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 26 namespace clang { 27 28 class ASTContext; 29 class 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. 38 class ASTRecordLayout { 39 public: 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; VBaseInfoVBaseInfo53 VBaseInfo(CharUnits VBaseOffset, bool hasVtorDisp) 54 : VBaseOffset(VBaseOffset), HasVtorDisp(hasVtorDisp) {} 55 hasVtorDispVBaseInfo56 bool hasVtorDisp() const { return HasVtorDisp; } 57 }; 58 59 using VBaseOffsetsMapTy = llvm::DenseMap<const CXXRecordDecl *, VBaseInfo>; 60 61 private: 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 // PreferredAlignment - Preferred alignment of record in characters. This 74 // can be different than Alignment in cases where it is beneficial for 75 // performance or backwards compatibility preserving (e.g. AIX-ABI). 76 CharUnits PreferredAlignment; 77 78 // UnadjustedAlignment - Maximum of the alignments of the record members in 79 // characters. 80 CharUnits UnadjustedAlignment; 81 82 /// RequiredAlignment - The required alignment of the object. In the MS-ABI 83 /// the __declspec(align()) trumps #pramga pack and must always be obeyed. 84 CharUnits RequiredAlignment; 85 86 /// FieldOffsets - Array of field offsets in bits. 87 ASTVector<uint64_t> FieldOffsets; 88 89 /// CXXRecordLayoutInfo - Contains C++ specific layout information. 90 struct CXXRecordLayoutInfo { 91 /// NonVirtualSize - The non-virtual size (in chars) of an object, which is 92 /// the size of the object without virtual bases. 93 CharUnits NonVirtualSize; 94 95 /// NonVirtualAlignment - The non-virtual alignment (in chars) of an object, 96 /// which is the alignment of the object without virtual bases. 97 CharUnits NonVirtualAlignment; 98 99 /// PreferredNVAlignment - The preferred non-virtual alignment (in chars) of 100 /// an object, which is the preferred alignment of the object without 101 /// virtual bases. 102 CharUnits PreferredNVAlignment; 103 104 /// SizeOfLargestEmptySubobject - The size of the largest empty subobject 105 /// (either a base or a member). Will be zero if the class doesn't contain 106 /// any empty subobjects. 107 CharUnits SizeOfLargestEmptySubobject; 108 109 /// VBPtrOffset - Virtual base table offset (Microsoft-only). 110 CharUnits VBPtrOffset; 111 112 /// HasOwnVFPtr - Does this class provide a virtual function table 113 /// (vtable in Itanium, vftbl in Microsoft) that is independent from 114 /// its base classes? 115 bool HasOwnVFPtr : 1; 116 117 /// HasVFPtr - Does this class have a vftable that could be extended by 118 /// a derived class. The class may have inherited this pointer from 119 /// a primary base class. 120 bool HasExtendableVFPtr : 1; 121 122 /// EndsWithZeroSizedObject - True if this class contains a zero sized 123 /// member or base or a base with a zero sized member or base. 124 /// Only used for MS-ABI. 125 bool EndsWithZeroSizedObject : 1; 126 127 /// True if this class is zero sized or first base is zero sized or 128 /// has this property. Only used for MS-ABI. 129 bool LeadsWithZeroSizedBase : 1; 130 131 /// PrimaryBase - The primary base info for this record. 132 llvm::PointerIntPair<const CXXRecordDecl *, 1, bool> PrimaryBase; 133 134 /// BaseSharingVBPtr - The base we share vbptr with. 135 const CXXRecordDecl *BaseSharingVBPtr; 136 137 /// FIXME: This should really use a SmallPtrMap, once we have one in LLVM :) 138 using BaseOffsetsMapTy = llvm::DenseMap<const CXXRecordDecl *, CharUnits>; 139 140 /// BaseOffsets - Contains a map from base classes to their offset. 141 BaseOffsetsMapTy BaseOffsets; 142 143 /// VBaseOffsets - Contains a map from vbase classes to their offset. 144 VBaseOffsetsMapTy VBaseOffsets; 145 }; 146 147 /// CXXInfo - If the record layout is for a C++ record, this will have 148 /// C++ specific information about the record. 