diff --git a/dnn/include/megdnn/basic_types.h b/dnn/include/megdnn/basic_types.h
index 673ed7af516420ece85a78bce53c3e98d860c44a..27746fb14b75e42cbe894e09e6484e3c44fc5663 100644
--- a/dnn/include/megdnn/basic_types.h
+++ b/dnn/include/megdnn/basic_types.h
@@ -285,7 +285,8 @@ struct TensorLayout : public TensorShape {
      *      stride
      */
     void add_axis_cont_inplace(size_t axis) {
-        add_axis_inplace(axis, 1, stride[axis] * shape[axis]);
+        ptrdiff_t stride_ = axis < ndim ? stride[axis] * shape[axis] : 1;
+        add_axis_inplace(axis, 1, stride_);
     }
 
     /*!
diff --git a/dnn/src/common/basic_types.cpp b/dnn/src/common/basic_types.cpp
index ba92ccb5aea35fa84ca6aef7df56de043428ae4b..370090bc4c64bef5784035dd862b22a0aedfaba3 100644
--- a/dnn/src/common/basic_types.cpp
+++ b/dnn/src/common/basic_types.cpp
@@ -382,7 +382,7 @@ bool TensorLayout::eq_layout(const TensorLayout& rhs) const {
     MEGDNN_STATIC_ASSERT(MAX_NDIM == 7, "please update the code");
 
     auto ax = [](size_t shape0, size_t shape1, ptrdiff_t stride0, ptrdiff_t stride1) {
-        return (shape0 == shape1) & ((shape0 == 1) | (stride0 == stride1));
+        return (shape0 == shape1) & ((shape0 <= 1) | (stride0 == stride1));
     };
     if (ndim == rhs.ndim) {
         size_t eq = 0;
diff --git a/dnn/src/common/opr_delegate.cpp b/dnn/src/common/opr_delegate.cpp
index 140e01120cd4263873550985d052acf41293e004..e50ff4413523da7c79d8e3c0a6c4848da508154e 100644
--- a/dnn/src/common/opr_delegate.cpp
+++ b/dnn/src/common/opr_delegate.cpp
@@ -13,7 +13,8 @@
 
 using namespace megdnn;
 
-const std::shared_ptr<Handle>& megdnn::inplace_cpu_handle(int debug_level) {
+MGE_WIN_DECLSPEC_FUC const std::shared_ptr<Handle>& megdnn::inplace_cpu_handle(
+        int debug_level) {
     auto make = [](int deb_level) {
         megcoreDeviceHandle_t dev_handle;
         megcoreCreateDeviceHandle(&dev_handle, megcorePlatformCPU);
diff --git a/imperative/python/src/tensor.cpp b/imperative/python/src/tensor.cpp
index d3c96fb4586e1766cae5ed0213ce6b07a404d959..a9d3495c6f5fe8625046ff7defb7c82776832c26 100644
--- a/imperative/python/src/tensor.cpp
+++ b/imperative/python/src/tensor.cpp
@@ -32,6 +32,7 @@
 #include "./module_trace.h"
 #include "./numpy_dtypes.h"
 #include "./tensor.h"
+#include "./tensor_utils.h"
 #include "./transformation.h"
 
 #include <object.h>
@@ -549,557 +550,6 @@ CompNode _get_device(PyObject* const* args, size_t nargs) {
     return cn;
 }
 
