https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126367
Bug ID: 126367
Summary: [17 Regression] 6% slowdown of milc on Zen4 since
r17-2163-ge754b70fe5470b
Product: gcc
Version: 17.0
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: hjl.tools at gmail dot com, 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
As seen here
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=991.70.0
there was a 6% exec time slowdown of the milc SPEC 2006
benchmark when compiled with -Ofast -march=native -g -flto=128 with PGO on an
Zen4
machine. I bisected it to r17-2163-ge754b70fe5470b.
e754b70fe5470b975d31887fa5647f1c92d6522d is the first bad commit
commit e754b70fe5470b975d31887fa5647f1c92d6522d
Author: H.J. Lu <[email protected]>
Date: Tue Apr 7 23:16:38 2026 +0800
x86: Rewrite ix86_find_max_used_stack_alignment
This <is (not)> a regression against GCC 16. See the comparison
here:
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=945.70.0&plot.1=989.70.0&plot.2=974.70.0&plot.3=1011.70.0&plot.4=1148.70.0&plot.5=1574.70.0&plot.6=991.70.0&;
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)
