//===- 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" 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); // Do not iterate on scalable vector. The num of elements is unknown at // compile-time. if (isa(DstTy)) return nullptr; // 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 = cast(DstTy)->getNumElements(); if (NumElts != cast(CV->getType())->getNumElements()) return nullptr; Type *DstEltTy = DstTy->getElementType(); // Fast path for splatted constants. if (Constant *Splat = CV->getSplatValue()) { return ConstantVector::getSplat(DstTy->getElementCount(), ConstantExpr::getBitCast(Splat, DstEltTy)); } SmallVector 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(V->getType())) if (PointerType *DPTy = dyn_cast(DestTy)) if (PTy->getAddressSpace() == DPTy->getAddressSpace() && !PTy->isOpaque() && !DPTy->isOpaque() && PTy->getNonOpaquePointerElementType()->isSized()) { SmallVector IdxList; Value *Zero = Constant::getNullValue(Type::getInt32Ty(DPTy->getContext())); IdxList.push_back(Zero); Type *ElTy = PTy->getNonOpaquePointerElementType(); while (ElTy && ElTy != DPTy->getNonOpaquePointerElementType()) { ElTy = GetElementPtrInst::getTypeAtIndex(ElTy, (uint64_t)0); IdxList.push_back(Zero); } if (ElTy == DPTy->getNonOpaquePointerElementType()) // This GEP is inbounds because all indices are zero. return ConstantExpr::getInBoundsGetElementPtr( PTy->getNonOpaquePointerElementType(), 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(DestTy)) { if (VectorType *SrcTy = dyn_cast(V->getType())) { assert(DestPTy->getPrimitiveSizeInBits() == SrcTy->getPrimitiveSizeInBits() && "Not cast between same sized vectors!"); SrcTy = nullptr; // First, check for null. Undef is already handled. if (isa(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(V) || isa(V)) return ConstantExpr::getBitCast(ConstantVector::get(V), DestPTy); } // Finally, implement bitcast folding now. The code below doesn't handle // bitcast right. if (isa(V)) // ptr->ptr cast. return ConstantPointerNull::get(cast(DestTy)); // Handle integral constant input. if (ConstantInt *CI = dyn_cast(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(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(C->getType())->getBitWidth() & 7) == 0 && "Non-byte sized integer input"); unsigned CSize = cast(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(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(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(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(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(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(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; } } } Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V, Type *DestTy) { if (isa(V)) return PoisonValue::get(DestTy); if (isa(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() && !DestTy->isX86_AMXTy() && opc != Instruction::AddrSpaceCast) return Constant::getNullValue(DestTy); // If the cast operand is a constant expression, there's a few things we can // do to try to simplify it. if (ConstantExpr *CE = dyn_cast(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(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(V) || isa(V)) && DestTy->isVectorTy() && cast(DestTy)->getNumElements() == cast(V->getType())->getNumElements()) { VectorType *DestVecTy = cast(DestTy); Type *DstEltTy = DestVecTy->getElementType(); // Fast path for splatted constants. if (Constant *Splat = V->getSplatValue()) { return ConstantVector::getSplat( cast(DestTy)->getElementCount(), ConstantExpr::getCast(opc, Splat, DstEltTy)); } SmallVector res; Type *Ty = IntegerType::get(V->getContext(), 32); for (unsigned i = 0, e = cast(V->getType())->getNumElements(); 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(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(V)) { const APFloat &V = FPC->getValueAPF(); bool ignored; uint32_t DestBitWidth = cast(DestTy)->getBitWidth(); APSInt IntVal(DestBitWidth, opc == Instruction::FPToUI); if (APFloat::opInvalidOp == V.convertToInteger(IntVal, APFloat::rmTowardZero, &ignored)) { // Undefined behavior invoked - the destination type can't represent // the input constant. return PoisonValue::get(DestTy); } return ConstantInt::get(FPC->getContext(), IntVal); } return nullptr; // Can't fold. case Instruction::IntToPtr: //always treated as unsigned if (V->isNullValue()) // Is it an integral null value? return ConstantPointerNull::get(cast(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); // Other pointer types cannot be casted return nullptr; case Instruction::UIToFP: case Instruction::SIToFP: if (ConstantInt *CI = dyn_cast(V)) { const APInt &api = CI->getValue(); APFloat apf(DestTy->getFltSemantics(), APInt::getZero(DestTy->getPrimitiveSizeInBits())); apf.convertFromAPInt(api, opc==Instruction::SIToFP, APFloat::rmNearestTiesToEven); return ConstantFP::get(V->getContext(), apf); } return nullptr; case Instruction::ZExt: if (ConstantInt *CI = dyn_cast(V)) { uint32_t BitWidth = cast(DestTy)->getBitWidth(); return ConstantInt::get(V->getContext(), CI->getValue().zext(BitWidth)); } return nullptr; case Instruction::SExt: if (ConstantInt *CI = dyn_cast(V)) { uint32_t BitWidth = cast(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(DestTy)->getBitWidth(); if (ConstantInt *CI = dyn_cast(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(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(Cond)) { auto *V1VTy = CondV->getType(); SmallVector Result; Type *Ty = IntegerType::get(CondV->getContext(), 32); for (unsigned i = 0, e = V1VTy->getNumElements(); i != e; ++i) { Constant *V; Constant *V1Element = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, i)); Constant *V2Element = ConstantExpr::getExtractElement(V2, ConstantInt::get(Ty, i)); auto *Cond = cast(CondV->getOperand(i)); if (isa(Cond)) { V = PoisonValue::get(V1Element->getType()); } else if (V1Element == V2Element) { V = V1Element; } else if (isa(Cond)) { V = isa(V1Element) ? V1Element : V2Element; } else { if (!isa(Cond)) break; V = Cond->isNullValue() ? V2Element : V1Element; } Result.push_back(V); } // If we were able to build the vector, return it. if (Result.size() == V1VTy->getNumElements()) return ConstantVector::get(Result); } if (isa(Cond)) return PoisonValue::get(V1->getType()); if (isa(Cond)) { if (isa(V1)) return V1; return V2; } if (V1 == V2) return V1; if (isa(V1)) return V2; if (isa(V2)) return V1; // If the true or false value is undef, we can fold to the other value as // long as the other value isn't poison. auto NotPoison = [](Constant *C) { if (isa(C)) return false; // TODO: We can analyze ConstExpr by opcode to determine if there is any // possibility of poison. if (isa(C)) return false; if (isa(C) || isa(C) || isa(C) || isa(C) || isa(C)) return true; if (C->getType()->isVectorTy()) return !C->containsPoisonElement() && !C->containsConstantExpression(); // TODO: Recursively analyze aggregates or other constants. return false; }; if (isa(V1) && NotPoison(V2)) return V2; if (isa(V2) && NotPoison(V1)) return V1; if (ConstantExpr *TrueVal = dyn_cast(V1)) { if (TrueVal->getOpcode() == Instruction::Select) if (TrueVal->getOperand(0) == Cond) return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2); } if (ConstantExpr *FalseVal = dyn_cast(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) { auto *ValVTy = cast(Val->getType()); // extractelt poison, C -> poison // extractelt C, undef -> poison if (isa(Val) || isa(Idx)) return PoisonValue::get(ValVTy->getElementType()); // extractelt undef, C -> undef if (isa(Val)) return UndefValue::get(ValVTy->getElementType()); auto *CIdx = dyn_cast(Idx); if (!CIdx) return nullptr; if (auto *ValFVTy = dyn_cast(Val->getType())) { // ee({w,x,y,z}, wrong_value) -> poison if (CIdx->uge(ValFVTy->getNumElements())) return PoisonValue::get(ValFVTy->getElementType()); } // ee (gep (ptr, idx0, ...), idx) -> gep (ee (ptr, idx), ee (idx0, idx), ...) if (auto *CE = dyn_cast(Val)) { if (auto *GEP = dyn_cast(CE)) { SmallVector Ops; Ops.reserve(CE->getNumOperands()); for (unsigned i = 0, e = CE->getNumOperands(); i != e; ++i) { Constant *Op = CE->getOperand(i); if (Op->getType()->isVectorTy()) { Constant *ScalarOp = ConstantExpr::getExtractElement(Op, Idx); if (!ScalarOp) return nullptr; Ops.push_back(ScalarOp); } else Ops.push_back(Op); } return CE->getWithOperands(Ops, ValVTy->getElementType(), false, GEP->getSourceElementType()); } else if (CE->getOpcode() == Instruction::InsertElement) { if (const auto *IEIdx = dyn_cast(CE->getOperand(2))) { if (APSInt::isSameValue(APSInt(IEIdx->getValue()), APSInt(CIdx->getValue()))) { return CE->getOperand(1); } else { return ConstantExpr::getExtractElement(CE->getOperand(0), CIdx); } } } } if (Constant *C = Val->getAggregateElement(CIdx)) return C; // Lane < Splat minimum vector width => extractelt Splat(x), Lane -> x if (CIdx->getValue().ult(ValVTy->getElementCount().getKnownMinValue())) { if (Constant *SplatVal = Val->getSplatValue()) return SplatVal; } return nullptr; } Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val, Constant *Elt, Constant *Idx) { if (isa(Idx)) return PoisonValue::get(Val->getType()); ConstantInt *CIdx = dyn_cast(Idx); if (!CIdx) return nullptr; // Do not iterate on scalable vector. The num of elements is unknown at // compile-time. if (isa(Val->getType())) return nullptr; auto *ValTy = cast(Val->getType()); unsigned NumElts = ValTy->getNumElements(); if (CIdx->uge(NumElts)) return PoisonValue::get(Val->getType()); SmallVector Result; Result.reserve(NumElts); auto *Ty = Type::getInt32Ty(Val->getContext()); uint64_t IdxVal = CIdx->getZExtValue(); for (unsigned i = 0; i != NumElts; ++i) { if (i == IdxVal) { Result.push_back(Elt); continue; } Constant *C = ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i)); Result.push_back(C); } return ConstantVector::get(Result); } Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1, Constant *V2, ArrayRef Mask) { auto *V1VTy = cast(V1->getType()); unsigned MaskNumElts = Mask.size(); auto MaskEltCount = ElementCount::get(MaskNumElts, isa(V1VTy)); Type *EltTy = V1VTy->getElementType(); // Undefined shuffle mask -> undefined value. if (all_of(Mask, [](int Elt) { return Elt == UndefMaskElem; })) { return UndefValue::get(FixedVectorType::get(EltTy, MaskNumElts)); } // If the mask is all zeros this is a splat, no need to go through all // elements. if (all_of(Mask, [](int Elt) { return Elt == 0; })) { Type *Ty = IntegerType::get(V1->getContext(), 32); Constant *Elt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, 0)); if (Elt->isNullValue()) { auto *VTy = VectorType::get(EltTy, MaskEltCount); return ConstantAggregateZero::get(VTy); } else if (!MaskEltCount.isScalable()) return ConstantVector::getSplat(MaskEltCount, Elt); } // Do not iterate on scalable vector. The num of elements is unknown at // compile-time. if (isa(V1VTy)) return nullptr; unsigned SrcNumElts = V1VTy->getElementCount().getKnownMinValue(); // Loop over the shuffle mask, evaluating