1 files changed, 65 insertions, 0 deletions
diff --git a/MdePkg/Library/BaseMemoryLibRepStr/X64/CopyMem.nasm b/MdePkg/Library/BaseMemoryLibRepStr/X64/CopyMem.nasm
new file mode 100644
index 000000000000..b30412399cf9
--- /dev/null
+++ b/MdePkg/Library/BaseMemoryLibRepStr/X64/CopyMem.nasm
@@ -0,0 +1,65 @@
+;------------------------------------------------------------------------------
+;
+; Copyright (c) 2006, 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:
+;
+;   CopyMem.Asm
+;
+; Abstract:
+;
+;   CopyMem function
+;
+; Notes:
+;
+;------------------------------------------------------------------------------
+
+    DEFAULT REL
+    SECTION .text
+
+;------------------------------------------------------------------------------
+;  VOID *
+;  EFIAPI
+;  InternalMemCopyMem (
+;    IN VOID   *Destination,
+;    IN VOID   *Source,
+;    IN UINTN  Count
+;    )
+;------------------------------------------------------------------------------
+global ASM_PFX(InternalMemCopyMem)
+ASM_PFX(InternalMemCopyMem):
+    push    rsi
+    push    rdi
+    mov     rsi, rdx                    ; rsi <- Source
+    mov     rdi, rcx                    ; rdi <- Destination
+    lea     r9, [rsi + r8 - 1]          ; r9 <- End of Source
+    cmp     rsi, rdi
+    mov     rax, rdi                    ; rax <- Destination as return value
+    jae     .0
+    cmp     r9, rdi
+    jae     @CopyBackward               ; Copy backward if overlapped
+.0:
+    mov     rcx, r8
+    and     r8, 7
+    shr     rcx, 3
+    rep     movsq                       ; Copy as many Qwords as possible
+    jmp     @CopyBytes
+@CopyBackward:
+    mov     rsi, r9                     ; rsi <- End of Source
+    lea     rdi, [rdi + r8 - 1]         ; esi <- End of Destination
+    std                                 ; set direction flag
+@CopyBytes:
+    mov     rcx, r8
+    rep     movsb                       ; Copy bytes backward
+    cld
+    pop     rdi
+    pop     rsi
+    ret
+