iverilog/elab_scope.cc

/*
 * Copyright (c) 2000-2008 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"
# include  "compiler.h"
# include  "netmisc.h"
# include  <cstring>
# include  <iostream>
# include  <cstdlib>
# include  <stdio.h>

/*
 * Elaboration happens in two passes, generally. The first scans the
 * pform to generate the NetScope tree and attach it to the Design
 * object. The methods in this source file implement the elaboration
 * of the scopes.
 */

# include  "Module.h"
# include  "PEvent.h"
# include  "PExpr.h"
# include  "PGate.h"
# include  "PGenerate.h"
# include  "PTask.h"
# include  "PWire.h"
# include  "Statement.h"
# include  "netlist.h"
# include  "util.h"
# include  <typeinfo>
# include  <assert.h>
# include  "ivl_assert.h"

void Module::elaborate_parm_item_(perm_string name, const param_expr_t&cur,
				  Design*des, NetScope*scope)
{
      PExpr*ex = cur.expr;
      assert(ex);

      NetExpr*val = ex->elaborate_pexpr(des, scope);
      if (val == 0) return;
      NetExpr*msb = 0;
      NetExpr*lsb = 0;
      bool signed_flag = cur.signed_flag;

	/* If the parameter declaration includes msb and lsb,
	   then use them to calculate a width for the
	   result. Then make sure the constant expression of the
	   parameter value is coerced to have the correct
	   and defined width. */
      if (cur.msb) {
	    assert(cur.lsb);
	    msb = cur.msb ->elaborate_pexpr(des, scope);
	    assert(msb);
	    lsb = cur.lsb ->elaborate_pexpr(des, scope);
	    assert(lsb);
      }

      if (signed_flag) {
	      /* If explicitly signed, then say so. */
	    val->cast_signed(true);
      } else if (cur.msb) {
	      /* If there is a range, then the signedness comes
		 from the type and not the expression. */
	    val->cast_signed(signed_flag);
      } else {
	      /* otherwise, let the expression describe
		 itself. */
	    signed_flag = val->has_sign();
      }

      NetScope::range_t*range_list = 0;
      for (Module::range_t*range = cur.range ; range ; range = range->next) {
	    NetScope::range_t*tmp = new NetScope::range_t;
	    tmp->exclude_flag = range->exclude_flag;
	    tmp->low_open_flag = range->low_open_flag;
	    tmp->high_open_flag = range->high_open_flag;

	    if (range->low_expr) {
		  tmp->low_expr = elab_and_eval(des, scope, range->low_expr, -1);
		  ivl_assert(*range->low_expr, tmp->low_expr);
	    } else {
		  tmp->low_expr = 0;
	    }

	    if (range->high_expr && range->high_expr==range->low_expr) {
		    // Detect the special case of a "point"
		    // range. These are called out by setting the high
		    // and low expression ranges to the same
		    // expression. The exclude_flags should be false
		    // in this case
		  ivl_assert(*range->high_expr, tmp->low_open_flag==false && tmp->high_open_flag==false);
		  tmp->high_expr = tmp->low_expr;

	    } else if (range->high_expr) {
		  tmp->high_expr = elab_and_eval(des, scope, range->high_expr, -1);
		  ivl_assert(*range->high_expr, tmp->high_expr);
	    } else {
		  tmp->high_expr = 0;
	    }

	    tmp->next = range_list;
	    range_list = tmp;
      }

      val = scope->set_parameter(name, val, cur.type, msb, lsb, signed_flag, range_list, cur);
      assert(val);
      delete val;
}

static void elaborate_scope_tasks(Design*des, NetScope*scope,
				  const LineInfo&loc,
				  const map<perm_string,PTask*>&tasks)
{
      typedef map<perm_string,PTask*>::const_iterator tasks_it_t;

      for (tasks_it_t cur = tasks.begin()
		 ; cur != tasks.end() ;  cur ++ ) {

	    hname_t use_name( (*cur).first );
	    if (scope->child(use_name)) {
		  cerr << loc.get_fileline() << ": error: task/scope name "
		       << use_name << " already used in this context."
		       << endl;
		  des->errors += 1;
		  continue;
	    }
	    NetScope*task_scope = new NetScope(scope, use_name,
					       NetScope::TASK);
	    task_scope->set_line((*cur).second);

	    if (debug_scopes)
		  cerr << cur->second->get_fileline() << ": debug: "
		       << "Elaborate task scope " << scope_path(task_scope) << endl;
	    (*cur).second->elaborate_scope(des, task_scope);
      }

