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.
374 Returns zero if no statement was changed, one if there were
375 changes and two if cfg_cleanup needs to run. */
378 forward_propagate_into_cond (tree cond_expr, tree stmt)
380 int did_something = 0;
383 tree tmp = NULL_TREE;
384 tree cond = COND_EXPR_COND (cond_expr);
385 tree name, def_stmt, rhs;
388 /* We can do tree combining on SSA_NAME and comparison expressions. */
389 if (COMPARISON_CLASS_P (cond)
390 && TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME)
392 /* For comparisons use the first operand, that is likely to
393 simplify comparisons against constants. */
394 name = TREE_OPERAND (cond, 0);
395 def_stmt = get_prop_source_stmt (name, false, &single_use_p);
396 if (def_stmt != NULL_TREE
397 && can_propagate_from (def_stmt))
399 tree op1 = TREE_OPERAND (cond, 1);
400 rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
401 tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
402 fold_convert (TREE_TYPE (op1), rhs),
405 /* If that wasn't successful, try the second operand. */
407 && TREE_CODE (TREE_OPERAND (cond, 1)) == SSA_NAME)
409 tree op0 = TREE_OPERAND (cond, 0);
410 name = TREE_OPERAND (cond, 1);
411 def_stmt = get_prop_source_stmt (name, false, &single_use_p);
412 if (def_stmt == NULL_TREE
413 || !can_propagate_from (def_stmt))
414 return did_something;
416 rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
417 tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
419 fold_convert (TREE_TYPE (op0), rhs),
423 else if (TREE_CODE (cond) == SSA_NAME)
426 def_stmt = get_prop_source_stmt (name, true, NULL);
427 if (def_stmt == NULL_TREE
428 || !can_propagate_from (def_stmt))
429 return did_something;
431 rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
432 tmp = combine_cond_expr_cond (NE_EXPR, boolean_type_node, rhs,
433 build_int_cst (TREE_TYPE (rhs), 0),
439 if (dump_file && tmp)
441 fprintf (dump_file, " Replaced '");
442 print_generic_expr (dump_file, cond, 0);
443 fprintf (dump_file, "' with '");
444 print_generic_expr (dump_file, tmp, 0);
445 fprintf (dump_file, "'\n");
448 COND_EXPR_COND (cond_expr) = unshare_expr (tmp);
451 /* Remove defining statements. */
452 remove_prop_source_from_use (name, NULL);
454 if (is_gimple_min_invariant (tmp))
456 else if (did_something == 0)
459 /* Continue combining. */
466 return did_something;
469 /* We've just substituted an ADDR_EXPR into stmt. Update all the
470 relevant data structures to match. */
473 tidy_after_forward_propagate_addr (tree stmt)
475 /* We may have turned a trapping insn into a non-trapping insn. */
476 if (maybe_clean_or_replace_eh_stmt (stmt, stmt)
477 && tree_purge_dead_eh_edges (bb_for_stmt (stmt)))
480 if (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == ADDR_EXPR)
481 recompute_tree_invariant_for_addr_expr (GIMPLE_STMT_OPERAND (stmt, 1));
483 mark_symbols_for_renaming (stmt);
486 /* DEF_RHS contains the address of the 0th element in an array.
487 USE_STMT uses type of DEF_RHS to compute the address of an
488 arbitrary element within the array. The (variable) byte offset
489 of the element is contained in OFFSET.
491 We walk back through the use-def chains of OFFSET to verify that
492 it is indeed computing the offset of an element within the array
493 and extract the index corresponding to the given byte offset.
