[llvm] [RISCV] Support P extension ABSW instruction. (PR #165047)

[Brandon Wu via llvm-commits]

4vtomat wrote:

Is there any reason we can't pattern match ISD::ABS -> absw, e.g. `def : PatGprGpr<binop_allwusers<abs>, ABSW>;`?

https://github.com/llvm/llvm-project/pull/165047