TLDR; If you want RR on ARM try UndoDB (which has a different instrumentation method). RR needs an accurate count of "retired instructions" to replay correctly.

TLDR; If you want RR on ARM try UndoDB (which has a different instrumentation method). RR needs an accurate count of "retired instructions" to replay correctly. ARM has non-deterministic behaviour for this count because an instruction may fail for example due to a cache miss or a hardware interrupt,the instruction would be re-tried of course but the retired instruction count for a code path run multiple times can vary even if identical branches are taken. Longer / better description at this URL. https://github.com/mozilla/rr/issues/1373 https://github.com/mozilla/rr/issues/1373