[PATCH] D96802: [Clang] Add proper target checks for SwiftAsync convention.

[John McCall via Phabricator via cfe-commits]

rjmccall added a comment.

In D96802#2569810 <https://reviews.llvm.org/D96802#2569810>, @varungandhi-apple wrote:

>> The TargetInfo classes are already target-architecture-specific, so it's somewhat strange for them all to funnel to a single function that then immediately switches on the target architecture.
>
> IMO ideally, the whole thing would be stored as a table of Target x CallingConvention. Each entry of the table would have a CallingConvCheckResult. That way, you can quickly figure out both:
>
> - which targets is a calling convention supported for
> - what calling conventions are supported for a particular target
>
> Certainly, that's not the state of the code right now. So I do agree with your point that it looks a bit strange. However, given that things are somewhat in flux for `CC_SwiftAsync`, I think it is valuable to centralize the information for it in one place instead of spreading it out over multiple files.

I don't see why.  I can't really imagine adding a second dimension to the decision here — there's no reason to ever make this OS-dependent, for example — and so the only likely evolution is adding support for a new architecture, which means adding another case to your centralized function instead of just changing how the CC is handled in the target-specific function.  And for this patch, just implementing the new case as `return CCCR_Error` seems much more obvious than calling a centralized function which just switches out again.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D96802/new/

https://reviews.llvm.org/D96802