| //===- ConstantFold.cpp - LLVM constant folder ----------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // 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 |
| // pieces that don't need DataLayout, and the pieces that do. This is to avoid |
| // a dependence in IR on Target. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/IR/ConstantFold.h" |
| #include "llvm/ADT/APSInt.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/IR/Constants.h" |
| #include "llvm/IR/DerivedTypes.h" |
| #include "llvm/IR/Function.h" |
| #include "llvm/IR/GetElementPtrTypeIterator.h" |
| #include "llvm/IR/GlobalAlias.h" |
| #include "llvm/IR/GlobalVariable.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/Module.h" |
| #include "llvm/IR/Operator.h" |
| #include "llvm/IR/PatternMatch.h" |
| #include "llvm/Support/ErrorHandling.h" |
| using namespace llvm; |
| using namespace llvm::PatternMatch; |
| |
| //===----------------------------------------------------------------------===// |
| // ConstantFold*Instruction Implementations |
| //===----------------------------------------------------------------------===// |
| |
| /// 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. |
| /// Determine if it is valid to fold a cast of a cast |
| static unsigned |
| foldConstantCastPair( |
| unsigned opc, ///< opcode of the second cast constant expression |
| ConstantExpr *Op, ///< the first cast constant expression |
| Type *DstTy ///< destination 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 types and opcodes for the two Cast constant expressions |
| Type *SrcTy = Op->getOperand(0)->getType(); |
| Type *MidTy = Op->getType(); |
| Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode()); |
| Instruction::CastOps secondOp = Instruction::CastOps(opc); |
| |
| // Assume that pointers are never more than 64 bits wide, and only use this |
| // for the middle type. Otherwise we could end up folding away illegal |
| // bitcasts between address spaces with different sizes. |
| IntegerType *FakeIntPtrTy = Type::getInt64Ty(DstTy->getContext()); |
| |
| // Let CastInst::isEliminableCastPair do the heavy lifting. |
| return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy, |
| nullptr, FakeIntPtrTy, nullptr); |
| } |
| |
| static Constant *FoldBitCast(Constant *V, Type *DestTy) { |
| Type *SrcTy = V->getType(); |
| if (SrcTy == DestTy) |
| return V; // no-op cast |
| |
| // 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 (VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) { |
| if (V->isAllOnesValue()) |
| return Constant::getAllOnesValue(DestTy); |
| |
| // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts |
| // This allows for other simplifications (although some of them |
| // can only be handled by Analysis/ConstantFolding.cpp). |
| if (isa<ConstantInt>(V) || isa<ConstantFP>(V)) |
| return ConstantExpr::getBitCast(ConstantVector::get(V), DestPTy); |
| return nullptr; |
| } |
| |
| // Handle integral constant input. |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { |
| // See note below regarding the PPC_FP128 restriction. |
| if (DestTy->isFloatingPointTy() && !DestTy->isPPC_FP128Ty()) |
| return ConstantFP::get(DestTy->getContext(), |
| APFloat(DestTy->getFltSemantics(), |
| CI->getValue())); |
| |
| // Otherwise, can't fold this (vector?) |
| return nullptr; |
| } |
| |
| // Handle ConstantFP input: FP -> Integral. |
| if (ConstantFP *FP = dyn_cast<ConstantFP>(V)) { |
| // PPC_FP128 is really the sum of two consecutive doubles, where the first |
| // double is always stored first in memory, regardless of the target |
| // endianness. The memory layout of i128, however, depends on the target |
| // endianness, and so we can't fold this without target endianness |
| // information. This should instead be handled by |
| // Analysis/ConstantFolding.cpp |
| if (FP->getType()->isPPC_FP128Ty()) |
| return nullptr; |
| |
| // Make sure dest type is compatible with the folded integer constant. |
| if (!DestTy->isIntegerTy()) |
| return nullptr; |
| |
| return ConstantInt::get(FP->getContext(), |
| FP->getValueAPF().bitcastToAPInt()); |
| } |
| |
| return nullptr; |
| } |
| |
| static Constant *foldMaybeUndesirableCast(unsigned opc, Constant *V, |
| Type *DestTy) { |
| return ConstantExpr::isDesirableCastOp(opc) |
| ? ConstantExpr::getCast(opc, V, DestTy) |
| : ConstantFoldCastInstruction(opc, V, DestTy); |
| } |
| |
| Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V, |
| Type *DestTy) { |
| if (isa<PoisonValue>(V)) |
| return PoisonValue::get(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); |
| } |
| |
| if (V->isNullValue() && !DestTy->isX86_AMXTy() && |
| opc != Instruction::AddrSpaceCast) |
| return Constant::getNullValue(DestTy); |
| |
| // If the cast operand is a constant expression, there's a few things we can |
| // do to try to simplify it. |
| if (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 foldMaybeUndesirableCast(newOpc, CE->getOperand(0), DestTy); |
| } |
| } |
| |
| // If the cast operand is a constant vector, perform the cast by |
| // operating on each element. In the cast of bitcasts, the element |
| // count may be mismatched; don't attempt to handle that here. |
| if ((isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) && |
| DestTy->isVectorTy() && |
| cast<FixedVectorType>(DestTy)->getNumElements() == |
| cast<FixedVectorType>(V->getType())->getNumElements()) { |
| VectorType *DestVecTy = cast<VectorType>(DestTy); |
| Type *DstEltTy = DestVecTy->getElementType(); |
| // Fast path for splatted constants. |
| if (Constant *Splat = V->getSplatValue()) { |
| Constant *Res = foldMaybeUndesirableCast(opc, Splat, DstEltTy); |
| if (!Res) |
| return nullptr; |
| return ConstantVector::getSplat( |
| cast<VectorType>(DestTy)->getElementCount(), Res); |
| } |
| SmallVector<Constant *, 16> res; |
| Type *Ty = IntegerType::get(V->getContext(), 32); |
| for (unsigned i = 0, |
