--- a/src/share/vm/opto/library_call.cpp	Thu Jul 21 17:14:02 2016 +0000
+++ b/src/share/vm/opto/library_call.cpp	Thu Jul 21 21:42:16 2016 +0000
@@ -2405,8 +2405,13 @@
   Compile::AliasType* alias_type = C->alias_type(adr_type);
   assert(alias_type->index() != Compile::AliasIdxBot, "no bare pointers here");
 
-  assert(alias_type->adr_type() == TypeRawPtr::BOTTOM || alias_type->adr_type() == TypeOopPtr::BOTTOM ||
-         alias_type->basic_type() != T_ILLEGAL, "field, array element or unknown");
+  // Only field, array element or unknown locations are supported.
+  if (alias_type->adr_type() != TypeRawPtr::BOTTOM &&
+      alias_type->adr_type() != TypeOopPtr::BOTTOM &&
+      alias_type->basic_type() == T_ILLEGAL) {
+    return false;
+  }
+
   bool mismatched = false;
   BasicType bt = alias_type->basic_type();
   if (bt != T_ILLEGAL) {
@@ -2782,12 +2787,6 @@
       ShouldNotReachHere();
   }
 
-  // Null check receiver.
-  receiver = null_check(receiver);
-  if (stopped()) {
-    return true;
-  }
-
   // Build field offset expression.
   // We currently rely on the cookies produced by Unsafe.xxxFieldOffset
   // to be plain byte offsets, which are also the same as those accepted
@@ -2799,8 +2798,6 @@
   const TypePtr *adr_type = _gvn.type(adr)->isa_ptr();
 
   Compile::AliasType* alias_type = C->alias_type(adr_type);
-  assert(alias_type->adr_type() == TypeRawPtr::BOTTOM || alias_type->adr_type() == TypeOopPtr::BOTTOM ||
-         alias_type->basic_type() != T_ILLEGAL, "field, array element or unknown");
   BasicType bt = alias_type->basic_type();
   if (bt != T_ILLEGAL &&
       ((bt == T_OBJECT || bt == T_ARRAY) != (type == T_OBJECT))) {
@@ -2832,6 +2829,12 @@
       ShouldNotReachHere();
   }
 
+  // Null check receiver.
+  receiver = null_check(receiver);
+  if (stopped()) {
+    return true;
+  }
+
   int alias_idx = C->get_alias_index(adr_type);
 
   // Memory-model-wise, a LoadStore acts like a little synchronized

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/compiler/unsafe/OpaqueAccesses.java	Thu Jul 21 21:42:16 2016 +0000
@@ -0,0 +1,134 @@
+/*
+ * Copyright (c) 2016, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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 8155781
+ * @modules java.base/jdk.internal.misc
+ *
+ * @run main/bootclasspath/othervm -XX:+IgnoreUnrecognizedVMOptions -XX:+UnlockDiagnosticVMOptions
+ *                                 -XX:-TieredCompilation -Xbatch
+ *                                 -XX:CompileCommand=dontinline,compiler.unsafe.OpaqueAccesses::test*
+ *                                 compiler.unsafe.OpaqueAccesses
+ */
+package compiler.unsafe;
+
+import jdk.internal.misc.Unsafe;
+
+import java.lang.reflect.Field;
+
+public class OpaqueAccesses {
+    private static final Unsafe UNSAFE = Unsafe.getUnsafe();
+
+    private static final Object INSTANCE = new OpaqueAccesses();
+
+    private static final Object[] ARRAY = new Object[10];
+
+    private static final long F_OFFSET;
+    private static final long E_OFFSET;
+
+    static {
+        try {
+            Field field = OpaqueAccesses.class.getDeclaredField("f");
+            F_OFFSET = UNSAFE.objectFieldOffset(field);
+
+            E_OFFSET = UNSAFE.arrayBaseOffset(ARRAY.getClass());
+        } catch (NoSuchFieldException e) {
+            throw new Error(e);
+        }
+    }
+
+    private Object f = new Object();
+
+    static Object testFixedOffsetField(Object o) {
+        return UNSAFE.getObject(o, F_OFFSET);
+    }
+
+    static int testFixedOffsetHeader0(Object o) {
+        return UNSAFE.getInt(o, 0);
+    }
+
+    static int testFixedOffsetHeader4(Object o) {
+        return UNSAFE.getInt(o, 4);
+    }
+
+    static Object testFixedBase(long off) {
+        return UNSAFE.getObject(INSTANCE, off);
+    }
+
+    static Object testOpaque(Object o, long off) {
+        return UNSAFE.getObject(o, off);
+    }
+
+    static int testFixedOffsetHeaderArray0(Object[] arr) {
+        return UNSAFE.getInt(arr, 0);
+    }
+
+    static int testFixedOffsetHeaderArray4(Object[] arr) {
+        return UNSAFE.getInt(arr, 4);
+    }
+
+    static Object testFixedOffsetArray(Object[] arr) {
+        return UNSAFE.getObject(arr, E_OFFSET);
+    }
+
+    static Object testFixedBaseArray(long off) {
+        return UNSAFE.getObject(ARRAY, off);
+    }
+
+    static Object testOpaqueArray(Object[] o, long off) {
+        return UNSAFE.getObject(o, off);
+    }
+
+    static final long ADDR = UNSAFE.allocateMemory(10);
+    static boolean flag;
+
+    static int testMixedAccess() {
+        flag = !flag;
+        Object o = (flag ? INSTANCE : null);
+        long off = (flag ? F_OFFSET : ADDR);
+        return UNSAFE.getInt(o, off);
+    }
+
+    public static void main(String[] args) {
+        for (int i = 0; i < 20_000; i++) {
+            // Instance
+            testFixedOffsetField(INSTANCE);
+            testFixedOffsetHeader0(INSTANCE);
+            testFixedOffsetHeader4(INSTANCE);
+            testFixedBase(F_OFFSET);
+            testOpaque(INSTANCE, F_OFFSET);
+            testMixedAccess();
+
+            // Array
+            testFixedOffsetHeaderArray0(ARRAY);
+            testFixedOffsetHeaderArray4(ARRAY);
+            testFixedOffsetArray(ARRAY);
+            testFixedBaseArray(E_OFFSET);
+            testOpaqueArray(ARRAY, E_OFFSET);
+        }
+        System.out.println("TEST PASSED");
+    }
+}