mulh.md

description	title	ms.date	f1_keywords	helpviewer_keywords	ms.assetid
Learn more about: __mulh	__mulh	09/02/2019	__mulh	__mulh intrinsic	cd2ab093-9ef6-404d-ac34-0bee033882f3

__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

a
[in] The first number to multiply.

b
[in] 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

END Microsoft Specific

See also

Compiler intrinsics