| e = cast<FixedVectorType>(V->getType())->getNumElements(); |
| i != e; ++i) { |
| Constant *C = ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i)); |
| Constant *Casted = foldMaybeUndesirableCast(opc, C, DstEltTy); |
| if (!Casted) |
| return nullptr; |
| res.push_back(Casted); |
| } |
| return ConstantVector::get(res); |
| } |
| |
| // We actually have to do a cast now. Perform the cast according to the |
| // opcode specified. |
| switch (opc) { |
| default: |
| llvm_unreachable("Failed to cast constant expression"); |
| case Instruction::FPTrunc: |
| case Instruction::FPExt: |
| if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { |
| bool ignored; |
| APFloat Val = FPC->getValueAPF(); |
| Val.convert(DestTy->getFltSemantics(), APFloat::rmNearestTiesToEven, |
| &ignored); |
| return ConstantFP::get(V->getContext(), Val); |
| } |
| return nullptr; // Can't fold. |
| case Instruction::FPToUI: |
| case Instruction::FPToSI: |
| if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { |
| const APFloat &V = FPC->getValueAPF(); |
| bool ignored; |
| uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); |
| APSInt IntVal(DestBitWidth, opc == Instruction::FPToUI); |
| if (APFloat::opInvalidOp == |
| V.convertToInteger(IntVal, APFloat::rmTowardZero, &ignored)) { |
| // Undefined behavior invoked - the destination type can't represent |
| // the input constant. |
| return PoisonValue::get(DestTy); |
| } |
| return ConstantInt::get(FPC->getContext(), IntVal); |
| } |
| return nullptr; // Can't fold. |
| case Instruction::UIToFP: |
| case Instruction::SIToFP: |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { |
| const APInt &api = CI->getValue(); |
| APFloat apf(DestTy->getFltSemantics(), |
| APInt::getZero(DestTy->getPrimitiveSizeInBits())); |
| apf.convertFromAPInt(api, opc==Instruction::SIToFP, |
| APFloat::rmNearestTiesToEven); |
| return ConstantFP::get(V->getContext(), apf); |
| } |
| return nullptr; |
| case Instruction::ZExt: |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { |
| uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); |
| return ConstantInt::get(V->getContext(), |
| CI->getValue().zext(BitWidth)); |
| } |
| return nullptr; |
| case Instruction::SExt: |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { |
| uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); |
| return ConstantInt::get(V->getContext(), |
| CI->getValue().sext(BitWidth)); |
| } |
| return nullptr; |
| case Instruction::Trunc: { |
| if (V->getType()->isVectorTy()) |
| return nullptr; |
| |
| uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { |
| return ConstantInt::get(V->getContext(), |
| CI->getValue().trunc(DestBitWidth)); |
| } |
| |
| return nullptr; |
| } |
| case Instruction::BitCast: |
| return FoldBitCast(V, DestTy); |
| case Instruction::AddrSpaceCast: |
| case Instruction::IntToPtr: |
| case Instruction::PtrToInt: |
| return nullptr; |
| } |
| } |
| |
| Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond, |
| Constant *V1, Constant *V2) { |
| // Check for i1 and vector true/false conditions. |
| if (Cond->isNullValue()) return V2; |
| if (Cond->isAllOnesValue()) return V1; |
| |
| // If the condition is a vector constant, fold the result elementwise. |
| if (ConstantVector *CondV = dyn_cast<ConstantVector>(Cond)) { |
| auto *V1VTy = CondV->getType(); |
| SmallVector<Constant*, 16> Result; |
| Type *Ty = IntegerType::get(CondV->getContext(), 32); |
| for (unsigned i = 0, e = V1VTy->getNumElements(); i != e; ++i) { |
| Constant *V; |
| Constant *V1Element = ConstantExpr::getExtractElement(V1, |
| ConstantInt::get(Ty, i)); |
| Constant *V2Element = ConstantExpr::getExtractElement(V2, |
| ConstantInt::get(Ty, i)); |
| auto *Cond = cast<Constant>(CondV->getOperand(i)); |
| if (isa<PoisonValue>(Cond)) { |
| V = PoisonValue::get(V1Element->getType()); |
| } else if (V1Element == V2Element) { |
| V = V1Element; |
| } else if (isa<UndefValue>(Cond)) { |
| V = isa<UndefValue>(V1Element) ? V1Element : V2Element; |
| } else { |
| if (!isa<ConstantInt>(Cond)) break; |
| V = Cond->isNullValue() ? V2Element : V1Element; |
| } |
| Result.push_back(V); |
| } |
| |
| // If we were able to build the vector, return it. |
| if (Result.size() == V1VTy->getNumElements()) |
| return ConstantVector::get(Result); |
| } |
| |
| if (isa<PoisonValue>(Cond)) |
| return PoisonValue::get(V1->getType()); |
| |
| if (isa<UndefValue>(Cond)) { |
| if (isa<UndefValue>(V1)) return V1; |
| return V2; |
| } |
| |
| if (V1 == V2) return V1; |
| |
| if (isa<PoisonValue>(V1)) |
| return V2; |
| if (isa<PoisonValue>(V2)) |
| return V1; |
| |
| // If the true or false value is undef, we can fold to the other value as |
| // long as the other value isn't poison. |
| auto NotPoison = [](Constant *C) { |
| if (isa<PoisonValue>(C)) |
| return false; |
| |
| // TODO: We can analyze ConstExpr by opcode to determine if there is any |
| // possibility of poison. |
| if (isa<ConstantExpr>(C)) |
| return false; |
| |
| if (isa<ConstantInt>(C) || isa<GlobalVariable>(C) || isa<ConstantFP>(C) || |
| isa<ConstantPointerNull>(C) || isa<Function>(C)) |
| return true; |
| |
| if (C->getType()->isVectorTy()) |
| return !C->containsPoisonElement() && !C->containsConstantExpression(); |
| |
| // TODO: Recursively analyze aggregates or other constants. |
| return false; |
| }; |
| if (isa<UndefValue>(V1) && NotPoison(V2)) return V2; |
| if (isa<UndefValue>(V2) && NotPoison(V1)) return V1; |
| |
| return nullptr; |
| } |
| |
| Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val, |
| Constant *Idx) { |
| auto *ValVTy = cast<VectorType>(Val->getType()); |
| |
| // extractelt poison, C -> poison |
| // extractelt C, undef -> poison |
| if (isa<PoisonValue>(Val) || isa<UndefValue>(Idx)) |
| return PoisonValue::get(ValVTy->getElementType()); |
| |
| // extractelt undef, C -> undef |
| if (isa<UndefValue>(Val)) |
| return UndefValue::get(ValVTy->getElementType()); |
