diff options
Diffstat (limited to 'lib/Analysis/ValueTracking.cpp')
| -rw-r--r-- | lib/Analysis/ValueTracking.cpp | 989 |
1 files changed, 549 insertions, 440 deletions
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp index 4d94f619fda1..a430f6281ef0 100644 --- a/lib/Analysis/ValueTracking.cpp +++ b/lib/Analysis/ValueTracking.cpp @@ -20,8 +20,10 @@ #include "llvm/GlobalAlias.h" #include "llvm/IntrinsicInst.h" #include "llvm/LLVMContext.h" +#include "llvm/Metadata.h" #include "llvm/Operator.h" #include "llvm/Target/TargetData.h" +#include "llvm/Support/ConstantRange.h" #include "llvm/Support/GetElementPtrTypeIterator.h" #include "llvm/Support/MathExtras.h" #include "llvm/Support/PatternMatch.h" @@ -41,10 +43,176 @@ static unsigned getBitWidth(Type *Ty, const TargetData *TD) { return TD ? TD->getPointerSizeInBits() : 0; } -/// 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 -/// processing. +static void ComputeMaskedBitsAddSub(bool Add, Value *Op0, Value *Op1, bool NSW, + APInt &KnownZero, APInt &KnownOne, + APInt &KnownZero2, APInt &KnownOne2, + const TargetData *TD, unsigned Depth) { + if (!Add) { + if (ConstantInt *CLHS = dyn_cast<ConstantInt>(Op0)) { + // We know that the top bits of C-X are clear if X contains less bits + // than C (i.e. no wrap-around can happen). For example, 20-X is + // positive if we can prove that X is >= 0 and < 16. + if (!CLHS->getValue().isNegative()) { + unsigned BitWidth = KnownZero.getBitWidth(); + unsigned NLZ = (CLHS->getValue()+1).countLeadingZeros(); + // NLZ can't be BitWidth with no sign bit + APInt MaskV = APInt::getHighBitsSet(BitWidth, NLZ+1); + llvm::ComputeMaskedBits(Op1, KnownZero2, KnownOne2, TD, Depth+1); + + // If all of the MaskV bits are known to be zero, then we know the + // output top bits are zero, because we now know that the output is + // from [0-C]. + if ((KnownZero2 & MaskV) == MaskV) { + unsigned NLZ2 = CLHS->getValue().countLeadingZeros(); + // Top bits known zero. + KnownZero = APInt::getHighBitsSet(BitWidth, NLZ2); + } + } + } + } + + unsigned BitWidth = KnownZero.getBitWidth(); + + // 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); + llvm::ComputeMaskedBits(Op0, LHSKnownZero, LHSKnownOne, TD, Depth+1); + assert((LHSKnownZero & LHSKnownOne) == 0 && + "Bits known to be one AND zero?"); + unsigned LHSKnownZeroOut = LHSKnownZero.countTrailingOnes(); + + llvm::ComputeMaskedBits(Op1, KnownZero2, KnownOne2, TD, Depth+1); + assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); + unsigned RHSKnownZeroOut = KnownZero2.countTrailingOnes(); + + // Determine which operand has more trailing zeros, and use that + // many bits from the other operand. + if (LHSKnownZeroOut > RHSKnownZeroOut) { + if (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; + } + + // Are we still trying to solve for the sign bit? + if (!KnownZero.isNegative() && !KnownOne.isNegative()) { + if (NSW) { + if (Add) { + // Adding two positive numbers can't wrap into negative + if (LHSKnownZero.isNegative() && KnownZero2.isNegative()) + KnownZero |= APInt::getSignBit(BitWidth); + // and adding two negative numbers can't wrap into positive. + else if (LHSKnownOne.isNegative() && KnownOne2.isNegative()) + KnownOne |= APInt::getSignBit(BitWidth); + } else { + // Subtracting a negative number from a positive one can't wrap + if (LHSKnownZero.isNegative() && KnownOne2.isNegative()) + KnownZero |= APInt::getSignBit(BitWidth); + // neither can subtracting a positive number from a negative one. + else if (LHSKnownOne.isNegative() && KnownZero2.isNegative()) + KnownOne |= APInt::getSignBit(BitWidth); + } + } + } +} + +static void ComputeMaskedBitsMul(Value *Op0, Value *Op1, bool NSW, + APInt &KnownZero, APInt &KnownOne, + APInt &KnownZero2, APInt &KnownOne2, + const TargetData *TD, unsigned Depth) { + unsigned BitWidth = KnownZero.getBitWidth(); + ComputeMaskedBits(Op1, KnownZero, KnownOne, TD, Depth+1); + ComputeMaskedBits(Op0, KnownZero2, KnownOne2, TD, Depth+1); + assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); + assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); + + bool isKnownNegative = false; + bool isKnownNonNegative = false; + // If the multiplication is known not to overflow, compute the sign bit. + if (NSW) { + if (Op0 == Op1) { + // The product of a number with itself is non-negative. + isKnownNonNegative = true; + } else { + bool isKnownNonNegativeOp1 = KnownZero.isNegative(); + bool isKnownNonNegativeOp0 = KnownZero2.isNegative(); + bool isKnownNegativeOp1 = KnownOne.isNegative(); + bool isKnownNegativeOp0 = KnownOne2.isNegative(); + // The product of two numbers with the same sign is non-negative. + isKnownNonNegative = (isKnownNegativeOp1 && isKnownNegativeOp0) || + (isKnownNonNegativeOp1 && isKnownNonNegativeOp0); + // The product of a negative number and a non-negative number is either + // negative or zero. + if (!isKnownNonNegative) + isKnownNegative = (isKnownNegativeOp1 && isKnownNonNegativeOp0 && + isKnownNonZero(Op0, TD, Depth)) || + (isKnownNegativeOp0 && isKnownNonNegativeOp1 && + isKnownNonZero(Op1, TD, Depth)); + } + } + + // If low bits are zero in either operand, output low known-0 bits. + // 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.clearAllBits(); + unsigned TrailZ = KnownZero.countTrailingOnes() + + KnownZero2.countTrailingOnes(); + unsigned LeadZ = std::max(KnownZero.countLeadingOnes() + + KnownZero2.countLeadingOnes(), + BitWidth) - BitWidth; + + TrailZ = std::min(TrailZ, BitWidth); + LeadZ = std::min(LeadZ, BitWidth); + KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) | + APInt::getHighBitsSet(BitWidth, LeadZ); + + // Only make use of no-wrap flags if we failed to compute the sign bit + // directly. This matters if the multiplication always overflows, in + // which case we prefer to follow the result of the direct computation, + // though as the program is invoking undefined behaviour we can choose + // whatever we like here. + if (isKnownNonNegative && !KnownOne.isNegative()) + KnownZero.setBit(BitWidth - 1); + else if (isKnownNegative && !KnownZero.isNegative()) + KnownOne.setBit(BitWidth - 1); +} + +void llvm::computeMaskedBitsLoad(const MDNode &Ranges, APInt &KnownZero) { + unsigned BitWidth = KnownZero.getBitWidth(); + unsigned NumRanges = Ranges.getNumOperands() / 2; + assert(NumRanges >= 1); + + // Use the high end of the ranges to find