aboutsummaryrefslogtreecommitdiffstats
path: root/lib/Analysis/ThreadSafety.cpp
blob: 5954682579d803dcdc82a9cbcd2e8877624915d4 (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
//===- ThreadSafety.cpp ----------------------------------------*- C++ --*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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/LanguageExtensions.html#threadsafety for more
// information.
//
//===----------------------------------------------------------------------===//

#include "clang/Analysis/Analyses/ThreadSafety.h"
#include "clang/Analysis/Analyses/PostOrderCFGView.h"
#include "clang/Analysis/AnalysisContext.h"
#include "clang/Analysis/CFG.h"
#include "clang/Analysis/CFGStmtMap.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/StmtCXX.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Basic/OperatorKinds.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/ImmutableMap.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <utility>
#include <vector>

using namespace clang;
using namespace thread_safety;

// Key method definition
ThreadSafetyHandler::~ThreadSafetyHandler() {}

namespace {

/// SExpr implements a simple expression language that is used to store,
/// compare, and pretty-print C++ expressions.  Unlike a clang Expr, a SExpr
/// does not capture surface syntax, and it does not distinguish between
/// C++ concepts, like pointers and references, that have no real semantic
/// differences.  This simplicity allows SExprs to be meaningfully compared,
/// e.g.
///        (x)          =  x
///        (*this).foo  =  this->foo
///        *&a          =  a
///
/// Thread-safety analysis works by comparing lock expressions.  Within the
/// body of a function, an expression such as "x->foo->bar.mu" will resolve to
/// a particular mutex object at run-time.  Subsequent occurrences of the same
/// expression (where "same" means syntactic equality) will refer to the same
/// run-time object if three conditions hold:
/// (1) Local variables in the expression, such as "x" have not changed.
/// (2) Values on the heap that affect the expression have not changed.
/// (3) The expression involves only pure function calls.
///
/// The current implementation assumes, but does not verify, that multiple uses
/// of the same lock expression satisfies these criteria.
class SExpr {
private:
  enum ExprOp {
    EOP_Nop,      //< No-op
    EOP_Wildcard, //< Matches anything.
    EOP_This,     //< This keyword.
    EOP_NVar,     //< Named variable.
    EOP_LVar,     //< Local variable.
    EOP_Dot,      //< Field access
    EOP_Call,     //< Function call
    EOP_MCall,    //< Method call
    EOP_Index,    //< Array index
    EOP_Unary,    //< Unary operation
    EOP_Binary,   //< Binary operation
    EOP_Unknown   //< Catchall for everything else
  };


  class SExprNode {
   private:
    unsigned char  Op;     //< Opcode of the root node
    unsigned char  Flags;  //< Additional opcode-specific data
    unsigned short Sz;     //< Number of child nodes
    const void*    Data;   //< Additional opcode-specific data

   public:
    SExprNode(ExprOp O, unsigned F, const void* D)
      : Op(static_cast<unsigned char>(O)),
        Flags(static_cast<unsigned char>(F)), Sz(1), Data(D)
    { }

    unsigned size() const        { return Sz; }
    void     setSize(unsigned S) { Sz = S;    }

    ExprOp   kind() const { return static_cast<ExprOp>(Op); }

    const NamedDecl* getNamedDecl() const {
      assert(Op == EOP_NVar || Op == EOP_LVar || Op == EOP_Dot);
      return reinterpret_cast<const NamedDecl*>(Data);
    }

    const NamedDecl* getFunctionDecl() const {
      assert(Op == EOP_Call || Op == EOP_MCall);
      return reinterpret_cast<const NamedDecl*>(Data);
    }

    bool isArrow() const { return Op == EOP_Dot && Flags == 1; }
    void setArrow(bool A) { Flags = A ? 1 : 0; }

    unsigned arity() const {
      switch (Op) {
        case EOP_Nop:      return 0;
        case EOP_Wildcard: return 0;
        case EOP_NVar:     return 0;
        case EOP_LVar:     return 0;
        case EOP_This:     return 0;
        case EOP_Dot:      return 1;
        case EOP_Call:     return Flags+1;  // First arg is function.
        case EOP_MCall:    return Flags+1;  // First arg is implicit obj.
        case EOP_Index:    return 2;
        case EOP_Unary:    return 1;
        case EOP_Binary:   return 2;
        case EOP_Unknown:  return Flags;
      }
      return 0;
    }

    bool operator==(const SExprNode& Other) const {
      // Ignore flags and size -- they don't matter.
      return (Op == Other.Op &&
              Data == Other.Data);
    }

    bool operator!=(const SExprNode& Other) const {
      return !(*this == Other);
    }

    bool matches(const SExprNode& Other) const {
      return (*this == Other) ||
             (Op == EOP_Wildcard) ||
             (Other.Op == EOP_Wildcard);
    }
  };


  /// \brief Encapsulates the lexical context of a function call.  The lexical
  /// context includes the arguments to the call, including the implicit object
  /// argument.  When an attribute containing a mutex expression is attached to
  /// a method, the expression may refer to formal parameters of the method.
  /// Actual arguments must be substituted for formal parameters to derive
  /// the appropriate mutex expression in the lexical context where the function
  /// is called.  PrevCtx holds the context in which the arguments themselves
  /// should be evaluated; multiple calling contexts can be chained together
  /// by the lock_returned attribute.
  struct CallingContext {
    const NamedDecl* AttrDecl;   // The decl to which the attribute is attached.
    Expr*            SelfArg;    // Implicit object argument -- e.g. 'this'
    bool             SelfArrow;  // is Self referred to with -> or .?
    unsigned         NumArgs;    // Number of funArgs
    Expr**           FunArgs;    // Function arguments
    CallingContext*  PrevCtx;    // The previous context; or 0 if none.

    CallingContext(const NamedDecl *D = 0, Expr *S = 0,
                   unsigned N = 0, Expr **A = 0, CallingContext *P = 0)
      : AttrDecl(D), SelfArg(S), SelfArrow(false),
        NumArgs(N), FunArgs(A), PrevCtx(P)
    { }
  };

  typedef SmallVector<SExprNode, 4> NodeVector;

private:
  // A SExpr is a list of SExprNodes in prefix order.  The Size field allows
  // the list to be traversed as a tree.
  NodeVector NodeVec;

private:
  unsigned makeNop() {
    NodeVec.push_back(SExprNode(EOP_Nop, 0, 0));
    return NodeVec.size()-1;
  }

  unsigned makeWildcard() {
    NodeVec.push_back(SExprNode(EOP_Wildcard, 0, 0));
    return NodeVec.size()-1;
  }

  unsigned makeNamedVar(const NamedDecl *D) {
    NodeVec.push_back(SExprNode(EOP_NVar, 0, D));
    return NodeVec.size()-1;
  }

  unsigned makeLocalVar(const NamedDecl *D) {
    NodeVec.push_back(SExprNode(EOP_LVar, 0, D));
    return NodeVec.size()-1;
  }

  unsigned makeThis() {
    NodeVec.push_back(SExprNode(EOP_This, 0, 0));
    return NodeVec.size()-1;
  }

  unsigned makeDot(const NamedDecl *D, bool Arrow) {
    NodeVec.push_back(SExprNode(EOP_Dot, Arrow ? 1 : 0, D));
    return NodeVec.size()-1;
  }

  unsigned makeCall(unsigned NumArgs, const NamedDecl *D) {
    NodeVec.push_back(SExprNode(EOP_Call, NumArgs, D));
    return NodeVec.size()-1;
  }

  unsigned makeMCall(unsigned NumArgs, const NamedDecl *D) {
    NodeVec.push_back(SExprNode(EOP_MCall, NumArgs, D));
    return NodeVec.size()-1;
  }

  unsigned makeIndex() {
    NodeVec.push_back(SExprNode(EOP_Index, 0, 0));
    return NodeVec.size()-1;
  }

  unsigned makeUnary() {
    NodeVec.push_back(SExprNode(EOP_Unary, 0, 0));
    return NodeVec.size()-1;
  }

  unsigned makeBinary() {
    NodeVec.push_back(SExprNode(EOP_Binary, 0, 0));
    return NodeVec.size()-1;
  }

  unsigned makeUnknown(unsigned Arity) {
    NodeVec.push_back(SExprNode(EOP_Unknown, Arity, 0));
    return NodeVec.size()-1;
  }

