✨ Add OpenQASM-to-QC translation (#1780)

## Description

This is a rebased version of #1671 after #1671 was automatically closed
when #1751 was merged.

Original description by @J4MMlE:

> ## Description
>
> This PR adds a direct OpenQASM-to-QC translation that bypasses the
`qc::QuantumComputation`.
> 
> The new flow reuses the existing parser and walks the AST directly to
emit QC dialect ops. Skipping `QuantumComputation` removes an
intermediate step and enables previously unsupported QASM3 features,
such as gate modifiers, classical computations, and control flow
structures.
> 
> ### What works
> 
> - All standard gates plus Qiskit-style MCX variants
> - Gate modifiers: `ctrl @`, `negctrl @`, `inv @`, nested combinations
> - Register declarations, qubit/bit allocation
> - Measure, reset, barrier
> - `if`/`else` over quantum statements
> - Hardware qubits convert to `qc.static`
> - Broadcasting (register-width gate calls)
> 
> ### Current limitations
> 
> - Gate parameters must be compile-time constants
> - `pow` modifier is unsupported (but will/should be once
[#1603](#1603) is
merged)
> - Layout pragmas are unsupported (they have no equivalent in `QC`)

## Checklist

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

---------

Signed-off-by: Daniel Haag <121057143+denialhaag@users.noreply.github.com>
Co-authored-by: Anatol Bussejahn <anatol.bussejahn@tum.de>
Co-authored-by: Lukas Burgholzer <burgholzer@me.com>

Author: 3 people

CHANGELOG.md

@@ -42,7 +42,7 @@ with the exception that minor releases may include breaking changes.
   [#1569], [#1570], [#1572], [#1573], [#1580], [#1602], [#1620], [#1623],
   [#1624], [#1626], [#1627], [#1635], [#1638], [#1673], [#1675], [#1700],
   [#1710], [#1717], [#1728], [#1730], [#1749], [#1751], [#1762], [#1765],
-  [#1774], [#1781], [#1782], [#1787])
+  [#1774], [#1780], [#1781], [#1782], [#1787])
   ([**@burgholzer**], [**@denialhaag**], [**@taminob**], [**@DRovara**],
   [**@li-mingbao**], [**@Ectras**], [**@MatthiasReumann**],
   [**@simon1hofmann**])
@@ -601,6 +601,7 @@ changelogs._
 [#1787]: https://github.com/munich-quantum-toolkit/core/pull/1787
 [#1782]: https://github.com/munich-quantum-toolkit/core/pull/1782
 [#1781]: https://github.com/munich-quantum-toolkit/core/pull/1781
+[#1780]: https://github.com/munich-quantum-toolkit/core/pull/1780
 [#1776]: https://github.com/munich-quantum-toolkit/core/pull/1776
 [#1774]: https://github.com/munich-quantum-toolkit/core/pull/1774
 [#1766]: https://github.com/munich-quantum-toolkit/core/pull/1766

mlir/include/mlir/Dialect/QC/Translation/TranslateQASM3ToQC.h

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2023 - 2026 Chair for Design Automation, TUM
+ * Copyright (c) 2025 - 2026 Munich Quantum Software Company GmbH
+ * All rights reserved.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Licensed under the MIT License
+ */
+
+#pragma once
+
+#include <llvm/Support/SourceMgr.h>
+#include <mlir/IR/OwningOpRef.h>
+#include <mlir/Support/LLVM.h>
+
+namespace mlir {
+
+// Forward declarations
+class MLIRContext;
+class ModuleOp;
+
+namespace qc {
+
+/**
+ * @brief Translate an OpenQASM 3 program to a QC program.
+ *
+ * @param sourceMgr Source manager containing the OpenQASM3 program.
+ * @param context MLIRContext to create the module in.
+ */
+[[nodiscard]] OwningOpRef<ModuleOp>
+translateQASM3ToQC(llvm::SourceMgr& sourceMgr, MLIRContext* context);
+
+/**
+ * @brief Translate an OpenQASM 3 program to a QC program.
+ *
+ * @param source String containing the OpenQASM3 program.
+ * @param context MLIRContext to create the module in.
+ */
+[[nodiscard]] OwningOpRef<ModuleOp> translateQASM3ToQC(StringRef source,
+                                                       MLIRContext* context);
+
+} // namespace qc
+
+} // namespace mlir

mlir/lib/Dialect/QC/Translation/CMakeLists.txt

@@ -9,13 +9,15 @@
 add_mlir_library(
   MLIRQCTranslation
   TranslateQuantumComputationToQC.cpp
+  TranslateQASM3ToQC.cpp
   LINK_LIBS
   MLIRArithDialect
   MLIRFuncDialect
   MLIRSCFDialect
   MLIRQCDialect
   MLIRQCProgramBuilder
-  MQT::CoreIR)
+  MQT::CoreIR
+  MQT::CoreQASM)
 
 mqt_mlir_target_use_project_options(MLIRQCTranslation)