Rework the shadow struct that is layed out for Objective-C classes.

 - Superclasses are now always laid out their shadow structure at the
   first field.

 - Prior to this, the entire class heirarchy was flattened into a
   single structure which meant that alignment, padding, and bitfields
   weren't packed correctly (the ASTRecordLayout was correct however,
   which meant our debug info didn't coincide with ivar offsets, for
   example).

 - This is still very suboptimal, but I believe the ivar layout itself
   is now at least close to correct.

 - <rdar://problem/6773388> error: objc[29823]: layout bitmap sliding
   backwards

llvm-svn: 69771

1 files changed, 23 insertions, 5 deletions

diff --git a/clang/lib/AST/DeclObjC.cpp b/clang/lib/AST/DeclObjC.cpp
index 5df5ff3a7ad..be23e3039d7 100644
--- a/clang/lib/AST/DeclObjC.cpp
+++ b/clang/lib/AST/DeclObjC.cpp
@@ -380,14 +380,32 @@ ObjCInterfaceDecl::FindCategoryDeclaration(IdentifierInfo *CategoryId) const {
 ///
 const FieldDecl *
 ObjCInterfaceDecl::lookupFieldDeclForIvar(ASTContext &Context, 
-                                          const ObjCIvarDecl *IVar) const {
+                                          const ObjCIvarDecl *OIVD) const {
   assert(!isForwardDecl() && "Invalid interface decl!");
   const RecordDecl *RecordForDecl = Context.addRecordToClass(this);
-  assert(RecordForDecl && "lookupFieldDeclForIvar no storage for class");
   DeclContext::lookup_const_result Lookup =
-    RecordForDecl->lookup(Context, IVar->getDeclName());
-  assert((Lookup.first != Lookup.second) && "field decl not found");
-  return cast<FieldDecl>(*Lookup.first);
+    RecordForDecl->lookup(Context, OIVD->getDeclName());
+
+  if (Lookup.first != Lookup.second)
+    return cast<FieldDecl>(*Lookup.first);
+
+  // If lookup failed, try the superclass.
+  //
+  // FIXME: This is very non-performant. However, the root problem
+  // here is not the lookup itself. The main issue is that we should
+  // be able to map from an IvarDecl back to the context it lives
+  // inside; then this problem goes away. Currently, however,
+  // IvarDecl's live inside the translation unit!!!!
+  //
+  // Fixing IvarDecl's is less obvious than it might appear, we need
+  // to choose where synthesized ivars should live, and we also need
+  // to decide where to put IvarDecl's which appeared in an
+  // implementation context (either in the situation where they must
+  // duplicate the instance variables, or if there was no instance
+  // declaration).
+  const ObjCInterfaceDecl *OID = getSuperClass();
+  assert(OID && "field decl not found!");
+  return OID->lookupFieldDeclForIvar(Context, OIVD);
 }
 
 //===----------------------------------------------------------------------===//