math/w_log2.c

   1 /* Copyright (C) 2011 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.
   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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <fenv.h>
  21 #include <math.h>
  22 #include <math_private.h>
  23
  24
  25 /* wrapper log2(x) */
  26 double
  27 __log2 (double x)
  28 {
  29   if (__builtin_expect (x <= 0.0, 0) && _LIB_VERSION != _IEEE_)
  30     {
  31       if (x == 0.0)
  32         {
  33           feraiseexcept (FE_DIVBYZERO);
  34           return __kernel_standard (x, x, 48); /* log2(0) */
  35         }
  36       else
  37         {
  38           feraiseexcept (FE_INVALID);
  39           return __kernel_standard (x, x, 49); /* log2(x<0) */
  40         }
  41     }
  42
  43   return  __ieee754_log2 (x);
  44 }
  45 weak_alias (__log2, log2)
  46 #ifdef NO_LONG_DOUBLE
  47 strong_alias (__log2, __log2l)
  48 weak_alias (__log2, log2l)
  49 #endif