summaryrefslogtreecommitdiff
path: root/gcc/auto-inc-dec.c
blob: def9c9adeaaa977fb2a6569f9e253ad8ff819ccd (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
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
/* Discovery of auto-inc and auto-dec instructions.
   Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012
   Free Software Foundation, Inc.
   Contributed by Kenneth Zadeck <zadeck@naturalbridge.com>

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 "tree.h"
#include "rtl.h"
#include "tm_p.h"
#include "hard-reg-set.h"
#include "basic-block.h"
#include "insn-config.h"
#include "regs.h"
#include "flags.h"
#include "function.h"
#include "except.h"
#include "diagnostic-core.h"
#include "recog.h"
#include "expr.h"
#include "tree-pass.h"
#include "df.h"
#include "dbgcnt.h"
#include "target.h"

/* This pass was originally removed from flow.c. However there is
   almost nothing that remains of that code.

   There are (4) basic forms that are matched:

      (1) FORM_PRE_ADD
           a <- b + c
           ...
           *a

        becomes

           a <- b
           ...
           *(a += c) pre


      (2) FORM_PRE_INC
           a += c
           ...
           *a

        becomes

           *(a += c) pre


      (3) FORM_POST_ADD
           *a
           ...
           b <- a + c

	   (For this case to be true, b must not be assigned or used between
	   the *a and the assignment to b.  B must also be a Pmode reg.)

        becomes

           b <- a
           ...
           *(b += c) post


      (4) FORM_POST_INC
           *a
           ...
           a <- a + c

        becomes

           *(a += c) post

  There are three types of values of c.

    1) c is a constant equal to the width of the value being accessed by
       the pointer.  This is useful for machines that have
       HAVE_PRE_INCREMENT, HAVE_POST_INCREMENT, HAVE_PRE_DECREMENT or
       HAVE_POST_DECREMENT defined.

    2) c is a constant not equal to the width of the value being accessed
       by the pointer.  This is useful for machines that have
       HAVE_PRE_MODIFY_DISP, HAVE_POST_MODIFY_DISP defined.

    3) c is a register.  This is useful for machines that have
       HAVE_PRE_MODIFY_REG,  HAVE_POST_MODIFY_REG

  The is one special case: if a already had an offset equal to it +-
  its width and that offset is equal to -c when the increment was
  before the ref or +c if the increment was after the ref, then if we
  can do the combination but switch the pre/post bit.  */

#ifdef AUTO_INC_DEC

enum form
{
  FORM_PRE_ADD,
  FORM_PRE_INC,
  FORM_POST_ADD,
  FORM_POST_INC,
  FORM_last
};

/* The states of the second operands of mem refs and inc insns.  If no
   second operand of the mem_ref was found, it is assumed to just be
   ZERO.  SIZE is the size of the mode accessed in the memref.  The
   ANY is used for constants that are not +-size or 0.  REG is used if
   the forms are reg1 + reg2.  */

enum inc_state
{
  INC_ZERO,           /* == 0  */
  INC_NEG_SIZE,       /* == +size  */
  INC_POS_SIZE,       /* == -size */
  INC_NEG_ANY,        /* == some -constant  */
  INC_POS_ANY,        /* == some +constant  */
  INC_REG,            /* == some register  */
  INC_last
};

/* The eight forms that pre/post inc/dec can take.  */
enum gen_form
{
  NOTHING,
  SIMPLE_PRE_INC,     /* ++size  */
  SIMPLE_POST_INC,    /* size++  */
  SIMPLE_PRE_DEC,     /* --size  */
  SIMPLE_POST_DEC,    /* size--  */
  DISP_PRE,           /* ++con   */
  DISP_POST,          /* con++   */
  REG_PRE,            /* ++reg   */
  REG_POST            /* reg++   */
};

/* Tmp mem rtx for use in cost modeling.  */
static rtx mem_tmp;

static enum inc_state
set_inc_state (HOST_WIDE_INT val, int size)
{
  if (val == 0)
    return INC_ZERO;
  if (val < 0)
    return (val == -size) ? INC_NEG_SIZE : INC_NEG_ANY;
  else
    return (val == size) ? INC_POS_SIZE : INC_POS_ANY;
}

/* The DECISION_TABLE that describes what form, if any, the increment
   or decrement will take. It is a three dimensional table.  The first
   index is the type of constant or register found as the second
   operand of the inc insn.  The second index is the type of constant
   or register found as the second operand of the memory reference (if
   no second operand exists, 0 is used).  The third index is the form
   and location (relative to the mem reference) of inc insn.  */

static bool initialized = false;
static enum gen_form decision_table[INC_last][INC_last][FORM_last];

static void
init_decision_table (void)
{
  enum gen_form value;

  if (HAVE_PRE_INCREMENT || HAVE_PRE_MODIFY_DISP)
    {
      /* Prefer the simple form if both are available.  */
      value = (HAVE_PRE_INCREMENT) ? SIMPLE_PRE_INC : DISP_PRE;

      decision_table[INC_POS_SIZE][INC_ZERO][FORM_PRE_ADD] = value;
      decision_table[INC_POS_SIZE][INC_ZERO][FORM_PRE_INC] = value;

      decision_table[INC_POS_SIZE][INC_POS_SIZE][FORM_POST_ADD] = value;
      decision_table[INC_POS_SIZE][INC_POS_SIZE][FORM_POST_INC] = value;
    }

  if (HAVE_POST_INCREMENT || HAVE_POST_MODIFY_DISP)
    {
      /* Prefer the simple form if both are available.  */
      value = (HAVE_POST_INCREMENT) ? SIMPLE_POST_INC : DISP_POST;

      decision_table[INC_POS_SIZE][INC_ZERO][FORM_POST_ADD] = value;
      decision_table[INC_POS_SIZE][INC_ZERO][FORM_POST_INC] = value;

      decision_table[INC_POS_SIZE][INC_NEG_SIZE][FORM_PRE_ADD] = value;
      decision_table[INC_POS_SIZE][INC_NEG_SIZE][FORM_PRE_INC] = value;
    }

  if (HAVE_PRE_DECREMENT || HAVE_PRE_MODIFY_DISP)
    {
      /* Prefer the simple form if both are available.  */
      value = (HAVE_PRE_DECREMENT) ? SIMPLE_PRE_DEC : DISP_PRE;

      decision_table[INC_NEG_SIZE][INC_ZERO][FORM_PRE_ADD] = value;
      decision_table[INC_NEG_SIZE][INC_ZERO][FORM_PRE_INC] = value;

