https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125660
Bug ID: 125660
Summary: [16/17 Regression] 6% slowdown of milc on Zen4 since
r16-6767-g948d33f490a6b0
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Keywords: deferred, missed-optimization
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: jmelcr at gcc dot gnu.org
CC: rguenth at gcc dot gnu.org
Blocks: 26163
Target Milestone: ---
Host: x86_64-suse-linux
Target: x86_64-suse-linux
Build: x86_64-suse-linux
This PR has been separated out of PR123603.
As seen here
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=1100.70.0
there was a 6% exec time slowdown of the milc SPEC 2006
benchmark when compiled with -O2 -g -flto=128 -U_FORTIFY_SOURCE
-D_FORTIFY_SOURCE=3 -fstack-protector-strong -funwind-tables
-fasynchronous-unwind-tables -fstack-clash-protection on a Zen4 machine. I
bisected it to r16-6767-g948d33f490a6b0.
948d33f490a6b0051376da6bdcf55223a552b30f is the first bad commit
commit 948d33f490a6b0051376da6bdcf55223a552b30f
Author: Richard Biener <[email protected]>
Date: Wed Jan 14 12:45:19 2026 +0100
tree-optimization/123190 - fix costing of permuted contiguous loads
This is a regression against GCC 15. See the comparison
here:
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=1112.70.0&plot.1=1129.70.0&plot.2=1120.70.0&plot.3=1105.70.0&plot.4=1143.70.0&plot.5=1100.70.0&;
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=26163
[Bug 26163] [meta-bug] missed optimization in SPEC (2026, 2k17, 2k and 2k6 and
95)
