# HG changeset patch
# User Peter Hofer <peter.hofer@jku.at>
# Date 1310127972 -7200
# Node ID 52087773be5b5e4fe5c27f2877aeaef8e5721b22
# Parent  f328020ca67fe546b3112d5f8d82e1b9a608ef19
IdealGraphVisualizer: Make scheduling more robust by ignoring graphs without any nodes and by using the node with the lowest id as root when there is no node labeled "Root" and no node without predecessors

diff -r f328020ca67f -r 52087773be5b src/share/tools/IdealGraphVisualizer/ServerCompiler/src/com/sun/hotspot/igv/servercompiler/ServerCompilerScheduler.java
--- a/src/share/tools/IdealGraphVisualizer/ServerCompiler/src/com/sun/hotspot/igv/servercompiler/ServerCompilerScheduler.java	Fri Jul 08 11:56:25 2011 +0200
+++ b/src/share/tools/IdealGraphVisualizer/ServerCompiler/src/com/sun/hotspot/igv/servercompiler/ServerCompilerScheduler.java	Fri Jul 08 14:26:12 2011 +0200
@@ -186,6 +186,10 @@
     }
 
     public Collection<InputBlock> schedule(InputGraph graph) {
+        if (graph.getNodes().isEmpty()) {
+            return Collections.emptyList();
+        }
+
         if (graph.getBlocks().size() > 0) {
             Collection<InputNode> tmpNodes = new ArrayList<InputNode>(graph.getNodes());
             for (InputNode n : tmpNodes) {
@@ -207,7 +211,6 @@
             buildCommonDominators();
             scheduleLatest();
 
-
             InputBlock noBlock = null;
             for (InputNode n : graph.getNodes()) {
                 if (graph.getBlock(n) == null) {
@@ -225,9 +228,7 @@
         }
     }
 
-    public void scheduleLatest() {
-
-
+    private void scheduleLatest() {
         Node root = findRoot();
         if(root == null) {
             assert false : "No root found!";
@@ -552,21 +553,30 @@
     }
 
     private Node findRoot() {
-
+        Node minNode = null;
         Node alternativeRoot = null;
-        for (Node n : nodes) {
-            InputNode inputNode = n.inputNode;
+
+        for (Node node : nodes) {
+            InputNode inputNode = node.inputNode;
             String s = inputNode.getProperties().get("name");
             if (s != null && s.equals("Root")) {
-                return n;
+                return node;
             }
 
-            if (n.preds.size() == 0) {
-                alternativeRoot = n;
+            if (alternativeRoot == null && node.preds.isEmpty()) {
+                alternativeRoot = node;
+            }
+
+            if (minNode == null || node.inputNode.getId() < minNode.inputNode.getId()) {
+                minNode = node;
             }
         }
 
-        return alternativeRoot;
+        if (alternativeRoot != null) {
+            return alternativeRoot;
+        } else {
+            return minNode;
+        }
     }
 
     public void buildUpGraph() {