[llvm] [GVN] Freeze value if `undef` when forwarding local memset to loads (PR #91376)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Is this fixing an end-to-end miscompile? Or just an alive2 report?

I don't really want to have any partial fixes around the handling of undef/poison and uninitialized memory in GVN, before we have a plan on how we're going to handle this in general. As far as I know, we still don't have a real consensus on this.

https://github.com/llvm/llvm-project/pull/91376