Compact Interface Method Table Layout

Abstract

This article describes a novel interface method table (IMT) layout approach, which allocates interface method tables inside virtual method table (VMT), allowing for table entries to be shared between VMT and multiple IMTs. Similarly to VMT layout inheritance for classes, a heuristical IMT layout inheritance scheme is implemented for interfaces. Unlike prior schemes, proposed “all or nothing” heuristic achieves considerable total table size reduction without any dispatch overhead. Together with combined layout of IMT and VMT, interface layout inheritance opens up even more opportunities for IMT layout reuse and total table size reduction. Application of all techniques outlined in this article results in a significant reduction of overall executable size.