--- a/hotspot/src/share/vm/c1/c1_Optimizer.cpp	Fri Jul 01 10:37:37 2011 -0700
+++ b/hotspot/src/share/vm/c1/c1_Optimizer.cpp	Tue Jul 05 16:07:54 2011 -0700
@@ -642,7 +642,7 @@
 void NullCheckVisitor::do_NewTypeArray   (NewTypeArray*    x) { nce()->handle_NewArray(x); }
 void NullCheckVisitor::do_NewObjectArray (NewObjectArray*  x) { nce()->handle_NewArray(x); }
 void NullCheckVisitor::do_NewMultiArray  (NewMultiArray*   x) { nce()->handle_NewArray(x); }
-void NullCheckVisitor::do_CheckCast      (CheckCast*       x) {}
+void NullCheckVisitor::do_CheckCast      (CheckCast*       x) { nce()->clear_last_explicit_null_check(); }
 void NullCheckVisitor::do_InstanceOf     (InstanceOf*      x) {}
 void NullCheckVisitor::do_MonitorEnter   (MonitorEnter*    x) { nce()->handle_AccessMonitor(x); }
 void NullCheckVisitor::do_MonitorExit    (MonitorExit*     x) { nce()->handle_AccessMonitor(x); }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/test/compiler/6478991/NullCheckTest.java	Tue Jul 05 16:07:54 2011 -0700
@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+/**
+ * @test
+ * @bug 6478991
+ * @summary C1 NullCheckEliminator yields incorrect exceptions
+ *
+ * @run main/othervm -XX:CompileOnly=NullCheckTest.test,NullCheckTest.inlined  -Xcomp NullCheckTest
+ */
+
+public class NullCheckTest {
+        static class A {
+                int f;
+
+                public final void inlined(A a) {
+                        // This cast is intended to fail.
+                        B b = ((B) a);
+                }
+        }
+
+        static class B extends A {
+        }
+
+
+        private static void test(A a1, A a2) {
+                // Inlined call must do a null check on a1.
+                // However, the exlipcit NullCheck instruction is eliminated and
+                // the null check is folded into the field load below, so the
+                // exception in the inlined method is thrown before the null check
+                // and the NullPointerException is not thrown.
+                a1.inlined(a2);
+
+                int x = a1.f;
+        }
+
+        public static void main(String[] args) {
+                // load classes
+                new B();
+                try {
+                        test(null, new A());
+
+                        throw new InternalError("FAILURE: no exception");
+                } catch (NullPointerException ex) {
+                        System.out.println("CORRECT: NullPointerException");
+                } catch (ClassCastException ex) {
+                        System.out.println("FAILURE: ClassCastException");
+                        throw ex;
+                }
+        }
+}