[llvm] [RISCV] and x (sub -1, y) -> andn x y (PR #129253)

[Gábor Spaits via llvm-commits]

spaits wrote:

And maybe, it will be enough to work on the IR level, if the suggested IR transformations are done, we will get `andn` generated: https://godbolt.org/z/z4fqW6Ejf . (When the ticket was reported it wasn't that way https://godbolt.org/z/EEvhK9ovx) .

Sorry for my negligence and Thank you for you time and patience.

https://github.com/llvm/llvm-project/pull/129253