1/*
2 * __strlen_aarch64_sve - compute the length of a string
3 *
4 * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 * See https://llvm.org/LICENSE.txt for license information.
6 * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 */
8
9#if __ARM_FEATURE_SVE
10/* Assumptions:
11 *
12 * ARMv8-a, AArch64
13 * SVE Available.
14 */
15
16	.arch	armv8-a+sve
17	.text
18
19	.globl	__strlen_aarch64_sve
20	.type	__strlen_aarch64_sve, %function
21	.p2align 4
22__strlen_aarch64_sve:
23	setffr			/* initialize FFR */
24	ptrue	p2.b		/* all ones; loop invariant */
25	mov	x1, 0		/* initialize length */
26	nop
27
28	/* Read a vector's worth of bytes, stopping on first fault.  */
290:	ldff1b	z0.b, p2/z, [x0, x1]
30	nop
31	rdffrs	p0.b, p2/z
32	b.nlast	2f
33
34	/* First fault did not fail: the whole vector is valid.
35	   Avoid depending on the contents of FFR beyond the branch.  */
36	incb	x1, all			/* speculate increment */
37	cmpeq	p1.b, p2/z, z0.b, 0	/* loop if no zeros */
38	b.none	0b
39	decb	x1, all			/* undo speculate */
40
41	/* Zero found.  Select the bytes before the first and count them.  */
421:	brkb	p0.b, p2/z, p1.b
43	incp	x1, p0.b
44	mov	x0, x1
45	ret
46
47	/* First fault failed: only some of the vector is valid.
48	   Perform the comparison only on the valid bytes.  */
492:	cmpeq	p1.b, p0/z, z0.b, 0
50	b.any	1b
51
52	/* No zero found.  Re-init FFR, increment, and loop.  */
53	setffr
54	incp	x1, p0.b
55	b	0b
56
57	.size	__strlen_aarch64_sve, . - __strlen_aarch64_sve
58#endif
59