A Uniform Approach for Compile-Time and Run-Time Specialization

As partial evaluation gets more mature it is now possible to use this program transformation technique to tackle realistic languages and real size application programs However this evolution raises a num ber of critical issues that need to be addressed before the approach be comes truly practical First of all most existing partial evaluators have been developed based on the assumption that they could process any kind of application pro gram This attempt to develop universal partial evaluators does not ad dress some critical needs of real size application programs Furthermore as partial evaluators treat richer and richer languages their size and com plexity increase drastically This increasing complexity revealed the need to enhance design principles Finally exclusively specializing programs at compile time seriously limits the applicability of partial evaluation since a large class of invariants in real size programs are not known until run time and therefore cannot be taken into account In this paper we propose design principles and techniques to deal with each of these issues By de ning an architecture for a partial evaluator and its essential com ponents we are able to tackle a rich language like C without compro mising the design and the structure of the resulting implementation By designing a partial evaluator targeted towards a speci c application area namely system software we have developed a system capable of treating realistic programs Because our approach to designing a partial evaluator clearly separates preprocessing and processing aspects we are able to introduce run time specialization in our partial evaluation system as a new way of exploiting information produced by the preprocessing phase