X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FValueTracking.cpp;h=6f58afe527906428fddb9659e6b40eadac6789b8;hb=124708d9b47cc53cb11d8bfed75b241b6eec86d4;hp=120dcd8ad2611f7bff350c2c572480a88bbec776;hpb=ceb4d1aecb9deffe59b3dcdc9a783ffde8477be9;p=oota-llvm.git diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp index 120dcd8ad26..6f58afe5279 100644 --- a/lib/Analysis/ValueTracking.cpp +++ b/lib/Analysis/ValueTracking.cpp @@ -13,28 +13,21 @@ //===----------------------------------------------------------------------===// #include "llvm/Analysis/ValueTracking.h" +#include "llvm/Analysis/InstructionSimplify.h" #include "llvm/Constants.h" #include "llvm/Instructions.h" #include "llvm/GlobalVariable.h" +#include "llvm/GlobalAlias.h" #include "llvm/IntrinsicInst.h" +#include "llvm/LLVMContext.h" +#include "llvm/Operator.h" #include "llvm/Target/TargetData.h" #include "llvm/Support/GetElementPtrTypeIterator.h" #include "llvm/Support/MathExtras.h" +#include "llvm/ADT/SmallPtrSet.h" #include using namespace llvm; -/// getOpcode - If this is an Instruction or a ConstantExpr, return the -/// opcode value. Otherwise return UserOp1. -static unsigned getOpcode(const Value *V) { - if (const Instruction *I = dyn_cast(V)) - return I->getOpcode(); - if (const ConstantExpr *CE = dyn_cast(V)) - return CE->getOpcode(); - // Use UserOp1 to mean there's no opcode. - return Instruction::UserOp1; -} - - /// ComputeMaskedBits - Determine which of the bits specified in Mask are /// known to be either zero or one and return them in the KnownZero/KnownOne /// bit sets. This code only analyzes bits in Mask, in order to short-circuit @@ -45,17 +38,25 @@ static unsigned getOpcode(const Value *V) { /// optimized based on the contradictory assumption that it is non-zero. /// Because instcombine aggressively folds operations with undef args anyway, /// this won't lose us code quality. +/// +/// This function is defined on values with integer type, values with pointer +/// type (but only if TD is non-null), and vectors of integers. In the case +/// where V is a vector, the mask, known zero, and known one values are the +/// same width as the vector element, and the bit is set only if it is true +/// for all of the elements in the vector. void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, APInt &KnownZero, APInt &KnownOne, - TargetData *TD, unsigned Depth) { + const TargetData *TD, unsigned Depth) { + const unsigned MaxDepth = 6; assert(V && "No Value?"); - assert(Depth <= 6 && "Limit Search Depth"); - uint32_t BitWidth = Mask.getBitWidth(); - assert((V->getType()->isInteger() || isa(V->getType())) && - "Not integer or pointer type!"); - assert((!TD || TD->getTypeSizeInBits(V->getType()) == BitWidth) && - (!isa(V->getType()) || - V->getType()->getPrimitiveSizeInBits() == BitWidth) && + assert(Depth <= MaxDepth && "Limit Search Depth"); + unsigned BitWidth = Mask.getBitWidth(); + assert((V->getType()->isIntOrIntVectorTy() || V->getType()->isPointerTy()) + && "Not integer or pointer type!"); + assert((!TD || + TD->getTypeSizeInBits(V->getType()->getScalarType()) == BitWidth) && + (!V->getType()->isIntOrIntVectorTy() || + V->getType()->getScalarSizeInBits() == BitWidth) && KnownZero.getBitWidth() == BitWidth && KnownOne.getBitWidth() == BitWidth && "V, Mask, KnownOne and KnownZero should have same BitWidth"); @@ -66,36 +67,69 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, KnownZero = ~KnownOne & Mask; return; } - // Null is all-zeros. - if (isa(V)) { - KnownOne.clear(); + // Null and aggregate-zero are all-zeros. + if (isa(V) || + isa(V)) { + KnownOne.clearAllBits(); KnownZero = Mask; return; } + // Handle a constant vector by taking the intersection of the known bits of + // each element. + if (ConstantVector *CV = dyn_cast(V)) { + KnownZero.setAllBits(); KnownOne.setAllBits(); + for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) { + APInt KnownZero2(BitWidth, 0), KnownOne2(BitWidth, 0); + ComputeMaskedBits(CV->getOperand(i), Mask, KnownZero2, KnownOne2, + TD, Depth); + KnownZero &= KnownZero2; + KnownOne &= KnownOne2; + } + return; + } // The address of an aligned GlobalValue has trailing zeros. if (GlobalValue *GV = dyn_cast(V)) { unsigned Align = GV->getAlignment(); - if (Align == 0 && TD && GV->getType()->getElementType()->isSized()) - Align = TD->getPrefTypeAlignment(GV->getType()->getElementType()); + if (Align == 0 && TD && GV->getType()->getElementType()->isSized()) { + const Type *ObjectType = GV->getType()->getElementType(); + // If the object is defined in the current Module, we'll be giving + // it the preferred alignment. Otherwise, we have to assume that it + // may only have the minimum ABI alignment. + if (!GV->isDeclaration() && !GV->mayBeOverridden()) + Align = TD->getPrefTypeAlignment(ObjectType); + else + Align = TD->getABITypeAlignment(ObjectType); + } if (Align > 0) KnownZero = Mask & APInt::getLowBitsSet(BitWidth, CountTrailingZeros_32(Align)); else - KnownZero.clear(); - KnownOne.clear(); + KnownZero.clearAllBits(); + KnownOne.clearAllBits(); + return; + } + // A weak GlobalAlias is totally unknown. A non-weak GlobalAlias has + // the bits of its aliasee. + if (GlobalAlias *GA = dyn_cast(V)) { + if (GA->mayBeOverridden()) { + KnownZero.clearAllBits(); KnownOne.clearAllBits(); + } else { + ComputeMaskedBits(GA->getAliasee(), Mask, KnownZero, KnownOne, + TD, Depth+1); + } return; } - KnownZero.clear(); KnownOne.clear(); // Start