Expansion of multiplication and division refers to bit shifts that allow faster multiplication and division while producing the same result. For example, the integer expression (I*17) can be calculated as I with a 4-bit shift plus the original value of I. This can be expressed using the Compaq Fortran ISHFT intrinsic function:
J1 = I*17
J2 = ISHFT(I,4) + I ! equivalent expression for I*17
The optimizer uses machine code that, like the ISHFT intrinsic function, shifts bits to expand multiplication and division by literals.