sysdeps/ieee754/dbl-64/s_llround.c

   1 /* Round double value to long long int.
   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
  24
  25 long long int
  26 __llround (double x)
  27 {
  28   int32_t j0;
  29   u_int32_t i1, i0;
  30   long long int result;
  31   int sign;
  32
  33   EXTRACT_WORDS (i0, i1, x);
  34   j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  35   sign = (i0 & 0x80000000) != 0 ? -1 : 1;
  36   i0 &= 0xfffff;
  37   i0 |= 0x100000;
  38
  39   if (j0 < 20)
  40     {
  41       if (j0 < 0)
  42         return j0 < -1 ? 0 : sign;
  43       else
  44         {
  45           i0 += 0x80000 >> j0;
  46
  47           result = i0 >> (20 - j0);
  48         }
  49     }
  50   else if (j0 < (int32_t) (8 * sizeof (long long int)) - 1)
  51     {
  52       if (j0 >= 52)
  53         result = (((long long int) i0 << 32) | i1) << (j0 - 52);
  54       else
  55         {
  56           u_int32_t j = i1 + (0x80000000 >> (j0 - 20));
  57           if (j < i1)
  58             ++i0;
  59
  60           if (j0 == 20)
  61             result = (long long int) i0;
  62           else
  63             result = ((long long int) i0 << (j0 - 20)) | (j >> (52 - j0));
  64         }
  65     }
  66   else
  67     {
  68       /* The number is too large.  It is left implementation defined
  69          what happens.  */
  70       return (long long int) x;
  71     }
  72
  73   return sign * result;
  74 }
  75
  76 weak_alias (__llround, llround)
  77 #ifdef NO_LONG_DOUBLE
  78 strong_alias (__llround, __llroundl)
  79 weak_alias (__llround, llroundl)
  80 #endif