--- a/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/cfg/ControlFlowGraph.java	Thu Feb 19 15:44:05 2015 +0100
+++ b/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/cfg/ControlFlowGraph.java	Thu Feb 19 20:31:06 2015 +0100
@@ -266,29 +266,30 @@
                     computeLoopBlocks(exitBlock.getFirstPredecessor(), loop);
                     loop.getExits().add(exitBlock);
                 }
-                List<Block> unexpected = new LinkedList<>();
-                for (Block b : loop.getBlocks()) {
+
+                // The following loop can add new blocks to the end of the loop's block list.
+                int size = loop.getBlocks().size();
+                for (int i = 0; i < size; ++i) {
+                    Block b = loop.getBlocks().get(i);
                     for (Block sux : b.getSuccessors()) {
                         if (sux.loop != loop) {
                             AbstractBeginNode begin = sux.getBeginNode();
                             if (!(begin instanceof LoopExitNode && ((LoopExitNode) begin).loopBegin() == loopBegin)) {
                                 Debug.log(3, "Unexpected loop exit with %s, including whole branch in the loop", sux);
-                                unexpected.add(sux);
+                                addBranchToLoop(loop, sux);
                             }
                         }
                     }
                 }
-                for (Block b : unexpected) {
-                    addBranchToLoop(loop, b);
-                }
             }
         }
     }
 
     private static void addBranchToLoop(Loop<Block> l, Block b) {
-        if (l.getBlocks().contains(b)) {
+        if (b.loop == l) {
             return;
         }
+        assert !(l.getBlocks().contains(b));
         l.getBlocks().add(b);
         b.loop = l;
         for (Block sux : b.getSuccessors()) {