1 /* RTL dead code elimination.
2 Copyright (C) 2005, 2006, 2007, 2008, 2009 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"
34 #include "tree-pass.h"
39 DEF_VEC_ALLOC_I(int,heap);
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 if (volatile_refs_p (body))
87 if (flag_non_call_exceptions && may_trap_p (body))
95 /* Return true if INSN is a normal instruction that can be deleted by
99 deletable_insn_p (rtx insn, bool fast, bitmap arg_stores)
105 /* We cannot delete calls inside of the recursive dce because
106 this may cause basic blocks to be deleted and this messes up
107 the rest of the stack of optimization passes. */
109 /* We cannot delete pure or const sibling calls because it is
110 hard to see the result. */
111 && (!SIBLING_CALL_P (insn))
112 /* We can delete dead const or pure calls as long as they do not
114 && (RTL_CONST_OR_PURE_CALL_P (insn)
115 && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn)))
116 return find_call_stack_args (insn, false, fast, arg_stores);
118 if (!NONJUMP_INSN_P (insn))
121 body = PATTERN (insn);
122 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 gcc_assert (!bitmap_bit_p (sp_bytes, byte - min_sp_off));
356 bitmap_set_bit (sp_bytes, byte - min_sp_off);
360 /* Walk backwards, looking for argument stores. The search stops
361 when seeting 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_bit_p (sp_bytes, byte - min_sp_off))
445 bitmap_clear_bit (sp_bytes, byte - min_sp_off);
448 if (!deletable_insn_p (insn, fast, NULL))
452 mark_insn (insn, fast);
454 bitmap_set_bit (arg_stores, INSN_UID (insn));
456 if (bitmap_empty_p (sp_bytes))
463 BITMAP_FREE (sp_bytes);
464 if (!ret && arg_stores)
465 bitmap_clear (arg_stores);
471 /* Delete all REG_EQUAL notes of the registers INSN writes, to prevent
472 bad dangling REG_EQUAL notes. */
475 delete_corresponding_reg_eq_notes (rtx insn)
478 for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
480 df_ref def = *def_rec;
481 unsigned int regno = DF_REF_REGNO (def);
482 /* This loop is a little tricky. We cannot just go down the
483 chain because it is being modified by the actions in the
484 loop. So we just get the head. We plan to drain the list
486 while (DF_REG_EQ_USE_CHAIN (regno))
488 df_ref eq_use = DF_REG_EQ_USE_CHAIN (regno);
489 rtx noted_insn = DF_REF_INSN (eq_use);
490 rtx note = find_reg_note (noted_insn, REG_EQUAL, NULL_RTX);
492 note = find_reg_note (noted_insn, REG_EQUIV, NULL_RTX);
494 /* This assert is generally triggered when someone deletes a
495 REG_EQUAL or REG_EQUIV note by hacking the list manually
496 rather than calling remove_note. */
498 remove_note (noted_insn, note);
504 /* Delete every instruction that hasn't been marked. */
507 delete_unmarked_insns (void)
511 bool must_clean = false;
514 FOR_BB_INSNS_SAFE (bb, insn, next)
517 /* Always delete no-op moves. */
518 if (noop_move_p (insn))
521 /* Otherwise rely only on the DCE algorithm. */
522 else if (marked_insn_p (insn))
525 /* Beware that reaching a dbg counter limit here can easily result
526 in miscompiled file, whenever some insn is eliminated, but
527 insn that depends on it is not. */
532 fprintf (dump_file, "DCE: Deleting insn %d\n", INSN_UID (insn));
534 /* Before we delete the insn we have to delete REG_EQUAL notes
535 for the destination regs in order to avoid dangling notes. */
536 delete_corresponding_reg_eq_notes (insn);
538 /* If a pure or const call is deleted, this may make the cfg
539 have unreachable blocks. We rememeber this and call
540 delete_unreachable_blocks at the end. */
544 /* Now delete the insn. */
545 delete_insn_and_edges (insn);
548 /* Deleted a pure or const call. */
550 delete_unreachable_blocks ();
554 /* Go through the instructions and mark those whose necessity is not
555 dependent on inter-instruction information. Make sure all other
556 instructions are not marked. */
559 prescan_insns_for_dce (bool fast)
563 bitmap arg_stores = NULL;