out not knowing anything. + KnownZero.clearAllBits(); KnownOne.clearAllBits(); // Start out not knowing anything. - if (Depth == 6 || Mask == 0) + if (Depth == MaxDepth || Mask == 0) return; // Limit search depth. - User *I = dyn_cast(V); + Operator *I = dyn_cast(V); if (!I) return; APInt KnownZero2(KnownZero), KnownOne2(KnownOne); - switch (getOpcode(I)) { + switch (I->getOpcode()) { default: break; case Instruction::And: { // If either the LHS or the RHS are Zero, the result is zero. @@ -152,7 +186,7 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, // Also compute a conserative estimate for high known-0 bits. // More trickiness is possible, but this is sufficient for the // interesting case of alignment computation. - KnownOne.clear(); + KnownOne.clearAllBits(); unsigned TrailZ = KnownZero.countTrailingOnes() + KnownZero2.countTrailingOnes(); unsigned LeadZ = std::max(KnownZero.countLeadingOnes() + @@ -175,8 +209,8 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, AllOnes, KnownZero2, KnownOne2, TD, Depth+1); unsigned LeadZ = KnownZero2.countLeadingOnes(); - KnownOne2.clear(); - KnownZero2.clear(); + KnownOne2.clearAllBits(); + KnownZero2.clearAllBits(); ComputeMaskedBits(I->getOperand(1), AllOnes, KnownZero2, KnownOne2, TD, Depth+1); unsigned RHSUnknownLeadingOnes = KnownOne2.countLeadingZeros(); @@ -212,20 +246,23 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, // FALL THROUGH and handle them the same as zext/trunc. case Instruction::ZExt: case Instruction::Trunc: { + const Type *SrcTy = I->getOperand(0)->getType(); + + unsigned SrcBitWidth; // Note that we handle pointer operands here because of inttoptr/ptrtoint // which fall through here. - const Type *SrcTy = I->getOperand(0)->getType(); - uint32_t SrcBitWidth = TD ? - TD->getTypeSizeInBits(SrcTy) : - SrcTy->getPrimitiveSizeInBits(); - APInt MaskIn(Mask); - MaskIn.zextOrTrunc(SrcBitWidth); - KnownZero.zextOrTrunc(SrcBitWidth); - KnownOne.zextOrTrunc(SrcBitWidth); + if (SrcTy->isPointerTy()) + SrcBitWidth = TD->getTypeSizeInBits(SrcTy); + else + SrcBitWidth = SrcTy->getScalarSizeInBits(); + + APInt MaskIn = Mask.zextOrTrunc(SrcBitWidth); + KnownZero = KnownZero.zextOrTrunc(SrcBitWidth); + KnownOne = KnownOne.zextOrTrunc(SrcBitWidth); ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, TD, Depth+1); - KnownZero.zextOrTrunc(BitWidth); - KnownOne.zextOrTrunc(BitWidth); + KnownZero = KnownZero.zextOrTrunc(BitWidth); + KnownOne = KnownOne.zextOrTrunc(BitWidth); // Any top bits are known to be zero. if (BitWidth > SrcBitWidth) KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth); @@ -233,7 +270,10 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, } case Instruction::BitCast: { const Type *SrcTy = I->getOperand(0)->getType(); - if (SrcTy->isInteger() || isa(SrcTy)) { + if ((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && + // TODO: For now, not handling conversions like: + // (bitcast i64 %x to <2 x i32>) + !I->getType()->isVectorTy()) { ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, TD, Depth+1); return; @@ -242,18 +282,16 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, } case Instruction::SExt: { // Compute the bits in the result that are not present in the input. - const IntegerType *SrcTy = cast(I->getOperand(0)->getType()); - uint32_t SrcBitWidth = SrcTy->getBitWidth(); + unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits(); - APInt MaskIn(Mask); - MaskIn.trunc(SrcBitWidth); - KnownZero.trunc(SrcBitWidth); - KnownOne.trunc(SrcBitWidth); + APInt MaskIn = Mask.trunc(SrcBitWidth); + KnownZero = KnownZero.trunc(SrcBitWidth); + KnownOne = KnownOne.trunc(SrcBitWidth); ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, TD, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); - KnownZero.zext(BitWidth); - KnownOne.zext(BitWidth); + KnownZero = KnownZero.zext(BitWidth); + KnownOne = KnownOne.zext(BitWidth); // If the sign bit of the input is known set or clear, then we know the // top bits of the result. @@ -287,7 +325,7 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, APInt Mask2(Mask.shl(ShiftAmt)); ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero,KnownOne, TD, Depth+1); - assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?"); + assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); KnownZero = APIntOps::lshr(KnownZero, ShiftAmt); KnownOne = APIntOps::lshr(KnownOne, ShiftAmt); // high bits known zero. @@ -305,7 +343,7 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, APInt Mask2(Mask.shl(ShiftAmt)); ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne, TD, Depth+1); - assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?"); + assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); KnownZero = APIntOps::lshr(KnownZero, ShiftAmt); KnownOne = APIntOps::lshr(KnownOne, ShiftAmt); @@ -342,42 +380,72 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, } // fall through case Instruction::Add: { - // Output known-0 bits are known if clear or set in both the low clear bits - // common to both LHS & RHS. For example, 8+(X<<3) is known to have the - // low 3 bits clear. - APInt Mask2 = APInt::getLowBitsSet(BitWidth, Mask.countTrailingOnes()); - ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD, + // If one of the operands has trailing zeros, then the bits that the + // other operand has in those bit positions will be preserved in the + // result. For