}

static void elaborate_scope_funcs(Design*des, NetScope*scope,
				  const LineInfo&loc,
				  const map<perm_string,PFunction*>&funcs)
{
      typedef map<perm_string,PFunction*>::const_iterator funcs_it_t;

      for (funcs_it_t cur = funcs.begin()
		 ; cur != funcs.end() ;  cur ++ ) {

	    hname_t use_name( (*cur).first );
	    if (scope->child(use_name)) {
		  cerr << loc.get_fileline() << ": error: function/scope name "
		       << use_name << " already used in this context."
		       << endl;
		  des->errors += 1;
		  continue;
	    }
	    NetScope*func_scope = new NetScope(scope, use_name,
					       NetScope::FUNC);
	    func_scope->set_line((*cur).second);

	    if (debug_scopes)
		  cerr << cur->second->get_fileline() << ": debug: "
		       << "Elaborate function scope " << scope_path(func_scope) << endl;
	    (*cur).second->elaborate_scope(des, func_scope);
      }

}

class generate_schemes_work_item_t : public elaborator_work_item_t {
    public:
      generate_schemes_work_item_t(Design*des, NetScope*scope, Module*mod)
      : elaborator_work_item_t(des), scope_(scope), mod_(mod)
      { }

      void elaborate_runrun()
      {
	    if (debug_scopes)
		  cerr << mod_->get_fileline() << ": debug: "
		       << "Processing generate schemes for "
		       << scope_path(scope_) << endl;

	      // Generate schemes can create new scopes in the form of
	      // generated code. Scan the generate schemes, and *generate*
	      // new scopes, which is slightly different from simple
	      // elaboration.
	    typedef list<PGenerate*>::const_iterator generate_it_t;
	    for (generate_it_t cur = mod_->generate_schemes.begin()
		       ; cur != mod_->generate_schemes.end() ; cur ++ ) {
		  (*cur) -> generate_scope(des, scope_);
	    }
      }

    private:
	// The scope_ is the scope that contains the generate scheme
	// we are to work on. the mod_ is the Module definition for
	// that scope, and contains the parsed generate schemes.
      NetScope*scope_;
      Module*mod_;
};

bool Module::elaborate_scope(Design*des, NetScope*scope,
			     const replace_t&replacements)
{
      if (debug_scopes) {
	    cerr << get_fileline() << ": debug: Elaborate scope "
		 << scope_path(scope) << "." << endl;
      }

	// Generate all the parameters that this instance of this
	// module introduces to the design. This loop elaborates the
	// parameters, but doesn't evaluate references to
	// parameters. This scan practically locates all the
	// parameters and puts them in the parameter table in the
	// design.

	// No expressions are evaluated, yet. For now, leave them in
	// the pform and just place a NetEParam placeholder in the
	// place of the elaborated expression.

      typedef map<perm_string,param_expr_t>::const_iterator mparm_it_t;

	// This loop scans the parameters in the module, and creates
	// stub parameter entries in the scope for the parameter name.

      for (mparm_it_t cur = parameters.begin()
		 ; cur != parameters.end() ;  cur ++) {

	    NetEParam*tmp = new NetEParam;
	    tmp->set_line(*((*cur).second.expr));
	    tmp->cast_signed( (*cur).second.signed_flag );

	    scope->set_parameter((*cur).first, tmp, (*cur).second.type,
				 0, 0, false, 0, (*cur).second);
      }

      for (mparm_it_t cur = localparams.begin()
		 ; cur != localparams.end() ;  cur ++) {

	    NetEParam*tmp = new NetEParam;
	    tmp->set_line(*((*cur).second.expr));
	    if ((*cur).second.msb)
		  tmp->cast_signed( (*cur).second.signed_flag );

	    scope->set_parameter((*cur).first, tmp, (*cur).second.type,
				 0, 0, false, 0, (*cur).second);
      }


	// Now scan the parameters again, this time elaborating them
	// for use as parameter values. This is after the previous
	// scan so that local parameter names can be used in the
	// r-value expressions.

      for (mparm_it_t cur = parameters.begin()
		 ; cur != parameters.end() ;  cur ++) {

	    elaborate_parm_item_((*cur).first, (*cur).second, des, scope);
      }

	/* run parameter replacements that were collected from the
	   containing scope and meant for me. */
      for (replace_t::const_iterator cur = replacements.begin()
		 ; cur != replacements.end() ;  cur ++) {

