1 /* Forward propagation of expressions for single use variables.
2 Copyright (C) 2004, 2005 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 2, 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 COPYING. If not, write to
18 the Free Software Foundation, 51 Franklin Street, Fifth Floor,
19 Boston, MA 02110-1301, USA. */
23 #include "coretypes.h"
29 #include "basic-block.h"
31 #include "diagnostic.h"
32 #include "tree-flow.h"
33 #include "tree-pass.h"
34 #include "tree-dump.h"
35 #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 Note carefully that after propagation the resulting statement
44 must still be a proper gimple statement. Right now we simply
45 only perform propagations we know will result in valid gimple
46 code. One day we'll want to generalize this code.
48 One class of common cases we handle is forward propagating a single use
49 variable into a COND_EXPR.
53 if (x) goto ... else goto ...
55 Will be transformed into:
58 if (a COND b) goto ... else goto ...
60 Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
62 Or (assuming c1 and c2 are constants):
66 if (x EQ/NEQ c2) goto ... else goto ...
68 Will be transformed into:
71 if (a EQ/NEQ (c2 - c1)) goto ... else goto ...
73 Similarly for x = a - c1.
79 if (x) goto ... else goto ...
81 Will be transformed into:
84 if (a == 0) goto ... else goto ...
86 Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
87 For these cases, we propagate A into all, possibly more than one,
88 COND_EXPRs that use X.
94 if (x) goto ... else goto ...
96 Will be transformed into:
99 if (a != 0) goto ... else goto ...
101 (Assuming a is an integral type and x is a boolean or x is an
102 integral and a is a boolean.)
104 Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
105 For these cases, we propagate A into all, possibly more than one,
106 COND_EXPRs that use X.
108 In addition to eliminating the variable and the statement which assigns
109 a value to the variable, we may be able to later thread the jump without
110 adding insane complexity in the dominator optimizer.
112 Also note these transformations can cascade. We handle this by having
113 a worklist of COND_EXPR statements to examine. As we make a change to
114 a statement, we put it back on the worklist to examine on the next
115 iteration of the main loop.
117 A second class of propagation opportunities arises for ADDR_EXPR
130 ptr2 = ptr + <constant>;
134 ptr2 = &x[constant/elementsize];
139 offset = index * element_size;
140 offset_p = (pointer) offset;
141 ptr2 = ptr + offset_p
143 Will get turned into:
147 We also propagate casts into SWITCH_EXPR and COND_EXPR conditions to
148 allow us to remove the cast and {NOT_EXPR,NEG_EXPR} into a subsequent
151 This will (of course) be extended as other needs arise. */
153 static bool forward_propagate_addr_expr (tree name, tree rhs);
155 /* Set to true if we delete EH edges during the optimization. */
156 static bool cfg_changed;
159 /* Get the next statement we can propagate NAME's value into skipping
160 trivial copies. Returns the statement that is suitable as a
161 propagation destination or NULL_TREE if there is no such one.
162 This only returns destinations in a single-use chain. FINAL_NAME_P
163 if non-NULL is written to the ssa name that represents the use. */
166 get_prop_dest_stmt (tree name, tree *final_name_p)
172 /* If name has multiple uses, bail out. */
173 if (!single_imm_use (name, &use, &use_stmt))
176 /* If this is not a trivial copy, we found it. */
177 if (TREE_CODE (use_stmt) != GIMPLE_MODIFY_STMT
178 || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) != SSA_NAME
179 || GIMPLE_STMT_OPERAND (use_stmt, 1) != name)
182 /* Continue searching uses of the copy destination. */
183 name = GIMPLE_STMT_OPERAND (use_stmt, 0);
187 *final_name_p = name;
192 /* Get the statement we can propagate from into NAME skipping
193 trivial copies. Returns the statement which defines the
194 propagation source or NULL_TREE if there is no such one.
