aboutsummaryrefslogtreecommitdiffstats
path: root/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
blob: c5a4860781b9f92fceb810544757fc6b44fe1f19 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
//===-- DataFlowSanitizer.cpp - dynamic data flow analysis ----------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
/// \file
/// This file is a part of DataFlowSanitizer, a generalised dynamic data flow
/// analysis.
///
/// Unlike other Sanitizer tools, this tool is not designed to detect a specific
/// class of bugs on its own.  Instead, it provides a generic dynamic data flow
/// analysis framework to be used by clients to help detect application-specific
/// issues within their own code.
///
/// The analysis is based on automatic propagation of data flow labels (also
/// known as taint labels) through a program as it performs computation.  Each
/// byte of application memory is backed by two bytes of shadow memory which
/// hold the label.  On Linux/x86_64, memory is laid out as follows:
///
/// +--------------------+ 0x800000000000 (top of memory)
/// | application memory |
/// +--------------------+ 0x700000008000 (kAppAddr)
/// |                    |
/// |       unused       |
/// |                    |
/// +--------------------+ 0x200200000000 (kUnusedAddr)
/// |    union table     |
/// +--------------------+ 0x200000000000 (kUnionTableAddr)
/// |   shadow memory    |
/// +--------------------+ 0x000000010000 (kShadowAddr)
/// | reserved by kernel |
/// +--------------------+ 0x000000000000
///
/// To derive a shadow memory address from an application memory address,
/// bits 44-46 are cleared to bring the address into the range
/// [0x000000008000,0x100000000000).  Then the address is shifted left by 1 to
/// account for the double byte representation of shadow labels and move the
/// address into the shadow memory range.  See the function
/// DataFlowSanitizer::getShadowAddress below.
///
/// For more information, please refer to the design document:
/// http://clang.llvm.org/docs/DataFlowSanitizerDesign.html

#include "llvm/Transforms/Instrumentation.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/SpecialCaseList.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
#include <iterator>
#include <set>
#include <utility>

using namespace llvm;

// The -dfsan-preserve-alignment flag controls whether this pass assumes that
// alignment requirements provided by the input IR are correct.  For example,
// if the input IR contains a load with alignment 8, this flag will cause
// the shadow load to have alignment 16.  This flag is disabled by default as
// we have unfortunately encountered too much code (including Clang itself;
// see PR14291) which performs misaligned access.
static cl::opt<bool> ClPreserveAlignment(
    "dfsan-preserve-alignment",
    cl::desc("respect alignment requirements provided by input IR"), cl::Hidden,
    cl::init(false));

// The ABI list file controls how shadow parameters are passed.  The pass treats
// every function labelled "uninstrumented" in the ABI list file as conforming
// to the "native" (i.e. unsanitized) ABI.  Unless the ABI list contains
// additional annotations for those functions, a call to one of those functions
// will produce a warning message, as the labelling behaviour of the function is
// unknown.  The other supported annotations are "functional" and "discard",
// which are described below under DataFlowSanitizer::WrapperKind.
static cl::opt<std::string> ClABIListFile(
    "dfsan-abilist",
    cl::desc("File listing native ABI functions and how the pass treats them"),
    cl::Hidden);

// Controls whether the pass uses IA_Args or IA_TLS as the ABI for instrumented
// functions (see DataFlowSanitizer::InstrumentedABI below).
static cl::opt<bool> ClArgsABI(
    "dfsan-args-abi",
    cl::desc("Use the argument ABI rather than the TLS ABI"),
    cl::Hidden);

// Controls whether the pass includes or ignores the labels of pointers in load
// instructions.
static cl::opt<bool> ClCombinePointerLabelsOnLoad(
    "dfsan-combine-pointer-labels-on-load",
    cl::desc("Combine the label of the pointer with the label of the data when "
             "loading from memory."),
    cl::Hidden, cl::init(true));

// Controls whether the pass includes or ignores the labels of pointers in
// stores instructions.
static cl::opt<bool> ClCombinePointerLabelsOnStore(
    "dfsan-combine-pointer-labels-on-store",
    cl::desc("Combine the label of the pointer with the label of the data when "
             "storing in memory."),
    cl::Hidden, cl::init(false));

static cl::opt<bool> ClDebugNonzeroLabels(
    "dfsan-debug-nonzero-labels",
    cl::desc("Insert calls to __dfsan_nonzero_label on observing a parameter, "
             "load or return with a nonzero label"),
    cl::Hidden);

namespace {

StringRef GetGlobalTypeString(const GlobalValue &G) {
  // Types of GlobalVariables are always pointer types.
  Type *GType = G.getType()->getElementType();
  // For now we support blacklisting struct types only.
  if (StructType *SGType = dyn_cast<StructType>(GType)) {
    if (!SGType->isLiteral())
      return SGType->getName();
  }
  return "<unknown type>";
}

class DFSanABIList {
  std::unique_ptr<SpecialCaseList> SCL;

 public:
  DFSanABIList(std::unique_ptr<SpecialCaseList> SCL) : SCL(std::move(SCL)) {}

  /// Returns whether either this function or its source file are listed in the
  /// given category.
  bool isIn(const Function &F, StringRef Category) const {
    return isIn(*F.getParent(), Category) ||
           SCL->inSection("fun", F.getName(), Category);
  }

  /// Returns whether this global alias is listed in the given category.
  ///
  /// If GA aliases a function, the alias's name is matched as a function name
  /// would be.  Similarly, aliases of globals are matched like globals.
  bool isIn(const GlobalAlias &GA, StringRef Category) const {
    if (isIn(*GA.getParent(), Category))
      return true;

    if (isa<FunctionType>(GA.getType()->getElementType()))
      return SCL->inSection("fun", GA.getName(), Category);

    return SCL->inSection("global", GA.getName(), Category) ||
           SCL->inSection("type", GetGlobalTypeString(GA), Category);
  }

  /// Returns whether this module is listed in the given category.
  bool isIn(const Module &M, StringRef Category) const {
    return SCL->inSection("src", M.getModuleIdentifier(), Category);
  }
};

class DataFlowSanitizer : public ModulePass {
  friend struct DFSanFunction;
  friend class DFSanVisitor;

  enum {
    ShadowWidth = 16
  };

  /// Which ABI should be used for instrumented functions?
  enum InstrumentedABI {
    /// Argument and return value labels are passed through additional
    /// arguments and by modifying the return type.
    IA_Args,

    /// Argument and return value labels are passed through TLS variables
    /// __dfsan_arg_tls and __dfsan_retval_tls.
    IA_TLS
  };

  /// How should calls to uninstrumented functions be handled?
  enum WrapperKind {
    /// This function is present in an uninstrumented form but we don't know
    /// how it should be handled.  Print a warning and call the function anyway.
    /// Don't label the return value.
    WK_Warning,

    /// This function does not write to (user-accessible) memory, and its return
    /// value is unlabelled.
    WK_Discard,

    /// This function does not write to (user-accessible) memory, and the label
    /// of its return value is the union of the label of its arguments.
    WK_Functional,

    /// Instead of calling the function, a custom wrapper __dfsw_F is called,
    /// where F is the name of the function.  This function may wrap the
    /// original function or provide its own implementation.  This is similar to
    /// the IA_Args ABI, except that IA_Args uses a struct return type to
    /// pass the return value shadow in a register, while WK_Custom uses an
    /// extra pointer argument to return the shadow.  This allows the wrapped
    /// form of the function type to be expressed in C.
    WK_Custom
  };

  const DataLayout *DL;
  Module *Mod;
  LLVMContext *Ctx;
  IntegerType *ShadowTy;
  PointerType *ShadowPtrTy;
  IntegerType *IntptrTy;
  ConstantInt *ZeroShadow;
  ConstantInt *ShadowPtrMask;
  ConstantInt *ShadowPtrMul;
  Constant *ArgTLS;
  Constant *RetvalTLS;
  void *(*GetArgTLSPtr)();
  void *(*GetRetvalTLSPtr)();
  Constant *GetArgTLS;
  Constant *GetRetvalTLS;
  FunctionType *DFSanUnionFnTy;
  FunctionType *DFSanUnionLoadFnTy;
  FunctionType *DFSanUnimplementedFnTy;
  FunctionType *DFSanSetLabelFnTy;
  FunctionType *DFSanNonzeroLabelFnTy;
  FunctionType *DFSanVarargWrapperFnTy;
  Constant *DFSanUnionFn;
  Constant *DFSanCheckedUnionFn;
  Constant *DFSanUnionLoadFn;
  Constant *DFSanUnimplementedFn;
  Constant *DFSanSetLabelFn;
  Constant *DFSanNonzeroLabelFn;
  Constant *DFSanVarargWrapperFn;
  MDNode *ColdCallWeights;
  DFSanABIList ABIList;
  DenseMap<Value *, Function *> UnwrappedFnMap;
  AttributeSet ReadOnlyNoneAttrs;
  DenseMap<const Function *, DISubprogram> FunctionDIs;

