[RS6000] lqarx and stqcx. registers
[official-gcc.git] / gcc / dce.c
blobea3fb00d433f60c4d58106ec917bc8d6a31f5aac
1 /* RTL dead code elimination.
2 Copyright (C) 2005-2016 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
9 version.
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
14 for more details.
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/>. */
20 #include "config.h"
21 #include "system.h"
22 #include "coretypes.h"
23 #include "backend.h"
24 #include "rtl.h"
25 #include "tree.h"
26 #include "predict.h"
27 #include "df.h"
28 #include "tm_p.h"
29 #include "emit-rtl.h" /* FIXME: Can go away once crtl is moved to rtl.h. */
30 #include "cfgrtl.h"
31 #include "cfgbuild.h"
32 #include "cfgcleanup.h"
33 #include "dce.h"
34 #include "valtrack.h"
35 #include "tree-pass.h"
36 #include "dbgcnt.h"
39 /* -------------------------------------------------------------------------
40 Core mark/delete routines
41 ------------------------------------------------------------------------- */
43 /* True if we are invoked while the df engine is running; in this case,
44 we don't want to reenter it. */
45 static bool df_in_progress = false;
47 /* True if we are allowed to alter the CFG in this pass. */
48 static bool can_alter_cfg = false;
50 /* Instructions that have been marked but whose dependencies have not
51 yet been processed. */
52 static vec<rtx_insn *> 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_call_insn *, 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. */
67 static bool
68 deletable_insn_p_1 (rtx body)
70 switch (GET_CODE (body))
72 case PREFETCH:
73 case TRAP_IF:
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. */
80 case UNSPEC:
81 return false;
83 default:
84 return !volatile_refs_p (body);
89 /* Return true if INSN is a normal instruction that can be deleted by
90 the DCE pass. */
92 static bool
93 deletable_insn_p (rtx_insn *insn, bool fast, bitmap arg_stores)
95 rtx body, x;
96 int i;
97 df_ref def;
99 if (CALL_P (insn)
100 /* We cannot delete calls inside of the recursive dce because
101 this may cause basic blocks to be deleted and this messes up
102 the rest of the stack of optimization passes. */
103 && (!df_in_progress)
104 /* We cannot delete pure or const sibling calls because it is
105 hard to see the result. */
106 && (!SIBLING_CALL_P (insn))
107 /* We can delete dead const or pure calls as long as they do not
108 infinite loop. */
109 && (RTL_CONST_OR_PURE_CALL_P (insn)
110 && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn)))
111 return find_call_stack_args (as_a <rtx_call_insn *> (insn), false,
112 fast, arg_stores);
114 /* Don't delete jumps, notes and the like. */
115 if (!NONJUMP_INSN_P (insn))
116 return false;
118 /* Don't delete insns that may throw if we cannot do so. */
119 if (!(cfun->can_delete_dead_exceptions && can_alter_cfg)
120 && !insn_nothrow_p (insn))
121 return false;
123 /* If INSN sets a global_reg, leave it untouched. */
124 FOR_EACH_INSN_DEF (def, insn)
125 if (HARD_REGISTER_NUM_P (DF_REF_REGNO (def))
126 && global_regs[DF_REF_REGNO (def)])
127 return false;
128 /* Initialization of pseudo PIC register should never be removed. */
129 else if (DF_REF_REG (def) == pic_offset_table_rtx
130 && REGNO (pic_offset_table_rtx) >= FIRST_PSEUDO_REGISTER)
131 return false;
133 body = PATTERN (insn);
134 switch (GET_CODE (body))
136 case USE:
137 case VAR_LOCATION:
138 return false;
140 case CLOBBER:
141 if (fast)
143 /* A CLOBBER of a dead pseudo register serves no purpose.
144 That is not necessarily true for hard registers until
145 after reload. */
146 x = XEXP (body, 0);
147 return REG_P (x) && (!HARD_REGISTER_P (x) || reload_completed);
149 else
150 /* Because of the way that use-def chains are built, it is not
151 possible to tell if the clobber is dead because it can
152 never be the target of a use-def chain. */
153 return false;
155 case PARALLEL:
156 for (i = XVECLEN (body, 0) - 1; i >= 0; i--)
157 if (!deletable_insn_p_1 (XVECEXP (body, 0, i)))
158 return false;
159 return true;
161 default:
162 return deletable_insn_p_1 (body);
167 /* Return true if INSN has been marked as needed. */
169 static inline int
170 marked_insn_p (rtx_insn *insn)
172 /* Artificial defs are always needed and they do not have an insn.
