| //===--- 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/DeclCXX.h" |
| #include "clang/AST/Expr.h" |
| #include "clang/AST/RecordLayout.h" |
| #include "CodeGenTypes.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/Type.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Target/TargetData.h" |
| using namespace clang; |
| using namespace CodeGen; |
| |
| namespace clang { |
| namespace CodeGen { |
| |
| class CGRecordLayoutBuilder { |
| public: |
| /// FieldTypes - Holds the LLVM types that the struct is created from. |
| std::vector<const llvm::Type *> FieldTypes; |
| |
| /// LLVMFieldInfo - Holds a field and its corresponding LLVM field number. |
| typedef std::pair<const FieldDecl *, unsigned> LLVMFieldInfo; |
| llvm::SmallVector<LLVMFieldInfo, 16> LLVMFields; |
| |
| /// LLVMBitFieldInfo - Holds location and size information about a bit field. |
| typedef std::pair<const FieldDecl *, CGBitFieldInfo> LLVMBitFieldInfo; |
| llvm::SmallVector<LLVMBitFieldInfo, 16> LLVMBitFields; |
| |
| /// ContainsPointerToDataMember - Whether one of the fields in this record |
| /// layout is a pointer to data member, or a struct that contains pointer to |
| /// data member. |
| bool ContainsPointerToDataMember; |
| |
| /// Packed - Whether the resulting LLVM struct will be packed or not. |
| bool Packed; |
| |
| private: |
| CodeGenTypes &Types; |
| |
| /// Alignment - Contains the alignment of the RecordDecl. |
| // |
| // FIXME: This is not needed and should be removed. |
| unsigned Alignment; |
| |
| /// AlignmentAsLLVMStruct - Will contain the maximum alignment of all the |
| /// LLVM types. |
| unsigned AlignmentAsLLVMStruct; |
| |
| /// 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; |
| |
| /// NextFieldOffsetInBytes - Holds the next field offset in bytes. |
| uint64_t NextFieldOffsetInBytes; |
| |
| /// 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); |
| |
| /// LayoutBases - layout the bases and vtable pointer of a record decl. |
| void LayoutBases(const CXXRecordDecl *RD, const ASTRecordLayout &Layout); |
| |
| /// LayoutField - layout a single field. Returns false if the operation failed |
| /// because the current struct is not packed. |
| bool LayoutField(const FieldDecl *D, uint64_t FieldOffset); |
| |
| /// LayoutBitField - layout a single bit field. |
| void LayoutBitField(const FieldDecl *D, uint64_t FieldOffset); |
| |
| /// AppendField - Appends a field with the given offset and type. |
| void AppendField(uint64_t FieldOffsetInBytes, const llvm::Type *FieldTy); |
| |
| /// AppendPadding - Appends enough padding bytes so that the total struct |
| /// size matches the alignment of the passed in type. |
| void AppendPadding(uint64_t FieldOffsetInBytes, const llvm::Type *FieldTy); |
| |
| /// AppendPadding - Appends enough padding bytes so that the total |
| /// struct size is a multiple of the field alignment. |
| void AppendPadding(uint64_t FieldOffsetInBytes, unsigned FieldAlignment); |
| |
| /// AppendBytes - Append a given number of bytes to the record. |
| void AppendBytes(uint64_t NumBytes); |
| |
| /// AppendTailPadding - Append enough tail padding so that the type will have |
| /// the passed size. |
