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_insn
*> 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_call_insn
*, 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
*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 (as_a
<rtx_call_insn
*> (insn
), false,
116 /* Don't delete jumps, notes and the like. */
117 if (!NONJUMP_INSN_P (insn
))
120 /* Don't delete insns that may throw if we cannot do so. */
121 if (!(cfun
->can_delete_dead_exceptions
&& can_alter_cfg
)
122 && !insn_nothrow_p (insn
))
125 /* If INSN sets a global_reg, leave it untouched. */
126 FOR_EACH_INSN_DEF (def
, insn
)
127 if (HARD_REGISTER_NUM_P (DF_REF_REGNO (def
))
128 && global_regs
[DF_REF_REGNO (def
)])
130 /* Initialization of pseudo PIC register should never be removed. */
131 else if (DF_REF_REG (def
) == pic_offset_table_rtx
132 && REGNO (pic_offset_table_rtx
) >= FIRST_PSEUDO_REGISTER
)
135 body
= PATTERN (insn
);
136 switch (GET_CODE (body
))
145 /* A CLOBBER of a dead pseudo register serves no purpose.
146 That is not necessarily true for hard registers until
149 return REG_P (x
) && (!HARD_REGISTER_P (x
) || reload_completed
);
152 /* Because of the way that use-def chains are built, it is not
153 possible to tell if the clobber is dead because it can
154 never be the target of a use-def chain. */
158 for (i
= XVECLEN (body
, 0) - 1; i
>= 0; i
--)
159 if (!deletable_insn_p_1 (XVECEXP (body
, 0, i
)))
164 return deletable_insn_p_1 (body
);
169 /* Return true if INSN has been marked as needed. */
172 marked_insn_p (rtx_insn
*insn
)
174 /* Artificial defs are always needed and they do not have an insn.
175 We should never see them here. */
177 return bitmap_bit_p (marked
, INSN_UID (insn
));
181 /* If INSN has not yet been marked as needed, mark it now, and add it to
185 mark_insn (rtx_insn
*insn
, bool fast
)
187 if (!marked_insn_p (insn
))
190 worklist
.safe_push (insn
);
191 bitmap_set_bit (marked
, INSN_UID (insn
));
193 fprintf (dump_file
, " Adding insn %d to worklist\n", INSN_UID (insn
));
196 && !SIBLING_CALL_P (insn
)
197 && (RTL_CONST_OR_PURE_CALL_P (insn
)
198 && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn
)))
199 find_call_stack_args (as_a
<rtx_call_insn
*> (insn
), true, fast
, NULL
);
204 /* A note_stores callback used by mark_nonreg_stores. DATA is the
205 instruction containing DEST. */
208 mark_nonreg_stores_1 (rtx dest
, const_rtx pattern
, void *data
)
210 if (GET_CODE (pattern
) != CLOBBER
&& !REG_P (dest
))
211 mark_insn ((rtx_insn
*) data
, true);
215 /* A note_stores callback used by mark_nonreg_stores. DATA is the
216 instruction containing DEST. */
219 mark_nonreg_stores_2 (rtx dest
, const_rtx pattern
, void *data
)
221 if (GET_CODE (pattern
) != CLOBBER
&& !REG_P (dest
))
222 mark_insn ((rtx_insn
*) data
, false);
226 /* Mark INSN if BODY stores to a non-register destination. */
229 mark_nonreg_stores (rtx body
, rtx_insn
*insn
, bool fast
)
232 note_stores (body
, mark_nonreg_stores_1
, insn
);
234 note_stores (body
, mark_nonreg_stores_2
, insn
);
238 /* Return true if store to MEM, starting OFF bytes from stack pointer,
239 is a call argument store, and clear corresponding bits from SP_BYTES
243 check_argument_store (rtx mem
, HOST_WIDE_INT off
, HOST_WIDE_INT min_sp_off
,
244 HOST_WIDE_INT max_sp_off
, bitmap sp_bytes
)
247 for (byte
= off
; byte
< off
+ GET_MODE_SIZE (GET_MODE (mem
