Separate Compilation for Synchronous Modules

Abstract

Synchronous models are useful for designing real-time embedded systems because they provide timing control and deterministic concurrency. However, the semantics of such models usually require an entire system to be compiled at once to analyze the dependencies among modules. The alternative is to write modules that can respond when the values of some of their inputs are unknown, a tedious and error-prone process. We present a compilation technique that allows a programmer to describe synchronous modules without having to consider undefined inputs. Our algorithm transforms such a description into code that does as much as it can with undefined inputs, allowing modules to be compiled separately and assembled later. We implemented our technique in a compiler for the Esterel language and present results that show the technique does not impose a substantial overhead.

A higher-order extension for imperative synchronous languages

“…Some works [24,26] address different notions of "modular compilation". In [26], the generated code is able to partially deal with undefined inputs by using a three-valued logic. The generated program tries to compute as many outputs as it can while ignoring inputs that are still unknown.…”

Modularity vs. Reusability: Code Generation from Synchronous Block Diagrams

“…Different notions of "modular" compilation are studied in [11,10]. [11] consider the partial evaluation of Esterel programs: they generate code that tries to compute as many outputs as possible, while some inputs may be still unknown.…”

“…[11] consider the partial evaluation of Esterel programs: they generate code that tries to compute as many outputs as possible, while some inputs may be still unknown. [10] consider a language similar to Esterel called Quarz and its compilation to a target "job language".…”

Modular Compilation of Synchronous Programs

“…• A fourth approach is based on the translation of programs into concurrent control data flow graphs [11], [17], [9], [10], [23], whose sizes depend linearly on the given program. At each instant, the control flow graph is traversed until active nodes are found to trigger the execution of the corresponding subtree.…”

“…However, with the exception of [23], essentially none of the above compilation techniques considered a modular compilation, which is standard for all sequential programming languages. Modular compilation of synchronous programs is not at all straightforward: A previously compiled module may start or end with an incomplete macro step whose micro steps can interact with the micro steps of later added modules.…”