As the use of embedded processors has spread throughout the society pervasively, the requirements for the processors have become much more diverse causing general purpose processors to be inefficient on many occasions. This creates the need for customized processors that are tailored for a particular use case. Transport triggered architecture is a processor architecture template that exploits the instruction level parallelism. The architecture provides the basic building blocks and means to construct custom tailored processors. Transport triggered architecture processors are statically scheduled, thus powerful instruction scheduling algorithms can bring up significant efficiency increases in terms of chip area, clock frequency, and energy consumption.
This thesis proposes an integer linear programming model for the instruction scheduling problem of the transport triggered architecture. The model describes the architecture characteristics, the particular processor resource constraints, and the operation dependencies of the scheduled program. It is possible to optimize the model for various criterion, for example to achieve as energy efficient processors as possible. This scheduling algorithm was implemented to the high-level language compiler of the TTA-based Co-design Environment, which is a toolset for designing processors using the transport triggered architecture template. The model was tested and measured with example problems such as complex number arithmetics, and vector dot product. Such example algorithms are typically executed in embedded processors and parallelize reasonably well. The performance results were compared to the existing heuristic graph-based scheduling algorithm of the toolset compiler.
The study indicates that the integer linear programming based instruction scheduler produced significantly shorter schedules compared to the heuristic scheduler. In addition, the amount of register access in the compiled programs was generally notably less than those of the heuristic scheduler. On the other hand, the proposed scheduler used distinctly more execution time than the heuristic scheduler
