AFReP: Application-guided Function-level Registerfile power-gating for embedded processors

With shrinking CMOS feature size, static power is growing significantly and power density has emerged as an increasing concern. At the same time, one trend of embedded processors is toward larger Register Files (RFs) which further increases static power dissipation and aggravating the issue. This paper introduces an Application-guided Function-level Register file Power-gating (AFReP) that reduces static power of RFs in embedded processors. Our AFReP approach is based on a automatic analysis of register lifetime in the application binary, followed an automatic binary instrumentation for runtime RF power-gating. The instrumented code executes on a processor with ISA and micro-architecture extension for power-gating control over individual registers. Our application binary analysis/instrumentation operates at function-level granularity, automatically gating the registers that do not contribute to program outcome. Our experimental results using an AFReP-enhanced Blackfin processor demonstrate average RF static power reduction by 60% and 52% for control and DSP applications from Mibench and DSPstone suites, respectively. The added instructions for run-time power-gating increase execution time by only 1% on average.