495 We then try to fold the entire address expression into a form
498 If we are successful, we replace the right hand side of USE_STMT
499 with the new address computation. */
502 forward_propagate_addr_into_variable_array_index (tree offset,
503 tree def_rhs, tree use_stmt)
507 /* The offset must be defined by a simple GIMPLE_MODIFY_STMT statement. */
508 if (TREE_CODE (offset) != GIMPLE_MODIFY_STMT)
511 /* The RHS of the statement which defines OFFSET must be a gimple
512 cast of another SSA_NAME. */
513 offset = GIMPLE_STMT_OPERAND (offset, 1);
514 if (!is_gimple_cast (offset))
517 offset = TREE_OPERAND (offset, 0);
518 if (TREE_CODE (offset) != SSA_NAME)
521 /* Try to find an expression for a proper index. This is either
522 a multiplication expression by the element size or just the
523 ssa name we came along in case the element size is one. */
524 if (integer_onep (TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs)))))
528 offset = SSA_NAME_DEF_STMT (offset);
530 /* The RHS of the statement which defines OFFSET must be a
531 multiplication of an object by the size of the array elements. */
532 if (TREE_CODE (offset) != GIMPLE_MODIFY_STMT)
535 offset = GIMPLE_STMT_OPERAND (offset, 1);
536 if (TREE_CODE (offset) != MULT_EXPR
537 || TREE_CODE (TREE_OPERAND (offset, 1)) != INTEGER_CST
538 || !simple_cst_equal (TREE_OPERAND (offset, 1),
539 TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs)))))
542 /* The first operand to the MULT_EXPR is the desired index. */
543 index = TREE_OPERAND (offset, 0);
546 /* Replace the pointer addition with array indexing. */
547 GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (def_rhs);
548 TREE_OPERAND (TREE_OPERAND (GIMPLE_STMT_OPERAND (use_stmt, 1), 0), 1)
551 /* That should have created gimple, so there is no need to
552 record information to undo the propagation. */
553 fold_stmt_inplace (use_stmt);
554 tidy_after_forward_propagate_addr (use_stmt);
558 /* NAME is a SSA_NAME representing DEF_RHS which is of the form
559 ADDR_EXPR <whatever>.
561 Try to forward propagate the ADDR_EXPR into the use USE_STMT.
562 Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
563 node or for recovery of array indexing from pointer arithmetic.
565 Return true if the propagation was successful (the propagation can
566 be not totally successful, yet things may have been changed). */
569 forward_propagate_addr_expr_1 (tree name, tree def_rhs, tree use_stmt,
572 tree lhs, rhs, array_ref;
574 /* Strip away any outer COMPONENT_REF/ARRAY_REF nodes from the LHS.
575 ADDR_EXPR will not appear on the LHS. */
576 lhs = GIMPLE_STMT_OPERAND (use_stmt, 0);
577 while (handled_component_p (lhs))
578 lhs = TREE_OPERAND (lhs, 0);
580 rhs = GIMPLE_STMT_OPERAND (use_stmt, 1);
582 /* Now see if the LHS node is an INDIRECT_REF using NAME. If so,
583 propagate the ADDR_EXPR into the use of NAME and fold the result. */
584 if (TREE_CODE (lhs) == INDIRECT_REF && TREE_OPERAND (lhs, 0) == name)
586 /* This should always succeed in creating gimple, so there is
587 no need to save enough state to undo this propagation. */
588 TREE_OPERAND (lhs, 0) = unshare_expr (def_rhs);
589 fold_stmt_inplace (use_stmt);
590 tidy_after_forward_propagate_addr (use_stmt);
592 /* Continue propagating into the RHS. */
595 /* Trivial cases. The use statement could be a trivial copy or a
596 useless conversion. Recurse to the uses of the lhs as copyprop does
597 not copy through differen variant pointers and FRE does not catch
598 all useless conversions. Treat the case of a single-use name and
599 a conversion to def_rhs type separate, though. */
600 else if (TREE_CODE (lhs) == SSA_NAME
601 && (TREE_CODE (rhs) == NOP_EXPR
