1 /* RTL dead code elimination.
2 Copyright (C) 2005-2015 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"
33 #include "cfgcleanup.h"
37 #include "tree-pass.h"
40 #include "emit-rtl.h" /* FIXME: Can go away once crtl is moved to rtl.h. */
43 /* -------------------------------------------------------------------------
44 Core mark/delete routines
45 ------------------------------------------------------------------------- */
47 /* True if we are invoked while the df engine is running; in this case,
48 we don't want to reenter it. */
49 static bool df_in_progress
= false;
51 /* True if we are allowed to alter the CFG in this pass. */
52 static bool can_alter_cfg
= false;
54 /* Instructions that have been marked but whose dependencies have not
55 yet been processed. */
56 static vec
<rtx_insn
*> worklist
;
58 /* Bitmap of instructions marked as needed indexed by INSN_UID. */
59 static sbitmap marked
;
61 /* Bitmap obstacks used for block processing by the fast algorithm. */
62 static bitmap_obstack dce_blocks_bitmap_obstack
;
63 static bitmap_obstack dce_tmp_bitmap_obstack
;
65 static bool find_call_stack_args (rtx_call_insn
*, bool, bool, bitmap
);
67 /* A subroutine for which BODY is part of the instruction being tested;
68 either the top-level pattern, or an element of a PARALLEL. The
69 instruction is known not to be a bare USE or CLOBBER. */
72 deletable_insn_p_1 (rtx body
)
74 switch (GET_CODE (body
))
78 /* The UNSPEC case was added here because the ia-64 claims that
79 USEs do not work after reload and generates UNSPECS rather
80 than USEs. Since dce is run after reload we need to avoid
81 deleting these even if they are dead. If it turns out that
82 USEs really do work after reload, the ia-64 should be
83 changed, and the UNSPEC case can be removed. */
88 return !volatile_refs_p (body
);
93 /* Return true if INSN is a normal instruction that can be deleted by
97 deletable_insn_p (rtx_insn
*insn
, bool fast
, bitmap arg_stores
)
104 /* We cannot delete calls inside of the recursive dce because
105 this may cause basic blocks to be deleted and this messes up
106 the rest of the stack of optimization passes. */
108 /* We cannot delete pure or const sibling calls because it is
109 hard to see the result. */
110 && (!SIBLING_CALL_P (insn
))
111 /* We can delete dead const or pure calls as long as they do not
113 && (RTL_CONST_OR_PURE_CALL_P (insn
)
114 && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn
)))
115 return find_call_stack_args (as_a
<rtx_call_insn
*> (insn
), false,
118 /* Don't delete jumps, notes and the like. */
119 if (!NONJUMP_INSN_P (insn
))
122 /* Don't delete insns that may throw if we cannot do so. */
123 if (!(cfun
->can_delete_dead_exceptions
&& can_alter_cfg
)
124 && !insn_nothrow_p (insn
))
127 /* If INSN sets a global_reg, leave it untouched. */
128 FOR_EACH_INSN_DEF (def
, insn
)
129 if (HARD_REGISTER_NUM_P (DF_REF_REGNO (def
))
130 && global_regs
[DF_REF_REGNO (def
)])
132 /* Initialization of pseudo PIC register should never be removed. */
133 else if (DF_REF_REG (def
) == pic_offset_table_rtx
134 && REGNO (pic_offset_table_rtx
) >= FIRST_PSEUDO_REGISTER
)
137 body
= PATTERN (insn
);
138 switch (GET_CODE (body
))
147 /* A CLOBBER of a dead pseudo register serves no purpose.
148 That is not necessarily true for hard registers until
151 return REG_P (x
) && (!HARD_REGISTER_P (x
) || reload_completed
);
154 /* Because of the way that use-def chains are built, it is not
155 possible to tell if the clobber is dead because it can
156 never be the target of a use-def chain. */
160 for (i
= XVECLEN (body
, 0) - 1; i
>= 0; i
--)
161 if (!deletable_insn_p_1 (XVECEXP (body
, 0, i
)))
166 return deletable_insn_p_1 (body
);
171 /* Return true if INSN has been marked as needed. */
174 marked_insn_p (rtx_insn
*insn
)
176 /* Artificial defs are always needed and they do not have an insn.
