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
)
667 FOR_EACH_ARTIFICIAL_USE (use
, bb
->index
)
668 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
669 if (!DF_REF_IS_ARTIFICIAL (defs
->ref
))
670 mark_insn (DF_REF_INSN (defs
->ref
), false);
674 /* Mark every instruction that defines a register value that INSN uses. */
677 mark_reg_dependencies (rtx insn
)
679 struct df_link
*defs
;
682 if (DEBUG_INSN_P (insn
))
685 FOR_EACH_INSN_USE (use
, insn
)
689 fprintf (dump_file
, "Processing use of ");
690 print_simple_rtl (dump_file
, DF_REF_REG (use
));
691 fprintf (dump_file
, " in insn %d:\n", INSN_UID (insn
));
693 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
694 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
695 mark_insn (DF_REF_INSN (defs
->ref
), false);
700 /* Initialize global variables for a new DCE pass. */
709 df_set_flags (DF_RD_PRUNE_DEAD_DEFS
);
710 df_chain_add_problem (DF_UD_CHAIN
);
720 bitmap_obstack_initialize (&dce_blocks_bitmap_obstack
);
721 bitmap_obstack_initialize (&dce_tmp_bitmap_obstack
);
722 can_alter_cfg
= false;
725 can_alter_cfg
= true;
727 marked
= sbitmap_alloc (get_max_uid () + 1);
728 bitmap_clear (marked
);
732 /* Free the data allocated by init_dce. */
737 sbitmap_free (marked
);
741 bitmap_obstack_release (&dce_blocks_bitmap_obstack
);
742 bitmap_obstack_release (&dce_tmp_bitmap_obstack
);
747 /* UD-chain based DCE. */
750 rest_of_handle_ud_dce (void)
756 prescan_insns_for_dce (false);
757 mark_artificial_uses ();
758 while (worklist
.length () > 0)
760 insn
= worklist
.pop ();
761 mark_reg_dependencies (insn
);
765 if (MAY_HAVE_DEBUG_INSNS
)
766 reset_unmarked_insns_debug_uses ();
768 /* Before any insns are deleted, we must remove the chains since
769 they are not bidirectional. */
770 df_remove_problem (df_chain
);
771 delete_unmarked_insns ();
780 const pass_data pass_data_ud_rtl_dce
=
784 OPTGROUP_NONE
, /* optinfo_flags */
785 true, /* has_execute */
787 0, /* properties_required */
788 0, /* properties_provided */
789 0, /* properties_destroyed */
790 0, /* todo_flags_start */
791 TODO_df_finish
, /* todo_flags_finish */
794 class pass_ud_rtl_dce
: public rtl_opt_pass
797 pass_ud_rtl_dce (gcc::context
*ctxt
)
798 : rtl_opt_pass (pass_data_ud_rtl_dce
, ctxt
)
801 /* opt_pass methods: */
802 virtual bool gate (function
*)
804 return optimize
> 1 && flag_dce
&& dbg_cnt (dce_ud
);
807 virtual unsigned int execute (function
*)
809 return rest_of_handle_ud_dce ();
812 }; // class pass_ud_rtl_dce
817 make_pass_ud_rtl_dce (gcc::context
*ctxt
)
819 return new pass_ud_rtl_dce (ctxt
);
823 /* -------------------------------------------------------------------------
825 ------------------------------------------------------------------------- */
827 /* Process basic block BB. Return true if the live_in set has
828 changed. REDO_OUT is true if the info at the bottom of the block
829 needs to be recalculated before starting. AU is the proper set of
830 artificial uses. Track global substitution of uses of dead pseudos
831 in debug insns using GLOBAL_DEBUG. */
834 word_dce_process_block (basic_block bb
, bool redo_out
,
835 struct dead_debug_global
*global_debug
)
837 bitmap local_live
= BITMAP_ALLOC (&dce_tmp_bitmap_obstack
);
840 struct dead_debug_local debug
;
844 /* Need to redo the live_out set of this block if when one of
