| //===- ConstantFold.cpp - LLVM constant folder ----------------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements folding of constants for LLVM. This implements the |
| // (internal) ConstantFold.h interface, which is used by the |
| // ConstantExpr::get* methods to automatically fold constants when possible. |
| // |
| // The current constant folding implementation is implemented in two pieces: the |
| // template-based folder for simple primitive constants like ConstantInt, and |
| // the special case hackery that we use to symbolically evaluate expressions |
| // that use ConstantExprs. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "ConstantFold.h" |
| #include "llvm/Constants.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/Function.h" |
| #include "llvm/GlobalAlias.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/Support/Compiler.h" |
| #include "llvm/Support/GetElementPtrTypeIterator.h" |
| #include "llvm/Support/ManagedStatic.h" |
| #include "llvm/Support/MathExtras.h" |
| #include <limits> |
| using namespace llvm; |
| |
| //===----------------------------------------------------------------------===// |
| // ConstantFold*Instruction Implementations |
| //===----------------------------------------------------------------------===// |
| |
| /// BitCastConstantVector - Convert the specified ConstantVector node to the |
| /// specified vector type. At this point, we know that the elements of the |
| /// input vector constant are all simple integer or FP values. |
| static Constant *BitCastConstantVector(ConstantVector *CV, |
| const VectorType *DstTy) { |
| // If this cast changes element count then we can't handle it here: |
| // doing so requires endianness information. This should be handled by |
| // Analysis/ConstantFolding.cpp |
| unsigned NumElts = DstTy->getNumElements(); |
| if (NumElts != CV->getNumOperands()) |
| return 0; |
| |
| // Check to verify that all elements of the input are simple. |
| for (unsigned i = 0; i != NumElts; ++i) { |
| if (!isa<ConstantInt>(CV->getOperand(i)) && |
| !isa<ConstantFP>(CV->getOperand(i))) |
| return 0; |
| } |
| |
| // Bitcast each element now. |
| std::vector<Constant*> Result; |
| const Type *DstEltTy = DstTy->getElementType(); |
| for (unsigned i = 0; i != NumElts; ++i) |
| Result.push_back(ConstantExpr::getBitCast(CV->getOperand(i), DstEltTy)); |
| return ConstantVector::get(Result); |
| } |
| |
| /// This function determines which opcode to use to fold two constant cast |
| /// expressions together. It uses CastInst::isEliminableCastPair to determine |
| /// the opcode. Consequently its just a wrapper around that function. |
| /// @brief Determine if it is valid to fold a cast of a cast |
| static unsigned |
| foldConstantCastPair( |
| unsigned opc, ///< opcode of the second cast constant expression |
| const ConstantExpr*Op, ///< the first cast constant expression |
| const Type *DstTy ///< desintation type of the first cast |
| ) { |
| assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!"); |
| assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type"); |
| assert(CastInst::isCast(opc) && "Invalid cast opcode"); |
| |
| // The the types and opcodes for the two Cast constant expressions |
| const Type *SrcTy = Op->getOperand(0)->getType(); |
| const Type *MidTy = Op->getType(); |
| Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode()); |
| Instruction::CastOps secondOp = Instruction::CastOps(opc); |
| |
| // Let CastInst::isEliminableCastPair do the heavy lifting. |
| return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy, |
| Type::Int64Ty); |
| } |
| |
| static Constant *FoldBitCast(Constant *V, const Type *DestTy) { |
| const Type *SrcTy = V->getType(); |
| if (SrcTy == DestTy) |
| return V; // no-op cast |
| |
| // Check to see if we are casting a pointer to an aggregate to a pointer to |
| // the first element. If so, return the appropriate GEP instruction. |
| if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) |
| if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) |
| if (PTy->getAddressSpace() == DPTy->getAddressSpace()) { |
| SmallVector<Value*, 8> IdxList; |
| IdxList.push_back(Constant::getNullValue(Type::Int32Ty)); |
| const Type *ElTy = PTy->getElementType(); |
| while (ElTy != DPTy->getElementType()) { |
| if (const StructType *STy = dyn_cast<StructType>(ElTy)) { |
| if (STy->getNumElements() == 0) break; |
| ElTy = STy->getElementType(0); |
| IdxList.push_back(Constant::getNullValue(Type::Int32Ty)); |
| } else if (const SequentialType *STy = |
| dyn_cast<SequentialType>(ElTy)) { |
| if (isa<PointerType>(ElTy)) break; // Can't index into pointers! |
| ElTy = STy->getElementType(); |
| IdxList.push_back(IdxList[0]); |
| } else { |
| break; |
| } |
| } |
| |
| if (ElTy == DPTy->getElementType()) |
| return ConstantExpr::getGetElementPtr(V, &IdxList[0], IdxList.size()); |
| } |
| |
| // Handle casts from one vector constant to another. We know that the src |
| // and dest type have the same size (otherwise its an illegal cast). |
| if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) { |
| if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) { |
| assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() && |
| "Not cast between same sized vectors!"); |
| // First, check for null. Undef is already handled. |
| if (isa<ConstantAggregateZero>(V)) |
| return Constant::getNullValue(DestTy); |
| |
| if (ConstantVector *CV = dyn_cast<ConstantVector>(V)) |
| return BitCastConstantVector(CV, DestPTy); |
| } |
| } |
| |
| // Finally, implement bitcast folding now. The code below doesn't handle |
| // bitcast right. |
| if (isa<ConstantPointerNull>(V)) // ptr->ptr cast. |
| return ConstantPointerNull::get(cast<PointerType>(DestTy)); |
| |
| // Handle integral constant input. |
| if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { |
| if (DestTy->isInteger()) |
| // Integral -> Integral. This is a no-op because the bit widths must |
| // be the same. Consequently, we just fold to V. |
| return V; |
| |
| if (DestTy->isFloatingPoint()) { |
| assert((DestTy == Type::DoubleTy || DestTy == Type::FloatTy) && |
| "Unknown FP type!"); |
| return ConstantFP::get(DestTy, APFloat(CI->getValue())); |
| } |
| // Otherwise, can't fold this (vector?) |
| return 0; |
| } |
| |
| // Handle ConstantFP input. |
| if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) { |
| // FP -> Integral. |
| if (DestTy == Type::Int32Ty) { |
| return ConstantInt::get(FP->getValueAPF().convertToAPInt()); |
| } else { |
| assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!"); |
| return ConstantInt::get(FP->getValueAPF().convertToAPInt()); |
| } |
| } |
| return 0; |
| } |
| |
| |
| Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V, |
| const Type *DestTy) { |
| if (isa<UndefValue>(V)) { |
| // zext(undef) = 0, because the top bits will be zero. |
| // sext(undef) = 0, because the top bits will all be the same. |
| // [us]itofp(undef) = 0, because the result value is bounded. |
| if (opc == Instruction::ZExt || opc == Instruction::SExt || |
| opc == Instruction::UIToFP || opc == Instruction::SIToFP) |
| return Constant::getNullValue(DestTy); |
| return UndefValue::get(DestTy); |
| } |
| // No compile-time operations on this type yet. |
| if (V->getType() == Type::PPC_FP128Ty || DestTy == Type::PPC_FP128Ty) |
| return 0; |
| |
| // If the cast operand is a constant expression, there's a few things we can |
| // do to try to simplify it. |
