aboutsummaryrefslogtreecommitdiff
path: root/gcc/store-motion.c
blob: c8beb24ed64aa584edd8ce73bb3037e828df1b54 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
/* Store motion via Lazy Code Motion on the reverse CFG.
   Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
   2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "diagnostic-core.h"
#include "toplev.h"

#include "rtl.h"
#include "tree.h"
#include "tm_p.h"
#include "regs.h"
#include "hard-reg-set.h"
#include "flags.h"
#include "insn-config.h"
#include "recog.h"
#include "basic-block.h"
#include "output.h"
#include "function.h"
#include "expr.h"
#include "except.h"
#include "ggc.h"
#include "intl.h"
#include "timevar.h"
#include "tree-pass.h"
#include "hashtab.h"
#include "df.h"
#include "dbgcnt.h"

/* This pass implements downward store motion.
   As of May 1, 2009, the pass is not enabled by default on any target,
   but bootstrap completes on ia64 and x86_64 with the pass enabled.  */

/* TODO:
   - remove_reachable_equiv_notes is an incomprehensible pile of goo and
     a compile time hog that needs a rewrite (maybe cache st_exprs to
     invalidate REG_EQUAL/REG_EQUIV notes for?).
   - pattern_regs in st_expr should be a regset (on its own obstack).
   - antic_stores and avail_stores should be VECs instead of lists.
   - store_motion_mems should be a VEC instead of a list.
   - there should be an alloc pool for struct st_expr objects.
   - investigate whether it is helpful to make the address of an st_expr
     a cselib VALUE.
   - when GIMPLE alias information is exported, the effectiveness of this
     pass should be re-evaluated.
*/

/* This is a list of store expressions (MEMs).  The structure is used
   as an expression table to track stores which look interesting, and
   might be moveable towards the exit block.  */

struct st_expr
{
  /* Pattern of this mem.  */
  rtx pattern;
  /* List of registers mentioned by the mem.  */
  rtx pattern_regs;
  /* INSN list of stores that are locally anticipatable.  */
  rtx antic_stores;
  /* INSN list of stores that are locally available.  */
  rtx avail_stores;
  /* Next in the list.  */
  struct st_expr * next;
  /* Store ID in the dataflow bitmaps.  */
  int index;
  /* Hash value for the hash table.  */
  unsigned int hash_index;
  /* Register holding the stored expression when a store is moved.
     This field is also used as a cache in find_moveable_store, see
     LAST_AVAIL_CHECK_FAILURE below.  */
  rtx reaching_reg;
};

/* Head of the list of load/store memory refs.  */
static struct st_expr * store_motion_mems = NULL;

/* Hashtable for the load/store memory refs.  */
static htab_t store_motion_mems_table = NULL;

/* These bitmaps will hold the local dataflow properties per basic block.  */
static sbitmap *st_kill, *st_avloc, *st_antloc, *st_transp;

/* Nonzero for expressions which should be inserted on a specific edge.  */
static sbitmap *st_insert_map;

/* Nonzero for expressions which should be deleted in a specific block.  */
static sbitmap *st_delete_map;

/* Global holding the number of store expressions we are dealing with.  */
static int num_stores;

/* Contains the edge_list returned by pre_edge_lcm.  */
static struct edge_list *edge_list;

static hashval_t
pre_st_expr_hash (const void *p)
{
  int do_not_record_p = 0;
  const struct st_expr *const x = (const struct st_expr *) p;
  return hash_rtx (x->pattern, GET_MODE (x->pattern), &do_not_record_p, NULL, false);
}

static int
pre_st_expr_eq (const void *p1, const void *p2)
{
  const struct st_expr *const ptr1 = (const struct st_expr *) p1,
    *const ptr2 = (const struct st_expr *) p2;
  return exp_equiv_p (ptr1->pattern, ptr2->pattern, 0, true);
}

/* This will search the st_expr list for a matching expression. If it
   doesn't find one, we create one and initialize it.  */

static struct st_expr *
st_expr_entry (rtx x)
{
  int do_not_record_p = 0;
  struct st_expr * ptr;
  unsigned int hash;
  void **slot;
  struct st_expr e;

  hash = hash_rtx (x, GET_MODE (x), &do_not_record_p,
		   NULL,  /*have_reg_qty=*/false);

  e.pattern = x;
  slot = htab_find_slot_with_hash (store_motion_mems_table, &e, hash, INSERT);
  if (*slot)
    return (struct st_expr *)*slot;

  ptr = XNEW (struct st_expr);

  ptr->next         = store_motion_mems;
  ptr->pattern      = x;
  ptr->pattern_regs = NULL_RTX;
  ptr->antic_stores = NULL_RTX;
  ptr->avail_stores = NULL_RTX;
  ptr->reaching_reg = NULL_RTX;
  ptr->index        = 0;
  ptr->hash_index   = hash;
  store_motion_mems = ptr;
  *slot = ptr;

  return ptr;
}

/* Free up an individual st_expr entry.  */

static void
free_st_expr_entry (struct st_expr * ptr)
{
  free_INSN_LIST_list (& ptr->antic_stores);
  free_INSN_LIST_list (& ptr->avail_stores);

  free (ptr);
}

/* Free up all memory associated with the st_expr list.  */

static void
free_store_motion_mems (void)
{
  if (store_motion_mems_table)
    htab_delete (store_motion_mems_table);
  store_motion_mems_table = NULL;

  while (store_motion_mems)
    {
      struct st_expr * tmp = store_motion_mems;
      store_motion_mems = store_motion_mems->next;
      free_st_expr_entry (tmp);
    }
  store_motion_mems = NULL;
}