  Value *getShadowAddress(Value *Addr, Instruction *Pos);
  bool isInstrumented(const Function *F);
  bool isInstrumented(const GlobalAlias *GA);
  FunctionType *getArgsFunctionType(FunctionType *T);
  FunctionType *getTrampolineFunctionType(FunctionType *T);
  FunctionType *getCustomFunctionType(FunctionType *T);
  InstrumentedABI getInstrumentedABI();
  WrapperKind getWrapperKind(Function *F);
  void addGlobalNamePrefix(GlobalValue *GV);
  Function *buildWrapperFunction(Function *F, StringRef NewFName,
                                 GlobalValue::LinkageTypes NewFLink,
                                 FunctionType *NewFT);
  Constant *getOrBuildTrampolineFunction(FunctionType *FT, StringRef FName);

 public:
  DataFlowSanitizer(StringRef ABIListFile = StringRef(),
                    void *(*getArgTLS)() = nullptr,
                    void *(*getRetValTLS)() = nullptr);
  static char ID;
  bool doInitialization(Module &M) override;
  bool runOnModule(Module &M) override;
};

struct DFSanFunction {
  DataFlowSanitizer &DFS;
  Function *F;
  DominatorTree DT;
  DataFlowSanitizer::InstrumentedABI IA;
  bool IsNativeABI;
  Value *ArgTLSPtr;
  Value *RetvalTLSPtr;
  AllocaInst *LabelReturnAlloca;
  DenseMap<Value *, Value *> ValShadowMap;
  DenseMap<AllocaInst *, AllocaInst *> AllocaShadowMap;
  std::vector<std::pair<PHINode *, PHINode *> > PHIFixups;
  DenseSet<Instruction *> SkipInsts;
  std::vector<Value *> NonZeroChecks;
  bool AvoidNewBlocks;

  struct CachedCombinedShadow {
    BasicBlock *Block;
    Value *Shadow;
  };
  DenseMap<std::pair<Value *, Value *>, CachedCombinedShadow>
      CachedCombinedShadows;
  DenseMap<Value *, std::set<Value *>> ShadowElements;

  DFSanFunction(DataFlowSanitizer &DFS, Function *F, bool IsNativeABI)
      : DFS(DFS), F(F), IA(DFS.getInstrumentedABI()),
        IsNativeABI(IsNativeABI), ArgTLSPtr(nullptr), RetvalTLSPtr(nullptr),
        LabelReturnAlloca(nullptr) {
    DT.recalculate(*F);
    // FIXME: Need to track down the register allocator issue which causes poor
    // performance in pathological cases with large numbers of basic blocks.
    AvoidNewBlocks = F->size() > 1000;
  }
  Value *getArgTLSPtr();
  Value *getArgTLS(unsigned Index, Instruction *Pos);
  Value *getRetvalTLS();
  Value *getShadow(Value *V);
  void setShadow(Instruction *I, Value *Shadow);
  Value *combineShadows(Value *V1, Value *V2, Instruction *Pos);
  Value *combineOperandShadows(Instruction *Inst);
  Value *loadShadow(Value *ShadowAddr, uint64_t Size, uint64_t Align,
                    Instruction *Pos);
  void storeShadow(Value *Addr, uint64_t Size, uint64_t Align, Value *Shadow,
                   Instruction *Pos);
};

class DFSanVisitor : public InstVisitor<DFSanVisitor> {
 public:
  DFSanFunction &DFSF;
  DFSanVisitor(DFSanFunction &DFSF) : DFSF(DFSF) {}

  void visitOperandShadowInst(Instruction &I);

  void visitBinaryOperator(BinaryOperator &BO);
  void visitCastInst(CastInst &CI);
  void visitCmpInst(CmpInst &CI);
  void visitGetElementPtrInst(GetElementPtrInst &GEPI);
  void visitLoadInst(LoadInst &LI);
  void visitStoreInst(StoreInst &SI);
  void visitReturnInst(ReturnInst &RI);
  void visitCallSite(CallSite CS);
  void visitPHINode(PHINode &PN);
  void visitExtractElementInst(ExtractElementInst &I);
  void visitInsertElementInst(InsertElementInst &I);
  void visitShuffleVectorInst(ShuffleVectorInst &I);
  void visitExtractValueInst(ExtractValueInst &I);
  void visitInsertValueInst(InsertValueInst &I);
  void visitAllocaInst(AllocaInst &I);
  void visitSelectInst(SelectInst &I);
  void visitMemSetInst(MemSetInst &I);
  void visitMemTransferInst(MemTransferInst &I);
};

}

char DataFlowSanitizer::ID;
INITIALIZE_PASS(DataFlowSanitizer, "dfsan",
                "DataFlowSanitizer: dynamic data flow analysis.", false, false)

ModulePass *llvm::createDataFlowSanitizerPass(StringRef ABIListFile,
                                              void *(*getArgTLS)(),
                                              void *(*getRetValTLS)()) {
  return new DataFlowSanitizer(ABIListFile, getArgTLS, getRetValTLS);
}

DataFlowSanitizer::DataFlowSanitizer(StringRef ABIListFile,
                                     void *(*getArgTLS)(),
                                     void *(*getRetValTLS)())
    : ModulePass(ID), GetArgTLSPtr(getArgTLS), GetRetvalTLSPtr(getRetValTLS),
      ABIList(SpecialCaseList::createOrDie(ABIListFile.empty() ? ClABIListFile
                                                               : ABIListFile)) {
}

FunctionType *DataFlowSanitizer::getArgsFunctionType(FunctionType *T) {
  llvm::SmallVector<Type *, 4> ArgTypes;
  std::copy(T->param_begin(), T->param_end(), std::back_inserter(ArgTypes));
  for (unsigned i = 0, e = T->getNumParams(); i != e; ++i)
    ArgTypes.push_back(ShadowTy);
  if (T->isVarArg())
    ArgTypes.push_back(ShadowPtrTy);
  Type *RetType = T->getReturnType();
  if (!RetType->isVoidTy())
    RetType = StructType::get(RetType, ShadowTy, (Type *)nullptr);
  return FunctionType::get(RetType, ArgTypes, T->isVarArg());
}

FunctionType *DataFlowSanitizer::getTrampolineFunctionType(FunctionType *T) {
  assert(!T->isVarArg());
  llvm::SmallVector<Type *, 4> ArgTypes;
  ArgTypes.push_back(T->getPointerTo());
  std::copy(T->param_begin(), T->param_end(), std::back_inserter(ArgTypes));
  for (unsigned i = 0, e = T->getNumParams(); i != e; ++i)
    ArgTypes.push_back(ShadowTy);
  Type *RetType = T->getReturnType();
  if (!RetType->isVoidTy())
    ArgTypes.push_back(ShadowPtrTy);
  return FunctionType::get(T->getReturnType(), ArgTypes, false);
}

FunctionType *DataFlowSanitizer::getCustomFunctionType(FunctionType *T) {
  llvm::SmallVector<Type *, 4> ArgTypes;
  for (FunctionType::param_iterator i = T->param_begin(), e = T->param_end();
       i != e; ++i) {
    FunctionType *FT;
    if (isa<PointerType>(*i) && (FT = dyn_cast<FunctionType>(cast<PointerType>(
                                     *i)->getElementType()))) {
      ArgTypes.push_back(getTrampolineFunctionType(FT)->getPointerTo());
      ArgTypes.push_back(Type::getInt8PtrTy(*Ctx));
    } else {
      ArgTypes.push_back(*i);
    }
  }
  for (unsigned i = 0, e = T->getNumParams(); i != e; ++i)
    ArgTypes.push_back(ShadowTy);
  if (T->isVarArg())
    ArgTypes.push_back(ShadowPtrTy);
  Type *RetType = T->getReturnType();
  if (!RetType->isVoidTy())
    ArgTypes.push_back(ShadowPtrTy);
  return FunctionType::get(T->getReturnType(), ArgTypes, T->isVarArg());
}

bool DataFlowSanitizer::doInitialization(Module &M) {
  DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
  if (!DLP)
    report_fatal_error("data layout missing");
  DL = &DLP->getDataLayout();

  Mod = &M;
  Ctx = &M.getContext();
  ShadowTy = IntegerType::get(*Ctx, ShadowWidth);
  ShadowPtrTy = PointerType::getUnqual(ShadowTy);
  IntptrTy = DL->getIntPtrType(*Ctx);
  ZeroShadow = ConstantInt::getSigned(ShadowTy, 0);
  ShadowPtrMask = ConstantInt::getSigned(IntptrTy, ~0x700000000000LL);
  ShadowPtrMul = ConstantInt::getSigned(IntptrTy, ShadowWidth / 8);