-bool is_scalar(PyObject* tensor) {
-    if (py::isinstance<PySymbolVar>(py::handle(tensor))) {
-        auto var = py::handle(tensor).cast<PySymbolVar*>();
-        return var->is_scalar;
-    }
-    auto* tw = TensorWrapper::try_cast(tensor);
-    if (tw) {
-        return tw->m_tensor->is_scalar();
-    }
-    return PyArray_CheckAnyScalar(tensor);
-}
-
-bool is_bool_list(PyObject* arg) {
-    if (!PyList_Check(arg)) {
-        return false;
-    }
-    size_t sz = PyList_Size(arg);
-    if (!sz) {
-        return false;
-    }
-    for (size_t i = 0; i < sz; ++i) {
-        PyObject* handle = PyList_GetItem(arg, i);
-        if (!PyBool_Check(handle)) {
-            return false;
-        }
-    }
-    return true;
-}
-
-bool is_bool_dtype(PyObject* args) {
-    if (!PyObject_HasAttrString(args, "dtype"))
-        return false;
-    PyObject* dobj = PyObject_GetAttrString(args, "dtype");
-    PyArray_Descr* dtype;
-    PyArray_DescrConverter(dobj, &dtype);
-    bool ret = (dtype->kind == 'b');
-    Py_XDECREF(dtype);
-    Py_XDECREF(dobj);
-    return ret;
-}
-
-py::object _Const(
-        py::handle value, py::handle dtype, py::handle device, py::handle ref) {
-    py::object val = py::reinterpret_borrow<py::object>(value);
-    if (PyArray_Check(value.ptr())) {
-        py::tuple strides =
-                py::reinterpret_borrow<py::tuple>(getattr(value, "strides"));
-        bool need_squeeze = false;
-        for (size_t i = 0; i < strides.size(); ++i) {
-            if (strides[i].cast<ptrdiff_t>() == 0) {
-                need_squeeze = true;
-            }
-        }
-        if (need_squeeze) {
-            val = py::reinterpret_borrow<py::array>(value);
-            val = val.attr("squeeze")();
-            val = val.attr("reshape")(val.attr("shape"));
-        }
-    }
-    if (py::isinstance<PySymbolVar>(ref)) {
-        auto ref_var = ref.cast<PySymbolVar*>();
-        auto* graph = ref_var->m_node->owner_graph();
-        auto cn = device.cast<CompNode>();
-        OperatorNodeConfig config(cn);
-        auto hv = npy::np2tensor(
-                val.ptr(), npy::Meth::borrow(cn), dtype.cast<mgb::DType>());
-        auto typeobj = ref.get_type();
-        return typeobj(opr::ImmutableTensor::make(*graph, hv, config).node());
-    }
-    py::tuple tup = py::make_tuple(val, dtype, device, true, false, py::none());
-    return TensorWrapper::make(py_tensor_type, tup.ptr(), nullptr);
-}
-
-py::tuple _make_shape_tuple(py::handle shape) {
-    py::list orig;
-    py::list ret(0);
-    auto solve_one = [&](py::handle val) {
-        if (TensorWrapper::try_cast(val.ptr()) || py::isinstance<PySymbolVar>(val)) {
-            py::object np = getattr(val, "numpy")();
-            PyArrayObject* arr = (PyArrayObject*)np.ptr();
-            PyObject* maybe_list = PyArray_ToList(arr);
-            if (PyList_Check(maybe_list)) {
-                py::list may = py::reinterpret_steal<py::list>(maybe_list);
-                for (size_t i = 0; i < may.size(); ++i) {
-                    ret.append(may[i]);
-                }
-            } else {
-                mgb_assert(PyLong_Check(maybe_list));
-                ret.append(PyLong_AsLong(maybe_list));
-                Py_XDECREF(maybe_list);
-            }
-        } else if (PyArray_Check(val.ptr())) {
-            ret.append(PyArray_PyIntAsInt(val.ptr()));
-        } else {
-            ret.append(PyLong_AsLong(val.ptr()));
-        }
-    };
-    if (PyArray_Check(shape.ptr()) && !PyArray_CheckAnyScalar(shape.ptr())) {
-        orig = py::reinterpret_steal<py::list>(
-                PyArray_ToList((PyArrayObject*)shape.ptr()));
-        for (size_t i = 0; i < orig.size(); ++i) {
-            solve_one(orig[i]);
-        }
-    } else if (PyList_Check(shape.ptr())) {
-        orig = py::reinterpret_borrow<py::list>(shape);
-        for (size_t i = 0; i < orig.size(); ++i) {
-            solve_one(orig[i]);
-        }
-    } else if (PyTuple_Check(shape.ptr())) {
-        py::tuple tup = py::reinterpret_borrow<py::tuple>(shape);
-        for (size_t i = 0; i < tup.size(); ++i) {
-            solve_one(tup[i]);
-        }
-    } else {
-        solve_one(shape);
-    }
-    return py::reinterpret_steal<py::tuple>(PyList_AsTuple(ret.ptr()));
-}
-
-py::object _get_index(py::object tensor, py::object src) {
-    if (!TensorWrapper::try_cast(tensor.ptr()) &&
-        !py::isinstance<PySymbolVar>(tensor)) {
-        auto get_const = [&](mgb::DType dtype) -> py::object {
-            return _Const(tensor, py::cast(dtype), src.attr("device"), src);
-        };
-        if (is_bool_list(tensor.ptr()) || is_bool_dtype(tensor.ptr())) {
-            tensor = get_const(dtype::Bool());
-        } else {
-            tensor = get_const(dtype::Int32());
-        }
-        if (!is_bool_dtype(tensor.ptr())) {
-            return tensor;
-        }
-    } else {
-        if (!is_bool_dtype(tensor.ptr())) {
-            return tensor;
-        }
-    }
-    static std::shared_ptr<OpDef> op = CondTake::make();
-    std::vector<PyObject*> p;
-    p.resize(3);
-    py::object Op = py::cast(op);
-    p[0] = Op.ptr();
-    p[1] = tensor.ptr();
-    p[2] = tensor.ptr();
-    py::tuple ret =
-            py::reinterpret_steal<py::object>(py_apply(NULL, p.data(), p.size()));
-    return ret[1];
-}
-
-py::tuple _try_cond_take(py::handle tensor, py::handle index) {
-    if (!hasattr(index, "dtype") || !hasattr(index, "shape")) {
-        return py::tuple();
-    }
-    if (!is_bool_dtype(index.ptr()) ||
-        _make_shape_tuple(getattr(index, "shape"))
-                .not_equal(_make_shape_tuple(getattr(tensor, "shape")))) {
-        return py::tuple();
-    }
-    py::object iobj;
-    if (PyArray_Check(index.ptr())) {
-        iobj =
-                _Const(index, py::cast((mgb::DType)dtype::Bool()),
-                       getattr(tensor, "device"), tensor);
-    } else {
-        iobj = py::reinterpret_borrow<py::object>(index);
-    }
-    static std::shared_ptr<OpDef> op = CondTake::make();
-    std::vector<PyObject*> p;
-    p.resize(3);
-    py::object Op = py::cast(op);
-    p[0] = Op.ptr();
-    p[1] = tensor.ptr();
-    p[2] = iobj.ptr();
-    py::tuple ret =
-            py::reinterpret_steal<py::object>(py_apply(NULL, p.data(), p.size()));
-    return ret;
-}
-
-py::tuple _remove_ellipsis(py::object tensor, py::tuple tuple_val) {
-    size_t tuple_size = tuple_val.size();
-    size_t ndim_sum = 0, cur_sum = 0;
-    int pos = -1;
-    bool has_unknown_ndim_bool_index = false;
-    for (size_t i = 0; i < tuple_size; ++i) {
-        py::object handle = tuple_val[i];
-        if (handle.ptr() == Py_Ellipsis) {
-            pos = static_cast<int>(i);
-            for (size_t j = 0; j < i; ++j) {
-                py::object t = tuple_val[j];
-                if (t.ptr() == Py_Ellipsis) {
-                    throw py::index_error("only one ellipsis is allowed.");
-                }
-            }
-        } else {
-            size_t ndim_incr = 1;
-            if (hasattr(handle, "dtype") && is_bool_dtype(handle.ptr()) &&
-                hasattr(handle, "ndim")) {
-                py::object ndim = getattr(handle, "ndim");
-                if (PyLong_Check(ndim.ptr())) {
-                    ndim_incr = PyLong_AsLong(ndim.ptr());
-                } else {
-                    has_unknown_ndim_bool_index = true;
-                }
-            }
-            cur_sum += ndim_incr;
-        }
-    }
-    if (pos == -1) {
-        return tuple_val;
-    } else {
-        if (has_unknown_ndim_bool_index) {
-            throw py::index_error(
-                    "does not support bool index with unknown shape when using "
-                    "Ellipsis.");
-        }
-        try {
-            ndim_sum = getattr(tensor, "ndim").cast<size_t>();
-        } catch (py::error_already_set& err) {
-            throw py::index_error(
-                    "does not support Ellipsis when tensor's ndim is unknown.");
-        }
-        py::tuple ret(ndim_sum - cur_sum + tuple_size - 1);
-        size_t idx = 0;
-        for (size_t i = 0; i < tuple_size; ++i) {
-            if (i == pos) {
-                for (size_t j = cur_sum; j < ndim_sum; ++j) {
-                    ret[idx++] = PySlice_New(NULL, NULL, NULL);
-                }
-            } else {
-                ret[idx++] = tuple_val[i];
-            }
-        }
-        return ret;
-    }
-}
-
-py::tuple _expand_bool_dim(py::object tensor, py::tuple tuple_val) {
-    py::tuple cur_shape = _make_shape_tuple(py::handle(getattr(tensor, "shape")));
-    py::list new_tuple_val(0);
-
-    size_t offset = 0;
-    size_t tdim = 0;
-    for (size_t i = 0; i < tuple_val.size(); ++i) {
-        py::handle k = tuple_val[i];
-        if (is_bool_dtype(k.ptr())) {
-            size_t ndim = getattr(k, "ndim").cast<size_t>();
-            if (ndim > 1) {
-                py::tuple ishape = _make_shape_tuple(py::handle(getattr(k, "shape")));
-                for (size_t j = 0; j < ndim; ++j) {
-                    if (cur_shape[tdim + j - offset].cast<size_t>() !=
-                        ishape[j].cast<size_t>()) {
-                        std::string msg =
-                                "boolean index did not match tensor along dimension " +
-                                std::to_string(tdim + j) + "; dimension is " +
-                                std::to_string(
-                                        cur_shape[tdim + j - offset].cast<size_t>()) +
-                                " but corresponding boolean dimension is " +
-                                std::to_string(ishape[j].cast<size_t>());
-                        throw py::index_error(msg.c_str());
-                    }
-                }
-                py::object new_k = getattr(k, "reshape")(-1);
-                py::object kshape = getattr(new_k, "shape");
-                py::list new_shape(0);
-                PyObject* sym = PyObject_CallObject(cpp_use_symbolic_shape, nullptr);
-                bool is_sym = (sym == Py_True);
-                Py_XDECREF(sym);
-                if (is_sym) {
-                    py::object tshape = getattr(tensor, "shape");
-                    for (size_t j = 0; j < i; ++j) {
-                        new_shape.append(tshape[py::int_(j)]);
-                    }
-                    new_shape.append(kshape[py::int_(0)]);
-                    for (size_t j = tdim + ndim - offset; j < cur_shape.size(); ++j) {
-                        new_shape.append(cur_shape[j]);
-                    }
-                    py::tuple args = py::make_tuple(new_shape);
-                    PyObject* shape_tensor =
-                            PyObject_CallObject(cpp_astensor1d, args.ptr());
-                    py::object reshape_func = getattr(tensor, "reshape");
-                    Py_INCREF(shape_tensor);
-                    PyObject* Args = PyTuple_New(1);
-                    PyTuple_SetItem(Args, 0, shape_tensor);
-                    PyObject* new_tensor =
-                            PyObject_CallObject(reshape_func.ptr(), Args);
-                    Py_XDECREF(Args);
-                    tensor = py::reinterpret_steal<py::object>(new_tensor);
-                    cur_shape = _make_shape_tuple(py::handle(shape_tensor));
-                    Py_XDECREF(shape_tensor);
-                } else {
-                    for (size_t j = 0; j < i; ++j) {
-                        new_shape.append(cur_shape[j]);
-                    }
-                    new_shape.append(py::reinterpret_borrow<py::tuple>(kshape)[0]);
-                    for (size_t j = tdim + ndim - offset; j < cur_shape.size(); ++j) {
-                        new_shape.append(cur_shape[j]);
-                    }
-                    cur_shape = new_shape;
-                    tensor = getattr(tensor, "reshape")(cur_shape);
-                }
-                offset++;
-                tdim += ndim;
-            }
-            new_tuple_val.append(k);
-        } else {
-            new_tuple_val.append(k);
-            tdim++;
-        }
-    }
-    return py::make_tuple(tensor, py::reinterpret_borrow<py::tuple>(new_tuple_val));
-}
-
-py::tuple _unpack_indexes(py::handle inp_hdl, py::handle idx_hdl) {
-    py::object inp = py::reinterpret_borrow<py::object>(inp_hdl);
-    py::tuple tuple_val;
-    if (py::isinstance<py::tuple>(idx_hdl)) {
-        tuple_val = py::reinterpret_borrow<py::tuple>(idx_hdl);
-    } else {
-        tuple_val = py::make_tuple(idx_hdl);
-    }
-
-    bool use_subtensor = true;
-    bool need_remove_ellipsis = false;
-    bool need_expand_bool_dim = false;
-    size_t idx_ndim = 0;
-    for (size_t i = 0; i < tuple_val.size(); ++i) {
-        py::object k = tuple_val[i];
-        if (k.ptr() == Py_None) {
-            throw py::index_error("newaxis is not allowed here");
-        } else if (k.ptr() == Py_Ellipsis) {
-            need_remove_ellipsis = true;
-        } else {
-            if (is_bool_dtype(k.ptr()) && hasattr(k, "ndim")) {
-                size_t ndim = getattr(k, "ndim").cast<size_t>();
-                idx_ndim += ndim;
-                if (ndim > 1) {
-                    need_expand_bool_dim = true;
-                }
-            } else {
-                idx_ndim++;
-            }
-        }
-    }
-    try {
-        size_t inp_ndim = getattr(inp, "ndim").cast<size_t>();
-        if (idx_ndim > inp_ndim) {
-            std::string msg = "too many indices for tensor: tensor is " +
-                              std::to_string(inp_ndim) + "-dimensional, but " +
-                              std::to_string(idx_ndim) + " were indexed";
-            throw py::index_error(msg.c_str());
-        }
-    } catch (py::error_already_set& err) {
-        ;  // ignore
-    }
-    if (need_remove_ellipsis) {
-        tuple_val = _remove_ellipsis(inp, tuple_val);
-    }
-
-    if (need_expand_bool_dim) {
-        py::object shape = getattr(inp, "shape");
-        if (shape.ptr() != Py_None) {
-            py::tuple ret = _expand_bool_dim(inp, tuple_val);
-            inp = ret[0];
-            tuple_val = ret[1];
-        }
-    }
-
-    py::list items;
-    py::list tensors;
-    int cur_axis = -1;
-
-    for (size_t i = 0; i < tuple_val.size(); ++i) {
-        py::object handle = tuple_val[i];
-        cur_axis++;
-        if (!is_scalar(handle.ptr()) && !PySlice_Check(handle.ptr())) {
-            use_subtensor = false;
-        }
-        py::list item;
-        item.append(cur_axis);
-        auto push = [&](PyObject* v) {
-            if (v == Py_None) {
-                item.append(false);
-            } else {
-                item.append(true);
-                tensors.append(_get_index(py::reinterpret_borrow<py::object>(v), inp));
-            }
-        };
-
-        if (PySlice_Check(handle.ptr())) {
-            PySliceObject* s = (PySliceObject*)handle.ptr();
-            if (s->start == Py_None && s->stop == Py_None && s->step == Py_None) {
-                continue;
-            }
-            push(s->start);
-            push(s->stop);
-            push(s->step);
-            item.append(false);
-        } else {
-            for (size_t j = 0; j < 3; j++)
-                item.append(false);
-            push(handle.ptr());
-        }
-        items.append(item);
-    }
-
-    return py::make_tuple(inp, tensors, items, use_subtensor, need_expand_bool_dim);
-}
-
-py::object _getitem_cpp(py::handle inp_hdl, py::handle idx_hdl) {
-    py::tuple try_res = _try_cond_take(inp_hdl, idx_hdl);
-    if (try_res.size() == 2) {
-        return try_res[0];
-    }
-    py::tuple up = _unpack_indexes(inp_hdl, idx_hdl);
-    py::object tensor = py::reinterpret_borrow<py::object>(up[0]);
-    py::list tensors = py::reinterpret_borrow<py::list>(up[1]);
-    py::list py_items = py::reinterpret_borrow<py::list>(up[2]);
-    std::vector<std::tuple<int8_t, bool, bool, bool, bool>> cpp_items;
-    for (size_t i = 0; i < py_items.size(); ++i) {
-        py::list item = py::reinterpret_borrow<py::list>(py_items[i]);
-        cpp_items.push_back(
-                {item[0].cast<int8_t>(), item[1].cast<bool>(), item[2].cast<bool>(),
-                 item[3].cast<bool>(), item[4].cast<bool>()});
-    }
-    static std::shared_ptr<OpDef> op;
-    if (up[3].cast<bool>()) {
-        op = Subtensor::make(cpp_items);
-    } else {
-        op = IndexingMultiAxisVec::make(cpp_items);
-    }
-    std::vector<PyObject*> p;
-    p.resize(tensors.size() + 2);
-    py::object Op = py::cast(op);
-    p[0] = Op.ptr();
-    p[1] = tensor.ptr();
-    for (size_t i = 0; i < tensors.size(); ++i) {
-        p[i + 2] = tensors[i].ptr();
-    }
-    py::tuple ret =
-            py::reinterpret_steal<py::object>(py_apply(NULL, p.data(), p.size()));
-    return ret[0];
-}
-
-py::object _setitem_cpp(py::handle inp_hdl, py::handle idx_hdl, py::handle val_hdl) {
-    py::object org_shape = getattr(inp_hdl, "shape");
-    py::object val = py::reinterpret_borrow<py::object>(val_hdl);
-    if (!TensorWrapper::try_cast(val.ptr()) && !py::isinstance<PySymbolVar>(val)) {
-        val =
-                _Const(val_hdl, getattr(inp_hdl, "dtype"), getattr(inp_hdl, "device"),
-                       inp_hdl);
-    }
-
-    py::tuple up = _unpack_indexes(inp_hdl, idx_hdl);
-    py::object tensor = py::reinterpret_borrow<py::object>(up[0]);
-    py::list tensors = py::reinterpret_borrow<py::list>(up[1]);
-    py::list py_items = py::reinterpret_borrow<py::list>(up[2]);
-    std::vector<std::tuple<int8_t, bool, bool, bool, bool>> cpp_items;
-    for (size_t i = 0; i < py_items.size(); ++i) {
-        py::list item = py::reinterpret_borrow<py::list>(py_items[i]);
-        cpp_items.push_back(
-                {item[0].cast<int8_t>(), item[1].cast<bool>(), item[2].cast<bool>(),
-                 item[3].cast<bool>(), item[4].cast<bool>()});
-    }
-    static std::shared_ptr<OpDef> op, set_op;
-    if (up[3].cast<bool>()) {
-        op = Subtensor::make(cpp_items);
-    } else {
-        op = IndexingMultiAxisVec::make(cpp_items);
-    }
-    std::vector<PyObject*> p;
-    p.resize(tensors.size() + 2);
-    py::object Op = py::cast(op);
-    p[0] = Op.ptr();
-    p[1] = tensor.ptr();
-    for (size_t i = 0; i < tensors.size(); ++i) {
-        p[i + 2] = tensors[i].ptr();
-    }
-    py::tuple ret =
-            py::reinterpret_steal<py::object>(py_apply(NULL, p.data(), p.size()));
-    py::object tmp_result = ret[0];
-
-    try {
-        py::object value_tuple_shape = val.attr("_tuple_shape");
-        py::object tmp_result_tuple_shape = tmp_result.attr("_tuple_shape");
-        py::tuple value_shape = py::reinterpret_borrow<py::tuple>(value_tuple_shape);
-        py::tuple tmp_result_shape =
-                py::reinterpret_borrow<py::tuple>(tmp_result_tuple_shape);
-        for (size_t i = 0; i < value_shape.size() && i < tmp_result_shape.size(); ++i) {
-            size_t vs = value_shape[value_shape.size() - i - 1].cast<size_t>();
-            size_t ts =
-                    tmp_result_shape[tmp_result_shape.size() - i - 1].cast<size_t>();
-            if (vs != 1 && vs != ts) {
-                std::string lhs = "", rhs = "";
-                for (size_t j = 0; j < tmp_result_shape.size(); ++j) {
-                    lhs += std::to_string(tmp_result_shape[j].cast<size_t>());
-                    if (j)
-                        lhs += ",";
-                }
-                for (size_t j = 0; j < value_shape.size(); ++j) {
-                    rhs += std::to_string(value_shape[j].cast<size_t>());
-                    if (j)
-                        rhs += ",";
-                }
-                throw py::value_error(
-                        "cannot copy tensor with shape (" + rhs +
-                        ") to subtensor with shape (" + lhs + ")");
-            }
-        }
-    } catch (py::error_already_set& err) {
-        ;
-    }
-
-    py::object broadcast_func = getattr(val, "_broadcast");
-    PyObject* Args = PyTuple_New(1);
-    PyTuple_SetItem(Args, 0, getattr(tmp_result, "shape").release().ptr());
-    PyObject* new_val = PyObject_CallObject(broadcast_func.ptr(), Args);
-    Py_XDECREF(Args);
-    val = py::reinterpret_steal<py::object>(new_val);
-
-    if (up[3].cast<bool>()) {
-        set_op = SetSubtensor::make(cpp_items);
-    } else {
-        set_op = IndexingSetMultiAxisVec::make(cpp_items);
-    }
-
-    std::vector<PyObject*> q;
-    q.resize(tensors.size() + 3);
-    py::object Set_Op = py::cast(set_op);
-    q[0] = Set_Op.ptr();
-    q[1] = tensor.ptr();
-    q[2] = val.ptr();
-    for (size_t i = 0; i < tensors.size(); ++i) {
-        q[i + 3] = tensors[i].ptr();
-    }
-    py::tuple result =
-            py::reinterpret_steal<py::object>(py_apply(NULL, q.data(), q.size()));
-    py::object res = result[0];
-
-    if (up[4].cast<bool>()) {
-        py::object reshape_func = getattr(res, "reshape");
-        PyObject* Args = PyTuple_New(1);
-        PyTuple_SetItem(Args, 0, org_shape.release().ptr());
-        PyObject* new_tensor = PyObject_CallObject(reshape_func.ptr(), Args);
-        Py_XDECREF(Args);
-        res = py::reinterpret_steal<py::object>(new_tensor);
-    }
-
-    return res;
-}
-
 // Returns the dtype that would result from performing an arithmetic
 // operation on the provided input tensors and scalars.
 PyObject* dtype_promotion(PyObject* self, PyObject* const* args, size_t nargs) {
@@ -1126,30 +576,6 @@ PyObject* get_device(PyObject* self, PyObject* const* args, size_t nargs) {
     PYEXT17_TRANSLATE_EXC_RET(nullptr)
 }
 
-PyObject* make_shape_tuple(PyObject* self, PyObject* const* args, size_t nargs) {
-    try {
-        return _make_shape_tuple(py::handle(args[0])).release().ptr();
-    }
-    PYEXT17_TRANSLATE_EXC_RET(nullptr)
-}
-
-PyObject* getitem_cpp(PyObject* self, PyObject* const* args, size_t nargs) {
-    try {
-        return _getitem_cpp(py::handle(args[0]), py::handle(args[1])).release().ptr();
-    }
-    PYEXT17_TRANSLATE_EXC_RET(nullptr)
-}
-
-PyObject* setitem_cpp(PyObject* self, PyObject* const* args, size_t nargs) {
-    try {
-        return _setitem_cpp(
-                       py::handle(args[0]), py::handle(args[1]), py::handle(args[2]))
-                .release()
-                .ptr();
-    }
-    PYEXT17_TRANSLATE_EXC_RET(nullptr)
-}
-
 #ifdef METH_FASTCALL
 #define MGE_PY_INTERFACE(NAME, FUNC) \
     { #NAME, (PyCFunction)FUNC, METH_FASTCALL, nullptr }
diff --git a/imperative/python/src/tensor.h b/imperative/python/src/tensor.h
index e2a02d1163a89ecce87b6802409d183146d6a16c..33b616eafe73896b18ca5591894d96102c4805ba 100644
--- a/imperative/python/src/tensor.h
+++ b/imperative/python/src/tensor.h
@@ -38,6 +38,8 @@ namespace mgb::imperative::python {
 
 extern interpreter::Interpreter::Channel* interpreter_for_py;
 extern PyTypeObject* py_tensor_type;
+extern PyObject* cpp_use_symbolic_shape;
+extern PyObject* cpp_astensor1d;
 
