https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109811
--- Comment #15 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
With SRA improvements r:aae723d360ca26cd9fd0b039fb0a616bd0eae363 we finally get
good performance at -O2. Improvements to push_back implementation also helps a
bit.
Mainline with default flags (-O2):
Input: JPEG - Quality: 90:
19.76
19.75
19.68
Mainline with -O2 -march=native:
Input: JPEG - Quality: 90:
20.01
20
19.98
Mainline with -O2 -march=native -flto
Input: JPEG - Quality: 90:
19.95
19.98
19.81
Mainline with -O2 -march=native -flto --param max-inline-insns-auto=80 (this
makes push_back inlined)
Input: JPEG - Quality: 90:
19.98
20.05
20.03
Mainline with -O2 -flto -march=native -I/usr/include/c++/v1 -nostdinc++ -lc++
(so clang's libc++)
21.38
21.37
21.32
Mainline with -O2 -flto -march=native run manualy since build machinery patch
is needed
23.03
22.85
23.04
Clang 17 with -O2 -march=native -flto and also -fno-tree-vectorize
-fno-tree-slp-vectorize added by cmake. This is with system libstdc++ from
GCC13 so before push_back improvements.
21.16
20.95
21.06
Clang 17 with -O2 -march=native -flto and also -fno-tree-vectorize
-fno-tree-slp-vectorize added by cmake. This is with trunk libstdc++ with
push_back improvements.
21.2
20.93
20.98
Clang 17 with -O2 -march=native -flto -stdlib=libc++ and also
-fno-tree-vectorize -fno-tree-slp-vectorize added by cmake. This is with clan'g
libc++
Input: JPEG - Quality: 90:
22.08
21.88
21.78
Clang 17 with -O3 -march=native -flto
23.08
22.90
22.84
libc++ declares push_back always_inline and splits out the slow copying path. I
think the inlined part is still bit too large for inlining at -O2.
We could still try to get remaining approx 10% without increasing code size at
-O2
However major part of the problem is solved.
