[CIR] Move CIR CXXABI lowering to a standlone pass

clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h

@@ -97,6 +97,10 @@ class CIRBaseBuilderTy : public mlir::OpBuilder {
     return getConstPtrAttr(t, 0);
   }
 
+  mlir::TypedAttr getNullDataMemberAttr(cir::DataMemberType ty) {
+    return cir::DataMemberAttr::get(ty);
+  }
+
   mlir::TypedAttr getZeroInitAttr(mlir::Type ty) {
     if (mlir::isa<cir::IntType>(ty))
       return cir::IntAttr::get(ty, 0);
@@ -112,6 +116,8 @@ class CIRBaseBuilderTy : public mlir::OpBuilder {
       return getConstNullPtrAttr(ptrTy);
     if (auto recordTy = mlir::dyn_cast<cir::RecordType>(ty))
       return cir::ZeroAttr::get(recordTy);
+    if (auto dataMemberTy = mlir::dyn_cast<cir::DataMemberType>(ty))
+      return getNullDataMemberAttr(dataMemberTy);
     if (mlir::isa<cir::BoolType>(ty)) {
       return getFalseAttr();
     }

clang/include/clang/CIR/Dialect/IR/CIROps.td

@@ -3614,6 +3614,8 @@ def CIR_GetRuntimeMemberOp : CIR_Op<"get_runtime_member"> {
   }];
 
   let hasVerifier = 1;
+
+  let hasLLVMLowering = false;
 }
 
 //===----------------------------------------------------------------------===//

clang/include/clang/CIR/Dialect/Passes.h

@@ -23,6 +23,7 @@ namespace mlir {
 std::unique_ptr<Pass> createCIRCanonicalizePass();
 std::unique_ptr<Pass> createCIRFlattenCFGPass();
 std::unique_ptr<Pass> createCIRSimplifyPass();
+std::unique_ptr<Pass> createCXXABILoweringPass();
 std::unique_ptr<Pass> createHoistAllocasPass();
 std::unique_ptr<Pass> createLoweringPreparePass();
 std::unique_ptr<Pass> createLoweringPreparePass(clang::ASTContext *astCtx);

clang/include/clang/CIR/Dialect/Passes.td

@@ -82,6 +82,17 @@ def GotoSolver : Pass<"cir-goto-solver"> {
   let dependentDialects = ["cir::CIRDialect"];
 }
 
+def CXXABILowering : Pass<"cir-cxxabi-lowering"> {
+  let summary = "Lower abstract C++ operations to target-specific ABI form";
+  let description = [{
+    This pass lowers high-level operations that represent C++ constructs in a
+    target-independent way to concrete, target specific operations.
+  }];
+  let constructor = "mlir::createCXXABILoweringPass()";
+  let dependentDialects = ["cir::CIRDialect"];
+}
+
+
 def LoweringPrepare : Pass<"cir-lowering-prepare"> {
   let summary = "Lower to more fine-grained CIR operations before lowering to "
     "other dialects";

clang/lib/CIR/CodeGen/CIRGenTypes.cpp

@@ -33,8 +33,10 @@ mlir::MLIRContext &CIRGenTypes::getMLIRContext() const {
 /// expanding the type because we're in a recursive context.
 bool CIRGenTypes::isFuncParamTypeConvertible(clang::QualType type) {
   // Some ABIs cannot have their member pointers represented in LLVM IR unless
-  // certain circumstances have been reached.
-  assert(!type->getAs<MemberPointerType>() && "NYI");
+  // certain circumstances have been reached, but in CIR we represent member
+  // pointer types abstractly at this point so they are always convertible.
+  if (type->getAs<MemberPointerType>())
+    return true;
 
   // If this isn't a tag type, we can convert it.
   const TagType *tagType = type->getAs<TagType>();

clang/lib/CIR/Dialect/Transforms/CMakeLists.txt

@@ -3,6 +3,7 @@ add_subdirectory(TargetLowering)
 add_clang_library(MLIRCIRTransforms
   CIRCanonicalize.cpp
   CIRSimplify.cpp
+  CXXABILowering.cpp
   FlattenCFG.cpp
   HoistAllocas.cpp
   LoweringPrepare.cpp