Post-silicon bug localization for processors using IFRA

IFRA, an acronym for Instruction Footprint Recording and Analysis, overcomes major challenges associated with a very expensive step in post-silicon validation of processors---pinpointing a bug location and the instruction sequence that exposes the bug from a system failure, such as a crash. Special on-chip recorders, inserted in a processor during design, collect instruction footprints---special information about flows of instructions, and what the instructions did as they passed through various microarchitectural blocks of the processor. The recording is done concurrently during the normal operation of the processor in a post-silicon system validation setup. Upon detection of a system failure, the recorded information is scanned out and analyzed offline for bug localization. Special self-consistency-based program analysis techniques, together with the test-program binary of the application executed during post-silicon validation, are used for this purpose. Major benefits of using IFRA over traditional techniques for post-silicon bug localization are (1) it does not require full system-level reproduction of bugs, and (2) it does not require full system-level simulation. Hence, it can overcome major hurdles that limit the scalability of traditional post-silicon validation methodologies. Simulation results on a complex superscalar processor demonstrate that IFRA is effective in accurately localizing electrical bugs with 1% chip-level area impact.