| void AppendTailPadding(uint64_t RecordSize); |
| |
| unsigned getTypeAlignment(const llvm::Type *Ty) const; |
| |
| /// CheckForPointerToDataMember - Check if the given type contains a pointer |
| /// to data member. |
| void CheckForPointerToDataMember(QualType T); |
| |
| public: |
| CGRecordLayoutBuilder(CodeGenTypes &Types) |
| : ContainsPointerToDataMember(false), Packed(false), Types(Types), |
| Alignment(0), AlignmentAsLLVMStruct(1), |
| BitsAvailableInLastField(0), NextFieldOffsetInBytes(0) { } |
| |
| /// Layout - Will layout a RecordDecl. |
| void Layout(const RecordDecl *D); |
| }; |
| |
| } |
| } |
| |
| void CGRecordLayoutBuilder::Layout(const RecordDecl *D) { |
| Alignment = Types.getContext().getASTRecordLayout(D).getAlignment() / 8; |
| Packed = D->hasAttr<PackedAttr>(); |
| |
| if (D->isUnion()) { |
| LayoutUnion(D); |
| return; |
| } |
| |
| if (LayoutFields(D)) |
| return; |
| |
| // We weren't able to layout the struct. Try again with a packed struct |
| Packed = true; |
| AlignmentAsLLVMStruct = 1; |
| NextFieldOffsetInBytes = 0; |
| FieldTypes.clear(); |
| LLVMFields.clear(); |
| LLVMBitFields.clear(); |
| |
| LayoutFields(D); |
| } |
| |
| static CGBitFieldInfo ComputeBitFieldInfo(CodeGenTypes &Types, |
| const FieldDecl *FD, |
| uint64_t FieldOffset, |
| uint64_t FieldSize) { |
| const llvm::Type *Ty = Types.ConvertTypeForMemRecursive(FD->getType()); |
| uint64_t TypeSizeInBytes = Types.getTargetData().getTypeAllocSize(Ty); |
| uint64_t TypeSizeInBits = TypeSizeInBytes * 8; |
| |
| unsigned StartBit = FieldOffset % TypeSizeInBits; |
| bool IsSigned = FD->getType()->isSignedIntegerType(); |
| |
| // The current policy is to always access the bit-field using the source type |
| // of the bit-field. With the C bit-field rules, this implies that we always |
| // use either one or two accesses, and two accesses can only occur with a |
| // packed structure when the bit-field straddles an alignment boundary. |
| CGBitFieldInfo::AccessInfo Components[2]; |
| |
| unsigned LowBits = std::min(FieldSize, TypeSizeInBits - StartBit); |
| bool NeedsHighAccess = LowBits != FieldSize; |
| unsigned NumComponents = 1 + NeedsHighAccess; |
| |
| // FIXME: This access policy is probably wrong on big-endian systems. |
| CGBitFieldInfo::AccessInfo &LowAccess = Components[0]; |
| LowAccess.FieldIndex = 0; |
| LowAccess.FieldByteOffset = |
| TypeSizeInBytes * ((FieldOffset / 8) / TypeSizeInBytes); |
| LowAccess.FieldBitStart = StartBit; |
| LowAccess.AccessWidth = TypeSizeInBits; |
| // FIXME: This might be wrong! |
| LowAccess.AccessAlignment = 0; |
| LowAccess.TargetBitOffset = 0; |
| LowAccess.TargetBitWidth = LowBits; |
| |
| if (NeedsHighAccess) { |
| CGBitFieldInfo::AccessInfo &HighAccess = Components[1]; |
| HighAccess.FieldIndex = 0; |
| HighAccess.FieldByteOffset = LowAccess.FieldByteOffset + TypeSizeInBytes; |
| HighAccess.FieldBitStart = 0; |
| HighAccess.AccessWidth = TypeSizeInBits; |
| // FIXME: This might be wrong! |
| HighAccess.AccessAlignment = 0; |
| HighAccess.TargetBitOffset = LowBits; |
| HighAccess.TargetBitWidth = FieldSize - LowBits; |
| } |
| |
| return CGBitFieldInfo(FieldSize, NumComponents, Components, IsSigned); |
| } |
| |
