aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/libs/llvm16/lib/Analysis/MemoryBuiltins.cpp
blob: 0edad0557369168449bc4fdcb46ae3c5ab7049e2 (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
//===- MemoryBuiltins.cpp - Identify calls to memory builtins -------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This family of functions identifies calls to builtin functions that allocate
// or free memory.
//
//===----------------------------------------------------------------------===//

#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/TargetFolder.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/Utils/Local.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Argument.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <cstdint>
#include <iterator>
#include <numeric>
#include <optional>
#include <type_traits>
#include <utility>

using namespace llvm;

#define DEBUG_TYPE "memory-builtins"

enum AllocType : uint8_t {
  OpNewLike          = 1<<0, // allocates; never returns null
  MallocLike         = 1<<1, // allocates; may return null
  StrDupLike         = 1<<2,
  MallocOrOpNewLike  = MallocLike | OpNewLike,
  AllocLike          = MallocOrOpNewLike | StrDupLike,
  AnyAlloc           = AllocLike
};

enum class MallocFamily {
  Malloc,
  CPPNew,             // new(unsigned int)
  CPPNewAligned,      // new(unsigned int, align_val_t)
  CPPNewArray,        // new[](unsigned int)
  CPPNewArrayAligned, // new[](unsigned long, align_val_t)
  MSVCNew,            // new(unsigned int)
  MSVCArrayNew,       // new[](unsigned int)
  VecMalloc,
  KmpcAllocShared,
};

StringRef mangledNameForMallocFamily(const MallocFamily &Family) {
  switch (Family) {
  case MallocFamily::Malloc:
    return "malloc";
  case MallocFamily::CPPNew:
    return "_Znwm";
  case MallocFamily::CPPNewAligned:
    return "_ZnwmSt11align_val_t";
  case MallocFamily::CPPNewArray:
    return "_Znam";
  case MallocFamily::CPPNewArrayAligned:
    return "_ZnamSt11align_val_t";
  case MallocFamily::MSVCNew:
    return "??2@YAPAXI@Z";
  case MallocFamily::MSVCArrayNew:
    return "??_U@YAPAXI@Z";
  case MallocFamily::VecMalloc:
    return "vec_malloc";
  case MallocFamily::KmpcAllocShared:
    return "__kmpc_alloc_shared";
  }
  llvm_unreachable("missing an alloc family");
}

struct AllocFnsTy {
  AllocType AllocTy;
  unsigned NumParams;
  // First and Second size parameters (or -1 if unused)
  int FstParam, SndParam;
  // Alignment parameter for aligned_alloc and aligned new
  int AlignParam;
  // Name of default allocator function to group malloc/free calls by family
  MallocFamily Family;
};

// clang-format off
// FIXME: certain users need more information. E.g., SimplifyLibCalls needs to
// know which functions are nounwind, noalias, nocapture parameters, etc.
static const std::pair<LibFunc, AllocFnsTy> AllocationFnData[] = {
    {LibFunc_Znwj,                              {OpNewLike,        1,  0, -1, -1, MallocFamily::CPPNew}},             // new(unsigned int)
    {LibFunc_ZnwjRKSt9nothrow_t,                {MallocLike,       2,  0, -1, -1, MallocFamily::CPPNew}},             // new(unsigned int, nothrow)
    {LibFunc_ZnwjSt11align_val_t,               {OpNewLike,        2,  0, -1,  1, MallocFamily::CPPNewAligned}},      // new(unsigned int, align_val_t)
    {LibFunc_ZnwjSt11align_val_tRKSt9nothrow_t, {MallocLike,       3,  0, -1,  1, MallocFamily::CPPNewAligned}},      // new(unsigned int, align_val_t, nothrow)
    {LibFunc_Znwm,                              {OpNewLike,        1,  0, -1, -1, MallocFamily::CPPNew}},             // new(unsigned long)
    {LibFunc_ZnwmRKSt9nothrow_t,                {MallocLike,       2,  0, -1, -1, MallocFamily::CPPNew}},             // new(unsigned long, nothrow)
    {LibFunc_ZnwmSt11align_val_t,               {OpNewLike,        2,  0, -1,  1, MallocFamily::CPPNewAligned}},      // new(unsigned long, align_val_t)
    {LibFunc_ZnwmSt11align_val_tRKSt9nothrow_t, {MallocLike,       3,  0, -1,  1, MallocFamily::CPPNewAligned}},      // new(unsigned long, align_val_t, nothrow)
    {LibFunc_Znaj,                              {OpNewLike,        1,  0, -1, -1, MallocFamily::CPPNewArray}},        // new[](unsigned int)
    {LibFunc_ZnajRKSt9nothrow_t,                {MallocLike,       2,  0, -1, -1, MallocFamily::CPPNewArray}},        // new[](unsigned int, nothrow)
    {LibFunc_ZnajSt11align_val_t,               {OpNewLike,        2,  0, -1,  1, MallocFamily::CPPNewArrayAligned}}, // new[](unsigned int, align_val_t)
    {LibFunc_ZnajSt11align_val_tRKSt9nothrow_t, {MallocLike,       3,  0, -1,  1, MallocFamily::CPPNewArrayAligned}}, // new[](unsigned int, align_val_t, nothrow)
    {LibFunc_Znam,                              {OpNewLike,        1,  0, -1, -1, MallocFamily::CPPNewArray}},        // new[](unsigned long)
    {LibFunc_ZnamRKSt9nothrow_t,                {MallocLike,       2,  0, -1, -1, MallocFamily::CPPNewArray}},        // new[](unsigned long, nothrow)
    {LibFunc_ZnamSt11align_val_t,               {OpNewLike,        2,  0, -1,  1, MallocFamily::CPPNewArrayAligned}}, // new[](unsigned long, align_val_t)
    {LibFunc_ZnamSt11align_val_tRKSt9nothrow_t, {MallocLike,       3,  0, -1,  1, MallocFamily::CPPNewArrayAligned}}, // new[](unsigned long, align_val_t, nothrow)
    {LibFunc_msvc_new_int,                      {OpNewLike,        1,  0, -1, -1, MallocFamily::MSVCNew}},            // new(unsigned int)
    {LibFunc_msvc_new_int_nothrow,              {MallocLike,       2,  0, -1, -1, MallocFamily::MSVCNew}},            // new(unsigned int, nothrow)
    {LibFunc_msvc_new_longlong,                 {OpNewLike,        1,  0, -1, -1, MallocFamily::MSVCNew}},            // new(unsigned long long)
    {LibFunc_msvc_new_longlong_nothrow,         {MallocLike,       2,  0, -1, -1, MallocFamily::MSVCNew}},            // new(unsigned long long, nothrow)
    {LibFunc_msvc_new_array_int,                {OpNewLike,        1,  0, -1, -1, MallocFamily::MSVCArrayNew}},       // new[](unsigned int)
    {LibFunc_msvc_new_array_int_nothrow,        {MallocLike,       2,  0, -1, -1, MallocFamily::MSVCArrayNew}},       // new[](unsigned int, nothrow)
    {LibFunc_msvc_new_array_longlong,           {OpNewLike,        1,  0, -1, -1, MallocFamily::MSVCArrayNew}},       // new[](unsigned long long)
    {LibFunc_msvc_new_array_longlong_nothrow,   {MallocLike,       2,  0, -1, -1, MallocFamily::MSVCArrayNew}},       // new[](unsigned long long, nothrow)
    {LibFunc_strdup,                            {StrDupLike,       1, -1, -1, -1, MallocFamily::Malloc}},
    {LibFunc_dunder_strdup,                     {StrDupLike,       1, -1, -1, -1, MallocFamily::Malloc}},
    {LibFunc_strndup,                           {StrDupLike,       2,  1, -1, -1, MallocFamily::Malloc}},
    {LibFunc_dunder_strndup,                    {StrDupLike,       2,  1, -1, -1, MallocFamily::Malloc}},
    {LibFunc___kmpc_alloc_shared,               {MallocLike,       1,  0, -1, -1, MallocFamily::KmpcAllocShared}},
};
// clang-format on