 struct Tensor : NonCopyableObj {
 private:
diff --git a/imperative/python/src/tensor_utils.cpp b/imperative/python/src/tensor_utils.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..6f5687cceedf6143fd1d2bf34528addee40b90d4
--- /dev/null
+++ b/imperative/python/src/tensor_utils.cpp
@@ -0,0 +1,630 @@
+/**
+ * \file imperative/python/src/tensor.cpp
+ * MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
+ *
+ * Copyright (c) 2014-2021 Megvii Inc. All rights reserved.
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ */
+
+#include "megbrain/common.h"
+#include "megbrain/dtype.h"
+#include "megbrain/imperative/ops/autogen.h"
+#include "megbrain/imperative/ops/backward_graph.h"
+#include "megbrain/imperative/ops/utility.h"
+#include "megbrain/imperative/profiler.h"
+#include "megbrain/imperative/transformations/eval.h"
+#include "megbrain/imperative/transformations/lazy.h"
+#include "megbrain/imperative/transformations/scalar.h"
+#include "megbrain/imperative/transformations/symbol.h"
+#include "megbrain/imperative/transformations/trace.h"
+#include "megbrain/imperative/utils/map.h"
+#include "megbrain/imperative/utils/stats.h"
+#include "megbrain/opr/io.h"
+#include "megbrain/plugin/profiler.h"
+
+#include "./common.h"
+#include "./grad.h"
+#include "./graph_rt.h"
+#include "./helper.h"
+#include "./module_trace.h"
+#include "./numpy_dtypes.h"
+#include "./tensor.h"
+#include "./tensor_utils.h"
+#include "./transformation.h"
+
+#include <object.h>
+#include <pybind11/numpy.h>
+#include <pybind11/operators.h>
+#include <pybind11/pytypes.h>
+#include <pyerrors.h>
+#include <range/v3/all.hpp>
+#include <string>
+
+#include <unordered_map>
+
+#include "../../src/impl/mgb_cg_impl.h"
+
+namespace py = pybind11;
+namespace views = ranges::views;
+
+namespace mgb::imperative::python {
+
+bool is_scalar(PyObject* tensor) {
+    if (py::isinstance<PySymbolVar>(py::handle(tensor))) {
+        auto var = py::handle(tensor).cast<PySymbolVar*>();
+        return var->is_scalar;
+    }
+    auto* tw = TensorWrapper::try_cast(tensor);
+    if (tw) {
+        return tw->m_tensor->is_scalar();
+    }
+    return PyArray_CheckAnyScalar(tensor);
+}
+
+bool is_bool_list(PyObject* arg) {
+    if (!PyList_Check(arg)) {
+        return false;
+    }
+    size_t sz = PyList_Size(arg);
+    if (!sz) {
+        return false;
+    }
+    for (size_t i = 0; i < sz; ++i) {
+        PyObject* handle = PyList_GetItem(arg, i);
+        if (!PyBool_Check(handle)) {
+            return false;
+        }
+    }
+    return true;
+}
+
+bool is_bool_dtype(PyObject* args) {
+    if (!PyObject_HasAttrString(args, "dtype"))
+        return false;
+    PyObject* dobj = PyObject_GetAttrString(args, "dtype");
+    PyArray_Descr* dtype;
+    PyArray_DescrConverter(dobj, &dtype);
+    bool ret = (dtype->kind == 'b');
+    Py_XDECREF(dtype);
+    Py_XDECREF(dobj);
+    return ret;
+}
+
+py::object _Const(
+        py::handle value, py::handle dtype, py::handle device, py::handle ref) {
+    py::object val = py::reinterpret_borrow<py::object>(value);
+    if (PyArray_Check(value.ptr())) {
+        py::tuple strides =
+                py::reinterpret_borrow<py::tuple>(getattr(value, "strides"));
+        bool need_squeeze = false;
+        for (size_t i = 0; i < strides.size(); ++i) {
+            if (strides[i].cast<ptrdiff_t>() == 0) {
+                need_squeeze = true;
+            }
+        }
+        if (need_squeeze) {
+            val = py::reinterpret_borrow<py::array>(value);
+            val = val.attr("squeeze")();
+            val = val.attr("reshape")(val.attr("shape"));
+        }
+    }
+    if (py::isinstance<PySymbolVar>(ref)) {
+        auto ref_var = ref.cast<PySymbolVar*>();
+        auto* graph = ref_var->m_node->owner_graph();
+        auto cn = device.cast<CompNode>();
+        OperatorNodeConfig config(cn);
+        auto hv = npy::np2tensor(
+                val.ptr(), npy::Meth::borrow(cn), dtype.cast<mgb::DType>());
+        auto typeobj = ref.get_type();
+        return typeobj(opr::ImmutableTensor::make(*graph, hv, config).node());
+    }
+    py::tuple tup = py::make_tuple(val, dtype, device, true, false, py::none());
+    return TensorWrapper::make(py_tensor_type, tup.ptr(), nullptr);
+}
+
+py::tuple _make_shape_tuple(py::handle shape) {
+    py::list orig;
+    py::list ret(0);
+    auto solve_one = [&](py::handle val) {
+        if (TensorWrapper::try_cast(val.ptr()) || py::isinstance<PySymbolVar>(val)) {
+            py::object np = getattr(val, "numpy")();
+            PyArrayObject* arr = (PyArrayObject*)np.ptr();
+            PyObject* maybe_list = PyArray_ToList(arr);
+            if (PyList_Check(maybe_list)) {
+                py::list may = py::reinterpret_steal<py::list>(maybe_list);
+                for (size_t i = 0; i < may.size(); ++i) {
+                    ret.append(may[i]);
+                }
+            } else {
+                mgb_assert(PyLong_Check(maybe_list));
+                ret.append(PyLong_AsLong(maybe_list));
+                Py_XDECREF(maybe_list);
+            }
+        } else if (PyArray_Check(val.ptr())) {
+            ret.append(PyArray_PyIntAsInt(val.ptr()));
+        } else {
+            ret.append(PyLong_AsLong(val.ptr()));
+        }
+    };
+    if (PyArray_Check(shape.ptr()) && !PyArray_CheckAnyScalar(shape.ptr())) {
+        orig = py::reinterpret_steal<py::list>(
+                PyArray_ToList((PyArrayObject*)shape.ptr()));
+        for (size_t i = 0; i < orig.size(); ++i) {
+            solve_one(orig[i]);
+        }
+    } else if (PyList_Check(shape.ptr())) {
+        orig = py::reinterpret_borrow<py::list>(shape);
+        for (size_t i = 0; i < orig.size(); ++i) {
+            solve_one(orig[i]);
+        }
+    } else if (PyTuple_Check(shape.ptr())) {
+        py::tuple tup = py::reinterpret_borrow<py::tuple>(shape);
+        for (size_t i = 0; i < tup.size(); ++i) {
+            solve_one(tup[i]);
+        }
+    } else {
+        solve_one(shape);
+    }
+    return py::reinterpret_steal<py::tuple>(PyList_AsTuple(ret.ptr()));
+}
+
+py::object _get_index(py::object tensor, py::object src) {
+    if (!TensorWrapper::try_cast(tensor.ptr()) &&
+        !py::isinstance<PySymbolVar>(tensor)) {
+        auto get_const = [&](mgb::DType dtype) -> py::object {
+            return _Const(tensor, py::cast(dtype), src.attr("device"), src);
+        };
+        if (is_bool_list(tensor.ptr()) || is_bool_dtype(tensor.ptr())) {
+            tensor = get_const(dtype::Bool());
+        } else {
+            tensor = get_const(dtype::Int32());
+        }
+        if (!is_bool_dtype(tensor.ptr())) {
+            return tensor;
+        }
+    } else {
+        if (!is_bool_dtype(tensor.ptr())) {
+            return tensor;
+        }
+    }
+    static std::shared_ptr<OpDef> op = CondTake::make();
+    std::vector<PyObject*> p;
+    p.resize(3);
+    py::object Op = py::cast(op);
+    p[0] = Op.ptr();
+    p[1] = tensor.ptr();
+    p[2] = tensor.ptr();
+    py::tuple ret =
+            py::reinterpret_steal<py::object>(py_apply(NULL, p.data(), p.size()));
+    return ret[1];
+}
+
+py::tuple _try_cond_take(py::handle tensor, py::handle index) {
+    if (!hasattr(index, "dtype") || !hasattr(index, "shape")) {
+        return py::tuple();
+    }
+    if (!is_bool_dtype(index.ptr()) ||
+        _make_shape_tuple(getattr(index, "shape"))
+                .not_equal(_make_shape_tuple(getattr(tensor, "shape")))) {
+        return py::tuple();
+    }
+    py::object iobj;
+    if (PyArray_Check(index.ptr())) {
+        iobj =
+                _Const(index, py::cast((mgb::DType)dtype::Bool()),
+                       getattr(tensor, "device"), tensor);
+    } else {
+        iobj = py::reinterpret_borrow<py::object>(index);
+    }
+    static std::shared_ptr<OpDef> op = CondTake::make();
+    std::vector<PyObject*> p;
+    p.resize(3);
+    py::object Op = py::cast(op);
+    p[0] = Op.ptr();
+    p[1] = tensor.ptr();
+    p[2] = iobj.ptr();
+    py::tuple ret =
+            py::reinterpret_steal<py::object>(py_apply(NULL, p.data(), p.size()));
+    return ret;
+}
+
+py::tuple _remove_ellipsis(py::object tensor, py::tuple tuple_val) {
+    size_t tuple_size = tuple_val.size();
+    size_t ndim_sum = 0, cur_sum = 0;
+    int pos = -1;
+    bool has_unknown_ndim_bool_index = false;
+    for (size_t i = 0; i < tuple_size; ++i) {
+        py::object handle = tuple_val[i];
+        if (handle.ptr() == Py_Ellipsis) {
+            pos = static_cast<int>(i);
+            for (size_t j = 0; j < i; ++j) {
+                py::object t = tuple_val[j];
+                if (t.ptr() == Py_Ellipsis) {
+                    throw py::index_error("only one ellipsis is allowed.");
+                }
+            }
+        } else {
+            size_t ndim_incr = 1;
+            if (hasattr(handle, "dtype") && is_bool_dtype(handle.ptr()) &&
+                hasattr(handle, "ndim")) {
+                py::object ndim = getattr(handle, "ndim");
+                if (PyLong_Check(ndim.ptr())) {
+                    ndim_incr = PyLong_AsLong(ndim.ptr());
+                } else {
+                    has_unknown_ndim_bool_index = true;
+                }
+            }
+            cur_sum += ndim_incr;
+        }
+    }
+    if (pos == -1) {
+        return tuple_val;
+    } else {
+        if (has_unknown_ndim_bool_index) {
+            throw py::index_error(
+                    "does not support bool index with unknown shape when using "
+                    "Ellipsis.");
+        }
+        try {
+            ndim_sum = getattr(tensor, "ndim").cast<size_t>();
+        } catch (py::error_already_set& err) {
+            throw py::index_error(
+                    "does not support Ellipsis when tensor's ndim is unknown.");
+        }
+        py::tuple ret(ndim_sum - cur_sum + tuple_size - 1);
+        size_t idx = 0;
+        for (size_t i = 0; i < tuple_size; ++i) {
+            if (i == pos) {
+                for (size_t j = cur_sum; j < ndim_sum; ++j) {
+                    ret[idx++] = PySlice_New(NULL, NULL, NULL);
+                }
+            } else {
+                ret[idx++] = tuple_val[i];
+            }
+        }
+        return ret;
+    }
+}
+
+py::tuple _expand_bool_dim(py::object tensor, py::tuple tuple_val) {
+    py::tuple cur_shape = _make_shape_tuple(py::handle(getattr(tensor, "shape")));
+    py::list new_tuple_val(0);
+
+    size_t offset = 0;
+    size_t tdim = 0;
+    for (size_t i = 0; i < tuple_val.size(); ++i) {
+        py::handle k = tuple_val[i];
+        if (is_bool_dtype(k.ptr())) {
+            size_t ndim = getattr(k, "ndim").cast<size_t>();
+            if (ndim > 1) {
+                py::tuple ishape = _make_shape_tuple(py::handle(getattr(k, "shape")));
+                for (size_t j = 0; j < ndim; ++j) {
+                    if (cur_shape[tdim + j - offset].cast<size_t>() !=
+                        ishape[j].cast<size_t>()) {
+                        std::string msg =
+                                "boolean index did not match tensor along dimension " +
+                                std::to_string(tdim + j) + "; dimension is " +
+                                std::to_string(
+                                        cur_shape[tdim + j - offset].cast<size_t>()) +
+                                " but corresponding boolean dimension is " +
+                                std::to_string(ishape[j].cast<size_t>());
+                        throw py::index_error(msg.c_str());
+                    }
+                }
+                py::object new_k = getattr(k, "reshape")(-1);
+                py::object kshape = getattr(new_k, "shape");
+                py::list new_shape(0);
+                PyObject* sym = PyObject_CallObject(cpp_use_symbolic_shape, nullptr);
+                bool is_sym = (sym == Py_True);
+                Py_XDECREF(sym);
+                if (is_sym) {
+                    py::object tshape = getattr(tensor, "shape");
+                    for (size_t j = 0; j < i; ++j) {
+                        new_shape.append(tshape[py::int_(j)]);
+                    }
+                    new_shape.append(kshape[py::int_(0)]);
+                    for (size_t j = tdim + ndim - offset; j < cur_shape.size(); ++j) {
+                        new_shape.append(cur_shape[j]);
+                    }
+                    py::tuple args = py::make_tuple(new_shape);
+                    PyObject* shape_tensor =
+                            PyObject_CallObject(cpp_astensor1d, args.ptr());
+                    py::object reshape_func = getattr(tensor, "reshape");
+                    Py_INCREF(shape_tensor);
+                    PyObject* Args = PyTuple_New(1);
+                    PyTuple_SetItem(Args, 0, shape_tensor);
+                    PyObject* new_tensor =
+                            PyObject_CallObject(reshape_func.ptr(), Args);
+                    Py_XDECREF(Args);
+                    tensor = py::reinterpret_steal<py::object>(new_tensor);
+                    cur_shape = _make_shape_tuple(py::handle(shape_tensor));
+                    Py_XDECREF(shape_tensor);
+                } else {
+                    for (size_t j = 0; j < i; ++j) {
+                        new_shape.append(cur_shape[j]);
+                    }
+                    new_shape.append(py::reinterpret_borrow<py::tuple>(kshape)[0]);
+                    for (size_t j = tdim + ndim - offset; j < cur_shape.size(); ++j) {
+                        new_shape.append(cur_shape[j]);
+                    }
+                    cur_shape = new_shape;
+                    tensor = getattr(tensor, "reshape")(cur_shape);
+                }
+                offset++;
+                tdim += ndim;
+            }
+            new_tuple_val.append(k);
+        } else {
+            new_tuple_val.append(k);
+            tdim++;
+        }
+    }
+    return py::make_tuple(tensor, py::reinterpret_borrow<py::tuple>(new_tuple_val));
+}
+
+py::tuple _unpack_indexes(py::handle inp_hdl, py::handle idx_hdl) {
+    py::object inp = py::reinterpret_borrow<py::object>(inp_hdl);
+    py::tuple tuple_val;
+    if (py::isinstance<py::tuple>(idx_hdl)) {
+        tuple_val = py::reinterpret_borrow<py::tuple>(idx_hdl);
+    } else {
+        tuple_val = py::make_tuple(idx_hdl);
+    }
+
+    bool use_subtensor = true;
+    bool need_remove_ellipsis = false;
+    bool need_expand_bool_dim = false;
+    size_t idx_ndim = 0;
+    for (size_t i = 0; i < tuple_val.size(); ++i) {
+        py::object k = tuple_val[i];
+        if (k.ptr() == Py_None) {
+            throw py::index_error("newaxis is not allowed here");
+        } else if (k.ptr() == Py_Ellipsis) {
+            need_remove_ellipsis = true;
+        } else {
+            if (is_bool_dtype(k.ptr()) && hasattr(k, "ndim")) {
+                size_t ndim = getattr(k, "ndim").cast<size_t>();
+                idx_ndim += ndim;
+                if (ndim > 1) {
+                    need_expand_bool_dim = true;
+                }
+            } else {
+                idx_ndim++;
+            }
+        }
+    }
+    try {
+        size_t inp_ndim = getattr(inp, "ndim").cast<size_t>();
+        if (idx_ndim > inp_ndim) {
+            std::string msg = "too many indices for tensor: tensor is " +
+                              std::to_string(inp_ndim) + "-dimensional, but " +
+                              std::to_string(idx_ndim) + " were indexed";
+            throw py::index_error(msg.c_str());
+        }
+    } catch (py::error_already_set& err) {
+        ;  // ignore
+    }
+    if (need_remove_ellipsis) {
+        tuple_val = _remove_ellipsis(inp, tuple_val);
+    }
+
+    if (need_expand_bool_dim) {
+        py::object shape = getattr(inp, "shape");
+        if (shape.ptr() != Py_None) {
+            py::tuple ret = _expand_bool_dim(inp, tuple_val);
+            inp = ret[0];
+            tuple_val = ret[1];
+        }
+    }
+
+    py::list items;
+    py::list tensors;
+    int cur_axis = -1;
+
+    for (size_t i = 0; i < tuple_val.size(); ++i) {
+        py::object handle = tuple_val[i];
+        cur_axis++;
+        if (!is_scalar(handle.ptr()) && !PySlice_Check(handle.ptr())) {
+            use_subtensor = false;
+        }
+        py::list item;
+        item.append(cur_axis);
+        auto push = [&](PyObject* v) {
+            if (v == Py_None) {
+                item.append(false);
+            } else {
+                item.append(true);
+                tensors.append(_get_index(py::reinterpret_borrow<py::object>(v), inp));
+            }
+        };
+
+        if (PySlice_Check(handle.ptr())) {
+            PySliceObject* s = (PySliceObject*)handle.ptr();
+            if (s->start == Py_None && s->stop == Py_None && s->step == Py_None) {
+                continue;
+            }
+            push(s->start);
+            push(s->stop);
+            push(s->step);
+            item.append(false);
+        } else {
+            for (size_t j = 0; j < 3; j++)
+                item.append(false);
+            push(handle.ptr());
+        }
+        items.append(item);
+    }
+
+    return py::make_tuple(inp, tensors, items, use_subtensor, need_expand_bool_dim);
+}
+
+py::object _getitem_cpp(py::handle inp_hdl, py::handle idx_hdl) {
+    py::tuple try_res = _try_cond_take(inp_hdl, idx_hdl);
+    if (try_res.size() == 2) {
+        return try_res[0];
+    }
+    py::tuple up = _unpack_indexes(inp_hdl, idx_hdl);
+    py::object tensor = py::reinterpret_borrow<py::object>(up[0]);
+    py::list tensors = py::reinterpret_borrow<py::list>(up[1]);
+    py::list py_items = py::reinterpret_borrow<py::list>(up[2]);
+    std::vector<std::tuple<int8_t, bool, bool, bool, bool>> cpp_items;
+    for (size_t i = 0; i < py_items.size(); ++i) {
+        py::list item = py::reinterpret_borrow<py::list>(py_items[i]);
+        cpp_items.push_back(
+                {item[0].cast<int8_t>(), item[1].cast<bool>(), item[2].cast<bool>(),
+                 item[3].cast<bool>(), item[4].cast<bool>()});
+    }
+    static std::shared_ptr<OpDef> op;
+    if (up[3].cast<bool>()) {
+        op = Subtensor::make(cpp_items);
+    } else {
+        op = IndexingMultiAxisVec::make(cpp_items);
+    }
+    std::vector<PyObject*> p;
+    p.resize(tensors.size() + 2);
+    py::object Op = py::cast(op);
+    p[0] = Op.ptr();
+    p[1] = tensor.ptr();
+    for (size_t i = 0; i < tensors.size(); ++i) {
+        p[i + 2] = tensors[i].ptr();
+    }
+    py::tuple ret =
+            py::reinterpret_steal<py::object>(py_apply(NULL, p.data(), p.size()));
+    return ret[0];
+}
+
+py::object _setitem_cpp(py::handle inp_hdl, py::handle idx_hdl, py::handle val_hdl) {
+    py::object org_shape = getattr(inp_hdl, "shape");
+    py::object val = py::reinterpret_borrow<py::object>(val_hdl);
+    if (!TensorWrapper::try_cast(val.ptr()) && !py::isinstance<PySymbolVar>(val)) {
+        val =
+                _Const(val_hdl, getattr(inp_hdl, "dtype"), getattr(inp_hdl, "device"),
+                       inp_hdl);
+    }
+
+    py::tuple up = _unpack_indexes(inp_hdl, idx_hdl);
+    py::object tensor = py::reinterpret_borrow<py::object>(up[0]);
+    py::list tensors = py::reinterpret_borrow<py::list>(up[1]);
+    py::list py_items = py::reinterpret_borrow<py::list>(up[2]);
+    std::vector<std::tuple<int8_t, bool, bool, bool, bool>> cpp_items;
+    for (size_t i = 0; i < py_items.size(); ++i) {
+        py::list item = py::reinterpret_borrow<py::list>(py_items[i]);
+        cpp_items.push_back(
+                {item[0].cast<int8_t>(), item[1].cast<bool>(), item[2].cast<bool>(),
+                 item[3].cast<bool>(), item[4].cast<bool>()});
+    }
+    static std::shared_ptr<OpDef> op, set_op;
+    if (up[3].cast<bool>()) {
+        op = Subtensor::make(cpp_items);
+    } else {
+        op = IndexingMultiAxisVec::make(cpp_items);
+    }
+    std::vector<PyObject*> p;
+    p.resize(tensors.size() + 2);
+    py::object Op = py::cast(op);
+    p[0] = Op.ptr();
+    p[1] = tensor.ptr();
+    for (size_t i = 0; i < tensors.size(); ++i) {
+        p[i + 2] = tensors[i].ptr();
+    }
+    py::tuple ret =
+            py::reinterpret_steal<py::object>(py_apply(NULL, p.data(), p.size()));
+    py::object tmp_result = ret[0];
+
+    try {
+        py::object value_tuple_shape = val.attr("_tuple_shape");
+        py::object tmp_result_tuple_shape = tmp_result.attr("_tuple_shape");
+        py::tuple value_shape = py::reinterpret_borrow<py::tuple>(value_tuple_shape);
+        py::tuple tmp_result_shape =
+                py::reinterpret_borrow<py::tuple>(tmp_result_tuple_shape);
+        for (size_t i = 0; i < value_shape.size() && i < tmp_result_shape.size(); ++i) {
+            size_t vs = value_shape[value_shape.size() - i - 1].cast<size_t>();
+            size_t ts =
+                    tmp_result_shape[tmp_result_shape.size() - i - 1].cast<size_t>();
+            if (vs != 1 && vs != ts) {
+                std::string lhs = "", rhs = "";
+                for (size_t j = 0; j < tmp_result_shape.size(); ++j) {
+                    lhs += std::to_string(tmp_result_shape[j].cast<size_t>());
+                    if (j)
+                        lhs += ",";
+                }
+                for (size_t j = 0; j < value_shape.size(); ++j) {
+                    rhs += std::to_string(value_shape[j].cast<size_t>());
+                    if (j)
+                        rhs += ",";
+                }
+                throw py::value_error(
+                        "cannot copy tensor with shape (" + rhs +
+                        ") to subtensor with shape (" + lhs + ")");
+            }
+        }
+    } catch (py::error_already_set& err) {
+        ;
+    }
+
+    py::object broadcast_func = getattr(val, "_broadcast");
+    PyObject* Args = PyTuple_New(1);
+    PyTuple_SetItem(Args, 0, getattr(tmp_result, "shape").release().ptr());
+    PyObject* new_val = PyObject_CallObject(broadcast_func.ptr(), Args);
+    Py_XDECREF(Args);
+    val = py::reinterpret_steal<py::object>(new_val);
+
+    if (up[3].cast<bool>()) {
+        set_op = SetSubtensor::make(cpp_items);
+    } else {
+        set_op = IndexingSetMultiAxisVec::make(cpp_items);
+    }
+
+    std::vector<PyObject*> q;
+    q.resize(tensors.size() + 3);
+    py::object Set_Op = py::cast(set_op);
+    q[0] = Set_Op.ptr();
+    q[1] = tensor.ptr();
+    q[2] = val.ptr();
+    for (size_t i = 0; i < tensors.size(); ++i) {
+        q[i + 3] = tensors[i].ptr();
+    }
+    py::tuple result =
+            py::reinterpret_steal<py::object>(py_apply(NULL, q.data(), q.size()));
+    py::object res = result[0];
+
+    if (up[4].cast<bool>()) {
+        py::object reshape_func = getattr(res, "reshape");
+        PyObject* Args = PyTuple_New(1);
+        PyTuple_SetItem(Args, 0, org_shape.release().ptr());
+        PyObject* new_tensor = PyObject_CallObject(reshape_func.ptr(), Args);
+        Py_XDECREF(Args);
+        res = py::reinterpret_steal<py::object>(new_tensor);
+    }
+
+    return res;
+}
+
+PyObject* make_shape_tuple(PyObject* self, PyObject* const* args, size_t nargs) {
+    try {
+        return _make_shape_tuple(py::handle(args[0])).release().ptr();
+    }
+    PYEXT17_TRANSLATE_EXC_RET(nullptr)
+}
+
+PyObject* getitem_cpp(PyObject* self, PyObject* const* args, size_t nargs) {
+    try {
+        return _getitem_cpp(py::handle(args[0]), py::handle(args[1])).release().ptr();
+    }
+    PYEXT17_TRANSLATE_EXC_RET(nullptr)
+}
+
+PyObject* setitem_cpp(PyObject* self, PyObject* const* args, size_t nargs) {
+    try {
+        return _setitem_cpp(
+                       py::handle(args[0]), py::handle(args[1]), py::handle(args[2]))
+                .release()
+                .ptr();
+    }
+    PYEXT17_TRANSLATE_EXC_RET(nullptr)
+}
+
+}  // namespace mgb::imperative::python
diff --git a/imperative/python/src/tensor_utils.h b/imperative/python/src/tensor_utils.h
new file mode 100644
index 0000000000000000000000000000000000000000..420b94bd34a25a202de233b3504871a2bdbbd639
--- /dev/null
+++ b/imperative/python/src/tensor_utils.h
@@ -0,0 +1,11 @@
+#pragma once
+
+namespace mgb::imperative::python {
+
+PyObject* make_shape_tuple(PyObject* self, PyObject* const* args, size_t nargs);
+
+PyObject* getitem_cpp(PyObject* self, PyObject* const* args, size_t nargs);
+
+PyObject* setitem_cpp(PyObject* self, PyObject* const* args, size_t nargs);
+
+}  // namespace mgb::imperative::python
\ No newline at end of file
diff --git a/imperative/src/impl/interpreter/interpreter_impl.cpp b/imperative/src/impl/interpreter/interpreter_impl.cpp
index 0925c010305fbc00ddb181728be87506ec5134b3..95b6d93de7e20a2e806cd01e9a0f787169e1a0e3 100644
--- a/imperative/src/impl/interpreter/interpreter_impl.cpp
+++ b/imperative/src/impl/interpreter/interpreter_impl.cpp
@@ -642,7 +642,7 @@ void ChannelImpl::produce_tensor(TensorInfo* dest, TensorPtr ptr) {
     m_dtr.update_used_time(dest);
     MGB_RECORD_EVENT(
             TensorProduceEvent, dest->id, ptr->layout(), ptr->comp_node(),
-            ptr->dev_tensor().raw_ptr());
+            ptr->dev_tensor(false).raw_ptr());
     // update tensor desc for static infer
     if (dest->desc.layout.ndim) {
         mgb_assert(
@@ -730,10 +730,20 @@ void ChannelImpl::do_apply_op(const ApplyOp& cmd, std::string reason) {
                     inputs, apply_functor, const_functor);
             return outputs;
         }
-        return OpDef::apply_on_physical_tensor(def, inputs, output_descs, validated);
+        // Check Input Layout
+        // Get the input layout constraints, and if the constraint is not satisfied
+        // inplace update the layout and blob to make the tensor contiguous
+        auto&& constraints = OpDef::get_input_layout_constraint(def, inputs);
+        for (size_t idx = 0; idx < inputs.size(); ++idx) {
+            auto&& layout_checker = constraints[idx];
+            if (layout_checker) {
+                inputs[idx]->to_contiguous_inplace(layout_checker);
+            }
+        }
+        return OpDef::apply_on_physical_tensor(
+                def, std::move(inputs), output_descs, validated);
     };
     MGB_RECORD_EVENT(OpExecuteEvent, apply_id, {}, reason);
-    // Begin profiling operator
     SmallVector<std::pair<CompNode, uint64_t>> kernels;
     if (profiling_device) {
         // Collecting devices
diff --git a/imperative/src/impl/mgb_cg_impl.h b/imperative/src/impl/mgb_cg_impl.h
index 8c10fc0d1ff4a81dcd5efb5893267dd83d9023e4..b95d23fc141b8ee506d63d408526a5f9060685d7 100644
--- a/imperative/src/impl/mgb_cg_impl.h
+++ b/imperative/src/impl/mgb_cg_impl.h
@@ -1 +1,2 @@
 #include "../../../src/core/impl/graph/cg_impl.h"
+#include "../../../src/core/impl/graph/var_node_mem_mgr.h"
diff --git a/imperative/src/impl/op_def.cpp b/imperative/src/impl/op_def.cpp
index c166861442e51db5a2237bb7de63fd278ec88c8d..c7e6734379cb5f5c53669aa2ddad552e835a149c 100644
--- a/imperative/src/impl/op_def.cpp
+++ b/imperative/src/impl/op_def.cpp
@@ -60,6 +60,11 @@ std::tuple<SmallVector<LogicalTensorDesc>, bool> OpDef::infer_output_attrs_falli
     return def.trait()->infer_output_attrs_fallible(def, inputs);
 }
 