leading zeros. + unsigned MinLeadingZeros = BitWidth; + for (unsigned i = 0; i < NumRanges; ++i) { + ConstantInt *Lower = cast<ConstantInt>(Ranges.getOperand(2*i + 0)); + ConstantInt *Upper = cast<ConstantInt>(Ranges.getOperand(2*i + 1)); + ConstantRange Range(Lower->getValue(), Upper->getValue()); + if (Range.isWrappedSet()) + MinLeadingZeros = 0; // -1 has no zeros + unsigned LeadingZeros = (Upper->getValue() - 1).countLeadingZeros(); + MinLeadingZeros = std::min(LeadingZeros, MinLeadingZeros); + } + + KnownZero = APInt::getHighBitsSet(BitWidth, MinLeadingZeros); +} +/// ComputeMaskedBits - Determine which of the bits are known to be either zero +/// or one and return them in the KnownZero/KnownOne bit sets. +/// /// NOTE: we cannot consider 'undef' to be "IsZero" here. The problem is that /// we cannot optimize based on the assumption that it is zero without changing /// it to be an explicit zero. If we don't change it to zero, other code could @@ -54,67 +222,75 @@ static unsigned getBitWidth(Type *Ty, const TargetData *TD) { /// /// 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 +/// where V is a vector, 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, +void llvm::ComputeMaskedBits(Value *V, APInt &KnownZero, APInt &KnownOne, const TargetData *TD, unsigned Depth) { assert(V && "No Value?"); assert(Depth <= MaxDepth && "Limit Search Depth"); - unsigned BitWidth = Mask.getBitWidth(); - assert((V->getType()->isIntOrIntVectorTy() || V->getType()->isPointerTy()) - && "Not integer or pointer type!"); + unsigned BitWidth = KnownZero.getBitWidth(); + + assert((V->getType()->isIntOrIntVectorTy() || + V->getType()->getScalarType()->isPointerTy()) && + "Not integer or pointer type!"); assert((!TD || TD->getTypeSizeInBits(V->getType()->getScalarType()) == BitWidth) && (!V->getType()->isIntOrIntVectorTy() || V->getType()->getScalarSizeInBits() == BitWidth) && - KnownZero.getBitWidth() == BitWidth && + KnownZero.getBitWidth() == BitWidth && KnownOne.getBitWidth() == BitWidth && "V, Mask, KnownOne and KnownZero should have same BitWidth"); if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { // We know all of the bits for a constant! - KnownOne = CI->getValue() & Mask; - KnownZero = ~KnownOne & Mask; + KnownOne = CI->getValue(); + KnownZero = ~KnownOne; return; } // Null and aggregate-zero are all-zeros. if (isa<ConstantPointerNull>(V) || isa<ConstantAggregateZero>(V)) { KnownOne.clearAllBits(); - KnownZero = Mask; + KnownZero = APInt::getAllOnesValue(BitWidth); return; } // Handle a constant vector by taking the intersection of the known bits of - // each element. - if (ConstantVector *CV = dyn_cast<ConstantVector>(V)) { + // each element. There is no real need to handle ConstantVector here, because + // we don't handle undef in any particularly useful way. + if (ConstantDataSequential *CDS = dyn_cast<ConstantDataSequential>(V)) { + // We know that CDS must be a vector of integers. Take the intersection of + // each element. 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; + APInt Elt(KnownZero.getBitWidth(), 0); + for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i) { + Elt = CDS->getElementAsInteger(i); + KnownZero &= ~Elt; + KnownOne &= Elt; } return; } + // The address of an aligned GlobalValue has trailing zeros. if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) { unsigned Align = GV->getAlignment(); - if (Align == 0 && TD && GV->getType()->getElementType()->isSized()) { - 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 && TD) { + if (GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV)) { + Type *ObjectType = GVar->getType()->getElementType(); + if (ObjectType->isSized()) { + // 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 (!GVar->isDeclaration() && !GVar->isWeakForLinker()) + Align = TD->getPreferredAlignment(GVar); + else + Align = TD->getABITypeAlignment(ObjectType); + } + } } if (Align > 0) - KnownZero = Mask & APInt::getLowBitsSet(BitWidth, - CountTrailingZeros_32(Align)); + KnownZero = APInt::getLowBitsSet(BitWidth, + CountTrailingZeros_32(Align)); else KnownZero.clearAllBits(); KnownOne.clearAllBits(); @@ -126,8 +302,7 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, if (GA->mayBeOverridden()) { KnownZero.clearAllBits(); KnownOne.clearAllBits(); } else { - ComputeMaskedBits(GA->getAliasee(), Mask, KnownZero, KnownOne, - TD, Depth+1); + ComputeMaskedBits(GA->getAliasee(), KnownZero, KnownOne, TD, Depth+1); } return; } @@ -136,15 +311,15 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, // Get alignment information off byval arguments if specified in the IR. if (A->hasByValAttr()) if (unsigned Align = A->getParamAlignment()) - KnownZero = Mask & APInt::getLowBitsSet(BitWidth, - CountTrailingZeros_32(Align)); + KnownZero = APInt::getLowBitsSet(BitWidth, + CountTrailingZeros_32(Align)); return; } // Start out not knowing anything. KnownZero.clearAllBits(); KnownOne.clearAllBits(); - if (Depth == MaxDepth || Mask == 0) + if (Depth == MaxDepth) return; // Limit search depth. Operator *I = dyn_cast<Operator>(V); @@ -153,12 +328,14 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, APInt KnownZero2(KnownZero), KnownOne2(KnownOne); switch (I->getOpcode()) { default: break; + case Instruction::Load: + if (MDNode *MD = cast<LoadInst>(I)->getMetadata(LLVMContext::MD_range)) + computeMaskedBitsLoad(*MD, KnownZero); + return; case Instruction::And: { // If either the LHS or the RHS are Zero, the result is zero. - ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, TD, Depth+1); - APInt Mask2(Mask & ~KnownZero); - ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD, - Depth+1); + ComputeMaskedBits(I->getOperand(1), KnownZero, KnownOne, TD, Depth+1); + ComputeMaskedBits(I->getOperand(0), KnownZero2, KnownOne2, TD, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); @@ -169,10 +346,8 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, return; } case Instruction::Or: { - ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, TD, Depth+1); - APInt Mask2(Mask & ~KnownOne); - ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD, - Depth+1); + ComputeMaskedBits(I->getOperand(1), KnownZero, KnownOne, TD, Depth+1); + ComputeMaskedBits(I->getOperand(0), KnownZero2, KnownOne2, TD, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); @@ -183,9 +358,8 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, return; } case