Add partial support for using anonymous bitfields (e.g., int : 0) to enforce

alignment.  This fixes cases where the anonymous bitfield is followed by a 
non-bitfield member.  E.g.,

struct t4
{
  int foo : 1;
  long : 0;
  char bar;
};

Part of rdar://9859156

llvm-svn: 136858

1 files changed, 10 insertions, 0 deletions

diff --git a/clang/lib/Basic/Targets.cpp b/clang/lib/Basic/Targets.cpp
index ec45a87fa02..89b6ce960b0 100644
--- a/clang/lib/Basic/Targets.cpp
+++ b/clang/lib/Basic/Targets.cpp
@@ -1963,6 +1963,16 @@ public:
       // structures. This corresponds to PCC_BITFIELD_TYPE_MATTERS in gcc.
       UseBitFieldTypeAlignment = false;
 
+      /// Do force alignment of members that follow zero length bitfields.  If
+      /// the alignment of the zero-length bitfield is greater than the member 
+      /// that follows it, `bar', `bar' will be aligned as the  type of the 
+      /// zero length bitfield.
+      UseZeroLengthBitfieldAlignment = true;
+
+      /// gcc forces the alignment to 4 bytes, regardless of the type of the
+      /// zero length bitfield.
+      ZeroLengthBitfieldBoundary = 32;
+
       if (IsThumb) {
         // Thumb1 add sp, #imm requires the immediate value be multiple of 4,
         // so set preferred for small types to 32.