mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-18 17:01:03 +00:00
2b778ceb40
I used these shell commands: ../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright (cd ../glibc && git commit -am"[this commit message]") and then ignored the output, which consisted lines saying "FOO: warning: copyright statement not found" for each of 6694 files FOO. I then removed trailing white space from benchtests/bench-pthread-locks.c and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this diagnostic from Savannah: remote: *** pre-commit check failed ... remote: *** error: lines with trailing whitespace found remote: error: hook declined to update refs/heads/master
215 lines
5.6 KiB
ArmAsm
215 lines
5.6 KiB
ArmAsm
/* Optimized strlen implementation using SIMD.
|
|
Copyright (C) 2018-2021 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
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#include <sysdep.h>
|
|
|
|
/* Assumptions:
|
|
*
|
|
* ARMv8-a, AArch64, Advanced SIMD, unaligned accesses.
|
|
* Not MTE compatible.
|
|
*/
|
|
|
|
#define srcin x0
|
|
#define len x0
|
|
|
|
#define src x1
|
|
#define data1 x2
|
|
#define data2 x3
|
|
#define has_nul1 x4
|
|
#define has_nul2 x5
|
|
#define tmp1 x4
|
|
#define tmp2 x5
|
|
#define tmp3 x6
|
|
#define tmp4 x7
|
|
#define zeroones x8
|
|
|
|
#define maskv v0
|
|
#define maskd d0
|
|
#define dataq1 q1
|
|
#define dataq2 q2
|
|
#define datav1 v1
|
|
#define datav2 v2
|
|
#define tmp x2
|
|
#define tmpw w2
|
|
#define synd x3
|
|
#define shift x4
|
|
|
|
/* For the first 32 bytes, NUL detection works on the principle that
|
|
(X - 1) & (~X) & 0x80 (=> (X - 1) & ~(X | 0x7f)) is non-zero if a
|
|
byte is zero, and can be done in parallel across the entire word. */
|
|
|
|
#define REP8_01 0x0101010101010101
|
|
#define REP8_7f 0x7f7f7f7f7f7f7f7f
|
|
|
|
/* To test the page crossing code path more thoroughly, compile with
|
|
-DTEST_PAGE_CROSS - this will force all calls through the slower
|
|
entry path. This option is not intended for production use. */
|
|
|
|
#ifdef TEST_PAGE_CROSS
|
|
# define MIN_PAGE_SIZE 32
|
|
#else
|
|
# define MIN_PAGE_SIZE 4096
|
|
#endif
|
|
|
|
/* Core algorithm:
|
|
|
|
Since strings are short on average, we check the first 32 bytes of the
|
|
string for a NUL character without aligning the string. In order to use
|
|
unaligned loads safely we must do a page cross check first.
|
|
|
|
If there is a NUL byte we calculate the length from the 2 8-byte words
|
|
using conditional select to reduce branch mispredictions (it is unlikely
|
|
strlen will be repeatedly called on strings with the same length).
|
|
|
|
If the string is longer than 32 bytes, align src so we don't need further
|
|
page cross checks, and process 32 bytes per iteration using a fast SIMD
|
|
loop.
|
|
|
|
If the page cross check fails, we read 32 bytes from an aligned address,
|
|
and ignore any characters before the string. If it contains a NUL
|
|
character, return the length, if not, continue in the main loop. */
|
|
|
|
ENTRY (__strlen_asimd)
|
|
PTR_ARG (0)
|
|
|
|
and tmp1, srcin, MIN_PAGE_SIZE - 1
|
|
cmp tmp1, MIN_PAGE_SIZE - 32
|
|
b.hi L(page_cross)
|
|
|
|
/* Look for a NUL byte in the first 16 bytes. */
|
|
ldp data1, data2, [srcin]
|
|
mov zeroones, REP8_01
|
|
|
|
#ifdef __AARCH64EB__
|
|
/* For big-endian, carry propagation (if the final byte in the
|
|
string is 0x01) means we cannot use has_nul1/2 directly.
