!7901 fix bug of pynative's mixprecision

Merge pull request !7901 from lianliguang/master

mindspore/nn/cell.py

@@ -261,6 +261,17 @@ class Cell(Cell_):
             object.__delattr__(self, name)
         self._attr_synced = False
 
+    def _cast_mixed_precision_inputs(self, inputs, dst_type):
+        res = list()
+        for item in inputs:
+            if isinstance(item, tuple):
+                res.append(self._cast_mixed_precision_inputs(item, dst_type))
+            elif item.dtype in {mstype.float16, mstype.float32}:
+                res.append(cast(item, dst_type))
+            else:
+                res.append(item)
+        return tuple(res)
+
     def cast_inputs(self, inputs, dst_type):
         res = list()
         for item in inputs:
@@ -299,9 +310,9 @@ class Cell(Cell_):
         cast_inputs = list()
         if hasattr(self, "_mindspore_flags"):
             if self._mindspore_flags.get('fp16'):
-                cast_inputs = self.cast_inputs(inputs, mstype.float16)
+                cast_inputs = self._cast_mixed_precision_inputs(inputs, mstype.float16)
             if self._mindspore_flags.get('fp32'):
-                cast_inputs = self.cast_inputs(inputs, mstype.float32)
+                cast_inputs = self._cast_mixed_precision_inputs(inputs, mstype.float32)
         if not cast_inputs:
             cast_inputs = inputs
         if self.enable_hook: