--- a/graal/com.oracle.graal.compiler.test/src/com/oracle/graal/compiler/test/GraalCompilerTest.java	Mon Jan 26 09:28:20 2015 -0800
+++ b/graal/com.oracle.graal.compiler.test/src/com/oracle/graal/compiler/test/GraalCompilerTest.java	Mon Jan 26 09:29:47 2015 -0800
@@ -142,21 +142,21 @@
 
             @Override
             protected void run(StructuredGraph graph) {
-                assert checkHighTierGraph(graph);
+                assert checkHighTierGraph(graph) : "failed HighTier graph check";
             }
         });
         ret.getMidTier().appendPhase(new Phase("CheckGraphPhase") {
 
             @Override
             protected void run(StructuredGraph graph) {
-                assert checkMidTierGraph(graph);
+                assert checkMidTierGraph(graph) : "failed MidTier graph check";
             }
         });
         ret.getLowTier().appendPhase(new Phase("CheckGraphPhase") {
 
             @Override
             protected void run(StructuredGraph graph) {
-                assert checkLowTierGraph(graph);
+                assert checkLowTierGraph(graph) : "failed LowTier graph check";
             }
         });
         return ret;

--- a/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/cfg/ControlFlowGraph.java	Mon Jan 26 09:28:20 2015 -0800
+++ b/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/cfg/ControlFlowGraph.java	Mon Jan 26 09:29:47 2015 -0800
@@ -222,6 +222,7 @@
                 probability *= loopBegin.loopFrequency();
                 for (LoopEndNode predNode : loopBegin.orderedLoopEnds()) {
                     Block predBlock = nodeToBlock.get(predNode);
+                    assert predBlock != null : predNode;
                     if (predBlock.getId() >= 0) {
                         predecessors.add(predBlock);
                     }