libquadmath/math/roundq.c

   1 /* Round __float128 to integer away from zero.
   2    Copyright (C) 1997-2013 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 static const __float128 huge = 1.0E4930Q;
  25
  26
  27 __float128
  28 roundq (__float128 x)
  29 {
  30   int32_t j0;
  31   uint64_t i1, i0;
  32
  33   GET_FLT128_WORDS64 (i0, i1, x);
  34   j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  35   if (j0 < 31)
  36     {
  37       if (j0 < 0)
  38         {
  39           if (huge + x > 0.0)
  40             {
  41               i0 &= 0x8000000000000000ULL;
  42               if (j0 == -1)
  43                 i0 |= 0x3fff000000000000LL;
  44               i1 = 0;
  45             }
  46         }
  47       else
  48         {
  49           uint64_t i = 0x0000ffffffffffffLL >> j0;
  50           if (((i0 & i) | i1) == 0)
  51             /* X is integral.  */
  52             return x;
  53           if (huge + x > 0.0)
  54             {
  55               /* Raise inexact if x != 0.  */
  56               i0 += 0x0000800000000000LL >> j0;
  57               i0 &= ~i;
  58               i1 = 0;
  59             }
  60         }
  61     }
  62   else if (j0 > 111)
  63     {
  64       if (j0 == 0x4000)
  65         /* Inf or NaN.  */
  66         return x + x;
  67       else
  68         return x;
  69     }
  70   else
  71     {
  72       uint64_t i = -1ULL >> (j0 - 48);
  73       if ((i1 & i) == 0)
  74         /* X is integral.  */
  75         return x;
  76
  77       if (huge + x > 0.0)
  78         {
  79           /* Raise inexact if x != 0.  */
  80           uint64_t j = i1 + (1LL << (111 - j0));
  81           if (j < i1)
  82             i0 += 1;
  83           i1 = j;
  84         }
  85       i1 &= ~i;
  86     }
  87
  88   SET_FLT128_WORDS64 (x, i0, i1);
  89   return x;
  90 }