summaryrefslogtreecommitdiff
path: root/gcc/tree-if-conv.c
blob: 107c7e3da127d5e93bedd864a729a47c4e5433cf (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
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
/* If-conversion for vectorizer.
   Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012
   Free Software Foundation, Inc.
   Contributed by Devang Patel <dpatel@apple.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/>.  */

/* This pass implements a tree level if-conversion of loops.  Its
   initial goal is to help the vectorizer to vectorize loops with
   conditions.

   A short description of if-conversion:

     o Decide if a loop is if-convertible or not.
     o Walk all loop basic blocks in breadth first order (BFS order).
       o Remove conditional statements (at the end of basic block)
         and propagate condition into destination basic blocks'
	 predicate list.
       o Replace modify expression with conditional modify expression
         using current basic block's condition.
     o Merge all basic blocks
       o Replace phi nodes with conditional modify expr
       o Merge all basic blocks into header

     Sample transformation:

     INPUT
     -----

     # i_23 = PHI <0(0), i_18(10)>;
     <L0>:;
     j_15 = A[i_23];
     if (j_15 > 41) goto <L1>; else goto <L17>;

     <L17>:;
     goto <bb 3> (<L3>);

     <L1>:;

     # iftmp.2_4 = PHI <0(8), 42(2)>;
     <L3>:;
     A[i_23] = iftmp.2_4;
     i_18 = i_23 + 1;
     if (i_18 <= 15) goto <L19>; else goto <L18>;

     <L19>:;
     goto <bb 1> (<L0>);

     <L18>:;

     OUTPUT
     ------

     # i_23 = PHI <0(0), i_18(10)>;
     <L0>:;
     j_15 = A[i_23];

     <L3>:;
     iftmp.2_4 = j_15 > 41 ? 42 : 0;
     A[i_23] = iftmp.2_4;
     i_18 = i_23 + 1;
     if (i_18 <= 15) goto <L19>; else goto <L18>;

     <L19>:;
     goto <bb 1> (<L0>);

     <L18>:;
*/

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "flags.h"
#include "timevar.h"
#include "basic-block.h"
#include "tree-pretty-print.h"
#include "gimple-pretty-print.h"
#include "tree-flow.h"
#include "tree-dump.h"
#include "cfgloop.h"
#include "tree-chrec.h"
#include "tree-data-ref.h"
#include "tree-scalar-evolution.h"
#include "tree-pass.h"
#include "dbgcnt.h"

/* List of basic blocks in if-conversion-suitable order.  */
static basic_block *ifc_bbs;

/* Structure used to predicate basic blocks.  This is attached to the
   ->aux field of the BBs in the loop to be if-converted.  */
typedef struct bb_predicate_s {

  /* The condition under which this basic block is executed.  */
  tree predicate;

  /* PREDICATE is gimplified, and the sequence of statements is
     recorded here, in order to avoid the duplication of computations
     that occur in previous conditions.  See PR44483.  */
  gimple_seq predicate_gimplified_stmts;
} *bb_predicate_p;

/* Returns true when the basic block BB has a predicate.  */

static inline bool
bb_has_predicate (basic_block bb)
{
  return bb->aux != NULL;
}

/* Returns the gimplified predicate for basic block BB.  */

static inline tree
bb_predicate (basic_block bb)
{
  return ((bb_predicate_p) bb->aux)->predicate;
}

/* Sets the gimplified predicate COND for basic block BB.  */

static inline void
set_bb_predicate (basic_block bb, tree cond)
{
  gcc_assert ((TREE_CODE (cond) == TRUTH_NOT_EXPR
	       && is_gimple_condexpr (TREE_OPERAND (cond, 0)))
	      || is_gimple_condexpr (cond));
  ((bb_predicate_p) bb->aux)->predicate = cond;
}

/* Returns the sequence of statements of the gimplification of the
   predicate for basic block BB.  */

static inline gimple_seq
bb_predicate_gimplified_stmts (basic_block bb)
{
  return ((bb_predicate_p) bb->aux)->predicate_gimplified_stmts;
}

/* Sets the sequence of statements STMTS of the gimplification of the
   predicate for basic block BB.  */

static inline void
set_bb_predicate_gimplified_stmts (basic_block bb, gimple_seq stmts)
{
  ((bb_predicate_p) bb->aux)->predicate_gimplified_stmts = stmts;
}

/* Adds the sequence of statements STMTS to the sequence of statements
   of the predicate for basic block BB.  */

static inline void
add_bb_predicate_gimplified_stmts (basic_block bb, gimple_seq stmts)
{
  gimple_seq_add_seq
    (&(((bb_predicate_p) bb->aux)->predicate_gimplified_stmts), stmts);
}

/* Initializes to TRUE the predicate of basic block BB.  */

static inline void
init_bb_predicate (basic_block bb)
{
  bb->aux = XNEW (struct bb_predicate_s);
  set_bb_predicate_gimplified_stmts (bb, NULL);
  set_bb_predicate (bb, boolean_true_node);
}

/* Free the predicate of basic block BB.  */

static inline void
free_bb_predicate (basic_block bb)
{
  gimple_seq stmts;

  if (!bb_has_predicate (bb))
    return;

  /* Release the SSA_NAMEs created for the gimplification of the
     predicate.  */
  stmts = bb_predicate_gimplified_stmts (bb);
  if (stmts)
    {
      gimple_stmt_iterator i;

      for (i = gsi_start (stmts); !gsi_end_p (i); gsi_next (&i))
	free_stmt_operands (gsi_stmt (i));
    }

  free (bb->aux);
  bb->aux = NULL;
}

/* Free the predicate of BB and reinitialize it with the true
   predicate.  */

static inline void
reset_bb_predicate (basic_block bb)
{
  free_bb_predicate (bb);
  init_bb_predicate (bb);
}

/* Returns a new SSA_NAME of type TYPE that is assigned the value of
   the expression EXPR.  Inserts the statement created for this
   computation before GSI and leaves the iterator GSI at the same
   statement.  */

static tree
ifc_temp_var (tree type, tree expr, gimple_stmt_iterator *gsi)
{
  const char *name = "_ifc_";
  tree var, new_name;
  gimple stmt;

  /* Create new temporary variable.  */
  var = create_tmp_var (type, name);
  add_referenced_var (var);

  /* Build new statement to assign EXPR to new variable.  */
  stmt = gimple_build_assign (var, expr);

  /* Get SSA name for the new variable and set make new statement
     its definition statement.  */
  new_name = make_ssa_name (var, stmt);
  gimple_assign_set_lhs (stmt, new_name);
  SSA_NAME_DEF_STMT (new_name) = stmt;
  update_stmt (stmt);

  gsi_insert_before (gsi, stmt, GSI_SAME_STMT);
  return gimple_assign_lhs (stmt);
}