/* Assign each element of the list of mems a monotonically increasing value.  */

static int
enumerate_store_motion_mems (void)
{
  struct st_expr * ptr;
  int n = 0;

  for (ptr = store_motion_mems; ptr != NULL; ptr = ptr->next)
    ptr->index = n++;

  return n;
}

/* Return first item in the list.  */

static inline struct st_expr *
first_st_expr (void)
{
  return store_motion_mems;
}

/* Return the next item in the list after the specified one.  */

static inline struct st_expr *
next_st_expr (struct st_expr * ptr)
{
  return ptr->next;
}

/* Dump debugging info about the store_motion_mems list.  */

static void
print_store_motion_mems (FILE * file)
{
  struct st_expr * ptr;

  fprintf (dump_file, "STORE_MOTION list of MEM exprs considered:\n");

  for (ptr = first_st_expr (); ptr != NULL; ptr = next_st_expr (ptr))
    {
      fprintf (file, "  Pattern (%3d): ", ptr->index);

      print_rtl (file, ptr->pattern);

      fprintf (file, "\n	 ANTIC stores : ");

      if (ptr->antic_stores)
	print_rtl (file, ptr->antic_stores);
      else
	fprintf (file, "(nil)");

      fprintf (file, "\n	 AVAIL stores : ");

      if (ptr->avail_stores)
	print_rtl (file, ptr->avail_stores);
      else
	fprintf (file, "(nil)");

      fprintf (file, "\n\n");
    }

  fprintf (file, "\n");
}

/* Return zero if some of the registers in list X are killed
   due to set of registers in bitmap REGS_SET.  */

static bool
store_ops_ok (const_rtx x, int *regs_set)
{
  const_rtx reg;

  for (; x; x = XEXP (x, 1))
    {
      reg = XEXP (x, 0);
      if (regs_set[REGNO(reg)])
	return false;
    }

  return true;
}

/* Helper for extract_mentioned_regs.  */

static int
extract_mentioned_regs_1 (rtx *loc, void *data)
{
  rtx *mentioned_regs_p = (rtx *) data;

  if (REG_P (*loc))
    *mentioned_regs_p = alloc_EXPR_LIST (0, *loc, *mentioned_regs_p);

  return 0;
}

/* Returns a list of registers mentioned in X.
   FIXME: A regset would be prettier and less expensive.  */

static rtx
extract_mentioned_regs (rtx x)
{
  rtx mentioned_regs = NULL;
  for_each_rtx (&x, extract_mentioned_regs_1, &mentioned_regs);
  return mentioned_regs;
}

/* Check to see if the load X is aliased with STORE_PATTERN.
   AFTER is true if we are checking the case when STORE_PATTERN occurs
   after the X.  */

static bool
load_kills_store (const_rtx x, const_rtx store_pattern, int after)
{
  if (after)
    return anti_dependence (x, store_pattern);
  else
    return true_dependence (store_pattern, GET_MODE (store_pattern), x,
			    rtx_addr_varies_p);
}

/* Go through the entire rtx X, looking for any loads which might alias
   STORE_PATTERN.  Return true if found.
   AFTER is true if we are checking the case when STORE_PATTERN occurs
   after the insn X.  */

static bool
find_loads (const_rtx x, const_rtx store_pattern, int after)
{
  const char * fmt;
  int i, j;
  int ret = false;

  if (!x)
    return false;

  if (GET_CODE (x) == SET)
    x = SET_SRC (x);

  if (MEM_P (x))
    {
      if (load_kills_store (x, store_pattern, after))
	return true;
    }

  /* Recursively process the insn.  */
  fmt = GET_RTX_FORMAT (GET_CODE (x));

  for (i = GET_RTX_LENGTH (GET_CODE (x)) - 1; i >= 0 && !ret; i--)
    {
      if (fmt[i] == 'e')
	ret |= find_loads (XEXP (x, i), store_pattern, after);
      else if (fmt[i] == 'E')
	for (j = XVECLEN (x, i) - 1; j >= 0; j--)
	  ret |= find_loads (XVECEXP (x, i, j), store_pattern, after);
    }
  return ret;
}

/* Go through pattern PAT looking for any loads which might kill the
   store in X.  Return true if found.
   AFTER is true if we are checking the case when loads kill X occurs
   after the insn for PAT.  */

static inline bool
store_killed_in_pat (const_rtx x, const_rtx pat, int after)
{
  if (GET_CODE (pat) == SET)
    {
      rtx dest = SET_DEST (pat);

      if (GET_CODE (dest) == ZERO_EXTRACT)
	dest = XEXP (dest, 0);

