diff options
Diffstat (limited to 'lib/libc/amd64/string/bzero.S')
| -rw-r--r-- | lib/libc/amd64/string/bzero.S | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/lib/libc/amd64/string/bzero.S b/lib/libc/amd64/string/bzero.S new file mode 100644 index 0000000..d9d2a45 --- /dev/null +++ b/lib/libc/amd64/string/bzero.S @@ -0,0 +1,43 @@ +/* + * 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: bzero.S,v 1.2 2003/07/26 19:24:38 salo Exp $") +#endif + +ENTRY(bzero) + cld /* set fill direction forward */ + xorq %rax,%rax /* set fill data to 0 */ + + /* + * 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 $16,%rsi + jb L1 + + movq %rdi,%rcx /* compute misalignment */ + negq %rcx + andq $7,%rcx + subq %rcx,%rsi + rep /* zero until word aligned */ + stosb + + movq %rsi,%rcx /* zero by words */ + shrq $3,%rcx + andq $7,%rsi + rep + stosq + +L1: movq %rsi,%rcx /* zero remainder by bytes */ + rep + stosb + + ret |