/* Return true when COND is a true predicate.  */

static inline bool
is_true_predicate (tree cond)
{
  return (cond == NULL_TREE
	  || cond == boolean_true_node
	  || integer_onep (cond));
}

/* Returns true when BB has a predicate that is not trivial: true or
   NULL_TREE.  */

static inline bool
is_predicated (basic_block bb)
{
  return !is_true_predicate (bb_predicate (bb));
}

/* Parses the predicate COND and returns its comparison code and
   operands OP0 and OP1.  */

static enum tree_code
parse_predicate (tree cond, tree *op0, tree *op1)
{
  gimple s;

  if (TREE_CODE (cond) == SSA_NAME
      && is_gimple_assign (s = SSA_NAME_DEF_STMT (cond)))
    {
      if (TREE_CODE_CLASS (gimple_assign_rhs_code (s)) == tcc_comparison)
	{
	  *op0 = gimple_assign_rhs1 (s);
	  *op1 = gimple_assign_rhs2 (s);
	  return gimple_assign_rhs_code (s);
	}

      else if (gimple_assign_rhs_code (s) == TRUTH_NOT_EXPR)
	{
	  tree op = gimple_assign_rhs1 (s);
	  tree type = TREE_TYPE (op);
	  enum tree_code code = parse_predicate (op, op0, op1);

	  return code == ERROR_MARK ? ERROR_MARK
	    : invert_tree_comparison (code, HONOR_NANS (TYPE_MODE (type)));
	}

      return ERROR_MARK;
    }

  if (TREE_CODE_CLASS (TREE_CODE (cond)) == tcc_comparison)
    {
      *op0 = TREE_OPERAND (cond, 0);
      *op1 = TREE_OPERAND (cond, 1);
      return TREE_CODE (cond);
    }

  return ERROR_MARK;
}

/* Returns the fold of predicate C1 OR C2 at location LOC.  */

static tree
fold_or_predicates (location_t loc, tree c1, tree c2)
{
  tree op1a, op1b, op2a, op2b;
  enum tree_code code1 = parse_predicate (c1, &op1a, &op1b);
  enum tree_code code2 = parse_predicate (c2, &op2a, &op2b);

  if (code1 != ERROR_MARK && code2 != ERROR_MARK)
    {
      tree t = maybe_fold_or_comparisons (code1, op1a, op1b,
					  code2, op2a, op2b);
      if (t)
	return t;
    }

  return fold_build2_loc (loc, TRUTH_OR_EXPR, boolean_type_node, c1, c2);
}

/* Add condition NC to the predicate list of basic block BB.  */

static inline void
add_to_predicate_list (basic_block bb, tree nc)
{
  tree bc, *tp;

  if (is_true_predicate (nc))
    return;

  if (!is_predicated (bb))
    bc = nc;
  else
    {
      bc = bb_predicate (bb);
      bc = fold_or_predicates (EXPR_LOCATION (bc), nc, bc);
      if (is_true_predicate (bc))
	{
	  reset_bb_predicate (bb);
	  return;
	}
    }

  /* Allow a TRUTH_NOT_EXPR around the main predicate.  */
  if (TREE_CODE (bc) == TRUTH_NOT_EXPR)
    tp = &TREE_OPERAND (bc, 0);
  else
    tp = &bc;
  if (!is_gimple_condexpr (*tp))
    {
      gimple_seq stmts;
      *tp = force_gimple_operand_1 (*tp, &stmts, is_gimple_condexpr, NULL_TREE);
      add_bb_predicate_gimplified_stmts (bb, stmts);
    }
  set_bb_predicate (bb, bc);
}

/* Add the condition COND to the previous condition PREV_COND, and add
   this to the predicate list of the destination of edge E.  LOOP is
   the loop to be if-converted.  */

static void
add_to_dst_predicate_list (struct loop *loop, edge e,
			   tree prev_cond, tree cond)
{
  if (!flow_bb_inside_loop_p (loop, e->dest))
    return;

  if (!is_true_predicate (prev_cond))
    cond = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
			prev_cond, cond);

  add_to_predicate_list (e->dest, cond);
}

/* Return true if one of the successor edges of BB exits LOOP.  */

static bool
bb_with_exit_edge_p (struct loop *loop, basic_block bb)
{
  edge e;
  edge_iterator ei;

  FOR_EACH_EDGE (e, ei, bb->succs)
    if (loop_exit_edge_p (loop, e))
      return true;

  return false;
}

/* Return true when PHI is if-convertible.  PHI is part of loop LOOP
   and it belongs to basic block BB.

   PHI is not if-convertible if:
   - it has more than 2 arguments.

   When the flag_tree_loop_if_convert_stores is not set, PHI is not
   if-convertible if:
   - a virtual PHI is immediately used in another PHI node,
   - there is a virtual PHI in a BB other than the loop->header.  */

static bool
if_convertible_phi_p (struct loop *loop, basic_block bb, gimple phi)
{
  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "-------------------------\n");
      print_gimple_stmt (dump_file, phi, 0, TDF_SLIM);
    }

  if (bb != loop->header && gimple_phi_num_args (phi) != 2)
    {
      if (dump_file && (dump_flags & TDF_DETAILS))
	fprintf (dump_file, "More than two phi node args.\n");
      return false;
    }

  if (flag_tree_loop_if_convert_stores)
    return true;

  /* When the flag_tree_loop_if_convert_stores is not set, check
     that there are no memory writes in the branches of the loop to be
     if-converted.  */
  if (!is_gimple_reg (SSA_NAME_VAR (gimple_phi_result (phi))))
    {
      imm_use_iterator imm_iter;
      use_operand_p use_p;

      if (bb != loop->header)
	{
	  if (dump_file && (dump_flags & TDF_DETAILS))
	    fprintf (dump_file, "Virtual phi not on loop->header.\n");
	  return false;
	}

      FOR_EACH_IMM_USE_FAST (use_p, imm_iter, gimple_phi_result (phi))
	{
	  if (gimple_code (USE_STMT (use_p)) == GIMPLE_PHI)
	    {
	      if (dump_file && (dump_flags & TDF_DETAILS))
		fprintf (dump_file, "Difficult to handle this virtual phi.\n");
	      return false;
	    }
	}
    }

  return true;
}

/* Records the status of a data reference.  This struct is attached to
   each DR->aux field.  */

struct ifc_dr {
  /* -1 when not initialized, 0 when false, 1 when true.  */
  int written_at_least_once;

  /* -1 when not initialized, 0 when false, 1 when true.  */
  int rw_unconditionally;
};

#define IFC_DR(DR) ((struct ifc_dr *) (DR)->aux)
#define DR_WRITTEN_AT_LEAST_ONCE(DR) (IFC_DR (DR)->written_at_least_once)
#define DR_RW_UNCONDITIONALLY(DR) (IFC_DR (DR)->rw_unconditionally)

