1 /* RTL dead code elimination.
2 Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011
3 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 3, or (at your option) any later
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
23 #include "coretypes.h"
29 #include "hard-reg-set.h"
36 #include "tree-pass.h"
39 #include "emit-rtl.h" /* FIXME: Can go away once crtl is moved to rtl.h. */
42 /* -------------------------------------------------------------------------
43 Core mark/delete routines
44 ------------------------------------------------------------------------- */
46 /* True if we are invoked while the df engine is running; in this case,
47 we don't want to reenter it. */
48 static bool df_in_progress
= false;
50 /* Instructions that have been marked but whose dependencies have not
51 yet been processed. */
52 static VEC(rtx
,heap
) *worklist
;
54 /* Bitmap of instructions marked as needed indexed by INSN_UID. */
55 static sbitmap marked
;
57 /* Bitmap obstacks used for block processing by the fast algorithm. */
58 static bitmap_obstack dce_blocks_bitmap_obstack
;
59 static bitmap_obstack dce_tmp_bitmap_obstack
;
61 static bool find_call_stack_args (rtx
, bool, bool, bitmap
);
63 /* A subroutine for which BODY is part of the instruction being tested;
64 either the top-level pattern, or an element of a PARALLEL. The
65 instruction is known not to be a bare USE or CLOBBER. */
68 deletable_insn_p_1 (rtx body
)
70 switch (GET_CODE (body
))
74 /* The UNSPEC case was added here because the ia-64 claims that
75 USEs do not work after reload and generates UNSPECS rather
76 than USEs. Since dce is run after reload we need to avoid
77 deleting these even if they are dead. If it turns out that
78 USEs really do work after reload, the ia-64 should be
79 changed, and the UNSPEC case can be removed. */
84 return !volatile_refs_p (body
);
89 /* Return true if INSN is a normal instruction that can be deleted by
93 deletable_insn_p (rtx insn
, bool fast
, bitmap arg_stores
)
99 /* We cannot delete calls inside of the recursive dce because
100 this may cause basic blocks to be deleted and this messes up
101 the rest of the stack of optimization passes. */
103 /* We cannot delete pure or const sibling calls because it is
104 hard to see the result. */
105 && (!SIBLING_CALL_P (insn
))
106 /* We can delete dead const or pure calls as long as they do not
108 && (RTL_CONST_OR_PURE_CALL_P (insn
)
109 && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn
)))
110 return find_call_stack_args (insn
, false, fast
, arg_stores
);
112 /* Don't delete jumps, notes and the like. */
113 if (!NONJUMP_INSN_P (insn
))
116 /* Don't delete insns that can throw. */
117 if (!insn_nothrow_p (insn
))
120 body
= PATTERN (insn
);
121 switch (GET_CODE (body
))
130 /* A CLOBBER of a dead pseudo register serves no purpose.
131 That is not necessarily true for hard registers until
134 return REG_P (x
) && (!HARD_REGISTER_P (x
) || reload_completed
);
137 /* Because of the way that use-def chains are built, it is not
138 possible to tell if the clobber is dead because it can
139 never be the target of a use-def chain. */
143 for (i
= XVECLEN (body
, 0) - 1; i
>= 0; i
--)
144 if (!deletable_insn_p_1 (XVECEXP (body
, 0, i
)))
149 return deletable_insn_p_1 (body
);
154 /* Return true if INSN has been marked as needed. */
157 marked_insn_p (rtx insn
)
159 /* Artificial defs are always needed and they do not have an insn.
