libquadmath/math/llrintq.c

   1 /* Round argument to nearest integral value according to current rounding
   2    direction.
   3    Copyright (C) 1997, 1999, 2006 Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997 and
   6                   Jakub Jelinek <jj@ultra.linux.cz>, 1999.
   7
   8    The GNU C Library is free software; you can redistribute it and/or
   9    modify it under the terms of the GNU Lesser General Public
  10    License as published by the Free Software Foundation; either
  11    version 2.1 of the License, or (at your option) any later version.
  12
  13    The GNU C Library is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16    Lesser General Public License for more details.
  17
  18    You should have received a copy of the GNU Lesser General Public
  19    License along with the GNU C Library; if not, write to the Free
  20    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  21    02111-1307 USA.  */
  22
  23 #include "quadmath-imp.h"
  24
  25 static const __float128 two112[2] =
  26 {
  27   5.19229685853482762853049632922009600E+33Q, /* 0x406F000000000000, 0 */
  28  -5.19229685853482762853049632922009600E+33Q  /* 0xC06F000000000000, 0 */
  29 };
  30
  31 long long int
  32 llrintq (__float128 x)
  33 {
  34   int32_t j0;
  35   uint64_t i0,i1;
  36   volatile __float128 w;
  37   __float128 t;
  38   long long int result;
  39   int sx;
  40
  41   GET_FLT128_WORDS64 (i0, i1, x);
  42   j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  43   sx = i0 >> 63;
  44   i0 &= 0x0000ffffffffffffLL;
  45   i0 |= 0x0001000000000000LL;
  46
  47   if (j0 < (int32_t) (8 * sizeof (long long int)) - 1)
  48     {
  49       w = two112[sx] + x;
  50       t = w - two112[sx];
  51       GET_FLT128_WORDS64 (i0, i1, t);
  52       j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  53       i0 &= 0x0000ffffffffffffLL;
  54       i0 |= 0x0001000000000000LL;
  55
  56       if (j0 < 0)
  57         result = 0;
  58       else if (j0 <= 48)
  59         result = i0 >> (48 - j0);
  60       else
  61         result = ((long long int) i0 << (j0 - 48)) | (i1 >> (112 - j0));
  62     }
  63   else
  64     {
  65       /* The number is too large.  It is left implementation defined
  66          what happens.  */
  67       return (long long int) x;
  68     }
  69
  70   return sx ? -result : result;
  71 }