A retargetable technique for predicting execution time of code segments

Abstract

Predicting the execution times of straight-line code sequences is a fundamental problem in the design and evaluation of hard real-time systems. The reliability of system-level timings and schedulability analysis rests on the accuracy of execution time predictions for the basic schedulable units of work. Obtaining such predictions for contemporary microprocessors is difficult. This paper presents a new technique called micro-analysis for predicting point-to-point execution times on code segments. It uses machine-description rules, similar to those that have proven useful for code generation and peephole optimization, to translate compiled object code into a sequence of very low-level (micro) instructions. The stream of micro-instructions is then analyzed for timing, via a three-level pattern matching scheme. At this low level, the effect of advanced features such as instruction caching and overlap can be taken into account. This technique is compiler and language-independent, and retargetable. This paper also describes a prototype system in which the micro-analysis technique is integrated with an existing C compiler. This system predicts the bounded execution time of statement ranges or simple (non-nested) C functions at compile time.