osprey/libm/drem.c

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/*
 * Copyright 2003, 2004 PathScale, Inc.  All Rights Reserved.
 */

/*

  Copyright (C) 2000, 2001 Silicon Graphics, Inc.  All Rights Reserved.

  This program is free software; you can redistribute it and/or modify it
  under the terms of version 2.1 of the GNU Lesser General Public License 
  as published by the Free Software Foundation.

  This program is distributed in the hope that it would be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  

  Further, this software is distributed without any warranty that it is
  free of the rightful claim of any third person regarding infringement 
  or the like.  Any license provided herein, whether implied or 
  otherwise, applies only to this software file.  Patent licenses, if
  any, provided herein do not apply to combinations of this program with 
  other software, or any other product whatsoever.  

  You should have received a copy of the GNU Lesser General Public 
  License along with this program; if not, write the Free Software 
  Foundation, Inc., 59 Temple Place - Suite 330, Boston MA 02111-1307, 
  USA.

  Contact information:  Silicon Graphics, Inc., 1600 Amphitheatre Pky,
  Mountain View, CA 94043, or:

  http://www.sgi.com

  For further information regarding this notice, see:

  http://oss.sgi.com/projects/GenInfo/NoticeExplan

*/


/* ====================================================================
 * ====================================================================
 *
 * Module: drem.c
 * $Revision: 1.1.1.1 $
 * $Date: 2005/10/21 19:00:00 $
 * $Author: marcel $
 * $Source: /proj/osprey/CVS/open64/osprey1.0/libm/drem.c,v $
 *
 * Revision history:
 *  09-Jun-93 - Original Version
 *
 * Description: source code for drem function
 *
 * ====================================================================
 * ====================================================================
 */

static char *rcs_id = "$Source: /proj/osprey/CVS/open64/osprey1.0/libm/drem.c,v $ $Revision: 1.1.1.1 $";

#ifdef _CALL_MATHERR
#include <stdio.h>
#include <math.h>
#endif

#include "libm.h"

#if defined(mips) && !defined(__GNUC__)

#include <ieeefp.h>

extern  fp_rnd  swapRM(fp_rnd);
#endif

#ifdef __GNUC__

#include <fenv.h>

extern  int swapRM(int);
#endif

#if defined(mips) && !defined(__GNUC__)
extern  double  drem(double, double);
extern  double  remainder(double, double);
extern  double  __remainder(double, double);

#pragma weak drem = __drem
#pragma weak remainder = __drem
#pragma weak __remainder = __drem
#endif

#if defined(BUILD_OS_DARWIN) /* Mach-O doesn't support aliases */
extern double __drem( double x, double y );
double drem( double x, double y ) {
  return __drem(x, y);
}
#pragma weak drem
double remainder( double x, double y ) {
  return __remainder(x, y);
}
#pragma weak remainder
#elif defined(__GNUC__)
extern  double  __drem(double, double);

double    drem() __attribute__ ((weak, alias ("__drem")));

extern  double  __remainder(double, double);

double    remainder() __attribute__ ((weak, alias ("__remainder")));

#endif

static const  du  Qnan =
{D(QNANHI, QNANLO)};

static  const du  twopm1021 =
{D(0x00200000, 0x00000000)};

static  const du  twopm104 =
{D(0x39700000, 0x00000000)};

static  const du  twop52 =
{D(0x43300000, 0x00000000)};

static  const du  twop104 =
{D(0x46700000, 0x00000000)};

static  const du  twop920 =
{D(0x79700000, 0x00000000)};

#define NO  0
#define YES 1


/* ====================================================================
 *
 * FunctionName   drem
 *
 * Description    computes remainder function
 *
 * ====================================================================
 */

double
__drem( double x, double y )
{
#ifdef _32BIT_MACHINE

int ix, iy;
int xptx, xpty;
int m;

#else

long long ix, iy;
long long xptx, xpty;
long long m;

