[llvm] pr/amdgpu closed world (PR #66488)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> @arsenm I rebased this, and moved the pass for now into the LTO pipeline. That breaks tests since they run the non-LTO one to check for the Attributor results. If I run it in the non-LTO pipeline, it only knows about closed world if you do thin-LTO, which is not ideal. Maybe there is a pipeline/extension point I missed? WDYT?

I'm confused, none of the codegen tests should be changing? LTO/Thin-LTO is upstream of all of the backend testing? 

https://github.com/llvm/llvm-project/pull/66488