1 /* Dead code elimination pass for the GNU compiler.
2 Copyright (C) 2002-2013 Free Software Foundation, Inc.
3 Contributed by Ben Elliston <bje@redhat.com>
4 and Andrew MacLeod <amacleod@redhat.com>
5 Adapted to use control dependence by Steven Bosscher, SUSE Labs.
7 This file is part of GCC.
9 GCC is free software; you can redistribute it and/or modify it
10 under the terms of the GNU General Public License as published by the
11 Free Software Foundation; either version 3, or (at your option) any
14 GCC is distributed in the hope that it will be useful, but WITHOUT
15 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
16 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
19 You should have received a copy of the GNU General Public License
20 along with GCC; see the file COPYING3. If not see
21 <http://www.gnu.org/licenses/>. */
23 /* Dead code elimination.
27 Building an Optimizing Compiler,
28 Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9.
30 Advanced Compiler Design and Implementation,
31 Steven Muchnick, Morgan Kaufmann, 1997, Section 18.10.
33 Dead-code elimination is the removal of statements which have no
34 impact on the program's output. "Dead statements" have no impact
35 on the program's output, while "necessary statements" may have
38 The algorithm consists of three phases:
39 1. Marking as necessary all statements known to be necessary,
40 e.g. most function calls, writing a value to memory, etc;
41 2. Propagating necessary statements, e.g., the statements
42 giving values to operands in necessary statements; and
43 3. Removing dead statements. */
47 #include "coretypes.h"
51 #include "gimple-pretty-print.h"
52 #include "basic-block.h"
54 #include "gimple-ssa.h"
56 #include "tree-phinodes.h"
57 #include "ssa-iterators.h"
58 #include "tree-ssanames.h"
59 #include "tree-ssa-loop.h"
60 #include "tree-into-ssa.h"
62 #include "tree-pass.h"
65 #include "tree-scalar-evolution.h"
67 static struct stmt_stats
75 #define STMT_NECESSARY GF_PLF_1
77 static vec
<gimple
> worklist
;
79 /* Vector indicating an SSA name has already been processed and marked
81 static sbitmap processed
;
83 /* Vector indicating that the last statement of a basic block has already
84 been marked as necessary. */
85 static sbitmap last_stmt_necessary
;
87 /* Vector indicating that BB contains statements that are live. */
88 static sbitmap bb_contains_live_stmts
;
90 /* Before we can determine whether a control branch is dead, we need to
91 compute which blocks are control dependent on which edges.
93 We expect each block to be control dependent on very few edges so we
94 use a bitmap for each block recording its edges. An array holds the
95 bitmap. The Ith bit in the bitmap is set if that block is dependent
97 static control_dependences
*cd
;
99 /* Vector indicating that a basic block has already had all the edges
100 processed that it is control dependent on. */
101 static sbitmap visited_control_parents
;
103 /* TRUE if this pass alters the CFG (by removing control statements).
106 If this pass alters the CFG, then it will arrange for the dominators
108 static bool cfg_altered
;
111 /* If STMT is not already marked necessary, mark it, and add it to the
112 worklist if ADD_TO_WORKLIST is true. */
115 mark_stmt_necessary (gimple stmt
, bool add_to_worklist
)
119 if (gimple_plf (stmt
, STMT_NECESSARY
))
122 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
124 fprintf (dump_file
, "Marking useful stmt: ");
125 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
126 fprintf (dump_file
, "\n");
129 gimple_set_plf (stmt
, STMT_NECESSARY
, true);
131 worklist
.safe_push (stmt
);
132 if (bb_contains_live_stmts
&& !is_gimple_debug (stmt
))
133 bitmap_set_bit (bb_contains_live_stmts
, gimple_bb (stmt
)->index
);
137 /* Mark the statement defining operand OP as necessary. */
140 mark_operand_necessary (tree op
)
147 ver
= SSA_NAME_VERSION (op
);
148 if (bitmap_bit_p (processed
, ver
))
150 stmt
= SSA_NAME_DEF_STMT (op
);
151 gcc_assert (gimple_nop_p (stmt
)
152 || gimple_plf (stmt
, STMT_NECESSARY
));
155 bitmap_set_bit (processed
, ver
);
157 stmt
= SSA_NAME_DEF_STMT (op
);
160 if (gimple_plf (stmt
, STMT_NECESSARY
) || gimple_nop_p (stmt
))
163 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
165 fprintf (dump_file
, "marking necessary through ");
166 print_generic_expr (dump_file
, op
, 0);
167 fprintf (dump_file
, " stmt ");
168 print_gimple_stmt (dump_file
, stmt
, 0, 0);
171 gimple_set_plf (stmt
, STMT_NECESSARY
, true);
172 if (bb_contains_live_stmts
)
173 bitmap_set_bit (bb_contains_live_stmts
, gimple_bb (stmt
)->index
);
174 worklist
.safe_push (stmt
);
178 /* Mark STMT as necessary if it obviously is. Add it to the worklist if
179 it can make other statements necessary.
