1 /* RTL dead code elimination.
2 Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010
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 /* Try to find all stack stores of CALL_INSN arguments if
224 ACCUMULATE_OUTGOING_ARGS. If all stack stores have been found
225 and it is therefore safe to eliminate the call, return true,
226 otherwise return false. This function should be first called
227 with DO_MARK false, and only when the CALL_INSN is actually
228 going to be marked called again with DO_MARK true. */
231 find_call_stack_args (rtx call_insn
, bool do_mark
, bool fast
,
234 rtx p
, insn
, prev_insn
;
236 HOST_WIDE_INT min_sp_off
, max_sp_off
;
239 gcc_assert (CALL_P (call_insn
));
240 if (!ACCUMULATE_OUTGOING_ARGS
)
245 gcc_assert (arg_stores
);
246 bitmap_clear (arg_stores
);
249 min_sp_off
= INTTYPE_MAXIMUM (HOST_WIDE_INT
);
252 /* First determine the minimum and maximum offset from sp for
254 for (p
= CALL_INSN_FUNCTION_USAGE (call_insn
); p
; p
= XEXP (p
, 1))
255 if (GET_CODE (XEXP (p
, 0)) == USE
256 && MEM_P (XEXP (XEXP (p
, 0), 0)))
258 rtx mem
= XEXP (XEXP (p
, 0), 0), addr
, size
;
259 HOST_WIDE_INT off
= 0;
260 size
= MEM_SIZE (mem
);
261 if (size
== NULL_RTX
)
263 addr
= XEXP (mem
, 0);
264 if (GET_CODE (addr
) == PLUS
265 && REG_P (XEXP (addr
, 0))
266 && CONST_INT_P (XEXP (addr
, 1)))
268 off
= INTVAL (XEXP (addr
, 1));
269 addr
= XEXP (addr
, 0);
271 if (addr
!= stack_pointer_rtx
)
275 /* If not fast, use chains to see if addr wasn't set to
280 struct df_link
*defs
;
283 for (use_rec
= DF_INSN_USES (call_insn
); *use_rec
; use_rec
++)
284 if (rtx_equal_p (addr
, DF_REF_REG (*use_rec
)))
287 if (*use_rec
== NULL
)
290 for (defs
= DF_REF_CHAIN (*use_rec
); defs
; defs
= defs
->next
)
291 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
297 set
= single_set (DF_REF_INSN (defs
->ref
));
301 if (GET_CODE (SET_SRC (set
)) != PLUS
302 || XEXP (SET_SRC (set
), 0) != stack_pointer_rtx
303 || !CONST_INT_P (XEXP (SET_SRC (set
), 1)))
306 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
311 min_sp_off
= MIN (min_sp_off
, off
);
312 max_sp_off
= MAX (max_sp_off
, off
+ INTVAL (size
));
315 if (min_sp_off
>= max_sp_off
)
317 sp_bytes
= BITMAP_ALLOC (NULL
);
319 /* Set bits in SP_BYTES bitmap for bytes relative to sp + min_sp_off
320 which contain arguments. Checking has been done in the previous
322 for (p
= CALL_INSN_FUNCTION_USAGE (call_insn
); p
; p
= XEXP (p
, 1))
323 if (GET_CODE (XEXP (p
, 0)) == USE
324 && MEM_P (XEXP (XEXP (p
, 0), 0)))
326 rtx mem
= XEXP (XEXP (p
, 0), 0), addr
;
327 HOST_WIDE_INT off
= 0, byte
;
328 addr
= XEXP (mem
, 0);
329 if (GET_CODE (addr
) == PLUS
330 && REG_P (XEXP (addr
, 0))
331 && CONST_INT_P (XEXP (addr
, 1)))
333 off
= INTVAL (XEXP (addr
, 1));
334 addr
= XEXP (addr
, 0);
336 if (addr
!= stack_pointer_rtx
)
339 struct df_link
*defs
;
342 for (use_rec
= DF_INSN_USES (call_insn
); *use_rec
; use_rec
++)
343 if (rtx_equal_p (addr
, DF_REF_REG (*use_rec
)))
346 for (defs
= DF_REF_CHAIN (*use_rec
); defs
; defs
= defs
->next
)
347 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
350 set
= single_set (DF_REF_INSN (defs
->ref
));
351 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
353 for (byte
= off
; byte
< off
