From 15becdaee44020b2c40033f1143a0f35e0d900c0 Mon Sep 17 00:00:00 2001
From: steve <steve>
Date: Thu, 18 Jul 2002 02:06:37 +0000
Subject: [PATCH]  Need driver for sure in assign feedback and other cases.

---
 elaborate.cc        | 52 +++++++++++++++++++++++++++++++++++++++------
 tgt-vvp/vvp_scope.c | 11 +++++++++-
 2 files changed, 56 insertions(+), 7 deletions(-)

diff --git a/elaborate.cc b/elaborate.cc
index 642867fa3..47e0ac99b 100644
--- a/elaborate.cc
+++ b/elaborate.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT) && !defined(macintosh)
-#ident "$Id: elaborate.cc,v 1.256 2002/07/18 00:24:22 steve Exp $"
+#ident "$Id: elaborate.cc,v 1.257 2002/07/18 02:06:37 steve Exp $"
 #endif
 
 # include "config.h"
@@ -122,12 +122,47 @@ void PGAssign::elaborate(Design*des, NetScope*scope) const
 	    if (rid->pin_count() < cnt)
 		  cnt = rid->pin_count();
 
-	    if ((rid->type() == lval->type()) && (rise_time == 0)) {
-		  unsigned idx;
-		  for (idx = 0 ;  idx < cnt; idx += 1) {
-			if (! lval->pin(idx) .is_linked (rid->pin(idx)))
-			      connect(lval->pin(idx), rid->pin(idx));
+	    bool need_driver_flag = false;
+
+	      /* If the device is linked to itself, a driver is
+		 needed. Should I print a warning here? */
+	    for (unsigned idx = 0 ;  idx < cnt ;  idx += 1) {
+		  if (lval->pin(idx) .is_linked (rid->pin(idx))) {
+			need_driver_flag = true;
+			break;
 		  }
+	    }
+
+	      /* If the nets are different type (i.e. reg vs tri) then
+		 a driver is needed. */
+	    if (rid->type() != lval->type())
+		  need_driver_flag = true;
+
+	      /* If there is a delay, then I need a driver to carry
+		 it. */
+	    if (rise_time || fall_time || decay_time)
+		  need_driver_flag = true;
+
+	      /* If there is a strength to be carried, then I need a
+		 driver to carry that strength. */
+	    for (unsigned idx = 0 ;  idx < cnt ;  idx += 1) {
+		  if (rid->pin(idx).drive0() != drive0) {
+			need_driver_flag = true;
+			break;
+		  }
+		  if (rid->pin(idx).drive1() != drive1) {
+			need_driver_flag = true;
+			break;
+		  }
+	    }
+
+	    if (! need_driver_flag) {
+		    /* Don't need a driver, presumably because the
+		       r-value already has the needed drivers. Just
+		       hook things up. */
+		  unsigned idx;
+		  for (idx = 0 ;  idx < cnt; idx += 1)
+			connect(lval->pin(idx), rid->pin(idx));
 
 		  if (cnt < lval->pin_count()) {
 			verinum tmpv (0UL, lval->pin_count()-cnt);
@@ -140,6 +175,8 @@ void PGAssign::elaborate(Design*des, NetScope*scope) const
 		  }
 
 	    } else {
+		    /* Do need a driver. Use BUFZ objects to carry the
+		       strength and delays. */
 		  unsigned idx;
 		  for (idx = 0 ; idx < cnt ;  idx += 1) {
 			NetBUFZ*dev = new NetBUFZ(scope,
@@ -2466,6 +2503,9 @@ Design* elaborate(list<const char*>roots)
 
 /*
  * $Log: elaborate.cc,v $
+ * Revision 1.257  2002/07/18 02:06:37  steve
+ *  Need driver for sure in assign feedback and other cases.
+ *
  * Revision 1.256  2002/07/18 00:24:22  steve
  *  Careful with assign to self.
  *
diff --git a/tgt-vvp/vvp_scope.c b/tgt-vvp/vvp_scope.c
index 0c6f81bf8..ea4283006 100644
--- a/tgt-vvp/vvp_scope.c
+++ b/tgt-vvp/vvp_scope.c
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: vvp_scope.c,v 1.73 2002/07/08 04:04:07 steve Exp $"
+#ident "$Id: vvp_scope.c,v 1.74 2002/07/18 02:06:37 steve Exp $"
 #endif
 
 # include  "vvp_priv.h"
@@ -253,6 +253,9 @@ static const char* draw_net_input_drive(ivl_nexus_t nex, ivl_nexus_ptr_t nptr)
 		  if (ivl_logic_delay(lptr, 0) != 0)
 			break;
 
+		  if (nex == ivl_logic_pin(lptr, 1))
+			break;
+
 		  return draw_net_input(ivl_logic_pin(lptr, 1));
 	    } while(0);
 
@@ -705,6 +708,9 @@ static void draw_logic_in_scope(ivl_net_logic_t lptr)
 		if (ivl_logic_delay(lptr, 0) != 0)
 		      break;
 
+		if (ivl_logic_pin(lptr, 0) == ivl_logic_pin(lptr, 1))
+		      break;
+
 		return;
 	  }
 
@@ -1460,6 +1466,9 @@ int draw_scope(ivl_scope_t net, ivl_scope_t parent)
 
 /*
  * $Log: vvp_scope.c,v $
+ * Revision 1.74  2002/07/18 02:06:37  steve
+ *  Need driver for sure in assign feedback and other cases.
+ *
  * Revision 1.73  2002/07/08 04:04:07  steve
  *  Generate code for wide muxes.
  *