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[ARM] 2947/1: copy template with new memcpy/memmove

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Patch from Nicolas Pitre

This patch provides a new implementation for optimized memory copy
functions on ARM.  It is made of two levels: a template that consists of
the core copy code and separate files that define macros to be used with
the core code depending on the type of copy needed. This allows for best
performances while sharing the same core for implementing memcpy(),
copy_from_user() and copy_to_user() for instance.

Two reasons for this work:

1) the current copy_to_user/copy_from_user implementation assumes no
   task switch will ever occur in the middle of each copied page making
   it completely unsafe with CONFIG_PREEMPT=y.

2) current copy implementations are measurably suboptimal and optimizing
   different implementations separately is a pain and more opportunities
   for bugs.

The reason for (1) is the fact that copy inside user pages are performed
with the ldm instruction which has no mean for testing user protections
and could possibly race with process preemption bypassing the COW mechanism
for example.  This is a longstanding issue that we said ought to be fixed
for about two years now.  The solution is to substitute those ldm insns
with a series of ldrt or strt insns to enforce user memory protection.
At least on StrongARM and XScale cores the ldm is not faster than the
equivalent ldr/str insns with a warm i-cache so there is no measurable
performance degradation with that change. The fact that the copy code is
a template makes it pretty easy to reuse the same core code as for memcpy
and benefit from the same performance optimizations.

Now (2) is best demonstrated with actual throughput measurements.
First, here is a summary of memcopy tests performed on a StrongARM core:

	PTR alignment	buffer size	kernel version	this version
	------------------------------------------------------------
	  aligned	     32		 59.73		107.43
	unaligned	     32		 61.31		 74.72
	  aligned	    100		132.47		136.15
	unaligned	    100	    	103.84		123.76
	  aligned	   4096		130.67		130.80
	unaligned	   4096	    	130.68		130.64
	  aligned	1048576		 68.03		68.18
	unaligned	1048576		 68.03		68.18

The buffer size is in bytes and the measured speed in MB/s.  The copy
was performed repeatedly with given buffer and throughput averaged over
3 seconds.

Here we can see that the current kernel version has a higher entry cost
that shows up with small buffers.  As buffer size grows both implementation
converge to the same throughput.

Now here's the exact same test performed on an XScale core (PXA255):

	PTR alignment	buffer size	kernel version	this version
	------------------------------------------------------------
	  aligned	     32		 46.99		 77.58
	unaligned	     32		 53.61		 59.59
	  aligned	    100		107.19		136.59
	unaligned	    100		 83.61		 97.58
	  aligned	   4096		129.13		129.98
	unaligned	   4096		128.36		128.53
	  aligned	1048576		 53.76		 59.41
	unaligned	1048576		 33.67		 56.96

Again we can see the entry setup cost being higher for the current kernel
before getting to the main copy loop.  Then throughput results converge
as long as the buffer remains in the cache. Then the 1MB case shows more
differences probably due to better pld placement and/or less instruction
interlocks in this proposed implementation.

Disclaimer: The PXA system was running with slower clocks than the
StrongARM system so trying to infer any conclusion by comparing those
separate sets of results side by side would be completely inappropriate.

So...  What this patch does is to replace both memcpy and memmove with
an implementation based on the provided copy code template.  The memmove
code is kept separate since it is used only if the memory areas involved
do overlap in which case the code is a transposition of the template but
with the copy occurring in the opposite direction (trying to fit that
mode into the template turned it into a mess not worth it for memmove
alone).  And obviously both memcpy and memmove were tested with all kinds
of pointer alignments and buffer sizes to exercise all code paths for
correctness.