177 We should never see them here. */
179 return bitmap_bit_p (marked
, INSN_UID (insn
));
183 /* If INSN has not yet been marked as needed, mark it now, and add it to
187 mark_insn (rtx_insn
*insn
, bool fast
)
189 if (!marked_insn_p (insn
))
192 worklist
.safe_push (insn
);
193 bitmap_set_bit (marked
, INSN_UID (insn
));
195 fprintf (dump_file
, " Adding insn %d to worklist\n", INSN_UID (insn
));
198 && !SIBLING_CALL_P (insn
)
199 && (RTL_CONST_OR_PURE_CALL_P (insn
)
200 && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn
)))
201 find_call_stack_args (as_a
<rtx_call_insn
*> (insn
), true, fast
, NULL
);
206 /* A note_stores callback used by mark_nonreg_stores. DATA is the
207 instruction containing DEST. */
210 mark_nonreg_stores_1 (rtx dest
, const_rtx pattern
, void *data
)
212 if (GET_CODE (pattern
) != CLOBBER
&& !REG_P (dest
))
213 mark_insn ((rtx_insn
*) data
, true);
217 /* A note_stores callback used by mark_nonreg_stores. DATA is the
218 instruction containing DEST. */
221 mark_nonreg_stores_2 (rtx dest
, const_rtx pattern
, void *data
)
223 if (GET_CODE (pattern
) != CLOBBER
&& !REG_P (dest
))
224 mark_insn ((rtx_insn
*) data
, false);
228 /* Mark INSN if BODY stores to a non-register destination. */
231 mark_nonreg_stores (rtx body
, rtx_insn
*insn
, bool fast
)
234 note_stores (body
, mark_nonreg_stores_1
, insn
);
236 note_stores (body
, mark_nonreg_stores_2
, insn
);
240 /* Return true if store to MEM, starting OFF bytes from stack pointer,
241 is a call argument store, and clear corresponding bits from SP_BYTES
245 check_argument_store (rtx mem
, HOST_WIDE_INT off
, HOST_WIDE_INT min_sp_off
,
246 HOST_WIDE_INT max_sp_off
, bitmap sp_bytes
)
249 for (byte
= off
; byte
< off
+ GET_MODE_SIZE (GET_MODE (mem
)); byte
++)
251 if (byte
< min_sp_off
252 || byte
>= max_sp_off
253 || !bitmap_clear_bit (sp_bytes
, byte
- min_sp_off
))
260 /* Try to find all stack stores of CALL_INSN arguments if
261 ACCUMULATE_OUTGOING_ARGS. If all stack stores have been found
262 and it is therefore safe to eliminate the call, return true,
263 otherwise return false. This function should be first called
264 with DO_MARK false, and only when the CALL_INSN is actually
265 going to be marked called again with DO_MARK true. */
268 find_call_stack_args (rtx_call_insn
*call_insn
, bool do_mark
, bool fast
,
272 rtx_insn
*insn
, *prev_insn
;
274 HOST_WIDE_INT min_sp_off
, max_sp_off
;
277 gcc_assert (CALL_P (call_insn
));
278 if (!ACCUMULATE_OUTGOING_ARGS
)
283 gcc_assert (arg_stores
);
284 bitmap_clear (arg_stores
);
287 min_sp_off
= INTTYPE_MAXIMUM (HOST_WIDE_INT
);
290 /* First determine the minimum and maximum offset from sp for
292 for (p
= CALL_INSN_FUNCTION_USAGE (call_insn
); p
; p
= XEXP (p
, 1))
293 if (GET_CODE (XEXP (p
, 0)) == USE
294 && MEM_P (XEXP (XEXP (p
, 0), 0)))
296 rtx mem
= XEXP (XEXP (p
, 0), 0), addr
;
297 HOST_WIDE_INT off
= 0, size
;
298 if (!MEM_SIZE_KNOWN_P (mem
))
300 size
= MEM_SIZE (mem
);
301 addr
= XEXP (mem
, 0);
302 if (GET_CODE (addr
) == PLUS
303 && REG_P (XEXP (addr
, 0))
304 && CONST_INT_P (XEXP (addr
, 1)))
306 off
= INTVAL (XEXP (addr
, 1));
307 addr
= XEXP (addr
, 0);
309 if (addr
!= stack_pointer_rtx
)
313 /* If not fast, use chains to see if addr wasn't set to
318 struct df_link
*defs
;
321 FOR_EACH_INSN_USE (use
, call_insn
)
322 if (rtx_equal_p (addr
, DF_REF_REG (use
)))
328 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
