| //===- InstCombineVectorOps.cpp -------------------------------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements instcombine for ExtractElement, InsertElement and |
| // ShuffleVector. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "InstCombine.h" |
| using namespace llvm; |
| |
| /// CheapToScalarize - Return true if the value is cheaper to scalarize than it |
| /// is to leave as a vector operation. |
| static bool CheapToScalarize(Value *V, bool isConstant) { |
| if (isa<ConstantAggregateZero>(V)) |
| return true; |
| if (ConstantVector *C = dyn_cast<ConstantVector>(V)) { |
| if (isConstant) return true; |
| // If all elts are the same, we can extract. |
| Constant *Op0 = C->getOperand(0); |
| for (unsigned i = 1; i < C->getNumOperands(); ++i) |
| if (C->getOperand(i) != Op0) |
| return false; |
| return true; |
| } |
| Instruction *I = dyn_cast<Instruction>(V); |
| if (!I) return false; |
| |
| // Insert element gets simplified to the inserted element or is deleted if |
| // this is constant idx extract element and its a constant idx insertelt. |
| if (I->getOpcode() == Instruction::InsertElement && isConstant && |
| isa<ConstantInt>(I->getOperand(2))) |
| return true; |
| if (I->getOpcode() == Instruction::Load && I->hasOneUse()) |
| return true; |
| if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) |
| if (BO->hasOneUse() && |
| (CheapToScalarize(BO->getOperand(0), isConstant) || |
| CheapToScalarize(BO->getOperand(1), isConstant))) |
| return true; |
| if (CmpInst *CI = dyn_cast<CmpInst>(I)) |
| if (CI->hasOneUse() && |
| (CheapToScalarize(CI->getOperand(0), isConstant) || |
| CheapToScalarize(CI->getOperand(1), isConstant))) |
| return true; |
| |
| return false; |
| } |
| |
| /// getShuffleMask - Read and decode a shufflevector mask. |
| /// Turn undef elements into negative values. |
| static std::vector<int> getShuffleMask(const ShuffleVectorInst *SVI) { |
| unsigned NElts = SVI->getType()->getNumElements(); |
| if (isa<ConstantAggregateZero>(SVI->getOperand(2))) |
| return std::vector<int>(NElts, 0); |
| if (isa<UndefValue>(SVI->getOperand(2))) |
| return std::vector<int>(NElts, -1); |
| |
| std::vector<int> Result; |
| const ConstantVector *CP = cast<ConstantVector>(SVI->getOperand(2)); |
| for (User::const_op_iterator i = CP->op_begin(), e = CP->op_end(); i!=e; ++i) |
| if (isa<UndefValue>(*i)) |
| Result.push_back(-1); // undef |
| else |
| Result.push_back(cast<ConstantInt>(*i)->getZExtValue()); |
| return Result; |
| } |
| |
| /// FindScalarElement - Given a vector and an element number, see if the scalar |
| /// value is already around as a register, for example if it were inserted then |
| /// extracted from the vector. |
| static Value *FindScalarElement(Value *V, unsigned EltNo) { |
| assert(V->getType()->isVectorTy() && "Not looking at a vector?"); |
| VectorType *PTy = cast<VectorType>(V->getType()); |
| unsigned Width = PTy->getNumElements(); |
| if (EltNo >= Width) // Out of range access. |
| return UndefValue::get(PTy->getElementType()); |
| |
| if (isa<UndefValue>(V)) |
| return UndefValue::get(PTy->getElementType()); |
| if (isa<ConstantAggregateZero>(V)) |
| return Constant::getNullValue(PTy->getElementType()); |
| if (ConstantVector *CP = dyn_cast<ConstantVector>(V)) |
| return CP->getOperand(EltNo); |
| |
| if (InsertElementInst *III = dyn_cast<InsertElementInst>(V)) { |
| // If this is an insert to a variable element, we don't know what it is. |
| if (!isa<ConstantInt>(III->getOperand(2))) |
| return 0; |
| unsigned IIElt = cast<ConstantInt>(III->getOperand(2))->getZExtValue(); |
| |
| // If this is an insert to the element we are looking for, return the |
