e_atan2f.c revision 176451 
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#include <sys/cdefs.h>
17__FBSDID("$FreeBSD: head/lib/msun/src/e_atan2f.c 176451 2008-02-22 02:30:36Z das $");
18
19#include "math.h"
20#include "math_private.h"
21
22static const float
23tiny  = 1.0e-30,
24zero  = 0.0,
25pi_o_4  = 7.8539818525e-01, /* 0x3f490fdb */
26pi_o_2  = 1.5707963705e+00, /* 0x3fc90fdb */
27pi      = 3.1415927410e+00, /* 0x40490fdb */
28pi_lo   = -8.7422776573e-08; /* 0xb3bbbd2e */
29
30float
31__ieee754_atan2f(float y, float x)
32{
33	float z;
34	int32_t k,m,hx,hy,ix,iy;
35
36	GET_FLOAT_WORD(hx,x);
37	ix = hx&0x7fffffff;
38	GET_FLOAT_WORD(hy,y);
39	iy = hy&0x7fffffff;
40	if((ix>0x7f800000)||
41	   (iy>0x7f800000))	/* x or y is NaN */
42	   return x+y;
43	if(hx==0x3f800000) return atanf(y);   /* x=1.0 */
44	m = ((hy>>31)&1)|((hx>>30)&2);	/* 2*sign(x)+sign(y) */
45
46    /* when y = 0 */
47	if(iy==0) {
48	    switch(m) {
49		case 0:
50		case 1: return y; 	/* atan(+-0,+anything)=+-0 */
51		case 2: return  pi+tiny;/* atan(+0,-anything) = pi */
52		case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
53	    }
54	}
55    /* when x = 0 */
56	if(ix==0) return (hy<0)?  -pi_o_2-tiny: pi_o_2+tiny;
57
58    /* when x is INF */
59	if(ix==0x7f800000) {
60	    if(iy==0x7f800000) {
61		switch(m) {
62		    case 0: return  pi_o_4+tiny;/* atan(+INF,+INF) */
63		    case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */
64		    case 2: return  (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
65		    case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/
66		}
67	    } else {
68		switch(m) {
69		    case 0: return  zero  ;	/* atan(+...,+INF) */
70		    case 1: return -zero  ;	/* atan(-...,+INF) */
71		    case 2: return  pi+tiny  ;	/* atan(+...,-INF) */
72		    case 3: return -pi-tiny  ;	/* atan(-...,-INF) */
73		}
74	    }
75	}
76    /* when y is INF */
77	if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
78
79    /* compute y/x */
80	k = (iy-ix)>>23;
81	if(k > 60) z=pi_o_2+(float)0.5*pi_lo; 	/* |y/x| >  2**60 */
82	else if(hx<0&&k<-60) z=0.0; 	/* |y|/x < -2**60 */
83	else z=atanf(fabsf(y/x));	/* safe to do y/x */
84	switch (m) {
85	    case 0: return       z  ;	/* atan(+,+) */
86	    case 1: {
87	    	      u_int32_t zh;
88		      GET_FLOAT_WORD(zh,z);
89		      SET_FLOAT_WORD(z,zh ^ 0x80000000);
90		    }
91		    return       z  ;	/* atan(-,+) */
92	    case 2: return  pi-(z-pi_lo);/* atan(+,-) */
93	    default: /* case 3 */
94	    	    return  (z-pi_lo)-pi;/* atan(-,-) */
95	}
96}
97