static const Function *getCalledFunction(const Value *V,
                                         bool &IsNoBuiltin) {
  // Don't care about intrinsics in this case.
  if (isa<IntrinsicInst>(V))
    return nullptr;

  const auto *CB = dyn_cast<CallBase>(V);
  if (!CB)
    return nullptr;

  IsNoBuiltin = CB->isNoBuiltin();

  if (const Function *Callee = CB->getCalledFunction())
    return Callee;
  return nullptr;
}

/// Returns the allocation data for the given value if it's a call to a known
/// allocation function.
static std::optional<AllocFnsTy>
getAllocationDataForFunction(const Function *Callee, AllocType AllocTy,
                             const TargetLibraryInfo *TLI) {
  // Don't perform a slow TLI lookup, if this function doesn't return a pointer
  // and thus can't be an allocation function.
  if (!Callee->getReturnType()->isPointerTy())
    return std::nullopt;

  // Make sure that the function is available.
  LibFunc TLIFn;
  if (!TLI || !TLI->getLibFunc(*Callee, TLIFn) || !TLI->has(TLIFn))
    return std::nullopt;

  const auto *Iter = find_if(
      AllocationFnData, [TLIFn](const std::pair<LibFunc, AllocFnsTy> &P) {
        return P.first == TLIFn;
      });

  if (Iter == std::end(AllocationFnData))
    return std::nullopt;

  const AllocFnsTy *FnData = &Iter->second;
  if ((FnData->AllocTy & AllocTy) != FnData->AllocTy)
    return std::nullopt;

  // Check function prototype.
  int FstParam = FnData->FstParam;
  int SndParam = FnData->SndParam;
  FunctionType *FTy = Callee->getFunctionType();

  if (FTy->getReturnType()->isPointerTy() &&
      FTy->getNumParams() == FnData->NumParams &&
      (FstParam < 0 ||
       (FTy->getParamType(FstParam)->isIntegerTy(32) ||
        FTy->getParamType(FstParam)->isIntegerTy(64))) &&
      (SndParam < 0 ||
       FTy->getParamType(SndParam)->isIntegerTy(32) ||
       FTy->getParamType(SndParam)->isIntegerTy(64)))
    return *FnData;
  return std::nullopt;
}

static std::optional<AllocFnsTy>
getAllocationData(const Value *V, AllocType AllocTy,
                  const TargetLibraryInfo *TLI) {
  bool IsNoBuiltinCall;
  if (const Function *Callee = getCalledFunction(V, IsNoBuiltinCall))
    if (!IsNoBuiltinCall)
      return getAllocationDataForFunction(Callee, AllocTy, TLI);
  return std::nullopt;
}

static std::optional<AllocFnsTy>
getAllocationData(const Value *V, AllocType AllocTy,
                  function_ref<const TargetLibraryInfo &(Function &)> GetTLI) {
  bool IsNoBuiltinCall;
  if (const Function *Callee = getCalledFunction(V, IsNoBuiltinCall))
    if (!IsNoBuiltinCall)
      return getAllocationDataForFunction(
          Callee, AllocTy, &GetTLI(const_cast<Function &>(*Callee)));
  return std::nullopt;
}

static std::optional<AllocFnsTy>
getAllocationSize(const Value *V, const TargetLibraryInfo *TLI) {
  bool IsNoBuiltinCall;
  const Function *Callee =
      getCalledFunction(V, IsNoBuiltinCall);
  if (!Callee)
    return std::nullopt;

  // Prefer to use existing information over allocsize. This will give us an
  // accurate AllocTy.
  if (!IsNoBuiltinCall)
    if (std::optional<AllocFnsTy> Data =
            getAllocationDataForFunction(Callee, AnyAlloc, TLI))
      return Data;

  Attribute Attr = Callee->getFnAttribute(Attribute::AllocSize);
  if (Attr == Attribute())
    return std::nullopt;

  std::pair<unsigned, std::optional<unsigned>> Args = Attr.getAllocSizeArgs();

  AllocFnsTy Result;
  // Because allocsize only tells us how many bytes are allocated, we're not
  // really allowed to assume anything, so we use MallocLike.
  Result.AllocTy = MallocLike;
  Result.NumParams = Callee->getNumOperands();
  Result.FstParam = Args.first;
  Result.SndParam = Args.second.value_or(-1);
  // Allocsize has no way to specify an alignment argument
  Result.AlignParam = -1;
  return Result;
}

static AllocFnKind getAllocFnKind(const Value *V) {
  if (const auto *CB = dyn_cast<CallBase>(V)) {
    Attribute Attr = CB->getFnAttr(Attribute::AllocKind);
    if (Attr.isValid())
      return AllocFnKind(Attr.getValueAsInt());
  }
  return AllocFnKind::Unknown;
}

static AllocFnKind getAllocFnKind(const Function *F) {
  Attribute Attr = F->getFnAttribute(Attribute::AllocKind);
  if (Attr.isValid())
    return AllocFnKind(Attr.getValueAsInt());
  return AllocFnKind::Unknown;
}

static bool checkFnAllocKind(const Value *V, AllocFnKind Wanted) {
  return (getAllocFnKind(V) & Wanted) != AllocFnKind::Unknown;
}

static bool checkFnAllocKind(const Function *F, AllocFnKind Wanted) {
  return (getAllocFnKind(F) & Wanted) != AllocFnKind::Unknown;
}