181 If AGGRESSIVE is false, control statements are conservatively marked as
185 mark_stmt_if_obviously_necessary (gimple stmt
, bool aggressive
)
187 /* With non-call exceptions, we have to assume that all statements could
188 throw. If a statement could throw, it can be deemed necessary. */
189 if (cfun
->can_throw_non_call_exceptions
190 && !cfun
->can_delete_dead_exceptions
191 && stmt_could_throw_p (stmt
))
193 mark_stmt_necessary (stmt
, true);
197 /* Statements that are implicitly live. Most function calls, asm
198 and return statements are required. Labels and GIMPLE_BIND nodes
199 are kept because they are control flow, and we have no way of
200 knowing whether they can be removed. DCE can eliminate all the
201 other statements in a block, and CFG can then remove the block
203 switch (gimple_code (stmt
))
207 mark_stmt_necessary (stmt
, false);
213 mark_stmt_necessary (stmt
, true);
218 tree callee
= gimple_call_fndecl (stmt
);
219 if (callee
!= NULL_TREE
220 && DECL_BUILT_IN_CLASS (callee
) == BUILT_IN_NORMAL
)
221 switch (DECL_FUNCTION_CODE (callee
))
223 case BUILT_IN_MALLOC
:
224 case BUILT_IN_CALLOC
:
225 case BUILT_IN_ALLOCA
:
226 case BUILT_IN_ALLOCA_WITH_ALIGN
:
231 /* Most, but not all function calls are required. Function calls that
232 produce no result and have no side effects (i.e. const pure
233 functions) are unnecessary. */
234 if (gimple_has_side_effects (stmt
))
236 mark_stmt_necessary (stmt
, true);
239 if (!gimple_call_lhs (stmt
))
245 /* Debug temps without a value are not useful. ??? If we could
246 easily locate the debug temp bind stmt for a use thereof,
247 would could refrain from marking all debug temps here, and
248 mark them only if they're used. */
249 if (!gimple_debug_bind_p (stmt
)
250 || gimple_debug_bind_has_value_p (stmt
)
251 || TREE_CODE (gimple_debug_bind_get_var (stmt
)) != DEBUG_EXPR_DECL
)
252 mark_stmt_necessary (stmt
, false);
256 gcc_assert (!simple_goto_p (stmt
));
257 mark_stmt_necessary (stmt
, true);
261 gcc_assert (EDGE_COUNT (gimple_bb (stmt
)->succs
) == 2);
266 mark_stmt_necessary (stmt
, true);
270 if (TREE_CODE (gimple_assign_lhs (stmt
)) == SSA_NAME
271 && TREE_CLOBBER_P (gimple_assign_rhs1 (stmt
)))
279 /* If the statement has volatile operands, it needs to be preserved.
280 Same for statements that can alter control flow in unpredictable
282 if (gimple_has_volatile_ops (stmt
) || is_ctrl_altering_stmt (stmt
))
284 mark_stmt_necessary (stmt
, true);
288 if (stmt_may_clobber_global_p (stmt
))
290 mark_stmt_necessary (stmt
, true);
298 /* Mark the last statement of BB as necessary. */
301 mark_last_stmt_necessary (basic_block bb
)
303 gimple stmt
= last_stmt (bb
);
305 bitmap_set_bit (last_stmt_necessary
, bb
->index
);
306 bitmap_set_bit (bb_contains_live_stmts
, bb
->index
);
308 /* We actually mark the statement only if it is a control statement. */
309 if (stmt
&& is_ctrl_stmt (stmt
))
310 mark_stmt_necessary (stmt
, true);
314 /* Mark control dependent edges of BB as necessary. We have to do this only
315 once for each basic block so we set the appropriate bit after we're done.
317 When IGNORE_SELF is true, ignore BB in the list of control dependences. */
320 mark_control_dependent_edges_necessary (basic_block bb
, bool ignore_self
)
323 unsigned edge_number
;
324 bool skipped
= false;
326 gcc_assert (bb
!= EXIT_BLOCK_PTR
);
328 if (bb
== ENTRY_BLOCK_PTR
)
331 EXECUTE_IF_SET_IN_BITMAP (cd
->get_edges_dependent_on (bb
->index
),
334 basic_block cd_bb
= cd
->get_edge (edge_number
)->src
;
336 if (ignore_self
&& cd_bb
== bb
)
342 if (!bitmap_bit_p (last_stmt_necessary
, cd_bb
->index
))
343 mark_last_stmt_necessary (cd_bb
);
347 bitmap_set_bit (visited_control_parents
, bb
->index
);
351 /* Find obviously necessary statements. These are things like most function
352 calls, and stores to file level variables.
354 If EL is NULL, control statements are conservatively marked as
355 necessary. Otherwise it contains the list of edges used by control
356 dependence analysis. */
359 find_obviously_necessary_stmts (bool aggressive
)
362 gimple_stmt_iterator gsi
;
369 /* PHI nodes are never inherently necessary. */
370 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
372 phi
= gsi_stmt (gsi
);
373 gimple_set_plf (phi
, STMT_NECESSARY
, false);
376 /* Check all statements in the block. */
377 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
379 stmt
= gsi_stmt (gsi
);
380 gimple_set_plf (stmt
, STMT_NECESSARY
, false);
381 mark_stmt_if_obviously_necessary (stmt
, aggressive
);
385 /* Pure and const functions are finite and thus have no infinite loops in
387 flags
= flags_from_decl_or_type (current_function_decl
);
388 if ((flags
& (ECF_CONST
|ECF_PURE
)) && !(flags
& ECF_LOOPING_CONST_OR_PURE
))
391 /* Prevent the empty possibly infinite loops from being removed. */
397 if (mark_irreducible_loops ())
401 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
402 if ((e
->flags
& EDGE_DFS_BACK
)
403 && (e
->flags
& EDGE_IRREDUCIBLE_LOOP
))
406 fprintf (dump_file
, "Marking back edge of irreducible loop %i->%i\n",
407 e
->src
->index
, e
->dest
->index
);
408 mark_control_dependent_edges_necessary (e
->dest
, false);
412 FOR_EACH_LOOP (li
, loop
, 0)
413 if (!finite_loop_p (loop
))
416 fprintf (dump_file
, "can not prove finiteness of loop %i\n", loop
->num
);
417 mark_control_dependent_edges_necessary (loop
->latch
, false);
424 /* Return true if REF is based on an aliased base, otherwise false. */
427 ref_may_be_aliased (tree ref
)
429 gcc_assert (TREE_CODE (ref
) != WITH_SIZE_EXPR
);
430 while (handled_component_p (ref
))
431 ref
= TREE_OPERAND (ref
, 0);
432 if (TREE_CODE (ref
) == MEM_REF
433 && TREE_CODE (TREE_OPERAND (ref
, 0)) == ADDR_EXPR
)
434 ref
= TREE_OPERAND (TREE_OPERAND (ref
, 0), 0);
435 return !(DECL_P (ref
)
436 && !may_be_aliased (ref
));
439 static bitmap visited
= NULL
;
440 static unsigned int longest_chain
= 0;
441 static unsigned int total_chain
= 0;
442 static unsigned int nr_walks
= 0;
443 static bool chain_ovfl
= false;
445 /* Worker for the walker that marks reaching definitions of REF,
446 which is based on a non-aliased decl, necessary. It returns
447 true whenever the defining statement of the current VDEF is
448 a kill for REF, as no dominating may-defs are necessary for REF
449 anymore. DATA points to the basic-block that contains the
450 stmt that refers to REF. */
453 mark_aliased_reaching_defs_necessary_1 (ao_ref
*ref
, tree vdef
, void *data
)
455 gimple def_stmt
= SSA_NAME_DEF_STMT (vdef
);
457 /* All stmts we visit are necessary. */
458 mark_operand_necessary (vdef
);
460 /* If the stmt lhs kills ref, then we can stop walking. */
461 if (gimple_has_lhs (def_stmt
)
462 && TREE_CODE (gimple_get_lhs (def_stmt
)) != SSA_NAME
463 /* The assignment is not necessarily carried out if it can throw
464 and we can catch it in the current function where we could inspect
466 ??? We only need to care about the RHS throwing. For aggregate
467 assignments or similar calls and non-call exceptions the LHS
468 might throw as well. */
469 && !stmt_can_throw_internal (def_stmt
))
471 tree base
, lhs
= gimple_get_lhs (def_stmt
);
472 HOST_WIDE_INT size
, offset
, max_size
;
474 base
= get_ref_base_and_extent (lhs
, &offset
, &size
, &max_size
);
475 /* We can get MEM[symbol: sZ, index: D.8862_1] here,
476 so base == refd->base does not always hold. */
477 if (base
== ref
->base
)
479 /* For a must-alias check we need to be able to constrain
480 the accesses properly. */
481 if (size
!= -1 && size
== max_size
482 && ref
->max_size
!= -1)
484 if (offset
<= ref
->offset
485 && offset
+ size
>= ref
->offset
+ ref
->max_size
)
488 /* Or they need to be exactly the same. */
490 /* Make sure there is no induction variable involved
491 in the references (gcc.c-torture/execute/pr42142.c).