      decision_table[INC_NEG_SIZE][INC_NEG_SIZE][FORM_POST_ADD] = value;
      decision_table[INC_NEG_SIZE][INC_NEG_SIZE][FORM_POST_INC] = value;
    }

  if (HAVE_POST_DECREMENT || HAVE_POST_MODIFY_DISP)
    {
      /* Prefer the simple form if both are available.  */
      value = (HAVE_POST_DECREMENT) ? SIMPLE_POST_DEC : DISP_POST;

      decision_table[INC_NEG_SIZE][INC_ZERO][FORM_POST_ADD] = value;
      decision_table[INC_NEG_SIZE][INC_ZERO][FORM_POST_INC] = value;

      decision_table[INC_NEG_SIZE][INC_POS_SIZE][FORM_PRE_ADD] = value;
      decision_table[INC_NEG_SIZE][INC_POS_SIZE][FORM_PRE_INC] = value;
    }

  if (HAVE_PRE_MODIFY_DISP)
    {
      decision_table[INC_POS_ANY][INC_ZERO][FORM_PRE_ADD] = DISP_PRE;
      decision_table[INC_POS_ANY][INC_ZERO][FORM_PRE_INC] = DISP_PRE;

      decision_table[INC_POS_ANY][INC_POS_ANY][FORM_POST_ADD] = DISP_PRE;
      decision_table[INC_POS_ANY][INC_POS_ANY][FORM_POST_INC] = DISP_PRE;

      decision_table[INC_NEG_ANY][INC_ZERO][FORM_PRE_ADD] = DISP_PRE;
      decision_table[INC_NEG_ANY][INC_ZERO][FORM_PRE_INC] = DISP_PRE;

      decision_table[INC_NEG_ANY][INC_NEG_ANY][FORM_POST_ADD] = DISP_PRE;
      decision_table[INC_NEG_ANY][INC_NEG_ANY][FORM_POST_INC] = DISP_PRE;
    }

  if (HAVE_POST_MODIFY_DISP)
    {
      decision_table[INC_POS_ANY][INC_ZERO][FORM_POST_ADD] = DISP_POST;
      decision_table[INC_POS_ANY][INC_ZERO][FORM_POST_INC] = DISP_POST;

      decision_table[INC_POS_ANY][INC_NEG_ANY][FORM_PRE_ADD] = DISP_POST;
      decision_table[INC_POS_ANY][INC_NEG_ANY][FORM_PRE_INC] = DISP_POST;

      decision_table[INC_NEG_ANY][INC_ZERO][FORM_POST_ADD] = DISP_POST;
      decision_table[INC_NEG_ANY][INC_ZERO][FORM_POST_INC] = DISP_POST;

      decision_table[INC_NEG_ANY][INC_POS_ANY][FORM_PRE_ADD] = DISP_POST;
      decision_table[INC_NEG_ANY][INC_POS_ANY][FORM_PRE_INC] = DISP_POST;
    }

  /* This is much simpler than the other cases because we do not look
     for the reg1-reg2 case.  Note that we do not have a INC_POS_REG
     and INC_NEG_REG states.  Most of the use of such states would be
     on a target that had an R1 - R2 update address form.

     There is the remote possibility that you could also catch a = a +
     b; *(a - b) as a postdecrement of (a + b).  However, it is
     unclear if *(a - b) would ever be generated on a machine that did
     not have that kind of addressing mode.  The IA-64 and RS6000 will
     not do this, and I cannot speak for any other.  If any
     architecture does have an a-b update for, these cases should be
     added.  */
  if (HAVE_PRE_MODIFY_REG)
    {
      decision_table[INC_REG][INC_ZERO][FORM_PRE_ADD] = REG_PRE;
      decision_table[INC_REG][INC_ZERO][FORM_PRE_INC] = REG_PRE;

      decision_table[INC_REG][INC_REG][FORM_POST_ADD] = REG_PRE;
      decision_table[INC_REG][INC_REG][FORM_POST_INC] = REG_PRE;
    }

  if (HAVE_POST_MODIFY_REG)
    {
      decision_table[INC_REG][INC_ZERO][FORM_POST_ADD] = REG_POST;
      decision_table[INC_REG][INC_ZERO][FORM_POST_INC] = REG_POST;
    }

  initialized = true;
}

/* Parsed fields of an inc insn of the form "reg_res = reg0+reg1" or
   "reg_res = reg0+c".  */

static struct inc_insn
{
  rtx insn;           /* The insn being parsed.  */
  rtx pat;            /* The pattern of the insn.  */
  bool reg1_is_const; /* True if reg1 is const, false if reg1 is a reg.  */
  enum form form;
  rtx reg_res;
  rtx reg0;
  rtx reg1;
  enum inc_state reg1_state;/* The form of the const if reg1 is a const.  */
  HOST_WIDE_INT reg1_val;/* Value if reg1 is const.  */
} inc_insn;


/* Dump the parsed inc insn to FILE.  */

static void
dump_inc_insn (FILE *file)
{
  const char *f = ((inc_insn.form == FORM_PRE_ADD)
	      || (inc_insn.form == FORM_PRE_INC)) ? "pre" : "post";

  dump_insn_slim (file, inc_insn.insn);

  switch (inc_insn.form)
    {
    case FORM_PRE_ADD:
    case FORM_POST_ADD:
      if (inc_insn.reg1_is_const)
	fprintf (file, "found %s add(%d) r[%d]=r[%d]+%d\n",
		 f, INSN_UID (inc_insn.insn),
		 REGNO (inc_insn.reg_res),
		 REGNO (inc_insn.reg0), (int) inc_insn.reg1_val);
      else
	fprintf (file, "found %s add(%d) r[%d]=r[%d]+r[%d]\n",
		 f, INSN_UID (inc_insn.insn),
		 REGNO (inc_insn.reg_res),
		 REGNO (inc_insn.reg0), REGNO (inc_insn.reg1));
      break;

    case FORM_PRE_INC:
    case FORM_POST_INC:
      if (inc_insn.reg1_is_const)
	fprintf (file, "found %s inc(%d) r[%d]+=%d\n",
		 f, INSN_UID (inc_insn.insn),
		 REGNO (inc_insn.reg_res), (int) inc_insn.reg1_val);
      else
	fprintf (file, "found %s inc(%d) r[%d]+=r[%d]\n",
		 f, INSN_UID (inc_insn.insn),
		 REGNO (inc_insn.reg_res), REGNO (inc_insn.reg1));
      break;

    default:
      break;
    }
}


/* Parsed fields of a mem ref of the form "*(reg0+reg1)" or "*(reg0+c)".  */

static struct mem_insn
{
  rtx insn;           /* The insn being parsed.  */
  rtx pat;            /* The pattern of the insn.  */
  rtx *mem_loc;       /* The address of the field that holds the mem */
                      /* that is to be replaced.  */
  bool reg1_is_const; /* True if reg1 is const, false if reg1 is a reg.  */
  rtx reg0;
  rtx reg1;           /* This is either a reg or a const depending on
			 reg1_is_const.  */
  enum inc_state reg1_state;/* The form of the const if reg1 is a const.  */
  HOST_WIDE_INT reg1_val;/* Value if reg1 is const.  */
} mem_insn;


