Subversion Repositories openrisc_2011-10-31

/* Adapted for Newlib, 2009.  (Allow for int < 32 bits; return *quo=0 during

 * errors to make test scripts easier.)  */

/* @(#)e_fmod.c 1.3 95/01/18 */

/*-

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

 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.

 *

 * Developed at SunSoft, a Sun Microsystems, Inc. business.

 * Permission to use, copy, modify, and distribute this

 * software is freely granted, provided that this notice

 * is preserved.

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

 */

#include <math.h>

#include "fdlibm.h"

/* For quotient, return either all 31 bits that can from calculation (using

 * int32_t), or as many as can fit into an int that is smaller than 32 bits.  */

#if INT_MAX > 0x7FFFFFFFL

  #define QUO_MASK 0x7FFFFFFF

# else

  #define QUO_MASK INT_MAX

#endif

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

/*

 * Return the IEEE remainder and set *quo to the last n bits of the

 * quotient, rounded to the nearest integer.  We choose n=31--if that many fit--

 * we wind up computing all the integer bits of the quotient anyway as

 * a side-effect of computing the remainder by the shift and subtract

 * method.  In practice, this is far more bits than are needed to use

 * remquo in reduction algorithms.

 */

float

remquof(float x, float y, int *quo)

{

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

        __uint32_t q,sxy;

        GET_FLOAT_WORD(hx,x);

        GET_FLOAT_WORD(hy,y);

        sxy = (hx ^ hy) & 0x80000000;

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

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

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

    /* purge off exception values */

        if(hy==0||hx>=0x7f800000||hy>0x7f800000) { /* y=0,NaN;or x not finite */

            *quo = 0;    /* Not necessary, but return consistent value */

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

        }

        if(hx<hy) {

            q = 0;

            goto fixup; /* |x|<|y| return x or x-y */

        } else if(hx==hy) {

            *quo = 1;

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

        }

    /* determine ix = ilogb(x) */

        if(hx<0x00800000) {     /* subnormal x */

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

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

    /* determine iy = ilogb(y) */

        if(hy<0x00800000) {     /* 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 <<= n;

        }

        if(iy >= -126)

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

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

            n = -126-iy;

            hy <<= n;

        }

    /* fix point fmod */

        n = ix - iy;

        q = 0;

        while(n--) {

            hz=hx-hy;

            if(hz<0) hx = hx << 1;

            else {hx = hz << 1; q++;}

            q <<= 1;

        }

        hz=hx-hy;

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

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

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

            *quo = (sxy ? -q : q);

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

        }

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

            hx <<= 1;

            iy -= 1;

        }

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

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

        } else {                /* subnormal output */

            n = -126 - iy;

            hx >>= n;

        }

fixup:

        SET_FLOAT_WORD(x,hx);

        y = fabsf(y);

        if (y < 0x1p-125f) {

            if (x+x>y || (x+x==y && (q & 1))) {

                q++;

                x-=y;

            }

        } else if (x>0.5f*y || (x==0.5f*y && (q & 1))) {

            q++;

            x-=y;

        }

        GET_FLOAT_WORD(hx,x);

        SET_FLOAT_WORD(x,hx^sx);

        q &= 0x7fffffff;

        *quo = (sxy ? -q : q);

        return x;

}