/// Tests if a value is a call or invoke to a library function that
/// allocates or reallocates memory (either malloc, calloc, realloc, or strdup
/// like).
bool llvm::isAllocationFn(const Value *V, const TargetLibraryInfo *TLI) {
  return getAllocationData(V, AnyAlloc, TLI).has_value() ||
         checkFnAllocKind(V, AllocFnKind::Alloc | AllocFnKind::Realloc);
}
bool llvm::isAllocationFn(
    const Value *V,
    function_ref<const TargetLibraryInfo &(Function &)> GetTLI) {
  return getAllocationData(V, AnyAlloc, GetTLI).has_value() ||
         checkFnAllocKind(V, AllocFnKind::Alloc | AllocFnKind::Realloc);
}

/// Tests if a value is a call or invoke to a library function that
/// allocates memory via new.
bool llvm::isNewLikeFn(const Value *V, const TargetLibraryInfo *TLI) {
  return getAllocationData(V, OpNewLike, TLI).has_value();
}

/// Tests if a value is a call or invoke to a library function that
/// allocates memory similar to malloc or calloc.
bool llvm::isMallocOrCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI) {
  // TODO: Function behavior does not match name.
  return getAllocationData(V, MallocOrOpNewLike, TLI).has_value();
}

/// Tests if a value is a call or invoke to a library function that
/// allocates memory (either malloc, calloc, or strdup like).
bool llvm::isAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI) {
  return getAllocationData(V, AllocLike, TLI).has_value() ||
         checkFnAllocKind(V, AllocFnKind::Alloc);
}

/// Tests if a functions is a call or invoke to a library function that
/// reallocates memory (e.g., realloc).
bool llvm::isReallocLikeFn(const Function *F) {
  return checkFnAllocKind(F, AllocFnKind::Realloc);
}

Value *llvm::getReallocatedOperand(const CallBase *CB) {
  if (checkFnAllocKind(CB, AllocFnKind::Realloc))
    return CB->getArgOperandWithAttribute(Attribute::AllocatedPointer);
  return nullptr;
}

bool llvm::isRemovableAlloc(const CallBase *CB, const TargetLibraryInfo *TLI) {
  // Note: Removability is highly dependent on the source language.  For
  // example, recent C++ requires direct calls to the global allocation
  // [basic.stc.dynamic.allocation] to be observable unless part of a new
  // expression [expr.new paragraph 13].

  // Historically we've treated the C family allocation routines and operator
  // new as removable
  return isAllocLikeFn(CB, TLI);
}

Value *llvm::getAllocAlignment(const CallBase *V,
                               const TargetLibraryInfo *TLI) {
  const std::optional<AllocFnsTy> FnData = getAllocationData(V, AnyAlloc, TLI);
  if (FnData && FnData->AlignParam >= 0) {
    return V->getOperand(FnData->AlignParam);
  }
  return V->getArgOperandWithAttribute(Attribute::AllocAlign);
}

/// When we're compiling N-bit code, and the user uses parameters that are
/// greater than N bits (e.g. uint64_t on a 32-bit build), we can run into
/// trouble with APInt size issues. This function handles resizing + overflow
/// checks for us. Check and zext or trunc \p I depending on IntTyBits and
/// I's value.
static bool CheckedZextOrTrunc(APInt &I, unsigned IntTyBits) {
  // More bits than we can handle. Checking the bit width isn't necessary, but
  // it's faster than checking active bits, and should give `false` in the
  // vast majority of cases.
  if (I.getBitWidth() > IntTyBits && I.getActiveBits() > IntTyBits)
    return false;
  if (I.getBitWidth() != IntTyBits)
    I = I.zextOrTrunc(IntTyBits);
  return true;
}

std::optional<APInt>
llvm::getAllocSize(const CallBase *CB, const TargetLibraryInfo *TLI,
                   function_ref<const Value *(const Value *)> Mapper) {
  // Note: This handles both explicitly listed allocation functions and
  // allocsize.  The code structure could stand to be cleaned up a bit.
  std::optional<AllocFnsTy> FnData = getAllocationSize(CB, TLI);
  if (!FnData)
    return std::nullopt;

  // Get the index type for this address space, results and intermediate
  // computations are performed at that width.
  auto &DL = CB->getModule()->getDataLayout();
  const unsigned IntTyBits = DL.getIndexTypeSizeInBits(CB->getType());

  // Handle strdup-like functions separately.
  if (FnData->AllocTy == StrDupLike) {
    APInt Size(IntTyBits, GetStringLength(Mapper(CB->getArgOperand(0))));
    if (!Size)
      return std::nullopt;

    // Strndup limits strlen.
    if (FnData->FstParam > 0) {
      const ConstantInt *Arg =
        dyn_cast<ConstantInt>(Mapper(CB->getArgOperand(FnData->FstParam)));
      if (!Arg)
        return std::nullopt;

      APInt MaxSize = Arg->getValue().zext(IntTyBits);
      if (Size.ugt(MaxSize))
        Size = MaxSize + 1;
    }
    return Size;
  }

  const ConstantInt *Arg =
    dyn_cast<ConstantInt>(Mapper(CB->getArgOperand(FnData->FstParam)));
  if (!Arg)
    return std::nullopt;

  APInt Size = Arg->getValue();
  if (!CheckedZextOrTrunc(Size, IntTyBits))
    return std::nullopt;

  // Size is determined by just 1 parameter.
  if (FnData->SndParam < 0)
    return Size;

  Arg = dyn_cast<ConstantInt>(Mapper(CB->getArgOperand(FnData->SndParam)));
  if (!Arg)
    return std::nullopt;

  APInt NumElems = Arg->getValue();
  if (!CheckedZextOrTrunc(NumElems, IntTyBits))
    return std::nullopt;

  bool Overflow;
  Size = Size.umul_ov(NumElems, Overflow);
  if (Overflow)
    return std::nullopt;
  return Size;
}

Constant *llvm::getInitialValueOfAllocation(const Value *V,
                                            const TargetLibraryInfo *TLI,
                                            Type *Ty) {
  auto *Alloc = dyn_cast<CallBase>(V);
  if (!Alloc)
    return nullptr;

  // malloc are uninitialized (undef)
  if (getAllocationData(Alloc, MallocOrOpNewLike, TLI).has_value())
    return UndefValue::get(Ty);

  AllocFnKind AK = getAllocFnKind(Alloc);
  if ((AK & AllocFnKind::Uninitialized) != AllocFnKind::Unknown)
    return UndefValue::get(Ty);
  if ((AK & AllocFnKind::Zeroed) != AllocFnKind::Unknown)
    return Constant::getNullValue(Ty);

  return nullptr;
}

struct FreeFnsTy {
  unsigned NumParams;
  // Name of default allocator function to group malloc/free calls by family
  MallocFamily Family;
};

