libm/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 <math.h>
  20 #include "math_private.h"
  21
  22 #if __UCLIBC_HAS_FENV__
  23 #include <errno.h>
  24
  25 static double
  26 __attribute__ ((noinline))
  27 sysv_scalb (double x, double fn)
  28 {
  29   double z = __ieee754_scalb (x, fn);
  30
  31   if (__builtin_expect (isinf (z), 0))
  32     {
  33       if (isfinite (x))
  34         return __kernel_standard (x, fn, 32); /* scalb overflow */
  35       else
  36         __set_errno (ERANGE);
  37     }
  38   else if (__builtin_expect (z == 0.0, 0) && z != x)
  39     return __kernel_standard (x, fn, 33); /* scalb underflow */
  40
  41   return z;
  42 }
  43 #endif /* __UCLIBC_HAS_FENV__ */
  44
  45 /* Here might be a check like "#if defined __UCLIBC_SUSV3_LEGACY__"
  46  * but because there is a sysv_scalb() func, it was decided
  47  * not to check yhis macro.
  48  */
  49
  50 /* Wrapper scalb */
  51 double
  52 scalb (double x, double fn)
  53 {
  54 #if __UCLIBC_HAS_FENV__
  55   if (__builtin_expect (_LIB_VERSION == _SVID_,0))
  56     return sysv_scalb (x, fn);
  57   else
  58     {
  59       double z = __ieee754_scalb (x, fn);
  60
  61       if (__builtin_expect (!isfinite (z) || z == 0.0, 0))
  62         {
  63           if (isnan (z))
  64             {
  65               if (!isnan (x) && !isnan (fn))
  66                 __set_errno (EDOM);
  67             }
  68           else if (isinf (z))
  69             {
  70               if (!isinf (x) && !isinf (fn))
  71                 __set_errno (ERANGE);
  72             }
  73           else
  74             {
  75               /* z == 0.  */
  76               if (x != 0.0 && !isinf (fn))
  77                 __set_errno (ERANGE);
  78             }
  79         }
  80       return z;
  81     }
  82 #else
  83   return __ieee754_scalb (x, fn);
  84 #endif /* __UCLIBC_HAS_FENV__ */
  85 }
  86 libm_hidden_def(scalb)