https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125934
Bug ID: 125934
Summary: [17 Regression] 7-9% slowdown of cactusADM on Zen4
since r17-1586-gc36539e6fd0dfa
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: 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=967.100.0
there was a 7-9% exec time slowdown of the cactusADM SPEC 2006
benchmark when compiled with -Ofast -g on an Zen4
machine. I bisected it to r17-1586-gc36539e6fd0dfa.
c36539e6fd0dfa6bd1ebb891df68da9a5bd96163 is the first bad commit
commit c36539e6fd0dfa6bd1ebb891df68da9a5bd96163
Author: Richard Biener <[email protected]>
Date: Thu Jun 11 15:51:02 2026 +0200
tree-optimization/125730 - avoid losing track of base in IVOPTs
This is a regression against GCC 16. See the comparison
here:
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=943.100.0&plot.1=1000.100.0&plot.2=985.100.0&plot.3=1013.100.0&plot.4=1162.100.0&plot.5=1580.100.0&plot.6=967.100.0&;
There were also these cactusADM slowdowns in the same timeframe (so probably
caused by the same commit):
8% Zen4 -Ofast -march=x86-64-v3 -g -flto=128
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=1119.100.0
14% aarch64 (Ampere Altra Neoverse N1) -Ofast -march=native -g with PGO
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=578.100.0
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)
