MdePkg/Library/BaseLib/Ia32/RRotU64.c

   1 /** @file
   2   64-bit right rotation for Ia32
   3
   4   Copyright (c) 2006 - 2007, Intel Corporation<BR>
   5   All rights reserved. This program and the accompanying materials
   6   are licensed and made available under the terms and conditions of the BSD License
   7   which accompanies this distribution.  The full text of the license may be found at
   8   http://opensource.org/licenses/bsd-license.php
   9
  10   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13 **/
  14
  15
  16
  17
  18 /**
  19   Rotates a 64-bit integer right between 0 and 63 bits, filling
  20   the high bits with the high low bits that were rotated.
  21
  22   This function rotates the 64-bit value Operand to the right by Count bits.
  23   The high Count bits are fill with the low Count bits of Operand. The rotated
  24   value is returned.
  25
  26   @param  Operand The 64-bit operand to rotate right.
  27   @param  Count   The number of bits to rotate right.
  28
  29   @return Operand >>> Count
  30
  31 **/
  32 UINT64
  33 EFIAPI
  34 InternalMathRRotU64 (
  35   IN      UINT64                    Operand,
  36   IN      UINTN                     Count
  37   )
  38 {
  39   _asm {
  40     mov     cl, byte ptr [Count]
  41     mov     eax, dword ptr [Operand + 0]
  42     mov     edx, dword ptr [Operand + 4]
  43     shrd    ebx, eax, cl
  44     shrd    eax, edx, cl
  45     rol     ebx, cl
  46     shrd    edx, ebx, cl
  47     test    cl, 32                      // Count >= 32?
  48     cmovnz  ecx, eax
  49     cmovnz  eax, edx
  50     cmovnz  edx, ecx
  51   }
  52 }
  53