aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/libs/clang16/lib/Analysis/ThreadSafety.cpp
blob: 899c6018895ef8601e2e64bc023c3b96f9330cb8 (plain) (blame)
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
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
//===- ThreadSafety.cpp ---------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// A intra-procedural analysis for thread safety (e.g. deadlocks and race
// conditions), based off of an annotation system.
//
// See http://clang.llvm.org/docs/ThreadSafetyAnalysis.html
// for more information.
//
//===----------------------------------------------------------------------===//

#include "clang/Analysis/Analyses/ThreadSafety.h"
#include "clang/AST/Attr.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclGroup.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/OperationKinds.h"
#include "clang/AST/Stmt.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/AST/Type.h"
#include "clang/Analysis/Analyses/PostOrderCFGView.h"
#include "clang/Analysis/Analyses/ThreadSafetyCommon.h"
#include "clang/Analysis/Analyses/ThreadSafetyTIL.h"
#include "clang/Analysis/Analyses/ThreadSafetyTraverse.h"
#include "clang/Analysis/Analyses/ThreadSafetyUtil.h"
#include "clang/Analysis/AnalysisDeclContext.h"
#include "clang/Analysis/CFG.h"
#include "clang/Basic/Builtins.h"
#include "clang/Basic/LLVM.h"
#include "clang/Basic/OperatorKinds.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Basic/Specifiers.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/ImmutableMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <functional>
#include <iterator>
#include <memory>
#include <optional>
#include <string>
#include <type_traits>
#include <utility>
#include <vector>

using namespace clang;
using namespace threadSafety;

// Key method definition
ThreadSafetyHandler::~ThreadSafetyHandler() = default;

/// Issue a warning about an invalid lock expression
static void warnInvalidLock(ThreadSafetyHandler &Handler,
                            const Expr *MutexExp, const NamedDecl *D,
                            const Expr *DeclExp, StringRef Kind) {
  SourceLocation Loc;
  if (DeclExp)
    Loc = DeclExp->getExprLoc();

  // FIXME: add a note about the attribute location in MutexExp or D
  if (Loc.isValid())
    Handler.handleInvalidLockExp(Loc);
}

namespace {

/// A set of CapabilityExpr objects, which are compiled from thread safety
/// attributes on a function.
class CapExprSet : public SmallVector<CapabilityExpr, 4> {
public:
  /// Push M onto list, but discard duplicates.
  void push_back_nodup(const CapabilityExpr &CapE) {
    if (llvm::none_of(*this, [=](const CapabilityExpr &CapE2) {
          return CapE.equals(CapE2);
        }))
      push_back(CapE);
  }
};

class FactManager;
class FactSet;

/// This is a helper class that stores a fact that is known at a
/// particular point in program execution.  Currently, a fact is a capability,
/// along with additional information, such as where it was acquired, whether
/// it is exclusive or shared, etc.
///
/// FIXME: this analysis does not currently support re-entrant locking.
class FactEntry : public CapabilityExpr {
public:
  /// Where a fact comes from.
  enum SourceKind {
    Acquired, ///< The fact has been directly acquired.
    Asserted, ///< The fact has been asserted to be held.
    Declared, ///< The fact is assumed to be held by callers.
    Managed,  ///< The fact has been acquired through a scoped capability.
  };

private:
  /// Exclusive or shared.
  LockKind LKind : 8;

  // How it was acquired.
  SourceKind Source : 8;

  /// Where it was acquired.
  SourceLocation AcquireLoc;

public:
  FactEntry(const CapabilityExpr &CE, LockKind LK, SourceLocation Loc,
            SourceKind Src)
      : CapabilityExpr(CE), LKind(LK), Source(Src), AcquireLoc(Loc) {}
  virtual ~FactEntry() = default;

  LockKind kind() const { return LKind;      }
  SourceLocation loc() const { return AcquireLoc; }

  bool asserted() const { return Source == Asserted; }
  bool declared() const { return Source == Declared; }
  bool managed() const { return Source == Managed; }

  virtual void
  handleRemovalFromIntersection(const FactSet &FSet, FactManager &FactMan,
                                SourceLocation JoinLoc, LockErrorKind LEK,
                                ThreadSafetyHandler &Handler) const = 0;
  virtual void handleLock(FactSet &FSet, FactManager &FactMan,
                          const FactEntry &entry,
                          ThreadSafetyHandler &Handler) const = 0;
  virtual void handleUnlock(FactSet &FSet, FactManager &FactMan,
                            const CapabilityExpr &Cp, SourceLocation UnlockLoc,
                            bool FullyRemove,
                            ThreadSafetyHandler &Handler) const = 0;

  // Return true if LKind >= LK, where exclusive > shared
  bool isAtLeast(LockKind LK) const {
    return  (LKind == LK_Exclusive) || (LK == LK_Shared);
  }
};

using FactID = unsigned short;

/// FactManager manages the memory for all facts that are created during
/// the analysis of a single routine.
class FactManager {
private:
  std::vector<std::unique_ptr<const FactEntry>> Facts;

public:
  FactID newFact(std::unique_ptr<FactEntry> Entry) {
    Facts.push_back(std::move(Entry));
    return static_cast<unsigned short>(Facts.size() - 1);
  }

  const FactEntry &operator[](FactID F) const { return *Facts[F]; }
};

/// A FactSet is the set of facts that are known to be true at a
/// particular program point.  FactSets must be small, because they are
/// frequently copied, and are thus implemented as a set of indices into a
/// table maintained by a FactManager.  A typical FactSet only holds 1 or 2
/// locks, so we can get away with doing a linear search for lookup.  Note
/// that a hashtable or map is inappropriate in this case, because lookups
/// may involve partial pattern matches, rather than exact matches.
class FactSet {
private:
  using FactVec = SmallVector<FactID, 4>;

  FactVec FactIDs;

public:
  using iterator = FactVec::iterator;
  using const_iterator = FactVec::const_iterator;

  iterator begin() { return FactIDs.begin(); }
  const_iterator begin() const { return FactIDs.begin(); }

  iterator end() { return FactIDs.end(); }
  const_iterator end() const { return FactIDs.end(); }

  bool isEmpty() const { return FactIDs.size() == 0; }

  // Return true if the set contains only negative facts
  bool isEmpty(FactManager &FactMan) const {
    for (const auto FID : *this) {
      if (!FactMan[FID].negative())
        return false;
    }
    return true;
  }

  void addLockByID(FactID ID) { FactIDs.push_back(ID); }

  FactID addLock(FactManager &FM, std::unique_ptr<FactEntry> Entry) {
    FactID F = FM.newFact(std::move(Entry));
    FactIDs.push_back(F);
    return F;
  }

  bool removeLock(FactManager& FM, const CapabilityExpr &CapE) {
    unsigned n = FactIDs.size();
    if (n == 0)
      return false;

    for (unsigned i = 0; i < n-1; ++i) {
      if (FM[FactIDs[i]].matches(CapE)) {
        FactIDs[i] = FactIDs[n-1];
        FactIDs.pop_back();
        return true;
      }
    }
    if (FM[FactIDs[n-1]].matches(CapE)) {
      FactIDs.pop_back();
      return true;
    }
    return false;
  }

  iterator findLockIter(FactManager &FM, const CapabilityExpr &CapE) {
    return std::find_if(begin(), end(), [&](FactID ID) {
      return FM[ID].matches(CapE);
    });
  }

  const FactEntry *findLock(FactManager &FM, const CapabilityExpr &CapE) const {
    auto I = std::find_if(begin(), end(), [&](FactID ID) {
      return FM[ID].matches(CapE);
    });
    return I != end() ? &FM[*I] : nullptr;
  }

  const FactEntry *findLockUniv(FactManager &FM,
                                const CapabilityExpr &CapE) const {
    auto I = std::find_if(begin(), end(), [&](FactID ID) -> bool {
      return FM[ID].matchesUniv(CapE);
    });
    return I != end() ? &FM[*I] : nullptr;
  }

  const FactEntry *findPartialMatch(FactManager &FM,
                                    const CapabilityExpr &CapE) const {
    auto I = std::find_if(begin(), end(), [&](FactID ID) -> bool {
      return FM[ID].partiallyMatches(CapE);
    });
    return I != end() ? &FM[*I] : nullptr;
  }

  bool containsMutexDecl(FactManager &FM, const ValueDecl* Vd) const {
    auto I = std::find_if(begin(), end(), [&](FactID ID) -> bool {
      return FM[ID].valueDecl() == Vd;
    });
    return I != end();
  }
};

class ThreadSafetyAnalyzer;

} // namespace

namespace clang {
namespace threadSafety {

class BeforeSet {
private:
  using BeforeVect = SmallVector<const ValueDecl *, 4>;

  struct BeforeInfo {
    BeforeVect Vect;
    int Visited = 0;

    BeforeInfo() = default;
    BeforeInfo(BeforeInfo &&) = default;
  };

  using BeforeMap =
      llvm::DenseMap<const ValueDecl *, std::unique_ptr<BeforeInfo>>;
  using CycleMap = llvm::DenseMap<const ValueDecl *, bool>;

public:
  BeforeSet() = default;

  BeforeInfo* insertAttrExprs(const ValueDecl* Vd,
                              ThreadSafetyAnalyzer& Analyzer);

  BeforeInfo *getBeforeInfoForDecl(const ValueDecl *Vd,
                                   ThreadSafetyAnalyzer &Analyzer);

  void checkBeforeAfter(const ValueDecl* Vd,
                        const FactSet& FSet,
                        ThreadSafetyAnalyzer& Analyzer,
                        SourceLocation Loc, StringRef CapKind);

private:
  BeforeMap BMap;
  CycleMap CycMap;
};

} // namespace threadSafety
} // namespace clang

namespace {

class LocalVariableMap;

using LocalVarContext = llvm::ImmutableMap<const NamedDecl *, unsigned>;

/// A side (entry or exit) of a CFG node.
enum CFGBlockSide { CBS_Entry, CBS_Exit };

/// CFGBlockInfo is a struct which contains all the information that is
/// maintained for each block in the CFG.  See LocalVariableMap for more
/// information about the contexts.
struct CFGBlockInfo {
  // Lockset held at entry to block
  FactSet EntrySet;

  // Lockset held at exit from block
  FactSet ExitSet;

  // Context held at entry to block
  LocalVarContext EntryContext;

  // Context held at exit from block
  LocalVarContext ExitContext;

  // Location of first statement in block
  SourceLocation EntryLoc;

  // Location of last statement in block.
  SourceLocation ExitLoc;

  // Used to replay contexts later
  unsigned EntryIndex;

  // Is this block reachable?
  bool Reachable = false;

  const FactSet &getSet(CFGBlockSide Side) const {
    return Side == CBS_Entry ? EntrySet : ExitSet;
  }

  SourceLocation getLocation(CFGBlockSide Side) const {
    return Side == CBS_Entry ? EntryLoc : ExitLoc;
  }

private:
  CFGBlockInfo(LocalVarContext EmptyCtx)
      : EntryContext(EmptyCtx), ExitContext(EmptyCtx) {}

public:
  static CFGBlockInfo getEmptyBlockInfo(LocalVariableMap &M);
};

// A LocalVariableMap maintains a map from local variables to their currently
// valid definitions.  It provides SSA-like functionality when traversing the
// CFG.  Like SSA, each definition or assignment to a variable is assigned a
// unique name (an integer), which acts as the SSA name for that definition.
// The total set of names is shared among all CFG basic blocks.
// Unlike SSA, we do not rewrite expressions to replace local variables declrefs
// with their SSA-names.  Instead, we compute a Context for each point in the
// code, which maps local variables to the appropriate SSA-name.  This map
// changes with each assignment.
//
// The map is computed in a single pass over the CFG.  Subsequent analyses can
// then query the map to find the appropriate Context for a statement, and use
// that Context to look up the definitions of variables.
class LocalVariableMap {
public:
  using Context = LocalVarContext;

  /// A VarDefinition consists of an expression, representing the value of the
  /// variable, along with the context in which that expression should be
  /// interpreted.  A reference VarDefinition does not itself contain this
  /// information, but instead contains a pointer to a previous VarDefinition.
  struct VarDefinition {
  public:
    friend class LocalVariableMap;

    // The original declaration for this variable.
    const NamedDecl *Dec;

    // The expression for this variable, OR
    const Expr *Exp = nullptr;

    // Reference to another VarDefinition
    unsigned Ref = 0;

