github.com/mtsmfm/go/src@v0.0.0-20221020090648-44bdcb9f8fde/runtime/memmove_loong64.s (about)

     1  // Copyright 2022 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  #include "textflag.h"
     6  
     7  // See memmove Go doc for important implementation constraints.
     8  
     9  // func memmove(to, from unsafe.Pointer, n uintptr)
    10  TEXT runtime·memmove(SB), NOSPLIT|NOFRAME, $0-24
    11  	MOVV	to+0(FP), R4
    12  	MOVV	from+8(FP), R5
    13  	MOVV	n+16(FP), R6
    14  	BNE	R6, check
    15  	RET
    16  
    17  check:
    18  	SGTU	R4, R5, R7
    19  	BNE	R7, backward
    20  
    21  	ADDV	R4, R6, R9 // end pointer
    22  
    23  	// if the two pointers are not of same alignments, do byte copying
    24  	SUBVU	R5, R4, R7
    25  	AND	$7, R7
    26  	BNE	R7, out
    27  
    28  	// if less than 8 bytes, do byte copying
    29  	SGTU	$8, R6, R7
    30  	BNE	R7, out
    31  
    32  	// do one byte at a time until 8-aligned
    33  	AND	$7, R4, R8
    34  	BEQ	R8, words
    35  	MOVB	(R5), R7
    36  	ADDV	$1, R5
    37  	MOVB	R7, (R4)
    38  	ADDV	$1, R4
    39  	JMP	-6(PC)
    40  
    41  words:
    42  	// do 8 bytes at a time if there is room
    43  	ADDV	$-7, R9, R6 // R6 is end pointer-7
    44  
    45  	SGTU	R6, R4, R8
    46  	BEQ	R8, out
    47  	MOVV	(R5), R7
    48  	ADDV	$8, R5
    49  	MOVV	R7, (R4)
    50  	ADDV	$8, R4
    51  	JMP	-6(PC)
    52  
    53  out:
    54  	BEQ	R4, R9, done
    55  	MOVB	(R5), R7
    56  	ADDV	$1, R5
    57  	MOVB	R7, (R4)
    58  	ADDV	$1, R4
    59  	JMP	-5(PC)
    60  done:
    61  	RET
    62  
    63  backward:
    64  	ADDV	R6, R5 // from-end pointer
    65  	ADDV	R4, R6, R9 // to-end pointer
    66  
    67  	// if the two pointers are not of same alignments, do byte copying
    68  	SUBVU	R9, R5, R7
    69  	AND	$7, R7
    70  	BNE	R7, out1
    71  
    72  	// if less than 8 bytes, do byte copying
    73  	SGTU	$8, R6, R7
    74  	BNE	R7, out1
    75  
    76  	// do one byte at a time until 8-aligned
    77  	AND	$7, R9, R8
    78  	BEQ	R8, words1
    79  	ADDV	$-1, R5
    80  	MOVB	(R5), R7
    81  	ADDV	$-1, R9
    82  	MOVB	R7, (R9)
    83  	JMP	-6(PC)
    84  
    85  words1:
    86  	// do 8 bytes at a time if there is room
    87  	ADDV	$7, R4, R6 // R6 is start pointer+7
    88  
    89  	SGTU	R9, R6, R8
    90  	BEQ	R8, out1
    91  	ADDV	$-8, R5
    92  	MOVV	(R5), R7
    93  	ADDV	$-8, R9
    94  	MOVV	R7, (R9)
    95  	JMP	-6(PC)
    96  
    97  out1:
    98  	BEQ	R4, R9, done1
    99  	ADDV	$-1, R5
   100  	MOVB	(R5), R7
   101  	ADDV	$-1, R9
   102  	MOVB	R7, (R9)
   103  	JMP	-5(PC)
   104  done1:
   105  	RET