llvm.org GIT mirror llvm / release_26 include / llvm / Target / TargetLowering.h
release_26

Tree @release_26 (Download .tar.gz)

TargetLowering.h @release_26raw · 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
//===-- llvm/Target/TargetLowering.h - Target Lowering Info -----*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file describes how to lower LLVM code to machine code.  This has two
// main components:
//
//  1. Which ValueTypes are natively supported by the target.
//  2. Which operations are supported for supported ValueTypes.
//  3. Cost thresholds for alternative implementations of certain operations.
//
// In addition it has a few other components, like information about FP
// immediates.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_TARGET_TARGETLOWERING_H
#define LLVM_TARGET_TARGETLOWERING_H

#include "llvm/CallingConv.h"
#include "llvm/InlineAsm.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/CodeGen/RuntimeLibcalls.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/DebugLoc.h"
#include "llvm/Target/TargetMachine.h"
#include <climits>
#include <map>
#include <vector>

namespace llvm {
  class AllocaInst;
  class CallInst;
  class Function;
  class FastISel;
  class MachineBasicBlock;
  class MachineFunction;
  class MachineFrameInfo;
  class MachineInstr;
  class MachineModuleInfo;
  class DwarfWriter;
  class SDNode;
  class SDValue;
  class SelectionDAG;
  class TargetData;
  class TargetMachine;
  class TargetRegisterClass;
  class TargetSubtarget;
  class TargetLoweringObjectFile;
  class Value;

  // FIXME: should this be here?
  namespace TLSModel {
    enum Model {
      GeneralDynamic,
      LocalDynamic,
      InitialExec,
      LocalExec
    };
  }
  TLSModel::Model getTLSModel(const GlobalValue *GV, Reloc::Model reloc);


//===----------------------------------------------------------------------===//
/// TargetLowering - This class defines information used to lower LLVM code to
/// legal SelectionDAG operators that the target instruction selector can accept
/// natively.
///
/// This class also defines callbacks that targets must implement to lower
/// target-specific constructs to SelectionDAG operators.
///
class TargetLowering {
  TargetLowering(const TargetLowering&);  // DO NOT IMPLEMENT
  void operator=(const TargetLowering&);  // DO NOT IMPLEMENT
public:
  /// LegalizeAction - This enum indicates whether operations are valid for a
  /// target, and if not, what action should be used to make them valid.
  enum LegalizeAction {
    Legal,      // The target natively supports this operation.
    Promote,    // This operation should be executed in a larger type.
    Expand,     // Try to expand this to other ops, otherwise use a libcall.
    Custom      // Use the LowerOperation hook to implement custom lowering.
  };

  enum BooleanContent { // How the target represents true/false values.
    UndefinedBooleanContent,    // Only bit 0 counts, the rest can hold garbage.
    ZeroOrOneBooleanContent,        // All bits zero except for bit 0.
    ZeroOrNegativeOneBooleanContent // All bits equal to bit 0.
  };

  enum SchedPreference {
    SchedulingForLatency,          // Scheduling for shortest total latency.
    SchedulingForRegPressure       // Scheduling for lowest register pressure.
  };

  /// NOTE: The constructor takes ownership of TLOF.
  explicit TargetLowering(TargetMachine &TM, TargetLoweringObjectFile *TLOF);
  virtual ~TargetLowering();

  TargetMachine &getTargetMachine() const { return TM; }
  const TargetData *getTargetData() const { return TD; }
  TargetLoweringObjectFile &getObjFileLowering() const { return TLOF; }

  bool isBigEndian() const { return !IsLittleEndian; }
  bool isLittleEndian() const { return IsLittleEndian; }
  MVT getPointerTy() const { return PointerTy; }
  MVT getShiftAmountTy() const { return ShiftAmountTy; }

  /// usesGlobalOffsetTable - Return true if this target uses a GOT for PIC
  /// codegen.
  bool usesGlobalOffsetTable() const { return UsesGlobalOffsetTable; }

  /// isSelectExpensive - Return true if the select operation is expensive for
  /// this target.
  bool isSelectExpensive() const { return SelectIsExpensive; }
  
  /// isIntDivCheap() - Return true if integer divide is usually cheaper than
  /// a sequence of several shifts, adds, and multiplies for this target.
  bool isIntDivCheap() const { return IntDivIsCheap; }

  /// isPow2DivCheap() - Return true if pow2 div is cheaper than a chain of
  /// srl/add/sra.
  bool isPow2DivCheap() const { return Pow2DivIsCheap; }

  /// getSetCCResultType - Return the ValueType of the result of SETCC
  /// operations.  Also used to obtain the target's preferred type for
  /// the condition operand of SELECT and BRCOND nodes.  In the case of
  /// BRCOND the argument passed is MVT::Other since there are no other
  /// operands to get a type hint from.
  virtual
  MVT::SimpleValueType getSetCCResultType(EVT VT) const;

  /// getBooleanContents - For targets without i1 registers, this gives the
  /// nature of the high-bits of boolean values held in types wider than i1.
  /// "Boolean values" are special true/false values produced by nodes like
  /// SETCC and consumed (as the condition) by nodes like SELECT and BRCOND.
  /// Not to be confused with general values promoted from i1.
  BooleanContent getBooleanContents() const { return BooleanContents;}

  /// getSchedulingPreference - Return target scheduling preference.
  SchedPreference getSchedulingPreference() const {
    return SchedPreferenceInfo;
  }

  /// getRegClassFor - Return the register class that should be used for the
  /// specified value type.  This may only be called on legal types.
  TargetRegisterClass *getRegClassFor(EVT VT) const {
    assert(VT.isSimple() && "getRegClassFor called on illegal type!");
    TargetRegisterClass *RC = RegClassForVT[VT.getSimpleVT().SimpleTy];
    assert(RC && "This value type is not natively supported!");
    return RC;
  }

  /// isTypeLegal - Return true if the target has native support for the
  /// specified value type.  This means that it has a register that directly
  /// holds it without promotions or expansions.
  bool isTypeLegal(EVT VT) const {
    assert(!VT.isSimple() ||
           (unsigned)VT.getSimpleVT().SimpleTy < array_lengthof(RegClassForVT));
    return VT.isSimple() && RegClassForVT[VT.getSimpleVT().SimpleTy] != 0;
  }

  class ValueTypeActionImpl {
    /// ValueTypeActions - This is a bitvector that contains two bits for each
    /// value type, where the two bits correspond to the LegalizeAction enum.
    /// This can be queried with "getTypeAction(VT)".
    /// dimension by (MVT::MAX_ALLOWED_VALUETYPE/32) * 2
    uint32_t ValueTypeActions[(MVT::MAX_ALLOWED_VALUETYPE/32)*2];
  public:
    ValueTypeActionImpl() {
      ValueTypeActions[0] = ValueTypeActions[1] = 0;
      ValueTypeActions[2] = ValueTypeActions[3] = 0;
    }
    ValueTypeActionImpl(const ValueTypeActionImpl &RHS) {
      ValueTypeActions[0] = RHS.ValueTypeActions[0];
      ValueTypeActions[1] = RHS.ValueTypeActions[1];
      ValueTypeActions[2] = RHS.ValueTypeActions[2];
      ValueTypeActions[3] = RHS.ValueTypeActions[3];
    }
    
    LegalizeAction getTypeAction(LLVMContext &Context, EVT VT) const {
      if (VT.isExtended()) {
        if (VT.isVector()) {
          return VT.isPow2VectorType() ? Expand : Promote;
        }
        if (VT.isInteger())
          // First promote to a power-of-two size, then expand if necessary.
          return VT == VT.getRoundIntegerType(Context) ? Expand : Promote;
        assert(0 && "Unsupported extended type!");
        return Legal;
      }
      unsigned I = VT.getSimpleVT().SimpleTy;
      assert(I<4*array_lengthof(ValueTypeActions)*sizeof(ValueTypeActions[0]));
      return (LegalizeAction)((ValueTypeActions[I>>4] >> ((2*I) & 31)) & 3);
    }
    void setTypeAction(EVT VT, LegalizeAction Action) {
      unsigned I = VT.getSimpleVT().SimpleTy;
      assert(I<4*array_lengthof(ValueTypeActions)*sizeof(ValueTypeActions[0]));
      ValueTypeActions[I>>4] |= Action << ((I*2) & 31);
    }
  };
  
  const ValueTypeActionImpl &getValueTypeActions() const {
    return ValueTypeActions;
  }

  /// getTypeAction - Return how we should legalize values of this type, either
  /// it is already legal (return 'Legal') or we need to promote it to a larger
  /// type (return 'Promote'), or we need to expand it into multiple registers
  /// of smaller integer type (return 'Expand').  'Custom' is not an option.
  LegalizeAction getTypeAction(LLVMContext &Context, EVT VT) const {
    return ValueTypeActions.getTypeAction(Context, VT);
  }

