summaryrefslogtreecommitdiff
path: root/gcc/tree-ssa-uninit.c
blob: c4bf08fc669c934539c4d14834499c687a8ef8ed (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
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
/* Predicate aware uninitialized variable warning.
   Copyright (C) 2001-2015 Free Software Foundation, Inc.
   Contributed by Xinliang David Li <davidxl@google.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 "flags.h"
#include "tm_p.h"
#include "predict.h"
#include "vec.h"
#include "hashtab.h"
#include "hash-set.h"
#include "machmode.h"
#include "hard-reg-set.h"
#include "input.h"
#include "function.h"
#include "dominance.h"
#include "cfg.h"
#include "basic-block.h"
#include "gimple-pretty-print.h"
#include "bitmap.h"
#include "tree-ssa-alias.h"
#include "internal-fn.h"
#include "gimple-expr.h"
#include "is-a.h"
#include "gimple.h"
#include "gimple-iterator.h"
#include "gimple-ssa.h"
#include "tree-phinodes.h"
#include "ssa-iterators.h"
#include "tree-ssa.h"
#include "tree-inline.h"
#include "tree-pass.h"
#include "diagnostic-core.h"
#include "params.h"

/* This implements the pass that does predicate aware warning on uses of
   possibly uninitialized variables. The pass first collects the set of
   possibly uninitialized SSA names. For each such name, it walks through
   all its immediate uses. For each immediate use, it rebuilds the condition
   expression (the predicate) that guards the use. The predicate is then
   examined to see if the variable is always defined under that same condition.
   This is done either by pruning the unrealizable paths that lead to the
   default definitions or by checking if the predicate set that guards the
   defining paths is a superset of the use predicate.  */


/* Pointer set of potentially undefined ssa names, i.e.,
   ssa names that are defined by phi with operands that
   are not defined or potentially undefined.  */
static hash_set<tree> *possibly_undefined_names = 0;

/* Bit mask handling macros.  */
#define MASK_SET_BIT(mask, pos) mask |= (1 << pos)
#define MASK_TEST_BIT(mask, pos) (mask & (1 << pos))
#define MASK_EMPTY(mask) (mask == 0)

/* Returns the first bit position (starting from LSB)
   in mask that is non zero. Returns -1 if the mask is empty.  */
static int
get_mask_first_set_bit (unsigned mask)
{
  int pos = 0;
  if (mask == 0)
    return -1;

  while ((mask & (1 << pos)) == 0)
    pos++;

  return pos;
}
#define MASK_FIRST_SET_BIT(mask) get_mask_first_set_bit (mask)

/* Return true if T, an SSA_NAME, has an undefined value.  */
static bool
has_undefined_value_p (tree t)
{
  return (ssa_undefined_value_p (t)
          || (possibly_undefined_names
              && possibly_undefined_names->contains (t)));
}



/* Like has_undefined_value_p, but don't return true if TREE_NO_WARNING
   is set on SSA_NAME_VAR.  */

static inline bool
uninit_undefined_value_p (tree t) {
  if (!has_undefined_value_p (t))
    return false;
  if (SSA_NAME_VAR (t) && TREE_NO_WARNING (SSA_NAME_VAR (t)))
    return false;
  return true;
}

/* Emit warnings for uninitialized variables.  This is done in two passes.

   The first pass notices real uses of SSA names with undefined values.
   Such uses are unconditionally uninitialized, and we can be certain that
   such a use is a mistake.  This pass is run before most optimizations,
   so that we catch as many as we can.

   The second pass follows PHI nodes to find uses that are potentially
   uninitialized.  In this case we can't necessarily prove that the use
   is really uninitialized.  This pass is run after most optimizations,
   so that we thread as many jumps and possible, and delete as much dead
   code as possible, in order to reduce false positives.  We also look
   again for plain uninitialized variables, since optimization may have
   changed conditionally uninitialized to unconditionally uninitialized.  */

/* Emit a warning for EXPR based on variable VAR at the point in the
   program T, an SSA_NAME, is used being uninitialized.  The exact
   warning text is in MSGID and DATA is the gimple stmt with info about
   the location in source code. When DATA is a GIMPLE_PHI, PHIARG_IDX
   gives which argument of the phi node to take the location from.  WC
   is the warning code.  */

static void
warn_uninit (enum opt_code wc, tree t, tree expr, tree var,
	     const char *gmsgid, void *data, location_t phiarg_loc)
{
  gimple context = (gimple) data;
  location_t location, cfun_loc;
  expanded_location xloc, floc;

  /* Ignore COMPLEX_EXPR as initializing only a part of a complex
     turns in a COMPLEX_EXPR with the not initialized part being
     set to its previous (undefined) value.  */
  if (is_gimple_assign (context)
      && gimple_assign_rhs_code (context) == COMPLEX_EXPR)
    return;
  if (!has_undefined_value_p (t))
    return;

  /* TREE_NO_WARNING either means we already warned, or the front end
     wishes to suppress the warning.  */
  if ((context
       && (gimple_no_warning_p (context)
	   || (gimple_assign_single_p (context)
	       && TREE_NO_WARNING (gimple_assign_rhs1 (context)))))
      || TREE_NO_WARNING (expr))
    return;

  if (context != NULL && gimple_has_location (context))
    location = gimple_location (context);
  else if (phiarg_loc != UNKNOWN_LOCATION)
    location = phiarg_loc;
  else
    location = DECL_SOURCE_LOCATION (var);
  location = linemap_resolve_location (line_table, location,
				       LRK_SPELLING_LOCATION,
				       NULL);
  cfun_loc = DECL_SOURCE_LOCATION (cfun->decl);
  xloc = expand_location (location);
  floc = expand_location (cfun_loc);
  if (warning_at (location, wc, gmsgid, expr))
    {
      TREE_NO_WARNING (expr) = 1;

      if (location == DECL_SOURCE_LOCATION (var))
	return;
      if (xloc.file != floc.file
	  || linemap_location_before_p (line_table,
					location, cfun_loc)
	  || linemap_location_before_p (line_table,
					cfun->function_end_locus,
					location))
	inform (DECL_SOURCE_LOCATION (var), "%qD was declared here", var);
    }
}

static unsigned int
warn_uninitialized_vars (bool warn_possibly_uninitialized)
{
  gimple_stmt_iterator gsi;
  basic_block bb;

  FOR_EACH_BB_FN (bb, cfun)
    {
      bool always_executed = dominated_by_p (CDI_POST_DOMINATORS,
					     single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun)), bb);
      for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
	{
	  gimple stmt = gsi_stmt (gsi);
	  use_operand_p use_p;
	  ssa_op_iter op_iter;
	  tree use;

	  if (is_gimple_debug (stmt))
	    continue;

	  /* We only do data flow with SSA_NAMEs, so that's all we
	     can warn about.  */
	  FOR_EACH_SSA_USE_OPERAND (use_p, stmt, op_iter, SSA_OP_USE)
	    {
	      use = USE_FROM_PTR (use_p);
	      if (always_executed)
		warn_uninit (OPT_Wuninitialized, use,
			     SSA_NAME_VAR (use), SSA_NAME_VAR (use),
			     "%qD is used uninitialized in this function",
			     stmt, UNKNOWN_LOCATION);
	      else if (warn_possibly_uninitialized)
		warn_uninit (OPT_Wmaybe_uninitialized, use,
			     SSA_NAME_VAR (use), SSA_NAME_VAR (use),
			     "%qD may be used uninitialized in this function",
			     stmt, UNKNOWN_LOCATION);
	    }

	  /* For memory the only cheap thing we can do is see if we
	     have a use of the default def of the virtual operand.
	     ???  Not so cheap would be to use the alias oracle via
	     walk_aliased_vdefs, if we don't find any aliasing vdef
	     warn as is-used-uninitialized, if we don't find an aliasing
	     vdef that kills our use (stmt_kills_ref_p), warn as
	     may-be-used-uninitialized.  But this walk is quadratic and
	     so must be limited which means we would miss warning
	     opportunities.  */
	  use = gimple_vuse (stmt);
	  if (use
	      && gimple_assign_single_p (stmt)
	      && !gimple_vdef (stmt)
	      && SSA_NAME_IS_DEFAULT_DEF (use))
	    {
	      tree rhs = gimple_assign_rhs1 (stmt);
	      tree base = get_base_address (rhs);