195 If SINGLE_USE_ONLY is set considers only sources which have
196 a single use chain up to NAME. If SINGLE_USE_P is non-null,
197 it is set to whether the chain to NAME is a single use chain
198 or not. SINGLE_USE_P is not written to if SINGLE_USE_ONLY is set. */
201 get_prop_source_stmt (tree name, bool single_use_only, bool *single_use_p)
203 bool single_use = true;
206 tree def_stmt = SSA_NAME_DEF_STMT (name);
208 if (!has_single_use (name))
215 /* If name is defined by a PHI node or is the default def, bail out. */
216 if (TREE_CODE (def_stmt) != GIMPLE_MODIFY_STMT)
219 /* If name is not a simple copy destination, we found it. */
220 if (TREE_CODE (GIMPLE_STMT_OPERAND (def_stmt, 1)) != SSA_NAME)
222 if (!single_use_only && single_use_p)
223 *single_use_p = single_use;
228 /* Continue searching the def of the copy source name. */
229 name = GIMPLE_STMT_OPERAND (def_stmt, 1);
233 /* Checks if the destination ssa name in DEF_STMT can be used as
234 propagation source. Returns true if so, otherwise false. */
237 can_propagate_from (tree def_stmt)
239 tree rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
241 /* We cannot propagate ssa names that occur in abnormal phi nodes. */
242 switch (TREE_CODE_LENGTH (TREE_CODE (rhs)))
245 if (TREE_OPERAND (rhs, 2) != NULL_TREE
246 && TREE_CODE (TREE_OPERAND (rhs, 2)) == SSA_NAME
247 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (rhs, 2)))
250 if (TREE_OPERAND (rhs, 1) != NULL_TREE
251 && TREE_CODE (TREE_OPERAND (rhs, 1)) == SSA_NAME
252 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (rhs, 1)))
255 if (TREE_OPERAND (rhs, 0) != NULL_TREE
256 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
257 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (rhs, 0)))
265 /* If the definition is a conversion of a pointer to a function type,
266 then we can not apply optimizations as some targets require function
267 pointers to be canonicalized and in this case this optimization could
268 eliminate a necessary canonicalization. */
269 if ((TREE_CODE (rhs) == NOP_EXPR
270 || TREE_CODE (rhs) == CONVERT_EXPR)
271 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0)))
272 && TREE_CODE (TREE_TYPE (TREE_TYPE
273 (TREE_OPERAND (rhs, 0)))) == FUNCTION_TYPE)
279 /* Remove a copy chain ending in NAME along the defs but not
280 further or including UP_TO_STMT. If NAME was replaced in
281 its only use then this function can be used to clean up
282 dead stmts. Returns true if UP_TO_STMT can be removed
283 as well, otherwise false. */
286 remove_prop_source_from_use (tree name, tree up_to_stmt)
288 block_stmt_iterator bsi;
292 if (!has_zero_uses (name))
295 stmt = SSA_NAME_DEF_STMT (name);
296 if (stmt == up_to_stmt)
299 bsi = bsi_for_stmt (stmt);
301 bsi_remove (&bsi, true);
303 name = GIMPLE_STMT_OPERAND (stmt, 1);
304 } while (TREE_CODE (name) == SSA_NAME);
309 /* Combine OP0 CODE OP1 in the context of a COND_EXPR. Returns
310 the folded result in a form suitable for COND_EXPR_COND or
311 NULL_TREE, if there is no suitable simplified form. If
312 INVARIANT_ONLY is true only gimple_min_invariant results are
313 considered simplified. */
316 combine_cond_expr_cond (enum tree_code code, tree type,
317 tree op0, tree op1, bool invariant_only)
321 gcc_assert (TREE_CODE_CLASS (code) == tcc_comparison);
323 t = fold_binary (code, type, op0, op1);
327 /* Require that we got a boolean type out if we put one in. */
328 gcc_assert (TREE_CODE (TREE_TYPE (t)) == TREE_CODE (type));
330 /* For (bool)x use x != 0. */
331 if (TREE_CODE (t) == NOP_EXPR
332 && TREE_TYPE (t) == boolean_type_node)
334 tree top0 = TREE_OPERAND (t, 0);
335 t = build2 (NE_EXPR, type,
336 top0, build_int_cst (TREE_TYPE (top0), 0));
338 /* For !x use x == 0. */
339 else if (TREE_CODE (t) == TRUTH_NOT_EXPR)
341 tree top0 = TREE_OPERAND (t, 0);
342 t = build2 (EQ_EXPR, type,
343 top0, build_int_cst (TREE_TYPE (top0), 0));
345 /* For cmp ? 1 : 0 use cmp. */
346 else if (TREE_CODE (t) == COND_EXPR
347 && COMPARISON_CLASS_P (TREE_OPERAND (t, 0))
348 && integer_onep (TREE_OPERAND (t, 1))
349 && integer_zerop (TREE_OPERAND (t, 2)))
351 tree top0 = TREE_OPERAND (t, 0);
352 t = build2 (TREE_CODE (top0), type,
353 TREE_OPERAND (top0, 0), TREE_OPERAND (top0, 1));
356 /* Bail out if we required an invariant but didn't get one. */
358 && !is_gimple_min_invariant (t))
361 /* A valid conditional for a COND_EXPR is either a gimple value
362 or a comparison with two gimple value operands. */
363 if (is_gimple_val (t)
364 || (COMPARISON_CLASS_P (t)
365 && is_gimple_val (TREE_OPERAND (t, 0))
366 && is_gimple_val (TREE_OPERAND (t, 1))))
372 /* Propagate from the ssa name definition statements of COND_EXPR
373 in statement STMT into the conditional if that simplifies it. */
376 forward_propagate_into_cond (tree cond_expr, tree stmt)
379 tree tmp = NULL_TREE;
380 tree cond = COND_EXPR_COND (cond_expr);
381 tree name, def_stmt, rhs;
384 /* We can do tree combining on SSA_NAME and comparison expressions. */
385 if (COMPARISON_CLASS_P (cond)
386 && TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME)
388 /* For comparisons use the first operand, that is likely to
