1  /* Round to 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  /* This has been coded in assembler because GCC makes such a mess of it
      21     when it's coded in C.  */
      22  
      23  #define NO_MATH_REDIRECT
      24  #include <math.h>
      25  #include <fenv.h>
      26  #include <math-barriers.h>
      27  #include <math_private.h>
      28  #include <fenv_private.h>
      29  #include <math_ldbl_opt.h>
      30  #include <float.h>
      31  #include <ieee754.h>
      32  
      33  #ifdef USE_AS_NEARBYINTL
      34  # define rintl nearbyintl
      35  # define __rintl __nearbyintl
      36  #endif
      37  
      38  
      39  long double
      40  __rintl (long double x)
      41  {
      42    double xh, xl, hi, lo;
      43  
      44    ldbl_unpack (x, &xh, &xl);
      45  
      46    /* Return Inf, Nan, +/-0 unchanged.  */
      47    if (__builtin_expect (xh != 0.0
      48  			&& __builtin_isless (__builtin_fabs (xh),
      49  					     __builtin_inf ()), 1))
      50      {
      51        double orig_xh;
      52        int save_round = fegetround ();
      53  
      54        /* Long double arithmetic, including the canonicalisation below,
      55  	 only works in round-to-nearest mode.  */
      56  #ifdef USE_AS_NEARBYINTL
      57        SET_RESTORE_ROUND_NOEX (FE_TONEAREST);
      58  #else
      59        fesetround (FE_TONEAREST);
      60  #endif
      61  
      62        /* Convert the high double to integer.  */
      63        orig_xh = xh;
      64        hi = ldbl_nearbyint (xh);
      65  
      66        /* Subtract integral high part from the value.  If the low double
      67  	 happens to be exactly 0.5 or -0.5, you might think that this
      68  	 subtraction could result in an incorrect conversion.  For
      69  	 instance, subtracting an odd number would cause this function
      70  	 to round in the wrong direction.  However, if we have a
      71  	 canonical long double with the low double 0.5 or -0.5, then the
      72  	 high double must be even.  */
      73        xh -= hi;
      74        ldbl_canonicalize (&xh, &xl);
      75  
      76        /* Now convert the low double, adjusted for any remainder from the
      77  	 high double.  */
      78        lo = ldbl_nearbyint (xh);
      79  
      80        xh -= lo;
      81        ldbl_canonicalize (&xh, &xl);
      82  
      83        switch (save_round)
      84  	{
      85  	case FE_TONEAREST:
      86  	  if (xl > 0.0 && xh == 0.5)
      87  	    lo += 1.0;
      88  	  else if (xl < 0.0 && -xh == 0.5)
      89  	    lo -= 1.0;
      90  	  break;
      91  
      92  	case FE_TOWARDZERO:
      93  	  if (orig_xh < 0.0)
      94  	    goto do_up;
      95  	  /* Fall thru */
      96  
      97  	case FE_DOWNWARD:
      98  	  if (xh < 0.0 || (xh == 0.0 && xl < 0.0))
      99  	    lo -= 1.0;
     100  	  break;
     101  
     102  	case FE_UPWARD:
     103  	do_up:
     104  	  if (xh > 0.0 || (xh == 0.0 && xl > 0.0))
     105  	    lo += 1.0;
     106  	  break;
     107  	}
     108  
     109        /* Ensure the final value is canonical.  In certain cases,
     110           rounding causes hi,lo calculated so far to be non-canonical.  */
     111        xh = hi;
     112        xl = lo;
     113        ldbl_canonicalize (&xh, &xl);
     114  
     115        /* Ensure we return -0 rather than +0 when appropriate.  */
     116        if (orig_xh < 0.0)
     117  	xh = -__builtin_fabs (xh);
     118  
     119  #ifdef USE_AS_NEARBYINTL
     120        math_force_eval (xh);
     121        math_force_eval (xl);
     122  #else
     123        fesetround (save_round);
     124  #endif
     125      }
     126    else
     127      /* Quiet signaling NaN arguments.  */
     128      xh += xh;
     129  
     130    return ldbl_pack (xh, xl);
     131  }
     132  
     133  long_double_symbol (libm, __rintl, rintl);