--- a/graal/com.oracle.graal.compiler/src/com/oracle/graal/compiler/GraalCompiler.java	Tue Nov 06 13:59:07 2012 +0100
+++ b/graal/com.oracle.graal.compiler/src/com/oracle/graal/compiler/GraalCompiler.java	Tue Nov 06 14:26:30 2012 +0100
@@ -189,6 +189,8 @@
             new CanonicalizerPhase(target, runtime, assumptions).apply(graph);
         }
 
+        new EliminatePartiallyRedundantGuardsPhase().apply(graph);
+
         if (GraalOptions.CheckCastElimination && GraalOptions.OptCanonicalizer) {
             new IterativeConditionalEliminationPhase(target, runtime, assumptions).apply(graph);
         }

--- a/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/ControlSplitNode.java	Tue Nov 06 13:59:07 2012 +0100
+++ b/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/ControlSplitNode.java	Tue Nov 06 14:26:30 2012 +0100
@@ -25,6 +25,7 @@
 import java.util.*;
 
 import com.oracle.graal.graph.*;
+import com.oracle.graal.graph.iterators.*;
 import com.oracle.graal.nodes.type.*;
 
 /**
@@ -61,7 +62,7 @@
         branchProbability[successorIndex] = x;
     }
 
-    public Iterable<BeginNode> blockSuccessors() {
+    public NodeIterable<BeginNode> blockSuccessors() {
         return blockSuccessors;
     }
 

--- a/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/GuardNode.java	Tue Nov 06 13:59:07 2012 +0100
+++ b/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/GuardNode.java	Tue Nov 06 14:26:30 2012 +0100
@@ -49,6 +49,15 @@
     private boolean negated;
     private final long leafGraphId;
 
+    public GuardNode(BooleanNode condition, FixedNode anchor, DeoptimizationReason reason, DeoptimizationAction action, boolean negated, long leafGraphId) {
+        super(StampFactory.dependency(), anchor);
+        this.condition = condition;
+        this.reason = reason;
+        this.action = action;
+        this.negated = negated;
+        this.leafGraphId = leafGraphId;
+    }
+
     /**
      * The instruction that produces the tested boolean value.
      */
@@ -73,13 +82,8 @@
         return action;
     }
 
-    public GuardNode(BooleanNode condition, FixedNode anchor, DeoptimizationReason reason, DeoptimizationAction action, boolean negated, long leafGraphId) {
-        super(StampFactory.dependency(), anchor);
-        this.condition = condition;
-        this.reason = reason;
-        this.action = action;
-        this.negated = negated;
-        this.leafGraphId = leafGraphId;
+    public long getLeafGraphId() {
+        return leafGraphId;
     }
 
     @Override

--- a/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/PhiNode.java	Tue Nov 06 13:59:07 2012 +0100
+++ b/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/PhiNode.java	Tue Nov 06 14:26:30 2012 +0100
@@ -37,6 +37,7 @@
 
     public static enum PhiType {
         Value(null), // normal value phis
+        Guard(StampFactory.dependency()),
         Memory(StampFactory.dependency());
 
         public final Stamp stamp;

