Source/JavaScriptCore/runtime/CodeCache.h - WebKit - Git at Google

 /*
  * Copyright (C) 2012-2019 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

 #include "BytecodeGenerator.h"
 #include "CachedTypes.h"
 #include "ExecutableInfo.h"
 #include "JSCInlines.h"
 #include "Parser.h"
 #include "ParserModes.h"
 #include "SourceCodeKey.h"
 #include "Strong.h"
 #include "StrongInlines.h"
 #include "UnlinkedCodeBlock.h"
 #include "UnlinkedEvalCodeBlock.h"
 #include "UnlinkedFunctionCodeBlock.h"
 #include "UnlinkedModuleProgramCodeBlock.h"
 #include "UnlinkedProgramCodeBlock.h"

 namespace JSC {

 class EvalExecutable;
 class IndirectEvalExecutable;
 class Identifier;
 class DirectEvalExecutable;
 class ModuleProgramExecutable;
 class ParserError;
 class ProgramExecutable;
 class SourceCode;
 class UnlinkedCodeBlock;
 class UnlinkedEvalCodeBlock;
 class UnlinkedFunctionExecutable;
 class UnlinkedModuleProgramCodeBlock;
 class UnlinkedProgramCodeBlock;
 class VM;
 class VariableEnvironment;

 namespace CodeCacheInternal {
 static constexpr bool verbose = false;
 } // namespace CodeCacheInternal

 struct SourceCodeValue {
     SourceCodeValue()
     {
     }

     SourceCodeValue(VM& vm, JSCell* cell, int64_t age)
         : cell(vm, cell)
         , age(age)
     {
     }

     Strong<JSCell> cell;
     int64_t age;
 };

 class CodeCacheMap {
 public:
     typedef HashMap<SourceCodeKey, SourceCodeValue, SourceCodeKey::Hash, SourceCodeKey::HashTraits> MapType;
     typedef MapType::iterator iterator;
     typedef MapType::AddResult AddResult;

     CodeCacheMap()
         : m_size(0)
         , m_sizeAtLastPrune(0)
         , m_timeAtLastPrune(MonotonicTime::now())
         , m_minCapacity(0)
         , m_capacity(0)
         , m_age(0)
     {
     }

     iterator begin() { return m_map.begin(); }
     iterator end() { return m_map.end(); }

     template<typename UnlinkedCodeBlockType>
     UnlinkedCodeBlockType* findCacheAndUpdateAge(VM& vm, const SourceCodeKey& key)
     {
         prune();

         iterator findResult = m_map.find(key);
         if (findResult == m_map.end())
             return fetchFromDisk<UnlinkedCodeBlockType>(vm, key);

         int64_t age = m_age - findResult->value.age;
         if (age > m_capacity) {
             // A requested object is older than the cache's capacity. We can
             // infer that requested objects are subject to high eviction probability,
             // so we grow the cache to improve our hit rate.
             m_capacity += recencyBias * oldObjectSamplingMultiplier * key.length();
         } else if (age < m_capacity / 2) {
             // A requested object is much younger than the cache's capacity. We can
             // infer that requested objects are subject to low eviction probability,
             // so we shrink the cache to save memory.
             m_capacity -= recencyBias * key.length();
             if (m_capacity < m_minCapacity)
                 m_capacity = m_minCapacity;
         }

         findResult->value.age = m_age;
         m_age += key.length();

         return jsCast<UnlinkedCodeBlockType*>(findResult->value.cell.get());
     }

     AddResult addCache(const SourceCodeKey& key, const SourceCodeValue& value)
     {
         prune();

         AddResult addResult = m_map.add(key, value);
         ASSERT(addResult.isNewEntry);

         m_size += key.length();
         m_age += key.length();
         return addResult;
     }

     void remove(iterator it)
     {
         m_size -= it->key.length();
         m_map.remove(it);
     }

     void clear()
     {
         m_size = 0;
         m_age = 0;
         m_map.clear();
     }

     int64_t age() { return m_age; }

 private:
     template<typename UnlinkedCodeBlockType>
     UnlinkedCodeBlockType* fetchFromDiskImpl(VM& vm, const SourceCodeKey& key)
     {
         RefPtr<CachedBytecode> cachedBytecode = key.source().provider().cachedBytecode();
         if (!cachedBytecode || !cachedBytecode->size())
             return nullptr;
         return decodeCodeBlock<UnlinkedCodeBlockType>(vm, key, *cachedBytecode);
     }

