_ _UMULH Intrinsic (Unsigned Quadword Multiply High)

The _ _UMULH intrinsic has the following declaration:

uint64 __UMULH( uint64 operand1, uint64 operand2 );

This intrinsic function multiplies the two operands as unsigned numbers to produce a 128-bit result. The high-order 64 bits of the result are returned.