	      /* Do not warn if it can be initialized outside this function.  */
	      if (TREE_CODE (base) != VAR_DECL
		  || DECL_HARD_REGISTER (base)
		  || is_global_var (base))
		continue;

	      if (always_executed)
		warn_uninit (OPT_Wuninitialized, use,
			     gimple_assign_rhs1 (stmt), base,
			     "%qE is used uninitialized in this function",
			     stmt, UNKNOWN_LOCATION);
	      else if (warn_possibly_uninitialized)
		warn_uninit (OPT_Wmaybe_uninitialized, use,
			     gimple_assign_rhs1 (stmt), base,
			     "%qE may be used uninitialized in this function",
			     stmt, UNKNOWN_LOCATION);
	    }
	}
    }

  return 0;
}

/* Checks if the operand OPND of PHI is defined by
   another phi with one operand defined by this PHI,
   but the rest operands are all defined. If yes,
   returns true to skip this this operand as being
   redundant. Can be enhanced to be more general.  */

static bool
can_skip_redundant_opnd (tree opnd, gimple phi)
{
  gimple op_def;
  tree phi_def;
  int i, n;

  phi_def = gimple_phi_result (phi);
  op_def = SSA_NAME_DEF_STMT (opnd);
  if (gimple_code (op_def) != GIMPLE_PHI)
    return false;
  n = gimple_phi_num_args (op_def);
  for (i = 0; i < n; ++i)
    {
      tree op = gimple_phi_arg_def (op_def, i);
      if (TREE_CODE (op) != SSA_NAME)
        continue;
      if (op != phi_def && uninit_undefined_value_p (op))
        return false;
    }

  return true;
}

/* Returns a bit mask holding the positions of arguments in PHI
   that have empty (or possibly empty) definitions.  */

static unsigned
compute_uninit_opnds_pos (gphi *phi)
{
  size_t i, n;
  unsigned uninit_opnds = 0;

  n = gimple_phi_num_args (phi);
  /* Bail out for phi with too many args.  */
  if (n > 32)
    return 0;

  for (i = 0; i < n; ++i)
    {
      tree op = gimple_phi_arg_def (phi, i);
      if (TREE_CODE (op) == SSA_NAME
          && uninit_undefined_value_p (op)
          && !can_skip_redundant_opnd (op, phi))
	{
          if (cfun->has_nonlocal_label || cfun->calls_setjmp)
	    {
	      /* Ignore SSA_NAMEs that appear on abnormal edges
		 somewhere.  */
	      if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op))
		continue;
	    }
	  MASK_SET_BIT (uninit_opnds, i);
	}
    }
  return uninit_opnds;
}

/* Find the immediate postdominator PDOM of the specified
   basic block BLOCK.  */

static inline basic_block
find_pdom (basic_block block)
{
   if (block == EXIT_BLOCK_PTR_FOR_FN (cfun))
     return EXIT_BLOCK_PTR_FOR_FN (cfun);
   else
     {
       basic_block bb
           = get_immediate_dominator (CDI_POST_DOMINATORS, block);
       if (! bb)
	 return EXIT_BLOCK_PTR_FOR_FN (cfun);
       return bb;
     }
}

/* Find the immediate DOM of the specified
   basic block BLOCK.  */

static inline basic_block
find_dom (basic_block block)
{
   if (block == ENTRY_BLOCK_PTR_FOR_FN (cfun))
     return ENTRY_BLOCK_PTR_FOR_FN (cfun);
   else
     {
       basic_block bb = get_immediate_dominator (CDI_DOMINATORS, block);
       if (! bb)
	 return ENTRY_BLOCK_PTR_FOR_FN (cfun);
       return bb;
     }
}

/* Returns true if BB1 is postdominating BB2 and BB1 is
   not a loop exit bb. The loop exit bb check is simple and does
   not cover all cases.  */

static bool
is_non_loop_exit_postdominating (basic_block bb1, basic_block bb2)
{
  if (!dominated_by_p (CDI_POST_DOMINATORS, bb2, bb1))
    return false;

  if (single_pred_p (bb1) && !single_succ_p (bb2))
    return false;

  return true;
}

/* Find the closest postdominator of a specified BB, which is control
   equivalent to BB.  */

static inline  basic_block
find_control_equiv_block (basic_block bb)
{
  basic_block pdom;

  pdom = find_pdom (bb);

  /* Skip the postdominating bb that is also loop exit.  */
  if (!is_non_loop_exit_postdominating (pdom, bb))
    return NULL;

  if (dominated_by_p (CDI_DOMINATORS, pdom, bb))
    return pdom;

  return NULL;
}

#define MAX_NUM_CHAINS 8
#define MAX_CHAIN_LEN 5
#define MAX_POSTDOM_CHECK 8

/* Computes the control dependence chains (paths of edges)
   for DEP_BB up to the dominating basic block BB (the head node of a
   chain should be dominated by it).  CD_CHAINS is pointer to an
   array holding the result chains.  CUR_CD_CHAIN is the current
   chain being computed.  *NUM_CHAINS is total number of chains.  The
   function returns true if the information is successfully computed,
   return false if there is no control dependence or not computed.  */

static bool
compute_control_dep_chain (basic_block bb, basic_block dep_bb,
                           vec<edge> *cd_chains,
                           size_t *num_chains,
			   vec<edge> *cur_cd_chain,
			   int *num_calls)
{
  edge_iterator ei;
  edge e;
  size_t i;
  bool found_cd_chain = false;
  size_t cur_chain_len = 0;

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

  if (*num_calls > PARAM_VALUE (PARAM_UNINIT_CONTROL_DEP_ATTEMPTS))
    return false;
  ++*num_calls;

  /* Could use a set instead.  */
  cur_chain_len = cur_cd_chain->length ();
  if (cur_chain_len > MAX_CHAIN_LEN)
    return false;

  for (i = 0; i < cur_chain_len; i++)
    {
      edge e = (*cur_cd_chain)[i];
      /* Cycle detected. */
      if (e->src == bb)
        return false;
    }

  FOR_EACH_EDGE (e, ei, bb->succs)
    {
      basic_block cd_bb;
      int post_dom_check = 0;
      if (e->flags & (EDGE_FAKE | EDGE_ABNORMAL))
        continue;

      cd_bb = e->dest;
      cur_cd_chain->safe_push (e);
      while (!is_non_loop_exit_postdominating (cd_bb, bb))
        {
          if (cd_bb == dep_bb)
            {
              /* Found a direct control dependence.  */
              if (*num_chains < MAX_NUM_CHAINS)
                {
                  cd_chains[*num_chains] = cur_cd_chain->copy ();
                  (*num_chains)++;
                }
              found_cd_chain = true;
              /* Check path from next edge.  */
              break;
            }

          /* Now check if DEP_BB is indirectly control dependent on BB.  */
          if (compute_control_dep_chain (cd_bb, dep_bb, cd_chains,
					 num_chains, cur_cd_chain, num_calls))
            {
              found_cd_chain = true;
              break;
            }

          cd_bb = find_pdom (cd_bb);
          post_dom_check++;
	  if (cd_bb == EXIT_BLOCK_PTR_FOR_FN (cfun) || post_dom_check >
	      MAX_POSTDOM_CHECK)
            break;
        }
      cur_cd_chain->pop ();
      gcc_assert (cur_cd_chain->length () == cur_chain_len);
    }
  gcc_assert (cur_cd_chain->length () == cur_chain_len);

  return found_cd_chain;
}

/* The type to represent a simple predicate  */

typedef struct use_def_pred_info
{
  tree pred_lhs;
  tree pred_rhs;
  enum tree_code cond_code;
  bool invert;
} pred_info;

/* The type to represent a sequence of predicates grouped
  with .AND. operation.  */

typedef vec<pred_info, va_heap, vl_ptr> pred_chain;

/* The type to represent a sequence of pred_chains grouped
  with .OR. operation.  */

typedef vec<pred_chain, va_heap, vl_ptr> pred_chain_union;

/* Converts the chains of control dependence edges into a set of
   predicates. A control dependence chain is represented by a vector
   edges. DEP_CHAINS points to an array of dependence chains.
   NUM_CHAINS is the size of the chain array. One edge in a dependence
   chain is mapped to predicate expression represented by pred_info
   type. One dependence chain is converted to a composite predicate that
   is the result of AND operation of pred_info mapped to each edge.
   A composite predicate is presented by a vector of pred_info. On
   return, *PREDS points to the resulting array of composite predicates.
   *NUM_PREDS is the number of composite predictes.  */

static bool
convert_control_dep_chain_into_preds (vec<edge> *dep_chains,
                                      size_t num_chains,
                                      pred_chain_union *preds)
{
  bool has_valid_pred = false;
  size_t i, j;
  if (num_chains == 0 || num_chains >= MAX_NUM_CHAINS)
    return false;

  /* Now convert the control dep chain into a set
     of predicates.  */
  preds->reserve (num_chains);

  for (i = 0; i < num_chains; i++)
    {
      vec<edge> one_cd_chain = dep_chains[i];

      has_valid_pred = false;
      pred_chain t_chain = vNULL;
      for (j = 0; j < one_cd_chain.length (); j++)
        {
          gimple cond_stmt;
          gimple_stmt_iterator gsi;
          basic_block guard_bb;
          pred_info one_pred;
          edge e;

          e = one_cd_chain[j];
          guard_bb = e->src;
          gsi = gsi_last_bb (guard_bb);
          if (gsi_end_p (gsi))
            {
              has_valid_pred = false;
              break;
            }
          cond_stmt = gsi_stmt (gsi);
          if (is_gimple_call (cond_stmt)
              && EDGE_COUNT (e->src->succs) >= 2)
            {
              /* Ignore EH edge. Can add assertion
                 on the other edge's flag.  */
              continue;
            }
          /* Skip if there is essentially one succesor.  */
          if (EDGE_COUNT (e->src->succs) == 2)
            {
              edge e1;
              edge_iterator ei1;
              bool skip = false;

              FOR_EACH_EDGE (e1, ei1, e->src->succs)
                {
                  if (EDGE_COUNT (e1->dest->succs) == 0)
                    {
                      skip = true;
                      break;
                    }
                }
              if (skip)
                continue;
            }
          if (gimple_code (cond_stmt) != GIMPLE_COND)
            {
              has_valid_pred = false;
              break;
            }
          one_pred.pred_lhs = gimple_cond_lhs (cond_stmt);
          one_pred.pred_rhs = gimple_cond_rhs (cond_stmt);
          one_pred.cond_code = gimple_cond_code (cond_stmt);
          one_pred.invert = !!(e->flags & EDGE_FALSE_VALUE);
          t_chain.safe_push (one_pred);
	  has_valid_pred = true;
        }

      if (!has_valid_pred)
        break;
      else
        preds->safe_push (t_chain);
    }
  return has_valid_pred;
}

