sysdeps/ieee754/ldbl-128/s_llroundl.c

   1 /* Round long double value to long long int.
   2    Copyright (C) 1997-2016 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 <fenv.h>
  22 #include <limits.h>
  23 #include <math.h>
  24
  25 #include <math_private.h>
  26
  27
  28 long long int
  29 __llroundl (long double x)
  30 {
  31   int64_t j0;
  32   u_int64_t i1, i0;
  33   long long int result;
  34   int sign;
  35
  36   GET_LDOUBLE_WORDS64 (i0, i1, x);
  37   j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  38   sign = (i0 & 0x8000000000000000ULL) != 0 ? -1 : 1;
  39   i0 &= 0x0000ffffffffffffLL;
  40   i0 |= 0x0001000000000000LL;
  41
  42   if (j0 < 48)
  43     {
  44       if (j0 < 0)
  45         return j0 < -1 ? 0 : sign;
  46       else
  47         {
  48           i0 += 0x0000800000000000LL >> j0;
  49           result = i0 >> (48 - j0);
  50         }
  51     }
  52   else if (j0 < (int32_t) (8 * sizeof (long long int)) - 1)
  53     {
  54       if (j0 >= 112)
  55         result = ((long long int) i0 << (j0 - 48)) | (i1 << (j0 - 112));
  56       else
  57         {
  58           u_int64_t j = i1 + (0x8000000000000000ULL >> (j0 - 48));
  59           if (j < i1)
  60             ++i0;
  61
  62           if (j0 == 48)
  63             result = (long long int) i0;
  64           else
  65             {
  66               result = ((long long int) i0 << (j0 - 48)) | (j >> (112 - j0));
  67 #ifdef FE_INVALID
  68               if (sign == 1 && result == LLONG_MIN)
  69                 /* Rounding brought the value out of range.  */
  70                 feraiseexcept (FE_INVALID);
  71 #endif
  72             }
  73         }
  74     }
  75   else
  76     {
  77       /* The number is too large.  Unless it rounds to LLONG_MIN,
  78          FE_INVALID must be raised and the return value is
  79          unspecified.  */
  80 #ifdef FE_INVALID
  81       if (x <= (long double) LLONG_MIN - 0.5L)
  82         {
  83           /* If truncation produces LLONG_MIN, the cast will not raise
  84              the exception, but may raise "inexact".  */
  85           feraiseexcept (FE_INVALID);
  86           return LLONG_MIN;
  87         }
  88 #endif
  89       return (long long int) x;
  90     }
  91
  92   return sign * result;
  93 }
  94
  95 weak_alias (__llroundl, llroundl)