[llvm] Reland "[ValueTracking] Compute knownbits from known fp classes" (PR #92084)

[Nikita Popov via llvm-commits]

nikic wrote:

> @nikic Do you have a plan that treating the use as a poison value when the knownbit of it has conflicts?

The plan is to remove all of these assertions and fold conflict to poison. Someone just needs to implement it :)

https://github.com/llvm/llvm-project/pull/92084