sc_nbfriends.inc

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

  The following code is derived, directly or indirectly, from the SystemC
  source code Copyright (c) 1996-2005 by all Contributors.
  All Rights reserved.

  The contents of this file are subject to the restrictions and limitations
  set forth in the SystemC Open Source License Version 2.3 (the "License");
  You may not use this file except in compliance with such restrictions and
  limitations. You may obtain instructions on how to receive a copy of the
  License at http://www.systemc.org/. Software distributed by Contributors
  under the License is distributed on an "AS IS" basis, WITHOUT WARRANTY OF
  ANY KIND, either express or implied. See the License for the specific
  language governing rights and limitations under the License.

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

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

  sc_nbfriends.cpp -- Friend functions for both sc_signed and sc_unsigned
                      classes. The vec_* functions are called through either
                      these functions or those in sc_nbexterns.cpp. These
                      functions perform their work on two inputs u and v, and
                      return the result object. The functions in
                      sc_nbexterns.cpp perform their work on one of their
                      inputs.

                      The functions here try to use faster algorithms in case
                      the input numbers are small. The bitwise functions (and,
                      or, and xor) need the 2's complement representations of
                      their inputs. Instead of complementing their inputs
                      first and then processing, they complement their inputs
                      while processing without allocating extra temporary
                      memory.

  Original Author: Ali Dasdan, Synopsys, Inc.

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

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

  MODIFICATION LOG - modifiers, enter your name, affiliation, date and
  changes you are making here.

      Name, Affiliation, Date:
  Description of Modification:

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


// ----------------------------------------------------------------------------
//  Naming conventions:
//  For sc_signed or sc_unsigned number u:
//    us : u's sign, unb : u's number of bits, 
//    und : u's number of digits, ud : u's digits array.
// ----------------------------------------------------------------------------

// ----------------------------------------------------------------------------
//  SECTION: Friend functions for PLUS operators.
// ----------------------------------------------------------------------------

// Handles cases 3 and 4 and returns the result.
CLASS_TYPE
ADD_HELPER(small_type us, int unb, int und,
           const sc_digit *ud, 
           small_type vs, int vnb, int vnd,
           const sc_digit *vd)
{

  und = vec_skip_leading_zeros(und, ud);
  vnd = vec_skip_leading_zeros(vnd, vd);

  int nb = sc_max(unb, vnb);
  int nd = sc_max(und, vnd) + 1;

#ifdef SC_MAX_NBITS
  test_bound(nb);
  sc_digit d[MAX_NDIGITS];
#else
  sc_digit *d = new sc_digit[nd];
#endif
  
  d[nd - 1] = d[nd - 2] = 0;

  // case 3
  if (us == vs) {

    ++nb;

    if ((und == 1) && (vnd == 1)) {
      sc_digit carry = (*ud) + (*vd);
      d[0] = carry & DIGIT_MASK;
      d[1] = carry >> BITS_PER_DIGIT;
    }

    else if (und >= vnd)
      vec_add(und, ud, vnd, vd, d);

    else
      vec_add(vnd, vd, und, ud, d);

  }

  // case 4
  else {

    int cmp_res = vec_cmp(und, ud, vnd, vd);
    
    if (cmp_res == 0) // u == v
      return CLASS_TYPE();
    
    if (cmp_res > 0)  { // u > v

      if ((und == 1) && (vnd == 1))
        d[0] = (*ud) - (*vd);
      else
        vec_sub(und, ud, vnd, vd, d);

    }
    else { // u < v

      us = -us;

      if ((und == 1) && (vnd == 1))
        d[0] = (*vd) - (*ud);
      else
        vec_sub(vnd, vd, und, ud, d);

    }
  }
  
  return CLASS_TYPE(us, nb, nd, d);
  
}


// ----------------------------------------------------------------------------
//  SECTION: Friend functions of MULTIPLICATION operators.
// ----------------------------------------------------------------------------

