llvm.org GIT mirror llvm / master include / llvm / Transforms / IPO / Attributor.h
master

Tree @master (Download .tar.gz)

Attributor.h @masterraw · 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
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
//===- Attributor.h --- Module-wide attribute deduction ---------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Attributor: An inter procedural (abstract) "attribute" deduction framework.
//
// The Attributor framework is an inter procedural abstract analysis (fixpoint
// iteration analysis). The goal is to allow easy deduction of new attributes as
// well as information exchange between abstract attributes in-flight.
//
// The Attributor class is the driver and the link between the various abstract
// attributes. The Attributor will iterate until a fixpoint state is reached by
// all abstract attributes in-flight, or until it will enforce a pessimistic fix
// point because an iteration limit is reached.
//
// Abstract attributes, derived from the AbstractAttribute class, actually
// describe properties of the code. They can correspond to actual LLVM-IR
// attributes, or they can be more general, ultimately unrelated to LLVM-IR
// attributes. The latter is useful when an abstract attributes provides
// information to other abstract attributes in-flight but we might not want to
// manifest the information. The Attributor allows to query in-flight abstract
// attributes through the `Attributor::getAAFor` method (see the method
// description for an example). If the method is used by an abstract attribute
// P, and it results in an abstract attribute Q, the Attributor will
// automatically capture a potential dependence from Q to P. This dependence
// will cause P to be reevaluated whenever Q changes in the future.
//
// The Attributor will only reevaluated abstract attributes that might have
// changed since the last iteration. That means that the Attribute will not
// revisit all instructions/blocks/functions in the module but only query
// an update from a subset of the abstract attributes.
//
// The update method `AbstractAttribute::updateImpl` is implemented by the
// specific "abstract attribute" subclasses. The method is invoked whenever the
// currently assumed state (see the AbstractState class) might not be valid
// anymore. This can, for example, happen if the state was dependent on another
// abstract attribute that changed. In every invocation, the update method has
// to adjust the internal state of an abstract attribute to a point that is
// justifiable by the underlying IR and the current state of abstract attributes
// in-flight. Since the IR is given and assumed to be valid, the information
// derived from it can be assumed to hold. However, information derived from
// other abstract attributes is conditional on various things. If the justifying
// state changed, the `updateImpl` has to revisit the situation and potentially
// find another justification or limit the optimistic assumes made.
//
// Change is the key in this framework. Until a state of no-change, thus a
// fixpoint, is reached, the Attributor will query the abstract attributes
// in-flight to re-evaluate their state. If the (current) state is too
// optimistic, hence it cannot be justified anymore through other abstract
// attributes or the state of the IR, the state of the abstract attribute will
// have to change. Generally, we assume abstract attribute state to be a finite
// height lattice and the update function to be monotone. However, these
// conditions are not enforced because the iteration limit will guarantee
// termination. If an optimistic fixpoint is reached, or a pessimistic fix
// point is enforced after a timeout, the abstract attributes are tasked to
// manifest their result in the IR for passes to come.
//
// Attribute manifestation is not mandatory. If desired, there is support to
// generate a single or multiple LLVM-IR attributes already in the helper struct
// IRAttribute. In the simplest case, a subclass inherits from IRAttribute with
// a proper Attribute::AttrKind as template parameter. The Attributor
// manifestation framework will then create and place a new attribute if it is
// allowed to do so (based on the abstract state). Other use cases can be
// achieved by overloading AbstractAttribute or IRAttribute methods.
//
//
// The "mechanics" of adding a new "abstract attribute":
// - Define a class (transitively) inheriting from AbstractAttribute and one
//   (which could be the same) that (transitively) inherits from AbstractState.
//   For the latter, consider the already available BooleanState and
//   IntegerState if they fit your needs, e.g., you require only a bit-encoding.
// - Implement all pure methods. Also use overloading if the attribute is not
//   conforming with the "default" behavior: A (set of) LLVM-IR attribute(s) for
//   an argument, call site argument, function return value, or function. See
//   the class and method descriptions for more information on the two
//   "Abstract" classes and their respective methods.
// - Register opportunities for the new abstract attribute in the
//   `Attributor::identifyDefaultAbstractAttributes` method if it should be
//   counted as a 'default' attribute.
// - Add sufficient tests.
// - Add a Statistics object for bookkeeping. If it is a simple (set of)
//   attribute(s) manifested through the Attributor manifestation framework, see
//   the bookkeeping function in Attributor.cpp.
// - If instructions with a certain opcode are interesting to the attribute, add
//   that opcode to the switch in `Attributor::identifyAbstractAttributes`. This
//   will make it possible to query all those instructions through the
//   `InformationCache::getOpcodeInstMapForFunction` interface and eliminate the
//   need to traverse the IR repeatedly.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_TRANSFORMS_IPO_ATTRIBUTOR_H
#define LLVM_TRANSFORMS_IPO_ATTRIBUTOR_H

#include "llvm/ADT/SetVector.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/PassManager.h"

namespace llvm {

struct AbstractAttribute;
struct InformationCache;
struct AAIsDead;

class Function;

/// Simple enum class that forces the status to be spelled out explicitly.
///
///{
enum class ChangeStatus {
  CHANGED,
  UNCHANGED,
};

ChangeStatus operator|(ChangeStatus l, ChangeStatus r);
ChangeStatus operator&(ChangeStatus l, ChangeStatus r);
///}

/// Helper to describe and deal with positions in the LLVM-IR.
///
/// A position in the IR is described by an anchor value and an "offset" that
/// could be the argument number, for call sites and arguments, or an indicator
/// of the "position kind". The kinds, specified in the Kind enum below, include
/// the locations in the attribute list, i.a., function scope and return value,
/// as well as a distinction between call sites and functions. Finally, there
/// are floating values that do not have a corresponding attribute list
/// position.
struct IRPosition {
  virtual ~IRPosition() {}

  /// The positions we distinguish in the IR.
  ///
  /// The values are chosen such that the KindOrArgNo member has a value >= 1
  /// if it is an argument or call site argument while a value < 1 indicates the
  /// respective kind of that value.
  enum Kind : int {
    IRP_INVALID = -6, ///< An invalid position.
    IRP_FLOAT = -5, ///< A position that is not associated with a spot suitable
                    ///< for attributes. This could be any value or instruction.
    IRP_RETURNED = -4, ///< An attribute for the function return value.
    IRP_CALL_SITE_RETURNED = -3, ///< An attribute for a call site return value.
    IRP_FUNCTION = -2,           ///< An attribute for a function (scope).
    IRP_CALL_SITE = -1, ///< An attribute for a call site (function scope).
    IRP_ARGUMENT = 0,   ///< An attribute for a function argument.
    IRP_CALL_SITE_ARGUMENT = 1, ///< An attribute for a call site argument.
  };

  /// Default constructor available to create invalid positions implicitly. All
  /// other positions need to be created explicitly through the appropriate
  /// static member function.
  IRPosition() : AnchorVal(nullptr), KindOrArgNo(IRP_INVALID) { verify(); }

  /// Create a position describing the value of \p V.
  static const IRPosition value(const Value &V) {
    if (auto *Arg = dyn_cast<Argument>(&V))
      return IRPosition::argument(*Arg);
    if (auto *CB = dyn_cast<CallBase>(&V))
      return IRPosition::callsite_returned(*CB);
    return IRPosition(const_cast<Value &>(V), IRP_FLOAT);
  }

  /// Create a position describing the function scope of \p F.
  static const IRPosition function(const Function &F) {
    return IRPosition(const_cast<Function &>(F), IRP_FUNCTION);
  }

  /// Create a position describing the returned value of \p F.
  static const IRPosition returned(const Function &F) {
    return IRPosition(const_cast<Function &>(F), IRP_RETURNED);
  }

  /// Create a position describing the argument \p Arg.
  static const IRPosition argument(const Argument &Arg) {
    return IRPosition(const_cast<Argument &>(Arg), Kind(Arg.getArgNo()));
  }

  /// Create a position describing the function scope of \p CB.
  static const IRPosition callsite_function(const CallBase &CB) {
    return IRPosition(const_cast<CallBase &>(CB), IRP_CALL_SITE);
  }

  /// Create a position describing the returned value of \p CB.
  static const IRPosition callsite_returned(const CallBase &CB) {
    return IRPosition(const_cast<CallBase &>(CB), IRP_CALL_SITE_RETURNED);
  }

  /// Create a position describing the argument of \p CB at position \p ArgNo.
  static const IRPosition callsite_argument(const CallBase &CB,
                                            unsigned ArgNo) {
    return IRPosition(const_cast<CallBase &>(CB), Kind(ArgNo));
  }

  /// Create a position describing the function scope of \p ICS.
  static const IRPosition callsite_function(ImmutableCallSite ICS) {
    return IRPosition::callsite_function(cast<CallBase>(*ICS.getInstruction()));
  }

