KnownZero = KnownZeroOut;
return;
}
+ case ISD::MUL: {
+ APInt Mask2 = APInt::getAllOnesValue(BitWidth);
+ ComputeMaskedBits(Op.getOperand(1), Mask2, KnownZero, KnownOne, Depth+1);
+ ComputeMaskedBits(Op.getOperand(0), Mask2, KnownZero2, KnownOne2, 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.clear();
+ unsigned TrailZ = KnownZero.countTrailingOnes() +
+ KnownZero2.countTrailingOnes();
+ unsigned LeadZ = std::max(KnownZero.countLeadingOnes() +
+ KnownZero2.countLeadingOnes() +
+ 1, BitWidth) - BitWidth;
+
+ TrailZ = std::min(TrailZ, BitWidth);
+ LeadZ = std::min(LeadZ, BitWidth);
+ KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) |
+ APInt::getHighBitsSet(BitWidth, LeadZ);
+ KnownZero &= Mask;
+ return;
+ }
+ case ISD::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 greater than the denominator.
+ APInt AllOnes = APInt::getAllOnesValue(BitWidth);
+ ComputeMaskedBits(Op.getOperand(0),
+ AllOnes, KnownZero2, KnownOne2, Depth+1);
+ unsigned LeadZ = KnownZero2.countLeadingOnes();
+
+ KnownOne2.clear();
+ KnownZero2.clear();
+ ComputeMaskedBits(Op.getOperand(1),
+ AllOnes, KnownZero2, KnownOne2, Depth+1);
+ LeadZ = std::min(BitWidth,
+ LeadZ + BitWidth - KnownOne2.countLeadingZeros());
+
+ KnownZero = APInt::getHighBitsSet(BitWidth, LeadZ) & Mask;
+ return;
+ }
case ISD::SELECT:
ComputeMaskedBits(Op.getOperand(2), Mask, KnownZero, KnownOne, Depth+1);
ComputeMaskedBits(Op.getOperand(1), Mask, KnownZero2, KnownOne2, Depth+1);
KnownZero = APInt::getHighBitsSet(BitWidth, BitWidth - 1);
return;
+ case ISD::SUB: {
+ if (ConstantSDNode *CLHS = dyn_cast<ConstantSDNode>(Op.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->getAPIntValue().isNonNegative()) {
+ unsigned NLZ = (CLHS->getAPIntValue()+1).countLeadingZeros();
+ // NLZ can't be BitWidth with no sign bit
+ APInt MaskV = APInt::getHighBitsSet(BitWidth, NLZ+1);
+ ComputeMaskedBits(Op.getOperand(1), MaskV, KnownZero2, KnownOne2,
+ 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->getAPIntValue().countLeadingZeros();
+ // Top bits known zero.
+ KnownZero = APInt::getHighBitsSet(BitWidth, NLZ2) & Mask;
+ }
+ }
+ }
+ }
+ // fall through
case ISD::ADD: {
- // If either the LHS or the RHS are Zero, the result is zero.
- ComputeMaskedBits(Op.getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
- ComputeMaskedBits(Op.getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
- assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
- assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
-
// Output known-0 bits are known if clear or set in both the low clear bits
// common to both LHS & RHS. For example, 8+(X<<3) is known to have the
// low 3 bits clear.
- unsigned KnownZeroOut = std::min(KnownZero.countTrailingOnes(),
- KnownZero2.countTrailingOnes());
-
- KnownZero = APInt::getLowBitsSet(BitWidth, KnownZeroOut);
- KnownOne = APInt(BitWidth, 0);
+ APInt Mask2 = APInt::getLowBitsSet(BitWidth, Mask.countTrailingOnes());
+ ComputeMaskedBits(Op.getOperand(0), Mask2, KnownZero2, KnownOne2, Depth+1);
+ assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
+ unsigned KnownZeroOut = KnownZero2.countTrailingOnes();
+
+ ComputeMaskedBits(Op.getOperand(1), Mask2, KnownZero2, KnownOne2, Depth+1);
+ assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
+ KnownZeroOut = std::min(KnownZeroOut,
+ KnownZero2.countTrailingOnes());
+
+ KnownZero |= APInt::getLowBitsSet(BitWidth, KnownZeroOut);
return;
}
- case ISD::SUB: {
- ConstantSDNode *CLHS = dyn_cast<ConstantSDNode>(Op.getOperand(0));
- if (!CLHS) return;
-
- // 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->getAPIntValue().isNonNegative()) {
- unsigned NLZ = (CLHS->getAPIntValue()+1).countLeadingZeros();
- // NLZ can't be BitWidth with no sign bit
- APInt MaskV = APInt::getHighBitsSet(BitWidth, NLZ+1);
- ComputeMaskedBits(Op.getOperand(1), MaskV, KnownZero, KnownOne, 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 ((KnownZero & MaskV) == MaskV) {
- unsigned NLZ2 = CLHS->getAPIntValue().countLeadingZeros();
- // Top bits known zero.
- KnownZero = APInt::getHighBitsSet(BitWidth, NLZ2) & Mask;
- KnownOne = APInt(BitWidth, 0); // No one bits known.
