Towards portable microcode

The implementation of a retargetable microcode generator system (RMGS) is described for a six-stage translation system. Portability of microcode is achieved by specifying microprograms in a C-like HLL (high-level language) and translating the specification into horizontal microcode. The HLL microprogram description is translated into an intermediate semantic description language (ISDL). The ISDL specification is then translated into a machine-dependent microcode using a heuristic pattern-matched code generator. Retargetability to a wide variety of machines is achieved through a semantic description of a particular machine. The code is compacted using a greedy heuristic strategy. Optimization techniques are applied to the intermediate form by shape analysis, during code generation through cost analysis, and during compaction through an optimal graph coloring inherent to the compaction strategy.<>