| void CGRecordLayoutBuilder::LayoutBitField(const FieldDecl *D, |
| uint64_t FieldOffset) { |
| uint64_t FieldSize = |
| D->getBitWidth()->EvaluateAsInt(Types.getContext()).getZExtValue(); |
| |
| if (FieldSize == 0) |
| return; |
| |
| uint64_t NextFieldOffset = NextFieldOffsetInBytes * 8; |
| unsigned NumBytesToAppend; |
| |
| if (FieldOffset < NextFieldOffset) { |
| assert(BitsAvailableInLastField && "Bitfield size mismatch!"); |
| assert(NextFieldOffsetInBytes && "Must have laid out at least one byte!"); |
| |
| // The bitfield begins in the previous bit-field. |
| NumBytesToAppend = |
| llvm::RoundUpToAlignment(FieldSize - BitsAvailableInLastField, 8) / 8; |
| } else { |
| assert(FieldOffset % 8 == 0 && "Field offset not aligned correctly"); |
| |
| // Append padding if necessary. |
| AppendBytes((FieldOffset - NextFieldOffset) / 8); |
| |
| NumBytesToAppend = |
| llvm::RoundUpToAlignment(FieldSize, 8) / 8; |
| |
| assert(NumBytesToAppend && "No bytes to append!"); |
| } |
| |
| // Add the bit field info. |
| LLVMBitFields.push_back( |
| LLVMBitFieldInfo(D, ComputeBitFieldInfo(Types, D, FieldOffset, FieldSize))); |
| |
| AppendBytes(NumBytesToAppend); |
| |
| BitsAvailableInLastField = |
| NextFieldOffsetInBytes * 8 - (FieldOffset + FieldSize); |
| } |
| |
| bool CGRecordLayoutBuilder::LayoutField(const FieldDecl *D, |
| uint64_t FieldOffset) { |
| // If the field is packed, then we need a packed struct. |
| if (!Packed && D->hasAttr<PackedAttr>()) |
| return false; |
| |
| if (D->isBitField()) { |
| // We must use packed structs for unnamed bit fields since they |
| // don't affect the struct alignment. |
| if (!Packed && !D->getDeclName()) |
| return false; |
| |
| LayoutBitField(D, FieldOffset); |
| return true; |
| } |
| |
| // Check if we have a pointer to data member in this field. |
| CheckForPointerToDataMember(D->getType()); |
| |
| assert(FieldOffset % 8 == 0 && "FieldOffset is not on a byte boundary!"); |
| uint64_t FieldOffsetInBytes = FieldOffset / 8; |
| |
| const llvm::Type *Ty = Types.ConvertTypeForMemRecursive(D->getType()); |
| unsigned TypeAlignment = getTypeAlignment(Ty); |
| |
| // If the type alignment is larger then the struct alignment, we must use |
| // a packed struct. |
| if (TypeAlignment > Alignment) { |
| assert(!Packed && "Alignment is wrong even with packed struct!"); |
| return false; |
| } |
| |
| if (const RecordType *RT = D->getType()->getAs<RecordType>()) { |
| const RecordDecl *RD = cast<RecordDecl>(RT->getDecl()); |
| if (const PragmaPackAttr *PPA = RD->getAttr<PragmaPackAttr>()) { |
| if (PPA->getAlignment() != TypeAlignment * 8 && !Packed) |
| return false; |
| } |
| } |
| |
| // Round up the field offset to the alignment of the field type. |
| uint64_t AlignedNextFieldOffsetInBytes = |
| llvm::RoundUpToAlignment(NextFieldOffsetInBytes, TypeAlignment); |
| |
| if (FieldOffsetInBytes < AlignedNextFieldOffsetInBytes) { |
| assert(!Packed && "Could not place field even with packed struct!"); |
| return false; |
| } |
| |
| if (AlignedNextFieldOffsetInBytes < FieldOffsetInBytes) { |
| // Even with alignment, the field offset is not at the right place, |
| // insert padding. |
| uint64_t PaddingInBytes = FieldOffsetInBytes - NextFieldOffsetInBytes; |
