audk/MdePkg/Library/BaseLib/Ia32/RShiftU64.c

/** @file
  64-bit logical right shift function for IA-32

  Copyright (c) 2006 - 2007, Intel Corporation<BR>
  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.

**/




/**
  Shifts a 64-bit integer right between 0 and 63 bits. This high bits
  are filled with zeros. The shifted value is returned.

  This function shifts the 64-bit value Operand to the right by Count bits. The
  high Count bits are set to zero. The shifted value is returned.

  @param  Operand The 64-bit operand to shift right.
  @param  Count   The number of bits to shift right.

  @return Operand >> Count

**/
UINT64
EFIAPI
InternalMathRShiftU64 (
  IN      UINT64                    Operand,
  IN      UINTN                     Count
  )
{
  _asm {
    mov     cl, byte ptr [Count]
    xor     edx, edx
    mov     eax, dword ptr [Operand + 4]
    test    cl, 32
    cmovz   edx, eax
    cmovz   eax, dword ptr [Operand + 0]
    shrd    eax, edx, cl
    shr     edx, cl
  }
}