| //===- 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" |
| #include "llvm/Support/PatternMatch.h" |
| using namespace llvm; |
| using namespace PatternMatch; |
| |
| /// CheapToScalarize - Return true if the value is cheaper to scalarize than it |
| /// is to leave as a vector operation. isConstant indicates whether we're |
| /// extracting one known element. If false we're extracting a variable index. |
| static bool CheapToScalarize(Value *V, bool isConstant) { |
| if (Constant *C = dyn_cast<Constant>(V)) { |
| if (isConstant) return true; |
| |
| // If all elts are the same, we can extract it and use any of the values. |
| Constant *Op0 = C->getAggregateElement(0U); |
| for (unsigned i = 1, e = V->getType()->getVectorNumElements(); i != e; ++i) |
| if (C->getAggregateElement(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; |
| } |
| |
| /// 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 *VTy = cast<VectorType>(V->getType()); |
| unsigned Width = VTy->getNumElements(); |
| if (EltNo >= Width) // Out of range access. |
| return UndefValue::get(VTy->getElementType()); |
| |
| if (Constant *C = dyn_cast<Constant>(V)) |
| return C->getAggregateElement(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 = SVI->getOperand(0)->getType()->getVectorNumElements(); |
| int InEl = SVI->getMaskValue(EltNo); |
| if (InEl < 0) |
| return UndefValue::get(VTy->getElementType()); |
| if (InEl < (int)LHSWidth) |
| return FindScalarElement(SVI->getOperand(0), InEl); |
| return FindScalarElement(SVI->getOperand(1), InEl - LHSWidth); |
| } |
| |
| // Extract a value from a vector add operation with a constant zero. |
| Value *Val = 0; Constant *Con = 0; |
| if (match(V, m_Add(m_Value(Val), m_Constant(Con)))) { |
| if (Con->getAggregateElement(EltNo)->isNullValue()) |
| return FindScalarElement(Val, EltNo); |
| } |
| |
| // Otherwise, we don't know. |
| return 0; |
| } |
| |
| Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) { |
| // If vector val is constant with all elements the same, replace EI with |
| // that element. We handle a known element # below. |
| if (Constant *C = dyn_cast<Constant>(EI.getOperand(0))) |
| if (CheapToScalarize(C, false)) |
| return ReplaceInstUsesWith(EI, C->getAggregateElement(0U)); |
| |
| // 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 = SVI->getMaskValue(Elt->getZExtValue()); |
| Value *Src; |
| unsigned LHSWidth = |
| SVI->getOperand(0)->getType()->getVectorNumElements(); |
| |
| 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, |
| SmallVectorImpl<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, SmallVectorImpl<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; |
| } |
| |
| if (isa<ConstantAggregateZero>(V)) { |
| Mask.assign(NumElts, ConstantInt::get(Type::getInt32Ty(V->getContext()),0)); |
| return V; |
| } |
| |
| 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())) { |
| SmallVector<Constant*, 16> 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); |
| SmallVector<int, 16> Mask = SVI.getShuffleMask(); |
| |
| 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(); |
| |
| 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; |
| } |
| |
| unsigned LHSWidth = cast<VectorType>(LHS->getType())->getNumElements(); |
| |
| // 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. |
| Value* result = (VWidth == LHSWidth) |
| ? LHS : UndefValue::get(SVI.getType()); |
| return ReplaceInstUsesWith(SVI, result); |
| } |
| |
| // Remap any references to RHS to use LHS. |
| SmallVector<Constant*, 16> Elts; |
| for (unsigned i = 0, e = LHSWidth; i != VWidth; ++i) { |
| if (Mask[i] < 0) { |
| Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext()))); |
| continue; |
| } |
| |
| 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; |
| } |
| |
| if (VWidth == LHSWidth) { |
| // 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. |
| // Cases that might be simplified: |
| // 1. |
| // x1=shuffle(v1,v2,mask1) |
| // x=shuffle(x1,undef,mask) |
| // ==> |
| // x=shuffle(v1,undef,newMask) |
| // newMask[i] = (mask[i] < x1.size()) ? mask1[mask[i]] : -1 |
| // 2. |
| // x1=shuffle(v1,undef,mask1) |
| // x=shuffle(x1,x2,mask) |
| // where v1.size() == mask1.size() |
| // ==> |
| // x=shuffle(v1,x2,newMask) |
| // newMask[i] = (mask[i] < x1.size()) ? mask1[mask[i]] : mask[i] |
| // 3. |
| // x2=shuffle(v2,undef,mask2) |
| // x=shuffle(x1,x2,mask) |
| // where v2.size() == mask2.size() |
| // ==> |
| // x=shuffle(x1,v2,newMask) |
| // newMask[i] = (mask[i] < x1.size()) |
| // ? mask[i] : mask2[mask[i]-x1.size()]+x1.size() |
| // 4. |
| // x1=shuffle(v1,undef,mask1) |
| // x2=shuffle(v2,undef,mask2) |
| // x=shuffle(x1,x2,mask) |
| // where v1.size() == v2.size() |
| // ==> |
| // x=shuffle(v1,v2,newMask) |
