llvm.org GIT mirror llvm / 1b27914 lib / Analysis / MemoryDependenceAnalysis.cpp
1b27914

Tree @1b27914 (Download .tar.gz)

MemoryDependenceAnalysis.cpp @1b27914raw · history · blame

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
//===- MemoryDependenceAnalysis.cpp - Mem Deps Implementation -------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements an analysis that determines, for a given memory
// operation, what preceding memory operations it depends on.  It builds on
// alias analysis information, and tries to provide a lazy, caching interface to
// a common kind of alias information query.
//
//===----------------------------------------------------------------------===//

#include "llvm/Analysis/MemoryDependenceAnalysis.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/PHITransAddr.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/PredIteratorCache.h"
#include "llvm/Support/Debug.h"
using namespace llvm;

#define DEBUG_TYPE "memdep"

STATISTIC(NumCacheNonLocal, "Number of fully cached non-local responses");
STATISTIC(NumCacheDirtyNonLocal, "Number of dirty cached non-local responses");
STATISTIC(NumUncacheNonLocal, "Number of uncached non-local responses");

STATISTIC(NumCacheNonLocalPtr,
          "Number of fully cached non-local ptr responses");
STATISTIC(NumCacheDirtyNonLocalPtr,
          "Number of cached, but dirty, non-local ptr responses");
STATISTIC(NumUncacheNonLocalPtr,
          "Number of uncached non-local ptr responses");
STATISTIC(NumCacheCompleteNonLocalPtr,
          "Number of block queries that were completely cached");

// Limit for the number of instructions to scan in a block.
static const unsigned int BlockScanLimit = 100;

// Limit on the number of memdep results to process.
static const unsigned int NumResultsLimit = 100;

char MemoryDependenceAnalysis::ID = 0;

// Register this pass...
INITIALIZE_PASS_BEGIN(MemoryDependenceAnalysis, "memdep",
                "Memory Dependence Analysis", false, true)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_END(MemoryDependenceAnalysis, "memdep",
                      "Memory Dependence Analysis", false, true)

MemoryDependenceAnalysis::MemoryDependenceAnalysis()
    : FunctionPass(ID), PredCache() {
  initializeMemoryDependenceAnalysisPass(*PassRegistry::getPassRegistry());
}
MemoryDependenceAnalysis::~MemoryDependenceAnalysis() {
}

/// Clean up memory in between runs
void MemoryDependenceAnalysis::releaseMemory() {
  LocalDeps.clear();
  NonLocalDeps.clear();
  NonLocalPointerDeps.clear();
  ReverseLocalDeps.clear();
  ReverseNonLocalDeps.clear();
  ReverseNonLocalPtrDeps.clear();
  PredCache->clear();
}



/// getAnalysisUsage - Does not modify anything.  It uses Alias Analysis.
///
void MemoryDependenceAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
  AU.setPreservesAll();
  AU.addRequired<AssumptionCacheTracker>();
  AU.addRequiredTransitive<AliasAnalysis>();
}

bool MemoryDependenceAnalysis::runOnFunction(Function &F) {
  AA = &getAnalysis<AliasAnalysis>();
  AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
  DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
  DL = DLP ? &DLP->getDataLayout() : nullptr;
  DominatorTreeWrapperPass *DTWP =
      getAnalysisIfAvailable<DominatorTreeWrapperPass>();
  DT = DTWP ? &DTWP->getDomTree() : nullptr;
  if (!PredCache)
    PredCache.reset(new PredIteratorCache());
  return false;
}

/// RemoveFromReverseMap - This is a helper function that removes Val from
/// 'Inst's set in ReverseMap.  If the set becomes empty, remove Inst's entry.
template <typename KeyTy>
static void RemoveFromReverseMap(DenseMap<Instruction*,
                                 SmallPtrSet<KeyTy, 4> > &ReverseMap,
                                 Instruction *Inst, KeyTy Val) {
  typename DenseMap<Instruction*, SmallPtrSet<KeyTy, 4> >::iterator
  InstIt = ReverseMap.find(Inst);
  assert(InstIt != ReverseMap.end() && "Reverse map out of sync?");
  bool Found = InstIt->second.erase(Val);
  assert(Found && "Invalid reverse map!"); (void)Found;
  if (InstIt->second.empty())
    ReverseMap.erase(InstIt);
}

/// GetLocation - If the given instruction references a specific memory
/// location, fill in Loc with the details, otherwise set Loc.Ptr to null.
/// Return a ModRefInfo value describing the general behavior of the
/// instruction.
static
AliasAnalysis::ModRefResult GetLocation(const Instruction *Inst,
                                        AliasAnalysis::Location &Loc,
                                        AliasAnalysis *AA) {
  if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
    if (LI->isUnordered()) {
      Loc = AA->getLocation(LI);
      return AliasAnalysis::Ref;
    }
    if (LI->getOrdering() == Monotonic) {
      Loc = AA->getLocation(LI);
      return AliasAnalysis::ModRef;
    }
    Loc = AliasAnalysis::Location();
    return AliasAnalysis::ModRef;
  }

  if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
    if (SI->isUnordered()) {
      Loc = AA->getLocation(SI);
      return AliasAnalysis::Mod;
    }
    if (SI->getOrdering() == Monotonic) {
      Loc = AA->getLocation(SI);
      return AliasAnalysis::ModRef;
    }
    Loc = AliasAnalysis::Location();
    return AliasAnalysis::ModRef;
  }

  if (const VAArgInst *V = dyn_cast<VAArgInst>(Inst)) {
    Loc = AA->getLocation(V);
    return AliasAnalysis::ModRef;
  }

  if (const CallInst *CI = isFreeCall(Inst, AA->getTargetLibraryInfo())) {
    // calls to free() deallocate the entire structure
    Loc = AliasAnalysis::Location(CI->getArgOperand(0));
    return AliasAnalysis::Mod;
  }

  if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
    AAMDNodes AAInfo;

    switch (II->getIntrinsicID()) {
    case Intrinsic::lifetime_start:
    case Intrinsic::lifetime_end:
    case Intrinsic::invariant_start:
      II->getAAMetadata(AAInfo);
      Loc = AliasAnalysis::Location(II->getArgOperand(1),
                                    cast<ConstantInt>(II->getArgOperand(0))
                                      ->getZExtValue(), AAInfo);
      // These intrinsics don't really modify the memory, but returning Mod
      // will allow them to be handled conservatively.
      return AliasAnalysis::Mod;
    case Intrinsic::invariant_end:
      II->getAAMetadata(AAInfo);
      Loc = AliasAnalysis::Location(II->getArgOperand(2),
                                    cast<ConstantInt>(II->getArgOperand(1))
                                      ->getZExtValue(), AAInfo);
      // These intrinsics don't really modify the memory, but returning Mod
      // will allow them to be handled conservatively.
      return AliasAnalysis::Mod;
    default:
      break;
    }
  }

  // Otherwise, just do the coarse-grained thing that always works.
  if (Inst->mayWriteToMemory())
    return AliasAnalysis::ModRef;
  if (Inst->mayReadFromMemory())
    return AliasAnalysis::Ref;
  return AliasAnalysis::NoModRef;
}

/// getCallSiteDependencyFrom - Private helper for finding the local
/// dependencies of a call site.
MemDepResult MemoryDependenceAnalysis::
getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall,
                          BasicBlock::iterator ScanIt, BasicBlock *BB) {
  unsigned Limit = BlockScanLimit;

  // Walk backwards through the block, looking for dependencies
  while (ScanIt != BB->begin()) {
    // Limit the amount of scanning we do so we don't end up with quadratic
    // running time on extreme testcases.
    --Limit;
    if (!Limit)
      return MemDepResult::getUnknown();

    Instruction *Inst = --ScanIt;

    // If this inst is a memory op, get the pointer it accessed
    AliasAnalysis::Location Loc;
    AliasAnalysis::ModRefResult MR = GetLocation(Inst, Loc, AA);
    if (Loc.Ptr) {
      // A simple instruction.
      if (AA->getModRefInfo(CS, Loc) != AliasAnalysis::NoModRef)
        return MemDepResult::getClobber(Inst);
      continue;
    }

    if (CallSite InstCS = cast<Value>(Inst)) {
      // Debug intrinsics don't cause dependences.
      if (isa<DbgInfoIntrinsic>(Inst)) continue;
      // If these two calls do not interfere, look past it.
      switch (AA->getModRefInfo(CS, InstCS)) {
      case AliasAnalysis::NoModRef:
        // If the two calls are the same, return InstCS as a Def, so that
        // CS can be found redundant and eliminated.
        if (isReadOnlyCall && !(MR & AliasAnalysis::Mod) &&
            CS.getInstruction()->isIdenticalToWhenDefined(Inst))
          return MemDepResult::getDef(Inst);

