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diff --git a/Source/JavaScriptCore/b3/B3SSACalculator.h b/Source/JavaScriptCore/b3/B3SSACalculator.h
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+++ b/Source/JavaScriptCore/b3/B3SSACalculator.h
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+/*
+ * Copyright (C) 2016 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. 
+ */
+
+#pragma once
+
+#if ENABLE(B3_JIT)
+
+#include "B3Dominators.h"
+#include "B3ProcedureInlines.h"
+#include <wtf/Bag.h>
+#include <wtf/IndexMap.h>
+#include <wtf/SegmentedVector.h>
+
+namespace JSC { namespace B3 {
+
+// SSACalculator provides a reusable tool for building SSA's. It's modeled after
+// DFG::SSACalculator.
+
+class SSACalculator {
+public:
+    SSACalculator(Procedure&);
+    ~SSACalculator();
+
+    void reset();
+
+    class Variable {
+    public:
+        unsigned index() const { return m_index; }
+        
+        void dump(PrintStream&) const;
+        void dumpVerbose(PrintStream&) const;
+        
+    private:
+        friend class SSACalculator;
+        
+        Variable()
+            : m_index(UINT_MAX)
+        {
+        }
+        
+        Variable(unsigned index)
+            : m_index(index)
+        {
+        }
+
+        Vector<BasicBlock*, 4> m_blocksWithDefs;
+        unsigned m_index;
+    };
+
+    class Def {
+    public:
+        Variable* variable() const { return m_variable; }
+        BasicBlock* block() const { return m_block; }
+        
+        Value* value() const { return m_value; }
+        
+        void dump(PrintStream&) const;
+        
+    private:
+        friend class SSACalculator;
+        
+        Def()
+            : m_variable(nullptr)
+            , m_block(nullptr)
+            , m_value(nullptr)
+        {
+        }
+        
+        Def(Variable* variable, BasicBlock* block, Value* value)
+            : m_variable(variable)
+            , m_block(block)
+            , m_value(value)
+        {
+        }
+        
+        Variable* m_variable;
+        BasicBlock* m_block;
+        Value* m_value;
+    };
+
+    Variable* newVariable();
+    Def* newDef(Variable*, BasicBlock*, Value*);
+
+    Variable* variable(unsigned index) { return &m_variables[index]; }
+
+    template<typename Functor>
+    void computePhis(const Functor& functor)
+    {
+        m_dominators = &m_proc.dominators();
+        for (Variable& variable : m_variables) {
+            m_dominators->forAllBlocksInPrunedIteratedDominanceFrontierOf(
+                variable.m_blocksWithDefs,
+                [&] (BasicBlock* block) -> bool {
+                    Value* phi = functor(&variable, block);
+                    if (!phi)
+                        return false;
+
+                    BlockData& data = m_data[block];
+                    Def* phiDef = m_phis.add(Def(&variable, block, phi));
+                    data.m_phis.append(phiDef);
+
+                    data.m_defs.add(&variable, phiDef);
+                    return true;
+                });
+        }
+    }
+
+    const Vector<Def*>& phisForBlock(BasicBlock* block)
+    {
+        return m_data[block].m_phis;
+    }
+    
+    // Ignores defs within the given block; it assumes that you've taken care of those
+    // yourself.
+    Def* nonLocalReachingDef(BasicBlock*, Variable*);
+    Def* reachingDefAtHead(BasicBlock* block, Variable* variable)
+    {
+        return nonLocalReachingDef(block, variable);
+    }
+    
+    // Considers the def within the given block, but only works at the tail of the block.
+    Def* reachingDefAtTail(BasicBlock*, Variable*);
+    
+    void dump(PrintStream&) const;
+    
+private:
+    SegmentedVector<Variable> m_variables;
+    Bag<Def> m_defs;
+    
+    Bag<Def> m_phis;
+    
+    struct BlockData {
+        HashMap<Variable*, Def*> m_defs;
+        Vector<Def*> m_phis;
+    };
+    
+    IndexMap<BasicBlock, BlockData> m_data;
+
+    Dominators* m_dominators { nullptr };
+    Procedure& m_proc;
+};
+
+} } // namespace JSC::B3
+
+#endif // ENABLE(B3_JIT)