/* Returns true when the memory references of STMT are read or written
   unconditionally.  In other words, this function returns true when
   for every data reference A in STMT there exist other accesses to
   a data reference with the same base with predicates that add up (OR-up) to
   the true predicate: this ensures that the data reference A is touched
   (read or written) on every iteration of the if-converted loop.  */

static bool
memrefs_read_or_written_unconditionally (gimple stmt,
					 VEC (data_reference_p, heap) *drs)
{
  int i, j;
  data_reference_p a, b;
  tree ca = bb_predicate (gimple_bb (stmt));

  for (i = 0; VEC_iterate (data_reference_p, drs, i, a); i++)
    if (DR_STMT (a) == stmt)
      {
	bool found = false;
	int x = DR_RW_UNCONDITIONALLY (a);

	if (x == 0)
	  return false;

	if (x == 1)
	  continue;

	for (j = 0; VEC_iterate (data_reference_p, drs, j, b); j++)
          {
            tree ref_base_a = DR_REF (a);
            tree ref_base_b = DR_REF (b);

            if (DR_STMT (b) == stmt)
              continue;

            while (TREE_CODE (ref_base_a) == COMPONENT_REF
                   || TREE_CODE (ref_base_a) == IMAGPART_EXPR
                   || TREE_CODE (ref_base_a) == REALPART_EXPR)
              ref_base_a = TREE_OPERAND (ref_base_a, 0);

            while (TREE_CODE (ref_base_b) == COMPONENT_REF
                   || TREE_CODE (ref_base_b) == IMAGPART_EXPR
                   || TREE_CODE (ref_base_b) == REALPART_EXPR)
              ref_base_b = TREE_OPERAND (ref_base_b, 0);

  	    if (!operand_equal_p (ref_base_a, ref_base_b, 0))
	      {
	        tree cb = bb_predicate (gimple_bb (DR_STMT (b)));

	        if (DR_RW_UNCONDITIONALLY (b) == 1
		    || is_true_predicate (cb)
		    || is_true_predicate (ca
                        = fold_or_predicates (EXPR_LOCATION (cb), ca, cb)))
		  {
		    DR_RW_UNCONDITIONALLY (a) = 1;
  		    DR_RW_UNCONDITIONALLY (b) = 1;
		    found = true;
		    break;
		  }
               }
	    }

	if (!found)
	  {
	    DR_RW_UNCONDITIONALLY (a) = 0;
	    return false;
	  }
      }

  return true;
}

/* Returns true when the memory references of STMT are unconditionally
   written.  In other words, this function returns true when for every
   data reference A written in STMT, there exist other writes to the
   same data reference with predicates that add up (OR-up) to the true
   predicate: this ensures that the data reference A is written on
   every iteration of the if-converted loop.  */

static bool
write_memrefs_written_at_least_once (gimple stmt,
				     VEC (data_reference_p, heap) *drs)
{
  int i, j;
  data_reference_p a, b;
  tree ca = bb_predicate (gimple_bb (stmt));

  for (i = 0; VEC_iterate (data_reference_p, drs, i, a); i++)
    if (DR_STMT (a) == stmt
	&& DR_IS_WRITE (a))
      {
	bool found = false;
	int x = DR_WRITTEN_AT_LEAST_ONCE (a);

	if (x == 0)
	  return false;

	if (x == 1)
	  continue;

	for (j = 0; VEC_iterate (data_reference_p, drs, j, b); j++)
	  if (DR_STMT (b) != stmt
	      && DR_IS_WRITE (b)
	      && same_data_refs_base_objects (a, b))
	    {
	      tree cb = bb_predicate (gimple_bb (DR_STMT (b)));

	      if (DR_WRITTEN_AT_LEAST_ONCE (b) == 1
		  || is_true_predicate (cb)
		  || is_true_predicate (ca = fold_or_predicates (EXPR_LOCATION (cb),
								 ca, cb)))
		{
		  DR_WRITTEN_AT_LEAST_ONCE (a) = 1;
		  DR_WRITTEN_AT_LEAST_ONCE (b) = 1;
		  found = true;
		  break;
		}
	    }

	if (!found)
	  {
	    DR_WRITTEN_AT_LEAST_ONCE (a) = 0;
	    return false;
	  }
      }

  return true;
}

/* Return true when the memory references of STMT won't trap in the
   if-converted code.  There are two things that we have to check for:

   - writes to memory occur to writable memory: if-conversion of
   memory writes transforms the conditional memory writes into
   unconditional writes, i.e. "if (cond) A[i] = foo" is transformed
   into "A[i] = cond ? foo : A[i]", and as the write to memory may not
   be executed at all in the original code, it may be a readonly
   memory.  To check that A is not const-qualified, we check that
   there exists at least an unconditional write to A in the current
   function.

   - reads or writes to memory are valid memory accesses for every
   iteration.  To check that the memory accesses are correctly formed
   and that we are allowed to read and write in these locations, we
   check that the memory accesses to be if-converted occur at every
   iteration unconditionally.  */

static bool
ifcvt_memrefs_wont_trap (gimple stmt, VEC (data_reference_p, heap) *refs)
{
  return write_memrefs_written_at_least_once (stmt, refs)
    && memrefs_read_or_written_unconditionally (stmt, refs);
}

/* Wrapper around gimple_could_trap_p refined for the needs of the
   if-conversion.  Try to prove that the memory accesses of STMT could
   not trap in the innermost loop containing STMT.  */

static bool
ifcvt_could_trap_p (gimple stmt, VEC (data_reference_p, heap) *refs)
{
  if (gimple_vuse (stmt)
      && !gimple_could_trap_p_1 (stmt, false, false)
      && ifcvt_memrefs_wont_trap (stmt, refs))
    return false;

  return gimple_could_trap_p (stmt);
}

/* Return true when STMT is if-convertible.

   GIMPLE_ASSIGN statement is not if-convertible if,
   - it is not movable,
   - it could trap,
   - LHS is not var decl.  */

static bool
if_convertible_gimple_assign_stmt_p (gimple stmt,
				     VEC (data_reference_p, heap) *refs)
{
  tree lhs = gimple_assign_lhs (stmt);
  basic_block bb;

  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "-------------------------\n");
      print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
    }

  if (!is_gimple_reg_type (TREE_TYPE (lhs)))
    return false;

  /* Some of these constrains might be too conservative.  */
  if (stmt_ends_bb_p (stmt)
      || gimple_has_volatile_ops (stmt)
      || (TREE_CODE (lhs) == SSA_NAME
          && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs))
      || gimple_has_side_effects (stmt))
    {
      if (dump_file && (dump_flags & TDF_DETAILS))
        fprintf (dump_file, "stmt not suitable for ifcvt\n");
      return false;
    }

  if (flag_tree_loop_if_convert_stores)
    {
      if (ifcvt_could_trap_p (stmt, refs))
	{
	  if (dump_file && (dump_flags & TDF_DETAILS))
	    fprintf (dump_file, "tree could trap...\n");
	  return false;
	}
      return true;
    }

  if (gimple_assign_rhs_could_trap_p (stmt))
    {
      if (dump_file && (dump_flags & TDF_DETAILS))
	fprintf (dump_file, "tree could trap...\n");
      return false;
    }

  bb = gimple_bb (stmt);

  if (TREE_CODE (lhs) != SSA_NAME
      && bb != bb->loop_father->header
      && !bb_with_exit_edge_p (bb->loop_father, bb))
    {
      if (dump_file && (dump_flags & TDF_DETAILS))
	{
	  fprintf (dump_file, "LHS is not var\n");
	  print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
	}
      return false;
    }

  return true;
}

/* Return true when STMT is if-convertible.

