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

   1 /* Round double value to long long int.
   2    Copyright (C) 1997-2017 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 #include <sysdep.h>
  25
  26 #include <math_private.h>
  27
  28
  29 long long int
  30 __llround (double x)
  31 {
  32   int32_t j0;
  33   int64_t i0;
  34   long long int result;
  35   int sign;
  36
  37   EXTRACT_WORDS64 (i0, x);
  38   j0 = ((i0 >> 52) & 0x7ff) - 0x3ff;
  39   sign = i0 < 0 ? -1 : 1;
  40   i0 &= UINT64_C(0xfffffffffffff);
  41   i0 |= UINT64_C(0x10000000000000);
  42
  43   if (j0 < (int32_t) (8 * sizeof (long long int)) - 1)
  44     {
  45       if (j0 < 0)
  46         return j0 < -1 ? 0 : sign;
  47       else if (j0 >= 52)
  48         result = i0 << (j0 - 52);
  49       else
  50         {
  51           i0 += UINT64_C(0x8000000000000) >> j0;
  52
  53           result = i0 >> (52 - j0);
  54         }
  55     }
  56   else
  57     {
  58       /* The number is too large.  It is left implementation defined
  59          what happens.  */
  60       return (long long int) x;
  61     }
  62
  63   return sign * result;
  64 }
  65
  66 weak_alias (__llround, llround)
  67 #ifdef NO_LONG_DOUBLE
  68 strong_alias (__llround, __llroundl)
  69 weak_alias (__llround, llroundl)
  70 #endif
  71
  72 /* long has the same width as long long on LP64 machines, so use an alias.  */
  73 #undef lround
  74 #undef __lround
  75 #ifdef _LP64
  76 strong_alias (__llround, __lround)
  77 weak_alias (__llround, lround)
  78 # ifdef NO_LONG_DOUBLE
  79 strong_alias (__llround, __lroundl)
  80 weak_alias (__llround, lroundl)
  81 # endif
  82 #endif