  Type *DFSanUnionArgs[2] = { ShadowTy, ShadowTy };
  DFSanUnionFnTy =
      FunctionType::get(ShadowTy, DFSanUnionArgs, /*isVarArg=*/ false);
  Type *DFSanUnionLoadArgs[2] = { ShadowPtrTy, IntptrTy };
  DFSanUnionLoadFnTy =
      FunctionType::get(ShadowTy, DFSanUnionLoadArgs, /*isVarArg=*/ false);
  DFSanUnimplementedFnTy = FunctionType::get(
      Type::getVoidTy(*Ctx), Type::getInt8PtrTy(*Ctx), /*isVarArg=*/false);
  Type *DFSanSetLabelArgs[3] = { ShadowTy, Type::getInt8PtrTy(*Ctx), IntptrTy };
  DFSanSetLabelFnTy = FunctionType::get(Type::getVoidTy(*Ctx),
                                        DFSanSetLabelArgs, /*isVarArg=*/false);
  DFSanNonzeroLabelFnTy = FunctionType::get(
      Type::getVoidTy(*Ctx), None, /*isVarArg=*/false);
  DFSanVarargWrapperFnTy = FunctionType::get(
      Type::getVoidTy(*Ctx), Type::getInt8PtrTy(*Ctx), /*isVarArg=*/false);

  if (GetArgTLSPtr) {
    Type *ArgTLSTy = ArrayType::get(ShadowTy, 64);
    ArgTLS = nullptr;
    GetArgTLS = ConstantExpr::getIntToPtr(
        ConstantInt::get(IntptrTy, uintptr_t(GetArgTLSPtr)),
        PointerType::getUnqual(
            FunctionType::get(PointerType::getUnqual(ArgTLSTy),
                              (Type *)nullptr)));
  }
  if (GetRetvalTLSPtr) {
    RetvalTLS = nullptr;
    GetRetvalTLS = ConstantExpr::getIntToPtr(
        ConstantInt::get(IntptrTy, uintptr_t(GetRetvalTLSPtr)),
        PointerType::getUnqual(
            FunctionType::get(PointerType::getUnqual(ShadowTy),
                              (Type *)nullptr)));
  }

  ColdCallWeights = MDBuilder(*Ctx).createBranchWeights(1, 1000);
  return true;
}

bool DataFlowSanitizer::isInstrumented(const Function *F) {
  return !ABIList.isIn(*F, "uninstrumented");
}

bool DataFlowSanitizer::isInstrumented(const GlobalAlias *GA) {
  return !ABIList.isIn(*GA, "uninstrumented");
}

DataFlowSanitizer::InstrumentedABI DataFlowSanitizer::getInstrumentedABI() {
  return ClArgsABI ? IA_Args : IA_TLS;
}

DataFlowSanitizer::WrapperKind DataFlowSanitizer::getWrapperKind(Function *F) {
  if (ABIList.isIn(*F, "functional"))
    return WK_Functional;
  if (ABIList.isIn(*F, "discard"))
    return WK_Discard;
  if (ABIList.isIn(*F, "custom"))
    return WK_Custom;

  return WK_Warning;
}

void DataFlowSanitizer::addGlobalNamePrefix(GlobalValue *GV) {
  std::string GVName = GV->getName(), Prefix = "dfs$";
  GV->setName(Prefix + GVName);

  // Try to change the name of the function in module inline asm.  We only do
  // this for specific asm directives, currently only ".symver", to try to avoid
  // corrupting asm which happens to contain the symbol name as a substring.
  // Note that the substitution for .symver assumes that the versioned symbol
  // also has an instrumented name.
  std::string Asm = GV->getParent()->getModuleInlineAsm();
  std::string SearchStr = ".symver " + GVName + ",";
  size_t Pos = Asm.find(SearchStr);
  if (Pos != std::string::npos) {
    Asm.replace(Pos, SearchStr.size(),
                ".symver " + Prefix + GVName + "," + Prefix);
    GV->getParent()->setModuleInlineAsm(Asm);
  }
}

Function *
DataFlowSanitizer::buildWrapperFunction(Function *F, StringRef NewFName,
                                        GlobalValue::LinkageTypes NewFLink,
                                        FunctionType *NewFT) {
  FunctionType *FT = F->getFunctionType();
  Function *NewF = Function::Create(NewFT, NewFLink, NewFName,
                                    F->getParent());
  NewF->copyAttributesFrom(F);
  NewF->removeAttributes(
      AttributeSet::ReturnIndex,
      AttributeFuncs::typeIncompatible(NewFT->getReturnType(),
                                       AttributeSet::ReturnIndex));

  BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", NewF);
  if (F->isVarArg()) {
    NewF->removeAttributes(
        AttributeSet::FunctionIndex,
        AttributeSet().addAttribute(*Ctx, AttributeSet::FunctionIndex,
                                    "split-stack"));
    CallInst::Create(DFSanVarargWrapperFn,
                     IRBuilder<>(BB).CreateGlobalStringPtr(F->getName()), "",
                     BB);
    new UnreachableInst(*Ctx, BB);
  } else {
    std::vector<Value *> Args;
    unsigned n = FT->getNumParams();
    for (Function::arg_iterator ai = NewF->arg_begin(); n != 0; ++ai, --n)
      Args.push_back(&*ai);
    CallInst *CI = CallInst::Create(F, Args, "", BB);
    if (FT->getReturnType()->isVoidTy())
      ReturnInst::Create(*Ctx, BB);
    else
      ReturnInst::Create(*Ctx, CI, BB);
  }

  return NewF;
}

Constant *DataFlowSanitizer::getOrBuildTrampolineFunction(FunctionType *FT,
                                                          StringRef FName) {
  FunctionType *FTT = getTrampolineFunctionType(FT);
  Constant *C = Mod->getOrInsertFunction(FName, FTT);
  Function *F = dyn_cast<Function>(C);
  if (F && F->isDeclaration()) {
    F->setLinkage(GlobalValue::LinkOnceODRLinkage);
    BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", F);
    std::vector<Value *> Args;
    Function::arg_iterator AI = F->arg_begin(); ++AI;
    for (unsigned N = FT->getNumParams(); N != 0; ++AI, --N)
      Args.push_back(&*AI);
    CallInst *CI =
        CallInst::Create(&F->getArgumentList().front(), Args, "", BB);
    ReturnInst *RI;
    if (FT->getReturnType()->isVoidTy())
      RI = ReturnInst::Create(*Ctx, BB);
    else
      RI = ReturnInst::Create(*Ctx, CI, BB);

    DFSanFunction DFSF(*this, F, /*IsNativeABI=*/true);
    Function::arg_iterator ValAI = F->arg_begin(), ShadowAI = AI; ++ValAI;
    for (unsigned N = FT->getNumParams(); N != 0; ++ValAI, ++ShadowAI, --N)
      DFSF.ValShadowMap[ValAI] = ShadowAI;
    DFSanVisitor(DFSF).visitCallInst(*CI);
    if (!FT->getReturnType()->isVoidTy())
      new StoreInst(DFSF.getShadow(RI->getReturnValue()),
                    &F->getArgumentList().back(), RI);
  }

  return C;
}

bool DataFlowSanitizer::runOnModule(Module &M) {
  if (!DL)
    return false;

  if (ABIList.isIn(M, "skip"))
    return false;

  FunctionDIs = makeSubprogramMap(M);

  if (!GetArgTLSPtr) {
    Type *ArgTLSTy = ArrayType::get(ShadowTy, 64);
    ArgTLS = Mod->getOrInsertGlobal("__dfsan_arg_tls", ArgTLSTy);
    if (GlobalVariable *G = dyn_cast<GlobalVariable>(ArgTLS))
      G->setThreadLocalMode(GlobalVariable::InitialExecTLSModel);
  }
  if (!GetRetvalTLSPtr) {
    RetvalTLS = Mod->getOrInsertGlobal("__dfsan_retval_tls", ShadowTy);
    if (GlobalVariable *G = dyn_cast<GlobalVariable>(RetvalTLS))
      G->setThreadLocalMode(GlobalVariable::InitialExecTLSModel);
  }

