[BYOC] Remove ext params stored in metadata from params to avoid dupl…

…ication (apache#7977)

* Remove ext params stored in metadata from params to avoid duplication

* Add test for duplicate params

src/relay/backend/build_module.cc

@@ -565,6 +565,19 @@ class RelayBuildModule : public runtime::ModuleNode {
     auto ext_mods = executor_codegen_->GetExternalModules();
     ret_.mod = tvm::codegen::CreateMetadataModule(ret_.params, ret_.mod, ext_mods, GetTargetHost(),
                                                   executor_codegen_->GetMetadata());
+    // Remove external params which were stored in metadata module.
+    for (tvm::runtime::Module mod : ext_mods) {
+      auto pf_var = mod.GetFunction("get_const_vars");
+      if (pf_var != nullptr) {
+        Array<String> variables = pf_var();
+        for (size_t i = 0; i < variables.size(); i++) {
+          auto it = ret_.params.find(variables[i].operator std::string());
+          if (it != ret_.params.end()) {
+            ret_.params.erase(it);
+          }
+        }
+      }
+    }
   }
 
  private:

tests/python/relay/test_external_codegen.py

@@ -352,6 +352,8 @@ def test_load_params_with_constants_in_ext_codegen():
     mod = transform.PartitionGraph()(mod)
 
     graph_module = relay.build(mod, target="llvm", params=params)
+    # Params will be stored in metadata module.
+    assert len(graph_module.get_params()) == 0
     lib = update_lib(graph_module.get_lib())
     rt_mod = tvm.contrib.graph_executor.create(graph_module.get_graph_json(), lib, tvm.cpu(0))
     rt_mod.load_params(runtime.save_param_dict(graph_module.get_params()))