--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/jdk.internal.vm.ci/share/classes/jdk.vm.ci.hotspot/src/jdk/vm/ci/hotspot/HotSpotObjectConstantScope.java	Fri Jun 21 16:21:13 2019 -0700
@@ -0,0 +1,121 @@
+/*
+ * Copyright (c) 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 java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+
+import jdk.vm.ci.services.Services;
+
+/**
+ * A mechanism for limiting the lifetime of a foreign object reference encapsulated in a
+ * {@link HotSpotObjectConstant}.
+ *
+ * A {@link HotSpotObjectConstant} allocated in a {@linkplain #openLocalScope local} scope will have
+ * its reference to any foreign object cleared when the scope {@linkplain #close() closes}. This
+ * allows the foreign memory manager to reclaim the foreign object (once there are no other strong
+ * references to it).
+ *
+ * {@link HotSpotObjectConstantScope}s have no impact on {@link HotSpotObjectConstant}s that do not
+ * encapsulate a foreign object reference.
+ *
+ * The object returned by {@link #enterGlobalScope()} or {@link #openLocalScope(Object)} should
+ * always be used in a try-with-resources statement. Failure to close a scope will almost certainly
+ * result in foreign objects being leaked.
+ */
+public final class HotSpotObjectConstantScope implements AutoCloseable {
+    static final ThreadLocal<HotSpotObjectConstantScope> CURRENT = new ThreadLocal<>();
+
+    private final HotSpotObjectConstantScope parent;
+    private List<IndirectHotSpotObjectConstantImpl> foreignObjects;
+
+    /**
+     * An object whose {@link Object#toString()} value describes a non-global scope. This is
+     * {@code null} iff this is a global scope.
+     */
+    final Object localScopeDescription;
+
+    /**
+     * Opens a local scope that upon closing, will release foreign object references encapsulated by
+     * {@link HotSpotObjectConstant}s created in the scope.
+     *
+     * @param description an non-null object whose {@link Object#toString()} value describes the
+     *            scope being opened
+     * @return {@code null} if the current runtime does not support remote object references
+     */
+    public static HotSpotObjectConstantScope openLocalScope(Object description) {
+        return Services.IS_IN_NATIVE_IMAGE ? new HotSpotObjectConstantScope(Objects.requireNonNull(description)) : null;
+    }
+
+    /**
+     * Enters the global scope. This is useful to escape a local scope for execution that will
+     * create foreign object references that need to outlive the local scope.
+     *
+     * Foreign object references encapsulated by {@link HotSpotObjectConstant}s created in the
+     * global scope are only subject to reclamation once the {@link HotSpotObjectConstant} wrapper
+     * dies.
+     *
+     * @return {@code null} if the current runtime does not support remote object references or if
+     *         this thread is currently in the global scope
+     */
+    public static HotSpotObjectConstantScope enterGlobalScope() {
+        return Services.IS_IN_NATIVE_IMAGE && CURRENT.get() != null ? new HotSpotObjectConstantScope(null) : null;
+    }
+
+    private HotSpotObjectConstantScope(Object localScopeDescription) {
+        this.parent = CURRENT.get();
+        CURRENT.set(this);
+        this.localScopeDescription = localScopeDescription;
+    }
+
+    /**
+     * Determines if this scope is global.
+     */
+    boolean isGlobal() {
+        return localScopeDescription == null;
+    }
+
+    void add(IndirectHotSpotObjectConstantImpl obj) {
+        assert !isGlobal();
+        if (foreignObjects == null) {
+            foreignObjects = new ArrayList<>();
+        }
+        foreignObjects.add(obj);
+    }
+
+    @VMEntryPoint
+    @Override
+    public void close() {
+        if (CURRENT.get() != this) {
+            throw new IllegalStateException("Cannot close non-active scope");
+        }
+        if (foreignObjects != null) {
+            for (IndirectHotSpotObjectConstantImpl obj : foreignObjects) {
+                obj.clear(localScopeDescription);
+            }
+            foreignObjects = null;
+        }
+        CURRENT.set(parent);
+    }
+}