iverilog/elab_lval.cc

/*
 * Copyright (c) 2000-2019 Stephen Williams (steve@icarus.com)
 * Copyright CERN 2012-2013 / 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  "PExpr.h"
# include  "PPackage.h"
# include  "netlist.h"
# include  "netmisc.h"
# include  "netstruct.h"
# include  "netclass.h"
# include  "netdarray.h"
# include  "netparray.h"
# include  "netvector.h"
# include  "netenum.h"
# include  "compiler.h"
# include  <cstdlib>
# include  <iostream>
# include  <climits>
# include  "ivl_assert.h"

/*
 * These methods generate a NetAssign_ object for the l-value of the
 * assignment. This is common code for the = and <= statements.
 *
 * What gets generated depends on the structure of the l-value. If the
 * l-value is a simple name (i.e., foo <= <value>) then the NetAssign_
 * is created the width of the foo reg and connected to all the
 * bits.
 *
 * If there is a part select (i.e., foo[3:1] <= <value>) the NetAssign_
 * is made only as wide as it needs to be (3 bits in this example) and
 * connected to the correct bits of foo. A constant bit select is a
 * special case of the part select.
 *
 * If the bit-select is non-constant (i.e., foo[<expr>] = <value>) the
 * NetAssign_ is made wide enough to connect to all the bits of foo,
 * then the mux expression is elaborated and attached to the
 * NetAssign_ node as a b_mux value. The target must interpret the
 * presence of a bmux value as taking a single bit and assigning it to
 * the bit selected by the bmux expression.
 *
 * If the l-value expression is non-trivial, but can be fully
 * evaluated at compile time (meaning any bit selects are constant)
 * then elaboration will make a single NetAssign_ that connects to a
 * synthetic reg that in turn connects to all the proper pins of the
 * l-value.
 *
 * This last case can turn up in statements like: {a, b[1]} = c;
 * rather than create a NetAssign_ for each item in the concatenation,
 * elaboration makes a single NetAssign_ and connects it up properly.
 */


/*
 * The default interpretation of an l-value to a procedural assignment
 * is to try to make a net elaboration, and see if the result is
 * suitable for assignment.
 */
NetAssign_* PExpr::elaborate_lval(Design*, NetScope*, bool, bool) const
{
      cerr << get_fileline() << ": Assignment l-value too complex." << endl;
      return 0;
}

/*
 * Concatenation expressions can appear as l-values. Handle them here.
 *
 * If adjacent l-values in the concatenation are not bit selects, then
 * merge them into a single NetAssign_ object. This can happen is code
 * like ``{ ...a, b, ...}''. As long as "a" and "b" do not have bit
 * selects (or the bit selects are constant) we can merge the
 * NetAssign_ objects.
 *
 * Be careful to get the bit order right. In the expression ``{a, b}''
 * a is the MSB and b the LSB. Connect the LSB to the low pins of the
 * NetAssign_ object.
 */
NetAssign_* PEConcat::elaborate_lval(Design*des,
				     NetScope*scope,
				     bool is_cassign,
				     bool is_force) const
{
      if (repeat_) {
	    cerr << get_fileline() << ": error: Repeat concatenations make "
		  "no sense in l-value expressions. I refuse." << endl;
	    des->errors += 1;
	    return 0;
      }

      NetAssign_*res = 0;

      for (unsigned idx = 0 ;  idx < parms_.size() ;  idx += 1) {

	    if (parms_[idx] == 0) {
		  cerr << get_fileline() << ": error: Empty expressions "
		       << "not allowed in concatenations." << endl;
		  des->errors += 1;
		  continue;
	    }

	    NetAssign_*tmp = parms_[idx]->elaborate_lval(des, scope,
							 is_cassign, is_force);

	      /* If the l-value doesn't elaborate, the error was
		 already detected and printed. We just skip it and let
		 the compiler catch more errors. */
	    if (tmp == 0) continue;

	    if (tmp->expr_type() == IVL_VT_REAL) {
		  cerr << parms_[idx]->get_fileline() << ": error: "
		       << "concatenation operand can not be real: "
		       << *parms_[idx] << endl;
		  des->errors += 1;
		  continue;
	    }

	      /* A concatenation is always unsigned. */
	    tmp->set_signed(false);

	      /* Link the new l-value to the previous one. */
	    NetAssign_*last = tmp;
	    while (last->more)
		  last = last->more;

	    last->more = res;
	    res = tmp;
      }

      return res;
}


/*
 * Handle the ident as an l-value. This includes bit and part selects
 * of that ident.
 */
NetAssign_* PEIdent::elaborate_lval(Design*des,
				    NetScope*scope,
				    bool is_cassign,
				    bool is_force) const
{
      NetNet*       reg = 0;
      const NetExpr*par = 0;
      NetEvent*     eve = 0;

      if (debug_elaborate) {
	    cerr << get_fileline() << ": PEIdent::elaborate_lval: "
		 << "Elaborate l-value ident expression: " << *this << endl;
      }

	/* Try to detect the special case that we are in a method and
	   the identifier is a member of the class. */
      if (NetAssign_*tmp = elaborate_lval_method_class_member_(des, scope))
	    return tmp;

	/* Normally find the name in the passed scope. But if this is
	   imported from a package, then located the variable from the
	   package scope. */
      NetScope*use_scope = scope;
      if (package_) {
	    use_scope = des->find_package(package_->pscope_name());
	    ivl_assert(*this, use_scope);
      }

	/* Try to find the base part of the path that names the
	   variable. The remainer is the member path. For example, if
	   the path is a.b.c.d, and a.b is the path to a variable,
	   then a.b becomes the base_path and c.d becomes the
	   member_path. If we cannot find the variable with any
	   prefix, then the base_path will be empty after this loop
	   and reg will remain nil. */
      pform_name_t base_path = path_;
      pform_name_t member_path;
      while (reg == 0 && base_path.size() > 0) {
	    symbol_search(this, des, use_scope, base_path, reg, par, eve);
	      // Found it!
	    if (reg != 0) break;
	      // Not found. Try to pop another name off the base_path
	      // and push it to the front of the member_path.
	    member_path.push_front( base_path.back() );
	    base_path.pop_back();
      }


	/* The l-value must be a variable. If not, then give up and
	   print a useful error message. */
      if (reg == 0) {
	    if (use_scope->type()==NetScope::FUNC
		&& use_scope->func_def()->is_void()
		&& use_scope->basename()==peek_tail_name(path_)) {
		  cerr << get_fileline() << ": error: "
		       << "Cannot assign to " << path_
		       << " because function " << scope_path(use_scope)
		       << " is void." << endl;
	    } else {
		  cerr << get_fileline() << ": error: Could not find variable ``"
		       << path_ << "'' in ``" << scope_path(use_scope) <<
			"''" << endl;
	    }
	    des->errors += 1;
	    return 0;
      }

      ivl_assert(*this, reg);

      if (debug_elaborate) {
	    cerr << get_fileline() << ": PEIdent::elaborate_lval: "
		 << "Found l-value path_=" << path_
		 << " as reg=" << reg->name()
		 << ", reg->type()=" << reg->type()
		 << " base_path=" << base_path
		 << ", member_path=" << member_path
		 << " unpacked_dimensions()=" << reg->unpacked_dimensions() << endl;
      }

