sysdeps/m68k/fpu/logb.c

   1 /* Copyright (C) 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <math.h>
  21
  22 #ifdef  __GNUC__
  23
  24 /* Return the base 2 signed integral exponent of X.  */
  25
  26 double
  27 DEFUN(__logb, (x), double x)
  28 {
  29   if (__isnan (x))
  30     return x;
  31   if (__isinf (x))
  32     return fabs (x);
  33
  34   if (x == 0.0)
  35     asm ("flog2%.x %0, %0" : "=f" (x) : "0" (x));
  36   else
  37     asm ("fgetexp%.x %0, %0" : "=f" (x) : "0" (x));
  38
  39   return x;
  40 }
  41
  42 weak_alias (__logb, logb)
  43
  44 #else
  45 #include <sysdeps/ieee754/logb.c>
  46 #endif