Instruction Splitting for Efficient Code Compression

The size of embedded software is rising at a rapid pace. It is often challenging and time consuming to fit an amount of required software functionality within a given hardware resource budget. Code compression is a means to alleviate the problem. In this paper we introduce a novel and efficient hardware-supported approach. Our scheme reduces the size of the generated decoding table by splitting instructions into portions of varying size (called patterns) before Huffman coding compression is applied. It improves the final compression ratio (including all overhead that incurs) by more than 20% compared to known schemes based on Huffman coding. We achieve allover compression ratios as low as 44%. Thereby, our scheme is orthogonal to approaches that take particularities of a certain instruction set architectures into account. We have conducted evaluations using a representative set of applications and have applied it to two major embedded processors, namely ARM and MIPS.