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powerpc/lib: optimise PPC32 memcmp

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At the time being, memcmp() compares two chunks of memory
byte per byte.

This patch optimises the comparison by comparing word by word.

On the same way as commit 15c2d45d17 ("powerpc: Add 64bit
optimised memcmp"), this patch moves memcmp() into a dedicated
file named memcmp_32.S

A small benchmark performed on an 8xx comparing two chuncks
of 512 bytes performed 100000 times gives:

Before : 5852274 TB ticks
After:   1488638 TB ticks

This is almost 4 times faster

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Christophe Leroy 2018-05-30 07:06:15 +00:00 committed by Michael Ellerman
parent f36bbf21e8
commit 2676b89eb8
3 changed files with 47 additions and 19 deletions
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4
arch/powerpc/lib/Makefile
View File

@ -26,14 +26,14 @@ obj-$(CONFIG_PPC_BOOK3S_64) += copyuser_power7.o copypage_power7.o \
memcpy_power7.o
obj64-y += copypage_64.o copyuser_64.o mem_64.o hweight_64.o \
memcpy_64.o memcmp_64.o pmem.o
memcpy_64.o pmem.o
obj64-$(CONFIG_SMP) += locks.o
obj64-$(CONFIG_ALTIVEC) += vmx-helper.o
obj64-$(CONFIG_KPROBES_SANITY_TEST) += test_emulate_step.o
obj-y += checksum_$(BITS).o checksum_wrappers.o \
string_$(BITS).o
string_$(BITS).o memcmp_$(BITS).o
obj-y += sstep.o ldstfp.o quad.o
obj64-y += quad.o

45
arch/powerpc/lib/memcmp_32.S Normal file
View File

@ -0,0 +1,45 @@
/* SPDX-License-Identifier: GPL-2.0 */
/*
* memcmp for PowerPC32
*
* Copyright (C) 1996 Paul Mackerras.
*
*/
#include <asm/ppc_asm.h>
#include <asm/export.h>
.text
_GLOBAL(memcmp)
srawi. r7, r5, 2 /* Divide len by 4 */
mr r6, r3
beq- 3f
mtctr r7
li r7, 0
1: lwzx r3, r6, r7
lwzx r0, r4, r7
addi r7, r7, 4
cmplw cr0, r3, r0
bdnzt eq, 1b
bne 5f
3: andi. r3, r5, 3
beqlr
cmplwi cr1, r3, 2
blt- cr1, 4f
lhzx r3, r6, r7
lhzx r0, r4, r7
addi r7, r7, 2
subf. r3, r0, r3
beqlr cr1
bnelr
4: lbzx r3, r6, r7
lbzx r0, r4, r7
subf. r3, r0, r3
blr
5: li r3, 1
bgtlr
li r3, -1
blr
EXPORT_SYMBOL(memcmp)

17
arch/powerpc/lib/string.S
View File

@ -54,23 +54,6 @@ _GLOBAL(strncmp)
blr
EXPORT_SYMBOL(strncmp)
#ifdef CONFIG_PPC32
_GLOBAL(memcmp)
PPC_LCMPI 0,r5,0
beq- 2f
mtctr r5
addi r6,r3,-1
addi r4,r4,-1
1: lbzu r3,1(r6)
lbzu r0,1(r4)
subf. r3,r0,r3
bdnzt 2,1b
blr
2: li r3,0
blr
EXPORT_SYMBOL(memcmp)
#endif
_GLOBAL(memchr)
PPC_LCMPI 0,r5,0
beq- 2f