fix: Fix additional mem copy of the model during re-export (#3302)

Author: peri044

py/torch_tensorrt/dynamo/runtime/register_fake_class.py

@@ -26,7 +26,7 @@ def fake_tensorrt_execute_engine(
         modes = ["opt"]
 
     # Get the TRTEngine class and infer output shapes based on input shapes
-    trt_engine = fake_trt_engine.wrapped_obj.engine
+    trt_engine = fake_trt_engine.real_obj
     outputs_mode_dict = defaultdict(list)
     for mode in modes:
         input_shapes = [unwrap_tensor_shape(input, mode=mode) for input in inputs]
@@ -79,7 +79,21 @@ def fake_tensorrt_execute_engine(
 @torch._library.register_fake_class("tensorrt::Engine")
 class FakeTRTEngine:
     def __init__(self, engine_info: List[str]) -> None:
-        self.engine = torch.classes.tensorrt.Engine(engine_info)
+        self.version = engine_info[torch.ops.tensorrt.ABI_TARGET_IDX()]
+        self.name = engine_info[torch.ops.tensorrt.NAME_IDX()]
+        self.device_info = engine_info[torch.ops.tensorrt.DEVICE_IDX()]
+        self.serialized_engine = engine_info[torch.ops.tensorrt.ENGINE_IDX()]
+        self.in_binding_names = engine_info[
+            torch.ops.tensorrt.INPUT_BINDING_NAMES_IDX()
+        ]
+        self.out_binding_names = engine_info[
+            torch.ops.tensorrt.OUTPUT_BINDING_NAMES_IDX()
+        ]
+        self.hardware_compatible = engine_info[torch.ops.tensorrt.HW_COMPATIBLE_IDX()]
+        self.serialized_metadata = engine_info[
+            torch.ops.tensorrt.SERIALIZED_METADATA_IDX()
+        ]
+        self.target_platform = engine_info[torch.ops.tensorrt.TARGET_PLATFORM_IDX()]
 
     @classmethod
     def __obj_unflatten__(cls, flattened_tq: Any) -> Any:
@@ -127,3 +141,6 @@ def infer_outputs(self, input_shapes: List[Any]) -> Any:
 
     def __setstate__(self, serialized_state: List[str]) -> Any:
         pass
+
+    def __getstate__(self) -> Any:
+        pass

tests/py/dynamo/models/test_reexport.py

@@ -106,7 +106,6 @@ def forward(self, x):
 
     exp_program = torchtrt.dynamo.trace(model, **compile_spec)
     trt_module = torchtrt.dynamo.compile(exp_program, **compile_spec)
-    torchtrt.save(trt_module, trt_ep_path)
 
     # Reexport
     trt_exp_program = torch.export.export(trt_module, (input,), strict=False)