diff --git a/MdePkg/Library/BaseMemoryLibRepStr/BaseMemoryLibRepStr.inf b/MdePkg/Library/BaseMemoryLibRepStr/BaseMemoryLibRepStr.inf
index 31e3973a86..5311d5df33 100644
--- a/MdePkg/Library/BaseMemoryLibRepStr/BaseMemoryLibRepStr.inf
+++ b/MdePkg/Library/BaseMemoryLibRepStr/BaseMemoryLibRepStr.inf
@@ -100,6 +100,7 @@
   X64/ScanMem16.S
   X64/ScanMem8.nasm
   X64/ScanMem8.S
+  X64/CompareMem.nasm
   X64/CompareMem.S
   X64/ZeroMem.S
   X64/SetMem64.S
@@ -115,6 +116,7 @@
   X64/ScanMem16.asm
   X64/ScanMem8.nasm
   X64/ScanMem8.asm
+  X64/CompareMem.nasm
   X64/CompareMem.asm
   X64/ZeroMem.asm
   X64/SetMem64.asm
diff --git a/MdePkg/Library/BaseMemoryLibRepStr/X64/CompareMem.nasm b/MdePkg/Library/BaseMemoryLibRepStr/X64/CompareMem.nasm
new file mode 100644
index 0000000000..293a39b256
--- /dev/null
+++ b/MdePkg/Library/BaseMemoryLibRepStr/X64/CompareMem.nasm
@@ -0,0 +1,58 @@
+;------------------------------------------------------------------------------
+;
+; Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
+; This program and the accompanying materials
+; are licensed and made available under the terms and conditions of the BSD License
+; which accompanies this distribution.  The full text of the license may be found at
+; http://opensource.org/licenses/bsd-license.php.
+;
+; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+;
+; Module Name:
+;
+;   CompareMem.Asm
+;
+; Abstract:
+;
+;   CompareMem function
+;
+; Notes:
+;
+;   The following BaseMemoryLib instances contain the same copy of this file:
+;
+;       BaseMemoryLibRepStr
+;       BaseMemoryLibMmx
+;       BaseMemoryLibSse2
+;       BaseMemoryLibOptDxe
+;       BaseMemoryLibOptPei
+;
+;------------------------------------------------------------------------------
+
+    DEFAULT REL
+    SECTION .text
+
+;------------------------------------------------------------------------------
+; INTN
+; EFIAPI
+; InternalMemCompareMem (
+;   IN      CONST VOID                *DestinationBuffer,
+;   IN      CONST VOID                *SourceBuffer,
+;   IN      UINTN                     Length
+;   );
+;------------------------------------------------------------------------------
+global ASM_PFX(InternalMemCompareMem)
+ASM_PFX(InternalMemCompareMem):
+    push    rsi
+    push    rdi
+    mov     rsi, rcx
+    mov     rdi, rdx
+    mov     rcx, r8
+    repe    cmpsb
+    movzx   rax, byte [rsi - 1]
+    movzx   rdx, byte [rdi - 1]
+    sub     rax, rdx
+    pop     rdi
+    pop     rsi
+    ret
+