  /// Create a position describing the returned value of \p ICS.
  static const IRPosition callsite_returned(ImmutableCallSite ICS) {
    return IRPosition::callsite_returned(cast<CallBase>(*ICS.getInstruction()));
  }

  /// Create a position describing the argument of \p ICS at position \p ArgNo.
  static const IRPosition callsite_argument(ImmutableCallSite ICS,
                                            unsigned ArgNo) {
    return IRPosition::callsite_argument(cast<CallBase>(*ICS.getInstruction()),
                                         ArgNo);
  }

  /// Create a position with function scope matching the "context" of \p IRP.
  /// If \p IRP is a call site (see isAnyCallSitePosition()) then the result
  /// will be a call site position, otherwise the function position of the
  /// associated function.
  static const IRPosition function_scope(const IRPosition &IRP) {
    if (IRP.isAnyCallSitePosition()) {
      return IRPosition::callsite_function(
          cast<CallBase>(IRP.getAnchorValue()));
    }
    assert(IRP.getAssociatedFunction());
    return IRPosition::function(*IRP.getAssociatedFunction());
  }

  bool operator==(const IRPosition &RHS) const {
    return (AnchorVal == RHS.AnchorVal) && (KindOrArgNo == RHS.KindOrArgNo);
  }
  bool operator!=(const IRPosition &RHS) const { return !(*this == RHS); }

  /// Return the value this abstract attribute is anchored with.
  ///
  /// The anchor value might not be the associated value if the latter is not
  /// sufficient to determine where arguments will be manifested. This is, so
  /// far, only the case for call site arguments as the value is not sufficient
  /// to pinpoint them. Instead, we can use the call site as an anchor.
  ///
  ///{
  Value &getAnchorValue() {
    assert(KindOrArgNo != IRP_INVALID &&
           "Invalid position does not have an anchor value!");
    return *AnchorVal;
  }
  const Value &getAnchorValue() const {
    return const_cast<IRPosition *>(this)->getAnchorValue();
  }
  ///}

  /// Return the associated function, if any.
  ///
  ///{
  Function *getAssociatedFunction() {
    if (auto *CB = dyn_cast<CallBase>(AnchorVal))
      return CB->getCalledFunction();
    assert(KindOrArgNo != IRP_INVALID &&
           "Invalid position does not have an anchor scope!");
    Value &V = getAnchorValue();
    if (isa<Function>(V))
      return &cast<Function>(V);
    if (isa<Argument>(V))
      return cast<Argument>(V).getParent();
    if (isa<Instruction>(V))
      return cast<Instruction>(V).getFunction();
    return nullptr;
  }
  const Function *getAssociatedFunction() const {
    return const_cast<IRPosition *>(this)->getAssociatedFunction();
  }
  ///}

  /// Return the associated argument, if any.
  ///
  ///{
  Argument *getAssociatedArgument() {
    if (auto *Arg = dyn_cast<Argument>(&getAnchorValue()))
      return Arg;
    int ArgNo = getArgNo();
    if (ArgNo < 0)
      return nullptr;
    Function *AssociatedFn = getAssociatedFunction();
    if (!AssociatedFn || AssociatedFn->arg_size() <= unsigned(ArgNo))
      return nullptr;
    return AssociatedFn->arg_begin() + ArgNo;
  }
  const Argument *getAssociatedArgument() const {
    return const_cast<IRPosition *>(this)->getAssociatedArgument();
  }
  ///}

  /// Return true if the position refers to a function interface, that is the
  /// function scope, the function return, or an argumnt.
  bool isFnInterfaceKind() const {
    switch (getPositionKind()) {
    case IRPosition::IRP_FUNCTION:
    case IRPosition::IRP_RETURNED:
    case IRPosition::IRP_ARGUMENT:
      return true;
    default:
      return false;
    }
  }

  /// Return the Function surrounding the anchor value.
  ///
  ///{
  Function *getAnchorScope() {
    Value &V = getAnchorValue();
    if (isa<Function>(V))
      return &cast<Function>(V);
    if (isa<Argument>(V))
      return cast<Argument>(V).getParent();
    if (isa<Instruction>(V))
      return cast<Instruction>(V).getFunction();
    return nullptr;
  }
  const Function *getAnchorScope() const {
    return const_cast<IRPosition *>(this)->getAnchorScope();
  }
  ///}

  /// Return the context instruction, if any.
  ///
  ///{
  Instruction *getCtxI() {
    Value &V = getAnchorValue();
    if (auto *I = dyn_cast<Instruction>(&V))
      return I;
    if (auto *Arg = dyn_cast<Argument>(&V))
      if (!Arg->getParent()->isDeclaration())
        return &Arg->getParent()->getEntryBlock().front();
    if (auto *F = dyn_cast<Function>(&V))
      if (!F->isDeclaration())
        return &(F->getEntryBlock().front());
    return nullptr;
  }
  const Instruction *getCtxI() const {
    return const_cast<IRPosition *>(this)->getCtxI();
  }
  ///}

  /// Return the value this abstract attribute is associated with.
  ///
  ///{
  Value &getAssociatedValue() {
    assert(KindOrArgNo != IRP_INVALID &&
           "Invalid position does not have an associated value!");
    if (getArgNo() < 0 || isa<Argument>(AnchorVal))
      return *AnchorVal;
    assert(isa<CallBase>(AnchorVal) && "Expected a call base!");
    return *cast<CallBase>(AnchorVal)->getArgOperand(getArgNo());
  }
  const Value &getAssociatedValue() const {
    return const_cast<IRPosition *>(this)->getAssociatedValue();
  }
  ///}

  /// Return the argument number of the associated value if it is an argument or
  /// call site argument, otherwise a negative value.
  int getArgNo() const { return KindOrArgNo; }

  /// Return the index in the attribute list for this position.
  unsigned getAttrIdx() const {
    switch (getPositionKind()) {
    case IRPosition::IRP_INVALID:
    case IRPosition::IRP_FLOAT:
      break;
    case IRPosition::IRP_FUNCTION:
    case IRPosition::IRP_CALL_SITE:
      return AttributeList::FunctionIndex;
    case IRPosition::IRP_RETURNED:
    case IRPosition::IRP_CALL_SITE_RETURNED:
      return AttributeList::ReturnIndex;
    case IRPosition::IRP_ARGUMENT:
    case IRPosition::IRP_CALL_SITE_ARGUMENT:
      return KindOrArgNo + AttributeList::FirstArgIndex;
    }
    llvm_unreachable(
        "There is no attribute index for a floating or invalid position!");
  }

  /// Return the associated position kind.
  Kind getPositionKind() const {
    if (getArgNo() >= 0) {
      assert(((isa<Argument>(getAnchorValue()) &&
               isa<Argument>(getAssociatedValue())) ||
              isa<CallBase>(getAnchorValue())) &&
             "Expected argument or call base due to argument number!");
      if (isa<CallBase>(getAnchorValue()))
        return IRP_CALL_SITE_ARGUMENT;
      return IRP_ARGUMENT;
    }

    assert(KindOrArgNo < 0 &&
           "Expected (call site) arguments to never reach this point!");
    assert(!isa<Argument>(getAnchorValue()) &&
           "Expected arguments to have an associated argument position!");
    return Kind(KindOrArgNo);
  }

  /// TODO: Figure out if the attribute related helper functions should live
  ///       here or somewhere else.

  /// Return true if any kind in \p AKs existing in the IR at a position that
  /// will affect this one. See also getAttrs(...).
  bool hasAttr(ArrayRef<Attribute::AttrKind> AKs) const;

  /// Return the attributes of any kind in \p AKs existing in the IR at a
  /// position that will affect this one. While each position can only have a
  /// single attribute of any kind in \p AKs, there are "subsuming" positions
  /// that could have an attribute as well. This method returns all attributes
  /// found in \p Attrs.
  void getAttrs(ArrayRef<Attribute::AttrKind> AKs,
                SmallVectorImpl<Attribute> &Attrs) const;

  /// Return the attribute of kind \p AK existing in the IR at this position.
  Attribute getAttr(Attribute::AttrKind AK) const {
    if (getPositionKind() == IRP_INVALID || getPositionKind() == IRP_FLOAT)
      return Attribute();

    AttributeList AttrList;
    if (ImmutableCallSite ICS = ImmutableCallSite(&getAnchorValue()))
      AttrList = ICS.getAttributes();
    else
      AttrList = getAssociatedFunction()->getAttributes();

    if (AttrList.hasAttribute(getAttrIdx(), AK))
      return AttrList.getAttribute(getAttrIdx(), AK);
    return Attribute();
  }

  bool isAnyCallSitePosition() const {
    switch (getPositionKind()) {
    case IRPosition::IRP_CALL_SITE:
    case IRPosition::IRP_CALL_SITE_RETURNED:
    case IRPosition::IRP_CALL_SITE_ARGUMENT:
      return true;
    default:
      return false;
    }
  }

