aboutsummaryrefslogtreecommitdiffstats
path: root/lib/Transforms/Scalar/Scalarizer.cpp
blob: a457cbaedbb61fb554c24ab518cc191f9cd09a11 (plain)
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
//===--- Scalarizer.cpp - Scalarize vector operations ---------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass converts vector operations into scalar operations, in order
// to expose optimization opportunities on the individual scalar operations.
// It is mainly intended for targets that do not have vector units, but it
// may also be useful for revectorizing code to different vector widths.
//
//===----------------------------------------------------------------------===//

#include "llvm/ADT/STLExtras.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"

using namespace llvm;

#define DEBUG_TYPE "scalarizer"

namespace {
// Used to store the scattered form of a vector.
typedef SmallVector<Value *, 8> ValueVector;

// Used to map a vector Value to its scattered form.  We use std::map
// because we want iterators to persist across insertion and because the
// values are relatively large.
typedef std::map<Value *, ValueVector> ScatterMap;

// Lists Instructions that have been replaced with scalar implementations,
// along with a pointer to their scattered forms.
typedef SmallVector<std::pair<Instruction *, ValueVector *>, 16> GatherList;

// Provides a very limited vector-like interface for lazily accessing one
// component of a scattered vector or vector pointer.
class Scatterer {
public:
  Scatterer() {}

  // Scatter V into Size components.  If new instructions are needed,
  // insert them before BBI in BB.  If Cache is nonnull, use it to cache
  // the results.
  Scatterer(BasicBlock *bb, BasicBlock::iterator bbi, Value *v,
            ValueVector *cachePtr = nullptr);

  // Return component I, creating a new Value for it if necessary.
  Value *operator[](unsigned I);

  // Return the number of components.
  unsigned size() const { return Size; }

private:
  BasicBlock *BB;
  BasicBlock::iterator BBI;
  Value *V;
  ValueVector *CachePtr;
  PointerType *PtrTy;
  ValueVector Tmp;
  unsigned Size;
};

// FCmpSpliiter(FCI)(Builder, X, Y, Name) uses Builder to create an FCmp
// called Name that compares X and Y in the same way as FCI.
struct FCmpSplitter {
  FCmpSplitter(FCmpInst &fci) : FCI(fci) {}
  Value *operator()(IRBuilder<> &Builder, Value *Op0, Value *Op1,
                    const Twine &Name) const {
    return Builder.CreateFCmp(FCI.getPredicate(), Op0, Op1, Name);
  }
  FCmpInst &FCI;
};

// ICmpSpliiter(ICI)(Builder, X, Y, Name) uses Builder to create an ICmp
// called Name that compares X and Y in the same way as ICI.
struct ICmpSplitter {
  ICmpSplitter(ICmpInst &ici) : ICI(ici) {}
  Value *operator()(IRBuilder<> &Builder, Value *Op0, Value *Op1,
                    const Twine &Name) const {
    return Builder.CreateICmp(ICI.getPredicate(), Op0, Op1, Name);
  }
  ICmpInst &ICI;
};

// BinarySpliiter(BO)(Builder, X, Y, Name) uses Builder to create
// a binary operator like BO called Name with operands X and Y.
struct BinarySplitter {
  BinarySplitter(BinaryOperator &bo) : BO(bo) {}
  Value *operator()(IRBuilder<> &Builder, Value *Op0, Value *Op1,
                    const Twine &Name) const {
    return Builder.CreateBinOp(BO.getOpcode(), Op0, Op1, Name);
  }
  BinaryOperator &BO;
};

// Information about a load or store that we're scalarizing.
struct VectorLayout {
  VectorLayout() : VecTy(nullptr), ElemTy(nullptr), VecAlign(0), ElemSize(0) {}

  // Return the alignment of element I.
  uint64_t getElemAlign(unsigned I) {
    return MinAlign(VecAlign, I * ElemSize);
  }

  // The type of the vector.
  VectorType *VecTy;

  // The type of each element.
  Type *ElemTy;

  // The alignment of the vector.
  uint64_t VecAlign;

  // The size of each element.
  uint64_t ElemSize;
};

class Scalarizer : public FunctionPass,
                   public InstVisitor<Scalarizer, bool> {
public:
  static char ID;

  Scalarizer() :
    FunctionPass(ID) {
    initializeScalarizerPass(*PassRegistry::getPassRegistry());
  }

  bool doInitialization(Module &M) override;
  bool runOnFunction(Function &F) override;