| if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { |
| if (CE->isCast()) { |
| // Try hard to fold cast of cast because they are often eliminable. |
| if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy)) |
| return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); |
| } else if (CE->getOpcode() == Instruction::GetElementPtr) { |
| // If all of the indexes in the GEP are null values, there is no pointer |
| // adjustment going on. We might as well cast the source pointer. |
| bool isAllNull = true; |
| for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) |
| if (!CE->getOperand(i)->isNullValue()) { |
| isAllNull = false; |
| break; |
| } |
| if (isAllNull) |
| // This is casting one pointer type to another, always BitCast |
| return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy); |
| } |
| } |
| |
| // We actually have to do a cast now. Perform the cast according to the |
| // opcode specified. |
| switch (opc) { |
| case Instruction::FPTrunc: |
| case Instruction::FPExt: |
| if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { |
| APFloat Val = FPC->getValueAPF(); |
| Val.convert(DestTy == Type::FloatTy ? APFloat::IEEEsingle : |
| DestTy == Type::DoubleTy ? APFloat::IEEEdouble : |
| DestTy == Type::X86_FP80Ty ? APFloat::x87DoubleExtended : |
| DestTy == Type::FP128Ty ? APFloat::IEEEquad : |
| APFloat::Bogus, |
| APFloat::rmNearestTiesToEven); |
| return ConstantFP::get(DestTy, Val); |
| } |
| return 0; // Can't fold. |
| case Instruction::FPToUI: |
| case Instruction::FPToSI: |
| if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { |
| const APFloat &V = FPC->getValueAPF(); |
| uint64_t x[2]; |
| uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); |
| (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI, |
| APFloat::rmTowardZero); |
| APInt Val(DestBitWidth, 2, x); |
| return ConstantInt::get(Val); |
| } |
| if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) { |
| std::vector<Constant*> res; |
| const VectorType *DestVecTy = cast<VectorType>(DestTy); |
| const Type *DstEltTy = DestVecTy->getElementType(); |
| for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i) |
| res.push_back(ConstantFoldCastInstruction(opc, V->getOperand(i), |
| DstEltTy)); |
| return ConstantVector::get(DestVecTy, res); |
| } |
| return 0; // Can't fold. |
| case Instruction::IntToPtr: //always treated as unsigned |
| if (V->isNullValue()) // Is it an integral null value? |
| return ConstantPointerNull::get(cast<PointerType>(DestTy)); |
| return 0; // Other pointer types cannot be casted |
| case Instruction::PtrToInt: // always treated as unsigned |
| if (V->isNullValue()) // is it a null pointer value? |
| return ConstantInt::get(DestTy, 0); |
| return 0; // Other pointer types cannot be casted |
| case Instruction::UIToFP: |
| case Instruction::SIToFP: |
| if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { |
| APInt api = CI->getValue(); |
| const uint64_t zero[] = {0, 0}; |
| APFloat apf = APFloat(APInt(DestTy->getPrimitiveSizeInBits(), |
| 2, zero)); |
| (void)apf.convertFromAPInt(api, |
| opc==Instruction::SIToFP, |
| APFloat::rmNearestTiesToEven); |
| return ConstantFP::get(DestTy, apf); |
| } |
| if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) { |
| std::vector<Constant*> res; |
| const VectorType *DestVecTy = cast<VectorType>(DestTy); |
| const Type *DstEltTy = DestVecTy->getElementType(); |
| for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i) |
| res.push_back(ConstantFoldCastInstruction(opc, V->getOperand(i), |
| DstEltTy)); |
| return ConstantVector::get(DestVecTy, res); |
| } |
| return 0; |
| case Instruction::ZExt: |
| if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { |
| uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); |
| APInt Result(CI->getValue()); |
| Result.zext(BitWidth); |
| return ConstantInt::get(Result); |
| } |
| return 0; |
| case Instruction::SExt: |
| if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { |
| uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); |
| APInt Result(CI->getValue()); |
| Result.sext(BitWidth); |
| return ConstantInt::get(Result); |
| } |
| return 0; |
| case Instruction::Trunc: |
| if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { |
| uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); |
| APInt Result(CI->getValue()); |
| Result.trunc(BitWidth); |
| return ConstantInt::get(Result); |
| } |
| return 0; |
| case Instruction::BitCast: |
| return FoldBitCast(const_cast<Constant*>(V), DestTy); |
| default: |
| assert(!"Invalid CE CastInst opcode"); |
| break; |
| } |
| |
| assert(0 && "Failed to cast constant expression"); |
| return 0; |
| } |
| |
| Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond, |
| const Constant *V1, |
| const Constant *V2) { |
| if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond)) |
| return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2); |
| |
| if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2); |
| if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1); |
| if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1); |
| if (V1 == V2) return const_cast<Constant*>(V1); |
| return 0; |
| } |
| |
| Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val, |
| const Constant *Idx) { |
| if (isa<UndefValue>(Val)) // ee(undef, x) -> undef |
| return UndefValue::get(cast<VectorType>(Val->getType())->getElementType()); |
| if (Val->isNullValue()) // ee(zero, x) -> zero |
| return Constant::getNullValue( |
| cast<VectorType>(Val->getType())->getElementType()); |
| |
| if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) { |
| if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) { |
| return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue())); |
| } else if (isa<UndefValue>(Idx)) { |
| // ee({w,x,y,z}, undef) -> w (an arbitrary value). |
| return const_cast<Constant*>(CVal->getOperand(0)); |
| } |
| } |
| return 0; |
| } |
| |
| Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val, |
| const Constant *Elt, |
| const Constant *Idx) { |
| const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx); |
| if (!CIdx) return 0; |
| APInt idxVal = CIdx->getValue(); |
| if (isa<UndefValue>(Val)) { |
| // Insertion of scalar constant into vector undef |
| // Optimize away insertion of undef |
| if (isa<UndefValue>(Elt)) |
| return const_cast<Constant*>(Val); |
| // Otherwise break the aggregate undef into multiple undefs and do |
| // the insertion |
| unsigned numOps = |
| cast<VectorType>(Val->getType())->getNumElements(); |
| std::vector<Constant*> Ops; |
| Ops.reserve(numOps); |
| for (unsigned i = 0; i < numOps; ++i) { |
| const Constant *Op = |
| (idxVal == i) ? Elt : UndefValue::get(Elt->getType()); |
| Ops.push_back(const_cast<Constant*>(Op)); |
| } |
| return ConstantVector::get(Ops); |
| } |
| if (isa<ConstantAggregateZero>(Val)) { |
| // Insertion of scalar constant into vector aggregate zero |
| // Optimize away insertion of zero |
| if (Elt->isNullValue()) |
| return const_cast<Constant*>(Val); |
| // Otherwise break the aggregate zero into multiple zeros and do |
| // the insertion |
| unsigned numOps = |
| cast<VectorType>(Val->getType())->getNumElements(); |
| std::vector<Constant*> Ops; |
| Ops.reserve(numOps); |
| for (unsigned i = 0; i < numOps; ++i) { |
| const Constant *Op = |
| (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType()); |
| Ops.push_back(const_cast<Constant*>(Op)); |
| } |
| return ConstantVector::get(Ops); |
