[clang] [llvm] Implement `preserve_none` for 32-bit x86 (PR #150106)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

> Okay, this is just adding them to the existing CSR_*_NoneRegs, correct?

Yes.

> Makes sense. Where do you think the best place to do this is?

I think similar sorts of diagnostics are in llvm/lib/Target/X86/X86ISelLoweringCall.cpp .  (Grep for errorUnsupported.)

> How about we add the base pointers to both callee-save lists here and leave the nest parameter as a future improvement for another PR? The calling convention is ABI-unstable, so we can always tweak it later.

That's probably fine.

https://github.com/llvm/llvm-project/pull/150106