602 || TREE_CODE (rhs) == CONVERT_EXPR)
603 && TREE_TYPE (rhs) == TREE_TYPE (def_rhs)
606 GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (def_rhs);
609 else if ((TREE_CODE (lhs) == SSA_NAME
611 || ((TREE_CODE (rhs) == NOP_EXPR
612 || TREE_CODE (rhs) == CONVERT_EXPR)
613 && tree_ssa_useless_type_conversion_1 (TREE_TYPE (rhs),
614 TREE_TYPE (def_rhs))))
615 return forward_propagate_addr_expr (lhs, def_rhs);
617 /* Strip away any outer COMPONENT_REF, ARRAY_REF or ADDR_EXPR
618 nodes from the RHS. */
619 while (handled_component_p (rhs)
620 || TREE_CODE (rhs) == ADDR_EXPR)
621 rhs = TREE_OPERAND (rhs, 0);
623 /* Now see if the RHS node is an INDIRECT_REF using NAME. If so,
624 propagate the ADDR_EXPR into the use of NAME and fold the result. */
625 if (TREE_CODE (rhs) == INDIRECT_REF && TREE_OPERAND (rhs, 0) == name)
627 /* This should always succeed in creating gimple, so there is
628 no need to save enough state to undo this propagation. */
629 TREE_OPERAND (rhs, 0) = unshare_expr (def_rhs);
630 fold_stmt_inplace (use_stmt);
631 tidy_after_forward_propagate_addr (use_stmt);
635 /* The remaining cases are all for turning pointer arithmetic into
636 array indexing. They only apply when we have the address of
637 element zero in an array. If that is not the case then there
639 array_ref = TREE_OPERAND (def_rhs, 0);
640 if (TREE_CODE (array_ref) != ARRAY_REF
641 || TREE_CODE (TREE_TYPE (TREE_OPERAND (array_ref, 0))) != ARRAY_TYPE
642 || !integer_zerop (TREE_OPERAND (array_ref, 1)))
645 /* If the use of the ADDR_EXPR must be a PLUS_EXPR, or else there
647 if (TREE_CODE (rhs) != PLUS_EXPR)
650 /* Try to optimize &x[0] + C where C is a multiple of the size
651 of the elements in X into &x[C/element size]. */
652 if (TREE_OPERAND (rhs, 0) == name
653 && TREE_CODE (TREE_OPERAND (rhs, 1)) == INTEGER_CST)
655 tree orig = unshare_expr (rhs);
656 TREE_OPERAND (rhs, 0) = unshare_expr (def_rhs);
658 /* If folding succeeds, then we have just exposed new variables
659 in USE_STMT which will need to be renamed. If folding fails,
660 then we need to put everything back the way it was. */
661 if (fold_stmt_inplace (use_stmt))
663 tidy_after_forward_propagate_addr (use_stmt);
668 GIMPLE_STMT_OPERAND (use_stmt, 1) = orig;
669 update_stmt (use_stmt);
674 /* Try to optimize &x[0] + OFFSET where OFFSET is defined by
675 converting a multiplication of an index by the size of the
676 array elements, then the result is converted into the proper
677 type for the arithmetic. */
678 if (TREE_OPERAND (rhs, 0) == name
679 && TREE_CODE (TREE_OPERAND (rhs, 1)) == SSA_NAME
680 /* Avoid problems with IVopts creating PLUS_EXPRs with a
681 different type than their operands. */
682 && lang_hooks.types_compatible_p (TREE_TYPE (name), TREE_TYPE (rhs)))
685 tree offset_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 1));
687 res = forward_propagate_addr_into_variable_array_index (offset_stmt,
692 /* Same as the previous case, except the operands of the PLUS_EXPR
694 if (TREE_OPERAND (rhs, 1) == name
695 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
696 /* Avoid problems with IVopts creating PLUS_EXPRs with a
697 different type than their operands. */
698 && lang_hooks.types_compatible_p (TREE_TYPE (name), TREE_TYPE (rhs)))
701 tree offset_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
702 res = forward_propagate_addr_into_variable_array_index (offset_stmt,
709 /* STMT is a statement of the form SSA_NAME = ADDR_EXPR <whatever>.
711 Try to forward propagate the ADDR_EXPR into all uses of the SSA_NAME.
712 Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
713 node or for recovery of array indexing from pointer arithmetic.
