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/* 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 multiply

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

 *

 *  Algorithm description:

 *

 *  if(number_digits(coefficient_x)+number_digits(coefficient_y) guaranteed

 *       below 16)

 *      return get_BID64(sign_x^sign_y, exponent_x + exponent_y - dec_bias,

 *                     coefficient_x*coefficient_y)

 *  else

 *      get long product: coefficient_x*coefficient_y

 *      determine number of digits to round off (extra_digits)

 *      rounding is performed as a 128x128-bit multiplication by

 *         2^M[extra_digits]/10^extra_digits, followed by a shift

 *         M[extra_digits] is sufficiently large for required accuracy

 *

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

#include "bid_internal.h"

#if DECIMAL_CALL_BY_REFERENCE

void

bid64_mul (UINT64 * pres, UINT64 * px,

           UINT64 *

           py _RND_MODE_PARAM _EXC_FLAGS_PARAM _EXC_MASKS_PARAM

           _EXC_INFO_PARAM) {

  UINT64 x, y;

#else

UINT64

bid64_mul (UINT64 x,

           UINT64 y _RND_MODE_PARAM _EXC_FLAGS_PARAM

           _EXC_MASKS_PARAM _EXC_INFO_PARAM) {

#endif

  UINT128 P, PU, C128, Q_high, Q_low, Stemp;

  UINT64 sign_x, sign_y, coefficient_x, coefficient_y;

  UINT64 C64, remainder_h, carry, CY, res;

  UINT64 valid_x, valid_y;

  int_double tempx, tempy;

  int extra_digits, exponent_x, exponent_y, bin_expon_cx, bin_expon_cy,

    bin_expon_product;

  int rmode, digits_p, bp, amount, amount2, final_exponent, round_up;

  unsigned status, uf_status;

#if DECIMAL_CALL_BY_REFERENCE

#if !DECIMAL_GLOBAL_ROUNDING

  _IDEC_round rnd_mode = *prnd_mode;

#endif

  x = *px;

  y = *py;

#endif

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

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

  // unpack arguments, check for NaN or Infinity

  if (!valid_x) {

#ifdef SET_STATUS_FLAGS

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

      __set_status_flags (pfpsf, INVALID_EXCEPTION);

#endif

    // x is Inf. or NaN

    // test if x is NaN

    if ((x & NAN_MASK64) == NAN_MASK64) {

#ifdef SET_STATUS_FLAGS

      if ((x & SNAN_MASK64) == SNAN_MASK64)     // sNaN

        __set_status_flags (pfpsf, INVALID_EXCEPTION);

#endif

      BID_RETURN (coefficient_x & QUIET_MASK64);

    }

    // x is Infinity?

    if ((x & INFINITY_MASK64) == INFINITY_MASK64) {

      // check if y is 0

      if (((y & INFINITY_MASK64) != INFINITY_MASK64)

          && !coefficient_y) {

#ifdef SET_STATUS_FLAGS

        __set_status_flags (pfpsf, INVALID_EXCEPTION);

#endif

        // y==0 , return NaN

        BID_RETURN (NAN_MASK64);

      }

      // check if y is NaN

      if ((y & NAN_MASK64) == NAN_MASK64)

        // y==NaN , return NaN

        BID_RETURN (coefficient_y & QUIET_MASK64);

      // otherwise return +/-Inf

      BID_RETURN (((x ^ y) & 0x8000000000000000ull) | INFINITY_MASK64);

    }

    // x is 0

    if (((y & INFINITY_MASK64) != INFINITY_MASK64)) {

      if ((y & SPECIAL_ENCODING_MASK64) == SPECIAL_ENCODING_MASK64)

        exponent_y = ((UINT32) (y >> 51)) & 0x3ff;

      else

        exponent_y = ((UINT32) (y >> 53)) & 0x3ff;

      sign_y = y & 0x8000000000000000ull;

      exponent_x += exponent_y - DECIMAL_EXPONENT_BIAS;

      if (exponent_x > DECIMAL_MAX_EXPON_64)

        exponent_x = DECIMAL_MAX_EXPON_64;

      else if (exponent_x < 0)

        exponent_x = 0;

      BID_RETURN ((sign_x ^ sign_y) | (((UINT64) exponent_x) << 53));

    }

  }

  if (!valid_y) {

    // y is Inf. or NaN

    // test if y is NaN

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

#ifdef SET_STATUS_FLAGS

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

        __set_status_flags (pfpsf, INVALID_EXCEPTION);

#endif

      BID_RETURN (coefficient_y & QUIET_MASK64);

    }

    // y is Infinity?