	// We are processing the tail of a string of names. For
	// example, the Verilog may be "a.b.c", so we are processing
	// "c" at this point.
      const name_component_t&name_tail = path_.back();

	// Use the last index to determine what kind of select
	// (bit/part/etc) we are processing. For example, the Verilog
	// may be "a.b.c[1][2][<index>]". All but the last index must
	// be simple expressions, only the <index> may be a part
	// select etc., so look at it to determine how we will be
	// proceeding.
      index_component_t::ctype_t use_sel = index_component_t::SEL_NONE;
      if (!name_tail.index.empty())
	    use_sel = name_tail.index.back().sel;

	// Special case: The l-value is an entire memory, or array
	// slice. This is, in fact, an error in l-values. Detect the
	// situation by noting if the index count is less than the
	// array dimensions (unpacked).
      if (reg->unpacked_dimensions() > name_tail.index.size()) {
	    cerr << get_fileline() << ": error: Cannot assign to array "
		 << path_ << ". Did you forget a word index?" << endl;
	    des->errors += 1;
	    return 0;
      }

	/* Get the signal referenced by the identifier, and make sure
	   it is a register. Wires are not allowed in this context,
	   unless this is the l-value of a force. */
      if ((reg->type() != NetNet::REG)
	  && (reg->type() != NetNet::UNRESOLVED_WIRE)
	  && !is_force) {
	    cerr << get_fileline() << ": error: " << path_ <<
		  " is not a valid l-value in " << scope_path(use_scope) <<
		  "." << endl;
	    cerr << reg->get_fileline() << ":      : " << path_ <<
		  " is declared here as " << reg->type() << "." << endl;
	    des->errors += 1;
	    return 0;
      }


	// If we find that the matched variable is a packed struct,
	// then we can handled it with the net_packed_member_ method.
      if (reg->struct_type() && member_path.size() > 0) {
	    NetAssign_*lv = new NetAssign_(reg);
	    elaborate_lval_net_packed_member_(des, use_scope, lv, member_path);
	    return lv;
      }

	// If the variable is a class object, then handle it with the
	// net_class_member_ method.
      if (reg->class_type() && member_path.size() > 0 && gn_system_verilog()) {
	    NetAssign_*lv = elaborate_lval_net_class_member_(des, use_scope, reg, member_path);
	    return lv;
      }


	// Past this point, we should have taken care of the cases
	// where the name is a member/method of a struct/class.
	// XXXX ivl_assert(*this, method_name.nil());
      ivl_assert(*this, member_path.size() == 0);

      bool need_const_idx = is_cassign || is_force || (reg->type()==NetNet::UNRESOLVED_WIRE);

      if (reg->unpacked_dimensions() > 0)
	    return elaborate_lval_net_word_(des, scope, reg, need_const_idx);

	// This must be after the array word elaboration above!
      if (reg->get_scalar() &&
          use_sel != index_component_t::SEL_NONE) {
	    cerr << get_fileline() << ": error: can not select part of ";
	    if (reg->data_type() == IVL_VT_REAL) cerr << "real: ";
	    else cerr << "scalar: ";
	    cerr << reg->name() << endl;
	    des->errors += 1;
	    return 0;
      }

      if (use_sel == index_component_t::SEL_PART) {
	    NetAssign_*lv = new NetAssign_(reg);
	    elaborate_lval_net_part_(des, scope, lv);
	    return lv;
      }

      if (use_sel == index_component_t::SEL_IDX_UP ||
          use_sel == index_component_t::SEL_IDX_DO) {
	    NetAssign_*lv = new NetAssign_(reg);
	    elaborate_lval_net_idx_(des, scope, lv, use_sel, need_const_idx);
	    return lv;
      }


      if (use_sel == index_component_t::SEL_BIT) {
	    if (reg->darray_type()) {
		  NetAssign_*lv = new NetAssign_(reg);
		  elaborate_lval_darray_bit_(des, scope, lv);
		  return lv;
	    } else {
		  NetAssign_*lv = new NetAssign_(reg);
		  elaborate_lval_net_bit_(des, scope, lv, need_const_idx);
		  return lv;
	    }
      }

      ivl_assert(*this, use_sel == index_component_t::SEL_NONE);

      if (reg->type()==NetNet::UNRESOLVED_WIRE && !is_force) {
	    cerr << get_fileline() << ": error: "
		 << path_ << " Unable to assign to unresolved wires."
		 << endl;
	    des->errors += 1;
	    return 0;
      }

	/* No select expressions. */

      NetAssign_*lv = new NetAssign_(reg);
      lv->set_signed(reg->get_signed());

      return lv;
}

NetAssign_* PEIdent::elaborate_lval_method_class_member_(Design*des,
							 NetScope*scope) const
{
      if (!gn_system_verilog())
	    return 0;
      if (scope->parent() == 0 || scope->type() == NetScope::CLASS)
	    return 0;
      if (path_.size() != 1)
	    return 0;

      const netclass_t*class_type = find_class_containing_scope(*this, scope);
      if (class_type == 0)
	    return 0;

      const name_component_t&name_comp = path_.back();

      perm_string member_name = name_comp.name;
      int pidx = class_type->property_idx_from_name(member_name);
      if (pidx < 0)
	    return 0;

      NetScope*scope_method = find_method_containing_scope(*this, scope);
      ivl_assert(*this, scope_method);

      NetNet*this_net = scope_method->find_signal(perm_string::literal(THIS_TOKEN));
      if (this_net == 0) {
	    cerr << get_fileline() << ": internal error: "
		 << "Unable to find 'this' port of " << scope_path(scope_method)
		 << "." << endl;
	    return 0;
      }

      if (debug_elaborate) {
	    cerr << get_fileline() << ": PEIdent::elaborate_lval_method_class_member_: "
		 << "Ident " << member_name
		 << " is a property of class " << class_type->get_name() << endl;
      }

      NetExpr*canon_index = 0;
      if (! name_comp.index.empty()) {
	    ivl_type_t property_type = class_type->get_prop_type(pidx);

	    if (const netsarray_t* stype = dynamic_cast<const netsarray_t*> (property_type)) {
		  canon_index = make_canonical_index(des, scope, this,
						     name_comp.index, stype, false);

	    } else {
		  cerr << get_fileline() << ": error: "
		       << "Index expressions don't apply to this type of property." << endl;
		  des->errors += 1;
	    }
      }