173 We should never see them here. */
174 gcc_assert (insn);
175 return bitmap_bit_p (marked, INSN_UID (insn));
179 /* If INSN has not yet been marked as needed, mark it now, and add it to
180 the worklist. */
182 static void
183 mark_insn (rtx_insn *insn, bool fast)
185 if (!marked_insn_p (insn))
187 if (!fast)
188 worklist.safe_push (insn);
189 bitmap_set_bit (marked, INSN_UID (insn));
190 if (dump_file)
191 fprintf (dump_file, " Adding insn %d to worklist\n", INSN_UID (insn));
192 if (CALL_P (insn)
193 && !df_in_progress
194 && !SIBLING_CALL_P (insn)
195 && (RTL_CONST_OR_PURE_CALL_P (insn)
196 && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn)))
197 find_call_stack_args (as_a <rtx_call_insn *> (insn), true, fast, NULL);
202 /* A note_stores callback used by mark_nonreg_stores. DATA is the
203 instruction containing DEST. */
205 static void
206 mark_nonreg_stores_1 (rtx dest, const_rtx pattern, void *data)
208 if (GET_CODE (pattern) != CLOBBER && !REG_P (dest))
209 mark_insn ((rtx_insn *) data, true);
213 /* A note_stores callback used by mark_nonreg_stores. DATA is the
214 instruction containing DEST. */
216 static void
217 mark_nonreg_stores_2 (rtx dest, const_rtx pattern, void *data)
219 if (GET_CODE (pattern) != CLOBBER && !REG_P (dest))
220 mark_insn ((rtx_insn *) data, false);
224 /* Mark INSN if BODY stores to a non-register destination. */
226 static void
227 mark_nonreg_stores (rtx body, rtx_insn *insn, bool fast)
229 if (fast)
230 note_stores (body, mark_nonreg_stores_1, insn);
231 else
232 note_stores (body, mark_nonreg_stores_2, insn);
236 /* Return true if store to MEM, starting OFF bytes from stack pointer,
237 is a call argument store, and clear corresponding bits from SP_BYTES
238 bitmap if it is. */
240 static bool
241 check_argument_store (rtx mem, HOST_WIDE_INT off, HOST_WIDE_INT min_sp_off,
242 HOST_WIDE_INT max_sp_off, bitmap sp_bytes)
244 HOST_WIDE_INT byte;
245 for (byte = off; byte < off + GET_MODE_SIZE (GET_MODE (mem)); byte++)
247 if (byte < min_sp_off
248 || byte >= max_sp_off
249 || !bitmap_clear_bit (sp_bytes, byte - min_sp_off))
250 return false;
252 return true;
256 /* Try to find all stack stores of CALL_INSN arguments if
257 ACCUMULATE_OUTGOING_ARGS. If all stack stores have been found
258 and it is therefore safe to eliminate the call, return true,
259 otherwise return false. This function should be first called
260 with DO_MARK false, and only when the CALL_INSN is actually
261 going to be marked called again with DO_MARK true. */
263 static bool
264 find_call_stack_args (rtx_call_insn *call_insn, bool do_mark, bool fast,
265 bitmap arg_stores)
267 rtx p;
268 rtx_insn *insn, *prev_insn;
269 bool ret;
270 HOST_WIDE_INT min_sp_off, max_sp_off;
271 bitmap sp_bytes;
273 gcc_assert (CALL_P (call_insn));
274 if (!ACCUMULATE_OUTGOING_ARGS)
275 return true;
277 if (!do_mark)
279 gcc_assert (arg_stores);
280 bitmap_clear (arg_stores);
283 min_sp_off = INTTYPE_MAXIMUM (HOST_WIDE_INT);
284 max_sp_off = 0;
286 /* First determine the minimum and maximum offset from sp for
287 stored arguments. */
288 for (p = CALL_INSN_FUNCTION_USAGE (call_insn); p; p = XEXP (p, 1))
289 if (GET_CODE (XEXP (p, 0)) == USE
290 && MEM_P (XEXP (XEXP (p, 0), 0)))
292 rtx mem = XEXP (XEXP (p, 0), 0), addr;
293 HOST_WIDE_INT off = 0, size;
294 if (!MEM_SIZE_KNOWN_P (mem))
295 return false;
296 size = MEM_SIZE (mem);
297 addr = XEXP (mem, 0);
298 if (GET_CODE (addr) == PLUS
299 && REG_P (XEXP (addr, 0))
300 && CONST_INT_P (XEXP (addr, 1)))
302 off = INTVAL (XEXP (addr, 1));
303 addr = XEXP (addr, 0);
305 if (addr != stack_pointer_rtx)
307 if (!REG_P (addr))
308 return false;
309 /* If not fast, use chains to see if addr wasn't set to
310 sp + offset. */
311 if (!fast)
313 df_ref use;
314 struct df_link *defs;
315 rtx set;
317 FOR_EACH_INSN_USE (use, call_insn)
318 if (rtx_equal_p (addr, DF_REF_REG (use)))
319 break;
321 if (use == NULL)
