A Hardware Approach to Real-Time Program Trace Compression for Embedded Processors

Collecting the program execution traces at full speed is essential to the analysis and debugging of real-time software behavior of a complex system. However, the generation rate and the size of real-time program traces are so huge such that real-time program tracing is often infeasible without proper hardware support. This paper presents a hardware approach to compress program execution traces in real time in order to reduce the trace size. The approach consists of three modularized phases: 1) branch/target filtering; 2) branch/target address encoding; 3) Lempel-Ziv (LZ)-based data compression. A synthesizable RTL code for the proposed hardware is constructed to analyze the hardware cost and speed and typical multimedia benchmarks are used to measure the compression results. The results show that our hardware is capable of real-time compression and achieving compression ratio of 454:1, far better than 5:1 achieved by typical existing hardware approaches. Furthermore, our modularized approach makes it possible to trade off between the hardware cost (typically from 1 to 50K gates) and the achievable compression ratio (typically from 5:1 to 454:1)