math/e_scalb.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 static double
  26 __attribute__ ((noinline))
  27 invalid_fn (double x, double fn)
  28 {
  29   if (__rint (fn) != fn)
  30     {
  31       feraiseexcept (FE_INVALID);
  32       return __nan ("");
  33     }
  34   else if (fn > 65000.0)
  35     return __scalbn (x, 65000);
  36   else
  37     return __scalbn (x,-65000);
  38 }
  39
  40
  41 double
  42 __ieee754_scalb (double x, double fn)
  43 {
  44   if (__builtin_expect (__isnan (x), 0))
  45     return x * fn;
  46   if (__builtin_expect (!__finite (fn), 0))
  47     {
  48       if (__isnan (fn) || fn > 0.0)
  49         return x * fn;
  50       if (x == 0.0)
  51         return x;
  52       return x / -fn;
  53     }
  54   if (__builtin_expect ((double) (int) fn != fn, 0))
  55     return invalid_fn (x, fn);
  56
  57   return __scalbn (x, (int) fn);
  58 }
  59 strong_alias (__ieee754_scalb, __scalb_finite)