From 0378bf0840335c6d56b2f1b51079522054f7da4f Mon Sep 17 00:00:00 2001
From: Anders Carlsson <andersca@mac.com>
Date: Sun, 28 Feb 2010 18:08:38 +0000
Subject: [PATCH] When laying out vtables for virtual bases in construction
 vtables, we need to check if the vtable is a primary base in the layout
 class.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@97402 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/CGVtable.cpp          | 19 ++++++++++++++++---
 test/CodeGenCXX/vtable-layout.cpp | 21 ++++++++++++++-------
 2 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/lib/CodeGen/CGVtable.cpp b/lib/CodeGen/CGVtable.cpp
index 4f3cdde2d8..40a7b2f180 100644
--- a/lib/CodeGen/CGVtable.cpp
+++ b/lib/CodeGen/CGVtable.cpp
@@ -1799,9 +1799,22 @@ VtableBuilder::DeterminePrimaryVirtualBases(const CXXRecordDecl *RD,
   
   // Check if this base has a primary base.
   if (const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase()) {
-    // Check if it's virtual
-    if (Layout.getPrimaryBaseWasVirtual())
-      PrimaryVirtualBases.insert(PrimaryBase);
+
+    // Check if it's virtual.
+    if (Layout.getPrimaryBaseWasVirtual()) {
+      bool IsPrimaryVirtualBase = true;
+
+      if (isBuildingConstructorVtable()) {
+        // Check if the base is actually a primary base in the class we use for
+        // layout.
+        // FIXME: Is this check enough?
+        if (MostDerivedClassOffset != 0)
+          IsPrimaryVirtualBase = false;
+      }
+        
+      if (IsPrimaryVirtualBase)
+        PrimaryVirtualBases.insert(PrimaryBase);
+    }
   }
 
   // Traverse bases, looking for more primary virtual bases.
diff --git a/test/CodeGenCXX/vtable-layout.cpp b/test/CodeGenCXX/vtable-layout.cpp
index dce7461e04..615ab6f564 100644
--- a/test/CodeGenCXX/vtable-layout.cpp
+++ b/test/CodeGenCXX/vtable-layout.cpp
@@ -926,6 +926,13 @@ namespace Test24 {
 
 // Another construction vtable test.
 
+struct A {
+  virtual void f();
+};
+
+struct B : virtual A { };
+struct C : virtual A { };
+
 // CHECK:      Vtable for 'Test24::D' (10 entries).
 // CHECK-NEXT:    0 | vbase_offset (0)
 // CHECK-NEXT:    1 | vcall_offset (0)
@@ -952,13 +959,13 @@ namespace Test24 {
 // CHECK-NEXT:        -- (Test24::B, 0) vtable address --
 // CHECK-NEXT:    4 | void Test24::A::f()
 
-struct A {
-  virtual void f();
-};
-
-struct B : virtual A { };
-struct C : virtual A { };
-
+// CHECK:      Construction vtable for ('Test24::C', 8) in 'Test24::D' (9 entries).
+// CHECK-NEXT:    0 | vbase_offset (-8)
+// CHECK-NEXT:    1 | vcall_offset (-8)
+// CHECK-NEXT:    2 | offset_to_top (0)
+// CHECK-NEXT:    3 | Test24::C RTTI
+// CHECK-NEXT:        -- (Test24::A, 8) vtable address --
+// CHECK-NEXT:        -- (Test24::C, 8) vtable address --
 struct D : B, C {
   virtual void f();
 };
-- 
2.40.0