| //=== ASTRecordLayoutBuilder.cpp - Helper class for building record layouts ==// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "RecordLayoutBuilder.h" |
| |
| #include "clang/AST/Attr.h" |
| #include "clang/AST/Decl.h" |
| #include "clang/AST/DeclCXX.h" |
| #include "clang/AST/DeclObjC.h" |
| #include "clang/AST/Expr.h" |
| #include "clang/AST/RecordLayout.h" |
| #include "clang/Basic/TargetInfo.h" |
| #include <llvm/ADT/SmallSet.h> |
| #include <llvm/Support/MathExtras.h> |
| |
| using namespace clang; |
| |
| ASTRecordLayoutBuilder::ASTRecordLayoutBuilder(ASTContext &Ctx) |
| : Ctx(Ctx), Size(0), Alignment(8), StructPacking(0), NextOffset(0), |
| IsUnion(false), NonVirtualSize(0), NonVirtualAlignment(8) {} |
| |
| /// LayoutVtable - Lay out the vtable and set PrimaryBase. |
| void ASTRecordLayoutBuilder::LayoutVtable(const CXXRecordDecl *RD) { |
| // FIXME: audit indirect virtual bases |
| if (!RD->isPolymorphic() && !RD->getNumVBases()) { |
| // There is no primary base in this case. |
| setPrimaryBase(0, false); |
| return; |
| } |
| |
| SelectPrimaryBase(RD); |
| if (PrimaryBase == 0) { |
| int AS = 0; |
| UpdateAlignment(Ctx.Target.getPointerAlign(AS)); |
| Size += Ctx.Target.getPointerWidth(AS); |
| NextOffset = Size; |
| } |
| } |
| |
| void |
| ASTRecordLayoutBuilder::LayoutNonVirtualBases(const CXXRecordDecl *RD) { |
| for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(), |
| e = RD->bases_end(); i != e; ++i) { |
| if (!i->isVirtual()) { |
| const CXXRecordDecl *Base = |
| cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl()); |
| // Skip the PrimaryBase here, as it is laid down first. |
| if (Base != PrimaryBase) |
| LayoutBaseNonVirtually(Base); |
| } |
| } |
| } |
| |
| // Helper routines related to the abi definition from: |
| // http://www.codesourcery.com/public/cxx-abi/abi.html |
| // |
| /// IsNearlyEmpty - Indicates when a class has a vtable pointer, but |
| /// no other data. |
| bool ASTRecordLayoutBuilder::IsNearlyEmpty(const CXXRecordDecl *RD) { |
| // FIXME: Audit the corners |
| if (!RD->isDynamicClass()) |
| return false; |
| const ASTRecordLayout &BaseInfo = Ctx.getASTRecordLayout(RD); |
| if (BaseInfo.getNonVirtualSize() == Ctx.Target.getPointerWidth(0)) |
| return true; |
| return false; |
| } |
| |
| void ASTRecordLayoutBuilder::SelectPrimaryForBase(const CXXRecordDecl *RD, |
| llvm::SmallSet<const CXXRecordDecl*, 32> &IndirectPrimary) { |
| for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(), |
| e = RD->bases_end(); i != e; ++i) { |
| if (!i->isVirtual()) { |
| const CXXRecordDecl *Base = |
| cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl()); |
| // Only bases with virtual bases participate in computing the |
| // indirect primary base classes. |
| // FIXME: audit indirect virtual bases |
| if (Base->getNumVBases() == 0) |
| return; |
| // FIXME: This information is recomputed a whole lot, cache it instead. |
| SelectPrimaryBase(Base); |
| IndirectPrimary.insert(PrimaryBase); |
| SelectPrimaryForBase(Base, IndirectPrimary); |
| } |
| } |
| } |
| |
| /// SelectPrimaryBase - Selects the primary base for the given class and |
| /// records that with setPrimaryBase. |
| void ASTRecordLayoutBuilder::SelectPrimaryBase(const CXXRecordDecl *RD) { |
| // The primary base is the first non-virtual indirect or direct base class, |
| // if one exists. |
| for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(), |
| e = RD->bases_end(); i != e; ++i) { |
| if (!i->isVirtual()) { |
| const CXXRecordDecl *Base = |
| cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl()); |
