1 /* RTL dead code elimination.
2 Copyright (C) 2005-2014 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
22 #include "coretypes.h"
28 #include "hard-reg-set.h"
35 #include "tree-pass.h"
38 #include "emit-rtl.h" /* FIXME: Can go away once crtl is moved to rtl.h. */
41 /* -------------------------------------------------------------------------
42 Core mark/delete routines
43 ------------------------------------------------------------------------- */
45 /* True if we are invoked while the df engine is running; in this case,
46 we don't want to reenter it. */
47 static bool df_in_progress
= false;
49 /* True if we are allowed to alter the CFG in this pass. */
50 static bool can_alter_cfg
= false;
52 /* Instructions that have been marked but whose dependencies have not
53 yet been processed. */
54 static vec
<rtx
> worklist
;
56 /* Bitmap of instructions marked as needed indexed by INSN_UID. */
57 static sbitmap marked
;
59 /* Bitmap obstacks used for block processing by the fast algorithm. */
60 static bitmap_obstack dce_blocks_bitmap_obstack
;
61 static bitmap_obstack dce_tmp_bitmap_obstack
;
63 static bool find_call_stack_args (rtx
, bool, bool, bitmap
);
65 /* A subroutine for which BODY is part of the instruction being tested;
66 either the top-level pattern, or an element of a PARALLEL. The
67 instruction is known not to be a bare USE or CLOBBER. */
70 deletable_insn_p_1 (rtx body
)
72 switch (GET_CODE (body
))
76 /* The UNSPEC case was added here because the ia-64 claims that
77 USEs do not work after reload and generates UNSPECS rather
78 than USEs. Since dce is run after reload we need to avoid
79 deleting these even if they are dead. If it turns out that
80 USEs really do work after reload, the ia-64 should be
81 changed, and the UNSPEC case can be removed. */
86 return !volatile_refs_p (body
);
91 /* Return true if INSN is a normal instruction that can be deleted by
95 deletable_insn_p (rtx insn
, bool fast
, bitmap arg_stores
)
102 /* We cannot delete calls inside of the recursive dce because
103 this may cause basic blocks to be deleted and this messes up
104 the rest of the stack of optimization passes. */
106 /* We cannot delete pure or const sibling calls because it is
107 hard to see the result. */
108 && (!SIBLING_CALL_P (insn
))
109 /* We can delete dead const or pure calls as long as they do not
111 && (RTL_CONST_OR_PURE_CALL_P (insn
)
112 && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn
)))
113 return find_call_stack_args (insn
, false, fast
, arg_stores
);
115 /* Don't delete jumps, notes and the like. */
116 if (!NONJUMP_INSN_P (insn
))
119 /* Don't delete insns that may throw if we cannot do so. */
120 if (!(cfun
->can_delete_dead_exceptions
&& can_alter_cfg
)
121 && !insn_nothrow_p (insn
))
124 /* If INSN sets a global_reg, leave it untouched. */
125 FOR_EACH_INSN_DEF (def
, insn
)
126 if (HARD_REGISTER_NUM_P (DF_REF_REGNO (def
))
127 && global_regs
[DF_REF_REGNO (def
)])
130 body
= PATTERN (insn
);
131 switch (GET_CODE (body
))
140 /* A CLOBBER of a dead pseudo register serves no purpose.
141 That is not necessarily true for hard registers until
144 return REG_P (x
) && (!HARD_REGISTER_P (x
) || reload_completed
);
147 /* Because of the way that use-def chains are built, it is not
148 possible to tell if the clobber is dead because it can
149 never be the target of a use-def chain. */
153 for (i
= XVECLEN (body
, 0) - 1; i
>= 0; i
--)
154 if (!deletable_insn_p_1 (XVECEXP (body
, 0, i
)))
159 return deletable_insn_p_1 (body
);
164 /* Return true if INSN has been marked as needed. */
167 marked_insn_p (rtx insn
)
169 /* Artificial defs are always needed and they do not have an insn.
