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Avoid setting bits that aren't demanded. 

llvm-svn: 47098
This commit is contained in:
Dan Gohman 2008-02-13 22:43:25 +00:00
parent ad66526ede
commit 95d25d39d0
1 changed files with 3 additions and 3 deletions
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6
llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
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@ -1237,7 +1237,7 @@ void SelectionDAG::ComputeMaskedBits(SDOperand Op, const APInt &Mask,
KnownZero = KnownZero.lshr(ShAmt); KnownZero = KnownZero.lshr(ShAmt);
KnownOne = KnownOne.lshr(ShAmt); KnownOne = KnownOne.lshr(ShAmt);
APInt HighBits = APInt::getHighBitsSet(BitWidth, ShAmt); APInt HighBits = APInt::getHighBitsSet(BitWidth, ShAmt) & Mask;
KnownZero |= HighBits; // High bits known zero. KnownZero |= HighBits; // High bits known zero.
} }
return; return;
@ -1248,8 +1248,8 @@ void SelectionDAG::ComputeMaskedBits(SDOperand Op, const APInt &Mask,
APInt InDemandedMask = (Mask << ShAmt); APInt InDemandedMask = (Mask << ShAmt);
// If any of the demanded bits are produced by the sign extension, we also // If any of the demanded bits are produced by the sign extension, we also
// demand the input sign bit. // demand the input sign bit.
APInt HighBits = APInt::getHighBitsSet(BitWidth, ShAmt); APInt HighBits = APInt::getHighBitsSet(BitWidth, ShAmt) & Mask;
if (!!(HighBits & Mask)) if (HighBits.getBoolValue())
InDemandedMask |= APInt::getSignBit(BitWidth); InDemandedMask |= APInt::getSignBit(BitWidth);
ComputeMaskedBits(Op.getOperand(0), InDemandedMask, KnownZero, KnownOne, ComputeMaskedBits(Op.getOperand(0), InDemandedMask, KnownZero, KnownOne,