)); byte
++)
249 if (byte
< min_sp_off
250 || byte
>= max_sp_off
251 || !bitmap_clear_bit (sp_bytes
, byte
- min_sp_off
))
258 /* Try to find all stack stores of CALL_INSN arguments if
259 ACCUMULATE_OUTGOING_ARGS. If all stack stores have been found
260 and it is therefore safe to eliminate the call, return true,
261 otherwise return false. This function should be first called
262 with DO_MARK false, and only when the CALL_INSN is actually
263 going to be marked called again with DO_MARK true. */
266 find_call_stack_args (rtx_call_insn
*call_insn
, bool do_mark
, bool fast
,
270 rtx_insn
*insn
, *prev_insn
;
272 HOST_WIDE_INT min_sp_off
, max_sp_off
;
275 gcc_assert (CALL_P (call_insn
));
276 if (!ACCUMULATE_OUTGOING_ARGS
)
281 gcc_assert (arg_stores
);
282 bitmap_clear (arg_stores
);
285 min_sp_off
= INTTYPE_MAXIMUM (HOST_WIDE_INT
);
288 /* First determine the minimum and maximum offset from sp for
290 for (p
= CALL_INSN_FUNCTION_USAGE (call_insn
); p
; p
= XEXP (p
, 1))
291 if (GET_CODE (XEXP (p
, 0)) == USE
292 && MEM_P (XEXP (XEXP (p
, 0), 0)))
294 rtx mem
= XEXP (XEXP (p
, 0), 0), addr
;
295 HOST_WIDE_INT off
= 0, size
;
296 if (!MEM_SIZE_KNOWN_P (mem
))
298 size
= MEM_SIZE (mem
);
299 addr
= XEXP (mem
, 0);
300 if (GET_CODE (addr
) == PLUS
301 && REG_P (XEXP (addr
, 0))
302 && CONST_INT_P (XEXP (addr
, 1)))
304 off
= INTVAL (XEXP (addr
, 1));
305 addr
= XEXP (addr
, 0);
307 if (addr
!= stack_pointer_rtx
)
311 /* If not fast, use chains to see if addr wasn't set to
316 struct df_link
*defs
;
319 FOR_EACH_INSN_USE (use
, call_insn
)
320 if (rtx_equal_p (addr
, DF_REF_REG (use
)))
326 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
327 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
333 set
= single_set (DF_REF_INSN (defs
->ref
));
337 if (GET_CODE (SET_SRC (set
)) != PLUS
338 || XEXP (SET_SRC (set
), 0) != stack_pointer_rtx
339 || !CONST_INT_P (XEXP (SET_SRC (set
), 1)))
342 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
347 min_sp_off
= MIN (min_sp_off
, off
);
348 max_sp_off
= MAX (max_sp_off
, off
+ size
);
351 if (min_sp_off
>= max_sp_off
)
353 sp_bytes
= BITMAP_ALLOC (NULL
);
355 /* Set bits in SP_BYTES bitmap for bytes relative to sp + min_sp_off
356 which contain arguments. Checking has been done in the previous
358 for (p
= CALL_INSN_FUNCTION_USAGE (call_insn
); p
; p
= XEXP (p
, 1))
359 if (GET_CODE (XEXP (p
, 0)) == USE
360 && MEM_P (XEXP (XEXP (p
, 0), 0)))
362 rtx mem
= XEXP (XEXP (p
, 0), 0), addr
;
363 HOST_WIDE_INT off
= 0, byte
;
364 addr
= XEXP (mem
, 0);
365 if (GET_CODE (addr
) == PLUS
366 && REG_P (XEXP (addr
, 0))
367 && CONST_INT_P (XEXP (addr
, 1)))
369 off
= INTVAL (XEXP (addr
, 1));
370 addr
= XEXP (addr
, 0);
372 if (addr
!= stack_pointer_rtx
)
375 struct df_link
*defs
;
378 FOR_EACH_INSN_USE (use
, call_insn
)
379 if (rtx_equal_p (addr
, DF_REF_REG (use
)))
382 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
383 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
386 set
= single_set (DF_REF_INSN (defs
->ref
));
387 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
389 for (byte
= off
; byte
< off
+ MEM_SIZE (mem
); byte
++)
391 if (!bitmap_set_bit (sp_bytes
, byte
- min_sp_off
))
396 /* Walk backwards, looking for argument stores. The search stops
397 when seeing another call, sp adjustment or memory store other than
400 for (insn
= PREV_INSN (call_insn