+SmallVector<VarNode::LayoutConstraintCallback> OpDef::get_input_layout_constraint(
+        const OpDef& def, const SmallVector<TensorPtr>& inputs) {
+    return def.trait()->get_input_layout_constraint(def, inputs);
+}
+
 EncodedSubgraph OpDef::make_backward_graph(
         const OpDef& def, const SmallVector<LogicalTensorDesc>& inputs,
         const SmallVector<bool>& input_requires_grad,
diff --git a/imperative/src/impl/op_trait.cpp b/imperative/src/impl/op_trait.cpp
index ab584b3c6180b7a20486fd907b61354080e0991d..6bfedc549731d24cfdaf74791cc2ae71c32dcdc1 100644
--- a/imperative/src/impl/op_trait.cpp
+++ b/imperative/src/impl/op_trait.cpp
@@ -47,6 +47,10 @@ void OpMethFallbackByProxyGraph::impl(
         InferOutputAttrsFallible& func, op_meth_tag::InferOutputAttrsFallible) {
     func.Base::operator=(proxy_graph_detail::infer_output_attrs_fallible);
 }
+void OpMethFallbackByProxyGraph::impl(
+        GetInputLayoutConstraint& func, op_meth_tag::GetInputLayoutConstraint) {
+    func.Base::operator=(proxy_graph_detail::get_input_layout_constraint);
+}
 void OpMethFallbackByProxyGraph::impl(GradMaker& func, op_meth_tag::GradMaker) {
     func.Base::operator=(proxy_graph_detail::make_backward_graph);
 }
@@ -63,6 +67,10 @@ void OpMethFallbackFromSubgraph::impl(
         InferOutputAttrsFallible& func, op_meth_tag::InferOutputAttrsFallible) {
     func.Base::operator=(subgraph_detail::infer_output_attrs_fallible);
 }
+void OpMethFallbackFromSubgraph::impl(
+        GetInputLayoutConstraint& func, op_meth_tag::GetInputLayoutConstraint) {
+    func.Base::operator=(subgraph_detail::get_input_layout_constraint);
+}
 void OpMethFallbackFromSubgraph::impl(GradMaker& func, op_meth_tag::GradMaker) {
     func.Base::operator=(subgraph_detail::make_backward_graph);
 }
diff --git a/imperative/src/impl/op_trait.h b/imperative/src/impl/op_trait.h
index 8db9a5c97ad95fedfb5db2c306cd7363ed09cbb1..08c2166ba440c46d6e912239167ac1b8752f4d12 100644
--- a/imperative/src/impl/op_trait.h
+++ b/imperative/src/impl/op_trait.h
@@ -73,6 +73,9 @@ OpMethType(ApplyOnVarNode,
 OpMethType(InferOutputAttrsFallible,
            decltype(OpDef::infer_output_attrs_fallible));
 
