[llvm] LoopSimplify: strip unused pass dependencies (NFC) (PR #107379)

[Florian Hahn via llvm-commits]

fhahn wrote:

> > The legacy pass is still used by the backend, and at least some of these preservations are important.
> 
> The CI failures should be fixed now, but how can we be confident that the patch is correct? What is this mysterious preservation?

Probably mostly in extra compile-time, if later passes now have to recompute otherwise preserved info. It might also impact codegen, e.g. GlobalsAAWrapperPass is  stateful IIRC, so not preserving it might throw away previous analysis results without recomputing them. The later could be checked by building a large set of programs and checking if there are binary changes

https://github.com/llvm/llvm-project/pull/107379