/* Dump the parsed mem insn to FILE.  */

static void
dump_mem_insn (FILE *file)
{
  dump_insn_slim (file, mem_insn.insn);

  if (mem_insn.reg1_is_const)
    fprintf (file, "found mem(%d) *(r[%d]+%d)\n",
	     INSN_UID (mem_insn.insn),
	     REGNO (mem_insn.reg0), (int) mem_insn.reg1_val);
  else
    fprintf (file, "found mem(%d) *(r[%d]+r[%d])\n",
	     INSN_UID (mem_insn.insn),
	     REGNO (mem_insn.reg0), REGNO (mem_insn.reg1));
}


/* The following three arrays contain pointers to instructions. They
   are indexed by REGNO.  At any point in the basic block where we are
   looking these three arrays contain, respectively, the next insn
   that uses REGNO, the next inc or add insn that uses REGNO and the
   next insn that sets REGNO.

   The arrays are not cleared when we move from block to block so
   whenever an insn is retrieved from these arrays, it's block number
   must be compared with the current block.
*/

static rtx *reg_next_use = NULL;
static rtx *reg_next_inc_use = NULL;
static rtx *reg_next_def = NULL;


/* Move dead note that match PATTERN to TO_INSN from FROM_INSN.  We do
   not really care about moving any other notes from the inc or add
   insn.  Moving the REG_EQUAL and REG_EQUIV is clearly wrong and it
   does not appear that there are any other kinds of relevant notes.  */

static void
move_dead_notes (rtx to_insn, rtx from_insn, rtx pattern)
{
  rtx note;
  rtx next_note;
  rtx prev_note = NULL;

  for (note = REG_NOTES (from_insn); note; note = next_note)
    {
      next_note = XEXP (note, 1);

      if ((REG_NOTE_KIND (note) == REG_DEAD)
	  && pattern == XEXP (note, 0))
	{
	  XEXP (note, 1) = REG_NOTES (to_insn);
	  REG_NOTES (to_insn) = note;
	  if (prev_note)
	    XEXP (prev_note, 1) = next_note;
	  else
	    REG_NOTES (from_insn) = next_note;
	}
      else prev_note = note;
    }
}


/* Create a mov insn DEST_REG <- SRC_REG and insert it before
   NEXT_INSN.  */

static rtx
insert_move_insn_before (rtx next_insn, rtx dest_reg, rtx src_reg)
{
  rtx insns;

  start_sequence ();
  emit_move_insn (dest_reg, src_reg);
  insns = get_insns ();
  end_sequence ();
  emit_insn_before (insns, next_insn);
  return insns;
}


/* Change mem_insn.mem_loc so that uses NEW_ADDR which has an
   increment of INC_REG.  To have reached this point, the change is a
   legitimate one from a dataflow point of view.  The only questions
   are is this a valid change to the instruction and is this a
   profitable change to the instruction.  */

static bool
attempt_change (rtx new_addr, rtx inc_reg)
{
  /* There are four cases: For the two cases that involve an add
     instruction, we are going to have to delete the add and insert a
     mov.  We are going to assume that the mov is free.  This is
     fairly early in the backend and there are a lot of opportunities
     for removing that move later.  In particular, there is the case
     where the move may be dead, this is what dead code elimination
     passes are for.  The two cases where we have an inc insn will be
     handled mov free.  */

  basic_block bb = BLOCK_FOR_INSN (mem_insn.insn);
  rtx mov_insn = NULL;
  int regno;
  rtx mem = *mem_insn.mem_loc;
  enum machine_mode mode = GET_MODE (mem);
  rtx new_mem;
  int old_cost = 0;
  int new_cost = 0;
  bool speed = optimize_bb_for_speed_p (bb);

  PUT_MODE (mem_tmp, mode);
  XEXP (mem_tmp, 0) = new_addr;

  old_cost = (set_src_cost (mem, speed)
	      + set_rtx_cost (PATTERN (inc_insn.insn), speed));
  new_cost = set_src_cost (mem_tmp, speed);

  /* The first item of business is to see if this is profitable.  */
  if (old_cost < new_cost)
    {
      if (dump_file)
	fprintf (dump_file, "cost failure old=%d new=%d\n", old_cost, new_cost);
      return false;
    }

  /* Jump through a lot of hoops to keep the attributes up to date.  We
     do not want to call one of the change address variants that take
     an offset even though we know the offset in many cases.  These
     assume you are changing where the address is pointing by the
     offset.  */
  new_mem = replace_equiv_address_nv (mem, new_addr);
  if (! validate_change (mem_insn.insn, mem_insn.mem_loc, new_mem, 0))
    {
      if (dump_file)
	fprintf (dump_file, "validation failure\n");
      return false;
    }

  /* From here to the end of the function we are committed to the
     change, i.e. nothing fails.  Generate any necessary movs, move
     any regnotes, and fix up the reg_next_{use,inc_use,def}.  */
  switch (inc_insn.form)
    {
    case FORM_PRE_ADD:
      /* Replace the addition with a move.  Do it at the location of
	 the addition since the operand of the addition may change
	 before the memory reference.  */
      mov_insn = insert_move_insn_before (inc_insn.insn,
					  inc_insn.reg_res, inc_insn.reg0);
      move_dead_notes (mov_insn, inc_insn.insn, inc_insn.reg0);

      regno = REGNO (inc_insn.reg_res);
      reg_next_def[regno] = mov_insn;
      reg_next_use[regno] = NULL;
      regno = REGNO (inc_insn.reg0);
      reg_next_use[regno] = mov_insn;
      df_recompute_luids (bb);
      break;

    case FORM_POST_INC:
      regno = REGNO (inc_insn.reg_res);
      if (reg_next_use[regno] == reg_next_inc_use[regno])
	reg_next_inc_use[regno] = NULL;

