MdePkg/Library/BaseLib/Ia32/RShiftU64.c

   1 /** @file
   2   64-bit logical right shift function for IA-32
   3
   4   Copyright (c) 2006 - 2015, Intel Corporation. All rights reserved.<BR>
   5   SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9
  10
  11
  12 /**
  13   Shifts a 64-bit integer right between 0 and 63 bits. This high bits
  14   are filled with zeros. The shifted value is returned.
  15
  16   This function shifts the 64-bit value Operand to the right by Count bits. The
  17   high Count bits are set to zero. The shifted value is returned.
  18
  19   @param  Operand The 64-bit operand to shift right.
  20   @param  Count   The number of bits to shift right.
  21
  22   @return Operand >> Count
  23
  24 **/
  25 UINT64
  26 EFIAPI
  27 InternalMathRShiftU64 (
  28   IN      UINT64                    Operand,
  29   IN      UINTN                     Count
  30   )
  31 {
  32   _asm {
  33     mov     cl, byte ptr [Count]
  34     xor     edx, edx
  35     mov     eax, dword ptr [Operand + 4]
  36     test    cl, 32
  37     jnz     L0
  38     mov     edx, eax
  39     mov     eax, dword ptr [Operand + 0]
  40 L0:
  41     shrd    eax, edx, cl
  42     shr     edx, cl
  43   }
  44 }
  45