Source/JavaScriptCore/bytecode/BytecodeBasicBlock.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2013-2017 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 "BytecodeBasicBlock.h"

 #include "CodeBlock.h"
 #include "PreciseJumpTargets.h"
 #include "UnlinkedCodeBlockGenerator.h"

 namespace JSC {

 DEFINE_ALLOCATOR_WITH_HEAP_IDENTIFIER(BytecodeBasicBlock);

 BytecodeBasicBlock::BytecodeBasicBlock(const InstructionStream::Ref& instruction, unsigned blockIndex)
     : m_leaderOffset(instruction.offset())
     , m_totalLength(0)
     , m_index(blockIndex)
 {
     addLength(instruction->size());
 }

 BytecodeBasicBlock::BytecodeBasicBlock(BytecodeBasicBlock::SpecialBlockType blockType, unsigned blockIndex)
     : m_leaderOffset(blockType == BytecodeBasicBlock::EntryBlock ? 0 : UINT_MAX)
     , m_totalLength(blockType == BytecodeBasicBlock::EntryBlock ? 0 : UINT_MAX)
     , m_index(blockIndex)
 {
 }

 void BytecodeBasicBlock::addLength(unsigned bytecodeLength)
 {
     m_delta.append(bytecodeLength);
     m_totalLength += bytecodeLength;
 }

 void BytecodeBasicBlock::shrinkToFit()
 {
     m_delta.shrinkToFit();
     m_successors.shrinkToFit();
 }

 static bool isJumpTarget(OpcodeID opcodeID, const Vector<InstructionStream::Offset, 32>& jumpTargets, unsigned bytecodeOffset)
 {
     if (opcodeID == op_catch)
         return true;

     return std::binary_search(jumpTargets.begin(), jumpTargets.end(), bytecodeOffset);
 }

 template<typename Block>
 auto BytecodeBasicBlock::computeImpl(Block* codeBlock, const InstructionStream& instructions) -> BasicBlockVector
 {
     BasicBlockVector basicBlocks;
     Vector<InstructionStream::Offset, 32> jumpTargets;
     computePreciseJumpTargets(codeBlock, instructions, jumpTargets);

     auto linkBlocks = [&] (BytecodeBasicBlock& from, BytecodeBasicBlock& to) {
         from.addSuccessor(to);
     };

     {
         // Create the entry and exit basic blocks.
         basicBlocks.reserveCapacity(jumpTargets.size() + 2);
         {
             // Entry block.
             basicBlocks.constructAndAppend(BytecodeBasicBlock::EntryBlock, basicBlocks.size());
             // First block.
             basicBlocks.constructAndAppend(BytecodeBasicBlock::EntryBlock, basicBlocks.size());
             linkBlocks(basicBlocks[0], basicBlocks[1]);
         }

         BytecodeBasicBlock* current = &basicBlocks.last();
         auto appendBlock = [&] (const InstructionStream::Ref& instruction) -> BytecodeBasicBlock* {
             basicBlocks.constructAndAppend(instruction, basicBlocks.size());
             return &basicBlocks.last();
         };
         bool nextInstructionIsLeader = false;
         for (const auto& instruction : instructions) {
             auto bytecodeOffset = instruction.offset();
             OpcodeID opcodeID = instruction->opcodeID();

             bool createdBlock = false;
             // If the current bytecode is a jump target, then it's the leader of its own basic block.
             if (nextInstructionIsLeader || isJumpTarget(opcodeID, jumpTargets, bytecodeOffset)) {
                 current = appendBlock(instruction);
                 createdBlock = true;
                 nextInstructionIsLeader = false;
             }

             // If the current bytecode is a branch or a return, then the next instruction is the leader of its own basic block.
             if (isBranch(opcodeID) || isTerminal(opcodeID) || isThrow(opcodeID))
                 nextInstructionIsLeader = true;

             if (createdBlock)
                 continue;

             // Otherwise, just add to the length of the current block.
             current->addLength(instruction->size());
         }
         // Exit block.
         basicBlocks.constructAndAppend(BytecodeBasicBlock::ExitBlock, basicBlocks.size());
         basicBlocks.shrinkToFit();
         ASSERT(basicBlocks.last().isExitBlock());
     }
     // After this point, we never change basicBlocks.