| |
| auto *CIdx = dyn_cast<ConstantInt>(Idx); |
| if (!CIdx) |
| return nullptr; |
| |
| if (auto *ValFVTy = dyn_cast<FixedVectorType>(Val->getType())) { |
| // ee({w,x,y,z}, wrong_value) -> poison |
| if (CIdx->uge(ValFVTy->getNumElements())) |
| return PoisonValue::get(ValFVTy->getElementType()); |
| } |
| |
| // ee (gep (ptr, idx0, ...), idx) -> gep (ee (ptr, idx), ee (idx0, idx), ...) |
| if (auto *CE = dyn_cast<ConstantExpr>(Val)) { |
| if (auto *GEP = dyn_cast<GEPOperator>(CE)) { |
| SmallVector<Constant *, 8> Ops; |
| Ops.reserve(CE->getNumOperands()); |
| for (unsigned i = 0, e = CE->getNumOperands(); i != e; ++i) { |
| Constant *Op = CE->getOperand(i); |
| if (Op->getType()->isVectorTy()) { |
| Constant *ScalarOp = ConstantExpr::getExtractElement(Op, Idx); |
| if (!ScalarOp) |
| return nullptr; |
| Ops.push_back(ScalarOp); |
| } else |
| Ops.push_back(Op); |
| } |
| return CE->getWithOperands(Ops, ValVTy->getElementType(), false, |
| GEP->getSourceElementType()); |
| } else if (CE->getOpcode() == Instruction::InsertElement) { |
| if (const auto *IEIdx = dyn_cast<ConstantInt>(CE->getOperand(2))) { |
| if (APSInt::isSameValue(APSInt(IEIdx->getValue()), |
| APSInt(CIdx->getValue()))) { |
| return CE->getOperand(1); |
| } else { |
| return ConstantExpr::getExtractElement(CE->getOperand(0), CIdx); |
| } |
| } |
| } |
| } |
| |
| if (Constant *C = Val->getAggregateElement(CIdx)) |
| return C; |
| |
| // Lane < Splat minimum vector width => extractelt Splat(x), Lane -> x |
| if (CIdx->getValue().ult(ValVTy->getElementCount().getKnownMinValue())) { |
| if (Constant *SplatVal = Val->getSplatValue()) |
| return SplatVal; |
| } |
| |
| return nullptr; |
| } |
| |
| Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val, |
| Constant *Elt, |
| Constant *Idx) { |
| if (isa<UndefValue>(Idx)) |
| return PoisonValue::get(Val->getType()); |
| |
| // Inserting null into all zeros is still all zeros. |
| // TODO: This is true for undef and poison splats too. |
| if (isa<ConstantAggregateZero>(Val) && Elt->isNullValue()) |
| return Val; |
| |
| ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx); |
| if (!CIdx) return nullptr; |
| |
| // Do not iterate on scalable vector. The num of elements is unknown at |
| // compile-time. |
| if (isa<ScalableVectorType>(Val->getType())) |
| return nullptr; |
| |
| auto *ValTy = cast<FixedVectorType>(Val->getType()); |
| |
| unsigned NumElts = ValTy->getNumElements(); |
| if (CIdx->uge(NumElts)) |
| return PoisonValue::get(Val->getType()); |
| |
| SmallVector<Constant*, 16> Result; |
| Result.reserve(NumElts); |
| auto *Ty = Type::getInt32Ty(Val->getContext()); |
| uint64_t IdxVal = CIdx->getZExtValue(); |
| for (unsigned i = 0; i != NumElts; ++i) { |
| if (i == IdxVal) { |
| Result.push_back(Elt); |
| continue; |
| } |
| |
| Constant *C = ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i)); |
| Result.push_back(C); |
| } |
| |
| return ConstantVector::get(Result); |
| } |
| |
| Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1, Constant *V2, |
| ArrayRef<int> Mask) { |
| auto *V1VTy = cast<VectorType>(V1->getType()); |
| unsigned MaskNumElts = Mask.size(); |
| auto MaskEltCount = |
| ElementCount::get(MaskNumElts, isa<ScalableVectorType>(V1VTy)); |
| Type *EltTy = V1VTy->getElementType(); |
| |
| // Poison shuffle mask -> poison value. |
| if (all_of(Mask, [](int Elt) { return Elt == PoisonMaskElem; })) { |
| return PoisonValue::get(VectorType::get(EltTy, MaskEltCount)); |
| } |
| |
| // If the mask is all zeros this is a splat, no need to go through all |
| // elements. |
| if (all_of(Mask, [](int Elt) { return Elt == 0; })) { |
| Type *Ty = IntegerType::get(V1->getContext(), 32); |
| Constant *Elt = |
| ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, 0)); |
| |
| if (Elt->isNullValue()) { |
| auto *VTy = VectorType::get(EltTy, MaskEltCount); |
| return ConstantAggregateZero::get(VTy); |
| } else if (!MaskEltCount.isScalable()) |
| return ConstantVector::getSplat(MaskEltCount, Elt); |
| } |
| |
| // Do not iterate on scalable vector. The num of elements is unknown at |
| // compile-time. |
| if (isa<ScalableVectorType>(V1VTy)) |
| return nullptr; |
| |
| unsigned SrcNumElts = V1VTy->getElementCount().getKnownMinValue(); |
| |
| // Loop over the shuffle mask, evaluating each element. |
| SmallVector<Constant*, 32> Result; |
| for (unsigned i = 0; i != MaskNumElts; ++i) { |
| int Elt = Mask[i]; |
| if (Elt == -1) { |
| Result.push_back(UndefValue::get(EltTy)); |
| continue; |
| } |
| Constant *InElt; |
| if (unsigned(Elt) >= SrcNumElts*2) |
| InElt = UndefValue::get(EltTy); |
| else if (unsigned(Elt) >= SrcNumElts) { |
| Type *Ty = IntegerType::get(V2->getContext(), 32); |
| InElt = |
| ConstantExpr::getExtractElement(V2, |
| ConstantInt::get(Ty, Elt - SrcNumElts)); |
| } else { |
| Type *Ty = IntegerType::get(V1->getContext(), 32); |
| InElt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, Elt)); |
| } |
| Result.push_back(InElt); |
| } |
| |
| return ConstantVector::get(Result); |
| } |
| |
| Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg, |
| ArrayRef<unsigned> Idxs) { |
| // Base case: no indices, so return the entire value. |
| if (Idxs.empty()) |
| return Agg; |
| |
| if (Constant *C = Agg->getAggregateElement(Idxs[0])) |
| return ConstantFoldExtractValueInstruction(C, Idxs.slice(1)); |
| |
| return nullptr; |
| } |
| |
| Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg, |
| Constant *Val, |
| ArrayRef<unsigned> Idxs) { |
| // Base case: no indices, so replace the entire value. |
| if (Idxs.empty()) |
| return Val; |
| |
| unsigned NumElts; |
| if (StructType *ST = dyn_cast<StructType>(Agg->getType())) |
| NumElts = ST->getNumElements(); |
| else |
| NumElts = cast<ArrayType>(Agg->getType())->getNumElements(); |
| |
| SmallVector<Constant*, 32> Result; |
| for (unsigned i = 0; i != NumElts; ++i) { |
