path: root/lib/CodeGen/CGRecordLayoutBuilder.cpp

//===--- CGRecordLayoutBuilder.cpp - CGRecordLayout builder  ----*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Builder implementation for CGRecordLayout objects.
//
//===----------------------------------------------------------------------===//

#include "CGRecordLayout.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Attr.h"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/Expr.h"
#include "clang/AST/RecordLayout.h"
#include "clang/Frontend/CodeGenOptions.h"
#include "CodeGenTypes.h"
#include "CGCXXABI.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Type.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetData.h"
using namespace clang;
using namespace CodeGen;

namespace {

class CGRecordLayoutBuilder {
public:
  /// FieldTypes - Holds the LLVM types that the struct is created from.
  /// 
  SmallVector<llvm::Type *, 16> FieldTypes;

  /// BaseSubobjectType - Holds the LLVM type for the non-virtual part
  /// of the struct. For example, consider:
  ///
  /// struct A { int i; };
  /// struct B { void *v; };
  /// struct C : virtual A, B { };
  ///
  /// The LLVM type of C will be
  /// %struct.C = type { i32 (...)**, %struct.A, i32, %struct.B }
  ///
  /// And the LLVM type of the non-virtual base struct will be
  /// %struct.C.base = type { i32 (...)**, %struct.A, i32 }
  ///
  /// This only gets initialized if the base subobject type is
  /// different from the complete-object type.
  llvm::StructType *BaseSubobjectType;

  /// FieldInfo - Holds a field and its corresponding LLVM field number.
  llvm::DenseMap<const FieldDecl *, unsigned> Fields;

  /// BitFieldInfo - Holds location and size information about a bit field.
  llvm::DenseMap<const FieldDecl *, CGBitFieldInfo> BitFields;

  llvm::DenseMap<const CXXRecordDecl *, unsigned> NonVirtualBases;
  llvm::DenseMap<const CXXRecordDecl *, unsigned> VirtualBases;

  /// IndirectPrimaryBases - Virtual base classes, direct or indirect, that are
  /// primary base classes for some other direct or indirect base class.
  CXXIndirectPrimaryBaseSet IndirectPrimaryBases;

  /// LaidOutVirtualBases - A set of all laid out virtual bases, used to avoid
  /// avoid laying out virtual bases more than once.
  llvm::SmallPtrSet<const CXXRecordDecl *, 4> LaidOutVirtualBases;
  
  /// IsZeroInitializable - Whether this struct can be C++
  /// zero-initialized with an LLVM zeroinitializer.
  bool IsZeroInitializable;
  bool IsZeroInitializableAsBase;

  /// Packed - Whether the resulting LLVM struct will be packed or not.
  bool Packed;
  
  /// IsMsStruct - Whether ms_struct is in effect or not
  bool IsMsStruct;

private:
  CodeGenTypes &Types;

  /// LastLaidOutBaseInfo - Contains the offset and non-virtual size of the
  /// last base laid out. Used so that we can replace the last laid out base
  /// type with an i8 array if needed.
  struct LastLaidOutBaseInfo {
    CharUnits Offset;
    CharUnits NonVirtualSize;

    bool isValid() const { return !NonVirtualSize.isZero(); }
    void invalidate() { NonVirtualSize = CharUnits::Zero(); }
  
  } LastLaidOutBase;

  /// Alignment - Contains the alignment of the RecordDecl.
  CharUnits Alignment;

  /// BitsAvailableInLastField - If a bit field spans only part of a LLVM field,
  /// this will have the number of bits still available in the field.
  char BitsAvailableInLastField;

  /// NextFieldOffset - Holds the next field offset.
  CharUnits NextFieldOffset;

  /// LayoutUnionField - Will layout a field in an union and return the type
  /// that the field will have.
  llvm::Type *LayoutUnionField(const FieldDecl *Field,
                               const ASTRecordLayout &Layout);
  
  /// LayoutUnion - Will layout a union RecordDecl.
  void LayoutUnion(const RecordDecl *D);

  /// LayoutField - try to layout all fields in the record decl.
  /// Returns false if the operation failed because the struct is not packed.
  bool LayoutFields(const RecordDecl *D);

  /// Layout a single base, virtual or non-virtual
  bool LayoutBase(const CXXRecordDecl *base,
                  const CGRecordLayout &baseLayout,
                  CharUnits baseOffset);

  /// LayoutVirtualBase - layout a single virtual base.
  bool LayoutVirtualBase(const CXXRecordDecl *base,
                         CharUnits baseOffset);

  /// LayoutVirtualBases - layout the virtual bases of a record decl.
  bool LayoutVirtualBases(const CXXRecordDecl *RD,
                          const ASTRecordLayout &Layout