Instruction Precomputation for Fault Detection

Fault tolerance (FT) is becoming increasingly important in computing systems. This work proposes and evaluates the instruction precomputation technique to detect hardware faults. Applications are profiled off-line, and the most frequent instruction instances with their operands and results are loaded into the precomputation table when executing. The precomputation-based error detection technique is used in conjunction with another method that duplicates all instructions and compares the results. In the precomputation-enabled version, whenever possible, the instruction compares its result with a precomputed value, rather than executing twice. Another precomputation-based scheme does not execute the precomputed instructions at all, assuming that precomputation provides sufficient reliability. Precomputation improves the fault coverage (including permanent and some other faults) and performance of the duplication method. The proposed method is compared to an instruction memoization-based technique. The performance improvements of the precomputation- and memoization-based schemes are comparable, while precomputation has a better long-lasting fault coverage and is considerably cheaper.