Add Clang support code.

4 files changed, 1251 insertions, 0 deletions

diff --git a/COPYING.Clang b/COPYING.Clang
new file mode 100644
index 0000000..21cb5c7
--- /dev/null
+++ b/COPYING.Clang
@@ -0,0 +1,63 @@
+==============================================================================
+LLVM Release License
+==============================================================================
+University of Illinois/NCSA
+Open Source License
+
+Copyright (c) 2007 University of Illinois at Urbana-Champaign.
+All rights reserved.
+
+Developed by:
+
+    LLVM Team
+
+    University of Illinois at Urbana-Champaign
+
+    http://llvm.org
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal with
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+    * Redistributions of source code must retain the above copyright notice,
+      this list of conditions and the following disclaimers.
+
+    * Redistributions in binary form must reproduce the above copyright notice,
+      this list of conditions and the following disclaimers in the
+      documentation and/or other materials provided with the distribution.
+
+    * Neither the names of the LLVM Team, University of Illinois at
+      Urbana-Champaign, nor the names of its contributors may be used to
+      endorse or promote products derived from this Software without specific
+      prior written permission.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH THE
+SOFTWARE.
+
+==============================================================================
+The LLVM software contains code written by third parties.  Such software will
+have its own individual LICENSE.TXT file in the directory in which it appears.
+This file will describe the copyrights, license, and restrictions which apply
+to that code.
+
+The disclaimer of warranty in the University of Illinois Open Source License
+applies to all code in the LLVM Distribution, and nothing in any of the
+other licenses gives permission to use the names of the LLVM Team or the
+University of Illinois to endorse or promote products derived from this
+Software.
+
+The following pieces of software have additional or alternate copyrights,
+licenses, and/or restrictions:
+
+Program             Directory
+-------             ---------
+<none yet>
+
diff --git a/Clang/CGObjC.cpp b/Clang/CGObjC.cpp
new file mode 100644
index 0000000..9bf53d9
--- /dev/null
+++ b/Clang/CGObjC.cpp
@@ -0,0 +1,193 @@
+//===---- CGBuiltin.cpp - Emit LLVM Code for builtins ---------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This contains code to emit Objective-C code as LLVM code.
+//
+//===----------------------------------------------------------------------===//
+
+#include "CGObjCRuntime.h"
+#include "CodeGenFunction.h"
+#include "CodeGenModule.h"
+#include "clang/AST/ExprObjC.h"
+#include "llvm/Constant.h"
+#include "llvm/Function.h"
+
+using namespace clang;
+using namespace CodeGen;
+
+/// Emits an instance of NSConstantString representing the object.
+llvm::Value *CodeGenFunction::EmitObjCStringLiteral(const ObjCStringLiteral *E){
+  return CGM.getObjCRuntime()->GenerateConstantString(
+      E->getString()->getStrData(), E->getString()->getByteLength());
+}
+
+/// Emit a selector.
+llvm::Value *CodeGenFunction::EmitObjCSelectorExpr(const ObjCSelectorExpr *E) {
+  // Untyped selector.
+  // Note that this implementation allows for non-constant strings to be passed
+  // as arguments to @selector().  Currently, the only thing preventing this
+  // behaviour is the type checking in the front end.
+  return CGM.getObjCRuntime()->GetSelector(Builder, E->getSelector());
+}
+
+
+
+llvm::Value *CodeGenFunction::EmitObjCMessageExpr(const ObjCMessageExpr *E) {
+  // Only the lookup mechanism and first two arguments of the method
+  // implementation vary between runtimes.  We can get the receiver and
+  // arguments in generic code.
+  
+  CGObjCRuntime *Runtime = CGM.getObjCRuntime();
+  const Expr *ReceiverExpr = E->getReceiver();
+  bool isSuperMessage = false;
+  // Find the receiver
+  llvm::Value *Receiver;
+  if (!ReceiverExpr) {
+    const char * classname = E->getClassName()->getName();
+    if (!strcmp(classname, "super")) {
+      classname = E->getMethodDecl()->getClassInterface()->getName();
+    }
+    llvm::Value *ClassName = CGM.GetAddrOfConstantString(classname);
+    ClassName = Builder.CreateStructGEP(ClassName, 0);
+    Receiver = Runtime->LookupClass(Builder, ClassName);
+  } else if (isa<PreDefinedExpr>(E->getReceiver())) {
+    assert(cast<PreDefinedExpr>(E->getReceiver())->getIdentType() == 
+           PreDefinedExpr::ObjCSuper);
+    isSuperMessage = true;
+    Receiver = LoadObjCSelf();
+  } else {
+   Receiver = EmitScalarExpr(E->getReceiver());
+  }
+
+  // Process the arguments
+  unsigned ArgC = E->getNumArgs();
+  llvm::SmallVector<llvm::Value*, 16> Args;
+  for (unsigned i = 0; i != ArgC; ++i) {
+    const Expr *ArgExpr = E->getArg(i);
+    QualType ArgTy = ArgExpr->getType();
+    if (!hasAggregateLLVMType(ArgTy)) {
+      // Scalar argument is passed by-value.
+      Args.push_back(EmitScalarExpr(ArgExpr));
+    } else if (ArgTy->isAnyComplexType()) {
+      // Make a temporary alloca to pass the argument.
+      llvm::Value *DestMem = CreateTempAlloca(ConvertType(ArgTy));
+      EmitComplexExprIntoAddr(ArgExpr, DestMem, false);
+      Args.push_back(DestMem);
+    } else {
+      llvm::Value *DestMem = CreateTempAlloca(ConvertType(ArgTy));
+      EmitAggExpr(ArgExpr, DestMem, false);
+      Args.push_back(DestMem);
+    }
+  }
+
+  if (isSuperMessage) {
+    // super is only valid in an Objective-C method
+    const ObjCMethodDecl *OMD = cast<ObjCMethodDecl>(CurFuncDecl);
+    const char *SuperClass =
+      OMD->getClassInterface()->getSuperClass()->getName();
+    return Runtime->GenerateMessageSendSuper(Builder, ConvertType(E->getType()),
+                                             Receiver, SuperClass,
+                                             Receiver, E->getSelector(),
+                                             &Args[0], Args.size());
+  }
+  return Runtime->GenerateMessageSend(Builder, ConvertType(E->getType()),
+                                      LoadObjCSelf(),
+                                      Receiver, E->getSelector(),
+                                      &Args[0], Args.size());
+}
+
+/// Generate an Objective-C method.  An Objective-C method is a C function with
+/// its pointer, name, and types registered in the class struture.  
+void CodeGenFunction::GenerateObjCMethod(const ObjCMethodDecl *OMD) {
+
+  llvm::SmallVector<const llvm::Type *, 16> ParamTypes;
+  for (unsigned i=0 ; i<OMD->param_size() ; i++) {
+    const llvm::Type *Ty = ConvertType(OMD->getParamDecl(i)->getType());
+    if (Ty->isFirstClassType())
+      ParamTypes.push_back(Ty);
+    else
+      ParamTypes.push_back(llvm::PointerType::getUnqual(Ty));
+  }
+  std::string CategoryName = "";
+  if (ObjCCategoryImplDecl *OCD =
+      dyn_cast<ObjCCategoryImplDecl>(OMD->getMethodContext())) {
+    CategoryName = OCD->getName();
+  }
+  const llvm::Type *ReturnTy = 
+    CGM.getTypes().ConvertReturnType(OMD->getResultType());
+  CurFn = CGM.getObjCRuntime()->MethodPreamble(
+                                          OMD->getClassInterface()->getName(),
+                                              CategoryName,
+                                              OMD->getSelector().getName(),
+                                              ReturnTy,
+                                              llvm::PointerType::getUnqual(
+                                              llvm::Type::Int32Ty),
+                                              ParamTypes.begin(),
+                                              OMD->param_size(),
+                                              !OMD->isInstance(),
+                                              OMD->isVariadic());
+  llvm::BasicBlock *EntryBB = llvm::BasicBlock::Create("entry", CurFn);
+  
+  // Create a marker to make it easy to insert allocas into the entryblock
+  // later.  Don't create this with the builder, because we don't want it
+  // folded.
