//===- ConstantFolding.cpp - LLVM constant folder -------------------------===// // // The LLVM Compiler Infrastructure // // This file was developed by the LLVM research group and is distributed under // the University of Illinois Open Source License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements folding of constants for LLVM. This implements the // (internal) ConstantFolding.h interface, which is used by the // ConstantExpr::get* methods to automatically fold constants when possible. // // The current constant folding implementation is implemented in two pieces: the // template-based folder for simple primitive constants like ConstantInt, and // the special case hackery that we use to symbolically evaluate expressions // that use ConstantExprs. // //===----------------------------------------------------------------------===// #include "ConstantFolding.h" #include "llvm/Constants.h" #include "llvm/Instructions.h" #include "llvm/DerivedTypes.h" #include "llvm/Function.h" #include "llvm/ADT/SmallVector.h" #include "llvm/Support/Compiler.h" #include "llvm/Support/GetElementPtrTypeIterator.h" #include "llvm/Support/ManagedStatic.h" #include "llvm/Support/MathExtras.h" #include using namespace llvm; //===----------------------------------------------------------------------===// // ConstantFold*Instruction Implementations //===----------------------------------------------------------------------===// /// CastConstantVector - Convert the specified ConstantVector node to the /// specified vector type. At this point, we know that the elements of the /// input packed constant are all simple integer or FP values. static Constant *CastConstantVector(ConstantVector *CP, const VectorType *DstTy) { unsigned SrcNumElts = CP->getType()->getNumElements(); unsigned DstNumElts = DstTy->getNumElements(); const Type *SrcEltTy = CP->getType()->getElementType(); const Type *DstEltTy = DstTy->getElementType(); // If both vectors have the same number of elements (thus, the elements // are the same size), perform the conversion now. if (SrcNumElts == DstNumElts) { std::vector Result; // If the src and dest elements are both integers, or both floats, we can // just BitCast each element because the elements are the same size. if ((SrcEltTy->isInteger() && DstEltTy->isInteger()) || (SrcEltTy->isFloatingPoint() && DstEltTy->isFloatingPoint())) { for (unsigned i = 0; i != SrcNumElts; ++i) Result.push_back( ConstantExpr::getBitCast(CP->getOperand(i), DstEltTy)); return ConstantVector::get(Result); } // If this is an int-to-fp cast .. if (SrcEltTy->isInteger()) { // Ensure that it is int-to-fp cast assert(DstEltTy->isFloatingPoint()); if (DstEltTy->getTypeID() == Type::DoubleTyID) { for (unsigned i = 0; i != SrcNumElts; ++i) { double V = BitsToDouble(cast(CP->getOperand(i))->getZExtValue()); Result.push_back(ConstantFP::get(Type::DoubleTy, V)); } return ConstantVector::get(Result); } assert(DstEltTy == Type::FloatTy && "Unknown fp type!"); for (unsigned i = 0; i != SrcNumElts; ++i) { float V = BitsToFloat(cast(CP->getOperand(i))->getZExtValue()); Result.push_back(ConstantFP::get(Type::FloatTy, V)); } return ConstantVector::get(Result); } // Otherwise, this is an fp-to-int cast. assert(SrcEltTy->isFloatingPoint() && DstEltTy->isInteger()); if (SrcEltTy->getTypeID() == Type::DoubleTyID) { for (unsigned i = 0; i != SrcNumElts; ++i) { uint64_t V = DoubleToBits(cast(CP->getOperand(i))->getValue()); Constant *C = ConstantInt::get(Type::Int64Ty, V); Result.push_back(ConstantExpr::getBitCast(C, DstEltTy )); } return ConstantVector::get(Result); } assert(SrcEltTy->getTypeID() == Type::FloatTyID); for (unsigned i = 0; i != SrcNumElts; ++i) { uint32_t V = FloatToBits(cast(CP->getOperand(i))->getValue()); Constant *C = ConstantInt::get(Type::Int32Ty, V); Result.push_back(ConstantExpr::getBitCast(C, DstEltTy)); } return ConstantVector::get(Result); } // Otherwise, this is a cast that changes element count and size. Handle // casts which shrink the elements here. // FIXME: We need to know endianness to do this! return 0; } /// 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 const ConstantExpr*Op, ///< the first cast constant expression const Type *DstTy ///< desintation type of the first cast ) { assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!"); assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type"); assert(CastInst::isCast(opc) && "Invalid cast opcode"); // The the types and opcodes for the two Cast constant expressions const Type *SrcTy = Op->getOperand(0)->getType(); const Type *MidTy = Op->getType(); Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode()); Instruction::CastOps secondOp = Instruction::CastOps(opc); // Let CastInst::isEliminableCastPair do the heavy lifting. return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy, Type::Int64Ty); } Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V, const Type *DestTy) { const Type *SrcTy = V->getType(); if (isa(V)) return UndefValue::get(DestTy); // If the cast operand is a constant expression, there's a few things we can // do to try to simplify it. if (const ConstantExpr *CE = dyn_cast(V)) { if (CE->isCast()) { // Try hard to fold cast of cast because they are often eliminable. if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy)) return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); } else if (CE->getOpcode() == Instruction::GetElementPtr) { // If all of the indexes in the GEP are null values, there is no pointer // adjustment going on. We might as well cast the source pointer. bool isAllNull = true; for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) if (!CE->getOperand(i)->isNullValue()) { isAllNull = false; break; } if (isAllNull) // This