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Diffstat (limited to 'lib/IR/ConstantFold.cpp')
| -rw-r--r-- | lib/IR/ConstantFold.cpp | 2066 |
1 files changed, 2066 insertions, 0 deletions
diff --git a/lib/IR/ConstantFold.cpp b/lib/IR/ConstantFold.cpp new file mode 100644 index 0000000000..91dc83f232 --- /dev/null +++ b/lib/IR/ConstantFold.cpp @@ -0,0 +1,2066 @@ +//===- 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 DataLayout, and the pieces that do. This is to avoid +// a dependence in IR on Target. +// +//===----------------------------------------------------------------------===// + +#include "ConstantFold.h" +#include "llvm/ADT/SmallVector.h" +#include "llvm/Constants.h" +#include "llvm/DerivedTypes.h" +#include "llvm/Function.h" +#include "llvm/GlobalAlias.h" +#include "llvm/GlobalVariable.h" +#include "llvm/Instructions.h" +#include "llvm/Operator.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 <limits> +using namespace llvm; + +//===----------------------------------------------------------------------===// +// ConstantFold*Instruction Implementations +//===----------------------------------------------------------------------===// + +/// BitCastConstantVector - Convert the specified vector Constant node to the +/// specified vector type. At this point, we know that the elements of the +/// input vector constant are all simple integer or FP values. +static Constant *BitCastConstantVector(Constant *CV, VectorType *DstTy) { + + if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy); + if (CV->isNullValue()) return Constant::getNullValue(DstTy); + + // If this cast changes element count then we can't handle it here: + // doing so requires endianness information. This should be handled by + // Analysis/ConstantFolding.cpp + unsigned NumElts = DstTy->getNumElements(); + if (NumElts != CV->getType()->getVectorNumElements()) + return 0; + + Type *DstEltTy = DstTy->getElementType(); + + SmallVector<Constant*, 16> Result; + Type *Ty = IntegerType::get(CV->getContext(), 32); + for (unsigned i = 0; i != NumElts; ++i) { + Constant *C = + ConstantExpr::getExtractElement(CV, ConstantInt::get(Ty, i)); + C = ConstantExpr::getBitCast(C, DstEltTy); + Result.push_back(C); + } + + return ConstantVector::get(Result); +} + +/// This function determines which opcode to use to fold two constant cast +/// expressions together. It uses CastInst::isEliminableCastPair to determine +/// the opcode. Consequently its just a wrapper around that function. +/// @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 + 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 + Type *SrcTy = Op->getOperand(0)->getType(); + Type *MidTy = Op->getType(); + Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode()); + Instruction::CastOps secondOp = Instruction::CastOps(opc); + + // Assume that pointers are never more than 64 bits wide. + IntegerType *FakeIntPtrTy = Type::getInt64Ty(DstTy->getContext()); + + // Let CastInst::isEliminableCastPair do the heavy lifting. + return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy, + FakeIntPtrTy, FakeIntPtrTy, + FakeIntPtrTy); +} + +static Constant *FoldBitCast(Constant *V, Type *DestTy) { + Type *SrcTy = V->getType(); + if (SrcTy == DestTy) + return V; // no-op cast + + // Check to see if we are casting a pointer to an aggregate to a pointer to + // the first element. If so, return the appropriate GEP instruction. + if (PointerType *PTy = dyn_cast<PointerType>(V->getType())) + if (PointerType *DPTy = dyn_cast<PointerType>(DestTy)) + if (PTy->getAddressSpace() == DPTy->getAddressSpace() + && DPTy->getElementType()->isSized()) { + SmallVector<Value*, 8> IdxList; + Value *Zero = + Constant::getNullValue(Type::getInt32Ty(DPTy->getContext())); + IdxList.push_back(Zero); + Type *ElTy = PTy->getElementType(); + while (ElTy != DPTy->getElementType()) { + if (StructType *STy = dyn_cast<StructType>(ElTy)) { + if (STy->getNumElements() == 0) break; + ElTy = STy->getElementType(0); + IdxList.push_back(Zero); + } else if (SequentialType *STy = + dyn_cast<SequentialType>(ElTy)) { + if (ElTy->isPointerTy()) 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); + } + + // Handle casts from one vector constant to another. We know that the src + // and dest type have the same size (otherwise its an illegal cast). + if (VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) { + if (VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) { + assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() && + "Not cast between same sized vectors!"); + SrcTy = NULL; + // First, check for null. Undef is already handled. + if (isa<ConstantAggregateZero>(V)) + return Constant::getNullValue(DestTy); + + // Handle ConstantVector and ConstantAggregateVector. + return BitCastConstantVector(V, DestPTy); + } + + // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts + // This allows for other simplifications (although some of them + // can only be handled by Analysis/ConstantFolding.cpp). + if (isa<ConstantInt>(V) || isa<ConstantFP>(V)) + return ConstantExpr::getBitCast(ConstantVector::get(V), DestPTy); + } + + // Finally, implement bitcast folding now. The code below doesn't handle + // bitcast right. + if (isa<ConstantPointerNull>(V)) // ptr->ptr cast. + return ConstantPointerNull::get(cast<PointerType>(DestTy)); + + // Handle integral constant input. + if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { + if (DestTy->isIntegerTy()) + // Integral -> Integral. This is a no-op because the bit widths must + // be the same. Consequently, we just fold to V. + return V; + + if (DestTy->isFloatingPointTy()) + 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<ConstantFP>(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(C->getType()->isIntegerTy() && + (cast<IntegerType>(C->getType())->getBitWidth() & 7) == 0 && + "Non-byte sized integer input"); + unsigned CSize = cast<IntegerType>(C->getType())->getBitWidth()/8; + assert(ByteSize && "Must be accessing some piece"); + assert(ByteStart+ByteSize <= CSize && "Extracting invalid piece from input"); + assert(ByteSize != CSize && "Should not extract everything"); + + // Constant Integers are simple. + if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) { + APInt V = CI->getValue(); + if (ByteStart) + V = V.lshr(ByteStart*8); + V = V.trunc(ByteSize*8); + return ConstantInt::get(CI->getContext(), V); + } + + // In the input is a constant expr, we might be able to recursively simplify. + // If not, we definitely can't do anything. + ConstantExpr *CE = dyn_cast<ConstantExpr>(C); + if (CE == 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<ConstantInt>(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<ConstantInt>(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<ConstantInt>(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<IntegerType>(CE->getOperand(0)->getType())->getBitWidth(); + + // If extracting something that is completely zero, return 0. + if (ByteStart*8 >= SrcBitSize) + return Constant::getNullValue(IntegerType::get(CE->getContext(), + ByteSize*8)); + + // If exactly extracting the input, return it. + if (ByteStart == 0 && ByteSize*8 == SrcBitSize) + return CE->getOperand(0); + + // If extracting something completely in the input, if 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(Type *Ty, Type *DestTy, + bool Folded) { + if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { + Constant *N = ConstantInt::get(DestTy, ATy->getNumElements()); + Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); + return ConstantExpr::getNUWMul(E, N); + } + + if (StructType *STy = dyn_cast<StructType>(Ty)) + if (!STy->isPacked()) { + unsigned NumElems = STy->getNumElements(); + // An empty struct has size zero. + if (NumElems == 0) + return ConstantExpr::getNullValue(DestTy); + // Check for a struct with all members having the same size. + Constant *MemberSize = + getFoldedSizeOf(STy->getElementType(0), DestTy, true); + bool AllSame = true; + for (unsigned i = 1; i != NumElems; ++i) + if (MemberSize != + getFoldedSizeOf(STy->getElementType(i), DestTy, true)) { + AllSame = false; + break; + } + if (AllSame) { + Constant *N = ConstantInt::get(DestTy, NumElems); + return ConstantExpr::getNUWMul(MemberSize, N); + } + } + + // Pointer size doesn't depend on the pointee type, so canonicalize them + // to an arbitrary pointee. + if (PointerType *PTy = dyn_cast<PointerType>(Ty)) + if (!PTy->getElementType()->isIntegerTy(1)) + return + getFoldedSizeOf(PointerType::get(IntegerType::get(PTy->getContext(), 1), + PTy->getAddressSpace()), + DestTy, true); + + // If there's no interesting folding happening, bail so that we don't create + // a constant that looks like it needs folding but really doesn't. + if (!Folded) + return 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(Type *Ty, Type *DestTy, + bool Folded) { + // The alignment of an array is equal to the alignment of the + // array element. Note that this is not always true for vectors. + if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { + Constant *C = ConstantExpr::getAlignOf(ATy->getElementType()); + C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, + DestTy, + false), + C, DestTy); + return C; + } + + if (StructType *STy = dyn_cast<StructType>(Ty)) { + // Packed structs always have an alignment of 1. + if (STy->isPacked()) + return ConstantInt::get(DestTy, 1); + + // Otherwise, struct alignment is the maximum alignment of any member. + // Without target data, we can't compare much, but we can check to see + // if all the members have the same alignment. + unsigned NumElems = STy->getNumElements(); + // An empty struct has minimal alignment. + if (NumElems == 0) + return ConstantInt::get(DestTy, 1); + // Check for a struct with all members having the same alignment. + Constant *MemberAlign = + getFoldedAlignOf(STy->getElementType(0), DestTy, true); + bool AllSame = true; + for (unsigned i = 1; i != NumElems; ++i) + if (MemberAlign != getFoldedAlignOf(STy->getElementType(i), DestTy, true)) { + AllSame = false; + break; + } + if (AllSame) + return MemberAlign; + } + + // Pointer alignment doesn't depend on the pointee type, so canonicalize them + // to an arbitrary pointee. + if (PointerType *PTy = dyn_cast<PointerType>(Ty)) + if (!PTy->getElementType()->isIntegerTy(1)) + return + getFoldedAlignOf(PointerType::get(IntegerType::get(PTy->getContext(), + 1), + PTy->getAddressSpace()), + DestTy, true); + + // If there's no interesting folding happening, bail so that we don't create + // a constant that looks like it needs folding but really doesn't. + if (!Folded) + return 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(Type *Ty, Constant *FieldNo, + Type *DestTy, + bool Folded) { + if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { + Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false, + DestTy, false), + FieldNo, DestTy); + Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); + return ConstantExpr::getNUWMul(E, N); + } + + if (StructType *STy = dyn_cast<StructType>(Ty)) + if (!STy->isPacked()) { + unsigned NumElems = STy->getNumElements(); + // An empty struct has no members. + if (NumElems == 0) + return 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, + Type *DestTy) { + if (isa<UndefValue>(V)) { + // zext(undef) = 0, because the top bits will be zero. + // sext(undef) = 0, because the top bits will all be the same. + // [us]itofp(undef) = 0, because the result value is bounded. + if (opc == Instruction::ZExt || opc == Instruction::SExt || + opc == Instruction::UIToFP || opc == Instruction::SIToFP) + return Constant::getNullValue(DestTy); + return UndefValue::get(DestTy); + } + + if (V->isNullValue() && !DestTy->isX86_MMXTy()) + return Constant::getNullValue(DestTy); + + // If the cast operand is a constant expression, there's a few things we can + // do to try to simplify it. + if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { + if (CE->isCast()) { + // Try hard to fold cast of cast because they are often eliminable. + if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy)) + return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); + } else