🐛 Fix SSA Dominance Issues for Mapping Pass for Circuits With Barriers

[MatthiasReumann]

Description

This pull request fixes an issue which occurs when running the mapping pass on circuits using barriers.

Checklist

• The pull request only contains commits that are focused and relevant to this change.
• I have added appropriate tests that cover the new/changed functionality.
• I have updated the documentation to reflect these changes.
• I have added entries to the changelog for any noteworthy additions, changes, fixes, or removals.
• I have added migration instructions to the upgrade guide (if needed).
• The changes follow the project's style guidelines and introduce no new warnings.
• The changes are fully tested and pass the CI checks.
• I have reviewed my own code changes.

If PR contains AI-assisted content:

• I have disclosed the use of AI tools in the PR description as per our AI Usage Guidelines.
• AI-assisted commits include an Assisted-by: [Model Name] via [Tool Name] footer.
• I confirm that I have personally reviewed and understood all AI-generated content, and accept full responsibility for it.

[MatthiasReumann]

@coderabbitai full review

[coderabbitai]

✅ Actions performed

Full review triggered.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: af523fd0-64aa-418c-b7bb-cdb796c4e3d9

📥 Commits

Reviewing files that changed from the base of the PR and between 8d7cc71 and 65ee83d.

📒 Files selected for processing (3)

• CHANGELOG.md
• mlir/lib/Dialect/QCO/Transforms/Mapping/Mapping.cpp
• mlir/unittests/Dialect/QCO/Transforms/Mapping/test_mapping.cpp

---

📝 Walkthrough

Summary by CodeRabbit

Release Notes

• Bug Fixes

  • Improved handling of barrier operations in the place-and-route pass
  • Enhanced synchronization of multi-qubit gate advancement

• Tests

  • Updated mapping tests to include barrier and measurement operations in generated sequences

Walkthrough

Updates changelog with PR #1581 reference, refactors QCO mapping pass wire traversal logic to handle barrier operations, introduces synchronization tracking for multi-qubit gate advancement, and updates corresponding test cases with barrier and measurement operations.

Changes

Cohort / File(s)	Summary
Documentation CHANGELOG.md	Added PR reference [#1581] to the place-and-route pass unreleased entry and corresponding link definition.
Mapping Pass Implementation mlir/lib/Dialect/QCO/Transforms/Mapping/Mapping.cpp	Reintroduced TrialResult as a nested type, added SynchronizationMap helper for tracking operation iterators and refcounts, modified collectLayers wire traversal to explicitly handle BarrierOp, and updated commitTrial gate-advancement logic with ref-counted synchronization for multi-qubit operations.
Mapping Tests mlir/unittests/Dialect/QCO/Transforms/Mapping/test_mapping.cpp	Updated IR validation walk to skip BarrierOp nodes and modified TEST_P(MappingPassTest, Sabre) to insert barrier and explicit measurement operations before deallocation.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Possibly related PRs

• #1568 — Modifies mapping pass implementation and trial-related logic, including TrialResult and commit mechanics.

Suggested labels

fix

Suggested reviewers

• burgholzer
• ystade

Poem

🐰 A barrier rises in the mapping dance,
Synchronization gives the gates a chance!
Trials advance with careful count,
Wire by wire, the qubits mount. ⚛️

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 60.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main fix: SSA dominance issues for the mapping pass when circuits use barriers.
Description check	✅ Passed	The description is minimal but covers the core issue, provides checklist confirmation, and discloses AI usage per guidelines.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch bug/ssa-dominance-issues-mapping-pass-wireing

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[burgholzer]

This looks very clean. Just one brief comment. Feel free to ignore and merge.