MdePkg/Library/BaseLib/Ia32/RRotU64.c

   1 /** @file
   2   64-bit right rotation for Ia32
   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   Rotates a 64-bit integer right between 0 and 63 bits, filling
  11   the high bits with the high low bits that were rotated.
  12
  13   This function rotates the 64-bit value Operand to the right by Count bits.
  14   The high Count bits are fill with the low Count bits of Operand. The rotated
  15   value is returned.
  16
  17   @param  Operand The 64-bit operand to rotate right.
  18   @param  Count   The number of bits to rotate right.
  19
  20   @return Operand >>> Count
  21
  22 **/
  23 UINT64
  24 EFIAPI
  25 InternalMathRRotU64 (
  26   IN      UINT64  Operand,
  27   IN      UINTN   Count
  28   )
  29 {
  30   _asm {
  31     mov     cl, byte ptr [Count]
  32     mov     eax, dword ptr [Operand + 0]
  33     mov     edx, dword ptr [Operand + 4]
  34     shrd    ebx, eax, cl
  35     shrd    eax, edx, cl
  36     rol     ebx, cl
  37     shrd    edx, ebx, cl
  38     test    cl, 32                      // Count >= 32?
  39     jz      L0
  40     mov     ecx, eax
  41     mov     eax, edx
  42     mov     edx, ecx
  43 L0:
  44   }
  45 }