  /// Special DenseMap key values.
  ///
  ///{
  static const IRPosition EmptyKey;
  static const IRPosition TombstoneKey;
  ///}

private:
  /// Private constructor for special values only!
  explicit IRPosition(int KindOrArgNo)
      : AnchorVal(0), KindOrArgNo(KindOrArgNo) {}

  /// IRPosition anchored at \p AnchorVal with kind/argument numbet \p PK.
  explicit IRPosition(Value &AnchorVal, Kind PK)
      : AnchorVal(&AnchorVal), KindOrArgNo(PK) {
    verify();
  }

  /// Verify internal invariants.
  void verify();

  /// The value this position is anchored at.
  Value *AnchorVal;

  /// The argument number, if non-negative, or the position "kind".
  int KindOrArgNo;
};

/// Helper that allows IRPosition as a key in a DenseMap.
template <> struct DenseMapInfo<IRPosition> {
  static inline IRPosition getEmptyKey() { return IRPosition::EmptyKey; }
  static inline IRPosition getTombstoneKey() {
    return IRPosition::TombstoneKey;
  }
  static unsigned getHashValue(const IRPosition &IRP) {
    return (DenseMapInfo<Value *>::getHashValue(&IRP.getAnchorValue()) << 4) ^
           (unsigned(IRP.getArgNo()));
  }
  static bool isEqual(const IRPosition &LHS, const IRPosition &RHS) {
    return LHS == RHS;
  }
};

/// A visitor class for IR positions.
///
/// Given a position P, the SubsumingPositionIterator allows to visit "subsuming
/// positions" wrt. attributes/information. Thus, if a piece of information
/// holds for a subsuming position, it also holds for the position P.
///
/// The subsuming positions always include the initial position and then,
/// depending on the position kind, additionally the following ones:
/// - for IRP_RETURNED:
///   - the function (IRP_FUNCTION)
/// - for IRP_ARGUMENT:
///   - the function (IRP_FUNCTION)
/// - for IRP_CALL_SITE:
///   - the callee (IRP_FUNCTION), if known
/// - for IRP_CALL_SITE_RETURNED:
///   - the callee (IRP_RETURNED), if known
///   - the call site (IRP_FUNCTION)
///   - the callee (IRP_FUNCTION), if known
/// - for IRP_CALL_SITE_ARGUMENT:
///   - the argument of the callee (IRP_ARGUMENT), if known
///   - the callee (IRP_FUNCTION), if known
///   - the position the call site argument is associated with if it is not
///     anchored to the call site, e.g., if it is an arugment then the argument
///     (IRP_ARGUMENT)
class SubsumingPositionIterator {
  SmallVector<IRPosition, 4> IRPositions;
  using iterator = decltype(IRPositions)::iterator;

public:
  SubsumingPositionIterator(const IRPosition &IRP);
  iterator begin() { return IRPositions.begin(); }
  iterator end() { return IRPositions.end(); }
};

/// Wrapper for FunctoinAnalysisManager.
struct AnalysisGetter {
  template <typename Analysis>
  typename Analysis::Result *getAnalysis(const Function &F) {
    if (!FAM)
      return nullptr;
    return &FAM->getResult<Analysis>(const_cast<Function &>(F));
  }
  AnalysisGetter(FunctionAnalysisManager &FAM) : FAM(&FAM) {}
  AnalysisGetter() {}

private:
  FunctionAnalysisManager *FAM = nullptr;
};

/// Data structure to hold cached (LLVM-IR) information.
///
/// All attributes are given an InformationCache object at creation time to
/// avoid inspection of the IR by all of them individually. This default
/// InformationCache will hold information required by 'default' attributes,
/// thus the ones deduced when Attributor::identifyDefaultAbstractAttributes(..)
/// is called.
///
/// If custom abstract attributes, registered manually through
/// Attributor::registerAA(...), need more information, especially if it is not
/// reusable, it is advised to inherit from the InformationCache and cast the
/// instance down in the abstract attributes.
struct InformationCache {
  InformationCache(const DataLayout &DL, AnalysisGetter &AG) : DL(DL), AG(AG) {}

  /// A map type from opcodes to instructions with this opcode.
  using OpcodeInstMapTy = DenseMap<unsigned, SmallVector<Instruction *, 32>>;

  /// Return the map that relates "interesting" opcodes with all instructions
  /// with that opcode in \p F.
  OpcodeInstMapTy &getOpcodeInstMapForFunction(const Function &F) {
    return FuncInstOpcodeMap[&F];
  }

  /// A vector type to hold instructions.
  using InstructionVectorTy = std::vector<Instruction *>;

  /// Return the instructions in \p F that may read or write memory.
  InstructionVectorTy &getReadOrWriteInstsForFunction(const Function &F) {
    return FuncRWInstsMap[&F];
  }

  /// Return TargetLibraryInfo for function \p F.
  TargetLibraryInfo *getTargetLibraryInfoForFunction(const Function &F) {
    return AG.getAnalysis<TargetLibraryAnalysis>(F);
  }

  /// Return AliasAnalysis Result for function \p F.
  AAResults *getAAResultsForFunction(const Function &F) {
    return AG.getAnalysis<AAManager>(F);
  }

  /// Return datalayout used in the module.
  const DataLayout &getDL() { return DL; }

private:
  /// A map type from functions to opcode to instruction maps.
  using FuncInstOpcodeMapTy = DenseMap<const Function *, OpcodeInstMapTy>;

  /// A map type from functions to their read or write instructions.
  using FuncRWInstsMapTy = DenseMap<const Function *, InstructionVectorTy>;

  /// A nested map that remembers all instructions in a function with a certain
  /// instruction opcode (Instruction::getOpcode()).
  FuncInstOpcodeMapTy FuncInstOpcodeMap;

  /// A map from functions to their instructions that may read or write memory.
  FuncRWInstsMapTy FuncRWInstsMap;

  /// A map from functions to their TLI.

  /// The datalayout used in the module.
  const DataLayout &DL;

  /// Getters for analysis.
  AnalysisGetter &AG;

  /// Give the Attributor access to the members so
  /// Attributor::identifyDefaultAbstractAttributes(...) can initialize them.
  friend struct Attributor;
};

/// The fixpoint analysis framework that orchestrates the attribute deduction.
///
/// The Attributor provides a general abstract analysis framework (guided
/// fixpoint iteration) as well as helper functions for the deduction of
/// (LLVM-IR) attributes. However, also other code properties can be deduced,
/// propagated, and ultimately manifested through the Attributor framework. This
/// is particularly useful if these properties interact with attributes and a
/// co-scheduled deduction allows to improve the solution. Even if not, thus if
/// attributes/properties are completely isolated, they should use the
/// Attributor framework to reduce the number of fixpoint iteration frameworks
/// in the code base. Note that the Attributor design makes sure that isolated
/// attributes are not impacted, in any way, by others derived at the same time
/// if there is no cross-reasoning performed.
///
/// The public facing interface of the Attributor is kept simple and basically
/// allows abstract attributes to one thing, query abstract attributes
/// in-flight. There are two reasons to do this:
///    a) The optimistic state of one abstract attribute can justify an
///       optimistic state of another, allowing to framework to end up with an
///       optimistic (=best possible) fixpoint instead of one based solely on
///       information in the IR.
///    b) This avoids reimplementing various kinds of lookups, e.g., to check
///       for existing IR attributes, in favor of a single lookups interface
///       provided by an abstract attribute subclass.
///
/// NOTE: The mechanics of adding a new "concrete" abstract attribute are
///       described in the file comment.
struct Attributor {
  /// Constructor
  ///
  /// \param InfoCache Cache to hold various information accessible for
  ///                  the abstract attributes.
  /// \param DepRecomputeInterval Number of iterations until the dependences
  ///                             between abstract attributes are recomputed.
  /// \param Whitelist If not null, a set limiting the attribute opportunities.
  Attributor(InformationCache &InfoCache, unsigned DepRecomputeInterval,
             DenseSet<const char *> *Whitelist = nullptr)
      : InfoCache(InfoCache), DepRecomputeInterval(DepRecomputeInterval),
        Whitelist(Whitelist) {}

  ~Attributor() { DeleteContainerPointers(AllAbstractAttributes); }

  /// Run the analyses until a fixpoint is reached or enforced (timeout).
  ///
  /// The attributes registered with this Attributor can be used after as long
  /// as the Attributor is not destroyed (it owns the attributes now).
  ///
  /// \Returns CHANGED if the IR was changed, otherwise UNCHANGED.
  ChangeStatus run(Module &M);

