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 const float
20tiny  = 1.0e-30,
21zero  = 0.0,
22pi_o_4  = 7.8539818525e-01, /* 0x3f490fdb */
23pi_o_2  = 1.5707963705e+00, /* 0x3fc90fdb */
24pi      = 3.1415925026e+00, /* 0x40490fda */
25pi_lo   = 1.5099578832e-07; /* 0x34222168 */
26
27float
28atan2f(float y, float x)
29{
30	float z;
31	int32_t k,m,hx,hy,ix,iy;
32
33	GET_FLOAT_WORD(hx,x);
34	ix = hx&0x7fffffff;
35	GET_FLOAT_WORD(hy,y);
36	iy = hy&0x7fffffff;
37	if((ix>0x7f800000)||
38	   (iy>0x7f800000))	/* x or y is NaN */
39	   return x+y;
40	if(hx==0x3f800000) return atanf(y);   /* x=1.0 */
41	m = ((hy>>31)&1)|((hx>>30)&2);	/* 2*sign(x)+sign(y) */
42
43    /* when y = 0 */
44	if(iy==0) {
45	    switch(m) {
46		case 0:
47		case 1: return y; 	/* atan(+-0,+anything)=+-0 */
48		case 2: return  pi+tiny;/* atan(+0,-anything) = pi */
49		case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
50	    }
51	}
52    /* when x = 0 */
53	if(ix==0) return (hy<0)?  -pi_o_2-tiny: pi_o_2+tiny;
54
55    /* when x is INF */
56	if(ix==0x7f800000) {
57	    if(iy==0x7f800000) {
58		switch(m) {
59		    case 0: return  pi_o_4+tiny;/* atan(+INF,+INF) */
60		    case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */
61		    case 2: return  (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
62		    case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/
63		}
64	    } else {
65		switch(m) {
66		    case 0: return  zero  ;	/* atan(+...,+INF) */
67		    case 1: return -zero  ;	/* atan(-...,+INF) */
68		    case 2: return  pi+tiny  ;	/* atan(+...,-INF) */
69		    case 3: return -pi-tiny  ;	/* atan(-...,-INF) */
70		}
71	    }
72	}
73    /* when y is INF */
74	if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
75
76    /* compute y/x */
77	k = (iy-ix)>>23;
78	if(k > 60) z=pi_o_2+(float)0.5*pi_lo; 	/* |y/x| >  2**60 */
79	else if(hx<0&&k<-60) z=0.0; 	/* |y|/x < -2**60 */
80	else z=atanf(fabsf(y/x));	/* safe to do y/x */
81	switch (m) {
82	    case 0: return       z  ;	/* atan(+,+) */
83	    case 1: {
84	    	      u_int32_t zh;
85		      GET_FLOAT_WORD(zh,z);
86		      SET_FLOAT_WORD(z,zh ^ 0x80000000);
87		    }
88		    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}
94DEF_STD(atan2f);
95