329 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
335 set
= single_set (DF_REF_INSN (defs
->ref
));
339 if (GET_CODE (SET_SRC (set
)) != PLUS
340 || XEXP (SET_SRC (set
), 0) != stack_pointer_rtx
341 || !CONST_INT_P (XEXP (SET_SRC (set
), 1)))
344 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
349 min_sp_off
= MIN (min_sp_off
, off
);
350 max_sp_off
= MAX (max_sp_off
, off
+ size
);
353 if (min_sp_off
>= max_sp_off
)
355 sp_bytes
= BITMAP_ALLOC (NULL
);
357 /* Set bits in SP_BYTES bitmap for bytes relative to sp + min_sp_off
358 which contain arguments. Checking has been done in the previous
360 for (p
= CALL_INSN_FUNCTION_USAGE (call_insn
); p
; p
= XEXP (p
, 1))
361 if (GET_CODE (XEXP (p
, 0)) == USE
362 && MEM_P (XEXP (XEXP (p
, 0), 0)))
364 rtx mem
= XEXP (XEXP (p
, 0), 0), addr
;
365 HOST_WIDE_INT off
= 0, byte
;
366 addr
= XEXP (mem
, 0);
367 if (GET_CODE (addr
) == PLUS
368 && REG_P (XEXP (addr
, 0))
369 && CONST_INT_P (XEXP (addr
, 1)))
371 off
= INTVAL (XEXP (addr
, 1));
372 addr
= XEXP (addr
, 0);
374 if (addr
!= stack_pointer_rtx
)
377 struct df_link
*defs
;
380 FOR_EACH_INSN_USE (use
, call_insn
)
381 if (rtx_equal_p (addr
, DF_REF_REG (use
)))
384 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
385 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
388 set
= single_set (DF_REF_INSN (defs
->ref
));
389 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
391 for (byte
= off
; byte
< off
+ MEM_SIZE (mem
); byte
++)
393 if (!bitmap_set_bit (sp_bytes
, byte
- min_sp_off
))
398 /* Walk backwards, looking for argument stores. The search stops
399 when seeing another call, sp adjustment or memory store other than
402 for (insn
= PREV_INSN (call_insn
); insn
; insn
= prev_insn
)
407 if (insn
== BB_HEAD (BLOCK_FOR_INSN (call_insn
)))
410 prev_insn
= PREV_INSN (insn
);
415 if (!NONDEBUG_INSN_P (insn
))
418 set
= single_set (insn
);
419 if (!set
|| SET_DEST (set
) == stack_pointer_rtx
)
422 if (!MEM_P (SET_DEST (set
)))
425 mem
= SET_DEST (set
);
426 addr
= XEXP (mem
, 0);
428 if (GET_CODE (addr
) == PLUS
429 && REG_P (XEXP (addr
, 0))
430 && CONST_INT_P (XEXP (addr
, 1)))
432 off
= INTVAL (XEXP (addr
, 1));
433 addr
= XEXP (addr
, 0);
435 if (addr
!= stack_pointer_rtx
)
442 struct df_link
*defs
;
445 FOR_EACH_INSN_USE (use
, insn
)
446 if (rtx_equal_p (addr
, DF_REF_REG (use
)))
452 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
453 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
459 set
= single_set (DF_REF_INSN (defs
->ref
));
463 if (GET_CODE (SET_SRC (set
)) != PLUS
464 || XEXP (SET_SRC (set
), 0) != stack_pointer_rtx
465 || !CONST_INT_P (XEXP (SET_SRC (set
), 1)))
468 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
474 if (GET_MODE_SIZE (GET_MODE (mem
)) == 0
475 || !check_argument_store (mem
, off
, min_sp_off
,
476 max_sp_off
, sp_bytes
))
479 if (!deletable_insn_p (insn
, fast
, NULL
))
483 mark_insn (insn
, fast
);
485 bitmap_set_bit (arg_stores
, INSN_UID (insn
));
487 if (bitmap_empty_p (sp_bytes
))
494 BITMAP_FREE (sp_bytes
);
495 if (!ret
&& arg_stores
)
496 bitmap_clear (arg_stores
);
502 /* Remove all REG_EQUAL and REG_EQUIV notes referring to the registers INSN
506 remove_reg_equal_equiv_notes_for_defs (rtx_insn
*insn
)
510 FOR_EACH_INSN_DEF (def
, insn
)
511 remove_reg_equal_equiv_notes_for_regno (DF_REF_REGNO (def
));
514 /* Scan all BBs for debug insns and reset those that reference values
