llvm.org GIT mirror llvm / release_24 lib / CodeGen / IntrinsicLowering.cpp
release_24

Tree @release_24 (Download .tar.gz)

IntrinsicLowering.cpp @release_24raw · 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
//===-- IntrinsicLowering.cpp - Intrinsic Lowering default implementation -===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the IntrinsicLowering class.
//
//===----------------------------------------------------------------------===//

#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Module.h"
#include "llvm/Instructions.h"
#include "llvm/Type.h"
#include "llvm/CodeGen/IntrinsicLowering.h"
#include "llvm/Support/Streams.h"
#include "llvm/Target/TargetData.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/STLExtras.h"
using namespace llvm;

template <class ArgIt>
static void EnsureFunctionExists(Module &M, const char *Name,
                                 ArgIt ArgBegin, ArgIt ArgEnd,
                                 const Type *RetTy) {
  // Insert a correctly-typed definition now.
  std::vector<const Type *> ParamTys;
  for (ArgIt I = ArgBegin; I != ArgEnd; ++I)
    ParamTys.push_back(I->getType());
  M.getOrInsertFunction(Name, FunctionType::get(RetTy, ParamTys, false));
}

static void EnsureFPIntrinsicsExist(Module &M, Module::iterator I,
                                 const char *FName,
                                 const char *DName, const char *LDName) {
  // Insert definitions for all the floating point types.
  switch((int)I->arg_begin()->getType()->getTypeID()) {
  case Type::FloatTyID:
    EnsureFunctionExists(M, FName, I->arg_begin(), I->arg_end(),
                         Type::FloatTy);
  case Type::DoubleTyID:
    EnsureFunctionExists(M, DName, I->arg_begin(), I->arg_end(),
                         Type::DoubleTy);
  case Type::X86_FP80TyID:
  case Type::FP128TyID:
  case Type::PPC_FP128TyID:
    EnsureFunctionExists(M, LDName, I->arg_begin(), I->arg_end(),
                         I->arg_begin()->getType());
  }
}

/// ReplaceCallWith - This function is used when we want to lower an intrinsic
/// call to a call of an external function.  This handles hard cases such as
/// when there was already a prototype for the external function, and if that
/// prototype doesn't match the arguments we expect to pass in.
template <class ArgIt>
static CallInst *ReplaceCallWith(const char *NewFn, CallInst *CI,
                                 ArgIt ArgBegin, ArgIt ArgEnd,
                                 const Type *RetTy, Constant *&FCache) {
  if (!FCache) {
    // If we haven't already looked up this function, check to see if the
    // program already contains a function with this name.
    Module *M = CI->getParent()->getParent()->getParent();
    // Get or insert the definition now.
    std::vector<const Type *> ParamTys;
    for (ArgIt I = ArgBegin; I != ArgEnd; ++I)
      ParamTys.push_back((*I)->getType());
    FCache = M->getOrInsertFunction(NewFn,
                                    FunctionType::get(RetTy, ParamTys, false));
  }

  SmallVector<Value *, 8> Args(ArgBegin, ArgEnd);
  CallInst *NewCI = CallInst::Create(FCache, Args.begin(), Args.end(),
                                     CI->getName(), CI);
  if (!CI->use_empty())
    CI->replaceAllUsesWith(NewCI);
  return NewCI;
}

void IntrinsicLowering::AddPrototypes(Module &M) {
  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
    if (I->isDeclaration() && !I->use_empty())
      switch (I->getIntrinsicID()) {
      default: break;
      case Intrinsic::setjmp:
        EnsureFunctionExists(M, "setjmp", I->arg_begin(), I->arg_end(),
                             Type::Int32Ty);
        break;
      case Intrinsic::longjmp:
        EnsureFunctionExists(M, "longjmp", I->arg_begin(), I->arg_end(),
                             Type::VoidTy);
        break;
      case Intrinsic::siglongjmp:
        EnsureFunctionExists(M, "abort", I->arg_end(), I->arg_end(),
                             Type::VoidTy);
        break;
      case Intrinsic::memcpy_i32:
      case Intrinsic::memcpy_i64:
        M.getOrInsertFunction("memcpy", PointerType::getUnqual(Type::Int8Ty),
                              PointerType::getUnqual(Type::Int8Ty), 
                              PointerType::getUnqual(Type::Int8Ty), 
                              TD.getIntPtrType(), (Type *)0);
        break;
      case Intrinsic::memmove_i32:
      case Intrinsic::memmove_i64:
        M.getOrInsertFunction("memmove", PointerType::getUnqual(Type::Int8Ty),
                              PointerType::getUnqual(Type::Int8Ty), 
                              PointerType::getUnqual(Type::Int8Ty), 
                              TD.getIntPtrType(), (Type *)0);
        break;
      case Intrinsic::memset_i32:
      case Intrinsic::memset_i64:
        M.getOrInsertFunction("memset", PointerType::getUnqual(Type::Int8Ty),
                              PointerType::getUnqual(Type::Int8Ty), 
                              Type::Int32Ty, 
                              TD.getIntPtrType(), (Type *)0);
        break;
      case Intrinsic::sqrt:
        EnsureFPIntrinsicsExist(M, I, "sqrtf", "sqrt", "sqrtl");
        break;
      case Intrinsic::sin:
        EnsureFPIntrinsicsExist(M, I, "sinf", "sin", "sinl");
        break;
      case Intrinsic::cos:
        EnsureFPIntrinsicsExist(M, I, "cosf", "cos", "cosl");
        break;
      case Intrinsic::pow:
        EnsureFPIntrinsicsExist(M, I, "powf", "pow", "powl");
        break;
      case Intrinsic::log:
        EnsureFPIntrinsicsExist(M, I, "logf", "log", "logl");
        break;
      case Intrinsic::log2:
        EnsureFPIntrinsicsExist(M, I, "log2f", "log2", "log2l");
        break;
      case Intrinsic::log10:
        EnsureFPIntrinsicsExist(M, I, "log10f", "log10", "log10l");
        break;
      case Intrinsic::exp:
        EnsureFPIntrinsicsExist(M, I, "expf", "exp", "expl");
        break;
      case Intrinsic::exp2:
        EnsureFPIntrinsicsExist(M, I, "exp2f", "exp2", "exp2l");
        break;
      }
}

