[PATCH v2 6/8] arm64: Import latest memcpy()/memmove() implementation

Tue Jun 8 04:15:33 PDT 2021

Hi Robin,

On 27.05.2021 17:34, Robin Murphy wrote:
> Import the latest implementation of memcpy(), based on the
> upstream code of string/aarch64/memcpy.S at commit afd6244 from
> https://github.com/ARM-software/optimized-routines, and subsuming
> memmove() in the process.
>
> Note that for simplicity Arm have chosen to contribute this code
> to Linux under GPLv2 rather than the original MIT license.
>
> Note also that the needs of the usercopy routines vs. regular memcpy()
> have now diverged so far that we abandon the shared template idea
> and the damage which that incurred to the tuning of LDP/STP loops.
> We'll be back to tackle those routines separately in future.
>
> Signed-off-by: Robin Murphy <robin.murphy at arm.com>

This patch landed recently in linux-next as commit 285133040e6c ("arm64: 
Import latest memcpy()/memmove() implementation"). Sadly it causes 
serious issues on Khadas VIM3 board. Reverting it on top of linux 
next-20210607 (together with 6b8f648959e5 and resolving the conflict in 
the Makefile) fixes the issue. Here is the kernel log:

Unable to handle kernel paging request at virtual address ffff8000136bd204
Mem abort info:
   ESR = 0x96000061
   EC = 0x25: DABT (current EL), IL = 32 bits
   SET = 0, FnV = 0
   EA = 0, S1PTW = 0
Data abort info:
   ISV = 0, ISS = 0x00000061
   CM = 0, WnR = 1
swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000009da6000
[ffff8000136bd204] pgd=10000000f4806003, p4d=10000000f4806003, 
pud=10000000f4805003, pmd=1000000000365003, pte=00680000ffe03713
Internal error: Oops: 96000061 [#1] PREEMPT SMP
Modules linked in: brcmfmac brcmutil cfg80211 dw_hdmi_i2s_audio 
meson_gxl hci_uart btqca btbcm bluetooth panfrost ecdh_generic ecc 
snd_soc_meson_axg_sound_card crct10dif_ce snd_soc_meson_card_utils 
rfkill rtc_hym8563 gpu_sched dwmac_generic rc_khadas meson_gxbb_wdt 
meson_ir pwm_meson snd_soc_meson_axg_tdmin snd_soc_meson_g12a_tohdmitx 
rtc_meson_vrtc snd_soc_meson_axg_tdmout snd_soc_meson_axg_frddr 
reset_meson_audio_arb snd_soc_meson_codec_glue axg_audio meson_rng 
sclk_div dwmac_meson8b snd_soc_meson_axg_toddr mdio_mux_meson_g12a 
clk_phase stmmac_platform rng_core snd_soc_meson_axg_fifo meson_dw_hdmi 
stmmac meson_drm meson_canvas dw_hdmi pcs_xpcs display_connector 
snd_soc_meson_axg_tdm_interface nvmem_meson_efuse adc_keys 
snd_soc_meson_axg_tdm_formatter
CPU: 4 PID: 135 Comm: kworker/4:3 Not tainted 5.13.0-rc5-next-20210607 
#10441
Hardware name: Khadas VIM3 (DT)
Workqueue: events request_firmware_work_func
pstate: 20000005 (nzCv daif -PAN -UAO -TCO BTYPE=--)
pc : __memcpy+0x2c/0x260
lr : sg_copy_buffer+0x90/0x118
...
Call trace:
  __memcpy+0x2c/0x260
  sg_copy_to_buffer+0x14/0x20
  meson_mmc_start_cmd+0xf4/0x2c8
  meson_mmc_request+0x4c/0xb8
  __mmc_start_request+0xa4/0x2a8
  mmc_start_request+0x80/0xa8
  mmc_wait_for_req+0x68/0xd8
  mmc_io_rw_extended+0x1d4/0x2e0
  sdio_io_rw_ext_helper+0xb0/0x1e8
  sdio_memcpy_toio+0x20/0x28
  brcmf_sdiod_skbuff_write.isra.18+0x2c/0x68 [brcmfmac]
  brcmf_sdiod_ramrw+0xe0/0x230 [brcmfmac]
  brcmf_sdio_firmware_callback+0xa8/0x7c8 [brcmfmac]
  brcmf_fw_request_done+0x7c/0x100 [brcmfmac]
  request_firmware_work_func+0x4c/0xd8
  process_one_work+0x2a8/0x718
  worker_thread+0x48/0x460
  kthread+0x12c/0x160
  ret_from_fork+0x10/0x18
Code: 540000c3 a9401c26 a97f348c a9001c06 (a93f34ac)
---[ end trace be83fa283dc82415 ]---

I hope that the above log helps fixing the issue. IIRC the SDHCI driver 
on VIM3 board uses internal SRAM for transferring data (instead of DMA), 
so the issue is somehow related to that.

