mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-25 12:11:10 +00:00
152 lines
3.9 KiB
ArmAsm
152 lines
3.9 KiB
ArmAsm
/* memcmp - compare memory
|
|
|
|
Copyright (C) 2013-2016 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
|
|
*/
|
|
|
|
/* Parameters and result. */
|
|
#define src1 x0
|
|
#define src2 x1
|
|
#define limit x2
|
|
#define result x0
|
|
|
|
/* Internal variables. */
|
|
#define data1 x3
|
|
#define data1w w3
|
|
#define data2 x4
|
|
#define data2w w4
|
|
#define has_nul x5
|
|
#define diff x6
|
|
#define endloop x7
|
|
#define tmp1 x8
|
|
#define tmp2 x9
|
|
#define tmp3 x10
|
|
#define pos x11
|
|
#define limit_wd x12
|
|
#define mask x13
|
|
|
|
ENTRY_ALIGN (memcmp, 6)
|
|
cbz limit, L(ret0)
|
|
eor tmp1, src1, src2
|
|
tst tmp1, #7
|
|
b.ne L(misaligned8)
|
|
ands tmp1, src1, #7
|
|
b.ne L(mutual_align)
|
|
add limit_wd, limit, #7
|
|
lsr limit_wd, limit_wd, #3
|
|
/* Start of performance-critical section -- one 64B cache line. */
|
|
L(loop_aligned):
|
|
ldr data1, [src1], #8
|
|
ldr data2, [src2], #8
|
|
L(start_realigned):
|
|
subs limit_wd, limit_wd, #1
|
|
eor diff, data1, data2 /* Non-zero if differences found. */
|
|
csinv endloop, diff, xzr, ne /* Last Dword or differences. */
|
|
cbz endloop, L(loop_aligned)
|
|
/* End of performance-critical section -- one 64B cache line. */
|
|
|
|
/* Not reached the limit, must have found a diff. */
|
|
cbnz limit_wd, L(not_limit)
|
|
|
|
/* Limit % 8 == 0 => all bytes significant. */
|
|
ands limit, limit, #7
|
|
b.eq L(not_limit)
|
|
|
|
lsl limit, limit, #3 /* Bits -> bytes. */
|
|
mov mask, #~0
|
|
#ifdef __AARCH64EB__
|
|
lsr mask, mask, limit
|
|
#else
|
|
lsl mask, mask, limit
|
|
#endif
|
|
bic data1, data1, mask
|
|
bic data2, data2, mask
|
|
|
|
orr diff, diff, mask
|
|
L(not_limit):
|
|
|
|
#ifndef __AARCH64EB__
|
|
rev diff, diff
|
|
rev data1, data1
|
|
rev data2, data2
|
|
#endif
|
|
/* The MS-non-zero bit of DIFF marks either the first bit
|
|
that is different, or the end of the significant data.
|
|
Shifting left now will bring the critical information into the
|
|
top bits. */
|
|
clz pos, diff
|
|
lsl data1, data1, pos
|
|
lsl data2, data2, pos
|
|
/* But we need to zero-extend (char is unsigned) the value and then
|
|
perform a signed 32-bit subtraction. */
|
|
lsr data1, data1, #56
|
|
sub result, data1, data2, lsr #56
|
|
RET
|
|
|
|
L(mutual_align):
|
|
/* Sources are mutually aligned, but are not currently at an
|
|
alignment boundary. Round down the addresses and then mask off
|
|
the bytes that precede the start point. */
|
|
bic src1, src1, #7
|
|
bic src2, src2, #7
|
|
add limit, limit, tmp1 /* Adjust the limit for the extra. */
|
|
lsl tmp1, tmp1, #3 /* Bytes beyond alignment -> bits. */
|
|
ldr data1, [src1], #8
|
|
neg tmp1, tmp1 /* Bits to alignment -64. */
|
|
ldr data2, [src2], #8
|
|
mov tmp2, #~0
|
|
#ifdef __AARCH64EB__
|
|
/* Big-endian. Early bytes are at MSB. */
|
|
lsl tmp2, tmp2, tmp1 /* Shift (tmp1 & 63). */
|
|
#else
|
|
/* Little-endian. Early bytes are at LSB. */
|
|
lsr tmp2, tmp2, tmp1 /* Shift (tmp1 & 63). */
|
|
#endif
|
|
add limit_wd, limit, #7
|
|
orr data1, data1, tmp2
|
|
orr data2, data2, tmp2
|
|
lsr limit_wd, limit_wd, #3
|
|
b L(start_realigned)
|
|
|
|
L(ret0):
|
|
mov result, #0
|
|
RET
|
|
|
|
.p2align 6
|
|
L(misaligned8):
|
|
sub limit, limit, #1
|
|
1:
|
|
/* Perhaps we can do better than this. */
|
|
ldrb data1w, [src1], #1
|
|
ldrb data2w, [src2], #1
|
|
subs limit, limit, #1
|
|
ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
|
|
b.eq 1b
|
|
sub result, data1, data2
|
|
RET
|
|
END (memcmp)
|
|
#undef bcmp
|
|
weak_alias (memcmp, bcmp)
|
|
libc_hidden_builtin_def (memcmp)
|