1 /* strnlen - calculate the length of a string with limit.
3 Copyright (C) 2013-2022 Free Software Foundation, Inc.
5 This file is part of the GNU C Library.
7 The GNU C Library is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Lesser General Public
9 License as published by the Free Software Foundation; either
10 version 2.1 of the License, or (at your option) any later version.
12 The GNU C Library is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
17 You should have received a copy of the GNU Lesser General Public
18 License along with the GNU C Library. If not, see
19 <https://www.gnu.org/licenses/>. */
25 * ARMv8-a, AArch64, Advanced SIMD.
48 For each 16-byte chunk we calculate a 64-bit nibble mask value with four bits
49 per byte. We take 4 bits of every comparison byte with shift right and narrow
50 by 4 instruction. Since the bits in the nibble mask reflect the order in
51 which things occur in the original string, counting trailing zeros identifies
52 exactly which byte matched. */
59 ld1 {vdata.16b}, [src], 16
60 cmeq vhas_chr.16b, vdata.16b, 0
62 shrn vend.8b, vhas_chr.8h, 4 /* 128->64 */
65 cbz synd, L(start_loop)
71 csel result, cntin, result, ls
76 subs cntrem, cntin, tmp
79 /* Make sure that it won't overread by a 16-byte chunk */
81 tbnz tmp, 4, L(loop32_2)
86 cmeq vhas_chr.16b, vdata.16b, 0
87 umaxp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */
92 subs cntrem, cntrem, 32
93 cmeq vhas_chr.16b, vdata.16b, 0
95 umaxp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */
100 shrn vend.8b, vhas_chr.8h, 4 /* 128->64 */
103 sub result, src, srcin
104 #ifndef __AARCH64EB__
108 add result, result, synd, lsr 2
110 csel result, cntin, result, ls
118 libc_hidden_def (__strnlen)
119 weak_alias (__strnlen, strnlen)
120 libc_hidden_def (strnlen)