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/* Copyright (C) 2017-2018 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, falkor, unaligned accesses. */
#define dstin x0
#define src x1
#define count x2
#define dst x3
#define srcend x4
#define dstend x5
#define A_x x6
#define B_x x7
#define A_w w6
#define B_w w7
#define tmp1 x14
#define Q_q q6
#define A_q q22
#define B_q q18
#define C_q q19
#define D_q q20
#define E_q q21
#define F_q q17
#define G_q q23
/* RATIONALE:
The move has 4 distinct parts:
* Small moves of 16 bytes and under
* Medium sized moves of 17-96 bytes
* Large moves where the source address is higher than the destination
(forward copies)
* Large moves where the destination address is higher than the source
(copy backward, or move).
We use only two registers q6 and q22 for the moves and move 32 bytes at a
time to correctly train the hardware prefetcher for better throughput. */
ENTRY_ALIGN (__memmove_falkor, 6)
sub tmp1, dstin, src
add srcend, src, count
add dstend, dstin, count
cmp count, 96
ccmp tmp1, count, 2, hi
b.lo L(move_long)
cmp count, 16
b.ls L(copy16)
cmp count, 96
b.hi L(copy_long)
/* Medium copies: 17..96 bytes. */
sub tmp1, count, 1
ldr A_q, [src]
tbnz tmp1, 6, L(copy96)
ldr D_q, [srcend, -16]
tbz tmp1, 5, 1f
ldr B_q, [src, 16]
ldr C_q, [srcend, -32]
str B_q, [dstin, 16]
str C_q, [dstend, -32]
1:
str A_q, [dstin]
str D_q, [dstend, -16]
ret
.p2align 4
/* Small copies: 0..16 bytes. */
L(copy16):
cmp count, 8
b.lo 1f
ldr A_x, [src]
ldr B_x, [srcend, -8]
str A_x, [dstin]
str B_x, [dstend, -8]
ret
.p2align 4
1:
/* 4-7 */
tbz count, 2, 1f
ldr A_w, [src]
ldr B_w, [srcend, -4]
str A_w, [dstin]
str B_w, [dstend, -4]
ret
.p2align 4
1:
/* 2-3 */
tbz count, 1, 1f
ldrh A_w, [src]
ldrh B_w, [srcend, -2]
strh A_w, [dstin]
strh B_w, [dstend, -2]
ret
.p2align 4
1:
/* 0-1 */
tbz count, 0, 1f
ldrb A_w, [src]
strb A_w, [dstin]
1: ret
.p2align 4
/* Copy 64..96 bytes. Copy 64 bytes from the start and
32 bytes from the end. */
L(copy96):
ldr B_q, [src, 16]
ldr C_q, [src, 32]
ldr D_q, [src, 48]
ldr E_q, [srcend, -32]
ldr F_q, [srcend, -16]
str A_q, [dstin]
str B_q, [dstin, 16]
str C_q, [dstin, 32]
str D_q, [dstin, 48]
str E_q, [dstend, -32]
str F_q, [dstend, -16]
ret
/* Align SRC to 16 byte alignment so that we don't cross cache line
boundaries on both loads and stores. There are at least 96 bytes
to copy, so copy 16 bytes unaligned and then align. The loop
copies 32 bytes per iteration and prefetches one iteration ahead. */
.p2align 4
L(copy_long):
ldr A_q, [src]
and tmp1, src, 15
bic src, src, 15
sub dst, dstin, tmp1
add count, count, tmp1 /* Count is now 16 too large. */
ldr Q_q, [src, 16]!
str A_q, [dstin]
ldr A_q, [src, 16]!
subs count, count, 32 + 64 + 16 /* Test and readjust count. */
b.ls L(last64)
L(loop64):
subs count, count, 32
str Q_q, [dst, 16]
ldr Q_q, [src, 16]!
str A_q, [dst, 32]!
ldr A_q, [src, 16]!
b.hi L(loop64)
/* Write the last full set of 64 bytes. The remainder is at most 64
bytes and at least 33 bytes, so it is safe to always copy 64 bytes
from the end. */
L(last64):
ldr C_q, [srcend, -64]
str Q_q, [dst, 16]
ldr B_q, [srcend, -48]
str A_q, [dst, 32]
ldr A_q, [srcend, -32]
ldr D_q, [srcend, -16]
str C_q, [dstend, -64]
str B_q, [dstend, -48]
str A_q, [dstend, -32]
str D_q, [dstend, -16]
ret
.p2align 4
L(move_long):
cbz tmp1, 3f
/* Align SRCEND to 16 byte alignment so that we don't cross cache line
boundaries on both loads and stores. There are at least 96 bytes
to copy, so copy 16 bytes unaligned and then align. The loop
copies 32 bytes per iteration and prefetches one iteration ahead. */
ldr A_q, [srcend, -16]
and tmp1, srcend, 15
sub srcend, srcend, tmp1
ldr Q_q, [srcend, -16]!
str A_q, [dstend, -16]
sub count, count, tmp1
ldr A_q, [srcend, -16]!
sub dstend, dstend, tmp1
subs count, count, 32 + 64
b.ls 2f
1:
subs count, count, 32
str Q_q, [dstend, -16]
ldr Q_q, [srcend, -16]!
str A_q, [dstend, -32]!
ldr A_q, [srcend, -16]!
b.hi 1b
/* Write the last full set of 64 bytes. The remainder is at most 64
bytes and at least 33 bytes, so it is safe to always copy 64 bytes
from the start. */
2:
ldr C_q, [src, 48]
str Q_q, [dstend, -16]
ldr B_q, [src, 32]
str A_q, [dstend, -32]
ldr A_q, [src, 16]
ldr D_q, [src]
str C_q, [dstin, 48]
str B_q, [dstin, 32]
str A_q, [dstin, 16]
str D_q, [dstin]
3: ret
END (__memmove_falkor)
libc_hidden_builtin_def (__memmove_falkor)
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