A Unifying Framework for Undoing Code Transformations

Abstract

A transformation applied to optimize or parallelize a program may be found to be ineffective, or may be made invalid by code changes. In this paper, we present a unifying framework to remove such transformations. The technique employs inverse primitive actions, making it transformation independent. The order of undoing the transformations is independent of the application order. The technique uses post conditions of a transformation to determine whether the transformation can be immediately removed. An undo algorithm and the analysis for correctness of the algorithm are presented. An undo facility has been implemented and experimental results for applicable transformations and enabled transformations are reported.