        // Otherwise if the two calls don't interact (e.g. InstCS is readnone)
        // keep scanning.
        continue;
      default:
        return MemDepResult::getClobber(Inst);
      }
    }

    // If we could not obtain a pointer for the instruction and the instruction
    // touches memory then assume that this is a dependency.
    if (MR != AliasAnalysis::NoModRef)
      return MemDepResult::getClobber(Inst);
  }

  // No dependence found.  If this is the entry block of the function, it is
  // unknown, otherwise it is non-local.
  if (BB != &BB->getParent()->getEntryBlock())
    return MemDepResult::getNonLocal();
  return MemDepResult::getNonFuncLocal();
}

/// isLoadLoadClobberIfExtendedToFullWidth - Return true if LI is a load that
/// would fully overlap MemLoc if done as a wider legal integer load.
///
/// MemLocBase, MemLocOffset are lazily computed here the first time the
/// base/offs of memloc is needed.
static bool
isLoadLoadClobberIfExtendedToFullWidth(const AliasAnalysis::Location &MemLoc,
                                       const Value *&MemLocBase,
                                       int64_t &MemLocOffs,
                                       const LoadInst *LI,
                                       const DataLayout *DL) {
  // If we have no target data, we can't do this.
  if (!DL) return false;

  // If we haven't already computed the base/offset of MemLoc, do so now.
  if (!MemLocBase)
    MemLocBase = GetPointerBaseWithConstantOffset(MemLoc.Ptr, MemLocOffs, DL);

  unsigned Size = MemoryDependenceAnalysis::
    getLoadLoadClobberFullWidthSize(MemLocBase, MemLocOffs, MemLoc.Size,
                                    LI, *DL);
  return Size != 0;
}

/// getLoadLoadClobberFullWidthSize - This is a little bit of analysis that
/// looks at a memory location for a load (specified by MemLocBase, Offs,
/// and Size) and compares it against a load.  If the specified load could
/// be safely widened to a larger integer load that is 1) still efficient,
/// 2) safe for the target, and 3) would provide the specified memory
/// location value, then this function returns the size in bytes of the
/// load width to use.  If not, this returns zero.
unsigned MemoryDependenceAnalysis::
getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs,
                                unsigned MemLocSize, const LoadInst *LI,
                                const DataLayout &DL) {
  // We can only extend simple integer loads.
  if (!isa<IntegerType>(LI->getType()) || !LI->isSimple()) return 0;

  // Load widening is hostile to ThreadSanitizer: it may cause false positives
  // or make the reports more cryptic (access sizes are wrong).
  if (LI->getParent()->getParent()->getAttributes().
      hasAttribute(AttributeSet::FunctionIndex, Attribute::SanitizeThread))
    return 0;

  // Get the base of this load.
  int64_t LIOffs = 0;
  const Value *LIBase =
    GetPointerBaseWithConstantOffset(LI->getPointerOperand(), LIOffs, &DL);

  // If the two pointers are not based on the same pointer, we can't tell that
  // they are related.
  if (LIBase != MemLocBase) return 0;

  // Okay, the two values are based on the same pointer, but returned as
  // no-alias.  This happens when we have things like two byte loads at "P+1"
  // and "P+3".  Check to see if increasing the size of the "LI" load up to its
  // alignment (or the largest native integer type) will allow us to load all
  // the bits required by MemLoc.

  // If MemLoc is before LI, then no widening of LI will help us out.
  if (MemLocOffs < LIOffs) return 0;

  // Get the alignment of the load in bytes.  We assume that it is safe to load
  // any legal integer up to this size without a problem.  For example, if we're
  // looking at an i8 load on x86-32 that is known 1024 byte aligned, we can
  // widen it up to an i32 load.  If it is known 2-byte aligned, we can widen it
  // to i16.
  unsigned LoadAlign = LI->getAlignment();

  int64_t MemLocEnd = MemLocOffs+MemLocSize;

  // If no amount of rounding up will let MemLoc fit into LI, then bail out.
  if (LIOffs+LoadAlign < MemLocEnd) return 0;

  // This is the size of the load to try.  Start with the next larger power of
  // two.
  unsigned NewLoadByteSize = LI->getType()->getPrimitiveSizeInBits()/8U;
  NewLoadByteSize = NextPowerOf2(NewLoadByteSize);

  while (1) {
    // If this load size is bigger than our known alignment or would not fit
    // into a native integer register, then we fail.
    if (NewLoadByteSize > LoadAlign ||
        !DL.fitsInLegalInteger(NewLoadByteSize*8))
      return 0;

    if (LIOffs+NewLoadByteSize > MemLocEnd &&
        LI->getParent()->getParent()->getAttributes().
          hasAttribute(AttributeSet::FunctionIndex, Attribute::SanitizeAddress))
      // We will be reading past the location accessed by the original program.
      // While this is safe in a regular build, Address Safety analysis tools
      // may start reporting false warnings. So, don't do widening.
      return 0;

    // If a load of this width would include all of MemLoc, then we succeed.
    if (LIOffs+NewLoadByteSize >= MemLocEnd)
      return NewLoadByteSize;

    NewLoadByteSize <<= 1;
  }
}

/// getPointerDependencyFrom - Return the instruction on which a memory
/// location depends.  If isLoad is true, this routine ignores may-aliases with
/// read-only operations.  If isLoad is false, this routine ignores may-aliases
/// with reads from read-only locations.  If possible, pass the query
/// instruction as well; this function may take advantage of the metadata
/// annotated to the query instruction to refine the result.
MemDepResult MemoryDependenceAnalysis::
getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
                         BasicBlock::iterator ScanIt, BasicBlock *BB,
                         Instruction *QueryInst) {

  const Value *MemLocBase = nullptr;
  int64_t MemLocOffset = 0;
  unsigned Limit = BlockScanLimit;
  bool isInvariantLoad = false;

  // We must be careful with atomic accesses, as they may allow another thread
  //   to touch this location, cloberring it. We are conservative: if the
  //   QueryInst is not a simple (non-atomic) memory access, we automatically
  //   return getClobber.
  // If it is simple, we know based on the results of
  // "Compiler testing via a theory of sound optimisations in the C11/C++11
  //   memory model" in PLDI 2013, that a non-atomic location can only be
  //   clobbered between a pair of a release and an acquire action, with no
  //   access to the location in between.
  // Here is an example for giving the general intuition behind this rule.
  // In the following code:
  //   store x 0;
  //   release action; [1]
  //   acquire action; [4]
  //   %val = load x;
  // It is unsafe to replace %val by 0 because another thread may be running:
  //   acquire action; [2]
  //   store x 42;
  //   release action; [3]
  // with synchronization from 1 to 2 and from 3 to 4, resulting in %val
  // being 42. A key property of this program however is that if either
  // 1 or 4 were missing, there would be a race between the store of 42
  // either the store of 0 or the load (making the whole progam racy).
  // The paper mentionned above shows that the same property is respected
  // by every program that can detect any optimisation of that kind: either
  // it is racy (undefined) or there is a release followed by an acquire
  // between the pair of accesses under consideration.
  bool HasSeenAcquire = false;

  if (isLoad && QueryInst) {
    LoadInst *LI = dyn_cast<LoadInst>(QueryInst);
    if (LI && LI->getMetadata(LLVMContext::MD_invariant_load) != nullptr)
      isInvariantLoad = true;
  }

  // Walk backwards through the basic block, looking for dependencies.
  while (ScanIt != BB->begin()) {
    Instruction *Inst = --ScanIt;

    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst))
      // Debug intrinsics don't (and can't) cause dependencies.
      if (isa<DbgInfoIntrinsic>(II)) continue;

    // Limit the amount of scanning we do so we don't end up with quadratic
    // running time on extreme testcases.
    --Limit;
    if (!Limit)
      return MemDepResult::getUnknown();

    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
      // If we reach a lifetime begin or end marker, then the query ends here
      // because the value is undefined.
      if (II->getIntrinsicID() == Intrinsic::lifetime_start) {
        // FIXME: This only considers queries directly on the invariant-tagged
        // pointer, not on query pointers that are indexed off of them.  It'd
        // be nice to handle that at some point (the right approach is to use
        // GetPointerBaseWithConstantOffset).
        if (AA->isMustAlias(AliasAnalysis::Location(II->getArgOperand(1)),
                            MemLoc))
          return MemDepResult::getDef(II);
        continue;
      }
    }

