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
)
101 /* We cannot delete calls inside of the recursive dce because
102 this may cause basic blocks to be deleted and this messes up
103 the rest of the stack of optimization passes. */
105 /* We cannot delete pure or const sibling calls because it is
106 hard to see the result. */
107 && (!SIBLING_CALL_P (insn
))
108 /* We can delete dead const or pure calls as long as they do not
110 && (RTL_CONST_OR_PURE_CALL_P (insn
)
111 && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn
)))
112 return find_call_stack_args (insn
, false, fast
, arg_stores
);
114 /* Don't delete jumps, notes and the like. */
115 if (!NONJUMP_INSN_P (insn
))
118 /* Don't delete insns that may throw if we cannot do so. */
119 if (!(cfun
->can_delete_dead_exceptions
&& can_alter_cfg
)
120 && !insn_nothrow_p (insn
))
123 /* If INSN sets a global_reg, leave it untouched. */
124 for (df_ref
*def_rec
= DF_INSN_DEFS (insn
); *def_rec
; def_rec
++)
125 if (HARD_REGISTER_NUM_P (DF_REF_REGNO (*def_rec
))
126 && global_regs
[DF_REF_REGNO (*def_rec
)])
129 body
= PATTERN (insn
);
130 switch (GET_CODE (body
))
139 /* A CLOBBER of a dead pseudo register serves no purpose.
140 That is not necessarily true for hard registers until
143 return REG_P (x
) && (!HARD_REGISTER_P (x
) || reload_completed
);
146 /* Because of the way that use-def chains are built, it is not
147 possible to tell if the clobber is dead because it can
148 never be the target of a use-def chain. */
152 for (i
= XVECLEN (body
, 0) - 1; i
>= 0; i
--)
153 if (!deletable_insn_p_1 (XVECEXP (body
, 0, i
)))
158 return deletable_insn_p_1 (body
);
163 /* Return true if INSN has been marked as needed. */
166 marked_insn_p (rtx insn
)
168 /* Artificial defs are always needed and they do not have an insn.
169 We should never see them here. */
171 return bitmap_bit_p (marked
, INSN_UID (insn
));
175 /* If INSN has not yet been marked as needed, mark it now, and add it to
179 mark_insn (rtx insn
, bool fast
)
181 if (!marked_insn_p (insn
))
184 worklist
.safe_push (insn
);
185 bitmap_set_bit (marked
, INSN_UID (insn
));
187 fprintf (dump_file
, " Adding insn %d to worklist\n", INSN_UID (insn
));
190 && !SIBLING_CALL_P (insn
)
191 && (RTL_CONST_OR_PURE_CALL_P (insn
)
192 && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn
)))
193 find_call_stack_args (insn
, true, fast
, NULL
);
198 /* A note_stores callback used by mark_nonreg_stores. DATA is the
199 instruction containing DEST. */
202 mark_nonreg_stores_1 (rtx dest
, const_rtx pattern
, void *data
)
204 if (GET_CODE (pattern
) != CLOBBER
&& !REG_P (dest
))
205 mark_insn ((rtx
) data
, true);
209 /* A note_stores callback used by mark_nonreg_stores. DATA is the
210 instruction containing DEST. */
213 mark_nonreg_stores_2 (rtx dest
, const_rtx pattern
, void *data
)
215 if (GET_CODE (pattern
) != CLOBBER
&& !REG_P (dest
))
216 mark_insn ((rtx
) data
, false);
220 /* Mark INSN if BODY stores to a non-register destination. */
223 mark_nonreg_stores (rtx body
, rtx insn
, bool fast
)
226 note_stores (body
, mark_nonreg_stores_1
, insn
);
228 note_stores (body
, mark_nonreg_stores_2
, insn
);
