qrt_mapper to provide fallback information for InstVisitor<Circuit> cast

      : kernelName(top_level_kernel_name) {}

  qrt_mapper() = default;

  // Workaround cross-boundary (dlopen) dynamic type-casting issue (Apple Clang)

  // Construct the RTTI pointer offset map as fallback for dynamic_cast.

  virtual std::unordered_map<std::string, ptrdiff_t>

  getVisitorRttiMap() const override {

    // Currently, looks like only xacc::InstructionVisitor<Circuit> is having

    // this issue, but, technically, we can add all types here if needed to.

    static const std::unordered_map<std::string, ptrdiff_t> result{

        {typeid(Circuit).name(),

         ComputePointerOffset<qrt_mapper,

                              xacc::InstructionVisitor<Circuit>>()}};

    return result;

  }

  auto get_new_src() { return ss.str(); }

  // One-qubit gates

  void visit(Hadamard &h) override { addOneQubitGate("h", h); }