diff options
Diffstat (limited to 'lib/libc/amd64/string/memcmp.S')
| -rw-r--r-- | lib/libc/amd64/string/memcmp.S | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/lib/libc/amd64/string/memcmp.S b/lib/libc/amd64/string/memcmp.S new file mode 100644 index 0000000..66d64a0 --- /dev/null +++ b/lib/libc/amd64/string/memcmp.S @@ -0,0 +1,44 @@ +/* + * 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: memcmp.S,v 1.2 2003/07/26 19:24:39 salo Exp $") +#endif + +ENTRY(memcmp) + cld /* set compare direction forward */ + movq %rdx,%rcx /* compare by longs */ + shrq $3,%rcx + repe + cmpsq + jne L5 /* do we match so far? */ + + movq %rdx,%rcx /* compare remainder by bytes */ + andq $7,%rcx + repe + cmpsb + jne L6 /* do we match? */ + + xorl %eax,%eax /* we match, return zero */ + ret + +L5: movl $8,%ecx /* We know that one of the next */ + subq %rcx,%rdi /* eight pairs of bytes do not */ + subq %rcx,%rsi /* match. */ + repe + cmpsb +L6: xorl %eax,%eax /* Perform unsigned comparison */ + movb -1(%rdi),%al + xorl %edx,%edx + movb -1(%rsi),%dl + subl %edx,%eax + ret +END(memcmp) + + .section .note.GNU-stack,"",%progbits |
