/* e_atan2f.c -- float version of e_atan2.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#include "math.h"
#include "math_private.h"

static volatile float
tiny  = 1.0e-30;
static const float
zero  = 0.0,
pi_o_4  = 7.8539818525e-01, /* 0x3f490fdb */
pi_o_2  = 1.5707963705e+00, /* 0x3fc90fdb */
pi      = 3.1415927410e+00; /* 0x40490fdb */
static volatile float
pi_lo   = -8.7422776573e-08; /* 0xb3bbbd2e */

float
atan2f(float y, float x)
{
        float z;
        int32_t k,m,hx,hy,ix,iy;

        GET_FLOAT_WORD(hx,x);
        ix = hx&0x7fffffff;
        GET_FLOAT_WORD(hy,y);
        iy = hy&0x7fffffff;
        if((ix>0x7f800000)||
           (iy>0x7f800000))     /* x or y is NaN */
            return nan_mix(x, y);
        if(hx==0x3f800000) return atanf(y);   /* x=1.0 */
        m = ((hy>>31)&1)|((hx>>30)&2);  /* 2*sign(x)+sign(y) */

    /* when y = 0 */
        if(iy==0) {
            switch(m) {
                case 0:
                case 1: return y;       /* atan(+-0,+anything)=+-0 */
                case 2: return  pi+tiny;/* atan(+0,-anything) = pi */
                case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
            }
        }
    /* when x = 0 */
        if(ix==0) return (hy<0)?  -pi_o_2-tiny: pi_o_2+tiny;

    /* when x is INF */
        if(ix==0x7f800000) {
            if(iy==0x7f800000) {
                switch(m) {
                    case 0: return  pi_o_4+tiny;/* atan(+INF,+INF) */
                    case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */
                    case 2: return  (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
                    case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/
                }
            } else {
                switch(m) {
                    case 0: return  zero  ;     /* atan(+...,+INF) */
                    case 1: return -zero  ;     /* atan(-...,+INF) */
                    case 2: return  pi+tiny  ;  /* atan(+...,-INF) */
                    case 3: return -pi-tiny  ;  /* atan(-...,-INF) */
                }
            }
        }
    /* when y is INF */
        if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;

    /* compute y/x */
        k = (iy-ix)>>23;
        if(k > 26) {                    /* |y/x| >  2**26 */
            z=pi_o_2+(float)0.5*pi_lo;
            m&=1;
        }
        else if(k<-26&&hx<0) z=0.0;     /* 0 > |y|/x > -2**-26 */
        else z=atanf(fabsf(y/x));       /* safe to do y/x */
        switch (m) {
            case 0: return       z  ;   /* atan(+,+) */
            case 1: return      -z  ;   /* atan(-,+) */
            case 2: return  pi-(z-pi_lo);/* atan(+,-) */
            default: /* case 3 */
                    return  (z-pi_lo)-pi;/* atan(-,-) */
        }
}