Class metadata fix for Windows [5.0, ABI] #20790
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This reverts commit b3a50ea9fdd6fb8cb0cbcba059dcb5b8029db7c4.
IRGen always just emits a simple implementation that immediately calls swift_relocateClassMetadata(); so allow the function to be null in this case to save on code size.
…ton metadata initialization On Windows the image format does not support cross-image absolute data symbol references. One case where we emit these is in class metadata, because the value witness table always points at the value witness table for Builtin.NativeObject, defined in the runtime. Instead, fill in the value witness table at runtime when doing singleton metadata initialization. Another change that will come later is to force use of singleton metadata initialization on Windows, even if the class is otherwise completely fixed.
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@swift-ci Please test |
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Convergence: no; ABI impact: yes |
slavapestov
changed the title
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I am merging this as it's a low risk ABI change. |
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On Windows we can't reference the runtime's Builtin.NativeObject value witness table directly from class metadata. Instead fill it in at runtime for singleton metadata initialization.
Do this on all platforms, even though its not needed on Linux or Darwin, for simplicity. A subsequent Windows-specific change will force the use of singleton metadata initialization for all classes, even when the class is otherwise fixed.