Nick Desaulniers a6036a41bf 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 15f5db60a1 ("kbuild,arc: add CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3 for ARC") without re-adding ARCH_CFLAGS Ever since commit cfdbc2e16e ("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>		2022-07-27 21:17:59 +09:00
..
calibrate.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
do_mounts_initrd.c	kernel/do_mount_initrd: move real_root_dev sysctls to its own file	2022-04-06 13:43:44 -07:00
do_mounts_rd.c	init: add an init_unlink helper	2020-07-31 08:17:52 +02:00
do_mounts.c	block: remove genhd.h	2022-02-02 07:49:59 -07:00
do_mounts.h	init: add an init_mknod helper	2020-07-31 08:17:54 +02:00
init_task.c	kcsan: Remove redundant zero-initialization of globals	2021-12-09 16:42:26 -08:00
initramfs.c	This set of changes updates init and user mode helper tasks to be	2022-06-03 16:03:05 -07:00
Kconfig	kbuild: drop support for CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3	2022-07-27 21:17:59 +09:00
main.c	This set of changes updates init and user mode helper tasks to be	2022-06-03 16:03:05 -07:00
Makefile	sched/preempt: Tell about PREEMPT_DYNAMIC on kernel headers	2022-03-11 15:36:35 +01:00
noinitramfs.c	init: move usermodehelper_enable() to populate_rootfs()	2021-09-08 11:50:27 -07:00
version.c	kbuild: add an elfnote for whether vmlinux is built with lto	2021-04-25 05:25:42 +09:00