/* Computes all control dependence chains for USE_BB. The control
   dependence chains are then converted to an array of composite
   predicates pointed to by PREDS.  PHI_BB is the basic block of
   the phi whose result is used in USE_BB.  */

static bool
find_predicates (pred_chain_union *preds,
                 basic_block phi_bb,
                 basic_block use_bb)
{
  size_t num_chains = 0, i;
  int num_calls = 0;
  vec<edge> dep_chains[MAX_NUM_CHAINS];
  auto_vec<edge, MAX_CHAIN_LEN + 1> cur_chain;
  bool has_valid_pred = false;
  basic_block cd_root = 0;

  /* First find the closest bb that is control equivalent to PHI_BB
     that also dominates USE_BB.  */
  cd_root = phi_bb;
  while (dominated_by_p (CDI_DOMINATORS, use_bb, cd_root))
    {
      basic_block ctrl_eq_bb = find_control_equiv_block (cd_root);
      if (ctrl_eq_bb && dominated_by_p (CDI_DOMINATORS, use_bb, ctrl_eq_bb))
        cd_root = ctrl_eq_bb;
      else
        break;
    }

  compute_control_dep_chain (cd_root, use_bb, dep_chains, &num_chains,
			     &cur_chain, &num_calls);

  has_valid_pred
    = convert_control_dep_chain_into_preds (dep_chains, num_chains, preds);
  for (i = 0; i < num_chains; i++)
    dep_chains[i].release ();
  return has_valid_pred;
}

/* Computes the set of incoming edges of PHI that have non empty
   definitions of a phi chain.  The collection will be done
   recursively on operands that are defined by phis. CD_ROOT
   is the control dependence root. *EDGES holds the result, and
   VISITED_PHIS is a pointer set for detecting cycles.  */

static void
collect_phi_def_edges (gphi *phi, basic_block cd_root,
                       vec<edge> *edges,
                       hash_set<gimple> *visited_phis)
{
  size_t i, n;
  edge opnd_edge;
  tree opnd;

  if (visited_phis->add (phi))
    return;

  n = gimple_phi_num_args (phi);
  for (i = 0; i < n; i++)
    {
      opnd_edge = gimple_phi_arg_edge (phi, i);
      opnd = gimple_phi_arg_def (phi, i);

      if (TREE_CODE (opnd) != SSA_NAME)
        {
          if (dump_file && (dump_flags & TDF_DETAILS))
            {
              fprintf (dump_file, "\n[CHECK] Found def edge %d in ", (int)i);
              print_gimple_stmt (dump_file, phi, 0, 0);
            }
          edges->safe_push (opnd_edge);
        }
      else
        {
          gimple def = SSA_NAME_DEF_STMT (opnd);

          if (gimple_code (def) == GIMPLE_PHI
              && dominated_by_p (CDI_DOMINATORS,
                                 gimple_bb (def), cd_root))
            collect_phi_def_edges (as_a <gphi *> (def), cd_root, edges,
                                   visited_phis);
          else if (!uninit_undefined_value_p (opnd))
            {
              if (dump_file && (dump_flags & TDF_DETAILS))
                {
                  fprintf (dump_file, "\n[CHECK] Found def edge %d in ", (int)i);
                  print_gimple_stmt (dump_file, phi, 0, 0);
                }
              edges->safe_push (opnd_edge);
            }
        }
    }
}

/* For each use edge of PHI, computes all control dependence chains.
   The control dependence chains are then converted to an array of
   composite predicates pointed to by PREDS.  */

static bool
find_def_preds (pred_chain_union *preds, gphi *phi)
{
  size_t num_chains = 0, i, n;
  vec<edge> dep_chains[MAX_NUM_CHAINS];
  auto_vec<edge, MAX_CHAIN_LEN + 1> cur_chain;
  vec<edge> def_edges = vNULL;
  bool has_valid_pred = false;
  basic_block phi_bb, cd_root = 0;

  phi_bb = gimple_bb (phi);
  /* First find the closest dominating bb to be
     the control dependence root  */
  cd_root = find_dom (phi_bb);
  if (!cd_root)
    return false;

  hash_set<gimple> visited_phis;
  collect_phi_def_edges (phi, cd_root, &def_edges, &visited_phis);

  n = def_edges.length ();
  if (n == 0)
    return false;

  for (i = 0; i < n; i++)
    {
      size_t prev_nc, j;
      int num_calls = 0;
      edge opnd_edge;

      opnd_edge = def_edges[i];
      prev_nc = num_chains;
      compute_control_dep_chain (cd_root, opnd_edge->src, dep_chains,
				 &num_chains, &cur_chain, &num_calls);

      /* Now update the newly added chains with
         the phi operand edge:  */
      if (EDGE_COUNT (opnd_edge->src->succs) > 1)
        {
	  if (prev_nc == num_chains && num_chains < MAX_NUM_CHAINS)
	    dep_chains[num_chains++] = vNULL;
          for (j = prev_nc; j < num_chains; j++)
	    dep_chains[j].safe_push (opnd_edge);
        }
    }

  has_valid_pred
    = convert_control_dep_chain_into_preds (dep_chains, num_chains, preds);
  for (i = 0; i < num_chains; i++)
    dep_chains[i].release ();
  return has_valid_pred;
}

/* Dumps the predicates (PREDS) for USESTMT.  */

static void
dump_predicates (gimple usestmt, pred_chain_union preds,
                 const char* msg)
{
  size_t i, j;
  pred_chain one_pred_chain = vNULL;
  fprintf (dump_file, msg);
  print_gimple_stmt (dump_file, usestmt, 0, 0);
  fprintf (dump_file, "is guarded by :\n\n");
  size_t num_preds = preds.length ();
  /* Do some dumping here:  */
  for (i = 0; i < num_preds; i++)
    {
      size_t np;

      one_pred_chain = preds[i];
      np = one_pred_chain.length ();

      for (j = 0; j < np; j++)
        {
          pred_info one_pred = one_pred_chain[j];
          if (one_pred.invert)
            fprintf (dump_file, " (.NOT.) ");
          print_generic_expr (dump_file, one_pred.pred_lhs, 0);
          fprintf (dump_file, " %s ", op_symbol_code (one_pred.cond_code));
          print_generic_expr (dump_file, one_pred.pred_rhs, 0);
          if (j < np - 1)
            fprintf (dump_file, " (.AND.) ");
          else
            fprintf (dump_file, "\n");
        }
      if (i < num_preds - 1)
        fprintf (dump_file, "(.OR.)\n");
      else
        fprintf (dump_file, "\n\n");
    }
}

/* Destroys the predicate set *PREDS.  */

static void
destroy_predicate_vecs (pred_chain_union preds)
{
  size_t i;

  size_t n = preds.length ();
  for (i = 0; i < n; i++)
    preds[i].release ();
  preds.release ();
}


/* Computes the 'normalized' conditional code with operand
   swapping and condition inversion.  */

static enum tree_code
get_cmp_code (enum tree_code orig_cmp_code,
              bool swap_cond, bool invert)
{
  enum tree_code tc = orig_cmp_code;

  if (swap_cond)
    tc = swap_tree_comparison (orig_cmp_code);
  if (invert)
    tc = invert_tree_comparison (tc, false);

  switch (tc)
    {
    case LT_EXPR:
    case LE_EXPR:
    case GT_EXPR:
    case GE_EXPR:
    case EQ_EXPR:
    case NE_EXPR:
      break;
    default:
      return ERROR_MARK;
    }
  return tc;
}

/* Returns true if VAL falls in the range defined by BOUNDARY and CMPC, i.e.
   all values in the range satisfies (x CMPC BOUNDARY) == true.  */

static bool
is_value_included_in (tree val, tree boundary, enum tree_code cmpc)
{
  bool inverted = false;
  bool is_unsigned;
  bool result;

  /* Only handle integer constant here.  */
  if (TREE_CODE (val) != INTEGER_CST
      || TREE_CODE (boundary) != INTEGER_CST)
    return true;

  is_unsigned = TYPE_UNSIGNED (TREE_TYPE (val));

  if (cmpc == GE_EXPR || cmpc == GT_EXPR
      || cmpc == NE_EXPR)
    {
      cmpc = invert_tree_comparison (cmpc, false);
      inverted = true;
    }

  if (is_unsigned)
    {
      if (cmpc == EQ_EXPR)
        result = tree_int_cst_equal (val, boundary);
      else if (cmpc == LT_EXPR)
        result = tree_int_cst_lt (val, boundary);
      else
        {
          gcc_assert (cmpc == LE_EXPR);
          result = tree_int_cst_le (val, boundary);
        }
    }
  else
    {
      if (cmpc == EQ_EXPR)
        result = tree_int_cst_equal (val, boundary);
      else if (cmpc == LT_EXPR)
        result = tree_int_cst_lt (val, boundary);
      else
        {
          gcc_assert (cmpc == LE_EXPR);
          result = (tree_int_cst_equal (val, boundary)
                    || tree_int_cst_lt (val, boundary));
        }
    }

  if (inverted)
    result ^= 1;

  return result;
}

/* Returns true if PRED is common among all the predicate
   chains (PREDS) (and therefore can be factored out).
   NUM_PRED_CHAIN is the size of array PREDS.  */

static bool
find_matching_predicate_in_rest_chains (pred_info pred,
                                        pred_chain_union preds,
                                        size_t num_pred_chains)
{
  size_t i, j, n;

