Add CancelConsecutiveHermitianGates Pass

[MatthiasReumann]

Description

The "Writing Your First Optimization Pass" section in #1555 requires a rather simple example of an optimization pass. I thought a CancelConsecutiveHermitianGates pass could be a good choice. Hence, this pull request.

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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[github-actions]

Cpp-Linter Report ⚠️

Some files did not pass the configured checks!

clang-tidy (v22.1.3) reports: 14 concern(s)

• mlir/lib/Dialect/QCO/Transforms/Optimizations/CancelConsecutiveHermitianGates.cpp:17:1: warning: [misc-include-cleaner]

  included header Debug.h is not used directly

     17 | #include <llvm/Support/Debug.h>
        | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     18 | #include <mlir/IR/Operation.h>

• mlir/lib/Dialect/QCO/Transforms/Optimizations/CancelConsecutiveHermitianGates.cpp:29:7: warning: [misc-include-cleaner]

  no header providing "mlir::OpInterfaceRewritePattern" is directly included

     20 | #include <mlir/Transforms/GreedyPatternRewriteDriver.h>
     21 | 
     22 | namespace mlir::qco {
     23 | 
     24 | #define GEN_PASS_DEF_CANCELCONSECUTIVEHERMITIANGATES
     25 | #include "mlir/Dialect/QCO/Transforms/Passes.h.inc"
     26 | 
     27 | namespace {
     28 | struct CancelConsecutiveHermitianGatesPattern final
     29 |     : OpInterfaceRewritePattern<UnitaryOpInterface> {
        |       ^

• mlir/lib/Dialect/QCO/Transforms/Optimizations/CancelConsecutiveHermitianGates.cpp:30:51: warning: [misc-include-cleaner]

  no header providing "mlir::MLIRContext" is directly included

     18 | #include <mlir/IR/Operation.h>
     19 | #include <mlir/IR/OperationSupport.h>
     20 | #include <mlir/Transforms/GreedyPatternRewriteDriver.h>
     21 | 
     22 | namespace mlir::qco {
     23 | 
     24 | #define GEN_PASS_DEF_CANCELCONSECUTIVEHERMITIANGATES
     25 | #include "mlir/Dialect/QCO/Transforms/Passes.h.inc"
     26 | 
     27 | namespace {
     28 | struct CancelConsecutiveHermitianGatesPattern final
     29 |     : OpInterfaceRewritePattern<UnitaryOpInterface> {
     30 |   explicit CancelConsecutiveHermitianGatesPattern(MLIRContext* context)
        |                                                   ^

• mlir/lib/Dialect/QCO/Transforms/Optimizations/CancelConsecutiveHermitianGates.cpp:31:9: warning: [misc-include-cleaner]

  no header providing "mlir::OpInterfaceRewritePattern" is directly included

     31 |       : OpInterfaceRewritePattern(context) {}
        |         ^

• mlir/lib/Dialect/QCO/Transforms/Optimizations/CancelConsecutiveHermitianGates.cpp:46:3: warning: [misc-include-cleaner]

  no header providing "mlir::LogicalResult" is directly included

     20 |   LogicalResult matchAndRewrite(UnitaryOpInterface op,
        |   ^

• mlir/lib/Dialect/QCO/Transforms/Optimizations/CancelConsecutiveHermitianGates.cpp:47:33: warning: [misc-include-cleaner]

  no header providing "mlir::PatternRewriter" is directly included

     47 |                                 PatternRewriter& rewriter) const override {
        |                                 ^

• mlir/lib/Dialect/QCO/Transforms/Optimizations/CancelConsecutiveHermitianGates.cpp:49:14: warning: [misc-include-cleaner]

  no header providing "mlir::failure" is directly included

     49 |       return failure();
        |              ^

• mlir/lib/Dialect/QCO/Transforms/Optimizations/CancelConsecutiveHermitianGates.cpp:80:12: warning: [misc-include-cleaner]

  no header providing "mlir::success" is directly included

     80 |     return success();
        |            ^

• mlir/lib/Dialect/QCO/Transforms/Optimizations/CancelConsecutiveHermitianGates.cpp:88:8: warning: [misc-use-internal-linkage]

  struct 'CancelConsecutiveHermitianGates' can be moved into an anonymous namespace to enforce internal linkage

     88 | struct CancelConsecutiveHermitianGates final
        |        ^

• mlir/lib/Dialect/QCO/Transforms/Optimizations/CancelConsecutiveHermitianGates.cpp:99:9: warning: [misc-include-cleaner]

  no header providing "mlir::failed" is directly included

     99 |     if (failed(applyPatternsGreedily(getOperation(), std::move(patterns)))) {
        |         ^

• mlir/lib/Dialect/QCO/Transforms/Optimizations/CancelConsecutiveHermitianGates.cpp:99:59: warning: [misc-include-cleaner]

  no header providing "std::move" is directly included

     21 |     if (failed(applyPatternsGreedily(getOperation(), std::move(patterns)))) {
        |                                                           ^

• mlir/unittests/Dialect/QCO/Transforms/Optimizations/test_cancel_consecutive_hermitian_gates.cpp:31:7: warning: [misc-use-internal-linkage]

  class 'CancelConsecutiveHermitianGatesTest' can be moved into an anonymous namespace to enforce internal linkage

     31 | class CancelConsecutiveHermitianGatesTest : public testing::Test {
        |       ^

• mlir/unittests/Dialect/QCO/Transforms/Optimizations/test_cancel_consecutive_hermitian_gates.cpp:37:20: warning: [misc-include-cleaner]

  no header providing "std::make_unique" is directly included

     27 | 
     28 | using namespace mlir;
     29 | using namespace mlir::qco;
     30 | 
     31 | class CancelConsecutiveHermitianGatesTest : public testing::Test {
     32 | protected:
     33 |   void SetUp() override {
     34 |     // Register all necessary dialects
     35 |     DialectRegistry registry;
     36 |     registry.insert<qco::QCODialect, arith::ArithDialect, func::FuncDialect>();
     37 |     context = std::make_unique<MLIRContext>();
        |                    ^

• mlir/unittests/Dialect/QCO/Transforms/Optimizations/test_cancel_consecutive_hermitian_gates.cpp:48:8: warning: [misc-include-cleaner]

  no header providing "std::unique_ptr" is directly included

     48 |   std::unique_ptr<MLIRContext> context;
        |        ^

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[MatthiasReumann]

I just saw that there are the removeInversePair (etc.) functions in the QCOUtils.h file, which are used for canonicalization. Consequently, this PR probably doesn't require to be merged. 😅 Bit unfortunate, but... 🫠

[burgholzer]

I just saw that there are the removeInversePair (etc.) functions in the QCOUtils.h file, which are used for canonicalization. Consequently, this PR probably doesn't require to be merged. 😅 Bit unfortunate, but... 🫠

I was just about to chime in here and say that the respective functionality is already covered by canonicalizations. 😅