Home | History | Annotate | Line # | Download | only in string 
      1 /*	$NetBSD: memset.S,v 1.5 2014/05/22 16:47:31 pooka Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2009 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by David Laight.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include <machine/asm.h>
     33 
     34 #if defined(LIBC_SCCS)
     35 	RCSID("$NetBSD: memset.S,v 1.5 2014/05/22 16:47:31 pooka Exp $")
     36 #endif
     37 
     38 #ifndef _KERNEL
     39 /* bzero, %rdi is buffer, %rsi length */
     40 
     41 ENTRY(bzero)
     42 	mov	%rsi,%rdx		/* length */
     43 	xor	%eax,%eax		/* value to write */
     44 	jmp	1f
     45 #endif
     46 
     47 /* memset, %rdi is buffer, %rsi char to fill, %rdx length */
     48 
     49 ENTRY(memset)
     50 	movzbq	%sil,%rax		/* byte value to fill */
     51 	mov	%rdx,%rsi		/* copy of length */
     52 	mov	$0x0101010101010101,%r9
     53 	imul	%r9,%rax		/* fill value in all bytes */
     54 
     55 1:
     56 	mov	%rdi,%r9		/* Need to return buffer address */
     57 	or	%edi,%edx		/* address | length */
     58 	mov	%rsi,%rcx
     59 	cmp	$7,%rsi
     60 	jbe	10f			/* jump if short fill */
     61 	test	$7,%dl			/* check for misaligned fill */
     62 	jnz	20f			/* jump if misaligned */
     63 
     64 /* Target aligned and length multiple of 8 */
     65 2:
     66 	shr	$3,%rcx
     67 	rep	stosq
     68 	mov	%r9,%rax
     69 	ret
     70 
     71 /*
     72  * Short transfer, any faffing here will generate mispredicted branches.
     73  * So we keep it simple.
     74  */
     75 10:	rep	stosb
     76 	mov	%r9,%rax
     77 	ret
     78 
     79 /*
     80  * Buffer or length misaligned.
     81  * Write pattern to first and last word of buffer, then fill middle.
     82  * (This writes to some bytes more than once - possibly three times!.)
     83  */
     84 20:
     85 	mov	%rax,(%rdi)
     86 	movzbq	%dil,%rdx		/* low address for alignment */
     87 	mov	%rax,-8(%rcx,%rdi)
     88 	and	$7,%dl			/* offset in word */
     89 	sub	%rdx,%rcx		/* adjust length ... */
     90 	add	%rdx,%rdi		/* ... and target */
     91 	jmp	2b
     92 END(memset)
     93 
     94 #ifndef _KERNEL
     95 END(bzero)
     96 #endif
     97