each element. SmallVector Result; for (unsigned i = 0; i != MaskNumElts; ++i) { int Elt = Mask[i]; if (Elt == -1) { Result.push_back(UndefValue::get(EltTy)); continue; } Constant *InElt; if (unsigned(Elt) >= SrcNumElts*2) InElt = UndefValue::get(EltTy); else if (unsigned(Elt) >= SrcNumElts) { Type *Ty = IntegerType::get(V2->getContext(), 32); InElt = ConstantExpr::getExtractElement(V2, ConstantInt::get(Ty, Elt - SrcNumElts)); } else { Type *Ty = IntegerType::get(V1->getContext(), 32); InElt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, Elt)); } Result.push_back(InElt); } return ConstantVector::get(Result); } Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg, ArrayRef 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 Idxs) { // Base case: no indices, so replace the entire value. if (Idxs.empty()) return Val; unsigned NumElts; if (StructType *ST = dyn_cast(Agg->getType())) NumElts = ST->getNumElements(); else NumElts = cast(Agg->getType())->getNumElements(); SmallVector 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(Agg->getType())) return ConstantStruct::get(ST, Result); return ConstantArray::get(cast(Agg->getType()), Result); } Constant *llvm::ConstantFoldUnaryInstruction(unsigned Opcode, Constant *C) { assert(Instruction::isUnaryOp(Opcode) && "Non-unary instruction detected"); // Handle scalar UndefValue and scalable vector UndefValue. Fixed-length // vectors are always evaluated per element. bool IsScalableVector = isa(C->getType()); bool HasScalarUndefOrScalableVectorUndef = (!C->getType()->isVectorTy() || IsScalableVector) && isa(C); if (HasScalarUndefOrScalableVectorUndef) { switch (static_cast(Opcode)) { case Instruction::FNeg: return C; // -undef -> undef case Instruction::UnaryOpsEnd: llvm_unreachable("Invalid UnaryOp"); } } // Constant should not be UndefValue, unless these are vector constants. assert(!HasScalarUndefOrScalableVectorUndef && "Unexpected UndefValue"); // We only have FP UnaryOps right now. assert(!isa(C) && "Unexpected Integer UnaryOp"); if (ConstantFP *CFP = dyn_cast(C)) { const APFloat &CV = CFP->getValueAPF(); switch (Opcode) { default: break; case Instruction::FNeg: return ConstantFP::get(C->getContext(), neg(CV)); } } else if (auto *VTy = dyn_cast(C->getType())) { Type *Ty = IntegerType::get(VTy->getContext(), 32); // Fast path for splatted constants. if (Constant *Splat = C->getSplatValue()) { Constant *Elt = ConstantExpr::get(Opcode, Splat); return ConstantVector::getSplat(VTy->getElementCount(), Elt); } // Fold each element and create a vector constant from those constants. SmallVector Result; for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { Constant *ExtractIdx = ConstantInt::get(Ty, i); Constant *Elt = ConstantExpr::getExtractElement(C, ExtractIdx); Result.push_back(ConstantExpr::get(Opcode, Elt)); } return ConstantVector::get(Result); } // We don't know how to fold this. return nullptr; } Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, Constant *C1, Constant *C2) { assert(Instruction::isBinaryOp(Opcode) && "Non-binary instruction detected"); // Simplify BinOps with their identity values first. They are no-ops and we // can always return the other value, including undef or poison values. // FIXME: remove unnecessary duplicated identity patterns below. // FIXME: Use AllowRHSConstant with getBinOpIdentity to handle additional ops, // like X << 0 = X. Constant *Identity = ConstantExpr::getBinOpIdentity(Opcode, C1->getType()); if (Identity) { if (C1 == Identity) return C2; if (C2 == Identity) return C1; } // Binary operations propagate poison. if (isa(C1) || isa(C2)) return PoisonValue::get(C1->getType()); // Handle scalar UndefValue and scalable vector UndefValue. Fixed-length // vectors are always evaluated per element. bool IsScalableVector = isa(C1->getType()); bool HasScalarUndefOrScalableVectorUndef = (!C1->getType()->isVectorTy() || IsScalableVector) && (isa(C1) || isa(C2)); if (HasScalarUndefOrScalableVectorUndef) { switch (static_cast(Opcode)) { case Instruction::Xor: if (isa(C1) && isa(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(C1) && isa(C2)) // undef & undef -> undef return C1; return Constant::getNullValue(C1->getType()); // undef & X -> 0 case Instruction::Mul: { // undef * undef -> undef if (isa(C1) && isa(C2)) return C1; const APInt *CV; // X * undef -> undef if X is odd if (match(C1, m_APInt(CV)) || match(C2, m_APInt(CV))) if ((*CV)[0]) return UndefValue::get(C1->getType()); // X * undef -> 0 otherwise return Constant::getNullValue(C1->getType()); } case Instruction::SDiv: case Instruction::UDiv: // X / undef -> poison // X / 0 -> poison if (match(C2, m_CombineOr(m_Undef(), m_Zero()))) return PoisonValue::get(C2->getType()); // undef / 1 -> undef if (match(C2, m_One())) return C1; // undef / X -> 0 otherwise return Constant::getNullValue(C1->getType()); case Instruction::URem: case Instruction::SRem: // X % undef -> poison // X % 0 -> poison if (match(C2, m_CombineOr(m_Undef(), m_Zero()))) return PoisonValue::get(C2->getType()); // undef % X -> 0 otherwise return Constant::getNullValue(C1->getType()); case Instruction::Or: // X | undef -> -1 if (isa(C1) && isa(C2)) // undef | undef -> undef return C1; return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0 case Instruction::LShr: // X >>l undef -> poison if (isa(C2)) return PoisonValue::get(C2->getType()); // 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 -> poison if (isa(C2)) return PoisonValue::get(C2->getType()); // undef >>a 0 -> undef if (match(C2, m_Zero())) return C1; // TODO: undef >>a X -> poison if the shift is exact // undef >>a X -> 0 return Constant::getNullValue(C1->getType()); case Instruction::Shl: // X << undef -> undef if (isa(C2)) return PoisonValue::get(C2->getType()); // undef << 0 -> undef if (match(C2, m_Zero())) return C1; // undef << X -> 0 return Constant::getNullValue(C1->getType()); case Instruction::FSub: // -0.0 - undef --> undef (consistent with "fneg undef") if (match(C1, m_NegZeroFP()) && isa(C2)) return C2; LLVM_FALLTHROUGH; case Instruction::FAdd: case Instruction::FMul: case Instruction::FDiv: case Instruction::FRem: // [any flop] undef, undef -> undef if (isa(C1) && isa(C2)) return C1; // [any flop] C, undef -> NaN // [any flop] undef, C -> NaN // We could potentially specialize NaN/Inf constants vs. 