More ms_struct bitfield stuff:

Adjacent bit fields are packed into the same 1-, 2-, or
4-byte allocation unit if the integral types are the same
size. // rdar://8823265.

llvm-svn: 130851

clang/include/clang/AST/ASTContext.h

@@ -406,6 +406,11 @@ public:
   /// bitfield which follows the bitfield 'LastFD'.
   bool ZeroBitfieldFollowsBitfield(const FieldDecl *FD,
                                    const FieldDecl *LastFD) const;
+  
+  /// BitfieldFollowsBitfield - return 'true" if 'FD' is a
+  /// bitfield which follows the bitfield 'LastFD'.
+  bool BitfieldFollowsBitfield(const FieldDecl *FD,
+                                   const FieldDecl *LastFD) const;
 
   // Access to the set of methods overridden by the given C++ method.
   typedef CXXMethodVector::iterator overridden_cxx_method_iterator;

clang/lib/AST/ASTContext.cpp

@@ -551,6 +551,13 @@ bool ASTContext::ZeroBitfieldFollowsBitfield(const FieldDecl *FD,
 
 }
 
+bool ASTContext::BitfieldFollowsBitfield(const FieldDecl *FD,
+                                         const FieldDecl *LastFD) const {
+  return (FD->isBitField() && LastFD && LastFD->isBitField() &&
+          FD->getBitWidth()-> EvaluateAsInt(*this).getZExtValue() &&
+          LastFD->getBitWidth()-> EvaluateAsInt(*this).getZExtValue());  
+}
+
 ASTContext::overridden_cxx_method_iterator
 ASTContext::overridden_methods_begin(const CXXMethodDecl *Method) const {
   llvm::DenseMap<const CXXMethodDecl *, CXXMethodVector>::const_iterator Pos

clang/lib/AST/RecordLayoutBuilder.cpp

@@ -1269,6 +1269,31 @@ void RecordLayoutBuilder::LayoutFields(const RecordDecl *D) {
       // ignored:
       else if (Context.ZeroBitfieldFollowsNonBitfield(FD, LastFD))
         continue;
+      else if (Context.BitfieldFollowsBitfield(FD, LastFD)) {
+        // Adjacent bit fields are packed into the same 1-, 2-, or
+        // 4-byte allocation unit if the integral types are the same
+        // size and if the next bit field fits into the current
+        // allocation unit without crossing the boundary imposed by the
+        // common alignment requirements of the bit fields.
+        std::pair<uint64_t, unsigned> FieldInfo = 
+          Context.getTypeInfo(FD->getType());
+        uint64_t TypeSize = FieldInfo.first;
+        unsigned FieldAlign = FieldInfo.second;
+        FieldInfo = Context.getTypeInfo(LastFD->getType());
+        uint64_t TypeSizeLastFD = FieldInfo.first;
+        unsigned FieldAlignLastFD = FieldInfo.second;
+        if (TypeSizeLastFD != TypeSize) {
+          uint64_t UnpaddedFieldOffset = 
+            getDataSizeInBits() - UnfilledBitsInLastByte;
+          FieldAlign = std::max(FieldAlign, FieldAlignLastFD);
+          uint64_t NewSizeInBits = 
+            llvm::RoundUpToAlignment(UnpaddedFieldOffset, FieldAlign);
+          setDataSize(llvm::RoundUpToAlignment(NewSizeInBits,
+                                               Context.Target.getCharAlign()));
+          UnfilledBitsInLastByte = getDataSizeInBits() - NewSizeInBits;
+          setSize(std::max(getSizeInBits(), getDataSizeInBits()));
+        }
+      }
       LastFD = FD;
     }
     LayoutField(*Field);
@@ -1480,7 +1505,7 @@ void RecordLayoutBuilder::LayoutField(const FieldDecl *D) {
       ZeroLengthBitfield = 0;
     }
 
-    if (Context.getLangOptions().MSBitfields) {
+    if (Context.getLangOptions().MSBitfields || IsMsStruct) {
       // If MS bitfield layout is required, figure out what type is being
       // laid out and align the field to the width of that type.
       

clang/test/CodeGen/ms_struct.c

@@ -0,0 +1,23 @@
+// RUN: %clang_cc1 -triple i386-apple-darwin10 -emit-llvm %s -o - | FileCheck %s
+
+#define ATTR __attribute__((__ms_struct__))
+struct s1 {
+  int       f32;
+  long long f64;
+} ATTR s1;
+
+// CHECK: %struct.s1 = type { i32, [4 x i8], i64 }
+
+struct s2 {
+  int       f32;
+  long long f64[4];
+} ATTR s2;
+
+// CHECK: %struct.s2 = type { i32, [4 x i8], [4 x i64] }
+
+struct s3 {
+  int       f32;
+  struct s1 s;
+} ATTR s3;
+
+// CHECK: %struct.s3 = type { i32, [4 x i8], %struct.s1 }