566 fprintf (dump_file, "Finding needed instructions:\n");
568 if (!df_in_progress && ACCUMULATE_OUTGOING_ARGS)
569 arg_stores = BITMAP_ALLOC (NULL);
573 FOR_BB_INSNS_REVERSE_SAFE (bb, insn, prev)
576 /* Don't mark argument stores now. They will be marked
577 if needed when the associated CALL is marked. */
578 if (arg_stores && bitmap_bit_p (arg_stores, INSN_UID (insn)))
580 if (deletable_insn_p (insn, fast, arg_stores))
581 mark_nonreg_stores (PATTERN (insn), insn, fast);
583 mark_insn (insn, fast);
585 /* find_call_stack_args only looks at argument stores in the
588 bitmap_clear (arg_stores);
592 BITMAP_FREE (arg_stores);
595 fprintf (dump_file, "Finished finding needed instructions:\n");
599 /* UD-based DSE routines. */
601 /* Mark instructions that define artificially-used registers, such as
602 the frame pointer and the stack pointer. */
605 mark_artificial_uses (void)
608 struct df_link *defs;
613 for (use_rec = df_get_artificial_uses (bb->index);
615 for (defs = DF_REF_CHAIN (*use_rec); defs; defs = defs->next)
616 if (! DF_REF_IS_ARTIFICIAL (defs->ref))
617 mark_insn (DF_REF_INSN (defs->ref), false);
622 /* Mark every instruction that defines a register value that INSN uses. */
625 mark_reg_dependencies (rtx insn)
627 struct df_link *defs;
630 for (use_rec = DF_INSN_USES (insn); *use_rec; use_rec++)
632 df_ref use = *use_rec;
635 fprintf (dump_file, "Processing use of ");
636 print_simple_rtl (dump_file, DF_REF_REG (use));
637 fprintf (dump_file, " in insn %d:\n", INSN_UID (insn));
639 for (defs = DF_REF_CHAIN (use); defs; defs = defs->next)
640 if (! DF_REF_IS_ARTIFICIAL (defs->ref))
641 mark_insn (DF_REF_INSN (defs->ref), false);
646 /* Initialize global variables for a new DCE pass. */
654 df_chain_add_problem (DF_UD_CHAIN);
663 bitmap_obstack_initialize (&dce_blocks_bitmap_obstack);
664 bitmap_obstack_initialize (&dce_tmp_bitmap_obstack);
667 marked = sbitmap_alloc (get_max_uid () + 1);
668 sbitmap_zero (marked);
672 /* Free the data allocated by init_dce. */
677 sbitmap_free (marked);
681 bitmap_obstack_release (&dce_blocks_bitmap_obstack);
682 bitmap_obstack_release (&dce_tmp_bitmap_obstack);
687 /* UD-chain based DCE. */
690 rest_of_handle_ud_dce (void)
696 prescan_insns_for_dce (false);
697 mark_artificial_uses ();
698 while (VEC_length (rtx, worklist) > 0)
700 insn = VEC_pop (rtx, worklist);
701 mark_reg_dependencies (insn);
703 VEC_free (rtx, heap, worklist);
705 /* Before any insns are deleted, we must remove the chains since
706 they are not bidirectional. */
707 df_remove_problem (df_chain);
708 delete_unmarked_insns ();
718 return optimize > 1 && flag_dce
722 struct rtl_opt_pass pass_ud_rtl_dce =
727 gate_ud_dce, /* gate */
728 rest_of_handle_ud_dce, /* execute */
731 0, /* static_pass_number */
733 0, /* properties_required */
734 0, /* properties_provided */
735 0, /* properties_destroyed */
736 0, /* todo_flags_start */
738 TODO_df_finish | TODO_verify_rtl_sharing |
739 TODO_ggc_collect /* todo_flags_finish */
744 /* -------------------------------------------------------------------------
746 ------------------------------------------------------------------------- */
748 /* Process basic block BB. Return true if the live_in set has
749 changed. REDO_OUT is true if the info at the bottom of the block
750 needs to be recalculated before starting. AU is the proper set of
754 byte_dce_process_block (basic_block bb, bool redo_out, bitmap au)
756 bitmap local_live = BITMAP_ALLOC (&dce_tmp_bitmap_obstack);
763 /* Need to redo the live_out set of this block if when one of
764 the succs of this block has had a change in it live in
768 df_confluence_function_n con_fun_n = df_byte_lr->problem->con_fun_n;
769 bitmap_clear (DF_BYTE_LR_OUT (bb));
770 FOR_EACH_EDGE (e, ei, bb->succs)
776 fprintf (dump_file, "processing block %d live out = ", bb->index);
777 df_print_byte_regset (dump_file, DF_BYTE_LR_OUT (bb));
780 bitmap_copy (local_live, DF_BYTE_LR_OUT (bb));