  /// Build an SExpr from the given C++ expression.
  /// Recursive function that terminates on DeclRefExpr.
  /// Note: this function merely creates a SExpr; it does not check to
  /// ensure that the original expression is a valid mutex expression.
  ///
  /// NDeref returns the number of Derefence and AddressOf operations
  /// preceeding the Expr; this is used to decide whether to pretty-print
  /// SExprs with . or ->.
  unsigned buildSExpr(Expr *Exp, CallingContext* CallCtx, int* NDeref = 0) {
    if (!Exp)
      return 0;

    if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Exp)) {
      NamedDecl *ND = cast<NamedDecl>(DRE->getDecl()->getCanonicalDecl());
      ParmVarDecl *PV = dyn_cast_or_null<ParmVarDecl>(ND);
      if (PV) {
        FunctionDecl *FD =
          cast<FunctionDecl>(PV->getDeclContext())->getCanonicalDecl();
        unsigned i = PV->getFunctionScopeIndex();

        if (CallCtx && CallCtx->FunArgs &&
            FD == CallCtx->AttrDecl->getCanonicalDecl()) {
          // Substitute call arguments for references to function parameters
          assert(i < CallCtx->NumArgs);
          return buildSExpr(CallCtx->FunArgs[i], CallCtx->PrevCtx, NDeref);
        }
        // Map the param back to the param of the original function declaration.
        makeNamedVar(FD->getParamDecl(i));
        return 1;
      }
      // Not a function parameter -- just store the reference.
      makeNamedVar(ND);
      return 1;
    } else if (isa<CXXThisExpr>(Exp)) {
      // Substitute parent for 'this'
      if (CallCtx && CallCtx->SelfArg) {
        if (!CallCtx->SelfArrow && NDeref)
          // 'this' is a pointer, but self is not, so need to take address.
          --(*NDeref);
        return buildSExpr(CallCtx->SelfArg, CallCtx->PrevCtx, NDeref);
      }
      else {
        makeThis();
        return 1;
      }
    } else if (MemberExpr *ME = dyn_cast<MemberExpr>(Exp)) {
      NamedDecl *ND = ME->getMemberDecl();
      int ImplicitDeref = ME->isArrow() ? 1 : 0;
      unsigned Root = makeDot(ND, false);
      unsigned Sz = buildSExpr(ME->getBase(), CallCtx, &ImplicitDeref);
      NodeVec[Root].setArrow(ImplicitDeref > 0);
      NodeVec[Root].setSize(Sz + 1);
      return Sz + 1;
    } else if (CXXMemberCallExpr *CMCE = dyn_cast<CXXMemberCallExpr>(Exp)) {
      // When calling a function with a lock_returned attribute, replace
      // the function call with the expression in lock_returned.
      if (LockReturnedAttr* At =
            CMCE->getMethodDecl()->getAttr<LockReturnedAttr>()) {
        CallingContext LRCallCtx(CMCE->getMethodDecl());
        LRCallCtx.SelfArg = CMCE->getImplicitObjectArgument();
        LRCallCtx.SelfArrow =
          dyn_cast<MemberExpr>(CMCE->getCallee())->isArrow();
        LRCallCtx.NumArgs = CMCE->getNumArgs();
        LRCallCtx.FunArgs = CMCE->getArgs();
        LRCallCtx.PrevCtx = CallCtx;
        return buildSExpr(At->getArg(), &LRCallCtx);
      }
      // Hack to treat smart pointers and iterators as pointers;
      // ignore any method named get().
      if (CMCE->getMethodDecl()->getNameAsString() == "get" &&
          CMCE->getNumArgs() == 0) {
        if (NDeref && dyn_cast<MemberExpr>(CMCE->getCallee())->isArrow())
          ++(*NDeref);
        return buildSExpr(CMCE->getImplicitObjectArgument(), CallCtx, NDeref);
      }
      unsigned NumCallArgs = CMCE->getNumArgs();
      unsigned Root =
        makeMCall(NumCallArgs, CMCE->getMethodDecl()->getCanonicalDecl());
      unsigned Sz = buildSExpr(CMCE->getImplicitObjectArgument(), CallCtx);
      Expr** CallArgs = CMCE->getArgs();
      for (unsigned i = 0; i < NumCallArgs; ++i) {
        Sz += buildSExpr(CallArgs[i], CallCtx);
      }
      NodeVec[Root].setSize(Sz + 1);
      return Sz + 1;
    } else if (CallExpr *CE = dyn_cast<CallExpr>(Exp)) {
      if (LockReturnedAttr* At =
            CE->getDirectCallee()->getAttr<LockReturnedAttr>()) {
        CallingContext LRCallCtx(CE->getDirectCallee());
        LRCallCtx.NumArgs = CE->getNumArgs();
        LRCallCtx.FunArgs = CE->getArgs();
        LRCallCtx.PrevCtx = CallCtx;
        return buildSExpr(At->getArg(), &LRCallCtx);
      }
      // Treat smart pointers and iterators as pointers;
      // ignore the * and -> operators.
      if (CXXOperatorCallExpr *OE = dyn_cast<CXXOperatorCallExpr>(CE)) {
        OverloadedOperatorKind k = OE->getOperator();
        if (k == OO_Star) {
          if (NDeref) ++(*NDeref);
          return buildSExpr(OE->getArg(0), CallCtx, NDeref);
        }
        else if (k == OO_Arrow) {
          return buildSExpr(OE->getArg(0), CallCtx, NDeref);
        }
      }
      unsigned NumCallArgs = CE->getNumArgs();
      unsigned Root = makeCall(NumCallArgs, 0);
      unsigned Sz = buildSExpr(CE->getCallee(), CallCtx);
      Expr** CallArgs = CE->getArgs();
      for (unsigned i = 0; i < NumCallArgs; ++i) {
        Sz += buildSExpr(CallArgs[i], CallCtx);
      }
      NodeVec[Root].setSize(Sz+1);
      return Sz+1;
    } else if (BinaryOperator *BOE = dyn_cast<BinaryOperator>(Exp)) {
      unsigned Root = makeBinary();
      unsigned Sz = buildSExpr(BOE->getLHS(), CallCtx);
      Sz += buildSExpr(BOE->getRHS(), CallCtx);
      NodeVec[Root].setSize(Sz);
      return Sz;
    } else if (UnaryOperator *UOE = dyn_cast<UnaryOperator>(Exp)) {
      // Ignore & and * operators -- they're no-ops.
      // However, we try to figure out whether the expression is a pointer,
      // so we can use . and -> appropriately in error messages.
      if (UOE->getOpcode() == UO_Deref) {
        if (NDeref) ++(*NDeref);
        return buildSExpr(UOE->getSubExpr(), CallCtx, NDeref);
      }
      if (UOE->getOpcode() == UO_AddrOf) {
        if (DeclRefExpr* DRE = dyn_cast<DeclRefExpr>(UOE->getSubExpr())) {
          if (DRE->getDecl()->isCXXInstanceMember()) {
            // This is a pointer-to-member expression, e.g. &MyClass::mu_.
            // We interpret this syntax specially, as a wildcard.
            unsigned Root = makeDot(DRE->getDecl(), false);
            makeWildcard();
            NodeVec[Root].setSize(2);
            return 2;
          }
        }
        if (NDeref) --(*NDeref);
        return buildSExpr(UOE->getSubExpr(), CallCtx, NDeref);
      }
      unsigned Root = makeUnary();
      unsigned Sz = buildSExpr(UOE->getSubExpr(), CallCtx);
      NodeVec[Root].setSize(Sz);
      return Sz;
    } else if (ArraySubscriptExpr *ASE = dyn_cast<ArraySubscriptExpr>(Exp)) {
      unsigned Root = makeIndex();
      unsigned Sz = buildSExpr(ASE->getBase(), CallCtx);
      Sz += buildSExpr(ASE->getIdx(), CallCtx);
      NodeVec[Root].setSize(Sz);
      return Sz;
    } else if (AbstractConditionalOperator *CE =
               dyn_cast<AbstractConditionalOperator>(Exp)) {
      unsigned Root = makeUnknown(3);
      unsigned Sz = buildSExpr(CE->getCond(), CallCtx);
      Sz += buildSExpr(CE->getTrueExpr(), CallCtx);
      Sz += buildSExpr(CE->getFalseExpr(), CallCtx);
      NodeVec[Root].setSize(Sz);
      return Sz;
    } else if (ChooseExpr *CE = dyn_cast<ChooseExpr>(Exp)) {
      unsigned Root = makeUnknown(3);
      unsigned Sz = buildSExpr(CE->getCond(), CallCtx);
      Sz += buildSExpr(CE->getLHS(), CallCtx);
      Sz += buildSExpr(CE->getRHS(), CallCtx);
      NodeVec[Root].setSize(Sz);
      return Sz;
    } else if (CastExpr *CE = dyn_cast<CastExpr>(Exp)) {
      return buildSExpr(CE->getSubExpr(), CallCtx, NDeref);
    } else if (ParenExpr *PE = dyn_cast<ParenExpr>(Exp)) {
      return buildSExpr(PE->getSubExpr(), CallCtx, NDeref);
    } else if (ExprWithCleanups *EWC = dyn_cast<ExprWithCleanups>(Exp)) {
      return buildSExpr(EWC->getSubExpr(), CallCtx, NDeref);
    } else if (CXXBindTemporaryExpr *E = dyn_cast<CXXBindTemporaryExpr>(Exp)) {
      return buildSExpr(E->getSubExpr(), CallCtx, NDeref);
    } else if (isa<CharacterLiteral>(Exp) ||
               isa<CXXNullPtrLiteralExpr>(Exp) ||
               isa<GNUNullExpr>(Exp) ||
               isa<CXXBoolLiteralExpr>(Exp) ||
               isa<FloatingLiteral>(Exp) ||
               isa<ImaginaryLiteral>(Exp) ||
               isa<IntegerLiteral>(Exp) ||
               isa<StringLiteral>(Exp) ||
               isa<ObjCStringLiteral>(Exp)) {
      makeNop();
      return 1;  // FIXME: Ignore literals for now
    } else {
      makeNop();
      return 1;  // Ignore.  FIXME: mark as invalid expression?
    }
  }

