github.com/twelsh-aw/go/src@v0.0.0-20230516233729-a56fe86a7c81/runtime/memclr_arm.s (about)

     1  // Inferno's libkern/memset-arm.s
     2  // https://bitbucket.org/inferno-os/inferno-os/src/master/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  // See memclrNoHeapPointers Go doc for important implementation constraints.
    34  
    35  // func memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr)
    36  // Also called from assembly in sys_windows_arm.s without g (but using Go stack convention).
    37  TEXT runtime·memclrNoHeapPointers(SB),NOSPLIT,$0-8
    38  	MOVW	ptr+0(FP), TO
    39  	MOVW	n+4(FP), N
    40  	MOVW	$0, R0
    41  
    42  	ADD	N, TO, TOE	/* to end pointer */
    43  
    44  	CMP	$4, N		/* need at least 4 bytes to copy */
    45  	BLT	_1tail
    46  
    47  _4align:				/* align on 4 */
    48  	AND.S	$3, TO, TMP
    49  	BEQ	_4aligned
    50  
    51  	MOVBU.P	R0, 1(TO)		/* implicit write back */
    52  	B	_4align
    53  
    54  _4aligned:
    55  	SUB	$31, TOE, TMP	/* do 32-byte chunks if possible */
    56  	CMP	TMP, TO
    57  	BHS	_4tail
    58  
    59  	MOVW	R0, R1			/* replicate */
    60  	MOVW	R0, R2
    61  	MOVW	R0, R3
    62  	MOVW	R0, R4
    63  	MOVW	R0, R5
    64  	MOVW	R0, R6
    65  	MOVW	R0, R7
    66  
    67  _f32loop:
    68  	CMP	TMP, TO
    69  	BHS	_4tail
    70  
    71  	MOVM.IA.W [R0-R7], (TO)
    72  	B	_f32loop
    73  
    74  _4tail:
    75  	SUB	$3, TOE, TMP	/* do remaining words if possible */
    76  _4loop:
    77  	CMP	TMP, TO
    78  	BHS	_1tail
    79  
    80  	MOVW.P	R0, 4(TO)		/* implicit write back */
    81  	B	_4loop
    82  
    83  _1tail:
    84  	CMP	TO, TOE
    85  	BEQ	_return
    86  
    87  	MOVBU.P	R0, 1(TO)		/* implicit write back */
    88  	B	_1tail
    89  
    90  _return:
    91  	RET