1  /* Round to nearest integer value, rounding halfway cases to even.
       2     ldbl-128ibm version.
       3     Copyright (C) 2016-2023 Free Software Foundation, Inc.
       4     This file is part of the GNU C Library.
       5  
       6     The GNU C Library is free software; you can redistribute it and/or
       7     modify it under the terms of the GNU Lesser General Public
       8     License as published by the Free Software Foundation; either
       9     version 2.1 of the License, or (at your option) any later version.
      10  
      11     The GNU C Library is distributed in the hope that it will be useful,
      12     but WITHOUT ANY WARRANTY; without even the implied warranty of
      13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      14     Lesser General Public License for more details.
      15  
      16     You should have received a copy of the GNU Lesser General Public
      17     License along with the GNU C Library; if not, see
      18     <https://www.gnu.org/licenses/>.  */
      19  
      20  #define NO_MATH_REDIRECT
      21  #include <math.h>
      22  #include <math_private.h>
      23  
      24  long double
      25  __roundevenl (long double x)
      26  {
      27    double xh, xl, hi;
      28  
      29    ldbl_unpack (x, &xh, &xl);
      30  
      31    if (xh != 0 && isfinite (xh))
      32      {
      33        hi = __roundeven (xh);
      34        if (hi != xh)
      35  	{
      36  	  /* The high part is not an integer; the low part only
      37  	     affects the result if the high part is exactly half way
      38  	     between two integers and the low part is nonzero in the
      39  	     opposite direction to the rounding of the high part.  */
      40  	  double diff = hi - xh;
      41  	  if (fabs (diff) == 0.5)
      42  	    {
      43  	      if (xl < 0 && diff > 0)
      44  		xh = hi - 1;
      45  	      else if (xl > 0 && diff < 0)
      46  		xh = hi + 1;
      47  	      else
      48  		xh = hi;
      49  	    }
      50  	  else
      51  	    xh = hi;
      52  	  xl = 0;
      53  	}
      54        else
      55  	{
      56  	  /* The high part is a nonzero integer.  Rounding the low
      57  	     part to nearest, ties round to even, is always correct,
      58  	     as a high part that is an odd integer together with a low
      59  	     part with magnitude 0.5 is not a valid long double.  */
      60  	  xl = __roundeven (xl);
      61  	  xh = hi;
      62  	  ldbl_canonicalize_int (&xh, &xl);
      63  	}
      64      }
      65    else
      66      /* Quiet signaling NaN arguments.  */
      67      xh += xh;
      68  
      69    return ldbl_pack (xh, xl);
      70  }
      71  weak_alias (__roundevenl, roundevenl)