is casting one pointer type to another, always BitCast return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy); } } // We actually have to do a cast now. Perform the cast according to the // opcode specified. switch (opc) { case Instruction::FPTrunc: case Instruction::FPExt: if (const ConstantFP *FPC = dyn_cast(V)) return ConstantFP::get(DestTy, FPC->getValue()); return 0; // Can't fold. case Instruction::FPToUI: if (const ConstantFP *FPC = dyn_cast(V)) return ConstantInt::get(DestTy,(uint64_t) FPC->getValue()); return 0; // Can't fold. case Instruction::FPToSI: if (const ConstantFP *FPC = dyn_cast(V)) return ConstantInt::get(DestTy,(int64_t) FPC->getValue()); return 0; // Can't fold. case Instruction::IntToPtr: //always treated as unsigned if (V->isNullValue()) // Is it an integral null value? return ConstantPointerNull::get(cast(DestTy)); return 0; // Other pointer types cannot be casted case Instruction::PtrToInt: // always treated as unsigned if (V->isNullValue()) // is it a null pointer value? return ConstantInt::get(DestTy, 0); return 0; // Other pointer types cannot be casted case Instruction::UIToFP: if (const ConstantInt *CI = dyn_cast(V)) return ConstantFP::get(DestTy, double(CI->getZExtValue())); return 0; case Instruction::SIToFP: if (const ConstantInt *CI = dyn_cast(V)) return ConstantFP::get(DestTy, double(CI->getSExtValue())); return 0; case Instruction::ZExt: if (const ConstantInt *CI = dyn_cast(V)) return ConstantInt::get(DestTy, CI->getZExtValue()); return 0; case Instruction::SExt: if (const ConstantInt *CI = dyn_cast(V)) return ConstantInt::get(DestTy, CI->getSExtValue()); return 0; case Instruction::Trunc: if (const ConstantInt *CI = dyn_cast(V)) // Can't trunc a bool return ConstantInt::get(DestTy, CI->getZExtValue()); return 0; case Instruction::BitCast: if (SrcTy == DestTy) return (Constant*)V; // no-op cast // Check to see if we are casting a pointer to an aggregate to a pointer to // the first element. If so, return the appropriate GEP instruction. if (const PointerType *PTy = dyn_cast(V->getType())) if (const PointerType *DPTy = dyn_cast(DestTy)) { SmallVector IdxList; IdxList.push_back(Constant::getNullValue(Type::Int32Ty)); const Type *ElTy = PTy->getElementType(); while (ElTy != DPTy->getElementType()) { if (const StructType *STy = dyn_cast(ElTy)) { if (STy->getNumElements() == 0) break; ElTy = STy->getElementType(0); IdxList.push_back(Constant::getNullValue(Type::Int32Ty)); } else if (const SequentialType *STy = dyn_cast(ElTy)) { if (isa(ElTy)) break; // Can't index into pointers! ElTy = STy->getElementType(); IdxList.push_back(IdxList[0]); } else { break; } } if (ElTy == DPTy->getElementType()) return ConstantExpr::getGetElementPtr( const_cast(V), &IdxList[0], IdxList.size()); } // Handle casts from one packed constant to another. We know that the src // and dest type have the same size (otherwise its an illegal cast). if (const VectorType *DestPTy = dyn_cast(DestTy)) { if (const VectorType *SrcTy = dyn_cast(V->getType())) { assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() && "Not cast between same sized vectors!"); // First, check for null and undef if (isa(V)) return Constant::getNullValue(DestTy); if (isa(V)) return UndefValue::get(DestTy); if (const ConstantVector *CP = dyn_cast(V)) { // This is a cast from a ConstantVector of one type to a // ConstantVector of another type. Check to see if all elements of // the input are simple. bool AllSimpleConstants = true; for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i) { if (!isa(CP->getOperand(i)) && !isa(CP->getOperand(i))) { AllSimpleConstants = false; break; } } // If all of the elements are simple constants, we can fold this. if (AllSimpleConstants) return CastConstantVector(const_cast(CP), 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 (const ConstantInt *CI = dyn_cast(V)) { // Integral -> Integral, must be changing sign. if (DestTy->isInteger()) return ConstantInt::get(DestTy, CI->getZExtValue()); if (DestTy->isFloatingPoint()) { if (DestTy == Type::FloatTy) return ConstantFP::get(DestTy, BitsToFloat(CI->getZExtValue())); assert(DestTy == Type::DoubleTy && "Unknown FP type!"); return ConstantFP::get(DestTy, BitsToDouble(CI->getZExtValue())); } // Otherwise, can't fold this (packed?) return 0; } // Handle ConstantFP input. if (const ConstantFP *FP = dyn_cast(V)) { // FP -> Integral. if (DestTy == Type::Int32Ty) { return ConstantInt::get(DestTy, FloatToBits(FP->getValue())); } else { assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!"); return ConstantInt::get(DestTy, DoubleToBits(FP->getValue())); } } return 0; default: assert(!"Invalid CE CastInst opcode"); break; } assert(0 && "Failed to cast constant expression"); return 0; } Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond, const Constant *V1, const Constant *V2) { if (const ConstantInt *CB = dyn_cast(Cond)) return const_cast(CB->getZExtValue() ? V1 : V2); if (isa(V1)) return const_cast(V2); if (isa(V2)) return const_cast(V1); if (isa(Cond)) return const_cast(V1); if (V1 == V2) return const_cast(V1); return 0; } Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val, const Constant *Idx) { if (isa(Val)) // ee(undef, x) -> undef return UndefValue::get(cast(Val->getType())->getElementType()); if (Val->isNullValue()) // ee(zero, x) -> zero return Constant::getNullValue( cast(Val->getType())->getElementType()); if (const ConstantVector *CVal = dyn_cast(Val)) { if (const ConstantInt *CIdx = dyn_cast(Idx)) { return const_cast(CVal->getOperand(CIdx->getZExtValue())); } else if (isa(Idx)) { // ee({w,x,y,z}, undef) -> w (an arbitrary value). return const_cast(CVal->getOperand(0)); } } return 0; } Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val, const