| |
| AppendBytes(PaddingInBytes); |
| } |
| |
| // Now append the field. |
| LLVMFields.push_back(LLVMFieldInfo(D, FieldTypes.size())); |
| AppendField(FieldOffsetInBytes, Ty); |
| |
| return true; |
| } |
| |
| void CGRecordLayoutBuilder::LayoutUnion(const RecordDecl *D) { |
| assert(D->isUnion() && "Can't call LayoutUnion on a non-union record!"); |
| |
| const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D); |
| |
| const llvm::Type *Ty = 0; |
| uint64_t Size = 0; |
| unsigned Align = 0; |
| |
| bool HasOnlyZeroSizedBitFields = true; |
| |
| unsigned FieldNo = 0; |
| for (RecordDecl::field_iterator Field = D->field_begin(), |
| FieldEnd = D->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { |
| assert(Layout.getFieldOffset(FieldNo) == 0 && |
| "Union field offset did not start at the beginning of record!"); |
| const llvm::Type *FieldTy = |
| Types.ConvertTypeForMemRecursive(Field->getType()); |
| |
| if (Field->isBitField()) { |
| uint64_t FieldSize = |
| Field->getBitWidth()->EvaluateAsInt(Types.getContext()).getZExtValue(); |
| |
| // Ignore zero sized bit fields. |
| if (FieldSize == 0) |
| continue; |
| |
| // Add the bit field info. |
| LLVMBitFields.push_back( |
| LLVMBitFieldInfo(*Field, ComputeBitFieldInfo(Types, *Field, |
| 0, FieldSize))); |
| } else { |
| LLVMFields.push_back(LLVMFieldInfo(*Field, 0)); |
| } |
| |
| HasOnlyZeroSizedBitFields = false; |
| |
| unsigned FieldAlign = Types.getTargetData().getABITypeAlignment(FieldTy); |
| uint64_t FieldSize = Types.getTargetData().getTypeAllocSize(FieldTy); |
| |
| if (FieldAlign < Align) |
| continue; |
| |
| if (FieldAlign > Align || FieldSize > Size) { |
| Ty = FieldTy; |
| Align = FieldAlign; |
| Size = FieldSize; |
| } |
| } |
| |
| // Now add our field. |
| if (Ty) { |
| AppendField(0, Ty); |
| |
| if (getTypeAlignment(Ty) > Layout.getAlignment() / 8) { |
| // We need a packed struct. |
| Packed = true; |
| Align = 1; |
| } |
| } |
| if (!Align) { |
| assert(HasOnlyZeroSizedBitFields && |
| "0-align record did not have all zero-sized bit-fields!"); |
| Align = 1; |
| } |
| |
| // Append tail padding. |
| if (Layout.getSize() / 8 > Size) |
| AppendPadding(Layout.getSize() / 8, Align); |
| } |
| |
| void CGRecordLayoutBuilder::LayoutBases(const CXXRecordDecl *RD, |
| const ASTRecordLayout &Layout) { |
| // Check if we need to add a vtable pointer. |
| if (RD->isDynamicClass() && !Layout.getPrimaryBase()) { |
| const llvm::Type *Int8PtrTy = |
| llvm::Type::getInt8PtrTy(Types.getLLVMContext()); |
| |
| assert(NextFieldOffsetInBytes == 0 && |
| "Vtable pointer must come first!"); |
| AppendField(NextFieldOffsetInBytes, Int8PtrTy->getPointerTo()); |
| } |
| } |
| |
| bool CGRecordLayoutBuilder::LayoutFields(const RecordDecl *D) { |
| assert(!D->isUnion() && "Can't call LayoutFields on a union!"); |
| assert(Alignment && "Did not set alignment!"); |
| |
| const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D); |
| |
| if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D)) |
| LayoutBases(RD, Layout); |
| |
| unsigned FieldNo = 0; |
| |
| for (RecordDecl::field_iterator Field = D->field_begin(), |
| FieldEnd = D->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { |
| if (!LayoutField(*Field, Layout.getFieldOffset(FieldNo))) { |
| assert(!Packed && |
| "Could not layout fields even with a packed LLVM struct!"); |
| return false; |
| } |
| } |
| |
| // Append tail padding if necessary. |
| AppendTailPadding(Layout.getSize()); |
| |
| return true; |
| } |
| |
| void CGRecordLayoutBuilder::AppendTailPadding(uint64_t RecordSize) { |
| assert(RecordSize % 8 == 0 && "Invalid record size!"); |
| |
| uint64_t RecordSizeInBytes = RecordSize / 8; |
| assert(NextFieldOffsetInBytes <= RecordSizeInBytes && "Size mismatch!"); |
| |
| uint64_t AlignedNextFieldOffset = |
| llvm::RoundUpToAlignment(NextFieldOffsetInBytes, AlignmentAsLLVMStruct); |
| |
| if (AlignedNextFieldOffset == RecordSizeInBytes) { |
| // We don't need any padding. |
| return; |
| } |
| |
| unsigned NumPadBytes = RecordSizeInBytes - NextFieldOffsetInBytes; |
| AppendBytes(NumPadBytes); |
| } |
| |
| void CGRecordLayoutBuilder::AppendField(uint64_t FieldOffsetInBytes, |
| const llvm::Type *FieldTy) { |
| AlignmentAsLLVMStruct = std::max(AlignmentAsLLVMStruct, |
| getTypeAlignment(FieldTy)); |
| |
| uint64_t FieldSizeInBytes = Types.getTargetData().getTypeAllocSize(FieldTy); |
| |
| FieldTypes.push_back(FieldTy); |
| |
| NextFieldOffsetInBytes = FieldOffsetInBytes + FieldSizeInBytes; |
| BitsAvailableInLastField = 0; |
| } |
| |
| void |
| CGRecordLayoutBuilder::AppendPadding(uint64_t FieldOffsetInBytes, |
| const llvm::Type *FieldTy) { |
| AppendPadding(FieldOffsetInBytes, getTypeAlignment(FieldTy)); |
| } |
| |
| void CGRecordLayoutBuilder::AppendPadding(uint64_t FieldOffsetInBytes, |
| unsigned FieldAlignment) { |
| assert(NextFieldOffsetInBytes <= FieldOffsetInBytes && |
| "Incorrect field layout!"); |
| |
| // Round up the field offset to the alignment of the field type. |
| uint64_t AlignedNextFieldOffsetInBytes = |
| llvm::RoundUpToAlignment(NextFieldOffsetInBytes, FieldAlignment); |
| |
| if (AlignedNextFieldOffsetInBytes < FieldOffsetInBytes) { |
| // Even with alignment, the field offset is not at the right place, |
| // insert padding. |
| uint64_t PaddingInBytes = FieldOffsetInBytes - NextFieldOffsetInBytes; |
| |
| AppendBytes(PaddingInBytes); |
| } |
| } |
| |
| void CGRecordLayoutBuilder::AppendBytes(uint64_t NumBytes) { |
| if (NumBytes == 0) |
| return; |
| |
| const llvm::Type *Ty = llvm::Type::getInt8Ty(Types.getLLVMContext()); |
| if (NumBytes > 1) |
| Ty = llvm::ArrayType::get(Ty, NumBytes); |
| |
| // Append the padding field |
| AppendField(NextFieldOffsetInBytes, Ty); |
| } |
| |
| unsigned CGRecordLayoutBuilder::getTypeAlignment(const llvm::Type *Ty) const { |
| if (Packed) |
| return 1; |
| |
| return Types.getTargetData().getABITypeAlignment(Ty); |
| } |
| |
| void CGRecordLayoutBuilder::CheckForPointerToDataMember(QualType T) { |
| // This record already contains a member pointer. |
| if (ContainsPointerToDataMember) |
| return; |
| |
| // Can only have member pointers if we're compiling C++. |
| if (!Types.getContext().getLangOptions().CPlusPlus) |
| return; |
| |
| T = Types.getContext().getBaseElementType(T); |
| |
| if (const MemberPointerType *MPT = T->getAs<MemberPointerType>()) { |
