Code Motioin and Code Placement : Just Synonyms?

摘要

We prove that there is no difference between code motion and code placement in the traditional syntactic setting, however, a dramatic difference in the semantic setting. We demonstrate this by re-investigating semantic CM under the persepctive of the recent development of syntactic CM. Besides clarifying and highlighting the analogies and essential differences between the syntacic and the semantic approach, this leads as a side-effect to a drastical reduction of the conceptual ocmplexity of the value-flow based procedure for semantic CM of [20], as the original bidirectional analysis is decomposed into purely unidirectional components. On the theoretical side, this establishes a natural semantical understanding in terms of the herbrand interpretation, and thus eases the proof of correctness; moreover, it shows the frontier of semantic CM, and gives reason for the lack of algorithms going beyond. On the practical side, it simplifies the implementation and increases the efficiency, which, like for its syntactic counterpart, can be the catalyst for its migration from academia into industrial practice.