libquadmath/math/llroundq.c

   1 /* Round __float128 value to long long int.
   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
  25 long long int
  26 llroundq (__float128 x)
  27 {
  28   int64_t j0;
  29   uint64_t i1, i0;
  30   long long int result;
  31   int sign;
  32
  33   GET_FLT128_WORDS64 (i0, i1, x);
  34   j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  35   sign = (i0 & 0x8000000000000000ULL) != 0 ? -1 : 1;
  36   i0 &= 0x0000ffffffffffffLL;
  37   i0 |= 0x0001000000000000LL;
  38
  39   if (j0 < 48)
  40     {
  41       if (j0 < 0)
  42         return j0 < -1 ? 0 : sign;
  43       else
  44         {
  45           i0 += 0x0000800000000000LL >> j0;
  46           result = i0 >> (48 - j0);
  47         }
  48     }
  49   else if (j0 < (int32_t) (8 * sizeof (long long int)) - 1)
  50     {
  51       if (j0 >= 112)
  52         result = ((long long int) i0 << (j0 - 48)) | (i1 << (j0 - 112));
  53       else
  54         {
  55           uint64_t j = i1 + (0x8000000000000000ULL >> (j0 - 48));
  56           if (j < i1)
  57             ++i0;
  58
  59           if (j0 == 48)
  60             result = (long long int) i0;
  61           else
  62             {
  63               result = ((long long int) i0 << (j0 - 48)) | (j >> (112 - j0));
  64 #if defined FE_INVALID && defined USE_FENV_H
  65               if (sign == 1 && result == LLONG_MIN)
  66                 /* Rounding brought the value out of range.  */
  67                 feraiseexcept (FE_INVALID);
  68 #endif
  69             }
  70         }
  71     }
  72   else
  73     {
  74       /* The number is too large.  Unless it rounds to LLONG_MIN,
  75          FE_INVALID must be raised and the return value is
  76          unspecified.  */
  77 #ifdef FE_INVALID
  78       if (x <= (__float128) LLONG_MIN - 0.5Q)
  79         {
  80           /* If truncation produces LLONG_MIN, the cast will not raise
  81              the exception, but may raise "inexact".  */
  82 #ifdef USE_FENV_H
  83           feraiseexcept (FE_INVALID);
  84 #endif
  85           return LLONG_MIN;
  86         }
  87 #endif
  88       return (long long int) x;
  89     }
  90
  91   return sign * result;
  92 }