515 defined in unmarked insns. */
518 reset_unmarked_insns_debug_uses (void)
521 rtx_insn
*insn
, *next
;
523 FOR_EACH_BB_REVERSE_FN (bb
, cfun
)
524 FOR_BB_INSNS_REVERSE_SAFE (bb
, insn
, next
)
525 if (DEBUG_INSN_P (insn
))
529 FOR_EACH_INSN_USE (use
, insn
)
531 struct df_link
*defs
;
532 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
535 if (DF_REF_IS_ARTIFICIAL (defs
->ref
))
537 ref_insn
= DF_REF_INSN (defs
->ref
);
538 if (!marked_insn_p (ref_insn
))
543 /* ??? FIXME could we propagate the values assigned to
545 INSN_VAR_LOCATION_LOC (insn
) = gen_rtx_UNKNOWN_VAR_LOC ();
546 df_insn_rescan_debug_internal (insn
);
552 /* Delete every instruction that hasn't been marked. */
555 delete_unmarked_insns (void)
558 rtx_insn
*insn
, *next
;
559 bool must_clean
= false;
561 FOR_EACH_BB_REVERSE_FN (bb
, cfun
)
562 FOR_BB_INSNS_REVERSE_SAFE (bb
, insn
, next
)
563 if (NONDEBUG_INSN_P (insn
))
565 /* Always delete no-op moves. */
566 if (noop_move_p (insn
))
569 /* Otherwise rely only on the DCE algorithm. */
570 else if (marked_insn_p (insn
))
573 /* Beware that reaching a dbg counter limit here can result
574 in miscompiled file. This occurs when a group of insns
575 must be deleted together, typically because the kept insn
576 depends on the output from the deleted insn. Deleting
577 this insns in reverse order (both at the bb level and
578 when looking at the blocks) minimizes this, but does not
579 eliminate it, since it is possible for the using insn to
580 be top of a block and the producer to be at the bottom of
581 the block. However, in most cases this will only result
582 in an uninitialized use of an insn that is dead anyway.
584 However, there is one rare case that will cause a
585 miscompile: deletion of non-looping pure and constant
586 calls on a machine where ACCUMULATE_OUTGOING_ARGS is true.
587 In this case it is possible to remove the call, but leave
588 the argument pushes to the stack. Because of the changes
589 to the stack pointer, this will almost always lead to a
595 fprintf (dump_file
, "DCE: Deleting insn %d\n", INSN_UID (insn
));
597 /* Before we delete the insn we have to remove the REG_EQUAL notes
598 for the destination regs in order to avoid dangling notes. */
599 remove_reg_equal_equiv_notes_for_defs (insn
);
601 /* If a pure or const call is deleted, this may make the cfg
602 have unreachable blocks. We rememeber this and call
603 delete_unreachable_blocks at the end. */
607 /* Now delete the insn. */
608 delete_insn_and_edges (insn
);
611 /* Deleted a pure or const call. */
613 delete_unreachable_blocks ();
617 /* Go through the instructions and mark those whose necessity is not
618 dependent on inter-instruction information. Make sure all other
619 instructions are not marked. */
622 prescan_insns_for_dce (bool fast
)
625 rtx_insn
*insn
, *prev
;
626 bitmap arg_stores
= NULL
;
629 fprintf (dump_file
, "Finding needed instructions:\n");
631 if (!df_in_progress
&& ACCUMULATE_OUTGOING_ARGS
)
632 arg_stores
= BITMAP_ALLOC (NULL
);
634 FOR_EACH_BB_FN (bb
, cfun
)
636 FOR_BB_INSNS_REVERSE_SAFE (bb
, insn
, prev
)
637 if (NONDEBUG_INSN_P (insn
))
639 /* Don't mark argument stores now. They will be marked
640 if needed when the associated CALL is marked. */
641 if (arg_stores
&& bitmap_bit_p (arg_stores
, INSN_UID (insn
)))
643 if (deletable_insn_p (insn
, fast
, arg_stores
))
644 mark_nonreg_stores (PATTERN (insn
