https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123328
Bug ID: 123328
Summary: 4% slowdown of povray on Zen5 since
r16-6152-g4204d3c46581bf 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: 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=1289.160.0
there was a 4% exec time slowdown of the povray SPEC 2006
benchmark when compiled with -O2 -march=x86-64-v3 -g -flto=128
-fprofile-generate on a Zen5 machine.
machine. I bisected it to r16-6152-g4204d3c46581bf.
4204d3c46581bff5461e7b837e8bd3e1f2c24a2e is the first bad commit
commit 4204d3c46581bff5461e7b837e8bd3e1f2c24a2e
Author: Andrew Pinski <[email protected]>
Date: Sat Dec 13 20:48:51 2025 -0800
final_cleanup: Don't create forwarder blocks for degenerate_phis that are
ifconvertable [PR123111]
We don't have any data for older gcc versions, so I am not sure whether this is
a 16 regression or not.
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)
