r206508 - MS ABI: Don't append to vbtables that we shouldn't extend

[Reid Kleckner]

Author: rnk
Date: Thu Apr 17 17:47:52 2014
New Revision: 206508

URL: http://llvm.org/viewvc/llvm-project?rev=206508&view=rev
Log:
MS ABI: Don't append to vbtables that we shouldn't extend

This was probably a benign bug, since nobody would look at the vbtable
slots that we were filling in.

Modified:
    cfe/trunk/lib/AST/VTableBuilder.cpp
    cfe/trunk/test/CodeGenCXX/microsoft-abi-vbtables.cpp

Modified: cfe/trunk/lib/AST/VTableBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/VTableBuilder.cpp?rev=206508&r1=206507&r2=206508&view=diff
==============================================================================
--- cfe/trunk/lib/AST/VTableBuilder.cpp (original)
+++ cfe/trunk/lib/AST/VTableBuilder.cpp Thu Apr 17 17:47:52 2014
@@ -3180,11 +3180,7 @@ void MicrosoftVTableContext::computeVTab
     const VPtrInfoVector &BasePaths =
         ForVBTables ? enumerateVBTables(Base) : getVFPtrOffsets(Base);
 
-    for (VPtrInfoVector::const_iterator II = BasePaths.begin(),
-                                        EE = BasePaths.end();
-         II != EE; ++II) {
-      VPtrInfo *BaseInfo = *II;
-
+    for (VPtrInfo *BaseInfo : BasePaths) {
       // Don't include the path if it goes through a virtual base that we've
       // already included.
       if (setsIntersect(VBasesSeen, BaseInfo->ContainingVBases))
@@ -3202,12 +3198,16 @@ void MicrosoftVTableContext::computeVTab
       // FIXME: Why do we need this?
       P->PathToBaseWithVPtr.insert(P->PathToBaseWithVPtr.begin(), Base);
 
-      // Keep track of which derived class ultimately uses the vtable, and what
-      // the full adjustment is from the MDC to this vtable.  The adjustment is
-      // captured by an optional vbase and a non-virtual offset.
-      if (Base == (ForVBTables ? Layout.getBaseSharingVBPtr()
+      // Keep track of which vtable the derived class is going to extend with
+      // new methods or bases.  We append to either the vftable of our primary
+      // base, or the first non-virtual base that has a vbtable.
+      if (P->ReusingBase == Base &&
+          Base == (ForVBTables ? Layout.getBaseSharingVBPtr()
                                : Layout.getPrimaryBase()))
         P->ReusingBase = RD;
+
+      // Keep track of the full adjustment from the MDC to this vtable.  The
+      // adjustment is captured by an optional vbase and a non-virtual offset.
       if (B.isVirtual())
         P->ContainingVBases.push_back(Base);
       else if (P->ContainingVBases.empty())

Modified: cfe/trunk/test/CodeGenCXX/microsoft-abi-vbtables.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/microsoft-abi-vbtables.cpp?rev=206508&r1=206507&r2=206508&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/microsoft-abi-vbtables.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/microsoft-abi-vbtables.cpp Thu Apr 17 17:47:52 2014
@@ -518,3 +518,13 @@ F x;
 // CHECK-DAG: @"\01??_8F at Test28@@7BD at 1@@" =
 // CHECK-DAG: @"\01??_8F at Test28@@7BE at 1@@" =
 }
+
+namespace Test29 {
+struct A {};
+struct B : virtual A {};
+struct C : virtual B {};
+struct D : C {};
+D d;
+
+// CHECK-DAG: @"\01??_8D at Test29@@7BB at 1@@" = linkonce_odr unnamed_addr constant [2 x i32] zeroinitializer
+}