multu64x32.c

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/*++

Copyright (c) 2006, Intel Corporation                                                         
All rights reserved. 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:

   MultU64x32.c

Abstract:

  64-bit Multiplication function for IA-32

--*/

#include "Tiano.h"

UINT64
MultU64x32 (
  IN UINT64   Multiplicand,
  IN UINTN    Multiplier
  )
/*++

Routine Description:

  This routine allows a 64 bit value to be multiplied with a 32 bit 
  value returns 64bit result.
  No checking if the result is greater than 64bits

Arguments:

  Multiplicand  - multiplicand
  Multiplier    - multiplier

Returns:

  Multiplicand * Multiplier

--*/
{
  __asm {
    mov    eax, dword ptr Multiplicand[0]
    mul    Multiplier
    push   eax
    push   edx
    mov    eax, dword ptr Multiplicand[4]
    mul    Multiplier
    ;
    ; The value in edx stored by second multiplication overflows
    ; the output and should be discarded. So here we overwrite it
    ; with the edx value of first multiplication.
    ;
    pop    edx
    add    edx, eax
    pop    eax
  }
}