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 "InterpreterInlines.h"
 #include "JSCInlines.h"
 #include "PreciseJumpTargets.h"

 namespace JSC {

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

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

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

 template<typename Block, typename Instruction>
 void BytecodeBasicBlock::computeImpl(Block* codeBlock, Instruction* instructionsBegin, unsigned instructionCount, Vector<std::unique_ptr<BytecodeBasicBlock>>& basicBlocks)
 {
     Vector<unsigned, 32> jumpTargets;
     computePreciseJumpTargets(codeBlock, instructionsBegin, instructionCount, jumpTargets);

     auto appendBlock = [&] (std::unique_ptr<BytecodeBasicBlock>&& block) {
         block->m_index = basicBlocks.size();
         basicBlocks.append(WTFMove(block));
     };

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

     // Create the entry and exit basic blocks.
     basicBlocks.reserveCapacity(jumpTargets.size() + 2);

     auto entry = std::make_unique<BytecodeBasicBlock>(BytecodeBasicBlock::EntryBlock);
     auto firstBlock = std::make_unique<BytecodeBasicBlock>(0, 0);
     linkBlocks(entry.get(), firstBlock.get());

     appendBlock(WTFMove(entry));
     BytecodeBasicBlock* current = firstBlock.get();
     appendBlock(WTFMove(firstBlock));

     auto exit = std::make_unique<BytecodeBasicBlock>(BytecodeBasicBlock::ExitBlock);

     bool nextInstructionIsLeader = false;

     for (unsigned bytecodeOffset = 0; bytecodeOffset < instructionCount;) {
         OpcodeID opcodeID = Interpreter::getOpcodeID(instructionsBegin[bytecodeOffset]);
         unsigned opcodeLength = opcodeLengths[opcodeID];

         bool createdBlock = false;
         // If the current bytecode is a jump target, then it's the leader of its own basic block.
         if (isJumpTarget(opcodeID, jumpTargets, bytecodeOffset) || nextInstructionIsLeader) {
             auto newBlock = std::make_unique<BytecodeBasicBlock>(bytecodeOffset, opcodeLength);
             current = newBlock.get();
             appendBlock(WTFMove(newBlock));
             createdBlock = true;
             nextInstructionIsLeader = false;
             bytecodeOffset += opcodeLength;
         }

         // 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(opcodeLength);
         bytecodeOffset += opcodeLength;
     }

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

         if (block->isEntryBlock() || block->isExitBlock())
             continue;

         bool fallsThrough = true;
         for (unsigned bytecodeOffset = block->leaderOffset(); bytecodeOffset < block->leaderOffset() + block->totalLength();) {
             OpcodeID opcodeID = Interpreter::getOpcodeID(instructionsBegin[bytecodeOffset]);
             unsigned opcodeLength = opcodeLengths[opcodeID];
             // If we found a terminal bytecode, link to the exit block.
             if (isTerminal(opcodeID)) {
                 ASSERT(bytecodeOffset + opcodeLength == block->leaderOffset() + block->totalLength());
                 linkBlocks(block, exit.get());
                 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(bytecodeOffset + opcodeLength == block->leaderOffset() + block->totalLength());
                 auto* handler = codeBlock->handlerForBytecodeOffset(bytecodeOffset);
                 fallsThrough = false;
                 if (!handler) {
                     linkBlocks(block, exit.get());
                     break;
                 }
                 for (unsigned i = 0; i < basicBlocks.size(); i++) {
                     BytecodeBasicBlock* otherBlock = basicBlocks[i].get();
                     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(bytecodeOffset + opcodeLength == block->leaderOffset() + block->totalLength());
                 Vector<unsigned, 1> bytecodeOffsetsJumpedTo;
                 findJumpTargetsForBytecodeOffset(codeBlock, instructionsBegin, bytecodeOffset, bytecodeOffsetsJumpedTo);

                 size_t numberOfJumpTargets = bytecodeOffsetsJumpedTo.size();
                 ASSERT(numberOfJumpTargets);
                 for (unsigned i = 0; i < basicBlocks.size(); i++) {
                     BytecodeBasicBlock* otherBlock = basicBlocks[i].get();
                     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;
             }
             bytecodeOffset += opcodeLength;
         }

         // 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].get();
             linkBlocks(block, nextBlock);
         }
     }

     appendBlock(WTFMove(exit));

     for (auto& basicBlock : basicBlocks)
         basicBlock->shrinkToFit();
 }

 void BytecodeBasicBlock::compute(CodeBlock* codeBlock, Instruction* instructionsBegin, unsigned instructionCount, Vector<std::unique_ptr<BytecodeBasicBlock>>& basicBlocks)
 {
     computeImpl(codeBlock, instructionsBegin, instructionCount, basicBlocks);
 }

 void BytecodeBasicBlock::compute(UnlinkedCodeBlock* codeBlock, UnlinkedInstruction* instructionsBegin, unsigned instructionCount, Vector<std::unique_ptr<BytecodeBasicBlock>>& basicBlocks)
 {
     BytecodeBasicBlock::computeImpl(codeBlock, instructionsBegin, instructionCount, basicBlocks);
 }