- } else {
- KnownZero = KnownOne = APInt(BitWidth, 0); // Otherwise, nothing known.
+ case ISD::SREM:
+ if (ConstantSDNode *Rem = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
+ APInt RA = Rem->getAPIntValue();
+ if (RA.isPowerOf2() || (-RA).isPowerOf2()) {
+ APInt LowBits = RA.isStrictlyPositive() ? ((RA - 1) | RA) : ~RA;
+ APInt Mask2 = LowBits | APInt::getSignBit(BitWidth);
+ ComputeMaskedBits(Op.getOperand(0), Mask2,KnownZero2,KnownOne2,Depth+1);
+
+ // The sign of a remainder is equal to the sign of the first
+ // operand (zero being positive).
+ if (KnownZero2[BitWidth-1] || ((KnownZero2 & LowBits) == LowBits))
+ KnownZero2 |= ~LowBits;
+ else if (KnownOne2[BitWidth-1])
+ KnownOne2 |= ~LowBits;
+
+ KnownZero |= KnownZero2 & Mask;
+ KnownOne |= KnownOne2 & Mask;
+
+ assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
+ }
+ }
+ return;
+ case ISD::UREM: {
+ if (ConstantSDNode *Rem = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
+ APInt RA = Rem->getAPIntValue();
+ if (RA.isStrictlyPositive() && RA.isPowerOf2()) {
+ APInt LowBits = (RA - 1) | RA;
+ APInt Mask2 = LowBits & Mask;
+ KnownZero |= ~LowBits & Mask;
+ ComputeMaskedBits(Op.getOperand(0), Mask2, KnownZero, KnownOne,Depth+1);
+ assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
+ 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(Op.getOperand(0), AllOnes, KnownZero, KnownOne,
+ Depth+1);
+ ComputeMaskedBits(Op.getOperand(1), AllOnes, KnownZero2, KnownOne2,
+ Depth+1);
+
+ uint32_t Leaders = std::max(KnownZero.countLeadingOnes(),
+ KnownZero2.countLeadingOnes());
+ KnownOne.clear();
+ KnownZero = APInt::getHighBitsSet(BitWidth, Leaders) & Mask;
return;
}
default:
return;
}
+ KnownZero.clear(); KnownOne.clear(); // Start out not knowing anything.
+
if (Depth == 6 || Mask == 0)
return; // Limit search depth.
User *I = dyn_cast<User>(V);
if (!I) return;
- KnownZero.clear(); KnownOne.clear(); // Don't know anything.
APInt KnownZero2(KnownZero), KnownOne2(KnownOne);
-
switch (getOpcode(I)) {
default: break;
case Instruction::And: {
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.clear();
unsigned TrailZ = KnownZero.countTrailingOnes() +
KnownZero2.countTrailingOnes();
+ unsigned LeadZ = std::max(KnownZero.countLeadingOnes() +
+ KnownZero2.countLeadingOnes() +
+ 1, BitWidth) - BitWidth;
+
TrailZ = std::min(TrailZ, BitWidth);
- KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ);
+ LeadZ = std::min(LeadZ, BitWidth);
+ KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) |
+ APInt::getHighBitsSet(BitWidth, LeadZ);
KnownZero &= Mask;
return;
}
+ 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 greater than the denominator.
+ APInt AllOnes = APInt::getAllOnesValue(BitWidth);
+ ComputeMaskedBits(I->getOperand(0),
+ AllOnes, KnownZero2, KnownOne2, Depth+1);
+ unsigned LeadZ = KnownZero2.countLeadingOnes();
+
+ KnownOne2.clear();
+ KnownZero2.clear();
+ ComputeMaskedBits(I->getOperand(1),
+ AllOnes, KnownZero2, KnownOne2, Depth+1);
+ LeadZ = std::min(BitWidth,
+ LeadZ + BitWidth - KnownOne2.countLeadingZeros());
+
+ KnownZero = APInt::getHighBitsSet(BitWidth, LeadZ) & Mask;
+ return;
+ }
case Instruction::Select:
ComputeMaskedBits(I->getOperand(2), Mask, KnownZero, KnownOne, Depth+1);
ComputeMaskedBits(I->getOperand(1), Mask, KnownZero2, KnownOne2, Depth+1);
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, KnownZero, KnownOne, Depth+1);
+ ComputeMaskedBits(I->getOperand(1), MaskV, KnownZero2, KnownOne2,
+ 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 ((KnownZero & MaskV) == MaskV) {
+ // 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;
- KnownOne = APInt(BitWidth, 0); // No one bits known.
- } else {
- KnownZero = KnownOne = APInt(BitWidth, 0); // Otherwise, nothing known.
}
- return;
}
}
}
// fall through
case Instruction::Add: {
- // If either the LHS or the RHS are Zero, the result is zero.
- ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
- ComputeMaskedBits(I->getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
- assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
- assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
-
// Output known-0 bits are known if clear or set in both the low clear bits
// common to both LHS & RHS. For example, 8+(X<<3) is known to have the
// low 3 bits clear.