	    NetExpr*val = (*cur).second;
	    if (val == 0) {
		  cerr << get_fileline() << ": internal error: "
		       << "Missing expression in parameter replacement for "
		       << (*cur).first;
	    }
	    assert(val);
	    if (debug_scopes) {
		  cerr << get_fileline() << ": debug: "
		       << "Replace " << (*cur).first
		       << " with expression " << *val
		       << " from " << val->get_fileline() << "." << endl;
		  cerr << get_fileline() << ":      : "
		       << "Type=" << val->expr_type() << endl;
	    }
	    bool flag = scope->replace_parameter((*cur).first, val);
	    if (! flag) {
		  cerr << val->get_fileline() << ": warning: parameter "
		       << (*cur).first << " not found in "
		       << scope_path(scope) << "." << endl;
	    }
      }

      for (mparm_it_t cur = localparams.begin()
		 ; cur != localparams.end() ;  cur ++) {

	    elaborate_parm_item_((*cur).first, (*cur).second, des, scope);
      }

	// Run through the defparams for this module, elaborate the
	// expressions in this context and save the result is a table
	// for later final override.

	// It is OK to elaborate the expressions of the defparam here
	// because Verilog requires that the expressions only use
	// local parameter names. It is *not* OK to do the override
	// here because the parameter receiving the assignment may be
	// in a scope not discovered by this pass.

      while (! defparms.empty()) {
	    Module::named_expr_t cur = defparms.front();
	    defparms.pop_front();

	    PExpr*ex = cur.second;
	    assert(ex);

	    NetExpr*val = ex->elaborate_pexpr(des, scope);
	    delete ex;
	    if (val == 0) continue;
	    scope->defparams.push_back(make_pair(cur.first, val));
      }

	// Evaluate the attributes. Evaluate them in the scope of the
	// module that the attribute is attached to. Is this correct?
      unsigned nattr;
      attrib_list_t*attr = evaluate_attributes(attributes, nattr, des, scope);

      for (unsigned idx = 0 ;  idx < nattr ;  idx += 1)
	    scope->attribute(attr[idx].key, attr[idx].val);

      delete[]attr;

	// Generate schemes need to have their scopes elaborated, but
	// we cannot do that until defparams are run, so push it off
	// into an elaborate work item.
      if (debug_scopes)
	    cerr << get_fileline() << ": debug: "
		 << "Schedule generates within " << scope_path(scope)
		 << " for elaboration after defparams." << endl;

      des->elaboration_work_list.push_back(new generate_schemes_work_item_t(des, scope, this));

	// Tasks introduce new scopes, so scan the tasks in this
	// module. Create a scope for the task and pass that to the
	// elaborate_scope method of the PTask for detailed
	// processing.

      elaborate_scope_tasks(des, scope, *this, tasks);


	// Functions are very similar to tasks, at least from the
	// perspective of scopes. So handle them exactly the same
	// way.

      elaborate_scope_funcs(des, scope, *this, funcs);

	// Gates include modules, which might introduce new scopes, so
	// scan all of them to create those scopes.

      typedef list<PGate*>::const_iterator gates_it_t;
      for (gates_it_t cur = gates_.begin()
		 ; cur != gates_.end() ;  cur ++ ) {

	    (*cur) -> elaborate_scope(des, scope);
      }


	// initial and always blocks may contain begin-end and
	// fork-join blocks that can introduce scopes. Therefore, I
	// get to scan processes here.

      typedef list<PProcess*>::const_iterator proc_it_t;

      for (proc_it_t cur = behaviors.begin()
		 ; cur != behaviors.end() ;  cur ++ ) {

	    (*cur) -> statement() -> elaborate_scope(des, scope);
      }

	// Scan through all the named events in this scope. We do not
	// need anything more than the current scope to do this
	// elaboration, so do it now. This allows for normal
	// elaboration to reference these events.

      for (map<perm_string,PEvent*>::const_iterator et = events.begin()
		 ; et != events.end() ;  et ++ ) {

	    (*et).second->elaborate_scope(des, scope);
      }

      return des->errors == 0;
}

bool PGenerate::generate_scope(Design*des, NetScope*container)
{
      switch (scheme_type) {
	  case GS_LOOP:
	    return generate_scope_loop_(des, container);

	  case GS_CONDIT:
	    return generate_scope_condit_(des, container, false);

	  case GS_ELSE:
	    return generate_scope_condit_(des, container, true);

	  case GS_CASE:
	    return generate_scope_case_(des, container);
	    return true;

	  case GS_CASE_ITEM:
	    cerr << get_fileline() << ": internal error: "
		 << "Case item outside of a case generate scheme?" << endl;
	    return false;

	  default:
	    cerr << get_fileline() << ": sorry: Generate of this sort"
		 << " is not supported yet!" << endl;
	    return false;
      }
}

/*
 * This is the elaborate scope method for a generate loop.
 */
bool PGenerate::generate_scope_loop_(Design*des, NetScope*container)
{
	// Check that the loop_index variable was declared in a
	// genvar statement.