| Constant *C = Agg->getAggregateElement(i); |
| if (!C) return nullptr; |
| |
| if (Idxs[0] == i) |
| C = ConstantFoldInsertValueInstruction(C, Val, Idxs.slice(1)); |
| |
| Result.push_back(C); |
| } |
| |
| if (StructType *ST = dyn_cast<StructType>(Agg->getType())) |
| return ConstantStruct::get(ST, Result); |
| return ConstantArray::get(cast<ArrayType>(Agg->getType()), Result); |
| } |
| |
| Constant *llvm::ConstantFoldUnaryInstruction(unsigned Opcode, Constant *C) { |
| assert(Instruction::isUnaryOp(Opcode) && "Non-unary instruction detected"); |
| |
| // Handle scalar UndefValue and scalable vector UndefValue. Fixed-length |
| // vectors are always evaluated per element. |
| bool IsScalableVector = isa<ScalableVectorType>(C->getType()); |
| bool HasScalarUndefOrScalableVectorUndef = |
| (!C->getType()->isVectorTy() || IsScalableVector) && isa<UndefValue>(C); |
| |
| if (HasScalarUndefOrScalableVectorUndef) { |
| switch (static_cast<Instruction::UnaryOps>(Opcode)) { |
| case Instruction::FNeg: |
| return C; // -undef -> undef |
| case Instruction::UnaryOpsEnd: |
| llvm_unreachable("Invalid UnaryOp"); |
| } |
| } |
| |
| // Constant should not be UndefValue, unless these are vector constants. |
| assert(!HasScalarUndefOrScalableVectorUndef && "Unexpected UndefValue"); |
| // We only have FP UnaryOps right now. |
| assert(!isa<ConstantInt>(C) && "Unexpected Integer UnaryOp"); |
| |
| if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) { |
| const APFloat &CV = CFP->getValueAPF(); |
| switch (Opcode) { |
| default: |
| break; |
| case Instruction::FNeg: |
| return ConstantFP::get(C->getContext(), neg(CV)); |
| } |
| } else if (auto *VTy = dyn_cast<FixedVectorType>(C->getType())) { |
| |
| Type *Ty = IntegerType::get(VTy->getContext(), 32); |
| // Fast path for splatted constants. |
| if (Constant *Splat = C->getSplatValue()) |
| if (Constant *Elt = ConstantFoldUnaryInstruction(Opcode, Splat)) |
| return ConstantVector::getSplat(VTy->getElementCount(), Elt); |
| |
| // Fold each element and create a vector constant from those constants. |
| SmallVector<Constant *, 16> Result; |
| for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { |
| Constant *ExtractIdx = ConstantInt::get(Ty, i); |
| Constant *Elt = ConstantExpr::getExtractElement(C, ExtractIdx); |
| Constant *Res = ConstantFoldUnaryInstruction(Opcode, Elt); |
| if (!Res) |
| return nullptr; |
| Result.push_back(Res); |
| } |
| |
| return ConstantVector::get(Result); |
| } |
| |
| // We don't know how to fold this. |
| return nullptr; |
| } |
| |
| Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, Constant *C1, |
| Constant *C2) { |
| assert(Instruction::isBinaryOp(Opcode) && "Non-binary instruction detected"); |
| |
| // Simplify BinOps with their identity values first. They are no-ops and we |
| // can always return the other value, including undef or poison values. |
| if (Constant *Identity = ConstantExpr::getBinOpIdentity( |
| Opcode, C1->getType(), /*AllowRHSIdentity*/ false)) { |
| if (C1 == Identity) |
| return C2; |
| if (C2 == Identity) |
| return C1; |
| } else if (Constant *Identity = ConstantExpr::getBinOpIdentity( |
| Opcode, C1->getType(), /*AllowRHSIdentity*/ true)) { |
| if (C2 == Identity) |
| return C1; |
| } |
| |
| // Binary operations propagate poison. |
| if (isa<PoisonValue>(C1) || isa<PoisonValue>(C2)) |
| return PoisonValue::get(C1->getType()); |
| |
| // Handle scalar UndefValue and scalable vector UndefValue. Fixed-length |
| // vectors are always evaluated per element. |
| bool IsScalableVector = isa<ScalableVectorType>(C1->getType()); |
| bool HasScalarUndefOrScalableVectorUndef = |
| (!C1->getType()->isVectorTy() || IsScalableVector) && |
| (isa<UndefValue>(C1) || isa<UndefValue>(C2)); |
| if (HasScalarUndefOrScalableVectorUndef) { |
| switch (static_cast<Instruction::BinaryOps>(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::And: |
| if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef & undef -> undef |
| return C1; |
| return Constant::getNullValue(C1->getType()); // undef & X -> 0 |
| case Instruction::Mul: { |
| // undef * undef -> undef |
| if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) |
| return C1; |
| const APInt *CV; |
| // X * undef -> undef if X is odd |
| if (match(C1, m_APInt(CV)) || match(C2, m_APInt(CV))) |
| if ((*CV)[0]) |
| return UndefValue::get(C1->getType()); |
| |
| // X * undef -> 0 otherwise |
| return Constant::getNullValue(C1->getType()); |
| } |
| case Instruction::SDiv: |
| case Instruction::UDiv: |
| // X / undef -> poison |
| // X / 0 -> poison |
| if (match(C2, m_CombineOr(m_Undef(), m_Zero()))) |
| return PoisonValue::get(C2->getType()); |
| // undef / X -> 0 otherwise |
| return Constant::getNullValue(C1->getType()); |
| case Instruction::URem: |
| case Instruction::SRem: |
| // X % undef -> poison |
| // X % 0 -> poison |
| if (match(C2, m_CombineOr(m_Undef(), m_Zero()))) |
| return PoisonValue::get(C2->getType()); |
| // undef % X -> 0 otherwise |
| return Constant::getNullValue(C1->getType()); |
| case Instruction::Or: // X | undef -> -1 |
| if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef |
| return C1; |
| return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0 |
| case Instruction::LShr: |
| // X >>l undef -> poison |
| if (isa<UndefValue>(C2)) |
| return PoisonValue::get(C2->getType()); |
| // undef >>l X -> 0 |
| return Constant::getNullValue(C1->getType()); |
| case Instruction::AShr: |
| // X >>a undef -> poison |
| if (isa<UndefValue>(C2)) |
| return PoisonValue::get(C2->getType()); |
| // TODO: undef >>a X -> poison if the shift is exact |
| // undef >>a X -> 0 |
| return Constant::getNullValue(C1->getType()); |
| case Instruction::Shl: |
| // X << undef -> undef |
| if (isa<UndefValue>(C2)) |
| return PoisonValue::get(C2->getType()); |
| // undef << X -> 0 |
| return Constant::getNullValue(C1->getType()); |
| case Instruction::FSub: |