    // The map with which Exp should be interpreted.
    Context Ctx;

    bool isReference() { return !Exp; }

  private:
    // Create ordinary variable definition
    VarDefinition(const NamedDecl *D, const Expr *E, Context C)
        : Dec(D), Exp(E), Ctx(C) {}

    // Create reference to previous definition
    VarDefinition(const NamedDecl *D, unsigned R, Context C)
        : Dec(D), Ref(R), Ctx(C) {}
  };

private:
  Context::Factory ContextFactory;
  std::vector<VarDefinition> VarDefinitions;
  std::vector<std::pair<const Stmt *, Context>> SavedContexts;

public:
  LocalVariableMap() {
    // index 0 is a placeholder for undefined variables (aka phi-nodes).
    VarDefinitions.push_back(VarDefinition(nullptr, 0u, getEmptyContext()));
  }

  /// Look up a definition, within the given context.
  const VarDefinition* lookup(const NamedDecl *D, Context Ctx) {
    const unsigned *i = Ctx.lookup(D);
    if (!i)
      return nullptr;
    assert(*i < VarDefinitions.size());
    return &VarDefinitions[*i];
  }

  /// Look up the definition for D within the given context.  Returns
  /// NULL if the expression is not statically known.  If successful, also
  /// modifies Ctx to hold the context of the return Expr.
  const Expr* lookupExpr(const NamedDecl *D, Context &Ctx) {
    const unsigned *P = Ctx.lookup(D);
    if (!P)
      return nullptr;

    unsigned i = *P;
    while (i > 0) {
      if (VarDefinitions[i].Exp) {
        Ctx = VarDefinitions[i].Ctx;
        return VarDefinitions[i].Exp;
      }
      i = VarDefinitions[i].Ref;
    }
    return nullptr;
  }

  Context getEmptyContext() { return ContextFactory.getEmptyMap(); }

  /// Return the next context after processing S.  This function is used by
  /// clients of the class to get the appropriate context when traversing the
  /// CFG.  It must be called for every assignment or DeclStmt.
  Context getNextContext(unsigned &CtxIndex, const Stmt *S, Context C) {
    if (SavedContexts[CtxIndex+1].first == S) {
      CtxIndex++;
      Context Result = SavedContexts[CtxIndex].second;
      return Result;
    }
    return C;
  }

  void dumpVarDefinitionName(unsigned i) {
    if (i == 0) {
      llvm::errs() << "Undefined";
      return;
    }
    const NamedDecl *Dec = VarDefinitions[i].Dec;
    if (!Dec) {
      llvm::errs() << "<<NULL>>";
      return;
    }
    Dec->printName(llvm::errs());
    llvm::errs() << "." << i << " " << ((const void*) Dec);
  }

  /// Dumps an ASCII representation of the variable map to llvm::errs()
  void dump() {
    for (unsigned i = 1, e = VarDefinitions.size(); i < e; ++i) {
      const Expr *Exp = VarDefinitions[i].Exp;
      unsigned Ref = VarDefinitions[i].Ref;

      dumpVarDefinitionName(i);
      llvm::errs() << " = ";
      if (Exp) Exp->dump();
      else {
        dumpVarDefinitionName(Ref);
        llvm::errs() << "\n";
      }
    }
  }

  /// Dumps an ASCII representation of a Context to llvm::errs()
  void dumpContext(Context C) {
    for (Context::iterator I = C.begin(), E = C.end(); I != E; ++I) {
      const NamedDecl *D = I.getKey();
      D->printName(llvm::errs());
      const unsigned *i = C.lookup(D);
      llvm::errs() << " -> ";
      dumpVarDefinitionName(*i);
      llvm::errs() << "\n";
    }
  }

  /// Builds the variable map.
  void traverseCFG(CFG *CFGraph, const PostOrderCFGView *SortedGraph,
                   std::vector<CFGBlockInfo> &BlockInfo);

protected:
  friend class VarMapBuilder;

  // Get the current context index
  unsigned getContextIndex() { return SavedContexts.size()-1; }

  // Save the current context for later replay
  void saveContext(const Stmt *S, Context C) {
    SavedContexts.push_back(std::make_pair(S, C));
  }

  // Adds a new definition to the given context, and returns a new context.
  // This method should be called when declaring a new variable.
  Context addDefinition(const NamedDecl *D, const Expr *Exp, Context Ctx) {
    assert(!Ctx.contains(D));
    unsigned newID = VarDefinitions.size();
    Context NewCtx = ContextFactory.add(Ctx, D, newID);
    VarDefinitions.push_back(VarDefinition(D, Exp, Ctx));
    return NewCtx;
  }

  // Add a new reference to an existing definition.
  Context addReference(const NamedDecl *D, unsigned i, Context Ctx) {
    unsigned newID = VarDefinitions.size();
    Context NewCtx = ContextFactory.add(Ctx, D, newID);
    VarDefinitions.push_back(VarDefinition(D, i, Ctx));
    return NewCtx;
  }

  // Updates a definition only if that definition is already in the map.
  // This method should be called when assigning to an existing variable.
  Context updateDefinition(const NamedDecl *D, Expr *Exp, Context Ctx) {
    if (Ctx.contains(D)) {
      unsigned newID = VarDefinitions.size();
      Context NewCtx = ContextFactory.remove(Ctx, D);
      NewCtx = ContextFactory.add(NewCtx, D, newID);
      VarDefinitions.push_back(VarDefinition(D, Exp, Ctx));
      return NewCtx;
    }
    return Ctx;
  }

  // Removes a definition from the context, but keeps the variable name
  // as a valid variable.  The index 0 is a placeholder for cleared definitions.
  Context clearDefinition(const NamedDecl *D, Context Ctx) {
    Context NewCtx = Ctx;
    if (NewCtx.contains(D)) {
      NewCtx = ContextFactory.remove(NewCtx, D);
      NewCtx = ContextFactory.add(NewCtx, D, 0);
    }
    return NewCtx;
  }

  // Remove a definition entirely frmo the context.
  Context removeDefinition(const NamedDecl *D, Context Ctx) {
    Context NewCtx = Ctx;
    if (NewCtx.contains(D)) {
      NewCtx = ContextFactory.remove(NewCtx, D);
    }
    return NewCtx;
  }

  Context intersectContexts(Context C1, Context C2);
  Context createReferenceContext(Context C);
  void intersectBackEdge(Context C1, Context C2);
};

} // namespace

// This has to be defined after LocalVariableMap.
CFGBlockInfo CFGBlockInfo::getEmptyBlockInfo(LocalVariableMap &M) {
  return CFGBlockInfo(M.getEmptyContext());
}

namespace {

/// Visitor which builds a LocalVariableMap
class VarMapBuilder : public ConstStmtVisitor<VarMapBuilder> {
public:
  LocalVariableMap* VMap;
  LocalVariableMap::Context Ctx;

  VarMapBuilder(LocalVariableMap *VM, LocalVariableMap::Context C)
      : VMap(VM), Ctx(C) {}

  void VisitDeclStmt(const DeclStmt *S);
  void VisitBinaryOperator(const BinaryOperator *BO);
};

} // namespace

// Add new local variables to the variable map
void VarMapBuilder::VisitDeclStmt(const DeclStmt *S) {
  bool modifiedCtx = false;
  const DeclGroupRef DGrp = S->getDeclGroup();
  for (const auto *D : DGrp) {
    if (const auto *VD = dyn_cast_or_null<VarDecl>(D)) {
      const Expr *E = VD->getInit();

      // Add local variables with trivial type to the variable map
      QualType T = VD->getType();
      if (T.isTrivialType(VD->getASTContext())) {
        Ctx = VMap->addDefinition(VD, E, Ctx);
        modifiedCtx = true;
      }
    }
  }
  if (modifiedCtx)
    VMap->saveContext(S, Ctx);
}

// Update local variable definitions in variable map
void VarMapBuilder::VisitBinaryOperator(const BinaryOperator *BO) {
  if (!BO->isAssignmentOp())
    return;

  Expr *LHSExp = BO->getLHS()->IgnoreParenCasts();

  // Update the variable map and current context.
  if (const auto *DRE = dyn_cast<DeclRefExpr>(LHSExp)) {
    const ValueDecl *VDec = DRE->getDecl();
    if (Ctx.lookup(VDec)) {
      if (BO->getOpcode() == BO_Assign)
        Ctx = VMap->updateDefinition(VDec, BO->getRHS(), Ctx);
      else
        // FIXME -- handle compound assignment operators
        Ctx = VMap->clearDefinition(VDec, Ctx);
      VMap->saveContext(BO, Ctx);
    }
  }
}

// Computes the intersection of two contexts.  The intersection is the
// set of variables which have the same definition in both contexts;
// variables with different definitions are discarded.
LocalVariableMap::Context
LocalVariableMap::intersectContexts(Context C1, Context C2) {
  Context Result = C1;
  for (const auto &P : C1) {
    const NamedDecl *Dec = P.first;
    const unsigned *i2 = C2.lookup(Dec);
    if (!i2)             // variable doesn't exist on second path
      Result = removeDefinition(Dec, Result);
    else if (*i2 != P.second)  // variable exists, but has different definition
      Result = clearDefinition(Dec, Result);
  }
  return Result;
}

// For every variable in C, create a new variable that refers to the
// definition in C.  Return a new context that contains these new variables.
// (We use this for a naive implementation of SSA on loop back-edges.)
LocalVariableMap::Context LocalVariableMap::createReferenceContext(Context C) {
  Context Result = getEmptyContext();
  for (const auto &P : C)
    Result = addReference(P.first, P.second, Result);
  return Result;
}

// This routine also takes the intersection of C1 and C2, but it does so by
// altering the VarDefinitions.  C1 must be the result of an earlier call to
// createReferenceContext.
void LocalVariableMap::intersectBackEdge(Context C1, Context C2) {
  for (const auto &P : C1) {
    unsigned i1 = P.second;
    VarDefinition *VDef = &VarDefinitions[i1];
    assert(VDef->isReference());

    const unsigned *i2 = C2.lookup(P.first);
    if (!i2 || (*i2 != i1))
      VDef->Ref = 0;    // Mark this variable as undefined
  }
}

// Traverse the CFG in topological order, so all predecessors of a block
// (excluding back-edges) are visited before the block itself.  At
// each point in the code, we calculate a Context, which holds the set of
// variable definitions which are visible at that point in execution.
// Visible variables are mapped to their definitions using an array that
// contains all definitions.
//
// At join points in the CFG, the set is computed as the intersection of
// the incoming sets along each edge, E.g.
//
//                       { Context                 | VarDefinitions }
//   int x = 0;          { x -> x1                 | x1 = 0 }
//   int y = 0;          { x -> x1, y -> y1        | y1 = 0, x1 = 0 }
//   if (b) x = 1;       { x -> x2, y -> y1        | x2 = 1, y1 = 0, ... }
//   else   x = 2;       { x -> x3, y -> y1        | x3 = 2, x2 = 1, ... }
//   ...                 { y -> y1  (x is unknown) | x3 = 2, x2 = 1, ... }
//
// This is essentially a simpler and more naive version of the standard SSA
// algorithm.  Those definitions that remain in the intersection are from blocks
// that strictly dominate the current block.  We do not bother to insert proper
// phi nodes, because they are not used in our analysis; instead, wherever
// a phi node would be required, we simply remove that definition from the
// context (E.g. x above).
//
// The initial traversal does not capture back-edges, so those need to be
// handled on a separate pass.  Whenever the first pass encounters an
// incoming back edge, it duplicates the context, creating new definitions
// that refer back to the originals.  (These correspond to places where SSA
// might have to insert a phi node.)  On the second pass, these definitions are
// set to NULL if the variable has changed on the back-edge (i.e. a phi
// node was actually required.)  E.g.
//
//                       { Context           | VarDefinitions }
//   int x = 0, y = 0;   { x -> x1, y -> y1  | y1 = 0, x1 = 0 }
//   while (b)           { x -> x2, y -> y1  | [1st:] x2=x1; [2nd:] x2=NULL; }
//     x = x+1;          { x -> x3, y -> y1  | x3 = x2 + 1, ... }
//   ...                 { y -> y1           | x3 = 2, x2 = 1, ... }
void LocalVariableMap::traverseCFG(CFG *CFGraph,
                                   const PostOrderCFGView *SortedGraph,
                                   std::vector<CFGBlockInfo> &BlockInfo) {
  PostOrderCFGView::CFGBlockSet VisitedBlocks(CFGraph);

  for (const auto *CurrBlock : *SortedGraph) {
    unsigned CurrBlockID = CurrBlock->getBlockID();
    CFGBlockInfo *CurrBlockInfo = &BlockInfo[CurrBlockID];

