mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-10 07:10:06 +00:00
22999b2f0f
Although static linker can optimize it to local call, it follows the internal scheme to provide hidden proto and definitions. Reviewed-by: Carlos Eduardo Seo <carlos.seo@linaro.org>
129 lines
3.0 KiB
ArmAsm
129 lines
3.0 KiB
ArmAsm
/* memrchr - find the last occurrence of a byte in a memory block
|
|
|
|
Copyright (C) 2015-2023 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.
|
|
* MTE compatible.
|
|
*/
|
|
|
|
#define srcin x0
|
|
#define chrin w1
|
|
#define cntin x2
|
|
#define result x0
|
|
|
|
#define src x3
|
|
#define cntrem x4
|
|
#define synd x5
|
|
#define shift x6
|
|
#define tmp x7
|
|
#define end x8
|
|
#define endm1 x9
|
|
|
|
#define vrepchr v0
|
|
#define qdata q1
|
|
#define vdata v1
|
|
#define vhas_chr v2
|
|
#define vend v3
|
|
#define dend d3
|
|
|
|
/*
|
|
Core algorithm:
|
|
For each 16-byte chunk we calculate a 64-bit nibble mask value with four bits
|
|
per byte. We take 4 bits of every comparison byte with shift right and narrow
|
|
by 4 instruction. Since the bits in the nibble mask reflect the order in
|
|
which things occur in the original string, counting leading zeros identifies
|
|
exactly which byte matched. */
|
|
|
|
ENTRY (__memrchr)
|
|
PTR_ARG (0)
|
|
SIZE_ARG (2)
|
|
add end, srcin, cntin
|
|
sub endm1, end, 1
|
|
bic src, endm1, 15
|
|
cbz cntin, L(nomatch)
|
|
ld1 {vdata.16b}, [src]
|
|
dup vrepchr.16b, chrin
|
|
cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
|
|
neg shift, end, lsl 2
|
|
shrn vend.8b, vhas_chr.8h, 4 /* 128->64 */
|
|
fmov synd, dend
|
|
lsl synd, synd, shift
|
|
cbz synd, L(start_loop)
|
|
|
|
clz synd, synd
|
|
sub result, endm1, synd, lsr 2
|
|
cmp cntin, synd, lsr 2
|
|
csel result, result, xzr, hi
|
|
ret
|
|
|
|
nop
|
|
L(start_loop):
|
|
subs cntrem, src, srcin
|
|
b.ls L(nomatch)
|
|
|
|
/* Make sure that it won't overread by a 16-byte chunk */
|
|
sub cntrem, cntrem, 1
|
|
tbz cntrem, 4, L(loop32_2)
|
|
add src, src, 16
|
|
|
|
.p2align 5
|
|
L(loop32):
|
|
ldr qdata, [src, -32]!
|
|
cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
|
|
umaxp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */
|
|
fmov synd, dend
|
|
cbnz synd, L(end)
|
|
|
|
L(loop32_2):
|
|
ldr qdata, [src, -16]
|
|
subs cntrem, cntrem, 32
|
|
cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
|
|
b.lo L(end_2)
|
|
umaxp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */
|
|
fmov synd, dend
|
|
cbz synd, L(loop32)
|
|
L(end_2):
|
|
sub src, src, 16
|
|
L(end):
|
|
shrn vend.8b, vhas_chr.8h, 4 /* 128->64 */
|
|
fmov synd, dend
|
|
|
|
add tmp, src, 15
|
|
#ifdef __AARCH64EB__
|
|
rbit synd, synd
|
|
#endif
|
|
clz synd, synd
|
|
sub tmp, tmp, synd, lsr 2
|
|
cmp tmp, srcin
|
|
csel result, tmp, xzr, hs
|
|
ret
|
|
|
|
L(nomatch):
|
|
mov result, 0
|
|
ret
|
|
|
|
END (__memrchr)
|
|
libc_hidden_def (__memrchr)
|
|
weak_alias (__memrchr, memrchr)
|
|
libc_hidden_builtin_def (memrchr)
|