1*05a0b428SJohn Marino /* e_atan2f.c -- float version of e_atan2.c.
2*05a0b428SJohn Marino * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3*05a0b428SJohn Marino */
4*05a0b428SJohn Marino
5*05a0b428SJohn Marino /*
6*05a0b428SJohn Marino * ====================================================
7*05a0b428SJohn Marino * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8*05a0b428SJohn Marino *
9*05a0b428SJohn Marino * Developed at SunPro, a Sun Microsystems, Inc. business.
10*05a0b428SJohn Marino * Permission to use, copy, modify, and distribute this
11*05a0b428SJohn Marino * software is freely granted, provided that this notice
12*05a0b428SJohn Marino * is preserved.
13*05a0b428SJohn Marino * ====================================================
14*05a0b428SJohn Marino */
15*05a0b428SJohn Marino
16*05a0b428SJohn Marino #include "math.h"
17*05a0b428SJohn Marino #include "math_private.h"
18*05a0b428SJohn Marino
19*05a0b428SJohn Marino static const float
20*05a0b428SJohn Marino tiny = 1.0e-30,
21*05a0b428SJohn Marino zero = 0.0,
22*05a0b428SJohn Marino pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */
23*05a0b428SJohn Marino pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */
24*05a0b428SJohn Marino pi = 3.1415925026e+00, /* 0x40490fda */
25*05a0b428SJohn Marino pi_lo = 1.5099578832e-07; /* 0x34222168 */
26*05a0b428SJohn Marino
27*05a0b428SJohn Marino float
atan2f(float y,float x)28*05a0b428SJohn Marino atan2f(float y, float x)
29*05a0b428SJohn Marino {
30*05a0b428SJohn Marino float z;
31*05a0b428SJohn Marino int32_t k,m,hx,hy,ix,iy;
32*05a0b428SJohn Marino
33*05a0b428SJohn Marino GET_FLOAT_WORD(hx,x);
34*05a0b428SJohn Marino ix = hx&0x7fffffff;
35*05a0b428SJohn Marino GET_FLOAT_WORD(hy,y);
36*05a0b428SJohn Marino iy = hy&0x7fffffff;
37*05a0b428SJohn Marino if((ix>0x7f800000)||
38*05a0b428SJohn Marino (iy>0x7f800000)) /* x or y is NaN */
39*05a0b428SJohn Marino return x+y;
40*05a0b428SJohn Marino if(hx==0x3f800000) return atanf(y); /* x=1.0 */
41*05a0b428SJohn Marino m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */
42*05a0b428SJohn Marino
43*05a0b428SJohn Marino /* when y = 0 */
44*05a0b428SJohn Marino if(iy==0) {
45*05a0b428SJohn Marino switch(m) {
46*05a0b428SJohn Marino case 0:
47*05a0b428SJohn Marino case 1: return y; /* atan(+-0,+anything)=+-0 */
48*05a0b428SJohn Marino case 2: return pi+tiny;/* atan(+0,-anything) = pi */
49*05a0b428SJohn Marino case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
50*05a0b428SJohn Marino }
51*05a0b428SJohn Marino }
52*05a0b428SJohn Marino /* when x = 0 */
53*05a0b428SJohn Marino if(ix==0) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
54*05a0b428SJohn Marino
55*05a0b428SJohn Marino /* when x is INF */
56*05a0b428SJohn Marino if(ix==0x7f800000) {
57*05a0b428SJohn Marino if(iy==0x7f800000) {
58*05a0b428SJohn Marino switch(m) {
59*05a0b428SJohn Marino case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */
60*05a0b428SJohn Marino case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */
61*05a0b428SJohn Marino case 2: return (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
62*05a0b428SJohn Marino case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/
63*05a0b428SJohn Marino }
64*05a0b428SJohn Marino } else {
65*05a0b428SJohn Marino switch(m) {
66*05a0b428SJohn Marino case 0: return zero ; /* atan(+...,+INF) */
67*05a0b428SJohn Marino case 1: return -zero ; /* atan(-...,+INF) */
68*05a0b428SJohn Marino case 2: return pi+tiny ; /* atan(+...,-INF) */
69*05a0b428SJohn Marino case 3: return -pi-tiny ; /* atan(-...,-INF) */
70*05a0b428SJohn Marino }
71*05a0b428SJohn Marino }
72*05a0b428SJohn Marino }
73*05a0b428SJohn Marino /* when y is INF */
74*05a0b428SJohn Marino if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
75*05a0b428SJohn Marino
76*05a0b428SJohn Marino /* compute y/x */
77*05a0b428SJohn Marino k = (iy-ix)>>23;
78*05a0b428SJohn Marino if(k > 60) z=pi_o_2+(float)0.5*pi_lo; /* |y/x| > 2**60 */
79*05a0b428SJohn Marino else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */
80*05a0b428SJohn Marino else z=atanf(fabsf(y/x)); /* safe to do y/x */
81*05a0b428SJohn Marino switch (m) {
82*05a0b428SJohn Marino case 0: return z ; /* atan(+,+) */
83*05a0b428SJohn Marino case 1: {
84*05a0b428SJohn Marino u_int32_t zh;
85*05a0b428SJohn Marino GET_FLOAT_WORD(zh,z);
86*05a0b428SJohn Marino SET_FLOAT_WORD(z,zh ^ 0x80000000);
87*05a0b428SJohn Marino }
88*05a0b428SJohn Marino return z ; /* atan(-,+) */
89*05a0b428SJohn Marino case 2: return pi-(z-pi_lo);/* atan(+,-) */
90*05a0b428SJohn Marino default: /* case 3 */
91*05a0b428SJohn Marino return (z-pi_lo)-pi;/* atan(-,-) */
92*05a0b428SJohn Marino }
93*05a0b428SJohn Marino }
94