> ---
>   arch/arm64/lib/Makefile  |   2 +-
>   arch/arm64/lib/memcpy.S  | 272 ++++++++++++++++++++++++++++++++-------
>   arch/arm64/lib/memmove.S | 189 ---------------------------
>   3 files changed, 230 insertions(+), 233 deletions(-)
>   delete mode 100644 arch/arm64/lib/memmove.S
>
> diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile
> index d31e1169d9b8..01c596aa539c 100644
> --- a/arch/arm64/lib/Makefile
> +++ b/arch/arm64/lib/Makefile
> @@ -1,7 +1,7 @@
>   # SPDX-License-Identifier: GPL-2.0
>   lib-y		:= clear_user.o delay.o copy_from_user.o		\
>   		   copy_to_user.o copy_in_user.o copy_page.o		\
> -		   clear_page.o csum.o memchr.o memcpy.o memmove.o	\
> +		   clear_page.o csum.o memchr.o memcpy.o		\
>   		   memset.o memcmp.o strcmp.o strncmp.o strlen.o	\
>   		   strnlen.o strchr.o strrchr.o tishift.o
>   
> diff --git a/arch/arm64/lib/memcpy.S b/arch/arm64/lib/memcpy.S
> index dc8d2a216a6e..31073a8304fb 100644
> --- a/arch/arm64/lib/memcpy.S
> +++ b/arch/arm64/lib/memcpy.S
> @@ -1,66 +1,252 @@
>   /* SPDX-License-Identifier: GPL-2.0-only */
>   /*
> - * Copyright (C) 2013 ARM Ltd.
> - * Copyright (C) 2013 Linaro.
> + * Copyright (c) 2012-2020, Arm Limited.
>    *
> - * This code is based on glibc cortex strings work originally authored by Linaro
> - * be found @
> - *
> - * http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
> - * files/head:/src/aarch64/
> + * Adapted from the original at:
> + * https://github.com/ARM-software/optimized-routines/blob/master/string/aarch64/memcpy.S
>    */
>   
>   #include <linux/linkage.h>
>   #include <asm/assembler.h>
> -#include <asm/cache.h>
>   
> -/*
> - * Copy a buffer from src to dest (alignment handled by the hardware)
> +/* Assumptions:
> + *
> + * ARMv8-a, AArch64, unaligned accesses.
>    *
> - * Parameters:
> - *	x0 - dest
> - *	x1 - src
> - *	x2 - n
> - * Returns:
> - *	x0 - dest
>    */
> -	.macro ldrb1 reg, ptr, val
> -	ldrb  \reg, [\ptr], \val
> -	.endm
>   
> -	.macro strb1 reg, ptr, val
> -	strb \reg, [\ptr], \val
> -	.endm
> +#define L(label) .L ## label
>   
> -	.macro ldrh1 reg, ptr, val
> -	ldrh  \reg, [\ptr], \val
> -	.endm
> +#define dstin	x0
> +#define src	x1
> +#define count	x2
> +#define dst	x3
> +#define srcend	x4
> +#define dstend	x5
> +#define A_l	x6
> +#define A_lw	w6
> +#define A_h	x7
> +#define B_l	x8
> +#define B_lw	w8
> +#define B_h	x9
> +#define C_l	x10
> +#define C_lw	w10
> +#define C_h	x11
> +#define D_l	x12
> +#define D_h	x13
> +#define E_l	x14
> +#define E_h	x15
> +#define F_l	x16
> +#define F_h	x17
> +#define G_l	count
> +#define G_h	dst
> +#define H_l	src
> +#define H_h	srcend
> +#define tmp1	x14
>   
> -	.macro strh1 reg, ptr, val
> -	strh \reg, [\ptr], \val
> -	.endm
> +/* This implementation handles overlaps and supports both memcpy and memmove
> +   from a single entry point.  It uses unaligned accesses and branchless
> +   sequences to keep the code small, simple and improve performance.
