sysdeps/ieee754/dbl-64/s_lround.c

   1 /* Round double value to long int.
   2    Copyright (C) 1997-2018 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 <libm-alias-double.h>
  26 #include <fix-fp-int-convert-overflow.h>
  27
  28
  29 long int
  30 __lround (double x)
  31 {
  32   int32_t j0;
  33   uint32_t i1, i0;
  34   long int result;
  35   int sign;
  36
  37   EXTRACT_WORDS (i0, i1, x);
  38   j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  39   sign = (i0 & 0x80000000) != 0 ? -1 : 1;
  40   i0 &= 0xfffff;
  41   i0 |= 0x100000;
  42
  43   if (j0 < 20)
  44     {
  45       if (j0 < 0)
  46         return j0 < -1 ? 0 : sign;
  47       else
  48         {
  49           i0 += 0x80000 >> j0;
  50
  51           result = i0 >> (20 - j0);
  52         }
  53     }
  54   else if (j0 < (int32_t) (8 * sizeof (long int)) - 1)
  55     {
  56       if (j0 >= 52)
  57         result = ((long int) i0 << (j0 - 20)) | ((long int) i1 << (j0 - 52));
  58       else
  59         {
  60           uint32_t j = i1 + (0x80000000 >> (j0 - 20));
  61           if (j < i1)
  62             ++i0;
  63
  64           if (j0 == 20)
  65             result = (long int) i0;
  66           else
  67             {
  68               result = ((long int) i0 << (j0 - 20)) | (j >> (52 - j0));
  69 #ifdef FE_INVALID
  70               if (sizeof (long int) == 4
  71                   && sign == 1
  72                   && result == LONG_MIN)
  73                 /* Rounding brought the value out of range.  */
  74                 feraiseexcept (FE_INVALID);
  75 #endif
  76             }
  77         }
  78     }
  79   else
  80     {
  81       /* The number is too large.  Unless it rounds to LONG_MIN,
  82          FE_INVALID must be raised and the return value is
  83          unspecified.  */
  84 #ifdef FE_INVALID
  85       if (FIX_DBL_LONG_CONVERT_OVERFLOW
  86           && !(sign == -1
  87                && (sizeof (long int) == 4
  88                    ? x > (double) LONG_MIN - 0.5
  89                    : x >= (double) LONG_MIN)))
  90         {
  91           feraiseexcept (FE_INVALID);
  92           return sign == 1 ? LONG_MAX : LONG_MIN;
  93         }
  94       else if (!FIX_DBL_LONG_CONVERT_OVERFLOW
  95                && sizeof (long int) == 4
  96                && x <= (double) LONG_MIN - 0.5)
  97         {
  98           /* If truncation produces LONG_MIN, the cast will not raise
  99              the exception, but may raise "inexact".  */
 100           feraiseexcept (FE_INVALID);
 101           return LONG_MIN;
 102         }
 103 #endif
 104       return (long int) x;
 105     }
 106
 107   return sign * result;
 108 }
 109
 110 libm_alias_double (__lround, lround)