1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * strlen.S (c) 1995 David Mosberger (davidm@cs.arizona.edu)
4 *
5 * Finds length of a 0-terminated string.  Optimized for the
6 * Alpha architecture:
7 *
8 *	- memory accessed as aligned quadwords only
9 *	- uses bcmpge to compare 8 bytes in parallel
10 *	- does binary search to find 0 byte in last
11 *	  quadword (HAKMEM needed 12 instructions to
12 *	  do this instead of the 9 instructions that
13 *	  binary search needs).
14 */
15#include <linux/export.h>
16	.set noreorder
17	.set noat
18
19	.align 3
20
21	.globl	strlen
22	.ent	strlen
23
24strlen:
25	ldq_u	$1, 0($16)	# load first quadword ($16  may be misaligned)
26	lda	$2, -1($31)
27	insqh	$2, $16, $2
28	andnot	$16, 7, $0
29	or	$2, $1, $1
30	cmpbge	$31, $1, $2	# $2  <- bitmask: bit i == 1 <==> i-th byte == 0
31	bne	$2, found
32
33loop:	ldq	$1, 8($0)
34	addq	$0, 8, $0	# addr += 8
35	nop			# helps dual issue last two insns
36	cmpbge	$31, $1, $2
37	beq	$2, loop
38
39found:	blbs	$2, done	# make aligned case fast
40	negq	$2, $3
41	and	$2, $3, $2
42
43	and	$2, 0x0f, $1
44	addq	$0, 4, $3
45	cmoveq	$1, $3, $0
46
47	and	$2, 0x33, $1
48	addq	$0, 2, $3
49	cmoveq	$1, $3, $0
50
51	and	$2, 0x55, $1
52	addq	$0, 1, $3
53	cmoveq	$1, $3, $0
54
55done:	subq	$0, $16, $0
56	ret	$31, ($26)
57
58	.end	strlen
59	EXPORT_SYMBOL(strlen)
60