+  llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
+  AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "allocapt",
+                                         EntryBB);
+
+  FnRetTy = OMD->getResultType();
+  CurFuncDecl = OMD;
+
+  Builder.SetInsertPoint(EntryBB);
+  
+  // Emit allocs for param decls.  Give the LLVM Argument nodes names.
+  llvm::Function::arg_iterator AI = CurFn->arg_begin();
+  
+  if (hasAggregateLLVMType(OMD->getResultType())) {
+    ++AI;
+  }
+  // Add implicit parameters to the decl map.
+  // TODO: Add something to AST to let the runtime specify the names and types
+  // of these.
+
+  llvm::Value *&SelfEntry = LocalDeclMap[OMD->getSelfDecl()];
+  const llvm::Type *IPTy = AI->getType();
+  llvm::Value *DeclPtr = new llvm::AllocaInst(IPTy, 0, AI->getName() +
+      ".addr", AllocaInsertPt);
+  // Store the initial value into the alloca.
+  Builder.CreateStore(AI, DeclPtr);
+  SelfEntry = DeclPtr;
+  ++AI;
+  llvm::Value *&CmdEntry = LocalDeclMap[OMD->getCmdDecl()];
+  IPTy = AI->getType();
+  DeclPtr = new llvm::AllocaInst(IPTy, 0, AI->getName() +
+      ".addr", AllocaInsertPt);
+  // Store the initial value into the alloca.
+  Builder.CreateStore(AI, DeclPtr);
+  CmdEntry = DeclPtr;
+
+  for (unsigned i = 0, e = OMD->getNumParams(); i != e; ++i, ++AI) {
+    assert(AI != CurFn->arg_end() && "Argument mismatch!");
+    EmitParmDecl(*OMD->getParamDecl(i), AI);
+  }
+  
+  GenerateFunction(OMD->getBody());
+}
+
+llvm::Value *CodeGenFunction::LoadObjCSelf(void)
+{
+  if (const ObjCMethodDecl *OMD = dyn_cast<ObjCMethodDecl>(CurFuncDecl)) {
+    ValueDecl *Decl = OMD->getSelfDecl();
+    llvm::Value *SelfPtr = LocalDeclMap[&(*(Decl))];
+    return Builder.CreateLoad(SelfPtr, "self");
+  }
+  return NULL;
+}
+
+CGObjCRuntime::~CGObjCRuntime() {}
diff --git a/Clang/CGObjCGNU.cpp b/Clang/CGObjCGNU.cpp
new file mode 100644
index 0000000..57c021f
--- /dev/null
+++ b/Clang/CGObjCGNU.cpp
@@ -0,0 +1,869 @@
+//===------- CGObjCGNU.cpp - Emit LLVM Code from ASTs for a Module --------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This provides Objective-C code generation targetting the GNU runtime.  The
+// class in this file generates structures used by the GNU Objective-C runtime
+// library.  These structures are defined in objc/objc.h and objc/objc-api.h in
+// the GNU runtime distribution.
+//
+//===----------------------------------------------------------------------===//
+
+#include "CGObjCRuntime.h"
+#include "CodeGenModule.h"
+#include "clang/AST/ASTContext.h"
+#include "llvm/Module.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/IRBuilder.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringMap.h"
+#include <map>
+using namespace clang;
+using llvm::dyn_cast;
+
+// The version of the runtime that this class targets.  Must match the version
+// in the runtime.
+static const int RuntimeVersion = 8;
+static const int ProtocolVersion = 2;
+
+namespace {
+class CGObjCGNU : public CodeGen::CGObjCRuntime {
+private:
+  CodeGen::CodeGenModule &CGM;
+  llvm::Module &TheModule;
+  const llvm::StructType *SelStructTy;
+  const llvm::Type *SelectorTy;
+  const llvm::Type *PtrToInt8Ty;
+  const llvm::Type *IMPTy;
+  const llvm::Type *IdTy;
+  const llvm::Type *IntTy;
+  const llvm::Type *PtrTy;
+  const llvm::Type *LongTy;
+  const llvm::Type *PtrToIntTy;
+  std::vector<llvm::Constant*> Classes;
+  std::vector<llvm::Constant*> Categories;
+  std::vector<llvm::Constant*> ConstantStrings;
+  llvm::Function *LoadFunction;
+  llvm::StringMap<llvm::Constant*> ExistingProtocols;
+  typedef std::pair<std::string, std::string> TypedSelector;
+  std::map<TypedSelector, llvm::GlobalAlias*> TypedSelectors;
+  llvm::StringMap<llvm::GlobalAlias*> UntypedSelectors;
+  // Some zeros used for GEPs in lots of places.
+  llvm::Constant *Zeros[2];
+  llvm::Constant *NULLPtr;
+private:
+  llvm::Constant *GenerateIvarList(
+      const llvm::SmallVectorImpl<llvm::Constant *>  &IvarNames,
+      const llvm::SmallVectorImpl<llvm::Constant *>  &IvarTypes,
+      const llvm::SmallVectorImpl<llvm::Constant *>  &IvarOffsets);
+  llvm::Constant *GenerateMethodList(const std::string &ClassName,
+      const std::string &CategoryName,
+      const llvm::SmallVectorImpl<Selector>  &MethodSels, 
+      const llvm::SmallVectorImpl<llvm::Constant *>  &MethodTypes, 
+      bool isClassMethodList);
+  llvm::Constant *GenerateProtocolList(
+      const llvm::SmallVectorImpl<std::string> &Protocols);
+  llvm::Constant *GenerateClassStructure(
+      llvm::Constant *MetaClass,
+      llvm::Constant *SuperClass,
+      unsigned info,
+      const char *Name,
+      llvm::Constant *Version,
+      llvm::Constant *InstanceSize,
+      llvm::Constant *IVars,
+      llvm::Constant *Methods,
+      llvm::Constant *Protocols);
+  llvm::Constant *GenerateProtocolMethodList(
+      const llvm::SmallVectorImpl<llvm::Constant *>  &MethodNames,
+      const llvm::SmallVectorImpl<llvm::Constant *>  &MethodTypes);
+  llvm::Constant *MakeConstantString(const std::string &Str, const std::string
+      &Name="");
+  llvm::Constant *MakeGlobal(const llvm::StructType *Ty,
+      std::vector<llvm::Constant*> &V, const std::string &Name="");
+  llvm::Constant *MakeGlobal(const llvm::ArrayType *Ty,
+      std::vector<llvm::Constant*> &V, const std::string &Name="");
+public:
+  CGObjCGNU(CodeGen::CodeGenModule &cgm);
+  virtual llvm::Constant *GenerateConstantString(const char *String, 
+      const size_t length);
+  virtual llvm::Value *GenerateMessageSend(llvm::IRBuilder &Builder,
+                                           const llvm::Type *ReturnTy,
+                                           llvm::Value *Sender,
+                                           llvm::Value *Receiver,
+                                           Selector Sel,
+                                           llvm::Value** ArgV,
+                                           unsigned ArgC);
+  virtual llvm::Value *GenerateMessageSendSuper(llvm::IRBuilder &Builder,
+                                                const llvm::Type *ReturnTy,
+                                                llvm::Value *Sender,
+                                                const char *SuperClassName,
+                                                llvm::Value *Receiver,
+                                                Selector Sel,
+                                                llvm::Value** ArgV,
+                                                unsigned ArgC);
+  virtual llvm::Value *LookupClass(llvm::IRBuilder &Builder,
+                                   llvm::Value *ClassName);
