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diff --git a/Source/JavaScriptCore/bytecode/BytecodeGeneratorification.cpp b/Source/JavaScriptCore/bytecode/BytecodeGeneratorification.cpp
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+++ b/Source/JavaScriptCore/bytecode/BytecodeGeneratorification.cpp
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+/*
+ * Copyright (C) 2016 Yusuke Suzuki <utatane.tea@gmail.com>
+ * 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. AND ITS CONTRIBUTORS ``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 ITS 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 "BytecodeGeneratorification.h"
+
+#include "BytecodeLivenessAnalysisInlines.h"
+#include "BytecodeRewriter.h"
+#include "BytecodeUseDef.h"
+#include "IdentifierInlines.h"
+#include "InterpreterInlines.h"
+#include "JSCInlines.h"
+#include "JSCJSValueInlines.h"
+#include "JSGeneratorFunction.h"
+#include "StrongInlines.h"
+#include "UnlinkedCodeBlock.h"
+#include <wtf/Optional.h>
+
+namespace JSC {
+
+struct YieldData {
+    size_t point { 0 };
+    int argument { 0 };
+    FastBitVector liveness;
+};
+
+class BytecodeGeneratorification {
+public:
+    typedef Vector<YieldData> Yields;
+
+    BytecodeGeneratorification(UnlinkedCodeBlock* codeBlock, UnlinkedCodeBlock::UnpackedInstructions& instructions, SymbolTable* generatorFrameSymbolTable, int generatorFrameSymbolTableIndex)
+        : m_graph(codeBlock, instructions)
+        , m_generatorFrameSymbolTable(*codeBlock->vm(), generatorFrameSymbolTable)
+        , m_generatorFrameSymbolTableIndex(generatorFrameSymbolTableIndex)
+    {
+        for (BytecodeBasicBlock* block : m_graph) {
+            for (unsigned bytecodeOffset : block->offsets()) {
+                const UnlinkedInstruction* pc = &m_graph.instructions()[bytecodeOffset];
+                switch (pc->u.opcode) {
+                case op_enter: {
+                    m_enterPoint = bytecodeOffset;
+                    break;
+                }
+
+                case op_yield: {
+                    unsigned liveCalleeLocalsIndex = pc[2].u.index;
+                    if (liveCalleeLocalsIndex >= m_yields.size())
+                        m_yields.resize(liveCalleeLocalsIndex + 1);
+                    YieldData& data = m_yields[liveCalleeLocalsIndex];
+                    data.point = bytecodeOffset;
+                    data.argument = pc[3].u.operand;
+                    break;
+                }
+
+                default:
+                    break;
+                }
+            }
+        }
+    }
+
+    struct Storage {
+        Identifier identifier;
+        unsigned identifierIndex;
+        ScopeOffset scopeOffset;
+    };
+
+    void run();
+
+    BytecodeGraph<UnlinkedCodeBlock>& graph() { return m_graph; }
+
+    const Yields& yields() const
+    {
+        return m_yields;
+    }
+
+    Yields& yields()
+    {
+        return m_yields;
+    }
+
+    unsigned enterPoint() const
+    {
+        return m_enterPoint;
+    }
+
+private:
+    Storage storageForGeneratorLocal(unsigned index)
+    {
+        // We assign a symbol to a register. There is one-on-one corresponding between a register and a symbol.
+        // By doing so, we allocate the specific storage to save the given register.
+        // This allow us not to save all the live registers even if the registers are not overwritten from the previous resuming time.
+        // It means that, the register can be retrieved even if the immediate previous op_save does not save it.
+
+        if (m_storages.size() <= index)
+            m_storages.resize(index + 1);
+        if (std::optional<Storage> storage = m_storages[index])
+            return *storage;
+
+        UnlinkedCodeBlock* codeBlock = m_graph.codeBlock();
+        Identifier identifier = Identifier::fromUid(PrivateName());
+        unsigned identifierIndex = codeBlock->numberOfIdentifiers();
+        codeBlock->addIdentifier(identifier);
+        ScopeOffset scopeOffset = m_generatorFrameSymbolTable->takeNextScopeOffset(NoLockingNecessary);
+        m_generatorFrameSymbolTable->set(NoLockingNecessary, identifier.impl(), SymbolTableEntry(VarOffset(scopeOffset)));
+
+        Storage storage = {
+            identifier,
+            identifierIndex,
+            scopeOffset
+        };
+        m_storages[index] = storage;
+        return storage;
+    }
+
+    unsigned m_enterPoint { 0 };
+    BytecodeGraph<UnlinkedCodeBlock> m_graph;
+    Vector<std::optional<Storage>> m_storages;
+    Yields m_yields;
+    Strong<SymbolTable> m_generatorFrameSymbolTable;
+    int m_generatorFrameSymbolTableIndex;
+};
+
+class GeneratorLivenessAnalysis : public BytecodeLivenessPropagation<GeneratorLivenessAnalysis> {
+public:
+    GeneratorLivenessAnalysis(BytecodeGeneratorification& generatorification)
+        : m_generatorification(generatorification)
+    {
+    }
+
+    template<typename Functor>
+    void computeDefsForBytecodeOffset(UnlinkedCodeBlock* codeBlock, OpcodeID opcodeID, UnlinkedInstruction* instruction, FastBitVector&, const Functor& functor)
+    {
+        JSC::computeDefsForBytecodeOffset(codeBlock, opcodeID, instruction, functor);
+    }
+
+    template<typename Functor>
+    void computeUsesForBytecodeOffset(UnlinkedCodeBlock* codeBlock, OpcodeID opcodeID, UnlinkedInstruction* instruction, FastBitVector&, const Functor& functor)
+    {
+        JSC::computeUsesForBytecodeOffset(codeBlock, opcodeID, instruction, functor);
+    }
+
+    void run()
+    {
+        // Perform modified liveness analysis to determine which locals are live at the merge points.