   A statement is if-convertible if:
   - it is an if-convertible GIMPLE_ASSIGN,
   - it is a GIMPLE_LABEL or a GIMPLE_COND.  */

static bool
if_convertible_stmt_p (gimple stmt, VEC (data_reference_p, heap) *refs)
{
  switch (gimple_code (stmt))
    {
    case GIMPLE_LABEL:
    case GIMPLE_DEBUG:
    case GIMPLE_COND:
      return true;

    case GIMPLE_ASSIGN:
      return if_convertible_gimple_assign_stmt_p (stmt, refs);

    case GIMPLE_CALL:
      {
	tree fndecl = gimple_call_fndecl (stmt);
	if (fndecl)
	  {
	    int flags = gimple_call_flags (stmt);
	    if ((flags & ECF_CONST)
		&& !(flags & ECF_LOOPING_CONST_OR_PURE)
		/* We can only vectorize some builtins at the moment,
		   so restrict if-conversion to those.  */
		&& DECL_BUILT_IN (fndecl))
	      return true;
	  }
	return false;
      }

    default:
      /* Don't know what to do with 'em so don't do anything.  */
      if (dump_file && (dump_flags & TDF_DETAILS))
	{
	  fprintf (dump_file, "don't know what to do\n");
	  print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
	}
      return false;
      break;
    }

  return true;
}

/* Return true when BB post-dominates all its predecessors.  */

static bool
bb_postdominates_preds (basic_block bb)
{
  unsigned i;

  for (i = 0; i < EDGE_COUNT (bb->preds); i++)
    if (!dominated_by_p (CDI_POST_DOMINATORS, EDGE_PRED (bb, i)->src, bb))
      return false;

  return true;
}

/* Return true when BB is if-convertible.  This routine does not check
   basic block's statements and phis.

   A basic block is not if-convertible if:
   - it is non-empty and it is after the exit block (in BFS order),
   - it is after the exit block but before the latch,
   - its edges are not normal.

   EXIT_BB is the basic block containing the exit of the LOOP.  BB is
   inside LOOP.  */

static bool
if_convertible_bb_p (struct loop *loop, basic_block bb, basic_block exit_bb)
{
  edge e;
  edge_iterator ei;

  if (dump_file && (dump_flags & TDF_DETAILS))
    fprintf (dump_file, "----------[%d]-------------\n", bb->index);

  if (EDGE_COUNT (bb->preds) > 2
      || EDGE_COUNT (bb->succs) > 2)
    return false;

  if (exit_bb)
    {
      if (bb != loop->latch)
	{
	  if (dump_file && (dump_flags & TDF_DETAILS))
	    fprintf (dump_file, "basic block after exit bb but before latch\n");
	  return false;
	}
      else if (!empty_block_p (bb))
	{
	  if (dump_file && (dump_flags & TDF_DETAILS))
	    fprintf (dump_file, "non empty basic block after exit bb\n");
	  return false;
	}
      else if (bb == loop->latch
	       && bb != exit_bb
	       && !dominated_by_p (CDI_DOMINATORS, bb, exit_bb))
	  {
	    if (dump_file && (dump_flags & TDF_DETAILS))
	      fprintf (dump_file, "latch is not dominated by exit_block\n");
	    return false;
	  }
    }

  /* Be less adventurous and handle only normal edges.  */
  FOR_EACH_EDGE (e, ei, bb->succs)
    if (e->flags &
	(EDGE_ABNORMAL_CALL | EDGE_EH | EDGE_ABNORMAL | EDGE_IRREDUCIBLE_LOOP))
      {
	if (dump_file && (dump_flags & TDF_DETAILS))
	  fprintf (dump_file, "Difficult to handle edges\n");
	return false;
      }

  if (EDGE_COUNT (bb->preds) == 2
      && bb != loop->header
      && !bb_postdominates_preds (bb))
    return false;

  return true;
}

/* Return true when all predecessor blocks of BB are visited.  The
   VISITED bitmap keeps track of the visited blocks.  */

static bool
pred_blocks_visited_p (basic_block bb, bitmap *visited)
{
  edge e;
  edge_iterator ei;
  FOR_EACH_EDGE (e, ei, bb->preds)
    if (!bitmap_bit_p (*visited, e->src->index))
      return false;

  return true;
}

/* Get body of a LOOP in suitable order for if-conversion.  It is
   caller's responsibility to deallocate basic block list.
   If-conversion suitable order is, breadth first sort (BFS) order
   with an additional constraint: select a block only if all its
   predecessors are already selected.  */

static basic_block *
get_loop_body_in_if_conv_order (const struct loop *loop)
{
  basic_block *blocks, *blocks_in_bfs_order;
  basic_block bb;
  bitmap visited;
  unsigned int index = 0;
  unsigned int visited_count = 0;

  gcc_assert (loop->num_nodes);
  gcc_assert (loop->latch != EXIT_BLOCK_PTR);

  blocks = XCNEWVEC (basic_block, loop->num_nodes);
  visited = BITMAP_ALLOC (NULL);

  blocks_in_bfs_order = get_loop_body_in_bfs_order (loop);

  index = 0;
  while (index < loop->num_nodes)
    {
      bb = blocks_in_bfs_order [index];

      if (bb->flags & BB_IRREDUCIBLE_LOOP)
	{
	  free (blocks_in_bfs_order);
	  BITMAP_FREE (visited);
	  free (blocks);
	  return NULL;
	}

      if (!bitmap_bit_p (visited, bb->index))
	{
	  if (pred_blocks_visited_p (bb, &visited)
	      || bb == loop->header)
	    {
	      /* This block is now visited.  */
	      bitmap_set_bit (visited, bb->index);
	      blocks[visited_count++] = bb;
	    }
	}

      index++;

      if (index == loop->num_nodes
	  && visited_count != loop->num_nodes)
	/* Not done yet.  */
	index = 0;
    }
  free (blocks_in_bfs_order);
  BITMAP_FREE (visited);
  return blocks;
}

/* Returns true when the analysis of the predicates for all the basic
   blocks in LOOP succeeded.