  DFSanUnionFn = Mod->getOrInsertFunction("__dfsan_union", DFSanUnionFnTy);
  if (Function *F = dyn_cast<Function>(DFSanUnionFn)) {
    F->addAttribute(AttributeSet::FunctionIndex, Attribute::NoUnwind);
    F->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadNone);
    F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
    F->addAttribute(1, Attribute::ZExt);
    F->addAttribute(2, Attribute::ZExt);
  }
  DFSanCheckedUnionFn = Mod->getOrInsertFunction("dfsan_union", DFSanUnionFnTy);
  if (Function *F = dyn_cast<Function>(DFSanCheckedUnionFn)) {
    F->addAttribute(AttributeSet::FunctionIndex, Attribute::NoUnwind);
    F->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadNone);
    F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
    F->addAttribute(1, Attribute::ZExt);
    F->addAttribute(2, Attribute::ZExt);
  }
  DFSanUnionLoadFn =
      Mod->getOrInsertFunction("__dfsan_union_load", DFSanUnionLoadFnTy);
  if (Function *F = dyn_cast<Function>(DFSanUnionLoadFn)) {
    F->addAttribute(AttributeSet::FunctionIndex, Attribute::NoUnwind);
    F->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadOnly);
    F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
  }
  DFSanUnimplementedFn =
      Mod->getOrInsertFunction("__dfsan_unimplemented", DFSanUnimplementedFnTy);
  DFSanSetLabelFn =
      Mod->getOrInsertFunction("__dfsan_set_label", DFSanSetLabelFnTy);
  if (Function *F = dyn_cast<Function>(DFSanSetLabelFn)) {
    F->addAttribute(1, Attribute::ZExt);
  }
  DFSanNonzeroLabelFn =
      Mod->getOrInsertFunction("__dfsan_nonzero_label", DFSanNonzeroLabelFnTy);
  DFSanVarargWrapperFn = Mod->getOrInsertFunction("__dfsan_vararg_wrapper",
                                                  DFSanVarargWrapperFnTy);

  std::vector<Function *> FnsToInstrument;
  llvm::SmallPtrSet<Function *, 2> FnsWithNativeABI;
  for (Module::iterator i = M.begin(), e = M.end(); i != e; ++i) {
    if (!i->isIntrinsic() &&
        i != DFSanUnionFn &&
        i != DFSanCheckedUnionFn &&
        i != DFSanUnionLoadFn &&
        i != DFSanUnimplementedFn &&
        i != DFSanSetLabelFn &&
        i != DFSanNonzeroLabelFn &&
        i != DFSanVarargWrapperFn)
      FnsToInstrument.push_back(&*i);
  }

  // Give function aliases prefixes when necessary, and build wrappers where the
  // instrumentedness is inconsistent.
  for (Module::alias_iterator i = M.alias_begin(), e = M.alias_end(); i != e;) {
    GlobalAlias *GA = &*i;
    ++i;
    // Don't stop on weak.  We assume people aren't playing games with the
    // instrumentedness of overridden weak aliases.
    if (auto F = dyn_cast<Function>(GA->getBaseObject())) {
      bool GAInst = isInstrumented(GA), FInst = isInstrumented(F);
      if (GAInst && FInst) {
        addGlobalNamePrefix(GA);
      } else if (GAInst != FInst) {
        // Non-instrumented alias of an instrumented function, or vice versa.
        // Replace the alias with a native-ABI wrapper of the aliasee.  The pass
        // below will take care of instrumenting it.
        Function *NewF =
            buildWrapperFunction(F, "", GA->getLinkage(), F->getFunctionType());
        GA->replaceAllUsesWith(ConstantExpr::getBitCast(NewF, GA->getType()));
        NewF->takeName(GA);
        GA->eraseFromParent();
        FnsToInstrument.push_back(NewF);
      }
    }
  }

  AttrBuilder B;
  B.addAttribute(Attribute::ReadOnly).addAttribute(Attribute::ReadNone);
  ReadOnlyNoneAttrs = AttributeSet::get(*Ctx, AttributeSet::FunctionIndex, B);

  // First, change the ABI of every function in the module.  ABI-listed
  // functions keep their original ABI and get a wrapper function.
  for (std::vector<Function *>::iterator i = FnsToInstrument.begin(),
                                         e = FnsToInstrument.end();
       i != e; ++i) {
    Function &F = **i;
    FunctionType *FT = F.getFunctionType();

    bool IsZeroArgsVoidRet = (FT->getNumParams() == 0 && !FT->isVarArg() &&
                              FT->getReturnType()->isVoidTy());

    if (isInstrumented(&F)) {
      // Instrumented functions get a 'dfs$' prefix.  This allows us to more
      // easily identify cases of mismatching ABIs.
      if (getInstrumentedABI() == IA_Args && !IsZeroArgsVoidRet) {
        FunctionType *NewFT = getArgsFunctionType(FT);
        Function *NewF = Function::Create(NewFT, F.getLinkage(), "", &M);
        NewF->copyAttributesFrom(&F);
        NewF->removeAttributes(
            AttributeSet::ReturnIndex,
            AttributeFuncs::typeIncompatible(NewFT->getReturnType(),
                                             AttributeSet::ReturnIndex));
        for (Function::arg_iterator FArg = F.arg_begin(),
                                    NewFArg = NewF->arg_begin(),
                                    FArgEnd = F.arg_end();
             FArg != FArgEnd; ++FArg, ++NewFArg) {
          FArg->replaceAllUsesWith(NewFArg);
        }
        NewF->getBasicBlockList().splice(NewF->begin(), F.getBasicBlockList());

        for (Function::user_iterator UI = F.user_begin(), UE = F.user_end();
             UI != UE;) {
          BlockAddress *BA = dyn_cast<BlockAddress>(*UI);
          ++UI;
          if (BA) {
            BA->replaceAllUsesWith(
                BlockAddress::get(NewF, BA->getBasicBlock()));
            delete BA;
          }
        }
        F.replaceAllUsesWith(
            ConstantExpr::getBitCast(NewF, PointerType::getUnqual(FT)));
        NewF->takeName(&F);
        F.eraseFromParent();
        *i = NewF;
        addGlobalNamePrefix(NewF);
      } else {
        addGlobalNamePrefix(&F);
      }
    } else if (!IsZeroArgsVoidRet || getWrapperKind(&F) == WK_Custom) {
      // Build a wrapper function for F.  The wrapper simply calls F, and is
      // added to FnsToInstrument so that any instrumentation according to its
      // WrapperKind is done in the second pass below.
      FunctionType *NewFT = getInstrumentedABI() == IA_Args
                                ? getArgsFunctionType(FT)
                                : FT;
      Function *NewF = buildWrapperFunction(
          &F, std::string("dfsw$") + std::string(F.getName()),
          GlobalValue::LinkOnceODRLinkage, NewFT);
      if (getInstrumentedABI() == IA_TLS)
        NewF->removeAttributes(AttributeSet::FunctionIndex, ReadOnlyNoneAttrs);

      Value *WrappedFnCst =
          ConstantExpr::getBitCast(NewF, PointerType::getUnqual(FT));
      F.replaceAllUsesWith(WrappedFnCst);

      // Patch the pointer to LLVM function in debug info descriptor.
      auto DI = FunctionDIs.find(&F);
      if (DI != FunctionDIs.end())
        DI->second.replaceFunction(&F);

      UnwrappedFnMap[WrappedFnCst] = &F;
      *i = NewF;

      if (!F.isDeclaration()) {
        // This function is probably defining an interposition of an
        // uninstrumented function and hence needs to keep the original ABI.
        // But any functions it may call need to use the instrumented ABI, so
        // we instrument it in a mode which preserves the original ABI.
        FnsWithNativeABI.insert(&F);

        // This code needs to rebuild the iterators, as they may be invalidated
        // by the push_back, taking care that the new range does not include
        // any functions added by this code.
        size_t N = i - FnsToInstrument.begin(),
               Count = e - FnsToInstrument.begin();
        FnsToInstrument.push_back(&F);
        i = FnsToInstrument.begin() + N;
        e = FnsToInstrument.begin() + Count;
      }
               // Hopefully, nobody will try to indirectly call a vararg
               // function... yet.
    } else if (FT->isVarArg()) {
      UnwrappedFnMap[&F] = &F;
      *i = nullptr;
    }
  }

  for (std::vector<Function *>::iterator i = FnsToInstrument.begin(),
                                         e = FnsToInstrument.end();
       i != e; ++i) {
    if (!*i || (*i)->isDeclaration())
      continue;

    removeUnreachableBlocks(**i);

    DFSanFunction DFSF(*this, *i, FnsWithNativeABI.count(*i));

    // DFSanVisitor may create new basic blocks, which confuses df_iterator.
    // Build a copy of the list before iterating over it.
    llvm::SmallVector<BasicBlock *, 4> BBList(
        depth_first(&(*i)->getEntryBlock()));

    for (llvm::SmallVector<BasicBlock *, 4>::iterator i = BBList.begin(),
                                                      e = BBList.end();
         i != e; ++i) {
      Instruction *Inst = &(*i)->front();
      while (1) {
        // DFSanVisitor may split the current basic block, changing the current
        // instruction's next pointer and moving the next instruction to the
        // tail block from which we should continue.
        Instruction *Next = Inst->getNextNode();
        // DFSanVisitor may delete Inst, so keep track of whether it was a
        // terminator.
        bool IsTerminator = isa<TerminatorInst>(Inst);
        if (!DFSF.SkipInsts.count(Inst))
          DFSanVisitor(DFSF).visit(Inst);
        if (IsTerminator)
          break;
        Inst = Next;
      }
    }

