freebsd-dev/lib/libc/amd64/string/memset.S
Alan Cox 91c09a383a Add machine-specific, optimized implementations of bcopy, bzero, memcpy,
memmove, and memset.

PR: 73111
Submitted by: Ville-Pertti Keinonen <will@iki.fi> (taken from NetBSD)
MFC after: 3 weeks
2005-04-07 03:56:03 +00:00

61 lines
1.0 KiB
ArmAsm

/*
* Written by J.T. Conklin <jtc@NetBSD.org>.
* Public domain.
* Adapted for NetBSD/x86_64 by Frank van der Linden <fvdl@wasabisystems.com>
*/
#include <machine/asm.h>
__FBSDID("$FreeBSD$");
#if 0
RCSID("$NetBSD: memset.S,v 1.3 2004/02/26 20:50:06 drochner Exp $")
#endif
ENTRY(memset)
movq %rsi,%rax
andq $0xff,%rax
movq %rdx,%rcx
movq %rdi,%r11
cld /* set fill direction forward */
/*
* if the string is too short, it's really not worth the overhead
* of aligning to word boundries, etc. So we jump to a plain
* unaligned set.
*/
cmpq $0x0f,%rcx
jle L1
movb %al,%ah /* copy char to all bytes in word */
movl %eax,%edx
sall $16,%eax
orl %edx,%eax
movl %eax,%edx
salq $32,%rax
orq %rdx,%rax
movq %rdi,%rdx /* compute misalignment */
negq %rdx
andq $7,%rdx
movq %rcx,%r8
subq %rdx,%r8
movq %rdx,%rcx /* set until word aligned */
rep
stosb
movq %r8,%rcx
shrq $3,%rcx /* set by words */
rep
stosq
movq %r8,%rcx /* set remainder by bytes */
andq $7,%rcx
L1: rep
stosb
movq %r11,%rax
ret