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// Inferno's libkern/memset-arm.s
// http://code.google.com/p/inferno-os/source/browse/libkern/memset-arm.s
//
// Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
// Revisions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com). All rights reserved.
// Portions Copyright 2009 The Go Authors. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
TO = 1
TOE = 2
N = 3
TMP = 3 /* N and TMP don't overlap */
// TODO(kaib): memset clobbers R9 and R10 (m and g). This makes the
// registers unpredictable if (when) memset SIGSEGV's. Fix it by
// moving the R4-R11 register bank.
TEXT runtime·memset(SB), $0
MOVW R0, R(TO)
MOVW data+4(FP), R(4)
MOVW n+8(FP), R(N)
ADD R(N), R(TO), R(TOE) /* to end pointer */
CMP $4, R(N) /* need at least 4 bytes to copy */
BLT _1tail
AND $0xFF, R(4) /* it's a byte */
SLL $8, R(4), R(TMP) /* replicate to a word */
ORR R(TMP), R(4)
SLL $16, R(4), R(TMP)
ORR R(TMP), R(4)
_4align: /* align on 4 */
AND.S $3, R(TO), R(TMP)
BEQ _4aligned
MOVBU.P R(4), 1(R(TO)) /* implicit write back */
B _4align
_4aligned:
SUB $31, R(TOE), R(TMP) /* do 32-byte chunks if possible */
CMP R(TMP), R(TO)
BHS _4tail
MOVW R4, R5 /* replicate */
MOVW R4, R6
MOVW R4, R7
MOVW R4, R8
MOVW R4, R9
MOVW R4, R10
MOVW R4, R11
_f32loop:
CMP R(TMP), R(TO)
BHS _4tail
MOVM.IA.W [R4-R11], (R(TO))
B _f32loop
_4tail:
SUB $3, R(TOE), R(TMP) /* do remaining words if possible */
_4loop:
CMP R(TMP), R(TO)
BHS _1tail
MOVW.P R(4), 4(R(TO)) /* implicit write back */
B _4loop
_1tail:
CMP R(TO), R(TOE)
BEQ _return
MOVBU.P R(4), 1(R(TO)) /* implicit write back */
B _1tail
_return:
RET