); insn
; insn
= prev_insn
)
405 if (insn
== BB_HEAD (BLOCK_FOR_INSN (call_insn
)))
408 prev_insn
= PREV_INSN (insn
);
413 if (!NONDEBUG_INSN_P (insn
))
416 set
= single_set (insn
);
417 if (!set
|| SET_DEST (set
) == stack_pointer_rtx
)
420 if (!MEM_P (SET_DEST (set
)))
423 mem
= SET_DEST (set
);
424 addr
= XEXP (mem
, 0);
426 if (GET_CODE (addr
) == PLUS
427 && REG_P (XEXP (addr
, 0))
428 && CONST_INT_P (XEXP (addr
, 1)))
430 off
= INTVAL (XEXP (addr
, 1));
431 addr
= XEXP (addr
, 0);
433 if (addr
!= stack_pointer_rtx
)
440 struct df_link
*defs
;
443 FOR_EACH_INSN_USE (use
, insn
)
444 if (rtx_equal_p (addr
, DF_REF_REG (use
)))
450 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
451 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
457 set
= single_set (DF_REF_INSN (defs
->ref
));
461 if (GET_CODE (SET_SRC (set
)) != PLUS
462 || XEXP (SET_SRC (set
), 0) != stack_pointer_rtx
463 || !CONST_INT_P (XEXP (SET_SRC (set
), 1)))
466 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
472 if (GET_MODE_SIZE (GET_MODE (mem
)) == 0
473 || !check_argument_store (mem
, off
, min_sp_off
,
474 max_sp_off
, sp_bytes
))
477 if (!deletable_insn_p (insn
, fast
, NULL
))
481 mark_insn (insn
, fast
);
483 bitmap_set_bit (arg_stores
, INSN_UID (insn
));
485 if (bitmap_empty_p (sp_bytes
))
492 BITMAP_FREE (sp_bytes
);
493 if (!ret
&& arg_stores
)
494 bitmap_clear (arg_stores
);
500 /* Remove all REG_EQUAL and REG_EQUIV notes referring to the registers INSN
504 remove_reg_equal_equiv_notes_for_defs (rtx_insn
*insn
)
508 FOR_EACH_INSN_DEF (def
, insn
)
509 remove_reg_equal_equiv_notes_for_regno (DF_REF_REGNO (def
));
512 /* Scan all BBs for debug insns and reset those that reference values
513 defined in unmarked insns. */
516 reset_unmarked_insns_debug_uses (void)
519 rtx_insn
*insn
, *next
;
521 FOR_EACH_BB_REVERSE_FN (bb
, cfun
)
522 FOR_BB_INSNS_REVERSE_SAFE (bb
, insn
, next
)
523 if (DEBUG_INSN_P (insn
))
527 FOR_EACH_INSN_USE (use
, insn
)
529 struct df_link
*defs
;
530 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
533 if (DF_REF_IS_ARTIFICIAL (defs
->ref
))
535 ref_insn
= DF_REF_INSN (defs
->ref
);
536 if (!marked_insn_p (ref_insn
))
541 /* ??? FIXME could we propagate the values assigned to
543 INSN_VAR_LOCATION_LOC (insn
) = gen_rtx_UNKNOWN_VAR_LOC ();
544 df_insn_rescan_debug_internal (insn
);
550 /* Delete every instruction that hasn't been marked. */
553 delete_unmarked_insns (void)
556 rtx_insn
*insn
, *next
;
557 bool must_clean
= false;
559 FOR_EACH_BB_REVERSE_FN (bb
, cfun
)
560 FOR_BB_INSNS_REVERSE_SAFE (bb
, insn
, next
)
561 if (NONDEBUG_INSN_P (insn
))
563 /* Always delete no-op moves. */
564 if (noop_move_p (insn
))
567 /* Otherwise rely only on the DCE algorithm. */
568 else if (marked_insn_p (insn
))
571 /* Beware that reaching a dbg counter limit here can result
572 in miscompiled file. This occurs when a group of insns
573 must be deleted together, typically because the kept insn
574 depends on the output from the deleted insn. Deleting
575 this insns in reverse order (both at the bb level and
576 when looking at the blocks) minimizes this, but does not
577 eliminate it, since it is possible for the using insn to
578 be top of a block and the producer to be at the bottom of
579 the block. However, in most cases this will only result
580 in an uninitialized use of an insn that is dead anyway.
