sysdeps/ieee754/dbl-64/wordsize-64/s_round.c

   1 /* Round double to integer away from zero.
   2    Copyright (C) 1997-2016 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   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    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <math.h>
  21
  22 #include <math_private.h>
  23 #include <stdint.h>
  24
  25
  26 double
  27 __round (double x)
  28 {
  29   int64_t i0, j0;
  30
  31   EXTRACT_WORDS64 (i0, x);
  32   j0 = ((i0 >> 52) & 0x7ff) - 0x3ff;
  33   if (__glibc_likely (j0 < 52))
  34     {
  35       if (j0 < 0)
  36         {
  37           i0 &= UINT64_C(0x8000000000000000);
  38           if (j0 == -1)
  39             i0 |= UINT64_C(0x3ff0000000000000);
  40         }
  41       else
  42         {
  43           uint64_t i = UINT64_C(0x000fffffffffffff) >> j0;
  44           if ((i0 & i) == 0)
  45             /* X is integral.  */
  46             return x;
  47
  48           i0 += UINT64_C(0x0008000000000000) >> j0;
  49           i0 &= ~i;
  50         }
  51     }
  52   else
  53     {
  54       if (j0 == 0x400)
  55         /* Inf or NaN.  */
  56         return x + x;
  57       else
  58         return x;
  59     }
  60
  61   INSERT_WORDS64 (x, i0);
  62   return x;
  63 }
  64 weak_alias (__round, round)
  65 #ifdef NO_LONG_DOUBLE
  66 strong_alias (__round, __roundl)
  67 weak_alias (__round, roundl)
  68 #endif