Composite-ISA Cores: Enabling Multi-ISA Heterogeneity Using a Single ISA

Heterogeneous multicore architectures comprise of multiple cores of different sizes, organizations, and capabilities. These architectures maximize both performance and energy efficiency by allowing applications to adapt to phase changes by migrating execution to the most efficient core. Multi-ISA heterogeneous architectures further take advantage of the inherent ISA-preferences of different code regions within an application to provide significant additional performance and efficiency gains. This work proposes composite-ISA cores that implement composite feature sets made available from a larger superset ISA. This architecture has the potential to recreate and in many cases, supersede the gains of multi-ISA heterogeneity, by leveraging a single composite-ISA. Composite-ISA CMPs enhance existing performance gains due to hardware heterogeneity by an average of 19%, and have the potential to achieve an additional 31% energy savings and 35% reduction in Energy Delay Product, without any loss in performance.