714 Returns true, if all uses have been propagated into. */
717 forward_propagate_addr_expr (tree name, tree rhs)
719 int stmt_loop_depth = bb_for_stmt (SSA_NAME_DEF_STMT (name))->loop_depth;
720 imm_use_iterator iter;
723 bool single_use_p = has_single_use (name);
725 FOR_EACH_IMM_USE_STMT (use_stmt, iter, name)
729 /* If the use is not in a simple assignment statement, then
730 there is nothing we can do. */
731 if (TREE_CODE (use_stmt) != GIMPLE_MODIFY_STMT)
737 /* If the use is in a deeper loop nest, then we do not want
738 to propagate the ADDR_EXPR into the loop as that is likely
739 adding expression evaluations into the loop. */
740 if (bb_for_stmt (use_stmt)->loop_depth > stmt_loop_depth)
746 /* If the use_stmt has side-effects, don't propagate into it. */
747 if (stmt_ann (use_stmt)->has_volatile_ops)
753 push_stmt_changes (&use_stmt);
755 result = forward_propagate_addr_expr_1 (name, rhs, use_stmt,
759 pop_stmt_changes (&use_stmt);
761 /* Remove intermediate now unused copy and conversion chains. */
763 && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME
764 && (TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == SSA_NAME
765 || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == NOP_EXPR
766 || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == CONVERT_EXPR))
768 block_stmt_iterator bsi = bsi_for_stmt (use_stmt);
769 release_defs (use_stmt);
770 bsi_remove (&bsi, true);
777 /* Forward propagate the comparison COND defined in STMT like
778 cond_1 = x CMP y to uses of the form
782 Returns true if stmt is now unused. */
785 forward_propagate_comparison (tree cond, tree stmt)
787 tree name = GIMPLE_STMT_OPERAND (stmt, 0);
788 tree use_stmt, tmp = NULL_TREE;
790 /* Don't propagate ssa names that occur in abnormal phis. */
791 if ((TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME
792 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (cond, 0)))
793 || (TREE_CODE (TREE_OPERAND (cond, 1)) == SSA_NAME
794 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (cond, 1))))
797 /* Do not un-cse comparisons. But propagate through copies. */
798 use_stmt = get_prop_dest_stmt (name, &name);
799 if (use_stmt == NULL_TREE)
802 /* Conversion of the condition result to another integral type. */
803 if (TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
804 && (TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == CONVERT_EXPR
805 || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == NOP_EXPR
806 || COMPARISON_CLASS_P (GIMPLE_STMT_OPERAND (use_stmt, 1))
807 || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == TRUTH_NOT_EXPR)
808 && INTEGRAL_TYPE_P (TREE_TYPE (GIMPLE_STMT_OPERAND (use_stmt, 0))))
810 tree lhs = GIMPLE_STMT_OPERAND (use_stmt, 0);
811 tree rhs = GIMPLE_STMT_OPERAND (use_stmt, 1);
813 /* We can propagate the condition into a conversion. */
814 if (TREE_CODE (rhs) == CONVERT_EXPR
815 || TREE_CODE (rhs) == NOP_EXPR)
817 /* Avoid using fold here as that may create a COND_EXPR with
818 non-boolean condition as canonical form. */
819 tmp = build2 (TREE_CODE (cond), TREE_TYPE (lhs),
820 TREE_OPERAND (cond, 0), TREE_OPERAND (cond, 1));
822 /* We can propagate the condition into X op CST where op
823 is EQ_EXRP or NE_EXPR and CST is either one or zero. */
824 else if (COMPARISON_CLASS_P (rhs)
825 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
826 && TREE_CODE (TREE_OPERAND (rhs, 1)) == INTEGER_CST)
828 enum tree_code code = TREE_CODE (rhs);
829 tree cst = TREE_OPERAND (rhs, 1);
831 tmp = combine_cond_expr_cond (code, TREE_TYPE (lhs),
832 fold_convert (TREE_TYPE (cst), cond),
834 if (tmp == NULL_TREE)
837 /* We can propagate the condition into a statement that
838 computes the logical negation of the comparison result. */
839 else if (TREE_CODE (rhs) == TRUTH_NOT_EXPR)
841 tree type = TREE_TYPE (TREE_OPERAND (cond, 0));
842 bool nans = HONOR_NANS (TYPE_MODE (type));
844 code = invert_tree_comparison (TREE_CODE (cond), nans);
845 if (code == ERROR_MARK)
848 tmp = build2 (code, TREE_TYPE (lhs), TREE_OPERAND (cond, 0),
849 TREE_OPERAND (cond, 1));
854 GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (tmp);
855 update_stmt (use_stmt);
857 /* Remove defining statements. */
858 remove_prop_source_from_use (name, stmt);
860 if (dump_file && (dump_flags & TDF_DETAILS))
862 fprintf (dump_file, " Replaced '");
863 print_generic_expr (dump_file, rhs, dump_flags);
864 fprintf (dump_file, "' with '");
865 print_generic_expr (dump_file, tmp, dump_flags);
866 fprintf (dump_file, "'\n");
875 /* If we have lhs = ~x (STMT), look and see if earlier we had x = ~y.
