diff --git a/eval_tree.cc b/eval_tree.cc
index a8c597de6..5591e31a5 100644
--- a/eval_tree.cc
+++ b/eval_tree.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT) && !defined(macintosh)
-#ident "$Id: eval_tree.cc,v 1.31 2001/12/30 00:39:25 steve Exp $"
+#ident "$Id: eval_tree.cc,v 1.32 2002/01/22 01:40:04 steve Exp $"
 #endif
 
 # include "config.h"
@@ -758,6 +758,50 @@ NetEConst* NetEConcat::eval_tree()
       return res;
 }
 
+/*
+ * There are limits to our ability to evaluate a memory reference
+ * expression, because the content of a memory is never
+ * constant. However, the index expression may be precalculated, and
+ * there are certain index values that do give us constant results.
+ */
+NetExpr* NetEMemory::eval_tree()
+{
+	/* Attempt to evaluate the index expression to a constant, if
+	   it is not already. */
+      if (idx_ && !dynamic_cast<NetEConst*>(idx_)) {
+	    NetExpr* tmp = idx_->eval_tree();
+	    if (tmp) {
+		  delete idx_;
+		  idx_ = tmp;
+	    }
+      }
+
+      NetEConst*itmp = dynamic_cast<NetEConst*>(idx_);
+      if (itmp == 0)
+	    return 0;
+
+      verinum ival = itmp->value();
+
+	/* If the index expression has any x or z bits, then we know
+	   already that the expression result is a constant x. */
+      if (! ival.is_defined()) {
+	    verinum xres (verinum::Vx, mem_->width(), false);
+	    NetEConst*res = new NetEConst(xres);
+	    return res;
+      }
+
+	/* If the index expression is outside the range of the memory,
+	   then the result is a constant x. */
+      unsigned norm_idx = mem_->index_to_address(ival.as_long());
+      if (norm_idx >= mem_->count()) {
+	    verinum xres (verinum::Vx, mem_->width(), false);
+	    NetEConst*res = new NetEConst(xres);
+	    return res;
+      }
+
+      return 0;
+}
+
 NetExpr* NetEParam::eval_tree()
 {
       if (des_ == 0)
@@ -1019,6 +1063,9 @@ NetEConst* NetEUReduce::eval_tree()
 
 /*
  * $Log: eval_tree.cc,v $
+ * Revision 1.32  2002/01/22 01:40:04  steve
+ *  Precalculate constant results of memory index expressions.
+ *
  * Revision 1.31  2001/12/30 00:39:25  steve
  *  Evaluate constant unary minus.
  *
diff --git a/netlist.cc b/netlist.cc
index e413b9326..a26237987 100644
--- a/netlist.cc
+++ b/netlist.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT) && !defined(macintosh)
-#ident "$Id: netlist.cc,v 1.179 2001/12/31 00:08:14 steve Exp $"
+#ident "$Id: netlist.cc,v 1.180 2002/01/22 01:40:04 steve Exp $"
 #endif
 
 # include "config.h"
@@ -2084,6 +2084,16 @@ NetEMemory::~NetEMemory()
 {
 }
 
+const string& NetEMemory::name() const
+{
+      return mem_->name();
+}
+
+const NetExpr* NetEMemory::index() const
+{
+      return idx_;
+}
+
 NetMemory::NetMemory(NetScope*sc, const string&n, long w, long s, long e)
 : name_(n), width_(w), idxh_(s), idxl_(e), ram_list_(0), scope_(sc)
 {
@@ -2405,6 +2415,9 @@ const NetProc*NetTaskDef::proc() const
 
 /*
  * $Log: netlist.cc,v $
+ * Revision 1.180  2002/01/22 01:40:04  steve
+ *  Precalculate constant results of memory index expressions.
+ *
  * Revision 1.179  2001/12/31 00:08:14  steve
  *  Support $signed cast of expressions.
  *
diff --git a/netlist.h b/netlist.h
index 1addf73de..cfa989b6d 100644
--- a/netlist.h
+++ b/netlist.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT) && !defined(macintosh)
-#ident "$Id: netlist.h,v 1.229 2002/01/19 19:02:08 steve Exp $"
+#ident "$Id: netlist.h,v 1.230 2002/01/22 01:40:04 steve Exp $"
 #endif
 
 /*
@@ -2467,11 +2467,12 @@ class NetEMemory  : public NetExpr {
       NetEMemory(NetMemory*mem, NetExpr*idx =0);
       virtual ~NetEMemory();
 
-      const string& name () const { return mem_->name(); }
-      const NetExpr* index() const { return idx_; }
+      const string& name () const;
+      const NetExpr* index() const;
 
       virtual bool set_width(unsigned);
 
+      NetExpr* eval_tree();
       virtual NetEMemory*dup_expr() const;
 
       virtual void expr_scan(struct expr_scan_t*) const;
@@ -2864,6 +2865,9 @@ extern ostream& operator << (ostream&, NetNet::Type);
 
 /*
  * $Log: netlist.h,v $
+ * Revision 1.230  2002/01/22 01:40:04  steve
+ *  Precalculate constant results of memory index expressions.
+ *
  * Revision 1.229  2002/01/19 19:02:08  steve
  *  Pass back target errors processing conditionals.
  *