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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libm/] [common/] [sf_remquo.c] - Blame information for rev 207

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1 207 jeremybenn
/* Adapted for Newlib, 2009.  (Allow for int < 32 bits; return *quo=0 during
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 * errors to make test scripts easier.)  */
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/* @(#)e_fmod.c 1.3 95/01/18 */
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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 SunSoft, 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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#include <math.h>
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#include "fdlibm.h"
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/* For quotient, return either all 31 bits that can from calculation (using
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 * int32_t), or as many as can fit into an int that is smaller than 32 bits.  */
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#if INT_MAX > 0x7FFFFFFFL
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  #define QUO_MASK 0x7FFFFFFF
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# else
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  #define QUO_MASK INT_MAX
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#endif
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static const float Zero[] = {0.0, -0.0,};
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/*
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 * Return the IEEE remainder and set *quo to the last n bits of the
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 * quotient, rounded to the nearest integer.  We choose n=31--if that many fit--
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 * we wind up computing all the integer bits of the quotient anyway as
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 * a side-effect of computing the remainder by the shift and subtract
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 * method.  In practice, this is far more bits than are needed to use
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 * remquo in reduction algorithms.
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 */
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float
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remquof(float x, float y, int *quo)
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{
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        __int32_t n,hx,hy,hz,ix,iy,sx,i;
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        __uint32_t q,sxy;
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        GET_FLOAT_WORD(hx,x);
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        GET_FLOAT_WORD(hy,y);
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        sxy = (hx ^ hy) & 0x80000000;
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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||hy>0x7f800000) { /* y=0,NaN;or x not finite */
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            *quo = 0;    /* Not necessary, but return consistent value */
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            return (x*y)/(x*y);
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        }
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        if(hx<hy) {
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            q = 0;
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            goto fixup; /* |x|<|y| return x or x-y */
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        } else if(hx==hy) {
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            *quo = 1;
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            return Zero[(__uint32_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<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 <<= 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 <<= n;
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        }
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    /* fix point fmod */
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        n = ix - iy;
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        q = 0;
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        while(n--) {
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            hz=hx-hy;
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            if(hz<0) hx = hx << 1;
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            else {hx = hz << 1; q++;}
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            q <<= 1;
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        }
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        hz=hx-hy;
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        if(hz>=0) {hx=hz;q++;}
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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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            *quo = (sxy ? -q : q);
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            return Zero[(__uint32_t)sx>>31];
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        }
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        while(hx<0x00800000) {          /* normalize x */
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            hx <<= 1;
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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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        } else {                /* subnormal output */
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            n = -126 - iy;
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            hx >>= n;
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        }
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fixup:
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        SET_FLOAT_WORD(x,hx);
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        y = fabsf(y);
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        if (y < 0x1p-125f) {
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            if (x+x>y || (x+x==y && (q & 1))) {
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                q++;
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                x-=y;
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            }
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        } else if (x>0.5f*y || (x==0.5f*y && (q & 1))) {
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            q++;
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            x-=y;
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        }
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        GET_FLOAT_WORD(hx,x);
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        SET_FLOAT_WORD(x,hx^sx);
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        q &= 0x7fffffff;
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        *quo = (sxy ? -q : q);
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        return x;
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}

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