Fix an IRGen bug related to re-use of type metadata #3468
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@swift-ci Please test |
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@rjmccall John, do you mind reviewing this small bugfix? It is in your IRGen code for the dominance-based metadata optimizations. |
| // for argTy, because it may be a metadata for a derived class. | ||
| // In all other cases, the metadata is exact. | ||
| // TODO: If it can be proved that the class has no subclasses | ||
| // (e.g. in WMO mode), then the metadata can be considered exact. |
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I would suggest this comment:
The self metadata here corresponds to the conforming type. For an inheritable conformance, that may be a subclass of the static type, and so the self metadata will be inexact. Currently, all conformances are inheritable.
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I'll update the comment.
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Conceptually LGTM. |
The self metadata in the changed method corresponds to the conforming type. For an inheritable conformance, that may be a subclass of the static type, and so the self metadata will be inexact. Currently, all conformances are inheritable. rdar://27301453
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@rjmccall Thanks for reviewing it! |
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@swift-ci Please test and merge. |
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@swift-ci Please test and merge |
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What's in this pull request?
Resolved bug number: (SR-)
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If Self type in a protocol conformance is a class which may have derived classes, it is not safe to assume that the metadata is exact for this type.
rdar://27301453