X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FValueTracking.cpp;h=b4c9884a20ed87c034f154849c6207422db8601a;hb=bb47d3b47187e5e0b8f1a627c172894c228199da;hp=32a77e6f4610bb2c2ce3c25a374045d33d443807;hpb=6d116bc7ced56a820d33b0dd35ee36af8a810eab;p=oota-llvm.git diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp index 32a77e6f461..b4c9884a20e 100644 --- a/lib/Analysis/ValueTracking.cpp +++ b/lib/Analysis/ValueTracking.cpp @@ -15,25 +15,18 @@ #include "llvm/Analysis/ValueTracking.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 @@ -44,17 +37,25 @@ 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"); @@ -65,17 +66,39 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, KnownZero = ~KnownOne & Mask; return; } - // Null is all-zeros. - if (isa(V)) { + // Null and aggregate-zero are all-zeros. + if (isa(V) || + isa(V)) { KnownOne.clear(); 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.set(); KnownOne.set(); + 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)); @@ -84,17 +107,28 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, KnownOne.clear(); 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.clear(); KnownOne.clear(); + } else { + ComputeMaskedBits(GA->getAliasee(), Mask, KnownZero, KnownOne, + TD, Depth+1); + } + return; + } KnownZero.clear(); KnownOne.clear(); // 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. @@ -211,12 +245,16 @@ 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(); + if (SrcTy->isPointerTy()) + SrcBitWidth = TD->getTypeSizeInBits(SrcTy); + else + SrcBitWidth = SrcTy->getScalarSizeInBits(); + APInt MaskIn(Mask); MaskIn.zextOrTrunc(SrcBitWidth); KnownZero.zextOrTrunc(SrcBitWidth); @@ -232,7 +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; @@ -241,8 +282,7 @@ 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); @@ -286,7 +326,7 @@ 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. @@ -304,7 +344,7 @@ 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); @@ -341,44 +381,72 @@ 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); - // The sign of a remainder is equal to the sign of the first - // operand (zero being positive). + // 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; - else if (KnownOne2[BitWidth-1]) - KnownOne2 |= ~LowBits; + KnownZero |= ~LowBits; - KnownZero |= KnownZero2 & Mask; - KnownOne |= KnownOne2 & 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; @@ -391,7 +459,7 @@ 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; } } @@ -404,31 +472,18 @@ 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(); 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->getPrefTypeAlignment(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, @@ -459,15 +514,15 @@ 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->getABITypeSize(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())); } } @@ -483,10 +538,10 @@ 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. @@ -510,16 +565,43 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, ComputeMaskedBits(R, Mask2, KnownZero2, KnownOne2, TD, Depth+1); Mask2 = APInt::getLowBitsSet(BitWidth, KnownZero2.countTrailingOnes()); - KnownOne2.clear(); - KnownZero2.clear(); - ComputeMaskedBits(L, Mask2, KnownZero2, KnownOne2, TD, Depth+1); + + // We need to take the minimum number of known bits + APInt KnownZero3(KnownZero), KnownOne3(KnownOne); + ComputeMaskedBits(L, Mask2, KnownZero3, KnownOne3, TD, Depth+1); + KnownZero = Mask & APInt::getLowBitsSet(BitWidth, - KnownZero2.countTrailingOnes()); + std::min(KnownZero2.countTrailingOnes(), + KnownZero3.countTrailingOnes())); break; } } } + + // 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: @@ -542,8 +624,14 @@ 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?"); @@ -560,9 +648,14 @@ 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; @@ -572,11 +665,11 @@ 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: @@ -623,7 +716,7 @@ 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); @@ -643,8 +736,7 @@ 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); @@ -674,8 +766,24 @@ 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. @@ -706,6 +814,116 @@ 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); + Op1 = ConstantInt::get(V->getContext(), + APInt(Op1Int.getBitWidth(), 0).set(BitToSet)); + } + + Value *Mul0 = NULL; + Value *Mul1 = NULL; + bool M0 = ComputeMultiple(Op0, Base, Mul0, + LookThroughSExt, Depth+1); + bool M1 = ComputeMultiple(Op1, Base, Mul1, + LookThroughSExt, Depth+1); + + if (M0) { + if (isa(Op1) && isa(Mul0)) { + // V == Base * (Mul0 * Op1), so return (Mul0 * Op1) + Multiple = ConstantExpr::getMul(cast(Mul0), + cast(Op1)); + return true; + } + + if (ConstantInt *Mul0CI = dyn_cast(Mul0)) + if (Mul0CI->getValue() == 1) { + // V == Base * Op1, so return Op1 + Multiple = Op1; + return true; + } + } + + if (M1) { + if (isa(Op0) && isa(Mul1)) { + // V == Base * (Mul1 * Op0), so return (Mul1 * Op0) + Multiple = ConstantExpr::getMul(cast(Mul1), + cast(Op0)); + 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. /// @@ -719,11 +937,11 @@ 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; @@ -735,36 +953,225 @@ 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; + // 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; +} + + +/// GetLinearExpression - Analyze the specified value as a linear expression: +/// "A*V + B", where A and B are constant integers. Return the scale and offset +/// values as APInts and return V as a Value*. The incoming Value is known to +/// have IntegerType. Note that this looks through extends, so the high bits +/// may not be represented in the result. +static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset, + const TargetData *TD, unsigned Depth) { + assert(V->getType()->isIntegerTy() && "Not an integer value"); + + // Limit our recursion depth. + if (Depth == 6) { + Scale = 1; + Offset = 0; + return V; + } + + if (BinaryOperator *BOp = dyn_cast(V)) { + if (ConstantInt *RHSC = dyn_cast(BOp->getOperand(1))) { + switch (BOp->getOpcode()) { + default: break; + case Instruction::Or: + // X|C == X+C if all the bits in C are unset in X. Otherwise we can't + // analyze it. + if (!MaskedValueIsZero(BOp->getOperand(0), RHSC->getValue(), TD)) break; - case 4: // abs[lf](x) != -0.0 - if (!strcmp(F->getNameStart(), "absf")) return true; - if (!strcmp(F->getNameStart(), "absl")) return true; + // FALL THROUGH. + case Instruction::Add: + V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD, Depth+1); + Offset += RHSC->getValue(); + return V; + case Instruction::Mul: + V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD, Depth+1); + Offset *= RHSC->getValue(); + Scale *= RHSC->getValue(); + return V; + case Instruction::Shl: + V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD, Depth+1); + Offset <<= RHSC->getValue().getLimitedValue(); + Scale <<= RHSC->getValue().getLimitedValue(); + return V; + } + } + } + + // Since clients don't care about the high bits of the value, just scales and + // offsets, we can look through extensions. + if (isa(V) || isa(V)) { + Value *CastOp = cast(V)->getOperand(0); + unsigned OldWidth = Scale.getBitWidth(); + unsigned SmallWidth = CastOp->getType()->getPrimitiveSizeInBits(); + Scale.trunc(SmallWidth); + Offset.trunc(SmallWidth); + Value *Result = GetLinearExpression(CastOp, Scale, Offset, TD, Depth+1); + Scale.zext(OldWidth); + Offset.zext(OldWidth); + return Result; + } + + Scale = 1; + Offset = 0; + return V; +} + +/// DecomposeGEPExpression - If V is a symbolic pointer expression, decompose it +/// into a base pointer with a constant offset and a number of scaled symbolic +/// offsets. +/// +/// The scaled symbolic offsets (represented by pairs of a Value* and a scale in +/// the VarIndices vector) are Value*'s that are known to be scaled by the +/// specified amount, but which may have other unrepresented high bits. As such, +/// the gep cannot necessarily be reconstructed from its decomposed form. +/// +/// When TargetData is around, this function is capable of analyzing everything +/// that Value::getUnderlyingObject() can look through. When not, it just looks +/// through pointer casts. +/// +const Value *llvm::DecomposeGEPExpression(const Value *V, int64_t &BaseOffs, + SmallVectorImpl > &VarIndices, + const TargetData *TD) { + // Limit recursion depth to limit compile time in crazy cases. + unsigned MaxLookup = 6; + + BaseOffs = 0; + do { + // See if this is a bitcast or GEP. + const Operator *Op = dyn_cast(V); + if (Op == 0) { + // The only non-operator case we can handle are GlobalAliases. + if (const GlobalAlias *GA = dyn_cast(V)) { + if (!GA->mayBeOverridden()) { + V = GA->getAliasee(); + continue; + } + } + return V; + } + + if (Op->getOpcode() == Instruction::BitCast) { + V = Op->getOperand(0); + continue; + } + + const GEPOperator *GEPOp = dyn_cast(Op); + if (GEPOp == 0) + return V; + + // Don't attempt to analyze GEPs over unsized objects. + if (!cast(GEPOp->getOperand(0)->getType()) + ->getElementType()->isSized()) + return V; + + // If we are lacking TargetData information, we can't compute the offets of + // elements computed by GEPs. However, we can handle bitcast equivalent + // GEPs. + if (!TD) { + if (!GEPOp->hasAllZeroIndices()) + return V; + V = GEPOp->getOperand(0); + continue; + } + + // Walk the indices of the GEP, accumulating them into