[IRGen] Emit a pointer from nominal type descriptor to concrete metadata. #79302
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mikeash
requested review from
rjmccall,
artemcm,
tshortli,
hborla,
slavapestov and
xedin
as code owners
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Could another way of implementing this just be to stuff this as an entry to the canonical specialized metadata entries? |
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That's pretty much what this is doing, but we're taking advantage of the fact that we know there can only be one when the type is not generic, so we don't have to emit the count, and save four bytes. |
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Ha, we are indeed saving 4 bytes (I'm just playing devil's advocate, I don't mind how you implement this). |
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Under what situations exactly do we want to emit this link? When the metadata is preallocated but not necessarily statically initialized? |
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We want it to be when the metadata is emitted by the compiler and can be used as-is, with no runtime initialization. Basically, if someone writes |
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Any further comments, or is this OK to get in? |
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It seems fine to me. |
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@swift-ci please test |
mikeash
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Linux tests failed because wasm didn't like the new test. I switched from |
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@swift-ci please test |
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And a test tweak for 32-bit. |
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@swift-ci please test |
…ata. This allows external tools to locate the metadata pointer without needing to call the accessor function. This is only useful for non-generic types, so we borrow the HasCanonicalMetadataPrespecializations flag to indicate the presence of this pointer on non-generic types, and it continues to indicate the presence of prespecializations for generic types. Only emit this pointer for internal/private types with no runtime initialization. Public type metadata can be found with the symbol, and it's not useful for types that require runtime initialization.
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@swift-ci please test |
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Windows timed out for what appears to be unrelated reasons. |
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@swift-ci please test Windows platform |
This allows external tools to locate the metadata pointer without needing to call the accessor function.
This is only useful for non-generic types, so we borrow the HasCanonicalMetadataPrespecializations flag to indicate the presence of this pointer on non-generic types, and it continues to indicate the presence of prespecializations for generic types.
Only emit this pointer for internal/private types with no runtime initialization. Public type metadata can be found with the symbol, and it's not useful for types that require runtime initialization.
rdar://144640722