| //===--- CGRecordLayoutBuilder.cpp - Record builder helper ------*- C++ -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This is a helper class used to build CGRecordLayout objects and LLVM types. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "CGRecordLayoutBuilder.h" |
| |
| #include "clang/AST/ASTContext.h" |
| #include "clang/AST/Attr.h" |
| #include "clang/AST/DeclCXX.h" |
| #include "clang/AST/Expr.h" |
| #include "clang/AST/RecordLayout.h" |
| #include "CodeGenTypes.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/Target/TargetData.h" |
| |
| |
| using namespace clang; |
| using namespace CodeGen; |
| |
| void CGRecordLayoutBuilder::Layout(const RecordDecl *D) { |
| if (D->isUnion()) { |
| LayoutUnion(D); |
| return; |
| } |
| |
| if (const PackedAttr* PA = D->getAttr<PackedAttr>()) |
| Packed = PA->getAlignment(); |
| |
| if (LayoutFields(D)) |
| return; |
| |
| // We weren't able to layout the struct. Try again with a packed struct |
| Packed = true; |
| AlignmentAsLLVMStruct = 1; |
| FieldTypes.clear(); |
| FieldInfos.clear(); |
| LLVMFields.clear(); |
| LLVMBitFields.clear(); |
| |
| LayoutFields(D); |
| } |
| |
| void CGRecordLayoutBuilder::LayoutBitField(const FieldDecl *D, |
| uint64_t FieldOffset) { |
| uint64_t FieldSize = |
| D->getBitWidth()->EvaluateAsInt(Types.getContext()).getZExtValue(); |
| |
| if (FieldSize == 0) |
| return; |
| |
| uint64_t NextFieldOffset = getNextFieldOffsetInBytes() * 8; |
| unsigned NumBytesToAppend; |
| |
| if (FieldOffset < NextFieldOffset) { |
| assert(BitsAvailableInLastField && "Bitfield size mismatch!"); |
| assert(!FieldInfos.empty() && "Field infos can't be empty!"); |
| |
| // The bitfield begins in the previous bit-field. |
| NumBytesToAppend = |
| llvm::RoundUpToAlignment(FieldSize - BitsAvailableInLastField, 8) / 8; |
| } else { |
| assert(FieldOffset % 8 == 0 && "Field offset not aligned correctly"); |
| |
| // Append padding if necessary. |
| AppendBytes((FieldOffset - NextFieldOffset) / 8); |
| |
| NumBytesToAppend = |
| llvm::RoundUpToAlignment(FieldSize, 8) / 8; |
| |
| assert(NumBytesToAppend && "No bytes to append!"); |
| } |
| |
| const llvm::Type *Ty = Types.ConvertTypeForMemRecursive(D->getType()); |
| uint64_t TypeSizeInBits = getTypeSizeInBytes(Ty) * 8; |
| |
| LLVMBitFields.push_back(LLVMBitFieldInfo(D, FieldOffset / TypeSizeInBits, |
| FieldOffset % TypeSizeInBits, |
| FieldSize)); |
| |
| AppendBytes(NumBytesToAppend); |
| |
| BitsAvailableInLastField = |
| getNextFieldOffsetInBytes() * 8 - (FieldOffset + FieldSize); |
| } |
| |
| bool CGRecordLayoutBuilder::LayoutField(const FieldDecl *D, |
| uint64_t FieldOffset) { |
| bool FieldPacked = Packed; |
| |
| // FIXME: Should this override struct packing? Probably we want to |
| // take the minimum? |
| if (const PackedAttr *PA = D->getAttr<PackedAttr>()) |
| FieldPacked = PA->getAlignment(); |
| |
| // If the field is packed, then we need a packed struct. |
| if (!Packed && FieldPacked) |
| return false; |
| |
| if (D->isBitField()) { |
| // We must use packed structs for unnamed bit fields since they |
| // don't affect the struct alignment. |
| if (!Packed && !D->getDeclName()) |