| if (!MPT->getPointeeType()->isFunctionType()) { |
| // We have a pointer to data member. |
| ContainsPointerToDataMember = true; |
| } |
| } else if (const RecordType *RT = T->getAs<RecordType>()) { |
| const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); |
| |
| // FIXME: It would be better if there was a way to explicitly compute the |
| // record layout instead of converting to a type. |
| Types.ConvertTagDeclType(RD); |
| |
| const CGRecordLayout &Layout = Types.getCGRecordLayout(RD); |
| |
| if (Layout.containsPointerToDataMember()) |
| ContainsPointerToDataMember = true; |
| } |
| } |
| |
| CGRecordLayout *CodeGenTypes::ComputeRecordLayout(const RecordDecl *D) { |
| CGRecordLayoutBuilder Builder(*this); |
| |
| Builder.Layout(D); |
| |
| const llvm::Type *Ty = llvm::StructType::get(getLLVMContext(), |
| Builder.FieldTypes, |
| Builder.Packed); |
| assert(getContext().getASTRecordLayout(D).getSize() / 8 == |
| getTargetData().getTypeAllocSize(Ty) && |
| "Type size mismatch!"); |
| |
| CGRecordLayout *RL = |
| new CGRecordLayout(Ty, Builder.ContainsPointerToDataMember); |
| |
| // Add all the field numbers. |
| for (unsigned i = 0, e = Builder.LLVMFields.size(); i != e; ++i) |
| RL->FieldInfo.insert(Builder.LLVMFields[i]); |
| |
| // Add bitfield info. |
| for (unsigned i = 0, e = Builder.LLVMBitFields.size(); i != e; ++i) |
| RL->BitFields.insert(Builder.LLVMBitFields[i]); |
| |
| if (getContext().getLangOptions().DumpRecordLayouts) { |
| llvm::errs() << "\n*** Dumping Record Layout\n"; |
| llvm::errs() << "Record: "; |
| D->dump(); |
| llvm::errs() << "\nLayout: "; |
| RL->dump(); |
| } |
| |
| return RL; |
| } |
| |
| void CGRecordLayout::print(llvm::raw_ostream &OS) const { |
| OS << "<CGRecordLayout\n"; |
| OS << " LLVMType:" << *LLVMType << "\n"; |
| OS << " ContainsPointerToDataMember:" << ContainsPointerToDataMember << "\n"; |
| OS << " BitFields:[\n"; |
| for (llvm::DenseMap<const FieldDecl*, CGBitFieldInfo>::const_iterator |
| it = BitFields.begin(), ie = BitFields.end(); |
| it != ie; ++it) { |
| OS.indent(4); |
| it->second.print(OS); |
| OS << "\n"; |
| } |
| OS << "]>\n"; |
| } |
| |
| void CGRecordLayout::dump() const { |
| print(llvm::errs()); |
| } |
| |
| void CGBitFieldInfo::print(llvm::raw_ostream &OS) const { |
| OS << "<CGBitFieldInfo"; |
| OS << " Size:" << Size; |
| OS << " IsSigned:" << IsSigned << "\n"; |
| |
| OS.indent(4 + strlen("<CGBitFieldInfo")); |
| OS << " NumComponents:" << getNumComponents(); |
| OS << " Components: ["; |
| if (getNumComponents()) { |
| OS << "\n"; |
| for (unsigned i = 0, e = getNumComponents(); i != e; ++i) { |
| const AccessInfo &AI = getComponent(i); |
| OS.indent(8); |
| OS << "<AccessInfo" |
| << " FieldIndex:" << AI.FieldIndex |
| << " FieldByteOffset:" << AI.FieldByteOffset |
| << " FieldBitStart:" << AI.FieldBitStart |
| << " AccessWidth:" << AI.AccessWidth << "\n"; |
| OS.indent(8 + strlen("<AccessInfo")); |
| OS << " AccessAlignment:" << AI.AccessAlignment |
| << " TargetBitOffset:" << AI.TargetBitOffset |
| << " TargetBitWidth:" << AI.TargetBitWidth |
| << ">\n"; |
| } |
| OS.indent(4); |
| } |
| OS << "]>"; |
| } |
| |
| void CGBitFieldInfo::dump() const { |
| print(llvm::errs()); |
| } |