      /* Check for memory stores to aliased objects.  */
      if (MEM_P (dest)
	  && !exp_equiv_p (dest, x, 0, true))
	{
	  if (after)
	    {
	      if (output_dependence (dest, x))
		return true;
	    }
	  else
	    {
	      if (output_dependence (x, dest))
		return true;
	    }
	}
    }

  if (find_loads (pat, x, after))
    return true;

  return false;
}

/* Check if INSN kills the store pattern X (is aliased with it).
   AFTER is true if we are checking the case when store X occurs
   after the insn.  Return true if it does.  */

static bool
store_killed_in_insn (const_rtx x, const_rtx x_regs, const_rtx insn, int after)
{
  const_rtx reg, base, note, pat;

  if (! NONDEBUG_INSN_P (insn))
    return false;

  if (CALL_P (insn))
    {
      /* A normal or pure call might read from pattern,
	 but a const call will not.  */
      if (!RTL_CONST_CALL_P (insn))
	return true;

      /* But even a const call reads its parameters.  Check whether the
	 base of some of registers used in mem is stack pointer.  */
      for (reg = x_regs; reg; reg = XEXP (reg, 1))
	{
	  base = find_base_term (XEXP (reg, 0));
	  if (!base
	      || (GET_CODE (base) == ADDRESS
		  && GET_MODE (base) == Pmode
		  && XEXP (base, 0) == stack_pointer_rtx))
	    return true;
	}

      return false;
    }

  pat = PATTERN (insn);
  if (GET_CODE (pat) == SET)
    {
      if (store_killed_in_pat (x, pat, after))
	return true;
    }
  else if (GET_CODE (pat) == PARALLEL)
    {
      int i;

      for (i = 0; i < XVECLEN (pat, 0); i++)
	if (store_killed_in_pat (x, XVECEXP (pat, 0, i), after))
	  return true;
    }
  else if (find_loads (PATTERN (insn), x, after))
    return true;

  /* If this insn has a REG_EQUAL or REG_EQUIV note referencing a memory
     location aliased with X, then this insn kills X.  */
  note = find_reg_equal_equiv_note (insn);
  if (! note)
    return false;
  note = XEXP (note, 0);

  /* However, if the note represents a must alias rather than a may
     alias relationship, then it does not kill X.  */
  if (exp_equiv_p (note, x, 0, true))
    return false;

  /* See if there are any aliased loads in the note.  */
  return find_loads (note, x, after);
}

/* Returns true if the expression X is loaded or clobbered on or after INSN
   within basic block BB.  REGS_SET_AFTER is bitmap of registers set in
   or after the insn.  X_REGS is list of registers mentioned in X. If the store
   is killed, return the last insn in that it occurs in FAIL_INSN.  */

static bool
store_killed_after (const_rtx x, const_rtx x_regs, const_rtx insn, const_basic_block bb,
		    int *regs_set_after, rtx *fail_insn)
{
  rtx last = BB_END (bb), act;

  if (!store_ops_ok (x_regs, regs_set_after))
    {
      /* We do not know where it will happen.  */
      if (fail_insn)
	*fail_insn = NULL_RTX;
      return true;
    }

  /* Scan from the end, so that fail_insn is determined correctly.  */
  for (act = last; act != PREV_INSN (insn); act = PREV_INSN (act))
    if (store_killed_in_insn (x, x_regs, act, false))
      {
	if (fail_insn)
	  *fail_insn = act;
	return true;
      }

  return false;
}

/* Returns true if the expression X is loaded or clobbered on or before INSN
   within basic block BB. X_REGS is list of registers mentioned in X.
   REGS_SET_BEFORE is bitmap of registers set before or in this insn.  */
static bool
store_killed_before (const_rtx x, const_rtx x_regs, const_rtx insn, const_basic_block bb,
		     int *regs_set_before)
{
  rtx first = BB_HEAD (bb);

  if (!store_ops_ok (x_regs, regs_set_before))
    return true;

  for ( ; insn != PREV_INSN (first); insn = PREV_INSN (insn))
    if (store_killed_in_insn (x, x_regs, insn, true))
      return true;

  return false;
}

/* The last insn in the basic block that compute_store_table is processing,
   where store_killed_after is true for X.
   Since we go through the basic block from BB_END to BB_HEAD, this is
   also the available store at the end of the basic block.  Therefore
   this is in effect a cache, to avoid calling store_killed_after for
   equivalent aliasing store expressions.
   This value is only meaningful during the computation of the store
   table.  We hi-jack the REACHING_REG field of struct st_expr to save
   a bit of memory.  */
#define LAST_AVAIL_CHECK_FAILURE(x)	((x)->reaching_reg)

/* Determine whether INSN is MEM store pattern that we will consider moving.
   REGS_SET_BEFORE is bitmap of registers set before (and including) the
   current insn, REGS_SET_AFTER is bitmap of registers set after (and
   including) the insn in this basic block.  We must be passing through BB from
   head to end, as we are using this fact to speed things up.

