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// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "textflag.h"
// See memmove Go doc for important implementation constraints.
// func memmove(to, from unsafe.Pointer, n uintptr)
TEXT runtime·memmove(SB), NOSPLIT|NOFRAME, $0-24
MOVV to+0(FP), R4
MOVV from+8(FP), R5
MOVV n+16(FP), R6
BNE R6, check
RET
check:
SGTU R4, R5, R7
BNE R7, backward
ADDV R4, R6, R9 // end pointer
// if the two pointers are not of same alignments, do byte copying
SUBVU R5, R4, R7
AND $7, R7
BNE R7, out
// if less than 8 bytes, do byte copying
SGTU $8, R6, R7
BNE R7, out
// do one byte at a time until 8-aligned
AND $7, R4, R8
BEQ R8, words
MOVB (R5), R7
ADDV $1, R5
MOVB R7, (R4)
ADDV $1, R4
JMP -6(PC)
words:
// do 8 bytes at a time if there is room
ADDV $-7, R9, R6 // R6 is end pointer-7
SGTU R6, R4, R8
BEQ R8, out
MOVV (R5), R7
ADDV $8, R5
MOVV R7, (R4)
ADDV $8, R4
JMP -6(PC)
out:
BEQ R4, R9, done
MOVB (R5), R7
ADDV $1, R5
MOVB R7, (R4)
ADDV $1, R4
JMP -5(PC)
done:
RET
backward:
ADDV R6, R5 // from-end pointer
ADDV R4, R6, R9 // to-end pointer
// if the two pointers are not of same alignments, do byte copying
SUBVU R9, R5, R7
AND $7, R7
BNE R7, out1
// if less than 8 bytes, do byte copying
SGTU $8, R6, R7
BNE R7, out1
// do one byte at a time until 8-aligned
AND $7, R9, R8
BEQ R8, words1
ADDV $-1, R5
MOVB (R5), R7
ADDV $-1, R9
MOVB R7, (R9)
JMP -6(PC)
words1:
// do 8 bytes at a time if there is room
ADDV $7, R4, R6 // R6 is start pointer+7
SGTU R9, R6, R8
BEQ R8, out1
ADDV $-8, R5
MOVV (R5), R7
ADDV $-8, R9
MOVV R7, (R9)
JMP -6(PC)
out1:
BEQ R4, R9, done1
ADDV $-1, R5
MOVB (R5), R7
ADDV $-1, R9
MOVB R7, (R9)
JMP -5(PC)
done1:
RET
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