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[SelectionDAG] Prefer to use ATOMIC_LOAD extension type over getExtendForAtomicOps() in computeKnownBits/ComputeNumSignBits. #136600

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Merged
merged 1 commit into from
Apr 21, 2025
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[SelectionDAG] Prefer to use ATOMIC_LOAD extension type over getExtendForAtomicOps() in computeKnownBits/ComputeNumSignBits. #136600

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40 changes: 26 additions & 14 deletions llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4406,14 +4406,19 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
case ISD::ATOMIC_LOAD_UMIN:
case ISD::ATOMIC_LOAD_UMAX:
case ISD::ATOMIC_LOAD: {
unsigned MemBits =
cast<AtomicSDNode>(Op)->getMemoryVT().getScalarSizeInBits();
// If we are looking at the loaded value.
if (Op.getResNo() == 0) {
if (TLI->getExtendForAtomicOps() == ISD::ZERO_EXTEND)
Known.Zero.setBitsFrom(MemBits);
else if (Op->getOpcode() == ISD::ATOMIC_LOAD &&
cast<AtomicSDNode>(Op)->getExtensionType() == ISD::ZEXTLOAD)
auto *AT = cast<AtomicSDNode>(Op);
unsigned MemBits = AT->getMemoryVT().getScalarSizeInBits();

// For atomic_load, prefer to use the extension type.
if (Op->getOpcode() == ISD::ATOMIC_LOAD) {
if (AT->getExtensionType() == ISD::ZEXTLOAD)
Known.Zero.setBitsFrom(MemBits);
else if (AT->getExtensionType() != ISD::SEXTLOAD &&
TLI->getExtendForAtomicOps() == ISD::ZERO_EXTEND)
Known.Zero.setBitsFrom(MemBits);
} else if (TLI->getExtendForAtomicOps() == ISD::ZERO_EXTEND)
Known.Zero.setBitsFrom(MemBits);
}
break;
Expand Down Expand Up @@ -5252,22 +5257,29 @@ unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, const APInt &DemandedElts,
case ISD::ATOMIC_LOAD_UMIN:
case ISD::ATOMIC_LOAD_UMAX:
case ISD::ATOMIC_LOAD: {
Tmp = cast<AtomicSDNode>(Op)->getMemoryVT().getScalarSizeInBits();
auto *AT = cast<AtomicSDNode>(Op);
// If we are looking at the loaded value.
if (Op.getResNo() == 0) {
Tmp = AT->getMemoryVT().getScalarSizeInBits();
if (Tmp == VTBits)
return 1; // early-out
if (TLI->getExtendForAtomicOps() == ISD::SIGN_EXTEND)
return VTBits - Tmp + 1;
if (TLI->getExtendForAtomicOps() == ISD::ZERO_EXTEND)
return VTBits - Tmp;

// For atomic_load, prefer to use the extension type.
if (Op->getOpcode() == ISD::ATOMIC_LOAD) {
ISD::LoadExtType ETy = cast<AtomicSDNode>(Op)->getExtensionType();
if (ETy == ISD::SEXTLOAD)
switch (AT->getExtensionType()) {
default:
break;
case ISD::SEXTLOAD:
return VTBits - Tmp + 1;
if (ETy == ISD::ZEXTLOAD)
case ISD::ZEXTLOAD:
return VTBits - Tmp;
}
}

if (TLI->getExtendForAtomicOps() == ISD::SIGN_EXTEND)
return VTBits - Tmp + 1;
if (TLI->getExtendForAtomicOps() == ISD::ZERO_EXTEND)
return VTBits - Tmp;
}
break;
}
Expand Down
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