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/*-
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2024 Getz Mikalsen <getz@FreeBSD.org>
*/
#include <machine/asm.h>
.weak strspn
.set strspn, __strspn
.text
ENTRY(__strspn)
/* check for special cases */
ldrb w4, [x1] // first character in set
cbz w4, .Lzero // empty set always returns 0
mov x15, #1 // preload register with 1 for stores
// set is only one character
ldrb w5, [x1, #1] // second character in the set
cbz w5, .Lsingle
stp x29, x30, [sp, #-16]!
mov x29, sp
sub sp, sp, #256 // allocate 256 bytes on the stack
/* no special case matches -- prepare lookup table */
mov w3, #28
0: add x9, sp, x3, lsl #3
stp xzr, xzr, [x9]
stp xzr, xzr, [x9, #16]
subs w3, w3, #4
b.cs 0b
strb w15, [sp, x4] // register first character in set
add x1, x1, #2
/* process remaining chars in set */
.p2align 4
0: ldrb w4, [x1] // next char in set
strb w15, [sp, x5] // register previous char
cbz w4, 1f // NUL encountered?
ldrb w5, [x1, #1]
add x1, x1, #2
strb w15, [sp, x4]
cbnz w5, 0b
1: mov x5, x0 // stash a copy of src
/* find mismatch */
.p2align 4
0: ldrb w8, [x0]
ldrb w9, [sp, x8]
cbz w9, 2f
ldrb w8, [x0, #1]
ldrb w9, [sp, x8]
cbz w9, 3f
ldrb w8, [x0, #2]
ldrb w9, [sp, x8]
cbz w9, 4f
ldrb w8, [x0, #3]
add x0, x0, #4
ldrb w9, [sp, x8]
cbnz w9, 0b
sub x0, x0, #3
4: sub x5, x5, #1
3: add x0, x0, #1
2: sub x0, x0, x5
mov sp, x29
ldp x29, x30, [sp], #16
ret
.Lzero:
mov x0, #0
ret
.Lsingle:
ldrb w8, [x0, x5]
cmp w4, w8
b.ne 1f
add x5, x5, #1
ldrb w8, [x0, x5]
cmp w4, w8
b.ne 1f
add x5, x5, #1
ldrb w8, [x0, x5]
cmp w4, w8
b.ne 1f
add x5, x5, #1
ldrb w8, [x0, x5]
add x5, x5, #1
cmp w4, w8
b.eq .Lsingle
sub x5, x5, #1
1: mov x0, x5
ret
END(__strspn)
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