  /// Lookup an abstract attribute of type \p AAType at position \p IRP. While
  /// no abstract attribute is found equivalent positions are checked, see
  /// SubsumingPositionIterator. Thus, the returned abstract attribute
  /// might be anchored at a different position, e.g., the callee if \p IRP is a
  /// call base.
  ///
  /// This method is the only (supported) way an abstract attribute can retrieve
  /// information from another abstract attribute. As an example, take an
  /// abstract attribute that determines the memory access behavior for a
  /// argument (readnone, readonly, ...). It should use `getAAFor` to get the
  /// most optimistic information for other abstract attributes in-flight, e.g.
  /// the one reasoning about the "captured" state for the argument or the one
  /// reasoning on the memory access behavior of the function as a whole.
  ///
  /// If the flag \p TrackDependence is set to false the dependence from
  /// \p QueryingAA to the return abstract attribute is not automatically
  /// recorded. This should only be used if the caller will record the
  /// dependence explicitly if necessary, thus if it the returned abstract
  /// attribute is used for reasoning. To record the dependences explicitly use
  /// the `Attributor::recordDependence` method.
  template <typename AAType>
  const AAType &getAAFor(const AbstractAttribute &QueryingAA,
                         const IRPosition &IRP, bool TrackDependence = true) {
    return getOrCreateAAFor<AAType>(IRP, &QueryingAA, TrackDependence);
  }

  /// Explicitly record a dependence from \p FromAA to \p ToAA, that is if
  /// \p FromAA changes \p ToAA should be updated as well.
  ///
  /// This method should be used in conjunction with the `getAAFor` method and
  /// with the TrackDependence flag passed to the method set to false. This can
  /// be beneficial to avoid false dependences but it requires the users of
  /// `getAAFor` to explicitly record true dependences through this method.
  void recordDependence(const AbstractAttribute &FromAA,
                        const AbstractAttribute &ToAA) {
    QueryMap[&FromAA].insert(const_cast<AbstractAttribute *>(&ToAA));
  }

  /// Introduce a new abstract attribute into the fixpoint analysis.
  ///
  /// Note that ownership of the attribute is given to the Attributor. It will
  /// invoke delete for the Attributor on destruction of the Attributor.
  ///
  /// Attributes are identified by their IR position (AAType::getIRPosition())
  /// and the address of their static member (see AAType::ID).
  template <typename AAType> AAType &registerAA(AAType &AA) {
    static_assert(std::is_base_of<AbstractAttribute, AAType>::value,
                  "Cannot register an attribute with a type not derived from "
                  "'AbstractAttribute'!");
    // Put the attribute in the lookup map structure and the container we use to
    // keep track of all attributes.
    IRPosition &IRP = AA.getIRPosition();
    auto &KindToAbstractAttributeMap = AAMap[IRP];
    assert(!KindToAbstractAttributeMap.count(&AAType::ID) &&
           "Attribute already in map!");
    KindToAbstractAttributeMap[&AAType::ID] = &AA;
    AllAbstractAttributes.push_back(&AA);
    return AA;
  }

  /// Return the internal information cache.
  InformationCache &getInfoCache() { return InfoCache; }

  /// Determine opportunities to derive 'default' attributes in \p F and create
  /// abstract attribute objects for them.
  ///
  /// \param F The function that is checked for attribute opportunities.
  /// \param TLIGetter helper function to get TargetLibraryInfo Analysis result.
  ///
  /// Note that abstract attribute instances are generally created even if the
  /// IR already contains the information they would deduce. The most important
  /// reason for this is the single interface, the one of the abstract attribute
  /// instance, which can be queried without the need to look at the IR in
  /// various places.
  void identifyDefaultAbstractAttributes(Function &F);

  /// Initialize the information cache for queries regarding function \p F.
  ///
  /// This method needs to be called for all function that might be looked at
  /// through the information cache interface *prior* to looking at them.
  void initializeInformationCache(Function &F);

  /// Mark the internal function \p F as live.
  ///
  /// This will trigger the identification and initialization of attributes for
  /// \p F.
  void markLiveInternalFunction(const Function &F) {
    assert(F.hasInternalLinkage() &&
           "Only internal linkage is assumed dead initially.");

    identifyDefaultAbstractAttributes(const_cast<Function &>(F));
  }

  /// Record that \p I is deleted after information was manifested.
  void deleteAfterManifest(Instruction &I) { ToBeDeletedInsts.insert(&I); }

  /// Record that \p BB is deleted after information was manifested.
  void deleteAfterManifest(BasicBlock &BB) { ToBeDeletedBlocks.insert(&BB); }

  /// Record that \p F is deleted after information was manifested.
  void deleteAfterManifest(Function &F) { ToBeDeletedFunctions.insert(&F); }

  /// Return true if \p AA (or its context instruction) is assumed dead.
  ///
  /// If \p LivenessAA is not provided it is queried.
  bool isAssumedDead(const AbstractAttribute &AA, const AAIsDead *LivenessAA);

  /// Check \p Pred on all function call sites.
  ///
  /// This method will evaluate \p Pred on call sites and return
  /// true if \p Pred holds in every call sites. However, this is only possible
  /// all call sites are known, hence the function has internal linkage.
  bool checkForAllCallSites(const function_ref<bool(CallSite)> &Pred,
                            const AbstractAttribute &QueryingAA,
                            bool RequireAllCallSites);

  /// Check \p Pred on all values potentially returned by \p F.
  ///
  /// This method will evaluate \p Pred on all values potentially returned by
  /// the function associated with \p QueryingAA. The returned values are
  /// matched with their respective return instructions. Returns true if \p Pred
  /// holds on all of them.
  bool checkForAllReturnedValuesAndReturnInsts(
      const function_ref<bool(Value &, const SmallSetVector<ReturnInst *, 4> &)>
          &Pred,
      const AbstractAttribute &QueryingAA);

  /// Check \p Pred on all values potentially returned by the function
  /// associated with \p QueryingAA.
  ///
  /// This is the context insensitive version of the method above.
  bool checkForAllReturnedValues(const function_ref<bool(Value &)> &Pred,
                                 const AbstractAttribute &QueryingAA);

  /// Check \p Pred on all instructions with an opcode present in \p Opcodes.
  ///
  /// This method will evaluate \p Pred on all instructions with an opcode
  /// present in \p Opcode and return true if \p Pred holds on all of them.
  bool checkForAllInstructions(const function_ref<bool(Instruction &)> &Pred,
                               const AbstractAttribute &QueryingAA,
                               const ArrayRef<unsigned> &Opcodes);

  /// Check \p Pred on all call-like instructions (=CallBased derived).
  ///
  /// See checkForAllCallLikeInstructions(...) for more information.
  bool
  checkForAllCallLikeInstructions(const function_ref<bool(Instruction &)> &Pred,
                                  const AbstractAttribute &QueryingAA) {
    return checkForAllInstructions(Pred, QueryingAA,
                                   {(unsigned)Instruction::Invoke,
                                    (unsigned)Instruction::CallBr,
                                    (unsigned)Instruction::Call});
  }

  /// Check \p Pred on all Read/Write instructions.
  ///
  /// This method will evaluate \p Pred on all instructions that read or write
  /// to memory present in the information cache and return true if \p Pred
  /// holds on all of them.
  bool checkForAllReadWriteInstructions(
      const llvm::function_ref<bool(Instruction &)> &Pred,
      AbstractAttribute &QueryingAA);

  /// Return the data layout associated with the anchor scope.
  const DataLayout &getDataLayout() const { return InfoCache.DL; }

private:

  /// The private version of getAAFor that allows to omit a querying abstract
  /// attribute. See also the public getAAFor method.
  template <typename AAType>
  const AAType &getOrCreateAAFor(const IRPosition &IRP,
                         const AbstractAttribute *QueryingAA = nullptr,
                         bool TrackDependence = false) {
    if (const AAType *AAPtr =
            lookupAAFor<AAType>(IRP, QueryingAA, TrackDependence))
      return *AAPtr;

    // No matching attribute found, create one.
    // Use the static create method.
    auto &AA = AAType::createForPosition(IRP, *this);
    registerAA(AA);
    AA.initialize(*this);

    // Bootstrap the new attribute with an initial update to propagate
    // information, e.g., function -> call site. If it is not on a given
    // whitelist we will not perform updates at all.
    if (Whitelist && !Whitelist->count(&AAType::ID))
      AA.getState().indicatePessimisticFixpoint();
    else
      AA.update(*this);

    if (TrackDependence && AA.getState().isValidState())
      QueryMap[&AA].insert(const_cast<AbstractAttribute *>(QueryingAA));
    return AA;
  }

  /// Return the attribute of \p AAType for \p IRP if existing.
  template <typename AAType>
  const AAType *lookupAAFor(const IRPosition &IRP,
                            const AbstractAttribute *QueryingAA = nullptr,
                            bool TrackDependence = false) {
    static_assert(std::is_base_of<AbstractAttribute, AAType>::value,
                  "Cannot query an attribute with a type not derived from "
                  "'AbstractAttribute'!");
    assert((QueryingAA || !TrackDependence) &&
           "Cannot track dependences without a QueryingAA!");

