libquadmath/math/lroundq.c

   1 /* Round long double value to 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 int
  24 lroundq (__float128 x)
  25 {
  26   int64_t j0;
  27   uint64_t i1, i0;
  28   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 < (int32_t) (8 * sizeof (long int)) - 1)
  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 #ifdef FE_INVALID
  48               if (sizeof (long int) == 4
  49                   && sign == 1
  50                   && result == LONG_MIN)
  51                 /* Rounding brought the value out of range.  */
  52                 feraiseexcept (FE_INVALID);
  53 #endif
  54             }
  55         }
  56       else if (j0 >= 112)
  57         result = ((long int) i0 << (j0 - 48)) | (i1 << (j0 - 112));
  58       else
  59         {
  60           uint64_t j = i1 + (0x8000000000000000ULL >> (j0 - 48));
  61           if (j < i1)
  62             ++i0;
  63
  64           if (j0 == 48)
  65             result = (long int) i0;
  66           else
  67             {
  68               result = ((long int) i0 << (j0 - 48)) | (j >> (112 - j0));
  69 #ifdef FE_INVALID
  70               if (sizeof (long int) == 8
  71                   && sign == 1
  72                   && result == LONG_MIN)
  73                 /* Rounding brought the value out of range.  */
  74                 feraiseexcept (FE_INVALID);
  75 #endif
  76             }
  77         }
  78     }
  79   else
  80     {
  81       /* The number is too large.  Unless it rounds to LONG_MIN,
  82          FE_INVALID must be raised and the return value is
  83          unspecified.  */
  84 #ifdef FE_INVALID
  85       if (FIX_FLT128_LONG_CONVERT_OVERFLOW
  86           && !(sign == -1 && x > (__float128) LONG_MIN - 0.5Q))
  87         {
  88           feraiseexcept (FE_INVALID);
  89           return sign == 1 ? LONG_MAX : LONG_MIN;
  90         }
  91       else if (!FIX_FLT128_LONG_CONVERT_OVERFLOW
  92                && x <= (__float128) LONG_MIN - 0.5Q)
  93         {
  94           /* If truncation produces LONG_MIN, the cast will not raise
  95              the exception, but may raise "inexact".  */
  96           feraiseexcept (FE_INVALID);
  97           return LONG_MIN;
  98         }
  99 #endif
 100       /* The number is too large.  It is left implementation defined
 101          what happens.  */
 102       return (long int) x;
 103     }
 104
 105   return sign * result;
 106 }