389 simplify comparisons against constants. */
390 name = TREE_OPERAND (cond, 0);
391 def_stmt = get_prop_source_stmt (name, false, &single_use_p);
392 if (def_stmt != NULL_TREE
393 && can_propagate_from (def_stmt))
395 tree op1 = TREE_OPERAND (cond, 1);
396 rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
397 tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
398 fold_convert (TREE_TYPE (op1), rhs),
401 /* If that wasn't successful, try the second operand. */
403 && TREE_CODE (TREE_OPERAND (cond, 1)) == SSA_NAME)
405 tree op0 = TREE_OPERAND (cond, 0);
406 name = TREE_OPERAND (cond, 1);
407 def_stmt = get_prop_source_stmt (name, false, &single_use_p);
408 if (def_stmt == NULL_TREE
409 || !can_propagate_from (def_stmt))
412 rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
413 tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
415 fold_convert (TREE_TYPE (op0), rhs),
419 else if (TREE_CODE (cond) == SSA_NAME)
422 def_stmt = get_prop_source_stmt (name, true, NULL);
423 if (def_stmt == NULL_TREE
424 || !can_propagate_from (def_stmt))
427 rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
428 tmp = combine_cond_expr_cond (NE_EXPR, boolean_type_node, rhs,
429 build_int_cst (TREE_TYPE (rhs), 0),
435 if (dump_file && tmp)
437 fprintf (dump_file, " Replaced '");
438 print_generic_expr (dump_file, cond, 0);
439 fprintf (dump_file, "' with '");
440 print_generic_expr (dump_file, tmp, 0);
441 fprintf (dump_file, "'\n");
444 COND_EXPR_COND (cond_expr) = unshare_expr (tmp);
447 /* Remove defining statements. */
448 remove_prop_source_from_use (name, NULL);
450 /* Continue combining. */
458 /* We've just substituted an ADDR_EXPR into stmt. Update all the
459 relevant data structures to match. */
462 tidy_after_forward_propagate_addr (tree stmt)
464 /* We may have turned a trapping insn into a non-trapping insn. */
465 if (maybe_clean_or_replace_eh_stmt (stmt, stmt)
466 && tree_purge_dead_eh_edges (bb_for_stmt (stmt)))
469 if (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == ADDR_EXPR)
470 recompute_tree_invariant_for_addr_expr (GIMPLE_STMT_OPERAND (stmt, 1));
472 mark_symbols_for_renaming (stmt);
475 /* DEF_RHS defines LHS which is contains the address of the 0th element
476 in an array. USE_STMT uses LHS to compute the address of an
477 arbitrary element within the array. The (variable) byte offset
478 of the element is contained in OFFSET.
480 We walk back through the use-def chains of OFFSET to verify that
481 it is indeed computing the offset of an element within the array
482 and extract the index corresponding to the given byte offset.
484 We then try to fold the entire address expression into a form
487 If we are successful, we replace the right hand side of USE_STMT
488 with the new address computation. */
491 forward_propagate_addr_into_variable_array_index (tree offset, tree lhs,
492 tree def_rhs, tree use_stmt)
496 /* The offset must be defined by a simple GIMPLE_MODIFY_STMT statement. */
497 if (TREE_CODE (offset) != GIMPLE_MODIFY_STMT)
500 /* The RHS of the statement which defines OFFSET must be a gimple
501 cast of another SSA_NAME. */
502 offset = GIMPLE_STMT_OPERAND (offset, 1);
503 if (!is_gimple_cast (offset))
506 offset = TREE_OPERAND (offset, 0);
507 if (TREE_CODE (offset) != SSA_NAME)
510 /* Get the defining statement of the offset before type
512 offset = SSA_NAME_DEF_STMT (offset);
514 /* The statement which defines OFFSET before type conversion
515 must be a simple GIMPLE_MODIFY_STMT. */
516 if (TREE_CODE (offset) != GIMPLE_MODIFY_STMT)
519 /* The RHS of the statement which defines OFFSET must be a
520 multiplication of an object by the size of the array elements.
521 This implicitly verifies that the size of the array elements
523 offset = GIMPLE_STMT_OPERAND (offset, 1);
524 if (TREE_CODE (offset) != MULT_EXPR
525 || TREE_CODE (TREE_OPERAND (offset, 1)) != INTEGER_CST
526 || !simple_cst_equal (TREE_OPERAND (offset, 1),
527 TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (lhs)))))
530 /* The first operand to the MULT_EXPR is the desired index. */
531 index = TREE_OPERAND (offset, 0);
533 /* Replace the pointer addition with array indexing. */
534 GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (def_rhs);
535 TREE_OPERAND (TREE_OPERAND (GIMPLE_STMT_OPERAND (use_stmt, 1), 0), 1)
538 /* That should have created gimple, so there is no need to
539 record information to undo the propagation. */
540 fold_stmt_inplace (use_stmt);
541 tidy_after_forward_propagate_addr (use_stmt);
545 /* NAME is a SSA_NAME representing DEF_RHS which is of the form
546 ADDR_EXPR <whatever>.
548 Try to forward propagate the ADDR_EXPR into the use USE_STMT.
549 Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
550 node or for recovery of array indexing from pointer arithmetic.
552 Return true if the propagation was successful (the propagation can
553 be not totally successful, yet things may have been changed). */
556 forward_propagate_addr_expr_1 (tree name, tree def_rhs, tree use_stmt)
558 tree lhs, rhs, array_ref;
560 /* Strip away any outer COMPONENT_REF/ARRAY_REF nodes from the LHS.
