fix(trace): constants in backward graph treat as ImmutableTensor corectlly

GitOrigin-RevId: 5fd6a5e00c5b5ddeb19cedde62f2739e76c7bf41

imperative/python/src/tensor.cpp

@@ -13,6 +13,7 @@
 #include "megbrain/common.h"
 #include "megbrain/imperative/ops/utility.h"
 #include "megbrain/imperative/ops/backward_graph.h"
+#include "megbrain/opr/io.h"
 
 #include "./tensor.h"
 #include "./grad.h"
@@ -39,6 +40,26 @@ interpreter::Interpreter::Channel* interpreter_for_py;
 PyObject *cpp_apply_with_tracing, *cpp_apply_const_with_tracing;
 PyObject *cpp_apply_backward_varnode;
 
+std::shared_ptr<Tensor> make_const(imperative::TensorPtr value) {
+    if (!(ApplyContext::global_enable & Tensor::Flags::TRACE)) {
+        return std::make_shared<Tensor>(interpreter_for_py->put(value->dev_tensor()));
+    }
+    py::tuple tup(6);
+    auto data = value->get_value();
+    tup[0] = py::reinterpret_steal<py::array>(ndarray_from_tensor(data, npy::ShareType::MUST_SHARE));
+    tup[1] = value->dtype();
+    tup[2] = value->comp_node();
+    tup[3] = true;
+    tup[4] = false;
+    tup[5] = py::none{};
+    auto py_ret = PyObject_Call(cpp_apply_const_with_tracing, tup.ptr(), nullptr);
+    if (!py_ret) throw py::error_already_set();
+    auto py_list = py::reinterpret_steal<py::list>(py_ret);
+    auto* tensor_wrapper = TensorWrapper::try_cast(py_list[0].ptr());
+    auto tensor = tensor_wrapper->m_tensor;
+    return tensor_wrapper->m_tensor;
+}
+
 #define REGISTE_APPLY_FUNC(mode)            \
         void set_##mode(py::object pyf) {   \
             mode = pyf.ptr();               \

imperative/python/src/tensor.h

@@ -271,18 +271,17 @@ auto apply(std::shared_ptr<OpDef> op, T&& tensors)
     return apply(op, args, nargs);
 }
 
+std::shared_ptr<Tensor> make_const(imperative::TensorPtr value);
+
 inline auto apply(Subgraph graph, Tensor*const* args, size_t nargs) {
     SmallVector<std::shared_ptr<Tensor>> inputs;
     for (size_t i = 0; i < nargs; ++i) {
         inputs.push_back(args[i]->shared_from_this());
     }
     auto apply_functor = [](std::shared_ptr<OpDef> op, SmallVector<std::shared_ptr<Tensor>> inputs) {
-        return apply(op, inputs);
-    };
-    auto const_functor = [](imperative::TensorPtr value) {
-        return std::make_shared<Tensor>(interpreter_for_py->put(value->dev_tensor()));
+        return apply(op, std::move(inputs));
     };
-    return graph.apply(inputs, apply_functor, const_functor);
+    return graph.apply(inputs, apply_functor, &make_const);
 }
 
 template <typename T>