>   
> -	.macro ldr1 reg, ptr, val
> -	ldr \reg, [\ptr], \val
> -	.endm
> +   Copies are split into 3 main cases: small copies of up to 32 bytes, medium
> +   copies of up to 128 bytes, and large copies.  The overhead of the overlap
> +   check is negligible since it is only required for large copies.
>   
> -	.macro str1 reg, ptr, val
> -	str \reg, [\ptr], \val
> -	.endm
> -
> -	.macro ldp1 reg1, reg2, ptr, val
> -	ldp \reg1, \reg2, [\ptr], \val
> -	.endm
> -
> -	.macro stp1 reg1, reg2, ptr, val
> -	stp \reg1, \reg2, [\ptr], \val
> -	.endm
> +   Large copies use a software pipelined loop processing 64 bytes per iteration.
> +   The destination pointer is 16-byte aligned to minimize unaligned accesses.
> +   The loop tail is handled by always copying 64 bytes from the end.
> +*/
>   
> +SYM_FUNC_START_ALIAS(__memmove)
> +SYM_FUNC_START_WEAK_ALIAS_PI(memmove)
>   SYM_FUNC_START_ALIAS(__memcpy)
>   SYM_FUNC_START_WEAK_PI(memcpy)
> -#include "copy_template.S"
> +	add	srcend, src, count
> +	add	dstend, dstin, count
> +	cmp	count, 128
> +	b.hi	L(copy_long)
> +	cmp	count, 32
> +	b.hi	L(copy32_128)
> +
> +	/* Small copies: 0..32 bytes.  */
> +	cmp	count, 16
> +	b.lo	L(copy16)
> +	ldp	A_l, A_h, [src]
> +	ldp	D_l, D_h, [srcend, -16]
> +	stp	A_l, A_h, [dstin]
> +	stp	D_l, D_h, [dstend, -16]
>   	ret
> +
> +	/* Copy 8-15 bytes.  */
> +L(copy16):
> +	tbz	count, 3, L(copy8)
> +	ldr	A_l, [src]
> +	ldr	A_h, [srcend, -8]
> +	str	A_l, [dstin]
> +	str	A_h, [dstend, -8]
> +	ret
> +
> +	.p2align 3
> +	/* Copy 4-7 bytes.  */
> +L(copy8):
> +	tbz	count, 2, L(copy4)
> +	ldr	A_lw, [src]
> +	ldr	B_lw, [srcend, -4]
> +	str	A_lw, [dstin]
> +	str	B_lw, [dstend, -4]
> +	ret
> +
> +	/* Copy 0..3 bytes using a branchless sequence.  */
> +L(copy4):
> +	cbz	count, L(copy0)
> +	lsr	tmp1, count, 1
> +	ldrb	A_lw, [src]
> +	ldrb	C_lw, [srcend, -1]
> +	ldrb	B_lw, [src, tmp1]
> +	strb	A_lw, [dstin]
> +	strb	B_lw, [dstin, tmp1]
> +	strb	C_lw, [dstend, -1]
> +L(copy0):
> +	ret
> +
> +	.p2align 4
> +	/* Medium copies: 33..128 bytes.  */
> +L(copy32_128):
> +	ldp	A_l, A_h, [src]
> +	ldp	B_l, B_h, [src, 16]
> +	ldp	C_l, C_h, [srcend, -32]
> +	ldp	D_l, D_h, [srcend, -16]
> +	cmp	count, 64
> +	b.hi	L(copy128)
> +	stp	A_l, A_h, [dstin]
> +	stp	B_l, B_h, [dstin, 16]
> +	stp	C_l, C_h, [dstend, -32]
> +	stp	D_l, D_h, [dstend, -16]
> +	ret
> +
> +	.p2align 4
> +	/* Copy 65..128 bytes.  */
> +L(copy128):
> +	ldp	E_l, E_h, [src, 32]
> +	ldp	F_l, F_h, [src, 48]
> +	cmp	count, 96
> +	b.ls	L(copy96)
> +	ldp	G_l, G_h, [srcend, -64]
> +	ldp	H_l, H_h, [srcend, -48]