     // Link basic blocks together.
     for (unsigned i = 0; i < basicBlocks.size(); i++) {
         BytecodeBasicBlock& block = basicBlocks[i];

         if (block.isEntryBlock() || block.isExitBlock())
             continue;

         bool fallsThrough = true;
         for (unsigned visitedLength = 0; visitedLength < block.totalLength();) {
             InstructionStream::Ref instruction = instructions.at(block.leaderOffset() + visitedLength);
             OpcodeID opcodeID = instruction->opcodeID();

             visitedLength += instruction->size();

             // If we found a terminal bytecode, link to the exit block.
             if (isTerminal(opcodeID)) {
                 ASSERT(instruction.offset() + instruction->size() == block.leaderOffset() + block.totalLength());
                 linkBlocks(block, basicBlocks.last());
                 fallsThrough = false;
                 break;
             }

             // If we found a throw, get the HandlerInfo for this instruction to see where we will jump.
             // If there isn't one, treat this throw as a terminal. This is true even if we have a finally
             // block because the finally block will create its own catch, which will generate a HandlerInfo.
             if (isThrow(opcodeID)) {
                 ASSERT(instruction.offset() + instruction->size() == block.leaderOffset() + block.totalLength());
                 auto* handler = codeBlock->handlerForBytecodeIndex(BytecodeIndex(instruction.offset()));
                 fallsThrough = false;
                 if (!handler) {
                     linkBlocks(block, basicBlocks.last());
                     break;
                 }
                 for (auto& otherBlock : basicBlocks) {
                     if (handler->target == otherBlock.leaderOffset()) {
                         linkBlocks(block, otherBlock);
                         break;
                     }
                 }
                 break;
             }

             // If we found a branch, link to the block(s) that we jump to.
             if (isBranch(opcodeID)) {
                 ASSERT(instruction.offset() + instruction->size() == block.leaderOffset() + block.totalLength());
                 Vector<InstructionStream::Offset, 1> bytecodeOffsetsJumpedTo;
                 findJumpTargetsForInstruction(codeBlock, instruction, bytecodeOffsetsJumpedTo);

                 size_t numberOfJumpTargets = bytecodeOffsetsJumpedTo.size();
                 ASSERT(numberOfJumpTargets);
                 for (auto& otherBlock : basicBlocks) {
                     if (bytecodeOffsetsJumpedTo.contains(otherBlock.leaderOffset())) {
                         linkBlocks(block, otherBlock);
                         --numberOfJumpTargets;
                         if (!numberOfJumpTargets)
                             break;
                     }
                 }
                 // numberOfJumpTargets may not be 0 here if there are multiple jumps targeting the same
                 // basic blocks (e.g. in a switch type opcode). Since we only decrement numberOfJumpTargets
                 // once per basic block, the duplicates are not accounted for. For our purpose here,
                 // that doesn't matter because we only need to link to the target block once regardless
                 // of how many ways this block can jump there.

                 if (isUnconditionalBranch(opcodeID))
                     fallsThrough = false;

                 break;
             }
         }

         // If we fall through then link to the next block in program order.
         if (fallsThrough) {
             ASSERT(i + 1 < basicBlocks.size());
             BytecodeBasicBlock& nextBlock = basicBlocks[i + 1];
             linkBlocks(block, nextBlock);
         }
     }

     unsigned index = 0;
     for (auto& basicBlock : basicBlocks) {
         basicBlock.shrinkToFit();
         ASSERT_UNUSED(index, basicBlock.index() == index++);
     }

     return basicBlocks;
 }

 auto BytecodeBasicBlock::compute(CodeBlock* codeBlock, const InstructionStream& instructions) -> BasicBlockVector
 {
     return computeImpl(codeBlock, instructions);
 }

 auto BytecodeBasicBlock::compute(UnlinkedCodeBlockGenerator* codeBlock, const InstructionStream& instructions) -> BasicBlockVector
 {
     return computeImpl(codeBlock, instructions);
 }