#endif

#if defined(mips) && !defined(__GNUC__)
fp_rnd  rm;
#endif

#ifdef __GNUC__
int rm;
#endif

int scaled;
int signx;
double  nd, yhi, ylo;
double  y1;
double  result;
int n, q;
#ifdef _CALL_MATHERR
struct exception  exstruct;
#endif

  /* extract exponents of y and x for some quick screening */

#ifdef _32BIT_MACHINE

  DBLHI2INT(x, ix); /* copy MSW's of x and y to integers  */
  DBLHI2INT(y, iy);
#else
  DBL2LL(x, ix);    /* copy x and y to long longs */
  DBL2LL(y, iy);
#endif
  xptx = (ix >> DMANTWIDTH);
  signx = (xptx >> DEXPWIDTH);
  xptx &= 0x7ff;
  signx &= 1;

  xpty = (iy >> DMANTWIDTH);
  xpty &= 0x7ff;

  /* filter out Nans */

  if ( (xpty == 0x7ff) || (xptx == 0x7ff) )
  {
    if ( (y != y) || (x != x) )
    {
      /* y or x is a NaN; return a quiet NaN */

#ifdef _CALL_MATHERR

      exstruct.type = DOMAIN;
      exstruct.name = "drem";
      exstruct.arg1 = x;
      exstruct.arg2 = y;
      exstruct.retval = Qnan.d;

      if ( matherr( &exstruct ) == 0 )
      {
        fprintf(stderr, "domain error in drem\n");
        SETERRNO(EDOM);
      }

      return ( exstruct.retval );
#else
      NAN_SETERRNO(EDOM);

      return ( Qnan.d );
#endif
    }
  }

  if ( (xptx == 0x7ff) || ((xpty == 0) && (y == 0.0)) )
  {
    /* x == +/- infinity or y == +/- 0.0; return a quiet NaN */

#ifdef _CALL_MATHERR

    exstruct.type = DOMAIN;
    exstruct.name = "drem";
    exstruct.arg1 = x;
    exstruct.arg2 = y;
    exstruct.retval = Qnan.d;

    if ( matherr( &exstruct ) == 0 )
    {
      fprintf(stderr, "domain error in drem\n");
      SETERRNO(EDOM);
    }

    return ( exstruct.retval );
#else
    SETERRNO(EDOM);

    return ( Qnan.d );
#endif
  }

  y = fabs(y);
  x = fabs(x);

  /* set rounding mode to round to zero */
  
#if defined(mips) && !defined(__GNUC__)
  rm = swapRM( FP_RZ );
#endif

#ifdef __GNUC__
  rm = swapRM( FE_TOWARDZERO );
#endif

  scaled = NO;

  q = 0;

  if ( x < y )
    goto L;

  if ( xpty < 0x035 )
  {
    while ( x >= twop920.d )
    {
  
      /* scale y up and compute x = x - floor(x/k*y)*k*y
      */
  
      y1 = twop52.d*y;


#ifdef _32BIT_MACHINE

      DBLHI2INT(y1, m);
      m &= DEXPMASK;
      m |= ((xptx - 25) << DMANTWIDTH);
      INT2DBLHI(m, y1);
#else
      DBL2LL(y1, m);
      m &= DEXPMASK;
      m |= ((xptx - 25) << DMANTWIDTH);
      LL2DBL(m, y1);
#endif
      nd = x/y1;
  
      yhi = y1;

#ifdef _32BIT_MACHINE

      DBLLO2INT(yhi, m);
      m >>= 27;
      m <<= 27;
      INT2DBLLO(m, yhi);
#else
      DBL2LL(yhi, m);
      m >>= 27;
      m <<= 27;
      LL2DBL(m, yhi);
#endif
      ylo = y1 - yhi;
    
      nd = n = nd;
    
      x = x - nd*yhi - nd*ylo;
  
#ifdef _32BIT_MACHINE

      DBLHI2INT(x, ix);
#else
      DBL2LL(x, ix);
#endif
      xptx = (ix >> DMANTWIDTH);
      xptx &= 0x7ff;
    }
  
    if ( x >= y )
    {
      /* scale both x and y up */
    
      x *= twop104.d;
      y *= twop104.d;
    