149 CXXRecordLayoutInfo *CXXInfo = nullptr; 150 151 ASTRecordLayout(const ASTContext &Ctx, CharUnits size, CharUnits alignment, 152 CharUnits preferredAlignment, CharUnits unadjustedAlignment, 153 CharUnits requiredAlignment, CharUnits datasize, 154 ArrayRef<uint64_t> fieldoffsets); 155 156 using BaseOffsetsMapTy = CXXRecordLayoutInfo::BaseOffsetsMapTy; 157 158 // Constructor for C++ records. 159 ASTRecordLayout(const ASTContext &Ctx, CharUnits size, CharUnits alignment, 160 CharUnits preferredAlignment, CharUnits unadjustedAlignment, 161 CharUnits requiredAlignment, bool hasOwnVFPtr, 162 bool hasExtendableVFPtr, CharUnits vbptroffset, 163 CharUnits datasize, ArrayRef<uint64_t> fieldoffsets, 164 CharUnits nonvirtualsize, CharUnits nonvirtualalignment, 165 CharUnits preferrednvalignment, 166 CharUnits SizeOfLargestEmptySubobject, 167 const CXXRecordDecl *PrimaryBase, bool IsPrimaryBaseVirtual, 168 const CXXRecordDecl *BaseSharingVBPtr, 169 bool EndsWithZeroSizedObject, bool LeadsWithZeroSizedBase, 170 const BaseOffsetsMapTy &BaseOffsets, 171 const VBaseOffsetsMapTy &VBaseOffsets); 172 173 ~ASTRecordLayout() = default; 174 175 void Destroy(ASTContext &Ctx); 176 177 public: 178 ASTRecordLayout(const ASTRecordLayout &) = delete; 179 ASTRecordLayout &operator=(const ASTRecordLayout &) = delete; 180 181 /// getAlignment - Get the record alignment in characters. getAlignment()182 CharUnits getAlignment() const { return Alignment; } 183 184 /// getPreferredFieldAlignment - Get the record preferred alignment in 185 /// characters. getPreferredAlignment()186 CharUnits getPreferredAlignment() const { return PreferredAlignment; } 187 188 /// getUnadjustedAlignment - Get the record alignment in characters, before 189 /// alignment adjustement. getUnadjustedAlignment()190 CharUnits getUnadjustedAlignment() const { return UnadjustedAlignment; } 191 192 /// getSize - Get the record size in characters. getSize()193 CharUnits getSize() const { return Size; } 194 195 /// getFieldCount - Get the number of fields in the layout. getFieldCount()196 unsigned getFieldCount() const { return FieldOffsets.size(); } 197 198 /// getFieldOffset - Get the offset of the given field index, in 199 /// bits. getFieldOffset(unsigned FieldNo)200 uint64_t getFieldOffset(unsigned FieldNo) const { 201 return FieldOffsets[FieldNo]; 202 } 203 204 /// getDataSize() - Get the record data size, which is the record size 205 /// without tail padding, in characters. getDataSize()206 CharUnits getDataSize() const { return DataSize; } 207 208 /// getNonVirtualSize - Get the non-virtual size (in chars) of an object, 209 /// which is the size of the object without virtual bases. getNonVirtualSize()210 CharUnits getNonVirtualSize() const { 211 assert(CXXInfo && "Record layout does not have C++ specific info!"); 212 213 return CXXInfo->NonVirtualSize; 214 } 215 216 /// getNonVirtualAlignment - Get the non-virtual alignment (in chars) of an 217 /// object, which is the alignment of the object without virtual bases. getNonVirtualAlignment()218 CharUnits getNonVirtualAlignment() const { 219 assert(CXXInfo && "Record layout does not have C++ specific info!"); 220 221 return CXXInfo->NonVirtualAlignment; 222 } 223 224 /// getPreferredNVAlignment - Get the preferred non-virtual alignment (in 225 /// chars) of an object, which is the preferred alignment of the object 226 /// without virtual bases. getPreferredNVAlignment()227 CharUnits getPreferredNVAlignment() const { 228 assert(CXXInfo && "Record layout does not have C++ specific info!"); 229 230 return CXXInfo->PreferredNVAlignment; 231 } 232 233 /// getPrimaryBase - Get the primary base for this record. getPrimaryBase()234 const CXXRecordDecl *getPrimaryBase() const { 235 assert(CXXInfo && "Record layout does not have C++ specific info!"); 236 237 return CXXInfo->PrimaryBase.getPointer(); 238 } 239 240 /// isPrimaryBaseVirtual - Get whether the primary base for this record 241 /// is virtual or not. isPrimaryBaseVirtual()242 bool isPrimaryBaseVirtual() const { 243 assert(CXXInfo && "Record layout does not have C++ specific info!"); 244 245 return