple_operand_gsi (use_stmt_gsi, index, true, NULL_TREE,
690 true, GSI_SAME_STMT);
691 gimple_assign_set_rhs_from_tree (use_stmt_gsi, unshare_expr (def_rhs));
692 use_stmt = gsi_stmt (*use_stmt_gsi);
693 TREE_OPERAND (TREE_OPERAND (gimple_assign_rhs1 (use_stmt), 0), 1)
696 /* That should have created gimple, so there is no need to
697 record information to undo the propagation. */
698 fold_stmt_inplace (use_stmt);
699 tidy_after_forward_propagate_addr (use_stmt);
703 /* NAME is a SSA_NAME representing DEF_RHS which is of the form
704 ADDR_EXPR <whatever>.
706 Try to forward propagate the ADDR_EXPR into the use USE_STMT.
707 Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
708 node or for recovery of array indexing from pointer arithmetic.
710 Return true if the propagation was successful (the propagation can
711 be not totally successful, yet things may have been changed). */
714 forward_propagate_addr_expr_1 (tree name, tree def_rhs,
715 gimple_stmt_iterator *use_stmt_gsi,
718 tree lhs, rhs, rhs2, array_ref;
720 gimple use_stmt = gsi_stmt (*use_stmt_gsi);
721 enum tree_code rhs_code;
723 gcc_assert (TREE_CODE (def_rhs) == ADDR_EXPR);
725 lhs = gimple_assign_lhs (use_stmt);
726 rhs_code = gimple_assign_rhs_code (use_stmt);
727 rhs = gimple_assign_rhs1 (use_stmt);
729 /* Trivial cases. The use statement could be a trivial copy or a
730 useless conversion. Recurse to the uses of the lhs as copyprop does
731 not copy through different variant pointers and FRE does not catch
732 all useless conversions. Treat the case of a single-use name and
733 a conversion to def_rhs type separate, though. */
734 if (TREE_CODE (lhs) == SSA_NAME
735 && ((rhs_code == SSA_NAME && rhs == name)
736 || CONVERT_EXPR_CODE_P (rhs_code)))
738 /* Only recurse if we don't deal with a single use or we cannot
739 do the propagation to the current statement. In particular
740 we can end up with a conversion needed for a non-invariant
741 address which we cannot do in a single statement. */
743 || (!useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (def_rhs))
744 && !is_gimple_min_invariant (def_rhs)))
745 return forward_propagate_addr_expr (lhs, def_rhs);
747 gimple_assign_set_rhs1 (use_stmt, unshare_expr (def_rhs));
748 if (useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (def_rhs)))
749 gimple_assign_set_rhs_code (use_stmt, TREE_CODE (def_rhs));
751 gimple_assign_set_rhs_code (use_stmt, NOP_EXPR);
755 /* Now strip away any outer COMPONENT_REF/ARRAY_REF nodes from the LHS.
