Check for extra digits in sized binary, octal and hex constants.

[iverilog.git] / elab_expr.cc

/*
 * Copyright (c) 1999-2007 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  "pform.h"
# include  "netlist.h"
# include  "netmisc.h"
# include  "util.h"
# include  "ivl_assert.h"

/*
 * The default behavor for the test_width method is to just return the
 * minimum width that is passed in.
 */
unsigned PExpr::test_width(Design*des, NetScope*scope,
                           unsigned min, unsigned lval, bool&) const
{
      if (debug_elaborate) {
            cerr << get_line() << ": debug: test_width defaults to "
                 << min << ", ignoring unsized_flag. typeid="
                 << typeid(*this).name() << endl;
      }
      return min;
}

NetExpr* PExpr::elaborate_expr(Design*des, NetScope*, int, bool) const
{
      cerr << get_line() << ": internal error: I do not know how to elaborate"
           << " expression. " << endl;
      cerr << get_line() << ":               : Expression is: " << *this
           << endl;
      des->errors += 1;
      return 0;
}

unsigned PEBinary::test_width(Design*des, NetScope*scope,
                              unsigned min, unsigned lval, bool&unsized_flag) const
{
      bool flag_left = false;
      bool flag_right = false;
      unsigned wid_left = left_->test_width(des,scope, min, lval, flag_left);
      unsigned wid_right = right_->test_width(des,scope, min, lval, flag_right);

      if (flag_left || flag_right)
            unsized_flag = true;

      switch (op_) {
          case '+':
          case '-':
            if (unsized_flag) {
                  wid_left += 1;
                  wid_right += 1;
            }
            if (wid_left > min)
                  min = wid_left;
            if (wid_right > min)
                  min = wid_right;
            if (lval > 0 && min > lval)
                  min = lval;
            break;

          default:
            if (wid_left > min)
                  min = wid_left;
            if (wid_right > min)
                  min = wid_right;
            break;
      }

      return min;
}

/*
 * Elaborate binary expressions. This involves elaborating the left
 * and right sides, and creating one of a variety of different NetExpr
 * types.
 */
NetEBinary* PEBinary::elaborate_expr(Design*des, NetScope*scope,
                                     int expr_wid, bool) const
{
      assert(left_);
      assert(right_);

      NetExpr*lp = left_->elaborate_expr(des, scope, expr_wid, false);
      NetExpr*rp = right_->elaborate_expr(des, scope, expr_wid, false);
      if ((lp == 0) || (rp == 0)) {
            delete lp;
            delete rp;
            return 0;
      }

      NetEBinary*tmp = elaborate_eval_expr_base_(des, lp, rp, expr_wid);
      return tmp;
}

NetEBinary* PEBinary::elaborate_eval_expr_base_(Design*des,
                                                NetExpr*lp,
                                                NetExpr*rp,
                                                int expr_wid) const
{
        /* If either expression can be evaluated ahead of time, then
           do so. This can prove helpful later. */
      { NetExpr*tmp;
        tmp = lp->eval_tree();
        if (tmp) {
              delete lp;
              lp = tmp;
        }

        tmp = rp->eval_tree();
        if (tmp) {
              delete rp;
              rp = tmp;
        }
      }

      return elaborate_expr_base_(des, lp, rp, expr_wid);
}

/*
 * This is common elaboration of the operator. It presumes that the
 * operands are elaborated as necessary, and all I need to do is make
 * the correct NetEBinary object and connect the parameters.
 */
NetEBinary* PEBinary::elaborate_expr_base_(Design*des,
                                           NetExpr*lp, NetExpr*rp,
                                           int expr_wid) const
{
      bool flag;

      if (debug_elaborate) {
            cerr << get_line() << ": debug: elaborate expression "
                 << *this << " expr_wid=" << expr_wid << endl;
      }

      NetEBinary*tmp;

      switch (op_) {
          default:
            tmp = new NetEBinary(op_, lp, rp);
            tmp->set_line(*this);
            break;

          case 'a':
          case 'o':
            tmp = new NetEBLogic(op_, lp, rp);
            tmp->set_line(*this);
            break;

          case 'p':
            tmp = new NetEBPow(op_, lp, rp);
            tmp->set_line(*this);
            break;

          case '*':
            tmp = new NetEBMult(op_, lp, rp);
            tmp->set_line(*this);
            break;

          case '%':
              /* The % operator does not support real arguments in
                 baseline Verilog. But we allow it in our extended
                 form of verilog. */
            if (generation_flag < GN_VER2001X) {
                  if (lp->expr_type()==IVL_VT_REAL || rp->expr_type()==IVL_VT_REAL) {
                        cerr << get_line() << ": error: Modulus operator may not "
                              "have REAL operands." << endl;
                        des->errors += 1;
                  }
            }
              /* Fall through to handle the % with the / operator. */
          case '/':
            tmp = new NetEBDiv(op_, lp, rp);
            tmp->set_line(*this);
            break;

          case 'l': // <<
          case 'r': // >>
          case 'R': // >>>
            tmp = new NetEBShift(op_, lp, rp);
            tmp->set_line(*this);
            break;

          case '^':
          case '&':
          case '|':
          case 'O': // NOR (~|)
          case 'A': // NAND (~&)
          case 'X':
            tmp = new NetEBBits(op_, lp, rp);
            tmp->set_line(*this);
            break;

          case '+':
          case '-':
            tmp = new NetEBAdd(op_, lp, rp, expr_wid==-2? true : false);
            if (expr_wid > 0 && (tmp->expr_type() == IVL_VT_BOOL
                                 || tmp->expr_type() == IVL_VT_LOGIC))
                  tmp->set_width(expr_wid);
            tmp->set_line(*this);
            break;

          case 'E': /* === */
          case 'N': /* !== */
            if (lp->expr_type() == IVL_VT_REAL
                || rp->expr_type() == IVL_VT_REAL) {
                  cerr << get_line() << ": error: Case equality may not "
                       << "have real operands." << endl;
                  return 0;
            }
              /* Fall through... */
          case 'e': /* == */
          case 'n': /* != */
            if (dynamic_cast<NetEConst*>(rp)
                && (lp->expr_width() > rp->expr_width()))
                  rp->set_width(lp->expr_width());

            if (dynamic_cast<NetEConst*>(lp)
                && (lp->expr_width() < rp->expr_width()))
                  lp->set_width(rp->expr_width());

              /* from here, handle this like other compares. */
          case 'L': /* <= */
          case 'G': /* >= */
          case '<':
          case '>':
            tmp = new NetEBComp(op_, lp, rp);
            tmp->set_line(*this);
            flag = tmp->set_width(1);
            if (flag == false) {
                  cerr << get_line() << ": internal error: "
                        "expression bit width of comparison != 1." << endl;
                  des->errors += 1;
            }
            break;
      }

      return tmp;
}

unsigned PEBComp::test_width(Design*, NetScope*,unsigned, unsigned, bool&) const
{
      return 1;
}

