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a024b39a4e
add a prefetch and improve small copies that are exact powers of 2.
* sysdeps/aarch64/memcpy.S (memcpy):
Further tuning for performance.
253 lines
6.3 KiB
ArmAsm
253 lines
6.3 KiB
ArmAsm
/* Copyright (C) 2012-2016 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library. If not, see
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<http://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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/* Assumptions:
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*
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* ARMv8-a, AArch64, unaligned accesses.
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*
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*/
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#define dstin x0
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#define src x1
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#define count x2
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#define dst x3
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#define srcend x4
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#define dstend x5
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#define A_l x6
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#define A_lw w6
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#define A_h x7
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#define A_hw w7
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#define B_l x8
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#define B_lw w8
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#define B_h x9
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#define C_l x10
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#define C_h x11
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#define D_l x12
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#define D_h x13
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#define E_l src
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#define E_h count
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#define F_l srcend
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#define F_h dst
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#define G_l count
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#define G_h dst
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#define tmp1 x14
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/* Copies are split into 3 main cases: small copies of up to 16 bytes,
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medium copies of 17..96 bytes which are fully unrolled. Large copies
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of more than 96 bytes align the destination and use an unrolled loop
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processing 64 bytes per iteration.
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In order to share code with memmove, small and medium copies read all
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data before writing, allowing any kind of overlap. So small, medium
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and large backwards memmoves are handled by falling through into memcpy.
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Overlapping large forward memmoves use a loop that copies backwards.
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*/
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ENTRY_ALIGN (memmove, 6)
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sub tmp1, dstin, src
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cmp count, 96
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ccmp tmp1, count, 2, hi
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b.lo L(move_long)
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/* Common case falls through into memcpy. */
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END (memmove)
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libc_hidden_builtin_def (memmove)
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ENTRY (memcpy)
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prfm PLDL1KEEP, [src]
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add srcend, src, count
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add dstend, dstin, count
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cmp count, 16
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b.ls L(copy16)
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cmp count, 96
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b.hi L(copy_long)
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/* Medium copies: 17..96 bytes. */
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sub tmp1, count, 1
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ldp A_l, A_h, [src]
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tbnz tmp1, 6, L(copy96)
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ldp D_l, D_h, [srcend, -16]
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tbz tmp1, 5, 1f
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ldp B_l, B_h, [src, 16]
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ldp C_l, C_h, [srcend, -32]
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stp B_l, B_h, [dstin, 16]
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stp C_l, C_h, [dstend, -32]
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1:
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stp A_l, A_h, [dstin]
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stp D_l, D_h, [dstend, -16]
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ret
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.p2align 4
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/* Small copies: 0..16 bytes. */
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L(copy16):
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cmp count, 8
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b.lo 1f
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ldr A_l, [src]
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ldr A_h, [srcend, -8]
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str A_l, [dstin]
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str A_h, [dstend, -8]
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ret
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.p2align 4
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1:
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tbz count, 2, 1f
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ldr A_lw, [src]
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ldr A_hw, [srcend, -4]
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str A_lw, [dstin]
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str A_hw, [dstend, -4]
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ret
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/* Copy 0..3 bytes. Use a branchless sequence that copies the same
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byte 3 times if count==1, or the 2nd byte twice if count==2. */
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1:
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cbz count, 2f
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lsr tmp1, count, 1
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ldrb A_lw, [src]
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ldrb A_hw, [srcend, -1]
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ldrb B_lw, [src, tmp1]
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strb A_lw, [dstin]
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strb B_lw, [dstin, tmp1]
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strb A_hw, [dstend, -1]
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2: ret
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.p2align 4
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/* Copy 64..96 bytes. Copy 64 bytes from the start and
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32 bytes from the end. */
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L(copy96):
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ldp B_l, B_h, [src, 16]
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ldp C_l, C_h, [src, 32]
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ldp D_l, D_h, [src, 48]
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ldp E_l, E_h, [srcend, -32]
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ldp F_l, F_h, [srcend, -16]
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stp A_l, A_h, [dstin]
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stp B_l, B_h, [dstin, 16]
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stp C_l, C_h, [dstin, 32]
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stp D_l, D_h, [dstin, 48]
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stp E_l, E_h, [dstend, -32]
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stp F_l, F_h, [dstend, -16]
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ret
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/* Align DST to 16 byte alignment so that we don't cross cache line
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boundaries on both loads and stores. There are at least 96 bytes
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to copy, so copy 16 bytes unaligned and then align. The loop
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copies 64 bytes per iteration and prefetches one iteration ahead. */
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.p2align 4
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L(copy_long):
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and tmp1, dstin, 15
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bic dst, dstin, 15
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ldp D_l, D_h, [src]
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sub src, src, tmp1
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add count, count, tmp1 /* Count is now 16 too large. */
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ldp A_l, A_h, [src, 16]
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stp D_l, D_h, [dstin]
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ldp B_l, B_h, [src, 32]
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ldp C_l, C_h, [src, 48]
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ldp D_l, D_h, [src, 64]!