170 We should never see them here. */
172 return bitmap_bit_p (marked
, INSN_UID (insn
));
176 /* If INSN has not yet been marked as needed, mark it now, and add it to
180 mark_insn (rtx insn
, bool fast
)
182 if (!marked_insn_p (insn
))
185 worklist
.safe_push (insn
);
186 bitmap_set_bit (marked
, INSN_UID (insn
));
188 fprintf (dump_file
, " Adding insn %d to worklist\n", INSN_UID (insn
));
191 && !SIBLING_CALL_P (insn
)
192 && (RTL_CONST_OR_PURE_CALL_P (insn
)
193 && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn
)))
194 find_call_stack_args (insn
, true, fast
, NULL
);
199 /* A note_stores callback used by mark_nonreg_stores. DATA is the
200 instruction containing DEST. */
203 mark_nonreg_stores_1 (rtx dest
, const_rtx pattern
, void *data
)
205 if (GET_CODE (pattern
) != CLOBBER
&& !REG_P (dest
))
206 mark_insn ((rtx
) data
, true);
210 /* A note_stores callback used by mark_nonreg_stores. DATA is the
211 instruction containing DEST. */
214 mark_nonreg_stores_2 (rtx dest
, const_rtx pattern
, void *data
)
216 if (GET_CODE (pattern
) != CLOBBER
&& !REG_P (dest
))
217 mark_insn ((rtx
) data
, false);
221 /* Mark INSN if BODY stores to a non-register destination. */
224 mark_nonreg_stores (rtx body
, rtx insn
, bool fast
)
227 note_stores (body
, mark_nonreg_stores_1
, insn
);
229 note_stores (body
, mark_nonreg_stores_2
, insn
);
233 /* Return true if store to MEM, starting OFF bytes from stack pointer,
234 is a call argument store, and clear corresponding bits from SP_BYTES
238 check_argument_store (rtx mem
, HOST_WIDE_INT off
, HOST_WIDE_INT min_sp_off
,
239 HOST_WIDE_INT max_sp_off
, bitmap sp_bytes
)
242 for (byte
= off
; byte
< off
+ GET_MODE_SIZE (GET_MODE (mem
)); byte
++)
244 if (byte
< min_sp_off
245 || byte
>= max_sp_off
246 || !bitmap_clear_bit (sp_bytes
, byte
- min_sp_off
))
253 /* Try to find all stack stores of CALL_INSN arguments if
254 ACCUMULATE_OUTGOING_ARGS. If all stack stores have been found
255 and it is therefore safe to eliminate the call, return true,
256 otherwise return false. This function should be first called
257 with DO_MARK false, and only when the CALL_INSN is actually
258 going to be marked called again with DO_MARK true. */
261 find_call_stack_args (rtx call_insn
, bool do_mark
, bool fast
,
264 rtx p
, insn
, prev_insn
;
266 HOST_WIDE_INT min_sp_off
, max_sp_off
;
269 gcc_assert (CALL_P (call_insn
));
270 if (!ACCUMULATE_OUTGOING_ARGS
)
275 gcc_assert (arg_stores
);
276 bitmap_clear (arg_stores
);
279 min_sp_off
= INTTYPE_MAXIMUM (HOST_WIDE_INT
);
282 /* First determine the minimum and maximum offset from sp for
284 for (p
= CALL_INSN_FUNCTION_USAGE (call_insn
); p
; p
= XEXP (p
, 1))
285 if (GET_CODE (XEXP (p
, 0)) == USE
286 && MEM_P (XEXP (XEXP (p
, 0), 0)))
288 rtx mem
= XEXP (XEXP (p
, 0), 0), addr
;
289 HOST_WIDE_INT off
= 0, size
;
290 if (!MEM_SIZE_KNOWN_P (mem
))
292 size
= MEM_SIZE (mem
);
293 addr
= XEXP (mem
, 0);
294 if (GET_CODE (addr
) == PLUS
295 && REG_P (XEXP (addr
, 0))
296 && CONST_INT_P (XEXP (addr
, 1)))
298 off
= INTVAL (XEXP (addr
, 1));
299 addr
= XEXP (addr
, 0);
301 if (addr
!= stack_pointer_rtx
)
305 /* If not fast, use chains to see if addr wasn't set to
310 struct df_link
*defs
;
313 FOR_EACH_INSN_USE (use
, call_insn
)
314 if (rtx_equal_p (addr
, DF_REF_REG (use
)))
320 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
321 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
