[llvm] [AArch64][ISel] Add custom lowering for clmul nxv8i16 (PR #195893)

[Paul Walker via llvm-commits]

paulwalker-arm wrote:

> I also didn't think eorbt and eortb are both necessary, either one or the other with an LSL or an AND is ok I think?

I think both are useful because the final `xor(pmullb, lsl(EORBT, 8)` is `eortb(pmullb, EORBT)`?


https://github.com/llvm/llvm-project/pull/195893