剖析時屬性計算

Abstract

Compilers automatically generated from attribute grammars (AGs) are usually slower than hand-coded ones. One of the reasons is that most attribute evaluators are invoked after parsing. This paper proposes two algorithms to insert attribute evaluation codes of AGs into parsing actions. The first algorithm combines tree construction sequences (parsing actions) and attribute evaluation sequences (visit sequences of AGs) into a parse-time visit sequence. The resulting sequence can be directly used in top-down parsing. For bottom-up parsing, another algorithm introduces additional steps to schedule the visit sequence according to the free positions in the grammar.