160 We should never see them here. */
162 return TEST_BIT (marked
, INSN_UID (insn
));
166 /* If INSN has not yet been marked as needed, mark it now, and add it to
170 mark_insn (rtx insn
, bool fast
)
172 if (!marked_insn_p (insn
))
175 VEC_safe_push (rtx
, heap
, worklist
, insn
);
176 SET_BIT (marked
, INSN_UID (insn
));
178 fprintf (dump_file
, " Adding insn %d to worklist\n", INSN_UID (insn
));
181 && !SIBLING_CALL_P (insn
)
182 && (RTL_CONST_OR_PURE_CALL_P (insn
)
183 && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn
)))
184 find_call_stack_args (insn
, true, fast
, NULL
);
189 /* A note_stores callback used by mark_nonreg_stores. DATA is the
190 instruction containing DEST. */
193 mark_nonreg_stores_1 (rtx dest
, const_rtx pattern
, void *data
)
195 if (GET_CODE (pattern
) != CLOBBER
&& !REG_P (dest
))
196 mark_insn ((rtx
) data
, true);
200 /* A note_stores callback used by mark_nonreg_stores. DATA is the
201 instruction containing DEST. */
204 mark_nonreg_stores_2 (rtx dest
, const_rtx pattern
, void *data
)
206 if (GET_CODE (pattern
) != CLOBBER
&& !REG_P (dest
))
207 mark_insn ((rtx
) data
, false);
211 /* Mark INSN if BODY stores to a non-register destination. */
214 mark_nonreg_stores (rtx body
, rtx insn
, bool fast
)
217 note_stores (body
, mark_nonreg_stores_1
, insn
);
219 note_stores (body
, mark_nonreg_stores_2
, insn
);
223 /* Return true if store to MEM, starting OFF bytes from stack pointer,
224 is a call argument store, and clear corresponding bits from SP_BYTES
228 check_argument_store (rtx mem
, HOST_WIDE_INT off
, HOST_WIDE_INT min_sp_off
,
229 HOST_WIDE_INT max_sp_off
, bitmap sp_bytes
)
232 for (byte
= off
; byte
< off
+ GET_MODE_SIZE (GET_MODE (mem
)); byte
++)
234 if (byte
< min_sp_off
235 || byte
>= max_sp_off
236 || !bitmap_clear_bit (sp_bytes
, byte
- min_sp_off
))
243 /* Try to find all stack stores of CALL_INSN arguments if
244 ACCUMULATE_OUTGOING_ARGS. If all stack stores have been found
245 and it is therefore safe to eliminate the call, return true,
246 otherwise return false. This function should be first called
247 with DO_MARK false, and only when the CALL_INSN is actually
248 going to be marked called again with DO_MARK true. */
251 find_call_stack_args (rtx call_insn
, bool do_mark
, bool fast
,
254 rtx p
, insn
, prev_insn
;
256 HOST_WIDE_INT min_sp_off
, max_sp_off
;
259 gcc_assert (CALL_P (call_insn
));
260 if (!ACCUMULATE_OUTGOING_ARGS
)
265 gcc_assert (arg_stores
);
266 bitmap_clear (arg_stores
);
269 min_sp_off
= INTTYPE_MAXIMUM (HOST_WIDE_INT
);
272 /* First determine the minimum and maximum offset from sp for
274 for (p
= CALL_INSN_FUNCTION_USAGE (call_insn
); p
; p
= XEXP (p
, 1))
275 if (GET_CODE (XEXP (p
, 0)) == USE
276 && MEM_P (XEXP (XEXP (p
, 0), 0)))
278 rtx mem
= XEXP (XEXP (p
, 0), 0), addr
;
279 HOST_WIDE_INT off
= 0, size
;
280 if (!MEM_SIZE_KNOWN_P (mem
))
282 size
= MEM_SIZE (mem
);
283 addr
= XEXP (mem
, 0);
284 if (GET_CODE (addr
) == PLUS
285 && REG_P (XEXP (addr
, 0))
286 && CONST_INT_P (XEXP (addr
, 1)))
288 off
= INTVAL (XEXP (addr
, 1));
289 addr
= XEXP (addr
, 0);
291 if (addr
!= stack_pointer_rtx
)
295 /* If not fast, use chains to see if addr wasn't set to
300 struct df_link
*defs
;
303 for (use_rec
= DF_INSN_USES (call_insn
); *use_rec
; use_rec
++)
304 if (rtx_equal_p (addr
, DF_REF_REG (*use_rec
)))
307 if (*use_rec
== NULL
)
310 for (defs
= DF_REF_CHAIN (*use_rec
); defs
; defs
= defs
->next
)
311 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
317 set
