--- old/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.core.common/src/org/graalvm/compiler/core/common/cfg/AbstractControlFlowGraph.java	2017-03-20 17:37:08.000000000 -0700
+++ new/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.core.common/src/org/graalvm/compiler/core/common/cfg/AbstractControlFlowGraph.java	2017-03-20 17:37:08.000000000 -0700
@@ -81,6 +81,8 @@
             return b;
         } else if (b == null) {
             return a;
+        } else if (a == b) {
+            return a;
         } else {
             int aDomDepth = a.getDominatorDepth();
             int bDomDepth = b.getDominatorDepth();