Subversion Repositories scarts

/* ef_fmod.c -- float version of e_fmod.c.

 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.

 */

/*

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

 * 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.

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

 */

/*

 * __ieee754_fmodf(x,y)

 * Return x mod y in exact arithmetic

 * Method: shift and subtract

 */

#include "fdlibm.h"

#ifdef __STDC__

static const float one = 1.0, Zero[] = {0.0, -0.0,};

#else

static float one = 1.0, Zero[] = {0.0, -0.0,};

#endif

#ifdef __STDC__

        float __ieee754_fmodf(float x, float y)

#else

        float __ieee754_fmodf(x,y)

        float x,y ;

#endif

{

        __int32_t n,hx,hy,hz,ix,iy,sx,i;

        GET_FLOAT_WORD(hx,x);

        GET_FLOAT_WORD(hy,y);

        sx = hx&0x80000000;             /* sign of x */

        hx ^=sx;                /* |x| */

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

    /* purge off exception values */

        if(FLT_UWORD_IS_ZERO(hy)||

           !FLT_UWORD_IS_FINITE(hx)||

           FLT_UWORD_IS_NAN(hy))

            return (x*y)/(x*y);

        if(hx<hy) return x;                     /* |x|<|y| return x */

        if(hx==hy)

            return Zero[(__uint32_t)sx>>31];    /* |x|=|y| return x*0*/

    /* Note: y cannot be zero if we reach here. */

    /* determine ix = ilogb(x) */

        if(FLT_UWORD_IS_SUBNORMAL(hx)) {        /* subnormal x */

            for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1;

        } else ix = (hx>>23)-127;

    /* determine iy = ilogb(y) */

        if(FLT_UWORD_IS_SUBNORMAL(hy)) {        /* subnormal y */

            for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1;

        } else iy = (hy>>23)-127;

    /* set up {hx,lx}, {hy,ly} and align y to x */

        if(ix >= -126)

            hx = 0x00800000|(0x007fffff&hx);

        else {          /* subnormal x, shift x to normal */

            n = -126-ix;

            hx = hx<<n;

        }

        if(iy >= -126)

            hy = 0x00800000|(0x007fffff&hy);

        else {          /* subnormal y, shift y to normal */

            n = -126-iy;

            hy = hy<<n;

        }

    /* fix point fmod */

        n = ix - iy;

        while(n--) {

            hz=hx-hy;

            if(hz<0){hx = hx+hx;}

            else {

                if(hz==0)                /* return sign(x)*0 */

                    return Zero[(__uint32_t)sx>>31];

                hx = hz+hz;

            }

        }

        hz=hx-hy;

        if(hz>=0) {hx=hz;}

    /* convert back to floating value and restore the sign */

        if(hx==0)                        /* return sign(x)*0 */

            return Zero[(__uint32_t)sx>>31];

        while(hx<0x00800000) {          /* normalize x */

            hx = hx+hx;

            iy -= 1;

        }

        if(iy>= -126) {         /* normalize output */

            hx = ((hx-0x00800000)|((iy+127)<<23));

            SET_FLOAT_WORD(x,hx|sx);

        } else {                /* subnormal output */

            /* If denormals are not supported, this code will generate a

               zero representation.  */

            n = -126 - iy;

            hx >>= n;

            SET_FLOAT_WORD(x,hx|sx);

            x *= one;           /* create necessary signal */

        }

        return x;               /* exact output */

}