845 the succs of this block has had a change in it live in
849 df_confluence_function_n con_fun_n
= df_word_lr
->problem
->con_fun_n
;
850 bitmap_clear (DF_WORD_LR_OUT (bb
));
851 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
857 fprintf (dump_file
, "processing block %d live out = ", bb
->index
);
858 df_print_word_regset (dump_file
, DF_WORD_LR_OUT (bb
));
861 bitmap_copy (local_live
, DF_WORD_LR_OUT (bb
));
862 dead_debug_local_init (&debug
, NULL
, global_debug
);
864 FOR_BB_INSNS_REVERSE (bb
, insn
)
865 if (DEBUG_INSN_P (insn
))
868 FOR_EACH_INSN_USE (use
, insn
)
869 if (DF_REF_REGNO (use
) >= FIRST_PSEUDO_REGISTER
870 && (GET_MODE_SIZE (GET_MODE (DF_REF_REAL_REG (use
)))
871 == 2 * UNITS_PER_WORD
)
872 && !bitmap_bit_p (local_live
, 2 * DF_REF_REGNO (use
))
873 && !bitmap_bit_p (local_live
, 2 * DF_REF_REGNO (use
) + 1))
874 dead_debug_add (&debug
, use
, DF_REF_REGNO (use
));
876 else if (INSN_P (insn
))
880 /* No matter if the instruction is needed or not, we remove
881 any regno in the defs from the live set. */
882 any_changed
= df_word_lr_simulate_defs (insn
, local_live
);
884 mark_insn (insn
, true);
886 /* On the other hand, we do not allow the dead uses to set
887 anything in local_live. */
888 if (marked_insn_p (insn
))
889 df_word_lr_simulate_uses (insn
, local_live
);
891 /* Insert debug temps for dead REGs used in subsequent debug
892 insns. We may have to emit a debug temp even if the insn
893 was marked, in case the debug use was after the point of
895 if (debug
.used
&& !bitmap_empty_p (debug
.used
))
899 FOR_EACH_INSN_DEF (def
, insn
)
900 dead_debug_insert_temp (&debug
, DF_REF_REGNO (def
), insn
,
902 && !control_flow_insn_p (insn
)
903 ? DEBUG_TEMP_AFTER_WITH_REG_FORCE
904 : DEBUG_TEMP_BEFORE_WITH_VALUE
);
909 fprintf (dump_file
, "finished processing insn %d live out = ",
911 df_print_word_regset (dump_file
, local_live
);
915 block_changed
= !bitmap_equal_p (local_live
, DF_WORD_LR_IN (bb
));
917 bitmap_copy (DF_WORD_LR_IN (bb
), local_live
);
919 dead_debug_local_finish (&debug
, NULL
);
920 BITMAP_FREE (local_live
);
921 return block_changed
;
925 /* Process basic block BB. Return true if the live_in set has
926 changed. REDO_OUT is true if the info at the bottom of the block
927 needs to be recalculated before starting. AU is the proper set of
928 artificial uses. Track global substitution of uses of dead pseudos
929 in debug insns using GLOBAL_DEBUG. */
932 dce_process_block (basic_block bb
, bool redo_out
, bitmap au
,
933 struct dead_debug_global
*global_debug
)
935 bitmap local_live
= BITMAP_ALLOC (&dce_tmp_bitmap_obstack
);
939 struct dead_debug_local debug
;
943 /* Need to redo the live_out set of this block if when one of
944 the succs of this block has had a change in it live in
948 df_confluence_function_n con_fun_n
= df_lr
->problem
->con_fun_n
;
949 bitmap_clear (DF_LR_OUT (bb
));
950 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
956 fprintf (dump_file
, "processing block %d lr out = ", bb
->index
);
957 df_print_regset (dump_file
, DF_LR_OUT (bb
));
960 bitmap_copy (local_live
, DF_LR_OUT (bb
));
962 df_simulate_initialize_backwards (bb
, local_live
);
963 dead_debug_local_init (&debug
, NULL
, global_debug
);
965 FOR_BB_INSNS_REVERSE (bb
, insn
)
966 if (DEBUG_INSN_P (insn
))
