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Static WCET Analysis based on Abstract Interpretation and Counting of Elements
Publication Type:
Licentiate Thesis
Publisher:
Mälardalen University Press
Abstract
In a real-time system, it is crucial to ensure that all tasks of the system hold
their deadlines. A missed deadline in a real-time system means that the system
has not been able to function correctly. If the system is safety critical, this can
lead to disaster. To ensure that all tasks keep their deadlines, the Worst-Case
Execution Time (WCET) of these tasks has to be known. This can be done by
measuring the execution times of a task, however, this is inflexible, time consuming
and in general not safe (i.e., the worst-casemight not be found). Unless
the task is measured with all possible input combinations and configurations,
which is in most cases out of the question, there is no way to guarantee that the
longest measured time actually corresponds to the real worst case.
Static analysis analyses a safe model of the hardware together with the
source or object code of a program to derive an estimate of theWCET. This estimate
is guaranteed to be equal to or greater than the real WCET. This is done
by making calculations which in all steps make sure that the time is exactly
or conservatively estimated. In many cases, however, the execution time of a
task or a program is highly dependent on the given input. Thus, the estimated
worst case may correspond to some input or configuration which is rarely (or
never) used in practice. For such systems, where execution time is highly input
dependent, a more accurate timing analysis which take input into consideration
is desired.
In this thesis we present a framework based on abstract interpretation and
counting of possible semantic states of a program. This is a general method
of WCET analysis, which is language independent and platform independent.
The two main applications of this framework are a loop bound analysis and a
parametric analysis. The loop bound analysis can be used to quickly find upper
bounds for loops in a program while the parametric framework provides an
input-dependent estimation of theWCET. The input-dependent estimation can
give much more accurate estimates if the input is known at run-time.
Bibtex
@misc{Bygde1789,
author = {Stefan Bygde},
title = {Static WCET Analysis based on Abstract Interpretation and Counting of Elements},
number = {115},
month = {March},
year = {2010},
publisher = {M{\"a}lardalen University Press},
url = {http://www.es.mdu.se/publications/1789-}
}
