/* ef_asin.c -- float version of e_asin.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 one = 1.0000000000e+00, /* 0x3F800000 */
    huge = 1.000e+30, pio2_hi = 1.57079637050628662109375f,
                   pio2_lo = -4.37113900018624283e-8f,
                   pio4_hi = 0.785398185253143310546875f,
                   /* coefficient for R(x^2) */
    pS0 = 1.6666667163e-01, /* 0x3e2aaaab */
    pS1 = -3.2556581497e-01, /* 0xbea6b090 */
    pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */
    pS3 = -4.0055535734e-02, /* 0xbd241146 */
    pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */
    pS5 = 3.4793309169e-05, /* 0x3811ef08 */
    qS1 = -2.4033949375e+00, /* 0xc019d139 */
    qS2 = 2.0209457874e+00, /* 0x4001572d */
    qS3 = -6.8828397989e-01, /* 0xbf303361 */
    qS4 = 7.7038154006e-02; /* 0x3d9dc62e */

float
asinf(float x)
{
    float t, w, p, q, c, r, s;
    __int32_t hx, ix;
    GET_FLOAT_WORD(hx, x);
    ix = hx & 0x7fffffff;
    if (ix == 0x3f800000) {
        /* asin(1)=+-pi/2 with inexact */
        return x * pio2_hi + x * pio2_lo;
    } else if (ix > 0x3f800000) { /* |x|>= 1 */
        return __math_invalidf(x); /* asin(|x|>1) is NaN */
    } else if (ix < 0x3f000000) { /* |x|<0.5 */
        if (ix < 0x32000000) { /* if |x| < 2**-27 */
            if (huge + x > one)
                return x; /* return x with inexact if x!=0*/
        } else {
            t = x * x;
            p = t *
                (pS0 + t * (pS1 + t * (pS2 + t * (pS3 + t * (pS4 + t * pS5)))));
            q = one + t * (qS1 + t * (qS2 + t * (qS3 + t * qS4)));
            w = p / q;
            return x + x * w;
        }
    }
    /* 1> |x|>= 0.5 */
    w = one - fabsf(x);
    t = w * (float)0.5;
    p = t * (pS0 + t * (pS1 + t * (pS2 + t * (pS3 + t * (pS4 + t * pS5)))));
    q = one + t * (qS1 + t * (qS2 + t * (qS3 + t * qS4)));
    s = sqrtf(t);
    if (ix >= 0x3F79999A) { /* if |x| > 0.975 */
        w = p / q;
        t = pio2_hi - ((float)2.0 * (s + s * w) - pio2_lo);
    } else {
        __int32_t iw;
        w = s;
        GET_FLOAT_WORD(iw, w);
        SET_FLOAT_WORD(w, iw & 0xfffff000);
        c = (t - w * w) / (s + w);
        r = p / q;
        p = (float)2.0 * s * r - (pio2_lo - (float)2.0 * c);
        q = pio4_hi - (float)2.0 * w;
        t = pio4_hi - (p - q);
    }
    if (hx > 0)
        return t;
    else
        return -t;
}

_MATH_ALIAS_f_f(asin)