+  virtual llvm::Value *GetSelector(llvm::IRBuilder &Builder, Selector Sel);
+  
+  virtual llvm::Function *MethodPreamble(
+                                         const std::string &ClassName,
+                                         const std::string &CategoryName,
+                                         const std::string &MethodName,
+                                         const llvm::Type *ReturnTy,
+                                         const llvm::Type *SelfTy,
+                                         const llvm::Type **ArgTy,
+                                         unsigned ArgC,
+                                         bool isClassMethod,
+                                         bool isVarArg);
+  virtual void GenerateCategory(const char *ClassName, const char *CategoryName,
+           const llvm::SmallVectorImpl<Selector>  &InstanceMethodSels,
+           const llvm::SmallVectorImpl<llvm::Constant *>  &InstanceMethodTypes,
+           const llvm::SmallVectorImpl<Selector>  &ClassMethodSels,
+           const llvm::SmallVectorImpl<llvm::Constant *>  &ClassMethodTypes,
+           const llvm::SmallVectorImpl<std::string> &Protocols);
+  virtual void GenerateClass(
+           const char *ClassName,
+           const char *SuperClassName,
+           const int instanceSize,
+           const llvm::SmallVectorImpl<llvm::Constant *>  &IvarNames,
+           const llvm::SmallVectorImpl<llvm::Constant *>  &IvarTypes,
+           const llvm::SmallVectorImpl<llvm::Constant *>  &IvarOffsets,
+           const llvm::SmallVectorImpl<Selector>  &InstanceMethodSels,
+           const llvm::SmallVectorImpl<llvm::Constant *>  &InstanceMethodTypes,
+           const llvm::SmallVectorImpl<Selector>  &ClassMethodSels,
+           const llvm::SmallVectorImpl<llvm::Constant *>  &ClassMethodTypes,
+           const llvm::SmallVectorImpl<std::string> &Protocols);
+  virtual llvm::Value *GenerateProtocolRef(llvm::IRBuilder &Builder, const char
+      *ProtocolName);
+  virtual void GenerateProtocol(const char *ProtocolName,
+      const llvm::SmallVectorImpl<std::string> &Protocols,
+      const llvm::SmallVectorImpl<llvm::Constant *>  &InstanceMethodNames,
+      const llvm::SmallVectorImpl<llvm::Constant *>  &InstanceMethodTypes,
+      const llvm::SmallVectorImpl<llvm::Constant *>  &ClassMethodNames,
+      const llvm::SmallVectorImpl<llvm::Constant *>  &ClassMethodTypes);
+  virtual llvm::Function *ModuleInitFunction();
+};
+} // end anonymous namespace
+
+
+
+static std::string SymbolNameForClass(const std::string &ClassName) {
+  return ".objc_class_" + ClassName;
+}
+
+static std::string SymbolNameForMethod(const std::string &ClassName, const
+  std::string &CategoryName, const std::string &MethodName, bool isClassMethod)
+{
+  return "._objc_method_" + ClassName +"("+CategoryName+")"+
+            (isClassMethod ? "+" : "-") + MethodName;
+}
+
+CGObjCGNU::CGObjCGNU(CodeGen::CodeGenModule &cgm)
+  : CGM(cgm), TheModule(CGM.getModule()) {
+  IntTy = CGM.getTypes().ConvertType(CGM.getContext().IntTy);
+  LongTy = CGM.getTypes().ConvertType(CGM.getContext().LongTy);
+    
+  Zeros[0] = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
+  Zeros[1] = Zeros[0];
+  NULLPtr = llvm::ConstantPointerNull::get(
+    llvm::PointerType::getUnqual(llvm::Type::Int8Ty));
+  // C string type.  Used in lots of places.
+  PtrToInt8Ty = 
+    llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
+  // Get the selector Type.
+  SelStructTy = llvm::StructType::get(
+      PtrToInt8Ty,
+      PtrToInt8Ty,
+      NULL);
+  SelectorTy = llvm::PointerType::getUnqual(SelStructTy);
+  PtrToIntTy = llvm::PointerType::getUnqual(IntTy);
+  PtrTy = PtrToInt8Ty;
+ 
+  // Object type
+  llvm::PATypeHolder OpaqueObjTy = llvm::OpaqueType::get();
+  llvm::Type *OpaqueIdTy = llvm::PointerType::getUnqual(OpaqueObjTy);
+  IdTy = llvm::StructType::get(OpaqueIdTy, NULL);
+  llvm::cast<llvm::OpaqueType>(OpaqueObjTy.get())->refineAbstractTypeTo(IdTy);
+  IdTy = llvm::cast<llvm::StructType>(OpaqueObjTy.get());
+  IdTy = llvm::PointerType::getUnqual(IdTy);
+ 
+  // IMP type
+  std::vector<const llvm::Type*> IMPArgs;
+  IMPArgs.push_back(IdTy);
+  IMPArgs.push_back(SelectorTy);
+  IMPTy = llvm::FunctionType::get(IdTy, IMPArgs, true);
+}
+// This has to perform the lookup every time, since posing and related
+// techniques can modify the name -> class mapping.
+llvm::Value *CGObjCGNU::LookupClass(llvm::IRBuilder &Builder,
+    llvm::Value *ClassName) {
+  llvm::Constant *ClassLookupFn =
+    TheModule.getOrInsertFunction("objc_lookup_class", IdTy, PtrToInt8Ty,
+        NULL);
+  return Builder.CreateCall(ClassLookupFn, ClassName);
+}
+
+/// GetSelector - Return the pointer to the unique'd string for this selector.
+llvm::Value *CGObjCGNU::GetSelector(llvm::IRBuilder &Builder, Selector Sel) {
+  // FIXME: uniquing on the string is wasteful, unique on Sel instead!
+  llvm::GlobalAlias *&US = UntypedSelectors[Sel.getName()];
+  if (US == 0)
+    US = new llvm::GlobalAlias(llvm::PointerType::getUnqual(SelectorTy),
+                               llvm::GlobalValue::InternalLinkage,
+                               ".objc_untyped_selector_alias",
+                               NULL, &TheModule);
+  
+  return Builder.CreateLoad(US);
+  
+}
+
+llvm::Constant *CGObjCGNU::MakeConstantString(const std::string &Str,
+                                              const std::string &Name) {
+  llvm::Constant * ConstStr = llvm::ConstantArray::get(Str);
+  ConstStr = new llvm::GlobalVariable(ConstStr->getType(), true, 
+                               llvm::GlobalValue::InternalLinkage,
+                               ConstStr, Name, &TheModule);
+  return llvm::ConstantExpr::getGetElementPtr(ConstStr, Zeros, 2);
+}
+llvm::Constant *CGObjCGNU::MakeGlobal(const llvm::StructType *Ty,
+    std::vector<llvm::Constant*> &V, const std::string &Name) {
+  llvm::Constant *C = llvm::ConstantStruct::get(Ty, V);
+  return new llvm::GlobalVariable(Ty, false,
+      llvm::GlobalValue::InternalLinkage, C, Name, &TheModule);
+}
+llvm::Constant *CGObjCGNU::MakeGlobal(const llvm::ArrayType *Ty,
+    std::vector<llvm::Constant*> &V, const std::string &Name) {
+  llvm::Constant *C = llvm::ConstantArray::get(Ty, V);
+  return new llvm::GlobalVariable(Ty, false,
+      llvm::GlobalValue::InternalLinkage, C, Name, &TheModule);
+}
+
+/// Generate an NSConstantString object.
+//TODO: In case there are any crazy people still using the GNU runtime without
+//an OpenStep implementation, this should let them select their own class for
+//constant strings.
