From 22949908f73f87104cd3d867b2f5ce0564b331f8 Mon Sep 17 00:00:00 2001
From: Yue Huang <yh548@cam.ac.uk>
Date: Tue, 1 Apr 2025 15:08:51 +0800
Subject: [PATCH] [CIR][ThroughMLIR] Lower UnreachableOp

---
 .../Lowering/ThroughMLIR/LowerCIRToMLIR.cpp   | 33 ++++++++++++-------
 .../Lowering/ThroughMLIR/LowerMLIRToLLVM.cpp  | 11 -------
 .../CIR/Lowering/ThroughMLIR/unreachable.cir  | 10 ++++++
 3 files changed, 32 insertions(+), 22 deletions(-)
 create mode 100644 clang/test/CIR/Lowering/ThroughMLIR/unreachable.cir

diff --git a/clang/lib/CIR/Lowering/ThroughMLIR/LowerCIRToMLIR.cpp b/clang/lib/CIR/Lowering/ThroughMLIR/LowerCIRToMLIR.cpp
index 6ee5c2b414d3..fd1531f8eee4 100644
--- a/clang/lib/CIR/Lowering/ThroughMLIR/LowerCIRToMLIR.cpp
+++ b/clang/lib/CIR/Lowering/ThroughMLIR/LowerCIRToMLIR.cpp
@@ -16,8 +16,6 @@
 #include "mlir/Conversion/ControlFlowToLLVM/ControlFlowToLLVM.h"
 #include "mlir/Conversion/FuncToLLVM/ConvertFuncToLLVM.h"
 #include "mlir/Conversion/FuncToLLVM/ConvertFuncToLLVMPass.h"
-#include "mlir/Conversion/LLVMCommon/ConversionTarget.h"
-#include "mlir/Conversion/LLVMCommon/TypeConverter.h"
 #include "mlir/Conversion/MemRefToLLVM/MemRefToLLVM.h"
 #include "mlir/Conversion/SCFToControlFlow/SCFToControlFlow.h"
 #include "mlir/Dialect/Affine/IR/AffineOps.h"
@@ -28,7 +26,6 @@
 #include "mlir/Dialect/Math/IR/Math.h"
 #include "mlir/Dialect/MemRef/IR/MemRef.h"
 #include "mlir/Dialect/SCF/IR/SCF.h"
-#include "mlir/Dialect/SCF/Transforms/Passes.h"
 #include "mlir/Dialect/Vector/IR/VectorOps.h"
 #include "mlir/IR/BuiltinDialect.h"
 #include "mlir/IR/BuiltinTypes.h"
@@ -52,7 +49,6 @@
 #include "clang/CIR/LoweringHelpers.h"
 #include "clang/CIR/Passes.h"
 #include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/Sequence.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/TypeSwitch.h"
 #include "llvm/Support/TimeProfiler.h"
@@ -83,7 +79,7 @@ struct ConvertCIRToMLIRPass
                     mlir::affine::AffineDialect, mlir::memref::MemRefDialect,
                     mlir::arith::ArithDialect, mlir::cf::ControlFlowDialect,
                     mlir::scf::SCFDialect, mlir::math::MathDialect,
-                    mlir::vector::VectorDialect>();
+                    mlir::vector::VectorDialect, mlir::LLVM::LLVMDialect>();
   }
   void runOnOperation() final;
 
@@ -1388,6 +1384,20 @@ class CIRPtrStrideOpLowering
   }
 };
 
+class CIRUnreachableOpLowering
+    : public mlir::OpConversionPattern<cir::UnreachableOp> {
+public:
+  using OpConversionPattern<cir::UnreachableOp>::OpConversionPattern;
+
+  mlir::LogicalResult
+  matchAndRewrite(cir::UnreachableOp op, OpAdaptor adaptor,
+                  mlir::ConversionPatternRewriter &rewriter) const override {
+    // match and rewrite.
+    rewriter.replaceOpWithNewOp<mlir::LLVM::UnreachableOp>(op);
+    return mlir::success();
+  }
+};
+
 void populateCIRToMLIRConversionPatterns(mlir::RewritePatternSet &patterns,
                                          mlir::TypeConverter &converter) {
   patterns.add<CIRReturnLowering, CIRBrOpLowering>(patterns.getContext());
@@ -1408,7 +1418,8 @@ void populateCIRToMLIRConversionPatterns(mlir::RewritePatternSet &patterns,
            CIRBitClrsbOpLowering, CIRBitFfsOpLowering, CIRBitParityOpLowering,
            CIRIfOpLowering, CIRVectorCreateLowering, CIRVectorInsertLowering,
            CIRVectorExtractLowering, CIRVectorCmpOpLowering, CIRACosOpLowering,
-           CIRASinOpLowering>(converter, patterns.getContext());
+           CIRASinOpLowering, CIRUnreachableOpLowering>(converter,
+                                                        patterns.getContext());
 }
 
