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Use APInt operators to calculate the carry bits, remove this loop.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35524 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Zhou Sheng 2007-03-31 02:38:39 +00:00
parent db5c993121
commit b9cb95f8e3
1 changed files with 2 additions and 16 deletions
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18
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -1243,22 +1243,8 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
// To compute this, we first compute the potential carry bits. These are
// the bits which may be modified. I'm not aware of a better way to do
// this scan.
APInt RHSVal(RHS->getValue());
bool CarryIn = false;
APInt CarryBits(BitWidth, 0);
const uint64_t *LHSKnownZeroRawVal = LHSKnownZero.getRawData(),
*RHSRawVal = RHSVal.getRawData();
for (uint32_t i = 0; i != RHSVal.getNumWords(); ++i) {
uint64_t AddVal = ~LHSKnownZeroRawVal[i] + RHSRawVal[i],
XorVal = ~LHSKnownZeroRawVal[i] ^ RHSRawVal[i];
uint64_t WordCarryBits = AddVal ^ XorVal + CarryIn;
if (AddVal < RHSRawVal[i])
CarryIn = true;
else
CarryIn = false;
CarryBits.setWordToValue(i, WordCarryBits);
}
const APInt& RHSVal = RHS->getValue();
APInt CarryBits((~LHSKnownZero + RHSVal) ^ (~LHSKnownZero ^ RHSVal));
// Now that we know which bits have carries, compute the known-1/0 sets.