In Search of an Optimal Machine Architecture for BCPL

This paper investigates the problem of generating optimal space-efficient code for the language BCPL. Designing such a code was seen to be a two-phase process. The first phase was to describe an internal representation scheme for BCPL programs which preserved those program features which are salient to translation and at the same time minimize the number of instructions generated. The second phase consisted of the realization of the internal representation as an actual machine taking into account the usage frequencies of instructions and other real world constraints such as word size and addressing space. The Intermediate CodE, called ICE and an encoding scheme (known as ESO, standing for Encoding Scheme 0) are described. ICE/ESO is seen to reduce code size by an average of about 32% compared to BCODE which is a realization of OCODE, the intermediate language currently used in BCPL program translation.