math/e_scalb_template.c

   1 /* Multiply by integral power of radix.
   2
   3    Copyright (C) 2011-2023 Free Software Foundation, Inc.
   4
   5    This file is part of the GNU C Library.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public
   9    License as published by the Free Software Foundation; either
  10    version 2.1 of the License, or (at your option) any later version.
  11
  12    The GNU C Library is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library; if not, see
  19    <https://www.gnu.org/licenses/>.  */
  20
  21 #include <math.h>
  22 #include <math_private.h>
  23 #include <libm-alias-finite.h>
  24
  25 static FLOAT
  26 __attribute__ ((noinline))
  27 invalid_fn (FLOAT x, FLOAT fn)
  28 {
  29   if (M_SUF (rint) (fn) != fn)
  30     return (fn - fn) / (fn - fn);
  31   else if (fn > M_LIT (65000.0))
  32     return M_SUF (__scalbn) (x, 65000);
  33   else
  34     return M_SUF (__scalbn) (x,-65000);
  35 }
  36
  37
  38 FLOAT
  39 M_DECL_FUNC (__ieee754_scalb) (FLOAT x, FLOAT fn)
  40 {
  41   if (__glibc_unlikely (isnan (x)))
  42     return x * fn;
  43   if (__glibc_unlikely (!isfinite (fn)))
  44     {
  45       if (isnan (fn) || fn > M_LIT (0.0))
  46         return x * fn;
  47       if (x == M_LIT (0.0))
  48         return x;
  49       return x / -fn;
  50     }
  51   if (__glibc_unlikely (M_FABS (fn) >= M_LIT (0x1p31)
  52                         || (FLOAT) (int) fn != fn))
  53     return invalid_fn (x, fn);
  54
  55   return M_SCALBN (x, (int) fn);
  56 }
  57 declare_mgen_finite_alias (__ieee754_scalb, __scalb)