   predicate_bbs first allocates the predicates of the basic blocks.
   These fields are then initialized with the tree expressions
   representing the predicates under which a basic block is executed
   in the LOOP.  As the loop->header is executed at each iteration, it
   has the "true" predicate.  Other statements executed under a
   condition are predicated with that condition, for example

   | if (x)
   |   S1;
   | else
   |   S2;

   S1 will be predicated with "x", and
   S2 will be predicated with "!x".  */

static bool
predicate_bbs (loop_p loop)
{
  unsigned int i;

  for (i = 0; i < loop->num_nodes; i++)
    init_bb_predicate (ifc_bbs[i]);

  for (i = 0; i < loop->num_nodes; i++)
    {
      basic_block bb = ifc_bbs[i];
      tree cond;
      gimple_stmt_iterator itr;

      /* The loop latch is always executed and has no extra conditions
	 to be processed: skip it.  */
      if (bb == loop->latch)
	{
	  reset_bb_predicate (loop->latch);
	  continue;
	}

      cond = bb_predicate (bb);

      for (itr = gsi_start_bb (bb); !gsi_end_p (itr); gsi_next (&itr))
	{
	  gimple stmt = gsi_stmt (itr);

	  switch (gimple_code (stmt))
	    {
	    case GIMPLE_LABEL:
	    case GIMPLE_ASSIGN:
	    case GIMPLE_CALL:
	    case GIMPLE_DEBUG:
	      break;

	    case GIMPLE_COND:
	      {
		tree c2;
		edge true_edge, false_edge;
		location_t loc = gimple_location (stmt);
		tree c = fold_build2_loc (loc, gimple_cond_code (stmt),
					  boolean_type_node,
					  gimple_cond_lhs (stmt),
					  gimple_cond_rhs (stmt));

		/* Add new condition into destination's predicate list.  */
		extract_true_false_edges_from_block (gimple_bb (stmt),
						     &true_edge, &false_edge);

		/* If C is true, then TRUE_EDGE is taken.  */
		add_to_dst_predicate_list (loop, true_edge,
					   unshare_expr (cond),
					   unshare_expr (c));

		/* If C is false, then FALSE_EDGE is taken.  */
		c2 = build1_loc (loc, TRUTH_NOT_EXPR,
				 boolean_type_node, unshare_expr (c));
		add_to_dst_predicate_list (loop, false_edge,
					   unshare_expr (cond), c2);

		cond = NULL_TREE;
		break;
	      }

	    default:
	      /* Not handled yet in if-conversion.  */
	      return false;
	    }
	}

      /* If current bb has only one successor, then consider it as an
	 unconditional goto.  */
      if (single_succ_p (bb))
	{
	  basic_block bb_n = single_succ (bb);

	  /* The successor bb inherits the predicate of its
	     predecessor.  If there is no predicate in the predecessor
	     bb, then consider the successor bb as always executed.  */
	  if (cond == NULL_TREE)
	    cond = boolean_true_node;

	  add_to_predicate_list (bb_n, cond);
	}
    }

  /* The loop header is always executed.  */
  reset_bb_predicate (loop->header);
  gcc_assert (bb_predicate_gimplified_stmts (loop->header) == NULL
	      && bb_predicate_gimplified_stmts (loop->latch) == NULL);

  return true;
}

/* Return true when LOOP is if-convertible.  This is a helper function
   for if_convertible_loop_p.  REFS and DDRS are initialized and freed
   in if_convertible_loop_p.  */

static bool
if_convertible_loop_p_1 (struct loop *loop,
			 VEC (loop_p, heap) **loop_nest,
			 VEC (data_reference_p, heap) **refs,
			 VEC (ddr_p, heap) **ddrs)
{
  bool res;
  unsigned int i;
  basic_block exit_bb = NULL;

  /* Don't if-convert the loop when the data dependences cannot be
     computed: the loop won't be vectorized in that case.  */
  res = compute_data_dependences_for_loop (loop, true, loop_nest, refs, ddrs);
  if (!res)
    return false;

  calculate_dominance_info (CDI_DOMINATORS);
  calculate_dominance_info (CDI_POST_DOMINATORS);

  /* Allow statements that can be handled during if-conversion.  */
  ifc_bbs = get_loop_body_in_if_conv_order (loop);
  if (!ifc_bbs)
    {
      if (dump_file && (dump_flags & TDF_DETAILS))
	fprintf (dump_file, "Irreducible loop\n");
      return false;
    }

  for (i = 0; i < loop->num_nodes; i++)
    {
      basic_block bb = ifc_bbs[i];

      if (!if_convertible_bb_p (loop, bb, exit_bb))
	return false;

      if (bb_with_exit_edge_p (loop, bb))
	exit_bb = bb;
    }

  res = predicate_bbs (loop);
  if (!res)
    return false;

  if (flag_tree_loop_if_convert_stores)
    {
      data_reference_p dr;

      for (i = 0; VEC_iterate (data_reference_p, *refs, i, dr); i++)
	{
	  dr->aux = XNEW (struct ifc_dr);
	  DR_WRITTEN_AT_LEAST_ONCE (dr) = -1;
	  DR_RW_UNCONDITIONALLY (dr) = -1;
	}
    }

  for (i = 0; i < loop->num_nodes; i++)
    {
      basic_block bb = ifc_bbs[i];
      gimple_stmt_iterator itr;

      for (itr = gsi_start_phis (bb); !gsi_end_p (itr); gsi_next (&itr))
	if (!if_convertible_phi_p (loop, bb, gsi_stmt (itr)))
	  return false;

      /* Check the if-convertibility of statements in predicated BBs.  */
      if (is_predicated (bb))
	for (itr = gsi_start_bb (bb); !gsi_end_p (itr); gsi_next (&itr))
	  if (!if_convertible_stmt_p (gsi_stmt (itr), *refs))
	    return false;
    }

  if (dump_file)
    fprintf (dump_file, "Applying if-conversion\n");

  return true;
}

/* Return true when LOOP is if-convertible.
   LOOP is if-convertible if:
   - it is innermost,
   - it has two or more basic blocks,
   - it has only one exit,
   - loop header is not the exit edge,
   - if its basic blocks and phi nodes are if convertible.  */

static bool
if_convertible_loop_p (struct loop *loop)
{
  edge e;
  edge_iterator ei;
  bool res = false;
  VEC (data_reference_p, heap) *refs;
  VEC (ddr_p, heap) *ddrs;
  VEC (loop_p, heap) *loop_nest;

  /* Handle only innermost loop.  */
  if (!loop || loop->inner)
    {
      if (dump_file && (dump_flags & TDF_DETAILS))
	fprintf (dump_file, "not innermost loop\n");
      return false;
    }

  /* If only one block, no need for if-conversion.  */
  if (loop->num_nodes <= 2)
    {
      if (dump_file && (dump_flags & TDF_DETAILS))
	fprintf (dump_file, "less than 2 basic blocks\n");
      return false;
    }