+llvm::Constant *CGObjCGNU::GenerateConstantString(const char *String, const
+    size_t length) {
+  std::string Str(String, String +length);
+  std::vector<llvm::Constant*> Ivars;
+  Ivars.push_back(NULLPtr);
+  Ivars.push_back(MakeConstantString(Str));
+  Ivars.push_back(llvm::ConstantInt::get(IntTy, length));
+  llvm::Constant *ObjCStr = MakeGlobal(
+    llvm::StructType::get(PtrToInt8Ty, PtrToInt8Ty, IntTy, NULL),
+    Ivars, ".objc_str");
+  ConstantStrings.push_back(
+      llvm::ConstantExpr::getBitCast(ObjCStr, PtrToInt8Ty));
+  return ObjCStr;
+}
+
+///Generates a message send where the super is the receiver.  This is a message
+///send to self with special delivery semantics indicating which class's method
+///should be called.
+llvm::Value *CGObjCGNU::GenerateMessageSendSuper(llvm::IRBuilder &Builder,
+                                                 const llvm::Type *ReturnTy,
+                                                 llvm::Value *Sender,
+                                                 const char *SuperClassName,
+                                                 llvm::Value *Receiver,
+                                                 Selector Sel,
+                                                 llvm::Value** ArgV,
+                                                 unsigned ArgC) {
+  // TODO: This should be cached, not looked up every time.
+  llvm::Value *ReceiverClass = LookupClass(Builder,
+      MakeConstantString(SuperClassName));
+  llvm::Value *cmd = GetSelector(Builder, Sel);
+  std::vector<const llvm::Type*> impArgTypes;
+  impArgTypes.push_back(Receiver->getType());
+  impArgTypes.push_back(SelectorTy);
+  
+  // Avoid an explicit cast on the IMP by getting a version that has the right
+  // return type.
+  llvm::FunctionType *impType = llvm::FunctionType::get(ReturnTy, impArgTypes,
+                                                        true);
+  // Construct the structure used to look up the IMP
+  llvm::StructType *ObjCSuperTy = llvm::StructType::get(Receiver->getType(),
+      IdTy, NULL);
+  llvm::Value *ObjCSuper = Builder.CreateAlloca(ObjCSuperTy);
+  // FIXME: volatility
+  Builder.CreateStore(Receiver, Builder.CreateStructGEP(ObjCSuper, 0));
+  Builder.CreateStore(ReceiverClass, Builder.CreateStructGEP(ObjCSuper, 1));
+
+  // Get the IMP
+  llvm::Constant *lookupFunction = 
+     TheModule.getOrInsertFunction("objc_msg_lookup_super",
+                                   llvm::PointerType::getUnqual(impType),
+                                   llvm::PointerType::getUnqual(ObjCSuperTy),
+                                   SelectorTy, NULL);
+  llvm::Value *lookupArgs[] = {ObjCSuper, cmd};
+  llvm::Value *imp = Builder.CreateCall(lookupFunction, lookupArgs,
+      lookupArgs+2);
+
+  // Call the method
+  llvm::SmallVector<llvm::Value*, 8> callArgs;
+  callArgs.push_back(Receiver);
+  callArgs.push_back(cmd);
+  callArgs.insert(callArgs.end(), ArgV, ArgV+ArgC);
+  return Builder.CreateCall(imp, callArgs.begin(), callArgs.end());
+}
+
+/// Generate code for a message send expression.  
+llvm::Value *CGObjCGNU::GenerateMessageSend(llvm::IRBuilder &Builder,
+                                            const llvm::Type *ReturnTy,
+                                            llvm::Value *Sender,
+                                            llvm::Value *Receiver,
+                                            Selector Sel,
+                                            llvm::Value** ArgV,
+                                            unsigned ArgC) {
+  llvm::Value *cmd = GetSelector(Builder, Sel);
+
+  // Look up the method implementation.
+  std::vector<const llvm::Type*> impArgTypes;
+  const llvm::Type *RetTy;
+  //TODO: Revisit this when LLVM supports aggregate return types.
+  if (ReturnTy->isSingleValueType() && ReturnTy != llvm::Type::VoidTy) {
+    RetTy = ReturnTy;
+  } else {
+    // For struct returns allocate the space in the caller and pass it up to
+    // the sender.
+    RetTy = llvm::Type::VoidTy;
+    impArgTypes.push_back(llvm::PointerType::getUnqual(ReturnTy));
+  }
+  impArgTypes.push_back(Receiver->getType());
+  impArgTypes.push_back(SelectorTy);
+  
+  // Avoid an explicit cast on the IMP by getting a version that has the right
+  // return type.
+  llvm::FunctionType *impType = llvm::FunctionType::get(RetTy, impArgTypes,
+                                                        true);
+  
+  llvm::Constant *lookupFunction = 
+     TheModule.getOrInsertFunction("objc_msg_lookup",
+                                   llvm::PointerType::getUnqual(impType),
+                                   Receiver->getType(), SelectorTy, NULL);
+  llvm::Value *imp = Builder.CreateCall2(lookupFunction, Receiver, cmd);
+
+  // Call the method.
+  llvm::SmallVector<llvm::Value*, 16> Args;
+  if (!ReturnTy->isSingleValueType()) {
+    llvm::Value *Return = Builder.CreateAlloca(ReturnTy);
+    Args.push_back(Return);
+  }
+  Args.push_back(Receiver);
+  Args.push_back(cmd);
+  Args.insert(Args.end(), ArgV, ArgV+ArgC);
+  if (!ReturnTy->isSingleValueType()) {
+    Builder.CreateCall(imp, Args.begin(), Args.end());
+    return Args[0];
+  }
+  return Builder.CreateCall(imp, Args.begin(), Args.end());
+}
+
+/// Generates a MethodList.  Used in construction of a objc_class and 
+/// objc_category structures.
+llvm::Constant *CGObjCGNU::GenerateMethodList(const std::string &ClassName,
+                                              const std::string &CategoryName, 
+    const llvm::SmallVectorImpl<Selector> &MethodSels, 
+    const llvm::SmallVectorImpl<llvm::Constant *> &MethodTypes, 
+    bool isClassMethodList) {
+  // Get the method structure type.  
+  llvm::StructType *ObjCMethodTy = llvm::StructType::get(
+    PtrToInt8Ty, // Really a selector, but the runtime creates it us.
+    PtrToInt8Ty, // Method types
+    llvm::PointerType::getUnqual(IMPTy), //Method pointer
+    NULL);
+  std::vector<llvm::Constant*> Methods;
+  std::vector<llvm::Constant*> Elements;
+  for (unsigned int i = 0, e = MethodTypes.size(); i < e; ++i) {
+    Elements.clear();
+    llvm::Constant *C = CGM.GetAddrOfConstantString(MethodSels[i].getName());
+    Elements.push_back(llvm::ConstantExpr::getGetElementPtr(C, Zeros, 2));
+    Elements.push_back(
+          llvm::ConstantExpr::getGetElementPtr(MethodTypes[i], Zeros, 2));
+    llvm::Constant *Method =
+      TheModule.getFunction(SymbolNameForMethod(ClassName, CategoryName,
+                                                MethodSels[i].getName(),
+                                                isClassMethodList));
+    Method = llvm::ConstantExpr::getBitCast(Method,
+        llvm::PointerType::getUnqual(IMPTy));
+    Elements.push_back(Method);
+    Methods.push_back(llvm::ConstantStruct::get(ObjCMethodTy, Elements));
+  }
+
+  // Array of method structures
+  llvm::ArrayType *ObjCMethodArrayTy = llvm::ArrayType::get(ObjCMethodTy,
+                                                            MethodSels.size());
+  llvm::Constant *MethodArray = llvm::ConstantArray::get(ObjCMethodArrayTy,
+                                                         Methods);
+
+  // Structure containing list pointer, array and array count
+  llvm::SmallVector<const llvm::Type*, 16> ObjCMethodListFields;
+  llvm::PATypeHolder OpaqueNextTy = llvm::OpaqueType::get();
+  llvm::Type *NextPtrTy = llvm::PointerType::getUnqual(OpaqueNextTy);
+  llvm::StructType *ObjCMethodListTy = llvm::StructType::get(NextPtrTy, 
+      IntTy, 
+      ObjCMethodArrayTy,
+      NULL);
+  // Refine next pointer type to concrete type
+  llvm::cast<llvm::OpaqueType>(
+      OpaqueNextTy.get())->refineAbstractTypeTo(ObjCMethodListTy);
+  ObjCMethodListTy = llvm::cast<llvm::StructType>(OpaqueNextTy.get());
+
+  Methods.clear();
+  Methods.push_back(llvm::ConstantPointerNull::get(
+        llvm::PointerType::getUnqual(ObjCMethodListTy)));
+  Methods.push_back(llvm::ConstantInt::get(llvm::Type::Int32Ty,
+        MethodTypes.size()));
+  Methods.push_back(MethodArray);
+  
+  // Create an instance of the structure
+  return MakeGlobal(ObjCMethodListTy, Methods, ".objc_method_list");
+}
+
+/// Generates an IvarList.  Used in construction of a objc_class.
