Case Study: How an Automotive Supplier Added WCET Checks to Prevent Regressions

Hook: Why timing regressions are your next certification risk

Late-stage timing regressions are one of the most painful, costly failures a supplier can face during ISO 26262 certification. Teams discover them after integration, debug stalls for weeks, and auditors demand evidence that the worst-case execution time (WCET) requirements are met for safety-critical functions. In 2026, with Vector's acquisition of StatInf's RocqStat technology and the announced VectorCAST integration, automotive suppliers must move from ad hoc timing checks to automated, traceable WCET gates in the toolchain.

Executive summary: What this templated case study shows

This is a hypothetical, practical case study (template-style) showing how an automotive supplier added RocqStat-like timing analysis into their existing toolchain to: prevent timing regressions, satisfy certification traceability, and keep CI fast and deterministic. You will get a stepwise plan, CI integration examples (GitLab/GitHub Actions/Jenkins), reporting templates, and a certification checklist aligned with 2026 industry trends.

Context: why now (2025–2026 trends)

Key trends driving this integration:

• Consolidation of timing-analysis technology into mainstream toolchains — exemplified by Vector's January 2026 move to bring RocqStat capabilities into VectorCAST — means teams can expect closer coupling between testing and timing verification.
• Automotive software complexity continues to rise with software-defined vehicles and multimodal compute, increasing the chance of unexpected timing regressions.
• Regulators and OEMs now expect continuous evidence that timing constraints are preserved across releases; manual WCET analysis during late-stage verification is no longer sufficient.

Hypothetical supplier profile

For this template we assume a Tier-1 automotive supplier with:

• Embedded C/C++ codebase (~300k SLOC), distributed across 40 modules
• Existing VectorCAST-based unit and integration test flows
• CI platform: GitLab CI (with Jenkins for nightly runs)
• Target processors: AUTOSAR-capable MCUs, single- and dual-core variants
• Certification target: ISO 26262 ASIL B/C for several ECUs

High-level approach (what we added)

1. Pick a RocqStat-like WCET analyzer and qualify it for tool-assurance workflows.
2. Establish per-module WCET baselines and safety margins.
3. Automate WCET checks as CI gates for every merge request and nightly full-suite runs.
4. Use change-impact analysis to limit WCET runs to affected modules for fast feedback.
5. Store machine-readable WCET artifacts and trace them to requirements for certification evidence.

Step 0 — Preparation and risk assessment

Before you touch CI, do the following:

• Tool selection: Evaluate static WCET analysis vs. measurement-based tools. RocqStat-like static analyzers provide conservative bounds useful for certification.
• Tool classification: Decide tool qualification level per ISO 26262: T1/T2/T3 depending on how the analyzer affects safety.
• Training: Upskill your verification engineers on control-flow analysis, loop bounds, and microarchitectural modeling.
• Baseline plan: Select representative modules for the initial PoC (e.g., scheduler, braking logic, communication stacks).

Step 1 — Proof-of-Concept (PoC)

Run the analyzer on 3–5 critical modules and validate results against hardware measurements:

• Instrumented runs on target hardware provide execution-time samples; static analyzer produces conservative WCET bounds.
• Compare static WCET to measured max-plus margin to calibrate microarchitectural parameters (cache, pipelines).
• Log discrepancies and resolve modeling gaps (e.g., missing interrupt models or peripheral timing).

Practical PoC commands (hypothetical)

# Run static WCET analyzer (RocqStat-like)
wcet-analyzer --input build/moduleA.elf \
             --cfg build/moduleA.cfg \
             --platform-target mcu_family_X \
             --output reports/moduleA-wcet.json

# Run hardware-in-loop measurement (sample)
run-hw-measure --target hw1 --binary build/moduleA.elf --log reports/moduleA-meas.csv

Step 2 — Baseline, margins and thresholds

Create the official baseline dataset. For each module record:

• Baseline WCET (static analysis)
• Measured max execution time
• Safety margin (e.g., 20–50% depending on ASIL and uncertainty)
• Certification threshold = baseline + safety margin

Example policy: For ASIL C functions use a minimum safety margin of 25%. For code with high microarchitectural uncertainty (e.g., heavy I/O or interrupts), increase margin to 40%.

