Programmable circuits such as general-purpose processors or FPGAs have their end-user energy efficiency strongly dependent on the program that they execute. Ultimately, it is the programmer's ability to code and, in the case of general purpose processors, the compiler's ability to translate source code into a sequence of native instructions that make the circuit deliver the expected performance to the end user. This way, the benefits of energy-efficient circuits build upon energy-efficient devices could be obfuscated by poorly written software. Clearly, having well-written software running on conventional circuits is no better in terms of energy efficiency than having poorly written software running on energy-efficient circuits. Therefore, to get the most out of the energy-saving capabilities of programmable circuits that support low voltage operating modes, it is necessary to address software issues that might work against the benefits of operating in such modes.