| } |
| if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) { |
| // Insertion of scalar constant into vector constant |
| std::vector<Constant*> Ops; |
| Ops.reserve(CVal->getNumOperands()); |
| for (unsigned i = 0; i < CVal->getNumOperands(); ++i) { |
| const Constant *Op = |
| (idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i)); |
| Ops.push_back(const_cast<Constant*>(Op)); |
| } |
| return ConstantVector::get(Ops); |
| } |
| return 0; |
| } |
| |
| /// GetVectorElement - If C is a ConstantVector, ConstantAggregateZero or Undef |
| /// return the specified element value. Otherwise return null. |
| static Constant *GetVectorElement(const Constant *C, unsigned EltNo) { |
| if (const ConstantVector *CV = dyn_cast<ConstantVector>(C)) |
| return const_cast<Constant*>(CV->getOperand(EltNo)); |
| |
| const Type *EltTy = cast<VectorType>(C->getType())->getElementType(); |
| if (isa<ConstantAggregateZero>(C)) |
| return Constant::getNullValue(EltTy); |
| if (isa<UndefValue>(C)) |
| return UndefValue::get(EltTy); |
| return 0; |
| } |
| |
| Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1, |
| const Constant *V2, |
| const Constant *Mask) { |
| // Undefined shuffle mask -> undefined value. |
| if (isa<UndefValue>(Mask)) return UndefValue::get(V1->getType()); |
| |
| unsigned NumElts = cast<VectorType>(V1->getType())->getNumElements(); |
| const Type *EltTy = cast<VectorType>(V1->getType())->getElementType(); |
| |
| // Loop over the shuffle mask, evaluating each element. |
| SmallVector<Constant*, 32> Result; |
| for (unsigned i = 0; i != NumElts; ++i) { |
| Constant *InElt = GetVectorElement(Mask, i); |
| if (InElt == 0) return 0; |
| |
| if (isa<UndefValue>(InElt)) |
| InElt = UndefValue::get(EltTy); |
| else if (ConstantInt *CI = dyn_cast<ConstantInt>(InElt)) { |
| unsigned Elt = CI->getZExtValue(); |
| if (Elt >= NumElts*2) |
| InElt = UndefValue::get(EltTy); |
| else if (Elt >= NumElts) |
| InElt = GetVectorElement(V2, Elt-NumElts); |
| else |
| InElt = GetVectorElement(V1, Elt); |
| if (InElt == 0) return 0; |
| } else { |
| // Unknown value. |
| return 0; |
| } |
| Result.push_back(InElt); |
| } |
| |
| return ConstantVector::get(&Result[0], Result.size()); |
| } |
| |
| /// EvalVectorOp - Given two vector constants and a function pointer, apply the |
| /// function pointer to each element pair, producing a new ConstantVector |
| /// constant. Either or both of V1 and V2 may be NULL, meaning a |
| /// ConstantAggregateZero operand. |
| static Constant *EvalVectorOp(const ConstantVector *V1, |
| const ConstantVector *V2, |
| const VectorType *VTy, |
| Constant *(*FP)(Constant*, Constant*)) { |
| std::vector<Constant*> Res; |
| const Type *EltTy = VTy->getElementType(); |
| for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { |
| const Constant *C1 = V1 ? V1->getOperand(i) : Constant::getNullValue(EltTy); |
| const Constant *C2 = V2 ? V2->getOperand(i) : Constant::getNullValue(EltTy); |
| Res.push_back(FP(const_cast<Constant*>(C1), |
| const_cast<Constant*>(C2))); |
| } |
| return ConstantVector::get(Res); |
| } |
| |
| Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, |
| const Constant *C1, |
| const Constant *C2) { |
| // No compile-time operations on this type yet. |
| if (C1->getType() == Type::PPC_FP128Ty) |
| return 0; |
| |
| // Handle UndefValue up front |
| if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { |
| switch (Opcode) { |
| case Instruction::Xor: |
| if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) |
| // Handle undef ^ undef -> 0 special case. This is a common |
| // idiom (misuse). |
| return Constant::getNullValue(C1->getType()); |
| // Fallthrough |
| case Instruction::Add: |
| case Instruction::Sub: |
| return UndefValue::get(C1->getType()); |
| case Instruction::Mul: |
| case Instruction::And: |
| return Constant::getNullValue(C1->getType()); |
| case Instruction::UDiv: |
| case Instruction::SDiv: |
| case Instruction::FDiv: |
| case Instruction::URem: |
| case Instruction::SRem: |
| case Instruction::FRem: |
| if (!isa<UndefValue>(C2)) // undef / X -> 0 |
| return Constant::getNullValue(C1->getType()); |
| return const_cast<Constant*>(C2); // X / undef -> undef |
| case Instruction::Or: // X | undef -> -1 |
| if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType())) |
| return ConstantVector::getAllOnesValue(PTy); |
| return ConstantInt::getAllOnesValue(C1->getType()); |
| case Instruction::LShr: |
| if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) |
| return const_cast<Constant*>(C1); // undef lshr undef -> undef |
| return Constant::getNullValue(C1->getType()); // X lshr undef -> 0 |
| // undef lshr X -> 0 |
| case Instruction::AShr: |
| if (!isa<UndefValue>(C2)) |
| return const_cast<Constant*>(C1); // undef ashr X --> undef |
| else if (isa<UndefValue>(C1)) |
| return const_cast<Constant*>(C1); // undef ashr undef -> undef |
| else |
| return const_cast<Constant*>(C1); // X ashr undef --> X |
| case Instruction::Shl: |
| // undef << X -> 0 or X << undef -> 0 |
| return Constant::getNullValue(C1->getType()); |
| } |
| } |
| |
| if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { |
| if (isa<ConstantExpr>(C2)) { |
| // There are many possible foldings we could do here. We should probably |
| // at least fold add of a pointer with an integer into the appropriate |
| // getelementptr. This will improve alias analysis a bit. |
| } else { |
| // Just implement a couple of simple identities. |
| switch (Opcode) { |
| case Instruction::Add: |
| if (C2->isNullValue()) return const_cast<Constant*>(C1); // X + 0 == X |
| break; |
| case Instruction::Sub: |
| if (C2->isNullValue()) return const_cast<Constant*>(C1); // X - 0 == X |
| break; |
| case Instruction::Mul: |
| if (C2->isNullValue()) return const_cast<Constant*>(C2); // X * 0 == 0 |
| if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) |
| if (CI->equalsInt(1)) |
| return const_cast<Constant*>(C1); // X * 1 == X |
| break; |
| case Instruction::UDiv: |
| case Instruction::SDiv: |
| if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) |
| if (CI->equalsInt(1)) |
| return const_cast<Constant*>(C1); // X / 1 == X |
| break; |
| case Instruction::URem: |
| case Instruction::SRem: |
| if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) |
| if (CI->equalsInt(1)) |
| return Constant::getNullValue(CI->getType()); // X % 1 == 0 |
| break; |
| case Instruction::And: |
| if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) { |
| if (CI->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0 |
| if (CI->isAllOnesValue()) |
| return const_cast<Constant*>(C1); // X & -1 == X |
| |
| // (zext i32 to i64) & 4294967295 -> (zext i32 to i64) |
| if (CE1->getOpcode() == Instruction::ZExt) { |
| APInt PossiblySetBits |
| = cast<IntegerType>(CE1->getOperand(0)->getType())->getMask(); |
| PossiblySetBits.zext(C1->getType()->getPrimitiveSizeInBits()); |
| if ((PossiblySetBits & CI->getValue()) == PossiblySetBits) |
| return const_cast<Constant*>(C1); |
| } |
| } |
| if (CE1->isCast() && isa<GlobalValue>(CE1->getOperand(0))) { |
| GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0)); |
| |
| // Functions are at least 4-byte aligned. If and'ing the address of a |
| // function with a constant < 4, fold it to zero. |
| if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) |
| if (CI->getValue().ult(APInt(CI->getType()->getBitWidth(),4)) && |
| isa<Function>(CPR)) |