	// MISSING CODE!

	// We're going to need a genvar...
      int genvar;

	// The initial value for the genvar does not need (nor can it
	// use) the genvar itself, so we can evaluate this expression
	// the same way any other parameter value is evaluated.
      NetExpr*init_ex = elab_and_eval(des, container, loop_init, -1);
      NetEConst*init = dynamic_cast<NetEConst*> (init_ex);
      if (init == 0) {
	    cerr << get_fileline() << ": error: Cannot evaluate genvar"
		 << " init expression: " << *loop_init << endl;
	    des->errors += 1;
	    return false;
      }

	// Since we will be adding the genvar value as a local parameter
	// to each instances scope. We need to make sure a parameter does
	// not already exist.
      const NetExpr*tmsb;
      const NetExpr*tlsb;
      const NetExpr*texpr = container->get_parameter(loop_index, tmsb, tlsb);
      if (texpr != 0) {
	    cerr << get_fileline() << ": error: Cannot have a genvar "
		 << "and parameter with the same name: " << loop_index << endl;
	    des->errors += 1;
	    return false;
      }

      genvar = init->value().as_long();
      delete init_ex;

      if (debug_scopes)
	    cerr << get_fileline() << ": debug: genvar init = " << genvar << endl;
      container->genvar_tmp = loop_index;
      container->genvar_tmp_val = genvar;
      NetExpr*test_ex = elab_and_eval(des, container, loop_test, -1);
      NetEConst*test = dynamic_cast<NetEConst*>(test_ex);
      assert(test);
      while (test->value().as_long()) {

	      // The actual name of the scope includes the genvar so
	      // that each instance has a unique name in the
	      // container. The format of using [] is part of the
	      // Verilog standard.
	    hname_t use_name (scope_name, genvar);
	    if (container->child(use_name)) {
		  cerr << get_fileline() << ": error: block/scope name "
		       << use_name << " already used in this context."
		       << endl;
		  des->errors += 1;
		  return false;
	    }
	    if (debug_scopes)
		  cerr << get_fileline() << ": debug: "
		       << "Create generated scope " << use_name << endl;

	    NetScope*scope = new NetScope(container, use_name,
					  NetScope::GENBLOCK);
	    scope->set_line(get_file(), get_lineno());

	      // Set in the scope a localparam for the value of the
	      // genvar within this instance of the generate
	      // block. Code within this scope thus has access to the
	      // genvar as a constant.
	    {
		  verinum genvar_verinum(genvar);
		  genvar_verinum.has_sign(true);
		  NetEConstParam*gp = new NetEConstParam(scope,
							 loop_index,
							 genvar_verinum);
		    // The file and line information should really come
		    // from the genvar statement, not the for loop.
		  scope->set_localparam(loop_index, gp, *this);
		  if (debug_scopes)
			cerr << get_fileline() << ": debug: "
			     << "Create implicit localparam "
			     << loop_index << " = " << genvar_verinum << endl;
	    }

	    elaborate_subscope_(des, scope);

	      // Calculate the step for the loop variable.
	    NetExpr*step_ex = elab_and_eval(des, container, loop_step, -1);
	    NetEConst*step = dynamic_cast<NetEConst*>(step_ex);
	    assert(step);
	    if (debug_scopes)
		  cerr << get_fileline() << ": debug: genvar step from "
		       << genvar << " to " << step->value().as_long() << endl;

	    genvar = step->value().as_long();
	    container->genvar_tmp_val = genvar;
	    delete step;
	    delete test_ex;
	    test_ex = elab_and_eval(des, container, loop_test, -1);
	    test = dynamic_cast<NetEConst*>(test_ex);
	    assert(test);
      }