    VisitedBlocks.insert(CurrBlock);

    // Calculate the entry context for the current block
    bool HasBackEdges = false;
    bool CtxInit = true;
    for (CFGBlock::const_pred_iterator PI = CurrBlock->pred_begin(),
         PE  = CurrBlock->pred_end(); PI != PE; ++PI) {
      // if *PI -> CurrBlock is a back edge, so skip it
      if (*PI == nullptr || !VisitedBlocks.alreadySet(*PI)) {
        HasBackEdges = true;
        continue;
      }

      unsigned PrevBlockID = (*PI)->getBlockID();
      CFGBlockInfo *PrevBlockInfo = &BlockInfo[PrevBlockID];

      if (CtxInit) {
        CurrBlockInfo->EntryContext = PrevBlockInfo->ExitContext;
        CtxInit = false;
      }
      else {
        CurrBlockInfo->EntryContext =
          intersectContexts(CurrBlockInfo->EntryContext,
                            PrevBlockInfo->ExitContext);
      }
    }

    // Duplicate the context if we have back-edges, so we can call
    // intersectBackEdges later.
    if (HasBackEdges)
      CurrBlockInfo->EntryContext =
        createReferenceContext(CurrBlockInfo->EntryContext);

    // Create a starting context index for the current block
    saveContext(nullptr, CurrBlockInfo->EntryContext);
    CurrBlockInfo->EntryIndex = getContextIndex();

    // Visit all the statements in the basic block.
    VarMapBuilder VMapBuilder(this, CurrBlockInfo->EntryContext);
    for (const auto &BI : *CurrBlock) {
      switch (BI.getKind()) {
        case CFGElement::Statement: {
          CFGStmt CS = BI.castAs<CFGStmt>();
          VMapBuilder.Visit(CS.getStmt());
          break;
        }
        default:
          break;
      }
    }
    CurrBlockInfo->ExitContext = VMapBuilder.Ctx;

    // Mark variables on back edges as "unknown" if they've been changed.
    for (CFGBlock::const_succ_iterator SI = CurrBlock->succ_begin(),
         SE  = CurrBlock->succ_end(); SI != SE; ++SI) {
      // if CurrBlock -> *SI is *not* a back edge
      if (*SI == nullptr || !VisitedBlocks.alreadySet(*SI))
        continue;

      CFGBlock *FirstLoopBlock = *SI;
      Context LoopBegin = BlockInfo[FirstLoopBlock->getBlockID()].EntryContext;
      Context LoopEnd   = CurrBlockInfo->ExitContext;
      intersectBackEdge(LoopBegin, LoopEnd);
    }
  }

  // Put an extra entry at the end of the indexed context array
  unsigned exitID = CFGraph->getExit().getBlockID();
  saveContext(nullptr, BlockInfo[exitID].ExitContext);
}

/// Find the appropriate source locations to use when producing diagnostics for
/// each block in the CFG.
static void findBlockLocations(CFG *CFGraph,
                               const PostOrderCFGView *SortedGraph,
                               std::vector<CFGBlockInfo> &BlockInfo) {
  for (const auto *CurrBlock : *SortedGraph) {
    CFGBlockInfo *CurrBlockInfo = &BlockInfo[CurrBlock->getBlockID()];

    // Find the source location of the last statement in the block, if the
    // block is not empty.
    if (const Stmt *S = CurrBlock->getTerminatorStmt()) {
      CurrBlockInfo->EntryLoc = CurrBlockInfo->ExitLoc = S->getBeginLoc();
    } else {
      for (CFGBlock::const_reverse_iterator BI = CurrBlock->rbegin(),
           BE = CurrBlock->rend(); BI != BE; ++BI) {
        // FIXME: Handle other CFGElement kinds.
        if (std::optional<CFGStmt> CS = BI->getAs<CFGStmt>()) {
          CurrBlockInfo->ExitLoc = CS->getStmt()->getBeginLoc();
          break;
        }
      }
    }

    if (CurrBlockInfo->ExitLoc.isValid()) {
      // This block contains at least one statement. Find the source location
      // of the first statement in the block.
      for (const auto &BI : *CurrBlock) {
        // FIXME: Handle other CFGElement kinds.
        if (std::optional<CFGStmt> CS = BI.getAs<CFGStmt>()) {
          CurrBlockInfo->EntryLoc = CS->getStmt()->getBeginLoc();
          break;
        }
      }
    } else if (CurrBlock->pred_size() == 1 && *CurrBlock->pred_begin() &&
               CurrBlock != &CFGraph->getExit()) {
      // The block is empty, and has a single predecessor. Use its exit
      // location.
      CurrBlockInfo->EntryLoc = CurrBlockInfo->ExitLoc =
          BlockInfo[(*CurrBlock->pred_begin())->getBlockID()].ExitLoc;
    } else if (CurrBlock->succ_size() == 1 && *CurrBlock->succ_begin()) {
      // The block is empty, and has a single successor. Use its entry
      // location.
      CurrBlockInfo->EntryLoc = CurrBlockInfo->ExitLoc =
          BlockInfo[(*CurrBlock->succ_begin())->getBlockID()].EntryLoc;
    }
  }
}

namespace {

class LockableFactEntry : public FactEntry {
public:
  LockableFactEntry(const CapabilityExpr &CE, LockKind LK, SourceLocation Loc,
                    SourceKind Src = Acquired)
      : FactEntry(CE, LK, Loc, Src) {}

  void
  handleRemovalFromIntersection(const FactSet &FSet, FactManager &FactMan,
                                SourceLocation JoinLoc, LockErrorKind LEK,
                                ThreadSafetyHandler &Handler) const override {
    if (!asserted() && !negative() && !isUniversal()) {
      Handler.handleMutexHeldEndOfScope(getKind(), toString(), loc(), JoinLoc,
                                        LEK);
    }
  }

  void handleLock(FactSet &FSet, FactManager &FactMan, const FactEntry &entry,
                  ThreadSafetyHandler &Handler) const override {
    Handler.handleDoubleLock(entry.getKind(), entry.toString(), loc(),
                             entry.loc());
  }

  void handleUnlock(FactSet &FSet, FactManager &FactMan,
                    const CapabilityExpr &Cp, SourceLocation UnlockLoc,
                    bool FullyRemove,
                    ThreadSafetyHandler &Handler) const override {
    FSet.removeLock(FactMan, Cp);
    if (!Cp.negative()) {
      FSet.addLock(FactMan, std::make_unique<LockableFactEntry>(
                                !Cp, LK_Exclusive, UnlockLoc));
    }
  }
};

class ScopedLockableFactEntry : public FactEntry {
private:
  enum UnderlyingCapabilityKind {
    UCK_Acquired,          ///< Any kind of acquired capability.
    UCK_ReleasedShared,    ///< Shared capability that was released.
    UCK_ReleasedExclusive, ///< Exclusive capability that was released.
  };

  struct UnderlyingCapability {
    CapabilityExpr Cap;
    UnderlyingCapabilityKind Kind;
  };

  SmallVector<UnderlyingCapability, 2> UnderlyingMutexes;

public:
  ScopedLockableFactEntry(const CapabilityExpr &CE, SourceLocation Loc)
      : FactEntry(CE, LK_Exclusive, Loc, Acquired) {}

  void addLock(const CapabilityExpr &M) {
    UnderlyingMutexes.push_back(UnderlyingCapability{M, UCK_Acquired});
  }

  void addExclusiveUnlock(const CapabilityExpr &M) {
    UnderlyingMutexes.push_back(UnderlyingCapability{M, UCK_ReleasedExclusive});
  }

  void addSharedUnlock(const CapabilityExpr &M) {
    UnderlyingMutexes.push_back(UnderlyingCapability{M, UCK_ReleasedShared});
  }

  void
  handleRemovalFromIntersection(const FactSet &FSet, FactManager &FactMan,
                                SourceLocation JoinLoc, LockErrorKind LEK,
                                ThreadSafetyHandler &Handler) const override {
    for (const auto &UnderlyingMutex : UnderlyingMutexes) {
      const auto *Entry = FSet.findLock(FactMan, UnderlyingMutex.Cap);
      if ((UnderlyingMutex.Kind == UCK_Acquired && Entry) ||
          (UnderlyingMutex.Kind != UCK_Acquired && !Entry)) {
        // If this scoped lock manages another mutex, and if the underlying
        // mutex is still/not held, then warn about the underlying mutex.
        Handler.handleMutexHeldEndOfScope(UnderlyingMutex.Cap.getKind(),
                                          UnderlyingMutex.Cap.toString(), loc(),
                                          JoinLoc, LEK);
      }
    }
  }

  void handleLock(FactSet &FSet, FactManager &FactMan, const FactEntry &entry,
                  ThreadSafetyHandler &Handler) const override {
    for (const auto &UnderlyingMutex : UnderlyingMutexes) {
      if (UnderlyingMutex.Kind == UCK_Acquired)
        lock(FSet, FactMan, UnderlyingMutex.Cap, entry.kind(), entry.loc(),
             &Handler);
      else
        unlock(FSet, FactMan, UnderlyingMutex.Cap, entry.loc(), &Handler);
    }
  }

  void handleUnlock(FactSet &FSet, FactManager &FactMan,
                    const CapabilityExpr &Cp, SourceLocation UnlockLoc,
                    bool FullyRemove,
                    ThreadSafetyHandler &Handler) const override {
    assert(!Cp.negative() && "Managing object cannot be negative.");
    for (const auto &UnderlyingMutex : UnderlyingMutexes) {
      // Remove/lock the underlying mutex if it exists/is still unlocked; warn
      // on double unlocking/locking if we're not destroying the scoped object.
      ThreadSafetyHandler *TSHandler = FullyRemove ? nullptr : &Handler;
      if (UnderlyingMutex.Kind == UCK_Acquired) {
        unlock(FSet, FactMan, UnderlyingMutex.Cap, UnlockLoc, TSHandler);
      } else {
        LockKind kind = UnderlyingMutex.Kind == UCK_ReleasedShared
                            ? LK_Shared
                            : LK_Exclusive;
        lock(FSet, FactMan, UnderlyingMutex.Cap, kind, UnlockLoc, TSHandler);
      }
    }
    if (FullyRemove)
      FSet.removeLock(FactMan, Cp);
  }

private:
  void lock(FactSet &FSet, FactManager &FactMan, const CapabilityExpr &Cp,
            LockKind kind, SourceLocation loc,
            ThreadSafetyHandler *Handler) const {
    if (const FactEntry *Fact = FSet.findLock(FactMan, Cp)) {
      if (Handler)
        Handler->handleDoubleLock(Cp.getKind(), Cp.toString(), Fact->loc(),
                                  loc);
    } else {
      FSet.removeLock(FactMan, !Cp);
      FSet.addLock(FactMan,
                   std::make_unique<LockableFactEntry>(Cp, kind, loc, Managed));
    }
  }

  void unlock(FactSet &FSet, FactManager &FactMan, const CapabilityExpr &Cp,
              SourceLocation loc, ThreadSafetyHandler *Handler) const {
    if (FSet.findLock(FactMan, Cp)) {
      FSet.removeLock(FactMan, Cp);
      FSet.addLock(FactMan, std::make_unique<LockableFactEntry>(
                                !Cp, LK_Exclusive, loc));
    } else if (Handler) {
      SourceLocation PrevLoc;
      if (const FactEntry *Neg = FSet.findLock(FactMan, !Cp))
        PrevLoc = Neg->loc();
      Handler->handleUnmatchedUnlock(Cp.getKind(), Cp.toString(), loc, PrevLoc);
    }
  }
};

/// Class which implements the core thread safety analysis routines.
class ThreadSafetyAnalyzer {
  friend class BuildLockset;
  friend class threadSafety::BeforeSet;

  llvm::BumpPtrAllocator Bpa;
  threadSafety::til::MemRegionRef Arena;
  threadSafety::SExprBuilder SxBuilder;

  ThreadSafetyHandler &Handler;
  const CXXMethodDecl *CurrentMethod;
  LocalVariableMap LocalVarMap;
  FactManager FactMan;
  std::vector<CFGBlockInfo> BlockInfo;

