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/* Generic optimized memset using SIMD.
Copyright (C) 2012-2025 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>
#ifndef MEMSET
# define MEMSET memset
#endif
/* Assumptions:
*
* ARMv8-a, AArch64, Advanced SIMD, unaligned accesses.
*
*/
#define dstin x0
#define valw w1
#define count x2
#define dst x3
#define dstend x4
#define zva_val x5
#define off x3
#define dstend2 x5
ENTRY (MEMSET)
dup v0.16B, valw
cmp count, 16
b.lo L(set_small)
add dstend, dstin, count
cmp count, 64
b.hs L(set_128)
/* Set 16..63 bytes. */
mov off, 16
and off, off, count, lsr 1
sub dstend2, dstend, off
str q0, [dstin]
str q0, [dstin, off]
str q0, [dstend2, -16]
str q0, [dstend, -16]
ret
.p2align 4
/* Set 0..15 bytes. */
L(set_small):
add dstend, dstin, count
cmp count, 4
b.lo 2f
lsr off, count, 3
sub dstend2, dstend, off, lsl 2
str s0, [dstin]
str s0, [dstin, off, lsl 2]
str s0, [dstend2, -4]
str s0, [dstend, -4]
ret
/* Set 0..3 bytes. */
2: cbz count, 3f
lsr off, count, 1
strb valw, [dstin]
strb valw, [dstin, off]
strb valw, [dstend, -1]
3: ret
.p2align 4
L(set_128):
bic dst, dstin, 15
cmp count, 128
b.hi L(set_long)
stp q0, q0, [dstin]
stp q0, q0, [dstin, 32]
stp q0, q0, [dstend, -64]
stp q0, q0, [dstend, -32]
ret
.p2align 4
L(set_long):
str q0, [dstin]
str q0, [dst, 16]
tst valw, 255
b.ne L(no_zva)
#ifndef ZVA64_ONLY
mrs zva_val, dczid_el0
and zva_val, zva_val, 31
cmp zva_val, 4 /* ZVA size is 64 bytes. */
b.ne L(no_zva)
#endif
stp q0, q0, [dst, 32]
bic dst, dstin, 63
sub count, dstend, dst /* Count is now 64 too large. */
sub count, count, 64 + 64 /* Adjust count and bias for loop. */
/* Write last bytes before ZVA loop. */
stp q0, q0, [dstend, -64]
stp q0, q0, [dstend, -32]
.p2align 4
L(zva64_loop):
add dst, dst, 64
dc zva, dst
subs count, count, 64
b.hi L(zva64_loop)
ret
.p2align 3
L(no_zva):
sub count, dstend, dst /* Count is 32 too large. */
sub count, count, 64 + 32 /* Adjust count and bias for loop. */
L(no_zva_loop):
stp q0, q0, [dst, 32]
stp q0, q0, [dst, 64]
add dst, dst, 64
subs count, count, 64
b.hi L(no_zva_loop)
stp q0, q0, [dstend, -64]
stp q0, q0, [dstend, -32]
ret
END (MEMSET)
libc_hidden_builtin_def (MEMSET)
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