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