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[ValueTracking] Prevent a call to computeKnownBits if we already know the state of the bit we would calculate. Also reuse a temporary APInt instead of creating a new one. 

llvm-svn: 300239
This commit is contained in:
Craig Topper 2017-04-13 19:04:45 +00:00
parent dcdb325fee
commit a80f2041f7
1 changed files with 8 additions and 7 deletions
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15
llvm/lib/Analysis/ValueTracking.cpp
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@ -918,13 +918,14 @@ static void computeKnownBitsFromOperator(const Operator *I, APInt &KnownZero,
// TODO: This could be generalized to clearing any bit set in y where the // TODO: This could be generalized to clearing any bit set in y where the
// following bit is known to be unset in y. // following bit is known to be unset in y.
Value *Y = nullptr; Value *Y = nullptr;
if (match(I->getOperand(0), m_Add(m_Specific(I->getOperand(1)), if (!KnownZero[0] && !KnownOne[0] &&
m_Value(Y))) || (match(I->getOperand(0), m_Add(m_Specific(I->getOperand(1)),
match(I->getOperand(1), m_Add(m_Specific(I->getOperand(0)), m_Value(Y))) ||
m_Value(Y)))) { match(I->getOperand(1), m_Add(m_Specific(I->getOperand(0)),
APInt KnownZero3(BitWidth, 0), KnownOne3(BitWidth, 0); m_Value(Y))))) {
computeKnownBits(Y, KnownZero3, KnownOne3, Depth + 1, Q); KnownZero2.clearAllBits(); KnownOne2.clearAllBits();
if (KnownOne3.countTrailingOnes() > 0) computeKnownBits(Y, KnownZero2, KnownOne2, Depth + 1, Q);
if (KnownOne2.countTrailingOnes() > 0)
KnownZero.setBit(0); KnownZero.setBit(0);
} }
break; break;