| //=== RecordLayoutBuilder.cpp - Helper class for building record layouts ---==// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "clang/AST/RecordLayout.h" |
| #include "clang/AST/ASTContext.h" |
| #include "clang/AST/ASTDiagnostic.h" |
| #include "clang/AST/Attr.h" |
| #include "clang/AST/CXXInheritance.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/ADT/SmallSet.h" |
| #include "llvm/Support/Format.h" |
| #include "llvm/Support/MathExtras.h" |
| |
| using namespace clang; |
| |
| namespace { |
| |
| /// BaseSubobjectInfo - Represents a single base subobject in a complete class. |
| /// For a class hierarchy like |
| /// |
| /// class A { }; |
| /// class B : A { }; |
| /// class C : A, B { }; |
| /// |
| /// The BaseSubobjectInfo graph for C will have three BaseSubobjectInfo |
| /// instances, one for B and two for A. |
| /// |
| /// If a base is virtual, it will only have one BaseSubobjectInfo allocated. |
| struct BaseSubobjectInfo { |
| /// Class - The class for this base info. |
| const CXXRecordDecl *Class; |
| |
| /// IsVirtual - Whether the BaseInfo represents a virtual base or not. |
| bool IsVirtual; |
| |
| /// Bases - Information about the base subobjects. |
| SmallVector<BaseSubobjectInfo*, 4> Bases; |
| |
| /// PrimaryVirtualBaseInfo - Holds the base info for the primary virtual base |
| /// of this base info (if one exists). |
| BaseSubobjectInfo *PrimaryVirtualBaseInfo; |
| |
| // FIXME: Document. |
| const BaseSubobjectInfo *Derived; |
| }; |
| |
| /// Externally provided layout. Typically used when the AST source, such |
| /// as DWARF, lacks all the information that was available at compile time, such |
| /// as alignment attributes on fields and pragmas in effect. |
| struct ExternalLayout { |
| ExternalLayout() : Size(0), Align(0) {} |
| |
| /// Overall record size in bits. |
| uint64_t Size; |
| |
| /// Overall record alignment in bits. |
| uint64_t Align; |
| |
| /// Record field offsets in bits. |
| llvm::DenseMap<const FieldDecl *, uint64_t> FieldOffsets; |
| |
| /// Direct, non-virtual base offsets. |
| llvm::DenseMap<const CXXRecordDecl *, CharUnits> BaseOffsets; |
| |
| /// Virtual base offsets. |
| llvm::DenseMap<const CXXRecordDecl *, CharUnits> VirtualBaseOffsets; |
| |
| /// Get the offset of the given field. The external source must provide |
| /// entries for all fields in the record. |
| uint64_t getExternalFieldOffset(const FieldDecl *FD) { |
| assert(FieldOffsets.count(FD) && |
| "Field does not have an external offset"); |
| return FieldOffsets[FD]; |
| } |
| |
| bool getExternalNVBaseOffset(const CXXRecordDecl *RD, CharUnits &BaseOffset) { |
| auto Known = BaseOffsets.find(RD); |
| if (Known == BaseOffsets.end()) |
| return false; |
| BaseOffset = Known->second; |
| return true; |
| } |
| |
| bool getExternalVBaseOffset(const CXXRecordDecl *RD, CharUnits &BaseOffset) { |
| auto Known = VirtualBaseOffsets.find(RD); |
| if (Known == VirtualBaseOffsets.end()) |
| return false; |
| BaseOffset = Known->second; |
| return true; |
| } |
| }; |
| |
| /// EmptySubobjectMap - Keeps track of which empty subobjects exist at different |
| /// offsets while laying out a C++ class. |
| class EmptySubobjectMap { |
| const ASTContext &Context; |
| uint64_t CharWidth; |
| |
| /// Class - The class whose empty entries we're keeping track of. |
| const CXXRecordDecl *Class; |
| |
| /// EmptyClassOffsets - A map from offsets to empty record decls. |
| typedef llvm::TinyPtrVector<const CXXRecordDecl *> ClassVectorTy; |
| typedef llvm::DenseMap<CharUnits, ClassVectorTy> EmptyClassOffsetsMapTy; |
| EmptyClassOffsetsMapTy EmptyClassOffsets; |
| |
| /// MaxEmptyClassOffset - The highest offset known to contain an empty |
| /// base subobject. |
| CharUnits MaxEmptyClassOffset; |
| |
| /// ComputeEmptySubobjectSizes - Compute the size of the largest base or |
| /// member subobject that is empty. |
| void ComputeEmptySubobjectSizes(); |
| |
| void AddSubobjectAtOffset(const CXXRecordDecl *RD, CharUnits Offset); |
| |
| void UpdateEmptyBaseSubobjects(const BaseSubobjectInfo *Info, |
| CharUnits Offset, bool PlacingEmptyBase); |
| |
| void UpdateEmptyFieldSubobjects(const CXXRecordDecl *RD, |
| const CXXRecordDecl *Class, CharUnits Offset, |
| bool PlacingOverlappingField); |
| void UpdateEmptyFieldSubobjects(const FieldDecl *FD, CharUnits Offset, |
| bool PlacingOverlappingField); |
| |
| /// AnyEmptySubobjectsBeyondOffset - Returns whether there are any empty |
| /// subobjects beyond the given offset. |
| bool AnyEmptySubobjectsBeyondOffset(CharUnits Offset) const { |
| return Offset <= MaxEmptyClassOffset; |
| } |
| |
| CharUnits |
| getFieldOffset(const ASTRecordLayout &Layout, unsigned FieldNo) const { |
| uint64_t FieldOffset = Layout.getFieldOffset(FieldNo); |
| assert(FieldOffset % CharWidth == 0 && |
| "Field offset not at char boundary!"); |
| |
| return Context.toCharUnitsFromBits(FieldOffset); |
| } |
| |
| protected: |
| bool CanPlaceSubobjectAtOffset(const CXXRecordDecl *RD, |
| CharUnits Offset) const; |
| |
| bool CanPlaceBaseSubobjectAtOffset(const BaseSubobjectInfo *Info, |
| CharUnits Offset); |
| |
| bool CanPlaceFieldSubobjectAtOffset(const CXXRecordDecl *RD, |
| const CXXRecordDecl *Class, |
| CharUnits Offset) const; |
| bool CanPlaceFieldSubobjectAtOffset(const FieldDecl *FD, |
| CharUnits Offset) const; |
| |
| public: |
| /// This holds the size of the largest empty subobject (either a base |
| /// or a member). Will be zero if the record being built doesn't contain |
| /// any empty classes. |
| CharUnits SizeOfLargestEmptySubobject; |
| |
| EmptySubobjectMap(const ASTContext &Context, const CXXRecordDecl *Class) |
| : Context(Context), CharWidth(Context.getCharWidth()), Class(Class) { |
| ComputeEmptySubobjectSizes(); |
| } |
| |
| /// CanPlaceBaseAtOffset - Return whether the given base class can be placed |
| /// at the given offset. |
| /// Returns false if placing the record will result in two components |
| /// (direct or indirect) of the same type having the same offset. |
| bool CanPlaceBaseAtOffset(const BaseSubobjectInfo *Info, |
| CharUnits Offset); |
| |
| /// CanPlaceFieldAtOffset - Return whether a field can be placed at the given |
| /// offset. |
| bool CanPlaceFieldAtOffset(const FieldDecl *FD, CharUnits Offset); |
| }; |
| |
| void EmptySubobjectMap::ComputeEmptySubobjectSizes() { |
| // Check the bases. |
| for (const CXXBaseSpecifier &Base : Class->bases()) { |
| const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl(); |
| |
| CharUnits EmptySize; |
| 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(); |
| } |
| |
| if (EmptySize > SizeOfLargestEmptySubobject) |
| SizeOfLargestEmptySubobject = EmptySize; |
| } |
| |
| // Check the fields. |
| for (const FieldDecl *FD : Class->fields()) { |
| const RecordType *RT = |
| Context.getBaseElementType(FD->getType())->getAs<RecordType>(); |
| |
| // We only care about record types. |
| if (!RT) |
| continue; |
| |
| CharUnits EmptySize; |
| const CXXRecordDecl *MemberDecl = RT->getAsCXXRecordDecl(); |
| 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(); |
| } |
| |
| if (EmptySize > SizeOfLargestEmptySubobject) |
| SizeOfLargestEmptySubobject = EmptySize; |
| } |
| } |
| |
| bool |
| EmptySubobjectMap::CanPlaceSubobjectAtOffset(const CXXRecordDecl *RD, |
| CharUnits Offset) const { |
| // We only need to check empty bases. |
| if (!RD->isEmpty()) |
| return true; |
| |
| EmptyClassOffsetsMapTy::const_iterator I = EmptyClassOffsets.find(Offset); |
| if (I == EmptyClassOffsets.end()) |
| return true; |
| |
| const ClassVectorTy &Classes = I->second; |
| if (llvm::find(Classes, RD) == Classes.end()) |
| return true; |
| |
| // There is already an empty class of the same type at this offset. |
| return false; |
| } |
| |
| void EmptySubobjectMap::AddSubobjectAtOffset(const CXXRecordDecl *RD, |
| CharUnits Offset) { |
| // We only care about empty bases. |
| if (!RD->isEmpty()) |
| return; |
| |
| // If we have empty structures inside a union, we can assign both |
| // the same offset. Just avoid pushing them twice in the list. |
| ClassVectorTy &Classes = EmptyClassOffsets[Offset]; |
| if (llvm::is_contained(Classes, RD)) |
| return; |
| |
| Classes.push_back(RD); |
| |
| // Update the empty class offset. |
| if (Offset > MaxEmptyClassOffset) |
| MaxEmptyClassOffset = Offset; |
| } |
| |
| bool |
| EmptySubobjectMap::CanPlaceBaseSubobjectAtOffset(const BaseSubobjectInfo *Info, |
| CharUnits Offset) { |
| // We don't have to keep looking past the maximum offset that's known to |
| // contain an empty class. |
| if (!AnyEmptySubobjectsBeyondOffset(Offset)) |
| return true; |
| |
| if (!CanPlaceSubobjectAtOffset(Info->Class, Offset)) |
| return false; |
| |
| // Traverse all non-virtual bases. |
| const ASTRecordLayout &Layout = Context.getASTRecordLayout(Info->Class); |
| for (const BaseSubobjectInfo *Base : Info->Bases) { |
| if (Base->IsVirtual) |
| continue; |
| |
| CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base->Class); |
| |
| if (!CanPlaceBaseSubobjectAtOffset(Base, BaseOffset)) |
| return false; |
| } |
| |
| if (Info->PrimaryVirtualBaseInfo) { |
| BaseSubobjectInfo *PrimaryVirtualBaseInfo = Info->PrimaryVirtualBaseInfo; |
| |
| if (Info == PrimaryVirtualBaseInfo->Derived) { |
| if (!CanPlaceBaseSubobjectAtOffset(PrimaryVirtualBaseInfo, Offset)) |
| return false; |
| } |
| } |
| |
| // Traverse all member variables. |
| unsigned FieldNo = 0; |
| for (CXXRecordDecl::field_iterator I = Info->Class->field_begin(), |
| E = Info->Class->field_end(); I != E; ++I, ++FieldNo) { |
| if (I->isBitField()) |
| continue; |
| |
| CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo); |
| if (!CanPlaceFieldSubobjectAtOffset(*I, FieldOffset)) |
| return false; |
| } |
| |
| return true; |
| } |
| |
| void EmptySubobjectMap::UpdateEmptyBaseSubobjects(const BaseSubobjectInfo *Info, |
| CharUnits Offset, |
| bool PlacingEmptyBase) { |
| if (!PlacingEmptyBase && Offset >= SizeOfLargestEmptySubobject) { |
| // We know that the only empty subobjects that can conflict with empty |
| // subobject of non-empty bases, are empty bases that can be placed at |
| // offset zero. Because of this, we only need to keep track of empty base |
| // subobjects with offsets less than the size of the largest empty |
| // subobject for our class. |
| return; |
| } |
| |
| AddSubobjectAtOffset(Info->Class, Offset); |
| |
| // Traverse all non-virtual bases. |
| const ASTRecordLayout &Layout = Context.getASTRecordLayout(Info->Class); |
| for (const BaseSubobjectInfo *Base : Info->Bases) { |
| if (Base->IsVirtual) |
| continue; |
| |
| CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base->Class); |
| UpdateEmptyBaseSubobjects(Base, BaseOffset, PlacingEmptyBase); |
| } |
| |
| if (Info->PrimaryVirtualBaseInfo) { |
| BaseSubobjectInfo *PrimaryVirtualBaseInfo = Info->PrimaryVirtualBaseInfo; |
| |
| if (Info == PrimaryVirtualBaseInfo->Derived) |
| UpdateEmptyBaseSubobjects(PrimaryVirtualBaseInfo, Offset, |
| PlacingEmptyBase); |
| } |
| |
| // Traverse all member variables. |
| unsigned FieldNo = 0; |
| for (CXXRecordDecl::field_iterator I = Info->Class->field_begin(), |
| E = Info->Class->field_end(); I != E; ++I, ++FieldNo) { |
| if (I->isBitField()) |
| continue; |
| |
| CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo); |
| UpdateEmptyFieldSubobjects(*I, FieldOffset, PlacingEmptyBase); |
| } |
| } |
| |
| bool EmptySubobjectMap::CanPlaceBaseAtOffset(const BaseSubobjectInfo *Info, |
| CharUnits Offset) { |
| // If we know this class doesn't have any empty subobjects we don't need to |
| // bother checking. |
| if (SizeOfLargestEmptySubobject.isZero()) |
| return true; |
| |
| if (!CanPlaceBaseSubobjectAtOffset(Info, Offset)) |
| return false; |
| |
| // We are able to place the base at this offset. Make sure to update the |
| // empty base subobject map. |
| UpdateEmptyBaseSubobjects(Info, Offset, Info->Class->isEmpty()); |
| return true; |
| } |
| |
| bool |
| EmptySubobjectMap::CanPlaceFieldSubobjectAtOffset(const CXXRecordDecl *RD, |
| const CXXRecordDecl *Class, |
| CharUnits Offset) const { |
| // We don't have to keep looking past the maximum offset that's known to |
| // contain an empty class. |
| if (!AnyEmptySubobjectsBeyondOffset(Offset)) |
| return true; |
| |
| if (!CanPlaceSubobjectAtOffset(RD, Offset)) |
| return false; |
| |
| const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD); |
| |
| // Traverse all non-virtual bases. |
| for (const CXXBaseSpecifier &Base : RD->bases()) { |
| if (Base.isVirtual()) |
| continue; |
| |
| const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl(); |
| |
| CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(BaseDecl); |
| if (!CanPlaceFieldSubobjectAtOffset(BaseDecl, Class, BaseOffset)) |
| return false; |
| } |
| |
| if (RD == Class) { |
| // This is the most derived class, traverse virtual bases as well. |
| for (const CXXBaseSpecifier &Base : RD->vbases()) { |
| const CXXRecordDecl *VBaseDecl = Base.getType()->getAsCXXRecordDecl(); |
| |
| CharUnits VBaseOffset = Offset + Layout.getVBaseClassOffset(VBaseDecl); |
| if (!CanPlaceFieldSubobjectAtOffset(VBaseDecl, Class, VBaseOffset)) |
| return false; |
| } |
| } |
| |
| // Traverse all member variables. |
| unsigned FieldNo = 0; |
| for (CXXRecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end(); |
| I != E; ++I, ++FieldNo) { |
| if (I->isBitField()) |