+llvm::Constant *CGObjCGNU::GenerateIvarList(
+    const llvm::SmallVectorImpl<llvm::Constant *>  &IvarNames,
+    const llvm::SmallVectorImpl<llvm::Constant *>  &IvarTypes,
+    const llvm::SmallVectorImpl<llvm::Constant *>  &IvarOffsets) {
+  // Get the method structure type.  
+  llvm::StructType *ObjCIvarTy = llvm::StructType::get(
+    PtrToInt8Ty,
+    PtrToInt8Ty,
+    IntTy,
+    NULL);
+  std::vector<llvm::Constant*> Ivars;
+  std::vector<llvm::Constant*> Elements;
+  for (unsigned int i = 0, e = IvarNames.size() ; i < e ; i++) {
+    Elements.clear();
+    Elements.push_back( llvm::ConstantExpr::getGetElementPtr(IvarNames[i],
+          Zeros, 2));
+    Elements.push_back( llvm::ConstantExpr::getGetElementPtr(IvarTypes[i],
+          Zeros, 2));
+    Elements.push_back(IvarOffsets[i]);
+    Ivars.push_back(llvm::ConstantStruct::get(ObjCIvarTy, Elements));
+  }
+
+  // Array of method structures
+  llvm::ArrayType *ObjCIvarArrayTy = llvm::ArrayType::get(ObjCIvarTy,
+      IvarNames.size());
+
+  
+  Elements.clear();
+  Elements.push_back(llvm::ConstantInt::get(
+        llvm::cast<llvm::IntegerType>(IntTy), (int)IvarNames.size()));
+  Elements.push_back(llvm::ConstantArray::get(ObjCIvarArrayTy, Ivars));
+  // Structure containing array and array count
+  llvm::StructType *ObjCIvarListTy = llvm::StructType::get(IntTy,
+    ObjCIvarArrayTy,
+    NULL);
+
+  // Create an instance of the structure
+  return MakeGlobal(ObjCIvarListTy, Elements, ".objc_ivar_list");
+}
+
+/// Generate a class structure
+llvm::Constant *CGObjCGNU::GenerateClassStructure(
+    llvm::Constant *MetaClass,
+    llvm::Constant *SuperClass,
+    unsigned info,
+    const char *Name,
+    llvm::Constant *Version,
+    llvm::Constant *InstanceSize,
+    llvm::Constant *IVars,
+    llvm::Constant *Methods,
+    llvm::Constant *Protocols) {
+  // Set up the class structure
+  // Note:  Several of these are char*s when they should be ids.  This is
+  // because the runtime performs this translation on load.
+  llvm::StructType *ClassTy = llvm::StructType::get(
+      PtrToInt8Ty,        // class_pointer
+      PtrToInt8Ty,        // super_class
+      PtrToInt8Ty,        // name
+      LongTy,             // version
+      LongTy,             // info
+      LongTy,             // instance_size
+      IVars->getType(),   // ivars
+      Methods->getType(), // methods
+      // These are all filled in by the runtime, so we pretend 
+      PtrTy,              // dtable
+      PtrTy,              // subclass_list
+      PtrTy,              // sibling_class
+      PtrTy,              // protocols
+      PtrTy,              // gc_object_type
+      NULL);
+  llvm::Constant *Zero = llvm::ConstantInt::get(LongTy, 0);
+  llvm::Constant *NullP =
+    llvm::ConstantPointerNull::get(llvm::cast<llvm::PointerType>(PtrTy));
+  // Fill in the structure
+  std::vector<llvm::Constant*> Elements;
+  Elements.push_back(llvm::ConstantExpr::getBitCast(MetaClass, PtrToInt8Ty));
+  Elements.push_back(SuperClass);
+  Elements.push_back(MakeConstantString(Name, ".class_name"));
+  Elements.push_back(Zero);
+  Elements.push_back(llvm::ConstantInt::get(LongTy, info));
+  Elements.push_back(InstanceSize);
+  Elements.push_back(IVars);
+  Elements.push_back(Methods);
+  Elements.push_back(NullP);
+  Elements.push_back(NullP);
+  Elements.push_back(NullP);
+  Elements.push_back(llvm::ConstantExpr::getBitCast(Protocols, PtrTy));
+  Elements.push_back(NullP);
+  // Create an instance of the structure
+  return MakeGlobal(ClassTy, Elements, SymbolNameForClass(Name));
+}
+
+llvm::Constant *CGObjCGNU::GenerateProtocolMethodList(
+    const llvm::SmallVectorImpl<llvm::Constant *>  &MethodNames,
+    const llvm::SmallVectorImpl<llvm::Constant *>  &MethodTypes) {
+  // Get the method structure type.  
+  llvm::StructType *ObjCMethodDescTy = llvm::StructType::get(
+    PtrToInt8Ty, // Really a selector, but the runtime does the casting for us.
+    PtrToInt8Ty,
+    NULL);
+  std::vector<llvm::Constant*> Methods;
+  std::vector<llvm::Constant*> Elements;
+  for (unsigned int i = 0, e = MethodTypes.size() ; i < e ; i++) {
+    Elements.clear();
+    Elements.push_back( llvm::ConstantExpr::getGetElementPtr(MethodNames[i],
+          Zeros, 2)); 
+    Elements.push_back(
+          llvm::ConstantExpr::getGetElementPtr(MethodTypes[i], Zeros, 2));
+    Methods.push_back(llvm::ConstantStruct::get(ObjCMethodDescTy, Elements));
+  }
+  llvm::ArrayType *ObjCMethodArrayTy = llvm::ArrayType::get(ObjCMethodDescTy,
+      MethodNames.size());
+  llvm::Constant *Array = llvm::ConstantArray::get(ObjCMethodArrayTy, Methods);
+  llvm::StructType *ObjCMethodDescListTy = llvm::StructType::get(
+      IntTy, ObjCMethodArrayTy, NULL);
+  Methods.clear();
+  Methods.push_back(llvm::ConstantInt::get(IntTy, MethodNames.size()));
+  Methods.push_back(Array);
+  return MakeGlobal(ObjCMethodDescListTy, Methods, ".objc_method_list");
+}
+// Create the protocol list structure used in classes, categories and so on
+llvm::Constant *CGObjCGNU::GenerateProtocolList(
+    const llvm::SmallVectorImpl<std::string> &Protocols) {
+  llvm::ArrayType *ProtocolArrayTy = llvm::ArrayType::get(PtrToInt8Ty,
+      Protocols.size());
+  llvm::StructType *ProtocolListTy = llvm::StructType::get(
+      PtrTy, //Should be a recurisve pointer, but it's always NULL here.