561 ADDR_EXPR will not appear on the LHS. */
562 lhs = GIMPLE_STMT_OPERAND (use_stmt, 0);
563 while (handled_component_p (lhs))
564 lhs = TREE_OPERAND (lhs, 0);
566 rhs = GIMPLE_STMT_OPERAND (use_stmt, 1);
568 /* Now see if the LHS node is an INDIRECT_REF using NAME. If so,
569 propagate the ADDR_EXPR into the use of NAME and fold the result. */
570 if (TREE_CODE (lhs) == INDIRECT_REF && TREE_OPERAND (lhs, 0) == name)
572 /* This should always succeed in creating gimple, so there is
573 no need to save enough state to undo this propagation. */
574 TREE_OPERAND (lhs, 0) = unshare_expr (def_rhs);
575 fold_stmt_inplace (use_stmt);
576 tidy_after_forward_propagate_addr (use_stmt);
578 /* Continue propagating into the RHS. */
581 /* Trivial case. The use statement could be a trivial copy or a
582 useless conversion. Recurse to the uses of the lhs as copyprop does
583 not copy through differen variant pointers and FRE does not catch
584 all useless conversions. */
585 else if ((TREE_CODE (lhs) == SSA_NAME
587 || ((TREE_CODE (rhs) == NOP_EXPR
588 || TREE_CODE (rhs) == CONVERT_EXPR)
589 && tree_ssa_useless_type_conversion_1 (TREE_TYPE (rhs),
590 TREE_TYPE (def_rhs))))
591 return forward_propagate_addr_expr (lhs, def_rhs);
593 /* Strip away any outer COMPONENT_REF, ARRAY_REF or ADDR_EXPR
594 nodes from the RHS. */
595 while (handled_component_p (rhs)
596 || TREE_CODE (rhs) == ADDR_EXPR)
597 rhs = TREE_OPERAND (rhs, 0);
599 /* Now see if the RHS node is an INDIRECT_REF using NAME. If so,
600 propagate the ADDR_EXPR into the use of NAME and fold the result. */
601 if (TREE_CODE (rhs) == INDIRECT_REF && TREE_OPERAND (rhs, 0) == name)
603 /* This should always succeed in creating gimple, so there is
604 no need to save enough state to undo this propagation. */
605 TREE_OPERAND (rhs, 0) = unshare_expr (def_rhs);
606 fold_stmt_inplace (use_stmt);
607 tidy_after_forward_propagate_addr (use_stmt);
611 /* The remaining cases are all for turning pointer arithmetic into
612 array indexing. They only apply when we have the address of
613 element zero in an array. If that is not the case then there
615 array_ref = TREE_OPERAND (def_rhs, 0);
616 if (TREE_CODE (array_ref) != ARRAY_REF
617 || TREE_CODE (TREE_TYPE (TREE_OPERAND (array_ref, 0))) != ARRAY_TYPE
618 || !integer_zerop (TREE_OPERAND (array_ref, 1)))
621 /* If the use of the ADDR_EXPR must be a PLUS_EXPR, or else there
623 if (TREE_CODE (rhs) != PLUS_EXPR)
626 /* Try to optimize &x[0] + C where C is a multiple of the size
627 of the elements in X into &x[C/element size]. */
628 if (TREE_OPERAND (rhs, 0) == name
629 && TREE_CODE (TREE_OPERAND (rhs, 1)) == INTEGER_CST)
631 tree orig = unshare_expr (rhs);
632 TREE_OPERAND (rhs, 0) = unshare_expr (def_rhs);
634 /* If folding succeeds, then we have just exposed new variables
635 in USE_STMT which will need to be renamed. If folding fails,
636 then we need to put everything back the way it was. */
637 if (fold_stmt_inplace (use_stmt))
639 tidy_after_forward_propagate_addr (use_stmt);
644 GIMPLE_STMT_OPERAND (use_stmt, 1) = orig;
645 update_stmt (use_stmt);
650 /* Try to optimize &x[0] + OFFSET where OFFSET is defined by
651 converting a multiplication of an index by the size of the
652 array elements, then the result is converted into the proper
653 type for the arithmetic. */
654 if (TREE_OPERAND (rhs, 0) == name
655 && TREE_CODE (TREE_OPERAND (rhs, 1)) == SSA_NAME
656 /* Avoid problems with IVopts creating PLUS_EXPRs with a
657 different type than their operands. */
658 && lang_hooks.types_compatible_p (TREE_TYPE (name), TREE_TYPE (rhs)))
661 tree offset_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 1));
663 res = forward_propagate_addr_into_variable_array_index (offset_stmt, lhs,
668 /* Same as the previous case, except the operands of the PLUS_EXPR
670 if (TREE_OPERAND (rhs, 1) == name
671 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
672 /* Avoid problems with IVopts creating PLUS_EXPRs with a
673 different type than their operands. */
674 && lang_hooks.types_compatible_p (TREE_TYPE (name), TREE_TYPE (rhs)))
677 tree offset_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
678 res = forward_propagate_addr_into_variable_array_index (offset_stmt, lhs,
685 /* STMT is a statement of the form SSA_NAME = ADDR_EXPR <whatever>.
