1. An apparatus comprising: an execution unit to execute at least one of a plurality of instructions; and a replay system to change a first of the plurality of instructions to a second of the plurality of instructions, wherein the first and the second instructions are different, and wherein the first of the plurality of instructions is a memory access instruction causing a page fault and the second of the plurality of instructions is an instruction to handle the page fault or the first of the plurality of instructions is dependent on a result of a previous instruction and the second of the plurality of instructions is not executed until the previous instruction has successfully executed.