1/* 2 * Written by J.T. Conklin <jtc@NetBSD.org>. 3 * Public domain. 4 * Adapted for NetBSD/x86_64 by Frank van der Linden <fvdl@wasabisystems.com> 5 * 6 * $NetBSD: bzero.S,v 1.2 2003/07/26 19:24:38 salo Exp $ 7 * $FreeBSD: src/lib/libc/amd64/string/bzero.S,v 1.3 2008/11/02 01:10:54 peter Exp $ 8 */ 9 10#include <machine/asm.h> 11 12ENTRY(bzero) 13 cld /* set fill direction forward */ 14 xorq %rax,%rax /* set fill data to 0 */ 15 16 /* 17 * if the string is too short, it's really not worth the overhead 18 * of aligning to word boundries, etc. So we jump to a plain 19 * unaligned set. 20 */ 21 cmpq $16,%rsi 22 jb L1 23 24 movq %rdi,%rcx /* compute misalignment */ 25 negq %rcx 26 andq $7,%rcx 27 subq %rcx,%rsi 28 rep /* zero until word aligned */ 29 stosb 30 31 movq %rsi,%rcx /* zero by words */ 32 shrq $3,%rcx 33 andq $7,%rsi 34 rep 35 stosq 36 37L1: movq %rsi,%rcx /* zero remainder by bytes */ 38 rep 39 stosb 40 41 ret 42END(bzero) 43 44 .section .note.GNU-stack,"",%progbits 45