| // inserted value. |
| if (EltNo == IIElt) |
| return III->getOperand(1); |
| |
| // Otherwise, the insertelement doesn't modify the value, recurse on its |
| // vector input. |
| return FindScalarElement(III->getOperand(0), EltNo); |
| } |
| |
| if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(V)) { |
| unsigned LHSWidth = |
| cast<VectorType>(SVI->getOperand(0)->getType())->getNumElements(); |
| int InEl = getShuffleMask(SVI)[EltNo]; |
| if (InEl < 0) |
| return UndefValue::get(PTy->getElementType()); |
| if (InEl < (int)LHSWidth) |
| return FindScalarElement(SVI->getOperand(0), InEl); |
| return FindScalarElement(SVI->getOperand(1), InEl - LHSWidth); |
| } |
| |
| // Otherwise, we don't know. |
| return 0; |
| } |
| |
| Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) { |
| // If vector val is undef, replace extract with scalar undef. |
| if (isa<UndefValue>(EI.getOperand(0))) |
| return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType())); |
| |
| // If vector val is constant 0, replace extract with scalar 0. |
| if (isa<ConstantAggregateZero>(EI.getOperand(0))) |
| return ReplaceInstUsesWith(EI, Constant::getNullValue(EI.getType())); |
| |
| if (ConstantVector *C = dyn_cast<ConstantVector>(EI.getOperand(0))) { |
| // If vector val is constant with all elements the same, replace EI with |
| // that element. When the elements are not identical, we cannot replace yet |
| // (we do that below, but only when the index is constant). |
| Constant *op0 = C->getOperand(0); |
| for (unsigned i = 1; i != C->getNumOperands(); ++i) |
| if (C->getOperand(i) != op0) { |
| op0 = 0; |
| break; |
| } |
| if (op0) |
| return ReplaceInstUsesWith(EI, op0); |
| } |
| |
| // If extracting a specified index from the vector, see if we can recursively |
| // find a previously computed scalar that was inserted into the vector. |
| if (ConstantInt *IdxC = dyn_cast<ConstantInt>(EI.getOperand(1))) { |
| unsigned IndexVal = IdxC->getZExtValue(); |
| unsigned VectorWidth = EI.getVectorOperandType()->getNumElements(); |
| |
| // If this is extracting an invalid index, turn this into undef, to avoid |
| // crashing the code below. |
| if (IndexVal >= VectorWidth) |
| return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType())); |
| |
| // This instruction only demands the single element from the input vector. |
| // If the input vector has a single use, simplify it based on this use |
| // property. |
| if (EI.getOperand(0)->hasOneUse() && VectorWidth != 1) { |
| APInt UndefElts(VectorWidth, 0); |
| APInt DemandedMask(VectorWidth, 0); |
| DemandedMask.setBit(IndexVal); |
| if (Value *V = SimplifyDemandedVectorElts(EI.getOperand(0), |
| DemandedMask, UndefElts)) { |
| EI.setOperand(0, V); |
| return &EI; |
| } |
| } |
| |
| if (Value *Elt = FindScalarElement(EI.getOperand(0), IndexVal)) |
| return ReplaceInstUsesWith(EI, Elt); |
| |
| // If the this extractelement is directly using a bitcast from a vector of |
| // the same number of elements, see if we can find the source element from |
| // it. In this case, we will end up needing to bitcast the scalars. |
| if (BitCastInst *BCI = dyn_cast<BitCastInst>(EI.getOperand(0))) { |
| if (VectorType *VT = |
| dyn_cast<VectorType>(BCI->getOperand(0)->getType())) |
| if (VT->getNumElements() == VectorWidth) |
| if (Value *Elt = FindScalarElement(BCI->getOperand(0), IndexVal)) |
| return new BitCastInst(Elt, EI.getType()); |
| } |
| } |
| |
| if (Instruction *I = dyn_cast<Instruction>(EI.getOperand(0))) { |
| // Push extractelement into predecessor operation if legal and |
| // profitable to do so |
| if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) { |
