Subversion Repositories openrisc_2011-10-31

/* @(#)s_rint.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

<<rint>>, <<rintf>>--round to integer

INDEX

        rint

INDEX

        rintf

ANSI_SYNOPSIS

        #include <math.h>

        double rint(double <[x]>);

        float rintf(float <[x]>);

DESCRIPTION

        The <<rint>> functions round their argument to an integer value in

        floating-point format, using the current rounding direction.  They

        raise the "inexact" floating-point exception if the result differs

        in value from the argument.  See the <<nearbyint>> functions for the

        same function with the "inexact" floating-point exception never being

        raised.  Newlib does not directly support floating-point exceptions.

        The <<rint>> functions are written so that the "inexact" exception is

        raised in hardware implementations that support it, even though Newlib

        does not provide access.

RETURNS

<[x]> rounded to an integral value, using the current rounding direction.

PORTABILITY

ANSI C, POSIX

SEEALSO

<<nearbyint>>, <<round>>

*/

/*

 * rint(x)

 * Return x rounded to integral value according to the prevailing

 * rounding mode.

 * Method:

 *      Using floating addition.

 * Exception:

 *      Inexact flag raised if x not equal to rint(x).

 */

#include "fdlibm.h"

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__

static const double

#else

static double

#endif

TWO52[2]={

  4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */

 -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */

};

#ifdef __STDC__

        double rint(double x)

#else

        double rint(x)

        double x;

#endif

{

        __int32_t i0,j0,sx;

        __uint32_t i,i1;

        double t;

        volatile double w;

        EXTRACT_WORDS(i0,i1,x);

        sx = (i0>>31)&1;

        j0 = ((i0>>20)&0x7ff)-0x3ff;

        if(j0<20) {

            if(j0<0) {

                if(((i0&0x7fffffff)|i1)==0) return x;

                i1 |= (i0&0x0fffff);

                i0 &= 0xfffe0000;

                i0 |= ((i1|-i1)>>12)&0x80000;

                SET_HIGH_WORD(x,i0);

                w = TWO52[sx]+x;

                t =  w-TWO52[sx];

                GET_HIGH_WORD(i0,t);

                SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31));

                return t;

            } else {

                i = (0x000fffff)>>j0;

                if(((i0&i)|i1)==0) return x; /* x is integral */

                i>>=1;

                if(((i0&i)|i1)!=0) {

                    if(j0==19) i1 = 0x40000000; else

                    i0 = (i0&(~i))|((0x20000)>>j0);

                }

            }

        } else if (j0>51) {

            if(j0==0x400) return x+x;   /* inf or NaN */

            else return x;              /* x is integral */

        } else {

            i = ((__uint32_t)(0xffffffff))>>(j0-20);

            if((i1&i)==0) return x;      /* x is integral */

            i>>=1;

            if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20));

        }

        INSERT_WORDS(x,i0,i1);

        w = TWO52[sx]+x;

        return w-TWO52[sx];

}

#endif /* _DOUBLE_IS_32BITS */