492 The simplest way is to check if the kill dominates
494 /* But when both are in the same block we cannot
495 easily tell whether we came from a backedge
496 unless we decide to compute stmt UIDs
498 && (basic_block
) data
!= gimple_bb (def_stmt
)
499 && dominated_by_p (CDI_DOMINATORS
, (basic_block
) data
,
500 gimple_bb (def_stmt
))
501 && operand_equal_p (ref
->ref
, lhs
, 0))
506 /* Otherwise keep walking. */
511 mark_aliased_reaching_defs_necessary (gimple stmt
, tree ref
)
515 gcc_assert (!chain_ovfl
);
516 ao_ref_init (&refd
, ref
);
517 chain
= walk_aliased_vdefs (&refd
, gimple_vuse (stmt
),
518 mark_aliased_reaching_defs_necessary_1
,
519 gimple_bb (stmt
), NULL
);
520 if (chain
> longest_chain
)
521 longest_chain
= chain
;
522 total_chain
+= chain
;
526 /* Worker for the walker that marks reaching definitions of REF, which
527 is not based on a non-aliased decl. For simplicity we need to end
528 up marking all may-defs necessary that are not based on a non-aliased
529 decl. The only job of this walker is to skip may-defs based on
530 a non-aliased decl. */
533 mark_all_reaching_defs_necessary_1 (ao_ref
*ref ATTRIBUTE_UNUSED
,
534 tree vdef
, void *data ATTRIBUTE_UNUSED
)
536 gimple def_stmt
= SSA_NAME_DEF_STMT (vdef
);
538 /* We have to skip already visited (and thus necessary) statements
539 to make the chaining work after we dropped back to simple mode. */
541 && bitmap_bit_p (processed
, SSA_NAME_VERSION (vdef
)))
543 gcc_assert (gimple_nop_p (def_stmt
)
544 || gimple_plf (def_stmt
, STMT_NECESSARY
));
548 /* We want to skip stores to non-aliased variables. */
550 && gimple_assign_single_p (def_stmt
))
552 tree lhs
= gimple_assign_lhs (def_stmt
);
553 if (!ref_may_be_aliased (lhs
))
557 /* We want to skip statments that do not constitute stores but have
558 a virtual definition. */
559 if (is_gimple_call (def_stmt
))
561 tree callee
= gimple_call_fndecl (def_stmt
);
562 if (callee
!= NULL_TREE
563 && DECL_BUILT_IN_CLASS (callee
) == BUILT_IN_NORMAL
)
564 switch (DECL_FUNCTION_CODE (callee
))
566 case BUILT_IN_MALLOC
:
567 case BUILT_IN_CALLOC
:
568 case BUILT_IN_ALLOCA
:
569 case BUILT_IN_ALLOCA_WITH_ALIGN
:
577 mark_operand_necessary (vdef
);
583 mark_all_reaching_defs_necessary (gimple stmt
)
585 walk_aliased_vdefs (NULL
, gimple_vuse (stmt
),
586 mark_all_reaching_defs_necessary_1
, NULL
, &visited
);
589 /* Return true for PHI nodes with one or identical arguments
592 degenerate_phi_p (gimple phi
)
595 tree op
= gimple_phi_arg_def (phi
, 0);
596 for (i
= 1; i
< gimple_phi_num_args (phi
); i
++)
597 if (gimple_phi_arg_def (phi
, i
) != op
)
602 /* Propagate necessity using the operands of necessary statements.
603 Process the uses on each statement in the worklist, and add all
604 feeding statements which contribute to the calculation of this
605 value to the worklist.
607 In conservative mode, EL is NULL. */
610 propagate_necessity (bool aggressive
)
614 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
615 fprintf (dump_file
, "\nProcessing worklist:\n");
617 while (worklist
.length () > 0)
619 /* Take STMT from worklist. */
620 stmt
= worklist
.pop ();
622 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
624 fprintf (dump_file
, "processing: ");
625 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
626 fprintf (dump_file
, "\n");
631 /* Mark the last statement of the basic blocks on which the block
632 containing STMT is control dependent, but only if we haven't
634 basic_block bb
= gimple_bb (stmt
);
635 if (bb
!= ENTRY_BLOCK_PTR
636 && !bitmap_bit_p (visited_control_parents
, bb
->index
))
637 mark_control_dependent_edges_necessary (bb
, false);
640 if (gimple_code (stmt
) == GIMPLE_PHI
641 /* We do not process virtual PHI nodes nor do we track their
643 && !virtual_operand_p (gimple_phi_result (stmt
)))
645 /* PHI nodes are somewhat special in that each PHI alternative has
646 data and control dependencies. All the statements feeding the
647 PHI node's arguments are always necessary. In aggressive mode,
648 we also consider the control dependent edges leading to the
649 predecessor block associated with each PHI alternative as
653 for (k
= 0; k
< gimple_phi_num_args (stmt
); k
++)
655 tree arg
= PHI_ARG_DEF (stmt
, k
);
656 if (TREE_CODE (arg
) == SSA_NAME
)
657 mark_operand_necessary (arg
);
660 /* For PHI operands it matters from where the control flow arrives
661 to the BB. Consider the following example:
671 We need to mark control dependence of the empty basic blocks, since they
672 contains computation of PHI operands.
