/* $NetBSD: memmove.S,v 1.3 2011/01/15 07:31:12 matt Exp $ */

/* stropt/memmove.S, pl_string_common, pl_linux 10/11/04 11:45:37
 * ==========================================================================
 * Optimized memmove implementation for IBM PowerPC 405/440.
 *
 *	Copyright (c) 2003, IBM Corporation
 *	All rights reserved.		
 *					
 *	Redistribution and use in source and binary forms, with or	
 *	without modification, are permitted provided that the following 
 *	conditions are met:						
 *									
 *	* Redistributions of source code must retain the above	
 *	copyright notice, this list of conditions and the following 
 *	disclaimer.						 
 *	* Redistributions in binary form must reproduce the above	
 *	copyright notice, this list of conditions and the following 
 *	disclaimer in the documentation and/or other materials	
 *	provided with the distribution.				
 *	* Neither the name of IBM nor the names of its contributors	
 *	may be used to endorse or promote products derived from this
 *	software without specific prior written permission.	 
 *									
 *	THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND		
 *	CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,	
 *	INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF	
 *	MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE	
 *	DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS	
 *	BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, 
 *	OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,		
 *	PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR	
 *	PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY 
 *	OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT	
 *	(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE	
 *	USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *										
 * ==========================================================================
 *
 * Function: Move memory area (handles overlapping regions)
 *
 *		void *memmove(void * dest, const void * src, int n) 
 *	
 * Input:	r3 - destination address 
 *	 r4 - source address 
 *	 r5 - byte count
 * Output: r3 - destination address
 *
 * ==========================================================================
 */

#include <machine/asm.h>

        .text
        .align 4
#ifdef _BCOPY
/* bcopy = memcpy/memmove with arguments reversed. */
/* LINTSTUB: Func: void bcopy(void *, void *, size_t) */
ENTRY(bcopy)
	mr	%r6, %r3		/* swap src/dst */
	mr	%r3, %r4
	mr	%r4, %r6
#else
/* LINTSTUB: Func: void *memmove(void *, const void *, size_t) */
ENTRY(memmove)
#endif

	mr	%r8, %r3		/* Save dst (return value)	*/
	
	cmpw	%r4, %r8		/* Branch to reverse if 	*/
	blt	reverse			/* src < dest. Don't want to	*/
					/* overwrite end of src with	*/
					/* start of dest 		*/

	addi	%r4, %r4, -4		/* Back up src and dst pointers */
	addi	%r8, %r8, -4		/* due to auto-update of 'load' */ 
	
	srwi.	%r9,%r5,2			/* How many words in total cnt	*/
	beq-	last1			/* Handle byte by byte if < 4	*/
					/* bytes total 			*/
	mtctr	%r9			/* Count of words for loop		*/
	lwzu	%r7, 4(%r4)		/* Preload first word		*/
	
	b	g1

g0:					/* Main loop			*/

	lwzu	%r7, 4(%r4)		/* Load a new word		*/
	stwu	%r6, 4(%r8)		/* Store previous word		*/
	
g1:

	bdz-	last			/* Dec cnt, and branch if just	*/
					/* one word to store		*/
	lwzu	%r6, 4(%r4)		/* Load another word		*/
	stwu	%r7, 4(%r8)		/* Store previous word		*/
	bdnz+	g0			/* Dec cnt, and loop again if	*/
					/* more words			*/
	mr	%r7, %r6			/* If word count -> 0, then...	*/
	
last:

	stwu	%r7, 4(%r8)		/* ... store last word		*/

last1:					/* Byte-by-byte copy		*/

	clrlwi.	%r5,%r5,30		/* If count -> 0, then ...	*/
	beqlr				/* we're done			*/
	
	mtctr	%r5			/* else load count for loop	*/
	
	lbzu	%r6, 4(%r4)		/* 1st byte: update addr by 4	*/
	stbu	%r6, 4(%r8)		/* since we pre-adjusted by 4	*/
	bdzlr-				/* in anticipation of main loop */
	
last2:

	lbzu	%r6, 1(%r4)		/* But handle the rest by		*/
	stbu	%r6, 1(%r8)		/* updating addr by 1		*/
	bdnz+	last2
	
	blr

	/* We're here since src < dest. Don't want to overwrite end of	*/
	/* src with start of dest						*/

reverse:

	add	%r4, %r4, %r5		/* Work from end to beginning	*/
	add	%r8, %r8, %r5 		/* so add count to string ptrs	*/
	srwi.	%r9,%r5,2			/* Words in total count		*/
	beq-	rlast1			/* Handle byte by byte if < 4	*/
					/* bytes total 			*/
	
	mtctr	%r9			/* Count of words for loop 	*/
	
	lwzu	%r7, -4(%r4)		/* Preload first word		*/
	b	rg1

rg0:					/* Main loop			*/

	lwzu	%r7, -4(%r4)		/* Load a new word		*/
	stwu	%r6, -4(%r8)		/* Store previous word		*/
	
rg1:

	bdz-	rlast			/* Dec cnt, and branch if just	*/
					/* one word to store		*/

	lwzu	%r6, -4(%r4)		/* Load another word		*/
	stwu	%r7, -4(%r8)		/* Store previous word		*/
	
	bdnz+	rg0			/* Dec cnt, and loop again if	*/
					/* more words			*/

	mr	%r7, %r6			/* If word count -> 0, then...	*/
	
rlast:

	stwu	%r7, -4(%r8)		/* ... store last word		*/

rlast1:					/* Byte-by-byte copy		*/

	clrlwi.	%r5,%r5,30		/* If count -> 0, then...	*/
	beqlr				/* ... we're done 		*/
	
	mtctr	%r5			/* else load count for loop 	*/
	
rlast2:

	lbzu	%r6, -1(%r4)		/* Handle the rest, byte by 	*/
	stbu	%r6, -1(%r8)		/* byte				*/
	
	bdnz+	rlast2		 	/* Dec ctr, and branch if more	*/
					/* bytes left			*/
	blr

#ifdef _BCOPY
END(bcopy)
#else
END(memmove)
#endif