The next patch will provide the now trivial replacement implementation
copy_to_user and copy_from_user.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Nicolas Pitre 2005-11-01 19:52:23 +00:00 committed by Russell King
parent a0c6fdb987
commit 7549423000
4 changed files with 508 additions and 380 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

5
arch/arm/lib/Makefile
View file

@ -7,8 +7,9 @@
lib-y := backtrace.o changebit.o csumipv6.o csumpartial.o \ lib-y := backtrace.o changebit.o csumipv6.o csumpartial.o \
csumpartialcopy.o csumpartialcopyuser.o clearbit.o \ csumpartialcopy.o csumpartialcopyuser.o clearbit.o \
copy_page.o delay.o findbit.o memchr.o memcpy.o \ copy_page.o delay.o findbit.o memchr.o memcpy.o \
memset.o memzero.o setbit.o strncpy_from_user.o \ memmove.o memset.o memzero.o setbit.o \
strnlen_user.o strchr.o strrchr.o testchangebit.o \ strncpy_from_user.o strnlen_user.o \
strchr.o strrchr.o testchangebit.o \
testclearbit.o testsetbit.o uaccess.o \ testclearbit.o testsetbit.o uaccess.o \
getuser.o putuser.o clear_user.o \ getuser.o putuser.o clear_user.o \
ashldi3.o ashrdi3.o lshrdi3.o muldi3.o \ ashldi3.o ashrdi3.o lshrdi3.o muldi3.o \

