ValueTracking: Teach computeKnownFPClass to look at bitcast + integer max (#184073)
The returned class will still be one of the bitpatterns.
This pattern is used in rocm device libraries in assorted functions,
e.g.,
https://github.com/ROCm/llvm-project/blob/amd-staging/amd/device-libs/ocml/src/rlen3F.cl#L20
I believe it is blocking the eliminationg of finite checks in some of
the more complex functions.