	// Detect assignment to constant properties. Note that the
	// initializer constructor MAY assign to constant properties,
	// as this is how the property gets its value.
      property_qualifier_t qual = class_type->get_prop_qual(pidx);
      if (qual.test_const()) {
	    if (class_type->get_prop_initialized(pidx)) {
		  cerr << get_fileline() << ": error: "
		       << "Property " << class_type->get_prop_name(pidx)
		       << " is constant in this method."
		       << " (scope=" << scope_path(scope) << ")" << endl;
		  des->errors += 1;

	    } else if (scope->basename()!="new" && scope->basename()!="new@") {
		  cerr << get_fileline() << ": error: "
		       << "Property " << class_type->get_prop_name(pidx)
		       << " is constant in this method."
		       << " (scope=" << scope_path(scope) << ")" << endl;
		  des->errors += 1;

	    } else {

		    // Mark this property as initialized. This is used
		    // to know that we have initialized the constant
		    // object so the next assignment will be marked as
		    // illegal.
		  class_type->set_prop_initialized(pidx);

		  if (debug_elaborate) {
			cerr << get_fileline() << ": PEIdent::elaborate_lval_method_class_member_: "
			     << "Found initializers for property " << class_type->get_prop_name(pidx) << endl;
		  }
	    }
      }

      ivl_type_t tmp_type = class_type->get_prop_type(pidx);
      if (const netuarray_t*tmp_ua = dynamic_cast<const netuarray_t*>(tmp_type)) {

	    const std::vector<netrange_t>&dims = tmp_ua->static_dimensions();

	    if (debug_elaborate) {
		  cerr << get_fileline() << ": PEIdent::elaborate_lval_method_class_member_: "
		       << "Property " << class_type->get_prop_name(pidx)
		       << " has " << dims.size() << " dimensions, "
		       << " got " << name_comp.index.size() << " indices." << endl;
		  if (canon_index) {
			cerr << get_fileline() << ": PEIdent::elaborate_lval_method_class_member_: "
			     << "Canonical index is:" << *canon_index << endl;
		  };
	    }

	    if (dims.size() != name_comp.index.size()) {
		  cerr << get_fileline() << ": error: "
		       << "Got " << name_comp.index.size() << " indices, "
		       << "expecting " << dims.size()
		       << " to index the property " << class_type->get_prop_name(pidx) << "." << endl;
		  des->errors += 1;
	    }
      }

      NetAssign_*this_lval = new NetAssign_(this_net);
      this_lval->set_property(member_name);
      if (canon_index) this_lval->set_word(canon_index);

      return this_lval;
}

NetAssign_* PEIdent::elaborate_lval_net_word_(Design*des,
					      NetScope*scope,
					      NetNet*reg,
					      bool need_const_idx) const
{
      const name_component_t&name_tail = path_.back();
      ivl_assert(*this, !name_tail.index.empty());

      if (debug_elaborate) {
	    cerr << get_fileline() << ": PEIdent::elaborate_lval_net_word_: "
		 << "Handle as n-dimensional array." << endl;
      }

      if (name_tail.index.size() < reg->unpacked_dimensions()) {
	    cerr << get_fileline() << ": error: Array " << reg->name()
		 << " needs " << reg->unpacked_dimensions() << " indices,"
		 << " but got only " << name_tail.index.size() << "." << endl;
	    des->errors += 1;
	    return 0;
      }

	// Make sure there are enough indices to address an array element.
      const index_component_t&index_head = name_tail.index.front();
      if (index_head.sel == index_component_t::SEL_PART) {
	    cerr << get_fileline() << ": error: cannot perform a part "
	         << "select on array " << reg->name() << "." << endl;
	    des->errors += 1;
	    return 0;
      }


	// Evaluate all the index expressions into an
	// "unpacked_indices" array.
      list<NetExpr*>unpacked_indices;
      list<long> unpacked_indices_const;
      indices_flags flags;
      indices_to_expressions(des, scope, this,
			     name_tail.index, reg->unpacked_dimensions(),
			     false,
			     flags,
			     unpacked_indices,
			     unpacked_indices_const);

      NetExpr*canon_index = 0;
      if (flags.invalid) {
	    // Nothing to do.

      } else if (flags.undefined) {
	    cerr << get_fileline() << ": warning: "
		 << "ignoring undefined l-value array access "
		 << reg->name() << as_indices(unpacked_indices)
		 << "." << endl;

      } else if (flags.variable) {
	    if (need_const_idx) {
		  cerr << get_fileline() << ": error: array '" << reg->name()
		       << "' index must be a constant in this context." << endl;
		  des->errors += 1;
		  return 0;
	    }
	    ivl_assert(*this, unpacked_indices.size() == reg->unpacked_dimensions());
	    canon_index = normalize_variable_unpacked(reg, unpacked_indices);

      } else {
	    ivl_assert(*this, unpacked_indices_const.size() == reg->unpacked_dimensions());
	    canon_index = normalize_variable_unpacked(reg, unpacked_indices_const);

	    if (canon_index == 0) {
		  cerr << get_fileline() << ": warning: "
		       << "ignoring out of bounds l-value array access "
		       << reg->name() << as_indices(unpacked_indices_const)
		       << "." << endl;
	    }
      }

	// Ensure invalid array accesses are ignored.
      if (canon_index == 0)
	    canon_index = new NetEConst(verinum(verinum::Vx));
      canon_index->set_line(*this);

      if (debug_elaborate) {
	    cerr << get_fileline() << ": PEIdent::elaborate_lval_net_word_: "
		 << "canon_index=" << *canon_index << endl;
      }

      if (reg->type()==NetNet::UNRESOLVED_WIRE) {
	    cerr << get_fileline() << ": error: "
		 << "Unable to assign words of unresolved wire array." << endl;
	    des->errors += 1;
	    return 0;
      }

      NetAssign_*lv = new NetAssign_(reg);
      lv->set_word(canon_index);

      if (debug_elaborate)
	    cerr << get_fileline() << ": debug: Set array word=" << *canon_index << endl;


