Complete worst-case execution time analysis of straight-line hard real-time programs

In this article, the problem of finding a tight estimate on the worst-case execution time (WCET) of a hard real-time program is addressed. The analysis is focused on straightline code (without loops and recursive function calls) which is quite commonly found in synthesised code for embedded systems. A comprehensive timing analysis system covering both low-level (assembler instruction level) as well as high-level aspects (programming language level) is presented. The low-level analysis covers all speed-up mechanisms used for modern superscalar processors: pipelining, instruction-level parallelism and caching. The high-level analysis uses the results from the low-level to compute the final estimate on the WCET. This is done by a heuristic for searching the longest really executable path in the control flow, based on the functional dependencies between various program parts.