weex_core/Source/include/JavaScriptCore/jit/CompactJITCodeMap.h - incubator-weex - Git at Google

 /*
  * Copyright (C) 2011 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.
  * 3.  Neither the name of Apple Inc. ("Apple") nor the names of
  *     its contributors may be used to endorse or promote products derived
  *     from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE 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 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.
  */

 #pragma once

 #include <wtf/Assertions.h>
 #include <wtf/FastMalloc.h>
 #include <wtf/FastMalloc.h>
 #include <wtf/Vector.h>

 namespace JSC {

 // Gives you a compressed map between between bytecode indices and machine code
 // entry points. The compression simply tries to use either 1, 2, or 4 bytes for
 // any given offset. The largest offset that can be stored is 2^30.

 // Example use:
 //
 // CompactJITCodeMap::Encoder encoder(map);
 // encoder.append(a, b);
 // encoder.append(c, d); // preconditions: c >= a, d >= b
 // auto map = encoder.finish();
 //
 // At some later time:
 //
 // Vector<BytecodeAndMachineOffset> decoded;
 // map->decode(decoded);

 struct BytecodeAndMachineOffset {
     BytecodeAndMachineOffset() { }

     BytecodeAndMachineOffset(unsigned bytecodeIndex, unsigned machineCodeOffset)
         : m_bytecodeIndex(bytecodeIndex)
         , m_machineCodeOffset(machineCodeOffset)
     {
     }

     unsigned m_bytecodeIndex;
     unsigned m_machineCodeOffset;

     static inline unsigned getBytecodeIndex(BytecodeAndMachineOffset* mapping)
     {
         return mapping->m_bytecodeIndex;
     }

     static inline unsigned getMachineCodeOffset(BytecodeAndMachineOffset* mapping)
     {
         return mapping->m_machineCodeOffset;
     }
 };

 class CompactJITCodeMap {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     CompactJITCodeMap(uint8_t* buffer, unsigned size, unsigned numberOfEntries)
         : m_buffer(buffer)
 #if !ASSERT_DISABLED
         , m_size(size)
 #endif
         , m_numberOfEntries(numberOfEntries)
     {
         UNUSED_PARAM(size);
     }

     ~CompactJITCodeMap()
     {
         if (m_buffer)
             fastFree(m_buffer);
     }

     unsigned numberOfEntries() const
     {
         return m_numberOfEntries;
     }

     void decode(Vector<BytecodeAndMachineOffset>& result) const;

 private:
     uint8_t at(unsigned index) const
     {
         ASSERT(index < m_size);
         return m_buffer[index];
     }

     unsigned decodeNumber(unsigned& index) const
     {
         uint8_t headValue = at(index++);
         if (!(headValue & 128))
             return headValue;
         if (!(headValue & 64))
             return (static_cast<unsigned>(headValue & ~128) << 8) | at(index++);
         unsigned second = at(index++);
         unsigned third  = at(index++);
         unsigned fourth = at(index++);
         return (static_cast<unsigned>(headValue & ~(128 + 64)) << 24) | (second << 16) | (third << 8) | fourth;
     }

     uint8_t* m_buffer;
 #if !ASSERT_DISABLED
     unsigned m_size;
 #endif
     unsigned m_numberOfEntries;

 public:
     class Encoder {
         WTF_MAKE_NONCOPYABLE(Encoder);
     public:
         Encoder();
         ~Encoder();

         void ensureCapacityFor(unsigned numberOfEntriesToAdd);
         void append(unsigned bytecodeIndex, unsigned machineCodeOffset);
         std::unique_ptr<CompactJITCodeMap> finish();

     private:
         void appendByte(uint8_t value);
         void encodeNumber(uint32_t value);

         uint8_t* m_buffer;
         unsigned m_size;
         unsigned m_capacity;
         unsigned m_numberOfEntries;

         unsigned m_previousBytecodeIndex;
         unsigned m_previousMachineCodeOffset;
     };

     class Decoder {
         WTF_MAKE_NONCOPYABLE(Decoder);
     public:
         Decoder(const CompactJITCodeMap*);

         unsigned numberOfEntriesRemaining() const;
         void read(unsigned& bytecodeIndex, unsigned& machineCodeOffset);

     private:
         const CompactJITCodeMap* m_jitCodeMap;
         unsigned m_previousBytecodeIndex;
         unsigned m_previousMachineCodeOffset;
         unsigned m_numberOfEntriesRemaining;
         unsigned m_bufferIndex;
     };

 private:
     friend class Encoder;
     friend class Decoder;
 };

 inline void CompactJITCodeMap::decode(Vector<BytecodeAndMachineOffset>& result) const
 {
     Decoder decoder(this);
     result.resize(decoder.numberOfEntriesRemaining());
     for (unsigned i = 0; i < result.size(); ++i)
         decoder.read(result[i].m_bytecodeIndex, result[i].m_machineCodeOffset);