    // We will not necessarily be able to compute the shadow for every phi node
    // until we have visited every block.  Therefore, the code that handles phi
    // nodes adds them to the PHIFixups list so that they can be properly
    // handled here.
    for (std::vector<std::pair<PHINode *, PHINode *> >::iterator
             i = DFSF.PHIFixups.begin(),
             e = DFSF.PHIFixups.end();
         i != e; ++i) {
      for (unsigned val = 0, n = i->first->getNumIncomingValues(); val != n;
           ++val) {
        i->second->setIncomingValue(
            val, DFSF.getShadow(i->first->getIncomingValue(val)));
      }
    }

    // -dfsan-debug-nonzero-labels will split the CFG in all kinds of crazy
    // places (i.e. instructions in basic blocks we haven't even begun visiting
    // yet).  To make our life easier, do this work in a pass after the main
    // instrumentation.
    if (ClDebugNonzeroLabels) {
      for (Value *V : DFSF.NonZeroChecks) {
        Instruction *Pos;
        if (Instruction *I = dyn_cast<Instruction>(V))
          Pos = I->getNextNode();
        else
          Pos = DFSF.F->getEntryBlock().begin();
        while (isa<PHINode>(Pos) || isa<AllocaInst>(Pos))
          Pos = Pos->getNextNode();
        IRBuilder<> IRB(Pos);
        Value *Ne = IRB.CreateICmpNE(V, DFSF.DFS.ZeroShadow);
        BranchInst *BI = cast<BranchInst>(SplitBlockAndInsertIfThen(
            Ne, Pos, /*Unreachable=*/false, ColdCallWeights));
        IRBuilder<> ThenIRB(BI);
        ThenIRB.CreateCall(DFSF.DFS.DFSanNonzeroLabelFn);
      }
    }
  }

  return false;
}

Value *DFSanFunction::getArgTLSPtr() {
  if (ArgTLSPtr)
    return ArgTLSPtr;
  if (DFS.ArgTLS)
    return ArgTLSPtr = DFS.ArgTLS;

  IRBuilder<> IRB(F->getEntryBlock().begin());
  return ArgTLSPtr = IRB.CreateCall(DFS.GetArgTLS);
}

Value *DFSanFunction::getRetvalTLS() {
  if (RetvalTLSPtr)
    return RetvalTLSPtr;
  if (DFS.RetvalTLS)
    return RetvalTLSPtr = DFS.RetvalTLS;

  IRBuilder<> IRB(F->getEntryBlock().begin());
  return RetvalTLSPtr = IRB.CreateCall(DFS.GetRetvalTLS);
}

Value *DFSanFunction::getArgTLS(unsigned Idx, Instruction *Pos) {
  IRBuilder<> IRB(Pos);
  return IRB.CreateConstGEP2_64(getArgTLSPtr(), 0, Idx);
}

Value *DFSanFunction::getShadow(Value *V) {
  if (!isa<Argument>(V) && !isa<Instruction>(V))
    return DFS.ZeroShadow;
  Value *&Shadow = ValShadowMap[V];
  if (!Shadow) {
    if (Argument *A = dyn_cast<Argument>(V)) {
      if (IsNativeABI)
        return DFS.ZeroShadow;
      switch (IA) {
      case DataFlowSanitizer::IA_TLS: {
        Value *ArgTLSPtr = getArgTLSPtr();
        Instruction *ArgTLSPos =
            DFS.ArgTLS ? &*F->getEntryBlock().begin()
                       : cast<Instruction>(ArgTLSPtr)->getNextNode();
        IRBuilder<> IRB(ArgTLSPos);
        Shadow = IRB.CreateLoad(getArgTLS(A->getArgNo(), ArgTLSPos));
        break;
      }
      case DataFlowSanitizer::IA_Args: {
        unsigned ArgIdx = A->getArgNo() + F->getArgumentList().size() / 2;
        Function::arg_iterator i = F->arg_begin();
        while (ArgIdx--)
          ++i;
        Shadow = i;
        assert(Shadow->getType() == DFS.ShadowTy);
        break;
      }
      }
      NonZeroChecks.push_back(Shadow);
    } else {
      Shadow = DFS.ZeroShadow;
    }
  }
  return Shadow;
}

void DFSanFunction::setShadow(Instruction *I, Value *Shadow) {
  assert(!ValShadowMap.count(I));
  assert(Shadow->getType() == DFS.ShadowTy);
  ValShadowMap[I] = Shadow;
}

Value *DataFlowSanitizer::getShadowAddress(Value *Addr, Instruction *Pos) {
  assert(Addr != RetvalTLS && "Reinstrumenting?");
  IRBuilder<> IRB(Pos);
  return IRB.CreateIntToPtr(
      IRB.CreateMul(
          IRB.CreateAnd(IRB.CreatePtrToInt(Addr, IntptrTy), ShadowPtrMask),
          ShadowPtrMul),
      ShadowPtrTy);
}

// Generates IR to compute the union of the two given shadows, inserting it
// before Pos.  Returns the computed union Value.
Value *DFSanFunction::combineShadows(Value *V1, Value *V2, Instruction *Pos) {
  if (V1 == DFS.ZeroShadow)
    return V2;
  if (V2 == DFS.ZeroShadow)
    return V1;
  if (V1 == V2)
    return V1;

  auto V1Elems = ShadowElements.find(V1);
  auto V2Elems = ShadowElements.find(V2);
  if (V1Elems != ShadowElements.end() && V2Elems != ShadowElements.end()) {
    if (std::includes(V1Elems->second.begin(), V1Elems->second.end(),
                      V2Elems->second.begin(), V2Elems->second.end())) {
      return V1;
    } else if (std::includes(V2Elems->second.begin(), V2Elems->second.end(),
                             V1Elems->second.begin(), V1Elems->second.end())) {
      return V2;
    }
  } else if (V1Elems != ShadowElements.end()) {
    if (V1Elems->second.count(V2))
      return V1;
  } else if (V2Elems != ShadowElements.end()) {
    if (V2Elems->second.count(V1))
      return V2;
  }

  auto Key = std::make_pair(V1, V2);
  if (V1 > V2)
    std::swap(Key.first, Key.second);
  CachedCombinedShadow &CCS = CachedCombinedShadows[Key];
  if (CCS.Block && DT.dominates(CCS.Block, Pos->getParent()))
    return CCS.Shadow;

  IRBuilder<> IRB(Pos);
  if (AvoidNewBlocks) {
    CallInst *Call = IRB.CreateCall2(DFS.DFSanCheckedUnionFn, V1, V2);
    Call->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
    Call->addAttribute(1, Attribute::ZExt);
    Call->addAttribute(2, Attribute::ZExt);

    CCS.Block = Pos->getParent();
    CCS.Shadow = Call;
  } else {
    BasicBlock *Head = Pos->getParent();
    Value *Ne = IRB.CreateICmpNE(V1, V2);
    BranchInst *BI = cast<BranchInst>(SplitBlockAndInsertIfThen(
        Ne, Pos, /*Unreachable=*/false, DFS.ColdCallWeights, &DT));
    IRBuilder<> ThenIRB(BI);
    CallInst *Call = ThenIRB.CreateCall2(DFS.DFSanUnionFn, V1, V2);
    Call->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
    Call->addAttribute(1, Attribute::ZExt);
    Call->addAttribute(2, Attribute::ZExt);

    BasicBlock *Tail = BI->getSuccessor(0);
    PHINode *Phi = PHINode::Create(DFS.ShadowTy, 2, "", Tail->begin());
    Phi->addIncoming(Call, Call->getParent());
    Phi->addIncoming(V1, Head);

    CCS.Block = Tail;
    CCS.Shadow = Phi;
  }

  std::set<Value *> UnionElems;
  if (V1Elems != ShadowElements.end()) {
    UnionElems = V1Elems->second;
  } else {
    UnionElems.insert(V1);
  }
  if (V2Elems != ShadowElements.end()) {
    UnionElems.insert(V2Elems->second.begin(), V2Elems->second.end());
  } else {
    UnionElems.insert(V2);
  }
  ShadowElements[CCS.Shadow] = std::move(UnionElems);

  return CCS.Shadow;
}

// A convenience function which folds the shadows of each of the operands
// of the provided instruction Inst, inserting the IR before Inst.  Returns
// the computed union Value.
Value *DFSanFunction::combineOperandShadows(Instruction *Inst) {
  if (Inst->getNumOperands() == 0)
    return DFS.ZeroShadow;

  Value *Shadow = getShadow(Inst->getOperand(0));
  for (unsigned i = 1, n = Inst->getNumOperands(); i != n; ++i) {
    Shadow = combineShadows(Shadow, getShadow(Inst->getOperand(i)), Inst);
  }
  return Shadow;
}

void DFSanVisitor::visitOperandShadowInst(Instruction &I) {
  Value *CombinedShadow = DFSF.combineOperandShadows(&I);
  DFSF.setShadow(&I, CombinedShadow);
}

