vivado 2018.3版本

提醒：

[Constraints 18-5210] No constraints selected for write.
Resolution: This message can indicate that there are no constraints for the design, or it can indicate that the used_in flags are set such that the constraints are ignored. This later case is used when running synth_design to not write synthesis constraints to the resulting checkpoint. Instead, project constraints are read when the synthesized design is opened.
 

应该是可以忽略的