     ASSERT(!decoder.numberOfEntriesRemaining());
 }

 inline CompactJITCodeMap::Encoder::Encoder()
     : m_buffer(0)
     , m_size(0)
     , m_capacity(0)
     , m_numberOfEntries(0)
     , m_previousBytecodeIndex(0)
     , m_previousMachineCodeOffset(0)
 {
 }

 inline CompactJITCodeMap::Encoder::~Encoder()
 {
     if (m_buffer)
         fastFree(m_buffer);
 }

 inline void CompactJITCodeMap::Encoder::append(unsigned bytecodeIndex, unsigned machineCodeOffset)
 {
     ASSERT(bytecodeIndex >= m_previousBytecodeIndex);
     ASSERT(machineCodeOffset >= m_previousMachineCodeOffset);
     ensureCapacityFor(1);
     encodeNumber(bytecodeIndex - m_previousBytecodeIndex);
     encodeNumber(machineCodeOffset - m_previousMachineCodeOffset);
     m_previousBytecodeIndex = bytecodeIndex;
     m_previousMachineCodeOffset = machineCodeOffset;
     m_numberOfEntries++;
 }

 inline std::unique_ptr<CompactJITCodeMap> CompactJITCodeMap::Encoder::finish()
 {
     m_capacity = m_size;
     m_buffer = static_cast<uint8_t*>(fastRealloc(m_buffer, m_capacity));
     auto result = std::make_unique<CompactJITCodeMap>(m_buffer, m_size, m_numberOfEntries);
     m_buffer = 0;
     m_size = 0;
     m_capacity = 0;
     m_numberOfEntries = 0;
     m_previousBytecodeIndex = 0;
     m_previousMachineCodeOffset = 0;
     return result;
 }

 inline void CompactJITCodeMap::Encoder::appendByte(uint8_t value)
 {
     ASSERT(m_size + 1 <= m_capacity);
     m_buffer[m_size++] = value;
 }

 inline void CompactJITCodeMap::Encoder::encodeNumber(uint32_t value)
 {
     ASSERT(m_size + 4 <= m_capacity);
     ASSERT(value < (1 << 30));
     if (value <= 127) {
         uint8_t headValue = static_cast<uint8_t>(value);
         ASSERT(!(headValue & 128));
         appendByte(headValue);
     } else if (value <= 16383) {
         uint8_t headValue = static_cast<uint8_t>(value >> 8);
         ASSERT(!(headValue & 128));
         ASSERT(!(headValue & 64));
         appendByte(headValue | 128);
         appendByte(static_cast<uint8_t>(value));
     } else {
         uint8_t headValue = static_cast<uint8_t>(value >> 24);
         ASSERT(!(headValue & 128));
         ASSERT(!(headValue & 64));
         appendByte(headValue | 128 | 64);
         appendByte(static_cast<uint8_t>(value >> 16));
         appendByte(static_cast<uint8_t>(value >> 8));
         appendByte(static_cast<uint8_t>(value));
     }
 }

 inline void CompactJITCodeMap::Encoder::ensureCapacityFor(unsigned numberOfEntriesToAdd)
 {
     unsigned capacityNeeded = m_size + numberOfEntriesToAdd * 2 * 4;
     if (capacityNeeded > m_capacity) {
         m_capacity = capacityNeeded * 2;
         m_buffer = static_cast<uint8_t*>(fastRealloc(m_buffer, m_capacity));
     }
 }

 inline CompactJITCodeMap::Decoder::Decoder(const CompactJITCodeMap* jitCodeMap)
     : m_jitCodeMap(jitCodeMap)
     , m_previousBytecodeIndex(0)
     , m_previousMachineCodeOffset(0)
     , m_numberOfEntriesRemaining(jitCodeMap->m_numberOfEntries)
     , m_bufferIndex(0)
 {
 }

 inline unsigned CompactJITCodeMap::Decoder::numberOfEntriesRemaining() const
 {
     ASSERT(m_numberOfEntriesRemaining || m_bufferIndex == m_jitCodeMap->m_size);
     return m_numberOfEntriesRemaining;
 }

 inline void CompactJITCodeMap::Decoder::read(unsigned& bytecodeIndex, unsigned& machineCodeOffset)
 {
     ASSERT(numberOfEntriesRemaining());

     m_previousBytecodeIndex += m_jitCodeMap->decodeNumber(m_bufferIndex);
     m_previousMachineCodeOffset += m_jitCodeMap->decodeNumber(m_bufferIndex);
     bytecodeIndex = m_previousBytecodeIndex;
     machineCodeOffset = m_previousMachineCodeOffset;
     m_numberOfEntriesRemaining--;
 }

 } // namespace JSC
	/*
	* Copyright (C) 2011 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.
	* 3. Neither the name of Apple Inc. ("Apple") nor the names of
	* its contributors may be used to endorse or promote products derived
	* from this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY APPLE 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 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.
	*/

	#pragma once

	#include <wtf/Assertions.h>
	#include <wtf/FastMalloc.h>
	#include <wtf/FastMalloc.h>
	#include <wtf/Vector.h>

	namespace JSC {

	// Gives you a compressed map between between bytecode indices and machine code
	// entry points. The compression simply tries to use either 1, 2, or 4 bytes for
	// any given offset. The largest offset that can be stored is 2^30.

