fix amp cast bug for bn (#47802)

paddle/fluid/eager/amp_utils.h

@@ -103,6 +103,9 @@ inline paddle::experimental::DataType GetAmpDestDtype(
         return paddle::experimental::DataType::FLOAT16;
       } else if (paddle::imperative::AmpOperators::Instance()
                      .GetMutableBlockOps()
+                     ->count(op_name) ||
+                 paddle::imperative::AmpOperators::Instance()
+                     .GetMutableUnsupportedFp16Ops()
                      ->count(op_name)) {
         return paddle::experimental::DataType::FLOAT32;
       } else {

paddle/fluid/imperative/amp_auto_cast.cc

@@ -353,7 +353,9 @@ NameVarMap<VarType> AutoCastInputs(const std::string& op_type,
       }
     }
     return new_ins;
-  } else if (AmpOperators::Instance().GetMutableBlockOps()->count(op_type)) {
+  } else if (AmpOperators::Instance().GetMutableBlockOps()->count(op_type) ||
+             AmpOperators::Instance().GetMutableUnsupportedFp16Ops()->count(
+                 op_type)) {
     for (auto& pair : new_ins) {
       VLOG(5) << "Op(" << op_type << "): Cast " << pair.first << " from "
               << GetDtypeStr(*pair.second.cbegin()) << " to float";