232 /* Return true if store to MEM, starting OFF bytes from stack pointer,
233 is a call argument store, and clear corresponding bits from SP_BYTES
237 check_argument_store (rtx mem
, HOST_WIDE_INT off
, HOST_WIDE_INT min_sp_off
,
238 HOST_WIDE_INT max_sp_off
, bitmap sp_bytes
)
241 for (byte
= off
; byte
< off
+ GET_MODE_SIZE (GET_MODE (mem
)); byte
++)
243 if (byte
< min_sp_off
244 || byte
>= max_sp_off
245 || !bitmap_clear_bit (sp_bytes
, byte
- min_sp_off
))
252 /* Try to find all stack stores of CALL_INSN arguments if
253 ACCUMULATE_OUTGOING_ARGS. If all stack stores have been found
254 and it is therefore safe to eliminate the call, return true,
255 otherwise return false. This function should be first called
256 with DO_MARK false, and only when the CALL_INSN is actually
257 going to be marked called again with DO_MARK true. */
260 find_call_stack_args (rtx call_insn
, bool do_mark
, bool fast
,
263 rtx p
, insn
, prev_insn
;
265 HOST_WIDE_INT min_sp_off
, max_sp_off
;
268 gcc_assert (CALL_P (call_insn
));
269 if (!ACCUMULATE_OUTGOING_ARGS
)
274 gcc_assert (arg_stores
);
275 bitmap_clear (arg_stores
);
278 min_sp_off
= INTTYPE_MAXIMUM (HOST_WIDE_INT
);
281 /* First determine the minimum and maximum offset from sp for
283 for (p
= CALL_INSN_FUNCTION_USAGE (call_insn
); p
; p
= XEXP (p
, 1))
284 if (GET_CODE (XEXP (p
, 0)) == USE
285 && MEM_P (XEXP (XEXP (p
, 0), 0)))
287 rtx mem
= XEXP (XEXP (p
, 0), 0), addr
;
288 HOST_WIDE_INT off
= 0, size
;
289 if (!MEM_SIZE_KNOWN_P (mem
))
291 size
= MEM_SIZE (mem
);
292 addr
= XEXP (mem
, 0);
293 if (GET_CODE (addr
) == PLUS
294 && REG_P (XEXP (addr
, 0))
295 && CONST_INT_P (XEXP (addr
, 1)))
297 off
= INTVAL (XEXP (addr
, 1));
298 addr
= XEXP (addr
, 0);
300 if (addr
!= stack_pointer_rtx
)
304 /* If not fast, use chains to see if addr wasn't set to
309 struct df_link
*defs
;
312 for (use_rec
= DF_INSN_USES (call_insn
); *use_rec
; use_rec
++)
313 if (rtx_equal_p (addr
, DF_REF_REG (*use_rec
)))
316 if (*use_rec
== NULL
)
319 for (defs
= DF_REF_CHAIN (*use_rec
); defs
; defs
= defs
->next
)
320 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
326 set
= single_set (DF_REF_INSN (defs
->ref
));
330 if (GET_CODE (SET_SRC (set
)) != PLUS
331 || XEXP (SET_SRC (set
), 0) != stack_pointer_rtx
332 || !CONST_INT_P (XEXP (SET_SRC (set
), 1)))
335 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
340 min_sp_off
= MIN (min_sp_off
, off
);
341 max_sp_off
= MAX (max_sp_off
, off
+ size
);
344 if (min_sp_off
>= max_sp_off
)
346 sp_bytes
= BITMAP_ALLOC (NULL
);
348 /* Set bits in SP_BYTES bitmap for bytes relative to sp + min_sp_off
349 which contain arguments. Checking has been done in the previous
351 for (p
= CALL_INSN_FUNCTION_USAGE (call_insn
); p
; p
= XEXP (p
, 1))
352 if (GET_CODE (XEXP (p
, 0)) == USE
353 && MEM_P (XEXP (XEXP (p
, 0), 0)))
355 rtx mem
= XEXP (XEXP (p
, 0), 0), addr
;
356 HOST_WIDE_INT off
= 0, byte
;
357 addr
= XEXP (mem
, 0);
358 if (GET_CODE (addr
) == PLUS
359 && REG_P (XEXP (addr
, 0))
360 && CONST_INT_P (XEXP (addr
, 1)))
362 off
= INTVAL (XEXP (addr
, 1));
363 addr
= XEXP (addr
, 0);
365 if (addr
!= stack_pointer_rtx
)
368 struct df_link
*defs
;
371 for (use_rec
= DF_INSN_USES (call_insn
); *use_rec
