/* @(#)s_rint.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.
 * ====================================================
 */

/*
 * rint(x)
 * Return x rounded to integral value according to the prevailing
 * rounding mode.
 * Method:
 *	Using floating addition.
 * Exception:
 *	Inexact flag raised if x not equal to rint(x).
 */

#include "fdlibm.h"

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__
static const double
#else
static double
#endif
  TWO52[2] = {
  4.50359962737049600000e+15,	/* 0x43300000, 0x00000000 */
  -4.50359962737049600000e+15,	/* 0xC3300000, 0x00000000 */
};

#ifdef __STDC__
double
rint (double x)
#else
double
rint (x)
     double x;
#endif
{
  int32_t i0, j0, sx;
  uint32_t i, i1;
  double t;
  volatile double w;
  EXTRACT_WORDS (i0, i1, x);
  sx = (i0 >> 31) & 1;
  j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  if (j0 < 20)
    {
      if (j0 < 0)
	{
	  if (((i0 & 0x7fffffff) | i1) == 0)
	    return x;
	  i1 |= (i0 & 0x0fffff);
	  i0 &= 0xfffe0000;
	  i0 |= ((i1 | -i1) >> 12) & 0x80000;
	  SET_HIGH_WORD (x, i0);
	  w = TWO52[sx] + x;
	  t = w - TWO52[sx];
	  GET_HIGH_WORD (i0, t);
	  SET_HIGH_WORD (t, (i0 & 0x7fffffff) | (sx << 31));
	  return t;
	}
      else
	{
	  i = (0x000fffff) >> j0;
	  if (((i0 & i) | i1) == 0)
	    return x;		/* x is integral */
	  i >>= 1;
	  if (((i0 & i) | i1) != 0)
	    {
	      if (j0 == 19)
		i1 = 0x40000000;
	      else
		i0 = (i0 & (~i)) | ((0x20000) >> j0);
	    }
	}
    }
  else if (j0 > 51)
    {
      if (j0 == 0x400)
	return x + x;		/* inf or NaN */
      else
	return x;		/* x is integral */
    }
  else
    {
      i = ((uint32_t) (0xffffffff)) >> (j0 - 20);
      if ((i1 & i) == 0)
	return x;		/* x is integral */
      i >>= 1;
      if ((i1 & i) != 0)
	i1 = (i1 & (~i)) | ((0x40000000) >> (j0 - 20));
    }
  INSERT_WORDS (x, i0, i1);
  w = TWO52[sx] + x;
  return w - TWO52[sx];
}

#endif /* _DOUBLE_IS_32BITS */