[llvm] [NVPTX] Make i16x2 a native type and add supported vec instructions (PR #65432)

[via llvm-commits]

ThomasRaoux wrote:




> Looks like we've missed lowering of bitcasts between v2f16 and v2i16 and it breaks XLA.
> 
> ```
> LLVM ERROR: Cannot select: t119: v2f16 = bitcast t118
>   t118: v2i16 = or t375, t401
>     t375: v2i16 = BUILD_VECTOR t374, t372
>       t374: i16 = select t247, Constant:i16<8960>, t360
> ```

Oops, I can send a patch today unless someone else already has a fix.

https://github.com/llvm/llvm-project/pull/65432