auto import from //depot/cupcake/@135843
diff --git a/libc/arch-x86/string/strncmp.S b/libc/arch-x86/string/strncmp.S
new file mode 100644
index 0000000..5aa88d7
--- /dev/null
+++ b/libc/arch-x86/string/strncmp.S
@@ -0,0 +1,113 @@
+/* $OpenBSD: strncmp.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>
+
+/*
+ * NOTE: I've unrolled the loop eight times: large enough to make a
+ * significant difference, and small enough not to totally trash the
+ * cache.
+ */
+
+ENTRY(strncmp)
+ pushl %ebx
+ movl 8(%esp),%eax
+ movl 12(%esp),%ecx
+ movl 16(%esp),%edx
+ testl %edx,%edx
+ jmp L2 /* Jump into the loop! */
+
+ .align 2,0x90
+L1: incl %eax
+ incl %ecx
+ decl %edx
+L2: jz L4 /* strings are equal */
+ movb (%eax),%bl
+ testb %bl,%bl
+ jz L3
+ cmpb %bl,(%ecx)
+ jne L3
+
+ incl %eax
+ incl %ecx
+ decl %edx
+ jz L4
+ movb (%eax),%bl
+ testb %bl,%bl
+ jz L3
+ cmpb %bl,(%ecx)
+ jne L3
+
+ incl %eax
+ incl %ecx
+ decl %edx
+ jz L4
+ movb (%eax),%bl
+ testb %bl,%bl
+ jz L3
+ cmpb %bl,(%ecx)
+ jne L3
+
+ incl %eax
+ incl %ecx
+ decl %edx
+ jz L4
+ movb (%eax),%bl
+ testb %bl,%bl
+ jz L3
+ cmpb %bl,(%ecx)
+ jne L3
+
+ incl %eax
+ incl %ecx
+ decl %edx
+ jz L4
+ movb (%eax),%bl
+ testb %bl,%bl
+ jz L3
+ cmpb %bl,(%ecx)
+ jne L3
+
+ incl %eax
+ incl %ecx
+ decl %edx
+ jz L4
+ movb (%eax),%bl
+ testb %bl,%bl
+ jz L3
+ cmpb %bl,(%ecx)
+ jne L3
+
+ incl %eax
+ incl %ecx
+ decl %edx
+ jz L4
+ movb (%eax),%bl
+ testb %bl,%bl
+ jz L3
+ cmpb %bl,(%ecx)
+ jne L3
+
+ incl %eax
+ incl %ecx
+ decl %edx
+ jz L4
+ movb (%eax),%bl
+ testb %bl,%bl
+ jz L3
+ cmpb %bl,(%ecx)
+ je L1
+
+ .align 2,0x90
+L3: movzbl (%eax),%eax /* unsigned comparision */
+ movzbl (%ecx),%ecx
+ subl %ecx,%eax
+ popl %ebx
+ ret
+ .align 2,0x90
+L4: xorl %eax,%eax
+ popl %ebx
+ ret