+      LongTy,//FIXME: Should be size_t
+      ProtocolArrayTy,
+      NULL);
+  std::vector<llvm::Constant*> Elements; 
+  for (const std::string *iter = Protocols.begin(), *endIter = Protocols.end();
+      iter != endIter ; iter++) {
+    llvm::Constant *Ptr =
+      llvm::ConstantExpr::getBitCast(ExistingProtocols[*iter], PtrToInt8Ty);
+    Elements.push_back(Ptr);
+  }
+  llvm::Constant * ProtocolArray = llvm::ConstantArray::get(ProtocolArrayTy,
+      Elements);
+  Elements.clear();
+  Elements.push_back(NULLPtr);
+  Elements.push_back(llvm::ConstantInt::get(
+        llvm::cast<llvm::IntegerType>(LongTy), Protocols.size()));
+  Elements.push_back(ProtocolArray);
+  return MakeGlobal(ProtocolListTy, Elements, ".objc_protocol_list");
+}
+
+llvm::Value *CGObjCGNU::GenerateProtocolRef(llvm::IRBuilder &Builder, const
+    char *ProtocolName) {
+  return ExistingProtocols[ProtocolName];
+}
+
+void CGObjCGNU::GenerateProtocol(const char *ProtocolName,
+    const llvm::SmallVectorImpl<std::string> &Protocols,
+    const llvm::SmallVectorImpl<llvm::Constant *>  &InstanceMethodNames,
+    const llvm::SmallVectorImpl<llvm::Constant *>  &InstanceMethodTypes,
+    const llvm::SmallVectorImpl<llvm::Constant *>  &ClassMethodNames,
+    const llvm::SmallVectorImpl<llvm::Constant *>  &ClassMethodTypes) {
+
+  llvm::Constant *ProtocolList = GenerateProtocolList(Protocols);
+  llvm::Constant *InstanceMethodList =
+    GenerateProtocolMethodList(InstanceMethodNames, InstanceMethodTypes);
+  llvm::Constant *ClassMethodList =
+    GenerateProtocolMethodList(ClassMethodNames, ClassMethodTypes);
+  // Protocols are objects containing lists of the methods implemented and
+  // protocols adopted.
+  llvm::StructType *ProtocolTy = llvm::StructType::get(IdTy,
+      PtrToInt8Ty,
+      ProtocolList->getType(),
+      InstanceMethodList->getType(),
+      ClassMethodList->getType(),
+      NULL);
+  std::vector<llvm::Constant*> Elements; 
+  // The isa pointer must be set to a magic number so the runtime knows it's
+  // the correct layout.
+  Elements.push_back(llvm::ConstantExpr::getIntToPtr(
+        llvm::ConstantInt::get(llvm::Type::Int32Ty, ProtocolVersion), IdTy));
+  Elements.push_back(MakeConstantString(ProtocolName, ".objc_protocol_name"));
+  Elements.push_back(ProtocolList);
+  Elements.push_back(InstanceMethodList);
+  Elements.push_back(ClassMethodList);
+  ExistingProtocols[ProtocolName] = 
+    llvm::ConstantExpr::getBitCast(MakeGlobal(ProtocolTy, Elements,
+          ".objc_protocol"), IdTy);
+}
+
+void CGObjCGNU::GenerateCategory(
+           const char *ClassName,
+           const char *CategoryName,
+           const llvm::SmallVectorImpl<Selector>  &InstanceMethodSels,
+           const llvm::SmallVectorImpl<llvm::Constant *>  &InstanceMethodTypes,
+           const llvm::SmallVectorImpl<Selector>  &ClassMethodSels,
+           const llvm::SmallVectorImpl<llvm::Constant *>  &ClassMethodTypes,
+           const llvm::SmallVectorImpl<std::string> &Protocols) {
+  std::vector<llvm::Constant*> Elements;
+  Elements.push_back(MakeConstantString(CategoryName));
+  Elements.push_back(MakeConstantString(ClassName));
+  // Instance method list 
+  Elements.push_back(llvm::ConstantExpr::getBitCast(GenerateMethodList(
+          ClassName, CategoryName, InstanceMethodSels, InstanceMethodTypes,
+          false), PtrTy));
+  // Class method list
+  Elements.push_back(llvm::ConstantExpr::getBitCast(GenerateMethodList(
+          ClassName, CategoryName, ClassMethodSels, ClassMethodTypes, true),
+        PtrTy));
+  // Protocol list
+  Elements.push_back(llvm::ConstantExpr::getBitCast(
+        GenerateProtocolList(Protocols), PtrTy));
+  Categories.push_back(llvm::ConstantExpr::getBitCast(
+        MakeGlobal(llvm::StructType::get(PtrToInt8Ty, PtrToInt8Ty, PtrTy,
+            PtrTy, PtrTy, NULL), Elements), PtrTy));
+}
+void CGObjCGNU::GenerateClass(
+           const char *ClassName,
+           const char *SuperClassName,
+           const int instanceSize,
+           const llvm::SmallVectorImpl<llvm::Constant *>  &IvarNames,
+           const llvm::SmallVectorImpl<llvm::Constant *>  &IvarTypes,
+           const llvm::SmallVectorImpl<llvm::Constant *>  &IvarOffsets,
+           const llvm::SmallVectorImpl<Selector>  &InstanceMethodSels,
+           const llvm::SmallVectorImpl<llvm::Constant *>  &InstanceMethodTypes,
+           const llvm::SmallVectorImpl<Selector>  &ClassMethodSels,
+           const llvm::SmallVectorImpl<llvm::Constant *>  &ClassMethodTypes,
+           const llvm::SmallVectorImpl<std::string> &Protocols) {
+  // Get the superclass pointer.
+  llvm::Constant *SuperClass;
+  if (SuperClassName) {
+    SuperClass = MakeConstantString(SuperClassName, ".super_class_name");
+  } else {
+    SuperClass = llvm::ConstantPointerNull::get(
+        llvm::cast<llvm::PointerType>(PtrToInt8Ty));
+  }
+  // Empty vector used to construct empty method lists
+  llvm::SmallVector<llvm::Constant*, 1>  empty;
+  // Generate the method and instance variable lists
+  llvm::Constant *MethodList = GenerateMethodList(ClassName, "",
+      InstanceMethodSels, InstanceMethodTypes, false);
+  llvm::Constant *ClassMethodList = GenerateMethodList(ClassName, "",
+      ClassMethodSels, ClassMethodTypes, true);
+  llvm::Constant *IvarList = GenerateIvarList(IvarNames, IvarTypes,
+      IvarOffsets);
+  //Generate metaclass for class methods
+  llvm::Constant *MetaClassStruct = GenerateClassStructure(NULLPtr,
+      NULLPtr, 0x2L, /*name*/"", 0, Zeros[0], GenerateIvarList(
+        empty, empty, empty), ClassMethodList, NULLPtr);
+  // Generate the class structure
+  llvm::Constant *ClassStruct = GenerateClassStructure(MetaClassStruct,
+      SuperClass, 0x1L, ClassName, 0,
+      llvm::ConstantInt::get(llvm::Type::Int32Ty, instanceSize), IvarList,
+      MethodList, GenerateProtocolList(Protocols));
+  // Add class structure to list to be added to the symtab later
+  ClassStruct = llvm::ConstantExpr::getBitCast(ClassStruct, PtrToInt8Ty);
+  Classes.push_back(ClassStruct);
+}
+
+llvm::Function *CGObjCGNU::ModuleInitFunction() { 
+  // Only emit an ObjC load function if no Objective-C stuff has been called
+  if (Classes.empty() && Categories.empty() && ConstantStrings.empty() &&
+      ExistingProtocols.empty() && TypedSelectors.empty() &&
+      UntypedSelectors.empty())
+    return NULL;
+
+  // Name the ObjC types to make the IR a bit easier to read
+  TheModule.addTypeName(".objc_selector", SelectorTy);
+  TheModule.addTypeName(".objc_id", IdTy);
+  TheModule.addTypeName(".objc_imp", IMPTy);
+
+  std::vector<llvm::Constant*> Elements;
+  // Generate statics list:
+  llvm::ArrayType *StaticsArrayTy = llvm::ArrayType::get(PtrToInt8Ty,
+      ConstantStrings.size() + 1);
+  ConstantStrings.push_back(NULLPtr);
+  Elements.push_back(MakeConstantString("NSConstantString",
+        ".objc_static_class_name"));
+  Elements.push_back(llvm::ConstantArray::get(StaticsArrayTy, ConstantStrings));
+  llvm::StructType *StaticsListTy = 
+    llvm::StructType::get(PtrToInt8Ty, StaticsArrayTy, NULL);
+  llvm::Type *StaticsListPtrTy = llvm::PointerType::getUnqual(StaticsListTy);
+  llvm::Constant *Statics = 
+    MakeGlobal(StaticsListTy, Elements, ".objc_statics");
+  llvm::ArrayType *StaticsListArrayTy =
+    llvm::ArrayType::get(StaticsListPtrTy, 2);
+  Elements.clear();
+  Elements.push_back(Statics);
+  Elements.push_back(llvm::Constant::getNullValue(StaticsListPtrTy));
+  Statics = MakeGlobal(StaticsListArrayTy, Elements, ".objc_statics_ptr");
+  Statics = llvm::ConstantExpr::getBitCast(Statics, PtrTy);
+  // Array of classes, categories, and constant objects
+  llvm::ArrayType *ClassListTy = llvm::ArrayType::get(PtrToInt8Ty,
+      Classes.size() + Categories.size()  + 2);
+  llvm::StructType *SymTabTy = llvm::StructType::get(LongTy, SelectorTy,
+                                                     llvm::Type::Int16Ty,
+                                                     llvm::Type::Int16Ty,
+                                                     ClassListTy, NULL);
+
+  Elements.clear();
+  // Pointer to an array of selectors used in this module.
