diff --git a/libc/arch-x86/string/memcmp.S b/libc/arch-x86/string/memcmp.S
new file mode 100644
index 0000000..1be189a
--- /dev/null
+++ b/libc/arch-x86/string/memcmp.S
@@ -0,0 +1,43 @@
+/*	$OpenBSD: memcmp.S,v 1.4 2005/08/07 11:30:38 espie Exp $ */
+/*
+ * Written by J.T. Conklin <jtc@netbsd.org>.
+ * Public domain.
+ */
+
+#include <machine/asm.h>
+
+ENTRY(memcmp)
+	pushl	%edi
+	pushl	%esi
+	movl	12(%esp),%edi
+	movl	16(%esp),%esi
+	cld				/* set compare direction forward */
+
+	movl	20(%esp),%ecx		/* compare by words */
+	shrl	$2,%ecx
+	repe
+	cmpsl
+	jne	L5			/* do we match so far? */
+
+	movl	20(%esp),%ecx		/* compare remainder by bytes */
+	andl	$3,%ecx
+	repe
+	cmpsb
+	jne	L6			/* do we match? */
+
+	xorl	%eax,%eax		/* we match, return zero	*/
+	popl	%esi
+	popl	%edi
+	ret
+
+L5:	movl	$4,%ecx			/* We know that one of the next	*/
+	subl	%ecx,%edi		/* four pairs of bytes do not	*/
+	subl	%ecx,%esi		/* match.			*/
+	repe
+	cmpsb
+L6:	movzbl  -1(%edi),%eax		/* Perform unsigned comparison	*/
+	movzbl	-1(%esi),%edx
+	subl	%edx,%eax
+	popl	%esi
+	popl	%edi
+	ret