[llvm] [InstCombine] Fold align assume into load's !align metadata if possible. (PR #108958)

[Florian Hahn via llvm-commits]

fhahn wrote:

> New results show about what I'd expect. Improvements for C++ which doesn't use `!align`, big regressions for Rust where ~all ptr loads are `!align`.

Yep, updating the patch to avoid adding assume() if the new pointer already has !align

https://github.com/llvm/llvm-project/pull/108958