+ INTVAL (MEM_SIZE (mem
)); byte
++)
355 if (!bitmap_set_bit (sp_bytes
, byte
- min_sp_off
))
360 /* Walk backwards, looking for argument stores. The search stops
361 when seeing another call, sp adjustment or memory store other than
364 for (insn
= PREV_INSN (call_insn
); insn
; insn
= prev_insn
)
367 HOST_WIDE_INT off
, byte
;
369 if (insn
== BB_HEAD (BLOCK_FOR_INSN (call_insn
)))
370 prev_insn
= NULL_RTX
;
372 prev_insn
= PREV_INSN (insn
);
380 set
= single_set (insn
);
381 if (!set
|| SET_DEST (set
) == stack_pointer_rtx
)
384 if (!MEM_P (SET_DEST (set
)))
387 mem
= SET_DEST (set
);
388 addr
= XEXP (mem
, 0);
390 if (GET_CODE (addr
) == PLUS
391 && REG_P (XEXP (addr
, 0))
392 && CONST_INT_P (XEXP (addr
, 1)))
394 off
= INTVAL (XEXP (addr
, 1));
395 addr
= XEXP (addr
, 0);
397 if (addr
!= stack_pointer_rtx
)
404 struct df_link
*defs
;
407 for (use_rec
= DF_INSN_USES (insn
); *use_rec
; use_rec
++)
408 if (rtx_equal_p (addr
, DF_REF_REG (*use_rec
)))
411 if (*use_rec
== NULL
)
414 for (defs
= DF_REF_CHAIN (*use_rec
); defs
; defs
= defs
->next
)
415 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
421 set
= single_set (DF_REF_INSN (defs
->ref
));
425 if (GET_CODE (SET_SRC (set
)) != PLUS
426 || XEXP (SET_SRC (set
), 0) != stack_pointer_rtx
427 || !CONST_INT_P (XEXP (SET_SRC (set
), 1)))
430 off
+= INTVAL (XEXP (SET_SRC (set
), 1));
436 if (GET_MODE_SIZE (GET_MODE (mem
)) == 0)
439 for (byte
= off
; byte
< off
+ GET_MODE_SIZE (GET_MODE (mem
)); byte
++)
441 if (byte
< min_sp_off
442 || byte
>= max_sp_off
443 || !bitmap_clear_bit (sp_bytes
, byte
- min_sp_off
))
447 if (!deletable_insn_p (insn
, fast
, NULL
))
451 mark_insn (insn
, fast
);
453 bitmap_set_bit (arg_stores
, INSN_UID (insn
));
455 if (bitmap_empty_p (sp_bytes
))
462 BITMAP_FREE (sp_bytes
);
463 if (!ret
&& arg_stores
)
464 bitmap_clear (arg_stores
);
470 /* Remove all REG_EQUAL and REG_EQUIV notes referring to the registers INSN
474 remove_reg_equal_equiv_notes_for_defs (rtx insn
)
478 for (def_rec
= DF_INSN_DEFS (insn
); *def_rec
; def_rec
++)
479 remove_reg_equal_equiv_notes_for_regno (DF_REF_REGNO (*def_rec
));
483 /* Delete every instruction that hasn't been marked. */
486 delete_unmarked_insns (void)
490 bool must_clean
= false;
492 FOR_EACH_BB_REVERSE (bb
)
493 FOR_BB_INSNS_REVERSE_SAFE (bb
, insn
, next
)
496 /* Always delete no-op moves. */
497 if (noop_move_p (insn
))
500 /* Otherwise rely only on the DCE algorithm. */
501 else if (marked_insn_p (insn
))
504 /* Beware that reaching a dbg counter limit here can result
505 in miscompiled file. This occurs when a group of insns
506 must be deleted together, typically because the kept insn
507 depends on the output from the deleted insn. Deleting
508 this insns in reverse order (both at the bb level and
509 when looking at the blocks) minimizes this, but does not
510 eliminate it, since it is possible for the using insn to
511 be top of a block and the producer to be at the bottom of
512 the block. However, in most cases this will only result
513 in an uninitialized use of an insn that is dead anyway.
515 However, there is one rare case that will cause a
516 miscompile: deletion of non-looping pure and constant
517 calls on a machine where ACCUMULATE_OUTGOING_ARGS is true.