), insn
, fast
);
646 mark_insn (insn
, fast
);
648 /* find_call_stack_args only looks at argument stores in the
651 bitmap_clear (arg_stores
);
655 BITMAP_FREE (arg_stores
);
658 fprintf (dump_file
, "Finished finding needed instructions:\n");
662 /* UD-based DSE routines. */
664 /* Mark instructions that define artificially-used registers, such as
665 the frame pointer and the stack pointer. */
668 mark_artificial_uses (void)
671 struct df_link
*defs
;
674 FOR_ALL_BB_FN (bb
, cfun
)
675 FOR_EACH_ARTIFICIAL_USE (use
, bb
->index
)
676 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
677 if (!DF_REF_IS_ARTIFICIAL (defs
->ref
))
678 mark_insn (DF_REF_INSN (defs
->ref
), false);
682 /* Mark every instruction that defines a register value that INSN uses. */
685 mark_reg_dependencies (rtx_insn
*insn
)
687 struct df_link
*defs
;
690 if (DEBUG_INSN_P (insn
))
693 FOR_EACH_INSN_USE (use
, insn
)
697 fprintf (dump_file
, "Processing use of ");
698 print_simple_rtl (dump_file
, DF_REF_REG (use
));
699 fprintf (dump_file
, " in insn %d:\n", INSN_UID (insn
));
701 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
702 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
703 mark_insn (DF_REF_INSN (defs
->ref
), false);
708 /* Initialize global variables for a new DCE pass. */
717 df_set_flags (DF_RD_PRUNE_DEAD_DEFS
);
718 df_chain_add_problem (DF_UD_CHAIN
);
728 bitmap_obstack_initialize (&dce_blocks_bitmap_obstack
);
729 bitmap_obstack_initialize (&dce_tmp_bitmap_obstack
);
730 can_alter_cfg
= false;
733 can_alter_cfg
= true;
735 marked
= sbitmap_alloc (get_max_uid () + 1);
736 bitmap_clear (marked
);
740 /* Free the data allocated by init_dce. */
745 sbitmap_free (marked
);
749 bitmap_obstack_release (&dce_blocks_bitmap_obstack
);
750 bitmap_obstack_release (&dce_tmp_bitmap_obstack
);
755 /* UD-chain based DCE. */
758 rest_of_handle_ud_dce (void)
764 prescan_insns_for_dce (false);
765 mark_artificial_uses ();
766 while (worklist
.length () > 0)
768 insn
= worklist
.pop ();
769 mark_reg_dependencies (insn
);
773 if (MAY_HAVE_DEBUG_INSNS
)
774 reset_unmarked_insns_debug_uses ();
776 /* Before any insns are deleted, we must remove the chains since
777 they are not bidirectional. */
778 df_remove_problem (df_chain
);
779 delete_unmarked_insns ();
788 const pass_data pass_data_ud_rtl_dce
=
792 OPTGROUP_NONE
, /* optinfo_flags */
794 0, /* properties_required */
795 0, /* properties_provided */
796 0, /* properties_destroyed */
797 0, /* todo_flags_start */
798 TODO_df_finish
, /* todo_flags_finish */
801 class pass_ud_rtl_dce
: public rtl_opt_pass
804 pass_ud_rtl_dce (gcc::context
*ctxt
)
805 : rtl_opt_pass (pass_data_ud_rtl_dce
, ctxt
)
808 /* opt_pass methods: */
809 virtual bool gate (function
*)
811 return optimize
> 1 && flag_dce
&& dbg_cnt (dce_ud
);
814 virtual unsigned int execute (function
*)
816 return rest_of_handle_ud_dce ();
819 }; // class pass_ud_rtl_dce
824 make_pass_ud_rtl_dce (gcc::context
*ctxt
)
826 return new pass_ud_rtl_dce (ctxt
);
830 /* -------------------------------------------------------------------------
832 ------------------------------------------------------------------------- */
834 /* Process basic block BB. Return true if the live_in set has
835 changed. REDO_OUT is true if the info at the bottom of the block
836 needs to be recalculated before starting. AU is the proper set of
837 artificial uses. Track global substitution of uses of dead pseudos
