[llvm] CodeGen: Derive ARM EH pointer/selector registers from MCAsmInfo (PR #226109)

[Peter Smith via llvm-commits]

smithp35 wrote:

> > My apologies if I'm misinterpreting your question.
> 
> > So I don't think anyone officially supports it outside of a target-triple. However I can't rule out someone has rolled their own system using the command-line options and has used an existing triple. Whether that's a use case that needs supporting is another matter.
> 
> My question is about the specific reason it's not supported; is it something not encodable in the object, or some other missing platform support? This patch is assuming it's an object format restriction, and not a platform feature set limitation

I agree with Eli about SjLj exceptions. The ARM exceptions rely on ELF's SHF_LINKORDER flag for correctness. I don't think that has a direct equivalent in COFF/MachO though. The .eh_frame for Dwarf exceptions doesn't need anything custom from the object file format. In practice to make .eh_frame work well the static linker needs to do quite a lot of rewriting to remove redundant entries, construct the .eh_frame_hdr, but this is not ELF specific.



https://github.com/llvm/llvm-project/pull/226109