     template<typename UnlinkedCodeBlockType>
     std::enable_if_t<std::is_base_of<UnlinkedCodeBlock, UnlinkedCodeBlockType>::value && !std::is_same<UnlinkedCodeBlockType, UnlinkedEvalCodeBlock>::value, UnlinkedCodeBlockType*>
     fetchFromDisk(VM& vm, const SourceCodeKey& key)
     {
         UnlinkedCodeBlockType* codeBlock = fetchFromDiskImpl<UnlinkedCodeBlockType>(vm, key);
         if (UNLIKELY(Options::forceDiskCache()))
             RELEASE_ASSERT(codeBlock);
         return codeBlock;
     }

     template<typename T>
     std::enable_if_t<!std::is_base_of<UnlinkedCodeBlock, T>::value || std::is_same<T, UnlinkedEvalCodeBlock>::value, T*>
     fetchFromDisk(VM&, const SourceCodeKey&) { return nullptr; }

     // This constant factor biases cache capacity toward allowing a minimum
     // working set to enter the cache before it starts evicting.
     static constexpr Seconds workingSetTime = 10_s;
     static constexpr int64_t workingSetMaxBytes = 16000000;
     static constexpr size_t workingSetMaxEntries = 2000;

     // This constant factor biases cache capacity toward recent activity. We
     // want to adapt to changing workloads.
     static constexpr int64_t recencyBias = 4;

     // This constant factor treats a sampled event for one old object as if it
     // happened for many old objects. Most old objects are evicted before we can
     // sample them, so we need to extrapolate from the ones we do sample.
     static constexpr int64_t oldObjectSamplingMultiplier = 32;

     size_t numberOfEntries() const { return static_cast<size_t>(m_map.size()); }
     bool canPruneQuickly() const { return numberOfEntries() < workingSetMaxEntries; }

     void pruneSlowCase();
     void prune()
     {
         if (m_size <= m_capacity && canPruneQuickly())
             return;

         if (MonotonicTime::now() - m_timeAtLastPrune < workingSetTime
             && m_size - m_sizeAtLastPrune < workingSetMaxBytes
             && canPruneQuickly())
                 return;

         pruneSlowCase();
     }

     MapType m_map;
     int64_t m_size;
     int64_t m_sizeAtLastPrune;
     MonotonicTime m_timeAtLastPrune;
     int64_t m_minCapacity;
     int64_t m_capacity;
     int64_t m_age;
 };

 // Caches top-level code such as <script>, window.eval(), new Function, and JSEvaluateScript().
 class CodeCache {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     UnlinkedProgramCodeBlock* getUnlinkedProgramCodeBlock(VM&, ProgramExecutable*, const SourceCode&, JSParserStrictMode, OptionSet<CodeGenerationMode>, ParserError&);
     UnlinkedEvalCodeBlock* getUnlinkedEvalCodeBlock(VM&, IndirectEvalExecutable*, const SourceCode&, JSParserStrictMode, OptionSet<CodeGenerationMode>, ParserError&, EvalContextType);
     UnlinkedModuleProgramCodeBlock* getUnlinkedModuleProgramCodeBlock(VM&, ModuleProgramExecutable*, const SourceCode&, OptionSet<CodeGenerationMode>, ParserError&);
     UnlinkedFunctionExecutable* getUnlinkedGlobalFunctionExecutable(VM&, const Identifier&, const SourceCode&, OptionSet<CodeGenerationMode>, Optional<int> functionConstructorParametersEndPosition, ParserError&);

     void updateCache(const UnlinkedFunctionExecutable*, const SourceCode&, CodeSpecializationKind, const UnlinkedFunctionCodeBlock*);

     void clear() { m_sourceCode.clear(); }
     JS_EXPORT_PRIVATE void write(VM&);

 private:
     template <class UnlinkedCodeBlockType, class ExecutableType>
     UnlinkedCodeBlockType* getUnlinkedGlobalCodeBlock(VM&, ExecutableType*, const SourceCode&, JSParserStrictMode, JSParserScriptMode, OptionSet<CodeGenerationMode>, ParserError&, EvalContextType);