; use_rec
++)
372 if (rtx_equal_p (addr
, DF_REF_REG (*use_rec
)))
375 for (defs
= DF_REF_CHAIN (*use_rec
); defs
; defs
= defs
->next
)
376 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
379 set
= single_set (DF_REF_INSN (defs
->ref
));
380 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
382 for (byte
= off
; byte
< off
+ MEM_SIZE (mem
); byte
++)
384 if (!bitmap_set_bit (sp_bytes
, byte
- min_sp_off
))
389 /* Walk backwards, looking for argument stores. The search stops
390 when seeing another call, sp adjustment or memory store other than
393 for (insn
= PREV_INSN (call_insn
); insn
; insn
= prev_insn
)
398 if (insn
== BB_HEAD (BLOCK_FOR_INSN (call_insn
)))
399 prev_insn
= NULL_RTX
;
401 prev_insn
= PREV_INSN (insn
);
406 if (!NONDEBUG_INSN_P (insn
))
409 set
= single_set (insn
);
410 if (!set
|| SET_DEST (set
) == stack_pointer_rtx
)
413 if (!MEM_P (SET_DEST (set
)))
416 mem
= SET_DEST (set
);
417 addr
= XEXP (mem
, 0);
419 if (GET_CODE (addr
) == PLUS
420 && REG_P (XEXP (addr
, 0))
421 && CONST_INT_P (XEXP (addr
, 1)))
423 off
= INTVAL (XEXP (addr
, 1));
424 addr
= XEXP (addr
, 0);
426 if (addr
!= stack_pointer_rtx
)
433 struct df_link
*defs
;
436 for (use_rec
= DF_INSN_USES (insn
); *use_rec
; use_rec
++)
437 if (rtx_equal_p (addr
, DF_REF_REG (*use_rec
)))
440 if (*use_rec
== NULL
)
443 for (defs
= DF_REF_CHAIN (*use_rec
); defs
; defs
= defs
->next
)
444 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
450 set
= single_set (DF_REF_INSN (defs
->ref
));
454 if (GET_CODE (SET_SRC (set
)) != PLUS
455 || XEXP (SET_SRC (set
), 0) != stack_pointer_rtx
456 || !CONST_INT_P (XEXP (SET_SRC (set
), 1)))
459 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
465 if (GET_MODE_SIZE (GET_MODE (mem
)) == 0
466 || !check_argument_store (mem
, off
, min_sp_off
,
467 max_sp_off
, sp_bytes
))
470 if (!deletable_insn_p (insn
, fast
, NULL
))
474 mark_insn (insn
, fast
);
476 bitmap_set_bit (arg_stores
, INSN_UID (insn
));
478 if (bitmap_empty_p (sp_bytes
))
485 BITMAP_FREE (sp_bytes
);
486 if (!ret
&& arg_stores
)
487 bitmap_clear (arg_stores
);
493 /* Remove all REG_EQUAL and REG_EQUIV notes referring to the registers INSN
497 remove_reg_equal_equiv_notes_for_defs (rtx insn
)
501 for (def_rec
= DF_INSN_DEFS (insn
); *def_rec
; def_rec
++)
502 remove_reg_equal_equiv_notes_for_regno (DF_REF_REGNO (*def_rec
));
505 /* Scan all BBs for debug insns and reset those that reference values
506 defined in unmarked insns. */
509 reset_unmarked_insns_debug_uses (void)
514 FOR_EACH_BB_REVERSE_FN (bb
, cfun
)
515 FOR_BB_INSNS_REVERSE_SAFE (bb
, insn
, next
)
516 if (DEBUG_INSN_P (insn
))
520 for (use_rec
= DF_INSN_USES (insn
); *use_rec
; use_rec
++)
522 df_ref use
= *use_rec
;
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 (use_rec
= DF_INSN_USES (insn
); *use_rec
; use_rec
++)
690 df_ref use
= *use_rec
;
693 fprintf (dump_file
, "Processing use of ");
694 print_simple_rtl (dump_file
, DF_REF_REG (use
));
695 fprintf (dump_file
, " in insn %d:\n", INSN_UID (insn
));
697 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
698 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
699 mark_insn (DF_REF_INSN (defs
->ref
), false);