   The results are stored this way:

   -- the first anticipatable expression is added into ANTIC_STORES
   -- if the processed expression is not anticipatable, NULL_RTX is added
      there instead, so that we can use it as indicator that no further
      expression of this type may be anticipatable
   -- if the expression is available, it is added as head of AVAIL_STORES;
      consequently, all of them but this head are dead and may be deleted.
   -- if the expression is not available, the insn due to that it fails to be
      available is stored in REACHING_REG (via LAST_AVAIL_CHECK_FAILURE).

   The things are complicated a bit by fact that there already may be stores
   to the same MEM from other blocks; also caller must take care of the
   necessary cleanup of the temporary markers after end of the basic block.
   */

static void
find_moveable_store (rtx insn, int *regs_set_before, int *regs_set_after)
{
  struct st_expr * ptr;
  rtx dest, set, tmp;
  int check_anticipatable, check_available;
  basic_block bb = BLOCK_FOR_INSN (insn);

  set = single_set (insn);
  if (!set)
    return;

  dest = SET_DEST (set);

  if (! MEM_P (dest) || MEM_VOLATILE_P (dest)
      || GET_MODE (dest) == BLKmode)
    return;

  if (side_effects_p (dest))
    return;

  /* If we are handling exceptions, we must be careful with memory references
     that may trap.  If we are not, the behavior is undefined, so we may just
     continue.  */
  if (cfun->can_throw_non_call_exceptions && may_trap_p (dest))
    return;

  /* Even if the destination cannot trap, the source may.  In this case we'd
     need to handle updating the REG_EH_REGION note.  */
  if (find_reg_note (insn, REG_EH_REGION, NULL_RTX))
    return;

  /* Make sure that the SET_SRC of this store insns can be assigned to
     a register, or we will fail later on in replace_store_insn, which
     assumes that we can do this.  But sometimes the target machine has
     oddities like MEM read-modify-write instruction.  See for example
     PR24257.  */
  if (!can_assign_to_reg_without_clobbers_p (SET_SRC (set)))
    return;

  ptr = st_expr_entry (dest);
  if (!ptr->pattern_regs)
    ptr->pattern_regs = extract_mentioned_regs (dest);

  /* Do not check for anticipatability if we either found one anticipatable
     store already, or tested for one and found out that it was killed.  */
  check_anticipatable = 0;
  if (!ptr->antic_stores)
    check_anticipatable = 1;
  else
    {
      tmp = XEXP (ptr->antic_stores, 0);
      if (tmp != NULL_RTX
	  && BLOCK_FOR_INSN (tmp) != bb)
	check_anticipatable = 1;
    }
  if (check_anticipatable)
    {
      if (store_killed_before (dest, ptr->pattern_regs, insn, bb, regs_set_before))
	tmp = NULL_RTX;
      else
	tmp = insn;
      ptr->antic_stores = alloc_INSN_LIST (tmp, ptr->antic_stores);
    }

  /* It is not necessary to check whether store is available if we did
     it successfully before; if we failed before, do not bother to check
     until we reach the insn that caused us to fail.  */
  check_available = 0;
  if (!ptr->avail_stores)
    check_available = 1;
  else
    {
      tmp = XEXP (ptr->avail_stores, 0);
      if (BLOCK_FOR_INSN (tmp) != bb)
	check_available = 1;
    }
  if (check_available)
    {
      /* Check that we have already reached the insn at that the check
	 failed last time.  */
      if (LAST_AVAIL_CHECK_FAILURE (ptr))
	{
	  for (tmp = BB_END (bb);
	       tmp != insn && tmp != LAST_AVAIL_CHECK_FAILURE (ptr);
	       tmp = PREV_INSN (tmp))
	    continue;
	  if (tmp == insn)
	    check_available = 0;
	}
      else
	check_available = store_killed_after (dest, ptr->pattern_regs, insn,
					      bb, regs_set_after,
					      &LAST_AVAIL_CHECK_FAILURE (ptr));
    }
  if (!check_available)
    ptr->avail_stores = alloc_INSN_LIST (insn, ptr->avail_stores);
}

/* Find available and anticipatable stores.  */

static int
compute_store_table (void)
{
  int ret;
  basic_block bb;
#ifdef ENABLE_CHECKING
  unsigned regno;
#endif
  rtx insn, tmp;
  df_ref *def_rec;
  int *last_set_in, *already_set;
  struct st_expr * ptr, **prev_next_ptr_ptr;
  unsigned int max_gcse_regno = max_reg_num ();

  store_motion_mems = NULL;
  store_motion_mems_table = htab_create (13, pre_st_expr_hash,
					 pre_st_expr_eq, NULL);
  last_set_in = XCNEWVEC (int, max_gcse_regno);
  already_set = XNEWVEC (int, max_gcse_regno);