    // Values depend on loads if the pointers are must aliased.  This means that
    // a load depends on another must aliased load from the same value.
    // One exception is atomic loads: a value can depend on an atomic load that it
    // does not alias with when this atomic load indicates that another thread may
    // be accessing the location.
    if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
      // Atomic loads have complications involved.
      // A Monotonic (or higher) load is OK if the query inst is itself not atomic.
      // An Acquire (or higher) load sets the HasSeenAcquire flag, so that any
      //   release store will know to return getClobber.
      // FIXME: This is overly conservative.
      if (!LI->isUnordered()) {
        if (!QueryInst)
          return MemDepResult::getClobber(LI);
        if (auto *QueryLI = dyn_cast<LoadInst>(QueryInst)) {
          if (!QueryLI->isSimple())
            return MemDepResult::getClobber(LI);
        } else if (auto *QuerySI = dyn_cast<StoreInst>(QueryInst)) {
          if (!QuerySI->isSimple())
            return MemDepResult::getClobber(LI);
        } else if (QueryInst->mayReadOrWriteMemory()) {
          return MemDepResult::getClobber(LI);
        }

        if (isAtLeastAcquire(LI->getOrdering()))
          HasSeenAcquire = true;
      }

      // FIXME: this is overly conservative.
      // While volatile access cannot be eliminated, they do not have to clobber
      // non-aliasing locations, as normal accesses can for example be reordered
      // with volatile accesses.
      if (LI->isVolatile())
        return MemDepResult::getClobber(LI);

      AliasAnalysis::Location LoadLoc = AA->getLocation(LI);

      // If we found a pointer, check if it could be the same as our pointer.
      AliasAnalysis::AliasResult R = AA->alias(LoadLoc, MemLoc);

      if (isLoad) {
        if (R == AliasAnalysis::NoAlias) {
          // If this is an over-aligned integer load (for example,
          // "load i8* %P, align 4") see if it would obviously overlap with the
          // queried location if widened to a larger load (e.g. if the queried
          // location is 1 byte at P+1).  If so, return it as a load/load
          // clobber result, allowing the client to decide to widen the load if
          // it wants to.
          if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType()))
            if (LI->getAlignment()*8 > ITy->getPrimitiveSizeInBits() &&
                isLoadLoadClobberIfExtendedToFullWidth(MemLoc, MemLocBase,
                                                       MemLocOffset, LI, DL))
              return MemDepResult::getClobber(Inst);

          continue;
        }

        // Must aliased loads are defs of each other.
        if (R == AliasAnalysis::MustAlias)
          return MemDepResult::getDef(Inst);

#if 0 // FIXME: Temporarily disabled. GVN is cleverly rewriting loads
      // in terms of clobbering loads, but since it does this by looking
      // at the clobbering load directly, it doesn't know about any
      // phi translation that may have happened along the way.

        // If we have a partial alias, then return this as a clobber for the
        // client to handle.
        if (R == AliasAnalysis::PartialAlias)
          return MemDepResult::getClobber(Inst);
#endif

        // Random may-alias loads don't depend on each other without a
        // dependence.
        continue;
      }

      // Stores don't depend on other no-aliased accesses.
      if (R == AliasAnalysis::NoAlias)
        continue;

      // Stores don't alias loads from read-only memory.
      if (AA->pointsToConstantMemory(LoadLoc))
        continue;

      // Stores depend on may/must aliased loads.
      return MemDepResult::getDef(Inst);
    }

    if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
      // Atomic stores have complications involved.
      // A Monotonic store is OK if the query inst is itself not atomic.
      // A Release (or higher) store further requires that no acquire load
      //   has been seen.
      // FIXME: This is overly conservative.
      if (!SI->isUnordered()) {
        if (!QueryInst)
          return MemDepResult::getClobber(SI);
        if (auto *QueryLI = dyn_cast<LoadInst>(QueryInst)) {
          if (!QueryLI->isSimple())
            return MemDepResult::getClobber(SI);
        } else if (auto *QuerySI = dyn_cast<StoreInst>(QueryInst)) {
          if (!QuerySI->isSimple())
            return MemDepResult::getClobber(SI);
        } else if (QueryInst->mayReadOrWriteMemory()) {
          return MemDepResult::getClobber(SI);
        }

        if (HasSeenAcquire && isAtLeastRelease(SI->getOrdering()))
          return MemDepResult::getClobber(SI);
      }

      // FIXME: this is overly conservative.
      // While volatile access cannot be eliminated, they do not have to clobber
      // non-aliasing locations, as normal accesses can for example be reordered
      // with volatile accesses.
      if (SI->isVolatile())
        return MemDepResult::getClobber(SI);

      // If alias analysis can tell that this store is guaranteed to not modify
      // the query pointer, ignore it.  Use getModRefInfo to handle cases where
      // the query pointer points to constant memory etc.
      if (AA->getModRefInfo(SI, MemLoc) == AliasAnalysis::NoModRef)
        continue;

      // Ok, this store might clobber the query pointer.  Check to see if it is
      // a must alias: in this case, we want to return this as a def.
      AliasAnalysis::Location StoreLoc = AA->getLocation(SI);

      // If we found a pointer, check if it could be the same as our pointer.
      AliasAnalysis::AliasResult R = AA->alias(StoreLoc, MemLoc);

      if (R == AliasAnalysis::NoAlias)
        continue;
      if (R == AliasAnalysis::MustAlias)
        return MemDepResult::getDef(Inst);
      if (isInvariantLoad)
       continue;
      return MemDepResult::getClobber(Inst);
    }

    // If this is an allocation, and if we know that the accessed pointer is to
    // the allocation, return Def.  This means that there is no dependence and
    // the access can be optimized based on that.  For example, a load could
    // turn into undef.
    // Note: Only determine this to be a malloc if Inst is the malloc call, not
    // a subsequent bitcast of the malloc call result.  There can be stores to
    // the malloced memory between the malloc call and its bitcast uses, and we
    // need to continue scanning until the malloc call.
    const TargetLibraryInfo *TLI = AA->getTargetLibraryInfo();
    if (isa<AllocaInst>(Inst) || isNoAliasFn(Inst, TLI)) {
      const Value *AccessPtr = GetUnderlyingObject(MemLoc.Ptr, DL);

      if (AccessPtr == Inst || AA->isMustAlias(Inst, AccessPtr))
        return MemDepResult::getDef(Inst);
      // Be conservative if the accessed pointer may alias the allocation.
      if (AA->alias(Inst, AccessPtr) != AliasAnalysis::NoAlias)
        return MemDepResult::getClobber(Inst);
      // If the allocation is not aliased and does not read memory (like
      // strdup), it is safe to ignore.
      if (isa<AllocaInst>(Inst) ||
          isMallocLikeFn(Inst, TLI) || isCallocLikeFn(Inst, TLI))
        continue;
    }

    // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
    AliasAnalysis::ModRefResult MR = AA->getModRefInfo(Inst, MemLoc);
    // If necessary, perform additional analysis.
    if (MR == AliasAnalysis::ModRef)
      MR = AA->callCapturesBefore(Inst, MemLoc, DT);
    switch (MR) {
    case AliasAnalysis::NoModRef:
      // If the call has no effect on the queried pointer, just ignore it.
      continue;
    case AliasAnalysis::Mod:
      return MemDepResult::getClobber(Inst);
    case AliasAnalysis::Ref:
      // If the call is known to never store to the pointer, and if this is a
      // load query, we can safely ignore it (scan past it).
      if (isLoad)
        continue;
    default:
      // Otherwise, there is a potential dependence.  Return a clobber.
      return MemDepResult::getClobber(Inst);
    }
  }

  // No dependence found.  If this is the entry block of the function, it is
  // unknown, otherwise it is non-local.
  if (BB != &BB->getParent()->getEntryBlock())
    return MemDepResult::getNonLocal();
  return MemDepResult::getNonFuncLocal();
}

/// getDependency - Return the instruction on which a memory operation
/// depends.
MemDepResult MemoryDependenceAnalysis::getDependency(Instruction *QueryInst) {
  Instruction *ScanPos = QueryInst;

  // Check for a cached result
  MemDepResult &LocalCache = LocalDeps[QueryInst];

  // If the cached entry is non-dirty, just return it.  Note that this depends
  // on MemDepResult's default constructing to 'dirty'.
  if (!LocalCache.isDirty())
    return LocalCache;