	/* An array word may also have part selects applied to them. */

      index_component_t::ctype_t use_sel = index_component_t::SEL_NONE;
      if (name_tail.index.size() > reg->unpacked_dimensions())
	    use_sel = name_tail.index.back().sel;

      if (reg->get_scalar() &&
          use_sel != index_component_t::SEL_NONE) {
	    cerr << get_fileline() << ": error: can not select part of ";
	    if (reg->data_type() == IVL_VT_REAL) cerr << "real";
	    else cerr << "scalar";
	    cerr << " array word: " << reg->name()
	         << as_indices(unpacked_indices) << endl;
	    des->errors += 1;
	    return 0;
      }

      if (use_sel == index_component_t::SEL_BIT)
	    elaborate_lval_net_bit_(des, scope, lv, need_const_idx);

      if (use_sel == index_component_t::SEL_PART)
	    elaborate_lval_net_part_(des, scope, lv);

      if (use_sel == index_component_t::SEL_IDX_UP ||
          use_sel == index_component_t::SEL_IDX_DO)
	    elaborate_lval_net_idx_(des, scope, lv, use_sel, need_const_idx);

      return lv;
}

bool PEIdent::elaborate_lval_net_bit_(Design*des,
				      NetScope*scope,
				      NetAssign_*lv,
				      bool need_const_idx) const
{
      list<long>prefix_indices;
      bool rc = calculate_packed_indices_(des, scope, lv->sig(), prefix_indices);
      if (!rc) return false;

      const name_component_t&name_tail = path_.back();
      ivl_assert(*this, !name_tail.index.empty());

      const index_component_t&index_tail = name_tail.index.back();
      ivl_assert(*this, index_tail.msb != 0);
      ivl_assert(*this, index_tail.lsb == 0);

      NetNet*reg = lv->sig();
      ivl_assert(*this, reg);

	// Bit selects have a single select expression. Evaluate the
	// constant value and treat it as a part select with a bit
	// width of 1.
      NetExpr*mux = elab_and_eval(des, scope, index_tail.msb, -1);
      long lsb = 0;

      if (NetEConst*index_con = dynamic_cast<NetEConst*> (mux)) {
	      // The index has a constant defined value.
	    if (index_con->value().is_defined()) {
		  lsb = index_con->value().as_long();
		  mux = 0;
	      // The index is undefined and this is a packed array.
	    } else if (prefix_indices.size()+2 <= reg->packed_dims().size()) {
		  long loff;
		  unsigned long lwid;
		  bool rcl = reg->sb_to_slice(prefix_indices, lsb, loff, lwid);
		  ivl_assert(*this, rcl);
		  if (warn_ob_select) {
			cerr << get_fileline()
			     << ": warning: L-value packed array select of "
			     << reg->name();
			if (reg->unpacked_dimensions() > 0) cerr << "[]";
			cerr << " has an undefined index." << endl;
		  }
		  lv->set_part(new NetEConst(verinum(verinum::Vx)), lwid);
		  return true;
	      // The index is undefined and this is a bit select.
	    } else {
		  if (warn_ob_select) {
			cerr << get_fileline()
			     << ": warning: L-value bit select of "
			     << reg->name();
			if (reg->unpacked_dimensions() > 0) cerr << "[]";
			cerr << " has an undefined index." << endl;
		  }
		  lv->set_part(new NetEConst(verinum(verinum::Vx)), 1);
		  return true;
	    }
      }

      if (debug_elaborate && (reg->type()==NetNet::UNRESOLVED_WIRE)) {
	    cerr << get_fileline() << ": PEIdent::elaborate_lval_net_bit_: "
		 << "Try to assign bits of unresolved wire."
		 << endl;
      }

	// Notice that we might be assigning to an unresolved wire. This
	// can happen if we are actually assigning to a variable that
	// has a partial continuous assignment to it. If that is the
	// case, then the bit select must be constant.
      ivl_assert(*this, need_const_idx || (reg->type()!=NetNet::UNRESOLVED_WIRE));


      if (prefix_indices.size()+2 <= reg->packed_dims().size()) {
	      // Special case: this is a slice of a multi-dimensional
	      // packed array. For example:
	      //   reg [3:0][7:0] x;
	      //   x[2] = ...
	      // This shows up as the prefix_indices being too short
	      // for the packed dimensions of the vector. What we do
	      // here is convert to a "slice" of the vector.
	    if (mux == 0) {
		  long loff;
		  unsigned long lwid;
		  bool rcl = reg->sb_to_slice(prefix_indices, lsb, loff, lwid);
		  ivl_assert(*this, rcl);

		  if (reg->type()==NetNet::UNRESOLVED_WIRE) {
			bool rct = reg->test_and_set_part_driver(loff+lwid-1, loff);
			if (rct) {
			      cerr << get_fileline() << ": error: "
				   << "These bits are already driven." << endl;
			      des->errors += 1;
			}
		  }

		  lv->set_part(new NetEConst(verinum(loff)), lwid);

	    } else {
		  ivl_assert(*this, reg->type()!=NetNet::UNRESOLVED_WIRE);
		  unsigned long lwid;
		  mux = normalize_variable_slice_base(prefix_indices, mux,
						      reg, lwid);
		  lv->set_part(mux, lwid);
	    }

      } else if (reg->data_type() == IVL_VT_STRING) {
	    ivl_assert(*this, reg->type()!=NetNet::UNRESOLVED_WIRE);
	      // Special case: This is a select of a string
	      // variable. The target of the assignment is a character
	      // select of a string. Force the r-value to be an 8bit
	      // vector and set the "part" to be the character select
	      // expression. The code generator knows what to do with
	      // this.
	    if (debug_elaborate) {
		  cerr << get_fileline() << ": debug: "
		       << "Bit select of string becomes character select." << endl;
	    }
	    if (mux)
		  lv->set_part(mux, 8);
	    else
		  lv->set_part(new NetEConst(verinum(lsb)), 8);

      } else if (mux) {
	    ivl_assert(*this, reg->type()!=NetNet::UNRESOLVED_WIRE);

	      // Non-constant bit mux. Correct the mux for the range
	      // of the vector, then set the l-value part select
	      // expression.
	    if (need_const_idx) {
		  cerr << get_fileline() << ": error: '" << reg->name()
		       << "' bit select must be a constant in this context."
		       << endl;
		  des->errors += 1;
		  return false;
	    }
	    mux = normalize_variable_bit_base(prefix_indices, mux, reg);
	    lv->set_part(mux, 1);

      } else if (reg->vector_width() == 1 && reg->sb_is_valid(prefix_indices,lsb)) {
	      // Constant bit mux that happens to select the only bit
	      // of the l-value. Don't bother with any select at all.

