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Christophe Leroy 3af722cb73 powerpc/net: Implement powerpc specific csum_shift() to remove branch 
Today's implementation of csum_shift() leads to branching based on
parity of 'offset'

	000002f8 <csum_block_add>:
	     2f8:	70 a5 00 01 	andi.   r5,r5,1
	     2fc:	41 a2 00 08 	beq     304 <csum_block_add+0xc>
	     300:	54 84 c0 3e 	rotlwi  r4,r4,24
	     304:	7c 63 20 14 	addc    r3,r3,r4
	     308:	7c 63 01 94 	addze   r3,r3
	     30c:	4e 80 00 20 	blr

Use first bit of 'offset' directly as input of the rotation instead of
branching.

	000002f8 <csum_block_add>:
	     2f8:	54 a5 1f 38 	rlwinm  r5,r5,3,28,28
	     2fc:	20 a5 00 20 	subfic  r5,r5,32
	     300:	5c 84 28 3e 	rotlw   r4,r4,r5
	     304:	7c 63 20 14 	addc    r3,r3,r4
	     308:	7c 63 01 94 	addze   r3,r3
	     30c:	4e 80 00 20 	blr

And change to left shift instead of right shift to skip one more
instruction. This has no impact on the final sum.

	000002f8 <csum_block_add>:
	     2f8:	54 a5 1f 38 	rlwinm  r5,r5,3,28,28
	     2fc:	5c 84 28 3e 	rotlw   r4,r4,r5
	     300:	7c 63 20 14 	addc    r3,r3,r4
	     304:	7c 63 01 94 	addze   r3,r3
	     308:	4e 80 00 20 	blr

Seems like only powerpc benefits from a branchless implementation.
Other main architectures like ARM or X86 get better code with
the generic implementation and its branch.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>
2022-03-11 10:57:22 +00:00
arch powerpc/net: Implement powerpc specific csum_shift() to remove branch 2022-03-11 10:57:22 +00:00
block block: fix blk_mq_attempt_bio_merge and rq_qos_throttle protection 2022-03-08 17:48:39 -07:00
certs certs: Fix build error when CONFIG_MODULE_SIG_KEY is empty 2022-01-23 00:08:44 +09:00
crypto crypto: af_alg - get rid of alg_memory_allocated 2022-02-15 14:29:04 +00:00
Documentation linux-can-next-for-5.18-20220310 2022-03-10 20:09:27 -08:00
drivers net/mlx5e: Remove overzealous validations in netlink EEPROM query 2022-03-10 23:38:25 -08:00
fs fuse fixes for 5.17-rc8 2022-03-08 09:41:18 -08:00
include powerpc/net: Implement powerpc specific csum_shift() to remove branch 2022-03-11 10:57:22 +00:00
init Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2022-02-09 18:40:56 -08:00
ipc ipc/sem: do not sleep with a spin lock held 2022-02-04 09:25:05 -08:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-03-10 17:16:56 -08:00
lib Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2022-03-04 19:28:17 -08:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mm: gup: make fault_in_safe_writeable() use fixup_user_fault() 2022-03-10 10:48:53 -08:00
net net: limit altnames to 64k total 2022-03-10 20:15:23 -08:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-02-17 11:44:20 -08:00
scripts scripts/pahole-flags.sh: Parse DWARF and generate BTF with multithreading. 2022-02-22 14:32:44 -08:00
security net: rtnetlink: Add RTM_SETSTATS 2022-03-03 10:37:23 +00:00
sound Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-03-10 17:16:56 -08:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-03-10 17:16:56 -08:00
usr kbuild: remove include/linux/cyclades.h from header file check 2022-01-27 08:51:08 +01:00
virt KVM: Fix lockdep false negative during host resume 2022-02-17 09:52:50 -05:00
.clang-format genirq/msi: Make interrupt allocation less convoluted 2021-12-16 22:22:20 +01:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap MAINTAINERS: Update Jisheng's email address 2022-03-08 17:30:32 +01:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: replace a Microchip AT91 maintainer 2022-02-09 11:30:01 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-03-10 17:16:56 -08:00
Makefile Linux 5.17-rc7 2022-03-06 14:28:31 -08:00
README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.