In theory. In practice, it's not as widely tested and so a lot more bugs survive. This search is approximate both ways, but still finds a lot of examples of O3

In theory. In practice, it's not as widely tested and so a lot more bugs survive. This search is approximate both ways, but still finds a lot of examples of O3 being outright broken: https://gcc.gnu.org/bugzilla/buglist.cgi?short_desc=O3&resolution=---&resolution=FIXED&order=Importance&query_format=advanced&bug_status=ASSIGNED&bug_status=RESOLVED&bug_status=VERIFIED&short_desc_type=allwordssubstr&cf_known_to_work_type=allwords&cf_known_to_fail_type=allwords https://gcc.gnu.org/bugzilla/buglist.cgi?short_desc=O3&resol...