NetEBinary* PEBComp::elaborate_expr(Design*des, NetScope*scope,
                                    int expr_width, bool sys_task_arg) const
{
      assert(left_);
      assert(right_);

      bool unsized_flag = false;
      unsigned left_width = left_->test_width(des, scope, 0, 0, unsized_flag);
      bool save_flag = unsized_flag;
      unsigned right_width = right_->test_width(des, scope, 0, 0, unsized_flag);

      if (save_flag != unsized_flag)
            left_width = left_->test_width(des, scope, 0, 0, unsized_flag);

        /* Width of operands is self-determined. */
      int use_wid = left_width;
      if (right_width > left_width)
            use_wid = right_width;

      if (debug_elaborate) {
            cerr << get_line() << ": debug: "
                 << "Comparison expression operands are "
                 << left_width << " bits and "
                 << right_width << " bits. Resorting to "
                 << use_wid << " bits." << endl;
      }

      NetExpr*lp = left_->elaborate_expr(des, scope, use_wid, false);
      NetExpr*rp = right_->elaborate_expr(des, scope, use_wid, false);
      if ((lp == 0) || (rp == 0)) {
            delete lp;
            delete rp;
            return 0;
      }

      return elaborate_eval_expr_base_(des, lp, rp, use_wid);
}

unsigned PEBShift::test_width(Design*des, NetScope*scope,
                              unsigned min, unsigned lval, bool&unsized_flag) const
{
      unsigned wid_left = left_->test_width(des,scope,min, 0, unsized_flag);

        // The right expression is self-determined and has no impact
        // on the expression size that is generated.

      return wid_left;
}

unsigned PECallFunction::test_width_sfunc_(Design*des, NetScope*scope,
                                           unsigned min, unsigned lval,
                                           bool&unsized_flag) const
{
      perm_string name = peek_tail_name(path_);

      if (name=="$signed"|| name=="$unsigned") {
            PExpr*expr = parms_[0];
            if (expr == 0)
                  return 0;
            unsigned wid = expr->test_width(des, scope, min, lval, unsized_flag);
            if (debug_elaborate)
                  cerr << get_line() << ": debug: test_width"
                       << " of $signed/$unsigned returns test_width"
                       << " of subexpression." << endl;
            return wid;
      }

      if (debug_elaborate)
            cerr << get_line() << ": debug: test_width "
                 << "of system function " << name
                 << " returns 32 always?" << endl;
      return 32;
}

unsigned PECallFunction::test_width(Design*des, NetScope*scope,
                                    unsigned min, unsigned lval,
                                    bool&unsized_flag) const
{
      if (peek_tail_name(path_)[0] == '$')
            return test_width_sfunc_(des, scope, min, lval, unsized_flag);

      NetFuncDef*def = des->find_function(scope, path_);
      if (def == 0) {
            if (debug_elaborate)
                  cerr << get_line() << ": debug: test_width "
                       << "cannot find definition of " << path_
                       << " in " << scope_path(scope) << "." << endl;
            return 0;
      }

      NetScope*dscope = def->scope();
      assert(dscope);

      if (NetNet*res = dscope->find_signal(dscope->basename())) {
            if (debug_elaborate)
                  cerr << get_line() << ": debug: test_width "
                       << "of function returns width " << res->vector_width()
                       << "." << endl;
            return res->vector_width();
      }

      ivl_assert(*this, 0);
      return 0;
}

/*
 * Given a call to a system function, generate the proper expression
 * nodes to represent the call in the netlist. Since we don't support
 * size_tf functions, make assumptions about widths based on some
 * known function names.
 */
NetExpr* PECallFunction::elaborate_sfunc_(Design*des, NetScope*scope, int expr_wid) const
{

        /* Catch the special case that the system function is the
           $signed function. This function is special, in that it does
           not lead to executable code but takes the single parameter
           and makes it into a signed expression. No bits are changed,
           it just changes the interpretation. */
      if (strcmp(peek_tail_name(path_), "$signed") == 0) {
            if ((parms_.count() != 1) || (parms_[0] == 0)) {
                  cerr << get_line() << ": error: The $signed() function "
                       << "takes exactly one(1) argument." << endl;
                  des->errors += 1;
                  return 0;
            }

            PExpr*expr = parms_[0];
            NetExpr*sub = expr->elaborate_expr(des, scope, -1, true);
            sub->cast_signed(true);
            return sub;
      }
      /* add $unsigned to match $signed */
      if (strcmp(peek_tail_name(path_), "$unsigned") == 0) {
            if ((parms_.count() != 1) || (parms_[0] == 0)) {
                  cerr << get_line() << ": error: The $unsigned() function "
                       << "takes exactly one(1) argument." << endl;
                  des->errors += 1;
                  return 0;
            }

            PExpr*expr = parms_[0];
            NetExpr*sub = expr->elaborate_expr(des, scope, -1, true);
            sub->cast_signed(false);

            if (expr_wid > 0 && (unsigned)expr_wid > sub->expr_width())
                  sub = pad_to_width(sub, expr_wid);

            return sub;
      }

        /* Interpret the internal $sizeof system function to return
           the bit width of the sub-expression. The value of the
           sub-expression is not used, so the expression itself can be
           deleted. */
      if ((strcmp(peek_tail_name(path_), "$sizeof") == 0)
          || (strcmp(peek_tail_name(path_), "$bits") == 0)) {
            if ((parms_.count() != 1) || (parms_[0] == 0)) {
                  cerr << get_line() << ": error: The $bits() function "
                       << "takes exactly one(1) argument." << endl;
                  des->errors += 1;
                  return 0;
            }

            if (strcmp(peek_tail_name(path_), "$sizeof") == 0)
                  cerr << get_line() << ": warning: $sizeof is deprecated."
                       << " Use $bits() instead." << endl;

            PExpr*expr = parms_[0];
            ivl_assert(*this, expr);

              /* Elaborate the sub-expression to get its
                 self-determined width, and save that width. Then
                 delete the expression because we don't really want
                 the expression itself. */ 
            long sub_expr_width = 0;
            if (NetExpr*tmp = expr->elaborate_expr(des, scope, -1, true)) {
                  sub_expr_width = tmp->expr_width();
                  delete tmp;
            }

            verinum val (sub_expr_width, 8*sizeof(unsigned));
            NetEConst*sub = new NetEConst(val);
            sub->set_line(*this);

            return sub;
      }

        /* Interpret the internal $is_signed system function to return
           a single bit flag -- 1 if the expression is signed, 0
           otherwise. The subexpression is elaborated but not
           evaluated. */
      if (strcmp(peek_tail_name(path_), "$is_signed") == 0) {
            if ((parms_.count() != 1) || (parms_[0] == 0)) {
                  cerr << get_line() << ": error: The $is_signed() function "
                       << "takes exactly one(1) argument." << endl;
                  des->errors += 1;
                  return 0;
            }

            PExpr*expr = parms_[0];
            NetExpr*sub = expr->elaborate_expr(des, scope, -1, true);

            verinum val (sub->has_sign()? verinum::V1 : verinum::V0, 1);
            delete sub;

            sub = new NetEConst(val);
            sub->set_line(*this);

            return sub;
      }

        /* Get the return type of the system function by looking it up
           in the sfunc_table. */
      const struct sfunc_return_type*sfunc_info
            = lookup_sys_func(peek_tail_name(path_));

      ivl_variable_type_t sfunc_type = sfunc_info->type;
      unsigned wid = sfunc_info->wid;


        /* How many parameters are there? The Verilog language allows
           empty parameters in certain contexts, so the parser will
           allow things like func(1,,3). It will also cause func() to
           be interpreted as a single empty parameter.

