[llvm] [ArgPromotion] Infer parameter attributes on functions (PR #110245)

[Nikita Popov via llvm-commits]

nikic wrote:

> This improves precision of alias analysis using the actual arguments of calling functions in cases where these attributes have not already been inferred.

I think this needs a PhaseOrdering test that shows why this is needed. I checked, and we run PostOrderFunctionAttrsPass before ArgumentPromotionPass. It's run in SkipNonRecursive mode, but the one thing that *does* get inferred in that mode is actually nocapture and readonly/etc. As such, it's not super clear to me why we need to redo this inference in ArgPromotion.

https://github.com/llvm/llvm-project/pull/110245