//===- ConstantFold.cpp - LLVM constant folder ----------------------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements folding of constants for LLVM. This implements the // (internal) ConstantFold.h interface, which is used by the // ConstantExpr::get* methods to automatically fold constants when possible. // // The current constant folding implementation is implemented in two pieces: the // pieces that don't need TargetData, and the pieces that do. This is to avoid // a dependence in VMCore on Target. // //===----------------------------------------------------------------------===// #include "ConstantFold.h" #include "llvm/Constants.h" #include "llvm/Instructions.h" #include "llvm/DerivedTypes.h" #include "llvm/Function.h" #include "llvm/GlobalAlias.h" #include "llvm/GlobalVariable.h" #include "llvm/ADT/SmallVector.h" #include "llvm/Support/Compiler.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/GetElementPtrTypeIterator.h" #include "llvm/Support/ManagedStatic.h" #include "llvm/Support/MathExtras.h" #include using namespace llvm; //===----------------------------------------------------------------------===// // ConstantFold*Instruction Implementations //===----------------------------------------------------------------------===// /// BitCastConstantVector - Convert the specified ConstantVector node to the /// specified vector type. At this point, we know that the elements of the /// input vector constant are all simple integer or FP values. static Constant *BitCastConstantVector(ConstantVector *CV, const VectorType *DstTy) { // If this cast changes element count then we can't handle it here: // doing so requires endianness information. This should be handled by // Analysis/ConstantFolding.cpp unsigned NumElts = DstTy->getNumElements(); if (NumElts != CV->getNumOperands()) return 0; // Check to verify that all elements of the input are simple. for (unsigned i = 0; i != NumElts; ++i) { if (!isa(CV->getOperand(i)) && !isa(CV->getOperand(i))) return 0; } // Bitcast each element now. std::vector Result; const Type *DstEltTy = DstTy->getElementType(); for (unsigned i = 0; i != NumElts; ++i) Result.push_back(ConstantExpr::getBitCast(CV->getOperand(i), DstEltTy)); return ConstantVector::get(Result); } /// This function determines which opcode to use to fold two constant cast /// expressions together. It uses CastInst::isEliminableCastPair to determine /// the opcode. Consequently its just a wrapper around that function. /// @brief Determine if it is valid to fold a cast of a cast static unsigned foldConstantCastPair( unsigned opc, ///< opcode of the second cast constant expression 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::getInt64Ty(DstTy->getContext())); } static Constant *FoldBitCast(Constant *V, const Type *DestTy) { const Type *SrcTy = V->getType(); if (SrcTy == DestTy) return V; // no-op cast // Check to see if we are casting a pointer to an aggregate to a pointer to // the first element. If so, return the appropriate GEP instruction. if (const PointerType *PTy = dyn_cast(V->getType())) if (const PointerType *DPTy = dyn_cast(DestTy)) if (PTy->getAddressSpace() == DPTy->getAddressSpace()) { SmallVector IdxList; Value *Zero = Constant::getNullValue(Type::getInt32Ty(DPTy->getContext())); IdxList.push_back(Zero); 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(Zero); } else if (const SequentialType *STy = dyn_cast(ElTy)) { if (isa(ElTy)) break; // Can't index into pointers! ElTy = STy->getElementType(); IdxList.push_back(Zero); } else { break; } } if (ElTy == DPTy->getElementType()) // This GEP is inbounds because all indices are zero. return ConstantExpr::getInBoundsGetElementPtr(V, &IdxList[0], IdxList.size()); } // Handle casts from one vector constant to another. We know that the src // and dest type have the same size (otherwise its an illegal cast). if (const VectorType *DestPTy = dyn_cast(DestTy)) { if (const VectorType *SrcTy = dyn_cast(V->getType())) { assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() && "Not cast between same sized vectors!"); SrcTy = NULL; // First, check for null. Undef is already handled. if (isa(V)) return Constant::getNullValue(DestTy); if (ConstantVector *CV = dyn_cast(V)) return BitCastConstantVector(CV, 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, 1), 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->isInteger()) // Integral -> Integral. This is a no-op because the bit widths must // be the same. Consequently, we just fold to V. return V; if (DestTy->isFloatingPoint()) return ConstantFP::get(DestTy->getContext(), APFloat(CI->getValue(), !DestTy->isPPC_FP128Ty())); // Otherwise, can't fold this (vector?) return 0; } // Handle ConstantFP input: FP -> Integral. if (ConstantFP *FP = dyn_cast(V)) return ConstantInt::get(FP->getContext(), FP->getValueAPF().bitcastToAPInt()); return 0; } /// ExtractConstantBytes - 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(isa(C->getType()) && (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 = V.lshr(ByteStart*8); 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 == 0) return 0; switch (CE->getOpcode()) { default: return 0; case Instruction::Or: { Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize); if (RHS == 0) return 0; // X | -1 -> -1. if (ConstantInt *RHSC = dyn_cast(RHS)) if (RHSC->isAllOnesValue()) return RHSC; Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize); if (LHS == 0) return 0; return ConstantExpr::getOr(LHS, RHS); } case Instruction::And: { Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize); if (RHS == 0) return 0; // X & 0 -> 0. if (RHS->isNullValue()) return RHS; Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize); if (LHS == 0) return 0; return ConstantExpr::getAnd(LHS, RHS); } case Instruction::LShr: { ConstantInt *Amt = dyn_cast(CE->getOperand(1)); if (Amt == 0) return 0; unsigned ShAmt = Amt->getZExtValue(); // Cannot analyze non-byte shifts. if ((ShAmt & 7) != 0) return 0; ShAmt >>= 3; // If the extract is known to be all zeros, return zero. if (ByteStart >= CSize-ShAmt) return Constant::getNullValue(IntegerType::get(CE->getContext(), ByteSize*8)); // If the extract is known to be fully