|
|
Since we expect strings to be small and early-exit,
|
|
byte-swap the data now so has_null1/2 will be correct. */
|
|
rev data1, data1
|
|
rev data2, data2
|
|
#endif
|
|
sub tmp1, data1, zeroones
|
|
orr tmp2, data1, REP8_7f
|
|
sub tmp3, data2, zeroones
|
|
orr tmp4, data2, REP8_7f
|
|
bics has_nul1, tmp1, tmp2
|
|
bic has_nul2, tmp3, tmp4
|
|
ccmp has_nul2, 0, 0, eq
|
|
b.eq L(bytes16_31)
|
|
|
|
/* Find the exact offset of the first NUL byte in the first 16 bytes
|
|
from the string start. Enter with C = has_nul1 == 0. */
|
|
csel has_nul1, has_nul1, has_nul2, cc
|
|
mov len, 8
|
|
rev has_nul1, has_nul1
|
|
csel len, xzr, len, cc
|
|
clz tmp1, has_nul1
|
|
add len, len, tmp1, lsr 3
|
|
ret
|
|
|
|
.p2align 3
|
|
/* Look for a NUL byte at offset 16..31 in the string. */
|
|
L(bytes16_31):
|
|
ldp data1, data2, [srcin, 16]
|
|
#ifdef __AARCH64EB__
|
|
rev data1, data1
|
|
rev data2, data2
|
|
#endif
|
|
sub tmp1, data1, zeroones
|
|
orr tmp2, data1, REP8_7f
|
|
sub tmp3, data2, zeroones
|
|
orr tmp4, data2, REP8_7f
|
|
bics has_nul1, tmp1, tmp2
|
|
bic has_nul2, tmp3, tmp4
|
|
ccmp has_nul2, 0, 0, eq
|
|
b.eq L(loop_entry)
|
|
|
|
/* Find the exact offset of the first NUL byte at offset 16..31 from
|
|
the string start. Enter with C = has_nul1 == 0. */
|
|
csel has_nul1, has_nul1, has_nul2, cc
|
|
mov len, 24
|
|
rev has_nul1, has_nul1
|
|
mov tmp3, 16
|
|
clz tmp1, has_nul1
|
|
csel len, tmp3, len, cc
|
|
add len, len, tmp1, lsr 3
|
|
ret
|
|
|
|
L(loop_entry):
|
|
bic src, srcin, 31
|
|
|
|
.p2align 5
|
|
L(loop):
|
|
ldp dataq1, dataq2, [src, 32]!
|
|
uminp maskv.16b, datav1.16b, datav2.16b
|
|
uminp maskv.16b, maskv.16b, maskv.16b
|
|
cmeq maskv.8b, maskv.8b, 0
|
|
fmov synd, maskd
|
|
cbz synd, L(loop)
|
|
|
|
/* Low 32 bits of synd are non-zero if a NUL was found in datav1. */
|
|
cmeq maskv.16b, datav1.16b, 0
|
|
sub len, src, srcin
|
|
tst synd, 0xffffffff
|
|
b.ne 1f
|
|
cmeq maskv.16b, datav2.16b, 0
|
|
add len, len, 16
|
|
1:
|
|
/* Generate a bitmask and compute correct byte offset. */
|
|
#ifdef __AARCH64EB__
|
|
bic maskv.8h, 0xf0
|
|
#else
|
|
bic maskv.8h, 0x0f, lsl 8
|
|
#endif
|
|
umaxp maskv.16b, maskv.16b, maskv.16b
|
|
fmov synd, maskd
|
|
#ifndef __AARCH64EB__
|
|
rbit synd, synd
|
|
#endif
|
|
clz tmp, synd
|
|
add len, len, tmp, lsr 2
|
|
ret
|
|
|
|
.p2align 4
|
|
|
|
L(page_cross):
|
|
bic src, srcin, 31
|
|
mov tmpw, 0x0c03
|
|
movk tmpw, 0xc030, lsl 16
|
|
ld1 {datav1.16b, datav2.16b}, [src]
|
|
dup maskv.4s, tmpw
|
|
cmeq datav1.16b, datav1.16b, 0
|
|
cmeq datav2.16b, datav2.16b, 0
|
|
and datav1.16b, datav1.16b, maskv.16b
|
|
and datav2.16b, datav2.16b, maskv.16b
|
|
addp maskv.16b, datav1.16b, datav2.16b
|
|
addp maskv.16b, maskv.16b, maskv.16b
|
|
fmov synd, maskd
|
|
lsl shift, srcin, 1
|
|
lsr synd, synd, shift
|
|
cbz synd, L(loop)
|
|
|
|
rbit synd, synd
|
|
clz len, synd
|
|
lsr len, len, 1
|
|
ret
|
|
|
|
END (__strlen_asimd)
|
|
libc_hidden_builtin_def (__strlen_asimd)
|