  /* Find all the stores we care about.  */
  FOR_EACH_BB (bb)
    {
      /* First compute the registers set in this block.  */
      FOR_BB_INSNS (bb, insn)
	{

	  if (! NONDEBUG_INSN_P (insn))
	    continue;

	  for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
	    last_set_in[DF_REF_REGNO (*def_rec)] = INSN_UID (insn);
	}

      /* Now find the stores.  */
      memset (already_set, 0, sizeof (int) * max_gcse_regno);
      FOR_BB_INSNS (bb, insn)
	{
	  if (! NONDEBUG_INSN_P (insn))
	    continue;

	  for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
	    already_set[DF_REF_REGNO (*def_rec)] = INSN_UID (insn);

	  /* Now that we've marked regs, look for stores.  */
	  find_moveable_store (insn, already_set, last_set_in);

	  /* Unmark regs that are no longer set.  */
	  for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
	    if (last_set_in[DF_REF_REGNO (*def_rec)] == INSN_UID (insn))
	      last_set_in[DF_REF_REGNO (*def_rec)] = 0;
	}

#ifdef ENABLE_CHECKING
      /* last_set_in should now be all-zero.  */
      for (regno = 0; regno < max_gcse_regno; regno++)
	gcc_assert (!last_set_in[regno]);
#endif

      /* Clear temporary marks.  */
      for (ptr = first_st_expr (); ptr != NULL; ptr = next_st_expr (ptr))
	{
	  LAST_AVAIL_CHECK_FAILURE (ptr) = NULL_RTX;
	  if (ptr->antic_stores
	      && (tmp = XEXP (ptr->antic_stores, 0)) == NULL_RTX)
	    ptr->antic_stores = XEXP (ptr->antic_stores, 1);
	}
    }

  /* Remove the stores that are not available anywhere, as there will
     be no opportunity to optimize them.  */
  for (ptr = store_motion_mems, prev_next_ptr_ptr = &store_motion_mems;
       ptr != NULL;
       ptr = *prev_next_ptr_ptr)
    {
      if (! ptr->avail_stores)
	{
	  *prev_next_ptr_ptr = ptr->next;
	  htab_remove_elt_with_hash (store_motion_mems_table,
				     ptr, ptr->hash_index);
	  free_st_expr_entry (ptr);
	}
      else
	prev_next_ptr_ptr = &ptr->next;
    }

  ret = enumerate_store_motion_mems ();

  if (dump_file)
    print_store_motion_mems (dump_file);

  free (last_set_in);
  free (already_set);
  return ret;
}

/* In all code following after this, REACHING_REG has its original
   meaning again.  Avoid confusion, and undef the accessor macro for
   the temporary marks usage in compute_store_table.  */
#undef LAST_AVAIL_CHECK_FAILURE

/* Insert an instruction at the beginning of a basic block, and update
   the BB_HEAD if needed.  */

static void
insert_insn_start_basic_block (rtx insn, basic_block bb)
{
  /* Insert at start of successor block.  */
  rtx prev = PREV_INSN (BB_HEAD (bb));
  rtx before = BB_HEAD (bb);
  while (before != 0)
    {
      if (! LABEL_P (before)
	  && !NOTE_INSN_BASIC_BLOCK_P (before))
	break;
      prev = before;
      if (prev == BB_END (bb))
	break;
      before = NEXT_INSN (before);
    }

  insn = emit_insn_after_noloc (insn, prev, bb);

  if (dump_file)
    {
      fprintf (dump_file, "STORE_MOTION  insert store at start of BB %d:\n",
	       bb->index);
      print_inline_rtx (dump_file, insn, 6);
      fprintf (dump_file, "\n");
    }
}

/* This routine will insert a store on an edge. EXPR is the st_expr entry for
   the memory reference, and E is the edge to insert it on.  Returns nonzero
   if an edge insertion was performed.  */

static int
insert_store (struct st_expr * expr, edge e)
{
  rtx reg, insn;
  basic_block bb;
  edge tmp;
  edge_iterator ei;

  /* We did all the deleted before this insert, so if we didn't delete a
     store, then we haven't set the reaching reg yet either.  */
  if (expr->reaching_reg == NULL_RTX)
    return 0;

  if (e->flags & EDGE_FAKE)
    return 0;

  reg = expr->reaching_reg;
  insn = gen_move_insn (copy_rtx (expr->pattern), reg);

  /* If we are inserting this expression on ALL predecessor edges of a BB,
     insert it at the start of the BB, and reset the insert bits on the other
     edges so we don't try to insert it on the other edges.  */
  bb = e->dest;
  FOR_EACH_EDGE (tmp, ei, e->dest->preds)
    if (!(tmp->flags & EDGE_FAKE))
      {
	int index = EDGE_INDEX (edge_list, tmp->src, tmp->dest);

	gcc_assert (index != EDGE_INDEX_NO_EDGE);
	if (! TEST_BIT (st_insert_map[index], expr->index))
	  break;
      }