255
arch/arm/lib/copy_template.S Normal file
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@ -0,0 +1,255 @@
/*
* linux/arch/arm/lib/copy_template.s
*
* Code template for optimized memory copy functions
*
* Author: Nicolas Pitre
* Created: Sep 28, 2005
* Copyright: MontaVista Software, Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
/*
* This can be used to enable code to cacheline align the source pointer.
* Experiments on tested architectures (StrongARM and XScale) didn't show
* this a worthwhile thing to do. That might be different in the future.
*/
//#define CALGN(code...) code
#define CALGN(code...)
/*
* Theory of operation
* -------------------
*
* This file provides the core code for a forward memory copy used in
* the implementation of memcopy(), copy_to_user() and copy_from_user().
*
* The including file must define the following accessor macros
* according to the need of the given function:
*
* ldr1w ptr reg abort
*
* This loads one word from 'ptr', stores it in 'reg' and increments
* 'ptr' to the next word. The 'abort' argument is used for fixup tables.
*
* ldr4w ptr reg1 reg2 reg3 reg4 abort
* ldr8w ptr, reg1 reg2 reg3 reg4 reg5 reg6 reg7 reg8 abort
*
* This loads four or eight words starting from 'ptr', stores them
* in provided registers and increments 'ptr' past those words.
* The'abort' argument is used for fixup tables.
*
* ldr1b ptr reg cond abort
*
* Similar to ldr1w, but it loads a byte and increments 'ptr' one byte.
* It also must apply the condition code if provided, otherwise the
* "al" condition is assumed by default.
*
* str1w ptr reg abort
* str8w ptr reg1 reg2 reg3 reg4 reg5 reg6 reg7 reg8 abort
* str1b ptr reg cond abort
*
* Same as their ldr* counterparts, but data is stored to 'ptr' location
* rather than being loaded.
*
* enter reg1 reg2
*
* Preserve the provided registers on the stack plus any additional
* data as needed by the implementation including this code. Called
* upon code entry.
*
* exit reg1 reg2
*
* Restore registers with the values previously saved with the
* 'preserv' macro. Called upon code termination.
*/
enter r4, lr
subs r2, r2, #4
blt 8f
ands ip, r0, #3
PLD( pld [r1, #0] )
bne 9f
ands ip, r1, #3
bne 10f
1: subs r2, r2, #(28)
stmfd sp!, {r5 - r8}
blt 5f
CALGN( ands ip, r1, #31 )
CALGN( rsb r3, ip, #32 )
CALGN( sbcnes r4, r3, r2 ) @ C is always set here
CALGN( bcs 2f )
CALGN( adr r4, 6f )
CALGN( subs r2, r2, r3 ) @ C gets set
CALGN( add pc, r4, ip )
PLD( pld [r1, #0] )
2: PLD( subs r2, r2, #96 )
PLD( pld [r1, #28] )
PLD( blt 4f )
PLD( pld [r1, #60] )
PLD( pld [r1, #92] )
3: PLD( pld [r1, #124] )
4: ldr8w r1, r3, r4, r5, r6, r7, r8, ip, lr, abort=20f
subs r2, r2, #32
str8w r0, r3, r4, r5, r6, r7, r8, ip, lr, abort=20f
