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[ValueTracking] Check both operands for being 0 and then the other for isKnownNonZero #147330

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[ValueTracking] Check both operands for being 0 and then the other for isKnownNonZero #147330

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9 changes: 8 additions & 1 deletion llvm/lib/Analysis/ValueTracking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2880,7 +2880,8 @@ static bool isNonZeroSub(const APInt &DemandedElts, const SimplifyQuery &Q,
if (matchOpWithOpEqZero(X, Y))
return true;

// TODO: Move this case into isKnownNonEqual().
// TODO: isKnownNonEqual() should catch these cases, but it is not, resulting
// in regressions.
if (auto *C = dyn_cast<Constant>(X))
if (C->isNullValue() && isKnownNonZero(Y, DemandedElts, Q, Depth))
return true;
Expand Down Expand Up @@ -3892,6 +3893,12 @@ static bool isKnownNonEqual(const Value *V1, const Value *V2,
if (Depth >= MaxAnalysisRecursionDepth)
return false;

// 0 vs known-non-zero
if (match(V1, m_Zero()) && isKnownNonZero(V2, DemandedElts, Q, Depth + 1))
return true;
if (match(V2, m_Zero()) && isKnownNonZero(V1, DemandedElts, Q, Depth + 1))
return true;
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I don't think this makes sense. x - 0 is just x and should get folded away.


// See if we can recurse through (exactly one of) our operands. This
// requires our operation be 1-to-1 and map every input value to exactly
// one output value. Such an operation is invertible.
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