| if (Base->isDynamicClass()) { |
| setPrimaryBase(Base, false); |
| return; |
| } |
| } |
| } |
| |
| // Otherwise, it is the first nearly empty virtual base that is not an |
| // indirect primary base class, if one exists. |
| |
| // If we have no virtual bases at this point, bail out as the searching below |
| // is expensive. |
| // FIXME: audit indirect virtual bases |
| if (RD->getNumVBases() == 0) { |
| setPrimaryBase(0, false); |
| return; |
| } |
| |
| // First, we compute all the primary bases for all of our direct and indirect |
| // non-virtual bases, and record all their primary base classes. |
| const CXXRecordDecl *FirstPrimary = 0; |
| llvm::SmallSet<const CXXRecordDecl*, 32> IndirectPrimary; |
| for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(), |
| e = RD->bases_end(); i != e; ++i) { |
| if (!i->isVirtual()) { |
| const CXXRecordDecl *Base = |
| cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl()); |
| SelectPrimaryForBase(Base, IndirectPrimary); |
| } |
| } |
| |
| // Then we can search for the first nearly empty virtual base itself. |
| // FIXME: audit indirect virtual bases |
| for (CXXRecordDecl::base_class_const_iterator i = RD->vbases_begin(), |
| e = RD->vbases_end(); i != e; ++i) { |
| const CXXRecordDecl *Base = |
| cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl()); |
| if (IsNearlyEmpty(Base)) { |
| if (FirstPrimary==0) |
| FirstPrimary = Base; |
| if (!IndirectPrimary.count(Base)) { |
| setPrimaryBase(Base, true); |
| return; |
| } |
| } |
| } |
| |
| // Otherwise if is the first nearly empty virtual base, if one exists, |
| // otherwise there is no primary base class. |
| setPrimaryBase(FirstPrimary, true); |
| return; |
| } |
| |
| void ASTRecordLayoutBuilder::LayoutVirtualBase(const CXXRecordDecl *RD) { |
| LayoutBaseNonVirtually(RD); |
| } |
| |
| void ASTRecordLayoutBuilder::LayoutVirtualBases(const CXXRecordDecl *RD) { |
| // FIXME: audit indirect virtual bases |
| for (CXXRecordDecl::base_class_const_iterator i = RD->vbases_begin(), |
| e = RD->vbases_end(); i != e; ++i) { |
| const CXXRecordDecl *Base = |
| cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl()); |
| if (Base != PrimaryBase) |
| LayoutVirtualBase(Base); |
| } |
| } |
| |
| void ASTRecordLayoutBuilder::LayoutBaseNonVirtually(const CXXRecordDecl *RD) { |
| const ASTRecordLayout &BaseInfo = Ctx.getASTRecordLayout(RD); |
| assert(BaseInfo.getDataSize() > 0 && |
| "FIXME: Handle empty classes."); |
| |
| unsigned BaseAlign = BaseInfo.getNonVirtualAlign(); |
| uint64_t BaseSize = BaseInfo.getNonVirtualSize(); |
| |
| // Round up the current record size to the base's alignment boundary. |
| Size = (Size + (BaseAlign-1)) & ~(BaseAlign-1); |
| |
| // Add base class offsets. |
| Bases.push_back(RD); |
| BaseOffsets.push_back(Size); |
| |
| // Reserve space for this base. |
| Size += BaseSize; |
| |
| // Remember the next available offset. |
| NextOffset = Size; |
| |
| // Remember max struct/class alignment. |
| UpdateAlignment(BaseAlign); |
| } |
| |
| void ASTRecordLayoutBuilder::Layout(const RecordDecl *D) { |
| IsUnion = D->isUnion(); |
| |
| if (D->hasAttr<PackedAttr>()) |
| StructPacking = 1; |
| if (const PragmaPackAttr *PPA = D->getAttr<PragmaPackAttr>()) |
| StructPacking = PPA->getAlignment(); |
| |
| if (const AlignedAttr *AA = D->getAttr<AlignedAttr>()) |
| UpdateAlignment(AA->getAlignment()); |
| |
| // If this is a C++ class, lay out the nonvirtual bases. |
| const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D); |
| if (RD) { |
| LayoutVtable(RD); |
| // PrimaryBase goes first. |
| if (PrimaryBase) |
