Add support for delaying constants at T0.

This patch adds support for delaying constants at time zero. It also
cleans up the code in elab_net.cc to use this capability instead of
building it with an extra BUFZ to carry the delay information.

design_dump.cc

@@ -372,7 +372,14 @@ void NetFF::dump_node(ostream&o, unsigned ind) const
 void NetLiteral::dump_node(ostream&o, unsigned ind) const
 {
       o << setw(ind) << "" << "constant real " << real_
-	<< ": " << name() << endl;
+	<< ": " << name();
+      if (rise_time())
+	    o << " #(" << *rise_time()
+	      << "," << *fall_time()
+	      << "," << *decay_time() << ")";
+      else
+	    o << " #(.,.,.)";
+      o << endl;
       dump_node_pins(o, ind+4);
 }
 

elab_net.cc

@@ -2381,6 +2381,11 @@ NetNet* PEFNumber::elaborate_net(Design*des, NetScope*scope,
 
       NetLiteral*obj = new NetLiteral(scope, scope->local_symbol(), value());
       obj->set_line(*this);
+      obj->rise_time(rise);
+      obj->fall_time(fall);
+      obj->decay_time(decay);
+      obj->pin(0).drive0(drive0);
+      obj->pin(0).drive1(drive1);
       des->add_node(obj);
 
       NetNet*net = new NetNet(scope, scope->local_symbol(), NetNet::WIRE, 1);
@@ -2389,30 +2394,7 @@ NetNet* PEFNumber::elaborate_net(Design*des, NetScope*scope,
       net->local_flag(true);
       net->set_line(*this);
 
-	/* If there are non-zero output delays, then create bufz
-	   devices to carry the propagation delays. Otherwise, just
-	   connect the result to the output. */
-      if (rise || fall || decay) {
-	    NetNet*tmp = new NetNet(scope, scope->local_symbol(),
-				    NetNet::WIRE, lwidth);
-	    tmp->data_type(IVL_VT_REAL);
-	    tmp->local_flag(true);
-
-	    NetBUFZ*tmpz = new NetBUFZ(scope, scope->local_symbol(), lwidth);
-	    tmpz->rise_time(rise);
-	    tmpz->fall_time(fall);
-	    tmpz->decay_time(decay);
-	    tmpz->pin(0).drive0(drive0);
-	    tmpz->pin(0).drive1(drive1);
-
-	    connect(obj->pin(0), tmp->pin(0));
-	    connect(tmp->pin(0), tmpz->pin(1));
-	    connect(tmpz->pin(0), net->pin(0));
-
-	    des->add_node(tmpz);
-      } else {
       connect(obj->pin(0), net->pin(0));
-      }
 
       return net;
 }
@@ -2872,8 +2854,6 @@ NetNet* PENumber::elaborate_net(Design*des, NetScope*scope,
 		  num = verinum(num, lwidth);
 
 	    con = new NetConst(scope, scope->local_symbol(), num);
-	    con->pin(0).drive0(drive0);
-	    con->pin(0).drive1(drive1);
 
 	/* If the number has a length, then use that to size the
 	   number. Generate a constant object of exactly the user
@@ -2928,31 +2908,13 @@ NetNet* PENumber::elaborate_net(Design*des, NetScope*scope,
 	    con = new NetConst(scope, scope->local_symbol(), num);
       }
 
-	/* If there are non-zero output delays, then create bufz
+      con->rise_time(rise);
-	   devices to carry the propagation delays. Otherwise, just
+      con->fall_time(fall);
-	   connect the result to the output. */
+      con->decay_time(decay);
-      if (rise || fall || decay) {
+      con->pin(0).drive0(drive0);
-	    NetNet*tmp = new NetNet(scope, scope->local_symbol(),
+      con->pin(0).drive1(drive1);
-				    NetNet::WIRE, net->vector_width());
-	    tmp->data_type(IVL_VT_LOGIC);
-	    tmp->local_flag(true);
 
-	    NetBUFZ*tmpz = new NetBUFZ(scope, scope->local_symbol(),
-	                               net->vector_width());
-	    tmpz->rise_time(rise);
-	    tmpz->fall_time(fall);
-	    tmpz->decay_time(decay);
-	    tmpz->pin(0).drive0(drive0);
-	    tmpz->pin(0).drive1(drive1);
-
-	    connect(con->pin(0), tmp->pin(0));
-	    connect(tmp->pin(0), tmpz->pin(1));
-	    connect(net->pin(0), tmpz->pin(0));
-
-	    des->add_node(tmpz);
-      } else {
       connect(con->pin(0), net->pin(0));
-      }
 
       des->add_node(con);
       return net;
@@ -3000,33 +2962,15 @@ NetNet* PEString::elaborate_net(Design*des, NetScope*scope,
 
       NetConst*con = new NetConst(scope, scope->local_symbol(), num);
       con->set_line(*this);
+      con->rise_time(rise);
+      con->fall_time(fall);
+      con->decay_time(decay);
+      con->pin(0).drive0(drive0);
+      con->pin(0).drive1(drive1);
+
       des->add_node(con);
 