327 set
= single_set (DF_REF_INSN (defs
->ref
));
331 if (GET_CODE (SET_SRC (set
)) != PLUS
332 || XEXP (SET_SRC (set
), 0) != stack_pointer_rtx
333 || !CONST_INT_P (XEXP (SET_SRC (set
), 1)))
336 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
341 min_sp_off
= MIN (min_sp_off
, off
);
342 max_sp_off
= MAX (max_sp_off
, off
+ size
);
345 if (min_sp_off
>= max_sp_off
)
347 sp_bytes
= BITMAP_ALLOC (NULL
);
349 /* Set bits in SP_BYTES bitmap for bytes relative to sp + min_sp_off
350 which contain arguments. Checking has been done in the previous
352 for (p
= CALL_INSN_FUNCTION_USAGE (call_insn
); p
; p
= XEXP (p
, 1))
353 if (GET_CODE (XEXP (p
, 0)) == USE
354 && MEM_P (XEXP (XEXP (p
, 0), 0)))
356 rtx mem
= XEXP (XEXP (p
, 0), 0), addr
;
357 HOST_WIDE_INT off
= 0, byte
;
358 addr
= XEXP (mem
, 0);
359 if (GET_CODE (addr
) == PLUS
360 && REG_P (XEXP (addr
, 0))
361 && CONST_INT_P (XEXP (addr
, 1)))
363 off
= INTVAL (XEXP (addr
, 1));
364 addr
= XEXP (addr
, 0);
366 if (addr
!= stack_pointer_rtx
)
369 struct df_link
*defs
;
372 FOR_EACH_INSN_USE (use
, call_insn
)
373 if (rtx_equal_p (addr
, DF_REF_REG (use
)))
376 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
377 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
380 set
= single_set (DF_REF_INSN (defs
->ref
));
381 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
383 for (byte
= off
; byte
< off
+ MEM_SIZE (mem
); byte
++)
385 if (!bitmap_set_bit (sp_bytes
, byte
- min_sp_off
))
390 /* Walk backwards, looking for argument stores. The search stops
391 when seeing another call, sp adjustment or memory store other than
394 for (insn
= PREV_INSN (call_insn
); insn
; insn
= prev_insn
)
399 if (insn
== BB_HEAD (BLOCK_FOR_INSN (call_insn
)))
400 prev_insn
= NULL_RTX
;
402 prev_insn
= PREV_INSN (insn
);
407 if (!NONDEBUG_INSN_P (insn
))
410 set
= single_set (insn
);
411 if (!set
|| SET_DEST (set
) == stack_pointer_rtx
)
414 if (!MEM_P (SET_DEST (set
)))
417 mem
= SET_DEST (set
);
418 addr
= XEXP (mem
, 0);
420 if (GET_CODE (addr
) == PLUS
421 && REG_P (XEXP (addr
, 0))
422 && CONST_INT_P (XEXP (addr
, 1)))
424 off
= INTVAL (XEXP (addr
, 1));
425 addr
= XEXP (addr
, 0);
427 if (addr
!= stack_pointer_rtx
)
434 struct df_link
*defs
;
437 FOR_EACH_INSN_USE (use
, insn
)
438 if (rtx_equal_p (addr
, DF_REF_REG (use
)))
444 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
445 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
451 set
= single_set (DF_REF_INSN (defs
->ref
));
455 if (GET_CODE (SET_SRC (set
)) != PLUS
456 || XEXP (SET_SRC (set
), 0) != stack_pointer_rtx
457 || !CONST_INT_P (XEXP (SET_SRC (set
), 1)))
460 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
466 if (GET_MODE_SIZE (GET_MODE (mem
)) == 0
467 || !check_argument_store (mem
, off
, min_sp_off
,
468 max_sp_off
, sp_bytes
))
471 if (!deletable_insn_p (insn
, fast
, NULL
))
475 mark_insn (insn
, fast
);
477 bitmap_set_bit (arg_stores
, INSN_UID (insn
));
479 if (bitmap_empty_p (sp_bytes
))
486 BITMAP_FREE (sp_bytes
);
487 if (!ret
&& arg_stores
)
488 bitmap_clear (arg_stores
);
494 /* Remove all REG_EQUAL and REG_EQUIV notes referring to the registers INSN
498 remove_reg_equal_equiv_notes_for_defs (rtx insn
)
502 FOR_EACH_INSN_DEF (def
, insn
)
503 remove_reg_equal_equiv_notes_for_regno (DF_REF_REGNO (def
));
506 /* Scan all BBs for debug insns and reset those that reference values
507 defined in unmarked insns. */
