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/>.  */

/*****************************************************************************

 *    BID64 remainder

 *****************************************************************************

 *

 *  Algorithm description:

 *

 *  if(exponent_x < exponent_y)

 *    scale coefficient_y so exponents are aligned

 *    perform coefficient divide (64-bit integer divide), unless

 *            coefficient_y is longer than 64 bits (clearly larger

 *                                               than coefficient_x)

 *  else  // exponent_x > exponent_y

 *     use a loop to scale coefficient_x to 18_digits, divide by

 *         coefficient_y (64-bit integer divide), calculate remainder

 *         as new_coefficient_x and repeat until final remainder is obtained

 *         (when new_exponent_x < exponent_y)

 *

 ****************************************************************************/

#include "bid_internal.h"

#define MAX_FORMAT_DIGITS     16

#define DECIMAL_EXPONENT_BIAS 398

#define MASK_BINARY_EXPONENT  0x7ff0000000000000ull

#define BINARY_EXPONENT_BIAS  0x3ff

#define UPPER_EXPON_LIMIT     51

#if DECIMAL_CALL_BY_REFERENCE

void

bid64_rem (UINT64 * pres, UINT64 * px,

           UINT64 *

           py _EXC_FLAGS_PARAM _EXC_MASKS_PARAM _EXC_INFO_PARAM) {

  UINT64 x, y;

#else

UINT64

bid64_rem (UINT64 x,

           UINT64 y _EXC_FLAGS_PARAM _EXC_MASKS_PARAM _EXC_INFO_PARAM) {

#endif

  UINT128 CY;

  UINT64 sign_x, sign_y, coefficient_x, coefficient_y, res;

  UINT64 Q, R, R2, T, valid_y, valid_x;

  int_float tempx;

  int exponent_x, exponent_y, bin_expon, e_scale;

  int digits_x, diff_expon;

#if DECIMAL_CALL_BY_REFERENCE

  x = *px;

  y = *py;

#endif

  valid_y = unpack_BID64 (&sign_y, &exponent_y, &coefficient_y, y);

  valid_x = unpack_BID64 (&sign_x, &exponent_x, &coefficient_x, x);

  // unpack arguments, check for NaN or Infinity

  if (!valid_x) {

    // x is Inf. or NaN or 0

#ifdef SET_STATUS_FLAGS

    if ((y & SNAN_MASK64) == SNAN_MASK64)       // y is sNaN

      __set_status_flags (pfpsf, INVALID_EXCEPTION);

#endif

    // test if x is NaN

    if ((x & 0x7c00000000000000ull) == 0x7c00000000000000ull) {

#ifdef SET_STATUS_FLAGS

      if (((x & SNAN_MASK64) == SNAN_MASK64))

        __set_status_flags (pfpsf, INVALID_EXCEPTION);

#endif

      res = coefficient_x & QUIET_MASK64;;

      BID_RETURN (res);

    }

    // x is Infinity?

    if ((x & 0x7800000000000000ull) == 0x7800000000000000ull) {

      if (((y & NAN_MASK64) != NAN_MASK64)) {

#ifdef SET_STATUS_FLAGS

        __set_status_flags (pfpsf, INVALID_EXCEPTION);

#endif

        // return NaN

        res = 0x7c00000000000000ull;

        BID_RETURN (res);

      }

    }

    // x is 0

    // return x if y != 0

    if (((y & 0x7800000000000000ull) < 0x7800000000000000ull) &&

        coefficient_y) {

      if ((y & 0x6000000000000000ull) == 0x6000000000000000ull)

        exponent_y = (y >> 51) & 0x3ff;

      else

        exponent_y = (y >> 53) & 0x3ff;

      if (exponent_y < exponent_x)

        exponent_x = exponent_y;

      x = exponent_x;

      x <<= 53;

      res = x | sign_x;

      BID_RETURN (res);

    }

  }

  if (!valid_y) {

    // y is Inf. or NaN

    // test if y is NaN

    if ((y & 0x7c00000000000000ull) == 0x7c00000000000000ull) {

#ifdef SET_STATUS_FLAGS

      if (((y & SNAN_MASK64) == SNAN_MASK64))

        __set_status_flags (pfpsf, INVALID_EXCEPTION);

#endif

      res = coefficient_y & QUIET_MASK64;;

      BID_RETURN (res);

    }

    // y is Infinity?

    if ((y & 0x7800000000000000ull) == 0x7800000000000000ull) {

      res = very_fast_get_BID64 (sign_x, exponent_x, coefficient_x);

      BID_RETURN (res);

    }

    // y is 0, return NaN

    {

#ifdef SET_STATUS_FLAGS

      __set_status_flags (pfpsf, INVALID_EXCEPTION);

#endif

      res = 0x7c00000000000000ull;

      BID_RETURN (res);

    }

  }

  diff_expon = exponent_x - exponent_y;

  if (diff_expon <= 0) {

    diff_expon = -diff_expon;

    if (diff_expon > 16) {

      // |x|<|y| in this case

      res = x;

      BID_RETURN (res);

    }

    // set exponent of y to exponent_x, scale coefficient_y

    T = power10_table_128[diff_expon].w[0];

    __mul_64x64_to_128 (CY, coefficient_y, T);

    if (CY.w[1] || CY.w[0] > (coefficient_x << 1)) {

      res = x;

      BID_RETURN (res);

    }

    Q = coefficient_x / CY.w[0];

    R = coefficient_x - Q * CY.w[0];

    R2 = R + R;

    if (R2 > CY.w[0] || (R2 == CY.w[0] && (Q & 1))) {

      R = CY.w[0] - R;

      sign_x ^= 0x8000000000000000ull;

    }

    res = very_fast_get_BID64 (sign_x, exponent_x, R);

    BID_RETURN (res);

  }

  while (diff_expon > 0) {

    // get number of digits in coeff_x

    tempx.d = (float) coefficient_x;

    bin_expon = ((tempx.i >> 23) & 0xff) - 0x7f;

    digits_x = estimate_decimal_digits[bin_expon];

    // will not use this test, dividend will have 18 or 19 digits

    //if(coefficient_x >= power10_table_128[digits_x].w[0])

    //      digits_x++;

    e_scale = 18 - digits_x;

    if (diff_expon >= e_scale) {

      diff_expon -= e_scale;

    } else {

      e_scale = diff_expon;

      diff_expon = 0;

    }

    // scale dividend to 18 or 19 digits

    coefficient_x *= power10_table_128[e_scale].w[0];

    // quotient

    Q = coefficient_x / coefficient_y;

    // remainder

    coefficient_x -= Q * coefficient_y;

    // check for remainder == 0

    if (!coefficient_x) {

      res = very_fast_get_BID64_small_mantissa (sign_x, exponent_y, 0);

      BID_RETURN (res);

    }

  }

  R2 = coefficient_x + coefficient_x;

  if (R2 > coefficient_y || (R2 == coefficient_y && (Q & 1))) {

    coefficient_x = coefficient_y - coefficient_x;

    sign_x ^= 0x8000000000000000ull;

  }

  res = very_fast_get_BID64 (sign_x, exponent_y, coefficient_x);

  BID_RETURN (res);

}