  /* Trival case.  */
  if (num_pred_chains == 1)
    return true;

  for (i = 1; i < num_pred_chains; i++)
    {
      bool found = false;
      pred_chain one_chain = preds[i];
      n = one_chain.length ();
      for (j = 0; j < n; j++)
        {
          pred_info pred2 = one_chain[j];
          /* Can relax the condition comparison to not
             use address comparison. However, the most common
             case is that multiple control dependent paths share
             a common path prefix, so address comparison should
             be ok.  */

          if (operand_equal_p (pred2.pred_lhs, pred.pred_lhs, 0)
              && operand_equal_p (pred2.pred_rhs, pred.pred_rhs, 0)
              && pred2.invert == pred.invert)
            {
              found = true;
              break;
            }
        }
      if (!found)
        return false;
    }
  return true;
}

/* Forward declaration.  */
static bool
is_use_properly_guarded (gimple use_stmt,
                         basic_block use_bb,
                         gphi *phi,
                         unsigned uninit_opnds,
                         hash_set<gphi *> *visited_phis);

/* Returns true if all uninitialized opnds are pruned. Returns false
   otherwise. PHI is the phi node with uninitialized operands,
   UNINIT_OPNDS is the bitmap of the uninitialize operand positions,
   FLAG_DEF is the statement defining the flag guarding the use of the
   PHI output, BOUNDARY_CST is the const value used in the predicate
   associated with the flag, CMP_CODE is the comparison code used in
   the predicate, VISITED_PHIS is the pointer set of phis visited, and
   VISITED_FLAG_PHIS is the pointer to the pointer set of flag definitions
   that are also phis.

   Example scenario:

   BB1:
   flag_1 = phi <0, 1>                  // (1)
   var_1  = phi <undef, some_val>


   BB2:
   flag_2 = phi <0,   flag_1, flag_1>   // (2)
   var_2  = phi <undef, var_1, var_1>
   if (flag_2 == 1)
      goto BB3;

   BB3:
   use of var_2                         // (3)

   Because some flag arg in (1) is not constant, if we do not look into the
   flag phis recursively, it is conservatively treated as unknown and var_1
   is thought to be flowed into use at (3). Since var_1 is potentially uninitialized
   a false warning will be emitted. Checking recursively into (1), the compiler can
   find out that only some_val (which is defined) can flow into (3) which is OK.

*/

static bool
prune_uninit_phi_opnds_in_unrealizable_paths (gphi *phi,
					      unsigned uninit_opnds,
					      gphi *flag_def,
					      tree boundary_cst,
					      enum tree_code cmp_code,
					      hash_set<gphi *> *visited_phis,
					      bitmap *visited_flag_phis)
{
  unsigned i;

  for (i = 0; i < MIN (32, gimple_phi_num_args (flag_def)); i++)
    {
      tree flag_arg;

      if (!MASK_TEST_BIT (uninit_opnds, i))
        continue;

      flag_arg = gimple_phi_arg_def (flag_def, i);
      if (!is_gimple_constant (flag_arg))
        {
          gphi *flag_arg_def, *phi_arg_def;
          tree phi_arg;
          unsigned uninit_opnds_arg_phi;

          if (TREE_CODE (flag_arg) != SSA_NAME)
            return false;
          flag_arg_def = dyn_cast <gphi *> (SSA_NAME_DEF_STMT (flag_arg));
	  if (!flag_arg_def)
            return false;

          phi_arg = gimple_phi_arg_def (phi, i);
          if (TREE_CODE (phi_arg) != SSA_NAME)
            return false;

          phi_arg_def = dyn_cast <gphi *> (SSA_NAME_DEF_STMT (phi_arg));
	  if (!phi_arg_def)
            return false;

          if (gimple_bb (phi_arg_def) != gimple_bb (flag_arg_def))
            return false;

          if (!*visited_flag_phis)
            *visited_flag_phis = BITMAP_ALLOC (NULL);

          if (bitmap_bit_p (*visited_flag_phis,
                            SSA_NAME_VERSION (gimple_phi_result (flag_arg_def))))
            return false;

          bitmap_set_bit (*visited_flag_phis,
                          SSA_NAME_VERSION (gimple_phi_result (flag_arg_def)));

          /* Now recursively prune the uninitialized phi args.  */
          uninit_opnds_arg_phi = compute_uninit_opnds_pos (phi_arg_def);
          if (!prune_uninit_phi_opnds_in_unrealizable_paths
		 (phi_arg_def, uninit_opnds_arg_phi, flag_arg_def,
		  boundary_cst, cmp_code, visited_phis, visited_flag_phis))
            return false;

          bitmap_clear_bit (*visited_flag_phis,
                            SSA_NAME_VERSION (gimple_phi_result (flag_arg_def)));
          continue;
        }

      /* Now check if the constant is in the guarded range.  */
      if (is_value_included_in (flag_arg, boundary_cst, cmp_code))
        {
          tree opnd;
          gimple opnd_def;

          /* Now that we know that this undefined edge is not
             pruned. If the operand is defined by another phi,
             we can further prune the incoming edges of that
             phi by checking the predicates of this operands.  */

          opnd = gimple_phi_arg_def (phi, i);
          opnd_def = SSA_NAME_DEF_STMT (opnd);
          if (gphi *opnd_def_phi = dyn_cast <gphi *> (opnd_def))
            {
              edge opnd_edge;
              unsigned uninit_opnds2
                  = compute_uninit_opnds_pos (opnd_def_phi);
              gcc_assert (!MASK_EMPTY (uninit_opnds2));
              opnd_edge = gimple_phi_arg_edge (phi, i);
              if (!is_use_properly_guarded (phi,
                                            opnd_edge->src,
                                            opnd_def_phi,
                                            uninit_opnds2,
                                            visited_phis))
                  return false;
            }
          else
            return false;
        }
    }

  return true;
}

/* A helper function that determines if the predicate set
   of the use is not overlapping with that of the uninit paths.
   The most common senario of guarded use is in Example 1:
     Example 1:
           if (some_cond)
           {
              x = ...;
              flag = true;
           }

            ... some code ...

           if (flag)
              use (x);

     The real world examples are usually more complicated, but similar
     and usually result from inlining:

         bool init_func (int * x)
         {
             if (some_cond)
                return false;
             *x  =  ..
             return true;
         }

         void foo(..)
         {
             int x;

             if (!init_func(&x))
                return;

             .. some_code ...
             use (x);
         }

     Another possible use scenario is in the following trivial example:

     Example 2:
          if (n > 0)
             x = 1;
          ...
          if (n > 0)
            {
              if (m < 2)
                 .. = x;
            }

     Predicate analysis needs to compute the composite predicate:

       1) 'x' use predicate: (n > 0) .AND. (m < 2)
       2) 'x' default value  (non-def) predicate: .NOT. (n > 0)
       (the predicate chain for phi operand defs can be computed
       starting from a bb that is control equivalent to the phi's
       bb and is dominating the operand def.)

       and check overlapping:
          (n > 0) .AND. (m < 2) .AND. (.NOT. (n > 0))
        <==> false

     This implementation provides framework that can handle
     scenarios. (Note that many simple cases are handled properly
     without the predicate analysis -- this is due to jump threading
     transformation which eliminates the merge point thus makes
     path sensitive analysis unnecessary.)

     NUM_PREDS is the number is the number predicate chains, PREDS is
     the array of chains, PHI is the phi node whose incoming (undefined)
     paths need to be pruned, and UNINIT_OPNDS is the bitmap holding
     uninit operand positions. VISITED_PHIS is the pointer set of phi
     stmts being checked.  */


static bool
use_pred_not_overlap_with_undef_path_pred (pred_chain_union preds,
				           gphi *phi, unsigned uninit_opnds,
					   hash_set<gphi *> *visited_phis)
{
  unsigned int i, n;
  gimple flag_def = 0;
  tree  boundary_cst = 0;
  enum tree_code cmp_code;
  bool swap_cond = false;
  bool invert = false;
  pred_chain the_pred_chain = vNULL;
  bitmap visited_flag_phis = NULL;
  bool all_pruned = false;
  size_t num_preds = preds.length ();

  gcc_assert (num_preds > 0);
  /* Find within the common prefix of multiple predicate chains
     a predicate that is a comparison of a flag variable against
     a constant.  */
  the_pred_chain = preds[0];
  n = the_pred_chain.length ();
  for (i = 0; i < n; i++)
    {
      tree cond_lhs, cond_rhs, flag = 0;

      pred_info the_pred = the_pred_chain[i];

      invert = the_pred.invert;
      cond_lhs = the_pred.pred_lhs;
      cond_rhs = the_pred.pred_rhs;
      cmp_code = the_pred.cond_code;

      if (cond_lhs != NULL_TREE && TREE_CODE (cond_lhs) == SSA_NAME
          && cond_rhs != NULL_TREE && is_gimple_constant (cond_rhs))
        {
          boundary_cst = cond_rhs;
          flag = cond_lhs;
        }
      else if (cond_rhs != NULL_TREE && TREE_CODE (cond_rhs) == SSA_NAME
               && cond_lhs != NULL_TREE && is_gimple_constant (cond_lhs))
        {
          boundary_cst = cond_lhs;
          flag = cond_rhs;
          swap_cond = true;
        }

      if (!flag)
        continue;

      flag_def = SSA_NAME_DEF_STMT (flag);

      if (!flag_def)
        continue;

      if ((gimple_code (flag_def) == GIMPLE_PHI)
          && (gimple_bb (flag_def) == gimple_bb (phi))
          && find_matching_predicate_in_rest_chains (the_pred, preds,
						     num_preds))
        break;

      flag_def = 0;
    }

  if (!flag_def)
    return false;