	// Example use:
	//
	// CompactJITCodeMap::Encoder encoder(map);
	// encoder.append(a, b);
	// encoder.append(c, d); // preconditions: c >= a, d >= b
	// auto map = encoder.finish();
	//
	// At some later time:
	//
	// Vector<BytecodeAndMachineOffset> decoded;
	// map->decode(decoded);

	struct BytecodeAndMachineOffset {
	BytecodeAndMachineOffset() { }

	BytecodeAndMachineOffset(unsigned bytecodeIndex, unsigned machineCodeOffset)
	: m_bytecodeIndex(bytecodeIndex)
	, m_machineCodeOffset(machineCodeOffset)
	{
	}

	unsigned m_bytecodeIndex;
	unsigned m_machineCodeOffset;

	static inline unsigned getBytecodeIndex(BytecodeAndMachineOffset* mapping)
	{
	return mapping->m_bytecodeIndex;
	}

	static inline unsigned getMachineCodeOffset(BytecodeAndMachineOffset* mapping)
	{
	return mapping->m_machineCodeOffset;
	}
	};

	class CompactJITCodeMap {
	WTF_MAKE_FAST_ALLOCATED;
	public:
	CompactJITCodeMap(uint8_t* buffer, unsigned size, unsigned numberOfEntries)
	: m_buffer(buffer)
	#if !ASSERT_DISABLED
	, m_size(size)
	#endif
	, m_numberOfEntries(numberOfEntries)
	{
	UNUSED_PARAM(size);
	}

	~CompactJITCodeMap()
	{
	if (m_buffer)
	fastFree(m_buffer);
	}

	unsigned numberOfEntries() const
	{
	return m_numberOfEntries;
	}

	void decode(Vector<BytecodeAndMachineOffset>& result) const;

	private:
	uint8_t at(unsigned index) const
	{
	ASSERT(index < m_size);
	return m_buffer[index];
	}

	unsigned decodeNumber(unsigned& index) const
	{
	uint8_t headValue = at(index++);
	if (!(headValue & 128))
	return headValue;
	if (!(headValue & 64))
	return (static_cast<unsigned>(headValue & ~128) << 8) \| at(index++);
	unsigned second = at(index++);
	unsigned third = at(index++);
	unsigned fourth = at(index++);
	return (static_cast<unsigned>(headValue & ~(128 + 64)) << 24) \| (second << 16) \| (third << 8) \| fourth;
	}

	uint8_t* m_buffer;
	#if !ASSERT_DISABLED
	unsigned m_size;
	#endif
	unsigned m_numberOfEntries;

	public:
	class Encoder {
	WTF_MAKE_NONCOPYABLE(Encoder);
	public:
	Encoder();
	~Encoder();

	void ensureCapacityFor(unsigned numberOfEntriesToAdd);
	void append(unsigned bytecodeIndex, unsigned machineCodeOffset);
	std::unique_ptr<CompactJITCodeMap> finish();

	private:
	void appendByte(uint8_t value);
	void encodeNumber(uint32_t value);

	uint8_t* m_buffer;
	unsigned m_size;
	unsigned m_capacity;
	unsigned m_numberOfEntries;

	unsigned m_previousBytecodeIndex;
	unsigned m_previousMachineCodeOffset;
	};

	class Decoder {
	WTF_MAKE_NONCOPYABLE(Decoder);
	public:
	Decoder(const CompactJITCodeMap*);

	unsigned numberOfEntriesRemaining() const;
	void read(unsigned& bytecodeIndex, unsigned& machineCodeOffset);

	private:
	const CompactJITCodeMap* m_jitCodeMap;
	unsigned m_previousBytecodeIndex;
	unsigned m_previousMachineCodeOffset;
	unsigned m_numberOfEntriesRemaining;
	unsigned m_bufferIndex;
	};

	private:
	friend class Encoder;
	friend class Decoder;
	};

	inline void CompactJITCodeMap::decode(Vector<BytecodeAndMachineOffset>& result) const
	{
	Decoder decoder(this);
	result.resize(decoder.numberOfEntriesRemaining());
	for (unsigned i = 0; i < result.size(); ++i)
	decoder.read(result[i].m_bytecodeIndex, result[i].m_machineCodeOffset);

