Improvement of Renamed Trace Cache through the Reduction of Dependent Path Length for High Energy Efficiency

Ryota SHIOYA  Hideki ANDO  

Publication
IEICE TRANSACTIONS on Information and Systems   Vol.E99-D   No.3   pp.630-640
Publication Date: 2016/03/01
Online ISSN: 1745-1361
DOI: 10.1587/transinf.2015EDP7270
Type of Manuscript: PAPER
Category: Computer System
Keyword: 
superscalar processor,  register renaming,  trace cache,  energy efficiency,  

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Summary: 
Out-of-order superscalar processors rename register numbers to remove false dependencies between instructions. A renaming logic for register renaming is a high-cost module in a superscalar processor, and it consumes considerable energy. A renamed trace cache (RTC) was proposed for reducing the energy consumption of a renaming logic. An RTC caches and reuses renamed operands, and thus, register renaming can be omitted on RTC hits. However, conventional RTCs suffer from several performance, energy consumption, and hardware overhead problems. We propose a semi-global renamed trace cache (SGRTC) that caches only renamed operands that are short distance from producers outside traces, and solves the problems of conventional RTCs. Evaluation results show that SGRTC achieves 64% lower energy consumption for renaming with a 0.2% performance overhead as compared to a conventional processor.