     CodeCacheMap m_sourceCode;
 };

 template <typename T> struct CacheTypes { };

 template <> struct CacheTypes<UnlinkedProgramCodeBlock> {
     typedef JSC::ProgramNode RootNode;
     static constexpr SourceCodeType codeType = SourceCodeType::ProgramType;
     static constexpr SourceParseMode parseMode = SourceParseMode::ProgramMode;
 };

 template <> struct CacheTypes<UnlinkedEvalCodeBlock> {
     typedef JSC::EvalNode RootNode;
     static constexpr SourceCodeType codeType = SourceCodeType::EvalType;
     static constexpr SourceParseMode parseMode = SourceParseMode::ProgramMode;
 };

 template <> struct CacheTypes<UnlinkedModuleProgramCodeBlock> {
     typedef JSC::ModuleProgramNode RootNode;
     static constexpr SourceCodeType codeType = SourceCodeType::ModuleType;
     static constexpr SourceParseMode parseMode = SourceParseMode::ModuleEvaluateMode;
 };

 template <class UnlinkedCodeBlockType, class ExecutableType = ScriptExecutable>
 UnlinkedCodeBlockType* generateUnlinkedCodeBlockImpl(VM& vm, const SourceCode& source, JSParserStrictMode strictMode, JSParserScriptMode scriptMode, OptionSet<CodeGenerationMode> codeGenerationMode, ParserError& error, EvalContextType evalContextType, DerivedContextType derivedContextType, bool isArrowFunctionContext, const VariableEnvironment* variablesUnderTDZ, ExecutableType* executable = nullptr)
 {
     typedef typename CacheTypes<UnlinkedCodeBlockType>::RootNode RootNode;
     std::unique_ptr<RootNode> rootNode = parse<RootNode>(
         vm, source, Identifier(), JSParserBuiltinMode::NotBuiltin, strictMode, scriptMode, CacheTypes<UnlinkedCodeBlockType>::parseMode, SuperBinding::NotNeeded, error, nullptr, ConstructorKind::None, derivedContextType, evalContextType);
     if (!rootNode)
         return nullptr;

     unsigned lineCount = rootNode->lastLine() - rootNode->firstLine();
     unsigned startColumn = rootNode->startColumn() + 1;
     bool endColumnIsOnStartLine = !lineCount;
     unsigned unlinkedEndColumn = rootNode->endColumn();
     unsigned endColumn = unlinkedEndColumn + (endColumnIsOnStartLine ? startColumn : 1);
     unsigned arrowContextFeature = isArrowFunctionContext ? ArrowFunctionContextFeature : 0;
     if (executable)
         executable->recordParse(rootNode->features() | arrowContextFeature, rootNode->hasCapturedVariables(), rootNode->lastLine(), endColumn);

     bool usesEval = rootNode->features() & EvalFeature;
     bool isStrictMode = rootNode->features() & StrictModeFeature;
     ExecutableInfo executableInfo(usesEval, isStrictMode, false, false, ConstructorKind::None, scriptMode, SuperBinding::NotNeeded, CacheTypes<UnlinkedCodeBlockType>::parseMode, derivedContextType, isArrowFunctionContext, false, evalContextType);

     UnlinkedCodeBlockType* unlinkedCodeBlock = UnlinkedCodeBlockType::create(vm, executableInfo, codeGenerationMode);
     unlinkedCodeBlock->recordParse(rootNode->features(), rootNode->hasCapturedVariables(), lineCount, unlinkedEndColumn);
     if (!source.provider()->sourceURLDirective().isNull())
         unlinkedCodeBlock->setSourceURLDirective(source.provider()->sourceURLDirective());
     if (!source.provider()->sourceMappingURLDirective().isNull())
         unlinkedCodeBlock->setSourceMappingURLDirective(source.provider()->sourceMappingURLDirective());

     error = BytecodeGenerator::generate(vm, rootNode.get(), source, unlinkedCodeBlock, codeGenerationMode, variablesUnderTDZ);

     if (error.isValid())
         return nullptr;

     return unlinkedCodeBlock;
 }

 template <class UnlinkedCodeBlockType, class ExecutableType>
 UnlinkedCodeBlockType* generateUnlinkedCodeBlock(VM& vm, ExecutableType* executable, const SourceCode& source, JSParserStrictMode strictMode, JSParserScriptMode scriptMode, OptionSet<CodeGenerationMode> codeGenerationMode, ParserError& error, EvalContextType evalContextType, const VariableEnvironment* variablesUnderTDZ)
 {
     return generateUnlinkedCodeBlockImpl<UnlinkedCodeBlockType, ExecutableType>(vm, source, strictMode, scriptMode, codeGenerationMode, error, evalContextType, executable->derivedContextType(), executable->isArrowFunctionContext(), variablesUnderTDZ, executable);
 }

