[MS-ABI] adds padding before all vbases after a bitfield

 
MS-ABI adds padding before *every* vbase if the last field in a record 
is a bit-field. This changes clangs behavior to match. I also fix some 
windows-style line endings in the test file.

Differential Revision: http://llvm-reviews.chandlerc.com/D2277

llvm-svn: 196605

1 files changed, 7 insertions, 8 deletions

diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index ec791564893..b692025aa0f 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -2014,9 +2014,9 @@ static bool isMsLayout(const RecordDecl* D) {
 //   one.
 // * The last zero size virtual base may be placed at the end of the struct.
 //   and can potentially alias a zero sized type in the next struct.
-// * If the last field is a non-zero length bitfield and we have any virtual
-//   bases then some extra padding is added before the virtual bases for no
-//   obvious reason.
+// * If the last field is a non-zero length bitfield, all virtual bases will
+//   have extra padding added before them for no obvious reason.  The padding
+//   has the same number of bits as the type of the bitfield.
 // * When laying out empty non-virtual bases, an extra byte of padding is added
 //   if the non-virtual base before the empty non-virtual base has a vbptr.
 // * The ABI attempts to avoid aliasing of zero sized bases by adding padding
@@ -2558,17 +2558,16 @@ void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) {
   llvm::SmallPtrSet<const CXXRecordDecl *, 2> HasVtordisp =
       computeVtorDispSet(RD);
 
-  // If the last field we laid out was a non-zero length bitfield then add some
-  // extra padding for no obvious reason.
-  if (LastFieldIsNonZeroWidthBitfield)
-    Size += CurrentBitfieldSize;
-
   // Iterate through the virtual bases and lay them out.
   for (CXXRecordDecl::base_class_const_iterator i = RD->vbases_begin(),
                                                 e = RD->vbases_end();
        i != e; ++i) {
     const CXXRecordDecl *BaseDecl =
         cast<CXXRecordDecl>(i->getType()->castAs<RecordType>()->getDecl());
+    // If the last field we laid out was a non-zero length bitfield then add
+    // some extra padding for no obvious reason.
+    if (LastFieldIsNonZeroWidthBitfield)
+      Size += CurrentBitfieldSize;
     layoutVirtualBase(BaseDecl, HasVtordisp.count(BaseDecl));
   }
 }