in the input, extract it. if (ByteStart+ByteSize+ShAmt <= CSize) return ExtractConstantBytes(CE->getOperand(0), ByteStart+ShAmt, ByteSize); // TODO: Handle the 'partially zero' case. return 0; } case Instruction::Shl: { ConstantInt *Amt = dyn_cast(CE->getOperand(1)); if (Amt == 0) return 0; unsigned ShAmt = Amt->getZExtValue(); // Cannot analyze non-byte shifts. if ((ShAmt & 7) != 0) return 0; ShAmt >>= 3; // If the extract is known to be all zeros, return zero. if (ByteStart+ByteSize <= ShAmt) return Constant::getNullValue(IntegerType::get(CE->getContext(), ByteSize*8)); // If the extract is known to be fully in the input, extract it. if (ByteStart >= ShAmt) return ExtractConstantBytes(CE->getOperand(0), ByteStart-ShAmt, ByteSize); // TODO: Handle the 'partially zero' case. return 0; } 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 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 0; } } } /// getFoldedSizeOf - Return a ConstantExpr with type DestTy for sizeof /// on Ty, with any known factors factored out. If Folded is false, /// return null if no factoring was possible, to avoid endlessly /// bouncing an unfoldable expression back into the top-level folder. /// static Constant *getFoldedSizeOf(const Type *Ty, const Type *DestTy, bool Folded) { if (const ArrayType *ATy = dyn_cast(Ty)) { Constant *N = ConstantInt::get(DestTy, ATy->getNumElements()); Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); return ConstantExpr::getNUWMul(E, N); } if (const VectorType *VTy = dyn_cast(Ty)) { Constant *N = ConstantInt::get(DestTy, VTy->getNumElements()); Constant *E = getFoldedSizeOf(VTy->getElementType(), DestTy, true); return ConstantExpr::getNUWMul(E, N); } if (const StructType *STy = dyn_cast(Ty)) if (!STy->isPacked()) { unsigned NumElems = STy->getNumElements(); // An empty struct has size zero. if (NumElems == 0) return ConstantExpr::getNullValue(DestTy); // Check for a struct with all members having the same size. Constant *MemberSize = getFoldedSizeOf(STy->getElementType(0), DestTy, true); bool AllSame = true; for (unsigned i = 1; i != NumElems; ++i) if (MemberSize != getFoldedSizeOf(STy->getElementType(i), DestTy, true)) { AllSame = false; break; } if (AllSame) { Constant *N = ConstantInt::get(DestTy, NumElems); return ConstantExpr::getNUWMul(MemberSize, N); } } // Pointer size doesn't depend on the pointee type, so canonicalize them // to an arbitrary pointee. if (const PointerType *PTy = dyn_cast(Ty)) if (!PTy->getElementType()->isInteger(1)) return getFoldedSizeOf(PointerType::get(IntegerType::get(PTy->getContext(), 1), PTy->getAddressSpace()), DestTy, true); // If there's no interesting folding happening, bail so that we don't create // a constant that looks like it needs folding but really doesn't. if (!Folded) return 0; // Base case: Get a regular sizeof expression. Constant *C = ConstantExpr::getSizeOf(Ty); C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, DestTy, false), C, DestTy); return C; } /// getFoldedAlignOf - Return a ConstantExpr with type DestTy for alignof /// on Ty, with any known factors factored out. If Folded is false, /// return null if no factoring was possible, to avoid endlessly /// bouncing an unfoldable expression back into the top-level folder. /// static Constant *getFoldedAlignOf(const Type *Ty, const Type *DestTy, bool Folded) { // The alignment of an array is equal to the alignment of the // array element. Note that this is not always true for vectors. if (const ArrayType *ATy = dyn_cast(Ty)) { Constant *C = ConstantExpr::getAlignOf(ATy->getElementType()); C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, DestTy, false), C, DestTy); return C; } if (const StructType *STy = dyn_cast(Ty)) { // Packed structs always have an alignment of 1. if (STy->isPacked()) return ConstantInt::get(DestTy, 1); // Otherwise, struct alignment is the maximum alignment of any member. // Without target data, we can't compare much, but we can check to see // if all the members have the same alignment. unsigned NumElems = STy->getNumElements(); // An empty struct has minimal alignment. if (NumElems == 0) return ConstantInt::get(DestTy, 1); // Check for a struct with all members having the same alignment. Constant *MemberAlign = getFoldedAlignOf(STy->getElementType(0), DestTy, true); bool AllSame = true; for (unsigned i = 1; i != NumElems; ++i) if (MemberAlign != getFoldedAlignOf(STy->getElementType(i), DestTy, true)) { AllSame = false; break; } if (AllSame) return MemberAlign; } // Pointer alignment doesn't depend on the pointee type, so canonicalize them // to an arbitrary pointee. if (const PointerType *PTy = dyn_cast(Ty)) if (!PTy->getElementType()->isInteger(1)) return getFoldedAlignOf(PointerType::get(IntegerType::get(PTy->getContext(), 1), PTy->getAddressSpace()), DestTy, true); // If there's no interesting folding happening, bail so that we don't create // a constant that looks like it needs folding but really doesn't. if (!Folded) return 0; // Base case: Get a regular alignof expression. Constant *C = ConstantExpr::getAlignOf(Ty); C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, DestTy, false), C, DestTy); return C; } /// getFoldedOffsetOf - Return a ConstantExpr with type DestTy for offsetof /// on Ty and FieldNo, with any known factors factored out. If Folded is false, /// return null if no factoring was possible, to avoid endlessly /// bouncing an unfoldable expression back into the top-level folder. /// static Constant *getFoldedOffsetOf(const Type *Ty, Constant *FieldNo, const Type *DestTy, bool Folded) { if (const ArrayType *ATy = dyn_cast(Ty)) { Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false, DestTy, false), FieldNo, DestTy); Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); return ConstantExpr::getNUWMul(E, N); } if (const VectorType *VTy = dyn_cast(Ty)) { Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false, DestTy, false), FieldNo, DestTy); Constant *E = getFoldedSizeOf(VTy->getElementType(), DestTy, true); return ConstantExpr::getNUWMul(E, N); } if (const StructType *STy = dyn_cast(Ty)) if (!STy->isPacked()) { unsigned NumElems = STy->getNumElements(); // An empty struct has no