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e_atan2f.c (2795B)
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1 /* e_atan2f.c -- float version of e_atan2.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3 */
4
5 /*
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8 *
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
12 * is preserved.
13 * ====================================================
14 */
15
16 #ifndef lint
17 static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_atan2f.c,v 1.7 2004/06/02 17:09:05 bde Exp $";
18 #endif
19
20 #include "math.h"
21 #include "math_private.h"
22
23 static const float
24 tiny = 1.0e-30,
25 zero = 0.0,
26 pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */
27 pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */
28 pi = 3.1415927410e+00, /* 0x40490fdb */
29 pi_lo = -8.7422776573e-08; /* 0xb3bbbd2e */
30
31 float
32 __ieee754_atan2f(float y, float x)
33 {
34 float z;
35 int32_t k,m,hx,hy,ix,iy;
36
37 GET_FLOAT_WORD(hx,x);
38 ix = hx&0x7fffffff;
39 GET_FLOAT_WORD(hy,y);
40 iy = hy&0x7fffffff;
41 if((ix>0x7f800000)||
42 (iy>0x7f800000)) /* x or y is NaN */
43 return x+y;
44 if(hx==0x3f800000) return atanf(y); /* x=1.0 */
45 m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */
46
47 /* when y = 0 */
48 if(iy==0) {
49 switch(m) {
50 case 0:
51 case 1: return y; /* atan(+-0,+anything)=+-0 */
52 case 2: return pi+tiny;/* atan(+0,-anything) = pi */
53 case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
54 }
55 }
56 /* when x = 0 */
57 if(ix==0) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
58
59 /* when x is INF */
60 if(ix==0x7f800000) {
61 if(iy==0x7f800000) {
62 switch(m) {
63 case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */
64 case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */
65 case 2: return (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
66 case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/
67 }
68 } else {
69 switch(m) {
70 case 0: return zero ; /* atan(+...,+INF) */
71 case 1: return -zero ; /* atan(-...,+INF) */
72 case 2: return pi+tiny ; /* atan(+...,-INF) */
73 case 3: return -pi-tiny ; /* atan(-...,-INF) */
74 }
75 }
76 }
77 /* when y is INF */
78 if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
79
80 /* compute y/x */
81 k = (iy-ix)>>23;
82 if(k > 60) z=pi_o_2+(float)0.5*pi_lo; /* |y/x| > 2**60 */
83 else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */
84 else z=atanf(fabsf(y/x)); /* safe to do y/x */
85 switch (m) {
86 case 0: return z ; /* atan(+,+) */
87 case 1: {
88 u_int32_t zh;
89 GET_FLOAT_WORD(zh,z);
90 SET_FLOAT_WORD(z,zh ^ 0x80000000);
91 }
92 return z ; /* atan(-,+) */
93 case 2: return pi-(z-pi_lo);/* atan(+,-) */
94 default: /* case 3 */
95 return (z-pi_lo)-pi;/* atan(-,-) */
96 }
97 }