756 ADDR_EXPR will not appear on the LHS. */
757 lhsp = gimple_assign_lhs_ptr (use_stmt);
758 while (handled_component_p (*lhsp))
759 lhsp = &TREE_OPERAND (*lhsp, 0);
762 /* Now see if the LHS node is an INDIRECT_REF using NAME. If so,
763 propagate the ADDR_EXPR into the use of NAME and fold the result. */
764 if (TREE_CODE (lhs) == INDIRECT_REF
765 && TREE_OPERAND (lhs, 0) == name
766 && may_propagate_address_into_dereference (def_rhs, lhs)
767 && (lhsp != gimple_assign_lhs_ptr (use_stmt)
768 || useless_type_conversion_p (TREE_TYPE (TREE_OPERAND (def_rhs, 0)),
771 *lhsp = unshare_expr (TREE_OPERAND (def_rhs, 0));
772 fold_stmt_inplace (use_stmt);
773 tidy_after_forward_propagate_addr (use_stmt);
775 /* Continue propagating into the RHS if this was not the only use. */
780 /* Strip away any outer COMPONENT_REF, ARRAY_REF or ADDR_EXPR
781 nodes from the RHS. */
782 rhsp = gimple_assign_rhs1_ptr (use_stmt);
783 while (handled_component_p (*rhsp)
784 || TREE_CODE (*rhsp) == ADDR_EXPR)
785 rhsp = &TREE_OPERAND (*rhsp, 0);
788 /* Now see if the RHS node is an INDIRECT_REF using NAME. If so,
789 propagate the ADDR_EXPR into the use of NAME and fold the result. */
790 if (TREE_CODE (rhs) == INDIRECT_REF
791 && TREE_OPERAND (rhs, 0) == name
792 && may_propagate_address_into_dereference (def_rhs, rhs))
794 *rhsp = unshare_expr (TREE_OPERAND (def_rhs, 0));
795 fold_stmt_inplace (use_stmt);
796 tidy_after_forward_propagate_addr (use_stmt);
800 /* Now see if the RHS node is an INDIRECT_REF using NAME. If so,
801 propagate the ADDR_EXPR into the use of NAME and try to
802 create a VCE and fold the result. */
803 if (TREE_CODE (rhs) == INDIRECT_REF
804 && TREE_OPERAND (rhs, 0) == name
805 && TYPE_SIZE (TREE_TYPE (rhs))
806 && TYPE_SIZE (TREE_TYPE (TREE_OPERAND (def_rhs, 0)))
807 /* Function decls should not be used for VCE either as it could be a
808 function descriptor that we want and not the actual function code. */
809 && TREE_CODE (TREE_OPERAND (def_rhs, 0)) != FUNCTION_DECL
810 /* We should not convert volatile loads to non volatile loads. */
811 && !TYPE_VOLATILE (TREE_TYPE (rhs))
812 && !TYPE_VOLATILE (TREE_TYPE (TREE_OPERAND (def_rhs, 0)))
813 && operand_equal_p (TYPE_SIZE (TREE_TYPE (rhs)),
814 TYPE_SIZE (TREE_TYPE (TREE_OPERAND (def_rhs, 0))), 0))
816 tree def_rhs_base, new_rhs = unshare_expr (TREE_OPERAND (def_rhs, 0));
817 new_rhs = fold_build1 (VIEW_CONVERT_EXPR, TREE_TYPE (rhs), new_rhs);
818 if (TREE_CODE (new_rhs) != VIEW_CONVERT_EXPR)
820 /* If we have folded the VIEW_CONVERT_EXPR then the result is only
821 valid if we can replace the whole rhs of the use statement. */
822 if (rhs != gimple_assign_rhs1 (use_stmt))
824 new_rhs = force_gimple_operand_gsi (use_stmt_gsi, new_rhs, true, NULL,
826 gimple_assign_set_rhs1 (use_stmt, new_rhs);
827 tidy_after_forward_propagate_addr (use_stmt);
830 /* If the defining rhs comes from an indirect reference, then do not
831 convert into a VIEW_CONVERT_EXPR. */
832 def_rhs_base = TREE_OPERAND (def_rhs, 0);
833 while (handled_component_p (def_rhs_base))
834 def_rhs_base = TREE_OPERAND (def_rhs_base, 0);
835 if (!INDIRECT_REF_P (def_rhs_base))
837 /* We may have arbitrary VIEW_CONVERT_EXPRs in a nested component
838 reference. Place it there and fold the thing. */
840 fold_stmt_inplace (use_stmt);
841 tidy_after_forward_propagate_addr (use_stmt);
