sysdeps/ieee754/ldbl-128ibm/s_lrintl.c

   1 /* Round to long int long double floating-point values.
   2    IBM extended format long double version.
   3    Copyright (C) 2006-2014 Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <math.h>
  21 #include <fenv_libc.h>
  22 #include <math_ldbl_opt.h>
  23 #include <float.h>
  24 #include <ieee754.h>
  25
  26
  27 long
  28 __lrintl (long double x)
  29 {
  30   double xh, xl;
  31   long res, hi, lo;
  32   int save_round;
  33
  34   ldbl_unpack (x, &xh, &xl);
  35
  36   /* Limit the range of values handled by the conversion to long.
  37      We do this because we aren't sure whether that conversion properly
  38      raises FE_INVALID.  */
  39   if (
  40 #if __LONG_MAX__ == 2147483647
  41       __builtin_expect
  42       ((__builtin_fabs (xh) <= (double) __LONG_MAX__ + 2), 1)
  43 #else
  44       __builtin_expect
  45       ((__builtin_fabs (xh) <= -(double) (-__LONG_MAX__ - 1)), 1)
  46 #endif
  47 #if !defined (FE_INVALID)
  48       || 1
  49 #endif
  50     )
  51     {
  52       save_round = __fegetround ();
  53
  54 #if __LONG_MAX__ == 2147483647
  55       long long llhi = (long long) xh;
  56       if (llhi != (long) llhi)
  57         hi = llhi < 0 ? -__LONG_MAX__ - 1 : __LONG_MAX__;
  58       else
  59         hi = llhi;
  60       xh -= hi;
  61 #else
  62       if (__builtin_expect ((xh == -(double) (-__LONG_MAX__ - 1)), 0))
  63         {
  64           /* When XH is 9223372036854775808.0, converting to long long will
  65              overflow, resulting in an invalid operation.  However, XL might
  66              be negative and of sufficient magnitude that the overall long
  67              double is in fact in range.  Avoid raising an exception.  In any
  68              case we need to convert this value specially, because
  69              the converted value is not exactly represented as a double
  70              thus subtracting HI from XH suffers rounding error.  */
  71           hi = __LONG_MAX__;
  72           xh = 1.0;
  73         }
  74       else
  75         {
  76           hi = (long) xh;
  77           xh -= hi;
  78         }
  79 #endif
  80       ldbl_canonicalize (&xh, &xl);
  81
  82       lo = (long) xh;
  83
  84       /* Peg at max/min values, assuming that the above conversions do so.
  85          Strictly speaking, we can return anything for values that overflow,
  86          but this is more useful.  */
  87       res = hi + lo;
  88
  89       /* This is just sign(hi) == sign(lo) && sign(res) != sign(hi).  */
  90       if (__builtin_expect (((~(hi ^ lo) & (res ^ hi)) < 0), 0))
  91         goto overflow;
  92
  93       xh -= lo;
  94       ldbl_canonicalize (&xh, &xl);
  95
  96       hi = res;
  97       switch (save_round)
  98         {
  99         case FE_TONEAREST:
 100           if (fabs (xh) < 0.5
 101               || (fabs (xh) == 0.5
 102                   && ((xh > 0.0 && xl < 0.0)
 103                       || (xh < 0.0 && xl > 0.0)
 104                       || (xl == 0.0 && (res & 1) == 0))))
 105             return res;
 106
 107           if (xh < 0.0)
 108             res -= 1;
 109           else
 110             res += 1;
 111           break;
 112
 113         case FE_TOWARDZERO:
 114           if (res > 0 && (xh < 0.0 || (xh == 0.0 && xl < 0.0)))
 115             res -= 1;
 116           else if (res < 0 && (xh > 0.0 || (xh == 0.0 && xl > 0.0)))
 117             res += 1;
 118           return res;
 119           break;
 120
 121         case FE_UPWARD:
 122           if (xh > 0.0 || (xh == 0.0 && xl > 0.0))
 123             res += 1;
 124           break;
 125
 126         case FE_DOWNWARD:
 127           if (xh < 0.0 || (xh == 0.0 && xl < 0.0))
 128             res -= 1;
 129           break;
 130         }
 131
 132       if (__builtin_expect (((~(hi ^ (res - hi)) & (res ^ hi)) < 0), 0))
 133         goto overflow;
 134
 135       return res;
 136     }
 137   else
 138     {
 139       if (xh > 0.0)
 140         hi = __LONG_MAX__;
 141       else if (xh < 0.0)
 142         hi = -__LONG_MAX__ - 1;
 143       else
 144         /* Nan */
 145         hi = 0;
 146     }
 147
 148 overflow:
 149 #ifdef FE_INVALID
 150   feraiseexcept (FE_INVALID);
 151 #endif
 152   return hi;
 153 }
 154
 155 long_double_symbol (libm, __lrintl, lrintl);