= single_set (DF_REF_INSN (defs
->ref
));
321 if (GET_CODE (SET_SRC (set
)) != PLUS
322 || XEXP (SET_SRC (set
), 0) != stack_pointer_rtx
323 || !CONST_INT_P (XEXP (SET_SRC (set
), 1)))
326 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
331 min_sp_off
= MIN (min_sp_off
, off
);
332 max_sp_off
= MAX (max_sp_off
, off
+ size
);
335 if (min_sp_off
>= max_sp_off
)
337 sp_bytes
= BITMAP_ALLOC (NULL
);
339 /* Set bits in SP_BYTES bitmap for bytes relative to sp + min_sp_off
340 which contain arguments. Checking has been done in the previous
342 for (p
= CALL_INSN_FUNCTION_USAGE (call_insn
); p
; p
= XEXP (p
, 1))
343 if (GET_CODE (XEXP (p
, 0)) == USE
344 && MEM_P (XEXP (XEXP (p
, 0), 0)))
346 rtx mem
= XEXP (XEXP (p
, 0), 0), addr
;
347 HOST_WIDE_INT off
= 0, byte
;
348 addr
= XEXP (mem
, 0);
349 if (GET_CODE (addr
) == PLUS
350 && REG_P (XEXP (addr
, 0))
351 && CONST_INT_P (XEXP (addr
, 1)))
353 off
= INTVAL (XEXP (addr
, 1));
354 addr
= XEXP (addr
, 0);
356 if (addr
!= stack_pointer_rtx
)
359 struct df_link
*defs
;
362 for (use_rec
= DF_INSN_USES (call_insn
); *use_rec
; use_rec
++)
363 if (rtx_equal_p (addr
, DF_REF_REG (*use_rec
)))
366 for (defs
= DF_REF_CHAIN (*use_rec
); defs
; defs
= defs
->next
)
367 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
370 set
= single_set (DF_REF_INSN (defs
->ref
));
371 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
373 for (byte
= off
; byte
< off
+ MEM_SIZE (mem
); byte
++)
375 if (!bitmap_set_bit (sp_bytes
, byte
- min_sp_off
))
380 /* Walk backwards, looking for argument stores. The search stops
381 when seeing another call, sp adjustment or memory store other than
384 for (insn
= PREV_INSN (call_insn
); insn
; insn
= prev_insn
)
389 if (insn
== BB_HEAD (BLOCK_FOR_INSN (call_insn
)))
390 prev_insn
= NULL_RTX
;
392 prev_insn
= PREV_INSN (insn
);
397 if (!NONDEBUG_INSN_P (insn
))
400 set
= single_set (insn
);
401 if (!set
|| SET_DEST (set
) == stack_pointer_rtx
)
404 if (!MEM_P (SET_DEST (set
)))
407 mem
= SET_DEST (set
);
408 addr
= XEXP (mem
, 0);
410 if (GET_CODE (addr
) == PLUS
411 && REG_P (XEXP (addr
, 0))
412 && CONST_INT_P (XEXP (addr
, 1)))
414 off
= INTVAL (XEXP (addr
, 1));
415 addr
= XEXP (addr
, 0);
417 if (addr
!= stack_pointer_rtx
)
424 struct df_link
*defs
;
427 for (use_rec
= DF_INSN_USES (insn
); *use_rec
; use_rec
++)
428 if (rtx_equal_p (addr
, DF_REF_REG (*use_rec
)))
431 if (*use_rec
== NULL
)
434 for (defs
= DF_REF_CHAIN (*use_rec
); defs
; defs
= defs
->next
)
435 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
441 set
= single_set (DF_REF_INSN (defs
->ref
));
445 if (GET_CODE (SET_SRC (set
)) != PLUS
446 || XEXP (SET_SRC (set
), 0) != stack_pointer_rtx
447 || !CONST_INT_P (XEXP (SET_SRC (set
), 1)))
450 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
456 if (GET_MODE_SIZE (GET_MODE (mem
)) == 0
457 || !check_argument_store (mem
, off
, min_sp_off
,
458 max_sp_off
, sp_bytes
))
461 if (!deletable_insn_p (insn
, fast
, NULL
))
465 mark_insn (insn
, fast
);
467 bitmap_set_bit (arg_stores
, INSN_UID (insn
));
469 if (bitmap_empty_p (sp_bytes
))
476 BITMAP_FREE (sp_bytes
);
477 if (!ret
&& arg_stores
)
478 bitmap_clear (arg_stores
);
484 /* Remove all REG_EQUAL and REG_EQUIV notes referring to the registers INSN
488 remove_reg_equal_equiv_notes_for_defs (rtx insn
)
492 for (def_rec
= DF_INSN_DEFS (insn
); *def_rec
; def_rec
++)
493 remove_reg_equal_equiv_notes_for_regno (DF_REF_REGNO (*def_rec
));
496 /* Scan all BBs for debug insns and reset those that reference values
