[llvm] [DAG] Add freeze(assertext(x)) -> assertext(x) folds (PR #94491)

[Björn Pettersson via llvm-commits]

bjope wrote:

> Can we make Assert* have an embedded freeze? If you're doing anything with the

Something along my earlier ideas here https://github.com/llvm/llvm-project/pull/84924#discussion_r1581183848  ?
I.e. adding some bool parameter to Assert*ext to indicate if it propagates poision or not. (ore one could see it as the bool controls if the Assert*ext also is a freeze).
I did try something simpler in this patch. But now I'm starting to think that it was a bad short-cut to skip that extra bool parameter. If adding such a paramter we can narrow the impact here to for example Assert*ext nodes introduced by call/argument lowering.

https://github.com/llvm/llvm-project/pull/94491