  // Otherwise, if we have a dirty entry, we know we can start the scan at that
  // instruction, which may save us some work.
  if (Instruction *Inst = LocalCache.getInst()) {
    ScanPos = Inst;

    RemoveFromReverseMap(ReverseLocalDeps, Inst, QueryInst);
  }

  BasicBlock *QueryParent = QueryInst->getParent();

  // Do the scan.
  if (BasicBlock::iterator(QueryInst) == QueryParent->begin()) {
    // No dependence found.  If this is the entry block of the function, it is
    // unknown, otherwise it is non-local.
    if (QueryParent != &QueryParent->getParent()->getEntryBlock())
      LocalCache = MemDepResult::getNonLocal();
    else
      LocalCache = MemDepResult::getNonFuncLocal();
  } else {
    AliasAnalysis::Location MemLoc;
    AliasAnalysis::ModRefResult MR = GetLocation(QueryInst, MemLoc, AA);
    if (MemLoc.Ptr) {
      // If we can do a pointer scan, make it happen.
      bool isLoad = !(MR & AliasAnalysis::Mod);
      if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(QueryInst))
        isLoad |= II->getIntrinsicID() == Intrinsic::lifetime_start;

      LocalCache = getPointerDependencyFrom(MemLoc, isLoad, ScanPos,
                                            QueryParent, QueryInst);
    } else if (isa<CallInst>(QueryInst) || isa<InvokeInst>(QueryInst)) {
      CallSite QueryCS(QueryInst);
      bool isReadOnly = AA->onlyReadsMemory(QueryCS);
      LocalCache = getCallSiteDependencyFrom(QueryCS, isReadOnly, ScanPos,
                                             QueryParent);
    } else
      // Non-memory instruction.
      LocalCache = MemDepResult::getUnknown();
  }

  // Remember the result!
  if (Instruction *I = LocalCache.getInst())
    ReverseLocalDeps[I].insert(QueryInst);

  return LocalCache;
}

#ifndef NDEBUG
/// AssertSorted - This method is used when -debug is specified to verify that
/// cache arrays are properly kept sorted.
static void AssertSorted(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
                         int Count = -1) {
  if (Count == -1) Count = Cache.size();
  if (Count == 0) return;

  for (unsigned i = 1; i != unsigned(Count); ++i)
    assert(!(Cache[i] < Cache[i-1]) && "Cache isn't sorted!");
}
#endif

/// getNonLocalCallDependency - Perform a full dependency query for the
/// specified call, returning the set of blocks that the value is
/// potentially live across.  The returned set of results will include a
/// "NonLocal" result for all blocks where the value is live across.
///
/// This method assumes the instruction returns a "NonLocal" dependency
/// within its own block.
///
/// This returns a reference to an internal data structure that may be
/// invalidated on the next non-local query or when an instruction is
/// removed.  Clients must copy this data if they want it around longer than
/// that.
const MemoryDependenceAnalysis::NonLocalDepInfo &
MemoryDependenceAnalysis::getNonLocalCallDependency(CallSite QueryCS) {
  assert(getDependency(QueryCS.getInstruction()).isNonLocal() &&
 "getNonLocalCallDependency should only be used on calls with non-local deps!");
  PerInstNLInfo &CacheP = NonLocalDeps[QueryCS.getInstruction()];
  NonLocalDepInfo &Cache = CacheP.first;

  /// DirtyBlocks - This is the set of blocks that need to be recomputed.  In
  /// the cached case, this can happen due to instructions being deleted etc. In
  /// the uncached case, this starts out as the set of predecessors we care
  /// about.
  SmallVector<BasicBlock*, 32> DirtyBlocks;

  if (!Cache.empty()) {
    // Okay, we have a cache entry.  If we know it is not dirty, just return it
    // with no computation.
    if (!CacheP.second) {
      ++NumCacheNonLocal;
      return Cache;
    }

    // If we already have a partially computed set of results, scan them to
    // determine what is dirty, seeding our initial DirtyBlocks worklist.
    for (NonLocalDepInfo::iterator I = Cache.begin(), E = Cache.end();
       I != E; ++I)
      if (I->getResult().isDirty())
        DirtyBlocks.push_back(I->getBB());

    // Sort the cache so that we can do fast binary search lookups below.
    std::sort(Cache.begin(), Cache.end());

    ++NumCacheDirtyNonLocal;
    //cerr << "CACHED CASE: " << DirtyBlocks.size() << " dirty: "
    //     << Cache.size() << " cached: " << *QueryInst;
  } else {
    // Seed DirtyBlocks with each of the preds of QueryInst's block.
    BasicBlock *QueryBB = QueryCS.getInstruction()->getParent();
    for (BasicBlock **PI = PredCache->GetPreds(QueryBB); *PI; ++PI)
      DirtyBlocks.push_back(*PI);
    ++NumUncacheNonLocal;
  }

  // isReadonlyCall - If this is a read-only call, we can be more aggressive.
  bool isReadonlyCall = AA->onlyReadsMemory(QueryCS);

  SmallPtrSet<BasicBlock*, 64> Visited;

  unsigned NumSortedEntries = Cache.size();
  DEBUG(AssertSorted(Cache));

  // Iterate while we still have blocks to update.
  while (!DirtyBlocks.empty()) {
    BasicBlock *DirtyBB = DirtyBlocks.back();
    DirtyBlocks.pop_back();

    // Already processed this block?
    if (!Visited.insert(DirtyBB).second)
      continue;

    // Do a binary search to see if we already have an entry for this block in
    // the cache set.  If so, find it.
    DEBUG(AssertSorted(Cache, NumSortedEntries));
    NonLocalDepInfo::iterator Entry =
      std::upper_bound(Cache.begin(), Cache.begin()+NumSortedEntries,
                       NonLocalDepEntry(DirtyBB));
    if (Entry != Cache.begin() && std::prev(Entry)->getBB() == DirtyBB)
      --Entry;

    NonLocalDepEntry *ExistingResult = nullptr;
    if (Entry != Cache.begin()+NumSortedEntries &&
        Entry->getBB() == DirtyBB) {
      // If we already have an entry, and if it isn't already dirty, the block
      // is done.
      if (!Entry->getResult().isDirty())
        continue;

      // Otherwise, remember this slot so we can update the value.
      ExistingResult = &*Entry;
    }

    // If the dirty entry has a pointer, start scanning from it so we don't have
    // to rescan the entire block.
    BasicBlock::iterator ScanPos = DirtyBB->end();
    if (ExistingResult) {
      if (Instruction *Inst = ExistingResult->getResult().getInst()) {
        ScanPos = Inst;
        // We're removing QueryInst's use of Inst.
        RemoveFromReverseMap(ReverseNonLocalDeps, Inst,
                             QueryCS.getInstruction());
      }
    }

    // Find out if this block has a local dependency for QueryInst.
    MemDepResult Dep;

    if (ScanPos != DirtyBB->begin()) {
      Dep = getCallSiteDependencyFrom(QueryCS, isReadonlyCall,ScanPos, DirtyBB);
    } else if (DirtyBB != &DirtyBB->getParent()->getEntryBlock()) {
      // No dependence found.  If this is the entry block of the function, it is
      // a clobber, otherwise it is unknown.
      Dep = MemDepResult::getNonLocal();
    } else {
      Dep = MemDepResult::getNonFuncLocal();
    }

    // If we had a dirty entry for the block, update it.  Otherwise, just add
    // a new entry.
    if (ExistingResult)
      ExistingResult->setResult(Dep);
    else
      Cache.push_back(NonLocalDepEntry(DirtyBB, Dep));

    // If the block has a dependency (i.e. it isn't completely transparent to
    // the value), remember the association!
    if (!Dep.isNonLocal()) {
      // Keep the ReverseNonLocalDeps map up to date so we can efficiently
      // update this when we remove instructions.
      if (Instruction *Inst = Dep.getInst())
        ReverseNonLocalDeps[Inst].insert(QueryCS.getInstruction());
    } else {