| continue; |
| |
| CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo); |
| |
| if (!CanPlaceFieldSubobjectAtOffset(*I, FieldOffset)) |
| return false; |
| } |
| |
| return true; |
| } |
| |
| bool |
| EmptySubobjectMap::CanPlaceFieldSubobjectAtOffset(const FieldDecl *FD, |
| CharUnits Offset) const { |
| // We don't have to keep looking past the maximum offset that's known to |
| // contain an empty class. |
| if (!AnyEmptySubobjectsBeyondOffset(Offset)) |
| return true; |
| |
| QualType T = FD->getType(); |
| if (const CXXRecordDecl *RD = T->getAsCXXRecordDecl()) |
| return CanPlaceFieldSubobjectAtOffset(RD, RD, Offset); |
| |
| // If we have an array type we need to look at every element. |
| if (const ConstantArrayType *AT = Context.getAsConstantArrayType(T)) { |
| QualType ElemTy = Context.getBaseElementType(AT); |
| const RecordType *RT = ElemTy->getAs<RecordType>(); |
| if (!RT) |
| return true; |
| |
| const CXXRecordDecl *RD = RT->getAsCXXRecordDecl(); |
| const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD); |
| |
| uint64_t NumElements = Context.getConstantArrayElementCount(AT); |
| CharUnits ElementOffset = Offset; |
| for (uint64_t I = 0; I != NumElements; ++I) { |
| // We don't have to keep looking past the maximum offset that's known to |
| // contain an empty class. |
| if (!AnyEmptySubobjectsBeyondOffset(ElementOffset)) |
| return true; |
| |
| if (!CanPlaceFieldSubobjectAtOffset(RD, RD, ElementOffset)) |
| return false; |
| |
| ElementOffset += Layout.getSize(); |
| } |
| } |
| |
| return true; |
| } |
| |
| bool |
| EmptySubobjectMap::CanPlaceFieldAtOffset(const FieldDecl *FD, |
| CharUnits Offset) { |
| if (!CanPlaceFieldSubobjectAtOffset(FD, Offset)) |
| return false; |
| |
| // We are able to place the member variable at this offset. |
| // Make sure to update the empty field subobject map. |
| UpdateEmptyFieldSubobjects(FD, Offset, FD->hasAttr<NoUniqueAddressAttr>()); |
| return true; |
| } |
| |
| void EmptySubobjectMap::UpdateEmptyFieldSubobjects( |
| const CXXRecordDecl *RD, const CXXRecordDecl *Class, CharUnits Offset, |
| bool PlacingOverlappingField) { |
| // We know that the only empty subobjects that can conflict with empty |
| // field subobjects are subobjects of empty bases and potentially-overlapping |
| // fields that can be placed at offset zero. Because of this, we only need to |
| // keep track of empty field subobjects with offsets less than the size of |
| // the largest empty subobject for our class. |
| // |
| // (Proof: we will only consider placing a subobject at offset zero or at |
| // >= the current dsize. The only cases where the earlier subobject can be |
| // placed beyond the end of dsize is if it's an empty base or a |
| // potentially-overlapping field.) |
| if (!PlacingOverlappingField && Offset >= SizeOfLargestEmptySubobject) |
| return; |
| |
| AddSubobjectAtOffset(RD, Offset); |
| |
| const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD); |
| |
| // Traverse all non-virtual bases. |
| for (const CXXBaseSpecifier &Base : RD->bases()) { |
| if (Base.isVirtual()) |
| continue; |
| |
| const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl(); |
| |
| CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(BaseDecl); |
| UpdateEmptyFieldSubobjects(BaseDecl, Class, BaseOffset, |
| PlacingOverlappingField); |
| } |
| |
| if (RD == Class) { |
| // This is the most derived class, traverse virtual bases as well. |
| for (const CXXBaseSpecifier &Base : RD->vbases()) { |
| const CXXRecordDecl *VBaseDecl = Base.getType()->getAsCXXRecordDecl(); |
| |
| CharUnits VBaseOffset = Offset + Layout.getVBaseClassOffset(VBaseDecl); |
| UpdateEmptyFieldSubobjects(VBaseDecl, Class, VBaseOffset, |
| PlacingOverlappingField); |
| } |
| } |
| |
| // Traverse all member variables. |
| unsigned FieldNo = 0; |
| for (CXXRecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end(); |
| I != E; ++I, ++FieldNo) { |
| if (I->isBitField()) |
| continue; |
| |
| CharUnits FieldOffset = Offset + getFieldOffset(Layout, FieldNo); |
| |
| UpdateEmptyFieldSubobjects(*I, FieldOffset, PlacingOverlappingField); |
| } |
| } |
| |
| void EmptySubobjectMap::UpdateEmptyFieldSubobjects( |
| const FieldDecl *FD, CharUnits Offset, bool PlacingOverlappingField) { |
| QualType T = FD->getType(); |
| if (const CXXRecordDecl *RD = T->getAsCXXRecordDecl()) { |
| UpdateEmptyFieldSubobjects(RD, RD, Offset, PlacingOverlappingField); |
| return; |
| } |
| |
| // If we have an array type we need to update every element. |
| if (const ConstantArrayType *AT = Context.getAsConstantArrayType(T)) { |
| QualType ElemTy = Context.getBaseElementType(AT); |
| const RecordType *RT = ElemTy->getAs<RecordType>(); |
| if (!RT) |
| return; |
| |
| const CXXRecordDecl *RD = RT->getAsCXXRecordDecl(); |
| const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD); |
| |
| uint64_t NumElements = Context.getConstantArrayElementCount(AT); |
| CharUnits ElementOffset = Offset; |
| |
| for (uint64_t I = 0; I != NumElements; ++I) { |
| // We know that the only empty subobjects that can conflict with empty |
| // field subobjects are subobjects of empty bases that can be placed at |
| // offset zero. Because of this, we only need to keep track of empty field |
| // subobjects with offsets less than the size of the largest empty |
| // subobject for our class. |
| if (!PlacingOverlappingField && |
| ElementOffset >= SizeOfLargestEmptySubobject) |
| return; |
| |
| UpdateEmptyFieldSubobjects(RD, RD, ElementOffset, |
| PlacingOverlappingField); |
| ElementOffset += Layout.getSize(); |
| } |
| } |
| } |
| |
| typedef llvm::SmallPtrSet<const CXXRecordDecl*, 4> ClassSetTy; |
| |
| class ItaniumRecordLayoutBuilder { |
| protected: |
| // FIXME: Remove this and make the appropriate fields public. |
| friend class clang::ASTContext; |
| |
| const ASTContext &Context; |
| |
| EmptySubobjectMap *EmptySubobjects; |
| |
| /// Size - The current size of the record layout. |
| uint64_t Size; |
| |
| /// Alignment - The current alignment of the record layout. |
| CharUnits Alignment; |
| |
| /// The alignment if attribute packed is not used. |
| CharUnits UnpackedAlignment; |
| |
| /// \brief The maximum of the alignments of top-level members. |
| CharUnits UnadjustedAlignment; |
| |
| SmallVector<uint64_t, 16> FieldOffsets; |
| |
| /// Whether the external AST source has provided a layout for this |
| /// record. |
| unsigned UseExternalLayout : 1; |
| |
| /// Whether we need to infer alignment, even when we have an |
| /// externally-provided layout. |
| unsigned InferAlignment : 1; |
| |
| /// Packed - Whether the record is packed or not. |
| unsigned Packed : 1; |
| |
| unsigned IsUnion : 1; |
| |
| unsigned IsMac68kAlign : 1; |
| |
| unsigned IsMsStruct : 1; |
| |
| /// UnfilledBitsInLastUnit - If the last field laid out was a bitfield, |
| /// this contains the number of bits in the last unit that can be used for |
| /// an adjacent bitfield if necessary. The unit in question is usually |
| /// a byte, but larger units are used if IsMsStruct. |
| unsigned char UnfilledBitsInLastUnit; |
| /// LastBitfieldTypeSize - If IsMsStruct, represents the size of the type |
| /// of the previous field if it was a bitfield. |
| unsigned char LastBitfieldTypeSize; |
| |
| /// MaxFieldAlignment - The maximum allowed field alignment. This is set by |
| /// #pragma pack. |
| CharUnits MaxFieldAlignment; |
| |
| /// DataSize - The data size of the record being laid out. |
| uint64_t DataSize; |
| |
| CharUnits NonVirtualSize; |
| CharUnits NonVirtualAlignment; |
| |
| /// If we've laid out a field but not included its tail padding in Size yet, |
| /// this is the size up to the end of that field. |
| CharUnits PaddedFieldSize; |
| |
| /// PrimaryBase - the primary base class (if one exists) of the class |
| /// we're laying out. |
| const CXXRecordDecl *PrimaryBase; |
| |
| /// PrimaryBaseIsVirtual - Whether the primary base of the class we're laying |
| /// out is virtual. |
| bool PrimaryBaseIsVirtual; |
| |
| /// HasOwnVFPtr - Whether the class provides its own vtable/vftbl |
| /// pointer, as opposed to inheriting one from a primary base class. |
| bool HasOwnVFPtr; |
| |
| /// the flag of field offset changing due to packed attribute. |
| bool HasPackedField; |
| |
| typedef llvm::DenseMap<const CXXRecordDecl *, CharUnits> BaseOffsetsMapTy; |
| |
| /// Bases - base classes and their offsets in the record. |
| BaseOffsetsMapTy Bases; |
| |
| // VBases - virtual base classes and their offsets in the record. |
| ASTRecordLayout::VBaseOffsetsMapTy VBases; |
| |
| /// IndirectPrimaryBases - Virtual base classes, direct or indirect, that are |
| /// primary base classes for some other direct or indirect base class. |
| CXXIndirectPrimaryBaseSet IndirectPrimaryBases; |
| |
| /// FirstNearlyEmptyVBase - The first nearly empty virtual base class in |
| /// inheritance graph order. Used for determining the primary base class. |
| const CXXRecordDecl *FirstNearlyEmptyVBase; |
| |
| /// VisitedVirtualBases - A set of all the visited virtual bases, used to |
| /// avoid visiting virtual bases more than once. |
| llvm::SmallPtrSet<const CXXRecordDecl *, 4> VisitedVirtualBases; |
| |
| /// Valid if UseExternalLayout is true. |
| ExternalLayout External; |
| |
| ItaniumRecordLayoutBuilder(const ASTContext &Context, |
| EmptySubobjectMap *EmptySubobjects) |
| : Context(Context), EmptySubobjects(EmptySubobjects), Size(0), |
| Alignment(CharUnits::One()), UnpackedAlignment(CharUnits::One()), |
| UnadjustedAlignment(CharUnits::One()), |
| UseExternalLayout(false), InferAlignment(false), Packed(false), |
| IsUnion(false), IsMac68kAlign(false), IsMsStruct(false), |
| UnfilledBitsInLastUnit(0), LastBitfieldTypeSize(0), |
| MaxFieldAlignment(CharUnits::Zero()), DataSize(0), |
| NonVirtualSize(CharUnits::Zero()), |
| NonVirtualAlignment(CharUnits::One()), |
| PaddedFieldSize(CharUnits::Zero()), PrimaryBase(nullptr), |
| PrimaryBaseIsVirtual(false), HasOwnVFPtr(false), |
| HasPackedField(false), FirstNearlyEmptyVBase(nullptr) {} |
| |
| 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, bool InsertExtraPadding); |
| void LayoutWideBitField(uint64_t FieldSize, uint64_t TypeSize, |
| bool FieldPacked, const FieldDecl *D); |
| void LayoutBitField(const FieldDecl *D); |
| |
| TargetCXXABI getCXXABI() const { |
| return Context.getTargetInfo().getCXXABI(); |
| } |
| |
| /// BaseSubobjectInfoAllocator - Allocator for BaseSubobjectInfo objects. |
| llvm::SpecificBumpPtrAllocator<BaseSubobjectInfo> BaseSubobjectInfoAllocator; |
| |
| typedef llvm::DenseMap<const CXXRecordDecl *, BaseSubobjectInfo *> |
| BaseSubobjectInfoMapTy; |
| |
| /// VirtualBaseInfo - Map from all the (direct or indirect) virtual bases |
| /// of the class we're laying out to their base subobject info. |
| BaseSubobjectInfoMapTy VirtualBaseInfo; |
| |
| /// NonVirtualBaseInfo - Map from all the direct non-virtual bases of the |
| /// class we're laying out to their base subobject info. |
| BaseSubobjectInfoMapTy NonVirtualBaseInfo; |
| |
| /// ComputeBaseSubobjectInfo - Compute the base subobject information for the |
| /// bases of the given class. |
| void ComputeBaseSubobjectInfo(const CXXRecordDecl *RD); |
| |
| /// ComputeBaseSubobjectInfo - Compute the base subobject information for a |
| /// single class and all of its base classes. |
| BaseSubobjectInfo *ComputeBaseSubobjectInfo(const CXXRecordDecl *RD, |
| bool IsVirtual, |
| BaseSubobjectInfo *Derived); |
| |
| /// DeterminePrimaryBase - Determine the primary base of the given class. |
| void DeterminePrimaryBase(const CXXRecordDecl *RD); |
| |
| void SelectPrimaryVBase(const CXXRecordDecl *RD); |
| |
| void EnsureVTablePointerAlignment(CharUnits UnpackedBaseAlign); |
| |
| /// LayoutNonVirtualBases - Determines the primary base class (if any) and |
| /// lays it out. Will then proceed to lay out all non-virtual base clasess. |
| void LayoutNonVirtualBases(const CXXRecordDecl *RD); |
| |
| /// LayoutNonVirtualBase - Lays out a single non-virtual base. |
| void LayoutNonVirtualBase(const BaseSubobjectInfo *Base); |
| |
| void AddPrimaryVirtualBaseOffsets(const BaseSubobjectInfo *Info, |
| CharUnits Offset); |
| |
| /// LayoutVirtualBases - Lays out all the virtual bases. |
| void LayoutVirtualBases(const CXXRecordDecl *RD, |
| const CXXRecordDecl *MostDerivedClass); |
| |
| /// LayoutVirtualBase - Lays out a single virtual base. |
| void LayoutVirtualBase(const BaseSubobjectInfo *Base); |
| |
| /// LayoutBase - Will lay out a base and return the offset where it was |
| /// placed, in chars. |
| CharUnits LayoutBase(const BaseSubobjectInfo *Base); |
| |
| /// InitializeLayout - Initialize record layout for the given record decl. |
| void InitializeLayout(const Decl *D); |
| |
| /// FinishLayout - Finalize record layout. Adjust record size based on the |
| /// alignment. |
| void FinishLayout(const NamedDecl *D); |
| |
| void UpdateAlignment(CharUnits NewAlignment, CharUnits UnpackedNewAlignment); |
| void UpdateAlignment(CharUnits NewAlignment) { |
| UpdateAlignment(NewAlignment, NewAlignment); |
| } |
| |
| /// Retrieve the externally-supplied field offset for the given |
| /// field. |
| /// |
| /// \param Field The field whose offset is being queried. |
| /// \param ComputedOffset The offset that we've computed for this field. |
| uint64_t updateExternalFieldOffset(const FieldDecl *Field, |
| uint64_t ComputedOffset); |