322 return false;
324 for (defs = DF_REF_CHAIN (use); defs; defs = defs->next)
325 if (! DF_REF_IS_ARTIFICIAL (defs->ref))
326 break;
328 if (defs == NULL)
329 return false;
331 set = single_set (DF_REF_INSN (defs->ref));
332 if (!set)
333 return false;
335 if (GET_CODE (SET_SRC (set)) != PLUS
336 || XEXP (SET_SRC (set), 0) != stack_pointer_rtx
337 || !CONST_INT_P (XEXP (SET_SRC (set), 1)))
338 return false;
340 off += INTVAL (XEXP (SET_SRC (set), 1));
342 else
343 return false;
345 min_sp_off = MIN (min_sp_off, off);
346 max_sp_off = MAX (max_sp_off, off + size);
349 if (min_sp_off >= max_sp_off)
350 return true;
351 sp_bytes = BITMAP_ALLOC (NULL);
353 /* Set bits in SP_BYTES bitmap for bytes relative to sp + min_sp_off
354 which contain arguments. Checking has been done in the previous
355 loop. */
356 for (p = CALL_INSN_FUNCTION_USAGE (call_insn); p; p = XEXP (p, 1))
357 if (GET_CODE (XEXP (p, 0)) == USE
358 && MEM_P (XEXP (XEXP (p, 0), 0)))
360 rtx mem = XEXP (XEXP (p, 0), 0), addr;
361 HOST_WIDE_INT off = 0, byte;
362 addr = XEXP (mem, 0);
363 if (GET_CODE (addr) == PLUS
364 && REG_P (XEXP (addr, 0))
365 && CONST_INT_P (XEXP (addr, 1)))
367 off = INTVAL (XEXP (addr, 1));
368 addr = XEXP (addr, 0);
370 if (addr != stack_pointer_rtx)
372 df_ref use;
373 struct df_link *defs;
374 rtx set;
376 FOR_EACH_INSN_USE (use, call_insn)
377 if (rtx_equal_p (addr, DF_REF_REG (use)))
378 break;
380 for (defs = DF_REF_CHAIN (use); defs; defs = defs->next)
381 if (! DF_REF_IS_ARTIFICIAL (defs->ref))
382 break;
384 set = single_set (DF_REF_INSN (defs->ref));
385 off += INTVAL (XEXP (SET_SRC (set), 1));
387 for (byte = off; byte < off + MEM_SIZE (mem); byte++)
389 if (!bitmap_set_bit (sp_bytes, byte - min_sp_off))
390 gcc_unreachable ();
394 /* Walk backwards, looking for argument stores. The search stops
395 when seeing another call, sp adjustment or memory store other than
396 argument store. */
397 ret = false;
398 for (insn = PREV_INSN (call_insn); insn; insn = prev_insn)
400 rtx set, mem, addr;
401 HOST_WIDE_INT off;
403 if (insn == BB_HEAD (BLOCK_FOR_INSN (call_insn)))
404 prev_insn = NULL;
405 else
406 prev_insn = PREV_INSN (insn);
408 if (CALL_P (insn))
409 break;
411 if (!NONDEBUG_INSN_P (insn))
412 continue;
414 set = single_set (insn);
415 if (!set || SET_DEST (set) == stack_pointer_rtx)
416 break;
418 if (!MEM_P (SET_DEST (set)))
419 continue;
421 mem = SET_DEST (set);
422 addr = XEXP (mem, 0);
423 off = 0;
424 if (GET_CODE (addr) == PLUS
425 && REG_P (XEXP (addr, 0))
426 && CONST_INT_P (XEXP (addr, 1)))
428 off = INTVAL (XEXP (addr, 1));
429 addr = XEXP (addr, 0);
431 if (addr != stack_pointer_rtx)
433 if (!REG_P (addr))
434 break;
435 if (!fast)
437 df_ref use;
438 struct df_link *defs;
439 rtx set;
441 FOR_EACH_INSN_USE (use, insn)
442 if (rtx_equal_p (addr, DF_REF_REG (use)))
443 break;
445 if (use == NULL)
446 break;
448 for (defs = DF_REF_CHAIN (use); defs; defs = defs->next)
449 if (! DF_REF_IS_ARTIFICIAL (defs->ref))
450 break;
452 if (defs == NULL)
453 break;
455 set = single_set (DF_REF_INSN (defs->ref));
456 if (!set)
457 break;
459 if (GET_CODE (SET_SRC (set)) != PLUS
460 || XEXP (SET_SRC (set), 0) != stack_pointer_rtx
461 || !CONST_INT_P (XEXP (SET_SRC (set), 1)))
462 break;
464 off += INTVAL (XEXP (SET_SRC (set), 1));
466 else
467 break;
470 if (GET_MODE_SIZE (GET_MODE (mem)) == 0
471 || !check_argument_store (mem, off, min_sp_off,
472 max_sp_off, sp_bytes))
473 break;
475 if (!deletable_insn_p (insn, fast, NULL))
476 break;
478 if (do_mark)
479 mark_insn (insn, fast);
480 else
481 bitmap_set_bit (arg_stores, INSN_UID (insn));
483 if (bitmap_empty_p (sp_bytes))
485 ret = true;
486 break;
490 BITMAP_FREE (sp_bytes);
491 if (!ret && arg_stores)
492 bitmap_clear (arg_stores);
494 return ret;
498 /* Remove all REG_EQUAL and REG_EQUIV notes referring to the registers INSN
499 writes to. */
501 static void
502 remove_reg_equal_equiv_notes_for_defs (rtx_insn *insn)
