Flow-Directed Closure Conversion for Typed Languages

• Authors: Henry Cejtin;Suresh Jagannathan;Stephen Weeks
• Venue: ESOP '00 Proceedings of the 9th European Symposium on Programming Languages and Systems
• Year: 2000

This paper presents a new closure conversion algorithm for simply-typed languages. We have have implemented the algorithm as part of MLton, a whole-program compiler for Standard ML (SML). MLton first applies all functors and eliminates polymorphism by code duplication to produce a simply-typed program. MLton then performs closure conversion to produce a first-order, simply-typed program. In contrast to typical functional language implementations, MLton performs most optimizations on the first-order language, after closure conversion. There are two notable contributions of our work: 1. The translation uses a general flow-analysis framework which includes OCFA. The types in the target language fully capture the results of the analysis. MLton uses the analysis to insert coercions to translate between different representations of a closure to preserve type correctness of the target language program. 2. The translation is practical. Experimental results over a range of benchmarks including large real-world programs such as the compiler itself and the ML-Kit [25] indicate that the compile-time cost of flow analysis and closure conversion is extremely small, and that the dispatches and coercions inserted by the algorithm are dynamically infrequent.