    // Lookup the abstract attribute of type AAType. If found, return it after
    // registering a dependence of QueryingAA on the one returned attribute.
    const auto &KindToAbstractAttributeMap = AAMap.lookup(IRP);
    if (AAType *AA = static_cast<AAType *>(
            KindToAbstractAttributeMap.lookup(&AAType::ID))) {
      // Do not register a dependence on an attribute with an invalid state.
      if (TrackDependence && AA->getState().isValidState())
        QueryMap[AA].insert(const_cast<AbstractAttribute *>(QueryingAA));
      return AA;
    }
    return nullptr;
  }

  /// The set of all abstract attributes.
  ///{
  using AAVector = SmallVector<AbstractAttribute *, 64>;
  AAVector AllAbstractAttributes;
  ///}

  /// A nested map to lookup abstract attributes based on the argument position
  /// on the outer level, and the addresses of the static member (AAType::ID) on
  /// the inner level.
  ///{
  using KindToAbstractAttributeMap =
      DenseMap<const char *, AbstractAttribute *>;
  DenseMap<IRPosition, KindToAbstractAttributeMap> AAMap;
  ///}

  /// A map from abstract attributes to the ones that queried them through calls
  /// to the getAAFor<...>(...) method.
  ///{
  using QueryMapTy =
      MapVector<const AbstractAttribute *, SetVector<AbstractAttribute *>>;
  QueryMapTy QueryMap;
  ///}

  /// The information cache that holds pre-processed (LLVM-IR) information.
  InformationCache &InfoCache;

  /// Number of iterations until the dependences between abstract attributes are
  /// recomputed.
  const unsigned DepRecomputeInterval;

  /// If not null, a set limiting the attribute opportunities.
  const DenseSet<const char *> *Whitelist;

  /// A set to remember the functions we already assume to be live and visited.
  DenseSet<const Function *> VisitedFunctions;

  /// Functions, blocks, and instructions we delete after manifest is done.
  ///
  ///{
  SmallPtrSet<Function *, 8> ToBeDeletedFunctions;
  SmallPtrSet<BasicBlock *, 8> ToBeDeletedBlocks;
  SmallPtrSet<Instruction *, 8> ToBeDeletedInsts;
  ///}
};

/// An interface to query the internal state of an abstract attribute.
///
/// The abstract state is a minimal interface that allows the Attributor to
/// communicate with the abstract attributes about their internal state without
/// enforcing or exposing implementation details, e.g., the (existence of an)
/// underlying lattice.
///
/// It is sufficient to be able to query if a state is (1) valid or invalid, (2)
/// at a fixpoint, and to indicate to the state that (3) an optimistic fixpoint
/// was reached or (4) a pessimistic fixpoint was enforced.
///
/// All methods need to be implemented by the subclass. For the common use case,
/// a single boolean state or a bit-encoded state, the BooleanState and
/// IntegerState classes are already provided. An abstract attribute can inherit
/// from them to get the abstract state interface and additional methods to
/// directly modify the state based if needed. See the class comments for help.
struct AbstractState {
  virtual ~AbstractState() {}

  /// Return if this abstract state is in a valid state. If false, no
  /// information provided should be used.
  virtual bool isValidState() const = 0;

  /// Return if this abstract state is fixed, thus does not need to be updated
  /// if information changes as it cannot change itself.
  virtual bool isAtFixpoint() const = 0;

  /// Indicate that the abstract state should converge to the optimistic state.
  ///
  /// This will usually make the optimistically assumed state the known to be
  /// true state.
  ///
  /// \returns ChangeStatus::UNCHANGED as the assumed value should not change.
  virtual ChangeStatus indicateOptimisticFixpoint() = 0;

  /// Indicate that the abstract state should converge to the pessimistic state.
  ///
  /// This will usually revert the optimistically assumed state to the known to
  /// be true state.
  ///
  /// \returns ChangeStatus::CHANGED as the assumed value may change.
  virtual ChangeStatus indicatePessimisticFixpoint() = 0;
};

/// Simple state with integers encoding.
///
/// The interface ensures that the assumed bits are always a subset of the known
/// bits. Users can only add known bits and, except through adding known bits,
/// they can only remove assumed bits. This should guarantee monotoniticy and
/// thereby the existence of a fixpoint (if used corretly). The fixpoint is
/// reached when the assumed and known state/bits are equal. Users can
/// force/inidicate a fixpoint. If an optimistic one is indicated, the known
/// state will catch up with the assumed one, for a pessimistic fixpoint it is
/// the other way around.
struct IntegerState : public AbstractState {
  /// Underlying integer type, we assume 32 bits to be enough.
  using base_t = uint32_t;

  /// Initialize the (best) state.
  IntegerState(base_t BestState = ~0) : Assumed(BestState) {}

  /// Return the worst possible representable state.
  static constexpr base_t getWorstState() { return 0; }

  /// See AbstractState::isValidState()
  /// NOTE: For now we simply pretend that the worst possible state is invalid.
  bool isValidState() const override { return Assumed != getWorstState(); }

  /// See AbstractState::isAtFixpoint()
  bool isAtFixpoint() const override { return Assumed == Known; }

  /// See AbstractState::indicateOptimisticFixpoint(...)
  ChangeStatus indicateOptimisticFixpoint() override {
    Known = Assumed;
    return ChangeStatus::UNCHANGED;
  }

  /// See AbstractState::indicatePessimisticFixpoint(...)
  ChangeStatus indicatePessimisticFixpoint() override {
    Assumed = Known;
    return ChangeStatus::CHANGED;
  }

  /// Return the known state encoding
  base_t getKnown() const { return Known; }

  /// Return the assumed state encoding.
  base_t getAssumed() const { return Assumed; }

  /// Return true if the bits set in \p BitsEncoding are "known bits".
  bool isKnown(base_t BitsEncoding) const {
    return (Known & BitsEncoding) == BitsEncoding;
  }

  /// Return true if the bits set in \p BitsEncoding are "assumed bits".
  bool isAssumed(base_t BitsEncoding) const {
    return (Assumed & BitsEncoding) == BitsEncoding;
  }

  /// Add the bits in \p BitsEncoding to the "known bits".
  IntegerState &addKnownBits(base_t Bits) {
    // Make sure we never miss any "known bits".
    Assumed |= Bits;
    Known |= Bits;
    return *this;
  }

  /// Remove the bits in \p BitsEncoding from the "assumed bits" if not known.
  IntegerState &removeAssumedBits(base_t BitsEncoding) {
    // Make sure we never loose any "known bits".
    Assumed = (Assumed & ~BitsEncoding) | Known;
    return *this;
  }

  /// Keep only "assumed bits" also set in \p BitsEncoding but all known ones.
  IntegerState &intersectAssumedBits(base_t BitsEncoding) {
    // Make sure we never loose any "known bits".
    Assumed = (Assumed & BitsEncoding) | Known;
    return *this;
  }

  /// Take minimum of assumed and \p Value.
  IntegerState &takeAssumedMinimum(base_t Value) {
    // Make sure we never loose "known value".
    Assumed = std::max(std::min(Assumed, Value), Known);
    return *this;
  }

  /// Take maximum of known and \p Value.
  IntegerState &takeKnownMaximum(base_t Value) {
    // Make sure we never loose "known value".
    Assumed = std::max(Value, Assumed);
    Known = std::max(Value, Known);
    return *this;
  }

  /// Equality for IntegerState.
  bool operator==(const IntegerState &R) const {
    return this->getAssumed() == R.getAssumed() &&
           this->getKnown() == R.getKnown();
  }

  /// Inequality for IntegerState.
  bool operator!=(const IntegerState &R) const { return !(*this == R); }

  /// "Clamp" this state with \p R. The result is the minimum of the assumed
  /// information but not less than what was known before.
  ///
  /// TODO: Consider replacing the operator with a call or using it only when
  ///       we can also take the maximum of the known information, thus when
  ///       \p R is not dependent on additional assumed state.
  IntegerState operator^=(const IntegerState &R) {
    takeAssumedMinimum(R.Assumed);
    return *this;
  }

  /// "Clamp" this state with \p R. The result is the maximum of the known
  /// information but not more than what was assumed before.
  IntegerState operator+=(const IntegerState &R) {
    takeKnownMaximum(R.Known);
    return *this;
  }

  /// Make this the minimum, known and assumed, of this state and \p R.
  IntegerState operator&=(const IntegerState &R) {
    Known = std::min(Known, R.Known);
    Assumed = std::min(Assumed, R.Assumed);
    return *this;
  }

