| //===- 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 "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" |
| #include "llvm/Support/ManagedStatic.h" |
| #include "llvm/Support/MathExtras.h" |
| using namespace llvm; |
| using namespace llvm::PatternMatch; |
| |
| //===----------------------------------------------------------------------===// |
| // ConstantFold*Instruction Implementations |
| //===----------------------------------------------------------------------===// |
| |
| /// Convert the specified vector Constant 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(Constant *CV, VectorType *DstTy) { |
| |
| if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy); |
| if (CV->isNullValue()) return Constant::getNullValue(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->getType()->getVectorNumElements()) |
| return nullptr; |
| |
| Type *DstEltTy = DstTy->getElementType(); |
| |
| SmallVector<Constant*, 16> Result; |
| Type *Ty = IntegerType::get(CV->getContext(), 32); |
| for (unsigned i = 0; i != NumElts; ++i) { |
| Constant *C = |
| ConstantExpr::getExtractElement(CV, ConstantInt::get(Ty, i)); |
| C = ConstantExpr::getBitCast(C, DstEltTy); |
| Result.push_back(C); |
| } |
| |
| 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. |
| /// 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 |
| |
| // 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 (PointerType *PTy = dyn_cast<PointerType>(V->getType())) |
| if (PointerType *DPTy = dyn_cast<PointerType>(DestTy)) |
| if (PTy->getAddressSpace() == DPTy->getAddressSpace() |
| && PTy->getElementType()->isSized()) { |
| SmallVector<Value*, 8> IdxList; |
| Value *Zero = |
| Constant::getNullValue(Type::getInt32Ty(DPTy->getContext())); |
| IdxList.push_back(Zero); |
| Type *ElTy = PTy->getElementType(); |
| while (ElTy != DPTy->getElementType()) { |
| if (StructType *STy = dyn_cast<StructType>(ElTy)) { |
| if (STy->getNumElements() == 0) break; |
| ElTy = STy->getElementType(0); |
| IdxList.push_back(Zero); |
| } else if (SequentialType *STy = |
| dyn_cast<SequentialType>(ElTy)) { |
| ElTy = STy->getElementType(); |
| IdxList.push_back(Zero); |
| } else { |
| break; |
| } |
| } |
| |
| if (ElTy == DPTy->getElementType()) |
| // This GEP is inbounds because all indices are zero. |
| return ConstantExpr::getInBoundsGetElementPtr(PTy->getElementType(), |
| V, IdxList); |
| } |
| |
| // 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 (VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) { |
| assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() && |
| "Not cast between same sized vectors!"); |
| SrcTy = nullptr; |
| // First, check for null. Undef is already handled. |
| if (isa<ConstantAggregateZero>(V)) |
| return Constant::getNullValue(DestTy); |
| |
| // Handle ConstantVector and ConstantAggregateVector. |
| return BitCastConstantVector(V, DestPTy); |
| } |
| |
| // 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); |
| } |
| |
| // 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 (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { |
| if (DestTy->isIntegerTy()) |
| // Integral -> Integral. This is a no-op because the bit widths must |
| // be the same. Consequently, we just fold to V. |
| return 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; |
| } |
| |
| |
| /// V is an integer constant which only has a subset of its bytes used. |
| /// The bytes used are indicated by ByteStart (which is the first byte used, |
| /// counting from the least significant byte) and ByteSize, which is the number |
| /// of bytes used. |
| /// |
| /// This function analyzes the specified constant to see if the specified byte |
| /// range can be returned as a simplified constant. If so, the constant is |
| /// returned, otherwise null is returned. |
| static Constant *ExtractConstantBytes(Constant *C, unsigned ByteStart, |
| unsigned ByteSize) { |
| assert(C->getType()->isIntegerTy() && |
| (cast<IntegerType>(C->getType())->getBitWidth() & 7) == 0 && |
| "Non-byte sized integer input"); |
| unsigned CSize = cast<IntegerType>(C->getType())->getBitWidth()/8; |
| assert(ByteSize && "Must be accessing some piece"); |
| assert(ByteStart+ByteSize <= CSize && "Extracting invalid piece from input"); |
| assert(ByteSize != CSize && "Should not extract everything"); |
| |
| // Constant Integers are simple. |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) { |
| APInt V = CI->getValue(); |
| if (ByteStart) |
| V.lshrInPlace(ByteStart*8); |
| V = V.trunc(ByteSize*8); |
| return ConstantInt::get(CI->getContext(), V); |
| } |
| |
| // In the input is a constant expr, we might be able to recursively simplify. |
| // If not, we definitely can't do anything. |
| ConstantExpr *CE = dyn_cast<ConstantExpr>(C); |
| if (!CE) return nullptr; |
| |
| switch (CE->getOpcode()) { |
| default: return nullptr; |
| case Instruction::Or: { |
| Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize); |
| if (!RHS) |
| return nullptr; |
| |
| // X | -1 -> -1. |
| if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) |
| if (RHSC->isMinusOne()) |
| return RHSC; |
| |
| Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize); |
| if (!LHS) |
| return nullptr; |
| return ConstantExpr::getOr(LHS, RHS); |
| } |
| case Instruction::And: { |
| Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize); |
| if (!RHS) |
| return nullptr; |
| |
| // X & 0 -> 0. |
| if (RHS->isNullValue()) |
| return RHS; |
| |
| Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize); |
| if (!LHS) |
| return nullptr; |
| return ConstantExpr::getAnd(LHS, RHS); |
| } |
| case Instruction::LShr: { |
| ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1)); |
| if (!Amt) |
| return nullptr; |
| APInt ShAmt = Amt->getValue(); |
| // Cannot analyze non-byte shifts. |
| if ((ShAmt & 7) != 0) |
| return nullptr; |
| ShAmt.lshrInPlace(3); |
| |
| // If the extract is known to be all zeros, return zero. |
| if (ShAmt.uge(CSize - ByteStart)) |
| return Constant::getNullValue( |
| IntegerType::get(CE->getContext(), ByteSize * 8)); |
| // If the extract is known to be fully in the input, extract it. |
| if (ShAmt.ule(CSize - (ByteStart + ByteSize))) |
| return ExtractConstantBytes(CE->getOperand(0), |
| ByteStart + ShAmt.getZExtValue(), ByteSize); |
| |
| // TODO: Handle the 'partially zero' case. |
| return nullptr; |
| } |
| |
| case Instruction::Shl: { |
| ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1)); |
| if (!Amt) |
| return nullptr; |
| APInt ShAmt = Amt->getValue(); |
| // Cannot analyze non-byte shifts. |
| if ((ShAmt & 7) != 0) |
| return nullptr; |
| ShAmt.lshrInPlace(3); |
| |
| // If the extract is known to be all zeros, return zero. |
| if (ShAmt.uge(ByteStart + ByteSize)) |
| return Constant::getNullValue( |
| IntegerType::get(CE->getContext(), ByteSize * 8)); |
| // If the extract is known to be fully in the input, extract it. |
| if (ShAmt.ule(ByteStart)) |
| return ExtractConstantBytes(CE->getOperand(0), |
| ByteStart - ShAmt.getZExtValue(), ByteSize); |
| |
| // TODO: Handle the 'partially zero' case. |
| return nullptr; |
| } |
| |
| case Instruction::ZExt: { |
| unsigned SrcBitSize = |
| cast<IntegerType>(CE->getOperand(0)->getType())->getBitWidth(); |
| |
| // If extracting something that is completely zero, return 0. |
| if (ByteStart*8 >= SrcBitSize) |
| return Constant::getNullValue(IntegerType::get(CE->getContext(), |
| ByteSize*8)); |
| |
| // If exactly extracting the input, return it. |
| if (ByteStart == 0 && ByteSize*8 == SrcBitSize) |
