path: root/lib/CodeGen/CGVtable.cpp

//===--- CGVtable.cpp - Emit LLVM Code for C++ vtables --------------------===//
//
//                     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 virtual tables.
//
//===----------------------------------------------------------------------===//

#include "CodeGenModule.h"
#include "CodeGenFunction.h"

#include "clang/AST/RecordLayout.h"

using namespace clang;
using namespace CodeGen;

class VtableBuilder {
public:
  /// Index_t - Vtable index type.
  typedef uint64_t Index_t;
private:
  std::vector<llvm::Constant *> &methods;
  std::vector<llvm::Constant *> submethods;
  llvm::Type *Ptr8Ty;
  /// Class - The most derived class that this vtable is being built for.
  const CXXRecordDecl *Class;
  /// BLayout - Layout for the most derived class that this vtable is being
  /// built for.
  const ASTRecordLayout &BLayout;
  llvm::SmallSet<const CXXRecordDecl *, 32> IndirectPrimary;
  llvm::SmallSet<const CXXRecordDecl *, 32> SeenVBase;
  llvm::Constant *rtti;
  llvm::LLVMContext &VMContext;
  CodeGenModule &CGM;  // Per-module state.
  /// Index - Maps a method decl into a vtable index.  Useful for virtual
  /// dispatch codegen.
  llvm::DenseMap<const CXXMethodDecl *, Index_t> Index;
  llvm::DenseMap<const CXXMethodDecl *, Index_t> VCall;
  llvm::DenseMap<const CXXMethodDecl *, Index_t> VCallOffset;
  // This is the offset to the nearest virtual base
  llvm::DenseMap<const CXXMethodDecl *, Index_t> NonVirtualOffset;
  llvm::DenseMap<const CXXRecordDecl *, Index_t> VBIndex;

  typedef llvm::DenseMap<const CXXMethodDecl *, int> Pures_t;
  Pures_t Pures;
  typedef std::pair<Index_t, Index_t>  CallOffset;
  typedef llvm::DenseMap<const CXXMethodDecl *, CallOffset> Thunks_t;
  Thunks_t Thunks;
  typedef llvm::DenseMap<const CXXMethodDecl *,
                         std::pair<std::pair<CallOffset, CallOffset>,
                                   CanQualType> > CovariantThunks_t;
  CovariantThunks_t CovariantThunks;
  std::vector<Index_t> VCalls;

  typedef std::pair<const CXXRecordDecl *, uint64_t> CtorVtable_t;
  // CtorVtable - Used to hold the AddressPoints (offsets) into the built vtable
  // for use in computing the initializers for the VTT.
  llvm::DenseMap<CtorVtable_t, int64_t> &AddressPoints;

  typedef CXXRecordDecl::method_iterator method_iter;
  // FIXME: Linkage should follow vtable
  const bool Extern;
  const uint32_t LLVMPointerWidth;
  Index_t extra;
  typedef std::vector<std::pair<const CXXRecordDecl *, int64_t> > Path_t;
  llvm::Constant *cxa_pure;
public:
  VtableBuilder(std::vector<llvm::Constant *> &meth,
                const CXXRecordDecl *c,
                CodeGenModule &cgm)
    : methods(meth), Class(c), BLayout(cgm.getContext().getASTRecordLayout(c)),
      rtti(cgm.GenerateRtti(c)), VMContext(cgm.getModule().getContext()),
      CGM(cgm), AddressPoints(*new llvm::DenseMap<CtorVtable_t, int64_t>),
      Extern(true),
      LLVMPointerWidth(cgm.getContext().Target.getPointerWidth(0)) {
    Ptr8Ty = llvm::PointerType::get(llvm::Type::getInt8Ty(VMContext), 0);

    // Calculate pointer for ___cxa_pure_virtual.
    const llvm::FunctionType *FTy;
    std::vector<const llvm::Type*> ArgTys;
    const llvm::Type *ResultType = llvm::Type::getVoidTy(VMContext);
    FTy = llvm::FunctionType::get(ResultType, ArgTys, false);
    cxa_pure = wrap(CGM.CreateRuntimeFunction(FTy, "__cxa_pure_virtual"));
  }

  llvm::DenseMap<const CXXMethodDecl *, Index_t> &getIndex() { return Index; }
  llvm::DenseMap<const CXXRecordDecl *, Index_t> &getVBIndex()
    { return VBIndex; }

  llvm::DenseMap<CtorVtable_t, int64_t> *getAddressPoints()
    { return &AddressPoints; }

  llvm::Constant *wrap(Index_t i) {
    llvm::Constant *m;
    m = llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext), i);
    return llvm::ConstantExpr::getIntToPtr(m, Ptr8Ty);
  }

  llvm::Constant *wrap(llvm::Constant *m) {
    return llvm::ConstantExpr::getBitCast(m, Ptr8Ty);
  }

#define D1(x)
//#define D1(X) do { if (getenv("DEBUG")) { X; } } while (0)

  void GenerateVBaseOffsets(const CXXRecordDecl *RD, uint64_t Offset,
                            bool updateVBIndex, Index_t current_vbindex) {
    for (CXXRecordDecl::base_class_const_iterator i = <