- unsigned KnownZeroOut = std::min(KnownZero.countTrailingOnes(),
- KnownZero2.countTrailingOnes());
-
- KnownZero = APInt::getLowBitsSet(BitWidth, KnownZeroOut);
- KnownOne = APInt(BitWidth, 0);
+ APInt Mask2 = APInt::getLowBitsSet(BitWidth, Mask.countTrailingOnes());
+ ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, Depth+1);
+ assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
+ unsigned KnownZeroOut = KnownZero2.countTrailingOnes();
+
+ ComputeMaskedBits(I->getOperand(1), Mask2, KnownZero2, KnownOne2, Depth+1);
+ assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
+ KnownZeroOut = std::min(KnownZeroOut,
+ KnownZero2.countTrailingOnes());
+
+ KnownZero |= APInt::getLowBitsSet(BitWidth, KnownZeroOut);
return;
}
case Instruction::SRem:
}
}
break;
- case Instruction::URem:
+ case Instruction::URem: {
if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) {
APInt RA = Rem->getValue();
if (RA.isStrictlyPositive() && RA.isPowerOf2()) {
KnownZero |= ~LowBits & Mask;
ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne,Depth+1);
assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
+ break;
}
- } else {
- // Since the result is less than or equal to RHS, any leading zero bits
- // in RHS must also exist in the result.
- APInt AllOnes = APInt::getAllOnesValue(BitWidth);
- ComputeMaskedBits(I->getOperand(1), AllOnes, KnownZero2, KnownOne2,
- Depth+1);
-
- uint32_t Leaders = KnownZero2.countLeadingOnes();
- KnownZero |= APInt::getHighBitsSet(BitWidth, Leaders) & Mask;
- assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
}
+
+ // 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,
+ Depth+1);
+ ComputeMaskedBits(I->getOperand(1), AllOnes, KnownZero2, KnownOne2,
+ Depth+1);
+
+ uint32_t Leaders = std::max(KnownZero.countLeadingOnes(),
+ KnownZero2.countLeadingOnes());
+ KnownOne.clear();
+ KnownZero = APInt::getHighBitsSet(BitWidth, Leaders) & Mask;
break;
+ }
case Instruction::Alloca:
case Instruction::Malloc: {
}
break;
}
+ case Instruction::Call:
+ 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;
+ KnownZero = APInt::getHighBitsSet(BitWidth, BitWidth - LowBits);
+ break;
+ }
+ }
+ }
+ break;
}
}
APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0);
APInt &RHSKnownZero = KnownZero, &RHSKnownOne = KnownOne;
switch (I->getOpcode()) {
- default: break;
+ default:
+ ComputeMaskedBits(V, DemandedMask, RHSKnownZero, RHSKnownOne, Depth);
+ break;
case Instruction::And:
// If either the LHS or the RHS are Zero, the result is zero.
if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
LHSKnownZero, LHSKnownOne, Depth+1))
return true;
}
+ // Otherwise just hand the sub off to ComputeMaskedBits to fill in
+ // the known zeros and ones.
+ ComputeMaskedBits(V, DemandedMask, RHSKnownZero, RHSKnownOne, Depth);
break;
case Instruction::Shl:
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
}
}
break;
- case Instruction::URem:
+ case Instruction::URem: {
if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) {
APInt RA = Rem->getValue();
- if (RA.isPowerOf2()) {
+ if (RA.isStrictlyPositive() && RA.isPowerOf2()) {
APInt LowBits = (RA - 1) | RA;
APInt Mask2 = LowBits & DemandedMask;
KnownZero |= ~LowBits & DemandedMask;
return true;
assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
+ break;
}
- } else {
- APInt KnownZero2(BitWidth, 0), KnownOne2(BitWidth, 0);
- APInt AllOnes = APInt::getAllOnesValue(BitWidth);
- if (SimplifyDemandedBits(I->getOperand(1), AllOnes,
- KnownZero2, KnownOne2, Depth+1))
- return true;
-
- uint32_t Leaders = KnownZero2.countLeadingOnes();
- KnownZero |= APInt::getHighBitsSet(BitWidth, Leaders) & DemandedMask;
}
+
+ APInt KnownZero2(BitWidth, 0), KnownOne2(BitWidth, 0);
+ APInt AllOnes = APInt::getAllOnesValue(BitWidth);
+ ComputeMaskedBits(I->getOperand(0), AllOnes,
+ KnownZero2, KnownOne2, Depth+1);
+ uint32_t Leaders = KnownZero2.countLeadingOnes();
+ APInt HighZeros = APInt::getHighBitsSet(BitWidth, Leaders);
+ if (SimplifyDemandedBits(I->getOperand(1), ~HighZeros,
+ KnownZero2, KnownOne2, Depth+1))
+ return true;
+
+ Leaders = std::max(Leaders,
+ KnownZero2.countLeadingOnes());
+ KnownZero = APInt::getHighBitsSet(BitWidth, Leaders) & DemandedMask;
break;
}
+ }
// If the client is only demanding bits that we know, return the known
// constant.
projects / oota-llvm.git / commitdiff