sc_nbexterns.cc

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  with this work for additional information regarding copyright ownership.
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  (the "License"); you may not use this file except in compliance with the
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/*****************************************************************************

  sc_nbexterns.cpp -- External functions for both sc_signed and sc_unsigned
                      classes. These functions work on two parameters u and
                      v, and copy the result to the first parameter u. This
                      is also the reason that they are suffixed with _on_help.

  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:

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


// $Log: sc_nbexterns.cpp,v $
// Revision 1.2  2011/02/18 20:19:15  acg
//  Andy Goodrich: updating Copyright notice.
//
// Revision 1.1.1.1  2006/12/15 20:20:05  acg
// SystemC 2.3
//
// Revision 1.3  2006/01/13 18:49:32  acg
// Added $Log command so that CVS check in comments are reproduced in the
// source.
//

#include "systemc/ext/dt/int/sc_nbexterns.hh"
#include "systemc/ext/utils/functions.hh"

namespace sc_dt
{

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

// Handles the cases 3 and 4 and returns the result in u.
void
add_on_help(small_type &us, int /* unb */, int und, sc_digit *ud,
            small_type vs, int /* vnb */, int vnd, const sc_digit *vd)
{
    vnd = vec_skip_leading_zeros(vnd, vd);

    if (us == vs) {  // case 3
        if (und >= vnd)
            vec_add_on(und, ud, vnd, vd);
        else
            vec_add_on2(und, ud, vnd, vd);

    } else {  // case 4
        // vec_cmp expects that und is the number of non-zero digits in ud.
        int new_und = vec_skip_leading_zeros(und, ud);
        int cmp_res = vec_cmp(new_und, ud, vnd, vd);

        if (cmp_res == 0) { // u == v
            us = SC_ZERO;
            vec_zero(und, ud);
            return;
        }

        if (cmp_res > 0) { // u > v
            vec_sub_on(und, ud, vnd, vd);
        } else { // u < v
            us = -us;
            vec_sub_on2(und, ud, vnd, vd);
        }
    }
}


// ----------------------------------------------------------------------------

/*

mul_on_help_signed and mul_on_help_unsigned have the same body except
that CONVERT_SM_to_2C_to_SM and COPY_DIGITS are defined for signed and
unsigned, respectively.  This comment also applies to the
signed/unsigned versions of div_on_help and mod_on_help. It is
possible to take COPY_DIGITS out of these functions and create a
single version of each of these helper functions; however, this will
impose an onverhead on performance. In the versions below, any change
in the signed version of a helper function must be carried to a
corresponding change in the unsigned verion of the same function or
vice versa.

*/


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

void
mul_on_help_signed(small_type &us, int unb, int und, sc_digit *ud,
                   int vnb, int vnd, const sc_digit *vd)
{
#define CONVERT_SM_to_2C_to_SM convert_signed_SM_to_2C_to_SM
#define COPY_DIGITS copy_digits_signed
    { // Body of mul_on_help
        int old_und = und;

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

        sc_digit ud0 = (*ud);
        sc_digit vd0 = (*vd);

        if ((vnd == 1) && (vd0 == 1)) {
            us = CONVERT_SM_to_2C_to_SM(us, unb, old_und, ud);
            return;
        }

        if ((und == 1) && (ud0 == 1)) {
            COPY_DIGITS(us, unb, old_und, ud, vnb, vnd, vd);
            return;
        }

        if ((und == 1) && (vnd == 1) &&
            (ud0 < HALF_DIGIT_RADIX) && (vd0 < HALF_DIGIT_RADIX)) {

            sc_digit d = ud0 * vd0;
            COPY_DIGITS(us, unb, old_und, ud, unb + vnb, 1, &d);
            return;
        }

        int nd = und + vnd;

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

        vec_zero(nd, d);

        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);

        COPY_DIGITS(us, unb, old_und, ud, unb + vnb, nd, d);

#ifndef SC_MAX_NBITS
        delete [] d;
#endif
    }
#undef COPY_DIGITS
#undef CONVERT_SM_to_2C_to_SM
}


void
mul_on_help_unsigned(small_type &us, int unb, int und, sc_digit *ud,
                     int vnb, int vnd, const sc_digit *vd)
{
#define CONVERT_SM_to_2C_to_SM convert_unsigned_SM_to_2C_to_SM
#define COPY_DIGITS copy_digits_unsigned
    { // Body of mul_on_help
        int old_und = und;

