1  /* Round double value to long int.
       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  #include <fenv.h>
      20  #include <limits.h>
      21  #include <math.h>
      22  
      23  #include <math_private.h>
      24  #include <libm-alias-double.h>
      25  #include <fix-fp-int-convert-overflow.h>
      26  
      27  /* For LP64, lround is an alias for llround.  */
      28  #ifndef _LP64
      29  
      30  long int
      31  __lround (double x)
      32  {
      33    int32_t j0;
      34    int64_t i0;
      35    long int result;
      36    int sign;
      37  
      38    EXTRACT_WORDS64 (i0, x);
      39    j0 = ((i0 >> 52) & 0x7ff) - 0x3ff;
      40    sign = i0 < 0 ? -1 : 1;
      41    i0 &= UINT64_C(0xfffffffffffff);
      42    i0 |= UINT64_C(0x10000000000000);
      43  
      44    if (j0 < (int32_t) (8 * sizeof (long int)) - 1)
      45      {
      46        if (j0 < 0)
      47  	return j0 < -1 ? 0 : sign;
      48        else if (j0 >= 52)
      49  	result = i0 << (j0 - 52);
      50        else
      51  	{
      52  	  i0 += UINT64_C(0x8000000000000) >> j0;
      53  
      54  	  result = i0 >> (52 - j0);
      55  #ifdef FE_INVALID
      56  	  if (sizeof (long int) == 4
      57  	      && sign == 1
      58  	      && result == LONG_MIN)
      59  	    /* Rounding brought the value out of range.  */
      60  	    feraiseexcept (FE_INVALID);
      61  #endif
      62  	}
      63      }
      64    else
      65      {
      66        /* The number is too large.  Unless it rounds to LONG_MIN,
      67  	 FE_INVALID must be raised and the return value is
      68  	 unspecified.  */
      69  #ifdef FE_INVALID
      70        if (FIX_DBL_LONG_CONVERT_OVERFLOW
      71  	  && !(sign == -1
      72  	       && (sizeof (long int) == 4
      73  		   ? x > (double) LONG_MIN - 0.5
      74  		   : x >= (double) LONG_MIN)))
      75  	{
      76  	  feraiseexcept (FE_INVALID);
      77  	  return sign == 1 ? LONG_MAX : LONG_MIN;
      78  	}
      79        else if (!FIX_DBL_LONG_CONVERT_OVERFLOW
      80  	  && sizeof (long int) == 4
      81  	  && x <= (double) LONG_MIN - 0.5)
      82  	{
      83  	  /* If truncation produces LONG_MIN, the cast will not raise
      84  	     the exception, but may raise "inexact".  */
      85  	  feraiseexcept (FE_INVALID);
      86  	  return LONG_MIN;
      87  	}
      88  #endif
      89        return (long int) x;
      90      }
      91  
      92    return sign * result;
      93  }
      94  
      95  libm_alias_double (__lround, lround)
      96  
      97  #endif