  /// \brief Construct a SExpr from an expression.
  /// \param MutexExp The original mutex expression within an attribute
  /// \param DeclExp An expression involving the Decl on which the attribute
  ///        occurs.
  /// \param D  The declaration to which the lock/unlock attribute is attached.
  void buildSExprFromExpr(Expr *MutexExp, Expr *DeclExp, const NamedDecl *D) {
    CallingContext CallCtx(D);

    // If we are processing a raw attribute expression, with no substitutions.
    if (DeclExp == 0) {
      buildSExpr(MutexExp, 0);
      return;
    }

    // Examine DeclExp to find SelfArg and FunArgs, which are used to substitute
    // for formal parameters when we call buildMutexID later.
    if (MemberExpr *ME = dyn_cast<MemberExpr>(DeclExp)) {
      CallCtx.SelfArg   = ME->getBase();
      CallCtx.SelfArrow = ME->isArrow();
    } else if (CXXMemberCallExpr *CE = dyn_cast<CXXMemberCallExpr>(DeclExp)) {
      CallCtx.SelfArg   = CE->getImplicitObjectArgument();
      CallCtx.SelfArrow = dyn_cast<MemberExpr>(CE->getCallee())->isArrow();
      CallCtx.NumArgs   = CE->getNumArgs();
      CallCtx.FunArgs   = CE->getArgs();
    } else if (CallExpr *CE = dyn_cast<CallExpr>(DeclExp)) {
      CallCtx.NumArgs = CE->getNumArgs();
      CallCtx.FunArgs = CE->getArgs();
    } else if (CXXConstructExpr *CE = dyn_cast<CXXConstructExpr>(DeclExp)) {
      CallCtx.SelfArg = 0;  // FIXME -- get the parent from DeclStmt
      CallCtx.NumArgs = CE->getNumArgs();
      CallCtx.FunArgs = CE->getArgs();
    } else if (D && isa<CXXDestructorDecl>(D)) {
      // There's no such thing as a "destructor call" in the AST.
      CallCtx.SelfArg = DeclExp;
    }

    // If the attribute has no arguments, then assume the argument is "this".
    if (MutexExp == 0) {
      buildSExpr(CallCtx.SelfArg, 0);
      return;
    }

    // For most attributes.
    buildSExpr(MutexExp, &CallCtx);
  }

  /// \brief Get index of next sibling of node i.
  unsigned getNextSibling(unsigned i) const {
    return i + NodeVec[i].size();
  }

public:
  explicit SExpr(clang::Decl::EmptyShell e) { NodeVec.clear(); }

  /// \param MutexExp The original mutex expression within an attribute
  /// \param DeclExp An expression involving the Decl on which the attribute
  ///        occurs.
  /// \param D  The declaration to which the lock/unlock attribute is attached.
  /// Caller must check isValid() after construction.
  SExpr(Expr* MutexExp, Expr *DeclExp, const NamedDecl* D) {
    buildSExprFromExpr(MutexExp, DeclExp, D);
  }

  /// Return true if this is a valid decl sequence.
  /// Caller must call this by hand after construction to handle errors.
  bool isValid() const {
    return !NodeVec.empty();
  }

  /// Issue a warning about an invalid lock expression
  static void warnInvalidLock(ThreadSafetyHandler &Handler, Expr* MutexExp,
                              Expr *DeclExp, const NamedDecl* D) {
    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);
  }

  bool operator==(const SExpr &other) const {
    return NodeVec == other.NodeVec;
  }

  bool operator!=(const SExpr &other) const {
    return !(*this == other);
  }

  bool matches(const SExpr &Other, unsigned i = 0, unsigned j = 0) const {
    if (NodeVec[i].matches(Other.NodeVec[j])) {
      unsigned n = NodeVec[i].arity();
      bool Result = true;
      unsigned ci = i+1;  // first child of i
      unsigned cj = j+1;  // first child of j
      for (unsigned k = 0; k < n;
           ++k, ci=getNextSibling(ci), cj = Other.getNextSibling(cj)) {
        Result = Result && matches(Other, ci, cj);
      }
      return Result;
    }
    return false;
  }

  /// \brief Pretty print a lock expression for use in error messages.
  std::string toString(unsigned i = 0) const {
    assert(isValid());
    if (i >= NodeVec.size())
      return "";

    const SExprNode* N = &NodeVec[i];
    switch (N->kind()) {
      case EOP_Nop:
        return "_";
      case EOP_Wildcard:
        return "(?)";
      case EOP_This:
        return "this";
      case EOP_NVar:
      case EOP_LVar: {
        return N->getNamedDecl()->getNameAsString();
      }
      case EOP_Dot: {
        if (NodeVec[i+1].kind() == EOP_Wildcard) {
          std::string S = "&";
          S += N->getNamedDecl()->getQualifiedNameAsString();
          return S;
        }
        std::string FieldName = N->getNamedDecl()->getNameAsString();
        if (NodeVec[i+1].kind() == EOP_This)
          return FieldName;

        std::string S = toString(i+1);
        if (N->isArrow())
          return S + "->" + FieldName;
        else
          return S + "." + FieldName;
      }
      case EOP_Call: {
        std::string S = toString(i+1) + "(";
        unsigned NumArgs = N->arity()-1;
        unsigned ci = getNextSibling(i+1);
        for (unsigned k=0; k<NumArgs; ++k, ci = getNextSibling(ci)) {
          S += toString(ci);
          if (k+1 < NumArgs) S += ",";
        }
        S += ")";
        return S;
      }
      case EOP_MCall: {
        std::string S = "";
        if (NodeVec[i+1].kind() != EOP_This)
          S = toString(i+1) + ".";
        if (const NamedDecl *D = N->getFunctionDecl())
          S += D->getNameAsString() + "(";
        else
          S += "#(";
        unsigned NumArgs = N->arity()-1;
        unsigned ci = getNextSibling(i+1);
        for (unsigned k=0; k<NumArgs; ++k, ci = getNextSibling(ci)) {
          S += toString(ci);
          if (k+1 < NumArgs) S += ",";
        }
        S += ")";
        return S;
      }
      case EOP_Index: {
        std::string S1 = toString(i+1);
        std::string S2 = toString(i+1 + NodeVec[i+1].size());
        return S1 + "[" + S2 + "]";
      }
      case EOP_Unary: {
        std::string S = toString(i+1);
        return "#" + S;
      }
      case EOP_Binary: {
        std::string S1 = toString(i+1);
        std::string S2 = toString(i+1 + NodeVec[i+1].size());
        return "(" + S1 + "#" + S2 + ")";
      }
      case EOP_Unknown: {
        unsigned NumChildren = N->arity();
        if (NumChildren == 0)
          return "(...)";
        std::string S = "(";
        unsigned ci = i+1;
        for (unsigned j = 0; j < NumChildren; ++j, ci = getNextSibling(ci)) {
          S += toString(ci);
          if (j+1 < NumChildren) S += "#";
        }
        S += ")";
        return S;
      }
    }
    return "";
  }
};