  /// getTypeToTransformTo - For types supported by the target, this is an
  /// identity function.  For types that must be promoted to larger types, this
  /// returns the larger type to promote to.  For integer types that are larger
  /// than the largest integer register, this contains one step in the expansion
  /// to get to the smaller register. For illegal floating point types, this
  /// returns the integer type to transform to.
  EVT getTypeToTransformTo(LLVMContext &Context, EVT VT) const {
    if (VT.isSimple()) {
      assert((unsigned)VT.getSimpleVT().SimpleTy < 
             array_lengthof(TransformToType));
      EVT NVT = TransformToType[VT.getSimpleVT().SimpleTy];
      assert(getTypeAction(Context, NVT) != Promote &&
             "Promote may not follow Expand or Promote");
      return NVT;
    }

    if (VT.isVector()) {
      EVT NVT = VT.getPow2VectorType(Context);
      if (NVT == VT) {
        // Vector length is a power of 2 - split to half the size.
        unsigned NumElts = VT.getVectorNumElements();
        EVT EltVT = VT.getVectorElementType();
        return (NumElts == 1) ?
          EltVT : EVT::getVectorVT(Context, EltVT, NumElts / 2);
      }
      // Promote to a power of two size, avoiding multi-step promotion.
      return getTypeAction(Context, NVT) == Promote ?
        getTypeToTransformTo(Context, NVT) : NVT;
    } else if (VT.isInteger()) {
      EVT NVT = VT.getRoundIntegerType(Context);
      if (NVT == VT)
        // Size is a power of two - expand to half the size.
        return EVT::getIntegerVT(Context, VT.getSizeInBits() / 2);
      else
        // Promote to a power of two size, avoiding multi-step promotion.
        return getTypeAction(Context, NVT) == Promote ? 
          getTypeToTransformTo(Context, NVT) : NVT;
    }
    assert(0 && "Unsupported extended type!");
    return MVT(MVT::Other); // Not reached
  }

  /// getTypeToExpandTo - For types supported by the target, this is an
  /// identity function.  For types that must be expanded (i.e. integer types
  /// that are larger than the largest integer register or illegal floating
  /// point types), this returns the largest legal type it will be expanded to.
  EVT getTypeToExpandTo(LLVMContext &Context, EVT VT) const {
    assert(!VT.isVector());
    while (true) {
      switch (getTypeAction(Context, VT)) {
      case Legal:
        return VT;
      case Expand:
        VT = getTypeToTransformTo(Context, VT);
        break;
      default:
        assert(false && "Type is not legal nor is it to be expanded!");
        return VT;
      }
    }
    return VT;
  }

  /// getVectorTypeBreakdown - Vector types are broken down into some number of
  /// legal first class types.  For example, EVT::v8f32 maps to 2 EVT::v4f32
  /// with Altivec or SSE1, or 8 promoted EVT::f64 values with the X86 FP stack.
  /// Similarly, EVT::v2i64 turns into 4 EVT::i32 values with both PPC and X86.
  ///
  /// This method returns the number of registers needed, and the VT for each
  /// register.  It also returns the VT and quantity of the intermediate values
  /// before they are promoted/expanded.
  ///
  unsigned getVectorTypeBreakdown(LLVMContext &Context, EVT VT,
                                  EVT &IntermediateVT,
                                  unsigned &NumIntermediates,
                                  EVT &RegisterVT) const;

  /// getTgtMemIntrinsic: Given an intrinsic, checks if on the target the
  /// intrinsic will need to map to a MemIntrinsicNode (touches memory). If
  /// this is the case, it returns true and store the intrinsic
  /// information into the IntrinsicInfo that was passed to the function.
  typedef struct IntrinsicInfo { 
    unsigned     opc;         // target opcode
    EVT          memVT;       // memory VT
    const Value* ptrVal;      // value representing memory location
    int          offset;      // offset off of ptrVal 
    unsigned     align;       // alignment
    bool         vol;         // is volatile?
    bool         readMem;     // reads memory?
    bool         writeMem;    // writes memory?
  } IntrinisicInfo;

  virtual bool getTgtMemIntrinsic(IntrinsicInfo& Info,
                                  CallInst &I, unsigned Intrinsic) {
    return false;
  }

  /// getWidenVectorType: given a vector type, returns the type to widen to
  /// (e.g., v7i8 to v8i8). If the vector type is legal, it returns itself.
  /// If there is no vector type that we want to widen to, returns MVT::Other
  /// When and were to widen is target dependent based on the cost of
  /// scalarizing vs using the wider vector type.
  virtual EVT getWidenVectorType(EVT VT) const;

  typedef std::vector<APFloat>::const_iterator legal_fpimm_iterator;
  legal_fpimm_iterator legal_fpimm_begin() const {
    return LegalFPImmediates.begin();
  }
  legal_fpimm_iterator legal_fpimm_end() const {
    return LegalFPImmediates.end();
  }
  
  /// isShuffleMaskLegal - Targets can use this to indicate that they only
  /// support *some* VECTOR_SHUFFLE operations, those with specific masks.
  /// By default, if a target supports the VECTOR_SHUFFLE node, all mask values
  /// are assumed to be legal.
  virtual bool isShuffleMaskLegal(const SmallVectorImpl<int> &Mask,
                                  EVT VT) const {
    return true;
  }

  /// isVectorClearMaskLegal - Similar to isShuffleMaskLegal. This is
  /// used by Targets can use this to indicate if there is a suitable
  /// VECTOR_SHUFFLE that can be used to replace a VAND with a constant
  /// pool entry.
  virtual bool isVectorClearMaskLegal(const SmallVectorImpl<int> &Mask,
                                      EVT VT) const {
    return false;
  }

  /// getOperationAction - Return how this operation should be treated: either
  /// it is legal, needs to be promoted to a larger size, needs to be
  /// expanded to some other code sequence, or the target has a custom expander
  /// for it.
  LegalizeAction getOperationAction(unsigned Op, EVT VT) const {
    if (VT.isExtended()) return Expand;
    assert(Op < array_lengthof(OpActions[0]) &&
           (unsigned)VT.getSimpleVT().SimpleTy < sizeof(OpActions[0][0])*8 &&
           "Table isn't big enough!");
    unsigned I = (unsigned) VT.getSimpleVT().SimpleTy;
    unsigned J = I & 31;
    I = I >> 5;
    return (LegalizeAction)((OpActions[I][Op] >> (J*2) ) & 3);
  }

  /// isOperationLegalOrCustom - Return true if the specified operation is
  /// legal on this target or can be made legal with custom lowering. This
  /// is used to help guide high-level lowering decisions.
  bool isOperationLegalOrCustom(unsigned Op, EVT VT) const {
    return (VT == MVT::Other || isTypeLegal(VT)) &&
      (getOperationAction(Op, VT) == Legal ||
       getOperationAction(Op, VT) == Custom);
  }

  /// isOperationLegal - Return true if the specified operation is legal on this
  /// target.
  bool isOperationLegal(unsigned Op, EVT VT) const {
    return (VT == MVT::Other || isTypeLegal(VT)) &&
           getOperationAction(Op, VT) == Legal;
  }

  /// getLoadExtAction - Return how this load with extension should be treated:
  /// either it is legal, needs to be promoted to a larger size, needs to be
  /// expanded to some other code sequence, or the target has a custom expander
  /// for it.
  LegalizeAction getLoadExtAction(unsigned LType, EVT VT) const {
    assert(LType < array_lengthof(LoadExtActions) &&
           (unsigned)VT.getSimpleVT().SimpleTy < sizeof(LoadExtActions[0])*4 &&
           "Table isn't big enough!");
    return (LegalizeAction)((LoadExtActions[LType] >> 
              (2*VT.getSimpleVT().SimpleTy)) & 3);
  }

  /// isLoadExtLegal - Return true if the specified load with extension is legal
  /// on this target.
  bool isLoadExtLegal(unsigned LType, EVT VT) const {
    return VT.isSimple() &&
      (getLoadExtAction(LType, VT) == Legal ||
       getLoadExtAction(LType, VT) == Custom);
  }

  /// getTruncStoreAction - Return how this store with truncation should be
  /// treated: either it is legal, needs to be promoted to a larger size, needs
  /// to be expanded to some other code sequence, or the target has a custom
  /// expander for it.
  LegalizeAction getTruncStoreAction(EVT ValVT,
                                     EVT MemVT) const {
    assert((unsigned)ValVT.getSimpleVT().SimpleTy <
             array_lengthof(TruncStoreActions) &&
           (unsigned)MemVT.getSimpleVT().SimpleTy <
             sizeof(TruncStoreActions[0])*4 &&
           "Table isn't big enough!");
    return (LegalizeAction)((TruncStoreActions[ValVT.getSimpleVT().SimpleTy] >>
                             (2*MemVT.getSimpleVT().SimpleTy)) & 3);
  }

  /// isTruncStoreLegal - Return true if the specified store with truncation is
  /// legal on this target.
  bool isTruncStoreLegal(EVT ValVT, EVT MemVT) const {
    return isTypeLegal(ValVT) && MemVT.isSimple() &&
      (getTruncStoreAction(ValVT, MemVT) == Legal ||
       getTruncStoreAction(ValVT, MemVT) == Custom);
  }

  /// getIndexedLoadAction - Return how the indexed load should be treated:
  /// either it is legal, needs to be promoted to a larger size, needs to be
  /// expanded to some other code sequence, or the target has a custom expander
  /// for it.
  LegalizeAction
  getIndexedLoadAction(unsigned IdxMode, EVT VT) const {
    assert( IdxMode < array_lengthof(IndexedModeActions[0][0]) &&
           ((unsigned)VT.getSimpleVT().SimpleTy) < MVT::LAST_VALUETYPE &&
           "Table isn't big enough!");
    return (LegalizeAction)((IndexedModeActions[
                             (unsigned)VT.getSimpleVT().SimpleTy][0][IdxMode]));
  }

  /// isIndexedLoadLegal - Return true if the specified indexed load is legal
  /// on this target.
  bool isIndexedLoadLegal(unsigned IdxMode, EVT VT) const {
    return VT.isSimple() &&
      (getIndexedLoadAction(IdxMode, VT) == Legal ||
       getIndexedLoadAction(IdxMode, VT) == Custom);
  }

  /// getIndexedStoreAction - Return how the indexed store should be treated:
  /// either it is legal, needs to be promoted to a larger size, needs to be
  /// expanded to some other code sequence, or the target has a custom expander
  /// for it.
  LegalizeAction
  getIndexedStoreAction(unsigned IdxMode, EVT VT) const {
    assert(IdxMode < array_lengthof(IndexedModeActions[0][1]) &&
           (unsigned)VT.getSimpleVT().SimpleTy < MVT::LAST_VALUETYPE &&
           "Table isn't big enough!");
    return (LegalizeAction)((IndexedModeActions[
              (unsigned)VT.getSimpleVT().SimpleTy][1][IdxMode]));
  }  