582 However, there is one rare case that will cause a
583 miscompile: deletion of non-looping pure and constant
584 calls on a machine where ACCUMULATE_OUTGOING_ARGS is true.
585 In this case it is possible to remove the call, but leave
586 the argument pushes to the stack. Because of the changes
587 to the stack pointer, this will almost always lead to a
593 fprintf (dump_file
, "DCE: Deleting insn %d\n", INSN_UID (insn
));
595 /* Before we delete the insn we have to remove the REG_EQUAL notes
596 for the destination regs in order to avoid dangling notes. */
597 remove_reg_equal_equiv_notes_for_defs (insn
);
599 /* If a pure or const call is deleted, this may make the cfg
600 have unreachable blocks. We rememeber this and call
601 delete_unreachable_blocks at the end. */
605 /* Now delete the insn. */
606 delete_insn_and_edges (insn
);
609 /* Deleted a pure or const call. */
611 delete_unreachable_blocks ();
615 /* Go through the instructions and mark those whose necessity is not
616 dependent on inter-instruction information. Make sure all other
617 instructions are not marked. */
620 prescan_insns_for_dce (bool fast
)
623 rtx_insn
*insn
, *prev
;
624 bitmap arg_stores
= NULL
;
627 fprintf (dump_file
, "Finding needed instructions:\n");
629 if (!df_in_progress
&& ACCUMULATE_OUTGOING_ARGS
)
630 arg_stores
= BITMAP_ALLOC (NULL
);
632 FOR_EACH_BB_FN (bb
, cfun
)
634 FOR_BB_INSNS_REVERSE_SAFE (bb
, insn
, prev
)
635 if (NONDEBUG_INSN_P (insn
))
637 /* Don't mark argument stores now. They will be marked
638 if needed when the associated CALL is marked. */
639 if (arg_stores
&& bitmap_bit_p (arg_stores
, INSN_UID (insn
)))
641 if (deletable_insn_p (insn
, fast
, arg_stores
))
642 mark_nonreg_stores (PATTERN (insn
), insn
, fast
);
644 mark_insn (insn
, fast
);
646 /* find_call_stack_args only looks at argument stores in the
649 bitmap_clear (arg_stores
);
653 BITMAP_FREE (arg_stores
);
656 fprintf (dump_file
, "Finished finding needed instructions:\n");
660 /* UD-based DSE routines. */
662 /* Mark instructions that define artificially-used registers, such as
663 the frame pointer and the stack pointer. */
666 mark_artificial_uses (void)
669 struct df_link
*defs
;
672 FOR_ALL_BB_FN (bb
, cfun
)
673 FOR_EACH_ARTIFICIAL_USE (use
, bb
->index
)
674 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
675 if (!DF_REF_IS_ARTIFICIAL (defs
->ref
))
676 mark_insn (DF_REF_INSN (defs
->ref
), false);
680 /* Mark every instruction that defines a register value that INSN uses. */
683 mark_reg_dependencies (rtx_insn
*insn
)
685 struct df_link
*defs
;
688 if (DEBUG_INSN_P (insn
))
691 FOR_EACH_INSN_USE (use
, insn
)
695 fprintf (dump_file
, "Processing use of ");
696 print_simple_rtl (dump_file
, DF_REF_REG (use
));
697 fprintf (dump_file
, " in insn %d:\n", INSN_UID (insn
));
699 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
700 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
701 mark_insn (DF_REF_INSN (defs
->ref
), false);
706 /* Initialize global variables for a new DCE pass. */
715 df_set_flags (DF_RD_PRUNE_DEAD_DEFS
);
