1  /* Copyright (C) 2011-2023 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 <inttypes.h>
      19  #include <math.h>
      20  #include <math_private.h>
      21  #include <libm-alias-double.h>
      22  
      23  /*
      24   * for non-zero, finite x
      25   *	x = frexp(arg,&exp);
      26   * return a double fp quantity x such that 0.5 <= |x| <1.0
      27   * and the corresponding binary exponent "exp". That is
      28   *	arg = x*2^exp.
      29   * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
      30   * with *exp=0.
      31   */
      32  
      33  
      34  double
      35  __frexp (double x, int *eptr)
      36  {
      37    int64_t ix;
      38    EXTRACT_WORDS64 (ix, x);
      39    int32_t ex = 0x7ff & (ix >> 52);
      40    int e = 0;
      41  
      42    if (__glibc_likely (ex != 0x7ff && x != 0.0))
      43      {
      44        /* Not zero and finite.  */
      45        e = ex - 1022;
      46        if (__glibc_unlikely (ex == 0))
      47  	{
      48  	  /* Subnormal.  */
      49  	  x *= 0x1p54;
      50  	  EXTRACT_WORDS64 (ix, x);
      51  	  ex = 0x7ff & (ix >> 52);
      52  	  e = ex - 1022 - 54;
      53  	}
      54  
      55        ix = (ix & INT64_C (0x800fffffffffffff)) | INT64_C (0x3fe0000000000000);
      56        INSERT_WORDS64 (x, ix);
      57      }
      58    else
      59      /* Quiet signaling NaNs.  */
      60      x += x;
      61  
      62    *eptr = e;
      63    return x;
      64  }
      65  libm_alias_double (__frexp, frexp)