687 Try to forward propagate the ADDR_EXPR into all uses of the SSA_NAME.
688 Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
689 node or for recovery of array indexing from pointer arithmetic.
690 Returns true, if all uses have been propagated into. */
693 forward_propagate_addr_expr (tree name, tree rhs)
695 int stmt_loop_depth = bb_for_stmt (SSA_NAME_DEF_STMT (name))->loop_depth;
696 imm_use_iterator iter;
700 FOR_EACH_IMM_USE_STMT (use_stmt, iter, name)
704 /* If the use is not in a simple assignment statement, then
705 there is nothing we can do. */
706 if (TREE_CODE (use_stmt) != GIMPLE_MODIFY_STMT)
712 /* If the use is in a deeper loop nest, then we do not want
713 to propagate the ADDR_EXPR into the loop as that is likely
714 adding expression evaluations into the loop. */
715 if (bb_for_stmt (use_stmt)->loop_depth > stmt_loop_depth)
721 push_stmt_changes (&use_stmt);
723 result = forward_propagate_addr_expr_1 (name, rhs, use_stmt);
726 pop_stmt_changes (&use_stmt);
728 /* Remove intermediate now unused copy and conversion chains. */
730 && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME
731 && (TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == SSA_NAME
732 || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == NOP_EXPR
733 || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == CONVERT_EXPR))
735 block_stmt_iterator bsi = bsi_for_stmt (use_stmt);
736 release_defs (use_stmt);
737 bsi_remove (&bsi, true);
744 /* Forward propagate the comparison COND defined in STMT like
745 cond_1 = x CMP y to uses of the form
749 Returns true if stmt is now unused. */
752 forward_propagate_comparison (tree cond, tree stmt)
754 tree name = GIMPLE_STMT_OPERAND (stmt, 0);
755 tree use_stmt, tmp = NULL_TREE;
757 /* Don't propagate ssa names that occur in abnormal phis. */
758 if ((TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME
759 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (cond, 0)))
760 || (TREE_CODE (TREE_OPERAND (cond, 1)) == SSA_NAME
761 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (cond, 1))))
764 /* Do not un-cse comparisons. But propagate through copies. */
765 use_stmt = get_prop_dest_stmt (name, &name);
766 if (use_stmt == NULL_TREE)
769 /* Conversion of the condition result to another integral type. */
770 if (TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
771 && (TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == CONVERT_EXPR
772 || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == NOP_EXPR
773 || COMPARISON_CLASS_P (GIMPLE_STMT_OPERAND (use_stmt, 1))
774 || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == TRUTH_NOT_EXPR)
775 && INTEGRAL_TYPE_P (TREE_TYPE (GIMPLE_STMT_OPERAND (use_stmt, 0))))
777 tree lhs = GIMPLE_STMT_OPERAND (use_stmt, 0);
778 tree rhs = GIMPLE_STMT_OPERAND (use_stmt, 1);
780 /* We can propagate the condition into a conversion. */
781 if (TREE_CODE (rhs) == CONVERT_EXPR
782 || TREE_CODE (rhs) == NOP_EXPR)
784 /* Avoid using fold here as that may create a COND_EXPR with
785 non-boolean condition as canonical form. */
786 tmp = build2 (TREE_CODE (cond), TREE_TYPE (lhs),
787 TREE_OPERAND (cond, 0), TREE_OPERAND (cond, 1));
789 /* We can propagate the condition into X op CST where op
790 is EQ_EXRP or NE_EXPR and CST is either one or zero. */
791 else if (COMPARISON_CLASS_P (rhs)
792 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
793 && TREE_CODE (TREE_OPERAND (rhs, 1)) == INTEGER_CST)
795 enum tree_code code = TREE_CODE (rhs);
796 tree cst = TREE_OPERAND (rhs, 1);
798 tmp = combine_cond_expr_cond (code, TREE_TYPE (lhs),
799 fold_convert (TREE_TYPE (cst), cond),
801 if (tmp == NULL_TREE)
804 /* We can propagate the condition into a statement that
805 computes the logical negation of the comparison result. */
806 else if (TREE_CODE (rhs) == TRUTH_NOT_EXPR)
808 tree type = TREE_TYPE (TREE_OPERAND (cond, 0));
809 bool nans = HONOR_NANS (TYPE_MODE (type));
811 code = invert_tree_comparison (TREE_CODE (cond), nans);
812 if (code == ERROR_MARK)
815 tmp = build2 (code, TREE_TYPE (lhs), TREE_OPERAND (cond, 0),
816 TREE_OPERAND (cond, 1));
821 GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (tmp);
822 update_stmt (use_stmt);
824 /* Remove defining statements. */
825 remove_prop_source_from_use (name, stmt);
827 if (dump_file && (dump_flags & TDF_DETAILS))
829 fprintf (dump_file, " Replaced '");
830 print_generic_expr (dump_file, rhs, dump_flags);
831 fprintf (dump_file, "' with '");
832 print_generic_expr (dump_file, tmp, dump_flags);
833 fprintf (dump_file, "'\n");
842 /* If we have lhs = ~x (STMT), look and see if earlier we had x = ~y.
