--- /dev/null	2016-05-31 09:42:47.975716356 -0700
+++ new/src/jdk.vm.compiler/share/classes/org.graalvm.compiler.hotspot/src/org/graalvm/compiler/hotspot/HotSpotLockStack.java	2016-12-07 13:50:08.844176016 -0800
@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2013, 2015, 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 org.graalvm.compiler.hotspot;
+
+import static org.graalvm.compiler.lir.LIRInstruction.OperandFlag.STACK;
+
+import java.util.Arrays;
+
+import org.graalvm.compiler.core.common.LIRKind;
+import org.graalvm.compiler.lir.LIRInstruction;
+import org.graalvm.compiler.lir.LIRInstructionClass;
+import org.graalvm.compiler.lir.VirtualStackSlot;
+import org.graalvm.compiler.lir.asm.CompilationResultBuilder;
+import org.graalvm.compiler.lir.framemap.FrameMapBuilder;
+
+import jdk.vm.ci.meta.AllocatableValue;
+
+/**
+ * Manages allocation and re-use of lock slots in a scoped manner. The slots are used in HotSpot's
+ * lightweight locking mechanism to store the mark word of an object being locked.
+ */
+public class HotSpotLockStack extends LIRInstruction {
+    public static final LIRInstructionClass<HotSpotLockStack> TYPE = LIRInstructionClass.create(HotSpotLockStack.class);
+    private static final AllocatableValue[] EMPTY = new AllocatableValue[0];
+
+    @Def({STACK}) private AllocatableValue[] locks;
+    private final FrameMapBuilder frameMapBuilder;
+    private final LIRKind slotKind;
+
+    public HotSpotLockStack(FrameMapBuilder frameMapBuilder, LIRKind slotKind) {
+        super(TYPE);
+        this.frameMapBuilder = frameMapBuilder;
+        this.slotKind = slotKind;
+        this.locks = EMPTY;
+    }
+
+    /**
+     * Gets a stack slot for a lock at a given lock nesting depth, allocating it first if necessary.
+     */
+    public VirtualStackSlot makeLockSlot(int lockDepth) {
+        if (locks == EMPTY) {
+            locks = new AllocatableValue[lockDepth + 1];
+        } else if (locks.length < lockDepth + 1) {
+            locks = Arrays.copyOf(locks, lockDepth + 1);
+        }
+        if (locks[lockDepth] == null) {
+            locks[lockDepth] = frameMapBuilder.allocateSpillSlot(slotKind);
+        }
+        return (VirtualStackSlot) locks[lockDepth];
+    }
+
+    @Override
+    public void emitCode(CompilationResultBuilder crb) {
+        // do nothing
+    }
+}