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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 00000000000..91dc83f232e --- /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<ConstantInt>(C2)) + if (CI2->isOne()) + return C1; + // FALL THROUGH + case Instruction::URem: + case Instruction::SRem: + if (!isa<UndefValue>(C2)) // undef / X -> 0 + return Constant::getNullValue(C1->getType()); + return C2; // X / undef -> undef + case Instruction::Or: // X | undef -> -1 + if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef + return C1; + return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0 + case Instruction::LShr: + if (isa<UndefValue>(C2) && isa<UndefValue>(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<UndefValue>(C2)) // undef ashr X --> all ones + return Constant::getAllOnesValue(C1->getType()); + else if (isa<UndefValue>(C1)) + return C1; // undef ashr undef -> undef + else + return C1; // X ashr undef --> X + case Instruction::Shl: + if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) + return C1; // undef shl undef -> undef + // 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<ConstantInt>(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<ConstantExpr>(C1)) { + // (zext i32 to i64) & 4294967295 -> (zext i32 to i64) + if (CE1->getOpcode() == Instruction::ZExt) { + unsigned DstWidth = CI2->getType()->getBitWidth(); + unsigned SrcWidth = + CE1->getOperand(0)->getType()->getPrimitiveSizeInBits(); + APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth)); + if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits) + return C1; + } + + // If and'ing the address of a global with a constant, fold it. + if (CE1->getOpcode() == Instruction::PtrToInt && + isa<GlobalValue>(CE1->getOperand(0))) { + GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0)); + + // Functions are at least 4-byte aligned. + unsigned GVAlign = GV->getAlignment(); + if (isa<Function>(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<ConstantExpr>(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<ConstantExpr>(C1)) + if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero. + return ConstantExpr::getLShr(C1, C2); + break; + } + } else if (isa<ConstantInt>(C1)) { + // If C1 is a ConstantInt and C2 is not, swap the operands. + if (Instruction::isCommutative(Opcode)) + return ConstantExpr::get(Opcode, C2, C1); + } + + // At this point we know neither constant is an UndefValue. + if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) { + if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { + const APInt &C1V = CI1->getValue(); + const APInt &C2V = CI2->getValue(); + switch (Opcode) { + default: + break; + case Instruction::Add: + return ConstantInt::get(CI1->getContext(), C1V + C2V); + case Instruction::Sub: + return ConstantInt::get(CI1->getContext(), C1V - C2V); + case Instruction::Mul: + return ConstantInt::get(CI1->getContext(), C1V * C2V); + case Instruction::UDiv: + assert(!CI2->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<ConstantFP>(C1)) { + if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(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 (VectorType *VTy = dyn_cast<VectorType>(C1->getType())) { + // Perform elementwise folding. + SmallVector<Constant*, 16> Result; + Type *Ty = IntegerType::get(VTy->getContext(), 32); + for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { + Constant *LHS = + ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i)); + Constant *RHS = + ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i)); + + Result.push_back(ConstantExpr::get(Opcode, LHS, RHS)); + } + + return ConstantVector::get(Result); + } + + if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { + // There are many possible foldings we could do here. We should probably + // at least fold add of a pointer with an integer into the appropriate + // getelementptr. This will improve alias analysis a bit. + + // Given ((a + b) + c), if (b + c) folds to something interesting, return + // (a + (b + c)). + if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) { + Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2); + if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode) + return ConstantExpr::get(Opcode, CE1->getOperand(0), T); + } + } else if (isa<ConstantExpr>(C2)) { + // If C2 is a constant expr and C1 isn't, flop them around and fold the + // other way if possible. + if (Instruction::isCommutative(Opcode)) + return ConstantFoldBinaryInstruction(Opcode, C2, C1); + } + + // i1 can be simplified in many cases. + if (C1->getType()->isIntegerTy(1)) { + switch (Opcode) { + case Instruction::Add: + case Instruction::Sub: + return ConstantExpr::getXor(C1, C2); + case Instruction::Mul: + return ConstantExpr::getAnd(C1, C2); + case Instruction::Shl: + case Instruction::LShr: + case Instruction::AShr: + // We can assume that C2 == 0. If it were one the result would be + // undefined because the shift value is as large as the bitwidth. + return C1; + case Instruction::SDiv: + case Instruction::UDiv: + // We can assume that C2 == 1. If it were zero the result would be + // undefined through division by zero. + return C1; + case Instruction::URem: + case Instruction::SRem: + // We can assume that C2 == 1. If it were zero the result would be + // undefined through division by zero. + return ConstantInt::getFalse(C1->getContext()); + default: + break; + } + } + + // We don't know how to fold this. + return 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(Type *Ty) { + if (StructType *STy = dyn_cast<StructType>(Ty)) { + if (STy->isOpaque()) return true; // Can't say. + + // If all of elements have zero size, this does too. + for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) + if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; + return true; + + } else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { + return isMaybeZeroSizedType(ATy->getElementType()); + } + return false; +} + +/// 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, Type *ElTy) { + if (C1 == C2) return 0; + + // Ok, we found a different index. If they are not ConstantInt, we can't do + // anything with them. + if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) + return -2; // don't know! + + // 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()->isIntegerTy(64)) + C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(C1->getContext())); + + if (!C2->getType()->isIntegerTy(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<ConstantInt>(C1)->getSExtValue() < + cast<ConstantInt>(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!"); + + // Handle degenerate case quickly + if (V1 == V2) return FCmpInst::FCMP_OEQ; + + if (!isa<ConstantExpr>(V1)) { + if (!isa<ConstantExpr>(V2)) { + // We distilled thisUse the standard constant folder for a few cases + ConstantInt *R = 0; + R = dyn_cast<ConstantInt>( + ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2)); + if (R && !R->isZero()) + return FCmpInst::FCMP_OEQ; + R = dyn_cast<ConstantInt>( + ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2)); + if (R && !R->isZero()) + return FCmpInst::FCMP_OLT; + R = dyn_cast<ConstantInt>( + ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2)); + if (R && !R->isZero()) + return FCmpInst::FCMP_OGT; + + // Nothing more we can do + return FCmpInst::BAD_FCMP_PREDICATE; + } + + // If the first operand is simple and second is ConstantExpr, swap operands. + FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); + if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) + return FCmpInst::getSwappedPredicate(SwappedRelation); + } else { + // Ok, the LHS is known to be a constantexpr. The RHS can be any of a + // constantexpr or a simple constant. + ConstantExpr *CE1 = cast<ConstantExpr>(V1); + switch (CE1->getOpcode()) { + case Instruction::FPTrunc: + case Instruction::FPExt: + case Instruction::UIToFP: + case Instruction::SIToFP: + // We might be able to do something with these but we don't right now. + break; + default: + break; + } + } + // There are MANY other foldings that we could perform here. They will + // probably be added on demand, as they seem needed. + return FCmpInst::BAD_FCMP_PREDICATE; +} + +/// 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<ConstantExpr>(V1) && !isa<GlobalValue>(V1) && + !isa<BlockAddress>(V1)) { + if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) && + !isa<BlockAddress>(V2)) { + // We distilled this down to a simple case, use the standard constant + // folder. + ConstantInt *R = 0; + ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; + R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); + if (R && !R->isZero()) + return pred; + pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; + R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); + if (R && !R->isZero()) + return pred; + pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; + R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); + if (R && !R->isZero()) + return pred; + + // If we couldn't figure it out, bail. + return ICmpInst::BAD_ICMP_PREDICATE; + } + + // If the first operand is simple, swap operands. + ICmpInst::Predicate SwappedRelation = + evaluateICmpRelation(V2, V1, isSigned); + if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) + return ICmpInst::getSwappedPredicate(SwappedRelation); + + } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) { + if (isa<ConstantExpr>(V2)) { // Swap as