math/w_scalb.c

   1 /* Copyright (C) 2011-2016 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 <errno.h>
  20 #include <math.h>
  21 #include <math_private.h>
  22
  23
  24 static double
  25 __attribute__ ((noinline))
  26 sysv_scalb (double x, double fn)
  27 {
  28   double z = __ieee754_scalb (x, fn);
  29
  30   if (__glibc_unlikely (isinf (z)))
  31     {
  32       if (isfinite (x))
  33         return __kernel_standard (x, fn, 32); /* scalb overflow */
  34       else
  35         __set_errno (ERANGE);
  36     }
  37   else if (__builtin_expect (z == 0.0, 0) && z != x)
  38     return __kernel_standard (x, fn, 33); /* scalb underflow */
  39
  40   return z;
  41 }
  42
  43
  44 /* Wrapper scalb */
  45 double
  46 __scalb (double x, double fn)
  47 {
  48   if (__glibc_unlikely (_LIB_VERSION == _SVID_))
  49     return sysv_scalb (x, fn);
  50   else
  51     {
  52       double z = __ieee754_scalb (x, fn);
  53
  54       if (__glibc_unlikely (!isfinite (z) || z == 0.0))
  55         {
  56           if (isnan (z))
  57             {
  58               if (!isnan (x) && !isnan (fn))
  59                 __set_errno (EDOM);
  60             }
  61           else if (isinf (z))
  62             {
  63               if (!isinf (x) && !isinf (fn))
  64                 __set_errno (ERANGE);
  65             }
  66           else
  67             {
  68               /* z == 0.  */
  69               if (x != 0.0 && !isinf (fn))
  70                 __set_errno (ERANGE);
  71             }
  72         }
  73       return z;
  74     }
  75 }
  76 weak_alias (__scalb, scalb)
  77 #ifdef NO_LONG_DOUBLE
  78 strong_alias (__scalb, __scalbl)
  79 weak_alias (__scalb, scalbl)
  80 #endif