https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125855
--- Comment #9 from Filip Kastl <pheeck at gcc dot gnu.org> --- So I verified some of the slowdowns and speedups. Here is what I found: What r17-1577 certainly slowed down: https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=956.70.0 5% milc SPEC 2006 with -O2 -g -flto=128 on an Zen4 slowdown lbm 6% Zen2 -Ofast -march=native -g with PGO https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=299.240.0 6% slowdown on Zen3 with the same flags: milc O2 lto https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=469.70.0 What r17-1577 certainly sped up: 8% lntzen5.spec2006.gcc-trunk.O2_native:1242 lbm https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=1242.240.0 11% benzen.spec2006.gcc-trunk.O2_generic_lto:292 cactusADM https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=292.100.0 5% speedup: benzen.spec2006.gcc-trunk.O2_native_lto:290 lbm https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=290.240.0 These speedups certainly weren't caused by r17-1577: 5% speedup lntzen4.spec2006.gcc-trunk.O2_x86_64v3_lto:1101 zeusmp https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=1101.80.0 7% speedup lntzen5.spec2006.gcc-trunk.Ofast_native_lto:1284 cactusADM https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=1284.100.0 What remains unsure: - This slowdown (but it likely is caused by r17-1577 IMO): https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=1100.70.0 9-12% Zen4 -O2 -g -flto=128 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=3 -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection - The small intel speedups So all in all I'd say there are both things that sped up and things that slowed down. Without running a lot of benchmarks on a lot of machines with a lot of cmdline flags combinations (what Josef talked about), I don't think we can really determine for sure if the patch is net gain or net loss for SPEC CPU. If it were up to me, I'd keep the patch.