| return Constant::getNullValue(CI->getType()); |
| } |
| break; |
| case Instruction::Or: |
| if (C2->isNullValue()) return const_cast<Constant*>(C1); // X | 0 == X |
| if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) |
| if (CI->isAllOnesValue()) |
| return const_cast<Constant*>(C2); // X | -1 == -1 |
| break; |
| case Instruction::Xor: |
| if (C2->isNullValue()) return const_cast<Constant*>(C1); // X ^ 0 == X |
| break; |
| case Instruction::AShr: |
| // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2 |
| if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero. |
| return ConstantExpr::getLShr(const_cast<Constant*>(C1), |
| const_cast<Constant*>(C2)); |
| break; |
| } |
| } |
| } else if (isa<ConstantExpr>(C2)) { |
| // If C2 is a constant expr and C1 isn't, flop them around and fold the |
| // other way if possible. |
| switch (Opcode) { |
| case Instruction::Add: |
| case Instruction::Mul: |
| case Instruction::And: |
| case Instruction::Or: |
| case Instruction::Xor: |
| // No change of opcode required. |
| return ConstantFoldBinaryInstruction(Opcode, C2, C1); |
| |
| case Instruction::Shl: |
| case Instruction::LShr: |
| case Instruction::AShr: |
| case Instruction::Sub: |
| case Instruction::SDiv: |
| case Instruction::UDiv: |
| case Instruction::FDiv: |
| case Instruction::URem: |
| case Instruction::SRem: |
| case Instruction::FRem: |
| default: // These instructions cannot be flopped around. |
| return 0; |
| } |
| } |
| |
| // At this point we know neither constant is an UndefValue nor a ConstantExpr |
| // so look at directly computing the value. |
| if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) { |
| if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { |
| using namespace APIntOps; |
| APInt C1V = CI1->getValue(); |
| APInt C2V = CI2->getValue(); |
| switch (Opcode) { |
| default: |
| break; |
| case Instruction::Add: |
| return ConstantInt::get(C1V + C2V); |
| case Instruction::Sub: |
| return ConstantInt::get(C1V - C2V); |
| case Instruction::Mul: |
| return ConstantInt::get(C1V * C2V); |
| case Instruction::UDiv: |
| if (CI2->isNullValue()) |
| return 0; // X / 0 -> can't fold |
| return ConstantInt::get(C1V.udiv(C2V)); |
| case Instruction::SDiv: |
| if (CI2->isNullValue()) |
| return 0; // X / 0 -> can't fold |
| if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) |
| return 0; // MIN_INT / -1 -> overflow |
| return ConstantInt::get(C1V.sdiv(C2V)); |
| case Instruction::URem: |
| if (C2->isNullValue()) |
| return 0; // X / 0 -> can't fold |
| return ConstantInt::get(C1V.urem(C2V)); |
| case Instruction::SRem: |
| if (CI2->isNullValue()) |
| return 0; // X % 0 -> can't fold |
| if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) |
| return 0; // MIN_INT % -1 -> overflow |
| return ConstantInt::get(C1V.srem(C2V)); |
| case Instruction::And: |
| return ConstantInt::get(C1V & C2V); |
| case Instruction::Or: |
| return ConstantInt::get(C1V | C2V); |
| case Instruction::Xor: |
| return ConstantInt::get(C1V ^ C2V); |
| case Instruction::Shl: |
| if (uint32_t shiftAmt = C2V.getZExtValue()) { |
| if (shiftAmt < C1V.getBitWidth()) |
| return ConstantInt::get(C1V.shl(shiftAmt)); |
| else |
| return UndefValue::get(C1->getType()); // too big shift is undef |
| } |
| return const_cast<ConstantInt*>(CI1); // Zero shift is identity |
| case Instruction::LShr: |
| if (uint32_t shiftAmt = C2V.getZExtValue()) { |
| if (shiftAmt < C1V.getBitWidth()) |
| return ConstantInt::get(C1V.lshr(shiftAmt)); |
| else |
| return UndefValue::get(C1->getType()); // too big shift is undef |
| } |
| return const_cast<ConstantInt*>(CI1); // Zero shift is identity |
| case Instruction::AShr: |
| if (uint32_t shiftAmt = C2V.getZExtValue()) { |
| if (shiftAmt < C1V.getBitWidth()) |
| return ConstantInt::get(C1V.ashr(shiftAmt)); |
| else |
| return UndefValue::get(C1->getType()); // too big shift is undef |
| } |
| return const_cast<ConstantInt*>(CI1); // Zero shift is identity |
| } |
| } |
| } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) { |
| if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) { |
| APFloat C1V = CFP1->getValueAPF(); |
| APFloat C2V = CFP2->getValueAPF(); |
| APFloat C3V = C1V; // copy for modification |
| bool isDouble = CFP1->getType()==Type::DoubleTy; |
| switch (Opcode) { |
| default: |
| break; |
| case Instruction::Add: |
| (void)C3V.add(C2V, APFloat::rmNearestTiesToEven); |
| return ConstantFP::get(CFP1->getType(), C3V); |
| case Instruction::Sub: |
| (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven); |
| return ConstantFP::get(CFP1->getType(), C3V); |
| case Instruction::Mul: |
| (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven); |
| return ConstantFP::get(CFP1->getType(), C3V); |
| case Instruction::FDiv: |
| (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven); |
| return ConstantFP::get(CFP1->getType(), C3V); |
| case Instruction::FRem: |
| if (C2V.isZero()) |
| // IEEE 754, Section 7.1, #5 |
| return ConstantFP::get(CFP1->getType(), isDouble ? |
| APFloat(std::numeric_limits<double>::quiet_NaN()) : |
| APFloat(std::numeric_limits<float>::quiet_NaN())); |
| (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven); |
| return ConstantFP::get(CFP1->getType(), C3V); |
| } |
| } |
| } else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) { |
| const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1); |
| const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2); |
| if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) && |
| (CP2 != NULL || isa<ConstantAggregateZero>(C2))) { |
| switch (Opcode) { |
| default: |
| break; |
| case Instruction::Add: |
| return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAdd); |
| case Instruction::Sub: |
| return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSub); |
| case Instruction::Mul: |
| return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getMul); |
| case Instruction::UDiv: |
| return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getUDiv); |
| case Instruction::SDiv: |
| return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSDiv); |
| case Instruction::FDiv: |
| return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFDiv); |
| case Instruction::URem: |
| return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getURem); |
| case Instruction::SRem: |
| return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getSRem); |
| case Instruction::FRem: |
| return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getFRem); |
| case Instruction::And: |
| return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getAnd); |
| case Instruction::Or: |
| return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getOr); |
| case Instruction::Xor: |
| return EvalVectorOp(CP1, CP2, VTy, ConstantExpr::getXor); |
| } |
| } |
| } |
| |
| // We don't know how to fold this |
| return 0; |
| } |
| |
| /// isZeroSizedType - This type is zero sized if its an array or structure of |
| /// zero sized types. The only leaf zero sized type is an empty structure. |
| static bool isMaybeZeroSizedType(const Type *Ty) { |
| if (isa<OpaqueType>(Ty)) return true; // Can't say. |
| if (const StructType *STy = dyn_cast<StructType>(Ty)) { |
| |
| // If all of elements have zero size, this does too. |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) |
| if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; |
| return true; |
| |
| } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { |
| return isMaybeZeroSizedType(ATy->getElementType()); |
| } |
| return false; |
| } |
| |
| /// IdxCompare - Compare the two constants as though they were getelementptr |
| /// indices. This allows coersion of the types to be the same thing. |
| /// |
| /// If the two constants are the "same" (after coersion), return 0. If the |
| /// first is less than the second, return -1, if the second is less than the |
| /// first, return 1. If the constants are not integral, return -2. |
| /// |
| static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) { |
| if (C1 == C2) return 0; |
| |
| // Ok, we found a different index. If they are not ConstantInt, we can't do |
| // anything with them. |
| if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) |
| return -2; // don't know! |
| |
| // Ok, we have two differing integer indices. Sign extend them to be the same |
| // type. Long is always big enough, so we use it. |
| if (C1->getType() != Type::Int64Ty) |
| C1 = ConstantExpr::getSExt(C1, Type::Int64Ty); |
| |
| if (C2->getType() != Type::Int64Ty) |
| C2 = ConstantExpr::getSExt(C2, Type::Int64Ty); |
| |
| if (C1 == C2) return 0; // They are equal |
| |
| // If the type being indexed over is really just a zero sized type, there is |
| // no pointer difference being made here. |
| if (isMaybeZeroSizedType(ElTy)) |
| return -2; // dunno. |
| |
| // If they are really different, now that they are the same type, then we |
| // found a difference! |
| if (cast<ConstantInt>(C1)->getSExtValue() < |
| cast<ConstantInt>(C2)->getSExtValue()) |
| return -1; |
| else |
| return 1; |
| } |
| |
| /// evaluateFCmpRelation - This function determines if there is anything we can |
| /// decide about the two constants provided. This doesn't need to handle simple |
| /// things like ConstantFP comparisons, but should instead handle ConstantExprs. |
| /// If we can determine that the two constants have a particular relation to |
| /// each other, we should return the corresponding FCmpInst predicate, |
| /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in |
| /// ConstantFoldCompareInstruction. |
| /// |
| /// To simplify this code we canonicalize the relation so that the first |
| /// operand is always the most "complex" of the two. We consider ConstantFP |
| /// to be the simplest, and ConstantExprs to be the most complex. |
| static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1, |
| const Constant *V2) { |
| assert(V1->getType() == V2->getType() && |
| "Cannot compare values of different types!"); |
| |
| // No compile-time operations on this type yet. |
| if (V1->getType() == Type::PPC_FP128Ty) |
| return FCmpInst::BAD_FCMP_PREDICATE; |
| |
| // Handle degenerate case quickly |
| if (V1 == V2) return FCmpInst::FCMP_OEQ; |
| |
| if (!isa<ConstantExpr>(V1)) { |
| if (!isa<ConstantExpr>(V2)) { |
| // We distilled thisUse the standard constant folder for a few cases |
| ConstantInt *R = 0; |
| Constant *C1 = const_cast<Constant*>(V1); |
| Constant *C2 = const_cast<Constant*>(V2); |
| R = dyn_cast<ConstantInt>( |
| ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2)); |
| if (R && !R->isZero()) |
| return FCmpInst::FCMP_OEQ; |
| R = dyn_cast<ConstantInt>( |
| ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2)); |
| if (R && !R->isZero()) |
| return FCmpInst::FCMP_OLT; |
| R = dyn_cast<ConstantInt>( |
| ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2)); |
| if (R && !R->isZero()) |
| return FCmpInst::FCMP_OGT; |
| |
| // Nothing more we can do |
| return FCmpInst::BAD_FCMP_PREDICATE; |
| } |
| |
| // If the first operand is simple and second is ConstantExpr, swap operands. |
| FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); |
| if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) |
| return FCmpInst::getSwappedPredicate(SwappedRelation); |
| } else { |
| // Ok, the LHS is known to be a constantexpr. The RHS can be any of a |
| // constantexpr or a simple constant. |
| const ConstantExpr *CE1 = cast<ConstantExpr>(V1); |
| switch (CE1->getOpcode()) { |
| case Instruction::FPTrunc: |
| case Instruction::FPExt: |
| case Instruction::UIToFP: |
| case Instruction::SIToFP: |
| // We might be able to do something with these but we don't right now. |
| break; |
| default: |
| break; |
| } |
| } |
| // There are MANY other foldings that we could perform here. They will |
| // probably be added on demand, as they seem needed. |
| return FCmpInst::BAD_FCMP_PREDICATE; |
| } |
| |
| /// evaluateICmpRelation - This function determines if there is anything we can |
| /// decide about the two constants provided. This doesn't need to handle simple |
| /// things like integer comparisons, but should instead handle ConstantExprs |
| /// and GlobalValues. If we can determine that the two constants have a |
| /// particular relation to each other, we should return the corresponding ICmp |
| /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE. |
| /// |
| /// To simplify this code we canonicalize the relation so that the first |
| /// operand is always the most "complex" of the two. We consider simple |
| /// constants (like ConstantInt) to be the simplest, followed by |
| /// GlobalValues, followed by ConstantExpr's (the most complex). |
| /// |
| static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1, |
| const Constant *V2, |
| bool isSigned) { |
| assert(V1->getType() == V2->getType() && |
| "Cannot compare different types of values!"); |
| if (V1 == V2) return ICmpInst::ICMP_EQ; |
| |
| if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) { |
| if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) { |
| // We distilled this down to a simple case, use the standard constant |
| // folder. |
| ConstantInt *R = 0; |
| Constant *C1 = const_cast<Constant*>(V1); |
| Constant *C2 = const_cast<Constant*>(V2); |
| ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; |
| R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); |
| if (R && !R->isZero()) |
| return pred; |
| pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; |
| R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); |
| if (R && !R->isZero()) |
| return pred; |
| pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; |
| R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); |
| if (R && !R->isZero()) |
| return pred; |
| |
| // If we couldn't figure it out, bail. |
| return ICmpInst::BAD_ICMP_PREDICATE; |
| } |
| |
| // If the first operand is simple, swap operands. |
| ICmpInst::Predicate SwappedRelation = |
| evaluateICmpRelation(V2, V1, isSigned); |
| if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) |
| return ICmpInst::getSwappedPredicate(SwappedRelation); |
| |
| } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) { |
| if (isa<ConstantExpr>(V2)) { // Swap as necessary. |
| ICmpInst::Predicate SwappedRelation = |
| evaluateICmpRelation(V2, V1, isSigned); |
| if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) |
| return ICmpInst::getSwappedPredicate(SwappedRelation); |
| else |
| return ICmpInst::BAD_ICMP_PREDICATE; |
| } |
| |
| // Now we know that the RHS is a GlobalValue or simple constant, |
| // which (since the types must match) means that it's a ConstantPointerNull. |
| if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { |
| // Don't try to decide equality of aliases. |
| if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2)) |
| if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage()) |
| return ICmpInst::ICMP_NE; |
| } else { |
| assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); |
| // GlobalVals can never be null. Don't try to evaluate aliases. |
| if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1)) |
| return ICmpInst::ICMP_NE; |
| } |
| } else { |
| // Ok, the LHS is known to be a constantexpr. The RHS can be any of a |
| // constantexpr, a CPR, or a simple constant. |
| const ConstantExpr *CE1 = cast<ConstantExpr>(V1); |
| const Constant *CE1Op0 = CE1->getOperand(0); |
| |
| switch (CE1->getOpcode()) { |
| case Instruction::Trunc: |
| case Instruction::FPTrunc: |
| case Instruction::FPExt: |
| case Instruction::FPToUI: |
| case Instruction::FPToSI: |
| break; // We can't evaluate floating point casts or truncations. |
| |
| case Instruction::UIToFP: |
| case Instruction::SIToFP: |
| case Instruction::BitCast: |
| case Instruction::ZExt: |
| case Instruction::SExt: |
| // If the cast is not actually changing bits, and the second operand is a |
| // null pointer, do the comparison with the pre-casted value. |
| if (V2->isNullValue() && |
| (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) { |
| bool sgnd = isSigned; |
| if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; |
| if (CE1->getOpcode() == Instruction::SExt) isSigned = true; |
| return evaluateICmpRelation(CE1Op0, |
| Constant::getNullValue(CE1Op0->getType()), |
| sgnd); |
| } |
| |
| // If the dest type is a pointer type, and the RHS is a constantexpr cast |
| // from the same type as the src of the LHS, evaluate the inputs. This is |
| // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)", |
| // which happens a lot in compilers with tagged integers. |
| if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) |
| if (CE2->isCast() && isa<PointerType>(CE1->getType()) && |
| CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() && |
| CE1->getOperand(0)->getType()->isInteger()) { |
| bool sgnd = isSigned; |
| if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; |
| if (CE1->getOpcode() == Instruction::SExt) isSigned = true; |
| return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0), |
| sgnd); |
| } |
| break; |
| |
| case Instruction::GetElementPtr: |
| // Ok, since this is a getelementptr, we know that the constant has a |
| // pointer type. Check the various cases. |
| if (isa<ConstantPointerNull>(V2)) { |
| // If we are comparing a GEP to a null pointer, check to see if the base |
| // of the GEP equals the null pointer. |
| if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { |
| if (GV->hasExternalWeakLinkage()) |
| // Weak linkage GVals could be zero or not. We're comparing that |
| // to null pointer so its greater-or-equal |
| return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; |
| else |
| // If its not weak linkage, the GVal must have a non-zero address |
| // so the result is greater-than |
| return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; |
| } else if (isa<ConstantPointerNull>(CE1Op0)) { |
| // If we are indexing from a null pointer, check to see if we have any |
| // non-zero indices. |
| for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) |
| if (!CE1->getOperand(i)->isNullValue()) |
| // Offsetting from null, must not be equal. |
| return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; |
| // Only zero indexes from null, must still be zero. |
| return ICmpInst::ICMP_EQ; |
| } |
| // Otherwise, we can't really say if the first operand is null or not. |
| } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { |
| if (isa<ConstantPointerNull>(CE1Op0)) { |
| if (CPR2->hasExternalWeakLinkage()) |
| // Weak linkage GVals could be zero or not. We're comparing it to |
| // a null pointer, so its less-or-equal |
| return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; |
| else |
| // If its not weak linkage, the GVal must have a non-zero address |
| // so the result is less-than |
| return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; |
| } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) { |
| if (CPR1 == CPR2) { |
| // If this is a getelementptr of the same global, then it must be |
| // different. Because the types must match, the getelementptr could |
| // only have at most one index, and because we fold getelementptr's |
| // with a single zero index, it must be nonzero. |
| assert(CE1->getNumOperands() == 2 && |
| !CE1->getOperand(1)->isNullValue() && |
| "Suprising getelementptr!"); |
| return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; |
| } else { |
| // If they are different globals, we don't know what the value is, |
| // but they can't be equal. |
| return ICmpInst::ICMP_NE; |
| } |
| } |
| } else { |
| const ConstantExpr *CE2 = cast<ConstantExpr>(V2); |
| const Constant *CE2Op0 = CE2->getOperand(0); |
| |
| // There are MANY other foldings that we could perform here. They will |
| // probably be added on demand, as they seem needed. |
| switch (CE2->getOpcode()) { |
| default: break; |
| case Instruction::GetElementPtr: |
| // By far the most common case to handle is when the base pointers are |
| // obviously to the same or different globals. |
| if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { |
| if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal |
| return ICmpInst::ICMP_NE; |
| // Ok, we know that both getelementptr instructions are based on the |
| // same global. From this, we can precisely determine the relative |
| // ordering of the resultant pointers. |
| unsigned i = 1; |
| |
| // Compare all of the operands the GEP's have in common. |
| gep_type_iterator GTI = gep_type_begin(CE1); |
| for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); |
| ++i, ++GTI) |
| switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i), |
| GTI.getIndexedType())) { |
| case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; |
| case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; |
| case -2: return ICmpInst::BAD_ICMP_PREDICATE; |
| } |
| |
| // Ok, we ran out of things they have in common. If any leftovers |
| // are non-zero then we have a difference, otherwise we are equal. |
| for (; i < CE1->getNumOperands(); ++i) |
| if (!CE1->getOperand(i)->isNullValue()) { |
| if (isa<ConstantInt>(CE1->getOperand(i))) |
| return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; |
| else |
| return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. |
| } |
| |
| for (; i < CE2->getNumOperands(); ++i) |
| if (!CE2->getOperand(i)->isNullValue()) { |
| if (isa<ConstantInt>(CE2->getOperand(i))) |
| return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; |
| else |
| return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. |
| } |
| return ICmpInst::ICMP_EQ; |
| } |
| } |
| } |
| default: |
| break; |
| } |
| } |
| |
| return ICmpInst::BAD_ICMP_PREDICATE; |
| } |
| |
| Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, |
| const Constant *C1, |
| const Constant *C2) { |
| |
| // Handle some degenerate cases first |
| if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) |
| return UndefValue::get(Type::Int1Ty); |
| |
| // No compile-time operations on this type yet. |
| if (C1->getType() == Type::PPC_FP128Ty) |
| return 0; |
| |
| // icmp eq/ne(null,GV) -> false/true |
| if (C1->isNullValue()) { |
| if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2)) |
| // Don't try to evaluate aliases. External weak GV can be null. |
| if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { |
| if (pred == ICmpInst::ICMP_EQ) |
| return ConstantInt::getFalse(); |
