MdePkg/BaseLib: Support IA32 processors without CMOVx

[mirror_edk2.git] / MdePkg / Library / BaseLib / Ia32 / RShiftU64.c

/** @file\r
  64-bit logical right shift function for IA-32\r
\r
  Copyright (c) 2006 - 2015, Intel Corporation. All rights reserved.<BR>\r
  This program and the accompanying materials\r
  are licensed and made available under the terms and conditions of the BSD License\r
  which accompanies this distribution.  The full text of the license may be found at\r
  http://opensource.org/licenses/bsd-license.php.\r
\r
  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
\r
**/\r
\r
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/**\r
  Shifts a 64-bit integer right between 0 and 63 bits. This high bits\r
  are filled with zeros. The shifted value is returned.\r
\r
  This function shifts the 64-bit value Operand to the right by Count bits. The\r
  high Count bits are set to zero. The shifted value is returned.\r
\r
  @param  Operand The 64-bit operand to shift right.\r
  @param  Count   The number of bits to shift right.\r
\r
  @return Operand >> Count\r
\r
**/\r
UINT64\r
EFIAPI\r
InternalMathRShiftU64 (\r
  IN      UINT64                    Operand,\r
  IN      UINTN                     Count\r
  )\r
{\r
  _asm {\r
    mov     cl, byte ptr [Count]\r
    xor     edx, edx\r
    mov     eax, dword ptr [Operand + 4]\r
    test    cl, 32\r
    jnz     L0\r
    mov     edx, eax\r
    mov     eax, dword ptr [Operand + 0]\r
L0:\r
    shrd    eax, edx, cl\r
    shr     edx, cl\r
  }\r
}\r
\r