674 Doing so is too restrictive in the case the predecestor block is in
680 for (i = 0; i<1000; ++i)
686 There is PHI for J in the BB containing return statement.
687 In this case the control dependence of predecestor block (that is
688 within the empty loop) also contains the block determining number
689 of iterations of the block that would prevent removing of empty
692 This scenario can be avoided by splitting critical edges.
693 To save the critical edge splitting pass we identify how the control
694 dependence would look like if the edge was split.
696 Consider the modified CFG created from current CFG by splitting
697 edge B->C. In the postdominance tree of modified CFG, C' is
698 always child of C. There are two cases how chlids of C' can look
703 In this case the only basic block C' is control dependent on is B.
705 2) C' has single child that is B
707 In this case control dependence of C' is same as control
708 dependence of B in original CFG except for block B itself.
709 (since C' postdominate B in modified CFG)
711 Now how to decide what case happens? There are two basic options:
713 a) C postdominate B. Then C immediately postdominate B and
714 case 2 happens iff there is no other way from B to C except
717 There is other way from B to C iff there is succesor of B that
718 is not postdominated by B. Testing this condition is somewhat
719 expensive, because we need to iterate all succesors of B.
720 We are safe to assume that this does not happen: we will mark B
721 as needed when processing the other path from B to C that is
722 conrol dependent on B and marking control dependencies of B
723 itself is harmless because they will be processed anyway after
724 processing control statement in B.
726 b) C does not postdominate B. Always case 1 happens since there is
727 path from C to exit that does not go through B and thus also C'. */
729 if (aggressive
&& !degenerate_phi_p (stmt
))
731 for (k
= 0; k
< gimple_phi_num_args (stmt
); k
++)
733 basic_block arg_bb
= gimple_phi_arg_edge (stmt
, k
)->src
;
736 != get_immediate_dominator (CDI_POST_DOMINATORS
, arg_bb
))
738 if (!bitmap_bit_p (last_stmt_necessary
, arg_bb
->index
))
739 mark_last_stmt_necessary (arg_bb
);
741 else if (arg_bb
!= ENTRY_BLOCK_PTR
742 && !bitmap_bit_p (visited_control_parents
,
744 mark_control_dependent_edges_necessary (arg_bb
, true);
750 /* Propagate through the operands. Examine all the USE, VUSE and
751 VDEF operands in this statement. Mark all the statements
752 which feed this statement's uses as necessary. */
756 /* If this is a call to free which is directly fed by an
757 allocation function do not mark that necessary through
758 processing the argument. */
759 if (gimple_call_builtin_p (stmt
, BUILT_IN_FREE
))
761 tree ptr
= gimple_call_arg (stmt
, 0);
764 /* If the pointer we free is defined by an allocation
765 function do not add the call to the worklist. */
766 if (TREE_CODE (ptr
) == SSA_NAME
767 && is_gimple_call (def_stmt
= SSA_NAME_DEF_STMT (ptr
))
768 && (def_callee
= gimple_call_fndecl (def_stmt
))
769 && DECL_BUILT_IN_CLASS (def_callee
) == BUILT_IN_NORMAL
770 && (DECL_FUNCTION_CODE (def_callee
) == BUILT_IN_MALLOC
771 || DECL_FUNCTION_CODE (def_callee
) == BUILT_IN_CALLOC
))
775 FOR_EACH_SSA_TREE_OPERAND (use
, stmt
, iter
, SSA_OP_USE
)
776 mark_operand_necessary (use
);
778 use
= gimple_vuse (stmt
);
782 /* If we dropped to simple mode make all immediately
783 reachable definitions necessary. */
786 mark_all_reaching_defs_necessary (stmt
);
790 /* For statements that may load from memory (have a VUSE) we
791 have to mark all reaching (may-)definitions as necessary.
792 We partition this task into two cases:
793 1) explicit loads based on decls that are not aliased
794 2) implicit loads (like calls) and explicit loads not
795 based on decls that are not aliased (like indirect
796 references or loads from globals)
797 For 1) we mark all reaching may-defs as necessary, stopping
798 at dominating kills. For 2) we want to mark all dominating
799 references necessary, but non-aliased ones which we handle
800 in 1). By keeping a global visited bitmap for references
801 we walk for 2) we avoid quadratic behavior for those. */
803 if (is_gimple_call (stmt
))
805 tree callee
= gimple_call_fndecl (stmt
);
808 /* Calls to functions that are merely acting as barriers
809 or that only store to memory do not make any previous
811 if (callee
!= NULL_TREE
812 && DECL_BUILT_IN_CLASS (callee
) == BUILT_IN_NORMAL
813 && (DECL_FUNCTION_CODE (callee
) == BUILT_IN_MEMSET
814 || DECL_FUNCTION_CODE (callee
) == BUILT_IN_MEMSET_CHK
815 || DECL_FUNCTION_CODE (callee
) == BUILT_IN_MALLOC
816 || DECL_FUNCTION_CODE (callee
) == BUILT_IN_CALLOC
817 || DECL_FUNCTION_CODE (callee
) == BUILT_IN_FREE
818 || DECL_FUNCTION_CODE (callee
) == BUILT_IN_VA_END
819 || DECL_FUNCTION_CODE (callee
) == BUILT_IN_ALLOCA
820 || (DECL_FUNCTION_CODE (callee
)
821 == BUILT_IN_ALLOCA_WITH_ALIGN
)
822 || DECL_FUNCTION_CODE (callee
