✨ Add DD buildFunctionality/simulate for static QCO funcs

CHANGELOG.md

@@ -12,6 +12,8 @@ releases may include breaking changes.
 
 ### Added
 
+- ✨ Add decision diagram-based construction and simulation of static unitary
+  QCO functions ([#1915]) ([**@simon1hofmann**])
 - ✨ Add native relative-phase CCX (`rccx`) support across the IR, DD package,
   ZX diagrams, OpenQASM import/export, and Python/Qiskit bindings ([#1886])
   ([**@simon1hofmann**])
@@ -642,6 +644,7 @@ changelogs._
 
 <!-- PR links -->
 
+[#1915]: https://github.com/munich-quantum-toolkit/core/pull/1915
 [#1914]: https://github.com/munich-quantum-toolkit/core/pull/1914
 [#1911]: https://github.com/munich-quantum-toolkit/core/pull/1911
 [#1904]: https://github.com/munich-quantum-toolkit/core/pull/1904

mlir/include/mlir/Dialect/QCO/Utils/DDFunctionality.h

@@ -0,0 +1,69 @@
+/*
+ * 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 "dd/Package_fwd.hpp"
+
+#include <mlir/Dialect/Func/IR/FuncOps.h>
+#include <mlir/Support/LogicalResult.h>
+
+namespace mlir::qco {
+
+/**
+ * @brief Sequentially build a matrix DD for a static unitary QCO `func.func`.
+ *
+ * @details Walks the entry block of @p func, maps `qco.static` SSA values to
+ * wire indices (or, if none are present, qubit-typed function arguments as
+ * wires `0..n-1`), and applies unitary operations via decision-diagram
+ * multiplication.
+ *
+ * Supported programs:
+ * - Standard single- and two-qubit gates with compile-time constant parameters
+ *   (sparse DD path)
+ * - `ctrl` with a sole standard-gate body (same sparse path)
+ * - Other `UnitaryOpInterface` ops with a compile-time known matrix (`inv`,
+ *   compound `ctrl`, ...), including `gphase` and `barrier`
+ * - Skips: `static`, `sink`, `arith.constant`; `func.return` accepts qubit
+ *   results only in canonical wire order
+ *
+ * Known one- and two-qubit matrices are constructed directly as DD gates. The
+ * dense matrix fallback accepts full-width unitaries on wires `0..n-1` and
+ * rewrites the QCO/MSB-first basis into the DD package's LSB-first indexing.
+ * Only this full-width fallback is limited to 12 qubits (dense `2^n × 2^n`
+ * storage). Measurements, resets, symbolic parameters, and control-flow ops
+ * are not supported.
+ *
+ * @param func The QCO function to construct the functionality for
+ * @param dd The DD package to use (must hold at least the function's qubits)
+ * @return The matrix DD on success, or failure for unsupported programs
+ */
+FailureOr<dd::MatrixDD> buildFunctionality(func::FuncOp func, dd::Package& dd);
+
+/**
+ * @brief Simulate a static unitary QCO `func.func` on a given input state.
+ *
+ * @details Same supported op set and limitations as @ref buildFunctionality.
+ * Mirrors @ref dd::simulate: sequentially applies unitaries to @p in via
+ * decision-diagram multiplication. Only purely quantum, measurement-free
+ * programs are supported. Consumes one reference to @p in regardless of
+ * whether simulation succeeds or fails.
+ *
+ * @param func The QCO function to simulate
+ * @param in The input state, represented as a vector DD; one reference is
+ * consumed
+ * @param dd The DD package to use (must hold at least the function's qubits)
+ * @return The output statevector DD on success, or failure for unsupported
+ *         programs
+ */
+FailureOr<dd::VectorDD> simulate(func::FuncOp func, const dd::VectorDD& in,
+                                 dd::Package& dd);
+
+} // namespace mlir::qco

mlir/lib/Dialect/QCO/Utils/CMakeLists.txt

@@ -14,7 +14,7 @@ target_sources(MLIRQCOMatrix PUBLIC FILE_SET HEADERS BASE_DIRS ${MQT_MLIR_SOURCE
                                     ${MQT_MLIR_SOURCE_INCLUDE_DIR}/mlir/Dialect/QCO/Utils/Matrix.h)
 
 file(GLOB_RECURSE UTILS_CPP "${CMAKE_CURRENT_SOURCE_DIR}/*.cpp")
-list(FILTER UTILS_CPP EXCLUDE REGEX "Matrix\\.cpp$")
+list(FILTER UTILS_CPP EXCLUDE REGEX "(DDFunctionality|Matrix)\\.cpp$")
 
 add_mlir_dialect_library(
   MLIRQCOUtils
@@ -34,7 +34,7 @@ mqt_mlir_target_use_project_options(MLIRQCOUtils)
 
 # collect header files
 file(GLOB_RECURSE UTILS_HEADERS_SOURCE "${MQT_MLIR_SOURCE_INCLUDE_DIR}/mlir/Dialect/QCO/Utils/*.h")
-list(FILTER UTILS_HEADERS_SOURCE EXCLUDE REGEX "Matrix\\.h$")
+list(FILTER UTILS_HEADERS_SOURCE EXCLUDE REGEX "(DDFunctionality|Matrix)\\.h$")
 file(GLOB_RECURSE UTILS_HEADERS_BUILD "${MQT_MLIR_BUILD_INCLUDE_DIR}/mlir/Dialect/QCO/Utils/*.inc")
 
 # add public headers using file sets
@@ -52,3 +52,24 @@ target_sources(
          ${MQT_MLIR_BUILD_INCLUDE_DIR}
          FILES
          ${UTILS_HEADERS_BUILD})
+
+add_mlir_library(
+  MLIRQCODDFunctionality
+  PARTIAL_SOURCES_INTENDED
+  DDFunctionality.cpp
+  DEPENDS
+  MLIRQCOOpsIncGen
+  MLIRQCOInterfacesIncGen
+  LINK_LIBS
+  PUBLIC
+  MLIRQCODialect
+  MLIRQCOMatrix
+  MLIRFuncDialect
+  MQT::CoreDD)
+
+mqt_mlir_target_use_project_options(MLIRQCODDFunctionality)
+
+target_sources(
+  MLIRQCODDFunctionality
+  PUBLIC FILE_SET HEADERS BASE_DIRS ${MQT_MLIR_SOURCE_INCLUDE_DIR} FILES
+         ${MQT_MLIR_SOURCE_INCLUDE_DIR}/mlir/Dialect/QCO/Utils/DDFunctionality.h)