iverilog/PDelays.cc

/*
 * Copyright (c) 1999-2011 Stephen Williams (steve@icarus.com)
 *
 *    This source code is free software; you can redistribute it
 *    and/or modify it in source code form under the terms of the GNU
 *    General Public License as published by the Free Software
 *    Foundation; either version 2 of the License, or (at your option)
 *    any later version.
 *
 *    This program 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.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

# include "config.h"

# include  <iostream>

# include  "PDelays.h"
# include  "PExpr.h"
# include  "verinum.h"
# include  "netmisc.h"

bool dly_used_no_timescale = false;
bool dly_used_timescale = false;
bool display_ts_dly_warning = true;


PDelays::PDelays()
{
      delete_flag_ = true;
      for (unsigned idx = 0 ;  idx < 3 ;  idx += 1)
	    delay_[idx] = 0;
}

PDelays::~PDelays()
{
      if (delete_flag_) {
	    for (unsigned idx = 0 ;  idx < 3 ;  idx += 1)
		  delete delay_[idx];
      }
}

void PDelays::set_delay(PExpr*del)
{
      assert(del);
      assert(delay_[0] == 0);
      delay_[0] = del;
      delete_flag_ = true;
}


void PDelays::set_delays(const list<PExpr*>*del, bool df)
{
      assert(del);
      assert(del->size() <= 3);

      list<PExpr*>::const_iterator cur = del->begin();
      for (unsigned idx = 0 ;  cur != del->end() ;  idx += 1, ++cur)
	    delay_[idx] = *cur;

      delete_flag_ = df;
}

unsigned PDelays::delay_count() const
{
      unsigned dly_cnt = 0;
      for (unsigned idx = 0 ;  idx < 3 ;  idx += 1)
	    if (delay_[idx]) dly_cnt += 1;

      return dly_cnt;
}

static NetExpr*calculate_val(Design*des, NetScope*scope, PExpr*expr)
{
      NetExpr*dex = elab_and_eval(des, scope, expr, -1);

	/* Print a warning if we find default and `timescale based
	 * delays in the design, since this is likely an error. */
      if (scope->time_from_timescale()) dly_used_timescale = true;
      else dly_used_no_timescale = true;

      if (display_ts_dly_warning &&
          dly_used_no_timescale && dly_used_timescale) {
	    cerr << "warning: Found both default and "
	            "`timescale based delays. Use" << endl;
	    cerr << "         -Wtimescale to find the "
	            "module(s) with no `timescale." << endl;
	    display_ts_dly_warning = false;
      }

	/* If the delay expression is a real constant or vector
	   constant, then evaluate it, scale it to the local time
	   units, and return an adjusted value. */

      if (NetECReal*tmp = dynamic_cast<NetECReal*>(dex)) {
	    uint64_t delay = get_scaled_time_from_real(des, scope, tmp);

	    delete tmp;
	    NetEConst*tmp2 = new NetEConst(verinum(delay, 64));
	    tmp2->set_line(*expr);
	    return tmp2;
      }


      if (NetEConst*tmp = dynamic_cast<NetEConst*>(dex)) {
	    verinum fn = tmp->value();
	    uint64_t delay = des->scale_to_precision(fn.as_ulong64(), scope);

	    delete tmp;
	    NetEConst*tmp2 = new NetEConst(verinum(delay, 64));
	    tmp2->set_line(*expr);
	    return tmp2;
      }

	/* Oops, cannot evaluate down to a constant. */
      return dex;
}

static NetExpr* make_delay_nets(Design*des, NetScope*scope, NetExpr*expr)
{
      if (expr == 0)
            return 0;

      if (dynamic_cast<NetESignal*> (expr))
	    return expr;

      if (dynamic_cast<NetEConst*> (expr))
	    return expr;

      NetNet*sig = expr->synthesize(des, scope, expr);
      if (sig == 0) {
	    cerr << expr->get_fileline() << ": error: Expression " << *expr
		 << " is not suitable as a delay expression." << endl;
	    des->errors += 1;
	    return 0;
      }

      expr = new NetESignal(sig);
      return expr;
}

static NetExpr* calc_decay_time(NetExpr *rise, NetExpr *fall)
{
      NetEConst *c_rise = dynamic_cast<NetEConst*>(rise);
      NetEConst *c_fall = dynamic_cast<NetEConst*>(fall);
      if (c_rise && c_fall) {
	    if (c_rise->value() < c_fall->value()) return rise;
	    else return fall;
      }

      return 0;
}

void PDelays::eval_delays(Design*des, NetScope*scope,
			  NetExpr*&rise_time,
			  NetExpr*&fall_time,
			  NetExpr*&decay_time,
			  bool as_nets_flag) const
{
      assert(scope);


      if (delay_[0]) {
	    rise_time = calculate_val(des, scope, delay_[0]);
	    if (as_nets_flag)
		  rise_time = make_delay_nets(des, scope, rise_time);

	    if (delay_[1]) {
		  fall_time = calculate_val(des, scope, delay_[1]);
		  if (as_nets_flag)
			fall_time = make_delay_nets(des, scope, fall_time);

		  if (delay_[2]) {
			decay_time = calculate_val(des, scope, delay_[2]);
			if (as_nets_flag)
			      decay_time = make_delay_nets(des, scope,
			                                   decay_time);

		  } else {
			// If this is zero then we need to do the min()
			// at run time.
			decay_time = calc_decay_time(rise_time, fall_time);
		  }
	    } else {
		  assert(delay_[2] == 0);
		  fall_time = rise_time;
		  decay_time = rise_time;
	    }
      } else {
	    rise_time = 0;
	    fall_time = 0;
	    decay_time = 0;
      }
}