	      // NOTE: Don't know what to do about unresolved wires
	      // here, but they are probably wrong.
	    ivl_assert(*this, reg->type()!=NetNet::UNRESOLVED_WIRE);

      } else {
	      // Constant bit select that does something useful.
	    long loff = reg->sb_to_idx(prefix_indices,lsb);

	    if (warn_ob_select && (loff < 0 || loff >= (long)reg->vector_width())) {
		  cerr << get_fileline() << ": warning: bit select "
		       << reg->name() << "[" <<lsb<<"]"
		       << " is out of range." << endl;
	    }

	    if (reg->type()==NetNet::UNRESOLVED_WIRE) {
		  bool rct = reg->test_and_set_part_driver(loff, loff);
		  if (rct) {
			cerr << get_fileline() << ": error: "
			     << "Bit " << loff << " is already driven." << endl;
			des->errors += 1;
		  }
	    }

	    lv->set_part(new NetEConst(verinum(loff)), 1);
      }

      return true;
}

bool PEIdent::elaborate_lval_darray_bit_(Design*des, NetScope*scope, NetAssign_*lv)const
{
      const name_component_t&name_tail = path_.back();
      ivl_assert(*this, !name_tail.index.empty());

	// For now, only support single-dimension dynamic arrays.
      ivl_assert(*this, name_tail.index.size() == 1);

      if (lv->sig()->type()==NetNet::UNRESOLVED_WIRE) {
	    cerr << get_fileline() << ": error: "
		 << path_ << " Unable to darray word select unresolved wires."
		 << endl;
	    des->errors += 1;
	    return false;
      }

      const index_component_t&index_tail = name_tail.index.back();
      ivl_assert(*this, index_tail.msb != 0);
      ivl_assert(*this, index_tail.lsb == 0);

	// Evaluate the select expression...
      NetExpr*mux = elab_and_eval(des, scope, index_tail.msb, -1);

      lv->set_word(mux);

      return true;
}

bool PEIdent::elaborate_lval_net_part_(Design*des,
				       NetScope*scope,
				       NetAssign_*lv) const
{
      list<long> prefix_indices;
      bool rc = calculate_packed_indices_(des, scope, lv->sig(), prefix_indices);
      ivl_assert(*this, rc);

	// The range expressions of a part select must be
	// constant. The calculate_parts_ function calculates the
	// values into msb and lsb.
      long msb, lsb;
      bool parts_defined_flag;
      bool flag = calculate_parts_(des, scope, msb, lsb, parts_defined_flag);
      if (!flag) return false;

      NetNet*reg = lv->sig();
      ivl_assert(*this, reg);

      if (! parts_defined_flag) {
	    if (warn_ob_select) {
		  cerr << get_fileline()
		       << ": warning: L-value part select of "
		       << reg->name();
		  if (reg->unpacked_dimensions() > 0) cerr << "[]";
		  cerr << " has an undefined index." << endl;
	    }
	      // Use a width of two here so we can distinguish between an
	      // undefined bit or part select.
	    lv->set_part(new NetEConst(verinum(verinum::Vx)), 2);
	    return true;
      }

      if (reg->type()==NetNet::UNRESOLVED_WIRE) {
	    bool rct = reg->test_and_set_part_driver(msb, lsb);
	    if (rct) {
		  cerr << get_fileline() << ": error: "
		       << path_ << "Part select is double-driving unresolved wire."
		       << endl;
		  des->errors += 1;
		  return false;
	    }
      }

      const vector<netrange_t>&packed = reg->packed_dims();

      long loff, moff;
      long wid;
      if (prefix_indices.size()+1 < packed.size()) {
	      // If there are fewer indices then there are packed
	      // dimensions, then this is a range of slices. Calculate
	      // it into a big slice.
	    bool lrc;
	    unsigned long tmp_lwid, tmp_mwid;
	    lrc = reg->sb_to_slice(prefix_indices,lsb, loff, tmp_lwid);
	    ivl_assert(*this, lrc);
	    lrc = reg->sb_to_slice(prefix_indices,msb, moff, tmp_mwid);
	    ivl_assert(*this, lrc);

	    if (loff < moff) {
		  moff = moff + tmp_mwid - 1;
	    } else {
		  long ltmp = moff;
		  moff = loff + tmp_lwid - 1;
		  loff = ltmp;
	    }
	    wid = moff - loff + 1;

      } else {
	    loff = reg->sb_to_idx(prefix_indices,lsb);
	    moff = reg->sb_to_idx(prefix_indices,msb);
	    wid = moff - loff + 1;

	    if (moff < loff) {
		  cerr << get_fileline() << ": error: part select "
		       << reg->name() << "[" << msb<<":"<<lsb<<"]"
		       << " is reversed." << endl;
		  des->errors += 1;
		  return false;
	    }
      }

	// Special case: The range winds up selecting the entire
	// vector. Treat this as no part select at all.
      if (loff == 0 && moff == (long)(reg->vector_width()-1)) {
	    return true;
      }

	/* If the part select extends beyond the extremes of the
	   variable, then output a warning. Note that loff is
	   converted to normalized form so is relative the
	   variable pins. */

      if (warn_ob_select && (loff < 0 || moff >= (long)reg->vector_width())) {
	    cerr << get_fileline() << ": warning: Part select "
		 << reg->name() << "[" << msb<<":"<<lsb<<"]"
		 << " is out of range." << endl;
      }

      lv->set_part(new NetEConst(verinum(loff)), wid);

      return true;
}

bool PEIdent::elaborate_lval_net_idx_(Design*des,
				      NetScope*scope,
				      NetAssign_*lv,
				      index_component_t::ctype_t use_sel,
				      bool need_const_idx) const
{
      list<long>prefix_indices;
      bool rc = calculate_packed_indices_(des, scope, lv->sig(), prefix_indices);
      ivl_assert(*this, rc);

      const name_component_t&name_tail = path_.back();;
      ivl_assert(*this, !name_tail.index.empty());

      const index_component_t&index_tail = name_tail.index.back();
      ivl_assert(*this, index_tail.msb != 0);
      ivl_assert(*this, index_tail.lsb != 0);

      NetNet*reg = lv->sig();
      assert(reg);

      unsigned long wid;
      calculate_up_do_width_(des, scope, wid);

      NetExpr*base = elab_and_eval(des, scope, index_tail.msb, -1);
      ivl_select_type_t sel_type = IVL_SEL_OTHER;

	// Handle the special case that the base is constant. For this
	// case we can reduce the expression.
      if (NetEConst*base_c = dynamic_cast<NetEConst*> (base)) {
	      // For the undefined case just let the constant pass and
	      // we will handle it in the code generator.
	    if (base_c->value().is_defined()) {
		  long lsv = base_c->value().as_long();
		  long offset = 0;
		    // Get the signal range.
		  const vector<netrange_t>&packed = reg->packed_dims();
		  ivl_assert(*this, packed.size() == prefix_indices.size()+1);

