1  /* Compute 2^x.
       2     Copyright (C) 2012-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       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 <math.h>
      20  #include <math_private.h>
      21  #include <math-underflow.h>
      22  #include <float.h>
      23  
      24  FLOAT
      25  M_DECL_FUNC (__ieee754_exp2) (FLOAT x)
      26  {
      27    if (__glibc_likely (isless (x, (FLOAT) M_MAX_EXP)))
      28      {
      29        if (__builtin_expect (isgreaterequal (x, (FLOAT) (M_MIN_EXP - M_MANT_DIG
      30  							- 1)), 1))
      31  	{
      32  	  int intx = (int) x;
      33  	  FLOAT fractx = x - intx;
      34  	  FLOAT result;
      35  	  if (M_FABS (fractx) < M_EPSILON / 4)
      36  	    result = M_SCALBN (1 + fractx, intx);
      37  	  else
      38  	    result = M_SCALBN (M_EXP (M_MLIT (M_LN2) * fractx), intx);
      39  	  math_check_force_underflow_nonneg (result);
      40  	  return result;
      41  	}
      42        else
      43  	{
      44  	  /* Underflow or exact zero.  */
      45  	  if (isinf (x))
      46  	    return 0;
      47  	  else
      48  	    return M_MIN * M_MIN;
      49  	}
      50      }
      51    else
      52      /* Infinity, NaN or overflow.  */
      53      return M_MAX * x;
      54  }
      55  declare_mgen_finite_alias (__ieee754_exp2, __exp2)