Suppose we have to groups of instruction that will use the same register , one set of instruction is executed first to leave the register to the other set , but if the other set is assigned to a different similar register both sets of instructions can be executed in parallel . Suppose we have two groups of instruction that will use the same register . One set of instructions is executed first to leave the register to the other set , but if the other set is assigned to a different similar register , both sets of instructions can be executed in parallel .