| |
| void CheckFieldPadding(uint64_t Offset, uint64_t UnpaddedOffset, |
| uint64_t UnpackedOffset, unsigned UnpackedAlign, |
| bool isPacked, const FieldDecl *D); |
| |
| DiagnosticBuilder Diag(SourceLocation Loc, unsigned DiagID); |
| |
| CharUnits getSize() const { |
| assert(Size % Context.getCharWidth() == 0); |
| return Context.toCharUnitsFromBits(Size); |
| } |
| uint64_t getSizeInBits() const { return Size; } |
| |
| void setSize(CharUnits NewSize) { Size = Context.toBits(NewSize); } |
| void setSize(uint64_t NewSize) { Size = NewSize; } |
| |
| CharUnits getAligment() const { return Alignment; } |
| |
| CharUnits getDataSize() const { |
| assert(DataSize % Context.getCharWidth() == 0); |
| return Context.toCharUnitsFromBits(DataSize); |
| } |
| uint64_t getDataSizeInBits() const { return DataSize; } |
| |
| void setDataSize(CharUnits NewSize) { DataSize = Context.toBits(NewSize); } |
| void setDataSize(uint64_t NewSize) { DataSize = NewSize; } |
| |
| ItaniumRecordLayoutBuilder(const ItaniumRecordLayoutBuilder &) = delete; |
| void operator=(const ItaniumRecordLayoutBuilder &) = delete; |
| }; |
| } // end anonymous namespace |
| |
| void ItaniumRecordLayoutBuilder::SelectPrimaryVBase(const CXXRecordDecl *RD) { |
| for (const auto &I : RD->bases()) { |
| assert(!I.getType()->isDependentType() && |
| "Cannot layout class with dependent bases."); |
| |
| const CXXRecordDecl *Base = I.getType()->getAsCXXRecordDecl(); |
| |
| // Check if this is a nearly empty virtual base. |
| if (I.isVirtual() && Context.isNearlyEmpty(Base)) { |
| // If it's not an indirect primary base, then we've found our primary |
| // base. |
| if (!IndirectPrimaryBases.count(Base)) { |
| PrimaryBase = Base; |
| PrimaryBaseIsVirtual = true; |
| return; |
| } |
| |
| // Is this the first nearly empty virtual base? |
| if (!FirstNearlyEmptyVBase) |
| FirstNearlyEmptyVBase = Base; |
| } |
| |
| SelectPrimaryVBase(Base); |
| if (PrimaryBase) |
| return; |
| } |
| } |
| |
| /// DeterminePrimaryBase - Determine the primary base of the given class. |
| void ItaniumRecordLayoutBuilder::DeterminePrimaryBase(const CXXRecordDecl *RD) { |
| // If the class isn't dynamic, it won't have a primary base. |
| if (!RD->isDynamicClass()) |
| return; |
| |
| // Compute all the primary virtual bases for all of our direct and |
| // indirect bases, and record all their primary virtual base classes. |
| RD->getIndirectPrimaryBases(IndirectPrimaryBases); |
| |
| // If the record has a dynamic base class, attempt to choose a primary base |
| // class. It is the first (in direct base class order) non-virtual dynamic |
| // base class, if one exists. |
| for (const auto &I : RD->bases()) { |
| // Ignore virtual bases. |
| if (I.isVirtual()) |
| continue; |
| |
| const CXXRecordDecl *Base = I.getType()->getAsCXXRecordDecl(); |
| |
| if (Base->isDynamicClass()) { |
| // We found it. |
| PrimaryBase = Base; |
| PrimaryBaseIsVirtual = false; |
| return; |
| } |
| } |
| |
| // Under the Itanium ABI, if there is no non-virtual primary base class, |
| // try to compute the primary virtual base. The primary virtual base is |
| // the first nearly empty virtual base that is not an indirect primary |
| // virtual base class, if one exists. |
| if (RD->getNumVBases() != 0) { |
| SelectPrimaryVBase(RD); |
| if (PrimaryBase) |
| return; |
| } |
| |
| // Otherwise, it is the first indirect primary base class, if one exists. |
| if (FirstNearlyEmptyVBase) { |
| PrimaryBase = FirstNearlyEmptyVBase; |
| PrimaryBaseIsVirtual = true; |
| return; |
| } |
| |
| assert(!PrimaryBase && "Should not get here with a primary base!"); |
| } |
| |
| BaseSubobjectInfo *ItaniumRecordLayoutBuilder::ComputeBaseSubobjectInfo( |
| const CXXRecordDecl *RD, bool IsVirtual, BaseSubobjectInfo *Derived) { |
| BaseSubobjectInfo *Info; |
| |
| if (IsVirtual) { |
| // Check if we already have info about this virtual base. |
| BaseSubobjectInfo *&InfoSlot = VirtualBaseInfo[RD]; |
| if (InfoSlot) { |
| assert(InfoSlot->Class == RD && "Wrong class for virtual base info!"); |
| return InfoSlot; |
| } |
| |
| // We don't, create it. |
| InfoSlot = new (BaseSubobjectInfoAllocator.Allocate()) BaseSubobjectInfo; |
| Info = InfoSlot; |
| } else { |
| Info = new (BaseSubobjectInfoAllocator.Allocate()) BaseSubobjectInfo; |
| } |
| |
| Info->Class = RD; |
| Info->IsVirtual = IsVirtual; |
| Info->Derived = nullptr; |
| Info->PrimaryVirtualBaseInfo = nullptr; |
| |
| const CXXRecordDecl *PrimaryVirtualBase = nullptr; |
| BaseSubobjectInfo *PrimaryVirtualBaseInfo = nullptr; |
| |
| // Check if this base has a primary virtual base. |
| if (RD->getNumVBases()) { |
| const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD); |
| if (Layout.isPrimaryBaseVirtual()) { |
| // This base does have a primary virtual base. |
| PrimaryVirtualBase = Layout.getPrimaryBase(); |
| assert(PrimaryVirtualBase && "Didn't have a primary virtual base!"); |
| |
| // Now check if we have base subobject info about this primary base. |
| PrimaryVirtualBaseInfo = VirtualBaseInfo.lookup(PrimaryVirtualBase); |
| |
| if (PrimaryVirtualBaseInfo) { |
| if (PrimaryVirtualBaseInfo->Derived) { |
| // We did have info about this primary base, and it turns out that it |
| // has already been claimed as a primary virtual base for another |
| // base. |
| PrimaryVirtualBase = nullptr; |
| } else { |
| // We can claim this base as our primary base. |
| Info->PrimaryVirtualBaseInfo = PrimaryVirtualBaseInfo; |
| PrimaryVirtualBaseInfo->Derived = Info; |
| } |
| } |
| } |
| } |
| |
| // Now go through all direct bases. |
| for (const auto &I : RD->bases()) { |
| bool IsVirtual = I.isVirtual(); |
| |
| const CXXRecordDecl *BaseDecl = I.getType()->getAsCXXRecordDecl(); |
| |
| Info->Bases.push_back(ComputeBaseSubobjectInfo(BaseDecl, IsVirtual, Info)); |
| } |
| |
| if (PrimaryVirtualBase && !PrimaryVirtualBaseInfo) { |
| // Traversing the bases must have created the base info for our primary |
| // virtual base. |
| PrimaryVirtualBaseInfo = VirtualBaseInfo.lookup(PrimaryVirtualBase); |
| assert(PrimaryVirtualBaseInfo && |
| "Did not create a primary virtual base!"); |
| |
| // Claim the primary virtual base as our primary virtual base. |
| Info->PrimaryVirtualBaseInfo = PrimaryVirtualBaseInfo; |
| PrimaryVirtualBaseInfo->Derived = Info; |
| } |
| |
| return Info; |
| } |
| |
| void ItaniumRecordLayoutBuilder::ComputeBaseSubobjectInfo( |
| const CXXRecordDecl *RD) { |
| for (const auto &I : RD->bases()) { |
| bool IsVirtual = I.isVirtual(); |
| |
| const CXXRecordDecl *BaseDecl = I.getType()->getAsCXXRecordDecl(); |
| |
| // Compute the base subobject info for this base. |
| BaseSubobjectInfo *Info = ComputeBaseSubobjectInfo(BaseDecl, IsVirtual, |
| nullptr); |
| |
| if (IsVirtual) { |
| // ComputeBaseInfo has already added this base for us. |
| assert(VirtualBaseInfo.count(BaseDecl) && |
| "Did not add virtual base!"); |
| } else { |
| // Add the base info to the map of non-virtual bases. |
| assert(!NonVirtualBaseInfo.count(BaseDecl) && |
| "Non-virtual base already exists!"); |
| NonVirtualBaseInfo.insert(std::make_pair(BaseDecl, Info)); |
| } |
| } |
| } |
| |
| void ItaniumRecordLayoutBuilder::EnsureVTablePointerAlignment( |
| CharUnits UnpackedBaseAlign) { |
| CharUnits BaseAlign = Packed ? CharUnits::One() : UnpackedBaseAlign; |
| |
| // The maximum field alignment overrides base align. |
| if (!MaxFieldAlignment.isZero()) { |
| BaseAlign = std::min(BaseAlign, MaxFieldAlignment); |
| UnpackedBaseAlign = std::min(UnpackedBaseAlign, MaxFieldAlignment); |
| } |
| |
| // Round up the current record size to pointer alignment. |
| setSize(getSize().alignTo(BaseAlign)); |
| |
| // Update the alignment. |
| UpdateAlignment(BaseAlign, UnpackedBaseAlign); |
| } |
| |
| void ItaniumRecordLayoutBuilder::LayoutNonVirtualBases( |
| const CXXRecordDecl *RD) { |
| // Then, determine the primary base class. |
| DeterminePrimaryBase(RD); |
| |
| // Compute base subobject info. |
| ComputeBaseSubobjectInfo(RD); |
| |
| // If we have a primary base class, lay it out. |
| if (PrimaryBase) { |
| if (PrimaryBaseIsVirtual) { |
| // If the primary virtual base was a primary virtual base of some other |
| // base class we'll have to steal it. |
| BaseSubobjectInfo *PrimaryBaseInfo = VirtualBaseInfo.lookup(PrimaryBase); |
| PrimaryBaseInfo->Derived = nullptr; |
| |
| // We have a virtual primary base, insert it as an indirect primary base. |
| IndirectPrimaryBases.insert(PrimaryBase); |
| |
| assert(!VisitedVirtualBases.count(PrimaryBase) && |
| "vbase already visited!"); |
| VisitedVirtualBases.insert(PrimaryBase); |
| |
| LayoutVirtualBase(PrimaryBaseInfo); |
| } else { |
| BaseSubobjectInfo *PrimaryBaseInfo = |
| NonVirtualBaseInfo.lookup(PrimaryBase); |
| assert(PrimaryBaseInfo && |
| "Did not find base info for non-virtual primary base!"); |
| |
| LayoutNonVirtualBase(PrimaryBaseInfo); |
| } |
| |
| // If this class needs a vtable/vf-table and didn't get one from a |
| // primary base, add it in now. |
| } else if (RD->isDynamicClass()) { |
| assert(DataSize == 0 && "Vtable pointer must be at offset zero!"); |
| CharUnits PtrWidth = |
| Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0)); |
| CharUnits PtrAlign = |
| Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerAlign(0)); |
| EnsureVTablePointerAlignment(PtrAlign); |
| HasOwnVFPtr = true; |
| setSize(getSize() + PtrWidth); |
| setDataSize(getSize()); |
| } |
| |
| // Now lay out the non-virtual bases. |
| for (const auto &I : RD->bases()) { |
| |
| // Ignore virtual bases. |
| if (I.isVirtual()) |
| continue; |
| |
| const CXXRecordDecl *BaseDecl = I.getType()->getAsCXXRecordDecl(); |
| |
| // Skip the primary base, because we've already laid it out. The |
| // !PrimaryBaseIsVirtual check is required because we might have a |
| // non-virtual base of the same type as a primary virtual base. |
| if (BaseDecl == PrimaryBase && !PrimaryBaseIsVirtual) |
| continue; |
| |
| // Lay out the base. |
| BaseSubobjectInfo *BaseInfo = NonVirtualBaseInfo.lookup(BaseDecl); |
| assert(BaseInfo && "Did not find base info for non-virtual base!"); |
| |
| LayoutNonVirtualBase(BaseInfo); |
| } |
| } |
| |
| void ItaniumRecordLayoutBuilder::LayoutNonVirtualBase( |
| const BaseSubobjectInfo *Base) { |
| // Layout the base. |
| CharUnits Offset = LayoutBase(Base); |
| |
| // Add its base class offset. |
| assert(!Bases.count(Base->Class) && "base offset already exists!"); |
| Bases.insert(std::make_pair(Base->Class, Offset)); |
| |
| AddPrimaryVirtualBaseOffsets(Base, Offset); |
| } |
| |
| void ItaniumRecordLayoutBuilder::AddPrimaryVirtualBaseOffsets( |
| const BaseSubobjectInfo *Info, CharUnits Offset) { |
| // This base isn't interesting, it has no virtual bases. |
| if (!Info->Class->getNumVBases()) |
| return; |
| |
| // First, check if we have a virtual primary base to add offsets for. |
| if (Info->PrimaryVirtualBaseInfo) { |
| assert(Info->PrimaryVirtualBaseInfo->IsVirtual && |
| "Primary virtual base is not virtual!"); |
| if (Info->PrimaryVirtualBaseInfo->Derived == Info) { |
| // Add the offset. |
| assert(!VBases.count(Info->PrimaryVirtualBaseInfo->Class) && |
| "primary vbase offset already exists!"); |
| VBases.insert(std::make_pair(Info->PrimaryVirtualBaseInfo->Class, |
| ASTRecordLayout::VBaseInfo(Offset, false))); |
| |
| // Traverse the primary virtual base. |
| AddPrimaryVirtualBaseOffsets(Info->PrimaryVirtualBaseInfo, Offset); |
| } |
| } |
| |
| // Now go through all direct non-virtual bases. |
| const ASTRecordLayout &Layout = Context.getASTRecordLayout(Info->Class); |
| for (const BaseSubobjectInfo *Base : Info->Bases) { |
| if (Base->IsVirtual) |
| continue; |
| |
| CharUnits BaseOffset = Offset + Layout.getBaseClassOffset(Base->Class); |
| AddPrimaryVirtualBaseOffsets(Base, BaseOffset); |
| } |
| } |
| |
| void ItaniumRecordLayoutBuilder::LayoutVirtualBases( |
| const CXXRecordDecl *RD, const CXXRecordDecl *MostDerivedClass) { |
| const CXXRecordDecl *PrimaryBase; |
| bool PrimaryBaseIsVirtual; |
| |
| if (MostDerivedClass == RD) { |
| PrimaryBase = this->PrimaryBase; |
| PrimaryBaseIsVirtual = this->PrimaryBaseIsVirtual; |
| } else { |
| const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD); |
| PrimaryBase = Layout.getPrimaryBase(); |
| PrimaryBaseIsVirtual = Layout.isPrimaryBaseVirtual(); |
| } |
| |
| for (const CXXBaseSpecifier &Base : RD->bases()) { |
| assert(!Base.getType()->isDependentType() && |
| "Cannot layout class with dependent bases."); |
| |
| const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl(); |
| |
| if (Base.isVirtual()) { |
| if (PrimaryBase != BaseDecl || !PrimaryBaseIsVirtual) { |
| bool IndirectPrimaryBase = IndirectPrimaryBases.count(BaseDecl); |
| |
| // 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).second) |
| continue; |
| |
| const BaseSubobjectInfo *BaseInfo = VirtualBaseInfo.lookup(BaseDecl); |
| assert(BaseInfo && "Did not find virtual base info!"); |
| LayoutVirtualBase(BaseInfo); |
| } |
| } |
| } |
| |
| if (!BaseDecl->getNumVBases()) { |
| // This base isn't interesting since it doesn't have any virtual bases. |
| continue; |
| } |
| |
| LayoutVirtualBases(BaseDecl, MostDerivedClass); |
| } |
| } |
| |
| void ItaniumRecordLayoutBuilder::LayoutVirtualBase( |
| const BaseSubobjectInfo *Base) { |
| assert(!Base->Derived && "Trying to lay out a primary virtual base!"); |
| |
| // Layout the base. |
