| /* strchr - find a character in a string |
| |
| Copyright (C) 2014-2018 Free Software Foundation, Inc. |
| |
| This file is part of the GNU C Library. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| The GNU C Library is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library. If not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include <sysdep.h> |
| |
| /* Assumptions: |
| * |
| * ARMv8-a, AArch64 |
| */ |
| |
| /* Arguments and results. */ |
| #define srcin x0 |
| #define chrin w1 |
| |
| #define result x0 |
| |
| #define src x2 |
| #define tmp1 x3 |
| #define wtmp2 w4 |
| #define tmp3 x5 |
| |
| #define vrepchr v0 |
| #define vdata1 v1 |
| #define vdata2 v2 |
| #define vhas_nul1 v3 |
| #define vhas_nul2 v4 |
| #define vhas_chr1 v5 |
| #define vhas_chr2 v6 |
| #define vrepmask_0 v7 |
| #define vrepmask_c v16 |
| #define vend1 v17 |
| #define vend2 v18 |
| |
| /* Core algorithm. |
| For each 32-byte hunk we calculate a 64-bit syndrome value, with |
| two bits per byte (LSB is always in bits 0 and 1, for both big |
| and little-endian systems). Bit 0 is set iff the relevant byte |
| matched the requested character. Bit 1 is set iff the |
| relevant byte matched the NUL end of string (we trigger off bit0 |
| for the special case of looking for NUL). Since the bits |
| in the syndrome reflect exactly the order in which things occur |
| in the original string a count_trailing_zeros() operation will |
| identify exactly which byte is causing the termination, and why. */ |
| |
| /* Locals and temporaries. */ |
| |
| ENTRY (strchr) |
| DELOUSE (0) |
| mov wtmp2, #0x0401 |
| movk wtmp2, #0x4010, lsl #16 |
| dup vrepchr.16b, chrin |
| bic src, srcin, #31 |
| dup vrepmask_c.4s, wtmp2 |
| ands tmp1, srcin, #31 |
| add vrepmask_0.4s, vrepmask_c.4s, vrepmask_c.4s // lsl #1 |
| b.eq L(loop) |
| |
| /* Input string is not 32-byte aligned. Rather than forcing |
| the padding bytes to a safe value, we calculate the syndrome |
| for all the bytes, but then mask off those bits of the |
| syndrome that are related to the padding. */ |
| ld1 {vdata1.16b, vdata2.16b}, [src], #32 |
| neg tmp1, tmp1 |
| cmeq vhas_nul1.16b, vdata1.16b, #0 |
| cmeq vhas_chr1.16b, vdata1.16b, vrepchr.16b |
| cmeq vhas_nul2.16b, vdata2.16b, #0 |
| cmeq vhas_chr2.16b, vdata2.16b, vrepchr.16b |
| and vhas_nul1.16b, vhas_nul1.16b, vrepmask_0.16b |
| and vhas_nul2.16b, vhas_nul2.16b, vrepmask_0.16b |
| and vhas_chr1.16b, vhas_chr1.16b, vrepmask_c.16b |
| and vhas_chr2.16b, vhas_chr2.16b, vrepmask_c.16b |
| orr vend1.16b, vhas_nul1.16b, vhas_chr1.16b |
| orr vend2.16b, vhas_nul2.16b, vhas_chr2.16b |
| lsl tmp1, tmp1, #1 |
| addp vend1.16b, vend1.16b, vend2.16b // 256->128 |
| mov tmp3, #~0 |
| addp vend1.16b, vend1.16b, vend2.16b // 128->64 |
| lsr tmp1, tmp3, tmp1 |
| |
| mov tmp3, vend1.d[0] |
| bic tmp1, tmp3, tmp1 // Mask padding bits. |
| cbnz tmp1, L(tail) |
| |
| L(loop): |
| ld1 {vdata1.16b, vdata2.16b}, [src], #32 |
| cmeq vhas_nul1.16b, vdata1.16b, #0 |
| cmeq vhas_chr1.16b, vdata1.16b, vrepchr.16b |
| cmeq vhas_nul2.16b, vdata2.16b, #0 |
| cmeq vhas_chr2.16b, vdata2.16b, vrepchr.16b |
| /* Use a fast check for the termination condition. */ |
| orr vend1.16b, vhas_nul1.16b, vhas_chr1.16b |
| orr vend2.16b, vhas_nul2.16b, vhas_chr2.16b |
| orr vend1.16b, vend1.16b, vend2.16b |
| addp vend1.2d, vend1.2d, vend1.2d |
| mov tmp1, vend1.d[0] |
| cbz tmp1, L(loop) |
| |
| /* Termination condition found. Now need to establish exactly why |
| we terminated. */ |
| and vhas_nul1.16b, vhas_nul1.16b, vrepmask_0.16b |
| and vhas_nul2.16b, vhas_nul2.16b, vrepmask_0.16b |
| and vhas_chr1.16b, vhas_chr1.16b, vrepmask_c.16b |
| and vhas_chr2.16b, vhas_chr2.16b, vrepmask_c.16b |
| orr vend1.16b, vhas_nul1.16b, vhas_chr1.16b |
| orr vend2.16b, vhas_nul2.16b, vhas_chr2.16b |
| addp vend1.16b, vend1.16b, vend2.16b // 256->128 |
| addp vend1.16b, vend1.16b, vend2.16b // 128->64 |
| |
| mov tmp1, vend1.d[0] |
| L(tail): |
| sub src, src, #32 |
| rbit tmp1, tmp1 |
| clz tmp1, tmp1 |
| /* Tmp1 is even if the target charager was found first. Otherwise |
| we've found the end of string and we weren't looking for NUL. */ |
| tst tmp1, #1 |
| add result, src, tmp1, lsr #1 |
| csel result, result, xzr, eq |
| ret |
| END (strchr) |
| libc_hidden_builtin_def (strchr) |
| weak_alias (strchr, index) |