 void generateUnlinkedCodeBlockForFunctions(VM&, UnlinkedCodeBlock*, const SourceCode&, OptionSet<CodeGenerationMode>, ParserError&);

 template <class UnlinkedCodeBlockType>
 std::enable_if_t<!std::is_same<UnlinkedCodeBlockType, UnlinkedEvalCodeBlock>::value, UnlinkedCodeBlockType*>
 recursivelyGenerateUnlinkedCodeBlock(VM& vm, const SourceCode& source, JSParserStrictMode strictMode, JSParserScriptMode scriptMode, OptionSet<CodeGenerationMode> codeGenerationMode, ParserError& error, EvalContextType evalContextType, const VariableEnvironment* variablesUnderTDZ)
 {
     bool isArrowFunctionContext = false;
     UnlinkedCodeBlockType* unlinkedCodeBlock = generateUnlinkedCodeBlockImpl<UnlinkedCodeBlockType>(vm, source, strictMode, scriptMode, codeGenerationMode, error, evalContextType, DerivedContextType::None, isArrowFunctionContext, variablesUnderTDZ);
     if (!unlinkedCodeBlock)
         return nullptr;

     generateUnlinkedCodeBlockForFunctions(vm, unlinkedCodeBlock, source, codeGenerationMode, error);
     return unlinkedCodeBlock;
 }

 void writeCodeBlock(VM&, const SourceCodeKey&, const SourceCodeValue&);
 RefPtr<CachedBytecode> serializeBytecode(VM&, UnlinkedCodeBlock*, const SourceCode&, SourceCodeType, JSParserStrictMode, JSParserScriptMode, FileSystem::PlatformFileHandle fd, BytecodeCacheError&, OptionSet<CodeGenerationMode>);
 SourceCodeKey sourceCodeKeyForSerializedProgram(VM&, const SourceCode&);
 SourceCodeKey sourceCodeKeyForSerializedModule(VM&, const SourceCode&);

 } // namespace JSC
	/*
	* Copyright (C) 2012-2019 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

	#include "BytecodeGenerator.h"
	#include "CachedTypes.h"
	#include "ExecutableInfo.h"
	#include "JSCInlines.h"
	#include "Parser.h"
	#include "ParserModes.h"
	#include "SourceCodeKey.h"
	#include "Strong.h"
	#include "StrongInlines.h"
	#include "UnlinkedCodeBlock.h"
	#include "UnlinkedEvalCodeBlock.h"
	#include "UnlinkedFunctionCodeBlock.h"
	#include "UnlinkedModuleProgramCodeBlock.h"
	#include "UnlinkedProgramCodeBlock.h"

	namespace JSC {

	class EvalExecutable;
	class IndirectEvalExecutable;
	class Identifier;
	class DirectEvalExecutable;
	class ModuleProgramExecutable;
	class ParserError;
	class ProgramExecutable;
	class SourceCode;
	class UnlinkedCodeBlock;
	class UnlinkedEvalCodeBlock;
	class UnlinkedFunctionExecutable;
	class UnlinkedModuleProgramCodeBlock;
	class UnlinkedProgramCodeBlock;
	class VM;
	class VariableEnvironment;

	namespace CodeCacheInternal {
	static constexpr bool verbose = false;
	} // namespace CodeCacheInternal

	struct SourceCodeValue {
	SourceCodeValue()
	{
	}

	SourceCodeValue(VM& vm, JSCell* cell, int64_t age)
	: cell(vm, cell)
	, age(age)
	{
	}

	Strong<JSCell> cell;
	int64_t age;
	};

	class CodeCacheMap {
	public:
	typedef HashMap<SourceCodeKey, SourceCodeValue, SourceCodeKey::Hash, SourceCodeKey::HashTraits> MapType;
	typedef MapType::iterator iterator;
	typedef MapType::AddResult AddResult;