> +	stp	G_l, G_h, [dstend, -64]
> +	stp	H_l, H_h, [dstend, -48]
> +L(copy96):
> +	stp	A_l, A_h, [dstin]
> +	stp	B_l, B_h, [dstin, 16]
> +	stp	E_l, E_h, [dstin, 32]
> +	stp	F_l, F_h, [dstin, 48]
> +	stp	C_l, C_h, [dstend, -32]
> +	stp	D_l, D_h, [dstend, -16]
> +	ret
> +
> +	.p2align 4
> +	/* Copy more than 128 bytes.  */
> +L(copy_long):
> +	/* Use backwards copy if there is an overlap.  */
> +	sub	tmp1, dstin, src
> +	cbz	tmp1, L(copy0)
> +	cmp	tmp1, count
> +	b.lo	L(copy_long_backwards)
> +
> +	/* Copy 16 bytes and then align dst to 16-byte alignment.  */
> +
> +	ldp	D_l, D_h, [src]
> +	and	tmp1, dstin, 15
> +	bic	dst, dstin, 15
> +	sub	src, src, tmp1
> +	add	count, count, tmp1	/* Count is now 16 too large.  */
> +	ldp	A_l, A_h, [src, 16]
> +	stp	D_l, D_h, [dstin]
> +	ldp	B_l, B_h, [src, 32]
> +	ldp	C_l, C_h, [src, 48]
> +	ldp	D_l, D_h, [src, 64]!
> +	subs	count, count, 128 + 16	/* Test and readjust count.  */
> +	b.ls	L(copy64_from_end)
> +
> +L(loop64):
> +	stp	A_l, A_h, [dst, 16]
> +	ldp	A_l, A_h, [src, 16]
> +	stp	B_l, B_h, [dst, 32]
> +	ldp	B_l, B_h, [src, 32]
> +	stp	C_l, C_h, [dst, 48]
> +	ldp	C_l, C_h, [src, 48]
> +	stp	D_l, D_h, [dst, 64]!
> +	ldp	D_l, D_h, [src, 64]!
> +	subs	count, count, 64
> +	b.hi	L(loop64)
> +
> +	/* Write the last iteration and copy 64 bytes from the end.  */
> +L(copy64_from_end):
> +	ldp	E_l, E_h, [srcend, -64]
> +	stp	A_l, A_h, [dst, 16]
> +	ldp	A_l, A_h, [srcend, -48]
> +	stp	B_l, B_h, [dst, 32]
> +	ldp	B_l, B_h, [srcend, -32]
> +	stp	C_l, C_h, [dst, 48]
> +	ldp	C_l, C_h, [srcend, -16]
> +	stp	D_l, D_h, [dst, 64]
> +	stp	E_l, E_h, [dstend, -64]
> +	stp	A_l, A_h, [dstend, -48]
> +	stp	B_l, B_h, [dstend, -32]
> +	stp	C_l, C_h, [dstend, -16]
> +	ret
> +
> +	.p2align 4
> +
> +	/* Large backwards copy for overlapping copies.
> +	   Copy 16 bytes and then align dst to 16-byte alignment.  */
> +L(copy_long_backwards):
> +	ldp	D_l, D_h, [srcend, -16]
> +	and	tmp1, dstend, 15
> +	sub	srcend, srcend, tmp1
> +	sub	count, count, tmp1
> +	ldp	A_l, A_h, [srcend, -16]
> +	stp	D_l, D_h, [dstend, -16]
> +	ldp	B_l, B_h, [srcend, -32]
> +	ldp	C_l, C_h, [srcend, -48]
> +	ldp	D_l, D_h, [srcend, -64]!
> +	sub	dstend, dstend, tmp1
> +	subs	count, count, 128
> +	b.ls	L(copy64_from_start)
> +
> +L(loop64_backwards):
> +	stp	A_l, A_h, [dstend, -16]
> +	ldp	A_l, A_h, [srcend, -16]
> +	stp	B_l, B_h, [dstend, -32]
> +	ldp	B_l, B_h, [srcend, -32]
> +	stp	C_l, C_h, [dstend, -48]
> +	ldp	C_l, C_h, [srcend, -48]
> +	stp	D_l, D_h, [dstend, -64]!
> +	ldp	D_l, D_h, [srcend, -64]!