  // InstVisitor methods.  They return true if the instruction was scalarized,
  // false if nothing changed.
  bool visitInstruction(Instruction &) { return false; }
  bool visitSelectInst(SelectInst &SI);
  bool visitICmpInst(ICmpInst &);
  bool visitFCmpInst(FCmpInst &);
  bool visitBinaryOperator(BinaryOperator &);
  bool visitGetElementPtrInst(GetElementPtrInst &);
  bool visitCastInst(CastInst &);
  bool visitBitCastInst(BitCastInst &);
  bool visitShuffleVectorInst(ShuffleVectorInst &);
  bool visitPHINode(PHINode &);
  bool visitLoadInst(LoadInst &);
  bool visitStoreInst(StoreInst &);

  static void registerOptions() {
    // This is disabled by default because having separate loads and stores
    // makes it more likely that the -combiner-alias-analysis limits will be
    // reached.
    OptionRegistry::registerOption<bool, Scalarizer,
                                 &Scalarizer::ScalarizeLoadStore>(
        "scalarize-load-store",
        "Allow the scalarizer pass to scalarize loads and store", false);
  }

private:
  Scatterer scatter(Instruction *, Value *);
  void gather(Instruction *, const ValueVector &);
  bool canTransferMetadata(unsigned Kind);
  void transferMetadata(Instruction *, const ValueVector &);
  bool getVectorLayout(Type *, unsigned, VectorLayout &, const DataLayout &);
  bool finish();

  template<typename T> bool splitBinary(Instruction &, const T &);

  ScatterMap Scattered;
  GatherList Gathered;
  unsigned ParallelLoopAccessMDKind;
  bool ScalarizeLoadStore;
};

char Scalarizer::ID = 0;
} // end anonymous namespace

INITIALIZE_PASS_WITH_OPTIONS(Scalarizer, "scalarizer",
                             "Scalarize vector operations", false, false)

Scatterer::Scatterer(BasicBlock *bb, BasicBlock::iterator bbi, Value *v,
                     ValueVector *cachePtr)
  : BB(bb), BBI(bbi), V(v), CachePtr(cachePtr) {
  Type *Ty = V->getType();
  PtrTy = dyn_cast<PointerType>(Ty);
  if (PtrTy)
    Ty = PtrTy->getElementType();
  Size = Ty->getVectorNumElements();
  if (!CachePtr)
    Tmp.resize(Size, nullptr);
  else if (CachePtr->empty())
    CachePtr->resize(Size, nullptr);
  else
    assert(Size == CachePtr->size() && "Inconsistent vector sizes");
}

// Return component I, creating a new Value for it if necessary.
Value *Scatterer::operator[](unsigned I) {
  ValueVector &CV = (CachePtr ? *CachePtr : Tmp);
  // Try to reuse a previous value.
  if (CV[I])
    return CV[I];
  IRBuilder<> Builder(BB, BBI);
  if (PtrTy) {
    if (!CV[0]) {
      Type *Ty =
        PointerType::get(PtrTy->getElementType()->getVectorElementType(),
                         PtrTy->getAddressSpace());
      CV[0] = Builder.CreateBitCast(V, Ty, V->getName() + ".i0");
    }
    if (I != 0)
      CV[I] = Builder.CreateConstGEP1_32(CV[0], I,
                                         V->getName() + ".i" + Twine(I));
  } else {
    // Search through a chain of InsertElementInsts looking for element I.
    // Record other elements in the cache.  The new V is still suitable
    // for all uncached indices.
    for (;;) {
      InsertElementInst *Insert = dyn_cast<InsertElementInst>(V);
      if (!Insert)
        break;
      ConstantInt *Idx = dyn_cast<ConstantInt>(Insert->getOperand(2));
      if (!Idx)
        break;
      unsigned J = Idx->getZExtValue();
      CV[J] = Insert->getOperand(1);
      V = Insert->getOperand(0);
      if (I == J)
        return CV[J];
    }
    CV[I] = Builder.CreateExtractElement(V, Builder.getInt32(I),
                                         V->getName() + ".i" + Twine(I));
  }
  return CV[I];
}

bool Scalarizer::doInitialization(Module &M) {
  ParallelLoopAccessMDKind =
      M.getContext().getMDKindID("llvm.mem.parallel_loop_access");
  ScalarizeLoadStore =
      M.getContext().getOption<bool, Scalarizer, &Scalarizer::ScalarizeLoadStore>();
  return false;
}

bool Scalarizer::runOnFunction(Function &F) {
  for (Function::iterator BBI = F.begin(), BBE = F.end(); BBI != BBE; ++BBI) {
    BasicBlock *BB = BBI;
    for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE;) {
      Instruction *I = II;
      bool Done = visit(I);
      ++II;
      if (Done && I->getType()->isVoidTy())
        I->eraseFromParent();
    }
  }
  return finish();
}