| return false; |
| |
| LayoutBitField(D, FieldOffset); |
| return true; |
| } |
| |
| const llvm::Type *Ty = Types.ConvertTypeForMemRecursive(D->getType()); |
| |
| // Check if the field is aligned. |
| if (const AlignedAttr *PA = D->getAttr<AlignedAttr>()) { |
| unsigned FieldAlign = PA->getAlignment(); |
| |
| if (!Packed && getTypeAlignment(Ty) > FieldAlign) |
| return false; |
| } |
| |
| assert(FieldOffset % 8 == 0 && "FieldOffset is not on a byte boundary!"); |
| |
| uint64_t FieldOffsetInBytes = FieldOffset / 8; |
| |
| // Append padding if necessary. |
| AppendPadding(FieldOffsetInBytes, Ty); |
| |
| // Now append the field. |
| LLVMFields.push_back(LLVMFieldInfo(D, FieldTypes.size())); |
| AppendField(FieldOffsetInBytes, Ty); |
| |
| return true; |
| } |
| |
| void CGRecordLayoutBuilder::LayoutUnion(const RecordDecl *D) { |
| assert(D->isUnion() && "Can't call LayoutUnion on a non-union record!"); |
| |
| const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D); |
| |
| const llvm::Type *Ty = 0; |
| uint64_t Size = 0; |
| unsigned Align = 0; |
| |
| unsigned FieldNo = 0; |
| for (RecordDecl::field_iterator Field = D->field_begin(), |
| FieldEnd = D->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { |
| assert(Layout.getFieldOffset(FieldNo) == 0 && |
| "Union field offset did not start at the beginning of record!"); |
| |
| if (Field->isBitField()) { |
| uint64_t FieldSize = |
| Field->getBitWidth()->EvaluateAsInt(Types.getContext()).getZExtValue(); |
| |
| // Ignore zero sized bit fields. |
| if (FieldSize == 0) |
| continue; |
| |
| // Add the bit field info. |
| Types.addBitFieldInfo(*Field, 0, 0, FieldSize); |
| } else |
| Types.addFieldInfo(*Field, 0); |
| |
| const llvm::Type *FieldTy = |
| Types.ConvertTypeForMemRecursive(Field->getType()); |
| unsigned FieldAlign = Types.getTargetData().getABITypeAlignment(FieldTy); |
| uint64_t FieldSize = Types.getTargetData().getTypeAllocSize(FieldTy); |
| |
| if (FieldAlign < Align) |
| continue; |
| |
| if (FieldAlign > Align || FieldSize > Size) { |
| Ty = FieldTy; |
| Align = FieldAlign; |
| Size = FieldSize; |
| } |
| } |
| |
| // Now add our field. |
| if (Ty) |
| AppendField(0, Ty); |
| |
| // Append tail padding. |
| if (Layout.getSize() / 8 > Size) |
| AppendPadding(Layout.getSize() / 8, Align); |
| } |
| |
| bool CGRecordLayoutBuilder::LayoutFields(const RecordDecl *D) { |
| assert(!D->isUnion() && "Can't call LayoutFields on a union!"); |
| |
| const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D); |
| |
| unsigned FieldNo = 0; |
| for (RecordDecl::field_iterator Field = D->field_begin(), |
| FieldEnd = D->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { |
| if (!LayoutField(*Field, Layout.getFieldOffset(FieldNo))) { |
| assert(!Packed && |
| "Could not layout fields even with a packed LLVM struct!"); |
| return false; |
| } |
| } |
| |
| // Append tail padding if necessary. |
| if (Layout.getSize() / 8 > getNextFieldOffsetInBytes()) |
| AppendPadding(Layout.getSize() / 8, AlignmentAsLLVMStruct); |
| |
| return true; |
| } |
| |
| void CGRecordLayoutBuilder::AppendField(uint64_t FieldOffsetInBytes, |