/// LowerBSWAP - Emit the code to lower bswap of V before the specified
/// instruction IP.
static Value *LowerBSWAP(Value *V, Instruction *IP) {
  assert(V->getType()->isInteger() && "Can't bswap a non-integer type!");

  unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
  
  switch(BitSize) {
  default: assert(0 && "Unhandled type size of value to byteswap!");
  case 16: {
    Value *Tmp1 = BinaryOperator::CreateShl(V,
                                ConstantInt::get(V->getType(),8),"bswap.2",IP);
    Value *Tmp2 = BinaryOperator::CreateLShr(V,
                                ConstantInt::get(V->getType(),8),"bswap.1",IP);
    V = BinaryOperator::CreateOr(Tmp1, Tmp2, "bswap.i16", IP);
    break;
  }
  case 32: {
    Value *Tmp4 = BinaryOperator::CreateShl(V,
                              ConstantInt::get(V->getType(),24),"bswap.4", IP);
    Value *Tmp3 = BinaryOperator::CreateShl(V,
                              ConstantInt::get(V->getType(),8),"bswap.3",IP);
    Value *Tmp2 = BinaryOperator::CreateLShr(V,
                              ConstantInt::get(V->getType(),8),"bswap.2",IP);
    Value *Tmp1 = BinaryOperator::CreateLShr(V,
                              ConstantInt::get(V->getType(),24),"bswap.1", IP);
    Tmp3 = BinaryOperator::CreateAnd(Tmp3, 
                                     ConstantInt::get(Type::Int32Ty, 0xFF0000),
                                     "bswap.and3", IP);
    Tmp2 = BinaryOperator::CreateAnd(Tmp2, 
                                     ConstantInt::get(Type::Int32Ty, 0xFF00),
                                     "bswap.and2", IP);
    Tmp4 = BinaryOperator::CreateOr(Tmp4, Tmp3, "bswap.or1", IP);
    Tmp2 = BinaryOperator::CreateOr(Tmp2, Tmp1, "bswap.or2", IP);
    V = BinaryOperator::CreateOr(Tmp4, Tmp2, "bswap.i32", IP);
    break;
  }
  case 64: {
    Value *Tmp8 = BinaryOperator::CreateShl(V,
                              ConstantInt::get(V->getType(),56),"bswap.8", IP);
    Value *Tmp7 = BinaryOperator::CreateShl(V,
                              ConstantInt::get(V->getType(),40),"bswap.7", IP);
    Value *Tmp6 = BinaryOperator::CreateShl(V,
                              ConstantInt::get(V->getType(),24),"bswap.6", IP);
    Value *Tmp5 = BinaryOperator::CreateShl(V,
                              ConstantInt::get(V->getType(),8),"bswap.5", IP);
    Value* Tmp4 = BinaryOperator::CreateLShr(V,
                              ConstantInt::get(V->getType(),8),"bswap.4", IP);
    Value* Tmp3 = BinaryOperator::CreateLShr(V,
                              ConstantInt::get(V->getType(),24),"bswap.3", IP);
    Value* Tmp2 = BinaryOperator::CreateLShr(V,
                              ConstantInt::get(V->getType(),40),"bswap.2", IP);
    Value* Tmp1 = BinaryOperator::CreateLShr(V,
                              ConstantInt::get(V->getType(),56),"bswap.1", IP);
    Tmp7 = BinaryOperator::CreateAnd(Tmp7,
                             ConstantInt::get(Type::Int64Ty, 
                               0xFF000000000000ULL),
                             "bswap.and7", IP);
    Tmp6 = BinaryOperator::CreateAnd(Tmp6,
                             ConstantInt::get(Type::Int64Ty, 0xFF0000000000ULL),
                             "bswap.and6", IP);
    Tmp5 = BinaryOperator::CreateAnd(Tmp5,
                             ConstantInt::get(Type::Int64Ty, 0xFF00000000ULL),
                             "bswap.and5", IP);
    Tmp4 = BinaryOperator::CreateAnd(Tmp4,
                             ConstantInt::get(Type::Int64Ty, 0xFF000000ULL),
                             "bswap.and4", IP);
    Tmp3 = BinaryOperator::CreateAnd(Tmp3,
                             ConstantInt::get(Type::Int64Ty, 0xFF0000ULL),
                             "bswap.and3", IP);
    Tmp2 = BinaryOperator::CreateAnd(Tmp2,
                             ConstantInt::get(Type::Int64Ty, 0xFF00ULL),
                             "bswap.and2", IP);
    Tmp8 = BinaryOperator::CreateOr(Tmp8, Tmp7, "bswap.or1", IP);
    Tmp6 = BinaryOperator::CreateOr(Tmp6, Tmp5, "bswap.or2", IP);
    Tmp4 = BinaryOperator::CreateOr(Tmp4, Tmp3, "bswap.or3", IP);
    Tmp2 = BinaryOperator::CreateOr(Tmp2, Tmp1, "bswap.or4", IP);
    Tmp8 = BinaryOperator::CreateOr(Tmp8, Tmp6, "bswap.or5", IP);
    Tmp4 = BinaryOperator::CreateOr(Tmp4, Tmp2, "bswap.or6", IP);
    V = BinaryOperator::CreateOr(Tmp8, Tmp4, "bswap.i64", IP);
    break;
  }
  }
  return V;
}

