[clang] [llvm] [RISCV] Inline Assembly Support for GPR Pairs ('Pr') (PR #112983)

[Sam Elliott via cfe-commits]

lenary wrote:

> > The Arch64 MVT::i64x8 may be a way to work around this. We could have a special pair MVT only used by inline assembly.
> 
> Ok, this sounds doable - so something like `MVT::xlen_pair` is the way I'll lean, rather than a different type for rv32/rv64.

Turns out that MVTs really want a size (unless they're overloadable, which is a complex and under-documented property), so I'll be going with two different MVTs rather than trying to share one.

https://github.com/llvm/llvm-project/pull/112983