message: renumber_registers should create and clear cfg only when editable cfg doesn't exist
  Summary: as in title
diff: @@ -107,7 +107,11 @@ bool Use::operator==(const Use& that) const {
  }
  void renumber_registers(IRCode* code, bool width_aware) {
  + bool should_clear_cfg = false;
  + if (!code->editable_cfg_built()) {
  code->build_cfg(/* editable */ true);
  + should_clear_cfg = true;
  + }
  auto& cfg = code->cfg();
  auto chains = calculate_ud_chains(cfg);
  @@ -136,7 +140,10 @@ void renumber_registers(IRCode* code, bool width_aware) {
  }
  }
  cfg.set_registers_size(sym_reg_mapper.regs_size());
  +
  + if (should_clear_cfg) {
  code->clear_cfg();
  }
  +}
  } // namespace live_range
  