trans const to variable in assign case

mindspore/ccsrc/transform/convert.cc

@@ -1154,6 +1154,9 @@ void DfGraphConvertor::SetOpControlInput(const AnfNodePtr node) {
   }
 }
 
+const std::vector<std::string> trans_var_list = {prim::kPrimAssign->name(), string(kNameAssignAdd),
+                                                 string(kNameAssignSub)};
+
 void DfGraphConvertor::SetOpInput(const OpAdapterPtr &adpt, const CNodePtr &node) {
   OperatorPtr src = Convert(node);
   auto &inputs = node->inputs();
@@ -1166,6 +1169,26 @@ void DfGraphConvertor::SetOpInput(const OpAdapterPtr &adpt, const CNodePtr &node
     if (IsValueNode<None>(pred)) {
       continue;
     }
+    // transform "Const" op to "Variable" op when the next node is "Assign" op.
+    std::string c_name = GetCNodeFuncName(node);
+    auto pos = std::find(trans_var_list.begin(), trans_var_list.end(), c_name);
+    if (!training_ && pos != trans_var_list.end() && pred->isa<Parameter>()) {
+      std::string name = std::static_pointer_cast<Parameter>(pred)->name();
+      auto op_itor = op_cache_.find(pred.get());
+      if (op_itor == op_cache_.end()) {
+        MS_LOG(EXCEPTION) << "Can not find op for node " << pred->ToString() << ".";
+      }
+      if (op_itor->second != nullptr &&
+          (op_itor->second->GetOpType() == "Constant" || op_itor->second->GetOpType() == "Const") &&
+          vars_.find(name) != vars_.end()) {
+        auto variable = std::make_shared<Variable>(name);
+        auto desc = vars_[name]->GetOutputDesc("y");
+        (void)variable->update_output_desc_y(desc);
+        MS_LOG(DEBUG) << "Trans to variable, var = " << variable->GetName() << ".";
+        op_itor->second = variable;  // replace parameter with variable
+        vars_[name] = variable;
+      }
+    }
     // find in out_hadnle_cache_ first
     auto it = out_handle_cache_.find(pred.get());
     if (it != out_handle_cache_.end()) {