An improvement of trace scheduling for global microcode compaction

Abstract

Fisher's trace scheduling procedure for global compaction has proven to be able to produce significant reduction in execution time of compacted microcode, however extra space may be sometimes required during bookkeeping, and the efficacy of compaction of microprogram loop is lower than that of hand compaction. This paper introduces an improved trace scheduling compaction algorithm to mitigate the drawbacks mentioned above. The improved algorithm is based on a modified menu of moving microoperations, an improved trace scheduling algorithm, and a special loop compaction algorithm. Preliminary tests indicate that this global compaction algorithm gives shorter execution time and less space requirement in comparison with Fisher's algorithm.