704 /* Initialize global variables for a new DCE pass. */
713 df_set_flags (DF_RD_PRUNE_DEAD_DEFS
);
714 df_chain_add_problem (DF_UD_CHAIN
);
724 bitmap_obstack_initialize (&dce_blocks_bitmap_obstack
);
725 bitmap_obstack_initialize (&dce_tmp_bitmap_obstack
);
726 can_alter_cfg
= false;
729 can_alter_cfg
= true;
731 marked
= sbitmap_alloc (get_max_uid () + 1);
732 bitmap_clear (marked
);
736 /* Free the data allocated by init_dce. */
741 sbitmap_free (marked
);
745 bitmap_obstack_release (&dce_blocks_bitmap_obstack
);
746 bitmap_obstack_release (&dce_tmp_bitmap_obstack
);
751 /* UD-chain based DCE. */
754 rest_of_handle_ud_dce (void)
758 if (df_check_ud_du_memory_usage ())
763 prescan_insns_for_dce (false);
764 mark_artificial_uses ();
765 while (worklist
.length () > 0)
767 insn
= worklist
.pop ();
768 mark_reg_dependencies (insn
);
772 if (MAY_HAVE_DEBUG_INSNS
)
773 reset_unmarked_insns_debug_uses ();
775 /* Before any insns are deleted, we must remove the chains since
776 they are not bidirectional. */
777 df_remove_problem (df_chain
);
778 delete_unmarked_insns ();
788 return optimize
> 1 && flag_dce
794 const pass_data pass_data_ud_rtl_dce
=
798 OPTGROUP_NONE
, /* optinfo_flags */
800 true, /* has_execute */
802 0, /* properties_required */
803 0, /* properties_provided */
804 0, /* properties_destroyed */
805 0, /* todo_flags_start */
806 ( TODO_df_finish
| TODO_verify_rtl_sharing
), /* todo_flags_finish */
809 class pass_ud_rtl_dce
: public rtl_opt_pass
812 pass_ud_rtl_dce (gcc::context
*ctxt
)
813 : rtl_opt_pass (pass_data_ud_rtl_dce
, ctxt
)
816 /* opt_pass methods: */
817 bool gate () { return gate_ud_dce (); }
818 unsigned int execute () { return rest_of_handle_ud_dce (); }
820 }; // class pass_ud_rtl_dce
825 make_pass_ud_rtl_dce (gcc::context
*ctxt
)
827 return new pass_ud_rtl_dce (ctxt
);
831 /* -------------------------------------------------------------------------
833 ------------------------------------------------------------------------- */
835 /* Process basic block BB. Return true if the live_in set has
836 changed. REDO_OUT is true if the info at the bottom of the block
837 needs to be recalculated before starting. AU is the proper set of
838 artificial uses. Track global substitution of uses of dead pseudos
839 in debug insns using GLOBAL_DEBUG. */
842 word_dce_process_block (basic_block bb
, bool redo_out
,
843 struct dead_debug_global
*global_debug
)
845 bitmap local_live
= BITMAP_ALLOC (&dce_tmp_bitmap_obstack
);
848 struct dead_debug_local debug
;
852 /* Need to redo the live_out set of this block if when one of
853 the succs of this block has had a change in it live in
857 df_confluence_function_n con_fun_n
= df_word_lr
->problem
->con_fun_n
;
858 bitmap_clear (DF_WORD_LR_OUT (bb
));
859 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
865 fprintf (dump_file
, "processing block %d live out = ", bb
->index
);
866 df_print_word_regset (dump_file
, DF_WORD_LR_OUT (bb
));
869 bitmap_copy (local_live
, DF_WORD_LR_OUT (bb
));
870 dead_debug_local_init (&debug
, NULL
, global_debug
);
872 FOR_BB_INSNS_REVERSE (bb
, insn
)
873 if (DEBUG_INSN_P (insn
))
876 for (use_rec
= DF_INSN_USES (insn
); *use_rec
; use_rec
++)
877 if (DF_REF_REGNO (*use_rec