	// Clear the genvar_tmp field in the scope to reflect that the
	// genvar is no longer value for evaluating expressions.
      container->genvar_tmp = perm_string();

      return true;
}

bool PGenerate::generate_scope_condit_(Design*des, NetScope*container, bool else_flag)
{
      NetExpr*test_ex = elab_and_eval(des, container, loop_test, -1);
      NetEConst*test = dynamic_cast<NetEConst*> (test_ex);
      assert(test);

	// If the condition evaluates as false, then do not create the
	// scope.
      if ( (test->value().as_long() == 0 && !else_flag)
	|| (test->value().as_long() != 0 &&  else_flag) ) {
	    if (debug_scopes)
		  cerr << get_fileline() << ": debug: Generate condition "
		       << (else_flag? "(else)" : "(if)")
		       << " value=" << test->value() << ": skip generation"
		       << endl;
	    delete test_ex;
	    return true;
      }

      hname_t use_name (scope_name);
      if (container->child(use_name)) {
	    cerr << get_fileline() << ": error: block/scope name "
		 << scope_name << " already used in this context."
		 << endl;
	    des->errors += 1;
	    return false;
      }
      if (debug_scopes)
	    cerr << get_fileline() << ": debug: Generate condition "
		 << (else_flag? "(else)" : "(if)")
		 << " value=" << test->value() << ": Generate scope="
		 << use_name << endl;

      NetScope*scope = new NetScope(container, use_name,
				    NetScope::GENBLOCK);
      scope->set_line(get_file(), get_lineno());

      elaborate_subscope_(des, scope);

      return true;
}

bool PGenerate::generate_scope_case_(Design*des, NetScope*container)
{
      NetExpr*case_value_ex = elab_and_eval(des, container, loop_test, -1);
      NetEConst*case_value_co = dynamic_cast<NetEConst*>(case_value_ex);
      assert(case_value_co);

	// The name of the scope to generate, whatever that item is.
      hname_t use_name (scope_name);

      if (debug_scopes)
	    cerr << get_fileline() << ": debug: Generate case "
		 << "switch value=" << case_value_co->value() << endl;

      PGenerate*default_item = 0;

      typedef list<PGenerate*>::const_iterator generator_it_t;
      generator_it_t cur = generate_schemes.begin();
      while (cur != generate_schemes.end()) {
	    PGenerate*item = *cur;
	    assert( item->scheme_type == PGenerate::GS_CASE_ITEM );

	      // Detect that the item is a default.
	    if (item->loop_test == 0) {
		  default_item = item;
		  cur ++;
		  continue;
	    }

	    NetExpr*item_value_ex = elab_and_eval(des, container, item->loop_test, -1);
	    NetEConst*item_value_co = dynamic_cast<NetEConst*>(item_value_ex);
	    assert(item_value_co);

	      // If we stumble on the item that matches, then break
	      // out now.
	    if (case_value_co->value() == item_value_co->value()) {
		  delete item_value_co;
		  break;
	    }

	    delete item_value_co;
	    cur ++;
      }

      delete case_value_co;
      case_value_co = 0;

      PGenerate*item = (cur == generate_schemes.end())? default_item : *cur;
      if (item == 0) {
	    cerr << get_fileline() << ": debug: "
		 << "No generate items found" << endl;
	    return true;
      }

      if (debug_scopes)
	    cerr << get_fileline() << ": debug: "
		 << "Generate case matches item at "
		 << item->get_fileline() << endl;

      NetScope*scope = new NetScope(container, use_name,
				    NetScope::GENBLOCK);
      scope->set_line(get_file(), get_lineno());
      item->elaborate_subscope_(des, scope);

      return true;
}

void PGenerate::elaborate_subscope_(Design*des, NetScope*scope)
{
	// Scan the generated scope for nested generate schemes,
	// and *generate* new scopes, which is slightly different
	// from simple elaboration.

      typedef list<PGenerate*>::const_iterator generate_it_t;
      for (generate_it_t cur = generate_schemes.begin()
		 ; cur != generate_schemes.end() ; cur ++ ) {
	    (*cur) -> generate_scope(des, scope);
      }

      elaborate_scope_tasks(des, scope, *this, tasks);
      elaborate_scope_funcs(des, scope, *this, funcs);

	// Scan the generated scope for gates that may create
	// their own scopes.
      typedef list<PGate*>::const_iterator pgate_list_it_t;
      for (pgate_list_it_t cur = gates.begin()
		 ; cur != gates.end() ;  cur ++) {
	    (*cur) ->elaborate_scope(des, scope);
      }

      typedef list<PProcess*>::const_iterator proc_it_t;
      for (proc_it_t cur = behaviors.begin()
		 ; cur != behaviors.end() ;  cur ++ ) {
	    (*cur) -> statement() -> elaborate_scope(des, scope);
      }

