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memcpy.S revision 1.2 
      1 /* $NetBSD: memcpy.S,v 1.2 2008/03/06 21:17:17 phx Exp $ */
      2 
      3 /* stropt/memcpy_440.S, pl_string_common, pl_linux 10/11/04 11:45:36
      4  * ==========================================================================
      5  * Optimized memcpy implementation for IBM PowerPC 440.
      6  *
      7  *  Copyright (c) 2003, IBM Corporation
      8  *  All rights reserved.
      9  *
     10  *  Redistribution and use in source and binary forms, with or
     11  *  without modification, are permitted provided that the following
     12  *  conditions are met:
     13  *
     14  *    * Redistributions of source code must retain the above
     15  *      copyright notice, this list of conditions and the following
     16  *      disclaimer.
     17  *    * Redistributions in binary form must reproduce the above
     18  *      copyright notice, this list of conditions and the following
     19  *      disclaimer in the documentation and/or other materials
     20  *      provided with the distribution.
     21  *    * Neither the name of IBM nor the names of its contributors
     22  *      may be used to endorse or promote products derived from this
     23  *      software without specific prior written permission.
     24  *
     25  *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
     26  *  CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
     27  *  INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     28  *  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     29  *  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
     30  *  BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
     31  *  OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     32  *  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
     33  *  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
     34  *  OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     35  *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
     36  *  USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     37  *
     38  * ==========================================================================
     39  *
     40  * Function: Copy n bytes of the source to the destination. Behavior is
     41  *	   undefined for objects that overlap.
     42  *
     43  *
     44  *	   void *memcpy(void * dest, const void * src, int n)
     45  *
     46  * Input:  r3 - destination address
     47  *	 r4 - source address
     48  *	 r5 - byte count
     49  * Output: r3 - destination address
     50  *
     51  * ==========================================================================
     52  */
     53 
     54 #define _NOREGNAMES
     55 #include <machine/asm.h>
     56 
     57 	.text
     58 	.align 4
     59 /* LINTSTUB: Func: void *memcpy(void *, const void *, size_t) */
     60 ENTRY(memcpy)
     61 	/*
     62 	 * Check count passed in R5. If zero, return; otherwise continue.
     63 	 */
     64 	cmpwi	%r5,0
     65 	beqlr-
     66 
     67 	mr	%r8, %r3		/* Copy dst (return value)	*/
     68 
     69 	addi	%r4, %r4, -4		/* Prepare for main loop's auto	*/
     70 	addi	%r8, %r8, -4		/* update		       */
     71 
     72 	srwi.	%r9,%r5,2		/* Word count -> r9 		*/
     73 	beq-	last1			/* Partial copy if <4 bytes	*/
     74 
     75 	mtctr	%r9			/* Word cnt in CTR for loop     */
     76 	lwzu	%r7, 4(%r4)		/* Preload for main loop	*/
     77 
     78 	b	g1
     79 
     80 g0:					/* Main loop			*/
     81 
     82 	lwzu	%r7, 4(%r4)		/* Load a new word		*/
     83 	stwu	%r6, 4(%r8)		/* Store previous word		*/
     84 
     85 g1:
     86 
     87 	bdz-	last			/* Dec ctr and exit loop if no  */
     88 					/* more words		   */
     89 	lwzu	%r6, 4(%r4)		/* Load another word		*/
     90 	stwu	%r7, 4(%r8)		/* Store previous word		*/
     91 	bdnz+	g0			/* Dec ctr and continue loop if */
     92 					/* more words		   */
     93 
     94 	mr	%r7, %r6
     95 
     96 last:
     97 
     98 	stwu	%r7, 4(%r8)		/* Store last word		*/
     99 
    100 last1:					/* Byte-by-byte copy		*/
    101 
    102 	clrlwi.	%r5,%r5,30
    103 	beqlr
    104 
    105 	mtctr	%r5
    106 
    107 	lbzu	%r6, 4(%r4)		/* 1st byte: update by word	*/
    108 	stbu	%r6, 4(%r8)
    109 	bdzlr-
    110 
    111 last2:
    112 
    113 	lbzu	%r6, 1(%r4)		/* Handle the rest		*/
    114 	stbu	%r6, 1(%r8)
    115 	bdnz+	last2
    116 
    117 	blr
    118 
    119