1  /* Round double to integer away from zero.
       2     Copyright (C) 1997-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #define NO_MATH_REDIRECT
      20  #include <math.h>
      21  
      22  #include <math_private.h>
      23  #include <libm-alias-double.h>
      24  #include <stdint.h>
      25  #include <math-use-builtins.h>
      26  
      27  
      28  double
      29  __round (double x)
      30  {
      31  #if USE_ROUND_BUILTIN
      32    return __builtin_round (x);
      33  #else
      34    /* Use generic implementation.  */
      35    int64_t i0, j0;
      36  
      37    EXTRACT_WORDS64 (i0, x);
      38    j0 = ((i0 >> 52) & 0x7ff) - 0x3ff;
      39    if (__glibc_likely (j0 < 52))
      40      {
      41        if (j0 < 0)
      42  	{
      43  	  i0 &= UINT64_C (0x8000000000000000);
      44  	  if (j0 == -1)
      45  	    i0 |= UINT64_C (0x3ff0000000000000);
      46  	}
      47        else
      48  	{
      49  	  uint64_t i = UINT64_C (0x000fffffffffffff) >> j0;
      50  	  if ((i0 & i) == 0)
      51  	    /* X is integral.  */
      52  	    return x;
      53  
      54  	  i0 += UINT64_C (0x0008000000000000) >> j0;
      55  	  i0 &= ~i;
      56  	}
      57      }
      58    else
      59      {
      60        if (j0 == 0x400)
      61  	/* Inf or NaN.  */
      62  	return x + x;
      63        else
      64  	return x;
      65      }
      66  
      67    INSERT_WORDS64 (x, i0);
      68    return x;
      69  #endif /* ! USE_ROUND_BUILTIN  */
      70  }
      71  libm_alias_double (__round, round)