On the optimal assignment of attributes to passes in multi-pass attribute evaluators

Abstract

The problem of constructing multi-pass evaluators for attribute grammars is studied. The algorithm used heretofore is demonstrated to be able to produce evaluators which perform almost twice as many passes through the parse tree as necessary. The problem of constructing a shortest possible evaluation order is then shown to be NP-complete. Based on a new characterization of multi-pass attribute grammars, a modified construction algorithm is then developed. The new heuristics is motivated by experience with real grammars.