	CodeCacheMap()
	: m_size(0)
	, m_sizeAtLastPrune(0)
	, m_timeAtLastPrune(MonotonicTime::now())
	, m_minCapacity(0)
	, m_capacity(0)
	, m_age(0)
	{
	}

	iterator begin() { return m_map.begin(); }
	iterator end() { return m_map.end(); }

	template<typename UnlinkedCodeBlockType>
	UnlinkedCodeBlockType* findCacheAndUpdateAge(VM& vm, const SourceCodeKey& key)
	{
	prune();

	iterator findResult = m_map.find(key);
	if (findResult == m_map.end())
	return fetchFromDisk<UnlinkedCodeBlockType>(vm, key);

	int64_t age = m_age - findResult->value.age;
	if (age > m_capacity) {
	// A requested object is older than the cache's capacity. We can
	// infer that requested objects are subject to high eviction probability,
	// so we grow the cache to improve our hit rate.
	m_capacity += recencyBias * oldObjectSamplingMultiplier * key.length();
	} else if (age < m_capacity / 2) {
	// A requested object is much younger than the cache's capacity. We can
	// infer that requested objects are subject to low eviction probability,
	// so we shrink the cache to save memory.
	m_capacity -= recencyBias * key.length();
	if (m_capacity < m_minCapacity)
	m_capacity = m_minCapacity;
	}

	findResult->value.age = m_age;
	m_age += key.length();

	return jsCast<UnlinkedCodeBlockType*>(findResult->value.cell.get());
	}

	AddResult addCache(const SourceCodeKey& key, const SourceCodeValue& value)
	{
	prune();

	AddResult addResult = m_map.add(key, value);
	ASSERT(addResult.isNewEntry);

	m_size += key.length();
	m_age += key.length();
	return addResult;
	}

	void remove(iterator it)
	{
	m_size -= it->key.length();
	m_map.remove(it);
	}

	void clear()
	{
	m_size = 0;
	m_age = 0;
	m_map.clear();
	}

	int64_t age() { return m_age; }

	private:
	template<typename UnlinkedCodeBlockType>
	UnlinkedCodeBlockType* fetchFromDiskImpl(VM& vm, const SourceCodeKey& key)
	{
	RefPtr<CachedBytecode> cachedBytecode = key.source().provider().cachedBytecode();
	if (!cachedBytecode \|\| !cachedBytecode->size())
	return nullptr;
	return decodeCodeBlock<UnlinkedCodeBlockType>(vm, key, *cachedBytecode);
	}

	template<typename UnlinkedCodeBlockType>
	std::enable_if_t<std::is_base_of<UnlinkedCodeBlock, UnlinkedCodeBlockType>::value && !std::is_same<UnlinkedCodeBlockType, UnlinkedEvalCodeBlock>::value, UnlinkedCodeBlockType*>
	fetchFromDisk(VM& vm, const SourceCodeKey& key)
	{
	UnlinkedCodeBlockType* codeBlock = fetchFromDiskImpl<UnlinkedCodeBlockType>(vm, key);
	if (UNLIKELY(Options::forceDiskCache()))
	RELEASE_ASSERT(codeBlock);
	return codeBlock;
	}

	template<typename T>
	std::enable_if_t<!std::is_base_of<UnlinkedCodeBlock, T>::value \|\| std::is_same<T, UnlinkedEvalCodeBlock>::value, T*>
	fetchFromDisk(VM&, const SourceCodeKey&) { return nullptr; }

	// This constant factor biases cache capacity toward allowing a minimum
	// working set to enter the cache before it starts evicting.
	static constexpr Seconds workingSetTime = 10_s;
	static constexpr int64_t workingSetMaxBytes = 16000000;
	static constexpr size_t workingSetMaxEntries = 2000;

	// This constant factor biases cache capacity toward recent activity. We
	// want to adapt to changing workloads.
	static constexpr int64_t recencyBias = 4;

	// This constant factor treats a sampled event for one old object as if it
	// happened for many old objects. Most old objects are evicted before we can
	// sample them, so we need to extrapolate from the ones we do sample.
	static constexpr int64_t oldObjectSamplingMultiplier = 32;

	size_t numberOfEntries() const { return static_cast<size_t>(m_map.size()); }
	bool canPruneQuickly() const { return numberOfEntries() < workingSetMaxEntries; }

	void pruneSlowCase();
	void prune()
	{
	if (m_size <= m_capacity && canPruneQuickly())
	return;

	if (MonotonicTime::now() - m_timeAtLastPrune < workingSetTime
	&& m_size - m_sizeAtLastPrune < workingSetMaxBytes
	&& canPruneQuickly())
	return;

	pruneSlowCase();
	}

	MapType m_map;
	int64_t m_size;
	int64_t m_sizeAtLastPrune;
	MonotonicTime m_timeAtLastPrune;
	int64_t m_minCapacity;
	int64_t m_capacity;
	int64_t m_age;
	};

