linux/arch/arm/lib/memmove.S

/*
 *  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