// clang-format off
static const std::pair<LibFunc, FreeFnsTy> FreeFnData[] = {
    {LibFunc_ZdlPv,                              {1, MallocFamily::CPPNew}},             // operator delete(void*)
    {LibFunc_ZdaPv,                              {1, MallocFamily::CPPNewArray}},        // operator delete[](void*)
    {LibFunc_msvc_delete_ptr32,                  {1, MallocFamily::MSVCNew}},            // operator delete(void*)
    {LibFunc_msvc_delete_ptr64,                  {1, MallocFamily::MSVCNew}},            // operator delete(void*)
    {LibFunc_msvc_delete_array_ptr32,            {1, MallocFamily::MSVCArrayNew}},       // operator delete[](void*)
    {LibFunc_msvc_delete_array_ptr64,            {1, MallocFamily::MSVCArrayNew}},       // operator delete[](void*)
    {LibFunc_ZdlPvj,                             {2, MallocFamily::CPPNew}},             // delete(void*, uint)
    {LibFunc_ZdlPvm,                             {2, MallocFamily::CPPNew}},             // delete(void*, ulong)
    {LibFunc_ZdlPvRKSt9nothrow_t,                {2, MallocFamily::CPPNew}},             // delete(void*, nothrow)
    {LibFunc_ZdlPvSt11align_val_t,               {2, MallocFamily::CPPNewAligned}},      // delete(void*, align_val_t)
    {LibFunc_ZdaPvj,                             {2, MallocFamily::CPPNewArray}},        // delete[](void*, uint)
    {LibFunc_ZdaPvm,                             {2, MallocFamily::CPPNewArray}},        // delete[](void*, ulong)
    {LibFunc_ZdaPvRKSt9nothrow_t,                {2, MallocFamily::CPPNewArray}},        // delete[](void*, nothrow)
    {LibFunc_ZdaPvSt11align_val_t,               {2, MallocFamily::CPPNewArrayAligned}}, // delete[](void*, align_val_t)
    {LibFunc_msvc_delete_ptr32_int,              {2, MallocFamily::MSVCNew}},            // delete(void*, uint)
    {LibFunc_msvc_delete_ptr64_longlong,         {2, MallocFamily::MSVCNew}},            // delete(void*, ulonglong)
    {LibFunc_msvc_delete_ptr32_nothrow,          {2, MallocFamily::MSVCNew}},            // delete(void*, nothrow)
    {LibFunc_msvc_delete_ptr64_nothrow,          {2, MallocFamily::MSVCNew}},            // delete(void*, nothrow)
    {LibFunc_msvc_delete_array_ptr32_int,        {2, MallocFamily::MSVCArrayNew}},       // delete[](void*, uint)
    {LibFunc_msvc_delete_array_ptr64_longlong,   {2, MallocFamily::MSVCArrayNew}},       // delete[](void*, ulonglong)
    {LibFunc_msvc_delete_array_ptr32_nothrow,    {2, MallocFamily::MSVCArrayNew}},       // delete[](void*, nothrow)
    {LibFunc_msvc_delete_array_ptr64_nothrow,    {2, MallocFamily::MSVCArrayNew}},       // delete[](void*, nothrow)
    {LibFunc___kmpc_free_shared,                 {2, MallocFamily::KmpcAllocShared}},    // OpenMP Offloading RTL free
    {LibFunc_ZdlPvSt11align_val_tRKSt9nothrow_t, {3, MallocFamily::CPPNewAligned}},      // delete(void*, align_val_t, nothrow)
    {LibFunc_ZdaPvSt11align_val_tRKSt9nothrow_t, {3, MallocFamily::CPPNewArrayAligned}}, // delete[](void*, align_val_t, nothrow)
    {LibFunc_ZdlPvjSt11align_val_t,              {3, MallocFamily::CPPNewAligned}},      // delete(void*, unsigned int, align_val_t)
    {LibFunc_ZdlPvmSt11align_val_t,              {3, MallocFamily::CPPNewAligned}},      // delete(void*, unsigned long, align_val_t)
    {LibFunc_ZdaPvjSt11align_val_t,              {3, MallocFamily::CPPNewArrayAligned}}, // delete[](void*, unsigned int, align_val_t)
    {LibFunc_ZdaPvmSt11align_val_t,              {3, MallocFamily::CPPNewArrayAligned}}, // delete[](void*, unsigned long, align_val_t)
};
// clang-format on

std::optional<FreeFnsTy> getFreeFunctionDataForFunction(const Function *Callee,
                                                        const LibFunc TLIFn) {
  const auto *Iter =
      find_if(FreeFnData, [TLIFn](const std::pair<LibFunc, FreeFnsTy> &P) {
        return P.first == TLIFn;
      });
  if (Iter == std::end(FreeFnData))
    return std::nullopt;
  return Iter->second;
}

std::optional<StringRef>
llvm::getAllocationFamily(const Value *I, const TargetLibraryInfo *TLI) {
  bool IsNoBuiltin;
  const Function *Callee = getCalledFunction(I, IsNoBuiltin);
  if (Callee == nullptr || IsNoBuiltin)
    return std::nullopt;
  LibFunc TLIFn;

  if (TLI && TLI->getLibFunc(*Callee, TLIFn) && TLI->has(TLIFn)) {
    // Callee is some known library function.
    const auto AllocData = getAllocationDataForFunction(Callee, AnyAlloc, TLI);
    if (AllocData)
      return mangledNameForMallocFamily(AllocData->Family);
    const auto FreeData = getFreeFunctionDataForFunction(Callee, TLIFn);
    if (FreeData)
      return mangledNameForMallocFamily(FreeData->Family);
  }
  // Callee isn't a known library function, still check attributes.
  if (checkFnAllocKind(I, AllocFnKind::Free | AllocFnKind::Alloc |
                              AllocFnKind::Realloc)) {
    Attribute Attr = cast<CallBase>(I)->getFnAttr("alloc-family");
    if (Attr.isValid())
      return Attr.getValueAsString();
  }
  return std::nullopt;
}

/// isLibFreeFunction - Returns true if the function is a builtin free()
bool llvm::isLibFreeFunction(const Function *F, const LibFunc TLIFn) {
  std::optional<FreeFnsTy> FnData = getFreeFunctionDataForFunction(F, TLIFn);
  if (!FnData)
    return checkFnAllocKind(F, AllocFnKind::Free);

  // Check free prototype.
  // FIXME: workaround for PR5130, this will be obsolete when a nobuiltin
  // attribute will exist.
  FunctionType *FTy = F->getFunctionType();
  if (!FTy->getReturnType()->isVoidTy())
    return false;
  if (FTy->getNumParams() != FnData->NumParams)
    return false;
  if (!FTy->getParamType(0)->isPointerTy())
    return false;

  return true;
}

Value *llvm::getFreedOperand(const CallBase *CB, const TargetLibraryInfo *TLI) {
  bool IsNoBuiltinCall;
  const Function *Callee = getCalledFunction(CB, IsNoBuiltinCall);
  if (Callee == nullptr || IsNoBuiltinCall)
    return nullptr;

