Structure splitting and inheritance

The increasing gap between memory and processor performance
drives the
research for cache optimizations. Recently research
concentrates on
optimizing pointer based applications. Structure splitting
is an
important enabling transformation for optimizations that
improve the
layout of dynamic data structures. Previous work has shown
the
potential of structure splitting in runtime optimizations.
This paper
discusses issues of structure splitting applied to
inheritance
hierarchies of object oriented languages. Inheritance
requires
similar layout of compound types to simplify type casts.
Structure
splitting, in contrast, requires a layout that is tailored
for a
single type. Therefore compatibility between the split
type and its
super and sub-types is lost. This issue was not addressed
by previous
work. We explain several strategies to deal with this type
compatibility issue and implement two as a compiler
optimization.
Our experiments show that a careful choice of the strategy
is
necessary, as they either increase the overhead for
accessing
cache-neutral data, or they can not achieve the full
possible speed up
for cache-critical data. ... mehr Nevertheless, both approaches show
considerable speed ups of our tests.