Fix TRT plugin registry without TRT lib (#25982)

* fix trt plugin registry without trt lib

* support trt4

* refine code style

paddle/fluid/inference/tensorrt/helper.h

@@ -56,9 +56,11 @@ static nvinfer1::IRuntime* createInferRuntime(nvinfer1::ILogger* logger) {
   return static_cast<nvinfer1::IRuntime*>(
       dy::createInferRuntime_INTERNAL(logger, NV_TENSORRT_VERSION));
 }
-static nvinfer1::IPluginRegistry* getPluginRegistry() {
+#if IS_TRT_VERSION_GE(6000)
+static nvinfer1::IPluginRegistry* GetPluginRegistry() {
   return static_cast<nvinfer1::IPluginRegistry*>(dy::getPluginRegistry());
 }
+#endif
 
 // A logger for create TensorRT infer builder.
 class NaiveLogger : public nvinfer1::ILogger {

paddle/fluid/inference/tensorrt/plugin/trt_plugin.h

@@ -178,12 +178,16 @@ class DynamicPluginTensorRT : public nvinfer1::IPluginV2DynamicExt {
   std::string name_space_;
   std::string plugin_base_;
 };
-#endif
 
 template <typename T>
 class TrtPluginRegistrarV2 {
  public:
-  TrtPluginRegistrarV2() { getPluginRegistry()->registerCreator(creator, ""); }
+  TrtPluginRegistrarV2() {
+    static auto func_ptr = GetPluginRegistry();
+    if (func_ptr != nullptr) {
+      func_ptr->registerCreator(creator, "");
+    }
+  }
 
  private:
   T creator;
@@ -193,6 +197,8 @@ class TrtPluginRegistrarV2 {
   static paddle::inference::tensorrt::plugin::TrtPluginRegistrarV2<name> \
       plugin_registrar_##name {}
 
+#endif
+
 }  // namespace plugin
 }  // namespace tensorrt
 }  // namespace inference

paddle/fluid/platform/dynload/tensorrt.h

@@ -36,26 +36,29 @@ extern void* tensorrt_dso_handle;
   struct DynLoad__##__name {                                                  \
     template <typename... Args>                                               \
     auto operator()(Args... args) -> DECLARE_TYPE(__name, args...) {          \
-      using tensorrt_func = decltype(&::__name);                              \
       std::call_once(tensorrt_dso_flag, []() {                                \
         tensorrt_dso_handle = paddle::platform::dynload::GetTensorRtHandle(); \
-        PADDLE_ENFORCE_NOT_NULL(tensorrt_dso_handle,                          \
-                                platform::errors::Unavailable(                \
-                                    "Load tensorrt %s failed", #__name));     \
       });                                                                     \
       static void* p_##__name = dlsym(tensorrt_dso_handle, #__name);          \
-      PADDLE_ENFORCE_NOT_NULL(                                                \
-          p_##__name,                                                         \
-          platform::errors::Unavailable("Load tensorrt %s failed", #__name)); \
+      if (p_##__name == nullptr) {                                            \
+        return nullptr;                                                       \
+      }                                                                       \
+      using tensorrt_func = decltype(&::__name);                              \
       return reinterpret_cast<tensorrt_func>(p_##__name)(args...);            \
     }                                                                         \
   };                                                                          \
   extern DynLoad__##__name __name
 
+#if (NV_TENSORRT_MAJOR >= 6)
 #define TENSORRT_RAND_ROUTINE_EACH(__macro) \
   __macro(createInferBuilder_INTERNAL);     \
   __macro(createInferRuntime_INTERNAL);     \
   __macro(getPluginRegistry);
+#else
+#define TENSORRT_RAND_ROUTINE_EACH(__macro) \
+  __macro(createInferBuilder_INTERNAL);     \
+  __macro(createInferRuntime_INTERNAL);
+#endif
 
 TENSORRT_RAND_ROUTINE_EACH(DECLARE_DYNAMIC_LOAD_TENSORRT_WRAP)