sysdeps/ieee754/dbl-64/s_lround.c

   1 /* Round double value to 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 #include <fenv.h>
  21 #include <limits.h>
  22 #include <math.h>
  23
  24 #include <math_private.h>
  25 #include <fix-fp-int-convert-overflow.h>
  26
  27
  28 long int
  29 __lround (double x)
  30 {
  31   int32_t j0;
  32   u_int32_t i1, i0;
  33   long int result;
  34   int sign;
  35
  36   EXTRACT_WORDS (i0, i1, x);
  37   j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  38   sign = (i0 & 0x80000000) != 0 ? -1 : 1;
  39   i0 &= 0xfffff;
  40   i0 |= 0x100000;
  41
  42   if (j0 < 20)
  43     {
  44       if (j0 < 0)
  45         return j0 < -1 ? 0 : sign;
  46       else
  47         {
  48           i0 += 0x80000 >> j0;
  49
  50           result = i0 >> (20 - j0);
  51         }
  52     }
  53   else if (j0 < (int32_t) (8 * sizeof (long int)) - 1)
  54     {
  55       if (j0 >= 52)
  56         result = ((long int) i0 << (j0 - 20)) | ((long int) i1 << (j0 - 52));
  57       else
  58         {
  59           u_int32_t j = i1 + (0x80000000 >> (j0 - 20));
  60           if (j < i1)
  61             ++i0;
  62
  63           if (j0 == 20)
  64             result = (long int) i0;
  65           else
  66             {
  67               result = ((long int) i0 << (j0 - 20)) | (j >> (52 - j0));
  68 #ifdef FE_INVALID
  69               if (sizeof (long int) == 4
  70                   && sign == 1
  71                   && result == LONG_MIN)
  72                 /* Rounding brought the value out of range.  */
  73                 feraiseexcept (FE_INVALID);
  74 #endif
  75             }
  76         }
  77     }
  78   else
  79     {
  80       /* The number is too large.  Unless it rounds to LONG_MIN,
  81          FE_INVALID must be raised and the return value is
  82          unspecified.  */
  83 #ifdef FE_INVALID
  84       if (FIX_DBL_LONG_CONVERT_OVERFLOW
  85           && !(sign == -1
  86                && (sizeof (long int) == 4
  87                    ? x > (double) LONG_MIN - 0.5
  88                    : x >= (double) LONG_MIN)))
  89         {
  90           feraiseexcept (FE_INVALID);
  91           return sign == 1 ? LONG_MAX : LONG_MIN;
  92         }
  93       else if (!FIX_DBL_LONG_CONVERT_OVERFLOW
  94                && sizeof (long int) == 4
  95                && x <= (double) LONG_MIN - 0.5)
  96         {
  97           /* If truncation produces LONG_MIN, the cast will not raise
  98              the exception, but may raise "inexact".  */
  99           feraiseexcept (FE_INVALID);
 100           return LONG_MIN;
 101         }
 102 #endif
 103       return (long int) x;
 104     }
 105
 106   return sign * result;
 107 }
 108
 109 weak_alias (__lround, lround)
 110 #ifdef NO_LONG_DOUBLE
 111 strong_alias (__lround, __lroundl)
 112 weak_alias (__lround, lroundl)
 113 #endif