https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107499
Bug ID: 107499
Summary: 433.milc regressed by 6-8% on zen3 at -O2 -flto
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: jamborm at gcc dot gnu.org
CC: rguenth at gcc dot gnu.org
Blocks: 26163
Target Milestone: ---
Host: x86_64-linux
Target: x86_64-linux
LNT reports a 8.5% regression of 433.milc when compiled with -O2 -flto
on a zen3 machine:
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=469.70.0
On a similar machine I reproduced it as a 6.5% regression and bisected
it to 19295e8607d (tree-optimization/100756 - niter analysis and
folding).
Possibly related, possibly not:
- An intel machine results show something which might be a 2%
regression around the same time at -O2 -flto -march=native.
See https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=790.70.0
- In the same time-frame there is also a 5% performance drop on zen2
with -Ofast -flto -march=native, but those results have been rather
flaky in the past (see PR 101296):
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=289.70.0
- there is a 11% regression reported on the same zen3 machine when
using O2 flto -march=native but either I cannot reproduce it or it
does not seem to be caused by the same commit. I'll wait for more
LNT results before investigating. See
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=465.70.0
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=26163
[Bug 26163] [meta-bug] missed optimization in SPEC (2k17, 2k and 2k6 and 95)