  /* If tmp is NULL, we found an insertion on every edge, blank the
     insertion vector for these edges, and insert at the start of the BB.  */
  if (!tmp && bb != EXIT_BLOCK_PTR)
    {
      FOR_EACH_EDGE (tmp, ei, e->dest->preds)
	{
	  int index = EDGE_INDEX (edge_list, tmp->src, tmp->dest);
	  RESET_BIT (st_insert_map[index], expr->index);
	}
      insert_insn_start_basic_block (insn, bb);
      return 0;
    }

  /* We can't put stores in the front of blocks pointed to by abnormal
     edges since that may put a store where one didn't used to be.  */
  gcc_assert (!(e->flags & EDGE_ABNORMAL));

  insert_insn_on_edge (insn, e);

  if (dump_file)
    {
      fprintf (dump_file, "STORE_MOTION  insert insn on edge (%d, %d):\n",
	       e->src->index, e->dest->index);
      print_inline_rtx (dump_file, insn, 6);
      fprintf (dump_file, "\n");
    }

  return 1;
}

/* Remove any REG_EQUAL or REG_EQUIV notes containing a reference to the
   memory location in SMEXPR set in basic block BB.

   This could be rather expensive.  */

static void
remove_reachable_equiv_notes (basic_block bb, struct st_expr *smexpr)
{
  edge_iterator *stack, ei;
  int sp;
  edge act;
  sbitmap visited = sbitmap_alloc (last_basic_block);
  rtx last, insn, note;
  rtx mem = smexpr->pattern;

  stack = XNEWVEC (edge_iterator, n_basic_blocks);
  sp = 0;
  ei = ei_start (bb->succs);

  sbitmap_zero (visited);

  act = (EDGE_COUNT (ei_container (ei)) > 0 ? EDGE_I (ei_container (ei), 0) : NULL);
  while (1)
    {
      if (!act)
	{
	  if (!sp)
	    {
	      free (stack);
	      sbitmap_free (visited);
	      return;
	    }
	  act = ei_edge (stack[--sp]);
	}
      bb = act->dest;

      if (bb == EXIT_BLOCK_PTR
	  || TEST_BIT (visited, bb->index))
	{
	  if (!ei_end_p (ei))
	      ei_next (&ei);
	  act = (! ei_end_p (ei)) ? ei_edge (ei) : NULL;
	  continue;
	}
      SET_BIT (visited, bb->index);

      if (TEST_BIT (st_antloc[bb->index], smexpr->index))
	{
	  for (last = smexpr->antic_stores;
	       BLOCK_FOR_INSN (XEXP (last, 0)) != bb;
	       last = XEXP (last, 1))
	    continue;
	  last = XEXP (last, 0);
	}
      else
	last = NEXT_INSN (BB_END (bb));

      for (insn = BB_HEAD (bb); insn != last; insn = NEXT_INSN (insn))
	if (NONDEBUG_INSN_P (insn))
	  {
	    note = find_reg_equal_equiv_note (insn);
	    if (!note || !exp_equiv_p (XEXP (note, 0), mem, 0, true))
	      continue;

	    if (dump_file)
	      fprintf (dump_file, "STORE_MOTION  drop REG_EQUAL note at insn %d:\n",
		       INSN_UID (insn));
	    remove_note (insn, note);
	  }

      if (!ei_end_p (ei))
	ei_next (&ei);
      act = (! ei_end_p (ei)) ? ei_edge (ei) : NULL;

      if (EDGE_COUNT (bb->succs) > 0)
	{
	  if (act)
	    stack[sp++] = ei;
	  ei = ei_start (bb->succs);
	  act = (EDGE_COUNT (ei_container (ei)) > 0 ? EDGE_I (ei_container (ei), 0) : NULL);
	}
    }
}

/* This routine will replace a store with a SET to a specified register.  */

static void
replace_store_insn (rtx reg, rtx del, basic_block bb, struct st_expr *smexpr)
{
  rtx insn, mem, note, set, ptr;

  mem = smexpr->pattern;
  insn = gen_move_insn (reg, SET_SRC (single_set (del)));

  for (ptr = smexpr->antic_stores; ptr; ptr = XEXP (ptr, 1))
    if (XEXP (ptr, 0) == del)
      {
	XEXP (ptr, 0) = insn;
	break;
      }

  /* Move the notes from the deleted insn to its replacement.  */
  REG_NOTES (insn) = REG_NOTES (del);

  /* Emit the insn AFTER all the notes are transferred.
     This is cheaper since we avoid df rescanning for the note change.  */
  insn = emit_insn_after (insn, del);

  if (dump_file)
    {
      fprintf (dump_file,
	       "STORE_MOTION  delete insn in BB %d:\n      ", bb->index);
      print_inline_rtx (dump_file, del, 6);
      fprintf (dump_file, "\nSTORE_MOTION  replaced with insn:\n      ");
      print_inline_rtx (dump_file, insn, 6);
      fprintf (dump_file, "\n");
    }

  delete_insn (del);

