1  /* Round to long int long double floating-point values.
       2     IBM extended format long double version.
       3     Copyright (C) 2006-2023 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     <https://www.gnu.org/licenses/>.  */
      19  
      20  #include <math.h>
      21  #include <fenv.h>
      22  #include <math_private.h>
      23  #include <math_ldbl_opt.h>
      24  #include <float.h>
      25  #include <ieee754.h>
      26  
      27  long
      28  __lroundl (long double x)
      29  {
      30    double xh, xl;
      31    long res, hi, lo;
      32  
      33    ldbl_unpack (x, &xh, &xl);
      34  
      35    /* Limit the range of values handled by the conversion to long.
      36       We do this because we aren't sure whether that conversion properly
      37       raises FE_INVALID.  */
      38    if (
      39  #if __LONG_MAX__ == 2147483647
      40        __builtin_expect
      41        ((__builtin_fabs (xh) <= (double) __LONG_MAX__ + 2), 1)
      42  #else
      43        __builtin_expect
      44        ((__builtin_fabs (xh) <= -(double) (-__LONG_MAX__ - 1)), 1)
      45  #endif
      46  #if !defined (FE_INVALID)
      47        || 1
      48  #endif
      49      )
      50      {
      51  #if __LONG_MAX__ == 2147483647
      52        long long llhi = (long long) xh;
      53        if (llhi != (long) llhi)
      54  	hi = llhi < 0 ? -__LONG_MAX__ - 1 : __LONG_MAX__;
      55        else
      56  	hi = llhi;
      57        xh -= hi;
      58  #else
      59        if (__glibc_unlikely ((xh == -(double) (-__LONG_MAX__ - 1))))
      60  	{
      61  	  /* When XH is 9223372036854775808.0, converting to long long will
      62  	     overflow, resulting in an invalid operation.  However, XL might
      63  	     be negative and of sufficient magnitude that the overall long
      64  	     double is in fact in range.  Avoid raising an exception.  In any
      65  	     case we need to convert this value specially, because
      66  	     the converted value is not exactly represented as a double
      67  	     thus subtracting HI from XH suffers rounding error.  */
      68  	  hi = __LONG_MAX__;
      69  	  xh = 1.0;
      70  	}
      71        else
      72  	{
      73  	  hi = (long) xh;
      74  	  xh -= hi;
      75  	}
      76  #endif
      77        ldbl_canonicalize (&xh, &xl);
      78  
      79        lo = (long) xh;
      80  
      81        /* Peg at max/min values, assuming that the above conversions do so.
      82           Strictly speaking, we can return anything for values that overflow,
      83           but this is more useful.  */
      84        res = (long int) ((unsigned long int) hi + (unsigned long int) lo);
      85  
      86        /* This is just sign(hi) == sign(lo) && sign(res) != sign(hi).  */
      87        if (__glibc_unlikely (((~(hi ^ lo) & (res ^ hi)) < 0)))
      88  	goto overflow;
      89  
      90        xh -= lo;
      91        ldbl_canonicalize (&xh, &xl);
      92  
      93        hi = res;
      94        if (xh > 0.5)
      95  	{
      96  	  res += 1UL;
      97  	}
      98        else if (xh == 0.5)
      99  	{
     100  	  if (xl > 0.0 || (xl == 0.0 && res >= 0))
     101  	    res += 1UL;
     102  	}
     103        else if (-xh > 0.5)
     104  	{
     105  	  res -= 1UL;
     106  	}
     107        else if (-xh == 0.5)
     108  	{
     109  	  if (xl < 0.0 || (xl == 0.0 && res <= 0))
     110  	    res -= 1UL;
     111  	}
     112  
     113        if (__glibc_unlikely (((~(hi ^ (res - hi)) & (res ^ hi)) < 0)))
     114  	goto overflow;
     115  
     116        return res;
     117      }
     118    else
     119      {
     120        if (xh > 0.0)
     121  	hi = __LONG_MAX__;
     122        else if (xh < 0.0)
     123  	hi = -__LONG_MAX__ - 1;
     124        else
     125  	/* Nan */
     126  	hi = 0;
     127      }
     128  
     129  overflow:
     130  #ifdef FE_INVALID
     131    feraiseexcept (FE_INVALID);
     132  #endif
     133    return hi;
     134  }
     135  
     136  long_double_symbol (libm, __lroundl, lroundl);