	// Caches top-level code such as <script>, window.eval(), new Function, and JSEvaluateScript().
	class CodeCache {
	WTF_MAKE_FAST_ALLOCATED;
	public:
	UnlinkedProgramCodeBlock* getUnlinkedProgramCodeBlock(VM&, ProgramExecutable*, const SourceCode&, JSParserStrictMode, OptionSet<CodeGenerationMode>, ParserError&);
	UnlinkedEvalCodeBlock* getUnlinkedEvalCodeBlock(VM&, IndirectEvalExecutable*, const SourceCode&, JSParserStrictMode, OptionSet<CodeGenerationMode>, ParserError&, EvalContextType);
	UnlinkedModuleProgramCodeBlock* getUnlinkedModuleProgramCodeBlock(VM&, ModuleProgramExecutable*, const SourceCode&, OptionSet<CodeGenerationMode>, ParserError&);
	UnlinkedFunctionExecutable* getUnlinkedGlobalFunctionExecutable(VM&, const Identifier&, const SourceCode&, OptionSet<CodeGenerationMode>, Optional<int> functionConstructorParametersEndPosition, ParserError&);

	void updateCache(const UnlinkedFunctionExecutable, const SourceCode&, CodeSpecializationKind, const UnlinkedFunctionCodeBlock);

	void clear() { m_sourceCode.clear(); }
	JS_EXPORT_PRIVATE void write(VM&);

	private:
	template <class UnlinkedCodeBlockType, class ExecutableType>
	UnlinkedCodeBlockType* getUnlinkedGlobalCodeBlock(VM&, ExecutableType*, const SourceCode&, JSParserStrictMode, JSParserScriptMode, OptionSet<CodeGenerationMode>, ParserError&, EvalContextType);

	CodeCacheMap m_sourceCode;
	};

	template <typename T> struct CacheTypes { };

	template <> struct CacheTypes<UnlinkedProgramCodeBlock> {
	typedef JSC::ProgramNode RootNode;
	static constexpr SourceCodeType codeType = SourceCodeType::ProgramType;
	static constexpr SourceParseMode parseMode = SourceParseMode::ProgramMode;
	};

	template <> struct CacheTypes<UnlinkedEvalCodeBlock> {
	typedef JSC::EvalNode RootNode;
	static constexpr SourceCodeType codeType = SourceCodeType::EvalType;
	static constexpr SourceParseMode parseMode = SourceParseMode::ProgramMode;
	};

	template <> struct CacheTypes<UnlinkedModuleProgramCodeBlock> {
	typedef JSC::ModuleProgramNode RootNode;
	static constexpr SourceCodeType codeType = SourceCodeType::ModuleType;
	static constexpr SourceParseMode parseMode = SourceParseMode::ModuleEvaluateMode;
	};

	template <class UnlinkedCodeBlockType, class ExecutableType = ScriptExecutable>
	UnlinkedCodeBlockType* generateUnlinkedCodeBlockImpl(VM& vm, const SourceCode& source, JSParserStrictMode strictMode, JSParserScriptMode scriptMode, OptionSet<CodeGenerationMode> codeGenerationMode, ParserError& error, EvalContextType evalContextType, DerivedContextType derivedContextType, bool isArrowFunctionContext, const VariableEnvironment* variablesUnderTDZ, ExecutableType* executable = nullptr)
	{
	typedef typename CacheTypes<UnlinkedCodeBlockType>::RootNode RootNode;
	std::unique_ptr<RootNode> rootNode = parse<RootNode>(
	vm, source, Identifier(), JSParserBuiltinMode::NotBuiltin, strictMode, scriptMode, CacheTypes<UnlinkedCodeBlockType>::parseMode, SuperBinding::NotNeeded, error, nullptr, ConstructorKind::None, derivedContextType, evalContextType);
	if (!rootNode)
	return nullptr;

