[llvm] [InstCombine] Check for undef first before freeze (PR #96769)

[via llvm-commits]

AtariDreams wrote:

> If it's known not to be undef/poison, the freeze will be folded away, no need to check for it.
> 
> What _would_ make sense is if you can check isGuaranteedNotToBeUndef (without the OrPoison). From a quick glance, you likely can, as these are multi-use freezes.

Fixed!

https://github.com/llvm/llvm-project/pull/96769