libquadmath/math/roundq.c

   1 /* Round long double to integer away from zero.
   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 and
   5                   Jakub Jelinek <jj@ultra.linux.cz>, 1999.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public
   9    License as published by the Free Software Foundation; either
  10    version 2.1 of the License, or (at your option) any later version.
  11
  12    The GNU C Library is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library; if not, see
  19    <http://www.gnu.org/licenses/>.  */
  20
  21 #define NO_MATH_REDIRECT
  22
  23 #include "quadmath-imp.h"
  24
  25 __float128
  26 roundq (__float128 x)
  27 {
  28   int32_t j0;
  29   uint64_t i1, i0;
  30
  31   GET_FLT128_WORDS64 (i0, i1, x);
  32   j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  33   if (j0 < 48)
  34     {
  35       if (j0 < 0)
  36         {
  37           i0 &= 0x8000000000000000ULL;
  38           if (j0 == -1)
  39             i0 |= 0x3fff000000000000LL;
  40           i1 = 0;
  41         }
  42       else
  43         {
  44           uint64_t i = 0x0000ffffffffffffLL >> j0;
  45           if (((i0 & i) | i1) == 0)
  46             /* X is integral.  */
  47             return x;
  48
  49           i0 += 0x0000800000000000LL >> j0;
  50           i0 &= ~i;
  51           i1 = 0;
  52         }
  53     }
  54   else if (j0 > 111)
  55     {
  56       if (j0 == 0x4000)
  57         /* Inf or NaN.  */
  58         return x + x;
  59       else
  60         return x;
  61     }
  62   else
  63     {
  64       uint64_t i = -1ULL >> (j0 - 48);
  65       if ((i1 & i) == 0)
  66         /* X is integral.  */
  67         return x;
  68
  69       uint64_t j = i1 + (1LL << (111 - j0));
  70       if (j < i1)
  71         i0 += 1;
  72       i1 = j;
  73       i1 &= ~i;
  74     }
  75
  76   SET_FLT128_WORDS64 (x, i0, i1);
  77   return x;
  78 }