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/* $NetBSD: memset.S,v 1.1 2014/08/10 05:47:35 matt Exp $ */
/*-
* Copyright (c) 2014 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Matt Thomas of 3am Software Foundry.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <machine/asm.h>
ENTRY(memset)
cbz x2, .Lret
mov x15, x0 /* working data pointer */
cbz x1, .Lzerofill
cbz x1, .Lfilled
/*
* Non zero fill, replicate to all 64 bits of x1.
*/
and x1, x1, #0xff
orr x1, x1, x1, lsl #8
orr x1, x1, x1, lsl #16
orr x1, x1, x1, lsl #32
.Lfilled:
cmp x2, #15 /* if it's small, ignore alignment */
b.ls .Llast_subqword
mov x6, x1
tst x15, #15
b.eq .Lqword_loop
/*
* We have at least 15 to copy which means we can get qword alignment
* without having to check the amount left.
*/
tbz x15, #0, .Lhword_aligned
strb w1, [x15], #1
.Lhword_aligned:
tbz x15, #1, .Lword_aligned
strh w1, [x15], #2
.Lword_aligned:
tbz x15, #2, .Ldword_aligned
str w1, [x15], #4
.Ldword_aligned:
tbz x15, #3, .Lqword_aligned
str x1, [x15], #8
/*
* Now we qword aligned. Figure how much we have to write to get here.
* Then subtract from the length. If we get 0, we're done.
*/
.Lqword_aligned:
sub x5, x15, x0
subs x2, x2, x5
b.eq .Lret
/*
* Write 16 bytes at time. If we don't have 16 bytes to write, bail.
* Keep looping if there's data to set.
*/
.Lqword_loop:
subs x2, x2, #16
b.mi .Llast_subqword
stp x1, x6, [x15], #16
b.ne .Lqword_loop
ret
/*
* We have less than a qword to write. We hope we are aligned but since
* unaligned access works, we don't have to be aligned.
*/
.Llast_subqword:
tbz x2, #3, .Llast_subdword
str x1, [x15], #8
.Llast_subdword:
tbz x2, #2, .Llast_subword
str w1, [x15], #4
.Llast_subword:
tbz x2, #1, .Llast_subhword
strh w1, [x15], #2
.Llast_subhword:
tbz x2, #0, .Lret
strb w1, [x15]
.Lret: ret
/*
* If we are filling with zeros then let's see if we can use the
* dc zva, <Xt>
* instruction to speed things up.
*/
.Lzerofill:
mrs x9, dczid_el0
/*
* Make sure we can the instruction isn't prohibited.
*/
tbnz x9, #4, .Lfilled
/*
* Now find out the block size.
*/
ubfx x9, x9, #0, #4 /* extract low 4 bits */
add x9, x9, #2 /* add log2(word) */
mov x10, #1 /* the value is log2(words) */
lsl x10, x10, x9 /* shift to get the block size */
cmp x2, x10 /* are we even copying a block? */
b.lt .Lfilled /* no, do it 16 bytes at a time */
/*
* Now we figure out how many aligned blocks we have
*/
sub x11, x10, #1 /* make block size a mask */
add x12, x15, x11 /* round start to a block boundary */
asr x12, x12, x9 /* "starting" block number */
add x13, x15, x2 /* get ending address */
asr x13, x13, x9 /* "ending" block numebr */
cmp x13, x12 /* how many blocks? */
b.eq .Lfilled /* none, do it 16 bytes at a time */
/*
* Now we have one or more blocks to deal with. First now we need
* to get block aligned.
*/
and x7, x15, x11 /* are already aligned on a block boundary? */
cbz x7, .Lblock_aligned
sub x7, x10, x7 /* subtract offset from block length */
sub x2, x2, x7 /* subtract that from length */
asr x7, x7, #2 /* qword -> word */
tbz x15, #0, .Lzero_hword_aligned
strb wzr, [x15], #1
.Lzero_hword_aligned:
tbz x15, #1, .Lzero_word_aligned
strh wzr, [x15], #2
.Lzero_word_aligned:
tbz x15, #2, .Lzero_dword_aligned
str wzr, [x15], #4
.Lzero_dword_aligned:
tbz x15, #3, .Lzero_qword_aligned
str xzr, [x15], #8
.Lzero_qword_aligned:
cbz x7, .Lblock_aligned /* no qwords? just branch */
adr x6, .Lblock_aligned
sub x6, x6, x7 /* backup to write the last N qwords */
br x6 /* and do it */
/*
* This is valid for cache lines <= 256 bytes.
*/
stp xzr, xzr, [x15], #16
stp xzr, xzr, [x15], #16
stp xzr, xzr, [x15], #16
stp xzr, xzr, [x15], #16
stp xzr, xzr, [x15], #16
stp xzr, xzr, [x15], #16
stp xzr, xzr, [x15], #16
stp xzr, xzr, [x15], #16
stp xzr, xzr, [x15], #16
stp xzr, xzr, [x15], #16
stp xzr, xzr, [x15], #16
stp xzr, xzr, [x15], #16
stp xzr, xzr, [x15], #16
stp xzr, xzr, [x15], #16
stp xzr, xzr, [x15], #16
/*
* Now we are block aligned.
*/
.Lblock_aligned:
subs x2, x2, x10
b.mi .Lblock_done
dc zva, x15
add x15, x15, x10
b.ne .Lblock_aligned
ret
.Lblock_done:
and x2, x2, x12 /* make positive again */
mov x6, xzr /* fill 2nd xword */
b .Lqword_loop /* and finish filling */
END(memset)
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