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

   1 /* Round double value to long long int.
   2    Copyright (C) 1997-2015 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 #define lround __hidden_lround
  21 #define __lround __hidden___lround
  22
  23 #include <math.h>
  24
  25 #include <math_private.h>
  26
  27
  28 long long int
  29 __llround (double x)
  30 {
  31   int32_t j0;
  32   int64_t i0;
  33   long long int result;
  34   int sign;
  35
  36   EXTRACT_WORDS64 (i0, x);
  37   j0 = ((i0 >> 52) & 0x7ff) - 0x3ff;
  38   sign = i0 < 0 ? -1 : 1;
  39   i0 &= UINT64_C(0xfffffffffffff);
  40   i0 |= UINT64_C(0x10000000000000);
  41
  42   if (j0 < (int32_t) (8 * sizeof (long long int)) - 1)
  43     {
  44       if (j0 < 0)
  45         return j0 < -1 ? 0 : sign;
  46       else if (j0 >= 52)
  47         result = i0 << (j0 - 52);
  48       else
  49         {
  50           i0 += UINT64_C(0x8000000000000) >> j0;
  51
  52           result = i0 >> (52 - j0);
  53         }
  54     }
  55   else
  56     {
  57       /* The number is too large.  It is left implementation defined
  58          what happens.  */
  59       return (long long int) x;
  60     }
  61
  62   return sign * result;
  63 }
  64
  65 weak_alias (__llround, llround)
  66 #ifdef NO_LONG_DOUBLE
  67 strong_alias (__llround, __lroundl)
  68 weak_alias (__llround, lroundl)
  69 #endif
  70
  71 /* long has the same width as long long on 64-bit machines.  */
  72 #undef lround
  73 #undef __lround
  74 strong_alias (__llround, __lround)
  75 weak_alias (__llround, lround)
  76 #ifdef NO_LONG_DOUBLE
  77 strong_alias (__llround, __llroundl)
  78 weak_alias (__llround, llroundl)
  79 #endif