  /* Now check all the uninit incoming edge has a constant flag value
     that is in conflict with the use guard/predicate.  */
  cmp_code = get_cmp_code (cmp_code, swap_cond, invert);

  if (cmp_code == ERROR_MARK)
    return false;

  all_pruned = prune_uninit_phi_opnds_in_unrealizable_paths (phi,
                                                             uninit_opnds,
                                                             as_a <gphi *> (flag_def),
                                                             boundary_cst,
                                                             cmp_code,
                                                             visited_phis,
                                                             &visited_flag_phis);

  if (visited_flag_phis)
    BITMAP_FREE (visited_flag_phis);

  return all_pruned;
}

/* The helper function returns true if two predicates X1 and X2
   are equivalent. It assumes the expressions have already
   properly re-associated.  */

static inline bool
pred_equal_p (pred_info x1, pred_info x2)
{
  enum tree_code c1, c2;
  if (!operand_equal_p (x1.pred_lhs, x2.pred_lhs, 0)
      || !operand_equal_p (x1.pred_rhs, x2.pred_rhs, 0))
    return false;

  c1 = x1.cond_code;
  if (x1.invert != x2.invert)
    c2 = invert_tree_comparison (x2.cond_code, false);
  else
    c2 = x2.cond_code;

  return c1 == c2;
}

/* Returns true if the predication is testing !=.  */

static inline bool
is_neq_relop_p (pred_info pred)
{

  return (pred.cond_code == NE_EXPR && !pred.invert) 
          || (pred.cond_code == EQ_EXPR && pred.invert);
}

/* Returns true if pred is of the form X != 0.  */

static inline bool 
is_neq_zero_form_p (pred_info pred)
{
  if (!is_neq_relop_p (pred) || !integer_zerop (pred.pred_rhs)
      || TREE_CODE (pred.pred_lhs) != SSA_NAME)
    return false;
  return true;
}

/* The helper function returns true if two predicates X1
   is equivalent to X2 != 0.  */

static inline bool
pred_expr_equal_p (pred_info x1, tree x2)
{
  if (!is_neq_zero_form_p (x1))
    return false;

  return operand_equal_p (x1.pred_lhs, x2, 0);
}

/* Returns true of the domain of single predicate expression
   EXPR1 is a subset of that of EXPR2. Returns false if it
   can not be proved.  */

static bool
is_pred_expr_subset_of (pred_info expr1, pred_info expr2)
{
  enum tree_code code1, code2;

  if (pred_equal_p (expr1, expr2))
    return true;

  if ((TREE_CODE (expr1.pred_rhs) != INTEGER_CST)
      || (TREE_CODE (expr2.pred_rhs) != INTEGER_CST))
    return false;

  if (!operand_equal_p (expr1.pred_lhs, expr2.pred_lhs, 0))
    return false;

  code1 = expr1.cond_code;
  if (expr1.invert)
    code1 = invert_tree_comparison (code1, false);
  code2 = expr2.cond_code;
  if (expr2.invert)
    code2 = invert_tree_comparison (code2, false);

  if (code1 != code2 && code2 != NE_EXPR)
    return false;

  if (is_value_included_in (expr1.pred_rhs, expr2.pred_rhs, code2))
    return true;

  return false;
}

/* Returns true if the domain of PRED1 is a subset
   of that of PRED2. Returns false if it can not be proved so.  */

static bool
is_pred_chain_subset_of (pred_chain pred1,
                         pred_chain pred2)
{
  size_t np1, np2, i1, i2;

  np1 = pred1.length ();
  np2 = pred2.length ();

  for (i2 = 0; i2 < np2; i2++)
    {
      bool found = false;
      pred_info info2 = pred2[i2];
      for (i1 = 0; i1 < np1; i1++)
        {
          pred_info info1 = pred1[i1];
          if (is_pred_expr_subset_of (info1, info2))
            {
              found = true;
              break;
            }
        }
      if (!found)
        return false;
    }
  return true;
}

/* Returns true if the domain defined by
   one pred chain ONE_PRED is a subset of the domain
   of *PREDS. It returns false if ONE_PRED's domain is
   not a subset of any of the sub-domains of PREDS
   (corresponding to each individual chains in it), even
   though it may be still be a subset of whole domain
   of PREDS which is the union (ORed) of all its subdomains.
   In other words, the result is conservative.  */

static bool
is_included_in (pred_chain one_pred, pred_chain_union preds)
{
  size_t i;
  size_t n = preds.length ();

  for (i = 0; i < n; i++)
    {
      if (is_pred_chain_subset_of (one_pred, preds[i]))
        return true;
    }

  return false;
}

/* Compares two predicate sets PREDS1 and PREDS2 and returns
   true if the domain defined by PREDS1 is a superset
   of PREDS2's domain. N1 and N2 are array sizes of PREDS1 and
   PREDS2 respectively. The implementation chooses not to build
   generic trees (and relying on the folding capability of the
   compiler), but instead performs brute force comparison of
   individual predicate chains (won't be a compile time problem
   as the chains are pretty short). When the function returns
   false, it does not necessarily mean *PREDS1 is not a superset
   of *PREDS2, but mean it may not be so since the analysis can
   not prove it. In such cases, false warnings may still be
   emitted.  */

static bool
is_superset_of (pred_chain_union preds1, pred_chain_union preds2)
{
  size_t i, n2;
  pred_chain one_pred_chain = vNULL;

  n2 = preds2.length ();

  for (i = 0; i < n2; i++)
    {
      one_pred_chain = preds2[i];
      if (!is_included_in (one_pred_chain, preds1))
        return false;
    }

  return true;
}

/* Returns true if TC is AND or OR.  */

static inline bool
is_and_or_or_p (enum tree_code tc, tree type)
{
  return (tc == BIT_IOR_EXPR
          || (tc == BIT_AND_EXPR
              && (type == 0 || TREE_CODE (type) == BOOLEAN_TYPE)));
}

/* Returns true if X1 is the negate of X2.  */

static inline bool
pred_neg_p (pred_info x1, pred_info x2)
{
  enum tree_code c1, c2;
  if (!operand_equal_p (x1.pred_lhs, x2.pred_lhs, 0)
      || !operand_equal_p (x1.pred_rhs, x2.pred_rhs, 0))
    return false;
      
  c1 = x1.cond_code;
  if (x1.invert == x2.invert)
    c2 = invert_tree_comparison (x2.cond_code, false);
  else
    c2 = x2.cond_code;

  return c1 == c2;
}

/* 1) ((x IOR y) != 0) AND (x != 0) is equivalent to (x != 0);
   2) (X AND Y) OR (!X AND Y) is equivalent to Y;
   3) X OR (!X AND Y) is equivalent to (X OR Y);
   4) ((x IAND y) != 0) || (x != 0 AND y != 0)) is equivalent to
      (x != 0 AND y != 0)
   5) (X AND Y) OR (!X AND Z) OR (!Y AND Z) is equivalent to
      (X AND Y) OR Z 

   PREDS is the predicate chains, and N is the number of chains.  */

/* Helper function to implement rule 1 above.  ONE_CHAIN is
   the AND predication to be simplified.  */

static void
simplify_pred (pred_chain *one_chain)
{
  size_t i, j, n;
  bool simplified = false;
  pred_chain s_chain = vNULL;

  n = one_chain->length ();

  for (i = 0; i < n; i++)
    {
      pred_info *a_pred = &(*one_chain)[i];

      if (!a_pred->pred_lhs)
        continue;
      if (!is_neq_zero_form_p (*a_pred))
        continue;

      gimple def_stmt = SSA_NAME_DEF_STMT (a_pred->pred_lhs);
      if (gimple_code (def_stmt) != GIMPLE_ASSIGN)
        continue;
      if (gimple_assign_rhs_code (def_stmt) == BIT_IOR_EXPR)
        {
          for (j = 0; j < n; j++)
            {
              pred_info *b_pred = &(*one_chain)[j];

              if (!b_pred->pred_lhs)
                continue;
              if (!is_neq_zero_form_p (*b_pred))
                continue;

              if (pred_expr_equal_p (*b_pred, gimple_assign_rhs1 (def_stmt))
                  || pred_expr_equal_p (*b_pred, gimple_assign_rhs2 (def_stmt)))
                 {
                   /* Mark a_pred for removal.  */
                   a_pred->pred_lhs = NULL;
                   a_pred->pred_rhs = NULL;
                   simplified = true;
                   break;
                 }
            }
        }
    }

  if (!simplified)
     return;

  for (i = 0; i < n; i++)
    {
      pred_info *a_pred = &(*one_chain)[i];
      if (!a_pred->pred_lhs)
        continue;
      s_chain.safe_push (*a_pred);
    }

   one_chain->release ();
   *one_chain = s_chain;
}

/* The helper function implements the rule 2 for the
   OR predicate PREDS.