/// \brief A short list of SExprs
class MutexIDList : public SmallVector<SExpr, 3> {
public:
  /// \brief Return true if the list contains the specified SExpr
  /// Performs a linear search, because these lists are almost always very small.
  bool contains(const SExpr& M) {
    for (iterator I=begin(),E=end(); I != E; ++I)
      if ((*I) == M) return true;
    return false;
  }

  /// \brief Push M onto list, bud discard duplicates
  void push_back_nodup(const SExpr& M) {
    if (!contains(M)) push_back(M);
  }
};



/// \brief This is a helper class that stores info about the most recent
/// accquire of a Lock.
///
/// The main body of the analysis maps MutexIDs to LockDatas.
struct LockData {
  SourceLocation AcquireLoc;

  /// \brief LKind stores whether a lock is held shared or exclusively.
  /// Note that this analysis does not currently support either re-entrant
  /// locking or lock "upgrading" and "downgrading" between exclusive and
  /// shared.
  ///
  /// FIXME: add support for re-entrant locking and lock up/downgrading
  LockKind LKind;
  bool     Managed;            // for ScopedLockable objects
  SExpr    UnderlyingMutex;    // for ScopedLockable objects

  LockData(SourceLocation AcquireLoc, LockKind LKind, bool M = false)
    : AcquireLoc(AcquireLoc), LKind(LKind), Managed(M),
      UnderlyingMutex(Decl::EmptyShell())
  {}

  LockData(SourceLocation AcquireLoc, LockKind LKind, const SExpr &Mu)
    : AcquireLoc(AcquireLoc), LKind(LKind), Managed(false),
      UnderlyingMutex(Mu)
  {}

  bool operator==(const LockData &other) const {
    return AcquireLoc == other.AcquireLoc && LKind == other.LKind;
  }

  bool operator!=(const LockData &other) const {
    return !(*this == other);
  }

  void Profile(llvm::FoldingSetNodeID &ID) const {
    ID.AddInteger(AcquireLoc.getRawEncoding());
    ID.AddInteger(LKind);
  }
};


/// \brief A FactEntry stores a single fact that is known at a particular point
/// in the program execution.  Currently, this is information regarding a lock
/// that is held at that point.  
struct FactEntry {
  SExpr    MutID;
  LockData LDat;

  FactEntry(const SExpr& M, const LockData& L)
    : MutID(M), LDat(L)
  { }
};


typedef unsigned short FactID;

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

public:
  FactID newLock(const SExpr& M, const LockData& L) {
    Facts.push_back(FactEntry(M,L));
    return static_cast<unsigned short>(Facts.size() - 1);
  }

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


/// \brief 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:
  typedef SmallVector<FactID, 4> FactVec;

  FactVec FactIDs;

public:
  typedef FactVec::iterator       iterator;
  typedef FactVec::const_iterator 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; }

  FactID addLock(FactManager& FM, const SExpr& M, const LockData& L) {
    FactID F = FM.newLock(M, L);
    FactIDs.push_back(F);
    return F;
  }

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

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

  LockData* findLock(FactManager& FM, const SExpr& M) const {
    for (const_iterator I=begin(), E=end(); I != E; ++I) {
      if (FM[*I].MutID.matches(M)) return &FM[*I].LDat;
    }
    return 0;
  }
};



/// A Lockset maps each SExpr (defined above) to information about how it has
/// been locked.
typedef llvm::ImmutableMap<SExpr, LockData> Lockset;
typedef llvm::ImmutableMap<const NamedDecl*, unsigned> LocalVarContext;

class LocalVariableMap;

/// 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 {
  FactSet EntrySet;             // Lockset held at entry to block
  FactSet ExitSet;              // Lockset held at exit from block
  LocalVarContext EntryContext; // Context held at entry to block
  LocalVarContext ExitContext;  // Context held at exit from block
  SourceLocation EntryLoc;      // Location of first statement in block
  SourceLocation ExitLoc;       // Location of last statement in block.
  unsigned EntryIndex;          // Used to replay contexts later

  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:
  typedef LocalVarContext Context;

  /// 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;

    const NamedDecl *Dec;  // The original declaration for this variable.
    const Expr *Exp;       // The expression for this variable, OR
    unsigned Ref;          // Reference to another VarDefinition
    Context Ctx;           // The map with which Exp should be interpreted.

    bool isReference() { return !Exp; }

  private:
    // Create ordinary variable definition
    VarDefinition(const NamedDecl *D, const Expr *E, Context C)
      : Dec(D), Exp(E), Ref(0), Ctx(C)
    { }

    // Create reference to previous definition
    VarDefinition(const NamedDecl *D, unsigned R, Context C)
      : Dec(D), Exp(0), Ref(R), Ctx(C)
    { }
  };

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

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

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

  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, 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 << " " << ((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, PostOrderCFGView *SortedGraph,
                     std::vector<CFGBlockInfo> &BlockInfo);

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

  // Save the current context for later replay
  void saveContext(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, 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);

  friend class VarMapBuilder;
};


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


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

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

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


// Add new local variables to the variable map
void VarMapBuilder::VisitDeclStmt(DeclStmt *S) {
  bool modifiedCtx = false;
  DeclGroupRef DGrp = S->getDeclGroup();
  for (DeclGroupRef::iterator I = DGrp.begin(), E = DGrp.end(); I != E; ++I) {
    if (VarDecl *VD = dyn_cast_or_null<VarDecl>(*I)) {
      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(BinaryOperator *BO) {
  if (!BO->isAssignmentOp())
    return;

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

  // Update the variable map and current context.
  if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(LHSExp)) {
    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 (Context::iterator I = C1.begin(), E = C1.end(); I != E; ++I) {
    const NamedDecl *Dec = I.getKey();
    unsigned i1 = I.getData();
    const unsigned *i2 = C2.lookup(Dec);
    if (!i2)             // variable doesn't exist on second path
      Result = removeDefinition(Dec, Result);
    else if (*i2 != i1)  // 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 (Context::iterator I = C.begin(), E = C.end(); I != E; ++I) {
    const NamedDecl *Dec = I.getKey();
    unsigned i = I.getData();
    Result = addReference(Dec, i, 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 (Context::iterator I = C1.begin(), E = C1.end(); I != E; ++I) {
    const NamedDecl *Dec = I.getKey();
    unsigned i1 = I.getData();
    VarDefinition *VDef = &VarDefinitions[i1];
    assert(VDef->isReference());

    const unsigned *i2 = C2.lookup(Dec);
    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,
                                   PostOrderCFGView *SortedGraph,
                                   std::vector<CFGBlockInfo> &BlockInfo) {
  PostOrderCFGView::CFGBlockSet VisitedBlocks(CFGraph);

  CtxIndices.resize(CFGraph->getNumBlockIDs());

  for (PostOrderCFGView::iterator I = SortedGraph->begin(),
       E = SortedGraph->end(); I!= E; ++I) {
    const CFGBlock *CurrBlock = *I;
    int 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 == 0 || !VisitedBlocks.alreadySet(*PI)) {
        HasBackEdges = true;
        continue;
      }

      int 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(0, CurrBlockInfo->EntryContext);
    CurrBlockInfo->EntryIndex = getContextIndex();

