Add SCF support to WireIterator

[MatthiasReumann]

Changes

✨Add SCF op switch cases in WireIterator.cpp and add unit tests

(Extracted from #1805 to decrease that PR size and ease reviewing)

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.

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• I have disclosed the use of AI tools in the PR description as per our AI Usage Guidelines.
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[codecov]

Codecov Report

❌ Patch coverage is 92.68293% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
mlir/lib/Dialect/QCO/Utils/WireIterator.cpp	92.3%	3 Missing ⚠️

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[MatthiasReumann]

@coderabbitai full review

[coderabbitai]

✅ Action performed

Full review finished.

[coderabbitai]

📝 Walkthrough

Walkthrough

WireIterator gains a isFinal_ state flag and two static helpers (isSinkLikeOperation, isSourceLikeOperation) to centralize boundary detection. forward() and backward() are refactored to use these helpers and to map tied results for scf::ForOp, scf::WhileOp, and qco::IfOp via TypeSwitch. Unit tests are updated with an SCF-based circuit and a new block-argument traversal subtest.

Changes

WireIterator SCF traversal refactor

Layer / File(s)	Summary
WireIterator header: isFinal_ flag and helper declarations mlir/include/mlir/Dialect/QCO/Utils/WireIterator.h	Adds mlir/IR/Value.h include, initializes isFinal_ = false in both constructors, and extends the private section with isSinkLikeOperation/isSourceLikeOperation static declarations and the bool isFinal_ data member.
WireIterator implementation: helpers, forward, and backward mlir/lib/Dialect/QCO/Utils/WireIterator.cpp	Introduces isSinkLikeOperation and isSourceLikeOperation; updates qubit() to use the former; reworks forward() so the sink-like boundary sets isFinal_ (not isSentinel_) and the next step promotes to sentinel, with a TypeSwitch for scf::ForOp/scf::WhileOp/qco::IfOp tied results; reworks backward() with symmetric sentinel→isFinal_ transition, isSinkLikeOperation-based detection, the same TypeSwitch for tied-init operand resolution, fatal error paths, and isFinal_ = false reset.
Unit tests: SCF circuit and block-argument traversal mlir/unittests/Dialect/QCO/Utils/test_wireiterator.cpp	Adds SCF headers and scf::SCFDialect; replaces the flat test circuit with an scf.for + qco.if qubit-carrying circuit and updates forward/backward traversal assertions; adds a new subtest verifying iteration from a loop block argument through internal ops, scf.yield, sentinel, and reverse.
CHANGELOG: reference PR #1806 CHANGELOG.md	Adds #1806 to the Unreleased/Added dialect infrastructure bullet and its link definition.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• munich-quantum-toolkit/core#1510: Introduced the mlir::qco::WireIterator class and its initial test_wireiterator.cpp; this PR directly extends that implementation.
• munich-quantum-toolkit/core#1569: Modified WireIterator terminal-operation handling (switching from DeallocOp to SinkOp), overlapping the same boundary-detection code refactored here.
• munich-quantum-toolkit/core#1674: Updated forward()/backward() traversal and qubit() sentinel handling in WireIterator.cpp, directly adjacent to the changes in this PR.

Suggested reviewers

• burgholzer

Poem

🐇 Hop through the qubit wire with glee,
Past scf.for loops and qco.if — wheee!
isFinal_ marks where the wire must end,
Then backward we bounce around every bend.
No inline isa<> lists left to dread,
Clean helper methods lead forward instead! 🎉

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: adding SCF support to WireIterator, which aligns with all the substantive changes in the PR.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	PR provides a clear summary of changes and completes all checklist items, though some sections lack detail.

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✨ Finishing Touches

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch enh/wire-iterator-scf-ops

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@mlir/lib/Dialect/QCO/Utils/WireIterator.cpp`:
- Around line 134-145: In the backward() method's qco::IfOp case, fix the mixed
iterator sources by replacing the llvm::find and std::distance calls with
getResults().begin() and getResults().end() to match the forward() method's
pattern for the same qco::IfOp case. Correct the assertion's result_end() call
from arrow notation (op->result_end()) to dot notation (op.result_end()) to
properly access the Operation members. Finally, update the error message in the
llvm::reportFatalInternalError call from "expected scf.for result for tied init
lookup" to reference qco.if instead of scf.for.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 8f75e50f-3377-4108-8602-ca040e5d2c9e

📥 Commits

Reviewing files that changed from the base of the PR and between 4065349 and 43b7539.

📒 Files selected for processing (4)

• CHANGELOG.md
• mlir/include/mlir/Dialect/QCO/Utils/WireIterator.h
• mlir/lib/Dialect/QCO/Utils/WireIterator.cpp
• mlir/unittests/Dialect/QCO/Utils/test_wireiterator.cpp