Bug fix

paddle/framework/backward.cc

@@ -147,7 +147,7 @@ static std::unique_ptr<OperatorBase> BackwardRecursive(
       for (size_t output_idx = 0; output_idx < dup_outputs.size() - 1;
            ++output_idx) {
         auto insert_add_x = dup_outputs[output_idx];
-        auto insert_add_y = dup_outputs[output_idx];
+        auto insert_add_y = dup_outputs[output_idx + 1];
         auto insert_add_out = name + "@SHARED@" + std::to_string(output_idx);
         // first add op inserted
         if (output_idx == dup_outputs.size() - 2) {