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ShiftAmt might equal to zero. Handle this situation.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35094 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Zhou Sheng 2007-03-14 09:07:33 +00:00
parent 9670445cd4
commit adc149549d
1 changed files with 9 additions and 7 deletions
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16
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -1997,7 +1997,8 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
RHSKnownZero <<= ShiftAmt;
RHSKnownOne <<= ShiftAmt;
// low bits known zero.
RHSKnownZero |= APInt::getAllOnesValue(ShiftAmt).zextOrCopy(BitWidth);
if (ShiftAmt)
RHSKnownZero |= APInt::getAllOnesValue(ShiftAmt).zextOrCopy(BitWidth);
}
break;
case Instruction::LShr:
@ -2013,14 +2014,16 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
return true;
assert((RHSKnownZero & RHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
// Compute the new bits that are at the top now.
APInt HighBits(APInt::getAllOnesValue(ShiftAmt).zextOrCopy(BitWidth).shl(
BitWidth - ShiftAmt));
RHSKnownZero &= TypeMask;
RHSKnownOne &= TypeMask;
RHSKnownZero = APIntOps::lshr(RHSKnownZero, ShiftAmt);
RHSKnownOne = APIntOps::lshr(RHSKnownOne, ShiftAmt);
RHSKnownZero |= HighBits; // high bits known zero.
if (ShiftAmt) {
// Compute the new bits that are at the top now.
APInt HighBits(APInt::getAllOnesValue(BitWidth).shl(
BitWidth - ShiftAmt));
RHSKnownZero |= HighBits; // high bits known zero.
}
}
break;
case Instruction::AShr:
@ -2048,8 +2051,7 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
assert((RHSKnownZero & RHSKnownOne) == 0 &&
"Bits known to be one AND zero?");
// Compute the new bits that are at the top now.
APInt HighBits(APInt::getAllOnesValue(ShiftAmt).zextOrCopy(BitWidth).shl(
BitWidth - ShiftAmt));
APInt HighBits(APInt::getAllOnesValue(BitWidth).shl(BitWidth - ShiftAmt));
RHSKnownZero &= TypeMask;
RHSKnownOne &= TypeMask;
RHSKnownZero = APIntOps::lshr(RHSKnownZero, ShiftAmt);