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diff --git a/Source/JavaScriptCore/dfg/DFGDCEPhase.cpp b/Source/JavaScriptCore/dfg/DFGDCEPhase.cpp
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+++ b/Source/JavaScriptCore/dfg/DFGDCEPhase.cpp
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+/*
+ * Copyright (C) 2013 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ */
+
+#include "config.h"
+#include "DFGDCEPhase.h"
+
+#if ENABLE(DFG_JIT)
+
+#include "DFGBasicBlockInlines.h"
+#include "DFGGraph.h"
+#include "DFGInsertionSet.h"
+#include "DFGPhase.h"
+#include "Operations.h"
+
+namespace JSC { namespace DFG {
+
+class DCEPhase : public Phase {
+public:
+    DCEPhase(Graph& graph)
+        : Phase(graph, "dead code elimination")
+    {
+    }
+    
+    bool run()
+    {
+        // First reset the counts to 0 for all nodes.
+        for (BlockIndex blockIndex = 0; blockIndex < m_graph.m_blocks.size(); ++blockIndex) {
+            BasicBlock* block = m_graph.m_blocks[blockIndex].get();
+            if (!block)
+                continue;
+            for (unsigned indexInBlock = block->size(); indexInBlock--;)
+                block->at(indexInBlock)->setRefCount(0);
+            for (unsigned phiIndex = block->phis.size(); phiIndex--;)
+                block->phis[phiIndex]->setRefCount(0);
+        }
+    
+        // Now find the roots:
+        // - Nodes that are must-generate.
+        // - Nodes that are reachable from type checks.
+        // Set their ref counts to 1 and put them on the worklist.
+        for (BlockIndex blockIndex = 0; blockIndex < m_graph.m_blocks.size(); ++blockIndex) {
+            BasicBlock* block = m_graph.m_blocks[blockIndex].get();
+            if (!block)
+                continue;
+            for (unsigned indexInBlock = block->size(); indexInBlock--;) {
+                Node* node = block->at(indexInBlock);
+                DFG_NODE_DO_TO_CHILDREN(m_graph, node, findTypeCheckRoot);
+                if (!(node->flags() & NodeMustGenerate))
+                    continue;
+                if (!node->postfixRef())
+                    m_worklist.append(node);
+            }
+        }
+        
+        while (!m_worklist.isEmpty()) {
+            Node* node = m_worklist.last();
+            m_worklist.removeLast();
+            ASSERT(node->shouldGenerate()); // It should not be on the worklist unless it's ref'ed.
+            DFG_NODE_DO_TO_CHILDREN(m_graph, node, countEdge);
+        }
+        
+        for (BlockIndex blockIndex = 0; blockIndex < m_graph.m_blocks.size(); ++blockIndex) {
+            BasicBlock* block = m_graph.m_blocks[blockIndex].get();
+            if (!block)
+                continue;
+
+            InsertionSet insertionSet(m_graph);
+
+            for (unsigned indexInBlock = block->size(); indexInBlock--;) {
+                Node* node = block->at(indexInBlock);
+                if (node->shouldGenerate())
+                    continue;
+                
+                switch (node->op()) {
+                case SetLocal: {
+                    if (node->child1().isProved() || node->child1().useKind() == UntypedUse) {
+                        // Consider the possibility that UInt32ToNumber is dead but its
+                        // child isn't; if so then we should MovHint the child.
+                        if (!node->child1()->shouldGenerate()
+                            && node->child1()->op() == UInt32ToNumber)
+                            node->child1() = node->child1()->child1();
+
+                        if (!node->child1()->shouldGenerate()) {
+                            node->setOpAndDefaultFlags(ZombieHint);
+                            node->child1() = Edge();
+                            break;
+                        }
+                        node->setOpAndDefaultFlags(MovHint);
+                        break;
+                    }
+                    node->setOpAndDefaultFlags(MovHintAndCheck);
+                    node->setRefCount(1);
+                    break;
+                }
+                    
+                case GetLocal:
+                case SetArgument: {
+                    // Leave them as not shouldGenerate.
+                    break;
+                }
+
+                default: {
+                    if (node->flags() & NodeHasVarArgs) {
+                        for (unsigned childIdx = node->firstChild(); childIdx < node->firstChild() + node->numChildren(); childIdx++) {
+                            Edge edge = m_graph.m_varArgChildren[childIdx];
+
+                            if (!edge || edge.isProved() || edge.useKind() == UntypedUse)
+                                continue;
+
+                            insertionSet.insertNode(indexInBlock, SpecNone, Phantom, node->codeOrigin, edge);
+                        }
+
+                        node->convertToPhantomUnchecked();
+                        node->children.reset();
+                        node->setRefCount(1);
+                        break;
+                    }
+
+                    node->convertToPhantom();
+                    eliminateIrrelevantPhantomChildren(node);
+                    node->setRefCount(1);
+                    break;
+                } }
+            }
+
+            insertionSet.execute(block);
+        }
+        
+        m_graph.m_refCountState = ExactRefCount;
+        
+        return true;
+    }
+
+private:
+    void findTypeCheckRoot(Node*, Edge edge)
+    {
+        // We may have an "unproved" untyped use for code that is unreachable. The CFA
+        // will just not have gotten around to it.
+        if (edge.isProved() || edge.useKind() == UntypedUse)
+            return;
+        if (!edge->postfixRef())
+            m_worklist.append(edge.node());
+    }
+    
+    void countEdge(Node*, Edge edge)
+    {
+        // Don't count edges that are already counted for their type checks.
+        if (!(edge.isProved() || edge.useKind() == UntypedUse))
+            return;
+        
+        if (edge->postfixRef())
+            return;
+        m_worklist.append(edge.node());
+    }
+    
+    void eliminateIrrelevantPhantomChildren(Node* node)
+    {
+        for (unsigned i = 0; i < AdjacencyList::Size; ++i) {
+            Edge edge = node->children.child(i);
+            if (!edge)
+                continue;
+            if (edge.isProved() || edge.useKind() == UntypedUse)
+                node->children.removeEdge(i--);
+        }
+    }
+    
+    Vector<Node*, 128> m_worklist;
+};
+
+bool performDCE(Graph& graph)
+{
+    SamplingRegion samplingRegion("DFG DCE Phase");
+    return runPhase<DCEPhase>(graph);
+}
+
+} } // namespace JSC::DFG
+
+#endif // ENABLE(DFG_JIT)
+