The Analytical Software Design (ASD) method of the company Verum has been designed to reduce the number of errors in embedded software. However, it does not take performance issues into account, which can also have a major impact on the duration of software development. This paper presents a discrete-event simulator for the performance evaluation of ASD-structured software as well as a compositional numerical analysis method using fixed-point iteration and phase-type distribution fitting. Whereas the numerical analysis is highly accurate for non-interfering tasks, its accuracy degrades when tasks run in opposite directions through interdependent software blocks and the utilization increases. A thorough validation identifies the underlying problems when analyzing the performance of embedded software.