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/* Copyright (C) 2012-2022 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, unaligned accesses.
*
*/
#define dstin x0
#define src x1
#define count x2
#define dst x3
#define srcend x4
#define dstend x5
#define A_l x6
#define A_lw w6
#define A_h x7
#define B_l x8
#define B_lw w8
#define B_h x9
#define C_l x10
#define C_lw w10
#define C_h x11
#define D_l x12
#define D_h x13
#define E_l x14
#define E_h x15
#define F_l x16
#define F_h x17
#define G_l count
#define G_h dst
#define H_l src
#define H_h srcend
#define tmp1 x14
#ifndef MEMMOVE
# define MEMMOVE memmove
#endif
#ifndef MEMCPY
# define MEMCPY memcpy
#endif
/* This implementation supports both memcpy and memmove and shares most code.
It uses unaligned accesses and branchless sequences to keep the code small,
simple and improve performance.
Copies are split into 3 main cases: small copies of up to 32 bytes, medium
copies of up to 128 bytes, and large copies. The overhead of the overlap
check in memmove is negligible since it is only required for large copies.
Large copies use a software pipelined loop processing 64 bytes per
iteration. The destination pointer is 16-byte aligned to minimize
unaligned accesses. The loop tail is handled by always copying 64 bytes
from the end.
*/
ENTRY_ALIGN (MEMCPY, 6)
PTR_ARG (0)
PTR_ARG (1)
SIZE_ARG (2)
add srcend, src, count
add dstend, dstin, count
cmp count, 128
b.hi L(copy_long)
cmp count, 32
b.hi L(copy32_128)
/* Small copies: 0..32 bytes. */
cmp count, 16
b.lo L(copy16)
ldp A_l, A_h, [src]
ldp D_l, D_h, [srcend, -16]
stp A_l, A_h, [dstin]
stp D_l, D_h, [dstend, -16]
ret
/* Copy 8-15 bytes. */
L(copy16):
tbz count, 3, L(copy8)
ldr A_l, [src]
ldr A_h, [srcend, -8]
str A_l, [dstin]
str A_h, [dstend, -8]
ret
.p2align 3
/* Copy 4-7 bytes. */
L(copy8):
tbz count, 2, L(copy4)
ldr A_lw, [src]
ldr B_lw, [srcend, -4]
str A_lw, [dstin]
str B_lw, [dstend, -4]
ret
/* Copy 0..3 bytes using a branchless sequence. */
L(copy4):
cbz count, L(copy0)
lsr tmp1, count, 1
ldrb A_lw, [src]
ldrb C_lw, [srcend, -1]
ldrb B_lw, [src, tmp1]
strb A_lw, [dstin]
strb B_lw, [dstin, tmp1]
strb C_lw, [dstend, -1]
L(copy0):
ret
.p2align 4
/* Medium copies: 33..128 bytes. */
L(copy32_128):
ldp A_l, A_h, [src]
ldp B_l, B_h, [src, 16]
ldp C_l, C_h, [srcend, -32]
ldp D_l, D_h, [srcend, -16]
cmp count, 64
b.hi L(copy128)
stp A_l, A_h, [dstin]
stp B_l, B_h, [dstin, 16]
stp C_l, C_h, [dstend, -32]
stp D_l, D_h, [dstend, -16]
ret
.p2align 4
/* Copy 65..128 bytes. */
L(copy128):
ldp E_l, E_h, [src, 32]
ldp F_l, F_h, [src, 48]
cmp count, 96
b.ls L(copy96)
ldp G_l, G_h, [srcend, -64]
ldp H_l, H_h, [srcend, -48]
stp G_l, G_h, [dstend, -64]
stp H_l, H_h, [dstend, -48]
L(copy96):
stp A_l, A_h, [dstin]
stp B_l, B_h, [dstin, 16]
stp E_l, E_h, [dstin, 32]
stp F_l, F_h, [dstin, 48]
stp C_l, C_h, [dstend, -32]
stp D_l, D_h, [dstend, -16]
ret
.p2align 4
/* Copy more than 128 bytes. */
L(copy_long):
/* Copy 16 bytes and then align dst to 16-byte alignment. */
ldp D_l, D_h, [src]
and tmp1, dstin, 15
bic dst, dstin, 15
sub src, src, tmp1
add count, count, tmp1 /* Count is now 16 too large. */
ldp A_l, A_h, [src, 16]
stp D_l, D_h, [dstin]
ldp B_l, B_h, [src, 32]
ldp C_l, C_h, [src, 48]
ldp D_l, D_h, [src, 64]!
