Source : Free On-Line Dictionary of Computing

constant folding
     
         A {compiler} {optimisation} technique where
        constant subexpressions are evaluated at {compile time}.  This
        is usually only applied to built-in numerical and {boolean}
        operators whereas {partial evaluation} is more general in that
        expressions involving user-defined functions may also be
        evaluated at compile time.
     
        (1997-02-20)