// Handles the case 4 and returns the result.
CLASS_TYPE 
MUL_HELPER(small_type s, 
           int unb, int und, 
           const sc_digit *ud, 
           int vnb, int vnd,
           const sc_digit *vd)
{

  und = vec_skip_leading_zeros(und, ud);
  vnd = vec_skip_leading_zeros(vnd, vd);

  int nb = unb + vnb;
  int nd = und + vnd;
  
#ifdef SC_MAX_NBITS
  test_bound(nb);
  sc_digit d[MAX_NDIGITS];
#else
  sc_digit *d = new sc_digit[nd];
#endif

  vec_zero(nd, d);
    
  sc_digit ud0 = (*ud);
  sc_digit vd0 = (*vd);

  if ((vnd == 1) && (vd0 == 1))
    vec_copy(und, d, ud);

  else if ((und == 1) && (ud0 == 1))
    vec_copy(vnd, d, vd);

  else if ((und == 1) && (vnd == 1) && 
      (ud0 < HALF_DIGIT_RADIX) && (vd0 < HALF_DIGIT_RADIX))
    d[0] = ud0 * vd0;
  
  else if ((und == 1) && (ud0 < HALF_DIGIT_RADIX))
    vec_mul_small(vnd, vd, ud0, d);

  else if ((vnd == 1) && (vd0 < HALF_DIGIT_RADIX))
    vec_mul_small(und, ud, vd0, d);

  else if (vnd < und)
    vec_mul(und, ud, vnd, vd, d);

  else
    vec_mul(vnd, vd, und, ud, d);
  
  return CLASS_TYPE(s, nb, nd, d);

}


// ----------------------------------------------------------------------------
//  SECTION: Friend functions for DIVISION operators.
// ----------------------------------------------------------------------------

// Handles the cases 3-4 and returns the result.
CLASS_TYPE 
DIV_HELPER(small_type s, 
           int unb, int und, 
           const sc_digit *ud, 
           int vnb, int vnd,
           const sc_digit *vd)
{

  und = vec_skip_leading_zeros(und, ud);
  vnd = vec_skip_leading_zeros(vnd, vd);

  int cmp_res = vec_cmp(und, ud, vnd, vd);

  // u < v => u / v = 0 - case 4
  if (cmp_res < 0) 
    return CLASS_TYPE();

  // One extra digit for d is allocated to simplify vec_div_*().
  int nd = sc_max(und, vnd) + 1;

#ifdef SC_MAX_NBITS
  sc_digit d[MAX_NDIGITS + 1];
#else
  sc_digit *d = new sc_digit[nd];
#endif

  vec_zero(nd, d);

  sc_digit vd0 = (*vd);

  // u = v => u / v = 1 - case 3
  if (cmp_res == 0)
    d[0] = 1;

  // else if u > v - case 5

  else if ((vnd == 1) && (vd0 == 1))
    vec_copy(und, d, ud);

  else if ((vnd == 1) && (und == 1))
    d[0] = (*ud) / vd0;
 
  else if ((vnd == 1) && (vd0 < HALF_DIGIT_RADIX))
    vec_div_small(und, ud, vd0, d);

  else
    vec_div_large(und, ud, vnd, vd, d);

  return CLASS_TYPE(s, sc_max(unb, vnb), nd - 1, d);
  
}


// ----------------------------------------------------------------------------
//  SECTION: Friend functions for MOD operators.
// ----------------------------------------------------------------------------

// Handles the cases 3-4 and returns the result.
CLASS_TYPE 
MOD_HELPER(small_type us, 
           int unb, int und, 
           const sc_digit *ud, 
           int vnb, int vnd,
           const sc_digit *vd)
{

  und = vec_skip_leading_zeros(und, ud);
  vnd = vec_skip_leading_zeros(vnd, vd);

  int cmp_res = vec_cmp(und, ud, vnd, vd);

