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WebSVN – planix.SVN – Blame – /os/branches/feature_unix/sys/src/libc/386/memmove.s – Rev 2

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2 - 1 
TEXT memmove(SB), $0
2 
	MOVL	p1+0(FP), DI
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	MOVL	DI, AX			/* return value */
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	MOVL	p2+4(FP), SI
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	MOVL	n+8(FP), BX
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	CMPL	BX, $0
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	JGT	_ok
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	JEQ	_return			/* nothing to do if n == 0 */
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	MOVL	$0, SI			/* fault if n < 0 */
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/*
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 * check and set for backwards:
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 *	(p2 < p1) && ((p2+n) > p1)
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 */
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_ok:
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	CMPL	SI, DI
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	JGT	_forward
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	JEQ	_return			/* nothing to do if p2 == p1 */
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	MOVL	SI, DX
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	ADDL	BX, DX
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	CMPL	DX, DI
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	JGT	_back
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/*
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 * copy whole longs
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 */
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_forward:
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	MOVL	BX, CX
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	CLD
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	SHRL	$2, CX
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	ANDL	$3, BX
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	REP;	MOVSL
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/*
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 * copy the rest, by bytes
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 */
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	JEQ	_return			/* flags set by above ANDL */
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	MOVL	BX, CX
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	REP;	MOVSB
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	RET
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/*
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 * whole thing backwards has
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 * adjusted addresses
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 */
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_back:
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	ADDL	BX, DI
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	ADDL	BX, SI
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	STD
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	SUBL	$4, DI
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	SUBL	$4, SI
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/*
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 * copy whole longs
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 */
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	MOVL	BX, CX
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	SHRL	$2, CX
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	ANDL	$3, BX
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	REP;	MOVSL
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/*
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 * copy the rest, by bytes
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 */
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	JEQ	_return			/* flags set by above ANDL */
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	ADDL	$3, DI
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	ADDL	$3, SI
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	MOVL	BX, CX
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	REP;	MOVSB
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_return:
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	RET