Constant *Elt, const Constant *Idx) { const ConstantInt *CIdx = dyn_cast(Idx); if (!CIdx) return 0; uint64_t idxVal = CIdx->getZExtValue(); if (isa(Val)) { // Insertion of scalar constant into packed undef // Optimize away insertion of undef if (isa(Elt)) return const_cast(Val); // Otherwise break the aggregate undef into multiple undefs and do // the insertion unsigned numOps = cast(Val->getType())->getNumElements(); std::vector Ops; Ops.reserve(numOps); for (unsigned i = 0; i < numOps; ++i) { const Constant *Op = (i == idxVal) ? Elt : UndefValue::get(Elt->getType()); Ops.push_back(const_cast(Op)); } return ConstantVector::get(Ops); } if (isa(Val)) { // Insertion of scalar constant into packed aggregate zero // Optimize away insertion of zero if (Elt->isNullValue()) return const_cast(Val); // Otherwise break the aggregate zero into multiple zeros and do // the insertion unsigned numOps = cast(Val->getType())->getNumElements(); std::vector Ops; Ops.reserve(numOps); for (unsigned i = 0; i < numOps; ++i) { const Constant *Op = (i == idxVal) ? Elt : Constant::getNullValue(Elt->getType()); Ops.push_back(const_cast(Op)); } return ConstantVector::get(Ops); } if (const ConstantVector *CVal = dyn_cast(Val)) { // Insertion of scalar constant into packed constant std::vector Ops; Ops.reserve(CVal->getNumOperands()); for (unsigned i = 0; i < CVal->getNumOperands(); ++i) { const Constant *Op = (i == idxVal) ? Elt : cast(CVal->getOperand(i)); Ops.push_back(const_cast(Op)); } return ConstantVector::get(Ops); } return 0; } Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1, const Constant *V2, const Constant *Mask) { // TODO: return 0; } /// EvalVectorOp - Given two packed constants and a function pointer, apply the /// function pointer to each element pair, producing a new ConstantVector /// constant. static Constant *EvalVectorOp(const ConstantVector *V1, const ConstantVector *V2, Constant *(*FP)(Constant*, Constant*)) { std::vector Res; for (unsigned i = 0, e = V1->getNumOperands(); i != e; ++i) Res.push_back(FP(const_cast(V1->getOperand(i)), const_cast(V2->getOperand(i)))); return ConstantVector::get(Res); } Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, const Constant *C1, const Constant *C2) { // Handle UndefValue up front if (isa(C1) || isa(C2)) { switch (Opcode) { case Instruction::Add: case Instruction::Sub: case Instruction::Xor: return UndefValue::get(C1->getType()); case Instruction::Mul: case Instruction::And: return Constant::getNullValue(C1->getType()); case Instruction::UDiv: case Instruction::SDiv: case Instruction::FDiv: case Instruction::URem: case Instruction::SRem: case Instruction::FRem: if (!isa(C2)) // undef / X -> 0 return Constant::getNullValue(C1->getType()); return const_cast(C2); // X / undef -> undef case Instruction::Or: // X | undef -> -1 if (const VectorType *PTy = dyn_cast(C1->getType())) return ConstantVector::getAllOnesValue(PTy); return ConstantInt::getAllOnesValue(C1->getType()); case Instruction::LShr: if (isa(C2) && isa(C1)) return const_cast(C1); // undef lshr undef -> undef return Constant::getNullValue(C1->getType()); // X lshr undef -> 0 // undef lshr X -> 0 case Instruction::AShr: if (!isa(C2)) return const_cast(C1); // undef ashr X --> undef else if (isa(C1)) return const_cast(C1); // undef ashr undef -> undef else return const_cast(C1); // X ashr undef --> X case Instruction::Shl: // undef << X -> 0 or X << undef -> 0 return Constant::getNullValue(C1->getType()); } } if (const ConstantExpr *CE1 = dyn_cast(C1)) { if (isa(C2)) { // There are many possible foldings we could do here. We should probably // at least fold add of a pointer with an integer into the appropriate // getelementptr. This will improve alias analysis a bit. } else { // Just implement a couple of simple identities. switch (Opcode) { case Instruction::Add: if (C2->isNullValue()) return const_cast(C1); // X + 0 == X break; case Instruction::Sub: if (C2->isNullValue()) return const_cast(C1); // X - 0 == X break; case Instruction::Mul: if (C2->isNullValue()) return const_cast(C2); // X * 0 == 0 if (const ConstantInt *CI = dyn_cast(C2)) if (CI->getZExtValue() == 1) return const_cast(C1); // X * 1 == X break; case Instruction::UDiv: case Instruction::SDiv: if (const ConstantInt *CI = dyn_cast(C2)) if (CI->getZExtValue() == 1) return const_cast(C1); // X / 1 == X break; case Instruction::URem: case Instruction::SRem: if (const ConstantInt *CI = dyn_cast(C2)) if (CI->getZExtValue() == 1) return Constant::getNullValue(CI->getType()); // X % 1 == 0 break; case Instruction::And: if (const ConstantInt *CI = dyn_cast(C2)) if (CI->isAllOnesValue()) return const_cast(C1); // X & -1 == X if (C2->isNullValue()) return const_cast(C2); // X & 0 == 0 if (CE1->isCast() && isa(CE1->getOperand(0))) { GlobalValue *CPR = cast(CE1->getOperand(0)); // Functions are at least 4-byte aligned. If and'ing the address of a // function with a constant < 4, fold it to zero. if (const ConstantInt *CI = dyn_cast(C2)) if (CI->getZExtValue() < 4 && isa(CPR)) return Constant::getNullValue(CI->getType()); } break; case Instruction::Or: if (C2->isNullValue()) return const_cast(C1); // X | 0 == X if (const ConstantInt *CI = dyn_cast(C2)) if (CI->isAllOnesValue()) return const_cast(C2); // X | -1 == -1 break; case Instruction::Xor: if (C2->isNullValue()) return const_cast(C1); // X ^ 0 == X break; } } } else if (isa(C2)) { // If C2 is a constant expr and C1 isn't, flop them around and fold the // other way if possible. switch (Opcode) { case Instruction::Add: case Instruction::Mul: case Instruction::And: case Instruction::Or: case Instruction::Xor: // No change of opcode required. return ConstantFoldBinaryInstruction(Opcode, C2, C1); case