HIFRACTION
if ((EXPONENT(x) == MAXEXP) && (HIFRACTION(x) || LOFRACTION(x)))
if ((EXPONENT(y) == MAXEXP) && (HIFRACTION(y) || LOFRACTION(y)))
if (HIFRACTION(x) || LOFRACTION(x)) /* de-normal */
if ((HIFRACTION(x) == 0) && (LOFRACTION(x) == 0)) /* infinity */