bge 3b
PLD( cmn r2, #96 )
PLD( bge 4b )
5: ands ip, r2, #28
rsb ip, ip, #32
addne pc, pc, ip @ C is always clear here
b 7f
6: nop
ldr1w r1, r3, abort=20f
ldr1w r1, r4, abort=20f
ldr1w r1, r5, abort=20f
ldr1w r1, r6, abort=20f
ldr1w r1, r7, abort=20f
ldr1w r1, r8, abort=20f
ldr1w r1, lr, abort=20f
add pc, pc, ip
nop
nop
str1w r0, r3, abort=20f
str1w r0, r4, abort=20f
str1w r0, r5, abort=20f
str1w r0, r6, abort=20f
str1w r0, r7, abort=20f
str1w r0, r8, abort=20f
str1w r0, lr, abort=20f
CALGN( bcs 2b )
7: ldmfd sp!, {r5 - r8}
8: movs r2, r2, lsl #31
ldr1b r1, r3, ne, abort=21f
ldr1b r1, r4, cs, abort=21f
ldr1b r1, ip, cs, abort=21f
str1b r0, r3, ne, abort=21f
str1b r0, r4, cs, abort=21f
str1b r0, ip, cs, abort=21f
exit r4, pc
9: rsb ip, ip, #4
cmp ip, #2
ldr1b r1, r3, gt, abort=21f
ldr1b r1, r4, ge, abort=21f
ldr1b r1, lr, abort=21f
str1b r0, r3, gt, abort=21f
str1b r0, r4, ge, abort=21f
subs r2, r2, ip
str1b r0, lr, abort=21f
blt 8b
ands ip, r1, #3
beq 1b
10: bic r1, r1, #3
cmp ip, #2
ldr1w r1, lr, abort=21f
beq 17f
bgt 18f
.macro forward_copy_shift pull push
subs r2, r2, #28
blt 14f
CALGN( ands ip, r1, #31 )
CALGN( rsb ip, ip, #32 )
CALGN( sbcnes r4, ip, r2 ) @ C is always set here
CALGN( subcc r2, r2, ip )
CALGN( bcc 15f )
11: stmfd sp!, {r5 - r9}
PLD( pld [r1, #0] )
PLD( subs r2, r2, #96 )
PLD( pld [r1, #28] )
PLD( blt 13f )
PLD( pld [r1, #60] )
PLD( pld [r1, #92] )
12: PLD( pld [r1, #124] )
13: ldr4w r1, r4, r5, r6, r7, abort=19f
mov r3, lr, pull #\pull
subs r2, r2, #32
ldr4w r1, r8, r9, ip, lr, abort=19f
orr r3, r3, r4, push #\push
mov r4, r4, pull #\pull
orr r4, r4, r5, push #\push
mov r5, r5, pull #\pull
orr r5, r5, r6, push #\push
mov r6, r6, pull #\pull
orr r6, r6, r7, push #\push
mov r7, r7, pull #\pull
orr r7, r7, r8, push #\push
mov r8, r8, pull #\pull
orr r8, r8, r9, push #\push
mov r9, r9, pull #\pull
orr r9, r9, ip, push #\push
mov ip, ip, pull #\pull
orr ip, ip, lr, push #\push
str8w r0, r3, r4, r5, r6, r7, r8, r9, ip, , abort=19f
bge 12b
PLD( cmn r2, #96 )
PLD( bge 13b )
ldmfd sp!, {r5 - r9}
14: ands ip, r2, #28
beq 16f
15: mov r3, lr, pull #\pull
ldr1w r1, lr, abort=21f
subs ip, ip, #4
orr r3, r3, lr, push #\push
str1w r0, r3, abort=21f
bgt 15b
CALGN( cmp r2, #0 )
CALGN( bge 11b )
16: sub r1, r1, #(\push / 8)
b 8b
.endm
forward_copy_shift pull=8 push=24
17: forward_copy_shift pull=16 push=16
18: forward_copy_shift pull=24 push=8
/*
* Abort preanble and completion macros.
* If a fixup handler is required then those macros must surround it.
* It is assumed that the fixup code will handle the private part of
* the exit macro.
*/
.macro copy_abort_preamble
19: ldmfd sp!, {r5 - r9}
b 21f
20: ldmfd sp!, {r5 - r8}
21:
.endm
.macro copy_abort_end
ldmfd sp!, {r4, pc}
.endm

