https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113847
Bug ID: 113847
Summary: [14 Regression] 10% slowdown of 462.libquantum on AMD
Ryzen 7700X and Ryzen 7900X
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Keywords: missed-optimization, needs-bisection
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: fkastl at suse dot cz
Target Milestone: ---
Host: x86_64-linux
Target: x86_64-linux
As seen here
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=956.210.0
between commits
g:d826596acb02edf4
and
g:23cd2961bd2ff635
there is about 10% slowdown of execution time of the 2006SPEC 462.libquantum
benchmark.
The test is run with -O2 and lto on an AMD Ryzen 7700X.
I also reproduced the slowdown on a AMD Ryzen 7900X machine. However I wasn't
able to reproduce the slowdown on an AMD EPYC machine - also Zen4
microarchitecture. So I suppose this slowdown occurs only on Zen4 Ryzen CPUs or
is maybe even more specific.
I'm not sure if we want to do anything about this. The same slowdown on the
same machine has already happened once, see pr112547. The benchmark results
eventually returned to the original values.
