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[glibc.git] / sysdeps / libm-ieee754 / e_atan2f.c
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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 */
5 /*
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
12 * is preserved.
13 * ====================================================
16 #if defined(LIBM_SCCS) && !defined(lint)
17 static char rcsid[] = "$NetBSD: e_atan2f.c,v 1.4 1995/05/10 20:44:53 jtc Exp $";
18 #endif
20 #include "math.h"
21 #include "math_private.h"
23 #ifdef __STDC__
24 static const float
25 #else
26 static float
27 #endif
28 tiny = 1.0e-30,
29 zero = 0.0,
30 pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */
31 pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */
32 pi = 3.1415927410e+00, /* 0x40490fdb */
33 pi_lo = -8.7422776573e-07; /* 0xb3bbbd2e */
35 #ifdef __STDC__
36 float __ieee754_atan2f(float y, float x)
37 #else
38 float __ieee754_atan2f(y,x)
39 float y,x;
40 #endif
42 float z;
43 int32_t k,m,hx,hy,ix,iy;
45 GET_FLOAT_WORD(hx,x);
46 ix = hx&0x7fffffff;
47 GET_FLOAT_WORD(hy,y);
48 iy = hy&0x7fffffff;
49 if((ix>0x7f800000)||
50 (iy>0x7f800000)) /* x or y is NaN */
51 return x+y;
52 if(hx==0x3f800000) return __atanf(y); /* x=1.0 */
53 m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */
55 /* when y = 0 */
56 if(iy==0) {
57 switch(m) {
58 case 0:
59 case 1: return y; /* atan(+-0,+anything)=+-0 */
60 case 2: return pi+tiny;/* atan(+0,-anything) = pi */
61 case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
64 /* when x = 0 */
65 if(ix==0) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
67 /* when x is INF */
68 if(ix==0x7f800000) {
69 if(iy==0x7f800000) {
70 switch(m) {
71 case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */
72 case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */
73 case 2: return (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
74 case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/
76 } else {
77 switch(m) {
78 case 0: return zero ; /* atan(+...,+INF) */
79 case 1: return -zero ; /* atan(-...,+INF) */
80 case 2: return pi+tiny ; /* atan(+...,-INF) */
81 case 3: return -pi-tiny ; /* atan(-...,-INF) */
85 /* when y is INF */
86 if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
88 /* compute y/x */
89 k = (iy-ix)>>23;
90 if(k > 60) z=pi_o_2+(float)0.5*pi_lo; /* |y/x| > 2**60 */
91 else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */
92 else z=__atanf(fabsf(y/x)); /* safe to do y/x */
93 switch (m) {
94 case 0: return z ; /* atan(+,+) */
95 case 1: {
96 u_int32_t zh;
97 GET_FLOAT_WORD(zh,z);
98 SET_FLOAT_WORD(z,zh ^ 0x80000000);
100 return z ; /* atan(-,+) */
101 case 2: return pi-(z-pi_lo);/* atan(+,-) */
102 default: /* case 3 */
103 return (z-pi_lo)-pi;/* atan(-,-) */