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

   1 /* Round to long int long double floating-point values.
   2    IBM extended format long double version.
   3    Copyright (C) 2006 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, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <math.h>
  22 #include <fenv_libc.h>
  23 #include <math_ldbl_opt.h>
  24 #include <float.h>
  25 #include <ieee754.h>
  26
  27 #ifdef __STDC__
  28 long
  29 __lroundl (long double x)
  30 #else
  31 long
  32 __lroundl (x)
  33      long double x;
  34 #endif
  35 {
  36   double xh, xl;
  37   long res, hi, lo;
  38
  39   ldbl_unpack (x, &xh, &xl);
  40
  41   /* Limit the range of values handled by the conversion to long.
  42      We do this because we aren't sure whether that conversion properly
  43      raises FE_INVALID.  */
  44   if (
  45 #if __LONG_MAX__ == 2147483647
  46       __builtin_expect
  47       ((__builtin_fabs (xh) <= (double) __LONG_MAX__ + 2), 1)
  48 #else
  49       __builtin_expect
  50       ((__builtin_fabs (xh) <= -(double) (-__LONG_MAX__ - 1)), 1)
  51 #endif
  52 #if !defined (FE_INVALID)
  53       || 1
  54 #endif
  55     )
  56     {
  57 #if __LONG_MAX__ == 2147483647
  58       long long llhi = (long long) xh;
  59       if (llhi != (long) llhi)
  60         hi = llhi < 0 ? -__LONG_MAX__ - 1 : __LONG_MAX__;
  61       else
  62         hi = llhi;
  63       xh -= hi;
  64 #else
  65       if (__builtin_expect ((xh == -(double) (-__LONG_MAX__ - 1)), 0))
  66         {
  67           /* When XH is 9223372036854775808.0, converting to long long will
  68              overflow, resulting in an invalid operation.  However, XL might
  69              be negative and of sufficient magnitude that the overall long
  70              double is in fact in range.  Avoid raising an exception.  In any
  71              case we need to convert this value specially, because
  72              the converted value is not exactly represented as a double
  73              thus subtracting HI from XH suffers rounding error.  */
  74           hi = __LONG_MAX__;
  75           xh = 1.0;
  76         }
  77       else
  78         {
  79           hi = (long) xh;
  80           xh -= hi;
  81         }
  82 #endif
  83       ldbl_canonicalize (&xh, &xl);
  84
  85       lo = (long) xh;
  86
  87       /* Peg at max/min values, assuming that the above conversions do so.
  88          Strictly speaking, we can return anything for values that overflow,
  89          but this is more useful.  */
  90       res = hi + lo;
  91
  92       /* This is just sign(hi) == sign(lo) && sign(res) != sign(hi).  */
  93       if (__builtin_expect (((~(hi ^ lo) & (res ^ hi)) < 0), 0))
  94         goto overflow;
  95
  96       xh -= lo;
  97       ldbl_canonicalize (&xh, &xl);
  98
  99       hi = res;
 100       if (xh > 0.5)
 101         {
 102           res += 1;
 103         }
 104       else if (xh == 0.5)
 105         {
 106           if (xl > 0.0 || (xl == 0.0 && res >= 0))
 107             res += 1;
 108         }
 109       else if (-xh > 0.5)
 110         {
 111           res -= 1;
 112         }
 113       else if (-xh == 0.5)
 114         {
 115           if (xl < 0.0 || (xl == 0.0 && res <= 0))
 116             res -= 1;
 117         }
 118
 119       if (__builtin_expect (((~(hi ^ (res - hi)) & (res ^ hi)) < 0), 0))
 120         goto overflow;
 121
 122       return res;
 123     }
 124   else
 125     {
 126       if (xh > 0.0)
 127         hi = __LONG_MAX__;
 128       else if (xh < 0.0)
 129         hi = -__LONG_MAX__ - 1;
 130       else
 131         /* Nan */
 132         hi = 0;
 133     }
 134
 135 overflow:
 136 #ifdef FE_INVALID
 137   feraiseexcept (FE_INVALID);
 138 #endif
 139   return hi;
 140 }
 141
 142 long_double_symbol (libm, __lroundl, lroundl);