497 defined in unmarked insns. */
500 reset_unmarked_insns_debug_uses (void)
505 FOR_EACH_BB_REVERSE (bb
)
506 FOR_BB_INSNS_REVERSE_SAFE (bb
, insn
, next
)
507 if (DEBUG_INSN_P (insn
))
511 for (use_rec
= DF_INSN_USES (insn
); *use_rec
; use_rec
++)
513 df_ref use
= *use_rec
;
514 struct df_link
*defs
;
515 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
518 if (DF_REF_IS_ARTIFICIAL (defs
->ref
))
520 ref_insn
= DF_REF_INSN (defs
->ref
);
521 if (!marked_insn_p (ref_insn
))
526 /* ??? FIXME could we propagate the values assigned to
528 INSN_VAR_LOCATION_LOC (insn
) = gen_rtx_UNKNOWN_VAR_LOC ();
529 df_insn_rescan_debug_internal (insn
);
535 /* Delete every instruction that hasn't been marked. */
538 delete_unmarked_insns (void)
542 bool must_clean
= false;
544 FOR_EACH_BB_REVERSE (bb
)
545 FOR_BB_INSNS_REVERSE_SAFE (bb
, insn
, next
)
546 if (NONDEBUG_INSN_P (insn
))
548 /* Always delete no-op moves. */
549 if (noop_move_p (insn
))
552 /* Otherwise rely only on the DCE algorithm. */
553 else if (marked_insn_p (insn
))
556 /* Beware that reaching a dbg counter limit here can result
557 in miscompiled file. This occurs when a group of insns
558 must be deleted together, typically because the kept insn
559 depends on the output from the deleted insn. Deleting
560 this insns in reverse order (both at the bb level and
561 when looking at the blocks) minimizes this, but does not
562 eliminate it, since it is possible for the using insn to
563 be top of a block and the producer to be at the bottom of
564 the block. However, in most cases this will only result
565 in an uninitialized use of an insn that is dead anyway.
567 However, there is one rare case that will cause a
568 miscompile: deletion of non-looping pure and constant
569 calls on a machine where ACCUMULATE_OUTGOING_ARGS is true.
570 In this case it is possible to remove the call, but leave
571 the argument pushes to the stack. Because of the changes
572 to the stack pointer, this will almost always lead to a
578 fprintf (dump_file
, "DCE: Deleting insn %d\n", INSN_UID (insn
));
580 /* Before we delete the insn we have to remove the REG_EQUAL notes
581 for the destination regs in order to avoid dangling notes. */
582 remove_reg_equal_equiv_notes_for_defs (insn
);
584 /* If a pure or const call is deleted, this may make the cfg
585 have unreachable blocks. We rememeber this and call
586 delete_unreachable_blocks at the end. */
590 /* Now delete the insn. */
591 delete_insn_and_edges (insn
);
594 /* Deleted a pure or const call. */
596 delete_unreachable_blocks ();
600 /* Go through the instructions and mark those whose necessity is not
601 dependent on inter-instruction information. Make sure all other
602 instructions are not marked. */
605 prescan_insns_for_dce (bool fast
)
609 bitmap arg_stores
= NULL
;
612 fprintf (dump_file
, "Finding needed instructions:\n");
614 if (!df_in_progress
&& ACCUMULATE_OUTGOING_ARGS
)
615 arg_stores
= BITMAP_ALLOC (NULL
);
619 FOR_BB_INSNS_REVERSE_SAFE (bb
, insn
, prev
)
620 if (NONDEBUG_INSN_P (insn
))
622 /* Don't mark argument stores now. They will be marked
623 if needed when the associated CALL is marked. */
624 if (arg_stores
&& bitmap_bit_p (arg_stores
, INSN_UID (insn
)))
626 if (deletable_insn_p (insn
, fast
, arg_stores
))
627 mark_nonreg_stores (PATTERN (insn
), insn
, fast
);
629 mark_insn (insn
, fast
);
631 /* find_call_stack_args only looks at argument stores in the
634 bitmap_clear (arg_stores
);
638 BITMAP_FREE (arg_stores
);
641 fprintf (dump_file
