[PATCH] D73208: [objc_direct] fix codegen for mismatched Decl/Impl return types

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

dexonsmith added a comment.

In D73208#1836722 <https://reviews.llvm.org/D73208#1836722>, @MadCoder wrote:

> In D73208#1836704 <https://reviews.llvm.org/D73208#1836704>, @dexonsmith wrote:
>
> > In D73208#1835264 <https://reviews.llvm.org/D73208#1835264>, @MadCoder wrote:
> >
> > > In D73208#1835051 <https://reviews.llvm.org/D73208#1835051>, @dexonsmith wrote:
> > >
> > > > Why isn't a similar dance needed for non-direct methods?
> > >
> > >
> > > because non direct methods do not need an `llvm::Function` to be synthesized at the call-site. direct methods do, and they form one with the type of the declaration they see. Then that same `llvm::Function` is used when you CodeGen the Implementation, so if there's a mismatch, sadness ensues because the LLVM IR verifier will notice the discrepancy between the declared return type of the function and the actual types coming out of the `ret` codepaths.
> > >
> > > Regular obj-C methods use the _implementation_ types for the codegen (the declaration(s) aren't even consulted) and I want to stick at what obj-c does as much as I can.
> > >
> > > (as a data point: If you use obj-C types with C functions, the type of the first declaration seen is used instead).
> >
> >
> > Okay, that makes sense to me.
> >
> > Another solution would be to change IRGen for the implementation: if the declaration already exists (`getFunction`), do a bitcast + RAUW dance to fix it up (and update the `DirectMethodDefinitions` table).  WDYT?
>
>
> I didn't want to do that because that would mean that the type used for the implementation would depart from dynamic Objective-C methods, and it feels that it shouldn't. hence I took this option.


I think we're talking across each other.  The idea is check the type when generating the implementation; if it's not correct, you fix it (need to update existing uses to bitcast).  So the type used for the implementation would match dynamic methods.


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