876 If so, we can change STMT into lhs = y which can later be copy
877 propagated. Similarly for negation.
879 This could trivially be formulated as a forward propagation
880 to immediate uses. However, we already had an implementation
881 from DOM which used backward propagation via the use-def links.
883 It turns out that backward propagation is actually faster as
884 there's less work to do for each NOT/NEG expression we find.
885 Backwards propagation needs to look at the statement in a single
886 backlink. Forward propagation needs to look at potentially more
887 than one forward link. */
890 simplify_not_neg_expr (tree stmt)
892 tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
893 tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
895 /* See if the RHS_DEF_STMT has the same form as our statement. */
896 if (TREE_CODE (rhs_def_stmt) == GIMPLE_MODIFY_STMT
897 && TREE_CODE (GIMPLE_STMT_OPERAND (rhs_def_stmt, 1)) == TREE_CODE (rhs))
899 tree rhs_def_operand =
900 TREE_OPERAND (GIMPLE_STMT_OPERAND (rhs_def_stmt, 1), 0);
902 /* Verify that RHS_DEF_OPERAND is a suitable SSA_NAME. */
903 if (TREE_CODE (rhs_def_operand) == SSA_NAME
904 && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))
906 GIMPLE_STMT_OPERAND (stmt, 1) = rhs_def_operand;
912 /* STMT is a SWITCH_EXPR for which we attempt to find equivalent forms of
913 the condition which we may be able to optimize better. */
916 simplify_switch_expr (tree stmt)
918 tree cond = SWITCH_COND (stmt);
921 /* The optimization that we really care about is removing unnecessary
922 casts. That will let us do much better in propagating the inferred
923 constant at the switch target. */
924 if (TREE_CODE (cond) == SSA_NAME)
926 def = SSA_NAME_DEF_STMT (cond);
927 if (TREE_CODE (def) == GIMPLE_MODIFY_STMT)
929 def = GIMPLE_STMT_OPERAND (def, 1);
930 if (TREE_CODE (def) == NOP_EXPR)
935 def = TREE_OPERAND (def, 0);
937 #ifdef ENABLE_CHECKING
938 /* ??? Why was Jeff testing this? We are gimple... */
939 gcc_assert (is_gimple_val (def));
942 to = TREE_TYPE (cond);
943 ti = TREE_TYPE (def);
945 /* If we have an extension that preserves value, then we
946 can copy the source value into the switch. */
948 need_precision = TYPE_PRECISION (ti);
950 if (! INTEGRAL_TYPE_P (ti))
952 else if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
954 else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
956 if (TYPE_PRECISION (to) < need_precision)
961 SWITCH_COND (stmt) = def;
969 /* Main entry point for the forward propagation optimizer. */
972 tree_ssa_forward_propagate_single_use_vars (void)
975 unsigned int todoflags = 0;
981 block_stmt_iterator bsi;
983 /* Note we update BSI within the loop as necessary. */
984 for (bsi = bsi_start (bb); !bsi_end_p (bsi); )
986 tree stmt = bsi_stmt (bsi);
988 /* If this statement sets an SSA_NAME to an address,
989 try to propagate the address into the uses of the SSA_NAME. */
990 if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
992 tree lhs = GIMPLE_STMT_OPERAND (stmt, 0);
993 tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
996 if (TREE_CODE (lhs) != SSA_NAME)
1002 if (TREE_CODE (rhs) == ADDR_EXPR)