      // If the block *is* completely transparent to the load, we need to check
      // the predecessors of this block.  Add them to our worklist.
      for (BasicBlock **PI = PredCache->GetPreds(DirtyBB); *PI; ++PI)
        DirtyBlocks.push_back(*PI);
    }
  }

  return Cache;
}

/// getNonLocalPointerDependency - Perform a full dependency query for an
/// access to the specified (non-volatile) memory location, returning the
/// set of instructions that either define or clobber the value.
///
/// This method assumes the pointer has a "NonLocal" dependency within its
/// own block.
///
void MemoryDependenceAnalysis::
getNonLocalPointerDependency(Instruction *QueryInst,
                             SmallVectorImpl<NonLocalDepResult> &Result) {

  auto getLocation = [](AliasAnalysis *AA, Instruction *Inst) {
    if (auto *I = dyn_cast<LoadInst>(Inst))
      return AA->getLocation(I);
    else if (auto *I = dyn_cast<StoreInst>(Inst))
      return AA->getLocation(I);
    else if (auto *I = dyn_cast<VAArgInst>(Inst))
      return AA->getLocation(I);
    else if (auto *I = dyn_cast<AtomicCmpXchgInst>(Inst))
      return AA->getLocation(I);
    else if (auto *I = dyn_cast<AtomicRMWInst>(Inst))
      return AA->getLocation(I);
    else
      llvm_unreachable("unsupported memory instruction");
  };
   
  const AliasAnalysis::Location Loc = getLocation(AA, QueryInst);
  bool isLoad = isa<LoadInst>(QueryInst);
  BasicBlock *FromBB = QueryInst->getParent();
  assert(FromBB);

  assert(Loc.Ptr->getType()->isPointerTy() &&
         "Can't get pointer deps of a non-pointer!");
  Result.clear();
  
  // This routine does not expect to deal with volatile instructions.
  // Doing so would require piping through the QueryInst all the way through.
  // TODO: volatiles can't be elided, but they can be reordered with other
  // non-volatile accesses.
  auto isVolatile = [](Instruction *Inst) {
    if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
      return LI->isVolatile();
    } else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
      return SI->isVolatile();
    }
    return false;
  };
  // We currently give up on any instruction which is ordered, but we do handle
  // atomic instructions which are unordered.
  // TODO: Handle ordered instructions
  auto isOrdered = [](Instruction *Inst) {
    if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
      return !LI->isUnordered();
    } else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
      return !SI->isUnordered();
    }
    return false;
  };
  if (isVolatile(QueryInst) || isOrdered(QueryInst)) {
    Result.push_back(NonLocalDepResult(FromBB,
                                       MemDepResult::getUnknown(),
                                       const_cast<Value *>(Loc.Ptr)));
    return;
  }


  PHITransAddr Address(const_cast<Value *>(Loc.Ptr), DL, AC);

  // This is the set of blocks we've inspected, and the pointer we consider in
  // each block.  Because of critical edges, we currently bail out if querying
  // a block with multiple different pointers.  This can happen during PHI
  // translation.
  DenseMap<BasicBlock*, Value*> Visited;
  if (!getNonLocalPointerDepFromBB(Address, Loc, isLoad, FromBB,
                                   Result, Visited, true))
    return;
  Result.clear();
  Result.push_back(NonLocalDepResult(FromBB,
                                     MemDepResult::getUnknown(),
                                     const_cast<Value *>(Loc.Ptr)));
}

/// GetNonLocalInfoForBlock - Compute the memdep value for BB with
/// Pointer/PointeeSize using either cached information in Cache or by doing a
/// lookup (which may use dirty cache info if available).  If we do a lookup,
/// add the result to the cache.
MemDepResult MemoryDependenceAnalysis::
GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc,
                        bool isLoad, BasicBlock *BB,
                        NonLocalDepInfo *Cache, unsigned NumSortedEntries) {

  // Do a binary search to see if we already have an entry for this block in
  // the cache set.  If so, find it.
  NonLocalDepInfo::iterator Entry =
    std::upper_bound(Cache->begin(), Cache->begin()+NumSortedEntries,
                     NonLocalDepEntry(BB));
  if (Entry != Cache->begin() && (Entry-1)->getBB() == BB)
    --Entry;

  NonLocalDepEntry *ExistingResult = nullptr;
  if (Entry != Cache->begin()+NumSortedEntries && Entry->getBB() == BB)
    ExistingResult = &*Entry;

  // If we have a cached entry, and it is non-dirty, use it as the value for
  // this dependency.
  if (ExistingResult && !ExistingResult->getResult().isDirty()) {
    ++NumCacheNonLocalPtr;
    return ExistingResult->getResult();
  }

  // Otherwise, we have to scan for the value.  If we have a dirty cache
  // entry, start scanning from its position, otherwise we scan from the end
  // of the block.
  BasicBlock::iterator ScanPos = BB->end();
  if (ExistingResult && ExistingResult->getResult().getInst()) {
    assert(ExistingResult->getResult().getInst()->getParent() == BB &&
           "Instruction invalidated?");
    ++NumCacheDirtyNonLocalPtr;
    ScanPos = ExistingResult->getResult().getInst();

    // Eliminating the dirty entry from 'Cache', so update the reverse info.
    ValueIsLoadPair CacheKey(Loc.Ptr, isLoad);
    RemoveFromReverseMap(ReverseNonLocalPtrDeps, ScanPos, CacheKey);
  } else {
    ++NumUncacheNonLocalPtr;
  }

  // Scan the block for the dependency.
  MemDepResult Dep = getPointerDependencyFrom(Loc, isLoad, ScanPos, BB);

  // If we had a dirty entry for the block, update it.  Otherwise, just add
  // a new entry.
  if (ExistingResult)
    ExistingResult->setResult(Dep);
  else
    Cache->push_back(NonLocalDepEntry(BB, Dep));

  // If the block has a dependency (i.e. it isn't completely transparent to
  // the value), remember the reverse association because we just added it
  // to Cache!
  if (!Dep.isDef() && !Dep.isClobber())
    return Dep;

  // Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently
  // update MemDep when we remove instructions.
  Instruction *Inst = Dep.getInst();
  assert(Inst && "Didn't depend on anything?");
  ValueIsLoadPair CacheKey(Loc.Ptr, isLoad);
  ReverseNonLocalPtrDeps[Inst].insert(CacheKey);
  return Dep;
}

/// SortNonLocalDepInfoCache - Sort the NonLocalDepInfo cache, given a certain
/// number of elements in the array that are already properly ordered.  This is
/// optimized for the case when only a few entries are added.
static void
SortNonLocalDepInfoCache(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
                         unsigned NumSortedEntries) {
  switch (Cache.size() - NumSortedEntries) {
  case 0:
    // done, no new entries.
    break;
  case 2: {
    // Two new entries, insert the last one into place.
    NonLocalDepEntry Val = Cache.back();
    Cache.pop_back();
    MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry =
      std::upper_bound(Cache.begin(), Cache.end()-1, Val);
    Cache.insert(Entry, Val);
    // FALL THROUGH.
  }
  case 1:
    // One new entry, Just insert the new value at the appropriate position.
    if (Cache.size() != 1) {
      NonLocalDepEntry Val = Cache.back();
      Cache.pop_back();
      MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry =
        std::upper_bound(Cache.begin(), Cache.end(), Val);
      Cache.insert(Entry, Val);
    }
    break;
  default:
    // Added many values, do a full scale sort.
    std::sort(Cache.begin(), Cache.end());
    break;
  }
}

/// getNonLocalPointerDepFromBB - Perform a dependency query based on
/// pointer/pointeesize starting at the end of StartBB.  Add any clobber/def
/// results to the results vector and keep track of which blocks are visited in
/// 'Visited'.
///
/// This has special behavior for the first block queries (when SkipFirstBlock
/// is true).  In this special case, it ignores the contents of the specified
/// block and starts returning dependence info for its predecessors.
///
/// This function returns false on success, or true to indicate that it could
/// not compute dependence information for some reason.  This should be treated
/// as a clobber dependence on the first instruction in the predecessor block.
bool MemoryDependenceAnalysis::
getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
                            const AliasAnalysis::Location &Loc,
                            bool isLoad, BasicBlock *StartBB,
                            SmallVectorImpl<NonLocalDepResult> &Result,
                            DenseMap<BasicBlock*, Value*> &Visited,
                            bool SkipFirstBlock) {
  // Look up the cached info for Pointer.
  ValueIsLoadPair CacheKey(Pointer.getAddr(), isLoad);

  // Set up a temporary NLPI value. If the map doesn't yet have an entry for
  // CacheKey, this value will be inserted as the associated value. Otherwise,
  // it'll be ignored, and we'll have to check to see if the cached size and
  // aa tags are consistent with the current query.
  NonLocalPointerInfo InitialNLPI;
  InitialNLPI.Size = Loc.Size;
  InitialNLPI.AATags = Loc.AATags;

  // Get the NLPI for CacheKey, inserting one into the map if it doesn't
  // already have one.
  std::pair<CachedNonLocalPointerInfo::iterator, bool> Pair =
    NonLocalPointerDeps.insert(std::make_pair(CacheKey, InitialNLPI));
  NonLocalPointerInfo *CacheInfo = &Pair.first->second;

