Reducing Code Size with Run-Time Decompression

Compressed representations of programs can be used to improve the code density in embedded systems. Several hardware decompression architectures have been proposed recently. In this paper, we present a method of decompressing programs using software. It relies on using a softwaremanaged instruction cache under control of the decompressor. This is achieved by employing a simple cache management instruction that allows explicit writing into a cache line. We also consider selective compression (determining which procedures in a program should be compressed) and show that selection based on cache miss profiles can substantially outperform the usual execution time based profiles for some benchmarks.