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Re: FPU test on RedHat7.1

To: "H . J . Lu" <hjl@lucon.org>
Subject: Re: FPU test on RedHat7.1
From: Carsten Langgaard <carstenl@mips.com>
Date: Fri, 23 Nov 2001 15:54:31 +0100
Cc: linux-mips@oss.sgi.com
References: <3BFD1BA7.C4490465@mips.com> <20011122103930.A2007@lucon.org>
Sender: owner-linux-mips@oss.sgi.com
The file sysdeps/ieee754/dbl-64/e_remainder.c seems to have changed since
glibc-2.2.2.
I have attached the glibc-2.2.2 remainder file, which seems to work
better.

/Carsten

"H . J . Lu" wrote:

> On Thu, Nov 22, 2001 at 04:37:11PM +0100, Carsten Langgaard wrote:
> > The attached tests fails on my RedHat7.1 system, but works fine on my
> > old HardHat5.1.
> > Anyone got any idea.
> >
> > compile:
> > g++ -o fpu_test fpu_test.cc
> >
>
> Many FPU related tests in the current glibc from CVS failed on MIPS. I
> am planning to look into them. But I need to find time and docs on MIPS
> FPU.
>
> H.J.

--
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/* @(#)e_remainder.c 5.1 93/09/24 */
/*
 * ====================================================
 * 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.
 * ====================================================
 */

#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] = "$NetBSD: e_remainder.c,v 1.8 1995/05/10 20:46:05 jtc Exp 
$";
#endif

/* __ieee754_remainder(x,p)
 * Return :                  
 *      returns  x REM p  =  x - [x/p]*p as if in infinite 
 *      precise arithmetic, where [x/p] is the (infinite bit) 
 *      integer nearest x/p (in half way case choose the even one).
 * Method : 
 *      Based on fmod() return x-[x/p]chopped*p exactlp.
 */

#include "math.h"
#include "math_private.h"

#ifdef __STDC__
static const double zero = 0.0;
#else
static double zero = 0.0;
#endif


#ifdef __STDC__
        double __ieee754_remainder(double x, double p)
#else
        double __ieee754_remainder(x,p)
        double x,p;
#endif
{
        int32_t hx,hp;
        u_int32_t sx,lx,lp;
        double p_half;

        EXTRACT_WORDS(hx,lx,x);
        EXTRACT_WORDS(hp,lp,p);
        sx = hx&0x80000000;
        hp &= 0x7fffffff;
        hx &= 0x7fffffff;

    /* purge off exception values */
        if((hp|lp)==0) return (x*p)/(x*p);      /* p = 0 */
        if((hx>=0x7ff00000)||                   /* x not finite */
          ((hp>=0x7ff00000)&&                   /* p is NaN */
          (((hp-0x7ff00000)|lp)!=0)))
            return (x*p)/(x*p);


        if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p);  /* now x < 2p */
        if (((hx-hp)|(lx-lp))==0) return zero*x;
        x  = fabs(x);
        p  = fabs(p);
        if (hp<0x00200000) {
            if(x+x>p) {
                x-=p;
                if(x+x>=p) x -= p;
            }
        } else {
            p_half = 0.5*p;
            if(x>p_half) {
                x-=p;
                if(x>=p_half) x -= p;
            }
        }
        GET_HIGH_WORD(hx,x);
        SET_HIGH_WORD(x,hx^sx);
        return x;
}
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