On Thu, 5 May 2022, Marc Glisse via Gcc-help wrote: > On Thu, 5 May 2022, Stéphane Glondu via Gcc-help wrote: > > > As additional data points, the performance with several versions of gcc > > (as packaged in Debian testing/unstable): > > > > | gcc-9 | gcc-10 | gcc-11 | gcc-12 | > > ------------|-------|--------|--------|--------| > > -std=c99 | 24 | 23.5 | 23 | 23 | > > -std=gnu18 | 43 | 16.8 | 38 | 38 | > > > > One can see that the performance stays relatively constant with > > -std=c99, but varies significantly with -std=gnu18. > > Could you compare with c18 or gnu99, to determine if the issue is with c vs > gnu (most likely since fma seems important) or 99 vs 18? Good point. Also could you please add latency metrics, I see that your testing framework already exposes the '--latency' flag. I could reproduce a similar though less dramatic slowdown and am investigating. Alexander
