1  /* lround function.  PowerPC32 version.
       2     Copyright (C) 2004-2023 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 lroundf __redirect_lroundf
      20  #define __lroundf __redirect___lroundf
      21  #include <math.h>
      22  #undef lroundf
      23  #undef __lroundf
      24  #include <libm-alias-float.h>
      25  #include <libm-alias-double.h>
      26  
      27  long int
      28  __lround (double x)
      29  {
      30  #ifdef _ARCH_PWR5X
      31    x = round (x);
      32  #else
      33    /* Ieee 1003.1 lround function.  ieee specifies "round to the nearest
      34       integer value, rounding halfway cases away from zero, regardless of
      35       the current rounding mode."  however powerpc architecture defines
      36       "round to nearest" as "choose the best approximation. in case of a
      37       tie, choose the one that is even (least significant bit o).".
      38       so we can't use the powerpc "round to nearest" mode. instead we set
      39       "round toward zero" mode and round by adding +-0.5 before rounding
      40       to the integer value.  it is necessary to detect when x is
      41       (+-)0x1.fffffffffffffp-2 because adding +-0.5 in this case will
      42       cause an erroneous shift, carry and round.  we simply return 0 if
      43       0.5 > x > -0.5.  */
      44  
      45    double ax = fabs (x);
      46  
      47    if (ax < 0.5)
      48      return 0;
      49  
      50    if (x >= 0x7fffffff.8p0 || x <= -0x80000000.8p0)
      51      x = (x < 0.0) ? -0x1p+52 : 0x1p+52;
      52    else
      53      {
      54        /* Test whether an integer to avoid spurious "inexact".  */
      55        double t = ax + 0x1p+52;
      56        t = t - 0x1p+52;
      57        if (ax != t)
      58          {
      59  	  ax = ax + 0.5;
      60  	  if (x < 0.0)
      61  	    ax = -fabs (ax);
      62  	  x = ax;
      63          }
      64      }
      65  #endif
      66    /* Force evaluation of values larger than long int, so invalid
      67       exceptions are raise.  */
      68    long long int ret;
      69    asm ("fctiwz %0, %1" : "=d" (ret) : "d" (x));
      70    return ret;
      71  }
      72  #ifndef __lround
      73  libm_alias_double (__lround, lround)
      74  
      75  strong_alias (__lround, __lroundf)
      76  libm_alias_float (__lround, lround)
      77  #endif