✨ Canonicalize equivalent qc.static operations

CHANGELOG.md

@@ -15,7 +15,7 @@ This project adheres to [Semantic Versioning], with the exception that minor rel
 - ✨ Add conversions between Jeff and QCO ([#1479], [#1548]) ([**@denialhaag**])
 - ✨ Add a `place-and-route` pass for mapping circuits to architectures with restricted topologies ([#1537], [#1547]) ([**@MatthiasReumann**])
 - ✨ Add initial infrastructure for new QC and QCO MLIR dialects
-  ([#1264], [#1330], [#1402], [#1428], [#1430], [#1436], [#1443], [#1446], [#1464], [#1465], [#1470], [#1471], [#1472], [#1474], [#1475], [#1506], [#1510], [#1513], [#1521], [#1548], [#1550], [#1554])
+  ([#1264], [#1330], [#1402], [#1428], [#1430], [#1436], [#1443], [#1446], [#1464], [#1465], [#1470], [#1471], [#1472], [#1474], [#1475], [#1506], [#1510], [#1513], [#1521], [#1548], [#1550], [#1554], [#1567])
   ([**@burgholzer**], [**@denialhaag**], [**@taminob**], [**@DRovara**], [**@li-mingbao**], [**@Ectras**], [**@MatthiasReumann**], [**@simon1hofmann**])
 
 ### Changed
@@ -331,6 +331,7 @@ _📚 Refer to the [GitHub Release Notes](https://github.com/munich-quantum-tool
 
 <!-- PR links -->
 
+[#1567]: https://github.com/munich-quantum-toolkit/core/pull/1567
 [#1554]: https://github.com/munich-quantum-toolkit/core/pull/1554
 [#1550]: https://github.com/munich-quantum-toolkit/core/pull/1550
 [#1549]: https://github.com/munich-quantum-toolkit/core/pull/1549

mlir/include/mlir/Compiler/CompilerPipeline.h

@@ -115,8 +115,8 @@ class QuantumCompilerPipeline {
    * @brief Add canonicalization and cleanup passes
    *
    * @details
-   * Always adds the standard MLIR canonicalization pass followed by dead
-   * value removal.
+   * Always adds the standard MLIR canonicalization pass followed by common
+   * sub-expression elimination and dead value removal.
    */
   static void addCleanupPasses(PassManager& pm);
 

mlir/lib/Compiler/CompilerPipeline.cpp

@@ -46,8 +46,10 @@ static void prettyPrintStage(ModuleOp module, const llvm::StringRef stageName,
 }
 
 void QuantumCompilerPipeline::addCleanupPasses(PassManager& pm) {
-  // Always run canonicalization and dead value removal
+  // Always run canonicalization, common sub-expression elimination, and dead
+  // value removal
   pm.addPass(createCanonicalizerPass());
+  pm.addPass(createCSEPass());
   pm.addPass(createRemoveDeadValuesPass());
 }
 

mlir/lib/Support/Passes.cpp

@@ -20,6 +20,7 @@ using namespace mlir;
 void runCanonicalizationPasses(ModuleOp module) {
   PassManager pm(module.getContext());
   pm.addPass(createCanonicalizerPass());
+  pm.addPass(createCSEPass());
   pm.addPass(createRemoveDeadValuesPass());
   if (pm.run(module).failed()) {
     llvm::errs() << "Failed to run canonicalization passes.\n";

mlir/unittests/Compiler/test_compiler_pipeline.cpp

@@ -185,6 +185,11 @@ INSTANTIATE_TEST_SUITE_P(
             "StaticQubits", nullptr, MQT_NAMED_BUILDER(mlir::qc::staticQubits),
             MQT_NAMED_BUILDER(mlir::qc::staticQubits),
             MQT_NAMED_BUILDER(mlir::qir::staticQubits), false},
+        CompilerPipelineTestCase{
+            "StaticQubitsWithDuplicates", nullptr,
+            MQT_NAMED_BUILDER(mlir::qc::staticQubitsWithDuplicates),
+            MQT_NAMED_BUILDER(mlir::qc::staticQubits),
+            MQT_NAMED_BUILDER(mlir::qir::staticQubits), false},
         CompilerPipelineTestCase{"AllocQubit",
                                  MQT_NAMED_BUILDER(qc::allocQubit), nullptr,
                                  MQT_NAMED_BUILDER(mlir::qc::allocQubit),

mlir/unittests/Dialect/QC/IR/test_qc_ir.cpp

@@ -894,6 +894,9 @@ INSTANTIATE_TEST_SUITE_P(
                    MQT_NAMED_BUILDER(emptyQC)},
         QCTestCase{"StaticQubits", MQT_NAMED_BUILDER(staticQubits),
                    MQT_NAMED_BUILDER(emptyQC)},
+        QCTestCase{"StaticQubitsWithDuplicates",
+                   MQT_NAMED_BUILDER(staticQubitsWithDuplicates),
+                   MQT_NAMED_BUILDER(staticQubitsCanonical)},
         QCTestCase{"AllocDeallocPair", MQT_NAMED_BUILDER(allocDeallocPair),
                    MQT_NAMED_BUILDER(emptyQC)}));
 /// @}

mlir/unittests/programs/qc_programs.cpp

@@ -34,6 +34,28 @@ void staticQubits(QCProgramBuilder& b) {
   b.staticQubit(1);
 }
 
+void staticQubitsWithDuplicates(QCProgramBuilder& b) {
+  const auto q0a = b.staticQubit(0);
+  const auto q1a = b.staticQubit(1);
+  const auto q0b = b.staticQubit(0);
+  const auto q1b = b.staticQubit(1);
+
+  b.h(q0a);
+  b.h(q1a);
+  b.x(q0b);
+  b.x(q1b);
+}
+
+void staticQubitsCanonical(QCProgramBuilder& b) {
+  const auto q0 = b.staticQubit(0);
+  const auto q1 = b.staticQubit(1);
+
+  b.h(q0);
+  b.h(q1);
+  b.x(q0);
+  b.x(q1);
+}
+
 void allocDeallocPair(QCProgramBuilder& b) {
   auto q = b.allocQubit();
   b.dealloc(q);

mlir/unittests/programs/qc_programs.h

@@ -33,6 +33,13 @@ void allocLargeRegister(QCProgramBuilder& b);
 /// Allocates two inline qubits.
 void staticQubits(QCProgramBuilder& b);
 
+/// Allocates duplicate static qubits for the same indices and applies gates.
+void staticQubitsWithDuplicates(QCProgramBuilder& b);
+
+/// Allocates canonical static qubits (one per index) and applies equivalent
+/// gates.
+void staticQubitsCanonical(QCProgramBuilder& b);
+
 /// Allocates and explicitly deallocates a single qubit.
 void allocDeallocPair(QCProgramBuilder& b);