  /// isIndexedStoreLegal - Return true if the specified indexed load is legal
  /// on this target.
  bool isIndexedStoreLegal(unsigned IdxMode, EVT VT) const {
    return VT.isSimple() &&
      (getIndexedStoreAction(IdxMode, VT) == Legal ||
       getIndexedStoreAction(IdxMode, VT) == Custom);
  }

  /// getConvertAction - Return how the conversion should be treated:
  /// either it is legal, needs to be promoted to a larger size, needs to be
  /// expanded to some other code sequence, or the target has a custom expander
  /// for it.
  LegalizeAction
  getConvertAction(EVT FromVT, EVT ToVT) const {
    assert((unsigned)FromVT.getSimpleVT().SimpleTy <
              array_lengthof(ConvertActions) &&
           (unsigned)ToVT.getSimpleVT().SimpleTy <
              sizeof(ConvertActions[0])*4 &&
           "Table isn't big enough!");
    return (LegalizeAction)((ConvertActions[FromVT.getSimpleVT().SimpleTy] >>
                             (2*ToVT.getSimpleVT().SimpleTy)) & 3);
  }

  /// isConvertLegal - Return true if the specified conversion is legal
  /// on this target.
  bool isConvertLegal(EVT FromVT, EVT ToVT) const {
    return isTypeLegal(FromVT) && isTypeLegal(ToVT) &&
      (getConvertAction(FromVT, ToVT) == Legal ||
       getConvertAction(FromVT, ToVT) == Custom);
  }

  /// getCondCodeAction - Return how the condition code should be treated:
  /// either it is legal, needs to be expanded to some other code sequence,
  /// or the target has a custom expander for it.
  LegalizeAction
  getCondCodeAction(ISD::CondCode CC, EVT VT) const {
    assert((unsigned)CC < array_lengthof(CondCodeActions) &&
           (unsigned)VT.getSimpleVT().SimpleTy < sizeof(CondCodeActions[0])*4 &&
           "Table isn't big enough!");
    LegalizeAction Action = (LegalizeAction)
      ((CondCodeActions[CC] >> (2*VT.getSimpleVT().SimpleTy)) & 3);
    assert(Action != Promote && "Can't promote condition code!");
    return Action;
  }

  /// isCondCodeLegal - Return true if the specified condition code is legal
  /// on this target.
  bool isCondCodeLegal(ISD::CondCode CC, EVT VT) const {
    return getCondCodeAction(CC, VT) == Legal ||
           getCondCodeAction(CC, VT) == Custom;
  }


  /// getTypeToPromoteTo - If the action for this operation is to promote, this
  /// method returns the ValueType to promote to.
  EVT getTypeToPromoteTo(unsigned Op, EVT VT) const {
    assert(getOperationAction(Op, VT) == Promote &&
           "This operation isn't promoted!");

    // See if this has an explicit type specified.
    std::map<std::pair<unsigned, MVT::SimpleValueType>,
             MVT::SimpleValueType>::const_iterator PTTI =
      PromoteToType.find(std::make_pair(Op, VT.getSimpleVT().SimpleTy));
    if (PTTI != PromoteToType.end()) return PTTI->second;

    assert((VT.isInteger() || VT.isFloatingPoint()) &&
           "Cannot autopromote this type, add it with AddPromotedToType.");
    
    EVT NVT = VT;
    do {
      NVT = (MVT::SimpleValueType)(NVT.getSimpleVT().SimpleTy+1);
      assert(NVT.isInteger() == VT.isInteger() && NVT != MVT::isVoid &&
             "Didn't find type to promote to!");
    } while (!isTypeLegal(NVT) ||
              getOperationAction(Op, NVT) == Promote);
    return NVT;
  }

  /// getValueType - Return the EVT corresponding to this LLVM type.
  /// This is fixed by the LLVM operations except for the pointer size.  If
  /// AllowUnknown is true, this will return MVT::Other for types with no EVT
  /// counterpart (e.g. structs), otherwise it will assert.
  EVT getValueType(const Type *Ty, bool AllowUnknown = false) const {
    EVT VT = EVT::getEVT(Ty, AllowUnknown);
    return VT == MVT:: iPTR ? PointerTy : VT;
  }

  /// getByValTypeAlignment - Return the desired alignment for ByVal aggregate
  /// function arguments in the caller parameter area.  This is the actual
  /// alignment, not its logarithm.
  virtual unsigned getByValTypeAlignment(const Type *Ty) const;
  
  /// getRegisterType - Return the type of registers that this ValueType will
  /// eventually require.
  EVT getRegisterType(MVT VT) const {
    assert((unsigned)VT.SimpleTy < array_lengthof(RegisterTypeForVT));
    return RegisterTypeForVT[VT.SimpleTy];
  }
  
  /// getRegisterType - Return the type of registers that this ValueType will
  /// eventually require.
  EVT getRegisterType(LLVMContext &Context, EVT VT) const {
    if (VT.isSimple()) {
      assert((unsigned)VT.getSimpleVT().SimpleTy <
                array_lengthof(RegisterTypeForVT));
      return RegisterTypeForVT[VT.getSimpleVT().SimpleTy];
    }
    if (VT.isVector()) {
      EVT VT1, RegisterVT;
      unsigned NumIntermediates;
      (void)getVectorTypeBreakdown(Context, VT, VT1,
                                   NumIntermediates, RegisterVT);
      return RegisterVT;
    }
    if (VT.isInteger()) {
      return getRegisterType(Context, getTypeToTransformTo(Context, VT));
    }
    assert(0 && "Unsupported extended type!");
    return EVT(MVT::Other); // Not reached
  }

  /// getNumRegisters - Return the number of registers that this ValueType will
  /// eventually require.  This is one for any types promoted to live in larger
  /// registers, but may be more than one for types (like i64) that are split
  /// into pieces.  For types like i140, which are first promoted then expanded,
  /// it is the number of registers needed to hold all the bits of the original
  /// type.  For an i140 on a 32 bit machine this means 5 registers.
  unsigned getNumRegisters(LLVMContext &Context, EVT VT) const {
    if (VT.isSimple()) {
      assert((unsigned)VT.getSimpleVT().SimpleTy <
                array_lengthof(NumRegistersForVT));
      return NumRegistersForVT[VT.getSimpleVT().SimpleTy];
    }
    if (VT.isVector()) {
      EVT VT1, VT2;
      unsigned NumIntermediates;
      return getVectorTypeBreakdown(Context, VT, VT1, NumIntermediates, VT2);
    }
    if (VT.isInteger()) {
      unsigned BitWidth = VT.getSizeInBits();
      unsigned RegWidth = getRegisterType(Context, VT).getSizeInBits();
      return (BitWidth + RegWidth - 1) / RegWidth;
    }
    assert(0 && "Unsupported extended type!");
    return 0; // Not reached
  }

  /// ShouldShrinkFPConstant - If true, then instruction selection should
  /// seek to shrink the FP constant of the specified type to a smaller type
  /// in order to save space and / or reduce runtime.
  virtual bool ShouldShrinkFPConstant(EVT VT) const { return true; }

  /// hasTargetDAGCombine - If true, the target has custom DAG combine
  /// transformations that it can perform for the specified node.
  bool hasTargetDAGCombine(ISD::NodeType NT) const {
    assert(unsigned(NT >> 3) < array_lengthof(TargetDAGCombineArray));
    return TargetDAGCombineArray[NT >> 3] & (1 << (NT&7));
  }

  /// This function returns the maximum number of store operations permitted
  /// to replace a call to llvm.memset. The value is set by the target at the
  /// performance threshold for such a replacement.
  /// @brief Get maximum # of store operations permitted for llvm.memset
  unsigned getMaxStoresPerMemset() const { return maxStoresPerMemset; }

  /// This function returns the maximum number of store operations permitted
  /// to replace a call to llvm.memcpy. The value is set by the target at the
  /// performance threshold for such a replacement.
  /// @brief Get maximum # of store operations permitted for llvm.memcpy
  unsigned getMaxStoresPerMemcpy() const { return maxStoresPerMemcpy; }

  /// This function returns the maximum number of store operations permitted
  /// to replace a call to llvm.memmove. The value is set by the target at the
  /// performance threshold for such a replacement.
  /// @brief Get maximum # of store operations permitted for llvm.memmove
  unsigned getMaxStoresPerMemmove() const { return maxStoresPerMemmove; }

  /// This function returns true if the target allows unaligned memory accesses.
  /// of the specified type. This is used, for example, in situations where an
  /// array copy/move/set is  converted to a sequence of store operations. It's
  /// use helps to ensure that such replacements don't generate code that causes
  /// an alignment error  (trap) on the target machine. 
  /// @brief Determine if the target supports unaligned memory accesses.
  virtual bool allowsUnalignedMemoryAccesses(EVT VT) const {
    return false;
  }

  /// This function returns true if the target would benefit from code placement
  /// optimization.
  /// @brief Determine if the target should perform code placement optimization.
  bool shouldOptimizeCodePlacement() const {
    return benefitFromCodePlacementOpt;
  }

  /// getOptimalMemOpType - Returns the target specific optimal type for load
  /// and store operations as a result of memset, memcpy, and memmove lowering.
  /// It returns EVT::iAny if SelectionDAG should be responsible for
  /// determining it.
  virtual EVT getOptimalMemOpType(uint64_t Size, unsigned Align,
                                  bool isSrcConst, bool isSrcStr,
                                  SelectionDAG &DAG) const {
    return MVT::iAny;
  }
  
