libquadmath/math/roundq.c

   1 /* Round __float128 to integer away from zero.
   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 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, write to the Free
  19    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  20    02111-1307 USA.  */
  21
  22 #include "quadmath-imp.h"
  23
  24 __float128
  25 roundq (__float128 x)
  26 {
  27   int32_t j0;
  28   uint64_t i1, i0;
  29
  30   GET_FLT128_WORDS64 (i0, i1, x);
  31   j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  32   if (j0 < 48)
  33     {
  34       if (j0 < 0)
  35         {
  36           i0 &= 0x8000000000000000ULL;
  37           if (j0 == -1)
  38             i0 |= 0x3fff000000000000LL;
  39           i1 = 0;
  40         }
  41       else
  42         {
  43           uint64_t i = 0x0000ffffffffffffLL >> j0;
  44           if (((i0 & i) | i1) == 0)
  45             /* X is integral.  */
  46             return x;
  47           i0 += 0x0000800000000000LL >> j0;
  48           i0 &= ~i;
  49           i1 = 0;
  50         }
  51     }
  52   else if (j0 > 111)
  53     {
  54       if (j0 == 0x4000)
  55         /* Inf or NaN.  */
  56         return x + x;
  57       else
  58         return x;
  59     }
  60   else
  61     {
  62       uint64_t i = -1ULL >> (j0 - 48);
  63       if ((i1 & i) == 0)
  64         /* X is integral.  */
  65         return x;
  66
  67       uint64_t j = i1 + (1LL << (111 - j0));
  68       if (j < i1)
  69         i0 += 1;
  70       i1 = j;
  71       i1 &= ~i;
  72     }
  73
  74   SET_FLT128_WORDS64 (x, i0, i1);
  75   return x;
  76 }