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subs count, count, 128 + 16 /* Test and readjust count. */
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b.ls 2f
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1:
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stp A_l, A_h, [dst, 16]
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ldp A_l, A_h, [src, 16]
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stp B_l, B_h, [dst, 32]
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ldp B_l, B_h, [src, 32]
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stp C_l, C_h, [dst, 48]
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ldp C_l, C_h, [src, 48]
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stp D_l, D_h, [dst, 64]!
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ldp D_l, D_h, [src, 64]!
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subs count, count, 64
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b.hi 1b
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/* Write the last full set of 64 bytes. The remainder is at most 64
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bytes, so it is safe to always copy 64 bytes from the end even if
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there is just 1 byte left. */
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2:
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ldp E_l, E_h, [srcend, -64]
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stp A_l, A_h, [dst, 16]
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ldp A_l, A_h, [srcend, -48]
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stp B_l, B_h, [dst, 32]
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ldp B_l, B_h, [srcend, -32]
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stp C_l, C_h, [dst, 48]
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ldp C_l, C_h, [srcend, -16]
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stp D_l, D_h, [dst, 64]
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stp E_l, E_h, [dstend, -64]
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stp A_l, A_h, [dstend, -48]
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stp B_l, B_h, [dstend, -32]
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stp C_l, C_h, [dstend, -16]
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ret
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.p2align 4
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L(move_long):
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cbz tmp1, 3f
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add srcend, src, count
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add dstend, dstin, count
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/* Align dstend to 16 byte alignment so that we don't cross cache line
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boundaries on both loads and stores. There are at least 96 bytes
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to copy, so copy 16 bytes unaligned and then align. The loop
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copies 64 bytes per iteration and prefetches one iteration ahead. */
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and tmp1, dstend, 15
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ldp D_l, D_h, [srcend, -16]
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sub srcend, srcend, tmp1
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sub count, count, tmp1
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ldp A_l, A_h, [srcend, -16]
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stp D_l, D_h, [dstend, -16]
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ldp B_l, B_h, [srcend, -32]
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ldp C_l, C_h, [srcend, -48]
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ldp D_l, D_h, [srcend, -64]!
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sub dstend, dstend, tmp1
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subs count, count, 128
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b.ls 2f
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nop
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1:
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stp A_l, A_h, [dstend, -16]
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ldp A_l, A_h, [srcend, -16]
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stp B_l, B_h, [dstend, -32]
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ldp B_l, B_h, [srcend, -32]
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stp C_l, C_h, [dstend, -48]
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ldp C_l, C_h, [srcend, -48]
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stp D_l, D_h, [dstend, -64]!
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ldp D_l, D_h, [srcend, -64]!
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subs count, count, 64
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b.hi 1b
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/* Write the last full set of 64 bytes. The remainder is at most 64
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bytes, so it is safe to always copy 64 bytes from the start even if
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there is just 1 byte left. */
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2:
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ldp G_l, G_h, [src, 48]
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stp A_l, A_h, [dstend, -16]
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ldp A_l, A_h, [src, 32]
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stp B_l, B_h, [dstend, -32]
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ldp B_l, B_h, [src, 16]
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stp C_l, C_h, [dstend, -48]
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ldp C_l, C_h, [src]
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stp D_l, D_h, [dstend, -64]
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stp G_l, G_h, [dstin, 48]
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stp A_l, A_h, [dstin, 32]
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stp B_l, B_h, [dstin, 16]
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stp C_l, C_h, [dstin]
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3: ret
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END (memcpy)
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libc_hidden_builtin_def (memcpy)
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