  /// usesUnderscoreSetJmp - Determine if we should use _setjmp or setjmp
  /// to implement llvm.setjmp.
  bool usesUnderscoreSetJmp() const {
    return UseUnderscoreSetJmp;
  }

  /// usesUnderscoreLongJmp - Determine if we should use _longjmp or longjmp
  /// to implement llvm.longjmp.
  bool usesUnderscoreLongJmp() const {
    return UseUnderscoreLongJmp;
  }

  /// getStackPointerRegisterToSaveRestore - If a physical register, this
  /// specifies the register that llvm.savestack/llvm.restorestack should save
  /// and restore.
  unsigned getStackPointerRegisterToSaveRestore() const {
    return StackPointerRegisterToSaveRestore;
  }

  /// getExceptionAddressRegister - If a physical register, this returns
  /// the register that receives the exception address on entry to a landing
  /// pad.
  unsigned getExceptionAddressRegister() const {
    return ExceptionPointerRegister;
  }

  /// getExceptionSelectorRegister - If a physical register, this returns
  /// the register that receives the exception typeid on entry to a landing
  /// pad.
  unsigned getExceptionSelectorRegister() const {
    return ExceptionSelectorRegister;
  }

  /// getJumpBufSize - returns the target's jmp_buf size in bytes (if never
  /// set, the default is 200)
  unsigned getJumpBufSize() const {
    return JumpBufSize;
  }

  /// getJumpBufAlignment - returns the target's jmp_buf alignment in bytes
  /// (if never set, the default is 0)
  unsigned getJumpBufAlignment() const {
    return JumpBufAlignment;
  }

  /// getIfCvtBlockLimit - returns the target specific if-conversion block size
  /// limit. Any block whose size is greater should not be predicated.
  unsigned getIfCvtBlockSizeLimit() const {
    return IfCvtBlockSizeLimit;
  }

  /// getIfCvtDupBlockLimit - returns the target specific size limit for a
  /// block to be considered for duplication. Any block whose size is greater
  /// should not be duplicated to facilitate its predication.
  unsigned getIfCvtDupBlockSizeLimit() const {
    return IfCvtDupBlockSizeLimit;
  }

  /// getPrefLoopAlignment - return the preferred loop alignment.
  ///
  unsigned getPrefLoopAlignment() const {
    return PrefLoopAlignment;
  }
  
  /// getPreIndexedAddressParts - returns true by value, base pointer and
  /// offset pointer and addressing mode by reference if the node's address
  /// can be legally represented as pre-indexed load / store address.
  virtual bool getPreIndexedAddressParts(SDNode *N, SDValue &Base,
                                         SDValue &Offset,
                                         ISD::MemIndexedMode &AM,
                                         SelectionDAG &DAG) const {
    return false;
  }
  
  /// getPostIndexedAddressParts - returns true by value, base pointer and
  /// offset pointer and addressing mode by reference if this node can be
  /// combined with a load / store to form a post-indexed load / store.
  virtual bool getPostIndexedAddressParts(SDNode *N, SDNode *Op,
                                          SDValue &Base, SDValue &Offset,
                                          ISD::MemIndexedMode &AM,
                                          SelectionDAG &DAG) const {
    return false;
  }
  
  /// getPICJumpTableRelocaBase - Returns relocation base for the given PIC
  /// jumptable.
  virtual SDValue getPICJumpTableRelocBase(SDValue Table,
                                             SelectionDAG &DAG) const;

  /// isOffsetFoldingLegal - Return true if folding a constant offset
  /// with the given GlobalAddress is legal.  It is frequently not legal in
  /// PIC relocation models.
  virtual bool isOffsetFoldingLegal(const GlobalAddressSDNode *GA) const;

  /// getFunctionAlignment - Return the Log2 alignment of this function.
  virtual unsigned getFunctionAlignment(const Function *) const = 0;

  //===--------------------------------------------------------------------===//
  // TargetLowering Optimization Methods
  //
  
  /// TargetLoweringOpt - A convenience struct that encapsulates a DAG, and two
  /// SDValues for returning information from TargetLowering to its clients
  /// that want to combine 
  struct TargetLoweringOpt {
    SelectionDAG &DAG;
    SDValue Old;
    SDValue New;

    explicit TargetLoweringOpt(SelectionDAG &InDAG) : DAG(InDAG) {}
    
    bool CombineTo(SDValue O, SDValue N) { 
      Old = O; 
      New = N; 
      return true;
    }
    
    /// ShrinkDemandedConstant - Check to see if the specified operand of the 
    /// specified instruction is a constant integer.  If so, check to see if
    /// there are any bits set in the constant that are not demanded.  If so,
    /// shrink the constant and return true.
    bool ShrinkDemandedConstant(SDValue Op, const APInt &Demanded);

    /// ShrinkDemandedOp - Convert x+y to (VT)((SmallVT)x+(SmallVT)y) if the
    /// casts are free.  This uses isZExtFree and ZERO_EXTEND for the widening
    /// cast, but it could be generalized for targets with other types of
    /// implicit widening casts.
    bool ShrinkDemandedOp(SDValue Op, unsigned BitWidth, const APInt &Demanded,
                          DebugLoc dl);
  };
                                                
  /// SimplifyDemandedBits - Look at Op.  At this point, we know that only the
  /// DemandedMask bits of the result of Op are ever used downstream.  If we can
  /// use this information to simplify Op, create a new simplified DAG node and
  /// return true, returning the original and new nodes in Old and New. 
  /// Otherwise, analyze the expression and return a mask of KnownOne and 
  /// KnownZero bits for the expression (used to simplify the caller).  
  /// The KnownZero/One bits may only be accurate for those bits in the 
  /// DemandedMask.
  bool SimplifyDemandedBits(SDValue Op, const APInt &DemandedMask, 
                            APInt &KnownZero, APInt &KnownOne,
                            TargetLoweringOpt &TLO, unsigned Depth = 0) const;
  
  /// computeMaskedBitsForTargetNode - Determine which of the bits specified in
  /// Mask are known to be either zero or one and return them in the 
  /// KnownZero/KnownOne bitsets.
  virtual void computeMaskedBitsForTargetNode(const SDValue Op,
                                              const APInt &Mask,
                                              APInt &KnownZero, 
                                              APInt &KnownOne,
                                              const SelectionDAG &DAG,
                                              unsigned Depth = 0) const;

  /// ComputeNumSignBitsForTargetNode - This method can be implemented by
  /// targets that want to expose additional information about sign bits to the
  /// DAG Combiner.
  virtual unsigned ComputeNumSignBitsForTargetNode(SDValue Op,
                                                   unsigned Depth = 0) const;
  
  struct DAGCombinerInfo {
    void *DC;  // The DAG Combiner object.
    bool BeforeLegalize;
    bool BeforeLegalizeOps;
    bool CalledByLegalizer;
  public:
    SelectionDAG &DAG;
    
    DAGCombinerInfo(SelectionDAG &dag, bool bl, bool blo, bool cl, void *dc)
      : DC(dc), BeforeLegalize(bl), BeforeLegalizeOps(blo),
        CalledByLegalizer(cl), DAG(dag) {}
    
    bool isBeforeLegalize() const { return BeforeLegalize; }
    bool isBeforeLegalizeOps() const { return BeforeLegalizeOps; }
    bool isCalledByLegalizer() const { return CalledByLegalizer; }
    
    void AddToWorklist(SDNode *N);
    SDValue CombineTo(SDNode *N, const std::vector<SDValue> &To,
                      bool AddTo = true);
    SDValue CombineTo(SDNode *N, SDValue Res, bool AddTo = true);
    SDValue CombineTo(SDNode *N, SDValue Res0, SDValue Res1, bool AddTo = true);

    void CommitTargetLoweringOpt(const TargetLoweringOpt &TLO);
  };

  /// SimplifySetCC - Try to simplify a setcc built with the specified operands 
  /// and cc. If it is unable to simplify it, return a null SDValue.
  SDValue SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
                          ISD::CondCode Cond, bool foldBooleans,
                          DAGCombinerInfo &DCI, DebugLoc dl) const;

  /// isGAPlusOffset - Returns true (and the GlobalValue and the offset) if the
  /// node is a GlobalAddress + offset.
  virtual bool
  isGAPlusOffset(SDNode *N, GlobalValue* &GA, int64_t &Offset) const;

  /// isConsecutiveLoad - Return true if LD is loading 'Bytes' bytes from a 
  /// location that is 'Dist' units away from the location that the 'Base' load 
  /// is loading from.
  bool isConsecutiveLoad(LoadSDNode *LD, LoadSDNode *Base, unsigned Bytes,
                         int Dist, const MachineFrameInfo *MFI) const;

  /// PerformDAGCombine - This method will be invoked for all target nodes and
  /// for any target-independent nodes that the target has registered with
  /// invoke it for.
  ///
  /// The semantics are as follows:
  /// Return Value:
  ///   SDValue.Val == 0   - No change was made
  ///   SDValue.Val == N   - N was replaced, is dead, and is already handled.
  ///   otherwise          - N should be replaced by the returned Operand.
  ///
  /// In addition, methods provided by DAGCombinerInfo may be used to perform
  /// more complex transformations.
  ///
  virtual SDValue PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const;
  
  //===--------------------------------------------------------------------===//
  // TargetLowering Configuration Methods - These methods should be invoked by
  // the derived class constructor to configure this object for the target.
  //

protected:
  /// setUsesGlobalOffsetTable - Specify that this target does or doesn't use a
  /// GOT for PC-relative code.
  void setUsesGlobalOffsetTable(bool V) { UsesGlobalOffsetTable = V; }

  /// setShiftAmountType - Describe the type that should be used for shift
  /// amounts.  This type defaults to the pointer type.
  void setShiftAmountType(MVT VT) { ShiftAmountTy = VT; }

