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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/arch/arm/lib/memset.S
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/* SPDX-License-Identifier: GPL-2.0-only */

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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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 *  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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#include <asm/unwind.h>

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	.text

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	.align	5

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ENTRY(__memset)

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ENTRY(mmioset)

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WEAK(memset)

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UNWIND( .fnstart         )

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	and	r1, r1, #255		@ cast to unsigned char

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	ands	r3, r0, #3		@ 1 unaligned?

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	mov	ip, r0			@ preserve r0 as return value

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	bne	6f			@ 1

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/*

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

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 */

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1:	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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7:	cmp	r2, #16

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	blt	4f

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UNWIND( .fnend              )

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#if ! CALGN(1)+0

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/*

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 * We need 2 extra registers for this loop - use r8 and the LR

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 */

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UNWIND( .fnstart            )

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UNWIND( .save {r8, lr}      )

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	stmfd	sp!, {r8, lr}

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	mov	r8, r1

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	mov	lr, r3

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2:	subs	r2, r2, #64

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	stmiage	ip!, {r1, r3, r8, lr}	@ 64 bytes at a time.

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	stmiage	ip!, {r1, r3, r8, lr}

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	stmiage	ip!, {r1, r3, r8, lr}

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	stmiage	ip!, {r1, r3, r8, lr}

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	bgt	2b

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	ldmfdeq	sp!, {r8, 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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	stmiane	ip!, {r1, r3, r8, lr}

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	stmiane	ip!, {r1, r3, r8, lr}

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	tst	r2, #16

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	stmiane	ip!, {r1, r3, r8, lr}

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	ldmfd	sp!, {r8, lr}

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UNWIND( .fnend              )

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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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UNWIND( .fnstart               )

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UNWIND( .save {r4-r8, lr}      )

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	stmfd	sp!, {r4-r8, lr}

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	mov	r4, r1

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	mov	r5, r3

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	mov	r6, r1

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	mov	r7, r3

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	mov	r8, r1

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	mov	lr, r3

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	cmp	r2, #96

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	tstgt	ip, #31

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	ble	3f

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	and	r8, ip, #31

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	rsb	r8, r8, #32

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	sub	r2, r2, r8

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	movs	r8, r8, lsl #(32 - 4)

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	stmiacs	ip!, {r4, r5, r6, r7}

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	stmiami	ip!, {r4, r5}

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	tst	r8, #(1 << 30)

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	mov	r8, r1

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	strne	r1, [ip], #4

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3:	subs	r2, r2, #64

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	stmiage	ip!, {r1, r3-r8, lr}

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	stmiage	ip!, {r1, r3-r8, lr}

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	bgt	3b

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	ldmfdeq	sp!, {r4-r8, pc}

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	tst	r2, #32

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	stmiane	ip!, {r1, r3-r8, lr}

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	tst	r2, #16

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	stmiane	ip!, {r4-r7}

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	ldmfd	sp!, {r4-r8, lr}

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UNWIND( .fnend                 )

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#endif

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UNWIND( .fnstart            )

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4:	tst	r2, #8

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	stmiane	ip!, {r1, r3}

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	tst	r2, #4

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	strne	r1, [ip], #4

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/*

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 * When we get here, we've got less than 4 bytes to set.  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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	strbne	r1, [ip], #1

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	strbne	r1, [ip], #1

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	tst	r2, #1

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	strbne	r1, [ip], #1

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	ret	lr

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

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	blt	5b			@ 1 bytes to align with?

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	cmp	r3, #2			@ 1

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	strblt	r1, [ip], #1		@ 1

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	strble	r1, [ip], #1		@ 1

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	strb	r1, [ip], #1		@ 1

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

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	b	1b

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UNWIND( .fnend   )

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ENDPROC(memset)

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ENDPROC(mmioset)

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ENDPROC(__memset)

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ENTRY(__memset32)

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UNWIND( .fnstart         )

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	mov	r3, r1			@ copy r1 to r3 and fall into memset64

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UNWIND( .fnend   )

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ENDPROC(__memset32)

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ENTRY(__memset64)

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UNWIND( .fnstart         )

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	mov	ip, r0			@ preserve r0 as return value

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	b	7b			@ jump into the middle of memset

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UNWIND( .fnend   )

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ENDPROC(__memset64)

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