| return CE->getOperand(0); |
| |
| // If extracting something completely in the input, if the input is a |
| // multiple of 8 bits, recurse. |
| if ((SrcBitSize&7) == 0 && (ByteStart+ByteSize)*8 <= SrcBitSize) |
| return ExtractConstantBytes(CE->getOperand(0), ByteStart, ByteSize); |
| |
| // Otherwise, if extracting a subset of the input, which is not multiple of |
| // 8 bits, do a shift and trunc to get the bits. |
| if ((ByteStart+ByteSize)*8 < SrcBitSize) { |
| assert((SrcBitSize&7) && "Shouldn't get byte sized case here"); |
| Constant *Res = CE->getOperand(0); |
| if (ByteStart) |
| Res = ConstantExpr::getLShr(Res, |
| ConstantInt::get(Res->getType(), ByteStart*8)); |
| return ConstantExpr::getTrunc(Res, IntegerType::get(C->getContext(), |
| ByteSize*8)); |
| } |
| |
| // TODO: Handle the 'partially zero' case. |
| return nullptr; |
| } |
| } |
| } |
| |
| /// Return a ConstantExpr with type DestTy for sizeof on Ty, with any known |
| /// factors factored out. If Folded is false, return null if no factoring was |
| /// possible, to avoid endlessly bouncing an unfoldable expression back into the |
| /// top-level folder. |
| static Constant *getFoldedSizeOf(Type *Ty, Type *DestTy, bool Folded) { |
| if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { |
| Constant *N = ConstantInt::get(DestTy, ATy->getNumElements()); |
| Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); |
| return ConstantExpr::getNUWMul(E, N); |
| } |
| |
| if (StructType *STy = dyn_cast<StructType>(Ty)) |
| if (!STy->isPacked()) { |
| unsigned NumElems = STy->getNumElements(); |
| // An empty struct has size zero. |
| if (NumElems == 0) |
| return ConstantExpr::getNullValue(DestTy); |
| // Check for a struct with all members having the same size. |
| Constant *MemberSize = |
| getFoldedSizeOf(STy->getElementType(0), DestTy, true); |
| bool AllSame = true; |
| for (unsigned i = 1; i != NumElems; ++i) |
| if (MemberSize != |
| getFoldedSizeOf(STy->getElementType(i), DestTy, true)) { |
| AllSame = false; |
| break; |
| } |
| if (AllSame) { |
| Constant *N = ConstantInt::get(DestTy, NumElems); |
| return ConstantExpr::getNUWMul(MemberSize, N); |
| } |
| } |
| |
| // Pointer size doesn't depend on the pointee type, so canonicalize them |
| // to an arbitrary pointee. |
| if (PointerType *PTy = dyn_cast<PointerType>(Ty)) |
| if (!PTy->getElementType()->isIntegerTy(1)) |
| return |
| getFoldedSizeOf(PointerType::get(IntegerType::get(PTy->getContext(), 1), |
| PTy->getAddressSpace()), |
| DestTy, true); |
| |
| // If there's no interesting folding happening, bail so that we don't create |
| // a constant that looks like it needs folding but really doesn't. |
| if (!Folded) |
| return nullptr; |
| |
| // Base case: Get a regular sizeof expression. |
| Constant *C = ConstantExpr::getSizeOf(Ty); |
| C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, |
| DestTy, false), |
| C, DestTy); |
| return C; |
| } |
| |
| /// Return a ConstantExpr with type DestTy for alignof on Ty, with any known |
| /// factors factored out. If Folded is false, return null if no factoring was |
| /// possible, to avoid endlessly bouncing an unfoldable expression back into the |
| /// top-level folder. |
| static Constant *getFoldedAlignOf(Type *Ty, Type *DestTy, bool Folded) { |
| // The alignment of an array is equal to the alignment of the |
| // array element. Note that this is not always true for vectors. |
| if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { |
| Constant *C = ConstantExpr::getAlignOf(ATy->getElementType()); |
| C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, |
| DestTy, |
| false), |
| C, DestTy); |
| return C; |
| } |
| |
| if (StructType *STy = dyn_cast<StructType>(Ty)) { |
| // Packed structs always have an alignment of 1. |
| if (STy->isPacked()) |
| return ConstantInt::get(DestTy, 1); |
| |
| // Otherwise, struct alignment is the maximum alignment of any member. |
| // Without target data, we can't compare much, but we can check to see |
| // if all the members have the same alignment. |
| unsigned NumElems = STy->getNumElements(); |
| // An empty struct has minimal alignment. |
| if (NumElems == 0) |
| return ConstantInt::get(DestTy, 1); |
| // Check for a struct with all members having the same alignment. |
| Constant *MemberAlign = |
| getFoldedAlignOf(STy->getElementType(0), DestTy, true); |
| bool AllSame = true; |
| for (unsigned i = 1; i != NumElems; ++i) |
| if (MemberAlign != getFoldedAlignOf(STy->getElementType(i), DestTy, true)) { |
| AllSame = false; |
| break; |
| } |
| if (AllSame) |
| return MemberAlign; |
| } |
| |
| // Pointer alignment doesn't depend on the pointee type, so canonicalize them |
| // to an arbitrary pointee. |
| if (PointerType *PTy = dyn_cast<PointerType>(Ty)) |
| if (!PTy->getElementType()->isIntegerTy(1)) |
| return |
| getFoldedAlignOf(PointerType::get(IntegerType::get(PTy->getContext(), |
| 1), |
| PTy->getAddressSpace()), |
| DestTy, true); |
| |
| // If there's no interesting folding happening, bail so that we don't create |
| // a constant that looks like it needs folding but really doesn't. |
| if (!Folded) |
| return nullptr; |
| |
| // Base case: Get a regular alignof expression. |
| Constant *C = ConstantExpr::getAlignOf(Ty); |
| C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, |
| DestTy, false), |
| C, DestTy); |
| return C; |
| } |
| |
| /// Return a ConstantExpr with type DestTy for offsetof on Ty and FieldNo, with |
| /// any known factors factored out. If Folded is false, return null if no |
| /// factoring was possible, to avoid endlessly bouncing an unfoldable expression |
| /// back into the top-level folder. |
| static Constant *getFoldedOffsetOf(Type *Ty, Constant *FieldNo, Type *DestTy, |
| bool Folded) { |
| if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { |
| Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false, |
| DestTy, false), |
| FieldNo, DestTy); |
| Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); |
| return ConstantExpr::getNUWMul(E, N); |
| } |
| |
| if (StructType *STy = dyn_cast<StructType>(Ty)) |
| if (!STy->isPacked()) { |
| unsigned NumElems = STy->getNumElements(); |
| // An empty struct has no members. |
| if (NumElems == 0) |
| return nullptr; |
| // Check for a struct with all members having the same size. |
| Constant *MemberSize = |
| getFoldedSizeOf(STy->getElementType(0), DestTy, true); |
| bool AllSame = true; |
| for (unsigned i = 1; i != NumElems; ++i) |
| if (MemberSize != |
| getFoldedSizeOf(STy->getElementType(i), DestTy, true)) { |
| AllSame = false; |
| break; |
| } |
| if (AllSame) { |
| Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, |
| false, |
| DestTy, |
| false), |
| FieldNo, DestTy); |
| return ConstantExpr::getNUWMul(MemberSize, N); |
| } |
| } |
| |
| // If there's no interesting folding happening, bail so that we don't create |
| // a constant that looks like it needs folding but really doesn't. |
| if (!Folded) |
| return nullptr; |
| |
| // Base case: Get a regular offsetof expression. |
| Constant *C = ConstantExpr::getOffsetOf(Ty, FieldNo); |
| C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, |
| DestTy, false), |
| C, DestTy); |
| return C; |
| } |
| |
| Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V, |
| 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); |
| } |
| |
| if (V->isNullValue() && !DestTy->isX86_MMXTy() && |
| 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 ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); |
| } else if (CE->getOpcode() == Instruction::GetElementPtr && |