| // -0.0 - undef --> undef (consistent with "fneg undef") |
| if (match(C1, m_NegZeroFP()) && isa<UndefValue>(C2)) |
| return C2; |
| [[fallthrough]]; |
| case Instruction::FAdd: |
| case Instruction::FMul: |
| case Instruction::FDiv: |
| case Instruction::FRem: |
| // [any flop] undef, undef -> undef |
| if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) |
| return C1; |
| // [any flop] C, undef -> NaN |
| // [any flop] undef, C -> NaN |
| // We could potentially specialize NaN/Inf constants vs. 'normal' |
| // constants (possibly differently depending on opcode and operand). This |
| // would allow returning undef sometimes. But it is always safe to fold to |
| // NaN because we can choose the undef operand as NaN, and any FP opcode |
| // with a NaN operand will propagate NaN. |
| return ConstantFP::getNaN(C1->getType()); |
| case Instruction::BinaryOpsEnd: |
| llvm_unreachable("Invalid BinaryOp"); |
| } |
| } |
| |
| // Neither constant should be UndefValue, unless these are vector constants. |
| assert((!HasScalarUndefOrScalableVectorUndef) && "Unexpected UndefValue"); |
| |
| // Handle simplifications when the RHS is a constant int. |
| if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { |
| switch (Opcode) { |
| case Instruction::Mul: |
| if (CI2->isZero()) |
| return C2; // X * 0 == 0 |
| break; |
| case Instruction::UDiv: |
| case Instruction::SDiv: |
| if (CI2->isZero()) |
| return PoisonValue::get(CI2->getType()); // X / 0 == poison |
| break; |
| case Instruction::URem: |
| case Instruction::SRem: |
| if (CI2->isOne()) |
| return Constant::getNullValue(CI2->getType()); // X % 1 == 0 |
| if (CI2->isZero()) |
| return PoisonValue::get(CI2->getType()); // X % 0 == poison |
| break; |
| case Instruction::And: |
| if (CI2->isZero()) |
| return C2; // X & 0 == 0 |
| |
| if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { |
| // If and'ing the address of a global with a constant, fold it. |
| if (CE1->getOpcode() == Instruction::PtrToInt && |
| isa<GlobalValue>(CE1->getOperand(0))) { |
| GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0)); |
| |
| Align GVAlign; // defaults to 1 |
| |
| if (Module *TheModule = GV->getParent()) { |
| const DataLayout &DL = TheModule->getDataLayout(); |
| GVAlign = GV->getPointerAlignment(DL); |
| |
| // If the function alignment is not specified then assume that it |
| // is 4. |
| // This is dangerous; on x86, the alignment of the pointer |
| // corresponds to the alignment of the function, but might be less |
| // than 4 if it isn't explicitly specified. |
| // However, a fix for this behaviour was reverted because it |
| // increased code size (see https://reviews.llvm.org/D55115) |
| // FIXME: This code should be deleted once existing targets have |
| // appropriate defaults |
| if (isa<Function>(GV) && !DL.getFunctionPtrAlign()) |
| GVAlign = Align(4); |
| } else if (isa<GlobalVariable>(GV)) { |
| GVAlign = cast<GlobalVariable>(GV)->getAlign().valueOrOne(); |
| } |
| |
| if (GVAlign > 1) { |
| unsigned DstWidth = CI2->getBitWidth(); |
| unsigned SrcWidth = std::min(DstWidth, Log2(GVAlign)); |
| APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth)); |
| |
| // If checking bits we know are clear, return zero. |
| if ((CI2->getValue() & BitsNotSet) == CI2->getValue()) |
| return Constant::getNullValue(CI2->getType()); |
| } |
| } |
| } |
| break; |
| case Instruction::Or: |
| if (CI2->isMinusOne()) |
| return C2; // X | -1 == -1 |
| break; |
| } |
| } else if (isa<ConstantInt>(C1)) { |
| // If C1 is a ConstantInt and C2 is not, swap the operands. |
| if (Instruction::isCommutative(Opcode)) |
| return ConstantExpr::isDesirableBinOp(Opcode) |
| ? ConstantExpr::get(Opcode, C2, C1) |
| : ConstantFoldBinaryInstruction(Opcode, C2, C1); |
| } |
| |
| if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) { |
| if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { |
| const APInt &C1V = CI1->getValue(); |
| const APInt &C2V = CI2->getValue(); |
| switch (Opcode) { |
| default: |
| break; |
| case Instruction::Add: |
| return ConstantInt::get(CI1->getContext(), C1V + C2V); |
| case Instruction::Sub: |
| return ConstantInt::get(CI1->getContext(), C1V - C2V); |
| case Instruction::Mul: |
| return ConstantInt::get(CI1->getContext(), C1V * C2V); |
| case Instruction::UDiv: |
| assert(!CI2->isZero() && "Div by zero handled above"); |
| return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V)); |
| case Instruction::SDiv: |
| assert(!CI2->isZero() && "Div by zero handled above"); |
| if (C2V.isAllOnes() && C1V.isMinSignedValue()) |
| return PoisonValue::get(CI1->getType()); // MIN_INT / -1 -> poison |
| return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V)); |
| case Instruction::URem: |
| assert(!CI2->isZero() && "Div by zero handled above"); |
| return ConstantInt::get(CI1->getContext(), C1V.urem(C2V)); |
| case Instruction::SRem: |
| assert(!CI2->isZero() && "Div by zero handled above"); |
| if (C2V.isAllOnes() && C1V.isMinSignedValue()) |
| return PoisonValue::get(CI1->getType()); // MIN_INT % -1 -> poison |
| return ConstantInt::get(CI1->getContext(), C1V.srem(C2V)); |
| case Instruction::And: |
| return ConstantInt::get(CI1->getContext(), C1V & C2V); |
| case Instruction::Or: |
| return ConstantInt::get(CI1->getContext(), C1V | C2V); |
| case Instruction::Xor: |
| return ConstantInt::get(CI1->getContext(), C1V ^ C2V); |
| case Instruction::Shl: |
| if (C2V.ult(C1V.getBitWidth())) |
| return ConstantInt::get(CI1->getContext(), C1V.shl(C2V)); |
| return PoisonValue::get(C1->getType()); // too big shift is poison |
| case Instruction::LShr: |
| if (C2V.ult(C1V.getBitWidth())) |
| return ConstantInt::get(CI1->getContext(), C1V.lshr(C2V)); |
| return PoisonValue::get(C1->getType()); // too big shift is poison |
| case Instruction::AShr: |
| if (C2V.ult(C1V.getBitWidth())) |
| return ConstantInt::get(CI1->getContext(), C1V.ashr(C2V)); |
