https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119596
--- Comment #4 from Mateusz Guzik <mjguzik at gmail dot com> --- Sorry guys, I must have pressed something by accident and the bug submitted before I typed it out. Anyhow the crux is: (In reply to Andrew Pinski from comment #1) > This is 100% a tuning issue. The generic tuning is tuned for a generic > target. You could use -mtune= to get a better tuning for the processor you > using. The gcc default for the generic target is poor. rep is known to be a problem on most uarchs. I verified clang 18 issues regular ops up to at least 128 bytes.