| // Do not fold addrspacecast (gep 0, .., 0). It might make the |
| // addrspacecast uncanonicalized. |
| opc != Instruction::AddrSpaceCast && |
| // Do not fold bitcast (gep) with inrange index, as this loses |
| // information. |
| !cast<GEPOperator>(CE)->getInRangeIndex().hasValue() && |
| // Do not fold if the gep type is a vector, as bitcasting |
| // operand 0 of a vector gep will result in a bitcast between |
| // different sizes. |
| !CE->getType()->isVectorTy()) { |
| // 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); |
| } |
| } |
| |
| // 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() && |
| DestTy->getVectorNumElements() == V->getType()->getVectorNumElements()) { |
| SmallVector<Constant*, 16> res; |
| VectorType *DestVecTy = cast<VectorType>(DestTy); |
| Type *DstEltTy = DestVecTy->getElementType(); |
| Type *Ty = IntegerType::get(V->getContext(), 32); |
| for (unsigned i = 0, e = V->getType()->getVectorNumElements(); i != e; ++i) { |
| Constant *C = |
| ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i)); |
| res.push_back(ConstantExpr::getCast(opc, C, DstEltTy)); |
| } |
| 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->isHalfTy() ? APFloat::IEEEhalf() : |
| DestTy->isFloatTy() ? APFloat::IEEEsingle() : |
| DestTy->isDoubleTy() ? APFloat::IEEEdouble() : |
| DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended() : |
| DestTy->isFP128Ty() ? APFloat::IEEEquad() : |
| DestTy->isPPC_FP128Ty() ? APFloat::PPCDoubleDouble() : |
| APFloat::Bogus(), |
| 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 UndefValue::get(DestTy); |
| } |
| return ConstantInt::get(FPC->getContext(), IntVal); |
| } |
| return nullptr; // 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 nullptr; // Other pointer types cannot be casted |
| case Instruction::PtrToInt: // always treated as unsigned |
| // Is it a null pointer value? |
| if (V->isNullValue()) |
| return ConstantInt::get(DestTy, 0); |
| // If this is a sizeof-like expression, pull out multiplications by |
| // known factors to expose them to subsequent folding. If it's an |
| // alignof-like expression, factor out known factors. |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) |
| if (CE->getOpcode() == Instruction::GetElementPtr && |
| CE->getOperand(0)->isNullValue()) { |
| // FIXME: Looks like getFoldedSizeOf(), getFoldedOffsetOf() and |
| // getFoldedAlignOf() don't handle the case when DestTy is a vector of |
| // pointers yet. We end up in asserts in CastInst::getCastOpcode (see |
| // test/Analysis/ConstantFolding/cast-vector.ll). I've only seen this |
| // happen in one "real" C-code test case, so it does not seem to be an |
| // important optimization to handle vectors here. For now, simply bail |
| // out. |
| if (DestTy->isVectorTy()) |
| return nullptr; |
| GEPOperator *GEPO = cast<GEPOperator>(CE); |
| Type *Ty = GEPO->getSourceElementType(); |
| if (CE->getNumOperands() == 2) { |
| // Handle a sizeof-like expression. |
| Constant *Idx = CE->getOperand(1); |
| bool isOne = isa<ConstantInt>(Idx) && cast<ConstantInt>(Idx)->isOne(); |
| if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) { |
| Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true, |
| DestTy, false), |
| Idx, DestTy); |
| return ConstantExpr::getMul(C, Idx); |
| } |
| } else if (CE->getNumOperands() == 3 && |
| CE->getOperand(1)->isNullValue()) { |
| // Handle an alignof-like expression. |
| if (StructType *STy = dyn_cast<StructType>(Ty)) |
| if (!STy->isPacked()) { |
| ConstantInt *CI = cast<ConstantInt>(CE->getOperand(2)); |
| if (CI->isOne() && |
| STy->getNumElements() == 2 && |
| STy->getElementType(0)->isIntegerTy(1)) { |
| return getFoldedAlignOf(STy->getElementType(1), DestTy, false); |
| } |
| } |
| // Handle an offsetof-like expression. |
| if (Ty->isStructTy() || Ty->isArrayTy()) { |
| if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2), |
| DestTy, false)) |
| return C; |
| } |
| } |
| } |
| // Other pointer types cannot be casted |
| return nullptr; |
| case Instruction::UIToFP: |
| case Instruction::SIToFP: |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { |
| const APInt &api = CI->getValue(); |
| APFloat apf(DestTy->getFltSemantics(), |
| APInt::getNullValue(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)); |
| } |
| |
| // The input must be a constantexpr. See if we can simplify this based on |
| // the bytes we are demanding. Only do this if the source and dest are an |
| // even multiple of a byte. |
| if ((DestBitWidth & 7) == 0 && |
| (cast<IntegerType>(V->getType())->getBitWidth() & 7) == 0) |
| if (Constant *Res = ExtractConstantBytes(V, 0, DestBitWidth / 8)) |
| return Res; |
| |
| return nullptr; |
| } |
| case Instruction::BitCast: |
| return FoldBitCast(V, DestTy); |
| case Instruction::AddrSpaceCast: |
| 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)) { |
| SmallVector<Constant*, 16> Result; |
| Type *Ty = IntegerType::get(CondV->getContext(), 32); |
| for (unsigned i = 0, e = V1->getType()->getVectorNumElements(); i != e;++i){ |
| Constant *V; |
| Constant *V1Element = ConstantExpr::getExtractElement(V1, |
| ConstantInt::get(Ty, i)); |
| Constant *V2Element = ConstantExpr::getExtractElement(V2, |
| ConstantInt::get(Ty, i)); |
| Constant *Cond = dyn_cast<Constant>(CondV->getOperand(i)); |
| 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() == V1->getType()->getVectorNumElements()) |
| return ConstantVector::get(Result); |
| } |
| |
| if (isa<UndefValue>(Cond)) { |
| if (isa<UndefValue>(V1)) return V1; |
| return V2; |
| } |
| if (isa<UndefValue>(V1)) return V2; |
| if (isa<UndefValue>(V2)) return V1; |
| if (V1 == V2) return V1; |
| |
| if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) { |
| if (TrueVal->getOpcode() == Instruction::Select) |
| if (TrueVal->getOperand(0) == Cond) |
| return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2); |
| } |
| if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) { |
| if (FalseVal->getOpcode() == Instruction::Select) |
| if (FalseVal->getOperand(0) == Cond) |
| return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2)); |
| } |
| |
| return nullptr; |
| } |
| |
| Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val, |
| Constant *Idx) { |
| if (isa<UndefValue>(Val)) // ee(undef, x) -> undef |
| return UndefValue::get(Val->getType()->getVectorElementType()); |
| if (Val->isNullValue()) // ee(zero, x) -> zero |
| return Constant::getNullValue(Val->getType()->getVectorElementType()); |
| // ee({w,x,y,z}, undef) -> undef |
| if (isa<UndefValue>(Idx)) |
| return UndefValue::get(Val->getType()->getVectorElementType()); |
| |
| if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) { |
| // ee({w,x,y,z}, wrong_value) -> undef |
| if (CIdx->uge(Val->getType()->getVectorNumElements())) |
| return UndefValue::get(Val->getType()->getVectorElementType()); |
| return Val->getAggregateElement(CIdx->getZExtValue()); |
| } |
| return nullptr; |
| } |
| |
| Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val, |
| Constant *Elt, |
| Constant *Idx) { |
| if (isa<UndefValue>(Idx)) |
| return UndefValue::get(Val->getType()); |
| |
| ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx); |
| if (!CIdx) return nullptr; |
| |
| unsigned NumElts = Val->getType()->getVectorNumElements(); |
| if (CIdx->uge(NumElts)) |
| return UndefValue::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, |
| Constant *Mask) { |
| unsigned MaskNumElts = Mask->getType()->getVectorNumElements(); |
