Rewrite record layout for ms_struct structs.

The old implementation of ms_struct in RecordLayoutBuilder was a
complete mess: it depended on complicated conditionals which didn't
really reflect the underlying logic, and placed a burden on users of
the resulting RecordLayout. This commit rips out almost all of the
old code, and replaces it with simple checks in
RecordLayoutBuilder::LayoutBitField.

This commit also fixes <rdar://problem/14252115>, a bug where class
inheritance would cause us to lay out bitfields incorrectly.

llvm-svn: 185018

1 files changed, 2 insertions, 30 deletions

diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
index 3e13e972801..c06cf2f1b22 100644
--- a/clang/lib/CodeGen/CGExprConstant.cpp
+++ b/clang/lib/CodeGen/CGExprConstant.cpp
@@ -373,30 +373,16 @@ bool ConstStructBuilder::Build(InitListExpr *ILE) {
 
   unsigned FieldNo = 0;
   unsigned ElementNo = 0;
-  const FieldDecl *LastFD = 0;
-  bool IsMsStruct = RD->isMsStruct(CGM.getContext());
   
   for (RecordDecl::field_iterator Field = RD->field_begin(),
        FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
-    if (IsMsStruct) {
-      // Zero-length bitfields following non-bitfield members are
-      // ignored:
-      if (CGM.getContext().ZeroBitfieldFollowsNonBitfield(*Field, LastFD)) {
-        --FieldNo;
-        continue;
-      }
-      LastFD = *Field;
-    }
-    
     // If this is a union, skip all the fields that aren't being initialized.
     if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field)
       continue;
 
     // Don't emit anonymous bitfields, they just affect layout.
-    if (Field->isUnnamedBitfield()) {
-      LastFD = *Field;
+    if (Field->isUnnamedBitfield())
       continue;
-    }
 
     // Get the initializer.  A struct can include fields without initializers,
     // we just use explicit null values for them.
@@ -472,31 +458,17 @@ void ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD,
   }
 
   unsigned FieldNo = 0;
-  const FieldDecl *LastFD = 0;
-  bool IsMsStruct = RD->isMsStruct(CGM.getContext());
   uint64_t OffsetBits = CGM.getContext().toBits(Offset);
 
   for (RecordDecl::field_iterator Field = RD->field_begin(),
        FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
-    if (IsMsStruct) {
-      // Zero-length bitfields following non-bitfield members are
-      // ignored:
-      if (CGM.getContext().ZeroBitfieldFollowsNonBitfield(*Field, LastFD)) {
-        --FieldNo;
-        continue;
-      }
-      LastFD = *Field;
-    }
-
     // If this is a union, skip all the fields that aren't being initialized.
     if (RD->isUnion() && Val.getUnionField() != *Field)
       continue;
 
     // Don't emit anonymous bitfields, they just affect layout.
-    if (Field->isUnnamedBitfield()) {
-      LastFD = *Field;
+    if (Field->isUnnamedBitfield())
       continue;
-    }
 
     // Emit the value of the initializer.
     const APValue &FieldValue =