1  /* Copyright (C) 2007-2023 Free Software Foundation, Inc.
       2  
       3  This file is part of GCC.
       4  
       5  GCC is free software; you can redistribute it and/or modify it under
       6  the terms of the GNU General Public License as published by the Free
       7  Software Foundation; either version 3, or (at your option) any later
       8  version.
       9  
      10  GCC is distributed in the hope that it will be useful, but WITHOUT ANY
      11  WARRANTY; without even the implied warranty of MERCHANTABILITY or
      12  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      13  for more details.
      14  
      15  Under Section 7 of GPL version 3, you are granted additional
      16  permissions described in the GCC Runtime Library Exception, version
      17  3.1, as published by the Free Software Foundation.
      18  
      19  You should have received a copy of the GNU General Public License and
      20  a copy of the GCC Runtime Library Exception along with this program;
      21  see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      22  <http://www.gnu.org/licenses/>.  */
      23  
      24  #include "bid_internal.h"
      25  
      26  #define MAX_FORMAT_DIGITS     16
      27  #define DECIMAL_EXPONENT_BIAS 398
      28  
      29  #if DECIMAL_CALL_BY_REFERENCE
      30  
      31  void
      32  bid64_logb (int * pres, UINT64 * px
      33  	    _EXC_FLAGS_PARAM _EXC_MASKS_PARAM _EXC_INFO_PARAM) {
      34    UINT64 x;
      35  #else
      36  
      37  int
      38  bid64_logb (UINT64 x _EXC_FLAGS_PARAM _EXC_MASKS_PARAM _EXC_INFO_PARAM) {
      39  #endif
      40    UINT64 sign_x, coefficient_x;
      41    int_double dx;
      42    int exponent_x, bin_expon_cx, digits;
      43  
      44  #if DECIMAL_CALL_BY_REFERENCE
      45    x = *px;
      46  #endif
      47    // unpack arguments, check for NaN or Infinity
      48    if (!unpack_BID64 (&sign_x, &exponent_x, &coefficient_x, x)) {
      49      // x is Inf. or NaN
      50  #ifdef SET_STATUS_FLAGS
      51        __set_status_flags (pfpsf, INVALID_EXCEPTION);
      52  #endif
      53        BID_RETURN (0x80000000);
      54    }
      55    // find number of digits in coefficient
      56    if (coefficient_x >= 1000000000000000ull) {
      57      digits = 16;
      58    } else {
      59      dx.d = (double)coefficient_x;   // exact conversion;
      60      bin_expon_cx = (int)(dx.i >> 52) - 1023;
      61      digits = estimate_decimal_digits[bin_expon_cx];
      62      if (coefficient_x >= power10_table_128[digits].w[0])
      63        digits++;
      64    }
      65    exponent_x = exponent_x - DECIMAL_EXPONENT_BIAS + digits - 1;
      66  
      67    BID_RETURN (exponent_x);
      68  }