[middle-end,patch] Making __builtin_signbit type-generic

[FX]

> .. I think this improvement means that in principle we could revert what we committed for libstdc++/58625, thus increasing a little the consistency wrt the other classification facilities in c_global/cmath (and c_std/cmath). Not sure it's worth it.

Can’t comment on whether it’s worth doing, but yes, with the type-generic __builtin_signbit you can revert that patch with no change to the generated code.

FX