504 df_ref def;
506 FOR_EACH_INSN_DEF (def, insn)
507 remove_reg_equal_equiv_notes_for_regno (DF_REF_REGNO (def));
510 /* Scan all BBs for debug insns and reset those that reference values
511 defined in unmarked insns. */
513 static void
514 reset_unmarked_insns_debug_uses (void)
516 basic_block bb;
517 rtx_insn *insn, *next;
519 FOR_EACH_BB_REVERSE_FN (bb, cfun)
520 FOR_BB_INSNS_REVERSE_SAFE (bb, insn, next)
521 if (DEBUG_INSN_P (insn))
523 df_ref use;
525 FOR_EACH_INSN_USE (use, insn)
527 struct df_link *defs;
528 for (defs = DF_REF_CHAIN (use); defs; defs = defs->next)
530 rtx_insn *ref_insn;
531 if (DF_REF_IS_ARTIFICIAL (defs->ref))
532 continue;
533 ref_insn = DF_REF_INSN (defs->ref);
534 if (!marked_insn_p (ref_insn))
535 break;
537 if (!defs)
538 continue;
539 /* ??? FIXME could we propagate the values assigned to
540 each of the DEFs? */
541 INSN_VAR_LOCATION_LOC (insn) = gen_rtx_UNKNOWN_VAR_LOC ();
542 df_insn_rescan_debug_internal (insn);
543 break;
548 /* Delete every instruction that hasn't been marked. */
550 static void
551 delete_unmarked_insns (void)
553 basic_block bb;
554 rtx_insn *insn, *next;
555 bool must_clean = false;
557 FOR_EACH_BB_REVERSE_FN (bb, cfun)
558 FOR_BB_INSNS_REVERSE_SAFE (bb, insn, next)
559 if (NONDEBUG_INSN_P (insn))
561 /* Always delete no-op moves. */
562 if (noop_move_p (insn))
565 /* Otherwise rely only on the DCE algorithm. */
566 else if (marked_insn_p (insn))
567 continue;
569 /* Beware that reaching a dbg counter limit here can result
570 in miscompiled file. This occurs when a group of insns
571 must be deleted together, typically because the kept insn
572 depends on the output from the deleted insn. Deleting
573 this insns in reverse order (both at the bb level and
574 when looking at the blocks) minimizes this, but does not
575 eliminate it, since it is possible for the using insn to
576 be top of a block and the producer to be at the bottom of
577 the block. However, in most cases this will only result
578 in an uninitialized use of an insn that is dead anyway.
580 However, there is one rare case that will cause a
581 miscompile: deletion of non-looping pure and constant
582 calls on a machine where ACCUMULATE_OUTGOING_ARGS is true.
583 In this case it is possible to remove the call, but leave
584 the argument pushes to the stack. Because of the changes
585 to the stack pointer, this will almost always lead to a
586 miscompile. */
587 if (!dbg_cnt (dce))
588 continue;
590 if (dump_file)
591 fprintf (dump_file, "DCE: Deleting insn %d\n", INSN_UID (insn));
593 /* Before we delete the insn we have to remove the REG_EQUAL notes
594 for the destination regs in order to avoid dangling notes. */
595 remove_reg_equal_equiv_notes_for_defs (insn);
597 /* If a pure or const call is deleted, this may make the cfg
598 have unreachable blocks. We rememeber this and call
599 delete_unreachable_blocks at the end. */
600 if (CALL_P (insn))
601 must_clean = true;
603 /* Now delete the insn. */
604 delete_insn_and_edges (insn);
607 /* Deleted a pure or const call. */
608 if (must_clean)
609 delete_unreachable_blocks ();
613 /* Go through the instructions and mark those whose necessity is not
614 dependent on inter-instruction information. Make sure all other
615 instructions are not marked. */
617 static void
618 prescan_insns_for_dce (bool fast)
620 basic_block bb;
621 rtx_insn *insn, *prev;
622 bitmap arg_stores = NULL;
624 if (dump_file)
625 fprintf (dump_file, "Finding needed instructions:\n");
627 if (!df_in_progress && ACCUMULATE_OUTGOING_ARGS)
628 arg_stores = BITMAP_ALLOC (NULL);
630 FOR_EACH_BB_FN (bb, cfun)
632 FOR_BB_INSNS_REVERSE_SAFE (bb, insn, prev)
633 if (NONDEBUG_INSN_P (insn))
635 /* Don't mark argument stores now. They will be marked
636 if needed when the associated CALL is marked. */
637 if (arg_stores && bitmap_bit_p (arg_stores, INSN_UID (insn)))
638 continue;