510 reset_unmarked_insns_debug_uses (void)
515 FOR_EACH_BB_REVERSE_FN (bb
, cfun
)
516 FOR_BB_INSNS_REVERSE_SAFE (bb
, insn
, next
)
517 if (DEBUG_INSN_P (insn
))
521 FOR_EACH_INSN_USE (use
, insn
)
523 struct df_link
*defs
;
524 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
527 if (DF_REF_IS_ARTIFICIAL (defs
->ref
))
529 ref_insn
= DF_REF_INSN (defs
->ref
);
530 if (!marked_insn_p (ref_insn
))
535 /* ??? FIXME could we propagate the values assigned to
537 INSN_VAR_LOCATION_LOC (insn
) = gen_rtx_UNKNOWN_VAR_LOC ();
538 df_insn_rescan_debug_internal (insn
);
544 /* Delete every instruction that hasn't been marked. */
547 delete_unmarked_insns (void)
551 bool must_clean
= false;
553 FOR_EACH_BB_REVERSE_FN (bb
, cfun
)
554 FOR_BB_INSNS_REVERSE_SAFE (bb
, insn
, next
)
555 if (NONDEBUG_INSN_P (insn
))
557 /* Always delete no-op moves. */
558 if (noop_move_p (insn
))
561 /* Otherwise rely only on the DCE algorithm. */
562 else if (marked_insn_p (insn
))
565 /* Beware that reaching a dbg counter limit here can result
566 in miscompiled file. This occurs when a group of insns
567 must be deleted together, typically because the kept insn
568 depends on the output from the deleted insn. Deleting
569 this insns in reverse order (both at the bb level and
570 when looking at the blocks) minimizes this, but does not
571 eliminate it, since it is possible for the using insn to
572 be top of a block and the producer to be at the bottom of
573 the block. However, in most cases this will only result
574 in an uninitialized use of an insn that is dead anyway.
576 However, there is one rare case that will cause a
577 miscompile: deletion of non-looping pure and constant
578 calls on a machine where ACCUMULATE_OUTGOING_ARGS is true.
579 In this case it is possible to remove the call, but leave
580 the argument pushes to the stack. Because of the changes
581 to the stack pointer, this will almost always lead to a
587 fprintf (dump_file
, "DCE: Deleting insn %d\n", INSN_UID (insn
));
589 /* Before we delete the insn we have to remove the REG_EQUAL notes
590 for the destination regs in order to avoid dangling notes. */
591 remove_reg_equal_equiv_notes_for_defs (insn
);
593 /* If a pure or const call is deleted, this may make the cfg
594 have unreachable blocks. We rememeber this and call
595 delete_unreachable_blocks at the end. */
599 /* Now delete the insn. */
600 delete_insn_and_edges (insn
);
603 /* Deleted a pure or const call. */
605 delete_unreachable_blocks ();
609 /* Go through the instructions and mark those whose necessity is not
610 dependent on inter-instruction information. Make sure all other
611 instructions are not marked. */
614 prescan_insns_for_dce (bool fast
)
618 bitmap arg_stores
= NULL
;
621 fprintf (dump_file
, "Finding needed instructions:\n");
623 if (!df_in_progress
&& ACCUMULATE_OUTGOING_ARGS
)
624 arg_stores
= BITMAP_ALLOC (NULL
);
626 FOR_EACH_BB_FN (bb
, cfun
)
628 FOR_BB_INSNS_REVERSE_SAFE (bb
, insn
, prev
)
629 if (NONDEBUG_INSN_P (insn
))
631 /* Don't mark argument stores now. They will be marked
632 if needed when the associated CALL is marked. */
633 if (arg_stores
&& bitmap_bit_p (arg_stores
, INSN_UID (insn
)))
635 if (deletable_insn_p (insn
, fast
, arg_stores
))
636 mark_nonreg_stores (PATTERN (insn
), insn
, fast
);
638 mark_insn (insn
, fast
);
640 /* find_call_stack_args only looks at argument stores in the