) == BUILT_IN_STACK_SAVE
823 || DECL_FUNCTION_CODE (callee
) == BUILT_IN_STACK_RESTORE
824 || DECL_FUNCTION_CODE (callee
) == BUILT_IN_ASSUME_ALIGNED
))
827 /* Calls implicitly load from memory, their arguments
828 in addition may explicitly perform memory loads. */
829 mark_all_reaching_defs_necessary (stmt
);
830 for (i
= 0; i
< gimple_call_num_args (stmt
); ++i
)
832 tree arg
= gimple_call_arg (stmt
, i
);
833 if (TREE_CODE (arg
) == SSA_NAME
834 || is_gimple_min_invariant (arg
))
836 if (TREE_CODE (arg
) == WITH_SIZE_EXPR
)
837 arg
= TREE_OPERAND (arg
, 0);
838 if (!ref_may_be_aliased (arg
))
839 mark_aliased_reaching_defs_necessary (stmt
, arg
);
842 else if (gimple_assign_single_p (stmt
))
845 /* If this is a load mark things necessary. */
846 rhs
= gimple_assign_rhs1 (stmt
);
847 if (TREE_CODE (rhs
) != SSA_NAME
848 && !is_gimple_min_invariant (rhs
)
849 && TREE_CODE (rhs
) != CONSTRUCTOR
)
851 if (!ref_may_be_aliased (rhs
))
852 mark_aliased_reaching_defs_necessary (stmt
, rhs
);
854 mark_all_reaching_defs_necessary (stmt
);
857 else if (gimple_code (stmt
) == GIMPLE_RETURN
)
859 tree rhs
= gimple_return_retval (stmt
);
860 /* A return statement may perform a load. */
862 && TREE_CODE (rhs
) != SSA_NAME
863 && !is_gimple_min_invariant (rhs
)
864 && TREE_CODE (rhs
) != CONSTRUCTOR
)
866 if (!ref_may_be_aliased (rhs
))
867 mark_aliased_reaching_defs_necessary (stmt
, rhs
);
869 mark_all_reaching_defs_necessary (stmt
);
872 else if (gimple_code (stmt
) == GIMPLE_ASM
)
875 mark_all_reaching_defs_necessary (stmt
);
876 /* Inputs may perform loads. */
877 for (i
= 0; i
< gimple_asm_ninputs (stmt
); ++i
)
879 tree op
= TREE_VALUE (gimple_asm_input_op (stmt
, i
));
880 if (TREE_CODE (op
) != SSA_NAME
881 && !is_gimple_min_invariant (op
)
882 && TREE_CODE (op
) != CONSTRUCTOR
883 && !ref_may_be_aliased (op
))
884 mark_aliased_reaching_defs_necessary (stmt
, op
);
887 else if (gimple_code (stmt
) == GIMPLE_TRANSACTION
)
889 /* The beginning of a transaction is a memory barrier. */
890 /* ??? If we were really cool, we'd only be a barrier
891 for the memories touched within the transaction. */
892 mark_all_reaching_defs_necessary (stmt
);
897 /* If we over-used our alias oracle budget drop to simple
898 mode. The cost metric allows quadratic behavior
899 (number of uses times number of may-defs queries) up to
900 a constant maximal number of queries and after that falls back to
901 super-linear complexity. */
902 if (/* Constant but quadratic for small functions. */
903 total_chain
> 128 * 128
904 /* Linear in the number of may-defs. */
905 && total_chain
> 32 * longest_chain
906 /* Linear in the number of uses. */
907 && total_chain
> nr_walks
* 32)
911 bitmap_clear (visited
);
917 /* Remove dead PHI nodes from block BB. */
920 remove_dead_phis (basic_block bb
)
922 bool something_changed
= false;
924 gimple_stmt_iterator gsi
;
926 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
);)
929 phi
= gsi_stmt (gsi
);
931 /* We do not track necessity of virtual PHI nodes. Instead do
932 very simple dead PHI removal here. */
933 if (virtual_operand_p (gimple_phi_result (phi
)))
935 /* Virtual PHI nodes with one or identical arguments
937 if (degenerate_phi_p (phi
))
939 tree vdef
= gimple_phi_result (phi
);
940 tree vuse
= gimple_phi_arg_def (phi
, 0);
943 imm_use_iterator iter
;
945 FOR_EACH_IMM_USE_STMT (use_stmt
, iter
, vdef
)
946 FOR_EACH_IMM_USE_ON_STMT (use_p
, iter
)
947 SET_USE (use_p
, vuse
);
948 if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (vdef
)
949 && TREE_CODE (vuse
) == SSA_NAME
)
950 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (vuse
) = 1;
953 gimple_set_plf (phi
, STMT_NECESSARY
, true);
956 if (!gimple_plf (phi
, STMT_NECESSARY
))
958 something_changed
= true;
959 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
961 fprintf (dump_file
, "Deleting : ");
962 print_gimple_stmt (dump_file
, phi
, 0, TDF_SLIM
);
963 fprintf (dump_file
, "\n");
966 remove_phi_node (&gsi
, true);
967 stats
.removed_phis
++;
973 return something_changed
;
976 /* Forward edge E to respective POST_DOM_BB and update PHIs. */
979 forward_edge_to_pdom (edge e
, basic_block post_dom_bb
)
981 gimple_stmt_iterator gsi
;
985 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
986 fprintf (dump_file
, "Redirecting edge %i->%i to %i\n", e
->src
->index
,
987 e
->dest
->index
, post_dom_bb
->index
);
989 e2
= redirect_edge_and_branch (e
, post_dom_bb
);
992 /* If edge was already around, no updating is necessary. */
996 if (!gimple_seq_empty_p (phi_nodes (post_dom_bb
)))
998 /* We are sure that for every live PHI we are seeing control dependent BB.
999 This means that we can pick any edge to duplicate PHI args from. */
1000 FOR_EACH_EDGE (e2
, ei
, post_dom_bb
->preds
)
1003 for (gsi
= gsi_start_phis (post_dom_bb
); !gsi_end_p (gsi
);)
1005 gimple phi
= gsi_stmt (gsi
);
1007 source_location locus
;
1009 /* PHIs for virtuals have no control dependency relation on them.
