[clang] [llvm] [ValueTracking] use KnownBits to compute fpclass from bitcast (PR #97762)

[Alex MacLean via cfe-commits]

AlexMaclean wrote:

@arsenm, @goldsteinn when you have a minute could you take another look at this? I think I've addressed all the issues you've raised. 

https://github.com/llvm/llvm-project/pull/97762