cpackl
result = cpackl(t, b / (2.0L * t));
result = cpackl(fabsl(b) / (2.0L * t), copysignl(t, b));
return (cpackl(0.0L, b));
return (cpackl(INFINITY, b));
return (cpackl(a, t)); /* return NaN + NaN i */
return (cpackl(fabsl(b - b), copysignl(a, b)));
return (cpackl(a, copysignl(b - b, b)));