According to Apple docs, the long double type is a double precision
IEEE754 binary floating-point type, which makes it identical to the
double type. This behavior contrasts to the standard specification,
in which a long double is a quad-precision, IEEE754 binary,
floating-point type.

Thus, we need to take this into account when using the compiler
intrinsics so that we select the correct function version for
FloatMulAdd.