      /* Fallthru.  */
    case FORM_PRE_INC:
      regno = REGNO (inc_insn.reg_res);
      reg_next_def[regno] = mem_insn.insn;
      reg_next_use[regno] = NULL;

      break;

    case FORM_POST_ADD:
      mov_insn = insert_move_insn_before (mem_insn.insn,
					  inc_insn.reg_res, inc_insn.reg0);
      move_dead_notes (mov_insn, inc_insn.insn, inc_insn.reg0);

      /* Do not move anything to the mov insn because the instruction
	 pointer for the main iteration has not yet hit that.  It is
	 still pointing to the mem insn. */
      regno = REGNO (inc_insn.reg_res);
      reg_next_def[regno] = mem_insn.insn;
      reg_next_use[regno] = NULL;

      regno = REGNO (inc_insn.reg0);
      reg_next_use[regno] = mem_insn.insn;
      if ((reg_next_use[regno] == reg_next_inc_use[regno])
	  || (reg_next_inc_use[regno] == inc_insn.insn))
	reg_next_inc_use[regno] = NULL;
      df_recompute_luids (bb);
      break;

    case FORM_last:
    default:
      gcc_unreachable ();
    }

  if (!inc_insn.reg1_is_const)
    {
      regno = REGNO (inc_insn.reg1);
      reg_next_use[regno] = mem_insn.insn;
      if ((reg_next_use[regno] == reg_next_inc_use[regno])
	  || (reg_next_inc_use[regno] == inc_insn.insn))
	reg_next_inc_use[regno] = NULL;
    }

  delete_insn (inc_insn.insn);

  if (dump_file && mov_insn)
    {
      fprintf (dump_file, "inserting mov ");
      dump_insn_slim (dump_file, mov_insn);
    }

  /* Record that this insn has an implicit side effect.  */
  add_reg_note (mem_insn.insn, REG_INC, inc_reg);

  if (dump_file)
    {
      fprintf (dump_file, "****success ");
      dump_insn_slim (dump_file, mem_insn.insn);
    }

  return true;
}


/* Try to combine the instruction in INC_INSN with the instruction in
   MEM_INSN.  First the form is determined using the DECISION_TABLE
   and the results of parsing the INC_INSN and the MEM_INSN.
   Assuming the form is ok, a prototype new address is built which is
   passed to ATTEMPT_CHANGE for final processing.  */

static bool
try_merge (void)
{
  enum gen_form gen_form;
  rtx mem = *mem_insn.mem_loc;
  rtx inc_reg = inc_insn.form == FORM_POST_ADD ?
    inc_insn.reg_res : mem_insn.reg0;

  /* The width of the mem being accessed.  */
  int size = GET_MODE_SIZE (GET_MODE (mem));
  rtx last_insn = NULL;
  enum machine_mode reg_mode = GET_MODE (inc_reg);

  switch (inc_insn.form)
    {
    case FORM_PRE_ADD:
    case FORM_PRE_INC:
      last_insn = mem_insn.insn;
      break;
    case FORM_POST_INC:
    case FORM_POST_ADD:
      last_insn = inc_insn.insn;
      break;
    case FORM_last:
    default:
      gcc_unreachable ();
    }

  /* Cannot handle auto inc of the stack.  */
  if (inc_reg == stack_pointer_rtx)
    {
      if (dump_file)
	fprintf (dump_file, "cannot inc stack %d failure\n", REGNO (inc_reg));
      return false;
    }

  /* Look to see if the inc register is dead after the memory
     reference.  If it is, do not do the combination.  */
  if (find_regno_note (last_insn, REG_DEAD, REGNO (inc_reg)))
    {
      if (dump_file)
	fprintf (dump_file, "dead failure %d\n", REGNO (inc_reg));
      return false;
    }

  mem_insn.reg1_state = (mem_insn.reg1_is_const)
    ? set_inc_state (mem_insn.reg1_val, size) : INC_REG;
  inc_insn.reg1_state = (inc_insn.reg1_is_const)
    ? set_inc_state (inc_insn.reg1_val, size) : INC_REG;

  /* Now get the form that we are generating.  */
  gen_form = decision_table
    [inc_insn.reg1_state][mem_insn.reg1_state][inc_insn.form];

  if (dbg_cnt (auto_inc_dec) == false)
    return false;

  switch (gen_form)
    {
    default:
    case NOTHING:
      return false;

    case SIMPLE_PRE_INC:     /* ++size  */
      if (dump_file)
	fprintf (dump_file, "trying SIMPLE_PRE_INC\n");
      return attempt_change (gen_rtx_PRE_INC (reg_mode, inc_reg), inc_reg);
      break;

    case SIMPLE_POST_INC:    /* size++  */
      if (dump_file)
	fprintf (dump_file, "trying SIMPLE_POST_INC\n");
      return attempt_change (gen_rtx_POST_INC (reg_mode, inc_reg), inc_reg);
      break;

    case SIMPLE_PRE_DEC:     /* --size  */
      if (dump_file)
	fprintf (dump_file, "trying SIMPLE_PRE_DEC\n");
      return attempt_change (gen_rtx_PRE_DEC (reg_mode, inc_reg), inc_reg);
      break;

    case SIMPLE_POST_DEC:    /* size--  */
      if (dump_file)
	fprintf (dump_file, "trying SIMPLE_POST_DEC\n");
      return attempt_change (gen_rtx_POST_DEC (reg_mode, inc_reg), inc_reg);
      break;

    case DISP_PRE:           /* ++con   */
      if (dump_file)
	fprintf (dump_file, "trying DISP_PRE\n");
      return attempt_change (gen_rtx_PRE_MODIFY (reg_mode,
						 inc_reg,
						 gen_rtx_PLUS (reg_mode,
							       inc_reg,
							       inc_insn.reg1)),
			     inc_reg);
      break;

    case DISP_POST:          /* con++   */
      if (dump_file)
	fprintf (dump_file, "trying POST_DISP\n");
      return attempt_change (gen_rtx_POST_MODIFY (reg_mode,
						  inc_reg,
						  gen_rtx_PLUS (reg_mode,
								inc_reg,
								inc_insn.reg1)),
			     inc_reg);
      break;

    case REG_PRE:            /* ++reg   */
      if (dump_file)
	fprintf (dump_file, "trying PRE_REG\n");
      return attempt_change (gen_rtx_PRE_MODIFY (reg_mode,
						 inc_reg,
						 gen_rtx_PLUS (reg_mode,
							       inc_reg,
							       inc_insn.reg1)),
			     inc_reg);
      break;

    case REG_POST:            /* reg++   */
      if (dump_file)
	fprintf (dump_file, "trying POST_REG\n");
      return attempt_change (gen_rtx_POST_MODIFY (reg_mode,
						  inc_reg,
						  gen_rtx_PLUS (reg_mode,
								inc_reg,
								inc_insn.reg1)),
			     inc_reg);
      break;
    }
}

