Interprocedural Compilation of Fortran D

Abstract

Fortran D is a version of Fortran extended with data decomposition specifications. It is designed to provide a machine-independent programming model for data-parallel applications and has heavily influenced the design of High Performance Fortran (HPF). In previous work we described Fortran D compilation algorithms for individual procedures. This paper presents an interprocedural approach to analyze data and computation partitions, optimize communication, support dynamic data decomposition, and perform other tasks required to compile Fortran D programs. Our algorithms are designed to make interprocedural compilation efficient. First, we collect summary information after edits to solve important data-flow problems in a separate interprocedural propagation phase. Second, for nonrecursive programs we compile procedures in reverse topological order to propagate additional interprocedural information during code generation. We thus limit compilation to a single pass over each procedure body. We also perform optimizations across procedure boundaries by delaying instantiation of the computation partition, communication, and dynamic data decomposition. Empirical results show that interprocedural optimization is crucial in achieving acceptable performance for a common application code.