Step 3 — CI integration: fast, deterministic gating

The goal: fail MRs that introduce WCET increases beyond thresholds. Implement two CI layers:

• Fast MR check — run impact-limited analysis on changed modules, quick static run, strict threshold.
• Nightly full check — run comprehensive analysis for all modules and regenerate baselines if needed.

GitLab CI example (simplified)

stages:
  - build
  - wcet-check

build:
  script:
    - make all

wcet-mr-check:
  stage: wcet-check
  script:
    - ./scripts/affected_modules.sh $CI_COMMIT_SHA > affected.txt
    - for mod in $(cat affected.txt); do \
        wcet-analyzer --input build/$mod.elf --output reports/$mod-wcet.json || exit 2; \
        python3 scripts/compare_wcet.py reports/$mod-wcet.json baselines/$mod-baseline.json || exit 3; \
      done
  only:
    - merge_requests

wcet-nightly:
  stage: wcet-check
  script:
    - ./scripts/run_full_wcet.sh
  only:
    - schedules

In this example, compare_wcet.py returns non-zero if the new WCET exceeds the certified threshold and thus blocks the MR.

compare_wcet.py (conceptual)

import json
import sys

new = json.load(open(sys.argv[1]))
baseline = json.load(open(sys.argv[2]))

if new['wcet_cycles'] > baseline['threshold_cycles']:
    print('WCET regression detected')
    sys.exit(1)
else:
    print('OK')
    sys.exit(0)

Step 4 — Make CI runs efficient

WCET analysis can be expensive. Use these optimizations:

• Change-impact analysis: only analyze modules that changed or depend on changed modules.
• Cached microarchitectural models: reuse validated platform models across runs.
• Parallelize per-module analysis in the CI runner farm.
• Incremental analysis: if the analyzer supports it, reuse prior results and only re-analyze changed functions.

Step 5 — Reporting, traceability and auditor evidence

Certification requires traceable artifacts. Store machine-readable reports and link them to requirements and test cases.

Suggested JSON report schema (machine friendly)

{
  "module": "brake_controller",
  "version": "1.2.7",
  "wcet_cycles": 123456,
  "wcet_ms": 5.12,
  "threshold_ms": 6.4,
  "analysis_tool": "rocqstat-like-1.0.0",
  "platform_model": "mcu_family_X-v2",
  "timestamp": "2026-01-10T12:34:56Z",
  "evidence": {
    "measurement_log": "reports/brake_controller-meas.csv",
    "config": "build/brake_controller.cfg"
  }
}

Link each report to the requirement ID (req-123) in your ALM system. For auditors, provide: tool qualification artifacts, analysis configuration, baselines, and run hashes.

Step 6 — Tool qualification and certification workflow

ISO 26262 expects you to justify tool impact and confidence. Practical items you need:

• Tool classification: document how the WCET analyzer impacts safety and the evidence required.
• Qualification kit: maintain tool version, configuration, installation record, and verification runbooks.
• Deterministic builds: pin compilers, linker scripts, and tool versions; archive build artifacts.
• Traceability: map WCET results to requirements and test cases — store in ALM.

"Timing safety is becoming a critical ..." — Eric Barton, Vector (context: Vector's 2026 acquisition of RocqStat capabilities)

Step 7 — Hardware, multi-core and microarchitectural reality

Static WCET analysis must model complex hardware effects: caches, pipelines, shared buses, and interrupts. For multicore systems, absolute WCET composability is challenging. Recommended practices:

• Use time-partitioning and run-to-completion semantics where possible.
• Model cross-core interference conservatively or bound it via system-level WCET composition.
• Combine static analysis with targeted measurements (hybrid approach) for parts of the system where modeling is uncertain.

