sysdeps/ieee754/dbl-64/s_llround.c

   1 /* Round double value to long long int.
   2    Copyright (C) 1997-2023 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #define lround __hidden_lround
  20 #define __lround __hidden___lround
  21
  22 #include <fenv.h>
  23 #include <limits.h>
  24 #include <math.h>
  25 #include <sysdep.h>
  26
  27 #include <math_private.h>
  28 #include <libm-alias-double.h>
  29 #include <fix-fp-int-convert-overflow.h>
  30
  31 long long int
  32 __llround (double x)
  33 {
  34   int32_t j0;
  35   int64_t i0;
  36   long long int result;
  37   int sign;
  38
  39   EXTRACT_WORDS64 (i0, x);
  40   j0 = ((i0 >> 52) & 0x7ff) - 0x3ff;
  41   sign = i0 < 0 ? -1 : 1;
  42   i0 &= UINT64_C(0xfffffffffffff);
  43   i0 |= UINT64_C(0x10000000000000);
  44
  45   if (j0 < (int32_t) (8 * sizeof (long long int)) - 1)
  46     {
  47       if (j0 < 0)
  48         return j0 < -1 ? 0 : sign;
  49       else if (j0 >= 52)
  50         result = i0 << (j0 - 52);
  51       else
  52         {
  53           i0 += UINT64_C(0x8000000000000) >> j0;
  54
  55           result = i0 >> (52 - j0);
  56         }
  57     }
  58   else
  59     {
  60 #ifdef FE_INVALID
  61       /* The number is too large.  Unless it rounds to LLONG_MIN,
  62          FE_INVALID must be raised and the return value is
  63          unspecified.  */
  64       if (FIX_DBL_LLONG_CONVERT_OVERFLOW && x != (double) LLONG_MIN)
  65         {
  66           feraiseexcept (FE_INVALID);
  67           return sign == 1 ? LLONG_MAX : LLONG_MIN;
  68         }
  69 #endif
  70       return (long long int) x;
  71     }
  72
  73   return sign * result;
  74 }
  75
  76 libm_alias_double (__llround, llround)
  77
  78 /* long has the same width as long long on LP64 machines, so use an alias.  */
  79 #undef lround
  80 #undef __lround
  81 #ifdef _LP64
  82 strong_alias (__llround, __lround)
  83 libm_alias_double (__lround, lround)
  84 #endif