[llvm] [RISCV] Select and/or/xor with certain constants to Zbb ANDN/ORN/XNOR (PR #120221)

[Piotr Fusik via llvm-commits]

pfusik wrote:

> Here's another case that might be useful to optimize https://godbolt.org/z/MEzP15sas it already generates a `not` but we don't fold it.

I can work on it.

https://github.com/llvm/llvm-project/pull/120221