| LayoutBaseNonVirtually(PrimaryBase); |
| LayoutNonVirtualBases(RD); |
| } |
| |
| LayoutFields(D); |
| |
| NonVirtualSize = Size; |
| NonVirtualAlignment = Alignment; |
| |
| if (RD) |
| LayoutVirtualBases(RD); |
| |
| // Finally, round the size of the total struct up to the alignment of the |
| // struct itself. |
| FinishLayout(); |
| } |
| |
| void ASTRecordLayoutBuilder::Layout(const ObjCInterfaceDecl *D, |
| const ObjCImplementationDecl *Impl) { |
| if (ObjCInterfaceDecl *SD = D->getSuperClass()) { |
| const ASTRecordLayout &SL = Ctx.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. |
| Size = llvm::RoundUpToAlignment(SL.getDataSize(), 8); |
| NextOffset = Size; |
| } |
| |
| if (D->hasAttr<PackedAttr>()) |
| StructPacking = 1; |
| |
| if (const AlignedAttr *AA = D->getAttr<AlignedAttr>()) |
| UpdateAlignment(AA->getAlignment()); |
| |
| // Layout each ivar sequentially. |
| llvm::SmallVector<ObjCIvarDecl*, 16> Ivars; |
| Ctx.ShallowCollectObjCIvars(D, Ivars, Impl); |
| for (unsigned i = 0, e = Ivars.size(); i != e; ++i) |
| LayoutField(Ivars[i]); |
| |
| // Finally, round the size of the total struct up to the alignment of the |
| // struct itself. |
| FinishLayout(); |
| } |
| |
| void ASTRecordLayoutBuilder::LayoutFields(const RecordDecl *D) { |
| // Layout each field, for now, just sequentially, respecting alignment. In |
| // the future, this will need to be tweakable by targets. |
| for (RecordDecl::field_iterator Field = D->field_begin(), |
| FieldEnd = D->field_end(); Field != FieldEnd; ++Field) |
| LayoutField(*Field); |
| } |
| |
| void ASTRecordLayoutBuilder::LayoutField(const FieldDecl *D) { |
| unsigned FieldPacking = StructPacking; |
| uint64_t FieldOffset = IsUnion ? 0 : Size; |
| uint64_t FieldSize; |
| unsigned FieldAlign; |
| |
| // FIXME: Should this override struct packing? Probably we want to |
| // take the minimum? |
| if (D->hasAttr<PackedAttr>()) |
| FieldPacking = 1; |
| |
| if (const Expr *BitWidthExpr = D->getBitWidth()) { |
| // TODO: Need to check this algorithm on other targets! |
| // (tested on Linux-X86) |
| FieldSize = BitWidthExpr->EvaluateAsInt(Ctx).getZExtValue(); |
| |
| std::pair<uint64_t, unsigned> FieldInfo = Ctx.getTypeInfo(D->getType()); |
| uint64_t TypeSize = FieldInfo.first; |
| |
| // Determine the alignment of this bitfield. The packing |
| // attributes define a maximum and the alignment attribute defines |
| // a minimum. |
| // FIXME: What is the right behavior when the specified alignment |
| // is smaller than the specified packing? |
| FieldAlign = FieldInfo.second; |
| if (FieldPacking) |
| FieldAlign = std::min(FieldAlign, FieldPacking); |
| if (const AlignedAttr *AA = D->getAttr<AlignedAttr>()) |
| FieldAlign = std::max(FieldAlign, AA->getAlignment()); |
| |
| // Check if we need to add padding to give the field the correct |
| // alignment. |
| if (FieldSize == 0 || (FieldOffset & (FieldAlign-1)) + FieldSize > TypeSize) |
| FieldOffset = (FieldOffset + (FieldAlign-1)) & ~(FieldAlign-1); |
| |
| // Padding members don't affect overall alignment |
| if (!D->getIdentifier()) |
| FieldAlign = 1; |
| } else { |
| 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. |
| FieldSize = 0; |
| const ArrayType* ATy = Ctx.getAsArrayType(D->getType()); |
| FieldAlign = Ctx.getTypeAlign(ATy->getElementType()); |
| } else if (const ReferenceType *RT = D->getType()->getAs<ReferenceType>()) { |
| unsigned AS = RT->getPointeeType().getAddressSpace(); |
| FieldSize = Ctx.Target.getPointerWidth(AS); |
| FieldAlign = Ctx.Target.getPointerAlign(AS); |
| } else { |