    if ((y & INFINITY_MASK64) == INFINITY_MASK64) {

      // check if x is 0

      if (!coefficient_x) {

        __set_status_flags (pfpsf, INVALID_EXCEPTION);

        // x==0, return NaN

        BID_RETURN (NAN_MASK64);

      }

      // otherwise return +/-Inf

      BID_RETURN (((x ^ y) & 0x8000000000000000ull) | INFINITY_MASK64);

    }

    // y is 0

    exponent_x += exponent_y - DECIMAL_EXPONENT_BIAS;

    if (exponent_x > DECIMAL_MAX_EXPON_64)

      exponent_x = DECIMAL_MAX_EXPON_64;

    else if (exponent_x < 0)

      exponent_x = 0;

    BID_RETURN ((sign_x ^ sign_y) | (((UINT64) exponent_x) << 53));

  }

  //--- get number of bits in the coefficients of x and y ---

  // version 2 (original)

  tempx.d = (double) coefficient_x;

  bin_expon_cx = ((tempx.i & MASK_BINARY_EXPONENT) >> 52);

  tempy.d = (double) coefficient_y;

  bin_expon_cy = ((tempy.i & MASK_BINARY_EXPONENT) >> 52);

  // magnitude estimate for coefficient_x*coefficient_y is 

  //        2^(unbiased_bin_expon_cx + unbiased_bin_expon_cx)

  bin_expon_product = bin_expon_cx + bin_expon_cy;

  // check if coefficient_x*coefficient_y<2^(10*k+3)

  // equivalent to unbiased_bin_expon_cx + unbiased_bin_expon_cx < 10*k+1

  if (bin_expon_product < UPPER_EXPON_LIMIT + 2 * BINARY_EXPONENT_BIAS) {

    //  easy multiply

    C64 = coefficient_x * coefficient_y;

    res =

      get_BID64_small_mantissa (sign_x ^ sign_y,

                                exponent_x + exponent_y -

                                DECIMAL_EXPONENT_BIAS, C64, rnd_mode,

                                pfpsf);

    BID_RETURN (res);

  } else {

    uf_status = 0;

    // get 128-bit product: coefficient_x*coefficient_y

    __mul_64x64_to_128 (P, coefficient_x, coefficient_y);

    // tighten binary range of P:  leading bit is 2^bp

    // unbiased_bin_expon_product <= bp <= unbiased_bin_expon_product+1

    bin_expon_product -= 2 * BINARY_EXPONENT_BIAS;

    __tight_bin_range_128 (bp, P, bin_expon_product);

    // get number of decimal digits in the product

    digits_p = estimate_decimal_digits[bp];

    if (!(__unsigned_compare_gt_128 (power10_table_128[digits_p], P)))

      digits_p++;       // if power10_table_128[digits_p] <= P

    // determine number of decimal digits to be rounded out

    extra_digits = digits_p - MAX_FORMAT_DIGITS;

    final_exponent =

      exponent_x + exponent_y + extra_digits - DECIMAL_EXPONENT_BIAS;

#ifndef IEEE_ROUND_NEAREST_TIES_AWAY

#ifndef IEEE_ROUND_NEAREST

    rmode = rnd_mode;

    if (sign_x ^ sign_y && (unsigned) (rmode - 1) < 2)

      rmode = 3 - rmode;

#else

    rmode = 0;

#endif

#else

    rmode = 0;

#endif

    round_up = 0;

    if (((unsigned) final_exponent) >= 3 * 256) {

      if (final_exponent < 0) {

        // underflow

        if (final_exponent + 16 < 0) {

          res = sign_x ^ sign_y;

          __set_status_flags (pfpsf,

                              UNDERFLOW_EXCEPTION | INEXACT_EXCEPTION);

          if (rmode == ROUNDING_UP)

            res |= 1;

          BID_RETURN (res);

        }

        uf_status = UNDERFLOW_EXCEPTION;

        if (final_exponent == -1) {

          __add_128_64 (PU, P, round_const_table[rmode][extra_digits]);

          if (__unsigned_compare_ge_128

              (PU, power10_table_128[extra_digits + 16]))

            uf_status = 0;

        }

        extra_digits -= final_exponent;

        final_exponent = 0;

        if (extra_digits > 17) {

          __mul_128x128_full (Q_high, Q_low, P, reciprocals10_128[16]);

          amount = recip_scale[16];

          __shr_128 (P, Q_high, amount);

          // get sticky bits

          amount2 = 64 - amount;

          remainder_h = 0;

          remainder_h--;

          remainder_h >>= amount2;

          remainder_h = remainder_h & Q_high.w[0];

          extra_digits -= 16;

          if (remainder_h || (Q_low.w[1] > reciprocals10_128[16].w[1]