639 if (deletable_insn_p (insn, fast, arg_stores))
640 mark_nonreg_stores (PATTERN (insn), insn, fast);
641 else
642 mark_insn (insn, fast);
644 /* find_call_stack_args only looks at argument stores in the
645 same bb. */
646 if (arg_stores)
647 bitmap_clear (arg_stores);
650 if (arg_stores)
651 BITMAP_FREE (arg_stores);
653 if (dump_file)
654 fprintf (dump_file, "Finished finding needed instructions:\n");
658 /* UD-based DSE routines. */
660 /* Mark instructions that define artificially-used registers, such as
661 the frame pointer and the stack pointer. */
663 static void
664 mark_artificial_uses (void)
666 basic_block bb;
667 struct df_link *defs;
668 df_ref use;
670 FOR_ALL_BB_FN (bb, cfun)
671 FOR_EACH_ARTIFICIAL_USE (use, bb->index)
672 for (defs = DF_REF_CHAIN (use); defs; defs = defs->next)
673 if (!DF_REF_IS_ARTIFICIAL (defs->ref))
674 mark_insn (DF_REF_INSN (defs->ref), false);
678 /* Mark every instruction that defines a register value that INSN uses. */
680 static void
681 mark_reg_dependencies (rtx_insn *insn)
683 struct df_link *defs;
684 df_ref use;
686 if (DEBUG_INSN_P (insn))
687 return;
689 FOR_EACH_INSN_USE (use, insn)
691 if (dump_file)
693 fprintf (dump_file, "Processing use of ");
694 print_simple_rtl (dump_file, DF_REF_REG (use));
695 fprintf (dump_file, " in insn %d:\n", INSN_UID (insn));
697 for (defs = DF_REF_CHAIN (use); defs; defs = defs->next)
698 if (! DF_REF_IS_ARTIFICIAL (defs->ref))
699 mark_insn (DF_REF_INSN (defs->ref), false);
704 /* Initialize global variables for a new DCE pass. */
706 static void
707 init_dce (bool fast)
709 if (!df_in_progress)
711 if (!fast)
713 df_set_flags (DF_RD_PRUNE_DEAD_DEFS);
714 df_chain_add_problem (DF_UD_CHAIN);
716 df_analyze ();
719 if (dump_file)
720 df_dump (dump_file);
722 if (fast)
724 bitmap_obstack_initialize (&dce_blocks_bitmap_obstack);
725 bitmap_obstack_initialize (&dce_tmp_bitmap_obstack);
726 can_alter_cfg = false;
728 else
729 can_alter_cfg = true;
731 marked = sbitmap_alloc (get_max_uid () + 1);
732 bitmap_clear (marked);
736 /* Free the data allocated by init_dce. */
738 static void
739 fini_dce (bool fast)
741 sbitmap_free (marked);
743 if (fast)
745 bitmap_obstack_release (&dce_blocks_bitmap_obstack);
746 bitmap_obstack_release (&dce_tmp_bitmap_obstack);
751 /* UD-chain based DCE. */
753 static unsigned int
754 rest_of_handle_ud_dce (void)
756 rtx_insn *insn;
758 init_dce (false);
760 prescan_insns_for_dce (false);
761 mark_artificial_uses ();
762 while (worklist.length () > 0)
764 insn = worklist.pop ();
765 mark_reg_dependencies (insn);
767 worklist.release ();
769 if (MAY_HAVE_DEBUG_INSNS)
770 reset_unmarked_insns_debug_uses ();
772 /* Before any insns are deleted, we must remove the chains since
773 they are not bidirectional. */
774 df_remove_problem (df_chain);
775 delete_unmarked_insns ();
777 fini_dce (false);
778 return 0;
782 namespace {
784 const pass_data pass_data_ud_rtl_dce =
786 RTL_PASS, /* type */
787 "ud_dce", /* name */
788 OPTGROUP_NONE, /* optinfo_flags */
789 TV_DCE, /* tv_id */
790 0, /* properties_required */
791 0, /* properties_provided */
792 0, /* properties_destroyed */
793 0, /* todo_flags_start */
794 TODO_df_finish, /* todo_flags_finish */
797 class pass_ud_rtl_dce : public rtl_opt_pass
799 public:
800 pass_ud_rtl_dce (gcc::context *ctxt)
801 : rtl_opt_pass (pass_data_ud_rtl_dce, ctxt)
804 /* opt_pass methods: */
805 virtual bool gate (function *)
807 return optimize > 1 && flag_dce && dbg_cnt (dce_ud);
810 virtual unsigned int execute (function *)
812 return rest_of_handle_ud_dce ();
815 }; // class pass_ud_rtl_dce
817 } // anon namespace
819 rtl_opt_pass *
820 make_pass_ud_rtl_dce (gcc::context *ctxt)
822 return new pass_ud_rtl_dce (ctxt);
826 /* -------------------------------------------------------------------------
827 Fast DCE functions
828 ------------------------------------------------------------------------- */
