[llvm] [DAG] isGuaranteedNotToBeUndefOrPoisonForTargetNode - add fallback implementation (PR #86125)

[Björn Pettersson via llvm-commits]

bjope wrote:

LG.

@uweigand : This makes me think that someone from SystemZ might wanna add a fallback call to TargetLowering::isGuaranteedNotToBeUndefOrPoisonForTargetNode now when the function actually is doing something.

https://github.com/llvm/llvm-project/pull/86125