[FxImporter] remove weakref finalizer of reftracker (#3995)

Fixes iree-org/iree-turbine#281.

**_TL;DR:_**

The `weakref.finalize` objects cause the model parameters to be kept in
memory in-between consecutive `aot.export` calls in the same process. We
remove them to enable releasing the memory, this does not change the
behavior of `RefTracker` or `RefMapping` classes anyhow else.

Signed-off-by: Ege Beysel <[email protected]>

Author: egebeysel

python/torch_mlir/extras/fx_importer.py

@@ -2247,13 +2247,15 @@ def track(self, referrent: Any) -> RefMapping:
         if existing:
             return existing
         info = RefMapping(referrent)
-        if referrent is not Empty:
-            weakref.finalize(referrent, self._ref_finalizer, ref_id)
+        # Finalizer is removed due to a memory leak
+        # See: https://github.com/iree-org/iree-turbine/issues/281
+        # if referrent is not Empty:
+        #    weakref.finalize(referrent, self._ref_finalizer, ref_id)
         self._refs[ref_id] = info
         return info
 
-    def _ref_finalizer(self, ref_id: int):
-        del self._refs[ref_id]
+    # def _ref_finalizer(self, ref_id: int):
+    #    del self._refs[ref_id]
 
 
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