diff options
Diffstat (limited to 'libc/arch-x86/string/bzero.S')
| -rw-r--r-- | libc/arch-x86/string/bzero.S | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/libc/arch-x86/string/bzero.S b/libc/arch-x86/string/bzero.S new file mode 100644 index 0000000..2ec9c7d --- /dev/null +++ b/libc/arch-x86/string/bzero.S @@ -0,0 +1,43 @@ +/* $OpenBSD: bzero.S,v 1.3 2005/08/07 11:30:38 espie Exp $ */ +/* + * Written by J.T. Conklin <jtc@netbsd.org>. + * Public domain. + */ + +#include <machine/asm.h> + +ENTRY(bzero) + pushl %edi + movl 8(%esp),%edi + movl 12(%esp),%edx + + cld /* set fill direction forward */ + xorl %eax,%eax /* 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. + */ + cmpl $16,%edx + jb L1 + + movl %edi,%ecx /* compute misalignment */ + negl %ecx + andl $3,%ecx + subl %ecx,%edx + rep /* zero until word aligned */ + stosb + + movl %edx,%ecx /* zero by words */ + shrl $2,%ecx + andl $3,%edx + rep + stosl + +L1: movl %edx,%ecx /* zero remainder by bytes */ + rep + stosb + + popl %edi + ret |