perf(interpreter): add fastpath for GetVarShape

GitOrigin-RevId: d1ac4e7fe38c8b8dc4d5141603ebea545a3c396f

imperative/src/impl/interpreter/interpreter_impl.cpp

@@ -269,7 +269,20 @@ void ChannelImpl::dispatch_default_cpu(
 
     uint64_t op_id = Profiler::next_id();
 
+    if (op->trait()->apply_on_device_tensornd) {
         OpDef::apply_on_device_tensornd(*op, input_tensornds, &output_tensornds);
+    } else {
+        // proxy to apply_on_physical_tensor
+        SmallVector<TensorPtr> input_tensors;
+        for (auto&& input_tensornd : input_tensornds) {
+            input_tensors.push_back(Tensor::make(
+                    input_tensornd, HostTensorND::make_proxy(input_tensornd)));
+        }
+        auto output_tensors = OpDef::apply_on_physical_tensor(*op, input_tensors);
+        for (size_t i = 0; i < output_tensors.size(); ++i) {
+            output_tensornds[i].copy_from_fixlayout(output_tensors[i]->dev_tensor());
+        }
+    }
 
     SmallVector<TensorInfo*> output_infos;
     output_infos.reserve(output_descs.size());
@@ -357,6 +370,17 @@ SmallVector<Handle> ChannelImpl::apply_op(
         std::shared_ptr<OpDef> op, const SmallVector<Handle>& inputs) {
     MGB_LOCK_GUARD(m_spin);
     mgb_assert(check_available(), "Channel already closed");
+    auto* input = reinterpret_cast<TensorInfo*>(inputs[0]);
+    if (op->same_type<GetVarShape>() && input->desc.layout.ndim) {
+        size_t ndim = input->desc.layout.ndim;
+        auto& gvs = op->cast_final_safe<GetVarShape>();
+        if (gvs.axis == MEGDNN_MAX_NDIM) {
+            HostTensorND shape_tensor{input->desc.comp_node, {ndim}, dtype::Int32()};
+            DeviceTensorND shape_tensor_device = shape_tensor.proxy_to_default_cpu();
+            cg::copy_shape_to_tensor_value(shape_tensor_device, input->desc.layout);
+            return {reinterpret_cast<Handle>(put_impl(shape_tensor, false))};
+        }
+    }
     return apply_op_impl(std::move(op), inputs);
 }
 
@@ -621,6 +645,12 @@ void ChannelImpl::produce_tensor(TensorInfo* dest, TensorPtr ptr) {
             TensorProduceEvent, dest->id, ptr->layout(), ptr->comp_node(),
             ptr->dev_tensor().raw_ptr());
     // update tensor desc for static infer
+    if (dest->desc.layout.ndim) {
+        mgb_assert(
+                dest->desc.layout.eq_shape(ptr->layout()),
+                "shape infer error, %s vs %s", dest->desc.layout.to_string().c_str(),
+                ptr->layout().to_string().c_str());
+    }
     dest->desc.layout = ptr->layout();
     dest->desc.comp_node = ptr->comp_node();
     dest->memory = ptr->blob()->size();