/// LowerCTPOP - Emit the code to lower ctpop of V before the specified
/// instruction IP.
static Value *LowerCTPOP(Value *V, Instruction *IP) {
  assert(V->getType()->isInteger() && "Can't ctpop a non-integer type!");

  static const uint64_t MaskValues[6] = {
    0x5555555555555555ULL, 0x3333333333333333ULL,
    0x0F0F0F0F0F0F0F0FULL, 0x00FF00FF00FF00FFULL,
    0x0000FFFF0000FFFFULL, 0x00000000FFFFFFFFULL
  };

  unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
  unsigned WordSize = (BitSize + 63) / 64;
  Value *Count = ConstantInt::get(V->getType(), 0);

  for (unsigned n = 0; n < WordSize; ++n) {
    Value *PartValue = V;
    for (unsigned i = 1, ct = 0; i < (BitSize>64 ? 64 : BitSize); 
         i <<= 1, ++ct) {
      Value *MaskCst = ConstantInt::get(V->getType(), MaskValues[ct]);
      Value *LHS = BinaryOperator::CreateAnd(
                     PartValue, MaskCst, "cppop.and1", IP);
      Value *VShift = BinaryOperator::CreateLShr(PartValue,
                        ConstantInt::get(V->getType(), i), "ctpop.sh", IP);
      Value *RHS = BinaryOperator::CreateAnd(VShift, MaskCst, "cppop.and2", IP);
      PartValue = BinaryOperator::CreateAdd(LHS, RHS, "ctpop.step", IP);
    }
    Count = BinaryOperator::CreateAdd(PartValue, Count, "ctpop.part", IP);
    if (BitSize > 64) {
      V = BinaryOperator::CreateLShr(V, ConstantInt::get(V->getType(), 64), 
                                     "ctpop.part.sh", IP);
      BitSize -= 64;
    }
  }

  return Count;
}

/// LowerCTLZ - Emit the code to lower ctlz of V before the specified
/// instruction IP.
static Value *LowerCTLZ(Value *V, Instruction *IP) {

  unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
  for (unsigned i = 1; i < BitSize; i <<= 1) {
    Value *ShVal = ConstantInt::get(V->getType(), i);
    ShVal = BinaryOperator::CreateLShr(V, ShVal, "ctlz.sh", IP);
    V = BinaryOperator::CreateOr(V, ShVal, "ctlz.step", IP);
  }

  V = BinaryOperator::CreateNot(V, "", IP);
  return LowerCTPOP(V, IP);
}

/// Convert the llvm.part.select.iX.iY intrinsic. This intrinsic takes 
/// three integer arguments. The first argument is the Value from which the
/// bits will be selected. It may be of any bit width. The second and third
/// arguments specify a range of bits to select with the second argument 
/// specifying the low bit and the third argument specifying the high bit. Both
/// must be type i32. The result is the corresponding selected bits from the
/// Value in the same width as the Value (first argument). If the low bit index
/// is higher than the high bit index then the inverse selection is done and 
/// the bits are returned in inverse order. 
/// @brief Lowering of llvm.part.select intrinsic.
static Instruction *LowerPartSelect(CallInst *CI) {
  // Make sure we're dealing with a part select intrinsic here
  Function *F = CI->getCalledFunction();
  const FunctionType *FT = F->getFunctionType();
  if (!F->isDeclaration() || !FT->getReturnType()->isInteger() ||
      FT->getNumParams() != 3 || !FT->getParamType(0)->isInteger() ||
      !FT->getParamType(1)->isInteger() || !FT->getParamType(2)->isInteger())
    return CI;

  // Get the intrinsic implementation function by converting all the . to _
  // in the intrinsic's function name and then reconstructing the function
  // declaration.
  std::string Name(F->getName());
  for (unsigned i = 4; i < Name.length(); ++i)
    if (Name[i] == '.')
      Name[i] = '_';
  Module* M = F->getParent();
  F = cast<Function>(M->getOrInsertFunction(Name, FT));
  F->setLinkage(GlobalValue::WeakLinkage);

  // If we haven't defined the impl function yet, do so now
  if (F->isDeclaration()) {

    // Get the arguments to the function
    Function::arg_iterator args = F->arg_begin();
    Value* Val = args++; Val->setName("Val");
    Value* Lo = args++; Lo->setName("Lo");
    Value* Hi = args++; Hi->setName("High");

    // We want to select a range of bits here such that [Hi, Lo] is shifted
    // down to the low bits. However, it is quite possible that Hi is smaller
    // than Lo in which case the bits have to be reversed. 
    
