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 "math.h"
17#include "math_private.h"
18
19static volatile float
20tiny  = 1.0e-30;
21static const float
22zero  = 0.0,
23pi_o_4  = 7.8539818525e-01, /* 0x3f490fdb */
24pi_o_2  = 1.5707963705e+00, /* 0x3fc90fdb */
25pi      = 3.1415927410e+00; /* 0x40490fdb */
26static volatile float
27pi_lo   = -8.7422776573e-08; /* 0xb3bbbd2e */
28
29float
30atan2f(float y, float x)
31{
32	float z;
33	int32_t k,m,hx,hy,ix,iy;
34
35	GET_FLOAT_WORD(hx,x);
36	ix = hx&0x7fffffff;
37	GET_FLOAT_WORD(hy,y);
38	iy = hy&0x7fffffff;
39	if((ix>0x7f800000)||
40	   (iy>0x7f800000))	/* x or y is NaN */
41	    return nan_mix(x, y);
42	if(hx==0x3f800000) return atanf(y);   /* x=1.0 */
43	m = ((hy>>31)&1)|((hx>>30)&2);	/* 2*sign(x)+sign(y) */
44
45    /* when y = 0 */
46	if(iy==0) {
47	    switch(m) {
48		case 0:
49		case 1: return y; 	/* atan(+-0,+anything)=+-0 */
50		case 2: return  pi+tiny;/* atan(+0,-anything) = pi */
51		case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
52	    }
53	}
54    /* when x = 0 */
55	if(ix==0) return (hy<0)?  -pi_o_2-tiny: pi_o_2+tiny;
56
57    /* when x is INF */
58	if(ix==0x7f800000) {
59	    if(iy==0x7f800000) {
60		switch(m) {
61		    case 0: return  pi_o_4+tiny;/* atan(+INF,+INF) */
62		    case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */
63		    case 2: return  (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
64		    case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/
65		}
66	    } else {
67		switch(m) {
68		    case 0: return  zero  ;	/* atan(+...,+INF) */
69		    case 1: return -zero  ;	/* atan(-...,+INF) */
70		    case 2: return  pi+tiny  ;	/* atan(+...,-INF) */
71		    case 3: return -pi-tiny  ;	/* atan(-...,-INF) */
72		}
73	    }
74	}
75    /* when y is INF */
76	if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
77
78    /* compute y/x */
79	k = (iy-ix)>>23;
80	if(k > 26) {			/* |y/x| >  2**26 */
81	    z=pi_o_2+(float)0.5*pi_lo;
82	    m&=1;
83	}
84	else if(k<-26&&hx<0) z=0.0; 	/* 0 > |y|/x > -2**-26 */
85	else z=atanf(fabsf(y/x));	/* safe to do y/x */
86	switch (m) {
87	    case 0: return       z  ;	/* atan(+,+) */
88	    case 1: return      -z  ;	/* atan(-,+) */
89	    case 2: return  pi-(z-pi_lo);/* atan(+,-) */
90	    default: /* case 3 */
91	    	    return  (z-pi_lo)-pi;/* atan(-,-) */
92	}
93}
94