	unsigned lineCount = rootNode->lastLine() - rootNode->firstLine();
	unsigned startColumn = rootNode->startColumn() + 1;
	bool endColumnIsOnStartLine = !lineCount;
	unsigned unlinkedEndColumn = rootNode->endColumn();
	unsigned endColumn = unlinkedEndColumn + (endColumnIsOnStartLine ? startColumn : 1);
	unsigned arrowContextFeature = isArrowFunctionContext ? ArrowFunctionContextFeature : 0;
	if (executable)
	executable->recordParse(rootNode->features() \| arrowContextFeature, rootNode->hasCapturedVariables(), rootNode->lastLine(), endColumn);

	bool usesEval = rootNode->features() & EvalFeature;
	bool isStrictMode = rootNode->features() & StrictModeFeature;
	ExecutableInfo executableInfo(usesEval, isStrictMode, false, false, ConstructorKind::None, scriptMode, SuperBinding::NotNeeded, CacheTypes<UnlinkedCodeBlockType>::parseMode, derivedContextType, isArrowFunctionContext, false, evalContextType);

	UnlinkedCodeBlockType* unlinkedCodeBlock = UnlinkedCodeBlockType::create(vm, executableInfo, codeGenerationMode);
	unlinkedCodeBlock->recordParse(rootNode->features(), rootNode->hasCapturedVariables(), lineCount, unlinkedEndColumn);
	if (!source.provider()->sourceURLDirective().isNull())
	unlinkedCodeBlock->setSourceURLDirective(source.provider()->sourceURLDirective());
	if (!source.provider()->sourceMappingURLDirective().isNull())
	unlinkedCodeBlock->setSourceMappingURLDirective(source.provider()->sourceMappingURLDirective());

	error = BytecodeGenerator::generate(vm, rootNode.get(), source, unlinkedCodeBlock, codeGenerationMode, variablesUnderTDZ);

	if (error.isValid())
	return nullptr;

	return unlinkedCodeBlock;
	}

	template <class UnlinkedCodeBlockType, class ExecutableType>
	UnlinkedCodeBlockType* generateUnlinkedCodeBlock(VM& vm, ExecutableType* executable, const SourceCode& source, JSParserStrictMode strictMode, JSParserScriptMode scriptMode, OptionSet<CodeGenerationMode> codeGenerationMode, ParserError& error, EvalContextType evalContextType, const VariableEnvironment* variablesUnderTDZ)
	{
	return generateUnlinkedCodeBlockImpl<UnlinkedCodeBlockType, ExecutableType>(vm, source, strictMode, scriptMode, codeGenerationMode, error, evalContextType, executable->derivedContextType(), executable->isArrowFunctionContext(), variablesUnderTDZ, executable);
	}

	void generateUnlinkedCodeBlockForFunctions(VM&, UnlinkedCodeBlock*, const SourceCode&, OptionSet<CodeGenerationMode>, ParserError&);

	template <class UnlinkedCodeBlockType>
	std::enable_if_t<!std::is_same<UnlinkedCodeBlockType, UnlinkedEvalCodeBlock>::value, UnlinkedCodeBlockType*>
	recursivelyGenerateUnlinkedCodeBlock(VM& vm, const SourceCode& source, JSParserStrictMode strictMode, JSParserScriptMode scriptMode, OptionSet<CodeGenerationMode> codeGenerationMode, ParserError& error, EvalContextType evalContextType, const VariableEnvironment* variablesUnderTDZ)
	{
	bool isArrowFunctionContext = false;
	UnlinkedCodeBlockType* unlinkedCodeBlock = generateUnlinkedCodeBlockImpl<UnlinkedCodeBlockType>(vm, source, strictMode, scriptMode, codeGenerationMode, error, evalContextType, DerivedContextType::None, isArrowFunctionContext, variablesUnderTDZ);
	if (!unlinkedCodeBlock)
	return nullptr;

	generateUnlinkedCodeBlockForFunctions(vm, unlinkedCodeBlock, source, codeGenerationMode, error);
	return unlinkedCodeBlock;
	}

	void writeCodeBlock(VM&, const SourceCodeKey&, const SourceCodeValue&);
	RefPtr<CachedBytecode> serializeBytecode(VM&, UnlinkedCodeBlock*, const SourceCode&, SourceCodeType, JSParserStrictMode, JSParserScriptMode, FileSystem::PlatformFileHandle fd, BytecodeCacheError&, OptionSet<CodeGenerationMode>);
	SourceCodeKey sourceCodeKeyForSerializedProgram(VM&, const SourceCode&);
	SourceCodeKey sourceCodeKeyForSerializedModule(VM&, const SourceCode&);

	} // namespace JSC