| Type *EltTy = V1->getType()->getVectorElementType(); |
| |
| // Undefined shuffle mask -> undefined value. |
| if (isa<UndefValue>(Mask)) |
| return UndefValue::get(VectorType::get(EltTy, MaskNumElts)); |
| |
| // Don't break the bitcode reader hack. |
| if (isa<ConstantExpr>(Mask)) return nullptr; |
| |
| unsigned SrcNumElts = V1->getType()->getVectorNumElements(); |
| |
| // Loop over the shuffle mask, evaluating each element. |
| SmallVector<Constant*, 32> Result; |
| for (unsigned i = 0; i != MaskNumElts; ++i) { |
| int Elt = ShuffleVectorInst::getMaskValue(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<SequentialType>(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); |
| if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType())) |
| return ConstantArray::get(AT, Result); |
| return ConstantVector::get(Result); |
| } |
| |
| Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, Constant *C1, |
| Constant *C2) { |
| assert(Instruction::isBinaryOp(Opcode) && "Non-binary instruction detected"); |
| |
| // Handle scalar UndefValue. Vectors are always evaluated per element. |
| bool HasScalarUndef = !C1->getType()->isVectorTy() && |
| (isa<UndefValue>(C1) || isa<UndefValue>(C2)); |
| if (HasScalarUndef) { |
| 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()); |
| LLVM_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 -> undef |
| if (isa<UndefValue>(C2)) |
| return C2; |
| // undef / 0 -> undef |
| // undef / 1 -> undef |
| if (match(C2, m_Zero()) || match(C2, m_One())) |
| return C1; |
| // undef / X -> 0 otherwise |
| return Constant::getNullValue(C1->getType()); |
| case Instruction::URem: |
| case Instruction::SRem: |
| // X % undef -> undef |
| if (match(C2, m_Undef())) |
| return C2; |
| // undef % 0 -> undef |
| if (match(C2, m_Zero())) |
| return C1; |
| // 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 -> undef |
| if (isa<UndefValue>(C2)) |
| return C2; |
| // undef >>l 0 -> undef |
| if (match(C2, m_Zero())) |
| return C1; |
| // undef >>l X -> 0 |
| return Constant::getNullValue(C1->getType()); |
| case Instruction::AShr: |
| // X >>a undef -> undef |
| if (isa<UndefValue>(C2)) |
| return C2; |
| // undef >>a 0 -> undef |
| if (match(C2, m_Zero())) |
| return C1; |
| // TODO: undef >>a X -> undef 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 C2; |
| // undef << 0 -> undef |
| if (match(C2, m_Zero())) |
| return C1; |
| // undef << X -> 0 |
| return Constant::getNullValue(C1->getType()); |
| case Instruction::FAdd: |
| case Instruction::FSub: |
| 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(!HasScalarUndef && "Unexpected UndefValue"); |
| |
| // Handle simplifications when the RHS is a constant int. |
| if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { |
| switch (Opcode) { |
| case Instruction::Add: |
| if (CI2->isZero()) return C1; // X + 0 == X |
| break; |
| case Instruction::Sub: |
| if (CI2->isZero()) return C1; // X - 0 == X |
| break; |
| case Instruction::Mul: |
| if (CI2->isZero()) return C2; // X * 0 == 0 |
| if (CI2->isOne()) |
| return C1; // X * 1 == X |
| break; |
| case Instruction::UDiv: |
| case Instruction::SDiv: |
| if (CI2->isOne()) |
| return C1; // X / 1 == X |
| if (CI2->isZero()) |
| return UndefValue::get(CI2->getType()); // X / 0 == undef |
| break; |
| case Instruction::URem: |
| case Instruction::SRem: |
| if (CI2->isOne()) |
| return Constant::getNullValue(CI2->getType()); // X % 1 == 0 |
| if (CI2->isZero()) |
| return UndefValue::get(CI2->getType()); // X % 0 == undef |
| break; |
| case Instruction::And: |
| if (CI2->isZero()) return C2; // X & 0 == 0 |
| if (CI2->isMinusOne()) |
| return C1; // X & -1 == X |
| |
| if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { |
| // (zext i32 to i64) & 4294967295 -> (zext i32 to i64) |
| if (CE1->getOpcode() == Instruction::ZExt) { |
| unsigned DstWidth = CI2->getType()->getBitWidth(); |
| unsigned SrcWidth = |
| CE1->getOperand(0)->getType()->getPrimitiveSizeInBits(); |
| APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth)); |
| if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits) |
| return 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)); |
| |
| unsigned GVAlign; |
| |
| if (Module *TheModule = GV->getParent()) { |
| GVAlign = GV->getPointerAlignment(TheModule->getDataLayout()); |
| |
| // 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 (GVAlign == 0U && isa<Function>(GV)) |
| GVAlign = 4U; |
| } else if (isa<Function>(GV)) { |
| // Without a datalayout we have to assume the worst case: that the |
| // function pointer isn't aligned at all. |
| GVAlign = 0U; |
| } else { |
| GVAlign = GV->getAlignment(); |
| } |
| |
| if (GVAlign > 1) { |
| unsigned DstWidth = CI2->getType()->getBitWidth(); |
| unsigned SrcWidth = std::min(DstWidth, Log2_32(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->isZero()) return C1; // X | 0 == X |
| if (CI2->isMinusOne()) |
| return C2; // X | -1 == -1 |
| break; |
| case Instruction::Xor: |
| if (CI2->isZero()) return C1; // X ^ 0 == X |
| |
| if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { |
| switch (CE1->getOpcode()) { |
| default: break; |
| case Instruction::ICmp: |
| case Instruction::FCmp: |
| // cmp pred ^ true -> cmp !pred |
| assert(CI2->isOne()); |
| CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate(); |
| pred = CmpInst::getInversePredicate(pred); |
| return ConstantExpr::getCompare(pred, CE1->getOperand(0), |
| CE1->getOperand(1)); |
| } |
| } |
| break; |
| case Instruction::AShr: |
| // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2 |
| if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) |
| if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero. |
| return ConstantExpr::getLShr(C1, C2); |
| break; |
| } |
| } else if (isa<ConstantInt>(C1)) { |
| // If C1 is a ConstantInt and C2 is not, swap the operands. |
| if (Instruction::isCommutative(Opcode)) |
| return ConstantExpr::get(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.isAllOnesValue() && C1V.isMinSignedValue()) |
| return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef |
| 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.isAllOnesValue() && C1V.isMinSignedValue()) |
| return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef |
| 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 UndefValue::get(C1->getType()); // too big shift is undef |
| case Instruction::LShr: |
| if (C2V.ult(C1V.getBitWidth())) |
| return ConstantInt::get(CI1->getContext(), C1V.lshr(C2V)); |
| return UndefValue::get(C1->getType()); // too big shift is undef |
| case Instruction::AShr: |
| if (C2V.ult(C1V.getBitWidth())) |
| return ConstantInt::get(CI1->getContext(), C1V.ashr(C2V)); |
| return UndefValue::get(C1->getType()); // too big shift is undef |
| } |
| } |
| |
| 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 (VectorType *VTy = dyn_cast<VectorType>(C1->getType())) { |
| // Fold each element and create a vector constant from those constants. |
| SmallVector<Constant*, 16> Result; |
| Type *Ty = IntegerType::get(VTy->getContext(), 32); |
| for (unsigned i = 0, e = VTy->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 undef. |
| if (Instruction::isIntDivRem(Opcode) && RHS->isNullValue()) |
| return UndefValue::get(VTy); |
| |
| Result.push_back(ConstantExpr::get(Opcode, LHS, RHS)); |
| } |
| |
| 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::Mul: |
| return ConstantExpr::getAnd(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; |
| } |
| |
| /// This type is zero-sized if it's an array or structure of zero-sized types. |