if (CE->getOpcode() == Instruction::GetElementPtr) { + // If all of the indexes in the GEP are null values, there is no pointer + // adjustment going on. We might as well cast the source pointer. + bool isAllNull = true; + for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) + if (!CE->getOperand(i)->isNullValue()) { + isAllNull = false; + break; + } + if (isAllNull) + // This is casting one pointer type to another, always BitCast + return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy); + } + } + + // If the cast operand is a constant vector, perform the cast by + // operating on each element. In the cast of bitcasts, the element + // count may be mismatched; don't attempt to handle that here. + if ((isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) && + DestTy->isVectorTy() && + DestTy->getVectorNumElements() == V->getType()->getVectorNumElements()) { + SmallVector<Constant*, 16> res; + VectorType *DestVecTy = cast<VectorType>(DestTy); + Type *DstEltTy = DestVecTy->getElementType(); + Type *Ty = IntegerType::get(V->getContext(), 32); + for (unsigned i = 0, e = V->getType()->getVectorNumElements(); i != e; ++i) { + Constant *C = + ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i)); + res.push_back(ConstantExpr::getCast(opc, C, DstEltTy)); + } + return ConstantVector::get(res); + } + + // We actually have to do a cast now. Perform the cast according to the + // opcode specified. + switch (opc) { + default: + llvm_unreachable("Failed to cast constant expression"); + case Instruction::FPTrunc: + case Instruction::FPExt: + if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { + bool ignored; + APFloat Val = FPC->getValueAPF(); + Val.convert(DestTy->isHalfTy() ? APFloat::IEEEhalf : + DestTy->isFloatTy() ? APFloat::IEEEsingle : + DestTy->isDoubleTy() ? APFloat::IEEEdouble : + DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended : + DestTy->isFP128Ty() ? APFloat::IEEEquad : + DestTy->isPPC_FP128Ty() ? APFloat::PPCDoubleDouble : + APFloat::Bogus, + APFloat::rmNearestTiesToEven, &ignored); + return ConstantFP::get(V->getContext(), Val); + } + return 0; // Can't fold. + case Instruction::FPToUI: + case Instruction::FPToSI: + if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { + const APFloat &V = FPC->getValueAPF(); + bool ignored; + uint64_t x[2]; + uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); + (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI, + APFloat::rmTowardZero, &ignored); + APInt Val(DestBitWidth, 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<PointerType>(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<ConstantExpr>(V)) + if (CE->getOpcode() == Instruction::GetElementPtr && + CE->getOperand(0)->isNullValue()) { + Type *Ty = + cast<PointerType>(CE->getOperand(0)->getType())->getElementType(); + if (CE->getNumOperands() == 2) { + // Handle a sizeof-like expression. + Constant *Idx = CE->getOperand(1); + bool isOne = isa<ConstantInt>(Idx) && cast<ConstantInt>(Idx)->isOne(); + if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) { + Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true, + DestTy, false), + Idx, DestTy); + return ConstantExpr::getMul(C, Idx); + } + } else if (CE->getNumOperands() == 3 && + CE->getOperand(1)->isNullValue()) { + // Handle an alignof-like expression. + if (StructType *STy = dyn_cast<StructType>(Ty)) + if (!STy->isPacked()) { + ConstantInt *CI = cast<ConstantInt>(CE->getOperand(2)); + if (CI->isOne() && + STy->getNumElements() == 2 && + STy->getElementType(0)->isIntegerTy(1)) { + return getFoldedAlignOf(STy->getElementType(1), DestTy, false); + } + } + // Handle an offsetof-like expression. + if (Ty->isStructTy() || Ty->isArrayTy()) { + if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2), + DestTy, false)) + return C; + } + } + } + // Other pointer types cannot be casted + return 0; + case Instruction::UIToFP: + case Instruction::SIToFP: + if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { + APInt api = CI->getValue(); + APFloat