+  std::vector<llvm::Constant*> Selectors;
+  for (std::map<TypedSelector, llvm::GlobalAlias*>::iterator
+     iter = TypedSelectors.begin(), iterEnd = TypedSelectors.end();
+     iter != iterEnd ; ++iter) {
+    Elements.push_back(MakeConstantString(iter->first.first, ".objc_sel_name"));
+    Elements.push_back(MakeConstantString(iter->first.second,
+                                          ".objc_sel_types"));
+    Selectors.push_back(llvm::ConstantStruct::get(SelStructTy, Elements));
+    Elements.clear();
+  }
+  for (llvm::StringMap<llvm::GlobalAlias*>::iterator
+      iter = UntypedSelectors.begin(), iterEnd = UntypedSelectors.end();
+      iter != iterEnd; ++iter) {
+    Elements.push_back(
+        MakeConstantString(iter->getKeyData(), ".objc_sel_name"));
+    Elements.push_back(NULLPtr);
+    Selectors.push_back(llvm::ConstantStruct::get(SelStructTy, Elements));
+    Elements.clear();
+  }
+  Elements.push_back(NULLPtr);
+  Elements.push_back(NULLPtr);
+  Selectors.push_back(llvm::ConstantStruct::get(SelStructTy, Elements));
+  Elements.clear();
+  // Number of static selectors
+  Elements.push_back(llvm::ConstantInt::get(LongTy, Selectors.size() ));
+  llvm::Constant *SelectorList = MakeGlobal(
+          llvm::ArrayType::get(SelStructTy, Selectors.size()), Selectors,
+          ".objc_selector_list");
+  Elements.push_back(llvm::ConstantExpr::getBitCast(SelectorList, SelectorTy));
+
+  // Now that all of the static selectors exist, create pointers to them.
+  int index = 0;
+  for (std::map<TypedSelector, llvm::GlobalAlias*>::iterator
+     iter=TypedSelectors.begin(), iterEnd =TypedSelectors.end();
+     iter != iterEnd; ++iter) {
+    llvm::Constant *Idxs[] = {Zeros[0],
+      llvm::ConstantInt::get(llvm::Type::Int32Ty, index++), Zeros[0]};
+    llvm::GlobalVariable *SelPtr = new llvm::GlobalVariable(SelectorTy, true,
+        llvm::GlobalValue::InternalLinkage,
+        llvm::ConstantExpr::getGetElementPtr(SelectorList, Idxs, 2),
+        ".objc_sel_ptr", &TheModule);
+    (*iter).second->setAliasee(SelPtr);
+  }
+  for (llvm::StringMap<llvm::GlobalAlias*>::iterator
+      iter=UntypedSelectors.begin(), iterEnd = UntypedSelectors.end();
+      iter != iterEnd; iter++) {
+    llvm::Constant *Idxs[] = {Zeros[0],
+      llvm::ConstantInt::get(llvm::Type::Int32Ty, index++), Zeros[0]};
+    llvm::GlobalVariable *SelPtr = new llvm::GlobalVariable(SelectorTy, true,
+        llvm::GlobalValue::InternalLinkage,
+        llvm::ConstantExpr::getGetElementPtr(SelectorList, Idxs, 2),
+        ".objc_sel_ptr", &TheModule);
+    (*iter).second->setAliasee(SelPtr);
+  }
+  // Number of classes defined.
+  Elements.push_back(llvm::ConstantInt::get(llvm::Type::Int16Ty, 
+        Classes.size()));
+  // Number of categories defined
+  Elements.push_back(llvm::ConstantInt::get(llvm::Type::Int16Ty, 
+        Categories.size()));
+  // Create an array of classes, then categories, then static object instances
+  Classes.insert(Classes.end(), Categories.begin(), Categories.end());
+  //  NULL-terminated list of static object instances (mainly constant strings)
+  Classes.push_back(Statics);
+  Classes.push_back(NULLPtr);
+  llvm::Constant *ClassList = llvm::ConstantArray::get(ClassListTy, Classes);
+  Elements.push_back(ClassList);
+  // Construct the symbol table 
+  llvm::Constant *SymTab= MakeGlobal(SymTabTy, Elements);
+
+  // The symbol table is contained in a module which has some version-checking
+  // constants
+  llvm::StructType * ModuleTy = llvm::StructType::get(LongTy, LongTy,
+      PtrToInt8Ty, llvm::PointerType::getUnqual(SymTabTy), NULL);
+  Elements.clear();
+  // Runtime version used for compatibility checking.
+  Elements.push_back(llvm::ConstantInt::get(LongTy, RuntimeVersion));
+  //FIXME: Should be sizeof(ModuleTy)
+  Elements.push_back(llvm::ConstantInt::get(LongTy, 16));
+  //FIXME: Should be the path to the file where this module was declared
+  Elements.push_back(NULLPtr);
+  Elements.push_back(SymTab);
+  llvm::Value *Module = MakeGlobal(ModuleTy, Elements);
+
+  // Create the load function calling the runtime entry point with the module
+  // structure
+  std::vector<const llvm::Type*> VoidArgs;
+  llvm::Function * LoadFunction = llvm::Function::Create(
+      llvm::FunctionType::get(llvm::Type::VoidTy, VoidArgs, false),
+      llvm::GlobalValue::InternalLinkage, ".objc_load_function",
+      &TheModule);
+  llvm::BasicBlock *EntryBB = llvm::BasicBlock::Create("entry", LoadFunction);
+  llvm::IRBuilder Builder;
+  Builder.SetInsertPoint(EntryBB);
+  llvm::Value *Register = TheModule.getOrInsertFunction("__objc_exec_class",
+      llvm::Type::VoidTy, llvm::PointerType::getUnqual(ModuleTy), NULL);
+  Builder.CreateCall(Register, Module);
+  Builder.CreateRetVoid();
+  return LoadFunction;
+}
+llvm::Function *CGObjCGNU::MethodPreamble(
+                                         const std::string &ClassName,
+                                         const std::string &CategoryName,
+                                         const std::string &MethodName,
+                                         const llvm::Type *ReturnTy,
+                                         const llvm::Type *SelfTy,
+                                         const llvm::Type **ArgTy,
+                                         unsigned ArgC,
+                                         bool isClassMethod,
+                                         bool isVarArg) {
+  std::vector<const llvm::Type*> Args;
+  if (!ReturnTy->isSingleValueType() && ReturnTy != llvm::Type::VoidTy) {
+    Args.push_back(llvm::PointerType::getUnqual(ReturnTy));
+    ReturnTy = llvm::Type::VoidTy;
+  }
+  Args.push_back(SelfTy);
+  Args.push_back(SelectorTy);
+  Args.insert(Args.end(), ArgTy, ArgTy+ArgC);
+
+  llvm::FunctionType *MethodTy = llvm::FunctionType::get(ReturnTy,
+      Args,
+      isVarArg);
+  std::string FunctionName = SymbolNameForMethod(ClassName, CategoryName,
+      MethodName, isClassMethod);
+
+  llvm::Function *Method = llvm::Function::Create(MethodTy,
+      llvm::GlobalValue::InternalLinkage,
+      FunctionName,
+      &TheModule);
+  llvm::Function::arg_iterator AI = Method->arg_begin();
+  // Name the struct return argument.
