Training courses

Kernel and Embedded Linux

Bootlin training courses

Embedded Linux, kernel,
Yocto Project, Buildroot, real-time,
graphics, boot time, debugging...

Bootlin logo

Elixir Cross Referencer

   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
//===- 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/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringRef.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 <utility>

using namespace llvm;

#define DEBUG_TYPE "memory-builtins"

enum AllocType : uint8_t {
  OpNewLike          = 1<<0, // allocates; never returns null
  MallocLike         = 1<<1 | OpNewLike, // allocates; may return null
  AlignedAllocLike   = 1<<2, // allocates with alignment; may return null
  CallocLike         = 1<<3, // allocates + bzero
  ReallocLike        = 1<<4, // reallocates
  StrDupLike         = 1<<5,
  MallocOrCallocLike = MallocLike | CallocLike | AlignedAllocLike,
  AllocLike          = MallocOrCallocLike | StrDupLike,
  AnyAlloc           = AllocLike | ReallocLike
};

struct AllocFnsTy {
  AllocType AllocTy;
  unsigned NumParams;
  // First and Second size parameters (or -1 if unused)
  int FstParam, SndParam;
};

// 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_malloc,              {MallocLike,  1, 0,  -1}},
  {LibFunc_valloc,              {MallocLike,  1, 0,  -1}},
  {LibFunc_Znwj,                {OpNewLike,   1, 0,  -1}}, // new(unsigned int)
  {LibFunc_ZnwjRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new(unsigned int, nothrow)
  {LibFunc_ZnwjSt11align_val_t, {OpNewLike,   2, 0,  -1}}, // new(unsigned int, align_val_t)
  {LibFunc_ZnwjSt11align_val_tRKSt9nothrow_t, // new(unsigned int, align_val_t, nothrow)
                                {MallocLike,  3, 0,  -1}},
  {LibFunc_Znwm,                {OpNewLike,   1, 0,  -1}}, // new(unsigned long)
  {LibFunc_ZnwmRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new(unsigned long, nothrow)
  {LibFunc_ZnwmSt11align_val_t, {OpNewLike,   2, 0,  -1}}, // new(unsigned long, align_val_t)
  {LibFunc_ZnwmSt11align_val_tRKSt9nothrow_t, // new(unsigned long, align_val_t, nothrow)
                                {MallocLike,  3, 0,  -1}},
  {LibFunc_Znaj,                {OpNewLike,   1, 0,  -1}}, // new[](unsigned int)
  {LibFunc_ZnajRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new[](unsigned int, nothrow)
  {LibFunc_ZnajSt11align_val_t, {OpNewLike,   2, 0,  -1}}, // new[](unsigned int, align_val_t)
  {LibFunc_ZnajSt11align_val_tRKSt9nothrow_t, // new[](unsigned int, align_val_t, nothrow)
                                {MallocLike,  3, 0,  -1}},
  {LibFunc_Znam,                {OpNewLike,   1, 0,  -1}}, // new[](unsigned long)
  {LibFunc_ZnamRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new[](unsigned long, nothrow)
  {LibFunc_ZnamSt11align_val_t, {OpNewLike,   2, 0,  -1}}, // new[](unsigned long, align_val_t)
  {LibFunc_ZnamSt11align_val_tRKSt9nothrow_t, // new[](unsigned long, align_val_t, nothrow)
                                 {MallocLike,  3, 0,  -1}},
  {LibFunc_msvc_new_int,         {OpNewLike,   1, 0,  -1}}, // new(unsigned int)
  {LibFunc_msvc_new_int_nothrow, {MallocLike,  2, 0,  -1}}, // new(unsigned int, nothrow)
  {LibFunc_msvc_new_longlong,         {OpNewLike,   1, 0,  -1}}, // new(unsigned long long)
  {LibFunc_msvc_new_longlong_nothrow, {MallocLike,  2, 0,  -1}}, // new(unsigned long long, nothrow)
  {LibFunc_msvc_new_array_int,         {OpNewLike,   1, 0,  -1}}, // new[](unsigned int)
  {LibFunc_msvc_new_array_int_nothrow, {MallocLike,  2, 0,  -1}}, // new[](unsigned int, nothrow)
  {LibFunc_msvc_new_array_longlong,         {OpNewLike,   1, 0,  -1}}, // new[](unsigned long long)
  {LibFunc_msvc_new_array_longlong_nothrow, {MallocLike,  2, 0,  -1}}, // new[](unsigned long long, nothrow)
  {LibFunc_aligned_alloc,       {AlignedAllocLike, 2, 1,  -1}},
  {LibFunc_calloc,              {CallocLike,  2, 0,   1}},
  {LibFunc_realloc,             {ReallocLike, 2, 1,  -1}},
  {LibFunc_reallocf,            {ReallocLike, 2, 1,  -1}},
  {LibFunc_strdup,              {StrDupLike,  1, -1, -1}},
  {LibFunc_strndup,             {StrDupLike,  2, 1,  -1}}
  // TODO: Handle "int posix_memalign(void **, size_t, size_t)"
};