418
arch/arm/lib/memcpy.S
View file

@ -1,393 +1,59 @@
/* /*
* linux/arch/arm/lib/memcpy.S * linux/arch/arm/lib/memcpy.S
* *
* Copyright (C) 1995-1999 Russell King * Author: Nicolas Pitre
* Created: Sep 28, 2005
* Copyright: MontaVista Software, Inc.
* *
* This program is free software; you can redistribute it and/or modify * This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as * it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation. * published by the Free Software Foundation.
*
* ASM optimised string functions
*/ */
#include <linux/linkage.h> #include <linux/linkage.h>
#include <asm/assembler.h> #include <asm/assembler.h>
.macro ldr1w ptr reg abort
ldr \reg, [\ptr], #4
.endm
.macro ldr4w ptr reg1 reg2 reg3 reg4 abort
ldmia \ptr!, {\reg1, \reg2, \reg3, \reg4}
.endm
.macro ldr8w ptr reg1 reg2 reg3 reg4 reg5 reg6 reg7 reg8 abort
ldmia \ptr!, {\reg1, \reg2, \reg3, \reg4, \reg5, \reg6, \reg7, \reg8}
.endm
.macro ldr1b ptr reg cond=al abort
ldr\cond\()b \reg, [\ptr], #1
.endm
.macro str1w ptr reg abort
str \reg, [\ptr], #4
.endm
.macro str8w ptr reg1 reg2 reg3 reg4 reg5 reg6 reg7 reg8 abort
stmia \ptr!, {\reg1, \reg2, \reg3, \reg4, \reg5, \reg6, \reg7, \reg8}
.endm
.macro str1b ptr reg cond=al abort
str\cond\()b \reg, [\ptr], #1
.endm
.macro enter reg1 reg2
stmdb sp!, {r0, \reg1, \reg2}
.endm
.macro exit reg1 reg2
ldmfd sp!, {r0, \reg1, \reg2}
.endm
.text .text
#define ENTER \ /* Prototype: void *memcpy(void *dest, const void *src, size_t n); */
mov ip,sp ;\
stmfd sp!,{r0,r4-r9,fp,ip,lr,pc} ;\
sub fp,ip,#4
#define EXIT \
LOADREGS(ea, fp, {r0, r4 - r9, fp, sp, pc})
#define EXITEQ \
LOADREGS(eqea, fp, {r0, r4 - r9, fp, sp, pc})
/*
* Prototype: void memcpy(void *to,const void *from,unsigned long n);
*/
ENTRY(memcpy) ENTRY(memcpy)
ENTRY(memmove)
ENTER
cmp r1, r0
bcc 23f
subs r2, r2, #4
blt 6f
PLD( pld [r1, #0] )
ands ip, r0, #3
bne 7f
ands ip, r1, #3
bne 8f
1: subs r2, r2, #8 #include "copy_template.S"
blt 5f
subs r2, r2, #20
blt 4f
PLD( pld [r1, #28] )
PLD( subs r2, r2, #64 )
PLD( blt 3f )
2: PLD( pld [r1, #60] )
PLD( pld [r1, #92] )
ldmia r1!, {r3 - r9, ip}
subs r2, r2, #32
stmgeia r0!, {r3 - r9, ip}
ldmgeia r1!, {r3 - r9, ip}
subges r2, r2, #32
stmia r0!, {r3 - r9, ip}
bge 2b
3: PLD( ldmia r1!, {r3 - r9, ip} )
PLD( adds r2, r2, #32 )
PLD( stmgeia r0!, {r3 - r9, ip} )
PLD( ldmgeia r1!, {r3 - r9, ip} )
PLD( subges r2, r2, #32 )
PLD( stmia r0!, {r3 - r9, ip} )
4: cmn r2, #16
ldmgeia r1!, {r3 - r6}
subge r2, r2, #16
stmgeia r0!, {r3 - r6}
adds r2, r2, #20
ldmgeia r1!, {r3 - r5}
subge r2, r2, #12
stmgeia r0!, {r3 - r5}
5: adds r2, r2, #8
blt 6f
subs r2, r2, #4
ldrlt r3, [r1], #4
ldmgeia r1!, {r4, r5}
subge r2, r2, #4
strlt r3, [r0], #4
stmgeia r0!, {r4, r5}
6: adds r2, r2, #4
EXITEQ