| else if (pred == ICmpInst::ICMP_NE) |
| return ConstantInt::getTrue(); |
| } |
| // icmp eq/ne(GV,null) -> false/true |
| } else if (C2->isNullValue()) { |
| if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) |
| // Don't try to evaluate aliases. External weak GV can be null. |
| if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { |
| if (pred == ICmpInst::ICMP_EQ) |
| return ConstantInt::getFalse(); |
| else if (pred == ICmpInst::ICMP_NE) |
| return ConstantInt::getTrue(); |
| } |
| } |
| |
| if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { |
| APInt V1 = cast<ConstantInt>(C1)->getValue(); |
| APInt V2 = cast<ConstantInt>(C2)->getValue(); |
| switch (pred) { |
| default: assert(0 && "Invalid ICmp Predicate"); return 0; |
| case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2); |
| case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2); |
| case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2)); |
| case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2)); |
| case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2)); |
| case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2)); |
| case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2)); |
| case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2)); |
| case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2)); |
| case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2)); |
| } |
| } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { |
| APFloat C1V = cast<ConstantFP>(C1)->getValueAPF(); |
| APFloat C2V = cast<ConstantFP>(C2)->getValueAPF(); |
| APFloat::cmpResult R = C1V.compare(C2V); |
| switch (pred) { |
| default: assert(0 && "Invalid FCmp Predicate"); return 0; |
| case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse(); |
| case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue(); |
| case FCmpInst::FCMP_UNO: |
| return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered); |
| case FCmpInst::FCMP_ORD: |
| return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpUnordered); |
| case FCmpInst::FCMP_UEQ: |
| return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered || |
| R==APFloat::cmpEqual); |
| case FCmpInst::FCMP_OEQ: |
| return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpEqual); |
| case FCmpInst::FCMP_UNE: |
| return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpEqual); |
| case FCmpInst::FCMP_ONE: |
| return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan || |
| R==APFloat::cmpGreaterThan); |
| case FCmpInst::FCMP_ULT: |
| return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered || |
| R==APFloat::cmpLessThan); |
| case FCmpInst::FCMP_OLT: |
| return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan); |
| case FCmpInst::FCMP_UGT: |
| return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpUnordered || |
| R==APFloat::cmpGreaterThan); |
| case FCmpInst::FCMP_OGT: |
| return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan); |
| case FCmpInst::FCMP_ULE: |
| return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpGreaterThan); |
| case FCmpInst::FCMP_OLE: |
| return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpLessThan || |
| R==APFloat::cmpEqual); |
| case FCmpInst::FCMP_UGE: |
| return ConstantInt::get(Type::Int1Ty, R!=APFloat::cmpLessThan); |
| case FCmpInst::FCMP_OGE: |
| return ConstantInt::get(Type::Int1Ty, R==APFloat::cmpGreaterThan || |
| R==APFloat::cmpEqual); |
| } |
| } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) { |
| if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) { |
| if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) { |
| for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) { |
| Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, |
| const_cast<Constant*>(CP1->getOperand(i)), |
| const_cast<Constant*>(CP2->getOperand(i))); |
| if (ConstantInt *CB = dyn_cast<ConstantInt>(C)) |
| return CB; |
| } |
| // Otherwise, could not decide from any element pairs. |
| return 0; |
| } else if (pred == ICmpInst::ICMP_EQ) { |
| for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) { |
| Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ, |
| const_cast<Constant*>(CP1->getOperand(i)), |
| const_cast<Constant*>(CP2->getOperand(i))); |
| if (ConstantInt *CB = dyn_cast<ConstantInt>(C)) |
| return CB; |
| } |
| // Otherwise, could not decide from any element pairs. |
| return 0; |
| } |
| } |
| } |
| |
| if (C1->getType()->isFloatingPoint()) { |
| switch (evaluateFCmpRelation(C1, C2)) { |
| default: assert(0 && "Unknown relation!"); |
| case FCmpInst::FCMP_UNO: |
| case FCmpInst::FCMP_ORD: |
| case FCmpInst::FCMP_UEQ: |
| case FCmpInst::FCMP_UNE: |
| case FCmpInst::FCMP_ULT: |
| case FCmpInst::FCMP_UGT: |
| case FCmpInst::FCMP_ULE: |
| case FCmpInst::FCMP_UGE: |
| case FCmpInst::FCMP_TRUE: |
| case FCmpInst::FCMP_FALSE: |
| case FCmpInst::BAD_FCMP_PREDICATE: |
| break; // Couldn't determine anything about these constants. |
| case FCmpInst::FCMP_OEQ: // We know that C1 == C2 |
| return ConstantInt::get(Type::Int1Ty, |
| pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || |
| pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || |
| pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); |
| case FCmpInst::FCMP_OLT: // We know that C1 < C2 |
| return ConstantInt::get(Type::Int1Ty, |
| pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || |
| pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || |
| pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); |
| case FCmpInst::FCMP_OGT: // We know that C1 > C2 |
| return ConstantInt::get(Type::Int1Ty, |
| pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || |
| pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || |
| pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); |
| case FCmpInst::FCMP_OLE: // We know that C1 <= C2 |
| // We can only partially decide this relation. |
| if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) |
| return ConstantInt::getFalse(); |
| if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) |
| return ConstantInt::getTrue(); |
| break; |
| case FCmpInst::FCMP_OGE: // We known that C1 >= C2 |
| // We can only partially decide this relation. |
| if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) |
| return ConstantInt::getFalse(); |
| if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) |
| return ConstantInt::getTrue(); |
| break; |
| case ICmpInst::ICMP_NE: // We know that C1 != C2 |
| // We can only partially decide this relation. |
| if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) |
| return ConstantInt::getFalse(); |
| if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) |
| return ConstantInt::getTrue(); |
| break; |
| } |
| } else { |
| // Evaluate the relation between the two constants, per the predicate. |
| switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) { |
| default: assert(0 && "Unknown relational!"); |
| case ICmpInst::BAD_ICMP_PREDICATE: |
| break; // Couldn't determine anything about these constants. |
| case ICmpInst::ICMP_EQ: // We know the constants are equal! |
| // If we know the constants are equal, we can decide the result of this |
| // computation precisely. |
| return ConstantInt::get(Type::Int1Ty, |
| pred == ICmpInst::ICMP_EQ || |
| pred == ICmpInst::ICMP_ULE || |
| pred == ICmpInst::ICMP_SLE || |
| pred == ICmpInst::ICMP_UGE || |
| pred == ICmpInst::ICMP_SGE); |
| case ICmpInst::ICMP_ULT: |
