libm/w_scalbf.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 defined(__UCLIBC_HAS_FENV__)
  23 #include <errno.h>
  24
  25 static float
  26 __attribute__ ((noinline))
  27 sysv_scalbf (float x, float fn)
  28 {
  29   float z = (float) __ieee754_scalb ((double) x, (double) fn);
  30
  31   if (__builtin_expect (isinf (z),0))
  32     {
  33       if (isfinite (x))
  34         return __kernel_standard_f (x, fn, 132); /* scalb overflow */
  35       else
  36         __set_errno (ERANGE);
  37     }
  38   else if (__builtin_expect (z == 0.0f, 0) && z != x)
  39     return __kernel_standard_f (x, fn, 133); /* scalb underflow */
  40
  41   return z;
  42 }
  43 #endif
  44
  45 /* Wrapper scalbf */
  46 float
  47 scalbf (float x, float fn)
  48 {
  49 #if defined(__UCLIBC_HAS_FENV__)
  50   if (__builtin_expect (_LIB_VERSION == _SVID_, 0))
  51     return sysv_scalbf (x, fn);
  52   else
  53     {
  54       float z = (float) __ieee754_scalb ((double) x, (double) fn);
  55
  56       if (__builtin_expect (!isfinite (z) || z == 0.0f, 0))
  57         {
  58           if (isnan (z))
  59             {
  60               if (!isnan (x) && !isnan (fn))
  61                 __set_errno (EDOM);
  62             }
  63           else if (isinf (z))
  64             {
  65               if (!isinf (x) && !isinf (fn))
  66                 __set_errno (ERANGE);
  67             }
  68           else
  69             {
  70               /* z == 0.  */
  71               if (x != 0.0f && !isinf (fn))
  72                 __set_errno (ERANGE);
  73             }
  74         }
  75       return z;
  76     }
  77 #else
  78     return (float) __ieee754_scalb ((double) x, (double) fn);
  79 #endif /* __UCLIBC_HAS_FENV__ */
  80 }