846 /* If the use of the ADDR_EXPR is not a POINTER_PLUS_EXPR, there
848 if (gimple_assign_rhs_code (use_stmt) != POINTER_PLUS_EXPR
849 || gimple_assign_rhs1 (use_stmt) != name)
852 /* The remaining cases are all for turning pointer arithmetic into
853 array indexing. They only apply when we have the address of
854 element zero in an array. If that is not the case then there
856 array_ref = TREE_OPERAND (def_rhs, 0);
857 if (TREE_CODE (array_ref) != ARRAY_REF
858 || TREE_CODE (TREE_TYPE (TREE_OPERAND (array_ref, 0))) != ARRAY_TYPE
859 || TREE_CODE (TREE_OPERAND (array_ref, 1)) != INTEGER_CST)
862 rhs2 = gimple_assign_rhs2 (use_stmt);
863 /* Try to optimize &x[C1] p+ C2 where C2 is a multiple of the size
864 of the elements in X into &x[C1 + C2/element size]. */
865 if (TREE_CODE (rhs2) == INTEGER_CST)
867 tree new_rhs = maybe_fold_stmt_addition (gimple_expr_type (use_stmt),
871 gimple_assign_set_rhs_from_tree (use_stmt_gsi,
872 unshare_expr (new_rhs));
873 use_stmt = gsi_stmt (*use_stmt_gsi);
874 update_stmt (use_stmt);
875 tidy_after_forward_propagate_addr (use_stmt);
880 /* Try to optimize &x[0] p+ OFFSET where OFFSET is defined by
881 converting a multiplication of an index by the size of the
882 array elements, then the result is converted into the proper
883 type for the arithmetic. */
884 if (TREE_CODE (rhs2) == SSA_NAME
885 && integer_zerop (TREE_OPERAND (array_ref, 1))
886 && useless_type_conversion_p (TREE_TYPE (name), TREE_TYPE (def_rhs))
887 /* Avoid problems with IVopts creating PLUS_EXPRs with a
888 different type than their operands. */
889 && useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (def_rhs)))
890 return forward_propagate_addr_into_variable_array_index (rhs2, def_rhs,
895 /* STMT is a statement of the form SSA_NAME = ADDR_EXPR <whatever>.
897 Try to forward propagate the ADDR_EXPR into all uses of the SSA_NAME.
898 Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
899 node or for recovery of array indexing from pointer arithmetic.
900 Returns true, if all uses have been propagated into. */
903 forward_propagate_addr_expr (tree name, tree rhs)
905 int stmt_loop_depth = gimple_bb (SSA_NAME_DEF_STMT (name))->loop_depth;
906 imm_use_iterator iter;
909 bool single_use_p = has_single_use (name);
911 FOR_EACH_IMM_USE_STMT (use_stmt, iter, name)
916 /* If the use is not in a simple assignment statement, then
917 there is nothing we can do. */
918 if (gimple_code (use_stmt) != GIMPLE_ASSIGN)
924 /* If the use is in a deeper loop nest, then we do not want
925 to propagate the ADDR_EXPR into the loop as that is likely
926 adding expression evaluations into the loop. */
927 if (gimple_bb (use_stmt)->loop_depth > stmt_loop_depth)
933 push_stmt_changes (&use_stmt);
936 gimple_stmt_iterator gsi = gsi_for_stmt (use_stmt);
937 result = forward_propagate_addr_expr_1 (name, rhs, &gsi,
939 use_stmt = gsi_stmt (gsi);
943 pop_stmt_changes (&use_stmt);
945 /* Remove intermediate now unused copy and conversion chains. */
946 use_rhs = gimple_assign_rhs1 (use_stmt);
948 && TREE_CODE (gimple_assign_lhs (use_stmt)) == SSA_NAME
949 && (TREE_CODE (use_rhs) == SSA_NAME
950 || (CONVERT_EXPR_P (use_rhs)
951 && TREE_CODE (TREE_OPERAND (use_rhs, 0)) == SSA_NAME)))
953 gimple_stmt_iterator gsi = gsi_for_stmt (use_stmt);
954 release_defs (use_stmt);
955 gsi_remove (&gsi, true);
