e_atan2f.c revision 97407 
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
17static char rcsid[] = "$FreeBSD: head/lib/msun/src/e_atan2f.c 97407 2002-05-28 17:03:12Z alfred $";
18#endif
19
20#include "math.h"
21#include "math_private.h"
22
23static const float
24tiny  = 1.0e-30,
25zero  = 0.0,
26pi_o_4  = 7.8539818525e-01, /* 0x3f490fdb */
27pi_o_2  = 1.5707963705e+00, /* 0x3fc90fdb */
28pi      = 3.1415925026e+00, /* 0x40490fda */
29pi_lo   = 1.5099578832e-07; /* 0x34222168 */
30
31float
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}
98