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

   1 /* Round double to integer away from zero.
   2    Copyright (C) 1997-2014 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 static const double huge = 1.0e300;
  26
  27
  28 double
  29 __round (double x)
  30 {
  31   int64_t i0, j0;
  32
  33   EXTRACT_WORDS64 (i0, x);
  34   j0 = ((i0 >> 52) & 0x7ff) - 0x3ff;
  35   if (__builtin_expect (j0 < 52, 1))
  36     {
  37       if (j0 < 0)
  38         {
  39           math_force_eval (huge + x);
  40
  41           i0 &= UINT64_C(0x8000000000000000);
  42           if (j0 == -1)
  43             i0 |= UINT64_C(0x3ff0000000000000);
  44         }
  45       else
  46         {
  47           uint64_t i = UINT64_C(0x000fffffffffffff) >> j0;
  48           if ((i0 & i) == 0)
  49             /* X is integral.  */
  50             return x;
  51           math_force_eval (huge + x);
  52
  53           /* Raise inexact if x != 0.  */
  54           i0 += UINT64_C(0x0008000000000000) >> j0;
  55           i0 &= ~i;
  56         }
  57     }
  58   else
  59     {
  60       if (j0 == 0x400)
  61         /* Inf or NaN.  */
  62         return x + x;
  63       else
  64         return x;
  65     }
  66
  67   INSERT_WORDS64 (x, i0);
  68   return x;
  69 }
  70 weak_alias (__round, round)
  71 #ifdef NO_LONG_DOUBLE
  72 strong_alias (__round, __roundl)
  73 weak_alias (__round, roundl)
  74 #endif