1004 if (forward_propagate_addr_expr (lhs, rhs))
1006 release_defs (stmt);
1007 todoflags |= TODO_remove_unused_locals;
1008 bsi_remove (&bsi, true);
1013 else if ((TREE_CODE (rhs) == BIT_NOT_EXPR
1014 || TREE_CODE (rhs) == NEGATE_EXPR)
1015 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
1017 simplify_not_neg_expr (stmt);
1020 else if (TREE_CODE (rhs) == COND_EXPR)
1023 fold_defer_overflow_warnings ();
1024 did_something = forward_propagate_into_cond (rhs, stmt);
1025 if (did_something == 2)
1027 fold_undefer_overflow_warnings (!TREE_NO_WARNING (rhs)
1028 && did_something, stmt, WARN_STRICT_OVERFLOW_CONDITIONAL);
1031 else if (COMPARISON_CLASS_P (rhs))
1033 if (forward_propagate_comparison (rhs, stmt))
1035 release_defs (stmt);
1036 todoflags |= TODO_remove_unused_locals;
1037 bsi_remove (&bsi, true);
1045 else if (TREE_CODE (stmt) == SWITCH_EXPR)
1047 simplify_switch_expr (stmt);
1050 else if (TREE_CODE (stmt) == COND_EXPR)
1053 fold_defer_overflow_warnings ();
1054 did_something = forward_propagate_into_cond (stmt, stmt);
1055 if (did_something == 2)
1057 fold_undefer_overflow_warnings (!TREE_NO_WARNING (stmt)
1058 && did_something, stmt,
1059 WARN_STRICT_OVERFLOW_CONDITIONAL);
1068 todoflags |= TODO_cleanup_cfg;
1074 gate_forwprop (void)
1079 struct tree_opt_pass pass_forwprop = {
1080 "forwprop", /* name */
1081 gate_forwprop, /* gate */
1082 tree_ssa_forward_propagate_single_use_vars, /* execute */
1085 0, /* static_pass_number */
1086 TV_TREE_FORWPROP, /* tv_id */
1087 PROP_cfg | PROP_ssa, /* properties_required */
1088 0, /* properties_provided */
1089 0, /* properties_destroyed */
1090 0, /* todo_flags_start */
1094 | TODO_verify_ssa, /* todo_flags_finish */
1099 /* Structure to keep track of the value of a dereferenced PHI result
1100 and the set of virtual operands used for that dereference. */
1108 /* Verify if the value recorded for NAME in PHIVN is still valid at
1109 the start of basic block BB. */
1112 phivn_valid_p (struct phiprop_d *phivn, tree name, basic_block bb)
1114 tree vop_stmt = phivn[SSA_NAME_VERSION (name)].vop_stmt;
1118 /* The def stmts of all virtual uses need to be post-dominated
1120 FOR_EACH_SSA_TREE_OPERAND (vuse, vop_stmt, ui, SSA_OP_VUSE)
1123 imm_use_iterator ui2;
1126 FOR_EACH_IMM_USE_STMT (use_stmt, ui2, vuse)
1128 /* If BB does not dominate a VDEF, the value is invalid. */
1129 if (((TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
1130 && !ZERO_SSA_OPERANDS (use_stmt, SSA_OP_VDEF))
1131 || TREE_CODE (use_stmt) == PHI_NODE)
1132 && !dominated_by_p (CDI_DOMINATORS, bb_for_stmt (use_stmt), bb))
1135 BREAK_FROM_IMM_USE_STMT (ui2);
1145 /* Insert a new phi node for the dereference of PHI at basic_block
1146 BB with the virtual operands from USE_STMT. */
1149 phiprop_insert_phi (basic_block bb, tree phi, tree use_stmt,
1150 struct phiprop_d *phivn, size_t n)
1156 /* Build a new PHI node to replace the definition of
1157 the indirect reference lhs. */
1158 res = GIMPLE_STMT_OPERAND (use_stmt, 0);
1159 SSA_NAME_DEF_STMT (res) = new_phi = create_phi_node (res, bb);
1161 /* Add PHI arguments for each edge inserting loads of the
