Using Lin-Kernighan algorithm for look-up table compression to improve code density

The presented work uses code compression to improve the design efficiency of an embedded system. In particular, we present a method and architecture for compressing the so-called Look-up Tables that are necessary for the de-compression process. No other work has yet focused on minimizing the Look-up Tables that, as we show, have a significant impact on the total overhead of a hardware-based decompression scheme. We introduce a novel and very efficient hardware-supported approach based on Canonical Huffman Coding. Using the Lin-Kernighan algorithm we reduce the Look-up Table size by up to 45%. As a result, we achieve all-over compression ratios as low as 45% (already including the overhead of the Look-up Tables). Thereby, our scheme is entirely orthogonal to approaches that take particularities of a certain instruction set architecture into account, meaning that compression could be further improved. Factoring in the orthogonality, our scheme is the basis for not-yet-achieved efficiency in hardware-supported compression schemes. We have conducted evaluations using a representative set (in terms of size and application domain) of applications and have applied it to three major embedded processor architectures, namely ARM, MIPS and PowerPC. The hardware evaluation shows no performance penalty.