diff --git a/paddle/framework/op_desc.cc b/paddle/framework/op_desc.cc
index 6ce453cc994c7168978709b3d4c3165bf7a2b99d..c4dcb2210d13d71e924ce9e0dfcae0715914476f 100644
--- a/paddle/framework/op_desc.cc
+++ b/paddle/framework/op_desc.cc
@@ -200,6 +200,7 @@ static InferShapeFuncMap &InferShapeFuncs() {
     // all registered kernels
     for (auto &pair : OperatorWithKernel::AllOpKernels()) {
       auto &info = info_map.Get(pair.first);
+      // use empty type here to avoid runtime checks.
       auto op =
           static_cast<OperatorWithKernel *>(info.Creator()("", {}, {}, {}));
       g_map->insert(