	// Save the scope that we created, for future use.
      scope_list_.push_back(scope);
}

class delayed_elaborate_scope_mod_instances : public elaborator_work_item_t {

    public:
      delayed_elaborate_scope_mod_instances(Design*des,
					    const PGModule*obj,
					    Module*mod,
					    NetScope*sc)
      : elaborator_work_item_t(des), obj_(obj), mod_(mod), sc_(sc)
      { }
      ~delayed_elaborate_scope_mod_instances() { }

      virtual void elaborate_runrun();

    private:
      const PGModule*obj_;
      Module*mod_;
      NetScope*sc_;
};

void delayed_elaborate_scope_mod_instances::elaborate_runrun()
{
      if (debug_scopes)
	    cerr << obj_->get_fileline() << ": debug: "
		 << "Resume scope elaboration of instances of "
		 << mod_->mod_name() << "." << endl;

      obj_->elaborate_scope_mod_instances_(des, mod_, sc_);
}

/*
 * Here we handle the elaborate scope of a module instance. The caller
 * has already figured out that this "gate" is a module, and has found
 * the module definition. The "sc" argument is the scope that will
 * contain this instance.
 */
void PGModule::elaborate_scope_mod_(Design*des, Module*mod, NetScope*sc) const
{
      if (get_name() == "") {
	    cerr << get_fileline() << ": error: Instantiation of module "
		 << mod->mod_name() << " requires an instance name." << endl;
	    des->errors += 1;
	    return;
      }

	// Missing module instance names have already been rejected.
      assert(get_name() != "");

	// Check for duplicate scopes. Simply look up the scope I'm
	// about to create, and if I find it then somebody beat me to
	// it.

      if (sc->child(hname_t(get_name()))) {
	    cerr << get_fileline() << ": error: Instance/Scope name " <<
		  get_name() << " already used in this context." <<
		  endl;
	    des->errors += 1;
	    return;
      }

	// check for recursive instantiation by scanning the current
	// scope and its parents. Look for a module instantiation of
	// the same module, but farther up in the scope.

      for (NetScope*scn = sc ;  scn ;  scn = scn->parent()) {
	    if (scn->type() != NetScope::MODULE)
		  continue;

	    if (strcmp(mod->mod_name(), scn->module_name()) != 0)
		  continue;

	    cerr << get_fileline() << ": error: You cannot instantiate "
		 << "module " << mod->mod_name() << " within itself." << endl;

	    cerr << get_fileline() << ":      : The offending instance is "
		 << scope_path(sc) << "." << get_name() << " within "
		 << scope_path(scn) << "." << endl;

	    des->errors += 1;
	    return;
      }

      if (msb_ || lsb_) {
	      // If there are expressions to evaluate in order to know
	      // the actual number of instances that will be
	      // instantiated, then we have to delay further scope
	      // elaboration until after defparams (above me) are
	      // run. Do that by appending a work item to the
	      // elaboration work list.
	    if (debug_scopes)
		  cerr << get_fileline() << ": debug: delay elaborate_scope"
		       << " of array of " << get_name()
		       << " in scope " << scope_path(sc) << "." << endl;

	    elaborator_work_item_t*tmp
		  = new delayed_elaborate_scope_mod_instances(des, this, mod, sc);
	    des->elaboration_work_list.push_back(tmp);

      } else {
	      // If there are no expressions that need to be evaluated
	      // to elaborate the scope of this next instances, then
	      // get right to it.
	    elaborate_scope_mod_instances_(des, mod, sc);
      }
}

/*
 * This method is called to process a module instantiation after basic
 * sanity testing is already complete.
 */
void PGModule::elaborate_scope_mod_instances_(Design*des, Module*mod, NetScope*sc) const
{
      NetExpr*mse = msb_ ? elab_and_eval(des, sc, msb_, -1) : 0;
      NetExpr*lse = lsb_ ? elab_and_eval(des, sc, lsb_, -1) : 0;
      NetEConst*msb = dynamic_cast<NetEConst*> (mse);
      NetEConst*lsb = dynamic_cast<NetEConst*> (lse);

      assert( (msb == 0) || (lsb != 0) );

      long instance_low  = 0;
      long instance_high = 0;
      long instance_count  = 1;
      bool instance_array = false;

      if (msb) {
	    instance_array = true;
	    instance_high = msb->value().as_long();
	    instance_low  = lsb->value().as_long();
	    if (instance_high > instance_low)
		  instance_count = instance_high - instance_low + 1;
	    else
		  instance_count = instance_low - instance_high + 1;

	    delete mse;
	    delete lse;
      }

      NetScope::scope_vec_t instances (instance_count);
      if (debug_scopes) {
	    cerr << get_fileline() << ": debug: Create " << instance_count
		 << " instances of " << get_name()
		 << "." << endl;
      }