  // u = v => u % v = 0 - case 3
  if (cmp_res == 0) 
    return CLASS_TYPE();

  sc_digit vd0 = (*vd);

  if ((cmp_res > 0) && (vnd == 1) && (vd0 == 1))
    return CLASS_TYPE();

  // One extra digit for d is allocated to simplify vec_div_*().
  int nd = sc_max(und, vnd) + 1;

#ifdef SC_MAX_NBITS
  sc_digit d[MAX_NDIGITS + 1];
#else
  sc_digit *d = new sc_digit[nd];
#endif

  vec_zero(nd, d);

  // u < v => u % v = u - case 4
  if (cmp_res < 0) 
    vec_copy(und, d, ud);

  // else if u > v - case 5

  else if ((vnd == 1) && (und == 1))
    d[0] = (*ud) % vd0;

  else if ((vnd == 1) && (vd0 < HALF_DIGIT_RADIX))
    d[0] = vec_rem_small(und, ud, vd0);

  else
    vec_rem_large(und, ud, vnd, vd, d);

  us = check_for_zero(us, nd - 1, d);

  if (us == SC_ZERO)
    return CLASS_TYPE();
  else
    return CLASS_TYPE(us, sc_min(unb, vnb), nd - 1, d);

}


// ----------------------------------------------------------------------------
//  SECTION: Friend functions for AND operators.
// ----------------------------------------------------------------------------

// Handles the cases 2-5 and returns the result.
CLASS_TYPE 
AND_HELPER(small_type us, 
           int unb, int und, 
           const sc_digit *ud, 
           small_type vs,
           int vnb, int vnd,
           const sc_digit *vd)
{

  int nb = sc_max(unb, vnb);
  int nd = sc_max(und, vnd);

#ifdef SC_MAX_NBITS
  sc_digit dbegin[MAX_NDIGITS];
#else
  sc_digit *dbegin = new sc_digit[nd];
#endif

  sc_digit *d = dbegin;

  register const sc_digit *x;
  register const sc_digit *y;
  int xnd;
  int ynd;
  small_type xs;
  small_type ys;

  if (und >= vnd) {
    x = ud;
    y = vd;
    xnd = und;
    ynd = vnd;
    xs = us;
    ys = vs;
  }
  else {
    y = ud;
    x = vd;
    ynd = und;
    xnd = vnd;
    ys = us;
    xs = vs;
  }

  const sc_digit *xend = (x + xnd);
  const sc_digit *yend = (y + ynd);

  // x is longer than y.

  small_type s = mul_signs(xs, ys);

  if (s > 0) {

    if (xs > 0) { // case 2

      while (y < yend)
        (*d++) = (*x++) & (*y++);

      while (x++ < xend) 
        (*d++) = 0;

    }
    else {  // case 3

      register sc_digit xcarry = 1;
      register sc_digit ycarry = 1;

      while (y < yend) {
        xcarry += (~(*x++) & DIGIT_MASK);
        ycarry += (~(*y++) & DIGIT_MASK);
        (*d++) = (xcarry & ycarry) & DIGIT_MASK;
        xcarry >>= BITS_PER_DIGIT;
        ycarry >>= BITS_PER_DIGIT;
      }

      while (x < xend) {
        xcarry += (~(*x++) & DIGIT_MASK);
        ycarry += DIGIT_MASK;
        (*d++) = (xcarry & ycarry) & DIGIT_MASK;
        xcarry >>= BITS_PER_DIGIT;
        ycarry >>= BITS_PER_DIGIT;
      }

    }
  }
  else {

    if (xs > 0) { // case 4

      register sc_digit ycarry = 1;

      while (y < yend) {
        ycarry += (~(*y++) & DIGIT_MASK);
        (*d++) = ((*x++) & ycarry) & DIGIT_MASK;
        ycarry >>= BITS_PER_DIGIT;
      }

      while (x < xend) {
        ycarry += DIGIT_MASK;
        (*d++) = ((*x++) & ycarry) & DIGIT_MASK;
        ycarry >>= BITS_PER_DIGIT;
      }

