Macro float_impl

macro_rules! float_impl {
    (
        $ty:ident,
        $ity:ident,
        $sity:ident,
        $bits:expr,
        $significand_bits:expr,
        $from_bits:path,
        $to_bits:path,
        $fma_fn:ident,
        $fma_intrinsic:ident
    ) => { ... };
}