Fix copy elision warning (#35885)

* Fix copy elision warning

* Remove redundand code

paddle/fluid/framework/fleet/gloo_wrapper.h

@@ -215,7 +215,7 @@ class GlooWrapper {
 #else
     LOG(WARNING) << "AllGather does nothing when WITH_GLOO=OFF";
 #endif
-    return std::move(ret);
+    return ret;
   }
 
  protected:

paddle/fluid/framework/ir/fc_gru_fuse_pass_tester.h

@@ -88,7 +88,7 @@ std::unique_ptr<ir::Graph> PrepareGraph(
              nullptr, false, false, activation, gate_activation);
 
   std::unique_ptr<ir::Graph> graph(new ir::Graph(layers.main_program()));
-  return std::move(graph);
+  return graph;
 }
 }  // namespace fc_gru_test
 }  // namespace ir

paddle/fluid/framework/ir/fc_lstm_fuse_pass_tester.h

@@ -91,7 +91,7 @@ std::unique_ptr<ir::Graph> PrepareGraph(
               false, gate_activation, cell_activation, candidate_activation);
 
   std::unique_ptr<ir::Graph> graph(new ir::Graph(layers.main_program()));
-  return std::move(graph);
+  return graph;
 }
 
 }  // namespace fc_lstm_test

paddle/fluid/framework/new_executor/interpretercore_util.cc

@@ -25,7 +25,7 @@ AtomicVectorSizeT AsyncWorkQueue::PrepareAtomicDeps(
     working_dependecy_count[i] =
         std::make_unique<std::atomic<size_t>>(dependecy_count[i]);
   }
-  return std::move(working_dependecy_count);
+  return working_dependecy_count;
 }
 
 AtomicVectorSizeT AsyncWorkQueue::PrepareAtomicVarRef(
@@ -36,7 +36,7 @@ AtomicVectorSizeT AsyncWorkQueue::PrepareAtomicVarRef(
     working_var_ref[i] =
         std::make_unique<std::atomic<size_t>>(vec_meta_info[i].var_ref_count_);
   }
-  return std::move(working_var_ref);
+  return working_var_ref;
 }
 
 bool var_can_be_deleted(const std::string& name, const BlockDesc& block) {

paddle/fluid/framework/new_executor/workqueue.cc

@@ -147,7 +147,7 @@ std::unique_ptr<WorkQueue> CreateSingleThreadedWorkQueue(
                         "For a SingleThreadedWorkQueue, "
                         "WorkQueueOptions.num_threads must equals to 1."));
   std::unique_ptr<WorkQueue> ptr(new WorkQueueImpl(options));
-  return std::move(ptr);
+  return ptr;
 }
 
 std::unique_ptr<WorkQueue> CreateMultiThreadedWorkQueue(
@@ -158,7 +158,7 @@ std::unique_ptr<WorkQueue> CreateMultiThreadedWorkQueue(
                                         "WorkQueueOptions.num_threads must be "
                                         "greater than 1."));
   std::unique_ptr<WorkQueue> ptr(new WorkQueueImpl(options));
-  return std::move(ptr);
+  return ptr;
 }
 
 std::unique_ptr<WorkQueueGroup> CreateWorkQueueGroup(
@@ -168,7 +168,7 @@ std::unique_ptr<WorkQueueGroup> CreateWorkQueueGroup(
                         "For a WorkQueueGroup, the number of WorkQueueOptions "
                         "must be greater than 1."));
   std::unique_ptr<WorkQueueGroup> ptr(new WorkQueueGroupImpl(queues_options));
-  return std::move(ptr);
+  return ptr;
 }
 
 }  // namespace framework

paddle/fluid/inference/api/api_impl.cc

@@ -192,14 +192,7 @@ std::unique_ptr<PaddlePredictor> NativePaddlePredictor::Clone() {
     LOG(ERROR) << "fail to call Init";
     return nullptr;
   }
-
-#ifdef __clang__
-  // fix clang compile error
   return cls;
-#else
-  // fix manylinux compile error.
-  return std::move(cls);
-#endif
 }
 
 bool NativePaddlePredictor::SetFeed(const std::vector<PaddleTensor> &inputs,
@@ -390,12 +383,7 @@ std::unique_ptr<PaddlePredictor> CreatePaddlePredictor<
   if (!dynamic_cast<NativePaddlePredictor *>(predictor.get())->Init(nullptr)) {
     return nullptr;
   }
-#ifdef __clang__
-  // fix clang compile error
   return predictor;
-#else
-  return std::move(predictor);
-#endif
 }
 
 template <>

paddle/fluid/memory/allocation/mmap_allocator.cc

@@ -59,7 +59,7 @@ std::string GetIPCName() {
 #endif
   handle += "_";
   handle += std::to_string(rd());
-  return std::move(handle);
+  return handle;
 }
 
 std::shared_ptr<MemoryMapWriterAllocation> AllocateMemoryMapWriterAllocation(

paddle/fluid/pybind/inference_api.cc

@@ -324,7 +324,7 @@ void BindInferenceApi(py::module *m) {
                                    auto pred =
                                        std::unique_ptr<paddle_infer::Predictor>(
                                            new paddle_infer::Predictor(config));
-                                   return std::move(pred);
+                                   return pred;
                                  });
   m->def("copy_tensor", &CopyPaddleInferTensor);
   m->def("paddle_dtype_size", &paddle::PaddleDtypeSize);

paddle/fluid/string/string_helper.h

@@ -53,7 +53,7 @@ template <class... ARGS>
 std::string format_string(const char* fmt, ARGS&&... args) {
   std::string str;
   format_string_append(str, fmt, args...);
-  return std::move(str);
+  return str;
 }
 
 template <class... ARGS>