Instruction::Shl: case Instruction::LShr: case Instruction::AShr: case Instruction::Sub: case Instruction::SDiv: case Instruction::UDiv: case Instruction::FDiv: case Instruction::URem: case Instruction::SRem: case Instruction::FRem: default: // These instructions cannot be flopped around. return 0; } } // At this point we know neither constant is an UndefValue nor a ConstantExpr // so look at directly computing the value. if (const ConstantInt *CI1 = dyn_cast(C1)) { if (const ConstantInt *CI2 = dyn_cast(C2)) { uint64_t C1Val = CI1->getZExtValue(); uint64_t C2Val = CI2->getZExtValue(); switch (Opcode) { default: break; case Instruction::Add: return ConstantInt::get(C1->getType(), C1Val + C2Val); case Instruction::Sub: return ConstantInt::get(C1->getType(), C1Val - C2Val); case Instruction::Mul: return ConstantInt::get(C1->getType(), C1Val * C2Val); case Instruction::UDiv: if (CI2->isNullValue()) // X / 0 -> can't fold return 0; return ConstantInt::get(C1->getType(), C1Val / C2Val); case Instruction::SDiv: if (CI2->isNullValue()) return 0; // X / 0 -> can't fold if (CI2->isAllOnesValue() && (((CI1->getType()->getPrimitiveSizeInBits() == 64) && (CI1->getSExtValue() == INT64_MIN)) || (CI1->getSExtValue() == -CI1->getSExtValue()))) return 0; // MIN_INT / -1 -> overflow return ConstantInt::get(C1->getType(), CI1->getSExtValue() / CI2->getSExtValue()); case Instruction::URem: if (C2->isNullValue()) return 0; // X / 0 -> can't fold return ConstantInt::get(C1->getType(), C1Val % C2Val); case Instruction::SRem: if (CI2->isNullValue()) return 0; // X % 0 -> can't fold if (CI2->isAllOnesValue() && (((CI1->getType()->getPrimitiveSizeInBits() == 64) && (CI1->getSExtValue() == INT64_MIN)) || (CI1->getSExtValue() == -CI1->getSExtValue()))) return 0; // MIN_INT % -1 -> overflow return ConstantInt::get(C1->getType(), CI1->getSExtValue() % CI2->getSExtValue()); case Instruction::And: return ConstantInt::get(C1->getType(), C1Val & C2Val); case Instruction::Or: return ConstantInt::get(C1->getType(), C1Val | C2Val); case Instruction::Xor: return ConstantInt::get(C1->getType(), C1Val ^ C2Val); case Instruction::Shl: return ConstantInt::get(C1->getType(), C1Val << C2Val); case Instruction::LShr: return ConstantInt::get(C1->getType(), C1Val >> C2Val); case Instruction::AShr: return ConstantInt::get(C1->getType(), CI1->getSExtValue() >> C2Val); } } } else if (const ConstantFP *CFP1 = dyn_cast(C1)) { if (const ConstantFP *CFP2 = dyn_cast(C2)) { double C1Val = CFP1->getValue(); double C2Val = CFP2->getValue(); switch (Opcode) { default: break; case Instruction::Add: return ConstantFP::get(CFP1->getType(), C1Val + C2Val); case Instruction::Sub: return ConstantFP::get(CFP1->getType(), C1Val - C2Val); case Instruction::Mul: return ConstantFP::get(CFP1->getType(), C1Val * C2Val); case Instruction::FDiv: if (CFP2->isExactlyValue(0.0)) return ConstantFP::get(CFP1->getType(), std::numeric_limits::infinity()); if (CFP2->isExactlyValue(-0.0)) return ConstantFP::get(CFP1->getType(), -std::numeric_limits::infinity()); return ConstantFP::get(CFP1->getType(), C1Val / C2Val); case Instruction::FRem: if (CFP2->isNullValue()) return 0; return ConstantFP::get(CFP1->getType(), std::fmod(C1Val, C2Val)); } } } else if (const ConstantVector *CP1 = dyn_cast(C1)) { if (const ConstantVector *CP2 = dyn_cast(C2)) { switch (Opcode) { default: break; case Instruction::Add: return EvalVectorOp(CP1, CP2, ConstantExpr::getAdd); case Instruction::Sub: return EvalVectorOp(CP1, CP2, ConstantExpr::getSub); case Instruction::Mul: return EvalVectorOp(CP1, CP2, ConstantExpr::getMul); case Instruction::UDiv: return EvalVectorOp(CP1, CP2, ConstantExpr::getUDiv); case Instruction::SDiv: return EvalVectorOp(CP1, CP2, ConstantExpr::getSDiv); case Instruction::FDiv: return EvalVectorOp(CP1, CP2, ConstantExpr::getFDiv); case Instruction::URem: return EvalVectorOp(CP1, CP2, ConstantExpr::getURem); case Instruction::SRem: return EvalVectorOp(CP1, CP2, ConstantExpr::getSRem); case Instruction::FRem: return EvalVectorOp(CP1, CP2, ConstantExpr::getFRem); case Instruction::And: return EvalVectorOp(CP1, CP2, ConstantExpr::getAnd); case Instruction::Or: return EvalVectorOp(CP1, CP2, ConstantExpr::getOr); case Instruction::Xor: return EvalVectorOp(CP1, CP2, ConstantExpr::getXor); } } } // We don't know how to fold this return 0; } /// isZeroSizedType - This type is zero sized if its an array or structure of /// zero sized types. The only leaf zero sized type is an empty structure. static bool isMaybeZeroSizedType(const Type *Ty) { if (isa(Ty)) return true; // Can't say. if (const StructType *STy = dyn_cast(Ty)) { // If all of elements have zero size, this does too. for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; return true; } else if (const ArrayType *ATy = dyn_cast(Ty)) { return isMaybeZeroSizedType(ATy->getElementType()); } return false; } /// IdxCompare - Compare the two constants as though they were getelementptr /// indices. This allows coersion of the types to be the same thing. /// /// If the two constants are the "same" (after coersion), return 0. If the /// first is less than the second, return -1, if the second is less than the /// first, return 1. If the constants are not integral, return -2. /// static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) { if (C1 == C2) return 0; // Ok, we found a different index. If they are not ConstantInt, we can't do // anything with them. if (!isa(C1) || !isa(C2)) return -2; // don't know! // Ok, we have two differing integer indices. Sign extend them to be the same // type. Long is always big enough, so we use it. if (C1->getType() != Type::Int64Ty) C1 = ConstantExpr::getSExt(C1, Type::Int64Ty); if (C2->getType() != Type::Int64Ty) C2 = ConstantExpr::getSExt(C2, Type::Int64Ty); if (C1 == C2) return 0; // They are equal // If the type being indexed over is really just a zero sized type, there is // no pointer difference being made here. if (isMaybeZeroSizedType(ElTy)) return -2; // dunno. // If they are really different, now that they are the same type, then we // found a difference! if (cast(C1)->getSExtValue() < cast(C2)->getSExtValue()) return -1; else return 1; } /// evaluateFCmpRelation - This function determines if there is anything we can /// decide about the two constants provided. This doesn't need to handle simple /// things like ConstantFP comparisons, but should instead handle ConstantExprs. /// If we can determine that the two constants have a particular relation to /// each other, we should return the corresponding FCmpInst predicate, /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in /// ConstantFoldCompareInstruction. /// /// To simplify this code we canonicalize the relation so that the first /// operand is always the most "complex" of the two. We consider ConstantFP /// to be the simplest, and ConstantExprs to be the most complex. static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1, const Constant *V2) { assert(V1->getType() == V2->getType() && "Cannot compare values of different types!"); // Handle degenerate case quickly if (V1 == V2) return FCmpInst::FCMP_OEQ; if (!isa(V1)) { if (!isa(V2)) { // We distilled thisUse the standard constant folder for a few cases ConstantInt *R = 0; Constant *C1 = const_cast(V1); Constant *C2 = const_cast(V2); R = dyn_cast( ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2)); if (R && R->getZExtValue()) return FCmpInst::FCMP_OEQ; R = dyn_cast( ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2)); if (R && R->getZExtValue()) return FCmpInst::FCMP_OLT; R = dyn_cast( ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2)); if (R && R->getZExtValue()) return FCmpInst::FCMP_OGT; // Nothing more we can do return FCmpInst::BAD_FCMP_PREDICATE; } // If the first operand is simple and second is ConstantExpr, swap operands. FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) return FCmpInst::getSwappedPredicate(SwappedRelation); } else { // Ok, the LHS is known to be a constantexpr. The RHS can be any of a // constantexpr or a simple constant. const ConstantExpr *CE1 = cast(V1); switch (CE1->getOpcode()) { case Instruction::FPTrunc: case Instruction::FPExt: case Instruction::UIToFP: case Instruction::SIToFP: // We might be able to do something with these but we don't right now. break; default: break; } } // There are MANY other foldings that we could perform here. They will // probably be added on demand, as they seem needed. return FCmpInst::BAD_FCMP_PREDICATE; } /// evaluateICmpRelation - This function determines if there is anything we can /// decide about the two constants provided. This doesn't need to handle simple /// things like integer comparisons, but should instead handle ConstantExprs /// and GlobalValues. If we can determine that the two constants have a /// particular relation to each other, we should return the corresponding ICmp /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE. /// /// To simplify this code we canonicalize the relation so that the first /// operand is always the most "complex" of the two. We consider simple /// constants (like ConstantInt) to be the simplest, followed by /// GlobalValues, followed by ConstantExpr's (the most complex). /// static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1, const Constant *V2, bool isSigned) { assert(V1->getType() == V2->getType() && "Cannot compare different types of values!"); if (V1 == V2) return ICmpInst::ICMP_EQ; if (!isa(V1) && !isa(V1)) { if (!isa(V2) && !isa(V2)) { // We distilled this down to a simple case, use the standard constant // folder. ConstantInt *R = 0; Constant *C1 = const_cast(V1); Constant *C2 = const_cast(V2); ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; R = dyn_cast(ConstantExpr::getICmp(pred, C1, C2)); if (R && R->getZExtValue()) return pred; pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; R = dyn_cast(ConstantExpr::getICmp(pred, C1, C2)); if (R && R->getZExtValue()) return pred; pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; R = dyn_cast(ConstantExpr::getICmp(pred, C1, C2)); if (R && R->getZExtValue()) return pred; // If we couldn't figure it out, bail. return ICmpInst::BAD_ICMP_PREDICATE; } // If the first operand is simple, swap operands. ICmpInst::Predicate SwappedRelation = evaluateICmpRelation(V2, V1, isSigned); if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) return ICmpInst::getSwappedPredicate(SwappedRelation); } else if (const GlobalValue *CPR1 = dyn_cast(V1)) { if (isa(V2)) { // Swap as necessary. ICmpInst::Predicate SwappedRelation = evaluateICmpRelation(V2, V1, isSigned); if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) return ICmpInst::getSwappedPredicate(SwappedRelation); else return ICmpInst::BAD_ICMP_PREDICATE; } // Now we know that the RHS is a GlobalValue or simple constant, // which (since the types must match) means that it's a ConstantPointerNull. if (const GlobalValue *CPR2 = dyn_cast(V2)) { if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage()) return ICmpInst::ICMP_NE; } else { // GlobalVals can never be null. assert(isa(V2) && "Canonicalization guarantee!"); if (!CPR1->hasExternalWeakLinkage()) return ICmpInst::ICMP_NE; } } else { // Ok, the LHS is known to be a constantexpr. The RHS can be any of a // constantexpr, a CPR, or a simple constant. const ConstantExpr *CE1 = cast(V1); const Constant *CE1Op0 = CE1->getOperand(0); switch (CE1->getOpcode()) { case