In this paper, we propose a guidance synthesis method for enhancing anti-ship missiles' survivability against ship-borne CIWS (close-in weapon system). Using CEALM (coevolutionary augmented Lagrangian method), a direct optimization technique, an optimal control problem to minimize time-varying weighted sum of the inverse of aiming errors of CIWS is solved. The optimal evasive trajectory exhibits sinusoidal acceleration commands, which results in barrel-roll type evasive maneuvers. Inspired by the optimization results, a 3-dimensional biased proportional navigation guidance (PNG) law to induce a barrel-roll maneuver during the homing phase is proposed. Capturability of the proposed guidance law is proved by using the Lyapunov stability theory. A proper choice of the barrel-roll direction also guarantees that the missile altitude can be made lower bounded. Performance of the proposed guidance laws is compared with conventional PNG via simulations.