-	/* If there are non-zero output delays, then create bufz
-	   devices to carry the propagation delays. Otherwise, just
-	   connect the result to the output. */
-      if (rise || fall || decay) {
-	    NetNet*tmp = new NetNet(scope, scope->local_symbol(),
-				    NetNet::WIRE, net->vector_width());
-	    tmp->data_type(IVL_VT_LOGIC);
-	    tmp->local_flag(true);
-
-	    NetBUFZ*tmpz = new NetBUFZ(scope, scope->local_symbol(),
-	                               net->vector_width());
-	    tmpz->rise_time(rise);
-	    tmpz->fall_time(fall);
-	    tmpz->decay_time(decay);
-	    tmpz->pin(0).drive0(drive0);
-	    tmpz->pin(0).drive1(drive1);
-
-	    connect(con->pin(0), tmp->pin(0));
-	    connect(tmp->pin(0), tmpz->pin(1));
-	    connect(net->pin(0), tmpz->pin(0));
-
-	    des->add_node(tmpz);
-      } else {
       connect(con->pin(0), net->pin(0));
-      }
 
       return net;
 }
@@ -3421,31 +3365,14 @@ NetNet* PEUnary::elab_net_uminus_const_logic_(Design*des, NetScope*scope,
 
       NetConst*con = new NetConst(scope, scope->local_symbol(), tmp);
 
-	/* If there are non-zero output delays, then create bufz
-	   devices to carry the propagation delays. Otherwise, just
-	   connect the result to the output. */
-      if (rise || fall || decay) {
-	    NetNet*tmp = new NetNet(scope, scope->local_symbol(),
-				    NetNet::WIRE, width);
-	    tmp->data_type(IVL_VT_LOGIC);
-	    tmp->local_flag(true);
-
-	    NetBUFZ*tmpz = new NetBUFZ(scope, scope->local_symbol(), width);
-	    tmpz->rise_time(rise);
-	    tmpz->fall_time(fall);
-	    tmpz->decay_time(decay);
-	    tmpz->pin(0).drive0(drive0);
-	    tmpz->pin(0).drive1(drive1);
-
-	    connect(con->pin(0), tmp->pin(0));
-	    connect(tmp->pin(0), tmpz->pin(1));
-	    connect(sig->pin(0), tmpz->pin(0));
-
-	    des->add_node(tmpz);
-      } else {
       connect(con->pin(0), sig->pin(0));
-      }
+
       con->set_line(*this);
+      con->rise_time(rise);
+      con->fall_time(fall);
+      con->decay_time(decay);
+      con->pin(0).drive0(drive0);
+      con->pin(0).drive1(drive1);
 
       des->add_node(con);
 
@@ -3479,31 +3406,14 @@ NetNet* PEUnary::elab_net_uminus_const_real_(Design*des, NetScope*scope,
 
       NetLiteral*con = new NetLiteral(scope, scope->local_symbol(), -val);
 
-	/* If there are non-zero output delays, then create bufz
-	   devices to carry the propagation delays. Otherwise, just
-	   connect the result to the output. */
-      if (rise || fall || decay) {
-	    NetNet*tmp = new NetNet(scope, scope->local_symbol(),
-				    NetNet::WIRE, width);
-	    tmp->data_type(IVL_VT_REAL);
-	    tmp->local_flag(true);
-
-	    NetBUFZ*tmpz = new NetBUFZ(scope, scope->local_symbol(), width);
-	    tmpz->rise_time(rise);
-	    tmpz->fall_time(fall);
-	    tmpz->decay_time(decay);
-	    tmpz->pin(0).drive0(drive0);
-	    tmpz->pin(0).drive1(drive1);
-
-	    connect(con->pin(0), tmp->pin(0));
-	    connect(tmp->pin(0), tmpz->pin(1));
-	    connect(sig->pin(0), tmpz->pin(0));
-
-	    des->add_node(tmpz);
-      } else {
       connect(con->pin(0), sig->pin(0));
-      }
+
       con->set_line(*this);
+      con->rise_time(rise);
+      con->fall_time(fall);
+      con->decay_time(decay);
+      con->pin(0).drive0(drive0);
+      con->pin(0).drive1(drive1);
 
       des->add_node(con);
 

ivl.def

@@ -9,6 +9,7 @@ ivl_design_roots
 ivl_design_time_precision
 
 ivl_const_bits
+ivl_const_delay
 ivl_const_real
 ivl_const_signed
 ivl_const_type

ivl_target.h

@@ -483,6 +483,9 @@ extern ivl_net_const_t ivl_design_const(ivl_design_t, unsigned idx);
  * ivl_const_width
  *    Return the width, in logical bits, of the constant.
  *
+ * ivl_const_delay
+ *    T0 delay for a transition (0, 1 and Z).
+ *
  * SEMANTIC NOTES
  *
  * The const_type of the literal constant must match the
@@ -498,6 +501,7 @@ extern ivl_net_const_t ivl_design_const(ivl_design_t, unsigned idx);
  */
 extern ivl_variable_type_t ivl_const_type(ivl_net_const_t net);
 extern const char* ivl_const_bits(ivl_net_const_t net);
+extern ivl_expr_t  ivl_const_delay(ivl_net_const_t net, unsigned transition);
 extern ivl_nexus_t ivl_const_nex(ivl_net_const_t net);
 extern int         ivl_const_signed(ivl_net_const_t net);
 extern unsigned    ivl_const_width(ivl_net_const_t net);

t-dll-api.cc

@@ -129,6 +129,12 @@ extern "C" const char*ivl_const_bits(ivl_net_const_t net)
       }
 }
 