| CharUnits Offset = LayoutBase(Base); |
| |
| // Add its base class offset. |
| assert(!VBases.count(Base->Class) && "vbase offset already exists!"); |
| VBases.insert(std::make_pair(Base->Class, |
| ASTRecordLayout::VBaseInfo(Offset, false))); |
| |
| AddPrimaryVirtualBaseOffsets(Base, Offset); |
| } |
| |
| CharUnits |
| ItaniumRecordLayoutBuilder::LayoutBase(const BaseSubobjectInfo *Base) { |
| const ASTRecordLayout &Layout = Context.getASTRecordLayout(Base->Class); |
| |
| |
| CharUnits Offset; |
| |
| // Query the external layout to see if it provides an offset. |
| bool HasExternalLayout = false; |
| if (UseExternalLayout) { |
| // FIXME: This appears to be reversed. |
| if (Base->IsVirtual) |
| HasExternalLayout = External.getExternalNVBaseOffset(Base->Class, Offset); |
| else |
| HasExternalLayout = External.getExternalVBaseOffset(Base->Class, Offset); |
| } |
| |
| // Clang <= 6 incorrectly applied the 'packed' attribute to base classes. |
| // Per GCC's documentation, it only applies to non-static data members. |
| CharUnits UnpackedBaseAlign = Layout.getNonVirtualAlignment(); |
| CharUnits BaseAlign = |
| (Packed && ((Context.getLangOpts().getClangABICompat() <= |
| LangOptions::ClangABI::Ver6) || |
| Context.getTargetInfo().getTriple().isPS4())) |
| ? CharUnits::One() |
| : UnpackedBaseAlign; |
| |
| // If we have an empty base class, try to place it at offset 0. |
| if (Base->Class->isEmpty() && |
| (!HasExternalLayout || Offset == CharUnits::Zero()) && |
| EmptySubobjects->CanPlaceBaseAtOffset(Base, CharUnits::Zero())) { |
| setSize(std::max(getSize(), Layout.getSize())); |
| UpdateAlignment(BaseAlign, UnpackedBaseAlign); |
| |
| return CharUnits::Zero(); |
| } |
| |
| // The maximum field alignment overrides base align. |
| if (!MaxFieldAlignment.isZero()) { |
| BaseAlign = std::min(BaseAlign, MaxFieldAlignment); |
| UnpackedBaseAlign = std::min(UnpackedBaseAlign, MaxFieldAlignment); |
| } |
| |
| if (!HasExternalLayout) { |
| // Round up the current record size to the base's alignment boundary. |
| Offset = getDataSize().alignTo(BaseAlign); |
| |
| // Try to place the base. |
| while (!EmptySubobjects->CanPlaceBaseAtOffset(Base, Offset)) |
| Offset += BaseAlign; |
| } else { |
| bool Allowed = EmptySubobjects->CanPlaceBaseAtOffset(Base, Offset); |
| (void)Allowed; |
| assert(Allowed && "Base subobject externally placed at overlapping offset"); |
| |
| if (InferAlignment && Offset < getDataSize().alignTo(BaseAlign)) { |
| // The externally-supplied base offset is before the base offset we |
| // computed. Assume that the structure is packed. |
| Alignment = CharUnits::One(); |
| InferAlignment = false; |
| } |
| } |
| |
| if (!Base->Class->isEmpty()) { |
| // Update the data size. |
| setDataSize(Offset + Layout.getNonVirtualSize()); |
| |
| setSize(std::max(getSize(), getDataSize())); |
| } else |
| setSize(std::max(getSize(), Offset + Layout.getSize())); |
| |
| // Remember max struct/class alignment. |
| UpdateAlignment(BaseAlign, UnpackedBaseAlign); |
| |
| return Offset; |
| } |
| |
| void ItaniumRecordLayoutBuilder::InitializeLayout(const Decl *D) { |
| if (const RecordDecl *RD = dyn_cast<RecordDecl>(D)) { |
| IsUnion = RD->isUnion(); |
| IsMsStruct = RD->isMsStruct(Context); |
| } |
| |
| Packed = D->hasAttr<PackedAttr>(); |
| |
| // Honor the default struct packing maximum alignment flag. |
| if (unsigned DefaultMaxFieldAlignment = Context.getLangOpts().PackStruct) { |
| MaxFieldAlignment = CharUnits::fromQuantity(DefaultMaxFieldAlignment); |
| } |
| |
| // mac68k alignment supersedes maximum field alignment and attribute aligned, |
| // and forces all structures to have 2-byte alignment. The IBM docs on it |
| // allude to additional (more complicated) semantics, especially with regard |
| // to bit-fields, but gcc appears not to follow that. |
| if (D->hasAttr<AlignMac68kAttr>()) { |
| IsMac68kAlign = true; |
| MaxFieldAlignment = CharUnits::fromQuantity(2); |
| Alignment = CharUnits::fromQuantity(2); |
| } else { |
| if (const MaxFieldAlignmentAttr *MFAA = D->getAttr<MaxFieldAlignmentAttr>()) |
| MaxFieldAlignment = Context.toCharUnitsFromBits(MFAA->getAlignment()); |
| |
| if (unsigned MaxAlign = D->getMaxAlignment()) |
| UpdateAlignment(Context.toCharUnitsFromBits(MaxAlign)); |
| } |
| |
| // If there is an external AST source, ask it for the various offsets. |
| if (const RecordDecl *RD = dyn_cast<RecordDecl>(D)) |
| if (ExternalASTSource *Source = Context.getExternalSource()) { |
| UseExternalLayout = Source->layoutRecordType( |
| RD, External.Size, External.Align, External.FieldOffsets, |
| External.BaseOffsets, External.VirtualBaseOffsets); |
| |
| // Update based on external alignment. |
| if (UseExternalLayout) { |
| if (External.Align > 0) { |
| Alignment = Context.toCharUnitsFromBits(External.Align); |
| } else { |
| // The external source didn't have alignment information; infer it. |
| InferAlignment = true; |
| } |
| } |
| } |
| } |
| |
| void ItaniumRecordLayoutBuilder::Layout(const RecordDecl *D) { |
| InitializeLayout(D); |
| LayoutFields(D); |
| |
| // Finally, round the size of the total struct up to the alignment of the |
| // struct itself. |
| FinishLayout(D); |
| } |
| |
| void ItaniumRecordLayoutBuilder::Layout(const CXXRecordDecl *RD) { |
| InitializeLayout(RD); |
| |
| // Lay out the vtable and the non-virtual bases. |
| LayoutNonVirtualBases(RD); |
| |
| LayoutFields(RD); |
| |
| NonVirtualSize = Context.toCharUnitsFromBits( |
| llvm::alignTo(getSizeInBits(), Context.getTargetInfo().getCharAlign())); |
| NonVirtualAlignment = Alignment; |
| |
| // Lay out the virtual bases and add the primary virtual base offsets. |
| LayoutVirtualBases(RD, RD); |
| |
| // Finally, round the size of the total struct up to the alignment |
| // of the struct itself. |
| FinishLayout(RD); |
| |
| #ifndef NDEBUG |
| // Check that we have base offsets for all bases. |
| for (const CXXBaseSpecifier &Base : RD->bases()) { |
| if (Base.isVirtual()) |
| continue; |
| |
| const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl(); |
| |
| assert(Bases.count(BaseDecl) && "Did not find base offset!"); |
| } |
| |
| // And all virtual bases. |
| for (const CXXBaseSpecifier &Base : RD->vbases()) { |
| const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl(); |
| |
| assert(VBases.count(BaseDecl) && "Did not find base offset!"); |
| } |
| #endif |
| } |
| |
| void ItaniumRecordLayoutBuilder::Layout(const ObjCInterfaceDecl *D) { |
| if (ObjCInterfaceDecl *SD = D->getSuperClass()) { |
| const ASTRecordLayout &SL = Context.getASTObjCInterfaceLayout(SD); |
| |
| UpdateAlignment(SL.getAlignment()); |
| |
| // We start laying out ivars not at the end of the superclass |
| // structure, but at the next byte following the last field. |
| setDataSize(SL.getDataSize()); |
| setSize(getDataSize()); |
| } |
| |
| InitializeLayout(D); |
| // Layout each ivar sequentially. |
| for (const ObjCIvarDecl *IVD = D->all_declared_ivar_begin(); IVD; |
| IVD = IVD->getNextIvar()) |
| LayoutField(IVD, false); |
| |
| // Finally, round the size of the total struct up to the alignment of the |
| // struct itself. |
| FinishLayout(D); |
| } |
| |
| void ItaniumRecordLayoutBuilder::LayoutFields(const RecordDecl *D) { |
| // Layout each field, for now, just sequentially, respecting alignment. In |
| // the future, this will need to be tweakable by targets. |
| 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::alignTo(Size, CharAlignment); |
| } |
| |
| void ItaniumRecordLayoutBuilder::LayoutWideBitField(uint64_t FieldSize, |
| uint64_t TypeSize, |
| bool FieldPacked, |
| const FieldDecl *D) { |
| assert(Context.getLangOpts().CPlusPlus && |
| "Can only have wide bit-fields in C++!"); |
| |
| // Itanium C++ ABI 2.4: |
| // If sizeof(T)*8 < n, let T' be the largest integral POD type with |
| // sizeof(T')*8 <= n. |
| |
| QualType IntegralPODTypes[] = { |
| Context.UnsignedCharTy, Context.UnsignedShortTy, Context.UnsignedIntTy, |
| Context.UnsignedLongTy, Context.UnsignedLongLongTy |
| }; |
| |
| QualType Type; |
| for (const QualType &QT : IntegralPODTypes) { |
| uint64_t Size = Context.getTypeSize(QT); |
| |
| if (Size > FieldSize) |
| break; |
| |
| Type = QT; |
| } |
| assert(!Type.isNull() && "Did not find a type!"); |
| |
| CharUnits TypeAlign = Context.getTypeAlignInChars(Type); |
| |
| // We're not going to use any of the unfilled bits in the last byte. |
| UnfilledBitsInLastUnit = 0; |
| LastBitfieldTypeSize = 0; |
| |
| uint64_t FieldOffset; |
| uint64_t UnpaddedFieldOffset = getDataSizeInBits() - UnfilledBitsInLastUnit; |
| |
| if (IsUnion) { |
| uint64_t RoundedFieldSize = roundUpSizeToCharAlignment(FieldSize, |
| Context); |
| setDataSize(std::max(getDataSizeInBits(), RoundedFieldSize)); |
| FieldOffset = 0; |
| } else { |
| // The bitfield is allocated starting at the next offset aligned |
| // appropriately for T', with length n bits. |
| FieldOffset = llvm::alignTo(getDataSizeInBits(), Context.toBits(TypeAlign)); |
| |
| uint64_t NewSizeInBits = FieldOffset + FieldSize; |
| |
| setDataSize( |
| llvm::alignTo(NewSizeInBits, Context.getTargetInfo().getCharAlign())); |
| UnfilledBitsInLastUnit = getDataSizeInBits() - NewSizeInBits; |
| } |
| |
| // Place this field at the current location. |
| FieldOffsets.push_back(FieldOffset); |
| |
| CheckFieldPadding(FieldOffset, UnpaddedFieldOffset, FieldOffset, |
| Context.toBits(TypeAlign), FieldPacked, D); |
| |
| // Update the size. |
| setSize(std::max(getSizeInBits(), getDataSizeInBits())); |
| |
| // Remember max struct/class alignment. |
| UpdateAlignment(TypeAlign); |
| } |
| |
| void ItaniumRecordLayoutBuilder::LayoutBitField(const FieldDecl *D) { |
| bool FieldPacked = Packed || D->hasAttr<PackedAttr>(); |
| uint64_t FieldSize = D->getBitWidthValue(Context); |
| 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 |
| // bitfields) and the end of the current data size in bits (i.e. the |
| // first bit offset available for non-bitfields). The current data |
| // size in bits is always a multiple of the char size; additionally, |
| // for ms_struct records it's also a multiple of the |
| // LastBitfieldTypeSize (if set). |
| |
| // The struct-layout algorithm is dictated by the platform ABI, |
| // which in principle could use almost any rules it likes. In |
| // practice, UNIXy targets tend to inherit the algorithm described |
| // in the System V generic ABI. The basic bitfield layout rule in |
| // System V is to place bitfields at the next available bit offset |
| // where the entire bitfield would fit in an aligned storage unit of |
| // the declared type; it's okay if an earlier or later non-bitfield |
| // is allocated in the same storage unit. However, some targets |
| // (those that !useBitFieldTypeAlignment(), e.g. ARM APCS) don't |
| // require this storage unit to be aligned, and therefore always put |
| // the bitfield at the next available bit offset. |
| |
| // ms_struct basically requests a complete replacement of the |
| // platform ABI's struct-layout algorithm, with the high-level goal |
| // of duplicating MSVC's layout. For non-bitfields, this follows |
| // the standard algorithm. The basic bitfield layout rule is to |
| // allocate an entire unit of the bitfield's declared type |
| // (e.g. 'unsigned long'), then parcel it up among successive |
| // bitfields whose declared types have the same size, making a new |
| // unit as soon as the last can no longer store the whole value. |
| // Since it completely replaces the platform ABI's algorithm, |
| // settings like !useBitFieldTypeAlignment() do not apply. |
| |
| // A zero-width bitfield forces the use of a new storage unit for |
| // later bitfields. In general, this occurs by rounding up the |
| // current size of the struct as if the algorithm were about to |
| // place a non-bitfield of the field's formal type. Usually this |
| // does not change the alignment of the struct itself, but it does |
| // on some targets (those that useZeroLengthBitfieldAlignment(), |
| // e.g. ARM). In ms_struct layout, zero-width bitfields are |
| // ignored unless they follow a non-zero-width bitfield. |
| |
| // A field alignment restriction (e.g. from #pragma pack) or |
| // specification (e.g. from __attribute__((aligned))) changes the |
| // formal alignment of the field. For System V, this alters the |
| // required alignment of the notional storage unit that must contain |
| // the bitfield. For ms_struct, this only affects the placement of |
| // new storage units. In both cases, the effect of #pragma pack is |
| // ignored on zero-width bitfields. |
| |
| // On System V, a packed field (e.g. from #pragma pack or |
| // __attribute__((packed))) always uses the next available bit |
| // offset. |
| |
| // In an ms_struct struct, the alignment of a fundamental type is |
| // always equal to its size. This is necessary in order to mimic |
| // the i386 alignment rules on targets which might not fully align |
| // all types (e.g. Darwin PPC32, where alignof(long long) == 4). |
| |
| // First, some simple bookkeeping to perform for ms_struct structs. |
| if (IsMsStruct) { |
| // The field alignment for integer types is always the size. |
| FieldAlign = TypeSize; |
| |
| // If the previous field was not a bitfield, or was a bitfield |
| // with a different storage unit size, or if this field doesn't fit into |
| // the current storage unit, we're done with that storage unit. |