// Return a scattered form of V that can be accessed by Point.  V must be a
// vector or a pointer to a vector.
Scatterer Scalarizer::scatter(Instruction *Point, Value *V) {
  if (Argument *VArg = dyn_cast<Argument>(V)) {
    // Put the scattered form of arguments in the entry block,
    // so that it can be used everywhere.
    Function *F = VArg->getParent();
    BasicBlock *BB = &F->getEntryBlock();
    return Scatterer(BB, BB->begin(), V, &Scattered[V]);
  }
  if (Instruction *VOp = dyn_cast<Instruction>(V)) {
    // Put the scattered form of an instruction directly after the
    // instruction.
    BasicBlock *BB = VOp->getParent();
    return Scatterer(BB, std::next(BasicBlock::iterator(VOp)),
                     V, &Scattered[V]);
  }
  // In the fallback case, just put the scattered before Point and
  // keep the result local to Point.
  return Scatterer(Point->getParent(), Point, V);
}

// Replace Op with the gathered form of the components in CV.  Defer the
// deletion of Op and creation of the gathered form to the end of the pass,
// so that we can avoid creating the gathered form if all uses of Op are
// replaced with uses of CV.
void Scalarizer::gather(Instruction *Op, const ValueVector &CV) {
  // Since we're not deleting Op yet, stub out its operands, so that it
  // doesn't make anything live unnecessarily.
  for (unsigned I = 0, E = Op->getNumOperands(); I != E; ++I)
    Op->setOperand(I, UndefValue::get(Op->getOperand(I)->getType()));

  transferMetadata(Op, CV);

  // If we already have a scattered form of Op (created from ExtractElements
  // of Op itself), replace them with the new form.
  ValueVector &SV = Scattered[Op];
  if (!SV.empty()) {
    for (unsigned I = 0, E = SV.size(); I != E; ++I) {
      Instruction *Old = cast<Instruction>(SV[I]);
      CV[I]->takeName(Old);
      Old->replaceAllUsesWith(CV[I]);
      Old->eraseFromParent();
    }
  }
  SV = CV;
  Gathered.push_back(GatherList::value_type(Op, &SV));
}

// Return true if it is safe to transfer the given metadata tag from
// vector to scalar instructions.
bool Scalarizer::canTransferMetadata(unsigned Tag) {
  return (Tag == LLVMContext::MD_tbaa
          || Tag == LLVMContext::MD_fpmath
          || Tag == LLVMContext::MD_tbaa_struct
          || Tag == LLVMContext::MD_invariant_load
          || Tag == LLVMContext::MD_alias_scope
          || Tag == LLVMContext::MD_noalias
          || Tag == ParallelLoopAccessMDKind);
}

// Transfer metadata from Op to the instructions in CV if it is known
// to be safe to do so.
void Scalarizer::transferMetadata(Instruction *Op, const ValueVector &CV) {
  SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
  Op->getAllMetadataOtherThanDebugLoc(MDs);
  for (unsigned I = 0, E = CV.size(); I != E; ++I) {
    if (Instruction *New = dyn_cast<Instruction>(CV[I])) {
      for (SmallVectorImpl<std::pair<unsigned, MDNode *>>::iterator
               MI = MDs.begin(),
               ME = MDs.end();
           MI != ME; ++MI)
        if (canTransferMetadata(MI->first))
          New->setMetadata(MI->first, MI->second);
      New->setDebugLoc(Op->getDebugLoc());
    }
  }
}

// Try to fill in Layout from Ty, returning true on success.  Alignment is
// the alignment of the vector, or 0 if the ABI default should be used.
bool Scalarizer::getVectorLayout(Type *Ty, unsigned Alignment,
                                 VectorLayout &Layout, const DataLayout &DL) {
  // Make sure we're dealing with a vector.
  Layout.VecTy = dyn_cast<VectorType>(Ty);
  if (!Layout.VecTy)
    return false;

