path: root/lib/AST/RecordLayoutBuilder.cpp

//=== ASTRecordLayoutBuilder.cpp - Helper class for building record layouts ==//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "RecordLayoutBuilder.h"

#include "clang/AST/Attr.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/Expr.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/Support/Format.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/Support/MathExtras.h"

using namespace clang;

ASTRecordLayoutBuilder::ASTRecordLayoutBuilder(ASTContext &Context)
  : Context(Context), Size(0), Alignment(8), Packed(false), 
  UnfilledBitsInLastByte(0), MaxFieldAlignment(0), DataSize(0), IsUnion(false),
  NonVirtualSize(0), NonVirtualAlignment(8), FirstNearlyEmptyVBase(0),
  SizeOfLargestEmptySubobject(0) { }

/// IsNearlyEmpty - Indicates when a class has a vtable pointer, but
/// no other data.
bool ASTRecordLayoutBuilder::IsNearlyEmpty(const CXXRecordDecl *RD) const {
  // FIXME: Audit the corners
  if (!RD->isDynamicClass())
    return false;
  const ASTRecordLayout &BaseInfo = Context.getASTRecordLayout(RD);
  if (BaseInfo.getNonVirtualSize() == Context.Target.getPointerWidth(0))
    return true;
  return false;
}

void 
ASTRecordLayoutBuilder::ComputeEmptySubobjectSizes(const CXXRecordDecl *RD) {
  // Check the bases.
  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
       E = RD->bases_end(); I != E; ++I) {
    const CXXRecordDecl *BaseDecl =
      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());

    uint64_t EmptySize = 0;
    const ASTRecordLayout &Layout = Context.getASTRecordLayout(BaseDecl);
    if (BaseDecl->isEmpty()) {
      // If the class decl is empty, get its size.
      EmptySize = Layout.getSize();
    } else {
      // Otherwise, we get the largest empty subobject for the decl.
      EmptySize = Layout.getSizeOfLargestEmptySubobject();
    }
    
    SizeOfLargestEmptySubobject = std::max(SizeOfLargestEmptySubobject, 
                                           EmptySize);
  }

  // Check the fields.
  for (CXXRecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end();
       I != E; ++I) {
    const FieldDecl *FD = *I;
    
    const RecordType *RT = 
      Context.getBaseElementType(FD->getType())->getAs<RecordType>();
    
    // We only care about record types.
    if (!RT)
      continue;

    uint64_t EmptySize = 0;
    const CXXRecordDecl *MemberDecl = cast<CXXRecordDecl>(RT->getDecl());
    const ASTRecordLayout &Layout = Context.getASTRecordLayout(MemberDecl);
    if (MemberDecl->isEmpty()) {
      // If the class decl is empty, get its size.
      EmptySize = Layout.getSize();
    } else {
      // Otherwise, we get the largest empty subobject for the decl.
      EmptySize = Layout.getSizeOfLargestEmptySubobject();
    }
      
   SizeOfLargestEmptySubobject = std::max(SizeOfLargestEmptySubobject, 
                                          EmptySize);
  }
}

void ASTRecordLayoutBuilder::IdentifyPrimaryBases(const CXXRecordDecl *RD) {
  const ASTRecordLayout::PrimaryBaseInfo &BaseInfo =
    Context.getASTRecordLayout(RD).getPrimaryBaseInfo();

  // If the record has a primary base class that is virtual, add it to the set
  // of primary bases.
  if (BaseInfo.isVirtual())
    IndirectPrimaryBases.insert(BaseInfo.getBase());

  // Now traverse all bases and find primary bases for them.
  for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(),
         e = RD->bases_end(); i != e; ++i) {
    assert(!i->getType()->isDependentType() &&
           "Cannot layout class with dependent bases.");
    const CXXRecordDecl *Base =
      cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()