[clang] [llvm] [RISCV] Add Xqccmp Assembly Support (PR #128731)

[Sam Elliott via cfe-commits]

lenary wrote:

I realise this extension will generate questions about what we do for CodeGen support for this extension. I have been thinking about this, and I do think it will be possible to extend the current codegen (prolog epilog inserter mostly) to support this, fairly easily. I can put up a draft patch, based on this one, in time for Thursday's RISC-V sync-up.

https://github.com/llvm/llvm-project/pull/128731