[llvm] [GVN] Support rnflow pattern matching and transform (PR #162259)

[Madhur Amilkanthwar via llvm-commits]

madhur13490 wrote:

> > I feel like I saw a comment somewhere that doing the GVN transform would improve performance slightly, but I have trouble finding it, maybe I imagined it...
> 
> Ah, I think it was this one, on the test case PR: [#141556 (comment)](https://github.com/llvm/llvm-project/pull/141556#discussion_r2165781518) I guess that one was an estimated number and not a measurement.

Yeah, that was an estimate, but unfortunately, in reality, it does not match (at least) on the Grace platform.

https://github.com/llvm/llvm-project/pull/162259