   2) (X AND Y) OR (!X AND Y) is equivalent to Y.  */

static bool
simplify_preds_2 (pred_chain_union *preds)
{
  size_t i, j, n;
  bool simplified = false;
  pred_chain_union s_preds = vNULL;

  /* (X AND Y) OR (!X AND Y) is equivalent to Y.  
     (X AND Y) OR (X AND !Y) is equivalent to X.  */

  n = preds->length ();
  for (i = 0; i < n; i++)
    {
      pred_info x, y;
      pred_chain *a_chain = &(*preds)[i];

      if (a_chain->length () != 2)
        continue;

      x = (*a_chain)[0];
      y = (*a_chain)[1];

      for (j = 0; j < n; j++)
        {
          pred_chain *b_chain;
          pred_info x2, y2;

          if (j == i)
            continue;

          b_chain = &(*preds)[j];
          if (b_chain->length () != 2)
            continue;

          x2 = (*b_chain)[0];
          y2 = (*b_chain)[1];

          if (pred_equal_p (x, x2) && pred_neg_p (y, y2))
            {
              /* Kill a_chain.  */
              a_chain->release ();
              b_chain->release ();
              b_chain->safe_push (x);
              simplified = true;
              break;
            }
          if (pred_neg_p (x, x2) && pred_equal_p (y, y2))
            {
              /* Kill a_chain.  */
              a_chain->release ();
              b_chain->release ();
              b_chain->safe_push (y);
              simplified = true;
              break;
            }
        }
    }
  /* Now clean up the chain.  */
  if (simplified)
    {
      for (i = 0; i < n; i++)
        {
          if ((*preds)[i].is_empty ())
            continue;
          s_preds.safe_push ((*preds)[i]);
        }
      preds->release ();
      (*preds) = s_preds;
      s_preds = vNULL;
    }

  return simplified;
}

/* The helper function implements the rule 2 for the
   OR predicate PREDS.

   3) x OR (!x AND y) is equivalent to x OR y.  */

static bool
simplify_preds_3 (pred_chain_union *preds)
{
  size_t i, j, n;
  bool simplified = false;

  /* Now iteratively simplify X OR (!X AND Z ..)
       into X OR (Z ...).  */

  n = preds->length ();
  if (n < 2)
    return false;

  for (i = 0; i < n; i++)
    {
      pred_info x;
      pred_chain *a_chain = &(*preds)[i];

      if (a_chain->length () != 1)
        continue;

      x = (*a_chain)[0];

      for (j = 0; j < n; j++)
        {
          pred_chain *b_chain;
          pred_info x2;
          size_t k;

          if (j == i)
            continue;

          b_chain = &(*preds)[j];
          if (b_chain->length () < 2)
            continue;

          for (k = 0; k < b_chain->length (); k++)
            {
              x2 = (*b_chain)[k];
              if (pred_neg_p (x, x2))
                {
                  b_chain->unordered_remove (k);
                  simplified = true;
                  break;
                }
            }
        }
    }
  return simplified;
}

/* The helper function implements the rule 4 for the
   OR predicate PREDS.

   2) ((x AND y) != 0) OR (x != 0 AND y != 0) is equivalent to
       (x != 0 ANd y != 0).   */

static bool
simplify_preds_4 (pred_chain_union *preds)
{
  size_t i, j, n;
  bool simplified = false;
  pred_chain_union s_preds = vNULL;
  gimple def_stmt;

  n = preds->length ();
  for (i = 0; i < n; i++)
    {
      pred_info z;
      pred_chain *a_chain = &(*preds)[i];

      if (a_chain->length () != 1)
        continue;

      z = (*a_chain)[0];

      if (!is_neq_zero_form_p (z))
        continue;

      def_stmt = SSA_NAME_DEF_STMT (z.pred_lhs);
      if (gimple_code (def_stmt) != GIMPLE_ASSIGN)
        continue;

      if (gimple_assign_rhs_code (def_stmt) != BIT_AND_EXPR)
        continue;

      for (j = 0; j < n; j++)
        {
          pred_chain *b_chain;
          pred_info x2, y2;

          if (j == i)
            continue;

          b_chain = &(*preds)[j];
          if (b_chain->length () != 2)
            continue;

          x2 = (*b_chain)[0];
          y2 = (*b_chain)[1];
          if (!is_neq_zero_form_p (x2)
              || !is_neq_zero_form_p (y2))
            continue;

          if ((pred_expr_equal_p (x2, gimple_assign_rhs1 (def_stmt))
               && pred_expr_equal_p (y2, gimple_assign_rhs2 (def_stmt)))
              || (pred_expr_equal_p (x2, gimple_assign_rhs2 (def_stmt))
                  && pred_expr_equal_p (y2, gimple_assign_rhs1 (def_stmt))))
            {
              /* Kill a_chain.  */
              a_chain->release ();
              simplified = true;
              break;
            }
        }
    }
  /* Now clean up the chain.  */
  if (simplified)
    {
      for (i = 0; i < n; i++)
        {
          if ((*preds)[i].is_empty ())
            continue;
          s_preds.safe_push ((*preds)[i]);
        }
      preds->release ();
      (*preds) = s_preds;
      s_preds = vNULL;
    }

  return simplified;
}


/* This function simplifies predicates in PREDS.  */

static void
simplify_preds (pred_chain_union *preds, gimple use_or_def, bool is_use)
{
  size_t i, n;
  bool changed = false;

  if (dump_file && dump_flags & TDF_DETAILS)
    {
      fprintf (dump_file, "[BEFORE SIMPLICATION -- ");
      dump_predicates (use_or_def, *preds, is_use ? "[USE]:\n" : "[DEF]:\n");
    }

  for (i = 0; i < preds->length (); i++)
    simplify_pred (&(*preds)[i]);

  n = preds->length ();
  if (n < 2)
    return;

  do
    {
      changed = false;
      if (simplify_preds_2 (preds))
        changed = true;

      /* Now iteratively simplify X OR (!X AND Z ..)
       into X OR (Z ...).  */
      if (simplify_preds_3 (preds))
        changed = true;

      if (simplify_preds_4 (preds))
        changed = true;

    } while (changed);

  return;
}

/* This is a helper function which attempts to normalize predicate chains
  by following UD chains. It basically builds up a big tree of either IOR
  operations or AND operations, and convert the IOR tree into a 
  pred_chain_union or BIT_AND tree into a pred_chain.
  Example:

  _3 = _2 RELOP1 _1;
  _6 = _5 RELOP2 _4;
  _9 = _8 RELOP3 _7;
  _10 = _3 | _6;
  _12 = _9 | _0;
  _t = _10 | _12;

 then _t != 0 will be normalized into a pred_chain_union

   (_2 RELOP1 _1) OR (_5 RELOP2 _4) OR (_8 RELOP3 _7) OR (_0 != 0)

 Similarly given,

  _3 = _2 RELOP1 _1;
  _6 = _5 RELOP2 _4;
  _9 = _8 RELOP3 _7;
  _10 = _3 & _6;
  _12 = _9 & _0;

 then _t != 0 will be normalized into a pred_chain:
   (_2 RELOP1 _1) AND (_5 RELOP2 _4) AND (_8 RELOP3 _7) AND (_0 != 0)
   
  */

/* This is a helper function that stores a PRED into NORM_PREDS.  */

inline static void
push_pred (pred_chain_union *norm_preds, pred_info pred)
{
  pred_chain pred_chain = vNULL;
  pred_chain.safe_push (pred);
  norm_preds->safe_push (pred_chain);
}

/* A helper function that creates a predicate of the form
   OP != 0 and push it WORK_LIST.  */

inline static void
push_to_worklist (tree op, vec<pred_info, va_heap, vl_ptr> *work_list,
                  hash_set<tree> *mark_set)
{
  if (mark_set->contains (op))
    return;
  mark_set->add (op);

  pred_info arg_pred;
  arg_pred.pred_lhs = op;
  arg_pred.pred_rhs = integer_zero_node;
  arg_pred.cond_code = NE_EXPR;
  arg_pred.invert = false;
  work_list->safe_push (arg_pred);
}

/* A helper that generates a pred_info from a gimple assignment
   CMP_ASSIGN with comparison rhs.  */

static pred_info
get_pred_info_from_cmp (gimple cmp_assign)
{
  pred_info n_pred;
  n_pred.pred_lhs = gimple_assign_rhs1 (cmp_assign);
  n_pred.pred_rhs = gimple_assign_rhs2 (cmp_assign);
  n_pred.cond_code = gimple_assign_rhs_code (cmp_assign);
  n_pred.invert = false;
  return n_pred;
}