) >= FIRST_PSEUDO_REGISTER
878 && (GET_MODE_SIZE (GET_MODE (DF_REF_REAL_REG (*use_rec
)))
879 == 2 * UNITS_PER_WORD
)
880 && !bitmap_bit_p (local_live
, 2 * DF_REF_REGNO (*use_rec
))
881 && !bitmap_bit_p (local_live
, 2 * DF_REF_REGNO (*use_rec
) + 1))
882 dead_debug_add (&debug
, *use_rec
, DF_REF_REGNO (*use_rec
));
884 else if (INSN_P (insn
))
888 /* No matter if the instruction is needed or not, we remove
889 any regno in the defs from the live set. */
890 any_changed
= df_word_lr_simulate_defs (insn
, local_live
);
892 mark_insn (insn
, true);
894 /* On the other hand, we do not allow the dead uses to set
895 anything in local_live. */
896 if (marked_insn_p (insn
))
897 df_word_lr_simulate_uses (insn
, local_live
);
899 /* Insert debug temps for dead REGs used in subsequent debug
900 insns. We may have to emit a debug temp even if the insn
901 was marked, in case the debug use was after the point of
903 if (debug
.used
&& !bitmap_empty_p (debug
.used
))
907 for (def_rec
= DF_INSN_DEFS (insn
); *def_rec
; def_rec
++)
908 dead_debug_insert_temp (&debug
, DF_REF_REGNO (*def_rec
), insn
,
910 && !control_flow_insn_p (insn
)
911 ? DEBUG_TEMP_AFTER_WITH_REG_FORCE
912 : DEBUG_TEMP_BEFORE_WITH_VALUE
);
917 fprintf (dump_file
, "finished processing insn %d live out = ",
919 df_print_word_regset (dump_file
, local_live
);
923 block_changed
= !bitmap_equal_p (local_live
, DF_WORD_LR_IN (bb
));
925 bitmap_copy (DF_WORD_LR_IN (bb
), local_live
);
927 dead_debug_local_finish (&debug
, NULL
);
928 BITMAP_FREE (local_live
);
929 return block_changed
;
933 /* Process basic block BB. Return true if the live_in set has
934 changed. REDO_OUT is true if the info at the bottom of the block
935 needs to be recalculated before starting. AU is the proper set of
936 artificial uses. Track global substitution of uses of dead pseudos
937 in debug insns using GLOBAL_DEBUG. */
940 dce_process_block (basic_block bb
, bool redo_out
, bitmap au
,
941 struct dead_debug_global
*global_debug
)
943 bitmap local_live
= BITMAP_ALLOC (&dce_tmp_bitmap_obstack
);
947 struct dead_debug_local debug
;
951 /* Need to redo the live_out set of this block if when one of
952 the succs of this block has had a change in it live in
956 df_confluence_function_n con_fun_n
= df_lr
->problem
->con_fun_n
;
957 bitmap_clear (DF_LR_OUT (bb
));
958 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
964 fprintf (dump_file
, "processing block %d lr out = ", bb
->index
);
965 df_print_regset (dump_file
, DF_LR_OUT (bb
));
968 bitmap_copy (local_live
, DF_LR_OUT (bb
));
970 df_simulate_initialize_backwards (bb
, local_live
);
971 dead_debug_local_init (&debug
, NULL
, global_debug
);
973 FOR_BB_INSNS_REVERSE (bb
, insn
)
974 if (DEBUG_INSN_P (insn
))
977 for (use_rec
= DF_INSN_USES (insn
); *use_rec
; use_rec
++)
978 if (!bitmap_bit_p (local_live
, DF_REF_REGNO (*use_rec
))
979 && !bitmap_bit_p (au
, DF_REF_REGNO (*use_rec
)))
980 dead_debug_add (&debug
, *use_rec
, DF_REF_REGNO (*use_rec
));
982 else if (INSN_P (insn
))
984 bool needed
= marked_insn_p (insn
);
986 /* The insn is needed if there is someone who uses the output. */
988 for (def_rec
= DF_INSN_DEFS (insn
); *def_rec
; def_rec