+extern "C" ivl_expr_t ivl_const_delay(ivl_net_const_t net, unsigned transition)
+{
+      assert(transition < 3);
+      return net->delay[transition];
+}
+
 extern "C" ivl_nexus_t ivl_const_nex(ivl_net_const_t net)
 {
       assert(net);

t-dll.cc

@@ -699,6 +699,44 @@ void dll_target::make_lpm_delays_(struct ivl_lpm_s*obj,
       }
 }
 
+void dll_target::make_const_delays_(struct ivl_net_const_s*obj,
+				    const NetObj*net)
+{
+      obj->delay[0] = 0;
+      obj->delay[1] = 0;
+      obj->delay[2] = 0;
+
+	/* Translate delay expressions to ivl_target form. Try to
+	   preserve pointer equality, not as a rule but to save on
+	   expression trees. */
+      if (net->rise_time()) {
+	    expr_ = 0;
+	    net->rise_time()->expr_scan(this);
+	    obj->delay[0] = expr_;
+	    expr_ = 0;
+      }
+      if (net->fall_time()) {
+	    if (net->fall_time() == net->rise_time()) {
+		  obj->delay[1] = obj->delay[0];
+	    } else {
+		  expr_ = 0;
+		  net->fall_time()->expr_scan(this);
+		  obj->delay[1] = expr_;
+		  expr_ = 0;
+	    }
+      }
+      if (net->decay_time()) {
+	    if (net->decay_time() == net->rise_time()) {
+		  obj->delay[2] = obj->delay[0];
+	    } else {
+		  expr_ = 0;
+		  net->decay_time()->expr_scan(this);
+		  obj->delay[2] = expr_;
+		  expr_ = 0;
+	    }
+      }
+}
+
 /*
  * Add a bufz object to the scope that contains it.
  *
@@ -2045,6 +2083,8 @@ bool dll_target::net_const(const NetConst*net)
 	    realloc(des_.consts, des_.nconsts * sizeof(ivl_net_const_t));
       des_.consts[des_.nconsts-1] = obj;
 
+      make_const_delays_(obj, net);
+
       return true;
 }
 
@@ -2074,6 +2114,8 @@ bool dll_target::net_literal(const NetLiteral*net)
 	    realloc(des_.consts, des_.nconsts * sizeof(ivl_net_const_t));
       des_.consts[des_.nconsts-1] = obj;
 
+      make_const_delays_(obj, net);
+
       return true;
 }
 

t-dll.h

@@ -163,6 +163,7 @@ struct dll_target  : public target_t, public expr_scan_t {
 
       void make_logic_delays_(struct ivl_net_logic_s*obj, const NetObj*net);
       void make_lpm_delays_(struct ivl_lpm_s*obj, const NetObj*net);
+      void make_const_delays_(struct ivl_net_const_s*obj, const NetObj*net);
       void make_scope_parameters(ivl_scope_t scope, const NetScope*net);
       void make_scope_param_expr(ivl_parameter_t cur_par, NetExpr*etmp);
 
@@ -417,6 +418,8 @@ struct ivl_net_const_s {
       } b;
 
       ivl_nexus_t pin_;
+
+      ivl_expr_t delay[3];
 };
 
 /*

tgt-vvp/vvp_scope.c

@@ -649,6 +649,30 @@ static char* draw_net_input_drive(ivl_nexus_t nex, ivl_nexus_ptr_t nptr)
 		  break;
 	    }
 
+	    ivl_expr_t d_rise = ivl_const_delay(cptr, 0);
+	    ivl_expr_t d_fall = ivl_const_delay(cptr, 1);
+	    ivl_expr_t d_decay = ivl_const_delay(cptr, 2);
+
+	      /* We have a delayed constant, so we need to build some code. */
+	    if (d_rise != 0) {
+		  assert(number_is_immediate(d_rise, 64));
+		  assert(number_is_immediate(d_fall, 64));
+		  assert(number_is_immediate(d_decay, 64));
+		  
+		  fprintf(vvp_out, "L_%p/d .functor BUFZ 1, %s, "
+		          "C4<0>, C4<0>, C4<0>;\n", cptr, result);
+		  
+		  fprintf(vvp_out, "L_%p .delay (%lu,%lu,%lu) L_%p/d;\n",
+	                  cptr, get_number_immediate(d_rise),
+	                  get_number_immediate(d_rise),
+	                  get_number_immediate(d_rise), cptr);
+
+		  free(result);
+		  char tmp[128];
+		  snprintf(tmp, sizeof tmp, "L_%p", cptr);
+		  result = strdup(tmp);
+	    }
+
 	    return result;
       }