Interprocedural optimization: eliminating unnecessary recompilation

While efficient new algorithms for interprocedural data flow analysis have made these techniques practical for use in production compilation systems, a new problem has arisen: collecting and using interprocedural information in a compiler introduces subtle dependences among the procedures of a program. If the compiler depends on interprocedural information to optimize a given module, a subsequent editing change to another module in the program may change the interprocedural information and necessitate recompilation. To avoid having to recompile every module in a program in response to a single editing change to one module, we must develop techniques to more precisely determine which compilations have actually been invalidated by a change to the program's source. This paper presents a general recompilation test to determine which procedures must be compiled in response to a series of editing changes. Three different implementation strategies, which demonstrate the fundamental tradeoff between the cost of analysis and the precision of the resulting test, are also discussed.