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Implement IsValueInlinedInExistentialContainer #40053

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Nov 8, 2021
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Implement IsValueInlinedInExistentialContainer #40053

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22 changes: 22 additions & 0 deletions include/swift/Remote/MetadataReader.h
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Original file line number Diff line number Diff line change
Expand Up @@ -690,6 +690,28 @@ class MetadataReader {
RemoteAddress(StartOfValue));
}

/// Given a known-opaque existential, discover if its value is inlined in
/// the existential container.
llvm::Optional<bool>
isValueInlinedInExistentialContainer(RemoteAddress ExistentialAddress) {
// OpaqueExistentialContainer is the layout of an opaque existential.
// `Type` is the pointer to the metadata.
TargetOpaqueExistentialContainer<Runtime> Container;
if (!Reader->readBytes(RemoteAddress(ExistentialAddress),
(uint8_t *)&Container, sizeof(Container)))
return None;
auto MetadataAddress = static_cast<StoredPointer>(Container.Type);
auto Metadata = readMetadata(MetadataAddress);
if (!Metadata)
return None;

auto VWT = readValueWitnessTable(MetadataAddress);
if (!VWT)
return None;

return VWT->isValueInline();
}

/// Read a protocol from a reference to said protocol.
template<typename Resolver>
typename Resolver::Result readProtocol(
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