An efficient implementation of visibility in Ada

Abstract

This paper discusses the efficient implementation of Ada's visibility requirements. A scope stack and an unstructured name space are used to facilitate separate compilation and ensure that each Ada declaration takes a constant unit of time. Visibility issues affect practically every aspect of semantic analysis in Ada: declarations, statements, expressions, and separate compilation. The design of the symbol table package is, thus, a critical one. In this paper, I discuss the design goals of the symbol table for the Ada Integrated Environment (AIE) bootstrap compiler front end, and how they were influenced by the Ada language. Since the compiler is being heavily used by the AIE project, we have ample data with which to measure symbol table performance.