1010 We are lost here and must force renaming of the symbol. */
1011 if (virtual_operand_p (gimple_phi_result (phi
)))
1013 mark_virtual_phi_result_for_renaming (phi
);
1014 remove_phi_node (&gsi
, true);
1018 /* Dead PHI do not imply control dependency. */
1019 if (!gimple_plf (phi
, STMT_NECESSARY
))
1025 op
= gimple_phi_arg_def (phi
, e2
->dest_idx
);
1026 locus
= gimple_phi_arg_location (phi
, e2
->dest_idx
);
1027 add_phi_arg (phi
, op
, e
, locus
);
1028 /* The resulting PHI if not dead can only be degenerate. */
1029 gcc_assert (degenerate_phi_p (phi
));
1036 /* Remove dead statement pointed to by iterator I. Receives the basic block BB
1037 containing I so that we don't have to look it up. */
1040 remove_dead_stmt (gimple_stmt_iterator
*i
, basic_block bb
)
1042 gimple stmt
= gsi_stmt (*i
);
1044 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1046 fprintf (dump_file
, "Deleting : ");
1047 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
1048 fprintf (dump_file
, "\n");
1053 /* If we have determined that a conditional branch statement contributes
1054 nothing to the program, then we not only remove it, but we also change
1055 the flow graph so that the current block will simply fall-thru to its
1056 immediate post-dominator. The blocks we are circumventing will be
1057 removed by cleanup_tree_cfg if this change in the flow graph makes them
1059 if (is_ctrl_stmt (stmt
))
1061 basic_block post_dom_bb
;
1065 post_dom_bb
= get_immediate_dominator (CDI_POST_DOMINATORS
, bb
);
1067 e
= find_edge (bb
, post_dom_bb
);
1069 /* If edge is already there, try to use it. This avoids need to update
1070 PHI nodes. Also watch for cases where post dominator does not exists
1071 or is exit block. These can happen for infinite loops as we create
1072 fake edges in the dominator tree. */
1075 else if (! post_dom_bb
|| post_dom_bb
== EXIT_BLOCK_PTR
)
1076 e
= EDGE_SUCC (bb
, 0);
1078 e
= forward_edge_to_pdom (EDGE_SUCC (bb
, 0), post_dom_bb
);
1080 e
->probability
= REG_BR_PROB_BASE
;
1081 e
->count
= bb
->count
;
1083 /* The edge is no longer associated with a conditional, so it does
1084 not have TRUE/FALSE flags. */
1085 e
->flags
&= ~(EDGE_TRUE_VALUE
| EDGE_FALSE_VALUE
);
1087 /* The lone outgoing edge from BB will be a fallthru edge. */
1088 e
->flags
|= EDGE_FALLTHRU
;
1090 /* Remove the remaining outgoing edges. */
1091 for (ei
= ei_start (bb
->succs
); (e2
= ei_safe_edge (ei
)); )
1101 /* If this is a store into a variable that is being optimized away,
1102 add a debug bind stmt if possible. */
1103 if (MAY_HAVE_DEBUG_STMTS
1104 && gimple_assign_single_p (stmt
)
1105 && is_gimple_val (gimple_assign_rhs1 (stmt
)))
1107 tree lhs
= gimple_assign_lhs (stmt
);
1108 if ((TREE_CODE (lhs
) == VAR_DECL
|| TREE_CODE (lhs
) == PARM_DECL
)
1109 && !DECL_IGNORED_P (lhs
)
1110 && is_gimple_reg_type (TREE_TYPE (lhs
))
1111 && !is_global_var (lhs
)
1112 && !DECL_HAS_VALUE_EXPR_P (lhs
))
1114 tree rhs
= gimple_assign_rhs1 (stmt
);
1116 = gimple_build_debug_bind (lhs
, unshare_expr (rhs
), stmt
);
1117 gsi_insert_after (i
, note
, GSI_SAME_STMT
);
1121 unlink_stmt_vdef (stmt
);
1122 gsi_remove (i
, true);
1123 release_defs (stmt
);
1126 /* Eliminate unnecessary statements. Any instruction not marked as necessary
1127 contributes nothing to the program, and can be deleted. */
1130 eliminate_unnecessary_stmts (void)
1132 bool something_changed
= false;
1134 gimple_stmt_iterator gsi
, psi
;
1139 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1140 fprintf (dump_file
, "\nEliminating unnecessary statements:\n");
1142 clear_special_calls ();
1144 /* Walking basic blocks and statements in reverse order avoids
1145 releasing SSA names before any other DEFs that refer to them are
1146 released. This helps avoid loss of debug information, as we get
1147 a chance to propagate all RHSs of removed SSAs into debug uses,
1148 rather than only the latest ones. E.g., consider:
1154 If we were to release x_3 before a_5, when we reached a_5 and
1155 tried to substitute it into the debug stmt, we'd see x_3 there,
1156 but x_3's DEF, type, etc would have already been disconnected.