BaseOff/VarIndices. + gep_type_iterator GTI = gep_type_begin(GEPOp); + for (User::const_op_iterator I = GEPOp->op_begin()+1, + E = GEPOp->op_end(); I != E; ++I) { + Value *Index = *I; + // Compute the (potentially symbolic) offset in bytes for this index. + if (const StructType *STy = dyn_cast(*GTI++)) { + // For a struct, add the member offset. + unsigned FieldNo = cast(Index)->getZExtValue(); + if (FieldNo == 0) continue; + + BaseOffs += TD->getStructLayout(STy)->getElementOffset(FieldNo); + continue; + } + + // For an array/pointer, add the element offset, explicitly scaled. + if (ConstantInt *CIdx = dyn_cast(Index)) { + if (CIdx->isZero()) continue; + BaseOffs += TD->getTypeAllocSize(*GTI)*CIdx->getSExtValue(); + continue; + } + + uint64_t Scale = TD->getTypeAllocSize(*GTI); + + // Use GetLinearExpression to decompose the index into a C1*V+C2 form. + unsigned Width = cast(Index->getType())->getBitWidth(); + APInt IndexScale(Width, 0), IndexOffset(Width, 0); + Index = GetLinearExpression(Index, IndexScale, IndexOffset, TD, 0); + + // The GEP index scale ("Scale") scales C1*V+C2, yielding (C1*V+C2)*Scale. + // This gives us an aggregate computation of (C1*Scale)*V + C2*Scale. + BaseOffs += IndexOffset.getZExtValue()*Scale; + Scale *= IndexScale.getZExtValue(); + + + // If we already had an occurrance of this index variable, merge this + // scale into it. For example, we want to handle: + // A[x][x] -> x*16 + x*4 -> x*20 + // This also ensures that 'x' only appears in the index list once. + for (unsigned i = 0, e = VarIndices.size(); i != e; ++i) { + if (VarIndices[i].first == Index) { + Scale += VarIndices[i].second; + VarIndices.erase(VarIndices.begin()+i); break; } } + + // Make sure that we have a scale that makes sense for this target's + // pointer size. + if (unsigned ShiftBits = 64-TD->getPointerSizeInBits()) { + Scale <<= ShiftBits; + Scale >>= ShiftBits; + } + + if (Scale) + VarIndices.push_back(std::make_pair(Index, Scale)); } + + // Analyze the base pointer next. + V = GEPOp->getOperand(0); + } while (--MaxLookup); - return false; + // If the chain of expressions is too deep, just return early. + return V; } + // 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 @@ -820,8 +1227,9 @@ 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, @@ -846,25 +1254,25 @@ 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, 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 @@ -930,3 +1338,231 @@ Value *llvm::FindInsertedValue(Value *V, const unsigned *idx_begin, // or load instruction) return 0; } + +/// 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(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 (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 + const User *GEP = 0; + if (const GetElementPtrInst *GEPI = dyn_cast(V)) { + GEP = GEPI; + } 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) + return false; + GEP = CE; + } + + if (GEP) { + // Make sure the GEP has exactly three arguments. + if (GEP->getNumOperands() != 3) + return false; + + // 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()->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. + const ConstantInt *FirstIdx = dyn_cast(GEP->getOperand(1)); + if (FirstIdx == 0 || !FirstIdx->isZero()) + return false; + + // 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 (const ConstantInt *CI = dyn_cast(GEP->getOperand(2))) + StartIdx = CI->getZExtValue(); + else + return false; + return GetConstantStringInfo(GEP->getOperand(0), Str, StartIdx+Offset, + StopAtNul); + } + + // 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. + const GlobalVariable* GV = dyn_cast(V); + if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer()) + return false; + const Constant *GlobalInit = GV->getInitializer(); + + // Handle the ConstantAggregateZero case + if (isa(GlobalInit)) { + // This is a degenerate case. The initializer is constant zero so the + // length of the string must be zero. + Str.clear(); + return true; + } + + // Must be a Constant Array + const ConstantArray *Array = dyn_cast(GlobalInit); + if (Array == 0 || !Array->getType()->getElementType()->isIntegerTy(8)) + return false; + + // Get the number of elements in the array + uint64_t NumElts = Array->getType()->getNumElements(); + + if (Offset > NumElts) + return false; + + // Traverse the constant array from 'Offset' which is the place the GEP refers + // to in the array. + Str.reserve(NumElts-Offset); + for (unsigned i = Offset; i != NumElts; ++i) { + 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()) + return true; // we found end of string, success! + Str += (char)CI->getZExtValue(); + } + + // 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; +}