[Runtime] Remove protocol descriptor overlap #18146
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…overlap. As a small step toward splitting apart the Swift and Objective-C protocol descriptors, eliminate most places where we rely on a shared representation.
Introduce TargetObjCProtocolPrefix, which describes just enough of the Objective-C runtime’s Protocol structure to extract the name without having to call Objective-C’s protocol_getName().
When reading the protocol metadata from existential type metadata, check the “isObjC” bit and handle the reading of the Objective-C protocol name (using TargetObjCProtocolPrefix) separately from the reading the name of a Swift protocol (using TargetProtocolDescriptor). More preparation for separating the layout of these two entities.
We don’t want the Swift runtime knowing the layout of Objective-C protocols. Rather, it should use protocol_getName() when it needs the (possibly mangled) name of an Objective-C protocol. Do so in the runtime. The code paths that handle ObjC vs. Swift protocols will diverge significantly soon, and “getName()” isn’t an API we expect to need in general. Sink TargetObjCProtocolPrefix down into MetadataReader, because that’s the only place where we want to expose the Objective-C protocol layout, so we can form metadata without running code.
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@swift-ci please smoke test |
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Bah, the last commit doesn't work. |
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Superseded by #18163 |
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In all of the places where we look into protocol descriptors in the runtime, remote AST, and remote mirrors, separate out of the code paths and data structures for Objective-C and Swift protocols. After this, there should be nothing remaining that relies on the layouts being identical (even though they still are).