Add hooks to print debug information into the graphml file

src/main/scala/diplomacy/LazyModule.scala

@@ -69,6 +69,7 @@ abstract class LazyModule()(implicit val p: Parameters)
     buf ++= "<graphml xmlns=\"http://graphml.graphdrawing.org/xmlns\" xmlns:y=\"http://www.yworks.com/xml/graphml\">\n"
     buf ++= "  <key for=\"node\" id=\"n\" yfiles.type=\"nodegraphics\"/>\n"
     buf ++= "  <key for=\"edge\" id=\"e\" yfiles.type=\"edgegraphics\"/>\n"
+    buf ++= "  <key for=\"node\" id=\"d\" attr.name=\"NodeDebugString\" attr.type=\"string\"/>\n"
     buf ++= "  <graph id=\"G\" edgedefault=\"directed\">\n"
     nodesGraphML(buf, "    ")
     edgesGraphML(buf, "    ")
@@ -84,7 +85,9 @@ abstract class LazyModule()(implicit val p: Parameters)
     buf ++= s"""${pad}  <data key=\"n\"><y:ShapeNode><y:NodeLabel modelName=\"sides\" modelPosition=\"w\" rotationAngle=\"270.0\">${module.instanceName}</y:NodeLabel></y:ShapeNode></data>\n"""
     buf ++= s"""${pad}  <graph id=\"${index}::\" edgedefault=\"directed\">\n"""
     nodes.filter(!_.omitGraphML).foreach { n =>
-      buf ++= s"""${pad}    <node id=\"${index}::${n.index}\"/>\n"""
+      buf ++= s"""${pad}    <node id=\"${index}::${n.index}\">\n"""
+      buf ++= s"""${pad}      <data key=\"d\">${n.nodedebugstring}</data>\n"""
+      buf ++= s"""${pad}    </node>\n"""
     }
     children.filter(!_.omitGraphML).foreach { _.nodesGraphML(buf, pad + "    ") }
     buf ++= s"""${pad}  </graph>\n"""

src/main/scala/diplomacy/Nodes.scala

@@ -60,6 +60,7 @@ abstract class BaseNode
   def nodename = getClass.getName.split('.').last
   def name = lazyModule.name + "." + nodename
   def omitGraphML = outputs.isEmpty && inputs.isEmpty
+  lazy val nodedebugstring: String = ""
 
   protected[diplomacy] def gci: Option[BaseNode] // greatest common inner
   protected[diplomacy] def gco: Option[BaseNode] // greatest common outer