/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2007 Steven G. Kargl
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Limited testing on pseudorandom numbers drawn within [-2e8:4e8] shows
 * an accuracy of <= 0.7412 ULP.
 */

#include <float.h>
#ifdef __i386__
#include <ieeefp.h>
#endif

#include "fpmath.h"
#include "math.h"
#include "math_private.h"
#if LDBL_MANT_DIG == 64
#include "../ld80/e_rem_pio2l.h"
static const union IEEEl2bits
pio4u = LD80C(0xc90fdaa22168c235, -00001,  7.85398163397448309628e-01L);
#define pio4    (pio4u.e)
#elif LDBL_MANT_DIG == 113
#include "../ld128/e_rem_pio2l.h"
long double pio4 =  7.85398163397448309615660845819875721e-1L;
#else
#error "Unsupported long double format"
#endif

long double
cosl(long double x)
{
        union IEEEl2bits z;
        int e0;
        long double y[2];
        long double hi, lo;

        z.e = x;
        z.bits.sign = 0;

        /* If x = +-0 or x is a subnormal number, then cos(x) = 1 */
        if (z.bits.exp == 0)
                return (1.0);

        /* If x = NaN or Inf, then cos(x) = NaN. */
        if (z.bits.exp == 32767)
                return ((x - x) / (x - x));

        ENTERI();

        /* Optimize the case where x is already within range. */
        if (z.e < pio4)
                RETURNI(__kernel_cosl(z.e, 0));

        e0 = __ieee754_rem_pio2l(x, y);
        hi = y[0];
        lo = y[1];

        switch (e0 & 3) {
        case 0:
            hi = __kernel_cosl(hi, lo);
            break;
        case 1:
            hi = - __kernel_sinl(hi, lo, 1);
            break;
        case 2:
            hi = - __kernel_cosl(hi, lo);
            break;
        case 3:
            hi = __kernel_sinl(hi, lo, 1);
            break;
        }
        
        RETURNI(hi);
}

#if LDBL_MANT_DIG == 113
__weak_reference(cosl, cosf128);
#endif