           Functions cannot really take empty parameters, but the
           case ``func()'' is the same as no parameters at all. So
           catch that special case here. */
      unsigned nparms = parms_.count();
      if ((nparms == 1) && (parms_[0] == 0))
            nparms = 0;

      NetESFunc*fun = new NetESFunc(peek_tail_name(path_), sfunc_type,
                                    wid, nparms);
      if (sfunc_info->signed_flag)
            fun->cast_signed(true);

        /* Now run through the expected parameters. If we find that
           there are missing parameters, print an error message.

           While we're at it, try to evaluate the function parameter
           expression as much as possible, and use the reduced
           expression if one is created. */

      unsigned missing_parms = 0;
      for (unsigned idx = 0 ;  idx < nparms ;  idx += 1) {
            PExpr*expr = parms_[idx];
            if (expr) {
                  NetExpr*tmp1 = expr->elaborate_expr(des, scope, -1, true);
                  if (NetExpr*tmp2 = tmp1->eval_tree()) {
                        delete tmp1;
                        fun->parm(idx, tmp2);
                  } else {
                        fun->parm(idx, tmp1);
                  }

            } else {
                  missing_parms += 1;
                  fun->parm(idx, 0);
            }
      }

      if (missing_parms > 0) {
            cerr << get_line() << ": error: The function "
                 << peek_tail_name(path_)
                 << " has been called with empty parameters." << endl;
            cerr << get_line() << ":      : Verilog doesn't allow "
                 << "passing empty parameters to functions." << endl;
            des->errors += 1;
      }

      return fun;
}

NetExpr* PECallFunction::elaborate_expr(Design*des, NetScope*scope,
                                        int expr_wid, bool) const
{
      if (peek_tail_name(path_)[0] == '$')
            return elaborate_sfunc_(des, scope, expr_wid);

      NetFuncDef*def = des->find_function(scope, path_);
      if (def == 0) {
            cerr << get_line() << ": error: No function " << path_ <<
                  " in this context (" << scope_path(scope) << ")." << endl;
            des->errors += 1;
            return 0;
      }
      assert(def);

      NetScope*dscope = def->scope();
      assert(dscope);

      if (! check_call_matches_definition_(des, dscope))
            return 0;

      unsigned parms_count = parms_.count();
      if ((parms_count == 1) && (parms_[0] == 0))
            parms_count = 0;



      svector<NetExpr*> parms (parms_count);

        /* Elaborate the input expressions for the function. This is
           done in the scope of the function call, and not the scope
           of the function being called. The scope of the called
           function is elaborated when the definition is elaborated. */

      unsigned missing_parms = 0;
      for (unsigned idx = 0 ;  idx < parms.count() ;  idx += 1) {
            PExpr*tmp = parms_[idx];
            if (tmp) {
                  int argwid = def->port(idx)->vector_width();
                  parms[idx] = elab_and_eval(des, scope, tmp, argwid);
                  if (debug_elaborate)
                        cerr << get_line() << ": debug:"
                             << " function " << path_
                             << " arg " << (idx+1)
                             << " argwid=" << argwid
                             << ": " << *parms[idx] << endl;

            } else {
                  missing_parms += 1;
                  parms[idx] = 0;
            }
      }

      if (missing_parms > 0) {
            cerr << get_line() << ": error: The function " << path_
                 << " has been called with empty parameters." << endl;
            cerr << get_line() << ":      : Verilog doesn't allow "
                 << "passing empty parameters to functions." << endl;
            des->errors += 1;
      }


        /* Look for the return value signal for the called
           function. This return value is a magic signal in the scope
           of the function, that has the name of the function. The
           function code assigns to this signal to return a value.

           dscope, in this case, is the scope of the function, so the
           return value is the name within that scope. */

      if (NetNet*res = dscope->find_signal(dscope->basename())) {
            NetESignal*eres = new NetESignal(res);
            NetEUFunc*func = new NetEUFunc(dscope, eres, parms);
            func->set_line(*this);
            func->cast_signed(res->get_signed());
            return func;
      }

      cerr << get_line() << ": internal error: Unable to locate "
            "function return value for " << path_
           << " in " << dscope->basename() << "." << endl;
      des->errors += 1;
      return 0;
}


NetExpr* PEConcat::elaborate_expr(Design*des, NetScope*scope,
                                  int expr_wid, bool) const
{
      NetExpr* repeat = 0;

      if (debug_elaborate) {
            cerr << get_line() << ": debug: Elaborate expr=" << *this
                 << ", expr_wid=" << expr_wid << endl;
      }

        /* If there is a repeat expression, then evaluate the constant
           value and set the repeat count. */
      if (repeat_) {
            NetExpr*tmp = elab_and_eval(des, scope, repeat_, -1);
            assert(tmp);
            NetEConst*rep = dynamic_cast<NetEConst*>(tmp);

            if (rep == 0) {
                  cerr << get_line() << ": error: "
                        "concatenation repeat expression cannot be evaluated."
                       << endl;
                  cerr << get_line() << ":      : The expression is: "
                       << *tmp << endl;
                  des->errors += 1;
            }

            repeat = rep;
      }

        /* Make the empty concat expression. */
      NetEConcat*tmp = new NetEConcat(parms_.count(), repeat);
      tmp->set_line(*this);

      unsigned wid_sum = 0;

        /* Elaborate all the parameters and attach them to the concat node. */
      for (unsigned idx = 0 ;  idx < parms_.count() ;  idx += 1) {
            if (parms_[idx] == 0) {
                  cerr << get_line() << ": error: Missing expression "
                       << (idx+1) << " of concatenation list." << endl;
                  des->errors += 1;
                  continue;
            }

            assert(parms_[idx]);
            NetExpr*ex = elab_and_eval(des, scope, parms_[idx], 0, 0);
            if (ex == 0) continue;

            ex->set_line(*parms_[idx]);

            if (! ex->has_width()) {
                  cerr << ex->get_line() << ": error: operand of "
                       << "concatenation has indefinite width: "
                       << *ex << endl;
                  des->errors += 1;
            }

            wid_sum += ex->expr_width();
            tmp->set(idx, ex);
      }

      tmp->set_width(wid_sum * tmp->repeat());

      return tmp;
}

NetExpr* PEFNumber::elaborate_expr(Design*des, NetScope*scope, int, bool) const
{
      NetECReal*tmp = new NetECReal(*value_);
      tmp->set_line(*this);
      tmp->set_width(1U, false);
      return tmp;
}

/*
 * Given that the msb_ and lsb_ are part select expressions, this
 * function calculates their values. Note that this method does *not*
 * convert the values to canonical form.
 */
bool PEIdent::calculate_parts_(Design*des, NetScope*scope,
                               long&msb, long&lsb) const
{
      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.sel == index_component_t::SEL_PART);
      ivl_assert(*this, index_tail.msb && index_tail.lsb);