> +	subs	count, count, 64
> +	b.hi	L(loop64_backwards)
> +
> +	/* Write the last iteration and copy 64 bytes from the start.  */
> +L(copy64_from_start):
> +	ldp	G_l, G_h, [src, 48]
> +	stp	A_l, A_h, [dstend, -16]
> +	ldp	A_l, A_h, [src, 32]
> +	stp	B_l, B_h, [dstend, -32]
> +	ldp	B_l, B_h, [src, 16]
> +	stp	C_l, C_h, [dstend, -48]
> +	ldp	C_l, C_h, [src]
> +	stp	D_l, D_h, [dstend, -64]
> +	stp	G_l, G_h, [dstin, 48]
> +	stp	A_l, A_h, [dstin, 32]
> +	stp	B_l, B_h, [dstin, 16]
> +	stp	C_l, C_h, [dstin]
> +	ret
> +
>   SYM_FUNC_END_PI(memcpy)
>   EXPORT_SYMBOL(memcpy)
>   SYM_FUNC_END_ALIAS(__memcpy)
>   EXPORT_SYMBOL(__memcpy)
> +SYM_FUNC_END_ALIAS_PI(memmove)
> +EXPORT_SYMBOL(memmove)
> +SYM_FUNC_END_ALIAS(__memmove)
> +EXPORT_SYMBOL(__memmove)
> \ No newline at end of file
> diff --git a/arch/arm64/lib/memmove.S b/arch/arm64/lib/memmove.S
> deleted file mode 100644
> index 1035dce4bdaf..000000000000
> --- a/arch/arm64/lib/memmove.S
> +++ /dev/null
> @@ -1,189 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0-only */
> -/*
> - * Copyright (C) 2013 ARM Ltd.
> - * Copyright (C) 2013 Linaro.
> - *
> - * This code is based on glibc cortex strings work originally authored by Linaro
> - * be found @
> - *
> - * http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
> - * files/head:/src/aarch64/
> - */
> -
> -#include <linux/linkage.h>
> -#include <asm/assembler.h>
> -#include <asm/cache.h>
> -
> -/*
> - * Move a buffer from src to test (alignment handled by the hardware).
> - * If dest <= src, call memcpy, otherwise copy in reverse order.
> - *
> - * Parameters:
> - *	x0 - dest
> - *	x1 - src
> - *	x2 - n
> - * Returns:
> - *	x0 - dest
> - */
> -dstin	.req	x0
> -src	.req	x1
> -count	.req	x2
> -tmp1	.req	x3
> -tmp1w	.req	w3
> -tmp2	.req	x4
> -tmp2w	.req	w4
> -tmp3	.req	x5
> -tmp3w	.req	w5
> -dst	.req	x6
> -
> -A_l	.req	x7
> -A_h	.req	x8
> -B_l	.req	x9
> -B_h	.req	x10
> -C_l	.req	x11
> -C_h	.req	x12
> -D_l	.req	x13
> -D_h	.req	x14
> -
> -SYM_FUNC_START_ALIAS(__memmove)
> -SYM_FUNC_START_WEAK_PI(memmove)
> -	cmp	dstin, src
> -	b.lo	__memcpy
> -	add	tmp1, src, count
> -	cmp	dstin, tmp1
> -	b.hs	__memcpy		/* No overlap.  */
> -
> -	add	dst, dstin, count
> -	add	src, src, count
> -	cmp	count, #16
> -	b.lo	.Ltail15  /*probably non-alignment accesses.*/
> -
> -	ands	tmp2, src, #15     /* Bytes to reach alignment.  */
> -	b.eq	.LSrcAligned
> -	sub	count, count, tmp2
> -	/*
> -	* process the aligned offset length to make the src aligned firstly.
> -	* those extra instructions' cost is acceptable. It also make the
> -	* coming accesses are based on aligned address.
> -	*/
> -	tbz	tmp2, #0, 1f
> -	ldrb	tmp1w, [src, #-1]!
> -	strb	tmp1w, [dst, #-1]!
> -1:
> -	tbz	tmp2, #1, 2f
> -	ldrh	tmp1w, [src, #-2]!
> -	strh	tmp1w, [dst, #-2]!
> -2:
> -	tbz	tmp2, #2, 3f
> -	ldr	tmp1w, [src, #-4]!
> -	str	tmp1w, [dst, #-4]!
> -3:
> -	tbz	tmp2, #3, .LSrcAligned
> -	ldr	tmp1, [src, #-8]!
