https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109690
--- Comment #7 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
Thanks a lot! There however still seems to be problem with vectorization
On zen4 i now get:
jh@ryzen4:~/gcc/build/gcc> ./xgcc -B ./ -O2 -march=native slp.c ; perf stat
./a.out
Performance counter stats for './a.out':
1,835.21 msec task-clock:u # 1.000 CPUs
utilized
0 context-switches:u # 0.000 /sec
0 cpu-migrations:u # 0.000 /sec
53 page-faults:u # 28.880 /sec
10,000,113,961 cycles:u # 5.449 GHz
(83.22%)
31,284 stalled-cycles-frontend:u # 0.00% frontend
cycles idle (83.23%)
64,771 stalled-cycles-backend:u # 0.00% backend
cycles idle (83.43%)
9,000,118,863 instructions:u # 0.90 insn per
cycle
# 0.00 stalled cycles per
insn (83.44%)
2,999,980,507 branches:u # 1.635 G/sec
(83.44%)
1,445 branch-misses:u # 0.00% of all
branches (83.25%)
1.835610338 seconds time elapsed
1.835628000 seconds user
0.000000000 seconds sys
jh@ryzen4:~/gcc/build/gcc> ./xgcc -B ./ -O2 -march=native -fno-tree-vectorize
slp.c ; perf stat ./a.out
Performance counter stats for './a.out':
1,107.63 msec task-clock:u # 1.000 CPUs
utilized
0 context-switches:u # 0.000 /sec
0 cpu-migrations:u # 0.000 /sec
53 page-faults:u # 47.850 /sec
6,000,774,547 cycles:u # 5.418 GHz
(83.35%)
32,208 stalled-cycles-frontend:u # 0.00% frontend
cycles idle (83.39%)
57,126 stalled-cycles-backend:u # 0.00% backend
cycles idle (83.39%)
7,999,763,446 instructions:u # 1.33 insn per
cycle
# 0.00 stalled cycles per
insn (83.39%)
2,999,982,314 branches:u # 2.708 G/sec
(83.39%)
911 branch-misses:u # 0.00% of all
branches (83.09%)
1.108032230 seconds time elapsed
1.104079000 seconds user
0.003985000 seconds sys
with -fno-tree-slp-vectorize I get:
loop:
.LFB0:
.cfi_startproc
sall a(%rip)
sall a+4(%rip)
sall a+8(%rip)
ret
Which seem to be still faster. It is same if I do a[i]++
jh@ryzen4:~/gcc/build/gcc> ./xgcc -B ./ -O2 -march=native slp2.c ; perf stat
./a.out
Performance counter stats for './a.out':
1,832.63 msec task-clock:u # 1.000 CPUs
utilized
0 context-switches:u # 0.000 /sec
0 cpu-migrations:u # 0.000 /sec
54 page-faults:u # 29.466 /sec
10,000,535,003 cycles:u # 5.457 GHz
(83.19%)
36,576 stalled-cycles-frontend:u # 0.00% frontend
cycles idle (83.34%)
75,320 stalled-cycles-backend:u # 0.00% backend
cycles idle (83.41%)
9,999,890,371 instructions:u # 1.00 insn per
cycle
# 0.00 stalled cycles per
insn (83.41%)
2,999,935,610 branches:u # 1.637 G/sec
(83.41%)
1,447 branch-misses:u # 0.00% of all
branches (83.23%)
1.833046939 seconds time elapsed
1.833062000 seconds user
0.000000000 seconds sys
jh@ryzen4:~/gcc/build/gcc> ./xgcc -B ./ -O2 -march=native slp2.c
-fno-tree-vectorize ; perf stat ./a.out
Performance counter stats for './a.out':
1,110.15 msec task-clock:u # 1.000 CPUs
utilized
0 context-switches:u # 0.000 /sec
0 cpu-migrations:u # 0.000 /sec
51 page-faults:u # 45.940 /sec
6,000,096,821 cycles:u # 5.405 GHz
(83.17%)
28,459 stalled-cycles-frontend:u # 0.00% frontend
cycles idle (83.43%)
48,165 stalled-cycles-backend:u # 0.00% backend
cycles idle (83.43%)
7,999,665,012 instructions:u # 1.33 insn per
cycle
# 0.00 stalled cycles per
insn (83.43%)
2,999,941,619 branches:u # 2.702 G/sec
(83.43%)
719 branch-misses:u # 0.00% of all
branches (83.12%)
1.110557635 seconds time elapsed
1.110575000 seconds user
0.000000000 seconds sys
jh@ryzen4:~/gcc/build/gcc> cat slp2.c
int a[100];
[[gnu::noipa]]
void loop()
{
for (int i = 0; i < 3; i++)
a[i]++;
}
int
main()
{
for (int j = 0; j < 1000000000; j++)
loop ();
return 0;
}
