| //===--- CGRecordLayout.h - LLVM Record Layout Information ------*- C++ -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef CLANG_CODEGEN_CGRECORDLAYOUT_H |
| #define CLANG_CODEGEN_CGRECORDLAYOUT_H |
| |
| #include "clang/AST/CharUnits.h" |
| #include "clang/AST/Decl.h" |
| #include "clang/Basic/LLVM.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/DerivedTypes.h" |
| |
| namespace llvm { |
| class StructType; |
| } |
| |
| namespace clang { |
| namespace CodeGen { |
| |
| /// \brief Helper object for describing how to generate the code for access to a |
| /// bit-field. |
| /// |
| /// This structure is intended to describe the "policy" of how the bit-field |
| /// should be accessed, which may be target, language, or ABI dependent. |
| class CGBitFieldInfo { |
| public: |
| /// Descriptor for a single component of a bit-field access. The entire |
| /// bit-field is constituted of a bitwise OR of all of the individual |
| /// components. |
| /// |
| /// Each component describes an accessed value, which is how the component |
| /// should be transferred to/from memory, and a target placement, which is how |
| /// that component fits into the constituted bit-field. The pseudo-IR for a |
| /// load is: |
| /// |
| /// %0 = gep %base, 0, FieldIndex |
| /// %1 = gep (i8*) %0, FieldByteOffset |
| /// %2 = (i(AccessWidth) *) %1 |
| /// %3 = load %2, align AccessAlignment |
| /// %4 = shr %3, FieldBitStart |
| /// |
| /// and the composed bit-field is formed as the boolean OR of all accesses, |
| /// masked to TargetBitWidth bits and shifted to TargetBitOffset. |
| struct AccessInfo { |
| /// Offset of the field to load in the LLVM structure, if any. |
| unsigned FieldIndex; |
| |
| /// Byte offset from the field address, if any. This should generally be |
| /// unused as the cleanest IR comes from having a well-constructed LLVM type |
| /// with proper GEP instructions, but sometimes its use is required, for |
| /// example if an access is intended to straddle an LLVM field boundary. |
| CharUnits FieldByteOffset; |
| |
| /// Bit offset in the accessed value to use. The width is implied by \see |
| /// TargetBitWidth. |
| unsigned FieldBitStart; |
| |
| /// Bit width of the memory access to perform. |
| unsigned AccessWidth; |
| |
| /// The alignment of the memory access, assuming the parent is aligned. |
| CharUnits AccessAlignment; |
| |
| /// Offset for the target value. |
| unsigned TargetBitOffset; |
| |
| /// Number of bits in the access that are destined for the bit-field. |
| unsigned TargetBitWidth; |
| }; |
| |
| private: |
| /// The components to use to access the bit-field. We may need up to three |
| /// separate components to support up to i64 bit-field access (4 + 2 + 1 byte |
| /// accesses). |
| // |
| // FIXME: De-hardcode this, just allocate following the struct. |
| AccessInfo Components[3]; |
| |
| /// The total size of the bit-field, in bits. |
| unsigned Size; |
| |
| /// The number of access components to use. |
| unsigned NumComponents; |
| |
| /// Whether the bit-field is signed. |
| bool IsSigned : 1; |
| |
| public: |
| CGBitFieldInfo(unsigned Size, unsigned NumComponents, AccessInfo *_Components, |
| bool IsSigned) : Size(Size), NumComponents(NumComponents), |
| IsSigned(IsSigned) { |
| assert(NumComponents <= 3 && "invalid number of components!"); |
| for (unsigned i = 0; i != NumComponents; ++i) |
| Components[i] = _Components[i]; |
| |
| // Check some invariants. |
| unsigned AccessedSize = 0; |
| for (unsigned i = 0, e = getNumComponents(); i != e; ++i) { |
| const AccessInfo &AI = getComponent(i); |
| AccessedSize += AI.TargetBitWidth; |
| |
| // We shouldn't try to load 0 bits. |
| assert(AI.TargetBitWidth > 0); |
| |
| // We can't load more bits than we accessed. |
| assert(AI.FieldBitStart + AI.TargetBitWidth <= AI.AccessWidth); |
| |
| // We shouldn't put any bits outside the result size. |
| assert(AI.TargetBitWidth + AI.TargetBitOffset <= Size); |
| } |
| |
| // Check that the total number of target bits matches the total bit-field |
| // size. |
| assert(AccessedSize == Size && "Total size does not match accessed size!"); |
| } |
| |
| public: |
| /// \brief Check whether this bit-field access is (i.e., should be sign |
| /// extended on loads). |
| bool isSigned() const { return IsSigned; } |
| |
| /// \brief Get the size of the bit-field, in bits. |
| unsigned getSize() const { return Size; } |
| |
| /// @name Component Access |
| /// @{ |
| |
| unsigned getNumComponents() const { return NumComponents; } |
| |
| const AccessInfo &getComponent(unsigned Index) const { |
| assert(Index < getNumComponents() && "Invalid access!"); |
| return Components[Index]; |
| } |
| |
| /// @} |
| |
| void print(raw_ostream &OS) const; |
| void dump() const; |
| |
| /// \brief Given a bit-field decl, build an appropriate helper object for |
| /// accessing that field (which is expected to have the given offset and |
| /// size). |
| static CGBitFieldInfo MakeInfo(class CodeGenTypes &Types, const FieldDecl *FD, |
| uint64_t FieldOffset, uint64_t FieldSize); |
