github.com/primecitizens/pcz/std@v0.2.1/core/mem/clear_arm.s (about)

     1  // SPDX-License-Identifier: Apache-2.0
     2  // Copyright 2023 The Prime Citizens
     3  //
     4  // Inferno's libkern/memset-arm.s
     5  // https://bitbucket.org/inferno-os/inferno-os/src/master/libkern/memset-arm.s
     6  //
     7  //         Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
     8  //         Revisions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com).  All rights reserved.
     9  //         Portions Copyright 2009 The Go Authors. All rights reserved.
    10  //
    11  // Permission is hereby granted, free of charge, to any person obtaining a copy
    12  // of this software and associated documentation files (the "Software"), to deal
    13  // in the Software without restriction, including without limitation the rights
    14  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    15  // copies of the Software, and to permit persons to whom the Software is
    16  // furnished to do so, subject to the following conditions:
    17  //
    18  // The above copyright notice and this permission notice shall be included in
    19  // all copies or substantial portions of the Software.
    20  //
    21  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    22  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    23  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
    24  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    25  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    26  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    27  // THE SOFTWARE.
    28  
    29  //go:build pcz && arm
    30  
    31  #include "textflag.h"
    32  
    33  #define TO R8
    34  #define TOE R11
    35  #define N R12
    36  #define TMP R12 /* N and TMP don't overlap */
    37  
    38  // See memclrNoHeapPointers Go doc for important implementation constraints.
    39  
    40  // func Clear(ptr unsafe.Pointer, n uintptr)
    41  // Also called from assembly in sys_windows_arm.s without g (but using Go stack convention).
    42  TEXT ·Clear(SB),NOSPLIT,$0-8
    43  	MOVW ptr+0(FP), TO
    44  	MOVW n+4(FP), N
    45  	MOVW $0, R0
    46  
    47  	ADD N, TO, TOE /* to end pointer */
    48  
    49  	CMP $4, N /* need at least 4 bytes to copy */
    50  	BLT _1tail
    51  
    52  _4align:				/* align on 4 */
    53  	AND.S $3, TO, TMP
    54  	BEQ _4aligned
    55  
    56  	MOVBU.P R0, 1(TO)		/* implicit write back */
    57  	B _4align
    58  
    59  _4aligned:
    60  	SUB $31, TOE, TMP /* do 32-byte chunks if possible */
    61  	CMP TMP, TO
    62  	BHS _4tail
    63  
    64  	MOVW R0, R1 /* replicate */
    65  	MOVW R0, R2
    66  	MOVW R0, R3
    67  	MOVW R0, R4
    68  	MOVW R0, R5
    69  	MOVW R0, R6
    70  	MOVW R0, R7
    71  
    72  _f32loop:
    73  	CMP TMP, TO
    74  	BHS _4tail
    75  
    76  	MOVM.IA.W [R0-R7], (TO)
    77  	B _f32loop
    78  
    79  _4tail:
    80  	SUB $3, TOE, TMP /* do remaining words if possible */
    81  _4loop:
    82  	CMP TMP, TO
    83  	BHS _1tail
    84  
    85  	MOVW.P R0, 4(TO)		/* implicit write back */
    86  	B _4loop
    87  
    88  _1tail:
    89  	CMP TO, TOE
    90  	BEQ _return
    91  
    92  	MOVBU.P R0, 1(TO)		/* implicit write back */
    93  	B _1tail
    94  
    95  _return:
    96  	RET