++)
989 if (bitmap_bit_p (local_live
, DF_REF_REGNO (*def_rec
))
990 || bitmap_bit_p (au
, DF_REF_REGNO (*def_rec
)))
993 mark_insn (insn
, true);
997 /* No matter if the instruction is needed or not, we remove
998 any regno in the defs from the live set. */
999 df_simulate_defs (insn
, local_live
);
1001 /* On the other hand, we do not allow the dead uses to set
1002 anything in local_live. */
1004 df_simulate_uses (insn
, local_live
);
1006 /* Insert debug temps for dead REGs used in subsequent debug
1007 insns. We may have to emit a debug temp even if the insn
1008 was marked, in case the debug use was after the point of
1010 if (debug
.used
&& !bitmap_empty_p (debug
.used
))
1011 for (def_rec
= DF_INSN_DEFS (insn
); *def_rec
; def_rec
++)
1012 dead_debug_insert_temp (&debug
, DF_REF_REGNO (*def_rec
), insn
,
1013 needed
&& !control_flow_insn_p (insn
)
1014 ? DEBUG_TEMP_AFTER_WITH_REG_FORCE
1015 : DEBUG_TEMP_BEFORE_WITH_VALUE
);
1018 dead_debug_local_finish (&debug
, NULL
);
1019 df_simulate_finalize_backwards (bb
, local_live
);
1021 block_changed
= !bitmap_equal_p (local_live
, DF_LR_IN (bb
));
1023 bitmap_copy (DF_LR_IN (bb
), local_live
);
1025 BITMAP_FREE (local_live
);
1026 return block_changed
;
1030 /* Perform fast DCE once initialization is done. If WORD_LEVEL is
1031 true, use the word level dce, otherwise do it at the pseudo
1035 fast_dce (bool word_level
)
1037 int *postorder
= df_get_postorder (DF_BACKWARD
);
1038 int n_blocks
= df_get_n_blocks (DF_BACKWARD
);
1039 /* The set of blocks that have been seen on this iteration. */
1040 bitmap processed
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
1041 /* The set of blocks that need to have the out vectors reset because
1042 the in of one of their successors has changed. */
1043 bitmap redo_out
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
1044 bitmap all_blocks
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
1045 bool global_changed
= true;
1047 /* These regs are considered always live so if they end up dying
1048 because of some def, we need to bring the back again. Calling
1049 df_simulate_fixup_sets has the disadvantage of calling
1050 bb_has_eh_pred once per insn, so we cache the information
1052 bitmap au
= &df
->regular_block_artificial_uses
;
1053 bitmap au_eh
= &df
->eh_block_artificial_uses
;
1055 struct dead_debug_global global_debug
;
1057 prescan_insns_for_dce (true);
1059 for (i
= 0; i
< n_blocks
; i
++)
1060 bitmap_set_bit (all_blocks
, postorder
[i
]);
1062 dead_debug_global_init (&global_debug
, NULL
);
1064 while (global_changed
)
1066 global_changed
= false;
1068 for (i
= 0; i
< n_blocks
; i
++)
1070 int index
= postorder
[i
];
1071 basic_block bb
= BASIC_BLOCK_FOR_FN (cfun
, index
);
1074 if (index
< NUM_FIXED_BLOCKS
)
1076 bitmap_set_bit (processed
, index
);
1082 = word_dce_process_block (bb
, bitmap_bit_p (redo_out
, index
),
1086 = dce_process_block (bb
, bitmap_bit_p (redo_out
, index
),
1087 bb_has_eh_pred (bb
) ? au_eh
: au
,
1089 bitmap_set_bit (processed
, index
);
1095 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1096 if (bitmap_bit_p (processed
, e
->src
->index
))
1097 /* Be tricky about when we need to iterate the