1162 addressable operands. */
1163 FOR_EACH_EDGE (e, ei, bb->preds)
1165 tree old_arg, new_var, tmp;
1167 old_arg = PHI_ARG_DEF_FROM_EDGE (phi, e);
1168 while (TREE_CODE (old_arg) == SSA_NAME
1169 && (SSA_NAME_VERSION (old_arg) >= n
1170 || phivn[SSA_NAME_VERSION (old_arg)].value == NULL_TREE))
1172 tree def_stmt = SSA_NAME_DEF_STMT (old_arg);
1173 old_arg = GIMPLE_STMT_OPERAND (def_stmt, 1);
1176 if (TREE_CODE (old_arg) == SSA_NAME)
1177 /* Reuse a formerly created dereference. */
1178 new_var = phivn[SSA_NAME_VERSION (old_arg)].value;
1181 old_arg = TREE_OPERAND (old_arg, 0);
1182 new_var = create_tmp_var (TREE_TYPE (old_arg), NULL);
1183 tmp = build2 (GIMPLE_MODIFY_STMT, void_type_node,
1184 NULL_TREE, unshare_expr (old_arg));
1185 if (TREE_CODE (TREE_TYPE (old_arg)) == COMPLEX_TYPE
1186 || TREE_CODE (TREE_TYPE (old_arg)) == VECTOR_TYPE)
1187 DECL_GIMPLE_REG_P (new_var) = 1;
1188 add_referenced_var (new_var);
1189 new_var = make_ssa_name (new_var, tmp);
1190 GIMPLE_STMT_OPERAND (tmp, 0) = new_var;
1192 bsi_insert_on_edge (e, tmp);
1195 mark_symbols_for_renaming (tmp);
1198 add_phi_arg (new_phi, new_var, e);
1201 update_stmt (new_phi);
1206 /* Propagate between the phi node arguments of PHI in BB and phi result
1207 users. For now this matches
1208 # p_2 = PHI <&x, &y>
1215 Returns true if a transformation was done and edge insertions
1216 need to be committed. Global data PHIVN and N is used to track
1217 past transformation results. We need to be especially careful here
1218 with aliasing issues as we are moving memory reads. */
1221 propagate_with_phi (basic_block bb, tree phi, struct phiprop_d *phivn, size_t n)
1223 tree ptr = PHI_RESULT (phi);
1224 tree use_stmt, res = NULL_TREE;
1225 block_stmt_iterator bsi;
1226 imm_use_iterator ui;
1227 use_operand_p arg_p, use;
1231 if (MTAG_P (SSA_NAME_VAR (ptr))
1232 || !POINTER_TYPE_P (TREE_TYPE (ptr))
1233 || !is_gimple_reg_type (TREE_TYPE (TREE_TYPE (ptr))))
1236 /* Check if we can "cheaply" dereference all phi arguments. */
1237 FOR_EACH_PHI_ARG (arg_p, phi, i, SSA_OP_USE)
1239 tree arg = USE_FROM_PTR (arg_p);
1240 /* Walk the ssa chain until we reach a ssa name we already
1241 created a value for or we reach a definition of the form
1242 ssa_name_n = &var; */
1243 while (TREE_CODE (arg) == SSA_NAME
1244 && !SSA_NAME_IS_DEFAULT_DEF (arg)
1245 && (SSA_NAME_VERSION (arg) >= n
1246 || phivn[SSA_NAME_VERSION (arg)].value == NULL_TREE))
1248 tree def_stmt = SSA_NAME_DEF_STMT (arg);
1249 if (TREE_CODE (def_stmt) != GIMPLE_MODIFY_STMT)
1251 arg = GIMPLE_STMT_OPERAND (def_stmt, 1);
1253 if ((TREE_CODE (arg) != ADDR_EXPR
1254 /* Avoid to have to decay *&a to a[0] later. */
1255 || !is_gimple_reg_type (TREE_TYPE (TREE_OPERAND (arg, 0))))
1256 && !(TREE_CODE (arg) == SSA_NAME
1257 && phivn[SSA_NAME_VERSION (arg)].value != NULL_TREE
1258 && phivn_valid_p (phivn, arg, bb)))
1262 /* Find a dereferencing use. First follow (single use) ssa
1263 copy chains for ptr. */
1264 while (single_imm_use (ptr, &use, &use_stmt)
1265 && TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
1266 && GIMPLE_STMT_OPERAND (use_stmt, 1) == ptr