'normal' // constants (possibly differently depending on opcode and operand). This // would allow returning undef sometimes. But it is always safe to fold to // NaN because we can choose the undef operand as NaN, and any FP opcode // with a NaN operand will propagate NaN. return ConstantFP::getNaN(C1->getType()); case Instruction::BinaryOpsEnd: llvm_unreachable("Invalid BinaryOp"); } } // Neither constant should be UndefValue, unless these are vector constants. assert((!HasScalarUndefOrScalableVectorUndef) && "Unexpected UndefValue"); // Handle simplifications when the RHS is a constant int. if (ConstantInt *CI2 = dyn_cast(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 PoisonValue::get(CI2->getType()); // X / 0 == poison break; case Instruction::URem: case Instruction::SRem: if (CI2->isOne()) return Constant::getNullValue(CI2->getType()); // X % 1 == 0 if (CI2->isZero()) return PoisonValue::get(CI2->getType()); // X % 0 == poison break; case Instruction::And: if (CI2->isZero()) return C2; // X & 0 == 0 if (CI2->isMinusOne()) return C1; // X & -1 == X if (ConstantExpr *CE1 = dyn_cast(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(CE1->getOperand(0))) { GlobalValue *GV = cast(CE1->getOperand(0)); MaybeAlign GVAlign; if (Module *TheModule = GV->getParent()) { const DataLayout &DL = TheModule->getDataLayout(); GVAlign = GV->getPointerAlignment(DL); // If the function alignment is not specified then assume that it // is 4. // This is dangerous; on x86, the alignment of the pointer // corresponds to the alignment of the function, but might be less // than 4 if it isn't explicitly specified. // However, a fix for this behaviour was reverted because it // increased code size (see https://reviews.llvm.org/D55115) // FIXME: This code should be deleted once existing targets have // appropriate defaults if (isa(GV) && !DL.getFunctionPtrAlign()) GVAlign = Align(4); } else if (isa(GV)) { // Without a datalayout we have to assume the worst case: that the // function pointer isn't aligned at all. GVAlign = llvm::None; } else if (isa(GV)) { GVAlign = cast(GV)->getAlign(); } if (GVAlign && *GVAlign > 1) { unsigned DstWidth = CI2->getType()->getBitWidth(); unsigned SrcWidth = std::min(DstWidth, Log2(*GVAlign)); APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth)); // If checking bits we know are clear, return zero. if ((CI2->getValue() & BitsNotSet) == CI2->getValue()) return Constant::getNullValue(CI2->getType()); } } } break; case Instruction::Or: if (CI2->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(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(C1)) if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero. return ConstantExpr::getLShr(C1, C2); break; } } else if (isa(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(C1)) { if (ConstantInt *CI2 = dyn_cast(C2)) { const APInt &C1V = CI1->getValue(); const APInt &C2V = CI2->getValue(); switch (Opcode) { default: break; case Instruction::Add: return ConstantInt::get(CI1->getContext(), C1V + C2V); case Instruction::Sub: return ConstantInt::get(CI1->getContext(), C1V - C2V); case Instruction::Mul: return ConstantInt::get(CI1->getContext(), C1V * C2V); case Instruction::UDiv: assert(!CI2->isZero() && "Div by zero handled above"); return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V)); case Instruction::SDiv: assert(!CI2->isZero() && "Div by zero handled above"); if (C2V.isAllOnes() && C1V.isMinSignedValue()) return PoisonValue::get(CI1->getType()); // MIN_INT / -1 -> poison return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V)); case Instruction::URem: assert(!CI2->isZero() && "Div by zero handled above"); return ConstantInt::get(CI1->getContext(), C1V.urem(C2V)); case Instruction::SRem: assert(!CI2->isZero() && "Div by zero handled above"); if (C2V.isAllOnes() && C1V.isMinSignedValue()) return PoisonValue::get(CI1->getType()); // MIN_INT % -1 -> poison return ConstantInt::get(CI1->getContext(), C1V.srem(C2V)); case Instruction::And: return ConstantInt::get(CI1->getContext(), C1V & C2V); case Instruction::Or: return ConstantInt::get(CI1->getContext(), C1V | C2V); case Instruction::Xor: return ConstantInt::get(CI1->getContext(), C1V ^ C2V); case Instruction::Shl: if (C2V.ult(C1V.getBitWidth())) return ConstantInt::get(CI1->getContext(), C1V.shl(C2V)); return PoisonValue::get(C1->getType()); // too big shift is poison case Instruction::LShr: if (C2V.ult(C1V.getBitWidth())) return ConstantInt::get(CI1->getContext(), C1V.lshr(C2V)); return PoisonValue::get(C1->getType()); // too big shift is poison case Instruction::AShr: if (C2V.ult(C1V.getBitWidth())) return ConstantInt::get(CI1->getContext(), C1V.ashr(C2V)); return