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

  if (LookThroughBitCast)
    V = V->stripPointerCasts();

  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 either a call to a
/// known allocation function, or a call to a function with the allocsize
/// attribute.
static Optional<AllocFnsTy>
getAllocationDataForFunction(const Function *Callee, AllocType AllocTy,
                             const TargetLibraryInfo *TLI) {
  // Make sure that the function is available.
  StringRef FnName = Callee->getName();
  LibFunc TLIFn;
  if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
    return None;

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

  if (Iter == std::end(AllocationFnData))
    return None;

  const AllocFnsTy *FnData = &Iter->second;
  if ((FnData->AllocTy & AllocTy) != FnData->AllocTy)
    return None;

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

  if (FTy->getReturnType() == Type::getInt8PtrTy(FTy->getContext()) &&
      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 None;
}

static Optional<AllocFnsTy> getAllocationData(const Value *V, AllocType AllocTy,
                                              const TargetLibraryInfo *TLI,
                                              bool LookThroughBitCast = false) {
  bool IsNoBuiltinCall;
  if (const Function *Callee =
          getCalledFunction(V, LookThroughBitCast, IsNoBuiltinCall))
    if (!IsNoBuiltinCall)
      return getAllocationDataForFunction(Callee, AllocTy, TLI);
  return None;
}

static Optional<AllocFnsTy>
getAllocationData(const Value *V, AllocType AllocTy,
                  function_ref<const TargetLibraryInfo &(Function &)> GetTLI,
                  bool LookThroughBitCast = false) {
  bool IsNoBuiltinCall;
  if (const Function *Callee =
          getCalledFunction(V, LookThroughBitCast, IsNoBuiltinCall))
    if (!IsNoBuiltinCall)
      return getAllocationDataForFunction(
          Callee, AllocTy, &GetTLI(const_cast<Function &>(*Callee)));
  return None;
}

static Optional<AllocFnsTy> getAllocationSize(const Value *V,
                                              const TargetLibraryInfo *TLI) {
  bool IsNoBuiltinCall;
  const Function *Callee =
      getCalledFunction(V, /*LookThroughBitCast=*/false, IsNoBuiltinCall);
  if (!Callee)
    return None;

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

  Attribute Attr = Callee->getFnAttribute(Attribute::AllocSize);
  if (Attr == Attribute())
    return None;

  std::pair<unsigned, 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.getValueOr(-1);
  return Result;
}

static bool hasNoAliasAttr(const Value *V, bool LookThroughBitCast) {
  const auto *CB =
      dyn_cast<CallBase>(LookThroughBitCast ? V->stripPointerCasts() : V);
  return CB && CB->hasRetAttr(Attribute::NoAlias);
}

/// 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,
                          bool LookThroughBitCast) {
  return getAllocationData(V, AnyAlloc, TLI, LookThroughBitCast).hasValue();
}
bool llvm::isAllocationFn(
    const Value *V, function_ref<const TargetLibraryInfo &(Function &)> GetTLI,
    bool LookThroughBitCast) {
  return getAllocationData(V, AnyAlloc, GetTLI, LookThroughBitCast).hasValue();
}

/// Tests if a value is a call or invoke to a function that returns a
/// NoAlias pointer (including malloc/calloc/realloc/strdup-like functions).
bool llvm::isNoAliasFn(const Value *V, const TargetLibraryInfo *TLI,
                       bool LookThroughBitCast) {
  // it's safe to consider realloc as noalias since accessing the original
  // pointer is undefined behavior
  return isAllocationFn(V, TLI, LookThroughBitCast) ||
         hasNoAliasAttr(V, LookThroughBitCast);
}

