Reapply r69771, with updates & fixes:

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

 - Superclasses are now always laid out in 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
   were incorrect (the ASTRecordLayout was correct however, which
   meant our debug info didn't coincide with ivar offsets, for
   example).

 - This is still very suboptimal (for example, ivar are looked up
   recursively, but I believe the ivar layout itself is now at least
   close to correct.

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


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@69811 91177308-0d34-0410-b5e6-96231b3b80d8

lib/AST/ASTContext.cpp

@@ -621,11 +621,9 @@ void ASTRecordLayout::LayoutField(const FieldDecl *FD, unsigned FieldNo,
   Alignment = std::max(Alignment, FieldAlign);
 }
 
-void ASTContext::CollectObjCIvars(const ObjCInterfaceDecl *OI,
-                             llvm::SmallVectorImpl<FieldDecl*> &Fields) {
-  const ObjCInterfaceDecl *SuperClass = OI->getSuperClass();
-  if (SuperClass)
-    CollectObjCIvars(SuperClass, Fields);
+static void CollectLocalObjCIvars(ASTContext *Ctx,
+                                  const ObjCInterfaceDecl *OI,
+                                  llvm::SmallVectorImpl<FieldDecl*> &Fields) {
   for (ObjCInterfaceDecl::ivar_iterator I = OI->ivar_begin(),
        E = OI->ivar_end(); I != E; ++I) {
     ObjCIvarDecl *IVDecl = *I;
@@ -633,31 +631,50 @@ void ASTContext::CollectObjCIvars(const ObjCInterfaceDecl *OI,
       Fields.push_back(cast<FieldDecl>(IVDecl));
   }
   // look into properties.
-  for (ObjCInterfaceDecl::prop_iterator I = OI->prop_begin(*this),
-       E = OI->prop_end(*this); I != E; ++I) {
+  for (ObjCInterfaceDecl::prop_iterator I = OI->prop_begin(*Ctx),
+       E = OI->prop_end(*Ctx); I != E; ++I) {
     if (ObjCIvarDecl *IV = (*I)->getPropertyIvarDecl())
       Fields.push_back(cast<FieldDecl>(IV));
   }
 }
 
+void ASTContext::CollectObjCIvars(const ObjCInterfaceDecl *OI,
+                             llvm::SmallVectorImpl<FieldDecl*> &Fields) {
+  if (const ObjCInterfaceDecl *SuperClass = OI->getSuperClass())
+    CollectObjCIvars(SuperClass, Fields);
+  CollectLocalObjCIvars(this, OI, Fields);
+}
+
 /// addRecordToClass - produces record info. for the class for its
 /// ivars and all those inherited.
 ///
 const RecordDecl *ASTContext::addRecordToClass(const ObjCInterfaceDecl *D) {
   assert(!D->isForwardDecl() && "Invalid decl!");
 
-  // FIXME: The only client relying on this working in the presence of
-  // forward declarations is IRgen, which should not need it. Fix
-  // and simplify this code.
   RecordDecl *&RD = ASTRecordForInterface[D];
   if (RD)
     return RD;
   
   llvm::SmallVector<FieldDecl*, 32> RecFields;
-  CollectObjCIvars(D, RecFields);
+  CollectLocalObjCIvars(this, D, RecFields);
   
   RD = RecordDecl::Create(*this, TagDecl::TK_struct, 0, D->getLocation(),
                           D->getIdentifier());
+  const RecordDecl *SRD;
+  if (const ObjCInterfaceDecl *SuperClass = D->getSuperClass()) {
+    SRD = addRecordToClass(SuperClass);
+  } else {
+    SRD = RecordDecl::Create(*this, TagDecl::TK_struct, 0, SourceLocation(), 0);
+    const_cast<RecordDecl*>(SRD)->completeDefinition(*this);
+  }
+
+  RD->addDecl(*this, 
+              FieldDecl::Create(*this, RD,
+                                SourceLocation(),
+                                0,
+                                getTagDeclType(const_cast<RecordDecl*>(SRD)),
+                                0, false));
+
   /// FIXME! Can do collection of ivars and adding to the record while
   /// doing it.
   for (unsigned i = 0, e = RecFields.size(); i != e; ++i) {

