--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.graal.lir/src/com/oracle/graal/lir/stackslotalloc/InstructionNumberer.java	Tue Feb 03 13:33:52 2015 +0100
@@ -0,0 +1,107 @@
+/*
+ * Copyright (c) 2014, 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 com.oracle.graal.lir.stackslotalloc;
+
+import static com.oracle.graal.api.code.CodeUtil.*;
+
+import java.util.*;
+
+import com.oracle.graal.compiler.common.cfg.*;
+import com.oracle.graal.lir.*;
+
+public class InstructionNumberer {
+
+    private final LIRInstruction[] opIdToInstructionMap;
+    private final AbstractBlock<?>[] opIdToBlockMap;
+
+    protected InstructionNumberer(LIR lir) {
+        // Assign IDs to LIR nodes and build a mapping, lirOps, from ID to LIRInstruction node.
+        int numInstructions = 0;
+        for (AbstractBlock<?> block : lir.getControlFlowGraph().getBlocks()) {
+            numInstructions += lir.getLIRforBlock(block).size();
+        }
+
+        // initialize with correct length
+        opIdToInstructionMap = new LIRInstruction[numInstructions];
+        opIdToBlockMap = new AbstractBlock<?>[numInstructions];
+    }
+
+    /**
+     * Converts an {@linkplain LIRInstruction#id instruction id} to an instruction index. All LIR
+     * instructions in a method have an index one greater than their linear-scan order predecessor
+     * with the first instruction having an index of 0.
+     */
+    private static int opIdToIndex(int opId) {
+        return opId >> 1;
+    }
+
+    /**
+     * Retrieves the {@link LIRInstruction} based on its {@linkplain LIRInstruction#id id}.
+     *
+     * @param opId an instruction {@linkplain LIRInstruction#id id}
+     * @return the instruction whose {@linkplain LIRInstruction#id} {@code == id}
+     */
+    protected LIRInstruction instructionForId(int opId) {
+        assert isEven(opId) : "opId not even";
+        LIRInstruction instr = opIdToInstructionMap[opIdToIndex(opId)];
+        assert instr.id() == opId;
+        return instr;
+    }
+
+    /**
+     * Numbers all instructions in all blocks.
+     */
+    protected void numberInstructions(LIR lir, List<? extends AbstractBlock<?>> sortedBlocks) {
+
+        int opId = 0;
+        int index = 0;
+        for (AbstractBlock<?> block : sortedBlocks) {
+
+            List<LIRInstruction> instructions = lir.getLIRforBlock(block);
+
+            int numInst = instructions.size();
+            for (int j = 0; j < numInst; j++) {
+                LIRInstruction op = instructions.get(j);
+                op.setId(opId);
+
+                opIdToInstructionMap[index] = op;
+                opIdToBlockMap[index] = block;
+                assert instructionForId(opId) == op : "must match";
+
+                index++;
+                opId += 2; // numbering of lirOps by two
+            }
+        }
+        assert index == opIdToBlockMap.length : "must match";
+        assert (index << 1) == opId : "must match: " + (index << 1);
+        assert opId - 2 == maxOpId() : "must match";
+    }
+
+    /**
+     * Gets the highest instruction id allocated by this object.
+     */
+    public int maxOpId() {
+        assert opIdToInstructionMap.length > 0 : "no operations";
+        return (opIdToInstructionMap.length - 1) << 1;
+    }
+}

--- a/graal/com.oracle.graal.lir/src/com/oracle/graal/lir/stackslotalloc/LSStackSlotAllocator.java	Tue Feb 03 15:12:29 2015 +0100
+++ b/graal/com.oracle.graal.lir/src/com/oracle/graal/lir/stackslotalloc/LSStackSlotAllocator.java	Tue Feb 03 13:33:52 2015 +0100
@@ -72,16 +72,16 @@
         }
     }
 
-    private static final class Allocator {
+    private static final class Allocator extends InstructionNumberer {
         private final LIR lir;
         private final FrameMapBuilderTool frameMapBuilder;
         private final StackInterval[] stackSlotMap;
         private final PriorityQueue<StackInterval> unhandled;
         private final PriorityQueue<StackInterval> active;
         private final List<? extends AbstractBlock<?>> sortedBlocks;
-        private final int maxOpId;
 
         private Allocator(LIR lir, FrameMapBuilderTool frameMapBuilder) {
+            super(lir);
             this.lir = lir;
             this.frameMapBuilder = frameMapBuilder;
             this.stackSlotMap = new StackInterval[frameMapBuilder.getNumberOfStackSlots()];
@@ -94,7 +94,7 @@
 
             try (TimerCloseable t = NumInstTimer.start()) {
                 // step 1: number instructions
-                this.maxOpId = numberInstructions(lir, sortedBlocks);
+                numberInstructions(lir, sortedBlocks);
             }
         }
 
@@ -134,35 +134,6 @@
         }
 
         // ====================
-        // step 1: number instructions
-        // ====================
-
-        /**
-         * Numbers all instructions in all blocks.
-         *
-         * @return The id of the last operation.
-         */
-        private static int numberInstructions(LIR lir, List<? extends AbstractBlock<?>> sortedBlocks) {
-            int opId = 0;
-            int index = 0;
-            for (AbstractBlock<?> block : sortedBlocks) {
-
-                List<LIRInstruction> instructions = lir.getLIRforBlock(block);
-
-                int numInst = instructions.size();
-                for (int j = 0; j < numInst; j++) {
-                    LIRInstruction op = instructions.get(j);
-                    op.setId(opId);
-
-                    index++;
-                    opId += 2; // numbering of lirOps by two
-                }
-            }
-            assert (index << 1) == opId : "must match: " + (index << 1);
-            return opId - 2;
-        }
-
-        // ====================
         // step 2: build intervals
         // ====================
 
@@ -386,13 +357,6 @@
         //
         // ====================
 
-        /**
-         * Gets the highest instruction id.
-         */
-        private int maxOpId() {
-            return maxOpId;
-        }
-
         private StackInterval get(VirtualStackSlot stackSlot) {
             return stackSlotMap[stackSlot.getId()];
         }