From ff4ba5dfa221380aeba85134c8e62266b27cd904 Mon Sep 17 00:00:00 2001
From: Andy Kaylor <akaylor@nvidia.com>
Date: Wed, 3 Sep 2025 16:12:58 -0700
Subject: [PATCH] [CIR] Finish record layout for classes with virtual bases

There was a small piece left unimplemented for classes with a primary
virtual base. This adds that implementation.
---
 .../CIR/CodeGen/CIRGenRecordLayoutBuilder.cpp |  5 ++--
 clang/test/CIR/CodeGen/vbase.cpp              | 23 +++++++++++++++++++
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/clang/lib/CIR/CodeGen/CIRGenRecordLayoutBuilder.cpp b/clang/lib/CIR/CodeGen/CIRGenRecordLayoutBuilder.cpp
index 6c7cf75aa2c99..d732248f31a00 100644
--- a/clang/lib/CIR/CodeGen/CIRGenRecordLayoutBuilder.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenRecordLayoutBuilder.cpp
@@ -913,8 +913,9 @@ void CIRRecordLowering::computeVolatileBitfields() {
 void CIRRecordLowering::accumulateBases() {
   // If we've got a primary virtual base, we need to add it with the bases.
   if (astRecordLayout.isPrimaryBaseVirtual()) {
-    cirGenTypes.getCGModule().errorNYI(recordDecl->getSourceRange(),
-                                       "accumulateBases: primary virtual base");
+    const CXXRecordDecl *baseDecl = astRecordLayout.getPrimaryBase();
+    members.push_back(MemberInfo(CharUnits::Zero(), MemberInfo::InfoKind::Base,
+                                 getStorageType(baseDecl), baseDecl));
   }
 
   // Accumulate the non-virtual bases.
diff --git a/clang/test/CIR/CodeGen/vbase.cpp b/clang/test/CIR/CodeGen/vbase.cpp
index 1d1b5e083bfc9..2e0345c24b069 100644
--- a/clang/test/CIR/CodeGen/vbase.cpp
+++ b/clang/test/CIR/CodeGen/vbase.cpp
@@ -5,6 +5,29 @@
 // RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu -emit-llvm %s -o %t.ll
 // RUN: FileCheck --input-file=%t.ll %s --check-prefix=OGCG
 
+// Test the record layout for a class with a primary virtual base.
+class Base {
+public:
+  virtual void f();
+};
+
+class Derived : public virtual Base {};
+
+// This is just here to force the record types to be emitted.
+void f() {
+  Derived d;
+}
+
+// CIR: !rec_Base = !cir.record<class "Base" {!cir.vptr}>
+// CIR: !rec_Derived = !cir.record<class "Derived" {!rec_Base}>
+
+// LLVM: %class.Derived = type { %class.Base }
+// LLVM: %class.Base = type { ptr }
+
+// OGCG: %class.Derived = type { %class.Base }
+// OGCG: %class.Base = type { ptr }
+
+// Test the constructor handling for a class with a virtual base.
 struct A {
   int a;
 };