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[ValueTracking][SelectionDAG] Use KnownBits::reverseBits/byteSwap. NFC #155847

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Merged
merged 1 commit into from
Aug 28, 2025
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[ValueTracking][SelectionDAG] Use KnownBits::reverseBits/byteSwap. NFC #155847

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6 changes: 2 additions & 4 deletions llvm/lib/Analysis/ValueTracking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1834,13 +1834,11 @@ static void computeKnownBitsFromOperator(const Operator *I,
}
case Intrinsic::bitreverse:
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Q, Depth + 1);
Known.Zero |= Known2.Zero.reverseBits();
Known.One |= Known2.One.reverseBits();
Known = Known.unionWith(Known2.reverseBits());
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why isn't this Known = Known2.reverseBits()?

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or why isn't the abs case Known = Known.unionWith(Known2.abs(IntMinIsPoison));?

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I guess they should all use unionWith, to take advantage of any ConstantRange info that might have been calculated before this switch.

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bitreverse and bswap started doing the union here ad5c2d0. abs was added later.

break;
case Intrinsic::bswap:
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Q, Depth + 1);
Known.Zero |= Known2.Zero.byteSwap();
Known.One |= Known2.One.byteSwap();
Known = Known.unionWith(Known2.byteSwap());
break;
case Intrinsic::ctlz: {
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Q, Depth + 1);
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6 changes: 2 additions & 4 deletions llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
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Expand Up @@ -2363,8 +2363,7 @@ bool TargetLowering::SimplifyDemandedBits(
if (SimplifyDemandedBits(Src, DemandedSrcBits, DemandedElts, Known2, TLO,
Depth + 1))
return true;
Known.One = Known2.One.reverseBits();
Known.Zero = Known2.Zero.reverseBits();
Known = Known2.reverseBits();
break;
}
case ISD::BSWAP: {
Expand Down Expand Up @@ -2397,8 +2396,7 @@ bool TargetLowering::SimplifyDemandedBits(
if (SimplifyDemandedBits(Src, DemandedSrcBits, DemandedElts, Known2, TLO,
Depth + 1))
return true;
Known.One = Known2.One.byteSwap();
Known.Zero = Known2.Zero.byteSwap();
Known = Known2.byteSwap();
break;
}
case ISD::CTPOP: {
Expand Down