| /// The only leaf zero-sized type is an empty structure. |
| static bool isMaybeZeroSizedType(Type *Ty) { |
| if (StructType *STy = dyn_cast<StructType>(Ty)) { |
| if (STy->isOpaque()) return true; // Can't say. |
| |
| // 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 (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { |
| return isMaybeZeroSizedType(ATy->getElementType()); |
| } |
| return false; |
| } |
| |
| /// Compare the two constants as though they were getelementptr indices. |
| /// This allows coercion of the types to be the same thing. |
| /// |
| /// If the two constants are the "same" (after coercion), 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, 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! |
| |
| // We cannot compare the indices if they don't fit in an int64_t. |
| if (cast<ConstantInt>(C1)->getValue().getActiveBits() > 64 || |
| cast<ConstantInt>(C2)->getValue().getActiveBits() > 64) |
| return -2; // don't know! |
| |
| // Ok, we have two differing integer indices. Sign extend them to be the same |
| // type. |
| int64_t C1Val = cast<ConstantInt>(C1)->getSExtValue(); |
| int64_t C2Val = cast<ConstantInt>(C2)->getSExtValue(); |
| |
| if (C1Val == C2Val) 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 (C1Val < C2Val) |
| return -1; |
| else |
| return 1; |
| } |
| |
| /// 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(Constant *V1, Constant *V2) { |
| assert(V1->getType() == V2->getType() && |
| "Cannot compare values of different types!"); |
| |
| // We do not know if a constant expression will evaluate to a number or NaN. |
| // Therefore, we can only say that the relation is unordered or equal. |
| if (V1 == V2) return FCmpInst::FCMP_UEQ; |
| |
| if (!isa<ConstantExpr>(V1)) { |
| if (!isa<ConstantExpr>(V2)) { |
| // Simple case, use the standard constant folder. |
| ConstantInt *R = nullptr; |
| R = dyn_cast<ConstantInt>( |
| ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2)); |
| if (R && !R->isZero()) |
| return FCmpInst::FCMP_OEQ; |
| R = dyn_cast<ConstantInt>( |
| ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2)); |
| if (R && !R->isZero()) |
| return FCmpInst::FCMP_OLT; |
| R = dyn_cast<ConstantInt>( |
| ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2)); |
| 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. |
| 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; |
| } |
| |
| static ICmpInst::Predicate areGlobalsPotentiallyEqual(const GlobalValue *GV1, |
| const GlobalValue *GV2) { |
| auto isGlobalUnsafeForEquality = [](const GlobalValue *GV) { |
| if (GV->hasExternalWeakLinkage() || GV->hasWeakAnyLinkage()) |
| 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. |
| /// |
| /// 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(Constant *V1, 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) && |
| !isa<BlockAddress>(V1)) { |
| if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) && |
| !isa<BlockAddress>(V2)) { |
| // We distilled this down to a simple case, use the standard constant |
| // folder. |
| ConstantInt *R = nullptr; |
| ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; |
| R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); |
| if (R && !R->isZero()) |
| return pred; |
| pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; |
| R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); |
| if (R && !R->isZero()) |
| return pred; |
| pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; |
| R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); |
| 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 *GV = 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); |
| return ICmpInst::BAD_ICMP_PREDICATE; |
| } |
| |
| // Now we know that the RHS is a GlobalValue, BlockAddress or simple |
| // constant (which, since the types must match, means that it's a |
| // ConstantPointerNull). |
| 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 { |
| assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); |
| // 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_NE; |
| } |
| } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(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); |
| return ICmpInst::BAD_ICMP_PREDICATE; |
| } |
| |
| // Now we know that the RHS is a GlobalValue, BlockAddress or simple |
| // constant (which, since the types must match, means that it is a |
| // ConstantPointerNull). |
| 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 { |
| // Block addresses aren't null, don't equal the address of globals. |
| assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) && |
| "Canonicalization guarantee!"); |
| return ICmpInst::ICMP_NE; |
| } |
| } else { |
| // 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. |
| ConstantExpr *CE1 = cast<ConstantExpr>(V1); |
| 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: |
| // We can't evaluate floating point casts or truncations. |
| if (CE1Op0->getType()->isFPOrFPVectorTy()) |
| break; |
| |
| // 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() && CE1->getType()->isIntOrPtrTy()) { |
| if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; |
| if (CE1->getOpcode() == Instruction::SExt) isSigned = true; |
| return evaluateICmpRelation(CE1Op0, |
| Constant::getNullValue(CE1Op0->getType()), |
| isSigned); |
| } |
| break; |
| |
| 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 (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 *GV2 = dyn_cast<GlobalValue>(V2)) { |
| if (isa<ConstantPointerNull>(CE1Op0)) { |
| if (GV2->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 *GV = dyn_cast<GlobalValue>(CE1Op0)) { |
| if (GV == GV2) { |
| // 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() && |
| "Surprising getelementptr!"); |
| return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; |
| } else { |
| if (CE1GEP->hasAllZeroIndices()) |
| return areGlobalsPotentiallyEqual(GV, GV2); |
| return ICmpInst::BAD_ICMP_PREDICATE; |
| } |
| } |
| } else { |
| ConstantExpr *CE2 = cast<ConstantExpr>(V2); |
| 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 global. |
| if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { |
| // Don't know relative ordering, but check for inequality. |
| if (CE1Op0 != CE2Op0) { |
| GEPOperator *CE2GEP = cast<GEPOperator>(CE2); |
| if (CE1GEP->hasAllZeroIndices() && CE2GEP->hasAllZeroIndices()) |
| return areGlobalsPotentiallyEqual(cast<GlobalValue>(CE1Op0), |
| cast<GlobalValue>(CE2Op0)); |
| return ICmpInst::BAD_ICMP_PREDICATE; |
| } |
| // 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; |
| |
| // The logic below assumes that the result of the comparison |
| // can be determined by finding the first index that differs. |
| // This doesn't work if there is over-indexing in any |
| // subsequent indices, so check for that case first. |
| if (!CE1->isGEPWithNoNotionalOverIndexing() || |
| !CE2->isGEPWithNoNotionalOverIndexing()) |
| return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. |
| |
| // 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; |
| } |
| } |
| } |
| break; |
| } |
| default: |
| break; |
| } |
| } |
| |
| return ICmpInst::BAD_ICMP_PREDICATE; |
| } |
| |
| Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, |
| Constant *C1, Constant *C2) { |
| Type *ResultTy; |
| if (VectorType *VT = dyn_cast<VectorType>(C1->getType())) |
| ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()), |
| VT->getNumElements()); |
| else |
| ResultTy = Type::getInt1Ty(C1->getContext()); |
| |
