[clang] [llvm] [MIPS] Add support for O64 Mips ABI (PR #223990)

[Jiaxun Yang via llvm-commits]

FlyGoat wrote:

> Just for reference, my experience with MIPS specifically is not that extensive, so besides local testing I'm not 100% sure on details in places.
> 
> My expertise is mostly in regard to SuperH. Hopefully I'm not too frustrating to work with here ^^;

No worries :-) I'm happy to help with the MIPS details where I can. Realy glad to see someone working on this!

https://github.com/llvm/llvm-project/pull/223990