Index: mlir/include/mlir/Analysis/CallGraph.h
===================================================================
--- mlir/include/mlir/Analysis/CallGraph.h
+++ mlir/include/mlir/Analysis/CallGraph.h
@@ -184,9 +184,14 @@
   /// registered.
   CallGraphNode *lookupNode(Region *region) const;
 
-  /// Return the callgraph node representing the indirect-external callee.
-  CallGraphNode *getExternalNode() const {
-    return const_cast<CallGraphNode *>(&externalNode);
+  /// Return the callgraph node representing an external caller.
+  CallGraphNode *getExternalCallerNode() const {
+    return const_cast<CallGraphNode *>(&externalCallerNode);
+  }
+
+  /// Return the callgraph node representing an indirect callee.
+  CallGraphNode *getUnknownCalleeNode() const {
+    return const_cast<CallGraphNode *>(&unknownCalleeNode);
   }
 
   /// Resolve the callable for given callee to a node in the callgraph, or the
@@ -212,8 +217,11 @@
   /// The set of nodes within the callgraph.
   NodeMapT nodes;
 
-  /// A special node used to indicate an external edges.
-  CallGraphNode externalNode;
+  /// A special node used to indicate an external caller.
+  CallGraphNode externalCallerNode;
+
+  /// A special node used to indicate an unknown callee.
+  CallGraphNode unknownCalleeNode;
 };
 
 } // namespace mlir
@@ -246,7 +254,7 @@
     : public GraphTraits<const mlir::CallGraphNode *> {
   /// The entry node into the graph is the external node.
   static NodeRef getEntryNode(const mlir::CallGraph *cg) {
-    return cg->getExternalNode();
+    return cg->getExternalCallerNode();
   }
 
   // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
Index: mlir/lib/Analysis/CallGraph.cpp
===================================================================
--- mlir/lib/Analysis/CallGraph.cpp
+++ mlir/lib/Analysis/CallGraph.cpp
@@ -92,7 +92,9 @@
       computeCallGraph(&nested, cg, symbolTable, parentNode, resolveCalls);
 }
 
-CallGraph::CallGraph(Operation *op) : externalNode(/*callableRegion=*/nullptr) {
+CallGraph::CallGraph(Operation *op)
+    : externalCallerNode(/*callableRegion=*/nullptr),
+      unknownCalleeNode(/*callableRegion=*/nullptr) {
   // Make two passes over the graph, one to compute the callables and one to
   // resolve the calls. We split these up as we may have nested callable objects
   // that need to be reserved before the calls.
@@ -122,7 +124,7 @@
       // that *could* be called from external sources. This requires extending
       // the interface for callables to check if they may be referenced
       // externally.
-      externalNode.addAbstractEdge(node.get());
+      externalCallerNode.addAbstractEdge(node.get());
     }
   }
   return node.get();
@@ -136,7 +138,7 @@
 }
 
 /// Resolve the callable for given callee to a node in the callgraph, or the
-/// external node if a valid node was not resolved.
+/// unknown callee node if a valid node was not resolved.
 CallGraphNode *
 CallGraph::resolveCallable(CallOpInterface call,
                            SymbolTableCollection &symbolTable) const {
@@ -145,8 +147,7 @@
     if (auto *node = lookupNode(callableOp.getCallableRegion()))
       return node;
 
-  // If we don't have a valid direct region, this is an external call.
-  return getExternalNode();
+  return getUnknownCalleeNode();
 }
 
 /// Erase the given node from the callgraph.
@@ -176,8 +177,12 @@
 
   // Functor used to output the name for the given node.
   auto emitNodeName = [&](const CallGraphNode *node) {
-    if (node->isExternal()) {
-      os << "<External-Node>";
+    if (node == getExternalCallerNode()) {
+      os << "<External-Caller-Node>";
+      return;
+    }
+    if (node == getUnknownCalleeNode()) {
+      os << "<Unknown-Callee-Node>";
       return;
     }
 
Index: mlir/test/Analysis/test-callgraph.mlir
===================================================================
--- mlir/test/Analysis/test-callgraph.mlir
+++ mlir/test/Analysis/test-callgraph.mlir
@@ -11,7 +11,7 @@
   func.func private @func_b()
 
   // CHECK: Node{{.*}}func_c
-  // CHECK-NEXT: Call-Edge{{.*}}External-Node
+  // CHECK-NEXT: Call-Edge{{.*}}Unknown-Callee-Node
   func.func @func_c() {
     call @func_b() : () -> ()
     return
@@ -69,3 +69,29 @@
     return
   }
 }
+
+// -----
+
+// CHECK-LABEL: Testing : "SCC"
+// CHECK: SCCs
+module attributes {test.name = "SCC"} {
+  // CHECK: SCC :
+  // CHECK-NEXT: Node{{.*}}Unknown-Callee-Node
+
+  // CHECK: SCC :
+  // CHECK-NEXT: Node{{.*}}foo
+  func.func @foo(%arg0 : () -> ()) {
+    call_indirect %arg0() : () -> ()
+    return
+  }
+
+  // CHECK: SCC :
+  // CHECK-NEXT: Node{{.*}}bar
+  func.func @bar() {
+    return
+  }
+
+  // CHECK: SCC :
+  // CHECK-NEXT: Node{{.*}}External-Caller-Node
+}
+