libquadmath/math/llroundq.c

   1 /* Round long double value to long long int.
   2    Copyright (C) 1997-2018 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, see
  19    <http://www.gnu.org/licenses/>.  */
  20
  21 #include "quadmath-imp.h"
  22
  23 long long int
  24 llroundq (__float128 x)
  25 {
  26   int64_t j0;
  27   uint64_t i1, i0;
  28   long long int result;
  29   int sign;
  30
  31   GET_FLT128_WORDS64 (i0, i1, x);
  32   j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  33   sign = (i0 & 0x8000000000000000ULL) != 0 ? -1 : 1;
  34   i0 &= 0x0000ffffffffffffLL;
  35   i0 |= 0x0001000000000000LL;
  36
  37   if (j0 < 48)
  38     {
  39       if (j0 < 0)
  40         return j0 < -1 ? 0 : sign;
  41       else
  42         {
  43           i0 += 0x0000800000000000LL >> j0;
  44           result = i0 >> (48 - j0);
  45         }
  46     }
  47   else if (j0 < (int32_t) (8 * sizeof (long long int)) - 1)
  48     {
  49       if (j0 >= 112)
  50         result = ((long long int) i0 << (j0 - 48)) | (i1 << (j0 - 112));
  51       else
  52         {
  53           uint64_t j = i1 + (0x8000000000000000ULL >> (j0 - 48));
  54           if (j < i1)
  55             ++i0;
  56
  57           if (j0 == 48)
  58             result = (long long int) i0;
  59           else
  60             {
  61               result = ((long long int) i0 << (j0 - 48)) | (j >> (112 - j0));
  62 #ifdef FE_INVALID
  63               if (sign == 1 && result == LLONG_MIN)
  64                 /* Rounding brought the value out of range.  */
  65                 feraiseexcept (FE_INVALID);
  66 #endif
  67             }
  68         }
  69     }
  70   else
  71     {
  72       /* The number is too large.  Unless it rounds to LLONG_MIN,
  73          FE_INVALID must be raised and the return value is
  74          unspecified.  */
  75 #ifdef FE_INVALID
  76       if (FIX_FLT128_LLONG_CONVERT_OVERFLOW
  77           && !(sign == -1 && x > (__float128) LLONG_MIN - 0.5Q))
  78         {
  79           feraiseexcept (FE_INVALID);
  80           return sign == 1 ? LLONG_MAX : LLONG_MIN;
  81         }
  82       else if (!FIX_FLT128_LLONG_CONVERT_OVERFLOW
  83                && x <= (__float128) LLONG_MIN - 0.5Q)
  84         {
  85           /* If truncation produces LLONG_MIN, the cast will not raise
  86              the exception, but may raise "inexact".  */
  87           feraiseexcept (FE_INVALID);
  88           return LLONG_MIN;
  89         }
  90 #endif
  91       return (long long int) x;
  92     }
  93
  94   return sign * result;
  95 }