  BeforeSet *GlobalBeforeSet;

public:
  ThreadSafetyAnalyzer(ThreadSafetyHandler &H, BeforeSet* Bset)
      : Arena(&Bpa), SxBuilder(Arena), Handler(H), GlobalBeforeSet(Bset) {}

  bool inCurrentScope(const CapabilityExpr &CapE);

  void addLock(FactSet &FSet, std::unique_ptr<FactEntry> Entry,
               bool ReqAttr = false);
  void removeLock(FactSet &FSet, const CapabilityExpr &CapE,
                  SourceLocation UnlockLoc, bool FullyRemove, LockKind Kind);

  template <typename AttrType>
  void getMutexIDs(CapExprSet &Mtxs, AttrType *Attr, const Expr *Exp,
                   const NamedDecl *D, til::SExpr *Self = nullptr);

  template <class AttrType>
  void getMutexIDs(CapExprSet &Mtxs, AttrType *Attr, const Expr *Exp,
                   const NamedDecl *D,
                   const CFGBlock *PredBlock, const CFGBlock *CurrBlock,
                   Expr *BrE, bool Neg);

  const CallExpr* getTrylockCallExpr(const Stmt *Cond, LocalVarContext C,
                                     bool &Negate);

  void getEdgeLockset(FactSet &Result, const FactSet &ExitSet,
                      const CFGBlock* PredBlock,
                      const CFGBlock *CurrBlock);

  bool join(const FactEntry &a, const FactEntry &b, bool CanModify);

  void intersectAndWarn(FactSet &EntrySet, const FactSet &ExitSet,
                        SourceLocation JoinLoc, LockErrorKind EntryLEK,
                        LockErrorKind ExitLEK);

  void intersectAndWarn(FactSet &EntrySet, const FactSet &ExitSet,
                        SourceLocation JoinLoc, LockErrorKind LEK) {
    intersectAndWarn(EntrySet, ExitSet, JoinLoc, LEK, LEK);
  }

  void runAnalysis(AnalysisDeclContext &AC);
};

} // namespace

/// Process acquired_before and acquired_after attributes on Vd.
BeforeSet::BeforeInfo* BeforeSet::insertAttrExprs(const ValueDecl* Vd,
    ThreadSafetyAnalyzer& Analyzer) {
  // Create a new entry for Vd.
  BeforeInfo *Info = nullptr;
  {
    // Keep InfoPtr in its own scope in case BMap is modified later and the
    // reference becomes invalid.
    std::unique_ptr<BeforeInfo> &InfoPtr = BMap[Vd];
    if (!InfoPtr)
      InfoPtr.reset(new BeforeInfo());
    Info = InfoPtr.get();
  }

  for (const auto *At : Vd->attrs()) {
    switch (At->getKind()) {
      case attr::AcquiredBefore: {
        const auto *A = cast<AcquiredBeforeAttr>(At);

        // Read exprs from the attribute, and add them to BeforeVect.
        for (const auto *Arg : A->args()) {
          CapabilityExpr Cp =
            Analyzer.SxBuilder.translateAttrExpr(Arg, nullptr);
          if (const ValueDecl *Cpvd = Cp.valueDecl()) {
            Info->Vect.push_back(Cpvd);
            const auto It = BMap.find(Cpvd);
            if (It == BMap.end())
              insertAttrExprs(Cpvd, Analyzer);
          }
        }
        break;
      }
      case attr::AcquiredAfter: {
        const auto *A = cast<AcquiredAfterAttr>(At);

        // Read exprs from the attribute, and add them to BeforeVect.
        for (const auto *Arg : A->args()) {
          CapabilityExpr Cp =
            Analyzer.SxBuilder.translateAttrExpr(Arg, nullptr);
          if (const ValueDecl *ArgVd = Cp.valueDecl()) {
            // Get entry for mutex listed in attribute
            BeforeInfo *ArgInfo = getBeforeInfoForDecl(ArgVd, Analyzer);
            ArgInfo->Vect.push_back(Vd);
          }
        }
        break;
      }
      default:
        break;
    }
  }

  return Info;
}

BeforeSet::BeforeInfo *
BeforeSet::getBeforeInfoForDecl(const ValueDecl *Vd,
                                ThreadSafetyAnalyzer &Analyzer) {
  auto It = BMap.find(Vd);
  BeforeInfo *Info = nullptr;
  if (It == BMap.end())
    Info = insertAttrExprs(Vd, Analyzer);
  else
    Info = It->second.get();
  assert(Info && "BMap contained nullptr?");
  return Info;
}

/// Return true if any mutexes in FSet are in the acquired_before set of Vd.
void BeforeSet::checkBeforeAfter(const ValueDecl* StartVd,
                                 const FactSet& FSet,
                                 ThreadSafetyAnalyzer& Analyzer,
                                 SourceLocation Loc, StringRef CapKind) {
  SmallVector<BeforeInfo*, 8> InfoVect;

  // Do a depth-first traversal of Vd.
  // Return true if there are cycles.
  std::function<bool (const ValueDecl*)> traverse = [&](const ValueDecl* Vd) {
    if (!Vd)
      return false;

    BeforeSet::BeforeInfo *Info = getBeforeInfoForDecl(Vd, Analyzer);

    if (Info->Visited == 1)
      return true;

    if (Info->Visited == 2)
      return false;

    if (Info->Vect.empty())
      return false;

    InfoVect.push_back(Info);
    Info->Visited = 1;
    for (const auto *Vdb : Info->Vect) {
      // Exclude mutexes in our immediate before set.
      if (FSet.containsMutexDecl(Analyzer.FactMan, Vdb)) {
        StringRef L1 = StartVd->getName();
        StringRef L2 = Vdb->getName();
        Analyzer.Handler.handleLockAcquiredBefore(CapKind, L1, L2, Loc);
      }
      // Transitively search other before sets, and warn on cycles.
      if (traverse(Vdb)) {
        if (CycMap.find(Vd) == CycMap.end()) {
          CycMap.insert(std::make_pair(Vd, true));
          StringRef L1 = Vd->getName();
          Analyzer.Handler.handleBeforeAfterCycle(L1, Vd->getLocation());
        }
      }
    }
    Info->Visited = 2;
    return false;
  };

  traverse(StartVd);

  for (auto *Info : InfoVect)
    Info->Visited = 0;
}

/// Gets the value decl pointer from DeclRefExprs or MemberExprs.
static const ValueDecl *getValueDecl(const Expr *Exp) {
  if (const auto *CE = dyn_cast<ImplicitCastExpr>(Exp))
    return getValueDecl(CE->getSubExpr());

  if (const auto *DR = dyn_cast<DeclRefExpr>(Exp))
    return DR->getDecl();

  if (const auto *ME = dyn_cast<MemberExpr>(Exp))
    return ME->getMemberDecl();

  return nullptr;
}

namespace {

template <typename Ty>
class has_arg_iterator_range {
  using yes = char[1];
  using no = char[2];

  template <typename Inner>
  static yes& test(Inner *I, decltype(I->args()) * = nullptr);

  template <typename>
  static no& test(...);

public:
  static const bool value = sizeof(test<Ty>(nullptr)) == sizeof(yes);
};

} // namespace

bool ThreadSafetyAnalyzer::inCurrentScope(const CapabilityExpr &CapE) {
  const threadSafety::til::SExpr *SExp = CapE.sexpr();
  assert(SExp && "Null expressions should be ignored");

  if (const auto *LP = dyn_cast<til::LiteralPtr>(SExp)) {
    const ValueDecl *VD = LP->clangDecl();
    // Variables defined in a function are always inaccessible.
    if (!VD || !VD->isDefinedOutsideFunctionOrMethod())
      return false;
    // For now we consider static class members to be inaccessible.
    if (isa<CXXRecordDecl>(VD->getDeclContext()))
      return false;
    // Global variables are always in scope.
    return true;
  }

  // Members are in scope from methods of the same class.
  if (const auto *P = dyn_cast<til::Project>(SExp)) {
    if (!CurrentMethod)
      return false;
    const ValueDecl *VD = P->clangDecl();
    return VD->getDeclContext() == CurrentMethod->getDeclContext();
  }

  return false;
}

/// Add a new lock to the lockset, warning if the lock is already there.
/// \param ReqAttr -- true if this is part of an initial Requires attribute.
void ThreadSafetyAnalyzer::addLock(FactSet &FSet,
                                   std::unique_ptr<FactEntry> Entry,
                                   bool ReqAttr) {
  if (Entry->shouldIgnore())
    return;

  if (!ReqAttr && !Entry->negative()) {
    // look for the negative capability, and remove it from the fact set.
    CapabilityExpr NegC = !*Entry;
    const FactEntry *Nen = FSet.findLock(FactMan, NegC);
    if (Nen) {
      FSet.removeLock(FactMan, NegC);
    }
    else {
      if (inCurrentScope(*Entry) && !Entry->asserted())
        Handler.handleNegativeNotHeld(Entry->getKind(), Entry->toString(),
                                      NegC.toString(), Entry->loc());
    }
  }

  // Check before/after constraints
  if (Handler.issueBetaWarnings() &&
      !Entry->asserted() && !Entry->declared()) {
    GlobalBeforeSet->checkBeforeAfter(Entry->valueDecl(), FSet, *this,
                                      Entry->loc(), Entry->getKind());
  }

  // FIXME: Don't always warn when we have support for reentrant locks.
  if (const FactEntry *Cp = FSet.findLock(FactMan, *Entry)) {
    if (!Entry->asserted())
      Cp->handleLock(FSet, FactMan, *Entry, Handler);
  } else {
    FSet.addLock(FactMan, std::move(Entry));
  }
}

/// Remove a lock from the lockset, warning if the lock is not there.
/// \param UnlockLoc The source location of the unlock (only used in error msg)
void ThreadSafetyAnalyzer::removeLock(FactSet &FSet, const CapabilityExpr &Cp,
                                      SourceLocation UnlockLoc,
                                      bool FullyRemove, LockKind ReceivedKind) {
  if (Cp.shouldIgnore())
    return;

  const FactEntry *LDat = FSet.findLock(FactMan, Cp);
  if (!LDat) {
    SourceLocation PrevLoc;
    if (const FactEntry *Neg = FSet.findLock(FactMan, !Cp))
      PrevLoc = Neg->loc();
    Handler.handleUnmatchedUnlock(Cp.getKind(), Cp.toString(), UnlockLoc,
                                  PrevLoc);
    return;
  }

  // Generic lock removal doesn't care about lock kind mismatches, but
  // otherwise diagnose when the lock kinds are mismatched.
  if (ReceivedKind != LK_Generic && LDat->kind() != ReceivedKind) {
    Handler.handleIncorrectUnlockKind(Cp.getKind(), Cp.toString(), LDat->kind(),
                                      ReceivedKind, LDat->loc(), UnlockLoc);
  }

  LDat->handleUnlock(FSet, FactMan, Cp, UnlockLoc, FullyRemove, Handler);
}

/// Extract the list of mutexIDs from the attribute on an expression,
/// and push them onto Mtxs, discarding any duplicates.
template <typename AttrType>
void ThreadSafetyAnalyzer::getMutexIDs(CapExprSet &Mtxs, AttrType *Attr,
                                       const Expr *Exp, const NamedDecl *D,
                                       til::SExpr *Self) {
  if (Attr->args_size() == 0) {
    // The mutex held is the "this" object.
    CapabilityExpr Cp = SxBuilder.translateAttrExpr(nullptr, D, Exp, Self);
    if (Cp.isInvalid()) {
      warnInvalidLock(Handler, nullptr, D, Exp, Cp.getKind());
      return;
    }
    //else
    if (!Cp.shouldIgnore())
      Mtxs.push_back_nodup(Cp);
    return;
  }

  for (const auto *Arg : Attr->args()) {
    CapabilityExpr Cp = SxBuilder.translateAttrExpr(Arg, D, Exp, Self);
    if (Cp.isInvalid()) {
      warnInvalidLock(Handler, nullptr, D, Exp, Cp.getKind());
      continue;
    }
    //else
    if (!Cp.shouldIgnore())
      Mtxs.push_back_nodup(Cp);
  }
}

/// Extract the list of mutexIDs from a trylock attribute.  If the
/// trylock applies to the given edge, then push them onto Mtxs, discarding
/// any duplicates.
template <class AttrType>
void ThreadSafetyAnalyzer::getMutexIDs(CapExprSet &Mtxs, AttrType *Attr,
                                       const Expr *Exp, const NamedDecl *D,
                                       const CFGBlock *PredBlock,
                                       const CFGBlock *CurrBlock,
                                       Expr *BrE, bool Neg) {
  // Find out which branch has the lock
  bool branch = false;
  if (const auto *BLE = dyn_cast_or_null<CXXBoolLiteralExpr>(BrE))
    branch = BLE->getValue();
  else if (const auto *ILE = dyn_cast_or_null<IntegerLiteral>(BrE))
    branch = ILE->getValue().getBoolValue();

  int branchnum = branch ? 0 : 1;
  if (Neg)
    branchnum = !branchnum;