    }
    else {  // case 5

      register sc_digit xcarry = 1;

      while (y < yend) {
        xcarry += (~(*x++) & DIGIT_MASK);
        (*d++) = (xcarry & (*y++)) & DIGIT_MASK;
        xcarry >>= BITS_PER_DIGIT;
      }

      while (x++ < xend)
        (*d++) = 0;

    }
  }

  s = convert_signed_2C_to_SM(nb, nd, dbegin);

  return CLASS_TYPE(s, nb, nd, dbegin);  

}


// ----------------------------------------------------------------------------
//  SECTION: Friend functions for OR operators.
// ----------------------------------------------------------------------------

// Handles the cases 3-5 and returns the result.
CLASS_TYPE 
OR_HELPER(small_type us, 
          int unb, int und, 
          const sc_digit *ud, 
          small_type vs,
          int vnb, int vnd,
          const sc_digit *vd)
{
  
  int nb = sc_max(unb, vnb);
  int nd = sc_max(und, vnd);

#ifdef SC_MAX_NBITS
  sc_digit dbegin[MAX_NDIGITS];
#else
  sc_digit *dbegin = new sc_digit[nd];
#endif

  sc_digit *d = dbegin;

  register const sc_digit *x;
  register const sc_digit *y;
  int xnd;
  int ynd;
  small_type xs;
  small_type ys;

  if (und >= vnd) {
    x = ud;
    y = vd;
    xnd = und;
    ynd = vnd;
    xs = us;
    ys = vs;
  }
  else {
    y = ud;
    x = vd;
    ynd = und;
    xnd = vnd;
    ys = us;
    xs = vs;
  }

  const sc_digit *xend = (x + xnd);
  const sc_digit *yend = (y + ynd);

  // x is longer than y.

  small_type s = mul_signs(xs, ys);

  if (s > 0) {

    if (xs > 0) { // case 3

      while (y < yend)
        (*d++) = (*x++) | (*y++);

      while (x < xend)
        (*d++) = (*x++);

    }
    else {  // case 4

      register sc_digit xcarry = 1;
      register sc_digit ycarry = 1;

      while (y < yend) {
        xcarry += (~(*x++) & DIGIT_MASK);
        ycarry += (~(*y++) & DIGIT_MASK);
        (*d++) = (xcarry | ycarry) & DIGIT_MASK;
        xcarry >>= BITS_PER_DIGIT;
        ycarry >>= BITS_PER_DIGIT;
      }

      while (x < xend) {
        xcarry += (~(*x++) & DIGIT_MASK);
        ycarry += DIGIT_MASK;
        (*d++) = (xcarry | ycarry) & DIGIT_MASK;
        xcarry >>= BITS_PER_DIGIT;
        ycarry >>= BITS_PER_DIGIT;
      }

    }

  }
  else {

    if (xs > 0) { // case 5

      register sc_digit ycarry = 1;

      while (y < yend) {
        ycarry += (~(*y++) & DIGIT_MASK);
        (*d++) = ((*x++) | ycarry) & DIGIT_MASK;
        ycarry >>= BITS_PER_DIGIT;
      }

      while (x < xend) {
        ycarry += DIGIT_MASK;
        (*d++) = ((*x++) | ycarry) & DIGIT_MASK;
        ycarry >>= BITS_PER_DIGIT;
      }

    }
    else {  // case 6

      register sc_digit xcarry = 1;

      while (y < yend) {
        xcarry += (~(*x++) & DIGIT_MASK);
        (*d++) = (xcarry | (*y++)) & DIGIT_MASK;
        xcarry >>= BITS_PER_DIGIT;
      }

      while (x < xend) {
        xcarry += (~(*x++) & DIGIT_MASK);
        (*d++) = xcarry & DIGIT_MASK;
        xcarry >>= BITS_PER_DIGIT;
      }
    }