/* Return the next insn that uses (if reg_next_use is passed in
   NEXT_ARRAY) or defines (if reg_next_def is passed in NEXT_ARRAY)
   REGNO in BB.  */

static rtx
get_next_ref (int regno, basic_block bb, rtx *next_array)
{
  rtx insn = next_array[regno];

  /* Lazy about cleaning out the next_arrays.  */
  if (insn && BLOCK_FOR_INSN (insn) != bb)
    {
      next_array[regno] = NULL;
      insn = NULL;
    }

  return insn;
}


/* Reverse the operands in a mem insn.  */

static void
reverse_mem (void)
{
  rtx tmp = mem_insn.reg1;
  mem_insn.reg1 = mem_insn.reg0;
  mem_insn.reg0 = tmp;
}


/* Reverse the operands in a inc insn.  */

static void
reverse_inc (void)
{
  rtx tmp = inc_insn.reg1;
  inc_insn.reg1 = inc_insn.reg0;
  inc_insn.reg0 = tmp;
}


/* Return true if INSN is of a form "a = b op c" where a and b are
   regs.  op is + if c is a reg and +|- if c is a const.  Fill in
   INC_INSN with what is found.

   This function is called in two contexts, if BEFORE_MEM is true,
   this is called for each insn in the basic block.  If BEFORE_MEM is
   false, it is called for the instruction in the block that uses the
   index register for some memory reference that is currently being
   processed.  */

static bool
parse_add_or_inc (rtx insn, bool before_mem)
{
  rtx pat = single_set (insn);
  if (!pat)
    return false;

  /* Result must be single reg.  */
  if (!REG_P (SET_DEST (pat)))
    return false;

  if ((GET_CODE (SET_SRC (pat)) != PLUS)
      && (GET_CODE (SET_SRC (pat)) != MINUS))
    return false;

  if (!REG_P (XEXP (SET_SRC (pat), 0)))
    return false;

  inc_insn.insn = insn;
  inc_insn.pat = pat;
  inc_insn.reg_res = SET_DEST (pat);
  inc_insn.reg0 = XEXP (SET_SRC (pat), 0);
  if (rtx_equal_p (inc_insn.reg_res, inc_insn.reg0))
    inc_insn.form = before_mem ? FORM_PRE_INC : FORM_POST_INC;
  else
    inc_insn.form = before_mem ? FORM_PRE_ADD : FORM_POST_ADD;

  if (CONST_INT_P (XEXP (SET_SRC (pat), 1)))
    {
      /* Process a = b + c where c is a const.  */
      inc_insn.reg1_is_const = true;
      if (GET_CODE (SET_SRC (pat)) == PLUS)
	{
	  inc_insn.reg1 = XEXP (SET_SRC (pat), 1);
	  inc_insn.reg1_val = INTVAL (inc_insn.reg1);
	}
      else
	{
	  inc_insn.reg1_val = -INTVAL (XEXP (SET_SRC (pat), 1));
	  inc_insn.reg1 = GEN_INT (inc_insn.reg1_val);
	}
      return true;
    }
  else if ((HAVE_PRE_MODIFY_REG || HAVE_POST_MODIFY_REG)
	   && (REG_P (XEXP (SET_SRC (pat), 1)))
	   && GET_CODE (SET_SRC (pat)) == PLUS)
    {
      /* Process a = b + c where c is a reg.  */
      inc_insn.reg1 = XEXP (SET_SRC (pat), 1);
      inc_insn.reg1_is_const = false;

      if (inc_insn.form == FORM_PRE_INC
	  || inc_insn.form == FORM_POST_INC)
	return true;
      else if (rtx_equal_p (inc_insn.reg_res, inc_insn.reg1))
	{
	  /* Reverse the two operands and turn *_ADD into *_INC since
	     a = c + a.  */
	  reverse_inc ();
	  inc_insn.form = before_mem ? FORM_PRE_INC : FORM_POST_INC;
	  return true;
	}
      else
	return true;
    }

  return false;
}


/* A recursive function that checks all of the mem uses in
   ADDRESS_OF_X to see if any single one of them is compatible with
   what has been found in inc_insn.

   -1 is returned for success.  0 is returned if nothing was found and
   1 is returned for failure. */

static int
find_address (rtx *address_of_x)
{
  rtx x = *address_of_x;
  enum rtx_code code = GET_CODE (x);
  const char *const fmt = GET_RTX_FORMAT (code);
  int i;
  int value = 0;
  int tem;

  if (code == MEM && rtx_equal_p (XEXP (x, 0), inc_insn.reg_res))
    {
      /* Match with *reg0.  */
      mem_insn.mem_loc = address_of_x;
      mem_insn.reg0 = inc_insn.reg_res;
      mem_insn.reg1_is_const = true;
      mem_insn.reg1_val = 0;
      mem_insn.reg1 = GEN_INT (0);
      return -1;
    }
  if (code == MEM && GET_CODE (XEXP (x, 0)) == PLUS
      && rtx_equal_p (XEXP (XEXP (x, 0), 0), inc_insn.reg_res))
    {
      rtx b = XEXP (XEXP (x, 0), 1);
      mem_insn.mem_loc = address_of_x;
      mem_insn.reg0 = inc_insn.reg_res;
      mem_insn.reg1 = b;
      mem_insn.reg1_is_const = inc_insn.reg1_is_const;
      if (CONST_INT_P (b))
	{
	  /* Match with *(reg0 + reg1) where reg1 is a const. */
	  HOST_WIDE_INT val = INTVAL (b);
	  if (inc_insn.reg1_is_const
	      && (inc_insn.reg1_val == val || inc_insn.reg1_val == -val))
	    {
	      mem_insn.reg1_val = val;
	      return -1;
	    }
	}
      else if (!inc_insn.reg1_is_const
	       && rtx_equal_p (inc_insn.reg1, b))
	/* Match with *(reg0 + reg1). */
	return -1;
    }

  if (code == SIGN_EXTRACT || code == ZERO_EXTRACT)
    {
      /* If REG occurs inside a MEM used in a bit-field reference,
	 that is unacceptable.  */
      if (find_address (&XEXP (x, 0)))
	return 1;
    }

  if (x == inc_insn.reg_res)
    return 1;

