C++ field_iterator::isUnnamedBitfield方法代码示例

/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
/// non-zero bytes that will be stored when outputting the initializer for the
/// specified initializer expression.
static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
  E = E->IgnoreParens();

  // 0 and 0.0 won't require any non-zero stores!
  if (isSimpleZero(E, CGF)) return CharUnits::Zero();

  // If this is an initlist expr, sum up the size of sizes of the (present)
  // elements.  If this is something weird, assume the whole thing is non-zero.
  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
  if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
    return CGF.getContext().getTypeSizeInChars(E->getType());
  
  // InitListExprs for structs have to be handled carefully.  If there are
  // reference members, we need to consider the size of the reference, not the
  // referencee.  InitListExprs for unions and arrays can't have references.
  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
    if (!RT->isUnionType()) {
      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
      CharUnits NumNonZeroBytes = CharUnits::Zero();
      
      unsigned ILEElement = 0;
      for (RecordDecl::field_iterator Field = SD->field_begin(),
           FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
        // We're done once we hit the flexible array member or run out of
        // InitListExpr elements.
        if (Field->getType()->isIncompleteArrayType() ||
            ILEElement == ILE->getNumInits())
          break;
        if (Field->isUnnamedBitfield())
          continue;

        const Expr *E = ILE->getInit(ILEElement++);
        
        // Reference values are always non-null and have the width of a pointer.
        if (Field->getType()->isReferenceType())
          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
              CGF.getContext().getTargetInfo().getPointerWidth(0));
        else
          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
      }
      
      return NumNonZeroBytes;
    }
  }
  
  
  CharUnits NumNonZeroBytes = CharUnits::Zero();
  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
  return NumNonZeroBytes;
}

  //--------------------------------------------------------- 
  void VisitInitListExpr(InitListExpr *RHS) 
  {
    unsigned elementNo = 0;
    for (RecordDecl::field_iterator i = RD->field_begin(), 
         e = RD->field_end(); i != e; ++i)
    {
      // how to handle?
      if (i->isUnnamedBitfield())
        continue;
    
      compoundStmts.push_back(Assign_(
        MemberPoint_(Paren_(Clone_(LHS)), *i), 
        elementNo < RHS->getNumInits() ?        
          Clone_ (RHS->getInit(elementNo)) : 
          Int_(0)));

      elementNo++;
    }
  }

//.........这里部分代码省略.........
      Builder.CreateCondBr(done, endBB, bodyBB);
      currentElement->addIncoming(nextElement, Builder.GetInsertBlock());

      CGF.EmitBlock(endBB);
    }

    // Leave the partial-array cleanup if we entered one.
    if (dtorKind) CGF.DeactivateCleanupBlock(cleanup, cleanupDominator);

    return;
  }

  assert(E->getType()->isRecordType() && "Only support structs/unions here!");

  // Do struct initialization; this code just sets each individual member
  // to the approprate value.  This makes bitfield support automatic;
  // the disadvantage is that the generated code is more difficult for
  // the optimizer, especially with bitfields.
  unsigned NumInitElements = E->getNumInits();
  RecordDecl *record = E->getType()->castAs<RecordType>()->getDecl();
  
  if (record->isUnion()) {
    // Only initialize one field of a union. The field itself is
    // specified by the initializer list.
    if (!E->getInitializedFieldInUnion()) {
      // Empty union; we have nothing to do.