716 df_chain_add_problem (DF_UD_CHAIN
);
726 bitmap_obstack_initialize (&dce_blocks_bitmap_obstack
);
727 bitmap_obstack_initialize (&dce_tmp_bitmap_obstack
);
728 can_alter_cfg
= false;
731 can_alter_cfg
= true;
733 marked
= sbitmap_alloc (get_max_uid () + 1);
734 bitmap_clear (marked
);
738 /* Free the data allocated by init_dce. */
743 sbitmap_free (marked
);
747 bitmap_obstack_release (&dce_blocks_bitmap_obstack
);
748 bitmap_obstack_release (&dce_tmp_bitmap_obstack
);
753 /* UD-chain based DCE. */
756 rest_of_handle_ud_dce (void)
762 prescan_insns_for_dce (false);
763 mark_artificial_uses ();
764 while (worklist
.length () > 0)
766 insn
= worklist
.pop ();
767 mark_reg_dependencies (insn
);
771 if (MAY_HAVE_DEBUG_INSNS
)
772 reset_unmarked_insns_debug_uses ();
774 /* Before any insns are deleted, we must remove the chains since
775 they are not bidirectional. */
776 df_remove_problem (df_chain
);
777 delete_unmarked_insns ();
786 const pass_data pass_data_ud_rtl_dce
=
790 OPTGROUP_NONE
, /* optinfo_flags */
792 0, /* properties_required */
793 0, /* properties_provided */
794 0, /* properties_destroyed */
795 0, /* todo_flags_start */
796 TODO_df_finish
, /* todo_flags_finish */
799 class pass_ud_rtl_dce
: public rtl_opt_pass
802 pass_ud_rtl_dce (gcc::context
*ctxt
)
803 : rtl_opt_pass (pass_data_ud_rtl_dce
, ctxt
)
806 /* opt_pass methods: */
807 virtual bool gate (function
*)
809 return optimize
> 1 && flag_dce
&& dbg_cnt (dce_ud
);
812 virtual unsigned int execute (function
*)
814 return rest_of_handle_ud_dce ();
817 }; // class pass_ud_rtl_dce
822 make_pass_ud_rtl_dce (gcc::context
*ctxt
)
824 return new pass_ud_rtl_dce (ctxt
);
828 /* -------------------------------------------------------------------------
830 ------------------------------------------------------------------------- */
832 /* Process basic block BB. Return true if the live_in set has
833 changed. REDO_OUT is true if the info at the bottom of the block
834 needs to be recalculated before starting. AU is the proper set of
835 artificial uses. Track global substitution of uses of dead pseudos
836 in debug insns using GLOBAL_DEBUG. */
839 word_dce_process_block (basic_block bb
, bool redo_out
,
840 struct dead_debug_global
*global_debug
)
842 bitmap local_live
= BITMAP_ALLOC (&dce_tmp_bitmap_obstack
);
845 struct dead_debug_local debug
;
849 /* Need to redo the live_out set of this block if when one of
850 the succs of this block has had a change in it live in
854 df_confluence_function_n con_fun_n
= df_word_lr
->problem
->con_fun_n
;
855 bitmap_clear (DF_WORD_LR_OUT (bb
));
856 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
862 fprintf (dump_file
, "processing block %d live out = ", bb
->index
);
863 df_print_word_regset (dump_file
, DF_WORD_LR_OUT (bb
));
866 bitmap_copy (local_live
, DF_WORD_LR_OUT (bb
));
867 dead_debug_local_init (&debug
, NULL
, global_debug
);
869 FOR_BB_INSNS_REVERSE (bb
, insn
)
870 if (DEBUG_INSN_P (insn
))
873 FOR_EACH_INSN_USE (use
, insn
)
874 if (DF_REF_REGNO (use
) >= FIRST_PSEUDO_REGISTER
875 && (GET_MODE_SIZE (GET_MODE (DF_REF_REAL_REG (use