/// Tests if a value is a call or invoke to a library function that
/// allocates uninitialized memory (such as malloc).
bool llvm::isMallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
                          bool LookThroughBitCast) {
  return getAllocationData(V, MallocLike, TLI, LookThroughBitCast).hasValue();
}
bool llvm::isMallocLikeFn(
    const Value *V, function_ref<const TargetLibraryInfo &(Function &)> GetTLI,
    bool LookThroughBitCast) {
  return getAllocationData(V, MallocLike, GetTLI, LookThroughBitCast)
      .hasValue();
}

/// Tests if a value is a call or invoke to a library function that
/// allocates uninitialized memory with alignment (such as aligned_alloc).
bool llvm::isAlignedAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
                                bool LookThroughBitCast) {
  return getAllocationData(V, AlignedAllocLike, TLI, LookThroughBitCast)
      .hasValue();
}
bool llvm::isAlignedAllocLikeFn(
    const Value *V, function_ref<const TargetLibraryInfo &(Function &)> GetTLI,
    bool LookThroughBitCast) {
  return getAllocationData(V, AlignedAllocLike, GetTLI, LookThroughBitCast)
      .hasValue();
}

/// Tests if a value is a call or invoke to a library function that
/// allocates zero-filled memory (such as calloc).
bool llvm::isCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
                          bool LookThroughBitCast) {
  return getAllocationData(V, CallocLike, TLI, LookThroughBitCast).hasValue();
}

/// 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,
                                  bool LookThroughBitCast) {
  return getAllocationData(V, MallocOrCallocLike, TLI,
                           LookThroughBitCast).hasValue();
}

/// 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,
                         bool LookThroughBitCast) {
  return getAllocationData(V, AllocLike, TLI, LookThroughBitCast).hasValue();
}

/// Tests if a value is a call or invoke to a library function that
/// reallocates memory (e.g., realloc).
bool llvm::isReallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
                     bool LookThroughBitCast) {
  return getAllocationData(V, ReallocLike, TLI, LookThroughBitCast).hasValue();
}

/// 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, const TargetLibraryInfo *TLI) {
  return getAllocationDataForFunction(F, ReallocLike, TLI).hasValue();
}

/// Tests if a value is a call or invoke to a library function that
/// allocates memory and throws if an allocation failed (e.g., new).
bool llvm::isOpNewLikeFn(const Value *V, const TargetLibraryInfo *TLI,
                     bool LookThroughBitCast) {
  return getAllocationData(V, OpNewLike, TLI, LookThroughBitCast).hasValue();
}

/// Tests if a value is a call or invoke to a library function that
/// allocates memory (strdup, strndup).
bool llvm::isStrdupLikeFn(const Value *V, const TargetLibraryInfo *TLI,
                          bool LookThroughBitCast) {
  return getAllocationData(V, StrDupLike, TLI, LookThroughBitCast).hasValue();
}

/// extractMallocCall - Returns the corresponding CallInst if the instruction
/// is a malloc call.  Since CallInst::CreateMalloc() only creates calls, we
/// ignore InvokeInst here.
const CallInst *llvm::extractMallocCall(
    const Value *I,
    function_ref<const TargetLibraryInfo &(Function &)> GetTLI) {
  return isMallocLikeFn(I, GetTLI) ? dyn_cast<CallInst>(I) : nullptr;
}

static Value *computeArraySize(const CallInst *CI, const DataLayout &DL,
                               const TargetLibraryInfo *TLI,
                               bool LookThroughSExt = false) {
  if (!CI)
    return nullptr;

  // The size of the malloc's result type must be known to determine array size.
  Type *T = getMallocAllocatedType(CI, TLI);
  if (!T || !T->isSized())
    return nullptr;

  unsigned ElementSize = DL.getTypeAllocSize(T);
  if (StructType *ST = dyn_cast<StructType>(T))
    ElementSize = DL.getStructLayout(ST)->getSizeInBytes();