#ifndef NDEBUG
      // Make sure that it's really an empty and not a failure of
      // semantic analysis.
      for (RecordDecl::field_iterator Field = record->field_begin(),
                                   FieldEnd = record->field_end();
           Field != FieldEnd; ++Field)
        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
#endif
      return;
    }

    // FIXME: volatility
    FieldDecl *Field = E->getInitializedFieldInUnion();

    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);
    if (NumInitElements) {
      // Store the initializer into the field
      EmitInitializationToLValue(E->getInit(0), FieldLoc);
    } else {
      // Default-initialize to null.
      EmitNullInitializationToLValue(FieldLoc);
    }

    return;
  }

  // We'll need to enter cleanup scopes in case any of the member
  // initializers throw an exception.
  SmallVector<EHScopeStack::stable_iterator, 16> cleanups;
  llvm::Instruction *cleanupDominator = 0;

  // Here we iterate over the fields; this makes it simpler to both
  // default-initialize fields and skip over unnamed fields.
  unsigned curInitIndex = 0;
  for (RecordDecl::field_iterator field = record->field_begin(),
                               fieldEnd = record->field_end();
       field != fieldEnd; ++field) {
    // We're done once we hit the flexible array member.
    if (field->getType()->isIncompleteArrayType())

void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
#if 0
  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
  // (Length of globals? Chunks of zeroed-out space?).
  //
  // If we can, prefer a copy from a global; this is a lot less code for long
  // globals, and it's easier for the current optimizers to analyze.
  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
    llvm::GlobalVariable* GV =
    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
                             llvm::GlobalValue::InternalLinkage, C, "");
    EmitFinalDestCopy(E, CGF.MakeAddrLValue(GV, E->getType()));
    return;
  }
#endif
  if (E->hadArrayRangeDesignator()) {
    CGF.ErrorUnsupported(E, "GNU array range designator extension");
  }

  // Handle initialization of an array.
  if (E->getType()->isArrayType()) {
    const llvm::PointerType *APType =
      cast<llvm::PointerType>(DestPtr->getType());
    const llvm::ArrayType *AType =
      cast<llvm::ArrayType>(APType->getElementType());

    uint64_t NumInitElements = E->getNumInits();

    if (E->getNumInits() > 0) {
      QualType T1 = E->getType();
      QualType T2 = E->getInit(0)->getType();
      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
        EmitAggLoadOfLValue(E->getInit(0));
        return;
      }
    }

    uint64_t NumArrayElements = AType->getNumElements();
    QualType ElementType = CGF.getContext().getCanonicalType(E->getType());
    ElementType = CGF.getContext().getAsArrayType(ElementType)->getElementType();

    // FIXME: were we intentionally ignoring address spaces and GC attributes?

    for (uint64_t i = 0; i != NumArrayElements; ++i) {
      llvm::Value *NextVal = Builder.CreateStructGEP(DestPtr, i, ".array");
      LValue LV = CGF.MakeAddrLValue(NextVal, ElementType);
      if (i < NumInitElements)
        EmitInitializationToLValue(E->getInit(i), LV, ElementType);

      else
        EmitNullInitializationToLValue(LV, ElementType);
    }
    return;
  }

  assert(E->getType()->isRecordType() && "Only support structs/unions here!");

  // Do struct initialization; this code just sets each individual member
  // to the approprate value.  This makes bitfield support automatic;
  // the disadvantage is that the generated code is more difficult for
  // the optimizer, especially with bitfields.
  unsigned NumInitElements = E->getNumInits();
  RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
  
  // If we're initializing the whole aggregate, just do it in place.
  // FIXME: This is a hack around an AST bug (PR6537).
  if (NumInitElements == 1 && E->getType() == E->getInit(0)->getType()) {
    EmitInitializationToLValue(E->getInit(0),
                               CGF.MakeAddrLValue(DestPtr, E->getType()),
                               E->getType());
    return;
  }
  
  
  if (E->getType()->isUnionType()) {
    // Only initialize one field of a union. The field itself is
    // specified by the initializer list.
    if (!E->getInitializedFieldInUnion()) {
      // Empty union; we have nothing to do.