        /* This handles part selects. In this case, there are
           two bit select expressions, and both must be
           constant. Evaluate them and pass the results back to
           the caller. */
      NetExpr*lsb_ex = elab_and_eval(des, scope, index_tail.lsb, -1);
      NetEConst*lsb_c = dynamic_cast<NetEConst*>(lsb_ex);
      if (lsb_c == 0) {
            cerr << index_tail.lsb->get_line() << ": error: "
                  "Part select expressions must be constant."
                 << endl;
            cerr << index_tail.lsb->get_line() << ":      : "
                  "This lsb expression violates the rule: "
                 << *index_tail.lsb << endl;
            des->errors += 1;
            return false;
      }

      NetExpr*msb_ex = elab_and_eval(des, scope, index_tail.msb, -1);
      NetEConst*msb_c = dynamic_cast<NetEConst*>(msb_ex);
      if (msb_c == 0) {
            cerr << index_tail.msb->get_line() << ": error: "
                  "Part select expressions must be constant."
                 << endl;
            cerr << index_tail.msb->get_line() << ":      : This msb expression "
                  "violates the rule: " << *index_tail.msb << endl;
            des->errors += 1;
            return false;
      }

      msb = msb_c->value().as_long();
      lsb = lsb_c->value().as_long();

      delete msb_ex;
      delete lsb_ex;
      return true;
}

bool PEIdent::calculate_up_do_width_(Design*des, NetScope*scope,
                                     unsigned long&wid) const
{
      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.lsb && index_tail.msb);

      bool flag = true;

        /* Calculate the width expression (in the lsb_ position)
           first. If the expression is not constant, error but guess 1
           so we can keep going and find more errors. */
      NetExpr*wid_ex = elab_and_eval(des, scope, index_tail.lsb, -1);
      NetEConst*wid_c = dynamic_cast<NetEConst*>(wid_ex);

      if (wid_c == 0) {
            cerr << get_line() << ": error: Indexed part width must be "
                 << "constant. Expression in question is..." << endl;
            cerr << get_line() << ":      : " << *wid_ex << endl;
            des->errors += 1;
            flag = false;
      }

      wid = wid_c? wid_c->value().as_ulong() : 1;
      delete wid_ex;

      return flag;
}

unsigned PEIdent::test_width(Design*des, NetScope*scope,
                             unsigned min, unsigned lval,
                             bool&unsized_flag) const
{
      NetNet*       net = 0;
      const NetExpr*par = 0;
      NetEvent*     eve = 0;

      const NetExpr*ex1, *ex2;

      symbol_search(des, scope, path_, net, par, eve, ex1, ex2);

      if (net != 0) {
            const name_component_t&name_tail = path_.back();
            index_component_t::ctype_t use_sel = index_component_t::SEL_NONE;
            if (!name_tail.index.empty())
                  use_sel = name_tail.index.back().sel;

            unsigned use_width = net->vector_width();
            switch (use_sel) {
                case index_component_t::SEL_NONE:
                  break;
                case index_component_t::SEL_PART:
                    { long msb, lsb;
                      calculate_parts_(des, scope, msb, lsb);
                      use_width = 1 + ((msb>lsb)? (msb-lsb) : (lsb-msb));
                      break;
                    }
                case index_component_t::SEL_IDX_UP:
                case index_component_t::SEL_IDX_DO:
                    { unsigned long tmp = 0;
                      calculate_up_do_width_(des, scope, tmp);
                      use_width = tmp;
                      break;
                    }
                case index_component_t::SEL_BIT:
                  use_width = 1;
                  break;
                default:
                  ivl_assert(*this, 0);
            }
            return use_width;
      }

      return min;
}

/*
 * Elaborate an identifier in an expression. The identifier can be a
 * parameter name, a signal name or a memory name. It can also be a
 * scope name (Return a NetEScope) but only certain callers can use
 * scope names. However, we still support it here.
 *
 * Function names are not handled here, they are detected by the
 * parser and are elaborated by PECallFunction.
 *
 * The signal name may be escaped, but that affects nothing here.
 */
NetExpr* PEIdent::elaborate_expr(Design*des, NetScope*scope,
                                 int expr_wid, bool sys_task_arg) const
{
      assert(scope);

      NetNet*       net = 0;
      const NetExpr*par = 0;
      NetEvent*     eve = 0;

      const NetExpr*ex1, *ex2;

      NetScope*found_in = symbol_search(des, scope, path_,
                                        net, par, eve,
                                        ex1, ex2);

        // If the identifier name is a parameter name, then return
        // a reference to the parameter expression.
      if (par != 0)
            return elaborate_expr_param(des, scope, par, found_in, ex1, ex2);


        // If the identifier names a signal (a register or wire)
        // then create a NetESignal node to handle it.
      if (net != 0)
            return elaborate_expr_net(des, scope, net, found_in, sys_task_arg);

        // If the identifier is a named event.
        // is a variable reference.
      if (eve != 0) {
            NetEEvent*tmp = new NetEEvent(eve);
            tmp->set_line(*this);
            return tmp;
      }

        // Hmm... maybe this is a genvar? This is only possible while
        // processing generate blocks, but then the genvar_tmp will be
        // set in the scope.
      if (path_.size() == 1
          && scope->genvar_tmp.str()
          && strcmp(peek_tail_name(path_), scope->genvar_tmp) == 0) {
            if (debug_elaborate)
                  cerr << get_line() << ": debug: " << path_
                       << " is genvar with value " << scope->genvar_tmp_val
                       << "." << endl;
            verinum val (scope->genvar_tmp_val);
            NetEConst*tmp = new NetEConst(val);
            tmp->set_line(*this);
            return tmp;
      }

        // A specparam? Look up the name to see if it is a
        // specparam. If we find it, then turn it into a NetEConst
        // value and return that. Of course, this does not apply if
        // specify blocks are disabled.

      if (gn_specify_blocks_flag) {
            map<perm_string,NetScope::spec_val_t>::const_iterator specp;
            perm_string key = peek_tail_name(path_);
            if (path_.size() == 1
                && ((specp = scope->specparams.find(key)) != scope->specparams.end())) {
                  NetScope::spec_val_t value = (*specp).second;
                  NetExpr*tmp = 0;
                  switch (value.type) {
                      case IVL_VT_BOOL:
                        tmp = new NetEConst(verinum(value.integer));
                        break;
                      case IVL_VT_REAL:
                        tmp = new NetECReal(verireal(value.real_val));
                        break;
                      default:
                        break;
                  }
                  assert(tmp);
                  tmp->set_line(*this);

                  if (debug_elaborate)
                        cerr << get_line() << ": debug: " << path_
                             << " is a specparam" << endl;
                  return tmp;
            }
      }

        // At this point we've exhausted all the possibilities that
        // are not scopes. If this is not a system task argument, then
        // it cannot be a scope name, so give up.

      if (! sys_task_arg) {
              // I cannot interpret this identifier. Error message.
            cerr << get_line() << ": error: Unable to bind wire/reg/memory "
                  "`" << path_ << "' in `" << scope_path(scope) << "'" << endl;
            des->errors += 1;
            return 0;
      }