cmp r2, #2
ldrb r3, [r1], #1
ldrgeb r4, [r1], #1
ldrgtb r5, [r1], #1
strb r3, [r0], #1
strgeb r4, [r0], #1
strgtb r5, [r0], #1
EXIT
7: rsb ip, ip, #4
cmp ip, #2
ldrb r3, [r1], #1
ldrgeb r4, [r1], #1
ldrgtb r5, [r1], #1
strb r3, [r0], #1
strgeb r4, [r0], #1
strgtb r5, [r0], #1
subs r2, r2, ip
blt 6b
ands ip, r1, #3
beq 1b
8: bic r1, r1, #3
ldr r7, [r1], #4
cmp ip, #2
bgt 18f
beq 13f
cmp r2, #12
blt 11f
PLD( pld [r1, #12] )
sub r2, r2, #12
PLD( subs r2, r2, #32 )
PLD( blt 10f )
PLD( pld [r1, #28] )
9: PLD( pld [r1, #44] )
10: mov r3, r7, pull #8
ldmia r1!, {r4 - r7}
subs r2, r2, #16
orr r3, r3, r4, push #24
mov r4, r4, pull #8
orr r4, r4, r5, push #24
mov r5, r5, pull #8
orr r5, r5, r6, push #24
mov r6, r6, pull #8
orr r6, r6, r7, push #24
stmia r0!, {r3 - r6}
bge 9b
PLD( cmn r2, #32 )
PLD( bge 10b )
PLD( add r2, r2, #32 )
adds r2, r2, #12
blt 12f
11: mov r3, r7, pull #8
ldr r7, [r1], #4
subs r2, r2, #4
orr r3, r3, r7, push #24
str r3, [r0], #4
bge 11b
12: sub r1, r1, #3
b 6b
13: cmp r2, #12
blt 16f
PLD( pld [r1, #12] )
sub r2, r2, #12
PLD( subs r2, r2, #32 )
PLD( blt 15f )
PLD( pld [r1, #28] )
14: PLD( pld [r1, #44] )
15: mov r3, r7, pull #16
ldmia r1!, {r4 - r7}
subs r2, r2, #16
orr r3, r3, r4, push #16
mov r4, r4, pull #16
orr r4, r4, r5, push #16
mov r5, r5, pull #16
orr r5, r5, r6, push #16
mov r6, r6, pull #16
orr r6, r6, r7, push #16
stmia r0!, {r3 - r6}
bge 14b
PLD( cmn r2, #32 )
PLD( bge 15b )
PLD( add r2, r2, #32 )
adds r2, r2, #12
blt 17f
16: mov r3, r7, pull #16
ldr r7, [r1], #4
subs r2, r2, #4
orr r3, r3, r7, push #16
str r3, [r0], #4
bge 16b
17: sub r1, r1, #2
b 6b
18: cmp r2, #12
blt 21f
PLD( pld [r1, #12] )
sub r2, r2, #12
PLD( subs r2, r2, #32 )
PLD( blt 20f )
PLD( pld [r1, #28] )
19: PLD( pld [r1, #44] )
20: mov r3, r7, pull #24
ldmia r1!, {r4 - r7}
subs r2, r2, #16
orr r3, r3, r4, push #8
mov r4, r4, pull #24
orr r4, r4, r5, push #8
mov r5, r5, pull #24
orr r5, r5, r6, push #8
mov r6, r6, pull #24
orr r6, r6, r7, push #8
stmia r0!, {r3 - r6}
bge 19b
PLD( cmn r2, #32 )
PLD( bge 20b )
PLD( add r2, r2, #32 )
adds r2, r2, #12
blt 22f
21: mov r3, r7, pull #24
ldr r7, [r1], #4
subs r2, r2, #4
orr r3, r3, r7, push #8
str r3, [r0], #4
bge 21b
22: sub r1, r1, #1
b 6b
23: add r1, r1, r2
add r0, r0, r2
subs r2, r2, #4
blt 29f
PLD( pld [r1, #-4] )
ands ip, r0, #3
bne 30f
ands ip, r1, #3
bne 31f
24: subs r2, r2, #8
blt 28f
subs r2, r2, #20
blt 27f
PLD( pld [r1, #-32] )
PLD( subs r2, r2, #64 )
PLD( blt 26f )
25: PLD( pld [r1, #-64] )
PLD( pld [r1, #-96] )
ldmdb r1!, {r3 - r9, ip}
subs r2, r2, #32
stmgedb r0!, {r3 - r9, ip}
ldmgedb r1!, {r3 - r9, ip}
subges r2, r2, #32
stmdb r0!, {r3 - r9, ip}
bge 25b
26: PLD( ldmdb r1!, {r3 - r9, ip} )
PLD( adds r2, r2, #32 )
PLD( stmgedb r0!, {r3 - r9, ip} )
