https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123250
Bug ID: 123250
Summary: [16 Regression] 9% slowdown of mcf on Zen5 since
r16-6233-g135fe58ec9a989 with PGO
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: jmelcr at gcc dot gnu.org
CC: pheeck at gcc dot gnu.org, pinskia at gcc dot gnu.org
Blocks: 26163
Target Milestone: ---
Host: x86_64-suse-linux
Target: x86_64-suse-linux
As seen here
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=1289.60.0
there was a 9% exec time slowdown of the mcf SPEC 2006
benchmark when compiled with -O2 -march=x86-64-v3 -flto on a Zen5
machine. I bisected it to r16-6233-g135fe58ec9a989.
commit 135fe58ec9a989fc301d762547325fd90ea37397
Author: Andrew Pinski <[email protected]>
Date: Mon Dec 15 12:36:44 2025 -0800
ch: Fix detection of non-executed loop exit
This is a regression against GCC 15. See the comparison
here:
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=1263.60.0&plot.1=1318.60.0&plot.2=1314.60.0&plot.3=1346.60.0&plot.4=1289.60.0&;
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)
