[llvm] [ValueTracking] AllowEphemerals for alignment assumptions. (PR #108632)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

> A reluctant LGTM. I think overall it's reasonable to ignore ephemerals for operand bundles by default and add a flag if/when we actively want to simplify them.
> 
> Always a good time to review our long tradition of "trying to fix the ephemeral value problem in SCEV":
> 
> https://reviews.llvm.org/D93974 https://reviews.llvm.org/D97077 https://reviews.llvm.org/D97092 https://reviews.llvm.org/D97099 https://reviews.llvm.org/D155389
> 
> I think https://reviews.llvm.org/D97092 has our latest understanding of this problem, and the discussion there at the end was leaning towards something along the lines of this PR.

Thanks for sharing the extra context!

https://github.com/llvm/llvm-project/pull/108632