https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102750
Bug ID: 102750
Summary: 433.milc regressed by 10% on AMD zen2 at -Ofast
-march=native -flto after r12-3893-g6390c5047adb75
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: jamborm at gcc dot gnu.org
CC: rguenth at gcc dot gnu.org
Blocks: 26163
Target Milestone: ---
Host: x86_64-linux
Target: x86_64-linux
I have bisected an AMD zen2 10% performance regression of SPEC 2006 FP
433.milc benchmark when compiled with -Ofast -march=native -flto to
commit r12-3893-g6390c5047adb75. See also:
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=412.70.0&plot.1=289.70.0&;
As Richi asked, I am filing this bug even though I cannot reproduce the
regression neither on an AMD zen3 machine nor on Intel CascadeLake, because
the history of the benchmark performance and because I know milc can be
sensitive to conditions outside our control. OTOH, the regression
reproduces reliably for me.
Some relevant perf data:
BEFORE:
# Samples: 585K of event 'cycles:u'
# Event count (approx.): 472738682838
#
# Overhead Samples Command Shared Object Symbol
# ........ ............ ............... ......................
.........................................
#
24.59% 140397 milc_peak.mine- milc_peak.mine-lto-nat [.]
u_shift_fermion
18.47% 105497 milc_peak.mine- milc_peak.mine-lto-nat [.]
add_force_to_mom
15.97% 96343 milc_peak.mine- milc_peak.mine-lto-nat [.]
mult_su3_na
15.29% 90027 milc_peak.mine- milc_peak.mine-lto-nat [.]
mult_su3_nn
5.55% 35114 milc_peak.mine- milc_peak.mine-lto-nat [.]
path_product
4.75% 27693 milc_peak.mine- milc_peak.mine-lto-nat [.]
compute_gen_staple
2.76% 16109 milc_peak.mine- milc_peak.mine-lto-nat [.]
mult_su3_an
2.42% 14255 milc_peak.mine- milc_peak.mine-lto-nat [.]
imp_gauge_force.constprop.0
2.02% 11561 milc_peak.mine- milc_peak.mine-lto-nat [.]
mult_adj_su3_mat_4vec
AFTER:
# Samples: 634K of event 'cycles:u'
# Event count (approx.): 513635733685
#
# Overhead Samples Command Shared Object Symbol
# ........ ............ ............... ......................
.........................................
#
24.04% 149010 milc_peak.mine- milc_peak.mine-lto-nat [.]
add_force_to_mom
23.76% 147370 milc_peak.mine- milc_peak.mine-lto-nat [.]
u_shift_fermion
14.19% 90929 milc_peak.mine- milc_peak.mine-lto-nat [.]
mult_su3_nn
14.14% 92912 milc_peak.mine- milc_peak.mine-lto-nat [.]
mult_su3_na
4.90% 33846 milc_peak.mine- milc_peak.mine-lto-nat [.]
path_product
3.89% 24621 milc_peak.mine- milc_peak.mine-lto-nat [.]
mult_su3_an
3.62% 22831 milc_peak.mine- milc_peak.mine-lto-nat [.]
compute_gen_staple
2.05% 13215 milc_peak.mine- milc_peak.mine-lto-nat [.]
imp_gauge_force.constprop.0
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)