| if (LastBitfieldTypeSize != TypeSize || |
| UnfilledBitsInLastUnit < FieldSize) { |
| // Also, ignore zero-length bitfields after non-bitfields. |
| if (!LastBitfieldTypeSize && !FieldSize) |
| FieldAlign = 1; |
| |
| UnfilledBitsInLastUnit = 0; |
| LastBitfieldTypeSize = 0; |
| } |
| } |
| |
| // If the field is wider than its declared type, it follows |
| // different rules in all cases. |
| if (FieldSize > TypeSize) { |
| LayoutWideBitField(FieldSize, TypeSize, FieldPacked, D); |
| return; |
| } |
| |
| // Compute the next available bit offset. |
| uint64_t FieldOffset = |
| IsUnion ? 0 : (getDataSizeInBits() - UnfilledBitsInLastUnit); |
| |
| // Handle targets that don't honor bitfield type alignment. |
| if (!IsMsStruct && !Context.getTargetInfo().useBitFieldTypeAlignment()) { |
| // Some such targets do honor it on zero-width bitfields. |
| if (FieldSize == 0 && |
| Context.getTargetInfo().useZeroLengthBitfieldAlignment()) { |
| // The alignment to round up to is the max of the field's natural |
| // alignment and a target-specific fixed value (sometimes zero). |
| unsigned ZeroLengthBitfieldBoundary = |
| Context.getTargetInfo().getZeroLengthBitfieldBoundary(); |
| FieldAlign = std::max(FieldAlign, ZeroLengthBitfieldBoundary); |
| |
| // If that doesn't apply, just ignore the field alignment. |
| } else { |
| FieldAlign = 1; |
| } |
| } |
| |
| // Remember the alignment we would have used if the field were not packed. |
| unsigned UnpackedFieldAlign = FieldAlign; |
| |
| // Ignore the field alignment if the field is packed unless it has zero-size. |
| if (!IsMsStruct && FieldPacked && FieldSize != 0) |
| FieldAlign = 1; |
| |
| // But, if there's an 'aligned' attribute on the field, honor that. |
| unsigned ExplicitFieldAlign = D->getMaxAlignment(); |
| if (ExplicitFieldAlign) { |
| FieldAlign = std::max(FieldAlign, ExplicitFieldAlign); |
| UnpackedFieldAlign = std::max(UnpackedFieldAlign, ExplicitFieldAlign); |
| } |
| |
| // But, if there's a #pragma pack in play, that takes precedent over |
| // even the 'aligned' attribute, for non-zero-width bitfields. |
| unsigned MaxFieldAlignmentInBits = Context.toBits(MaxFieldAlignment); |
| if (!MaxFieldAlignment.isZero() && FieldSize) { |
| UnpackedFieldAlign = std::min(UnpackedFieldAlign, MaxFieldAlignmentInBits); |
| if (FieldPacked) |
| FieldAlign = UnpackedFieldAlign; |
| else |
| FieldAlign = std::min(FieldAlign, MaxFieldAlignmentInBits); |
| } |
| |
| // But, ms_struct just ignores all of that in unions, even explicit |
| // alignment attributes. |
| if (IsMsStruct && IsUnion) { |
| FieldAlign = UnpackedFieldAlign = 1; |
| } |
| |
| // For purposes of diagnostics, we're going to simultaneously |
| // compute the field offsets that we would have used if we weren't |
| // adding any alignment padding or if the field weren't packed. |
| uint64_t UnpaddedFieldOffset = FieldOffset; |
| uint64_t UnpackedFieldOffset = FieldOffset; |
| |
| // Check if we need to add padding to fit the bitfield within an |
| // allocation unit with the right size and alignment. The rules are |
| // somewhat different here for ms_struct structs. |
| if (IsMsStruct) { |
| // If it's not a zero-width bitfield, and we can fit the bitfield |
| // into the active storage unit (and we haven't already decided to |
| // start a new storage unit), just do so, regardless of any other |
| // other consideration. Otherwise, round up to the right alignment. |
| if (FieldSize == 0 || FieldSize > UnfilledBitsInLastUnit) { |
| FieldOffset = llvm::alignTo(FieldOffset, FieldAlign); |
| UnpackedFieldOffset = |
| llvm::alignTo(UnpackedFieldOffset, UnpackedFieldAlign); |
| UnfilledBitsInLastUnit = 0; |
| } |
| |
| } else { |
| // #pragma pack, with any value, suppresses the insertion of padding. |
| bool AllowPadding = MaxFieldAlignment.isZero(); |
| |
| // Compute the real offset. |
| if (FieldSize == 0 || |
| (AllowPadding && |
| (FieldOffset & (FieldAlign-1)) + FieldSize > TypeSize)) { |
| FieldOffset = llvm::alignTo(FieldOffset, FieldAlign); |
| } else if (ExplicitFieldAlign && |
| (MaxFieldAlignmentInBits == 0 || |
| ExplicitFieldAlign <= MaxFieldAlignmentInBits) && |
| Context.getTargetInfo().useExplicitBitFieldAlignment()) { |
| // TODO: figure it out what needs to be done on targets that don't honor |
| // bit-field type alignment like ARM APCS ABI. |
| FieldOffset = llvm::alignTo(FieldOffset, ExplicitFieldAlign); |
| } |
| |
| // Repeat the computation for diagnostic purposes. |
| if (FieldSize == 0 || |
| (AllowPadding && |
| (UnpackedFieldOffset & (UnpackedFieldAlign-1)) + FieldSize > TypeSize)) |
| UnpackedFieldOffset = |
| llvm::alignTo(UnpackedFieldOffset, UnpackedFieldAlign); |
| else if (ExplicitFieldAlign && |
| (MaxFieldAlignmentInBits == 0 || |
| ExplicitFieldAlign <= MaxFieldAlignmentInBits) && |
| Context.getTargetInfo().useExplicitBitFieldAlignment()) |
| UnpackedFieldOffset = |
| llvm::alignTo(UnpackedFieldOffset, ExplicitFieldAlign); |
| } |
| |
| // If we're using external layout, give the external layout a chance |
| // to override this information. |
| if (UseExternalLayout) |
| FieldOffset = updateExternalFieldOffset(D, FieldOffset); |
| |
| // Okay, place the bitfield at the calculated offset. |
| FieldOffsets.push_back(FieldOffset); |
| |
| // Bookkeeping: |
| |
| // Anonymous members don't affect the overall record alignment, |
| // except on targets where they do. |
| if (!IsMsStruct && |
| !Context.getTargetInfo().useZeroLengthBitfieldAlignment() && |
| !D->getIdentifier()) |
| FieldAlign = UnpackedFieldAlign = 1; |
| |
| // Diagnose differences in layout due to padding or packing. |
| if (!UseExternalLayout) |
| CheckFieldPadding(FieldOffset, UnpaddedFieldOffset, UnpackedFieldOffset, |
| UnpackedFieldAlign, FieldPacked, D); |
| |
| // Update DataSize to include the last byte containing (part of) the bitfield. |
| |
| // For unions, this is just a max operation, as usual. |
| if (IsUnion) { |
| // For ms_struct, allocate the entire storage unit --- unless this |
| // is a zero-width bitfield, in which case just use a size of 1. |
| uint64_t RoundedFieldSize; |
| if (IsMsStruct) { |
| RoundedFieldSize = |
| (FieldSize ? TypeSize : Context.getTargetInfo().getCharWidth()); |
| |
| // Otherwise, allocate just the number of bytes required to store |
| // the bitfield. |
| } else { |
| 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) { |
| // We should have cleared UnfilledBitsInLastUnit in every case |
| // where we changed storage units. |
| if (!UnfilledBitsInLastUnit) { |
| setDataSize(FieldOffset + TypeSize); |
| UnfilledBitsInLastUnit = TypeSize; |
| } |
| UnfilledBitsInLastUnit -= FieldSize; |
| LastBitfieldTypeSize = TypeSize; |
| |
| // Otherwise, bump the data size up to include the bitfield, |
| // including padding up to char alignment, and then remember how |
| // bits we didn't use. |
| } else { |
| uint64_t NewSizeInBits = FieldOffset + FieldSize; |
| uint64_t CharAlignment = Context.getTargetInfo().getCharAlign(); |
| setDataSize(llvm::alignTo(NewSizeInBits, CharAlignment)); |
| UnfilledBitsInLastUnit = getDataSizeInBits() - NewSizeInBits; |
| |
| // The only time we can get here for an ms_struct is if this is a |
| // zero-width bitfield, which doesn't count as anything for the |
| // purposes of unfilled bits. |
| LastBitfieldTypeSize = 0; |
| } |
| |
| // Update the size. |
| setSize(std::max(getSizeInBits(), getDataSizeInBits())); |
| |
| // Remember max struct/class alignment. |
| UnadjustedAlignment = |
| std::max(UnadjustedAlignment, Context.toCharUnitsFromBits(FieldAlign)); |
| UpdateAlignment(Context.toCharUnitsFromBits(FieldAlign), |
| Context.toCharUnitsFromBits(UnpackedFieldAlign)); |
| } |
| |
| void ItaniumRecordLayoutBuilder::LayoutField(const FieldDecl *D, |
| bool InsertExtraPadding) { |
| if (D->isBitField()) { |
| LayoutBitField(D); |
| return; |
| } |
| |
| uint64_t UnpaddedFieldOffset = getDataSizeInBits() - UnfilledBitsInLastUnit; |
| |
| // Reset the unfilled bits. |
| UnfilledBitsInLastUnit = 0; |
| LastBitfieldTypeSize = 0; |
| |
| auto *FieldClass = D->getType()->getAsCXXRecordDecl(); |
| bool PotentiallyOverlapping = D->hasAttr<NoUniqueAddressAttr>() && FieldClass; |
| bool IsOverlappingEmptyField = PotentiallyOverlapping && FieldClass->isEmpty(); |
| bool FieldPacked = Packed || D->hasAttr<PackedAttr>(); |
| |
| CharUnits FieldOffset = (IsUnion || IsOverlappingEmptyField) |
| ? CharUnits::Zero() |
| : getDataSize(); |
| CharUnits FieldSize; |
| CharUnits FieldAlign; |
| // The amount of this class's dsize occupied by the field. |
| // This is equal to FieldSize unless we're permitted to pack |
| // into the field's tail padding. |
| CharUnits EffectiveFieldSize; |
| |
| if (D->getType()->isIncompleteArrayType()) { |
| // This is a flexible array member; we can't directly |
| // query getTypeInfo about these, so we figure it out here. |
| // Flexible array members don't have any size, but they |
| // have to be aligned appropriately for their element type. |
| EffectiveFieldSize = FieldSize = CharUnits::Zero(); |
| const ArrayType* ATy = Context.getAsArrayType(D->getType()); |
| FieldAlign = Context.getTypeAlignInChars(ATy->getElementType()); |
| } else if (const ReferenceType *RT = D->getType()->getAs<ReferenceType>()) { |
| unsigned AS = Context.getTargetAddressSpace(RT->getPointeeType()); |
| EffectiveFieldSize = FieldSize = |
| Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(AS)); |
| FieldAlign = |
| Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerAlign(AS)); |
| } else { |
| std::pair<CharUnits, CharUnits> FieldInfo = |
| Context.getTypeInfoInChars(D->getType()); |
| EffectiveFieldSize = FieldSize = FieldInfo.first; |
| FieldAlign = FieldInfo.second; |
| |
| // A potentially-overlapping field occupies its dsize or nvsize, whichever |
| // is larger. |
| if (PotentiallyOverlapping) { |
| const ASTRecordLayout &Layout = Context.getASTRecordLayout(FieldClass); |
| EffectiveFieldSize = |
| std::max(Layout.getNonVirtualSize(), Layout.getDataSize()); |
| } |
| |
| if (IsMsStruct) { |
| // If MS bitfield layout is required, figure out what type is being |
| // laid out and align the field to the width of that type. |
| |
| // Resolve all typedefs down to their base type and round up the field |
| // alignment if necessary. |
| QualType T = Context.getBaseElementType(D->getType()); |
| if (const BuiltinType *BTy = T->getAs<BuiltinType>()) { |
| CharUnits TypeSize = Context.getTypeSizeInChars(BTy); |
| |
| if (!llvm::isPowerOf2_64(TypeSize.getQuantity())) { |
| assert( |
| !Context.getTargetInfo().getTriple().isWindowsMSVCEnvironment() && |
| "Non PowerOf2 size in MSVC mode"); |
| // Base types with sizes that aren't a power of two don't work |
| // with the layout rules for MS structs. This isn't an issue in |
| // MSVC itself since there are no such base data types there. |
| // On e.g. x86_32 mingw and linux, long double is 12 bytes though. |
| // Any structs involving that data type obviously can't be ABI |
| // compatible with MSVC regardless of how it is laid out. |
| |
| // Since ms_struct can be mass enabled (via a pragma or via the |
| // -mms-bitfields command line parameter), this can trigger for |
| // structs that don't actually need MSVC compatibility, so we |
| // need to be able to sidestep the ms_struct layout for these types. |
| |
| // Since the combination of -mms-bitfields together with structs |
| // like max_align_t (which contains a long double) for mingw is |
| // quite comon (and GCC handles it silently), just handle it |
| // silently there. For other targets that have ms_struct enabled |
| // (most probably via a pragma or attribute), trigger a diagnostic |
| // that defaults to an error. |
| if (!Context.getTargetInfo().getTriple().isWindowsGNUEnvironment()) |
| Diag(D->getLocation(), diag::warn_npot_ms_struct); |
| } |
| if (TypeSize > FieldAlign && |
| llvm::isPowerOf2_64(TypeSize.getQuantity())) |
| FieldAlign = TypeSize; |
| } |
| } |
| } |
| |
| // The align if the field is not packed. This is to check if the attribute |
| // was unnecessary (-Wpacked). |
| CharUnits UnpackedFieldAlign = FieldAlign; |
| CharUnits UnpackedFieldOffset = FieldOffset; |
| |
| if (FieldPacked) |
| FieldAlign = CharUnits::One(); |
| CharUnits MaxAlignmentInChars = |
| Context.toCharUnitsFromBits(D->getMaxAlignment()); |
| FieldAlign = std::max(FieldAlign, MaxAlignmentInChars); |
| UnpackedFieldAlign = std::max(UnpackedFieldAlign, MaxAlignmentInChars); |
| |
| // The maximum field alignment overrides the aligned attribute. |
| if (!MaxFieldAlignment.isZero()) { |
| FieldAlign = std::min(FieldAlign, MaxFieldAlignment); |
| UnpackedFieldAlign = std::min(UnpackedFieldAlign, MaxFieldAlignment); |
| } |
| |
| // Round up the current record size to the field's alignment boundary. |
| FieldOffset = FieldOffset.alignTo(FieldAlign); |
| UnpackedFieldOffset = UnpackedFieldOffset.alignTo(UnpackedFieldAlign); |
| |
| if (UseExternalLayout) { |
| FieldOffset = Context.toCharUnitsFromBits( |
| updateExternalFieldOffset(D, Context.toBits(FieldOffset))); |
| |
| if (!IsUnion && EmptySubobjects) { |
| // Record the fact that we're placing a field at this offset. |
| bool Allowed = EmptySubobjects->CanPlaceFieldAtOffset(D, FieldOffset); |
| (void)Allowed; |
| assert(Allowed && "Externally-placed field cannot be placed here"); |
| } |
| } else { |
| if (!IsUnion && EmptySubobjects) { |