  /* More than one loop exit is too much to handle.  */
  if (!single_exit (loop))
    {
      if (dump_file && (dump_flags & TDF_DETAILS))
	fprintf (dump_file, "multiple exits\n");
      return false;
    }

  /* If one of the loop header's edge is an exit edge then do not
     apply if-conversion.  */
  FOR_EACH_EDGE (e, ei, loop->header->succs)
    if (loop_exit_edge_p (loop, e))
      return false;

  refs = VEC_alloc (data_reference_p, heap, 5);
  ddrs = VEC_alloc (ddr_p, heap, 25);
  loop_nest = VEC_alloc (loop_p, heap, 3);
  res = if_convertible_loop_p_1 (loop, &loop_nest, &refs, &ddrs);

  if (flag_tree_loop_if_convert_stores)
    {
      data_reference_p dr;
      unsigned int i;

      for (i = 0; VEC_iterate (data_reference_p, refs, i, dr); i++)
	free (dr->aux);
    }

  VEC_free (loop_p, heap, loop_nest);
  free_data_refs (refs);
  free_dependence_relations (ddrs);
  return res;
}

/* Basic block BB has two predecessors.  Using predecessor's bb
   predicate, set an appropriate condition COND for the PHI node
   replacement.  Return the true block whose phi arguments are
   selected when cond is true.  LOOP is the loop containing the
   if-converted region, GSI is the place to insert the code for the
   if-conversion.  */

static basic_block
find_phi_replacement_condition (struct loop *loop,
				basic_block bb, tree *cond,
				gimple_stmt_iterator *gsi)
{
  edge first_edge, second_edge;
  tree tmp_cond;

  gcc_assert (EDGE_COUNT (bb->preds) == 2);
  first_edge = EDGE_PRED (bb, 0);
  second_edge = EDGE_PRED (bb, 1);

  /* Use condition based on following criteria:
     1)
       S1: x = !c ? a : b;

       S2: x = c ? b : a;

       S2 is preferred over S1. Make 'b' first_bb and use its condition.

     2) Do not make loop header first_bb.

     3)
       S1: x = !(c == d)? a : b;

       S21: t1 = c == d;
       S22: x = t1 ? b : a;

       S3: x = (c == d) ? b : a;

       S3 is preferred over S1 and S2*, Make 'b' first_bb and use
       its condition.

     4) If  pred B is dominated by pred A then use pred B's condition.
        See PR23115.  */

  /* Select condition that is not TRUTH_NOT_EXPR.  */
  tmp_cond = bb_predicate (first_edge->src);
  gcc_assert (tmp_cond);

  if (TREE_CODE (tmp_cond) == TRUTH_NOT_EXPR)
    {
      edge tmp_edge;

      tmp_edge = first_edge;
      first_edge = second_edge;
      second_edge = tmp_edge;
    }

  /* Check if FIRST_BB is loop header or not and make sure that
     FIRST_BB does not dominate SECOND_BB.  */
  if (first_edge->src == loop->header
      || dominated_by_p (CDI_DOMINATORS,
			 second_edge->src, first_edge->src))
    {
      *cond = bb_predicate (second_edge->src);

      if (TREE_CODE (*cond) == TRUTH_NOT_EXPR)
	*cond = TREE_OPERAND (*cond, 0);
      else
	/* Select non loop header bb.  */
	first_edge = second_edge;
    }
  else
    *cond = bb_predicate (first_edge->src);

  /* Gimplify the condition to a valid cond-expr conditonal operand.  */
  *cond = force_gimple_operand_gsi_1 (gsi, unshare_expr (*cond),
				      is_gimple_condexpr, NULL_TREE,
				      true, GSI_SAME_STMT);

  return first_edge->src;
}

/* Replace a scalar PHI node with a COND_EXPR using COND as condition.
   This routine does not handle PHI nodes with more than two
   arguments.

   For example,
     S1: A = PHI <x1(1), x2(5)>
   is converted into,
     S2: A = cond ? x1 : x2;

   The generated code is inserted at GSI that points to the top of
   basic block's statement list.  When COND is true, phi arg from
   TRUE_BB is selected.  */

static void
predicate_scalar_phi (gimple phi, tree cond,
		      basic_block true_bb,
		      gimple_stmt_iterator *gsi)
{
  gimple new_stmt;
  basic_block bb;
  tree rhs, res, arg, scev;

  gcc_assert (gimple_code (phi) == GIMPLE_PHI
	      && gimple_phi_num_args (phi) == 2);

  res = gimple_phi_result (phi);
  /* Do not handle virtual phi nodes.  */
  if (!is_gimple_reg (SSA_NAME_VAR (res)))
    return;

  bb = gimple_bb (phi);

  if ((arg = degenerate_phi_result (phi))
      || ((scev = analyze_scalar_evolution (gimple_bb (phi)->loop_father,
					    res))
	  && !chrec_contains_undetermined (scev)
	  && scev != res
	  && (arg = gimple_phi_arg_def (phi, 0))))
    rhs = arg;
  else
    {
      tree arg_0, arg_1;
      /* Use condition that is not TRUTH_NOT_EXPR in conditional modify expr.  */
      if (EDGE_PRED (bb, 1)->src == true_bb)
	{
	  arg_0 = gimple_phi_arg_def (phi, 1);
	  arg_1 = gimple_phi_arg_def (phi, 0);
	}
      else
	{
	  arg_0 = gimple_phi_arg_def (phi, 0);
	  arg_1 = gimple_phi_arg_def (phi, 1);
	}

      gcc_checking_assert (bb == bb->loop_father->header
			   || bb_postdominates_preds (bb));

      /* Build new RHS using selected condition and arguments.  */
      rhs = build3 (COND_EXPR, TREE_TYPE (res),
		    unshare_expr (cond), arg_0, arg_1);
    }

  new_stmt = gimple_build_assign (res, rhs);
  SSA_NAME_DEF_STMT (gimple_phi_result (phi)) = new_stmt;
  gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
  update_stmt (new_stmt);

  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "new phi replacement stmt\n");
      print_gimple_stmt (dump_file, new_stmt, 0, TDF_SLIM);
    }
}

/* Replaces in LOOP all the scalar phi nodes other than those in the
   LOOP->header block with conditional modify expressions.  */

static void
predicate_all_scalar_phis (struct loop *loop)
{
  basic_block bb;
  unsigned int orig_loop_num_nodes = loop->num_nodes;
  unsigned int i;

  for (i = 1; i < orig_loop_num_nodes; i++)
    {
      gimple phi;
      tree cond = NULL_TREE;
      gimple_stmt_iterator gsi, phi_gsi;
      basic_block true_bb = NULL;
      bb = ifc_bbs[i];

      if (bb == loop->header)
	continue;

      phi_gsi = gsi_start_phis (bb);
      if (gsi_end_p (phi_gsi))
	continue;

