Simultaneous Optimization of Skew and Control Step Assignments in RT-Datapath Synthesis

Takayuki OBATA  Mineo KANEKO  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E91-A   No.12   pp.3585-3595
Publication Date: 2008/12/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e91-a.12.3585
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on VLSI Design and CAD Algorithms)
Category: High-Level Synthesis and System-Level Design
Keyword: 
high level synthesis,  RT datapath,  skew,  wiring delay,  scheduling,  

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Summary: 
As well as the schedule affects system performance, the control skew, i.e., the arrival time difference of control signals between registers, can be utilized for improving the system performance, enhancing robustness against delay variations, etc. The simultaneous optimization of the control step assignment and the control skew assignment is more powerful technique in improving performance. In this paper, firstly, we prove that, even if the execution sequence of operations which are assigned to the same resource is fixed, the simultaneous optimization problem under a fixed clock period is NP-hard. Secondly, we propose a heuristic algorithm for the simultaneous control step and skew optimization under given clock period, and we show how much the simultaneous optimization improves system performance. This paper is the first one that uses the intentional skew to shorten control steps under a specified clock period. The proposed algorithm has the potential to play a central role in various scenarios of skew-aware high level synthesis.