/* ef_atan2.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 "fdlibm.h"

static const float tiny = 1.0e-30, zero = 0.0,
                   pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */
    pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */
    pi = 3.1415927410e+00, /* 0x40490fdb */
    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 (FLT_UWORD_IS_NAN(ix) || FLT_UWORD_IS_NAN(iy)) /* x or y is NaN */
        return 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 (FLT_UWORD_IS_ZERO(iy)) {
        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 (FLT_UWORD_IS_ZERO(ix))
        return (hy < 0) ? -pi_o_2 - tiny : pi_o_2 + tiny;

    /* when x is INF */
    if (FLT_UWORD_IS_INFINITE(ix)) {
        if (FLT_UWORD_IS_INFINITE(iy)) {
            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 (FLT_UWORD_IS_INFINITE(iy))
        return (hy < 0) ? -pi_o_2 - tiny : pi_o_2 + tiny;

    /* compute y/x */
    k = (iy - ix) >> 23;
    if (k > 60)
        z = pi_o_2 + (float)0.5 * pi_lo; /* |y/x| >  2**60 */
    else if (hx < 0 && k < -60)
        z = 0.0f; /* |y|/x < -2**60 */
    else
        z = atanf(check_uflowf(fabsf(y / x))); /* safe to do y/x */
    switch (m) {
    case 0:
        return z; /* atan(+,+) */
    case 1: {
        __uint32_t zh;
        GET_FLOAT_WORD(zh, z);
        SET_FLOAT_WORD(z, zh ^ 0x80000000);
    }
        return z; /* atan(-,+) */
    case 2:
        return pi - (z - pi_lo); /* atan(+,-) */
    default: /* case 3 */
        return (z - pi_lo) - pi; /* atan(-,-) */
    }
}

_MATH_ALIAS_f_ff(atan2)