  /// Make this the maximum, known and assumed, of this state and \p R.
  IntegerState operator|=(const IntegerState &R) {
    Known = std::max(Known, R.Known);
    Assumed = std::max(Assumed, R.Assumed);
    return *this;
  }

private:
  /// The known state encoding in an integer of type base_t.
  base_t Known = getWorstState();

  /// The assumed state encoding in an integer of type base_t.
  base_t Assumed;
};

/// Simple wrapper for a single bit (boolean) state.
struct BooleanState : public IntegerState {
  BooleanState() : IntegerState(1){};
};

/// Helper struct necessary as the modular build fails if the virtual method
/// IRAttribute::manifest is defined in the Attributor.cpp.
struct IRAttributeManifest {
  static ChangeStatus manifestAttrs(Attributor &A, IRPosition &IRP,
                                    const ArrayRef<Attribute> &DeducedAttrs);
};

/// Helper to tie a abstract state implementation to an abstract attribute.
template <typename StateTy, typename Base>
struct StateWrapper : public StateTy, public Base {
  /// Provide static access to the type of the state.
  using StateType = StateTy;

  /// See AbstractAttribute::getState(...).
  StateType &getState() override { return *this; }

  /// See AbstractAttribute::getState(...).
  const AbstractState &getState() const override { return *this; }
};

/// Helper class that provides common functionality to manifest IR attributes.
template <Attribute::AttrKind AK, typename Base>
struct IRAttribute : public IRPosition, public Base {
  IRAttribute(const IRPosition &IRP) : IRPosition(IRP) {}
  ~IRAttribute() {}

  /// See AbstractAttribute::initialize(...).
  virtual void initialize(Attributor &A) override {
    if (hasAttr(getAttrKind())) {
      this->getState().indicateOptimisticFixpoint();
      return;
    }

    const IRPosition &IRP = this->getIRPosition();
    bool IsFnInterface = IRP.isFnInterfaceKind();
    const Function *FnScope = IRP.getAnchorScope();
    // TODO: Not all attributes require an exact definition. Find a way to
    //       enable deduction for some but not all attributes in case the
    //       definition might be changed at runtime, see also
    //       http://lists.llvm.org/pipermail/llvm-dev/2018-February/121275.html.
    // TODO: We could always determine abstract attributes and if sufficient
    //       information was found we could duplicate the functions that do not
    //       have an exact definition.
    if (IsFnInterface && (!FnScope || !FnScope->hasExactDefinition()))
      this->getState().indicatePessimisticFixpoint();
  }

  /// See AbstractAttribute::manifest(...).
  ChangeStatus manifest(Attributor &A) override {
    SmallVector<Attribute, 4> DeducedAttrs;
    getDeducedAttributes(getAnchorValue().getContext(), DeducedAttrs);
    return IRAttributeManifest::manifestAttrs(A, getIRPosition(), DeducedAttrs);
  }

  /// Return the kind that identifies the abstract attribute implementation.
  Attribute::AttrKind getAttrKind() const { return AK; }

  /// Return the deduced attributes in \p Attrs.
  virtual void getDeducedAttributes(LLVMContext &Ctx,
                                    SmallVectorImpl<Attribute> &Attrs) const {
    Attrs.emplace_back(Attribute::get(Ctx, getAttrKind()));
  }

  /// Return an IR position, see struct IRPosition.
  ///
  ///{
  IRPosition &getIRPosition() override { return *this; }
  const IRPosition &getIRPosition() const override { return *this; }
  ///}
};

/// Base struct for all "concrete attribute" deductions.
///
/// The abstract attribute is a minimal interface that allows the Attributor to
/// orchestrate the abstract/fixpoint analysis. The design allows to hide away
/// implementation choices made for the subclasses but also to structure their
/// implementation and simplify the use of other abstract attributes in-flight.
///
/// To allow easy creation of new attributes, most methods have default
/// implementations. The ones that do not are generally straight forward, except
/// `AbstractAttribute::updateImpl` which is the location of most reasoning
/// associated with the abstract attribute. The update is invoked by the
/// Attributor in case the situation used to justify the current optimistic
/// state might have changed. The Attributor determines this automatically
/// by monitoring the `Attributor::getAAFor` calls made by abstract attributes.
///
/// The `updateImpl` method should inspect the IR and other abstract attributes
/// in-flight to justify the best possible (=optimistic) state. The actual
/// implementation is, similar to the underlying abstract state encoding, not
/// exposed. In the most common case, the `updateImpl` will go through a list of
/// reasons why its optimistic state is valid given the current information. If
/// any combination of them holds and is sufficient to justify the current
/// optimistic state, the method shall return UNCHAGED. If not, the optimistic
/// state is adjusted to the situation and the method shall return CHANGED.
///
/// If the manifestation of the "concrete attribute" deduced by the subclass
/// differs from the "default" behavior, which is a (set of) LLVM-IR
/// attribute(s) for an argument, call site argument, function return value, or
/// function, the `AbstractAttribute::manifest` method should be overloaded.
///
/// NOTE: If the state obtained via getState() is INVALID, thus if
///       AbstractAttribute::getState().isValidState() returns false, no
///       information provided by the methods of this class should be used.
/// NOTE: The Attributor currently has certain limitations to what we can do.
///       As a general rule of thumb, "concrete" abstract attributes should *for
///       now* only perform "backward" information propagation. That means
///       optimistic information obtained through abstract attributes should
///       only be used at positions that precede the origin of the information
///       with regards to the program flow. More practically, information can
///       *now* be propagated from instructions to their enclosing function, but
///       *not* from call sites to the called function. The mechanisms to allow
///       both directions will be added in the future.
/// NOTE: The mechanics of adding a new "concrete" abstract attribute are
///       described in the file comment.
struct AbstractAttribute {
  using StateType = AbstractState;

  /// Virtual destructor.
  virtual ~AbstractAttribute() {}

  /// Initialize the state with the information in the Attributor \p A.
  ///
  /// This function is called by the Attributor once all abstract attributes
  /// have been identified. It can and shall be used for task like:
  ///  - identify existing knowledge in the IR and use it for the "known state"
  ///  - perform any work that is not going to change over time, e.g., determine
  ///    a subset of the IR, or attributes in-flight, that have to be looked at
  ///    in the `updateImpl` method.
  virtual void initialize(Attributor &A) {}

  /// Return the internal abstract state for inspection.
  virtual StateType &getState() = 0;
  virtual const StateType &getState() const = 0;

  /// Return an IR position, see struct IRPosition.
  virtual const IRPosition &getIRPosition() const = 0;

  /// Helper functions, for debug purposes only.
  ///{
  virtual void print(raw_ostream &OS) const;
  void dump() const { print(dbgs()); }

  /// This function should return the "summarized" assumed state as string.
  virtual const std::string getAsStr() const = 0;
  ///}

  /// Allow the Attributor access to the protected methods.
  friend struct Attributor;

protected:
  /// Hook for the Attributor to trigger an update of the internal state.
  ///
  /// If this attribute is already fixed, this method will return UNCHANGED,
  /// otherwise it delegates to `AbstractAttribute::updateImpl`.
  ///
  /// \Return CHANGED if the internal state changed, otherwise UNCHANGED.
  ChangeStatus update(Attributor &A);

  /// Hook for the Attributor to trigger the manifestation of the information
  /// represented by the abstract attribute in the LLVM-IR.
  ///
  /// \Return CHANGED if the IR was altered, otherwise UNCHANGED.
  virtual ChangeStatus manifest(Attributor &A) {
    return ChangeStatus::UNCHANGED;
  }

  /// Hook to enable custom statistic tracking, called after manifest that
  /// resulted in a change if statistics are enabled.
  ///
  /// We require subclasses to provide an implementation so we remember to
  /// add statistics for them.
  virtual void trackStatistics() const = 0;

  /// Return an IR position, see struct IRPosition.
  virtual IRPosition &getIRPosition() = 0;

  /// The actual update/transfer function which has to be implemented by the
  /// derived classes.
  ///
  /// If it is called, the environment has changed and we have to determine if
  /// the current information is still valid or adjust it otherwise.
  ///
  /// \Return CHANGED if the internal state changed, otherwise UNCHANGED.
  virtual ChangeStatus updateImpl(Attributor &A) = 0;
};

/// Forward declarations of output streams for debug purposes.
///
///{
raw_ostream &operator<<(raw_ostream &OS, const AbstractAttribute &AA);
raw_ostream &operator<<(raw_ostream &OS, ChangeStatus S);
raw_ostream &operator<<(raw_ostream &OS, IRPosition::Kind);
raw_ostream &operator<<(raw_ostream &OS, const IRPosition &);
raw_ostream &operator<<(raw_ostream &OS, const AbstractState &State);
raw_ostream &operator<<(raw_ostream &OS, const IntegerState &S);
///}

struct AttributorPass : public PassInfoMixin<AttributorPass> {
  PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
};

Pass *createAttributorLegacyPass();