  // If we already have a cache entry for this CacheKey, we may need to do some
  // work to reconcile the cache entry and the current query.
  if (!Pair.second) {
    if (CacheInfo->Size < Loc.Size) {
      // The query's Size is greater than the cached one. Throw out the
      // cached data and proceed with the query at the greater size.
      CacheInfo->Pair = BBSkipFirstBlockPair();
      CacheInfo->Size = Loc.Size;
      for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(),
           DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI)
        if (Instruction *Inst = DI->getResult().getInst())
          RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
      CacheInfo->NonLocalDeps.clear();
    } else if (CacheInfo->Size > Loc.Size) {
      // This query's Size is less than the cached one. Conservatively restart
      // the query using the greater size.
      return getNonLocalPointerDepFromBB(Pointer,
                                         Loc.getWithNewSize(CacheInfo->Size),
                                         isLoad, StartBB, Result, Visited,
                                         SkipFirstBlock);
    }

    // If the query's AATags are inconsistent with the cached one,
    // conservatively throw out the cached data and restart the query with
    // no tag if needed.
    if (CacheInfo->AATags != Loc.AATags) {
      if (CacheInfo->AATags) {
        CacheInfo->Pair = BBSkipFirstBlockPair();
        CacheInfo->AATags = AAMDNodes();
        for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(),
             DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI)
          if (Instruction *Inst = DI->getResult().getInst())
            RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
        CacheInfo->NonLocalDeps.clear();
      }
      if (Loc.AATags)
        return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutAATags(),
                                           isLoad, StartBB, Result, Visited,
                                           SkipFirstBlock);
    }
  }

  NonLocalDepInfo *Cache = &CacheInfo->NonLocalDeps;

  // If we have valid cached information for exactly the block we are
  // investigating, just return it with no recomputation.
  if (CacheInfo->Pair == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) {
    // We have a fully cached result for this query then we can just return the
    // cached results and populate the visited set.  However, we have to verify
    // that we don't already have conflicting results for these blocks.  Check
    // to ensure that if a block in the results set is in the visited set that
    // it was for the same pointer query.
    if (!Visited.empty()) {
      for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
           I != E; ++I) {
        DenseMap<BasicBlock*, Value*>::iterator VI = Visited.find(I->getBB());
        if (VI == Visited.end() || VI->second == Pointer.getAddr())
          continue;

        // We have a pointer mismatch in a block.  Just return clobber, saying
        // that something was clobbered in this result.  We could also do a
        // non-fully cached query, but there is little point in doing this.
        return true;
      }
    }

    Value *Addr = Pointer.getAddr();
    for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
         I != E; ++I) {
      Visited.insert(std::make_pair(I->getBB(), Addr));
      if (I->getResult().isNonLocal()) {
        continue;
      }

      if (!DT) {
        Result.push_back(NonLocalDepResult(I->getBB(),
                                           MemDepResult::getUnknown(),
                                           Addr));
      } else if (DT->isReachableFromEntry(I->getBB())) {
        Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(), Addr));
      }
    }
    ++NumCacheCompleteNonLocalPtr;
    return false;
  }

  // Otherwise, either this is a new block, a block with an invalid cache
  // pointer or one that we're about to invalidate by putting more info into it
  // than its valid cache info.  If empty, the result will be valid cache info,
  // otherwise it isn't.
  if (Cache->empty())
    CacheInfo->Pair = BBSkipFirstBlockPair(StartBB, SkipFirstBlock);
  else
    CacheInfo->Pair = BBSkipFirstBlockPair();

  SmallVector<BasicBlock*, 32> Worklist;
  Worklist.push_back(StartBB);

  // PredList used inside loop.
  SmallVector<std::pair<BasicBlock*, PHITransAddr>, 16> PredList;

  // Keep track of the entries that we know are sorted.  Previously cached
  // entries will all be sorted.  The entries we add we only sort on demand (we
  // don't insert every element into its sorted position).  We know that we
  // won't get any reuse from currently inserted values, because we don't
  // revisit blocks after we insert info for them.
  unsigned NumSortedEntries = Cache->size();
  DEBUG(AssertSorted(*Cache));

  while (!Worklist.empty()) {
    BasicBlock *BB = Worklist.pop_back_val();

    // If we do process a large number of blocks it becomes very expensive and
    // likely it isn't worth worrying about
    if (Result.size() > NumResultsLimit) {
      Worklist.clear();
      // Sort it now (if needed) so that recursive invocations of
      // getNonLocalPointerDepFromBB and other routines that could reuse the
      // cache value will only see properly sorted cache arrays.
      if (Cache && NumSortedEntries != Cache->size()) {
        SortNonLocalDepInfoCache(*Cache, NumSortedEntries);
      }
      // Since we bail out, the "Cache" set won't contain all of the
      // results for the query.  This is ok (we can still use it to accelerate
      // specific block queries) but we can't do the fastpath "return all
      // results from the set".  Clear out the indicator for this.
      CacheInfo->Pair = BBSkipFirstBlockPair();
      return true;
    }

    // Skip the first block if we have it.
    if (!SkipFirstBlock) {
      // Analyze the dependency of *Pointer in FromBB.  See if we already have
      // been here.
      assert(Visited.count(BB) && "Should check 'visited' before adding to WL");

      // Get the dependency info for Pointer in BB.  If we have cached
      // information, we will use it, otherwise we compute it.
      DEBUG(AssertSorted(*Cache, NumSortedEntries));
      MemDepResult Dep = GetNonLocalInfoForBlock(Loc, isLoad, BB, Cache,
                                                 NumSortedEntries);

      // If we got a Def or Clobber, add this to the list of results.
      if (!Dep.isNonLocal()) {
        if (!DT) {
          Result.push_back(NonLocalDepResult(BB,
                                             MemDepResult::getUnknown(),
                                             Pointer.getAddr()));
          continue;
        } else if (DT->isReachableFromEntry(BB)) {
          Result.push_back(NonLocalDepResult(BB, Dep, Pointer.getAddr()));
          continue;
        }
      }
    }

    // If 'Pointer' is an instruction defined in this block, then we need to do
    // phi translation to change it into a value live in the predecessor block.
    // If not, we just add the predecessors to the worklist and scan them with
    // the same Pointer.
    if (!Pointer.NeedsPHITranslationFromBlock(BB)) {
      SkipFirstBlock = false;
      SmallVector<BasicBlock*, 16> NewBlocks;
      for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
        // Verify that we haven't looked at this block yet.
        std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
          InsertRes = Visited.insert(std::make_pair(*PI, Pointer.getAddr()));
        if (InsertRes.second) {
          // First time we've looked at *PI.
          NewBlocks.push_back(*PI);
          continue;
        }

        // If we have seen this block before, but it was with a different
        // pointer then we have a phi translation failure and we have to treat
        // this as a clobber.
        if (InsertRes.first->second != Pointer.getAddr()) {
          // Make sure to clean up the Visited map before continuing on to
          // PredTranslationFailure.
          for (unsigned i = 0; i < NewBlocks.size(); i++)
            Visited.erase(NewBlocks[i]);
          goto PredTranslationFailure;
        }
      }
      Worklist.append(NewBlocks.begin(), NewBlocks.end());
      continue;
    }

    // We do need to do phi translation, if we know ahead of time we can't phi
    // translate this value, don't even try.
    if (!Pointer.IsPotentiallyPHITranslatable())
      goto PredTranslationFailure;

    // We may have added values to the cache list before this PHI translation.
    // If so, we haven't done anything to ensure that the cache remains sorted.
    // Sort it now (if needed) so that recursive invocations of
    // getNonLocalPointerDepFromBB and other routines that could reuse the cache
    // value will only see properly sorted cache arrays.
    if (Cache && NumSortedEntries != Cache->size()) {
      SortNonLocalDepInfoCache(*Cache, NumSortedEntries);
      NumSortedEntries = Cache->size();
    }
    Cache = nullptr;

    PredList.clear();
    for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
      BasicBlock *Pred = *PI;
      PredList.push_back(std::make_pair(Pred, Pointer));

      // Get the PHI translated pointer in this predecessor.  This can fail if
      // not translatable, in which case the getAddr() returns null.
      PHITransAddr &PredPointer = PredList.back().second;
      PredPointer.PHITranslateValue(BB, Pred, nullptr);

      Value *PredPtrVal = PredPointer.getAddr();

      // Check to see if we have already visited this pred block with another
      // pointer.  If so, we can't do this lookup.  This failure can occur
      // with PHI translation when a critical edge exists and the PHI node in
      // the successor translates to a pointer value different than the
      // pointer the block was first analyzed with.
      std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
        InsertRes = Visited.insert(std::make_pair(Pred, PredPtrVal));

      if (!InsertRes.second) {
        // We found the pred; take it off the list of preds to visit.
        PredList.pop_back();

        // If the predecessor was visited with PredPtr, then we already did
        // the analysis and can ignore it.
        if (InsertRes.first->second == PredPtrVal)
          continue;

        // Otherwise, the block was previously analyzed with a different
        // pointer.  We can't represent the result of this case, so we just
        // treat this as a phi translation failure.

