Subversion Repositories openrisc_2011-10-31

/* @(#)s_sin.c 5.1 93/09/24 */

/*

 * ====================================================

 * 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.

 * ====================================================

 */

/*

FUNCTION

        <<sin>>, <<sinf>>, <<cos>>, <<cosf>>---sine or cosine

INDEX

sin

INDEX

sinf

INDEX

cos

INDEX

cosf

ANSI_SYNOPSIS

        #include <math.h>

        double sin(double <[x]>);

        float  sinf(float <[x]>);

        double cos(double <[x]>);

        float cosf(float <[x]>);

TRAD_SYNOPSIS

        #include <math.h>

        double sin(<[x]>)

        double <[x]>;

        float  sinf(<[x]>)

        float <[x]>;

        double cos(<[x]>)

        double <[x]>;

        float cosf(<[x]>)

        float <[x]>;

DESCRIPTION

        <<sin>> and <<cos>> compute (respectively) the sine and cosine

        of the argument <[x]>.  Angles are specified in radians.

        <<sinf>> and <<cosf>> are identical, save that they take and

        return <<float>> values.

RETURNS

        The sine or cosine of <[x]> is returned.

PORTABILITY

        <<sin>> and <<cos>> are ANSI C.

        <<sinf>> and <<cosf>> are extensions.

QUICKREF

        sin ansi pure

        sinf - pure

*/

/* sin(x)

 * Return sine function of x.

 *

 * kernel function:

 *      __kernel_sin            ... sine function on [-pi/4,pi/4]

 *      __kernel_cos            ... cose function on [-pi/4,pi/4]

 *      __ieee754_rem_pio2      ... argument reduction routine

 *

 * Method.

 *      Let S,C and T denote the sin, cos and tan respectively on

 *      [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2

 *      in [-pi/4 , +pi/4], and let n = k mod 4.

 *      We have

 *

 *          n        sin(x)      cos(x)        tan(x)

 *     ----------------------------------------------------------

 *          0          S           C             T

 *          1          C          -S            -1/T

 *          2         -S          -C             T

 *          3         -C           S            -1/T

 *     ----------------------------------------------------------

 *

 * Special cases:

 *      Let trig be any of sin, cos, or tan.

 *      trig(+-INF)  is NaN, with signals;

 *      trig(NaN)    is that NaN;

 *

 * Accuracy:

 *      TRIG(x) returns trig(x) nearly rounded

 */

#include "fdlibm.h"

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__

        double sin(double x)

#else

        double sin(x)

        double x;

#endif

{

        double y[2],z=0.0;

        __int32_t n,ix;

    /* High word of x. */

        GET_HIGH_WORD(ix,x);

    /* |x| ~< pi/4 */

        ix &= 0x7fffffff;

        if(ix <= 0x3fe921fb) return __kernel_sin(x,z,0);

    /* sin(Inf or NaN) is NaN */

        else if (ix>=0x7ff00000) return x-x;

    /* argument reduction needed */

        else {

            n = __ieee754_rem_pio2(x,y);

            switch(n&3) {

                case 0: return  __kernel_sin(y[0],y[1],1);

                case 1: return  __kernel_cos(y[0],y[1]);

                case 2: return -__kernel_sin(y[0],y[1],1);

                default:

                        return -__kernel_cos(y[0],y[1]);

            }

        }

}

#endif /* _DOUBLE_IS_32BITS */