necessary. + ICmpInst::Predicate SwappedRelation = + evaluateICmpRelation(V2, V1, isSigned); + if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) + return ICmpInst::getSwappedPredicate(SwappedRelation); + return ICmpInst::BAD_ICMP_PREDICATE; + } + + // Now we know that the RHS is a GlobalValue, BlockAddress or simple + // constant (which, since the types must match, means that it's a + // ConstantPointerNull). + if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { + // Don't try to decide equality of aliases. + if (!isa<GlobalAlias>(GV) && !isa<GlobalAlias>(GV2)) + if (!GV->hasExternalWeakLinkage() || !GV2->hasExternalWeakLinkage()) + return ICmpInst::ICMP_NE; + } else if (isa<BlockAddress>(V2)) { + return ICmpInst::ICMP_NE; // Globals never equal labels. + } else { + assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); + // GlobalVals can never be null unless they have external weak linkage. + // We don't try to evaluate aliases here. + if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV)) + return ICmpInst::ICMP_NE; + } + } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) { + if (isa<ConstantExpr>(V2)) { // Swap as necessary. + ICmpInst::Predicate SwappedRelation = + evaluateICmpRelation(V2, V1, isSigned); + if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) + return ICmpInst::getSwappedPredicate(SwappedRelation); + return ICmpInst::BAD_ICMP_PREDICATE; + } + + // Now we know that the RHS is a GlobalValue, BlockAddress or simple + // constant (which, since the types must match, means that it is a + // ConstantPointerNull). + if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) { + // Block address in another function can't equal this one, but block + // addresses in the current function might be the same if blocks are + // empty. + if (BA2->getFunction() != BA->getFunction()) + return ICmpInst::ICMP_NE; + } else { + // Block addresses aren't null, don't equal the address of globals. + assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) && + "Canonicalization guarantee!"); + return ICmpInst::ICMP_NE; + } + } else { + // Ok, the LHS is known to be a constantexpr. The RHS can be any of a + // constantexpr, a global, block address, or a simple constant. + ConstantExpr *CE1 = cast<ConstantExpr>(V1); + Constant *CE1Op0 = CE1->getOperand(0); + + switch (CE1->getOpcode()) { + case Instruction::Trunc: + case Instruction::FPTrunc: + case Instruction::FPExt: + case Instruction::FPToUI: + case Instruction::FPToSI: + break; // We can't evaluate floating point casts or truncations. + + case Instruction::UIToFP: + case Instruction::SIToFP: + case Instruction::BitCast: + case Instruction::ZExt: + case Instruction::SExt: + // If the cast is not actually changing bits, and the second operand is a + // null pointer, do the comparison with the pre-casted value. + if (V2->isNullValue() && + (CE1->getType()->isPointerTy() || CE1->getType()->isIntegerTy())) { + 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<ConstantPointerNull>(V2)) { + // If we are comparing a GEP to a null pointer, check to see if the base + // of the GEP equals the null pointer. + if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { + if (GV->hasExternalWeakLinkage()) + // Weak linkage GVals could be zero or not. We're comparing that + // to null pointer so its greater-or-equal + return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; + else + // If its not weak linkage, the GVal must have a non-zero address + // so the result is greater-than + return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; + } else if (isa<ConstantPointerNull>(CE1Op0)) { + // If we are indexing from a null pointer, check to see if we have any + // non-zero indices. + for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) + if (!CE1->getOperand(i)->isNullValue()) + // Offsetting from null, must not be equal. + return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; + // Only zero indexes from null, must still be zero. + return ICmpInst::ICMP_EQ; + } + // Otherwise, we can't really say if the first operand is null or not. + } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { + if (isa<ConstantPointerNull>(CE1Op0)) { + if (GV2->hasExternalWeakLinkage()) + // Weak linkage GVals could be zero or not. We're comparing it to + // a null pointer, so its less-or-equal + return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; + else + // If its not weak linkage, the GVal must have a non-zero address + // so the result is less-than + return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; + } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { + if (GV == GV2) { + // If this is a getelementptr of the same global, then it must be + // different. Because