  // If we've taken the trylock branch, then add the lock
  int i = 0;
  for (CFGBlock::const_succ_iterator SI = PredBlock->succ_begin(),
       SE = PredBlock->succ_end(); SI != SE && i < 2; ++SI, ++i) {
    if (*SI == CurrBlock && i == branchnum)
      getMutexIDs(Mtxs, Attr, Exp, D);
  }
}

static bool getStaticBooleanValue(Expr *E, bool &TCond) {
  if (isa<CXXNullPtrLiteralExpr>(E) || isa<GNUNullExpr>(E)) {
    TCond = false;
    return true;
  } else if (const auto *BLE = dyn_cast<CXXBoolLiteralExpr>(E)) {
    TCond = BLE->getValue();
    return true;
  } else if (const auto *ILE = dyn_cast<IntegerLiteral>(E)) {
    TCond = ILE->getValue().getBoolValue();
    return true;
  } else if (auto *CE = dyn_cast<ImplicitCastExpr>(E))
    return getStaticBooleanValue(CE->getSubExpr(), TCond);
  return false;
}

// If Cond can be traced back to a function call, return the call expression.
// The negate variable should be called with false, and will be set to true
// if the function call is negated, e.g. if (!mu.tryLock(...))
const CallExpr* ThreadSafetyAnalyzer::getTrylockCallExpr(const Stmt *Cond,
                                                         LocalVarContext C,
                                                         bool &Negate) {
  if (!Cond)
    return nullptr;

  if (const auto *CallExp = dyn_cast<CallExpr>(Cond)) {
    if (CallExp->getBuiltinCallee() == Builtin::BI__builtin_expect)
      return getTrylockCallExpr(CallExp->getArg(0), C, Negate);
    return CallExp;
  }
  else if (const auto *PE = dyn_cast<ParenExpr>(Cond))
    return getTrylockCallExpr(PE->getSubExpr(), C, Negate);
  else if (const auto *CE = dyn_cast<ImplicitCastExpr>(Cond))
    return getTrylockCallExpr(CE->getSubExpr(), C, Negate);
  else if (const auto *FE = dyn_cast<FullExpr>(Cond))
    return getTrylockCallExpr(FE->getSubExpr(), C, Negate);
  else if (const auto *DRE = dyn_cast<DeclRefExpr>(Cond)) {
    const Expr *E = LocalVarMap.lookupExpr(DRE->getDecl(), C);
    return getTrylockCallExpr(E, C, Negate);
  }
  else if (const auto *UOP = dyn_cast<UnaryOperator>(Cond)) {
    if (UOP->getOpcode() == UO_LNot) {
      Negate = !Negate;
      return getTrylockCallExpr(UOP->getSubExpr(), C, Negate);
    }
    return nullptr;
  }
  else if (const auto *BOP = dyn_cast<BinaryOperator>(Cond)) {
    if (BOP->getOpcode() == BO_EQ || BOP->getOpcode() == BO_NE) {
      if (BOP->getOpcode() == BO_NE)
        Negate = !Negate;

      bool TCond = false;
      if (getStaticBooleanValue(BOP->getRHS(), TCond)) {
        if (!TCond) Negate = !Negate;
        return getTrylockCallExpr(BOP->getLHS(), C, Negate);
      }
      TCond = false;
      if (getStaticBooleanValue(BOP->getLHS(), TCond)) {
        if (!TCond) Negate = !Negate;
        return getTrylockCallExpr(BOP->getRHS(), C, Negate);
      }
      return nullptr;
    }
    if (BOP->getOpcode() == BO_LAnd) {
      // LHS must have been evaluated in a different block.
      return getTrylockCallExpr(BOP->getRHS(), C, Negate);
    }
    if (BOP->getOpcode() == BO_LOr)
      return getTrylockCallExpr(BOP->getRHS(), C, Negate);
    return nullptr;
  } else if (const auto *COP = dyn_cast<ConditionalOperator>(Cond)) {
    bool TCond, FCond;
    if (getStaticBooleanValue(COP->getTrueExpr(), TCond) &&
        getStaticBooleanValue(COP->getFalseExpr(), FCond)) {
      if (TCond && !FCond)
        return getTrylockCallExpr(COP->getCond(), C, Negate);
      if (!TCond && FCond) {
        Negate = !Negate;
        return getTrylockCallExpr(COP->getCond(), C, Negate);
      }
    }
  }
  return nullptr;
}

/// Find the lockset that holds on the edge between PredBlock
/// and CurrBlock.  The edge set is the exit set of PredBlock (passed
/// as the ExitSet parameter) plus any trylocks, which are conditionally held.
void ThreadSafetyAnalyzer::getEdgeLockset(FactSet& Result,
                                          const FactSet &ExitSet,
                                          const CFGBlock *PredBlock,
                                          const CFGBlock *CurrBlock) {
  Result = ExitSet;

  const Stmt *Cond = PredBlock->getTerminatorCondition();
  // We don't acquire try-locks on ?: branches, only when its result is used.
  if (!Cond || isa<ConditionalOperator>(PredBlock->getTerminatorStmt()))
    return;

  bool Negate = false;
  const CFGBlockInfo *PredBlockInfo = &BlockInfo[PredBlock->getBlockID()];
  const LocalVarContext &LVarCtx = PredBlockInfo->ExitContext;

  const auto *Exp = getTrylockCallExpr(Cond, LVarCtx, Negate);
  if (!Exp)
    return;

  auto *FunDecl = dyn_cast_or_null<NamedDecl>(Exp->getCalleeDecl());
  if(!FunDecl || !FunDecl->hasAttrs())
    return;

  CapExprSet ExclusiveLocksToAdd;
  CapExprSet SharedLocksToAdd;

  // If the condition is a call to a Trylock function, then grab the attributes
  for (const auto *Attr : FunDecl->attrs()) {
    switch (Attr->getKind()) {
      case attr::TryAcquireCapability: {
        auto *A = cast<TryAcquireCapabilityAttr>(Attr);
        getMutexIDs(A->isShared() ? SharedLocksToAdd : ExclusiveLocksToAdd, A,
                    Exp, FunDecl, PredBlock, CurrBlock, A->getSuccessValue(),
                    Negate);
        break;
      };
      case attr::ExclusiveTrylockFunction: {
        const auto *A = cast<ExclusiveTrylockFunctionAttr>(Attr);
        getMutexIDs(ExclusiveLocksToAdd, A, Exp, FunDecl, PredBlock, CurrBlock,
                    A->getSuccessValue(), Negate);
        break;
      }
      case attr::SharedTrylockFunction: {
        const auto *A = cast<SharedTrylockFunctionAttr>(Attr);
        getMutexIDs(SharedLocksToAdd, A, Exp, FunDecl, PredBlock, CurrBlock,
                    A->getSuccessValue(), Negate);
        break;
      }
      default:
        break;
    }
  }

  // Add and remove locks.
  SourceLocation Loc = Exp->getExprLoc();
  for (const auto &ExclusiveLockToAdd : ExclusiveLocksToAdd)
    addLock(Result, std::make_unique<LockableFactEntry>(ExclusiveLockToAdd,
                                                        LK_Exclusive, Loc));
  for (const auto &SharedLockToAdd : SharedLocksToAdd)
    addLock(Result, std::make_unique<LockableFactEntry>(SharedLockToAdd,
                                                        LK_Shared, Loc));
}

namespace {

/// We use this class to visit different types of expressions in
/// CFGBlocks, and build up the lockset.
/// An expression may cause us to add or remove locks from the lockset, or else
/// output error messages related to missing locks.
/// FIXME: In future, we may be able to not inherit from a visitor.
class BuildLockset : public ConstStmtVisitor<BuildLockset> {
  friend class ThreadSafetyAnalyzer;

  ThreadSafetyAnalyzer *Analyzer;
  FactSet FSet;
  /// Maps constructed objects to `this` placeholder prior to initialization.
  llvm::SmallDenseMap<const Expr *, til::LiteralPtr *> ConstructedObjects;
  LocalVariableMap::Context LVarCtx;
  unsigned CtxIndex;

  // helper functions
  void warnIfMutexNotHeld(const NamedDecl *D, const Expr *Exp, AccessKind AK,
                          Expr *MutexExp, ProtectedOperationKind POK,
                          til::LiteralPtr *Self, SourceLocation Loc);
  void warnIfMutexHeld(const NamedDecl *D, const Expr *Exp, Expr *MutexExp,
                       til::LiteralPtr *Self, SourceLocation Loc);

  void checkAccess(const Expr *Exp, AccessKind AK,
                   ProtectedOperationKind POK = POK_VarAccess);
  void checkPtAccess(const Expr *Exp, AccessKind AK,
                     ProtectedOperationKind POK = POK_VarAccess);

  void handleCall(const Expr *Exp, const NamedDecl *D,
                  til::LiteralPtr *Self = nullptr,
                  SourceLocation Loc = SourceLocation());
  void examineArguments(const FunctionDecl *FD,
                        CallExpr::const_arg_iterator ArgBegin,
                        CallExpr::const_arg_iterator ArgEnd,
                        bool SkipFirstParam = false);

public:
  BuildLockset(ThreadSafetyAnalyzer *Anlzr, CFGBlockInfo &Info)
      : ConstStmtVisitor<BuildLockset>(), Analyzer(Anlzr), FSet(Info.EntrySet),
        LVarCtx(Info.EntryContext), CtxIndex(Info.EntryIndex) {}

  void VisitUnaryOperator(const UnaryOperator *UO);
  void VisitBinaryOperator(const BinaryOperator *BO);
  void VisitCastExpr(const CastExpr *CE);
  void VisitCallExpr(const CallExpr *Exp);
  void VisitCXXConstructExpr(const CXXConstructExpr *Exp);
  void VisitDeclStmt(const DeclStmt *S);
  void VisitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *Exp);
};

} // namespace

/// Warn if the LSet does not contain a lock sufficient to protect access
/// of at least the passed in AccessKind.
void BuildLockset::warnIfMutexNotHeld(const NamedDecl *D, const Expr *Exp,
                                      AccessKind AK, Expr *MutexExp,
                                      ProtectedOperationKind POK,
                                      til::LiteralPtr *Self,
                                      SourceLocation Loc) {
  LockKind LK = getLockKindFromAccessKind(AK);

  CapabilityExpr Cp =
      Analyzer->SxBuilder.translateAttrExpr(MutexExp, D, Exp, Self);
  if (Cp.isInvalid()) {
    warnInvalidLock(Analyzer->Handler, MutexExp, D, Exp, Cp.getKind());
    return;
  } else if (Cp.shouldIgnore()) {
    return;
  }

  if (Cp.negative()) {
    // Negative capabilities act like locks excluded
    const FactEntry *LDat = FSet.findLock(Analyzer->FactMan, !Cp);
    if (LDat) {
      Analyzer->Handler.handleFunExcludesLock(
          Cp.getKind(), D->getNameAsString(), (!Cp).toString(), Loc);
      return;
    }

    // If this does not refer to a negative capability in the same class,
    // then stop here.
    if (!Analyzer->inCurrentScope(Cp))
      return;

    // Otherwise the negative requirement must be propagated to the caller.
    LDat = FSet.findLock(Analyzer->FactMan, Cp);
    if (!LDat) {
      Analyzer->Handler.handleNegativeNotHeld(D, Cp.toString(), Loc);
    }
    return;
  }

  const FactEntry *LDat = FSet.findLockUniv(Analyzer->FactMan, Cp);
  bool NoError = true;
  if (!LDat) {
    // No exact match found.  Look for a partial match.
    LDat = FSet.findPartialMatch(Analyzer->FactMan, Cp);
    if (LDat) {
      // Warn that there's no precise match.
      std::string PartMatchStr = LDat->toString();
      StringRef   PartMatchName(PartMatchStr);
      Analyzer->Handler.handleMutexNotHeld(Cp.getKind(), D, POK, Cp.toString(),
                                           LK, Loc, &PartMatchName);
    } else {
      // Warn that there's no match at all.
      Analyzer->Handler.handleMutexNotHeld(Cp.getKind(), D, POK, Cp.toString(),
                                           LK, Loc);
    }
    NoError = false;
  }
  // Make sure the mutex we found is the right kind.
  if (NoError && LDat && !LDat->isAtLeast(LK)) {
    Analyzer->Handler.handleMutexNotHeld(Cp.getKind(), D, POK, Cp.toString(),
                                         LK, Loc);
  }
}

