In this note ‘linear combination’ means the sum of a constant and several products of a constant and an integer program index variable.
In early compilers ‘constant’ meant known at compile time; later it meant known at routine prolog time.
The critical math is that a linear combination of linear combinations is another linear combination and the constants of the latter are each, a sum of products of the constants from the input linear combinations.
All these products and sums can be done modulo 2<sup>n</sup> and the resulting linear combination, when computed and runtime, will be correct mod 2<sup>n</sup>.