Instruction::Xor: { - ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, TD, Depth+1); - ComputeMaskedBits(I->getOperand(0), Mask, KnownZero2, KnownOne2, TD, - Depth+1); + ComputeMaskedBits(I->getOperand(1), KnownZero, KnownOne, TD, Depth+1); + ComputeMaskedBits(I->getOperand(0), KnownZero2, KnownOne2, TD, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); @@ -197,55 +371,32 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, return; } case Instruction::Mul: { - APInt Mask2 = APInt::getAllOnesValue(BitWidth); - ComputeMaskedBits(I->getOperand(1), Mask2, KnownZero, KnownOne, TD,Depth+1); - ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD, - Depth+1); - assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); - assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); - - // If low bits are zero in either operand, output low known-0 bits. - // 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.clearAllBits(); - unsigned TrailZ = KnownZero.countTrailingOnes() + - KnownZero2.countTrailingOnes(); - unsigned LeadZ = std::max(KnownZero.countLeadingOnes() + - KnownZero2.countLeadingOnes(), - BitWidth) - BitWidth; - - TrailZ = std::min(TrailZ, BitWidth); - LeadZ = std::min(LeadZ, BitWidth); - KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) | - APInt::getHighBitsSet(BitWidth, LeadZ); - KnownZero &= Mask; - return; + bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap(); + ComputeMaskedBitsMul(I->getOperand(0), I->getOperand(1), NSW, + KnownZero, KnownOne, KnownZero2, KnownOne2, TD, Depth); + break; } case Instruction::UDiv: { // For the purposes of computing leading zeros we can conservatively // treat a udiv as a logical right shift by the power of 2 known to // be less than the denominator. - APInt AllOnes = APInt::getAllOnesValue(BitWidth); - ComputeMaskedBits(I->getOperand(0), - AllOnes, KnownZero2, KnownOne2, TD, Depth+1); + ComputeMaskedBits(I->getOperand(0), KnownZero2, KnownOne2, TD, Depth+1); unsigned LeadZ = KnownZero2.countLeadingOnes(); KnownOne2.clearAllBits(); KnownZero2.clearAllBits(); - ComputeMaskedBits(I->getOperand(1), - AllOnes, KnownZero2, KnownOne2, TD, Depth+1); + ComputeMaskedBits(I->getOperand(1), KnownZero2, KnownOne2, TD, Depth+1); unsigned RHSUnknownLeadingOnes = KnownOne2.countLeadingZeros(); if (RHSUnknownLeadingOnes != BitWidth) LeadZ = std::min(BitWidth, LeadZ + BitWidth - RHSUnknownLeadingOnes - 1); - KnownZero = APInt::getHighBitsSet(BitWidth, LeadZ) & Mask; + KnownZero = APInt::getHighBitsSet(BitWidth, LeadZ); return; } case Instruction::Select: - ComputeMaskedBits(I->getOperand(2), Mask, KnownZero, KnownOne, TD, Depth+1); - ComputeMaskedBits(I->getOperand(1), Mask, KnownZero2, KnownOne2, TD, + ComputeMaskedBits(I->getOperand(2), KnownZero, KnownOne, TD, Depth+1); + ComputeMaskedBits(I->getOperand(1), KnownZero2, KnownOne2, TD, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); @@ -278,11 +429,9 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, 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); + ComputeMaskedBits(I->getOperand(0), KnownZero, KnownOne, TD, Depth+1); KnownZero = KnownZero.zextOrTrunc(BitWidth); KnownOne = KnownOne.zextOrTrunc(BitWidth); // Any top bits are known to be zero. @@ -296,8 +445,7 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, // 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); + ComputeMaskedBits(I->getOperand(0), KnownZero, KnownOne, TD, Depth+1); return; } break; @@ -306,11 +454,9 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, // Compute the bits in the result that are not present in the input. unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits(); - APInt MaskIn = Mask.trunc(SrcBitWidth); KnownZero = KnownZero.trunc(SrcBitWidth); KnownOne = KnownOne.trunc(SrcBitWidth); - ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, TD, - Depth+1); + ComputeMaskedBits(I->getOperand(0), KnownZero, KnownOne, TD, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); KnownZero = KnownZero.zext(BitWidth); KnownOne = KnownOne.zext(BitWidth); @@ -327,9 +473,7 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, // (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0 if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) { uint64_t ShiftAmt = SA->getLimitedValue(BitWidth); - APInt Mask2(Mask.lshr(ShiftAmt)); - ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne, TD, - Depth+1); + ComputeMaskedBits(I->getOperand(0), KnownZero, KnownOne, TD, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); KnownZero <<= ShiftAmt; KnownOne <<= ShiftAmt; @@ -344,9 +488,7 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, uint64_t ShiftAmt = SA->getLimitedValue(BitWidth); // Unsigned shift right. - APInt Mask2(Mask.shl(ShiftAmt)); - ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero,KnownOne, TD, - Depth+1); + ComputeMaskedBits(I->getOperand(0), KnownZero,KnownOne, TD, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); KnownZero = APIntOps::lshr(KnownZero, ShiftAmt); KnownOne = APIntOps::lshr(KnownOne, ShiftAmt); @@ -362,9 +504,7 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, uint64_t ShiftAmt = SA->getLimitedValue(BitWidth-1); // Signed shift right. - APInt Mask2(Mask.shl(ShiftAmt)); - ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne, TD, - Depth+1); + ComputeMaskedBits(I->getOperand(0), KnownZero, KnownOne, TD, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); KnownZero = APIntOps::lshr(KnownZero, ShiftAmt); KnownOne = APIntOps::lshr(KnownOne, ShiftAmt); @@ -378,100 +518,25 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, } break; case Instruction::Sub: { - if (ConstantInt *CLHS = dyn_cast<ConstantInt>(I->getOperand(0))) { - // We know that the top bits of C-X are clear if X contains less bits - // than C (i.e. no wrap-around can happen). For example, 20-X is - // positive if we can prove that X is >= 0 and < 16. - if (!CLHS->getValue().isNegative()) { - unsigned NLZ = (CLHS->getValue()+1).countLeadingZeros(); - // NLZ can't be BitWidth with no sign bit - APInt MaskV = APInt::getHighBitsSet(BitWidth, NLZ+1); - ComputeMaskedBits(I->getOperand(1), MaskV, KnownZero2, KnownOne2, - TD, Depth+1); - - // If all of the MaskV bits are known to be zero, then we know the - // output top bits are zero, because we now know that the output is - // from [0-C]. - if ((KnownZero2 & MaskV) == MaskV) { - unsigned NLZ2 = CLHS->getValue().countLeadingZeros(); - // Top bits known zero. - KnownZero = APInt::getHighBitsSet(BitWidth, NLZ2) & Mask; - } - } - } + bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap(); + ComputeMaskedBitsAddSub(false, I->getOperand(0), I->getOperand(1), NSW, + KnownZero, KnownOne, KnownZero2, KnownOne2, TD, + Depth); + break; } - // fall through case Instruction::Add: { - // 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((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?"); - unsigned RHSKnownZeroOut = KnownZero2.countTrailingOnes(); - - // 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; - } - - // Are we still trying to solve for the sign bit? - if (Mask.isNegative() && !KnownZero.isNegative() && !KnownOne.isNegative()){ - OverflowingBinaryOperator *OBO = cast<OverflowingBinaryOperator>(I); - if (OBO->hasNoSignedWrap()) { - if (I->getOpcode() == Instruction::Add) { - // Adding two positive numbers can't wrap into negative - if (LHSKnownZero.isNegative() && KnownZero2.isNegative()) - KnownZero |= APInt::getSignBit(BitWidth); - // and adding two negative numbers can't wrap into positive. - else if (LHSKnownOne.isNegative() && KnownOne2.isNegative()) - KnownOne |= APInt::getSignBit(BitWidth); - } else { - // Subtracting a negative number from a positive one can't wrap - if (LHSKnownZero.isNegative() && KnownOne2.isNegative()) - KnownZero |= APInt::getSignBit(BitWidth); - // neither can subtracting a positive number from a negative one. - else if (LHSKnownOne.isNegative() && KnownZero2.isNegative()) - KnownOne |= APInt::getSignBit(BitWidth); - } - } - } - - return; + bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap(); + ComputeMaskedBitsAddSub(true, I->getOperand(0), I->getOperand(1), NSW, + KnownZero, KnownOne, KnownZero2, KnownOne2, TD, + Depth); + break; } case Instruction::SRem: if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) { 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); + ComputeMaskedBits(I->getOperand(0), KnownZero2, KnownOne2, TD, Depth+1); // The low bits of the first operand are unchanged by the srem. KnownZero = KnownZero2 & LowBits; @@ -487,19 +552,15 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, if (KnownOne2[BitWidth-1] && ((KnownOne2 & LowBits) != 0)) KnownOne |= ~LowBits; - KnownZero &= Mask; - KnownOne &= Mask; - assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); } } // The sign bit is the LHS's sign bit, except when the result of the // remainder is zero. - if (Mask.isNegative() && KnownZero.isNonNegative()) { - APInt Mask2 = APInt::getSignBit(BitWidth); + if (KnownZero.isNonNegative()) { APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0); - ComputeMaskedBits(I->getOperand(0), Mask2, LHSKnownZero, LHSKnownOne, TD, + ComputeMaskedBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, TD, Depth+1); // If it's known zero, our sign bit is also zero. if (LHSKnownZero.isNegative()) @@ -512,27 +573,24 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, APInt RA = Rem->getValue(); if (RA.isPowerOf2()) { APInt LowBits = (RA - 1); - APInt Mask2 = LowBits & Mask; - KnownZero |= ~LowBits & Mask; - ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne, TD, + ComputeMaskedBits(I->getOperand(0), KnownZero, KnownOne, TD, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); + KnownZero |= ~LowBits; + KnownOne &= LowBits; break; } } // Since the result is less than or equal to either operand, any leading // zero bits in either operand must also exist in the result. - APInt AllOnes = APInt::getAllOnesValue(BitWidth); - ComputeMaskedBits(I->getOperand(0), AllOnes, KnownZero, KnownOne, - TD, Depth+1); - ComputeMaskedBits(I->getOperand(1), AllOnes, KnownZero2, KnownOne2, - TD, Depth+1); + ComputeMaskedBits(I->getOperand(0), KnownZero, KnownOne, TD, Depth+1); + ComputeMaskedBits(I->getOperand(1), KnownZero2, KnownOne2, TD, Depth+1); unsigned Leaders = std::max(KnownZero.countLeadingOnes(), KnownZero2.countLeadingOnes()); KnownOne.clearAllBits(); - KnownZero = APInt::getHighBitsSet(BitWidth, Leaders) & Mask; + KnownZero = APInt::getHighBitsSet(BitWidth, Leaders); break; } @@ -543,17 +601,15 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, Align = TD->getABITypeAlignment(AI->getType()->getElementType()); if (Align > 0) - KnownZero = Mask & APInt::getLowBitsSet(BitWidth, - CountTrailingZeros_32(Align)); + KnownZero = APInt::getLowBitsSet(BitWidth, CountTrailingZeros_32(Align)); break; } case Instruction::GetElementPtr: { // Analyze all of the subscripts of this getelementptr instruction // to determine if we can prove known low zero bits. - APInt LocalMask = APInt::getAllOnesValue(BitWidth); APInt LocalKnownZero(BitWidth, 0), LocalKnownOne(BitWidth, 0); - ComputeMaskedBits(I->getOperand(0), LocalMask, - LocalKnownZero, LocalKnownOne, TD, Depth+1); + ComputeMaskedBits(I->getOperand(0), LocalKnownZero, LocalKnownOne, TD, + Depth+1); unsigned TrailZ = LocalKnownZero.countTrailingOnes(); gep_type_iterator GTI = gep_type_begin(I); @@ -573,17 +629,15 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, if (!IndexedTy->isSized()) return; 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); + ComputeMaskedBits(Index, LocalKnownZero, LocalKnownOne, TD, Depth+1); TrailZ = std::min(TrailZ, unsigned(CountTrailingZeros_64(TypeSize) + LocalKnownZero.countTrailingOnes())); } } - KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) & Mask; + KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ); break; } case Instruction::PHI: { @@ -618,17 +672,13 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, break; // Ok, we have a PHI of the form L op= R. Check for low // zero bits. - APInt Mask2 = APInt::getAllOnesValue(BitWidth); - ComputeMaskedBits(R, Mask2, KnownZero2, KnownOne2, TD, Depth+1); - Mask2 = APInt::getLowBitsSet(BitWidth, - KnownZero2.countTrailingOnes()); + ComputeMaskedBits(R, 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); + ComputeMaskedBits(L, KnownZero3, KnownOne3, TD, Depth+1); - KnownZero = Mask & - APInt::getLowBitsSet(BitWidth, + KnownZero = APInt::getLowBitsSet(BitWidth, std::min(KnownZero2.countTrailingOnes(), KnownZero3.countTrailingOnes())); break; @@ -657,8 +707,8 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, 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); + ComputeMaskedBits(P->getIncomingValue(i), KnownZero2, KnownOne2, TD, + MaxDepth-1); KnownZero &= KnownZero2; KnownOne &= KnownOne2; // If all bits have been ruled out, there's no need to check @@ -673,10 +723,17 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { switch (II->getIntrinsicID()) { default: break; - case Intrinsic::ctpop: case Intrinsic::ctlz: case Intrinsic::cttz: { unsigned LowBits = Log2_32(BitWidth)+1; + // If this call is undefined for 0, the result will be less than 2^n. + if (II->getArgOperand(1) == ConstantInt::getTrue(II->getContext())) + LowBits -= 1; + KnownZero = APInt::getHighBitsSet(BitWidth, BitWidth - LowBits); + break; + } + case Intrinsic::ctpop: { + unsigned LowBits = Log2_32(BitWidth)+1; KnownZero = APInt::getHighBitsSet(BitWidth, BitWidth - LowBits); break; } @@ -687,6 +744,34 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, } } break; + case Instruction::ExtractValue: + if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I->getOperand(0))) { + ExtractValueInst *EVI = cast<ExtractValueInst>(I); + if (EVI->getNumIndices() != 1) break; + if (EVI->getIndices()[0] == 0) { + switch (II->getIntrinsicID()) { + default: break; + case Intrinsic::uadd_with_overflow: + case Intrinsic::sadd_with_overflow: + ComputeMaskedBitsAddSub(true, II->getArgOperand(0), + II->getArgOperand(1), false, KnownZero, + KnownOne, KnownZero2, KnownOne2, TD, Depth); + break; + case Intrinsic::usub_with_overflow: + case Intrinsic::ssub_with_overflow: + ComputeMaskedBitsAddSub(false, II->getArgOperand(0), + II->getArgOperand(1), false, KnownZero, + KnownOne, KnownZero2, KnownOne2, TD, Depth); + break; + case Intrinsic::umul_with_overflow: + case Intrinsic::smul_with_overflow: + ComputeMaskedBitsMul(II->getArgOperand(0), II->getArgOperand(1), + false, KnownZero, KnownOne, + KnownZero2, KnownOne2, TD, Depth); + break; + } + } + } } } @@ -702,8 +787,7 @@ void llvm::ComputeSignBit(Value *V, bool &KnownZero, bool &KnownOne, } APInt ZeroBits(BitWidth, 0); APInt OneBits(BitWidth, 0); - ComputeMaskedBits(V, APInt::getSignBit(BitWidth), ZeroBits, OneBits, TD, - Depth); + ComputeMaskedBits(V, ZeroBits, OneBits, TD, Depth); KnownOne = OneBits[BitWidth - 1]; KnownZero = ZeroBits[BitWidth - 1]; } @@ -712,10 +796,15 @@ void llvm::ComputeSignBit(Value *V, bool &KnownZero, bool &KnownOne, /// bit set when defined. For vectors return true if every element is known to /// be a power of two when defined. Supports values with integer or pointer /// types and vectors of integers. -bool llvm::isPowerOfTwo(Value *V, const TargetData *TD, unsigned Depth) { - if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) - return CI->getValue().isPowerOf2(); - // TODO: Handle vector constants. +bool llvm::isPowerOfTwo(Value *V, const TargetData *TD, bool OrZero, + unsigned Depth) { + if (Constant *C = dyn_cast<Constant>(V)) { + if (C->isNullValue()) + return OrZero; + if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) + return CI->getValue().isPowerOf2(); + // TODO: Handle vector constants. + } // 1 << X is clearly a power of two if the one is not shifted off the end. If // it is shifted off the end then the result is undefined. @@ -731,21 +820,36 @@ bool llvm::isPowerOfTwo(Value *V, const TargetData *TD, unsigned Depth) { if (Depth++ == MaxDepth) return false; + Value *X = 0, *Y = 0; + // A shift of a power of two is a power of two or zero. + if (OrZero && (match(V, m_Shl(m_Value(X), m_Value())) || + match(V, m_Shr(m_Value(X), m_Value())))) + return isPowerOfTwo(X, TD, /*OrZero*/true, Depth); + if (ZExtInst *ZI = dyn_cast<ZExtInst>(V)) - return isPowerOfTwo(ZI->getOperand(0), TD, Depth); + return isPowerOfTwo(ZI->getOperand(0), TD, OrZero, Depth); if (SelectInst *SI = dyn_cast<SelectInst>(V)) - return isPowerOfTwo(SI->getTrueValue(), TD, Depth) && - isPowerOfTwo(SI->getFalseValue(), TD, Depth); + return isPowerOfTwo(SI->getTrueValue(), TD, OrZero, Depth) && + isPowerOfTwo(SI->getFalseValue(), TD, OrZero, Depth); + + if (OrZero && match(V, m_And(m_Value(X), m_Value(Y)))) { + // A power of two and'd with anything is a power of two or zero. + if (isPowerOfTwo(X, TD, /*OrZero*/true, Depth) || + isPowerOfTwo(Y, TD, /*OrZero*/true, Depth)) + return true; + // X & (-X) is always a power of two or zero. + if (match(X, m_Neg(m_Specific(Y))) || match(Y, m_Neg(m_Specific(X)))) + return true; + return false; + } // An exact divide or right shift can only shift off zero bits, so the result // is a power of two only if the first operand is a power of two and not // copying a sign bit (sdiv int_min, 2). - if (match(V, m_LShr(m_Value(), m_Value())) || - match(V, m_UDiv(m_Value(), m_Value()))) { - PossiblyExactOperator *PEO = cast<PossiblyExactOperator>(V); - if (PEO->isExact()) - return isPowerOfTwo(PEO->getOperand(0), TD, Depth); + if (match(V, m_Exact(m_LShr(m_Value(), m_Value()))) || + match(V, m_Exact(m_UDiv(m_Value(), m_Value())))) { + return isPowerOfTwo(cast<Operator>(V)->getOperand(0), TD, OrZero, Depth); } return false; @@ -767,7 +871,7 @@ bool llvm::isKnownNonZero(Value *V, const TargetData *TD, unsigned Depth) { } // The remaining tests are all recursive, so bail out if we hit the limit. - if (Depth++ == MaxDepth) + if (Depth++ >= MaxDepth) return false; unsigned BitWidth = getBitWidth(V->getType(), TD); @@ -785,13 +889,13 @@ bool llvm::isKnownNonZero(Value *V, const TargetData *TD, unsigned Depth) { // if the lowest bit is shifted off the end. if (BitWidth && match(V, m_Shl(m_Value(X), m_Value(Y)))) { // shl nuw can't remove any non-zero bits. - BinaryOperator *BO = cast<BinaryOperator>(V); + OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(V); if (BO->hasNoUnsignedWrap()) return isKnownNonZero(X, TD, Depth); APInt KnownZero(BitWidth, 0); APInt KnownOne(BitWidth, 0); - ComputeMaskedBits(X, APInt(BitWidth, 1), KnownZero, KnownOne, TD, Depth); + ComputeMaskedBits(X, KnownZero, KnownOne, TD, Depth); if (KnownOne[0]) return true; } @@ -799,7 +903,7 @@ bool llvm::isKnownNonZero(Value *V, const TargetData *TD, unsigned Depth) { // defined if the sign bit is shifted off the end. else if (match(V, m_Shr(m_Value(X), m_Value(Y)))) { // shr exact can only shift out zero bits. - BinaryOperator *BO = cast<BinaryOperator>(V); + PossiblyExactOperator *BO = cast<PossiblyExactOperator>(V); if (BO->isExact()) return isKnownNonZero(X, TD, Depth); @@ -809,10 +913,8 @@ bool llvm::isKnownNonZero(Value *V, const TargetData *TD, unsigned Depth) { return true; } // div exact can only produce a zero if the dividend is zero. - else if (match(V, m_IDiv(m_Value(X), m_Value()))) { - BinaryOperator *BO = cast<BinaryOperator>(V); - if (BO->isExact()) - return isKnownNonZero(X, TD, Depth); + else if (match(V, m_Exact(m_IDiv(m_Value(X), m_Value())))) { + return isKnownNonZero(X, TD, Depth); } // X + Y. else if (match(V, m_Add(m_Value(X), m_Value(Y)))) { @@ -835,20 +937,29 @@ bool llvm::isKnownNonZero(Value *V, const TargetData *TD, unsigned Depth) { APInt Mask = APInt::getSignedMaxValue(BitWidth); // The sign bit of X is set. If some other bit is set then X is not equal // to INT_MIN. - ComputeMaskedBits(X, Mask, KnownZero, KnownOne, TD, Depth); + ComputeMaskedBits(X, KnownZero, KnownOne, TD, Depth); if ((KnownOne & Mask) != 0) return true; // The sign bit of Y is set. If some other bit is set then Y is not equal // to INT_MIN. - ComputeMaskedBits(Y, Mask, KnownZero, KnownOne, TD, Depth); + ComputeMaskedBits(Y, KnownZero, KnownOne, TD, Depth); if ((KnownOne & Mask) != 0) return true; } // The sum of a non-negative number and a power of two is not zero. - if (XKnownNonNegative && isPowerOfTwo(Y, TD, Depth)) + if (XKnownNonNegative && isPowerOfTwo(Y, TD, /*OrZero*/false, Depth)) return true; - if (YKnownNonNegative && isPowerOfTwo(X, TD, Depth)) + if (YKnownNonNegative && isPowerOfTwo(X, TD, /*OrZero*/false, Depth)) + return true; + } + // X * Y. + else if (match(V, m_Mul(m_Value(X), m_Value(Y)))) { + OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(V); + // If X and Y are non-zero then so is X * Y as long as the multiplication + // does not overflow. + if ((BO->hasNoSignedWrap() || BO->hasNoUnsignedWrap()) && + isKnownNonZero(X, TD, Depth) && isKnownNonZero(Y, TD, Depth)) return true; } // (C ? X : Y) != 0 if X != 0 and Y != 0. @@ -861,8 +972,7 @@ bool llvm::isKnownNonZero(Value *V, const TargetData *TD, unsigned Depth) { if (!BitWidth) return false; APInt KnownZero(BitWidth, 0); APInt KnownOne(BitWidth, 0); - ComputeMaskedBits(V, APInt::getAllOnesValue(BitWidth), KnownZero, KnownOne, - TD, Depth); + ComputeMaskedBits(V, KnownZero, KnownOne, TD, Depth); return KnownOne != 0; } @@ -878,7 +988,7 @@ bool llvm::isKnownNonZero(Value *V, const TargetData *TD, unsigned Depth) { bool llvm::MaskedValueIsZero(Value *V, const APInt &Mask, const TargetData *TD, unsigned Depth) { APInt KnownZero(Mask.getBitWidth(), 0), KnownOne(Mask.getBitWidth(), 0); - ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD, Depth); + ComputeMaskedBits(V, KnownZero, KnownOne, TD, Depth); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); return (KnownZero & Mask) == Mask; } @@ -917,30 +1027,28 @@ unsigned llvm::ComputeNumSignBits(Value *V, const TargetData *TD, Tmp = TyBits - U->getOperand(0)->getType()->getScalarSizeInBits(); return ComputeNumSignBits(U->getOperand(0), TD, Depth+1) + Tmp; - case Instruction::AShr: + case Instruction::AShr: { Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1); - // ashr X, C -> adds C sign bits. - if (ConstantInt *C = dyn_cast<ConstantInt>(U->getOperand(1))) { - Tmp += C->getZExtValue(); + // ashr X, C -> adds C sign bits. Vectors too. + const APInt *ShAmt; + if (match(U->getOperand(1), m_APInt(ShAmt))) { + Tmp += ShAmt->getZExtValue(); if (Tmp > TyBits) Tmp = TyBits; } - // vector ashr X, <C, C, C, C> -> adds C sign bits - if (ConstantVector *C = dyn_cast<ConstantVector>(U->getOperand(1))) { - if (ConstantInt *CI = dyn_cast_or_null<ConstantInt>(C->getSplatValue())) { - Tmp += CI->getZExtValue(); - if (Tmp > TyBits) Tmp = TyBits; - } - } return Tmp; - case Instruction::Shl: - if (ConstantInt *C = dyn_cast<ConstantInt>(U->getOperand(1))) { + } + case Instruction::Shl: { + const APInt *ShAmt; + if (match(U->getOperand(1), m_APInt(ShAmt))) { // shl destroys sign bits. Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1); - if (C->getZExtValue() >= TyBits || // Bad shift. - C->getZExtValue() >= Tmp) break; // Shifted all sign bits out. - return Tmp - C->getZExtValue(); + Tmp2 = ShAmt->getZExtValue(); + if (Tmp2 >= TyBits || // Bad shift. + Tmp2 >= Tmp) break; // Shifted all sign bits out. + return Tmp - Tmp2; } break; + } case Instruction::And: case Instruction::Or: case Instruction::Xor: // NOT is handled here. @@ -971,13 +1079,11 @@ unsigned llvm::ComputeNumSignBits(Value *V, const TargetData *TD, if (ConstantInt *CRHS = dyn_cast<ConstantInt>(U->getOperand(1))) if (CRHS->isAllOnesValue()) { APInt KnownZero(TyBits, 0), KnownOne(TyBits, 0); - APInt Mask = APInt::getAllOnesValue(TyBits); - ComputeMaskedBits(U->getOperand(0), Mask, KnownZero, KnownOne, TD, - Depth+1); + ComputeMaskedBits(U->getOperand(0), KnownZero, KnownOne, TD, Depth+1); // If the input is known to be 0 or 1, the output is 0/-1, which is all // sign bits set. - if ((KnownZero | APInt(TyBits, 1)) == Mask) + if ((KnownZero | APInt(TyBits, 1)).isAllOnesValue()) return TyBits; // If we are subtracting one from a positive number, there is no carry @@ -998,12 +1104,10 @@ unsigned llvm::ComputeNumSignBits(Value *V, const TargetData *TD, if (ConstantInt *CLHS = dyn_cast<ConstantInt>(U->getOperand(0))) if (CLHS->isNullValue()) { APInt KnownZero(TyBits, 0), KnownOne(TyBits, 0); - APInt Mask = APInt::getAllOnesValue(TyBits); - ComputeMaskedBits(U->getOperand(1), Mask, KnownZero, KnownOne, - TD, Depth+1); + ComputeMaskedBits(U->getOperand(1), KnownZero, KnownOne, TD, Depth+1); // If the input is known to be 0 or 1, the output is 0/-1, which is all // sign bits set. - if ((KnownZero | APInt(TyBits, 1)) == Mask) + if ((KnownZero | APInt(TyBits, 1)).isAllOnesValue()) return TyBits; // If the input is known to be positive (the sign bit is known clear), @@ -1045,8 +1149,8 @@ unsigned llvm::ComputeNumSignBits(Value *V, const TargetData *TD, // Finally, if we can prove that the top bits of the result are 0's or 1's, // use this information. APInt KnownZero(TyBits, 0), KnownOne(TyBits, 0); - APInt Mask = APInt::getAllOnesValue(TyBits); - ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD, Depth); + APInt Mask; + ComputeMaskedBits(V, KnownZero, KnownOne, TD, Depth); if (KnownZero.isNegative()) { // sign bit is 0 Mask = KnownZero; @@ -1282,23 +1386,21 @@ Value *llvm::isBytewiseValue(Value *V) { } } - // A ConstantArray is splatable if all its members are equal and also - // splatable. - if (ConstantArray *CA = dyn_cast<ConstantArray>(V)) { - if (CA->getNumOperands() == 0) - return 0; - - Value *Val = isBytewiseValue(CA->getOperand(0)); + // A ConstantDataArray/Vector is splatable if all its members are equal and + // also splatable. + if (ConstantDataSequential *CA = dyn_cast<ConstantDataSequential>(V)) { + Value *Elt = CA->getElementAsConstant(0); + Value *Val = isBytewiseValue(Elt); if (!Val) return 0; - for (unsigned I = 1, E = CA->getNumOperands(); I != E; ++I) - if (CA->getOperand(I-1) != CA->getOperand(I)) + for (unsigned I = 1, E = CA->getNumElements(); I != E; ++I) + if (CA->getElementAsConstant(I) != Elt) return 0; return Val; } - + // Conceptually, we could handle things like: // %a = zext i8 %X to i16 // %b = shl i16 %a, 8 @@ -1395,50 +1497,44 @@ static Value *BuildSubAggregate(Value *From, ArrayRef<unsigned> idx_range, Value *llvm::FindInsertedValue(Value *V, ArrayRef<unsigned> idx_range, Instruction *InsertBefore) { // Nothing to index? Just return V then (this is useful at the end of our - // recursion) + // recursion). if (idx_range.empty()) return V; - // We have indices, so V should have an indexable type - assert((V->getType()->isStructTy() || V->getType()->isArrayTy()) - && "Not looking at a struct or array?"); - assert(ExtractValueInst::getIndexedType(V->getType(), idx_range) - && "Invalid indices for type?"); - CompositeType *PTy = cast<CompositeType>(V->getType()); - - if (isa<UndefValue>(V)) - return UndefValue::get(ExtractValueInst::getIndexedType(PTy, - idx_range)); - else if (isa<ConstantAggregateZero>(V)) - return Constant::getNullValue(ExtractValueInst::getIndexedType(PTy, - idx_range)); - else if (Constant *C = dyn_cast<Constant>(V)) { - if (isa<ConstantArray>(C) || isa<ConstantStruct>(C)) - // Recursively process this constant - return FindInsertedValue(C->getOperand(idx_range[0]), idx_range.slice(1), - InsertBefore); - } else if (InsertValueInst *I = dyn_cast<InsertValueInst>(V)) { + // We have indices, so V should have an indexable type. + assert((V->getType()->isStructTy() || V->getType()->isArrayTy()) && + "Not looking at a struct or array?"); + assert(ExtractValueInst::getIndexedType(V->getType(), idx_range) && + "Invalid indices for type?"); + + if (Constant *C = dyn_cast<Constant>(V)) { + C = C->getAggregateElement(idx_range[0]); + if (C == 0) return 0; + return FindInsertedValue(C, idx_range.slice(1), InsertBefore); + } + + if (InsertValueInst *I = dyn_cast<InsertValueInst>(V)) { // Loop the indices for the insertvalue instruction in parallel with the // requested indices const unsigned *req_idx = idx_range.begin(); for (const unsigned *i = I->idx_begin(), *e = I->idx_end(); i != e; ++i, ++req_idx) { if (req_idx == idx_range.end()) { - if (InsertBefore) - // The requested index identifies a part of a nested aggregate. Handle - // this specially. For example, - // %A = insertvalue { i32, {i32, i32 } } undef, i32 10, 1, 0 - // %B = insertvalue { i32, {i32, i32 } } %A, i32 11, 1, 1 - // %C = extractvalue {i32, { i32, i32 } } %B, 1 - // This can be changed into - // %A = insertvalue {i32, i32 } undef, i32 10, 0 - // %C = insertvalue {i32, i32 } %A, i32 11, 1 - // which allows the unused 0,0 element from the nested struct to be - // removed. - return BuildSubAggregate(V, makeArrayRef(idx_range.begin(), req_idx), - InsertBefore); - else - // We can't handle this without inserting insertvalues + // We can't handle this without inserting insertvalues + if (!InsertBefore) return 0; + + // The requested index identifies a part of a nested aggregate. Handle + // this specially. For example, + // %A = insertvalue { i32, {i32, i32 } } undef, i32 10, 1, 0 + // %B = insertvalue { i32, {i32, i32 } } %A, i32 11, 1, 1 + // %C = extractvalue {i32, { i32, i32 } } %B, 1 + // This can be changed into + // %A = insertvalue {i32, i32 } undef, i32 10, 0 + // %C = insertvalue {i32, i32 } %A, i32 11, 1 + // which allows the unused 0,0 element from the nested struct to be + // removed. + return BuildSubAggregate(V, makeArrayRef(idx_range.begin(), req_idx), + InsertBefore); } // This insert value inserts something else than what we are looking for. @@ -1454,7 +1550,9 @@ Value *llvm::FindInsertedValue(Value *V, ArrayRef<unsigned> idx_range, return FindInsertedValue(I->getInsertedValueOperand(), makeArrayRef(req_idx, idx_range.end()), InsertBefore); - } else if (ExtractValueInst *I = dyn_cast<ExtractValueInst>(V)) { + } + + if (ExtractValueInst *I = dyn_cast<ExtractValueInst>(V)) { // If we're extracting a value from an aggregrate that was extracted from // something else, we can extract from that something else directly instead. // However, we will need to chain I's indices with the requested indices. @@ -1486,7 +1584,8 @@ Value *llvm::FindInsertedValue(Value *V, ArrayRef<unsigned> idx_range, Value *llvm::GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset, const TargetData &TD) { Operator *PtrOp = dyn_cast<Operator>(Ptr); - if (PtrOp == 0) return Ptr; + if (PtrOp == 0 || Ptr->getType()->isVectorTy()) + return Ptr; // Just look through bitcasts. if (PtrOp->getOpcode() == Instruction::BitCast) @@ -1521,34 +1620,19 @@ Value *llvm::GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset, } -/// GetConstantStringInfo - This function computes the length of a +/// 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<BitCastInst>(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<GetElementPtrInst>(V)) { - GEP = GEPI; - } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { - if (CE->getOpcode() == Instruction::BitCast) - return GetConstantStringInfo(CE->getOperand(0), Str, Offset, StopAtNul); - if (CE->getOpcode() != Instruction::GetElementPtr) - return false; - GEP = CE; - } +bool llvm::getConstantStringInfo(const Value *V, StringRef &Str, + uint64_t Offset, bool TrimAtNul) { + assert(V); + + // Look through bitcast instructions and geps. + V = V->stripPointerCasts(); - if (GEP) { + // If the value is a GEP instructionor constant expression, treat it as an + // offset. + if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) { // Make sure the GEP has exactly three arguments. if (GEP->getNumOperands() != 3) return false; @@ -1573,51 +1657,48 @@ bool llvm::GetConstantStringInfo(const Value *V, std::string &Str, StartIdx = CI->getZExtValue(); else return false; - return GetConstantStringInfo(GEP->getOperand(0), Str, StartIdx+Offset, - StopAtNul); + return