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[/] [or1k/] [trunk/] [newlib/] [newlib/] [libm/] [mathfp/] [sf_fmod.c] - Blame information for rev 1774

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1 56 joel 
/* ef_fmod.c -- float version of e_fmod.c.
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 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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 */
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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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/*
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 * fmodf(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 "fdlibm.h"
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#include "zmath.h"
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static const float one = 1.0, Zero[] = {0.0, -0.0,};
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float
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_DEFUN (fmodf, (float, float),
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        float x _AND
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        float y)
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{
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        __int32_t n,hx,hy,hz,ix,iy,sx,i;
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        GET_FLOAT_WORD(hx,x);
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        GET_FLOAT_WORD(hy,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==0||(hx>=0x7f800000)||             /* y=0,or x not finite */
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           (hy>0x7f800000))                     /* or y is NaN */
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            return (x*y)/(x*y);
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        if(hx<hy) return x;                     /* |x|<|y| return x */
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        if(hx==hy)
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            return Zero[(__uint32_t)sx>>31];    /* |x|=|y| return x*0*/
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    /* determine ix = ilogb(x) */
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        if(hx<0x00800000) {     /* subnormal x */
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            for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1;
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        } else ix = (hx>>23)-127;
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    /* determine iy = ilogb(y) */
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        if(hy<0x00800000) {     /* subnormal y */
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            for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1;
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        } else iy = (hy>>23)-127;
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    /* set up {hx,lx}, {hy,ly} and align y to x */
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        if(ix >= -126)
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            hx = 0x00800000|(0x007fffff&hx);
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        else {          /* subnormal x, shift x to normal */
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            n = -126-ix;
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            hx = hx<<n;
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        }
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        if(iy >= -126)
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            hy = 0x00800000|(0x007fffff&hy);
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        else {          /* subnormal y, shift y to normal */
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            n = -126-iy;
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            hy = hy<<n;
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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;
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            if(hz<0){hx = hx+hx;}
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            else {
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                if(hz==0)                /* return sign(x)*0 */
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                    return Zero[(__uint32_t)sx>>31];
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                hx = hz+hz;
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            }
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        }
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        hz=hx-hy;
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        if(hz>=0) {hx=hz;}
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    /* convert back to floating value and restore the sign */
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        if(hx==0)                        /* return sign(x)*0 */
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            return Zero[(__uint32_t)sx>>31];
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        while(hx<0x00800000) {          /* normalize x */
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            hx = hx+hx;
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            iy -= 1;
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        }
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        if(iy>= -126) {         /* normalize output */
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            hx = ((hx-0x00800000)|((iy+127)<<23));
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            SET_FLOAT_WORD(x,hx|sx);
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        } else {                /* subnormal output */
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            n = -126 - iy;
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            hx >>= n;
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            SET_FLOAT_WORD(x,hx|sx);
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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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