 } // 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 "InterpreterInlines.h"
	#include "JSCInlines.h"
	#include "PreciseJumpTargets.h"

	namespace JSC {

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

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

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

	template<typename Block, typename Instruction>
	void BytecodeBasicBlock::computeImpl(Block* codeBlock, Instruction* instructionsBegin, unsigned instructionCount, Vector<std::unique_ptr<BytecodeBasicBlock>>& basicBlocks)
	{
	Vector<unsigned, 32> jumpTargets;
	computePreciseJumpTargets(codeBlock, instructionsBegin, instructionCount, jumpTargets);

	auto appendBlock = [&] (std::unique_ptr<BytecodeBasicBlock>&& block) {
	block->m_index = basicBlocks.size();
	basicBlocks.append(WTFMove(block));
	};

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

	// Create the entry and exit basic blocks.
	basicBlocks.reserveCapacity(jumpTargets.size() + 2);

	auto entry = std::make_unique<BytecodeBasicBlock>(BytecodeBasicBlock::EntryBlock);
	auto firstBlock = std::make_unique<BytecodeBasicBlock>(0, 0);
	linkBlocks(entry.get(), firstBlock.get());

	appendBlock(WTFMove(entry));
	BytecodeBasicBlock* current = firstBlock.get();
	appendBlock(WTFMove(firstBlock));

	auto exit = std::make_unique<BytecodeBasicBlock>(BytecodeBasicBlock::ExitBlock);

	bool nextInstructionIsLeader = false;

	for (unsigned bytecodeOffset = 0; bytecodeOffset < instructionCount;) {
	OpcodeID opcodeID = Interpreter::getOpcodeID(instructionsBegin[bytecodeOffset]);
	unsigned opcodeLength = opcodeLengths[opcodeID];

	bool createdBlock = false;
	// If the current bytecode is a jump target, then it's the leader of its own basic block.
	if (isJumpTarget(opcodeID, jumpTargets, bytecodeOffset) \|\| nextInstructionIsLeader) {
	auto newBlock = std::make_unique<BytecodeBasicBlock>(bytecodeOffset, opcodeLength);
	current = newBlock.get();
	appendBlock(WTFMove(newBlock));
	createdBlock = true;
	nextInstructionIsLeader = false;
	bytecodeOffset += opcodeLength;
	}

	// 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(opcodeLength);
	bytecodeOffset += opcodeLength;
	}

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

	if (block->isEntryBlock() \|\| block->isExitBlock())
	continue;

	bool fallsThrough = true;
	for (unsigned bytecodeOffset = block->leaderOffset(); bytecodeOffset < block->leaderOffset() + block->totalLength();) {
	OpcodeID opcodeID = Interpreter::getOpcodeID(instructionsBegin[bytecodeOffset]);
	unsigned opcodeLength = opcodeLengths[opcodeID];
	// If we found a terminal bytecode, link to the exit block.
	if (isTerminal(opcodeID)) {
	ASSERT(bytecodeOffset + opcodeLength == block->leaderOffset() + block->totalLength());
	linkBlocks(block, exit.get());
	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(bytecodeOffset + opcodeLength == block->leaderOffset() + block->totalLength());
	auto* handler = codeBlock->handlerForBytecodeOffset(bytecodeOffset);
	fallsThrough = false;
	if (!handler) {
	linkBlocks(block, exit.get());
	break;
	}
	for (unsigned i = 0; i < basicBlocks.size(); i++) {
	BytecodeBasicBlock* otherBlock = basicBlocks[i].get();
	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(bytecodeOffset + opcodeLength == block->leaderOffset() + block->totalLength());
	Vector<unsigned, 1> bytecodeOffsetsJumpedTo;
	findJumpTargetsForBytecodeOffset(codeBlock, instructionsBegin, bytecodeOffset, bytecodeOffsetsJumpedTo);

	size_t numberOfJumpTargets = bytecodeOffsetsJumpedTo.size();
	ASSERT(numberOfJumpTargets);
	for (unsigned i = 0; i < basicBlocks.size(); i++) {
	BytecodeBasicBlock* otherBlock = basicBlocks[i].get();
	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;
	}
	bytecodeOffset += opcodeLength;
	}

	// 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].get();
	linkBlocks(block, nextBlock);
	}
	}

	appendBlock(WTFMove(exit));

	for (auto& basicBlock : basicBlocks)
	basicBlock->shrinkToFit();
	}

	void BytecodeBasicBlock::compute(CodeBlock* codeBlock, Instruction* instructionsBegin, unsigned instructionCount, Vector<std::unique_ptr<BytecodeBasicBlock>>& basicBlocks)
	{
	computeImpl(codeBlock, instructionsBegin, instructionCount, basicBlocks);
	}

	void BytecodeBasicBlock::compute(UnlinkedCodeBlock* codeBlock, UnlinkedInstruction* instructionsBegin, unsigned instructionCount, Vector<std::unique_ptr<BytecodeBasicBlock>>& basicBlocks)
	{
	BytecodeBasicBlock::computeImpl(codeBlock, instructionsBegin, instructionCount, basicBlocks);
	}

	} // namespace JSC