[PATCH] D75574: RFC: Implement objc_direct_protocol attribute to remove protocol metadata

[Nathan Lanza via Phabricator via cfe-commits]

lanza created this revision.
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Motivated by the new objc_direct attribute, this change aims to limit
metadata generation from Protocols that the programmer knows isn't
going to be used at runtime. This attribute simply causes the frontend
to not generate any protocol metadata entries (e.g. OBJC_CLASS_NAME,
_OBJC_$_PROTOCOL_INSTANCE_METHDOS, _OBJC_PROTOCOL, etc) for a protocol
marked with `__attribute__((objc_direct))`.

There are a few APIs used to retrieve a protocol at runtime.
`@protocol(SomeProtocol)` will now error out of the requested protocol
is marked with attribute. `objc_getProtocol` will returl `NULL` which
is consistent with the behavior of a non-existing protocol.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D75574

Files:
  clang/include/clang/AST/DeclObjC.h
  clang/include/clang/Basic/Attr.td
  clang/include/clang/Basic/AttrDocs.td
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/include/clang/Basic/ObjCRuntime.h
  clang/lib/AST/DeclObjC.cpp
  clang/lib/CodeGen/CGObjCMac.cpp
  clang/lib/Sema/SemaDeclAttr.cpp
  clang/lib/Sema/SemaExprObjC.cpp
  clang/test/CodeGenObjC/static-protocol.m

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