// Generates IR to load shadow corresponding to bytes [Addr, Addr+Size), where
// Addr has alignment Align, and take the union of each of those shadows.
Value *DFSanFunction::loadShadow(Value *Addr, uint64_t Size, uint64_t Align,
                                 Instruction *Pos) {
  if (AllocaInst *AI = dyn_cast<AllocaInst>(Addr)) {
    llvm::DenseMap<AllocaInst *, AllocaInst *>::iterator i =
        AllocaShadowMap.find(AI);
    if (i != AllocaShadowMap.end()) {
      IRBuilder<> IRB(Pos);
      return IRB.CreateLoad(i->second);
    }
  }

  uint64_t ShadowAlign = Align * DFS.ShadowWidth / 8;
  SmallVector<Value *, 2> Objs;
  GetUnderlyingObjects(Addr, Objs, DFS.DL);
  bool AllConstants = true;
  for (SmallVector<Value *, 2>::iterator i = Objs.begin(), e = Objs.end();
       i != e; ++i) {
    if (isa<Function>(*i) || isa<BlockAddress>(*i))
      continue;
    if (isa<GlobalVariable>(*i) && cast<GlobalVariable>(*i)->isConstant())
      continue;

    AllConstants = false;
    break;
  }
  if (AllConstants)
    return DFS.ZeroShadow;

  Value *ShadowAddr = DFS.getShadowAddress(Addr, Pos);
  switch (Size) {
  case 0:
    return DFS.ZeroShadow;
  case 1: {
    LoadInst *LI = new LoadInst(ShadowAddr, "", Pos);
    LI->setAlignment(ShadowAlign);
    return LI;
  }
  case 2: {
    IRBuilder<> IRB(Pos);
    Value *ShadowAddr1 =
        IRB.CreateGEP(ShadowAddr, ConstantInt::get(DFS.IntptrTy, 1));
    return combineShadows(IRB.CreateAlignedLoad(ShadowAddr, ShadowAlign),
                          IRB.CreateAlignedLoad(ShadowAddr1, ShadowAlign), Pos);
  }
  }
  if (!AvoidNewBlocks && Size % (64 / DFS.ShadowWidth) == 0) {
    // Fast path for the common case where each byte has identical shadow: load
    // shadow 64 bits at a time, fall out to a __dfsan_union_load call if any
    // shadow is non-equal.
    BasicBlock *FallbackBB = BasicBlock::Create(*DFS.Ctx, "", F);
    IRBuilder<> FallbackIRB(FallbackBB);
    CallInst *FallbackCall = FallbackIRB.CreateCall2(
        DFS.DFSanUnionLoadFn, ShadowAddr, ConstantInt::get(DFS.IntptrTy, Size));
    FallbackCall->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);

    // Compare each of the shadows stored in the loaded 64 bits to each other,
    // by computing (WideShadow rotl ShadowWidth) == WideShadow.
    IRBuilder<> IRB(Pos);
    Value *WideAddr =
        IRB.CreateBitCast(ShadowAddr, Type::getInt64PtrTy(*DFS.Ctx));
    Value *WideShadow = IRB.CreateAlignedLoad(WideAddr, ShadowAlign);
    Value *TruncShadow = IRB.CreateTrunc(WideShadow, DFS.ShadowTy);
    Value *ShlShadow = IRB.CreateShl(WideShadow, DFS.ShadowWidth);
    Value *ShrShadow = IRB.CreateLShr(WideShadow, 64 - DFS.ShadowWidth);
    Value *RotShadow = IRB.CreateOr(ShlShadow, ShrShadow);
    Value *ShadowsEq = IRB.CreateICmpEQ(WideShadow, RotShadow);

    BasicBlock *Head = Pos->getParent();
    BasicBlock *Tail = Head->splitBasicBlock(Pos);

    if (DomTreeNode *OldNode = DT.getNode(Head)) {
      std::vector<DomTreeNode *> Children(OldNode->begin(), OldNode->end());

      DomTreeNode *NewNode = DT.addNewBlock(Tail, Head);
      for (auto Child : Children)
        DT.changeImmediateDominator(Child, NewNode);
    }

    // In the following code LastBr will refer to the previous basic block's
    // conditional branch instruction, whose true successor is fixed up to point
    // to the next block during the loop below or to the tail after the final
    // iteration.
    BranchInst *LastBr = BranchInst::Create(FallbackBB, FallbackBB, ShadowsEq);
    ReplaceInstWithInst(Head->getTerminator(), LastBr);
    DT.addNewBlock(FallbackBB, Head);

    for (uint64_t Ofs = 64 / DFS.ShadowWidth; Ofs != Size;
         Ofs += 64 / DFS.ShadowWidth) {
      BasicBlock *NextBB = BasicBlock::Create(*DFS.Ctx, "", F);
      DT.addNewBlock(NextBB, LastBr->getParent());
      IRBuilder<> NextIRB(NextBB);
      WideAddr = NextIRB.CreateGEP(WideAddr, ConstantInt::get(DFS.IntptrTy, 1));
      Value *NextWideShadow = NextIRB.CreateAlignedLoad(WideAddr, ShadowAlign);
      ShadowsEq = NextIRB.CreateICmpEQ(WideShadow, NextWideShadow);
      LastBr->setSuccessor(0, NextBB);
      LastBr = NextIRB.CreateCondBr(ShadowsEq, FallbackBB, FallbackBB);
    }

    LastBr->setSuccessor(0, Tail);
    FallbackIRB.CreateBr(Tail);
    PHINode *Shadow = PHINode::Create(DFS.ShadowTy, 2, "", &Tail->front());
    Shadow->addIncoming(FallbackCall, FallbackBB);
    Shadow->addIncoming(TruncShadow, LastBr->getParent());
    return Shadow;
  }

  IRBuilder<> IRB(Pos);
  CallInst *FallbackCall = IRB.CreateCall2(
      DFS.DFSanUnionLoadFn, ShadowAddr, ConstantInt::get(DFS.IntptrTy, Size));
  FallbackCall->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
  return FallbackCall;
}

void DFSanVisitor::visitLoadInst(LoadInst &LI) {
  uint64_t Size = DFSF.DFS.DL->getTypeStoreSize(LI.getType());
  if (Size == 0) {
    DFSF.setShadow(&LI, DFSF.DFS.ZeroShadow);
    return;
  }

  uint64_t Align;
  if (ClPreserveAlignment) {
    Align = LI.getAlignment();
    if (Align == 0)
      Align = DFSF.DFS.DL->getABITypeAlignment(LI.getType());
  } else {
    Align = 1;
  }
  IRBuilder<> IRB(&LI);
  Value *Shadow = DFSF.loadShadow(LI.getPointerOperand(), Size, Align, &LI);
  if (ClCombinePointerLabelsOnLoad) {
    Value *PtrShadow = DFSF.getShadow(LI.getPointerOperand());
    Shadow = DFSF.combineShadows(Shadow, PtrShadow, &LI);
  }
  if (Shadow != DFSF.DFS.ZeroShadow)
    DFSF.NonZeroChecks.push_back(Shadow);

  DFSF.setShadow(&LI, Shadow);
}

void DFSanFunction::storeShadow(Value *Addr, uint64_t Size, uint64_t Align,
                                Value *Shadow, Instruction *Pos) {
  if (AllocaInst *AI = dyn_cast<AllocaInst>(Addr)) {
    llvm::DenseMap<AllocaInst *, AllocaInst *>::iterator i =
        AllocaShadowMap.find(AI);
    if (i != AllocaShadowMap.end()) {
      IRBuilder<> IRB(Pos);
      IRB.CreateStore(Shadow, i->second);
      return;
    }
  }

  uint64_t ShadowAlign = Align * DFS.ShadowWidth / 8;
  IRBuilder<> IRB(Pos);
  Value *ShadowAddr = DFS.getShadowAddress(Addr, Pos);
  if (Shadow == DFS.ZeroShadow) {
    IntegerType *ShadowTy = IntegerType::get(*DFS.Ctx, Size * DFS.ShadowWidth);
    Value *ExtZeroShadow = ConstantInt::get(ShadowTy, 0);
    Value *ExtShadowAddr =
        IRB.CreateBitCast(ShadowAddr, PointerType::getUnqual(ShadowTy));
    IRB.CreateAlignedStore(ExtZeroShadow, ExtShadowAddr, ShadowAlign);
    return;
  }

