[inductor] add FreeLibrary to DLLWrapper for Windows. (#133184)

For previous PR https://github.com/pytorch/pytorch/pull/132630 . We found `DLLWrapper` class doesn't have `_dlclose` implemention for Windows.

I write a small test project to figure out how to make it works on Windows: https://github.com/xuhancn/ctypes_all_lifecycle/blob/main/pysrc/module_manage.py#L30-L61
Test result: https://github.com/xuhancn/ctypes_all_lifecycle/tree/main?tab=readme-ov-file#ctypes_cyclepy

So, I have port the Windows FreeLibrary implemention to pytorch DLLWrapper in this PR.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/133184
Approved by: https://github.com/jgong5, https://github.com/jansel

torch/_inductor/codecache.py

@@ -100,6 +100,7 @@ from torch._inductor.utils import (
     BoxedBool,
     clear_on_fresh_inductor_cache,
     is_linux,
+    is_windows,
     set_tracing_context_output_strides,
 )
 from torch._logging import trace_structured
@@ -3017,12 +3018,25 @@ class DLLWrapper:
 
             if hasattr(syms, "dlclose"):
                 f_dlclose = syms.dlclose
+        elif is_windows():
+            import ctypes
+
+            kernel32 = ctypes.CDLL("kernel32", use_last_error=True)
+
+            f_dlclose = kernel32.FreeLibrary
         else:
             raise NotImplementedError("Unsupported env, failed to do dlclose!")
 
         if f_dlclose is not None:
-            f_dlclose.argtypes = [c_void_p]
-            f_dlclose(self.DLL._handle)
+            if is_linux():
+                f_dlclose.argtypes = [c_void_p]
+                f_dlclose(self.DLL._handle)
+            elif is_windows():
+                import ctypes
+                from ctypes import wintypes
+
+                f_dlclose.argtypes = [wintypes.HMODULE]
+                f_dlclose(self.DLL._handle)
         else:
             log.warning(
                 "dll unloading function was not found, library may not be unloaded properly!"

torch/_inductor/utils.py

@@ -1521,6 +1521,10 @@ def is_linux() -> bool:
     return platform.system() == "Linux"
 
 
+def is_windows():
+    return sys.platform == "win32"
+
+
 def has_free_symbols(itr: Iterable[Any]):
     return any(isinstance(x, sympy.Expr) and not x.is_number for x in itr)