+OpMethType(GetInputLayoutConstraint,
+           decltype(OpDef::get_input_layout_constraint));
+
 OpMethType(GradMaker,
            decltype(OpDef::make_backward_graph));
 
@@ -119,6 +122,8 @@ struct OpMethFallbackByProxyGraph : OpMethImplBase {
     static void impl(ApplyOnPhysicalTensor& func, op_meth_tag::ApplyOnPhysicalTensor);
     static void impl(
             InferOutputAttrsFallible& func, op_meth_tag::InferOutputAttrsFallible);
+    static void impl(
+            GetInputLayoutConstraint& func, op_meth_tag::GetInputLayoutConstraint);
     static void impl(GradMaker& func, op_meth_tag::GradMaker);
 };
 
@@ -128,6 +133,8 @@ struct OpMethFallbackFromSubgraph : OpMethImplBase {
     static void impl(ApplyOnVarNode& func, op_meth_tag::ApplyOnVarNode);
     static void impl(
             InferOutputAttrsFallible& func, op_meth_tag::InferOutputAttrsFallible);
+    static void impl(
+            GetInputLayoutConstraint& func, op_meth_tag::GetInputLayoutConstraint);
     static void impl(GradMaker& func, op_meth_tag::GradMaker);
 };
 
@@ -179,6 +186,7 @@ struct OpTrait {
     ApplyOnDeviceTensorND apply_on_device_tensornd;
     ApplyOnVarNode apply_on_var_node;
     InferOutputAttrsFallible infer_output_attrs_fallible;
+    GetInputLayoutConstraint get_input_layout_constraint;
     GradMaker make_backward_graph;
     Props props;
     HashFunc hash;
@@ -199,6 +207,7 @@ struct OpTrait {
     cb(apply_on_device_tensornd)    \
     cb(apply_on_var_node)           \
     cb(infer_output_attrs_fallible) \
+    cb(get_input_layout_constraint) \
     cb(make_backward_graph)         \
     cb(props)                       \
     cb(hash)                        \
diff --git a/imperative/src/impl/opr_utility.cpp b/imperative/src/impl/opr_utility.cpp
index 3b61ded3af63f644e1980bc176295c3e6dbb7475..2f5e1de20725cb5a8b5cbdaf6d11cac1cafe3fd1 100644
--- a/imperative/src/impl/opr_utility.cpp
+++ b/imperative/src/impl/opr_utility.cpp
@@ -117,7 +117,7 @@ void InputCallback::scn_do_execute() {
         layout.init_contiguous_stride();
         dev_tensor.reset(dev_tensor.storage(), layout);
     }
-    output(0)->reset_dev_tensor_from_tensor(dev_tensor);
+    output(0)->force_assign_dev_tensor_from_tensor(dev_tensor);
 }
 
 cg::OperatorNodeBase* InputCallback::shallow_copy(
@@ -311,7 +311,7 @@ cg::OperatorNodeBase::NodeProp* MutableTensor::do_make_node_prop() const {
 }
 
 void MutableTensor::scn_do_execute() {
-    output(0)->reset_dev_tensor_from_tensor(*m_dev_tensor);
+    output(0)->force_assign_dev_tensor_from_tensor(*m_dev_tensor);
 }
 
 void MutableTensor::init_output_static_infer_desc() {
diff --git a/imperative/src/impl/ops/broadcast.cpp b/imperative/src/impl/ops/broadcast.cpp
index 1690365b90a82e8407b827317bc92074ce0e679b..e97ef497200ac26a213ae2d55e676a414268d6e2 100644
--- a/imperative/src/impl/ops/broadcast.cpp
+++ b/imperative/src/impl/ops/broadcast.cpp
@@ -83,28 +83,18 @@ std::tuple<SmallVector<LogicalTensorDesc>, bool> infer_output_attrs_fallible(
 SmallVector<TensorPtr> apply_on_physical_tensor(
         const OpDef& def, const SmallVector<TensorPtr>& inputs,
         SmallVector<LogicalTensorDesc>& output_descs, const bool& validated) {
-    auto& input = inputs[0];
-    TensorShape target_shape;
-    if (validated) {
-        target_shape = output_descs[0].layout;
-    } else {
-        cg::copy_tensor_value_to_shape(
-                target_shape, inputs[1]->get_value().proxy_to_default_cpu());
-    }
-    TensorPtr output = Tensor::make(
-            TensorLayout(target_shape, input->dtype()), input->comp_node());
-    if (output->layout().is_empty()) {
-        return {output};
-    }
-    if (input->shape().eq_shape(output->shape())) {
-        mgb_assert(input->layout().eq_layout(output->layout()));
-        output->dev_tensor().copy_from_fixlayout(input->dev_tensor());
-    } else {
-        TensorLayout input_layout = input->layout().broadcast(output->shape());
-        output->dev_tensor().copy_from_fixlayout(
-                input->dev_tensor().sub(SubTensorSpec::make_from_layout(input_layout)));
-    }
-    return {output};
+    def.cast_final_safe<Broadcast>();
+    size_t nr_inp = inputs.size();
+    mgb_assert(nr_inp == 2, "Broadcast expects 2 inputs; got %lu actually", nr_inp);
+    auto&& src = inputs[0];
+    auto&& tshp_nd = inputs[1];
+    auto slayout = src->layout();
+
+    TensorShape tshp;
+    cg::copy_tensor_value_to_shape(tshp, tshp_nd->get_value().proxy_to_default_cpu());
+    TensorLayout tlayout = slayout.broadcast(tshp);
+    // memory forward
+    return {Tensor::make(src->blob(), src->offset(), tlayout)};
 }
 
 OP_TRAIT_REG(Broadcast, Broadcast, opr::Broadcast)
@@ -184,10 +174,6 @@ SmallVector<TensorPtr> apply_on_physical_tensor(
     auto&& tshp_nd = inputs[1];
     auto slayout = src->layout();
 
-    if (validated) {
-        return {Tensor::make(src->blob(), 0, output_descs[0].layout)};
-    }
-
     TensorShape tshp;
     cg::copy_tensor_value_to_shape(tshp, tshp_nd->get_value().proxy_to_default_cpu());
     if (op_def.axis != opr::Reshape::Param::INVALID_AXIS) {
@@ -195,13 +181,39 @@ SmallVector<TensorPtr> apply_on_physical_tensor(
         tshp[op_def.axis] = 1;
         tshp[op_def.axis] = src->layout().total_nr_elems() / tshp.total_nr_elems();
     }
-    return {Tensor::make(src->blob(), 0, slayout.reshape(tshp))};
+    TensorLayout tlayout;
+    mgb_assert(slayout.try_reshape(tlayout, tshp));
+    return {Tensor::make(src->blob(), src->offset(), tlayout)};
+}
+
+SmallVector<VarNode::LayoutConstraintCallback> get_input_layout_constraint(
+        const OpDef& def, const SmallVector<TensorPtr>& inputs) {
+    auto&& op_def = def.cast_final_safe<Reshape>();
+    SmallVector<VarNode::LayoutConstraintCallback> layout_checker(inputs.size());
+    layout_checker[0] = [&](const TensorLayout& layout) {
+        TensorShape tshp;
+        TensorLayout ret;
+        cg::copy_tensor_value_to_shape(
+                tshp, inputs[1]->get_value().proxy_to_default_cpu());
+        if (op_def.axis != opr::Reshape::Param::INVALID_AXIS) {
+            mgb_assert(tshp[op_def.axis] == -1);
+            tshp[op_def.axis] = 1;
+            tshp[op_def.axis] = layout.total_nr_elems() / tshp.total_nr_elems();
+        }
+        if (layout.try_reshape(ret, tshp)) {
+            return true;
+        } else {
+            return false;
+        }
+    };
+    return layout_checker;
 }
 
 OP_TRAIT_REG(Reshape, Reshape)
         .apply_on_var_node(apply_on_var_node)
         .infer_output_attrs_fallible(infer_output_attrs_fallible)
         .apply_on_physical_tensor(apply_on_physical_tensor)
+        .get_input_layout_constraint(get_input_layout_constraint)
         .fallback();
 }  // namespace reshape
 
diff --git a/imperative/src/impl/ops/elemwise.cpp b/imperative/src/impl/ops/elemwise.cpp
index b43f37fc56d2d89cc812dec112a930ccebfe8f30..7d45232b46444d6db491785ff5afe02edacf2f5f 100644
--- a/imperative/src/impl/ops/elemwise.cpp
+++ b/imperative/src/impl/ops/elemwise.cpp
@@ -220,12 +220,22 @@ cg::OperatorNodeBase* apply_inplace_add_on_var_node(
 SmallVector<TensorPtr> apply_inplace_add_on_physical_tensor(
         const OpDef& def, const SmallVector<TensorPtr>& inputs,
         SmallVector<LogicalTensorDesc>& output_descs, const bool& validated) {
-    mgb_assert(
-            inputs[0]->blob().use_count() == 1 && inputs[0]->blob()->storage().unique(),
-            "This inplace modification may change the elements of other tensors. "
-            "Please set MEGENGINE_INPLACE_UPDATE to 0 to ensure the program runs "
-            "correctly.");
     auto dest = inputs[0], delta = inputs[1], alpha = inputs[2], beta = inputs[3];
+    if (!(inputs[0]->blob().unique() && inputs[0]->blob()->storage().unique())) {
+        mgb_log_warn(
+                "This inplace modification may change the elements of other tensors. "
+                "Fallback to non-inplace update.");
+
+        DeviceTensorStorage storage;
+        storage.reset(dest->comp_node(), dest->blob()->size(), dest->blob()->storage());
+        storage = storage.sub(dest->offset());
+        DeviceTensorND dv;
+        dv.reset(storage, dest->layout());
+
+        DeviceTensorND dv_new;
+        dv_new.copy_from(dv);
+        dest = Tensor::make(dv_new);
+    }
     auto tensor_to_scalar = [](const TensorPtr& tensor) -> float {
         return *tensor->get_value().ptr<float>();
     };
diff --git a/imperative/src/impl/ops/reduce.cpp b/imperative/src/impl/ops/reduce.cpp
index 75918bade7e86c21f6298405a68d1f812252b1f1..9be904175ae4090272fb016f94b728b1784fd270 100644
--- a/imperative/src/impl/ops/reduce.cpp
+++ b/imperative/src/impl/ops/reduce.cpp
@@ -54,7 +54,8 @@ SmallVector<TensorPtr> apply_on_physical_tensor(
         const OpDef& def, const SmallVector<TensorPtr>& inputs,
         SmallVector<LogicalTensorDesc>& output_descs, const bool& validated) {
     if (memory_forward_success(def, inputs)) {
-        return {Tensor::make(inputs[0]->blob(), 0, inputs[0]->layout())};
+        return {Tensor::make(
+                inputs[0]->blob(), inputs[0]->offset(), inputs[0]->layout())};
     }
     return proxy_graph_detail::apply_on_physical_tensor(
             def, inputs, output_descs, validated);
@@ -73,11 +74,21 @@ std::tuple<SmallVector<LogicalTensorDesc>, bool> infer_output_attrs_fallible(
     return {output_descs, validated};
 }
 
+SmallVector<VarNode::LayoutConstraintCallback> get_input_layout_constraint(
+        const OpDef& def, const SmallVector<TensorPtr>& inputs) {
+    SmallVector<VarNode::LayoutConstraintCallback> layout_checker(inputs.size());
+    layout_checker[0] = [](const TensorLayout& layout) {
+        return layout.is_contiguous();
+    };
+    return layout_checker;
+}
+
 OP_TRAIT_REG(Reduce, Reduce, opr::Reduce)
         .make_from_op_node(make_from_op_node)
         .apply_on_var_node(apply_on_var_node)
         .apply_on_physical_tensor(apply_on_physical_tensor)
         .infer_output_attrs_fallible(infer_output_attrs_fallible)
+        .get_input_layout_constraint(get_input_layout_constraint)
         .fallback();
 }  // namespace reduce
 }  // namespace
diff --git a/imperative/src/impl/ops/rng.cpp b/imperative/src/impl/ops/rng.cpp
index 6a8e67b2982407adfbd66b6c6b402249be62987a..1f969f43bda5ab9de3de8c159b3ae2b549522ad5 100644
--- a/imperative/src/impl/ops/rng.cpp
+++ b/imperative/src/impl/ops/rng.cpp
@@ -594,6 +594,13 @@ std::tuple<SmallVector<LogicalTensorDesc>, bool> infer_output_attrs_fallible<Dro
     return {dests, true};
 }
 
+template <typename Op>
+SmallVector<VarNode::LayoutConstraintCallback> get_input_layout_constraint(
+        const OpDef& def, const SmallVector<TensorPtr>& inputs) {
+    SmallVector<VarNode::LayoutConstraintCallback> layout_checker(inputs.size());
+    return layout_checker;
+}
+
 }  // anonymous namespace
 
 Handle new_handle(CompNode comp_node, uint64_t seed) {
@@ -622,6 +629,7 @@ CompNode get_rng_handle_compnode(Handle handle) {
             .apply_on_var_node(apply_on_var_node<NAME, Output>)             \
             .apply_on_physical_tensor(apply_on_physical_tensor<NAME>)       \
             .infer_output_attrs_fallible(infer_output_attrs_fallible<NAME>) \
+            .get_input_layout_constraint(get_input_layout_constraint<NAME>) \
             .fallback();                                                    \
     }
 
diff --git a/imperative/src/impl/ops/specializations.cpp b/imperative/src/impl/ops/specializations.cpp
index d3819a0471a81c29e1bf861aaa03f4e894165441..80868a87ed0e76043ec8c5bbeda40802afc88e31 100644
--- a/imperative/src/impl/ops/specializations.cpp
+++ b/imperative/src/impl/ops/specializations.cpp
@@ -60,9 +60,55 @@ auto apply_on_var_node(const OpDef& def, const VarNodeArray& inputs) {
     return opr::Dimshuffle::make(inputs[0], ds.pattern, 0UL, config);
 }
 
+SmallVector<TensorPtr> apply_on_physical_tensor(
+        const OpDef& def, const SmallVector<TensorPtr>& inputs,
+        SmallVector<LogicalTensorDesc>& output_descs, const bool& validated) {
+    auto&& ds = static_cast<const Dimshuffle&>(def);
+    mgb_assert(
+            ds.pattern.size() <= TensorShape::MAX_NDIM,
+            "Dimshuffle pattern exceeds max length of %zd", TensorShape::MAX_NDIM);
+    size_t nr_inp = inputs.size();
+    mgb_assert(nr_inp == 1, "Dimshuffle expects 1 inputs; got %lu actually", nr_inp);
+    auto&& src = inputs[0];
+    auto inp_layout = src->layout();
+    size_t pattern_ndim = *std::max_element(ds.pattern.begin(), ds.pattern.end()) + 1;
+    mgb_assert(
+            inp_layout.ndim == pattern_ndim,
+            "input ndim mismatch for Dimshuffle: expect=%zd actual=%zd", pattern_ndim,
+            inp_layout.ndim);
+    TensorLayout out_layout{inp_layout.dtype};
+    out_layout.ndim = ds.pattern.size();
+
+    size_t idx = 0;
+    bool input_used[TensorLayout::MAX_NDIM] = {0};
+    for (auto i : ds.pattern) {
+        if (i < 0) {
+            out_layout.shape[idx] = 1;
+            out_layout.stride[idx] = 1;
+        } else {
+            input_used[i] = true;
+            out_layout.shape[idx] = inp_layout.shape[i];
+            out_layout.stride[idx] = inp_layout.stride[i];
+        }
+        ++idx;
+    }
+    if (out_layout.is_contiguous()) {
+        out_layout.init_contiguous_stride();
+    }
+    for (size_t i = 0; i < pattern_ndim; ++i) {
+        mgb_assert(
+                input_used[i] || inp_layout.shape[i] == 1,
+                "non-1 dim discarded in Dimshuffle: ishp=%s dim=%zd",
+                inp_layout.megdnn::TensorShape::to_string().c_str(), i);
+    }
+    // memory forward
+    return {Tensor::make(src->blob(), src->offset(), out_layout)};
+}
+
 OP_TRAIT_REG(Dimshuffle, Dimshuffle, opr::Dimshuffle)
         .make_from_op_node(make_from_op_node)
         .apply_on_var_node(apply_on_var_node)
+        .apply_on_physical_tensor(apply_on_physical_tensor)
         .fallback();
 }  // namespace dimshuffle
 }  // namespace
@@ -80,7 +126,25 @@ auto apply_on_var_node(const OpDef& def, const VarNodeArray& inputs) {
     return opr::AxisAddRemove::make(inputs[0], param, config);
 }
 
-OP_TRAIT_REG(AddAxis, AddAxis).apply_on_var_node(apply_on_var_node).fallback();
+SmallVector<TensorPtr> apply_on_physical_tensor(
+        const OpDef& def, const SmallVector<TensorPtr>& inputs,
+        SmallVector<LogicalTensorDesc>& output_descs, const bool& validated) {
+    auto&& op_def = def.cast_final_safe<AddAxis>();
+    size_t nr_inp = inputs.size();
+    mgb_assert(nr_inp == 1, "AddAxis expects 1 inputs; got %lu actually", nr_inp);
+    auto&& src = inputs[0];
+    auto tlayout = src->layout();
+    for (auto&& i : op_def.axis) {
+        tlayout.add_axis_cont_inplace(i);
+    }
+    // memory forward
+    return {Tensor::make(src->blob(), src->offset(), tlayout)};
+}
+
+OP_TRAIT_REG(AddAxis, AddAxis)
+        .apply_on_var_node(apply_on_var_node)
+        .apply_on_physical_tensor(apply_on_physical_tensor)
+        .fallback();
 }  // namespace add_axis
 }  // namespace
 
@@ -97,7 +161,36 @@ auto apply_on_var_node(const OpDef& def, const VarNodeArray& inputs) {
     return opr::AxisAddRemove::make(inputs[0], param, config);
 }
 
-OP_TRAIT_REG(RemoveAxis, RemoveAxis).apply_on_var_node(apply_on_var_node).fallback();
+SmallVector<TensorPtr> apply_on_physical_tensor(
+        const OpDef& def, const SmallVector<TensorPtr>& inputs,
+        SmallVector<LogicalTensorDesc>& output_descs, const bool& validated) {
+    auto&& op_def = def.cast_final_safe<RemoveAxis>();
+    size_t nr_inp = inputs.size();
+    mgb_assert(nr_inp == 1, "RemoveAxis expects 1 inputs; got %lu actually", nr_inp);
+    auto&& src = inputs[0];
+    auto tlayout = src->layout();
+    for (auto&& i : op_def.axis) {
+        if (tlayout.ndim == 1) {
+            mgb_assert(
+                    tlayout.shape[0] == 1 && i == 0,
+                    "can not remove axis %u from tensor of shape=%s", i,
+                    tlayout.megdnn::TensorShape::to_string().c_str());
+        } else {
+            mgb_assert(
+                    i < tlayout.ndim && tlayout.shape[i] == 1,
+                    "can not remove axis %u from tensor of shape=%s", i,
+                    tlayout.megdnn::TensorShape::to_string().c_str());
+            tlayout.remove_axis_inplace(i);
+        }
+    }
+    // memory forward
+    return {Tensor::make(src->blob(), src->offset(), tlayout)};
+}
+
+OP_TRAIT_REG(RemoveAxis, RemoveAxis)
+        .apply_on_var_node(apply_on_var_node)
+        .apply_on_physical_tensor(apply_on_physical_tensor)
+        .fallback();
 }  // namespace remove_axis
 }  // namespace
 
diff --git a/imperative/src/impl/ops/utility.cpp b/imperative/src/impl/ops/utility.cpp
index d2aabed58018f8d68cad3088032ae7578039b5bf..d39a5958aae0d3e156434fa5e023464516971a0a 100644
--- a/imperative/src/impl/ops/utility.cpp
+++ b/imperative/src/impl/ops/utility.cpp
@@ -411,7 +411,7 @@ struct ComputingGraphHolder {
         executable->wait();
         size_t nr_inputs = inputs.size();
         for (size_t i = 0; i < nr_inputs; ++i) {
-            auto input_dev_tensor = input_tensors[i]->dev_tensor();
+            auto input_dev_tensor = input_tensors[i]->dev_tensor(false);
             inputs[i].device_value->reset(
                     input_dev_tensor.storage(), input_dev_tensor.layout());
             if (inputs[i].host_value) {
diff --git a/imperative/src/impl/physical_tensor.cpp b/imperative/src/impl/physical_tensor.cpp
index 5b0f52943896e653dab9e71901c4b27fbc4842b6..2a0994d7bf47f852039d01e1e1468e2a8afd142e 100644
--- a/imperative/src/impl/physical_tensor.cpp
+++ b/imperative/src/impl/physical_tensor.cpp
@@ -95,7 +95,13 @@ const Blob::RawStorage& Blob::storage() {
 
 Tensor::Tensor(
         BlobPtr blob, const TensorLayout& layout, size_t offset, const HostTensorND& hv)
-        : m_layout(layout), m_blob(std::move(blob)), m_offset(offset), m_value(hv) {}
+        : m_cn(blob->comp_node()),
+          m_shape(layout),
+          m_dtype(layout.dtype),
+          m_layout(layout),
+          m_blob(std::move(blob)),
+          m_offset(offset),
+          m_value(hv) {}
 
 Tensor::Tensor(const HostTensorND& hv) : Tensor(hv.layout(), hv.comp_node()) {
     constexpr int size_threshold = TensorShape::MAX_NDIM;
@@ -107,7 +113,12 @@ Tensor::Tensor(const HostTensorND& hv) : Tensor(hv.layout(), hv.comp_node()) {
         MGB_RECORD_EVENT(
                 profiler::HostToDeviceEvent, hv.layout(), hv.comp_node(), hv.raw_ptr(),
                 dev_tensor().raw_ptr());
-        dev_tensor().copy_from_fixlayout(hv);
+        DeviceTensorStorage storage;
+        storage.reset(m_cn, m_blob->size(), m_blob->storage());
+        storage = storage.sub(m_offset);
+        DeviceTensorND dv;
+        dv.reset(storage, m_layout);
+        dv.copy_from_fixlayout(hv);
         // even though hv is saved in m_value, Tensor itself could be
         // released before copy completes
         MGB_RECORD_EVENT(
@@ -117,25 +128,36 @@ Tensor::Tensor(const HostTensorND& hv) : Tensor(hv.layout(), hv.comp_node()) {
     }
 }
 
-Tensor::Tensor(const DeviceTensorND& dv, const HostTensorND& hv) {
+Tensor::Tensor(const DeviceTensorND& dv, const HostTensorND& hv)
+        : m_offset(dv.storage().offset()),
+          m_cn(dv.comp_node()),
+          m_shape(dv.layout()),
+          m_dtype(dv.layout().dtype),
+          m_blob(Blob::make(dv.storage())),
+          m_layout(dv.layout()) {
     if (!hv.empty()) {
         mgb_assert(dv.comp_node() == hv.comp_node());
         mgb_assert(dv.dtype() == hv.dtype());
         mgb_assert(dv.shape().eq_shape(hv.shape()));
         m_value = hv;
     }
-    m_layout = dv.layout();
-    m_blob = Blob::make(dv.storage());
-    m_offset = dv.storage().offset();
 }
 
 Tensor::Tensor(const TensorLayout& layout, const CompNode& cn)
         : m_layout{layout},
           m_blob{Blob::make(cn, layout.span().dist_byte())},
-          m_offset{0} {}
+          m_offset{0},
+          m_cn(cn),
+          m_shape(layout),
+          m_dtype(layout.dtype) {}
 
 Tensor::Tensor(const BlobPtr blob, const size_t offset, const TensorLayout& layout)
-        : m_layout{layout}, m_blob{blob}, m_offset{offset} {}
+        : m_layout{layout},
+          m_blob{blob},
+          m_offset{offset},
+          m_cn(blob->comp_node()),
+          m_shape(layout),
+          m_dtype(layout.dtype) {}
 
 TensorPtr Tensor::make(const HostTensorND& hv) {
     auto&& blob = MultiCNConstTensorCache::inst().lookup(hv);
@@ -145,10 +167,45 @@ TensorPtr Tensor::make(const HostTensorND& hv) {
     return std::make_shared<Tensor>(hv);
 }
 
-DeviceTensorND Tensor::dev_tensor() {
+void Tensor::to_contiguous_inplace(VarNode::LayoutConstraintCallback& layout_checker) {
+    MGB_LOCK_GUARD(m_blob_mtx);
+    if (!m_layout.is_empty() && !layout_checker(m_layout)) {
+        DeviceTensorStorage storage;
+        storage.reset(m_cn, m_blob->size(), m_blob->storage());
+        storage = storage.sub(m_offset);
+        DeviceTensorND dv;
+        dv.reset(storage, m_layout);
+
+        DeviceTensorND dv_contig;
+        dv_contig.copy_from(dv);
+        m_layout = dv_contig.layout();
+        std::atomic_store(&m_blob, Blob::make(dv_contig.storage()));
+        mgb_assert(m_layout.is_contiguous());
+        m_offset = 0;
+    }
+}
+
+void Tensor::to_contiguous_inplace() {
+    static VarNode::LayoutConstraintCallback default_cb =
+            [](const TensorLayout& layout) { return layout.is_contiguous(); };
+    to_contiguous_inplace(default_cb);
+}
+
+void Tensor::assign_from_dev_tensor(DeviceTensorND dv) {
+    MGB_LOCK_GUARD(m_blob_mtx);
+    std::atomic_store(&m_blob, Blob::make(dv.storage()));
+    m_offset = dv.storage().offset();
+    m_layout = dv.layout();
+}
+
+DeviceTensorND Tensor::dev_tensor(bool contiguous) {
     mgb_assert(m_blob, "uninitialized tensor.");
+    if (contiguous) {
+        to_contiguous_inplace();
+    }
+    MGB_LOCK_GUARD(m_blob_mtx);
     DeviceTensorStorage storage;
-    storage.reset(m_blob->comp_node(), m_blob->size(), m_blob->storage());
+    storage.reset(m_cn, m_blob->size(), m_blob->storage());
     storage = storage.sub(m_offset);
     DeviceTensorND ret;
     ret.reset(storage, m_layout);
@@ -156,16 +213,22 @@ DeviceTensorND Tensor::dev_tensor() {
 }
 
 void Tensor::fetch_value() {
-    MGB_LOCK_GUARD(m_mtx);
+    MGB_LOCK_GUARD(m_blob_mtx);
+    MGB_LOCK_GUARD(m_value_mtx);
     if (m_value.empty()) {
-        m_value.copy_from(dev_tensor());
+        DeviceTensorStorage storage;
+        storage.reset(m_cn, m_blob->size(), m_blob->storage());
+        storage = storage.sub(m_offset);
+        DeviceTensorND dv;
+        dv.reset(storage, m_layout);
+        m_value.copy_from(dv);
         m_value_ready.reset(EventPool::without_timer().alloc(comp_node()));
         m_value_ready->record();
     }
 }
 
 bool Tensor::value_fetched() {
-    MGB_LOCK_GUARD(m_mtx);
+    MGB_LOCK_GUARD(m_value_mtx);
     return m_value.layout().ndim != 0;
 }
 