an add, this works with either operand. For a subtract, + // this only works if the known zeros are in the right operand. + APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0); + APInt Mask2 = APInt::getLowBitsSet(BitWidth, + BitWidth - Mask.countLeadingZeros()); + ComputeMaskedBits(I->getOperand(0), Mask2, LHSKnownZero, LHSKnownOne, TD, Depth+1); - assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); - unsigned KnownZeroOut = KnownZero2.countTrailingOnes(); + assert((LHSKnownZero & LHSKnownOne) == 0 && + "Bits known to be one AND zero?"); + unsigned LHSKnownZeroOut = LHSKnownZero.countTrailingOnes(); ComputeMaskedBits(I->getOperand(1), Mask2, KnownZero2, KnownOne2, TD, Depth+1); assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); - KnownZeroOut = std::min(KnownZeroOut, - KnownZero2.countTrailingOnes()); + unsigned RHSKnownZeroOut = KnownZero2.countTrailingOnes(); - KnownZero |= APInt::getLowBitsSet(BitWidth, KnownZeroOut); + // Determine which operand has more trailing zeros, and use that + // many bits from the other operand. + if (LHSKnownZeroOut > RHSKnownZeroOut) { + if (I->getOpcode() == Instruction::Add) { + APInt Mask = APInt::getLowBitsSet(BitWidth, LHSKnownZeroOut); + KnownZero |= KnownZero2 & Mask; + KnownOne |= KnownOne2 & Mask; + } else { + // If the known zeros are in the left operand for a subtract, + // fall back to the minimum known zeros in both operands. + KnownZero |= APInt::getLowBitsSet(BitWidth, + std::min(LHSKnownZeroOut, + RHSKnownZeroOut)); + } + } else if (RHSKnownZeroOut >= LHSKnownZeroOut) { + APInt Mask = APInt::getLowBitsSet(BitWidth, RHSKnownZeroOut); + KnownZero |= LHSKnownZero & Mask; + KnownOne |= LHSKnownOne & Mask; + } return; } case Instruction::SRem: if (ConstantInt *Rem = dyn_cast(I->getOperand(1))) { - APInt RA = Rem->getValue(); - if (RA.isPowerOf2() || (-RA).isPowerOf2()) { - APInt LowBits = RA.isStrictlyPositive() ? (RA - 1) : ~RA; + APInt RA = Rem->getValue().abs(); + if (RA.isPowerOf2()) { + APInt LowBits = RA - 1; APInt Mask2 = LowBits | APInt::getSignBit(BitWidth); ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD, Depth+1); - // If the sign bit of the first operand is zero, the sign bit of - // the result is zero. If the first operand has no one bits below - // the second operand's single 1 bit, its sign will be zero. + // The low bits of the first operand are unchanged by the srem. + KnownZero = KnownZero2 & LowBits; + KnownOne = KnownOne2 & LowBits; + + // If the first operand is non-negative or has all low bits zero, then + // the upper bits are all zero. if (KnownZero2[BitWidth-1] || ((KnownZero2 & LowBits) == LowBits)) - KnownZero2 |= ~LowBits; + KnownZero |= ~LowBits; - KnownZero |= KnownZero2 & Mask; + // If the first operand is negative and not all low bits are zero, then + // the upper bits are all one. + if (KnownOne2[BitWidth-1] && ((KnownOne2 & LowBits) != 0)) + KnownOne |= ~LowBits; + + KnownZero &= Mask; + KnownOne &= Mask; - assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?"); + assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); } } break; @@ -390,7 +458,7 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, KnownZero |= ~LowBits & Mask; ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne, TD, Depth+1); - assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?"); + assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); break; } } @@ -403,31 +471,18 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, ComputeMaskedBits(I->getOperand(1), AllOnes, KnownZero2, KnownOne2, TD, Depth+1); - uint32_t Leaders = std::max(KnownZero.countLeadingOnes(), + unsigned Leaders = std::max(KnownZero.countLeadingOnes(), KnownZero2.countLeadingOnes()); - KnownOne.clear(); + KnownOne.clearAllBits(); KnownZero = APInt::getHighBitsSet(BitWidth, Leaders) & Mask; break; } - case Instruction::Alloca: - case Instruction::Malloc: { - AllocationInst *AI = cast(V); + case Instruction::Alloca: { + AllocaInst *AI = cast(V); unsigned Align = AI->getAlignment(); - if (Align == 0 && TD) { - if (isa(AI)) - Align = TD->getABITypeAlignment(AI->getType()->getElementType()); - else if (isa(AI)) { - // Malloc returns maximally aligned memory. - Align = TD->getABITypeAlignment(AI->getType()->getElementType()); - Align = - std::max(Align, - (unsigned)TD->getABITypeAlignment(Type::DoubleTy)); - Align = - std::max(Align, - (unsigned)TD->getABITypeAlignment(Type::Int64Ty)); - } - } + if (Align == 0 && TD) + Align = TD->getABITypeAlignment(AI->getType()->getElementType()); if (Align > 0) KnownZero = Mask & APInt::getLowBitsSet(BitWidth, @@ -458,15 +513,15 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, // Handle array index arithmetic. const Type *IndexedTy = GTI.getIndexedType(); if (!IndexedTy->isSized()) return; - unsigned GEPOpiBits = Index->getType()->getPrimitiveSizeInBits(); - uint64_t TypeSize = TD ? TD->getTypePaddedSize(IndexedTy) : 1; + unsigned GEPOpiBits = Index->getType()->getScalarSizeInBits(); + uint64_t TypeSize = TD ? TD->getTypeAllocSize(IndexedTy) : 1; LocalMask = APInt::getAllOnesValue(GEPOpiBits); LocalKnownZero = LocalKnownOne = APInt(GEPOpiBits, 0); ComputeMaskedBits(Index, LocalMask, LocalKnownZero, LocalKnownOne, TD, Depth+1); TrailZ = std::min(TrailZ, - CountTrailingZeros_64(TypeSize) + - LocalKnownZero.countTrailingOnes()); + unsigned(CountTrailingZeros_64(TypeSize) + + LocalKnownZero.countTrailingOnes())); } } @@ -482,10 +537,10 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, for (unsigned i = 0; i != 2; ++i) { Value *L = P->getIncomingValue(i); Value *R = P->getIncomingValue(!i); - User *LU = dyn_cast(L); + Operator *LU = dyn_cast(L); if (!LU) continue; - unsigned Opcode = getOpcode(LU); + unsigned Opcode = LU->getOpcode(); // Check for operations that have the property that if // both their operands have low zero bits, the result // will have low zero bits. @@ -522,6 +577,30 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, } } } + + // Otherwise take the unions of the known bit sets of the operands, + // taking conservative care to avoid excessive recursion. + if (Depth < MaxDepth - 1 && !KnownZero && !KnownOne) { + KnownZero = APInt::getAllOnesValue(BitWidth); + KnownOne = APInt::getAllOnesValue(BitWidth); + for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i) { + // Skip direct self references. + if (P->getIncomingValue(i) == P) continue; + + KnownZero2 = APInt(BitWidth, 0); + KnownOne2 = APInt(BitWidth, 0); + // Recurse, but cap the recursion to one level, because we don't + // want to waste time spinning around in loops. + ComputeMaskedBits(P->getIncomingValue(i), KnownZero | KnownOne, + KnownZero2, KnownOne2, TD, MaxDepth-1); + KnownZero &= KnownZero2; + KnownOne &= KnownOne2; + // If all bits have been ruled out, there's no need to check + // more operands. + if (!KnownZero && !KnownOne) + break; + } + } break; } case Instruction::Call: @@ -544,8 +623,14 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, /// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use /// this predicate to simplify operations downstream. Mask is known to be zero /// for bits that V cannot have. +/// +/// This function is defined on values with integer type, values with pointer +/// type (but only if TD is non-null), and vectors of integers. In the case +/// where V is a vector, the mask, known zero, and known one values are the +/// same width as the vector element, and the bit is set only if it is true +/// for all of the elements in the vector. bool llvm::MaskedValueIsZero(Value *V, const APInt &Mask, - TargetData *TD, unsigned Depth) { + const TargetData *TD, unsigned Depth) { APInt KnownZero(Mask.getBitWidth(), 0), KnownOne(Mask.getBitWidth(), 0); ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD, Depth); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); @@ -562,9 +647,14 @@ bool llvm::MaskedValueIsZero(Value *V, const APInt &Mask, /// /// 'Op' must have a scalar integer type. /// -unsigned llvm::ComputeNumSignBits(Value *V, TargetData *TD, unsigned Depth) { - const IntegerType *Ty = cast(V->getType()); - unsigned TyBits = Ty->getBitWidth(); +unsigned llvm::ComputeNumSignBits(Value *V, const TargetData *TD, + unsigned Depth) { + assert((TD || V->getType()->isIntOrIntVectorTy()) && + "ComputeNumSignBits requires a TargetData object to operate " + "on non-integer values!"); + const Type *Ty = V->getType(); + unsigned TyBits = TD ? TD->getTypeSizeInBits(V->getType()->getScalarType()) : + Ty->getScalarSizeInBits(); unsigned Tmp, Tmp2; unsigned FirstAnswer = 1; @@ -574,11 +664,11 @@ unsigned llvm::ComputeNumSignBits(Value *V, TargetData *TD, unsigned Depth) { if (Depth == 6) return 1; // Limit search depth. - User *U = dyn_cast(V); - switch (getOpcode(V)) { + Operator *U = dyn_cast(V); + switch (Operator::getOpcode(V)) { default: break; case Instruction::SExt: - Tmp = TyBits-cast(U->getOperand(0)->getType())->getBitWidth(); + Tmp = TyBits - U->getOperand(0)->getType()->getScalarSizeInBits(); return ComputeNumSignBits(U->getOperand(0), TD, Depth+1) + Tmp; case Instruction::AShr: @@ -588,6 +678,13 @@ unsigned llvm::ComputeNumSignBits(Value *V, TargetData *TD, unsigned Depth) { Tmp += C->getZExtValue(); if (Tmp > TyBits) Tmp = TyBits; } + // vector ashr X, -> adds C sign bits + if (ConstantVector *C = dyn_cast(U->getOperand(1))) { + if (ConstantInt *CI = dyn_cast_or_null(C->getSplatValue())) { + Tmp += CI->getZExtValue(); + if (Tmp > TyBits) Tmp = TyBits; + } + } return Tmp; case Instruction::Shl: if (ConstantInt *C = dyn_cast(U->getOperand(1))) { @@ -625,7 +722,7 @@ unsigned llvm::ComputeNumSignBits(Value *V, TargetData *TD, unsigned Depth) { if (Tmp == 1) return 1; // Early out. // Special case decrementing a value (ADD X, -1): - if (ConstantInt *CRHS = dyn_cast(U->getOperand(0))) + if (ConstantInt *CRHS = dyn_cast(U->getOperand(1))) if (CRHS->isAllOnesValue()) { APInt KnownZero(TyBits, 0), KnownOne(TyBits, 0); APInt Mask = APInt::getAllOnesValue(TyBits); @@ -645,8 +742,7 @@ unsigned llvm::ComputeNumSignBits(Value *V, TargetData *TD, unsigned Depth) { Tmp2 = ComputeNumSignBits(U->getOperand(1), TD, Depth+1); if (Tmp2 == 1) return 1; - return std::min(Tmp, Tmp2)-1; - break; + return std::min(Tmp, Tmp2)-1; case Instruction::Sub: Tmp2 = ComputeNumSignBits(U->getOperand(1), TD, Depth+1); @@ -676,8 +772,24 @@ unsigned llvm::ComputeNumSignBits(Value *V, TargetData *TD, unsigned Depth) { // is, at worst, one more bit than the inputs. Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1); if (Tmp == 1) return 1; // Early out. - return std::min(Tmp, Tmp2)-1; - break; + return std::min(Tmp, Tmp2)-1; + + case Instruction::PHI: { + PHINode *PN = cast(U); + // Don't analyze large in-degree PHIs. + if (PN->getNumIncomingValues() > 4) break; + + // Take the minimum of all incoming values. This can't infinitely loop + // because of our depth threshold. + Tmp = ComputeNumSignBits(PN->getIncomingValue(0), TD, Depth+1); + for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) { + if (Tmp == 1) return Tmp; + Tmp = std::min(Tmp, + ComputeNumSignBits(PN->getIncomingValue(i), TD, Depth+1)); + } + return Tmp; + } + case Instruction::Trunc: // FIXME: it's tricky to do anything useful for this, but it is an important // case for targets like X86. @@ -708,6 +820,126 @@ unsigned llvm::ComputeNumSignBits(Value *V, TargetData *TD, unsigned Depth) { return std::max(FirstAnswer, std::min(TyBits, Mask.countLeadingZeros())); } +/// ComputeMultiple - This function computes the integer multiple of Base that +/// equals V. If successful, it returns true and returns the multiple in +/// Multiple. If unsuccessful, it returns false. It looks +/// through SExt instructions only if LookThroughSExt is true. +bool llvm::ComputeMultiple(Value *V, unsigned Base, Value *&Multiple, + bool LookThroughSExt, unsigned Depth) { + const unsigned MaxDepth = 6; + + assert(V && "No Value?"); + assert(Depth <= MaxDepth && "Limit Search Depth"); + assert(V->getType()->isIntegerTy() && "Not integer or pointer type!"); + + const Type *T = V->getType(); + + ConstantInt *CI = dyn_cast(V); + + if (Base == 0) + return false; + + if (Base == 1) { + Multiple = V; + return true; + } + + ConstantExpr *CO = dyn_cast(V); + Constant *BaseVal = ConstantInt::get(T, Base); + if (CO && CO == BaseVal) { + // Multiple is 1. + Multiple = ConstantInt::get(T, 1); + return true; + } + + if (CI && CI->getZExtValue() % Base == 0) { + Multiple = ConstantInt::get(T, CI->getZExtValue() / Base); + return true; + } + + if (Depth == MaxDepth) return false; // Limit search depth. + + Operator *I = dyn_cast(V); + if (!I) return false; + + switch (I->getOpcode()) { + default: break; + case Instruction::SExt: + if (!LookThroughSExt) return false; + // otherwise fall through to ZExt + case Instruction::ZExt: + return ComputeMultiple(I->getOperand(0), Base, Multiple, + LookThroughSExt, Depth+1); + case Instruction::Shl: + case Instruction::Mul: { + Value *Op0 = I->getOperand(0); + Value *Op1 = I->getOperand(1); + + if (I->getOpcode() == Instruction::Shl) { + ConstantInt *Op1CI = dyn_cast(Op1); + if (!Op1CI) return false; + // Turn Op0 << Op1 into Op0 * 2^Op1 + APInt Op1Int = Op1CI->getValue(); + uint64_t BitToSet = Op1Int.getLimitedValue(Op1Int.getBitWidth() - 1); + APInt API(Op1Int.getBitWidth(), 0); + API.setBit(BitToSet); + Op1 = ConstantInt::get(V->getContext(), API); + } + + Value *Mul0 = NULL; + if (ComputeMultiple(Op0, Base, Mul0, LookThroughSExt, Depth+1)) { + if (Constant *Op1C = dyn_cast(Op1)) + if (Constant *MulC = dyn_cast(Mul0)) { + if (Op1C->getType()->getPrimitiveSizeInBits() < + MulC->getType()->getPrimitiveSizeInBits()) + Op1C = ConstantExpr::getZExt(Op1C, MulC->getType()); + if (Op1C->getType()->getPrimitiveSizeInBits() > + MulC->getType()->getPrimitiveSizeInBits()) + MulC = ConstantExpr::getZExt(MulC, Op1C->getType()); + + // V == Base * (Mul0 * Op1), so return (Mul0 * Op1) + Multiple = ConstantExpr::getMul(MulC, Op1C); + return true; + } + + if (ConstantInt *Mul0CI = dyn_cast(Mul0)) + if (Mul0CI->getValue() == 1) { + // V == Base * Op1, so return Op1 + Multiple = Op1; + return true; + } + } + + Value *Mul1 = NULL; + if (ComputeMultiple(Op1, Base, Mul1, LookThroughSExt, Depth+1)) { + if (Constant *Op0C = dyn_cast(Op0)) + if (Constant *MulC = dyn_cast(Mul1)) { + if (Op0C->getType()->getPrimitiveSizeInBits() < + MulC->getType()->getPrimitiveSizeInBits()) + Op0C = ConstantExpr::getZExt(Op0C, MulC->getType()); + if (Op0C->getType()->getPrimitiveSizeInBits() > + MulC->getType()->getPrimitiveSizeInBits()) + MulC = ConstantExpr::getZExt(MulC, Op0C->getType()); + + // V == Base * (Mul1 * Op0), so return (Mul1 * Op0) + Multiple = ConstantExpr::getMul(MulC, Op0C); + return true; + } + + if (ConstantInt *Mul1CI = dyn_cast(Mul1)) + if (Mul1CI->getValue() == 1) { + // V == Base * Op0, so return Op0 + Multiple = Op0; + return true; + } + } + } + } + + // We could not determine if V is a multiple of Base. + return false; +} + /// CannotBeNegativeZero - Return true if we can prove that the specified FP /// value is never equal to -0.0. /// @@ -721,11 +953,11 @@ bool llvm::CannotBeNegativeZero(const Value *V, unsigned Depth) { if (Depth == 6) return 1; // Limit search depth. - const Instruction *I = dyn_cast(V); + const Operator *I = dyn_cast(V); if (I == 0) return false; // (add x, 0.0) is guaranteed to return +0.0, not -0.0. - if (I->getOpcode() == Instruction::Add && + if (I->getOpcode() == Instruction::FAdd && isa(I->getOperand(1)) && cast(I->getOperand(1))->isNullValue()) return true; @@ -737,36 +969,105 @@ bool llvm::CannotBeNegativeZero(const Value *V, unsigned Depth) { if (const IntrinsicInst *II = dyn_cast(I)) // sqrt(-0.0) = -0.0, no other negative results are possible. if (II->getIntrinsicID() == Intrinsic::sqrt) - return CannotBeNegativeZero(II->getOperand(1), Depth+1); + return CannotBeNegativeZero(II->getArgOperand(0), Depth+1); if (const CallInst *CI = dyn_cast(I)) if (const Function *F = CI->getCalledFunction()) { if (F->isDeclaration()) { - switch (F->getNameLen()) { - case 3: // abs(x) != -0.0 - if (!strcmp(F->getNameStart(), "abs")) return true; - break; - case 4: // abs[lf](x) != -0.0 - if (!strcmp(F->getNameStart(), "absf")) return true; - if (!strcmp(F->getNameStart(), "absl")) return