https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120959
Bug ID: 120959
Summary: [16 Regression] 9% slowdown of 549.fotonik3d_r on Zen5
since r16-1645-g309dbcea2cabb3
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: pheeck at gcc dot gnu.org
CC: tnfchris at gcc dot gnu.org
Blocks: 26163
Target Milestone: ---
Host: x86_64-pc-linux-gnu
Target: x86_64-pc-linux-gnu
As seen here
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=1244.527.0
there was a 9% exec time slowdown of the 549.fotonik3d_r SPEC 2017
benchmark when run with -O2 -flto -fprofile-use (generic march) on an AMD Zen 5
machine.
I bisected it to r16-1645-g309dbcea2cabb3.
commit 309dbcea2cabb31bde1a65cdfd30bb7f87b170a2
Author: Tamar Christina <tamar.christ...@arm.com>
AuthorDate: Tue Jun 24 07:13:22 2025 +0100
Commit: Tamar Christina <tamar.christ...@arm.com>
CommitDate: Tue Jun 24 07:13:22 2025 +0100
middle-end: replace log_vf usages with vf to allow support for non-power of
two vf
This is a regression against GCC 15. If I measure manually the most recent
commit of releases/gcc-15, I get the same exec time as before Tamar's commit on
trunk.
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)