        // Make sure to clean up the Visited map before continuing on to
        // PredTranslationFailure.
        for (unsigned i = 0, n = PredList.size(); i < n; ++i)
          Visited.erase(PredList[i].first);

        goto PredTranslationFailure;
      }
    }

    // Actually process results here; this need to be a separate loop to avoid
    // calling getNonLocalPointerDepFromBB for blocks we don't want to return
    // any results for.  (getNonLocalPointerDepFromBB will modify our
    // datastructures in ways the code after the PredTranslationFailure label
    // doesn't expect.)
    for (unsigned i = 0, n = PredList.size(); i < n; ++i) {
      BasicBlock *Pred = PredList[i].first;
      PHITransAddr &PredPointer = PredList[i].second;
      Value *PredPtrVal = PredPointer.getAddr();

      bool CanTranslate = true;
      // If PHI translation was unable to find an available pointer in this
      // predecessor, then we have to assume that the pointer is clobbered in
      // that predecessor.  We can still do PRE of the load, which would insert
      // a computation of the pointer in this predecessor.
      if (!PredPtrVal)
        CanTranslate = false;

      // FIXME: it is entirely possible that PHI translating will end up with
      // the same value.  Consider PHI translating something like:
      // X = phi [x, bb1], [y, bb2].  PHI translating for bb1 doesn't *need*
      // to recurse here, pedantically speaking.

      // If getNonLocalPointerDepFromBB fails here, that means the cached
      // result conflicted with the Visited list; we have to conservatively
      // assume it is unknown, but this also does not block PRE of the load.
      if (!CanTranslate ||
          getNonLocalPointerDepFromBB(PredPointer,
                                      Loc.getWithNewPtr(PredPtrVal),
                                      isLoad, Pred,
                                      Result, Visited)) {
        // Add the entry to the Result list.
        NonLocalDepResult Entry(Pred, MemDepResult::getUnknown(), PredPtrVal);
        Result.push_back(Entry);

        // Since we had a phi translation failure, the cache for CacheKey won't
        // include all of the entries that we need to immediately satisfy future
        // queries.  Mark this in NonLocalPointerDeps by setting the
        // BBSkipFirstBlockPair pointer to null.  This requires reuse of the
        // cached value to do more work but not miss the phi trans failure.
        NonLocalPointerInfo &NLPI = NonLocalPointerDeps[CacheKey];
        NLPI.Pair = BBSkipFirstBlockPair();
        continue;
      }
    }

    // Refresh the CacheInfo/Cache pointer so that it isn't invalidated.
    CacheInfo = &NonLocalPointerDeps[CacheKey];
    Cache = &CacheInfo->NonLocalDeps;
    NumSortedEntries = Cache->size();

    // Since we did phi translation, the "Cache" set won't contain all of the
    // results for the query.  This is ok (we can still use it to accelerate
    // specific block queries) but we can't do the fastpath "return all
    // results from the set"  Clear out the indicator for this.
    CacheInfo->Pair = BBSkipFirstBlockPair();
    SkipFirstBlock = false;
    continue;

  PredTranslationFailure:
    // The following code is "failure"; we can't produce a sane translation
    // for the given block.  It assumes that we haven't modified any of
    // our datastructures while processing the current block.

    if (!Cache) {
      // Refresh the CacheInfo/Cache pointer if it got invalidated.
      CacheInfo = &NonLocalPointerDeps[CacheKey];
      Cache = &CacheInfo->NonLocalDeps;
      NumSortedEntries = Cache->size();
    }

    // Since we failed phi translation, the "Cache" set won't contain all of the
    // results for the query.  This is ok (we can still use it to accelerate
    // specific block queries) but we can't do the fastpath "return all
    // results from the set".  Clear out the indicator for this.
    CacheInfo->Pair = BBSkipFirstBlockPair();

    // If *nothing* works, mark the pointer as unknown.
    //
    // If this is the magic first block, return this as a clobber of the whole
    // incoming value.  Since we can't phi translate to one of the predecessors,
    // we have to bail out.
    if (SkipFirstBlock)
      return true;

    for (NonLocalDepInfo::reverse_iterator I = Cache->rbegin(); ; ++I) {
      assert(I != Cache->rend() && "Didn't find current block??");
      if (I->getBB() != BB)
        continue;

      assert((I->getResult().isNonLocal() || !DT->isReachableFromEntry(BB)) &&
             "Should only be here with transparent block");
      I->setResult(MemDepResult::getUnknown());
      Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(),
                                         Pointer.getAddr()));
      break;
    }
  }

  // Okay, we're done now.  If we added new values to the cache, re-sort it.
  SortNonLocalDepInfoCache(*Cache, NumSortedEntries);
  DEBUG(AssertSorted(*Cache));
  return false;
}

/// RemoveCachedNonLocalPointerDependencies - If P exists in
/// CachedNonLocalPointerInfo, remove it.
void MemoryDependenceAnalysis::
RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P) {
  CachedNonLocalPointerInfo::iterator It =
    NonLocalPointerDeps.find(P);
  if (It == NonLocalPointerDeps.end()) return;

  // Remove all of the entries in the BB->val map.  This involves removing
  // instructions from the reverse map.
  NonLocalDepInfo &PInfo = It->second.NonLocalDeps;

  for (unsigned i = 0, e = PInfo.size(); i != e; ++i) {
    Instruction *Target = PInfo[i].getResult().getInst();
    if (!Target) continue;  // Ignore non-local dep results.
    assert(Target->getParent() == PInfo[i].getBB());

    // Eliminating the dirty entry from 'Cache', so update the reverse info.
    RemoveFromReverseMap(ReverseNonLocalPtrDeps, Target, P);
  }

  // Remove P from NonLocalPointerDeps (which deletes NonLocalDepInfo).
  NonLocalPointerDeps.erase(It);
}


/// invalidateCachedPointerInfo - This method is used to invalidate cached
/// information about the specified pointer, because it may be too
/// conservative in memdep.  This is an optional call that can be used when
/// the client detects an equivalence between the pointer and some other
/// value and replaces the other value with ptr. This can make Ptr available
/// in more places that cached info does not necessarily keep.
void MemoryDependenceAnalysis::invalidateCachedPointerInfo(Value *Ptr) {
  // If Ptr isn't really a pointer, just ignore it.
  if (!Ptr->getType()->isPointerTy()) return;
  // Flush store info for the pointer.
  RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, false));
  // Flush load info for the pointer.
  RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, true));
}

/// invalidateCachedPredecessors - Clear the PredIteratorCache info.
/// This needs to be done when the CFG changes, e.g., due to splitting
/// critical edges.
void MemoryDependenceAnalysis::invalidateCachedPredecessors() {
  PredCache->clear();
}

/// removeInstruction - Remove an instruction from the dependence analysis,
/// updating the dependence of instructions that previously depended on it.
/// This method attempts to keep the cache coherent using the reverse map.
void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) {
  // Walk through the Non-local dependencies, removing this one as the value
  // for any cached queries.
  NonLocalDepMapType::iterator NLDI = NonLocalDeps.find(RemInst);
  if (NLDI != NonLocalDeps.end()) {
    NonLocalDepInfo &BlockMap = NLDI->second.first;
    for (NonLocalDepInfo::iterator DI = BlockMap.begin(), DE = BlockMap.end();
         DI != DE; ++DI)
      if (Instruction *Inst = DI->getResult().getInst())
        RemoveFromReverseMap(ReverseNonLocalDeps, Inst, RemInst);
    NonLocalDeps.erase(NLDI);
  }

  // If we have a cached local dependence query for this instruction, remove it.
  //
  LocalDepMapType::iterator LocalDepEntry = LocalDeps.find(RemInst);
  if (LocalDepEntry != LocalDeps.end()) {
    // Remove us from DepInst's reverse set now that the local dep info is gone.
    if (Instruction *Inst = LocalDepEntry->second.getInst())
      RemoveFromReverseMap(ReverseLocalDeps, Inst, RemInst);

    // Remove this local dependency info.
    LocalDeps.erase(LocalDepEntry);
  }

  // If we have any cached pointer dependencies on this instruction, remove
  // them.  If the instruction has non-pointer type, then it can't be a pointer
  // base.

