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memset.S revision 1.3.4.3 
      1 /*	$NetBSD: memset.S,v 1.3.4.3 2004/09/18 14:54:01 skrll Exp $ */
      2 
      3 /*-
      4  * Copyright (C) 2003	Matt Thomas <matt (at) 3am-software.com>
      5  * Copyright (C) 2001	Martin J. Laubach <mjl (at) NetBSD.org>
      6  * All rights reserved.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. The name of the author may not be used to endorse or promote products
     17  *    derived from this software without specific prior written permission.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     21  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     22  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     24  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  */
     30 /*----------------------------------------------------------------------*/
     31 
     32 #define _NOREGNAMES
     33 #include <machine/asm.h>
     34 
     35 /*----------------------------------------------------------------------*/
     36 /*
     37      void bzero(void *b r3, size_t len r4);
     38      void * memset(void *b r3, int c r4, size_t len r5);
     39 */
     40 /*----------------------------------------------------------------------*/
     41 
     42 #define r_dst	%r4
     43 #define r_len	%r5
     44 #define r_tmp	%r6
     45 #define r_val	%r0
     46 
     47 ENTRY(bzero)
     48 		li	r_val, 0		/* Value to fill with */
     49 		mr	r_len, %r4
     50 		b	cb_memset
     51 
     52 ENTRY(memset)
     53 		mr	r_val, %r4		/* Value to fill with */
     54 
     55 cb_memset:
     56 		cmplwi	r_len, 0		/* is the length 0? */
     57 		beqlr-				/*    nothing to do */
     58 		mr	r_dst, %r3
     59 		/*
     60 		 * r3=start, r4=dstptr, r5=length, r0=fill-val
     61 		 */
     62 		cmplwi	r_len, 6		/* more than 6 bytes? */
     63 		bgt	complex_fill		/*    do it the complex way */
     64 		subi	r_dst, r_dst, 1		/* presubtract for stbu */
     65 simple_fill:	mtctr	r_len			/* set CTR */
     66 1:		stbu	r_val, 1(r_dst)		/* update memory */
     67 		bdnz+	1b			/*    until CTR is 0 */
     68 		blr				/* return */
     69 
     70 complex_fill:
     71 		rlwimi	r_val, r_val, 8, 16, 23	/* word extend fill value */
     72 		rlwimi	r_val, r_val, 16, 0, 15
     73 		andi.	r_tmp, r_dst, 0x03
     74 		beq+	word_fill		/* already aligned to word? */
     75 		andi.	r_tmp, r_dst, 0x01
     76 		beq	half_fill		/* aligned to halfword? */
     77 		stb	r_val, 0(r_dst)
     78 		addi	r_dst, r_dst, 1
     79 		subi	r_len, r_len, 1		/* subtract byte */
     80 		andi.	r_tmp, r_dst, 0x02
     81 		beq	word_fill		/* aligned to word? */
     82 half_fill:
     83 		sth	r_val, 0(r_dst)
     84 		addi	r_dst, r_dst, 2
     85 		subi	r_len, r_len, 2		/* subtract halfword */
     86 
     87 word_fill:
     88 		cmplwi	r_len, 4		/* we have more than 4 bytes? */
     89 		blt-	trailing_bytes		/* no?  finish writing */
     90 		srwi	r_tmp, r_len, 2		/* get word count */
     91 		mtctr	r_tmp
     92 		subi	r_dst, r_dst, 4
     93 1:		stwu	r_val, 4(r_dst)
     94 		bdnz+	1b
     95 
     96 trailing_bytes:
     97 		andi.	r_len, r_len, 0x03	/* how much left? */
     98 		beqlr+				/* nothing? return */
     99 		addi	r_dst, r_dst, 3
    100 		b	simple_fill
    101