Retargetable microcode synthesis

Abstract

Most work on automating the translation of high-level microprogramming languages into microcode has dealt with lexical and syntactic analysis and the use of manually produced macro tables for code generation. We describe an approach to and some results on the formalization and automation of the more difficult problem of retargeting local code generation in a machine-independent, optimizing microcode synthesis system. Whereas this problem is similar in many ways to that of retargeting local code generation in high-level language compilers, there are some major differences that call for new approaches. The primary issues addressed in this paper are the representation of target microprogrammable machines, the intermediate representation of local microprogram function, and general algorithmic methods for deriving local microcode from target machine and microcode function specifications. Of particular interest are the use of formal semantics and data flow principles in achieving both a general and reasonably efficient solution. Examples of the modeling of a representative horizontal machine (the PUMA) and the generation of microcode for the PUMA machine model from our working implementation are presented.