// Inferno's libkern/memmove-386.s
// http://code.google.com/p/inferno-os/source/browse/libkern/memmove-386.s
//
// Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
// Revisions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com). All rights reserved.
// Portions Copyright 2009 The Go Authors. All rights reserved.
//
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// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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#include "../../cmd/ld/textflag.h"
TEXT runtime·memmove(SB), NOSPLIT, $0-12
MOVL to+0(FP), DI
MOVL fr+4(FP), SI
MOVL n+8(FP), BX
// REP instructions have a high startup cost, so we handle small sizes
// with some straightline code. The REP MOVSL instruction is really fast
// for large sizes. The cutover is approximately 1K.
tail:
TESTL BX, BX
JEQ move_0
CMPL BX, $2
JBE move_1or2
CMPL BX, $4
JBE move_3or4
CMPL BX, $8
JBE move_5through8
CMPL BX, $16
JBE move_9through16
/*
* check and set for backwards
*/
CMPL SI, DI
JLS back
/*
* forward copy loop
*/
forward:
MOVL BX, CX
SHRL $2, CX
ANDL $3, BX
REP; MOVSL
JMP tail
/*
* check overlap
*/
back:
MOVL SI, CX
ADDL BX, CX
CMPL CX, DI
JLS forward
/*
* whole thing backwards has
* adjusted addresses
*/
ADDL BX, DI
ADDL BX, SI
STD
/*
* copy
*/
MOVL BX, CX
SHRL $2, CX
ANDL $3, BX
SUBL $4, DI
SUBL $4, SI
REP; MOVSL
CLD
ADDL $4, DI
ADDL $4, SI
SUBL BX, DI
SUBL BX, SI
JMP tail
move_1or2:
MOVB (SI), AX
MOVB -1(SI)(BX*1), CX
MOVB AX, (DI)
MOVB CX, -1(DI)(BX*1)
move_0:
RET
move_3or4:
MOVW (SI), AX
MOVW -2(SI)(BX*1), CX
MOVW AX, (DI)
MOVW CX, -2(DI)(BX*1)
RET
move_5through8:
MOVL (SI), AX
MOVL -4(SI)(BX*1), CX
MOVL AX, (DI)
MOVL CX, -4(DI)(BX*1)
RET
move_9through16:
MOVL (SI), AX
MOVL 4(SI), CX
MOVL -8(SI)(BX*1), DX
MOVL -4(SI)(BX*1), BP
MOVL AX, (DI)
MOVL CX, 4(DI)
MOVL DX, -8(DI)(BX*1)
MOVL BP, -4(DI)(BX*1)
RET