962 /* Forward propagate the comparison defined in STMT like
963 cond_1 = x CMP y to uses of the form
967 Returns true if stmt is now unused. */
970 forward_propagate_comparison (gimple stmt)
972 tree name = gimple_assign_lhs (stmt);
974 tree tmp = NULL_TREE;
976 /* Don't propagate ssa names that occur in abnormal phis. */
977 if ((TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME
978 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_assign_rhs1 (stmt)))
979 || (TREE_CODE (gimple_assign_rhs2 (stmt)) == SSA_NAME
980 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_assign_rhs2 (stmt))))
983 /* Do not un-cse comparisons. But propagate through copies. */
984 use_stmt = get_prop_dest_stmt (name, &name);
988 /* Conversion of the condition result to another integral type. */
989 if (is_gimple_assign (use_stmt)
990 && (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (use_stmt))
991 || TREE_CODE_CLASS (gimple_assign_rhs_code (use_stmt))
993 || gimple_assign_rhs_code (use_stmt) == TRUTH_NOT_EXPR)
994 && INTEGRAL_TYPE_P (TREE_TYPE (gimple_assign_lhs (use_stmt))))
996 tree lhs = gimple_assign_lhs (use_stmt);
998 /* We can propagate the condition into a conversion. */
999 if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (use_stmt)))
1001 /* Avoid using fold here as that may create a COND_EXPR with
1002 non-boolean condition as canonical form. */
1003 tmp = build2 (gimple_assign_rhs_code (stmt), TREE_TYPE (lhs),
1004 gimple_assign_rhs1 (stmt), gimple_assign_rhs2 (stmt));
1006 /* We can propagate the condition into X op CST where op
1007 is EQ_EXPR or NE_EXPR and CST is either one or zero. */
1008 else if (TREE_CODE_CLASS (gimple_assign_rhs_code (use_stmt))
1010 && TREE_CODE (gimple_assign_rhs1 (use_stmt)) == SSA_NAME
1011 && TREE_CODE (gimple_assign_rhs2 (use_stmt)) == INTEGER_CST)
1013 enum tree_code code = gimple_assign_rhs_code (use_stmt);
1014 tree cst = gimple_assign_rhs2 (use_stmt);
1017 cond = build2 (gimple_assign_rhs_code (stmt),
1019 gimple_assign_rhs1 (stmt),
1020 gimple_assign_rhs2 (stmt));
1022 tmp = combine_cond_expr_cond (code, TREE_TYPE (lhs), cond, cst, false);
1023 if (tmp == NULL_TREE)
1026 /* We can propagate the condition into a statement that
1027 computes the logical negation of the comparison result. */
1028 else if (gimple_assign_rhs_code (use_stmt) == TRUTH_NOT_EXPR)
1030 tree type = TREE_TYPE (gimple_assign_rhs1 (stmt));
1031 bool nans = HONOR_NANS (TYPE_MODE (type));
1032 enum tree_code code;
1033 code = invert_tree_comparison (gimple_assign_rhs_code (stmt), nans);
1034 if (code == ERROR_MARK)
1037 tmp = build2 (code, TREE_TYPE (lhs), gimple_assign_rhs1 (stmt),
1038 gimple_assign_rhs2 (stmt));
1044 gimple_stmt_iterator gsi = gsi_for_stmt (use_stmt);
1045 gimple_assign_set_rhs_from_tree (&gsi, unshare_expr (tmp));
1046 use_stmt = gsi_stmt (gsi);
1047 update_stmt (use_stmt);
1050 /* Remove defining statements. */
1051 remove_prop_source_from_use (name, stmt);
1053 if (dump_file && (dump_flags & TDF_DETAILS))
1055 tree old_rhs = rhs_to_tree (TREE_TYPE (gimple_assign_lhs (stmt)),
1057 fprintf (dump_file, " Replaced '");
1058 print_generic_expr (dump_file, old_rhs, dump_flags);
1059 fprintf (dump_file, "' with '");
1060 print_generic_expr (dump_file, tmp, dump_flags);
1061 fprintf (dump_file, "'\n");
1070 /* If we have lhs = ~x (STMT), look and see if earlier we had x = ~y.
