♻️ Generalize MLIR compiler target facts by burgholzer · Pull Request #2218 · munich-quantum-toolkit/core

burgholzer · 2026-08-23T17:32:58Z

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Description

Generalize the unreleased MLIR compiler target contract before serializing it in mqt.target_env.

Distinguish unknown, unrestricted, and explicit connectivity and native-operation facts.
Use site and operation-arity vocabulary throughout the C++ and Python APIs.
Make mapping, synthesis, and conformance request facts only when the residual program needs them.
Keep missing QDMI topology or operation applicability unknown instead of granting support.
Preserve cheap CompilerTarget copies and move target metadata into immutable storage.

This is the context-free target prerequisite for #2215. It deliberately does not add payload capabilities or depend on the WIP QDMI v1.4 API.

Validation:

Compiler unit tests: 131 passed.
Mapping unit tests: 83 passed.
Native-synthesis unit tests: 24 passed.
Focused Python tests: 223 passed.
Generated stubs are current.
Focused clang-tidy, uvx nox -s lint, and git diff --check pass.

Implementation and pull-request text were prepared with OpenAI Codex.

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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codecov · 2026-08-23T17:40:22Z

Codecov Report

❌ Patch coverage is 92.30769% with 12 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
mlir/lib/Compiler/Target.cpp	88.9%	12 Missing ⚠️

📢 Thoughts on this report? Let us know!

burgholzer

This one feels close to ready.

coderabbitai · 2026-08-24T12:40:06Z

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Represent unknown, unrestricted, and explicit connectivity and native-operation facts separately. Use site and arity vocabulary, and make target passes request facts only when needed. Assisted-by: OpenAI Codex

Assisted-by: OpenAI Codex

Keep unavailable QDMI v1.3 properties unknown while preserving the compile-and-execute integration with explicit simulator capabilities. Assisted-by: OpenAI Codex

Replace ordered sets with the project's LLVM containers and in-place canonicalization. Assisted-by: OpenAI Codex

Copy public collection views into compact LLVM storage and document the explicit DDSIM synthesis basis used until QDMI v1.4 reports all-to-all connectivity. Assisted-by: GPT-5.6 Sol via Codex

denialhaag

I just had a free minute to go through this, and it looks really clean to me!

simon1hofmann

This also looks quite good, just a few comments about the documentation and two concerns flagged by another LLM review run.

