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

   1 /* Round double value to long int.
   2    Copyright (C) 1997-2015 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <fenv.h>
  20 #include <limits.h>
  21 #include <math.h>
  22
  23 #include <math_private.h>
  24
  25 /* For LP64, lround is an alias for llround.  */
  26 #ifndef _LP64
  27
  28 long int
  29 __lround (double x)
  30 {
  31   int32_t j0;
  32   int64_t i0;
  33   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 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 #ifdef FE_INVALID
  54           if (sizeof (long int) == 4
  55               && sign == 1
  56               && result == LONG_MIN)
  57             /* Rounding brought the value out of range.  */
  58             feraiseexcept (FE_INVALID);
  59 #endif
  60         }
  61     }
  62   else
  63     {
  64       /* The number is too large.  Unless it rounds to LONG_MIN,
  65          FE_INVALID must be raised and the return value is
  66          unspecified.  */
  67 #ifdef FE_INVALID
  68       if (sizeof (long int) == 4
  69           && x <= (double) LONG_MIN - 0.5)
  70         {
  71           /* If truncation produces LONG_MIN, the cast will not raise
  72              the exception, but may raise "inexact".  */
  73           feraiseexcept (FE_INVALID);
  74           return LONG_MIN;
  75         }
  76 #endif
  77       return (long int) x;
  78     }
  79
  80   return sign * result;
  81 }
  82
  83 weak_alias (__lround, lround)
  84 # ifdef NO_LONG_DOUBLE
  85 strong_alias (__lround, __lroundl)
  86 weak_alias (__lround, lroundl)
  87 # endif
  88
  89 #endif