  /* Now we must handle REG_EQUAL notes whose contents is equal to the mem;
     they are no longer accurate provided that they are reached by this
     definition, so drop them.  */
  for (; insn != NEXT_INSN (BB_END (bb)); insn = NEXT_INSN (insn))
    if (NONDEBUG_INSN_P (insn))
      {
	set = single_set (insn);
	if (!set)
	  continue;
	if (exp_equiv_p (SET_DEST (set), mem, 0, true))
	  return;
	note = find_reg_equal_equiv_note (insn);
	if (!note || !exp_equiv_p (XEXP (note, 0), mem, 0, true))
	  continue;

	if (dump_file)
	  fprintf (dump_file, "STORE_MOTION  drop REG_EQUAL note at insn %d:\n",
		   INSN_UID (insn));
	remove_note (insn, note);
      }
  remove_reachable_equiv_notes (bb, smexpr);
}


/* Delete a store, but copy the value that would have been stored into
   the reaching_reg for later storing.  */

static void
delete_store (struct st_expr * expr, basic_block bb)
{
  rtx reg, i, del;

  if (expr->reaching_reg == NULL_RTX)
    expr->reaching_reg = gen_reg_rtx_and_attrs (expr->pattern);

  reg = expr->reaching_reg;

  for (i = expr->avail_stores; i; i = XEXP (i, 1))
    {
      del = XEXP (i, 0);
      if (BLOCK_FOR_INSN (del) == bb)
	{
	  /* We know there is only one since we deleted redundant
	     ones during the available computation.  */
	  replace_store_insn (reg, del, bb, expr);
	  break;
	}
    }
}

/* Fill in available, anticipatable, transparent and kill vectors in
   STORE_DATA, based on lists of available and anticipatable stores.  */
static void
build_store_vectors (void)
{
  basic_block bb;
  int *regs_set_in_block;
  rtx insn, st;
  struct st_expr * ptr;
  unsigned int max_gcse_regno = max_reg_num ();

  /* Build the gen_vector. This is any store in the table which is not killed
     by aliasing later in its block.  */
  st_avloc = sbitmap_vector_alloc (last_basic_block, num_stores);
  sbitmap_vector_zero (st_avloc, last_basic_block);

  st_antloc = sbitmap_vector_alloc (last_basic_block, num_stores);
  sbitmap_vector_zero (st_antloc, last_basic_block);

  for (ptr = first_st_expr (); ptr != NULL; ptr = next_st_expr (ptr))
    {
      for (st = ptr->avail_stores; st != NULL; st = XEXP (st, 1))
	{
	  insn = XEXP (st, 0);
	  bb = BLOCK_FOR_INSN (insn);

	  /* If we've already seen an available expression in this block,
	     we can delete this one (It occurs earlier in the block). We'll
	     copy the SRC expression to an unused register in case there
	     are any side effects.  */
	  if (TEST_BIT (st_avloc[bb->index], ptr->index))
	    {
	      rtx r = gen_reg_rtx_and_attrs (ptr->pattern);
	      if (dump_file)
		fprintf (dump_file, "Removing redundant store:\n");
	      replace_store_insn (r, XEXP (st, 0), bb, ptr);
	      continue;
	    }
	  SET_BIT (st_avloc[bb->index], ptr->index);
	}

      for (st = ptr->antic_stores; st != NULL; st = XEXP (st, 1))
	{
	  insn = XEXP (st, 0);
	  bb = BLOCK_FOR_INSN (insn);
	  SET_BIT (st_antloc[bb->index], ptr->index);
	}
    }

  st_kill = sbitmap_vector_alloc (last_basic_block, num_stores);
  sbitmap_vector_zero (st_kill, last_basic_block);

  st_transp = sbitmap_vector_alloc (last_basic_block, num_stores);
  sbitmap_vector_zero (st_transp, last_basic_block);
  regs_set_in_block = XNEWVEC (int, max_gcse_regno);

  FOR_EACH_BB (bb)
    {
      memset (regs_set_in_block, 0, sizeof (int) * max_gcse_regno);

      FOR_BB_INSNS (bb, insn)
	if (NONDEBUG_INSN_P (insn))
	  {
	    df_ref *def_rec;
	    for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
	      {
		unsigned int ref_regno = DF_REF_REGNO (*def_rec);
		if (ref_regno < max_gcse_regno)
		  regs_set_in_block[DF_REF_REGNO (*def_rec)] = 1;
	      }
	  }

      for (ptr = first_st_expr (); ptr != NULL; ptr = next_st_expr (ptr))
	{
	  if (store_killed_after (ptr->pattern, ptr->pattern_regs, BB_HEAD (bb),
				  bb, regs_set_in_block, NULL))
	    {
	      /* It should not be necessary to consider the expression
		 killed if it is both anticipatable and available.  */
	      if (!TEST_BIT (st_antloc[bb->index], ptr->index)
		  || !TEST_BIT (st_avloc[bb->index], ptr->index))
		SET_BIT (st_kill[bb->index], ptr->index);
	    }
	  else
	    SET_BIT (st_transp[bb->index], ptr->index);
	}
    }

  free (regs_set_in_block);

  if (dump_file)
    {
      dump_sbitmap_vector (dump_file, "st_antloc", "", st_antloc, last_basic_block);
      dump_sbitmap_vector (dump_file, "st_kill", "", st_kill, last_basic_block);
      dump_sbitmap_vector (dump_file, "st_transp", "", st_transp, last_basic_block);
      dump_sbitmap_vector (dump_file, "st_avloc", "", st_avloc, last_basic_block);
    }
}

