Subversion Repositories openrisc_2011-10-31

/* @(#)e_remainder.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

<<remainder>>, <<remainderf>>---round and  remainder

INDEX

        remainder

INDEX

        remainderf

ANSI_SYNOPSIS

        #include <math.h>

        double remainder(double <[x]>, double <[y]>);

        float remainderf(float <[x]>, float <[y]>);

TRAD_SYNOPSIS

        #include <math.h>

        double remainder(<[x]>,<[y]>)

        double <[x]>, <[y]>;

        float remainderf(<[x]>,<[y]>)

        float <[x]>, <[y]>;

DESCRIPTION

<<remainder>> and <<remainderf>> find the remainder of

<[x]>/<[y]>; this value is in the range -<[y]>/2 .. +<[y]>/2.

RETURNS

<<remainder>> returns the integer result as a double.

PORTABILITY

<<remainder>> is a System V release 4.

<<remainderf>> is an extension.

*/

/* remainder(x,p)

 * Return :

 *      returns  x REM p  =  x - [x/p]*p as if in infinite

 *      precise arithmetic, where [x/p] is the (infinite bit)

 *      integer nearest x/p (in half way case choose the even one).

 * Method :

 *      Based on fmod() return x-[x/p]chopped*p exactlp.

 */

#include "fdlibm.h"

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__

static const double zero = 0.0;

#else

static double zero = 0.0;

#endif

#ifdef __STDC__

        double remainder(double x, double p)

#else

        double remainder(x,p)

        double x,p;

#endif

{

        __int32_t hx,hp;

        __uint32_t sx,lx,lp;

        double p_half;

        EXTRACT_WORDS(hx,lx,x);

        EXTRACT_WORDS(hp,lp,p);

        sx = hx&0x80000000;

        hp &= 0x7fffffff;

        hx &= 0x7fffffff;

    /* purge off exception values */

        if((hp|lp)==0) return (x*p)/(x*p);       /* p = 0 */

        if((hx>=0x7ff00000)||                   /* x not finite */

          ((hp>=0x7ff00000)&&                   /* p is NaN */

          (((hp-0x7ff00000)|lp)!=0)))

            return (x*p)/(x*p);

        if (hp<=0x7fdfffff) x = fmod(x,p+p);    /* now x < 2p */

        if (((hx-hp)|(lx-lp))==0) return zero*x;

        x  = fabs(x);

        p  = fabs(p);

        if (hp<0x00200000) {

            if(x+x>p) {

                x-=p;

                if(x+x>=p) x -= p;

            }

        } else {

            p_half = 0.5*p;

            if(x>p_half) {

                x-=p;

                if(x>=p_half) x -= p;

            }

        }

        GET_HIGH_WORD(hx,x);

        SET_HIGH_WORD(x,hx^sx);

        return x;

}

#endif /* defined(_DOUBLE_IS_32BITS) */