[pc] introduce ProgressiveCompilationState and clear callback (#157619)

followup from https://github.com/pytorch/pytorch/pull/157305 where
@aorenste correctly suggested clearing callback. this refactor
introduces a new dataclass so we don't need to check nullability for
each field

Pull Request resolved: https://github.com/pytorch/pytorch/pull/157619
Approved by: https://github.com/aorenste
ghstack dependencies: #157305, #157614

torch/_inductor/compile_fx_async.py

@@ -33,6 +33,48 @@ class _PostCompileData:
     graph_kwargs: _CompileFxKwargs
 
 
+@dataclass
+class ProgressiveCompilationState:
+    progression_futures: deque[Future[_WireProtocolPickledOutput]]
+    callback: Callable[[_WireProtocolPickledOutput], OutputCode]
+    post_compile_data: Optional[_PostCompileData]
+
+    def check_and_get_ready_stage(self) -> int:
+        """Check if any progression stage is ready and return its index, or -1 if none are ready."""
+        if not self.progression_futures:
+            return -1
+
+        stage_index = -1
+        if self.post_compile_data:
+            for i, future in enumerate(self.progression_futures):
+                if future.done():
+                    stage_index = i
+
+        return stage_index
+
+    def switch_to_progression_stage(self, stage_index: int) -> tuple[OutputCode, bool]:
+        """
+        Switch to the specified progression stage and return the optimized output code.
+        Returns a tuple of (optimized_output_code, should_clear_compilation_state).
+        """
+        future = self.progression_futures[stage_index]
+        assert future is not None
+        optimized_output_code = self.callback(future.result())
+
+        if pcd := self.post_compile_data:
+            optimized_output_code.post_compile(
+                pcd.example_inputs, pcd.constants, pcd.graph_kwargs
+            )
+
+        # Clear earlier progression futures to free memory
+        for _ in range(stage_index + 1):
+            self.progression_futures.popleft()
+
+        # Return whether all compilation state should be cleared
+        should_clear_state = not self.progression_futures
+        return optimized_output_code, should_clear_state
+
+
 # _AsyncOutputCode handles the actual management of waiting for an
 # out-of-process compile to finish and then switching over to it.
 @final
@@ -192,9 +234,7 @@ class _AsyncFxCompile(FxCompile):
 class _ProgressiveOutputCode(OutputCode):
     _fast_output_code: Optional[OutputCode]
     _optimized_output_code: Optional[OutputCode]
-    _progression_futures: deque[Future[_WireProtocolPickledOutput]]
-    _callback: Callable[[_WireProtocolPickledOutput], OutputCode]
-    _post_compile_data: Optional[_PostCompileData] = None
+    _compilation_state: Optional[ProgressiveCompilationState]
     # _boxed_call state is effectively cached (we sometimes wrap unboxed w/
     # lambdas to box them) so we can't change it mid-way. Since _boxed_call=True
     # is more common let's default to that and we'll convert if necessary.
@@ -211,8 +251,11 @@ class _ProgressiveOutputCode(OutputCode):
     ) -> None:
         self._fast_output_code = fast_output_code
         self._optimized_output_code = None
-        self._progression_futures = deque(progression_futures)
-        self._callback = callback
+        self._compilation_state = ProgressiveCompilationState(
+            progression_futures=deque(progression_futures),
+            callback=callback,
+            post_compile_data=None,
+        )
 
     @override
     def __call__(self, args: Sequence[Any]) -> Any:
@@ -235,15 +278,10 @@ class _ProgressiveOutputCode(OutputCode):
         return res
 
     def _check_and_switch_progression(self) -> None:
-        if not self._progression_futures:
+        if not self._compilation_state:
             return
 
-        stage_index = -1
-        if self._post_compile_data:
-            for i, future in enumerate(self._progression_futures):
-                if future.done():
-                    stage_index = i
-
+        stage_index = self._compilation_state.check_and_get_ready_stage()
         if stage_index == -1:
             # no futures are ready
             return
@@ -251,24 +289,17 @@ class _ProgressiveOutputCode(OutputCode):
         self._switch_to_progression_stage(stage_index)
 
     def _switch_to_progression_stage(self, stage_index: int) -> None:
-        future = self._progression_futures[stage_index]
-        assert future is not None
-        optimized_output_code = self._callback(future.result())
-
-        if pcd := self._post_compile_data:
-            # Only clear post_compile_data if this is the final progression stage
-            if stage_index == len(self._progression_futures) - 1:
-                self._post_compile_data = None
-            optimized_output_code.post_compile(
-                pcd.example_inputs, pcd.constants, pcd.graph_kwargs
-            )
+        assert self._compilation_state is not None
+        optimized_output_code, should_clear_state = (
+            self._compilation_state.switch_to_progression_stage(stage_index)
+        )
 
         self._optimized_output_code = optimized_output_code
         self._fast_output_code = None
 
-        # Clear earlier progression futures to free memory
-        for _ in range(stage_index + 1):
-            self._progression_futures.popleft()
+        # Clear all compilation state if no more progression futures are left
+        if should_clear_state:
+            self._compilation_state = None
 
     @override
     def post_compile(
@@ -279,8 +310,10 @@ class _ProgressiveOutputCode(OutputCode):
     ) -> None:
         assert self._fast_output_code is not None
         self._fast_output_code.post_compile(example_inputs, constants, graph_kwargs)
-        # Store for later when  optimized version is ready
-        self._post_compile_data = _PostCompileData(
+
+        assert self._compilation_state is not None
+        # Store for later when optimized version is ready
+        self._compilation_state.post_compile_data = _PostCompileData(
             example_inputs, constants, graph_kwargs
         )