 static mlir::TypeConverter prepareTypeConverter() {
@@ -1490,11 +1501,11 @@ void ConvertCIRToMLIRPass::runOnOperation() {
 
   mlir::ConversionTarget target(getContext());
   target.addLegalOp<mlir::ModuleOp>();
-  target
-      .addLegalDialect<mlir::affine::AffineDialect, mlir::arith::ArithDialect,
-                       mlir::memref::MemRefDialect, mlir::func::FuncDialect,
-                       mlir::scf::SCFDialect, mlir::cf::ControlFlowDialect,
-                       mlir::math::MathDialect, mlir::vector::VectorDialect>();
+  target.addLegalDialect<mlir::affine::AffineDialect, mlir::arith::ArithDialect,
+                         mlir::memref::MemRefDialect, mlir::func::FuncDialect,
+                         mlir::scf::SCFDialect, mlir::cf::ControlFlowDialect,
+                         mlir::math::MathDialect, mlir::vector::VectorDialect,
+                         mlir::LLVM::LLVMDialect>();
   target.addIllegalDialect<cir::CIRDialect>();
 
   if (failed(applyPartialConversion(module, target, std::move(patterns))))
diff --git a/clang/lib/CIR/Lowering/ThroughMLIR/LowerMLIRToLLVM.cpp b/clang/lib/CIR/Lowering/ThroughMLIR/LowerMLIRToLLVM.cpp
index 728c061dcac0..f46fe4533c2f 100644
--- a/clang/lib/CIR/Lowering/ThroughMLIR/LowerMLIRToLLVM.cpp
+++ b/clang/lib/CIR/Lowering/ThroughMLIR/LowerMLIRToLLVM.cpp
@@ -19,23 +19,12 @@
 #include "mlir/Conversion/LLVMCommon/TypeConverter.h"
 #include "mlir/Conversion/MemRefToLLVM/MemRefToLLVM.h"
 #include "mlir/Conversion/SCFToControlFlow/SCFToControlFlow.h"
-#include "mlir/Dialect/Affine/IR/AffineOps.h"
-#include "mlir/Dialect/Arith/IR/Arith.h"
-#include "mlir/Dialect/ControlFlow/IR/ControlFlowOps.h"
-#include "mlir/Dialect/Func/IR/FuncOps.h"
 #include "mlir/Dialect/LLVMIR/LLVMDialect.h"
-#include "mlir/Dialect/MemRef/IR/MemRef.h"
-#include "mlir/Dialect/SCF/IR/SCF.h"
-#include "mlir/Dialect/SCF/Transforms/Passes.h"
-#include "mlir/IR/BuiltinDialect.h"
 #include "mlir/Pass/Pass.h"
 #include "mlir/Pass/PassManager.h"
 #include "mlir/Target/LLVMIR/Dialect/LLVMIR/LLVMToLLVMIRTranslation.h"
-#include "mlir/Target/LLVMIR/Export.h"
 #include "mlir/Transforms/DialectConversion.h"
-#include "clang/CIR/Dialect/IR/CIRDialect.h"
 #include "clang/CIR/Passes.h"
-#include "llvm/ADT/Sequence.h"
 
 using namespace cir;
 using namespace llvm;
diff --git a/clang/test/CIR/Lowering/ThroughMLIR/unreachable.cir b/clang/test/CIR/Lowering/ThroughMLIR/unreachable.cir
new file mode 100644
index 000000000000..1e94300b1b60
--- /dev/null
+++ b/clang/test/CIR/Lowering/ThroughMLIR/unreachable.cir
@@ -0,0 +1,10 @@
+// RUN: cir-opt %s -cir-to-mlir -o - | FileCheck %s -check-prefix=MLIR
+
+module {
+  cir.func @test_unreachable() {
+    cir.unreachable
+  }
+
+  //      MLIR: func.func @test_unreachable()
+  // MLIR-NEXT:   llvm.unreachable
+}