838 in debug insns using GLOBAL_DEBUG. */
841 word_dce_process_block (basic_block bb
, bool redo_out
,
842 struct dead_debug_global
*global_debug
)
844 bitmap local_live
= BITMAP_ALLOC (&dce_tmp_bitmap_obstack
);
847 struct dead_debug_local debug
;
851 /* Need to redo the live_out set of this block if when one of
852 the succs of this block has had a change in it live in
856 df_confluence_function_n con_fun_n
= df_word_lr
->problem
->con_fun_n
;
857 bitmap_clear (DF_WORD_LR_OUT (bb
));
858 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
864 fprintf (dump_file
, "processing block %d live out = ", bb
->index
);
865 df_print_word_regset (dump_file
, DF_WORD_LR_OUT (bb
));
868 bitmap_copy (local_live
, DF_WORD_LR_OUT (bb
));
869 dead_debug_local_init (&debug
, NULL
, global_debug
);
871 FOR_BB_INSNS_REVERSE (bb
, insn
)
872 if (DEBUG_INSN_P (insn
))
875 FOR_EACH_INSN_USE (use
, insn
)
876 if (DF_REF_REGNO (use
) >= FIRST_PSEUDO_REGISTER
877 && (GET_MODE_SIZE (GET_MODE (DF_REF_REAL_REG (use
)))
878 == 2 * UNITS_PER_WORD
)
879 && !bitmap_bit_p (local_live
, 2 * DF_REF_REGNO (use
))
880 && !bitmap_bit_p (local_live
, 2 * DF_REF_REGNO (use
) + 1))
881 dead_debug_add (&debug
, use
, DF_REF_REGNO (use
));
883 else if (INSN_P (insn
))
887 /* No matter if the instruction is needed or not, we remove
888 any regno in the defs from the live set. */
889 any_changed
= df_word_lr_simulate_defs (insn
, local_live
);
891 mark_insn (insn
, true);
893 /* On the other hand, we do not allow the dead uses to set
894 anything in local_live. */
895 if (marked_insn_p (insn
))
896 df_word_lr_simulate_uses (insn
, local_live
);
898 /* Insert debug temps for dead REGs used in subsequent debug
899 insns. We may have to emit a debug temp even if the insn
900 was marked, in case the debug use was after the point of
902 if (debug
.used
&& !bitmap_empty_p (debug
.used
))
906 FOR_EACH_INSN_DEF (def
, insn
)
907 dead_debug_insert_temp (&debug
, DF_REF_REGNO (def
), insn
,
909 && !control_flow_insn_p (insn
)
910 ? DEBUG_TEMP_AFTER_WITH_REG_FORCE
911 : DEBUG_TEMP_BEFORE_WITH_VALUE
);
916 fprintf (dump_file
, "finished processing insn %d live out = ",
918 df_print_word_regset (dump_file
, local_live
);
922 block_changed
= !bitmap_equal_p (local_live
, DF_WORD_LR_IN (bb
));
924 bitmap_copy (DF_WORD_LR_IN (bb
), local_live
);
926 dead_debug_local_finish (&debug
, NULL
);
927 BITMAP_FREE (local_live
);
928 return block_changed
;
932 /* Process basic block BB. Return true if the live_in set has
933 changed. REDO_OUT is true if the info at the bottom of the block
934 needs to be recalculated before starting. AU is the proper set of
935 artificial uses. Track global substitution of uses of dead pseudos
936 in debug insns using GLOBAL_DEBUG. */
939 dce_process_block (basic_block bb
, bool redo_out
, bitmap au
,
940 struct dead_debug_global
*global_debug
)
942 bitmap local_live
= BITMAP_ALLOC (&dce_tmp_bitmap_obstack
);
946 struct dead_debug_local debug
;
950 /* Need to redo the live_out set of this block if when one of
951 the succs of this block has had a change in it live in
955 df_confluence_function_n con_fun_n
= df_lr
->problem
->con_fun_n
;
956 bitmap_clear (DF_LR_OUT (bb
));
957 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
963 fprintf (dump_file
, "processing block %d lr out = ", bb
->index
);
964 df_print_regset (dump_file
, DF_LR_OUT (bb
));
967 bitmap_copy (local_live
