Automatic Derivation of Loop Bounds and Infeasible Paths for WCET Analysis Using Abstract Execution

Abstract

Static Worst-Case Execution Time (WCET) analysis is a technique to derive upper bounds for the execution times of programs. Such bounds are crucial when designing and verifying real-time systems. A key component for statically deriving safe and tight WCET bounds is information on the possible program flow through the program. Such flow information can be provided manually by user annotations, or automatically by a flow analysis. To make WCET analysis as simple and safe as possible, it should preferably be automatically derived, with no or very limited user interaction.In this paper we present a method for deriving such flow information called abstract execution. This method can automatically calculate loop bounds, bounds for including nested loops, as well as many types of infeasible paths. Our evaluations show that it can calculate WCET estimates automatically, without any user annotations, for a range of benchmark programs, and that our techniques for nested loops and infeasible paths sometimes can give substantially better WCET estimates than using loop bounds analysis only.

Approximate Worst-Case Execution Time Analysis for Early Stage Embedded Systems Development

“…We will also do the flow analysis on ALF, using SWEET's powerful flow analysis methods [23,24,25]. The result will be given as constraints on the number of times different basic blocks of the ALF code can be executed and edges of the control flow graph can be followed.…”

Towards Interactive Timing Analysis for Designing Reactive Systems

“…This includes, for instance, loop and infeasible paths analyses [7,8], cache analysis [9], and path enumeration techniques [10]. There exist several commercial tools, such as aiT 2 and Bound-T 3 , as well as academic implementations, such as SWEET 4 from Mälardalen University.…”

“…Although there exists a large body of work in the area of WCET analysis [7,8,9,10,11], surprisingly little has been done with interactive timing analsysis. Previous work addresses fast WCET analysis [12], interactive C code analysis [13], analysis of Java code [14] and timing analysis of Matlab/Simulink models [15].…”

Resource Sharing under Multiprocessor Semi-partitioned Scheduling

“…taskss possible execution flows, i.e., different execution paths in the code cause certain variations of executions for a typical task. Variations in the execution of a task can happen in terms of different input data, and software characteristics such as loop iterations, nested loops, infeasible paths, execution frequencies of code parts, etc [15,11,28]. As a general model of this behavior, it can be observed that the critical sections of tasks may happen at different times within the task execution.…”