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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 __mulh.
Microsoft Specific**
Returns the high 64 bits of the product of two 64-bit signed integers.
Syntax
__int64 __mulh(
__int64 a,
__int64 b
);
Parameters
[in] a
The first number to multiply.
[in] b
The second number to multiply.
Return Value
The high 64 bits of the 128-bit result of the multiplication.
Requirements
| Intrinsic | Architecture |
|---|---|
__mulh |
x64 |
Header file <intrin.h>
Remarks
This routine is only available as an intrinsic.
Example
// mulh.cpp
// processor: x64
#include <stdio.h>
#include <intrin.h>
#pragma intrinsic (__mulh)
int main()
{
__int64 a = 0x0fffffffffffffffI64;
__int64 b = 0xf0000000I64;
__int64 result = __mulh(a, b); // the high 64 bits
__int64 result2 = a * b; // the low 64 bits
printf_s(" %#I64x * %#I64x = %#I64x%I64x\n",
a, b, result, result2);
}
0xfffffffffffffff * 0xf0000000 = 0xeffffffffffffff10000000