843 If so, we can change STMT into lhs = y which can later be copy
844 propagated. Similarly for negation.
846 This could trivially be formulated as a forward propagation
847 to immediate uses. However, we already had an implementation
848 from DOM which used backward propagation via the use-def links.
850 It turns out that backward propagation is actually faster as
851 there's less work to do for each NOT/NEG expression we find.
852 Backwards propagation needs to look at the statement in a single
853 backlink. Forward propagation needs to look at potentially more
854 than one forward link. */
857 simplify_not_neg_expr (tree stmt)
859 tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
860 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
862 /* See if the RHS_DEF_STMT has the same form as our statement. */
863 if (TREE_CODE (rhs_def_stmt) == GIMPLE_MODIFY_STMT
864 && TREE_CODE (GIMPLE_STMT_OPERAND (rhs_def_stmt, 1)) == TREE_CODE (rhs))
866 tree rhs_def_operand =
867 TREE_OPERAND (GIMPLE_STMT_OPERAND (rhs_def_stmt, 1), 0);
869 /* Verify that RHS_DEF_OPERAND is a suitable SSA_NAME. */
870 if (TREE_CODE (rhs_def_operand) == SSA_NAME
871 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))
873 GIMPLE_STMT_OPERAND (stmt, 1) = rhs_def_operand;
879 /* STMT is a SWITCH_EXPR for which we attempt to find equivalent forms of
880 the condition which we may be able to optimize better. */
883 simplify_switch_expr (tree stmt)
885 tree cond = SWITCH_COND (stmt);
888 /* The optimization that we really care about is removing unnecessary
889 casts. That will let us do much better in propagating the inferred
890 constant at the switch target. */
891 if (TREE_CODE (cond) == SSA_NAME)
893 def = SSA_NAME_DEF_STMT (cond);
894 if (TREE_CODE (def) == GIMPLE_MODIFY_STMT)
896 def = GIMPLE_STMT_OPERAND (def, 1);
897 if (TREE_CODE (def) == NOP_EXPR)
902 def = TREE_OPERAND (def, 0);
904 #ifdef ENABLE_CHECKING
905 /* ??? Why was Jeff testing this? We are gimple... */
906 gcc_assert (is_gimple_val (def));
909 to = TREE_TYPE (cond);
910 ti = TREE_TYPE (def);
912 /* If we have an extension that preserves value, then we
913 can copy the source value into the switch. */
915 need_precision = TYPE_PRECISION (ti);
917 if (! INTEGRAL_TYPE_P (ti))
919 else if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
921 else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
923 if (TYPE_PRECISION (to) < need_precision)
928 SWITCH_COND (stmt) = def;
936 /* Main entry point for the forward propagation optimizer. */
939 tree_ssa_forward_propagate_single_use_vars (void)
942 unsigned int todoflags = 0;
948 block_stmt_iterator bsi;
950 /* Note we update BSI within the loop as necessary. */
951 for (bsi = bsi_start (bb); !bsi_end_p (bsi); )
953 tree stmt = bsi_stmt (bsi);
955 /* If this statement sets an SSA_NAME to an address,
956 try to propagate the address into the uses of the SSA_NAME. */
957 if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
959 tree lhs = GIMPLE_STMT_OPERAND (stmt, 0);
960 tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
963 if (TREE_CODE (lhs) != SSA_NAME)
969 if (TREE_CODE (rhs) == ADDR_EXPR)
971 if (forward_propagate_addr_expr (lhs, rhs))
974 todoflags |= TODO_remove_unused_locals;
975 bsi_remove (&bsi, true);
980 else if ((TREE_CODE (rhs) == BIT_NOT_EXPR
981 || TREE_CODE (rhs) == NEGATE_EXPR)
982 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
984 simplify_not_neg_expr (stmt);
987 else if (TREE_CODE (rhs) == COND_EXPR)
989 forward_propagate_into_cond (rhs, stmt);
992 else if (COMPARISON_CLASS_P (rhs))
994 if (forward_propagate_comparison (rhs, stmt))
997 todoflags |= TODO_remove_unused_locals;
998 bsi_remove (&bsi, true);
1006 else if (TREE_CODE (stmt) == SWITCH_EXPR)
1008 simplify_switch_expr (stmt);
1011 else if (TREE_CODE (stmt) == COND_EXPR)
1013 forward_propagate_into_cond (stmt, stmt);
1022 todoflags |= TODO_cleanup_cfg;
1028 gate_forwprop (void)
1033 struct tree_opt_pass pass_forwprop = {
1034 "forwprop", /* name */
