MS ABI: Bitfields FielDecls only align if they allocate

Don't consider a __declspec(align) on a bitfield's declaration if it didn't
allocate any underlying storage.

This fixes PR19414.

llvm-svn: 206132

1 files changed, 5 insertions, 3 deletions

diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index 04a0fab737a..5eb87e7fc75 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -2291,9 +2291,6 @@ MicrosoftRecordLayoutBuilder::getAdjustedElementInfo(
   if (FD->hasAttr<PackedAttr>())
     Info.Alignment = CharUnits::One();
   Info.Alignment = std::max(Info.Alignment, FieldRequiredAlignment);
-  // TODO: Add a Sema warning that MS ignores bitfield alignment in unions.
-  if (!(FD->isBitField() && IsUnion))
-    Alignment = std::max(Alignment, Info.Alignment);
   return Info;
 }
 
@@ -2472,6 +2469,7 @@ void MicrosoftRecordLayoutBuilder::layoutField(const FieldDecl *FD) {
   }
   LastFieldIsNonZeroWidthBitfield = false;
   ElementInfo Info = getAdjustedElementInfo(FD);
+  Alignment = std::max(Alignment, Info.Alignment);
   if (IsUnion) {
     placeFieldAtOffset(CharUnits::Zero());
     Size = std::max(Size, Info.Size);
@@ -2507,11 +2505,13 @@ void MicrosoftRecordLayoutBuilder::layoutBitField(const FieldDecl *FD) {
   if (IsUnion) {
     placeFieldAtOffset(CharUnits::Zero());
     Size = std::max(Size, Info.Size);
+    // TODO: Add a Sema warning that MS ignores bitfield alignment in unions.
   } else {
     // Allocate a new block of memory and place the bitfield in it.
     CharUnits FieldOffset = Size.RoundUpToAlignment(Info.Alignment);
     placeFieldAtOffset(FieldOffset);
     Size = FieldOffset + Info.Size;
+    Alignment = std::max(Alignment, Info.Alignment);
     RemainingBitsInField = Context.toBits(Info.Size) - Width;
   }
 }
@@ -2531,11 +2531,13 @@ MicrosoftRecordLayoutBuilder::layoutZeroWidthBitField(const FieldDecl *FD) {
   if (IsUnion) {
     placeFieldAtOffset(CharUnits::Zero());
     Size = std::max(Size, Info.Size);
+    // TODO: Add a Sema warning that MS ignores bitfield alignment in unions.
   } else {
     // Round up the current record size to the field's alignment boundary.
     CharUnits FieldOffset = Size.RoundUpToAlignment(Info.Alignment);
     placeFieldAtOffset(FieldOffset);
     Size = FieldOffset;
+    Alignment = std::max(Alignment, Info.Alignment);
   }
 }