  LibFunc TLIFn;
  if (TLI && TLI->getLibFunc(*Callee, TLIFn) && TLI->has(TLIFn) &&
      isLibFreeFunction(Callee, TLIFn)) {
    // All currently supported free functions free the first argument.
    return CB->getArgOperand(0);
  }

  if (checkFnAllocKind(CB, AllocFnKind::Free))
    return CB->getArgOperandWithAttribute(Attribute::AllocatedPointer);

  return nullptr;
}

//===----------------------------------------------------------------------===//
//  Utility functions to compute size of objects.
//
static APInt getSizeWithOverflow(const SizeOffsetType &Data) {
  if (Data.second.isNegative() || Data.first.ult(Data.second))
    return APInt(Data.first.getBitWidth(), 0);
  return Data.first - Data.second;
}

/// Compute the size of the object pointed by Ptr. Returns true and the
/// object size in Size if successful, and false otherwise.
/// If RoundToAlign is true, then Size is rounded up to the alignment of
/// allocas, byval arguments, and global variables.
bool llvm::getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout &DL,
                         const TargetLibraryInfo *TLI, ObjectSizeOpts Opts) {
  ObjectSizeOffsetVisitor Visitor(DL, TLI, Ptr->getContext(), Opts);
  SizeOffsetType Data = Visitor.compute(const_cast<Value*>(Ptr));
  if (!Visitor.bothKnown(Data))
    return false;

  Size = getSizeWithOverflow(Data).getZExtValue();
  return true;
}

Value *llvm::lowerObjectSizeCall(IntrinsicInst *ObjectSize,
                                 const DataLayout &DL,
                                 const TargetLibraryInfo *TLI,
                                 bool MustSucceed) {
  return lowerObjectSizeCall(ObjectSize, DL, TLI, /*AAResults=*/nullptr,
                             MustSucceed);
}

Value *llvm::lowerObjectSizeCall(IntrinsicInst *ObjectSize,
                                 const DataLayout &DL,
                                 const TargetLibraryInfo *TLI, AAResults *AA,
                                 bool MustSucceed) {
  assert(ObjectSize->getIntrinsicID() == Intrinsic::objectsize &&
         "ObjectSize must be a call to llvm.objectsize!");

  bool MaxVal = cast<ConstantInt>(ObjectSize->getArgOperand(1))->isZero();
  ObjectSizeOpts EvalOptions;
  EvalOptions.AA = AA;

  // Unless we have to fold this to something, try to be as accurate as
  // possible.
  if (MustSucceed)
    EvalOptions.EvalMode =
        MaxVal ? ObjectSizeOpts::Mode::Max : ObjectSizeOpts::Mode::Min;
  else
    EvalOptions.EvalMode = ObjectSizeOpts::Mode::ExactSizeFromOffset;

  EvalOptions.NullIsUnknownSize =
      cast<ConstantInt>(ObjectSize->getArgOperand(2))->isOne();

  auto *ResultType = cast<IntegerType>(ObjectSize->getType());
  bool StaticOnly = cast<ConstantInt>(ObjectSize->getArgOperand(3))->isZero();
  if (StaticOnly) {
    // FIXME: Does it make sense to just return a failure value if the size won't
    // fit in the output and `!MustSucceed`?
    uint64_t Size;
    if (getObjectSize(ObjectSize->getArgOperand(0), Size, DL, TLI, EvalOptions) &&
        isUIntN(ResultType->getBitWidth(), Size))
      return ConstantInt::get(ResultType, Size);
  } else {
    LLVMContext &Ctx = ObjectSize->getFunction()->getContext();
    ObjectSizeOffsetEvaluator Eval(DL, TLI, Ctx, EvalOptions);
    SizeOffsetEvalType SizeOffsetPair =
        Eval.compute(ObjectSize->getArgOperand(0));

    if (SizeOffsetPair != ObjectSizeOffsetEvaluator::unknown()) {
      IRBuilder<TargetFolder> Builder(Ctx, TargetFolder(DL));
      Builder.SetInsertPoint(ObjectSize);

      // If we've outside the end of the object, then we can always access
      // exactly 0 bytes.
      Value *ResultSize =
          Builder.CreateSub(SizeOffsetPair.first, SizeOffsetPair.second);
      Value *UseZero =
          Builder.CreateICmpULT(SizeOffsetPair.first, SizeOffsetPair.second);
      ResultSize = Builder.CreateZExtOrTrunc(ResultSize, ResultType);
      Value *Ret = Builder.CreateSelect(
          UseZero, ConstantInt::get(ResultType, 0), ResultSize);

      // The non-constant size expression cannot evaluate to -1.
      if (!isa<Constant>(SizeOffsetPair.first) ||
          !isa<Constant>(SizeOffsetPair.second))
        Builder.CreateAssumption(
            Builder.CreateICmpNE(Ret, ConstantInt::get(ResultType, -1)));

      return Ret;
    }
  }

  if (!MustSucceed)
    return nullptr;

  return ConstantInt::get(ResultType, MaxVal ? -1ULL : 0);
}

STATISTIC(ObjectVisitorArgument,
          "Number of arguments with unsolved size and offset");
STATISTIC(ObjectVisitorLoad,
          "Number of load instructions with unsolved size and offset");

APInt ObjectSizeOffsetVisitor::align(APInt Size, MaybeAlign Alignment) {
  if (Options.RoundToAlign && Alignment)
    return APInt(IntTyBits, alignTo(Size.getZExtValue(), *Alignment));
  return Size;
}

ObjectSizeOffsetVisitor::ObjectSizeOffsetVisitor(const DataLayout &DL,
                                                 const TargetLibraryInfo *TLI,
                                                 LLVMContext &Context,
                                                 ObjectSizeOpts Options)
    : DL(DL), TLI(TLI), Options(Options) {
  // Pointer size must be rechecked for each object visited since it could have
  // a different address space.
}

SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
  unsigned InitialIntTyBits = DL.getIndexTypeSizeInBits(V->getType());

  // Stripping pointer casts can strip address space casts which can change the
  // index type size. The invariant is that we use the value type to determine
  // the index type size and if we stripped address space casts we have to
  // readjust the APInt as we pass it upwards in order for the APInt to match
  // the type the caller passed in.
  APInt Offset(InitialIntTyBits, 0);
  V = V->stripAndAccumulateConstantOffsets(
      DL, Offset, /* AllowNonInbounds */ true, /* AllowInvariantGroup */ true);

  // Later we use the index type size and zero but it will match the type of the
  // value that is passed to computeImpl.
  IntTyBits = DL.getIndexTypeSizeInBits(V->getType());
  Zero = APInt::getZero(IntTyBits);

  bool IndexTypeSizeChanged = InitialIntTyBits != IntTyBits;
  if (!IndexTypeSizeChanged && Offset.isZero())
    return computeImpl(V);