1035 gate_forwprop, /* gate */
1036 tree_ssa_forward_propagate_single_use_vars, /* execute */
1039 0, /* static_pass_number */
1040 TV_TREE_FORWPROP, /* tv_id */
1041 PROP_cfg | PROP_ssa, /* properties_required */
1042 0, /* properties_provided */
1043 0, /* properties_destroyed */
1044 0, /* todo_flags_start */
1048 | TODO_verify_ssa, /* todo_flags_finish */
1053 /* Structure to keep track of the value of a dereferenced PHI result
1054 and the set of virtual operands used for that dereference. */
1062 /* Verify if the value recorded for NAME in PHIVN is still valid at
1063 the start of basic block BB. */
1066 phivn_valid_p (struct phiprop_d *phivn, tree name, basic_block bb)
1068 tree vop_stmt = phivn[SSA_NAME_VERSION (name)].vop_stmt;
1072 /* The def stmts of all virtual uses need to be post-dominated
1074 FOR_EACH_SSA_TREE_OPERAND (vuse, vop_stmt, ui, SSA_OP_VUSE)
1077 imm_use_iterator ui2;
1080 FOR_EACH_IMM_USE_STMT (use_stmt, ui2, vuse)
1082 /* If BB does not dominate a VDEF, the value is invalid. */
1083 if (((TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
1084 && !ZERO_SSA_OPERANDS (use_stmt, SSA_OP_VDEF))
1085 || TREE_CODE (use_stmt) == PHI_NODE)
1086 && !dominated_by_p (CDI_DOMINATORS, bb_for_stmt (use_stmt), bb))
1089 BREAK_FROM_IMM_USE_STMT (ui2);
1099 /* Insert a new phi node for the dereference of PHI at basic_block
1100 BB with the virtual operands from USE_STMT. */
1103 phiprop_insert_phi (basic_block bb, tree phi, tree use_stmt,
1104 struct phiprop_d *phivn, size_t n)
1110 /* Build a new PHI node to replace the definition of
1111 the indirect reference lhs. */
1112 res = GIMPLE_STMT_OPERAND (use_stmt, 0);
1113 SSA_NAME_DEF_STMT (res) = new_phi = create_phi_node (res, bb);
1115 /* Add PHI arguments for each edge inserting loads of the
1116 addressable operands. */
1117 FOR_EACH_EDGE (e, ei, bb->preds)
1119 tree old_arg, new_var, tmp;
1121 old_arg = PHI_ARG_DEF_FROM_EDGE (phi, e);
1122 while (TREE_CODE (old_arg) == SSA_NAME
1123 && (SSA_NAME_VERSION (old_arg) >= n
1124 || phivn[SSA_NAME_VERSION (old_arg)].value == NULL_TREE))
1126 tree def_stmt = SSA_NAME_DEF_STMT (old_arg);
1127 old_arg = GIMPLE_STMT_OPERAND (def_stmt, 1);
1130 if (TREE_CODE (old_arg) == SSA_NAME)
1131 /* Reuse a formely created dereference. */
1132 new_var = phivn[SSA_NAME_VERSION (old_arg)].value;
1135 old_arg = TREE_OPERAND (old_arg, 0);
1136 new_var = create_tmp_var (TREE_TYPE (old_arg), NULL);
1137 tmp = build2 (GIMPLE_MODIFY_STMT, void_type_node,
1138 NULL_TREE, unshare_expr (old_arg));
1139 if (TREE_CODE (TREE_TYPE (old_arg)) == COMPLEX_TYPE
1140 || TREE_CODE (TREE_TYPE (old_arg)) == VECTOR_TYPE)
1141 DECL_GIMPLE_REG_P (new_var) = 1;
1142 add_referenced_var (new_var);
1143 new_var = make_ssa_name (new_var, tmp);
1144 GIMPLE_STMT_OPERAND (tmp, 0) = new_var;
1146 bsi_insert_on_edge (e, tmp);
1149 mark_symbols_for_renaming (tmp);
1152 add_phi_arg (new_phi, new_var, e);
1155 update_stmt (new_phi);
1160 /* Propagate between the phi node arguments of PHI in BB and phi result
1161 users. For now this matches
1162 # p_2 = PHI <&x, &y>
1169 Returns true if a transformation was done and edge insertions
1170 need to be committed. Global data PHIVN and N is used to track
1171 past transformation results. We need to be especially careful here
1172 with aliasing issues as we are moving memory reads. */
1175 propagate_with_phi (basic_block bb, tree phi, struct phiprop_d *phivn, size_t n)
1177 tree ptr = PHI_RESULT (phi);
1178 tree use_stmt, res = NULL_TREE;
1179 block_stmt_iterator bsi;
1180 imm_use_iterator ui;
1181 use_operand_p arg_p, use;
1185 if (MTAG_P (SSA_NAME_VAR (ptr))
1186 || !POINTER_TYPE_P (TREE_TYPE (ptr))
1187 || !is_gimple_reg_type (TREE_TYPE (TREE_TYPE (ptr))))
1190 /* Check if we can "cheaply" dereference all phi arguments. */
1191 FOR_EACH_PHI_ARG (arg_p, phi, i, SSA_OP_USE)
1193 tree arg = USE_FROM_PTR (arg_p);
1194 /* Walk the ssa chain until we reach a ssa name we already
1195 created a value for or we reach a definition of the form
1196 ssa_name_n = &var; */
