/* origin: FreeBSD /usr/src/lib/msun/src/e_asinl.c */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunSoft, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */
/*
 * See comments in asin.c.
 * Converted to long double by David Schultz <das@FreeBSD.ORG>.
 */

#include "libm.h"

#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
long double asinl(long double x)
{
    return asin(x);
}
#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
#    include "__invtrigl.h"
#    if LDBL_MANT_DIG == 64
#        define CLOSETO1(u) (u.i.m >> 56 >= 0xf7)
#        define CLEARBOTTOM(u) (u.i.m &= -1ULL << 32)
#    elif LDBL_MANT_DIG == 113
#        define CLOSETO1(u) (u.i.top >= 0xee00)
#        define CLEARBOTTOM(u) (u.i.lo = 0)
#    endif

long double asinl(long double x)
{
    union ldshape u = {x};
    long double z, r, s;
    uint16_t e = u.i.se & 0x7fff;
    int sign = u.i.se >> 15;

    if (e >= 0x3fff)
    { /* |x| >= 1 or nan */
        /* asin(+-1)=+-pi/2 with inexact */
        if (x == 1 || x == -1)
            return x * pio2_hi + 0x1p-120f;
        return 0 / (x - x);
    }
    if (e < 0x3fff - 1)
    { /* |x| < 0.5 */
        if (e < 0x3fff - (LDBL_MANT_DIG + 1) / 2)
        {
            /* return x with inexact if x!=0 */
            FORCE_EVAL(x + 0x1p120f);
            return x;
        }
        return x + x * __invtrigl_R(x * x);
    }
    /* 1 > |x| >= 0.5 */
    z = (1.0 - fabsl(x)) * 0.5;
    s = sqrtl(z);
    r = __invtrigl_R(z);
    if (CLOSETO1(u))
    {
        x = pio2_hi - (2 * (s + s * r) - pio2_lo);
    }
    else
    {
        long double f, c;
        u.f = s;
        CLEARBOTTOM(u);
        f = u.f;
        c = (z - f * f) / (s + f);
        x = 0.5 * pio2_hi - (2 * s * r - (pio2_lo - 2 * c) - (0.5 * pio2_hi - 2 * f));
    }
    return sign ? -x : x;
}
#endif
