private void preProcess() {
final InstructionCollection instructions = _instructions;
final List<ExceptionHandler> handlers = _exceptionHandlers;
final ControlFlowGraph cfg = ControlFlowGraphBuilder.build(instructions, handlers);
cfg.computeDominance();
cfg.computeDominanceFrontier();
for (int i = 0; i < handlers.size(); i++) {
final ExceptionHandler handler = handlers.get(i);