/**
* Create all blocks and edges for one Func.
*/
Graph* GraphBuilder::build() {
assert(!funcInstrs(m_func).empty());
m_graph = new (m_arena) Graph();
createBlocks();
createExBlocks();
linkBlocks();
linkExBlocks();
return m_graph;
}
void computeBytecodeBasicBlocks(CodeBlock* codeBlock, Vector<RefPtr<BytecodeBasicBlock> >& basicBlocks)
{
Vector<unsigned, 32> jumpTargets;
computePreciseJumpTargets(codeBlock, jumpTargets);
// Create the entry and exit basic blocks.
BytecodeBasicBlock* entry = new BytecodeBasicBlock(BytecodeBasicBlock::EntryBlock);
basicBlocks.append(adoptRef(entry));
BytecodeBasicBlock* exit = new BytecodeBasicBlock(BytecodeBasicBlock::ExitBlock);
// Find basic block boundaries.
BytecodeBasicBlock* current = new BytecodeBasicBlock(0, 0);
linkBlocks(entry, current);
basicBlocks.append(adoptRef(current));
bool nextInstructionIsLeader = false;
Interpreter* interpreter = codeBlock->vm()->interpreter;
Instruction* instructionsBegin = codeBlock->instructions().begin();
unsigned instructionCount = codeBlock->instructions().size();
for (unsigned bytecodeOffset = 0; bytecodeOffset < instructionCount;) {
OpcodeID opcodeID = interpreter->getOpcodeID(instructionsBegin[bytecodeOffset].u.opcode);
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) {
BytecodeBasicBlock* block = new BytecodeBasicBlock(bytecodeOffset, opcodeLength);
basicBlocks.append(adoptRef(block));
current = block;
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->addBytecodeLength(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->leaderBytecodeOffset(); bytecodeOffset < block->leaderBytecodeOffset() + block->totalBytecodeLength();) {
const Instruction& currentInstruction = instructionsBegin[bytecodeOffset];
OpcodeID opcodeID = interpreter->getOpcodeID(currentInstruction.u.opcode);
unsigned opcodeLength = opcodeLengths[opcodeID];
// If we found a terminal bytecode, link to the exit block.
if (isTerminal(opcodeID)) {
ASSERT(bytecodeOffset + opcodeLength == block->leaderBytecodeOffset() + block->totalBytecodeLength());
linkBlocks(block, exit);
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->leaderBytecodeOffset() + block->totalBytecodeLength());
HandlerInfo* handler = codeBlock->handlerForBytecodeOffset(bytecodeOffset);
fallsThrough = false;
if (!handler) {
linkBlocks(block, exit);
break;
}
for (unsigned i = 0; i < basicBlocks.size(); i++) {
BytecodeBasicBlock* otherBlock = basicBlocks[i].get();
if (handler->target == otherBlock->leaderBytecodeOffset()) {
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->leaderBytecodeOffset() + block->totalBytecodeLength());
Vector<unsigned, 1> bytecodeOffsetsJumpedTo;
findJumpTargetsForBytecodeOffset(codeBlock, bytecodeOffset, bytecodeOffsetsJumpedTo);
for (unsigned i = 0; i < basicBlocks.size(); i++) {
BytecodeBasicBlock* otherBlock = basicBlocks[i].get();
if (bytecodeOffsetsJumpedTo.contains(otherBlock->leaderBytecodeOffset()))
linkBlocks(block, otherBlock);
}
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);
}
}
basicBlocks.append(adoptRef(exit));
}
