Fix compilation warnings of fix_split_ids_op.h (#9619)

paddle/fluid/operators/split_ids_op.h

@@ -30,19 +30,16 @@ class SplitIdsOpKernel : public framework::OpKernel<T> {
       PADDLE_THROW("SplitIds do not support GPU kernel");
     }
 
-    const auto* ids_t = ctx.Input<framework::LoDTensor>("Ids");
-    auto& ids_dims = ids_t->dims();
+    auto& ids_dims = ctx.Input<framework::LoDTensor>("Ids")->dims();
+    const T* ids = ctx.Input<framework::LoDTensor>("Ids")->data<T>();
     auto outs = ctx.MultiOutput<framework::LoDTensor>("Out");
-
-    const T* ids = ids_t->data<T>();
-
     const size_t shard_num = outs.size();
 
     std::vector<std::vector<T>> out_ids;
     out_ids.resize(outs.size());
 
     // split id by their shard_num.
-    for (size_t i = 0; i < ids_dims[0]; ++i) {
+    for (int i = 0; i < ids_dims[0]; ++i) {
       T id = ids[i];
       size_t shard_id = static_cast<size_t>(id) % shard_num;
       out_ids[shard_id].push_back(id);