1071 If so, we can change STMT into lhs = y which can later be copy
1072 propagated. Similarly for negation.
1074 This could trivially be formulated as a forward propagation
1075 to immediate uses. However, we already had an implementation
1076 from DOM which used backward propagation via the use-def links.
1078 It turns out that backward propagation is actually faster as
1079 there's less work to do for each NOT/NEG expression we find.
1080 Backwards propagation needs to look at the statement in a single
1081 backlink. Forward propagation needs to look at potentially more
1082 than one forward link. */
1085 simplify_not_neg_expr (gimple_stmt_iterator *gsi_p)
1087 gimple stmt = gsi_stmt (*gsi_p);
1088 tree rhs = gimple_assign_rhs1 (stmt);
1089 gimple rhs_def_stmt = SSA_NAME_DEF_STMT (rhs);
1091 /* See if the RHS_DEF_STMT has the same form as our statement. */
1092 if (is_gimple_assign (rhs_def_stmt)
1093 && gimple_assign_rhs_code (rhs_def_stmt) == gimple_assign_rhs_code (stmt))
1095 tree rhs_def_operand = gimple_assign_rhs1 (rhs_def_stmt);
1097 /* Verify that RHS_DEF_OPERAND is a suitable SSA_NAME. */
1098 if (TREE_CODE (rhs_def_operand) == SSA_NAME
1099 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))
1101 gimple_assign_set_rhs_from_tree (gsi_p, rhs_def_operand);
1102 stmt = gsi_stmt (*gsi_p);
1108 /* STMT is a SWITCH_EXPR for which we attempt to find equivalent forms of
1109 the condition which we may be able to optimize better. */
1112 simplify_gimple_switch (gimple stmt)
1114 tree cond = gimple_switch_index (stmt);
1118 /* The optimization that we really care about is removing unnecessary
1119 casts. That will let us do much better in propagating the inferred
1120 constant at the switch target. */
1121 if (TREE_CODE (cond) == SSA_NAME)
1123 def_stmt = SSA_NAME_DEF_STMT (cond);
1124 if (is_gimple_assign (def_stmt))
1126 if (gimple_assign_rhs_code (def_stmt) == NOP_EXPR)
1131 def = gimple_assign_rhs1 (def_stmt);
1133 #ifdef ENABLE_CHECKING
1134 /* ??? Why was Jeff testing this? We are gimple... */
1135 gcc_assert (is_gimple_val (def));
1138 to = TREE_TYPE (cond);
1139 ti = TREE_TYPE (def);
1141 /* If we have an extension that preserves value, then we
1142 can copy the source value into the switch. */
1144 need_precision = TYPE_PRECISION (ti);
1146 if (! INTEGRAL_TYPE_P (ti))
1148 else if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
1150 else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
1151 need_precision += 1;
1152 if (TYPE_PRECISION (to) < need_precision)
1157 gimple_switch_set_index (stmt, def);
1165 /* Run bitwise and assignments throug the folder. If the first argument is an
1166 ssa name that is itself a result of a typecast of an ADDR_EXPR to an
1167 integer, feed the ADDR_EXPR to the folder rather than the ssa name.
