1//===- RecordLayout.h - Layout information for a struct/union ---*- C++ -*-===// 2// 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4// See https://llvm.org/LICENSE.txt for license information. 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6// 7//===----------------------------------------------------------------------===// 8// 9// This file defines the RecordLayout interface. 10// 11//===----------------------------------------------------------------------===// 12 13#ifndef LLVM_CLANG_AST_RECORDLAYOUT_H 14#define LLVM_CLANG_AST_RECORDLAYOUT_H 15 16#include "clang/AST/ASTVector.h" 17#include "clang/AST/CharUnits.h" 18#include "clang/AST/DeclCXX.h" 19#include "clang/Basic/LLVM.h" 20#include "llvm/ADT/ArrayRef.h" 21#include "llvm/ADT/DenseMap.h" 22#include "llvm/ADT/PointerIntPair.h" 23#include <cassert> 24#include <cstdint> 25 26namespace clang { 27 28class ASTContext; 29class CXXRecordDecl; 30 31/// ASTRecordLayout - 32/// This class contains layout information for one RecordDecl, 33/// which is a struct/union/class. The decl represented must be a definition, 34/// not a forward declaration. 35/// This class is also used to contain layout information for one 36/// ObjCInterfaceDecl. FIXME - Find appropriate name. 37/// These objects are managed by ASTContext. 38class ASTRecordLayout { 39public: 40 struct VBaseInfo { 41 /// The offset to this virtual base in the complete-object layout 42 /// of this class. 43 CharUnits VBaseOffset; 44 45 private: 46 /// Whether this virtual base requires a vtordisp field in the 47 /// Microsoft ABI. These fields are required for certain operations 48 /// in constructors and destructors. 49 bool HasVtorDisp = false; 50 51 public: 52 VBaseInfo() = default; 53 VBaseInfo(CharUnits VBaseOffset, bool hasVtorDisp) 54 : VBaseOffset(VBaseOffset), HasVtorDisp(hasVtorDisp) {} 55 56 bool hasVtorDisp() const { return HasVtorDisp; } 57 }; 58 59 using VBaseOffsetsMapTy = llvm::DenseMap<const CXXRecordDecl *, VBaseInfo>; 60 61private: 62 friend class ASTContext; 63 64 /// Size - Size of record in characters. 65 CharUnits Size; 66 67 /// DataSize - Size of record in characters without tail padding. 68 CharUnits DataSize; 69 70 // Alignment - Alignment of record in characters. 71 CharUnits Alignment; 72 73 // UnadjustedAlignment - Maximum of the alignments of the record members in 74 // characters. 75 CharUnits UnadjustedAlignment; 76 77 /// RequiredAlignment - The required alignment of the object. In the MS-ABI 78 /// the __declspec(align()) trumps #pramga pack and must always be obeyed. 79 CharUnits RequiredAlignment; 80 81 /// FieldOffsets - Array of field offsets in bits. 82 ASTVector<uint64_t> FieldOffsets; 83 84 /// CXXRecordLayoutInfo - Contains C++ specific layout information. 85 struct CXXRecordLayoutInfo { 86 /// NonVirtualSize - The non-virtual size (in chars) of an object, which is 87 /// the size of the object without virtual bases. 88 CharUnits NonVirtualSize; 89 90 /// NonVirtualAlignment - The non-virtual alignment (in chars) of an object, 91 /// which is the alignment of the object without virtual bases. 92 CharUnits NonVirtualAlignment; 93 94 /// SizeOfLargestEmptySubobject - The size of the largest empty subobject 95 /// (either a base or a member). Will be zero if the class doesn't contain 96 /// any empty subobjects. 97 CharUnits SizeOfLargestEmptySubobject; 98 99 /// VBPtrOffset - Virtual base table offset (Microsoft-only). 100 CharUnits VBPtrOffset; 101 102 /// HasOwnVFPtr - Does this class provide a virtual function table 103 /// (vtable in Itanium, vftbl in Microsoft) that is independent from 104 /// its base classes? 105 bool HasOwnVFPtr : 1; 106 107 /// HasVFPtr - Does this class have a vftable that could be extended by 108 /// a derived class. The class may have inherited this pointer from 109 /// a primary base class. 