                              || (Q_low.w[1] ==

                                  reciprocals10_128[16].w[1]

                                  && Q_low.w[0] >=

                                  reciprocals10_128[16].w[0]))) {

            round_up = 1;

            __set_status_flags (pfpsf,

                                UNDERFLOW_EXCEPTION |

                                INEXACT_EXCEPTION);

            P.w[0] = (P.w[0] << 3) + (P.w[0] << 1);

            P.w[0] |= 1;

            extra_digits++;

          }

        }

      } else {

        res =

          fast_get_BID64_check_OF (sign_x ^ sign_y, final_exponent,

                                   1000000000000000ull, rnd_mode,

                                   pfpsf);

        BID_RETURN (res);

      }

    }

    if (extra_digits > 0) {

      // will divide by 10^(digits_p - 16)

      // add a constant to P, depending on rounding mode

      // 0.5*10^(digits_p - 16) for round-to-nearest

      __add_128_64 (P, P, round_const_table[rmode][extra_digits]);

      // get P*(2^M[extra_digits])/10^extra_digits

      __mul_128x128_full (Q_high, Q_low, P,

                          reciprocals10_128[extra_digits]);

      // now get P/10^extra_digits: shift Q_high right by M[extra_digits]-128

      amount = recip_scale[extra_digits];

      __shr_128 (C128, Q_high, amount);

      C64 = __low_64 (C128);

#ifndef IEEE_ROUND_NEAREST_TIES_AWAY

#ifndef IEEE_ROUND_NEAREST

      if (rmode == 0)    //ROUNDING_TO_NEAREST

#endif

        if ((C64 & 1) && !round_up) {

          // check whether fractional part of initial_P/10^extra_digits 

          // is exactly .5

          // this is the same as fractional part of 

          // (initial_P + 0.5*10^extra_digits)/10^extra_digits is exactly zero

          // get remainder

          remainder_h = Q_high.w[0] << (64 - amount);

          // test whether fractional part is 0

          if (!remainder_h

              && (Q_low.w[1] < reciprocals10_128[extra_digits].w[1]

                  || (Q_low.w[1] == reciprocals10_128[extra_digits].w[1]

                      && Q_low.w[0] <

                      reciprocals10_128[extra_digits].w[0]))) {

            C64--;

          }

        }

#endif

#ifdef SET_STATUS_FLAGS

      status = INEXACT_EXCEPTION | uf_status;

      // get remainder

      remainder_h = Q_high.w[0] << (64 - amount);

      switch (rmode) {

      case ROUNDING_TO_NEAREST:

      case ROUNDING_TIES_AWAY:

        // test whether fractional part is 0

        if (remainder_h == 0x8000000000000000ull

            && (Q_low.w[1] < reciprocals10_128[extra_digits].w[1]

                || (Q_low.w[1] == reciprocals10_128[extra_digits].w[1]

                    && Q_low.w[0] <

                    reciprocals10_128[extra_digits].w[0])))

          status = EXACT_STATUS;

        break;

      case ROUNDING_DOWN:

      case ROUNDING_TO_ZERO:

        if (!remainder_h

            && (Q_low.w[1] < reciprocals10_128[extra_digits].w[1]

                || (Q_low.w[1] == reciprocals10_128[extra_digits].w[1]

                    && Q_low.w[0] <

                    reciprocals10_128[extra_digits].w[0])))

          status = EXACT_STATUS;

        break;

      default:

        // round up

        __add_carry_out (Stemp.w[0], CY, Q_low.w[0],

                         reciprocals10_128[extra_digits].w[0]);

        __add_carry_in_out (Stemp.w[1], carry, Q_low.w[1],

                            reciprocals10_128[extra_digits].w[1], CY);

        if ((remainder_h >> (64 - amount)) + carry >=

            (((UINT64) 1) << amount))

          status = EXACT_STATUS;

      }

      __set_status_flags (pfpsf, status);

#endif

      // convert to BID and return

      res =

        fast_get_BID64_check_OF (sign_x ^ sign_y, final_exponent, C64,

                                 rmode, pfpsf);

      BID_RETURN (res);

    }

    // go to convert_format and exit

    C64 = __low_64 (P);

    res =

      get_BID64 (sign_x ^ sign_y,

                 exponent_x + exponent_y - DECIMAL_EXPONENT_BIAS, C64,

                 rmode, pfpsf);

    BID_RETURN (res);

  }

}