CXXInfo->PrimaryBase.getInt(); 246 } 247 248 /// getBaseClassOffset - Get the offset, in chars, for the given base class. getBaseClassOffset(const CXXRecordDecl * Base)249 CharUnits getBaseClassOffset(const CXXRecordDecl *Base) const { 250 assert(CXXInfo && "Record layout does not have C++ specific info!"); 251 252 Base = Base->getDefinition(); 253 assert(CXXInfo->BaseOffsets.count(Base) && "Did not find base!"); 254 255 return CXXInfo->BaseOffsets[Base]; 256 } 257 258 /// getVBaseClassOffset - Get the offset, in chars, for the given base class. getVBaseClassOffset(const CXXRecordDecl * VBase)259 CharUnits getVBaseClassOffset(const CXXRecordDecl *VBase) const { 260 assert(CXXInfo && "Record layout does not have C++ specific info!"); 261 262 VBase = VBase->getDefinition(); 263 assert(CXXInfo->VBaseOffsets.count(VBase) && "Did not find base!"); 264 265 return CXXInfo->VBaseOffsets[VBase].VBaseOffset; 266 } 267 getSizeOfLargestEmptySubobject()268 CharUnits getSizeOfLargestEmptySubobject() const { 269 assert(CXXInfo && "Record layout does not have C++ specific info!"); 270 return CXXInfo->SizeOfLargestEmptySubobject; 271 } 272 273 /// hasOwnVFPtr - Does this class provide its own virtual-function 274 /// table pointer, rather than inheriting one from a primary base 275 /// class? If so, it is at offset zero. 276 /// 277 /// This implies that the ABI has no primary base class, meaning 278 /// that it has no base classes that are suitable under the conditions 279 /// of the ABI. hasOwnVFPtr()280 bool hasOwnVFPtr() const { 281 assert(CXXInfo && "Record layout does not have C++ specific info!"); 282 return CXXInfo->HasOwnVFPtr; 283 } 284 285 /// hasVFPtr - Does this class have a virtual function table pointer 286 /// that can be extended by a derived class? This is synonymous with 287 /// this class having a VFPtr at offset zero. hasExtendableVFPtr()288 bool hasExtendableVFPtr() const { 289 assert(CXXInfo && "Record layout does not have C++ specific info!"); 290 return CXXInfo->HasExtendableVFPtr; 291 } 292 293 /// hasOwnVBPtr - Does this class provide its own virtual-base 294 /// table pointer, rather than inheriting one from a primary base 295 /// class? 296 /// 297 /// This implies that the ABI has no primary base class, meaning 298 /// that it has no base classes that are suitable under the conditions 299 /// of the ABI. hasOwnVBPtr()300 bool hasOwnVBPtr() const { 301 assert(CXXInfo && "Record layout does not have C++ specific info!"); 302 return hasVBPtr() && !CXXInfo->BaseSharingVBPtr; 303 } 304 305 /// hasVBPtr - Does this class have a virtual function table pointer. hasVBPtr()306 bool hasVBPtr() const { 307 assert(CXXInfo && "Record layout does not have C++ specific info!"); 308 return !CXXInfo->VBPtrOffset.isNegative(); 309 } 310 getRequiredAlignment()311 CharUnits getRequiredAlignment() const { return RequiredAlignment; } 312 endsWithZeroSizedObject()313 bool endsWithZeroSizedObject() const { 314 return CXXInfo && CXXInfo->EndsWithZeroSizedObject; 315 } 316 leadsWithZeroSizedBase()317 bool leadsWithZeroSizedBase() const { 318 assert(CXXInfo && "Record layout does not have C++ specific info!"); 319 return CXXInfo->LeadsWithZeroSizedBase; 320 } 321 322 /// getVBPtrOffset - Get the offset for virtual base table pointer. 323 /// This is only meaningful with the Microsoft ABI. getVBPtrOffset()324 CharUnits getVBPtrOffset() const { 325 assert(CXXInfo && "Record layout does not have C++ specific info!"); 326 return CXXInfo->VBPtrOffset; 327 } 328 getBaseSharingVBPtr()329 const CXXRecordDecl *getBaseSharingVBPtr() const { 330 assert(CXXInfo && "Record layout does not have C++ specific info!"); 331 return CXXInfo->BaseSharingVBPtr; 332 } 333 getVBaseOffsetsMap()334 const VBaseOffsetsMapTy &getVBaseOffsetsMap() const { 335 assert(CXXInfo && "Record layout does not have C++ specific info!"); 336 return CXXInfo->VBaseOffsets; 337 } 338 }; 339 340 } // namespace clang 341 342 #endif // LLVM_CLANG_AST_RECORDLAYOUT_H 343