110 bool HasExtendableVFPtr : 1; 111 112 /// EndsWithZeroSizedObject - True if this class contains a zero sized 113 /// member or base or a base with a zero sized member or base. 114 /// Only used for MS-ABI. 115 bool EndsWithZeroSizedObject : 1; 116 117 /// True if this class is zero sized or first base is zero sized or 118 /// has this property. Only used for MS-ABI. 119 bool LeadsWithZeroSizedBase : 1; 120 121 /// PrimaryBase - The primary base info for this record. 122 llvm::PointerIntPair<const CXXRecordDecl *, 1, bool> PrimaryBase; 123 124 /// BaseSharingVBPtr - The base we share vbptr with. 125 const CXXRecordDecl *BaseSharingVBPtr; 126 127 /// FIXME: This should really use a SmallPtrMap, once we have one in LLVM :) 128 using BaseOffsetsMapTy = llvm::DenseMap<const CXXRecordDecl *, CharUnits>; 129 130 /// BaseOffsets - Contains a map from base classes to their offset. 131 BaseOffsetsMapTy BaseOffsets; 132 133 /// VBaseOffsets - Contains a map from vbase classes to their offset. 134 VBaseOffsetsMapTy VBaseOffsets; 135 }; 136 137 /// CXXInfo - If the record layout is for a C++ record, this will have 138 /// C++ specific information about the record. 139 CXXRecordLayoutInfo *CXXInfo = nullptr; 140 141 ASTRecordLayout(const ASTContext &Ctx, CharUnits size, CharUnits alignment, 142 CharUnits unadjustedAlignment, 143 CharUnits requiredAlignment, CharUnits datasize, 144 ArrayRef<uint64_t> fieldoffsets); 145 146 using BaseOffsetsMapTy = CXXRecordLayoutInfo::BaseOffsetsMapTy; 147 148 // Constructor for C++ records. 149 ASTRecordLayout(const ASTContext &Ctx, 150 CharUnits size, CharUnits alignment, 151 CharUnits unadjustedAlignment, 152 CharUnits requiredAlignment, 153 bool hasOwnVFPtr, bool hasExtendableVFPtr, 154 CharUnits vbptroffset, 155 CharUnits datasize, 156 ArrayRef<uint64_t> fieldoffsets, 157 CharUnits nonvirtualsize, CharUnits nonvirtualalignment, 158 CharUnits SizeOfLargestEmptySubobject, 159 const CXXRecordDecl *PrimaryBase, 160 bool IsPrimaryBaseVirtual, 161 const CXXRecordDecl *BaseSharingVBPtr, 162 bool EndsWithZeroSizedObject, 163 bool LeadsWithZeroSizedBase, 164 const BaseOffsetsMapTy& BaseOffsets, 165 const VBaseOffsetsMapTy& VBaseOffsets); 166 167 ~ASTRecordLayout() = default; 168 169 void Destroy(ASTContext &Ctx); 170 171public: 172 ASTRecordLayout(const ASTRecordLayout &) = delete; 173 ASTRecordLayout &operator=(const ASTRecordLayout &) = delete; 174 175 /// getAlignment - Get the record alignment in characters. 176 CharUnits getAlignment() const { return Alignment; } 177 178 /// getUnadjustedAlignment - Get the record alignment in characters, before 179 /// alignment adjustement. 180 CharUnits getUnadjustedAlignment() const { return UnadjustedAlignment; } 181 182 /// getSize - Get the record size in characters. 183 CharUnits getSize() const { return Size; } 184 185 /// getFieldCount - Get the number of fields in the layout. 186 unsigned getFieldCount() const { return FieldOffsets.size(); } 187 188 /// getFieldOffset - Get the offset of the given field index, in 189 /// bits. 190 uint64_t getFieldOffset(unsigned FieldNo) const { 191 return FieldOffsets[FieldNo]; 192 } 193 194 /// getDataSize() - Get the record data size, which is the record size 195 /// without tail padding, in characters. 196 CharUnits getDataSize() const { 197 return DataSize; 198 } 199 200 /// getNonVirtualSize - Get the non-virtual size (in chars) of an object, 201 /// which is the size of the object without virtual bases. 202 CharUnits getNonVirtualSize() const { 203 assert(CXXInfo && "Record layout does not have C++ specific info!"); 204 205 return CXXInfo->NonVirtualSize; 206 } 207 208 /// getNonVirtualSize - Get the non-virtual alignment (in chars) of an object, 209 /// which is the alignment of the object without virtual bases. 210 CharUnits getNonVirtualAlignment() const { 211 assert(CXXInfo && "Record layout does not have C++ specific info!"); 212 213 return CXXInfo->NonVirtualAlignment; 214 } 215 216 /// getPrimaryBase - Get the primary base for this record. 