, "Finished finding needed instructions:\n");
645 /* UD-based DSE routines. */
647 /* Mark instructions that define artificially-used registers, such as
648 the frame pointer and the stack pointer. */
651 mark_artificial_uses (void)
654 struct df_link
*defs
;
659 for (use_rec
= df_get_artificial_uses (bb
->index
);
661 for (defs
= DF_REF_CHAIN (*use_rec
); defs
; defs
= defs
->next
)
662 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
663 mark_insn (DF_REF_INSN (defs
->ref
), false);
668 /* Mark every instruction that defines a register value that INSN uses. */
671 mark_reg_dependencies (rtx insn
)
673 struct df_link
*defs
;
676 if (DEBUG_INSN_P (insn
))
679 for (use_rec
= DF_INSN_USES (insn
); *use_rec
; use_rec
++)
681 df_ref use
= *use_rec
;
684 fprintf (dump_file
, "Processing use of ");
685 print_simple_rtl (dump_file
, DF_REF_REG (use
));
686 fprintf (dump_file
, " in insn %d:\n", INSN_UID (insn
));
688 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
689 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
690 mark_insn (DF_REF_INSN (defs
->ref
), false);
695 /* Initialize global variables for a new DCE pass. */
703 df_chain_add_problem (DF_UD_CHAIN
);
712 bitmap_obstack_initialize (&dce_blocks_bitmap_obstack
);
713 bitmap_obstack_initialize (&dce_tmp_bitmap_obstack
);
716 marked
= sbitmap_alloc (get_max_uid () + 1);
717 sbitmap_zero (marked
);
721 /* Free the data allocated by init_dce. */
726 sbitmap_free (marked
);
730 bitmap_obstack_release (&dce_blocks_bitmap_obstack
);
731 bitmap_obstack_release (&dce_tmp_bitmap_obstack
);
736 /* UD-chain based DCE. */
739 rest_of_handle_ud_dce (void)
743 if (df_check_ud_du_memory_usage ())
748 prescan_insns_for_dce (false);
749 mark_artificial_uses ();
750 while (VEC_length (rtx
, worklist
) > 0)
752 insn
= VEC_pop (rtx
, worklist
);
753 mark_reg_dependencies (insn
);
755 VEC_free (rtx
, heap
, worklist
);
757 if (MAY_HAVE_DEBUG_INSNS
)
758 reset_unmarked_insns_debug_uses ();
760 /* Before any insns are deleted, we must remove the chains since
761 they are not bidirectional. */
762 df_remove_problem (df_chain
);
763 delete_unmarked_insns ();
773 return optimize
> 1 && flag_dce
777 struct rtl_opt_pass pass_ud_rtl_dce
=
782 gate_ud_dce
, /* gate */
783 rest_of_handle_ud_dce
, /* execute */
786 0, /* static_pass_number */
788 0, /* properties_required */
789 0, /* properties_provided */
790 0, /* properties_destroyed */
791 0, /* todo_flags_start */
792 TODO_df_finish
| TODO_verify_rtl_sharing
|
793 TODO_ggc_collect
/* todo_flags_finish */
798 /* -------------------------------------------------------------------------
800 ------------------------------------------------------------------------- */
802 /* Process basic block BB. Return true if the live_in set has
803 changed. REDO_OUT is true if the info at the bottom of the block
804 needs to be recalculated before starting. AU is the proper set of
808 word_dce_process_block (basic_block bb
, bool redo_out
)
810 bitmap local_live
= BITMAP_ALLOC (&dce_tmp_bitmap_obstack
);
816 /* Need to redo the live_out set of this block if when one of
817 the succs of this block has had a change in it live in
821 df_confluence_function_n con_fun_n
= df_word_lr
->problem
->con_fun_n
;
822 bitmap_clear (DF_WORD_LR_OUT (bb
));
823 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
829 fprintf (dump_file
, "processing block %d live out = ", bb
->index
);
830 df_print_word_regset (dump_file
, DF_WORD_LR_OUT (bb
));
833 bitmap_copy (local_live
, DF_WORD_LR_OUT (bb
));
