🎨 Clean up MLIR code here and there (#1521)

## Description

This PR contains minor improvements to the MLIR code that I have
stumbled across during #1479. I'm opening up this PR to keep #1479 a bit
leaner.

## 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: Lukas Burgholzer <burgholzer@me.com>

Author: denialhaag

CHANGELOG.md

@@ -12,7 +12,7 @@ This project adheres to [Semantic Versioning], with the exception that minor rel
 ### Added
 
 - ✨ 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], [#1513])
+  ([#1264], [#1330], [#1402], [#1428], [#1430], [#1436], [#1443], [#1446], [#1464], [#1465], [#1470], [#1471], [#1472], [#1474], [#1475], [#1513], [#1521])
   ([**@burgholzer**], [**@denialhaag**], [**@taminob**], [**@DRovara**], [**@li-mingbao**], [**@Ectras**])
 
 ### Changed
@@ -327,6 +327,7 @@ _📚 Refer to the [GitHub Release Notes](https://github.com/munich-quantum-tool
 
 <!-- PR links -->
 
+[#1521]: https://github.com/munich-quantum-toolkit/core/pull/1521
 [#1513]: https://github.com/munich-quantum-toolkit/core/pull/1513
 [#1481]: https://github.com/munich-quantum-toolkit/core/pull/1481
 [#1475]: https://github.com/munich-quantum-toolkit/core/pull/1475

mlir/include/mlir/Conversion/QCOToQC/QCOToQC.h

@@ -10,7 +10,7 @@
 
 #pragma once
 
-#include <mlir/Pass/Pass.h> // from @llvm-project
+#include <mlir/Pass/Pass.h>
 
 namespace mlir {
 #define GEN_PASS_DECL_QCOTOQC

mlir/include/mlir/Conversion/QCToQCO/QCToQCO.h

@@ -10,7 +10,7 @@
 
 #pragma once
 
-#include <mlir/Pass/Pass.h> // from @llvm-project
+#include <mlir/Pass/Pass.h>
 
 namespace mlir {
 #define GEN_PASS_DECL_QCTOQCO

mlir/include/mlir/Conversion/QCToQIR/QCToQIR.h

@@ -10,7 +10,7 @@
 
 #pragma once
 
-#include <mlir/Pass/Pass.h> // from @llvm-project
+#include <mlir/Pass/Pass.h>
 
 namespace mlir {
 #define GEN_PASS_DECL_QCTOQIR

mlir/include/mlir/Dialect/QC/IR/QCOps.td

@@ -943,7 +943,7 @@ def CtrlOp : QCOp<"ctrl",
         ```mlir
         qc.ctrl(%q0) {
           qc.x %q1 : !qc.qubit
-        }
+        } : !qc.qubit
         ```
     }];
 

mlir/lib/Conversion/QCOToQC/QCOToQC.cpp

@@ -68,7 +68,7 @@ static LogicalResult
 convertOneTargetZeroParameter(QCOOpType& op, QCOOpAdaptorType& adaptor,
                               ConversionPatternRewriter& rewriter) {
   // OpAdaptor provides the already type-converted input qubit
-  const auto& qcQubit = adaptor.getQubitIn();
+  auto qcQubit = adaptor.getQubitIn();
 
   // Create the QC operation (in-place, no result)
   rewriter.create<QCOpType>(op.getLoc(), qcQubit);
@@ -95,7 +95,7 @@ static LogicalResult
 convertOneTargetOneParameter(QCOOpType& op, QCOOpAdaptorType& adaptor,
                              ConversionPatternRewriter& rewriter) {
   // OpAdaptor provides the already type-converted input qubit
-  const auto& qcQubit = adaptor.getQubitIn();
+  auto qcQubit = adaptor.getQubitIn();
 
   // Create the QC operation (in-place, no result)
   rewriter.create<QCOpType>(op.getLoc(), qcQubit, op.getParameter(0));
@@ -122,7 +122,7 @@ static LogicalResult
 convertOneTargetTwoParameter(QCOOpType& op, QCOOpAdaptorType& adaptor,
                              ConversionPatternRewriter& rewriter) {
   // OpAdaptor provides the already type-converted input qubit
-  const auto& qcQubit = adaptor.getQubitIn();
+  auto qcQubit = adaptor.getQubitIn();
 
   // Create the QC operation (in-place, no result)
   rewriter.create<QCOpType>(op.getLoc(), qcQubit, op.getParameter(0),
@@ -150,7 +150,7 @@ static LogicalResult
 convertOneTargetThreeParameter(QCOOpType& op, QCOOpAdaptorType& adaptor,
                                ConversionPatternRewriter& rewriter) {
   // OpAdaptor provides the already type-converted input qubit
-  const auto& qcQubit = adaptor.getQubitIn();
+  auto qcQubit = adaptor.getQubitIn();
 
