Asymmetrically banked value-aware register files for low-energy and high-performance

Designing high-performance low-energy register files is of critical importance to the continuation of current performance advances in wide-issue and deeply pipelined superscalar microprocessors. In this paper, we propose a new microarchitecture, the asymmetrically banked value-aware register file (AB-VARF), to exploit the prevailing narrow-width register values for low-latency and energy-efficient register file designs. The register bit-widths of different banks in our AB-VARF register files are specifically customized to capture different narrow-width values. Augmented with a value width predictor, the register renaming logic is slightly tuned to rename predicted narrow-width registers to the corresponding narrow-width banks. Our experimental evaluation with SPEC CINT2000 benchmark suite shows that AB-VARF reduces the energy consumption by 78.4% over a conventional register file, on the average, at the cost of a 0.7% performance loss to an ideal 1-cycle monolithic register file.