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[InstCombine] Remove redundant shift folds (NFCI) #90016

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Merged
merged 1 commit into from
Apr 25, 2024
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[InstCombine] Remove redundant shift folds (NFCI) #90016

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16 changes: 0 additions & 16 deletions llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1120,14 +1120,6 @@ Instruction *InstCombinerImpl::visitShl(BinaryOperator &I) {
return BinaryOperator::CreateAnd(Trunc, ConstantInt::get(Ty, Mask));
}

if (match(Op0, m_Shl(m_Value(X), m_APInt(C1))) && C1->ult(BitWidth)) {
unsigned AmtSum = ShAmtC + C1->getZExtValue();
// Oversized shifts are simplified to zero in InstSimplify.
if (AmtSum < BitWidth)
// (X << C1) << C2 --> X << (C1 + C2)
return BinaryOperator::CreateShl(X, ConstantInt::get(Ty, AmtSum));
}

// If we have an opposite shift by the same amount, we may be able to
// reorder binops and shifts to eliminate math/logic.
auto isSuitableBinOpcode = [](Instruction::BinaryOps BinOpcode) {
Expand Down Expand Up @@ -1394,14 +1386,6 @@ Instruction *InstCombinerImpl::visitLShr(BinaryOperator &I) {
}
}

// (X >>u C1) >>u C --> X >>u (C1 + C)
if (match(Op0, m_LShr(m_Value(X), m_APInt(C1)))) {
// Oversized shifts are simplified to zero in InstSimplify.
unsigned AmtSum = ShAmtC + C1->getZExtValue();
if (AmtSum < BitWidth)
return BinaryOperator::CreateLShr(X, ConstantInt::get(Ty, AmtSum));
}

Instruction *TruncSrc;
if (match(Op0, m_OneUse(m_Trunc(m_Instruction(TruncSrc)))) &&
match(TruncSrc, m_LShr(m_Value(X), m_APInt(C1)))) {
Expand Down