[CIR] Add support for delegating constructor initialization (#156757)

This adds support for zero-initialization during delegating constructor
processing.

Note, this also adds code to skip emitting constructors that are trivial
and default to match the classic codegen behavior. The incubator does
not skip these constructors, but I have found a case where this results
in a call to a default constructor that is never defined.

1 files changed, 9 insertions, 0 deletions

diff --git a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
index 3b76c0981fe8..ee9f58c829ca 100644
--- a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
+++ b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
@@ -1368,6 +1368,15 @@ mlir::LogicalResult CIRToLLVMConstantOpLowering::matchAndRewrite(
     rewriter.replaceOp(op, lowerCirAttrAsValue(op, op.getValue(), rewriter,
                                                getTypeConverter()));
     return mlir::success();
+  } else if (auto recTy = mlir::dyn_cast<cir::RecordType>(op.getType())) {
+    if (mlir::isa<cir::ZeroAttr, cir::UndefAttr>(attr)) {
+      mlir::Value initVal =
+          lowerCirAttrAsValue(op, attr, rewriter, typeConverter);
+      rewriter.replaceOp(op, initVal);
+      return mlir::success();
+    }
+    return op.emitError() << "unsupported lowering for record constant type "
+                          << op.getType();
   } else if (auto complexTy = mlir::dyn_cast<cir::ComplexType>(op.getType())) {
     mlir::Type complexElemTy = complexTy.getElementType();
     mlir::Type complexElemLLVMTy = typeConverter->convertType(complexElemTy);