Index: head/sys/amd64/amd64/support.S
===================================================================
--- head/sys/amd64/amd64/support.S
+++ head/sys/amd64/amd64/support.S
@@ -101,6 +101,100 @@
 END(sse2_pagezero)
 
 /*
+ * memcmpy(b1, b2, len)
+ *	   rdi,rsi,len
+ */
+ENTRY(memcmp)
+	PUSH_FRAME_POINTER
+	cmpq	$16,%rdx
+	jae	5f
+1:
+	testq	%rdx,%rdx
+	je	3f
+	xorl	%ecx,%ecx
+2:
+	movzbl	(%rdi,%rcx,1),%eax
+	movzbl	(%rsi,%rcx,1),%r8d
+	cmpb	%r8b,%al
+	jne	4f
+	addq    $1,%rcx
+	cmpq    %rcx,%rdx
+	jz	3f
+	movzbl	(%rdi,%rcx,1),%eax
+	movzbl	(%rsi,%rcx,1),%r8d
+	cmpb	%r8b,%al
+	jne	4f
+	addq	$1,%rcx
+	cmpq	%rcx,%rdx
+	jz	3f
+	movzbl	(%rdi,%rcx,1),%eax
+	movzbl	(%rsi,%rcx,1),%r8d
+	cmpb	%r8b,%al
+	jne	4f
+	addq	$1,%rcx
+	cmpq	%rcx,%rdx
+	jz	3f
+	movzbl	(%rdi,%rcx,1),%eax
+	movzbl	(%rsi,%rcx,1),%r8d
+	cmpb	%r8b,%al
+	jne	4f
+	addq	$1,%rcx
+	cmpq	%rcx,%rdx
+	jne	2b
+3:
+	xorl	%eax,%eax
+	POP_FRAME_POINTER
+	ret
+4:
+	subl	%r8d,%eax
+	POP_FRAME_POINTER
+	ret
+5:
+	cmpq	$32,%rdx
+	jae	7f
+6:
+	/*
+	 * 8 bytes
+	 */
+	movq    (%rdi),%r8
+	movq    (%rsi),%r9
+	cmpq    %r8,%r9
+	jne	1b
+	leaq	8(%rdi),%rdi
+	leaq	8(%rsi),%rsi
+	subq	$8,%rdx
+	cmpq	$8,%rdx
+	jae	6b
+	jl	1b
+	jmp	3b
+7:
+	/*
+	 * 32 bytes
+	 */
+	movq    (%rsi),%r8
+	movq    8(%rsi),%r9
+	subq    (%rdi),%r8
+	subq    8(%rdi),%r9
+	or	%r8,%r9
+	jnz	1b
+
+	movq    16(%rsi),%r8
+	movq    24(%rsi),%r9
+	subq    16(%rdi),%r8
+	subq    24(%rdi),%r9
+	or	%r8,%r9
+	jnz	1b
+
+	leaq    32(%rdi),%rdi
+	leaq    32(%rsi),%rsi
+	subq    $32,%rdx
+	cmpq    $32,%rdx
+	jae	7b
+	jnz	1b
+	jmp	3b
+END(memcmp)
+
+/*
  * memmove(dst, src, cnt)
  *         rdi, rsi, rdx
  * Adapted from bcopy written by:
Index: head/sys/conf/files
===================================================================
--- head/sys/conf/files
+++ head/sys/conf/files
@@ -4041,7 +4041,6 @@
 libkern/mcount.c		optional profiling-routine
 libkern/memcchr.c		standard
 libkern/memchr.c		standard
-libkern/memcmp.c		standard
 libkern/memmem.c		optional gdb
 libkern/qsort.c			standard
 libkern/qsort_r.c		standard
Index: head/sys/conf/files.arm
===================================================================
--- head/sys/conf/files.arm
+++ head/sys/conf/files.arm
@@ -163,6 +163,7 @@
 libkern/flsl.c			standard
 libkern/flsll.c			standard
 libkern/lshrdi3.c		standard
+libkern/memcmp.c		standard
 libkern/moddi3.c		standard
 libkern/qdivrem.c		standard
 libkern/ucmpdi2.c		standard
Index: head/sys/conf/files.arm64
===================================================================
--- head/sys/conf/files.arm64
+++ head/sys/conf/files.arm64
@@ -244,6 +244,7 @@
 libkern/fls.c			standard
 libkern/flsl.c			standard
 libkern/flsll.c			standard
+libkern/memcmp.c		standard
 libkern/memset.c		standard
 libkern/arm64/crc32c_armv8.S	standard
 cddl/contrib/opensolaris/common/atomic/aarch64/opensolaris_atomic.S	optional zfs | dtrace compile-with "${CDDL_C}"
Index: head/sys/conf/files.i386
===================================================================
--- head/sys/conf/files.i386
+++ head/sys/conf/files.i386
@@ -548,6 +548,7 @@
 libkern/divdi3.c		standard
 libkern/ffsll.c			standard
 libkern/flsll.c			standard
+libkern/memcmp.c		standard
 libkern/memset.c		standard
 libkern/moddi3.c		standard
 libkern/qdivrem.c		standard
Index: head/sys/conf/files.mips
===================================================================
--- head/sys/conf/files.mips
+++ head/sys/conf/files.mips
@@ -65,6 +65,7 @@
 libkern/ucmpdi2.c			optional	mips | mipshf | mipsel | mipselhf
 libkern/ashldi3.c			standard
 libkern/ashrdi3.c			standard
+libkern/memcmp.c			standard
 
 # cfe support
 dev/cfe/cfe_api.c			optional	cfe
Index: head/sys/conf/files.powerpc
===================================================================
--- head/sys/conf/files.powerpc
+++ head/sys/conf/files.powerpc
@@ -98,6 +98,7 @@
 libkern/flsl.c			standard
 libkern/flsll.c			standard
 libkern/lshrdi3.c		optional	powerpc | powerpcspe
+libkern/memcmp.c		standard
 libkern/memset.c		standard
 libkern/moddi3.c		optional	powerpc | powerpcspe
 libkern/qdivrem.c		optional	powerpc | powerpcspe
Index: head/sys/conf/files.riscv
===================================================================
--- head/sys/conf/files.riscv
+++ head/sys/conf/files.riscv
@@ -22,6 +22,7 @@
 libkern/fls.c			standard
 libkern/flsl.c			standard
 libkern/flsll.c			standard
+libkern/memcmp.c		standard
 libkern/memset.c		standard
 riscv/riscv/autoconf.c		standard
 riscv/riscv/bus_machdep.c	standard
Index: head/sys/conf/files.sparc64
===================================================================
--- head/sys/conf/files.sparc64
+++ head/sys/conf/files.sparc64
@@ -71,6 +71,7 @@
 libkern/fls.c			standard
 libkern/flsl.c			standard
 libkern/flsll.c			standard
+libkern/memcmp.c		standard
 sparc64/central/central.c	optional	central
 sparc64/ebus/ebus.c		optional	ebus
 sparc64/ebus/epic.c		optional	epic ebus