    // Visit all the statements in the basic block.
    VarMapBuilder VMapBuilder(this, CurrBlockInfo->EntryContext);
    for (CFGBlock::const_iterator BI = CurrBlock->begin(),
         BE = CurrBlock->end(); BI != BE; ++BI) {
      switch (BI->getKind()) {
        case CFGElement::Statement: {
          const CFGStmt *CS = cast<CFGStmt>(&*BI);
          VMapBuilder.Visit(const_cast<Stmt*>(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 == 0 || !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(0, BlockInfo[exitID].ExitContext);
}

/// Find the appropriate source locations to use when producing diagnostics for
/// each block in the CFG.
static void findBlockLocations(CFG *CFGraph,
                               PostOrderCFGView *SortedGraph,
                               std::vector<CFGBlockInfo> &BlockInfo) {
  for (PostOrderCFGView::iterator I = SortedGraph->begin(),
       E = SortedGraph->end(); I!= E; ++I) {
    const CFGBlock *CurrBlock = *I;
    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->getTerminator()) {
      CurrBlockInfo->EntryLoc = CurrBlockInfo->ExitLoc = S->getLocStart();
    } else {
      for (CFGBlock::const_reverse_iterator BI = CurrBlock->rbegin(),
           BE = CurrBlock->rend(); BI != BE; ++BI) {
        // FIXME: Handle other CFGElement kinds.
        if (const CFGStmt *CS = dyn_cast<CFGStmt>(&*BI)) {
          CurrBlockInfo->ExitLoc = CS->getStmt()->getLocStart();
          break;
        }
      }
    }

    if (!CurrBlockInfo->ExitLoc.isInvalid()) {
      // This block contains at least one statement. Find the source location
      // of the first statement in the block.
      for (CFGBlock::const_iterator BI = CurrBlock->begin(),
           BE = CurrBlock->end(); BI != BE; ++BI) {
        // FIXME: Handle other CFGElement kinds.
        if (const CFGStmt *CS = dyn_cast<CFGStmt>(&*BI)) {
          CurrBlockInfo->EntryLoc = CS->getStmt()->getLocStart();
          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;
    }
  }
}

/// \brief Class which implements the core thread safety analysis routines.
class ThreadSafetyAnalyzer {
  friend class BuildLockset;

  ThreadSafetyHandler       &Handler;
  LocalVariableMap          LocalVarMap;
  FactManager               FactMan;
  std::vector<CFGBlockInfo> BlockInfo;

public:
  ThreadSafetyAnalyzer(ThreadSafetyHandler &H) : Handler(H) {}

  void addLock(FactSet &FSet, const SExpr &Mutex, const LockData &LDat);
  void removeLock(FactSet &FSet, const SExpr &Mutex,
                  SourceLocation UnlockLoc, bool FullyRemove=false);

  template <typename AttrType>
  void getMutexIDs(MutexIDList &Mtxs, AttrType *Attr, Expr *Exp,
                   const NamedDecl *D);

  template <class AttrType>
  void getMutexIDs(MutexIDList &Mtxs, AttrType *Attr, 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);

  void intersectAndWarn(FactSet &FSet1, const FactSet &FSet2,
                        SourceLocation JoinLoc,
                        LockErrorKind LEK1, LockErrorKind LEK2,
                        bool Modify=true);

  void intersectAndWarn(FactSet &FSet1, const FactSet &FSet2,
                        SourceLocation JoinLoc, LockErrorKind LEK1,
                        bool Modify=true) {
    intersectAndWarn(FSet1, FSet2, JoinLoc, LEK1, LEK1, Modify);
  }

  void runAnalysis(AnalysisDeclContext &AC);
};


/// \brief Add a new lock to the lockset, warning if the lock is already there.
/// \param Mutex -- the Mutex expression for the lock
/// \param LDat  -- the LockData for the lock
void ThreadSafetyAnalyzer::addLock(FactSet &FSet, const SExpr &Mutex,
                                   const LockData &LDat) {
  // FIXME: deal with acquired before/after annotations.
  // FIXME: Don't always warn when we have support for reentrant locks.
  if (FSet.findLock(FactMan, Mutex)) {
    Handler.handleDoubleLock(Mutex.toString(), LDat.AcquireLoc);
  } else {
    FSet.addLock(FactMan, Mutex, LDat);
  }
}


/// \brief Remove a lock from the lockset, warning if the lock is not there.
/// \param LockExp The lock expression corresponding to the lock to be removed
/// \param UnlockLoc The source location of the unlock (only used in error msg)
void ThreadSafetyAnalyzer::removeLock(FactSet &FSet,
                                      const SExpr &Mutex,
                                      SourceLocation UnlockLoc,
                                      bool FullyRemove) {
  const LockData *LDat = FSet.findLock(FactMan, Mutex);
  if (!LDat) {
    Handler.handleUnmatchedUnlock(Mutex.toString(), UnlockLoc);
    return;
  }

  if (LDat->UnderlyingMutex.isValid()) {
    // This is scoped lockable object, which manages the real mutex.
    if (FullyRemove) {
      // We're destroying the managing object.
      // Remove the underlying mutex if it exists; but don't warn.
      if (FSet.findLock(FactMan, LDat->UnderlyingMutex))
        FSet.removeLock(FactMan, LDat->UnderlyingMutex);
    } else {
      // We're releasing the underlying mutex, but not destroying the
      // managing object.  Warn on dual release.
      if (!FSet.findLock(FactMan, LDat->UnderlyingMutex)) {
        Handler.handleUnmatchedUnlock(LDat->UnderlyingMutex.toString(),
                                      UnlockLoc);
      }
      FSet.removeLock(FactMan, LDat->UnderlyingMutex);
      return;
    }
  }
  FSet.removeLock(FactMan, Mutex);
}


/// \brief 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(MutexIDList &Mtxs, AttrType *Attr,
                                       Expr *Exp, const NamedDecl *D) {
  typedef typename AttrType::args_iterator iterator_type;

  if (Attr->args_size() == 0) {
    // The mutex held is the "this" object.
    SExpr Mu(0, Exp, D);
    if (!Mu.isValid())
      SExpr::warnInvalidLock(Handler, 0, Exp, D);
    else
      Mtxs.push_back_nodup(Mu);
    return;
  }

  for (iterator_type I=Attr->args_begin(), E=Attr->args_end(); I != E; ++I) {
    SExpr Mu(*I, Exp, D);
    if (!Mu.isValid())
      SExpr::warnInvalidLock(Handler, *I, Exp, D);
    else
      Mtxs.push_back_nodup(Mu);
  }
}


/// \brief 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(MutexIDList &Mtxs, AttrType *Attr,
                                       Expr *Exp, const NamedDecl *D,
                                       const CFGBlock *PredBlock,
                                       const CFGBlock *CurrBlock,
                                       Expr *BrE, bool Neg) {
  // Find out which branch has the lock
  bool branch = 0;
  if (CXXBoolLiteralExpr *BLE = dyn_cast_or_null<CXXBoolLiteralExpr>(BrE)) {
    branch = BLE->getValue();
  }
  else if (IntegerLiteral *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);
    }
  }
}


bool getStaticBooleanValue(Expr* E, bool& TCond) {
  if (isa<CXXNullPtrLiteralExpr>(E) || isa<GNUNullExpr>(E)) {
    TCond = false;
    return true;
  } else if (CXXBoolLiteralExpr *BLE = dyn_cast<CXXBoolLiteralExpr>(E)) {
    TCond = BLE->getValue();
    return true;
  } else if (IntegerLiteral *ILE = dyn_cast<IntegerLiteral>(E)) {
    TCond = ILE->getValue().getBoolValue();
    return true;
  } else if (ImplicitCastExpr *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 0;

  if (const CallExpr *CallExp = dyn_cast<CallExpr>(Cond)) {
    return CallExp;
  }
  else if (const ParenExpr *PE = dyn_cast<ParenExpr>(Cond)) {
    return getTrylockCallExpr(PE->getSubExpr(), C, Negate);
  }
  else if (const ImplicitCastExpr *CE = dyn_cast<ImplicitCastExpr>(Cond)) {
    return getTrylockCallExpr(CE->getSubExpr(), C, Negate);
  }
  else if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Cond)) {
    const Expr *E = LocalVarMap.lookupExpr(DRE->getDecl(), C);
    return getTrylockCallExpr(E, C, Negate);
  }
  else if (const UnaryOperator *UOP = dyn_cast<UnaryOperator>(Cond)) {
    if (UOP->getOpcode() == UO_LNot) {
      Negate = !Negate;
      return getTrylockCallExpr(UOP->getSubExpr(), C, Negate);
    }
    return 0;
  }
  else if (const BinaryOperator *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);
      }
      else if (getStaticBooleanValue(BOP->getLHS(), TCond)) {
        if (!TCond) Negate = !Negate;
        return getTrylockCallExpr(BOP->getRHS(), C, Negate);
      }
      return 0;
    }
    return 0;
  }
  // FIXME -- handle && and || as well.
  return 0;
}


