Function grad

src/opr/impl/loop/grad.cpp:337–342

    void scn_do_execute() override {}

    static VarNode* grad(
            OperatorNodeBase* opr, size_t wrt_idx, const VarNodeArray& out_grad) {
        MGB_MARK_USED_VAR(out_grad);
        auto&& info = opr->cast_final_safe<GradProxy>().m_grad.at(wrt_idx);
        return info.grad;
    }

    class _RegGrad {
        static _RegGrad ins;