[llvm] AMDGPU: Use helper function for use/def chain walk (PR #129052)

[Janek van Oirschot via llvm-commits]

https://github.com/JanekvO approved this pull request.

LGTM, but:

> PeepholeOpt has a nicer version of this which handles more cases.

Which function/mechanism would this be? And is this the implication that we'll move towards using what peepholeopt is using (or perhaps modify this into something that's as encompassing as the peepholeopt one)?

https://github.com/llvm/llvm-project/pull/129052