1/*
  2 *  linux/arch/arm/lib/memzero.S
  3 *
  4 *  Copyright (C) 1995-2000 Russell King
  5 *
  6 * This program is free software; you can redistribute it and/or modify
  7 * it under the terms of the GNU General Public License version 2 as
  8 * published by the Free Software Foundation.
  9 */
 10#include <linux/linkage.h>
 11#include <asm/assembler.h>
 12
 13	.text
 14	.align	5
 15	.word	0
 16/*
 17 * Align the pointer in r0.  r3 contains the number of bytes that we are
 18 * mis-aligned by, and r1 is the number of bytes.  If r1 < 4, then we
 19 * don't bother; we use byte stores instead.
 20 */
 211:	subs	r1, r1, #4		@ 1 do we have enough
 22	blt	5f			@ 1 bytes to align with?
 23	cmp	r3, #2			@ 1
 24	strltb	r2, [r0], #1		@ 1
 25	strleb	r2, [r0], #1		@ 1
 26	strb	r2, [r0], #1		@ 1
 27	add	r1, r1, r3		@ 1 (r1 = r1 - (4 - r3))
 28/*
 29 * The pointer is now aligned and the length is adjusted.  Try doing the
 30 * memzero again.
 31 */
 32
 33ENTRY(__memzero)
 34	mov	r2, #0			@ 1
 35	ands	r3, r0, #3		@ 1 unaligned?
 36	bne	1b			@ 1
 37/*
 38 * r3 = 0, and we know that the pointer in r0 is aligned to a word boundary.
 39 */
 40	cmp	r1, #16			@ 1 we can skip this chunk if we
 41	blt	4f			@ 1 have < 16 bytes
 42
 43#if ! CALGN(1)+0
 44
 45/*
 46 * We need an extra register for this loop - save the return address and
 47 * use the LR
 48 */
 49	str	lr, [sp, #-4]!		@ 1
 50	mov	ip, r2			@ 1
 51	mov	lr, r2			@ 1
 52
 533:	subs	r1, r1, #64		@ 1 write 32 bytes out per loop
 54	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
 55	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
 56	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
 57	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
 58	bgt	3b			@ 1
 59	ldmeqfd	sp!, {pc}		@ 1/2 quick exit
 60/*
 61 * No need to correct the count; we're only testing bits from now on
 62 */
 63	tst	r1, #32			@ 1
 64	stmneia	r0!, {r2, r3, ip, lr}	@ 4
 65	stmneia	r0!, {r2, r3, ip, lr}	@ 4
 66	tst	r1, #16			@ 1 16 bytes or more?
 67	stmneia	r0!, {r2, r3, ip, lr}	@ 4
 68	ldr	lr, [sp], #4		@ 1
 69
 70#else
 71
 72/*
 73 * This version aligns the destination pointer in order to write
 74 * whole cache lines at once.
 75 */
 76
 77	stmfd	sp!, {r4-r7, lr}
 78	mov	r4, r2
 79	mov	r5, r2
 80	mov	r6, r2
 81	mov	r7, r2
 82	mov	ip, r2
 83	mov	lr, r2
 84
 85	cmp	r1, #96
 86	andgts	ip, r0, #31
 87	ble	3f
 88
 89	rsb	ip, ip, #32
 90	sub	r1, r1, ip
 91	movs	ip, ip, lsl #(32 - 4)
 92	stmcsia	r0!, {r4, r5, r6, r7}
 93	stmmiia	r0!, {r4, r5}
 94	movs	ip, ip, lsl #2
 95	strcs	r2, [r0], #4
 96
 973:	subs	r1, r1, #64
 98	stmgeia	r0!, {r2-r7, ip, lr}
 99	stmgeia	r0!, {r2-r7, ip, lr}
100	bgt	3b
101	ldmeqfd	sp!, {r4-r7, pc}
102
103	tst	r1, #32
104	stmneia	r0!, {r2-r7, ip, lr}
105	tst	r1, #16
106	stmneia	r0!, {r4-r7}
107	ldmfd	sp!, {r4-r7, lr}
108
109#endif
110
1114:	tst	r1, #8			@ 1 8 bytes or more?
112	stmneia	r0!, {r2, r3}		@ 2
113	tst	r1, #4			@ 1 4 bytes or more?
114	strne	r2, [r0], #4		@ 1
115/*
116 * When we get here, we've got less than 4 bytes to zero.  We
117 * may have an unaligned pointer as well.
118 */
1195:	tst	r1, #2			@ 1 2 bytes or more?
120	strneb	r2, [r0], #1		@ 1
121	strneb	r2, [r0], #1		@ 1
122	tst	r1, #1			@ 1 a byte left over
123	strneb	r2, [r0], #1		@ 1
124	mov	pc, lr			@ 1
125ENDPROC(__memzero)