1098 analysis. We only have redo the analysis if the
1099 bitmaps change at the top of a block that is the
1101 global_changed
= true;
1103 bitmap_set_bit (redo_out
, e
->src
->index
);
1109 /* Turn off the RUN_DCE flag to prevent recursive calls to
1111 int old_flag
= df_clear_flags (DF_LR_RUN_DCE
);
1113 /* So something was deleted that requires a redo. Do it on
1115 delete_unmarked_insns ();
1116 bitmap_clear (marked
);
1117 bitmap_clear (processed
);
1118 bitmap_clear (redo_out
);
1120 /* We do not need to rescan any instructions. We only need
1121 to redo the dataflow equations for the blocks that had a
1122 change at the top of the block. Then we need to redo the
1125 df_analyze_problem (df_word_lr
, all_blocks
, postorder
, n_blocks
);
1127 df_analyze_problem (df_lr
, all_blocks
, postorder
, n_blocks
);
1129 if (old_flag
& DF_LR_RUN_DCE
)
1130 df_set_flags (DF_LR_RUN_DCE
);
1132 prescan_insns_for_dce (true);
1136 dead_debug_global_finish (&global_debug
, NULL
);
1138 delete_unmarked_insns ();
1140 BITMAP_FREE (processed
);
1141 BITMAP_FREE (redo_out
);
1142 BITMAP_FREE (all_blocks
);
1146 /* Fast register level DCE. */
1149 rest_of_handle_fast_dce (void)
1158 /* Fast byte level DCE. */
1168 timevar_push (TV_DCE
);
1169 old_flags
= df_clear_flags (DF_DEFER_INSN_RESCAN
+ DF_NO_INSN_RESCAN
);
1170 df_word_lr_add_problem ();
1174 df_set_flags (old_flags
);
1175 timevar_pop (TV_DCE
);
1179 /* This is an internal call that is used by the df live register
1180 problem to run fast dce as a side effect of creating the live
1181 information. The stack is organized so that the lr problem is run,
1182 this pass is run, which updates the live info and the df scanning
1183 info, and then returns to allow the rest of the problems to be run.
1185 This can be called by elsewhere but it will not update the bit
1186 vectors for any other problems than LR. */
1189 run_fast_df_dce (void)
1193 /* If dce is able to delete something, it has to happen
1194 immediately. Otherwise there will be problems handling the
1197 df_clear_flags (DF_DEFER_INSN_RESCAN
+ DF_NO_INSN_RESCAN
);
1199 df_in_progress
= true;
1200 rest_of_handle_fast_dce ();
1201 df_in_progress
= false;
1203 df_set_flags (old_flags
);
1208 /* Run a fast DCE pass. */
1214 rest_of_handle_fast_dce ();
1219 gate_fast_dce (void)
1221 return optimize
> 0 && flag_dce
1222 && dbg_cnt (dce_fast
);
1227 const pass_data pass_data_fast_rtl_dce
=
1229 RTL_PASS
, /* type */
1230 "rtl_dce", /* name */
1231 OPTGROUP_NONE
, /* optinfo_flags */
1232 true, /* has_gate */
1233 true, /* has_execute */
1235 0, /* properties_required */
1236 0, /* properties_provided */
1237 0, /* properties_destroyed */
1238 0, /* todo_flags_start */
1239 ( TODO_df_finish
| TODO_verify_rtl_sharing
), /* todo_flags_finish */
1242 class pass_fast_rtl_dce
: public rtl_opt_pass
1245 pass_fast_rtl_dce (gcc::context
*ctxt
)
1246 : rtl_opt_pass (pass_data_fast_rtl_dce
, ctxt
)
1249 /* opt_pass methods: */
1250 bool gate () { return gate_fast_dce (); }
1251 unsigned int execute () { return rest_of_handle_fast_dce (); }
1253 }; // class pass_fast_rtl_dce
1258 make_pass_fast_rtl_dce (gcc::context
*ctxt
)
1260 return new pass_fast_rtl_dce (ctxt
);