MdePkg/Library/BaseLib/Ia32/LShiftU64.c

/** @file
  64-bit left shift function for IA-32.

  Copyright (c) 2006 - 2015, 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.

**/




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

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

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

  @return Operand << Count

**/
UINT64
EFIAPI
InternalMathLShiftU64 (
  IN      UINT64                    Operand,
  IN      UINTN                     Count
  )
{
  _asm {
    mov     cl, byte ptr [Count]
    xor     eax, eax
    mov     edx, dword ptr [Operand + 0]
    test    cl, 32                      // Count >= 32?
    jnz     L0
    mov     eax, edx
    mov     edx, dword ptr [Operand + 4]
L0:
    shld    edx, eax, cl
    shl     eax, cl
  }
}