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.graal.phases.common/src/com/oracle/graal/phases/common/EliminatePartiallyRedundantGuardsPhase.java	Tue Nov 06 14:26:30 2012 +0100
@@ -0,0 +1,195 @@
+/*
+ * Copyright (c) 2012, 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.phases.common;
+
+import java.util.*;
+import java.util.Map.*;
+
+import com.oracle.graal.api.code.*;
+import com.oracle.graal.api.meta.*;
+import com.oracle.graal.debug.*;
+import com.oracle.graal.graph.*;
+import com.oracle.graal.nodes.*;
+import com.oracle.graal.nodes.PhiNode.PhiType;
+import com.oracle.graal.phases.*;
+
+
+public class EliminatePartiallyRedundantGuardsPhase extends Phase {
+
+    private static final DebugMetric metricPRGuardsEliminatedAtMerge = Debug.metric("PRGuardsEliminatedAtMerge");
+    private static final DebugMetric metricPRGuardsEliminatedAtSplit = Debug.metric("PRGuardsEliminatedAtSplit");
+
+    private static class Condition {
+        final BooleanNode conditionNode;
+        final boolean negated;
+        public Condition(BooleanNode conditionNode, boolean negated) {
+            this.conditionNode = conditionNode;
+            this.negated = negated;
+        }
+        @Override
+        public int hashCode() {
+            final int prime = 31;
+            int result = 1;
+            result = prime * result + ((conditionNode == null) ? 0 : conditionNode.hashCode());
+            result = prime * result + (negated ? 1231 : 1237);
+            return result;
+        }
+        @Override
+        public boolean equals(Object obj) {
+            if (this == obj) {
+                return true;
+            }
+            if (obj == null) {
+                return false;
+            }
+            if (getClass() != obj.getClass()) {
+                return false;
+            }
+            Condition other = (Condition) obj;
+            if (conditionNode == null) {
+                if (other.conditionNode != null) {
+                    return false;
+                }
+            } else if (!conditionNode.equals(other.conditionNode)) {
+                return false;
+            }
+            if (negated != other.negated) {
+                return false;
+            }
+            return true;
+        }
+    }
+
+    @Override
+    protected void run(StructuredGraph graph) {
+        boolean hits;
+        do {
+            hits = false;
+            for (MergeNode merge : graph.getNodes(MergeNode.class)) {
+                hits |= eliminateAtMerge(merge);
+            }
+            for (ControlSplitNode controlSplit : graph.getNodes().filter(ControlSplitNode.class)) {
+                hits |= eliminateAtControlSplit(controlSplit);
+            }
+        } while(hits);
+    }
+
+    private static boolean eliminateAtMerge(MergeNode merge) {
+        if (merge.forwardEndCount() < 2) {
+            return false;
+        }
+        Collection<GuardNode> hits = new LinkedList<>();
+        for (GuardNode guard : merge.guards()) {
+            if (guard.dependencies().size() != 1) {
+                continue;
+            }
+            for (EndNode end : merge.forwardEnds()) {
+                BeginNode begin = BeginNode.prevBegin(end);
+                boolean found = false;
+                for (GuardNode predecessorGuard : begin.guards()) {
+                    if (predecessorGuard.dependencies().size() != 1) {
+                        continue;
+                    }
+                    if (guard.condition() == predecessorGuard.condition() && guard.negated() == predecessorGuard.negated()) {
+                        hits.add(guard);
+                        found = true;
+                        break;
+                    }
+                }
+                if (found) {
+                    break;
+                }
+            }
+        }
+        Graph graph = merge.graph();
+        for (GuardNode guard : hits) {
+            PhiNode phi = graph.add(new PhiNode(PhiType.Guard, merge));
+            for (EndNode otherEnd : merge.forwardEnds()) {
+                phi.addInput(graph.unique(new GuardNode(guard.condition(), BeginNode.prevBegin(otherEnd), guard.reason(), guard.action(), guard.negated(), guard.getLeafGraphId())));
+            }
+            guard.replaceAndDelete(phi);
+            metricPRGuardsEliminatedAtMerge.increment();
+        }
+        return !hits.isEmpty();
+    }
+
+    private static boolean eliminateAtControlSplit(ControlSplitNode controlSplit) {
+        Map<Condition, Collection<GuardNode>> conditionToGuard = new HashMap<>();
+        for (BeginNode begin : controlSplit.blockSuccessors()) {
+            for (GuardNode guard : begin.guards()) {
+                if (guard.dependencies().size() != 1) {
+                    continue;
+                }
+                Condition condition = new Condition(guard.condition(), guard.negated());
+                Collection<GuardNode> guards = conditionToGuard.get(condition);
+                if (guards == null) {
+                    guards = new LinkedList<>();
+                    conditionToGuard.put(condition, guards);
+                }
+                guards.add(guard);
+            }
+        }
+
+        boolean hits = false;
+        for (Entry<Condition, Collection<GuardNode>> entry : conditionToGuard.entrySet()) {
+            Collection<GuardNode> guards = entry.getValue();
+            if (guards.size() < 2) {
+                continue;
+            }
+            DeoptimizationReason reason = null;
+            DeoptimizationAction action = DeoptimizationAction.None;
+            long leafGraphId = -1;
+            Set<BeginNode> begins = new HashSet<>(3);
+            for (GuardNode guard : guards) {
+                BeginNode begin = (BeginNode) guard.dependencies().first();
+                begins.add(begin);
+                if (guard.action().ordinal() > action.ordinal()) {
+                    action = guard.action();
+                }
+                if (reason == null) {
+                    reason = guard.reason();
+                } else if (reason != guard.reason()) {
+                    reason = DeoptimizationReason.None;
+                }
+                if (leafGraphId == -1) {
+                    leafGraphId = guard.getLeafGraphId();
+                } else if (leafGraphId != guard.getLeafGraphId()) {
+                    leafGraphId = -1;
+                }
+            }
+            if (leafGraphId < 0) {
+                continue;
+            }
+            if (begins.size() == controlSplit.blockSuccessors().count()) {
+                hits = true;
+                Condition condition = entry.getKey();
+                GuardNode newGuard = controlSplit.graph().unique(new GuardNode(condition.conditionNode, BeginNode.prevBegin(controlSplit), reason, action, condition.negated, leafGraphId));
+                for (GuardNode guard : guards) {
+                    guard.replaceAndDelete(newGuard);
+                    metricPRGuardsEliminatedAtSplit.increment();
+                }
+            }
+        }
+        return hits;
+    }
+}