Type overriding using UVM factory

Type overriding means that every time a component class type is created in the Testbench hierarchy, a substitute type i.e. derived class of the original component class, is created in its place, which applies to all the instances of that component type. In UVM, below are the methods by which we can override the class:

• set_type_override_by_type
• set_type_override_by_name

There's no difference in the final result either we override by type or name.

In below example, our purpose is to override driver class without making change in existing environment, so we created extended class which is extended from the original driver class.

Factory Code:

class uvm_factory; ... function void set_type_override_by_type (uvm_object_wrapper original_type, uvm_object_wrapper override_type, bit replace=1); function void set_type_override_by_name (string original_type_name, string override_type_name, bit replace=1); ... endclass

// When ~replace~ is 1, a previous override on ~original_type_name~ is replaced, otherwise a previous override, if any, remains intact. Yet to check.

Driver Code:

class my_driver extends uvm_driver; `uvm_component_utils(my_driver) function new (string name = "", uvm_component parent = null); super.new (name, parent); endfunction: new task run_phase(uvm_phase phase); super.run_phase(phase); `uvm_info(get_name(), $sformatf("My_driver: run_phase"), UVM_LOW); endtask: run_phase endclass: my_driver

Extended driver Code:

class my_driver_ext extends my_driver; `uvm_component_utils(my_driver_ext) function new (string name = "", uvm_component parent = null); super.new (name, parent); endfunction: new task run_phase(uvm_phase phase); super.run_phase(phase); `uvm_info(get_name(), $sformatf("My_driver_ext: run_phase"), UVM_LOW); endtask: run_phase endclass: my_driver_ext

In test, we can override the driver class by using "set_type_override_by_type" function.

Overriding in Test:

class my_test extends uvm_test; ... virtual function void build_phase(uvm_phase phase); super.build_phase(phase); factory.set_type_override_by_type (my_driver::get_type(), // Original type my_driver_ext::get_type()); // Override type env = my_env::type_id::create("env", this); endfunction: build_phase ... endclass: my_test

Output:
UVM_INFO @ 0: reporter [RNTST] Running test my_test... UVM_INFO @ 0: uvm_test_top.env.agent.driver [driver] My_driver: run_phase UVM_INFO @ 0: uvm_test_top.env.agent.driver [driver] My_driver_ext: run_phase

In test, we can override the driver class by using "set_type_override_by_name" function.

Overriding in Test:

class my_test extends uvm_test; ... virtual function void build_phase(uvm_phase phase); super.build_phase(phase); factory.set_type_override_by_name ("my_driver", // Original type "my_driver_ext"); // Override type env = my_env::type_id::create("env", this); endfunction: build_phase ... endclass: my_test

Output:
UVM_INFO @ 0: reporter [RNTST] Running test my_test... UVM_INFO @ 0: uvm_test_top.env.agent.driver [driver] My_driver: run_phase UVM_INFO @ 0: uvm_test_top.env.agent.driver [driver] My_driver_ext: run_phase