1 files changed, 56 insertions, 0 deletions
diff --git a/roms/edk2/MdePkg/Library/BaseMemoryLibOptPei/Ia32/CopyMem.nasm b/roms/edk2/MdePkg/Library/BaseMemoryLibOptPei/Ia32/CopyMem.nasm
new file mode 100644
index 000000000..b598caa54
--- /dev/null
+++ b/roms/edk2/MdePkg/Library/BaseMemoryLibOptPei/Ia32/CopyMem.nasm
@@ -0,0 +1,56 @@
+;------------------------------------------------------------------------------
+;
+; Copyright (c) 2006, Intel Corporation. All rights reserved.<BR>
+; SPDX-License-Identifier: BSD-2-Clause-Patent
+;
+; Module Name:
+;
+;   CopyMem.Asm
+;
+; Abstract:
+;
+;   CopyMem function
+;
+; Notes:
+;
+;------------------------------------------------------------------------------
+
+    SECTION .text
+
+;------------------------------------------------------------------------------
+;  VOID *
+;  InternalMemCopyMem (
+;    IN VOID   *Destination,
+;    IN VOID   *Source,
+;    IN UINTN  Count
+;    )
+;------------------------------------------------------------------------------
+global ASM_PFX(InternalMemCopyMem)
+ASM_PFX(InternalMemCopyMem):
+    push    esi
+    push    edi
+    mov     esi, [esp+16]                ; esi <- Source
+    mov     edi, [esp+12]                ; edi <- Destination
+    mov     edx, [esp+20]                ; edx <- Count
+    cmp     esi, edi
+    je      @CopyDone
+    cmp     edx, 0
+    je      @CopyDone
+    lea     eax, [esi + edx - 1]         ; eax <- End of Source
+    cmp     esi, edi
+    jae     @CopyBytes
+    cmp     eax, edi
+    jb      @CopyBytes                   ; Copy backward if overlapped
+    mov     esi, eax                     ; esi <- End of Source
+    lea     edi, [edi + edx - 1]         ; edi <- End of Destination
+    std
+@CopyBytes:
+    mov     ecx, edx
+    rep     movsb                        ; Copy bytes backward
+    cld
+@CopyDone:
+    mov     eax, [esp + 12]             ; eax <- Destination as return value
+    pop     edi
+    pop     esi
+    ret
+