@@ -178,7 +241,7 @@ const HostTensorND& Tensor::get_value() {
 }
 
 const HostTensorND* Tensor::try_get_value() {
-    MGB_LOCK_GUARD(m_mtx);
+    MGB_LOCK_GUARD(m_value_mtx);
     if (!m_value.empty() && (!m_value_ready || m_value_ready->finished())) {
         return &m_value;
     }
@@ -193,7 +256,7 @@ TensorPtr Tensor::make_scalar(DTypeScalar value, CompNode cn) {
 }
 
 TensorPtr Tensor::sub(size_t offset, TensorShape shape) {
-    TensorLayout layout(shape, m_layout.dtype);
+    TensorLayout layout(shape, m_dtype);
     return Tensor::make(m_blob, offset + m_offset, layout);
 }
 
diff --git a/imperative/src/impl/proxy_graph.cpp b/imperative/src/impl/proxy_graph.cpp
index 8248c6946280f4263792eb98eeba806d841c9c41..8cb19e987c865bd21b494b5c505db028172689f6 100644
--- a/imperative/src/impl/proxy_graph.cpp
+++ b/imperative/src/impl/proxy_graph.cpp
@@ -73,7 +73,7 @@ public:
     static SymbolVar make(ComputingGraph& graph, Tensor& tensor) {
         auto opr = graph.insert_opr(std::make_unique<InputPlaceholder>(graph, &tensor));
         auto var = opr->output(0);
-        auto&& dev_tensor = tensor.dev_tensor();
+        auto&& dev_tensor = tensor.dev_tensor(false);
         var->m_comp_node = dev_tensor.comp_node();
         var->m_shape = dev_tensor.shape();
         if (dev_tensor.empty()) {
@@ -81,10 +81,7 @@ public:
             layout.init_contiguous_stride();
             dev_tensor.reset(dev_tensor.storage(), layout);
         }
-        var->m_dev_tensor = dev_tensor;
-        var->m_mem_plan.reset_from_owner_var()
-                .chunk()
-                .mem_alloc_status.set_from_owner_var();
+        var->force_assign_dev_tensor_from_tensor(dev_tensor);
         return var;
     }
 
diff --git a/imperative/src/impl/proxy_graph/mini_graph.h b/imperative/src/impl/proxy_graph/mini_graph.h
index 1bc4482ca146bde7997a4de143597a239d7ecf27..67cc292ab469544a4ff9c13d9138d6326e7f691d 100644
--- a/imperative/src/impl/proxy_graph/mini_graph.h
+++ b/imperative/src/impl/proxy_graph/mini_graph.h
@@ -314,15 +314,11 @@ public:
         size_t idx = 0;
         for (auto&& input : opr_inputs) {
             mgb_assert(input->owner_opr()->same_type<InputPlaceholder>());
-            input->m_dev_tensor.storage({});
-            auto&& dev_tensor = inputs[input_remap[idx]]->dev_tensor();
+            auto&& dev_tensor = inputs[input_remap[idx]]->dev_tensor(false);
             auto&& layout = dev_tensor.layout();
             input->shape(dev_tensor.shape());
 
-            auto&& chk = input->m_mem_plan.reset_from_owner_var().chunk();
-            input->m_dev_tensor.reset(dev_tensor.storage(), layout);
-            input->m_mem_plan.layout(layout);
-            chk.mem_alloc_status.set_from_owner_var();
+            input->force_assign_dev_tensor_from_tensor(dev_tensor);
 
             mgb_assert(input->comp_node() == dev_tensor.comp_node());
             mgb_assert(input->shape().eq_shape(layout));
@@ -335,9 +331,14 @@ public:
         mgb_assert(m_opr->usable_output().size() == outputs.size());
         ::mgb::opr::intl::WorkspaceLimitHook::set_impl(
                 m_opr->owner_graph(), get_workspace_limit);
-        size_t j = 0;
+
         for (auto&& var : m_opr->output()) {
             auto&& chk = var->m_mem_plan.reset_from_owner_var().chunk();
+            chk.mem_alloc_status.set_from_owner_var();
+        }
+        m_opr->mem_plan_fwd_in2out_readonly();
+        size_t j = 0;
+        for (auto&& var : m_opr->output()) {
             if (var->contain_flag(VarNode::Flag::VOLATILE_CONTENT)) {
                 TensorLayout layout{var->shape(), var->dtype(), var->format()};
                 var->m_dev_tensor = BlobManager::inst()->alloc_workspace_with_defrag(
@@ -349,18 +350,16 @@ public:
                 mgb_assert(var->comp_node() == tensor->comp_node());
                 mgb_assert(var->shape().eq_shape(layout));
                 mgb_assert(var->dtype() == layout.dtype);
-                var->assign_dev_tensor_from_tensor(tensor->dev_tensor());
+                if (var->m_mem_plan.chunk().owner_var != var) {
+                    tensor->assign_from_dev_tensor(
+                            var->m_dev_tensor);  // memory forwarding
+                } else {
+                    var->assign_dev_tensor_from_tensor(tensor->dev_tensor());
+                }
                 ++j;
             }
-            chk.mem_alloc_status.set_from_owner_var();
         }
         mgb_assert(j == outputs.size());
-
-        // Memory forwarding was bypassed in megbrain with graph option
-        // imerative_proxy_graph on, here we call mem_plan_fwd_in2out_readonly
-        // to initialize some opr(e.g. Subtensor)'s internal state
-        // TODO: implement memory forwarding
-        m_opr->mem_plan_fwd_in2out_readonly();
         {
             // some opr (e.g. Reduce) rely on on_mem_status_changed to set
             // input/output tensor corretly, since we bypass var_node_mem_mgr
@@ -840,7 +839,7 @@ public:
                     Tensor::make(output_descs[i].layout, output_descs[i].comp_node);
         }
 
-        auto raw_outputs = to_raw_ptr_array(outputs);
+        auto raw_outputs = to_raw_ptr_array(outputs, false);
         CompNode::UnorderedSet used_cns;
         for (auto&& out : raw_outputs) {
             auto cn = out->comp_node();
diff --git a/imperative/src/impl/proxy_graph/proxy_graph.cpp b/imperative/src/impl/proxy_graph/proxy_graph.cpp
index e41469f0c4a511b77fb23a9d8eeac98e5f09015a..85345fb82f629c6484e8c04676fac73677b234e1 100644
--- a/imperative/src/impl/proxy_graph/proxy_graph.cpp
+++ b/imperative/src/impl/proxy_graph/proxy_graph.cpp
@@ -9,8 +9,12 @@
  * "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  */
 
+#include "../mgb_cg_impl.h"
 #include "./mini_graph.h"
+#include "megbrain/opr/io.h"
 
+using LayoutConstraintLevel = mgb::cg::VarNodeMemManager::LayoutConstraintLevel;
+using LayoutConstraintCallback = mgb::VarNode::LayoutConstraintCallback;
 namespace mgb::imperative::proxy_graph {
 MGB_DYN_TYPE_OBJ_FINAL_IMPL(ProxyGraph::InputPlaceholder);
 
@@ -34,4 +38,81 @@ SmallVector<TensorPtr> apply_on_physical_tensor(
     return ret;
 }
 
+std::unordered_map<size_t, SmallVector<LayoutConstraintCallback>>
+        input_layout_constraints_cache;
+
+SmallVector<LayoutConstraintCallback> get_input_layout_constraint(
+        const OpDef& def, const SmallVector<TensorPtr>& inputs) {
+    auto get_input_layout_constraint_hash_key =
+            [](const OpDef& def, const SmallVector<TensorPtr>& inputs) {
+                XXHash state;
+                size_t length = 0, data[1 + inputs.size()];
+                data[length++] = def.hash();
+                for (auto&& i : inputs) {
+                    data[length++] = mgb::hash(i->comp_node());
+                }
+                state.update(data, length * sizeof(size_t));
+                return state.digest();
+            };
+    auto hash_key = get_input_layout_constraint_hash_key(def, inputs);
+    auto&& iter = input_layout_constraints_cache.find(hash_key);
+    if (iter != input_layout_constraints_cache.end()) {
+        return iter->second;
+    }
+    static cg::ComputingGraphImpl* graph =
+            imperative::ResourceManager::create_global<cg::ComputingGraphImpl>();
+    VarNodeArray vinputs(inputs.size());
+    for (size_t i = 0; i < inputs.size(); ++i) {
+        OperatorNodeConfig config;
+        auto&& layout = inputs[i]->layout();
+        layout.init_contiguous_stride();
+        vinputs[i] = graph->insert_opr(std::make_unique<mgb::opr::SharedDeviceTensor>(
+                                               *graph,
+                                               std::make_shared<DeviceTensorND>(
+                                                       inputs[i]->comp_node(), layout),
+                                               false, config))
+                             ->output(0);
+    }
+    auto&& opr = OpDef::apply_on_var_node(def, vinputs)[0]->owner_opr();
+    opr->add_input_layout_constraint();
+
+    SmallVector<LayoutConstraintCallback> res(inputs.size());
+    auto& mem_mgr = graph->var_node_mem_manager();
+    for (size_t i = 0; i < vinputs.size(); ++i) {
+        auto& trait = mem_mgr.get_var_node_mem_trait(vinputs[i]);
+        switch (trait.layout_constraint.level) {
+            case LayoutConstraintLevel::CONTIG:
+                res[i] = [](const TensorLayout& layout) {
+                    return layout.is_contiguous();
+                };
+                break;
+            case LayoutConstraintLevel::MONOTONE:
+                res[i] = [&trait](const TensorLayout& layout) {
+                    if (!layout.is_abs_monotonous_allow_brdcst()) {
+                        return false;
+                    }
+                    for (auto&& i : trait.layout_constraint.custom)
+                        if (!i(layout))
+                            return false;
+                    return true;
+                };
+                break;
+            case LayoutConstraintLevel::NONE:
+                if (!trait.layout_constraint.custom.empty()) {
+                    res[i] = [&trait](const TensorLayout& layout) {
+                        for (auto&& i : trait.layout_constraint.custom)
+                            if (!i(layout))
+                                return false;
+                        return true;
+                    };
+                }
+                break;
+            default:
+                mgb_throw(InternalError, "invalid layout_constraint_level");
+        }
+    }
+    input_layout_constraints_cache.emplace(hash_key, res);
+    return res;
+}
+
 }  // namespace mgb::imperative::proxy_graph_detail
diff --git a/imperative/src/impl/subgraph_detail.cpp b/imperative/src/impl/subgraph_detail.cpp
index d9deef5ae8a540cd5a32c04e02bc0afc479270dd..ecf0044764e6c81a453eb2e00881c51604bdbbe7 100644
--- a/imperative/src/impl/subgraph_detail.cpp
+++ b/imperative/src/impl/subgraph_detail.cpp
@@ -17,6 +17,8 @@
 
 #include "./op_trait.h"
 
+using LayoutConstraintCallback = mgb::VarNode::LayoutConstraintCallback;
+
 namespace mgb {
 namespace imperative {
 namespace subgraph_detail {
@@ -73,6 +75,13 @@ SmallVector<TensorPtr> apply_on_physical_tensor(
                                  const std::shared_ptr<OpDef>& op,
                                  const SmallVector<TensorPtr>& inputs,
                                  size_t nr_outputs) {
+        auto&& constraints = OpDef::get_input_layout_constraint(*op, inputs);
+        for (size_t idx = 0; idx < inputs.size(); ++idx) {
+            auto&& layout_checker = constraints[idx];
+            if (layout_checker) {
+                inputs[idx]->to_contiguous_inplace(layout_checker);
+            }
+        }
         // do not use infered output_desc in subgraph
         return OpDef::apply_on_physical_tensor(*op, inputs, output_descs, false);
     };
@@ -81,6 +90,12 @@ SmallVector<TensorPtr> apply_on_physical_tensor(
     return outputs;
 }
 
+SmallVector<LayoutConstraintCallback> get_input_layout_constraint(
+        const OpDef& def, const SmallVector<TensorPtr>& inputs) {
+    SmallVector<LayoutConstraintCallback> res(inputs.size());
+    return res;
+}
+
 static EncodedSubgraph make_backward_graph_from_forward(
         const SmallVector<LogicalTensorDesc>& inputs,
         const SmallVector<bool>& input_requires_grad,
diff --git a/imperative/src/include/megbrain/imperative/op_def.h b/imperative/src/include/megbrain/imperative/op_def.h
index d38d1447908ccb7752e2ecc27ae2deeacaaa9515..8bd01fba5b3de5a19f7787fdd2a6ec811d696a18 100644
--- a/imperative/src/include/megbrain/imperative/op_def.h
+++ b/imperative/src/include/megbrain/imperative/op_def.h
@@ -78,6 +78,9 @@ public:
     static EncodedSubgraph make_forward_graph(
             const OpDef& def, const SmallVector<LogicalTensorDesc>& inputs);
 
+    static SmallVector<VarNode::LayoutConstraintCallback> get_input_layout_constraint(
+            const OpDef& def, const SmallVector<TensorPtr>& inputs);
+
     const OpTrait* trait() const;
 
     std::string to_string() const;
diff --git a/imperative/src/include/megbrain/imperative/physical_tensor.h b/imperative/src/include/megbrain/imperative/physical_tensor.h
index 46ef85047083124e5503bfb0015974165a8c94a5..ca2232f00bc27a0be37469e2b29717be769032db 100644
--- a/imperative/src/include/megbrain/imperative/physical_tensor.h
+++ b/imperative/src/include/megbrain/imperative/physical_tensor.h
@@ -14,6 +14,7 @@
 #include <memory>
 #include <mutex>
 
+#include "megbrain/graph.h"
 #include "megbrain/imperative/resource_manager.h"
 #include "megbrain/tensor.h"
 
@@ -90,18 +91,24 @@ public:
 
     CompNode comp_node() const {
         mgb_assert(m_blob, "uninitialized tensor.");
-        return m_blob->comp_node();
+        return m_cn;
     }
 
-    DType dtype() const { return m_layout.dtype; }
+    DType dtype() const { return m_dtype; }
 
