MdePkg/Library/BaseLib/Ia32/RRotU64.c

/** @file
  64-bit right rotation for Ia32

  Copyright (c) 2006 - 2015, Intel Corporation. All rights reserved.<BR>
  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

/**
  Rotates a 64-bit integer right between 0 and 63 bits, filling
  the high bits with the high low bits that were rotated.

  This function rotates the 64-bit value Operand to the right by Count bits.
  The high Count bits are fill with the low Count bits of Operand. The rotated
  value is returned.

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

  @return Operand >>> Count

**/
UINT64
EFIAPI
InternalMathRRotU64 (
  IN      UINT64  Operand,
  IN      UINTN   Count
  )
{
  _asm {
    mov     cl, byte ptr [Count]
    mov     eax, dword ptr [Operand + 0]
    mov     edx, dword ptr [Operand + 4]
    shrd    ebx, eax, cl
    shrd    eax, edx, cl
    rol     ebx, cl
    shrd    edx, ebx, cl
    test    cl, 32                      // Count >= 32?
    jz      L0
    mov     ecx, eax
    mov     eax, edx
    mov     edx, ecx
L0:
  }
}