969 FOR_EACH_INSN_USE (use
, insn
)
970 if (!bitmap_bit_p (local_live
, DF_REF_REGNO (use
))
971 && !bitmap_bit_p (au
, DF_REF_REGNO (use
)))
972 dead_debug_add (&debug
, use
, DF_REF_REGNO (use
));
974 else if (INSN_P (insn
))
976 bool needed
= marked_insn_p (insn
);
978 /* The insn is needed if there is someone who uses the output. */
980 FOR_EACH_INSN_DEF (def
, insn
)
981 if (bitmap_bit_p (local_live
, DF_REF_REGNO (def
))
982 || bitmap_bit_p (au
, DF_REF_REGNO (def
)))
985 mark_insn (insn
, true);
989 /* No matter if the instruction is needed or not, we remove
990 any regno in the defs from the live set. */
991 df_simulate_defs (insn
, local_live
);
993 /* On the other hand, we do not allow the dead uses to set
994 anything in local_live. */
996 df_simulate_uses (insn
, local_live
);
998 /* Insert debug temps for dead REGs used in subsequent debug
999 insns. We may have to emit a debug temp even if the insn
1000 was marked, in case the debug use was after the point of
1002 if (debug
.used
&& !bitmap_empty_p (debug
.used
))
1003 FOR_EACH_INSN_DEF (def
, insn
)
1004 dead_debug_insert_temp (&debug
, DF_REF_REGNO (def
), insn
,
1005 needed
&& !control_flow_insn_p (insn
)
1006 ? DEBUG_TEMP_AFTER_WITH_REG_FORCE
1007 : DEBUG_TEMP_BEFORE_WITH_VALUE
);
1010 dead_debug_local_finish (&debug
, NULL
);
1011 df_simulate_finalize_backwards (bb
, local_live
);
1013 block_changed
= !bitmap_equal_p (local_live
, DF_LR_IN (bb
));
1015 bitmap_copy (DF_LR_IN (bb
), local_live
);
1017 BITMAP_FREE (local_live
);
1018 return block_changed
;
1022 /* Perform fast DCE once initialization is done. If WORD_LEVEL is
1023 true, use the word level dce, otherwise do it at the pseudo
1027 fast_dce (bool word_level
)
1029 int *postorder
= df_get_postorder (DF_BACKWARD
);
1030 int n_blocks
= df_get_n_blocks (DF_BACKWARD
);
1031 /* The set of blocks that have been seen on this iteration. */
1032 bitmap processed
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
1033 /* The set of blocks that need to have the out vectors reset because
1034 the in of one of their successors has changed. */
1035 bitmap redo_out
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
1036 bitmap all_blocks
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
1037 bool global_changed
= true;
1039 /* These regs are considered always live so if they end up dying
1040 because of some def, we need to bring the back again. Calling
1041 df_simulate_fixup_sets has the disadvantage of calling
1042 bb_has_eh_pred once per insn, so we cache the information
1044 bitmap au
= &df
->regular_block_artificial_uses
;
1045 bitmap au_eh
= &df
->eh_block_artificial_uses
;
1047 struct dead_debug_global global_debug
;
1049 prescan_insns_for_dce (true);
1051 for (i
= 0; i
< n_blocks
; i
++)
1052 bitmap_set_bit (all_blocks
, postorder
[i
]);
1054 dead_debug_global_init (&global_debug
, NULL
);
1056 while (global_changed
)
1058 global_changed
= false;
1060 for (i
= 0; i
< n_blocks
; i
++)
1062 int index
= postorder
[i
];
1063 basic_block bb
= BASIC_BLOCK_FOR_FN (cfun
, index
);
1066 if (index
< NUM_FIXED_BLOCKS
)
1068 bitmap_set_bit (processed
, index
);
1074 = word_dce_process_block (bb
, bitmap_bit_p (redo_out
, index
),
1078 = dce_process_block (bb
, bitmap_bit_p (redo_out
, index
),
1079 bb_has_eh_pred (bb
) ? au_eh
: au
,
