1. A method, comprising: in response to executing an instruction that modifies a mapping of an architectural register to a physical register, storing information indicating the modified mapping of the architectural register in an entry of an array that only includes entries corresponding to architectural registers that have been modified by execution of instructions; and recovering a checkpointed state of a set of architectural registers indicative of a state of the set of architectural registers prior to modification of the architectural register by the instruction by modifying a reference mapping of physical registers to the set of architectural registers using the information stored in the entries of the array.