835 FOR_BB_INSNS_REVERSE (bb
, insn
)
836 if (NONDEBUG_INSN_P (insn
))
839 /* No matter if the instruction is needed or not, we remove
840 any regno in the defs from the live set. */
841 any_changed
= df_word_lr_simulate_defs (insn
, local_live
);
843 mark_insn (insn
, true);
845 /* On the other hand, we do not allow the dead uses to set
846 anything in local_live. */
847 if (marked_insn_p (insn
))
848 df_word_lr_simulate_uses (insn
, local_live
);
852 fprintf (dump_file
, "finished processing insn %d live out = ",
854 df_print_word_regset (dump_file
, local_live
);
858 block_changed
= !bitmap_equal_p (local_live
, DF_WORD_LR_IN (bb
));
860 bitmap_copy (DF_WORD_LR_IN (bb
), local_live
);
862 BITMAP_FREE (local_live
);
863 return block_changed
;
867 /* Process basic block BB. Return true if the live_in set has
868 changed. REDO_OUT is true if the info at the bottom of the block
869 needs to be recalculated before starting. AU is the proper set of
873 dce_process_block (basic_block bb
, bool redo_out
, bitmap au
)
875 bitmap local_live
= BITMAP_ALLOC (&dce_tmp_bitmap_obstack
);
882 /* Need to redo the live_out set of this block if when one of
883 the succs of this block has had a change in it live in
887 df_confluence_function_n con_fun_n
= df_lr
->problem
->con_fun_n
;
888 bitmap_clear (DF_LR_OUT (bb
));
889 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
895 fprintf (dump_file
, "processing block %d lr out = ", bb
->index
);
896 df_print_regset (dump_file
, DF_LR_OUT (bb
));
899 bitmap_copy (local_live
, DF_LR_OUT (bb
));
901 df_simulate_initialize_backwards (bb
, local_live
);
903 FOR_BB_INSNS_REVERSE (bb
, insn
)
906 bool needed
= marked_insn_p (insn
);
908 /* The insn is needed if there is someone who uses the output. */
910 for (def_rec
= DF_INSN_DEFS (insn
); *def_rec
; def_rec
++)
911 if (bitmap_bit_p (local_live
, DF_REF_REGNO (*def_rec
))
912 || bitmap_bit_p (au
, DF_REF_REGNO (*def_rec
)))
915 mark_insn (insn
, true);
919 /* No matter if the instruction is needed or not, we remove
920 any regno in the defs from the live set. */
921 df_simulate_defs (insn
, local_live
);
923 /* On the other hand, we do not allow the dead uses to set
924 anything in local_live. */
926 df_simulate_uses (insn
, local_live
);
929 df_simulate_finalize_backwards (bb
, local_live
);
931 block_changed
= !bitmap_equal_p (local_live
, DF_LR_IN (bb
));
933 bitmap_copy (DF_LR_IN (bb
), local_live
);
935 BITMAP_FREE (local_live
);
936 return block_changed
;
940 /* Perform fast DCE once initialization is done. If WORD_LEVEL is
941 true, use the word level dce, otherwise do it at the pseudo
945 fast_dce (bool word_level
)
947 int *postorder
= df_get_postorder (DF_BACKWARD
);
948 int n_blocks
= df_get_n_blocks (DF_BACKWARD
);
949 /* The set of blocks that have been seen on this iteration. */
950 bitmap processed
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
951 /* The set of blocks that need to have the out vectors reset because
952 the in of one of their successors has changed. */
953 bitmap redo_out
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
954 bitmap all_blocks
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
955 bool global_changed
= true;
957 /* These regs are considered always live so if they end up dying
958 because of some def, we need to bring the back again. Calling
959 df_simulate_fixup_sets has the disadvantage of calling
960 bb_has_eh_pred once per insn, so we cache the information
962 bitmap au
= &df
->regular_block_artificial_uses
;
