xref: /openbmc/linux/arch/alpha/lib/strchr.S (revision cfbb9be8) 
1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * arch/alpha/lib/strchr.S
4 * Contributed by Richard Henderson (rth@tamu.edu)
5 *
6 * Return the address of a given character within a null-terminated
7 * string, or null if it is not found.
8 */
9#include <asm/export.h>
10#include <asm/regdef.h>
11
12	.set noreorder
13	.set noat
14
15	.align 3
16	.globl strchr
17	.ent strchr
18strchr:
19	.frame sp, 0, ra
20	.prologue 0
21
22	zapnot	a1, 1, a1	# e0    : zero extend the search character
23	ldq_u   t0, 0(a0)	# .. e1 : load first quadword
24	sll	a1, 8, t5	# e0    : replicate the search character
25	andnot  a0, 7, v0	# .. e1 : align our loop pointer
26	or	t5, a1, a1	# e0    :
27	lda	t4, -1		# .. e1 : build garbage mask
28	sll	a1, 16, t5	# e0    :
29	cmpbge  zero, t0, t2	# .. e1 : bits set iff byte == zero
30	mskqh	t4, a0, t4	# e0    :
31	or	t5, a1, a1	# .. e1 :
32	sll	a1, 32, t5	# e0    :
33	cmpbge	zero, t4, t4	# .. e1 : bits set iff byte is garbage
34	or	t5, a1, a1	# e0    :
35	xor	t0, a1, t1	# .. e1 : make bytes == c zero
36	cmpbge  zero, t1, t3	# e0    : bits set iff byte == c
37	or	t2, t3, t0	# e1    : bits set iff char match or zero match
38	andnot	t0, t4, t0	# e0    : clear garbage bits
39	bne	t0, $found	# .. e1 (zdb)
40
41$loop:	ldq	t0, 8(v0)	# e0    :
42	addq	v0, 8, v0	# .. e1 :
43	nop			# e0    :
44	xor	t0, a1, t1	# .. e1 (ev5 data stall)
45	cmpbge	zero, t0, t2	# e0    : bits set iff byte == 0
46	cmpbge	zero, t1, t3	# .. e1 : bits set iff byte == c
47	or	t2, t3, t0	# e0    :
48	beq	t0, $loop	# .. e1 (zdb)
49
50$found:	negq    t0, t1		# e0    : clear all but least set bit
51	and     t0, t1, t0	# e1 (stall)
52
53	and	t0, t3, t1	# e0    : bit set iff byte was the char
54	beq	t1, $retnull	# .. e1 (zdb)
55
56	and     t0, 0xf0, t2	# e0    : binary search for that set bit
57	and	t0, 0xcc, t3	# .. e1 :
58	and	t0, 0xaa, t4	# e0    :
59	cmovne	t2, 4, t2	# .. e1 :
60	cmovne	t3, 2, t3	# e0    :
61	cmovne	t4, 1, t4	# .. e1 :
62	addq	t2, t3, t2	# e0    :
63	addq	v0, t4, v0	# .. e1 :
64	addq	v0, t2, v0	# e0    :
65	ret			# .. e1 :
66
67$retnull:
68	mov	zero, v0	# e0    :
69	ret			# .. e1 :
70
71	.end strchr
72	EXPORT_SYMBOL(strchr)
73