  /* Time for some deep diving.  */
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    {
      if (fmt[i] == 'e')
	{
	  tem = find_address (&XEXP (x, i));
	  /* If this is the first use, let it go so the rest of the
	     insn can be checked.  */
	  if (value == 0)
	    value = tem;
	  else if (tem != 0)
	    /* More than one match was found.  */
	    return 1;
	}
      else if (fmt[i] == 'E')
	{
	  int j;
	  for (j = XVECLEN (x, i) - 1; j >= 0; j--)
	    {
	      tem = find_address (&XVECEXP (x, i, j));
	      /* If this is the first use, let it go so the rest of
		 the insn can be checked.  */
	      if (value == 0)
		value = tem;
	      else if (tem != 0)
		/* More than one match was found.  */
		return 1;
	    }
	}
    }
  return value;
}

/* Once a suitable mem reference has been found and the MEM_INSN
   structure has been filled in, FIND_INC is called to see if there is
   a suitable add or inc insn that follows the mem reference and
   determine if it is suitable to merge.

   In the case where the MEM_INSN has two registers in the reference,
   this function may be called recursively.  The first time looking
   for an add of the first register, and if that fails, looking for an
   add of the second register.  The FIRST_TRY parameter is used to
   only allow the parameters to be reversed once.  */

static bool
find_inc (bool first_try)
{
  rtx insn;
  basic_block bb = BLOCK_FOR_INSN (mem_insn.insn);
  rtx other_insn;
  df_ref *def_rec;

  /* Make sure this reg appears only once in this insn.  */
  if (count_occurrences (PATTERN (mem_insn.insn), mem_insn.reg0, 1) != 1)
    {
      if (dump_file)
	fprintf (dump_file, "mem count failure\n");
      return false;
    }

  if (dump_file)
    dump_mem_insn (dump_file);

  /* Find the next use that is an inc.  */
  insn = get_next_ref (REGNO (mem_insn.reg0),
		       BLOCK_FOR_INSN (mem_insn.insn),
		       reg_next_inc_use);
  if (!insn)
    return false;

  /* Even though we know the next use is an add or inc because it came
     from the reg_next_inc_use, we must still reparse.  */
  if (!parse_add_or_inc (insn, false))
    {
      /* Next use was not an add.  Look for one extra case. It could be
	 that we have:

	 *(a + b)
	 ...= a;
	 ...= b + a

	 if we reverse the operands in the mem ref we would
	 find this.  Only try it once though.  */
      if (first_try && !mem_insn.reg1_is_const)
	{
	  reverse_mem ();
	  return find_inc (false);
	}
      else
	return false;
    }

  /* Need to assure that none of the operands of the inc instruction are
     assigned to by the mem insn.  */
  for (def_rec = DF_INSN_DEFS (mem_insn.insn); *def_rec; def_rec++)
    {
      df_ref def = *def_rec;
      unsigned int regno = DF_REF_REGNO (def);
      if ((regno == REGNO (inc_insn.reg0))
	  || (regno == REGNO (inc_insn.reg_res)))
	{
	  if (dump_file)
	    fprintf (dump_file, "inc conflicts with store failure.\n");
	  return false;
	}
      if (!inc_insn.reg1_is_const && (regno == REGNO (inc_insn.reg1)))
	{
	  if (dump_file)
	    fprintf (dump_file, "inc conflicts with store failure.\n");
	  return false;
	}
    }

  if (dump_file)
    dump_inc_insn (dump_file);

  if (inc_insn.form == FORM_POST_ADD)
    {
      /* Make sure that there is no insn that assigns to inc_insn.res
	 between the mem_insn and the inc_insn.  */
      rtx other_insn = get_next_ref (REGNO (inc_insn.reg_res),
				     BLOCK_FOR_INSN (mem_insn.insn),
				     reg_next_def);
      if (other_insn != inc_insn.insn)
	{
	  if (dump_file)
	    fprintf (dump_file,
		     "result of add is assigned to between mem and inc insns.\n");
	  return false;
	}

      other_insn = get_next_ref (REGNO (inc_insn.reg_res),
				 BLOCK_FOR_INSN (mem_insn.insn),
				 reg_next_use);
      if (other_insn
	  && (other_insn != inc_insn.insn)
	  && (DF_INSN_LUID (inc_insn.insn) > DF_INSN_LUID (other_insn)))
	{
	  if (dump_file)
	    fprintf (dump_file,
		     "result of add is used between mem and inc insns.\n");
	  return false;
	}

      /* For the post_add to work, the result_reg of the inc must not be
	 used in the mem insn since this will become the new index
	 register.  */
      if (reg_overlap_mentioned_p (inc_insn.reg_res, PATTERN (mem_insn.insn)))
	{
	  if (dump_file)
	    fprintf (dump_file, "base reg replacement failure.\n");
	  return false;
	}
    }

  if (mem_insn.reg1_is_const)
    {
      if (mem_insn.reg1_val == 0)
	{
	  if (!inc_insn.reg1_is_const)
	    {
	      /* The mem looks like *r0 and the rhs of the add has two
		 registers.  */
	      int luid = DF_INSN_LUID (inc_insn.insn);
	      if (inc_insn.form == FORM_POST_ADD)
		{
		  /* The trick is that we are not going to increment r0,
		     we are going to increment the result of the add insn.
		     For this trick to be correct, the result reg of
		     the inc must be a valid addressing reg.  */
		  addr_space_t as = MEM_ADDR_SPACE (*mem_insn.mem_loc);
		  if (GET_MODE (inc_insn.reg_res)
		      != targetm.addr_space.address_mode (as))
		    {
		      if (dump_file)
			fprintf (dump_file, "base reg mode failure.\n");
		      return false;
		    }