	// Run through the module instances, and make scopes out of
	// them. Also do parameter overrides that are done on the
	// instantiation line.
      for (int idx = 0 ;  idx < instance_count ;  idx += 1) {

	    hname_t use_name (get_name());

	    if (instance_array) {
		  int instance_idx = idx;
		  if (instance_low < instance_high)
			instance_idx = instance_low + idx;
		  else
			instance_idx = instance_low - idx;

		  use_name = hname_t(get_name(), instance_idx);
	    }

	    if (debug_scopes) {
		  cerr << get_fileline() << ": debug: Module instance " << use_name
		       << " becomes child of " << scope_path(sc)
		       << "." << endl;
	    }

	      // Create the new scope as a MODULE with my name.
	    NetScope*my_scope = new NetScope(sc, use_name, NetScope::MODULE);
	    my_scope->set_line(get_file(), mod->get_file(),
	                       get_lineno(), mod->get_lineno());
	    my_scope->set_module_name(mod->mod_name());
	    my_scope->default_nettype(mod->default_nettype);

	    instances[idx] = my_scope;

	      // Set time units and precision.
	    my_scope->time_unit(mod->time_unit);
	    my_scope->time_precision(mod->time_precision);
	    des->set_precision(mod->time_precision);

	      // Look for module parameter replacements. The "replace" map
	      // maps parameter name to replacement expression that is
	      // passed. It is built up by the ordered overrides or named
	      // overrides.

	    typedef map<perm_string,PExpr*>::const_iterator mparm_it_t;
	    map<perm_string,PExpr*> replace;


	      // Positional parameter overrides are matched to parameter
	      // names by using the param_names list of parameter
	      // names. This is an ordered list of names so the first name
	      // is parameter 0, the second parameter 1, and so on.

	    if (overrides_) {
		  assert(parms_ == 0);
		  list<perm_string>::const_iterator cur
			= mod->param_names.begin();
		  unsigned idx = 0;
		  for (;;) {
			if (idx >= overrides_->count())
			      break;
			if (cur == mod->param_names.end())
			      break;

			replace[*cur] = (*overrides_)[idx];

			idx += 1;
			cur ++;
		  }
	    }

	      // Named parameter overrides carry a name with each override
	      // so the mapping into the replace list is much easier.
	    if (parms_) {
		  assert(overrides_ == 0);
		  for (unsigned idx = 0 ;  idx < nparms_ ;  idx += 1)
			replace[parms_[idx].name] = parms_[idx].parm;

	    }


	    Module::replace_t replace_net;

	      // And here we scan the replacements we collected. Elaborate
	      // the expression in my context, then replace the sub-scope
	      // parameter value with the new expression.

	    for (mparm_it_t cur = replace.begin()
		       ; cur != replace.end() ;  cur ++ ) {

		  PExpr*tmp = (*cur).second;
		    // No expression means that the parameter is not
		    // replaced at all.
		  if (tmp == 0)
			continue;
		  NetExpr*val = tmp->elaborate_pexpr(des, sc);
		  replace_net[(*cur).first] = val;
	    }

	      // This call actually arranges for the description of the
	      // module type to process this instance and handle parameters
	      // and sub-scopes that might occur. Parameters are also
	      // created in that scope, as they exist. (I'll override them
	      // later.)
	    mod->elaborate_scope(des, my_scope, replace_net);

      }

	/* Stash the instance array of scopes into the parent
	   scope. Later elaboration passes will use this vector to
	   further elaborate the array.