        // Finally, if this is a scope name, then return that. Look
        // first to see if this is a name of a local scope. Failing
        // that, search globally for a hierarchical name.
      if ((path_.size() == 1)) {
            hname_t use_name ( peek_tail_name(path_) );
            if (NetScope*nsc = scope->child(use_name)) {
                  NetEScope*tmp = new NetEScope(nsc);
                  tmp->set_line(*this);

                  if (debug_elaborate)
                        cerr << get_line() << ": debug: Found scope "
                             << use_name << " in scope " << scope->basename()
                             << endl;

                  return tmp;
            }
      }

      list<hname_t> spath = eval_scope_path(des, scope, path_);

      ivl_assert(*this, spath.size() == path_.size());

        // Try full hierarchical scope name.
      if (NetScope*nsc = des->find_scope(spath)) {
            NetEScope*tmp = new NetEScope(nsc);
            tmp->set_line(*this);

            if (debug_elaborate)
                  cerr << get_line() << ": debug: Found scope "
                       << nsc->basename()
                       << " path=" << path_ << endl;

            if (! sys_task_arg) {
                  cerr << get_line() << ": error: Scope name "
                       << nsc->basename() << " not allowed here." << endl;
                  des->errors += 1;
            }

            return tmp;
      }

        // Try relative scope name.
      if (NetScope*nsc = des->find_scope(scope, spath)) {
            NetEScope*tmp = new NetEScope(nsc);
            tmp->set_line(*this);

            if (debug_elaborate)
                  cerr << get_line() << ": debug: Found scope "
                       << nsc->basename() << " in " << scope_path(scope) << endl;

            return tmp;
      }

        // I cannot interpret this identifier. Error message.
      cerr << get_line() << ": error: Unable to bind wire/reg/memory "
            "`" << path_ << "' in `" << scope_path(scope) << "'" << endl;
      des->errors += 1;
      return 0;
}

/*
 * Handle the case that the identifier is a parameter reference. The
 * parameter expression has already been located for us (as the par
 * argument) so we just need to process the sub-expression.
 */
NetExpr* PEIdent::elaborate_expr_param(Design*des,
                                       NetScope*scope,
                                       const NetExpr*par,
                                       NetScope*found_in,
                                       const NetExpr*par_msb,
                                       const NetExpr*par_lsb) const
{
      NetExpr*tmp = par->dup_expr();

      const name_component_t&name_tail = path_.back();
      index_component_t::ctype_t use_sel = index_component_t::SEL_NONE;
      if (!name_tail.index.empty())
            use_sel = name_tail.index.back().sel;

      if (use_sel == index_component_t::SEL_PART) {
            ivl_assert(*this, !name_tail.index.empty());
            const index_component_t&index_tail = name_tail.index.back();
            ivl_assert(*this, index_tail.msb);
            ivl_assert(*this, index_tail.lsb);

              /* If the identifier has a part select, we support
                 it by pulling the right bits out and making a
                 sized unsigned constant. This code assumes the
                 lsb of a parameter is 0 and the msb is the
                 width of the parameter. */

            verinum*lsn = index_tail.lsb->eval_const(des, scope);
            verinum*msn = index_tail.msb->eval_const(des, scope);
            if ((lsn == 0) || (msn == 0)) {
                  cerr << get_line() << ": error: "
                        "Part select expressions must be "
                        "constant expressions." << endl;
                  des->errors += 1;
                  return 0;
            }

            long lsb = lsn->as_long();
            long msb = msn->as_long();
            if ((lsb < 0) || (msb < lsb)) {
                  cerr << get_line() << ": error: invalid part "
                       << "select: " << path_
                       << "["<<msb<<":"<<lsb<<"]" << endl;
                  des->errors += 1;
                  return 0;
            }
            unsigned long ulsb=lsb;
            unsigned long umsb=msb;

            NetEConst*le = dynamic_cast<NetEConst*>(tmp);
            assert(le);

            verinum result (verinum::V0, msb-lsb+1, true);
            verinum exl = le->value();

              /* Pull the bits from the parameter, one at a
                 time. If the bit is within the range, simply
                 copy it to the result. If the bit is outside
                 the range, we sign extend signed unsized
                 numbers, zero extend unsigned unsigned numbers,
                 and X extend sized numbers. */
            for (unsigned long idx = ulsb ;  idx <= umsb ;  idx += 1) {
                  if (idx < exl.len())
                        result.set(idx-lsb, exl.get(idx));
                  else if (exl.is_string())
                        result.set(idx-lsb, verinum::V0);
                  else if (exl.has_len())
                        result.set(idx-lsb, verinum::Vx);
                  else if (exl.has_sign())
                        result.set(idx-lsb, exl.get(exl.len()-1));
                  else
                        result.set(idx-lsb, verinum::V0);
            }

              /* If the input is a string, and the part select
                 is working on byte boundaries, then the result
                 can be made into a string. */
            if (exl.is_string()
                && (lsb%8 == 0)
                && (result.len()%8 == 0))
                  result = verinum(result.as_string());

            delete tmp;
            tmp = new NetEConst(result);

      } else if (use_sel == index_component_t::SEL_IDX_UP || use_sel == index_component_t::SEL_IDX_DO) {

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

              /* Get and evaluate the width of the index
                 select. This must be constant. */
            NetExpr*wid_ex = elab_and_eval(des, scope, index_tail.lsb, -1);
            NetEConst*wid_ec = dynamic_cast<NetEConst*> (wid_ex);
            if (wid_ec == 0) {
                  cerr << index_tail.lsb->get_line() << ": error: "
                       << "Second expression of indexed part select "
                       << "most be constant." << endl;
                  des->errors += 1;
                  return 0;
            }

            unsigned wid = wid_ec->value().as_ulong();

            NetExpr*idx_ex = elab_and_eval(des, scope, index_tail.msb, -1);
            if (idx_ex == 0) {
                  return 0;
            }

            if (use_sel == index_component_t::SEL_IDX_DO && wid > 1) {
                  idx_ex = make_add_expr(idx_ex, 1-(long)wid);
            }


              /* Wrap the param expression with a part select. */
            tmp = new NetESelect(tmp, idx_ex, wid);


      } else if (use_sel == index_component_t::SEL_BIT) {
            ivl_assert(*this, !name_tail.index.empty());
            const index_component_t&index_tail = name_tail.index.back();
            ivl_assert(*this, index_tail.msb);
            ivl_assert(*this, !index_tail.lsb);

              /* Handle the case where a parameter has a bit
                 select attached to it. Generate a NetESelect
                 object to select the bit as desired. */
            NetExpr*mtmp = index_tail.msb->elaborate_expr(des, scope, -1,false);
            if (! dynamic_cast<NetEConst*>(mtmp)) {
                  NetExpr*re = mtmp->eval_tree();
                  if (re) {
                        delete mtmp;
                        mtmp = re;
                  }
            }

              /* Let's first try to get constant values for both
                 the parameter and the bit select. If they are
                 both constant, then evaluate the bit select and
                 return instead a single-bit constant. */

            NetEConst*le = dynamic_cast<NetEConst*>(tmp);
            NetEConst*re = dynamic_cast<NetEConst*>(mtmp);
            if (le && re) {