PLD( ldmgedb r1!, {r3 - r9, ip} )
PLD( subges r2, r2, #32 )
PLD( stmdb r0!, {r3 - r9, ip} )
27: cmn r2, #16
ldmgedb r1!, {r3 - r6}
subge r2, r2, #16
stmgedb r0!, {r3 - r6}
adds r2, r2, #20
ldmgedb r1!, {r3 - r5}
subge r2, r2, #12
stmgedb r0!, {r3 - r5}
28: adds r2, r2, #8
blt 29f
subs r2, r2, #4
ldrlt r3, [r1, #-4]!
ldmgedb r1!, {r4, r5}
subge r2, r2, #4
strlt r3, [r0, #-4]!
stmgedb r0!, {r4, r5}
29: adds r2, r2, #4
EXITEQ
cmp r2, #2
ldrb r3, [r1, #-1]!
ldrgeb r4, [r1, #-1]!
ldrgtb r5, [r1, #-1]!
strb r3, [r0, #-1]!
strgeb r4, [r0, #-1]!
strgtb r5, [r0, #-1]!
EXIT
30: cmp ip, #2
ldrb r3, [r1, #-1]!
ldrgeb r4, [r1, #-1]!
ldrgtb r5, [r1, #-1]!
strb r3, [r0, #-1]!
strgeb r4, [r0, #-1]!
strgtb r5, [r0, #-1]!
subs r2, r2, ip
blt 29b
ands ip, r1, #3
beq 24b
31: bic r1, r1, #3
ldr r3, [r1], #0
cmp ip, #2
blt 41f
beq 36f
cmp r2, #12
blt 34f
PLD( pld [r1, #-16] )
sub r2, r2, #12
PLD( subs r2, r2, #32 )
PLD( blt 33f )
PLD( pld [r1, #-32] )
32: PLD( pld [r1, #-48] )
33: mov r7, r3, push #8
ldmdb r1!, {r3, r4, r5, r6}
subs r2, r2, #16
orr r7, r7, r6, pull #24
mov r6, r6, push #8
orr r6, r6, r5, pull #24
mov r5, r5, push #8
orr r5, r5, r4, pull #24
mov r4, r4, push #8
orr r4, r4, r3, pull #24
stmdb r0!, {r4, r5, r6, r7}
bge 32b
PLD( cmn r2, #32 )
PLD( bge 33b )
PLD( add r2, r2, #32 )
adds r2, r2, #12
blt 35f
34: mov ip, r3, push #8
ldr r3, [r1, #-4]!
subs r2, r2, #4
orr ip, ip, r3, pull #24
str ip, [r0, #-4]!
bge 34b
35: add r1, r1, #3
b 29b
36: cmp r2, #12
blt 39f
PLD( pld [r1, #-16] )
sub r2, r2, #12
PLD( subs r2, r2, #32 )
PLD( blt 38f )
PLD( pld [r1, #-32] )
37: PLD( pld [r1, #-48] )
38: mov r7, r3, push #16
ldmdb r1!, {r3, r4, r5, r6}
subs r2, r2, #16
orr r7, r7, r6, pull #16
mov r6, r6, push #16
orr r6, r6, r5, pull #16
mov r5, r5, push #16
orr r5, r5, r4, pull #16
mov r4, r4, push #16
orr r4, r4, r3, pull #16
stmdb r0!, {r4, r5, r6, r7}
bge 37b
PLD( cmn r2, #32 )
PLD( bge 38b )
PLD( add r2, r2, #32 )
adds r2, r2, #12
blt 40f
39: mov ip, r3, push #16
ldr r3, [r1, #-4]!
subs r2, r2, #4
orr ip, ip, r3, pull #16
str ip, [r0, #-4]!
bge 39b
40: add r1, r1, #2
b 29b
41: cmp r2, #12
blt 44f
PLD( pld [r1, #-16] )
sub r2, r2, #12
PLD( subs r2, r2, #32 )
PLD( blt 43f )
PLD( pld [r1, #-32] )
42: PLD( pld [r1, #-48] )
43: mov r7, r3, push #24
ldmdb r1!, {r3, r4, r5, r6}
subs r2, r2, #16
orr r7, r7, r6, pull #8
mov r6, r6, push #24
orr r6, r6, r5, pull #8
mov r5, r5, push #24
orr r5, r5, r4, pull #8
mov r4, r4, push #24
orr r4, r4, r3, pull #8
stmdb r0!, {r4, r5, r6, r7}
bge 42b
PLD( cmn r2, #32 )
PLD( bge 43b )
PLD( add r2, r2, #32 )
adds r2, r2, #12
blt 45f
44: mov ip, r3, push #24
ldr r3, [r1, #-4]!
subs r2, r2, #4
orr ip, ip, r3, pull #8
str ip, [r0, #-4]!
bge 44b
45: add r1, r1, #1
b 29b