  // Check that we're dealing with full-byte elements.
  Layout.ElemTy = Layout.VecTy->getElementType();
  if (DL.getTypeSizeInBits(Layout.ElemTy) !=
      DL.getTypeStoreSizeInBits(Layout.ElemTy))
    return false;

  if (Alignment)
    Layout.VecAlign = Alignment;
  else
    Layout.VecAlign = DL.getABITypeAlignment(Layout.VecTy);
  Layout.ElemSize = DL.getTypeStoreSize(Layout.ElemTy);
  return true;
}

// Scalarize two-operand instruction I, using Split(Builder, X, Y, Name)
// to create an instruction like I with operands X and Y and name Name.
template<typename Splitter>
bool Scalarizer::splitBinary(Instruction &I, const Splitter &Split) {
  VectorType *VT = dyn_cast<VectorType>(I.getType());
  if (!VT)
    return false;

  unsigned NumElems = VT->getNumElements();
  IRBuilder<> Builder(I.getParent(), &I);
  Scatterer Op0 = scatter(&I, I.getOperand(0));
  Scatterer Op1 = scatter(&I, I.getOperand(1));
  assert(Op0.size() == NumElems && "Mismatched binary operation");
  assert(Op1.size() == NumElems && "Mismatched binary operation");
  ValueVector Res;
  Res.resize(NumElems);
  for (unsigned Elem = 0; Elem < NumElems; ++Elem)
    Res[Elem] = Split(Builder, Op0[Elem], Op1[Elem],
                      I.getName() + ".i" + Twine(Elem));
  gather(&I, Res);
  return true;
}

bool Scalarizer::visitSelectInst(SelectInst &SI) {
  VectorType *VT = dyn_cast<VectorType>(SI.getType());
  if (!VT)
    return false;

  unsigned NumElems = VT->getNumElements();
  IRBuilder<> Builder(SI.getParent(), &SI);
  Scatterer Op1 = scatter(&SI, SI.getOperand(1));
  Scatterer Op2 = scatter(&SI, SI.getOperand(2));
  assert(Op1.size() == NumElems && "Mismatched select");
  assert(Op2.size() == NumElems && "Mismatched select");
  ValueVector Res;
  Res.resize(NumElems);

  if (SI.getOperand(0)->getType()->isVectorTy()) {
    Scatterer Op0 = scatter(&SI, SI.getOperand(0));
    assert(Op0.size() == NumElems && "Mismatched select");
    for (unsigned I = 0; I < NumElems; ++I)
      Res[I] = Builder.CreateSelect(Op0[I], Op1[I], Op2[I],
                                    SI.getName() + ".i" + Twine(I));
  } else {
    Value *Op0 = SI.getOperand(0);
    for (unsigned I = 0; I < NumElems; ++I)
      Res[I] = Builder.CreateSelect(Op0, Op1[I], Op2[I],
                                    SI.getName() + ".i" + Twine(I));
  }
  gather(&SI, Res);
  return true;
}

bool Scalarizer::visitICmpInst(ICmpInst &ICI) {
  return splitBinary(ICI, ICmpSplitter(ICI));
}

bool Scalarizer::visitFCmpInst(FCmpInst &FCI) {
  return splitBinary(FCI, FCmpSplitter(FCI));
}

bool Scalarizer::visitBinaryOperator(BinaryOperator &BO) {
  return splitBinary(BO, BinarySplitter(BO));
}

bool Scalarizer::visitGetElementPtrInst(GetElementPtrInst &GEPI) {
  VectorType *VT = dyn_cast<VectorType>(GEPI.getType());
  if (!VT)
    return false;

  IRBuilder<> Builder(GEPI.getParent(), &GEPI);
  unsigned NumElems = VT->getNumElements();
  unsigned NumIndices = GEPI.getNumIndices();

  Scatterer Base = scatter(&GEPI, GEPI.getOperand(0));

  SmallVector<Scatterer, 8> Ops;
  Ops.resize(NumIndices);
  for (unsigned I = 0; I < NumIndices; ++I)
    Ops[I] = scatter(&GEPI, GEPI.getOperand(I + 1));

