[llvm-dev] [RFC] Introducing an explicit calling convention

David Greene via llvm-dev llvm-dev at lists.llvm.org
Tue Jan 15 10:23:37 PST 2019

Reid Kleckner via llvm-dev <llvm-dev at lists.llvm.org> writes:

>     +1. Coordinating ABI semantics between the frontend and LLVM is
>     tricky.
>     It would be super helpful to have a formal way of expressing ABI
>     semantics in the IR.
> I agree with that, but I think most users want LLVM to go the other
> way from what the OP is suggesting. I think non-clang frontends would
> prefer it if we pushed more calling convention details down into LLVM,
> not the other way around.

That would be great, but I'm not even sure how it would be possible
given the multitude of frontend languages and their ABI expectations.
Wouldn't we have to carry quite a lot of language semantic information
around?  For example, AFAIK right now LLVM can't distinguish between an
ordinary struct containing two doubles and double complex.  The various
vector ABIs may treat those two types differently, for example.


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