1  /* Round float value to long 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 <math.h>
      20  #include <math_private.h>
      21  #include <stdint.h>
      22  #include <libm-alias-float.h>
      23  
      24  /* Round to the nearest integer, with values exactly on a 0.5 boundary
      25     rounded away from zero, regardless of the current rounding mode.
      26     If (long long)x, when x is out of range of a long long, clips at
      27     LLONG_MAX or LLONG_MIN, then this implementation also clips.  */
      28  
      29  long long int
      30  __llroundf (float x)
      31  {
      32    long long xr;
      33    if (HAVE_PPC_FCTIDZ)
      34      xr = (long long) x;
      35    else
      36      {
      37        float ax = fabsf (x);
      38        /* Avoid incorrect exceptions from libgcc conversions (as of GCC
      39  	 5): <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59412>.  */
      40        if (ax < 0x1p31f)
      41  	xr = (long long int) (long int) x;
      42        else if (!(ax < 0x1p55f))
      43  	xr = (long long int) (long int) (x * 0x1p-32f) << 32;
      44        else
      45  	{
      46  	  uint32_t i0;
      47  	  GET_FLOAT_WORD (i0, x);
      48  	  int exponent = ((i0 >> 23) & 0xff) - 0x7f;
      49  	  unsigned long long int mant = (i0 & 0x7fffff) | 0x800000;
      50  	  mant <<= exponent - 23;
      51  	  xr = (long long int) ((i0 & 0x80000000) != 0 ? -mant : mant);
      52  	}
      53      }
      54    /* Avoid spurious "inexact" converting LLONG_MAX to float, and from
      55       subtraction when the result is out of range, by returning early
      56       for arguments large enough that no rounding is needed.  */
      57    if (!(fabsf (x) < 0x1p23f))
      58      return xr;
      59    float xrf = (float) xr;
      60  
      61    if (x >= 0.0)
      62      {
      63        if (x - xrf >= 0.5)
      64  	xr += (long long) ((unsigned long long) xr + 1) > 0;
      65      }
      66    else
      67      {
      68        if (xrf - x >= 0.5)
      69  	xr -= (long long) ((unsigned long long) xr - 1) < 0;
      70      }
      71    return xr;
      72  }
      73  libm_alias_float (__llround, llround)