/// \brief 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;

  if (!PredBlock->getTerminatorCondition())
    return;

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

  CallExpr *Exp =
    const_cast<CallExpr*>(getTrylockCallExpr(Cond, LVarCtx, Negate));
  if (!Exp)
    return;

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


  MutexIDList ExclusiveLocksToAdd;
  MutexIDList SharedLocksToAdd;

  // If the condition is a call to a Trylock function, then grab the attributes
  AttrVec &ArgAttrs = FunDecl->getAttrs();
  for (unsigned i = 0; i < ArgAttrs.size(); ++i) {
    Attr *Attr = ArgAttrs[i];
    switch (Attr->getKind()) {
      case attr::ExclusiveTrylockFunction: {
        ExclusiveTrylockFunctionAttr *A =
          cast<ExclusiveTrylockFunctionAttr>(Attr);
        getMutexIDs(ExclusiveLocksToAdd, A, Exp, FunDecl,
                    PredBlock, CurrBlock, A->getSuccessValue(), Negate);
        break;
      }
      case attr::SharedTrylockFunction: {
        SharedTrylockFunctionAttr *A =
          cast<SharedTrylockFunctionAttr>(Attr);
        getMutexIDs(ExclusiveLocksToAdd, A, Exp, FunDecl,
                    PredBlock, CurrBlock, A->getSuccessValue(), Negate);
        break;
      }
      default:
        break;
    }
  }

  // Add and remove locks.
  SourceLocation Loc = Exp->getExprLoc();
  for (unsigned i=0,n=ExclusiveLocksToAdd.size(); i<n; ++i) {
    addLock(Result, ExclusiveLocksToAdd[i],
            LockData(Loc, LK_Exclusive));
  }
  for (unsigned i=0,n=SharedLocksToAdd.size(); i<n; ++i) {
    addLock(Result, SharedLocksToAdd[i],
            LockData(Loc, LK_Shared));
  }
}


/// \brief 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 StmtVisitor<BuildLockset> {
  friend class ThreadSafetyAnalyzer;

  ThreadSafetyAnalyzer *Analyzer;
  FactSet FSet;
  LocalVariableMap::Context LVarCtx;
  unsigned CtxIndex;

  // Helper functions
  const ValueDecl *getValueDecl(Expr *Exp);

  void warnIfMutexNotHeld(const NamedDecl *D, Expr *Exp, AccessKind AK,
                          Expr *MutexExp, ProtectedOperationKind POK);

  void checkAccess(Expr *Exp, AccessKind AK);
  void checkDereference(Expr *Exp, AccessKind AK);
  void handleCall(Expr *Exp, const NamedDecl *D, VarDecl *VD = 0);

  /// \brief Returns true if the lockset contains a lock, regardless of whether
  /// the lock is held exclusively or shared.
  bool locksetContains(const SExpr &Mu) const {
    return FSet.findLock(Analyzer->FactMan, Mu);
  }

  /// \brief Returns true if the lockset contains a lock with the passed in
  /// locktype.
  bool locksetContains(const SExpr &Mu, LockKind KindRequested) const {
    const LockData *LockHeld = FSet.findLock(Analyzer->FactMan, Mu);
    return (LockHeld && KindRequested == LockHeld->LKind);
  }

  /// \brief Returns true if the lockset contains a lock with at least the
  /// passed in locktype. So for example, if we pass in LK_Shared, this function
  /// returns true if the lock is held LK_Shared or LK_Exclusive. If we pass in
  /// LK_Exclusive, this function returns true if the lock is held LK_Exclusive.
  bool locksetContainsAtLeast(const SExpr &Lock,
                              LockKind KindRequested) const {
    switch (KindRequested) {
      case LK_Shared:
        return locksetContains(Lock);
      case LK_Exclusive:
        return locksetContains(Lock, KindRequested);
    }
    llvm_unreachable("Unknown LockKind");
  }

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

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


/// \brief Gets the value decl pointer from DeclRefExprs or MemberExprs
const ValueDecl *BuildLockset::getValueDecl(Expr *Exp) {
  if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Exp))
    return DR->getDecl();

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

  return 0;
}

/// \brief 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, Expr *Exp,
                                      AccessKind AK, Expr *MutexExp,
                                      ProtectedOperationKind POK) {
  LockKind LK = getLockKindFromAccessKind(AK);

  SExpr Mutex(MutexExp, Exp, D);
  if (!Mutex.isValid())
    SExpr::warnInvalidLock(Analyzer->Handler, MutexExp, Exp, D);
  else if (!locksetContainsAtLeast(Mutex, LK))
    Analyzer->Handler.handleMutexNotHeld(D, POK, Mutex.toString(), LK,
                                         Exp->getExprLoc());
}

/// \brief This method identifies variable dereferences and checks pt_guarded_by
/// and pt_guarded_var annotations. Note that we only check these annotations
/// at the time a pointer is dereferenced.
/// FIXME: We need to check for other types of pointer dereferences
/// (e.g. [], ->) and deal with them here.
/// \param Exp An expression that has been read or written.
void BuildLockset::checkDereference(Expr *Exp, AccessKind AK) {
  UnaryOperator *UO = dyn_cast<UnaryOperator>(Exp);
  if (!UO || UO->getOpcode() != clang::UO_Deref)
    return;
  Exp = UO->getSubExpr()->IgnoreParenCasts();

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

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

  const AttrVec &ArgAttrs = D->getAttrs();
  for(unsigned i = 0, Size = ArgAttrs.size(); i < Size; ++i)
    if (PtGuardedByAttr *PGBAttr = dyn_cast<PtGuardedByAttr>(ArgAttrs[i]))
      warnIfMutexNotHeld(D, Exp, AK, PGBAttr->getArg(), POK_VarDereference);
}

/// \brief Checks guarded_by and guarded_var attributes.
/// Whenever we identify an access (read or write) of a DeclRefExpr or
/// MemberExpr, we need to check whether there are any guarded_by or
/// guarded_var attributes, and make sure we hold the appropriate mutexes.
void BuildLockset::checkAccess(Expr *Exp, AccessKind AK) {
  const ValueDecl *D = getValueDecl(Exp);
  if(!D || !D->hasAttrs())
    return;

  if (D->getAttr<GuardedVarAttr>() && FSet.isEmpty())
    Analyzer->Handler.handleNoMutexHeld(D, POK_VarAccess, AK,
                                        Exp->getExprLoc());

  const AttrVec &ArgAttrs = D->getAttrs();
  for(unsigned i = 0, Size = ArgAttrs.size(); i < Size; ++i)
    if (GuardedByAttr *GBAttr = dyn_cast<GuardedByAttr>(ArgAttrs[i]))
      warnIfMutexNotHeld(D, Exp, AK, GBAttr->getArg(), POK_VarAccess);
}

/// \brief 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.
///
void BuildLockset::handleCall(Expr *Exp, const NamedDecl *D, VarDecl *VD) {
  const AttrVec &ArgAttrs = D->getAttrs();
  MutexIDList ExclusiveLocksToAdd;
  MutexIDList SharedLocksToAdd;
  MutexIDList LocksToRemove;

  for(unsigned i = 0; i < ArgAttrs.size(); ++i) {
    Attr *At = const_cast<Attr*>(ArgAttrs[i]);
    switch (At->getKind()) {
      // When we encounter an exclusive lock function, we need to add the lock
      // to our lockset with kind exclusive.
      case attr::ExclusiveLockFunction: {
        ExclusiveLockFunctionAttr *A = cast<ExclusiveLockFunctionAttr>(At);
        Analyzer->getMutexIDs(ExclusiveLocksToAdd, A, Exp, D);
        break;
      }

