libquadmath/math/lrintq.c

   1 /* Round argument to nearest integral value according to current rounding
   2    direction.
   3    Copyright (C) 1997, 1999, 2004, 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 int
  32 lrintq (__float128 x)
  33 {
  34   int32_t j0;
  35   uint64_t i0,i1;
  36   volatile __float128 w;
  37   __float128 t;
  38   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 < 48)
  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       result = (j0 < 0 ? 0 : i0 >> (48 - j0));
  57     }
  58   else if (j0 < (int32_t) (8 * sizeof (long int)) - 1)
  59     {
  60       if (j0 >= 112)
  61         result = ((long int) i0 << (j0 - 48)) | (i1 << (j0 - 112));
  62       else
  63         {
  64           w = two112[sx] + x;
  65           t = w - two112[sx];
  66           GET_FLT128_WORDS64 (i0, i1, t);
  67           j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  68           i0 &= 0x0000ffffffffffffLL;
  69           i0 |= 0x0001000000000000LL;
  70
  71           if (j0 == 48)
  72             result = (long int) i0;
  73           else
  74             result = ((long int) i0 << (j0 - 48)) | (i1 >> (112 - j0));
  75         }
  76     }
  77   else
  78     {
  79       /* The number is too large.  It is left implementation defined
  80          what happens.  */
  81       return (long int) x;
  82     }
  83
  84   return sx ? -result : result;
  85 }