#ifdef _32BIT_MACHINE

      DBLHI2INT(x, ix);
      DBLHI2INT(y, iy);
#else
      DBL2LL(x, ix);
      DBL2LL(y, iy);
#endif
      xptx = (ix >> DMANTWIDTH);
      xptx &= 0x7ff;

      xpty = (iy >> DMANTWIDTH);
      xpty &= 0x7ff;
    
      scaled = YES;
    }
  }

  while ( xptx >= xpty + 26 )
  {
    /* scale y up and compute x = x - floor(x/k*y)*k*y
    */

    y1 = y;

#ifdef _32BIT_MACHINE

    DBLHI2INT(y1, m);
    m &= DEXPMASK;
    m |= ((xptx - 25) << 20);
    INT2DBLHI(m, y1);
#else
    DBL2LL(y1, m);
    m &= DEXPMASK;
    m |= ((xptx - 25) << DMANTWIDTH);
    LL2DBL(m, y1);
#endif
    nd = x/y1;

    yhi = y1;

#ifdef _32BIT_MACHINE

    DBLLO2INT(yhi, m);
    m >>= 27;
    m <<= 27;
    INT2DBLLO(m, yhi);
#else
    DBL2LL(yhi, m);
    m >>= 27;
    m <<= 27;
    LL2DBL(m, yhi);
#endif
    ylo = y1 - yhi;

    nd = n = nd;

    x = x - nd*yhi - nd*ylo;

#ifdef _32BIT_MACHINE

    DBLHI2INT(x, ix);
#else
    DBL2LL(x, ix);
#endif
    xptx = (ix >> DMANTWIDTH);
    xptx &= 0x7ff;
  }

  if ( x >= y )
  {
    nd = x/y;

    yhi = y;

#ifdef _32BIT_MACHINE

    DBLLO2INT(yhi, m);
    m >>= 27;
    m <<= 27;
    INT2DBLLO(m, yhi);
#else
    DBL2LL(yhi, m);
    m >>= 27;
    m <<= 27;
    LL2DBL(m, yhi);
#endif
    ylo = y - yhi;

    nd = n = nd;
    q ^= n;

    x = x - nd*yhi - nd*ylo;
  }

L:
  if ( y > twopm1021.d )
  {
    if ( x < 0.5*y )
    {
      result = x;
    }
    else if ( (x > 0.5*y) || (q & 1) )
    {
      result = x - y;
    }
    else
    {
      result = x;
    }
  }
  else
  {
    if ( 2.0*x < y )
    {
      result = x;
    }
    else if ( (2.0*x > y) || (q & 1) )
    {
      result = x - y;
    }
    else
    {
      result = x;
    }
  }

  if ( scaled == YES )
    result *= twopm104.d;

  rm = swapRM( rm );

  if ( signx != 0 )
    result = -result;

  return ( result );
}

#ifdef __GNUC__

double
__remainder( double x, double y )
{
  return ( __drem(x, y) );
}

#endif

#ifdef NO_LONG_DOUBLE

#if defined(BUILD_OS_DARWIN) /* Mach-O doesn't support aliases */
long double dreml( long double x, long double y ) {
  return __dreml(x, y);
}
#pragma weak dreml
long double remainderl( long double x, long double y ) {
  return __remainderl(x, y);
}
#pragma weak remainderl
#elif defined(__GNUC__)
extern  long double  __dreml(long double, long double);

long double    dreml() __attribute__ ((weak, alias ("__dreml")));

extern  long double  __remainderl(long double, long double);

long double    remainderl() __attribute__ ((weak, alias ("__remainderl")));

#endif

long double
__dreml( long double x, long double y )
{
  return ( (long double)__drem((double)x, (double)y) );
}

long double
__remainderl( long double x, long double y )
{
  return ( (long double)__remainder((double)x, (double)y) );
}

#endif

---