✨ Enhance QCOProgramBuilder with tracked qubit and tensor structures by simon1hofmann · Pull Request #2017 · munich-quantum-toolkit/core

simon1hofmann · 2026-08-07T08:43:00Z

🤖 AI text below 🤖

Description

Replace DenseMap<Value, QubitInfo/TensorInfo> with DenseSet<Qubit/Tensor> keyed on the SSA Value, keeping register metadata on the handle itself.
Return thin Qubit handles from allocQubit() / staticQubit() (implicitly convertible to Value); add small getType() / getDefiningOp() forwards so common call sites stay ergonomic.
Leave gate / modifier / SCF APIs on Value / ValueRange.

Fixes #1628

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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- Introduced `Qubit` and `Tensor` structs to encapsulate SSA values along with their register information. - Updated methods `allocQubit` and `staticQubit` to return `Qubit` instances instead of raw `Value`. - Modified internal tracking of valid qubits and tensors to utilize `DenseSet` for improved management. - Enhanced unit tests to validate the new structures and their integration within the builder. * Updated CHANGELOG to reflect changes related to PR #2017.

codecov · 2026-08-07T08:59:48Z

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✅ All modified and coverable lines are covered by tests.

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simon1hofmann · 2026-08-07T10:01:28Z

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coderabbitai · 2026-08-07T10:01:36Z

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coderabbitai · 2026-08-07T10:04:16Z

📝 Walkthrough

Summary by CodeRabbit

New Features
- Improved quantum program building with tracked qubit and tensor metadata, including register identifiers and indices.
- Enhanced interoperability between tracked qubits and their underlying values.
- Improved qubit allocation, reuse validation, tensor lifecycle management, and finalization.
Tests
- Added coverage for tracked qubit conversions, metadata, reuse behavior, and operation integration.
- Updated index-switch and measurement-lifting tests for improved builder APIs.
Documentation
- Updated the unreleased changelog with the corresponding pull request reference.

Walkthrough

QCOProgramBuilder now returns tracked Qubit handles and stores qubit and tensor metadata in dense sets. Builder operations and tests use these wrappers across allocation, replacement, extraction, initialization, and finalization.

Changes

QCO tracking refactor

Layer / File(s)	Summary
Tracked wrapper contracts `mlir/include/mlir/Dialect/QCO/Builder/QCOProgramBuilder.h`	Added `Qubit` and `Tensor` wrappers. Allocation APIs now return tracked qubits. Dense sets replace metadata maps.
Builder tracking and finalization `mlir/lib/Dialect/QCO/Builder/QCOProgramBuilder.cpp`	Updated allocation, replacement, tensor creation, extraction, initialization, sinking, and finalization to preserve wrapper metadata.
API validation and release metadata `mlir/unittests/Dialect/QCO/IR/test_qco_ir.cpp`, `mlir/unittests/Dialect/QCO/Transforms/Optimizations/test_qco_measurement_lifting.cpp`, `CHANGELOG.md`	Updated tests for tracked-handle conversions and single-value APIs. Added the PR reference to the changelog.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Possibly related PRs

munich-quantum-toolkit/core#1627: Related to register-aware qubit tracking in QCOProgramBuilder.
munich-quantum-toolkit/core#1700: Related to QCO qubit tracking and insertion or extraction behavior.
munich-quantum-toolkit/core#1869: Related to single-qubit builder APIs used by the updated tests.

Suggested labels: refactor

Suggested reviewers: burgholzer, denialhaag

Poem

I’m a rabbit with qubits tucked tight,
Dense sets keep register IDs right.
Handles hop through each builder call,
Tensors remember their place through it all.
Tests confirm reuse stays controlled.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: adding tracked qubit and tensor structures to QCOProgramBuilder.
Description check	✅ Passed	The description includes the change summary, issue reference, checklist, tests, changelog, and AI disclosure details; only minor checklist items remain incomplete.
Linked Issues check	✅ Passed	The changes satisfy issue `#1628` by introducing Qubit and Tensor handles, replacing metadata maps with DenseSet tracking, and avoiding QubitRegister tracking.
Out of Scope Changes check	✅ Passed	The implementation, tests, and changelog updates directly support issue `#1628` and the stated QCOProgramBuilder API and tracking changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

✨ Simplify code

Create PR with simplified code
Commit simplified code in branch linear_tracking_helpers

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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/include/mlir/Dialect/QCO/Builder/QCOProgramBuilder.h`:
- Around line 173-206: Add Doxygen documentation to the public Qubit and Tensor
constructors, implicit Value conversion operators, getType(), and both
getDefiningOp() overloads. Describe the conversion direction and state that
getDefiningOp() may return a null operation when the value has no defining
operation; document both the non-templated and templated accessors consistently.