518 In this case it is possible to remove the call, but leave
519 the argument pushes to the stack. Because of the changes
520 to the stack pointer, this will almost always lead to a
526 fprintf (dump_file
, "DCE: Deleting insn %d\n", INSN_UID (insn
));
528 /* Before we delete the insn we have to remove the REG_EQUAL notes
529 for the destination regs in order to avoid dangling notes. */
530 remove_reg_equal_equiv_notes_for_defs (insn
);
532 /* If a pure or const call is deleted, this may make the cfg
533 have unreachable blocks. We rememeber this and call
534 delete_unreachable_blocks at the end. */
538 /* Now delete the insn. */
539 delete_insn_and_edges (insn
);
542 /* Deleted a pure or const call. */
544 delete_unreachable_blocks ();
548 /* Go through the instructions and mark those whose necessity is not
549 dependent on inter-instruction information. Make sure all other
550 instructions are not marked. */
553 prescan_insns_for_dce (bool fast
)
557 bitmap arg_stores
= NULL
;
560 fprintf (dump_file
, "Finding needed instructions:\n");
562 if (!df_in_progress
&& ACCUMULATE_OUTGOING_ARGS
)
563 arg_stores
= BITMAP_ALLOC (NULL
);
567 FOR_BB_INSNS_REVERSE_SAFE (bb
, insn
, prev
)
570 /* Don't mark argument stores now. They will be marked
571 if needed when the associated CALL is marked. */
572 if (arg_stores
&& bitmap_bit_p (arg_stores
, INSN_UID (insn
)))
574 if (deletable_insn_p (insn
, fast
, arg_stores
))
575 mark_nonreg_stores (PATTERN (insn
), insn
, fast
);
577 mark_insn (insn
, fast
);
579 /* find_call_stack_args only looks at argument stores in the
582 bitmap_clear (arg_stores
);
586 BITMAP_FREE (arg_stores
);
589 fprintf (dump_file
, "Finished finding needed instructions:\n");
593 /* UD-based DSE routines. */
595 /* Mark instructions that define artificially-used registers, such as
596 the frame pointer and the stack pointer. */
599 mark_artificial_uses (void)
602 struct df_link
*defs
;
607 for (use_rec
= df_get_artificial_uses (bb
->index
);
609 for (defs
= DF_REF_CHAIN (*use_rec
); defs
; defs
= defs
->next
)
610 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
611 mark_insn (DF_REF_INSN (defs
->ref
), false);
616 /* Mark every instruction that defines a register value that INSN uses. */
619 mark_reg_dependencies (rtx insn
)
621 struct df_link
*defs
;
624 if (DEBUG_INSN_P (insn
))
627 for (use_rec
= DF_INSN_USES (insn
); *use_rec
; use_rec
++)
629 df_ref use
= *use_rec
;
632 fprintf (dump_file
, "Processing use of ");
633 print_simple_rtl (dump_file
, DF_REF_REG (use
));
634 fprintf (dump_file
, " in insn %d:\n", INSN_UID (insn
));
636 for (defs
= DF_REF_CHAIN (use
); defs
; defs
= defs
->next
)
637 if (! DF_REF_IS_ARTIFICIAL (defs
->ref
))
638 mark_insn (DF_REF_INSN (defs
->ref
), false);
643 /* Initialize global variables for a new DCE pass. */
651 df_chain_add_problem (DF_UD_CHAIN
);
660 bitmap_obstack_initialize (&dce_blocks_bitmap_obstack
);
661 bitmap_obstack_initialize (&dce_tmp_bitmap_obstack
);
664 marked
= sbitmap_alloc (get_max_uid () + 1);
665 sbitmap_zero (marked
);
669 /* Free the data allocated by init_dce. */
674 sbitmap_free (marked
);
678 bitmap_obstack_release (&dce_blocks_bitmap_obstack
);
679 bitmap_obstack_release (&dce_tmp_bitmap_obstack
);
684 /* UD-chain based DCE. */
687 rest_of_handle_ud_dce (void)
693 prescan_insns_for_dce (false);
694 mark_artificial_uses ();
695 while (VEC_length (rtx
, worklist
) > 0)
697 insn
= VEC_pop (rtx
, worklist
);
698 mark_reg_dependencies (insn
);
700 VEC_free (rtx
, heap
, worklist
);
702 /* Before any insns are deleted, we must remove the chains since
703 they are not bidirectional. */
704 df_remove_problem (df_chain
);
705 delete_unmarked_insns ();
715 return optimize
> 1 && flag_dce
719 struct rtl_opt_pass pass_ud_rtl_dce
=
724 gate_ud_dce
, /* gate */
725 rest_of_handle_ud_dce
, /* execute */
728 0, /* static_pass_number */
730 0, /* properties_required */
731 0, /* properties_provided */
732 0, /* properties_destroyed */
733 0, /* todo_flags_start */
735 TODO_df_finish