| // Fold FCMP_FALSE/FCMP_TRUE unconditionally. |
| if (pred == FCmpInst::FCMP_FALSE) |
| return Constant::getNullValue(ResultTy); |
| |
| if (pred == FCmpInst::FCMP_TRUE) |
| return Constant::getAllOnesValue(ResultTy); |
| |
| // Handle some degenerate cases first |
| if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { |
| CmpInst::Predicate Predicate = CmpInst::Predicate(pred); |
| 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)); |
| } |
| |
| // 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() && |
| !NullPointerIsDefined(nullptr /* F */, |
| GV->getType()->getAddressSpace())) { |
| if (pred == ICmpInst::ICMP_EQ) |
| return ConstantInt::getFalse(C1->getContext()); |
| else if (pred == ICmpInst::ICMP_NE) |
| return ConstantInt::getTrue(C1->getContext()); |
| } |
| // 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() && |
| !NullPointerIsDefined(nullptr /* F */, |
| GV->getType()->getAddressSpace())) { |
| if (pred == ICmpInst::ICMP_EQ) |
| return ConstantInt::getFalse(C1->getContext()); |
| else if (pred == ICmpInst::ICMP_NE) |
| return ConstantInt::getTrue(C1->getContext()); |
| } |
| } |
| |
| // If the comparison is a comparison between two i1's, simplify it. |
| if (C1->getType()->isIntegerTy(1)) { |
| switch(pred) { |
| 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(); |
| switch (pred) { |
| default: llvm_unreachable("Invalid ICmp Predicate"); |
| case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2); |
| case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2); |
| case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2)); |
| case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2)); |
| case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2)); |
| case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2)); |
| case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2)); |
| case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2)); |
| case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2)); |
| case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2)); |
| } |
| } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { |
| const APFloat &C1V = cast<ConstantFP>(C1)->getValueAPF(); |
| const APFloat &C2V = cast<ConstantFP>(C2)->getValueAPF(); |
| APFloat::cmpResult R = C1V.compare(C2V); |
| switch (pred) { |
| default: llvm_unreachable("Invalid FCmp Predicate"); |
| case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy); |
| case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy); |
| case FCmpInst::FCMP_UNO: |
| return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered); |
| case FCmpInst::FCMP_ORD: |
| return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered); |
| case FCmpInst::FCMP_UEQ: |
| return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || |
| R==APFloat::cmpEqual); |
| case FCmpInst::FCMP_OEQ: |
| return ConstantInt::get(ResultTy, R==APFloat::cmpEqual); |
| case FCmpInst::FCMP_UNE: |
| return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual); |
| case FCmpInst::FCMP_ONE: |
| return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || |
| R==APFloat::cmpGreaterThan); |
| case FCmpInst::FCMP_ULT: |
| return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || |
| R==APFloat::cmpLessThan); |
| case FCmpInst::FCMP_OLT: |
| return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan); |
| case FCmpInst::FCMP_UGT: |
| return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || |
| R==APFloat::cmpGreaterThan); |
| case FCmpInst::FCMP_OGT: |
| return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan); |
| case FCmpInst::FCMP_ULE: |
| return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan); |
| case FCmpInst::FCMP_OLE: |
| return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || |
| R==APFloat::cmpEqual); |
| case FCmpInst::FCMP_UGE: |
| return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan); |
| case FCmpInst::FCMP_OGE: |
| return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan || |
| R==APFloat::cmpEqual); |
| } |
| } else if (C1->getType()->isVectorTy()) { |
| // 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 = C1->getType()->getVectorNumElements(); i != e;++i){ |
| Constant *C1E = |
| ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i)); |
| Constant *C2E = |
| ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i)); |
| |
| ResElts.push_back(ConstantExpr::getCompare(pred, C1E, C2E)); |
| } |
| |
| return ConstantVector::get(ResElts); |
| } |
| |
| if (C1->getType()->isFloatingPointTy() && |
| // Only call evaluateFCmpRelation if we have a constant expr to avoid |
| // infinite recursive loop |
| (isa<ConstantExpr>(C1) || isa<ConstantExpr>(C2))) { |
| int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. |
| switch (evaluateFCmpRelation(C1, C2)) { |
| default: llvm_unreachable("Unknown relation!"); |
| case FCmpInst::FCMP_UNO: |
| case FCmpInst::FCMP_ORD: |
| 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 |
| Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || |
| pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || |
| pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); |
| break; |
| case FCmpInst::FCMP_OLT: // We know that C1 < C2 |
| Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || |
| pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || |
| pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); |
| break; |
| case FCmpInst::FCMP_OGT: // We know that C1 > C2 |
| Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || |
| pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || |
| pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); |
| break; |
| 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) |
| Result = 0; |
| else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) |
| Result = 1; |
| 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) |
| Result = 0; |
| else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) |
| Result = 1; |
| break; |
| case FCmpInst::FCMP_ONE: // We know that C1 != C2 |
| // We can only partially decide this relation. |
| if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) |
| Result = 0; |
| else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) |
| Result = 1; |
| break; |
| case FCmpInst::FCMP_UEQ: // We know that C1 == C2 || isUnordered(C1, C2). |
| // We can only partially decide this relation. |
| if (pred == FCmpInst::FCMP_ONE) |
| Result = 0; |
| else if (pred == FCmpInst::FCMP_UEQ) |
| Result = 1; |
| break; |
| } |
| |
| // If we evaluated the result, return it now. |
| if (Result != -1) |
| return ConstantInt::get(ResultTy, Result); |
| |
| } 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, |
| CmpInst::isSigned((CmpInst::Predicate)pred))) { |
| 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((ICmpInst::Predicate)pred); |
| break; |
| case ICmpInst::ICMP_ULT: |
| switch (pred) { |
| 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; |
| } |
| break; |
| case ICmpInst::ICMP_SLT: |
| switch (pred) { |
| 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; |
| } |
| break; |
| case ICmpInst::ICMP_UGT: |
| switch (pred) { |
| 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; |
| } |
| break; |
| case ICmpInst::ICMP_SGT: |
| switch (pred) { |
| 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; |
| } |
| break; |
| case ICmpInst::ICMP_ULE: |
| if (pred == ICmpInst::ICMP_UGT) Result = 0; |
| if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1; |
| break; |
| case ICmpInst::ICMP_SLE: |
| if (pred == ICmpInst::ICMP_SGT) Result = 0; |