| return PoisonValue::get(C1->getType()); // too big shift is poison |
| } |
| } |
| |
| switch (Opcode) { |
| case Instruction::SDiv: |
| case Instruction::UDiv: |
| case Instruction::URem: |
| case Instruction::SRem: |
| case Instruction::LShr: |
| case Instruction::AShr: |
| case Instruction::Shl: |
| if (CI1->isZero()) return C1; |
| break; |
| default: |
| break; |
| } |
| } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) { |
| if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) { |
| const APFloat &C1V = CFP1->getValueAPF(); |
| const APFloat &C2V = CFP2->getValueAPF(); |
| APFloat C3V = C1V; // copy for modification |
| switch (Opcode) { |
| default: |
| break; |
| case Instruction::FAdd: |
| (void)C3V.add(C2V, APFloat::rmNearestTiesToEven); |
| return ConstantFP::get(C1->getContext(), C3V); |
| case Instruction::FSub: |
| (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven); |
| return ConstantFP::get(C1->getContext(), C3V); |
| case Instruction::FMul: |
| (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven); |
| return ConstantFP::get(C1->getContext(), C3V); |
| case Instruction::FDiv: |
| (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven); |
| return ConstantFP::get(C1->getContext(), C3V); |
| case Instruction::FRem: |
| (void)C3V.mod(C2V); |
| return ConstantFP::get(C1->getContext(), C3V); |
| } |
| } |
| } else if (auto *VTy = dyn_cast<VectorType>(C1->getType())) { |
| // Fast path for splatted constants. |
| if (Constant *C2Splat = C2->getSplatValue()) { |
| if (Instruction::isIntDivRem(Opcode) && C2Splat->isNullValue()) |
| return PoisonValue::get(VTy); |
| if (Constant *C1Splat = C1->getSplatValue()) { |
| Constant *Res = |
| ConstantExpr::isDesirableBinOp(Opcode) |
| ? ConstantExpr::get(Opcode, C1Splat, C2Splat) |
| : ConstantFoldBinaryInstruction(Opcode, C1Splat, C2Splat); |
| if (!Res) |
| return nullptr; |
| return ConstantVector::getSplat(VTy->getElementCount(), Res); |
| } |
| } |
| |
| if (auto *FVTy = dyn_cast<FixedVectorType>(VTy)) { |
| // Fold each element and create a vector constant from those constants. |
| SmallVector<Constant*, 16> Result; |
| Type *Ty = IntegerType::get(FVTy->getContext(), 32); |
| for (unsigned i = 0, e = FVTy->getNumElements(); i != e; ++i) { |
| Constant *ExtractIdx = ConstantInt::get(Ty, i); |
| Constant *LHS = ConstantExpr::getExtractElement(C1, ExtractIdx); |
| Constant *RHS = ConstantExpr::getExtractElement(C2, ExtractIdx); |
| |
| // If any element of a divisor vector is zero, the whole op is poison. |
| if (Instruction::isIntDivRem(Opcode) && RHS->isNullValue()) |
| return PoisonValue::get(VTy); |
| |
| Constant *Res = ConstantExpr::isDesirableBinOp(Opcode) |
| ? ConstantExpr::get(Opcode, LHS, RHS) |
| : ConstantFoldBinaryInstruction(Opcode, LHS, RHS); |
| if (!Res) |
| return nullptr; |
| Result.push_back(Res); |
| } |
| |
| return ConstantVector::get(Result); |
| } |
| } |
| |
| if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { |
| // 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. |
| |
| // Given ((a + b) + c), if (b + c) folds to something interesting, return |
| // (a + (b + c)). |
| if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) { |
| Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2); |
| if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode) |
| return ConstantExpr::get(Opcode, CE1->getOperand(0), T); |
| } |
| } 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. |
| if (Instruction::isCommutative(Opcode)) |
| return ConstantFoldBinaryInstruction(Opcode, C2, C1); |
| } |
| |
| // i1 can be simplified in many cases. |
| if (C1->getType()->isIntegerTy(1)) { |
| switch (Opcode) { |
| case Instruction::Add: |
| case Instruction::Sub: |
| return ConstantExpr::getXor(C1, C2); |
| case Instruction::Shl: |
| case Instruction::LShr: |
| case Instruction::AShr: |
| // We can assume that C2 == 0. If it were one the result would be |
| // undefined because the shift value is as large as the bitwidth. |
| return C1; |
| case Instruction::SDiv: |
| case Instruction::UDiv: |
| // We can assume that C2 == 1. If it were zero the result would be |
| // undefined through division by zero. |
| return C1; |
| case Instruction::URem: |
| case Instruction::SRem: |
| // We can assume that C2 == 1. If it were zero the result would be |
| // undefined through division by zero. |
| return ConstantInt::getFalse(C1->getContext()); |
| default: |
| break; |
| } |
| } |
| |
| // We don't know how to fold this. |
| return nullptr; |
| } |
| |
| static ICmpInst::Predicate areGlobalsPotentiallyEqual(const GlobalValue *GV1, |
| const GlobalValue *GV2) { |
| auto isGlobalUnsafeForEquality = [](const GlobalValue *GV) { |
| if (GV->isInterposable() || GV->hasGlobalUnnamedAddr()) |
| return true; |
| if (const auto *GVar = dyn_cast<GlobalVariable>(GV)) { |
| Type *Ty = GVar->getValueType(); |
| // A global with opaque type might end up being zero sized. |
| if (!Ty->isSized()) |
| return true; |
| // A global with an empty type might lie at the address of any other |
| // global. |
| if (Ty->isEmptyTy()) |
| return true; |
| } |
| return false; |
| }; |
| // Don't try to decide equality of aliases. |
| if (!isa<GlobalAlias>(GV1) && !isa<GlobalAlias>(GV2)) |
| if (!isGlobalUnsafeForEquality(GV1) && !isGlobalUnsafeForEquality(GV2)) |
| return ICmpInst::ICMP_NE; |
| return ICmpInst::BAD_ICMP_PREDICATE; |
| } |
| |
| /// 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. |
| static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2) { |
| assert(V1->getType() == V2->getType() && |
| "Cannot compare different types of values!"); |
| if (V1 == V2) return ICmpInst::ICMP_EQ; |
| |
| // The following folds only apply to pointers. |
| if (!V1->getType()->isPointerTy()) |
| 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 ConstantPointerNull) to be the simplest, followed by |
| // BlockAddress, GlobalValues, and ConstantExpr's (the most complex). |
