[llvm] [VectorUtils] Allow just poison in mask*All(Ones|Zero)OrUndef (PR #168388)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

> It looks like there were no test changes with the patch. Are we missing some test coverage?

We sure are, but I think a more comprehensive patch would strip the touched functions, update callers to directly use PM, and s/undef/poison/ in tests. Not sure if it's really worth the effort for the moment.

https://github.com/llvm/llvm-project/pull/168388