| if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1; |
| break; |
| case ICmpInst::ICMP_UGE: |
| if (pred == ICmpInst::ICMP_ULT) Result = 0; |
| if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1; |
| break; |
| case ICmpInst::ICMP_SGE: |
| if (pred == ICmpInst::ICMP_SLT) Result = 0; |
| if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1; |
| break; |
| case ICmpInst::ICMP_NE: |
| if (pred == ICmpInst::ICMP_EQ) Result = 0; |
| if (pred == ICmpInst::ICMP_NE) Result = 1; |
| break; |
| } |
| |
| // If we evaluated the result, return it now. |
| if (Result != -1) |
| return ConstantInt::get(ResultTy, Result); |
| |
| // If the right hand side is a bitcast, try using its inverse to simplify |
| // it by moving it to the left hand side. We can't do this if it would turn |
| // a vector compare into a scalar compare or visa versa, or if it would turn |
| // the operands into FP values. |
| if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) { |
| Constant *CE2Op0 = CE2->getOperand(0); |
| if (CE2->getOpcode() == Instruction::BitCast && |
| CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy() && |
| !CE2Op0->getType()->isFPOrFPVectorTy()) { |
| Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType()); |
| return ConstantExpr::getICmp(pred, Inverse, CE2Op0); |
| } |
| } |
| |
| // If the left hand side is an extension, try eliminating it. |
| if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { |
| if ((CE1->getOpcode() == Instruction::SExt && |
| ICmpInst::isSigned((ICmpInst::Predicate)pred)) || |
| (CE1->getOpcode() == Instruction::ZExt && |
| !ICmpInst::isSigned((ICmpInst::Predicate)pred))){ |
| Constant *CE1Op0 = CE1->getOperand(0); |
| Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType()); |
| if (CE1Inverse == CE1Op0) { |
| // Check whether we can safely truncate the right hand side. |
| Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType()); |
| if (ConstantExpr::getCast(CE1->getOpcode(), C2Inverse, |
| C2->getType()) == C2) |
| return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse); |
| } |
| } |
| } |
| |
| 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. |
| pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); |
| return ConstantExpr::getICmp(pred, C2, C1); |
| } |
| } |
| return nullptr; |
| } |
| |
| /// Test whether the given sequence of *normalized* indices is "inbounds". |
| template<typename IndexTy> |
| static bool isInBoundsIndices(ArrayRef<IndexTy> Idxs) { |
| // No indices means nothing that could be out of bounds. |
| if (Idxs.empty()) return true; |
| |
| // If the first index is zero, it's in bounds. |
| if (cast<Constant>(Idxs[0])->isNullValue()) return true; |
| |
| // If the first index is one and all the rest are zero, it's in bounds, |
| // by the one-past-the-end rule. |
| if (auto *CI = dyn_cast<ConstantInt>(Idxs[0])) { |
| if (!CI->isOne()) |
| return false; |
| } else { |
| auto *CV = cast<ConstantDataVector>(Idxs[0]); |
| CI = dyn_cast_or_null<ConstantInt>(CV->getSplatValue()); |
| if (!CI || !CI->isOne()) |
| return false; |
| } |
| |
| for (unsigned i = 1, e = Idxs.size(); i != e; ++i) |
| if (!cast<Constant>(Idxs[i])->isNullValue()) |
| return false; |
| return true; |
| } |
| |
| /// Test whether a given ConstantInt is in-range for a SequentialType. |
| static bool isIndexInRangeOfArrayType(uint64_t NumElements, |
| const ConstantInt *CI) { |
| // We cannot bounds check the index if it doesn't fit in an int64_t. |
| if (CI->getValue().getMinSignedBits() > 64) |
| return false; |
| |
| // A negative index or an index past the end of our sequential type is |
| // considered out-of-range. |
| int64_t IndexVal = CI->getSExtValue(); |
| if (IndexVal < 0 || (NumElements > 0 && (uint64_t)IndexVal >= NumElements)) |
| return false; |
| |
| // Otherwise, it is in-range. |
| return true; |
| } |
| |
| Constant *llvm::ConstantFoldGetElementPtr(Type *PointeeTy, Constant *C, |
| bool InBounds, |
| Optional<unsigned> InRangeIndex, |
| ArrayRef<Value *> Idxs) { |
| if (Idxs.empty()) return C; |
| |
| Type *GEPTy = GetElementPtrInst::getGEPReturnType( |
| PointeeTy, C, makeArrayRef((Value *const *)Idxs.data(), Idxs.size())); |
| |
| if (isa<UndefValue>(C)) |
| return UndefValue::get(GEPTy); |
| |
| Constant *Idx0 = cast<Constant>(Idxs[0]); |
| if (Idxs.size() == 1 && (Idx0->isNullValue() || isa<UndefValue>(Idx0))) |
| return GEPTy->isVectorTy() && !C->getType()->isVectorTy() |
| ? ConstantVector::getSplat( |
| cast<VectorType>(GEPTy)->getNumElements(), C) |
| : C; |
| |
| if (C->isNullValue()) { |
| bool isNull = true; |
| for (unsigned i = 0, e = Idxs.size(); i != e; ++i) |
| if (!isa<UndefValue>(Idxs[i]) && |
| !cast<Constant>(Idxs[i])->isNullValue()) { |
| isNull = false; |
| break; |
| } |
| if (isNull) { |
| PointerType *PtrTy = cast<PointerType>(C->getType()->getScalarType()); |
| Type *Ty = GetElementPtrInst::getIndexedType(PointeeTy, Idxs); |
| |
| assert(Ty && "Invalid indices for GEP!"); |
| Type *OrigGEPTy = PointerType::get(Ty, PtrTy->getAddressSpace()); |
| Type *GEPTy = PointerType::get(Ty, PtrTy->getAddressSpace()); |
| if (VectorType *VT = dyn_cast<VectorType>(C->getType())) |
| GEPTy = VectorType::get(OrigGEPTy, VT->getNumElements()); |
| |
| // The GEP returns a vector of pointers when one of more of |
| // its arguments is a vector. |
| for (unsigned i = 0, e = Idxs.size(); i != e; ++i) { |
| if (auto *VT = dyn_cast<VectorType>(Idxs[i]->getType())) { |
| GEPTy = VectorType::get(OrigGEPTy, VT->getNumElements()); |
| break; |
| } |
| } |
| |
| return Constant::getNullValue(GEPTy); |
| } |
| } |
| |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(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) { |
| gep_type_iterator LastI = gep_type_end(CE); |
| for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); |
| I != E; ++I) |
| LastI = I; |
| |
| // We cannot combine indices if doing so would take us outside of an |
| // array or vector. Doing otherwise could trick us if we evaluated such a |
| // GEP as part of a load. |
| // |
| // e.g. Consider if the original GEP was: |
| // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c, |
| // i32 0, i32 0, i64 0) |
| // |
| // If we then tried to offset it by '8' to get to the third element, |
| // an i8, we should *not* get: |
| // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c, |
| // i32 0, i32 0, i64 8) |
| // |
| // This GEP tries to index array element '8 which runs out-of-bounds. |
| // Subsequent evaluation would get confused and produce erroneous results. |
| // |
| // The following prohibits such a GEP from being formed by checking to see |
| // if the index is in-range with respect to an array. |
| // TODO: This code may be extended to handle vectors as well. |
| bool PerformFold = false; |
| if (Idx0->isNullValue()) |
| PerformFold = true; |
| else if (LastI.isSequential()) |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx0)) |
| PerformFold = (!LastI.isBoundedSequential() || |
| isIndexInRangeOfArrayType( |
| LastI.getSequentialNumElements(), CI)) && |
| !CE->getOperand(CE->getNumOperands() - 1) |
| ->getType() |
| ->isVectorTy(); |
| |
| if (PerformFold) { |
| SmallVector<Value*, 16> NewIndices; |
| NewIndices.reserve(Idxs.size() + CE->getNumOperands()); |
| NewIndices.append(CE->op_begin() + 1, CE->op_end() - 1); |
| |
| // 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()) { |
| Type *IdxTy = Combined->getType(); |
| if (IdxTy != Idx0->getType()) { |
| unsigned CommonExtendedWidth = |
| std::max(IdxTy->getIntegerBitWidth(), |
