Instruction Level Loop De-optimization

Instruction level loop optimization has been widely used in modern compilers. Decompilation—the reverse of compilation—has also generated much interest for its applications in porting legacy software written in assembly language to new architectures, re-optimizing assembly code, and more recently, in detecting and analyzing malware. However, little work has been reported on loop decompilation at instruction level. In this paper, we report our work on loop de-optimization at instruction level. We demonstrate our approach with a practical working example and carried out experiments on TIC6x, a digital signal processor with a compiler supporting instruction level parallelism. The algorithms developed in this paper should help interested readers gain insight especially in the difficult tasks of loop rerolling and software de-pipelining, the necessary steps to decompile loops at instruction level.