      // When we encounter a shared lock function, we need to add the lock
      // to our lockset with kind shared.
      case attr::SharedLockFunction: {
        SharedLockFunctionAttr *A = cast<SharedLockFunctionAttr>(At);
        Analyzer->getMutexIDs(SharedLocksToAdd, A, Exp, D);
        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::UnlockFunction: {
        UnlockFunctionAttr *A = cast<UnlockFunctionAttr>(At);
        Analyzer->getMutexIDs(LocksToRemove, A, Exp, D);
        break;
      }

      case attr::ExclusiveLocksRequired: {
        ExclusiveLocksRequiredAttr *A = cast<ExclusiveLocksRequiredAttr>(At);

        for (ExclusiveLocksRequiredAttr::args_iterator
             I = A->args_begin(), E = A->args_end(); I != E; ++I)
          warnIfMutexNotHeld(D, Exp, AK_Written, *I, POK_FunctionCall);
        break;
      }

      case attr::SharedLocksRequired: {
        SharedLocksRequiredAttr *A = cast<SharedLocksRequiredAttr>(At);

        for (SharedLocksRequiredAttr::args_iterator I = A->args_begin(),
             E = A->args_end(); I != E; ++I)
          warnIfMutexNotHeld(D, Exp, AK_Read, *I, POK_FunctionCall);
        break;
      }

      case attr::LocksExcluded: {
        LocksExcludedAttr *A = cast<LocksExcludedAttr>(At);
        for (LocksExcludedAttr::args_iterator I = A->args_begin(),
            E = A->args_end(); I != E; ++I) {
          SExpr Mutex(*I, Exp, D);
          if (!Mutex.isValid())
            SExpr::warnInvalidLock(Analyzer->Handler, *I, Exp, D);
          else if (locksetContains(Mutex))
            Analyzer->Handler.handleFunExcludesLock(D->getName(),
                                                    Mutex.toString(),
                                                    Exp->getExprLoc());
        }
        break;
      }

      // Ignore other (non thread-safety) attributes
      default:
        break;
    }
  }

  // Figure out if we're calling the constructor of scoped lockable class
  bool isScopedVar = false;
  if (VD) {
    if (const CXXConstructorDecl *CD = dyn_cast<const CXXConstructorDecl>(D)) {
      const CXXRecordDecl* PD = CD->getParent();
      if (PD && PD->getAttr<ScopedLockableAttr>())
        isScopedVar = true;
    }
  }

  // Add locks.
  SourceLocation Loc = Exp->getExprLoc();
  for (unsigned i=0,n=ExclusiveLocksToAdd.size(); i<n; ++i) {
    Analyzer->addLock(FSet, ExclusiveLocksToAdd[i],
                            LockData(Loc, LK_Exclusive, isScopedVar));
  }
  for (unsigned i=0,n=SharedLocksToAdd.size(); i<n; ++i) {
    Analyzer->addLock(FSet, SharedLocksToAdd[i],
                            LockData(Loc, LK_Shared, isScopedVar));
  }

  // Add the managing object as a dummy mutex, mapped to the underlying mutex.
  // FIXME -- this doesn't work if we acquire multiple locks.
  if (isScopedVar) {
    SourceLocation MLoc = VD->getLocation();
    DeclRefExpr DRE(VD, false, VD->getType(), VK_LValue, VD->getLocation());
    SExpr SMutex(&DRE, 0, 0);

    for (unsigned i=0,n=ExclusiveLocksToAdd.size(); i<n; ++i) {
      Analyzer->addLock(FSet, SMutex, LockData(MLoc, LK_Exclusive,
                                               ExclusiveLocksToAdd[i]));
    }
    for (unsigned i=0,n=SharedLocksToAdd.size(); i<n; ++i) {
      Analyzer->addLock(FSet, SMutex, LockData(MLoc, LK_Shared,
                                               SharedLocksToAdd[i]));
    }
  }

  // Remove locks.
  // FIXME -- should only fully remove if the attribute refers to 'this'.
  bool Dtor = isa<CXXDestructorDecl>(D);
  for (unsigned i=0,n=LocksToRemove.size(); i<n; ++i) {
    Analyzer->removeLock(FSet, LocksToRemove[i], Loc, Dtor);
  }
}


/// \brief 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(UnaryOperator *UO) {
  switch (UO->getOpcode()) {
    case clang::UO_PostDec:
    case clang::UO_PostInc:
    case clang::UO_PreDec:
    case clang::UO_PreInc: {
      Expr *SubExp = UO->getSubExpr()->IgnoreParenCasts();
      checkAccess(SubExp, AK_Written);
      checkDereference(SubExp, 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(BinaryOperator *BO) {
  if (!BO->isAssignmentOp())
    return;

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

  Expr *LHSExp = BO->getLHS()->IgnoreParenCasts();
  checkAccess(LHSExp, AK_Written);
  checkDereference(LHSExp, 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(CastExpr *CE) {
  if (CE->getCastKind() != CK_LValueToRValue)
    return;
  Expr *SubExp = CE->getSubExpr()->IgnoreParenCasts();
  checkAccess(SubExp, AK_Read);
  checkDereference(SubExp, AK_Read);
}


void BuildLockset::VisitCallExpr(CallExpr *Exp) {
  NamedDecl *D = dyn_cast_or_null<NamedDecl>(Exp->getCalleeDecl());
  if(!D || !D->hasAttrs())
    return;
  handleCall(Exp, D);
}

void BuildLockset::VisitCXXConstructExpr(CXXConstructExpr *Exp) {
  // FIXME -- only handles constructors in DeclStmt below.
}

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

  DeclGroupRef DGrp = S->getDeclGroup();
  for (DeclGroupRef::iterator I = DGrp.begin(), E = DGrp.end(); I != E; ++I) {
    Decl *D = *I;
    if (VarDecl *VD = dyn_cast_or_null<VarDecl>(D)) {
      Expr *E = VD->getInit();
      // handle constructors that involve temporaries
      if (ExprWithCleanups *EWC = dyn_cast_or_null<ExprWithCleanups>(E))
        E = EWC->getSubExpr();

      if (CXXConstructExpr *CE = dyn_cast_or_null<CXXConstructExpr>(E)) {
        NamedDecl *CtorD = dyn_cast_or_null<NamedDecl>(CE->getConstructor());
        if (!CtorD || !CtorD->hasAttrs())
          return;
        handleCall(CE, CtorD, VD);
      }
    }
  }
}



/// \brief 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 LSet1 The first lockset.
/// \param LSet2 The second lockset.
/// \param JoinLoc The location of the join point for error reporting
/// \param LEK1 The error message to report if a mutex is missing from LSet1
/// \param LEK2 The error message to report if a mutex is missing from Lset2
void ThreadSafetyAnalyzer::intersectAndWarn(FactSet &FSet1,
                                            const FactSet &FSet2,
                                            SourceLocation JoinLoc,
                                            LockErrorKind LEK1,
                                            LockErrorKind LEK2,
                                            bool Modify) {
  FactSet FSet1Orig = FSet1;

  for (FactSet::const_iterator I = FSet2.begin(), E = FSet2.end();
       I != E; ++I) {
    const SExpr &FSet2Mutex = FactMan[*I].MutID;
    const LockData &LDat2 = FactMan[*I].LDat;

    if (const LockData *LDat1 = FSet1.findLock(FactMan, FSet2Mutex)) {
      if (LDat1->LKind != LDat2.LKind) {
        Handler.handleExclusiveAndShared(FSet2Mutex.toString(),
                                         LDat2.AcquireLoc,
                                         LDat1->AcquireLoc);
        if (Modify && LDat1->LKind != LK_Exclusive) {
          FSet1.removeLock(FactMan, FSet2Mutex);
          FSet1.addLock(FactMan, FSet2Mutex, LDat2);
        }
      }
    } else {
      if (LDat2.UnderlyingMutex.isValid()) {
        if (FSet2.findLock(FactMan, LDat2.UnderlyingMutex)) {
          // If this is a scoped lock that manages another mutex, and if the
          // underlying mutex is still held, then warn about the underlying
          // mutex.
          Handler.handleMutexHeldEndOfScope(LDat2.UnderlyingMutex.toString(),
                                            LDat2.AcquireLoc,
                                            JoinLoc, LEK1);
        }
      }
      else if (!LDat2.Managed)
        Handler.handleMutexHeldEndOfScope(FSet2Mutex.toString(),
                                          LDat2.AcquireLoc,
                                          JoinLoc, LEK1);
    }
  }