/* Free memory used by store motion.  */

static void
free_store_memory (void)
{
  free_store_motion_mems ();

  if (st_avloc)
    sbitmap_vector_free (st_avloc);
  if (st_kill)
    sbitmap_vector_free (st_kill);
  if (st_transp)
    sbitmap_vector_free (st_transp);
  if (st_antloc)
    sbitmap_vector_free (st_antloc);
  if (st_insert_map)
    sbitmap_vector_free (st_insert_map);
  if (st_delete_map)
    sbitmap_vector_free (st_delete_map);

  st_avloc = st_kill = st_transp = st_antloc = NULL;
  st_insert_map = st_delete_map = NULL;
}

/* Perform store motion. Much like gcse, except we move expressions the
   other way by looking at the flowgraph in reverse.
   Return non-zero if transformations are performed by the pass.  */

static int
one_store_motion_pass (void)
{
  basic_block bb;
  int x;
  struct st_expr * ptr;
  int did_edge_inserts = 0;
  int n_stores_deleted = 0;
  int n_stores_created = 0;

  init_alias_analysis ();

  /* Find all the available and anticipatable stores.  */
  num_stores = compute_store_table ();
  if (num_stores == 0)
    {
      htab_delete (store_motion_mems_table);
      store_motion_mems_table = NULL;
      end_alias_analysis ();
      return 0;
    }

  /* Now compute kill & transp vectors.  */
  build_store_vectors ();
  add_noreturn_fake_exit_edges ();
  connect_infinite_loops_to_exit ();

  edge_list = pre_edge_rev_lcm (num_stores, st_transp, st_avloc,
				st_antloc, st_kill, &st_insert_map,
				&st_delete_map);

  /* Now we want to insert the new stores which are going to be needed.  */
  for (ptr = first_st_expr (); ptr != NULL; ptr = next_st_expr (ptr))
    {
      /* If any of the edges we have above are abnormal, we can't move this
	 store.  */
      for (x = NUM_EDGES (edge_list) - 1; x >= 0; x--)
	if (TEST_BIT (st_insert_map[x], ptr->index)
	    && (INDEX_EDGE (edge_list, x)->flags & EDGE_ABNORMAL))
	  break;

      if (x >= 0)
	{
	  if (dump_file != NULL)
	    fprintf (dump_file,
		     "Can't replace store %d: abnormal edge from %d to %d\n",
		     ptr->index, INDEX_EDGE (edge_list, x)->src->index,
		     INDEX_EDGE (edge_list, x)->dest->index);
	  continue;
	}

      /* Now we want to insert the new stores which are going to be needed.  */

      FOR_EACH_BB (bb)
	if (TEST_BIT (st_delete_map[bb->index], ptr->index))
	  {
	    delete_store (ptr, bb);
	    n_stores_deleted++;
	  }

      for (x = 0; x < NUM_EDGES (edge_list); x++)
	if (TEST_BIT (st_insert_map[x], ptr->index))
	  {
	    did_edge_inserts |= insert_store (ptr, INDEX_EDGE (edge_list, x));
	    n_stores_created++;
	  }
    }

  if (did_edge_inserts)
    commit_edge_insertions ();

  free_store_memory ();
  free_edge_list (edge_list);
  remove_fake_exit_edges ();
  end_alias_analysis ();

  if (dump_file)
    {
      fprintf (dump_file, "STORE_MOTION of %s, %d basic blocks, ",
	       current_function_name (), n_basic_blocks);
      fprintf (dump_file, "%d insns deleted, %d insns created\n",
	       n_stores_deleted, n_stores_created);
    }

  return (n_stores_deleted > 0 || n_stores_created > 0);
}


static bool
gate_rtl_store_motion (void)
{
  return optimize > 0 && flag_gcse_sm
    && !cfun->calls_setjmp
    && optimize_function_for_speed_p (cfun)
    && dbg_cnt (store_motion);
}

static unsigned int
execute_rtl_store_motion (void)
{
  delete_unreachable_blocks ();
  df_analyze ();
  flag_rerun_cse_after_global_opts |= one_store_motion_pass ();
  return 0;
}

struct rtl_opt_pass pass_rtl_store_motion =
{
 {
  RTL_PASS,
  "store_motion",                       /* name */
  gate_rtl_store_motion,                /* gate */
  execute_rtl_store_motion,		/* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_LSM,                               /* tv_id */
  PROP_cfglayout,                       /* properties_required */
  0,                                    /* properties_provided */
  0,                                    /* properties_destroyed */
  0,                                    /* todo_flags_start */
  TODO_df_finish | TODO_verify_rtl_sharing |
  TODO_verify_flow | TODO_ggc_collect   /* todo_flags_finish */
 }
};