[RFC] Exposing ghccc calling convention as preserve_none to clang

Clang Frontend
21

So, what should the next step be if this is something we want to see in Clang 18? Open an issue?

22

Note that there are a couple additional architectures that support ghccc. These include AArch64 and RISCV. Not sure if there are any others. The LangRef still specifies that ghccc is x86/x86-64 only because (it seems like) everyone just didn’t bother to update the LangRef after doing the implementation for each architecture.

There are a couple additional architectures that could also probably easily have supported added for ghccc, namely the ones listed at https://github.com/ghc/ghc/tree/master/rts/include/stg/MachRegs that don’t already have an existing implementation within LLVM.