| TODO_verify_rtl_sharing
|
736 TODO_ggc_collect
/* todo_flags_finish */
741 /* -------------------------------------------------------------------------
743 ------------------------------------------------------------------------- */
745 /* Process basic block BB. Return true if the live_in set has
746 changed. REDO_OUT is true if the info at the bottom of the block
747 needs to be recalculated before starting. AU is the proper set of
751 word_dce_process_block (basic_block bb
, bool redo_out
)
753 bitmap local_live
= BITMAP_ALLOC (&dce_tmp_bitmap_obstack
);
759 /* Need to redo the live_out set of this block if when one of
760 the succs of this block has had a change in it live in
764 df_confluence_function_n con_fun_n
= df_word_lr
->problem
->con_fun_n
;
765 bitmap_clear (DF_WORD_LR_OUT (bb
));
766 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
772 fprintf (dump_file
, "processing block %d live out = ", bb
->index
);
773 df_print_word_regset (dump_file
, DF_WORD_LR_OUT (bb
));
776 bitmap_copy (local_live
, DF_WORD_LR_OUT (bb
));
778 FOR_BB_INSNS_REVERSE (bb
, insn
)
779 if (NONDEBUG_INSN_P (insn
))
782 /* No matter if the instruction is needed or not, we remove
783 any regno in the defs from the live set. */
784 any_changed
= df_word_lr_simulate_defs (insn
, local_live
);
786 mark_insn (insn
, true);
788 /* On the other hand, we do not allow the dead uses to set
789 anything in local_live. */
790 if (marked_insn_p (insn
))
791 df_word_lr_simulate_uses (insn
, local_live
);
795 fprintf (dump_file
, "finished processing insn %d live out = ",
797 df_print_word_regset (dump_file
, local_live
);
801 block_changed
= !bitmap_equal_p (local_live
, DF_WORD_LR_IN (bb
));
803 bitmap_copy (DF_WORD_LR_IN (bb
), local_live
);
805 BITMAP_FREE (local_live
);
806 return block_changed
;
810 /* Process basic block BB. Return true if the live_in set has
811 changed. REDO_OUT is true if the info at the bottom of the block
812 needs to be recalculated before starting. AU is the proper set of
816 dce_process_block (basic_block bb
, bool redo_out
, bitmap au
)
818 bitmap local_live
= BITMAP_ALLOC (&dce_tmp_bitmap_obstack
);
825 /* Need to redo the live_out set of this block if when one of
826 the succs of this block has had a change in it live in
830 df_confluence_function_n con_fun_n
= df_lr
->problem
->con_fun_n
;
831 bitmap_clear (DF_LR_OUT (bb
));
832 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
838 fprintf (dump_file
, "processing block %d lr out = ", bb
->index
);
839 df_print_regset (dump_file
, DF_LR_OUT (bb
));
842 bitmap_copy (local_live
, DF_LR_OUT (bb
));
844 df_simulate_initialize_backwards (bb
, local_live
);
846 FOR_BB_INSNS_REVERSE (bb
, insn
)
849 bool needed
= marked_insn_p (insn
);
851 /* The insn is needed if there is someone who uses the output. */
853 for (def_rec
= DF_INSN_DEFS (insn
); *def_rec
; def_rec
++)
854 if (bitmap_bit_p (local_live
, DF_REF_REGNO (*def_rec
))
855 || bitmap_bit_p (au
, DF_REF_REGNO (*def_rec
)))
858 mark_insn (insn
, true);
862 /* No matter if the instruction is needed or not, we remove
863 any regno in the defs from the live set. */
864 df_simulate_defs (insn
, local_live
);
866 /* On the other hand, we do not allow the dead uses to set
867 anything in local_live. */
869 df_simulate_uses (insn
, local_live
);
872 df_simulate_finalize_backwards (bb
, local_live
);
874 block_changed
= !bitmap_equal_p (local_live
, DF_LR_IN (bb
));
876 bitmap_copy (DF_LR_IN (bb
), local_live
);
878 BITMAP_FREE (local_live
);
879 return block_changed
;
883 /* Perform fast DCE once initialization is done. If WORD_LEVEL is
884 true, use the word level dce, otherwise do it at the pseudo
888 fast_dce (bool word_level
)
890 int *postorder
= df_get_postorder (DF_BACKWARD
);
891 int n_blocks
= df_get_n_blocks (DF_BACKWARD
);
892 /* The set of blocks that have been seen on this iteration. */
893 bitmap processed
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
894 /* The set of blocks that need to have the out vectors reset because