		    // We want the last range, which is where we work.
		  const netrange_t&rng = packed.back();
		  if (((rng.get_msb() < rng.get_lsb()) &&
                       use_sel == index_component_t::SEL_IDX_UP) ||
		      ((rng.get_msb() > rng.get_lsb()) &&
		       use_sel == index_component_t::SEL_IDX_DO)) {
			offset = -wid + 1;
		  }
		  delete base;
		  long rel_base = reg->sb_to_idx(prefix_indices,lsv) + offset;
		    /* If we cover the entire lvalue just skip the select. */
		  if (rel_base == 0 && wid == reg->vector_width()) return true;
		  base = new NetEConst(verinum(rel_base));
		  if (warn_ob_select) {
			if (rel_base < 0) {
			      cerr << get_fileline() << ": warning: " << reg->name();
			      if (reg->unpacked_dimensions() > 0) cerr << "[]";
			      cerr << "[" << lsv;
			      if (use_sel == index_component_t::SEL_IDX_UP) {
				    cerr << "+:";
			      } else {
				    cerr << "-:";
			      }
			      cerr << wid << "] is selecting before vector." << endl;
			}
			if (rel_base + wid > reg->vector_width()) {
			      cerr << get_fileline() << ": warning: " << reg->name();
			      if (reg->unpacked_dimensions() > 0) cerr << "[]";
			      cerr << "[" << lsv;
			      if (use_sel == index_component_t::SEL_IDX_UP) {
				    cerr << "+:";
			      } else {
				    cerr << "-:";
			      }
			      cerr << wid << "] is selecting after vector." << endl;
			}
		  }
	    } else {
		  cerr << get_fileline() << ": warning: L-value indexed part "
		       << "select of " << reg->name();
		  if (reg->unpacked_dimensions() > 0) cerr << "[]";
		  cerr << " has an undefined base." << endl;
	    }
      } else {
	    if (need_const_idx) {
		  cerr << get_fileline() << ": error: '" << reg->name()
		       << "' base index must be a constant in this context."
		       << endl;
		  des->errors += 1;
		  return false;
	    }
	    ivl_assert(*this, prefix_indices.size()+1 == reg->packed_dims().size());
	      /* Correct the mux for the range of the vector. */
	    if (use_sel == index_component_t::SEL_IDX_UP) {
		  base = normalize_variable_part_base(prefix_indices, base,
						      reg, wid, true);
		  sel_type = IVL_SEL_IDX_UP;
	    } else {
		    // This is assumed to be a SEL_IDX_DO.
		  base = normalize_variable_part_base(prefix_indices, base,
						      reg, wid, false);
		  sel_type = IVL_SEL_IDX_DOWN;
	    }
      }

      if (debug_elaborate)
	    cerr << get_fileline() << ": debug: Set part select width="
		 << wid << ", base=" << *base << endl;

      lv->set_part(base, wid, sel_type);

      return true;
}

/*
 * When the l-value turns out to be a class object, this method is
 * called with the bound variable, and the method path. For example,
 * if path_=a.b.c and a.b binds to the variable, then sig is b, and
 * member_path=c. if path_=obj.base.x, and base_path=obj, then sig is
 * obj, and member_path=base.x.
 */
NetAssign_* PEIdent::elaborate_lval_net_class_member_(Design*des, NetScope*scope,
				    NetNet*sig, pform_name_t member_path) const
{
      if (debug_elaborate) {
	    cerr << get_fileline() << ": PEIdent::elaborate_lval_net_class_member_: "
		 << "l-value is property " << member_path
		 << " of " << sig->name() << "." << endl;
      }

      const netclass_t*class_type = sig->class_type();
      ivl_assert(*this, class_type);

	// Iterate over the member_path. This handles nested class
	// object, by generating nested NetAssign_ object. We start
	// with lv==0, so the front of the member_path is the member
	// of the outermost class. This generates an lv from sig. Then
	// iterate over the remaining of the member_path, replacing
	// the outer lv with an lv that nests the lv from the previous
	// iteration.
      NetAssign_*lv = 0;
      do {
	      // Start with the first component of the member path...
	    perm_string method_name = peek_head_name(member_path);
	      // Pull that component from the member_path. We need to
	      // know the current member being worked on, and will
	      // need to know if there are more members to be worked on.
	    name_component_t member_cur = member_path.front();
	    member_path.pop_front();

	    if (debug_elaborate) {
		  cerr << get_fileline() << ": PEIdent::elaborate_lval_net_class_member_: "
		       << "Processing member_cur=" << member_cur
		       << endl;
	    }

	      // Make sure the property is really present in the class. If
	      // not, then generate an error message and return an error.
	    int pidx = class_type->property_idx_from_name(method_name);
	    if (pidx < 0) {
		  cerr << get_fileline() << ": error: Class " << class_type->get_name()
		       << " does not have a property " << method_name << "." << endl;
		  des->errors += 1;
		  return 0;
	    }

	    property_qualifier_t qual = class_type->get_prop_qual(pidx);
	    if (qual.test_local() && ! class_type->test_scope_is_method(scope)) {
		  cerr << get_fileline() << ": error: "
		       << "Local property " << class_type->get_prop_name(pidx)
		       << " is not accessible (l-value) in this context."
		       << " (scope=" << scope_path(scope) << ")" << endl;
		  des->errors += 1;

	    } else if (qual.test_static()) {

		    // Special case: this is a static property. Ignore the
		    // "this" sig and use the property itself, which is not
		    // part of the sig, as the l-value.
		  NetNet*psig = class_type->find_static_property(method_name);
		  ivl_assert(*this, psig);

		  lv = new NetAssign_(psig);
		  return lv;

	    } else if (qual.test_const()) {
		  cerr << get_fileline() << ": error: "
		       << "Property " << class_type->get_prop_name(pidx)
		       << " is constant in this context." << endl;
		  des->errors += 1;
	    }

	    lv = lv? new NetAssign_(lv) : new NetAssign_(sig);
	    lv->set_property(method_name);

	      // Now get the type of the property.
	    ivl_type_t ptype = class_type->get_prop_type(pidx);
	    const netdarray_t*mtype = dynamic_cast<const netdarray_t*> (ptype);
	    if (mtype) {
		  if (! member_cur.index.empty()) {
			cerr << get_fileline() << ": sorry: "
			     << "Array index of array properties not supported."
			     << endl;
			des->errors += 1;
		  }
	    }

	      // If the current member is a class object, then get the
	      // type. We may wind up iterating, and need the proper
	      // class type.
	    class_type = dynamic_cast<const netclass_t*>(ptype);

      } while (member_path.size() > 0);


      return lv;
}

/*
 * This method is caled to handle l-value identifiers that are packed
 * structs. The lv is already attached to the variable, so this method
 * calculates the part select that is defined by the member_path. For
 * example, if the path_ is main.sub.sub_local, and the variable is
 * main, then we know at this point that main is a packed struct, and
 * lv contains the reference to the bound variable (main). In this
 * case member_path==sub.sub_local, and it is up to this method to
 * work out the part select that the member_path represents.
 */
bool PEIdent::elaborate_lval_net_packed_member_(Design*des, NetScope*scope,
						NetAssign_*lv,
						pform_name_t member_path) const
{
      if (debug_elaborate) {
	    cerr << get_fileline() << ": PEIdent::elaborate_lval_net_packed_member_: "
		 << "path_=" << path_
		 << " member_path=" << member_path
		 << endl;
      }