  ValueVector Res;
  Res.resize(NumElems);
  for (unsigned I = 0; I < NumElems; ++I) {
    SmallVector<Value *, 8> Indices;
    Indices.resize(NumIndices);
    for (unsigned J = 0; J < NumIndices; ++J)
      Indices[J] = Ops[J][I];
    Res[I] = Builder.CreateGEP(GEPI.getSourceElementType(), Base[I], Indices,
                               GEPI.getName() + ".i" + Twine(I));
    if (GEPI.isInBounds())
      if (GetElementPtrInst *NewGEPI = dyn_cast<GetElementPtrInst>(Res[I]))
        NewGEPI->setIsInBounds();
  }
  gather(&GEPI, Res);
  return true;
}

bool Scalarizer::visitCastInst(CastInst &CI) {
  VectorType *VT = dyn_cast<VectorType>(CI.getDestTy());
  if (!VT)
    return false;

  unsigned NumElems = VT->getNumElements();
  IRBuilder<> Builder(CI.getParent(), &CI);
  Scatterer Op0 = scatter(&CI, CI.getOperand(0));
  assert(Op0.size() == NumElems && "Mismatched cast");
  ValueVector Res;
  Res.resize(NumElems);
  for (unsigned I = 0; I < NumElems; ++I)
    Res[I] = Builder.CreateCast(CI.getOpcode(), Op0[I], VT->getElementType(),
                                CI.getName() + ".i" + Twine(I));
  gather(&CI, Res);
  return true;
}

bool Scalarizer::visitBitCastInst(BitCastInst &BCI) {
  VectorType *DstVT = dyn_cast<VectorType>(BCI.getDestTy());
  VectorType *SrcVT = dyn_cast<VectorType>(BCI.getSrcTy());
  if (!DstVT || !SrcVT)
    return false;

  unsigned DstNumElems = DstVT->getNumElements();
  unsigned SrcNumElems = SrcVT->getNumElements();
  IRBuilder<> Builder(BCI.getParent(), &BCI);
  Scatterer Op0 = scatter(&BCI, BCI.getOperand(0));
  ValueVector Res;
  Res.resize(DstNumElems);

  if (DstNumElems == SrcNumElems) {
    for (unsigned I = 0; I < DstNumElems; ++I)
      Res[I] = Builder.CreateBitCast(Op0[I], DstVT->getElementType(),
                                     BCI.getName() + ".i" + Twine(I));
  } else if (DstNumElems > SrcNumElems) {
    // <M x t1> -> <N*M x t2>.  Convert each t1 to <N x t2> and copy the
    // individual elements to the destination.
    unsigned FanOut = DstNumElems / SrcNumElems;
    Type *MidTy = VectorType::get(DstVT->getElementType(), FanOut);
    unsigned ResI = 0;
    for (unsigned Op0I = 0; Op0I < SrcNumElems; ++Op0I) {
      Value *V = Op0[Op0I];
      Instruction *VI;
      // Look through any existing bitcasts before converting to <N x t2>.
      // In the best case, the resulting conversion might be a no-op.
      while ((VI = dyn_cast<Instruction>(V)) &&
             VI->getOpcode() == Instruction::BitCast)
        V = VI->getOperand(0);
      V = Builder.CreateBitCast(V, MidTy, V->getName() + ".cast");
      Scatterer Mid = scatter(&BCI, V);
      for (unsigned MidI = 0; MidI < FanOut; ++MidI)
        Res[ResI++] = Mid[MidI];
    }
  } else {
    // <N*M x t1> -> <M x t2>.  Convert each group of <N x t1> into a t2.
    unsigned FanIn = SrcNumElems / DstNumElems;
    Type *MidTy = VectorType::get(SrcVT->getElementType(), FanIn);
    unsigned Op0I = 0;
    for (unsigned ResI = 0; ResI < DstNumElems; ++ResI) {
      Value *V = UndefValue::get(MidTy);
      for (unsigned MidI = 0; MidI < FanIn; ++MidI)
        V = Builder.CreateInsertElement(V, Op0[Op0I++], Builder.getInt32(MidI),
                                        BCI.getName() + ".i" + Twine(ResI)
                                        + ".upto" + Twine(MidI));
      Res[ResI] = Builder.CreateBitCast(V, DstVT->getElementType(),
                                        BCI.getName() + ".i" + Twine(ResI));
    }
  }
  gather(&BCI, Res);
  return true;
}

bool Scalarizer::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
  VectorType *VT = dyn_cast<VectorType>(SVI.getType());
  if (!VT)
    return false;

  unsigned NumElems = VT->getNumElements();
  Scatterer Op0 = scatter(&SVI, SVI.getOperand(0));
  Scatterer Op1 = scatter(&SVI, SVI.getOperand(1));
  ValueVector Res;
  Res.resize(NumElems);

  for (unsigned I = 0; I < NumElems; ++I) {
    int Selector = SVI.getMaskValue(I);
    if (Selector < 0)
      Res[I] = UndefValue::get(VT->getElementType());
    else if (unsigned(Selector) < Op0.size())
      Res[I] = Op0[Selector];
    else
      Res[I] = Op1[Selector - Op0.size()];
  }
  gather(&SVI, Res);
  return true;
}

