--- a/hotspot/src/share/vm/opto/cfgnode.cpp	Thu Jul 16 14:10:42 2009 -0700
+++ b/hotspot/src/share/vm/opto/cfgnode.cpp	Thu Jul 16 16:29:55 2009 -0700
@@ -1796,8 +1796,12 @@
     for (uint i=1; i<req(); ++i) {// For all paths in
       Node *ii = in(i);
       if (ii->is_DecodeN() && ii->bottom_type() == bottom_type()) {
-        has_decodeN = true;
-        in_decodeN = ii->in(1);
+        // Note: in_decodeN is used only to define the type of new phi.
+        // Find a non dead path otherwise phi type will be wrong.
+        if (ii->in(1)->bottom_type() != Type::TOP) {
+          has_decodeN = true;
+          in_decodeN = ii->in(1);
+        }
       } else if (!ii->is_Phi()) {
         may_push = false;
       }
@@ -1805,7 +1809,6 @@
 
     if (has_decodeN && may_push) {
       PhaseIterGVN *igvn = phase->is_IterGVN();
-      // Note: in_decodeN is used only to define the type of new phi here.
       PhiNode *new_phi = PhiNode::make_blank(in(0), in_decodeN);
       uint orig_cnt = req();
       for (uint i=1; i<req(); ++i) {// For all paths in

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/test/compiler/6851282/Test.java	Thu Jul 16 16:29:55 2009 -0700
@@ -0,0 +1,124 @@
+/*
+ * Copyright 2009 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+/**
+ * @test
+ * @bug 6851282
+ * @summary JIT miscompilation results in null entry in array when using CompressedOops
+ *
+ * @run main/othervm -XX:+IgnoreUnrecognizedVMOptions -XX:+UseCompressedOops Test
+ */
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Test {
+  void foo(A a, A[] as) {
+    for (A a1 : as) {
+      B[] filtered = a.c(a1);
+      for (B b : filtered) {
+        if (b == null) {
+          System.out.println("bug: b == null");
+          System.exit(97);
+        }
+      }
+    }
+  }
+
+  public static void main(String[] args) {
+    List<A> as = new ArrayList<A>();
+    for (int i = 0; i < 5000; i++) {
+      List<B> bs = new ArrayList<B>();
+      for (int j = i; j < i + 1000; j++)
+        bs.add(new B(j));
+      as.add(new A(bs.toArray(new B[0])));
+    }
+    new Test().foo(as.get(0), as.subList(1, as.size()).toArray(new A[0]));
+  }
+}
+
+class A {
+  final B[] bs;
+
+  public A(B[] bs) {
+    this.bs = bs;
+  }
+
+  final B[] c(final A a) {
+    return new BoxedArray<B>(bs).filter(new Function<B, Boolean>() {
+      public Boolean apply(B arg) {
+        for (B b : a.bs) {
+          if (b.d == arg.d)
+            return true;
+        }
+        return false;
+      }
+    });
+  }
+}
+
+class BoxedArray<T> {
+
+  private final T[] array;
+
+  BoxedArray(T[] array) {
+    this.array = array;
+  }
+
+  public T[] filter(Function<T, Boolean> function) {
+    boolean[] include = new boolean[array.length];
+    int len = 0;
+    int i = 0;
+    while (i < array.length) {
+      if (function.apply(array[i])) {
+        include[i] = true;
+        len += 1;
+      }
+      i += 1;
+    }
+    T[] result = (T[]) java.lang.reflect.Array.newInstance(array.getClass().getComponentType(), len);
+    len = 0;
+    i = 0;
+    while (len < result.length) {
+      if (include[i]) {
+        result[len] = array[i];
+        len += 1;
+      }
+      i += 1;
+    }
+    return result;
+  }
+}
+
+interface Function<T, R> {
+  R apply(T arg);
+}
+
+class B {
+  final int d;
+  public B(int d) {
+    this.d = d;
+  }
+}
+