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awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/arch/arm/lib/memset.S
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/*

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 *  linux/arch/arm/lib/memset.S

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 *

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 *  Copyright (C) 1995-2000 Russell King

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 *

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 * This program is free software; you can redistribute it and/or modify

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 * it under the terms of the GNU General Public License version 2 as

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 * published by the Free Software Foundation.

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 *

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 *  ASM optimised string functions

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 */

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#include <linux/linkage.h>

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#include <asm/assembler.h>

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	.text

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	.align	5

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	.word	0

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1:	subs	r2, r2, #4		@ 1 do we have enough

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	blt	5f			@ 1 bytes to align with?

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	cmp	r3, #2			@ 1

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	strltb	r1, [r0], #1		@ 1

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	strleb	r1, [r0], #1		@ 1

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	strb	r1, [r0], #1		@ 1

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	add	r2, r2, r3		@ 1 (r2 = r2 - (4 - r3))

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/*

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 * The pointer is now aligned and the length is adjusted.  Try doing the

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 * memset again.

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 */

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ENTRY(memset)

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	ands	r3, r0, #3		@ 1 unaligned?

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	bne	1b			@ 1

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/*

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 * we know that the pointer in r0 is aligned to a word boundary.

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 */

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	orr	r1, r1, r1, lsl #8

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	orr	r1, r1, r1, lsl #16

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	mov	r3, r1

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	cmp	r2, #16

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	blt	4f

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#if ! CALGN(1)+0

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/*

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 * We need an extra register for this loop - save the return address and

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 * use the LR

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 */

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	str	lr, [sp, #-4]!

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	mov	ip, r1

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	mov	lr, r1

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2:	subs	r2, r2, #64

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	stmgeia	r0!, {r1, r3, ip, lr}	@ 64 bytes at a time.

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	stmgeia	r0!, {r1, r3, ip, lr}

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	stmgeia	r0!, {r1, r3, ip, lr}

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	stmgeia	r0!, {r1, r3, ip, lr}

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	bgt	2b

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	ldmeqfd	sp!, {pc}		@ Now <64 bytes to go.

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/*

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 * No need to correct the count; we're only testing bits from now on

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 */

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	tst	r2, #32

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	stmneia	r0!, {r1, r3, ip, lr}

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	stmneia	r0!, {r1, r3, ip, lr}

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	tst	r2, #16

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	stmneia	r0!, {r1, r3, ip, lr}

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	ldr	lr, [sp], #4

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#else

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/*

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 * This version aligns the destination pointer in order to write

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 * whole cache lines at once.

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 */

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	stmfd	sp!, {r4-r7, lr}

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	mov	r4, r1

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	mov	r5, r1

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	mov	r6, r1

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	mov	r7, r1

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	mov	ip, r1

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	mov	lr, r1

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	cmp	r2, #96

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	tstgt	r0, #31

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	ble	3f

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	and	ip, r0, #31

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	rsb	ip, ip, #32

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	sub	r2, r2, ip

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	movs	ip, ip, lsl #(32 - 4)

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	stmcsia	r0!, {r4, r5, r6, r7}

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	stmmiia	r0!, {r4, r5}

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	tst	ip, #(1 << 30)

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	mov	ip, r1

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	strne	r1, [r0], #4

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3:	subs	r2, r2, #64

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	stmgeia	r0!, {r1, r3-r7, ip, lr}

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	stmgeia	r0!, {r1, r3-r7, ip, lr}

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	bgt	3b

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	ldmeqfd	sp!, {r4-r7, pc}

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	tst	r2, #32

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	stmneia	r0!, {r1, r3-r7, ip, lr}

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	tst	r2, #16

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	stmneia	r0!, {r4-r7}

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	ldmfd	sp!, {r4-r7, lr}

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#endif

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4:	tst	r2, #8

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	stmneia	r0!, {r1, r3}

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	tst	r2, #4

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	strne	r1, [r0], #4

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/*

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 * When we get here, we've got less than 4 bytes to zero.  We

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 * may have an unaligned pointer as well.

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 */

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5:	tst	r2, #2

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	strneb	r1, [r0], #1

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	strneb	r1, [r0], #1

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	tst	r2, #1

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	strneb	r1, [r0], #1

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	mov	pc, lr

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ENDPROC(memset)

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