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[SCCP] Simplify general icmp instructions #165976

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[SCCP] Simplify general icmp instructions #165976

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6 changes: 5 additions & 1 deletion llvm/lib/Transforms/Utils/SCCPSolver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -299,6 +299,7 @@ static Value *simplifyInstruction(SCCPSolver &Solver,
Value *LHS = ICmp->getOperand(0);
ICmpInst::Predicate Pred = ICmp->getPredicate();
const APInt *Offset;
// Match icmp X + Offset, C
if (match(LHS, m_OneUse(m_AddLike(m_Value(X), m_APInt(Offset)))))
return ConstantRange::makeExactICmpRegion(Pred, *RHSC).sub(*Offset);
// Match icmp eq/ne X & NegPow2, C
Expand All @@ -310,7 +311,10 @@ static Value *simplifyInstruction(SCCPSolver &Solver,
return Pred == ICmpInst::ICMP_EQ ? CR : CR.inverse();
}
}
return std::nullopt;
// Fallback: Match icmp X, C
// E.g., if X ∈ [0, 4], this can simplify icmp uge X, 4 to icmp eq X, 4
X = LHS;
return ConstantRange::makeExactICmpRegion(Pred, *RHSC);
};

if (auto CR = MatchTwoInstructionExactRangeCheck()) {
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