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/* Optimized memcpy for Qualcomm Falkor processor.
Copyright (C) 2017-2020 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, falkor, unaligned accesses. */
#define dstin x0
#define src x1
#define count x2
#define dst x3
#define srcend x4
#define dstend x5
#define tmp1 x14
#define A_x x6
#define B_x x7
#define A_w w6
#define B_w w7
#define A_q q0
#define B_q q1
#define C_q q2
#define D_q q3
#define E_q q4
#define F_q q5
#define G_q q6
/* Copies are split into 3 main cases:
1. Small copies of up to 32 bytes
2. Medium copies of 33..128 bytes which are fully unrolled
3. Large copies of more than 128 bytes.
Large copies align the sourceto a quad word and use an unrolled loop
processing 64 bytes per iteration.
FALKOR-SPECIFIC DESIGN:
The smallest copies (32 bytes or less) focus on optimal pipeline usage,
which is why the redundant copies of 0-3 bytes have been replaced with
conditionals, since the former would unnecessarily break across multiple
issue groups. The medium copy group has been enlarged to 128 bytes since
bumping up the small copies up to 32 bytes allows us to do that without
cost and also allows us to reduce the size of the prep code before loop64.
The copy loop uses only one register q0. This is to ensure that all loads
hit a single hardware prefetcher which can get correctly trained to prefetch
a single stream.
The non-temporal stores help optimize cache utilization. */
#if IS_IN (libc)
ENTRY_ALIGN (__memcpy_falkor, 6)
cmp count, 32
add srcend, src, count
add dstend, dstin, count
b.ls L(copy32)
ldr A_q, [src]
cmp count, 128
str A_q, [dstin]
b.hi L(copy_long)
/* Medium copies: 33..128 bytes. */
sub tmp1, count, 1
ldr A_q, [src, 16]
ldr B_q, [srcend, -32]
ldr C_q, [srcend, -16]
tbz tmp1, 6, 1f
ldr D_q, [src, 32]
ldr E_q, [src, 48]
str D_q, [dstin, 32]
str E_q, [dstin, 48]
ldr F_q, [srcend, -64]
ldr G_q, [srcend, -48]
str F_q, [dstend, -64]
str G_q, [dstend, -48]
1:
str A_q, [dstin, 16]
str B_q, [dstend, -32]
str C_q, [dstend, -16]
ret
.p2align 4
/* Small copies: 0..32 bytes. */
L(copy32):
/* 16-32 */
cmp count, 16
b.lo 1f
ldr A_q, [src]
ldr B_q, [srcend, -16]
str A_q, [dstin]
str B_q, [dstend, -16]
ret
.p2align 4
1:
/* 8-15 */
tbz count, 3, 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
/* Align SRC to 16 bytes and copy; that way at least one of the
accesses is aligned throughout the copy sequence.
The count is off by 0 to 15 bytes, but this is OK because we trim
off the last 64 bytes to copy off from the end. Due to this the
loop never runs out of bounds. */
.p2align 6
L(copy_long):
sub count, count, 64 + 16
and tmp1, src, 15
bic src, src, 15
sub dst, dstin, tmp1
add count, count, tmp1
L(loop64):
ldr A_q, [src, 16]!
str A_q, [dst, 16]
ldr A_q, [src, 16]!
subs count, count, 64
str A_q, [dst, 32]
ldr A_q, [src, 16]!
str A_q, [dst, 48]
ldr A_q, [src, 16]!
str A_q, [dst, 64]!
b.hi L(loop64)
/* Write the last full set of 64 bytes. The remainder is at most 64
bytes, so it is safe to always copy 64 bytes from the end even if
there is just 1 byte left. */
L(last64):
ldr E_q, [srcend, -64]
str E_q, [dstend, -64]
ldr D_q, [srcend, -48]
str D_q, [dstend, -48]
ldr C_q, [srcend, -32]
str C_q, [dstend, -32]
ldr B_q, [srcend, -16]
str B_q, [dstend, -16]
ret
END (__memcpy_falkor)
libc_hidden_builtin_def (__memcpy_falkor)
#endif
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