When re-using a vtable slot for the nearest overridden method, just because

there's no return adjustment from the overridden to the overrider doesn't
mean there isn't a return adjustment from the overrider to the final
overrider.  This matters if we're emitting a virtual this-adjustment thunk
because the overrider virtually inherits from the class providing the
nearest overridden method.  Do the appropriate return adjustment in this case.

Fixes PR7611.

llvm-svn: 118466

clang/lib/CodeGen/CGVTables.cpp

@@ -1664,9 +1664,18 @@ VTableBuilder::AddMethods(BaseSubobject Base, uint64_t BaseOffsetInLayoutClass,
 
           if (ThisAdjustment.VCallOffsetOffset &&
               Overrider.Method->getParent() == MostDerivedClass) {
+
+            // There's no return adjustment from OverriddenMD and MD,
+            // but that doesn't mean there isn't one between MD and
+            // the final overrider.
+            BaseOffset ReturnAdjustmentOffset =
+              ComputeReturnAdjustmentBaseOffset(Context, Overrider.Method, MD);
+            ReturnAdjustment ReturnAdjustment = 
+              ComputeReturnAdjustment(ReturnAdjustmentOffset);
+
             // This is a virtual thunk for the most derived class, add it.
             AddThunk(Overrider.Method, 
-                     ThunkInfo(ThisAdjustment, ReturnAdjustment()));
+                     ThunkInfo(ThisAdjustment, ReturnAdjustment));
           }
         }