members. if (NumElems == 0) return 0; // Check for a struct with all members having the same size. Constant *MemberSize = getFoldedSizeOf(STy->getElementType(0), DestTy, true); bool AllSame = true; for (unsigned i = 1; i != NumElems; ++i) if (MemberSize != getFoldedSizeOf(STy->getElementType(i), DestTy, true)) { AllSame = false; break; } if (AllSame) { Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false, DestTy, false), FieldNo, DestTy); return ConstantExpr::getNUWMul(MemberSize, N); } } // If there's no interesting folding happening, bail so that we don't create // a constant that looks like it needs folding but really doesn't. if (!Folded) return 0; // Base case: Get a regular offsetof expression. Constant *C = ConstantExpr::getOffsetOf(Ty, FieldNo); C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, DestTy, false), C, DestTy); return C; } Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V, const Type *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); } // No compile-time operations on this type yet. if (V->getType()->isPPC_FP128Ty() || DestTy->isPPC_FP128Ty()) return 0; // If the cast operand is a constant expression, there's a few things we can // do to try to simplify it. if (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); } } // 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 (ConstantVector *CV = dyn_cast(V)) if (isa(DestTy) && cast(DestTy)->getNumElements() == CV->getType()->getNumElements()) { std::vector res; const VectorType *DestVecTy = cast(DestTy); const Type *DstEltTy = DestVecTy->getElementType(); for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i) res.push_back(ConstantExpr::getCast(opc, CV->getOperand(i), DstEltTy)); return ConstantVector::get(DestVecTy, 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->isFloatTy() ? APFloat::IEEEsingle : DestTy->isDoubleTy() ? APFloat::IEEEdouble : DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended : DestTy->isFP128Ty() ? APFloat::IEEEquad : APFloat::Bogus, APFloat::rmNearestTiesToEven, &ignored); return ConstantFP::get(V->getContext(), Val); } return 0; // Can't fold. case Instruction::FPToUI: case Instruction::FPToSI: if (ConstantFP *FPC = dyn_cast(V)) { const APFloat &V = FPC->getValueAPF(); bool ignored; uint64_t x[2]; uint32_t DestBitWidth = cast(DestTy)->getBitWidth(); (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI, APFloat::rmTowardZero, &ignored); APInt Val(DestBitWidth, 2, x); return ConstantInt::get(FPC->getContext(), Val); } 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 // Is it a null pointer value? if (V->isNullValue()) return ConstantInt::get(DestTy, 0); // If this is a sizeof-like expression, pull out multiplications by // known factors to expose them to subsequent folding. If it's an // alignof-like expression, factor out known factors. if (ConstantExpr *CE = dyn_cast(V)) if (CE->getOpcode() == Instruction::GetElementPtr && CE->getOperand(0)->isNullValue()) { const Type *Ty = cast(CE->getOperand(0)->getType())->getElementType(); if (CE->getNumOperands() == 2) { // Handle a sizeof-like expression. Constant *Idx = CE->getOperand(1); bool isOne = isa(Idx) && cast(Idx)->isOne(); if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) { Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true, DestTy, false), Idx, DestTy); return ConstantExpr::getMul(C, Idx); } } else if (CE->getNumOperands() == 3 && CE->getOperand(1)->isNullValue()) { // Handle an alignof-like expression. if (const StructType *STy = dyn_cast(Ty)) if (!STy->isPacked()) { ConstantInt *CI = cast(CE->getOperand(2)); if (CI->isOne() && STy->getNumElements() == 2 && STy->getElementType(0)->isInteger(1)) { return getFoldedAlignOf(STy->getElementType(1), DestTy, false); } } // Handle an offsetof-like expression. if (isa(Ty) || isa(Ty) || isa(Ty)){ if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2), DestTy, false)) return C; } } } // Other pointer types cannot be casted return 0; case Instruction::UIToFP: case Instruction::SIToFP: if (ConstantInt *CI = dyn_cast(V)) { APInt api = CI->getValue(); const uint64_t zero[] = {0, 0}; APFloat apf = APFloat(APInt(DestTy->getPrimitiveSizeInBits(), 2, zero)); (void)apf.convertFromAPInt(api, opc==Instruction::SIToFP, APFloat::rmNearestTiesToEven); return ConstantFP::get(V->getContext(), apf); } return 0; case Instruction::ZExt: if (ConstantInt *CI = dyn_cast(V)) { uint32_t BitWidth = cast(DestTy)->getBitWidth(); APInt Result(CI->getValue()); Result.zext(BitWidth); return ConstantInt::get(V->getContext(), Result); } return 0; case Instruction::SExt: if (ConstantInt *CI = dyn_cast(V)) { uint32_t BitWidth = cast(DestTy)->getBitWidth(); APInt Result(CI->getValue()); Result.sext(BitWidth); return ConstantInt::get(V->getContext(), Result); } return 0; case Instruction::Trunc: { uint32_t DestBitWidth = cast(DestTy)->getBitWidth(); if (ConstantInt *CI = dyn_cast(V)) { APInt Result(CI->getValue()); Result.trunc(DestBitWidth); return ConstantInt::get(V->getContext(), Result); } // 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 0; } case Instruction::BitCast: return FoldBitCast(V, DestTy); } } Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond, Constant *V1, Constant *V2) { if (ConstantInt *CB = dyn_cast(Cond)) return CB->getZExtValue() ? V1 : V2; if (isa(V1)) return V2; if (isa(V2)) return V1; if (isa(Cond)) return V1; if (V1 == V2) return V1; return 0; } Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val, 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 (ConstantVector *CVal = dyn_cast(Val)) { if (ConstantInt *CIdx = dyn_cast(Idx)) { return CVal->getOperand(CIdx->getZExtValue()); } else if (isa(Idx)) { // ee({w,x,y,z}, undef) -> w (an arbitrary value). return CVal->getOperand(0); } } return 0; } Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val, Constant *Elt, Constant *Idx) { ConstantInt *CIdx = dyn_cast(Idx); if (!CIdx) return 0; APInt idxVal = CIdx->getValue(); if (isa(Val)) { // Insertion of scalar constant into vector undef // Optimize away insertion of undef if (isa(Elt)) return 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) { Constant *Op = (idxVal == i) ? Elt : UndefValue::get(Elt->getType()); Ops.push_back(Op); } return