  There exist several results on deciding termination and computing runtime
bounds for triangular weakly non-linear loops (twn-loops). We show how to use
results on such subclasses of programs where complexity bounds are computable
within incomplete approaches for complexity analysis of full integer programs.
To this end, we present a novel modular approach which computes local runtime
bounds for subprograms which can be transformed into twn-loops. These local
runtime bounds are then lifted to global runtime bounds for the whole program.
The power of our approach is shown by our implementation in the tool KoAT which
analyzes complexity of programs where all other state-of-the-art tools fail.