    // Create the blocks we will need for the two cases (forward, reverse)
    BasicBlock* CurBB   = BasicBlock::Create("entry", F);
    BasicBlock *RevSize = BasicBlock::Create("revsize", CurBB->getParent());
    BasicBlock *FwdSize = BasicBlock::Create("fwdsize", CurBB->getParent());
    BasicBlock *Compute = BasicBlock::Create("compute", CurBB->getParent());
    BasicBlock *Reverse = BasicBlock::Create("reverse", CurBB->getParent());
    BasicBlock *RsltBlk = BasicBlock::Create("result",  CurBB->getParent());

    // Cast Hi and Lo to the size of Val so the widths are all the same
    if (Hi->getType() != Val->getType())
      Hi = CastInst::CreateIntegerCast(Hi, Val->getType(), false, 
                                         "tmp", CurBB);
    if (Lo->getType() != Val->getType())
      Lo = CastInst::CreateIntegerCast(Lo, Val->getType(), false, 
                                          "tmp", CurBB);

    // Compute a few things that both cases will need, up front.
    Constant* Zero = ConstantInt::get(Val->getType(), 0);
    Constant* One = ConstantInt::get(Val->getType(), 1);
    Constant* AllOnes = ConstantInt::getAllOnesValue(Val->getType());

    // Compare the Hi and Lo bit positions. This is used to determine 
    // which case we have (forward or reverse)
    ICmpInst *Cmp = new ICmpInst(ICmpInst::ICMP_ULT, Hi, Lo, "less",CurBB);
    BranchInst::Create(RevSize, FwdSize, Cmp, CurBB);

    // First, copmute the number of bits in the forward case.
    Instruction* FBitSize = 
      BinaryOperator::CreateSub(Hi, Lo,"fbits", FwdSize);
    BranchInst::Create(Compute, FwdSize);

    // Second, compute the number of bits in the reverse case.
    Instruction* RBitSize = 
      BinaryOperator::CreateSub(Lo, Hi, "rbits", RevSize);
    BranchInst::Create(Compute, RevSize);

    // Now, compute the bit range. Start by getting the bitsize and the shift
    // amount (either Hi or Lo) from PHI nodes. Then we compute a mask for 
    // the number of bits we want in the range. We shift the bits down to the 
    // least significant bits, apply the mask to zero out unwanted high bits, 
    // and we have computed the "forward" result. It may still need to be 
    // reversed.

    // Get the BitSize from one of the two subtractions
    PHINode *BitSize = PHINode::Create(Val->getType(), "bits", Compute);
    BitSize->reserveOperandSpace(2);
    BitSize->addIncoming(FBitSize, FwdSize);
    BitSize->addIncoming(RBitSize, RevSize);

    // Get the ShiftAmount as the smaller of Hi/Lo
    PHINode *ShiftAmt = PHINode::Create(Val->getType(), "shiftamt", Compute);
    ShiftAmt->reserveOperandSpace(2);
    ShiftAmt->addIncoming(Lo, FwdSize);
    ShiftAmt->addIncoming(Hi, RevSize);

    // Increment the bit size
    Instruction *BitSizePlusOne = 
      BinaryOperator::CreateAdd(BitSize, One, "bits", Compute);

    // Create a Mask to zero out the high order bits.
    Instruction* Mask = 
      BinaryOperator::CreateShl(AllOnes, BitSizePlusOne, "mask", Compute);
    Mask = BinaryOperator::CreateNot(Mask, "mask", Compute);

    // Shift the bits down and apply the mask
    Instruction* FRes = 
      BinaryOperator::CreateLShr(Val, ShiftAmt, "fres", Compute);
    FRes = BinaryOperator::CreateAnd(FRes, Mask, "fres", Compute);
    BranchInst::Create(Reverse, RsltBlk, Cmp, Compute);

    // In the Reverse block we have the mask already in FRes but we must reverse
    // it by shifting FRes bits right and putting them in RRes by shifting them 
    // in from left.

    // First set up our loop counters
    PHINode *Count = PHINode::Create(Val->getType(), "count", Reverse);
    Count->reserveOperandSpace(2);
    Count->addIncoming(BitSizePlusOne, Compute);

    // Next, get the value that we are shifting.
    PHINode *BitsToShift = PHINode::Create(Val->getType(), "val", Reverse);
    BitsToShift->reserveOperandSpace(2);
    BitsToShift->addIncoming(FRes, Compute);

    // Finally, get the result of the last computation
    PHINode *RRes = PHINode::Create(Val->getType(), "rres", Reverse);
    RRes->reserveOperandSpace(2);
    RRes->addIncoming(Zero, Compute);

    // Decrement the counter
    Instruction *Decr = BinaryOperator::CreateSub(Count, One, "decr", Reverse);
    Count->addIncoming(Decr, Reverse);

    // Compute the Bit that we want to move
    Instruction *Bit = 
      BinaryOperator::CreateAnd(BitsToShift, One, "bit", Reverse);

    // Compute the new value for next iteration.
    Instruction *NewVal = 
      BinaryOperator::CreateLShr(BitsToShift, One, "rshift", Reverse);
    BitsToShift->addIncoming(NewVal, Reverse);

    // Shift the bit into the low bits of the result.
    Instruction *NewRes = 
      BinaryOperator::CreateShl(RRes, One, "lshift", Reverse);
    NewRes = BinaryOperator::CreateOr(NewRes, Bit, "addbit", Reverse);
    RRes->addIncoming(NewRes, Reverse);
    