| // If we know that C1 < C2, we can decide the result of this computation |
| // precisely. |
| return ConstantInt::get(Type::Int1Ty, |
| pred == ICmpInst::ICMP_ULT || |
| pred == ICmpInst::ICMP_NE || |
| pred == ICmpInst::ICMP_ULE); |
| case ICmpInst::ICMP_SLT: |
| // If we know that C1 < C2, we can decide the result of this computation |
| // precisely. |
| return ConstantInt::get(Type::Int1Ty, |
| pred == ICmpInst::ICMP_SLT || |
| pred == ICmpInst::ICMP_NE || |
| pred == ICmpInst::ICMP_SLE); |
| case ICmpInst::ICMP_UGT: |
| // If we know that C1 > C2, we can decide the result of this computation |
| // precisely. |
| return ConstantInt::get(Type::Int1Ty, |
| pred == ICmpInst::ICMP_UGT || |
| pred == ICmpInst::ICMP_NE || |
| pred == ICmpInst::ICMP_UGE); |
| case ICmpInst::ICMP_SGT: |
| // If we know that C1 > C2, we can decide the result of this computation |
| // precisely. |
| return ConstantInt::get(Type::Int1Ty, |
| pred == ICmpInst::ICMP_SGT || |
| pred == ICmpInst::ICMP_NE || |
| pred == ICmpInst::ICMP_SGE); |
| case ICmpInst::ICMP_ULE: |
| // If we know that C1 <= C2, we can only partially decide this relation. |
| if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse(); |
| if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue(); |
| break; |
| case ICmpInst::ICMP_SLE: |
| // If we know that C1 <= C2, we can only partially decide this relation. |
| if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse(); |
| if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue(); |
| break; |
| |
| case ICmpInst::ICMP_UGE: |
| // If we know that C1 >= C2, we can only partially decide this relation. |
| if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse(); |
| if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue(); |
| break; |
| case ICmpInst::ICMP_SGE: |
| // If we know that C1 >= C2, we can only partially decide this relation. |
| if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse(); |
| if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue(); |
| break; |
| |
| case ICmpInst::ICMP_NE: |
| // If we know that C1 != C2, we can only partially decide this relation. |
| if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(); |
| if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue(); |
| break; |
| } |
| |
| if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) { |
| // If C2 is a constant expr and C1 isn't, flop them around and fold the |
| // other way if possible. |
| switch (pred) { |
| case ICmpInst::ICMP_EQ: |
| case ICmpInst::ICMP_NE: |
| // No change of predicate required. |
| return ConstantFoldCompareInstruction(pred, C2, C1); |
| |
| case ICmpInst::ICMP_ULT: |
| case ICmpInst::ICMP_SLT: |
| case ICmpInst::ICMP_UGT: |
| case ICmpInst::ICMP_SGT: |
| case ICmpInst::ICMP_ULE: |
| case ICmpInst::ICMP_SLE: |
| case ICmpInst::ICMP_UGE: |
| case ICmpInst::ICMP_SGE: |
| // Change the predicate as necessary to swap the operands. |
| pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); |
| return ConstantFoldCompareInstruction(pred, C2, C1); |
| |
| default: // These predicates cannot be flopped around. |
| break; |
| } |
| } |
| } |
| return 0; |
| } |
| |
| Constant *llvm::ConstantFoldGetElementPtr(const Constant *C, |
| Constant* const *Idxs, |
| unsigned NumIdx) { |
| if (NumIdx == 0 || |
| (NumIdx == 1 && Idxs[0]->isNullValue())) |
| return const_cast<Constant*>(C); |
| |
| if (isa<UndefValue>(C)) { |
| const PointerType *Ptr = cast<PointerType>(C->getType()); |
| const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, |
| (Value **)Idxs, |
| (Value **)Idxs+NumIdx, |
| true); |
| assert(Ty != 0 && "Invalid indices for GEP!"); |
| return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace())); |
| } |
| |
| Constant *Idx0 = Idxs[0]; |
| if (C->isNullValue()) { |
| bool isNull = true; |
| for (unsigned i = 0, e = NumIdx; i != e; ++i) |
| if (!Idxs[i]->isNullValue()) { |
| isNull = false; |
| break; |
| } |
| if (isNull) { |
| const PointerType *Ptr = cast<PointerType>(C->getType()); |
| const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, |
| (Value**)Idxs, |
| (Value**)Idxs+NumIdx, |
| true); |
| assert(Ty != 0 && "Invalid indices for GEP!"); |
| return |
| ConstantPointerNull::get(PointerType::get(Ty,Ptr->getAddressSpace())); |
| } |
| } |
| |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) { |
| // Combine Indices - If the source pointer to this getelementptr instruction |
| // is a getelementptr instruction, combine the indices of the two |
| // getelementptr instructions into a single instruction. |
| // |
| if (CE->getOpcode() == Instruction::GetElementPtr) { |
| const Type *LastTy = 0; |
| for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); |
| I != E; ++I) |
| LastTy = *I; |
| |
| if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) { |
| SmallVector<Value*, 16> NewIndices; |
| NewIndices.reserve(NumIdx + CE->getNumOperands()); |
| for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) |
| NewIndices.push_back(CE->getOperand(i)); |
| |
| // Add the last index of the source with the first index of the new GEP. |
| // Make sure to handle the case when they are actually different types. |
| Constant *Combined = CE->getOperand(CE->getNumOperands()-1); |
| // Otherwise it must be an array. |
| if (!Idx0->isNullValue()) { |
| const Type *IdxTy = Combined->getType(); |
| if (IdxTy != Idx0->getType()) { |
| Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty); |
| Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, |
| Type::Int64Ty); |
| Combined = ConstantExpr::get(Instruction::Add, C1, C2); |
| } else { |
| Combined = |
| ConstantExpr::get(Instruction::Add, Idx0, Combined); |
| } |
| } |
| |
| NewIndices.push_back(Combined); |
| NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx); |
| return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0], |
| NewIndices.size()); |
| } |
| } |
| |
| // Implement folding of: |
| // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*), |
| // long 0, long 0) |
| // To: int* getelementptr ([3 x int]* %X, long 0, long 0) |
| // |
| if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) { |
| if (const PointerType *SPT = |
| dyn_cast<PointerType>(CE->getOperand(0)->getType())) |
| if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType())) |
| if (const ArrayType *CAT = |
| dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType())) |
| if (CAT->getElementType() == SAT->getElementType()) |
| return ConstantExpr::getGetElementPtr( |
| (Constant*)CE->getOperand(0), Idxs, NumIdx); |
| } |
| |
| // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1) |
| // Into: inttoptr (i64 0 to i8*) |
| // This happens with pointers to member functions in C++. |
| if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 && |
| isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) && |
| cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) { |
| Constant *Base = CE->getOperand(0); |
| Constant *Offset = Idxs[0]; |
| |
| // Convert the smaller integer to the larger type. |
| if (Offset->getType()->getPrimitiveSizeInBits() < |
| Base->getType()->getPrimitiveSizeInBits()) |
| Offset = ConstantExpr::getSExt(Offset, Base->getType()); |
| else if (Base->getType()->getPrimitiveSizeInBits() < |
| Offset->getType()->getPrimitiveSizeInBits()) |
| Base = ConstantExpr::getZExt(Base, Base->getType()); |
| |
| Base = ConstantExpr::getAdd(Base, Offset); |
| return ConstantExpr::getIntToPtr(Base, CE->getType()); |
| } |
| } |
| return 0; |
| } |
| |