- case 0: return pio2_hi*0.5+0x1p-1000; /* atan(+INF,+INF) */
- case 1: return -pio2_hi*0.5-0x1p-1000; /* atan(-INF,+INF) */
- case 2: return 1.5*pio2_hi+0x1p-1000; /* atan(+INF,-INF) */
- case 3: return -1.5*pio2_hi-0x1p-1000; /* atan(-INF,-INF) */
+ case 0: return pio2_hi/2; /* atan(+INF,+INF) */
+ case 1: return -pio2_hi/2; /* atan(-INF,+INF) */
+ case 2: return 1.5*pio2_hi; /* atan(+INF,-INF) */
+ case 3: return -1.5*pio2_hi; /* atan(-INF,-INF) */