    // Terminate loop if we've moved all the bits.
    ICmpInst *Cond = 
      new ICmpInst(ICmpInst::ICMP_EQ, Decr, Zero, "cond", Reverse);
    BranchInst::Create(RsltBlk, Reverse, Cond, Reverse);

    // Finally, in the result block, select one of the two results with a PHI
    // node and return the result;
    CurBB = RsltBlk;
    PHINode *BitSelect = PHINode::Create(Val->getType(), "part_select", CurBB);
    BitSelect->reserveOperandSpace(2);
    BitSelect->addIncoming(FRes, Compute);
    BitSelect->addIncoming(NewRes, Reverse);
    ReturnInst::Create(BitSelect, CurBB);
  }

  // Return a call to the implementation function
  Value *Args[] = {
    CI->getOperand(1),
    CI->getOperand(2),
    CI->getOperand(3)
  };
  return CallInst::Create(F, Args, array_endof(Args), CI->getName(), CI);
}

/// Convert the llvm.part.set.iX.iY.iZ intrinsic. This intrinsic takes 
/// four integer arguments (iAny %Value, iAny %Replacement, i32 %Low, i32 %High)
/// The first two arguments can be any bit width. The result is the same width
/// as %Value. The operation replaces bits between %Low and %High with the value
/// in %Replacement. If %Replacement is not the same width, it is truncated or
/// zero extended as appropriate to fit the bits being replaced. If %Low is
/// greater than %High then the inverse set of bits are replaced.
/// @brief Lowering of llvm.bit.part.set intrinsic.
static Instruction *LowerPartSet(CallInst *CI) {
  // Make sure we're dealing with a part select intrinsic here
  Function *F = CI->getCalledFunction();
  const FunctionType *FT = F->getFunctionType();
  if (!F->isDeclaration() || !FT->getReturnType()->isInteger() ||
      FT->getNumParams() != 4 || !FT->getParamType(0)->isInteger() ||
      !FT->getParamType(1)->isInteger() || !FT->getParamType(2)->isInteger() ||
      !FT->getParamType(3)->isInteger())
    return CI;

  // Get the intrinsic implementation function by converting all the . to _
  // in the intrinsic's function name and then reconstructing the function
  // declaration.
  std::string Name(F->getName());
  for (unsigned i = 4; i < Name.length(); ++i)
    if (Name[i] == '.')
      Name[i] = '_';
  Module* M = F->getParent();
  F = cast<Function>(M->getOrInsertFunction(Name, FT));
  F->setLinkage(GlobalValue::WeakLinkage);

  // If we haven't defined the impl function yet, do so now
  if (F->isDeclaration()) {
    // Get the arguments for the function.
    Function::arg_iterator args = F->arg_begin();
    Value* Val = args++; Val->setName("Val");
    Value* Rep = args++; Rep->setName("Rep");
    Value* Lo  = args++; Lo->setName("Lo");
    Value* Hi  = args++; Hi->setName("Hi");

    // Get some types we need
    const IntegerType* ValTy = cast<IntegerType>(Val->getType());
    const IntegerType* RepTy = cast<IntegerType>(Rep->getType());
    uint32_t ValBits = ValTy->getBitWidth();
    uint32_t RepBits = RepTy->getBitWidth();

    // Constant Definitions
    ConstantInt* RepBitWidth = ConstantInt::get(Type::Int32Ty, RepBits);
    ConstantInt* RepMask = ConstantInt::getAllOnesValue(RepTy);
    ConstantInt* ValMask = ConstantInt::getAllOnesValue(ValTy);
    ConstantInt* One = ConstantInt::get(Type::Int32Ty, 1);
    ConstantInt* ValOne = ConstantInt::get(ValTy, 1);
    ConstantInt* Zero = ConstantInt::get(Type::Int32Ty, 0);
    ConstantInt* ValZero = ConstantInt::get(ValTy, 0);

    // Basic blocks we fill in below.
    BasicBlock* entry = BasicBlock::Create("entry", F, 0);
    BasicBlock* large = BasicBlock::Create("large", F, 0);
    BasicBlock* small = BasicBlock::Create("small", F, 0);
    BasicBlock* reverse = BasicBlock::Create("reverse", F, 0);
    BasicBlock* result = BasicBlock::Create("result", F, 0);

    // BASIC BLOCK: entry
    // First, get the number of bits that we're placing as an i32
    ICmpInst* is_forward = 
      new ICmpInst(ICmpInst::ICMP_ULT, Lo, Hi, "", entry);
    SelectInst* Hi_pn = SelectInst::Create(is_forward, Hi, Lo, "", entry);
    SelectInst* Lo_pn = SelectInst::Create(is_forward, Lo, Hi, "", entry);
    BinaryOperator* NumBits = BinaryOperator::CreateSub(Hi_pn, Lo_pn, "",entry);
    NumBits = BinaryOperator::CreateAdd(NumBits, One, "", entry);
    // Now, convert Lo and Hi to ValTy bit width
    if (ValBits > 32) {
      Lo = new ZExtInst(Lo_pn, ValTy, "", entry);
    } else if (ValBits < 32) {
      Lo = new TruncInst(Lo_pn, ValTy, "", entry);
    }
    // Determine if the replacement bits are larger than the number of bits we
    // are replacing and deal with it.
    ICmpInst* is_large = 
      new ICmpInst(ICmpInst::ICMP_ULT, NumBits, RepBitWidth, "", entry);
    BranchInst::Create(large, small, is_large, entry);