the types must match, the getelementptr could + // only have at most one index, and because we fold getelementptr's + // with a single zero index, it must be nonzero. + assert(CE1->getNumOperands() == 2 && + !CE1->getOperand(1)->isNullValue() && + "Surprising getelementptr!"); + return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; + } else { + // If 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<ConstantExpr>(V2); + Constant *CE2Op0 = CE2->getOperand(0); + + // There are MANY other foldings that we could perform here. They will + // probably be added on demand, as they seem needed. + switch (CE2->getOpcode()) { + default: break; + case Instruction::GetElementPtr: + // By far the most common case to handle is when the base pointers are + // obviously to the same or different globals. + if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(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<ConstantInt>(CE1->getOperand(i))) + return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; + else + return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. + } + + for (; i < CE2->getNumOperands(); ++i) + if (!CE2->getOperand(i)->isNullValue()) { + if (isa<ConstantInt>(CE2->getOperand(i))) + return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; + else + return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. + } + return ICmpInst::ICMP_EQ; + } + } + } + default: + break; + } + } + + return ICmpInst::BAD_ICMP_PREDICATE; +} + +Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, + Constant *C1, Constant *C2) { + Type *ResultTy; + if (VectorType *VT = dyn_cast<VectorType>(C1->getType())) + ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()), + VT->getNumElements()); + else + ResultTy = Type::getInt1Ty(C1->getContext()); + + // Fold FCMP_FALSE/FCMP_TRUE unconditionally. + if (pred == FCmpInst::FCMP_FALSE) + return Constant::getNullValue(ResultTy); + + if (pred == FCmpInst::FCMP_TRUE) + return Constant::getAllOnesValue(ResultTy); + + // Handle some degenerate cases first + if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { + // For EQ and NE, we can always pick a value for the undef to make the + // predicate pass or fail, so we can return undef. + // Also, if both operands are undef, we can return undef. + if (ICmpInst::isEquality(ICmpInst::Predicate(pred)) || + (isa<UndefValue>(C1) && isa<UndefValue>(C2))) + return UndefValue::get(ResultTy); + // Otherwise, pick the same value as the non-undef operand, and fold + // it to true or false. + return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(pred)); + } + + // icmp eq/ne(null,GV) -> false/true + if (C1->isNullValue()) { + if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2)) + // Don't try to evaluate aliases. External weak GV can be null. + if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { + if (pred == ICmpInst::ICMP_EQ) + return ConstantInt::getFalse(C1->getContext()); + else if (pred == ICmpInst::ICMP_NE) + return ConstantInt::getTrue(C1->getContext()); + } + // icmp eq/ne(GV,null) -> false/true + } else if (C2->isNullValue()) { + if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) + // Don't try to evaluate aliases. External weak GV can be null. + if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { + if (pred == ICmpInst::ICMP_EQ) + return ConstantInt::getFalse(C1->getContext()); + else if (pred == ICmpInst::ICMP_NE) + return ConstantInt::getTrue(C1->getContext()); + } + } + + // If the comparison is a comparison between two i1's, simplify it. + if (C1->getType()->isIntegerTy(1)) { + switch(pred) { + case ICmpInst::ICMP_EQ: + if (isa<ConstantInt>(C2)) + return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2)); + return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2); + case ICmpInst::ICMP_NE: + return ConstantExpr::getXor(C1, C2); + default: + break; + } + } + + if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { + APInt V1 = cast<ConstantInt>(C1)->getValue(); + APInt V2 = cast<ConstantInt>(C2)->getValue(); + switch (pred) { + default: llvm_unreachable("Invalid ICmp Predicate"); + case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2); + case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2); + case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2)); + case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2)); + case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2)); + case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2)); + case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2)); + case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2)); + case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2)); + case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2)); + } + } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { + APFloat C1V = cast<ConstantFP>(C1)->getValueAPF(); + APFloat C2V = cast<ConstantFP>(C2)->getValueAPF(); + APFloat::cmpResult R = C1V.compare(C2V); + switch (pred) { + default: llvm_unreachable("Invalid FCmp Predicate"); + case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy); + case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy); + case FCmpInst::FCMP_UNO: + return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered); + case FCmpInst::FCMP_ORD: + return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered); + case FCmpInst::FCMP_UEQ: + return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || + R==APFloat::cmpEqual); + case FCmpInst::FCMP_OEQ: + return ConstantInt::get(ResultTy, R==APFloat::cmpEqual); + case FCmpInst::FCMP_UNE: + return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual); + case FCmpInst::FCMP_ONE: + return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || + R==APFloat::cmpGreaterThan); + case FCmpInst::FCMP_ULT: + return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || + R==APFloat::cmpLessThan); + case FCmpInst::FCMP_OLT: + return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan); + case FCmpInst::FCMP_UGT: + return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || + R==APFloat::cmpGreaterThan); + case FCmpInst::FCMP_OGT: + return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan); + case FCmpInst::FCMP_ULE: + return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan); + case FCmpInst::FCMP_OLE: + return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || + R==APFloat::cmpEqual); + case FCmpInst::FCMP_UGE: + return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan); + case FCmpInst::FCMP_OGE: + return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan || + R==APFloat::cmpEqual); + } + } else if (C1->getType()->isVectorTy()) { + // If we can constant fold the comparison of each element, constant fold + // the whole vector comparison. + SmallVector<Constant*, 4> ResElts; + Type *Ty = IntegerType::get(C1->getContext(), 32); + // Compare the elements, producing an i1 result or constant expr. + for (unsigned i = 0, e = C1->getType()->getVectorNumElements(); i != e;++i){ + Constant *C1E = + ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i)); + Constant *C2E = + ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i)); + + ResElts.push_back(ConstantExpr::getCompare(pred, C1E, C2E)); + } + + return ConstantVector::get(ResElts); + } + + if (C1->getType()->isFloatingPointTy()) { + 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 FCmpInst::FCMP_ONE: // We know that C1 != C2 + // We can only partially decide this relation. + if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) + Result = 0; + else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) + Result = 1; + break; + } + + // 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<ConstantExpr>(C2)) { + Constant *CE2Op0 = CE2->getOperand(0); + if (CE2->getOpcode() == Instruction::BitCast && + CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy()) { + Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType()); + return ConstantExpr::getICmp(pred, Inverse, CE2Op0); + } + } + + // If the left hand side is an extension, try eliminating it. + if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { + if ((CE1->getOpcode() == Instruction::SExt && ICmpInst::isSigned(pred)) || + (CE1->getOpcode() == Instruction::ZExt && !ICmpInst::isSigned(pred))){ + Constant *CE1Op0 = CE1->getOperand(0); + Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType()); + if (CE1Inverse == CE1Op0) { + // Check whether we can safely truncate the right hand side. + Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType()); + if (ConstantExpr::getZExt(C2Inverse, C2->getType()) == C2) { + return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse); + } + } + } + } + + if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) || + (C1->isNullValue() && !C2->isNullValue())) { + // If C2 is a constant expr and C1 isn't, flip them around and fold the + // other way if possible. + // Also, if C1 is null and C2 isn't, flip them around. + pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); + return ConstantExpr::getICmp(pred, C2, C1); + } + } + return 0; +} + +/// isInBoundsIndices - Test whether the given sequence of *normalized* indices +/// is "inbounds". +template<typename IndexTy> +static bool isInBoundsIndices(ArrayRef<IndexTy> Idxs) { + // No indices means nothing that could be out of bounds. + if (Idxs.empty()) return true; + + // If the first index is zero, it's in bounds. + if (cast<Constant>(Idxs[0])->isNullValue()) return