[Static Runtime] [Code Cleanup] Encapsulate function objects within ProcessedFunction (pytorch#69595)

Summary:
Pull Request resolved: pytorch#69595

This changes encapsulates `function` object in `ProcessedFunction` objects instead of exposing it unnecessarily just for executing it.

Test Plan: Existing tests

Reviewed By: mikeiovine

Differential Revision: D32908341

fbshipit-source-id: 5ff4951cbe276c5c6292227124d9eec1dd16e364

Author: d1jang

benchmarks/static_runtime/test_static_module.cc

@@ -976,7 +976,6 @@ TEST(ProcessedFunction, ProcessedFunction) {
       sigmoid_node,
       /*enable_out_variant=*/true,
       /*check_memory_overlap=*/false);
-  EXPECT_TRUE(sigmoid_fn.f());
   EXPECT_EQ(sigmoid_fn.kind(), ProcessedFunction::Kind::kOutVariant);
   EXPECT_FALSE(sigmoid_fn.checkMemoryOverlap());
 
@@ -985,7 +984,6 @@ TEST(ProcessedFunction, ProcessedFunction) {
       transpose_node,
       /*enable_out_variant=*/true,
       /*check_memory_overlap=*/false);
-  EXPECT_TRUE(transpose_fn.f());
   EXPECT_EQ(transpose_fn.kind(), ProcessedFunction::Kind::kNativeFunction);
   EXPECT_FALSE(transpose_fn.checkMemoryOverlap());
 }

torch/csrc/jit/runtime/static/impl.cpp

@@ -1700,12 +1700,12 @@ void ProcessedNode::run() {
         guard.before(get_op_name());
       }
     }
-    fn_->f()(this);
+    fn_->run(this);
   } else {
-    fn_->f()(this);
+    fn_->run(this);
   }
 #else
-  fn_->f()(this);
+  fn_->run(this);
 #endif
 #ifndef NDEBUG
   if (FLAGS_static_runtime_disable_debug_memory_overlap_check) {

torch/csrc/jit/runtime/static/impl.h

@@ -570,8 +570,8 @@ class TORCH_API ProcessedFunction {
     kInterpreterFallback,
   };
 
-  const std::function<void(ProcessedNode*)>& f() const {
-    return f_;
+  void run(ProcessedNode* pnode) const {
+    return f_(pnode);
   }
 
   Kind kind() const {