MdePkg/Library/BaseLib/Ia32/RShiftU64.c

   1 /** @file
   2   64-bit logical right shift function for IA-32
   3
   4   Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
   5   This program and the accompanying materials
   6   are licensed and made available under the terms and conditions of the BSD License
   7   which accompanies this distribution.  The full text of the license may be found at
   8   http://opensource.org/licenses/bsd-license.php
   9
  10   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13 **/
  14
  15
  16
  17
  18 /**
  19   Shifts a 64-bit integer right between 0 and 63 bits. This high bits
  20   are filled with zeros. The shifted value is returned.
  21
  22   This function shifts the 64-bit value Operand to the right by Count bits. The
  23   high Count bits are set to zero. The shifted value is returned.
  24
  25   @param  Operand The 64-bit operand to shift right.
  26   @param  Count   The number of bits to shift right.
  27
  28   @return Operand >> Count
  29
  30 **/
  31 UINT64
  32 EFIAPI
  33 InternalMathRShiftU64 (
  34   IN      UINT64                    Operand,
  35   IN      UINTN                     Count
  36   )
  37 {
  38   _asm {
  39     mov     cl, byte ptr [Count]
  40     xor     edx, edx
  41     mov     eax, dword ptr [Operand + 4]
  42     test    cl, 32
  43     cmovz   edx, eax
  44     cmovz   eax, dword ptr [Operand + 0]
  45     shrd    eax, edx, cl
  46     shr     edx, cl
  47   }
  48 }
  49