                    /* Argument and bit select are constant. Calculate
                       the final result. */
                  verinum lv = le->value();
                  verinum rv = re->value();
                  verinum::V rb = verinum::Vx;

                  long ridx = rv.as_long();
                  if ((ridx >= 0) && ((unsigned long) ridx < lv.len())) {
                        rb = lv[ridx];

                  } else if ((ridx >= 0) && (!lv.has_len())) {
                        if (lv.has_sign())
                              rb = lv[lv.len()-1];
                        else
                              rb = verinum::V0;
                  }

                  NetEConst*re = new NetEConst(verinum(rb, 1));
                  delete tmp;
                  delete mtmp;
                  tmp = re;

            } else {

                  const NetEConst*par_me =dynamic_cast<const NetEConst*>(par_msb);
                  const NetEConst*par_le =dynamic_cast<const NetEConst*>(par_lsb);

                  assert(par_me || !par_msb);
                  assert(par_le || !par_lsb);
                  assert(par_me || !par_le);

                  if (par_me) {
                        long par_mv = par_me->value().as_long();
                        long par_lv = par_le->value().as_long();
                        if (par_mv >= par_lv) {
                              mtmp = par_lv
                                    ? make_add_expr(mtmp, 0-par_lv)
                                    : mtmp;
                        } else {
                              if (par_lv != 0)
                                    mtmp = make_add_expr(mtmp, 0-par_mv);
                              mtmp = make_sub_expr(par_lv-par_mv, mtmp);
                        }
                  }

                    /* The value is constant, but the bit select
                       expression is not. Elaborate a NetESelect to
                       evaluate the select at run-time. */

                  NetESelect*stmp = new NetESelect(tmp, mtmp, 1);
                  tmp->set_line(*this);
                  tmp = stmp;
            }

      } else {
              /* No bit or part select. Make the constant into a
                 NetEConstParam if possible. */
            NetEConst*ctmp = dynamic_cast<NetEConst*>(tmp);
            if (ctmp != 0) {
                  perm_string name = peek_tail_name(path_);
                  NetEConstParam*ptmp
                        = new NetEConstParam(found_in, name, ctmp->value());
                  delete tmp;
                  tmp = ptmp;
            }
      }

      tmp->set_line(*this);
      return tmp;
}

/*
 * Handle word selects of vector arrays.
 */
NetExpr* PEIdent::elaborate_expr_net_word_(Design*des, NetScope*scope,
                                           NetNet*net, NetScope*found_in,
                                           bool sys_task_arg) const
{
      const name_component_t&name_tail = path_.back();

      if (name_tail.index.empty() && !sys_task_arg) {
            cerr << get_line() << ": error: Array " << path()
                 << " Needs an array index here." << endl;
            des->errors += 1;
            return 0;
      }

      index_component_t index_front;
      if (! name_tail.index.empty()) {
            index_front = name_tail.index.front();
            ivl_assert(*this, index_front.sel != index_component_t::SEL_NONE);
            if (index_front.sel != index_component_t::SEL_BIT) {
                  cerr << get_line() << ": error: Array " << path_
                       << " cannot be indexed by a range." << endl;
                  des->errors += 1;
                  return 0;
            }
            ivl_assert(*this, index_front.msb);
            ivl_assert(*this, !index_front.lsb);
      }

      NetExpr*word_index = index_front.sel == index_component_t::SEL_NONE
            ? 0
            : elab_and_eval(des, scope, index_front.msb, -1);
      if (word_index == 0 && !sys_task_arg)
            return 0;

      if (NetEConst*word_addr = dynamic_cast<NetEConst*>(word_index)) {
            long addr = word_addr->value().as_long();

              // Special case: The index is out of range, so the value
              // of this expression is a 'bx vector the width of a word.
            if (!net->array_index_is_valid(addr)) {
                  verinum xxx (verinum::Vx, net->vector_width());
                  NetEConst*resx = new NetEConst(xxx);
                  resx->set_line(*this);
                  delete word_index;
                  return resx;
            }

              // Recalculate the constant address with the adjusted base.
            unsigned use_addr = net->array_index_to_address(addr);
            if (addr < 0 || use_addr != (unsigned long)addr) {
                  verinum val (use_addr, 8*sizeof(use_addr));
                  NetEConst*tmp = new NetEConst(val);
                  tmp->set_line(*this);
                  delete word_index;
                  word_index = tmp;
            }

      } else if (word_index) {
              // If there is a non-zero base to the memory, then build an
              // expression to calculate the canonical address.
            if (long base = net->array_first()) {

                  word_index = make_add_expr(word_index, 0-base);
                  if (NetExpr*tmp = word_index->eval_tree()) {
                        word_index = tmp;
                  }
            }
      }

      NetESignal*res = new NetESignal(net, word_index);
      res->set_line(*this);

        // Detect that the word has a bit/part select as well.

      index_component_t::ctype_t word_sel = index_component_t::SEL_NONE;
      if (name_tail.index.size() > 1)
            word_sel = name_tail.index.back().sel;

      if (word_sel == index_component_t::SEL_PART)
            return elaborate_expr_net_part_(des, scope, res, found_in);

      if (word_sel == index_component_t::SEL_IDX_UP)
            return elaborate_expr_net_idx_up_(des, scope, res, found_in);

      if (word_sel == index_component_t::SEL_IDX_DO)
            return elaborate_expr_net_idx_do_(des, scope, res, found_in);

      if (word_sel == index_component_t::SEL_BIT)
            return elaborate_expr_net_bit_(des, scope, res, found_in);

      ivl_assert(*this, word_sel == index_component_t::SEL_NONE);
      return res;
}

/*
 * Handle part selects of NetNet identifiers.
 */
NetExpr* PEIdent::elaborate_expr_net_part_(Design*des, NetScope*scope,
                                      NetESignal*net, NetScope*found_in) const
{
      long msv, lsv;
      bool flag = calculate_parts_(des, scope, msv, lsv);
      if (!flag)
            return 0;

        /* The indices of part selects are signed integers, so allow
           negative values. However, the width that they represent is
           unsigned. Remember that any order is possible,
           i.e., [1:0], [-4:6], etc. */
      unsigned long wid = 1 + ((msv>lsv)? (msv-lsv) : (lsv-msv));
      if (wid > net->vector_width()) {
            cerr << get_line() << ": error: part select ["
                 << msv << ":" << lsv << "] out of range." << endl;
            des->errors += 1;
              //delete lsn;
              //delete msn;
            return net;
      }
      ivl_assert(*this, wid <= net->vector_width());

      if (net->sig()->sb_to_idx(msv) < net->sig()->sb_to_idx(lsv)) {
            cerr << get_line() << ": error: part select ["
                 << msv << ":" << lsv << "] out of order." << endl;
            des->errors += 1;
              //delete lsn;
              //delete msn;
            return net;
      }


      if (net->sig()->sb_to_idx(msv) >= net->vector_width()) {
            cerr << get_line() << ": error: part select ["
                 << msv << ":" << lsv << "] out of range." << endl;
            des->errors += 1;
              //delete lsn;
              //delete msn;
            return net;
      }

        // If the part select convers exactly the entire
        // vector, then do not bother with it. Return the
        // signal itself.
      if (net->sig()->sb_to_idx(lsv) == 0 && wid == net->vector_width())
            return net;