| if (I->hasOneUse() && |
| CheapToScalarize(BO, isa<ConstantInt>(EI.getOperand(1)))) { |
| Value *newEI0 = |
| Builder->CreateExtractElement(BO->getOperand(0), EI.getOperand(1), |
| EI.getName()+".lhs"); |
| Value *newEI1 = |
| Builder->CreateExtractElement(BO->getOperand(1), EI.getOperand(1), |
| EI.getName()+".rhs"); |
| return BinaryOperator::Create(BO->getOpcode(), newEI0, newEI1); |
| } |
| } else if (InsertElementInst *IE = dyn_cast<InsertElementInst>(I)) { |
| // Extracting the inserted element? |
| if (IE->getOperand(2) == EI.getOperand(1)) |
| return ReplaceInstUsesWith(EI, IE->getOperand(1)); |
| // If the inserted and extracted elements are constants, they must not |
| // be the same value, extract from the pre-inserted value instead. |
| if (isa<Constant>(IE->getOperand(2)) && isa<Constant>(EI.getOperand(1))) { |
| Worklist.AddValue(EI.getOperand(0)); |
| EI.setOperand(0, IE->getOperand(0)); |
| return &EI; |
| } |
| } else if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(I)) { |
| // If this is extracting an element from a shufflevector, figure out where |
| // it came from and extract from the appropriate input element instead. |
| if (ConstantInt *Elt = dyn_cast<ConstantInt>(EI.getOperand(1))) { |
| int SrcIdx = getShuffleMask(SVI)[Elt->getZExtValue()]; |
| Value *Src; |
| unsigned LHSWidth = |
| cast<VectorType>(SVI->getOperand(0)->getType())->getNumElements(); |
| |
| if (SrcIdx < 0) |
| return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType())); |
| if (SrcIdx < (int)LHSWidth) |
| Src = SVI->getOperand(0); |
| else { |
| SrcIdx -= LHSWidth; |
| Src = SVI->getOperand(1); |
| } |
| Type *Int32Ty = Type::getInt32Ty(EI.getContext()); |
| return ExtractElementInst::Create(Src, |
| ConstantInt::get(Int32Ty, |
| SrcIdx, false)); |
| } |
| } else if (CastInst *CI = dyn_cast<CastInst>(I)) { |
| // Canonicalize extractelement(cast) -> cast(extractelement) |
| // bitcasts can change the number of vector elements and they cost nothing |
| if (CI->hasOneUse() && EI.hasOneUse() && |
| (CI->getOpcode() != Instruction::BitCast)) { |
| Value *EE = Builder->CreateExtractElement(CI->getOperand(0), |
| EI.getIndexOperand()); |
| return CastInst::Create(CI->getOpcode(), EE, EI.getType()); |
| } |
| } |
| } |
| return 0; |
| } |
| |
| /// CollectSingleShuffleElements - If V is a shuffle of values that ONLY returns |
| /// elements from either LHS or RHS, return the shuffle mask and true. |
| /// Otherwise, return false. |
| static bool CollectSingleShuffleElements(Value *V, Value *LHS, Value *RHS, |
| std::vector<Constant*> &Mask) { |
| assert(V->getType() == LHS->getType() && V->getType() == RHS->getType() && |
| "Invalid CollectSingleShuffleElements"); |
| unsigned NumElts = cast<VectorType>(V->getType())->getNumElements(); |
| |
| if (isa<UndefValue>(V)) { |
| Mask.assign(NumElts, UndefValue::get(Type::getInt32Ty(V->getContext()))); |
| return true; |
| } |
| |
| if (V == LHS) { |
| for (unsigned i = 0; i != NumElts; ++i) |
| Mask.push_back(ConstantInt::get(Type::getInt32Ty(V->getContext()), i)); |
| return true; |
| } |
| |
| if (V == RHS) { |
| for (unsigned i = 0; i != NumElts; ++i) |
| Mask.push_back(ConstantInt::get(Type::getInt32Ty(V->getContext()), |
| i+NumElts)); |
| return true; |
| } |
| |
| if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(V)) { |
| // If this is an insert of an extract from some other vector, include it. |
| Value *VecOp = IEI->getOperand(0); |
| Value *ScalarOp = IEI->getOperand(1); |
| Value *IdxOp = IEI->getOperand(2); |
| |
| if (!isa<ConstantInt>(IdxOp)) |
| return false; |
| unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue(); |
