memmove_riscv64.s

     1  // Copyright 2016 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  // void runtime·memmove(void*, void*, uintptr)
    10  TEXT runtime·memmove<ABIInternal>(SB),NOSPLIT,$-0-24
    11  #ifndef GOEXPERIMENT_regabiargs
    12  	MOV	to+0(FP), A0
    13  	MOV	from+8(FP), A1
    14  	MOV	n+16(FP), A2
    15  #endif
    16  	ADD	A1, A2, T5
    17  
    18  	// If the destination is ahead of the source, start at the end of the
    19  	// buffer and go backward.
    20  	BLTU	A1, A0, b
    21  
    22  	// If less than eight bytes, do one byte at a time.
    23  	SLTU	$8, A2, T3
    24  	BNE	T3, ZERO, f_outcheck
    25  
    26  	// Do one byte at a time until from is eight-aligned.
    27  	JMP	f_aligncheck
    28  f_align:
    29  	MOVB	(A1), T3
    30  	MOVB	T3, (A0)
    31  	ADD	$1, A0
    32  	ADD	$1, A1
    33  f_aligncheck:
    34  	AND	$7, A1, T3
    35  	BNE	T3, ZERO, f_align
    36  
    37  	// Do eight bytes at a time as long as there is room.
    38  	ADD	$-7, T5, T6
    39  	JMP	f_wordscheck
    40  f_words:
    41  	MOV	(A1), T3
    42  	MOV	T3, (A0)
    43  	ADD	$8, A0
    44  	ADD	$8, A1
    45  f_wordscheck:
    46  	SLTU	T6, A1, T3
    47  	BNE	T3, ZERO, f_words
    48  
    49  	// Finish off the remaining partial word.
    50  	JMP 	f_outcheck
    51  f_out:
    52  	MOVB	(A1), T3
    53  	MOVB	T3, (A0)
    54  	ADD	$1, A0
    55  	ADD	$1, A1
    56  f_outcheck:
    57  	BNE	A1, T5, f_out
    58  
    59  	RET
    60  
    61  b:
    62  	ADD	A0, A2, T4
    63  	// If less than eight bytes, do one byte at a time.
    64  	SLTU	$8, A2, T3
    65  	BNE	T3, ZERO, b_outcheck
    66  
    67  	// Do one byte at a time until from+n is eight-aligned.
    68  	JMP	b_aligncheck
    69  b_align:
    70  	ADD	$-1, T4
    71  	ADD	$-1, T5
    72  	MOVB	(T5), T3
    73  	MOVB	T3, (T4)
    74  b_aligncheck:
    75  	AND	$7, T5, T3
    76  	BNE	T3, ZERO, b_align
    77  
    78  	// Do eight bytes at a time as long as there is room.
    79  	ADD	$7, A1, T6
    80  	JMP	b_wordscheck
    81  b_words:
    82  	ADD	$-8, T4
    83  	ADD	$-8, T5
    84  	MOV	(T5), T3
    85  	MOV	T3, (T4)
    86  b_wordscheck:
    87  	SLTU	T5, T6, T3
    88  	BNE	T3, ZERO, b_words
    89  
    90  	// Finish off the remaining partial word.
    91  	JMP	b_outcheck
    92  b_out:
    93  	ADD	$-1, T4
    94  	ADD	$-1, T5
    95  	MOVB	(T5), T3
    96  	MOVB	T3, (T4)
    97  b_outcheck:
    98  	BNE	T5, A1, b_out
    99  
   100  	RET
   101
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