| auto GetComplexity = [](Constant *V) { |
| if (isa<ConstantExpr>(V)) |
| return 3; |
| if (isa<GlobalValue>(V)) |
| return 2; |
| if (isa<BlockAddress>(V)) |
| return 1; |
| return 0; |
| }; |
| if (GetComplexity(V1) < GetComplexity(V2)) { |
| ICmpInst::Predicate SwappedRelation = evaluateICmpRelation(V2, V1); |
| if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) |
| return ICmpInst::getSwappedPredicate(SwappedRelation); |
| return ICmpInst::BAD_ICMP_PREDICATE; |
| } |
| |
| if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) { |
| // Now we know that the RHS is a BlockAddress or simple constant. |
| if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) { |
| // Block address in another function can't equal this one, but block |
| // addresses in the current function might be the same if blocks are |
| // empty. |
| if (BA2->getFunction() != BA->getFunction()) |
| return ICmpInst::ICMP_NE; |
| } else if (isa<ConstantPointerNull>(V2)) { |
| return ICmpInst::ICMP_NE; |
| } |
| } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) { |
| // Now we know that the RHS is a GlobalValue, BlockAddress or simple |
| // constant. |
| if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { |
| return areGlobalsPotentiallyEqual(GV, GV2); |
| } else if (isa<BlockAddress>(V2)) { |
| return ICmpInst::ICMP_NE; // Globals never equal labels. |
| } else if (isa<ConstantPointerNull>(V2)) { |
| // GlobalVals can never be null unless they have external weak linkage. |
| // We don't try to evaluate aliases here. |
| // NOTE: We should not be doing this constant folding if null pointer |
| // is considered valid for the function. But currently there is no way to |
| // query it from the Constant type. |
| if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV) && |
| !NullPointerIsDefined(nullptr /* F */, |
| GV->getType()->getAddressSpace())) |
| return ICmpInst::ICMP_UGT; |
| } |
| } else if (auto *CE1 = dyn_cast<ConstantExpr>(V1)) { |
| // Ok, the LHS is known to be a constantexpr. The RHS can be any of a |
| // constantexpr, a global, block address, or a simple constant. |
| Constant *CE1Op0 = CE1->getOperand(0); |
| |
| switch (CE1->getOpcode()) { |
| case Instruction::GetElementPtr: { |
| GEPOperator *CE1GEP = cast<GEPOperator>(CE1); |
| // 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 its not weak linkage, the GVal must have a non-zero address |
| // so the result is greater-than |
| if (!GV->hasExternalWeakLinkage() && CE1GEP->isInBounds()) |
| return ICmpInst::ICMP_UGT; |
| } |
| } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { |
| if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { |
| if (GV != GV2) { |
| if (CE1GEP->hasAllZeroIndices()) |
| return areGlobalsPotentiallyEqual(GV, GV2); |
| return ICmpInst::BAD_ICMP_PREDICATE; |
| } |
| } |
| } else if (const auto *CE2GEP = dyn_cast<GEPOperator>(V2)) { |
| // By far the most common case to handle is when the base pointers are |
| // obviously to the same global. |
| const Constant *CE2Op0 = cast<Constant>(CE2GEP->getPointerOperand()); |
| if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { |
| // Don't know relative ordering, but check for inequality. |
| if (CE1Op0 != CE2Op0) { |
| if (CE1GEP->hasAllZeroIndices() && CE2GEP->hasAllZeroIndices()) |
| return areGlobalsPotentiallyEqual(cast<GlobalValue>(CE1Op0), |
| cast<GlobalValue>(CE2Op0)); |
| return ICmpInst::BAD_ICMP_PREDICATE; |
| } |
| } |
| } |
| break; |
| } |
| default: |
| break; |
| } |
| } |
| |
| return ICmpInst::BAD_ICMP_PREDICATE; |
| } |
| |
| Constant *llvm::ConstantFoldCompareInstruction(CmpInst::Predicate Predicate, |
| Constant *C1, Constant *C2) { |
| Type *ResultTy; |
| if (VectorType *VT = dyn_cast<VectorType>(C1->getType())) |
| ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()), |
| VT->getElementCount()); |
| else |
| ResultTy = Type::getInt1Ty(C1->getContext()); |
| |
| // Fold FCMP_FALSE/FCMP_TRUE unconditionally. |
| if (Predicate == FCmpInst::FCMP_FALSE) |
| return Constant::getNullValue(ResultTy); |
| |
| if (Predicate == FCmpInst::FCMP_TRUE) |
| return Constant::getAllOnesValue(ResultTy); |
| |
| // Handle some degenerate cases first |
| if (isa<PoisonValue>(C1) || isa<PoisonValue>(C2)) |
| return PoisonValue::get(ResultTy); |
| |
| if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { |
| bool isIntegerPredicate = ICmpInst::isIntPredicate(Predicate); |
| // For EQ and NE, we can always pick a value for the undef to make the |
| // predicate pass or fail, so we can return undef. |
| // Also, if both operands are undef, we can return undef for int comparison. |
| if (ICmpInst::isEquality(Predicate) || (isIntegerPredicate && C1 == C2)) |
| return UndefValue::get(ResultTy); |
| |
| // Otherwise, for integer compare, pick the same value as the non-undef |
| // operand, and fold it to true or false. |
| if (isIntegerPredicate) |
| return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(Predicate)); |
| |
| // Choosing NaN for the undef will always make unordered comparison succeed |
| // and ordered comparison fails. |
| return ConstantInt::get(ResultTy, CmpInst::isUnordered(Predicate)); |
| } |
| |
| if (C2->isNullValue()) { |
| // The caller is expected to commute the operands if the constant expression |
| // is C2. |
| // C1 >= 0 --> true |
| if (Predicate == ICmpInst::ICMP_UGE) |
| return Constant::getAllOnesValue(ResultTy); |
| // C1 < 0 --> false |
| if (Predicate == ICmpInst::ICMP_ULT) |
| return Constant::getNullValue(ResultTy); |
| } |
| |
| // If the comparison is a comparison between two i1's, simplify it. |
| if (C1->getType()->isIntegerTy(1)) { |
| switch (Predicate) { |
| case ICmpInst::ICMP_EQ: |
| if (isa<ConstantInt>(C2)) |
| return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2)); |
| return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2); |
| case ICmpInst::ICMP_NE: |
| return ConstantExpr::getXor(C1, C2); |
