Generic control flow reconstruction from assembly code

Processors used in embedded systems are usually characterized by specialized irregular hardware architectures for which traditional code generation and optimization techniques fail. Especially for these types of processors the Propan system has been developed that enables high-quality machine-dependent postpass optimizers to be generated from a concise hardware specification. Optimizing code transformations as featured by Propan require the control flow graph of the input program to be known. The control flow reconstruction algorithm is generic, i.e. machine-independent, and automatically derives the required hardware-specific knowledge from the machine specification. The reconstruction is based on an extended program slicing mechanism and is tailored to assembly programs. It has been retargeted to assembly programs of two contemporary microprocessors, the Analog Devices SHARC and the Philips TriMedia TM1000. Experimental results show that the assembly-based slicing enables the control flow graph of large assembly programs to be constructed in short time. Our experiments also demonstrate that the hardware design significantly influences the precision of the control flow reconstruction and the required computation time.