[clang] [llvm] [RISCV] Add MC layer support for XSfmm*. (PR #133031)

[Pengcheng Wang via llvm-commits]

wangpc-pp wrote:

> > but won't merge them until they are ratified just like Zvzip/Zvabd/Zibimm
> 
> I think this patch is supported to be the vendor instruction set of `SiFive Xsfmm* Attached Matrix Extensions` if I understand correctly of this PR.
> 
> AME is another issue that we don’t have ratified AME but just SiFive AME proposal, XuanTie AME proposal.

SiFive's AME proposal locates in OP-V/OP-VE category, I think it is not designed as vendor extension. IIUC, this patch is just for early evaluation.

https://github.com/llvm/llvm-project/pull/133031