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arch/arm/lib/memmove.S Normal file
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/*
* linux/arch/arm/lib/memmove.S
*
* Author: Nicolas Pitre
* Created: Sep 28, 2005
* Copyright: (C) MontaVista Software Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
/*
* This can be used to enable code to cacheline align the source pointer.
* Experiments on tested architectures (StrongARM and XScale) didn't show
* this a worthwhile thing to do. That might be different in the future.
*/
//#define CALGN(code...) code
#define CALGN(code...)
.text
/*
* Prototype: void *memmove(void *dest, const void *src, size_t n);
*
* Note:
*
* If the memory regions don't overlap, we simply branch to memcpy which is
* normally a bit faster. Otherwise the copy is done going downwards. This
* is a transposition of the code from copy_template.S but with the copy
* occurring in the opposite direction.
*/
ENTRY(memmove)
subs ip, r0, r1
cmphi r2, ip
bls memcpy
stmfd sp!, {r0, r4, lr}
add r1, r1, r2
add r0, r0, r2
subs r2, r2, #4
blt 8f
ands ip, r0, #3
PLD( pld [r1, #-4] )
bne 9f
ands ip, r1, #3
bne 10f
1: subs r2, r2, #(28)
stmfd sp!, {r5 - r8}
blt 5f
CALGN( ands ip, r1, #31 )
CALGN( sbcnes r4, ip, r2 ) @ C is always set here
CALGN( bcs 2f )
CALGN( adr r4, 6f )
CALGN( subs r2, r2, ip ) @ C is set here
CALGN( add pc, r4, ip )
PLD( pld [r1, #-4] )
2: PLD( subs r2, r2, #96 )
PLD( pld [r1, #-32] )
PLD( blt 4f )
PLD( pld [r1, #-64] )
PLD( pld [r1, #-96] )
3: PLD( pld [r1, #-128] )
4: ldmdb r1!, {r3, r4, r5, r6, r7, r8, ip, lr}
subs r2, r2, #32
stmdb r0!, {r3, r4, r5, r6, r7, r8, ip, lr}
bge 3b
PLD( cmn r2, #96 )
PLD( bge 4b )
5: ands ip, r2, #28
rsb ip, ip, #32
addne pc, pc, ip @ C is always clear here
b 7f
6: nop
ldr r3, [r1, #-4]!
ldr r4, [r1, #-4]!
ldr r5, [r1, #-4]!
ldr r6, [r1, #-4]!
ldr r7, [r1, #-4]!
ldr r8, [r1, #-4]!
ldr lr, [r1, #-4]!
add pc, pc, ip
nop
nop
str r3, [r0, #-4]!
str r4, [r0, #-4]!
str r5, [r0, #-4]!
str r6, [r0, #-4]!
str r7, [r0, #-4]!
str r8, [r0, #-4]!
str lr, [r0, #-4]!
CALGN( bcs 2b )
7: ldmfd sp!, {r5 - r8}
8: movs r2, r2, lsl #31
ldrneb r3, [r1, #-1]!
ldrcsb r4, [r1, #-1]!
ldrcsb ip, [r1, #-1]
strneb r3, [r0, #-1]!
strcsb r4, [r0, #-1]!
strcsb ip, [r0, #-1]
ldmfd sp!, {r0, r4, pc}
9: cmp ip, #2
ldrgtb r3, [r1, #-1]!
ldrgeb r4, [r1, #-1]!
ldrb lr, [r1, #-1]!
strgtb r3, [r0, #-1]!
strgeb r4, [r0, #-1]!
subs r2, r2, ip
strb lr, [r0, #-1]!
blt 8b
ands ip, r1, #3
beq 1b
10: bic r1, r1, #3
cmp ip, #2
ldr r3, [r1, #0]
beq 17f
blt 18f
.macro backward_copy_shift push pull
subs r2, r2, #28
blt 14f
CALGN( ands ip, r1, #31 )
CALGN( rsb ip, ip, #32 )
CALGN( sbcnes r4, ip, r2 ) @ C is always set here
CALGN( subcc r2, r2, ip )
CALGN( bcc 15f )
11: stmfd sp!, {r5 - r9}
PLD( pld [r1, #-4] )
PLD( subs r2, r2, #96 )
PLD( pld [r1, #-32] )
PLD( blt 13f )
PLD( pld [r1, #-64] )
PLD( pld [r1, #-96] )
12: PLD( pld [r1, #-128] )
13: ldmdb r1!, {r7, r8, r9, ip}
mov lr, r3, push #\push
subs r2, r2, #32
ldmdb r1!, {r3, r4, r5, r6}
orr lr, lr, ip, pull #\pull
mov ip, ip, push #\push
orr ip, ip, r9, pull #\pull
mov r9, r9, push #\push
orr r9, r9, r8, pull #\pull
mov r8, r8, push #\push
orr r8, r8, r7, pull #\pull
mov r7, r7, push #\push
orr r7, r7, r6, pull #\pull
mov r6, r6, push #\push
orr r6, r6, r5, pull #\pull
mov r5, r5, push #\push
orr r5, r5, r4, pull #\pull
mov r4, r4, push #\push
orr r4, r4, r3, pull #\pull
stmdb r0!, {r4 - r9, ip, lr}
bge 12b
PLD( cmn r2, #96 )
PLD( bge 13b )
ldmfd sp!, {r5 - r9}
14: ands ip, r2, #28
beq 16f
15: mov lr, r3, push #\push
ldr r3, [r1, #-4]!
subs ip, ip, #4
orr lr, lr, r3, pull #\pull
str lr, [r0, #-4]!
bgt 15b
CALGN( cmp r2, #0 )
CALGN( bge 11b )
16: add r1, r1, #(\pull / 8)
b 8b
.endm
backward_copy_shift push=8 pull=24
17: backward_copy_shift push=16 pull=16
18: backward_copy_shift push=24 pull=8