[TIR][Schedule] Method returning the function being worked on

PR apache#11999 introduces the sugar method `work_on` to TIR Schedule, with
a field `func_working_on_` newly added to the ScheduleNode. In some
cases we may want to know which function a ScheduleNode is working on,
which is not supported previously.

Therefore, this PR introduces a method to ScheduleNode that returns
the function (more accurately, GlobalVar) currently being worked on.
With this we are able to know the function being worked on.

include/tvm/tir/schedule/schedule.h

@@ -115,6 +115,8 @@ class ScheduleNode : public runtime::Object {
   virtual ScheduleState state() const = 0;
   /*! \return The internally maintained trace of scheduling program execution */
   virtual Optional<Trace> trace() const = 0;
+  /*! \return The GlobalVar of the func that the schedule is currently working on */
+  virtual Optional<GlobalVar> func_working_on() const = 0;
   /*!
    * \brief Instruct the schedule to work on a function in the IRModule.
    *

python/tvm/tir/schedule/schedule.py

@@ -19,7 +19,7 @@
 
 from tvm._ffi import register_object as _register_object
 from tvm.error import TVMError, register_error
-from tvm.ir import IRModule, PrimExpr
+from tvm.ir import GlobalVar, IRModule, PrimExpr
 from tvm.runtime import Object, String
 from tvm.tir import Block, Buffer, FloatImm, For, IntImm, PrimFunc
 
@@ -207,6 +207,11 @@ def trace(self) -> Optional[Trace]:
         """Returns the internally maintained trace of scheduling program execution"""
         return _ffi_api.ScheduleGetTrace(self)  # type: ignore # pylint: disable=no-member
 
+    @property
+    def func_working_on(self) -> Optional[GlobalVar]:
+        """Returns the GlobalVar of the func that the schedule is currently working on"""
+        return _ffi_api.ScheduleGetFuncWorkingOn(self)  # type: ignore # pylint: disable=no-member
+
     def work_on(self, func_name: str) -> None:
         """Instruct the schedule to work on a function in the IRModule.
 

src/tir/schedule/concrete_schedule.h

@@ -64,6 +64,7 @@ class ConcreteScheduleNode : public ScheduleNode {
  public:
   ScheduleState state() const final { return state_; }
   Optional<Trace> trace() const override { return NullOpt; }
+  Optional<GlobalVar> func_working_on() const final { return func_working_on_; }
   void WorkOn(const String& func_name) final;
   Schedule Copy() override;
   void Seed(support::LinearCongruentialEngine::TRandState seed) final;

src/tir/schedule/schedule.cc

@@ -50,6 +50,8 @@ TVM_REGISTER_GLOBAL("tir.schedule.ScheduleGetState")  //
     .set_body_method<Schedule>(&ScheduleNode::state);
 TVM_REGISTER_GLOBAL("tir.schedule.ScheduleGetTrace")  //
     .set_body_method<Schedule>(&ScheduleNode::trace);
+TVM_REGISTER_GLOBAL("tir.schedule.ScheduleGetFuncWorkingOn")  //
+    .set_body_method<Schedule>(&ScheduleNode::func_working_on);
 TVM_REGISTER_GLOBAL("tir.schedule.ScheduleCopy")  //
     .set_body_method<Schedule>(&ScheduleNode::Copy);
 TVM_REGISTER_GLOBAL("tir.schedule.ScheduleSeed")  //

tests/python/unittest/test_tir_schedule_utilities.py

@@ -193,6 +193,7 @@ def test_tir_schedule_work_on():
         sch.get_block(name="init")
     sch.work_on(func_name="vector_add")
     sch.get_block(name="init")
+    assert sch.func_working_on == sch.mod.get_global_var("vector_add")
 
 
 def test_tir_schedule_get_loops(use_block_name):