> -	str	tmp1, [dst, #-8]!
> -
> -.LSrcAligned:
> -	cmp	count, #64
> -	b.ge	.Lcpy_over64
> -
> -	/*
> -	* Deal with small copies quickly by dropping straight into the
> -	* exit block.
> -	*/
> -.Ltail63:
> -	/*
> -	* Copy up to 48 bytes of data. At this point we only need the
> -	* bottom 6 bits of count to be accurate.
> -	*/
> -	ands	tmp1, count, #0x30
> -	b.eq	.Ltail15
> -	cmp	tmp1w, #0x20
> -	b.eq	1f
> -	b.lt	2f
> -	ldp	A_l, A_h, [src, #-16]!
> -	stp	A_l, A_h, [dst, #-16]!
> -1:
> -	ldp	A_l, A_h, [src, #-16]!
> -	stp	A_l, A_h, [dst, #-16]!
> -2:
> -	ldp	A_l, A_h, [src, #-16]!
> -	stp	A_l, A_h, [dst, #-16]!
> -
> -.Ltail15:
> -	tbz	count, #3, 1f
> -	ldr	tmp1, [src, #-8]!
> -	str	tmp1, [dst, #-8]!
> -1:
> -	tbz	count, #2, 2f
> -	ldr	tmp1w, [src, #-4]!
> -	str	tmp1w, [dst, #-4]!
> -2:
> -	tbz	count, #1, 3f
> -	ldrh	tmp1w, [src, #-2]!
> -	strh	tmp1w, [dst, #-2]!
> -3:
> -	tbz	count, #0, .Lexitfunc
> -	ldrb	tmp1w, [src, #-1]
> -	strb	tmp1w, [dst, #-1]
> -
> -.Lexitfunc:
> -	ret
> -
> -.Lcpy_over64:
> -	subs	count, count, #128
> -	b.ge	.Lcpy_body_large
> -	/*
> -	* Less than 128 bytes to copy, so handle 64 bytes here and then jump
> -	* to the tail.
> -	*/
> -	ldp	A_l, A_h, [src, #-16]
> -	stp	A_l, A_h, [dst, #-16]
> -	ldp	B_l, B_h, [src, #-32]
> -	ldp	C_l, C_h, [src, #-48]
> -	stp	B_l, B_h, [dst, #-32]
> -	stp	C_l, C_h, [dst, #-48]
> -	ldp	D_l, D_h, [src, #-64]!
> -	stp	D_l, D_h, [dst, #-64]!
> -
> -	tst	count, #0x3f
> -	b.ne	.Ltail63
> -	ret
> -
> -	/*
> -	* Critical loop. Start at a new cache line boundary. Assuming
> -	* 64 bytes per line this ensures the entire loop is in one line.
> -	*/
> -	.p2align	L1_CACHE_SHIFT
> -.Lcpy_body_large:
> -	/* pre-load 64 bytes data. */
> -	ldp	A_l, A_h, [src, #-16]
> -	ldp	B_l, B_h, [src, #-32]
> -	ldp	C_l, C_h, [src, #-48]
> -	ldp	D_l, D_h, [src, #-64]!
> -1:
> -	/*
> -	* interlace the load of next 64 bytes data block with store of the last
> -	* loaded 64 bytes data.
> -	*/
> -	stp	A_l, A_h, [dst, #-16]
> -	ldp	A_l, A_h, [src, #-16]
> -	stp	B_l, B_h, [dst, #-32]
> -	ldp	B_l, B_h, [src, #-32]
> -	stp	C_l, C_h, [dst, #-48]
> -	ldp	C_l, C_h, [src, #-48]
> -	stp	D_l, D_h, [dst, #-64]!
> -	ldp	D_l, D_h, [src, #-64]!
> -	subs	count, count, #64
> -	b.ge	1b
> -	stp	A_l, A_h, [dst, #-16]
> -	stp	B_l, B_h, [dst, #-32]
> -	stp	C_l, C_h, [dst, #-48]
> -	stp	D_l, D_h, [dst, #-64]!
> -
> -	tst	count, #0x3f
> -	b.ne	.Ltail63
> -	ret
> -SYM_FUNC_END_PI(memmove)
> -EXPORT_SYMBOL(memmove)
> -SYM_FUNC_END_ALIAS(__memmove)
> -EXPORT_SYMBOL(__memmove)

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland