sysdeps/ieee754/dbl-64/s_llround.c

   1 /* Round double value to long long int.
   2    Copyright (C) 1997-2019 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 long int
  30 __llround (double x)
  31 {
  32   int32_t j0;
  33   uint32_t i1, i0;
  34   long 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 long int)) - 1)
  55     {
  56       if (j0 >= 52)
  57         result = (((long long int) i0 << 32) | 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 long int) i0;
  66           else
  67             result = ((long long int) i0 << (j0 - 20)) | (j >> (52 - j0));
  68         }
  69     }
  70   else
  71     {
  72 #ifdef FE_INVALID
  73       /* The number is too large.  Unless it rounds to LLONG_MIN,
  74          FE_INVALID must be raised and the return value is
  75          unspecified.  */
  76       if (FIX_DBL_LLONG_CONVERT_OVERFLOW && x != (double) LLONG_MIN)
  77         {
  78           feraiseexcept (FE_INVALID);
  79           return sign == 1 ? LLONG_MAX : LLONG_MIN;
  80         }
  81 #endif
  82       return (long long int) x;
  83     }
  84
  85   return sign * result;
  86 }
  87
  88 libm_alias_double (__llround, llround)