ConstantVector::get(Ops); } if (isa(Val)) { // Insertion of scalar constant into vector aggregate zero // Optimize away insertion of zero if (Elt->isNullValue()) return 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) { Constant *Op = (idxVal == i) ? Elt : Constant::getNullValue(Elt->getType()); Ops.push_back(Op); } return ConstantVector::get(Ops); } if (ConstantVector *CVal = dyn_cast(Val)) { // Insertion of scalar constant into vector constant std::vector Ops; Ops.reserve(CVal->getNumOperands()); for (unsigned i = 0; i < CVal->getNumOperands(); ++i) { Constant *Op = (idxVal == i) ? Elt : cast(CVal->getOperand(i)); Ops.push_back(Op); } return ConstantVector::get(Ops); } return 0; } /// GetVectorElement - If C is a ConstantVector, ConstantAggregateZero or Undef /// return the specified element value. Otherwise return null. static Constant *GetVectorElement(Constant *C, unsigned EltNo) { if (ConstantVector *CV = dyn_cast(C)) return CV->getOperand(EltNo); const Type *EltTy = cast(C->getType())->getElementType(); if (isa(C)) return Constant::getNullValue(EltTy); if (isa(C)) return UndefValue::get(EltTy); return 0; } Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1, Constant *V2, Constant *Mask) { // Undefined shuffle mask -> undefined value. if (isa(Mask)) return UndefValue::get(V1->getType()); unsigned MaskNumElts = cast(Mask->getType())->getNumElements(); unsigned SrcNumElts = cast(V1->getType())->getNumElements(); const Type *EltTy = cast(V1->getType())->getElementType(); // Loop over the shuffle mask, evaluating each element. SmallVector Result; for (unsigned i = 0; i != MaskNumElts; ++i) { Constant *InElt = GetVectorElement(Mask, i); if (InElt == 0) return 0; if (isa(InElt)) InElt = UndefValue::get(EltTy); else if (ConstantInt *CI = dyn_cast(InElt)) { unsigned Elt = CI->getZExtValue(); if (Elt >= SrcNumElts*2) InElt = UndefValue::get(EltTy); else if (Elt >= SrcNumElts) InElt = GetVectorElement(V2, Elt - SrcNumElts); else InElt = GetVectorElement(V1, Elt); if (InElt == 0) return 0; } else { // Unknown value. return 0; } Result.push_back(InElt); } return ConstantVector::get(&Result[0], Result.size()); } Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg, const unsigned *Idxs, unsigned NumIdx) { // Base case: no indices, so return the entire value. if (NumIdx == 0) return Agg; if (isa(Agg)) // ev(undef, x) -> undef return UndefValue::get(ExtractValueInst::getIndexedType(Agg->getType(), Idxs, Idxs + NumIdx)); if (isa(Agg)) // ev(0, x) -> 0 return Constant::getNullValue(ExtractValueInst::getIndexedType(Agg->getType(), Idxs, Idxs + NumIdx)); // Otherwise recurse. if (ConstantStruct *CS = dyn_cast(Agg)) return ConstantFoldExtractValueInstruction(CS->getOperand(*Idxs), Idxs+1, NumIdx-1); if (ConstantArray *CA = dyn_cast(Agg)) return ConstantFoldExtractValueInstruction(CA->getOperand(*Idxs), Idxs+1, NumIdx-1); ConstantVector *CV = cast(Agg); return ConstantFoldExtractValueInstruction(CV->getOperand(*Idxs), Idxs+1, NumIdx-1); } Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg, Constant *Val, const unsigned *Idxs, unsigned NumIdx) { // Base case: no indices, so replace the entire value. if (NumIdx == 0) return Val; if (isa(Agg)) { // Insertion of constant into aggregate undef // Optimize away insertion of undef. if (isa(Val)) return Agg; // Otherwise break the aggregate undef into multiple undefs and do // the insertion. const CompositeType *AggTy = cast(Agg->getType()); unsigned numOps; if (const ArrayType *AR = dyn_cast(AggTy)) numOps = AR->getNumElements(); else numOps = cast(AggTy)->getNumElements(); std::vector Ops(numOps); for (unsigned i = 0; i < numOps; ++i) { const Type *MemberTy = AggTy->getTypeAtIndex(i); Constant *Op = (*Idxs == i) ? ConstantFoldInsertValueInstruction(UndefValue::get(MemberTy), Val, Idxs+1, NumIdx-1) : UndefValue::get(MemberTy); Ops[i] = Op; } if (const StructType* ST = dyn_cast(AggTy)) return ConstantStruct::get(ST->getContext(), Ops, ST->isPacked()); return ConstantArray::get(cast(AggTy), Ops); } if (isa(Agg)) { // Insertion of constant into aggregate zero // Optimize away insertion of zero. if (Val->isNullValue()) return Agg; // Otherwise break the aggregate zero into multiple zeros and do // the insertion. const CompositeType *AggTy = cast(Agg->getType()); unsigned numOps; if (const ArrayType *AR = dyn_cast(AggTy)) numOps = AR->getNumElements(); else numOps = cast(AggTy)->getNumElements(); std::vector Ops(numOps); for (unsigned i = 0; i < numOps; ++i) { const Type *MemberTy = AggTy->getTypeAtIndex(i); Constant *Op = (*Idxs == i) ? ConstantFoldInsertValueInstruction(Constant::getNullValue(MemberTy), Val, Idxs+1, NumIdx-1) : Constant::getNullValue(MemberTy); Ops[i] = Op; } if (const StructType *ST = dyn_cast(AggTy)) return ConstantStruct::get(ST->getContext(), Ops, ST->isPacked()); return ConstantArray::get(cast(AggTy), Ops); } if (isa(Agg) || isa(Agg)) { // Insertion of constant into aggregate constant. std::vector Ops(Agg->getNumOperands()); for (unsigned i = 0; i < Agg->getNumOperands(); ++i) { Constant *Op = cast(Agg->getOperand(i)); if (*Idxs == i) Op = ConstantFoldInsertValueInstruction(Op, Val, Idxs+1, NumIdx-1); Ops[i] = Op; } if (const StructType* ST = dyn_cast(Agg->getType())) return ConstantStruct::get(ST->getContext(), Ops, ST->isPacked()); return ConstantArray::get(cast(Agg->getType()), Ops); } return 0; } Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, Constant *C1, Constant *C2) { // No compile-time operations on this type yet. if (C1->getType()->isPPC_FP128Ty()) return 0; // Handle UndefValue up front. if (isa(C1) || isa(C2)) { switch (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()); // Fallthrough case Instruction::Add: case Instruction::Sub: return UndefValue::get(C1->getType()); case Instruction::Mul: case Instruction::And: return Constant::getNullValue(C1->getType()); case Instruction::UDiv: case Instruction::SDiv: case Instruction::URem: case Instruction::SRem: if (!isa(C2)) // undef / X -> 0 return Constant::getNullValue(C1->getType()); return C2; // X / undef -> undef case Instruction::Or: // X | undef -> -1 if (const VectorType *PTy = dyn_cast(C1->getType())) return