| Idx0->getType()->getIntegerBitWidth()); |
| CommonExtendedWidth = std::max(CommonExtendedWidth, 64U); |
| |
| Type *CommonTy = |
| Type::getIntNTy(IdxTy->getContext(), CommonExtendedWidth); |
| Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, CommonTy); |
| Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, CommonTy); |
| Combined = ConstantExpr::get(Instruction::Add, C1, C2); |
| } else { |
| Combined = |
| ConstantExpr::get(Instruction::Add, Idx0, Combined); |
| } |
| } |
| |
| NewIndices.push_back(Combined); |
| NewIndices.append(Idxs.begin() + 1, Idxs.end()); |
| |
| // The combined GEP normally inherits its index inrange attribute from |
| // the inner GEP, but if the inner GEP's last index was adjusted by the |
| // outer GEP, any inbounds attribute on that index is invalidated. |
| Optional<unsigned> IRIndex = cast<GEPOperator>(CE)->getInRangeIndex(); |
| if (IRIndex && *IRIndex == CE->getNumOperands() - 2 && !Idx0->isNullValue()) |
| IRIndex = None; |
| |
| return ConstantExpr::getGetElementPtr( |
| cast<GEPOperator>(CE)->getSourceElementType(), CE->getOperand(0), |
| NewIndices, InBounds && cast<GEPOperator>(CE)->isInBounds(), |
| IRIndex); |
| } |
| } |
| |
| // Attempt to fold casts to the same type away. For example, folding: |
| // |
| // i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*), |
| // i64 0, i64 0) |
| // into: |
| // |
| // i32* getelementptr ([3 x i32]* %X, i64 0, i64 0) |
| // |
| // Don't fold if the cast is changing address spaces. |
| if (CE->isCast() && Idxs.size() > 1 && Idx0->isNullValue()) { |
| PointerType *SrcPtrTy = |
| dyn_cast<PointerType>(CE->getOperand(0)->getType()); |
| PointerType *DstPtrTy = dyn_cast<PointerType>(CE->getType()); |
| if (SrcPtrTy && DstPtrTy) { |
| ArrayType *SrcArrayTy = |
| dyn_cast<ArrayType>(SrcPtrTy->getElementType()); |
| ArrayType *DstArrayTy = |
| dyn_cast<ArrayType>(DstPtrTy->getElementType()); |
| if (SrcArrayTy && DstArrayTy |
| && SrcArrayTy->getElementType() == DstArrayTy->getElementType() |
| && SrcPtrTy->getAddressSpace() == DstPtrTy->getAddressSpace()) |
| return ConstantExpr::getGetElementPtr(SrcArrayTy, |
| (Constant *)CE->getOperand(0), |
| Idxs, InBounds, InRangeIndex); |
| } |
| } |
| } |
| |
| // Check to see if any array indices are not within the corresponding |
| // notional array or vector bounds. If so, try to determine if they can be |
| // factored out into preceding dimensions. |
| SmallVector<Constant *, 8> NewIdxs; |
| Type *Ty = PointeeTy; |
| Type *Prev = C->getType(); |
| bool Unknown = |
| !isa<ConstantInt>(Idxs[0]) && !isa<ConstantDataVector>(Idxs[0]); |
| for (unsigned i = 1, e = Idxs.size(); i != e; |
| Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) { |
| if (!isa<ConstantInt>(Idxs[i]) && !isa<ConstantDataVector>(Idxs[i])) { |
| // We don't know if it's in range or not. |
| Unknown = true; |
| continue; |
| } |
| if (!isa<ConstantInt>(Idxs[i - 1]) && !isa<ConstantDataVector>(Idxs[i - 1])) |
| // Skip if the type of the previous index is not supported. |
| continue; |
| if (InRangeIndex && i == *InRangeIndex + 1) { |
| // If an index is marked inrange, we cannot apply this canonicalization to |
| // the following index, as that will cause the inrange index to point to |
| // the wrong element. |
| continue; |
| } |
| if (isa<StructType>(Ty)) { |
| // The verify makes sure that GEPs into a struct are in range. |
| continue; |
| } |
| auto *STy = cast<SequentialType>(Ty); |
| if (isa<VectorType>(STy)) { |
| // There can be awkward padding in after a non-power of two vector. |
| Unknown = true; |
| continue; |
| } |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) { |
| if (isIndexInRangeOfArrayType(STy->getNumElements(), CI)) |
| // It's in range, skip to the next index. |
| continue; |
| if (CI->getSExtValue() < 0) { |
| // It's out of range and negative, don't try to factor it. |
| Unknown = true; |
| continue; |
| } |
| } else { |
| auto *CV = cast<ConstantDataVector>(Idxs[i]); |
| bool InRange = true; |
| for (unsigned I = 0, E = CV->getNumElements(); I != E; ++I) { |
| auto *CI = cast<ConstantInt>(CV->getElementAsConstant(I)); |
| InRange &= isIndexInRangeOfArrayType(STy->getNumElements(), CI); |
| if (CI->getSExtValue() < 0) { |
| Unknown = true; |
| break; |
| } |
| } |
| if (InRange || Unknown) |
| // It's in range, skip to the next index. |
| // It's out of range and negative, don't try to factor it. |
| continue; |
| } |
| if (isa<StructType>(Prev)) { |
| // It's out of range, but the prior dimension is a struct |
| // so we can't do anything about it. |
| Unknown = true; |
| continue; |
| } |
| // It's out of range, but we can factor it into the prior |
| // dimension. |
| NewIdxs.resize(Idxs.size()); |
| // Determine the number of elements in our sequential type. |
| uint64_t NumElements = STy->getArrayNumElements(); |
| |
| // Expand the current index or the previous index to a vector from a scalar |
| // if necessary. |
| Constant *CurrIdx = cast<Constant>(Idxs[i]); |
| auto *PrevIdx = |
| NewIdxs[i - 1] ? NewIdxs[i - 1] : cast<Constant>(Idxs[i - 1]); |
| bool IsCurrIdxVector = CurrIdx->getType()->isVectorTy(); |
| bool IsPrevIdxVector = PrevIdx->getType()->isVectorTy(); |
| bool UseVector = IsCurrIdxVector || IsPrevIdxVector; |
| |
| if (!IsCurrIdxVector && IsPrevIdxVector) |
| CurrIdx = ConstantDataVector::getSplat( |
| PrevIdx->getType()->getVectorNumElements(), CurrIdx); |
| |
| if (!IsPrevIdxVector && IsCurrIdxVector) |
| PrevIdx = ConstantDataVector::getSplat( |
| CurrIdx->getType()->getVectorNumElements(), PrevIdx); |
| |
| Constant *Factor = |
| ConstantInt::get(CurrIdx->getType()->getScalarType(), NumElements); |
| if (UseVector) |
| Factor = ConstantDataVector::getSplat( |
| IsPrevIdxVector ? PrevIdx->getType()->getVectorNumElements() |
| : CurrIdx->getType()->getVectorNumElements(), |
| Factor); |
| |
| NewIdxs[i] = ConstantExpr::getSRem(CurrIdx, Factor); |
| |
| Constant *Div = ConstantExpr::getSDiv(CurrIdx, Factor); |
| |
| unsigned CommonExtendedWidth = |
| std::max(PrevIdx->getType()->getScalarSizeInBits(), |
| Div->getType()->getScalarSizeInBits()); |
| CommonExtendedWidth = std::max(CommonExtendedWidth, 64U); |
| |
| // Before adding, extend both operands to i64 to avoid |
| // overflow trouble. |
| Type *ExtendedTy = Type::getIntNTy(Div->getContext(), CommonExtendedWidth); |
| if (UseVector) |
| ExtendedTy = VectorType::get( |
| ExtendedTy, IsPrevIdxVector |
| ? PrevIdx->getType()->getVectorNumElements() |
| : CurrIdx->getType()->getVectorNumElements()); |
| |
| if (!PrevIdx->getType()->isIntOrIntVectorTy(CommonExtendedWidth)) |
| PrevIdx = ConstantExpr::getSExt(PrevIdx, ExtendedTy); |
| |
| if (!Div->getType()->isIntOrIntVectorTy(CommonExtendedWidth)) |
| Div = ConstantExpr::getSExt(Div, ExtendedTy); |
| |
| NewIdxs[i - 1] = ConstantExpr::getAdd(PrevIdx, Div); |
| } |
| |
| // If we did any factoring, start over with the adjusted indices. |
| if (!NewIdxs.empty()) { |
| for (unsigned i = 0, e = Idxs.size(); i != e; ++i) |
| if (!NewIdxs[i]) NewIdxs[i] = cast<Constant>(Idxs[i]); |
| return ConstantExpr::getGetElementPtr(PointeeTy, C, NewIdxs, InBounds, |
| InRangeIndex); |
| } |
| |
| // If all indices are known integers and normalized, we can do a simple |
| // check for the "inbounds" property. |
| if (!Unknown && !InBounds) |
| if (auto *GV = dyn_cast<GlobalVariable>(C)) |
| if (!GV->hasExternalWeakLinkage() && isInBoundsIndices(Idxs)) |
| return ConstantExpr::getGetElementPtr(PointeeTy, C, Idxs, |
| /*InBounds=*/true, InRangeIndex); |
| |
| return nullptr; |
| } |