  /// setBooleanContents - Specify how the target extends the result of a
  /// boolean value from i1 to a wider type.  See getBooleanContents.
  void setBooleanContents(BooleanContent Ty) { BooleanContents = Ty; }

  /// setSchedulingPreference - Specify the target scheduling preference.
  void setSchedulingPreference(SchedPreference Pref) {
    SchedPreferenceInfo = Pref;
  }

  /// setUseUnderscoreSetJmp - Indicate whether this target prefers to
  /// use _setjmp to implement llvm.setjmp or the non _ version.
  /// Defaults to false.
  void setUseUnderscoreSetJmp(bool Val) {
    UseUnderscoreSetJmp = Val;
  }

  /// setUseUnderscoreLongJmp - Indicate whether this target prefers to
  /// use _longjmp to implement llvm.longjmp or the non _ version.
  /// Defaults to false.
  void setUseUnderscoreLongJmp(bool Val) {
    UseUnderscoreLongJmp = Val;
  }

  /// setStackPointerRegisterToSaveRestore - If set to a physical register, this
  /// specifies the register that llvm.savestack/llvm.restorestack should save
  /// and restore.
  void setStackPointerRegisterToSaveRestore(unsigned R) {
    StackPointerRegisterToSaveRestore = R;
  }
  
  /// setExceptionPointerRegister - If set to a physical register, this sets
  /// the register that receives the exception address on entry to a landing
  /// pad.
  void setExceptionPointerRegister(unsigned R) {
    ExceptionPointerRegister = R;
  }

  /// setExceptionSelectorRegister - If set to a physical register, this sets
  /// the register that receives the exception typeid on entry to a landing
  /// pad.
  void setExceptionSelectorRegister(unsigned R) {
    ExceptionSelectorRegister = R;
  }

  /// SelectIsExpensive - Tells the code generator not to expand operations
  /// into sequences that use the select operations if possible.
  void setSelectIsExpensive() { SelectIsExpensive = true; }

  /// setIntDivIsCheap - Tells the code generator that integer divide is
  /// expensive, and if possible, should be replaced by an alternate sequence
  /// of instructions not containing an integer divide.
  void setIntDivIsCheap(bool isCheap = true) { IntDivIsCheap = isCheap; }
  
  /// setPow2DivIsCheap - Tells the code generator that it shouldn't generate
  /// srl/add/sra for a signed divide by power of two, and let the target handle
  /// it.
  void setPow2DivIsCheap(bool isCheap = true) { Pow2DivIsCheap = isCheap; }
  
  /// addRegisterClass - Add the specified register class as an available
  /// regclass for the specified value type.  This indicates the selector can
  /// handle values of that class natively.
  void addRegisterClass(EVT VT, TargetRegisterClass *RC) {
    assert((unsigned)VT.getSimpleVT().SimpleTy < array_lengthof(RegClassForVT));
    AvailableRegClasses.push_back(std::make_pair(VT, RC));
    RegClassForVT[VT.getSimpleVT().SimpleTy] = RC;
  }

  /// computeRegisterProperties - Once all of the register classes are added,
  /// this allows us to compute derived properties we expose.
  void computeRegisterProperties();

  /// setOperationAction - Indicate that the specified operation does not work
  /// with the specified type and indicate what to do about it.
  void setOperationAction(unsigned Op, MVT VT,
                          LegalizeAction Action) {
    unsigned I = (unsigned)VT.SimpleTy;
    unsigned J = I & 31;
    I = I >> 5;
    OpActions[I][Op] &= ~(uint64_t(3UL) << (J*2));
    OpActions[I][Op] |= (uint64_t)Action << (J*2);
  }
  
  /// setLoadExtAction - Indicate that the specified load with extension does
  /// not work with the with specified type and indicate what to do about it.
  void setLoadExtAction(unsigned ExtType, MVT VT,
                      LegalizeAction Action) {
    assert((unsigned)VT.SimpleTy < sizeof(LoadExtActions[0])*4 &&
           ExtType < array_lengthof(LoadExtActions) &&
           "Table isn't big enough!");
    LoadExtActions[ExtType] &= ~(uint64_t(3UL) << VT.SimpleTy*2);
    LoadExtActions[ExtType] |= (uint64_t)Action << VT.SimpleTy*2;
  }
  
  /// setTruncStoreAction - Indicate that the specified truncating store does
  /// not work with the with specified type and indicate what to do about it.
  void setTruncStoreAction(MVT ValVT, MVT MemVT,
                           LegalizeAction Action) {
    assert((unsigned)ValVT.SimpleTy < array_lengthof(TruncStoreActions) &&
           (unsigned)MemVT.SimpleTy < sizeof(TruncStoreActions[0])*4 &&
           "Table isn't big enough!");
    TruncStoreActions[ValVT.SimpleTy] &= ~(uint64_t(3UL)  << MemVT.SimpleTy*2);
    TruncStoreActions[ValVT.SimpleTy] |= (uint64_t)Action << MemVT.SimpleTy*2;
  }

  /// setIndexedLoadAction - Indicate that the specified indexed load does or
  /// does not work with the with specified type and indicate what to do abort
  /// it. NOTE: All indexed mode loads are initialized to Expand in
  /// TargetLowering.cpp
  void setIndexedLoadAction(unsigned IdxMode, MVT VT,
                            LegalizeAction Action) {
    assert((unsigned)VT.SimpleTy < MVT::LAST_VALUETYPE &&
           IdxMode < array_lengthof(IndexedModeActions[0][0]) &&
           "Table isn't big enough!");
    IndexedModeActions[(unsigned)VT.SimpleTy][0][IdxMode] = (uint8_t)Action;
  }
  
  /// setIndexedStoreAction - Indicate that the specified indexed store does or
  /// does not work with the with specified type and indicate what to do about
  /// it. NOTE: All indexed mode stores are initialized to Expand in
  /// TargetLowering.cpp
  void setIndexedStoreAction(unsigned IdxMode, MVT VT,
                             LegalizeAction Action) {
    assert((unsigned)VT.SimpleTy < MVT::LAST_VALUETYPE &&
           IdxMode < array_lengthof(IndexedModeActions[0][1] ) &&
           "Table isn't big enough!");
    IndexedModeActions[(unsigned)VT.SimpleTy][1][IdxMode] = (uint8_t)Action;
  }
  
  /// setConvertAction - Indicate that the specified conversion does or does
  /// not work with the with specified type and indicate what to do about it.
  void setConvertAction(MVT FromVT, MVT ToVT,
                        LegalizeAction Action) {
    assert((unsigned)FromVT.SimpleTy < array_lengthof(ConvertActions) &&
           (unsigned)ToVT.SimpleTy < sizeof(ConvertActions[0])*4 &&
           "Table isn't big enough!");
    ConvertActions[FromVT.SimpleTy] &= ~(uint64_t(3UL)  << ToVT.SimpleTy*2);
    ConvertActions[FromVT.SimpleTy] |= (uint64_t)Action << ToVT.SimpleTy*2;
  }

  /// setCondCodeAction - Indicate that the specified condition code is or isn't
  /// supported on the target and indicate what to do about it.
  void setCondCodeAction(ISD::CondCode CC, MVT VT,
                         LegalizeAction Action) {
    assert((unsigned)VT.SimpleTy < sizeof(CondCodeActions[0])*4 &&
           (unsigned)CC < array_lengthof(CondCodeActions) &&
           "Table isn't big enough!");
    CondCodeActions[(unsigned)CC] &= ~(uint64_t(3UL)  << VT.SimpleTy*2);
    CondCodeActions[(unsigned)CC] |= (uint64_t)Action << VT.SimpleTy*2;
  }

  /// AddPromotedToType - If Opc/OrigVT is specified as being promoted, the
  /// promotion code defaults to trying a larger integer/fp until it can find
  /// one that works.  If that default is insufficient, this method can be used
  /// by the target to override the default.
  void AddPromotedToType(unsigned Opc, MVT OrigVT, MVT DestVT) {
    PromoteToType[std::make_pair(Opc, OrigVT.SimpleTy)] = DestVT.SimpleTy;
  }

  /// addLegalFPImmediate - Indicate that this target can instruction select
  /// the specified FP immediate natively.
  void addLegalFPImmediate(const APFloat& Imm) {
    LegalFPImmediates.push_back(Imm);
  }

  /// setTargetDAGCombine - Targets should invoke this method for each target
  /// independent node that they want to provide a custom DAG combiner for by
  /// implementing the PerformDAGCombine virtual method.
  void setTargetDAGCombine(ISD::NodeType NT) {
    assert(unsigned(NT >> 3) < array_lengthof(TargetDAGCombineArray));
    TargetDAGCombineArray[NT >> 3] |= 1 << (NT&7);
  }
  
  /// setJumpBufSize - Set the target's required jmp_buf buffer size (in
  /// bytes); default is 200
  void setJumpBufSize(unsigned Size) {
    JumpBufSize = Size;
  }

  /// setJumpBufAlignment - Set the target's required jmp_buf buffer
  /// alignment (in bytes); default is 0
  void setJumpBufAlignment(unsigned Align) {
    JumpBufAlignment = Align;
  }

  /// setIfCvtBlockSizeLimit - Set the target's if-conversion block size
  /// limit (in number of instructions); default is 2.
  void setIfCvtBlockSizeLimit(unsigned Limit) {
    IfCvtBlockSizeLimit = Limit;
  }
  
  /// setIfCvtDupBlockSizeLimit - Set the target's block size limit (in number
  /// of instructions) to be considered for code duplication during
  /// if-conversion; default is 2.
  void setIfCvtDupBlockSizeLimit(unsigned Limit) {
    IfCvtDupBlockSizeLimit = Limit;
  }