/* Returns true if the PHI is a degenerated phi with
   all args with the same value (relop). In that case, *PRED
   will be updated to that value.  */

static bool
is_degenerated_phi (gimple phi, pred_info *pred_p)
{
  int i, n;
  tree op0;
  gimple def0;
  pred_info pred0;

  n = gimple_phi_num_args (phi);
  op0 = gimple_phi_arg_def (phi, 0);

  if (TREE_CODE (op0) != SSA_NAME)
    return false;

  def0 = SSA_NAME_DEF_STMT (op0);
  if (gimple_code (def0) != GIMPLE_ASSIGN)
    return false;
  if (TREE_CODE_CLASS (gimple_assign_rhs_code (def0))
      != tcc_comparison)
    return false;
  pred0 = get_pred_info_from_cmp (def0);

  for (i = 1; i < n; ++i)
    {
      gimple def;
      pred_info pred;
      tree op = gimple_phi_arg_def (phi, i);

      if (TREE_CODE (op) != SSA_NAME)
        return false;

      def = SSA_NAME_DEF_STMT (op);
      if (gimple_code (def) != GIMPLE_ASSIGN)
        return false;
      if (TREE_CODE_CLASS (gimple_assign_rhs_code (def))
          != tcc_comparison)
        return false;
      pred = get_pred_info_from_cmp (def);
      if (!pred_equal_p (pred, pred0))
        return false;
    }

  *pred_p = pred0;
  return true;
}

/* Normalize one predicate PRED  
   1) if PRED can no longer be normlized, put it into NORM_PREDS.
   2) otherwise if PRED is of the form x != 0, follow x's definition
      and put normalized predicates into WORK_LIST.  */
 
static void
normalize_one_pred_1 (pred_chain_union *norm_preds, 
                      pred_chain *norm_chain,
                      pred_info pred,
                      enum tree_code and_or_code,
                      vec<pred_info, va_heap, vl_ptr> *work_list,
		      hash_set<tree> *mark_set)
{
  if (!is_neq_zero_form_p (pred))
    {
      if (and_or_code == BIT_IOR_EXPR)
        push_pred (norm_preds, pred);
      else
        norm_chain->safe_push (pred);
      return;
    }

  gimple def_stmt = SSA_NAME_DEF_STMT (pred.pred_lhs);
 
  if (gimple_code (def_stmt) == GIMPLE_PHI
      && is_degenerated_phi (def_stmt, &pred))
    work_list->safe_push (pred);
  else if (gimple_code (def_stmt) == GIMPLE_PHI
           && and_or_code == BIT_IOR_EXPR)
    {
      int i, n;
      n = gimple_phi_num_args (def_stmt);

      /* If we see non zero constant, we should punt. The predicate
       * should be one guarding the phi edge.  */
      for (i = 0; i < n; ++i)
        {
          tree op = gimple_phi_arg_def (def_stmt, i);
          if (TREE_CODE (op) == INTEGER_CST && !integer_zerop (op))
            {
              push_pred (norm_preds, pred);
              return;
            }
        }

      for (i = 0; i < n; ++i)
        {
          tree op = gimple_phi_arg_def (def_stmt, i);
          if (integer_zerop (op))
            continue;

          push_to_worklist (op, work_list, mark_set);
        }
    }
  else if (gimple_code (def_stmt) != GIMPLE_ASSIGN)
    {
      if (and_or_code == BIT_IOR_EXPR)
	push_pred (norm_preds, pred);
      else
	norm_chain->safe_push (pred);
    }
  else if (gimple_assign_rhs_code (def_stmt) == and_or_code)
    {
      push_to_worklist (gimple_assign_rhs1 (def_stmt), work_list, mark_set);
      push_to_worklist (gimple_assign_rhs2 (def_stmt), work_list, mark_set);
    }
  else if (TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt))
	   == tcc_comparison)
    {
      pred_info n_pred = get_pred_info_from_cmp (def_stmt);
      if (and_or_code == BIT_IOR_EXPR)
	push_pred (norm_preds, n_pred);
      else
	norm_chain->safe_push (n_pred);
    }
  else
    {
      if (and_or_code == BIT_IOR_EXPR)
	push_pred (norm_preds, pred);
      else
	norm_chain->safe_push (pred);
    }
}

/* Normalize PRED and store the normalized predicates into NORM_PREDS.  */

static void
normalize_one_pred (pred_chain_union *norm_preds,
                    pred_info pred)
{
  vec<pred_info, va_heap, vl_ptr> work_list = vNULL;
  enum tree_code and_or_code = ERROR_MARK;
  pred_chain norm_chain = vNULL;

  if (!is_neq_zero_form_p (pred))
    {
      push_pred (norm_preds, pred);
      return;
    }

  gimple def_stmt = SSA_NAME_DEF_STMT (pred.pred_lhs);
  if (gimple_code (def_stmt) == GIMPLE_ASSIGN)
    and_or_code = gimple_assign_rhs_code (def_stmt);
  if (and_or_code != BIT_IOR_EXPR
      && and_or_code != BIT_AND_EXPR)
    {
      if (TREE_CODE_CLASS (and_or_code)
          == tcc_comparison)
        {
          pred_info n_pred = get_pred_info_from_cmp (def_stmt);
          push_pred (norm_preds, n_pred);
        } 
       else
          push_pred (norm_preds, pred);
      return;
    }

  work_list.safe_push (pred);
  hash_set<tree> mark_set;

  while (!work_list.is_empty ())
    {
      pred_info a_pred = work_list.pop ();
      normalize_one_pred_1 (norm_preds, &norm_chain, a_pred,
                            and_or_code, &work_list, &mark_set);
    }
  if (and_or_code == BIT_AND_EXPR)
    norm_preds->safe_push (norm_chain);

  work_list.release ();
}

static void
normalize_one_pred_chain (pred_chain_union *norm_preds,
                          pred_chain one_chain)
{
  vec<pred_info, va_heap, vl_ptr> work_list = vNULL;
  hash_set<tree> mark_set;
  pred_chain norm_chain = vNULL;
  size_t i;

  for (i = 0; i < one_chain.length (); i++)
    {
      work_list.safe_push (one_chain[i]);
      mark_set.add (one_chain[i].pred_lhs);
    }

  while (!work_list.is_empty ())
    {
      pred_info a_pred = work_list.pop ();
      normalize_one_pred_1 (0, &norm_chain, a_pred,
                            BIT_AND_EXPR, &work_list, &mark_set);
    }

  norm_preds->safe_push (norm_chain);
  work_list.release ();
}

/* Normalize predicate chains PREDS and returns the normalized one.  */

static pred_chain_union
normalize_preds (pred_chain_union preds, gimple use_or_def, bool is_use)
{
  pred_chain_union norm_preds = vNULL;
  size_t n = preds.length ();
  size_t i;

  if (dump_file && dump_flags & TDF_DETAILS)
    {
      fprintf (dump_file, "[BEFORE NORMALIZATION --");
      dump_predicates (use_or_def, preds, is_use ? "[USE]:\n" : "[DEF]:\n");
    }

  for (i = 0; i < n; i++)
    {
      if (preds[i].length () != 1)
        normalize_one_pred_chain (&norm_preds, preds[i]);
      else
        {
          normalize_one_pred (&norm_preds, preds[i][0]);
          preds[i].release ();
        }
    }

  if (dump_file)
    {
      fprintf (dump_file, "[AFTER NORMALIZATION -- ");
      dump_predicates (use_or_def, norm_preds, is_use ? "[USE]:\n" : "[DEF]:\n");
    }

  preds.release ();
  return norm_preds;
}


/* Computes the predicates that guard the use and checks
   if the incoming paths that have empty (or possibly
   empty) definition can be pruned/filtered. The function returns
   true if it can be determined that the use of PHI's def in
   USE_STMT is guarded with a predicate set not overlapping with
   predicate sets of all runtime paths that do not have a definition.
   Returns false if it is not or it can not be determined. USE_BB is
   the bb of the use (for phi operand use, the bb is not the bb of
   the phi stmt, but the src bb of the operand edge). UNINIT_OPNDS
   is a bit vector. If an operand of PHI is uninitialized, the
   corresponding bit in the vector is 1.  VISIED_PHIS is a pointer
   set of phis being visted.  */

static bool
is_use_properly_guarded (gimple use_stmt,
                         basic_block use_bb,
                         gphi *phi,
                         unsigned uninit_opnds,
                         hash_set<gphi *> *visited_phis)
{
  basic_block phi_bb;
  pred_chain_union preds = vNULL;
  pred_chain_union def_preds = vNULL;
  bool has_valid_preds = false;
  bool is_properly_guarded = false;

  if (visited_phis->add (phi))
    return false;

  phi_bb = gimple_bb (phi);

  if (is_non_loop_exit_postdominating (use_bb, phi_bb))
    return false;

  has_valid_preds = find_predicates (&preds, phi_bb, use_bb);

  if (!has_valid_preds)
    {
      destroy_predicate_vecs (preds);
      return false;
    }

  /* Try to prune the dead incoming phi edges. */
  is_properly_guarded
    = use_pred_not_overlap_with_undef_path_pred (preds, phi, uninit_opnds,
						 visited_phis);

  if (is_properly_guarded)
    {
      destroy_predicate_vecs (preds);
      return true;
    }

  has_valid_preds = find_def_preds (&def_preds, phi);

  if (!has_valid_preds)
    {
      destroy_predicate_vecs (preds);
      destroy_predicate_vecs (def_preds);
      return false;
    }

  simplify_preds (&preds, use_stmt, true);
  preds = normalize_preds (preds, use_stmt, true);

  simplify_preds (&def_preds, phi, false);
  def_preds = normalize_preds (def_preds, phi, false);

  is_properly_guarded = is_superset_of (def_preds, preds);

  destroy_predicate_vecs (preds);
  destroy_predicate_vecs (def_preds);
  return is_properly_guarded;
}