, DF_LR_OUT (bb
));
969 df_simulate_initialize_backwards (bb
, local_live
);
970 dead_debug_local_init (&debug
, NULL
, global_debug
);
972 FOR_BB_INSNS_REVERSE (bb
, insn
)
973 if (DEBUG_INSN_P (insn
))
976 FOR_EACH_INSN_USE (use
, insn
)
977 if (!bitmap_bit_p (local_live
, DF_REF_REGNO (use
))
978 && !bitmap_bit_p (au
, DF_REF_REGNO (use
)))
979 dead_debug_add (&debug
, use
, DF_REF_REGNO (use
));
981 else if (INSN_P (insn
))
983 bool needed
= marked_insn_p (insn
);
985 /* The insn is needed if there is someone who uses the output. */
987 FOR_EACH_INSN_DEF (def
, insn
)
988 if (bitmap_bit_p (local_live
, DF_REF_REGNO (def
))
989 || bitmap_bit_p (au
, DF_REF_REGNO (def
)))
992 mark_insn (insn
, true);
996 /* No matter if the instruction is needed or not, we remove
997 any regno in the defs from the live set. */
998 df_simulate_defs (insn
, local_live
);
1000 /* On the other hand, we do not allow the dead uses to set
1001 anything in local_live. */
1003 df_simulate_uses (insn
, local_live
);
1005 /* Insert debug temps for dead REGs used in subsequent debug
1006 insns. We may have to emit a debug temp even if the insn
1007 was marked, in case the debug use was after the point of
1009 if (debug
.used
&& !bitmap_empty_p (debug
.used
))
1010 FOR_EACH_INSN_DEF (def
, insn
)
1011 dead_debug_insert_temp (&debug
, DF_REF_REGNO (def
), insn
,
1012 needed
&& !control_flow_insn_p (insn
)
1013 ? DEBUG_TEMP_AFTER_WITH_REG_FORCE
1014 : DEBUG_TEMP_BEFORE_WITH_VALUE
);
1017 dead_debug_local_finish (&debug
, NULL
);
1018 df_simulate_finalize_backwards (bb
, local_live
);
1020 block_changed
= !bitmap_equal_p (local_live
, DF_LR_IN (bb
));
1022 bitmap_copy (DF_LR_IN (bb
), local_live
);
1024 BITMAP_FREE (local_live
);
1025 return block_changed
;
1029 /* Perform fast DCE once initialization is done. If WORD_LEVEL is
1030 true, use the word level dce, otherwise do it at the pseudo
1034 fast_dce (bool word_level
)
1036 int *postorder
= df_get_postorder (DF_BACKWARD
);
1037 int n_blocks
= df_get_n_blocks (DF_BACKWARD
);
1038 /* The set of blocks that have been seen on this iteration. */
1039 bitmap processed
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
1040 /* The set of blocks that need to have the out vectors reset because
1041 the in of one of their successors has changed. */
1042 bitmap redo_out
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
1043 bitmap all_blocks
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
1044 bool global_changed
= true;
1046 /* These regs are considered always live so if they end up dying
1047 because of some def, we need to bring the back again. Calling
1048 df_simulate_fixup_sets has the disadvantage of calling
1049 bb_has_eh_pred once per insn, so we cache the information
1051 bitmap au
= &df
->regular_block_artificial_uses
;
1052 bitmap au_eh
= &df
->eh_block_artificial_uses
;
1054 struct dead_debug_global global_debug
;
1056 prescan_insns_for_dce (true);
1058 for (i
= 0; i
< n_blocks
; i
++)
1059 bitmap_set_bit (all_blocks
, postorder
[i
]);
1061 dead_debug_global_init (&global_debug
, NULL
);
1063 while (global_changed
)
1065 global_changed
= false;
1067 for (i
= 0; i
< n_blocks
; i
++)
1069 int index
= postorder
[i
];
1070 basic_block bb
= BASIC_BLOCK_FOR_FN (cfun
, index
);
1073 if (index
< NUM_FIXED_BLOCKS
)
1075 bitmap_set_bit (processed
, index
);
1081 = word_dce_process_block (bb
, bitmap_bit_p (redo_out