/// Warn if the LSet contains the given lock.
void BuildLockset::warnIfMutexHeld(const NamedDecl *D, const Expr *Exp,
                                   Expr *MutexExp, til::LiteralPtr *Self,
                                   SourceLocation Loc) {
  CapabilityExpr Cp =
      Analyzer->SxBuilder.translateAttrExpr(MutexExp, D, Exp, Self);
  if (Cp.isInvalid()) {
    warnInvalidLock(Analyzer->Handler, MutexExp, D, Exp, Cp.getKind());
    return;
  } else if (Cp.shouldIgnore()) {
    return;
  }

  const FactEntry *LDat = FSet.findLock(Analyzer->FactMan, Cp);
  if (LDat) {
    Analyzer->Handler.handleFunExcludesLock(Cp.getKind(), D->getNameAsString(),
                                            Cp.toString(), Loc);
  }
}

/// Checks guarded_by and pt_guarded_by attributes.
/// Whenever we identify an access (read or write) to a DeclRefExpr that is
/// marked with guarded_by, we must ensure the appropriate mutexes are held.
/// Similarly, we check if the access is to an expression that dereferences
/// a pointer marked with pt_guarded_by.
void BuildLockset::checkAccess(const Expr *Exp, AccessKind AK,
                               ProtectedOperationKind POK) {
  Exp = Exp->IgnoreImplicit()->IgnoreParenCasts();

  SourceLocation Loc = Exp->getExprLoc();

  // Local variables of reference type cannot be re-assigned;
  // map them to their initializer.
  while (const auto *DRE = dyn_cast<DeclRefExpr>(Exp)) {
    const auto *VD = dyn_cast<VarDecl>(DRE->getDecl()->getCanonicalDecl());
    if (VD && VD->isLocalVarDecl() && VD->getType()->isReferenceType()) {
      if (const auto *E = VD->getInit()) {
        // Guard against self-initialization. e.g., int &i = i;
        if (E == Exp)
          break;
        Exp = E;
        continue;
      }
    }
    break;
  }

  if (const auto *UO = dyn_cast<UnaryOperator>(Exp)) {
    // For dereferences
    if (UO->getOpcode() == UO_Deref)
      checkPtAccess(UO->getSubExpr(), AK, POK);
    return;
  }

  if (const auto *BO = dyn_cast<BinaryOperator>(Exp)) {
    switch (BO->getOpcode()) {
    case BO_PtrMemD: // .*
      return checkAccess(BO->getLHS(), AK, POK);
    case BO_PtrMemI: // ->*
      return checkPtAccess(BO->getLHS(), AK, POK);
    default:
      return;
    }
  }

  if (const auto *AE = dyn_cast<ArraySubscriptExpr>(Exp)) {
    checkPtAccess(AE->getLHS(), AK, POK);
    return;
  }

  if (const auto *ME = dyn_cast<MemberExpr>(Exp)) {
    if (ME->isArrow())
      checkPtAccess(ME->getBase(), AK, POK);
    else
      checkAccess(ME->getBase(), AK, POK);
  }

  const ValueDecl *D = getValueDecl(Exp);
  if (!D || !D->hasAttrs())
    return;

  if (D->hasAttr<GuardedVarAttr>() && FSet.isEmpty(Analyzer->FactMan)) {
    Analyzer->Handler.handleNoMutexHeld(D, POK, AK, Loc);
  }

  for (const auto *I : D->specific_attrs<GuardedByAttr>())
    warnIfMutexNotHeld(D, Exp, AK, I->getArg(), POK, nullptr, Loc);
}

/// Checks pt_guarded_by and pt_guarded_var attributes.
/// POK is the same  operationKind that was passed to checkAccess.
void BuildLockset::checkPtAccess(const Expr *Exp, AccessKind AK,
                                 ProtectedOperationKind POK) {
  while (true) {
    if (const auto *PE = dyn_cast<ParenExpr>(Exp)) {
      Exp = PE->getSubExpr();
      continue;
    }
    if (const auto *CE = dyn_cast<CastExpr>(Exp)) {
      if (CE->getCastKind() == CK_ArrayToPointerDecay) {
        // If it's an actual array, and not a pointer, then it's elements
        // are protected by GUARDED_BY, not PT_GUARDED_BY;
        checkAccess(CE->getSubExpr(), AK, POK);
        return;
      }
      Exp = CE->getSubExpr();
      continue;
    }
    break;
  }

  // Pass by reference warnings are under a different flag.
  ProtectedOperationKind PtPOK = POK_VarDereference;
  if (POK == POK_PassByRef) PtPOK = POK_PtPassByRef;

  const ValueDecl *D = getValueDecl(Exp);
  if (!D || !D->hasAttrs())
    return;

  if (D->hasAttr<PtGuardedVarAttr>() && FSet.isEmpty(Analyzer->FactMan))
    Analyzer->Handler.handleNoMutexHeld(D, PtPOK, AK, Exp->getExprLoc());

  for (auto const *I : D->specific_attrs<PtGuardedByAttr>())
    warnIfMutexNotHeld(D, Exp, AK, I->getArg(), PtPOK, nullptr,
                       Exp->getExprLoc());
}

/// Process a function call, method call, constructor call,
/// or destructor call.  This involves looking at the attributes on the
/// corresponding function/method/constructor/destructor, issuing warnings,
/// and updating the locksets accordingly.
///
/// FIXME: For classes annotated with one of the guarded annotations, we need
/// to treat const method calls as reads and non-const method calls as writes,
/// and check that the appropriate locks are held. Non-const method calls with
/// the same signature as const method calls can be also treated as reads.
///
/// \param Exp   The call expression.
/// \param D     The callee declaration.
/// \param Self  If \p Exp = nullptr, the implicit this argument.
/// \param Loc   If \p Exp = nullptr, the location.
void BuildLockset::handleCall(const Expr *Exp, const NamedDecl *D,
                              til::LiteralPtr *Self, SourceLocation Loc) {
  CapExprSet ExclusiveLocksToAdd, SharedLocksToAdd;
  CapExprSet ExclusiveLocksToRemove, SharedLocksToRemove, GenericLocksToRemove;
  CapExprSet ScopedReqsAndExcludes;

  // Figure out if we're constructing an object of scoped lockable class
  CapabilityExpr Scp;
  if (Exp) {
    assert(!Self);
    const auto *TagT = Exp->getType()->getAs<TagType>();
    if (TagT && Exp->isPRValue()) {
      std::pair<til::LiteralPtr *, StringRef> Placeholder =
          Analyzer->SxBuilder.createThisPlaceholder(Exp);
      [[maybe_unused]] auto inserted =
          ConstructedObjects.insert({Exp, Placeholder.first});
      assert(inserted.second && "Are we visiting the same expression again?");
      if (isa<CXXConstructExpr>(Exp))
        Self = Placeholder.first;
      if (TagT->getDecl()->hasAttr<ScopedLockableAttr>())
        Scp = CapabilityExpr(Placeholder.first, Placeholder.second, false);
    }

    assert(Loc.isInvalid());
    Loc = Exp->getExprLoc();
  }

  for(const Attr *At : D->attrs()) {
    switch (At->getKind()) {
      // When we encounter a lock function, we need to add the lock to our
      // lockset.
      case attr::AcquireCapability: {
        const auto *A = cast<AcquireCapabilityAttr>(At);
        Analyzer->getMutexIDs(A->isShared() ? SharedLocksToAdd
                                            : ExclusiveLocksToAdd,
                              A, Exp, D, Self);
        break;
      }

      // An assert will add a lock to the lockset, but will not generate
      // a warning if it is already there, and will not generate a warning
      // if it is not removed.
      case attr::AssertExclusiveLock: {
        const auto *A = cast<AssertExclusiveLockAttr>(At);

        CapExprSet AssertLocks;
        Analyzer->getMutexIDs(AssertLocks, A, Exp, D, Self);
        for (const auto &AssertLock : AssertLocks)
          Analyzer->addLock(
              FSet, std::make_unique<LockableFactEntry>(
                        AssertLock, LK_Exclusive, Loc, FactEntry::Asserted));
        break;
      }
      case attr::AssertSharedLock: {
        const auto *A = cast<AssertSharedLockAttr>(At);

        CapExprSet AssertLocks;
        Analyzer->getMutexIDs(AssertLocks, A, Exp, D, Self);
        for (const auto &AssertLock : AssertLocks)
          Analyzer->addLock(
              FSet, std::make_unique<LockableFactEntry>(
                        AssertLock, LK_Shared, Loc, FactEntry::Asserted));
        break;
      }

      case attr::AssertCapability: {
        const auto *A = cast<AssertCapabilityAttr>(At);
        CapExprSet AssertLocks;
        Analyzer->getMutexIDs(AssertLocks, A, Exp, D, Self);
        for (const auto &AssertLock : AssertLocks)
          Analyzer->addLock(FSet, std::make_unique<LockableFactEntry>(
                                      AssertLock,
                                      A->isShared() ? LK_Shared : LK_Exclusive,
                                      Loc, FactEntry::Asserted));
        break;
      }

      // When we encounter an unlock function, we need to remove unlocked
      // mutexes from the lockset, and flag a warning if they are not there.
      case attr::ReleaseCapability: {
        const auto *A = cast<ReleaseCapabilityAttr>(At);
        if (A->isGeneric())
          Analyzer->getMutexIDs(GenericLocksToRemove, A, Exp, D, Self);
        else if (A->isShared())
          Analyzer->getMutexIDs(SharedLocksToRemove, A, Exp, D, Self);
        else
          Analyzer->getMutexIDs(ExclusiveLocksToRemove, A, Exp, D, Self);
        break;
      }

      case attr::RequiresCapability: {
        const auto *A = cast<RequiresCapabilityAttr>(At);
        for (auto *Arg : A->args()) {
          warnIfMutexNotHeld(D, Exp, A->isShared() ? AK_Read : AK_Written, Arg,
                             POK_FunctionCall, Self, Loc);
          // use for adopting a lock
          if (!Scp.shouldIgnore())
            Analyzer->getMutexIDs(ScopedReqsAndExcludes, A, Exp, D, Self);
        }
        break;
      }

      case attr::LocksExcluded: {
        const auto *A = cast<LocksExcludedAttr>(At);
        for (auto *Arg : A->args()) {
          warnIfMutexHeld(D, Exp, Arg, Self, Loc);
          // use for deferring a lock
          if (!Scp.shouldIgnore())
            Analyzer->getMutexIDs(ScopedReqsAndExcludes, A, Exp, D, Self);
        }
        break;
      }

      // Ignore attributes unrelated to thread-safety
      default:
        break;
    }
  }

  // Remove locks first to allow lock upgrading/downgrading.
  // FIXME -- should only fully remove if the attribute refers to 'this'.
  bool Dtor = isa<CXXDestructorDecl>(D);
  for (const auto &M : ExclusiveLocksToRemove)
    Analyzer->removeLock(FSet, M, Loc, Dtor, LK_Exclusive);
  for (const auto &M : SharedLocksToRemove)
    Analyzer->removeLock(FSet, M, Loc, Dtor, LK_Shared);
  for (const auto &M : GenericLocksToRemove)
    Analyzer->removeLock(FSet, M, Loc, Dtor, LK_Generic);

  // Add locks.
  FactEntry::SourceKind Source =
      !Scp.shouldIgnore() ? FactEntry::Managed : FactEntry::Acquired;
  for (const auto &M : ExclusiveLocksToAdd)
    Analyzer->addLock(FSet, std::make_unique<LockableFactEntry>(M, LK_Exclusive,
                                                                Loc, Source));
  for (const auto &M : SharedLocksToAdd)
    Analyzer->addLock(
        FSet, std::make_unique<LockableFactEntry>(M, LK_Shared, Loc, Source));

  if (!Scp.shouldIgnore()) {
    // Add the managing object as a dummy mutex, mapped to the underlying mutex.
    auto ScopedEntry = std::make_unique<ScopedLockableFactEntry>(Scp, Loc);
    for (const auto &M : ExclusiveLocksToAdd)
      ScopedEntry->addLock(M);
    for (const auto &M : SharedLocksToAdd)
      ScopedEntry->addLock(M);
    for (const auto &M : ScopedReqsAndExcludes)
      ScopedEntry->addLock(M);
    for (const auto &M : ExclusiveLocksToRemove)
      ScopedEntry->addExclusiveUnlock(M);
    for (const auto &M : SharedLocksToRemove)
      ScopedEntry->addSharedUnlock(M);
    Analyzer->addLock(FSet, std::move(ScopedEntry));
  }
}