  // If malloc call's arg can be determined to be a multiple of ElementSize,
  // return the multiple.  Otherwise, return NULL.
  Value *MallocArg = CI->getArgOperand(0);
  Value *Multiple = nullptr;
  if (ComputeMultiple(MallocArg, ElementSize, Multiple, LookThroughSExt))
    return Multiple;

  return nullptr;
}

/// getMallocType - Returns the PointerType resulting from the malloc call.
/// The PointerType depends on the number of bitcast uses of the malloc call:
///   0: PointerType is the calls' return type.
///   1: PointerType is the bitcast's result type.
///  >1: Unique PointerType cannot be determined, return NULL.
PointerType *llvm::getMallocType(const CallInst *CI,
                                 const TargetLibraryInfo *TLI) {
  assert(isMallocLikeFn(CI, TLI) && "getMallocType and not malloc call");

  PointerType *MallocType = nullptr;
  unsigned NumOfBitCastUses = 0;

  // Determine if CallInst has a bitcast use.
  for (Value::const_user_iterator UI = CI->user_begin(), E = CI->user_end();
       UI != E;)
    if (const BitCastInst *BCI = dyn_cast<BitCastInst>(*UI++)) {
      MallocType = cast<PointerType>(BCI->getDestTy());
      NumOfBitCastUses++;
    }

  // Malloc call has 1 bitcast use, so type is the bitcast's destination type.
  if (NumOfBitCastUses == 1)
    return MallocType;

  // Malloc call was not bitcast, so type is the malloc function's return type.
  if (NumOfBitCastUses == 0)
    return cast<PointerType>(CI->getType());

  // Type could not be determined.
  return nullptr;
}

/// getMallocAllocatedType - Returns the Type allocated by malloc call.
/// The Type depends on the number of bitcast uses of the malloc call:
///   0: PointerType is the malloc calls' return type.
///   1: PointerType is the bitcast's result type.
///  >1: Unique PointerType cannot be determined, return NULL.
Type *llvm::getMallocAllocatedType(const CallInst *CI,
                                   const TargetLibraryInfo *TLI) {
  PointerType *PT = getMallocType(CI, TLI);
  return PT ? PT->getElementType() : nullptr;
}

/// getMallocArraySize - Returns the array size of a malloc call.  If the
/// argument passed to malloc is a multiple of the size of the malloced type,
/// then return that multiple.  For non-array mallocs, the multiple is
/// constant 1.  Otherwise, return NULL for mallocs whose array size cannot be
/// determined.
Value *llvm::getMallocArraySize(CallInst *CI, const DataLayout &DL,
                                const TargetLibraryInfo *TLI,
                                bool LookThroughSExt) {
  assert(isMallocLikeFn(CI, TLI) && "getMallocArraySize and not malloc call");
  return computeArraySize(CI, DL, TLI, LookThroughSExt);
}

/// extractCallocCall - Returns the corresponding CallInst if the instruction
/// is a calloc call.
const CallInst *llvm::extractCallocCall(const Value *I,
                                        const TargetLibraryInfo *TLI) {
  return isCallocLikeFn(I, TLI) ? cast<CallInst>(I) : nullptr;
}

