Add default value of op_role

paddle/fluid/framework/op_proto_maker.cc

@@ -69,7 +69,9 @@ void OpProtoAndCheckerMaker::operator()(proto::OpProto* proto,
            static_cast<int>(OpRole::kOptimize),
            static_cast<int>(OpRole::kLoss) | static_cast<int>(OpRole::kForward),
            static_cast<int>(OpRole::kLoss) |
-               static_cast<int>(OpRole::kBackward)});
+               static_cast<int>(OpRole::kBackward),
+           static_cast<int>(OpRole::kNotSpecified)})
+      .SetDefault(static_cast<int>(OpRole::kNotSpecified));
   AddAttr<std::vector<std::string>>(OpRoleVarAttrName(),
                                     "Optimized for variable")
       .SetDefault({});

paddle/fluid/framework/op_proto_maker.h

@@ -26,6 +26,9 @@ enum class OpRole {
   kOptimize = 0x0002,
 
   kLoss = 0x0100,
+  // The default value of op's role. This should be only used for unittests and
+  // CreateOp inside a operator.
+  kNotSpecified = 0x1000,
 };
 
 // this class not only make proto but also init attribute checkers.