true; - break; - } + // abs(x) != -0.0 + if (F->getName() == "abs") return true; + // fabs[lf](x) != -0.0 + if (F->getName() == "fabs") return true; + if (F->getName() == "fabsf") return true; + if (F->getName() == "fabsl") return true; + if (F->getName() == "sqrt" || F->getName() == "sqrtf" || + F->getName() == "sqrtl") + return CannotBeNegativeZero(CI->getArgOperand(0), Depth+1); } } return false; } +/// isBytewiseValue - If the specified value can be set by repeating the same +/// byte in memory, return the i8 value that it is represented with. This is +/// true for all i8 values obviously, but is also true for i32 0, i32 -1, +/// i16 0xF0F0, double 0.0 etc. If the value can't be handled with a repeated +/// byte store (e.g. i16 0x1234), return null. +Value *llvm::isBytewiseValue(Value *V) { + // All byte-wide stores are splatable, even of arbitrary variables. + if (V->getType()->isIntegerTy(8)) return V; + + // Constant float and double values can be handled as integer values if the + // corresponding integer value is "byteable". An important case is 0.0. + if (ConstantFP *CFP = dyn_cast(V)) { + if (CFP->getType()->isFloatTy()) + V = ConstantExpr::getBitCast(CFP, Type::getInt32Ty(V->getContext())); + if (CFP->getType()->isDoubleTy()) + V = ConstantExpr::getBitCast(CFP, Type::getInt64Ty(V->getContext())); + // Don't handle long double formats, which have strange constraints. + } + + // We can handle constant integers that are power of two in size and a + // multiple of 8 bits. + if (ConstantInt *CI = dyn_cast(V)) { + unsigned Width = CI->getBitWidth(); + if (isPowerOf2_32(Width) && Width > 8) { + // We can handle this value if the recursive binary decomposition is the + // same at all levels. + APInt Val = CI->getValue(); + APInt Val2; + while (Val.getBitWidth() != 8) { + unsigned NextWidth = Val.getBitWidth()/2; + Val2 = Val.lshr(NextWidth); + Val2 = Val2.trunc(Val.getBitWidth()/2); + Val = Val.trunc(Val.getBitWidth()/2); + + // If the top/bottom halves aren't the same, reject it. + if (Val != Val2) + return 0; + } + return ConstantInt::get(V->getContext(), Val); + } + } + + // A ConstantArray is splatable if all its members are equal and also + // splatable. + if (ConstantArray *CA = dyn_cast(V)) { + if (CA->getNumOperands() == 0) + return 0; + + Value *Val = isBytewiseValue(CA->getOperand(0)); + if (!Val) + return 0; + + for (unsigned I = 1, E = CA->getNumOperands(); I != E; ++I) + if (CA->getOperand(I-1) != CA->getOperand(I)) + return 0; + + return Val; + } + + // Conceptually, we could handle things like: + // %a = zext i8 %X to i16 + // %b = shl i16 %a, 8 + // %c = or i16 %a, %b + // but until there is an example that actually needs this, it doesn't seem + // worth worrying about. + return 0; +} + + // This is the recursive version of BuildSubAggregate. It takes a few different // arguments. Idxs is the index within the nested struct From that we are // looking at now (which is of type IndexedType). IdxSkip is the number of // indices from Idxs that should be left out when inserting into the resulting // struct. To is the result struct built so far, new insertvalue instructions // build on that. -Value *BuildSubAggregate(Value *From, Value* To, const Type *IndexedType, - SmallVector &Idxs, - unsigned IdxSkip, - Instruction *InsertBefore) { +static Value *BuildSubAggregate(Value *From, Value* To, const Type *IndexedType, + SmallVector &Idxs, + unsigned IdxSkip, + Instruction *InsertBefore) { const llvm::StructType *STy = llvm::dyn_cast(IndexedType); if (STy) { // Save the original To argument so we can modify it @@ -822,8 +1123,9 @@ Value *BuildSubAggregate(Value *From, Value* To, const Type *IndexedType, // insertvalue instruction somewhere). // // All inserted insertvalue instructions are inserted before InsertBefore -Value *BuildSubAggregate(Value *From, const unsigned *idx_begin, - const unsigned *idx_end, Instruction *InsertBefore) { +static Value *BuildSubAggregate(Value *From, const unsigned *idx_begin, + const unsigned *idx_end, + Instruction *InsertBefore) { assert(InsertBefore && "Must have someplace to insert!"); const Type *IndexedType = ExtractValueInst::getIndexedType(From->getType(), idx_begin, @@ -848,25 +1150,25 @@ Value *llvm::FindInsertedValue(Value *V, const unsigned *idx_begin, if (idx_begin == idx_end) return V; // We have indices, so V should have an indexable type - assert((isa(V->getType()) || isa(V->getType())) + assert((V->getType()->isStructTy() || V->getType()->isArrayTy()) && "Not looking at a struct or array?"); assert(ExtractValueInst::getIndexedType(V->getType(), idx_begin, idx_end) && "Invalid indices for type?"); const CompositeType *PTy = cast(V->getType()); - + if (isa(V)) return UndefValue::get(ExtractValueInst::getIndexedType(PTy, idx_begin, idx_end)); else if (isa(V)) return Constant::getNullValue(ExtractValueInst::getIndexedType(PTy, - idx_begin, - idx_end)); + idx_begin, + idx_end)); else if (Constant *C = dyn_cast(V)) { if (isa(C) || isa(C)) // Recursively process this constant - return FindInsertedValue(C->getOperand(*idx_begin), idx_begin + 1, idx_end, - InsertBefore); + return FindInsertedValue(C->getOperand(*idx_begin), idx_begin + 1, + idx_end, InsertBefore); } else if (InsertValueInst *I = dyn_cast(V)) { // Loop the indices for the insertvalue instruction in parallel with the // requested indices @@ -933,25 +1235,67 @@ Value *llvm::FindInsertedValue(Value *V, const unsigned *idx_begin, return 0; } +/// GetPointerBaseWithConstantOffset - Analyze the specified pointer to see if +/// it can be expressed as a base pointer plus a constant offset. Return the +/// base and offset to the caller. +Value *llvm::GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset, + const TargetData &TD) { + Operator *PtrOp = dyn_cast(Ptr); + if (PtrOp == 0) return Ptr; + + // Just look through bitcasts. + if (PtrOp->getOpcode() == Instruction::BitCast) + return GetPointerBaseWithConstantOffset(PtrOp->getOperand(0), Offset, TD); + + // If this is a GEP with constant indices, we can look through it. + GEPOperator *GEP = dyn_cast(PtrOp); + if (GEP == 0 || !GEP->hasAllConstantIndices()) return Ptr; + + gep_type_iterator GTI = gep_type_begin(GEP); + for (User::op_iterator I = GEP->idx_begin(), E = GEP->idx_end(); I != E; + ++I, ++GTI) { + ConstantInt *OpC = cast(*I); + if (OpC->isZero()) continue; + + // Handle a struct and array indices which add their offset to the pointer. + if (const StructType *STy = dyn_cast(*GTI)) { + Offset += TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue()); + } else { + uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()); + Offset += OpC->getSExtValue()*Size; + } + } + + // Re-sign extend from the pointer size if needed to get overflow edge cases + // right. + unsigned PtrSize = TD.getPointerSizeInBits(); + if (PtrSize < 64) + Offset = (Offset << (64-PtrSize)) >> (64-PtrSize); + + return GetPointerBaseWithConstantOffset(GEP->getPointerOperand(), Offset, TD); +} + + /// GetConstantStringInfo - This function computes the length of a /// null-terminated C string pointed to by V. If successful, it returns true /// and returns the string in Str. If unsuccessful, it returns false. -bool llvm::GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset, +bool llvm::GetConstantStringInfo(const Value *V, std::string &Str, + uint64_t Offset, bool StopAtNul) { // If V is NULL then return false; if (V == NULL) return false; // Look through bitcast instructions. - if (BitCastInst *BCI = dyn_cast(V)) + if (const BitCastInst *BCI = dyn_cast(V)) return GetConstantStringInfo(BCI->getOperand(0), Str, Offset, StopAtNul); // If the value is not a GEP instruction nor a constant expression with a // GEP instruction, then return false because ConstantArray can't occur // any other way - User *GEP = 0; - if (GetElementPtrInst *GEPI = dyn_cast(V)) { + const User *GEP = 0; + if (const GetElementPtrInst *GEPI = dyn_cast(V)) { GEP = GEPI; - } else if (ConstantExpr *CE = dyn_cast(V)) { + } else if (const ConstantExpr *CE = dyn_cast(V)) { if (CE->getOpcode() == Instruction::BitCast) return GetConstantStringInfo(CE->getOperand(0), Str, Offset, StopAtNul); if (CE->getOpcode() != Instruction::GetElementPtr) @@ -967,12 +1311,12 @@ bool llvm::GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset, // Make sure the index-ee is a pointer to array of i8. const PointerType *PT = cast(GEP->getOperand(0)->getType()); const ArrayType *AT = dyn_cast(PT->getElementType()); - if (AT == 0 || AT->getElementType() != Type::Int8Ty) + if (AT == 0 || !AT->getElementType()->isIntegerTy(8)) return false; // Check to make sure that the first operand of the GEP is an integer and // has value 0 so that we are sure we're indexing into the initializer. - ConstantInt *FirstIdx = dyn_cast(GEP->getOperand(1)); + const ConstantInt *FirstIdx = dyn_cast(GEP->getOperand(1)); if (FirstIdx == 0 || !FirstIdx->isZero()) return false; @@ -980,7 +1324,7 @@ bool llvm::GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset, // into the array. If this occurs, we can't say anything meaningful about // the string. uint64_t StartIdx = 0; - if (ConstantInt *CI = dyn_cast(GEP->getOperand(2))) + if (const ConstantInt *CI = dyn_cast(GEP->getOperand(2))) StartIdx = CI->getZExtValue(); else return false; @@ -991,10 +1335,10 @@ bool llvm::GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset, // The GEP instruction, constant or instruction, must reference a global // variable that is a constant and is initialized. The referenced constant // initializer is the array that we'll use for optimization. - GlobalVariable* GV = dyn_cast(V); - if (!GV || !GV->isConstant() || !GV->hasInitializer()) + const GlobalVariable* GV = dyn_cast(V); + if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer()) return false; - Constant *GlobalInit = GV->getInitializer(); + const Constant *GlobalInit = GV->getInitializer(); // Handle the ConstantAggregateZero case if (isa(GlobalInit)) { @@ -1005,8 +1349,8 @@ bool llvm::GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset, } // Must be a Constant Array - ConstantArray *Array = dyn_cast(GlobalInit); - if (Array == 0 || Array->getType()->getElementType() != Type::Int8Ty) + const ConstantArray *Array = dyn_cast(GlobalInit); + if (Array == 0 || !Array->getType()->getElementType()->isIntegerTy(8)) return false; // Get the number of elements in the array @@ -1019,8 +1363,8 @@ bool llvm::GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset, // to in the array. Str.reserve(NumElts-Offset); for (unsigned i = Offset; i != NumElts; ++i) { - Constant *Elt = Array->getOperand(i); - ConstantInt *CI = dyn_cast(Elt); + const Constant *Elt = Array->getOperand(i); + const ConstantInt *CI = dyn_cast(Elt); if (!CI) // This array isn't suitable, non-int initializer. return false; if (StopAtNul && CI->isZero()) @@ -1031,3 +1375,159 @@ bool llvm::GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset, // The array isn't null terminated, but maybe this is a memcpy, not a strcpy. return true; } + +// These next two are very similar to the above, but also look through PHI +// nodes. +// TODO: See if we can integrate these two together. + +/// GetStringLengthH - If we can compute the length of the string pointed to by +/// the specified pointer, return 'len+1'. If we can't, return 0. +static uint64_t GetStringLengthH(Value *V, SmallPtrSet &PHIs) { + // Look through noop bitcast instructions. + if (BitCastInst *BCI = dyn_cast(V)) + return GetStringLengthH(BCI->getOperand(0), PHIs); + + // If this is a PHI node, there are two cases: either we have already seen it + // or we haven't. + if (PHINode *PN = dyn_cast(V)) { + if (!PHIs.insert(PN)) + return ~0ULL; // already in the set. + + // If it was new, see if all the input strings are the same length. + uint64_t LenSoFar = ~0ULL; + for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { + uint64_t Len = GetStringLengthH(PN->getIncomingValue(i), PHIs); + if (Len == 0) return 0; // Unknown length -> unknown. + + if (Len == ~0ULL) continue; + + if (Len != LenSoFar && LenSoFar != ~0ULL) + return 0; // Disagree -> unknown. + LenSoFar = Len; + } + + // Success, all agree. + return LenSoFar; + } + + // strlen(select(c,x,y)) -> strlen(x) ^ strlen(y) + if (SelectInst *SI = dyn_cast(V)) { + uint64_t Len1 = GetStringLengthH(SI->getTrueValue(), PHIs); + if (Len1 == 0) return 0; + uint64_t Len2 = GetStringLengthH(SI->getFalseValue(), PHIs); + if (Len2 == 0) return 0; + if (Len1 == ~0ULL) return Len2; + if (Len2 == ~0ULL) return Len1; + if (Len1 != Len2) return 0; + return Len1; + } + + // If the value is not a GEP instruction nor a constant expression with a + // GEP instruction, then return unknown. + User *GEP = 0; + if (GetElementPtrInst *GEPI = dyn_cast(V)) { + GEP = GEPI; + } else if (ConstantExpr *CE = dyn_cast(V)) { + if (CE->getOpcode() != Instruction::GetElementPtr) + return 0; + GEP = CE; + } else { + return 0; + } + + // Make sure the GEP has exactly three arguments. + if (GEP->getNumOperands() != 3) + return 0; + + // Check to make sure that the first operand of the GEP is an integer and + // has value 0 so that we are sure we're indexing into the initializer. + if (ConstantInt *Idx = dyn_cast(GEP->getOperand(1))) { + if (!Idx->isZero()) + return 0; + } else + return 0; + + // If the second index isn't a ConstantInt, then this is a variable index + // into the array. If this occurs, we can't say anything meaningful about + // the string. + uint64_t StartIdx = 0; + if (ConstantInt *CI = dyn_cast(GEP->getOperand(2))) + StartIdx = CI->getZExtValue(); + else + return 0; + + // The GEP instruction, constant or instruction, must reference a global + // variable that is a constant and is initialized. The referenced constant + // initializer is the array that we'll use for optimization. + GlobalVariable* GV = dyn_cast(GEP->getOperand(0)); + if (!GV || !GV->isConstant() || !GV->hasInitializer() || + GV->mayBeOverridden()) + return 0; + Constant *GlobalInit = GV->getInitializer(); + + // Handle the ConstantAggregateZero case, which is a degenerate case. The + // initializer is constant zero so the length of the string must be zero. + if (isa(GlobalInit)) + return 1; // Len = 0 offset by 1. + + // Must be a Constant Array + ConstantArray *Array = dyn_cast(GlobalInit); + if (!Array || !Array->getType()->getElementType()->isIntegerTy(8)) + return false; + + // Get the number of elements in the array + uint64_t NumElts = Array->getType()->getNumElements(); + + // Traverse the constant array from StartIdx (derived above) which is + // the place the GEP refers to in the array. + for (unsigned i = StartIdx; i != NumElts; ++i) { + Constant *Elt = Array->getOperand(i); + ConstantInt *CI = dyn_cast(Elt); + if (!CI) // This array isn't suitable, non-int initializer. + return 0; + if (CI->isZero()) + return i-StartIdx+1; // We found end of string, success! + } + + return 0; // The array isn't null terminated, conservatively return 'unknown'. +} + +/// GetStringLength - If we can compute the length of the string pointed to by +/// the specified pointer, return 'len+1'. If we can't, return 0. +uint64_t llvm::GetStringLength(Value *V) { + if (!V->getType()->isPointerTy()) return 0; + + SmallPtrSet PHIs; + uint64_t Len = GetStringLengthH(V, PHIs); + // If Len is ~0ULL, we had an infinite phi cycle: this is dead code, so return + // an empty string as a length. + return Len == ~0ULL ? 1 : Len; +} + +Value *llvm::GetUnderlyingObject(Value *V, unsigned MaxLookup) { + if (!V->getType()->isPointerTy()) + return V; + for (unsigned Count = 0; MaxLookup == 0 || Count < MaxLookup; ++Count) { + if (GEPOperator *GEP = dyn_cast(V)) { + V = GEP->getPointerOperand(); + } else if (Operator::getOpcode(V) == Instruction::BitCast) { + V = cast(V)->getOperand(0); + } else if (GlobalAlias *GA = dyn_cast(V)) { + if (GA->mayBeOverridden()) + return V; + V = GA->getAliasee(); + } else { + // See if InstructionSimplify knows any relevant tricks. + if (Instruction *I = dyn_cast(V)) + // TODO: Aquire TargetData and DominatorTree and use them. + if (Value *Simplified = SimplifyInstruction(I, 0, 0)) { + V = Simplified; + continue; + } + + return V; + } + assert(V->getType()->isPointerTy() && "Unexpected operand type!"); + } + return V; +}