auto import from //depot/cupcake/@135843
diff --git a/libc/arch-x86/string/bcopy.S b/libc/arch-x86/string/bcopy.S
new file mode 100644
index 0000000..dde5ae1
--- /dev/null
+++ b/libc/arch-x86/string/bcopy.S
@@ -0,0 +1,93 @@
+/* $OpenBSD: bcopy.S,v 1.5 2005/08/07 11:30:38 espie Exp $ */
+
+/*-
+ * Copyright (c) 1990 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * This code is derived from locore.s.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <machine/asm.h>
+
+ /*
+ * (ov)bcopy (src,dst,cnt)
+ * ws@tools.de (Wolfgang Solfrank, TooLs GmbH) +49-228-985800
+ */
+
+#ifdef MEMCOPY
+ENTRY(memcpy)
+#else
+#ifdef MEMMOVE
+ENTRY(memmove)
+#else
+ENTRY(bcopy)
+#endif
+#endif
+ pushl %esi
+ pushl %edi
+#if defined(MEMCOPY) || defined(MEMMOVE)
+ movl 12(%esp),%edi
+ movl 16(%esp),%esi
+ movl %edi, %eax
+#else
+ movl 12(%esp),%esi
+ movl 16(%esp),%edi
+#endif
+ movl 20(%esp),%ecx
+ movl %ecx,%edx
+ cmpl %esi,%edi /* potentially overlapping? */
+ jnb 1f
+ cld /* nope, copy forwards. */
+ shrl $2,%ecx /* copy by words */
+ rep
+ movsl
+ movl %edx,%ecx
+ andl $3,%ecx /* any bytes left? */
+ rep
+ movsb
+ popl %edi
+ popl %esi
+ ret
+1:
+ addl %ecx,%edi /* copy backwards. */
+ addl %ecx,%esi
+ std
+ andl $3,%ecx /* any fractional bytes? */
+ decl %edi
+ decl %esi
+ rep
+ movsb
+ movl %edx,%ecx
+ shrl $2,%ecx
+ subl $3,%esi
+ subl $3,%edi
+ rep
+ movsl
+ popl %edi
+ popl %esi
+ cld
+ ret