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

        sc_digit ud0 = (*ud);
        sc_digit vd0 = (*vd);

        if ((vnd == 1) && (vd0 == 1)) {
            us = CONVERT_SM_to_2C_to_SM(us, unb, old_und, ud);
            return;
        }

        if ((und == 1) && (ud0 == 1)) {
            COPY_DIGITS(us, unb, old_und, ud, vnb, vnd, vd);
            return;
        }

        if ((und == 1) && (vnd == 1) &&
            (ud0 < HALF_DIGIT_RADIX) && (vd0 < HALF_DIGIT_RADIX)) {

            sc_digit d = ud0 * vd0;
            COPY_DIGITS(us, unb, old_und, ud, unb + vnb, 1, &d);
            return;
        }

        int nd = und + vnd;

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

        vec_zero(nd, d);

        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);

        COPY_DIGITS(us, unb, old_und, ud, unb + vnb, nd, d);

#ifndef SC_MAX_NBITS
        delete [] d;
#endif
      }
#undef COPY_DIGITS
#undef CONVERT_SM_to_2C_to_SM
}


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

void
div_on_help_signed(small_type &us, int unb, int und, sc_digit *ud,
                   int vnb, int vnd, const sc_digit *vd)
{
#define CONVERT_SM_to_2C_to_SM convert_signed_SM_to_2C_to_SM
#define COPY_DIGITS copy_digits_signed
    {  // Body of div_on_help
        int old_und = und;

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

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

        if (cmp_res < 0) { // u < v => u / v = 0 - case 4
            us = SC_ZERO;
            vec_zero(old_und, ud);
            return;
        }

        sc_digit vd0 = (*vd);

        if ((cmp_res > 0) && (vnd == 1) && (vd0 == 1)) {
            us = CONVERT_SM_to_2C_to_SM(us, unb, old_und, ud);
            return;
        }

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

        COPY_DIGITS(us, unb, old_und, ud, sc_max(unb, vnb), nd - 1, d);

#ifndef SC_MAX_NBITS
        delete [] d;
#endif
    }
#undef COPY_DIGITS
#undef CONVERT_SM_to_2C_to_SM
}


void
div_on_help_unsigned(small_type &us, int unb, int und, sc_digit *ud,
                     int vnb, int vnd, const sc_digit *vd)
{
#define CONVERT_SM_to_2C_to_SM convert_unsigned_SM_to_2C_to_SM
#define COPY_DIGITS copy_digits_unsigned
    { // Body of div_on_help
        int old_und = und;

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

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

        if (cmp_res < 0) { // u < v => u / v = 0 - case 4
            us = SC_ZERO;
            vec_zero(old_und, ud);
            return;
        }

        sc_digit vd0 = (*vd);

        if ((cmp_res > 0) && (vnd == 1) && (vd0 == 1))  {
            us = CONVERT_SM_to_2C_to_SM(us, unb, old_und, ud);
            return;
        }

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

        COPY_DIGITS(us, unb, old_und, ud, sc_max(unb, vnb), nd - 1, d);

#ifndef SC_MAX_NBITS
        delete [] d;
#endif
      }
#undef COPY_DIGITS
#undef CONVERT_SM_to_2C_to_SM
}


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

void
mod_on_help_signed(small_type &us, int unb, int und, sc_digit *ud,
                   int /* vnb */, int vnd, const sc_digit *vd)
{
#define COPY_DIGITS copy_digits_signed
    { // Body of mod_on_help
        int old_und = und;

        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 = u - case 4
        if (cmp_res < 0)
            return;

        // u = v => u % v = 0 - case 3
        if (cmp_res == 0) {
            us = SC_ZERO;
            vec_zero(old_und, ud);
            return;
        }
        // else if u > v - case 5

        sc_digit vd0 = (*vd);

        if ((vnd == 1) && (vd0 == 1)) {
            us = SC_ZERO;
            vec_zero(old_und, ud);
            return;
        }

        // 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);

        if ((vnd == 1) && (und == 1))
            d[0] = (*ud) % vd0;
        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)
            vec_zero(old_und, ud);
        else
            COPY_DIGITS(us, unb, old_und, ud, sc_min(unb, vnd), nd - 1, d);

