diff options
Diffstat (limited to 'lib/AST/RecordLayoutBuilder.cpp')
| -rw-r--r-- | lib/AST/RecordLayoutBuilder.cpp | 120 |
1 files changed, 75 insertions, 45 deletions
diff --git a/lib/AST/RecordLayoutBuilder.cpp b/lib/AST/RecordLayoutBuilder.cpp index b3deeba..0d070a4 100644 --- a/lib/AST/RecordLayoutBuilder.cpp +++ b/lib/AST/RecordLayoutBuilder.cpp @@ -636,23 +636,12 @@ protected: HasOwnVFPtr(false), FirstNearlyEmptyVBase(nullptr) {} - /// Reset this RecordLayoutBuilder to a fresh state, using the given - /// alignment as the initial alignment. This is used for the - /// correct layout of vb-table pointers in MSVC. - void resetWithTargetAlignment(CharUnits TargetAlignment) { - const ASTContext &Context = this->Context; - EmptySubobjectMap *EmptySubobjects = this->EmptySubobjects; - this->~RecordLayoutBuilder(); - new (this) RecordLayoutBuilder(Context, EmptySubobjects); - Alignment = UnpackedAlignment = TargetAlignment; - } - void Layout(const RecordDecl *D); void Layout(const CXXRecordDecl *D); void Layout(const ObjCInterfaceDecl *D); void LayoutFields(const RecordDecl *D); - void LayoutField(const FieldDecl *D); + void LayoutField(const FieldDecl *D, bool InsertExtraPadding); void LayoutWideBitField(uint64_t FieldSize, uint64_t TypeSize, bool FieldPacked, const FieldDecl *D); void LayoutBitField(const FieldDecl *D); @@ -1104,7 +1093,7 @@ RecordLayoutBuilder::LayoutVirtualBases(const CXXRecordDecl *RD, // Only lay out the virtual base if it's not an indirect primary base. if (!IndirectPrimaryBase) { // Only visit virtual bases once. - if (!VisitedVirtualBases.insert(BaseDecl)) + if (!VisitedVirtualBases.insert(BaseDecl).second) continue; const BaseSubobjectInfo *BaseInfo = VirtualBaseInfo.lookup(BaseDecl); @@ -1331,7 +1320,7 @@ void RecordLayoutBuilder::Layout(const ObjCInterfaceDecl *D) { // Layout each ivar sequentially. for (const ObjCIvarDecl *IVD = D->all_declared_ivar_begin(); IVD; IVD = IVD->getNextIvar()) - LayoutField(IVD); + LayoutField(IVD, false); // Finally, round the size of the total struct up to the alignment of the // struct itself. @@ -1341,8 +1330,22 @@ void RecordLayoutBuilder::Layout(const ObjCInterfaceDecl *D) { void RecordLayoutBuilder::LayoutFields(const RecordDecl *D) { // Layout each field, for now, just sequentially, respecting alignment. In // the future, this will need to be tweakable by targets. - for (const auto *Field : D->fields()) - LayoutField(Field); + bool InsertExtraPadding = D->mayInsertExtraPadding(/*EmitRemark=*/true); + bool HasFlexibleArrayMember = D->hasFlexibleArrayMember(); + for (auto I = D->field_begin(), End = D->field_end(); I != End; ++I) { + auto Next(I); + ++Next; + LayoutField(*I, + InsertExtraPadding && (Next != End || !HasFlexibleArrayMember)); + } +} + +// Rounds the specified size to have it a multiple of the char size. +static uint64_t +roundUpSizeToCharAlignment(uint64_t Size, + const ASTContext &Context) { + uint64_t CharAlignment = Context.getTargetInfo().getCharAlign(); + return llvm::RoundUpToAlignment(Size, CharAlignment); } void RecordLayoutBuilder::LayoutWideBitField(uint64_t FieldSize, @@ -1382,7 +1385,9 @@ void RecordLayoutBuilder::LayoutWideBitField(uint64_t FieldSize, uint64_t UnpaddedFieldOffset = getDataSizeInBits() - UnfilledBitsInLastUnit; if (IsUnion) { - setDataSize(std::max(getDataSizeInBits(), FieldSize)); + uint64_t RoundedFieldSize = roundUpSizeToCharAlignment(FieldSize, + Context); + setDataSize(std::max(getDataSizeInBits(), RoundedFieldSize)); FieldOffset = 0; } else { // The bitfield is allocated starting at the next offset aligned @@ -1413,9 +1418,9 @@ void RecordLayoutBuilder::LayoutWideBitField(uint64_t FieldSize, void RecordLayoutBuilder::LayoutBitField(const FieldDecl *D) { bool FieldPacked = Packed || D->hasAttr<PackedAttr>(); uint64_t FieldSize = D->getBitWidthValue(Context); - std::pair<uint64_t, unsigned> FieldInfo = Context.getTypeInfo(D->getType()); - uint64_t TypeSize = FieldInfo.first; - unsigned FieldAlign = FieldInfo.second; + TypeInfo FieldInfo = Context.getTypeInfo(D->getType()); + uint64_t TypeSize = FieldInfo.Width; + unsigned FieldAlign = FieldInfo.Align; // UnfilledBitsInLastUnit is the difference between the end of the // last allocated bitfield (i.e. the first bit offset available for @@ -1607,9 +1612,9 @@ void RecordLayoutBuilder::LayoutBitField(const FieldDecl *D) { // For unions, this is just a max operation, as usual. if (IsUnion) { - // FIXME: I think FieldSize should be TypeSize here. - setDataSize(std::max(getDataSizeInBits(), FieldSize)); - + uint64_t RoundedFieldSize = roundUpSizeToCharAlignment(FieldSize, + Context); + setDataSize(std::max(getDataSizeInBits(), RoundedFieldSize)); // For non-zero-width bitfields in ms_struct structs, allocate a new // storage unit if necessary. } else if (IsMsStruct && FieldSize) { @@ -1645,7 +1650,8 @@ void RecordLayoutBuilder::LayoutBitField(const FieldDecl *D) { Context.toCharUnitsFromBits(UnpackedFieldAlign)); } -void RecordLayoutBuilder::LayoutField(const FieldDecl *D) { +void RecordLayoutBuilder::LayoutField(const FieldDecl *D, + bool InsertExtraPadding) { if (D->isBitField()) { LayoutBitField(D); return; @@ -1749,6 +1755,15 @@ void RecordLayoutBuilder::LayoutField(const FieldDecl *D) { Context.toBits(UnpackedFieldOffset), Context.toBits(UnpackedFieldAlign), FieldPacked, D); + if (InsertExtraPadding) { + CharUnits ASanAlignment = CharUnits::fromQuantity(8); + CharUnits ExtraSizeForAsan = ASanAlignment; + if (FieldSize % ASanAlignment) + ExtraSizeForAsan += + ASanAlignment - CharUnits::fromQuantity(FieldSize % ASanAlignment); + FieldSize += ExtraSizeForAsan; + } + // Reserve space for this field. uint64_t FieldSizeInBits = Context.toBits(FieldSize); if (IsUnion) @@ -2097,7 +2112,7 @@ static bool isMsLayout(const RecordDecl* D) { // * There is a distinction between alignment and required alignment. // __declspec(align) changes the required alignment of a struct. This // alignment is _always_ obeyed, even in the presence of #pragma pack. A -// record inherites required alignment from all of its fields an bases. +// record inherits required alignment from all of its fields and bases. // * __declspec(align) on bitfields has the effect of changing the bitfield's // alignment instead of its required alignment. This is the only known way // to make the alignment of a struct bigger than 8. Interestingly enough @@ -2181,8 +2196,9 @@ public: FieldOffsets.push_back(FieldOffset); } /// \brief Compute the set of virtual bases for which vtordisps are required. - llvm::SmallPtrSet<const CXXRecordDecl *, 2> - computeVtorDispSet(const CXXRecordDecl *RD); + void