Constant::getAllOnesValue(PTy); return Constant::getAllOnesValue(C1->getType()); case Instruction::LShr: if (isa(C2) && isa(C1)) return 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 C1; // undef ashr X --> undef else if (isa(C1)) return C1; // undef ashr undef -> undef else return C1; // X ashr undef --> X case Instruction::Shl: // undef << X -> 0 or X << undef -> 0 return Constant::getNullValue(C1->getType()); } } // Handle simplifications when the RHS is a constant int. if (ConstantInt *CI2 = dyn_cast(C2)) { switch (Opcode) { case Instruction::Add: if (CI2->equalsInt(0)) return C1; // X + 0 == X break; case Instruction::Sub: if (CI2->equalsInt(0)) return C1; // X - 0 == X break; case Instruction::Mul: if (CI2->equalsInt(0)) return C2; // X * 0 == 0 if (CI2->equalsInt(1)) return C1; // X * 1 == X break; case Instruction::UDiv: case Instruction::SDiv: if (CI2->equalsInt(1)) return C1; // X / 1 == X if (CI2->equalsInt(0)) return UndefValue::get(CI2->getType()); // X / 0 == undef break; case Instruction::URem: case Instruction::SRem: if (CI2->equalsInt(1)) return Constant::getNullValue(CI2->getType()); // X % 1 == 0 if (CI2->equalsInt(0)) return UndefValue::get(CI2->getType()); // X % 0 == undef break; case Instruction::And: if (CI2->isZero()) return C2; // X & 0 == 0 if (CI2->isAllOnesValue()) 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)); // Functions are at least 4-byte aligned. unsigned GVAlign = GV->getAlignment(); if (isa(GV)) GVAlign = std::max(GVAlign, 4U); if (GVAlign > 1) { unsigned DstWidth = CI2->getType()->getBitWidth(); unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign)); APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth)); // If checking bits we know are clear, return zero. if ((CI2->getValue() & BitsNotSet) == CI2->getValue()) return Constant::getNullValue(CI2->getType()); } } } break; case Instruction::Or: if (CI2->equalsInt(0)) return C1; // X | 0 == X if (CI2->isAllOnesValue()) return C2; // X | -1 == -1 break; case Instruction::Xor: if (CI2->equalsInt(0)) 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->equalsInt(1)); 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; } } // At this point we know neither constant is an UndefValue. if (ConstantInt *CI1 = dyn_cast(C1)) { if (ConstantInt *CI2 = dyn_cast(C2)) { using namespace APIntOps; 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->isNullValue() && "Div by zero handled above"); return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V)); case Instruction::SDiv: assert(!CI2->isNullValue() && "Div by zero handled above"); if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V)); case Instruction::URem: assert(!CI2->isNullValue() && "Div by zero handled above"); return ConstantInt::get(CI1->getContext(), C1V.urem(C2V)); case Instruction::SRem: assert(!CI2->isNullValue() && "Div by zero handled above"); if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef return ConstantInt::get(CI1->getContext(), C1V.srem(C2V)); case Instruction::And: return ConstantInt::get(CI1->getContext(), C1V & C2V); case Instruction::Or: return ConstantInt::get(CI1->getContext(), C1V | C2V); case Instruction::Xor: return ConstantInt::get(CI1->getContext(), C1V ^ C2V); case Instruction::Shl: { uint32_t shiftAmt = C2V.getZExtValue(); if (shiftAmt < C1V.getBitWidth()) return ConstantInt::get(CI1->getContext(), C1V.shl(shiftAmt)); else return UndefValue::get(C1->getType()); // too big shift is undef } case Instruction::LShr: { uint32_t shiftAmt = C2V.getZExtValue(); if (shiftAmt < C1V.getBitWidth()) return ConstantInt::get(CI1->getContext(), C1V.lshr(shiftAmt)); else return UndefValue::get(C1->getType()); // too big shift is undef } case Instruction::AShr: { uint32_t shiftAmt = C2V.getZExtValue(); if (shiftAmt < C1V.getBitWidth()) return ConstantInt::get(CI1->getContext(), C1V.ashr(shiftAmt)); else return UndefValue::get(C1->getType()); // too big shift is undef } } } switch (Opcode) { case Instruction::SDiv: case Instruction::UDiv: case Instruction::URem: case Instruction::SRem: case Instruction::LShr: case Instruction::AShr: case Instruction::Shl: if (CI1->equalsInt(0)) return C1; break; default: break; } } else if (ConstantFP *CFP1 = dyn_cast(C1)) { if (ConstantFP *CFP2 = dyn_cast(C2)) { APFloat C1V = CFP1->getValueAPF(); 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, APFloat::rmNearestTiesToEven); return ConstantFP::get(C1->getContext(), C3V); } } } else if (const VectorType *VTy = dyn_cast(C1->getType())) { ConstantVector *CP1 = dyn_cast(C1); ConstantVector *CP2 = dyn_cast(C2); if ((CP1 != NULL || isa(C1)) && (CP2 != NULL || isa(C2))) { std::vector Res; const Type* EltTy = VTy->getElementType(); Constant *C1 = 0; Constant *C2 = 0; switch (Opcode) { default: break; case Instruction::Add: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getAdd(C1, C2)); } return ConstantVector::get(Res); case Instruction::FAdd: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getFAdd(C1, C2)); } return ConstantVector::get(Res); case Instruction::Sub: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getSub(C1, C2)); } return ConstantVector::get(Res); case Instruction::FSub: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getFSub(C1, C2)); } return ConstantVector::get(Res); case Instruction::Mul: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getMul(C1, C2)); } return ConstantVector::get(Res); case Instruction::FMul: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getFMul(C1, C2)); } return ConstantVector::get(Res); case Instruction::UDiv: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getUDiv(C1, C2)); } return ConstantVector::get(Res); case Instruction::SDiv: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getSDiv(C1, C2)); } return ConstantVector::get(Res); case Instruction::FDiv: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getFDiv(C1, C2)); } return ConstantVector::get(Res); case Instruction::URem: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getURem(C1, C2)); } return ConstantVector::get(Res); case Instruction::SRem: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getSRem(C1, C2)); } return ConstantVector::get(Res); case