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/* Optimized memset for AmpereComputing emag processor.
Copyright (C) 2018-2022 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>
#include "memset-reg.h"
/* Assumptions:
*
* ARMv8-a, AArch64, unaligned accesses
*
*/
ENTRY (__memset_emag)
PTR_ARG (0)
SIZE_ARG (2)
bfi valw, valw, 8, 8
bfi valw, valw, 16, 16
bfi val, val, 32, 32
add dstend, dstin, count
cmp count, 96
b.hi L(set_long)
cmp count, 16
b.hs L(set_medium)
/* Set 0..15 bytes. */
tbz count, 3, 1f
str val, [dstin]
str val, [dstend, -8]
ret
.p2align 3
1: tbz count, 2, 2f
str valw, [dstin]
str valw, [dstend, -4]
ret
2: cbz count, 3f
strb valw, [dstin]
tbz count, 1, 3f
strh valw, [dstend, -2]
3: ret
.p2align 3
/* Set 16..96 bytes. */
L(set_medium):
stp val, val, [dstin]
tbnz count, 6, L(set96)
stp val, val, [dstend, -16]
tbz count, 5, 1f
stp val, val, [dstin, 16]
stp val, val, [dstend, -32]
1: ret
.p2align 4
/* Set 64..96 bytes. Write 64 bytes from the start and
32 bytes from the end. */
L(set96):
stp val, val, [dstin, 16]
stp val, val, [dstin, 32]
stp val, val, [dstin, 48]
stp val, val, [dstend, -32]
stp val, val, [dstend, -16]
ret
.p2align 4
L(set_long):
stp val, val, [dstin]
bic dst, dstin, 15
/* Small-size or non-zero memset does not use DC ZVA. */
sub count, dstend, dst
/*
* Adjust count and bias for loop. By subtracting extra 1 from count,
* it is easy to use tbz instruction to check whether loop tailing
* count is less than 33 bytes, so as to bypass 2 unnecessary stps.
*/
sub count, count, 64+16+1
1: stp val, val, [dst, 16]
stp val, val, [dst, 32]
stp val, val, [dst, 48]
stp val, val, [dst, 64]!
subs count, count, 64
b.hs 1b
tbz count, 5, 1f /* Remaining count is less than 33 bytes? */
stp val, val, [dst, 16]
stp val, val, [dst, 32]
1: stp val, val, [dstend, -32]
stp val, val, [dstend, -16]
ret
END (__memset_emag)
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