github.com/tidwall/go@v0.0.0-20170415222209-6694a6888b7d/src/runtime/memclr_arm.s (about)

     1  // Inferno's libkern/memset-arm.s
     2  // https://bitbucket.org/inferno-os/inferno-os/src/default/libkern/memset-arm.s
     3  //
     4  //         Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
     5  //         Revisions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com).  All rights reserved.
     6  //         Portions Copyright 2009 The Go Authors. All rights reserved.
     7  //
     8  // Permission is hereby granted, free of charge, to any person obtaining a copy
     9  // of this software and associated documentation files (the "Software"), to deal
    10  // in the Software without restriction, including without limitation the rights
    11  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    12  // copies of the Software, and to permit persons to whom the Software is
    13  // furnished to do so, subject to the following conditions:
    14  //
    15  // The above copyright notice and this permission notice shall be included in
    16  // all copies or substantial portions of the Software.
    17  //
    18  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    19  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    20  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
    21  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    22  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    23  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    24  // THE SOFTWARE.
    25  
    26  #include "textflag.h"
    27  
    28  #define TO	R8
    29  #define TOE	R11
    30  #define N	R12
    31  #define TMP	R12				/* N and TMP don't overlap */
    32  
    33  TEXT runtime·memclrNoHeapPointers(SB),NOSPLIT,$0-8
    34  	MOVW	ptr+0(FP), TO
    35  	MOVW	n+4(FP), N
    36  	MOVW	$0, R0
    37  
    38  	ADD	N, TO, TOE	/* to end pointer */
    39  
    40  	CMP	$4, N		/* need at least 4 bytes to copy */
    41  	BLT	_1tail
    42  
    43  _4align:				/* align on 4 */
    44  	AND.S	$3, TO, TMP
    45  	BEQ	_4aligned
    46  
    47  	MOVBU.P	R0, 1(TO)		/* implicit write back */
    48  	B	_4align
    49  
    50  _4aligned:
    51  	SUB	$31, TOE, TMP	/* do 32-byte chunks if possible */
    52  	CMP	TMP, TO
    53  	BHS	_4tail
    54  
    55  	MOVW	R0, R1			/* replicate */
    56  	MOVW	R0, R2
    57  	MOVW	R0, R3
    58  	MOVW	R0, R4
    59  	MOVW	R0, R5
    60  	MOVW	R0, R6
    61  	MOVW	R0, R7
    62  
    63  _f32loop:
    64  	CMP	TMP, TO
    65  	BHS	_4tail
    66  
    67  	MOVM.IA.W [R0-R7], (TO)
    68  	B	_f32loop
    69  
    70  _4tail:
    71  	SUB	$3, TOE, TMP	/* do remaining words if possible */
    72  _4loop:
    73  	CMP	TMP, TO
    74  	BHS	_1tail
    75  
    76  	MOVW.P	R0, 4(TO)		/* implicit write back */
    77  	B	_4loop
    78  
    79  _1tail:
    80  	CMP	TO, TOE
    81  	BEQ	_return
    82  
    83  	MOVBU.P	R0, 1(TO)		/* implicit write back */
    84  	B	_1tail
    85  
    86  _return:
    87  	RET