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?
--
Marc Glisse
