#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"
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
///
/// 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();
+ unsigned BitWidth = KnownZero.getBitWidth();
+
assert((V->getType()->isIntOrIntVectorTy() ||
V->getType()->getScalarType()->isPointerTy()) &&
"Not integer or pointer type!");
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.
- // FIXME: Remove.
- if (ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
- KnownZero.setAllBits(); KnownOne.setAllBits();
- for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
- APInt KnownZero2(BitWidth, 0), KnownOne2(BitWidth, 0);
- ComputeMaskedBits(CV->getOperand(i), Mask, KnownZero2, KnownOne2,
- TD, Depth);
- KnownZero &= KnownZero2;
- KnownOne &= KnownOne2;
- }
- return;
- }
+ // 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.
// 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()) {
+ if (Align == 0 && TD) {
if (GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV)) {
Type *ObjectType = GVar->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 (!GVar->isDeclaration() && !GVar->isWeakForLinker())
- Align = TD->getPreferredAlignment(GVar);
- else
- Align = TD->getABITypeAlignment(ObjectType);
+ 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();
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;
}
// 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);
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?");
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?");
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?");
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?");
-
- bool isKnownNegative = false;
- bool isKnownNonNegative = false;
- // If the multiplication is known not to overflow, compute the sign bit.
- if (Mask.isNegative() &&
- cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap()) {
- Value *Op1 = I->getOperand(1), *Op2 = I->getOperand(0);
- if (Op1 == Op2) {
- // The product of a number with itself is non-negative.
- isKnownNonNegative = true;
- } else {
- bool isKnownNonNegative1 = KnownZero.isNegative();
- bool isKnownNonNegative2 = KnownZero2.isNegative();
- bool isKnownNegative1 = KnownOne.isNegative();
- bool isKnownNegative2 = KnownOne2.isNegative();
- // The product of two numbers with the same sign is non-negative.
- isKnownNonNegative = (isKnownNegative1 && isKnownNegative2) ||
- (isKnownNonNegative1 && isKnownNonNegative2);
- // The product of a negative number and a non-negative number is either
- // negative or zero.
- if (!isKnownNonNegative)
- isKnownNegative = (isKnownNegative1 && isKnownNonNegative2 &&
- isKnownNonZero(Op2, TD, Depth)) ||
- (isKnownNegative2 && isKnownNonNegative1 &&
- 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);
- KnownZero &= Mask;
-
- // 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);
-
- 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?");
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.
// 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;
// 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);
// (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;
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);
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);
}
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;
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())
- KnownZero |= LHSKnownZero;
+ KnownZero.setBit(BitWidth - 1);
}
break;
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;
}
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);
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: {
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;
// taking conservative care to avoid excessive recursion.
if (Depth < MaxDepth - 1 && !KnownZero && !KnownOne) {
// Skip if every incoming value references to ourself.
- if (P->hasConstantValue() == P)
+ if (dyn_cast_or_null<UndefValue>(P->hasConstantValue()))
break;
KnownZero = APInt::getAllOnesValue(BitWidth);
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
}
}
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;
+ }
+ }
+ }
}
}
}
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];
}
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;
}
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;
}
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;
}
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;
}
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
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),
// 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;
// right.
unsigned PtrSize = TD.getPointerSizeInBits();
if (PtrSize < 64)
- Offset = (Offset << (64-PtrSize)) >> (64-PtrSize);
+ Offset = SignExtend64(Offset, PtrSize);
return GetPointerBaseWithConstantOffset(GEP->getPointerOperand(), Offset, TD);
}
-// FIXME: Remove this.
-bool llvm::GetConstantStringInfo(const Value *V, std::string &Str,
- uint64_t Offset) {
- StringRef Tmp;
- if (!getConstantStringInfo(V, Tmp, Offset))
- return false;
- Str = Tmp.str();
- return true;
-}
-
/// 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, StringRef &Str,
- uint64_t Offset) {
+ uint64_t Offset, bool TrimAtNul) {
assert(V);
// Look through bitcast instructions and geps.
// Skip over 'offset' bytes.
Str = Str.substr(Offset);
- // 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'));
+
+ 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;
}
return V;
}
+void
+llvm::GetUnderlyingObjects(Value *V,
+ SmallVectorImpl<Value *> &Objects,
+ const TargetData *TD,
+ unsigned MaxLookup) {
+ SmallPtrSet<Value *, 4> Visited;
+ SmallVector<Value *, 4> Worklist;
+ Worklist.push_back(V);
+ do {
+ Value *P = Worklist.pop_back_val();
+ P = GetUnderlyingObject(P, TD, MaxLookup);
+
+ if (!Visited.insert(P))
+ continue;
+
+ if (SelectInst *SI = dyn_cast<SelectInst>(P)) {
+ Worklist.push_back(SI->getTrueValue());
+ Worklist.push_back(SI->getFalseValue());
+ continue;
+ }
+
+ if (PHINode *PN = dyn_cast<PHINode>(P)) {
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ Worklist.push_back(PN->getIncomingValue(i));
+ continue;
+ }
+
+ Objects.push_back(P);
+ } while (!Worklist.empty());
+}
+
/// onlyUsedByLifetimeMarkers - Return true if the only users of this pointer
/// are lifetime markers.
///
return false;
APInt KnownZero(BitWidth, 0);
APInt KnownOne(BitWidth, 0);
- ComputeMaskedBits(Op, APInt::getAllOnesValue(BitWidth),
- KnownZero, KnownOne, TD);
+ ComputeMaskedBits(Op, KnownZero, KnownOne, TD);
return !!KnownZero;
}
case Instruction::Load: {
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 Instruction::Br:
case Instruction::IndirectBr:
case Instruction::Switch:
- case Instruction::Unwind:
case Instruction::Unreachable:
case Instruction::Fence:
case Instruction::LandingPad:
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