1267 && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME)
1268 ptr = GIMPLE_STMT_OPERAND (use_stmt, 0);
1270 /* Replace the first dereference of *ptr if there is one and if we
1271 can move the loads to the place of the ptr phi node. */
1272 phi_inserted = false;
1273 FOR_EACH_IMM_USE_STMT (use_stmt, ui, ptr)
1278 /* Check whether this is a load of *ptr. */
1279 if (!(TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
1280 && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME
1281 && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == INDIRECT_REF
1282 && TREE_OPERAND (GIMPLE_STMT_OPERAND (use_stmt, 1), 0) == ptr
1283 /* We cannot replace a load that may throw or is volatile. */
1284 && !tree_can_throw_internal (use_stmt)))
1287 /* Check if we can move the loads. The def stmts of all virtual uses
1288 need to be post-dominated by bb. */
1289 FOR_EACH_SSA_TREE_OPERAND (vuse, use_stmt, ui2, SSA_OP_VUSE)
1291 tree def_stmt = SSA_NAME_DEF_STMT (vuse);
1292 if (!SSA_NAME_IS_DEFAULT_DEF (vuse)
1293 && (bb_for_stmt (def_stmt) == bb
1294 || !dominated_by_p (CDI_DOMINATORS,
1295 bb, bb_for_stmt (def_stmt))))
1299 /* Found a proper dereference. Insert a phi node if this
1300 is the first load transformation. */
1303 res = phiprop_insert_phi (bb, phi, use_stmt, phivn, n);
1305 /* Remember the value we created for *ptr. */
1306 phivn[SSA_NAME_VERSION (ptr)].value = res;
1307 phivn[SSA_NAME_VERSION (ptr)].vop_stmt = use_stmt;
1309 /* Remove old stmt. The phi is taken care of by DCE, if we
1310 want to delete it here we also have to delete all intermediate
1312 bsi = bsi_for_stmt (use_stmt);
1313 bsi_remove (&bsi, 0);
1315 phi_inserted = true;
1319 /* Further replacements are easy, just make a copy out of the
1321 GIMPLE_STMT_OPERAND (use_stmt, 1) = res;
1322 update_stmt (use_stmt);
1326 /* Continue searching for a proper dereference. */
1329 return phi_inserted;
1332 /* Helper walking the dominator tree starting from BB and processing
1333 phi nodes with global data PHIVN and N. */
1336 tree_ssa_phiprop_1 (basic_block bb, struct phiprop_d *phivn, size_t n)
1338 bool did_something = false;
1342 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1343 did_something |= propagate_with_phi (bb, phi, phivn, n);
1345 for (son = first_dom_son (CDI_DOMINATORS, bb);
1347 son = next_dom_son (CDI_DOMINATORS, son))
1348 did_something |= tree_ssa_phiprop_1 (son, phivn, n);
1350 return did_something;
1353 /* Main entry for phiprop pass. */
1356 tree_ssa_phiprop (void)
1358 struct phiprop_d *phivn;
1360 calculate_dominance_info (CDI_DOMINATORS);
1362 phivn = XCNEWVEC (struct phiprop_d, num_ssa_names);
1364 if (tree_ssa_phiprop_1 (ENTRY_BLOCK_PTR, phivn, num_ssa_names))
1365 bsi_commit_edge_inserts ();
1378 struct tree_opt_pass pass_phiprop = {
1379 "phiprop", /* name */
1380 gate_phiprop, /* gate */
1381 tree_ssa_phiprop, /* execute */
1384 0, /* static_pass_number */
1385 TV_TREE_FORWPROP, /* tv_id */
1386 PROP_cfg | PROP_ssa, /* properties_required */
1387 0, /* properties_provided */
1388 0, /* properties_destroyed */
1389 0, /* todo_flags_start */
1393 | TODO_verify_ssa, /* todo_flags_finish */