    // BASIC BLOCK: large
    Instruction* MaskBits = 
      BinaryOperator::CreateSub(RepBitWidth, NumBits, "", large);
    MaskBits = CastInst::CreateIntegerCast(MaskBits, RepMask->getType(), 
                                           false, "", large);
    BinaryOperator* Mask1 = 
      BinaryOperator::CreateLShr(RepMask, MaskBits, "", large);
    BinaryOperator* Rep2 = BinaryOperator::CreateAnd(Mask1, Rep, "", large);
    BranchInst::Create(small, large);

    // BASIC BLOCK: small
    PHINode* Rep3 = PHINode::Create(RepTy, "", small);
    Rep3->reserveOperandSpace(2);
    Rep3->addIncoming(Rep2, large);
    Rep3->addIncoming(Rep, entry);
    Value* Rep4 = Rep3;
    if (ValBits > RepBits)
      Rep4 = new ZExtInst(Rep3, ValTy, "", small);
    else if (ValBits < RepBits)
      Rep4 = new TruncInst(Rep3, ValTy, "", small);
    BranchInst::Create(result, reverse, is_forward, small);

    // BASIC BLOCK: reverse (reverses the bits of the replacement)
    // Set up our loop counter as a PHI so we can decrement on each iteration.
    // We will loop for the number of bits in the replacement value.
    PHINode *Count = PHINode::Create(Type::Int32Ty, "count", reverse);
    Count->reserveOperandSpace(2);
    Count->addIncoming(NumBits, small);

    // Get the value that we are shifting bits out of as a PHI because
    // we'll change this with each iteration.
    PHINode *BitsToShift = PHINode::Create(Val->getType(), "val", reverse);
    BitsToShift->reserveOperandSpace(2);
    BitsToShift->addIncoming(Rep4, small);

    // Get the result of the last computation or zero on first iteration
    PHINode *RRes = PHINode::Create(Val->getType(), "rres", reverse);
    RRes->reserveOperandSpace(2);
    RRes->addIncoming(ValZero, small);

    // Decrement the loop counter by one
    Instruction *Decr = BinaryOperator::CreateSub(Count, One, "", reverse);
    Count->addIncoming(Decr, reverse);

    // Get the bit that we want to move into the result
    Value *Bit = BinaryOperator::CreateAnd(BitsToShift, ValOne, "", reverse);

    // Compute the new value of the bits to shift for the next iteration.
    Value *NewVal = BinaryOperator::CreateLShr(BitsToShift, ValOne,"", reverse);
    BitsToShift->addIncoming(NewVal, reverse);

    // Shift the bit we extracted into the low bit of the result.
    Instruction *NewRes = BinaryOperator::CreateShl(RRes, ValOne, "", reverse);
    NewRes = BinaryOperator::CreateOr(NewRes, Bit, "", reverse);
    RRes->addIncoming(NewRes, reverse);
    
    // Terminate loop if we've moved all the bits.
    ICmpInst *Cond = new ICmpInst(ICmpInst::ICMP_EQ, Decr, Zero, "", reverse);
    BranchInst::Create(result, reverse, Cond, reverse);

    // BASIC BLOCK: result
    PHINode *Rplcmnt = PHINode::Create(Val->getType(), "", result);
    Rplcmnt->reserveOperandSpace(2);
    Rplcmnt->addIncoming(NewRes, reverse);
    Rplcmnt->addIncoming(Rep4, small);
    Value* t0   = CastInst::CreateIntegerCast(NumBits,ValTy,false,"",result);
    Value* t1   = BinaryOperator::CreateShl(ValMask, Lo, "", result);
    Value* t2   = BinaryOperator::CreateNot(t1, "", result);
    Value* t3   = BinaryOperator::CreateShl(t1, t0, "", result);
    Value* t4   = BinaryOperator::CreateOr(t2, t3, "", result);
    Value* t5   = BinaryOperator::CreateAnd(t4, Val, "", result);
    Value* t6   = BinaryOperator::CreateShl(Rplcmnt, Lo, "", result);
    Value* Rslt = BinaryOperator::CreateOr(t5, t6, "part_set", result);
    ReturnInst::Create(Rslt, result);
  }

  // Return a call to the implementation function
  Value *Args[] = {
    CI->getOperand(1),
    CI->getOperand(2),
    CI->getOperand(3),
    CI->getOperand(4)
  };
  return CallInst::Create(F, Args, array_endof(Args), CI->getName(), CI);
}

static void ReplaceFPIntrinsicWithCall(CallInst *CI, Constant *FCache,
                                       Constant *DCache, Constant *LDCache,
                                       const char *Fname, const char *Dname,
                                       const char *LDname) {
  switch (CI->getOperand(1)->getType()->getTypeID()) {
  default: assert(0 && "Invalid type in intrinsic"); abort();
  case Type::FloatTyID:
    ReplaceCallWith(Fname, CI, CI->op_begin()+1, CI->op_end(),
                  Type::FloatTy, FCache);
    break;
  case Type::DoubleTyID:
    ReplaceCallWith(Dname, CI, CI->op_begin()+1, CI->op_end(),
                  Type::DoubleTy, DCache);
    break;
  case Type::X86_FP80TyID:
  case Type::FP128TyID:
  case Type::PPC_FP128TyID:
    ReplaceCallWith(LDname, CI, CI->op_begin()+1, CI->op_end(),
                  CI->getOperand(1)->getType(), LDCache);
    break;
  }
}

void IntrinsicLowering::LowerIntrinsicCall(CallInst *CI) {
  Function *Callee = CI->getCalledFunction();
  assert(Callee && "Cannot lower an indirect call!");

  switch (Callee->getIntrinsicID()) {
  case Intrinsic::not_intrinsic:
    cerr << "Cannot lower a call to a non-intrinsic function '"
         << Callee->getName() << "'!\n";
    abort();
  default:
    cerr << "Error: Code generator does not support intrinsic function '"
         << Callee->getName() << "'!\n";
    abort();