/* Searches through all uses of a potentially
   uninitialized variable defined by PHI and returns a use
   statement if the use is not properly guarded. It returns
   NULL if all uses are guarded. UNINIT_OPNDS is a bitvector
   holding the position(s) of uninit PHI operands. WORKLIST
   is the vector of candidate phis that may be updated by this
   function. ADDED_TO_WORKLIST is the pointer set tracking
   if the new phi is already in the worklist.  */

static gimple
find_uninit_use (gphi *phi, unsigned uninit_opnds,
                 vec<gphi *> *worklist,
		 hash_set<gphi *> *added_to_worklist)
{
  tree phi_result;
  use_operand_p use_p;
  gimple use_stmt;
  imm_use_iterator iter;

  phi_result = gimple_phi_result (phi);

  FOR_EACH_IMM_USE_FAST (use_p, iter, phi_result)
    {
      basic_block use_bb;

      use_stmt = USE_STMT (use_p);
      if (is_gimple_debug (use_stmt))
	continue;

      if (gphi *use_phi = dyn_cast <gphi *> (use_stmt))
	use_bb = gimple_phi_arg_edge (use_phi,
				      PHI_ARG_INDEX_FROM_USE (use_p))->src;
      else
	use_bb = gimple_bb (use_stmt);

      hash_set<gphi *> visited_phis;
      if (is_use_properly_guarded (use_stmt, use_bb, phi, uninit_opnds,
                                   &visited_phis))
	continue;

      if (dump_file && (dump_flags & TDF_DETAILS))
        {
          fprintf (dump_file, "[CHECK]: Found unguarded use: ");
          print_gimple_stmt (dump_file, use_stmt, 0, 0);
        }
      /* Found one real use, return.  */
      if (gimple_code (use_stmt) != GIMPLE_PHI)
        return use_stmt;

      /* Found a phi use that is not guarded,
         add the phi to the worklist.  */
      if (!added_to_worklist->add (as_a <gphi *> (use_stmt)))
        {
          if (dump_file && (dump_flags & TDF_DETAILS))
            {
              fprintf (dump_file, "[WORKLIST]: Update worklist with phi: ");
              print_gimple_stmt (dump_file, use_stmt, 0, 0);
            }

          worklist->safe_push (as_a <gphi *> (use_stmt));
          possibly_undefined_names->add (phi_result);
        }
    }

  return NULL;
}

/* Look for inputs to PHI that are SSA_NAMEs that have empty definitions
   and gives warning if there exists a runtime path from the entry to a
   use of the PHI def that does not contain a definition. In other words,
   the warning is on the real use. The more dead paths that can be pruned
   by the compiler, the fewer false positives the warning is. WORKLIST
   is a vector of candidate phis to be examined. ADDED_TO_WORKLIST is
   a pointer set tracking if the new phi is added to the worklist or not.  */

static void
warn_uninitialized_phi (gphi *phi, vec<gphi *> *worklist,
                        hash_set<gphi *> *added_to_worklist)
{
  unsigned uninit_opnds;
  gimple uninit_use_stmt = 0;
  tree uninit_op;
  int phiarg_index;
  location_t loc;

  /* Don't look at virtual operands.  */
  if (virtual_operand_p (gimple_phi_result (phi)))
    return;

  uninit_opnds = compute_uninit_opnds_pos (phi);

  if  (MASK_EMPTY (uninit_opnds))
    return;

  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "[CHECK]: examining phi: ");
      print_gimple_stmt (dump_file, phi, 0, 0);
    }

  /* Now check if we have any use of the value without proper guard.  */
  uninit_use_stmt = find_uninit_use (phi, uninit_opnds,
                                     worklist, added_to_worklist);

  /* All uses are properly guarded.  */
  if (!uninit_use_stmt)
    return;

  phiarg_index = MASK_FIRST_SET_BIT (uninit_opnds);
  uninit_op = gimple_phi_arg_def (phi, phiarg_index);
  if (SSA_NAME_VAR (uninit_op) == NULL_TREE)
    return;
  if (gimple_phi_arg_has_location (phi, phiarg_index))
    loc = gimple_phi_arg_location (phi, phiarg_index);
  else
    loc = UNKNOWN_LOCATION;
  warn_uninit (OPT_Wmaybe_uninitialized, uninit_op, SSA_NAME_VAR (uninit_op),
	       SSA_NAME_VAR (uninit_op),
               "%qD may be used uninitialized in this function",
               uninit_use_stmt, loc);

}

static bool
gate_warn_uninitialized (void)
{
  return warn_uninitialized || warn_maybe_uninitialized;
}

namespace {

const pass_data pass_data_late_warn_uninitialized =
{
  GIMPLE_PASS, /* type */
  "uninit", /* name */
  OPTGROUP_NONE, /* optinfo_flags */
  TV_NONE, /* tv_id */
  PROP_ssa, /* properties_required */
  0, /* properties_provided */
  0, /* properties_destroyed */
  0, /* todo_flags_start */
  0, /* todo_flags_finish */
};

class pass_late_warn_uninitialized : public gimple_opt_pass
{
public:
  pass_late_warn_uninitialized (gcc::context *ctxt)
    : gimple_opt_pass (pass_data_late_warn_uninitialized, ctxt)
  {}

  /* opt_pass methods: */
  opt_pass * clone () { return new pass_late_warn_uninitialized (m_ctxt); }
  virtual bool gate (function *) { return gate_warn_uninitialized (); }
  virtual unsigned int execute (function *);

}; // class pass_late_warn_uninitialized

unsigned int
pass_late_warn_uninitialized::execute (function *fun)
{
  basic_block bb;
  gphi_iterator gsi;
  vec<gphi *> worklist = vNULL;

  calculate_dominance_info (CDI_DOMINATORS);
  calculate_dominance_info (CDI_POST_DOMINATORS);
  /* Re-do the plain uninitialized variable check, as optimization may have
     straightened control flow.  Do this first so that we don't accidentally
     get a "may be" warning when we'd have seen an "is" warning later.  */
  warn_uninitialized_vars (/*warn_possibly_uninitialized=*/1);

  timevar_push (TV_TREE_UNINIT);

  possibly_undefined_names = new hash_set<tree>;
  hash_set<gphi *> added_to_worklist;

  /* Initialize worklist  */
  FOR_EACH_BB_FN (bb, fun)
    for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
      {
	gphi *phi = gsi.phi ();
	size_t n, i;

	n = gimple_phi_num_args (phi);

	/* Don't look at virtual operands.  */
	if (virtual_operand_p (gimple_phi_result (phi)))
	  continue;

	for (i = 0; i < n; ++i)
	  {
	    tree op = gimple_phi_arg_def (phi, i);
	    if (TREE_CODE (op) == SSA_NAME
		&& uninit_undefined_value_p (op))
	      {
		worklist.safe_push (phi);
		added_to_worklist.add (phi);
		if (dump_file && (dump_flags & TDF_DETAILS))
		  {
		    fprintf (dump_file, "[WORKLIST]: add to initial list: ");
		    print_gimple_stmt (dump_file, phi, 0, 0);
		  }
		break;
	      }
	  }
      }

  while (worklist.length () != 0)
    {
      gphi *cur_phi = 0;
      cur_phi = worklist.pop ();
      warn_uninitialized_phi (cur_phi, &worklist, &added_to_worklist);
    }

  worklist.release ();
  delete possibly_undefined_names;
  possibly_undefined_names = NULL;
  free_dominance_info (CDI_POST_DOMINATORS);
  timevar_pop (TV_TREE_UNINIT);
  return 0;
}

} // anon namespace

gimple_opt_pass *
make_pass_late_warn_uninitialized (gcc::context *ctxt)
{
  return new pass_late_warn_uninitialized (ctxt);
}


static unsigned int
execute_early_warn_uninitialized (void)
{
  /* Currently, this pass runs always but
     execute_late_warn_uninitialized only runs with optimization. With
     optimization we want to warn about possible uninitialized as late
     as possible, thus don't do it here.  However, without
     optimization we need to warn here about "may be uninitialized".  */
  calculate_dominance_info (CDI_POST_DOMINATORS);

  warn_uninitialized_vars (/*warn_possibly_uninitialized=*/!optimize);

  /* Post-dominator information can not be reliably updated. Free it
     after the use.  */

  free_dominance_info (CDI_POST_DOMINATORS);
  return 0;
}


namespace {

const pass_data pass_data_early_warn_uninitialized =
{
  GIMPLE_PASS, /* type */
  "*early_warn_uninitialized", /* name */
  OPTGROUP_NONE, /* optinfo_flags */
  TV_TREE_UNINIT, /* tv_id */
  PROP_ssa, /* properties_required */
  0, /* properties_provided */
  0, /* properties_destroyed */
  0, /* todo_flags_start */
  0, /* todo_flags_finish */
};

class pass_early_warn_uninitialized : public gimple_opt_pass
{
public:
  pass_early_warn_uninitialized (gcc::context *ctxt)
    : gimple_opt_pass (pass_data_early_warn_uninitialized, ctxt)
  {}

  /* opt_pass methods: */
  virtual bool gate (function *) { return gate_warn_uninitialized (); }
  virtual unsigned int execute (function *)
    {
      return execute_early_warn_uninitialized ();
    }

}; // class pass_early_warn_uninitialized

} // anon namespace

gimple_opt_pass *
make_pass_early_warn_uninitialized (gcc::context *ctxt)
{
  return new pass_early_warn_uninitialized (ctxt);
}