      NetNet*reg = lv->sig();
      ivl_assert(*this, reg);

      const netstruct_t*struct_type = reg->struct_type();
      ivl_assert(*this, struct_type);
      if (debug_elaborate) {
	    cerr << get_fileline() << ": PEIdent::elaborate_lval_net_packed_member_: "
		 << "Type=" << *struct_type
		 << endl;
      }

      if (! struct_type->packed()) {
	    cerr << get_fileline() << ": sorry: Only packed structures "
		 << "are supported in l-value." << endl;
	    des->errors += 1;
	    return false;
      }

	// Looking for the base name. We need that to know about
	// indices we may need to apply. This is to handle the case
	// that the base is an array of structs, and not just a
	// struct.
      pform_name_t::const_reverse_iterator name_idx = path_.rbegin();
      for (size_t idx = 1 ; idx < member_path.size() ; idx += 1)
	    ++ name_idx;
      if (name_idx->name != peek_head_name(member_path)) {
	    cerr << get_fileline() << ": internal error: "
		 << "name_idx=" << name_idx->name
		 << ", expecting member_name=" << peek_head_name(member_path)
		 << endl;
	    des->errors += 1;
	    return false;
      }
      ivl_assert(*this, name_idx->name == peek_head_name(member_path));
      ++ name_idx;
      const name_component_t&name_base = *name_idx;

	// Shouldn't be seeing unpacked arrays of packed structs...
      ivl_assert(*this, reg->unpacked_dimensions() == 0);

	// These make up the "part" select that is the equivilent of
	// following the member path through the nested structs. To
	// start with, the off[set] is zero, and use_width is the
	// width of the entire variable. The first member_comp is at
	// some offset within the variable, and will have a reduced
	// width. As we step through the member_path the off
	// increases, and use_width shrinks.
      unsigned long off = 0;
      unsigned long use_width = struct_type->packed_width();

      pform_name_t completed_path;
      do {
	    const name_component_t member_comp = member_path.front();
	    const perm_string&member_name = member_comp.name;

	    if (debug_elaborate) {
		  cerr << get_fileline() << ": PEIdent::elaborate_lval_net_packed_member_: "
		       << "Processing member_comp=" << member_comp
		       << " (completed_path=" << completed_path << ")"
		       << endl;
	    }

	      // This is a packed member, so the name is of the form
	      // "a.b[...].c[...]" which means that the path_ must have at
	      // least 2 components. We are processing "c[...]" at that
	      // point (otherwise known as member_name) and we have a
	      // reference to it in member_comp.

	      // The member_path is the members we want to follow for the
	      // variable. For example, main[N].a.b may have main[N] as the
	      // base_name, and member_path=a.b. The member_name is the
	      // start of the member_path, and is "a". The member_name
	      // should be a member of the struct_type type.

	      // Calculate the offset within the packed structure of the
	      // member, and any indices. We will add in the offset of the
	      // struct into the packed array later. Note that this works
	      // for packed unions as well (although the offset will be 0
	      // for union members).
	    unsigned long tmp_off;
	    const netstruct_t::member_t* member = struct_type->packed_member(member_name, tmp_off);

	    if (member == 0) {
		  cerr << get_fileline() << ": error: Member " << member_name
		       << " is not a member of struct type of "
		       << reg->name()
		       << "." << completed_path << endl;
		  des->errors += 1;
		  return false;
	    }
	    if (debug_elaborate) {
		  cerr << get_fileline() << ": PEIdent::elaborate_lval_net_packed_member_: "
		       << "Member type: " << *(member->net_type)
		       << endl;
	    }

	    off += tmp_off;
	    ivl_assert(*this, use_width >= (unsigned long)member->net_type->packed_width());
	    use_width = member->net_type->packed_width();

	      // At this point, off and use_width are the part select
	      // expressed by the member_comp, which is a member of the
	      // struct. We can further refine the part select with any
	      // indices that might be present.

	      // Get the index component type. At this point, we only
	      // support bit select or none.
	    index_component_t::ctype_t use_sel = index_component_t::SEL_NONE;
	    if (!member_comp.index.empty())
		  use_sel = member_comp.index.back().sel;

	    if (use_sel != index_component_t::SEL_NONE
		&& use_sel != index_component_t::SEL_BIT
		&& use_sel != index_component_t::SEL_PART) {
		  cerr << get_fileline() << ": sorry: Assignments to part selects of "
			"a struct member are not yet supported." << endl;
		  des->errors += 1;
		  return false;
	    }

	    if (const netvector_t*mem_vec = dynamic_cast<const netvector_t*>(member->net_type)) {
		    // If the member type is a netvector_t, then it is a
		    // vector of atom or scaler objects. For example, if the
		    // l-value expression is "foo.member[1][2]",
		    // then the member should be something like:
		    //    ... logic [h:l][m:n] member;
		    // There should be index expressions index the vector
		    // down, but there doesn't need to be all of them. We
		    // can, for example, be selecting a part of the vector.

		    // We only need to process this if there are any
		    // index expressions. If not, then the packed
		    // vector can be handled atomically.

		    // In any case, this should be the tail of the
		    // member_path, because the array element of this
		    // kind of array cannot be a struct.
		  if (member_comp.index.size() > 0) {
			  // These are the dimensions defined by the type
			const vector<netrange_t>&mem_packed_dims = mem_vec->packed_dims();

			if (member_comp.index.size() > mem_packed_dims.size()) {
			      cerr << get_fileline() << ": error: "
				   << "Too many index expressions for member." << endl;
			      des->errors += 1;
			      return false;
			}

			  // Evaluate all but the last index expression, into prefix_indices.
			list<long>prefix_indices;
			bool rc = evaluate_index_prefix(des, scope, prefix_indices, member_comp.index);
			ivl_assert(*this, rc);

			if (debug_elaborate) {
			      cerr << get_fileline() << ": PEIdent::elaborate_lval_net_packed_member_: "
				   << "prefix_indices.size()==" << prefix_indices.size()
				   << ", mem_packed_dims.size()==" << mem_packed_dims.size()
				   << " (netvector_t context)"
				   << endl;
			}

			long tail_off = 0;
			unsigned long tail_wid = 0;
			rc = calculate_part(this, des, scope, member_comp.index.back(), tail_off, tail_wid);
			ivl_assert(*this, rc);

			if (debug_elaborate) {
			      cerr << get_fileline() << ": PEIdent::elaborate_lval_net_packed_member_: "
				   << "calculate_part for tail returns tail_off=" << tail_off
				   << ", tail_wid=" << tail_wid
				   << endl;
			}