#ifndef SC_MAX_NBITS
        delete [] d;
#endif
    }
#undef COPY_DIGITS
}


void
mod_on_help_unsigned(small_type &us, int unb, int und, sc_digit *ud,
                     int /* vnb */, int vnd, const sc_digit *vd)
{
#define COPY_DIGITS copy_digits_unsigned
    { // Body of mod_on_help
        int old_und = und;

        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 = u - case 4
        if (cmp_res < 0)
            return;

        // u = v => u % v = 0 - case 3
        if (cmp_res == 0) {
            us = SC_ZERO;
            vec_zero(old_und, ud);
            return;
        }

        // else if u > v - case 5

        sc_digit vd0 = (*vd);

        if ((vnd == 1) && (vd0 == 1)) {
            us = SC_ZERO;
            vec_zero(old_und, ud);
            return;
        }

        // 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);

        if ((vnd == 1) && (und == 1))
            d[0] = (*ud) % vd0;
        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)
            vec_zero(old_und, ud);
        else
            COPY_DIGITS(us, unb, old_und, ud, sc_min(unb, vnd), nd - 1, d);

#ifndef SC_MAX_NBITS
        delete [] d;
#endif
    }
#undef COPY_DIGITS
}


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

// Handles the cases 2-5 and returns the result in u.
void
and_on_help(small_type us, int /* unb */, int und, sc_digit *ud,
            small_type vs, int /* vnb */, int vnd, const sc_digit *vd)
{
    sc_digit *x = ud;
    const sc_digit *y = vd;
    int xnd = und;
    int ynd = vnd;

    // Truncate y.
    if (xnd < ynd)
        ynd = xnd;

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

    // x is longer than y.
    small_type s = mul_signs(us, vs);

    if (s > 0) {
        if (us > 0) { // case 2
            while (y < yend)
                (*x++) &= (*y++);
            while (x < xend)
                (*x++) = 0;
        } else { // case 3
            sc_digit xcarry = 1;
            sc_digit ycarry = 1;
            while (y < yend) {
                xcarry += (~(*x) & DIGIT_MASK);
                ycarry += (~(*y++) & DIGIT_MASK);
                (*x++) = (xcarry & ycarry) & DIGIT_MASK;
                xcarry >>= BITS_PER_DIGIT;
                ycarry >>= BITS_PER_DIGIT;
            }
            while (x < xend) {
                xcarry += (~(*x) & DIGIT_MASK);
                ycarry += DIGIT_MASK;
                (*x++) = (xcarry & ycarry) & DIGIT_MASK;
                xcarry >>= BITS_PER_DIGIT;
                ycarry >>= BITS_PER_DIGIT;
            }

        }
    } else {
        if (us > 0) { // case 4
            sc_digit ycarry = 1;
            while (y < yend) {
                ycarry += (~(*y++) & DIGIT_MASK);
                (*x++) &= ycarry & DIGIT_MASK;
                ycarry >>= BITS_PER_DIGIT;
            }
            while (x < xend) {
                ycarry += DIGIT_MASK;
                (*x++) &= ycarry & DIGIT_MASK;
                ycarry >>= BITS_PER_DIGIT;
            }
        } else { // case 5
            sc_digit xcarry = 1;
            while (y < yend) {
                xcarry += (~(*x) & DIGIT_MASK);
                (*x++) = (xcarry & (*y++)) & DIGIT_MASK;
                xcarry >>= BITS_PER_DIGIT;
            }
            while (x < xend)
                (*x++) = 0;
        }
    }
}


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

// Handles the cases 3-5 and returns the result in u.
void
or_on_help(small_type us, int /* unb */, int und, sc_digit *ud,
           small_type vs, int /* vnb */, int vnd, const sc_digit *vd)
{
    sc_digit *x = ud;
    const sc_digit *y = vd;
    int xnd = und;
    int ynd = vnd;

    if (xnd < ynd)
        ynd = xnd;