Instruction::Trunc: case Instruction::FPTrunc: case Instruction::FPExt: case Instruction::FPToUI: case Instruction::FPToSI: break; // We can't evaluate floating point casts or truncations. case Instruction::UIToFP: case Instruction::SIToFP: case Instruction::IntToPtr: case Instruction::BitCast: case Instruction::ZExt: case Instruction::SExt: case Instruction::PtrToInt: // If the cast is not actually changing bits, and the second operand is a // null pointer, do the comparison with the pre-casted value. if (V2->isNullValue() && (isa(CE1->getType()) || CE1->getType()->isInteger())) { bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false : (CE1->getOpcode() == Instruction::SExt ? true : (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned)); return evaluateICmpRelation( CE1Op0, Constant::getNullValue(CE1Op0->getType()), sgnd); } // If the dest type is a pointer type, and the RHS is a constantexpr cast // from the same type as the src of the LHS, evaluate the inputs. This is // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)", // which happens a lot in compilers with tagged integers. if (const ConstantExpr *CE2 = dyn_cast(V2)) if (CE2->isCast() && isa(CE1->getType()) && CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() && CE1->getOperand(0)->getType()->isInteger()) { bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false : (CE1->getOpcode() == Instruction::SExt ? true : (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned)); return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0), sgnd); } break; case Instruction::GetElementPtr: // Ok, since this is a getelementptr, we know that the constant has a // pointer type. Check the various cases. if (isa(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 (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(CE1Op0)) { // If we are indexing from a null pointer, check to see if we have any // non-zero indices. for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) if (!CE1->getOperand(i)->isNullValue()) // Offsetting from null, must not be equal. return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; // Only zero indexes from null, must still be zero. return ICmpInst::ICMP_EQ; } // Otherwise, we can't really say if the first operand is null or not. } else if (const GlobalValue *CPR2 = dyn_cast(V2)) { if (isa(CE1Op0)) { if (CPR2->hasExternalWeakLinkage()) // Weak linkage GVals could be zero or not. We're comparing it to // a null pointer, so its less-or-equal return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; else // If its not weak linkage, the GVal must have a non-zero address // so the result is less-than return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; } else if (const GlobalValue *CPR1 = dyn_cast(CE1Op0)) { if (CPR1 == CPR2) { // If this is a getelementptr of the same global, then it must be // different. Because the types must match, the getelementptr could // only have at most one index, and because we fold getelementptr's // with a single zero index, it must be nonzero. assert(CE1->getNumOperands() == 2 && !CE1->getOperand(1)->isNullValue() && "Suprising getelementptr!"); return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; } else { // If they are different globals, we don't know what the value is, // but they can't be equal. return ICmpInst::ICMP_NE; } } } else { const ConstantExpr *CE2 = cast(V2); const Constant *CE2Op0 = CE2->getOperand(0); // There are MANY other foldings that we could perform here. They will // probably be added on demand, as they seem needed. switch (CE2->getOpcode()) { default: break; case Instruction::GetElementPtr: // By far the most common case to handle is when the base pointers are // obviously to the same or different globals. if (isa(CE1Op0) && isa(CE2Op0)) { if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal return ICmpInst::ICMP_NE; // Ok, we know that both getelementptr instructions are based on the // same global. From this, we can precisely determine the relative // ordering of the resultant pointers. unsigned i = 1; // Compare all of the operands the GEP's have in common. gep_type_iterator GTI = gep_type_begin(CE1); for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); ++i, ++GTI) switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i), GTI.getIndexedType())) { case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; case -2: return ICmpInst::BAD_ICMP_PREDICATE; } // Ok, we ran out of things they have in common. If any leftovers // are non-zero then we have a difference, otherwise we are equal. for (; i < CE1->getNumOperands(); ++i) if (!CE1->getOperand(i)->isNullValue()) if (isa(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(CE2->getOperand(i))) return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; else return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. return ICmpInst::ICMP_EQ; } } } default: break; } } return ICmpInst::BAD_ICMP_PREDICATE; } Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, const Constant *C1, const Constant *C2) { // Handle some degenerate cases first if (isa(C1) || isa(C2)) return UndefValue::get(Type::Int1Ty); // icmp eq/ne(null,GV) -> false/true if (C1->isNullValue()) { if (const GlobalValue *GV = dyn_cast(C2)) if (!GV->hasExternalWeakLinkage()) // External weak GV can be null if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(); else if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue(); // icmp eq/ne(GV,null) -> false/true } else if (C2->isNullValue()) { if (const GlobalValue *GV = dyn_cast(C1)) if (!GV->hasExternalWeakLinkage()) // External weak GV can be null if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(); else if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue(); } if (isa(C1) && isa(C2)) { if (ICmpInst::isSignedPredicate(ICmpInst::Predicate(pred))) { int64_t V1 = cast(C1)->getSExtValue(); int64_t V2 = cast(C2)->getSExtValue(); switch (pred) { default: assert(0 && "Invalid ICmp Predicate"); return 0; case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1 < V2); case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1 > V2); case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1 <= V2); case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1 >= V2); } } else { uint64_t V1 = cast(C1)->getZExtValue(); uint64_t V2 = cast(C2)->getZExtValue(); switch (pred) { default: assert(0 && "Invalid ICmp Predicate"); return 0; case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2); case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2); case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1 < V2); case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1 > V2); case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1 <= V2); case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1 >= V2); } } } else if (isa(C1) && isa(C2)) { double C1Val = cast(C1)->getValue(); double C2Val = cast(C2)->getValue(); switch (pred) { default: assert(0 && "Invalid FCmp Predicate"); return 0; case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse(); case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue(); case FCmpInst::FCMP_UNO: return ConstantInt::get(Type::Int1Ty, C1Val != C1Val || C2Val != C2Val); case FCmpInst::FCMP_ORD: return ConstantInt::get(Type::Int1Ty, C1Val == C1Val && C2Val == C2Val); case FCmpInst::FCMP_UEQ: if (C1Val != C1Val || C2Val != C2Val) return ConstantInt::getTrue(); /* FALL THROUGH */ case FCmpInst::FCMP_OEQ: return ConstantInt::get(Type::Int1Ty, C1Val == C2Val); case FCmpInst::FCMP_UNE: if (C1Val != C1Val || C2Val != C2Val) return ConstantInt::getTrue(); /* FALL THROUGH */ case FCmpInst::FCMP_ONE: return ConstantInt::get(Type::Int1Ty, C1Val != C2Val); case FCmpInst::FCMP_ULT: if (C1Val != C1Val || C2Val != C2Val) return ConstantInt::getTrue(); /* FALL THROUGH */ case FCmpInst::FCMP_OLT: return ConstantInt::get(Type::Int1Ty, C1Val < C2Val); case FCmpInst::FCMP_UGT: if (C1Val != C1Val || C2Val != C2Val) return ConstantInt::getTrue(); /* FALL THROUGH */ case FCmpInst::FCMP_OGT: return ConstantInt::get(Type::Int1Ty, C1Val > C2Val); case FCmpInst::FCMP_ULE: if (C1Val != C1Val || C2Val != C2Val) return ConstantInt::getTrue(); /* FALL THROUGH */ case FCmpInst::FCMP_OLE: return ConstantInt::get(Type::Int1Ty, C1Val <= C2Val); case FCmpInst::FCMP_UGE: if (C1Val != C1Val || C2Val != C2Val) return ConstantInt::getTrue(); /* FALL THROUGH */ case FCmpInst::FCMP_OGE: return ConstantInt::get(Type::Int1Ty, C1Val >= C2Val); } } else if (const ConstantVector *CP1 = dyn_cast(C1)) { if (const ConstantVector *CP2 = dyn_cast(C2)) { if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) { for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) { Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, const_cast(CP1->getOperand(i)), const_cast(CP2->getOperand(i))); if (ConstantInt *CB = dyn_cast(C)) return CB; } // Otherwise, could not decide from any element pairs. return 0; } else if (pred == ICmpInst::ICMP_EQ) { for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) { Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ, const_cast(CP1->getOperand(i)), const_cast(CP2->getOperand(i))); if (ConstantInt *CB = dyn_cast(C)) return CB; } // Otherwise, could not decide from any element pairs. return 0; } } } if (C1->getType()->isFloatingPoint()) { switch (evaluateFCmpRelation(C1, C2)) { default: assert(0 && "Unknown relation!"); case FCmpInst::FCMP_UNO: case FCmpInst::FCMP_ORD: case FCmpInst::FCMP_UEQ: case FCmpInst::FCMP_UNE: case FCmpInst::FCMP_ULT: case FCmpInst::FCMP_UGT: case FCmpInst::FCMP_ULE: case FCmpInst::FCMP_UGE: case FCmpInst::FCMP_TRUE: case FCmpInst::FCMP_FALSE: case FCmpInst::BAD_FCMP_PREDICATE: break; // Couldn't determine anything about these constants. case FCmpInst::FCMP_OEQ: // We know that C1 == C2 return ConstantInt::get(Type::Int1Ty, pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); case FCmpInst::FCMP_OLT: // We know that C1 < C2 return ConstantInt::get(Type::Int1Ty, pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); case FCmpInst::FCMP_OGT: // We know that C1 > C2 return ConstantInt::get(Type::Int1Ty, pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); case FCmpInst::FCMP_OLE: // We know that C1 <= C2 // We can only partially decide this relation. if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) return ConstantInt::getFalse(); if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) return ConstantInt::getTrue(); break; case FCmpInst::FCMP_OGE: // We known that C1 >= C2 // We can only partially decide this relation. if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) return ConstantInt::getFalse(); if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) return ConstantInt::getTrue(); break; case ICmpInst::ICMP_NE: // We know that C1 != C2 // We can only partially decide this relation. if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) return ConstantInt::getFalse(); if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) return ConstantInt::getTrue(); break; } } else { // Evaluate the relation between the two constants, per the predicate. switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) { default: assert(0 && "Unknown relational!"); case ICmpInst::BAD_ICMP_PREDICATE: break; // Couldn't determine anything about these constants. case ICmpInst::ICMP_EQ: // We know the constants are equal! // If we know the constants are equal, we can decide the result of this // computation precisely. return