| // Check if we can place the field at this offset. |
| while (!EmptySubobjects->CanPlaceFieldAtOffset(D, FieldOffset)) { |
| // We couldn't place the field at the offset. Try again at a new offset. |
| // We try offset 0 (for an empty field) and then dsize(C) onwards. |
| if (FieldOffset == CharUnits::Zero() && |
| getDataSize() != CharUnits::Zero()) |
| FieldOffset = getDataSize().alignTo(FieldAlign); |
| else |
| FieldOffset += FieldAlign; |
| } |
| } |
| } |
| |
| // Place this field at the current location. |
| FieldOffsets.push_back(Context.toBits(FieldOffset)); |
| |
| if (!UseExternalLayout) |
| CheckFieldPadding(Context.toBits(FieldOffset), UnpaddedFieldOffset, |
| 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); |
| EffectiveFieldSize = FieldSize = FieldSize + ExtraSizeForAsan; |
| } |
| |
| // Reserve space for this field. |
| if (!IsOverlappingEmptyField) { |
| uint64_t EffectiveFieldSizeInBits = Context.toBits(EffectiveFieldSize); |
| if (IsUnion) |
| setDataSize(std::max(getDataSizeInBits(), EffectiveFieldSizeInBits)); |
| else |
| setDataSize(FieldOffset + EffectiveFieldSize); |
| |
| PaddedFieldSize = std::max(PaddedFieldSize, FieldOffset + FieldSize); |
| setSize(std::max(getSizeInBits(), getDataSizeInBits())); |
| } else { |
| setSize(std::max(getSizeInBits(), |
| (uint64_t)Context.toBits(FieldOffset + FieldSize))); |
| } |
| |
| // Remember max struct/class alignment. |
| UnadjustedAlignment = std::max(UnadjustedAlignment, FieldAlign); |
| UpdateAlignment(FieldAlign, UnpackedFieldAlign); |
| } |
| |
| void ItaniumRecordLayoutBuilder::FinishLayout(const NamedDecl *D) { |
| // In C++, records cannot be of size 0. |
| if (Context.getLangOpts().CPlusPlus && getSizeInBits() == 0) { |
| if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D)) { |
| // Compatibility with gcc requires a class (pod or non-pod) |
| // which is not empty but of size 0; such as having fields of |
| // array of zero-length, remains of Size 0 |
| if (RD->isEmpty()) |
| setSize(CharUnits::One()); |
| } |
| else |
| setSize(CharUnits::One()); |
| } |
| |
| // If we have any remaining field tail padding, include that in the overall |
| // size. |
| setSize(std::max(getSizeInBits(), (uint64_t)Context.toBits(PaddedFieldSize))); |
| |
| // Finally, round the size of the record up to the alignment of the |
| // record itself. |
| uint64_t UnpaddedSize = getSizeInBits() - UnfilledBitsInLastUnit; |
| uint64_t UnpackedSizeInBits = |
| llvm::alignTo(getSizeInBits(), Context.toBits(UnpackedAlignment)); |
| uint64_t RoundedSize = |
| llvm::alignTo(getSizeInBits(), Context.toBits(Alignment)); |
| |
| if (UseExternalLayout) { |
| // If we're inferring alignment, and the external size is smaller than |
| // our size after we've rounded up to alignment, conservatively set the |
| // alignment to 1. |
| if (InferAlignment && External.Size < RoundedSize) { |
| Alignment = CharUnits::One(); |
| InferAlignment = false; |
| } |
| setSize(External.Size); |
| return; |
| } |
| |
| // Set the size to the final size. |
| setSize(RoundedSize); |
| |
| unsigned CharBitNum = Context.getTargetInfo().getCharWidth(); |
| if (const RecordDecl *RD = dyn_cast<RecordDecl>(D)) { |
| // Warn if padding was introduced to the struct/class/union. |
| if (getSizeInBits() > UnpaddedSize) { |
| unsigned PadSize = getSizeInBits() - UnpaddedSize; |
| bool InBits = true; |
| if (PadSize % CharBitNum == 0) { |
| PadSize = PadSize / CharBitNum; |
| InBits = false; |
| } |
| Diag(RD->getLocation(), diag::warn_padded_struct_size) |
| << Context.getTypeDeclType(RD) |
| << PadSize |
| << (InBits ? 1 : 0); // (byte|bit) |
| } |
| |
| // Warn if we packed it unnecessarily, when the unpacked alignment is not |
| // greater than the one after packing, the size in bits doesn't change and |
| // the offset of each field is identical. |
| if (Packed && UnpackedAlignment <= Alignment && |
| UnpackedSizeInBits == getSizeInBits() && !HasPackedField) |
| Diag(D->getLocation(), diag::warn_unnecessary_packed) |
| << Context.getTypeDeclType(RD); |
| } |
| } |
| |
| void ItaniumRecordLayoutBuilder::UpdateAlignment( |
| CharUnits NewAlignment, CharUnits UnpackedNewAlignment) { |
| // The alignment is not modified when using 'mac68k' alignment or when |
| // we have an externally-supplied layout that also provides overall alignment. |
| if (IsMac68kAlign || (UseExternalLayout && !InferAlignment)) |
| return; |
| |
| if (NewAlignment > Alignment) { |
| assert(llvm::isPowerOf2_64(NewAlignment.getQuantity()) && |
| "Alignment not a power of 2"); |
| Alignment = NewAlignment; |
| } |
| |
| if (UnpackedNewAlignment > UnpackedAlignment) { |
| assert(llvm::isPowerOf2_64(UnpackedNewAlignment.getQuantity()) && |
| "Alignment not a power of 2"); |
| UnpackedAlignment = UnpackedNewAlignment; |
| } |
| } |
| |
| uint64_t |
| ItaniumRecordLayoutBuilder::updateExternalFieldOffset(const FieldDecl *Field, |
| uint64_t ComputedOffset) { |
| uint64_t ExternalFieldOffset = External.getExternalFieldOffset(Field); |
| |
| if (InferAlignment && ExternalFieldOffset < ComputedOffset) { |
| // The externally-supplied field offset is before the field offset we |
| // computed. Assume that the structure is packed. |
| Alignment = CharUnits::One(); |
| InferAlignment = false; |
| } |
| |
| // Use the externally-supplied field offset. |
| return ExternalFieldOffset; |
| } |
| |
| /// Get diagnostic %select index for tag kind for |
| /// field padding diagnostic message. |
| /// WARNING: Indexes apply to particular diagnostics only! |
| /// |
| /// \returns diagnostic %select index. |
| static unsigned getPaddingDiagFromTagKind(TagTypeKind Tag) { |
| switch (Tag) { |
| case TTK_Struct: return 0; |
| case TTK_Interface: return 1; |
| case TTK_Class: return 2; |
| default: llvm_unreachable("Invalid tag kind for field padding diagnostic!"); |
| } |
| } |
| |
| void ItaniumRecordLayoutBuilder::CheckFieldPadding( |
| uint64_t Offset, uint64_t UnpaddedOffset, uint64_t UnpackedOffset, |
| unsigned UnpackedAlign, bool isPacked, const FieldDecl *D) { |
| // We let objc ivars without warning, objc interfaces generally are not used |
| // for padding tricks. |
| if (isa<ObjCIvarDecl>(D)) |
| return; |
| |
| // Don't warn about structs created without a SourceLocation. This can |
| // be done by clients of the AST, such as codegen. |
| if (D->getLocation().isInvalid()) |
| return; |
| |
| unsigned CharBitNum = Context.getTargetInfo().getCharWidth(); |
| |
| // Warn if padding was introduced to the struct/class. |
| if (!IsUnion && Offset > UnpaddedOffset) { |
| unsigned PadSize = Offset - UnpaddedOffset; |
| bool InBits = true; |
| if (PadSize % CharBitNum == 0) { |
| PadSize = PadSize / CharBitNum; |
| InBits = false; |
| } |
| if (D->getIdentifier()) |
| Diag(D->getLocation(), diag::warn_padded_struct_field) |
| << getPaddingDiagFromTagKind(D->getParent()->getTagKind()) |
| << Context.getTypeDeclType(D->getParent()) |
| << PadSize |
| << (InBits ? 1 : 0) // (byte|bit) |
| << D->getIdentifier(); |
| else |
| Diag(D->getLocation(), diag::warn_padded_struct_anon_field) |
| << getPaddingDiagFromTagKind(D->getParent()->getTagKind()) |
| << Context.getTypeDeclType(D->getParent()) |
| << PadSize |
| << (InBits ? 1 : 0); // (byte|bit) |
| } |
| if (isPacked && Offset != UnpackedOffset) { |
| HasPackedField = true; |
| } |
| } |
| |
| static const CXXMethodDecl *computeKeyFunction(ASTContext &Context, |
| const CXXRecordDecl *RD) { |
| // If a class isn't polymorphic it doesn't have a key function. |
| if (!RD->isPolymorphic()) |
| return nullptr; |
| |
| // A class that is not externally visible doesn't have a key function. (Or |
| // at least, there's no point to assigning a key function to such a class; |
| // this doesn't affect the ABI.) |
| if (!RD->isExternallyVisible()) |
| return nullptr; |
| |
| // Template instantiations don't have key functions per Itanium C++ ABI 5.2.6. |
| // Same behavior as GCC. |
| TemplateSpecializationKind TSK = RD->getTemplateSpecializationKind(); |
| if (TSK == TSK_ImplicitInstantiation || |
| TSK == TSK_ExplicitInstantiationDeclaration || |
| TSK == TSK_ExplicitInstantiationDefinition) |
| return nullptr; |
| |
| bool allowInlineFunctions = |
| Context.getTargetInfo().getCXXABI().canKeyFunctionBeInline(); |
| |
| for (const CXXMethodDecl *MD : RD->methods()) { |
| if (!MD->isVirtual()) |
| continue; |
| |
| if (MD->isPure()) |
| continue; |
| |
| // Ignore implicit member functions, they are always marked as inline, but |
| // they don't have a body until they're defined. |
| if (MD->isImplicit()) |
| continue; |
| |
| if (MD->isInlineSpecified()) |
| continue; |
| |
| if (MD->hasInlineBody()) |
| continue; |
| |
| // Ignore inline deleted or defaulted functions. |
| if (!MD->isUserProvided()) |
| continue; |
| |
| // In certain ABIs, ignore functions with out-of-line inline definitions. |
| if (!allowInlineFunctions) { |
| const FunctionDecl *Def; |
| if (MD->hasBody(Def) && Def->isInlineSpecified()) |
| continue; |
| } |
| |
| if (Context.getLangOpts().CUDA) { |
| // While compiler may see key method in this TU, during CUDA |
| // compilation we should ignore methods that are not accessible |
| // on this side of compilation. |
| if (Context.getLangOpts().CUDAIsDevice) { |
| // In device mode ignore methods without __device__ attribute. |
| if (!MD->hasAttr<CUDADeviceAttr>()) |
| continue; |
| } else { |
| // In host mode ignore __device__-only methods. |
| if (!MD->hasAttr<CUDAHostAttr>() && MD->hasAttr<CUDADeviceAttr>()) |
| continue; |
| } |
| } |
| |
| // If the key function is dllimport but the class isn't, then the class has |
| // no key function. The DLL that exports the key function won't export the |
| // vtable in this case. |
| if (MD->hasAttr<DLLImportAttr>() && !RD->hasAttr<DLLImportAttr>()) |
| return nullptr; |
| |
| // We found it. |
| return MD; |
| } |
| |
| return nullptr; |
| } |
| |
| DiagnosticBuilder ItaniumRecordLayoutBuilder::Diag(SourceLocation Loc, |
| unsigned DiagID) { |
| return Context.getDiagnostics().Report(Loc, DiagID); |
| } |
| |
| /// Does the target C++ ABI require us to skip over the tail-padding |
| /// of the given class (considering it as a base class) when allocating |
| /// objects? |
| static bool mustSkipTailPadding(TargetCXXABI ABI, const CXXRecordDecl *RD) { |
| switch (ABI.getTailPaddingUseRules()) { |
| case TargetCXXABI::AlwaysUseTailPadding: |
| return false; |
| |
| case TargetCXXABI::UseTailPaddingUnlessPOD03: |
| // FIXME: To the extent that this is meant to cover the Itanium ABI |
| // rules, we should implement the restrictions about over-sized |
| // bitfields: |
| // |
| // http://itanium-cxx-abi.github.io/cxx-abi/abi.html#POD : |
| // In general, a type is considered a POD for the purposes of |
| // layout if it is a POD type (in the sense of ISO C++ |
| // [basic.types]). However, a POD-struct or POD-union (in the |
| // sense of ISO C++ [class]) with a bitfield member whose |
| // declared width is wider than the declared type of the |
| // bitfield is not a POD for the purpose of layout. Similarly, |
| // an array type is not a POD for the purpose of layout if the |
| // element type of the array is not a POD for the purpose of |
| // layout. |
| // |
| // Where references to the ISO C++ are made in this paragraph, |
| // the Technical Corrigendum 1 version of the standard is |
| // intended. |
| return RD->isPOD(); |
| |
| case TargetCXXABI::UseTailPaddingUnlessPOD11: |
| // This is equivalent to RD->getTypeForDecl().isCXX11PODType(), |
| // but with a lot of abstraction penalty stripped off. This does |
| // assume that these properties are set correctly even in C++98 |
| // mode; fortunately, that is true because we want to assign |
| // consistently semantics to the type-traits intrinsics (or at |
| // least as many of them as possible). |
| return RD->isTrivial() && RD->isCXX11StandardLayout(); |
| } |
| |
| llvm_unreachable("bad tail-padding use kind"); |
| } |
| |
| static bool isMsLayout(const ASTContext &Context) { |
| return Context.getTargetInfo().getCXXABI().isMicrosoft(); |
| } |
| |
| // This section contains an implementation of struct layout that is, up to the |
| // included tests, compatible with cl.exe (2013). The layout produced is |
| // significantly different than those produced by the Itanium ABI. Here we note |
| // the most important differences. |
| // |
| // * The alignment of bitfields in unions is ignored when computing the |
| // alignment of the union. |
| // * The existence of zero-width bitfield that occurs after anything other than |
| // a non-zero length bitfield is ignored. |
| // * There is no explicit primary base for the purposes of layout. All bases |
| // with vfptrs are laid out first, followed by all bases without vfptrs. |
| // * The Itanium equivalent vtable pointers are split into a vfptr (virtual |
| // function pointer) and a vbptr (virtual base pointer). They can each be |
| // shared with a, non-virtual bases. These bases need not be the same. vfptrs |
| // always occur at offset 0. vbptrs can occur at an arbitrary offset and are |
| // placed after the lexicographically last non-virtual base. This placement |
| // is always before fields but can be in the middle of the non-virtual bases |
| // due to the two-pass layout scheme for non-virtual-bases. |
| // * Virtual bases sometimes require a 'vtordisp' field that is laid out before |