/// For unary operations which read and write a variable, we need to
/// check whether we hold any required mutexes. Reads are checked in
/// VisitCastExpr.
void BuildLockset::VisitUnaryOperator(const UnaryOperator *UO) {
  switch (UO->getOpcode()) {
    case UO_PostDec:
    case UO_PostInc:
    case UO_PreDec:
    case UO_PreInc:
      checkAccess(UO->getSubExpr(), AK_Written);
      break;
    default:
      break;
  }
}

/// For binary operations which assign to a variable (writes), we need to check
/// whether we hold any required mutexes.
/// FIXME: Deal with non-primitive types.
void BuildLockset::VisitBinaryOperator(const BinaryOperator *BO) {
  if (!BO->isAssignmentOp())
    return;

  // adjust the context
  LVarCtx = Analyzer->LocalVarMap.getNextContext(CtxIndex, BO, LVarCtx);

  checkAccess(BO->getLHS(), AK_Written);
}

/// Whenever we do an LValue to Rvalue cast, we are reading a variable and
/// need to ensure we hold any required mutexes.
/// FIXME: Deal with non-primitive types.
void BuildLockset::VisitCastExpr(const CastExpr *CE) {
  if (CE->getCastKind() != CK_LValueToRValue)
    return;
  checkAccess(CE->getSubExpr(), AK_Read);
}

void BuildLockset::examineArguments(const FunctionDecl *FD,
                                    CallExpr::const_arg_iterator ArgBegin,
                                    CallExpr::const_arg_iterator ArgEnd,
                                    bool SkipFirstParam) {
  // Currently we can't do anything if we don't know the function declaration.
  if (!FD)
    return;

  // NO_THREAD_SAFETY_ANALYSIS does double duty here.  Normally it
  // only turns off checking within the body of a function, but we also
  // use it to turn off checking in arguments to the function.  This
  // could result in some false negatives, but the alternative is to
  // create yet another attribute.
  if (FD->hasAttr<NoThreadSafetyAnalysisAttr>())
    return;

  const ArrayRef<ParmVarDecl *> Params = FD->parameters();
  auto Param = Params.begin();
  if (SkipFirstParam)
    ++Param;

  // There can be default arguments, so we stop when one iterator is at end().
  for (auto Arg = ArgBegin; Param != Params.end() && Arg != ArgEnd;
       ++Param, ++Arg) {
    QualType Qt = (*Param)->getType();
    if (Qt->isReferenceType())
      checkAccess(*Arg, AK_Read, POK_PassByRef);
  }
}

void BuildLockset::VisitCallExpr(const CallExpr *Exp) {
  if (const auto *CE = dyn_cast<CXXMemberCallExpr>(Exp)) {
    const auto *ME = dyn_cast<MemberExpr>(CE->getCallee());
    // ME can be null when calling a method pointer
    const CXXMethodDecl *MD = CE->getMethodDecl();

    if (ME && MD) {
      if (ME->isArrow()) {
        // Should perhaps be AK_Written if !MD->isConst().
        checkPtAccess(CE->getImplicitObjectArgument(), AK_Read);
      } else {
        // Should perhaps be AK_Written if !MD->isConst().
        checkAccess(CE->getImplicitObjectArgument(), AK_Read);
      }
    }

    examineArguments(CE->getDirectCallee(), CE->arg_begin(), CE->arg_end());
  } else if (const auto *OE = dyn_cast<CXXOperatorCallExpr>(Exp)) {
    OverloadedOperatorKind OEop = OE->getOperator();
    switch (OEop) {
      case OO_Equal:
      case OO_PlusEqual:
      case OO_MinusEqual:
      case OO_StarEqual:
      case OO_SlashEqual:
      case OO_PercentEqual:
      case OO_CaretEqual:
      case OO_AmpEqual:
      case OO_PipeEqual:
      case OO_LessLessEqual:
      case OO_GreaterGreaterEqual:
        checkAccess(OE->getArg(1), AK_Read);
        [[fallthrough]];
      case OO_PlusPlus:
      case OO_MinusMinus:
        checkAccess(OE->getArg(0), AK_Written);
        break;
      case OO_Star:
      case OO_ArrowStar:
      case OO_Arrow:
      case OO_Subscript:
        if (!(OEop == OO_Star && OE->getNumArgs() > 1)) {
          // Grrr.  operator* can be multiplication...
          checkPtAccess(OE->getArg(0), AK_Read);
        }
        [[fallthrough]];
      default: {
        // TODO: get rid of this, and rely on pass-by-ref instead.
        const Expr *Obj = OE->getArg(0);
        checkAccess(Obj, AK_Read);
        // Check the remaining arguments. For method operators, the first
        // argument is the implicit self argument, and doesn't appear in the
        // FunctionDecl, but for non-methods it does.
        const FunctionDecl *FD = OE->getDirectCallee();
        examineArguments(FD, std::next(OE->arg_begin()), OE->arg_end(),
                         /*SkipFirstParam*/ !isa<CXXMethodDecl>(FD));
        break;
      }
    }
  } else {
    examineArguments(Exp->getDirectCallee(), Exp->arg_begin(), Exp->arg_end());
  }

  auto *D = dyn_cast_or_null<NamedDecl>(Exp->getCalleeDecl());
  if(!D || !D->hasAttrs())
    return;
  handleCall(Exp, D);
}

void BuildLockset::VisitCXXConstructExpr(const CXXConstructExpr *Exp) {
  const CXXConstructorDecl *D = Exp->getConstructor();
  if (D && D->isCopyConstructor()) {
    const Expr* Source = Exp->getArg(0);
    checkAccess(Source, AK_Read);
  } else {
    examineArguments(D, Exp->arg_begin(), Exp->arg_end());
  }
  if (D && D->hasAttrs())
    handleCall(Exp, D);
}

static const Expr *UnpackConstruction(const Expr *E) {
  if (auto *CE = dyn_cast<CastExpr>(E))
    if (CE->getCastKind() == CK_NoOp)
      E = CE->getSubExpr()->IgnoreParens();
  if (auto *CE = dyn_cast<CastExpr>(E))
    if (CE->getCastKind() == CK_ConstructorConversion ||
        CE->getCastKind() == CK_UserDefinedConversion)
      E = CE->getSubExpr();
  if (auto *BTE = dyn_cast<CXXBindTemporaryExpr>(E))
    E = BTE->getSubExpr();
  return E;
}

void BuildLockset::VisitDeclStmt(const DeclStmt *S) {
  // adjust the context
  LVarCtx = Analyzer->LocalVarMap.getNextContext(CtxIndex, S, LVarCtx);

  for (auto *D : S->getDeclGroup()) {
    if (auto *VD = dyn_cast_or_null<VarDecl>(D)) {
      const Expr *E = VD->getInit();
      if (!E)
        continue;
      E = E->IgnoreParens();

      // handle constructors that involve temporaries
      if (auto *EWC = dyn_cast<ExprWithCleanups>(E))
        E = EWC->getSubExpr()->IgnoreParens();
      E = UnpackConstruction(E);

      if (auto Object = ConstructedObjects.find(E);
          Object != ConstructedObjects.end()) {
        Object->second->setClangDecl(VD);
        ConstructedObjects.erase(Object);
      }
    }
  }
}

void BuildLockset::VisitMaterializeTemporaryExpr(
    const MaterializeTemporaryExpr *Exp) {
  if (const ValueDecl *ExtD = Exp->getExtendingDecl()) {
    if (auto Object =
            ConstructedObjects.find(UnpackConstruction(Exp->getSubExpr()));
        Object != ConstructedObjects.end()) {
      Object->second->setClangDecl(ExtD);
      ConstructedObjects.erase(Object);
    }
  }
}

/// Given two facts merging on a join point, possibly warn and decide whether to
/// keep or replace.
///
/// \param CanModify Whether we can replace \p A by \p B.
/// \return  false if we should keep \p A, true if we should take \p B.
bool ThreadSafetyAnalyzer::join(const FactEntry &A, const FactEntry &B,
                                bool CanModify) {
  if (A.kind() != B.kind()) {
    // For managed capabilities, the destructor should unlock in the right mode
    // anyway. For asserted capabilities no unlocking is needed.
    if ((A.managed() || A.asserted()) && (B.managed() || B.asserted())) {
      // The shared capability subsumes the exclusive capability, if possible.
      bool ShouldTakeB = B.kind() == LK_Shared;
      if (CanModify || !ShouldTakeB)
        return ShouldTakeB;
    }
    Handler.handleExclusiveAndShared(B.getKind(), B.toString(), B.loc(),
                                     A.loc());
    // Take the exclusive capability to reduce further warnings.
    return CanModify && B.kind() == LK_Exclusive;
  } else {
    // The non-asserted capability is the one we want to track.
    return CanModify && A.asserted() && !B.asserted();
  }
}

/// Compute the intersection of two locksets and issue warnings for any
/// locks in the symmetric difference.
///
/// This function is used at a merge point in the CFG when comparing the lockset
/// of each branch being merged. For example, given the following sequence:
/// A; if () then B; else C; D; we need to check that the lockset after B and C
/// are the same. In the event of a difference, we use the intersection of these
/// two locksets at the start of D.
///
/// \param EntrySet A lockset for entry into a (possibly new) block.
/// \param ExitSet The lockset on exiting a preceding block.
/// \param JoinLoc The location of the join point for error reporting
/// \param EntryLEK The warning if a mutex is missing from \p EntrySet.
/// \param ExitLEK The warning if a mutex is missing from \p ExitSet.
void ThreadSafetyAnalyzer::intersectAndWarn(FactSet &EntrySet,
                                            const FactSet &ExitSet,
                                            SourceLocation JoinLoc,
                                            LockErrorKind EntryLEK,
                                            LockErrorKind ExitLEK) {
  FactSet EntrySetOrig = EntrySet;

  // Find locks in ExitSet that conflict or are not in EntrySet, and warn.
  for (const auto &Fact : ExitSet) {
    const FactEntry &ExitFact = FactMan[Fact];

    FactSet::iterator EntryIt = EntrySet.findLockIter(FactMan, ExitFact);
    if (EntryIt != EntrySet.end()) {
      if (join(FactMan[*EntryIt], ExitFact,
               EntryLEK != LEK_LockedSomeLoopIterations))
        *EntryIt = Fact;
    } else if (!ExitFact.managed()) {
      ExitFact.handleRemovalFromIntersection(ExitSet, FactMan, JoinLoc,
                                             EntryLEK, Handler);
    }
  }

  // Find locks in EntrySet that are not in ExitSet, and remove them.
  for (const auto &Fact : EntrySetOrig) {
    const FactEntry *EntryFact = &FactMan[Fact];
    const FactEntry *ExitFact = ExitSet.findLock(FactMan, *EntryFact);

    if (!ExitFact) {
      if (!EntryFact->managed() || ExitLEK == LEK_LockedSomeLoopIterations)
        EntryFact->handleRemovalFromIntersection(EntrySetOrig, FactMan, JoinLoc,
                                                 ExitLEK, Handler);
      if (ExitLEK == LEK_LockedSomePredecessors)
        EntrySet.removeLock(FactMan, *EntryFact);
    }
  }
}

// Return true if block B never continues to its successors.
static bool neverReturns(const CFGBlock *B) {
  if (B->hasNoReturnElement())
    return true;
  if (B->empty())
    return false;

  CFGElement Last = B->back();
  if (std::optional<CFGStmt> S = Last.getAs<CFGStmt>()) {
    if (isa<CXXThrowExpr>(S->getStmt()))
      return true;
  }
  return false;
}

/// Check a function's CFG for thread-safety violations.
///
/// We traverse the blocks in the CFG, compute the set of mutexes that are held
/// at the end of each block, and issue warnings for thread safety violations.
/// Each block in the CFG is traversed exactly once.
void ThreadSafetyAnalyzer::runAnalysis(AnalysisDeclContext &AC) {
  // TODO: this whole function needs be rewritten as a visitor for CFGWalker.
  // For now, we just use the walker to set things up.
  threadSafety::CFGWalker walker;
  if (!walker.init(AC))
    return;

  // AC.dumpCFG(true);
  // threadSafety::printSCFG(walker);

  CFG *CFGraph = walker.getGraph();
  const NamedDecl *D = walker.getDecl();
  const auto *CurrentFunction = dyn_cast<FunctionDecl>(D);
  CurrentMethod = dyn_cast<CXXMethodDecl>(D);

  if (D->hasAttr<NoThreadSafetyAnalysisAttr>())
    return;

  // FIXME: Do something a bit more intelligent inside constructor and
  // destructor code.  Constructors and destructors must assume unique access
  // to 'this', so checks on member variable access is disabled, but we should
  // still enable checks on other objects.
  if (isa<CXXConstructorDecl>(D))
    return;  // Don't check inside constructors.
  if (isa<CXXDestructorDecl>(D))
    return;  // Don't check inside destructors.