| // newMask[i] = (mask[i] < x1.size()) |
| // ? mask1[mask[i]] : mask2[mask[i]-x1.size()]+v1.size() |
| // |
| // 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 |
| // 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, or |
| // merge(V[0..n], V[n+1..2n]) -> V[0..2n] |
| ShuffleVectorInst* LHSShuffle = dyn_cast<ShuffleVectorInst>(LHS); |
| ShuffleVectorInst* RHSShuffle = dyn_cast<ShuffleVectorInst>(RHS); |
| if (LHSShuffle) |
| if (!isa<UndefValue>(LHSShuffle->getOperand(1)) && !isa<UndefValue>(RHS)) |
| LHSShuffle = NULL; |
| if (RHSShuffle) |
| if (!isa<UndefValue>(RHSShuffle->getOperand(1))) |
| RHSShuffle = NULL; |
| if (!LHSShuffle && !RHSShuffle) |
| return MadeChange ? &SVI : 0; |
| |
| Value* LHSOp0 = NULL; |
| Value* LHSOp1 = NULL; |
| Value* RHSOp0 = NULL; |
| unsigned LHSOp0Width = 0; |
| unsigned RHSOp0Width = 0; |
| if (LHSShuffle) { |
| LHSOp0 = LHSShuffle->getOperand(0); |
| LHSOp1 = LHSShuffle->getOperand(1); |
| LHSOp0Width = cast<VectorType>(LHSOp0->getType())->getNumElements(); |
| } |
| if (RHSShuffle) { |
| RHSOp0 = RHSShuffle->getOperand(0); |
| RHSOp0Width = cast<VectorType>(RHSOp0->getType())->getNumElements(); |
| } |
| Value* newLHS = LHS; |
| Value* newRHS = RHS; |
| if (LHSShuffle) { |
| // case 1 |
| if (isa<UndefValue>(RHS)) { |
| newLHS = LHSOp0; |
| newRHS = LHSOp1; |
| } |
| // case 2 or 4 |
| else if (LHSOp0Width == LHSWidth) { |
| newLHS = LHSOp0; |
| } |
| } |
| // case 3 or 4 |
| if (RHSShuffle && RHSOp0Width == LHSWidth) { |
| newRHS = RHSOp0; |
| } |
| // case 4 |
| if (LHSOp0 == RHSOp0) { |
| newLHS = LHSOp0; |
| newRHS = NULL; |
| } |
| |
| if (newLHS == LHS && newRHS == RHS) |
| return MadeChange ? &SVI : 0; |
| |
| SmallVector<int, 16> LHSMask; |
| SmallVector<int, 16> RHSMask; |
| if (newLHS != LHS) |
| LHSMask = LHSShuffle->getShuffleMask(); |
| if (RHSShuffle && newRHS != RHS) |
| RHSMask = RHSShuffle->getShuffleMask(); |
| |
| unsigned newLHSWidth = (newLHS != LHS) ? LHSOp0Width : LHSWidth; |
| SmallVector<int, 16> newMask; |
| bool isSplat = true; |
| int SplatElt = -1; |
| // Create a new mask for the new ShuffleVectorInst so that the new |
| // ShuffleVectorInst is equivalent to the original one. |
| for (unsigned i = 0; i < VWidth; ++i) { |
| int eltMask; |
| if (Mask[i] < 0) { |
| // This element is an undef value. |
| eltMask = -1; |
| } else if (Mask[i] < (int)LHSWidth) { |
| // This element is from left hand side vector operand. |
| // |
| // If LHS is going to be replaced (case 1, 2, or 4), calculate the |
| // new mask value for the element. |
| if (newLHS != LHS) { |
| eltMask = LHSMask[Mask[i]]; |
| // If the value selected is an undef value, explicitly specify it |
| // with a -1 mask value. |
| if (eltMask >= (int)LHSOp0Width && isa<UndefValue>(LHSOp1)) |
| eltMask = -1; |
| } else |
| eltMask = Mask[i]; |
| } else { |
| // This element is from right hand side vector operand |
| // |
| // If the value selected is an undef value, explicitly specify it |
| // with a -1 mask value. (case 1) |
| if (isa<UndefValue>(RHS)) |
| eltMask = -1; |
| // If RHS is going to be replaced (case 3 or 4), calculate the |
| // new mask value for the element. |
| else if (newRHS != RHS) { |
| eltMask = RHSMask[Mask[i]-LHSWidth]; |
| // If the value selected is an undef value, explicitly specify it |
| // with a -1 mask value. |
| if (eltMask >= (int)RHSOp0Width) { |
| assert(isa<UndefValue>(RHSShuffle->getOperand(1)) |
| && "should have been check above"); |
| eltMask = -1; |
| } |
| } else |
| eltMask = Mask[i]-LHSWidth; |
| |
| // If LHS's width is changed, shift the mask value accordingly. |
| // If newRHS == NULL, i.e. LHSOp0 == RHSOp0, we want to remap any |
| // references from RHSOp0 to LHSOp0, so we don't need to shift the mask. |
| // If newRHS == newLHS, we want to remap any references from newRHS to |
| // newLHS so that we can properly identify splats that may occur due to |
| // obfuscation accross the two vectors. |
| if (eltMask >= 0 && newRHS != NULL && newLHS != newRHS) |
| eltMask += newLHSWidth; |
| } |
| |
| // Check if this could still be a splat. |
| if (eltMask >= 0) { |
| if (SplatElt >= 0 && SplatElt != eltMask) |
| isSplat = false; |
| SplatElt = eltMask; |
| } |
| |
| newMask.push_back(eltMask); |
| } |
| |
| // If the result mask is equal to one of the original shuffle masks, |
| // or is a splat, do the replacement. |
| if (isSplat || newMask == LHSMask || newMask == RHSMask || newMask == Mask) { |
| SmallVector<Constant*, 16> 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])); |
| } |
| } |
| if (newRHS == NULL) |
| newRHS = UndefValue::get(newLHS->getType()); |
| return new ShuffleVectorInst(newLHS, newRHS, ConstantVector::get(Elts)); |
| } |
| |
| return MadeChange ? &SVI : 0; |
| } |
