/* e_asinf.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 "math.h"
#include "math_private.h"

static const float
one =  1.0000000000e+00, /* 0x3F800000 */
huge =  1.000e+30;

/*
 * The coefficients for the rational approximation were generated over
 *  0x1p-12f <= x <= 0.5f.  The maximum error satisfies log2(e) < -30.084.
 */
static const float
pS0 =  1.66666672e-01f, /* 0x3e2aaaab */
pS1 = -1.19510300e-01f, /* 0xbdf4c1d1 */
pS2 =  5.47002675e-03f, /* 0x3bb33de9 */
qS1 = -1.16706085e+00f, /* 0xbf956240 */
qS2 =  2.90115148e-01f; /* 0x3e9489f9 */

static const double
pio2 =  1.570796326794896558e+00;

float
asinf(float x)
{
        double s;
        float t,w,p,q;
        int32_t hx,ix;
        GET_FLOAT_WORD(hx,x);
        ix = hx&0x7fffffff;
        if(ix>=0x3f800000) {            /* |x| >= 1 */
            if(ix==0x3f800000)          /* |x| == 1 */
                return x*pio2;          /* asin(+-1) = +-pi/2 with inexact */
            return (x-x)/(x-x);         /* asin(|x|>1) is NaN */
        } else if (ix<0x3f000000) {     /* |x|<0.5 */
            if(ix<0x39800000) {         /* |x| < 2**-12 */
                if(huge+x>one) return x;/* return x with inexact if x!=0*/
            }
            t = x*x;
            p = t*(pS0+t*(pS1+t*pS2));
            q = one+t*(qS1+t*qS2);
            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));
        q = one+t*(qS1+t*qS2);
        s = sqrt(t);
        w = p/q;
        t = pio2-2.0*(s+s*w);
        if(hx>0) return t; else return -t;
}