[ms-abi] Adjusting Rules for Padding Between Bases

The presence of a VBPtr suppresses the presence of zero sized 
sub-objects in the non-virtual portion of the object in the context of 
determining if two base objects need alias-avoidance padding placed 
between them.

Test cases included.

llvm-svn: 198975

1 files changed, 6 insertions, 0 deletions

diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index 30293c27c17..6a708a7e8d7 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -2477,6 +2477,9 @@ void MicrosoftRecordLayoutBuilder::injectVBPtr(const CXXRecordDecl *RD) {
          i->second += Offset;
   // Update the object alignment.
   updateAlignment(PointerInfo.Alignment);
+  // The presence of a vbptr suppresses zero sized objects that are not in
+  // virtual bases.
+  HasZeroSizedSubObject = false;
 }
 
 void MicrosoftRecordLayoutBuilder::injectVFPtr(const CXXRecordDecl *RD) {
@@ -2566,6 +2569,9 @@ void MicrosoftRecordLayoutBuilder::injectVPtrs(const CXXRecordDecl *RD) {
     }
   }
   layoutFields(RD);
+  // The presence of a vbptr suppresses zero sized objects that are not in
+  // virtual bases.
+  HasZeroSizedSubObject = false;
 }
 
 void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) {