| |
| /// \brief Given a bit-field decl, build an appropriate helper object for |
| /// accessing that field (which is expected to have the given offset and |
| /// size). The field decl should be known to be contained within a type of at |
| /// least the given size and with the given alignment. |
| static CGBitFieldInfo MakeInfo(CodeGenTypes &Types, const FieldDecl *FD, |
| uint64_t FieldOffset, uint64_t FieldSize, |
| uint64_t ContainingTypeSizeInBits, |
| unsigned ContainingTypeAlign); |
| }; |
| |
| /// CGRecordLayout - This class handles struct and union layout info while |
| /// lowering AST types to LLVM types. |
| /// |
| /// These layout objects are only created on demand as IR generation requires. |
| class CGRecordLayout { |
| friend class CodeGenTypes; |
| |
| CGRecordLayout(const CGRecordLayout&); // DO NOT IMPLEMENT |
| void operator=(const CGRecordLayout&); // DO NOT IMPLEMENT |
| |
| private: |
| /// The LLVM type corresponding to this record layout; used when |
| /// laying it out as a complete object. |
| llvm::StructType *CompleteObjectType; |
| |
| /// The LLVM type for the non-virtual part of this record layout; |
| /// used when laying it out as a base subobject. |
| llvm::StructType *BaseSubobjectType; |
| |
| /// Map from (non-bit-field) struct field to the corresponding llvm struct |
| /// type field no. This info is populated by record builder. |
| llvm::DenseMap<const FieldDecl *, unsigned> FieldInfo; |
| |
| /// Map from (bit-field) struct field to the corresponding llvm struct type |
| /// field no. This info is populated by record builder. |
| llvm::DenseMap<const FieldDecl *, CGBitFieldInfo> BitFields; |
| |
| // FIXME: Maybe we could use a CXXBaseSpecifier as the key and use a single |
| // map for both virtual and non virtual bases. |
| llvm::DenseMap<const CXXRecordDecl *, unsigned> NonVirtualBases; |
| |
| /// Map from virtual bases to their field index in the complete object. |
| llvm::DenseMap<const CXXRecordDecl *, unsigned> CompleteObjectVirtualBases; |
| |
| /// False if any direct or indirect subobject of this class, when |
| /// considered as a complete object, requires a non-zero bitpattern |
| /// when zero-initialized. |
| bool IsZeroInitializable : 1; |
| |
| /// False if any direct or indirect subobject of this class, when |
| /// considered as a base subobject, requires a non-zero bitpattern |
| /// when zero-initialized. |
| bool IsZeroInitializableAsBase : 1; |
| |
| public: |
| CGRecordLayout(llvm::StructType *CompleteObjectType, |
| llvm::StructType *BaseSubobjectType, |
| bool IsZeroInitializable, |
| bool IsZeroInitializableAsBase) |
| : CompleteObjectType(CompleteObjectType), |
| BaseSubobjectType(BaseSubobjectType), |
| IsZeroInitializable(IsZeroInitializable), |
| IsZeroInitializableAsBase(IsZeroInitializableAsBase) {} |
| |
| /// \brief Return the "complete object" LLVM type associated with |
| /// this record. |
| llvm::StructType *getLLVMType() const { |
| return CompleteObjectType; |
| } |
| |
| /// \brief Return the "base subobject" LLVM type associated with |
| /// this record. |
| llvm::StructType *getBaseSubobjectLLVMType() const { |
| return BaseSubobjectType; |
| } |
| |
| /// \brief Check whether this struct can be C++ zero-initialized |
| /// with a zeroinitializer. |
| bool isZeroInitializable() const { |
| return IsZeroInitializable; |
| } |
| |
| /// \brief Check whether this struct can be C++ zero-initialized |
| /// with a zeroinitializer when considered as a base subobject. |
| bool isZeroInitializableAsBase() const { |
| return IsZeroInitializableAsBase; |
| } |
| |
| /// \brief Return llvm::StructType element number that corresponds to the |
| /// field FD. |
| unsigned getLLVMFieldNo(const FieldDecl *FD) const { |
| assert(!FD->isBitField() && "Invalid call for bit-field decl!"); |
| assert(FieldInfo.count(FD) && "Invalid field for record!"); |
| return FieldInfo.lookup(FD); |
| } |
| |
| unsigned getNonVirtualBaseLLVMFieldNo(const CXXRecordDecl *RD) const { |
| assert(NonVirtualBases.count(RD) && "Invalid non-virtual base!"); |
| return NonVirtualBases.lookup(RD); |
| } |
| |
| /// \brief Return the LLVM field index corresponding to the given |
| /// virtual base. Only valid when operating on the complete object. |
| unsigned getVirtualBaseIndex(const CXXRecordDecl *base) const { |
| assert(CompleteObjectVirtualBases.count(base) && "Invalid virtual base!"); |
| return CompleteObjectVirtualBases.lookup(base); |
| } |
| |
| /// \brief Return the BitFieldInfo that corresponds to the field FD. |
| const CGBitFieldInfo &getBitFieldInfo(const FieldDecl *FD) const { |
| assert(FD->isBitField() && "Invalid call for non bit-field decl!"); |
| llvm::DenseMap<const FieldDecl *, CGBitFieldInfo>::const_iterator |
| it = BitFields.find(FD); |
| assert(it != BitFields.end() && "Unable to find bitfield info"); |
| return it->second; |
| } |
| |
| void print(raw_ostream &OS) const; |
| void dump() const; |
| }; |
| |
| } // end namespace CodeGen |
| } // end namespace clang |
| |
| #endif |