I understand the need for re-order buffer in speculative execution. However, given a sequence of non-speculative instructions without any branches, why is it that all these instructions still have to go through the ROB and then commit in order? Since there is no control hazard and assuming the presence of register renaming to avoid WAR and WAW hazards, is ROB a necessity in such a case?
One reason I could think of, is for handling imprecise exceptions. Is there any other reason?