The Halstead theory of software science is used to describe the compilation process and generate a compiler performance index. A nonlinear model of compile time is estimated for four Ada compilers. A fundamental relation between compile time and program modularity is proposed. Issues considered include data collection procedures, the development of a counting strategy, the analysis of the complexity measures used, and the investigation of significant relationships between program characteristics and compile time. The results indicate that the model has a high predictive power and provides interesting insights into compiler performance phenomena. The research suggests that the discrimination rate of a compiler is a valuable performance index and is preferred to average compile-time statistics.>