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[/] [or1k_old/] [trunk/] [linux/] [uClibc/] [libm/] [e_fmod.c] - Blame information for rev 1782

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1 1325 phoenix 
/* @(#)e_fmod.c 5.1 93/09/24 */
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/*
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 * ====================================================
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 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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 *
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 * Developed at SunPro, a Sun Microsystems, Inc. business.
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 * Permission to use, copy, modify, and distribute this
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 * software is freely granted, provided that this notice
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 * is preserved.
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 * ====================================================
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 */
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#if defined(LIBM_SCCS) && !defined(lint)
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static char rcsid[] = "$NetBSD: e_fmod.c,v 1.8 1995/05/10 20:45:07 jtc Exp $";
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#endif
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/*
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 * __ieee754_fmod(x,y)
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 * Return x mod y in exact arithmetic
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 * Method: shift and subtract
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 */
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#include "math.h"
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#include "math_private.h"
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#ifdef __STDC__
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static const double one = 1.0, Zero[] = {0.0, -0.0,};
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#else
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static double one = 1.0, Zero[] = {0.0, -0.0,};
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#endif
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#ifdef __STDC__
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        double __ieee754_fmod(double x, double y)
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#else
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        double __ieee754_fmod(x,y)
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        double x,y ;
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#endif
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{
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        int32_t n,hx,hy,hz,ix,iy,sx,i;
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        u_int32_t lx,ly,lz;
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        EXTRACT_WORDS(hx,lx,x);
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        EXTRACT_WORDS(hy,ly,y);
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        sx = hx&0x80000000;             /* sign of x */
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        hx ^=sx;                /* |x| */
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        hy &= 0x7fffffff;       /* |y| */
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    /* purge off exception values */
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        if((hy|ly)==0||(hx>=0x7ff00000)||        /* y=0,or x not finite */
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          ((hy|((ly|-ly)>>31))>0x7ff00000))     /* or y is NaN */
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            return (x*y)/(x*y);
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        if(hx<=hy) {
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            if((hx<hy)||(lx<ly)) return x;      /* |x|<|y| return x */
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            if(lx==ly)
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                return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/
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        }
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    /* determine ix = ilogb(x) */
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        if(hx<0x00100000) {     /* subnormal x */
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            if(hx==0) {
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                for (ix = -1043, i=lx; i>0; i<<=1) ix -=1;
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            } else {
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                for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1;
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            }
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        } else ix = (hx>>20)-1023;
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    /* determine iy = ilogb(y) */
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        if(hy<0x00100000) {     /* subnormal y */
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            if(hy==0) {
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                for (iy = -1043, i=ly; i>0; i<<=1) iy -=1;
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            } else {
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                for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1;
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            }
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        } else iy = (hy>>20)-1023;
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    /* set up {hx,lx}, {hy,ly} and align y to x */
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        if(ix >= -1022)
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            hx = 0x00100000|(0x000fffff&hx);
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        else {          /* subnormal x, shift x to normal */
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            n = -1022-ix;
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            if(n<=31) {
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                hx = (hx<<n)|(lx>>(32-n));
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                lx <<= n;
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            } else {
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                hx = lx<<(n-32);
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                lx = 0;
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            }
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        }
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        if(iy >= -1022)
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            hy = 0x00100000|(0x000fffff&hy);
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        else {          /* subnormal y, shift y to normal */
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            n = -1022-iy;
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            if(n<=31) {
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                hy = (hy<<n)|(ly>>(32-n));
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                ly <<= n;
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            } else {
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                hy = ly<<(n-32);
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                ly = 0;
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            }
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        }
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    /* fix point fmod */
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        n = ix - iy;
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        while(n--) {
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            hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
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            if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;}
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            else {
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                if((hz|lz)==0)           /* return sign(x)*0 */
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                    return Zero[(u_int32_t)sx>>31];
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                hx = hz+hz+(lz>>31); lx = lz+lz;
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            }
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        }
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        hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
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        if(hz>=0) {hx=hz;lx=lz;}
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    /* convert back to floating value and restore the sign */
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        if((hx|lx)==0)                   /* return sign(x)*0 */
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            return Zero[(u_int32_t)sx>>31];
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        while(hx<0x00100000) {          /* normalize x */
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            hx = hx+hx+(lx>>31); lx = lx+lx;
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            iy -= 1;
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        }
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        if(iy>= -1022) {        /* normalize output */
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            hx = ((hx-0x00100000)|((iy+1023)<<20));
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            INSERT_WORDS(x,hx|sx,lx);
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        } else {                /* subnormal output */
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            n = -1022 - iy;
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            if(n<=20) {
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                lx = (lx>>n)|((u_int32_t)hx<<(32-n));
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                hx >>= n;
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            } else if (n<=31) {
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                lx = (hx<<(32-n))|(lx>>n); hx = sx;
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            } else {
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                lx = hx>>(n-32); hx = sx;
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            }
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            INSERT_WORDS(x,hx|sx,lx);
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            x *= one;           /* create necessary signal */
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        }
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        return x;               /* exact output */
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}

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