apf(APInt::getNullValue(DestTy->getPrimitiveSizeInBits()), + !DestTy->isPPC_FP128Ty() /* isEEEE */); + (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<ConstantInt>(V)) { + uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); + return ConstantInt::get(V->getContext(), + CI->getValue().zext(BitWidth)); + } + return 0; + case Instruction::SExt: + if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { + uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); + return ConstantInt::get(V->getContext(), + CI->getValue().sext(BitWidth)); + } + return 0; + case Instruction::Trunc: { + uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); + if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { + return ConstantInt::get(V->getContext(), + CI->getValue().trunc(DestBitWidth)); + } + + // The input must be a constantexpr. See if we can simplify this based on + // the bytes we are demanding. Only do this if the source and dest are an + // even multiple of a byte. + if ((DestBitWidth & 7) == 0 && + (cast<IntegerType>(V->getType())->getBitWidth() & 7) == 0) + if (Constant *Res = ExtractConstantBytes(V, 0, DestBitWidth / 8)) + return Res; + + return 0; + } + case Instruction::BitCast: + return FoldBitCast(V, DestTy); + } +} + +Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond, + Constant *V1, Constant *V2) { + // Check for i1 and vector true/false conditions. + if (Cond->isNullValue()) return V2; + if (Cond->isAllOnesValue()) return V1; + + // If the condition is a vector constant, fold the result elementwise. + if (ConstantVector *CondV = dyn_cast<ConstantVector>(Cond)) { + SmallVector<Constant*, 16> Result; + Type *Ty = IntegerType::get(CondV->getContext(), 32); + for (unsigned i = 0, e = V1->getType()->getVectorNumElements(); i != e;++i){ + ConstantInt *Cond = dyn_cast<ConstantInt>(CondV->getOperand(i)); + if (Cond == 0) break; + + Constant *V = Cond->isNullValue() ? V2 : V1; + Constant *Res = ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i)); + Result.push_back(Res); + } + + // If we were able to build the vector, return it. + if (Result.size() == V1->getType()->getVectorNumElements()) + return ConstantVector::get(Result); + } + + if (isa<UndefValue>(Cond)) { + if (isa<UndefValue>(V1)) return V1; + return V2; + } + if (isa<UndefValue>(V1)) return V2; + if (isa<UndefValue>(V2)) return V1; + if (V1 == V2) return V1; + + if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) { + if (TrueVal->getOpcode() == Instruction::Select) + if (TrueVal->getOperand(0) == Cond) + return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2); + } + if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) { + if (FalseVal->getOpcode() == Instruction::Select) + if (FalseVal->getOperand(0) == Cond) + return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2)); + } + + return 0; +} + +Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val, + Constant *Idx) { + if (isa<UndefValue>(Val)) // ee(undef, x) -> undef + return UndefValue::get(Val->getType()->getVectorElementType()); + if (Val->isNullValue()) // ee(zero, x) -> zero + return Constant::getNullValue(Val->getType()->getVectorElementType()); + // ee({w,x,y,z}, undef) -> undef + if (isa<UndefValue>(Idx)) + return UndefValue::get(Val->getType()->getVectorElementType()); + + if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) { + uint64_t Index = CIdx->getZExtValue(); + // ee({w,x,y,z}, wrong_value) -> undef + if (Index >= Val->getType()->getVectorNumElements()) + return UndefValue::get(Val->getType()->getVectorElementType()); + return Val->getAggregateElement(Index); + } + return 0; +} + +Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val, + Constant *Elt, + Constant *Idx) { + ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx); + if (!CIdx) return 0; + const APInt &IdxVal = CIdx->getValue(); + + SmallVector<Constant*, 16> Result; + Type *Ty = IntegerType::get(Val->getContext(), 32); + for (unsigned i = 0, e = Val->getType()->getVectorNumElements(); i != e; ++i){ + if (i == IdxVal) { + Result.push_back(Elt); + continue; + } + + Constant *C = + ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i)); + Result.push_back(C); + } + + return ConstantVector::get(Result); +} + +Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1, + Constant *V2, + Constant *Mask) { + unsigned MaskNumElts = Mask->getType()->getVectorNumElements(); + Type *EltTy = V1->getType()->getVectorElementType(); + + // Undefined shuffle mask -> undefined value. + if (isa<UndefValue>(Mask)) + return UndefValue::get(VectorType::get(EltTy, MaskNumElts)); + + // Don't break the bitcode reader hack. + if (isa<ConstantExpr>(Mask)) return 0; + + unsigned SrcNumElts = V1->getType()->getVectorNumElements(); + + // Loop over the shuffle mask, evaluating each element. + SmallVector<Constant*, 32> Result; + for (unsigned i = 0; i != MaskNumElts; ++i) { + int Elt = ShuffleVectorInst::getMaskValue(Mask, i); + if (Elt == -1) { + Result.push_back(UndefValue::get(EltTy)); + continue; + } + Constant *InElt; + if (unsigned(Elt) >= SrcNumElts*2) + InElt = UndefValue::get(EltTy); + else if (unsigned(Elt) >= SrcNumElts) { + Type *Ty = IntegerType::get(V2->getContext(), 32); + InElt = + ConstantExpr::getExtractElement(V2, + ConstantInt::get(Ty, Elt - SrcNumElts)); + } else { + Type *Ty = IntegerType::get(V1->getContext(), 32); + InElt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, Elt)); + } + Result.push_back(InElt); + } + + return ConstantVector::get(Result); +} + +Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg, + ArrayRef<unsigned> Idxs) { + // Base case: no indices, so return the entire value. + if (Idxs.empty()) + return Agg; + + if (Constant *C = Agg->getAggregateElement(Idxs[0])) + return ConstantFoldExtractValueInstruction(C, Idxs.slice(1)); + + return 0; +} + +Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg, + Constant *Val, + ArrayRef<unsigned> Idxs) { + // Base case: no indices, so replace the entire value. + if (Idxs.empty()) + return Val; + + unsigned NumElts; + if (StructType *ST = dyn_cast<StructType>(Agg->getType())) + NumElts = ST->getNumElements(); + else if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType())) + NumElts = AT->getNumElements(); + else + NumElts = AT->getVectorNumElements(); + + SmallVector<Constant*, 32> Result; + for (unsigned i = 0; i != NumElts; ++i) { + Constant *C = Agg->getAggregateElement(i); + if (C == 0) return 0; + + if (Idxs[0] == i) + C = ConstantFoldInsertValueInstruction(C, Val, Idxs.slice(1)); + + Result.push_back(C); + } + + if (StructType *ST = dyn_cast<StructType>(Agg->getType())) + return ConstantStruct::get(ST, Result); + if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType())) + return ConstantArray::get(AT, Result); + return ConstantVector::get(Result); +} + + +Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, + Constant *C1, Constant *C2) { + // Handle UndefValue up front. + if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { + switch (Opcode) { + case Instruction::Xor: + if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) + // Handle undef ^ undef -> 0 special case. This is a common + // idiom (misuse). + return Constant::getNullValue(C1->getType()); + // Fallthrough + case Instruction::Add: + case Instruction::Sub: + return UndefValue::get(C1->getType()); + case Instruction::And: + if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef & undef -> undef + return C1; + return Constant::getNullValue(C1->getType()); // undef & X -> 0 + case Instruction::Mul: { + ConstantInt *CI; + // X * undef -> undef if X is odd or undef + if (((CI = dyn_cast<ConstantInt>(C1)) && CI->getValue()[0]) || + ((CI = dyn_cast<ConstantInt>(C2)) && CI->getValue()[0]) || + (isa<UndefValue>(C1) && isa<UndefValue>(C2))) + return UndefValue::get(C1->getType()); + + // X * undef -> 0 otherwise + return Constant::getNullValue(C1->getType()); + } + case Instruction::UDiv: + case Instruction::SDiv: + // undef / 1 -> undef + if (Opcode == Instruction::UDiv || Opcode == Instruction::SDiv) + if (ConstantInt *CI2 = dyn_cast |