		  /* We also need to make sure that the next use of
		     inc result is after the inc.  */
		  other_insn
		    = get_next_ref (REGNO (inc_insn.reg1), bb, reg_next_use);
		  if (other_insn && luid > DF_INSN_LUID (other_insn))
		    return false;

		  if (!rtx_equal_p (mem_insn.reg0, inc_insn.reg0))
		    reverse_inc ();
		}

	      other_insn
		= get_next_ref (REGNO (inc_insn.reg1), bb, reg_next_def);
	      if (other_insn && luid > DF_INSN_LUID (other_insn))
		return false;
	    }
	}
      /* Both the inc/add and the mem have a constant.  Need to check
	 that the constants are ok. */
      else if ((mem_insn.reg1_val != inc_insn.reg1_val)
	       && (mem_insn.reg1_val != -inc_insn.reg1_val))
	return false;
    }
  else
    {
      /* The mem insn is of the form *(a + b) where a and b are both
	 regs.  It may be that in order to match the add or inc we
	 need to treat it as if it was *(b + a).  It may also be that
	 the add is of the form a + c where c does not match b and
	 then we just abandon this.  */

      int luid = DF_INSN_LUID (inc_insn.insn);
      rtx other_insn;

      /* Make sure this reg appears only once in this insn.  */
      if (count_occurrences (PATTERN (mem_insn.insn), mem_insn.reg1, 1) != 1)
	return false;

      if (inc_insn.form == FORM_POST_ADD)
	{
	  /* For this trick to be correct, the result reg of the inc
	     must be a valid addressing reg.  */
	  addr_space_t as = MEM_ADDR_SPACE (*mem_insn.mem_loc);
	  if (GET_MODE (inc_insn.reg_res)
	      != targetm.addr_space.address_mode (as))
	    {
	      if (dump_file)
		fprintf (dump_file, "base reg mode failure.\n");
	      return false;
	    }

	  if (rtx_equal_p (mem_insn.reg0, inc_insn.reg0))
	    {
	      if (!rtx_equal_p (mem_insn.reg1, inc_insn.reg1))
		{
		  /* See comment above on find_inc (false) call.  */
		  if (first_try)
		    {
		      reverse_mem ();
		      return find_inc (false);
		    }
		  else
		    return false;
		}

	      /* Need to check that there are no assignments to b
		 before the add insn.  */
	      other_insn
		= get_next_ref (REGNO (inc_insn.reg1), bb, reg_next_def);
	      if (other_insn && luid > DF_INSN_LUID (other_insn))
		return false;
	      /* All ok for the next step.  */
	    }
	  else
	    {
	      /* We know that mem_insn.reg0 must equal inc_insn.reg1
		 or else we would not have found the inc insn.  */
	      reverse_mem ();
	      if (!rtx_equal_p (mem_insn.reg0, inc_insn.reg0))
		{
		  /* See comment above on find_inc (false) call.  */
		  if (first_try)
		    return find_inc (false);
		  else
		    return false;
		}
	      /* To have gotten here know that.
	       *(b + a)

	       ... = (b + a)

	       We also know that the lhs of the inc is not b or a.  We
	       need to make sure that there are no assignments to b
	       between the mem ref and the inc.  */

	      other_insn
		= get_next_ref (REGNO (inc_insn.reg0), bb, reg_next_def);
	      if (other_insn && luid > DF_INSN_LUID (other_insn))
		return false;
	    }

	  /* Need to check that the next use of the add result is later than
	     add insn since this will be the reg incremented.  */
	  other_insn
	    = get_next_ref (REGNO (inc_insn.reg_res), bb, reg_next_use);
	  if (other_insn && luid > DF_INSN_LUID (other_insn))
	    return false;
	}
      else /* FORM_POST_INC.  There is less to check here because we
	      know that operands must line up.  */
	{
	  if (!rtx_equal_p (mem_insn.reg1, inc_insn.reg1))
	    /* See comment above on find_inc (false) call.  */
	    {
	      if (first_try)
		{
		  reverse_mem ();
		  return find_inc (false);
		}
	      else
		return false;
	    }

	  /* To have gotten here know that.
	   *(a + b)

	   ... = (a + b)

	   We also know that the lhs of the inc is not b.  We need to make
	   sure that there are no assignments to b between the mem ref and
	   the inc.  */
	  other_insn
	    = get_next_ref (REGNO (inc_insn.reg1), bb, reg_next_def);
	  if (other_insn && luid > DF_INSN_LUID (other_insn))
	    return false;
	}
    }

  if (inc_insn.form == FORM_POST_INC)
    {
      other_insn
	= get_next_ref (REGNO (inc_insn.reg0), bb, reg_next_use);
      /* When we found inc_insn, we were looking for the
	 next add or inc, not the next insn that used the
	 reg.  Because we are going to increment the reg
	 in this form, we need to make sure that there
	 were no intervening uses of reg.  */
      if (inc_insn.insn != other_insn)
	return false;
    }

  return try_merge ();
}


/* A recursive function that walks ADDRESS_OF_X to find all of the mem
   uses in pat that could be used as an auto inc or dec.  It then
   calls FIND_INC for each one.  */

static bool
find_mem (rtx *address_of_x)
{
  rtx x = *address_of_x;
  enum rtx_code code = GET_CODE (x);
  const char *const fmt = GET_RTX_FORMAT (code);
  int i;

  if (code == MEM && REG_P (XEXP (x, 0)))
    {
      /* Match with *reg0.  */
      mem_insn.mem_loc = address_of_x;
      mem_insn.reg0 = XEXP (x, 0);
      mem_insn.reg1_is_const = true;
      mem_insn.reg1_val = 0;
      mem_insn.reg1 = GEN_INT (0);
      if (find_inc (true))
	return true;
    }
  if (code == MEM && GET_CODE (XEXP (x, 0)) == PLUS
      && REG_P (XEXP (XEXP (x, 0), 0)))
    {
      rtx reg1 = XEXP (XEXP (x, 0), 1);
      mem_insn.mem_loc = address_of_x;
      mem_insn.reg0 = XEXP (XEXP (x, 0), 0);
      mem_insn.reg1 = reg1;
      if (CONST_INT_P (reg1))
	{
	  mem_insn.reg1_is_const = true;
	  /* Match with *(reg0 + c) where c is a const. */
	  mem_insn.reg1_val = INTVAL (reg1);
	  if (find_inc (true))
	    return true;
	}
      else if (REG_P (reg1))
	{
	  /* Match with *(reg0 + reg1).  */
	  mem_insn.reg1_is_const = false;
	  if (find_inc (true))
	    return true;
	}
    }

  if (code == SIGN_EXTRACT || code == ZERO_EXTRACT)
    {
      /* If REG occurs inside a MEM used in a bit-field reference,
	 that is unacceptable.  */
      return false;
    }