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📒 Files selected for processing (5)

CHANGELOG.md
mlir/include/mlir/Dialect/QCO/Builder/QCOProgramBuilder.h
mlir/lib/Dialect/QCO/Builder/QCOProgramBuilder.cpp
mlir/unittests/Dialect/QCO/IR/test_qco_ir.cpp
mlir/unittests/Dialect/QCO/Transforms/Optimizations/test_qco_measurement_lifting.cpp

…ed documentation

simon1hofmann · 2026-08-07T10:29:01Z

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coderabbitai · 2026-08-07T10:29:08Z

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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/include/mlir/Dialect/QCO/Builder/QCOProgramBuilder.h`:
- Around line 179-180: Make the Qubit(Value, int64_t, Value) constructor
explicit to prevent implicit Value-to-Qubit conversions from discarding regId
and regIndex. Preserve explicit assignment-from-Value behavior only in
intentional metadata-reset paths such as updateQubitTracking.

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mlir/include/mlir/Dialect/QCO/Builder/QCOProgramBuilder.h

simon1hofmann · 2026-08-07T11:30:57Z

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coderabbitai · 2026-08-07T11:31:03Z

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Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

mlir/lib/Dialect/QCO/Builder/QCOProgramBuilder.cpp (1)
242-250: 🩺 Stability & Availability | 🟠 Major | ⚡ Quick win

🤖 AI text below 🤖

Validate the tensor before dereferencing find.

checkQubitType checks the tensor type, but it does not verify tracking membership. If an untracked tensor reaches prepareInitArg, validTensors.find(initArg) returns end(), and ->regId dereferences an invalid iterator. Call validateTensorValue(initArg) before the lookup.
Suggested fix
   if (isa<QubitType>(initArg.getType())) {
     return initArg;
   }

+  validateTensorValue(initArg);
   const auto regId = validTensors.find(initArg)->regId;
🤖 Prompt for 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.

In `@mlir/lib/Dialect/QCO/Builder/QCOProgramBuilder.cpp` around lines 242 - 250,
In prepareInitArg, validate initArg with validateTensorValue before
dereferencing the validTensors.find(initArg) result. Preserve the existing
register-ID lookup and initialization flow after validation.

🤖 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.

Outside diff comments:
In `@mlir/lib/Dialect/QCO/Builder/QCOProgramBuilder.cpp`:
- Around line 242-250: In prepareInitArg, validate initArg with
validateTensorValue before dereferencing the validTensors.find(initArg) result.
Preserve the existing register-ID lookup and initialization flow after
validation.

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📒 Files selected for processing (3)

mlir/include/mlir/Dialect/QCO/Builder/QCOProgramBuilder.h
mlir/lib/Dialect/QCO/Builder/QCOProgramBuilder.cpp
mlir/unittests/Dialect/QCO/IR/test_qco_ir.cpp

…ntracked tensor initialization

denialhaag

Apart from the two small comments below, this LGTM! Thanks for the improvements to the QCOProgramBuilder, @simon1hofmann! 🙂

denialhaag · 2026-08-07T14:48:13Z

Just as a reminder for ourselves: Depending on which of #2014 and #2017 gets merged second, we can mark it as fixing #1614. 🎉

Co-authored-by: Daniel Haag <121057143+denialhaag@users.noreply.github.com> Signed-off-by: simon1hofmann <119581649+simon1hofmann@users.noreply.github.com>

simon1hofmann self-assigned this Aug 7, 2026

simon1hofmann added enhancement Improvement of existing feature c++ Anything related to C++ code MLIR Anything related to MLIR labels Aug 7, 2026

simon1hofmann added this to the MLIR Support milestone Aug 7, 2026

coderabbitai Bot requested changes Aug 7, 2026

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Comment thread mlir/include/mlir/Dialect/QCO/Builder/QCOProgramBuilder.h Outdated

📝 Expand Qubit and Tensor structures in QCOProgramBuilder with detail…

75970c6

…ed documentation

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Comment thread mlir/include/mlir/Dialect/QCO/Builder/QCOProgramBuilder.h Outdated

🐇 Address rabbit's comments

24c21b0

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✨ Validate tensor values in QCOProgramBuilder and add unit test for u…

718e3d7

…ntracked tensor initialization

simon1hofmann marked this pull request as ready for review August 7, 2026 12:32

simon1hofmann requested a review from denialhaag August 7, 2026 12:33

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Comment thread mlir/unittests/Dialect/QCO/IR/test_qco_ir.cpp Outdated

Comment thread mlir/unittests/Dialect/QCO/IR/test_qco_ir.cpp Outdated

denialhaag requested a review from burgholzer August 7, 2026 14:44

denialhaag mentioned this pull request Aug 7, 2026

🎨 Retain register name #2014

Open

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simon1hofmann and others added 3 commits August 7, 2026 21:29

Update mlir/unittests/Dialect/QCO/IR/test_qco_ir.cpp

d64f955

Co-authored-by: Daniel Haag <121057143+denialhaag@users.noreply.github.com> Signed-off-by: simon1hofmann <119581649+simon1hofmann@users.noreply.github.com>

🎨 Move test

4a4dfd8

🎨 Move test

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