MdePkg/Library/BaseLib/Ia32/LShiftU64.c

   1 /** @file
   2   64-bit left 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   Shifts a 64-bit integer left between 0 and 63 bits. The low bits
  11   are filled with zeros. The shifted value is returned.
  12
  13   This function shifts the 64-bit value Operand to the left by Count bits. The
  14   low Count bits are set to zero. The shifted value is returned.
  15
  16   @param  Operand The 64-bit operand to shift left.
  17   @param  Count   The number of bits to shift left.
  18
  19   @return Operand << Count
  20
  21 **/
  22 UINT64
  23 EFIAPI
  24 InternalMathLShiftU64 (
  25   IN      UINT64  Operand,
  26   IN      UINTN   Count
  27   )
  28 {
  29   _asm {
  30     mov     cl, byte ptr [Count]
  31     xor     eax, eax
  32     mov     edx, dword ptr [Operand + 0]
  33     test    cl, 32                      // Count >= 32?
  34     jnz     L0
  35     mov     eax, edx
  36     mov     edx, dword ptr [Operand + 4]
  37 L0:
  38     shld    edx, eax, cl
  39     shl     eax, cl
  40   }
  41 }