  const unsigned ShadowVecSize = 128 / DFS.ShadowWidth;
  uint64_t Offset = 0;
  if (Size >= ShadowVecSize) {
    VectorType *ShadowVecTy = VectorType::get(DFS.ShadowTy, ShadowVecSize);
    Value *ShadowVec = UndefValue::get(ShadowVecTy);
    for (unsigned i = 0; i != ShadowVecSize; ++i) {
      ShadowVec = IRB.CreateInsertElement(
          ShadowVec, Shadow, ConstantInt::get(Type::getInt32Ty(*DFS.Ctx), i));
    }
    Value *ShadowVecAddr =
        IRB.CreateBitCast(ShadowAddr, PointerType::getUnqual(ShadowVecTy));
    do {
      Value *CurShadowVecAddr = IRB.CreateConstGEP1_32(ShadowVecAddr, Offset);
      IRB.CreateAlignedStore(ShadowVec, CurShadowVecAddr, ShadowAlign);
      Size -= ShadowVecSize;
      ++Offset;
    } while (Size >= ShadowVecSize);
    Offset *= ShadowVecSize;
  }
  while (Size > 0) {
    Value *CurShadowAddr = IRB.CreateConstGEP1_32(ShadowAddr, Offset);
    IRB.CreateAlignedStore(Shadow, CurShadowAddr, ShadowAlign);
    --Size;
    ++Offset;
  }
}

void DFSanVisitor::visitStoreInst(StoreInst &SI) {
  uint64_t Size =
      DFSF.DFS.DL->getTypeStoreSize(SI.getValueOperand()->getType());
  if (Size == 0)
    return;

  uint64_t Align;
  if (ClPreserveAlignment) {
    Align = SI.getAlignment();
    if (Align == 0)
      Align = DFSF.DFS.DL->getABITypeAlignment(SI.getValueOperand()->getType());
  } else {
    Align = 1;
  }

  Value* Shadow = DFSF.getShadow(SI.getValueOperand());
  if (ClCombinePointerLabelsOnStore) {
    Value *PtrShadow = DFSF.getShadow(SI.getPointerOperand());
    Shadow = DFSF.combineShadows(Shadow, PtrShadow, &SI);
  }
  DFSF.storeShadow(SI.getPointerOperand(), Size, Align, Shadow, &SI);
}

void DFSanVisitor::visitBinaryOperator(BinaryOperator &BO) {
  visitOperandShadowInst(BO);
}

void DFSanVisitor::visitCastInst(CastInst &CI) { visitOperandShadowInst(CI); }

void DFSanVisitor::visitCmpInst(CmpInst &CI) { visitOperandShadowInst(CI); }

void DFSanVisitor::visitGetElementPtrInst(GetElementPtrInst &GEPI) {
  visitOperandShadowInst(GEPI);
}

void DFSanVisitor::visitExtractElementInst(ExtractElementInst &I) {
  visitOperandShadowInst(I);
}

void DFSanVisitor::visitInsertElementInst(InsertElementInst &I) {
  visitOperandShadowInst(I);
}

void DFSanVisitor::visitShuffleVectorInst(ShuffleVectorInst &I) {
  visitOperandShadowInst(I);
}

void DFSanVisitor::visitExtractValueInst(ExtractValueInst &I) {
  visitOperandShadowInst(I);
}

void DFSanVisitor::visitInsertValueInst(InsertValueInst &I) {
  visitOperandShadowInst(I);
}

void DFSanVisitor::visitAllocaInst(AllocaInst &I) {
  bool AllLoadsStores = true;
  for (User *U : I.users()) {
    if (isa<LoadInst>(U))
      continue;

    if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
      if (SI->getPointerOperand() == &I)
        continue;
    }

    AllLoadsStores = false;
    break;
  }
  if (AllLoadsStores) {
    IRBuilder<> IRB(&I);
    DFSF.AllocaShadowMap[&I] = IRB.CreateAlloca(DFSF.DFS.ShadowTy);
  }
  DFSF.setShadow(&I, DFSF.DFS.ZeroShadow);
}

void DFSanVisitor::visitSelectInst(SelectInst &I) {
  Value *CondShadow = DFSF.getShadow(I.getCondition());
  Value *TrueShadow = DFSF.getShadow(I.getTrueValue());
  Value *FalseShadow = DFSF.getShadow(I.getFalseValue());

  if (isa<VectorType>(I.getCondition()->getType())) {
    DFSF.setShadow(
        &I,
        DFSF.combineShadows(
            CondShadow, DFSF.combineShadows(TrueShadow, FalseShadow, &I), &I));
  } else {
    Value *ShadowSel;
    if (TrueShadow == FalseShadow) {
      ShadowSel = TrueShadow;
    } else {
      ShadowSel =
          SelectInst::Create(I.getCondition(), TrueShadow, FalseShadow, "", &I);
    }
    DFSF.setShadow(&I, DFSF.combineShadows(CondShadow, ShadowSel, &I));
  }
}

void DFSanVisitor::visitMemSetInst(MemSetInst &I) {
  IRBuilder<> IRB(&I);
  Value *ValShadow = DFSF.getShadow(I.getValue());
  IRB.CreateCall3(
      DFSF.DFS.DFSanSetLabelFn, ValShadow,
      IRB.CreateBitCast(I.getDest(), Type::getInt8PtrTy(*DFSF.DFS.Ctx)),
      IRB.CreateZExtOrTrunc(I.getLength(), DFSF.DFS.IntptrTy));
}

void DFSanVisitor::visitMemTransferInst(MemTransferInst &I) {
  IRBuilder<> IRB(&I);
  Value *DestShadow = DFSF.DFS.getShadowAddress(I.getDest(), &I);
  Value *SrcShadow = DFSF.DFS.getShadowAddress(I.getSource(), &I);
  Value *LenShadow = IRB.CreateMul(
      I.getLength(),
      ConstantInt::get(I.getLength()->getType(), DFSF.DFS.ShadowWidth / 8));
  Value *AlignShadow;
  if (ClPreserveAlignment) {
    AlignShadow = IRB.CreateMul(I.getAlignmentCst(),
                                ConstantInt::get(I.getAlignmentCst()->getType(),
                                                 DFSF.DFS.ShadowWidth / 8));
  } else {
    AlignShadow = ConstantInt::get(I.getAlignmentCst()->getType(),
                                   DFSF.DFS.ShadowWidth / 8);
  }
  Type *Int8Ptr = Type::getInt8PtrTy(*DFSF.DFS.Ctx);
  DestShadow = IRB.CreateBitCast(DestShadow, Int8Ptr);
  SrcShadow = IRB.CreateBitCast(SrcShadow, Int8Ptr);
  IRB.CreateCall5(I.getCalledValue(), DestShadow, SrcShadow, LenShadow,
                  AlignShadow, I.getVolatileCst());
}

void DFSanVisitor::visitReturnInst(ReturnInst &RI) {
  if (!DFSF.IsNativeABI && RI.getReturnValue()) {
    switch (DFSF.IA) {
    case DataFlowSanitizer::IA_TLS: {
      Value *S = DFSF.getShadow(RI.getReturnValue());
      IRBuilder<> IRB(&RI);
      IRB.CreateStore(S, DFSF.getRetvalTLS());
      break;
    }
    case DataFlowSanitizer::IA_Args: {
      IRBuilder<> IRB(&RI);
      Type *RT = DFSF.F->getFunctionType()->getReturnType();
      Value *InsVal =
          IRB.CreateInsertValue(UndefValue::get(RT), RI.getReturnValue(), 0);
      Value *InsShadow =
          IRB.CreateInsertValue(InsVal, DFSF.getShadow(RI.getReturnValue()), 1);
      RI.setOperand(0, InsShadow);
      break;
    }
    }
  }
}

void DFSanVisitor::visitCallSite(CallSite CS) {
  Function *F = CS.getCalledFunction();
  if ((F && F->isIntrinsic()) || isa<InlineAsm>(CS.getCalledValue())) {
    visitOperandShadowInst(*CS.getInstruction());
    return;
  }

  // Calls to this function are synthesized in wrappers, and we shouldn't
  // instrument them.
  if (F == DFSF.DFS.DFSanVarargWrapperFn)
    return;

  assert(!(cast<FunctionType>(
      CS.getCalledValue()->getType()->getPointerElementType())->isVarArg() &&
           dyn_cast<InvokeInst>(CS.getInstruction())));

  IRBuilder<> IRB(CS.getInstruction());