| // the virtual base and is used in conjunction with virtual overrides during |
| // construction and destruction. This is always a 4 byte value and is used as |
| // an alternative to constructor vtables. |
| // * vtordisps are allocated in a block of memory with size and alignment equal |
| // to the alignment of the completed structure (before applying __declspec( |
| // align())). The vtordisp always occur at the end of the allocation block, |
| // immediately prior to the virtual base. |
| // * vfptrs are injected after all bases and fields have been laid out. In |
| // order to guarantee proper alignment of all fields, the vfptr injection |
| // pushes all bases and fields back by the alignment imposed by those bases |
| // and fields. This can potentially add a significant amount of padding. |
| // vfptrs are always injected at offset 0. |
| // * vbptrs are injected after all bases and fields have been laid out. In |
| // order to guarantee proper alignment of all fields, the vfptr injection |
| // pushes all bases and fields back by the alignment imposed by those bases |
| // and fields. This can potentially add a significant amount of padding. |
| // vbptrs are injected immediately after the last non-virtual base as |
| // lexicographically ordered in the code. If this site isn't pointer aligned |
| // the vbptr is placed at the next properly aligned location. Enough padding |
| // is added to guarantee a fit. |
| // * The last zero sized non-virtual base can be placed at the end of the |
| // struct (potentially aliasing another object), or may alias with the first |
| // field, even if they are of the same type. |
| // * The last zero size virtual base may be placed at the end of the struct |
| // potentially aliasing another object. |
| // * The ABI attempts to avoid aliasing of zero sized bases by adding padding |
| // between bases or vbases with specific properties. The criteria for |
| // additional padding between two bases is that the first base is zero sized |
| // or ends with a zero sized subobject and the second base is zero sized or |
| // trails with a zero sized base or field (sharing of vfptrs can reorder the |
| // layout of the so the leading base is not always the first one declared). |
| // This rule does take into account fields that are not records, so padding |
| // will occur even if the last field is, e.g. an int. The padding added for |
| // bases is 1 byte. The padding added between vbases depends on the alignment |
| // of the object but is at least 4 bytes (in both 32 and 64 bit modes). |
| // * There is no concept of non-virtual alignment, non-virtual alignment and |
| // alignment are always identical. |
| // * 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 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 |
| // this alignment is also immune to the effects of #pragma pack and can be |
| // used to create structures with large alignment under #pragma pack. |
| // However, because it does not impact required alignment, such a structure, |
| // when used as a field or base, will not be aligned if #pragma pack is |
| // still active at the time of use. |
| // |
| // Known incompatibilities: |
| // * all: #pragma pack between fields in a record |
| // * 2010 and back: If the last field in a record is a bitfield, every object |
| // laid out after the record will have extra padding inserted before it. The |
| // extra padding will have size equal to the size of the storage class of the |
| // bitfield. 0 sized bitfields don't exhibit this behavior and the extra |
| // padding can be avoided by adding a 0 sized bitfield after the non-zero- |
| // sized bitfield. |
| // * 2012 and back: In 64-bit mode, if the alignment of a record is 16 or |
| // greater due to __declspec(align()) then a second layout phase occurs after |
| // The locations of the vf and vb pointers are known. This layout phase |
| // suffers from the "last field is a bitfield" bug in 2010 and results in |
| // _every_ field getting padding put in front of it, potentially including the |
| // vfptr, leaving the vfprt at a non-zero location which results in a fault if |
| // anything tries to read the vftbl. The second layout phase also treats |
| // bitfields as separate entities and gives them each storage rather than |
| // packing them. Additionally, because this phase appears to perform a |
| // (an unstable) sort on the members before laying them out and because merged |
| // bitfields have the same address, the bitfields end up in whatever order |
| // the sort left them in, a behavior we could never hope to replicate. |
| |
| namespace { |
| struct MicrosoftRecordLayoutBuilder { |
| struct ElementInfo { |
| CharUnits Size; |
| CharUnits Alignment; |
| }; |
| typedef llvm::DenseMap<const CXXRecordDecl *, CharUnits> BaseOffsetsMapTy; |
| MicrosoftRecordLayoutBuilder(const ASTContext &Context) : Context(Context) {} |
| private: |
| MicrosoftRecordLayoutBuilder(const MicrosoftRecordLayoutBuilder &) = delete; |
| void operator=(const MicrosoftRecordLayoutBuilder &) = delete; |
| public: |
| void layout(const RecordDecl *RD); |
| void cxxLayout(const CXXRecordDecl *RD); |
| /// Initializes size and alignment and honors some flags. |
| void initializeLayout(const RecordDecl *RD); |
| /// Initialized C++ layout, compute alignment and virtual alignment and |
| /// existence of vfptrs and vbptrs. Alignment is needed before the vfptr is |
| /// laid out. |
| void initializeCXXLayout(const CXXRecordDecl *RD); |
| void layoutNonVirtualBases(const CXXRecordDecl *RD); |
| void layoutNonVirtualBase(const CXXRecordDecl *RD, |
| const CXXRecordDecl *BaseDecl, |
| const ASTRecordLayout &BaseLayout, |
| const ASTRecordLayout *&PreviousBaseLayout); |
| void injectVFPtr(const CXXRecordDecl *RD); |
| void injectVBPtr(const CXXRecordDecl *RD); |
| /// Lays out the fields of the record. Also rounds size up to |
| /// alignment. |
| void layoutFields(const RecordDecl *RD); |
| void layoutField(const FieldDecl *FD); |
| void layoutBitField(const FieldDecl *FD); |
| /// Lays out a single zero-width bit-field in the record and handles |
| /// special cases associated with zero-width bit-fields. |
| void layoutZeroWidthBitField(const FieldDecl *FD); |
| void layoutVirtualBases(const CXXRecordDecl *RD); |
| void finalizeLayout(const RecordDecl *RD); |
| /// Gets the size and alignment of a base taking pragma pack and |
| /// __declspec(align) into account. |
| ElementInfo getAdjustedElementInfo(const ASTRecordLayout &Layout); |
| /// Gets the size and alignment of a field taking pragma pack and |
| /// __declspec(align) into account. It also updates RequiredAlignment as a |
| /// side effect because it is most convenient to do so here. |
| ElementInfo getAdjustedElementInfo(const FieldDecl *FD); |
| /// Places a field at an offset in CharUnits. |
| void placeFieldAtOffset(CharUnits FieldOffset) { |
| FieldOffsets.push_back(Context.toBits(FieldOffset)); |
| } |
| /// Places a bitfield at a bit offset. |
| void placeFieldAtBitOffset(uint64_t FieldOffset) { |
| FieldOffsets.push_back(FieldOffset); |
| } |
| /// Compute the set of virtual bases for which vtordisps are required. |
| void computeVtorDispSet( |
| llvm::SmallPtrSetImpl<const CXXRecordDecl *> &HasVtorDispSet, |
| const CXXRecordDecl *RD) const; |
| const ASTContext &Context; |
| /// The size of the record being laid out. |
| CharUnits Size; |
| /// The non-virtual size of the record layout. |
| CharUnits NonVirtualSize; |
| /// The data size of the record layout. |
| CharUnits DataSize; |
| /// The current alignment of the record layout. |
| CharUnits Alignment; |
| /// The maximum allowed field alignment. This is set by #pragma pack. |
| CharUnits MaxFieldAlignment; |
| /// The alignment that this record must obey. This is imposed by |
| /// __declspec(align()) on the record itself or one of its fields or bases. |
| CharUnits RequiredAlignment; |
| /// The size of the allocation of the currently active bitfield. |
| /// This value isn't meaningful unless LastFieldIsNonZeroWidthBitfield |
| /// is true. |
| CharUnits CurrentBitfieldSize; |
| /// Offset to the virtual base table pointer (if one exists). |
| CharUnits VBPtrOffset; |
| /// Minimum record size possible. |
| CharUnits MinEmptyStructSize; |
| /// The size and alignment info of a pointer. |
| ElementInfo PointerInfo; |
| /// The primary base class (if one exists). |
| const CXXRecordDecl *PrimaryBase; |
| /// The class we share our vb-pointer with. |
| const CXXRecordDecl *SharedVBPtrBase; |
| /// The collection of field offsets. |
| SmallVector<uint64_t, 16> FieldOffsets; |
| /// Base classes and their offsets in the record. |
| BaseOffsetsMapTy Bases; |
| /// virtual base classes and their offsets in the record. |
| ASTRecordLayout::VBaseOffsetsMapTy VBases; |
| /// The number of remaining bits in our last bitfield allocation. |
| /// This value isn't meaningful unless LastFieldIsNonZeroWidthBitfield is |
| /// true. |
| unsigned RemainingBitsInField; |
| bool IsUnion : 1; |
| /// True if the last field laid out was a bitfield and was not 0 |
| /// width. |
| bool LastFieldIsNonZeroWidthBitfield : 1; |
| /// True if the class has its own vftable pointer. |
| bool HasOwnVFPtr : 1; |
| /// True if the class has a vbtable pointer. |
| bool HasVBPtr : 1; |
| /// True if the last sub-object within the type is zero sized or the |
| /// object itself is zero sized. This *does not* count members that are not |
| /// records. Only used for MS-ABI. |
| bool EndsWithZeroSizedObject : 1; |
| /// True if this class is zero sized or first base is zero sized or |
| /// has this property. Only used for MS-ABI. |
| bool LeadsWithZeroSizedBase : 1; |
| |
| /// True if the external AST source provided a layout for this record. |
| bool UseExternalLayout : 1; |
| |
| /// The layout provided by the external AST source. Only active if |
| /// UseExternalLayout is true. |
| ExternalLayout External; |
| }; |
| } // namespace |
| |
| MicrosoftRecordLayoutBuilder::ElementInfo |
| MicrosoftRecordLayoutBuilder::getAdjustedElementInfo( |
| const ASTRecordLayout &Layout) { |
| ElementInfo Info; |
| Info.Alignment = Layout.getAlignment(); |
| // Respect pragma pack. |
| if (!MaxFieldAlignment.isZero()) |
| Info.Alignment = std::min(Info.Alignment, MaxFieldAlignment); |
| // Track zero-sized subobjects here where it's already available. |
| EndsWithZeroSizedObject = Layout.endsWithZeroSizedObject(); |
| // Respect required alignment, this is necessary because we may have adjusted |
| // the alignment in the case of pragam pack. Note that the required alignment |
| // doesn't actually apply to the struct alignment at this point. |
| Alignment = std::max(Alignment, Info.Alignment); |
| RequiredAlignment = std::max(RequiredAlignment, Layout.getRequiredAlignment()); |
| Info.Alignment = std::max(Info.Alignment, Layout.getRequiredAlignment()); |
| Info.Size = Layout.getNonVirtualSize(); |
| return Info; |
| } |
| |
| 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()->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 |
| // alignment when it is applied to bitfields. |
| Info.Alignment = std::max(Info.Alignment, FieldRequiredAlignment); |
| else { |
| if (auto RT = |
| FD->getType()->getBaseElementTypeUnsafe()->getAs<RecordType>()) { |
| auto const &Layout = Context.getASTRecordLayout(RT->getDecl()); |
| EndsWithZeroSizedObject = Layout.endsWithZeroSizedObject(); |
| FieldRequiredAlignment = std::max(FieldRequiredAlignment, |
| Layout.getRequiredAlignment()); |
| } |
| // Capture required alignment as a side-effect. |
| RequiredAlignment = std::max(RequiredAlignment, FieldRequiredAlignment); |
| } |
| // Respect pragma pack, attribute pack and declspec align |
| if (!MaxFieldAlignment.isZero()) |
| Info.Alignment = std::min(Info.Alignment, MaxFieldAlignment); |
| if (FD->hasAttr<PackedAttr>()) |
| Info.Alignment = CharUnits::One(); |
| Info.Alignment = std::max(Info.Alignment, FieldRequiredAlignment); |
| return Info; |
| } |
| |
| 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.alignTo(Alignment); |
| RequiredAlignment = std::max( |
| RequiredAlignment, Context.toCharUnitsFromBits(RD->getMaxAlignment())); |
| finalizeLayout(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); |
| layoutFields(RD); |
| injectVBPtr(RD); |
| injectVFPtr(RD); |
| if (HasOwnVFPtr || (HasVBPtr && !SharedVBPtrBase)) |
| Alignment = std::max(Alignment, PointerInfo.Alignment); |
| auto RoundingAlignment = Alignment; |
| if (!MaxFieldAlignment.isZero()) |
| RoundingAlignment = std::min(RoundingAlignment, MaxFieldAlignment); |
| if (!UseExternalLayout) |
| Size = Size.alignTo(RoundingAlignment); |
| NonVirtualSize = Size; |
| RequiredAlignment = std::max( |
| RequiredAlignment, Context.toCharUnitsFromBits(RD->getMaxAlignment())); |
| layoutVirtualBases(RD); |
| finalizeLayout(RD); |
| } |
| |
| void MicrosoftRecordLayoutBuilder::initializeLayout(const RecordDecl *RD) { |
| IsUnion = RD->isUnion(); |
| Size = CharUnits::Zero(); |
| Alignment = CharUnits::One(); |
| // In 64-bit mode we always perform an alignment step after laying out vbases. |
| // In 32-bit mode we do not. The check to see if we need to perform alignment |
| // checks the RequiredAlignment field and performs alignment if it isn't 0. |
| RequiredAlignment = Context.getTargetInfo().getTriple().isArch64Bit() |
| ? CharUnits::One() |
| : CharUnits::Zero(); |
| // Compute the maximum field alignment. |
