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[InstSimplify] Guard against large shift amounts. 

These are always UB, but can happen for large integer inputs. Testing it
is very fragile as -simplifycfg will nuke the UB top-down.

llvm-svn: 339515
This commit is contained in:
Benjamin Kramer 2018-08-12 11:43:03 +00:00
parent 25cd609a64
commit bae6aab6fb
1 changed files with 3 additions and 3 deletions
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6
llvm/lib/Analysis/InstructionSimplify.cpp
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@ -1338,7 +1338,7 @@ static Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact,
const KnownBits YKnown = computeKnownBits(Y, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
const unsigned Width = Op0->getType()->getScalarSizeInBits();
const unsigned EffWidthY = Width - YKnown.countMinLeadingZeros();
if (EffWidthY <= ShRAmt->getZExtValue())
if (ShRAmt->uge(EffWidthY))
return X;
}
@ -1880,9 +1880,9 @@ static Value *SimplifyAndInst(Value *Op0, Value *Op1, const SimplifyQuery &Q,
match(Op0, m_c_Or(m_CombineAnd(m_NUWShl(m_Value(X), m_APInt(ShAmt)),
m_Value(XShifted)),
m_Value(Y)))) {
const unsigned ShftCnt = ShAmt->getZExtValue();
const KnownBits YKnown = computeKnownBits(Y, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
const unsigned Width = Op0->getType()->getScalarSizeInBits();
const unsigned ShftCnt = ShAmt->getLimitedValue(Width);
const KnownBits YKnown = computeKnownBits(Y, Q.DL, 0, Q.AC, Q.CxtI, Q.DT);
const unsigned EffWidthY = Width - YKnown.countMinLeadingZeros();
if (EffWidthY <= ShftCnt) {
const KnownBits XKnown = computeKnownBits(X, Q.DL, 0, Q.AC, Q.CxtI,