  /// setPrefLoopAlignment - Set the target's preferred loop alignment. Default
  /// alignment is zero, it means the target does not care about loop alignment.
  void setPrefLoopAlignment(unsigned Align) {
    PrefLoopAlignment = Align;
  }
  
public:

  virtual const TargetSubtarget *getSubtarget() {
    assert(0 && "Not Implemented");
    return NULL;    // this is here to silence compiler errors
  }

  //===--------------------------------------------------------------------===//
  // Lowering methods - These methods must be implemented by targets so that
  // the SelectionDAGLowering code knows how to lower these.
  //

  /// LowerFormalArguments - This hook must be implemented to lower the
  /// incoming (formal) arguments, described by the Ins array, into the
  /// specified DAG. The implementation should fill in the InVals array
  /// with legal-type argument values, and return the resulting token
  /// chain value.
  ///
  virtual SDValue
    LowerFormalArguments(SDValue Chain,
                         unsigned CallConv, bool isVarArg,
                         const SmallVectorImpl<ISD::InputArg> &Ins,
                         DebugLoc dl, SelectionDAG &DAG,
                         SmallVectorImpl<SDValue> &InVals) {
    assert(0 && "Not Implemented");
    return SDValue();    // this is here to silence compiler errors
  }

  /// LowerCallTo - This function lowers an abstract call to a function into an
  /// actual call.  This returns a pair of operands.  The first element is the
  /// return value for the function (if RetTy is not VoidTy).  The second
  /// element is the outgoing token chain. It calls LowerCall to do the actual
  /// lowering.
  struct ArgListEntry {
    SDValue Node;
    const Type* Ty;
    bool isSExt  : 1;
    bool isZExt  : 1;
    bool isInReg : 1;
    bool isSRet  : 1;
    bool isNest  : 1;
    bool isByVal : 1;
    uint16_t Alignment;

    ArgListEntry() : isSExt(false), isZExt(false), isInReg(false),
      isSRet(false), isNest(false), isByVal(false), Alignment(0) { }
  };
  typedef std::vector<ArgListEntry> ArgListTy;
  std::pair<SDValue, SDValue>
  LowerCallTo(SDValue Chain, const Type *RetTy, bool RetSExt, bool RetZExt,
              bool isVarArg, bool isInreg, unsigned NumFixedArgs,
              unsigned CallConv, bool isTailCall, bool isReturnValueUsed,
              SDValue Callee, ArgListTy &Args, SelectionDAG &DAG, DebugLoc dl);

  /// LowerCall - This hook must be implemented to lower calls into the
  /// the specified DAG. The outgoing arguments to the call are described
  /// by the Outs array, and the values to be returned by the call are
  /// described by the Ins array. The implementation should fill in the
  /// InVals array with legal-type return values from the call, and return
  /// the resulting token chain value.
  ///
  /// The isTailCall flag here is normative. If it is true, the
  /// implementation must emit a tail call. The
  /// IsEligibleForTailCallOptimization hook should be used to catch
  /// cases that cannot be handled.
  ///
  virtual SDValue
    LowerCall(SDValue Chain, SDValue Callee,
              unsigned CallConv, bool isVarArg, bool isTailCall,
              const SmallVectorImpl<ISD::OutputArg> &Outs,
              const SmallVectorImpl<ISD::InputArg> &Ins,
              DebugLoc dl, SelectionDAG &DAG,
              SmallVectorImpl<SDValue> &InVals) {
    assert(0 && "Not Implemented");
    return SDValue();    // this is here to silence compiler errors
  }

  /// LowerReturn - This hook must be implemented to lower outgoing
  /// return values, described by the Outs array, into the specified
  /// DAG. The implementation should return the resulting token chain
  /// value.
  ///
  virtual SDValue
    LowerReturn(SDValue Chain, unsigned CallConv, bool isVarArg,
                const SmallVectorImpl<ISD::OutputArg> &Outs,
                DebugLoc dl, SelectionDAG &DAG) {
    assert(0 && "Not Implemented");
    return SDValue();    // this is here to silence compiler errors
  }

  /// EmitTargetCodeForMemcpy - Emit target-specific code that performs a
  /// memcpy. This can be used by targets to provide code sequences for cases
  /// that don't fit the target's parameters for simple loads/stores and can be
  /// more efficient than using a library call. This function can return a null
  /// SDValue if the target declines to use custom code and a different
  /// lowering strategy should be used.
  /// 
  /// If AlwaysInline is true, the size is constant and the target should not
  /// emit any calls and is strongly encouraged to attempt to emit inline code
  /// even if it is beyond the usual threshold because this intrinsic is being
  /// expanded in a place where calls are not feasible (e.g. within the prologue
  /// for another call). If the target chooses to decline an AlwaysInline
  /// request here, legalize will resort to using simple loads and stores.
  virtual SDValue
  EmitTargetCodeForMemcpy(SelectionDAG &DAG, DebugLoc dl,
                          SDValue Chain,
                          SDValue Op1, SDValue Op2,
                          SDValue Op3, unsigned Align,
                          bool AlwaysInline,
                          const Value *DstSV, uint64_t DstOff,
                          const Value *SrcSV, uint64_t SrcOff) {
    return SDValue();
  }

  /// EmitTargetCodeForMemmove - Emit target-specific code that performs a
  /// memmove. This can be used by targets to provide code sequences for cases
  /// that don't fit the target's parameters for simple loads/stores and can be
  /// more efficient than using a library call. This function can return a null
  /// SDValue if the target declines to use custom code and a different
  /// lowering strategy should be used.
  virtual SDValue
  EmitTargetCodeForMemmove(SelectionDAG &DAG, DebugLoc dl,
                           SDValue Chain,
                           SDValue Op1, SDValue Op2,
                           SDValue Op3, unsigned Align,
                           const Value *DstSV, uint64_t DstOff,
                           const Value *SrcSV, uint64_t SrcOff) {
    return SDValue();
  }

  /// EmitTargetCodeForMemset - Emit target-specific code that performs a
  /// memset. This can be used by targets to provide code sequences for cases
  /// that don't fit the target's parameters for simple stores and can be more
  /// efficient than using a library call. This function can return a null
  /// SDValue if the target declines to use custom code and a different
  /// lowering strategy should be used.
  virtual SDValue
  EmitTargetCodeForMemset(SelectionDAG &DAG, DebugLoc dl,
                          SDValue Chain,
                          SDValue Op1, SDValue Op2,
                          SDValue Op3, unsigned Align,
                          const Value *DstSV, uint64_t DstOff) {
    return SDValue();
  }

  /// LowerOperationWrapper - This callback is invoked by the type legalizer
  /// to legalize nodes with an illegal operand type but legal result types.
  /// It replaces the LowerOperation callback in the type Legalizer.
  /// The reason we can not do away with LowerOperation entirely is that
  /// LegalizeDAG isn't yet ready to use this callback.
  /// TODO: Consider merging with ReplaceNodeResults.

  /// The target places new result values for the node in Results (their number
  /// and types must exactly match those of the original return values of
  /// the node), or leaves Results empty, which indicates that the node is not
  /// to be custom lowered after all.
  /// The default implementation calls LowerOperation.
  virtual void LowerOperationWrapper(SDNode *N,
                                     SmallVectorImpl<SDValue> &Results,
                                     SelectionDAG &DAG);

  /// LowerOperation - This callback is invoked for operations that are 
  /// unsupported by the target, which are registered to use 'custom' lowering,
  /// and whose defined values are all legal.
  /// If the target has no operations that require custom lowering, it need not
  /// implement this.  The default implementation of this aborts.
  virtual SDValue LowerOperation(SDValue Op, SelectionDAG &DAG);

  /// ReplaceNodeResults - This callback is invoked when a node result type is
  /// illegal for the target, and the operation was registered to use 'custom'
  /// lowering for that result type.  The target places new result values for
  /// the node in Results (their number and types must exactly match those of
  /// the original return values of the node), or leaves Results empty, which
  /// indicates that the node is not to be custom lowered after all.
  ///
  /// If the target has no operations that require custom lowering, it need not
  /// implement this.  The default implementation aborts.
  virtual void ReplaceNodeResults(SDNode *N, SmallVectorImpl<SDValue> &Results,
                                  SelectionDAG &DAG) {
    assert(0 && "ReplaceNodeResults not implemented for this target!");
  }

  /// IsEligibleForTailCallOptimization - Check whether the call is eligible for
  /// tail call optimization. Targets which want to do tail call optimization
  /// should override this function.
  virtual bool
  IsEligibleForTailCallOptimization(SDValue Callee,
                                    unsigned CalleeCC,
                                    bool isVarArg,
                                    const SmallVectorImpl<ISD::InputArg> &Ins,
                                    SelectionDAG& DAG) const {
    // Conservative default: no calls are eligible.
    return false;
  }

  /// GetPossiblePreceedingTailCall - Get preceeding TailCallNodeOpCode node if
  /// it exists. Skip a possible ISD::TokenFactor.
  static SDValue GetPossiblePreceedingTailCall(SDValue Chain,
                                                 unsigned TailCallNodeOpCode) {
    if (Chain.getOpcode() == TailCallNodeOpCode) {
      return Chain;
    } else if (Chain.getOpcode() == ISD::TokenFactor) {
      if (Chain.getNumOperands() &&
          Chain.getOperand(0).getOpcode() == TailCallNodeOpCode)
        return Chain.getOperand(0);
    }
    return Chain;
  }

  /// getTargetNodeName() - This method returns the name of a target specific
  /// DAG node.
  virtual const char *getTargetNodeName(unsigned Opcode) const;

  /// createFastISel - This method returns a target specific FastISel object,
  /// or null if the target does not support "fast" ISel.
  virtual FastISel *
  createFastISel(MachineFunction &,
                 MachineModuleInfo *, DwarfWriter *,
                 DenseMap<const Value *, unsigned> &,
                 DenseMap<const BasicBlock *, MachineBasicBlock *> &,
                 DenseMap<const AllocaInst *, int> &
#ifndef NDEBUG
                 , SmallSet<Instruction*, 8> &CatchInfoLost
#endif
                 ) {
    return 0;
  }