bool Scalarizer::visitPHINode(PHINode &PHI) {
  VectorType *VT = dyn_cast<VectorType>(PHI.getType());
  if (!VT)
    return false;

  unsigned NumElems = VT->getNumElements();
  IRBuilder<> Builder(PHI.getParent(), &PHI);
  ValueVector Res;
  Res.resize(NumElems);

  unsigned NumOps = PHI.getNumOperands();
  for (unsigned I = 0; I < NumElems; ++I)
    Res[I] = Builder.CreatePHI(VT->getElementType(), NumOps,
                               PHI.getName() + ".i" + Twine(I));

  for (unsigned I = 0; I < NumOps; ++I) {
    Scatterer Op = scatter(&PHI, PHI.getIncomingValue(I));
    BasicBlock *IncomingBlock = PHI.getIncomingBlock(I);
    for (unsigned J = 0; J < NumElems; ++J)
      cast<PHINode>(Res[J])->addIncoming(Op[J], IncomingBlock);
  }
  gather(&PHI, Res);
  return true;
}

bool Scalarizer::visitLoadInst(LoadInst &LI) {
  if (!ScalarizeLoadStore)
    return false;
  if (!LI.isSimple())
    return false;

  VectorLayout Layout;
  if (!getVectorLayout(LI.getType(), LI.getAlignment(), Layout,
                       LI.getModule()->getDataLayout()))
    return false;

  unsigned NumElems = Layout.VecTy->getNumElements();
  IRBuilder<> Builder(LI.getParent(), &LI);
  Scatterer Ptr = scatter(&LI, LI.getPointerOperand());
  ValueVector Res;
  Res.resize(NumElems);

  for (unsigned I = 0; I < NumElems; ++I)
    Res[I] = Builder.CreateAlignedLoad(Ptr[I], Layout.getElemAlign(I),
                                       LI.getName() + ".i" + Twine(I));
  gather(&LI, Res);
  return true;
}

bool Scalarizer::visitStoreInst(StoreInst &SI) {
  if (!ScalarizeLoadStore)
    return false;
  if (!SI.isSimple())
    return false;

  VectorLayout Layout;
  Value *FullValue = SI.getValueOperand();
  if (!getVectorLayout(FullValue->getType(), SI.getAlignment(), Layout,
                       SI.getModule()->getDataLayout()))
    return false;

  unsigned NumElems = Layout.VecTy->getNumElements();
  IRBuilder<> Builder(SI.getParent(), &SI);
  Scatterer Ptr = scatter(&SI, SI.getPointerOperand());
  Scatterer Val = scatter(&SI, FullValue);

  ValueVector Stores;
  Stores.resize(NumElems);
  for (unsigned I = 0; I < NumElems; ++I) {
    unsigned Align = Layout.getElemAlign(I);
    Stores[I] = Builder.CreateAlignedStore(Val[I], Ptr[I], Align);
  }
  transferMetadata(&SI, Stores);
  return true;
}

// Delete the instructions that we scalarized.  If a full vector result
// is still needed, recreate it using InsertElements.
bool Scalarizer::finish() {
  if (Gathered.empty())
    return false;
  for (GatherList::iterator GMI = Gathered.begin(), GME = Gathered.end();
       GMI != GME; ++GMI) {
    Instruction *Op = GMI->first;
    ValueVector &CV = *GMI->second;
    if (!Op->use_empty()) {
      // The value is still needed, so recreate it using a series of
      // InsertElements.
      Type *Ty = Op->getType();
      Value *Res = UndefValue::get(Ty);
      BasicBlock *BB = Op->getParent();
      unsigned Count = Ty->getVectorNumElements();
      IRBuilder<> Builder(BB, Op);
      if (isa<PHINode>(Op))
        Builder.SetInsertPoint(BB, BB->getFirstInsertionPt());
      for (unsigned I = 0; I < Count; ++I)
        Res = Builder.CreateInsertElement(Res, CV[I], Builder.getInt32(I),
                                          Op->getName() + ".upto" + Twine(I));
      Res->takeName(Op);
      Op->replaceAllUsesWith(Res);
    }
    Op->eraseFromParent();
  }
  Gathered.clear();
  Scattered.clear();
  return true;
}

FunctionPass *llvm::createScalarizerPass() {
  return new Scalarizer();
}