1 /*****************************************************************************/
2 /*****************************************************************************/
3 // atan2f from musl-0.9.15
4 /*****************************************************************************/
5 /*****************************************************************************/
6
7 /* origin: FreeBSD /usr/src/lib/msun/src/e_atan2f.c */
8 /*
9 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
10 */
11 /*
12 * ====================================================
13 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
14 *
15 * Developed at SunPro, a Sun Microsystems, Inc. business.
16 * Permission to use, copy, modify, and distribute this
17 * software is freely granted, provided that this notice
18 * is preserved.
19 * ====================================================
20 */
21
22 #include "libm.h"
23
24 static const float
25 pi = 3.1415927410e+00f, /* 0x40490fdb */
26 pi_lo = -8.7422776573e-08f; /* 0xb3bbbd2e */
27
atan2f(float y,float x)28 float atan2f(float y, float x)
29 {
30 float z;
31 uint32_t m,ix,iy;
32
33 if (isnan(x) || isnan(y))
34 return x+y;
35 GET_FLOAT_WORD(ix, x);
36 GET_FLOAT_WORD(iy, y);
37 if (ix == 0x3f800000) /* x=1.0 */
38 return atanf(y);
39 m = ((iy>>31)&1) | ((ix>>30)&2); /* 2*sign(x)+sign(y) */
40 ix &= 0x7fffffff;
41 iy &= 0x7fffffff;
42
43 /* when y = 0 */
44 if (iy == 0) {
45 switch (m) {
46 case 0:
47 case 1: return y; /* atan(+-0,+anything)=+-0 */
48 case 2: return pi; /* atan(+0,-anything) = pi */
49 case 3: return -pi; /* atan(-0,-anything) =-pi */
50 }
51 }
52 /* when x = 0 */
53 if (ix == 0)
54 return m&1 ? -pi/2 : pi/2;
55 /* when x is INF */
56 if (ix == 0x7f800000) {
57 if (iy == 0x7f800000) {
58 switch (m) {
59 case 0: return pi/4; /* atan(+INF,+INF) */
60 case 1: return -pi/4; /* atan(-INF,+INF) */
61 case 2: return 3*pi/4; /*atan(+INF,-INF)*/
62 case 3: return -3*pi/4; /*atan(-INF,-INF)*/
63 }
64 } else {
65 switch (m) {
66 case 0: return 0.0f; /* atan(+...,+INF) */
67 case 1: return -0.0f; /* atan(-...,+INF) */
68 case 2: return pi; /* atan(+...,-INF) */
69 case 3: return -pi; /* atan(-...,-INF) */
70 }
71 }
72 }
73 /* |y/x| > 0x1p26 */
74 if (ix+(26<<23) < iy || iy == 0x7f800000)
75 return m&1 ? -pi/2 : pi/2;
76
77 /* z = atan(|y/x|) with correct underflow */
78 if ((m&2) && iy+(26<<23) < ix) /*|y/x| < 0x1p-26, x < 0 */
79 z = 0.0;
80 else
81 z = atanf(fabsf(y/x));
82 switch (m) {
83 case 0: return z; /* atan(+,+) */
84 case 1: return -z; /* atan(-,+) */
85 case 2: return pi - (z-pi_lo); /* atan(+,-) */
86 default: /* case 3 */
87 return (z-pi_lo) - pi; /* atan(-,-) */
88 }
89 }
90