)))
876 == 2 * UNITS_PER_WORD
)
877 && !bitmap_bit_p (local_live
, 2 * DF_REF_REGNO (use
))
878 && !bitmap_bit_p (local_live
, 2 * DF_REF_REGNO (use
) + 1))
879 dead_debug_add (&debug
, use
, DF_REF_REGNO (use
));
881 else if (INSN_P (insn
))
885 /* No matter if the instruction is needed or not, we remove
886 any regno in the defs from the live set. */
887 any_changed
= df_word_lr_simulate_defs (insn
, local_live
);
889 mark_insn (insn
, true);
891 /* On the other hand, we do not allow the dead uses to set
892 anything in local_live. */
893 if (marked_insn_p (insn
))
894 df_word_lr_simulate_uses (insn
, local_live
);
896 /* Insert debug temps for dead REGs used in subsequent debug
897 insns. We may have to emit a debug temp even if the insn
898 was marked, in case the debug use was after the point of
900 if (debug
.used
&& !bitmap_empty_p (debug
.used
))
904 FOR_EACH_INSN_DEF (def
, insn
)
905 dead_debug_insert_temp (&debug
, DF_REF_REGNO (def
), insn
,
907 && !control_flow_insn_p (insn
)
908 ? DEBUG_TEMP_AFTER_WITH_REG_FORCE
909 : DEBUG_TEMP_BEFORE_WITH_VALUE
);
914 fprintf (dump_file
, "finished processing insn %d live out = ",
916 df_print_word_regset (dump_file
, local_live
);
920 block_changed
= !bitmap_equal_p (local_live
, DF_WORD_LR_IN (bb
));
922 bitmap_copy (DF_WORD_LR_IN (bb
), local_live
);
924 dead_debug_local_finish (&debug
, NULL
);
925 BITMAP_FREE (local_live
);
926 return block_changed
;
930 /* Process basic block BB. Return true if the live_in set has
931 changed. REDO_OUT is true if the info at the bottom of the block
932 needs to be recalculated before starting. AU is the proper set of
933 artificial uses. Track global substitution of uses of dead pseudos
934 in debug insns using GLOBAL_DEBUG. */
937 dce_process_block (basic_block bb
, bool redo_out
, bitmap au
,
938 struct dead_debug_global
*global_debug
)
940 bitmap local_live
= BITMAP_ALLOC (&dce_tmp_bitmap_obstack
);
944 struct dead_debug_local debug
;
948 /* Need to redo the live_out set of this block if when one of
949 the succs of this block has had a change in it live in
953 df_confluence_function_n con_fun_n
= df_lr
->problem
->con_fun_n
;
954 bitmap_clear (DF_LR_OUT (bb
));
955 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
961 fprintf (dump_file
, "processing block %d lr out = ", bb
->index
);
962 df_print_regset (dump_file
, DF_LR_OUT (bb
));
965 bitmap_copy (local_live
, DF_LR_OUT (bb
));
967 df_simulate_initialize_backwards (bb
, local_live
);
968 dead_debug_local_init (&debug
, NULL
, global_debug
);
970 FOR_BB_INSNS_REVERSE (bb
, insn
)
971 if (DEBUG_INSN_P (insn
))
974 FOR_EACH_INSN_USE (use
, insn
)
975 if (!bitmap_bit_p (local_live
, DF_REF_REGNO (use
))
976 && !bitmap_bit_p (au
, DF_REF_REGNO (use
)))
977 dead_debug_add (&debug
, use
, DF_REF_REGNO (use
));
979 else if (INSN_P (insn
))
981 bool needed
= marked_insn_p (insn
);
983 /* The insn is needed if there is someone who uses the output. */
985 FOR_EACH_INSN_DEF (def
, insn
)
986 if (bitmap_bit_p (local_live
, DF_REF_REGNO (def
))
987 || bitmap_bit_p (au
