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path: root/MdePkg/Library/BaseMemoryLibOptPei/X64/CompareMem.nasm
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;------------------------------------------------------------------------------
;
; 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