InterProcedural Alias Analiysis: Implementation and Empirical Results

We report our experiences with the implementation of InterProcedural Alias Analysis (IPA) for Fortran. Implicit aliasing caused by reference parameter passing can be uncovered in a program with multiple compilation units by interprocedural analysis. For scalar objects and for full arrays, the IPA processor described here finds all alias relations. For indexed array elements and partial arrays, conservative assumptions must still be made in the absence of precise knowledge about the subscripts. IPA has been integrated into nascent, the front-end of a Fortran translator under development at the Oregon Graduate Institute (OGI). This report explains the goals and limitations of alias analysis for conventional procedural languages with reference parameters, shows in detail the actual design and implementation of IPA, and provides algorithmic and speed improvements over the best previously known aliasing algorithms. Empirical results gathered during the analysis of large Fortran programs are also listed and discussed.