643 bitmap_clear (arg_stores
);
647 BITMAP_FREE (arg_stores
);
650 fprintf (dump_file
, "Finished finding needed instructions:\n");
654 /* UD-based DSE routines. */
656 /* Mark instructions that define artificially-used registers, such as
657 the frame pointer and the stack pointer. */
660 mark_artificial_uses (void)
663 struct df_link
*defs
;
666 FOR_ALL_BB_FN (bb
, cfun
)
668 for (use_rec
= df_get_artificial_uses (bb
->index
);
670 for (defs
= DF_REF_CHAIN (*use_rec
); defs
; defs
= defs
->next
)
671 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
672 mark_insn (DF_REF_INSN (defs
->ref
), false);
677 /* Mark every instruction that defines a register value that INSN uses. */
680 mark_reg_dependencies (rtx insn
)
682 struct df_link
*defs
;
685 if (DEBUG_INSN_P (insn
))
688 FOR_EACH_INSN_USE (use
, insn
)
692 fprintf (dump_file
, "Processing use of ");
693 print_simple_rtl (dump_file
, DF_REF_REG (use
));
694 fprintf (dump_file
, " in insn %d:\n", INSN_UID (insn
));
696 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
697 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
698 mark_insn (DF_REF_INSN (defs
->ref
), false);
703 /* Initialize global variables for a new DCE pass. */
712 df_set_flags (DF_RD_PRUNE_DEAD_DEFS
);
713 df_chain_add_problem (DF_UD_CHAIN
);
723 bitmap_obstack_initialize (&dce_blocks_bitmap_obstack
);
724 bitmap_obstack_initialize (&dce_tmp_bitmap_obstack
);
725 can_alter_cfg
= false;
728 can_alter_cfg
= true;
730 marked
= sbitmap_alloc (get_max_uid () + 1);
731 bitmap_clear (marked
);
735 /* Free the data allocated by init_dce. */
740 sbitmap_free (marked
);
744 bitmap_obstack_release (&dce_blocks_bitmap_obstack
);
745 bitmap_obstack_release (&dce_tmp_bitmap_obstack
);
750 /* UD-chain based DCE. */
753 rest_of_handle_ud_dce (void)
759 prescan_insns_for_dce (false);
760 mark_artificial_uses ();
761 while (worklist
.length () > 0)
763 insn
= worklist
.pop ();
764 mark_reg_dependencies (insn
);
768 if (MAY_HAVE_DEBUG_INSNS
)
769 reset_unmarked_insns_debug_uses ();
771 /* Before any insns are deleted, we must remove the chains since
772 they are not bidirectional. */
773 df_remove_problem (df_chain
);
774 delete_unmarked_insns ();
783 const pass_data pass_data_ud_rtl_dce
=
787 OPTGROUP_NONE
, /* optinfo_flags */
788 true, /* has_execute */
790 0, /* properties_required */
791 0, /* properties_provided */
792 0, /* properties_destroyed */
793 0, /* todo_flags_start */
794 TODO_df_finish
, /* todo_flags_finish */
797 class pass_ud_rtl_dce
: public rtl_opt_pass
800 pass_ud_rtl_dce (gcc::context
*ctxt
)
801 : rtl_opt_pass (pass_data_ud_rtl_dce
, ctxt
)
804 /* opt_pass methods: */
805 virtual bool gate (function
*)
807 return optimize
> 1 && flag_dce
&& dbg_cnt (dce_ud
);
810 virtual unsigned int execute (function
*)
812 return rest_of_handle_ud_dce ();
815 }; // class pass_ud_rtl_dce
820 make_pass_ud_rtl_dce (gcc::context
*ctxt
)
822 return new pass_ud_rtl_dce (ctxt
);
826 /* -------------------------------------------------------------------------
828 ------------------------------------------------------------------------- */
830 /* Process basic block BB. Return true if the live_in set has
831 changed. REDO_OUT is true if the info at the bottom of the block
832 needs to be recalculated before starting. AU is the proper set of
833 artificial uses. Track global substitution of uses of dead pseudos
834 in debug insns using GLOBAL_DEBUG. */