simon1hofmann · 2026-08-25T08:44:53Z

 ```

+Use `CompilerTarget.Connectivity.all_to_all()` for an all-to-all target. An
+empty `CompilerTarget.NativeOperations([])` means that no operation is native.


Does that mean native synthesis is not called at all? Should we add an example for a target with a specific set of native operations?

I'd rather argue that "no operation is native" is a misconfiguration as this essentially means that you cannot compile to the target (it lacks an ISA).
Maybe this part of the documentation should make this more explicit (and the code should likely fail early on such targets)

simon1hofmann · 2026-08-25T08:48:09Z

+target = CompilerTarget(
+    device.qubits_num(),
+    connectivity=CompilerTarget.Connectivity.all_to_all(),
+    native_operations=CompilerTarget.NativeOperations([


An example like this in target_compilation.md.

simon1hofmann · 2026-08-25T08:49:46Z

+        CompilerTarget.Operation("u", 1, 3),
+        CompilerTarget.Operation("cx", 2, 0),
+        CompilerTarget.Operation("measure", 1, 0),
+        CompilerTarget.Operation("reset", 1, 0),


Is it clear/explained somewhere what the second and third argument in Operation represent?

Likely no really. Maybe it would help to add keyword arguments here in the docs to make this more explicit.

simon1hofmann · 2026-08-25T08:56:44Z

 """
-    target = CompilerTarget.from_device(ddsim_device)
+    target = CompilerTarget(
+        ddsim_device.qubits_num(),


Unrelated to this PR, but is there any reason why it is called qubits_num and not num_qubits?

None that I could think of. We can happily rename consistently.

simon1hofmann · 2026-08-25T09:05:46Z

      signalPassFailure();
      return;
    }
+    if (comp->hasTwoQubitOperations &&


This permits unknown connectivity without two-qubit gates, but control-flow reconciliation still queries topology at Mapping.cpp:899-908, reaching the fatal branch at Target.cpp:753-758.

Thanks for pointing that out. We should definitely fix this!

simon1hofmann · 2026-08-25T09:15:03Z

                                  const std::optional<uint64_t> duration,
                                  const std::optional<double> fidelity) {
-  std::set<SiteId> uniqueSites;
+  llvm::SmallDenseSet<SiteId> uniqueSites;


This stores nonnegative int64_t IDs in SmallDenseSet, whose sentinel values overlap the advertised domain (INT64_MAX, and on LP64 also INT64_MAX-1)

Thanks. I think we could be limiting the sites to 32bits. IIRC site IDs should also be non-negative (might be worth double-checking).
Reducing to 32-bits may even increase efficiency throughout the implementation.

burgholzer · 2026-08-25T09:41:09Z

Thanks @denialhaag and @simon1hofmann 🙏🏼
Given how this is at the very bottom of an 11 PR stack, I'd like to only touch this once more and freeze the implementation afterwards. Are there any further comments on the above from your side?
Quick signal would be good. Then I'll kick off the implementation and the rebase.

simon1hofmann · 2026-08-25T10:16:33Z

Thanks @denialhaag and @simon1hofmann 🙏🏼

Given how this is at the very bottom of an 11 PR stack, I'd like to only touch this once more and freeze the implementation afterwards. Are there any further comments on the above from your side?

Quick signal would be good. Then I'll kick off the implementation and the rebase.

Thanks for addressing my comments, I agree with all your answers.

denialhaag · 2026-08-25T17:29:33Z

Thanks @denialhaag and @simon1hofmann 🙏🏼
Given how this is at the very bottom of an 11 PR stack, I'd like to only touch this once more and freeze the implementation afterwards. Are there any further comments on the above from your side?
Quick signal would be good. Then I'll kick off the implementation and the rebase.

Thanks for addressing my comments, I agree with all your answers.

Go also from my side!

burgholzer added refactor Anything related to code refactoring c++ Anything related to C++ code python Anything related to Python code MLIR Anything related to MLIR labels Aug 23, 2026

burgholzer self-assigned this Aug 23, 2026

burgholzer mentioned this pull request Aug 23, 2026

✨ Record typed compiler target environments in MQT IR #2215

Open

12 tasks

burgholzer added this to the MLIR Support milestone Aug 23, 2026

burgholzer commented Aug 24, 2026

View reviewed changes

Comment thread docs/qdmi/ddsim_device.md Outdated

Comment thread docs/qdmi/ddsim_device.md Outdated

Comment thread mlir/include/mlir/Compiler/Target.h Outdated

Comment thread mlir/include/mlir/Compiler/Target.h Outdated

Comment thread mlir/include/mlir/Compiler/Target.h Outdated

burgholzer mentioned this pull request Aug 24, 2026

✨ Legalize control flow for selected payloads #2162

Draft

12 tasks

burgholzer force-pushed the codex/generalize-compiler-target branch from 9b961b2 to 8fafa97 Compare August 24, 2026 13:52

mergify Bot added the conflict label Aug 24, 2026

burgholzer and others added 6 commits August 24, 2026 23:33

♻️ Generalize compiler target facts

82c99f0

Represent unknown, unrestricted, and explicit connectivity and native-operation facts separately. Use site and arity vocabulary, and make target passes request facts only when needed. Assisted-by: OpenAI Codex

🎨 pre-commit fixes

0bdeab5

📝 Fold compiler target work into launch changelog

3381293

Assisted-by: OpenAI Codex

🧪 State DDSIM target facts explicitly

e07e268

Keep unavailable QDMI v1.3 properties unknown while preserving the compile-and-execute integration with explicit simulator capabilities. Assisted-by: OpenAI Codex

⚡️ Use compact LLVM target checks

3a71e2b

Replace ordered sets with the project's LLVM containers and in-place canonicalization. Assisted-by: OpenAI Codex

♻️ Use LLVM views for target collections

a6f7fd1

Copy public collection views into compact LLVM storage and document the explicit DDSIM synthesis basis used until QDMI v1.4 reports all-to-all connectivity. Assisted-by: GPT-5.6 Sol via Codex

burgholzer force-pushed the codex/generalize-compiler-target branch from 8fafa97 to a6f7fd1 Compare August 24, 2026 23:47

burgholzer removed the conflict label Aug 24, 2026

denialhaag approved these changes Aug 25, 2026

View reviewed changes

simon1hofmann requested changes Aug 25, 2026

View reviewed changes

mergify Bot added the conflict label Aug 26, 2026

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