	ASSERT(!decoder.numberOfEntriesRemaining());
	}

	inline CompactJITCodeMap::Encoder::Encoder()
	: m_buffer(0)
	, m_size(0)
	, m_capacity(0)
	, m_numberOfEntries(0)
	, m_previousBytecodeIndex(0)
	, m_previousMachineCodeOffset(0)
	{
	}

	inline CompactJITCodeMap::Encoder::~Encoder()
	{
	if (m_buffer)
	fastFree(m_buffer);
	}

	inline void CompactJITCodeMap::Encoder::append(unsigned bytecodeIndex, unsigned machineCodeOffset)
	{
	ASSERT(bytecodeIndex >= m_previousBytecodeIndex);
	ASSERT(machineCodeOffset >= m_previousMachineCodeOffset);
	ensureCapacityFor(1);
	encodeNumber(bytecodeIndex - m_previousBytecodeIndex);
	encodeNumber(machineCodeOffset - m_previousMachineCodeOffset);
	m_previousBytecodeIndex = bytecodeIndex;
	m_previousMachineCodeOffset = machineCodeOffset;
	m_numberOfEntries++;
	}

	inline std::unique_ptr<CompactJITCodeMap> CompactJITCodeMap::Encoder::finish()
	{
	m_capacity = m_size;
	m_buffer = static_cast<uint8_t*>(fastRealloc(m_buffer, m_capacity));
	auto result = std::make_unique<CompactJITCodeMap>(m_buffer, m_size, m_numberOfEntries);
	m_buffer = 0;
	m_size = 0;
	m_capacity = 0;
	m_numberOfEntries = 0;
	m_previousBytecodeIndex = 0;
	m_previousMachineCodeOffset = 0;
	return result;
	}

	inline void CompactJITCodeMap::Encoder::appendByte(uint8_t value)
	{
	ASSERT(m_size + 1 <= m_capacity);
	m_buffer[m_size++] = value;
	}

	inline void CompactJITCodeMap::Encoder::encodeNumber(uint32_t value)
	{
	ASSERT(m_size + 4 <= m_capacity);
	ASSERT(value < (1 << 30));
	if (value <= 127) {
	uint8_t headValue = static_cast<uint8_t>(value);
	ASSERT(!(headValue & 128));
	appendByte(headValue);
	} else if (value <= 16383) {
	uint8_t headValue = static_cast<uint8_t>(value >> 8);
	ASSERT(!(headValue & 128));
	ASSERT(!(headValue & 64));
	appendByte(headValue \| 128);
	appendByte(static_cast<uint8_t>(value));
	} else {
	uint8_t headValue = static_cast<uint8_t>(value >> 24);
	ASSERT(!(headValue & 128));
	ASSERT(!(headValue & 64));
	appendByte(headValue \| 128 \| 64);
	appendByte(static_cast<uint8_t>(value >> 16));
	appendByte(static_cast<uint8_t>(value >> 8));
	appendByte(static_cast<uint8_t>(value));
	}
	}

	inline void CompactJITCodeMap::Encoder::ensureCapacityFor(unsigned numberOfEntriesToAdd)
	{
	unsigned capacityNeeded = m_size + numberOfEntriesToAdd * 2 * 4;
	if (capacityNeeded > m_capacity) {
	m_capacity = capacityNeeded * 2;
	m_buffer = static_cast<uint8_t*>(fastRealloc(m_buffer, m_capacity));
	}
	}

	inline CompactJITCodeMap::Decoder::Decoder(const CompactJITCodeMap* jitCodeMap)
	: m_jitCodeMap(jitCodeMap)
	, m_previousBytecodeIndex(0)
	, m_previousMachineCodeOffset(0)
	, m_numberOfEntriesRemaining(jitCodeMap->m_numberOfEntries)
	, m_bufferIndex(0)
	{
	}

	inline unsigned CompactJITCodeMap::Decoder::numberOfEntriesRemaining() const
	{
	ASSERT(m_numberOfEntriesRemaining \|\| m_bufferIndex == m_jitCodeMap->m_size);
	return m_numberOfEntriesRemaining;
	}

	inline void CompactJITCodeMap::Decoder::read(unsigned& bytecodeIndex, unsigned& machineCodeOffset)
	{
	ASSERT(numberOfEntriesRemaining());

	m_previousBytecodeIndex += m_jitCodeMap->decodeNumber(m_bufferIndex);
	m_previousMachineCodeOffset += m_jitCodeMap->decodeNumber(m_bufferIndex);
	bytecodeIndex = m_previousBytecodeIndex;
	machineCodeOffset = m_previousMachineCodeOffset;
	m_numberOfEntriesRemaining--;
	}

	} // namespace JSC