Subversion Repositories openrisc_2011-10-31

/* @(#)s_nextafter.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

       <<nextafter>>, <<nextafterf>>---get next number

INDEX

        nextafter

INDEX

        nextafterf

ANSI_SYNOPSIS

       #include <math.h>

       double nextafter(double <[val]>, double <[dir]>);

       float nextafterf(float <[val]>, float <[dir]>);

TRAD_SYNOPSIS

       #include <math.h>

       double nextafter(<[val]>, <[dir]>)

              double <[val]>;

              double <[exp]>;

       float nextafter(<[val]>, <[dir]>)

              float <[val]>;

              float <[dir]>;

DESCRIPTION

<<nextafter>> returns the double-precision floating-point number

closest to <[val]> in the direction toward <[dir]>.  <<nextafterf>>

performs the same operation in single precision.  For example,

<<nextafter(0.0,1.0)>> returns the smallest positive number which is

representable in double precision.

RETURNS

Returns the next closest number to <[val]> in the direction toward

<[dir]>.

PORTABILITY

        Neither <<nextafter>> nor <<nextafterf>> is required by ANSI C

        or by the System V Interface Definition (Issue 2).

*/

/* IEEE functions

 *      nextafter(x,y)

 *      return the next machine floating-point number of x in the

 *      direction toward y.

 *   Special cases:

 */

#include "fdlibm.h"

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__

        double nextafter(double x, double y)

#else

        double nextafter(x,y)

        double x,y;

#endif

{

        __int32_t       hx,hy,ix,iy;

        __uint32_t lx,ly;

        EXTRACT_WORDS(hx,lx,x);

        EXTRACT_WORDS(hy,ly,y);

        ix = hx&0x7fffffff;             /* |x| */

        iy = hy&0x7fffffff;             /* |y| */

        if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */

           ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0))     /* y is nan */

           return x+y;

        if(x==y) return x;              /* x=y, return x */

        if((ix|lx)==0) {                 /* x == 0 */

            INSERT_WORDS(x,hy&0x80000000,1);    /* return +-minsubnormal */

            y = x*x;

            if(y==x) return y; else return x;   /* raise underflow flag */

        }

        if(hx>=0) {                              /* x > 0 */

            if(hx>hy||((hx==hy)&&(lx>ly))) {    /* x > y, x -= ulp */

                if(lx==0) hx -= 1;

                lx -= 1;

            } else {                            /* x < y, x += ulp */

                lx += 1;

                if(lx==0) hx += 1;

            }

        } else {                                /* x < 0 */

            if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */

                if(lx==0) hx -= 1;

                lx -= 1;

            } else {                            /* x > y, x += ulp */

                lx += 1;

                if(lx==0) hx += 1;

            }

        }

        hy = hx&0x7ff00000;

        if(hy>=0x7ff00000) return x+x;  /* overflow  */

        if(hy<0x00100000) {             /* underflow */

            y = x*x;

            if(y!=x) {          /* raise underflow flag */

                INSERT_WORDS(y,hx,lx);

                return y;

            }

        }

        INSERT_WORDS(x,hx,lx);

        return x;

}

#endif /* _DOUBLE_IS_32BITS */