1. A processor-implemented method comprising: receiving an atomic instruction block which includes a plurality of instructions; determining a characteristic of the atomic instruction block based at least in part on metadata associated with the atomic instruction block, the metadata set by a compiler, or on an identifier associated with the atomic instruction block; and switching between an out-of-order instruction issue mode of a processor and an in-order instruction issue mode of the processor based at least in part on the characteristic and a charge state of a computing device which includes the processor for executing at least a portion of the plurality of the instructions, wherein the out-of-order instruction issue mode and the in-order instruction issue mode are associated with different energy consumption characteristics.