217 const CXXRecordDecl *getPrimaryBase() const { 218 assert(CXXInfo && "Record layout does not have C++ specific info!"); 219 220 return CXXInfo->PrimaryBase.getPointer(); 221 } 222 223 /// isPrimaryBaseVirtual - Get whether the primary base for this record 224 /// is virtual or not. 225 bool isPrimaryBaseVirtual() const { 226 assert(CXXInfo && "Record layout does not have C++ specific info!"); 227 228 return CXXInfo->PrimaryBase.getInt(); 229 } 230 231 /// getBaseClassOffset - Get the offset, in chars, for the given base class. 232 CharUnits getBaseClassOffset(const CXXRecordDecl *Base) const { 233 assert(CXXInfo && "Record layout does not have C++ specific info!"); 234 assert(CXXInfo->BaseOffsets.count(Base) && "Did not find base!"); 235 236 return CXXInfo->BaseOffsets[Base]; 237 } 238 239 /// getVBaseClassOffset - Get the offset, in chars, for the given base class. 240 CharUnits getVBaseClassOffset(const CXXRecordDecl *VBase) const { 241 assert(CXXInfo && "Record layout does not have C++ specific info!"); 242 assert(CXXInfo->VBaseOffsets.count(VBase) && "Did not find base!"); 243 244 return CXXInfo->VBaseOffsets[VBase].VBaseOffset; 245 } 246 247 CharUnits getSizeOfLargestEmptySubobject() const { 248 assert(CXXInfo && "Record layout does not have C++ specific info!"); 249 return CXXInfo->SizeOfLargestEmptySubobject; 250 } 251 252 /// hasOwnVFPtr - Does this class provide its own virtual-function 253 /// table pointer, rather than inheriting one from a primary base 254 /// class? If so, it is at offset zero. 255 /// 256 /// This implies that the ABI has no primary base class, meaning 257 /// that it has no base classes that are suitable under the conditions 258 /// of the ABI. 259 bool hasOwnVFPtr() const { 260 assert(CXXInfo && "Record layout does not have C++ specific info!"); 261 return CXXInfo->HasOwnVFPtr; 262 } 263 264 /// hasVFPtr - Does this class have a virtual function table pointer 265 /// that can be extended by a derived class? This is synonymous with 266 /// this class having a VFPtr at offset zero. 267 bool hasExtendableVFPtr() const { 268 assert(CXXInfo && "Record layout does not have C++ specific info!"); 269 return CXXInfo->HasExtendableVFPtr; 270 } 271 272 /// hasOwnVBPtr - Does this class provide its own virtual-base 273 /// table pointer, rather than inheriting one from a primary base 274 /// class? 275 /// 276 /// This implies that the ABI has no primary base class, meaning 277 /// that it has no base classes that are suitable under the conditions 278 /// of the ABI. 279 bool hasOwnVBPtr() const { 280 assert(CXXInfo && "Record layout does not have C++ specific info!"); 281 return hasVBPtr() && !CXXInfo->BaseSharingVBPtr; 282 } 283 284 /// hasVBPtr - Does this class have a virtual function table pointer. 285 bool hasVBPtr() const { 286 assert(CXXInfo && "Record layout does not have C++ specific info!"); 287 return !CXXInfo->VBPtrOffset.isNegative(); 288 } 289 290 CharUnits getRequiredAlignment() const { 291 return RequiredAlignment; 292 } 293 294 bool endsWithZeroSizedObject() const { 295 return CXXInfo && CXXInfo->EndsWithZeroSizedObject; 296 } 297 298 bool leadsWithZeroSizedBase() const { 299 assert(CXXInfo && "Record layout does not have C++ specific info!"); 300 return CXXInfo->LeadsWithZeroSizedBase; 301 } 302 303 /// getVBPtrOffset - Get the offset for virtual base table pointer. 304 /// This is only meaningful with the Microsoft ABI. 305 CharUnits getVBPtrOffset() const { 306 assert(CXXInfo && "Record layout does not have C++ specific info!"); 307 return CXXInfo->VBPtrOffset; 308 } 309 310 const CXXRecordDecl *getBaseSharingVBPtr() const { 311 assert(CXXInfo && "Record layout does not have C++ specific info!"); 312 return CXXInfo->BaseSharingVBPtr; 313 } 314 315 const VBaseOffsetsMapTy &getVBaseOffsetsMap() const { 316 assert(CXXInfo && "Record layout does not have C++ specific info!"); 317 return CXXInfo->VBaseOffsets; 318 } 319}; 320 321} // namespace clang 322 323#endif // LLVM_CLANG_AST_RECORDLAYOUT_H 324