1 /* origin: FreeBSD /usr/src/lib/msun/src/e_atan2f.c */
3 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
9 * Developed at SunPro, a Sun Microsystems, Inc. business.
10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice
13 * ====================================================
18 static const volatile float
21 pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */
22 pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */
23 pi = 3.1415927410e+00; /* 0x40490fdb */
24 static const volatile float
25 pi_lo = -8.7422776573e-08; /* 0xb3bbbd2e */
27 float atan2f(float y, float x)
30 int32_t k,m,hx,hy,ix,iy;
32 GET_FLOAT_WORD(hx, x);
34 GET_FLOAT_WORD(hy, y);
36 if (ix > 0x7f800000 || iy > 0x7f800000) /* x or y is NaN */
38 if (hx == 0x3f800000) /* x=1.0 */
40 m = ((hy>>31)&1) | ((hx>>30)&2); /* 2*sign(x)+sign(y) */
46 case 1: return y; /* atan(+-0,+anything)=+-0 */
47 case 2: return pi+tiny; /* atan(+0,-anything) = pi */
48 case 3: return -pi-tiny; /* atan(-0,-anything) =-pi */
53 return hy < 0 ? -pi_o_2-tiny : pi_o_2+tiny;
55 if (ix == 0x7f800000) {
56 if (iy == 0x7f800000) {
58 case 0: return pi_o_4+tiny; /* atan(+INF,+INF) */
59 case 1: return -pi_o_4-tiny; /* atan(-INF,+INF) */
60 case 2: return 3.0f*pi_o_4+tiny; /*atan(+INF,-INF)*/
61 case 3: return -3.0f*pi_o_4-tiny; /*atan(-INF,-INF)*/
65 case 0: return 0.0f; /* atan(+...,+INF) */
66 case 1: return -0.0f; /* atan(-...,+INF) */
67 case 2: return pi+tiny; /* atan(+...,-INF) */
68 case 3: return -pi-tiny; /* atan(-...,-INF) */
74 return hy < 0 ? -pi_o_2-tiny : pi_o_2+tiny;
78 if (k > 26) { /* |y/x| > 2**26 */
79 z = pi_o_2 + 0.5f*pi_lo;
81 } else if (k < -26 && hx < 0) /* 0 > |y|/x > -2**-26 */
83 else /* safe to do y/x */
84 z = atanf(fabsf(y/x));
86 case 0: return z; /* atan(+,+) */
87 case 1: return -z; /* atan(-,+) */
88 case 2: return pi - (z-pi_lo); /* atan(+,-) */
90 return (z-pi_lo) - pi; /* atan(-,-) */