830 /* Process basic block BB. Return true if the live_in set has
831 changed. REDO_OUT is true if the info at the bottom of the block
832 needs to be recalculated before starting. AU is the proper set of
833 artificial uses. Track global substitution of uses of dead pseudos
834 in debug insns using GLOBAL_DEBUG. */
836 static bool
837 word_dce_process_block (basic_block bb, bool redo_out,
838 struct dead_debug_global *global_debug)
840 bitmap local_live = BITMAP_ALLOC (&dce_tmp_bitmap_obstack);
841 rtx_insn *insn;
842 bool block_changed;
843 struct dead_debug_local debug;
845 if (redo_out)
847 /* Need to redo the live_out set of this block if when one of
848 the succs of this block has had a change in it live in
849 set. */
850 edge e;
851 edge_iterator ei;
852 df_confluence_function_n con_fun_n = df_word_lr->problem->con_fun_n;
853 bitmap_clear (DF_WORD_LR_OUT (bb));
854 FOR_EACH_EDGE (e, ei, bb->succs)
855 (*con_fun_n) (e);
858 if (dump_file)
860 fprintf (dump_file, "processing block %d live out = ", bb->index);
861 df_print_word_regset (dump_file, DF_WORD_LR_OUT (bb));
864 bitmap_copy (local_live, DF_WORD_LR_OUT (bb));
865 dead_debug_local_init (&debug, NULL, global_debug);
867 FOR_BB_INSNS_REVERSE (bb, insn)
868 if (DEBUG_INSN_P (insn))
870 df_ref use;
871 FOR_EACH_INSN_USE (use, insn)
872 if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER
873 && (GET_MODE_SIZE (GET_MODE (DF_REF_REAL_REG (use)))
874 == 2 * UNITS_PER_WORD)
875 && !bitmap_bit_p (local_live, 2 * DF_REF_REGNO (use))
876 && !bitmap_bit_p (local_live, 2 * DF_REF_REGNO (use) + 1))
877 dead_debug_add (&debug, use, DF_REF_REGNO (use));
879 else if (INSN_P (insn))
881 bool any_changed;
883 /* No matter if the instruction is needed or not, we remove
884 any regno in the defs from the live set. */
885 any_changed = df_word_lr_simulate_defs (insn, local_live);
886 if (any_changed)
887 mark_insn (insn, true);
889 /* On the other hand, we do not allow the dead uses to set
890 anything in local_live. */
891 if (marked_insn_p (insn))
892 df_word_lr_simulate_uses (insn, local_live);
894 /* Insert debug temps for dead REGs used in subsequent debug
895 insns. We may have to emit a debug temp even if the insn
896 was marked, in case the debug use was after the point of
897 death. */
898 if (debug.used && !bitmap_empty_p (debug.used))
900 df_ref def;
902 FOR_EACH_INSN_DEF (def, insn)
903 dead_debug_insert_temp (&debug, DF_REF_REGNO (def), insn,
904 marked_insn_p (insn)
905 && !control_flow_insn_p (insn)
906 ? DEBUG_TEMP_AFTER_WITH_REG_FORCE
907 : DEBUG_TEMP_BEFORE_WITH_VALUE);
910 if (dump_file)
912 fprintf (dump_file, "finished processing insn %d live out = ",
913 INSN_UID (insn));
914 df_print_word_regset (dump_file, local_live);
918 block_changed = !bitmap_equal_p (local_live, DF_WORD_LR_IN (bb));
919 if (block_changed)
920 bitmap_copy (DF_WORD_LR_IN (bb), local_live);
922 dead_debug_local_finish (&debug, NULL);
923 BITMAP_FREE (local_live);
924 return block_changed;
928 /* Process basic block BB. Return true if the live_in set has
929 changed. REDO_OUT is true if the info at the bottom of the block
930 needs to be recalculated before starting. AU is the proper set of
931 artificial uses. Track global substitution of uses of dead pseudos
932 in debug insns using GLOBAL_DEBUG. */
934 static bool
935 dce_process_block (basic_block bb, bool redo_out, bitmap au,
936 struct dead_debug_global *global_debug)
938 bitmap local_live = BITMAP_ALLOC (&dce_tmp_bitmap_obstack);
939 rtx_insn *insn;
940 bool block_changed;
941 df_ref def;
942 struct dead_debug_local debug;
944 if (redo_out)
946 /* Need to redo the live_out set of this block if when one of
947 the succs of this block has had a change in it live in
948 set. */
949 edge e;
950 edge_iterator ei;
951 df_confluence_function_n con_fun_n = df_lr->problem->con_fun_n;
952 bitmap_clear (DF_LR_OUT (bb));
953 FOR_EACH_EDGE (e, ei, bb->succs)
954 (*con_fun_n) (e);
