https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89853
Bug ID: 89853
Summary: Regression of 525.x264_r at -O2 (and generic tuning)
on AMD EPYC
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: jamborm at gcc dot gnu.org
Target Milestone: ---
I have detected a 7% regression of 525.x264_r from SPEC INTrate 2017
at -O2 and generic march/tuning on AMD EPYC (znver1) CPUs (I have not seen
it on an Intel CPU), compared to the gcc-8-branch.
I have bisected it to r264897.
With revision 264896 I get:
perf stat:
Performance counter stats for 'numactl -C 0 -l specinvoke':
495413.105450 task-clock:u (msec) # 0.999 CPUs utilized
0 context-switches:u # 0.000 K/sec
0 cpu-migrations:u # 0.000 K/sec
80572 page-faults:u # 0.163 K/sec
1573525941814 cycles:u # 3.176 GHz
(83.33%)
56730573392 stalled-cycles-frontend:u # 3.61% frontend cycles
idle (83.33%)
397644125819 stalled-cycles-backend:u # 25.27% backend cycles
idle (83.33%)
5157395976259 instructions:u # 3.28 insn per cycle
# 0.08 stalled cycles
per insn (83.33%)
421019689027 branches:u # 849.836 M/sec
(83.33%)
10705813341 branch-misses:u # 2.54% of all branches
(83.33%)
495.869208013 seconds time elapsed
perf report -n --percent-limit 2
# Event count (approx.): 1576108148398
#
# Overhead Samples Command Shared Object Symbol
# ........ ......... ........... ..............
............................
#
14.20% 282290 x264_r_base x264_r_base.mi [.] x264_pixel_satd_8x4
11.19% 222403 x264_r_base x264_r_base.mi [.] get_ref
10.82% 215061 x264_r_base x264_r_base.mi [.]
x264_pixel_sad_x4_16x16
7.00% 139082 x264_r_base x264_r_base.mi [.] x264_pixel_sad_16x16
6.11% 121470 x264_r_base x264_r_base.mi [.]
x264_pixel_sad_x3_16x16
5.89% 116939 x264_r_base x264_r_base.mi [.]
x264_pixel_sad_x4_8x8
5.09% 101266 x264_r_base x264_r_base.mi [.] quant_4x4
4.10% 81471 x264_r_base x264_r_base.mi [.] mc_chroma
2.47% 49122 x264_r_base x264_r_base.mi [.]
x264_pixel_sad_x3_8x8
2.21% 43928 x264_r_base x264_r_base.mi [.] sub4x4_dct
2.14% 42598 x264_r_base x264_r_base.mi [.] pixel_hadamard_ac
With revision 264897 I get:
perf stat
Performance counter stats for 'numactl -C 0 -l specinvoke':
495413.105450 task-clock:u (msec) # 0.999 CPUs utilized
0 context-switches:u # 0.000 K/sec
0 cpu-migrations:u # 0.000 K/sec
80572 page-faults:u # 0.163 K/sec
1573525941814 cycles:u # 3.176 GHz
(83.33%)
56730573392 stalled-cycles-frontend:u # 3.61% frontend cycles
idle (83.33%)
397644125819 stalled-cycles-backend:u # 25.27% backend cycles
idle (83.33%)
5157395976259 instructions:u # 3.28 insn per cycle
# 0.08 stalled cycles
per insn (83.33%)
421019689027 branches:u # 849.836 M/sec
(83.33%)
10705813341 branch-misses:u # 2.54% of all branches
(83.33%)
495.869208013 seconds time elapsed
perf report -n --percent-limit 2
# Event count (approx.): 1576108148398
#
# Overhead Samples Command Shared Object
Symbol
# ........ ............ ............... ............................
.................................................
#
14.20% 282290 x264_r_base.min x264_r_base.mine-gen-std-m64 [.]
x264_pixel_satd_8x4
11.19% 222403 x264_r_base.min x264_r_base.mine-gen-std-m64 [.]
get_ref
10.82% 215061 x264_r_base.min x264_r_base.mine-gen-std-m64 [.]
x264_pixel_sad_x4_16x16
7.00% 139082 x264_r_base.min x264_r_base.mine-gen-std-m64 [.]
x264_pixel_sad_16x16
6.11% 121470 x264_r_base.min x264_r_base.mine-gen-std-m64 [.]
x264_pixel_sad_x3_16x16
5.89% 116939 x264_r_base.min x264_r_base.mine-gen-std-m64 [.]
x264_pixel_sad_x4_8x8
5.09% 101266 x264_r_base.min x264_r_base.mine-gen-std-m64 [.]
quant_4x4
4.10% 81471 x264_r_base.min x264_r_base.mine-gen-std-m64 [.]
mc_chroma
2.47% 49122 x264_r_base.min x264_r_base.mine-gen-std-m64 [.]
x264_pixel_sad_x3_8x8
2.21% 43928 x264_r_base.min x264_r_base.mine-gen-std-m64 [.]
sub4x4_dct
2.14% 42598 x264_r_base.min x264_r_base.mine-gen-std-m64 [.]
pixel_hadamard_ac
