[PATCH] D56802: [CodeGenObjC] Treat ivar offsets variables as constant if they refer to ivars of a direct subclass of NSObject with an @implementation

[Duncan P. N. Exon Smith via Phabricator via cfe-commits]

dexonsmith added a comment.

In D56802#1360316 <https://reviews.llvm.org/D56802#1360316>, @rjmccall wrote:

> We've tossed around the idea of doing things like this before, but I was hoping that it wouldn't have to be specific to `NSObject` and that we'd e.g. have an attribute that guarantees that the `@interface` declares all the ivars for a class.  Are we still thinking that?


The attribute idea hasn't yet survived language discussions (too much of an ABI foot-gun for library evolution).  But it's safe to move forward with something `NSObject`-specific since it's already baked into the ABI.

> Even if this is just a step towards that, I think we should at least add a method to answer whether we have a statically-known layout for the class, rather than hard-coding that decision at the leaves like this.

A method makes sense to me too.


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  rC Clang

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  https://reviews.llvm.org/D56802/new/

https://reviews.llvm.org/D56802