Description and Optimization of Abstract Machines in a Dialect of Prolog

TL;DR

This paper demonstrates how describing Prolog abstract machines in a high-level Prolog dialect and compiling to C can simplify development and optimization, achieving performance comparable to or better than traditional low-level implementations.

Contribution

It introduces a method to describe and optimize Prolog abstract machines using high-level Prolog, facilitating easier maintenance and potential performance improvements.

Findings

High-level Prolog descriptions enable effective optimization.

Generated emulators match or surpass hand-crafted performance.

The approach simplifies development and extension of abstract machines.

Abstract

In order to achieve competitive performance, abstract machines for Prolog and related languages end up being large and intricate, and incorporate sophisticated optimizations, both at the design and at the implementation levels. At the same time, efficiency considerations make it necessary to use low-level languages in their implementation. This makes them laborious to code, optimize, and, especially, maintain and extend. Writing the abstract machine (and ancillary code) in a higher-level language can help tame this inherent complexity. We show how the semantics of most basic components of an efficient virtual machine for Prolog can be described using (a variant of) Prolog. These descriptions are then compiled to C and assembled to build a complete bytecode emulator. Thanks to the high level of the language used and its closeness to Prolog, the abstract machine description can be manipulated using standard Prolog compilation and optimization techniques with relative ease. We also show how, by applying program transformations selectively, we obtain abstract machine implementations whose performance can match and even exceed that of state-of-the-art, highly-tuned, hand-crafted emulators.