[ms-abi] Fixes improperly sized vfptrs with pragma pack

With pragma pack, the layout engine would produce vfptrs that were 
packed width rather than pointer width.  This patch addresses the issue 
and adds a test case.

llvm-svn: 198059

1 files changed, 4 insertions, 5 deletions

diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index 74010ce7aa0..832bfef90c9 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -2316,15 +2316,14 @@ void MicrosoftRecordLayoutBuilder::layoutVFPtr(const CXXRecordDecl *RD) {
   if (!HasExtendableVFPtr)
     return;
 
+  updateAlignment(PointerAlignment);
+  Size = Size.RoundUpToAlignment(PointerAlignment) + PointerSize;
   // MSVC 32 (but not 64) potentially over-aligns the vf-table pointer by giving
   // it the max alignment of all the non-virtual data in the class.  The
   // resulting layout is essentially { vftbl, { nvdata } }.  This is completely
   // unnecessary, but we're not here to pass judgment.
-  updateAlignment(PointerAlignment);
-  if (Is64BitMode)
-    Size = Size.RoundUpToAlignment(PointerAlignment) + PointerSize;
-  else
-    Size = Size.RoundUpToAlignment(PointerAlignment) + Alignment;
+  if (!Is64BitMode && Alignment > PointerSize)
+    Size += Alignment - PointerSize;
 }
 
 void