Hybrid worst-case timing analysis

TimeWeaver combines static analysis with non-intrusive measurements to provide worst-case execution time estimates.

The tool estimates the worst-case execution time (WCET) of tasks based on the exe­cution time of trace segments obtained from real-time instruction-level tracing. The computed time bounds are valuable for soft real-time systems and provide feedback for optimizing worst-case performance.

Your benefits

• The hybrid approach works for a wide range of modern high-performance processors that are not predictable through static analysis alone. This includes multi-core processors where inter-core interferences cannot be prevented or controlled in a satisfactory way, as well as derivates insufficiently documented to build a static timing model.
• TimeWeaver is non-intrusive. It needs no code instrumentation that distorts timing measurements. It uses the embedded trace units of modern embedded processors (Nexus 5001, CoreSight ETM, etc.) to observe program flow. Interference effects included in the traces, such as access delays to shared resources, are taken into account. This approach is compliant with EASA AMC 20-193 and FAA AC 20-193.
• Thanks to the static analysis of paths, loops, and values, TimeWeaver frees you from the burden of manually identifying and stimulating the overall worst-case path.

Workflow

TimeWeaver takes as input:

1. a binary executable
2. execution traces,
   e.g. BHM traces compliant to the IEEE-ISTO 5001 standard
3. optional user annotations,
   e.g. on loop bounds, in the same format as other AbsInt analyzers such as aiT or StackAnalyzer

TimeWeaver then provides an upper bound of the length of the longest execution path, based on the local time measurements in the traces.

Exceptional precision

The following table compares TimeWeaver results with maximum observed end-to-end times for a variety of benchmark applications executed on an NXP T1040 evaluation board and recorded with a Lauterbach PowerDebug Pro JTAG debugger.

Some of the benchmarks (e.g. edn, nestedDepLoops) consist only of a single path. For these, the delta reflects TimeWeaver’s ability to combine measurements of different hardware states.

Other benchmarks (notably, the avionics and automotive tasks) contain quite complex control flow. For these, the static path analysis is able to construct scenarios for which no single trace has been recorded.

Features

The analysis results reported by TimeWeaver include:

• global end-to-end time, based on the maximum observed trace segment times combined to an overall bound
• end-to-end bounds for specific functions, depending on trace points
• coverage of the control-flow graph by the input traces
• maximum possible and maximum observed iteration counts for loops
• time variance of each code segment over all traces

TimeWeaver offers the same powerful user interface you are used to from working with other AbsInt tools, with fully integrated graphical and textual viewers for control flow, analysis results, source code, assembly code, and configuration files. You can:

• interactively explore analysis results
• save, restore, and compare analysis scenarios
• export customizable reports for documentation and certification purposes
• start all analyses from the same GUI and handle all the tools with the same look and feel

Qualification support

Your usage of TimeWeaver can be qualified according to ISO 26262, DO-178B/C, and other safety standards. We offer special Qualification Support Kits that help you simplify and automate your qualification process.

Supported targets

TimeWeaver is available for a growing variety of processors, compilers, and trace formats.

Free 30-day trial

Request your free trial package today, complete with free training and support.