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 "clang/AST/Type.h"
#include "clang/AST/RecordLayout.h"
#include "CodeGenModule.h"
using namespace clang;
using namespace CodeGen;

namespace {
class RTTIBuilder {
  CodeGenModule &CGM;  // Per-module state.
  llvm::LLVMContext &VMContext;
  const llvm::Type *Int8PtrTy;
  llvm::SmallSet<const CXXRecordDecl *, 16> SeenVBase;
  llvm::SmallSet<const CXXRecordDecl *, 32> SeenBase;
  
  std::vector<llvm::Constant *> Info;

  /// GetAddrOfExternalRTTIDescriptor - Returns the constant for the RTTI 
  /// descriptor of the given type.
  llvm::Constant *GetAddrOfExternalRTTIDescriptor(QualType Ty);
  
  /// BuildTypeInfo - Build the RTTI type info struct for the given type.
  llvm::Constant *BuildTypeInfo(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, 2.95p6b.
  void BuildSIClassTypeInfo(const CXXRecordDecl *RD);
  
  /// BuildPointerTypeInfo - Build an abi::__pointer_type_info struct, used
  /// for pointer types.
  void BuildPointerTypeInfo(const PointerType *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()),
      Int8PtrTy(llvm::Type::getInt8PtrTy(VMContext)) { }

  /// BuildVtableRef - Build a reference to a vtable.
  llvm::Constant *BuildVtableRef(const char *Name) {
    // Build a descriptor for Name
    llvm::Constant *GV = CGM.getModule().getNamedGlobal(Name);
    if (GV)
      GV = llvm::ConstantExpr::getBitCast(GV,
                                          llvm::PointerType::get(Int8PtrTy, 0));
    else {
      llvm::GlobalVariable::LinkageTypes linktype;
      linktype = llvm::GlobalValue::ExternalLinkage;
      GV = new llvm::GlobalVariable(CGM.getModule(), Int8PtrTy,
                                    true, linktype, 0, Name);
    }
    llvm::Constant *C;
    C = llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext), 2);
    C = llvm::ConstantExpr::getInBoundsGetElementPtr(GV, &C, 1);
    return llvm::ConstantExpr::getBitCast(C, Int8PtrTy);
  }

  // FIXME: This should be removed, and clients should pass in the linkage
  // directly instead.
  static inline llvm::GlobalVariable::LinkageTypes
  GetLinkageFromExternFlag(bool Extern) {
    if (Extern)
      return llvm::GlobalValue::WeakODRLinkage;
    
    return llvm::GlobalValue::InternalLinkage;
  }
  
  // FIXME: This should be removed, and clients should pass in the linkage
  // directly instead.
  llvm::Constant *BuildName(QualType Ty, bool Hidden, bool Extern) {
    return BuildName(Ty, Hidden, GetLinkageFromExternFlag(Extern));
  }

  llvm::Constant *BuildName(QualType Ty, bool Hidden, 
                            llvm::GlobalVariable::LinkageTypes Linkage) {
    llvm::SmallString<256> OutName;
    CGM.getMangleContext().mangleCXXRTTIName(Ty, OutName);
    llvm::StringRef Name = OutName.str();

    llvm::GlobalVariable *OGV = CGM.getModule().getNamedGlobal(Name);
    if (OGV && !OGV->isDeclaration())
      return llvm::ConstantExpr::getBitCast(OGV, Int8PtrTy);

    llvm::Constant *C = llvm::ConstantArray::get(VMContext, Name.substr(4));

    llvm::GlobalVariable *GV = 
      new llvm::GlobalVariable(CGM.getModule(), C->getType(), true, Linkage,
                               C, Name);
    if (OGV) {
      GV->takeName(OGV);
      llvm::Constant *NewPtr = llvm::ConstantExpr::getBitCast(GV,
                                                              OGV->getType());
      OGV->replaceAllUsesWith(NewPtr);
      OGV->eraseFromParent();
    }
    if (Hidden)
      GV->setVisibility(llvm::GlobalVariable::HiddenVisibility);
    return llvm::ConstantExpr::getBitCast(GV, Int8PtrTy);
  }

  /// - BuildFlags - Build a psABI __flags value for __vmi_class_type_info.
  llvm::Constant *BuildFlags(int f) {
    return llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext), f);
  }

  /// BuildBaseCount - Build a psABI __base_count value for
  /// __vmi_class_type_info.
  llvm::Constant *BuildBaseCount(unsigned c) {
    return llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext), c);
  }

  /// CalculateFlags - Calculate the flags for the __vmi_class_type_info
  /// datastru