Loop quantization or unwinding done right

Abstract

Loop unwinding is a known technique for reducing loop overhead, exposing parallelism and increasing the efficiency of pipelining. Traditional loop unwinding is limited to the innermost loop in a group of nested loops and the amount of unwinding is either fixed or has to be specified by the user, on a case by case basis. In this paper we present a general technique for automatically unwinding multiply nested loops, explain its advantages over other transformation techniques and illustrate its practical effectiveness. Loop Quantization could be beneficial by itself, or coupled with other loop transformations (e.g., Do-across).