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

    // x is longer than y.
    small_type s = mul_signs(us, vs);

    if (s > 0) {
        if (us > 0) { // case 3
            while (y < yend)
                (*x++) |= (*y++);
            // No change for the rest of x.
        } else { // case 4
            sc_digit xcarry = 1;
            sc_digit ycarry = 1;
            while (y < yend) {
                xcarry += (~(*x) & DIGIT_MASK);
                ycarry += (~(*y++) & DIGIT_MASK);
                (*x++) = (xcarry | ycarry) & DIGIT_MASK;
                xcarry >>= BITS_PER_DIGIT;
                ycarry >>= BITS_PER_DIGIT;
            }
            while (x < xend) {
                xcarry += (~(*x) & DIGIT_MASK);
                ycarry += DIGIT_MASK;
                (*x++) = (xcarry | ycarry) & DIGIT_MASK;
                xcarry >>= BITS_PER_DIGIT;
                ycarry >>= BITS_PER_DIGIT;
            }
        }
    } else {
        if (us > 0) { // case 5
            sc_digit ycarry = 1;
            while (y < yend) {
                ycarry += (~(*y++) & DIGIT_MASK);
                (*x) = ((*x) | ycarry) & DIGIT_MASK;
                x++;
                ycarry >>= BITS_PER_DIGIT;
            }
            while (x < xend) {
                ycarry += DIGIT_MASK;
                (*x) = ((*x) | ycarry) & DIGIT_MASK;
                x++;
                ycarry >>= BITS_PER_DIGIT;
            }
        } else { // case 6
            sc_digit xcarry = 1;
            while (y < yend) {
                xcarry += (~(*x) & DIGIT_MASK);
                (*x++) = (xcarry | (*y++)) & DIGIT_MASK;
                xcarry >>= BITS_PER_DIGIT;
            }
            while (x < xend) {
                xcarry += (~(*x) & DIGIT_MASK);
                (*x++) = xcarry & DIGIT_MASK;
                xcarry >>= BITS_PER_DIGIT;
            }
        }
    }
}


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

// Handles the cases 3-5 and returns the result in u.
void
xor_on_help(small_type us, int /* unb */, int und, sc_digit *ud,
            small_type vs, int /* vnb */, int vnd, const sc_digit *vd)
{
    sc_digit *x = ud;
    const sc_digit *y = vd;
    int xnd = und;
    int ynd = vnd;

    if (xnd < ynd)
        ynd = xnd;

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

    // x is longer than y.
    small_type s = mul_signs(us, vs);

    if (s > 0) {
        if (us > 0) { // case 3
            while (y < yend) {
                (*x) = ((*x) ^ (*y)) & DIGIT_MASK;
                x++;
                y++;
            }
            // No change for the rest of x.
        } else { // case 4
            sc_digit xcarry = 1;
            sc_digit ycarry = 1;
            while (y < yend) {
                xcarry += (~(*x) & DIGIT_MASK);
                ycarry += (~(*y++) & DIGIT_MASK);
                (*x++) = (xcarry ^ ycarry) & DIGIT_MASK;
                xcarry >>= BITS_PER_DIGIT;
                ycarry >>= BITS_PER_DIGIT;
            }
            while (x < xend) {
                xcarry += (~(*x) & DIGIT_MASK);
                ycarry += DIGIT_MASK;
                (*x++) = (xcarry ^ ycarry) & DIGIT_MASK;
                xcarry >>= BITS_PER_DIGIT;
                ycarry >>= BITS_PER_DIGIT;
            }
        }
    } else {
        if (us > 0) { // case 5
            sc_digit ycarry = 1;
            while (y < yend) {
                ycarry += (~(*y++) & DIGIT_MASK);
                (*x) = ((*x) ^ ycarry) & DIGIT_MASK;
                x++;
                ycarry >>= BITS_PER_DIGIT;
            }
            while (x < xend) {
                ycarry += DIGIT_MASK;
                (*x) = ((*x) ^ ycarry) & DIGIT_MASK;
                x++;
                ycarry >>= BITS_PER_DIGIT;
            }
        } else { // case 6
            sc_digit xcarry = 1;
            while (y < yend) {
                xcarry += (~(*x) & DIGIT_MASK);
                (*x++) = (xcarry ^ (*y++)) & DIGIT_MASK;
                xcarry >>= BITS_PER_DIGIT;
            }
            while (x < xend) {
                xcarry += (~(*x) & DIGIT_MASK);
                (*x++) = xcarry & DIGIT_MASK;
                xcarry >>= BITS_PER_DIGIT;
            }
        }
    }
}

} // namespace sc_dt