    // The setjmp/longjmp intrinsics should only exist in the code if it was
    // never optimized (ie, right out of the CFE), or if it has been hacked on
    // by the lowerinvoke pass.  In both cases, the right thing to do is to
    // convert the call to an explicit setjmp or longjmp call.
  case Intrinsic::setjmp: {
    static Constant *SetjmpFCache = 0;
    Value *V = ReplaceCallWith("setjmp", CI, CI->op_begin()+1, CI->op_end(),
                               Type::Int32Ty, SetjmpFCache);
    if (CI->getType() != Type::VoidTy)
      CI->replaceAllUsesWith(V);
    break;
  }
  case Intrinsic::sigsetjmp:
     if (CI->getType() != Type::VoidTy)
       CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
     break;

  case Intrinsic::longjmp: {
    static Constant *LongjmpFCache = 0;
    ReplaceCallWith("longjmp", CI, CI->op_begin()+1, CI->op_end(),
                    Type::VoidTy, LongjmpFCache);
    break;
  }

  case Intrinsic::siglongjmp: {
    // Insert the call to abort
    static Constant *AbortFCache = 0;
    ReplaceCallWith("abort", CI, CI->op_end(), CI->op_end(), 
                    Type::VoidTy, AbortFCache);
    break;
  }
  case Intrinsic::ctpop:
    CI->replaceAllUsesWith(LowerCTPOP(CI->getOperand(1), CI));
    break;

  case Intrinsic::bswap:
    CI->replaceAllUsesWith(LowerBSWAP(CI->getOperand(1), CI));
    break;
    
  case Intrinsic::ctlz:
    CI->replaceAllUsesWith(LowerCTLZ(CI->getOperand(1), CI));
    break;

  case Intrinsic::cttz: {
    // cttz(x) -> ctpop(~X & (X-1))
    Value *Src = CI->getOperand(1);
    Value *NotSrc = BinaryOperator::CreateNot(Src, Src->getName()+".not", CI);
    Value *SrcM1 = ConstantInt::get(Src->getType(), 1);
    SrcM1 = BinaryOperator::CreateSub(Src, SrcM1, "", CI);
    Src = LowerCTPOP(BinaryOperator::CreateAnd(NotSrc, SrcM1, "", CI), CI);
    CI->replaceAllUsesWith(Src);
    break;
  }

  case Intrinsic::part_select:
    CI->replaceAllUsesWith(LowerPartSelect(CI));
    break;

  case Intrinsic::part_set:
    CI->replaceAllUsesWith(LowerPartSet(CI));
    break;

  case Intrinsic::stacksave:
  case Intrinsic::stackrestore: {
    static bool Warned = false;
    if (!Warned)
      cerr << "WARNING: this target does not support the llvm.stack"
           << (Callee->getIntrinsicID() == Intrinsic::stacksave ?
               "save" : "restore") << " intrinsic.\n";
    Warned = true;
    if (Callee->getIntrinsicID() == Intrinsic::stacksave)
      CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
    break;
  }
    
  case Intrinsic::returnaddress:
  case Intrinsic::frameaddress:
    cerr << "WARNING: this target does not support the llvm."
         << (Callee->getIntrinsicID() == Intrinsic::returnaddress ?
             "return" : "frame") << "address intrinsic.\n";
    CI->replaceAllUsesWith(ConstantPointerNull::get(
                                            cast<PointerType>(CI->getType())));
    break;

  case Intrinsic::prefetch:
    break;    // Simply strip out prefetches on unsupported architectures

  case Intrinsic::pcmarker:
    break;    // Simply strip out pcmarker on unsupported architectures
  case Intrinsic::readcyclecounter: {
    cerr << "WARNING: this target does not support the llvm.readcyclecoun"
         << "ter intrinsic.  It is being lowered to a constant 0\n";
    CI->replaceAllUsesWith(ConstantInt::get(Type::Int64Ty, 0));
    break;
  }

  case Intrinsic::dbg_stoppoint:
  case Intrinsic::dbg_region_start:
  case Intrinsic::dbg_region_end:
  case Intrinsic::dbg_func_start:
  case Intrinsic::dbg_declare:
    break;    // Simply strip out debugging intrinsics

  case Intrinsic::eh_exception:
  case Intrinsic::eh_selector_i32:
  case Intrinsic::eh_selector_i64:
    CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
    break;

  case Intrinsic::eh_typeid_for_i32:
  case Intrinsic::eh_typeid_for_i64:
    // Return something different to eh_selector.
    CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), 1));
    break;