| |
| if (isa<UndefValue>(ScalarOp)) { // inserting undef into vector. |
| // Okay, we can handle this if the vector we are insertinting into is |
| // transitively ok. |
| if (CollectSingleShuffleElements(VecOp, LHS, RHS, Mask)) { |
| // If so, update the mask to reflect the inserted undef. |
| Mask[InsertedIdx] = UndefValue::get(Type::getInt32Ty(V->getContext())); |
| return true; |
| } |
| } else if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)){ |
| if (isa<ConstantInt>(EI->getOperand(1)) && |
| EI->getOperand(0)->getType() == V->getType()) { |
| unsigned ExtractedIdx = |
| cast<ConstantInt>(EI->getOperand(1))->getZExtValue(); |
| |
| // This must be extracting from either LHS or RHS. |
| if (EI->getOperand(0) == LHS || EI->getOperand(0) == RHS) { |
| // Okay, we can handle this if the vector we are insertinting into is |
| // transitively ok. |
| if (CollectSingleShuffleElements(VecOp, LHS, RHS, Mask)) { |
| // If so, update the mask to reflect the inserted value. |
| if (EI->getOperand(0) == LHS) { |
| Mask[InsertedIdx % NumElts] = |
| ConstantInt::get(Type::getInt32Ty(V->getContext()), |
| ExtractedIdx); |
| } else { |
| assert(EI->getOperand(0) == RHS); |
| Mask[InsertedIdx % NumElts] = |
| ConstantInt::get(Type::getInt32Ty(V->getContext()), |
| ExtractedIdx+NumElts); |
| } |
| return true; |
| } |
| } |
| } |
| } |
| } |
| // TODO: Handle shufflevector here! |
| |
| return false; |
| } |
| |
| /// CollectShuffleElements - We are building a shuffle of V, using RHS as the |
| /// RHS of the shuffle instruction, if it is not null. Return a shuffle mask |
| /// that computes V and the LHS value of the shuffle. |
| static Value *CollectShuffleElements(Value *V, std::vector<Constant*> &Mask, |
| Value *&RHS) { |
| assert(V->getType()->isVectorTy() && |
| (RHS == 0 || V->getType() == RHS->getType()) && |
| "Invalid shuffle!"); |
| unsigned NumElts = cast<VectorType>(V->getType())->getNumElements(); |
| |
| if (isa<UndefValue>(V)) { |
| Mask.assign(NumElts, UndefValue::get(Type::getInt32Ty(V->getContext()))); |
| return V; |
| } else if (isa<ConstantAggregateZero>(V)) { |
| Mask.assign(NumElts, ConstantInt::get(Type::getInt32Ty(V->getContext()),0)); |
| return V; |
| } else if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(V)) { |
| // If this is an insert of an extract from some other vector, include it. |
| Value *VecOp = IEI->getOperand(0); |
| Value *ScalarOp = IEI->getOperand(1); |
| Value *IdxOp = IEI->getOperand(2); |
| |
| if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)) { |
| if (isa<ConstantInt>(EI->getOperand(1)) && isa<ConstantInt>(IdxOp) && |
| EI->getOperand(0)->getType() == V->getType()) { |
| unsigned ExtractedIdx = |
| cast<ConstantInt>(EI->getOperand(1))->getZExtValue(); |
| unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue(); |
| |
| // Either the extracted from or inserted into vector must be RHSVec, |
| // otherwise we'd end up with a shuffle of three inputs. |
| if (EI->getOperand(0) == RHS || RHS == 0) { |
| RHS = EI->getOperand(0); |
| Value *V = CollectShuffleElements(VecOp, Mask, RHS); |
| Mask[InsertedIdx % NumElts] = |
| ConstantInt::get(Type::getInt32Ty(V->getContext()), |
| NumElts+ExtractedIdx); |
| return V; |
| } |
| |
| if (VecOp == RHS) { |
| Value *V = CollectShuffleElements(EI->getOperand(0), Mask, RHS); |
| // Everything but the extracted element is replaced with the RHS. |
| for (unsigned i = 0; i != NumElts; ++i) { |
| if (i != InsertedIdx) |
| Mask[i] = ConstantInt::get(Type::getInt32Ty(V->getContext()), |
| NumElts+i); |
| } |
| return V; |
| } |
| |
| // If this insertelement is a chain that comes from exactly these two |