     TensorLayout layout() const { return m_layout; }
 
-    const TensorShape& shape() const { return m_layout; }
+    const TensorShape& shape() const { return m_shape; }
 
     size_t offset() const { return m_offset; }
 
-    DeviceTensorND dev_tensor();
+    void to_contiguous_inplace(VarNode::LayoutConstraintCallback&);
+
+    void to_contiguous_inplace();
+
+    DeviceTensorND dev_tensor(bool contiguous = true);
+
+    void assign_from_dev_tensor(DeviceTensorND);
 
     static TensorPtr make_scalar(DTypeScalar value, CompNode cn);
 
@@ -110,7 +117,7 @@ public:
         return make_scalar(value, m_blob->comp_node());
     }
 
-    BlobPtr& blob() { return m_blob; }
+    BlobPtr blob() { return m_blob; }
 
     void fetch_value();
     bool value_fetched();
@@ -131,10 +138,16 @@ public:
     static void static_initialize();
 
 private:
-    TensorLayout m_layout;
-    BlobPtr m_blob;
     size_t m_offset;
-    std::mutex m_mtx;
+    const CompNode m_cn;
+    const TensorShape m_shape;
+    const DType m_dtype;
+
+    std::mutex m_blob_mtx;
+    BlobPtr m_blob;
+    TensorLayout m_layout;
+
+    std::mutex m_value_mtx;
     HostTensorND m_value;
     EventPtr m_value_ready = nullptr;
 };
diff --git a/imperative/src/include/megbrain/imperative/proxy_graph_detail.h b/imperative/src/include/megbrain/imperative/proxy_graph_detail.h
index f249c52b9afb4f96999e8993ace94479d55e5afb..f67ff10c09057bf087ee0e62cb09682e46ec97c1 100644
--- a/imperative/src/include/megbrain/imperative/proxy_graph_detail.h
+++ b/imperative/src/include/megbrain/imperative/proxy_graph_detail.h
@@ -33,6 +33,9 @@ EncodedSubgraph make_backward_graph(
         const SmallVector<bool>& input_requires_grad,
         const SmallVector<bool>& output_has_grad);
 
+SmallVector<VarNode::LayoutConstraintCallback> get_input_layout_constraint(
+        const OpDef& def, const SmallVector<TensorPtr>& inputs);
+
 }  // namespace proxy_graph_detail
 }  // namespace imperative
 }  // namespace mgb
diff --git a/imperative/src/include/megbrain/imperative/subgraph_detail.h b/imperative/src/include/megbrain/imperative/subgraph_detail.h
index 7e463dfcd2fc0e20a38478f5a9c92ba2ebbf0412..d180fb3947915e054e1deb2a00784b7bf04728f4 100644
--- a/imperative/src/include/megbrain/imperative/subgraph_detail.h
+++ b/imperative/src/include/megbrain/imperative/subgraph_detail.h
@@ -36,6 +36,9 @@ EncodedSubgraph make_backward_graph(
         const SmallVector<bool>& input_requires_grad,
         const SmallVector<bool>& output_has_grad);
 
+SmallVector<VarNode::LayoutConstraintCallback> get_input_layout_constraint(
+        const OpDef& def, const SmallVector<TensorPtr>& inputs);
+
 }  // namespace subgraph_detail
 }  // namespace imperative
 }  // namespace mgb
\ No newline at end of file
diff --git a/src/core/impl/graph/cg_impl.cpp b/src/core/impl/graph/cg_impl.cpp
index 1822b318a0e74192813e163e91bcde8cab907fd4..59979a16c76cfdf7f65053409f889fe3b4389815 100644
--- a/src/core/impl/graph/cg_impl.cpp
+++ b/src/core/impl/graph/cg_impl.cpp
@@ -322,7 +322,7 @@ void ComputingGraphImpl::free_varnode_storage(void* ptr) {
     m_var_node_pool.free_raw(ptr);
 };
 
-OperatorNodeBase* ComputingGraphImpl::insert_opr(
+MGE_WIN_DECLSPEC_FUC OperatorNodeBase* ComputingGraphImpl::insert_opr(
         std::unique_ptr<OperatorNodeBase> opr_uniqp) {
     auto opr = opr_uniqp.get();
 
diff --git a/src/core/impl/graph/cg_impl.h b/src/core/impl/graph/cg_impl.h
index 07b8b0bd133e62ee718609ca3011a1b5ba05ee4d..00fadd40ddaa4661fc62d7c9c28e3f87d9f6fc6d 100644
--- a/src/core/impl/graph/cg_impl.h
+++ b/src/core/impl/graph/cg_impl.h
@@ -148,8 +148,8 @@ class ComputingGraphImpl final : public ComputingGraph {
 public:
     class ComputingSequence;
 
-    ComputingGraphImpl();
-    ~ComputingGraphImpl();
+    MGE_WIN_DECLSPEC_FUC ComputingGraphImpl();
+    MGE_WIN_DECLSPEC_FUC ~ComputingGraphImpl();
 
     template <typename T>
     static ComputingGraphImpl* downcast(T* ptr) = delete;
@@ -166,7 +166,8 @@ public:
     SmallVector<std::unique_ptr<AsyncExecutable>> compile_multi_part(
             const SmallVector<OutputSpec>& out_specs) override;
 
-    OperatorNodeBase* insert_opr(std::unique_ptr<OperatorNodeBase> opr) override;
+    MGE_WIN_DECLSPEC_FUC OperatorNodeBase* insert_opr(
+            std::unique_ptr<OperatorNodeBase> opr) override;
 
     void* alloc_varnode_storage() override;
 
diff --git a/src/core/impl/graph/var_node.cpp b/src/core/impl/graph/var_node.cpp
index a9ceb3646ad702dc94944f6ad97021abb7dd8ba8..2abec6eee3d2cfa9d6759dc55164cbad750a8168 100644
--- a/src/core/impl/graph/var_node.cpp
+++ b/src/core/impl/graph/var_node.cpp
@@ -93,6 +93,23 @@ MemAllocPlan& MemAllocPlan::assign_for_forward(
     return *this;
 }
 
+MemAllocPlan& MemAllocPlan::force_assign_for_forward(
+        const MemAllocPlan& src, const SubTensorSpec& sub) {
+    mgb_assert(valid() && src.valid() && m_layout.eq_shape(sub.layout()));
+    ++(m_chunk = src.m_chunk)->m_refcnt;
+    m_layout = sub.layout();
+    // make layout strong-contig
+    for (int i = static_cast<int>(m_layout.ndim) - 1; i >= 0; --i) {
+        if (m_layout.shape[i] == 1) {
+            m_layout.stride[i] = i + 1 < static_cast<int>(m_layout.ndim)
+                                       ? m_layout.stride[i + 1] * m_layout.shape[i + 1]
+                                       : 1;
+        }
+    }
+    m_layout.dtype = dtype();
+    return *this;
+}
+
 MemAllocPlan& MemAllocPlan::reset_from_owner_var() {
     auto owner_var = m_chunk_storage.owner_var;
     m_layout.dtype = dtype();
@@ -223,7 +240,12 @@ VarNode& VarNode::format(TensorFormat format) {
 
 bool VarNode::set_fwd_in2out_readonly(VarNode* input, const SubTensorSpec& sub) {
     if (owner_graph()->options().imperative_proxy_graph) {
-        return false;
+        if (input->comp_node() != comp_node()) {
+            return false;
+        }
+        m_mem_plan.force_assign_for_forward(input->m_mem_plan, sub);
+        m_dev_tensor = input->dev_tensor().sub(sub);
+        return true;
     }
     return ComputingGraphImpl::downcast(owner_graph())
             ->var_node_mem_manager()
@@ -361,6 +383,13 @@ VarNode& VarNode::reset_dev_tensor_from_tensor(const DeviceTensorND& value) {
     return *this;
 }
 
+void VarNode::force_assign_dev_tensor_from_tensor(const DeviceTensorND& value) {
+    m_dev_tensor = value;
+    shape(value.shape());
+    m_mem_plan.reset_from_owner_var().chunk().mem_alloc_status.set_from_owner_var();
+    m_mem_plan.layout(value.layout());
+}
+
 void VarNode::assign_dev_tensor_from_tensor(const DeviceTensorND& value) {
     mgb_assert(
             (value.layout().is_contiguous() || value.empty()) &&
diff --git a/src/core/impl/tensor.cpp b/src/core/impl/tensor.cpp
index 0939ee05b0af44ecab47c996a49e72983e6305d9..eef3d805a9c52418e6ad9c46ccd45ff27eb8569c 100644
--- a/src/core/impl/tensor.cpp
+++ b/src/core/impl/tensor.cpp
@@ -475,7 +475,7 @@ DEF(CompNode node, const TensorShape& shape, DType dtype, TensorFormat format)
 DEF(CompNode node, const TensorLayout& layout)
         : TensorND(node, layout, layout.dtype, layout.format) {
     mgb_assert(
-            layout.is_contiguous(),
+            layout.is_contiguous() || layout.is_empty(),
             "non-contiguous layout used for initializing a tensor: %s",
             layout.to_string().c_str());
 }
diff --git a/src/core/include/megbrain/graph/cg.h b/src/core/include/megbrain/graph/cg.h
index ae1d4a16554eb8e598b682394781da95cf1c16c6..49a6eaf0861a4a1424cf26ad39607552e0b147bd 100644
--- a/src/core/include/megbrain/graph/cg.h
+++ b/src/core/include/megbrain/graph/cg.h
@@ -241,7 +241,8 @@ public:
      * \return the node in the graph (maybe another node due to
      *      deduplication)
      */
-    virtual OperatorNodeBase* insert_opr(std::unique_ptr<OperatorNodeBase> opr) = 0;
+    MGE_WIN_DECLSPEC_FUC virtual OperatorNodeBase* insert_opr(
+            std::unique_ptr<OperatorNodeBase> opr) = 0;
 
     /*!
      * \brief used by OperatorNodeBase to allocate its outputs
diff --git a/src/core/include/megbrain/graph/var_node.h b/src/core/include/megbrain/graph/var_node.h
index 670333ec71cebe81e4d46b8ee3834b6ceba8a360..271581af5dfe30aecb96e6723d140922162627ab 100644
--- a/src/core/include/megbrain/graph/var_node.h
+++ b/src/core/include/megbrain/graph/var_node.h
@@ -194,6 +194,10 @@ public:
     MGE_WIN_DECLSPEC_FUC MemAllocPlan& assign_for_forward(
             const MemAllocPlan& src, const SubTensorSpec& sub);
 
+    //! force assign for readonly forward
+    MGE_WIN_DECLSPEC_FUC MemAllocPlan& force_assign_for_forward(
+            const MemAllocPlan& src, const SubTensorSpec& sub);
+
     /*!
      * \brief next readonly-forward reader of this MemAllocPlan
      *
@@ -509,6 +513,9 @@ public:
     //! NO_SYS_MEM_ALLOC can be modified.
     MGE_WIN_DECLSPEC_FUC bool is_graph_dest_varnode();
 
+    MGE_WIN_DECLSPEC_FUC void force_assign_dev_tensor_from_tensor(
+            const DeviceTensorND& value);
+
 private:
     //! whether its memory should be allocated by mgb system during graph
     //! execution; initialized in VarNodeMemManager::reset_opr_seq()
diff --git a/src/opr/include/megbrain/opr/io.h b/src/opr/include/megbrain/opr/io.h
index a1aba48df6712e4ff0cc2814351e7abc5b7fcaeb..562fe76710cb2ebb25749de04b90a807c627521b 100644
--- a/src/opr/include/megbrain/opr/io.h
+++ b/src/opr/include/megbrain/opr/io.h
@@ -24,7 +24,7 @@ namespace intl {
  * \brief base class for IO nodes between device and host
  */
 class HostIONodeBase : public cg::SingleCNOperatorNodeBase {
-    void init_output_static_infer_desc() override final;
+    MGE_WIN_DECLSPEC_FUC void init_output_static_infer_desc() override final;
 
 protected:
     using cg::SingleCNOperatorNodeBase::SingleCNOperatorNodeBase;
@@ -32,9 +32,10 @@ protected:
     /*!
      * \brief src_type for static shape and value infer
      */
-    virtual cg::static_infer::SourceType static_infer_src_type() const;
+    MGE_WIN_DECLSPEC_FUC virtual cg::static_infer::SourceType static_infer_src_type()
+            const;
 
-    virtual const TensorShape& get_output_shape() = 0;
+    MGE_WIN_DECLSPEC_FUC virtual const TensorShape& get_output_shape() = 0;
 
     /*!
      * \brief fill value in *dest* for static inference
@@ -52,10 +53,10 @@ protected:
 class DeviceTensorHolder : public HostIONodeBase {
     class DevValueExecDep;
 
-    void init_output_format() override;
-    void init_output_mem_plan(bool dynamic) override final;
-    void scn_do_execute() override final;
-    void record_execute_deps(ExecDependencyArray& deps) override;
+    MGE_WIN_DECLSPEC_FUC void init_output_format() override;
+    MGE_WIN_DECLSPEC_FUC void init_output_mem_plan(bool dynamic) override final;
+    MGE_WIN_DECLSPEC_FUC void scn_do_execute() override final;
+    MGE_WIN_DECLSPEC_FUC void record_execute_deps(ExecDependencyArray& deps) override;
 
 protected:
     using HostIONodeBase::HostIONodeBase;
@@ -77,20 +78,20 @@ MGB_DEFINE_CLS_WITH_SUPER(SharedDeviceTensorBase, DeviceTensorHolder) // {
     std::shared_ptr<DeviceTensorND> m_dev_data;
     bool m_const_value;
 
-    const TensorShape& get_output_shape() override;
+    MGE_WIN_DECLSPEC_FUC const TensorShape& get_output_shape() override;
 
     bool fill_in_static_infer(DeviceTensorND* dest) override {
         MGB_MARK_USED_VAR(dest);
         return false;
     }
 
-    void init_output_comp_node() override;
+    MGE_WIN_DECLSPEC_FUC void init_output_comp_node() override;
 
 public:
     //! const_value marks whether the device value of this operator should
     //! be treated as constant during graph execution. Should be false in
     //! most cases.
-    SharedDeviceTensorBase(
+    MGE_WIN_DECLSPEC_FUC SharedDeviceTensorBase(
             ComputingGraph& graph, const std::shared_ptr<DeviceTensorND>& dev_data,
             bool const_value, const OperatorNodeConfig& config);
 
@@ -248,7 +249,8 @@ private:
  */
 MGB_DEFINE_OPR_CLASS_WITH_EXPORT(
         SharedDeviceTensor, intl::SharedDeviceTensorBase) // {
-    cg::static_infer::SourceType static_infer_src_type() const override;
+    MGE_WIN_DECLSPEC_FUC cg::static_infer::SourceType static_infer_src_type()
+            const override;
 
 public:
     using Super::Super;