/// isLibFreeFunction - Returns true if the function is a builtin free()
bool llvm::isLibFreeFunction(const Function *F, const LibFunc TLIFn) {
  unsigned ExpectedNumParams;
  if (TLIFn == LibFunc_free ||
      TLIFn == LibFunc_ZdlPv || // operator delete(void*)
      TLIFn == LibFunc_ZdaPv || // operator delete[](void*)
      TLIFn == LibFunc_msvc_delete_ptr32 || // operator delete(void*)
      TLIFn == LibFunc_msvc_delete_ptr64 || // operator delete(void*)
      TLIFn == LibFunc_msvc_delete_array_ptr32 || // operator delete[](void*)
      TLIFn == LibFunc_msvc_delete_array_ptr64)   // operator delete[](void*)
    ExpectedNumParams = 1;
  else if (TLIFn == LibFunc_ZdlPvj ||              // delete(void*, uint)
           TLIFn == LibFunc_ZdlPvm ||              // delete(void*, ulong)
           TLIFn == LibFunc_ZdlPvRKSt9nothrow_t || // delete(void*, nothrow)
           TLIFn == LibFunc_ZdlPvSt11align_val_t || // delete(void*, align_val_t)
           TLIFn == LibFunc_ZdaPvj ||              // delete[](void*, uint)
           TLIFn == LibFunc_ZdaPvm ||              // delete[](void*, ulong)
           TLIFn == LibFunc_ZdaPvRKSt9nothrow_t || // delete[](void*, nothrow)
           TLIFn == LibFunc_ZdaPvSt11align_val_t || // delete[](void*, align_val_t)
           TLIFn == LibFunc_msvc_delete_ptr32_int ||      // delete(void*, uint)
           TLIFn == LibFunc_msvc_delete_ptr64_longlong || // delete(void*, ulonglong)
           TLIFn == LibFunc_msvc_delete_ptr32_nothrow || // delete(void*, nothrow)
           TLIFn == LibFunc_msvc_delete_ptr64_nothrow || // delete(void*, nothrow)
           TLIFn == LibFunc_msvc_delete_array_ptr32_int ||      // delete[](void*, uint)
           TLIFn == LibFunc_msvc_delete_array_ptr64_longlong || // delete[](void*, ulonglong)
           TLIFn == LibFunc_msvc_delete_array_ptr32_nothrow || // delete[](void*, nothrow)
           TLIFn == LibFunc_msvc_delete_array_ptr64_nothrow)   // delete[](void*, nothrow)
    ExpectedNumParams = 2;
  else if (TLIFn == LibFunc_ZdaPvSt11align_val_tRKSt9nothrow_t || // delete(void*, align_val_t, nothrow)
           TLIFn == LibFunc_ZdlPvSt11align_val_tRKSt9nothrow_t || // delete[](void*, align_val_t, nothrow)
           TLIFn == LibFunc_ZdlPvjSt11align_val_t || // delete(void*, unsigned long, align_val_t)
           TLIFn == LibFunc_ZdlPvmSt11align_val_t || // delete(void*, unsigned long, align_val_t)
           TLIFn == LibFunc_ZdaPvjSt11align_val_t || // delete[](void*, unsigned int, align_val_t)
           TLIFn == LibFunc_ZdaPvmSt11align_val_t) // delete[](void*, unsigned long, align_val_t)
    ExpectedNumParams = 3;
  else
    return false;

  // 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() != ExpectedNumParams)
    return false;
  if (FTy->getParamType(0) != Type::getInt8PtrTy(F->getContext()))
    return false;

  return true;
}

/// isFreeCall - Returns non-null if the value is a call to the builtin free()
const CallInst *llvm::isFreeCall(const Value *I, const TargetLibraryInfo *TLI) {
  bool IsNoBuiltinCall;
  const Function *Callee =
      getCalledFunction(I, /*LookThroughBitCast=*/false, IsNoBuiltinCall);
  if (Callee == nullptr || IsNoBuiltinCall)
    return nullptr;

  StringRef FnName = Callee->getName();
  LibFunc TLIFn;
  if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
    return nullptr;

  return isLibFreeFunction(Callee, TLIFn) ? dyn_cast<CallInst>(I) : 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) {
  assert(ObjectSize->getIntrinsicID() == Intrinsic::objectsize &&
         "ObjectSize must be a call to llvm.objectsize!");

  bool MaxVal = cast<ConstantInt>(ObjectSize->getArgOperand(1))->isZero();
  ObjectSizeOpts EvalOptions;
  // 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::Exact;

  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);
      return Builder.CreateSelect(UseZero, ConstantInt::get(ResultType, 0),
                                  ResultSize);
    }
  }

  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, uint64_t Alignment) {
  if (Options.RoundToAlign && Alignment)
    return APInt(IntTyBits, alignTo(Size.getZExtValue(), Align(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) {
  IntTyBits = DL.getIndexTypeSizeInBits(V->getType());
  Zero = APInt::getNullValue(IntTyBits);

  V = V->stripPointerCasts();
  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();

    if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
      return visitGEPOperator(*GEP);
    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);
  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
    if (CE->getOpcode() == Instruction::IntToPtr)
      return unknown(); // clueless
    if (CE->getOpcode() == Instruction::GetElementPtr)
      return visitGEPOperator(cast<GEPOperator>(*CE));
  }

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

/// 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.
bool ObjectSizeOffsetVisitor::CheckedZextOrTrunc(APInt &I) {
  // 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;
}

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

  if (isa<ScalableVectorType>(I.getAllocatedType()))
    return unknown();

  APInt Size(IntTyBits, DL.getTypeAllocSize(I.getAllocatedType()));
  if (!I.isArrayAllocation())
    return std::make_pair(align(Size, I.getAlignment()), 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.getAlignment()),
                                                 Zero);
  }
  return unknown();
}

