// Inferno's libkern/memmove-386.s
// http://code.google.com/p/inferno-os/source/browse/libkern/memmove-386.s
//
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TEXT runtime·memmove(SB), 7, $0
	MOVL	to+0(FP), DI
	MOVL	fr+4(FP), SI
	MOVL	n+8(FP), BX
	CMPL	BX, $0
	JLT	fault

/*
 * 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
	MOVL	BX, CX
	REP;	MOVSB

	MOVL	to+0(FP),AX
	RET
/*
 * 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

	ADDL	$3, DI
	ADDL	$3, SI
	MOVL	BX, CX
	REP;	MOVSB

	CLD
	MOVL	to+0(FP),AX
	RET

/*
 * if called with negative count,
 * treat as error rather than
 * rotating all of memory
 */
fault:
	MOVL	$0,SI
	MOVL	0(SI), AX
	RET