  // We stripped an address space cast that changed the index type size or we
  // accumulated some constant offset (or both). Readjust the bit width to match
  // the argument index type size and apply the offset, as required.
  SizeOffsetType SOT = computeImpl(V);
  if (IndexTypeSizeChanged) {
    if (knownSize(SOT) && !::CheckedZextOrTrunc(SOT.first, InitialIntTyBits))
      SOT.first = APInt();
    if (knownOffset(SOT) && !::CheckedZextOrTrunc(SOT.second, InitialIntTyBits))
      SOT.second = APInt();
  }
  // If the computed offset is "unknown" we cannot add the stripped offset.
  return {SOT.first,
          SOT.second.getBitWidth() > 1 ? SOT.second + Offset : SOT.second};
}

SizeOffsetType ObjectSizeOffsetVisitor::computeImpl(Value *V) {
  if (Instruction *I = dyn_cast<Instruction>(V)) {
    // If we have already seen this instruction, bail out. Cycles can happen in
    // unreachable code after constant propagation.
    if (!SeenInsts.insert(I).second)
      return unknown();

    return visit(*I);
  }
  if (Argument *A = dyn_cast<Argument>(V))
    return visitArgument(*A);
  if (ConstantPointerNull *P = dyn_cast<ConstantPointerNull>(V))
    return visitConstantPointerNull(*P);
  if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
    return visitGlobalAlias(*GA);
  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
    return visitGlobalVariable(*GV);
  if (UndefValue *UV = dyn_cast<UndefValue>(V))
    return visitUndefValue(*UV);

  LLVM_DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: "
                    << *V << '\n');
  return unknown();
}

bool ObjectSizeOffsetVisitor::CheckedZextOrTrunc(APInt &I) {
  return ::CheckedZextOrTrunc(I, IntTyBits);
}

SizeOffsetType ObjectSizeOffsetVisitor::visitAllocaInst(AllocaInst &I) {
  TypeSize ElemSize = DL.getTypeAllocSize(I.getAllocatedType());
  if (ElemSize.isScalable() && Options.EvalMode != ObjectSizeOpts::Mode::Min)
    return unknown();
  APInt Size(IntTyBits, ElemSize.getKnownMinValue());
  if (!I.isArrayAllocation())
    return std::make_pair(align(Size, I.getAlign()), Zero);

  Value *ArraySize = I.getArraySize();
  if (const ConstantInt *C = dyn_cast<ConstantInt>(ArraySize)) {
    APInt NumElems = C->getValue();
    if (!CheckedZextOrTrunc(NumElems))
      return unknown();

    bool Overflow;
    Size = Size.umul_ov(NumElems, Overflow);
    return Overflow ? unknown()
                    : std::make_pair(align(Size, I.getAlign()), Zero);
  }
  return unknown();
}

SizeOffsetType ObjectSizeOffsetVisitor::visitArgument(Argument &A) {
  Type *MemoryTy = A.getPointeeInMemoryValueType();
  // No interprocedural analysis is done at the moment.
  if (!MemoryTy|| !MemoryTy->isSized()) {
    ++ObjectVisitorArgument;
    return unknown();
  }

  APInt Size(IntTyBits, DL.getTypeAllocSize(MemoryTy));
  return std::make_pair(align(Size, A.getParamAlign()), Zero);
}

SizeOffsetType ObjectSizeOffsetVisitor::visitCallBase(CallBase &CB) {
  if (std::optional<APInt> Size = getAllocSize(&CB, TLI))
    return std::make_pair(*Size, Zero);
  return unknown();
}

SizeOffsetType
ObjectSizeOffsetVisitor::visitConstantPointerNull(ConstantPointerNull& CPN) {
  // If null is unknown, there's nothing we can do. Additionally, non-zero
  // address spaces can make use of null, so we don't presume to know anything
  // about that.
  //
  // TODO: How should this work with address space casts? We currently just drop
  // them on the floor, but it's unclear what we should do when a NULL from
  // addrspace(1) gets casted to addrspace(0) (or vice-versa).
  if (Options.NullIsUnknownSize || CPN.getType()->getAddressSpace())
    return unknown();
  return std::make_pair(Zero, Zero);
}

SizeOffsetType
ObjectSizeOffsetVisitor::visitExtractElementInst(ExtractElementInst&) {
  return unknown();
}

SizeOffsetType
ObjectSizeOffsetVisitor::visitExtractValueInst(ExtractValueInst&) {
  // Easy cases were already folded by previous passes.
  return unknown();
}

SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalAlias(GlobalAlias &GA) {
  if (GA.isInterposable())
    return unknown();
  return compute(GA.getAliasee());
}

SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalVariable(GlobalVariable &GV){
  if (!GV.hasDefinitiveInitializer())
    return unknown();

  APInt Size(IntTyBits, DL.getTypeAllocSize(GV.getValueType()));
  return std::make_pair(align(Size, GV.getAlign()), Zero);
}

SizeOffsetType ObjectSizeOffsetVisitor::visitIntToPtrInst(IntToPtrInst&) {
  // clueless
  return unknown();
}

SizeOffsetType ObjectSizeOffsetVisitor::findLoadSizeOffset(
    LoadInst &Load, BasicBlock &BB, BasicBlock::iterator From,
    SmallDenseMap<BasicBlock *, SizeOffsetType, 8> &VisitedBlocks,
    unsigned &ScannedInstCount) {
  constexpr unsigned MaxInstsToScan = 128;

  auto Where = VisitedBlocks.find(&BB);
  if (Where != VisitedBlocks.end())
    return Where->second;

  auto Unknown = [this, &BB, &VisitedBlocks]() {
    return VisitedBlocks[&BB] = unknown();
  };
  auto Known = [&BB, &VisitedBlocks](SizeOffsetType SO) {
    return VisitedBlocks[&BB] = SO;
  };

  do {
    Instruction &I = *From;

    if (I.isDebugOrPseudoInst())
      continue;

    if (++ScannedInstCount > MaxInstsToScan)
      return Unknown();

    if (!I.mayWriteToMemory())
      continue;

    if (auto *SI = dyn_cast<StoreInst>(&I)) {
      AliasResult AR =
          Options.AA->alias(SI->getPointerOperand(), Load.getPointerOperand());
      switch ((AliasResult::Kind)AR) {
      case AliasResult::NoAlias:
        continue;
      case AliasResult::MustAlias:
        if (SI->getValueOperand()->getType()->isPointerTy())
          return Known(compute(SI->getValueOperand()));
        else
          return Unknown(); // No handling of non-pointer values by `compute`.
      default:
        return Unknown();
      }
    }

    if (auto *CB = dyn_cast<CallBase>(&I)) {
      Function *Callee = CB->getCalledFunction();
      // Bail out on indirect call.
      if (!Callee)
        return Unknown();