SizeOffsetType ObjectSizeOffsetVisitor::visitArgument(Argument &A) {
  // No interprocedural analysis is done at the moment.
  if (!A.hasPassPointeeByValueAttr()) {
    ++ObjectVisitorArgument;
    return unknown();
  }
  PointerType *PT = cast<PointerType>(A.getType());
  APInt Size(IntTyBits, DL.getTypeAllocSize(PT->getElementType()));
  return std::make_pair(align(Size, A.getParamAlignment()), Zero);
}

SizeOffsetType ObjectSizeOffsetVisitor::visitCallBase(CallBase &CB) {
  Optional<AllocFnsTy> FnData = getAllocationSize(&CB, TLI);
  if (!FnData)
    return unknown();

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

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

      APInt MaxSize = Arg->getValue().zextOrSelf(IntTyBits);
      if (Size.ugt(MaxSize))
        Size = MaxSize + 1;
    }
    return std::make_pair(Size, Zero);
  }

  ConstantInt *Arg = dyn_cast<ConstantInt>(CB.getArgOperand(FnData->FstParam));
  if (!Arg)
    return unknown();

  APInt Size = Arg->getValue();
  if (!CheckedZextOrTrunc(Size))
    return unknown();

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

  Arg = dyn_cast<ConstantInt>(CB.getArgOperand(FnData->SndParam));
  if (!Arg)
    return unknown();

  APInt NumElems = Arg->getValue();
  if (!CheckedZextOrTrunc(NumElems))
    return unknown();

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

  // TODO: handle more standard functions (+ wchar cousins):
  // - strdup / strndup
  // - strcpy / strncpy
  // - strcat / strncat
  // - memcpy / memmove
  // - strcat / strncat
  // - memset
}

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::visitGEPOperator(GEPOperator &GEP) {
  SizeOffsetType PtrData = compute(GEP.getPointerOperand());
  APInt Offset(DL.getIndexTypeSizeInBits(GEP.getPointerOperand()->getType()), 0);
  if (!bothKnown(PtrData) || !GEP.accumulateConstantOffset(DL, Offset))
    return unknown();

  return std::make_pair(PtrData.first, PtrData.second + Offset);
}

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.getAlignment()), Zero);
}

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

SizeOffsetType ObjectSizeOffsetVisitor::visitLoadInst(LoadInst&) {
  ++ObjectVisitorLoad;
  return unknown();
}

SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) {
  // too complex to analyze statically.
  return unknown();
}

SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) {
  SizeOffsetType TrueSide  = compute(I.getTrueValue());
  SizeOffsetType FalseSide = compute(I.getFalseValue());
  if (bothKnown(TrueSide) && bothKnown(FalseSide)) {
    if (TrueSide == FalseSide) {
        return TrueSide;
    }

    APInt TrueResult = getSizeWithOverflow(TrueSide);
    APInt FalseResult = getSizeWithOverflow(FalseSide);

    if (TrueResult == FalseResult) {
      return TrueSide;
    }
    if (Options.EvalMode == ObjectSizeOpts::Mode::Min) {
      if (TrueResult.slt(FalseResult))
        return TrueSide;
      return FalseSide;
    }
    if (Options.EvalMode == ObjectSizeOpts::Mode::Max) {
      if (TrueResult.sgt(FalseResult))
        return TrueSide;
      return FalseSide;
    }
  }
  return unknown();
}

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(UndefValue::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());
  Value *ArraySize = I.getArraySize();
  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) {
  Optional<AllocFnsTy> FnData = getAllocationSize(&CB, TLI);
  if (!FnData)
    return unknown();

  // Handle strdup-like functions separately.
  if (FnData->AllocTy == StrDupLike) {
    // TODO
    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);

  // TODO: handle more standard functions (+ wchar cousins):
  // - strdup / strndup
  // - strcpy / strncpy
  // - strcat / strncat
  // - memcpy / memmove
  // - strcat / strncat
  // - memset
}

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&) {
  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(UndefValue::get(IntTy));
      OffsetPHI->eraseFromParent();
      InsertedInstructions.erase(OffsetPHI);
      SizePHI->replaceAllUsesWith(UndefValue::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();
}