| // vectors, return the vector and the effective shuffle. |
| if (CollectSingleShuffleElements(IEI, EI->getOperand(0), RHS, Mask)) |
| return EI->getOperand(0); |
| } |
| } |
| } |
| // TODO: Handle shufflevector here! |
| |
| // Otherwise, can't do anything fancy. Return an identity vector. |
| for (unsigned i = 0; i != NumElts; ++i) |
| Mask.push_back(ConstantInt::get(Type::getInt32Ty(V->getContext()), i)); |
| return V; |
| } |
| |
| Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) { |
| Value *VecOp = IE.getOperand(0); |
| Value *ScalarOp = IE.getOperand(1); |
| Value *IdxOp = IE.getOperand(2); |
| |
| // Inserting an undef or into an undefined place, remove this. |
| if (isa<UndefValue>(ScalarOp) || isa<UndefValue>(IdxOp)) |
| ReplaceInstUsesWith(IE, VecOp); |
| |
| // If the inserted element was extracted from some other vector, and if the |
| // indexes are constant, try to turn this into a shufflevector operation. |
| if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)) { |
| if (isa<ConstantInt>(EI->getOperand(1)) && isa<ConstantInt>(IdxOp) && |
| EI->getOperand(0)->getType() == IE.getType()) { |
| unsigned NumVectorElts = IE.getType()->getNumElements(); |
| unsigned ExtractedIdx = |
| cast<ConstantInt>(EI->getOperand(1))->getZExtValue(); |
| unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue(); |
| |
| if (ExtractedIdx >= NumVectorElts) // Out of range extract. |
| return ReplaceInstUsesWith(IE, VecOp); |
| |
| if (InsertedIdx >= NumVectorElts) // Out of range insert. |
| return ReplaceInstUsesWith(IE, UndefValue::get(IE.getType())); |
| |
| // If we are extracting a value from a vector, then inserting it right |
| // back into the same place, just use the input vector. |
| if (EI->getOperand(0) == VecOp && ExtractedIdx == InsertedIdx) |
| return ReplaceInstUsesWith(IE, VecOp); |
| |
| // If this insertelement isn't used by some other insertelement, turn it |
| // (and any insertelements it points to), into one big shuffle. |
| if (!IE.hasOneUse() || !isa<InsertElementInst>(IE.use_back())) { |
| std::vector<Constant*> Mask; |
| Value *RHS = 0; |
| Value *LHS = CollectShuffleElements(&IE, Mask, RHS); |
| if (RHS == 0) RHS = UndefValue::get(LHS->getType()); |
| // We now have a shuffle of LHS, RHS, Mask. |
| return new ShuffleVectorInst(LHS, RHS, ConstantVector::get(Mask)); |
| } |
| } |
| } |
| |
| unsigned VWidth = cast<VectorType>(VecOp->getType())->getNumElements(); |
| APInt UndefElts(VWidth, 0); |
| APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth)); |
| if (Value *V = SimplifyDemandedVectorElts(&IE, AllOnesEltMask, UndefElts)) { |
| if (V != &IE) |
| return ReplaceInstUsesWith(IE, V); |
| return &IE; |
| } |
| |
| return 0; |
| } |
| |
| |
| Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) { |
| Value *LHS = SVI.getOperand(0); |
| Value *RHS = SVI.getOperand(1); |
| std::vector<int> Mask = getShuffleMask(&SVI); |
| |
| bool MadeChange = false; |
| |
| // Undefined shuffle mask -> undefined value. |
| if (isa<UndefValue>(SVI.getOperand(2))) |
| return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType())); |
| |
| unsigned VWidth = cast<VectorType>(SVI.getType())->getNumElements(); |
| |
| if (VWidth != cast<VectorType>(LHS->getType())->getNumElements()) |
| return 0; |
| |
| APInt UndefElts(VWidth, 0); |
| APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth)); |
| if (Value *V = SimplifyDemandedVectorElts(&SVI, AllOnesEltMask, UndefElts)) { |
| if (V != &SVI) |
| return ReplaceInstUsesWith(SVI, V); |
| LHS = SVI.getOperand(0); |
| RHS = SVI.getOperand(1); |
| MadeChange = true; |
| } |
| |
| // Canonicalize shuffle(x ,x,mask) -> shuffle(x, undef,mask') |
| // Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask'). |
| if (LHS == RHS || isa<UndefValue>(LHS)) { |
| if (isa<UndefValue>(LHS) && LHS == RHS) { |
| // shuffle(undef,undef,mask) -> undef. |
| return ReplaceInstUsesWith(SVI, LHS); |
| } |
| |
| // Remap any references to RHS to use LHS. |
| std::vector<Constant*> Elts; |
| for (unsigned i = 0, e = Mask.size(); i != e; ++i) { |
| if (Mask[i] < 0) |
| Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext()))); |
| else { |
| if ((Mask[i] >= (int)e && isa<UndefValue>(RHS)) || |
| (Mask[i] < (int)e && isa<UndefValue>(LHS))) { |
| Mask[i] = -1; // Turn into undef. |
| Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext()))); |
| } else { |
| Mask[i] = Mask[i] % e; // Force to LHS. |
| Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()), |
| Mask[i])); |
| } |
| } |
| } |
| SVI.setOperand(0, SVI.getOperand(1)); |
| SVI.setOperand(1, UndefValue::get(RHS->getType())); |
| SVI.setOperand(2, ConstantVector::get(Elts)); |
| LHS = SVI.getOperand(0); |
| RHS = SVI.getOperand(1); |
| MadeChange = true; |
| } |
| |
| // Analyze the shuffle, are the LHS or RHS and identity shuffles? |
| bool isLHSID = true, isRHSID = true; |
| |
| for (unsigned i = 0, e = Mask.size(); i != e; ++i) { |
| if (Mask[i] < 0) continue; // Ignore undef values. |
| // Is this an identity shuffle of the LHS value? |
| isLHSID &= (Mask[i] == (int)i); |
| |
| // Is this an identity shuffle of the RHS value? |
| isRHSID &= (Mask[i]-e == i); |
| } |
| |
| // Eliminate identity shuffles. |
| if (isLHSID) return ReplaceInstUsesWith(SVI, LHS); |
| if (isRHSID) return ReplaceInstUsesWith(SVI, RHS); |
| |
| // If the LHS is a shufflevector itself, see if we can combine it with this |
| // one without producing an unusual shuffle. Here we are really conservative: |
| // we are absolutely afraid of producing a shuffle mask not in the input |
| // program, because the code gen may not be smart enough to turn a merged |
| // shuffle into two specific shuffles: it may produce worse code. As such, |
| // we only merge two shuffles if the result is either a splat or one of the |
| // two input shuffle masks. In this case, merging the shuffles just removes |
| // one instruction, which we know is safe. This is good for things like |
| // turning: (splat(splat)) -> splat. |
| if (ShuffleVectorInst *LHSSVI = dyn_cast<ShuffleVectorInst>(LHS)) { |
| if (isa<UndefValue>(RHS)) { |
| std::vector<int> LHSMask = getShuffleMask(LHSSVI); |
| |
| if (LHSMask.size() == Mask.size()) { |
| std::vector<int> NewMask; |
| bool isSplat = true; |
| int SplatElt = -1; // undef |
| for (unsigned i = 0, e = Mask.size(); i != e; ++i) { |
| int MaskElt; |
| if (Mask[i] < 0 || Mask[i] >= (int)e) |
| MaskElt = -1; // undef |
| else |
| MaskElt = LHSMask[Mask[i]]; |
| // Check if this could still be a splat. |
| if (MaskElt >= 0) { |
| if (SplatElt >=0 && SplatElt != MaskElt) |
| isSplat = false; |
| SplatElt = MaskElt; |
| } |
| NewMask.push_back(MaskElt); |
| } |
| |
| // If the result mask is equal to the src shuffle or this |
| // shuffle mask, do the replacement. |
| if (isSplat || NewMask == LHSMask || NewMask == Mask) { |
| std::vector<Constant*> Elts; |
| Type *Int32Ty = Type::getInt32Ty(SVI.getContext()); |
| for (unsigned i = 0, e = NewMask.size(); i != e; ++i) { |
| if (NewMask[i] < 0) { |
| Elts.push_back(UndefValue::get(Int32Ty)); |
| } else { |
| Elts.push_back(ConstantInt::get(Int32Ty, NewMask[i])); |
| } |
| } |
| return new ShuffleVectorInst(LHSSVI->getOperand(0), |
| LHSSVI->getOperand(1), |
| ConstantVector::get(Elts)); |
| } |
| } |
| } |
| } |
| |
| return MadeChange ? &SVI : 0; |
| } |