1171 simplify_bitwise_and (gimple_stmt_iterator *gsi, gimple stmt)
1174 tree arg1 = gimple_assign_rhs1 (stmt);
1175 tree arg2 = gimple_assign_rhs2 (stmt);
1177 if (TREE_CODE (arg2) != INTEGER_CST)
1180 if (TREE_CODE (arg1) == SSA_NAME && !SSA_NAME_IS_DEFAULT_DEF (arg1))
1182 gimple def = SSA_NAME_DEF_STMT (arg1);
1184 if (gimple_assign_cast_p (def)
1185 && INTEGRAL_TYPE_P (gimple_expr_type (def)))
1187 tree op = gimple_assign_rhs1 (def);
1189 if (TREE_CODE (op) == ADDR_EXPR)
1194 res = fold_binary (BIT_AND_EXPR, TREE_TYPE (gimple_assign_lhs (stmt)),
1196 if (res && is_gimple_min_invariant (res))
1198 gimple_assign_set_rhs_from_tree (gsi, res);
1204 /* Main entry point for the forward propagation optimizer. */
1207 tree_ssa_forward_propagate_single_use_vars (void)
1210 unsigned int todoflags = 0;
1212 cfg_changed = false;
1216 gimple_stmt_iterator gsi;
1218 /* Note we update GSI within the loop as necessary. */
1219 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
1221 gimple stmt = gsi_stmt (gsi);
1223 /* If this statement sets an SSA_NAME to an address,
1224 try to propagate the address into the uses of the SSA_NAME. */
1225 if (is_gimple_assign (stmt))
1227 tree lhs = gimple_assign_lhs (stmt);
1228 tree rhs = gimple_assign_rhs1 (stmt);
1230 if (TREE_CODE (lhs) != SSA_NAME)
1236 if (gimple_assign_rhs_code (stmt) == ADDR_EXPR
1237 /* Handle pointer conversions on invariant addresses
1238 as well, as this is valid gimple. */
1239 || (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (stmt))
1240 && TREE_CODE (rhs) == ADDR_EXPR
1241 && POINTER_TYPE_P (TREE_TYPE (lhs))))
1244 if (!stmt_references_abnormal_ssa_name (stmt)
1245 && forward_propagate_addr_expr (lhs, rhs))
1247 release_defs (stmt);
1248 todoflags |= TODO_remove_unused_locals;
1249 gsi_remove (&gsi, true);
1254 else if ((gimple_assign_rhs_code (stmt) == BIT_NOT_EXPR
1255 || gimple_assign_rhs_code (stmt) == NEGATE_EXPR)
1256 && TREE_CODE (rhs) == SSA_NAME)
1258 simplify_not_neg_expr (&gsi);
1261 else if (gimple_assign_rhs_code (stmt) == COND_EXPR)
1263 /* In this case the entire COND_EXPR is in rhs1. */
1265 fold_defer_overflow_warnings ();
1266 did_something = forward_propagate_into_cond (&gsi);
1267 stmt = gsi_stmt (gsi);
1268 if (did_something == 2)
1270 fold_undefer_overflow_warnings (!TREE_NO_WARNING (rhs)
1271 && did_something, stmt, WARN_STRICT_OVERFLOW_CONDITIONAL);
1274 else if (TREE_CODE_CLASS (gimple_assign_rhs_code (stmt))
1277 if (forward_propagate_comparison (stmt))
1279 release_defs (stmt);
1280 todoflags |= TODO_remove_unused_locals;
1281 gsi_remove (&gsi, true);
1286 else if (gimple_assign_rhs_code (stmt) == BIT_AND_EXPR)
1288 simplify_bitwise_and (&gsi, stmt);
1294 else if (gimple_code (stmt) == GIMPLE_SWITCH)
1296 simplify_gimple_switch (stmt);
1299 else if (gimple_code (stmt) == GIMPLE_COND)
1302 fold_defer_overflow_warnings ();
1303 did_something = forward_propagate_into_gimple_cond (stmt);
1304 if (did_something == 2)
1306 fold_undefer_overflow_warnings (did_something, stmt,
1307 WARN_STRICT_OVERFLOW_CONDITIONAL);
1316 todoflags |= TODO_cleanup_cfg;
1322 gate_forwprop (void)
1327 struct gimple_opt_pass pass_forwprop =
1331 "forwprop", /* name */
1332 gate_forwprop, /* gate */
1333 tree_ssa_forward_propagate_single_use_vars, /* execute */
1336 0, /* static_pass_number */
1337 TV_TREE_FORWPROP, /* tv_id */
1338 PROP_cfg | PROP_ssa, /* properties_required */
1339 0, /* properties_provided */
1340 0, /* properties_destroyed */
1341 0, /* todo_flags_start */
1345 | TODO_verify_ssa /* todo_flags_finish */