fix(mge/quantization): handle empty Observer in QATModule

GitOrigin-RevId: e8a62297bc513a30be900743c3c199ccc2b30273

python_module/megengine/module/qat/module.py

@@ -70,10 +70,13 @@ class QATModule(Module):
     def _apply_fakequant_with_observer(
         self, target: Tensor, fake_quant: FakeQuantize, observer: Observer
     ):
+        # do observer
         if observer is None:
-            return target
-        oup = observer(target)
+            q_dict = None
+            oup = target
+        else:
             q_dict = observer.get_qparams()
+            oup = observer(target)
         # do fake quant
         if fake_quant is not None:
             oup = fake_quant(oup, q_dict)
@@ -81,6 +84,7 @@ class QATModule(Module):
             if hasattr(fake_quant, "get_qparams"):
                 q_dict = fake_quant.get_qparams()
         # set to tensor qparams.
+        if q_dict is not None:
             oup.q_dict.update(q_dict)
         return oup
 
@@ -100,42 +104,46 @@ class QATModule(Module):
             target, self.act_fake_quant, self.act_observer
         )
 
+    def _get_method_result(
+        self, method: str, fake_quant: FakeQuantize, observer: Observer
+    ):
+        if hasattr(fake_quant, method):
+            return getattr(fake_quant, method)()
+        elif hasattr(observer, method):
+            return getattr(observer, method)()
+        return None
+
     def get_weight_dtype(self):
         r"""
         Get weight's quantization dtype as the method from ``qconfig``.
         """
-        if hasattr(self.weight_fake_quant, "get_dtype"):
-            return self.weight_fake_quant.get_dtype()
-        else:
-            return self.weight_observer.get_dtype()
+        return self._get_method_result(
+            "get_dtype", self.weight_fake_quant, self.weight_observer
+        )
 
     def get_activation_dtype(self):
         r"""
         Get activation's quantization dtype as the method from ``qconfig``.
         """
-        if hasattr(self.act_fake_quant, "get_dtype"):
-            return self.act_fake_quant.get_dtype()
-        else:
-            return self.act_observer.get_dtype()
-
-    def _get_qparams(self, fake_quant: FakeQuantize, observer: Observer):
-        if hasattr(fake_quant, "get_qparams"):
-            return fake_quant.get_qparams()
-        elif observer is not None:
-            return observer.get_qparams()
-        return None
+        return self._get_method_result(
+            "get_dtype", self.act_fake_quant, self.act_observer
+        )
 
     def get_weight_qparams(self):
         r"""
         Get weight's quantization parameters.
         """
-        return self._get_qparams(self.weight_fake_quant, self.weight_observer)
+        return self._get_method_result(
+            "get_qparams", self.weight_fake_quant, self.weight_observer
+        )
 
     def get_activation_qparams(self):
         r"""
         Get activation's quantization parameters.
         """
-        return self._get_qparams(self.act_fake_quant, self.act_observer)
+        return self._get_method_result(
+            "get_qparams", self.act_fake_quant, self.act_observer
+        )
 
     @classmethod
     @abstractmethod