   // Create the QC operation (in-place, no result)
   rewriter.create<QCOpType>(op.getLoc(), qcQubit, op.getParameter(0),
@@ -178,8 +178,8 @@ static LogicalResult
 convertTwoTargetZeroParameter(QCOOpType& op, QCOOpAdaptorType& adaptor,
                               ConversionPatternRewriter& rewriter) {
   // OpAdaptor provides the already type-converted input qubits
-  const auto& qcQubit0 = adaptor.getQubit0In();
-  const auto& qcQubit1 = adaptor.getQubit1In();
+  auto qcQubit0 = adaptor.getQubit0In();
+  auto qcQubit1 = adaptor.getQubit1In();
 
   // Create the QC operation (in-place, no result)
   rewriter.create<QCOpType>(op.getLoc(), qcQubit0, qcQubit1);
@@ -206,8 +206,8 @@ static LogicalResult
 convertTwoTargetOneParameter(QCOOpType& op, QCOOpAdaptorType& adaptor,
                              ConversionPatternRewriter& rewriter) {
   // OpAdaptor provides the already type-converted input qubits
-  const auto& qcQubit0 = adaptor.getQubit0In();
-  const auto& qcQubit1 = adaptor.getQubit1In();
+  auto qcQubit0 = adaptor.getQubit0In();
+  auto qcQubit1 = adaptor.getQubit1In();
 
   // Create the QC operation (in-place, no result)
   rewriter.create<QCOpType>(op.getLoc(), qcQubit0, qcQubit1,
@@ -235,8 +235,8 @@ static LogicalResult
 convertTwoTargetTwoParameter(QCOOpType& op, QCOOpAdaptorType& adaptor,
                              ConversionPatternRewriter& rewriter) {
   // OpAdaptor provides the already type-converted input qubits
-  const auto& qcQubit0 = adaptor.getQubit0In();
-  const auto& qcQubit1 = adaptor.getQubit1In();
+  auto qcQubit0 = adaptor.getQubit0In();
+  auto qcQubit1 = adaptor.getQubit1In();
 
   // Create the QC operation (in-place, no result)
   rewriter.create<QCOpType>(op.getLoc(), qcQubit0, qcQubit1, op.getParameter(0),
@@ -392,7 +392,7 @@ struct ConvertQCOMeasureOp final : OpConversionPattern<qco::MeasureOp> {
   matchAndRewrite(qco::MeasureOp op, OpAdaptor adaptor,
                   ConversionPatternRewriter& rewriter) const override {
     // OpAdaptor provides the already type-converted input qubit
-    const auto& qcQubit = adaptor.getQubitIn();
+    auto qcQubit = adaptor.getQubitIn();
 
     // Create qc.measure (in-place operation, returns only bit)
     // Preserve register metadata for output recording
@@ -437,7 +437,7 @@ struct ConvertQCOResetOp final : OpConversionPattern<qco::ResetOp> {
   matchAndRewrite(qco::ResetOp op, OpAdaptor adaptor,
                   ConversionPatternRewriter& rewriter) const override {
     // OpAdaptor provides the already type-converted input qubit
-    const auto& qcQubit = adaptor.getQubitIn();
+    auto qcQubit = adaptor.getQubitIn();
 
     // Create qc.reset (in-place operation, no result)
     rewriter.create<qc::ResetOp>(op.getLoc(), qcQubit);
@@ -737,7 +737,7 @@ struct ConvertQCOBarrierOp final : OpConversionPattern<qco::BarrierOp> {
   matchAndRewrite(qco::BarrierOp op, OpAdaptor adaptor,
                   ConversionPatternRewriter& rewriter) const override {
     // OpAdaptor provides the already type-converted qubits
-    const auto& qcQubits = adaptor.getQubitsIn();
+    auto qcQubits = adaptor.getQubitsIn();
 
     // Create qc.barrier operation
     rewriter.create<qc::BarrierOp>(op.getLoc(), qcQubits);
@@ -763,7 +763,7 @@ struct ConvertQCOBarrierOp final : OpConversionPattern<qco::BarrierOp> {
  * ```mlir
  * qc.ctrl(%q0) {
  *   qc.x %q1 : !qc.qubit
- * }
+ * } : !qc.qubit
  * ```
  */
 struct ConvertQCOCtrlOp final : OpConversionPattern<qco::CtrlOp> {
@@ -773,7 +773,7 @@ struct ConvertQCOCtrlOp final : OpConversionPattern<qco::CtrlOp> {
   matchAndRewrite(qco::CtrlOp op, OpAdaptor adaptor,
                   ConversionPatternRewriter& rewriter) const override {
     // Get QC controls
-    const auto& qcControls = adaptor.getControlsIn();
+    auto qcControls = adaptor.getControlsIn();
 
     // Create qc.ctrl operation
     auto qcOp = qc::CtrlOp::create(rewriter, op.getLoc(), qcControls);