782 df_byte_lr_simulate_artificial_refs_at_end (bb, local_live);
784 FOR_BB_INSNS_REVERSE (bb, insn)
787 /* The insn is needed if there is someone who uses the output. */
788 for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
790 df_ref def = *def_rec;
792 unsigned int dregno = DF_REF_REGNO (def);
793 unsigned int start = df_byte_lr_get_regno_start (dregno);
794 unsigned int len = df_byte_lr_get_regno_len (dregno);
798 /* This is one of the only places where DF_MM_MAY should
799 be used for defs. Need to make sure that we are
800 checking for all of the bits that may be used. */
802 if (!df_compute_accessed_bytes (def, DF_MM_MAY, &sb, &lb))
808 if (bitmap_bit_p (au, dregno))
810 mark_insn (insn, true);
816 if (bitmap_bit_p (local_live, start++))
818 mark_insn (insn, true);
825 /* No matter if the instruction is needed or not, we remove
826 any regno in the defs from the live set. */
827 df_byte_lr_simulate_defs (insn, local_live);
829 /* On the other hand, we do not allow the dead uses to set
830 anything in local_live. */
831 if (marked_insn_p (insn))
832 df_byte_lr_simulate_uses (insn, local_live);
836 fprintf (dump_file, "finished processing insn %d live out = ",
838 df_print_byte_regset (dump_file, local_live);
842 df_byte_lr_simulate_artificial_refs_at_top (bb, local_live);
844 block_changed = !bitmap_equal_p (local_live, DF_BYTE_LR_IN (bb));
846 bitmap_copy (DF_BYTE_LR_IN (bb), local_live);
847 BITMAP_FREE (local_live);
848 return block_changed;
852 /* Process basic block BB. Return true if the live_in set has
853 changed. REDO_OUT is true if the info at the bottom of the block
854 needs to be recalculated before starting. AU is the proper set of
858 dce_process_block (basic_block bb, bool redo_out, bitmap au)
860 bitmap local_live = BITMAP_ALLOC (&dce_tmp_bitmap_obstack);
867 /* Need to redo the live_out set of this block if when one of
868 the succs of this block has had a change in it live in
872 df_confluence_function_n con_fun_n = df_lr->problem->con_fun_n;
873 bitmap_clear (DF_LR_OUT (bb));
874 FOR_EACH_EDGE (e, ei, bb->succs)
880 fprintf (dump_file, "processing block %d lr out = ", bb->index);
881 df_print_regset (dump_file, DF_LR_OUT (bb));
884 bitmap_copy (local_live, DF_LR_OUT (bb));
886 df_simulate_initialize_backwards (bb, local_live);
888 FOR_BB_INSNS_REVERSE (bb, insn)
893 /* The insn is needed if there is someone who uses the output. */
894 for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
895 if (bitmap_bit_p (local_live, DF_REF_REGNO (*def_rec))
896 || bitmap_bit_p (au, DF_REF_REGNO (*def_rec)))
903 mark_insn (insn, true);
905 /* No matter if the instruction is needed or not, we remove
906 any regno in the defs from the live set. */
907 df_simulate_defs (insn, local_live);
909 /* On the other hand, we do not allow the dead uses to set
910 anything in local_live. */
911 if (marked_insn_p (insn))
912 df_simulate_uses (insn, local_live);
915 df_simulate_finalize_backwards (bb, local_live);
917 block_changed = !bitmap_equal_p (local_live, DF_LR_IN (bb));
919 bitmap_copy (DF_LR_IN (bb), local_live);
921 BITMAP_FREE (local_live);
922 return block_changed;
926 /* Perform fast DCE once initialization is done. If BYTE_LEVEL is
927 true, use the byte level dce, otherwise do it at the pseudo
931 fast_dce (bool byte_level)
933 int *postorder = df_get_postorder (DF_BACKWARD);
934 int n_blocks = df_get_n_blocks (DF_BACKWARD);
935 /* The set of blocks that have been seen on this iteration. */
936 bitmap processed = BITMAP_ALLOC (&dce_blocks_bitmap_obstack);
937 /* The set of blocks that need to have the out vectors reset because
938 the in of one of their successors has changed. */
939 bitmap redo_out = BITMAP_ALLOC (&dce_blocks_bitmap_obstack);
940 bitmap all_blocks = BITMAP_ALLOC (&dce_blocks_bitmap_obstack);
941 bool global_changed = true;
943 /* These regs are considered always live so if they end up dying
944 because of some def, we need to bring the back again. Calling