, DF_REF_REGNO (def
)))
990 mark_insn (insn
, true);
994 /* No matter if the instruction is needed or not, we remove
995 any regno in the defs from the live set. */
996 df_simulate_defs (insn
, local_live
);
998 /* On the other hand, we do not allow the dead uses to set
999 anything in local_live. */
1001 df_simulate_uses (insn
, local_live
);
1003 /* Insert debug temps for dead REGs used in subsequent debug
1004 insns. We may have to emit a debug temp even if the insn
1005 was marked, in case the debug use was after the point of
1007 if (debug
.used
&& !bitmap_empty_p (debug
.used
))
1008 FOR_EACH_INSN_DEF (def
, insn
)
1009 dead_debug_insert_temp (&debug
, DF_REF_REGNO (def
), insn
,
1010 needed
&& !control_flow_insn_p (insn
)
1011 ? DEBUG_TEMP_AFTER_WITH_REG_FORCE
1012 : DEBUG_TEMP_BEFORE_WITH_VALUE
);
1015 dead_debug_local_finish (&debug
, NULL
);
1016 df_simulate_finalize_backwards (bb
, local_live
);
1018 block_changed
= !bitmap_equal_p (local_live
, DF_LR_IN (bb
));
1020 bitmap_copy (DF_LR_IN (bb
), local_live
);
1022 BITMAP_FREE (local_live
);
1023 return block_changed
;
1027 /* Perform fast DCE once initialization is done. If WORD_LEVEL is
1028 true, use the word level dce, otherwise do it at the pseudo
1032 fast_dce (bool word_level
)
1034 int *postorder
= df_get_postorder (DF_BACKWARD
);
1035 int n_blocks
= df_get_n_blocks (DF_BACKWARD
);
1036 /* The set of blocks that have been seen on this iteration. */
1037 bitmap processed
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
1038 /* The set of blocks that need to have the out vectors reset because
1039 the in of one of their successors has changed. */
1040 bitmap redo_out
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
1041 bitmap all_blocks
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
1042 bool global_changed
= true;
1044 /* These regs are considered always live so if they end up dying
1045 because of some def, we need to bring the back again. Calling
1046 df_simulate_fixup_sets has the disadvantage of calling
1047 bb_has_eh_pred once per insn, so we cache the information
1049 bitmap au
= &df
->regular_block_artificial_uses
;
1050 bitmap au_eh
= &df
->eh_block_artificial_uses
;
1052 struct dead_debug_global global_debug
;
1054 prescan_insns_for_dce (true);
1056 for (i
= 0; i
< n_blocks
; i
++)
1057 bitmap_set_bit (all_blocks
, postorder
[i
]);
1059 dead_debug_global_init (&global_debug
, NULL
);
1061 while (global_changed
)
1063 global_changed
= false;
1065 for (i
= 0; i
< n_blocks
; i
++)
1067 int index
= postorder
[i
];
1068 basic_block bb
= BASIC_BLOCK_FOR_FN (cfun
, index
);
1071 if (index
< NUM_FIXED_BLOCKS
)
1073 bitmap_set_bit (processed
, index
);
1079 = word_dce_process_block (bb
, bitmap_bit_p (redo_out
, index
),
1083 = dce_process_block (bb
, bitmap_bit_p (redo_out
, index
),
1084 bb_has_eh_pred (bb
) ? au_eh
: au
,
1086 bitmap_set_bit (processed
, index
);
1092 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1093 if (bitmap_bit_p (processed
, e
->src
->index
))
1094 /* Be tricky about when we need to iterate the