  /* Time for some deep diving.  */
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    {
      if (fmt[i] == 'e')
	{
	  if (find_mem (&XEXP (x, i)))
	    return true;
	}
      else if (fmt[i] == 'E')
	{
	  int j;
	  for (j = XVECLEN (x, i) - 1; j >= 0; j--)
	    if (find_mem (&XVECEXP (x, i, j)))
	      return true;
	}
    }
  return false;
}


/* Try to combine all incs and decs by constant values with memory
   references in BB.  */

static void
merge_in_block (int max_reg, basic_block bb)
{
  rtx insn;
  rtx curr;
  int success_in_block = 0;

  if (dump_file)
    fprintf (dump_file, "\n\nstarting bb %d\n", bb->index);

  FOR_BB_INSNS_REVERSE_SAFE (bb, insn, curr)
    {
      unsigned int uid = INSN_UID (insn);
      bool insn_is_add_or_inc = true;

      if (!NONDEBUG_INSN_P (insn))
	continue;

      /* This continue is deliberate.  We do not want the uses of the
	 jump put into reg_next_use because it is not considered safe to
	 combine a preincrement with a jump.  */
      if (JUMP_P (insn))
	continue;

      if (dump_file)
	dump_insn_slim (dump_file, insn);

      /* Does this instruction increment or decrement a register?  */
      if (parse_add_or_inc (insn, true))
	{
	  int regno = REGNO (inc_insn.reg_res);
	  /* Cannot handle case where there are three separate regs
	     before a mem ref.  Too many moves would be needed to be
	     profitable.  */
	  if ((inc_insn.form == FORM_PRE_INC) || inc_insn.reg1_is_const)
	    {
	      mem_insn.insn = get_next_ref (regno, bb, reg_next_use);
	      if (mem_insn.insn)
		{
		  bool ok = true;
		  if (!inc_insn.reg1_is_const)
		    {
		      /* We are only here if we are going to try a
			 HAVE_*_MODIFY_REG type transformation.  c is a
			 reg and we must sure that the path from the
			 inc_insn to the mem_insn.insn is both def and use
			 clear of c because the inc insn is going to move
			 into the mem_insn.insn.  */
		      int luid = DF_INSN_LUID (mem_insn.insn);
		      rtx other_insn
			= get_next_ref (REGNO (inc_insn.reg1), bb, reg_next_use);

		      if (other_insn && luid > DF_INSN_LUID (other_insn))
			ok = false;

		      other_insn
			= get_next_ref (REGNO (inc_insn.reg1), bb, reg_next_def);

		      if (other_insn && luid > DF_INSN_LUID (other_insn))
			ok = false;
		    }

		  if (dump_file)
		    dump_inc_insn (dump_file);

		  if (ok && find_address (&PATTERN (mem_insn.insn)) == -1)
		    {
		      if (dump_file)
			dump_mem_insn (dump_file);
		      if (try_merge ())
			{
			  success_in_block++;
			  insn_is_add_or_inc = false;
			}
		    }
		}
	    }
	}
      else
	{
	  insn_is_add_or_inc = false;
	  mem_insn.insn = insn;
	  if (find_mem (&PATTERN (insn)))
	    success_in_block++;
	}

      /* If the inc insn was merged with a mem, the inc insn is gone
	 and there is noting to update.  */
      if (DF_INSN_UID_GET (uid))
	{
	  df_ref *def_rec;
	  df_ref *use_rec;
	  /* Need to update next use.  */
	  for (def_rec = DF_INSN_UID_DEFS (uid); *def_rec; def_rec++)
	    {
	      df_ref def = *def_rec;
	      reg_next_use[DF_REF_REGNO (def)] = NULL;
	      reg_next_inc_use[DF_REF_REGNO (def)] = NULL;
	      reg_next_def[DF_REF_REGNO (def)] = insn;
	    }

	  for (use_rec = DF_INSN_UID_USES (uid); *use_rec; use_rec++)
	    {
	      df_ref use = *use_rec;
	      reg_next_use[DF_REF_REGNO (use)] = insn;
	      if (insn_is_add_or_inc)
		reg_next_inc_use[DF_REF_REGNO (use)] = insn;
	      else
		reg_next_inc_use[DF_REF_REGNO (use)] = NULL;
	    }
	}
      else if (dump_file)
	fprintf (dump_file, "skipping update of deleted insn %d\n", uid);
    }

  /* If we were successful, try again.  There may have been several
     opportunities that were interleaved.  This is rare but
     gcc.c-torture/compile/pr17273.c actually exhibits this.  */
  if (success_in_block)
    {
      /* In this case, we must clear these vectors since the trick of
	 testing if the stale insn in the block will not work.  */
      memset (reg_next_use, 0, max_reg * sizeof(rtx));
      memset (reg_next_inc_use, 0, max_reg * sizeof(rtx));
      memset (reg_next_def, 0, max_reg * sizeof(rtx));
      df_recompute_luids (bb);
      merge_in_block (max_reg, bb);
    }
}

#endif

static unsigned int
rest_of_handle_auto_inc_dec (void)
{
#ifdef AUTO_INC_DEC
  basic_block bb;
  int max_reg = max_reg_num ();

  if (!initialized)
    init_decision_table ();

  mem_tmp = gen_rtx_MEM (Pmode, NULL_RTX);

  df_note_add_problem ();
  df_analyze ();

  reg_next_use = XCNEWVEC (rtx, max_reg);
  reg_next_inc_use = XCNEWVEC (rtx, max_reg);
  reg_next_def = XCNEWVEC (rtx, max_reg);
  FOR_EACH_BB (bb)
    merge_in_block (max_reg, bb);

  free (reg_next_use);
  free (reg_next_inc_use);
  free (reg_next_def);

  mem_tmp = NULL;
#endif
  return 0;
}


/* Discover auto-inc auto-dec instructions.  */

static bool
gate_auto_inc_dec (void)
{
#ifdef AUTO_INC_DEC
  return (optimize > 0 && flag_auto_inc_dec);
#else
  return false;
#endif
}


struct rtl_opt_pass pass_inc_dec =
{
 {
  RTL_PASS,
  "auto_inc_dec",                       /* name */
  OPTGROUP_NONE,                        /* optinfo_flags */
  gate_auto_inc_dec,                    /* gate */
  rest_of_handle_auto_inc_dec,          /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_AUTO_INC_DEC,                      /* tv_id */
  0,                                    /* properties_required */
  0,                                    /* properties_provided */
  0,                                    /* properties_destroyed */
  0,                                    /* todo_flags_start */
  TODO_df_finish,                       /* todo_flags_finish */
 }
};