  for (FactSet::const_iterator I = FSet1.begin(), E = FSet1.end();
       I != E; ++I) {
    const SExpr &FSet1Mutex = FactMan[*I].MutID;
    const LockData &LDat1 = FactMan[*I].LDat;

    if (!FSet2.findLock(FactMan, FSet1Mutex)) {
      if (LDat1.UnderlyingMutex.isValid()) {
        if (FSet1Orig.findLock(FactMan, LDat1.UnderlyingMutex)) {
          // If this is a scoped lock that manages another mutex, and if the
          // underlying mutex is still held, then warn about the underlying
          // mutex.
          Handler.handleMutexHeldEndOfScope(LDat1.UnderlyingMutex.toString(),
                                            LDat1.AcquireLoc,
                                            JoinLoc, LEK1);
        }
      }
      else if (!LDat1.Managed)
        Handler.handleMutexHeldEndOfScope(FSet1Mutex.toString(),
                                          LDat1.AcquireLoc,
                                          JoinLoc, LEK2);
      if (Modify)
        FSet1.removeLock(FactMan, FSet1Mutex);
    }
  }
}



/// \brief 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) {
  CFG *CFGraph = AC.getCFG();
  if (!CFGraph) return;
  const NamedDecl *D = dyn_cast_or_null<NamedDecl>(AC.getDecl());

  // AC.dumpCFG(true);

  if (!D)
    return;  // Ignore anonymous functions for now.
  if (D->getAttr<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.

  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.
  PostOrderCFGView *SortedGraph = AC.getAnalysis<PostOrderCFGView>();
  PostOrderCFGView::CFGBlockSet VisitedBlocks(CFGraph);

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

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

  // 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;
    const AttrVec &ArgAttrs = D->getAttrs();

    MutexIDList ExclusiveLocksToAdd;
    MutexIDList SharedLocksToAdd;

    SourceLocation Loc = D->getLocation();
    for (unsigned i = 0; i < ArgAttrs.size(); ++i) {
      Attr *Attr = ArgAttrs[i];
      Loc = Attr->getLocation();
      if (ExclusiveLocksRequiredAttr *A
            = dyn_cast<ExclusiveLocksRequiredAttr>(Attr)) {
        getMutexIDs(ExclusiveLocksToAdd, A, (Expr*) 0, D);
      } else if (SharedLocksRequiredAttr *A
                   = dyn_cast<SharedLocksRequiredAttr>(Attr)) {
        getMutexIDs(SharedLocksToAdd, A, (Expr*) 0, D);
      } else if (isa<UnlockFunctionAttr>(Attr)) {
        // Don't try to check unlock functions for now
        return;
      } else if (isa<ExclusiveLockFunctionAttr>(Attr)) {
        // Don't try to check lock functions for now
        return;
      } else if (isa<SharedLockFunctionAttr>(Attr)) {
        // Don't try to check lock functions for now
        return;
      } 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;
      }
    }

    // FIXME -- Loc can be wrong here.
    for (unsigned i=0,n=ExclusiveLocksToAdd.size(); i<n; ++i) {
      addLock(InitialLockset, ExclusiveLocksToAdd[i],
              LockData(Loc, LK_Exclusive));
    }
    for (unsigned i=0,n=SharedLocksToAdd.size(); i<n; ++i) {
      addLock(InitialLockset, SharedLocksToAdd[i],
              LockData(Loc, LK_Shared));
    }
  }

  for (PostOrderCFGView::iterator I = SortedGraph->begin(),
       E = SortedGraph->end(); I!= E; ++I) {
    const CFGBlock *CurrBlock = *I;
    int 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;
    llvm::SmallVector<CFGBlock*, 8> SpecialBlocks;
    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 == 0 || !VisitedBlocks.alreadySet(*PI))
        continue;

      // Ignore edges from blocks that can't return.
      if ((*PI)->hasNoReturnElement())
        continue;

      // If the previous block ended in a 'continue' or 'break' statement, then
      // a difference in locksets is probably due to a bug in that block, rather
      // than in some other predecessor. In that case, keep the other
      // predecessor's lockset.
      if (const Stmt *Terminator = (*PI)->getTerminator()) {
        if (isa<ContinueStmt>(Terminator) || isa<BreakStmt>(Terminator)) {
          SpecialBlocks.push_back(*PI);
          continue;
        }
      }

      int PrevBlockID = (*PI)->getBlockID();
      CFGBlockInfo *PrevBlockInfo = &BlockInfo[PrevBlockID];
      FactSet PrevLockset;
      getEdgeLockset(PrevLockset, PrevBlockInfo->ExitSet, *PI, CurrBlock);

      if (!LocksetInitialized) {
        CurrBlockInfo->EntrySet = PrevLockset;
        LocksetInitialized = true;
      } else {
        intersectAndWarn(CurrBlockInfo->EntrySet, PrevLockset,
                         CurrBlockInfo->EntryLoc,
                         LEK_LockedSomePredecessors);
      }
    }

    // Process continue and break blocks. Assume that the lockset for the
    // resulting block is unaffected by any discrepancies in them.
    for (unsigned SpecialI = 0, SpecialN = SpecialBlocks.size();
         SpecialI < SpecialN; ++SpecialI) {
      CFGBlock *PrevBlock = SpecialBlocks[SpecialI];
      int PrevBlockID = PrevBlock->getBlockID();
      CFGBlockInfo *PrevBlockInfo = &BlockInfo[PrevBlockID];

      if (!LocksetInitialized) {
        CurrBlockInfo->EntrySet = PrevBlockInfo->ExitSet;
        LocksetInitialized = true;
      } else {
        // Determine whether this edge is a loop terminator for diagnostic
        // purposes. FIXME: A 'break' statement might be a loop terminator, but
        // it might also be part of a switch. Also, a subsequent destructor
        // might add to the lockset, in which case the real issue might be a
        // double lock on the other path.
        const Stmt *Terminator = PrevBlock->getTerminator();
        bool IsLoop = Terminator && isa<ContinueStmt>(Terminator);

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

        // Do not update EntrySet.
        intersectAndWarn(CurrBlockInfo->EntrySet, PrevLockset,
                         PrevBlockInfo->ExitLoc,
                         IsLoop ? LEK_LockedSomeLoopIterations
                                : LEK_LockedSomePredecessors,
                         false);
      }
    }

    BuildLockset LocksetBuilder(this, *CurrBlockInfo);

    // Visit all the statements in the basic block.
    for (CFGBlock::const_iterator BI = CurrBlock->begin(),
         BE = CurrBlock->end(); BI != BE; ++BI) {
      switch (BI->getKind()) {
        case CFGElement::Statement: {
          const CFGStmt *CS = cast<CFGStmt>(&*BI);
          LocksetBuilder.Visit(const_cast<Stmt*>(CS->getStmt()));
          break;
        }
        // Ignore BaseDtor, MemberDtor, and TemporaryDtor for now.
        case CFGElement::AutomaticObjectDtor: {
          const CFGAutomaticObjDtor *AD = cast<CFGAutomaticObjDtor>(&*BI);
          CXXDestructorDecl *DD = const_cast<CXXDestructorDecl*>(
            AD->getDestructorDecl(AC.getASTContext()));
          if (!DD->hasAttrs())
            break;

          // Create a dummy expression,
          VarDecl *VD = const_cast<VarDecl*>(AD->getVarDecl());
          DeclRefExpr DRE(VD, false, VD->getType(), VK_LValue,
                          AD->getTriggerStmt()->getLocEnd());
          LocksetBuilder.handleCall(&DRE, DD);
          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 == 0 || !VisitedBlocks.alreadySet(*SI))
        continue;

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

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

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

} // end anonymous namespace


namespace clang {
namespace thread_safety {

/// \brief 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 runThreadSafetyAnalysis(AnalysisDeclContext &AC,
                             ThreadSafetyHandler &Handler) {
  ThreadSafetyAnalyzer Analyzer(Handler);
  Analyzer.runAnalysis(AC);
}

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

}} // end namespace clang::thread_safety