https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126056
Bug ID: 126056
Summary: [17 Regression] 25% slowdown of 470.lbm on AMD Zen5
since r17-1845-g23b6a9a41a5c05
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: pheeck at gcc dot gnu.org
CC: konstantinos.eleftheriou at vrull dot eu,
ptomsich at gcc dot gnu.org
Blocks: 26163
Target Milestone: ---
Host: x86_64-pc-linux-gnu
Target: x86_64-pc-linux-gnu
As shown here
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=1283.240.0
there was a 25% slowdown of the SPEC CPU 2006 benchmark lbm on AMD Zen5 when
built with -Ofast -march=native -flto PGO (-fprofile-use).
I've bisected this to r17-1845-g23b6a9a41a5c05
commit 23b6a9a41a5c052f880f26b896357c5b207ca24a
Author: Konstantinos Eleftheriou <[email protected]>
AuthorDate: Thu Jun 18 09:48:05 2026 +0200
Commit: Philipp Tomsich <[email protected]>
CommitDate: Thu Jun 25 13:18:54 2026 +0200
tail-merge: Combine conditions of merged blocks for ccmp [PR102793]
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)
