Toward Optimization of Concurrent Ml

Concurrent ML (CML) is a statically-typed higher-order concurrent language that is embedded in Standard ML. Its most notable feature are first-class synchronous operations, which allow programmers to encapsulate complicated communication and synchronization protocols as first-class abstractions. This feature encourages a modular style of programming, where the actual underlying channels used to communicate with a given thread are hidden behind data and type abstraction. While CML has been in active use for well over a decade, little attention has been paid to optimizing CML programs. In this paper, we present a new program analysis for statically-typed higher-order concurrent languages that is a significant step toward optimization of CML. Our technique is modular (i.e., it analyses and optimizes a single unit of abstraction at a time), which plays to the modular style of many CML programs. The analysis consists of two major components: the first is a type-sensitive control-flow analysis that uses the program’s type-abstractions to compute more precise results. We then construct a control-flow graph from the results of the CFA and analyze the flow of known channel values using the graph. Our analysis is designed to detect special patterns of use, such as one-shot channels, fan-in channels, and fan-out channels. These special patterns can be exploited by using more efficient implementations of channel primitives. We show that our analysis is correct.