[llvm] VT: don't create undef in isBytewiseValue (PR #119411)

[Nikita Popov via llvm-commits]

https://github.com/nikic requested changes to this pull request.

I don't understand what exactly alive2 is complaining about in that example. But in any case, supporting undef in this function is important, because it's used to mark explicitly uninitialized regions of globals.

Generally, I would strongly recommend against submitting fixes for undef-only miscompiles unless you reduced the issue from a real-world miscompile. We usually do not accept such fixes.

https://github.com/llvm/llvm-project/pull/119411