| std::pair<uint64_t, unsigned> FieldInfo = Ctx.getTypeInfo(D->getType()); |
| FieldSize = FieldInfo.first; |
| FieldAlign = FieldInfo.second; |
| } |
| |
| // Determine the alignment of this bitfield. The packing |
| // attributes define a maximum and the alignment attribute defines |
| // a minimum. Additionally, the packing alignment must be at least |
| // a byte for non-bitfields. |
| // |
| // FIXME: What is the right behavior when the specified alignment |
| // is smaller than the specified packing? |
| if (FieldPacking) |
| FieldAlign = std::min(FieldAlign, std::max(8U, FieldPacking)); |
| if (const AlignedAttr *AA = D->getAttr<AlignedAttr>()) |
| FieldAlign = std::max(FieldAlign, AA->getAlignment()); |
| |
| // Round up the current record size to the field's alignment boundary. |
| FieldOffset = (FieldOffset + (FieldAlign-1)) & ~(FieldAlign-1); |
| } |
| |
| // Place this field at the current location. |
| FieldOffsets.push_back(FieldOffset); |
| |
| // Reserve space for this field. |
| if (IsUnion) |
| Size = std::max(Size, FieldSize); |
| else |
| Size = FieldOffset + FieldSize; |
| |
| // Remember the next available offset. |
| NextOffset = Size; |
| |
| // Remember max struct/class alignment. |
| UpdateAlignment(FieldAlign); |
| } |
| |
| void ASTRecordLayoutBuilder::FinishLayout() { |
| // In C++, records cannot be of size 0. |
| if (Ctx.getLangOptions().CPlusPlus && Size == 0) |
| Size = 8; |
| // Finally, round the size of the record up to the alignment of the |
| // record itself. |
| Size = (Size + (Alignment-1)) & ~(Alignment-1); |
| } |
| |
| void ASTRecordLayoutBuilder::UpdateAlignment(unsigned NewAlignment) { |
| if (NewAlignment <= Alignment) |
| return; |
| |
| assert(llvm::isPowerOf2_32(NewAlignment && "Alignment not a power of 2")); |
| |
| Alignment = NewAlignment; |
| } |
| |
| const ASTRecordLayout * |
| ASTRecordLayoutBuilder::ComputeLayout(ASTContext &Ctx, |
| const RecordDecl *D) { |
| ASTRecordLayoutBuilder Builder(Ctx); |
| |
| Builder.Layout(D); |
| |
| if (!isa<CXXRecordDecl>(D)) |
| return new ASTRecordLayout(Builder.Size, Builder.Alignment, Builder.Size, |
| Builder.FieldOffsets.data(), |
| Builder.FieldOffsets.size()); |
| |
| // FIXME: This is not always correct. See the part about bitfields at |
| // http://www.codesourcery.com/public/cxx-abi/abi.html#POD for more info. |
| // FIXME: IsPODForThePurposeOfLayout should be stored in the record layout. |
| bool IsPODForThePurposeOfLayout = cast<CXXRecordDecl>(D)->isPOD(); |
| |
| assert(Builder.Bases.size() == Builder.BaseOffsets.size() && |
| "Base offsets vector must be same size as bases vector!"); |
| |
| // FIXME: This should be done in FinalizeLayout. |
| uint64_t DataSize = |
| IsPODForThePurposeOfLayout ? Builder.Size : Builder.NextOffset; |
| uint64_t NonVirtualSize = |
| IsPODForThePurposeOfLayout ? DataSize : Builder.NonVirtualSize; |
| |
| return new ASTRecordLayout(Builder.Size, Builder.Alignment, DataSize, |
| Builder.FieldOffsets.data(), |
| Builder.FieldOffsets.size(), |
| NonVirtualSize, |
| Builder.NonVirtualAlignment, |
| Builder.PrimaryBase, |
| Builder.PrimaryBaseWasVirtual, |
| Builder.Bases.data(), |
| Builder.BaseOffsets.data(), |
| Builder.Bases.size()); |
| } |
| |
| const ASTRecordLayout * |
| ASTRecordLayoutBuilder::ComputeLayout(ASTContext &Ctx, |
| const ObjCInterfaceDecl *D, |
| const ObjCImplementationDecl *Impl) { |
| ASTRecordLayoutBuilder Builder(Ctx); |
| |
| Builder.Layout(D, Impl); |
| |
| return new ASTRecordLayout(Builder.Size, Builder.Alignment, |
| Builder.NextOffset, |
| Builder.FieldOffsets.data(), |
| Builder.FieldOffsets.size()); |
| } |