__mul128
Microsoft Specific
Multiplies two 64-bit integers passed in as the first two arguments and puts the high 64 bits of the product in the 64-bit integer pointed to by HighProduct and returns the low 64 bits of the product.
__int64 _mul128( __int64 Multiplier, __int64 Multiplicand, __int64 *HighProduct );
// mul128.c
// processor: IPF, x64
#include <stdio.h>
#include <intrin.h>
#pragma intrinsic(_mul128)
int main()
{
__int64 a = 0x0fffffffffffffffI64;
__int64 b = 0xf0000000I64;
__int64 c, d;
d = _mul128(a, b, &c);
printf_s("%#I64x * %#I64x = %#I64x%I64x\n", a, b, c, d);
}
0xfffffffffffffff * 0xf0000000 = 0xeffffffffffffff10000000