 } // namespace JSC
	/*
	* Copyright (C) 2013-2017 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 "BytecodeBasicBlock.h"

	#include "CodeBlock.h"
	#include "PreciseJumpTargets.h"
	#include "UnlinkedCodeBlockGenerator.h"

	namespace JSC {

	DEFINE_ALLOCATOR_WITH_HEAP_IDENTIFIER(BytecodeBasicBlock);

	BytecodeBasicBlock::BytecodeBasicBlock(const InstructionStream::Ref& instruction, unsigned blockIndex)
	: m_leaderOffset(instruction.offset())
	, m_totalLength(0)
	, m_index(blockIndex)
	{
	addLength(instruction->size());
	}

	BytecodeBasicBlock::BytecodeBasicBlock(BytecodeBasicBlock::SpecialBlockType blockType, unsigned blockIndex)
	: m_leaderOffset(blockType == BytecodeBasicBlock::EntryBlock ? 0 : UINT_MAX)
	, m_totalLength(blockType == BytecodeBasicBlock::EntryBlock ? 0 : UINT_MAX)
	, m_index(blockIndex)
	{
	}

	void BytecodeBasicBlock::addLength(unsigned bytecodeLength)
	{
	m_delta.append(bytecodeLength);
	m_totalLength += bytecodeLength;
	}

	void BytecodeBasicBlock::shrinkToFit()
	{
	m_delta.shrinkToFit();
	m_successors.shrinkToFit();
	}

	static bool isJumpTarget(OpcodeID opcodeID, const Vector<InstructionStream::Offset, 32>& jumpTargets, unsigned bytecodeOffset)
	{
	if (opcodeID == op_catch)
	return true;

	return std::binary_search(jumpTargets.begin(), jumpTargets.end(), bytecodeOffset);
	}

	template<typename Block>
	auto BytecodeBasicBlock::computeImpl(Block* codeBlock, const InstructionStream& instructions) -> BasicBlockVector
	{
	BasicBlockVector basicBlocks;
	Vector<InstructionStream::Offset, 32> jumpTargets;
	computePreciseJumpTargets(codeBlock, instructions, jumpTargets);

	auto linkBlocks = [&] (BytecodeBasicBlock& from, BytecodeBasicBlock& to) {
	from.addSuccessor(to);
	};

	{
	// Create the entry and exit basic blocks.
	basicBlocks.reserveCapacity(jumpTargets.size() + 2);
	{
	// Entry block.
	basicBlocks.constructAndAppend(BytecodeBasicBlock::EntryBlock, basicBlocks.size());
	// First block.
	basicBlocks.constructAndAppend(BytecodeBasicBlock::EntryBlock, basicBlocks.size());
	linkBlocks(basicBlocks[0], basicBlocks[1]);
	}

	BytecodeBasicBlock* current = &basicBlocks.last();
	auto appendBlock = [&] (const InstructionStream::Ref& instruction) -> BytecodeBasicBlock* {
	basicBlocks.constructAndAppend(instruction, basicBlocks.size());
	return &basicBlocks.last();
	};
	bool nextInstructionIsLeader = false;
	for (const auto& instruction : instructions) {
	auto bytecodeOffset = instruction.offset();
	OpcodeID opcodeID = instruction->opcodeID();

	bool createdBlock = false;
	// If the current bytecode is a jump target, then it's the leader of its own basic block.
	if (nextInstructionIsLeader \|\| isJumpTarget(opcodeID, jumpTargets, bytecodeOffset)) {
	current = appendBlock(instruction);
	createdBlock = true;
	nextInstructionIsLeader = false;
	}

	// If the current bytecode is a branch or a return, then the next instruction is the leader of its own basic block.
	if (isBranch(opcodeID) \|\| isTerminal(opcodeID) \|\| isThrow(opcodeID))
	nextInstructionIsLeader = true;

	if (createdBlock)
	continue;

	// Otherwise, just add to the length of the current block.
	current->addLength(instruction->size());
	}
	// Exit block.
	basicBlocks.constructAndAppend(BytecodeBasicBlock::ExitBlock, basicBlocks.size());
	basicBlocks.shrinkToFit();
	ASSERT(basicBlocks.last().isExitBlock());
	}
	// After this point, we never change basicBlocks.