1095 analysis. We only have redo the analysis if the
1096 bitmaps change at the top of a block that is the
1098 global_changed
= true;
1100 bitmap_set_bit (redo_out
, e
->src
->index
);
1106 /* Turn off the RUN_DCE flag to prevent recursive calls to
1108 int old_flag
= df_clear_flags (DF_LR_RUN_DCE
);
1110 /* So something was deleted that requires a redo. Do it on
1112 delete_unmarked_insns ();
1113 bitmap_clear (marked
);
1114 bitmap_clear (processed
);
1115 bitmap_clear (redo_out
);
1117 /* We do not need to rescan any instructions. We only need
1118 to redo the dataflow equations for the blocks that had a
1119 change at the top of the block. Then we need to redo the
1122 df_analyze_problem (df_word_lr
, all_blocks
, postorder
, n_blocks
);
1124 df_analyze_problem (df_lr
, all_blocks
, postorder
, n_blocks
);
1126 if (old_flag
& DF_LR_RUN_DCE
)
1127 df_set_flags (DF_LR_RUN_DCE
);
1129 prescan_insns_for_dce (true);
1133 dead_debug_global_finish (&global_debug
, NULL
);
1135 delete_unmarked_insns ();
1137 BITMAP_FREE (processed
);
1138 BITMAP_FREE (redo_out
);
1139 BITMAP_FREE (all_blocks
);
1143 /* Fast register level DCE. */
1146 rest_of_handle_fast_dce (void)
1155 /* Fast byte level DCE. */
1165 timevar_push (TV_DCE
);
1166 old_flags
= df_clear_flags (DF_DEFER_INSN_RESCAN
+ DF_NO_INSN_RESCAN
);
1167 df_word_lr_add_problem ();
1171 df_set_flags (old_flags
);
1172 timevar_pop (TV_DCE
);
1176 /* This is an internal call that is used by the df live register
1177 problem to run fast dce as a side effect of creating the live
1178 information. The stack is organized so that the lr problem is run,
1179 this pass is run, which updates the live info and the df scanning
1180 info, and then returns to allow the rest of the problems to be run.
1182 This can be called by elsewhere but it will not update the bit
1183 vectors for any other problems than LR. */
1186 run_fast_df_dce (void)
1190 /* If dce is able to delete something, it has to happen
1191 immediately. Otherwise there will be problems handling the
1194 df_clear_flags (DF_DEFER_INSN_RESCAN
+ DF_NO_INSN_RESCAN
);
1196 df_in_progress
= true;
1197 rest_of_handle_fast_dce ();
1198 df_in_progress
= false;
1200 df_set_flags (old_flags
);
1205 /* Run a fast DCE pass. */
1211 rest_of_handle_fast_dce ();
1217 const pass_data pass_data_fast_rtl_dce
=
1219 RTL_PASS
, /* type */
1220 "rtl_dce", /* name */
1221 OPTGROUP_NONE
, /* optinfo_flags */
1223 0, /* properties_required */
1224 0, /* properties_provided */
1225 0, /* properties_destroyed */
1226 0, /* todo_flags_start */
1227 TODO_df_finish
, /* todo_flags_finish */
1230 class pass_fast_rtl_dce
: public rtl_opt_pass
1233 pass_fast_rtl_dce (gcc::context
*ctxt
)
1234 : rtl_opt_pass (pass_data_fast_rtl_dce
, ctxt
)
1237 /* opt_pass methods: */
1238 virtual bool gate (function
*)
1240 return optimize
> 0 && flag_dce
&& dbg_cnt (dce_fast
);
1243 virtual unsigned int execute (function
*)
1245 return rest_of_handle_fast_dce ();
1248 }; // class pass_fast_rtl_dce
1253 make_pass_fast_rtl_dce (gcc::context
*ctxt
)
1255 return new pass_fast_rtl_dce (ctxt
);