/// ----------------------------------------------------------------------------
///                       Abstract Attribute Classes
/// ----------------------------------------------------------------------------

/// An abstract attribute for the returned values of a function.
struct AAReturnedValues
    : public IRAttribute<Attribute::Returned, AbstractAttribute> {
  AAReturnedValues(const IRPosition &IRP) : IRAttribute(IRP) {}

  /// Return an assumed unique return value if a single candidate is found. If
  /// there cannot be one, return a nullptr. If it is not clear yet, return the
  /// Optional::NoneType.
  Optional<Value *> getAssumedUniqueReturnValue(Attributor &A) const;

  /// Check \p Pred on all returned values.
  ///
  /// This method will evaluate \p Pred on returned values and return
  /// true if (1) all returned values are known, and (2) \p Pred returned true
  /// for all returned values.
  ///
  /// Note: Unlike the Attributor::checkForAllReturnedValuesAndReturnInsts
  /// method, this one will not filter dead return instructions.
  virtual bool checkForAllReturnedValuesAndReturnInsts(
      const function_ref<bool(Value &, const SmallSetVector<ReturnInst *, 4> &)>
          &Pred) const = 0;

  using iterator = MapVector<Value *, SmallSetVector<ReturnInst *, 4>>::iterator;
  using const_iterator =
      MapVector<Value *, SmallSetVector<ReturnInst *, 4>>::const_iterator;
  virtual llvm::iterator_range<iterator> returned_values() = 0;
  virtual llvm::iterator_range<const_iterator> returned_values() const = 0;

  virtual size_t getNumReturnValues() const = 0;
  virtual const SmallSetVector<CallBase *, 4> &getUnresolvedCalls() const = 0;

  /// Create an abstract attribute view for the position \p IRP.
  static AAReturnedValues &createForPosition(const IRPosition &IRP,
                                             Attributor &A);

  /// Unique ID (due to the unique address)
  static const char ID;
};

struct AANoUnwind
    : public IRAttribute<Attribute::NoUnwind,
                         StateWrapper<BooleanState, AbstractAttribute>> {
  AANoUnwind(const IRPosition &IRP) : IRAttribute(IRP) {}

  /// Returns true if nounwind is assumed.
  bool isAssumedNoUnwind() const { return getAssumed(); }

  /// Returns true if nounwind is known.
  bool isKnownNoUnwind() const { return getKnown(); }

  /// Create an abstract attribute view for the position \p IRP.
  static AANoUnwind &createForPosition(const IRPosition &IRP, Attributor &A);

  /// Unique ID (due to the unique address)
  static const char ID;
};

struct AANoSync
    : public IRAttribute<Attribute::NoSync,
                         StateWrapper<BooleanState, AbstractAttribute>> {
  AANoSync(const IRPosition &IRP) : IRAttribute(IRP) {}

  /// Returns true if "nosync" is assumed.
  bool isAssumedNoSync() const { return getAssumed(); }

  /// Returns true if "nosync" is known.
  bool isKnownNoSync() const { return getKnown(); }

  /// Create an abstract attribute view for the position \p IRP.
  static AANoSync &createForPosition(const IRPosition &IRP, Attributor &A);

  /// Unique ID (due to the unique address)
  static const char ID;
};

/// An abstract interface for all nonnull attributes.
struct AANonNull
    : public IRAttribute<Attribute::NonNull,
                         StateWrapper<BooleanState, AbstractAttribute>> {
  AANonNull(const IRPosition &IRP) : IRAttribute(IRP) {}

  /// Return true if we assume that the underlying value is nonnull.
  bool isAssumedNonNull() const { return getAssumed(); }

  /// Return true if we know that underlying value is nonnull.
  bool isKnownNonNull() const { return getKnown(); }

  /// Create an abstract attribute view for the position \p IRP.
  static AANonNull &createForPosition(const IRPosition &IRP, Attributor &A);

  /// Unique ID (due to the unique address)
  static const char ID;
};

/// An abstract attribute for norecurse.
struct AANoRecurse
    : public IRAttribute<Attribute::NoRecurse,
                         StateWrapper<BooleanState, AbstractAttribute>> {
  AANoRecurse(const IRPosition &IRP) : IRAttribute(IRP) {}

  /// Return true if "norecurse" is assumed.
  bool isAssumedNoRecurse() const { return getAssumed(); }

  /// Return true if "norecurse" is known.
  bool isKnownNoRecurse() const { return getKnown(); }

  /// Create an abstract attribute view for the position \p IRP.
  static AANoRecurse &createForPosition(const IRPosition &IRP, Attributor &A);

  /// Unique ID (due to the unique address)
  static const char ID;
};

/// An abstract attribute for willreturn.
struct AAWillReturn
    : public IRAttribute<Attribute::WillReturn,
                         StateWrapper<BooleanState, AbstractAttribute>> {
  AAWillReturn(const IRPosition &IRP) : IRAttribute(IRP) {}

  /// Return true if "willreturn" is assumed.
  bool isAssumedWillReturn() const { return getAssumed(); }

  /// Return true if "willreturn" is known.
  bool isKnownWillReturn() const { return getKnown(); }

  /// Create an abstract attribute view for the position \p IRP.
  static AAWillReturn &createForPosition(const IRPosition &IRP, Attributor &A);

  /// Unique ID (due to the unique address)
  static const char ID;
};

/// An abstract interface for all noalias attributes.
struct AANoAlias
    : public IRAttribute<Attribute::NoAlias,
                         StateWrapper<BooleanState, AbstractAttribute>> {
  AANoAlias(const IRPosition &IRP) : IRAttribute(IRP) {}

  /// Return true if we assume that the underlying value is alias.
  bool isAssumedNoAlias() const { return getAssumed(); }

  /// Return true if we know that underlying value is noalias.
  bool isKnownNoAlias() const { return getKnown(); }

  /// Create an abstract attribute view for the position \p IRP.
  static AANoAlias &createForPosition(const IRPosition &IRP, Attributor &A);

  /// Unique ID (due to the unique address)
  static const char ID;
};

/// An AbstractAttribute for nofree.
struct AANoFree
    : public IRAttribute<Attribute::NoFree,
                         StateWrapper<BooleanState, AbstractAttribute>> {
  AANoFree(const IRPosition &IRP) : IRAttribute(IRP) {}

  /// Return true if "nofree" is assumed.
  bool isAssumedNoFree() const { return getAssumed(); }

  /// Return true if "nofree" is known.
  bool isKnownNoFree() const { return getKnown(); }

  /// Create an abstract attribute view for the position \p IRP.
  static AANoFree &createForPosition(const IRPosition &IRP, Attributor &A);

  /// Unique ID (due to the unique address)
  static const char ID;
};

/// An AbstractAttribute for noreturn.
struct AANoReturn
    : public IRAttribute<Attribute::NoReturn,
                         StateWrapper<BooleanState, AbstractAttribute>> {
  AANoReturn(const IRPosition &IRP) : IRAttribute(IRP) {}

  /// Return true if the underlying object is assumed to never return.
  bool isAssumedNoReturn() const { return getAssumed(); }

  /// Return true if the underlying object is known to never return.
  bool isKnownNoReturn() const { return getKnown(); }

  /// Create an abstract attribute view for the position \p IRP.
  static AANoReturn &createForPosition(const IRPosition &IRP, Attributor &A);

  /// Unique ID (due to the unique address)
  static const char ID;
};

/// An abstract interface for liveness abstract attribute.
struct AAIsDead : public StateWrapper<BooleanState, AbstractAttribute>,
                  public IRPosition {
  AAIsDead(const IRPosition &IRP) : IRPosition(IRP) {}

  /// Returns true if \p BB is assumed dead.
  virtual bool isAssumedDead(const BasicBlock *BB) const = 0;

  /// Returns true if \p BB is known dead.
  virtual bool isKnownDead(const BasicBlock *BB) const = 0;

  /// Returns true if \p I is assumed dead.
  virtual bool isAssumedDead(const Instruction *I) const = 0;

  /// Returns true if \p I is known dead.
  virtual bool isKnownDead(const Instruction *I) const = 0;

  /// This method is used to check if at least one instruction in a collection
  /// of instructions is live.
  template <typename T> bool isLiveInstSet(T begin, T end) const {
    for (const auto &I : llvm::make_range(begin, end)) {
      assert(I->getFunction() == getIRPosition().getAssociatedFunction() &&
             "Instruction must be in the same anchor scope function.");

      if (!isAssumedDead(I))
        return true;
    }

    return false;
  }

  /// Return an IR position, see struct IRPosition.
  ///
  ///{
  IRPosition &getIRPosition() override { return *this; }
  const IRPosition &getIRPosition() const override { return *this; }
  ///}

  /// Create an abstract attribute view for the position \p IRP.
  static AAIsDead &createForPosition(const IRPosition &IRP, Attributor &A);

