--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.graal.phases.common/src/com/oracle/graal/phases/common/OptimizeGuardAnchorsPhase.java	Fri Jan 17 16:23:18 2014 +0100
@@ -0,0 +1,143 @@
+/*
+ * Copyright (c) 2013, 2013, 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 com.oracle.graal.debug.*;
+import com.oracle.graal.graph.NodeClass.NodeClassIterator;
+import com.oracle.graal.graph.iterators.*;
+import com.oracle.graal.nodes.*;
+import com.oracle.graal.nodes.cfg.*;
+import com.oracle.graal.nodes.extended.*;
+import com.oracle.graal.phases.*;
+
+public class OptimizeGuardAnchorsPhase extends Phase {
+    private static final DebugMetric metricGuardsAnchorOptimized = Debug.metric("GuardsAnchorOptimized");
+    private static final DebugMetric metricGuardsOptimizedAtSplit = Debug.metric("GuardsOptimizedAtSplit");
+
+    public static class LazyCFG {
+        private ControlFlowGraph cfg;
+        private StructuredGraph graph;
+
+        public LazyCFG(StructuredGraph graph) {
+            this.graph = graph;
+        }
+
+        public ControlFlowGraph get() {
+            if (cfg == null) {
+                cfg = ControlFlowGraph.compute(graph, true, false, true, true);
+            }
+            return cfg;
+        }
+    }
+
+    @Override
+    protected void run(StructuredGraph graph) {
+        LazyCFG cfg = new LazyCFG(graph);
+        for (AbstractBeginNode begin : graph.getNodes(AbstractBeginNode.class)) {
+            if (!(begin instanceof StartNode || begin.predecessor() instanceof ControlSplitNode)) {
+                NodeIterable<GuardNode> guards = begin.guards();
+                if (guards.isNotEmpty()) {
+                    AbstractBeginNode newAnchor = computeOptimalAnchor(cfg.get(), begin);
+                    // newAnchor == begin is possible because postdominator computation assumes that
+                    // loops never end
+                    if (newAnchor != begin) {
+                        for (GuardNode guard : guards.snapshot()) {
+                            guard.setGuard(newAnchor);
+                        }
+                        metricGuardsAnchorOptimized.increment();
+                    }
+                }
+            }
+        }
+        for (ControlSplitNode controlSplit : graph.getNodes(ControlSplitNode.class)) {
+            optimizeAtControlSplit(controlSplit, cfg);
+        }
+    }
+
+    public static AbstractBeginNode getOptimalAnchor(LazyCFG cfg, AbstractBeginNode begin) {
+        if (begin instanceof StartNode || begin.predecessor() instanceof ControlSplitNode) {
+            return begin;
+        }
+        return computeOptimalAnchor(cfg.get(), begin);
+    }
+
+    private static AbstractBeginNode computeOptimalAnchor(ControlFlowGraph cfg, AbstractBeginNode begin) {
+        Block anchor = cfg.blockFor(begin);
+        while (anchor.getDominator() != null && anchor.getDominator().getPostdominator() == anchor) {
+            anchor = anchor.getDominator();
+        }
+        return anchor.getBeginNode();
+    }
+
+    private static void optimizeAtControlSplit(ControlSplitNode controlSplit, LazyCFG cfg) {
+        AbstractBeginNode successor = findMinimumUsagesSuccessor(controlSplit);
+        int successorCount = controlSplit.successors().count();
+        List<GuardNode> otherGuards = new ArrayList<>(successorCount - 1);
+        for (GuardNode guard : successor.guards().snapshot()) {
+            if (guard.isDeleted() || guard.condition().usages().count() < successorCount) {
+                continue;
+            }
+            for (GuardNode conditonGuard : guard.condition().usages().filter(GuardNode.class)) {
+                if (conditonGuard != guard) {
+                    GuardingNode conditonGuardAnchor = conditonGuard.getGuard();
+                    if (conditonGuardAnchor.asNode().predecessor() == controlSplit && compatibleGuards(guard, conditonGuard)) {
+                        otherGuards.add(conditonGuard);
+                    }
+                }
+            }
+
+            if (otherGuards.size() == successorCount - 1) {
+                AbstractBeginNode anchor = computeOptimalAnchor(cfg.get(), AbstractBeginNode.prevBegin(controlSplit));
+                GuardNode newGuard = controlSplit.graph().unique(new GuardNode(guard.condition(), anchor, guard.reason(), guard.action(), guard.negated(), guard.getSpeculation()));
+                for (GuardNode otherGuard : otherGuards) {
+                    otherGuard.replaceAndDelete(newGuard);
+                }
+                guard.replaceAndDelete(newGuard);
+                metricGuardsOptimizedAtSplit.increment();
+            }
+            otherGuards.clear();
+        }
+    }
+
+    private static boolean compatibleGuards(GuardNode guard, GuardNode conditonGuard) {
+        return conditonGuard.negated() == guard.negated() && conditonGuard.action() == guard.action() && conditonGuard.reason() == guard.reason() &&
+                        conditonGuard.getSpeculation().equals(guard.getSpeculation());
+    }
+
+    private static AbstractBeginNode findMinimumUsagesSuccessor(ControlSplitNode controlSplit) {
+        NodeClassIterator successors = controlSplit.successors().iterator();
+        AbstractBeginNode min = (AbstractBeginNode) successors.next();
+        int minUsages = min.usages().count();
+        while (successors.hasNext()) {
+            AbstractBeginNode successor = (AbstractBeginNode) successors.next();
+            int count = successor.usages().count();
+            if (count < minUsages) {
+                minUsages = count;
+                min = successor;
+            }
+        }
+        return min;
+    }
+}