			  // Now use the prefix_to_slice function to calculate the
			  // offset and width of the addressed slice of the member.
			long loff;
			unsigned long lwid;
			prefix_to_slice(mem_packed_dims, prefix_indices, tail_off, loff, lwid);

			if (debug_elaborate) {
			      cerr << get_fileline() << ": PEIdent::elaborate_lval_net_packed_member_: "
				   << "Calculate loff=" << loff << " lwid=" << lwid
				   << " tail_off=" << tail_off << " tail_wid=" << tail_wid
				   << " off=" << off << " use_width=" << use_width
				   << endl;
			}

			off += loff;
			use_width = lwid * tail_wid;
		  }

		    // The netvector_t only has atom elements, to
		    // there is no next struct type.
		  struct_type = 0;

	    } else if (const netparray_t*array = dynamic_cast<const netparray_t*> (member->net_type)) {
		    // If the member is a parray, then the elements
		    // are themselves packed object, including
		    // possibly a struct. Handle this by taking the
		    // part select of the current part of the
		    // variable, then stepping to the element type to
		    // possibly iterate through more of the member_path.

		  ivl_assert(*this, array->packed());
		  ivl_assert(*this, member_comp.index.size() > 0);

		    // These are the dimensions defined by the type
		  const vector<netrange_t>&mem_packed_dims = array->static_dimensions();

		  if (member_comp.index.size() != mem_packed_dims.size()) {
			cerr << get_fileline() << ": error: "
			     << "Incorrect number of index expressions for member "
			     << member_name << "." << endl;
			des->errors += 1;
			return false;
		  }

		    // Evaluate all but the last index expression, into prefix_indices.
		  list<long>prefix_indices;
		  bool rc = evaluate_index_prefix(des, scope, prefix_indices, member_comp.index);
		  ivl_assert(*this, rc);

		  if (debug_elaborate) {
			cerr << get_fileline() << ": PEIdent::elaborate_lval_net_packed_member_: "
			     << "prefix_indices.size()==" << prefix_indices.size()
			     << ", mem_packed_dims.size()==" << mem_packed_dims.size()
			     << " (netparray_t context)"
			     << endl;
		  }

		    // Evaluate the last index expression into a constant long.
		  NetExpr*texpr = elab_and_eval(des, scope, member_comp.index.back().msb, -1, true);
		  long tmp;
		  if (texpr == 0 || !eval_as_long(tmp, texpr)) {
			cerr << get_fileline() << ": error: "
			     << "Array index expressions for member " << member_name
			     << " must be constant here." << endl;
			des->errors += 1;
			return false;
		  }

		  delete texpr;

		    // Now use the prefix_to_slice function to calculate the
		    // offset and width of the addressed slice of the member.
		  long loff;
		  unsigned long lwid;
		  prefix_to_slice(mem_packed_dims, prefix_indices, tmp, loff, lwid);

		  ivl_type_t element_type = array->element_type();
		  long element_width = element_type->packed_width();
		  if (debug_elaborate) {
			cerr << get_fileline() << ": PEIdent::elaborate_lval_net_packed_member_: "
			     << "parray subselection loff=" << loff
			     << ", lwid=" << lwid
			     << ", element_width=" << element_width
			     << endl;
		  }

		    // The width and offset calculated from the
		    // indices is actually in elements, and not
		    // bits. In fact, in this context, the lwid should
		    // come down to 1 (one element).
		  off += loff * element_width;
		  ivl_assert(*this, lwid==1);
		  use_width = element_width;

		    // To move on to the next component in the member
		    // path, get the element type. For example, for
		    // the path a.b[1].c, we are processing b[1] here,
		    // and the element type should be a netstruct_t
		    // that will wind up containing the member c.
		  struct_type = dynamic_cast<const netstruct_t*> (element_type);

	    } else if (const netstruct_t*tmp_struct = dynamic_cast<const netstruct_t*> (member->net_type)) {
		    // If the member is itself a struct, then get
		    // ready to go on to the next iteration.
		  struct_type = tmp_struct;

	    } else if (const netenum_t*tmp_enum = dynamic_cast<const netenum_t*> (member->net_type)) {
		    // If the element is an enum, then we don't have
		    // anything special to do.
		  if (debug_elaborate) {
			cerr << get_fileline() << ": PEIdent::elaborate_lval_net_packed_member_: "
			     << "Tail element is an enum: " << *tmp_enum
			     << endl;
		  }
		  struct_type = 0;

	    } else {
		    // Unknown type?
		  cerr << get_fileline() << ": internal error: "
		       << "Unexpected member type? " << *(member->net_type)
		       << endl;
		  des->errors += 1;
		  return false;
		  struct_type = 0;
	    }

	      // Complete this component of the path, mark it
	      // completed, and set up for the next component.
	    completed_path .push_back(member_comp);
	    member_path.pop_front();

      } while (member_path.size() > 0 && struct_type != 0);

      if (debug_elaborate) {
	    cerr << get_fileline() << ": PEIdent::elaborate_lval_net_packed_member_: "
		 << "After processing member_path, "
		 << "off=" << off
		 << ", use_width=" << use_width
		 << ", completed_path=" << completed_path
		 << ", member_path=" << member_path
		 << endl;
      }

	// The dimensions in the expression must match the packed
	// dimensions that are declared for the variable. For example,
	// if foo is a packed array of struct, then this expression
	// must be "b[n][m]" with the right number of dimensions to
	// match the declaration of "b".
	// Note that one of the packed dimensions is the packed struct
	// itself.
      ivl_assert(*this, name_base.index.size()+1 == reg->packed_dimensions());

	// Generate an expression that takes the input array of
	// expressions and generates a canonical offset into the
	// packed array.
      NetExpr*packed_base = 0;
      if (reg->packed_dimensions() > 1) {
	    list<index_component_t>tmp_index = name_base.index;
	    index_component_t member_select;
	    member_select.sel = index_component_t::SEL_BIT;
	    member_select.msb = new PENumber(new verinum(off));
	    tmp_index.push_back(member_select);
	    packed_base = collapse_array_indices(des, scope, reg, tmp_index);
      }

      long tmp;
      if (packed_base && eval_as_long(tmp, packed_base)) {
	    off = tmp;
	    delete packed_base;
	    packed_base = 0;
      }

      if (reg->type()==NetNet::UNRESOLVED_WIRE) {
	    cerr << get_fileline() << ": error: "
		 << path_ << " Unable to member-select unresolved wires."
		 << endl;
	    des->errors += 1;
	    return false;
      }

      if (packed_base == 0) {
	    lv->set_part(new NetEConst(verinum(off)), use_width);
	    return true;
      }

	// Oops, packed_base is not fully evaluated, so I don't know
	// yet what to do with it.
      cerr << get_fileline() << ": internal error: "
	   << "I don't know how to handle this index expression? " << *packed_base << endl;
      ivl_assert(*this, 0);
      return false;
}

NetAssign_* PENumber::elaborate_lval(Design*des, NetScope*, bool, bool) const
{
      cerr << get_fileline() << ": error: Constant values not allowed "
	   << "in l-value expressions." << endl;
      des->errors += 1;
      return 0;
}