DESW
ha += DESW(MAX_EXP/2+88);
hb += DESW(MAX_EXP/2+88);
SET_HIGH_WORD(t1,high+DESW(k));
if((ha-hb)>DESW(MANT_DIG+7)) {return a+b;} /* x/y > 2**(MANT_DIG+7) */
ha -= DESW(MAX_EXP/2+88); hb -= DESW(MAX_EXP/2+88);