subs count, count, 128 + 16 /* Test and readjust count. */
b.ls L(copy64_from_end)
L(loop64):
stp A_l, A_h, [dst, 16]
ldp A_l, A_h, [src, 16]
stp B_l, B_h, [dst, 32]
ldp B_l, B_h, [src, 32]
stp C_l, C_h, [dst, 48]
ldp C_l, C_h, [src, 48]
stp D_l, D_h, [dst, 64]!
ldp D_l, D_h, [src, 64]!
subs count, count, 64
b.hi L(loop64)
/* Write the last iteration and copy 64 bytes from the end. */
L(copy64_from_end):
ldp E_l, E_h, [srcend, -64]
stp A_l, A_h, [dst, 16]
ldp A_l, A_h, [srcend, -48]
stp B_l, B_h, [dst, 32]
ldp B_l, B_h, [srcend, -32]
stp C_l, C_h, [dst, 48]
ldp C_l, C_h, [srcend, -16]
stp D_l, D_h, [dst, 64]
stp E_l, E_h, [dstend, -64]
stp A_l, A_h, [dstend, -48]
stp B_l, B_h, [dstend, -32]
stp C_l, C_h, [dstend, -16]
ret
END (MEMCPY)
libc_hidden_builtin_def (MEMCPY)
ENTRY_ALIGN (MEMMOVE, 4)
PTR_ARG (0)
PTR_ARG (1)
SIZE_ARG (2)
add srcend, src, count
add dstend, dstin, count
cmp count, 128
b.hi L(move_long)
cmp count, 32
b.hi L(copy32_128)
/* Small copies: 0..32 bytes. */
cmp count, 16
b.lo L(copy16)
ldp A_l, A_h, [src]
ldp D_l, D_h, [srcend, -16]
stp A_l, A_h, [dstin]
stp D_l, D_h, [dstend, -16]
ret
.p2align 4
L(move_long):
/* Only use backward copy if there is an overlap. */
sub tmp1, dstin, src
cbz tmp1, L(copy0)
cmp tmp1, count
b.hs L(copy_long)
/* Large backwards copy for overlapping copies.
Copy 16 bytes and then align dst to 16-byte alignment. */
ldp D_l, D_h, [srcend, -16]
and tmp1, dstend, 15
sub srcend, srcend, tmp1
sub count, count, tmp1
ldp A_l, A_h, [srcend, -16]
stp D_l, D_h, [dstend, -16]
ldp B_l, B_h, [srcend, -32]
ldp C_l, C_h, [srcend, -48]
ldp D_l, D_h, [srcend, -64]!
sub dstend, dstend, tmp1
subs count, count, 128
b.ls L(copy64_from_start)
L(loop64_backwards):
stp A_l, A_h, [dstend, -16]
ldp A_l, A_h, [srcend, -16]
stp B_l, B_h, [dstend, -32]
ldp B_l, B_h, [srcend, -32]
stp C_l, C_h, [dstend, -48]
ldp C_l, C_h, [srcend, -48]
stp D_l, D_h, [dstend, -64]!
ldp D_l, D_h, [srcend, -64]!
subs count, count, 64
b.hi L(loop64_backwards)
/* Write the last iteration and copy 64 bytes from the start. */
L(copy64_from_start):
ldp G_l, G_h, [src, 48]
stp A_l, A_h, [dstend, -16]
ldp A_l, A_h, [src, 32]
stp B_l, B_h, [dstend, -32]
ldp B_l, B_h, [src, 16]
stp C_l, C_h, [dstend, -48]
ldp C_l, C_h, [src]
stp D_l, D_h, [dstend, -64]
stp G_l, G_h, [dstin, 48]
stp A_l, A_h, [dstin, 32]
stp B_l, B_h, [dstin, 16]
stp C_l, C_h, [dstin]
ret
END (MEMMOVE)
libc_hidden_builtin_def (MEMMOVE)
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