, index
),
1085 = dce_process_block (bb
, bitmap_bit_p (redo_out
, index
),
1086 bb_has_eh_pred (bb
) ? au_eh
: au
,
1088 bitmap_set_bit (processed
, index
);
1094 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1095 if (bitmap_bit_p (processed
, e
->src
->index
))
1096 /* Be tricky about when we need to iterate the
1097 analysis. We only have redo the analysis if the
1098 bitmaps change at the top of a block that is the
1100 global_changed
= true;
1102 bitmap_set_bit (redo_out
, e
->src
->index
);
1108 /* Turn off the RUN_DCE flag to prevent recursive calls to
1110 int old_flag
= df_clear_flags (DF_LR_RUN_DCE
);
1112 /* So something was deleted that requires a redo. Do it on
1114 delete_unmarked_insns ();
1115 bitmap_clear (marked
);
1116 bitmap_clear (processed
);
1117 bitmap_clear (redo_out
);
1119 /* We do not need to rescan any instructions. We only need
1120 to redo the dataflow equations for the blocks that had a
1121 change at the top of the block. Then we need to redo the
1124 df_analyze_problem (df_word_lr
, all_blocks
, postorder
, n_blocks
);
1126 df_analyze_problem (df_lr
, all_blocks
, postorder
, n_blocks
);
1128 if (old_flag
& DF_LR_RUN_DCE
)
1129 df_set_flags (DF_LR_RUN_DCE
);
1131 prescan_insns_for_dce (true);
1135 dead_debug_global_finish (&global_debug
, NULL
);
1137 delete_unmarked_insns ();
1139 BITMAP_FREE (processed
);
1140 BITMAP_FREE (redo_out
);
1141 BITMAP_FREE (all_blocks
);
1145 /* Fast register level DCE. */
1148 rest_of_handle_fast_dce (void)
1157 /* Fast byte level DCE. */
1167 timevar_push (TV_DCE
);
1168 old_flags
= df_clear_flags (DF_DEFER_INSN_RESCAN
+ DF_NO_INSN_RESCAN
);
1169 df_word_lr_add_problem ();
1173 df_set_flags (old_flags
);
1174 timevar_pop (TV_DCE
);
1178 /* This is an internal call that is used by the df live register
1179 problem to run fast dce as a side effect of creating the live
1180 information. The stack is organized so that the lr problem is run,
1181 this pass is run, which updates the live info and the df scanning
1182 info, and then returns to allow the rest of the problems to be run.
1184 This can be called by elsewhere but it will not update the bit
1185 vectors for any other problems than LR. */
1188 run_fast_df_dce (void)
1192 /* If dce is able to delete something, it has to happen
1193 immediately. Otherwise there will be problems handling the
1196 df_clear_flags (DF_DEFER_INSN_RESCAN
+ DF_NO_INSN_RESCAN
);
1198 df_in_progress
= true;
1199 rest_of_handle_fast_dce ();
1200 df_in_progress
= false;
1202 df_set_flags (old_flags
);
1207 /* Run a fast DCE pass. */
1213 rest_of_handle_fast_dce ();
1219 const pass_data pass_data_fast_rtl_dce
=
1221 RTL_PASS
, /* type */
1222 "rtl_dce", /* name */
1223 OPTGROUP_NONE
, /* optinfo_flags */
1225 0, /* properties_required */
1226 0, /* properties_provided */
1227 0, /* properties_destroyed */
1228 0, /* todo_flags_start */
1229 TODO_df_finish
, /* todo_flags_finish */
1232 class pass_fast_rtl_dce
: public rtl_opt_pass
1235 pass_fast_rtl_dce (gcc::context
*ctxt
)
1236 : rtl_opt_pass (pass_data_fast_rtl_dce
, ctxt
)
1239 /* opt_pass methods: */
1240 virtual bool gate (function
*)
1242 return optimize
> 0 && flag_dce
&& dbg_cnt (dce_fast
);
1245 virtual unsigned int execute (function
*)
1247 return rest_of_handle_fast_dce ();
1250 }; // class pass_fast_rtl_dce
1255 make_pass_fast_rtl_dce (gcc::context
*ctxt
)
1257 return new pass_fast_rtl_dce (ctxt
);