      /* BB has two predecessors.  Using predecessor's aux field, set
	 appropriate condition for the PHI node replacement.  */
      gsi = gsi_after_labels (bb);
      true_bb = find_phi_replacement_condition (loop, bb, &cond, &gsi);

      while (!gsi_end_p (phi_gsi))
	{
	  phi = gsi_stmt (phi_gsi);
	  predicate_scalar_phi (phi, cond, true_bb, &gsi);
	  release_phi_node (phi);
	  gsi_next (&phi_gsi);
	}

      set_phi_nodes (bb, NULL);
    }
}

/* Insert in each basic block of LOOP the statements produced by the
   gimplification of the predicates.  */

static void
insert_gimplified_predicates (loop_p loop)
{
  unsigned int i;

  for (i = 0; i < loop->num_nodes; i++)
    {
      basic_block bb = ifc_bbs[i];
      gimple_seq stmts;

      if (!is_predicated (bb))
	{
	  /* Do not insert statements for a basic block that is not
	     predicated.  Also make sure that the predicate of the
	     basic block is set to true.  */
	  reset_bb_predicate (bb);
	  continue;
	}

      stmts = bb_predicate_gimplified_stmts (bb);
      if (stmts)
	{
	  if (flag_tree_loop_if_convert_stores)
	    {
	      /* Insert the predicate of the BB just after the label,
		 as the if-conversion of memory writes will use this
		 predicate.  */
	      gimple_stmt_iterator gsi = gsi_after_labels (bb);
	      gsi_insert_seq_before (&gsi, stmts, GSI_SAME_STMT);
	    }
	  else
	    {
	      /* Insert the predicate of the BB at the end of the BB
		 as this would reduce the register pressure: the only
		 use of this predicate will be in successor BBs.  */
	      gimple_stmt_iterator gsi = gsi_last_bb (bb);

	      if (gsi_end_p (gsi)
		  || stmt_ends_bb_p (gsi_stmt (gsi)))
		gsi_insert_seq_before (&gsi, stmts, GSI_SAME_STMT);
	      else
		gsi_insert_seq_after (&gsi, stmts, GSI_SAME_STMT);
	    }

	  /* Once the sequence is code generated, set it to NULL.  */
	  set_bb_predicate_gimplified_stmts (bb, NULL);
	}
    }
}

/* Predicate each write to memory in LOOP.

   This function transforms control flow constructs containing memory
   writes of the form:

   | for (i = 0; i < N; i++)
   |   if (cond)
   |     A[i] = expr;

   into the following form that does not contain control flow:

   | for (i = 0; i < N; i++)
   |   A[i] = cond ? expr : A[i];

   The original CFG looks like this:

   | bb_0
   |   i = 0
   | end_bb_0
   |
   | bb_1
   |   if (i < N) goto bb_5 else goto bb_2
   | end_bb_1
   |
   | bb_2
   |   cond = some_computation;
   |   if (cond) goto bb_3 else goto bb_4
   | end_bb_2
   |
   | bb_3
   |   A[i] = expr;
   |   goto bb_4
   | end_bb_3
   |
   | bb_4
   |   goto bb_1
   | end_bb_4

   insert_gimplified_predicates inserts the computation of the COND
   expression at the beginning of the destination basic block:

   | bb_0
   |   i = 0
   | end_bb_0
   |
   | bb_1
   |   if (i < N) goto bb_5 else goto bb_2
   | end_bb_1
   |
   | bb_2
   |   cond = some_computation;
   |   if (cond) goto bb_3 else goto bb_4
   | end_bb_2
   |
   | bb_3
   |   cond = some_computation;
   |   A[i] = expr;
   |   goto bb_4
   | end_bb_3
   |
   | bb_4
   |   goto bb_1
   | end_bb_4

   predicate_mem_writes is then predicating the memory write as follows:

   | bb_0
   |   i = 0
   | end_bb_0
   |
   | bb_1
   |   if (i < N) goto bb_5 else goto bb_2
   | end_bb_1
   |
   | bb_2
   |   if (cond) goto bb_3 else goto bb_4
   | end_bb_2
   |
   | bb_3
   |   cond = some_computation;
   |   A[i] = cond ? expr : A[i];
   |   goto bb_4
   | end_bb_3
   |
   | bb_4
   |   goto bb_1
   | end_bb_4

   and finally combine_blocks removes the basic block boundaries making
   the loop vectorizable:

   | bb_0
   |   i = 0
   |   if (i < N) goto bb_5 else goto bb_1
   | end_bb_0
   |
   | bb_1
   |   cond = some_computation;
   |   A[i] = cond ? expr : A[i];
   |   if (i < N) goto bb_5 else goto bb_4
   | end_bb_1
   |
   | bb_4
   |   goto bb_1
   | end_bb_4
*/

static void
predicate_mem_writes (loop_p loop)
{
  unsigned int i, orig_loop_num_nodes = loop->num_nodes;

  for (i = 1; i < orig_loop_num_nodes; i++)
    {
      gimple_stmt_iterator gsi;
      basic_block bb = ifc_bbs[i];
      tree cond = bb_predicate (bb);
      bool swap;
      gimple stmt;

      if (is_true_predicate (cond))
	continue;

      swap = false;
      if (TREE_CODE (cond) == TRUTH_NOT_EXPR)
	{
	  swap = true;
	  cond = TREE_OPERAND (cond, 0);
	}

      for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
	if ((stmt = gsi_stmt (gsi))
	    && gimple_assign_single_p (stmt)
	    && gimple_vdef (stmt))
	  {
	    tree lhs = gimple_assign_lhs (stmt);
	    tree rhs = gimple_assign_rhs1 (stmt);
	    tree type = TREE_TYPE (lhs);

	    lhs = ifc_temp_var (type, unshare_expr (lhs), &gsi);
	    rhs = ifc_temp_var (type, unshare_expr (rhs), &gsi);
	    if (swap)
	      {
		tree tem = lhs;
		lhs = rhs;
		rhs = tem;
	      }
	    cond = force_gimple_operand_gsi_1 (&gsi, unshare_expr (cond),
					       is_gimple_condexpr, NULL_TREE,
					       true, GSI_SAME_STMT);
	    rhs = build3 (COND_EXPR, type, unshare_expr (cond), rhs, lhs);
	    gimple_assign_set_rhs1 (stmt, ifc_temp_var (type, rhs, &gsi));
	    update_stmt (stmt);
	  }
    }
}

