--- /dev/null	2019-03-28 11:24:58.000000000 -0700
+++ new/src/jdk.internal.vm.ci/share/classes/jdk.vm.ci.hotspot/src/jdk/vm/ci/hotspot/HandleCleaner.java	2019-03-28 11:24:57.000000000 -0700
@@ -0,0 +1,84 @@
+/*
+ * Copyright (c) 2018, 2019, 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.
+ */
+package jdk.vm.ci.hotspot;
+
+import static jdk.vm.ci.hotspot.UnsafeAccess.UNSAFE;
+
+/**
+ * This class manages a set of {@code jobject} and {@code jmetadata} handles whose lifetimes are
+ * dependent on associated {@link IndirectHotSpotObjectConstantImpl} and
+ * {@link MetaspaceHandleObject} wrapper objects respectively.
+ *
+ * The general theory of operation is that all wrappers are created by calling into the VM which
+ * calls back out to actually create the wrapper instance. During the call the VM keeps the object
+ * or metadata reference alive through the use of handles. Once the call completes the wrapper
+ * object is registered here and will be scanned during metadata scanning. The weakness of the
+ * reference to the wrapper object allows the handles to be reclaimed when they are no longer used.
+ */
+final class HandleCleaner extends Cleaner {
+
+    /**
+     * A {@code jmetadata} or {@code jobject} handle.
+     */
+    private final long handle;
+
+    /**
+     * Specifies if {@link #handle} is a {@code jobject} or {@code jmetadata}.
+     */
+    private final boolean isJObject;
+
+    private HandleCleaner(Object wrapper, long handle, boolean isJObject) {
+        super(wrapper);
+        this.handle = handle;
+        this.isJObject = isJObject;
+    }
+
+    /**
+     * Releases the resource associated with {@code this.handle}.
+     */
+    @Override
+    void doCleanup() {
+        if (isJObject) {
+            // The sentinel value used to denote a free handle is
+            // an object on the HotSpot heap so we call into the
+            // VM to set the target of an object handle to this value.
+            CompilerToVM.compilerToVM().deleteGlobalHandle(handle);
+        } else {
+            // Setting the target of a jmetadata handle to 0 enables
+            // the handle to be reused. See MetadataHandleBlock in
+            // jvmciRuntime.cpp for more info.
+            long value = UNSAFE.getLong(null, handle);
+            UNSAFE.compareAndSetLong(null, handle, value, 0);
+        }
+    }
+
+    /**
+     * Registers a cleaner for {@code handle}. The cleaner will release the handle some time after
+     * {@code wrapper} is detected as unreachable by the garbage collector.
+     */
+    @SuppressWarnings("unused")
+    static void create(Object wrapper, long handle) {
+        assert wrapper instanceof IndirectHotSpotObjectConstantImpl || wrapper instanceof MetaspaceHandleObject;
+        new HandleCleaner(wrapper, handle, wrapper instanceof IndirectHotSpotObjectConstantImpl);
+    }
+}