945 df_simulate_fixup_sets has the disadvantage of calling
946 bb_has_eh_pred once per insn, so we cache the information
948 bitmap au = df->regular_block_artificial_uses;
949 bitmap au_eh = df->eh_block_artificial_uses;
952 prescan_insns_for_dce (true);
954 for (i = 0; i < n_blocks; i++)
955 bitmap_set_bit (all_blocks, postorder[i]);
957 while (global_changed)
959 global_changed = false;
961 for (i = 0; i < n_blocks; i++)
963 int index = postorder[i];
964 basic_block bb = BASIC_BLOCK (index);
967 if (index < NUM_FIXED_BLOCKS)
969 bitmap_set_bit (processed, index);
975 = byte_dce_process_block (bb, bitmap_bit_p (redo_out, index),
976 bb_has_eh_pred (bb) ? au_eh : au);
979 = dce_process_block (bb, bitmap_bit_p (redo_out, index),
980 bb_has_eh_pred (bb) ? au_eh : au);
981 bitmap_set_bit (processed, index);
987 FOR_EACH_EDGE (e, ei, bb->preds)
988 if (bitmap_bit_p (processed, e->src->index))
989 /* Be tricky about when we need to iterate the
990 analysis. We only have redo the analysis if the
991 bitmaps change at the top of a block that is the
993 global_changed = true;
995 bitmap_set_bit (redo_out, e->src->index);
1001 /* Turn off the RUN_DCE flag to prevent recursive calls to
1003 int old_flag = df_clear_flags (DF_LR_RUN_DCE);
1005 /* So something was deleted that requires a redo. Do it on
1007 delete_unmarked_insns ();
1008 sbitmap_zero (marked);
1009 bitmap_clear (processed);
1010 bitmap_clear (redo_out);
1012 /* We do not need to rescan any instructions. We only need
1013 to redo the dataflow equations for the blocks that had a
1014 change at the top of the block. Then we need to redo the
1017 df_analyze_problem (df_byte_lr, all_blocks, postorder, n_blocks);
1019 df_analyze_problem (df_lr, all_blocks, postorder, n_blocks);
1021 if (old_flag & DF_LR_RUN_DCE)
1022 df_set_flags (DF_LR_RUN_DCE);
1024 prescan_insns_for_dce (true);
1028 delete_unmarked_insns ();
1030 BITMAP_FREE (processed);
1031 BITMAP_FREE (redo_out);
1032 BITMAP_FREE (all_blocks);
1036 /* Fast register level DCE. */
1039 rest_of_handle_fast_dce (void)
1048 /* Fast byte level DCE. */
1051 rest_of_handle_fast_byte_dce (void)
1053 df_byte_lr_add_problem ();
1061 /* This is an internal call that is used by the df live register
1062 problem to run fast dce as a side effect of creating the live
1063 information. The stack is organized so that the lr problem is run,
1064 this pass is run, which updates the live info and the df scanning
1065 info, and then returns to allow the rest of the problems to be run.
1067 This can be called by elsewhere but it will not update the bit
1068 vectors for any other problems than LR. */
1071 run_fast_df_dce (void)
1075 /* If dce is able to delete something, it has to happen
1076 immediately. Otherwise there will be problems handling the
1078 enum df_changeable_flags old_flags
1079 = df_clear_flags (DF_DEFER_INSN_RESCAN + DF_NO_INSN_RESCAN);
1081 df_in_progress = true;
1082 rest_of_handle_fast_dce ();
1083 df_in_progress = false;
1085 df_set_flags (old_flags);
1090 /* Run a fast DCE pass. */
1096 rest_of_handle_fast_dce ();
1101 gate_fast_dce (void)
1103 return optimize > 0 && flag_dce
1104 && dbg_cnt (dce_fast);
1107 struct rtl_opt_pass pass_fast_rtl_dce =
1112 gate_fast_dce, /* gate */
1113 rest_of_handle_fast_dce, /* execute */
1116 0, /* static_pass_number */
1118 0, /* properties_required */
1119 0, /* properties_provided */
1120 0, /* properties_destroyed */
1121 0, /* todo_flags_start */
1123 TODO_df_finish | TODO_verify_rtl_sharing |
1124 TODO_ggc_collect /* todo_flags_finish */
1128 struct rtl_opt_pass pass_fast_rtl_byte_dce =
1132 "byte-dce", /* name */
1133 gate_fast_dce, /* gate */
1134 rest_of_handle_fast_byte_dce, /* execute */
1137 0, /* static_pass_number */
1139 0, /* properties_required */
1140 0, /* properties_provided */
1141 0, /* properties_destroyed */
1142 0, /* todo_flags_start */
1144 TODO_df_finish | TODO_verify_rtl_sharing |
1145 TODO_ggc_collect /* todo_flags_finish */