963 bitmap au_eh
= &df
->eh_block_artificial_uses
;
966 prescan_insns_for_dce (true);
968 for (i
= 0; i
< n_blocks
; i
++)
969 bitmap_set_bit (all_blocks
, postorder
[i
]);
971 while (global_changed
)
973 global_changed
= false;
975 for (i
= 0; i
< n_blocks
; i
++)
977 int index
= postorder
[i
];
978 basic_block bb
= BASIC_BLOCK (index
);
981 if (index
< NUM_FIXED_BLOCKS
)
983 bitmap_set_bit (processed
, index
);
989 = word_dce_process_block (bb
, bitmap_bit_p (redo_out
, index
));
992 = dce_process_block (bb
, bitmap_bit_p (redo_out
, index
),
993 bb_has_eh_pred (bb
) ? au_eh
: au
);
994 bitmap_set_bit (processed
, index
);
1000 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1001 if (bitmap_bit_p (processed
, e
->src
->index
))
1002 /* Be tricky about when we need to iterate the
1003 analysis. We only have redo the analysis if the
1004 bitmaps change at the top of a block that is the
1006 global_changed
= true;
1008 bitmap_set_bit (redo_out
, e
->src
->index
);
1014 /* Turn off the RUN_DCE flag to prevent recursive calls to
1016 int old_flag
= df_clear_flags (DF_LR_RUN_DCE
);
1018 /* So something was deleted that requires a redo. Do it on
1020 delete_unmarked_insns ();
1021 sbitmap_zero (marked
);
1022 bitmap_clear (processed
);
1023 bitmap_clear (redo_out
);
1025 /* We do not need to rescan any instructions. We only need
1026 to redo the dataflow equations for the blocks that had a
1027 change at the top of the block. Then we need to redo the
1030 df_analyze_problem (df_word_lr
, all_blocks
, postorder
, n_blocks
);
1032 df_analyze_problem (df_lr
, all_blocks
, postorder
, n_blocks
);
1034 if (old_flag
& DF_LR_RUN_DCE
)
1035 df_set_flags (DF_LR_RUN_DCE
);
1037 prescan_insns_for_dce (true);
1041 delete_unmarked_insns ();
1043 BITMAP_FREE (processed
);
1044 BITMAP_FREE (redo_out
);
1045 BITMAP_FREE (all_blocks
);
1049 /* Fast register level DCE. */
1052 rest_of_handle_fast_dce (void)
1061 /* Fast byte level DCE. */
1071 timevar_push (TV_DCE
);
1072 old_flags
= df_clear_flags (DF_DEFER_INSN_RESCAN
+ DF_NO_INSN_RESCAN
);
1073 df_word_lr_add_problem ();
1077 df_set_flags (old_flags
);
1078 timevar_pop (TV_DCE
);
1082 /* This is an internal call that is used by the df live register
1083 problem to run fast dce as a side effect of creating the live
1084 information. The stack is organized so that the lr problem is run,
1085 this pass is run, which updates the live info and the df scanning
1086 info, and then returns to allow the rest of the problems to be run.
1088 This can be called by elsewhere but it will not update the bit
1089 vectors for any other problems than LR. */
1092 run_fast_df_dce (void)
1096 /* If dce is able to delete something, it has to happen
1097 immediately. Otherwise there will be problems handling the
1100 df_clear_flags (DF_DEFER_INSN_RESCAN
+ DF_NO_INSN_RESCAN
);
1102 df_in_progress
= true;
1103 rest_of_handle_fast_dce ();
1104 df_in_progress
= false;
1106 df_set_flags (old_flags
);
1111 /* Run a fast DCE pass. */
1117 rest_of_handle_fast_dce ();
1122 gate_fast_dce (void)
1124 return optimize
> 0 && flag_dce
1125 && dbg_cnt (dce_fast
);
1128 struct rtl_opt_pass pass_fast_rtl_dce
=
1132 "rtl_dce", /* name */
1133 gate_fast_dce
, /* gate */
1134 rest_of_handle_fast_dce
, /* execute */
1137 0, /* static_pass_number */
1139 0, /* properties_required */
1140 0, /* properties_provided */
1141 0, /* properties_destroyed */
1142 0, /* todo_flags_start */
1143 TODO_df_finish
| TODO_verify_rtl_sharing
|
1144 TODO_ggc_collect
/* todo_flags_finish */