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/*
* Copyright (c) 1999-2010 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/

# include "config.h"

/*
* This functor scans the design looking for dangling objects and
* excess local signals. These deletions are not necessarily required
* for proper functioning of anything, but they can clean up the
* appearance of design files that are generated.
*/
# include "functor.h"
# include "netlist.h"
# include "compiler.h"

class nodangle_f : public functor_t {
    public:
      void event(Design*des, NetEvent*ev);
      void signal(Design*des, NetNet*sig);

      unsigned iteration;
      unsigned stotal, etotal;
      bool scontinue, econtinue;
      bool scomplete, ecomplete;
};

void nodangle_f::event(Design*des, NetEvent*ev)
{
      if (ecomplete) return;

/* If there are no references to this event, then go right
ahead and delete it. There is no use looking further at
it. */
      if ((ev->nwait() + ev->ntrig() + ev->nexpr()) == 0) {
delete ev;
etotal += 1;
return;
      }

      if (iteration == 0) {
              /* Try to remove duplicate probes from the event. This
is done as a separate initial pass to ensure similar
events are detected as soon as possible in subsequent
iterations. */
            for (unsigned idx = 0 ; idx < ev->nprobe() ; idx += 1) {
                  unsigned jdx = idx + 1;
                  while (jdx < ev->nprobe()) {
                        NetEvProbe*ip = ev->probe(idx);
                        NetEvProbe*jp = ev->probe(jdx);

                        if (ip->edge() != jp->edge()) {
                              jdx += 1;
                              continue;
                        }

                        bool fully_connected = true;
                        for (unsigned jpin = 0; jpin < jp->pin_count(); jpin += 1) {
                              unsigned ipin = 0;
                              bool connected_flag = false;
                              for (ipin = 0 ; ipin < ip->pin_count(); ipin += 1)
                                    if (connected(ip->pin(ipin), jp->pin(jpin))) {
                                          connected_flag = true;
                                          break;
                                    }

                              if (!connected_flag) {
                                    fully_connected = false;
                                    break;
                              }
                        }

                        if (fully_connected) {
                              delete jp;
                        } else {
                              jdx += 1;
                        }
                  }
            }
            econtinue = true;
      } else {
              /* Postpone examining events in an automatic scope until the
third (optional) pass. This will mean similar events are
biased towards being stored in static scopes. */
            if (ev->scope()->is_auto()) {
                  if (iteration == 1) {
                        econtinue = true;
                        return;
                  }
            } else {
                  if (iteration == 2) {
                        return;
                  }
            }

              /* Try to find all the events that are similar to me, and
replace their references with references to me. */
            list<NetEvent*> match;
            ev->find_similar_event(match);
            for (list<NetEvent*>::iterator idx = match.begin()
                       ; idx != match.end() ; idx ++) {

                  NetEvent*tmp = *idx;
                  assert(tmp != ev);
                  tmp ->replace_event(ev);
            }
      }
}

void nodangle_f::signal(Design*des, NetNet*sig)
{
      if (scomplete) return;

/* Cannot delete signals referenced in an expression
or an l-value. */
      if (sig->get_refs() > 0)
return;

/* Cannot delete the ports of tasks, functions or modules. There
are too many places where they are referenced. */
      if ((sig->port_type() != NetNet::NOT_A_PORT) &&
((sig->scope()->type() == NetScope::TASK) ||
(sig->scope()->type() == NetScope::FUNC) ||
(sig->scope()->type() == NetScope::MODULE)))
return;

/* Can't delete ports of cells. */
      if ((sig->port_type() != NetNet::NOT_A_PORT)
&& (sig->scope()->attribute(perm_string::literal("ivl_synthesis_cell")) != verinum()))
return;

/* Check to see if the signal is completely unconnected. If
all the bits are unlinked, then delete it. */
      if (! sig->is_linked()) {
delete sig;
stotal += 1;
return;
      }

/* The remaining things can only be done to synthesized
signals, not ones that appear in the original Verilog. */
      if (! sig->local_flag())
return;

/* Check to see if there is some significant signal connected
to every pin of this signal. */
      unsigned significant_flags = 0;
      for (unsigned idx = 0 ; idx < sig->pin_count() ; idx += 1) {
Nexus*nex = sig->pin(idx).nexus();

for (Link*cur = nex->first_nlink()
; cur ; cur = cur->next_nlink()) {

if (cur == &sig->pin(idx))
continue;

NetNet*cursig = dynamic_cast<NetNet*>(cur->get_obj());
if (cursig == 0)
continue;

if (cursig->local_flag())
continue;

significant_flags += 1;
break;
}

if (significant_flags <= idx)
break;
      }

/* If every pin is connected to another significant signal,
then I can delete this one. */
      if (significant_flags == sig->pin_count()) {
scontinue = true;
delete sig;
stotal += 1;
      }
}

void nodangle(Design*des)
{
      nodangle_f fun;
      fun.iteration = 0;
      fun.stotal = 0;
      fun.etotal = 0;
      fun.scomplete = false;
      fun.ecomplete = false;
      do {
            fun.scontinue = false;
            fun.econtinue = false;
des->functor(&fun);
fun.iteration += 1;
            fun.scomplete = !fun.scontinue;
            fun.ecomplete = !fun.econtinue;

if (verbose_flag) {
cout << " ... " << fun.iteration << " iterations"
<< " deleted " << fun.stotal << " dangling signals"
<< " and " << fun.etotal << " events." << endl;
}

      } while (fun.scontinue || fun.econtinue);

}
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