+        // This produces the conservative results for the question, "which variables should be saved and resumed?".
+
+        runLivenessFixpoint(m_generatorification.graph());
+
+        for (YieldData& data : m_generatorification.yields())
+            data.liveness = getLivenessInfoAtBytecodeOffset(m_generatorification.graph(), data.point + opcodeLength(op_yield));
+    }
+
+private:
+    BytecodeGeneratorification& m_generatorification;
+};
+
+void BytecodeGeneratorification::run()
+{
+    // We calculate the liveness at each merge point. This gives us the information which registers should be saved and resumed conservatively.
+
+    {
+        GeneratorLivenessAnalysis pass(*this);
+        pass.run();
+    }
+
+    UnlinkedCodeBlock* codeBlock = m_graph.codeBlock();
+    BytecodeRewriter rewriter(m_graph);
+
+    // Setup the global switch for the generator.
+    {
+        unsigned nextToEnterPoint = enterPoint() + opcodeLength(op_enter);
+        unsigned switchTableIndex = m_graph.codeBlock()->numberOfSwitchJumpTables();
+        VirtualRegister state = virtualRegisterForArgument(static_cast<int32_t>(JSGeneratorFunction::GeneratorArgument::State));
+        auto& jumpTable = m_graph.codeBlock()->addSwitchJumpTable();
+        jumpTable.min = 0;
+        jumpTable.branchOffsets.resize(m_yields.size() + 1);
+        jumpTable.branchOffsets.fill(0);
+        jumpTable.add(0, nextToEnterPoint);
+        for (unsigned i = 0; i < m_yields.size(); ++i)
+            jumpTable.add(i + 1, m_yields[i].point);
+
+        rewriter.insertFragmentBefore(nextToEnterPoint, [&](BytecodeRewriter::Fragment& fragment) {
+            fragment.appendInstruction(op_switch_imm, switchTableIndex, nextToEnterPoint, state.offset());
+        });
+    }
+
+    for (const YieldData& data : m_yields) {
+        VirtualRegister scope = virtualRegisterForArgument(static_cast<int32_t>(JSGeneratorFunction::GeneratorArgument::Frame));
+
+        // Emit save sequence.
+        rewriter.insertFragmentBefore(data.point, [&](BytecodeRewriter::Fragment& fragment) {
+            data.liveness.forEachSetBit([&](size_t index) {
+                VirtualRegister operand = virtualRegisterForLocal(index);
+                Storage storage = storageForGeneratorLocal(index);
+
+                fragment.appendInstruction(
+                    op_put_to_scope,
+                    scope.offset(), // scope
+                    storage.identifierIndex, // identifier
+                    operand.offset(), // value
+                    GetPutInfo(DoNotThrowIfNotFound, LocalClosureVar, InitializationMode::NotInitialization).operand(), // info
+                    m_generatorFrameSymbolTableIndex, // symbol table constant index
+                    storage.scopeOffset.offset() // scope offset
+                );
+            });
+
+            // Insert op_ret just after save sequence.
+            fragment.appendInstruction(op_ret, data.argument);
+        });
+
+        // Emit resume sequence.
+        rewriter.insertFragmentAfter(data.point, [&](BytecodeRewriter::Fragment& fragment) {
+            data.liveness.forEachSetBit([&](size_t index) {
+                VirtualRegister operand = virtualRegisterForLocal(index);
+                Storage storage = storageForGeneratorLocal(index);
+
+                UnlinkedValueProfile profile = codeBlock->addValueProfile();
+                fragment.appendInstruction(
+                    op_get_from_scope,
+                    operand.offset(), // dst
+                    scope.offset(), // scope
+                    storage.identifierIndex, // identifier
+                    GetPutInfo(DoNotThrowIfNotFound, LocalClosureVar, InitializationMode::NotInitialization).operand(), // info
+                    0, // local scope depth
+                    storage.scopeOffset.offset(), // scope offset
+                    profile // profile
+                );
+            });
+        });
+
+        // Clip the unnecessary bytecodes.
+        rewriter.removeBytecode(data.point);
+    }
+
+    rewriter.execute();
+}
+
+void performGeneratorification(UnlinkedCodeBlock* codeBlock, UnlinkedCodeBlock::UnpackedInstructions& instructions, SymbolTable* generatorFrameSymbolTable, int generatorFrameSymbolTableIndex)
+{
+    BytecodeGeneratorification pass(codeBlock, instructions, generatorFrameSymbolTable, generatorFrameSymbolTableIndex);
+    pass.run();
+}
+
+} // namespace JSC