PoisonValue::get(C1->getType()); // too big shift is poison } } switch (Opcode) { case Instruction::SDiv: case Instruction::UDiv: case Instruction::URem: case Instruction::SRem: case Instruction::LShr: case Instruction::AShr: case Instruction::Shl: if (CI1->isZero()) return C1; break; default: break; } } else if (ConstantFP *CFP1 = dyn_cast(C1)) { if (ConstantFP *CFP2 = dyn_cast(C2)) { const APFloat &C1V = CFP1->getValueAPF(); const APFloat &C2V = CFP2->getValueAPF(); APFloat C3V = C1V; // copy for modification switch (Opcode) { default: break; case Instruction::FAdd: (void)C3V.add(C2V, APFloat::rmNearestTiesToEven); return ConstantFP::get(C1->getContext(), C3V); case Instruction::FSub: (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven); return ConstantFP::get(C1->getContext(), C3V); case Instruction::FMul: (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven); return ConstantFP::get(C1->getContext(), C3V); case Instruction::FDiv: (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven); return ConstantFP::get(C1->getContext(), C3V); case Instruction::FRem: (void)C3V.mod(C2V); return ConstantFP::get(C1->getContext(), C3V); } } } else if (auto *VTy = dyn_cast(C1->getType())) { // Fast path for splatted constants. if (Constant *C2Splat = C2->getSplatValue()) { if (Instruction::isIntDivRem(Opcode) && C2Splat->isNullValue()) return PoisonValue::get(VTy); if (Constant *C1Splat = C1->getSplatValue()) { return ConstantVector::getSplat( VTy->getElementCount(), ConstantExpr::get(Opcode, C1Splat, C2Splat)); } } if (auto *FVTy = dyn_cast(VTy)) { // Fold each element and create a vector constant from those constants. SmallVector Result; Type *Ty = IntegerType::get(FVTy->getContext(), 32); for (unsigned i = 0, e = FVTy->getNumElements(); i != e; ++i) { Constant *ExtractIdx = ConstantInt::get(Ty, i); Constant *LHS = ConstantExpr::getExtractElement(C1, ExtractIdx); Constant *RHS = ConstantExpr::getExtractElement(C2, ExtractIdx); // If any element of a divisor vector is zero, the whole op is poison. if (Instruction::isIntDivRem(Opcode) && RHS->isNullValue()) return PoisonValue::get(VTy); Result.push_back(ConstantExpr::get(Opcode, LHS, RHS)); } return ConstantVector::get(Result); } } if (ConstantExpr *CE1 = dyn_cast(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(T) || cast(T)->getOpcode() != Opcode) return ConstantExpr::get(Opcode, CE1->getOperand(0), T); } } else if (isa(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 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(V1)) { if (!isa(V2)) { // Simple case, use the standard constant folder. ConstantInt *R = nullptr; R = dyn_cast( ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2)); if (R && !R->isZero()) return FCmpInst::FCMP_OEQ; R = dyn_cast( ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2)); if (R && !R->isZero()) return FCmpInst::FCMP_OLT; R = dyn_cast( 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(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->isInterposable() || GV->hasGlobalUnnamedAddr()) return true; if (const auto *GVar = dyn_cast(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(GV1) && !isa(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(V1) && !isa(V1) && !isa(V1)) { if (!isa(V2) && !isa(V2) && !isa(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(ConstantExpr::getICmp(pred, V1, V2)); if (R && !R->isZero()) return pred; pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; R = dyn_cast(ConstantExpr::getICmp(pred, V1, V2)); if (R && !R->isZero()) return pred; pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; R = dyn_cast(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(V1)) { if (isa(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(V2)) { return areGlobalsPotentiallyEqual(GV, GV2); } else if (isa(V2)) { return ICmpInst::ICMP_NE; // Globals never equal labels. } else { assert(isa(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(GV) && !NullPointerIsDefined(nullptr /* F */, GV->getType()->getAddressSpace())) return ICmpInst::ICMP_UGT; } } else if (const BlockAddress *BA = dyn_cast(V1)) { if (isa(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(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(V2) || isa(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(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::BitCast: // If this is a global value cast, check to see if the RHS is also a // GlobalValue. if (const GlobalValue *GV = dyn_cast(CE1Op0)) if (const GlobalValue *GV2 = dyn_cast(V2)) return areGlobalsPotentiallyEqual(GV, GV2); LLVM_FALLTHROUGH; case Instruction::UIToFP: case Instruction::SIToFP: 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(CE1); // Ok, since this is a getelementptr, we know that the constant has a // pointer type. Check the various cases. if (isa(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(CE1Op0)) { // If its not weak linkage, the GVal must have a non-zero address // so the result is greater-than if (!GV->hasExternalWeakLinkage() && CE1GEP->isInBounds()) return ICmpInst::ICMP_UGT; } } else if (const GlobalValue *GV2 = dyn_cast(V2)) { if (const GlobalValue *GV = dyn_cast(CE1Op0)) { if (GV != GV2) { if (CE1GEP->hasAllZeroIndices()) return areGlobalsPotentiallyEqual(GV, GV2); return ICmpInst::BAD_ICMP_PREDICATE; } } } else if (const auto *CE2GEP = dyn_cast(V2)) { // By far the most common case to handle is when the base pointers are // obviously to the same global. const Constant *CE2Op0 = cast(CE2GEP->getPointerOperand()); if (isa(CE1Op0) && isa(CE2Op0)) { // Don't know relative ordering, but check for inequality. if (CE1Op0 != CE2Op0) { if (CE1GEP->hasAllZeroIndices() && CE2GEP->hasAllZeroIndices()) return areGlobalsPotentiallyEqual(cast(CE1Op0), cast(CE2Op0)); return ICmpInst::BAD_ICMP_PREDICATE; } } } break; } default: break; } } return ICmpInst::BAD_ICMP_PREDICATE; } Constant *llvm::ConstantFoldCompareInstruction(CmpInst::Predicate Predicate, Constant *C1, Constant *C2) { Type *ResultTy; if (VectorType *VT = dyn_cast(C1->getType())) ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()), VT->getElementCount()); else ResultTy = Type::getInt1Ty(C1->getContext()); // Fold FCMP_FALSE/FCMP_TRUE unconditionally. if (Predicate == FCmpInst::FCMP_FALSE) return Constant::getNullValue(ResultTy); if (Predicate == FCmpInst::FCMP_TRUE) return Constant::getAllOnesValue(ResultTy); // Handle some degenerate cases first if (isa(C1) || isa(C2)) return PoisonValue::get(ResultTy); if (isa(C1) || isa(C2)) { bool isIntegerPredicate = ICmpInst::isIntPredicate(Predicate); // For EQ and NE, we can always pick a value for the undef to make the // predicate pass or fail, so we can return undef. // Also, if both operands are undef, we can return undef for int comparison. if (ICmpInst::isEquality(Predicate) || (isIntegerPredicate && C1 == C2)) return UndefValue::get(ResultTy); // Otherwise, for integer compare, pick the same value as the non-undef // operand, and fold it to true or false. if (isIntegerPredicate) return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(Predicate)); // Choosing NaN for the undef will always make unordered comparison succeed // and ordered comparison fails. return ConstantInt::get(ResultTy, CmpInst::isUnordered(Predicate)); } // icmp eq/ne(null,GV) -> false/true if (C1->isNullValue()) { if (const GlobalValue *GV = dyn_cast(C2)) // Don't try to evaluate aliases. External weak GV can be null. if (!isa(GV) && !GV->hasExternalWeakLinkage() && !NullPointerIsDefined(nullptr /* F */, GV->getType()->getAddressSpace())) { if (Predicate == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(C1->getContext()); else if (Predicate == 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(C1)) { // Don't try to evaluate aliases. External weak GV can be null. if (!isa(GV) && !GV->hasExternalWeakLinkage() && !NullPointerIsDefined(nullptr /* F */, GV->getType()->getAddressSpace())) { if (Predicate == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(C1->getContext()); else if (Predicate == ICmpInst::ICMP_NE) return ConstantInt::getTrue(C1->getContext()); } } // The caller is expected to commute the operands if the constant expression // is C2. // C1 >= 0 --> true if (Predicate == ICmpInst::ICMP_UGE) return Constant::getAllOnesValue(ResultTy); // C1 < 0 --> false if (Predicate == ICmpInst::ICMP_ULT) return Constant::getNullValue(ResultTy); } // If the comparison is a comparison between two i1's, simplify it. if (C1->getType()->isIntegerTy(1)) { switch (Predicate) { case ICmpInst::ICMP_EQ: if (isa(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(C1) && isa(C2)) { const APInt &V1 = cast(C1)->getValue(); const APInt &V2 = cast(C2)->getValue(); return ConstantInt::get(ResultTy, ICmpInst::compare(V1, V2, Predicate)); } else if (isa(C1) && isa(C2)) { const APFloat &C1V = cast(C1)->getValueAPF(); const APFloat &C2V = cast(C2)->getValueAPF(); return ConstantInt::get(ResultTy, FCmpInst::compare(C1V, C2V, Predicate)); } else if (auto *C1VTy = dyn_cast(C1->getType())) { // Fast path for splatted constants. if (Constant *C1Splat = C1->getSplatValue()) if (Constant *C2Splat = C2->getSplatValue()) return ConstantVector::getSplat( C1VTy->getElementCount(), ConstantExpr::getCompare(Predicate, C1Splat, C2Splat)); // Do not iterate on scalable vector. The number of elements is unknown at // compile-time. if (isa(C1VTy)) return nullptr; // If we can constant fold the comparison of each element, constant fold // the whole vector comparison. SmallVector ResElts; Type *Ty = IntegerType::get(C1->getContext(), 32); // Compare the elements, producing an i1 result or constant expr. for (unsigned I = 0, E = C1VTy->getElementCount().getKnownMinValue(); I != E; ++I) { Constant *C1E = ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, I)); Constant *C2E = ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, I)); ResElts.push_back(ConstantExpr::getCompare(Predicate, 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(C1) || isa(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 = (Predicate == FCmpInst::FCMP_UEQ || Predicate == FCmpInst::FCMP_OEQ || Predicate == FCmpInst::FCMP_ULE || Predicate == FCmpInst::FCMP_OLE || Predicate == FCmpInst::FCMP_UGE || Predicate == FCmpInst::FCMP_OGE); break; case FCmpInst::FCMP_OLT: // We know that C1 < C2 Result = (Predicate == FCmpInst::FCMP_UNE || Predicate == FCmpInst::FCMP_ONE || Predicate == FCmpInst::FCMP_ULT || Predicate == FCmpInst::FCMP_OLT || Predicate == FCmpInst::FCMP_ULE || Predicate == FCmpInst::FCMP_OLE); break; case FCmpInst::FCMP_OGT: // We know that C1 > C2 Result = (Predicate == FCmpInst::FCMP_UNE || Predicate == FCmpInst::FCMP_ONE || Predicate == FCmpInst::FCMP_UGT || Predicate == FCmpInst::FCMP_OGT || Predicate == FCmpInst::FCMP_UGE || Predicate == FCmpInst::FCMP_OGE); break; case FCmpInst::FCMP_OLE: // We know that C1 <= C2 // We can only partially decide this relation. if (Predicate == FCmpInst::FCMP_UGT || Predicate == FCmpInst::FCMP_OGT) Result = 0; else if (Predicate == FCmpInst::FCMP_ULT || Predicate == FCmpInst::FCMP_OLT) Result = 1; break; case FCmpInst::FCMP_OGE: // We known that C1 >= C2 // We can only partially decide this relation. if (Predicate == FCmpInst::FCMP_ULT || Predicate == FCmpInst::FCMP_OLT) Result = 0; else if (Predicate == FCmpInst::FCMP_UGT || Predicate == FCmpInst::FCMP_OGT) Result = 1; break; case FCmpInst::FCMP_ONE: // We know that C1 != C2 // We can only partially decide this relation. if (Predicate == FCmpInst::FCMP_OEQ || Predicate == FCmpInst::FCMP_UEQ) Result = 0; else if (Predicate == FCmpInst::FCMP_ONE || Predicate == 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 (Predicate == FCmpInst::FCMP_ONE) Result = 0; else if (Predicate == 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(Predicate))) { default: llvm_unreachable("Unknown relational!"); case ICmpInst::BAD_ICMP_PREDICATE: break; // Couldn't determine anything about these constants. case ICmpInst::ICMP_EQ: // We know the constants are equal! // If we know the constants are equal, we can decide the result of this // computation precisely. Result = ICmpInst::isTrueWhenEqual(Predicate); break; case ICmpInst::ICMP_ULT: switch (Predicate) { case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE: Result = 1; break; case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE: Result = 0; break; default: break; } break; case ICmpInst::ICMP_SLT: switch (Predicate) { case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE: Result = 1; break; case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE: Result = 0; break; default: break; } break; case ICmpInst::ICMP_UGT: switch (Predicate) { case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE: Result = 1; break; case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE: Result = 0; break; default: break; } break; case ICmpInst::ICMP_SGT: switch (Predicate) { case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE: Result = 1; break; case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE: Result = 0; break; default: break; } break; case ICmpInst::ICMP_ULE: if (Predicate == ICmpInst::ICMP_UGT) Result = 0; if (Predicate == ICmpInst::ICMP_ULT || Predicate == ICmpInst::ICMP_ULE) Result = 1; break; case ICmpInst::ICMP_SLE: if (Predicate == ICmpInst::ICMP_SGT) Result = 0; if (Predicate == ICmpInst::ICMP_SLT || Predicate == ICmpInst::ICMP_SLE) Result = 1; break; case ICmpInst::ICMP_UGE: if (Predicate == ICmpInst::ICMP_ULT) Result = 0; if (Predicate == ICmpInst::ICMP_UGT || Predicate == ICmpInst::ICMP_UGE) Result = 1; break; case ICmpInst::ICMP_SGE: if (Predicate == ICmpInst::ICMP_SLT) Result = 0; if (Predicate == ICmpInst::ICMP_SGT || Predicate == ICmpInst::ICMP_SGE) Result = 1; break; case ICmpInst::ICMP_NE: if (Predicate == ICmpInst::ICMP_EQ) Result = 0; if (Predicate == ICmpInst::ICMP_NE) Result = 1; break; } // If we evaluated the result, return it now. if (Result != -1) return ConstantInt::get(ResultTy, Result); // If 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(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(Predicate, Inverse, CE2Op0); } } // If the left hand side is an extension, try eliminating it. if (ConstantExpr *CE1 = dyn_cast(C1)) { if ((CE1->getOpcode() == Instruction::SExt && ICmpInst::isSigned(Predicate)) || (CE1->getOpcode() == Instruction::ZExt && !ICmpInst::isSigned(Predicate))) { 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(Predicate, CE1Inverse, C2Inverse); } } } if ((!isa(C1) && isa(C2)) || (C1->isNullValue() && !C2->isNullValue())) { // If C2 is a constant expr and C1 isn't, flip them around and fold the // other way if possible. // Also, if C1 is null and C2 isn't, flip them around. Predicate = ICmpInst::getSwappedPredicate(Predicate); return ConstantExpr::getICmp(Predicate, C2, C1); } } return nullptr; } /// Test whether the given sequence of *normalized* indices is "inbounds". template static bool isInBoundsIndices(ArrayRef 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(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(Idxs[0])) { if (!CI->isOne()) return false; } else { auto *CV = cast(Idxs[0]); CI = dyn_cast_or_null(CV->getSplatValue()); if (!CI || !CI->isOne()) return false; } for (unsigned i = 1, e = Idxs.size(); i != e; ++i) if (!cast(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; } // 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. static Constant *foldGEPOfGEP(GEPOperator *GEP, Type *PointeeTy, bool InBounds, ArrayRef Idxs) { if (PointeeTy != GEP->getResultElementType()) return nullptr; Constant *Idx0 = cast(Idxs[0]); if (Idx0->isNullValue()) { // Handle the simple case of a zero index. SmallVector NewIndices; NewIndices.reserve(Idxs.size() + GEP->getNumIndices()); NewIndices.append(GEP->idx_begin(), GEP->idx_end()); NewIndices.append(Idxs.begin() + 1, Idxs.end()); return ConstantExpr::getGetElementPtr( GEP->getSourceElementType(), cast(GEP->getPointerOperand()), NewIndices, InBounds && GEP->isInBounds(), GEP->getInRangeIndex()); } gep_type_iterator LastI = gep_type_end(GEP); for (gep_type_iterator I = gep_type_begin(GEP), E = gep_type_end(GEP); I != E; ++I) LastI = I; // We can't combine GEPs if the last index is a struct type. if (!LastI.isSequential()) return nullptr; // We could perform the transform with non-constant index, but prefer leaving // it as GEP of GEP rather than GEP of add for now. ConstantInt *CI = dyn_cast(Idx0); if (!CI) return nullptr; // TODO: This code may be extended to handle vectors as well. auto *LastIdx = cast(GEP->getOperand(GEP->getNumOperands()-1)); Type *LastIdxTy = LastIdx->getType(); if (LastIdxTy->isVectorTy()) return nullptr; SmallVector NewIndices; NewIndices.reserve(Idxs.size() + GEP->getNumIndices()); NewIndices.append(GEP->idx_begin(), GEP->idx_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. if (LastIdxTy != Idx0->getType()) { unsigned CommonExtendedWidth = std::max(LastIdxTy->getIntegerBitWidth(), Idx0->getType()->getIntegerBitWidth()); CommonExtendedWidth = std::max(CommonExtendedWidth, 64U); Type *CommonTy = Type::getIntNTy(LastIdxTy->getContext(), CommonExtendedWidth); Idx0 = ConstantExpr::getSExtOrBitCast(Idx0, CommonTy); LastIdx = ConstantExpr::getSExtOrBitCast(LastIdx, CommonTy); } NewIndices.push_back(ConstantExpr::get(Instruction::Add, Idx0, LastIdx)); 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 IRIndex = GEP->getInRangeIndex(); if (IRIndex && *IRIndex == GEP->getNumIndices() - 1) IRIndex = None; return ConstantExpr::getGetElementPtr( GEP->getSourceElementType(), cast(GEP->getPointerOperand()), NewIndices, InBounds && GEP->isInBounds(), IRIndex); } Constant *llvm::ConstantFoldGetElementPtr(Type *PointeeTy, Constant *C, bool InBounds, Optional InRangeIndex, ArrayRef Idxs) { if (Idxs.empty()) return C; Type *GEPTy = GetElementPtrInst::getGEPReturnType( PointeeTy, C, makeArrayRef((Value *const *)Idxs.data(), Idxs.size())); if (isa(C)) return PoisonValue::get(GEPTy); if (isa(C)) // If inbounds, we can choose an out-of-bounds pointer as a base pointer. return InBounds ? PoisonValue::get(GEPTy) : UndefValue::get(GEPTy); Constant *Idx0 = cast(Idxs[0]); if (Idxs.size() == 1 && (Idx0->isNullValue() || isa(Idx0))) return GEPTy->isVectorTy() && !C->getType()->isVectorTy() ? ConstantVector::getSplat( cast(GEPTy)->getElementCount(), C) : C; if (C->isNullValue()) { bool isNull = true; for (Value *Idx : Idxs) if (!isa(Idx) && !cast(Idx)->isNullValue()) { isNull = false; break; } if (isNull) { PointerType *PtrTy = cast(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(C->getType())) GEPTy = VectorType::get(OrigGEPTy, VT->getElementCount()); // The GEP returns a vector of pointers when one of more of // its arguments is a vector. for (Value *Idx : Idxs) { if (auto *VT = dyn_cast(Idx->getType())) { assert((!isa(GEPTy) || isa(GEPTy) == isa(VT)) && "Mismatched GEPTy vector types"); GEPTy = VectorType::get(OrigGEPTy, VT->getElementCount()); break; } } return Constant::getNullValue(GEPTy); } } if (ConstantExpr *CE = dyn_cast(C)) { if (auto *GEP = dyn_cast(CE)) if (Constant *C = foldGEPOfGEP(GEP, PointeeTy, InBounds, Idxs)) return C; // 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(CE->getOperand(0)->getType()); PointerType *DstPtrTy = dyn_cast(CE->getType()); if (SrcPtrTy && DstPtrTy && !SrcPtrTy->isOpaque() && !DstPtrTy->isOpaque()) { ArrayType *SrcArrayTy = dyn_cast(SrcPtrTy->getNonOpaquePointerElementType()); ArrayType *DstArrayTy = dyn_cast(DstPtrTy->getNonOpaquePointerElementType()); 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 NewIdxs; Type *Ty = PointeeTy; Type *Prev = C->getType(); auto GEPIter = gep_type_begin(PointeeTy, Idxs); bool Unknown = !isa(Idxs[0]) && !isa(Idxs[0]); for (unsigned i = 1, e = Idxs.size(); i != e; Prev = Ty, Ty = (++GEPIter).getIndexedType(), ++i) { if (!isa(Idxs[i]) && !isa(Idxs[i])) { // We don't know if it's in range or not. Unknown = true; continue; } if (!isa(Idxs[i - 1]) && !isa(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(Ty)) { // The verify makes sure that GEPs into a struct are in range. continue; } if (isa(Ty)) { // There can be awkward padding in after a non-power of two vector. Unknown = true; continue; } auto *STy = cast(Ty); if (ConstantInt *CI = dyn_cast(Idxs[i])) { if (isIndexInRangeOfArrayType(STy->getNumElements(), CI)) // It's in range, skip to the next index. continue; if (CI->isNegative()) { // It's out of range and negative, don't try to factor it. Unknown = true; continue; } } else { auto *CV = cast(Idxs[i]); bool InRange = true; for (unsigned I = 0, E = CV->getNumElements(); I != E; ++I) { auto *CI = cast(CV->getElementAsConstant(I)); InRange &= isIndexInRangeOfArrayType(STy->getNumElements(), CI); if (CI->isNegative()) { 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(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(Idxs[i]); auto *PrevIdx = NewIdxs[i - 1] ? NewIdxs[i - 1] : cast(Idxs[i - 1]); bool IsCurrIdxVector = CurrIdx->getType()->isVectorTy(); bool IsPrevIdxVector = PrevIdx->getType()->isVectorTy(); bool UseVector = IsCurrIdxVector || IsPrevIdxVector; if (!IsCurrIdxVector && IsPrevIdxVector) CurrIdx = ConstantDataVector::getSplat( cast(PrevIdx->getType())->getNumElements(), CurrIdx); if (!IsPrevIdxVector && IsCurrIdxVector) PrevIdx = ConstantDataVector::getSplat( cast(CurrIdx->getType())->getNumElements(), PrevIdx); Constant *Factor = ConstantInt::get(CurrIdx->getType()->getScalarType(), NumElements); if (UseVector) Factor = ConstantDataVector::getSplat( IsPrevIdxVector ? cast(PrevIdx->getType())->getNumElements() : cast(CurrIdx->getType())->getNumElements(), 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 = FixedVectorType::get( ExtendedTy, IsPrevIdxVector ? cast(PrevIdx->getType())->getNumElements() : cast(CurrIdx->getType())->getNumElements()); 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(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(C)) if (!GV->hasExternalWeakLinkage() && isInBoundsIndices(Idxs)) return ConstantExpr::getGetElementPtr(PointeeTy, C, Idxs, /*InBounds=*/true, InRangeIndex); return nullptr; }