path: root/lib/CodeGen/CGRTTI.cpp

//===--- CGCXXRTTI.cpp - Emit LLVM Code for C++ RTTI descriptors ----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This contains code dealing with C++ code generation of RTTI descriptors.
//
//===----------------------------------------------------------------------===//

#include "CodeGenModule.h"
#include "CGCXXABI.h"
#include "CGObjCRuntime.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/Type.h"
#include "clang/Frontend/CodeGenOptions.h"

using namespace clang;
using namespace CodeGen;

namespace {
class RTTIBuilder {
  CodeGenModule &CGM;  // Per-module state.
  llvm::LLVMContext &VMContext;
  
  /// Fields - The fields of the RTTI descriptor currently being built.
  SmallVector<llvm::Constant *, 16> Fields;

  /// GetAddrOfTypeName - Returns the mangled type name of the given type.
  llvm::GlobalVariable *
  GetAddrOfTypeName(QualType Ty, llvm::GlobalVariable::LinkageTypes Linkage);

  /// GetAddrOfExternalRTTIDescriptor - Returns the constant for the RTTI 
  /// descriptor of the given type.
  llvm::Constant *GetAddrOfExternalRTTIDescriptor(QualType Ty);
  
  /// BuildVTablePointer - Build the vtable pointer for the given type.
  void BuildVTablePointer(const Type *Ty);
  
  /// BuildSIClassTypeInfo - Build an abi::__si_class_type_info, used for single
  /// inheritance, according to the Itanium C++ ABI, 2.9.5p6b.
  void BuildSIClassTypeInfo(const CXXRecordDecl *RD);
  
  /// BuildVMIClassTypeInfo - Build an abi::__vmi_class_type_info, used for
  /// classes with bases that do not satisfy the abi::__si_class_type_info 
  /// constraints, according ti the Itanium C++ ABI, 2.9.5p5c.
  void BuildVMIClassTypeInfo(const CXXRecordDecl *RD);
  
  /// BuildPointerTypeInfo - Build an abi::__pointer_type_info struct, used
  /// for pointer types.
  void BuildPointerTypeInfo(QualType PointeeTy);

  /// BuildObjCObjectTypeInfo - Build the appropriate kind of
  /// type_info for an object type.
  void BuildObjCObjectTypeInfo(const ObjCObjectType *Ty);
  
  /// BuildPointerToMemberTypeInfo - Build an abi::__pointer_to_member_type_info 
  /// struct, used for member pointer types.
  void BuildPointerToMemberTypeInfo(const MemberPointerType *Ty);
  
public:
  RTTIBuilder(CodeGenModule &CGM) : CGM(CGM), 
    VMContext(CGM.getModule().getContext()) { }

  // Pointer type info flags.
  enum {
    /// PTI_Const - Type has const qualifier.
    PTI_Const = 0x1,
    
    /// PTI_Volatile - Type has volatile qualifier.
    PTI_Volatile = 0x2,
    
    /// PTI_Restrict - Type has restrict qualifier.
    PTI_Restrict = 0x4,
    
    /// PTI_Incomplete - Type is incomplete.
    PTI_Incomplete = 0x8,
    
    /// PTI_ContainingClassIncomplete - Containing class is incomplete.
    /// (in pointer to member).
    PTI_ContainingClassIncomplete = 0x10
  };
  
  // VMI type info flags.
  enum {
    /// VMI_NonDiamondRepeat - Class has non-diamond repeated inheritance.
    VMI_NonDiamondRepeat = 0x1,
    
    /// VMI_DiamondShaped - Class is diamond shaped.
    VMI_DiamondShaped = 0x2
  };
  
  // Base class type info flags.
  enum {
    /// BCTI_Virtual - Base class is virtual.
    BCTI_Virtual = 0x1,
    
    /// BCTI_Public - Base class is public.
    BCTI_Public = 0x2
  };
  
  /// BuildTypeInfo - Build the RTTI type info struct for the given type.
  ///
  /// \param Force - true to force the creation of this RTTI value
  llvm::Constant *BuildTypeInfo(QualType Ty, bool Force = false);
};
}

llvm::GlobalVariable *
RTTIBuilder::GetAddrOfTypeName(QualType Ty, 
                               llvm::GlobalVariable::LinkageTypes Linkage) {
  SmallString<256> OutName;
  llvm::raw_svector_ostream Out(OutName);
  CGM.getCXXABI().getMangleContext().mangleCXXRTTIName(Ty, Out);
  Out.flush();
  StringRef Name = OutName.str();

  // We know that the mangled name of the type starts at index 4 of the
  // mangled name of the typename, so we can just index into it in order to
  // get the mangled name of the type.
  llvm::Constant *Init = llvm::ConstantDataArray::getString(VMContext,
                                                            Name.substr(4));

  llvm::GlobalVariable *GV = 
    CGM.CreateOrReplaceCXXRuntimeVariable(Name, Init->getType(), Linkage);

  GV->setInitializer(Init);

  return GV;
}

llvm::Constant *RTTIBuilder::GetAddrOfExternalRTTIDescriptor(QualType Ty) {
  // Mangle the RTTI name.
  SmallString<256> OutName;
  llvm::raw_svector_ostream Out(OutName);
  CGM.getCXXABI().getMangleContext().mangleCXXRTTI(Ty, Out);
  Out.flush();
  StringRef Name = OutName.str();

  // Look for an existing global.
  llvm::GlobalVariable *GV = CGM.getModule().getNamedGlobal(Name);
  
  if (!GV) {
    // Create a new global variable.
    GV = new llvm::GlobalVariable(CGM.getModule(), CGM.Int8PtrTy,
                                  /*Constant=*/true,
                                  llvm::GlobalValue::ExternalLinkage, 0, Name);
  }
  
  return llvm::ConstantExpr::getBitCast(GV, CGM.Int8PtrTy);
}

/// TypeInfoIsInStandardLibrary - Given a builtin type, returns whether the type
/// info for that type is defined in the standard library.
static bool TypeInfoIsInStandardLibrary(const BuiltinType *Ty) {
  // Itanium C++ ABI 2.9.2:
  <