This is motivated by patterns like !isfinite || zero. The AMDGPU math
libraries have a lot of patterns like this, and I'm trying to fix the
code to be more portable and less dependent on directly calling class
intrinsics.
I believe this is the first place where new is.fpclass calls are
introduced. There are more class-like compares that could be
recognized; this is a set I currently care about plus a few extras.
I swear I posted this before but can't seem to find it
Do you need to worry about IsLogicalSelect here? (@nikic, @craig.topper?)