/*++

Copyright (c) 2006, 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.             

Module Name:

  LShiftU64.c

Abstract:

  64-bit left shift function for IA-32

--*/

#include "Tiano.h"

UINT64
LShiftU64 (
  IN UINT64   Operand,
  IN UINTN    Count
  )
/*++

Routine Description:
 
  This routine allows a 64 bit value to be left shifted by 32 bits and 
  returns the shifted value.
  Count is valid up 63. (Only Bits 0-5 is valid for Count)

Arguments:

  Operand - Value to be shifted
  Count   - Number of times to shift left.
  
Returns:

  Value shifted left identified by the Count.

--*/
{
  __asm {
  
    mov    eax, dword ptr Operand[0]
    mov    edx, dword ptr Operand[4]
  
    ;
    ; CL is valid from 0 - 31. shld will move EDX:EAX by CL times but EAX is not touched
    ; For CL of 32 - 63, it will be shifted 0 - 31 so we will move eax to edx later. 
    ;
    mov    ecx, Count
    and    ecx, 63
    shld   edx, eax, cl
    shl    eax, cl
  
    ;
    ; Since Count is 32 - 63, eax will have been shifted  by 0 - 31                                                     
    ; If shifted by 32 or more, set lower 32 bits to zero.
    ;
    cmp    ecx, 32
    jc     short _LShiftU64_Done
  
    mov    edx, eax
    xor    eax, eax

_LShiftU64_Done:
  }
}
