Instruction-level parallelism in Prolog

Abstract

The demand of increasing computation power for symbolic processing has given a strong impulse to the development of ASICs dedicated to the execution of prolog. Unlike past microcoded implementation based on the Warren machine model, novel trends in high performance Prolog processors suggest the implementation of RISC-based processors committed to prolog only through the adoption of a few basic dedicated features, like the Berkeley Abstract Machine (BAM) processor. Following the idea of using a smart compiler for a simple instruction set, the SYMBOL project represents an experiment in applying global compaction techniques and VLIW design philosophy to the static exploitation of instruction-level parallelism in Prolog. This paper presents code analysis results and shows how we can approach the theoretical speed-up limit (about 3) imposed by Amdahl's law on shared memory models, by means of global code optimizations and a suitable architectural support. In addition, we show implementation details and some preliminary data of a VLSI prototype architecture.