Instruction-set-extension exploration using decomposable heuristic search

Instruction-set-extensions (ISEs) are custom instructions designed specifically for a class of applications. Hence extracting the maximum benefit out of them is any designer´s goal. ISE application is the problem of efficiently applying custom instructions such that some gain function like code-size is optimized. Traditional algorithmic techniques like ILP and state space search have failed to address practical designs. Hence a considerable effort has been put on the design of heuristic algorithms. In this paper we present a new optimal algorithm DCA* that combines divide-and-conquer technique with heuristic search to address this problem. We demonstrate the effectiveness of this novel algorithm on real life designs.