--- /dev/null	2017-01-22 10:16:57.869617664 -0800
+++ new/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.lir/src/org/graalvm/compiler/lir/LabelRef.java	2017-02-15 17:05:21.867334805 -0800
@@ -0,0 +1,84 @@
+/*
+ * Copyright (c) 2011, 2011, 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.lir;
+
+import org.graalvm.compiler.asm.Label;
+import org.graalvm.compiler.core.common.cfg.AbstractBlockBase;
+import org.graalvm.compiler.lir.StandardOp.BranchOp;
+import org.graalvm.compiler.lir.StandardOp.JumpOp;
+
+/**
+ * LIR instructions such as {@link JumpOp} and {@link BranchOp} need to reference their target
+ * {@link AbstractBlockBase}. However, direct references are not possible since the control flow
+ * graph (and therefore successors lists) can be changed by optimizations - and fixing the
+ * instructions is error prone. Therefore, we represent an edge to block B from block A via the
+ * tuple {@code (A,
+ * successor-index-of-B)}. That is, indirectly by storing the index into the successor list of A.
+ * Note therefore that the successor list cannot be re-ordered.
+ */
+public final class LabelRef {
+
+    private final LIR lir;
+    private final AbstractBlockBase<?> block;
+    private final int suxIndex;
+
+    /**
+     * Returns a new reference to a successor of the given block.
+     *
+     * @param block The base block that contains the successor list.
+     * @param suxIndex The index of the successor.
+     * @return The newly created label reference.
+     */
+    public static LabelRef forSuccessor(final LIR lir, final AbstractBlockBase<?> block, final int suxIndex) {
+        return new LabelRef(lir, block, suxIndex);
+    }
+
+    /**
+     * Returns a new reference to a successor of the given block.
+     *
+     * @param block The base block that contains the successor list.
+     * @param suxIndex The index of the successor.
+     */
+    private LabelRef(final LIR lir, final AbstractBlockBase<?> block, final int suxIndex) {
+        this.lir = lir;
+        this.block = block;
+        this.suxIndex = suxIndex;
+    }
+
+    public AbstractBlockBase<?> getSourceBlock() {
+        return block;
+    }
+
+    public AbstractBlockBase<?> getTargetBlock() {
+        return block.getSuccessors()[suxIndex];
+    }
+
+    public Label label() {
+        return ((StandardOp.LabelOp) lir.getLIRforBlock(getTargetBlock()).get(0)).getLabel();
+    }
+
+    @Override
+    public String toString() {
+        return getSourceBlock() + " -> " + (suxIndex < block.getSuccessors().length ? getTargetBlock() : "?");
+    }
+}