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/* A Thunderx Optimized memcpy implementation for AARCH64.
Copyright (C) 2017-2024 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/>. */
/* The actual code in this memcpy and memmove should be identical to the
generic version except for the code under '#ifdef THUNDERX'. This is
to make is easier to keep this version and the generic version in sync
for changes that are not specific to thunderx. */
#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 A_hw w7
#define B_l x8
#define B_lw w8
#define B_h x9
#define C_l x10
#define C_h x11
#define D_l x12
#define D_h x13
#define E_l src
#define E_h count
#define F_l srcend
#define F_h dst
#define G_l count
#define G_h dst
#define tmp1 x14
/* Copies are split into 3 main cases: small copies of up to 16 bytes,
medium copies of 17..96 bytes which are fully unrolled. Large copies
of more than 96 bytes align the destination and use an unrolled loop
processing 64 bytes per iteration.
In order to share code with memmove, small and medium copies read all
data before writing, allowing any kind of overlap. So small, medium
and large backwards memmoves are handled by falling through into memcpy.
Overlapping large forward memmoves use a loop that copies backwards.
*/
ENTRY (__memmove_thunderx)
PTR_ARG (0)
PTR_ARG (1)
SIZE_ARG (2)
sub tmp1, dstin, src
cmp count, 96
ccmp tmp1, count, 2, hi
b.lo L(move_long)
/* Common case falls through into memcpy. */
END (__memmove_thunderx)
ENTRY (__memcpy_thunderx)
PTR_ARG (0)
PTR_ARG (1)
SIZE_ARG (2)
prfm PLDL1KEEP, [src]
add srcend, src, count
add dstend, dstin, count
cmp count, 16
b.ls L(copy16)
cmp count, 96
b.hi L(copy_long)
/* Medium copies: 17..96 bytes. */
sub tmp1, count, 1
ldp A_l, A_h, [src]
tbnz tmp1, 6, L(copy96)
ldp D_l, D_h, [srcend, -16]
tbz tmp1, 5, 1f
ldp B_l, B_h, [src, 16]
ldp C_l, C_h, [srcend, -32]
stp B_l, B_h, [dstin, 16]
stp C_l, C_h, [dstend, -32]
1:
stp A_l, A_h, [dstin]
stp D_l, D_h, [dstend, -16]
ret
.p2align 4
/* Small copies: 0..16 bytes. */
L(copy16):
cmp count, 8
b.lo 1f
ldr A_l, [src]
ldr A_h, [srcend, -8]
str A_l, [dstin]
str A_h, [dstend, -8]
ret
.p2align 4
1:
tbz count, 2, 1f
ldr A_lw, [src]
ldr A_hw, [srcend, -4]
str A_lw, [dstin]
str A_hw, [dstend, -4]
ret
/* Copy 0..3 bytes. Use a branchless sequence that copies the same
byte 3 times if count==1, or the 2nd byte twice if count==2. */
1:
cbz count, 2f
lsr tmp1, count, 1
ldrb A_lw, [src]
ldrb A_hw, [srcend, -1]
ldrb B_lw, [src, tmp1]
strb A_lw, [dstin]
strb B_lw, [dstin, tmp1]
strb A_hw, [dstend, -1]
2: ret
.p2align 4
/* Copy 64..96 bytes. Copy 64 bytes from the start and
32 bytes from the end. */
L(copy96):
ldp B_l, B_h, [src, 16]
ldp C_l, C_h, [src, 32]
ldp D_l, D_h, [src, 48]
ldp E_l, E_h, [srcend, -32]
ldp F_l, F_h, [srcend, -16]
stp A_l, A_h, [dstin]
stp B_l, B_h, [dstin, 16]
stp C_l, C_h, [dstin, 32]
stp D_l, D_h, [dstin, 48]
stp E_l, E_h, [dstend, -32]
stp F_l, F_h, [dstend, -16]
ret
/* Align DST 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 64 bytes per iteration and prefetches one iteration ahead. */
.p2align 4
L(copy_long):
/* On thunderx, large memcpy's are helped by software prefetching.
This loop is identical to the one below it but with prefetching
instructions included. For loops that are less than 32768 bytes,
the prefetching does not help and slow the code down so we only
use the prefetching loop for the largest memcpys. */
cmp count, #32768
b.lo L(copy_long_without_prefetch)
and tmp1, dstin, 15
bic dst, dstin, 15
ldp D_l, D_h, [src]
sub src, src, tmp1
prfm pldl1strm, [src, 384]
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. */
L(prefetch_loop64):
tbz src, #6, 1f
prfm pldl1strm, [src, 512]
1:
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(prefetch_loop64)
b L(last64)
L(copy_long_without_prefetch):
and tmp1, dstin, 15
bic dst, dstin, 15
ldp D_l, D_h, [src]
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(last64)
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 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):
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
.p2align 4
L(move_long):
cbz tmp1, 3f
add srcend, src, count
add dstend, dstin, count
/* Align dstend 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 64 bytes per iteration and prefetches one iteration ahead. */
and tmp1, dstend, 15
ldp D_l, D_h, [srcend, -16]
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 2f
nop
1:
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 1b
/* 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 start even if
there is just 1 byte left. */
2:
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]
3: ret
END (__memcpy_thunderx)
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