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0aec4c1d18
Vector registers perform better than scalar register pairs for copying data so prefer them instead. This results in a time reduction of over 50% (i.e. 2x speed improvemnet) for some smaller sizes for memcpy-walk. Larger sizes show improvements of around 1% to 2%. memcpy-random shows a very small improvement, in the range of 1-2%. * sysdeps/aarch64/multiarch/memcpy_falkor.S (__memcpy_falkor): Use vector registers.
192 lines
4.5 KiB
ArmAsm
192 lines
4.5 KiB
ArmAsm
/* Optimized memcpy for Qualcomm Falkor processor.
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Copyright (C) 2017-2018 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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ARMv8-a, AArch64, falkor, unaligned accesses. */
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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 tmp1 x14
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#define A_x x6
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#define B_x x7
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#define A_w w6
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#define B_w w7
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#define A_q q0
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#define B_q q1
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#define C_q q2
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#define D_q q3
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#define E_q q4
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#define F_q q5
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#define G_q q6
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/* Copies are split into 3 main cases:
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1. Small copies of up to 32 bytes
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2. Medium copies of 33..128 bytes which are fully unrolled
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3. Large copies of more than 128 bytes.
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Large copies align the sourceto a quad word and use an unrolled loop
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processing 64 bytes per iteration.
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FALKOR-SPECIFIC DESIGN:
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The smallest copies (32 bytes or less) focus on optimal pipeline usage,
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which is why the redundant copies of 0-3 bytes have been replaced with
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conditionals, since the former would unnecessarily break across multiple
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issue groups. The medium copy group has been enlarged to 128 bytes since
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bumping up the small copies up to 32 bytes allows us to do that without
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cost and also allows us to reduce the size of the prep code before loop64.
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The copy loop uses only one register q0. This is to ensure that all loads
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hit a single hardware prefetcher which can get correctly trained to prefetch
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a single stream.
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The non-temporal stores help optimize cache utilization. */
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#if IS_IN (libc)
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ENTRY_ALIGN (__memcpy_falkor, 6)
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cmp count, 32
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add srcend, src, count
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add dstend, dstin, count
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b.ls L(copy32)
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ldr A_q, [src]
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cmp count, 128
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str A_q, [dstin]
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b.hi L(copy_long)
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/* Medium copies: 33..128 bytes. */
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sub tmp1, count, 1
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ldr A_q, [src, 16]
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ldr B_q, [srcend, -32]
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ldr C_q, [srcend, -16]
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tbz tmp1, 6, 1f
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ldr D_q, [src, 32]
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ldr E_q, [src, 48]
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str D_q, [dstin, 32]
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str E_q, [dstin, 48]
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ldr F_q, [srcend, -64]
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ldr G_q, [srcend, -48]
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str F_q, [dstend, -64]
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str G_q, [dstend, -48]
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1:
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str A_q, [dstin, 16]
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str B_q, [dstend, -32]
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str C_q, [dstend, -16]
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ret
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.p2align 4
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/* Small copies: 0..32 bytes. */
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L(copy32):
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/* 16-32 */
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cmp count, 16
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b.lo 1f
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ldr A_q, [src]
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ldr B_q, [srcend, -16]
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str A_q, [dstin]
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str B_q, [dstend, -16]
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ret
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.p2align 4
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1:
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/* 8-15 */
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tbz count, 3, 1f
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ldr A_x, [src]
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ldr B_x, [srcend, -8]
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str A_x, [dstin]
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str B_x, [dstend, -8]
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ret
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.p2align 4
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1:
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/* 4-7 */
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tbz count, 2, 1f
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ldr A_w, [src]
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ldr B_w, [srcend, -4]
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str A_w, [dstin]
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str B_w, [dstend, -4]
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ret
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.p2align 4
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1:
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/* 2-3 */
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tbz count, 1, 1f
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ldrh A_w, [src]
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ldrh B_w, [srcend, -2]
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strh A_w, [dstin]
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strh B_w, [dstend, -2]
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ret
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.p2align 4
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1:
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/* 0-1 */
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tbz count, 0, 1f
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ldrb A_w, [src]
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strb A_w, [dstin]
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1:
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ret
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/* Align SRC to 16 bytes and copy; that way at least one of the
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accesses is aligned throughout the copy sequence.
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The count is off by 0 to 15 bytes, but this is OK because we trim
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off the last 64 bytes to copy off from the end. Due to this the
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loop never runs out of bounds. */
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.p2align 6
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L(copy_long):
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sub count, count, 64 + 16
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and tmp1, src, 15
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bic src, src, 15
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sub dst, dstin, tmp1
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add count, count, tmp1
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L(loop64):
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ldr A_q, [src, 16]!
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str A_q, [dst, 16]
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ldr A_q, [src, 16]!
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subs count, count, 64
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str A_q, [dst, 32]
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ldr A_q, [src, 16]!
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str A_q, [dst, 48]
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ldr A_q, [src, 16]!
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str A_q, [dst, 64]!
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b.hi L(loop64)
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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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L(last64):
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ldr E_q, [srcend, -64]
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str E_q, [dstend, -64]
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ldr D_q, [srcend, -48]
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str D_q, [dstend, -48]
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ldr C_q, [srcend, -32]
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str C_q, [dstend, -32]
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ldr B_q, [srcend, -16]
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str B_q, [dstend, -16]
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ret
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END (__memcpy_falkor)
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libc_hidden_builtin_def (__memcpy_falkor)
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#endif
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