| const llvm::Type *FieldTy) { |
| AlignmentAsLLVMStruct = std::max(AlignmentAsLLVMStruct, |
| getTypeAlignment(FieldTy)); |
| |
| uint64_t FieldSizeInBytes = getTypeSizeInBytes(FieldTy); |
| |
| FieldTypes.push_back(FieldTy); |
| FieldInfos.push_back(FieldInfo(FieldOffsetInBytes, FieldSizeInBytes)); |
| |
| BitsAvailableInLastField = 0; |
| } |
| |
| void |
| CGRecordLayoutBuilder::AppendPadding(uint64_t FieldOffsetInBytes, |
| const llvm::Type *FieldTy) { |
| AppendPadding(FieldOffsetInBytes, getTypeAlignment(FieldTy)); |
| } |
| |
| void CGRecordLayoutBuilder::AppendPadding(uint64_t FieldOffsetInBytes, |
| unsigned FieldAlignment) { |
| uint64_t NextFieldOffsetInBytes = getNextFieldOffsetInBytes(); |
| assert(NextFieldOffsetInBytes <= FieldOffsetInBytes && |
| "Incorrect field layout!"); |
| |
| // Round up the field offset to the alignment of the field type. |
| uint64_t AlignedNextFieldOffsetInBytes = |
| llvm::RoundUpToAlignment(NextFieldOffsetInBytes, FieldAlignment); |
| |
| if (AlignedNextFieldOffsetInBytes < FieldOffsetInBytes) { |
| // Even with alignment, the field offset is not at the right place, |
| // insert padding. |
| uint64_t PaddingInBytes = FieldOffsetInBytes - NextFieldOffsetInBytes; |
| |
| AppendBytes(PaddingInBytes); |
| } |
| } |
| |
| void CGRecordLayoutBuilder::AppendBytes(uint64_t NumBytes) { |
| if (NumBytes == 0) |
| return; |
| |
| const llvm::Type *Ty = llvm::Type::Int8Ty; |
| if (NumBytes > 1) { |
| // FIXME: Use a VMContext. |
| Ty = llvm::ArrayType::get(Ty, NumBytes); |
| } |
| |
| // Append the padding field |
| AppendField(getNextFieldOffsetInBytes(), Ty); |
| } |
| |
| uint64_t CGRecordLayoutBuilder::getNextFieldOffsetInBytes() const { |
| if (FieldInfos.empty()) |
| return 0; |
| |
| const FieldInfo &LastInfo = FieldInfos.back(); |
| return LastInfo.OffsetInBytes + LastInfo.SizeInBytes; |
| } |
| |
| unsigned CGRecordLayoutBuilder::getTypeAlignment(const llvm::Type *Ty) const { |
| if (Packed) |
| return 1; |
| |
| return Types.getTargetData().getABITypeAlignment(Ty); |
| } |
| |
| uint64_t CGRecordLayoutBuilder::getTypeSizeInBytes(const llvm::Type *Ty) const { |
| return Types.getTargetData().getTypeAllocSize(Ty); |
| } |
| |
| CGRecordLayout * |
| CGRecordLayoutBuilder::ComputeLayout(CodeGenTypes &Types, |
| const RecordDecl *D) { |
| CGRecordLayoutBuilder Builder(Types); |
| |
| Builder.Layout(D); |
| |
| // FIXME: Once this works well enough, enable it. |
| return 0; |
| |
| // FIXME: Use a VMContext. |
| const llvm::Type *Ty = llvm::StructType::get(Builder.FieldTypes, |
| Builder.Packed); |
| |
| // Add all the field numbers. |
| for (unsigned i = 0, e = Builder.LLVMFields.size(); i != e; ++i) { |
| const FieldDecl *FD = Builder.LLVMFields[i].first; |
| unsigned FieldNo = Builder.LLVMFields[i].second; |
| |
| Types.addFieldInfo(FD, FieldNo); |
| } |
| |
| // Add bitfield info. |
| for (unsigned i = 0, e = Builder.LLVMBitFields.size(); i != e; ++i) { |
| const LLVMBitFieldInfo &Info = Builder.LLVMBitFields[i]; |
| |
| Types.addBitFieldInfo(Info.FD, Info.FieldNo, Info.Start, Info.Size); |
| } |
| |
| return new CGRecordLayout(Ty, llvm::SmallSet<unsigned, 8>()); |
| } |