#ifndef NDEBUG
      // Make sure that it's really an empty and not a failure of
      // semantic analysis.
      for (RecordDecl::field_iterator Field = SD->field_begin(),
                                   FieldEnd = SD->field_end();
           Field != FieldEnd; ++Field)
        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
#endif
      return;
    }

    // FIXME: volatility
    FieldDecl *Field = E->getInitializedFieldInUnion();
    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);

    if (NumInitElements) {
      // Store the initializer into the field
      EmitInitializationToLValue(E->getInit(0), FieldLoc, Field->getType());
    } else {
      // Default-initialize to null
//.........这里部分代码省略.........

//.........这里部分代码省略.........
        BaseOrMemberType::getFromOpaqueValue(Path[I].BaseOrMember).getPointer();
        if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(BaseOrMember)) {
          CastToBase = RD;
          ElemTy = Ctx.getRecordType(RD);
        } else {
          const ValueDecl *VD = cast<ValueDecl>(BaseOrMember);
          Out << ".";
          if (CastToBase)
            Out << *CastToBase << "::";
          Out << *VD;
          ElemTy = VD->getType();
        }
      } else {
        // The lvalue must refer to an array.
        Out << '[' << Path[I].ArrayIndex << ']';
        ElemTy = Ctx.getAsArrayType(ElemTy)->getElementType();
      }
    }

    // Handle formatting of one-past-the-end lvalues.
    if (isLValueOnePastTheEnd()) {
      // FIXME: If CastToBase is non-0, we should prefix the output with
      // "(CastToBase*)".
      Out << " + 1";
      if (IsReference)
        Out << ')';
    }
    return;
  }
  case APValue::Array: {
    const ArrayType *AT = Ctx.getAsArrayType(Ty);
    QualType ElemTy = AT->getElementType();
    Out << '{';
    if (unsigned N = getArrayInitializedElts()) {
      getArrayInitializedElt(0).printPretty(Out, Ctx, ElemTy);
      for (unsigned I = 1; I != N; ++I) {
        Out << ", ";
        if (I == 10) {
          // Avoid printing out the entire contents of large arrays.
          Out << "...";
          break;
        }
        getArrayInitializedElt(I).printPretty(Out, Ctx, ElemTy);
      }
    }
    Out << '}';
    return;
  }
  case APValue::Struct: {
    Out << '{';
    const RecordDecl *RD = Ty->getAs<RecordType>()->getDecl();
    bool First = true;
    if (unsigned N = getStructNumBases()) {
      const CXXRecordDecl *CD = cast<CXXRecordDecl>(RD);
      CXXRecordDecl::base_class_const_iterator BI = CD->bases_begin();
      for (unsigned I = 0; I != N; ++I, ++BI) {
        assert(BI != CD->bases_end());
        if (!First)
          Out << ", ";
        getStructBase(I).printPretty(Out, Ctx, BI->getType());
        First = false;
      }
    }
    for (RecordDecl::field_iterator FI = RD->field_begin();
         FI != RD->field_end(); ++FI) {
      if (!First)
        Out << ", ";
      if (FI->isUnnamedBitfield()) continue;
      getStructField(FI->getFieldIndex()).
        printPretty(Out, Ctx, FI->getType());
      First = false;
    }
    Out << '}';
    return;
  }
  case APValue::Union:
    Out << '{';
    if (const FieldDecl *FD = getUnionField()) {
      Out << "." << *FD << " = ";
      getUnionValue().printPretty(Out, Ctx, FD->getType());
    }
    Out << '}';
    return;
  case APValue::MemberPointer:
    // FIXME: This is not enough to unambiguously identify the member in a
    // multiple-inheritance scenario.
    if (const ValueDecl *VD = getMemberPointerDecl()) {
      Out << '&' << *cast<CXXRecordDecl>(VD->getDeclContext()) << "::" << *VD;
      return;
    }
    Out << "0";
    return;
  case APValue::AddrLabelDiff:
    Out << "&&" << getAddrLabelDiffLHS()->getLabel()->getName();
    Out << " - ";
    Out << "&&" << getAddrLabelDiffRHS()->getLabel()->getName();
    return;
  }
  llvm_unreachable("Unknown APValue kind!");
}