Step 8 — Prevent regressions: policy and cultural changes

Tooling alone won’t stop regressions. Add these organizational controls:

• WCET ownership: assign module-level owners responsible for timing budgets.
• Pre-merge checklists: every MR modifying critical code must include WCET analysis results or a justification comment.
• Performance KPIs: monitor average WCET drift and number of blocked MRs to detect process issues.
• Training & feedback: share examples of regressions and root-cause analyses in retrospectives.

Example: MR workflow that blocks on WCET

1. Developer opens MR modifying path planning logic.
2. CI triggers impact-limited WCET run for affected modules.
3. If WCET > threshold, pipeline fails and MR is blocked with a report link.
4. Developer optimizes or provides a safety rationale; reviewer approves post-fix.

Metrics & hypothetical outcomes (sample results)

After six months of integration a supplier reports (hypothetical):

• MR-feedback latency for timing regressions reduced from ~3 days to <30 minutes (fast-checks plus MR automations).
• Number of late-stage integration WCET issues dropped by 70%.
• Audit time to collect timing evidence reduced by 60% because reports are machine-readable and traceable.

Advanced strategies & 2026 forward-looking tactics

Looking ahead to late 2026 and beyond, consider:

• Tight VectorCAST + RocqStat integration: expect more unified workflows as Vector folds RocqStat-like timing analysis into test toolchains; plan for richer test-to-timing traceability.
• Cloud-assisted analysis: offload heavy WCET runs to secure build farms with certified hardware profiles for faster turnaround.
• ML-assisted impact prediction: use lightweight models to predict likely WCET regressions before running full analysis and prioritize runs.
• Standardized artifacts: push for or adopt industry-wide WCET report formats to ease OEM/auditor exchanges.

Actionable checklist (downloadable template ready)

• Choose a certified/static WCET analyzer and create a tool qualification plan.
• Define baseline modules and run a PoC comparing static WCET to measurements.
• Set per-module thresholds with safety margins based on ASIL and uncertainty.
• Implement MR-gating CI that runs impact-limited WCET checks.
• Store machine-readable WCET reports and link them to requirements in ALM.
• Document deterministic build and toolchain versioning for auditor evidence.
• Monitor KPIs and hold timing-focused retrospectives quarterly.

Template artifacts included in this case study

• GitLab CI sample job for MR-checks (see above)
• Minimal compare_wcet.py comparator (conceptual)
• JSON result schema for WCET reports
• Certification evidence checklist aligned to ISO 26262 tool qualification

Common pitfalls and how to avoid them

• Pitfall: Running full WCET on every MR — this stalls development.
  Fix: use change-impact analysis and incremental runs.
• Pitfall: Poor baseline hygiene — thresholds drift and become meaningless.
  Fix: freeze baselines for each release, version them, and require formal re-baselining processes.
• Pitfall: Lack of ties between timing results and requirements.
  Fix: enforce traceability in ALM and include report links in requirement evidence.

Conclusion: timing safety as a continuous verification practice

Integrating a RocqStat-like WCET analyzer into your automotive toolchain is not a one-off task — it is a shift to continuous timing verification. By combining baseline-driven thresholds, CI gating, efficient impact analysis, and auditable artifacts, suppliers can detect and prevent regressions early, speed up certification evidence collection, and reduce late-stage rework.

Next steps & call-to-action

If you’re preparing for ISO 26262 audits or want to add WCET gates to your VectorCAST workflows, start with our downloadable checklist and CI templates. Contact our engineering team to get a tailored integration plan for your stack — we help map your modules, set baselines, and automate WCET gates so you pass certification with confidence.

Download the WCET integration template and checklist or request a 1:1 workshop: contact@upfiles.cloud

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