	// Link basic blocks together.
	for (unsigned i = 0; i < basicBlocks.size(); i++) {
	BytecodeBasicBlock& block = basicBlocks[i];

	if (block.isEntryBlock() \|\| block.isExitBlock())
	continue;

	bool fallsThrough = true;
	for (unsigned visitedLength = 0; visitedLength < block.totalLength();) {
	InstructionStream::Ref instruction = instructions.at(block.leaderOffset() + visitedLength);
	OpcodeID opcodeID = instruction->opcodeID();

	visitedLength += instruction->size();

	// If we found a terminal bytecode, link to the exit block.
	if (isTerminal(opcodeID)) {
	ASSERT(instruction.offset() + instruction->size() == block.leaderOffset() + block.totalLength());
	linkBlocks(block, basicBlocks.last());
	fallsThrough = false;
	break;
	}

	// If we found a throw, get the HandlerInfo for this instruction to see where we will jump.
	// If there isn't one, treat this throw as a terminal. This is true even if we have a finally
	// block because the finally block will create its own catch, which will generate a HandlerInfo.
	if (isThrow(opcodeID)) {
	ASSERT(instruction.offset() + instruction->size() == block.leaderOffset() + block.totalLength());
	auto* handler = codeBlock->handlerForBytecodeIndex(BytecodeIndex(instruction.offset()));
	fallsThrough = false;
	if (!handler) {
	linkBlocks(block, basicBlocks.last());
	break;
	}
	for (auto& otherBlock : basicBlocks) {
	if (handler->target == otherBlock.leaderOffset()) {
	linkBlocks(block, otherBlock);
	break;
	}
	}
	break;
	}

	// If we found a branch, link to the block(s) that we jump to.
	if (isBranch(opcodeID)) {
	ASSERT(instruction.offset() + instruction->size() == block.leaderOffset() + block.totalLength());
	Vector<InstructionStream::Offset, 1> bytecodeOffsetsJumpedTo;
	findJumpTargetsForInstruction(codeBlock, instruction, bytecodeOffsetsJumpedTo);

	size_t numberOfJumpTargets = bytecodeOffsetsJumpedTo.size();
	ASSERT(numberOfJumpTargets);
	for (auto& otherBlock : basicBlocks) {
	if (bytecodeOffsetsJumpedTo.contains(otherBlock.leaderOffset())) {
	linkBlocks(block, otherBlock);
	--numberOfJumpTargets;
	if (!numberOfJumpTargets)
	break;
	}
	}
	// numberOfJumpTargets may not be 0 here if there are multiple jumps targeting the same
	// basic blocks (e.g. in a switch type opcode). Since we only decrement numberOfJumpTargets
	// once per basic block, the duplicates are not accounted for. For our purpose here,
	// that doesn't matter because we only need to link to the target block once regardless
	// of how many ways this block can jump there.

	if (isUnconditionalBranch(opcodeID))
	fallsThrough = false;

	break;
	}
	}

	// If we fall through then link to the next block in program order.
	if (fallsThrough) {
	ASSERT(i + 1 < basicBlocks.size());
	BytecodeBasicBlock& nextBlock = basicBlocks[i + 1];
	linkBlocks(block, nextBlock);
	}
	}

	unsigned index = 0;
	for (auto& basicBlock : basicBlocks) {
	basicBlock.shrinkToFit();
	ASSERT_UNUSED(index, basicBlock.index() == index++);
	}

	return basicBlocks;
	}

	auto BytecodeBasicBlock::compute(CodeBlock* codeBlock, const InstructionStream& instructions) -> BasicBlockVector
	{
	return computeImpl(codeBlock, instructions);
	}

	auto BytecodeBasicBlock::compute(UnlinkedCodeBlockGenerator* codeBlock, const InstructionStream& instructions) -> BasicBlockVector
	{
	return computeImpl(codeBlock, instructions);
	}

	} // namespace JSC