EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/MultU64x32.c

   1 /*++
   2
   3 Copyright (c) 2006, Intel Corporation
   4 All rights reserved. This program and the accompanying materials
   5 are licensed and made available under the terms and conditions of the BSD License
   6 which accompanies this distribution.  The full text of the license may be found at
   7 http://opensource.org/licenses/bsd-license.php
   8
   9 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  10 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  11
  12 Module Name:
  13
  14    MultU64x32.c
  15
  16 Abstract:
  17
  18   64-bit Multiplication function for IA-32
  19
  20 --*/
  21
  22 #include "Tiano.h"
  23
  24 UINT64
  25 MultU64x32 (
  26   IN UINT64   Multiplicand,
  27   IN UINTN    Multiplier
  28   )
  29 /*++
  30
  31 Routine Description:
  32
  33   This routine allows a 64 bit value to be multiplied with a 32 bit
  34   value returns 64bit result.
  35   No checking if the result is greater than 64bits
  36
  37 Arguments:
  38
  39   Multiplicand  - multiplicand
  40   Multiplier    - multiplier
  41
  42 Returns:
  43
  44   Multiplicand * Multiplier
  45
  46 --*/
  47 {
  48   __asm {
  49     mov    eax, dword ptr Multiplicand[0]
  50     mul    Multiplier
  51     push   eax
  52     push   edx
  53     mov    eax, dword ptr Multiplicand[4]
  54     mul    Multiplier
  55     ;
  56     ; The value in edx stored by second multiplication overflows
  57     ; the output and should be discarded. So here we overwrite it
  58     ; with the edx value of first multiplication.
  59     ;
  60     pop    edx
  61     add    edx, eax
  62     pop    eax
  63   }
  64 }