[CIR] Lower struct/union/class to tuple

Forward the data layout to the type converter.
This is not a current solution since it is not possible for now to have a memref
of tuple in MLIR yet.

Author: keryell

clang/include/clang/CIR/LowerToMLIR.h

@@ -20,7 +20,7 @@ namespace cir {
 void populateCIRLoopToSCFConversionPatterns(mlir::RewritePatternSet &patterns,
                                             mlir::TypeConverter &converter);
 
-mlir::TypeConverter prepareTypeConverter();
+mlir::TypeConverter prepareTypeConverter(mlir::DataLayout &dataLayout);
 
 void runAtStartOfConvertCIRToMLIRPass(std::function<void(mlir::ConversionTarget)>);
 

clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp

@@ -584,7 +584,7 @@ mlir::Value CirAttrToValue::visitCirAttr(cir::ConstArrayAttr constArr) {
   auto loc = parentOp->getLoc();
   mlir::Value result;
 
-  if (auto zeros = constArr.getTrailingZerosNum()) {
+  if (constArr.getTrailingZerosNum()) {
     auto arrayTy = constArr.getType();
     result = rewriter.create<mlir::LLVM::ZeroOp>(
         loc, converter->convertType(arrayTy));

clang/lib/CIR/Lowering/ThroughMLIR/LowerCIRToMLIR.cpp

@@ -1378,7 +1378,7 @@ void populateCIRToMLIRConversionPatterns(mlir::RewritePatternSet &patterns,
                                                         patterns.getContext());
 }
 
-mlir::TypeConverter prepareTypeConverter() {
+mlir::TypeConverter prepareTypeConverter(mlir::DataLayout &dataLayout) {
   mlir::TypeConverter converter;
   converter.addConversion([&](cir::PointerType type) -> mlir::Type {
     auto ty = convertTypeForMemory(converter, type.getPointee());
@@ -1441,14 +1441,41 @@ mlir::TypeConverter prepareTypeConverter() {
     auto ty = converter.convertType(type.getEltType());
     return mlir::VectorType::get(type.getSize(), ty);
   });
+  converter.addConversion([&](cir::StructType type) -> mlir::Type {
+    // FIXME(cir): create separate unions, struct, and classes types.
+    // Convert struct members.
+    llvm::SmallVector<mlir::Type> mlirMembers;
+    switch (type.getKind()) {
+    case cir::StructType::Class:
+      // TODO(cir): This should be properly validated.
+    case cir::StructType::Struct:
+      for (auto ty : type.getMembers())
+        mlirMembers.push_back(converter.convertType(ty));
+      break;
+    // Unions are lowered as only the largest member.
+    case cir::StructType::Union: {
+      auto largestMember = type.getLargestMember(dataLayout);
+      if (largestMember)
+        mlirMembers.push_back(converter.convertType(largestMember));
+      break;
+    }
+    }
+
+    // Struct has a name: lower as an identified struct.
+    mlir::TupleType tuple;
+    // FIXME(cir): all the following has to be somehow kept. With some
+    // attributes?
+    tuple = mlir::TupleType::get(type.getContext(), mlirMembers);
+    return tuple;
+  });
 
   return converter;
 }
 
 void ConvertCIRToMLIRPass::runOnOperation() {
   auto module = getOperation();
-
-  auto converter = prepareTypeConverter();
+  mlir::DataLayout dataLayout{module};
+  auto converter = prepareTypeConverter(dataLayout);
 
   mlir::RewritePatternSet patterns(&getContext());