| //===--- CGRecordLayoutBuilder.cpp - Record builder helper ------*- C++ -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This is a helper class used to build CGRecordLayout objects and LLVM types. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "CGRecordLayoutBuilder.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/Target/TargetData.h" |
| |
| |
| using namespace clang; |
| using namespace CodeGen; |
| |
| 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); |
| } |
| |
| 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!"); |
| } |
| |
| const llvm::Type *Ty = Types.ConvertTypeForMemRecursive(D->getType()); |
| uint64_t TypeSizeInBits = getTypeSizeInBytes(Ty) * 8; |
| |
| LLVMBitFields.push_back(LLVMBitFieldInfo(D, FieldOffset / TypeSizeInBits, |
| FieldOffset % TypeSizeInBits, |
| 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!"); |
| |
| 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. |
| Types.addBitFieldInfo(*Field, 0, 0, FieldSize); |
| } else |
| Types.addFieldInfo(*Field, 0); |
| |
| HasOnlyZeroSizedBitFields = false; |
| |
| const llvm::Type *FieldTy = |
| Types.ConvertTypeForMemRecursive(Field->getType()); |
| 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 = getTypeSizeInBytes(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); |
| } |
| |
| uint64_t CGRecordLayoutBuilder::getTypeSizeInBytes(const llvm::Type *Ty) const { |
| return Types.getTargetData().getTypeAllocSize(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 * |
| CGRecordLayoutBuilder::ComputeLayout(CodeGenTypes &Types, |
| const RecordDecl *D) { |
| CGRecordLayoutBuilder Builder(Types); |
| |
| Builder.Layout(D); |
| |
| const llvm::Type *Ty = llvm::StructType::get(Types.getLLVMContext(), |
| Builder.FieldTypes, |
| Builder.Packed); |
| assert(Types.getContext().getASTRecordLayout(D).getSize() / 8 == |
| Types.getTargetData().getTypeAllocSize(Ty) && |
| "Type size mismatch!"); |
| |
| // Add all the field numbers. |
| for (unsigned i = 0, e = Builder.LLVMFields.size(); i != e; ++i) { |
| const FieldDecl *FD = Builder.LLVMFields[i].first; |
| unsigned FieldNo = Builder.LLVMFields[i].second; |
| |
| Types.addFieldInfo(FD, FieldNo); |
| } |
| |
| // Add bitfield info. |
| for (unsigned i = 0, e = Builder.LLVMBitFields.size(); i != e; ++i) { |
| const LLVMBitFieldInfo &Info = Builder.LLVMBitFields[i]; |
| |
| Types.addBitFieldInfo(Info.FD, Info.FieldNo, Info.Start, Info.Size); |
| } |
| |
| return new CGRecordLayout(Ty, Builder.ContainsPointerToDataMember); |
| } |