Instruction::FRem: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getFRem(C1, C2)); } return ConstantVector::get(Res); case Instruction::And: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getAnd(C1, C2)); } return ConstantVector::get(Res); case Instruction::Or: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getOr(C1, C2)); } return ConstantVector::get(Res); case Instruction::Xor: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getXor(C1, C2)); } return ConstantVector::get(Res); case Instruction::LShr: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getLShr(C1, C2)); } return ConstantVector::get(Res); case Instruction::AShr: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getAShr(C1, C2)); } return ConstantVector::get(Res); case Instruction::Shl: for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy); C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy); Res.push_back(ConstantExpr::getShl(C1, C2)); } return ConstantVector::get(Res); } } } 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, C1->getType()) && 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. switch (Opcode) { case Instruction::Add: case Instruction::FAdd: case Instruction::Mul: case Instruction::FMul: 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::FSub: 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. break; } } // i1 can be simplified in many cases. if (C1->getType()->isInteger(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 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()->isInteger(64)) C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(C1->getContext())); if (!C2->getType()->isInteger(64)) C2 = ConstantExpr::getSExt(C2, Type::getInt64Ty(C1->getContext())); 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(Constant *V1, Constant *V2) { assert(V1->getType() == V2->getType() && "Cannot compare values of different types!"); // No compile-time operations on this type yet. if (V1->getType()->isPPC_FP128Ty()) return FCmpInst::BAD_FCMP_PREDICATE; // 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; 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; } /// 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(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 = 0; 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)) { // Don't try to decide equality of aliases. if (!isa(GV) && !isa(GV2)) if (!GV->hasExternalWeakLinkage() || !GV2->hasExternalWeakLinkage()) return ICmpInst::ICMP_NE; } 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. if (!GV->hasExternalWeakLinkage() && !isa(GV)) return ICmpInst::ICMP_NE; } } 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::UIToFP: case Instruction::SIToFP: case Instruction::BitCast: case Instruction::ZExt: case Instruction::SExt: // If the cast is not actually changing bits, and the second operand is a // null pointer, do the comparison with the pre-casted value. if (V2->isNullValue() && (isa(CE1->getType()) || CE1->getType()->isInteger())) { 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: // 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 *GV2 = dyn_cast(V2)) { if (isa(CE1Op0)) { if (GV2->hasExternalWeakLinkage()) // Weak linkage GVals could be zero or not. We're comparing it to // a null pointer, so its less-or-equal return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; else // If its not weak linkage, the GVal must have a non-zero address // so the result is less-than return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; } else if (const GlobalValue *GV = dyn_cast(CE1Op0)) { if (GV == GV2) { // If this is a getelementptr of the same global, then it must be // different. Because the types must match, the getelementptr could // only have at most one index, and because we fold getelementptr's // with a single zero index, it must be nonzero. assert(CE1->getNumOperands() == 2 && !CE1->getOperand(1)->isNullValue() && "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 { ConstantExpr *CE2 = cast(V2); Constant *CE2Op0 = CE2->getOperand(0); // There are MANY other foldings that we could perform here. They will // probably be added on demand, as they seem needed. switch (CE2->getOpcode()) { default: break; case Instruction::GetElementPtr: // By far the most common case to handle is when the base pointers are // obviously to the same 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; // The logic below assumes that the result of the comparison // can be determined by finding the first index that differs. // This doesn't work if there is over-indexing in any // subsequent indices, so check for that case first. if (!CE1->isGEPWithNoNotionalOverIndexing() || !CE2->isGEPWithNoNotionalOverIndexing()) return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. // Compare all of the operands the GEP's have in common. gep_type_iterator GTI = gep_type_begin(CE1); for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); ++i, ++GTI) switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i), GTI.getIndexedType())) { case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; case -2: return ICmpInst::BAD_ICMP_PREDICATE; } // Ok, we ran out of things they have in common. If any leftovers // are non-zero then we have a difference, otherwise we are equal. for (; i < CE1->getNumOperands(); ++i) if (!CE1->getOperand(i)->isNullValue()) { if (isa(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, Constant *C1, Constant *C2) { const Type *ResultTy; if (const VectorType *VT = dyn_cast(C1->getType())) ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()), VT->getNumElements()); else ResultTy = Type::getInt1Ty(C1->getContext()); // Fold FCMP_FALSE/FCMP_TRUE unconditionally. if (pred == FCmpInst::FCMP_FALSE) return Constant::getNullValue(ResultTy); if (pred == FCmpInst::FCMP_TRUE) return Constant::getAllOnesValue(ResultTy); // Handle some degenerate cases first if (isa(C1) || isa(C2)) return UndefValue::get(ResultTy); // No compile-time operations on this type yet. if (C1->getType()->isPPC_FP128Ty()) return 0; // 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()) { if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(C1->getContext()); else