audk/EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/EfiCopyMemRep4.c

/*++

Copyright (c) 2007, Intel Corporation                                                         
All rights reserved. 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:

  EfiCopyMemRep4.c

Abstract:

  This is the code that uses rep movsd CopyMem service

--*/

#include "Tiano.h"

VOID
EfiCommonLibCopyMem (
  IN VOID   *Destination,
  IN VOID   *Source,
  IN UINTN  Count
  )
/*++

Routine Description:

  Copy Length bytes from Source to Destination.

Arguments:

  Destination - Target of copy

  Source      - Place to copy from

  Length      - Number of bytes to copy

Returns:

  None

--*/
{
  __asm {
    mov     esi, Source                  ; esi <- Source
    mov     edi, Destination             ; edi <- Destination
    mov     edx, Count                   ; 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     _CopyDWord
    cmp     eax, edi
    jae     _CopyBackward                ; Copy backward if overlapped
_CopyDWord:
    mov     ecx, edx
    and     edx, 3
    shr     ecx, 2
    rep     movsd                        ; Copy as many Dwords as possible
    jmp     _CopyBytes
_CopyBackward:
    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:
  }
}