1081 bitmap_set_bit (processed
, index
);
1087 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1088 if (bitmap_bit_p (processed
, e
->src
->index
))
1089 /* Be tricky about when we need to iterate the
1090 analysis. We only have redo the analysis if the
1091 bitmaps change at the top of a block that is the
1093 global_changed
= true;
1095 bitmap_set_bit (redo_out
, e
->src
->index
);
1101 /* Turn off the RUN_DCE flag to prevent recursive calls to
1103 int old_flag
= df_clear_flags (DF_LR_RUN_DCE
);
1105 /* So something was deleted that requires a redo. Do it on
1107 delete_unmarked_insns ();
1108 bitmap_clear (marked
);
1109 bitmap_clear (processed
);
1110 bitmap_clear (redo_out
);
1112 /* We do not need to rescan any instructions. We only need
1113 to redo the dataflow equations for the blocks that had a
1114 change at the top of the block. Then we need to redo the
1117 df_analyze_problem (df_word_lr
, all_blocks
, postorder
, n_blocks
);
1119 df_analyze_problem (df_lr
, all_blocks
, postorder
, n_blocks
);
1121 if (old_flag
& DF_LR_RUN_DCE
)
1122 df_set_flags (DF_LR_RUN_DCE
);
1124 prescan_insns_for_dce (true);
1128 dead_debug_global_finish (&global_debug
, NULL
);
1130 delete_unmarked_insns ();
1132 BITMAP_FREE (processed
);
1133 BITMAP_FREE (redo_out
);
1134 BITMAP_FREE (all_blocks
);
1138 /* Fast register level DCE. */
1141 rest_of_handle_fast_dce (void)
1150 /* Fast byte level DCE. */
1160 timevar_push (TV_DCE
);
1161 old_flags
= df_clear_flags (DF_DEFER_INSN_RESCAN
+ DF_NO_INSN_RESCAN
);
1162 df_word_lr_add_problem ();
1166 df_set_flags (old_flags
);
1167 timevar_pop (TV_DCE
);
1171 /* This is an internal call that is used by the df live register
1172 problem to run fast dce as a side effect of creating the live
1173 information. The stack is organized so that the lr problem is run,
1174 this pass is run, which updates the live info and the df scanning
1175 info, and then returns to allow the rest of the problems to be run.
1177 This can be called by elsewhere but it will not update the bit
1178 vectors for any other problems than LR. */
1181 run_fast_df_dce (void)
1185 /* If dce is able to delete something, it has to happen
1186 immediately. Otherwise there will be problems handling the
1189 df_clear_flags (DF_DEFER_INSN_RESCAN
+ DF_NO_INSN_RESCAN
);
1191 df_in_progress
= true;
1192 rest_of_handle_fast_dce ();
1193 df_in_progress
= false;
1195 df_set_flags (old_flags
);
1200 /* Run a fast DCE pass. */
1206 rest_of_handle_fast_dce ();
1212 const pass_data pass_data_fast_rtl_dce
=
1214 RTL_PASS
, /* type */
1215 "rtl_dce", /* name */
1216 OPTGROUP_NONE
, /* optinfo_flags */
1217 true, /* has_execute */
1219 0, /* properties_required */
1220 0, /* properties_provided */
1221 0, /* properties_destroyed */
1222 0, /* todo_flags_start */
1223 TODO_df_finish
, /* todo_flags_finish */
1226 class pass_fast_rtl_dce
: public rtl_opt_pass
1229 pass_fast_rtl_dce (gcc::context
*ctxt
)
1230 : rtl_opt_pass (pass_data_fast_rtl_dce
, ctxt
)
1233 /* opt_pass methods: */
1234 virtual bool gate (function
*)
1236 return optimize
> 0 && flag_dce
&& dbg_cnt (dce_fast
);
1239 virtual unsigned int execute (function
*)
1241 return rest_of_handle_fast_dce ();
1244 }; // class pass_fast_rtl_dce
1249 make_pass_fast_rtl_dce (gcc::context
*ctxt
)
1251 return new pass_fast_rtl_dce (ctxt
);