/* Remove all GIMPLE_CONDs and GIMPLE_LABELs of all the basic blocks
   other than the exit and latch of the LOOP.  Also resets the
   GIMPLE_DEBUG information.  */

static void
remove_conditions_and_labels (loop_p loop)
{
  gimple_stmt_iterator gsi;
  unsigned int i;

  for (i = 0; i < loop->num_nodes; i++)
    {
      basic_block bb = ifc_bbs[i];

      if (bb_with_exit_edge_p (loop, bb)
        || bb == loop->latch)
      continue;

      for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
	switch (gimple_code (gsi_stmt (gsi)))
	  {
	  case GIMPLE_COND:
	  case GIMPLE_LABEL:
	    gsi_remove (&gsi, true);
	    break;

	  case GIMPLE_DEBUG:
	    /* ??? Should there be conditional GIMPLE_DEBUG_BINDs?  */
	    if (gimple_debug_bind_p (gsi_stmt (gsi)))
	      {
		gimple_debug_bind_reset_value (gsi_stmt (gsi));
		update_stmt (gsi_stmt (gsi));
	      }
	    gsi_next (&gsi);
	    break;

	  default:
	    gsi_next (&gsi);
	  }
    }
}

/* Combine all the basic blocks from LOOP into one or two super basic
   blocks.  Replace PHI nodes with conditional modify expressions.  */

static void
combine_blocks (struct loop *loop)
{
  basic_block bb, exit_bb, merge_target_bb;
  unsigned int orig_loop_num_nodes = loop->num_nodes;
  unsigned int i;
  edge e;
  edge_iterator ei;

  remove_conditions_and_labels (loop);
  insert_gimplified_predicates (loop);
  predicate_all_scalar_phis (loop);

  if (flag_tree_loop_if_convert_stores)
    predicate_mem_writes (loop);

  /* Merge basic blocks: first remove all the edges in the loop,
     except for those from the exit block.  */
  exit_bb = NULL;
  for (i = 0; i < orig_loop_num_nodes; i++)
    {
      bb = ifc_bbs[i];
      free_bb_predicate (bb);
      if (bb_with_exit_edge_p (loop, bb))
	{
	  gcc_assert (exit_bb == NULL);
	  exit_bb = bb;
	}
    }
  gcc_assert (exit_bb != loop->latch);

  for (i = 1; i < orig_loop_num_nodes; i++)
    {
      bb = ifc_bbs[i];

      for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei));)
	{
	  if (e->src == exit_bb)
	    ei_next (&ei);
	  else
	    remove_edge (e);
	}
    }

  if (exit_bb != NULL)
    {
      if (exit_bb != loop->header)
	{
	  /* Connect this node to loop header.  */
	  make_edge (loop->header, exit_bb, EDGE_FALLTHRU);
	  set_immediate_dominator (CDI_DOMINATORS, exit_bb, loop->header);
	}

      /* Redirect non-exit edges to loop->latch.  */
      FOR_EACH_EDGE (e, ei, exit_bb->succs)
	{
	  if (!loop_exit_edge_p (loop, e))
	    redirect_edge_and_branch (e, loop->latch);
	}
      set_immediate_dominator (CDI_DOMINATORS, loop->latch, exit_bb);
    }
  else
    {
      /* If the loop does not have an exit, reconnect header and latch.  */
      make_edge (loop->header, loop->latch, EDGE_FALLTHRU);
      set_immediate_dominator (CDI_DOMINATORS, loop->latch, loop->header);
    }

  merge_target_bb = loop->header;
  for (i = 1; i < orig_loop_num_nodes; i++)
    {
      gimple_stmt_iterator gsi;
      gimple_stmt_iterator last;

      bb = ifc_bbs[i];

      if (bb == exit_bb || bb == loop->latch)
	continue;

      /* Make stmts member of loop->header.  */
      for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
	gimple_set_bb (gsi_stmt (gsi), merge_target_bb);

      /* Update stmt list.  */
      last = gsi_last_bb (merge_target_bb);
      gsi_insert_seq_after (&last, bb_seq (bb), GSI_NEW_STMT);
      set_bb_seq (bb, NULL);

      delete_basic_block (bb);
    }

  /* If possible, merge loop header to the block with the exit edge.
     This reduces the number of basic blocks to two, to please the
     vectorizer that handles only loops with two nodes.  */
  if (exit_bb
      && exit_bb != loop->header
      && can_merge_blocks_p (loop->header, exit_bb))
    merge_blocks (loop->header, exit_bb);

  free (ifc_bbs);
  ifc_bbs = NULL;

  /* Post-dominators are corrupt now.  */
  free_dominance_info (CDI_POST_DOMINATORS);
}

/* If-convert LOOP when it is legal.  For the moment this pass has no
   profitability analysis.  Returns true when something changed.  */

static bool
tree_if_conversion (struct loop *loop)
{
  bool changed = false;
  ifc_bbs = NULL;

  if (!if_convertible_loop_p (loop)
      || !dbg_cnt (if_conversion_tree))
    goto cleanup;

  /* Now all statements are if-convertible.  Combine all the basic
     blocks into one huge basic block doing the if-conversion
     on-the-fly.  */
  combine_blocks (loop);

  if (flag_tree_loop_if_convert_stores)
    mark_sym_for_renaming (gimple_vop (cfun));

  changed = true;

 cleanup:
  if (ifc_bbs)
    {
      unsigned int i;

      for (i = 0; i < loop->num_nodes; i++)
	free_bb_predicate (ifc_bbs[i]);

      free (ifc_bbs);
      ifc_bbs = NULL;
    }

  return changed;
}

/* Tree if-conversion pass management.  */

static unsigned int
main_tree_if_conversion (void)
{
  loop_iterator li;
  struct loop *loop;
  bool changed = false;
  unsigned todo = 0;

  if (number_of_loops () <= 1)
    return 0;

  FOR_EACH_LOOP (li, loop, 0)
    changed |= tree_if_conversion (loop);

  if (changed)
    todo |= TODO_cleanup_cfg;

  if (changed && flag_tree_loop_if_convert_stores)
    todo |= TODO_update_ssa_only_virtuals;

  free_dominance_info (CDI_POST_DOMINATORS);

#ifdef ENABLE_CHECKING
  {
    basic_block bb;
    FOR_EACH_BB (bb)
      gcc_assert (!bb->aux);
  }
#endif

  return todo;
}

/* Returns true when the if-conversion pass is enabled.  */

static bool
gate_tree_if_conversion (void)
{
  return ((flag_tree_vectorize && flag_tree_loop_if_convert != 0)
	  || flag_tree_loop_if_convert == 1
	  || flag_tree_loop_if_convert_stores == 1);
}

struct gimple_opt_pass pass_if_conversion =
{
 {
  GIMPLE_PASS,
  "ifcvt",				/* name */
  gate_tree_if_conversion,		/* gate */
  main_tree_if_conversion,		/* execute */
  NULL,					/* sub */
  NULL,					/* next */
  0,					/* static_pass_number */
  TV_NONE,				/* tv_id */
  PROP_cfg | PROP_ssa,			/* properties_required */
  0,					/* properties_provided */
  0,					/* properties_destroyed */
  0,					/* todo_flags_start */
  TODO_verify_stmts | TODO_verify_flow
                                        /* todo_flags_finish */
 }
};