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/*
* Copyright (C) 2013, 2015 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;
Interpreter* interpreter = codeBlock->vm()->interpreter;
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
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