  DenseMap<Value *, Function *>::iterator i =
      DFSF.DFS.UnwrappedFnMap.find(CS.getCalledValue());
  if (i != DFSF.DFS.UnwrappedFnMap.end()) {
    Function *F = i->second;
    switch (DFSF.DFS.getWrapperKind(F)) {
    case DataFlowSanitizer::WK_Warning: {
      CS.setCalledFunction(F);
      IRB.CreateCall(DFSF.DFS.DFSanUnimplementedFn,
                     IRB.CreateGlobalStringPtr(F->getName()));
      DFSF.setShadow(CS.getInstruction(), DFSF.DFS.ZeroShadow);
      return;
    }
    case DataFlowSanitizer::WK_Discard: {
      CS.setCalledFunction(F);
      DFSF.setShadow(CS.getInstruction(), DFSF.DFS.ZeroShadow);
      return;
    }
    case DataFlowSanitizer::WK_Functional: {
      CS.setCalledFunction(F);
      visitOperandShadowInst(*CS.getInstruction());
      return;
    }
    case DataFlowSanitizer::WK_Custom: {
      // Don't try to handle invokes of custom functions, it's too complicated.
      // Instead, invoke the dfsw$ wrapper, which will in turn call the __dfsw_
      // wrapper.
      if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction())) {
        FunctionType *FT = F->getFunctionType();
        FunctionType *CustomFT = DFSF.DFS.getCustomFunctionType(FT);
        std::string CustomFName = "__dfsw_";
        CustomFName += F->getName();
        Constant *CustomF =
            DFSF.DFS.Mod->getOrInsertFunction(CustomFName, CustomFT);
        if (Function *CustomFn = dyn_cast<Function>(CustomF)) {
          CustomFn->copyAttributesFrom(F);

          // Custom functions returning non-void will write to the return label.
          if (!FT->getReturnType()->isVoidTy()) {
            CustomFn->removeAttributes(AttributeSet::FunctionIndex,
                                       DFSF.DFS.ReadOnlyNoneAttrs);
          }
        }

        std::vector<Value *> Args;

        CallSite::arg_iterator i = CS.arg_begin();
        for (unsigned n = FT->getNumParams(); n != 0; ++i, --n) {
          Type *T = (*i)->getType();
          FunctionType *ParamFT;
          if (isa<PointerType>(T) &&
              (ParamFT = dyn_cast<FunctionType>(
                   cast<PointerType>(T)->getElementType()))) {
            std::string TName = "dfst";
            TName += utostr(FT->getNumParams() - n);
            TName += "$";
            TName += F->getName();
            Constant *T = DFSF.DFS.getOrBuildTrampolineFunction(ParamFT, TName);
            Args.push_back(T);
            Args.push_back(
                IRB.CreateBitCast(*i, Type::getInt8PtrTy(*DFSF.DFS.Ctx)));
          } else {
            Args.push_back(*i);
          }
        }

        i = CS.arg_begin();
        for (unsigned n = FT->getNumParams(); n != 0; ++i, --n)
          Args.push_back(DFSF.getShadow(*i));

        if (FT->isVarArg()) {
          auto LabelVAAlloca =
              new AllocaInst(ArrayType::get(DFSF.DFS.ShadowTy,
                                            CS.arg_size() - FT->getNumParams()),
                             "labelva", DFSF.F->getEntryBlock().begin());

          for (unsigned n = 0; i != CS.arg_end(); ++i, ++n) {
            auto LabelVAPtr = IRB.CreateStructGEP(LabelVAAlloca, n);
            IRB.CreateStore(DFSF.getShadow(*i), LabelVAPtr);
          }

          Args.push_back(IRB.CreateStructGEP(LabelVAAlloca, 0));
        }

        if (!FT->getReturnType()->isVoidTy()) {
          if (!DFSF.LabelReturnAlloca) {
            DFSF.LabelReturnAlloca =
                new AllocaInst(DFSF.DFS.ShadowTy, "labelreturn",
                               DFSF.F->getEntryBlock().begin());
          }
          Args.push_back(DFSF.LabelReturnAlloca);
        }

        for (i = CS.arg_begin() + FT->getNumParams(); i != CS.arg_end(); ++i)
          Args.push_back(*i);

        CallInst *CustomCI = IRB.CreateCall(CustomF, Args);
        CustomCI->setCallingConv(CI->getCallingConv());
        CustomCI->setAttributes(CI->getAttributes());

        if (!FT->getReturnType()->isVoidTy()) {
          LoadInst *LabelLoad = IRB.CreateLoad(DFSF.LabelReturnAlloca);
          DFSF.setShadow(CustomCI, LabelLoad);
        }

        CI->replaceAllUsesWith(CustomCI);
        CI->eraseFromParent();
        return;
      }
      break;
    }
    }
  }

  FunctionType *FT = cast<FunctionType>(
      CS.getCalledValue()->getType()->getPointerElementType());
  if (DFSF.DFS.getInstrumentedABI() == DataFlowSanitizer::IA_TLS) {
    for (unsigned i = 0, n = FT->getNumParams(); i != n; ++i) {
      IRB.CreateStore(DFSF.getShadow(CS.getArgument(i)),
                      DFSF.getArgTLS(i, CS.getInstruction()));
    }
  }

  Instruction *Next = nullptr;
  if (!CS.getType()->isVoidTy()) {
    if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
      if (II->getNormalDest()->getSinglePredecessor()) {
        Next = II->getNormalDest()->begin();
      } else {
        BasicBlock *NewBB =
            SplitEdge(II->getParent(), II->getNormalDest(), &DFSF.DFS);
        Next = NewBB->begin();
      }
    } else {
      Next = CS->getNextNode();
    }

    if (DFSF.DFS.getInstrumentedABI() == DataFlowSanitizer::IA_TLS) {
      IRBuilder<> NextIRB(Next);
      LoadInst *LI = NextIRB.CreateLoad(DFSF.getRetvalTLS());
      DFSF.SkipInsts.insert(LI);
      DFSF.setShadow(CS.getInstruction(), LI);
      DFSF.NonZeroChecks.push_back(LI);
    }
  }

  // Do all instrumentation for IA_Args down here to defer tampering with the
  // CFG in a way that SplitEdge may be able to detect.
  if (DFSF.DFS.getInstrumentedABI() == DataFlowSanitizer::IA_Args) {
    FunctionType *NewFT = DFSF.DFS.getArgsFunctionType(FT);
    Value *Func =
        IRB.CreateBitCast(CS.getCalledValue(), PointerType::getUnqual(NewFT));
    std::vector<Value *> Args;

    CallSite::arg_iterator i = CS.arg_begin(), e = CS.arg_end();
    for (unsigned n = FT->getNumParams(); n != 0; ++i, --n)
      Args.push_back(*i);

    i = CS.arg_begin();
    for (unsigned n = FT->getNumParams(); n != 0; ++i, --n)
      Args.push_back(DFSF.getShadow(*i));

    if (FT->isVarArg()) {
      unsigned VarArgSize = CS.arg_size() - FT->getNumParams();
      ArrayType *VarArgArrayTy = ArrayType::get(DFSF.DFS.ShadowTy, VarArgSize);
      AllocaInst *VarArgShadow =
          new AllocaInst(VarArgArrayTy, "", DFSF.F->getEntryBlock().begin());
      Args.push_back(IRB.CreateConstGEP2_32(VarArgShadow, 0, 0));
      for (unsigned n = 0; i != e; ++i, ++n) {
        IRB.CreateStore(DFSF.getShadow(*i),
                        IRB.CreateConstGEP2_32(VarArgShadow, 0, n));
        Args.push_back(*i);
      }
    }

    CallSite NewCS;
    if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
      NewCS = IRB.CreateInvoke(Func, II->getNormalDest(), II->getUnwindDest(),
                               Args);
    } else {
      NewCS = IRB.CreateCall(Func, Args);
    }
    NewCS.setCallingConv(CS.getCallingConv());
    NewCS.setAttributes(CS.getAttributes().removeAttributes(
        *DFSF.DFS.Ctx, AttributeSet::ReturnIndex,
        AttributeFuncs::typeIncompatible(NewCS.getInstruction()->getType(),
                                         AttributeSet::ReturnIndex)));

    if (Next) {
      ExtractValueInst *ExVal =
          ExtractValueInst::Create(NewCS.getInstruction(), 0, "", Next);
      DFSF.SkipInsts.insert(ExVal);
      ExtractValueInst *ExShadow =
          ExtractValueInst::Create(NewCS.getInstruction(), 1, "", Next);
      DFSF.SkipInsts.insert(ExShadow);
      DFSF.setShadow(ExVal, ExShadow);
      DFSF.NonZeroChecks.push_back(ExShadow);

      CS.getInstruction()->replaceAllUsesWith(ExVal);
    }

    CS.getInstruction()->eraseFromParent();
  }
}

void DFSanVisitor::visitPHINode(PHINode &PN) {
  PHINode *ShadowPN =
      PHINode::Create(DFSF.DFS.ShadowTy, PN.getNumIncomingValues(), "", &PN);

  // Give the shadow phi node valid predecessors to fool SplitEdge into working.
  Value *UndefShadow = UndefValue::get(DFSF.DFS.ShadowTy);
  for (PHINode::block_iterator i = PN.block_begin(), e = PN.block_end(); i != e;
       ++i) {
    ShadowPN->addIncoming(UndefShadow, *i);
  }

  DFSF.PHIFixups.push_back(std::make_pair(&PN, ShadowPN));
  DFSF.setShadow(&PN, ShadowPN);
}