Partial Translation

Traditional simulation of a target architecture by interpreting object code can be improved by translating the object code to an intermediate format. This approach is called interpretive translation. Despite a substantial performance improvement over traditional interpretation, a large part of the overhead is unnecessary. An alternative approach is block translation, where one or more simulated instructions are translated to directly executable code. This approach has several drawbacks. We discuss the problems with block translation, analyse the overhead of interpretive translation, and describe a hybrid approach—partial translation—that combines the benefits of both approaches. Partial translation implements an intermediate format that supports the addition of run-time generated code whenever appropriate. The performance limit (slowdown) of interpetive translation is around 15, and real implementations have achieved 20-30. Partial translation will perform considerably better. Finally, we present results from an aggressive implementation of interpretive translation, and results from a proof-of-concept implementation of partial translation.