computeVtorDispSet( + llvm::SmallPtrSetImpl<const CXXRecordDecl *> &HasVtorDispSet, + const CXXRecordDecl *RD) const; const ASTContext &Context; /// \brief The size of the record being laid out. CharUnits Size; @@ -2203,6 +2219,8 @@ public: CharUnits CurrentBitfieldSize; /// \brief Offset to the virtual base table pointer (if one exists). CharUnits VBPtrOffset; + /// \brief Minimum record size possible. + CharUnits MinEmptyStructSize; /// \brief The size and alignment info of a pointer. ElementInfo PointerInfo; /// \brief The primary base class (if one exists). @@ -2260,12 +2278,18 @@ MicrosoftRecordLayoutBuilder::getAdjustedElementInfo( MicrosoftRecordLayoutBuilder::ElementInfo MicrosoftRecordLayoutBuilder::getAdjustedElementInfo( const FieldDecl *FD) { + // Get the alignment of the field type's natural alignment, ignore any + // alignment attributes. ElementInfo Info; std::tie(Info.Size, Info.Alignment) = - Context.getTypeInfoInChars(FD->getType()); - // Respect align attributes. - CharUnits FieldRequiredAlignment = + Context.getTypeInfoInChars(FD->getType()->getUnqualifiedDesugaredType()); + // Respect align attributes on the field. + CharUnits FieldRequiredAlignment = Context.toCharUnitsFromBits(FD->getMaxAlignment()); + // Respect align attributes on the type. + if (Context.isAlignmentRequired(FD->getType())) + FieldRequiredAlignment = std::max( + Context.getTypeAlignInChars(FD->getType()), FieldRequiredAlignment); // Respect attributes applied to subobjects of the field. if (FD->isBitField()) // For some reason __declspec align impacts alignment rather than required @@ -2292,6 +2316,8 @@ MicrosoftRecordLayoutBuilder::getAdjustedElementInfo( } void MicrosoftRecordLayoutBuilder::layout(const RecordDecl *RD) { + // For C record layout, zero-sized records always have size 4. + MinEmptyStructSize = CharUnits::fromQuantity(4); initializeLayout(RD); layoutFields(RD); DataSize = Size = Size.RoundUpToAlignment(Alignment); @@ -2301,6 +2327,8 @@ void MicrosoftRecordLayoutBuilder::layout(const RecordDecl *RD) { } void MicrosoftRecordLayoutBuilder::cxxLayout(const CXXRecordDecl *RD) { + // The C++ standard says that empty structs have size 1. + MinEmptyStructSize = CharUnits::One(); initializeLayout(RD); initializeCXXLayout(RD); layoutNonVirtualBases(RD); @@ -2599,14 +2627,14 @@ void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) { } VtorDispAlignment = std::max(VtorDispAlignment, RequiredAlignment); // Compute the vtordisp set. - llvm::SmallPtrSet<const CXXRecordDecl *, 2> HasVtordispSet = - computeVtorDispSet(RD); + llvm::SmallPtrSet<const CXXRecordDecl *, 2> HasVtorDispSet; + computeVtorDispSet(HasVtorDispSet, RD); // Iterate through the virtual bases and lay them out. const ASTRecordLayout *PreviousBaseLayout = nullptr; for (const CXXBaseSpecifier &VBase : RD->vbases()) { const CXXRecordDecl *BaseDecl = VBase.getType()->getAsCXXRecordDecl(); const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl); - bool HasVtordisp = HasVtordispSet.count(BaseDecl); + bool HasVtordisp = HasVtorDispSet.count(BaseDecl) > 0; // Insert padding between two bases if the left first one is zero sized or // contains a zero sized subobject and the right is zero sized or one leads // with a zero sized base. The padding between virtual bases is 4 @@ -2629,7 +2657,7 @@ void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) { void MicrosoftRecordLayoutBuilder::finalizeLayout(const RecordDecl *RD) { // Respect required alignment. Note that in 32-bit mode Required alignment - // may be 0 nad cause size not to be updated. + // may be 0 and cause size not to be updated. DataSize = Size; if (!RequiredAlignment.isZero()) { Alignment = std::max(Alignment, RequiredAlignment); @@ -2639,11 +2667,15 @@ void MicrosoftRecordLayoutBuilder::finalizeLayout(const RecordDecl *RD) { RoundingAlignment = std::max(RoundingAlignment, RequiredAlignment); Size = Size.RoundUpToAlignment(RoundingAlignment); } - // Zero-sized structures have size equal to their alignment. if (Size.isZero()) { EndsWithZeroSizedObject = true; LeadsWithZeroSizedBase = true; - Size = Alignment; + // Zero-sized structures have size equal to their alignment if a + // __declspec(align) came into play. + if (RequiredAlignment >= MinEmptyStructSize) + Size = Alignment; + else + Size = MinEmptyStructSize; } } @@ -2665,10 +2697,9 @@ RequiresVtordisp(const llvm::SmallPtrSetImpl<const CXXRecordDecl *> & return false; } -llvm::SmallPtrSet<const CXXRecordDecl *, 2> -MicrosoftRecordLayoutBuilder::computeVtorDispSet(const CXXRecordDecl *RD) { - llvm::SmallPtrSet<const CXXRecordDecl *, 2> HasVtordispSet; - +void MicrosoftRecordLayoutBuilder::computeVtorDispSet( + llvm::SmallPtrSetImpl<const CXXRecordDecl *> &HasVtordispSet, + const CXXRecordDecl *RD) const { // /vd2 or #pragma vtordisp(2): Always use vtordisps for virtual bases with // vftables. if (RD->getMSVtorDispMode() == MSVtorDispAttr::ForVFTable) { @@ -2678,7 +2709,7 @@ MicrosoftRecordLayoutBuilder::computeVtorDispSet(const CXXRecordDecl *RD) { if (Layout.hasExtendableVFPtr()) HasVtordispSet.insert(BaseDecl); } - return HasVtordispSet; + return; } // If any of our bases need a vtordisp for this type, so do we. Check our @@ -2695,7 +2726,7 @@ MicrosoftRecordLayoutBuilder::computeVtorDispSet(const CXXRecordDecl *RD) { // * #pragma vtordisp(0) or the /vd0 flag are in use. if ((!RD->hasUserDeclaredConstructor() && !RD->hasUserDeclaredDestructor()) || RD->getMSVtorDispMode() == MSVtorDispAttr::Never) - return HasVtordispSet; + return; // /vd1 or #pragma vtordisp(1): Try to guess based on whether we think it's // possible for a partially constructed object with virtual base overrides to // escape a non-trivial constructor. @@ -2706,9 +2737,9 @@ MicrosoftRecordLayoutBuilder::computeVtorDispSet(const CXXRecordDecl *RD) { // vtordisp. llvm::SmallPtrSet<const CXXMethodDecl *, 8> Work; llvm::SmallPtrSet<const CXXRecordDecl *, 2> BasesWithOverriddenMethods; - // Seed the working set with our non-destructor virtual methods. + // Seed the working set with our non-destructor, non-pure virtual methods. for (const CXXMethodDecl *MD : RD->methods()) - if (MD->isVirtual() && !isa<CXXDestructorDecl>(MD)) + if (MD->isVirtual() && !isa<CXXDestructorDecl>(MD) && !MD->isPure()) Work.insert(MD); while (!Work.empty()) { const CXXMethodDecl *MD = *Work.begin(); @@ -2730,7 +2761,6 @@ MicrosoftRecordLayoutBuilder::computeVtorDispSet(const CXXRecordDecl *RD) { RequiresVtordisp(BasesWithOverriddenMethods, BaseDecl)) HasVtordispSet.insert(BaseDecl); } - return HasVtordispSet; } /// \brief Get or compute information about the layout of the specified record |