| MaxFieldAlignment = CharUnits::Zero(); |
| // Honor the default struct packing maximum alignment flag. |
| if (unsigned DefaultMaxFieldAlignment = Context.getLangOpts().PackStruct) |
| MaxFieldAlignment = CharUnits::fromQuantity(DefaultMaxFieldAlignment); |
| // Honor the packing attribute. The MS-ABI ignores pragma pack if its larger |
| // than the pointer size. |
| if (const MaxFieldAlignmentAttr *MFAA = RD->getAttr<MaxFieldAlignmentAttr>()){ |
| unsigned PackedAlignment = MFAA->getAlignment(); |
| if (PackedAlignment <= Context.getTargetInfo().getPointerWidth(0)) |
| MaxFieldAlignment = Context.toCharUnitsFromBits(PackedAlignment); |
| } |
| // Packed attribute forces max field alignment to be 1. |
| if (RD->hasAttr<PackedAttr>()) |
| MaxFieldAlignment = CharUnits::One(); |
| |
| // Try to respect the external layout if present. |
| UseExternalLayout = false; |
| if (ExternalASTSource *Source = Context.getExternalSource()) |
| UseExternalLayout = Source->layoutRecordType( |
| RD, External.Size, External.Align, External.FieldOffsets, |
| External.BaseOffsets, External.VirtualBaseOffsets); |
| } |
| |
| void |
| MicrosoftRecordLayoutBuilder::initializeCXXLayout(const CXXRecordDecl *RD) { |
| EndsWithZeroSizedObject = false; |
| LeadsWithZeroSizedBase = false; |
| HasOwnVFPtr = false; |
| HasVBPtr = false; |
| PrimaryBase = nullptr; |
| SharedVBPtrBase = nullptr; |
| // Calculate pointer size and alignment. These are used for vfptr and vbprt |
| // injection. |
| PointerInfo.Size = |
| Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0)); |
| PointerInfo.Alignment = |
| Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerAlign(0)); |
| // Respect pragma pack. |
| if (!MaxFieldAlignment.isZero()) |
| PointerInfo.Alignment = std::min(PointerInfo.Alignment, MaxFieldAlignment); |
| } |
| |
| void |
| MicrosoftRecordLayoutBuilder::layoutNonVirtualBases(const CXXRecordDecl *RD) { |
| // The MS-ABI lays out all bases that contain leading vfptrs before it lays |
| // out any bases that do not contain vfptrs. We implement this as two passes |
| // over the bases. This approach guarantees that the primary base is laid out |
| // first. We use these passes to calculate some additional aggregated |
| // information about the bases, such as required alignment and the presence of |
| // zero sized members. |
| const ASTRecordLayout *PreviousBaseLayout = nullptr; |
| // Iterate through the bases and lay out the non-virtual ones. |
| for (const CXXBaseSpecifier &Base : RD->bases()) { |
| const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl(); |
| const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl); |
| // Mark and skip virtual bases. |
| if (Base.isVirtual()) { |
| HasVBPtr = true; |
| continue; |
| } |
| // Check for a base to share a VBPtr with. |
| if (!SharedVBPtrBase && BaseLayout.hasVBPtr()) { |
| SharedVBPtrBase = BaseDecl; |
| HasVBPtr = true; |
| } |
| // Only lay out bases with extendable VFPtrs on the first pass. |
| if (!BaseLayout.hasExtendableVFPtr()) |
| continue; |
| // If we don't have a primary base, this one qualifies. |
| if (!PrimaryBase) { |
| PrimaryBase = BaseDecl; |
| LeadsWithZeroSizedBase = BaseLayout.leadsWithZeroSizedBase(); |
| } |
| // Lay out the base. |
| layoutNonVirtualBase(RD, BaseDecl, BaseLayout, PreviousBaseLayout); |
| } |
| // Figure out if we need a fresh VFPtr for this class. |
| if (!PrimaryBase && RD->isDynamicClass()) |
| for (CXXRecordDecl::method_iterator i = RD->method_begin(), |
| e = RD->method_end(); |
| !HasOwnVFPtr && i != e; ++i) |
| HasOwnVFPtr = i->isVirtual() && i->size_overridden_methods() == 0; |
| // If we don't have a primary base then we have a leading object that could |
| // itself lead with a zero-sized object, something we track. |
| bool CheckLeadingLayout = !PrimaryBase; |
| // Iterate through the bases and lay out the non-virtual ones. |
| for (const CXXBaseSpecifier &Base : RD->bases()) { |
| if (Base.isVirtual()) |
| continue; |
| const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl(); |
| const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl); |
| // Only lay out bases without extendable VFPtrs on the second pass. |
| if (BaseLayout.hasExtendableVFPtr()) { |
| VBPtrOffset = Bases[BaseDecl] + BaseLayout.getNonVirtualSize(); |
| continue; |
| } |
| // If this is the first layout, check to see if it leads with a zero sized |
| // object. If it does, so do we. |
| if (CheckLeadingLayout) { |
| CheckLeadingLayout = false; |
| LeadsWithZeroSizedBase = BaseLayout.leadsWithZeroSizedBase(); |
| } |
| // Lay out the base. |
| layoutNonVirtualBase(RD, BaseDecl, BaseLayout, PreviousBaseLayout); |
| VBPtrOffset = Bases[BaseDecl] + BaseLayout.getNonVirtualSize(); |
| } |
| // Set our VBPtroffset if we know it at this point. |
| if (!HasVBPtr) |
| VBPtrOffset = CharUnits::fromQuantity(-1); |
| else if (SharedVBPtrBase) { |
| const ASTRecordLayout &Layout = Context.getASTRecordLayout(SharedVBPtrBase); |
| VBPtrOffset = Bases[SharedVBPtrBase] + Layout.getVBPtrOffset(); |
| } |
| } |
| |
| static bool recordUsesEBO(const RecordDecl *RD) { |
| if (!isa<CXXRecordDecl>(RD)) |
| return false; |
| if (RD->hasAttr<EmptyBasesAttr>()) |
| return true; |
| if (auto *LVA = RD->getAttr<LayoutVersionAttr>()) |
| // TODO: Double check with the next version of MSVC. |
| if (LVA->getVersion() <= LangOptions::MSVC2015) |
| return false; |
| // TODO: Some later version of MSVC will change the default behavior of the |
| // compiler to enable EBO by default. When this happens, we will need an |
| // additional isCompatibleWithMSVC check. |
| return false; |
| } |
| |
| void MicrosoftRecordLayoutBuilder::layoutNonVirtualBase( |
| const CXXRecordDecl *RD, |
| const CXXRecordDecl *BaseDecl, |
| const ASTRecordLayout &BaseLayout, |
| const ASTRecordLayout *&PreviousBaseLayout) { |
| // 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. |
| bool MDCUsesEBO = recordUsesEBO(RD); |
| if (PreviousBaseLayout && PreviousBaseLayout->endsWithZeroSizedObject() && |
| BaseLayout.leadsWithZeroSizedBase() && !MDCUsesEBO) |
| Size++; |
| ElementInfo Info = getAdjustedElementInfo(BaseLayout); |
| CharUnits BaseOffset; |
| |
| // Respect the external AST source base offset, if present. |
| bool FoundBase = false; |
| if (UseExternalLayout) { |
| FoundBase = External.getExternalNVBaseOffset(BaseDecl, BaseOffset); |
| if (FoundBase) { |
| assert(BaseOffset >= Size && "base offset already allocated"); |
| Size = BaseOffset; |
| } |
| } |
| |
| if (!FoundBase) { |
| if (MDCUsesEBO && BaseDecl->isEmpty()) { |
| assert(BaseLayout.getNonVirtualSize() == CharUnits::Zero()); |
| BaseOffset = CharUnits::Zero(); |
| } else { |
| // Otherwise, lay the base out at the end of the MDC. |
| BaseOffset = Size = Size.alignTo(Info.Alignment); |
| } |
| } |
| Bases.insert(std::make_pair(BaseDecl, BaseOffset)); |
| Size += BaseLayout.getNonVirtualSize(); |
| PreviousBaseLayout = &BaseLayout; |
| } |
| |
| void MicrosoftRecordLayoutBuilder::layoutFields(const RecordDecl *RD) { |
| LastFieldIsNonZeroWidthBitfield = false; |
| for (const FieldDecl *Field : RD->fields()) |
| layoutField(Field); |
| } |
| |
| void MicrosoftRecordLayoutBuilder::layoutField(const FieldDecl *FD) { |
| if (FD->isBitField()) { |
| layoutBitField(FD); |
| return; |
| } |
| LastFieldIsNonZeroWidthBitfield = false; |
| ElementInfo Info = getAdjustedElementInfo(FD); |
| Alignment = std::max(Alignment, Info.Alignment); |
| CharUnits FieldOffset; |
| if (UseExternalLayout) |
| FieldOffset = |
| Context.toCharUnitsFromBits(External.getExternalFieldOffset(FD)); |
| else if (IsUnion) |
| FieldOffset = CharUnits::Zero(); |
| else |
| FieldOffset = Size.alignTo(Info.Alignment); |
| placeFieldAtOffset(FieldOffset); |
| Size = std::max(Size, FieldOffset + Info.Size); |
| } |
| |
| void MicrosoftRecordLayoutBuilder::layoutBitField(const FieldDecl *FD) { |
| unsigned Width = FD->getBitWidthValue(Context); |
| if (Width == 0) { |
| layoutZeroWidthBitField(FD); |
| return; |
| } |
| ElementInfo Info = getAdjustedElementInfo(FD); |
| // Clamp the bitfield to a containable size for the sake of being able |
| // to lay them out. Sema will throw an error. |
| if (Width > Context.toBits(Info.Size)) |
| Width = Context.toBits(Info.Size); |
| // Check to see if this bitfield fits into an existing allocation. Note: |
| // MSVC refuses to pack bitfields of formal types with different sizes |
| // into the same allocation. |
| if (!UseExternalLayout && !IsUnion && LastFieldIsNonZeroWidthBitfield && |
| CurrentBitfieldSize == Info.Size && Width <= RemainingBitsInField) { |
| placeFieldAtBitOffset(Context.toBits(Size) - RemainingBitsInField); |
| RemainingBitsInField -= Width; |
| return; |
| } |
| LastFieldIsNonZeroWidthBitfield = true; |
| CurrentBitfieldSize = Info.Size; |
| if (UseExternalLayout) { |
| auto FieldBitOffset = External.getExternalFieldOffset(FD); |
| placeFieldAtBitOffset(FieldBitOffset); |
| auto NewSize = Context.toCharUnitsFromBits( |
| llvm::alignDown(FieldBitOffset, Context.toBits(Info.Alignment)) + |
| Context.toBits(Info.Size)); |
| Size = std::max(Size, NewSize); |
| Alignment = std::max(Alignment, Info.Alignment); |
| } else if (IsUnion) { |
| placeFieldAtOffset(CharUnits::Zero()); |
| Size = std::max(Size, Info.Size); |
| // TODO: Add a Sema warning that MS ignores bitfield alignment in unions. |
| } else { |
| // Allocate a new block of memory and place the bitfield in it. |
| CharUnits FieldOffset = Size.alignTo(Info.Alignment); |
| placeFieldAtOffset(FieldOffset); |
| Size = FieldOffset + Info.Size; |
| Alignment = std::max(Alignment, Info.Alignment); |
| RemainingBitsInField = Context.toBits(Info.Size) - Width; |
| } |
| } |
| |
| void |
| MicrosoftRecordLayoutBuilder::layoutZeroWidthBitField(const FieldDecl *FD) { |
| // Zero-width bitfields are ignored unless they follow a non-zero-width |
| // bitfield. |
| if (!LastFieldIsNonZeroWidthBitfield) { |
| placeFieldAtOffset(IsUnion ? CharUnits::Zero() : Size); |
| // TODO: Add a Sema warning that MS ignores alignment for zero |
| // sized bitfields that occur after zero-size bitfields or non-bitfields. |
| return; |
| } |
| LastFieldIsNonZeroWidthBitfield = false; |
| ElementInfo Info = getAdjustedElementInfo(FD); |
| if (IsUnion) { |
| placeFieldAtOffset(CharUnits::Zero()); |
| Size = std::max(Size, Info.Size); |
| // TODO: Add a Sema warning that MS ignores bitfield alignment in unions. |
| } else { |
| // Round up the current record size to the field's alignment boundary. |
| CharUnits FieldOffset = Size.alignTo(Info.Alignment); |
| placeFieldAtOffset(FieldOffset); |
| Size = FieldOffset; |
| Alignment = std::max(Alignment, Info.Alignment); |
| } |
| } |
| |
| void MicrosoftRecordLayoutBuilder::injectVBPtr(const CXXRecordDecl *RD) { |
| if (!HasVBPtr || SharedVBPtrBase) |
| return; |
| // Inject the VBPointer at the injection site. |
| CharUnits InjectionSite = VBPtrOffset; |
| // But before we do, make sure it's properly aligned. |
| VBPtrOffset = VBPtrOffset.alignTo(PointerInfo.Alignment); |
| // Determine where the first field should be laid out after the vbptr. |
| CharUnits FieldStart = VBPtrOffset + PointerInfo.Size; |
| // Shift everything after the vbptr down, unless we're using an external |
| // layout. |
| if (UseExternalLayout) { |
| // It is possible that there were no fields or bases located after vbptr, |
| // so the size was not adjusted before. |
| if (Size < FieldStart) |
| Size = FieldStart; |
| return; |
| } |
| // Make sure that the amount we push the fields back by is a multiple of the |
| // alignment. |
| CharUnits Offset = (FieldStart - InjectionSite) |
| .alignTo(std::max(RequiredAlignment, Alignment)); |
| Size += Offset; |
| for (uint64_t &FieldOffset : FieldOffsets) |
| FieldOffset += Context.toBits(Offset); |
| for (BaseOffsetsMapTy::value_type &Base : Bases) |
| if (Base.second >= InjectionSite) |
| Base.second += Offset; |
| } |
| |
| void MicrosoftRecordLayoutBuilder::injectVFPtr(const CXXRecordDecl *RD) { |
| if (!HasOwnVFPtr) |
| return; |
| // Make sure that the amount we push the struct back by is a multiple of the |
| // alignment. |
| CharUnits Offset = |
| PointerInfo.Size.alignTo(std::max(RequiredAlignment, Alignment)); |
| // Push back the vbptr, but increase the size of the object and push back |
| // regular fields by the offset only if not using external record layout. |
| if (HasVBPtr) |
| VBPtrOffset += Offset; |
| |
| if (UseExternalLayout) { |
| // The class may have no bases or fields, but still have a vfptr |
| // (e.g. it's an interface class). The size was not correctly set before |
| // in this case. |
| if (FieldOffsets.empty() && Bases.empty()) |
| Size += Offset; |
| return; |
| } |
| |
| Size += Offset; |
| |
| // If we're using an external layout, the fields offsets have already |
| // accounted for this adjustment. |
| for (uint64_t &FieldOffset : FieldOffsets) |
| FieldOffset += Context.toBits(Offset); |
| for (BaseOffsetsMapTy::value_type &Base : Bases) |
| Base.second += Offset; |
| } |
| |
| void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) { |
| if (!HasVBPtr) |
| return; |
| // Vtordisps are always 4 bytes (even in 64-bit mode) |
| CharUnits VtorDispSize = CharUnits::fromQuantity(4); |
| CharUnits VtorDispAlignment = VtorDispSize; |
| // vtordisps respect pragma pack. |
| if (!MaxFieldAlignment.isZero()) |
| VtorDispAlignment = std::min(VtorDispAlignment |