emul, emulu

Visual Studio 2015

The new home for Visual Studio documentation is Visual Studio 2017 Documentation on docs.microsoft.com.

The latest version of this topic can be found at __emul, __emulu.

Microsoft Specific**

Performs multiplications that overflow what a 32-bit integer can hold.

Syntax

__int64 __emul(  
   int a,  
   int b  
);  
unsigned __int64 __emulu(  
   unsigned int a,  
   unsigned int b  
);

Parameters

[in] a
The first integer operand of the multiplication.

[in] b
The second integer operand of the multiplication.

Return Value

The result of the multiplication.

Requirements

Intrinsic	Architecture
`__emul`	x86, x64
`__emulu`	x86, x64

Header file <intrin.h>

Remarks

__emul takes two 32-bit signed values and returns the result of the multiplication as a 64-bit signed integer value.

__emulu takes two 32-bit unsigned integer values and returns the result of the multiplication as a 64-bit unsigned integer value.

Example

// emul.cpp  
// compile with: /EHsc  
// processor: x86, x64  
#include <iostream>  
#include <intrin.h>  
using namespace std;  
  
#pragma intrinsic(__emul)  
#pragma intrinsic(__emulu)  
  
int main()  
{  
   int a = -268435456;   
   int b = 2;   
  
   __int64 result = __emul(a, b);  
  
   cout << a << " * " << b << " = " << result << endl;  
  
   unsigned int ua = 0xFFFFFFFF; // Dec value: 4294967295  
   unsigned int ub = 0xF000000;  // Dec value: 251658240  
  
   unsigned __int64 uresult = __emulu(ua, ub);  
  
   cout << ua << " * " << ub << " = " << uresult << endl;  
  
}

Output

-268435456 * 2 = -536870912  
4294967295 * 251658240 = 1080863910317260800