Subversion Repositories openrisc_2011-10-31

/* Copyright (C) 2007, 2009  Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under

the terms of the GNU General Public License as published by the Free

Software Foundation; either version 3, or (at your option) any later

version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY

WARRANTY; without even the implied warranty of MERCHANTABILITY or

FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

for more details.

Under Section 7 of GPL version 3, you are granted additional

permissions described in the GCC Runtime Library Exception, version

3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and

a copy of the GCC Runtime Library Exception along with this program;

see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

<http://www.gnu.org/licenses/>.  */

#define BID_128RES

#include "bid_internal.h"

BID128_FUNCTION_ARG1_NORND_CUSTOMRESTYPE(int, bid128_logb, x)

  UINT128 CX;

  UINT64 sign_x;

  SINT64 D;

  int_float f64, fx;

  int exponent_x, bin_expon_cx, digits;

  if (!unpack_BID128_value (&sign_x, &exponent_x, &CX, x)) {

#ifdef SET_STATUS_FLAGS

      __set_status_flags (pfpsf, INVALID_EXCEPTION);

#endif

    BID_RETURN_VAL (0x80000000);

  }

  // find number of digits in coefficient

  // 2^64

  f64.i = 0x5f800000;

  // fx ~ CX

  fx.d = (float) CX.w[1] * f64.d + (float) CX.w[0];

  bin_expon_cx = ((fx.i >> 23) & 0xff) - 0x7f;

  digits = estimate_decimal_digits[bin_expon_cx];

  // scale = 38-estimate_decimal_digits[bin_expon_cx];

  D = CX.w[1] - power10_index_binexp_128[bin_expon_cx].w[1];

  if (D > 0 || (!D && CX.w[0] >= power10_index_binexp_128[bin_expon_cx].w[0])) {

    digits++;

  }

  exponent_x = exponent_x - DECIMAL_EXPONENT_BIAS_128 - 1 + digits;

  BID_RETURN_VAL (exponent_x);

}