[llvm] [InstCombine] Drop alignment assumptions more aggressively (PR #196060)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

It looks like this defaults AllowEphemerals=true and then only actually uses Q.AllowEphemerals in the single place that used the true value.

What I would expect is that AllowEphemerals=false, Q.AllowEphemerals is used in all the isValidAssumeForContext() calls in ValueTracking, and then we explicitly opt-in to allowing ephemerals in the places where it's safe.

https://github.com/llvm/llvm-project/pull/196060