math/w_log2_compat.c

   1 /* Copyright (C) 2011-2017 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <fenv.h>
  20 #include <math.h>
  21 #include <math_private.h>
  22 #include <math-svid-compat.h>
  23 #include <libm-alias-double.h>
  24
  25
  26 #if LIBM_SVID_COMPAT
  27 /* wrapper log2(x) */
  28 double
  29 __log2 (double x)
  30 {
  31   if (__builtin_expect (islessequal (x, 0.0), 0) && _LIB_VERSION != _IEEE_)
  32     {
  33       if (x == 0.0)
  34         {
  35           feraiseexcept (FE_DIVBYZERO);
  36           return __kernel_standard (x, x, 48); /* log2(0) */
  37         }
  38       else
  39         {
  40           feraiseexcept (FE_INVALID);
  41           return __kernel_standard (x, x, 49); /* log2(x<0) */
  42         }
  43     }
  44
  45   return  __ieee754_log2 (x);
  46 }
  47 libm_alias_double (__log2, log2)
  48 #endif