Optimizing directly executable LR parsers

Abstract

Traditionally, LR parsers are implemented as table interpreters. A parser generator creates tables whose entries are interpreted by the parser driver. Recent research shows that much faster LR parsers can be obtained by converting the table entries into directly executed code. This paper introduces new techniques for optimizing directly executable parsers. The optimization methods proposed here are based on the analysis of the characteristical properties of large programming language grammars. They include a new structure for the parsing algorithm, an adaptation of the classical chain rule optimization and a systematic approach to stack access minimization. A parser generator based on these techniques was developed. It generates directly executable LR parsers running up to seven times faster than comparable table interpreting parsers.