  Handler.enterFunction(CurrentFunction);

  BlockInfo.resize(CFGraph->getNumBlockIDs(),
    CFGBlockInfo::getEmptyBlockInfo(LocalVarMap));

  // We need to explore the CFG via a "topological" ordering.
  // That way, we will be guaranteed to have information about required
  // predecessor locksets when exploring a new block.
  const PostOrderCFGView *SortedGraph = walker.getSortedGraph();
  PostOrderCFGView::CFGBlockSet VisitedBlocks(CFGraph);

  // Mark entry block as reachable
  BlockInfo[CFGraph->getEntry().getBlockID()].Reachable = true;

  // Compute SSA names for local variables
  LocalVarMap.traverseCFG(CFGraph, SortedGraph, BlockInfo);

  // Fill in source locations for all CFGBlocks.
  findBlockLocations(CFGraph, SortedGraph, BlockInfo);

  CapExprSet ExclusiveLocksAcquired;
  CapExprSet SharedLocksAcquired;
  CapExprSet LocksReleased;

  // Add locks from exclusive_locks_required and shared_locks_required
  // to initial lockset. Also turn off checking for lock and unlock functions.
  // FIXME: is there a more intelligent way to check lock/unlock functions?
  if (!SortedGraph->empty() && D->hasAttrs()) {
    const CFGBlock *FirstBlock = *SortedGraph->begin();
    FactSet &InitialLockset = BlockInfo[FirstBlock->getBlockID()].EntrySet;

    CapExprSet ExclusiveLocksToAdd;
    CapExprSet SharedLocksToAdd;

    SourceLocation Loc = D->getLocation();
    for (const auto *Attr : D->attrs()) {
      Loc = Attr->getLocation();
      if (const auto *A = dyn_cast<RequiresCapabilityAttr>(Attr)) {
        getMutexIDs(A->isShared() ? SharedLocksToAdd : ExclusiveLocksToAdd, A,
                    nullptr, D);
      } else if (const auto *A = dyn_cast<ReleaseCapabilityAttr>(Attr)) {
        // UNLOCK_FUNCTION() is used to hide the underlying lock implementation.
        // We must ignore such methods.
        if (A->args_size() == 0)
          return;
        getMutexIDs(A->isShared() ? SharedLocksToAdd : ExclusiveLocksToAdd, A,
                    nullptr, D);
        getMutexIDs(LocksReleased, A, nullptr, D);
      } else if (const auto *A = dyn_cast<AcquireCapabilityAttr>(Attr)) {
        if (A->args_size() == 0)
          return;
        getMutexIDs(A->isShared() ? SharedLocksAcquired
                                  : ExclusiveLocksAcquired,
                    A, nullptr, D);
      } else if (isa<ExclusiveTrylockFunctionAttr>(Attr)) {
        // Don't try to check trylock functions for now.
        return;
      } else if (isa<SharedTrylockFunctionAttr>(Attr)) {
        // Don't try to check trylock functions for now.
        return;
      } else if (isa<TryAcquireCapabilityAttr>(Attr)) {
        // Don't try to check trylock functions for now.
        return;
      }
    }

    // FIXME -- Loc can be wrong here.
    for (const auto &Mu : ExclusiveLocksToAdd) {
      auto Entry = std::make_unique<LockableFactEntry>(Mu, LK_Exclusive, Loc,
                                                       FactEntry::Declared);
      addLock(InitialLockset, std::move(Entry), true);
    }
    for (const auto &Mu : SharedLocksToAdd) {
      auto Entry = std::make_unique<LockableFactEntry>(Mu, LK_Shared, Loc,
                                                       FactEntry::Declared);
      addLock(InitialLockset, std::move(Entry), true);
    }
  }

  for (const auto *CurrBlock : *SortedGraph) {
    unsigned CurrBlockID = CurrBlock->getBlockID();
    CFGBlockInfo *CurrBlockInfo = &BlockInfo[CurrBlockID];

    // Use the default initial lockset in case there are no predecessors.
    VisitedBlocks.insert(CurrBlock);

    // Iterate through the predecessor blocks and warn if the lockset for all
    // predecessors is not the same. We take the entry lockset of the current
    // block to be the intersection of all previous locksets.
    // FIXME: By keeping the intersection, we may output more errors in future
    // for a lock which is not in the intersection, but was in the union. We
    // may want to also keep the union in future. As an example, let's say
    // the intersection contains Mutex L, and the union contains L and M.
    // Later we unlock M. At this point, we would output an error because we
    // never locked M; although the real error is probably that we forgot to
    // lock M on all code paths. Conversely, let's say that later we lock M.
    // In this case, we should compare against the intersection instead of the
    // union because the real error is probably that we forgot to unlock M on
    // all code paths.
    bool LocksetInitialized = false;
    for (CFGBlock::const_pred_iterator PI = CurrBlock->pred_begin(),
         PE  = CurrBlock->pred_end(); PI != PE; ++PI) {
      // if *PI -> CurrBlock is a back edge
      if (*PI == nullptr || !VisitedBlocks.alreadySet(*PI))
        continue;

      unsigned PrevBlockID = (*PI)->getBlockID();
      CFGBlockInfo *PrevBlockInfo = &BlockInfo[PrevBlockID];

      // Ignore edges from blocks that can't return.
      if (neverReturns(*PI) || !PrevBlockInfo->Reachable)
        continue;

      // Okay, we can reach this block from the entry.
      CurrBlockInfo->Reachable = true;

      FactSet PrevLockset;
      getEdgeLockset(PrevLockset, PrevBlockInfo->ExitSet, *PI, CurrBlock);

      if (!LocksetInitialized) {
        CurrBlockInfo->EntrySet = PrevLockset;
        LocksetInitialized = true;
      } else {
        // Surprisingly 'continue' doesn't always produce back edges, because
        // the CFG has empty "transition" blocks where they meet with the end
        // of the regular loop body. We still want to diagnose them as loop.
        intersectAndWarn(
            CurrBlockInfo->EntrySet, PrevLockset, CurrBlockInfo->EntryLoc,
            isa_and_nonnull<ContinueStmt>((*PI)->getTerminatorStmt())
                ? LEK_LockedSomeLoopIterations
                : LEK_LockedSomePredecessors);
      }
    }

    // Skip rest of block if it's not reachable.
    if (!CurrBlockInfo->Reachable)
      continue;

    BuildLockset LocksetBuilder(this, *CurrBlockInfo);

    // Visit all the statements in the basic block.
    for (const auto &BI : *CurrBlock) {
      switch (BI.getKind()) {
        case CFGElement::Statement: {
          CFGStmt CS = BI.castAs<CFGStmt>();
          LocksetBuilder.Visit(CS.getStmt());
          break;
        }
        // Ignore BaseDtor and MemberDtor for now.
        case CFGElement::AutomaticObjectDtor: {
          CFGAutomaticObjDtor AD = BI.castAs<CFGAutomaticObjDtor>();
          const auto *DD = AD.getDestructorDecl(AC.getASTContext());
          if (!DD->hasAttrs())
            break;

          LocksetBuilder.handleCall(nullptr, DD,
                                    SxBuilder.createVariable(AD.getVarDecl()),
                                    AD.getTriggerStmt()->getEndLoc());
          break;
        }
        case CFGElement::TemporaryDtor: {
          auto TD = BI.castAs<CFGTemporaryDtor>();

          // Clean up constructed object even if there are no attributes to
          // keep the number of objects in limbo as small as possible.
          if (auto Object = LocksetBuilder.ConstructedObjects.find(
                  TD.getBindTemporaryExpr()->getSubExpr());
              Object != LocksetBuilder.ConstructedObjects.end()) {
            const auto *DD = TD.getDestructorDecl(AC.getASTContext());
            if (DD->hasAttrs())
              // TODO: the location here isn't quite correct.
              LocksetBuilder.handleCall(nullptr, DD, Object->second,
                                        TD.getBindTemporaryExpr()->getEndLoc());
            LocksetBuilder.ConstructedObjects.erase(Object);
          }
          break;
        }
        default:
          break;
      }
    }
    CurrBlockInfo->ExitSet = LocksetBuilder.FSet;

    // For every back edge from CurrBlock (the end of the loop) to another block
    // (FirstLoopBlock) we need to check that the Lockset of Block is equal to
    // the one held at the beginning of FirstLoopBlock. We can look up the
    // Lockset held at the beginning of FirstLoopBlock in the EntryLockSets map.
    for (CFGBlock::const_succ_iterator SI = CurrBlock->succ_begin(),
         SE  = CurrBlock->succ_end(); SI != SE; ++SI) {
      // if CurrBlock -> *SI is *not* a back edge
      if (*SI == nullptr || !VisitedBlocks.alreadySet(*SI))
        continue;

      CFGBlock *FirstLoopBlock = *SI;
      CFGBlockInfo *PreLoop = &BlockInfo[FirstLoopBlock->getBlockID()];
      CFGBlockInfo *LoopEnd = &BlockInfo[CurrBlockID];
      intersectAndWarn(PreLoop->EntrySet, LoopEnd->ExitSet, PreLoop->EntryLoc,
                       LEK_LockedSomeLoopIterations);
    }
  }

  CFGBlockInfo *Initial = &BlockInfo[CFGraph->getEntry().getBlockID()];
  CFGBlockInfo *Final   = &BlockInfo[CFGraph->getExit().getBlockID()];

  // Skip the final check if the exit block is unreachable.
  if (!Final->Reachable)
    return;

  // By default, we expect all locks held on entry to be held on exit.
  FactSet ExpectedExitSet = Initial->EntrySet;

  // Adjust the expected exit set by adding or removing locks, as declared
  // by *-LOCK_FUNCTION and UNLOCK_FUNCTION.  The intersect below will then
  // issue the appropriate warning.
  // FIXME: the location here is not quite right.
  for (const auto &Lock : ExclusiveLocksAcquired)
    ExpectedExitSet.addLock(FactMan, std::make_unique<LockableFactEntry>(
                                         Lock, LK_Exclusive, D->getLocation()));
  for (const auto &Lock : SharedLocksAcquired)
    ExpectedExitSet.addLock(FactMan, std::make_unique<LockableFactEntry>(
                                         Lock, LK_Shared, D->getLocation()));
  for (const auto &Lock : LocksReleased)
    ExpectedExitSet.removeLock(FactMan, Lock);

  // FIXME: Should we call this function for all blocks which exit the function?
  intersectAndWarn(ExpectedExitSet, Final->ExitSet, Final->ExitLoc,
                   LEK_LockedAtEndOfFunction, LEK_NotLockedAtEndOfFunction);

  Handler.leaveFunction(CurrentFunction);
}

/// Check a function's CFG for thread-safety violations.
///
/// We traverse the blocks in the CFG, compute the set of mutexes that are held
/// at the end of each block, and issue warnings for thread safety violations.
/// Each block in the CFG is traversed exactly once.
void threadSafety::runThreadSafetyAnalysis(AnalysisDeclContext &AC,
                                           ThreadSafetyHandler &Handler,
                                           BeforeSet **BSet) {
  if (!*BSet)
    *BSet = new BeforeSet;
  ThreadSafetyAnalyzer Analyzer(Handler, *BSet);
  Analyzer.runAnalysis(AC);
}

void threadSafety::threadSafetyCleanup(BeforeSet *Cache) { delete Cache; }

/// Helper function that returns a LockKind required for the given level
/// of access.
LockKind threadSafety::getLockKindFromAccessKind(AccessKind AK) {
  switch (AK) {
    case AK_Read :
      return LK_Shared;
    case AK_Written :
      return LK_Exclusive;
  }
  llvm_unreachable("Unknown AccessKind");
}