      NetExpr*ex = new NetEConst(verinum(net->sig()->sb_to_idx(lsv)));
      NetESelect*ss = new NetESelect(net, ex, wid);
      ss->set_line(*this);

      return ss;
}

/*
 * Part select indexed up, i.e. net[<m> +: <l>]
 */
NetExpr* PEIdent::elaborate_expr_net_idx_up_(Design*des, NetScope*scope,
                                      NetESignal*net, NetScope*found_in) const
{
      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.lsb != 0);
      ivl_assert(*this, index_tail.msb != 0);

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

      unsigned long wid = 0;
      calculate_up_do_width_(des, scope, wid);


        // Handle the special case that the base is constant as
        // well. In this case it can be converted to a conventional
        // part select.
      if (NetEConst*base_c = dynamic_cast<NetEConst*> (base)) {
            long lsv = base_c->value().as_long();

              // If the part select convers exactly the entire
              // vector, then do not bother with it. Return the
              // signal itself.
            if (net->sig()->sb_to_idx(lsv) == 0 && wid == net->vector_width())
                  return net;

              // Otherwise, make a part select that covers the right range.
            NetExpr*ex = new NetEConst(verinum(net->sig()->sb_to_idx(lsv)));
            NetESelect*ss = new NetESelect(net, ex, wid);
            ss->set_line(*this);

            delete base;
            return ss;
      }

      if (net->msi() > net->lsi()) {
            if (long offset = net->lsi())
                  base = make_add_expr(base, 0-offset);
      } else {
            long vwid = net->lsi() - net->msi() + 1;
            long offset = net->msi();
            base = make_sub_expr(vwid-offset-wid, base);
      }

      NetESelect*ss = new NetESelect(net, base, wid);
      ss->set_line(*this);

      if (debug_elaborate) {
            cerr << get_line() << ": debug: Elaborate part "
                 << "select base="<< *base << ", wid="<< wid << endl;
      }

      return ss;
}

/*
 * Part select indexed down, i.e. net[<m> -: <l>]
 */
NetExpr* PEIdent::elaborate_expr_net_idx_do_(Design*des, NetScope*scope,
                                           NetESignal*net, NetScope*found_in)const
{
      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.lsb != 0);
      ivl_assert(*this, index_tail.msb != 0);

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

      unsigned long wid = 0;
      calculate_up_do_width_(des, scope, wid);

        // Handle the special case that the base is constant as
        // well. In this case it can be converted to a conventional
        // part select.
      if (NetEConst*base_c = dynamic_cast<NetEConst*> (base)) {
            long lsv = base_c->value().as_long();

              // If the part select convers exactly the entire
              // vector, then do not bother with it. Return the
              // signal itself.
            if (net->sig()->sb_to_idx(lsv) == (wid-1) && wid == net->vector_width())
                  return net;

              // Otherwise, make a part select that covers the right range.
            NetExpr*ex = new NetEConst(verinum(net->sig()->sb_to_idx(lsv)-wid+1));
            NetESelect*ss = new NetESelect(net, ex, wid);
            ss->set_line(*this);

            delete base;
            return ss;
      }

      long offset = net->lsi();
      NetExpr*base_adjusted = wid > 1
            ? make_add_expr(base,1-(long)wid-offset)
            : (offset == 0? base : make_add_expr(base, 0-offset));
      NetESelect*ss = new NetESelect(net, base_adjusted, wid);
      ss->set_line(*this);

      if (debug_elaborate) {
            cerr << get_line() << ": debug: Elaborate part "
                 << "select base="<< *base_adjusted << ", wid="<< wid << endl;
      }

      return ss;
}

NetExpr* PEIdent::elaborate_expr_net_bit_(Design*des, NetScope*scope,
                                      NetESignal*net, NetScope*found_in) const
{
      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);

      NetExpr*ex = elab_and_eval(des, scope, index_tail.msb, -1);

        // If the bit select is constant, then treat it similar
        // to the part select, so that I save the effort of
        // making a mux part in the netlist.
      if (NetEConst*msc = dynamic_cast<NetEConst*> (ex)) {
            long msv = msc->value().as_long();
            unsigned idx = net->sig()->sb_to_idx(msv);

            if (idx >= net->vector_width()) {
                    /* The bit select is out of range of the
                       vector. This is legal, but returns a
                       constant 1'bx value. */
                  verinum x (verinum::Vx);
                  NetEConst*tmp = new NetEConst(x);
                  tmp->set_line(*this);

                  cerr << get_line() << ": warning: Bit select ["
                       << msv << "] out of range of vector "
                       << net->name() << "[" << net->sig()->msb()
                       << ":" << net->sig()->lsb() << "]." << endl;
                  cerr << get_line() << ":        : Replacing "
                       << "expression with a constant 1'bx." << endl;
                  delete ex;
                  return tmp;
            }

              // If the vector is only one bit, we are done. The
              // bit select will return the scaler itself.
            if (net->vector_width() == 1)
                  return net;

              // Make an expression out of the index
            NetEConst*idx_c = new NetEConst(verinum(idx));
            idx_c->set_line(*net);

              // Make a bit select with the canonical index
            NetESelect*res = new NetESelect(net, idx_c, 1);
            res->set_line(*net);

            return res;
      }

        // Non-constant bit select? punt and make a subsignal
        // device to mux the bit in the net. This is a fairly
        // complicated task because we need to generate
        // expressions to convert calculated bit select
        // values to canonical values that are used internally.

      if (net->sig()->msb() < net->sig()->lsb()) {
            ex = make_sub_expr(net->sig()->lsb(), ex);
      } else {
            ex = make_add_expr(ex, - net->sig()->lsb());
      }

      NetESelect*ss = new NetESelect(net, ex, 1);
      ss->set_line(*this);
      return ss;
}

NetExpr* PEIdent::elaborate_expr_net(Design*des, NetScope*scope,
                                     NetNet*net, NetScope*found_in,
                                     bool sys_task_arg) const
{
      if (net->array_dimensions() > 0)
            return elaborate_expr_net_word_(des, scope, net, found_in, sys_task_arg);

      NetESignal*node = new NetESignal(net);
      node->set_line(*this);

      index_component_t::ctype_t use_sel = index_component_t::SEL_NONE;
      if (! path_.back().index.empty())
            use_sel = path_.back().index.back().sel;

        // If this is a part select of a signal, then make a new
        // temporary signal that is connected to just the
        // selected bits. The lsb_ and msb_ expressions are from
        // the foo[msb:lsb] expression in the original.
      if (use_sel == index_component_t::SEL_PART)
            return elaborate_expr_net_part_(des, scope, node, found_in);

      if (use_sel == index_component_t::SEL_IDX_UP)
            return elaborate_expr_net_idx_up_(des, scope, node, found_in);

      if (use_sel == index_component_t::SEL_IDX_DO)
            return elaborate_expr_net_idx_do_(des, scope, node, found_in);

      if (use_sel == index_component_t::SEL_BIT)
            return elaborate_expr_net_bit_(des, scope, node, found_in);

