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187 lines
4.3 KiB
ArmAsm
187 lines
4.3 KiB
ArmAsm
/* Copyright (C) 2018-2023 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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<https://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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#include "memset-reg.h"
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#ifndef MEMSET
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# define MEMSET __memset_base64
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#endif
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/* To disable DC ZVA, set this threshold to 0. */
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#ifndef DC_ZVA_THRESHOLD
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# define DC_ZVA_THRESHOLD 512
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#endif
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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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ENTRY_ALIGN (MEMSET, 6)
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PTR_ARG (0)
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SIZE_ARG (2)
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bfi valw, valw, 8, 8
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bfi valw, valw, 16, 16
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bfi val, val, 32, 32
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add dstend, dstin, count
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cmp count, 96
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b.hi L(set_long)
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cmp count, 16
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b.hs L(set_medium)
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/* Set 0..15 bytes. */
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tbz count, 3, 1f
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str val, [dstin]
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str val, [dstend, -8]
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ret
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.p2align 3
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1: tbz count, 2, 2f
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str valw, [dstin]
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str valw, [dstend, -4]
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ret
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2: cbz count, 3f
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strb valw, [dstin]
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tbz count, 1, 3f
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strh valw, [dstend, -2]
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3: ret
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.p2align 3
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/* Set 16..96 bytes. */
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L(set_medium):
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stp val, val, [dstin]
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tbnz count, 6, L(set96)
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stp val, val, [dstend, -16]
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tbz count, 5, 1f
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stp val, val, [dstin, 16]
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stp val, val, [dstend, -32]
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1: ret
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.p2align 4
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/* Set 64..96 bytes. Write 64 bytes from the start and
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32 bytes from the end. */
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L(set96):
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stp val, val, [dstin, 16]
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stp val, val, [dstin, 32]
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stp val, val, [dstin, 48]
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stp val, val, [dstend, -32]
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stp val, val, [dstend, -16]
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ret
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.p2align 4
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L(set_long):
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stp val, val, [dstin]
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bic dst, dstin, 15
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#if DC_ZVA_THRESHOLD
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cmp count, DC_ZVA_THRESHOLD
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ccmp val, 0, 0, cs
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b.eq L(zva_64)
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#endif
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/* Small-size or non-zero memset does not use DC ZVA. */
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sub count, dstend, dst
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/*
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* Adjust count and bias for loop. By substracting extra 1 from count,
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* it is easy to use tbz instruction to check whether loop tailing
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* count is less than 33 bytes, so as to bypass 2 unneccesary stps.
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*/
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sub count, count, 64+16+1
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#if DC_ZVA_THRESHOLD
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/* Align loop on 16-byte boundary, this might be friendly to i-cache. */
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nop
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#endif
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1: stp val, val, [dst, 16]
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stp val, val, [dst, 32]
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stp val, val, [dst, 48]
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stp val, val, [dst, 64]!
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subs count, count, 64
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b.hs 1b
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tbz count, 5, 1f /* Remaining count is less than 33 bytes? */
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stp val, val, [dst, 16]
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stp val, val, [dst, 32]
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1: stp val, val, [dstend, -32]
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stp val, val, [dstend, -16]
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ret
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#if DC_ZVA_THRESHOLD
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.p2align 3
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L(zva_64):
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stp val, val, [dst, 16]
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stp val, val, [dst, 32]
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stp val, val, [dst, 48]
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bic dst, dst, 63
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/*
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* Previous memory writes might cross cache line boundary, and cause
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* cache line partially dirty. Zeroing this kind of cache line using
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* DC ZVA will incur extra cost, for it requires loading untouched
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* part of the line from memory before zeoring.
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*
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* So, write the first 64 byte aligned block using stp to force
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* fully dirty cache line.
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*/
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stp val, val, [dst, 64]
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stp val, val, [dst, 80]
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stp val, val, [dst, 96]
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stp val, val, [dst, 112]
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sub count, dstend, dst
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/*
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* Adjust count and bias for loop. By substracting extra 1 from count,
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* it is easy to use tbz instruction to check whether loop tailing
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* count is less than 33 bytes, so as to bypass 2 unneccesary stps.
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*/
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sub count, count, 128+64+64+1
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add dst, dst, 128
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nop
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/* DC ZVA sets 64 bytes each time. */
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1: dc zva, dst
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add dst, dst, 64
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subs count, count, 64
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b.hs 1b
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/*
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* Write the last 64 byte aligned block using stp to force fully
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* dirty cache line.
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*/
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stp val, val, [dst, 0]
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stp val, val, [dst, 16]
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stp val, val, [dst, 32]
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stp val, val, [dst, 48]
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tbz count, 5, 1f /* Remaining count is less than 33 bytes? */
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stp val, val, [dst, 64]
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stp val, val, [dst, 80]
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1: stp val, val, [dstend, -32]
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stp val, val, [dstend, -16]
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ret
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#endif
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END (MEMSET)
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libc_hidden_builtin_def (MEMSET)
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