  //===--------------------------------------------------------------------===//
  // Inline Asm Support hooks
  //
  
  /// ExpandInlineAsm - This hook allows the target to expand an inline asm
  /// call to be explicit llvm code if it wants to.  This is useful for
  /// turning simple inline asms into LLVM intrinsics, which gives the
  /// compiler more information about the behavior of the code.
  virtual bool ExpandInlineAsm(CallInst *CI) const {
    return false;
  }
  
  enum ConstraintType {
    C_Register,            // Constraint represents specific register(s).
    C_RegisterClass,       // Constraint represents any of register(s) in class.
    C_Memory,              // Memory constraint.
    C_Other,               // Something else.
    C_Unknown              // Unsupported constraint.
  };
  
  /// AsmOperandInfo - This contains information for each constraint that we are
  /// lowering.
  struct AsmOperandInfo : public InlineAsm::ConstraintInfo {
    /// ConstraintCode - This contains the actual string for the code, like "m".
    /// TargetLowering picks the 'best' code from ConstraintInfo::Codes that
    /// most closely matches the operand.
    std::string ConstraintCode;

    /// ConstraintType - Information about the constraint code, e.g. Register,
    /// RegisterClass, Memory, Other, Unknown.
    TargetLowering::ConstraintType ConstraintType;
  
    /// CallOperandval - If this is the result output operand or a
    /// clobber, this is null, otherwise it is the incoming operand to the
    /// CallInst.  This gets modified as the asm is processed.
    Value *CallOperandVal;
  
    /// ConstraintVT - The ValueType for the operand value.
    EVT ConstraintVT;
    
    /// isMatchingInputConstraint - Return true of this is an input operand that
    /// is a matching constraint like "4".
    bool isMatchingInputConstraint() const;
    
    /// getMatchedOperand - If this is an input matching constraint, this method
    /// returns the output operand it matches.
    unsigned getMatchedOperand() const;
  
    AsmOperandInfo(const InlineAsm::ConstraintInfo &info)
      : InlineAsm::ConstraintInfo(info), 
        ConstraintType(TargetLowering::C_Unknown),
        CallOperandVal(0), ConstraintVT(MVT::Other) {
    }
  };

  /// ComputeConstraintToUse - Determines the constraint code and constraint
  /// type to use for the specific AsmOperandInfo, setting
  /// OpInfo.ConstraintCode and OpInfo.ConstraintType.  If the actual operand
  /// being passed in is available, it can be passed in as Op, otherwise an
  /// empty SDValue can be passed. If hasMemory is true it means one of the asm
  /// constraint of the inline asm instruction being processed is 'm'.
  virtual void ComputeConstraintToUse(AsmOperandInfo &OpInfo,
                                      SDValue Op,
                                      bool hasMemory,
                                      SelectionDAG *DAG = 0) const;
  
  /// getConstraintType - Given a constraint, return the type of constraint it
  /// is for this target.
  virtual ConstraintType getConstraintType(const std::string &Constraint) const;
  
  /// getRegClassForInlineAsmConstraint - Given a constraint letter (e.g. "r"),
  /// return a list of registers that can be used to satisfy the constraint.
  /// This should only be used for C_RegisterClass constraints.
  virtual std::vector<unsigned> 
  getRegClassForInlineAsmConstraint(const std::string &Constraint,
                                    EVT VT) const;

  /// getRegForInlineAsmConstraint - Given a physical register constraint (e.g.
  /// {edx}), return the register number and the register class for the
  /// register.
  ///
  /// Given a register class constraint, like 'r', if this corresponds directly
  /// to an LLVM register class, return a register of 0 and the register class
  /// pointer.
  ///
  /// This should only be used for C_Register constraints.  On error,
  /// this returns a register number of 0 and a null register class pointer..
  virtual std::pair<unsigned, const TargetRegisterClass*> 
    getRegForInlineAsmConstraint(const std::string &Constraint,
                                 EVT VT) const;
  
  /// LowerXConstraint - try to replace an X constraint, which matches anything,
  /// with another that has more specific requirements based on the type of the
  /// corresponding operand.  This returns null if there is no replacement to
  /// make.
  virtual const char *LowerXConstraint(EVT ConstraintVT) const;
  
  /// LowerAsmOperandForConstraint - Lower the specified operand into the Ops
  /// vector.  If it is invalid, don't add anything to Ops. If hasMemory is true
  /// it means one of the asm constraint of the inline asm instruction being
  /// processed is 'm'.
  virtual void LowerAsmOperandForConstraint(SDValue Op, char ConstraintLetter,
                                            bool hasMemory,
                                            std::vector<SDValue> &Ops,
                                            SelectionDAG &DAG) const;
  
  //===--------------------------------------------------------------------===//
  // Scheduler hooks
  //
  
  // EmitInstrWithCustomInserter - This method should be implemented by targets
  // that mark instructions with the 'usesCustomDAGSchedInserter' flag.  These
  // instructions are special in various ways, which require special support to
  // insert.  The specified MachineInstr is created but not inserted into any
  // basic blocks, and the scheduler passes ownership of it to this method.
  virtual MachineBasicBlock *EmitInstrWithCustomInserter(MachineInstr *MI,
                                                  MachineBasicBlock *MBB) const;

  //===--------------------------------------------------------------------===//
  // Addressing mode description hooks (used by LSR etc).
  //

  /// AddrMode - This represents an addressing mode of:
  ///    BaseGV + BaseOffs + BaseReg + Scale*ScaleReg
  /// If BaseGV is null,  there is no BaseGV.
  /// If BaseOffs is zero, there is no base offset.
  /// If HasBaseReg is false, there is no base register.
  /// If Scale is zero, there is no ScaleReg.  Scale of 1 indicates a reg with
  /// no scale.
  ///
  struct AddrMode {
    GlobalValue *BaseGV;
    int64_t      BaseOffs;
    bool         HasBaseReg;
    int64_t      Scale;
    AddrMode() : BaseGV(0), BaseOffs(0), HasBaseReg(false), Scale(0) {}
  };
  
  /// isLegalAddressingMode - Return true if the addressing mode represented by
  /// AM is legal for this target, for a load/store of the specified type.
  /// The type may be VoidTy, in which case only return true if the addressing
  /// mode is legal for a load/store of any legal type.
  /// TODO: Handle pre/postinc as well.
  virtual bool isLegalAddressingMode(const AddrMode &AM, const Type *Ty) const;

  /// isTruncateFree - Return true if it's free to truncate a value of
  /// type Ty1 to type Ty2. e.g. On x86 it's free to truncate a i32 value in
  /// register EAX to i16 by referencing its sub-register AX.
  virtual bool isTruncateFree(const Type *Ty1, const Type *Ty2) const {
    return false;
  }

  virtual bool isTruncateFree(EVT VT1, EVT VT2) const {
    return false;
  }

  /// isZExtFree - Return true if any actual instruction that defines a
  /// value of type Ty1 implicit zero-extends the value to Ty2 in the result
  /// register. This does not necessarily include registers defined in
  /// unknown ways, such as incoming arguments, or copies from unknown
  /// virtual registers. Also, if isTruncateFree(Ty2, Ty1) is true, this
  /// does not necessarily apply to truncate instructions. e.g. on x86-64,
  /// all instructions that define 32-bit values implicit zero-extend the
  /// result out to 64 bits.
  virtual bool isZExtFree(const Type *Ty1, const Type *Ty2) const {
    return false;
  }

  virtual bool isZExtFree(EVT VT1, EVT VT2) const {
    return false;
  }

  /// isNarrowingProfitable - Return true if it's profitable to narrow
  /// operations of type VT1 to VT2. e.g. on x86, it's profitable to narrow
  /// from i32 to i8 but not from i32 to i16.
  virtual bool isNarrowingProfitable(EVT VT1, EVT VT2) const {
    return false;
  }

  //===--------------------------------------------------------------------===//
  // Div utility functions
  //
  SDValue BuildSDIV(SDNode *N, SelectionDAG &DAG, 
                      std::vector<SDNode*>* Created) const;
  SDValue BuildUDIV(SDNode *N, SelectionDAG &DAG, 
                      std::vector<SDNode*>* Created) const;


  //===--------------------------------------------------------------------===//
  // Runtime Library hooks
  //

  /// setLibcallName - Rename the default libcall routine name for the specified
  /// libcall.
  void setLibcallName(RTLIB::Libcall Call, const char *Name) {
    LibcallRoutineNames[Call] = Name;
  }

  /// getLibcallName - Get the libcall routine name for the specified libcall.
  ///
  const char *getLibcallName(RTLIB::Libcall Call) const {
    return LibcallRoutineNames[Call];
  }

  /// setCmpLibcallCC - Override the default CondCode to be used to test the
  /// result of the comparison libcall against zero.
  void setCmpLibcallCC(RTLIB::Libcall Call, ISD::CondCode CC) {
    CmpLibcallCCs[Call] = CC;
  }

  /// getCmpLibcallCC - Get the CondCode that's to be used to test the result of
  /// the comparison libcall against zero.
  ISD::CondCode getCmpLibcallCC(RTLIB::Libcall Call) const {
    return CmpLibcallCCs[Call];
  }

  /// setLibcallCallingConv - Set the CallingConv that should be used for the
  /// specified libcall.
  void setLibcallCallingConv(RTLIB::Libcall Call, CallingConv::ID CC) {
    LibcallCallingConvs[Call] = CC;
  }
  