ConstantInt::get(Type::Int1Ty, pred == ICmpInst::ICMP_EQ || pred == ICmpInst::ICMP_ULE || pred == ICmpInst::ICMP_SLE || pred == ICmpInst::ICMP_UGE || pred == ICmpInst::ICMP_SGE); case ICmpInst::ICMP_ULT: // If we know that C1 < C2, we can decide the result of this computation // precisely. return ConstantInt::get(Type::Int1Ty, pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_NE || pred == ICmpInst::ICMP_ULE); case ICmpInst::ICMP_SLT: // If we know that C1 < C2, we can decide the result of this computation // precisely. return ConstantInt::get(Type::Int1Ty, pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_NE || pred == ICmpInst::ICMP_SLE); case ICmpInst::ICMP_UGT: // If we know that C1 > C2, we can decide the result of this computation // precisely. return ConstantInt::get(Type::Int1Ty, pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_NE || pred == ICmpInst::ICMP_UGE); case ICmpInst::ICMP_SGT: // If we know that C1 > C2, we can decide the result of this computation // precisely. return ConstantInt::get(Type::Int1Ty, pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_NE || pred == ICmpInst::ICMP_SGE); case ICmpInst::ICMP_ULE: // If we know that C1 <= C2, we can only partially decide this relation. if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse(); if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue(); break; case ICmpInst::ICMP_SLE: // If we know that C1 <= C2, we can only partially decide this relation. if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse(); if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue(); break; case ICmpInst::ICMP_UGE: // If we know that C1 >= C2, we can only partially decide this relation. if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse(); if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue(); break; case ICmpInst::ICMP_SGE: // If we know that C1 >= C2, we can only partially decide this relation. if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse(); if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue(); break; case ICmpInst::ICMP_NE: // If we know that C1 != C2, we can only partially decide this relation. if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(); if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue(); break; } if (!isa(C1) && isa(C2)) { // If C2 is a constant expr and C1 isn't, flop them around and fold the // other way if possible. switch (pred) { case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_NE: // No change of predicate required. return ConstantFoldCompareInstruction(pred, C2, C1); case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_ULE: case ICmpInst::ICMP_SLE: case ICmpInst::ICMP_UGE: case ICmpInst::ICMP_SGE: // Change the predicate as necessary to swap the operands. pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); return ConstantFoldCompareInstruction(pred, C2, C1); default: // These predicates cannot be flopped around. break; } } } return 0; } Constant *llvm::ConstantFoldGetElementPtr(const Constant *C, Constant* const *Idxs, unsigned NumIdx) { if (NumIdx == 0 || (NumIdx == 1 && Idxs[0]->isNullValue())) return const_cast(C); if (isa(C)) { const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), (Value**)Idxs, NumIdx, true); assert(Ty != 0 && "Invalid indices for GEP!"); return UndefValue::get(PointerType::get(Ty)); } Constant *Idx0 = Idxs[0]; if (C->isNullValue()) { bool isNull = true; for (unsigned i = 0, e = NumIdx; i != e; ++i) if (!Idxs[i]->isNullValue()) { isNull = false; break; } if (isNull) { const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), (Value**)Idxs, NumIdx, true); assert(Ty != 0 && "Invalid indices for GEP!"); return ConstantPointerNull::get(PointerType::get(Ty)); } } if (ConstantExpr *CE = dyn_cast(const_cast(C))) { // Combine Indices - If the source pointer to this getelementptr instruction // is a getelementptr instruction, combine the indices of the two // getelementptr instructions into a single instruction. // if (CE->getOpcode() == Instruction::GetElementPtr) { const Type *LastTy = 0; for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); I != E; ++I) LastTy = *I; if ((LastTy && isa(LastTy)) || Idx0->isNullValue()) { SmallVector NewIndices; NewIndices.reserve(NumIdx + CE->getNumOperands()); for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) NewIndices.push_back(CE->getOperand(i)); // Add the last index of the source with the first index of the new GEP. // Make sure to handle the case when they are actually different types. Constant *Combined = CE->getOperand(CE->getNumOperands()-1); // Otherwise it must be an array. if (!Idx0->isNullValue()) { const Type *IdxTy = Combined->getType(); if (IdxTy != Idx0->getType()) { Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty); Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, Type::Int64Ty); Combined = ConstantExpr::get(Instruction::Add, C1, C2); } else { Combined = ConstantExpr::get(Instruction::Add, Idx0, Combined); } } NewIndices.push_back(Combined); NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx); return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0], NewIndices.size()); } } // Implement folding of: // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*), // long 0, long 0) // To: int* getelementptr ([3 x int]* %X, long 0, long 0) // if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) if (const PointerType *SPT = dyn_cast(CE->getOperand(0)->getType())) if (const ArrayType *SAT = dyn_cast(SPT->getElementType())) if (const ArrayType *CAT = dyn_cast(cast(C->getType())->getElementType())) if (CAT->getElementType() == SAT->getElementType()) return ConstantExpr::getGetElementPtr( (Constant*)CE->getOperand(0), Idxs, NumIdx); } return 0; }