837 word_dce_process_block (basic_block bb
, bool redo_out
,
838 struct dead_debug_global
*global_debug
)
840 bitmap local_live
= BITMAP_ALLOC (&dce_tmp_bitmap_obstack
);
843 struct dead_debug_local debug
;
847 /* Need to redo the live_out set of this block if when one of
848 the succs of this block has had a change in it live in
852 df_confluence_function_n con_fun_n
= df_word_lr
->problem
->con_fun_n
;
853 bitmap_clear (DF_WORD_LR_OUT (bb
));
854 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
860 fprintf (dump_file
, "processing block %d live out = ", bb
->index
);
861 df_print_word_regset (dump_file
, DF_WORD_LR_OUT (bb
));
864 bitmap_copy (local_live
, DF_WORD_LR_OUT (bb
));
865 dead_debug_local_init (&debug
, NULL
, global_debug
);
867 FOR_BB_INSNS_REVERSE (bb
, insn
)
868 if (DEBUG_INSN_P (insn
))
871 FOR_EACH_INSN_USE (use
, insn
)
872 if (DF_REF_REGNO (use
) >= FIRST_PSEUDO_REGISTER
873 && (GET_MODE_SIZE (GET_MODE (DF_REF_REAL_REG (use
)))
874 == 2 * UNITS_PER_WORD
)
875 && !bitmap_bit_p (local_live
, 2 * DF_REF_REGNO (use
))
876 && !bitmap_bit_p (local_live
, 2 * DF_REF_REGNO (use
) + 1))
877 dead_debug_add (&debug
, use
, DF_REF_REGNO (use
));
879 else if (INSN_P (insn
))
883 /* No matter if the instruction is needed or not, we remove
884 any regno in the defs from the live set. */
885 any_changed
= df_word_lr_simulate_defs (insn
, local_live
);
887 mark_insn (insn
, true);
889 /* On the other hand, we do not allow the dead uses to set
890 anything in local_live. */
891 if (marked_insn_p (insn
))
892 df_word_lr_simulate_uses (insn
, local_live
);
894 /* Insert debug temps for dead REGs used in subsequent debug
895 insns. We may have to emit a debug temp even if the insn
896 was marked, in case the debug use was after the point of
898 if (debug
.used
&& !bitmap_empty_p (debug
.used
))
902 FOR_EACH_INSN_DEF (def
, insn
)
903 dead_debug_insert_temp (&debug
, DF_REF_REGNO (def
), insn
,
905 && !control_flow_insn_p (insn
)
906 ? DEBUG_TEMP_AFTER_WITH_REG_FORCE
907 : DEBUG_TEMP_BEFORE_WITH_VALUE
);
912 fprintf (dump_file
, "finished processing insn %d live out = ",
914 df_print_word_regset (dump_file
, local_live
);
918 block_changed
= !bitmap_equal_p (local_live
, DF_WORD_LR_IN (bb
));
920 bitmap_copy (DF_WORD_LR_IN (bb
), local_live
);
922 dead_debug_local_finish (&debug
, NULL
);
923 BITMAP_FREE (local_live
);
924 return block_changed
;
928 /* Process basic block BB. Return true if the live_in set has
929 changed. REDO_OUT is true if the info at the bottom of the block
930 needs to be recalculated before starting. AU is the proper set of
931 artificial uses. Track global substitution of uses of dead pseudos
932 in debug insns using GLOBAL_DEBUG. */
935 dce_process_block (basic_block bb
, bool redo_out
, bitmap au
,
936 struct dead_debug_global
*global_debug
)
938 bitmap local_live
= BITMAP_ALLOC (&dce_tmp_bitmap_obstack
);
942 struct dead_debug_local debug
;
946 /* Need to redo the live_out set of this block if when one of
947 the succs of this block has had a change in it live in
951 df_confluence_function_n con_fun_n
= df_lr
->problem
->con_fun_n
;
952 bitmap_clear (DF_LR_OUT (bb
));
953 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
959 fprintf (dump_file
, "processing block %d lr out = ", bb
->index
);
960 df_print_regset (dump_file
, DF_LR_OUT (bb
));
963 bitmap_copy (local_live
, DF_LR_OUT (bb
));