1197 while (TREE_CODE (arg) == SSA_NAME
1198 && !SSA_NAME_IS_DEFAULT_DEF (arg)
1199 && (SSA_NAME_VERSION (arg) >= n
1200 || phivn[SSA_NAME_VERSION (arg)].value == NULL_TREE))
1202 tree def_stmt = SSA_NAME_DEF_STMT (arg);
1203 if (TREE_CODE (def_stmt) != GIMPLE_MODIFY_STMT)
1205 arg = GIMPLE_STMT_OPERAND (def_stmt, 1);
1207 if ((TREE_CODE (arg) != ADDR_EXPR
1208 /* Avoid to have to decay *&a to a[0] later. */
1209 || !is_gimple_reg_type (TREE_TYPE (TREE_OPERAND (arg, 0))))
1210 && !(TREE_CODE (arg) == SSA_NAME
1211 && phivn[SSA_NAME_VERSION (arg)].value != NULL_TREE
1212 && phivn_valid_p (phivn, arg, bb)))
1216 /* Find a dereferencing use. First follow (single use) ssa
1217 copy chains for ptr. */
1218 while (single_imm_use (ptr, &use, &use_stmt)
1219 && TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
1220 && GIMPLE_STMT_OPERAND (use_stmt, 1) == ptr
1221 && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME)
1222 ptr = GIMPLE_STMT_OPERAND (use_stmt, 0);
1224 /* Replace the first dereference of *ptr if there is one and if we
1225 can move the loads to the place of the ptr phi node. */
1226 phi_inserted = false;
1227 FOR_EACH_IMM_USE_STMT (use_stmt, ui, ptr)
1232 /* Check whether this is a load of *ptr. */
1233 if (!(TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
1234 && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME
1235 && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == INDIRECT_REF
1236 && TREE_OPERAND (GIMPLE_STMT_OPERAND (use_stmt, 1), 0) == ptr
1237 /* We cannot replace a load that may throw or is volatile. */
1238 && !tree_can_throw_internal (use_stmt)))
1241 /* Check if we can move the loads. The def stmts of all virtual uses
1242 need to be post-dominated by bb. */
1243 FOR_EACH_SSA_TREE_OPERAND (vuse, use_stmt, ui2, SSA_OP_VUSE)
1245 tree def_stmt = SSA_NAME_DEF_STMT (vuse);
1246 if (!SSA_NAME_IS_DEFAULT_DEF (vuse)
1247 && (bb_for_stmt (def_stmt) == bb
1248 || !dominated_by_p (CDI_DOMINATORS,
1249 bb, bb_for_stmt (def_stmt))))
1253 /* Found a proper dereference. Insert a phi node if this
1254 is the first load transformation. */
1257 res = phiprop_insert_phi (bb, phi, use_stmt, phivn, n);
1259 /* Remember the value we created for *ptr. */
1260 phivn[SSA_NAME_VERSION (ptr)].value = res;
1261 phivn[SSA_NAME_VERSION (ptr)].vop_stmt = use_stmt;
1263 /* Remove old stmt. The phi is taken care of by DCE, if we
1264 want to delete it here we also have to delete all intermediate
1266 bsi = bsi_for_stmt (use_stmt);
1267 bsi_remove (&bsi, 0);
1269 phi_inserted = true;
1273 /* Further replacements are easy, just make a copy out of the
1275 GIMPLE_STMT_OPERAND (use_stmt, 1) = res;
1276 update_stmt (use_stmt);
1280 /* Continue searching for a proper dereference. */
1283 return phi_inserted;
1286 /* Helper walking the dominator tree starting from BB and processing
1287 phi nodes with global data PHIVN and N. */
1290 tree_ssa_phiprop_1 (basic_block bb, struct phiprop_d *phivn, size_t n)
1292 bool did_something = false;
1296 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1297 did_something |= propagate_with_phi (bb, phi, phivn, n);
1299 for (son = first_dom_son (CDI_DOMINATORS, bb);
1301 son = next_dom_son (CDI_DOMINATORS, son))
1302 did_something |= tree_ssa_phiprop_1 (son, phivn, n);
1304 return did_something;
1307 /* Main entry for phiprop pass. */
1310 tree_ssa_phiprop (void)
1312 struct phiprop_d *phivn;
1314 calculate_dominance_info (CDI_DOMINATORS);
1316 phivn = XCNEWVEC (struct phiprop_d, num_ssa_names);
1318 if (tree_ssa_phiprop_1 (ENTRY_BLOCK_PTR, phivn, num_ssa_names))
1319 bsi_commit_edge_inserts ();
1332 struct tree_opt_pass pass_phiprop = {
1333 "phiprop", /* name */
1334 gate_phiprop, /* gate */
1335 tree_ssa_phiprop, /* execute */
1338 0, /* static_pass_number */
1339 TV_TREE_FORWPROP, /* tv_id */
1340 PROP_cfg | PROP_ssa, /* properties_required */
1341 0, /* properties_provided */
1342 0, /* properties_destroyed */
1343 0, /* todo_flags_start */
1347 | TODO_verify_ssa, /* todo_flags_finish */