!10432 keep nop node in execution order if it's graph's output

From: @liubuyu
Reviewed-by: @zhoufeng54,@kisnwang
Signed-off-by: @kisnwang

mindspore/ccsrc/backend/optimizer/common/helper.cc

@@ -317,17 +317,35 @@ bool IsAllNopNode(const session::KernelGraph *const graph) {
   return true;
 }
 
+bool CheckNopNodeIsOutputNode(const std::vector<AnfNodePtr> &outputs, const AnfNodePtr &node, bool is_dynamic_graph) {
+  MS_EXCEPTION_IF_NULL(node);
+  // if node is not a nop node, keep it in execution order
+  if (!IsNopNode(node)) {
+    return true;
+  }
+  // if node is nop node and the graph is dynamic graph, check if the nop node is graph's output.
+  if (is_dynamic_graph) {
+    auto iter = find(outputs.begin(), outputs.end(), node);
+    if (iter != outputs.end()) {
+      return true;
+    }
+  }
+  return false;
+}
+
 void HideNopNode(session::KernelGraph *const graph) {
   MS_EXCEPTION_IF_NULL(graph);
   if (IsAllNopNode(graph) == true) {
     return;
   }
   auto execution_order = graph->execution_order();
+  auto outputs = graph->outputs();
+  bool is_dynamic_graph = graph->is_dynamic_shape();
   MS_LOG(INFO) << "nop node info (Before Remove) size: " << execution_order.size();
   std::vector<CNodePtr> new_nodes;
   for (auto &cnode : execution_order) {
     MS_EXCEPTION_IF_NULL(cnode);
-    if (!IsNopNode(cnode)) {
+    if (CheckNopNodeIsOutputNode(outputs, cnode, is_dynamic_graph)) {
       new_nodes.push_back(cnode);
     }
   }
@@ -344,10 +362,12 @@ void RemoveNopNode(session::KernelGraph *const graph) {
   while (changed) {
     changed = false;
     std::vector<CNodePtr> new_nodes;
+    auto outputs = graph->outputs();
+    bool is_dynamic_graph = graph->is_dynamic_shape();
     for (auto &cnode : graph->execution_order()) {
       MS_EXCEPTION_IF_NULL(cnode);
       // ignore nop node itself
-      if (IsNopNode(cnode)) {
+      if (!CheckNopNodeIsOutputNode(outputs, cnode, is_dynamic_graph)) {
         continue;
       }
       // Replace the input which is nop node