      LibFunc TLIFn;
      if (!TLI || !TLI->getLibFunc(*CB->getCalledFunction(), TLIFn) ||
          !TLI->has(TLIFn))
        return Unknown();

      // TODO: There's probably more interesting case to support here.
      if (TLIFn != LibFunc_posix_memalign)
        return Unknown();

      AliasResult AR =
          Options.AA->alias(CB->getOperand(0), Load.getPointerOperand());
      switch ((AliasResult::Kind)AR) {
      case AliasResult::NoAlias:
        continue;
      case AliasResult::MustAlias:
        break;
      default:
        return Unknown();
      }

      // Is the error status of posix_memalign correctly checked? If not it
      // would be incorrect to assume it succeeds and load doesn't see the
      // previous value.
      std::optional<bool> Checked = isImpliedByDomCondition(
          ICmpInst::ICMP_EQ, CB, ConstantInt::get(CB->getType(), 0), &Load, DL);
      if (!Checked || !*Checked)
        return Unknown();

      Value *Size = CB->getOperand(2);
      auto *C = dyn_cast<ConstantInt>(Size);
      if (!C)
        return Unknown();

      return Known({C->getValue(), APInt(C->getValue().getBitWidth(), 0)});
    }

    return Unknown();
  } while (From-- != BB.begin());

  SmallVector<SizeOffsetType> PredecessorSizeOffsets;
  for (auto *PredBB : predecessors(&BB)) {
    PredecessorSizeOffsets.push_back(findLoadSizeOffset(
        Load, *PredBB, BasicBlock::iterator(PredBB->getTerminator()),
        VisitedBlocks, ScannedInstCount));
    if (!bothKnown(PredecessorSizeOffsets.back()))
      return Unknown();
  }

  if (PredecessorSizeOffsets.empty())
    return Unknown();

  return Known(std::accumulate(PredecessorSizeOffsets.begin() + 1,
                               PredecessorSizeOffsets.end(),
                               PredecessorSizeOffsets.front(),
                               [this](SizeOffsetType LHS, SizeOffsetType RHS) {
                                 return combineSizeOffset(LHS, RHS);
                               }));
}

SizeOffsetType ObjectSizeOffsetVisitor::visitLoadInst(LoadInst &LI) {
  if (!Options.AA) {
    ++ObjectVisitorLoad;
    return unknown();
  }

  SmallDenseMap<BasicBlock *, SizeOffsetType, 8> VisitedBlocks;
  unsigned ScannedInstCount = 0;
  SizeOffsetType SO =
      findLoadSizeOffset(LI, *LI.getParent(), BasicBlock::iterator(LI),
                         VisitedBlocks, ScannedInstCount);
  if (!bothKnown(SO))
    ++ObjectVisitorLoad;
  return SO;
}

SizeOffsetType ObjectSizeOffsetVisitor::combineSizeOffset(SizeOffsetType LHS,
                                                          SizeOffsetType RHS) {
  if (!bothKnown(LHS) || !bothKnown(RHS))
    return unknown();

  switch (Options.EvalMode) {
  case ObjectSizeOpts::Mode::Min:
    return (getSizeWithOverflow(LHS).slt(getSizeWithOverflow(RHS))) ? LHS : RHS;
  case ObjectSizeOpts::Mode::Max:
    return (getSizeWithOverflow(LHS).sgt(getSizeWithOverflow(RHS))) ? LHS : RHS;
  case ObjectSizeOpts::Mode::ExactSizeFromOffset:
    return (getSizeWithOverflow(LHS).eq(getSizeWithOverflow(RHS))) ? LHS
                                                                   : unknown();
  case ObjectSizeOpts::Mode::ExactUnderlyingSizeAndOffset:
    return LHS == RHS && LHS.second.eq(RHS.second) ? LHS : unknown();
  }
  llvm_unreachable("missing an eval mode");
}

SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode &PN) {
  auto IncomingValues = PN.incoming_values();
  return std::accumulate(IncomingValues.begin() + 1, IncomingValues.end(),
                         compute(*IncomingValues.begin()),
                         [this](SizeOffsetType LHS, Value *VRHS) {
                           return combineSizeOffset(LHS, compute(VRHS));
                         });
}

SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) {
  return combineSizeOffset(compute(I.getTrueValue()),
                           compute(I.getFalseValue()));
}

SizeOffsetType ObjectSizeOffsetVisitor::visitUndefValue(UndefValue&) {
  return std::make_pair(Zero, Zero);
}

SizeOffsetType ObjectSizeOffsetVisitor::visitInstruction(Instruction &I) {
  LLVM_DEBUG(dbgs() << "ObjectSizeOffsetVisitor unknown instruction:" << I
                    << '\n');
  return unknown();
}

ObjectSizeOffsetEvaluator::ObjectSizeOffsetEvaluator(
    const DataLayout &DL, const TargetLibraryInfo *TLI, LLVMContext &Context,
    ObjectSizeOpts EvalOpts)
    : DL(DL), TLI(TLI), Context(Context),
      Builder(Context, TargetFolder(DL),
              IRBuilderCallbackInserter(
                  [&](Instruction *I) { InsertedInstructions.insert(I); })),
      EvalOpts(EvalOpts) {
  // IntTy and Zero must be set for each compute() since the address space may
  // be different for later objects.
}

SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute(Value *V) {
  // XXX - Are vectors of pointers possible here?
  IntTy = cast<IntegerType>(DL.getIndexType(V->getType()));
  Zero = ConstantInt::get(IntTy, 0);

  SizeOffsetEvalType Result = compute_(V);

  if (!bothKnown(Result)) {
    // Erase everything that was computed in this iteration from the cache, so
    // that no dangling references are left behind. We could be a bit smarter if
    // we kept a dependency graph. It's probably not worth the complexity.
    for (const Value *SeenVal : SeenVals) {
      CacheMapTy::iterator CacheIt = CacheMap.find(SeenVal);
      // non-computable results can be safely cached
      if (CacheIt != CacheMap.end() && anyKnown(CacheIt->second))
        CacheMap.erase(CacheIt);
    }

    // Erase any instructions we inserted as part of the traversal.
    for (Instruction *I : InsertedInstructions) {
      I->replaceAllUsesWith(PoisonValue::get(I->getType()));
      I->eraseFromParent();
    }
  }

  SeenVals.clear();
  InsertedInstructions.clear();
  return Result;
}

SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute_(Value *V) {
  ObjectSizeOffsetVisitor Visitor(DL, TLI, Context, EvalOpts);
  SizeOffsetType Const = Visitor.compute(V);
  if (Visitor.bothKnown(Const))
    return std::make_pair(ConstantInt::get(Context, Const.first),
                          ConstantInt::get(Context, Const.second));

  V = V->stripPointerCasts();

  // Check cache.
  CacheMapTy::iterator CacheIt = CacheMap.find(V);
  if (CacheIt != CacheMap.end())
    return CacheIt->second;