1157 By going backwards, the debug stmt first changes to:
1159 # DEBUG a => x_3 - b_4
1163 # DEBUG a => y_1 + z_2 - b_4
1166 gcc_assert (dom_info_available_p (CDI_DOMINATORS
));
1167 h
= get_all_dominated_blocks (CDI_DOMINATORS
, single_succ (ENTRY_BLOCK_PTR
));
1173 /* Remove dead statements. */
1174 for (gsi
= gsi_last_bb (bb
); !gsi_end_p (gsi
); gsi
= psi
)
1176 stmt
= gsi_stmt (gsi
);
1183 /* We can mark a call to free as not necessary if the
1184 defining statement of its argument is an allocation
1185 function and that is not necessary itself. */
1186 if (gimple_call_builtin_p (stmt
, BUILT_IN_FREE
))
1188 tree ptr
= gimple_call_arg (stmt
, 0);
1191 if (TREE_CODE (ptr
) != SSA_NAME
)
1193 def_stmt
= SSA_NAME_DEF_STMT (ptr
);
1194 if (!is_gimple_call (def_stmt
)
1195 || gimple_plf (def_stmt
, STMT_NECESSARY
))
1197 callee2
= gimple_call_fndecl (def_stmt
);
1198 if (callee2
== NULL_TREE
1199 || DECL_BUILT_IN_CLASS (callee2
) != BUILT_IN_NORMAL
1200 || (DECL_FUNCTION_CODE (callee2
) != BUILT_IN_MALLOC
1201 && DECL_FUNCTION_CODE (callee2
) != BUILT_IN_CALLOC
))
1203 gimple_set_plf (stmt
, STMT_NECESSARY
, false);
1206 /* If GSI is not necessary then remove it. */
1207 if (!gimple_plf (stmt
, STMT_NECESSARY
))
1209 if (!is_gimple_debug (stmt
))
1210 something_changed
= true;
1211 remove_dead_stmt (&gsi
, bb
);
1213 else if (is_gimple_call (stmt
))
1215 tree name
= gimple_call_lhs (stmt
);
1217 notice_special_calls (stmt
);
1219 /* When LHS of var = call (); is dead, simplify it into
1220 call (); saving one operand. */
1222 && TREE_CODE (name
) == SSA_NAME
1223 && !bitmap_bit_p (processed
, SSA_NAME_VERSION (name
))
1224 /* Avoid doing so for allocation calls which we
1225 did not mark as necessary, it will confuse the
1226 special logic we apply to malloc/free pair removal. */
1227 && (!(call
= gimple_call_fndecl (stmt
))
1228 || DECL_BUILT_IN_CLASS (call
) != BUILT_IN_NORMAL
1229 || (DECL_FUNCTION_CODE (call
) != BUILT_IN_MALLOC
1230 && DECL_FUNCTION_CODE (call
) != BUILT_IN_CALLOC
1231 && DECL_FUNCTION_CODE (call
) != BUILT_IN_ALLOCA
1232 && (DECL_FUNCTION_CODE (call
)
1233 != BUILT_IN_ALLOCA_WITH_ALIGN
))))
1235 something_changed
= true;
1236 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1238 fprintf (dump_file
, "Deleting LHS of call: ");
1239 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
1240 fprintf (dump_file
, "\n");
1243 gimple_call_set_lhs (stmt
, NULL_TREE
);
1244 maybe_clean_or_replace_eh_stmt (stmt
, stmt
);
1246 release_ssa_name (name
);
1254 /* Since we don't track liveness of virtual PHI nodes, it is possible that we
1255 rendered some PHI nodes unreachable while they are still in use.
1256 Mark them for renaming. */
1259 basic_block prev_bb
;
1261 find_unreachable_blocks ();
1263 /* Delete all unreachable basic blocks in reverse dominator order. */
1264 for (bb
= EXIT_BLOCK_PTR
->prev_bb
; bb
!= ENTRY_BLOCK_PTR
; bb
= prev_bb
)
1266 prev_bb
= bb
->prev_bb
;
1268 if (!bitmap_bit_p (bb_contains_live_stmts
, bb
->index
)
1269 || !(bb
->flags
& BB_REACHABLE
))
1271 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1272 if (virtual_operand_p (gimple_phi_result (gsi_stmt (gsi
))))
1275 imm_use_iterator iter
;
1277 FOR_EACH_IMM_USE_STMT (stmt
, iter
, gimple_phi_result (gsi_stmt (gsi
)))
1279 if (!(gimple_bb (stmt
)->flags
& BB_REACHABLE
))
1281 if (gimple_code (stmt
) == GIMPLE_PHI
1282 || gimple_plf (stmt
, STMT_NECESSARY
))
1285 BREAK_FROM_IMM_USE_STMT (iter
);
1289 mark_virtual_phi_result_for_renaming (gsi_stmt (gsi
));
1292 if (!(bb
->flags
& BB_REACHABLE
))
1294 /* Speed up the removal of blocks that don't
1295 dominate others. Walking backwards, this should
1296 be the common case. ??? Do we need to recompute
1297 dominators because of cfg_altered? */
1298 if (!MAY_HAVE_DEBUG_STMTS
1299 || !first_dom_son (CDI_DOMINATORS
, bb
))
1300 delete_basic_block (bb
);
1303 h
= get_all_dominated_blocks (CDI_DOMINATORS
, bb
);
1308 prev_bb
= bb
->prev_bb
;
1309 /* Rearrangements to the CFG may have failed
1310 to update the dominators tree, so that
1311 formerly-dominated blocks are now
1312 otherwise reachable. */
1313 if (!!(bb
->flags
& BB_REACHABLE
))
1315 delete_basic_block (bb
);
1326 /* Remove dead PHI nodes. */
1327 something_changed
|= remove_dead_phis (bb
);
1330 return something_changed
;
1334 /* Print out removed statement statistics. */
1341 percg
= ((float) stats
.removed
/ (float) stats
.total
) * 100;
1342 fprintf (dump_file
, "Removed %d of %d statements (%d%%)\n",
1343 stats
.removed
, stats
.total
, (int) percg
);
1345 if (stats
.total_phis
== 0)
1348 percg
= ((float) stats
.removed_phis
/ (float) stats
.total_phis
) * 100;
1350 fprintf (dump_file
, "Removed %d of %d PHI nodes (%d%%)\n",
1351 stats
.removed_phis
, stats
.total_phis
, (int) percg
);
1354 /* Initialization for this pass. Set up the used data structures. */
1357 tree_dce_init (bool aggressive
)
1359 memset ((void *) &stats
, 0, sizeof (stats
));
1363 last_stmt_necessary
= sbitmap_alloc (last_basic_block
);
1364 bitmap_clear (last_stmt_necessary
);
1365 bb_contains_live_stmts
= sbitmap_alloc (last_basic_block
);
1366 bitmap_clear (bb_contains_live_stmts
);
1369 processed
= sbitmap_alloc (num_ssa_names
+ 1);
1370 bitmap_clear (processed
);
1372 worklist
.create (64);
1373 cfg_altered
= false;
1376 /* Cleanup after this pass. */
1379 tree_dce_done (bool aggressive
)
1384 sbitmap_free (visited_control_parents
);
1385 sbitmap_free (last_stmt_necessary
);
1386 sbitmap_free (bb_contains_live_stmts
);
1387 bb_contains_live_stmts
= NULL
;
1390 sbitmap_free (processed
);
1392 worklist
.release ();
1395 /* Main routine to eliminate dead code.
1397 AGGRESSIVE controls the aggressiveness of the algorithm.
1398 In conservative mode, we ignore control dependence and simply declare
1399 all but the most trivially dead branches necessary. This mode is fast.
1400 In aggressive mode, control dependences are taken into account, which
1401 results in more dead code elimination, but at the cost of some time.