if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue(C1->getContext()); } // icmp eq/ne(GV,null) -> false/true } else if (C2->isNullValue()) { if (const GlobalValue *GV = dyn_cast(C1)) // Don't try to evaluate aliases. External weak GV can be null. if (!isa(GV) && !GV->hasExternalWeakLinkage()) { if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(C1->getContext()); else if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue(C1->getContext()); } } // If the comparison is a comparison between two i1's, simplify it. if (C1->getType()->isInteger(1)) { switch(pred) { 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)) { APInt V1 = cast(C1)->getValue(); APInt V2 = cast(C2)->getValue(); switch (pred) { default: llvm_unreachable("Invalid ICmp Predicate"); return 0; case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2); case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2); case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2)); case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2)); case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2)); case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2)); case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2)); case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2)); case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2)); case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2)); } } else if (isa(C1) && isa(C2)) { APFloat C1V = cast(C1)->getValueAPF(); APFloat C2V = cast(C2)->getValueAPF(); APFloat::cmpResult R = C1V.compare(C2V); switch (pred) { default: llvm_unreachable("Invalid FCmp Predicate"); return 0; case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy); case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy); case FCmpInst::FCMP_UNO: return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered); case FCmpInst::FCMP_ORD: return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered); case FCmpInst::FCMP_UEQ: return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || R==APFloat::cmpEqual); case FCmpInst::FCMP_OEQ: return ConstantInt::get(ResultTy, R==APFloat::cmpEqual); case FCmpInst::FCMP_UNE: return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual); case FCmpInst::FCMP_ONE: return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || R==APFloat::cmpGreaterThan); case FCmpInst::FCMP_ULT: return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || R==APFloat::cmpLessThan); case FCmpInst::FCMP_OLT: return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan); case FCmpInst::FCMP_UGT: return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || R==APFloat::cmpGreaterThan); case FCmpInst::FCMP_OGT: return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan); case FCmpInst::FCMP_ULE: return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan); case FCmpInst::FCMP_OLE: return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || R==APFloat::cmpEqual); case FCmpInst::FCMP_UGE: return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan); case FCmpInst::FCMP_OGE: return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan || R==APFloat::cmpEqual); } } else if (isa(C1->getType())) { SmallVector C1Elts, C2Elts; C1->getVectorElements(C1Elts); C2->getVectorElements(C2Elts); if (C1Elts.empty() || C2Elts.empty()) return 0; // If we can constant fold the comparison of each element, constant fold // the whole vector comparison. SmallVector ResElts; for (unsigned i = 0, e = C1Elts.size(); i != e; ++i) { // Compare the elements, producing an i1 result or constant expr. ResElts.push_back(ConstantExpr::getCompare(pred, C1Elts[i], C2Elts[i])); } return ConstantVector::get(&ResElts[0], ResElts.size()); } if (C1->getType()->isFloatingPoint()) { 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_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 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); break; case FCmpInst::FCMP_OLT: // We know that C1 < C2 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); break; case FCmpInst::FCMP_OGT: // We know that C1 > C2 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); break; case FCmpInst::FCMP_OLE: // We know that C1 <= C2 // We can only partially decide this relation. if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) Result = 0; else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) Result = 1; break; case FCmpInst::FCMP_OGE: // We known that C1 >= C2 // We can only partially decide this relation. if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) Result = 0; else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) Result = 1; break; case ICmpInst::ICMP_NE: // We know that C1 != C2 // We can only partially decide this relation. if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) Result = 0; else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) Result = 1; break; } // 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(pred))) { default: llvm_unreachable("Unknown relational!"); case ICmpInst::BAD_ICMP_PREDICATE: break; // Couldn't determine anything about these constants. case ICmpInst::ICMP_EQ: // We know the constants are equal! // If we know the constants are equal, we can decide the result of this // computation precisely. Result = ICmpInst::isTrueWhenEqual((ICmpInst::Predicate)pred); break; case ICmpInst::ICMP_ULT: switch (pred) { case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE: Result = 1; break; case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE: Result = 0; break; } break; case ICmpInst::ICMP_SLT: switch (pred) { case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE: Result = 1; break; case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE: Result = 0; break; } break; case ICmpInst::ICMP_UGT: switch (pred) { case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE: Result = 1; break; case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE: Result = 0; break; } break; case ICmpInst::ICMP_SGT: switch (pred) { case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE: Result = 1; break; case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE: Result = 0; break; } break; case ICmpInst::ICMP_ULE: if (pred == ICmpInst::ICMP_UGT) Result = 0; if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1; break; case ICmpInst::ICMP_SLE: if (pred == ICmpInst::ICMP_SGT) Result = 0; if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1; break; case ICmpInst::ICMP_UGE: if (pred == ICmpInst::ICMP_ULT) Result = 0; if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1; break; case ICmpInst::ICMP_SGE: if (pred == ICmpInst::ICMP_SLT) Result = 0; if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1; break; case ICmpInst::ICMP_NE: if (pred == ICmpInst::ICMP_EQ) Result = 0; if (pred == ICmpInst::ICMP_NE) Result = 1; break; } // If we evaluated the result, return it now. if (Result != -1) return ConstantInt::get(ResultTy, Result); // If the right hand side is a bitcast, try using its inverse to simplify // it by moving it to the left hand side. We can't do this if it would turn // a vector compare into a scalar compare or visa versa. if (ConstantExpr *CE2 = dyn_cast(C2)) { Constant *CE2Op0 = CE2->getOperand(0); if (CE2->getOpcode() == Instruction::BitCast && isa(CE2->getType())==isa(CE2Op0->getType())) { Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType()); return ConstantExpr::getICmp(pred, Inverse, CE2Op0); } } // If the left hand side is an extension, try eliminating it. if (ConstantExpr *CE1 = dyn_cast(C1)) { if (CE1->getOpcode() == Instruction::SExt || CE1->getOpcode() == Instruction::ZExt) { 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::getZExt(C2Inverse, C2->getType()) == C2) { return ConstantExpr::getICmp(pred, 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. switch (pred) { case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_NE: // No change of predicate required. return ConstantExpr::getICmp(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 ConstantExpr::getICmp(pred, C2, C1); default: // These predicates cannot be flopped around. break; } } } return 0; } /// isInBoundsIndices - Test whether the given sequence of *normalized* indices /// is "inbounds". static bool isInBoundsIndices(Constant *const *Idxs, size_t NumIdx) { // No indices means nothing that could be out of bounds. if (NumIdx == 0) return true; // If the first index is zero, it's in bounds. if (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 (!cast(Idxs[0])->isOne()) return false; for (unsigned i = 1, e = NumIdx; i != e; ++i) if (!Idxs[i]->isNullValue()) return false; return true; } Constant *llvm::ConstantFoldGetElementPtr(Constant *C, bool inBounds, Constant* const *Idxs, unsigned NumIdx) { if (NumIdx == 0 || (NumIdx == 1 && Idxs[0]->isNullValue())) return C; if (isa(C)) { const PointerType *Ptr = cast(C->getType()); const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, (Value **)Idxs, (Value **)Idxs+NumIdx); assert(Ty != 0 && "Invalid indices for GEP!"); return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace())); } Constant *Idx0 = Idxs[0]; if (C->isNullValue()) { bool isNull = true; for (unsigned i = 0, e = NumIdx; i != e; ++i) if (!Idxs[i]->isNullValue()) { isNull = false; break; } if (isNull) { const PointerType *Ptr = cast(C->getType()); const Type *Ty = GetElementPtrInst::getIndexedType(Ptr, (Value**)Idxs, (Value**)Idxs+NumIdx); assert(Ty != 0 && "Invalid indices for GEP!"); return ConstantPointerNull::get( PointerType::get(Ty,Ptr->getAddressSpace())); } } if (ConstantExpr *CE = dyn_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()) { const Type *Int64Ty = Type::getInt64Ty(IdxTy->getContext()); Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Int64Ty); Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, 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 (inBounds && cast(CE)->isInBounds()) ? ConstantExpr::getInBoundsGetElementPtr(CE->getOperand(0), &NewIndices[0], NewIndices.size()) : ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0], NewIndices.size()); } } // Implement folding of: // int* getelementptr ([2 x int]* bitcast ([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 inBounds ? ConstantExpr::getInBoundsGetElementPtr( (Constant*)CE->getOperand(0), Idxs, NumIdx) : ConstantExpr::getGetElementPtr( (Constant*)CE->getOperand(0), Idxs, NumIdx); } } // Check to see if any array indices are not within the corresponding // notional array bounds. If so, try to determine if they can be factored // out into preceding dimensions. bool Unknown = false; SmallVector NewIdxs; const Type *Ty = C->getType(); const Type *Prev = 0; for (unsigned i = 0; i != NumIdx; Prev = Ty, Ty = cast(Ty)->getTypeAtIndex(Idxs[i]), ++i) { if (ConstantInt *CI = dyn_cast(Idxs[i])) { if (const ArrayType *ATy = dyn_cast(Ty)) if (ATy->getNumElements() <= INT64_MAX && ATy->getNumElements() != 0 && CI->getSExtValue() >= (int64_t)ATy->getNumElements()) { if (isa(Prev)) { // It's out of range, but we can factor it into the prior // dimension. NewIdxs.resize(NumIdx); ConstantInt *Factor = ConstantInt::get(CI->getType(), ATy->getNumElements()); NewIdxs[i] = ConstantExpr::getSRem(CI, Factor); Constant *PrevIdx = Idxs[i-1]; Constant *Div = ConstantExpr::getSDiv(CI, Factor); // Before adding, extend both operands to i64 to avoid // overflow trouble. if (!PrevIdx->getType()->isInteger(64)) PrevIdx = ConstantExpr::getSExt(PrevIdx, Type::getInt64Ty(Div->getContext())); if (!Div->getType()->isInteger(64)) Div = ConstantExpr::getSExt(Div, Type::getInt64Ty(Div->getContext())); NewIdxs[i-1] = ConstantExpr::getAdd(PrevIdx, Div); } else { // It's out of range, but the prior dimension is a struct // so we can't do anything about it. Unknown = true; } } } else { // We don't know if it's in range or not. Unknown = true; } } // If we did any factoring, start over with the adjusted indices. if (!NewIdxs.empty()) { for (unsigned i = 0; i != NumIdx; ++i) if (!NewIdxs[i]) NewIdxs[i] = Idxs[i]; return inBounds ? ConstantExpr::getInBoundsGetElementPtr(C, NewIdxs.data(), NewIdxs.size()) : ConstantExpr::getGetElementPtr(C, NewIdxs.data(), NewIdxs.size()); } // If all indices are known integers and normalized, we can do a simple // check for the "inbounds" property. if (!Unknown && !inBounds && isa(C) && isInBoundsIndices(Idxs, NumIdx)) return ConstantExpr::getInBoundsGetElementPtr(C, Idxs, NumIdx); return 0; }