895 the in of one of their successors has changed. */
896 bitmap redo_out
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
897 bitmap all_blocks
= BITMAP_ALLOC (&dce_blocks_bitmap_obstack
);
898 bool global_changed
= true;
900 /* These regs are considered always live so if they end up dying
901 because of some def, we need to bring the back again. Calling
902 df_simulate_fixup_sets has the disadvantage of calling
903 bb_has_eh_pred once per insn, so we cache the information
905 bitmap au
= &df
->regular_block_artificial_uses
;
906 bitmap au_eh
= &df
->eh_block_artificial_uses
;
909 prescan_insns_for_dce (true);
911 for (i
= 0; i
< n_blocks
; i
++)
912 bitmap_set_bit (all_blocks
, postorder
[i
]);
914 while (global_changed
)
916 global_changed
= false;
918 for (i
= 0; i
< n_blocks
; i
++)
920 int index
= postorder
[i
];
921 basic_block bb
= BASIC_BLOCK (index
);
924 if (index
< NUM_FIXED_BLOCKS
)
926 bitmap_set_bit (processed
, index
);
932 = word_dce_process_block (bb
, bitmap_bit_p (redo_out
, index
));
935 = dce_process_block (bb
, bitmap_bit_p (redo_out
, index
),
936 bb_has_eh_pred (bb
) ? au_eh
: au
);
937 bitmap_set_bit (processed
, index
);
943 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
944 if (bitmap_bit_p (processed
, e
->src
->index
))
945 /* Be tricky about when we need to iterate the
946 analysis. We only have redo the analysis if the
947 bitmaps change at the top of a block that is the
949 global_changed
= true;
951 bitmap_set_bit (redo_out
, e
->src
->index
);
957 /* Turn off the RUN_DCE flag to prevent recursive calls to
959 int old_flag
= df_clear_flags (DF_LR_RUN_DCE
);
961 /* So something was deleted that requires a redo. Do it on
963 delete_unmarked_insns ();
964 sbitmap_zero (marked
);
965 bitmap_clear (processed
);
966 bitmap_clear (redo_out
);
968 /* We do not need to rescan any instructions. We only need
969 to redo the dataflow equations for the blocks that had a
970 change at the top of the block. Then we need to redo the
973 df_analyze_problem (df_word_lr
, all_blocks
, postorder
, n_blocks
);
975 df_analyze_problem (df_lr
, all_blocks
, postorder
, n_blocks
);
977 if (old_flag
& DF_LR_RUN_DCE
)
978 df_set_flags (DF_LR_RUN_DCE
);
980 prescan_insns_for_dce (true);
984 delete_unmarked_insns ();
986 BITMAP_FREE (processed
);
987 BITMAP_FREE (redo_out
);
988 BITMAP_FREE (all_blocks
);
992 /* Fast register level DCE. */
995 rest_of_handle_fast_dce (void)
1004 /* Fast byte level DCE. */
1014 timevar_push (TV_DCE
);
1015 old_flags
= df_clear_flags (DF_DEFER_INSN_RESCAN
+ DF_NO_INSN_RESCAN
);
1016 df_word_lr_add_problem ();
1020 df_set_flags (old_flags
);
1021 timevar_pop (TV_DCE
);
1025 /* This is an internal call that is used by the df live register
1026 problem to run fast dce as a side effect of creating the live
1027 information. The stack is organized so that the lr problem is run,
1028 this pass is run, which updates the live info and the df scanning
1029 info, and then returns to allow the rest of the problems to be run.
1031 This can be called by elsewhere but it will not update the bit
1032 vectors for any other problems than LR. */
1035 run_fast_df_dce (void)
1039 /* If dce is able to delete something, it has to happen
1040 immediately. Otherwise there will be problems handling the
1043 df_clear_flags (DF_DEFER_INSN_RESCAN
+ DF_NO_INSN_RESCAN
);
1045 df_in_progress
= true;
1046 rest_of_handle_fast_dce ();
1047 df_in_progress
= false;
1049 df_set_flags (old_flags
);
1054 /* Run a fast DCE pass. */
1060 rest_of_handle_fast_dce ();
1065 gate_fast_dce (void)
1067 return optimize
> 0 && flag_dce
1068 && dbg_cnt (dce_fast
);
1071 struct rtl_opt_pass pass_fast_rtl_dce
=
1075 "rtl dce", /* name */
1076 gate_fast_dce
, /* gate */
1077 rest_of_handle_fast_dce
, /* execute */
1080 0, /* static_pass_number */
1082 0, /* properties_required */
1083 0, /* properties_provided */
1084 0, /* properties_destroyed */
1085 0, /* todo_flags_start */
1087 TODO_df_finish
| TODO_verify_rtl_sharing
|
1088 TODO_ggc_collect
/* todo_flags_finish */