  // Remove it from both the load info and the store info.  The instruction
  // can't be in either of these maps if it is non-pointer.
  if (RemInst->getType()->isPointerTy()) {
    RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, false));
    RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, true));
  }

  // Loop over all of the things that depend on the instruction we're removing.
  //
  SmallVector<std::pair<Instruction*, Instruction*>, 8> ReverseDepsToAdd;

  // If we find RemInst as a clobber or Def in any of the maps for other values,
  // we need to replace its entry with a dirty version of the instruction after
  // it.  If RemInst is a terminator, we use a null dirty value.
  //
  // Using a dirty version of the instruction after RemInst saves having to scan
  // the entire block to get to this point.
  MemDepResult NewDirtyVal;
  if (!RemInst->isTerminator())
    NewDirtyVal = MemDepResult::getDirty(++BasicBlock::iterator(RemInst));

  ReverseDepMapType::iterator ReverseDepIt = ReverseLocalDeps.find(RemInst);
  if (ReverseDepIt != ReverseLocalDeps.end()) {
    // RemInst can't be the terminator if it has local stuff depending on it.
    assert(!ReverseDepIt->second.empty() && !isa<TerminatorInst>(RemInst) &&
           "Nothing can locally depend on a terminator");

    for (Instruction *InstDependingOnRemInst : ReverseDepIt->second) {
      assert(InstDependingOnRemInst != RemInst &&
             "Already removed our local dep info");

      LocalDeps[InstDependingOnRemInst] = NewDirtyVal;

      // Make sure to remember that new things depend on NewDepInst.
      assert(NewDirtyVal.getInst() && "There is no way something else can have "
             "a local dep on this if it is a terminator!");
      ReverseDepsToAdd.push_back(std::make_pair(NewDirtyVal.getInst(),
                                                InstDependingOnRemInst));
    }

    ReverseLocalDeps.erase(ReverseDepIt);

    // Add new reverse deps after scanning the set, to avoid invalidating the
    // 'ReverseDeps' reference.
    while (!ReverseDepsToAdd.empty()) {
      ReverseLocalDeps[ReverseDepsToAdd.back().first]
        .insert(ReverseDepsToAdd.back().second);
      ReverseDepsToAdd.pop_back();
    }
  }

  ReverseDepIt = ReverseNonLocalDeps.find(RemInst);
  if (ReverseDepIt != ReverseNonLocalDeps.end()) {
    for (Instruction *I : ReverseDepIt->second) {
      assert(I != RemInst && "Already removed NonLocalDep info for RemInst");

      PerInstNLInfo &INLD = NonLocalDeps[I];
      // The information is now dirty!
      INLD.second = true;

      for (NonLocalDepInfo::iterator DI = INLD.first.begin(),
           DE = INLD.first.end(); DI != DE; ++DI) {
        if (DI->getResult().getInst() != RemInst) continue;

        // Convert to a dirty entry for the subsequent instruction.
        DI->setResult(NewDirtyVal);

        if (Instruction *NextI = NewDirtyVal.getInst())
          ReverseDepsToAdd.push_back(std::make_pair(NextI, I));
      }
    }

    ReverseNonLocalDeps.erase(ReverseDepIt);

    // Add new reverse deps after scanning the set, to avoid invalidating 'Set'
    while (!ReverseDepsToAdd.empty()) {
      ReverseNonLocalDeps[ReverseDepsToAdd.back().first]
        .insert(ReverseDepsToAdd.back().second);
      ReverseDepsToAdd.pop_back();
    }
  }

  // If the instruction is in ReverseNonLocalPtrDeps then it appears as a
  // value in the NonLocalPointerDeps info.
  ReverseNonLocalPtrDepTy::iterator ReversePtrDepIt =
    ReverseNonLocalPtrDeps.find(RemInst);
  if (ReversePtrDepIt != ReverseNonLocalPtrDeps.end()) {
    SmallVector<std::pair<Instruction*, ValueIsLoadPair>,8> ReversePtrDepsToAdd;

    for (ValueIsLoadPair P : ReversePtrDepIt->second) {
      assert(P.getPointer() != RemInst &&
             "Already removed NonLocalPointerDeps info for RemInst");

      NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].NonLocalDeps;

      // The cache is not valid for any specific block anymore.
      NonLocalPointerDeps[P].Pair = BBSkipFirstBlockPair();

      // Update any entries for RemInst to use the instruction after it.
      for (NonLocalDepInfo::iterator DI = NLPDI.begin(), DE = NLPDI.end();
           DI != DE; ++DI) {
        if (DI->getResult().getInst() != RemInst) continue;

        // Convert to a dirty entry for the subsequent instruction.
        DI->setResult(NewDirtyVal);

        if (Instruction *NewDirtyInst = NewDirtyVal.getInst())
          ReversePtrDepsToAdd.push_back(std::make_pair(NewDirtyInst, P));
      }

      // Re-sort the NonLocalDepInfo.  Changing the dirty entry to its
      // subsequent value may invalidate the sortedness.
      std::sort(NLPDI.begin(), NLPDI.end());
    }

    ReverseNonLocalPtrDeps.erase(ReversePtrDepIt);

    while (!ReversePtrDepsToAdd.empty()) {
      ReverseNonLocalPtrDeps[ReversePtrDepsToAdd.back().first]
        .insert(ReversePtrDepsToAdd.back().second);
      ReversePtrDepsToAdd.pop_back();
    }
  }


  assert(!NonLocalDeps.count(RemInst) && "RemInst got reinserted?");
  AA->deleteValue(RemInst);
  DEBUG(verifyRemoved(RemInst));
}
/// verifyRemoved - Verify that the specified instruction does not occur
/// in our internal data structures. This function verifies by asserting in
/// debug builds.
void MemoryDependenceAnalysis::verifyRemoved(Instruction *D) const {
#ifndef NDEBUG
  for (LocalDepMapType::const_iterator I = LocalDeps.begin(),
       E = LocalDeps.end(); I != E; ++I) {
    assert(I->first != D && "Inst occurs in data structures");
    assert(I->second.getInst() != D &&
           "Inst occurs in data structures");
  }

  for (CachedNonLocalPointerInfo::const_iterator I =NonLocalPointerDeps.begin(),
       E = NonLocalPointerDeps.end(); I != E; ++I) {
    assert(I->first.getPointer() != D && "Inst occurs in NLPD map key");
    const NonLocalDepInfo &Val = I->second.NonLocalDeps;
    for (NonLocalDepInfo::const_iterator II = Val.begin(), E = Val.end();
         II != E; ++II)
      assert(II->getResult().getInst() != D && "Inst occurs as NLPD value");
  }

  for (NonLocalDepMapType::const_iterator I = NonLocalDeps.begin(),
       E = NonLocalDeps.end(); I != E; ++I) {
    assert(I->first != D && "Inst occurs in data structures");
    const PerInstNLInfo &INLD = I->second;
    for (NonLocalDepInfo::const_iterator II = INLD.first.begin(),
         EE = INLD.first.end(); II  != EE; ++II)
      assert(II->getResult().getInst() != D && "Inst occurs in data structures");
  }

  for (ReverseDepMapType::const_iterator I = ReverseLocalDeps.begin(),
       E = ReverseLocalDeps.end(); I != E; ++I) {
    assert(I->first != D && "Inst occurs in data structures");
    for (Instruction *Inst : I->second)
      assert(Inst != D && "Inst occurs in data structures");
  }

  for (ReverseDepMapType::const_iterator I = ReverseNonLocalDeps.begin(),
       E = ReverseNonLocalDeps.end();
       I != E; ++I) {
    assert(I->first != D && "Inst occurs in data structures");
    for (Instruction *Inst : I->second)
      assert(Inst != D && "Inst occurs in data structures");
  }

  for (ReverseNonLocalPtrDepTy::const_iterator
       I = ReverseNonLocalPtrDeps.begin(),
       E = ReverseNonLocalPtrDeps.end(); I != E; ++I) {
    assert(I->first != D && "Inst occurs in rev NLPD map");

    for (ValueIsLoadPair P : I->second)
      assert(P != ValueIsLoadPair(D, false) &&
             P != ValueIsLoadPair(D, true) &&
             "Inst occurs in ReverseNonLocalPtrDeps map");
  }
#endif
}