Hardware-Software Co-Design: Not Just a Cliché

The age of the air-tight hardware abstraction is over. As the computing ecosystem moves beyond the predictable yearly advances of Moore's Law, appeals to familiarity and backwards compatibility will become less convincing: fundamental shifts in abstraction and design will look more enticing. It is time to embrace hardware-software co-design in earnest, to cooperate between programming languages and architecture to upend legacy constraints on computing. We describe our work on approximate computing, a new avenue spanning the system stack from applications and languages to microarchitectures. We reflect on the challenges and successes of approximation research and, with these lessons in mind, distill opportunities for future hardware-software co-design efforts.