957 if (dump_file)
959 fprintf (dump_file, "processing block %d lr out = ", bb->index);
960 df_print_regset (dump_file, DF_LR_OUT (bb));
963 bitmap_copy (local_live, DF_LR_OUT (bb));
965 df_simulate_initialize_backwards (bb, local_live);
966 dead_debug_local_init (&debug, NULL, global_debug);
968 FOR_BB_INSNS_REVERSE (bb, insn)
969 if (DEBUG_INSN_P (insn))
971 df_ref use;
972 FOR_EACH_INSN_USE (use, insn)
973 if (!bitmap_bit_p (local_live, DF_REF_REGNO (use))
974 && !bitmap_bit_p (au, DF_REF_REGNO (use)))
975 dead_debug_add (&debug, use, DF_REF_REGNO (use));
977 else if (INSN_P (insn))
979 bool needed = marked_insn_p (insn);
981 /* The insn is needed if there is someone who uses the output. */
982 if (!needed)
983 FOR_EACH_INSN_DEF (def, insn)
984 if (bitmap_bit_p (local_live, DF_REF_REGNO (def))
985 || bitmap_bit_p (au, DF_REF_REGNO (def)))
987 needed = true;
988 mark_insn (insn, true);
989 break;
992 /* No matter if the instruction is needed or not, we remove
993 any regno in the defs from the live set. */
994 df_simulate_defs (insn, local_live);
996 /* On the other hand, we do not allow the dead uses to set
997 anything in local_live. */
998 if (needed)
999 df_simulate_uses (insn, local_live);
1001 /* Insert debug temps for dead REGs used in subsequent debug
1002 insns. We may have to emit a debug temp even if the insn
1003 was marked, in case the debug use was after the point of
1004 death. */
1005 if (debug.used && !bitmap_empty_p (debug.used))
1006 FOR_EACH_INSN_DEF (def, insn)
1007 dead_debug_insert_temp (&debug, DF_REF_REGNO (def), insn,
1008 needed && !control_flow_insn_p (insn)
1009 ? DEBUG_TEMP_AFTER_WITH_REG_FORCE
1010 : DEBUG_TEMP_BEFORE_WITH_VALUE);
1013 dead_debug_local_finish (&debug, NULL);
1014 df_simulate_finalize_backwards (bb, local_live);
1016 block_changed = !bitmap_equal_p (local_live, DF_LR_IN (bb));
1017 if (block_changed)
1018 bitmap_copy (DF_LR_IN (bb), local_live);
1020 BITMAP_FREE (local_live);
1021 return block_changed;
1025 /* Perform fast DCE once initialization is done. If WORD_LEVEL is
1026 true, use the word level dce, otherwise do it at the pseudo
1027 level. */
1029 static void
1030 fast_dce (bool word_level)
1032 int *postorder = df_get_postorder (DF_BACKWARD);
1033 int n_blocks = df_get_n_blocks (DF_BACKWARD);
1034 /* The set of blocks that have been seen on this iteration. */
1035 bitmap processed = BITMAP_ALLOC (&dce_blocks_bitmap_obstack);
1036 /* The set of blocks that need to have the out vectors reset because
1037 the in of one of their successors has changed. */
1038 bitmap redo_out = BITMAP_ALLOC (&dce_blocks_bitmap_obstack);
1039 bitmap all_blocks = BITMAP_ALLOC (&dce_blocks_bitmap_obstack);
1040 bool global_changed = true;
1042 /* These regs are considered always live so if they end up dying
1043 because of some def, we need to bring the back again. Calling
1044 df_simulate_fixup_sets has the disadvantage of calling
1045 bb_has_eh_pred once per insn, so we cache the information
1046 here. */
1047 bitmap au = &df->regular_block_artificial_uses;
1048 bitmap au_eh = &df->eh_block_artificial_uses;
1049 int i;
1050 struct dead_debug_global global_debug;
1052 prescan_insns_for_dce (true);
1054 for (i = 0; i < n_blocks; i++)
1055 bitmap_set_bit (all_blocks, postorder[i]);
1057 dead_debug_global_init (&global_debug, NULL);
1059 while (global_changed)
1061 global_changed = false;
1063 for (i = 0; i < n_blocks; i++)
1065 int index = postorder[i];
1066 basic_block bb = BASIC_BLOCK_FOR_FN (cfun, index);
1067 bool local_changed;
1069 if (index < NUM_FIXED_BLOCKS)
1071 bitmap_set_bit (processed, index);
1072 continue;
1075 if (word_level)
1076 local_changed
1077 = word_dce_process_block (bb, bitmap_bit_p (redo_out, index),
1078 &global_debug);
1079 else
1080 local_changed
1081 = dce_process_block (bb, bitmap_bit_p (redo_out, index),
1082 bb_has_eh_pred (bb) ? au_eh : au,
1083 &global_debug);
