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Alexey Dobriyan 4c6080cd6f lib/list: tweak LIST_POISON2 for better code generation on x86_64 
list_del() poisoning can generate 2 64-bit immediate loads but it also can
generate one 64-bit immediate load and an addition:

	48 b8 00 01 00 00 00 00 ad de	movabs rax,0xdead000000000100
	48 89 47 58			mov    QWORD PTR [rdi+0x58],rax
	48 05 00 01 00 00   <=====>	add    rax,0x100
	48 89 47 60			mov    QWORD PTR [rdi+0x60],rax

However on x86_64 not all constants are equal: those within [-128, 127]
range can be added with shorter "add r64, imm32" instruction:

	48 b8 00 01 00 00 00 00 ad de	movabs rax,0xdead000000000100
	48 89 47 58			mov    QWORD PTR [rdi+0x58],rax
	48 83 c0 22	<======>	add    rax,0x22
	48 89 47 60			mov    QWORD PTR [rdi+0x60],rax

Patch saves 2 bytes per some LIST_POISON2 usage.

(Slightly disappointing) space savings on F29 x86_64 config:

	add/remove: 0/0 grow/shrink: 0/2164 up/down: 0/-5184 (-5184)
	Function                                     old     new   delta
	zstd_get_workspace                           548     546      -2
		...
	mlx4_delete_all_resources_for_slave         4826    4804     -22
	Total: Before=83304131, After=83298947, chg -0.01%

New constants are:

	0xdead000000000100
	0xdead000000000122

Note: LIST_POISON1 can't be changed to ...11 because something in page
allocator requires low bit unset.

Link: http://lkml.kernel.org/r/20190513191502.GA8492@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Vasiliy Kulikov <segoon@openwall.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2019-07-16 19:23:22 -07:00
..
acpi It's been a relatively busy cycle for docs: 2019-07-09 12:34:26 -07:00
asm-generic asm-generic: fix a compilation warning 2019-07-16 19:23:22 -07:00
clocksource clocksource/drivers: Continue making Hyper-V clocksource ISA agnostic 2019-07-03 11:00:59 +02:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2019-07-08 20:57:08 -07:00
drm drm main pull request for v5.3-rc1 (sans mm changes) 2019-07-15 19:04:27 -07:00
dt-bindings Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2019-07-11 10:55:49 -07:00
keys request_key improvements 2019-07-08 19:19:37 -07:00
kvm KVM: arm/arm64: Support chained PMU counters 2019-07-05 13:56:22 +01:00
linux lib/list: tweak LIST_POISON2 for better code generation on x86_64 2019-07-16 19:23:22 -07:00
math-emu
…
media media updates for v5.3-rc1 2019-07-09 09:47:22 -07:00
memory treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
misc powerpc updates for 5.3 2019-07-13 16:08:36 -07:00
net net: sched: Fix NULL-pointer dereference in tc_indr_block_ing_cmd() 2019-07-12 15:21:53 -07:00
pcmcia It's been a relatively busy cycle for docs: 2019-07-09 12:34:26 -07:00
ras
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rdma RDMA/core: Make rdma_counter.h compile stand alone 2019-07-09 09:44:47 -03:00
scsi SCSI misc on 20190709 2019-07-11 15:14:01 -07:00
soc treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
sound ASoC: Updates for v5.3 2019-07-08 14:45:34 +02:00
target
…
trace f2fs-for-5.3-rc1 2019-07-12 17:28:24 -07:00
uapi mm: fix the MAP_UNINITIALIZED flag 2019-07-16 19:23:21 -07:00
vdso vdso: Remove superfluous #ifdef __KERNEL__ in vdso/datapage.h 2019-06-26 07:28:09 +02:00
video drm main pull request for v5.3-rc1 (sans mm changes) 2019-07-15 19:04:27 -07:00
xen
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Kbuild kbuild: compile-test kernel headers to ensure they are self-contained 2019-07-09 21:44:37 +09:00