1  /* Copyright (C) 2012-2023 Free Software Foundation, Inc.
       2     This file is part of the GNU C Library.
       3  
       4     The GNU C Library is free software; you can redistribute it and/or
       5     modify it under the terms of the GNU Lesser General Public
       6     License as published by the Free Software Foundation; either
       7     version 2.1 of the License, or (at your option) any later version.
       8  
       9     The GNU C Library is distributed in the hope that it will be useful,
      10     but WITHOUT ANY WARRANTY; without even the implied warranty of
      11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      12     Lesser General Public License for more details.
      13  
      14     You should have received a copy of the GNU Lesser General Public
      15     License along with the GNU C Library; if not, see
      16     <https://www.gnu.org/licenses/>.  */
      17  
      18  #include <math.h>
      19  #include <math_private.h>
      20  #include <float.h>
      21  #include <libm-alias-finite.h>
      22  
      23  static const long double log10_high = 0x2.4d763776aaap+0L;
      24  static const long double log10_low = 0x2.b05ba95b58ae0b4c28a38a3fb4p-48L;
      25  
      26  long double
      27  __ieee754_exp10l (long double arg)
      28  {
      29    union ibm_extended_long_double u;
      30    long double arg_high, arg_low;
      31    long double exp_high, exp_low;
      32  
      33    if (!isfinite (arg))
      34      return __ieee754_expl (arg);
      35    if (arg < LDBL_MIN_10_EXP - LDBL_DIG - 10)
      36      return LDBL_MIN * LDBL_MIN;
      37    else if (arg > LDBL_MAX_10_EXP + 1)
      38      return LDBL_MAX * LDBL_MAX;
      39    else if (fabsl (arg) < 0x1p-109L)
      40      return 1.0L;
      41  
      42    u.ld = arg;
      43    arg_high = u.d[0].d;
      44    arg_low = u.d[1].d;
      45    exp_high = arg_high * log10_high;
      46    exp_low = arg_high * log10_low + arg_low * M_LN10l;
      47    return __ieee754_expl (exp_high) * __ieee754_expl (exp_low);
      48  }
      49  libm_alias_finite (__ieee754_exp10l, __exp10l)