  case Intrinsic::var_annotation:
    break;   // Strip out annotate intrinsic
    
  case Intrinsic::memcpy_i32:
  case Intrinsic::memcpy_i64: {
    static Constant *MemcpyFCache = 0;
    Value *Size = CI->getOperand(3);
    const Type *IntPtr = TD.getIntPtrType();
    if (Size->getType()->getPrimitiveSizeInBits() <
        IntPtr->getPrimitiveSizeInBits())
      Size = new ZExtInst(Size, IntPtr, "", CI);
    else if (Size->getType()->getPrimitiveSizeInBits() >
             IntPtr->getPrimitiveSizeInBits())
      Size = new TruncInst(Size, IntPtr, "", CI);
    Value *Ops[3];
    Ops[0] = CI->getOperand(1);
    Ops[1] = CI->getOperand(2);
    Ops[2] = Size;
    ReplaceCallWith("memcpy", CI, Ops, Ops+3, CI->getOperand(1)->getType(),
                    MemcpyFCache);
    break;
  }
  case Intrinsic::memmove_i32: 
  case Intrinsic::memmove_i64: {
    static Constant *MemmoveFCache = 0;
    Value *Size = CI->getOperand(3);
    const Type *IntPtr = TD.getIntPtrType();
    if (Size->getType()->getPrimitiveSizeInBits() <
        IntPtr->getPrimitiveSizeInBits())
      Size = new ZExtInst(Size, IntPtr, "", CI);
    else if (Size->getType()->getPrimitiveSizeInBits() >
             IntPtr->getPrimitiveSizeInBits())
      Size = new TruncInst(Size, IntPtr, "", CI);
    Value *Ops[3];
    Ops[0] = CI->getOperand(1);
    Ops[1] = CI->getOperand(2);
    Ops[2] = Size;
    ReplaceCallWith("memmove", CI, Ops, Ops+3, CI->getOperand(1)->getType(),
                    MemmoveFCache);
    break;
  }
  case Intrinsic::memset_i32:
  case Intrinsic::memset_i64: {
    static Constant *MemsetFCache = 0;
    Value *Size = CI->getOperand(3);
    const Type *IntPtr = TD.getIntPtrType();
    if (Size->getType()->getPrimitiveSizeInBits() <
        IntPtr->getPrimitiveSizeInBits())
      Size = new ZExtInst(Size, IntPtr, "", CI);
    else if (Size->getType()->getPrimitiveSizeInBits() >
             IntPtr->getPrimitiveSizeInBits())
      Size = new TruncInst(Size, IntPtr, "", CI);
    Value *Ops[3];
    Ops[0] = CI->getOperand(1);
    // Extend the amount to i32.
    Ops[1] = new ZExtInst(CI->getOperand(2), Type::Int32Ty, "", CI);
    Ops[2] = Size;
    ReplaceCallWith("memset", CI, Ops, Ops+3, CI->getOperand(1)->getType(),
                    MemsetFCache);
    break;
  }
  case Intrinsic::sqrt: {
    static Constant *sqrtFCache = 0;
    static Constant *sqrtDCache = 0;
    static Constant *sqrtLDCache = 0;
    ReplaceFPIntrinsicWithCall(CI, sqrtFCache, sqrtDCache, sqrtLDCache,
                               "sqrtf", "sqrt", "sqrtl");
    break;
  }
  case Intrinsic::log: {
    static Constant *logFCache = 0;
    static Constant *logDCache = 0;
    static Constant *logLDCache = 0;
    ReplaceFPIntrinsicWithCall(CI, logFCache, logDCache, logLDCache,
                               "logf", "log", "logl");
    break;
  }
  case Intrinsic::log2: {
    static Constant *log2FCache = 0;
    static Constant *log2DCache = 0;
    static Constant *log2LDCache = 0;
    ReplaceFPIntrinsicWithCall(CI, log2FCache, log2DCache, log2LDCache,
                               "log2f", "log2", "log2l");
    break;
  }
  case Intrinsic::log10: {
    static Constant *log10FCache = 0;
    static Constant *log10DCache = 0;
    static Constant *log10LDCache = 0;
    ReplaceFPIntrinsicWithCall(CI, log10FCache, log10DCache, log10LDCache,
                               "log10f", "log10", "log10l");
    break;
  }
  case Intrinsic::exp: {
    static Constant *expFCache = 0;
    static Constant *expDCache = 0;
    static Constant *expLDCache = 0;
    ReplaceFPIntrinsicWithCall(CI, expFCache, expDCache, expLDCache,
                               "expf", "exp", "expl");
    break;
  }
  case Intrinsic::exp2: {
    static Constant *exp2FCache = 0;
    static Constant *exp2DCache = 0;
    static Constant *exp2LDCache = 0;
    ReplaceFPIntrinsicWithCall(CI, exp2FCache, exp2DCache, exp2LDCache,
                               "exp2f", "exp2", "exp2l");
    break;
  }
  case Intrinsic::pow: {
    static Constant *powFCache = 0;
    static Constant *powDCache = 0;
    static Constant *powLDCache = 0;
    ReplaceFPIntrinsicWithCall(CI, powFCache, powDCache, powLDCache,
                               "powf", "pow", "powl");
    break;
  }
  case Intrinsic::flt_rounds:
     // Lower to "round to the nearest"
     if (CI->getType() != Type::VoidTy)
       CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), 1));
     break;
  }

  assert(CI->use_empty() &&
         "Lowering should have eliminated any uses of the intrinsic call!");
  CI->eraseFromParent();
}