true; + + // If the first index is one and all the rest are zero, it's in bounds, + // by the one-past-the-end rule. + if (!cast<ConstantInt>(Idxs[0])->isOne()) + return false; + for (unsigned i = 1, e = Idxs.size(); i != e; ++i) + if (!cast<Constant>(Idxs[i])->isNullValue()) + return false; + return true; +} + +template<typename IndexTy> +static Constant *ConstantFoldGetElementPtrImpl(Constant *C, + bool inBounds, + ArrayRef<IndexTy> Idxs) { + if (Idxs.empty()) return C; + Constant *Idx0 = cast<Constant>(Idxs[0]); + if ((Idxs.size() == 1 && Idx0->isNullValue())) + return C; + + if (isa<UndefValue>(C)) { + PointerType *Ptr = cast<PointerType>(C->getType()); + Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs); + assert(Ty != 0 && "Invalid indices for GEP!"); + return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace())); + } + + if (C->isNullValue()) { + bool isNull = true; + for (unsigned i = 0, e = Idxs.size(); i != e; ++i) + if (!cast<Constant>(Idxs[i])->isNullValue()) { + isNull = false; + break; + } + if (isNull) { + PointerType *Ptr = cast<PointerType>(C->getType()); + Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs); + assert(Ty != 0 && "Invalid indices for GEP!"); + return ConstantPointerNull::get(PointerType::get(Ty, + Ptr->getAddressSpace())); + } + } + + if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { + // Combine Indices - If the source pointer to this getelementptr instruction + // is a getelementptr instruction, combine the indices of the two + // getelementptr instructions into a single instruction. + // + if (CE->getOpcode() == Instruction::GetElementPtr) { + 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<SequentialType>(LastTy)) || Idx0->isNullValue()) { + SmallVector<Value*, 16> NewIndices; + NewIndices.reserve(Idxs.size() + 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()) { + Type *IdxTy = Combined->getType(); + if (IdxTy != Idx0->getType()) { + 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.append(Idxs.begin() + 1, Idxs.end()); + return + ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices, + inBounds && + cast<GEPOperator>(CE)->isInBounds()); + } + } + + // Implement folding of: + // i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*), + // i64 0, i64 0) + // To: i32* getelementptr ([3 x i32]* %X, i64 0, i64 0) + // + if (CE->isCast() && Idxs.size() > 1 && Idx0->isNullValue()) { + if (PointerType *SPT = + dyn_cast<PointerType>(CE->getOperand(0)->getType())) + if (ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType())) + if (ArrayType *CAT = + dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType())) + if (CAT->getElementType() == SAT->getElementType()) + return + ConstantExpr::getGetElementPtr((Constant*)CE->getOperand(0), + Idxs, inBounds); + } + } + + // 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<Constant *, 8> NewIdxs; + Type *Ty = C->getType(); + Type *Prev = 0; + for (unsigned i = 0, e = Idxs.size(); i != e; + Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) { + if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) { + if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) + if (ATy->getNumElements() <= INT64_MAX && + ATy->getNumElements() != 0 && + CI->getSExtValue() >= (int64_t)ATy->getNumElements()) { + if (isa<SequentialType>(Prev)) { + // It's out of range, but we can factor it into the prior + // dimension. + NewIdxs.resize(Idxs.size()); + ConstantInt *Factor = ConstantInt::get(CI->getType(), + ATy->getNumElements()); + NewIdxs[i] = ConstantExpr::getSRem(CI, Factor); + + Constant *PrevIdx = cast<Constant>(Idxs[i-1]); + Constant *Div = ConstantExpr::getSDiv(CI, Factor); + + // Before adding, extend both operands to i64 to avoid + // overflow trouble. + if (!PrevIdx->getType()->isIntegerTy(64)) + PrevIdx = ConstantExpr::getSExt(PrevIdx, + Type::getInt64Ty(Div->getContext())); + if (!Div->getType()->isIntegerTy(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, e = Idxs.size(); i != e; ++i) + if (!NewIdxs[i]) NewIdxs[i] = cast<Constant>(Idxs[i]); + return ConstantExpr::getGetElementPtr(C, NewIdxs, inBounds); + } + + // If all indices are known integers and normalized, we can do a simple + // check for the "inbounds" property. + if (!Unknown && !inBounds && + isa<GlobalVariable>(C) && isInBoundsIndices(Idxs)) + return ConstantExpr::getInBoundsGetElementPtr(C, Idxs); + + return 0; +} + +Constant *llvm::ConstantFoldGetElementPtr(Constant *C, + bool inBounds, + ArrayRef<Constant *> Idxs) { + return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs); +} + +Constant *llvm::ConstantFoldGetElementPtr(Constant *C, + bool inBounds, + ArrayRef<Value *> Idxs) { + return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs); +} |