  /// Unique ID (due to the unique address)
  static const char ID;
};

/// State for dereferenceable attribute
struct DerefState : AbstractState {

  /// State representing for dereferenceable bytes.
  IntegerState DerefBytesState;

  /// State representing that whether the value is globaly dereferenceable.
  BooleanState GlobalState;

  /// See AbstractState::isValidState()
  bool isValidState() const override { return DerefBytesState.isValidState(); }

  /// See AbstractState::isAtFixpoint()
  bool isAtFixpoint() const override {
    return !isValidState() ||
           (DerefBytesState.isAtFixpoint() && GlobalState.isAtFixpoint());
  }

  /// See AbstractState::indicateOptimisticFixpoint(...)
  ChangeStatus indicateOptimisticFixpoint() override {
    DerefBytesState.indicateOptimisticFixpoint();
    GlobalState.indicateOptimisticFixpoint();
    return ChangeStatus::UNCHANGED;
  }

  /// See AbstractState::indicatePessimisticFixpoint(...)
  ChangeStatus indicatePessimisticFixpoint() override {
    DerefBytesState.indicatePessimisticFixpoint();
    GlobalState.indicatePessimisticFixpoint();
    return ChangeStatus::CHANGED;
  }

  /// Update known dereferenceable bytes.
  void takeKnownDerefBytesMaximum(uint64_t Bytes) {
    DerefBytesState.takeKnownMaximum(Bytes);
  }

  /// Update assumed dereferenceable bytes.
  void takeAssumedDerefBytesMinimum(uint64_t Bytes) {
    DerefBytesState.takeAssumedMinimum(Bytes);
  }

  /// Equality for DerefState.
  bool operator==(const DerefState &R) {
    return this->DerefBytesState == R.DerefBytesState &&
           this->GlobalState == R.GlobalState;
  }

  /// Inequality for IntegerState.
  bool operator!=(const DerefState &R) { return !(*this == R); }

  /// See IntegerState::operator^=
  DerefState operator^=(const DerefState &R) {
    DerefBytesState ^= R.DerefBytesState;
    GlobalState ^= R.GlobalState;
    return *this;
  }

  /// See IntegerState::operator+=
  DerefState operator+=(const DerefState &R) {
    DerefBytesState += R.DerefBytesState;
    GlobalState += R.GlobalState;
    return *this;
  }

  /// See IntegerState::operator&=
  DerefState operator&=(const DerefState &R) {
    DerefBytesState &= R.DerefBytesState;
    GlobalState &= R.GlobalState;
    return *this;
  }

  /// See IntegerState::operator|=
  DerefState operator|=(const DerefState &R) {
    DerefBytesState |= R.DerefBytesState;
    GlobalState |= R.GlobalState;
    return *this;
  }

protected:
  const AANonNull *NonNullAA = nullptr;
};

/// An abstract interface for all dereferenceable attribute.
struct AADereferenceable
    : public IRAttribute<Attribute::Dereferenceable,
                         StateWrapper<DerefState, AbstractAttribute>> {
  AADereferenceable(const IRPosition &IRP) : IRAttribute(IRP) {}

  /// Return true if we assume that the underlying value is nonnull.
  bool isAssumedNonNull() const {
    return NonNullAA && NonNullAA->isAssumedNonNull();
  }

  /// Return true if we assume that underlying value is
  /// dereferenceable(_or_null) globally.
  bool isAssumedGlobal() const { return GlobalState.getAssumed(); }

  /// Return true if we know that underlying value is
  /// dereferenceable(_or_null) globally.
  bool isKnownGlobal() const { return GlobalState.getKnown(); }

  /// Return assumed dereferenceable bytes.
  uint32_t getAssumedDereferenceableBytes() const {
    return DerefBytesState.getAssumed();
  }

  /// Return known dereferenceable bytes.
  uint32_t getKnownDereferenceableBytes() const {
    return DerefBytesState.getKnown();
  }

  /// Create an abstract attribute view for the position \p IRP.
  static AADereferenceable &createForPosition(const IRPosition &IRP,
                                              Attributor &A);

  /// Unique ID (due to the unique address)
  static const char ID;
};

/// An abstract interface for all align attributes.
struct AAAlign
    : public IRAttribute<Attribute::Alignment,
                         StateWrapper<IntegerState, AbstractAttribute>> {
  AAAlign(const IRPosition &IRP) : IRAttribute(IRP) {}

  /// Return assumed alignment.
  unsigned getAssumedAlign() const { return getAssumed(); }

  /// Return known alignemnt.
  unsigned getKnownAlign() const { return getKnown(); }

  /// Create an abstract attribute view for the position \p IRP.
  static AAAlign &createForPosition(const IRPosition &IRP, Attributor &A);

  /// Unique ID (due to the unique address)
  static const char ID;
};

/// An abstract interface for all nocapture attributes.
struct AANoCapture
    : public IRAttribute<Attribute::NoCapture,
                         StateWrapper<IntegerState, AbstractAttribute>> {
  AANoCapture(const IRPosition &IRP) : IRAttribute(IRP) {}

  /// State encoding bits. A set bit in the state means the property holds.
  /// NO_CAPTURE is the best possible state, 0 the worst possible state.
  enum {
    NOT_CAPTURED_IN_MEM = 1 << 0,
    NOT_CAPTURED_IN_INT = 1 << 1,
    NOT_CAPTURED_IN_RET = 1 << 2,

    /// If we do not capture the value in memory or through integers we can only
    /// communicate it back as a derived pointer.
    NO_CAPTURE_MAYBE_RETURNED = NOT_CAPTURED_IN_MEM | NOT_CAPTURED_IN_INT,

    /// If we do not capture the value in memory, through integers, or as a
    /// derived pointer we know it is not captured.
    NO_CAPTURE =
        NOT_CAPTURED_IN_MEM | NOT_CAPTURED_IN_INT | NOT_CAPTURED_IN_RET,
  };

  /// Return true if we know that the underlying value is not captured in its
  /// respective scope.
  bool isKnownNoCapture() const { return isKnown(NO_CAPTURE); }

  /// Return true if we assume that the underlying value is not captured in its
  /// respective scope.
  bool isAssumedNoCapture() const { return isAssumed(NO_CAPTURE); }

  /// Return true if we know that the underlying value is not captured in its
  /// respective scope but we allow it to escape through a "return".
  bool isKnownNoCaptureMaybeReturned() const {
    return isKnown(NO_CAPTURE_MAYBE_RETURNED);
  }

  /// Return true if we assume that the underlying value is not captured in its
  /// respective scope but we allow it to escape through a "return".
  bool isAssumedNoCaptureMaybeReturned() const {
    return isAssumed(NO_CAPTURE_MAYBE_RETURNED);
  }

  /// Create an abstract attribute view for the position \p IRP.
  static AANoCapture &createForPosition(const IRPosition &IRP, Attributor &A);

  /// Unique ID (due to the unique address)
  static const char ID;
};

/// An abstract interface for value simplify abstract attribute.
struct AAValueSimplify : public StateWrapper<BooleanState, AbstractAttribute>,
                         public IRPosition {
  AAValueSimplify(const IRPosition &IRP) : IRPosition(IRP) {}

  /// Return an IR position, see struct IRPosition.
  ///
  ///{
  IRPosition &getIRPosition() { return *this; }
  const IRPosition &getIRPosition() const { return *this; }
  ///}

  /// Return an assumed simplified value if a single candidate is found. If
  /// there cannot be one, return original value. If it is not clear yet, return
  /// the Optional::NoneType.
  virtual Optional<Value *> getAssumedSimplifiedValue(Attributor &A) const = 0;

  /// Create an abstract attribute view for the position \p IRP.
  static AAValueSimplify &createForPosition(const IRPosition &IRP,
                                            Attributor &A);

  /// Unique ID (due to the unique address)
  static const char ID;
};

struct AAHeapToStack : public StateWrapper<BooleanState, AbstractAttribute>,
                       public IRPosition {
  AAHeapToStack(const IRPosition &IRP) : IRPosition(IRP) {}

  /// Returns true if HeapToStack conversion is assumed to be possible.
  bool isAssumedHeapToStack() const { return getAssumed(); }

  /// Returns true if HeapToStack conversion is known to be possible.
  bool isKnownHeapToStack() const { return getKnown(); }

  /// Return an IR position, see struct IRPosition.
  ///
  ///{
  IRPosition &getIRPosition() { return *this; }
  const IRPosition &getIRPosition() const { return *this; }
  ///}

  /// Create an abstract attribute view for the position \p IRP.
  static AAHeapToStack &createForPosition(const IRPosition &IRP, Attributor &A);

  /// Unique ID (due to the unique address)
  static const char ID;
};

} // end namespace llvm

#endif // LLVM_TRANSFORMS_IPO_FUNCTIONATTRS_H