> Date: Thu, 5 May 2022 16:41:28 +0200 (CEST)
> From: Marc Glisse <marc.glisse@xxxxxxxx>
>
> 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?
yes it is easy. On another i5:
| gcc-9 | gcc-10 | gcc-11 |
------------|-------|--------|--------|
-std=c99 | 24.3 | 23.8 | 23.8 |
-std=c18 | 24.4 | 23.8 | 23.9 |
-std=gnu99 | 42.9 | 19.2 | 35.0 |
-std=gnu18 | 42.9 | 19.2 | 35.0 |
Thus the issue is definitely c vs gnu.
Paul