        // It's not anything else, so this must be a simple identifier
        // expression with no part or bit select. Return the signal
        // itself as the expression.
      assert(use_sel == index_component_t::SEL_NONE);

      return node;
}

unsigned PENumber::test_width(Design*, NetScope*,
                              unsigned min, unsigned lval, bool&unsized_flag) const
{
      unsigned use_wid = value_->len();
      if (min > use_wid)
            use_wid = min;

      if (! value_->has_len())
            unsized_flag = true;

      return use_wid;
}

NetEConst* PENumber::elaborate_expr(Design*des, NetScope*,
                                    int expr_width, bool) const
{
      assert(value_);
      verinum tvalue = *value_;

        // If the expr_width is >0, then the context is requesting a
        // specific size (for example this is part of the r-values of
        // an assignment) so we pad to the desired width and ignore
        // the self-determined size.
      if (expr_width > 0) {
            tvalue = pad_to_width(tvalue, expr_width);
      }

      NetEConst*tmp = new NetEConst(tvalue);
      tmp->set_line(*this);
      return tmp;
}

unsigned PEString::test_width(Design*des, NetScope*scope,
                              unsigned min, unsigned lval,
                              bool&unsized_flag) const
{
      unsigned use_wid = text_? 8*strlen(text_) : 0;
      if (min > use_wid)
            use_wid = min;

      return use_wid;
}

NetEConst* PEString::elaborate_expr(Design*des, NetScope*,
                                    int expr_width, bool) const
{
      NetEConst*tmp = new NetEConst(value());
      tmp->set_line(*this);
      return tmp;
}

unsigned PETernary::test_width(Design*des, NetScope*scope,
                               unsigned min, unsigned lval,
                               bool&flag) const
{
      unsigned tru_wid = tru_->test_width(des, scope, min, lval, flag);
      unsigned fal_wid = fal_->test_width(des, scope, min, lval, flag);
      return max(tru_wid,fal_wid);
}

static bool test_ternary_operand_compat(ivl_variable_type_t l,
                                        ivl_variable_type_t r)
{
      if (l == IVL_VT_LOGIC && r == IVL_VT_BOOL)
            return true;
      if (l == IVL_VT_BOOL && r == IVL_VT_LOGIC)
            return true;
      if (l == r)
            return true;

      return false;
}

/*
 * Elaborate the Ternary operator. I know that the expressions were
 * parsed so I can presume that they exist, and call elaboration
 * methods. If any elaboration fails, then give up and return 0.
 */
NetETernary*PETernary::elaborate_expr(Design*des, NetScope*scope,
                                      int expr_wid, bool) const
{
      assert(expr_);
      assert(tru_);
      assert(fal_);

      if (expr_wid < 0) {
            bool flag = false;
            unsigned tru_wid = tru_->test_width(des, scope, 0, 0, flag);
            unsigned fal_wid = fal_->test_width(des, scope, 0, 0, flag);
            expr_wid = max(tru_wid, fal_wid);
            if (debug_elaborate)
                  cerr << get_line() << ": debug: "
                       << "Self-sized ternary chooses wid="<< expr_wid
                       << " from " <<tru_wid
                       << " and " << fal_wid << endl;
      }

      NetExpr*con = expr_->elaborate_expr(des, scope, -1, false);
      if (con == 0)
            return 0;

      NetExpr*tru = tru_->elaborate_expr(des, scope, expr_wid, false);
      if (tru == 0) {
            delete con;
            return 0;
      }

      NetExpr*fal = fal_->elaborate_expr(des, scope, expr_wid, false);
      if (fal == 0) {
            delete con;
            delete tru;
            return 0;
      }

      if (! test_ternary_operand_compat(tru->expr_type(), fal->expr_type())) {
            cerr << get_line() << ": error: Data types "
                 << tru->expr_type() << " and "
                 << fal->expr_type() << " of ternary"
                 << " do not match." << endl;
            des->errors += 1;
            return 0;
      }

        /* Whatever the width we choose for the ternary operator, we
        need to make sure the operands match. */
      tru = pad_to_width(tru, expr_wid);
      fal = pad_to_width(fal, expr_wid);

      NetETernary*res = new NetETernary(con, tru, fal);
      res->set_line(*this);
      return res;
}

NetExpr* PEUnary::elaborate_expr(Design*des, NetScope*scope,
                                 int expr_wid, bool) const
{
      NetExpr*ip = expr_->elaborate_expr(des, scope, expr_wid, false);
      if (ip == 0) return 0;

      /* Should we evaluate expressions ahead of time,
       * just like in PEBinary::elaborate_expr() ?
       */

      NetExpr*tmp;
      switch (op_) {
          default:
            tmp = new NetEUnary(op_, ip);
            tmp->set_line(*this);
            break;

          case '-':
            if (NetEConst*ipc = dynamic_cast<NetEConst*>(ip)) {

                  verinum val = ipc->value();
                  if (expr_wid > 0)
                        val = pad_to_width(val, expr_wid);

                    /* When taking the - of a number, turn it into a
                       signed expression and extend it one bit to
                       accommodate a possible sign bit. */
                  verinum zero (verinum::V0, val.len()+1, val.has_len());
                  verinum nval = zero - val;

                  if (val.has_len())
                        nval = verinum(nval, val.len());
                  nval.has_sign(true);
                  tmp = new NetEConst(nval);
                  tmp->set_line(*this);
                  delete ip;

            } else if (NetECReal*ipc = dynamic_cast<NetECReal*>(ip)) {

                    /* When taking the - of a real, fold this into the
                       constant value. */
                  verireal val = - ipc->value();
                  tmp = new NetECReal(val);
                  tmp->set_line( *ip );
                  delete ip;

            } else {
                  tmp = new NetEUnary(op_, ip);
                  tmp->set_line(*this);
            }
            break;

          case '+':
            tmp = ip;
            break;

          case '!': // Logical NOT
              /* If the operand to unary ! is a constant, then I can
                 evaluate this expression here and return a logical
                 constant in its place. */
            if (NetEConst*ipc = dynamic_cast<NetEConst*>(ip)) {
                  verinum val = ipc->value();
                  unsigned v1 = 0;
                  unsigned vx = 0;
                  for (unsigned idx = 0 ;  idx < val.len() ;  idx += 1)
                        switch (val[idx]) {
                            case verinum::V0:
                              break;
                            case verinum::V1:
                              v1 += 1;
                              break;
                            default:
                              vx += 1;
                              break;
                        }

                  verinum::V res;
                  if (v1 > 0)
                        res = verinum::V0;
                  else if (vx > 0)
                        res = verinum::Vx;
                  else
                        res = verinum::V1;

                  verinum vres (res, 1, true);
                  tmp = new NetEConst(vres);
                  tmp->set_line(*this);
                  delete ip;
            } else {
                  tmp = new NetEUReduce(op_, ip);
                  tmp->set_line(*this);
            }
            break;

          case '&': // Reduction AND
          case '|': // Reduction OR
          case '^': // Reduction XOR
          case 'A': // Reduction NAND (~&)
          case 'N': // Reduction NOR (~|)
          case 'X': // Reduction NXOR (~^)
            tmp = new NetEUReduce(op_, ip);
            tmp->set_line(*this);
            break;

          case '~':
            tmp = new NetEUBits(op_, ip);
            tmp->set_line(*this);
            break;
      }

      return tmp;
}