+  // FIXME: This is probably the wrong test.
+  if (!ReturnTy->isFirstClassType() && ReturnTy != llvm::Type::VoidTy) {
+    AI->setName("agg.result");
+    ++AI;
+  }
+  AI->setName("self");
+  ++AI;
+  AI->setName("_cmd");
+  return Method;
+}
+
+CodeGen::CGObjCRuntime *CodeGen::CreateObjCRuntime(CodeGen::CodeGenModule &CGM){
+  return new CGObjCGNU(CGM);
+}
diff --git a/Clang/CGObjCRuntime.h b/Clang/CGObjCRuntime.h
new file mode 100644
index 0000000..a5d88c3
--- /dev/null
+++ b/Clang/CGObjCRuntime.h
@@ -0,0 +1,126 @@
+//===----- CGObjCRuntime.h - Emit LLVM Code from ASTs for a Module --------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This provides an abstract class for Objective-C code generation.  Concrete
+// subclasses of this implement code generation for specific Objective-C
+// runtime libraries.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef CLANG_CODEGEN_OBCJRUNTIME_H
+#define CLANG_CODEGEN_OBCJRUNTIME_H
+#include "llvm/ADT/SmallVector.h"
+#include <string>
+
+namespace llvm {
+  class IRBuilder;
+  class Constant;
+  class Type;
+  class Value;
+  class Module;
+  class Function;
+}
+
+namespace clang {
+  class Selector;
+  
+namespace CodeGen {
+  class CodeGenModule;
+
+//FIXME Several methods should be pure virtual but aren't to avoid the
+//partially-implemented subclass breaking.
+
+/// Implements runtime-specific code generation functions.
+class CGObjCRuntime {
+public:
+  virtual ~CGObjCRuntime();
+  
+  /// Generate an Objective-C message send operation
+  virtual llvm::Value *GenerateMessageSend(llvm::IRBuilder &Builder,
+                                           const llvm::Type *ReturnTy,
+                                           llvm::Value *Sender,
+                                           llvm::Value *Receiver,
+                                           Selector Sel,
+                                           llvm::Value** ArgV,
+                                           unsigned ArgC) =0;
+  /// Generate the function required to register all Objective-C components in
+  /// this compilation unit with the runtime library.
+  virtual llvm::Function *ModuleInitFunction() =0;
+  /// Get a selector for the specified name and type values
+  virtual llvm::Value *GetSelector(llvm::IRBuilder &Builder, Selector Sel) = 0;
+  /// Generate a constant string object
+  virtual llvm::Constant *GenerateConstantString(const char *String,
+                                                 const size_t Length) = 0;
+  /// Generate a category.  A category contains a list of methods (and
+  /// accompanying metadata) and a list of protocols.
+  virtual void GenerateCategory(const char *ClassName, const char *CategoryName,
+             const llvm::SmallVectorImpl<Selector>  &InstanceMethodSels,
+             const llvm::SmallVectorImpl<llvm::Constant *>  &InstanceMethodTypes,
+             const llvm::SmallVectorImpl<Selector>  &ClassMethodSels,
+             const llvm::SmallVectorImpl<llvm::Constant *>  &ClassMethodTypes,
+             const llvm::SmallVectorImpl<std::string> &Protocols) =0;
+  /// Generate a class stucture for this class.
+  virtual void GenerateClass(
+             const char *ClassName,
+             const char *SuperClassName,
+             const int instanceSize,
+             const llvm::SmallVectorImpl<llvm::Constant *>  &IvarNames,
+             const llvm::SmallVectorImpl<llvm::Constant *>  &IvarTypes,
+             const llvm::SmallVectorImpl<llvm::Constant *>  &IvarOffsets,
+             const llvm::SmallVectorImpl<Selector>  &InstanceMethodSels,
+             const llvm::SmallVectorImpl<llvm::Constant *>  &InstanceMethodTypes,
+             const llvm::SmallVectorImpl<Selector>  &ClassMethodSels,
+             const llvm::SmallVectorImpl<llvm::Constant *>  &ClassMethodTypes,
+             const llvm::SmallVectorImpl<std::string> &Protocols) =0;
+  /// Generate a reference to the named protocol.
+  virtual llvm::Value *GenerateProtocolRef(llvm::IRBuilder &Builder, const char
+      *ProtocolName) =0;
+  virtual llvm::Value *GenerateMessageSendSuper(llvm::IRBuilder &Builder,
+                                                const llvm::Type *ReturnTy,
+                                                llvm::Value *Sender,
+                                                const char *SuperClassName,
+                                                llvm::Value *Receiver,
+                                                Selector Sel,
+                                                llvm::Value** ArgV,
+                                                unsigned ArgC) = 0;
+  /// Generate the named protocol.  Protocols contain method metadata but no 
+  /// implementations. 
+  virtual void GenerateProtocol(const char *ProtocolName,
+    const llvm::SmallVectorImpl<std::string> &Protocols,
+    const llvm::SmallVectorImpl<llvm::Constant *>  &InstanceMethodNames,
+    const llvm::SmallVectorImpl<llvm::Constant *>  &InstanceMethodTypes,
+    const llvm::SmallVectorImpl<llvm::Constant *>  &ClassMethodNames,
+    const llvm::SmallVectorImpl<llvm::Constant *>  &ClassMethodTypes) =0;
+  /// Generate a function preamble for a method with the specified types
+  virtual llvm::Function *MethodPreamble(
+                                         const std::string &ClassName,
+                                         const std::string &CategoryName,
+                                         const std::string &MethodName,
+                                         const llvm::Type *ReturnTy,
+                                         const llvm::Type *SelfTy,
+                                         const llvm::Type **ArgTy,
+                                         unsigned ArgC,
+                                         bool isClassMethod,
+                                         bool isVarArg) = 0;
+  /// Look up the class for the specified name
+  virtual llvm::Value *LookupClass(llvm::IRBuilder &Builder, llvm::Value
+      *ClassName) =0;
+  /// If instance variable addresses are determined at runtime then this should
+  /// return true, otherwise instance variables will be accessed directly from
+  /// the structure.  If this returns true then @defs is invalid for this
+  /// runtime and a warning should be generated.
+  virtual bool LateBoundIVars() { return false; }
+};
+
+/// Creates an instance of an Objective-C runtime class.  
+//TODO: This should include some way of selecting which runtime to target.
+CGObjCRuntime *CreateObjCRuntime(CodeGenModule &CGM);
+}
+}
+#endif