1084 bitmap_set_bit (processed, index);
1086 if (local_changed)
1088 edge e;
1089 edge_iterator ei;
1090 FOR_EACH_EDGE (e, ei, bb->preds)
1091 if (bitmap_bit_p (processed, e->src->index))
1092 /* Be tricky about when we need to iterate the
1093 analysis. We only have redo the analysis if the
1094 bitmaps change at the top of a block that is the
1095 entry to a loop. */
1096 global_changed = true;
1097 else
1098 bitmap_set_bit (redo_out, e->src->index);
1102 if (global_changed)
1104 /* Turn off the RUN_DCE flag to prevent recursive calls to
1105 dce. */
1106 int old_flag = df_clear_flags (DF_LR_RUN_DCE);
1108 /* So something was deleted that requires a redo. Do it on
1109 the cheap. */
1110 delete_unmarked_insns ();
1111 bitmap_clear (marked);
1112 bitmap_clear (processed);
1113 bitmap_clear (redo_out);
1115 /* We do not need to rescan any instructions. We only need
1116 to redo the dataflow equations for the blocks that had a
1117 change at the top of the block. Then we need to redo the
1118 iteration. */
1119 if (word_level)
1120 df_analyze_problem (df_word_lr, all_blocks, postorder, n_blocks);
1121 else
1122 df_analyze_problem (df_lr, all_blocks, postorder, n_blocks);
1124 if (old_flag & DF_LR_RUN_DCE)
1125 df_set_flags (DF_LR_RUN_DCE);
1127 prescan_insns_for_dce (true);
1131 dead_debug_global_finish (&global_debug, NULL);
1133 delete_unmarked_insns ();
1135 BITMAP_FREE (processed);
1136 BITMAP_FREE (redo_out);
1137 BITMAP_FREE (all_blocks);
1141 /* Fast register level DCE. */
1143 static unsigned int
1144 rest_of_handle_fast_dce (void)
1146 init_dce (true);
1147 fast_dce (false);
1148 fini_dce (true);
1149 return 0;
1153 /* Fast byte level DCE. */
1155 void
1156 run_word_dce (void)
1158 int old_flags;
1160 if (!flag_dce)
1161 return;
1163 timevar_push (TV_DCE);
1164 old_flags = df_clear_flags (DF_DEFER_INSN_RESCAN + DF_NO_INSN_RESCAN);
1165 df_word_lr_add_problem ();
1166 init_dce (true);
1167 fast_dce (true);
1168 fini_dce (true);
1169 df_set_flags (old_flags);
1170 timevar_pop (TV_DCE);
1174 /* This is an internal call that is used by the df live register
1175 problem to run fast dce as a side effect of creating the live
1176 information. The stack is organized so that the lr problem is run,
1177 this pass is run, which updates the live info and the df scanning
1178 info, and then returns to allow the rest of the problems to be run.
1180 This can be called by elsewhere but it will not update the bit
1181 vectors for any other problems than LR. */
1183 void
1184 run_fast_df_dce (void)
1186 if (flag_dce)
1188 /* If dce is able to delete something, it has to happen
1189 immediately. Otherwise there will be problems handling the
1190 eq_notes. */
1191 int old_flags =
1192 df_clear_flags (DF_DEFER_INSN_RESCAN + DF_NO_INSN_RESCAN);
1194 df_in_progress = true;
1195 rest_of_handle_fast_dce ();
1196 df_in_progress = false;
1198 df_set_flags (old_flags);
1203 /* Run a fast DCE pass. */
1205 void
1206 run_fast_dce (void)
1208 if (flag_dce)
1209 rest_of_handle_fast_dce ();
1213 namespace {
1215 const pass_data pass_data_fast_rtl_dce =
1217 RTL_PASS, /* type */
1218 "rtl_dce", /* name */
1219 OPTGROUP_NONE, /* optinfo_flags */
1220 TV_DCE, /* tv_id */
1221 0, /* properties_required */
1222 0, /* properties_provided */
1223 0, /* properties_destroyed */
1224 0, /* todo_flags_start */
1225 TODO_df_finish, /* todo_flags_finish */
1228 class pass_fast_rtl_dce : public rtl_opt_pass
1230 public:
1231 pass_fast_rtl_dce (gcc::context *ctxt)
1232 : rtl_opt_pass (pass_data_fast_rtl_dce, ctxt)
1235 /* opt_pass methods: */
1236 virtual bool gate (function *)
1238 return optimize > 0 && flag_dce && dbg_cnt (dce_fast);
1241 virtual unsigned int execute (function *)
1243 return rest_of_handle_fast_dce ();
1246 }; // class pass_fast_rtl_dce
1248 } // anon namespace
1250 rtl_opt_pass *
1251 make_pass_fast_rtl_dce (gcc::context *ctxt)
1253 return new pass_fast_rtl_dce (ctxt);