lib/CodeGen/CGObjCMac.cpp

@@ -47,26 +47,38 @@ CGObjCRuntime::GetConcreteClassStruct(CodeGen::CodeGenModule &CGM,
 ///
 static const FieldDecl *LookupFieldDeclForIvar(ASTContext &Context, 
                                                const ObjCInterfaceDecl *OID,
-                                               const ObjCIvarDecl *OIVD) {
+                                               const ObjCIvarDecl *OIVD,
+                                               const ObjCInterfaceDecl *&Found) {
   assert(!OID->isForwardDecl() && "Invalid interface decl!");
   const RecordDecl *RecordForDecl = Context.addRecordToClass(OID);
   assert(RecordForDecl && "lookupFieldDeclForIvar no storage for class");
   DeclContext::lookup_const_result Lookup =
     RecordForDecl->lookup(Context, OIVD->getDeclName());
-  assert((Lookup.first != Lookup.second) && "field decl not found");
-  return cast<FieldDecl>(*Lookup.first);
+
+  if (Lookup.first != Lookup.second) {
+    Found = OID;
+    return cast<FieldDecl>(*Lookup.first);
+  }
+
+  // If lookup failed, try the superclass.
+  //
+  // FIXME: This is slow, we shouldn't need to do this.
+  const ObjCInterfaceDecl *Super = OID->getSuperClass();
+  assert(OID && "field decl not found!");
+  return LookupFieldDeclForIvar(Context, Super, OIVD, Found);
 }
 
 uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
                                               const ObjCInterfaceDecl *OID,
                                               const ObjCIvarDecl *Ivar) {
   assert(!OID->isForwardDecl() && "Invalid interface decl!");
-  QualType T = CGM.getContext().getObjCInterfaceType(OID);
-  const llvm::StructType *STy = GetConcreteClassStruct(CGM, OID);
+  const ObjCInterfaceDecl *Container;
+  const FieldDecl *Field = 
+    LookupFieldDeclForIvar(CGM.getContext(), OID, Ivar, Container);
+  QualType T = CGM.getContext().getObjCInterfaceType(Container);
+  const llvm::StructType *STy = GetConcreteClassStruct(CGM, Container);
   const llvm::StructLayout *Layout = 
     CGM.getTargetData().getStructLayout(STy);
-  const FieldDecl *Field = 
-    LookupFieldDeclForIvar(CGM.getContext(), OID, Ivar);
   if (!Field->isBitField())
     return Layout->getElementOffset(CGM.getTypes().getLLVMFieldNo(Field));
   
@@ -97,8 +109,9 @@ LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF,
   // purposes, it would be cleaner to use a GEP on the proper type
   // since the structure layout is fixed; however for that we need to
   // be able to walk the class chain for an Ivar.
+  const ObjCInterfaceDecl *Container;
   const FieldDecl *Field = 
-    LookupFieldDeclForIvar(CGF.CGM.getContext(), OID, Ivar);
+    LookupFieldDeclForIvar(CGF.CGM.getContext(), OID, Ivar, Container);
   
   // (char *) BaseValue
   llvm::Type *I8Ptr = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);

test/CodeGenObjC/ivar-layout-64.m

@@ -0,0 +1,56 @@
+// RUN: clang-cc -triple x86_64-apple-darwin9 -emit-llvm -o %t %s &&
+// RUNX: llvm-gcc -m64 -emit-llvm -S -o %t %s &&
+
+// RUN: grep '@"OBJC_IVAR_$_I3._iv2" = global i64 8, section "__DATA, __objc_const", align 8' %t &&
+// RUN: grep '@"OBJC_IVAR_$_I3._iv3" = global i64 12, section "__DATA, __objc_const", align 8' %t &&
+// RUN: grep '@"OBJC_IVAR_$_I4._iv4" = global i64 16, section "__DATA, __objc_const", align 8' %t &&
+// RUN: grep '@"OBJC_IVAR_$_I5._iv5" = global i64 24, section "__DATA, __objc_const", align 8' %t &&
+// RUN: grep '@"OBJC_IVAR_$_I5._iv6_synth" = global i64 28, section "__DATA, __objc_const", align 8' %t &&
+// RUN: grep '@"OBJC_IVAR_$_I5._iv7_synth" = global i64 32, section "__DATA, __objc_const", align 8' %t &&
+
+// RUN: true
+
+struct s0 {
+  double x;
+};
+
+@interface I2 {
+  struct s0 _iv1;
+}
+@end
+
+@interface I3 : I2 {
+  unsigned int _iv2 :1;
+  unsigned : 0;
+  unsigned int _iv3 : 3;
+}
+@end
+
+@interface I4 : I3 {
+ char _iv4;
+}
+@end
+
+@interface I5 : I4 {
+ char _iv5;
+}
+
+@property int prop0;
+@end
+
+@implementation I3
+@end
+
+@implementation I4 
+@end
+
+@interface I5 ()
+@property int prop1;
+@property char prop2;
+@end
+
+@implementation I5
+@synthesize prop0 = _iv6_synth;
+@synthesize prop1 = _iv7_synth;
+@synthesize prop2 = _iv5;
+@end