[clang] [llvm] [RISCV][llvm] Support fixed-length vector inline assembly constraints (PR #150724)

[Sam Elliott via llvm-commits]

https://github.com/lenary commented:

Please can you add a LLVM IR test for `llc`?

I don't think I know enough about the "fixed vectors in scalable vectors" lowering to know if `splitValueIntoRegisterParts` and `joinRegisterPartsIntoValue` are correct but they don't seem so wrong at a glance. I might have expected to see a call to `convertFromScalableVector` (as join and split tend to be symmetric) but I see there's a `getExtractSubvector` already.

https://github.com/llvm/llvm-project/pull/150724