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| author | Nick Desaulniers <ndesaulniers@google.com> | 2022-06-29 00:04:07 +0300 |
|---|---|---|
| committer | Masahiro Yamada <masahiroy@kernel.org> | 2022-07-27 15:17:59 +0300 |
| commit | a6036a41bffba3d5007e377483b425d470ad8042 (patch) | |
| tree | 5e2922a9b7700c8c702df80b7d6d0272996d6b1c /arch/arc/configs/nsim_700_defconfig | |
| parent | 5439d4d4dcee548b1ad984c293225c1668045ad2 (diff) | |
| download | linux-a6036a41bffba3d5007e377483b425d470ad8042.tar.xz | |
kbuild: drop support for CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3
The difference in most compilers between `-O3` and `-O2` is mostly down
to whether loops with statically determinable trip counts are fully
unrolled vs unrolled to a multiple of SIMD width.
This patch is effectively a revert of
commit 15f5db60a137 ("kbuild,arc: add
CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3 for ARC") without re-adding
ARCH_CFLAGS
Ever since
commit cfdbc2e16e65 ("ARC: Build system: Makefiles, Kconfig, Linker
script")
ARC has been built with -O3, though the reason for doing so was not
specified in inline comments or the commit message. This commit does not
re-add -O3 to arch/arc/Makefile.
Folks looking to experiment with `-O3` (or any compiler flag for that
matter) may pass them along to the command line invocation of make:
$ make KCFLAGS=-O3
Code that looks to re-add an explicit Kconfig option for `-O3` should
provide:
1. A rigorous and reproducible performance profile of a reasonable
userspace workload that demonstrates a hot loop in the kernel that
would benefit from `-O3` over `-O2`.
2. Disassembly of said loop body before and after.
3. Provides stats on terms of increase in file size.
Link: https://lore.kernel.org/linux-kbuild/CA+55aFz2sNBbZyg-_i8_Ldr2e8o9dfvdSfHHuRzVtP2VMAUWPg@mail.gmail.com/
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Diffstat (limited to 'arch/arc/configs/nsim_700_defconfig')
| -rw-r--r-- | arch/arc/configs/nsim_700_defconfig | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/arch/arc/configs/nsim_700_defconfig b/arch/arc/configs/nsim_700_defconfig index 326f6cde7826..a1ce12bf5b16 100644 --- a/arch/arc/configs/nsim_700_defconfig +++ b/arch/arc/configs/nsim_700_defconfig @@ -11,7 +11,6 @@ CONFIG_NAMESPACES=y # CONFIG_UTS_NS is not set # CONFIG_PID_NS is not set CONFIG_BLK_DEV_INITRD=y -CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3=y CONFIG_KALLSYMS_ALL=y CONFIG_EMBEDDED=y CONFIG_PERF_EVENTS=y |