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

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/*

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

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 *

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 *  Copyright (C) 1995, 1996 Russell King.

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 *

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 *  Speedups & 1bpp code (C) 1996 Philip Blundell & Russell King.

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 *

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 *  10-04-96	RMK	Various cleanups & reduced register usage.

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 *  08-04-98	RMK	Shifts re-ordered

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 */

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@ Regs: [] = corruptible

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@       {} = used

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@       () = do not use

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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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LC0:	.word	LC0

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	.word	bytes_per_char_h

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	.word	video_size_row

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	.word	acorndata_8x8

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	.word	con_charconvtable

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/*

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 * r0 = ptr

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 * r1 = char

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 * r2 = white

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 */

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ENTRY(ll_write_char)

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	stmfd	sp!, {r4 - r7, lr}

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@

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@ Smashable regs: {r0 - r3}, [r4 - r7], (r8 - fp), [ip], (sp), [lr], (pc)

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@

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	/*

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	 * calculate offset into character table

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	 */

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	mov	r1, r1, lsl #3

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	/*

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	 * calculate offset required for each row.

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	 */

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	adr	ip, LC0

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	ldmia	ip, {r3, r4, r5, r6, lr}

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	sub	ip, ip, r3

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	add	r6, r6, ip

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	add	lr, lr, ip

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	ldr	r4, [r4, ip]

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	ldr	r5, [r5, ip]

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	/*

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	 * Go to resolution-dependent routine...

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	 */

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	cmp	r4, #4

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	blt	Lrow1bpp

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	add	r0, r0, r5, lsl #3		@ Move to bottom of character

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	orr	r1, r1, #7

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	ldrb	r7, [r6, r1]

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	teq	r4, #8

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	beq	Lrow8bpplp

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@

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@ Smashable regs: {r0 - r3}, [r4], {r5 - r7}, (r8 - fp), [ip], (sp), {lr}, (pc)

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@

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Lrow4bpplp:

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	ldr	r7, [lr, r7, lsl #2]

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	mul	r7, r2, r7

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	sub	r1, r1, #1			@ avoid using r7 directly after

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	str	r7, [r0, -r5]!

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	ldrb	r7, [r6, r1]

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	ldr	r7, [lr, r7, lsl #2]

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	mul	r7, r2, r7

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	tst	r1, #7				@ avoid using r7 directly after

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	str	r7, [r0, -r5]!

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	subne	r1, r1, #1

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	ldrbne	r7, [r6, r1]

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	bne	Lrow4bpplp

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	ldmfd	sp!, {r4 - r7, pc}

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@

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@ Smashable regs: {r0 - r3}, [r4], {r5 - r7}, (r8 - fp), [ip], (sp), {lr}, (pc)

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@

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Lrow8bpplp:

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	mov	ip, r7, lsr #4

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	ldr	ip, [lr, ip, lsl #2]

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	mul	r4, r2, ip

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	and	ip, r7, #15			@ avoid r4

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	ldr	ip, [lr, ip, lsl #2]		@ avoid r4

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	mul	ip, r2, ip			@ avoid r4

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	sub	r1, r1, #1			@ avoid ip

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	sub	r0, r0, r5			@ avoid ip

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	stmia	r0, {r4, ip}

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	ldrb	r7, [r6, r1]

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	mov	ip, r7, lsr #4

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	ldr	ip, [lr, ip, lsl #2]

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	mul	r4, r2, ip

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	and	ip, r7, #15			@ avoid r4

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	ldr	ip, [lr, ip, lsl #2]		@ avoid r4

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	mul	ip, r2, ip			@ avoid r4

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	tst	r1, #7				@ avoid ip

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	sub	r0, r0, r5			@ avoid ip

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	stmia	r0, {r4, ip}

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	subne	r1, r1, #1

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	ldrbne	r7, [r6, r1]

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	bne	Lrow8bpplp

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	ldmfd	sp!, {r4 - r7, pc}

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@

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@ Smashable regs: {r0 - r3}, [r4], {r5, r6}, [r7], (r8 - fp), [ip], (sp), [lr], (pc)

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@

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Lrow1bpp:

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	add	r6, r6, r1

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	ldmia	r6, {r4, r7}

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	strb	r4, [r0], r5

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	mov	r4, r4, lsr #8

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	strb	r4, [r0], r5

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	mov	r4, r4, lsr #8

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	strb	r4, [r0], r5

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	mov	r4, r4, lsr #8

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	strb	r4, [r0], r5

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	strb	r7, [r0], r5

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	mov	r7, r7, lsr #8

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	strb	r7, [r0], r5

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	mov	r7, r7, lsr #8

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	strb	r7, [r0], r5

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	mov	r7, r7, lsr #8

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	strb	r7, [r0], r5

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	ldmfd	sp!, {r4 - r7, pc}

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	.bss

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ENTRY(con_charconvtable)

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	.space	1024

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