math/w_scalb_compat.c

   1 /* Copyright (C) 2011-2021 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <math.h>
  21 #include <math_private.h>
  22 #include <math-svid-compat.h>
  23
  24
  25 #if LIBM_SVID_COMPAT
  26 static double
  27 __attribute__ ((noinline))
  28 sysv_scalb (double x, double fn)
  29 {
  30   double z = __ieee754_scalb (x, fn);
  31
  32   if (__glibc_unlikely (isinf (z)))
  33     {
  34       if (isfinite (x))
  35         return __kernel_standard (x, fn, 32); /* scalb overflow */
  36       else
  37         __set_errno (ERANGE);
  38     }
  39   else if (__builtin_expect (z == 0.0, 0) && z != x)
  40     return __kernel_standard (x, fn, 33); /* scalb underflow */
  41
  42   return z;
  43 }
  44
  45
  46 /* Wrapper scalb */
  47 double
  48 __scalb (double x, double fn)
  49 {
  50   if (__glibc_unlikely (_LIB_VERSION == _SVID_))
  51     return sysv_scalb (x, fn);
  52   else
  53     {
  54       double z = __ieee754_scalb (x, fn);
  55
  56       if (__glibc_unlikely (!isfinite (z) || z == 0.0))
  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 != 0.0 && !isinf (fn))
  72                 __set_errno (ERANGE);
  73             }
  74         }
  75       return z;
  76     }
  77 }
  78 weak_alias (__scalb, scalb)
  79 # ifdef NO_LONG_DOUBLE
  80 strong_alias (__scalb, __scalbl)
  81 weak_alias (__scalb, scalbl)
  82 # endif
  83 #endif