__mulh
Microsoft Specific
Returns the high 64 bits of the product of two 64-bit signed integers.
__int64 __mulh( __int64 a, __int64 b );
// 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