getConstantStringInfo(GEP->getOperand(0), Str, StartIdx+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. - const GlobalVariable* GV = dyn_cast<GlobalVariable>(V); + const GlobalVariable *GV = dyn_cast<GlobalVariable>(V); if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer()) return false; - const Constant *GlobalInit = GV->getInitializer(); - - // Handle the ConstantAggregateZero case - if (isa<ConstantAggregateZero>(GlobalInit)) { + + // Handle the all-zeros case + if (GV->getInitializer()->isNullValue()) { // This is a degenerate case. The initializer is constant zero so the // length of the string must be zero. - Str.clear(); + Str = ""; return true; } // Must be a Constant Array - const ConstantArray *Array = dyn_cast<ConstantArray>(GlobalInit); - if (Array == 0 || !Array->getType()->getElementType()->isIntegerTy(8)) + const ConstantDataArray *Array = + dyn_cast<ConstantDataArray>(GV->getInitializer()); + if (Array == 0 || !Array->isString()) return false; // Get the number of elements in the array - uint64_t NumElts = Array->getType()->getNumElements(); - + uint64_t NumElts = Array->getType()->getArrayNumElements(); + + // Start out with the entire array in the StringRef. + Str = Array->getAsString(); + 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<ConstantInt>(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(); - } + // Skip over 'offset' bytes. + Str = Str.substr(Offset); - // The array isn't null terminated, but maybe this is a memcpy, not a strcpy. + if (TrimAtNul) { + // Trim off the \0 and anything after it. If the array is not nul + // terminated, we just return the whole end of string. The client may know + // some other way that the string is length-bound. + Str = Str.substr(0, Str.find('\0')); + } return true; } @@ -1629,8 +1710,7 @@ bool llvm::GetConstantStringInfo(const Value *V, std::string &Str, /// the specified pointer, return 'len+1'. If we can't, return 0. static uint64_t GetStringLengthH(Value *V, SmallPtrSet<PHINode*, 32> &PHIs) { // Look through noop bitcast instructions. - if (BitCastInst *BCI = dyn_cast<BitCastInst>(V)) - return GetStringLengthH(BCI->getOperand(0), PHIs); + V = V->stripPointerCasts(); // If this is a PHI node, there are two cases: either we have already seen it // or we haven't. @@ -1666,75 +1746,13 @@ static uint64_t GetStringLengthH(Value *V, SmallPtrSet<PHINode*, 32> &PHIs) { 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<GetElementPtrInst>(V)) { - GEP = GEPI; - } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(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<ConstantInt>(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<ConstantInt>(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<GlobalVariable>(GEP->getOperand(0)); - if (!GV || !GV->isConstant() || !GV->hasInitializer() || - GV->mayBeOverridden()) + + // Otherwise, see if we can read the string. + StringRef StrData; + if (!getConstantStringInfo(V, StrData)) 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<ConstantAggregateZero>(GlobalInit)) - return 1; // Len = 0 offset by 1. - - // Must be a Constant Array - ConstantArray *Array = dyn_cast<ConstantArray>(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<ConstantInt>(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'. + return StrData.size()+1; } /// GetStringLength - If we can compute the length of the string pointed to by @@ -1793,3 +1811,94 @@ bool llvm::onlyUsedByLifetimeMarkers(const Value *V) { } return true; } + +bool llvm::isSafeToSpeculativelyExecute(const Value *V, + const TargetData *TD) { + const Operator *Inst = dyn_cast<Operator>(V); + if (!Inst) + return false; + + for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i) + if (Constant *C = dyn_cast<Constant>(Inst->getOperand(i))) + if (C->canTrap()) + return false; + + switch (Inst->getOpcode()) { + default: + return true; + case Instruction::UDiv: + case Instruction::URem: + // x / y is undefined if y == 0, but calcuations like x / 3 are safe. + return isKnownNonZero(Inst->getOperand(1), TD); + case Instruction::SDiv: + case Instruction::SRem: { + Value *Op = Inst->getOperand(1); + // x / y is undefined if y == 0 + if (!isKnownNonZero(Op, TD)) + return false; + // x / y might be undefined if y == -1 + unsigned BitWidth = getBitWidth(Op->getType(), TD); + if (BitWidth == 0) + return false; + APInt KnownZero(BitWidth, 0); + APInt KnownOne(BitWidth, 0); + ComputeMaskedBits(Op, KnownZero, KnownOne, TD); + return !!KnownZero; + } + case Instruction::Load: { + const LoadInst *LI = cast<LoadInst>(Inst); + if (!LI->isUnordered()) + return false; + return LI->getPointerOperand()->isDereferenceablePointer(); + } + case Instruction::Call: { + if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { + switch (II->getIntrinsicID()) { + // These synthetic intrinsics have no side-effects, and just mark + // information about their operands. + // FIXME: There are other no-op synthetic instructions that potentially + // should be considered at least *safe* to speculate... + case Intrinsic::dbg_declare: + case Intrinsic::dbg_value: + return true; + + case Intrinsic::bswap: + case Intrinsic::ctlz: + case Intrinsic::ctpop: + case Intrinsic::cttz: + case Intrinsic::objectsize: + case Intrinsic::sadd_with_overflow: + case Intrinsic::smul_with_overflow: + case Intrinsic::ssub_with_overflow: + case Intrinsic::uadd_with_overflow: + case Intrinsic::umul_with_overflow: + case Intrinsic::usub_with_overflow: + return true; + // TODO: some fp intrinsics are marked as having the same error handling + // as libm. They're safe to speculate when they won't error. + // TODO: are convert_{from,to}_fp16 safe? + // TODO: can we list target-specific intrinsics here? + default: break; + } + } + return false; // The called function could have undefined behavior or + // side-effects, even if marked readnone nounwind. + } + case Instruction::VAArg: + case Instruction::Alloca: + case Instruction::Invoke: + case Instruction::PHI: + case Instruction::Store: + case Instruction::Ret: + case Instruction::Br: + case Instruction::IndirectBr: + case Instruction::Switch: + case Instruction::Unreachable: + case Instruction::Fence: + case Instruction::LandingPad: + case Instruction::AtomicRMW: + case Instruction::AtomicCmpXchg: + case Instruction::Resume: + return false; // Misc instructions which have effects + } +} |