1403 FIXME: Aggressive mode before PRE doesn't work currently because
1404 the dominance info is not invalidated after DCE1. This is
1405 not an issue right now because we only run aggressive DCE
1406 as the last tree SSA pass, but keep this in mind when you
1407 start experimenting with pass ordering. */
1410 perform_tree_ssa_dce (bool aggressive
)
1412 bool something_changed
= 0;
1414 calculate_dominance_info (CDI_DOMINATORS
);
1416 /* Preheaders are needed for SCEV to work.
1417 Simple lateches and recorded exits improve chances that loop will
1418 proved to be finite in testcases such as in loop-15.c and loop-24.c */
1420 loop_optimizer_init (LOOPS_NORMAL
1421 | LOOPS_HAVE_RECORDED_EXITS
);
1423 tree_dce_init (aggressive
);
1427 /* Compute control dependence. */
1428 calculate_dominance_info (CDI_POST_DOMINATORS
);
1429 cd
= new control_dependences (create_edge_list ());
1431 visited_control_parents
= sbitmap_alloc (last_basic_block
);
1432 bitmap_clear (visited_control_parents
);
1434 mark_dfs_back_edges ();
1437 find_obviously_necessary_stmts (aggressive
);
1440 loop_optimizer_finalize ();
1446 visited
= BITMAP_ALLOC (NULL
);
1447 propagate_necessity (aggressive
);
1448 BITMAP_FREE (visited
);
1450 something_changed
|= eliminate_unnecessary_stmts ();
1451 something_changed
|= cfg_altered
;
1453 /* We do not update postdominators, so free them unconditionally. */
1454 free_dominance_info (CDI_POST_DOMINATORS
);
1456 /* If we removed paths in the CFG, then we need to update
1457 dominators as well. I haven't investigated the possibility
1458 of incrementally updating dominators. */
1460 free_dominance_info (CDI_DOMINATORS
);
1462 statistics_counter_event (cfun
, "Statements deleted", stats
.removed
);
1463 statistics_counter_event (cfun
, "PHI nodes deleted", stats
.removed_phis
);
1465 /* Debugging dumps. */
1466 if (dump_file
&& (dump_flags
& (TDF_STATS
|TDF_DETAILS
)))
1469 tree_dce_done (aggressive
);
1471 if (something_changed
)
1472 return TODO_update_ssa
| TODO_cleanup_cfg
;
1476 /* Pass entry points. */
1480 return perform_tree_ssa_dce (/*aggressive=*/false);
1484 tree_ssa_dce_loop (void)
1487 todo
= perform_tree_ssa_dce (/*aggressive=*/false);
1490 free_numbers_of_iterations_estimates ();
1497 tree_ssa_cd_dce (void)
1499 return perform_tree_ssa_dce (/*aggressive=*/optimize
>= 2);
1505 return flag_tree_dce
!= 0;
1510 const pass_data pass_data_dce
=
1512 GIMPLE_PASS
, /* type */
1514 OPTGROUP_NONE
, /* optinfo_flags */
1515 true, /* has_gate */
1516 true, /* has_execute */
1517 TV_TREE_DCE
, /* tv_id */
1518 ( PROP_cfg
| PROP_ssa
), /* properties_required */
1519 0, /* properties_provided */
1520 0, /* properties_destroyed */
1521 0, /* todo_flags_start */
1522 TODO_verify_ssa
, /* todo_flags_finish */
1525 class pass_dce
: public gimple_opt_pass
1528 pass_dce (gcc::context
*ctxt
)
1529 : gimple_opt_pass (pass_data_dce
, ctxt
)
1532 /* opt_pass methods: */
1533 opt_pass
* clone () { return new pass_dce (m_ctxt
); }
1534 bool gate () { return gate_dce (); }
1535 unsigned int execute () { return tree_ssa_dce (); }
1537 }; // class pass_dce
1542 make_pass_dce (gcc::context
*ctxt
)
1544 return new pass_dce (ctxt
);
1549 const pass_data pass_data_dce_loop
=
1551 GIMPLE_PASS
, /* type */
1552 "dceloop", /* name */
1553 OPTGROUP_NONE
, /* optinfo_flags */
1554 true, /* has_gate */
1555 true, /* has_execute */
1556 TV_TREE_DCE
, /* tv_id */
1557 ( PROP_cfg
| PROP_ssa
), /* properties_required */
1558 0, /* properties_provided */
1559 0, /* properties_destroyed */
1560 0, /* todo_flags_start */
1561 TODO_verify_ssa
, /* todo_flags_finish */
1564 class pass_dce_loop
: public gimple_opt_pass
1567 pass_dce_loop (gcc::context
*ctxt
)
1568 : gimple_opt_pass (pass_data_dce_loop
, ctxt
)
1571 /* opt_pass methods: */
1572 opt_pass
* clone () { return new pass_dce_loop (m_ctxt
); }
1573 bool gate () { return gate_dce (); }
1574 unsigned int execute () { return tree_ssa_dce_loop (); }
1576 }; // class pass_dce_loop
1581 make_pass_dce_loop (gcc::context
*ctxt
)
1583 return new pass_dce_loop (ctxt
);
1588 const pass_data pass_data_cd_dce
=
1590 GIMPLE_PASS
, /* type */
1592 OPTGROUP_NONE
, /* optinfo_flags */
1593 true, /* has_gate */
1594 true, /* has_execute */
1595 TV_TREE_CD_DCE
, /* tv_id */
1596 ( PROP_cfg
| PROP_ssa
), /* properties_required */
1597 0, /* properties_provided */
1598 0, /* properties_destroyed */
1599 0, /* todo_flags_start */
1600 ( TODO_verify_ssa
| TODO_verify_flow
), /* todo_flags_finish */
1603 class pass_cd_dce
: public gimple_opt_pass
1606 pass_cd_dce (gcc::context
*ctxt
)
1607 : gimple_opt_pass (pass_data_cd_dce
, ctxt
)
1610 /* opt_pass methods: */
1611 opt_pass
* clone () { return new pass_cd_dce (m_ctxt
); }
1612 bool gate () { return gate_dce (); }
1613 unsigned int execute () { return tree_ssa_cd_dce (); }
1615 }; // class pass_cd_dce
1620 make_pass_cd_dce (gcc::context
*ctxt
)
1622 return new pass_cd_dce (ctxt
);