  // Always generate code immediately before the instruction being
  // processed, so that the generated code dominates the same BBs.
  BuilderTy::InsertPointGuard Guard(Builder);
  if (Instruction *I = dyn_cast<Instruction>(V))
    Builder.SetInsertPoint(I);

  // Now compute the size and offset.
  SizeOffsetEvalType Result;

  // Record the pointers that were handled in this run, so that they can be
  // cleaned later if something fails. We also use this set to break cycles that
  // can occur in dead code.
  if (!SeenVals.insert(V).second) {
    Result = unknown();
  } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
    Result = visitGEPOperator(*GEP);
  } else if (Instruction *I = dyn_cast<Instruction>(V)) {
    Result = visit(*I);
  } else if (isa<Argument>(V) ||
             (isa<ConstantExpr>(V) &&
              cast<ConstantExpr>(V)->getOpcode() == Instruction::IntToPtr) ||
             isa<GlobalAlias>(V) ||
             isa<GlobalVariable>(V)) {
    // Ignore values where we cannot do more than ObjectSizeVisitor.
    Result = unknown();
  } else {
    LLVM_DEBUG(
        dbgs() << "ObjectSizeOffsetEvaluator::compute() unhandled value: " << *V
               << '\n');
    Result = unknown();
  }

  // Don't reuse CacheIt since it may be invalid at this point.
  CacheMap[V] = Result;
  return Result;
}

SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitAllocaInst(AllocaInst &I) {
  if (!I.getAllocatedType()->isSized())
    return unknown();

  // must be a VLA
  assert(I.isArrayAllocation());

  // If needed, adjust the alloca's operand size to match the pointer size.
  // Subsequent math operations expect the types to match.
  Value *ArraySize = Builder.CreateZExtOrTrunc(
      I.getArraySize(), DL.getIntPtrType(I.getContext()));
  assert(ArraySize->getType() == Zero->getType() &&
         "Expected zero constant to have pointer type");

  Value *Size = ConstantInt::get(ArraySize->getType(),
                                 DL.getTypeAllocSize(I.getAllocatedType()));
  Size = Builder.CreateMul(Size, ArraySize);
  return std::make_pair(Size, Zero);
}

SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitCallBase(CallBase &CB) {
  std::optional<AllocFnsTy> FnData = getAllocationSize(&CB, TLI);
  if (!FnData)
    return unknown();

  // Handle strdup-like functions separately.
  if (FnData->AllocTy == StrDupLike) {
    // TODO: implement evaluation of strdup/strndup
    return unknown();
  }

  Value *FirstArg = CB.getArgOperand(FnData->FstParam);
  FirstArg = Builder.CreateZExtOrTrunc(FirstArg, IntTy);
  if (FnData->SndParam < 0)
    return std::make_pair(FirstArg, Zero);

  Value *SecondArg = CB.getArgOperand(FnData->SndParam);
  SecondArg = Builder.CreateZExtOrTrunc(SecondArg, IntTy);
  Value *Size = Builder.CreateMul(FirstArg, SecondArg);
  return std::make_pair(Size, Zero);
}

SizeOffsetEvalType
ObjectSizeOffsetEvaluator::visitExtractElementInst(ExtractElementInst&) {
  return unknown();
}

SizeOffsetEvalType
ObjectSizeOffsetEvaluator::visitExtractValueInst(ExtractValueInst&) {
  return unknown();
}

SizeOffsetEvalType
ObjectSizeOffsetEvaluator::visitGEPOperator(GEPOperator &GEP) {
  SizeOffsetEvalType PtrData = compute_(GEP.getPointerOperand());
  if (!bothKnown(PtrData))
    return unknown();

  Value *Offset = emitGEPOffset(&Builder, DL, &GEP, /*NoAssumptions=*/true);
  Offset = Builder.CreateAdd(PtrData.second, Offset);
  return std::make_pair(PtrData.first, Offset);
}

SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitIntToPtrInst(IntToPtrInst&) {
  // clueless
  return unknown();
}

SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitLoadInst(LoadInst &LI) {
  return unknown();
}

SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitPHINode(PHINode &PHI) {
  // Create 2 PHIs: one for size and another for offset.
  PHINode *SizePHI   = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());
  PHINode *OffsetPHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());

  // Insert right away in the cache to handle recursive PHIs.
  CacheMap[&PHI] = std::make_pair(SizePHI, OffsetPHI);

  // Compute offset/size for each PHI incoming pointer.
  for (unsigned i = 0, e = PHI.getNumIncomingValues(); i != e; ++i) {
    Builder.SetInsertPoint(&*PHI.getIncomingBlock(i)->getFirstInsertionPt());
    SizeOffsetEvalType EdgeData = compute_(PHI.getIncomingValue(i));

    if (!bothKnown(EdgeData)) {
      OffsetPHI->replaceAllUsesWith(PoisonValue::get(IntTy));
      OffsetPHI->eraseFromParent();
      InsertedInstructions.erase(OffsetPHI);
      SizePHI->replaceAllUsesWith(PoisonValue::get(IntTy));
      SizePHI->eraseFromParent();
      InsertedInstructions.erase(SizePHI);
      return unknown();
    }
    SizePHI->addIncoming(EdgeData.first, PHI.getIncomingBlock(i));
    OffsetPHI->addIncoming(EdgeData.second, PHI.getIncomingBlock(i));
  }

  Value *Size = SizePHI, *Offset = OffsetPHI;
  if (Value *Tmp = SizePHI->hasConstantValue()) {
    Size = Tmp;
    SizePHI->replaceAllUsesWith(Size);
    SizePHI->eraseFromParent();
    InsertedInstructions.erase(SizePHI);
  }
  if (Value *Tmp = OffsetPHI->hasConstantValue()) {
    Offset = Tmp;
    OffsetPHI->replaceAllUsesWith(Offset);
    OffsetPHI->eraseFromParent();
    InsertedInstructions.erase(OffsetPHI);
  }
  return std::make_pair(Size, Offset);
}

SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitSelectInst(SelectInst &I) {
  SizeOffsetEvalType TrueSide  = compute_(I.getTrueValue());
  SizeOffsetEvalType FalseSide = compute_(I.getFalseValue());

  if (!bothKnown(TrueSide) || !bothKnown(FalseSide))
    return unknown();
  if (TrueSide == FalseSide)
    return TrueSide;

  Value *Size = Builder.CreateSelect(I.getCondition(), TrueSide.first,
                                     FalseSide.first);
  Value *Offset = Builder.CreateSelect(I.getCondition(), TrueSide.second,
                                       FalseSide.second);
  return std::make_pair(Size, Offset);
}

SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitInstruction(Instruction &I) {
  LLVM_DEBUG(dbgs() << "ObjectSizeOffsetEvaluator unknown instruction:" << I
                    << '\n');
  return unknown();
}