| default: |
| break; |
| } |
| } |
| |
| if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { |
| const APInt &V1 = cast<ConstantInt>(C1)->getValue(); |
| const APInt &V2 = cast<ConstantInt>(C2)->getValue(); |
| return ConstantInt::get(ResultTy, ICmpInst::compare(V1, V2, Predicate)); |
| } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { |
| const APFloat &C1V = cast<ConstantFP>(C1)->getValueAPF(); |
| const APFloat &C2V = cast<ConstantFP>(C2)->getValueAPF(); |
| return ConstantInt::get(ResultTy, FCmpInst::compare(C1V, C2V, Predicate)); |
| } else if (auto *C1VTy = dyn_cast<VectorType>(C1->getType())) { |
| |
| // Fast path for splatted constants. |
| if (Constant *C1Splat = C1->getSplatValue()) |
| if (Constant *C2Splat = C2->getSplatValue()) |
| if (Constant *Elt = |
| ConstantFoldCompareInstruction(Predicate, C1Splat, C2Splat)) |
| return ConstantVector::getSplat(C1VTy->getElementCount(), Elt); |
| |
| // Do not iterate on scalable vector. The number of elements is unknown at |
| // compile-time. |
| if (isa<ScalableVectorType>(C1VTy)) |
| return nullptr; |
| |
| // If we can constant fold the comparison of each element, constant fold |
| // the whole vector comparison. |
| SmallVector<Constant*, 4> ResElts; |
| Type *Ty = IntegerType::get(C1->getContext(), 32); |
| // Compare the elements, producing an i1 result or constant expr. |
| for (unsigned I = 0, E = C1VTy->getElementCount().getKnownMinValue(); |
| I != E; ++I) { |
| Constant *C1E = |
| ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, I)); |
| Constant *C2E = |
| ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, I)); |
| Constant *Elt = ConstantFoldCompareInstruction(Predicate, C1E, C2E); |
| if (!Elt) |
| return nullptr; |
| |
| ResElts.push_back(Elt); |
| } |
| |
| return ConstantVector::get(ResElts); |
| } |
| |
| if (C1->getType()->isFPOrFPVectorTy()) { |
| if (C1 == C2) { |
| // We know that C1 == C2 || isUnordered(C1, C2). |
| if (Predicate == FCmpInst::FCMP_ONE) |
| return ConstantInt::getFalse(ResultTy); |
| else if (Predicate == FCmpInst::FCMP_UEQ) |
| return ConstantInt::getTrue(ResultTy); |
| } |
| } else { |
| // Evaluate the relation between the two constants, per the predicate. |
| int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. |
| switch (evaluateICmpRelation(C1, C2)) { |
| default: llvm_unreachable("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. |
| Result = ICmpInst::isTrueWhenEqual(Predicate); |
| break; |
| case ICmpInst::ICMP_ULT: |
| switch (Predicate) { |
| case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE: |
| Result = 1; break; |
| case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE: |
| Result = 0; break; |
| default: |
| break; |
| } |
| break; |
| case ICmpInst::ICMP_SLT: |
| switch (Predicate) { |
| case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE: |
| Result = 1; break; |
| case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE: |
| Result = 0; break; |
| default: |
| break; |
| } |
| break; |
| case ICmpInst::ICMP_UGT: |
| switch (Predicate) { |
| case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE: |
| Result = 1; break; |
| case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE: |
| Result = 0; break; |
| default: |
| break; |
| } |
| break; |
| case ICmpInst::ICMP_SGT: |
| switch (Predicate) { |
| case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE: |
| Result = 1; break; |
| case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE: |
| Result = 0; break; |
| default: |
| break; |
| } |
| break; |
| case ICmpInst::ICMP_ULE: |
| if (Predicate == ICmpInst::ICMP_UGT) |
| Result = 0; |
| if (Predicate == ICmpInst::ICMP_ULT || Predicate == ICmpInst::ICMP_ULE) |
| Result = 1; |
| break; |
| case ICmpInst::ICMP_SLE: |
| if (Predicate == ICmpInst::ICMP_SGT) |
| Result = 0; |
| if (Predicate == ICmpInst::ICMP_SLT || Predicate == ICmpInst::ICMP_SLE) |
| Result = 1; |
| break; |
| case ICmpInst::ICMP_UGE: |
| if (Predicate == ICmpInst::ICMP_ULT) |
| Result = 0; |
| if (Predicate == ICmpInst::ICMP_UGT || Predicate == ICmpInst::ICMP_UGE) |
| Result = 1; |
| break; |
| case ICmpInst::ICMP_SGE: |
| if (Predicate == ICmpInst::ICMP_SLT) |
| Result = 0; |
| if (Predicate == ICmpInst::ICMP_SGT || Predicate == ICmpInst::ICMP_SGE) |
| Result = 1; |
| break; |
| case ICmpInst::ICMP_NE: |
| if (Predicate == ICmpInst::ICMP_EQ) |
| Result = 0; |
| if (Predicate == ICmpInst::ICMP_NE) |
| Result = 1; |
| break; |
| } |
| |
| // If we evaluated the result, return it now. |
| if (Result != -1) |
| return ConstantInt::get(ResultTy, Result); |
| |
| if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) || |
| (C1->isNullValue() && !C2->isNullValue())) { |
| // If C2 is a constant expr and C1 isn't, flip them around and fold the |
| // other way if possible. |
| // Also, if C1 is null and C2 isn't, flip them around. |
| Predicate = ICmpInst::getSwappedPredicate(Predicate); |
| return ConstantFoldCompareInstruction(Predicate, C2, C1); |
| } |
| } |
| return nullptr; |
| } |
| |
| Constant *llvm::ConstantFoldGetElementPtr(Type *PointeeTy, Constant *C, |
| std::optional<ConstantRange> InRange, |
| ArrayRef<Value *> Idxs) { |
| if (Idxs.empty()) return C; |
| |
| Type *GEPTy = GetElementPtrInst::getGEPReturnType( |
| C, ArrayRef((Value *const *)Idxs.data(), Idxs.size())); |
| |
| if (isa<PoisonValue>(C)) |
| return PoisonValue::get(GEPTy); |
| |
| if (isa<UndefValue>(C)) |
| return UndefValue::get(GEPTy); |
| |
| auto IsNoOp = [&]() { |
| // Avoid losing inrange information. |
| if (InRange) |
| return false; |
| |
| return all_of(Idxs, [](Value *Idx) { |
| Constant *IdxC = cast<Constant>(Idx); |
| return IdxC->isNullValue() || isa<UndefValue>(IdxC); |
| }); |
| }; |
| if (IsNoOp()) |
| return GEPTy->isVectorTy() && !C->getType()->isVectorTy() |
| ? ConstantVector::getSplat( |
| cast<VectorType>(GEPTy)->getElementCount(), C) |
| : C; |
| |
| return nullptr; |
| } |
