[llvm] [RISCV] Use `experimental-p` extension for zero-extended narrow unsigned types (PR #213260)

[Rajveer Singh Bharadwaj via llvm-commits]

Rajveer100 wrote:

I get your point, there a bunch of patterns that can be handled so we have greater coverage which it right now only fixes a few basic cases.

A comprehensive list would be good know apart from the already few of them you told.

Also, this is possible in ISel in my opinion. We just need to handle the specific patterns and at each changed visit we would optimise it.

Like for 3 add's we just need another pattern of padd+add and padd+padd that way we take care of multiple uses, same for sub, or other ops.

https://github.com/llvm/llvm-project/pull/213260