	   Note that the array is ordered from LSB to MSB. We will use
	   that fact in the main elaborate to connect things in the
	   correct order. */
      sc->instance_arrays[get_name()] = instances;
}

/*
 * The isn't really able to create new scopes, but it does create the
 * event name in the current scope, so can be done during the
 * elaborate_scope scan. Note that the name_ of the PEvent object has
 * no hierarchy, but neither does the NetEvent, until it is stored in
 * the NetScope object.
 */
void PEvent::elaborate_scope(Design*des, NetScope*scope) const
{
      NetEvent*ev = new NetEvent(name_);
      ev->set_line(*this);
      scope->add_event(ev);
}

void PFunction::elaborate_scope(Design*des, NetScope*scope) const
{
      assert(scope->type() == NetScope::FUNC);

      if (statement_)
	    statement_->elaborate_scope(des, scope);
}

void PTask::elaborate_scope(Design*des, NetScope*scope) const
{
      assert(scope->type() == NetScope::TASK);

      if (statement_)
	    statement_->elaborate_scope(des, scope);
}


/*
 * The base statement does not have sub-statements and does not
 * introduce any scope, so this is a no-op.
 */
void Statement::elaborate_scope(Design*, NetScope*) const
{
}

/*
 * When I get a behavioral block, check to see if it has a name. If it
 * does, then create a new scope for the statements within it,
 * otherwise use the current scope. Use the selected scope to scan the
 * statements that I contain.
 */
void PBlock::elaborate_scope(Design*des, NetScope*scope) const
{
      NetScope*my_scope = scope;

      if (pscope_name() != 0) {
	    hname_t use_name(pscope_name());
	    if (scope->child(use_name)) {
		  cerr << get_fileline() << ": error: block/scope name "
		       << use_name << " already used in this context."
		       << endl;
		  des->errors += 1;
		  return;
	    }
	    my_scope = new NetScope(scope, use_name, bl_type_==BL_PAR
				    ? NetScope::FORK_JOIN
				    : NetScope::BEGIN_END);
	    my_scope->set_line(get_file(), get_lineno());
      }

      for (unsigned idx = 0 ;  idx < list_.count() ;  idx += 1)
	    list_[idx] -> elaborate_scope(des, my_scope);

}

/*
 * The case statement itself does not introduce scope, but contains
 * other statements that may be named blocks. So scan the case items
 * with the elaborate_scope method.
 */
void PCase::elaborate_scope(Design*des, NetScope*scope) const
{
      assert(items_);
      for (unsigned idx = 0 ;  idx < (*items_).count() ;  idx += 1) {
	    assert( (*items_)[idx] );

	    if (Statement*sp = (*items_)[idx]->stat)
		  sp -> elaborate_scope(des, scope);
      }
}

/*
 * The conditional statement (if-else) does not introduce scope, but
 * the statements of the clauses may, so elaborate_scope the contained
 * statements.
 */
void PCondit::elaborate_scope(Design*des, NetScope*scope) const
{
      if (if_)
	    if_ -> elaborate_scope(des, scope);

      if (else_)
	    else_ -> elaborate_scope(des, scope);
}

/*
 * Statements that contain a further statement but do not
 * intrinsically add a scope need to elaborate_scope the contained
 * statement.
 */
void PDelayStatement::elaborate_scope(Design*des, NetScope*scope) const
{
      if (statement_)
	    statement_ -> elaborate_scope(des, scope);
}

/*
 * Statements that contain a further statement but do not
 * intrinsically add a scope need to elaborate_scope the contained
 * statement.
 */
void PEventStatement::elaborate_scope(Design*des, NetScope*scope) const
{
      if (statement_)
	    statement_ -> elaborate_scope(des, scope);
}

/*
 * Statements that contain a further statement but do not
 * intrinsically add a scope need to elaborate_scope the contained
 * statement.
 */
void PForever::elaborate_scope(Design*des, NetScope*scope) const
{
      if (statement_)
	    statement_ -> elaborate_scope(des, scope);
}

/*
 * Statements that contain a further statement but do not
 * intrinsically add a scope need to elaborate_scope the contained
 * statement.
 */
void PForStatement::elaborate_scope(Design*des, NetScope*scope) const
{
      if (statement_)
	    statement_ -> elaborate_scope(des, scope);
}

/*
 * Statements that contain a further statement but do not
 * intrinsically add a scope need to elaborate_scope the contained
 * statement.
 */
void PRepeat::elaborate_scope(Design*des, NetScope*scope) const
{
      if (statement_)
	    statement_ -> elaborate_scope(des, scope);
}

/*
 * Statements that contain a further statement but do not
 * intrinsically add a scope need to elaborate_scope the contained
 * statement.
 */
void PWhile::elaborate_scope(Design*des, NetScope*scope) const
{
      if (statement_)
	    statement_ -> elaborate_scope(des, scope);
}