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/*
* strnlen - calculate the length of a string with limit.
*
* Copyright (c) 2019-2022, Arm Limited.
* SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
*/
#include "asmdefs.h"
#if __ARM_FEATURE_SVE
/* Assumptions:
*
* ARMv8-a, AArch64
* SVE Available.
*/
ENTRY (__strnlen_aarch64_sve)
PTR_ARG (0)
SIZE_ARG (1)
setffr /* initialize FFR */
mov x2, 0 /* initialize len */
b 1f
.p2align 4
/* We have off + vl <= max, and so may read the whole vector. */
0: ldff1b z0.b, p0/z, [x0, x2]
rdffrs p1.b, p0/z
b.nlast 2f
/* First fault did not fail: the whole vector is valid.
Avoid depending on the contents of FFR beyond the branch. */
cmpeq p2.b, p0/z, z0.b, 0
b.any 8f
incb x2
1: whilelo p0.b, x2, x1
b.last 0b
/* We have off + vl < max. Test for off == max before proceeding. */
b.none 9f
ldff1b z0.b, p0/z, [x0, x2]
rdffrs p1.b, p0/z
b.nlast 2f
/* First fault did not fail: the vector up to max is valid.
Avoid depending on the contents of FFR beyond the branch.
Compare for end-of-string, but there are no more bytes. */
cmpeq p2.b, p0/z, z0.b, 0
/* Found end-of-string or zero. */
8: brkb p2.b, p0/z, p2.b
mov x0, x2
incp x0, p2.b
ret
/* First fault failed: only some of the vector is valid.
Perform the comparison only on the valid bytes. */
2: cmpeq p2.b, p1/z, z0.b, 0
b.any 8b
/* No inequality or zero found. Re-init FFR, incr and loop. */
setffr
incp x2, p1.b
b 1b
/* End of count. Return max. */
9: mov x0, x1
ret
END (__strnlen_aarch64_sve)
#endif
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