  /// getLibcallCallingConv - Get the CallingConv that should be used for the
  /// specified libcall.
  CallingConv::ID getLibcallCallingConv(RTLIB::Libcall Call) const {
    return LibcallCallingConvs[Call];
  }

private:
  TargetMachine &TM;
  const TargetData *TD;
  TargetLoweringObjectFile &TLOF;

  /// PointerTy - The type to use for pointers, usually i32 or i64.
  ///
  MVT PointerTy;

  /// IsLittleEndian - True if this is a little endian target.
  ///
  bool IsLittleEndian;

  /// UsesGlobalOffsetTable - True if this target uses a GOT for PIC codegen.
  ///
  bool UsesGlobalOffsetTable;
  
  /// SelectIsExpensive - Tells the code generator not to expand operations
  /// into sequences that use the select operations if possible.
  bool SelectIsExpensive;

  /// IntDivIsCheap - Tells the code generator not to expand integer divides by
  /// constants into a sequence of muls, adds, and shifts.  This is a hack until
  /// a real cost model is in place.  If we ever optimize for size, this will be
  /// set to true unconditionally.
  bool IntDivIsCheap;
  
  /// Pow2DivIsCheap - Tells the code generator that it shouldn't generate
  /// srl/add/sra for a signed divide by power of two, and let the target handle
  /// it.
  bool Pow2DivIsCheap;
  
  /// UseUnderscoreSetJmp - This target prefers to use _setjmp to implement
  /// llvm.setjmp.  Defaults to false.
  bool UseUnderscoreSetJmp;

  /// UseUnderscoreLongJmp - This target prefers to use _longjmp to implement
  /// llvm.longjmp.  Defaults to false.
  bool UseUnderscoreLongJmp;

  /// ShiftAmountTy - The type to use for shift amounts, usually i8 or whatever
  /// PointerTy is.
  MVT ShiftAmountTy;

  /// BooleanContents - Information about the contents of the high-bits in
  /// boolean values held in a type wider than i1.  See getBooleanContents.
  BooleanContent BooleanContents;

  /// SchedPreferenceInfo - The target scheduling preference: shortest possible
  /// total cycles or lowest register usage.
  SchedPreference SchedPreferenceInfo;
  
  /// JumpBufSize - The size, in bytes, of the target's jmp_buf buffers
  unsigned JumpBufSize;
  
  /// JumpBufAlignment - The alignment, in bytes, of the target's jmp_buf
  /// buffers
  unsigned JumpBufAlignment;

  /// IfCvtBlockSizeLimit - The maximum allowed size for a block to be
  /// if-converted.
  unsigned IfCvtBlockSizeLimit;
  
  /// IfCvtDupBlockSizeLimit - The maximum allowed size for a block to be
  /// duplicated during if-conversion.
  unsigned IfCvtDupBlockSizeLimit;

  /// PrefLoopAlignment - The perferred loop alignment.
  ///
  unsigned PrefLoopAlignment;

  /// StackPointerRegisterToSaveRestore - If set to a physical register, this
  /// specifies the register that llvm.savestack/llvm.restorestack should save
  /// and restore.
  unsigned StackPointerRegisterToSaveRestore;

  /// ExceptionPointerRegister - If set to a physical register, this specifies
  /// the register that receives the exception address on entry to a landing
  /// pad.
  unsigned ExceptionPointerRegister;

  /// ExceptionSelectorRegister - If set to a physical register, this specifies
  /// the register that receives the exception typeid on entry to a landing
  /// pad.
  unsigned ExceptionSelectorRegister;

  /// RegClassForVT - This indicates the default register class to use for
  /// each ValueType the target supports natively.
  TargetRegisterClass *RegClassForVT[MVT::LAST_VALUETYPE];
  unsigned char NumRegistersForVT[MVT::LAST_VALUETYPE];
  EVT RegisterTypeForVT[MVT::LAST_VALUETYPE];

  /// TransformToType - For any value types we are promoting or expanding, this
  /// contains the value type that we are changing to.  For Expanded types, this
  /// contains one step of the expand (e.g. i64 -> i32), even if there are
  /// multiple steps required (e.g. i64 -> i16).  For types natively supported
  /// by the system, this holds the same type (e.g. i32 -> i32).
  EVT TransformToType[MVT::LAST_VALUETYPE];

  /// OpActions - For each operation and each value type, keep a LegalizeAction
  /// that indicates how instruction selection should deal with the operation.
  /// Most operations are Legal (aka, supported natively by the target), but
  /// operations that are not should be described.  Note that operations on
  /// non-legal value types are not described here.
  /// This array is accessed using VT.getSimpleVT(), so it is subject to
  /// the MVT::MAX_ALLOWED_VALUETYPE * 2 bits.
  uint64_t OpActions[MVT::MAX_ALLOWED_VALUETYPE/(sizeof(uint64_t)*4)][ISD::BUILTIN_OP_END];
  
  /// LoadExtActions - For each load of load extension type and each value type,
  /// keep a LegalizeAction that indicates how instruction selection should deal
  /// with the load.
  uint64_t LoadExtActions[ISD::LAST_LOADEXT_TYPE];
  
  /// TruncStoreActions - For each truncating store, keep a LegalizeAction that
  /// indicates how instruction selection should deal with the store.
  uint64_t TruncStoreActions[MVT::LAST_VALUETYPE];

  /// IndexedModeActions - For each indexed mode and each value type,
  /// keep a pair of LegalizeAction that indicates how instruction
  /// selection should deal with the load / store.  The first
  /// dimension is now the value_type for the reference.  The second
  /// dimension is the load [0] vs. store[1].  The third dimension
  /// represents the various modes for load store.
  uint8_t IndexedModeActions[MVT::LAST_VALUETYPE][2][ISD::LAST_INDEXED_MODE];
  
  /// ConvertActions - For each conversion from source type to destination type,
  /// keep a LegalizeAction that indicates how instruction selection should
  /// deal with the conversion.
  /// Currently, this is used only for floating->floating conversions
  /// (FP_EXTEND and FP_ROUND).
  uint64_t ConvertActions[MVT::LAST_VALUETYPE];

  /// CondCodeActions - For each condition code (ISD::CondCode) keep a
  /// LegalizeAction that indicates how instruction selection should
  /// deal with the condition code.
  uint64_t CondCodeActions[ISD::SETCC_INVALID];

  ValueTypeActionImpl ValueTypeActions;

  std::vector<APFloat> LegalFPImmediates;

  std::vector<std::pair<EVT, TargetRegisterClass*> > AvailableRegClasses;

  /// TargetDAGCombineArray - Targets can specify ISD nodes that they would
  /// like PerformDAGCombine callbacks for by calling setTargetDAGCombine(),
  /// which sets a bit in this array.
  unsigned char
  TargetDAGCombineArray[(ISD::BUILTIN_OP_END+CHAR_BIT-1)/CHAR_BIT];
  
  /// PromoteToType - For operations that must be promoted to a specific type,
  /// this holds the destination type.  This map should be sparse, so don't hold
  /// it as an array.
  ///
  /// Targets add entries to this map with AddPromotedToType(..), clients access
  /// this with getTypeToPromoteTo(..).
  std::map<std::pair<unsigned, MVT::SimpleValueType>, MVT::SimpleValueType>
    PromoteToType;

  /// LibcallRoutineNames - Stores the name each libcall.
  ///
  const char *LibcallRoutineNames[RTLIB::UNKNOWN_LIBCALL];

  /// CmpLibcallCCs - The ISD::CondCode that should be used to test the result
  /// of each of the comparison libcall against zero.
  ISD::CondCode CmpLibcallCCs[RTLIB::UNKNOWN_LIBCALL];

  /// LibcallCallingConvs - Stores the CallingConv that should be used for each
  /// libcall.
  CallingConv::ID LibcallCallingConvs[RTLIB::UNKNOWN_LIBCALL];

protected:
  /// When lowering \@llvm.memset this field specifies the maximum number of
  /// store operations that may be substituted for the call to memset. Targets
  /// must set this value based on the cost threshold for that target. Targets
  /// should assume that the memset will be done using as many of the largest
  /// store operations first, followed by smaller ones, if necessary, per
  /// alignment restrictions. For example, storing 9 bytes on a 32-bit machine
  /// with 16-bit alignment would result in four 2-byte stores and one 1-byte
  /// store.  This only applies to setting a constant array of a constant size.
  /// @brief Specify maximum number of store instructions per memset call.
  unsigned maxStoresPerMemset;

  /// When lowering \@llvm.memcpy this field specifies the maximum number of
  /// store operations that may be substituted for a call to memcpy. Targets
  /// must set this value based on the cost threshold for that target. Targets
  /// should assume that the memcpy will be done using as many of the largest
  /// store operations first, followed by smaller ones, if necessary, per
  /// alignment restrictions. For example, storing 7 bytes on a 32-bit machine
  /// with 32-bit alignment would result in one 4-byte store, a one 2-byte store
  /// and one 1-byte store. This only applies to copying a constant array of
  /// constant size.
  /// @brief Specify maximum bytes of store instructions per memcpy call.
  unsigned maxStoresPerMemcpy;

  /// When lowering \@llvm.memmove this field specifies the maximum number of
  /// store instructions that may be substituted for a call to memmove. Targets
  /// must set this value based on the cost threshold for that target. Targets
  /// should assume that the memmove will be done using as many of the largest
  /// store operations first, followed by smaller ones, if necessary, per
  /// alignment restrictions. For example, moving 9 bytes on a 32-bit machine
  /// with 8-bit alignment would result in nine 1-byte stores.  This only
  /// applies to copying a constant array of constant size.
  /// @brief Specify maximum bytes of store instructions per memmove call.
  unsigned maxStoresPerMemmove;

  /// This field specifies whether the target can benefit from code placement
  /// optimization.
  bool benefitFromCodePlacementOpt;
};
} // end llvm namespace

#endif