965 df_simulate_initialize_backwards (bb
, local_live
);
966 dead_debug_local_init (&debug
, NULL
, global_debug
);
968 FOR_BB_INSNS_REVERSE (bb
, insn
)
969 if (DEBUG_INSN_P (insn
))
972 FOR_EACH_INSN_USE (use
, insn
)
973 if (!bitmap_bit_p (local_live
, DF_REF_REGNO (use
))
974 && !bitmap_bit_p (au
, DF_REF_REGNO (use
)))
975 dead_debug_add (&debug
, use
, DF_REF_REGNO (use
));
977 else if (INSN_P (insn
))
979 bool needed
= marked_insn_p (insn
);
981 /* The insn is needed if there is someone who uses the output. */
983 FOR_EACH_INSN_DEF (def
, insn
)
984 if (bitmap_bit_p (local_live
, DF_REF_REGNO (def
))
985 || bitmap_bit_p (au
, DF_REF_REGNO (def
)))
988 mark_insn (insn
, true);
992 /* No matter if the instruction is needed or not, we remove
993 any regno in the defs from the live set. */
994 df_simulate_defs (insn
, local_live
);
996 /* On the other hand, we do not allow the dead uses to set
997 anything in local_live. */
999 df_simulate_uses (insn
, local_live
);
1001 /* Insert debug temps for dead REGs used in subsequent debug
1002 insns. We may have to emit a debug temp even if the insn
1003 was marked, in case the debug use was after the point of
1005 if (debug
.used
&& !bitmap_empty_p (debug
.used
))
1006 FOR_EACH_INSN_DEF (def
, insn
)
1007 dead_debug_insert_temp (&debug
, DF_REF_REGNO (def
), insn
,
1008 needed
&& !control_flow_insn_p (insn
)
1009 ? DEBUG_TEMP_AFTER_WITH_REG_FORCE
1010 : DEBUG_TEMP_BEFORE_WITH_VALUE
);
1013 dead_debug_local_finish (&debug
, NULL
);
1014 df_simulate_finalize_backwards (bb
, local_live
);
1016 block_changed
= !bitmap_equal_p (local_live
, DF_LR_IN (bb
));
1018 bitmap_copy (DF_LR_IN (bb
), local_live
);
1020 BITMAP_FREE (local_live
);
1021 return block_changed
;
1025 /* Perform fast DCE once initialization is done. If WORD_LEVEL is
1026 true, use the word level dce, otherwise do it at the pseudo
1030 fast_dce (bool word_level
)
1032 int *postorder
= df_get_postorder (DF_BACKWARD
);
1033 int n_blocks
= df_get_n_blocks (DF_BACKWARD
);
1034 /* The set of blocks that have been seen on this iteration. */
1035 bitmap processed
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
1036 /* The set of blocks that need to have the out vectors reset because
1037 the in of one of their successors has changed. */
1038 bitmap redo_out
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
1039 bitmap all_blocks
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
1040 bool global_changed
= true;
1042 /* These regs are considered always live so if they end up dying
1043 because of some def, we need to bring the back again. Calling
1044 df_simulate_fixup_sets has the disadvantage of calling
1045 bb_has_eh_pred once per insn, so we cache the information
1047 bitmap au
= &df
->regular_block_artificial_uses
;
1048 bitmap au_eh
= &df
->eh_block_artificial_uses
;
1050 struct dead_debug_global global_debug
;
1052 prescan_insns_for_dce (true);
1054 for (i
= 0; i
< n_blocks
; i
++)
1055 bitmap_set_bit (all_blocks
, postorder
[i
]);
1057 dead_debug_global_init (&global_debug
, NULL
);
1059 while (global_changed
)
1061 global_changed
= false;
1063 for (i
= 0; i
< n_blocks
; i
++)
1065 int index
= postorder
[i
];
1066 basic_block bb
= BASIC_BLOCK_FOR_FN (cfun
, index
);
1069 if (index
< NUM_FIXED_BLOCKS
)
1071 bitmap_set_bit (processed
, index
);
1077 = word_dce_process_block (bb
, bitmap_bit_p (redo_out
, index
),
1081 = dce_process_block (bb