  }

  s = convert_signed_2C_to_SM(nb, nd, dbegin);

  return CLASS_TYPE(s, nb, nd, dbegin);

}


// ----------------------------------------------------------------------------
//  SECTION: Friend functions for XOR operators.
// ----------------------------------------------------------------------------

// Handles the cases 3-5 and returns the result.
CLASS_TYPE 
XOR_HELPER(small_type us, 
           int unb, int und, 
           const sc_digit *ud, 
           small_type vs,
           int vnb, int vnd,
           const sc_digit *vd)
{
  
  int nb = sc_max(unb, vnb);
  int nd = sc_max(und, vnd);

#ifdef SC_MAX_NBITS
  sc_digit dbegin[MAX_NDIGITS];
#else
  sc_digit *dbegin = new sc_digit[nd];
#endif

  sc_digit *d = dbegin;

  register const sc_digit *x;
  register const sc_digit *y;
  int xnd;
  int ynd;
  small_type xs;
  small_type ys;

  if (und >= vnd) {
    x = ud;
    y = vd;
    xnd = und;
    ynd = vnd;
    xs = us;
    ys = vs;
  }
  else {
    y = ud;
    x = vd;
    ynd = und;
    xnd = vnd;
    ys = us;
    xs = vs;
  }

  const sc_digit *xend = (x + xnd);
  const sc_digit *yend = (y + ynd);

  // x is longer than y.

  small_type s = mul_signs(xs, ys);

  if (s > 0) {

    if (xs > 0) { // case 3

      while (y < yend)
        (*d++) = ((*x++) ^ (*y++)) & DIGIT_MASK;

      while (x < xend)
        (*d++) = (*x++);

    }
    else {  // case 4

      register sc_digit xcarry = 1;
      register sc_digit ycarry = 1;

      while (y < yend) {
        xcarry += (~(*x++) & DIGIT_MASK);
        ycarry += (~(*y++) & DIGIT_MASK);
        (*d++) = (xcarry ^ ycarry) & DIGIT_MASK;
        xcarry >>= BITS_PER_DIGIT;
        ycarry >>= BITS_PER_DIGIT;
      }

      while (x < xend) {
        xcarry += (~(*x++) & DIGIT_MASK);
        ycarry += DIGIT_MASK;
        (*d++) = (xcarry ^ ycarry) & DIGIT_MASK;
        xcarry >>= BITS_PER_DIGIT;
        ycarry >>= BITS_PER_DIGIT;
      }

    }
  }
  else {

    if (xs > 0) { // case 5

      register sc_digit ycarry = 1;

      while (y < yend) {
        ycarry += (~(*y++) & DIGIT_MASK);
        (*d++) = ((*x++) ^ ycarry) & DIGIT_MASK;
        ycarry >>= BITS_PER_DIGIT;
      }

      while (x < xend) {
        ycarry += DIGIT_MASK;
        (*d++) = ((*x++) ^ ycarry) & DIGIT_MASK;
        ycarry >>= BITS_PER_DIGIT;
      }

    }
    else {  // case 6

      register sc_digit xcarry = 1;

      while (y < yend) {
        xcarry += (~(*x++) & DIGIT_MASK);
        (*d++) = (xcarry ^ (*y++)) & DIGIT_MASK;
        xcarry >>= BITS_PER_DIGIT;
      }

      while (x < xend) {
        xcarry += (~(*x++) & DIGIT_MASK);
        (*d++) = xcarry & DIGIT_MASK;
        xcarry >>= BITS_PER_DIGIT;
      }
    }
  }

  s = convert_signed_2C_to_SM(nb, nd, dbegin);

  return CLASS_TYPE(s, nb, nd, dbegin);

}

// End of file.

---