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      1 /*
      2  * CDDL HEADER START
      3  *
      4  * The contents of this file are subject to the terms of the
      5  * Common Development and Distribution License (the "License").
      6  * You may not use this file except in compliance with the License.
      7  *
      8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      9  * or http://www.opensolaris.org/os/licensing.
     10  * See the License for the specific language governing permissions
     11  * and limitations under the License.
     12  *
     13  * When distributing Covered Code, include this CDDL HEADER in each
     14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     15  * If applicable, add the following below this CDDL HEADER, with the
     16  * fields enclosed by brackets "[]" replaced with your own identifying
     17  * information: Portions Copyright [yyyy] [name of copyright owner]
     18  *
     19  * CDDL HEADER END
     20  */
     21 
     22 /*
     23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
     24  * Use is subject to license terms.
     25  */
     26 
     27 	.file	"memset.s"
     28 
     29 /*
     30  * memset(sp, c, n)
     31  *
     32  * Set an array of n chars starting at sp to the character c.
     33  * Return sp.
     34  *
     35  * Fast assembler language version of the following C-program for memset
     36  * which represents the `standard' for the C-library.
     37  *
     38  *	void *
     39  *	memset(void *sp1, int c, size_t n)
     40  *	{
     41  *	    if (n != 0) {
     42  *		char *sp = sp1;
     43  *		do {
     44  *		    *sp++ = (char)c;
     45  *		} while (--n != 0);
     46  *	    }
     47  *	    return (sp1);
     48  *	}
     49  *
     50  *
     51  *
     52  * Algorithm used:
     53  *	For small stores (6 or fewer bytes), bytes will be stored one at a time.
     54  *
     55  *	When setting 15 or more bytes, there will be at least 8 bytes aligned
     56  *	on an 8-byte boundary.  So, leading bytes will be set, then as many
     57  *	8-byte aligned chunks as possible will be set, followed by any trailing
     58  *	bytes.
     59  *
     60  *	For between 8 and 14 bytes (inclusive), leading odd bytes will be
     61  *	set, followed by 4-byte chunks, followed by trailing bytes.
     62  *
     63  * Inputs:
     64  *	o0:  pointer to start of area to be set to a given value
     65  *	o1:  character used to set memory at location in i0
     66  *	o2:  number of bytes to be set
     67  *
     68  * Outputs:
     69  *	o0:  pointer to start of area set (same as input value in o0)
     70  *
     71  */
     72 
     73 #include <sys/asm_linkage.h>
     74 
     75 	ANSI_PRAGMA_WEAK(memset,function)
     76 
     77 	ENTRY(memset)
     78 	mov	%o0, %o5		! need to return this value
     79 	cmp	%o2, 7
     80 	blu,pn	%xcc, .wrchar		! small count:  just set bytes
     81 	and	%o1, 0xff, %o1
     82 
     83 	sll	%o1, 8, %o4		! generate 4 bytes filled with char
     84 	or 	%o1, %o4, %o1
     85 	sll	%o1, 16, %o4
     86 	cmp	%o2, 15
     87 	blu,pn	%xcc, .walign		! not enough to guarantee 8-byte align
     88 	or	%o1, %o4, %o1
     89 
     90 	sllx	%o1, 32, %o4		! now fill the other 4 bytes with char
     91 	or 	%o1, %o4, %o1
     92 
     93 .dalign:			! Set bytes until 8-byte aligned
     94 	btst	7, %o5			! 8-byte aligned?
     95 	bz,a,pn	%icc, .wrdbl
     96 	andn	%o2, 7, %o3		! o3 has 8-byte multiple
     97 
     98 	dec	%o2
     99 	stb	%o1, [%o5]		! clear a byte
    100 	b	.dalign			! go see if aligned yet
    101 	inc	%o5
    102 
    103 	.align	32
    104 .wrdbl:
    105 	stx	%o1, [%o5]		! write aligned 8 bytes
    106 	subcc	%o3, 8, %o3
    107 	bnz,pt	%xcc, .wrdbl
    108 	inc	8, %o5
    109 
    110 	b	.wrchar			! write the remaining bytes
    111 	and	%o2, 7, %o2		! leftover count, if any
    112 
    113 .walign:			! Set bytes until 4-byte aligned
    114 	btst	3, %o5			! if bigger, align to 4 bytes
    115 	bz,pn	%icc, .wrword
    116 	andn	%o2, 3, %o3		! create word sized count in %o3
    117 
    118 	dec	%o2			! decrement count
    119 	stb	%o1, [%o5]		! clear a byte
    120 	b	.walign
    121 	inc	%o5			! next byte
    122 
    123 .wrword:
    124 	st	%o1, [%o5]		! 4-byte writing loop
    125 	subcc	%o3, 4, %o3
    126 	bnz,pn	%xcc, .wrword
    127 	inc	4, %o5
    128 
    129 	and	%o2, 3, %o2		! leftover count, if any
    130 
    131 .wrchar:
    132 	deccc	%o2			! byte clearing loop
    133 	inc	%o5
    134 	bgeu,a,pt %xcc, .wrchar
    135 	stb	%o1, [%o5 + -1]		! we've already incremented the address
    136 
    137 	retl
    138 	sub	%o0, %g0, %o0
    139 
    140 	SET_SIZE(memset)
    141