, bitmap_bit_p (redo_out
, index
),
1082 bb_has_eh_pred (bb
) ? au_eh
: au
,
1084 bitmap_set_bit (processed
, index
);
1090 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1091 if (bitmap_bit_p (processed
, e
->src
->index
))
1092 /* Be tricky about when we need to iterate the
1093 analysis. We only have redo the analysis if the
1094 bitmaps change at the top of a block that is the
1096 global_changed
= true;
1098 bitmap_set_bit (redo_out
, e
->src
->index
);
1104 /* Turn off the RUN_DCE flag to prevent recursive calls to
1106 int old_flag
= df_clear_flags (DF_LR_RUN_DCE
);
1108 /* So something was deleted that requires a redo. Do it on
1110 delete_unmarked_insns ();
1111 bitmap_clear (marked
);
1112 bitmap_clear (processed
);
1113 bitmap_clear (redo_out
);
1115 /* We do not need to rescan any instructions. We only need
1116 to redo the dataflow equations for the blocks that had a
1117 change at the top of the block. Then we need to redo the
1120 df_analyze_problem (df_word_lr
, all_blocks
, postorder
, n_blocks
);
1122 df_analyze_problem (df_lr
, all_blocks
, postorder
, n_blocks
);
1124 if (old_flag
& DF_LR_RUN_DCE
)
1125 df_set_flags (DF_LR_RUN_DCE
);
1127 prescan_insns_for_dce (true);
1131 dead_debug_global_finish (&global_debug
, NULL
);
1133 delete_unmarked_insns ();
1135 BITMAP_FREE (processed
);
1136 BITMAP_FREE (redo_out
);
1137 BITMAP_FREE (all_blocks
);
1141 /* Fast register level DCE. */
1144 rest_of_handle_fast_dce (void)
1153 /* Fast byte level DCE. */
1163 timevar_push (TV_DCE
);
1164 old_flags
= df_clear_flags (DF_DEFER_INSN_RESCAN
+ DF_NO_INSN_RESCAN
);
1165 df_word_lr_add_problem ();
1169 df_set_flags (old_flags
);
1170 timevar_pop (TV_DCE
);
1174 /* This is an internal call that is used by the df live register
1175 problem to run fast dce as a side effect of creating the live
1176 information. The stack is organized so that the lr problem is run,
1177 this pass is run, which updates the live info and the df scanning
1178 info, and then returns to allow the rest of the problems to be run.
1180 This can be called by elsewhere but it will not update the bit
1181 vectors for any other problems than LR. */
1184 run_fast_df_dce (void)
1188 /* If dce is able to delete something, it has to happen
1189 immediately. Otherwise there will be problems handling the
1192 df_clear_flags (DF_DEFER_INSN_RESCAN
+ DF_NO_INSN_RESCAN
);
1194 df_in_progress
= true;
1195 rest_of_handle_fast_dce ();
1196 df_in_progress
= false;
1198 df_set_flags (old_flags
);
1203 /* Run a fast DCE pass. */
1209 rest_of_handle_fast_dce ();
1215 const pass_data pass_data_fast_rtl_dce
=
1217 RTL_PASS
, /* type */
1218 "rtl_dce", /* name */
1219 OPTGROUP_NONE
, /* optinfo_flags */
1220 true, /* has_execute */
1222 0, /* properties_required */
1223 0, /* properties_provided */
1224 0, /* properties_destroyed */
1225 0, /* todo_flags_start */
1226 TODO_df_finish
, /* todo_flags_finish */
1229 class pass_fast_rtl_dce
: public rtl_opt_pass
1232 pass_fast_rtl_dce (gcc::context
*ctxt
)
1233 : rtl_opt_pass (pass_data_fast_rtl_dce
, ctxt
)
1236 /* opt_pass methods: */
1237 virtual bool gate (function
*)
1239 return optimize
> 0 && flag_dce
&& dbg_cnt (dce_fast
);
1242 virtual unsigned int execute (function
*)
1244 return rest_of_handle_fast_dce ();
1247 }; // class pass_fast_rtl_dce
1252 make_pass_fast_rtl_dce (gcc::context
*ctxt
)
1254 return new pass_fast_rtl_dce (ctxt
);